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19133	----	OF A LOCOMOTIVE ENGINE*** Transcribed from the 1841 edition by David Price, ccx074@pglaf.org PRACTICAL RULES FOR THE MANAGEMENT OF A LOCOMOTIVE ENGINE: IN THE STATION, ON THE ROAD, AND IN CASES OF ACCIDENT. BY CHARLES HUTTON GREGORY, CIVIL ENGINEER. PREFACE. The substance of the following pages was written several months since, and subsequently sent to the Institution of Civil Engineers, where it was read in abstract on the 16th of February in the present session. While our Engineering Literature contains several valuable Treatises on the Theory and Construction of the Locomotive Engine, it has, as yet, produced no work illustrating its Use. This circumstance, added to the recommendation of several competent authorities, has induced the writer to apply to the Council of the Institution of Civil Engineers for permission to lay before the public these Practical Rules for the Management of a Locomotive Engine, drawn up from individual experience, in the hope that they may be acceptable, at a period when any subject connected with the efficiency and safety of Railway travelling is deservedly engaging attention. At the end of the Paper will be found some Regulations for the first appointment of Engine-men, adopted by the Directors of the London and Croydon Railway, and framed by the writer in his official capacity as their Resident Engineer. Also, a Table of Railway Velocities, indicated by the time occupied in passing over given distances, which he has frequently found to save him the trouble of calculation, and which he hopes may be similarly useful to others. CHARLES HUTTON GREGORY. London, March, 1841. PRACTICAL RULES, &c. THE MANAGEMENT OF A LOCOMOTIVE ENGINE IN THE STATION. The careful examination of a Locomotive Engine when in the Station, and its judicious management while running, are essential to the full performance of its duty, and to ensure the safety of the passengers by the train. While an Engine is stopping at the Station before a trip, the fire should be properly kept up,--the tubes clear at both ends,--and the fire-bars picked free from clinkers: the regulator should be closed and locked,--the tender-break screwed down tight,--the reversing-lever fixed in the middle position, so that the slides may be out of gear,--the cocks of the oil-vessels and feed-pipes turned off,--and the steam blowing off from the safety-valve at a pressure of 35 lbs. per square inch; if blowing off in any excess, the waste steam may be turned into the Tender-cistern to heat the water, and the door of the smoke-box may be opened to check the fire, but it should be fastened up again 10 or 15 minutes before the time of starting. Before an Engine starts with a train, the attention of the Engine-man should first be directed to its being in complete working order; with this view he should go beneath the Engine, and carefully examine the working gear in detail. The connecting-rod is a very important part, and more liable perhaps than any other to fail for want of proper examination. The cotters must be secure, and in case the brasses have too much play they must be tightened up; observing, however, that brasses should never be set so hard as to cause friction. If there are set-screws at the side of the cotters, they should be tight, and all cotters should have a split-pin at the bottom for greater security. The cotters which fasten the piston-rods to the cross-heads should be firm in their place, as well as the set-screws, keys, or other connections, by which the feed-pump pistons are secured to the piston-rod. The brasses of the inner framing which carry the inside bearings of the cranked axle must be examined, and any considerable play prevented by screwing them up if necessary. The wheels ought to be accurately square and firm on their axles, and the keys driven up tight. All the pins, bolts, &c., by which the slide-valve gear is connected, the lifting-links, and the slings of the slide-spindles, must be secure in their proper places; the spanners ought to be fast on the lifting and weigh-bars, and the studs on the spanners of the weigh-bars should be particularly noticed, as, if loose, they may be shaken off on the road and cause the stoppage of the Engine. A similar examination must be extended to the hand-gear, if there be any; and the bolts which fasten the plummer-blocks of the weigh-bars, &c., must be screwed up if they are loose. The straps of the eccentrics should work with sufficient freedom, and the eccentrics must be firm in their right position on the axle, or the Engine will beat unevenly: if any escape of steam has been observed in the stuffing-boxes of the piston-rod and slide-valve spindle, or of water from the joints of the feed-pumps and suction-pipes, they must be screwed up; and any dirt that may have collected near any of the bearings or connections must be carefully wiped off with cotton waste. The inspection beneath the Engine being complete, the Engine-man should examine the ends of the tubes of the boiler, and if there should be leakage to any serious extent, it would be prudent to drive in a plug at each end of the defective tube. A small quantity of Russian tallow should occasionally be introduced into the steam-chests and cylinders, to grease the slides and pistons. This is done, either by cocks on the outside of the smoke-box or in the cylinder covers, or through holes secured by plugs, in the steam-chest covers. The ashes should be emptied out of the smoke-box, and the small ash-door carefully secured. Occasionally the gauge should be applied to the wheels, and the Engine should never be allowed to run when they are found to be at all incorrect or out of the square. If there are oil-vessels at the side of the Engine with pipes to the pistons, bearings, &c., the Engine-man must see that they are filled, and the cotton wicks in the top of the pipes, and hanging over into the oil; that the grease-boxes of the axle-bearings are filled; and the pins, links, &c., of the springs right and sound. The draw-bar connecting the Engine and Tender must be secure, and the safety-chains attached. The Tender must be replenished with coke and water. An Engine-man should never run with an Engine without knowing what stock of both the Tender will carry. It is impossible to lay down any general rule for the quantity of water evaporated and the coke consumed per mile with the same Engine, as the amount depends entirely on the extent of duty performed. The stock of coke is usually nearly twice as much as that of water,--the water which most Tenders contain is ordinarily sufficient for running 30 miles with certainty; but when the gradients are steep, the load heavy, and stoppages frequent, additional water may be oftener required; and on the other hand, with light duty, an Engine may sometimes run further without any stoppage. The inconvenience attached to the necessity of frequent stoppages, and the expense of maintaining a large number of coke and water stations, have lately induced the manufacture of a larger class of Tender on six wheels, which, from superior capacity, will admit of a much longer run. After a little practice, the examination described above occupies a very short time: it ought to be completed, and the Engine in its position at the head of the train, at least five minutes before the hour of starting, when oil must be copiously supplied by the small oiling-can, to the oil-cups of the guides, connecting-rods, &c., and to all rubbing parts not fed by the oiling-pipes; the cocks of the large oil-vessels must be opened, and the safety-valve screwed down to the working pressure, say 45 lbs. per square inch. It would ensure a careful inspection, if, before any train starts, the Engine-man were required to deliver to the Superintendent of the Station a certificate that he has examined his Engine, and finds it in good working order. Several articles should be constantly carried on the Tender, as either being frequently required in the working of the Engine, or occasionally in cases of derangement or accident. The following may be taken as a list: One large can of oil, and one or two small oiling-cans and an oiling-tube, a box of Russian tallow, a quantity of cotton waste, hemp, and gasken, a hand-brush, keys fitted to all the principal bolts, one large and one small monkey-wrench, rods for clearing the tubes and fire, an arrow-headed poker, a shovel, and a rake. A number of iron or wooden plugs, an iron plug-holder, and a 7 lb. maul, two cold chisels, a hammer and a file, spare washers, and duplicates of the principal bolts, nuts, pins, cotters, &c., a quantity of thick and thin cord, and some tarred line, a fire-bucket, two long crow-bars, a spare coupling-chain, with shackle and hook complete, several wooden wedges, about 2 feet long, 4 or 5 inches wide and 3 inches thick, and, if running long journeys, two spare ball-clacks, and a screw-jack. THE MANAGEMENT OF A LOCOMOTIVE ENGINE ON THE ROAD. In the management of a Locomotive Engine, many unforeseen circumstances may occur, requiring the use of that discretion which experience alone can confer, and which it would be almost impossible to comprise in the particular instructions contained in the following pages, which, however, the writer believes to contain all the leading principles of Engine-driving. On receiving the signal to start, the Engine-man should only slightly open the regulator, and let the train run for several yards, before he opens it, by slow degrees, to the full extent. The object of thus giving a slight aperture to the regulator in starting, is to avoid any jerk to the carriages, by which passengers might be annoyed, or even the coupling-irons broken; to prevent the slipping of the driving-wheels, from their adhesion being unequal to the inertia of the train, when the full power of the Engine is suddenly used; and because fully opening the regulator at starting generally causes the Engine to _prime_ considerably, from the quantity of water condensed in the cylinders and steam-passages while the Engine was standing. When _priming_ occurs at starting, the discharge-cocks of the cylinders should be opened to remove the water. On leaving the station, and frequently on the road, the Engine-man should watch the train behind him, to see that it is all right and its motion regular. The Engine-man should now be standing on the foot-board of the Engine, which he ought never to leave, unless the machinery is out of order, when he may leave the Stoker in his place; he should as much as possible be in such a position as to command, without moving from his place, the reversing-lever, the whistle, and the regulator, these being the parts which he is most frequently obliged to use at the shortest notice; his hand should be upon the regulator, which, when he has arrived at a good speed, he will gradually ease off, so as to economise steam without retarding the train: his eye should be constantly directed to the rails in front of him, that he may be immediately aware of any obstruction, and at the same time his full attention must be given to the maintaining a sufficiency of steam at an equable pressure; this is to be done by using the requisite care in the manner and time of supplying _water_ and _fuel_. Water is supplied by opening the cocks in the feed-pipes, which allow the pumps to act; and the height of water in the boiler is commonly shown by a glass gauge-tube, and by three gauge-cocks at the side, which should be opened from time to time, (especially when stopping,) as they afford a more correct indication of the quantity of water and steam than the gauge-tube. One pump, if constantly at work, would, in most Engines, supply as much, or rather more water than is required by the Engine as equivalent to the steam consumed; so that by turning on or off either or both pumps, the Engine-man has the power of regulating the height of the water in the boiler at discretion. It may be laid down as an invariable rule, that water alone should always blow off from the bottom cock (which is from 1 inch to 1.5 inch above the top of the fire-box), in order that there may be enough water over the fire-box and tubes to prevent their burning; and few Engines will carry their water much above the top cock without _priming_, so that the height of the water may be made to range between these two points, according as more or less steam is required. The water is higher when the Engine is running than when stopping: a good working height for it in most Engines is when _water_ blows off from the middle cock while running, and _water and steam_ when stopping: an Engine-man is sometimes obliged to run the water rather lower, if he has heavy work; but it is always better to keep the level of the water as high as possible. It is observed that when any variation takes place in the pressure of the steam, a corresponding change occurs in the level of the water,--that when the pressure of the steam rises or falls, the height of the water rises or falls simultaneously. Partly for this reason, and partly to allow the more rapid generation of steam, the feed-pumps are not generally allowed to act when the Engine starts: a knowledge of this fact also shows the necessity of the water being above the ordinary level, before a decrease is allowed in the pressure of the steam. When the Engine is highest on an inclined plane, rather a greater height of water must be kept over the fire-box than on a level, in order that the chimney ends of the tubes may be well covered. The most favourable time for allowing the feed-pumps to act, is when the steam is blowing off with force from the safety-valve, and the fire strong; and the least favourable time is when the steam and fire are low: indeed the Engine-man should manage that it may never be necessary in the latter case, as the addition of water rapidly lowers the steam. In order to know the force of the steam, one hand may occasionally lift or depress for a moment the lever of the safety-valve, according as the steam is under or over the working pressure; and a little practice will soon enable a person to judge the extent of excess or deficiency. Both feed-pumps should not commence working at the same time. The water should never be allowed to run low before arriving at any part of the road where considerable power is required, as steam is produced more rapidly when both pumps are turned off,--a measure which is imprudent unless the water is high. When "the feed" is turned on, the Engine-man should try the pet-cock to see whether the pump is acting freely: the water thrown from it should be in forcible intermittent jets; warm water with a little steam will frequently escape from it at first; if this should continue, it may be concluded that the upper clack does not act; and if the water is in a continuous stream without pulsations, the lower clack is out of order. In either case it will not be prudent to trust too much to the faulty pump, but the evil may frequently be remedied by working the pump a short time with the pet-cock open, or alternately turned on and off. Coke is put on the fire by the Stoker, at the order of the Engine-man, who should hold the chain of the fire-door in his hand, and open it for as short a time as possible, while the Stoker throws on each shovelful of coke: the shovel should be well filled, and the coke distributed equally over the fire. In most Engines, the fuel need not be higher than the bottom of the fire-door; and if allowed to fall more than 6 or 8 inches below it, it must not be expected that the pressure of the steam will be maintained, if the Engine has a load. The supply of fuel should be regular, and so arranged that the fire may have burned up well by the time the steam is most required. As the addition of fuel causes a temporary reduction of the force of the fire, coke should not be laid on immediately before arriving at an inclined plane or any part of the road where much power is required; but when ascending an incline, coke should be gradually added when the Engine begins to _beat heavily_,--the draught is then powerful, and a regular supply of fuel required to keep up the fire. In other circumstances, provided the fire is low enough to require fuel, the best time to put on coke is when the water is sufficiently high to turn off the feed-pumps, the steam slightly blowing off, and the Engine travelling at a good speed. No definite instructions can be given for the frequency with which coke must be laid on the fire, as it varies according to the duty to be done, and the water consequently to be evaporated: in cases of heavy duty and bad gradients, it may at times be necessary even at as short an interval as 2 miles; under contrary circumstances an Engine may sometimes run as much as 15 miles without adding fresh coke. The fire should be allowed to run rather low before arriving at the top of an inclined plane down which the steam will not be used: on beginning to descend the plane, fuel should be put on the fire, which will burn up by the time the train reaches the bottom of the plane. If it is wished to keep up the steam, it is better not to supply water and fuel at the same time. While running, the Stoker should occasionally pick the ashes from the tubes to clear the draught. By observing the above rules for the supply of water and coke, an efficient pressure and quantity of steam will be produced, which it must be the study of the Engine-man to economise. With this view the regulator should never be kept too far open;--as soon as the train has acquired the velocity wished, the aperture may be considerably reduced without diminishing the speed. As any diminution in the amount of steam used causes a corresponding diminution in the quantity of coke consumed, the skill of the Engine-man should be unceasingly directed to the reduction of so heavy an item of Railway expenditure. If there should be, at any time, an unnecessary quantity and force of steam, it is readily reduced by opening the fire-door, and by turning on the feed-pumps; if there should be too little, the Engine-man must be content to run slowly for a short time, keep the regulator only partially open, and put on a gradual supply of coke. When the water in the boiler is high, many Engines begin to prime, especially after running for several days. When this occurs, the aperture of the regulator should be diminished, and the fire-door and the discharge cocks of the cylinders opened: if the height of the water will allow it, the blow-off cock of the boiler may be opened for a short time to carry off the sediment, which will be found advantageous. The Engine-man should frequently look to the working gear, to see that it is in proper order, and to rectify any deficiency at the next Station. On nearing a Station where it is intended to stop, the regulator should be gradually eased off at about five-eighths of a mile from the Station, so that the train may be more under control, and when from a quarter to half a mile distant, according to the velocity and weight of the train, the steam should be completely shut off, and the train brought to rest by the breaks. In approaching terminal Stations the steam should be shut off at a greater distance than at the intermediate Stations, to prevent the possibility of overrunning the mark from the failure of breaks. It must be borne in mind that the breaks act much less efficiently in wet or frosty weather, when it becomes necessary to shut off the steam further from the Stations. The use of the reversing-lever ought, as much as possible, to be avoided: it may sometimes be placed in the middle position (in which the valves do not act), but it should never be completely reversed unless absolutely necessary for the stoppage of the train. At the intermediate Stations, the Stoker should frequently oil all the bearings not supplied by the large oil-vessels, and fill the oil-cups of the connecting-rods, slides, &c., and if any of the bearings, brasses, &c., are hot, they should be more copiously oiled, and eased if necessary. He should also examine all the working gear cursorily to see if it is in a complete state; particular attention should be given to the axle-bearings, and especially those of the cranked axle, which sometimes become so hot by running as to require cooling by throwing on water. In case of the driving wheels slipping much in starting from a Station, the opening of the regulator should be reduced, and only gradually opened as the wheel bites; the Stoker is sometimes obliged to scatter ashes, sand, &c., before the wheels: some Engines are now furnished with hoppers in front, opened by a handle from the foot-board, by means of which sand may be dropped on the rails in front of the driving wheels. If slipping is observed to an unusual extent, it may be inferred that there is not sufficient weight on the driving wheels, and the springs ought to be tightened by screwing up the nuts of the bearing bolts: or where the framing is hung to the springs by plain links, the spring pins must be lengthened the next time the Engine is in the repairing shops. A deficiency of weight on the front or hind wheels is indicated by the pitching of the Engine, and should be remedied in a similar manner. The regulator should be gradually and completely closed, when the Engine or train pitches or rocks violently,--in passing a series of points and crossings,--in very sharp curves, especially if double,--in rough parts of the permanent way,--and in descending planes whose inclination is sufficient to carry the train down, without steam, at a velocity of 30 miles per hour. In descending such an inclined plane, if it should be found that the velocity is greater than 30 miles per hour, it should be reduced by gently applying the break. On every Railway there is a prescribed limit to the pressure of the steam, and no circumstance should induce the Engine-man to use steam at a higher pressure, or in any case to weight the lever, or hold it down for more than a moment. When there are two safety-valves, that which is out of reach may be set at the limit of pressure, and the valve next the foot-board some pounds lower. It is an advantage to have a stop placed below the lever of the safety-valve on the screw of the spring balance, to prevent its being inadvertently screwed down to more than the working pressure. The steam whistle is obviously intended to give notice of danger: on this account its use is forbidden on some Railways, excepting on occasions of extreme emergency; but the variety of modulation of which it is susceptible has in others induced its adoption as a frequent warning. When the latter is the case, it has been found a safe measure to sound the whistle directly the steam has been shut off previously to stopping at a Station, and to give two short whistles the moment before starting, to warn parties of the approach and departure of the train. When this system is practised, the Engine-man should not turn on the full power of the whistle, but reserve it exclusively for cases of danger. When near the end of the trip very little fire is wanted, and both feed-pumps should be turned on for a short distance before arriving at the Station, unless the Engine is to start again immediately. If it is intended to remain at the Station about an hour, the water should be considerably above the middle cock (when the Engine is standing), which will be effected by keeping on both feed-pumps from a half to three-quarters of a mile. The safety-valve should, at the same time, be eased off to 35 lbs. If the train is brought into the Station by a tow-rope, great care must be taken to stretch the rope gradually by a gentle advance of the Engine, which must be stopped at a signal from the tow-rope man. It would be prudent to conduct the examination described at the commencement, directly the Engine arrives at the Station, in order to leave time for any repair which may be required. When an Engine is running the last trip for the day, no fuel need be put on for the last 10, 15, or 20 miles, according as the duty is heavy or light; indeed, the fire may be nearly run out by the time the Engine stops, if the gradients, &c., are favourable. For a considerable distance before stopping both pumps should be at work, so that the water in the boiler may be at or above the top cock when the Engine stops, and the safety-valve should be eased off to 25 lbs. per square inch. On stopping over the pit, the fire is drawn by opening the fire-door, introducing the arrow-headed poker through the fire-bars, and pulling up two or three of them from the bottom of the furnace, by which room will be allowed for the rest to be separated, and the fire fall through into the ash-pan, from which it is raked out by the Stoker. The practice of blowing off all the water from a boiler by the pressure of the steam should never be allowed, without an express order from the Superintendent of Locomotives, when the boiler is unusually full of mud; as, if frequently practised, it will seriously injure the fire-box and tubes. THE MANAGEMENT OF A LOCOMOTIVE ENGINE IN CASES OF ACCIDENT. An Engine is liable to several accidents while running, and it is important that the Engine-man should know how to act promptly under the circumstances. In the following list several cases are enumerated, with the particular steps to be taken in each. 1. _The bursting of a tube_.--The Engine-man should stop the Engine, and drive a plug into each end of the tube. It frequently happens that the water and steam blow out with so much force, that it is impossible even to discover the defective tube: by running the Engine for a short distance with both pumps acting, the pressure of the steam will perhaps be sufficiently reduced to enable the Engine-man to work with safety; but if the escape of water and steam is still too great to do so, he must run his Engine and train, if possible, off the main line into a siding, and draw the fire, to prevent its injuring the fire-box and tubes: when the water has run out down to the level of the defective tube, it may be easily plugged, and a fresh fire laid and lighted. A tube will frequently leak to a considerable extent without absolutely requiring the stoppage of the train; but in this case great care is necessary not to use much steam, or urge the fire too far. The bursting of a tube or other causes will sometimes lead to the lagging or casing of the boiler catching fire, which should be extinguished by throwing on water from the Tender-cistern in a fire-bucket, or from the water crane at a Station. 2. _The failing of one of the feed pumps_.--In this case the adequate supply of water may, with care, be maintained by one pump only. The supply of coke must be regular, and not in large quantities; and the steam must be economised, or the water may run low. The pump should be repaired as soon as possible; this may frequently be done in the interval between two trips. 3. _The breaking of a spring_.--This is an accident which does not necessarily involve the stoppage of the train; but as working the Engine in such a state causes an unequal strain, it should run very gently over rough parts of the road; and if the derangement is considerable, and cannot be repaired at the Stations, the Engine should cease running as soon as possible. 4. _The breaking of a connecting-rod_, _or its disconnection_ by the loss of cotters, fracture of the straps, &c. This accident, or any disconnection which allows the piston to be driven from end to end of the cylinder without restraint, causes expensive damage to the cylinders and covers; and the connecting-rod, if loose, will seriously injure the smaller gear, or may even throw the Engine off the road. The Engine should therefore be instantly stopped, and if possible the connection restored; if that cannot be done, the connecting-rod must be taken off, and if on a level or a descending gradient, the train may sometimes be drawn by a single cylinder: to do so, the slide-valve spindle of the defective cylinder must be detached from the valve gear, by unscrewing the nuts, and setting the slide at the middle of its stroke so as to cover both ports. If it should be found impracticable to move the train, the Engine might run on alone for assistance; but in any case where the Engine is obliged to remain stationary, the fire must be drawn directly the water is down to the bottom cock. 5. _The fracture or disconnection of the eccentrics, or any of the slide-valve gear_.--In Engines without hand-gear, if the connection cannot be restored, the attempt may be made, as in the previous instance, to work with one cylinder. When the slide-valve gear is disabled, Engines with hand-gear possess an advantage which others want, in being able to be worked by hand, when a single cylinder would be unequal to the duty, from not being able to move the crank over the centres at starting. 6. _The fracture of the strap which holds the slide-valve_, renders unavailable the cylinder on that side where it occurs, without affecting the other side. The slide should be detached and placed in the middle of its stroke, and the attempt made to work with one cylinder. 7. _The disconnection of a piston_, by the fracture of either cotter, is sometimes caused by shutting off the steam too suddenly when the Engine is travelling fast with a heavy load. In this case also the slide should be detached and set in the middle position, and the piston-rod uncoupled from the connecting-rod, which should be removed to prevent its damaging the small gear. 8. _The breaking of an axle_, in a four-wheeled Engine is an accident which is almost of necessity attended with the overturn of the Engine. In a six-wheeled Engine it requires the stoppage of the train until assistance arrives. 9. _The Engine running off the rails_. With an Engine-man who drives carefully, watching well the position of the switches, and the signals given him, and stopping when he sees any danger attending his further course, this is an accident of very rare occurrence. If the Engine should run off on hard ground and near the rails, it may sometimes be lifted on again at once, by screw-jacks, crow-bars, and long sways; but if on soft ground or far from the rails, the fire must be drawn, and instant attention given to prevent its sinking deep into the ground. The Engine should first be separated from the Tender, which, being a lighter weight, may be pushed out of the way, and leave more room for operating on the Engine; this, if it has fallen over on its side, should be lifted as quickly as may be into a vertical position; to do so, a purchase should be obtained under the framing on the lowest side, in two places if possible; two long and tough sways should be brought to bear on these points, and several men placed to weigh upon each; and as the Engine is gradually lifted by the sways, every movement should be followed up and supported by screw-jacks bedded on timber blocking. When the Engine has been lifted upright, it should be firmly supported by timbers placed as stanchions under the framing; the earth may then be cautiously removed from under the wheels, and a length of rail introduced, taking care to bed it as securely as possible on the blockings previously laid down, without disturbing them: the same process should be repeated on the other side, and cross sleepers driven in under both rails to secure the foundation. As soon as the Engine is in a vertical position and rails inserted under the wheels, a temporary railway may be laid down in continuation, and the Engine again drawn on the main line. It will much facilitate the raising of the Engine if the water is drawn away out of the boiler as soon as it is sufficiently cool. * * * * * In all cases of accident involving stoppage on the main line, it is of the highest importance that some person should immediately be sent back about three-quarters of a mile along the road, to give the proper signal of obstruction, and prevent any following train from running in unexpectedly. * * * * * The most essential personal qualifications of an Engine-man are, sobriety and steadiness, activity, presence of mind, and unceasing watchfulness; and wherever these are combined with an accurate knowledge of the construction of a Locomotive Engine and the principles of its management, they tend in no small degree towards rendering Railways, what they properly are, the safest as well as the most agreeable mode of travelling. REGULATIONS FOR THE FIRST APPOINTMENT OF AN ENGINE-MAN, ADOPTED BY THE DIRECTORS OF THE LONDON AND CROYDON RAILWAY. 1840. 1. The candidate must not be under twenty-one years of age, and must produce a certificate of a sound constitution and steady habits. 2. He must be able to read and write, and, if possible, understand the rudimental principles of mechanics. 3. It will be a great recommendation if he has served his time to any mechanical art, especially as a Fitter of Locomotive Engines; and, if possible, he should produce testimonials stating his qualifications as such. 4. If the candidate has been a Fitter or a stationary Engine-man, he must, for several months at least, have been a Stoker on a Locomotive Engine, under the direction of a steady and competent Engine-man; and before his appointment, he should produce a testimonial from the Superintendent of Locomotives, or at least from the Engine-man under whom he has served, stating full confidence in his acquaintance with the construction of an Engine and the principles of its management. 5. If the candidate has not been a Fitter or a stationary Engine-man, he must have served as a Stoker for at least two years, and produce the testimonials named in the preceding rules. 6. If required by the Board of Directors, for greater security, the candidate must undergo an examination from their Engineer, Superintendent of Locomotives, or other competent person, as to his knowledge of an Engine and its management, and the general result of this examination must be committed to paper, signed by the examiner, and presented to the Board. 7. The Engineer or Superintendent of Locomotives of the Railway to which the candidate is desirous of being appointed, shall sign a certificate stating that he has conversed with him, has seen him drive, and has confidence in his steadiness and ability. 8. Before being allowed to take the entire charge of an Engine and train, the candidate must drive for several days under the direction of an experienced Engine-man, who must be on his Engine, and certify to his ability. 9. All certificates and testimonials must be deposited with the Secretary of the Company, who will restore them to the owner on his leaving their service. A TABLE OF VELOCITIES. Time occupied in Time occupied in Velocity Travelling one eight Travelling quarter of of a mile a mile 7.5 15 60.0 8 16 56.2 8.5 17 52.9 9 18 50.0 9.5 19 47.4 10 20 45.0 10.5 21 42.9 11 22 40.9 11.5 23 39.1 12 24 37.5 12.5 25 36.0 13 26 34.6 13.5 27 33.3 14 28 32.1 14.5 29 31.0 15 30 30.0 15.5 31 29.0 16 32 28.1 16.5 33 27.3 17 34 26.5 17.5 35 25.7 18 36 25.0 18.5 37 24.3 19 38 23.7 19.5 39 23.1 20 40 22.5 20.5 41 21.9 21 42 21.4 21.5 43 20.9 22 44 20.4 22.5 45 20.0 23 46 19.6 23.5 47 19.1 24 48 18.7 24.5 49 18.4 25 50 18.0 25.5 51 17.7 26 52 17.3 26.5 53 17.0 27 54 16.7 28 56 16.0 29 58 15.5 30 60 15.0 31 62 14.5 32 64 14.1 33 66 13.6 34 68 13.2 35 70 12.8 36 72 12.5 37 74 12.2 38 76 11.8 39 78 11.5 40 80 11.25 41 82 11.0 42 84 10.7 43 86 10.5 44 88 10.2 45 90 10.0 
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11164	----	ROUGH AND TUMBLE ENGINEERING By James H. Maggard PREFACE_______ In placing this book before the public the author wishes it understood that it is not his intention to produce a scientific work on engineering. Such a book would be valuable only to engineers of large stationary engines. In a nice engine room nice theories and scientific calculations are practical. This book is intended for engineers of farm and traction engines, "rough and tumble engineers," who have everything in their favor today, and tomorrow are in mud holes, who with the same engine do eight horse work one day and sixteen horse work the next day. Reader, the author has had all these experiences and you will have them, but don't get discouraged. You can get through them to your entire satisfaction. Don't conclude that all you are to do is to read this book. It will not make an engineer of you. But read it carefully, use good judgment and common sense, do as it tells you, and my word for it, in one month, you, for all practical purposes, will be a better engineer than four-fifths of the so-called engineers today, who think what they don't know would not make much of a book. Don't deceive yourself with the idea that what you get out of this will be merely "book learning." What is said in this will be plain, unvarnished, practical facts. It is not the author's intention to use any scientific terms, but plain, everyday field terms. There will be a number of things you will not find in this book, but nothing will be left out that would be of practical value to you. You will not find any geometrical figures made up of circles, curves, angles, letters and figures in a vain effort to make you understand the principle of an eccentric. While it is all very nice to know these things, it is not necessary, and the putting of them in this book would defeat the very object for which it was intended. Be content with being a good, practical, everyday engineer, and all these things will come in time. INTRODUCTORY ________ If you have not read the preface on the preceding pages, turn back and read it. You will see that we have stated there that we will use no scientific terms, but plain every day talk. It is presumed by us that there will be more young men, wishing to become good engineers, read this work than old engineers. We will, therefore, be all the more plain and say as little as possible that will tend to confuse the learner, and what we do say will be said in the same language that we would use if we were in the field, instructing you how to handle your engine. So if the more experienced engineer thinks we might have gone further in some certain points, he will please remember that by so doing we might confuse the less experienced, and thereby cover up the very point we tried to make. And yet it is not to be supposed that we will endeavor to make an engineer out of a man who never saw an engine. It is, therefore, not necessary to tell the learner how an engine is made or what it looks like. We are not trying to teach you how to build an engine, but rather how to handle one after it is built; how to know when it is in proper shape and how to let it alone when it is in shape. We will suppose that you already know as much as an ordinary water boy, and just here we will say that we have seen water haulers that were more capable of handling the engine for which they were hauling water, than the engineer, and the engineer would not have made a good water boy, for the reason that he was lazy, and we want the reader to stick a pin here, and if he has any symptoms of that complaint, don't undertake to run an engine, for a lazy engineer will spoil a good engine, if by no other means than getting it in the habit of loafing. PART FIRST ______ In order to get the learner started, it is reasonable to suppose that the engine he is to run is in good running order. It would not be fair to put the green boy onto an old dilapidated, worn-out engine, for he might have to learn too fast, in order to get the engine running in good shape. He might have to learn so fast that he would get the big head, or have no head at all, by the time he got through with it. And I don't know but that a boy without a head is about as good as an engineer with the big head. We will, therefore, suppose that his engine is in good running order. By good running order we mean that it is all there, and in its proper place, and that with from ten to twenty pounds of steam, the engine will start off at a good lively pace. And let us say here, (remember that we are talking of the lone engine, no load considered,) that if you are starting a new engine and it starts off nice and easy with twenty pounds, you can make up your mind that you have an engine that is going to be nice to handle and give you but little, if any, trouble. But if it should require fifty or sixty pounds to start it, you want to keep your eyes open, something is tight; but don't take it to pieces. You might get more pieces than you would know what to do with. Oil the bearings freely and put your engine in motion and run it carefully for a while and see if you don't find something getting warm. If you do, stop and loosen up a very little and start it up again. If it still heats, loosen about the same as before, and you will find that it will soon be all right. But remember to loosen but very little at a time, for a box or journal will heat from being too loose as quickly as from being too tight, and you will make trouble for yourself, for, inexperienced as you are, you don't know whether it is too loose or too tight, and if you have found a warm box, don't let that box take all of your attention, but keep an eye on all other bearings. Remember that we are not threshing yet, we just run the engine out of shed, (and for the sake of the engine and the young engineer, we hope that it did not stand out all winter) and are getting in shape for a good fall's run. In the meantime, to find out if anything heats, you can try your pumps, but to help you along, we will suppose that your pump, or injector, as the case may be, works all right. Now suppose we go back where we started this new engine that was slow to start with less than fifty pounds, and when it did start, we watched it carefully and found after oiling thoroughly that nothing heated as far as we could see. So we conclude that the trouble must be in the cylinder. Well, what next? Must we take off the cylinder head and look for the trouble? Oh, no, not by any means. The trouble is not serious. The rings are a little tight, which is no serious fault. Keep them well oiled and in a day or two ten pounds will start the empty engine in good shape. If you are starting an engine that has been run, the above instructions are not necessary, but if it is a new one these precautions are not out of the way, and a great deal of the trouble caused in starting a new engine, can be avoided if these precautions are observed. It is not uncommon for a hot box to be caused from a coal cinder dropping in the box in shipment, and before starting a new engine, clean out the boxes thoroughly, which can be done by taking off the caps, or top box, and wiping the journal clean with an oily rag or waste, and every engineer should supply himself with this very necessary article, especially if he is the kind of an engineer who intends to keep his engine clean. The engine should be run slowly and carefully for a while, to give a chance to find out if anything is going to heat, before putting on any load. Now if your engine is all right, you can run the pressure up to the point of blowing off, which is from one hundred to one hundred and ten pounds. Most new pop valves, or safety valves, are set at this pressure. I would advise you to fire to this point, to see that your safety is all right. It is not uncommon for a new pop to stick, and as the steam runs up it is well to try it, by pulling the relief lever. If, on letting it go, it stops the escaping, steam at once, it is all right. If, however, the steam continues to escape, the valve sticks in the chamber. Usually a slight tap with a wrench or a hammer will stop it at once, but never get excited over escaping steam, and perhaps here is as good a place as any to say to you, don't get excited over anything. As long as you have plenty of water, and know you have, there is no danger. The young engineer will most likely wonder why we have not said something about the danger of explosions. We did not start to write about explosions. That is just what we don't want to have anything to do with. But, you say, is there no danger of a boiler exploding? Yes. But if you wish to explode your boiler you must treat it very differently from the way we advise. We have just stated, that as long as you have plenty of water, and know you have, there is no danger. Well, how are you to know? This is not a difficult thing to know, provided your boiler is fitted with the proper appliances, and all builders of any prominence, at this date, fit their boilers with from two to four try-cocks, and a glass gauge. The boiler is tapped in from two to four places for the try-cocks, the location of the cocks ranging from a line on a level with the crown sheet, or top of fire box, to eight inches above, depending somewhat on the amount of water space above the crown sheet, as this space differs very materially in different makes of the same sized boiler. The boiler is also tapped on or near the level of crown sheet, to receive the lower water glass cock and directly above this, for the top cock. The space between this shows the safe variation of the water. Don't let the water get above the top of the glass, for if you are running your engine at hard work, you may knock out a cylinder head, and don't let it get below the lower gauge, or you may get your head knocked off. Now the glass gauge is put on for your convenience, as you can determine the location of the water as correctly by this as if you are looking directly into the boiler, provided, the glass gauge is in perfect order. But as there are a number of ways in which it may become disarranged or unreliable, we want to impress on your mind that you, must not depend on it entirely. We will give these causes further on. You are not only provided with the glass gauge, but with the try-cocks. These cocks are located so that the upper and lower cock is on or near the level with the lower and upper end of the glass gauge. With another try-cock about on a level with the center of glass gauge, or in other words, if the water stands about the center of glass it will at the same time show at the cock when tried. Now we will suppose that your glass gauge is in perfect condition and the water shows two inches in the glass. You now try the lower cock, and find plenty of water; you will then try the next upper cock and get steam. Now as the lower cock is located below the water line, shown by the glass, and the second cock above this line, you not only see the water line by the glass, but you have a way of proving it. Should the water be within two inches of the top of glass you again have the line between two cocks and can also prove it. Now you can know for a certainty, where the water stands in the boiler, and we repeat when you know this, there is nothing to fear from this source, and as a properly constructed boiler never explodes, except from low water or high pressure, and as we have already cautioned you about your safety valve, you have nothing to fear, provided you have made up your mind to follow these instructions, and unless you can do this, let your job to one who can. Well, you say you will do as we have directed, we will then go back to the gauges. Don't depend on your glass gauge alone, for several reasons. One is, if you depend on the glass entirely, the try-cocks become limed up and are useless, solely because they are not used. Some time ago the writer was standing near a traction engine, when the engineer, (I guess I must call him that) asked me to stay with the engine a few minutes. I consented. After he had been gone a short time I thought I would look after the water. It showed about two inches in the glass, which was all right, but as I have advised you, I proposed to know that it was there and thought I would prove it by trying the cocks. But on attempting to try them I found them limed up solid. Had I been hunting an engineer, that fellow would not have secured the job. Suppose that before I had looked at the glass, it had bursted, which it is liable to do any time. I would have shut the gauge cocks off as soon as possible to stop the escaping steam and water. Then I would have tried the cocks to find where the water was in the boiler. I would have been in a bad boat, not knowing whether I had water or not. Shortly after this the fellow that was helping the engine run (I guess I will put it that way) came back. I asked him what the trouble was with his try cocks. He said, "Oh, I don't bother with them." I asked him what he would do if his glass should break. His reply was, "Oh, that won't break." Now just such an engineer as that spoils many a good engine, and then blames it on the manufacturer. Now this is one good reason why you are not to depend entirely on the glass gauge. Another equally as good reason is, that your glass may fool you, for you see the try-cocks may lime up, so may your glass gauge cocks, but you say you use them. You use them by looking at them. You are not letting the steam or water escape from them every few minutes and thereby cutting the lime away, as is the case with try-cocks. Now you want to know how you are to keep them open. Well, that is easy. Shut off the top gauge and open the drain cock at bottom of gauge cock. This allows the water and steam to flow out of the lower cock. Then after allowing it to escape a few seconds, shut off the lower gauge and open the top one, and allow it to blow about the same time. Then shut the drain cock and open both gauge cocks and you will see the water seek its level, and you can rest assured that it is reliable. This little operation I want you to perform every day you run an engine. It will prevent you from thinking you have water. I don't want you to think so. I intend that you shall know it. You remember we said, if you know you have water, you are safe, and every one around you will be safe. Now here is something I want you to remember. Never be guilty of going to your engine in the morning and building a fire simply because you see water in the glass. We could give you the names of a score of men who have ruined their engines by doing this very thing. You, as a matter of course, want to know why this can do any harm. It could not, if the water in the boiler was as high as it shows in the glass, but it is not always there, and that is what causes the trouble. Well, if it showed in the glass, why was it not there? You probably have lived long enough in the world to know that there are a great many boys in it, and it seems to be second nature with them to turn everything on an engine that is possible to turn. All glass gauge cocks are fitted with a small hand wheel. The small boy sees this about the first thing and he begins to turn it, and he generally turns as long as it turns easy, and when it stops he will try the other one, and when it stops he has done the mischief, by shutting the water off from the boiler, and all the water that was in the glass remains there. You may have stopped work with an ordinary gauge of water, and as water expands when heated, it also contracts when it becomes cool. Water will also simmer away, if there is any fire left in the fire box, especially if there should be any vent or leak in the boiler, and the water may by morning have dropped to as much as an inch below the crown sheet. You approach the engine and on looking at the glass, see two or three inches of water. Should you start a fire without investigating any further, you will have done the damage, while if you try the gauge cocks first you will discover that some one has tampered with the engine. The boy did the mischief through no malicious motives, but we regret to say that there are people in this world who are mean enough to do this very thing, and not stop at what the boy did unconsciously, but after shutting the water in the gauge for the purpose of deceiving you, they then go to the blow-off cock and let enough water out to insure a dry crown sheet. While I detest a human being guilty of such a dastardly trick, I have no sympathy to waste on an engineer who can be caught in this way. So, if by this time you have made up your mind never to build a fire until you know where the water is, you will never be fooled and will never have to explain an accident by saying, "I thought I had plenty of water." You may be fooled in another way. You are aware that when a boiler is fired up or in other words has a steam pressure on, the air is excluded, so when the boiler cools down, the steam condenses and becomes water again, hence the space which was occupied by steam now when cold becomes a vacuum. Now should your boiler be in perfect shape, we mean perfectly tight, your throttle equally as tight, your pump or injector in perfect condition and you were to' leave your engine with the hose in the tank, and the supply globe to your pump open, you will find on returning to your engine in the morning that the boiler will be nearly if not quite full of water. I have heard engineers say that someone had been tampering with their engines and storm around about it, while the facts were that the supply being open the water simply flowed in from atmospheric pressure, in order to fill the space made vacant by the condensed steam. You will find further on that all check valves are arranged to prevent any flowing out from the boiler, but nothing to prevent water flowing in. Such an occurrence will do no harm but the knowing how it was done may prevent your giving yourself away. A good authority on steam boilers, says: "All explosions come either from poor material, poor workmanship, too high pressure, or a too low gauge of water." Now to protect yourself from the first two causes, buy your engine from some factory having a reputation for doing good work and for using good material. The last two causes depend very much on yourself, if you are running your own engine. If not, then see that you have an engineer who knows when his safety valve is in good shape and who knows when he has plenty of water, or knows enough to pull his fire, when for some reason, the water should become low. If poor material and poor workmanship were unknown and carelessness in engineers were unknown, such a thing as a boiler explosion would also be unknown. You no doubt have made up your mind by this time that I have no use for a careless engineer, and let me add right here, that if you are inclined to be careless, forgetful,(they both mean about the same thing,) you are a mighty poor risk for an insurance company, but on the other hand if you are careful and attentive to business, you are as safe a risk as any one, and your success and the durability and life of your engine depends entirely upon you, and it is not worth your while to try to shift the responsibility of an accident to your engine upon some one else. If you should go away from your engine and leave it with the water boy, or anyone who might be handy, or leave it alone, as is often done, and something goes wrong with the engine, you are at fault. You had no business to leave it, but you say you had to go to the separator and help fix something there. At the separator is not your place. It is not our intention to tell you how to run both ends of an outfit. We could not tell you if we wanted to. If the men at the separator can't handle it, get some one or get your boss to get some one who can. Your place is at the engine. If your engine is running nicely, there is all the more reason why you should stay by it, as that is the way to keep it running nicely. I have seen twenty dollars damage done to the separator and two days time lost all because the engineer was as near the separator as he was to the engine when a root went into the cylinder. Stay with your engine, and if anything goes wrong at the separator, you are ready to stop and stop quickly, and if you are signalled to start you are ready to start at once You are therefore making time for your employer or for yourself and to make time while running a threshing outfit, means to make money. There are engineers running engines today who waste time enough every day to pay their wages. There is one thing that may be a little difficult to learn, and that is to let your engine alone when it is all right. I once gave a young fellow a recommendation to a farmer who wanted an engineer, and afterward noticed that when I happened around he immediately picked up a wrench and commenced to loosen up first one thing and then another. If that engineer ever loses that recommendation he will be out of a job, if his getting one depends on my giving him another. I wish to say to the learner that that is not the way to run an engine. Whenever I happen to go around an engine, (and I never lose an opportunity) and see an engineer watching his engine, (now don't understand me to mean standing and gazing at it,) I conclude that he knows his business. What I mean by watching an engine is, every few minutes let your eye wander over the engine and you will be surprised to see how quickly you will detect anything out of place. So when I see an engineer watching his engine closely while running, I am most certain to see another commendable feature in a good engineer, and that is, when he stops his engine he will pick up a greasy rag and go over his engine carefully, wiping every working part, watching or looking carefully at every point that he touches. If a nut is working loose he finds it, if a bearing is hot he finds it. If any part of his engine has been cutting, he finds it. He picked up, a greasy rag instead of a wrench, for the engineer that understands his business and attends to it never picks up a wrench unless he has something to do with it. The good engineer took a greasy rag and while he was using it to clean his engine, he was at the same time carefully examining every part. His main object was to see that everything was all right. If he had found a nut loose or any part out of place, then he would have taken his wrench, for he had use for it. Now what a contrast there is between this engineer and a poor one, and unfortunately there are hundreds of poor engineers running portable and traction engines. You will find a poor engineer very willing to talk. This is bad habit number one. He cannot talk and have his mind on his work. Beginners must not forget this. When I tell you how to fire an engine you will understand how important it is, The poor engineer is very apt to ask an outsider to stay at his engine while he goes to the separator to talk. This is bad habit number two. Even if the outsider is a good engineer, he does not know whether the pump is throwing more water than is being used or whether it is throwing less. He can only ascertain this by watching the column of water in the glass, and he hardly knows whether to throw in fuel or not. He don't want the steam to go down and he don't know at what pressure the pop valve will blow off. There may be a box or journal that has been giving the engineer trouble and the outsider knows nothing about it. There are a dozen other good reasons why bad habit number two is very bad. If you will watch the poor engineer when he stops his engine, he will, if he does anything, pick up a wrench, go around to the wrist pin, strike the key a little crack, draw a nut or peck away at something else, and can't see anything for grease and dirt. When he starts up, ten to one the wrist pin heats and he stops and loosens it up and then it knocks. Now if he had picked up a rag instead of a wrench, he would not have hit that key but he would have run his hand over it and if he had found it all right, he would have let it alone, and would have gone over the balance of the engine and when he started up again his engine would have looked better for the wiping it got and would have run just as well as before he stopped it. Now you will understand why a good engineer wears out more rags than wrenches, while a poor one wears out more wrenches than rags. Never bother an engine until it bothers you. If you do, you will make lots of grief for yourself. I have mentioned the bad habits of a poor engineer so that you may avoid them. If you carefully avoid all the bad habits connected with the running of an engine, you will be certain to fall into good habits and will become a good engineer. TINKERING ENGINEERS After carelessness, meddling with an engine comes next in the list of bad habits. The tinkering engineer never knows whether his engine is in good shape or not, and the chances are that if he should get it in good shape he would not know enough to let it alone. If anything does actually get wrong with your engine, do not be afraid to take hold of it, for something must be done, and you are the one to do it, but before you do anything be certain that you know what is wrong. For instance, should the valve become disarranged on the valve stem or in any other way, do not try to remedy the trouble by changing the eccentric, or if the eccentric slips do not go to the valve to mend the trouble. I am well aware that among young engineers the impression prevails that a valve is a wonderful piece of mechanism liable to kick out of place and play smash generally. Now let me tell you right here that a valve (I mean the ordinary slide valve, such as is used on traction and portable engines), is one of the simplest parts of an engine, and you are not to lose any sleep about it, so be patient until I am ready to introduce you to this part of your work. You have a perfect right to know what is wrong with the engine. The trouble may not be so serious and it is evident to you that the engine is not running just as nicely as it should. Now, if your engine runs irregularly, that is if it runs up to a higher speed than you want, and then runs down, you are likely to say at once, "Oh I know what the trouble is, it is the governor." Well, suppose it is, what are you going to do about it, are you going to shut down at once and go to tinkering with it? No, don't do that, stay close to the throttle valve and watch the governor closely. Keep your eye on the governor stem, and when the engine starts off on one of its high speed tilts, you will see the stem go down through the stuffing box and then stop and stick in one place until the engine slows down below its regular speed, and it then lets loose and goes up quickly and your engine lopes off again. You have now located the trouble. It is in the stuffing box around the little brass rod or governor stem. The packing has become dry and by loosening it up and applying oil you may remedy the trouble until such time as you can repack it with fresh packing. Candle wick is as good for this purpose as anything you can use. But if the governor does not act as I have described and the stem seems to be perfectly free and easy in the box, and the governor still acts queerly, starting off and running fast for a few seconds, and then suddenly concluding to take it easy and away goes the engine again, see if the governor belt is all right, and if it is, it would be well for you to stop and see if a wheel is not loose. It might be either the little belt wheel or one of the little cog wheels. If you find these are all right, examine the spool on the crank shaft from which the governor is run and you will probably find it loose. If the engine has been run for any length of time, you will always find the trouble in one of these places, but if it is a new one the governor valve might fit a little tight in the valve chamber and you may have to take it out and use a little emery paper to take off the rough projections on the valve. Never use a file on this valve if you can get emery paper, and I would advise you to always have some of it with you. It will often come handy. Now if the engine should start off at a lively gait and continue to run still faster, you must stop at once. The trouble this time is surely in the governor. If the belt is all right, examine the jam nuts on the top of the governor valve stem. You will probably find that these nuts have worked loose and the rod is working up, which will increase the speed of the engine. If these are all right, you will find that either a pulley or a little cog wheel is loose. A quick eye will locate the trouble before you have time to stop. If the belt is loose, the governor will lag while the engine will run away. If the wheel is loose, the governor will most likely stop and the engine will go on a tear. If the jam nut has worked loose, the governor will run as usual, except that it will increase its speed as the speed of the engine is increased. Now any of these little things may happen and are likely to. None of them are serious, provided you take my advice, and remain near the engine. Now if you are thirty or forty feet away from the engine and the governor belt slips, or gets unlaced, or the pulley gets off, about the first thing the engine would do would be to jump out of the belt and by the time you get to it, it will be having a mighty lively time all alone. This might happen once and do no harm, and it might happen again and do a great deal of damage, and you are being paid to run the engine and you must stay by it. The governor is not a difficult thing to handle, but it requires your attention. Now if I should drop the governor, you might say that I had not given you any instructions about how to regulate it to speed. I really do not know whether it is worth while to say much about it, for governors are of different designs and are necessarily differently arranged for regulating, but to help young learners I will take the Waters governors which I think the most generally used on threshing and farm engines. You will find on the upper end of the valve or governor stem two little brass nuts. The upper one is a thumb nut and is made fast to the stem. The second nut is a loose jam nut. To increase the speed of the engine loosen this jam nut and take hold of the thumb nut and turn it back slowly, watching the motion of your engine all the while. When you have obtained the speed you require, run the thumb nut down as tight as you can with your fingers. Never use a wrench on these nuts. To slow or slacken the speed, loosen the jam nut as before, except that you must run it up a few turns, then taking hold of the thumb nut, turn down slowly until you have the speed required, when you again set the thumb nut secure. In regulating the speed, be careful not to press down on the stem when turning, as this will make the engine run a little slower than it will after the pressure of your hand is removed. If at any time your engine refuses to start with an open throttle, notice your governor stem, and you will find that it has been screwed down as far as it will go. This frequently happens with a new engine, the stem having been screwed down for its protection in transportation. In traveling through timber with an engine, be very careful not to let any over-hanging limbs come in contact with the governor. Now I think what I have said regarding this particular governor will enable you to handle any one you may come in contact with, as they are all very much alike in these respects. It is not my intention to take time and space to describe a governor in detail. If you will follow the instructions I have given you the governor will attend to the rest. PART SECOND ________ WATER SUPPLY If you want to be a successful engineer it is necessary to know all about the pump. I have no doubt that many who read this book, cannot tell why the old wooden pump (from which he has pumped water ever since he was tall enough to reach the handle) will pump water simply because he works the handle up and down. If you don't know this I have quite a task on my hands, for you must not attempt to run an engine until you know the principle of the pump. If you do understand the old town pump, I will not have much trouble with you, for while there is no old style wooden pump used on the engine, the same principles are used in the cross head pump. Do not imagine that a cross head pump means something to be dreaded. It is only a simple lift and force pump, driven from the cross head. That is where it gets its name and it don't mean that you are to get cross at it if it don't work, for nine times out of ten the fault will be yours. Now I am well aware that all engines do not have cross head pumps and with all respect to the builders of engines who do not use them, I am inclined to think that all standard farm engines ought to have a cross head pump, because it is the most simple and is the most economical, and if properly constructed, is the most reliable. A cross head pump consists of a pump barrel, a plunger, one vertical check valve and two horizontal check valves, a globe valve and one stop cock, with more or less piping. We will now locate each of these parts and will then note the part that each performs in the process of feeding the boiler. You will find all, or most pump barrels, located under the cylinder of the engine. It is placed here for several reasons. It is out of the way. It is a convenient place from which to connect it to the cross head by which it is driven. On some engines it is located on the top or at the side of the cylinder and will work equally well. The plunger is connected with the cross head and in direct line with the pump barrel, and plays back and forth in the barrel. The vertical check valve is placed between the pump and the water supply. It is not absolutely necessary that the first check be a vertical one, but a check of some kind must be so placed. As the water is lifted up to the boiler it is more convenient to use a vertical check at this point. Just ahead and a few inches from the pump barrel is a horizontal check valve. Following the course of the water toward the point where it enters the boiler, you will find another check valve. This is called a "hot water check." just below this check, or between it and where the water enters the boiler, you will find a stop cock or it may be a globe valve. They both answer the same purpose. I will tell you further on why a stop cock is preferable to a globe valve. While the cross head pumps may differ as to location and arrangement, you will find that they all require the parts described and that the checks are so placed that they bear the same relation to each other. No fewer parts can be used in a pump required to lift water and force it against steam pressure. More check valves may be used, but it would not do to use less. Each has its work to do, and the failure of one defeats all the others. The pump barrel is a hollow cylinder, the chamber being large enough to admit the plunger which varies in size from 5/8 of an inch to I inch in diameter, depending upon the size of the boiler to be supplied. The barrel is usually a few inches longer than the stroke of the engine, and is provided at the cross head end with a stuffing box and nut. At the discharge end it is tapped out to admit of piping to conduct water from the pump. At the same end and at the extreme end of the travel of the plunger it is tapped for a second pipe through which the water from the supply reaches the pump barrel. The plunger is usually made of steel and turned down to fit snug in the chamber, and is long enough to play the full stroke of engine between the stuffing box and point of supply and to connect with the driver on the cross head. Now, we will take it for granted, that, to begin with, the pump is in good order, and we will start it up stroke at a time and watch its work. Now, if everything be in good order, we should have good water and a good hard rubber suction hose attached to the supply pipe just under the globe valve. When we start the pump we must open the little pet cock between the two horizontal check valves. The globe valve must be open so as to let the water in. A check valve, whether it is vertical or horizontal, will allow water to pass through it one way only, if it is in good working order. If the water will pass through both ways, it is of no account. Now, the engine starts on the outward stroke and draws the-plunger out of the chamber. This leaves a space in the barrel which must be filled. Air cannot get into it, because the pump is in perfect order, neither can the air get to it through the hose, as it is in the water, so that the pressure on the outside of the water causes it to flow up through the pipes through the first check valve and into the pump barrel, and fills the space, and if the engine has a I2-inch stroke, and the plunger is I inch in diameter, we have a column of water in the pump I2 inches long and I inch in diameter. The engine has now reached its outward stroke and starts back. The plunger comes back with it and takes the space occupied by the water, which must get out of the way for the plunger. The water came up through the first check valve, but it can't get back that way as we have stated. There is another check valve just ahead, and as the plunger travels back it drives the water through this second check. When the plunger reaches the end of the backward stroke, it has driven the water all out. It then starts forward again, but the water which has been driven through the second check cannot get back and this space must again be filled from supply, and the plunger continues to force more water through the second check, taking four or five strokes of the plunger to fill the pipes between the second check valve and the hot water check valve. If the gauge shows I00 pounds of steam, the hot water check is held shut by I00 pounds pressure, and when the space between the check valves is filled with water, the next stroke of the plunger will force the water through the hot water check valve, which is held shut by the I00 pounds steam pressure so that the pump must force the water against this hot water check valve with a power greater than I00 pounds pressure. If the pump is in good condition, the plunger does its work and the water is forced through into the boiler. A clear sharp click of the valves at each stroke of the plunger is certain evidence that the pump is working well. The small drain cock between the horizontal checks is placed there to assist in starting the pump, to tell when the pump is working and to drain the water off to prevent freezing. When the pump is started to work and this drain cock is opened, and the hot water in the pipes drained off, the globe valve is then opened, and after a few strokes of the plunger, the water will begin to flow out through the drain cock, which is then closed, and you may be reasonably certain that the pump is working all right. If at any time you are in doubt as to whether the pump is forcing the water through the pipes, you can easily ascertain by opening this drain cock. It will always discharge cold water when the pump is working. Another way to tell if the pump is working, is by placing your hand on the first two check valves. If they are cold, the pump is working all right, but if they are warm, the cold water is not being forced through them. A stop cock should be used next to boiler, as you ascertain whether it is open or shut by merely looking at it, while the globe valve can be closed by some meddlesome party and you would not discover it, and would burst some part of your pump by forcing water against it. PART THIRD _________ It is very important when the pump fails to work to ascertain what the trouble is. If it should stop suddenly, examine the tank and ascertain if you have any water. If you have sufficient water, it may be that there is air in the pump chamber, and the only way that it can get in is through the stuffing box around the plunger, if the pipes are all tight. Give this stuffing nut a turn, and if the pump starts off all right, you have found the trouble, and it would be well to re-pack the pump the first chance you get. If the trouble is not in the stuffing box, go to the tank and see if there is anything over the screen or strainer at the end of the hose. If there is not, take hold of the hose and you can tell if there is any suction. Then ascertain if the water flows in and then out of the hose again. You can tell this by holding your hand loosely over the end of the hose. If you find that it draws the water in and then forces it out again, the trouble is with the first check valve. There is something under it which prevents its shutting down. If, however, you find that there is no suction at the end of hose examine the second check. If there should be something under it, it would prevent the pump working, because the pump forces the water through it; and, as the plunger starts back, if the check fails to hold, the water flows back and fills the pump barrel again and there would be no suction. The trouble may, however, be in the hot water check, and it can always be told whether it is in the second check or hot water check by opening the little drain cock. If the water which goes out through it is cold, the trouble is in the second check; but, if hot water and steam are blown out through this little drain cock, the trouble is in the hot water check, or the one next to the boiler. This check must never be tampered with without first turning the stop cock between this check and the boiler. The valve can then be taken out and the obstruction removed. Be very careful never to take out the hot water check without closing the stop cock, for if you do you will get badly scalded; and never start the pump without opening this valve, for if you do, it will burst the pump. The obstruction under the valves is sometimes hard to find. A young man in southern Iowa got badly fooled by a little pebble about the size of a pea, which got into the pipe, and when he started his pump the pebble would be forced up under the check and let the water back. When he took the check out the pebble was not there, for it had dropped back into the pipe. You will see that it is necessary to make a careful examinations and not get mad, pick up a wrench and whack away at the check valve, bruising it so that it will not work. Remember that it would work if it could, and make up your mind to find out why, it don't work. A few years ago I was called several miles to see an engine on which the pump would not work. The engine had been idle for two days and the engineer had been trying all that time to make the pump work. I took the cap off of the horizontal check, just forward of the pump barrel, and took the valve out and discovered that the check was reversed. I told the engineer that if he would put the check in so that the water could get through, he would have no more trouble. This fellow had lost his head. He was completely rattled. He insisted that "the valve had always been on that way," although the engine had been run two years. Now the facts in this case were as follows: The old check valve in place of the one referred to had been one known as a stem valve, or floating valve. This stem by some means, had broken off but it did not prevent the valve from working. The stem, however, worked forward till it reached the hot water check, and lodged under the valve, which prevented this check from working and his pump refused to work, the engineer soon found where the stem had broken off, and instead of looking for the stem, sent to town for a new check, after putting this on the pump now refused to work for two reasons. One was, he had not removed the broken stem from the hot water check, and another was, that the new check was in wrong end to. After wasting another hour or two he finally found and-removed the stem from the hot water check, but his pump still refused to work. And then as the boys say, "he laid down," and when I called his attention to the new valve being in wrong, he was so completely rattled that he made use of the above expression. There are other causes that would prevent the pump working besides lack of packing and obstructions under the valves. The valve may stick. When it is raised to allow the water to flow through, it may stick in the valve chamber and refuse to settle back in the seat. This may be caused by a little rough place in the chamber, or a little projection on the valve, and can generally be remedied by tapping the under side of check with a wrench or hammer. Do not strike it so hard as to bruise the check, but simply tap it. If this don't remedy the trouble, take the valve out, bore a hole in a board about I/2 inch deep and large enough to permit the valve to be turned. Drop a little emery dust in this hole. If you haven't any emery dust, scrape some grit from a common whetstone. If you have no whetstone, put some fine sand or gritty soil in the hole, put the valve on top of it, put your brace on the valve and turn it vigorously for a few minutes, and you will remove all roughness. Constant use may sometimes make a burr on the valve which will cause it to stick. Put it through the above course and it will be as good as new. If this little process was generally known, a great deal of trouble and annoyance could be avoided. It will not be necessary to describe other styles of pumps. If you know how to run the cross head pump, you can run any of the others. Some engines have cross head pump only. Others have an independent pump. Others have an injector, or inspirator, and some have both cross head pump and injector. I think a farm engine should be supplied with both. It is neither wise nor necessary to go into a detailed description of an injector. The young reader will be likely to become convinced if an injector works for five minutes, it will continue to work, if the conditions remain the same. If the water in the tank does not become heated, and no foreign substance is permitted to enter the injector, there is nothing to prevent its working properly as long as the conditions are within the range of a good injector. It is a fact that with all injectors as the vertical distance the injector lifts is increased, it requires a greater steam pressure to start the injector, and the highest steam pressure at which the injector will work is greatly decreased. If the feed water is heated, a greater steam pressure is required to start the injector and it will not work with as high steam pressure. The capacity of an injector is always decreased as the lift is increased, or the feed water heated. To obtain the most economical results the proper sized injector must be used. When the exact quantity of water consumed per hour is known it can be easily determined from the capacities given in the price lists which sized injector must be selected. An injector must always be selected having a maximum capacity in excess of the water consumed. If the exact amount of water consumed per hour is not known, and cannot be easily determined, the proper size can be approximately determined from the nominal H. P. of the boiler. The usual custom has been to allow 7 I/2 gallons of water per hour, which is a safe rule for the ordinary type of boiler. WHAT A GOOD INJECTOR OUGHT TO DO. With cold feed water, a good injector with a two foot lift ought to start with 25 pounds pressure and work up to I50 pounds. With 8 foot lift, ought to start at 30 pounds and work up to I30. With feed water heated to I00 degrees Fahrenheit it should start with the same lift, that is, will say 2 foot, at 26 and work Up to I20, and at 8, from 33 up to I00. You will see by this that conditions, consisting of variation of temperature in the feed water and different lifts, change the efficiency of your injector very materially, and the water can soon get beyond the ability of your injector to work at all. The above refers more particularly to the single tube injector. The double tube injector under the same conditions as above should work from I4 pounds to 250, and from I5 to 2I0, but as this injector is not generally used on farm engines you will most likely not meet with it very often. The injector should not be placed too near the boiler, as the heat from it will make it difficult to start the injector each time after it has been standing idle. If the injector is so hot that it will not lift the cold water, there is no way of cooling it except by applying the water on the outside. This is most effectively done by covering the injector with a cloth and pouring water over the cloth. If, after the injector has become cool, it still refuses to work, you may be sure that there is some obstruction in it that must be removed. This can be done by taking off the cap, or plug-nut, and running a fine wire through the cone valve or cylinder valve. The automatic injector requires only the manipulation of the steam valve to start it. There are other makes that require, first: that the injector be given steam and then the water. To start an injector requires some little tact, (and you will discover that tact is the handiest tools you can have to make you a good engineer). To start an injector of the Pemberthy type; first give it sufficient steam to lift the water, allowing the water to escape at overflow for a moment or long enough to cool the injector, then with a quick turn shut off and open up the supply which requires merely a twist of the wrist. If the injector fails to take hold at once don't get ruffled but repeat the above move a few times and you will soon start it, and if you have tact, (it is only another word for natural ability) you will need no further instructions to start your injector. But remember that no injector can work coal cinders or chaf and that all joints must be air tight. Don't forget this. It is now time to give some attention to the heater. While the heater is no part of the pump, it is connected with it and does its work between the two horizontal check valves. Its purpose is to heat the water before it passes into the boiler. The water on its way from the pump to the boiler is forced through a coil of pipes around which the exhaust steam passes on its way from the cylinder to the exhaust nozzle in the smokestack. The heaters are made in several different designs, but it is not necessary to describe all of them, as they require little attention and they all answer the same purpose. The most of them are made by the use of a hollow bedplate with steam fitted heads or plates. The water pipe passes through the plate at the end of the heater into the hollow chamber, and a coil of pipes is formed, and the pipe then passes back through the head or plate to the hot water check valve and into the boiler. The steam enters the cylinder from the boiler, varying in degrees of heat from 300 to 500. After acting on the piston head, it is exhausted directly into the chamber or hollow bed-plate through which the pipes pass. The water, when it enters the heater, is as cold as when it left the tank, but the steam which surrounds the pipes has lost but little of its heat, and by the time the water passes through the coil of pipes it is heated to nearly boiling point and can be introduced into the boiler with little tendency to reduce the steam. This use of the exhaust steam is economical, as it saves fuel, and it would be injurious to pump cold water directly into a hot boiler. If your engine is fitted with both cross head pump and injector, you use the injector for pumping water when the engine is not running. The injector heats the water almost as hot as the heater. If your engine is running and doing no work, use your injector and stop the pump, for, while the engine is running light, the small amount of exhaust steam is not sufficient to heat the water and the pressure will be reduced rapidly. You will understand, therefore, that the injector is intended principally for an emergency rather than for general use. It should always be kept in order, for, should the pump refuse to work, you have only to start your injector and use it until such time as you can remedy the trouble. We have now explained how you get your water supply. You understand that you must have water first and then fire. Be sure that you have the water supply first. THE BLOWER The blower is an appliance for creating artificial draught and consists of a small pipe leading from some point above the water line into the smoke stack, directly over the tubes, and should extend to the center of stack and terminate with a nozzle pointing directly to top and center of stack; this pipe is fitted with a globe valve. When it is required to rush your fire, you can do so by opening this globe and allowing the steam to escape into the stack. The force of the steam tends to drive the air out of the stack and the smoke box, this creates a strong draught. But you say, "What if I have no steam?" Well, then don't blow, and be patient till you have enough to create a draught; and it has been my experience that there is nothing gained by putting on the blower before having fifteen pounds of steam, as less pressure than this will create but little draught and the steam will escape about as fast as it is being generated. Be patient and don't be everlastingly punching at the fire. Get your fuel in good shape in fire box and shut the door and go about your business and let the fire burn. Must the blower be used while working the engine. No. The exhaust steam which escapes into the stack, does exactly what we stated the blower does, and if it is necessary to use the blower in order to keep up steam, you can conclude that your engine is in bad shape, and yet there are times when the blower is necessary, even when your engine is in the best of condition. For instance, when you have poor fuel and are working your engine very light, the exhaust steam may not be sufficient to create enough draught for poor coal, or wet or green wood. But if you are working your engine hard the blower should never be used; if you have bad fuel and it is necessary to stop your engine you will find it very convenient to put on the blower slightly, in order to hold your steam and keep the fire lively until you start again. It will be a good plan for you to take a look at the nozzle on blower now and then, to see that it does not become limed up and to see that it is not turned to the side so that it directs the steam to the side of stack. Should it do this, you will be using the steam and getting but little, if any, benefit. It will also be well for you to remember that you can create too much draught as well as too little; too much draught will consume your fuel and produce but little steam. A GOOD FIREMAN. What constitutes a good fireman? You no doubt have heard this expression: "Where there is so much smoke, there must be some fire." Well, that is true, but a good fireman don't make much smoke. We are speaking of firing with coal, now. If I can see the smoke ten miles from a threshing engine, I can tell what kind of a fireman is running the engine; and if there is a continuous cloud of black smoke being thrown out of the smokestack, I make up my mind that the engineer is having all he can do to keep the steam up, and also conclude that there will not be much coal left by the time he gets through with the job; while on the other hand, should I see at regular intervals a cloud of smoke going up, and lasting for a few moments, and for the next few moments see nothing, then I conclude that the engineer of that engine knows his business, and that he is not working hard; he has plenty of steam all the time, and has coal left when he is through. So let us go and see what makes this difference and learn a valuable lesson. We will first go to the engine that is making such a smoke, and we will find that the engineer has a big coal shovel just small enough to allow it to enter the fire door. You will see the engineer throw in about two, or perhaps three shovels of coal and as a matter of course, we will see a volume of black smoke issuing from the stack; the engineer stands leaning on his shovel watching the steam gauge, and he finds that the steam don't run up very fast, and about the time the coal gets hot enough to consume the smoke, we will see him drop his shovel, pick up a poker, throw open the fire door and commence a vigorous punching and digging at the fire. This starts the black smoke again, and about this time we will see him down on his knees with his poker, punching at the underside of the grate bars, about the time he is through with this operation the smoke is coming out less dense, and he thinks it time to throw in more coal, and he does it. Now this is kept up all day, and you must not read this and say it is overdrawn, for it is not, and you can see it every day, and the engineer that fires in this way, works hard, burns a great amount of coal, and is afraid all the time that the steam will run down on him. Before leaving him let us take a look at his firebox, and we will see that it is full of coal, at least up to the level of the door. We will also see quite a pile of ashes under the ash pan. You can better understand the disadvantage of this way of firing after we visit the next man. I think a good way to know how to do a thing, is to know also, how not to do it. Well, we will now go across to the man who is making but little smoke, and making that at regular intervals. We will be likely to find that he has only a little hand shovel. He picks this up, takes up a small amount of coal, opens the fire door and spreads the coal nicely over the grates; does this quickly and shuts the door; for a minute black smoke is thrown out, but only for a minute. Why? Because he only threw in enough to replenish the fire, and not to choke it in the least, and in a minute the heat is great enough to consume all the smoke before it reaches the stack, and as smoke is unconsumed fuel, he gains that much if he can consume it. We will see this engineer standing around for the next few minutes perfectly, at ease. He is not in the least afraid of his steam going down. At the end of three to five minutes, owing to the amount of work he is doing, you will see him pick up his little shovel and throw in a little coal; he does exactly as he did before, and if we stay there for an hour we will not see him pick up a poker. We will look in at his firebox, and we will see what is called a "thin fire," but every part of the firebox is hot. We will see but a small pile of ashes under the engine and he is not working hard. If you happen to be thinking of buying an engine, you will say that this last fellow "has a dandy engine." "That is the kind of an engine I want," when the facts in the case may be that the first man may have a better engine, but don't know how to fire it. Now, don't you see how important it is that you know how to fire an engine? I am aware that some big coal wasters will say, "It is easy to talk about firing with a little hand shovel, but just get out in the field as we do and get some of the kind of fuel we have to burn, and see how you get along." Well, I am aware that you will have some bad coal. It is much better to handle bad coal in a good way than to handle good coal in a bad way. Learn to handle your fuel in the proper way and you will be a good fireman. Don't get careless and then blame the coal for what is your own fault. Be careful about this, you might give yourself away. I have seen engineers make a big kick about the fuel and claim that it was no good, when some other fellow would take hold of the engine and have no trouble whatever. Now, this is what I call a clean give away on the kicker. Don't allow any one to be a better fireman than yourself. You will see a good fireman do exactly as I have stated. He fires often, always keeps a level fire, never allows the coal to get up to the lower tubes, always puts in coal before the steam begins to drop, keeps the fire door open as little as possible, preventing any cold air from striking the tubes, which will not only check the steam, but is injurious to the boiler. It is no small matter to know just how to handle your dampers; don't allow too much of an opening here. You will keep a much more even fire by keeping the damper down, just allowing draught enough to allow free combustion; more than this is a waste of heat. Get all out of the coal you can, and save all you get. Learn the little points that half the engineers never think of. WOOD You will find wood quite different in some respects, but the good points you have learned will be useful now. Fire quick and often, but unlike coal, you must keep your fire box full. Place your wood as loosely as possible. I mean by this, place in all directions to allow the draft to pass freely through it. Keep adding a couple sticks as fast as there is room for it; don't disturb the under sticks. Use short wood and fire close to the door. When firing with wood I would advise you to keep your screen down. There is much more danger of setting fire with wood than with coal. If you are in a dangerous place, owing to the wind and the surroundings, don't hesitate to state your fears to the man for whom you are threshing. He is not supposed to know the danger as well as you, and if, after your advice, he says go ahead, you have placed the responsibility on him; but even after you have done this, it sometimes shows a good head to refuse to fire with wood, especially when you are required to fire with old rails, which is a common fuel in a timbered country. While they make a hot fire in a firebox, they sometimes start a hot one outside of it. It is part of your business to be as careful as you can. What I mean is take reasonable precaution, in looking after the screen in stack. If it burns out get a new one. With reasonable diligence and care, you will never set anything on fire, while on the other hand, a careless engineer may do quite a lot of damage. There is fire about an engine, and you are provided with the proper appliances to control it. See that you do it. WHY GRATES BURN OUT Grates burn through carelessness. You may as well make up your mind to this at the start. You never saw grate bars burn out with a clean ash box. They can only be burned by allowing the ashes to accumulate under them till they exclude the air when the bars at once become red hot. The first thing, they do is to warp, and if the ashes are not removed at once, the grate bar will burn off. Carelessness is neglecting something which is a part of your business, and as part of it is to keep your ash box clean, it certainly is carelessness if you neglect it. Your coal may melt and run down on the bars, but if the cold air can get to the grates, the only damage this will do is to form a clinker on the top of grates, and shut off your draught. When you find that you have this kind of coal you will want to look after these clinkers. Now if you should have good success in keeping steam, keep improving on what you know, and if you run on 1000 pounds of coal today, try and do it with 900 tomorrow. That is the kind of stuff a good fireman is made of. But don't conclude that you can do the same amount of work each day in the week on the same amount of fuel, even should it be of the same kind. You will that with all your care and skill, your engine will differ very materially both as to the amount of fuel and water that it will require, though the conditions may apparently be the same. This may be as good a time as any to say to you, remember that a blast of cold air against the tubes is a bad thing, so be careful about your firedoor; open it as little as, possible; when you want to throw in fuel, don't open the door, and then go a rod away after a shovel of coal; and I will say here that I have seen this thing done by men who flattered themselves that they were about at the top in the matter of running an engine. That kind of treatment will ruin the best boiler in existence. I don't mean that once or twice will do it, but to keep it up will do it. Get your shovel of coal and when you are ready to throw it in, open the door quickly and close it at once. Make it one of your habits to do this, and you will never think of doing it in any other way. If it becomes necessary to stop your engine with a hot fire and a high pressure of steam, don't throw your door open, but drop your damper and open the smoke box door. If, however, you only expect to stop a minute or two, drop your damper, and start your injector if you have one. If you have none, get one. An independent boiler feeder is a very nice thing, if constructed on the proper principles. You can't have your boiler too well equipped in this particular. PART FOUR. _______ A boiler should be kept clean, outside and inside. Outside for your own credit, and inside for the credit of the manufacturers. A dirty boiler requires hard firing, takes lots of fuel, and is unsatisfactory in every way. The best way to keep it clean is not to let it get dirty. The place to begin work, is with your "water boy," pursuade him to be very careful of the water he brings you, if you can't succeed in this, ask him to resign. I have seen a water-hauler back into a stream, and then dip the water from the lowerside of tank, the muddy water always goes down stream and the wheels stir up the mud; and your bright water hauler dips it into the tank. While if he had dipped it from the upper side he would have gotten clear water. However, the days of dipping water are past, but a water boy that will do as I have stated is just as liable to throw his hose into the muddy water or lower side of tank as on the upper side, where it is clear. See that he keeps his tank clean. We have seen tanks with one-half inch of mud in the bottom. We know that there are times when you are compelled to use muddy water, but as soon as it is possible to get clear water make him wash out his tank, and don't let him haul it around till the boiler gets it all. Allow me just here to tell you how to construct a good tank for a traction engine. You can make the dimensions to suit yourself, but across the front end and about two feet back fit a partition or second head; in the center of this head and about an inch from the bottom bore a two inch hole. Place a screen over this hole on the side next the rear, and on the other side, or side next front end, put a valve. You can construct the valve in this way: Take a piece of thick leather, about four inches long, and two and a half inches wide; fit a block of wood (a large bung answers the purpose nicely) on one end, trimming the leather around one side of the wood, then nail the long part of the valve just above the hole, so that the valve will fit nicely over the hole in partition. When properly constructed, this valve will allow the water to flow into the front end of tank, but will prevent its running back. So, when you are on the road with part of a tank of water, and start down hill, this front part fills full of water, and when you start up hill, it can not get back, and your pumps will work as well as if you had a full tank of water, without this arrangement you cannot get your pumps to work well in going up a steep hill with anything less than a full tank. Now, this may be considered a little out of the engineer's duty, but it will save lots of annoyance if he has his tank supplied with this little appliance, which is simple but does the business. A boiler should be washed out and not blown out, I believe I am safe in saying that more than half the engineers of threshing engines today depend on the "blowing out" process to clean their boilers. I don't intend to tell you to do anything without giving my reasons. We will take a hot boiler, for instance; say, 50 pounds steam. We will, of course, take out the fire. It is not supposed that anyone will attempt to blow out the water with any fire in the firebox. We will, after removing the fire, open the blow-off valve, which will be found at the bottom or lowest water point. The water is forced out very rapidly with this pressure, and the last thing that comes out is the steam. This steam keeps the entire boiler hot till everything is blown out, and the result is that all the dirt, sediment and lime is baked solid on the tubes and side of firebox. But you say you know enough to not blow off at 50 pounds pressure. Well, we will say 5 pounds, then. You will admit that the boiler is not cold by any means, even at only 5 pounds, and if you know enough not to blow off at 50 pounds, you certainly know that at 5 pounds pressure the damage is not entirely avoided. As long as the iron is hot, the dirt will dry out quickly, and by the time the boiler is cold enough to force cold water through it safely, the mud is dry and adheres closely to the iron. Some of the foreign matter will be blown out, but you will find it a difficult matter to wash out what sticks to the hot iron. I am aware that some engineers claim that the boiler should be blown out at about 5 pounds or I0 pounds pressure, but I believe in taking the common sense view. They will advise you to blow out at a low pressure, and then, as soon as the boiler is cool enough, to wash it thoroughly. Now, if you must wait till the boiler is cool before washing, why not let it cool with the water in it? Then, when you let the water out, your work is easy, and the moment you begin to force water through it, you will see the dirty water flowing out at the man or hand hole. The dirt is soft and washes very easily; but, if it had dried on the inside of boiler while you were waiting for it to cool, you would find it very difficult to wash off. . You say I said to force the water through the boiler, and to do this you must use a force pump. No engineer ought to attempt to run an engine without a force pump. It is one of the necessities. You say, can't you wash out a boiler without a force pump? Oh, yes! You can do it just like some people do business. But I started out to tell you how to keep your boiler clean, and the way to do it is to wash it out, and the way to wash it out is with a good force pump. There are a number of good pumps made, especially for threshing engines. They are fitted to the tank for lifting water for filling, and are fitted with a discharge hose and nozzle. You will find at the bottom of boiler one or two hand hole plates-if your boiler has a water bottom-if not, they will be found at the bottom of sides of firebox. Take out these hand hole plates. You will also find another plate near the top, on firebox end of boiler; take this out, then open up smoke box door and you will find another hand hole plate or plug near lower row of tubes; take this out, and you are ready for your water works, and you want to use them vigorously; don't throw in a few buckets of water, but continue to direct the nozzle to every part of the boiler, and don't stop as long as there is any muddy water flowing at the bottom hand holes. This is the way to clean your boiler, and don't think that you can be a success as an engineer without this process, and once a week is none too often. If you want satisfactory results from your engine, you must keep a clean boiler, and to keep it clean requires care and labor. If you neglect it you can expect trouble. If you blow out your boiler hot, or if the mud and slush bakes on the tubes, there is soon a scale formed on the tubes, which decreases the boiler's evaporating capacity. You, therefore, in order to make sufficient amount of steam, must increase the amount of fuel, which of itself is a source of expense, to say nothing of extra labor and the danger of causing the tubes to leak from the increased heat you must produce in the firebox in order to make steam sufficient to do the work. You must not expect economy of fuel, and keep a dirty boiler, and don't condemn a boiler because of hard firing until you know it is clean, and don't say it is clean when it can be shown to be half full of mud. SCALE Advertisements say that certain compounds will prevent scale on boilers, and I think they tell the truth, as far as they go; but they don't say what the result may be on iron. I will not advise the use of any of these preparations, for several reasons. In the first place, certain chemicals will successfully remove the scale formed by water charged with bicarbonate of lime, and have no effect on water charged with sulphate of lime. Some kinds of bark-summac, logwood, etc.,-are sufficient to remove the scale from water charged with magnesia or carbonate of lime, but they are injurious to the iron owing to the tannic acid with which they are charged. Vinegar, rotten apples, slop, etc., owing to their containing acetic acid, will remove scale, but this is even more injurious to the iron than the barks. Alkalies of any kind, such as soda, will be found good in water containing sulphate of lime, by converting it into a carbonate and thereby forming a soft scale, which is easily washed out; but these have their objections, for, when used to excess, they cause foaming. Petroleum is not a bad thing in water where sulphate of lime prevails; but you should use only the refined, as crude oil sometimes helps to form a very injurious scale. Carbonate of soda and corn-starch have been recommended as a scale preventative, and I am inclined to think they are as good as anything, but as we are out in the country most of the time I can tell you of a simple little thing that will answer the same purpose, and can usually be had with little trouble. Every Monday morning just dump a hatful of potatoes into your boiler, and Saturday night wash the boiler out, as I have already suggested, and when the fall's run is over there will not be much scale in the boiler. CLEAN FLUES. We have been urging you to keep your boiler clean. Now, to get the best results from your fuel, it will also be necessary to keep your flues clean; as soot and ashes are non-conductors of heat, you will find it very difficult to get up steam with a coating of soot in your tubes. Most factories furnish with each engine a flue cleaner and rod. This cleaner should be made to fit the tubes snug, and should be forced through each separate tube every morning before building a fire. Some engineers never touch their flues with a cleaner, but when they choke the exhaust sufficiently to create such a draught as to clean the flues, they are working the engine at a great disadvantage, besides being much more liable to pull the fire out at the top of smokestack. If it were not necessary to create draught by reducing your exhaust nozzle, your engine would run much nicer and be much more powerful if your nozzle was not reduced at all. However, you must reduce it sufficiently to give draught, but don't impair the power by making the engine clean its own flues. I think ninety per cent of the fires started by. traction engines can be traced to the engineer having his engine choked at the exhaust nozzle. This is dangerous for the reason that the excessive draught created throws fire out at the stack. It cuts the power of the engine by creating back pressure. We will illustrate this: Suppose you close the exhaust entirely, and the engine would not turn itself. If this is true, you can readily understand that partly closing it will weaken it to a certain extent. So, remember that the nozzle has something to do with the power of the engine, and you can see why the fellow that makes his engine clean its own flues is not the brightest engineer in the world. While it is not my intention to encourage the foolish habit of pulling engines, to see which is the best puller, should you get into this kind of a test, you will show the other fellow a trick by dropping the exhaust nozzle off entirely, and no one need know it. Your engine will not appear to be making any effort, either, in making the pull. Many a test has been won more through the shrewdness of the operator than the superiority of the engine. The knowing of this little trick may also help you out of a bad hole some time when you want a little extra power. And this brings us to the point to which I want you to pay special attention. The majority of engineers, when they want a little extra power, give the safety valve a twist. Now, I have already told you to carry a good head of steam, anywhere from 100 to 120 pounds of steam is good pressure and is plenty, and if you have your valve set to blow off at 115, let it be there; and don't screw it down every time you want more power, for if you do you will soon have it up to I25, and should you want more steam at some other time you will find yourself screwing it down again, and what was really intended for a safety valve loses all its virtue as a safety, as far as you and those around you are concerned. If you know you have a good boiler you are safe in setting it at I25 pounds, provided you are determined to not set it up to any higher pressure. But my advice to you is that if your engine won't do the work required of it at 115 pounds, you had best do what you can with it until you can get a larger one. A safety valve is exactly what its name implies, and there should be a heavy penalty for anyone taking that power away from it. If you refuse to set your safety down at any time, it does not imply that you are afraid of your boiler, but rather you understand your business and realize your responsibility. I stated before what you should do with the safety valve in starting a new engine. You should also attend to this part of it every few days. See that it does not become slow to work. You should note the pressure every time it blows off; you know where it ought to blow off, so don't allow it to stick or hold the steam beyond this pressure. If you are careful about this, there is no danger about it sticking some time when you don't happen to be watching the gauge. The steam gauge will tell you when the pop ought to blow off, and you want to see that it does it. PART FIVE _______ STEAM GAUGE Some engineers call a steam gauge a "clock." I suppose they do this because they think it tells them when it is time to throw in coal, and when it is time to quit, and when it is time for the safety valve to blow off. If that is what they think a steam gauge is for, I can tell them that it is time for them to learn differently. It is true that in a certain sense it does tell the engineer when to do certain things, but not as a clock would tell the time of day. The office of a steam gauge is to enable you to read the pressure on your boiler at all times, the same as a scale will enable you to determine the weight of any object. As this is the duty of the steam gauge, it is necessary that it be absolutely correct. By the use of an unreliable gauge you may become thoroughly bewildered, and in reality know nothing of what pressure you are carrying. This will occur in about this way: Your steam gauge becomes weak, and if your safety is set at I00 pounds, it will show I00 or even more before the pop allows the steam to escape; or if the gauge becomes clogged, the pop may blow off when the gauge only shows go pounds or less. This latter is really more dangerous than the former. As you would most naturally conclude that your safety was getting weak, and about the first thing you would do would be to screw it down so that the gauge would show I00 before the pop would blow off, when in fact you would have I00 or more. So you can see at once how important it is that your gauge and safety should work exactly together, and there is but one way to make certain of this, and that is to test your steam gauge. If you know the steam gauge is correct, you can make your safety valve agree with it; but never try to make it do it till you know the gauge is reliable. HOW TO TEST A STEAM GAUGE Take it off, and take it to some shop where there is a steam boiler in active use; have the engineer attach your gauge where it will receive the direct pressure, and if it shows the same as his gauge, it is reasonable to suppose that your gauge is correct. If the engineer to whom you take your gauge should say he thinks his gauge is weak, or a little strong, then go somewhere else. I have already told you that I did not want you to think anything about your engine-I want you to know it. However, should you find that your gauge shows when tested with another gauge, that it is weak, or unreliable in any way, you want to repair it at once, and the safest way is to get a new one; and yet I would advise you first to examine it and see if you cannot discover the trouble. It frequently happens that the pointer becomes loosened on the journal or spindle, which attaches it to the mechanism that operates it. If this is the trouble, it is easily remedied, but should the trouble prove to be in the spring, or the delicate mechanism, it would be much more satisfactory to get a new one. In selecting a new gauge you will be better satisfied with a gauge having a double spring or tube, as they are less liable to freeze or become strained from a high pressure, and the double spring will not allow the needle or pointer to vibrate when subject to a shock or sudden increase of pressure, as with the single spring. A careful engineer will have nothing to do with a defective steam gauge or an unreliable safety valve. Some steam gauges are provided with a seal, and as long as this seal is not broken the factory will make it good. FUSIBLE PLUG We have told you about a safety valve, we will now have something to say of a safety plug. A safety, or fusible plug, is a hollow brass plug or bolt, screwed into the top crown sheet. The hole through the plug being filled with some soft metal that will fuse at a much less temperature than is required to burn iron. The heat from the firebox will have no effect on this fusible plug as long as the crown sheet is covered with water, but the moment that the water level falls below the top of the crown sheet, thereby exposing the plug, this soft metal is melted and runs out, allows the steam to rush down through the opening in the lug, putting out the fire and preventing any injury to the boiler. This all sounds very nice, but I am free to confess that I am not an advocate of a fusible plug. After telling you to never allow the water to get low, and then to say there is something to even make this allowable, sounds very much like the preacher who told his boy "never to go fishing on Sunday, but if he did go, to be sure and bring home the fish." I would have no objection to the safety plug if the engineer did not know it was there. I am aware that some states require that all engines be fitted with a fusible plug. I do not question their good intentions, but I do question their good judgment. It seems to me the are granting a license to carelessness. For instance, an engineer is running with a low gauge of water, owing possibly to the tank being delayed longer than usual, he knows the water is getting low, but he says to himself, "well, if the water gets too low I will only blow out the plug," and so he continues to run until the tank arrives. If the plug holds, he at once begins to pump in cold water, and most likely does it on a very hot sheet, which of itself, is something he never should do; and if the plug does blow out he is delayed a couple of hours, at least, before he can put in a new plug and get up steam again. Now suppose he had not had a soft plug (as they are sometimes called). He would have stopped before he had low water. He would not even have had a hot crown sheet, and would only have lost the time he waited on the tank. This is not a fancied circumstance by any means, for it happens every day. The engineer running an engine with a safety plug seldom stops for a load of water until he blows out the plug. It frequently happens that a fusible plug becomes corroded to such an extent that it will stand a heat sufficient to burn the iron. This is my greatest objection to it. The engineer continues to rely on it for safety, the same as if it were in perfect order, and the ultimate result is he burns or cracks his crown sheet. I have already stated that I have no objection to the plug, if the engineer did not know it was there, so if you must use one, attend to it, and every time you clean your boiler scrape the upper or water end of the plug with a knife, and be careful to remove any corrosive matter that may have collected on it, and then treat your boiler exactly as though there was no such a thing as a safety plug in it. A safety plug was not designed to let you run with any lower gauge of water. It is placed there to prevent injury to the boiler, in case of an accident or when, by some means, you might be deceived in your gauge of water, or if by mistake, a fire was started without any water in the boiler. Should the plug melt out, it is necessary to replace it at once, or as soon as the heat will permit you to do so. It might be a saving of time to have an extra plug always ready, then all you have to do is to remove the melted one by unscrewing it from the crown sheet and screwing the extra one in. But if you have no extra plug you must remove the first one and refill it with babbitt. You can do this by filling one end of the plug with wet clay and pouring the metal into the other end, and then pounding it down smooth to prevent any leaking. This done, you can screw the plug back into its place. If you should have two plugs, as soon as you have melted out one replace it with the new one, and refill the other at your earliest convenience. By the time you have replaced a fusible plug a few times in a hot boiler you will conclude it is better to keep water over your crown sheet. LEAKY FLUES What makes flues leak? I asked this question once, and the answer was that the flues were not large enough to fill up the hole in flue sheet. This struck me as being funny at first, but on second thought I concluded it was about correct. Flues may leak from several causes, but usually it can be traced to the carelessness of some one. You may have noticed before this that I am inclined to blame a great many things to carelessness. Well, by the time you have run an engine a year or two you will conclude that I am not unjust in my suspicions. I do not blame engineers for everything, but I do say that they are responsible for a great many things which they endeavor to shift on to the manufacturer. If the flues in a new boiler leak, it is evident that they were slighted by the boiler-maker; but should they run a season or part of a season before leaking, then it would indicate that the boiler-maker did his duty, but the engineer did not do his. He has been building too hot a fire to begin with, or has, been letting his fire door stand open; or he may have overtaxed his boiler; or else he has been blowing out his boiler when too hot; or has at some time blown out with some fire in firebox. Now, any one of these things, repeated a few times, will make the best of them leak. You have been advised already not to do these things, and if you do them, or any one of them, I want to know what better word there is to express it than "carelessness." There are other things that will make your flues leak. Pumping cold water into a boiler with a low gauge of water will do it, if it does nothing more serious. Pouring cold water into a hot boiler will do it. For instance, if for any reason you should blow out your boiler while in the field, and as you might be in a hurry to get to work, you would not let the iron cool, before beginning to refill. I have seen an engineer pour water into a boiler as soon as the escaping steam would admit it. The flues cannot stand such treatment, as they are thinner than the shell or flue sheet, and therefore cool much quicker, and in contracting are drawn from the flue sheet, and as a matter of course must leak. A flue, when once started to leak, seldom stops without being set up, and one leaky flue will start others, and what are you going to do about it? Are you going to send to a boiler shop and get a boilermaker to come out and fix them and pay him from forty to sixty cents an hour for doing it? I don't know but that you must the first time, but if you are going to make a business of making your flues leak, you had best learn how to do it yourself. You can do it if you are not too big to get into the fire door. You should provide yourself with a flue expander and a calking tool, with a machinist's hammer, (not too heavy). Take into the firebox with you a piece of clean waste with which you will wipe off the ends of the flues and flue sheet to remove any soot or ashes that may have collected around them. After this is done you will force the expander into the flues driving it well up, in order to bring the shoulder of expander up snug against the head of the flue. Then drive the tapering pin into the expander. By driving the pin in too far you may spread the flue sufficient to crack it or you are more liable, by expanding too hard, to spread the hole in flue sheet and thereby loosen other flues. You must be careful about this. When you think you have expanded sufficient, hit the pin a side blow in order to loosen it, and turn the expander about one-quarter of a turn, and drive it up as before; loosen up and continue to turn as before until you have made the entire circle of flues. Then remove the expander, and you are ready for your header or calking tool. It is best to expand all the flues that are leaking before beginning with the header. The header is used by placing the gauge or guide end within the flue, and with your light hammer the flue can be calked or beaded down against the flue sheet. Be careful to use your hammer lightly, so as not to bruise the flues or sheet. When you have gone over all the expanded flues in this way, you, (if you have been careful) will not only have a good job, but will conclude that you are somewhat of an expert at it. I never saw a man go into a firebox and stop the leak but that he came out well pleased with himself. The fact that a firebox is no pleasant workshop may have had something to do with it. If your flues have been leaking badly, and you have expanded them, it would be well to test your boiler with cold water pressure to make sure that you have a good job. How are you going to test your boiler? If you can attach to a hydrant, do so, and when you have given your boiler all the pressure you want, you can then examine your flues carefully, and should you find any seeping of water, you can use your beader lightly untill such leaks are stopped. If the waterworks will not afford you sufficient pressure, you can bring it up to the required pressure, by attaching a hydraulic pump or a good force pump. In testing for the purpose of ascertaining if you have a good job on your flues, it is not necessary to put on any greater cold water pressure than you are in the habit of carrying. For instance, if your safety valve is set at one hundred and ten pounds, this pressure of cold water will be sufficient to test the flues. Now, suppose you are out in the field and want to test your flues. Of course you have no hydrant to attach to, and you happen not to have a force pump, it would seem you were in bad shape to test your boiler with cold water. Well, you can do it by proceeding in this way: When you have expanded and beaded all the flues that were leaking, you will then close the throttle tight, take off the safety valve (as this is generally attached at the highest point) and fill the boiler full, as it is absolutely necessary that all the space in the boiler should be filled with cold water. Then screw the safety valve back in its place. You will then get back in the firebox with your tools and have someone place a small sheaf of wheat or oat straw under the firebox or under waist of boiler if open firebox, and set fire to it. The expansive force of the water caused by the heat from the burning straw will produce pressure desired. You should know, however, that your safety is in perfect order. When the water begins to escape at the safety valve, you can readily see if you have expanded your flues sufficiently to keep them from leaking. This makes a very nice and steady pressure, and although the pressure is caused by heat, it is a cold water pressure, as the water is not heated beyond one or two degrees. This mode of testing, however, cannot be applied in very cold weather, as water has no expansive force five degrees above or five degrees below the freezing point. These tests, however, are only for the purpose of trying your flues and are not intended to ascertain the efficiency or strength of your boiler. When this is required, I would advise you to get an expert to do it, as the best test for this is the hammer test, and only an expert should attempt it. PART SIX ________ Any young engineer who will make use of what he has read will never get his engine into much trouble. Manufacturers of farm engines to-day make a specialty of this class of goods, as they endeavor to build them as simple and of as few parts as possible. They do this well knowing that, as a rule, they must be run by men who cannot take a course in practical engineering. If each one of the many thousands of engines that are turned out every year had to have a practical engineer to run it, it would be better to be an engineer than to own the engine; and manufacturers knowing this, they therefore make their engines as simple and with as little liability to get out of order as possible. The simplest form of an engine, however, requires of the operator a certain amount of brains and a willingness to do that which he knows should be done; and if you will follow the instructions you have already received, you can run your engine as successfully as any one can wish as long as your engine is in order, and, as I have just stated, it is not liable to get out of order, except from constant wear, and this wear will appear in the boxes, journals and valve. The brasses on wrist pin and cross-head will probably require your first and most careful attention, and of these two the wrist or crank box will require the most; and what is true of one is true of both boxes. It is, therefore, not necessary to take up both boxes in instructing you how to handle them. We will take up the box most likely to require your attention. This is the wrist box. You will find this box in two parts or halves. In a new engine you will find that these two halves do not meet on the wrist pin by at least one-eighth of an inch. They are brought up to the pin by means of a wedge-shaped key. (I am speaking now of the most common form of wrist boxes. If your engine should not have this key, it will have something which serves the same purpose.) As the brasses wear you can take up this wear by forcing the key down, which brings the two halves nearer together. You can continue to gradually take up this wear until you have brought them together. You will then see that it is necessary to do something, in order to take up any more wear, and this "something" is to take out the brasses and file about one-sixteenth of an inch off of each brass. This will allow you another eighth of an inch to take up in wear. Now here is a nice little problem for you to solve and I want you to solve it to your own satisfaction, and when you do, you will thoroughly understand it, and to understand it is to never allow it to get you into trouble. We started out by saying that in a new engine you would most likely find about one-eighth of an inch between the brasses, and we said you would finally get these brasses, or halves together, and would have to take them out and file them. Now we have taken up one-eighth of an inch and the result is, we have lengthened our pitman just one-sixteenth of an inch; or in other words, the center of wrist pin and the center of cross-head are just one-sixteenth of an inch further apart than they were before any wear had taken place, and the piston head has one-sixteenth of an inch more clearance at one end, and one-sixteenth of an inch less at the other end than it had before. Now if we take out the boxes and file them so we have, another eighth of an inch, by the time we have taken up this wear, we will then have this distance doubled, and we will soon have the piston head striking the end of the cylinder, and besides, the engine will not run as smooth as it did. Half of the wear comes off of each half, and the half next to the key is brought up to the wrist pin because of the tapering key, while the outside half remains in one place. You must therefore place back of this half a thin piece of sheet copper, or a piece of tin will do. Now suppose our boxes had one-eighth of an inch for wear. When we have taken up this much we must put in one-sixteenth of an inch backing (as it is called), for we have reduced the outside half by just that amount. We have also reduced the front half the same, but as we have said, the tapering key brings this half up to its place. Now we think we have made this clear enough and we will leave this and go back to the key again. You must remember that we stated that the key was tapering or a wedged shape, and as a wedge, is equally as powerful as a screw, and you must bear in mind that a slight tap will bring these two boxes up tight against the wrist pin. Young engineers experience more trouble with this box than with any other part of the engine, and all because they do not know how to manage it. You should be very careful not to get your box too tight, and don't imagine that every time there is a little knock about your engine that you can stop it by driving the key down a little more. This is a great mistake that many, and even old engineers make. I at one time seen a wrist pin and boxes ruined by the engineer trying to stop a knock that came from a loose fly-wheel. It is a fact, and one that has never been satisfactorily explained, that a knock coming from almost any part of an engine will appear to be in the wrist. So bear this in mind and don't allow yourself to be deceived in this way, and never try to stop a knock until you have first located the trouble beyond a doubt. When it becomes necessary to key up your brasses, you will find it a good safe way to loosen up the set screw which holds the key, then drive it down till you are satisfied you have it tight. Then drive it back again and then with your fist drive the key down as far as you can. You may consider this a peculiar kind of a hammer, but your boxes will rarely ever heat after being keyed in this manner. KNOCK IN ENGINES What makes an engine knock or pound? A loose pillow block box is a good "knocker." The pillow block is a box next crank or disc wheel. This box is usually fitted with set bolts and jam nuts. You must also be careful not to set this up too tight, remembering always that a box when too tight begins to heat and this expands the journal, causing greater friction. A slight turn of a set bolt one way or the other may be sufficient to cool a box that may be running hot, or to heat one that may be running cool. A hot box from neglect of oiling can be cooled by supplying oil, provided it has not already commenced to cut. If it shows any sign of cutting, the only safe way is to remove the box and clean it thoroughly. Loose eccentric yokes will make a knock in an engine, and it may appear to be in the wrist. You will find packing between the two halves of the yoke. Take out a thin sheet of this packing, but don't take out too much, as you are liable then to get them too tight and they may stick and cause your eccentrics to slip. We will have more to say about the slipping of the eccentrics. The piston rod loose in cross-head will make a knock, which also appears in the wrist, but it is not there. Tighten the piston and you will stop it. The piston rod may be keyed in cross head, or it may be held in place by a nut. The key is less liable to get loose, but should it work loose a few times it may be necessary to replace it with a new one. And this is one of the things that cause a bad break when it works out or gets loose. If it gets loose it may not come out, but it will not stand the strain very long in this condition, and will break, allowing the piston to come out of cross head, and you are certain to knock out one cylinder head and possibly both of them. The nut will do the same thing if allowed to come off. So this is one of the connections that will claim your attention once in a while, but if you train your ear to detect any unusual noise you will discover it as soon as it gives the least in either key or nut. The cross-head loose in the guides will make it knock. If the cross-head is not provided for taking up this wear, you can take off the guides and file them enough to allow them to come up to the cross-head, but it is much better to have them planed off, which insures the guides coming up square against the cross-head and thus prevent any heating or cutting. A loose fly-wheel will most likely puzzle you more than anything else to find the knock. So remember this. The wheel may apparently be tight, but should the key be the least bit narrow for the groove in shaft, it will make your engine bump very similar to that caused by too much or too little "lead." LEAD What is lead? Lead is space or opening of port on steam end of cylinder, when engine is on dead center. (Dead center is the two points of disc or crank wheel at which the crank pin is in direct line with piston and at which no amount of steam will start the engine.) Different makes of engines differ to such an extent that it is impossible to give any rule or any definite amount of lead for an engine. For instance, an engine with a port six inches long and one-half inch wide would require much less lead than one with a port four inches long and one inch wide. Suppose I should say one-sixteenth of an inch was the proper lead. In one engine you would have an opening one-sixteenth of an inch wide and six inches long and in the other you would have one-sixteenth of an inch wide and four inches long; so you can readily see that it is impossible to give the amount of lead for an engine without knowing the piston area, length of port, speed, etc. Lead allows live steam to enter the cylinder just ahead of the piston at the point of finishing the stroke, and forms a "cushion," and enables the engine to pass the center without a jar. Too much lead is a source of weakness to an engine, as it allows the steam to enter the cylinder too soon and forms a back pressure and tends to prevent the engine from passing the center. It will, therefore, make your engine bump, and make it very difficult to hold the packing in stuffing box. Insufficient lead will not allow enough steam to enter the cylinder ahead of piston to afford cushion enough to stop the inertia, and the result will be that your engine will pound on the wrist pin. You most likely have concluded by this time that "lead" is no small factor in the smooth running of an engine, and you, as a matter of course, will want to know how you are to obtain the proper lead. Well don't worry yourself. Your engine is not going to have too much lead today and not enough tomorrow. If your engine was properly set up in the first place the lead will be all right, and continue to afford the proper lead as long as the valve has not been disturbed from its original position; and this brings us to the most important duty of an engineer as far as the engine is concerned, viz: Setting the Valve. SETTING A VALVE. The proper and accurate setting of a valve on a steam engine is one of the most important duties that you will have to perform, as it requires a nicety of calculation and a mechanical accuracy. And when we remember also, that this is another one of the things for which no uniform rule can be adopted, owing to the many circumstances which go to make an engine so different under different conditions, we find it very difficult to give you the light on this part of your duty which we would wish to. We, however, hope to make it so clear to you that by the aid of the engine before you, you can readily understand the conditions and principles which control the valve in the particular engine which you may have under your management. The power and economy of an engine depends largely on the accurate operation of its valve. It is, therefore, necessary that you know how to reset it, should it become necessary to do so. An authority says, "Bring your engine to a dead center and then adjust your valve to the proper lead." This is all right as far as it goes, but how are you to find the dead center. I know that it is a common custom in the field to bring the engine to a center by the use of the eye. You may have a good eye, but it is not good enough to depend on for the accurate setting of a valve. HOW TO FIND THE DEAD CENTER First, provide yourself with a "tram." This you can do by taking a 1/4 inch iron rod, about 18 inches long, and bend about two inches of one end to a sharp angle. Then sharpen both ends to a nice sharp point. Now, fasten securely a block of hard wood somewhere near the face of the fly wheel, so that when the straight end of your tram is placed at a definite point in the block the other, or hook end, will reach the crown of fly wheel. Be certain that the block cannot move from its place, and be careful to place the tram at exactly the same point on the block at each time you bring the tram into use. You are now ready to proceed to find the dead center, and in doing this remember to turn the fly wheel always in the same direction. Now, turn your engine over till it nears one of the centers, but not quite to it. You will then, by the aid of a straight-edge make a clear and distinct mark across the guides and cross head. Now, go around to the fly wheel and place the straight end of the tram at same point on the block, and with the hook end make a mark across the crown or center of face of fly wheel; now turn your engine past the center and on to the point at which the line on cross head is exactly in line with the lines on guides. Now, place your tram in the same place as before, and make another mark across the crown of fly wheel. By the use of dividers find the exact center between the two marks made on fly wheel; mark this point with a center punch. Now, bring the fly wheel to the point at which the tram, when placed at its proper place on block, the hook end, or point, will touch this punch mark, and you will have one of the exact dead centers. Now, turn the engine over till it nears the other center, and proceed exactly as before, remembering always to place the straight end of tram exactly in same place in block, and you will find both dead centers as accurately as if you had all the fine tools of an engine builder. You are now ready to proceed with the setting of your valve, and as you have both dead centers to work from you ought to be able to do it, as you do not have to depend on your eye to find them, and by the use of the tram You turn your engine to exactly the same point every time you wish to get a center. Now remove the cap on steam chest, bring your engine to a dead center and give your valve the necessary amount of lead on the steam end. Now, we have already stated that we could not give you the proper amount of lead for an engine. It is presumed that the maker of your engine knew the amount best adapted to this engine, and you can ascertain his idea of this by first allowing, we will say, about 1/16 of an inch. Now bring your engine to the other center, and if the lead at the other end is less than 1/16, then you must conclude that he intended to allow less than 1/16, but should it show more than this, then it is evident that he intended more than I/I16 lead; but in either case you must adjust your valve so as to divide the space, in order to secure the same lead when on either center. In the absence of any better tool to ascertain if the lead is the same, make a tapering wooden wedge of soft wood, turn the engine to a center and force the wedge in the opening made by the valve hard enough to mark the wood; then turn to the next center, and if the wedge enters the same distance, you are correct; if not, adjust till it does, and when you have it set at the proper place you had best mark it by taking a sharp cold chisel and place it so that it will cut into the hub of eccentric and in the shaft; then hit it a smart blow with a hammer. This should be done after you have set the set screws in eccentric down solid on the shaft. Then, at any time should your eccentric slip, you have only to bring it back to the chisel mark and fasten it, and you are ready to go ahead again. This is for a plain or single eccentric engine. A double or reversible engine, however, is somewhat more difficult to handle in setting the valve. Not that the valve itself is any different from a plain engine, but from the fact that the link may confuse you, and while the link may be in position to run the engine one way you may be endeavoring to set the valve to run it the other way. The proper way to proceed with this kind of an engine is to bring the reverse lever to a position to run the engine forward, then proceed to set your valve the same as on a plain engine. When you have it at the proper place, tighten just enough to keep from slipping, then bring your reverse lever to the reverse position and bring your engine to the center. If it shows the same lead for the reverse motion you are then ready to tighten your eccentrics securely, and they should be marked as before. You may imagine that you will have this to do often. Well don't be scared about it. You may run an engine a long time, and never have to set a valve. I have heard these windy engineers (you have seen them), say that they had to go and set Mr. A's or Mr. B's valve, when the facts were, if they did anything, it was simply to bring the eccentrics back to their original position. They happened to know that most all engines are plainly marked at the factory, and all there was to do was to bring the eccentrics back to these marks and fasten them, and the valve was set. The slipping of the eccentrics is about the only cause for a valve working badly. You should therefore keep all grease and dirt away from these marks; keep the set screws well tightened, and notice them frequently to see that they do not slip. Should they slip a I/I6 part of an inch, a well educated ear can detect it in the exhaust. Should they slip a part of a turn as they will some times, the engine may stop instantly, or it may cut a few peculiar circles for a minute or two, but don't get excited, look to the eccentrics at once for the trouble. Your engine may however act very queer some time, and you may find the eccentrics in their proper place. Then you must go into the steam chest for the trouble. The valves in different engines are fastened on valve rod in different ways. Some are held in place by jam nuts; a nut may have worked loose, causing lost motion on the valve. This will make your engine work badly. Other engines hold their valve by a clamp and pin. This pin may work out, and when it does, your engine will stop, very quickly to. If you thoroughly understand the working of the steam, you can readily detect any defect in your cylinder or steam chest, by the use of your cylinder cocks. Suppose we try them once. Turn your engine on the forward center, now open the cocks and give the engine the steam pressure. If the steam blows out at the forward cock we know that we have sufficient lead. Now turn back to the back center, and give it steam again; if it blows out the same at this cock, we can conclude that our valve is in its proper position. Now reverse the engine and do the same thing; if the cocks act the same, we know we are right. Suppose the steam blows out of one cock all right, and when we bring the engine to the other center no steam escapes from this cock, then we know that something is wrong with the valve, and if the eccentrics are in their proper position the trouble must be in the steam chest, and if we open it up we will find the valve has become loosened on the rod. Again suppose we put the engine on a center, and on giving it steam, we find the steam blowing out at both cocks. Now what is the trouble, for no engine in perfect shape will allow the steam to blow out of both cocks at the same time. It is one of two things, and it is difficult to tell. Either the cylinder rings leak and allow the steam to blow through, or else the valve is cut on the seat, and allows the steam to blow over. Either of these two causes is bad, as it not only weakens your engine, but is a great waste of fuel and water. The way to determine which of the two causes this, is to take off the cylinder head, turn engine on forward center and open throttle slightly. If the steam is seen to blow out of the port at open end of cylinder, then the trouble is in the valve, but if not, you will see it blowing through from forward end of cylinder, and the trouble is in the cylinder rings. What is the remedy? Well, if the "rings" are the trouble, a new set will most likely remedy it should they be of the automatic or self-setting pattern, but should they be of the spring or adjusting pattern, you can take out the head and set the rings out to stop this blowing. As most all engines now are using the self-setting rings, you will most likely require a new set. If the trouble is in the valve or steam chest, you had best take it off and have the valve seat planed down, and the valve seated to it. This is the safest and best way. Never attempt to dress a valve down, you are most certain to make a bad job of it. And yet I don't like the idea of advising you not to do a thing that can be done, for I do like an engineer who does not run to the shop for every little trouble. However, unless you have the proper tools you had best not attempt it. The only safe way is to scrape them down, for if your valve is cut, you will find the valve seat is cut equally as bad, and they must both be scraped to a perfect fit. Provide yourself with a piece of flat steel, very hard, 3x4 inches by about I/8 inch, with a perfect straight edge. With this scrape the valve and seat to a perfect flat surface, It will be a slower process than scraping wood with a piece of glass, but you can do it. Never use a chisel or a file on a valve. LUBRICATING OIL What is oil? Oil is a coating for a journal, or in other words is a lining between bearings. Did you ever stop long enough to ask yourself the question? I doubt it. A great many people buy something to use on their engine, because it is called oil. Now if the object in using oil is to keep a lining between the bearings, is it not reasonable that you use something that will adhere to that which it is to line or cover? Gasoline will cover a journal for a minute or two, and oil a grade better would last a few minutes longer. Still another grade would do some better. Now if you are running your own engine, buy the best oil you can buy. You will find it very poor economy to buy cheap oil, and if you are not posted, you may pay price enough, but get a very poor article. If you are running an engine for some one else, make it part of your contract that you are furnished with a good oil. You can not keep an engine in good shape with a cheap oil. You say "you are going to keep your engine clean and bright." Not if you must use a poor oil. Poor oil is largely responsible for the fast going out of use of the link reverse among the makers of traction engines. While I think it very doubtful if this "reverse motion" can be equalled by any of the late devices. Its construction is such as to require the best grade of cylinder oil, and without this it is very unsatisfactory, (not because the valves of other valve-motions will do with a poorer grade of oil) but because its construction is such that as soon as the valve becomes dry it causes the link to jump and pound, and very soon requires repairing. While the construction of various other devices are such, that while the valve may be equally as dry it does not show the want of oil so clearly as the old style link. Yet as a fact I care not what the valve motion may be, it requires a good grade of oil. You may ask "how am I to know when I am getting a good grade of oil." The best way is to ascertain a good brand of oil then use that and nothing else. We are not selling oil, or advertising oil. However before I get through I propose to give you the name of a good brand of cylinder oil, a good engine oil as well as good articles of various attachments, which cut no small figure in the success you may have in running an engine. It is not an uncommon thing for an engineer (I don't like to call him an engineer either) to fill his sight feed lubricator with ordinary engine oil, and then wonder why his cylinder squeaks. The reason is that this grade of oil cannot stand the heat in the cylinder or steam chest. If you are carrying 90 pounds of steam you have about 320 degrees of heat in your cylinder, with I20 to I25 pounds you will have about 350 degrees of heat, and in order to lubricate your valve and valve-seat, and also the cylinder surface, you must use an oil, that will not only stand this heat but considerable more so that it will have some staying qualities. Then if you are using a good quality of oil and your link or reverse begins to knock, it is because some part of it wants attention, and you must look after it. And here is where I want to insist that you teach your ear to be your guide. You ought to be able to detect the slightest sound that is unnatural to your engine. Your eyes may be deceived, but a well trained ear can not be fooled. I was once invited by an engineer to come out and see how nice his engine was running. I went, and found that the engine itself was running very smooth, in fact almost noiseless, but he looked very much disappointed when I asked him why he was doing all his work with one end of cylinder. He asked me what I meant, and I had some difficulty in getting him to detect the difference in the exhaust of the two ends, in fact the engine was only making one exhaust to a revolution. He was one of those engineers who never discovered anything wrong until he could see it. Did you know that there are people in the world whose mental capacity can only grasp one idea at a time. That is when their minds are on any one object or principle they can not see or observe anything else. That was the case with this engineer, his mind had been thoroughly occupied in getting all the reciprocating (moving) parts perfectly adjusted, and if the exhaust had made all sorts of peculiar noises, he would not have discovered it. The one idead man will not make a successful engineer. The good engineer can stand by and at a glance take in the entire engine, from tank to top of smoke stack. He has the faculty of noting mentally, what he sees, and what he hears, and by combining the results of the two, he is enabled to size up the condition of the engine at a glance. This, however, only come with experience, and verges on expertness. And if you wish to be an expert, learn to be observing. It is getting very common among engineers to use "hard grease" on the crank pin and main journals, and it will very soon be used exclusively. With a good grade of grease your crank will not heat near so quickly as with oil and your engine will be much easier to keep clean; and if you are going to be an engineer be a neat one, keep your engine clean and keep yourself clean. You say you can't do that; but you can at least keep yourself respectable. You will most certainly keep your engine looking as though it had an engineer. Keep a good bunch of waste handy, and when it is necessary to wipe your hands use the waste and not your overalls, and when you go in to a nice dinner the cook will not say after you go out, "Look here where that dirty engineer sat." Now boys, these are things worth heeding. I have actually known threshing crews to lose good customers simply because of their dirty clothes. The women kicked and they had a right to kick. But to return to hard grease and suitable cups for same. In attaching these grease cups on boxes not previously arranged for them, it would be well for you to know how to do it properly. You will remove the journal, take a gouge and cut a clean groove across the box, starting in at one corner, about I/8 of an inch from the point of box and cut diagonally across coming out at the opposite corner on the other end of box. Then start at the opposite corner and run through as before, crossing the first groove in the center of box. Groove both halves of box the same, being careful not to cut out at either end, as this will allow the grease to escape from box and cause unnecessary waste. The chimming or packing in box should be cut so as to touch the journal at both ends of box, but not in the center or between these two points. So, when the top box is brought down tight, this will form another reservoir for the grease. If the box is not tapped directly in the center for cup, it will be necessary to cut other grooves from where it is tapped into the grooves already made. A box prepared in his way will require but little attention if you use good grease. A HOT BOX You will sometimes get a hot box. What is the best remedy? Well, I might name you a dozen, and if I did you would most likely never have one on hand when it was wanted. So will only give you one, and that is white lead and oil, and I want you to provide yourself with a can of this useful article. And should a journal or box get hot on your hands and refuse to cool with the usual methods, remove the cup, and after mixing a portion of the lead with oil, put a heavy coat of it on the journal, put back the cup and your journal will cool off very quickly. Be careful to keep all grit or dust out of your can of lead. Look after this part of it yourself. It is your business. PART SEVEN ________ Before taking up the handling of a Traction Engine, we want to tell you of a number of things you are likely to do which you ought not to do. Don't open the throttle too quickly, or you may throw the drive belt off, and are also more apt to raise the water and start priming. Don't attempt to start the engine with the cylinder cocks closed, but make it a habit to open them when you stop; this will always insure your cylinder being free from water on starting. Don't talk too much while on duty. Don't pull the ashes out of ash pan unless you have a bucket of water handy. Don't start the pump when you know you have low water. Don't let it get low. Don't let your engine get dirty. Don't say you can't keep it clean. Don't leave your engine at night till you have covered it up. Don't let the exhaust nozzle lime up, and don't allow lime to collect where the water enters the boiler, or you may split a heater pipe or knock the top off of a check valve. Don't leave your engine in cold weather without first draining all pipes. Don't disconnect your engine with a leaky throttle. Don't allow the steam to vary more than I0 or I5 pounds while at work. Don't allow anyone to fool with your engine. Don't try any foolish experiments on your engine. Don't run an old boiler without first having it thoroughly tested. Don't stop when descending a steep grade. Don't pull through a stockyard without first closing the damper tight. Don't pull onto a strange bridge without first examining it. Don't run any risk on a bad bridge. A TRACTION ENGINE ON THE ROAD You may know all about an engine. You may be able to build one, and yet run a traction in the ditch the first jump. It is a fact that some men never can become good operators of a traction engine, and I can't give you the reason why any more than you can tell why one man can handle a pair of horses better than another man who has had the same advantages. And yet if you do ditch your engine a few times, don't conclude that you can never handle a traction. If you are going to run a traction engine I would advise you to use your best efforts to become an expert at it. For the expert will hook up to his load and get out of the neighborhood while the awkward fellow is getting his engine around ready to hook up. The expert will line up to the separator the first time, while the other fellow will back and twist around for half an hour, and then not have a good job. Now don't make the fatal mistake of thinking that the fellow is an expert who jumps up on his engine and jerks the throttle open and yanks it around backward and forward, reversing with a snap, and makes it stand-up on its hind wheels. If you want to be an expert you must begin with the throttle, therein lies the secret of the real expert. He feels the power of his engine through the throttle. He opens it just enough to do what he wants it to do. He therefore has complete control of his engine. The fellow who backs his engine up to the separator with an open throttle and must reverse it to keep from running into and breaking something, is running his engine on his muscle and is entitled to small pay. The expert brings his engine back under full control, and stops it exactly where he wants it. He handles his engine with his head and should be paid accordingly. He never makes a false move, loses no time, breaks nothing, makes no unnecessary noise, does not get the water all stirred up in the boiler, hooks up and moves out in the same quiet manner, and the onlookers think he could pull two such loads, and say he has a great engine, while the engineer of muscle would back up and jerk his engine around a half dozen times before he could make the coupling, then with a jerk and a snort he yanks the separator out of the holes, and the onlookers think he has about all he can pull. Now these are facts, and they cannot be put too strong, and if you are going to depend on your muscle to run your engine, don't ask any more money than you would get at any other day labor. You are not expected to become an expert all at once. Three things are essential to be able to handle a traction engine as it should be handled. First, a thorough knowledge of the throttle. I don't mean that you should simply know how to pull it open and shut it. Any boy can do that. But I mean that you should be a good judge of the amount of power it will require to do what you may wish to do, and then give it the amount of throttle that it will require and no more. To illustrate this I will give an instance. An expert was called a long distance to see an engine that the operator said would not pull its load over the hills he had to travel. The first pull he had to make after the expert arrived was up the worst hill he had. When he approached the grade he threw off the governor belt, opened the throttle as wide as he could get it, and made a run for the hill. The result was, that he lifted the water and choked the engine down before he was half way up. He stepped off with the remark, "That is the way the thing does." The expert then locked the hind wheels of the separator with a timber, and without raising the pressure a pound, pulled it over the hill. He gave it just throttle enough to pull the load, and made no effort to hurry ii, and still had power to spare. A locomotive engineer makes a run for a hill in order that the momentum of his train will help carry him over. It is not so with a traction and its load; the momentum that you get don't push very hard. The engineer who don't know how to throttle his engine never knows what it will do, and therefore has but little confidence in it; while the engineer who has a thorough knowledge of the throttle and uses it, always has power to spare and has perfect confidence in his engine. He knows exactly what he can do and what he cannot do. The second thing for you to know is to get onto the tricks of the steer wheel. This will come to you naturally, and it is not necessary for me to spend much time on it. All new beginners make the mistakes of turning the wheel too often. Remember this-that every extra turn to the right requires two turns to the left, and every extra turn to the left requires two more to the right; especially is this the care if your engine is fast on the road. The third thing for you to learn, is to keep your eyes on the front wheels of your engine, and not be looking back to see if your load in coming. In making a difficult turn you will find it very much to your advantage to go slow, as it gives you much better control of your front wheels, and it is not a bad plan for a beginner to continue to go slow till he has perfect confidence in his ability to handle the steer wheel as it may keep you out of some bad scrapes. How about getting into a hole? Well, you are not interested half as much in knowing how to get into a hole as You are in knowing how to get out. An engineer never shows the stuff he is made of to such good advantage as when he gets into a hole; and he is sure to get there, for one of the traits of a traction engine is its natural ability to find a soft place in the ground. Head work will get you out of a bad place quicker than all the steam you can get in your boiler. Never allow the drivers to turn without doing some good. If you are in a hole, and you are able to turn your wheels, you are not stuck; but don't allow your wheels to slip, it only lets you in deeper. If your wheels can't get a footing, you want to give them something to hold to. Most smart engineers will tell you that the best thing is a heavy chain. That is true. So are gold dollars the best things to buy bread with, but you have not always got the gold dollars, neither have you always got the chain. Old hay or straw is a good thing; old rails or timber of any kind. The engineer with a head spends more time trying to give his wheels a hold than he does trying to pull out, while the one without a head spends more time trying to pull out than he does trying to secure a footing, and the result is, that the first fellow generally gets out the first attempt, while the other fellow is lucky if he gets out the first half day. If you have one wheel perfectly secure, don't spoil it by starting your engine till you have the other just as secure. If you get into a place where your engine is unable to turn its wheels, then your are stuck, and the only thing for you to do is to lighten your load or dig out. But under all circumstances your engine should be given the benefit of your judgment. All traction engines to be practical must of a necessity, be reversible. To accomplish this, the link with the double eccentric is the one most generally used, although various other devices are used with more or less success. As they all accomplish the same purpose it is not necessary for us to discuss the merits or demerits of either. The main object is to enable the operator to run his engine either backward or forward at will, but the link is also a great cause of economy, as it enables the engineer to use the steam more or less expansively, as he may use more or less power, and, especially is this true, while the engine is on the road, as the power required may vary in going a short distance, anywhere from nothing in going down hill, to the full power of your engine in going up. By using steam expansively, we mean the cutting off of the steam from the cylinder, when the piston has traveled a certain part of its stroke. The earlier in the stroke this is accomplished the more benefit you get of the expansive force of the steam. The reverse on traction engines is usually arranged to cut off at I/4, I/2 or 3/4. To illustrate what is meant by "cutting off" at I/4, I/2 or 3/4, we will suppose the engine has a I2 inch stroke. The piston begins its stroke at the end of cylinder, and is driven by live steam through an open port, 3 inches or one quarter of the stroke, when the port is closed by the valve shutting the steam from the cylinder, and the piston is driven the remaining 9 inches of its stroke by the expansive force of the steam. By cutting off at I/2 we mean that the piston is driven half its stroke or 6 inches by live steam, and by the expansion of the steam the remaining 6 inches; by 3/4 we mean that live steam is used 9 inches before cutting off, and expansively the remaining 3 inches of stroke. Here is something for you to remember: "The earlier in the stroke you cut off the greater the economy, but less the power; the later you cut off the less the economy and greater the power." Suppose we go into this a little farther. If you are carrying I00 pounds pressure and cut off at I/4, you can readily see the economy of fuel and water, for the steam is only allowed to enter the cylinder during I/4 of its stroke; but by reason of this, you only get an average pressure on the piston head of 59 pounds throughout the stroke. But if this is sufficient to do the work, why not take advantage of it and thereby save your fuel and water? Now, with the same pressure as before, and cutting off at I/2, you have an average pressure on piston head of 84 pounds, a loss of 50 per cent in economy and a gain of 42 per cent in power. Cutting of at 3/4 gives you an average pressure of 96 pounds throughout the stroke. A loss on cutting off at I/4 of 75 per cent in economy, and a gain of nearly 63 per cent in power. This shows that the most available point at which to work steam expansively is at I/4, as the percentage of increase of power does not equal the percentage of loss in economy. The nearer you bring the reverse lever to center of quadrant, the earlier will the valve cut the steam and the less will be the average pressure, while the farther away from the center the later in the stroke will the valve cut the steam, and the greater the average pressure, and, consequently, the greater the power. We have seen engineers drop the reverse back in the last notch in order to make a hard pull, and were unable to tell why they did so. Now, as far as doing the work is concerned, it is not absolutely necessary that you know this; but if you do know it, you are more likely to profit by it and thereby get the best results out of your engine. And as this is our object, we want you to know it, and be benefitted by the knowledge. Suppose you are on the road with your engine and load, and you have a stretch of nice road. You are carrying a good head of steam and running with lever back in the corner or lower notch. Now your engine will travel along its regular speed, and say you run a mile this way and fire twice in making it. You now ought to be able to turn around and go back on the same road with one fire by simply hooking the lever up as short as it will allow to do the work. Your engine will make the same time with half the fuel and water, simply because you utilize the expansive force of the steam instead of using the live steam from boiler. A great many good engines are condemned and said to use too much fuel, and all because the engineer takes no pains to utilize the steam to the best advantage. I have already advised you to carry a "high pressure;" by a high pressure I mean any where from I00 to I25 lbs. I have done this expecting you to use the steam expansively whenever possible, and the expansive force of steam increases very rapidly after you have reached 70 lbs. Steam at 80 lbs. used expansively will do nine times the work of steam at 25 lbs. Note the difference. Pressure 3 I-5 times greater. Work performed, 9 times greater. I give you these facts trusting that you will take advantage of them, and if your engine at I00 or I00 lbs. will do your work cutting off at I/4, don't allow it to cut off at I/2. If cutting off at I/2 will do the work, don't allow it to cut off at 3/4, and the result will be that you will do the work with the least possible amount of fuel, and no one will have any reason to find fault with you or your engine. Now we have given you the three points which are absolutely necessary to the successful handling of a traction engine, We went through it with you when running as a stationary; then we gave you the pointers-to be observed when running as a traction or road engine. We have also given you hints on economy, and if you do not already know too much to follow our advice, you can go into the field with an engine and have no fears as to the results. How about bad bridges? Well, a bad bridge is a bad thing, and you cannot be too careful. When you have questionable bridges to cross over, you should provide yourself with good hard-wood planks. If you can have them sawed to order have them 3 inches in the center and tapering to 2 inches at the ends. You should have two of these about 16 feet long, and two 2x12 planks about 8 feet long. The short ones for culverts, and for helping with the longer ones in crossing longer bridges. An engine should never be allowed to drop from a set of planks down onto the floor of bridge. This is why I advocate four planks. Don't hesitate to use the plank. You had better plank a dozen bridges that don't need it than to attempt to cross one that does need it. You will also find it very convenient to carry at least 50 feet of good heavy rope. Don't attempt to pull across a doubtful bridge with the separator or tank hooked directly to the engine. It is dangerous. Here is where you want the rope. An engine should be run across a bad bridge very slowly and carefully, and not allowed to jerk. In extreme cases it is better to run across by hand; don't do this but once; get after the road supervisors. SAND. An engineer wants a sufficient amount of "sand," but he don't want it in the road. However, you will find it there and it is the meanest road you will have to travel. A bad sand road requires considerable sleight of hand on the part of the engineer if he wishes to pull much of a load through it. You will find it to your advantage to keep your engine as straight as possible, as you are not so liable to start one wheel to slipping any sooner than the other. Never attempt to "wiggle" through a sand bar, and don't try to hurry through; be satisfied with going slow, just so you are going. An engine will stand a certain speed through sand, and the moment you attempt to increase that speed, you break its footing, and then you are gone. In a case of this kind, a few bundles of hay is about the best thing you can use under your drivers in order to get started again. But don't loose your temper; it won't help the sand any. Now no doubt the reader wonders why I have said nothing about compound engines. Well in the first place, it is not necessary to assist you in your work, and if you can handle the single cylinder engine, you can handle the compound. The question as to the advantage of a compound engine is, or would be an interesting one if we cared to discuss it. The compound traction engine has come into use within the past few years, and I am inclined to think more for sort of a novelty or talking point rather than to produce a better engine. There is no question but that there is a great advantage in the compound engine, for stationary and marine engines. In a compound engine the steam first enters the small or high pressure cylinder and is then exhausted into the large or low pressure cylinder, where the expansive force is all obtained. Two cylinders are used because we can get better results from high pressure in the use of two cylinders of different areas than by using but one cylinder, or simple engine. That there is a gain in a high pressure, can be shown very easily: For instance, 100 pounds of coal will raise a certain amount of water from 60 degrees, to 5 pounds steam pressure, and 102.9 pounds would raise the same water to 80 pounds, and 104.4 would raise it to 160 pounds, and this 160 pounds would produce a large increase of power over the 80 pounds at a very slight increase of fuel. The compound engine will furnish the same number of horse power, with less fuel than the simple engine, but only when they are run at the full load all the time. If, however, the load fluctuates and should the load be light for any considerable part of the day, they will waste the fuel instead of saving it over the simple engine. No engine can be subjected to more variation of loads than the traction engine, and as the above are facts the reader can draw his own conclusions. FRICTION CLUTCH The friction clutch is now used almost exclusively for engaging the engine with the propelling gearing of the traction drivers, and it will most likely give you more trouble than any one thing on your engine, from the fact that to be satisfactory they require a nicety of adjustment, that is very difficult to attain, a half turn of the expansion bolt one way or the other may make your clutch work very nicely, or very unsatisfactory, and you can only learn this by carefully adjusting of friction shoes, until you learn just how much clearance they will stand when lever is out, in order to hold sufficient when lever is thrown in. If your clutch fails to hold, or sticks, it is not the fault of the clutch, it is not adjusted properly. And you may have it correct today and tomorrow it will need readjustment, caused by the wear in the shoes; you will have to learn the clutch by patience and experience. But I want to say to you that the friction clutch is a source of abuse to many a good engineer, because the engineer uses no judgment in its use. A certain writer on engineering makes use of the following, and gives me credit: "Sometimes you may come to an obstacle in the road, over which your engine refuses to go, you may perhaps get over it in this way, throw the clutch-lever so as to disconnect the road wheels, let the engine get up to full speed and then throw the clutch level back so as to connect the road wheels." Now I don't thank any one for giving me credit for saying any such thing. That kind of thing is the hight of abuse of an engine. I am aware that when the friction clutch first came into use, their representatives made a great talk on that sort of thing to the green buyer. But the good engineer knows better than to treat his engine that way. Never attempt to pull your loads over a steep hill without being certain that your clutch is in good shape, and if you have any doubts about it put in the tight gear pin. Most all engines have both the friction and the tight gear pin. The pin is much the safer in a hilly country, and if you have learned the secret of the throttle you can handle just as big load with the pin as with the clutch, and will never tear your gearing off or lose the stud bolts in boiler. The following may assist you in determining or arriving at some idea of the amount of power you are supplying with your engine: For instance, a I inch belt of the standard grade with the proper tention, neither too tight or too loose, running at a. maximum spead of 800 ft. a minute will transmit one horse power, running 1600 ft. 2 horse power and 2400 ft. 3 horse power. A 2 inch belt, at the same speed, twice the power. Now if you know the circumference of your fly wheel, the number of revolutions your engine is making and the width of belt, you can figure very nearly the amount of power you can supply without slipping your belt. For instance, we will say your fly wheel is 40 inches in diameter or 10.5 feet nearly in circumference and your engine was running 225 revolutions a minute, your belt would be traveling 225 x 10.5 feet = 2362.5 feet or very nearly 2400 ft. and if I inch of belt would transmit 3 H. P. running this speed, a 6 inch belt would transmit 18 H.P., a 7 inch belt, 21 H.P., an 8 inch belt 24 H.P., and so on. With the above as a basis for figuring you can satisfy yourself as to the power you are furnishing. To get the best results a belt wants to sag slightly as it hugs the pulley closer, and will last much longer. SOMETHING ABOUT SIGHT-FEED LUBRICATORS All such lubricators feed oil through the drop-nipple by hydrostatic pressure; that is, the water of condensation in the condenser and its pipe being elevated above the oil magazine forces the oil out of the latter by just so much pressure as the column of water is higher than the exit or outlet of oil-nipple. The higher the column of water the more positive will the oil feeds. As soon as the oil drop leaves the nipple it ceases to be actuated by the hydrostatic pressure, and rises through the water in the sight-glass merely by the difference of its specific gravity, as compared with water and then passes off through the ducts provided to the parts to be lubricated. For stationary engines the double connection is preferable, and should always be connected to the live steam pipe above the throttle. The discharge arm should always be long enough (4 to 6 inches) to insure the oil magazine and condenser from getting too hot, otherwise it will not condense fast enough to give continuous feed of oil. For traction or road engines the single connection is used. These can be connected to live steam pipe or directly to steam chest. In a general way it may be stated that certain precaution must be taken to insure the satisfactory operation of all sight-feed lubricators. Use only the best of oil, one gallon of which is worth five gallons of cheap stuff and do far better service, as inferior grades not only clog the lubricator but chokes the ducts and blurs the sight-glass, etc., and the refuse of such oil will accumulate in the cylinder sufficiently to cause damage and loss of power, far exceeding the difference in cost of good oil over the cheap grades. After attaching a lubricator, all valves should be opened wide and live steam blown through the outer vents for a few minutes to insure the openings clean and free. Then follow the usual directions given with all lubricators. Be particular in getting your lubricator attached so it will stand perfectly plum, in order that the drop can pass up through the glass without touching the sides, and keep the drop-nipple clean, be particular to drain in cold weather. Now, I am about to leave you alone with your engine, just as I have left any number of young engineers after spending a day with them in the field and on the road. And I never left one, that I had not already made up my mind fully, as to what kind of an engineer he would make. TWO WAYS OF READING __________ Now there are two ways to read this book, and if I know just how you had read it I could tell you in a minute whether to take hold of an engine or leave it alone. If you have read it one way, you are most likely to say "it is no trick to run an engine." If you have read it the other way you will say, "It is no trouble to learn how to run an engine." Now this fellow will make an engineer, and will be a good one. He has read it carefully, noting the drift of my advice. Has discovered that the engineer is not expected to build an engine, or to improve it after it has been built. Has recognized the fact that the principle thing is to attend to his own business and let other people attend to theirs. That a monkey wrench is a tool to be left in the tool box till he knows he needs it. That muscle is a good thing to have but not necessary to the successful engineer. That an engineer with a bunch of waste in his hand is a better recommendation than an "engineer license." That good common sense, and a cool head is the very best tools he can have. Has learned that carelessness will get him into trouble, and that to "forget" costs money. Now the fellow who said "It is no trick to run an engine," read this book another way. He did not see the little points. He was hunting for big theories, scientific theories, something he could not understand, and didn't find them. He expected to find some bright scheme to prevent a boiler from exploding, didn't notice the simple little statement, "keep water in it," that was too commonplace to notice. He was looking for cuts, diagrams, geometrical figures, theories for constructing engines and boilers and all that sort of thing and didn't find them. Hence "It is no trick to run an engine." If this has been your idea of "Rough and Tumble Engineering" forget all about your theory, and go back and read it over and remember the little suggestions and don't expect this book to teach you how to build an engine. We didn't start out to teach you anything of the kind. That is a business of itself. A good engineer gets better money than the man who builds them. Read it as if you wanted to know how to run an engine and not how to build one. Study the following questions and answers carefully. Don't learn them like you would a piece of poetry, but study them, see if they are practical; make yourself thoroughly acquainted with the rule for measuring the horse-power of an engine; make yourself so familiar with it that you could figure any engine without referring to the book. Don't stop at this, learn to figure the heating surface in any boiler. It will enable you to satisfy yourself whether you are working your boiler or engine too hard or what it ought to be capable of doing. SOME THINGS TO KNOW Q. What is fire? A. Fire is the rapid combustion or consuming of organic matter. Q. What is water? A. Water is a compound of oxygen and hydrogen. In weight 88 9-I0 parts oxygen to II I-I0 hydrogen. It has its maximum density at 39 degrees Fahr., changes to steam at 2I2 degrees, and to ice at 32 degrees. Q. What is smoke? A. It is unconsumed carbon finely divided escaping into open air. Q. Is excessive smoke a waste of fuel? A. Yes. Q. How will you prevent it A. Keep a thin fire, and admit cold air sufficient to insure perfect combustion. Q. What is low water as applied to a boiler? A. It is when the water is insufficient to cover all parts exposed to the flames. Q. What is the first thing to do on discovering that you have low water? A. Pull out the fire. Q. Would it be safe to open the safety valve at such time? A. No. Q. Why not? A. It would relieve the pressure on the water which being allowed to flow over the excessive hot iron would flash into steam, and might cause an explosion. Q. Why do boilers sometimes explode just on the point of starting the engine? A. Because starting the engine has the same effect as opening the safety valve. Q. Are there any circumstances under which an engineer is justified in allowing the water to get low? A. No. Q. Why do they sometimes do it? A. From carelessness or ignorance. Q. May not an engineer be deceived in the gauge of water? A. Yes. Q. Is he to be blamed under such circumstances? A. Yes. Q. Why? A. Because if he is deceived by it it shows he has neglected something. Q. What is meant by "Priming." A. It is the passing of water in visible quantities into the cylinder with the steam. Q. What would you consider the first duty of an engineer on discovering that the water was foaming or priming A. Open the cylinder cocks at once, and throttle the steam. Q. Why would you do this? A. Open the cocks to enable the water to escape, and throttle the steam so that the water would settle. Q. Is foaming the same as priming? A. Yes and no. Q. How do you make that out? A. A boiler may foam without priming, but it can't prime without first foaming.. Q. Where will you first discover that the water is foaming? A. It will appear in the glass gauge, the glass will have a milky appearance and the water will seem to be running down from the top, There will be a snapping or cracking in the cylinder as quick as priming begins. Q. What causes a boiler to foam? A. There are a number of causes. It may come from faulty construction of boiler; it may have insufficient steam room. It may be, and usually is, from the use of bad water, muddy or stagnant water, or water containing any soapy substance. Q. What would you do after being bothered in this way? A. Clean out the-boiler and get better water if possible. Q. How would you manage your pumps while the water was foaming. A. Keep them running full. Q. Why? A. In order to make up for the extra amount of water going out with the steam. Q. What is "cushion?" A. Cushion is steam retained or admitted in front of the piston head at the finish of stroke, or when the engine is on "center." Q. What is it for? A. It helps to overcome the "inertia" and momentum of the reciprocating parts of the engine, and enables the engine to pass the center without a jar. Q. How would you increase the cushion in an engine? A. By increasing the lead. Q. What is lead? A. It is the amount of opening the port shows on steam end of cylinder when the engine is on dead center. Q. Is there any rule for giving an engine the proper lead? A. No. Q. Why not? A. Owing to their variation in construction, speed, etc. Q. What would you consider the proper amount of lead, generally. A. From I/32 to I/I6. Q. What is "lap?" A. It is the distance the valve overlaps the steam ports when in mid position. Q. What is lap for? A. In order that the steam may be worked expansively. Q. When does expansion occur in a cylinder? A. During the time between which the port closes and the point at which the exhaust opens. Q. What would be the effect on an engine if the exhaust opened too soon? A. It would greatly lessen the power of the engine. Q. What effect would too much lead have. A. It would also weaken the engine, as the steam would enter before the piston had reached the end of the stroke, and would tend to prevent it passing the center. Q. What is the stroke of an engine? A. It is the distance the piston travels in the cylinder. Q. How do you find the speed of a piston per minute? A. Double the stroke and multiply it by the number of revolutions a minuet. Thus an engine with a 12 inch stroke would travel 24 inches, or 2 feet, at a revolution. If it made 200 revolutions a minute, the travel of piston would be 400 feet a minute. Q. What is considered a horse power as applied to an engine? A. It is power sufficient to lift 33,000 pounds one foot high in one minute. Q. What is the indicated horse power of an engine? A. It is the actual work done by the steam in the cylinder as shown by an indicator. Q. What is the actual horse power? A. It is the power actually given off by the driving belt and pulley. Q. How would you find the horse power of an engine? A. Multiply the area of the piston by the average pressure, less 5; multiply this product by the number of feet the piston travels per minute; divide the product by 33,000; the result will be horse power of the engine. Q. How will you find the area of piston? A. Square the diameter of piston and multiply it by .7854. Q. What do you mean by squaring the diameter? A. Multiplying it by itself. If a cylinder is 6 inches in diameter, 36 multiplied by .7854, gives the area in square inches. Q. What do you mean by average pressure? A. If the pressure on boiler is 60 pounds, and the engine is cutting off at 1/2 stroke, the pressure for the full stroke would be 50 pounds. Q. Why do you say less 5 pounds? A. To allow for friction and condensation. Q. What is the power of a 7 x 10 engine, running 200 revolutions, cutting off at 1/2 stroke with 60 pounds steam? A. 7 x 7 = 49 x .7854 = 38.4846. The average pressure of 60 pounds would be 50 pounds less 5 = 45 pounds; 38-4846 x 45 = 1731.8070 x .333 1/3, (the number of feet the piston travels per minute) 577,269.0000 by 33,000=17 1/2 horse power. Q. What is a high pressure engine? A. It is an engine using steam at a high pressure and exhausting into the open air. Q. What is a low pressure engine? A. It is one using steam at a low pressure and exhausting into a condenser, producing a vacuum, the piston being under steam pressure on one side and vacuum on the other. Q. What class of engines are farm engines? A. They are high pressure. Q. Why? A. They are less complicated and less expensive. Q. What is the most economical pressure to carry on high pressure engine? A. From 90 to 110 pounds. Q. Why is high pressure more economical than low pressure? A. Because the loss is greater in low pressure owing to the atmospheric pressure. With 45 pounds steam the pressure from the atmosphere is 15 pounds, or 1/3, leaving only 30 pounds of effective power; while with 90 pounds the atmospheric pressure is only 1-6 of the boiler pressure. Q. Does it require any more fuel to carry I00 pounds than it does to carry 60 pounds? A. It don't require quite as much. Q. If that is the case why not increase the pressure beyond this and save more fuel? A. Because we would soon pass the point of safety in a boiler, and the result would be the loss of life and property. Q. What do you consider a safe working pressure on a boiler? A. That depends entirely on its diameter. While a boiler of 30 inches in diameter 3/8 inch iron would carry I40 pounds, a boiler of the same thickness 80 inches in diameter would have a safe working pressure of only 50 pounds, which shows that the safe working pressure decreases very rapidly as we increase the diameter of boiler. This is the safe working pressure for single riveted boilers of this diameter. To find the safe working pressure of a double riveted boiler of same diameter multiply the safe pressure of the single riveted by 70, and divide by 56, will give a safe pressure of a double riveted boiler. Q. Why is a steel boiler superior to an iron boiler? A. Because it is much lighter and stronger. Q. Does boiler plate become stronger or weaker as it becomes heated? A. It becomes tougher or stronger as it is heated, till it reaches a temperature Of 550 degrees when it rapidly decreases its power of resistance as it is heated beyond this temperature. Q. How do you account for this? A. Because after you pass the maximum temperature of 550 degrees, the more you raise the temperature the nearer you approach its fusing point when its tenacity or resisting power is nothing. Q. What is the degree of heat necessary to fuse iron? A. 2912 degrees. Q. Steel? A. 2532 degrees. Q. What class of boilers are generally used in a threshing engine? A. The flue boiler and the tubular boiler. Q. About what amount of heating and grate surface is required per horse power in a flue boiler. A. About 15 square feet of heating surface and 3/4 square feet of grate surface. Q. What would you consider a fair evaporation in a flue boiler? A. Six pounds of water to I pound of coal. Q. How do these dimensions compare in a tubular boiler. A. A tubular boiler will require I/4 less grate surface, and will evaporate about 8 pounds of water to I pound of coal. Q. Which do you consider the most available? A. The tubular boiler. Q. Why? A. It is more economical and is less liable to "collapse?" Q. What do you mean by "collapse?" A. It is a crushing in of a flue by external pressure. Q. Is a tube of a large diameter more liable to collapse than one of small diameter? A. Yes. Q. Why? A. Because its power of resistance is much less than a tube of small diameter. Q. Is the pressure on the shell of a boiler the same as on the tubes? A. No. Q. What is the difference? A. The shell of boiler has a tearing or internal pressure while the tubes have a crushing or external pressure. Q. What causes an explosion? A. An explosion occurs generally from low water, allowing the iron to become overheated and thereby weakened and unable to withstand the pressure. Q. What is a "burst?" A. It is that which occurs when through any defect the water and steam are allowed to escape freely without further injury to boiler. Q. What is the best way to prevent an explosion or burst? A. (I) Never go beyond a safe working pressure. (2) Keep the boiler clean and in good repair. (3) Keep the safety valves in good shape and the water at its proper height. Q. What is the first thing to do on going to your engine in the morning? A. See that the water is at its proper level. Q. What is the proper level? A. Up to the second gauge. Q. When should you test or try the pop valve? A. As soon as there is a sufficient pressure. Q. How would you start your engine after it had been standing over night? A. Slowly. Q. Why? A. In order to allow the cylinder to become hot, and that the water or condensed steam may escape without injury to the cylinder. Q. What is the last thing to do at night? A. See that there is plenty of water in boiler, and if the weather is cold drain all pipes. Q. What care should be taken of the fusable plug? A. Keep it scraped clean, and not allow it to become corroded on top. Q. What is a fusible plug? A. It is a hollow cast plug screwed into the crown sheet or top of fire box, and having the hollow or center filled with lead or babbit. Q. Is such a plug a protection to a boiler? A. It is if kept in proper condition. Q. Can you explain the principle of the fusible or soft plug as it is sometimes called? A. It is placed directly over the fire, and should the water fall below the crown sheet the lead fuses or melts and allows the steam to flow down on top of the fire, destroys the heat and prevents the burning of crown sheet. Q. Why don't the lead fuse with water over it? A. Because the water absorbs the heat and prevents it reaching the fusing point. Q. What is the fusing point of lead? A. 618 degrees. Q. Is there any objection to the soft plug? A. There is, in the hands of some engineers. Q. Why? A. It relieves him of the fear of a dry crown sheet, and gives him an apparent excuse for low water. Q. Is this a real or legitimate objection? A. It is not. Q. What are the two distinct classes of boilers? A. The externally and internally fired boilers. Q. Which is the most economical? A. The internally fired boiler. Q. Why? A. Because the fuel is all consumed in close contact with the sides of furnace and the loss from radiation is less than in the externally fired. Q. To what class does the farm or traction engine belong? A. To the internally fired. Q. How would you find the H.P. of such a boiler? A. Multiply in inches the circumference or square of furnace, by its length, then multiply, the circumference of one tube by its total length, and this product by the number of tubes also taking into account the surface in tube sheet, add these products together and divide by I44, this will give you the number of square feet of heating surface in boiler. Divide this by 14 or 15 which will give the H.P. of boiler. Q. Why do you say 14 or 15? A. Because some claim that it requires 14 feet of heating surface to the H.P. and others 15. To give you my personal opinion I believe that any of the standard engines today with good coal and properly handled, will and are producing 1 H.P. for as low as every 10 feet of surface. But to be on the safe side it is well to divide by 15 to get the H.P. of your boiler, when good and bad fuel is considered. Q. How would you find the approximate weight of a boiler by measurement? A. Find the number of square feet in surface of boiler and fire box, and as a sheet of boiler iron or steel 1/16 of an inch thick, and one foot square, weighs 2.52 pounds, would multiply the number of square feet by 2.52 and this product by the number of 16ths or thickness of boiler sheet, which would give the approximate, or very near the weight of the boiler. Q. What would you recognize as points in a good engineer. A. A good engineer keeps his engine clean, washes the boiler whenever he thinks it needs it. Never meddles with his engine, and allows no one else to do so. Goes about his work quietly, and is always in his place, only talks when necessary, never hammers or bruises any part of his engine, allows no packing to become baked or burnt in the stuffing box or glands, renews them as quick as they show that they require it. Never neglects to oil, and then uses no more than is necessary. He carries a good gauge of water and a uniform pressure of steam. He allows no unusual noise about his engine to escape his notice he has taught his ear to be his guide. When a job is about finished you will see him cleaning his ash pan, getting his tools together, a good fire in fire box, in fact all ready to go, and he looses no time after the belt is thrown off. He hooks up to his load quietly, and is the first man ready to go. *Q. When the piston head is in the exact center of cylinder, is the engine on the quarter? *A. It is supposed to be, but is not. *Q. Why not? A. The angularity of the rod prevents it reaching the quarter. *Q. Then when the engine is on the exact quarter what position does the piston head occupy? A. It is nearest the end next to crank. Q. If this is the case, which end of cylinder is supposed to be the stronger? A. The opposite end, or end furtherest from crank. Q. Why? A. Because this end gets the benefit of the most travel, and as it makes it in the same time, it must travel faster. *Q. At what part of the cylinder does the piston head reach the greatest speed? A. At and near the center. *Q. Why? Figure this out for yourself. *Note. The above few questions are given for the purpose of getting you to notice the little peculiarities of the crank engine, and are not to be taken into consideration in the operation of the same. Q. If you were on the road and should discover that you had low water, what would you do? A. I would drop my load and hunt a high place for the front end of my engine, and would do it quickly to. Q. If by some accident the front end of your engine should drop down allowing the water to expose the crown sheet, what would you do? A. If I had a heavy and hot fire, would shovel dirt into the fire and smother it out. Q. Why would you prefer this to drawing the fire? A. Because it would reduce the heat at once, instead of increasing it for a few minutes while drawing out the hot bed of coals, which is a very unpleasant job. Q. Would you ever throw water in the fire box? A. No. It might crack the side sheets, and would most certainly start the flues. Q. You say, in finding low water while on the road, you would run your engine with the front end on high ground. Why would you do this? A. In order that the water would raise over the crown sheet, and thus make it safe to pump up the water. Q. While your engine was in this shape would you not expose the front end of flues'? A. Yes, but as the engine would not be working this would do no damage. Q. If you were running in a hilly country how would you manage the boiler as regards water? A. Would carry as high as the engine would allow, without priming. Q. Suppose you had a heavy load or about all you could handle, and should approach a long steep hill, what condition should the water and fire be to give you the most advantage? A. A moderately low gauge of water and a very hot fire. Q. Why a moderately low gauge of water? A. Because the engine would not be so liable to draw the water or prime in making the hard pull. Q. Why a very hot fire? A. So I could start the pumps full without impairing or cutting the pressure. Q. When would you start your pump? A. As soon as fairly started up the hill. Q. Why? A. As most hills have two sides, I would start them full in order to have a safe gauge to go down, without stoping to pump up. Q. What would a careful engineer do before starting to pull a load over a steep hill? A. He would examine his clutch, or gear pin. Q. How would you proceed to figure the road speed of traction. A. Would first determine the circumference of driver, then ascertain how many revolutions the engine made to one of the drivers. Multiply the number of revolutions the engine makes per minute by 60, this will give the number of revolutions of engine per hour. Divide this by the number of revolutions the engine makes to the drivers once, and this will give you the number of revolutions the drivers will make in one hour, and multiplying this by the circumference of driver in feet, and it will tell you how many feet your engine is traveling per hour, and this divided by 5280, the number of feet in a mile, would tell you just what speed your engine would make on the road. THINGS HANDY FOR THE ENGINEER ____________ The first edition of this work brought me a great many letters asking where certain articles could be procured, what I would recommend, etc. These questions required attention and as the writers had bought and paid for their book it was due them that they get the benefit of my experience, as nothing is so discouraging to the young engineer as to be continually annoyed by unreliable and inferior fittings used more or less on all engines. I have gone over my letter file and every article asked for will be taken up in the order, showing the relative importance of each article in the minds of engineers. For instance, more letters reached me asking for a good brand of oil than any other one article. Then comes injectors, lubricators have third place, and so on down the list. Now without any intention of advertising anybody's goods I will give you the benefit of my years of experience and will be very careful not to mention or recommend anything which is not strictly first class, at least so in my opinion, and as good as can be had in its class, yet in saying that these articles are good does not say that others are not equally as good. I am simply anticipating the numerous letters I otherwise would receive and am answering them in a lump bunch. If you have no occasion to procure any of these articles, the naming of them will do no harm, but should you want one or more you will make no mistake in any one of them. OIL As I have stated, more engineers asked for a good brand of oil than for any other one article and I will answer this with less satisfaction to myself than any other for this reason: You may know what you want, but you do not always get what you call for. Oil is one of those things that cannot be branded, the barrel can, but then it can be filled with the cheapest stuff on the market. If you can get Capital Cylinder Oil your valve will give you no trouble. If you call for this particular brand and it does not give you satisfaction don't blame me or the oil, go after the dealer; he did not give you what you called for. The same can be said of Renown Engine Oil. If you can always have this oil you will have no fault to find with its wearing qualities, and it will not gum on your engine, but as I have said, you may call for it and get something else. If your valve or cylinder is giving you any trouble and you have not perfect confidence in the dealer from whom you usually get your cylinder oil send direct to The Standard Oil Company for some Capital Cylinder Oil and you will get an oil that will go through your cylinder and come out the exhaust and still have some staying qualities to it. The trouble with so much of the so called cylinder oil is that it is so light that the moment it strikes the extreme heat in the steam chest it vaporizes and goes through the cylinder in the form of vapor and the valve and cylinder are getting no oil, although you are going through all the necessary means to oil them. It is somewhat difficult to get a young engineer to understand why the cylinder requires one grade of oil and the engine another. This is only necessary as a matter of economy, cylinder or valve oil will do very well on the engine, but engine oil will not do for the cylinder. And as a less expensive oil will do for the engine we therefore use two grades of oil. Engine oil however should be but little lower in quality than the cylinder oil, owing to the proximity of the bearings to the boiler, they are at all times more or less heated, and require a much heavier oil than a journal subject only to the heat of its own friction. The Renown Engine Oil has the peculiarity of body or lasting qualities combined with the fact that it does not gum on the hot iron and allows the engine to be wiped clean. INJECTORS The next in the list of inquiries was for a reliable injector. I was not surprised at this for up to a few years ago there were a great many engines running throughout the country with only the independent or cross-head pump, and engineers wishing to adopt the injector naturally want the best, while others had injectors more or less unsatisfactory. In replying to these letters I recommend one of three or four different makes (all of which I had found satisfactory) with a request that the party asking for same should write to me if the injector proved unsatisfactory in any way. Of all the letters received, I never got one stating any objection to either the Penberthy or the Metropolitan. This fact has led me to think that probably my reputation as a judge of a good article was safer by sticking to the two named, which I shall do until I know there is something better. This does not mean that there are not other good injectors, but I am telling you what I know to be good, and not what may be good. The fact that I never received a single complaint from either of them was evidence to me that the makers of these two injectors are very careful not to allow any slighting of the work. They therefore get out no defective injectors. The Penberthy is made by The Penberthy Injector Co., of Detroit, Mich., and the Metropolitan by The Hayden & Derby Mfg. Co., New York, N. Y. SIGHT FEED LUBRICATOR These come next in the long list of inquiries and wishing to satisfy myself as to the relative superiority of various cylinder Lubricators, I resorted to the same method as persued in regard to injectors. This method is very satisfactory to me from the fact that it gives us the actual experience of a class of engineers who have all conditions with which to contend, and especially the unfavorable conditions. I have possibly written more letters in answer to such questions as: "Why my Lubricator does this or that; and why it don't do so and so?" than of any other one part of an engine, (as a Sight Feed Lubricator might in this day be considered a part of an engine.) Of all the queries and objections made of the many Lubricators, there are two showing the least trouble to the operator. There are the Wm. Powell Sight Feed Lubricator (class "A") especially adapted to traction and road engines owing to the sight-glass being of large diameter, which prevents the drop touching the side of glass, while the engine is making steep grades and rough uneven roads, made by The Wm. Powell Co., Cincinnati, O., and for sale by any good jobbing house, and the Detroit Lubricator made by the Detroit Lubricator Co., of Detroit, Mich. I have never received a legitimate objection to either of these two Lubricators, but I received the same query concerning both, and this objection, if it may be called such, is so clearly no fault of the construction or principle of the Lubricator that I have concluded that they are among if not actually the best sight feed Lubricator on the market to-day. The query referred to was: "Why does my glass fill with oil?" Now the answer to this is so simple and so clearly no fault of the Lubricator that I am entirely satisfied that by recommending either of these Lubricators you will get value received; and here is a good place to answer the above query. If you have run a threshing engine a season or part of a season you have learned that it is much easier to get a poor grade of oil than a good one, yet your Lubricator will do this at times even with best of oil, and the reason is due to the condition of the feed nozzle at the bottom of the feed glass. The surface around the needle point in the nozzle becomes coated or rough from sediment from the oil. This coating allows the drop to adhere to it until it becomes too large to pass up through the glass without striking the sides and the glass becomes blurred and has the appearance of being full of oil, so in a measure to obviate this Powell's Lubricators are fitted with 3/4 glasses-being of large internal diameter. The permanent remedy however is to take out the glass and clean the nozzle with waste or a rag, rubbing the points smooth and clean. The drop will then release itself at a moderate size and pass up through the glass without any danger of striking the sides. However, if the Lubricator is on crooked it may do this same thing. The remedy is very simple-straighten it up. While talking of the various appliances for oiling your engine you will pardon me if I say that I think every traction engine ought to be supplied with an oil pump as you will find it very convenient for a traction engine especially on the road. For instance, should the engine prime to any great extent your cylinder will require more oil for a few minutes than your sight feed will supply, and here is where, your little pump will help you out. Either the Detroit or Powell people make as good an article of this kind as you can find anywhere, and can furnish you either the glass or metal body. Hard Grease and a good Cup come next. In my trips over various parts of the country I visit a great many engineers and find a great part of them using hard grease and I also find the quality varying all the way from the very best down to the cheapest grade of axle grease. The Badger Oil I think is the best that can be procured for this purpose, and while I do not know just who makes it, you will probably have but little trouble in finding it, and if you are looking for a first class automatic cup for your wrist pin or crank box get the Wm. Powell Cup from any jobbing supply house. These people also make a very neat little attachment for their Class "A" Lubricator which is a decided convenience for the engineer, and is called a "Filler." It consists of a second reservoir or cup, of about the same capacity of the reservoir of Lubricator, thus doubling the capacity. It is attached at the filling plug, and is supplied with a fine strainer, which catches all dirt, and grit, allowing only clear oil to enter the lubricator, and by properly manipulating the little shut-off valve the strainer can be removed and cleaned and the cup refilled without disturbing the working of the Lubricator. This little attachment will soon be in general use. BOILER FEEDERS Injectors have a dangerous rival in the Moore Steam Pump or boiler feeder for traction engines, and the reason this little pump is not in more general use is the fact that among the oldest methods for feeding a boiler is the independent steam pump and they were always unsatisfactory from the fact that they were a steam engine within themselves, having a crank or disc, flywheel, eccentric, eccentric yoke, valve, valve stem, crosshead, slides, and all the reciprocating parts of a complete engine. Being necessarily very small, these parts of course are very frail and delicate, were easily broken or damaged by the rough usage to which they were subjected while bumping around over rough roads on a traction engine. The Moore Pump, manufactured by The Union Steam Pump Company, of Battle Creek, Mich., is a complete departure from the old steam engine pump, and if you take any interest in any of the novel ways in which steam can be utilized send to them for a circular and sectional cuts and you can spend several hours very profitably in determining just how the direct pressure from the boiler can be made to drive the piston head the full stroke of cylinder, open exhaust port, shift the valve open steam port and drive the piston back again and repeat the operation as long as the boiler pressure is allowed to reach the pump and yet have no connection whatever with any of the reciprocating parts of the pump, and at the same time lift and force water into the boiler in any quantity desired. Another novel feature in this "little boiler feeder" is that after the steam has acted on the cylinder it can be exhausted directly into the feed water, thus utilizing all its heat to warm the water before entering the boiler. Now it required a certain number of heat units to produce this steam which after doing its work gives back all its heat again to the feed water and it would be a very interesting problem for some of the young engineers, as well as the old ones, to determine just what loss if any is sustained in this manner of supplying a boiler. If you are thinking of trying an independent pump, don't be afraid of this one. I take particular pride in recommending anything that I have tried myself, and know to be as recommended. And a boiler feeder of this kind has all the advantage of the injector, as it will supply the boiler without running the engine, and it has the advantage over the injector, in not being so delicate, and will work water that can not be handled by the best of injectors. We have very frequently had this question put to us: "Ought I to grease my gearing?" If I said "yes," I had an argument on my hands at once. If I said "no," some one would disagree just as quickly, and how shall I answer it to the satisfaction of most engineers of a traction engine? I always say what I have to say and stay by it until I am convinced of the error. Now some of you will smile when I say that the only thing for gear where there is dust, is "Mica Axle Grease." And you smile because you don't know what it is made of, but think it some common grease named for some old saint, but that is not the case. If these people who make this lubricant would give it another name, and get it introduced among engineers, nothing else would be used. You have seen it advertised for years as an axle grease and think that is all it is good for; and there is where you make a mistake. It is made of a combination of solid lubricant and ground or pulverized mica, that is where it gets its name, and nothing can equal mica as a lubricant if you could apply it to your gear; and to do this it has been combined with a heavy grease. This in being applied to the gear retains the small particles of mica, which soon imbed themselves in every little abrasion or rough place in the gearing, and the surface quickly becomes hard and smooth throughout the entire face of the engaging gear, and your gear will run quiet, and if your gearing is not out of line will stop cutting if applied in time. It will run dry and dust will not collect on the surface of your cogs, and after a coating is once formed it should never be disturbed by scraping the face of the gear, and a very little added from time to time will keep your gear in fine shape. Its name is against it and if the makers would take a tumble to themselves and call it "Mica Oil" or some catchy name and get it introduced among the users of tight gearing, they would sell just as much axle grease and all the grease for gearings. FORCE FEED OILER Force feed oiler come next on the list. This is something not generally understood by engineers of traction and farm engines, and accounts for it being so far down the list. But we think it will come into general use within a few years, as an oiler of this kind forces the oil instead of depending on gravity. The Acorn Brass Works of Chicago make a very unique and successful little oiler which forces a small portion of oil in a spray into the valve and cylinder, and repeats the operation at each stroke of the engine, and is so arranged that it stops automatically as soon as the oil is out of the reservoir; and at once calls the attention of the engineer to the fact, and it can be regulated to throw any quantity of oil desired. Is made for any size or make of engine. SPEEDER One of the little things, that every engineer ought to have is a Motion counter or speeder. Of course, you can count the revolutions of your engine, but you frequently want to know the speed of the driven pulley, cylinder for instance: When you know the exact size of engine pulley and your cylinder pulley, and the exact speed of your engine, and there was no such thing as the slipping of drive belt, you could figure the speed of your cylinder, but by knowing this and then applying the speeder, you can determine the loss by comparing the figured speed with the actual speed shown by the speeder. If you have a good speeder you can make good use of it every day you run machinery. If you want one you want the best and there is nothing better than the one made by The Tabor Manufacturing Co., of Philadelphia, Pa. We use no other. You will see their advertisement in the American Thresherman. SPARK ARRESTER But one article in the entire list did I find to be sectional, and that was for a spark arrester. These inquiries were all without exception from the wooded country, that is, from a section where it is cheaper to burn wood than coal. There is nothing strange that parties running engines in these sections should ask for a spark arrester, as builders of this class of engines usually supply their engines with a "smoke stack", with little or no reference to safety from fire. This being recognized by some genius in one of our wooded states who has profited by it and has produced a "smoke stack" which is also a "spark arrester." This stack is a success in every sense of the word, and is made for any and all styles of farm and saw mill engines. It is made by the South Bend Spark Arrester Co., of South Bend, Indiana, and if you are running an engine and firing with wood or straw, don't run too much risk for the engineer usually comes in for a big share of the blame if a fire is started from the engine. And as the above company make a specialty of this particular article, you will get something reliable if you are in a section where you need it. LIFTING JACK Next comes enquiries for a good lifting Jack. This would indicate that the boys had been getting their engine in a hole, but there are a great many times when a good Jack comes handy, and it will save its cost many times every season. Too many engineers forget that when he is fooling around that he is the only one losing time. The facts are the entire crew are doing nothing, besides the outfit is making no money unless running. You want to equip yourself with any tool that will save time. The Barth Mfg, Co., of Milwaukee, make a Jack especially adapted to this particular work, and every engine should have a "mascot" in the shape of a lifting Jack. Now before dropping the subject of "handy things for an engineer," I want to say to the engineer who takes pride in his work, that if you would enjoy a touch of high life in engineering, persuade your boss, if you have one, to get you a Fuller Tender made by the Parson's Band Cutter and Feeder Co., Newton, Iowa, and attach to your engine. It may look a little expensive, but a luxury usually costs something and by having one you will do away with a great deal of the rough and tumble part of an engineers life. And if you want to keep yourself posted as to what is being done by other threshermen throughout the world, read some good "Threshermen's Home journal." The American Thresherman for instance is the "warmest baby in the bunch." And if anything new under the sun comes out you will find it in the pages of this bright and newsy journal. Keep to the front in your business. Your business is as much a business as any other profession, and while it may not be quite as remunerative as a R. R. attorney, or the president of a life insurance company it is just as honorable, and a good engineer is appreciated by his employer just as much as a good man in any other business. A good engineer can not only always have a job, but he can select his work. That is if there is any choice of engines in a neighborhood the best man gets it. SOMETHING ABOUT PRESSURE _________ Now before bringing this somewhat lengthy lecture to a close, (for I consider it a mere lecture, a talk with the boys) I want to say something more about pressure. You notice that I have not advocated a very high pressure; I have not gone beyond 125 lbs. and yet you know and I know that very much higher pressure is being carried wherever the traction engine is used, and I want to say that a very high pressure is no gauge or guarantee of the intelligence of the engineer. The less a reckless individual knows about steam the higher pressure he will carry. A good engineer is never afraid of his engine without a good reason, and then he refuses to run it. He knows something of the enormous pressure in the boiler, while the reckless fellow never thinks of any pressure beyond the I00 or I40 pounds that his gauge shows. He says, "'O! That,' that aint much of a pressure, that boiler is good for 200 pounds." It has never dawned on his mind (if he has one) that that I40 pounds mean I40 pounds on every square inch in that boiler shell, and I40 on each square inch of tube sheets. Not only this but every square inch in the shell is subjected to two times this pressure as the boiler has two sides or in other words, each square inch has a corresponding opposite square inch, and the seam of shell must sustain this pressure, and as a single riveted boiler only affords 62 per cent of the strength of solid iron. It is something that every engineer ought to consider. He ought to be able to thoroughly appreciate this almost inconceivable pressure. How many engineers are today running 18 and 20 horse power engines that realizes that a boiler of this diameter is not capable of sustaining the pressure he had been accustomed to carry in his little 26 or 30 inch boiler? On page 114 You will get some idea of the difference in safe working pressure of boilers, of different diameters. On the other hand this is not intended to make you timid or afraid of your engine, as there is nothing to be afraid of if you realize what you are handling, and try to comprehend the fact that your steam gauge represents less than one 1-1000 part of the power you have under your management. You never had this put to you in this light before, did you? If you thoroughly appreciate this fact and will try to comprehend this power confined in your boiler by noting the pressure, or power exerted by your cylinder through the small supply pipe, you will soon be an engineer who will only carry a safe and economical pressure, and if there comes a time when it is necessary to carry a higher pressure, you will be an engineer who will set the pop back again, when or as soon as this extra pressure is not necessary. If I can get you to comprehend this power proposition no student of "Rough and Tumble Engineering" will ever blow up a boiler. When I started out to talk engine to you I stated plainly that this book would not be filled up with scientific theories, that while they were very nice they would do no good in this work. Now I am aware that I could have made a book four times as large as this and if I had, it would not be as valuable to the beginner as it is now. From the fact that there is not a problem or a question contained in it that any one who has a common school education can not solve or answer without referring to any textbooks The very best engineer in the country need not know any more than he will find in these pages. Yet I don't advise you to stop here, go to the top if you have the time and opportunity. Should I have taken up each step theoretically and given forms, tables, rules and demonstrations, the young engineer would have become discouraged and would never have read it through. He would have become discouraged because he could not understand it. Now to illustrate what I mean, we will go a little deeper and then still deeper, and you will begin to appreciate the simple way of putting the things which you as a plain engineer are interested in. For example on page 114 we talked about the safe working pressure of different sized boilers. It was most likely natural for you to say "How do I find the safe working pressure?" Well, to find the safe working pressure of a boiler it is first necessary to find the total pressure necessary to burst the boiler. It requires about twice as much pressure to tear the ends out of a boiler as it does to burst the shell, and as the weakest point is the basis for determining the safe pressure, we will make use of the shell only. We will take for example a steel boiler 32 inches in diameter and 6 ft. long, 3/8 in. thick, tensile strength 60,000 lbs. The total pressure required to burst this shell would be the area exposed times the pressure. The thickness multiplied by the length then by 2 (as there are two sides) then by the tensile strength equals the bursting pressure: 3/8 x 72 X 2 x 60,000 = 3,240,000 the total bursting pressure and the pressure per square inch required to burst the shell is found by dividing the total bursting pressure 3,240,000 pounds by the diameter times the length 3,240,000 / (32 x 72) = 1406 lbs. It would require 1406 lbs. per square inch to burst this shell if it were solid, that is if it had no seam, a single seam affords 62 per cent of the strength of shell, 1406 x .62 = 871 lbs. to burst the seam if single riveted; add 20 per cent if double riveted. To determine the safe working pressure divide the bursting pressure of the weakest place by the factor of safety. The United States Government use a factor of 6 for single riveted and add 20 per cent for double riveted, 871 / 6 = 145 lbs. the safe working pressure of this particular boiler, if single riveted and 145 + 20 per cent=174 double riveted. Now suppose you take a boiler the same length and of the same material, but 80 inches in diameter. The bursting pressure would be 3,240,000 / (80 x 72) = 560 lbs., and the safe working pressure would be 560 / 6 = 93 lbs. You will see by this that the diameter has much to do with the safe working pressure, also the diameter and different lengths makes a difference in working pressure. Now all of this is nice for you to know, and it may start you on a higher course, it will not make you handle your engine any better, but it may convince you that there is something to learn. Suppose we give you a little touch of rules, and formula in boiler making. For instance you want to know the percent of strength of single riveted and double riveted as compared to solid iron. Some very simple rules, or formula, are applicable. Find the percent of strength to the solid iron in a single-riveted seam, 1/4 inch plate, 5/8 inch rivet, pitched or spaced 2 inch centers. First reduce all to decimal form, as it simplifies the calculation; 1/4=.25 and 5/8 inch rivets will require 11/16 inch hole, this hole is supposed to be filled by the rivet, after driving, consequently this diameter is used in the calculation, 11/16 inches=.6875. First find the percent of strength of the sheet. P-D ----- The formula is P = percent. P = the pitch, D = the diameter of the rivet hole, percent = percent of strength of the solid iron. 2 -.6875 -------- Substituting values, 2 = .66. Now of course you understand all about that, but it is Greek to some people. So you see I have no apologies to make for following out my plain comprehensive talk, have not confused you, or lead you to believe that it requires a great amount of study to become an engineer. I mean a practical engineer, not a mechanical engineer. I just touch mechanical engineering to show you that that is something else. If you are made of the proper stuff you can get enough out of this little book to make you as good an engineer as ever pulled a throttle on a traction engine. But this is no novel. Go back and read it again, and ever time you read it you will find something you had not noticed before. INDEX ----- PART FIRST PAGE Tinkering Engineers . . . . . . . . . . . 5 PART SECOND Water Supply . . . . . . . . . . . . . . 31 PART THIRD What a Good Injector Ought to Do . . . 45 The Blower . . . . . . . . . . . . . . . 49 A Good Fireman . . . . . . . . . . . . 51 Wood . . . . . . . . . . . . . . . . . . 56 Why Grates Burn Out . . . . . . . . . . 57 PART FOUR Scale . . . . . . . . . . . . . . . . . 65 Clean Flues . . . . . . . . . . . . . . 67 PART FIVE Steam Gauge . . . . . . . . . . . . . . 72 How to Test a Steam Gauge . . . . . . . 74 Fusible Plug . . . . . . . . . . . . . . 76 Leaky Flues . . . . . . . . . . . . . . 79 PART SIX Knock in Engine . . . . . . . . . . . . 90 Lead . . . . . . . . . . . . . . . . . 92 Setting a Valve . . . . . . . . . . . . 94 How to Find the Dead Center . . . . . . 95 Lubricating Oil . . . . . . . . . . . . 103 A Hot Box . . . . . . . . . . . . . . . 109 PART SEVEN A Traction Engine on the Road . . . . . 111 Sand . . . . . . . . . . . . . . . . . 122 Friction Clutch . . . . . . . . . . . . 124 Something About Sight-Feed Lubricators 132 Two Ways of Reading . . . . . . . . . . 137 Some Things to Know . . . . . . . . . . 139 Things Handy for an Engineer . . . . . 159 Something About Pressure . . . . . . . . 184 
28160	----	[Transcriber's Notes: This is Paper 42 from the Smithsonian Institution United States National Museum Bulletin 240, comprising Papers 34-44, which will also be available as a complete e-book. The front material, introduction and relevant index entries from the Bulletin are included in each single-paper e-book. The Sections entitled "Alba F. Smith" and "Seth Wilmarth" appear in the original as boxed "side bars". They have been moved, along with Figure 13, from their original locations to the end of the paper to preserve the flow of the text. Typographical errors have been corrected as follows: p259: "as late as 1880 and has been under steam" (was stream). p267: "made with parabolic reflectors" (was parobolic).] SMITHSONIAN INSTITUTION UNITED STATES NATIONAL MUSEUM BULLETIN 240 [Illustration] SMITHSONIAN PRESS MUSEUM OF HISTORY AND TECHNOLOGY CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY _Papers 34-44_ _On Science and Technology_ SMITHSONIAN INSTITUTION · WASHINGTON, D.C. 1966 _Publications of the United States National Museum_ The scholarly and scientific publications of the United States National Museum include two series, _Proceedings of the United States National Museum_ and _United States National Museum Bulletin_. In these series, the Museum publishes original articles and monographs dealing with the collections and work of its constituent museums--The Museum of Natural History and the Museum of History and Technology--setting forth newly acquired facts in the fields of anthropology, biology, history, geology, and technology. Copies of each publication are distributed to libraries, to cultural and scientific organizations, and to specialists and others interested in the different subjects. The _Proceedings_, begun in 1878, are intended for the publication, in separate form, of shorter papers from the Museum of Natural History. These are gathered in volumes, octavo in size, with the publication date of each paper recorded in the table of contents of the volume. In the _Bulletin_ series, the first of which was issued in 1875, appear longer, separate publications consisting of monographs (occasionally in several parts) and volumes in which are collected works on related subjects. _Bulletins_ are either octavo or quarto in size, depending on the needs of the presentation. Since 1902 papers relating to the botanical collections of the Museum of Natural History have been published in the _Bulletin_ series under the heading _Contributions from the United States National Herbarium_, and since 1959, in _Bulletins_ titled "Contributions from the Museum of History and Technology," have been gathered shorter papers relating to the collections and research of that Museum. The present collection of Contributions, Papers 34-44, comprises Bulletin 240. Each of these papers has been previously published in separate form. The year of publication is shown on the last page of each paper. FRANK A. TAYLOR _Director, United States National Museum_ CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY: PAPER 42 THE "PIONEER": LIGHT PASSENGER LOCOMOTIVE OF 1851 IN THE MUSEUM OF HISTORY AND TECHNOLOGY _John H. White_ THE CUMBERLAND VALLEY RAILROAD 244 SERVICE HISTORY OF THE "PIONEER" 249 MECHANICAL DESCRIPTION OF THE "PIONEER" 251 [FOOTNOTES] [INDEX] [Illustration: Figure 1.--THE "PIONEER," BUILT IN 1851, shown here as renovated and exhibited in the Museum of History and Technology, 1964. In 1960 the locomotive was given to the Smithsonian Institution by the Pennsylvania Railroad through John S. Fair, Jr. (Smithsonian photo 63344B.)] _John H. White_ The "PIONEER": LIGHT PASSENGER LOCOMOTIVE of 1851 _In the Museum of History and Technology_ _In the mid-nineteenth century there was a renewed interest in the light, single-axle locomotives which were proving so very successful for passenger traffic. These engines were built in limited number by nearly every well-known maker, and among the few remaining is the 6-wheel "Pioneer," on display in the Museum of History and Technology, Smithsonian Institution. This locomotive is a true representation of a light passenger locomotive of 1851 and a historic relic of the mid-nineteenth century._ THE AUTHOR: _John H. White is associate curator of transportation in the Smithsonian Institution's Museum of History and Technology._ The "PIONEER" is an unusual locomotive and on first inspection would seem to be imperfect for service on an American railroad of the 1850's. This locomotive has only one pair of driving wheels and no truck, an arrangement which marks it as very different from the highly successful standard 8-wheel engine of this period. All six wheels of the _Pioneer_ are rigidly attached to the frame. It is only half the size of an 8-wheel engine of 1851 and about the same size of the 4--2--0 so common in this country some 20 years earlier. Its general arrangement is that of the rigid English locomotive which had, years earlier, proven unsuitable for use on U.S. railroads. These objections are more apparent than real, for the _Pioneer_, and other engines of the same design, proved eminently successful when used in the service for which they were built, that of light passenger traffic. The _Pioneer's_ rigid wheelbase is no problem, for when it is compared to that of an 8-wheel engine it is found to be about four feet less; and its small size is no problem when we realize it was not intended for heavy service. Figure 2, a diagram, is a comparison of the _Pioneer_ and a standard 8-wheel locomotive. Since the service life of the _Pioneer_ was spent on the Cumberland Valley Railroad, a brief account of that line is necessary to an understanding of the service history of this locomotive. _Exhibits of the "Pioneer"_ The _Pioneer_ has been a historic relic since 1901. In the fall of that year minor repairs were made to the locomotive so that it might be used in the sesquicentennial celebration at Carlisle, Pennsylvania. On October 22, 1901, the engine was ready for service, but as it neared Carlisle a copper flue burst. The fire was extinguished and the _Pioneer_ was pushed into town by another engine. In the twentieth century, the _Pioneer_ was displayed at the Louisiana Purchase Exposition, St. Louis, Missouri, in 1904, and at the Wheeling, West Virginia, semicentennial in 1913. In 1927 it joined many other historic locomotives at the Baltimore and Ohio Railroad's "Fair of the Iron Horse" which commemorated the first one hundred years of that company. From about 1913 to 1925 the _Pioneer_ also appeared a number of times at the Apple-blossom Festival at Winchester, Virginia. In 1933-1934 it was displayed at the World's Fair in Chicago, and in 1948 at the Railroad Fair in the same city. Between 1934 and March 1947 it was exhibited at the Franklin Institute, Philadelphia, Pennsylvania. The Cumberland Valley Railroad The Cumberland Valley Railroad (C.V.R.R.) was chartered on April 2, 1831, to connect the Susquehanna and Potomac Rivers by a railroad through the Cumberland Valley in south-central Pennsylvania. The Cumberland Valley, with its rich farmland and iron-ore deposits, was a natural north-south route long used as a portage between these two rivers. Construction began in 1836, and because of the level valley some 52 miles of line was completed between Harrisburg and Chambersburg by November 16, 1837. In 1860, by way of the Franklin Railroad, the line extended to Hagerstown, Maryland. It was not until 1871 that the Cumberland Valley Railroad reached its projected southern terminus, the Potomac River, by extending to Powells Bend, Maryland. Winchester, Virginia, was entered in 1890 giving the Cumberland Valley Railroad about 165 miles of line. The railroad which had become associated with the Pennsylvania Railroad in 1859, was merged with that company in 1919. By 1849 the Cumberland Valley Railroad was in poor condition; the strap-rail track was worn out and new locomotives were needed. Captain Daniel Tyler was hired to supervise rebuilding the line with T-rail, and easy grades and curves. Tyler recommended that a young friend of his, Alba F. Smith, be put in charge of modernizing and acquiring new equipment. Smith recommended to the railroad's Board of Managers on June 25, 1851, that "much lighter engines than those now in use may be substituted for the passenger transportation and thereby effect a great saving both in point of fuel and road repairs...."[1] Smith may well have gone on to explain that the road was operating 3- and 4-car passenger trains with a locomotive weighing about 20 tons; the total weight was about 75 tons, equalling the uneconomical deadweight of 1200 pounds per passenger. Since speed was not an important consideration (30 mph being a good average), the use of lighter engines would improve the deadweight-to-passenger ratio and would not result in a slower schedule. The Board of Managers agreed with Smith's recommendations and instructed him "... to examine the two locomotives lately built by Mr. Wilmarth and now in the [protection?] of Captain Tyler at Norwich and if in his judgment they are adequate to our wants ... have them forwarded to the road."[2] Smith inspected the locomotives not long after this resolution was passed, for they were on the road by the time he made the following report[3] to the Board on September 24, 1851: In accordance with a resolution passed at the last meeting of your body relative to the small engines built by Mr. Wilmarth I proceeded to Norwich to make trial of their capacity--fitness or suitability to the Passenger transportation of our Road--and after as thorough a trial as circumstances would admit (being on another Road than our own) I became satisfied that with some necessary improvements which would not be expensive (and are now being made at our shop) the engines would do the business of our Road not only in a manner satisfactory in point of speed and certainty but with greater ultimate economy in Expenses than has before been practised in this Country. [Illustration: Figure 2.--DIAGRAM COMPARING the _Pioneer_ (shaded drawing) with the _Columbia_, a standard 8-wheel engine of 1851. (Drawing by J. H. White.)] _Columbia_ Hudson River Railroad Lowell Machine Shop, 1852 Wt. 27-1/2 tons (engine only) Cyl. 16-1/2 x 22 inches Wheel diam. 84 inches _Pioneer_ Cumberland Valley Railroad Seth Wilmarth, 1851 12-1/2 tons 8-1/2 x 14 inches 54 inches After making the above trial of the Engines--I stated to your Hon. President the result of the trial--with my opinion of their Capacity to carry our passenger trains at the speed required which was decidedly in favor of the ability of the Engines. He accordingly agreed that the Engines should at once be forwarded to the Road in compliance with the Resolution of your Board. I immediately ordered the Engines shipped at the most favorable rates. They came to our Road safely in the Condition in which they were shipped. One of the Engines has been placed on the Road and I believe performed in such a manner as to convince all who are able to judge of this ability to perform--although the maximum duty of the Engines was not performed on account of some original defects which are now being remedied as I before stated. Within ten days the Engine will be able to run regularly with a train on the Road where in shall be enabled to judge correctly of their merits. An accident occurred during the trial of the Small Engine at Norwich which caused a damage of about $300 in which condition the Engine came here and is now being repaired--the cost of which will be presented to your Board hereafter. As to the fault or blame of parties connected with the accident as also the question of responsibility for Repairs are questions for your disposal. I therefore leave the matter until further called upon. The Expenses necessarily incurred by the trial of the Engines and also the Expenses of transporting the same are not included in the Statement herewith presented, the whole amount of which will not probably exceed $400.00. These two locomotives became the Cumberland Valley Railroad's _Pioneer_ (number 13) and _Jenny Lind_ (number 14). While Smith notes that one of the engines was damaged during the inspection trials, Joseph Winters, an employee of the Cumberland Valley who claimed he was accompanying the engine enroute to Chambersburg at the time of their delivery, later recalled that both engines were damaged in transit.[4] According to Winters a train ran into the rear of the _Jenny Lind_, damaging both it and the _Pioneer_, the accident occurring near Middletown, Pennsylvania. The _Jenny Lind_ was repaired at Harrisburg but the _Pioneer_, less seriously damaged, was taken for repairs to the main shops of the Cumberland Valley road at Chambersburg. [Illustration: Figure 3.--"PIONEER," ABOUT 1901, showing the sandbox and large headlamp. Note the lamp on the cab roof, now used as the headlight. (Smithsonian photo 49272.)] While there seems little question that these locomotives were not built as a direct order for the Cumberland Valley Railroad, an article[5] appearing in the _Railroad Advocate_ in 1855 credits their design to Smith. The article speaks of a 2--2--4 built for the Macon and Western Railroad and says in part: This engine is designed and built very generally upon the ideas, embodied in some small tank engines designed by A. F. Smith, Esq., for the Cumberland Valley road. Mr. Smith is a strong advocate of light engines, and his novel style and proportions of engines, as built for him a few years since, by Seth Wilmarth, at Boston, are known to some of our readers. Without knowing all the circumstances under which these engines are worked on the Cumberland Valley road, we should not venture to repeat all that we have heard of their performances, it is enough to say that they are said to do more, in proportion to their weight, than any other engines now in use. The author believes that the _Railroad Advocate's_ claim of Smith's design of the _Pioneer_ has been confused with his design of the _Utility_ (figs. 6, 7). Smith designed this compensating-lever engine to haul trains over the C.V.R.R. bridge at Harrisburg. It was built by Wilmarth in 1854. [Illustration: Figure 4.--MAP OF THE CUMBERLAND VALLEY Railroad as it appeared in 1919.] According to statements of Smith and the Board of Managers quoted on page 244, the _Pioneer_ and the _Jenny Lind_ were not new when purchased from their maker, Seth Wilmarth. Although of recent manufacture, previous to June 1851, they were apparently doing service on a road in Norwich, Connecticut. It should be mentioned that both Smith and Tyler were formerly associated with the Norwich and Worcester Railroad and they probably learned of these two engines through this former association. It is possible that the engines were purchased from Wilmarth by the Cumberland Valley road, which had bought several other locomotives from Wilmarth in previous years. It was the practice of at least one other New England engine builder, the Taunton Locomotive Works, to manufacture engines on the speculation that a buyer would be found; if no immediate buyers appeared the engine was leased to a local road until a sale was made.[6] [Illustration: Figure 5.--AN EARLY BROADSIDE of the Cumberland Valley Railroad.] Regarding the _Jenny Lind_ and _Pioneer_, Smith reported[7] to the Board of Managers at their meeting of March 17, 1852: The small tank engines which were purchased last year ... and which I spoke in a former report as undergoing at that time some necessary improvements have since that time been fairly tested as to their capacity to run our passenger trains and proved to be equal to the duty. The improvements proposed to be made have been completed only on one engine [_Jenny Lind_] which is now running regularly with passenger trains--the cost of repairs and improvements on this engine (this being the one accidentally broken on the trial) amounted to $476.51. The other engine is now in the shop, not yet ready for service but will be at an early day. [Illustration: Figure 6.--THE "UTILITY" AS REBUILT TO AN 8-WHEEL ENGINE, about 1863 or 1864. It was purchased by the Carlisle Manufacturing Co. in 1882 and was last used in 1896. (Smithsonian photo 36716F.)] [Illustration: Figure 7.--THE "UTILITY," DESIGNED BY SMITH A. F. and constructed by Seth Wilmarth in 1854, was built to haul trains across the bridge at Harrisburg, Pa.] [Illustration: Figure 8.--THE EARLIEST KNOWN ILLUSTRATION of the _Pioneer_, drawn by A. S. Hull, master mechanic of the Cumberland Valley Railroad in 1876. It depicts the engine as it appeared in 1871. (_Courtesy of Paul Westhaeffer._)] The _Pioneer_ and _Jenny Lind_ achieved such success in action that the president of the road, Frederick Watts, commented on their performance in the annual report of the Cumberland Valley Railroad for 1851. Watts stated that since their passenger trains were rarely more than a baggage car and two coaches, the light locomotives "... have been found to be admirably adapted to our business." The Cumberland Valley Railroad, therefore, added two more locomotives of similar design in the next few years. These engines were the _Boston_ and the _Enterprise_, also built by Wilmarth in 1854-1855. Watts reported the _Pioneer_ and _Jenny Lind_ cost $7,642. A standard 8-wheel engine cost about $6,500 to $8,000 each during this period. In recent years, the Pennsylvania Railroad has stated the _Pioneer_ cost $6,200 in gold, but is unable to give the source for this information. The author can discount this statement for it does not seem reasonable that a light, cheap engine of the pattern of the _Pioneer_ could cost as much as a machine nearly twice its size. [Illustration: Figure 9.--ANNUAL PASS of the Cumberland Valley Railroad issued in 1863.] [Illustration: Figure 10.--TIMETABLE OF THE Cumberland Valley Railroad for 1878.] Service History of the _Pioneer_ After being put in service, the _Pioneer_ continued to perform well and was credited as able to move a 4-car passenger train along smartly at 40 mph.[8] This tranquility was shattered in October 1862 by a raiding party led by Confederate General J. E. B. Stuart which burned the Chambersburg shops of the Cumberland Valley Railroad. The _Pioneer_, _Jenny Lind_, and _Utility_ were partially destroyed. The Cumberland Valley Railroad in its report for 1862 stated: The Wood-shop, Machine-shop, Black-smith-shop, Engine-house, Wood-sheds, and Passenger Depot were totally consumed, and with the Engine-house three second-class Engines were much injured by the fire, but not so destroyed but that they may be restored to usefulness. However, no record can be found of the extent or exact nature of the damage. The shops and a number of cars were burned so it is reasonable to assume that the cab and other wooden parts of the locomotive were damaged. One unverified report in the files of the Pennsylvania Railroad states that part of the roof and brick wall fell on the _Pioneer_ during the fire causing considerable damage. In June 1864 the Chambersburg shops were again burned by the Confederates, but on this occasion the railroad managed to remove all its locomotives before the raid. During the Civil War, the Cumberland Valley Railroad was obliged to operate longer passenger trains to satisfy the enlarged traffic. The _Pioneer_ and its sister single-axle engines were found too light for these trains and were used only on work and special trains. Reference to table 1 will show that the mileage of the _Pioneer_ fell off sharply for the years 1860-1865. TABLE 1.--YEARLY MILEAGE OF THE PIONEER (From Annual Reports of the Cumberland Valley Railroad) _Year_: _Miles_ 1852 3,182[a] 1853 20,722[b] 1854 18,087 1855 14,151 1856 20,998 1857 22,779 1858 29,094 1859 29,571 1860 4,824 1861 4,346 1862 ([c]) 1863 5,339 1864 224 1865 2,215 1866 20,546 1867 5,709 1868 13,626 1869 1,372 1870 ... 1871 2,102 1872 4,002 1873 3,721 1874 3,466 1875 636 1876 870 1877 406 1878 4,433 1879 ... 1880 8,306 1881 ([d]) --------- Total 244,727[e] FOOTNOTES TO TABLE 1: [a] Mileage 1852 for January to September (no record of mileage recorded in Annual Reports previous to 1852). [b] 15,000 to 20,000 miles per year was considered very high mileage for a locomotive of the 1850's. [c] No mileage reported for any engines due to fire. [d] Not listed on roster. [e] The Pennsylvania Railroad claims a total mileage of 255,675. This may be accounted for by records of mileages for 1862, 1870, and 1879. In 1871 the _Pioneer_ was remodeled by A. S. Hull, master mechanic of the railroad. The exact nature of the alterations cannot be determined, as no drawings or photographs of the engine previous to this time are known to exist. In fact, the drawing (fig. 8) prepared by Hull in 1876 to show the engine as remodeled in 1871 is the oldest known illustration of the _Pioneer_. Paul Westhaeffer, a lifelong student of Cumberland Valley R. R. history, states that according to an interview with one of Hull's descendants the only alteration made to the _Pioneer_ during the 1871 "remodeling" was the addition of a handbrake. The road's annual report of 1853 describes the _Pioneer_ as a six-wheel tank engine. The report of 1854 mentions that the _Pioneer_ used link motion. These statements are enough to give substance to the idea that the basic arrangement has survived unaltered and that it has not been extensively rebuilt, as was the _Jenny Lind_ in 1878. By the 1870's, the _Pioneer_ was too light for the heavier cars then in use and by 1880 it had reached the end of its usefulness for regular service. After nearly thirty years on the road it had run 255,675 miles. Two new passenger locomotives were purchased in 1880 to handle the heavier trains. In 1881 the _Pioneer_ was dropped from the roster, but was used until about 1890 for work trains. After this time it was stored in a shed at Falling Spring, Pennsylvania, near the Chambersburg yards of the C.V.R.R. Mechanical Description of the _Pioneer_ [Illustration: Figure 11.--"PIONEER," ABOUT 1901, scene unknown. (_Photo courtesy of Thomas Norrell._)] After the early 1840's the single-axle locomotive, having one pair of driving wheels, was largely superseded by the 8-wheel engine. The desire to operate longer trains and the need for engines of greater traction to overcome the steep grades of American roads called for coupled driving wheels and machines of greater weight than the 4--2--0. After the introduction of the 4--4--0, the single-axle engine received little attention in this country except for light service or such special tasks as inspection or dummy engines. [Illustration: Figure 12.--THE "PIONEER" IN CARLISLE, PA., 1901. (_Photo courtesy of Thomas Norrell._)] There was, however, a renewed interest in "singles" in the early 1850's because of W. B. Adams' experiments with light passenger locomotives in England. In 1850 Adams built a light single-axle tank locomotive for the Eastern Counties Railway which proved very economical for light passenger traffic. It was such a success that considerable interest in light locomotives was generated in this country as well as in England. Nearly 100 single-axle locomotives were built in the United States between about 1845-1870. These engines were built by nearly every well-known maker, from Hinkley in Boston to the Vulcan Foundry in San Francisco. Danforth Cooke & Co. of Paterson built a standard pattern 4--2--4 used by many roads. One of these, the _C. P. Huntington_, survives to the present time. The following paragraphs describe the mechanical details of the _Pioneer_ as it appears on exhibition in the Smithsonian Institution's new Museum of History and Technology. BOILER The boiler is the most important and costly part of a steam locomotive, representing one-fourth to one-third of the total cost. A poorly built or designed boiler will produce a poor locomotive no matter how well made the remainder of mechanism. The boiler of the _Pioneer_ is of the wagon-top, crownbar, fire-tube style and is made of a 5/16-inch thick, wrought-iron plate. The barrel is very small, in keeping with the size of the engine, being only 27 inches in diameter. While some readers may believe this to be an extremely early example of a wagon-top boiler, we should remember that most New England builders produced few locomotives with the Bury (dome) boiler and that the chief advocates of this later style were the Philadelphia builders. By the early 1850's the Bury boiler passed out of favor entirely and the wagon top became the standard type of boiler with all builders in this country. Sixty-three iron tubes, 1-7/8 inches by 85 inches long are used. The original tubes may have been copper or brass since these were easier to keep tight than the less malleable iron tubes. The present tube sheet is of iron but was originally copper. Its thickness cannot be conveniently measured, but it is greater than that of the boiler shell, probably about 1/2 to 5/8 inch. While copper tubes and tube sheets were not much used in this country after about 1870, copper was employed as recently as 1950 by Robert Stephenson & Hawthorns, Ltd., on some small industrial locomotives. The boiler shell is lagged with wooden tongue-and-groove strips about 2-1/2 inches wide (felt also was used for insulation during this period). The wooden lagging is covered with Russia sheet iron which is held in place and the joints covered by polished brass bands. Russia sheet iron is a planish iron having a lustrous, metallic gray finish. [Illustration: Figure 14.--THE "FURY," BUILT FOR THE Boston and Worcester Railroad in 1849 by Wilmarth. It was known as a "Shanghai" because of its great height. (Smithsonian Chaney photo 6443.)] [Illustration: Figure 15.--THE "NEPTUNE," BUILT FOR THE Boston and Worcester in 1847 by Hinkley and Drury. Note the similarity of this engine and the _Fury_.] [Illustration: Figure 16.--THE "PIONEER" AS FIRST EXHIBITED in the Arts and Industries building of the Smithsonian Institution prior to restoration of the sandbox. (Smithsonian photo 48069D.)] The steam dome (fig. 18) is located directly over the firebox, inside the cab. It is lagged and jacketed in an identical manner to the boiler. The shell of the dome is of 5/16-inch wrought iron, the top cap is a cast-iron plate which also serves as a manhole cover offering access to the boiler's interior for inspection and repair. [Illustration: Figure 17.--"PIONEER" locomotive. (Drawing by J. H. White.)] [Illustration: Figure 18.--"PIONEER" LOCOMOTIVE, (1) Safety valve, (2) spring balance, (3) steam jet, (4) dry pipe, (5) throttle lever, (6) throttle, (7) crown bar, (8) front tube sheet, (9) check valve, (10) top rail, (11) rear-boiler bracket, (12) pedestal, (13) rocker bearing, (14) damper, (15) grate, (16) bottom rail, (17) pump heater valve, (18) cylinder lubricator, (19) reversing lever, (20) brake shoe, (21) mud ring, (22) blowoff cock, (23) ashpan. (Drawing by J. H. White.)] A round plate, 20 inches in diameter, riveted on the forward end of the boiler, just behind the bell stand, was found when the old jacket was removed in May 1963. The size and shape of the hole, which the plate covers, indicate that a steam dome or manhole was located at this point. It is possible that this was the original location of the steam dome since many builders in the early 1850's preferred to mount the dome forward of the firebox. This was done in the belief that there was less danger of priming because the water was less agitated forward of the firebox. The firebox is as narrow as the boiler shell and fits easily between the frame. It is a deep and narrow box, measuring 27 inches by 28 inches by about 40 inches deep, and is well suited to burning wood. A deep firebox was necessary because a wide, shallow box suitable for coal burning, allowed the fuel to burn so quickly it was difficult to fire the engine effectively. With the deep, narrow firebox, wood was filled up to the level of the fire door. In this way, the fire did not burn so furiously and did not keep ahead of the fireman; at the same time, since it burned so freely, a good fire was always on hand. The _Pioneer_ burned oak and hickory.[14] For the firebox 5/16-inch thick sheet was used, for heavier sheet would have blistered and flaked off because of the intense heat of the fire and the fibrous quality of wrought-iron sheet of the period. Sheet iron was fabricated from many small strips of iron rolled together while hot. These strips were ideally welded into a homogeneous sheet, but in practice it was found the thicker the sheet the less sure the weld. The fire grates are cast iron and set just a few inches above the bottom of the water space so that the water below the grates remains less turbulent and mud or other impurities in the water settle here. Four bronze mud plugs and a blowoff cock are fitted to the base of the firebox so that the sediment thus collected can be removed (figs. 17, 18). The front of the boiler is attached to the frame by the smokebox, which is a cylinder, bolted on a light, cast-iron saddle (not part of the cylinder castings nor attached to them, but bolted directly to the top rail of the frame; it may be a hastily made repair put on at the shops of the C.V.R.R.). The rear of the boiler is attached to the frame by two large cast-iron brackets, one on each side of the firebox (fig. 18). These are bolted to the top rail of the frame but the holes in the brackets are undoubtedly slotted, so that they may slide since the boiler will expand about 1/4 inch when heated. In addition to the crown bars, which strengthen the crown sheet, the boiler is further strengthened by stay bolts and braces located in the wagon top over the firebox, where the boiler had been weakened by the large hole necessary for the steam dome. This boiler is a remarkably light, strong, and compact structure. BOILER FITTINGS Few boiler fittings are found on the _Pioneer_ and it appears that little was done to update the engine with more modern devices during its many years of service. With the exception of the steam gauge, it has no more boiler fitting than when it left the builder's shop in 1851. The throttle valve is a simple slide valve and must have been primitive for the time, for the balance-poppet throttle valve was in use in this country previous to 1851. It is located directly below the steam dome even though it was common practice to place the throttle valve at the front of the boiler in the smokebox. Considering the cramped condition inside the smokebox, there would seem to be little space for the addition of the throttle valve; hence its present location. The dry pipe projects up into the steam dome to gather the hottest, driest steam for the cylinders. The inverted, funnel-like cap on the top of the dry pipe is to prevent priming, as drops of water may travel up the sides of the pipe and then to the cylinders, with the possibility of great damage. After the steam enters the throttle valve it passes through the front end of the valve, through the top of the boiler via the dry pipe (fig. 18), through the front tube sheet, and then to the cylinders via the petticoat pipes. The throttle lever is a simple arrangement readily understood from the drawings. It has no latch and the throttle lever is held in any desired setting by the wingnut and quadrant shown in figure 18. The water level in the boiler is indicated by the three brass cocks located on the backhead. No gauge glass is used; they were not employed in this country until the 1870's, although they were commonly used in England at the time the _Pioneer_ was built. While two safety valves were commonly required, only one was used on the _Pioneer_. The safety valve is located on top of the steam dome. Pressure is exerted on the lever by a spring balance, fixed at the forward end by a knife-blade bearing. The pressure can be adjusted by the thumbscrew on the balance. The graduated scale on the balance gave a general but uncertain indication of the boiler pressure. The valve itself is a poppet held against the face of the valve seat by a second knife blade attached to the lever. The ornamental column forming the stand of the safety valve is cast iron and does much to decorate the interior of the cab. The pipe carrying the escaping steam projects through the cab roof. It is made of copper with a decorative brass band. This entire mechanism was replaced by a modern safety valve for use at the Chicago Railroad Fair (1949). Fortunately, the old valve was preserved and has since been replaced on the engine. The steam gauge is a later addition, but could have been put on as early as the 1860's, since the most recent patent date that it bears is 1859. It is an Ashcroft gauge having a handsome 4--4--0 locomotive engraved on its silver face. The steam jet (item 3, fig. 18) is one of the simplest yet most notable boiler fitting of the _Pioneer_, being nothing more than a valve tapped into the base of the steam dome with a line running under the boiler jacket to the smokestack. When the valve is opened a jet of steam goes up the stack, creating a draft useful for starting the fire or enlivening it as necessary. This device was the invention of Alba F. Smith in 1852, according to the eminent 19th-century technical writer and engineer Zerah Colburn.[15] The two feedwater pumps (fig. 20) are located beneath the cab deck (1, fig. 17). They are cast-iron construction and are driven by an eccentric on the driving-wheel axle (fig. 27). The airchamber or dome (1, fig. 27) imparts a more steady flow of the water to the boiler by equalizing the surges of water from the reciprocating pump plunger. A steam line (3, fig. 18), which heats the pump and prevents freezing in cold weather, is regulated by a valve in the cab (figs. 18, 27). Note that the line on the right side of the cab has been disconnected and plugged. The eccentric drive for the pumps is unusual, and the author knows of no other American locomotive so equipped. Eastwick and Harrison, it is true, favored an eccentric drive for feed pumps, but they mounted the eccentric on the crankpin of the rear driving wheel and thus produced in effect a half-stroke pump. This was not an unusual arrangement, though a small crank was usually employed in place of the eccentric. The full-stroke crosshead pump with which the _Jenny Lind_ (fig. 22) is equipped, was of course the most common style of feed pump used in this country in the 19th century. [Illustration: Figure 19.--BACKHEAD of the _Pioneer_. (Smithsonian photo 48069F.)] Of all the mechanisms on a 19th-century locomotive, the feed pump was the most troublesome. If an engineer could think of nothing else to complain about, he could usually call attention to a defective pump and not be found a liar. Because of this, injectors were adopted after their introduction in 1860. It is surprising that the _Pioneer_, which was in regular service as late as 1880 and has been under steam many times since for numerous exhibitions, was never fitted with one of these devices. Because its stroke is short and the plunger is in less rapid motion, the present eccentric arrangement is more complex but less prone to disorder than the simpler but faster crosshead pump. [Illustration: Figure 20.--FEEDWATER PUMP of the _Pioneer_. (Smithsonian photo 63344.)] The check valves are placed slightly below the centerline of the boiler (fig. 18). These valves are an unfinished bronze casting and appear to be of a recent pattern, probably dating from the 1901 renovation. At the time the engine was built, it was usual to house these valves in an ornamental spun-brass casing. The smokestack is of the bonnet type commonly used on wood-burning locomotives in this country between about 1845 and 1870. The exhaust steam from the cylinders is directed up the straight stack (shown in phantom in fig. 27) by the blast pipe. This creates a partial vacuum in the smokebox that draws the fire, gases, ash, and smoke through the boiler tubes from the firebox. The force of the exhausting steam blows them out the stack. At the top of the straight stack is a deflecting cone which slows the velocity of the exhaust and changes its direction causing it to go down into the funnel-shaped outer casing of the stack. Here, the heavy embers and cinders are collected and prevented from directly discharging into the countryside as dangerous firebrands. Wire netting is stretched overtop of the deflecting cone to catch the lighter, more volatile embers which may defy the action of the cone. The term "bonnet stack" results from the fact that this netting is similar in shape to a lady's bonnet. The cinders thus accumulated in the stack's hopper could be emptied by opening a plug at the base of the stack. While the deflecting cone was regarded highly as a spark arrester and used practically to the exclusion of any other arrangement, it had the basic defect of keeping the smoke low and close to the train. This was a great nuisance to passengers, as the low trailing smoke blew into the cars. If the exhaust had been allowed to blast straight out the stack high into the air, most of the sparks would have burned out before touching the ground. [Illustration: Figure 21.--"PIONEER" ON EXHIBIT in old Arts and Industries building of the Smithsonian Institution. In this view can be seen the bonnet screen of the stack and arrangement of the boiler-frame braces and other details not visible from the floor. (Smithsonian photo 48069A.)] [Illustration: Figure 22.--"JENNY LIND," SISTER ENGINE of the _Pioneer_, shown here as rebuilt in 1878 for use as an inspection engine. It was scrapped in March 1905. (_Photo courtesy of E. P. Alexander._)] [Illustration: Figure 23.--CYLINDER head with valve box removed.] [Illustration: Figure 24.--BOTTOM of valve box with slide valve removed.] [Illustration: Figures 25 and 26.--CYLINDER with valve box removed, showing valve face.] FRAME The frame of the _Pioneer_ defies an exact classification but it more closely resembles the riveted- or sandwich-type frame than any other (figs. 18, 27). While the simple bar frame enjoyed the greatest popularity in the last century, riveted frames were widely used in this country, particularly by the New England builders between about 1840 and 1860. The riveted frame was fabricated from two plates of iron, about 5/8-inch thick, cut to the shape of the top rail and the pedestal. A bar about 2 inches square was riveted between the two plates. A careful study of photographs of Hinkley and other New England-built engines of the period will reveal this style of construction. The frame of the _Pioneer_ differs from the usual riveted frame in that the top rail is 1-3/4 inches thick by 4-1/8 inches deep and runs the length of the locomotive. The pedestals are made of two 3/8-inch plates flush-riveted to each side of the top rail. The cast-iron shoes which serve as guides for the journal boxes also act as spacers between the pedestal plates. The bottom rail of the frame is a 1-1/8-inch diameter rod which is forged square at the pedestals and forms the pedestal cap. The frame is further stiffened by two diagonal rods running from the top of each truck-wheel pedestal to the base of the driving-wheel pedestal, forming a truss. Six rods, riveted to the boiler shell and bolted to the frame's top rail, strengthen the frame laterally. Four of these rods can be seen easily as they run from the frame to the middle of the boiler; the other two are riveted to the underside of the boiler. The attachment of these rods to the boiler was an undesirable practice, for the boiler shell was thus subjected to the additional strain of the locomotive's vibrations as it passed over the road. In later years, as locomotives grew in size, this practice was avoided and frames were made sufficiently strong to hold the engine's machinery in line without using the boiler shell. The front and rear frame beams are of flat iron plate bolted to the frame. The rear beam had been pushed in during an accident, and instead of its being replaced, another plate was riveted on and bent out in the opposite direction to form a pocket for the rear coupling pin. Note that there is no drawbar and that the coupler is merely bolted to the beams. Since the engine only pulled light trains, the arrangement was sufficiently strong. RUNNING GEAR The running gear is simply sprung with individual leaf springs for each axle; it is not connected by equalizing levers. To find an American locomotive not equipped with equalizers is surprising since they were almost a necessity to produce a reasonably smooth ride on the rough tracks of American railroads. Equalizers steadied the motion of the engine by distributing the shock received by any one wheel or axle to all the other wheels and axles so connected, thus minimizing the effects of an uneven roadbed. The author believes that the _Pioneer_ is a hard-riding engine. The springs of the main drives are mounted in the usual fashion. The rear boiler bracket (fig. 18) is slotted so that the spring hanger may pass through for its connection with the frame. The spring of the leading wheels is set at right angles to the frame (fig. 27) and bears on a beam, fabricated of iron plate, which in turn bears on the journal boxes. The springs of the trailing wheels are set parallel with the frame and are mounted between the pedestal plates (fig. 18). The center of the driving wheel is cast iron and has spokes of the old rib pattern, which is a T in cross section, and was used previous to the adoption of the hollow spoke wheel. In the mid-1830's Baldwin and others used this rib-pattern style of wheel, except that the rib faced inside. The present driving-wheel centers are unquestionably original. The sister engine _Jenny Lind_ (fig. 22) was equipped with identical driving wheels. The present tires are very thin and beyond their last turning. They are wrought iron and shrunk to fit the wheel centers. Flush rivets are used for further security. The left wheel, shown in figure 17, is cracked at the hub and is fitted with an iron ring to prevent its breaking. The truck wheels, of the hollow spoke pattern, are cast iron with chilled treads. They were made by Asa Whitney, one of the leading car-wheel manufacturers in this country, whose extensive plant was located in Philadelphia. Made under Whitney's patent of 1866, these wheels may well have been added to the _Pioneer_ during the 1871 rebuilding. Railroad wheels were not cast from ordinary cast iron, which was too weak and brittle to stand the severe service for which they were intended, but from a high-quality cast iron similar to that used for cannons. Its tensile strength, which ranged from 31,000 to 36,000 psi, was remarkably high and very nearly approached that of the best wrought-iron plate. The cylinders are cast iron with an 8-1/2-inch bore about half the size of the cylinders of a standard 8-wheel engine. The cylinders are bolted to the frame but not to the saddle, and are set at a 9° angle to clear the leading wheels and at the same time to line up with the center of the driving-wheel axle. The wood lagging is covered with a decorative brass jacket. Ornamental brass jacketing was extensively used on mid-19th-century American locomotives to cover not only the cylinders but steam and sand boxes, check valves, and valve boxes. The greater expense for brass (Russia iron or painted sheet iron were a cheaper substitute) was justified by the argument that brass lasted the life of the engine, and could be reclaimed for scrap at a price approaching the original cost; and also that when brightly polished it reflected the heat, preventing loss by radiation, and its bright surface could be seen a great distance, thus helping to prevent accidents at grade crossings. The reader should be careful not to misconstrue the above arguments simply as rationalization on the part of master mechanics more intent on highly decorative machines than on the practical considerations involved. The valve box, a separate casting, is fastened to the cylinder casting by six bolts. The side cover plates when removed show only a small opening suitable for inspection and adjustment of the valve. The valve box must be removed to permit repair or removal of the valve. A better understanding of this mechanism and the layout of the parts can be gained from a study of figures 23-26, 28 (8, 8A, and 8B). [Illustration: Figure 27.--"PIONEER" LOCOMOTIVE. (1) Air chamber, (2) reversing lever, (3) counterweight, (4) reversing shaft, (5) link hanger, (6) rocker, (7) feedwater line to boiler, (8) link block, (9) link, (10) eccentric, (11) pump plunger, (12) pump steamheater line, (13) feedwater pump, (14) wire netting [bonnet], (15) deflecting cone, (16) stack, (17) stack hopper. (Drawing by J. H. White.)] [Illustration: Figure 28.--REAR ELEVATION of _Pioneer_ and detail of valve shifter; valve face and valve. (Drawing by J. H. White.)] Both crossheads were originally of cast iron but one of these has been replaced and is of steel. They run into steel guides, bolted at the forward end to the rear cylinder head and supported in the rear by a yoke. The yoke is one of the more finished and better made pieces on the entire engine (fig. 27). The main rod is of the old pattern, round in cross section, and only 1-1/2 inches in diameter at the largest point. VALVE GEAR The valve gear is of the Stephenson shifting-link pattern (see fig. 27), a simple and dependable motion used extensively in this country between about 1850 and 1900. The author believes that this is the original valve gear of the _Pioneer_, since the first mention (1854) in the _Annual Report_ of the Cumberland Valley Railroad of the style of valve gear used by each engine, states that the _Pioneer_ was equipped with a shifting-link motion. Assuming this to be the original valve gear of the _Pioneer_, it must be regarded as an early application, because the Stephenson motion was just being introduced into American locomotive practice in the early 1850's. Four eccentrics drive the motion; two are for forward motion and two for reverse. The link is split and made of two curved pieces. The rocker is fabricated of several forged pieces keyed and bolted together. On better made engines the rocker would be a one-piece forging. The lower arm of each rocker is curiously shaped, made with a slot so that the link block may be adjusted. Generally, the only adjustment possible was effected by varying the length of the valve stem by the adjusting nuts provided. A simple weight and lever attached to the reversing shaft serve as a counterbalance for the links and thus assist the engineer in shifting the valve motion. There are eight positions on the quadrant of the reversing lever. [Illustration: Figure 29.--"PIONEER" on exhibit in old Arts and Industries building, showing the tank and backhead. (Smithsonian photo 48069E.)] MISCELLANEOUS NOTES The cab is solid walnut with a natural finish. It is very possible that the second cab was added to the locomotive after the 1862 fire. A brass gong used by the conductor to signal the engineer is fastened to the underside of the cab roof. This style of gong was in use in the 1850's and may well be original equipment. The water tank is in two sections, one part extending below the deck, between the frame. The tank holds 600 gallons of water. The tender holds one cord of wood. The small pedestal-mounted sandbox was used on several Cumberland Valley engines including the _Pioneer_. This box was removed from the engine sometime between 1901 and 1904. It was on the engine at the time of the Carlisle sesquicentennial but disappeared by the time of the St. Louis exposition. Two small sandboxes, mounted on the driving-wheel splash guards, replaced the original box. The large headlamp (fig. 3) apparently disappeared at the same time and was replaced by a crudely made lamp formerly mounted on the cab roof as a backup light. Headlamps of commercial manufacture were carefully finished and made with parabolic reflectors, elaborate burners, and handsomely fitted cases. Such a lamp could throw a beam of light for 1000 feet. The present lamp has a flat cone-shaped piece of tin for a reflector. The brushes attached to the pilot were used in the winter to brush snow and loose ice off the rail and thus improve traction. In good weather the brushes were set up to clear the tracks. [Illustration: Figure 30.--RECONSTRUCTED SANDBOX replaced on the locomotive, August 1962. (Drawing by J. H. White.)] After the _Pioneer_ had come to the National Museum, it was decided that some refinishing was required to return it as nearly as possible to the state of the original engine. Replacing the sandbox was an obvious change.[20] The brass cylinder jackets were also replaced. The cab was stripped and carefully refinished as natural wood. The old safety valve was replaced, as already mentioned. Rejacketing the boiler with simulated Russia iron produced a most pleasing effect, adding not only to the authenticity of the display but making the engine appear lighter and relieving the somber blackness which was not characteristic of a locomotive of the 1850's. Several minor replacements are yet to be done; chiefly among these are the cylinder-cock linkage and a proper headlamp. The question arises, has the engine survived as a true and accurate representation of the original machine built in 1851? In answer, it can be said that although the _Pioneer_ was damaged en route to the Cumberland Valley Railroad, modified on receipt, burned in 1862, and operated for altogether nearly 40 years, surprisingly few new appliances have been added, nor has the general arrangement been changed. Undoubtedly, the main reason the engine is so little changed is that its small size and odd framing did not invite any large investment for extensive alteration for other uses. But there can be no positive answer as to its present variance from the original appearance as represented in the oldest known illustration of it--the Hull drawing of 1871 (fig. 8). There are few, if any, surviving 19th-century locomotives that have not suffered numerous rebuildings and are not greatly altered from the original. The _John Bull_, also in the U.S. National Museum collection, is a good example of a machine many times rebuilt in its 30 years of service.[21] Unless other information is uncovered to the contrary, it can be stated that the _Pioneer_ is a true representation of a light passenger locomotive of 1851. _Alba F. Smith_ Alba F. Smith, the man responsible for the purchase of the _Pioneer_, was born in Lebanon, Connecticut, June 28, 1817.[9] Smith showed promise as a mechanic at an early age and by the time he was 22 had established leadpipe works in Norwich. His attention was drawn particularly to locomotives since the tracks of the Norwich and Worcester Railroad passed his shop. His attempts to develop a spark arrester for locomotives brought Smith to the favorable attention of Captain Daniel Tyler (1799-1882), president of the Norwich and Worcester Railroad. When Tyler was hired by the Cumberland Valley Railroad in 1850 to supervise the line's rebuilding, he persuaded the managers of that road to hire Smith as superintendent of machinery.[10] Smith was appointed as superintendent of the machine shop of the Cumberland Valley Railroad on July 22, 1850.[11] On January 1, 1851, he became superintendent of the road. In March of 1856 Smith resigned his position with the Cumberland Valley Railroad and became superintendent of the Hudson River Railroad, where he remained for only a year. During that time he designed the coal-burning locomotive _Irvington_, rebuilt the Waterman condensing dummy locomotive for use in hauling trains through city streets, and developed a superheater.[12] After retiring from the Hudson River Railroad he returned to Norwich and became active in enterprises in that area, including the presidency of the Norwich and Worcester Railroad. While the last years of Smith's life were devoted to administrative work, he found time for mechanical invention as well. In 1862 he patented a safety truck for locomotives, and became president of a concern which controlled the most important patents for such devices.[13] Alba F. Smith died on July 21, 1879, in Norwich, Connecticut. [Illustration: UNION WORKS, SOUTH BOSTON, SETH WILMARTH, Proprietor, [Illustration] MANUFACTURER OF LOCOMOTIVES, STATIONARY STEAM ENGINES AND STEAM BOILERS, OF THE VARIOUS SIZES REQUIRED, _Parts connected with Railroads, including Frogs, Switches, Chairs and Hand Cars._ MACHINISTS' TOOLS, of all descriptions, including _TURNING LATHES_, of sizes varying from 6 feet to 50 feet in length, and weighing from 500 pounds to 40 tons each; the latter capable of turning a wheel or pulley, _thirty feet in diameter_. PLANING MACHINES, Varying from 2 feet to 60 feet in length, and weighing from 200 lbs. to 70 tons each, and will plane up to 55 feet long and 7 feet square. Boring Mills, Vertical and Horizontal Drills, Slotting Machines, Punching Presses, Gear and Screw Cutting Machines, &c. &c. Also, Mill Gearing and Shafting. JOBBING AND REPAIRS, and any kind of work usually done in Machine Shops, executed at short notice. Figure 13.--ADVERTISEMENT OF SETH WILMARTH appearing in Boston city directory for 1848-1849.] _Seth Wilmarth_ Little is known of the builder of the _Pioneer_, Seth Wilmarth, and nothing in the way of a satisfactory history of his business is available. For the reader's general interest the following information is noted.[16] Seth Wilmarth was born in Brattleboro, Vermont, on September 8, 1810. He is thought to have learned the machinist trade in Pawtucket, Rhode Island, before coming to Boston and working for the Boston Locomotive Works, Hinkley and Drury proprietors. In about 1836 he opened a machine shop and, encouraged by an expanding business, in 1841 he built a new shop in South Boston which became known as the Union Works.[17] Wilmarth was in the general machine business but his reputation was made in the manufacture of machine tools, notably lathes. He is believed to have built his first locomotive in 1842, but locomotive building never became his main line of work. Wilmarth patterned his engines after those of Hinkley and undoubtedly, in common with the other New England builders of this period, favored the steady-riding, inside-connection engines. The "Shanghais," so-called because of their great height, built for the Boston and Worcester Railroad by Wilmarth in 1849, were among the best known inside-connection engines operated in this country (fig. 14). While the greater part of Wilmarth's engines was built for New England roads, many were constructed for lines outside that area, including the Pennsylvania Railroad, Ohio and Pennsylvania Railroad, and the Erie. A comparison of the surviving illustrations of Hinkley and Wilmarth engines of the 1850's reveals a remarkable similarity in their details (figs. 14 and 15). Notice particularly the straight boiler, riveted frame, closely set truck wheels, feedwater pump driven by a pin on the crank of the driving wheel, and details of the dome cover. All of the features are duplicated exactly by both builders. This is not surprising considering the proximity of the plants and the fact that Wilmarth had been previously employed by Hinkley. In 1854 Wilmarth was engaged by the New York and Erie Railroad to build fifty 6-foot gauge engines.[18] After work had been started on these engines, and a large store of material had been purchased for their construction, Wilmarth was informed that the railroad could not pay cash but that he would have to take notes in payment.[19] There was at this time a mild economic panic and notes could be sold only at a heavy discount. This crisis closed the Union Works. The next year, 1855, Seth Wilmarth was appointed master mechanic of the Charlestown Navy Yard, Boston, where he worked for twenty years. He died in Malden, Massachusetts, on November 5, 1886. Footnotes [1] _Minutes of the Board of Managers of the Cumberland Valley Railroad._ This book may be found in the office of the Secretary, Pennsylvania Railroad, Philadelphia, Pa., June 25, 1851. Hereafter cited as "Minutes C.V.R.R." [2] Ibid. [3] Minutes C.V.R.R. [4] _Franklin Repository_ (Chambersburg, Pa.), August 26, 1909. [5] _Railroad Advocate_ (December 29, 1855), vol. 2, p. 3. [6] C. E. FISHER, "Locomotives of the New Haven Railroad," _Railway and Locomotive Historical Society Bulletin_ (April 1938), no. 46, p. 48. [7] Minutes C.V.R.R. [8] _Evening Sentinel_ (Carlisle, Pa.), October 23, 1901. [9] _Norwich Bulletin_ (Norwich, Conn.), July 24, 1879. All data regarding A. F. Smith is from this source unless otherwise noted. [10] _Railway Age_ (September 13, 1889), vol. 14, no. 37. Page 600 notes that Tyler worked on C.V.R.R. 1851-1852; Smith's obituary (footnote 9) mentions 1849 as the year; and minutes of C.V.R.R. mention Tyler as early as 1850. [11] Minutes C.V.R.R. [12] A. F. HOLLEY, _American and European Railway Practice_ (New York: 1861). An illustration of Smith's superheater is shown on plate 58, figure 13. [13] JOHN H. WHITE, "Introduction of the Locomotive Safety Truck," (Paper 24, 1961, in _Contributions from the Museum of History and Technology: Papers 19-30_, U.S. National Museum Bulletin 228; Washington: Smithsonian Institution, 1963), p. 117. [14] _Annual Report_, C.V.R.R., 1853. [15] ZERAH COLBURN, _Recent Practice in Locomotive Engines_ (1860), p. 71. [16] _Railroad Gazette_ (September 27, 1907), vol. 43, no. 13, pp. 357-360. These notes on Wilmarth locomotives by C. H. Caruthers were printed with several errors concerning the locomotives of the Cumberland Valley Railroad and prompted the preparation of these present remarks on the history of Wilmarth's activities. Note that on page 359 it is reported that only one compensating-lever engine was built for the C.V.R.R. in 1854, and not two such engines in 1852. The _Pioneer_ is incorrectly identified as a "Shanghai," and as being one of three such engines built in 1871 by Wilmarth. [17] The author is indebted to Thomas Norrell for these and many of the other facts relating to Wilmarth's Union Works. [18] _Railroad Gazette_ (October 1907), vol. 43, p. 382. [19] _Boston Daily Evening Telegraph_ (Boston, Mass.), August 11, 1854. The article stated that one engine a week was built and that 10 engines were already completed for the Erie. Construction had started on 30 others. [20] The restoration work has been ably handled by John Stine of the Museum staff. Restoration started in October 1961. [21] S. H. OLIVER, _The First Quarter Century of the Steam Locomotive in America_ (U.S. National Museum Bulletin 210; Washington: Smithsonian Institution, 1956), pp. 38-46. U.S. GOVERNMENT PRINTING OFFICE: 1964 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402--Price 30 cents. Index Adams, W. B., 252 Baldwin, Matthias William, 264 Boston Locomotive Works, 260 Colburn, Zerah, 259 Danforth Cooke & Co., 252 Drury, Gardner P., 260 Eastwick, Andrew M., 259 Harrison, Joseph, Jr., 259 Hinkley, Holmes, 252, 260, 263 Hull, A. S., 251, 268 Smith, Alba F., 244, 246, 247, 259 Stephenson, Robert, & Hawthorns, Ltd., 253 Stuart, J. E. B., 249 Taunton Locomotive Works, 247 Tyler, Daniel, 244, 253 Union Works, 260 Vulcan Foundry, 252 Watts, Frederick, 249 
28166	----	INSTALLATION AND Operation Instructions FOR CUSTOM MARK III CP SERIES OIL FIRED UNIT MANUFACTURED BY AXEMAN-ANDERSON COMPANY 300 East Mountain Avenue South Williamsport, PA 17701 CPO2O--8410--5C INSTALLATION AND OPERATING INSTRUCTIONS CUSTOM MARK III CP SERIES OIL FIRED UNIT _GENERAL_ The Custom Mark III CP Series Oil Fired Unit is a high quality heating unit that will provide many years of comfortable and economical heat if properly installed and given proper care. It is _IMPORTANT_ therefore that these instructions should be followed carefully. _SHIPMENT_ The unit is completely assembled at the factory except for the following parts which are packed in a separate carton and strapped to the skids inside the shipping carton: 1 - 3/4" × Close Steel Nipple 1 - 3/4" × 3/4" × 1/2" Tee 1 - Fig. 105 Tridicator 1 - 3/4" No. 10-402-05 ASME Relief Valve 1 - 3/4" No. 600-19 Boiler Drain 1 - T87F-2055 Thermostat The jacket extension for 128CPO is shipped in separate carton. _DAMAGE IN TRANSIT_ Upon receipt of shipment of this material, inspect all cartons for external damage. If external damage is noted, open the carton and inspect for damage to equipment. Mark the number of cartons received in this condition on the delivering carrier's waybill, and request the services of their inspector. If, upon opening a carton, concealed damage is discovered, open the entire shipment and note all equipment so damaged. Contact the delivering carrier and request inspection of the damaged equipment. Do not destroy the carton. The inspector from the freight company will need this to determine reason for damage. Normally claims for any and all damages should be filed with the freight company within five working days after receipt of shipment. All materials are sold F.O.B. Factory. It is the responsibility of the consignee to file claim with the delivering carrier for material received in a damaged condition. _LOCATING UNIT_ _BEFORE REMOVING SHIPPING CARTON, LOCATE UNIT IN ITS FINAL POSITION_ The carton is plainly marked so as to indicate which is the outlet burner end of the unit which is also the end where the return and flue are located. Clearance should be provided in both the front and rear of the unit for cleaning. Where possible it is good practice to locate the unit so its sides are parallel to the chimney flue. In all instances locate unit as near chimney flue as possible in order to avoid use of a long flue pipe. _REMOVING CARTON_ Once the packaged unit is in its proper place, cut all around the carton on the scored line as shown on carton. The entire carton may then be lifted from the skids. If it is found necessary to move the unit a little more to place it in the exact location ready for piping, do so before removing skids. DO NOT PUSH AGAINST ANY PART OF JACKET OR OIL BURNER WHEN MOVING UNIT. TO MOVE UNIT, PUSH AGAINST _SKIDS, FLUE BOX OR SMOKE BOX_. PUSHING AGAINST JACKET WILL RESULT IN DAMAGE. _REMOVING SKIDS_ The skids are specially designed for easy removal. It is necessary, however, to follow these instructions carefully. A. After unit is in proper place, remove the two cross pieces from skids by pulling out all scaffolding (double headed) nails. B. By inserting pinch bar or 2" × 4" underneath the smoke box (rear of unit), tilt one side of unit just high enough to lift lugs out of holes in skid, then knock skid out from underneath unit. Then do the same thing on the other side of unit. _THE UNIT IS NOT BOLTED TO THE SKIDS._ The 3/4" lugs welded to the unit simply fit into the 3/4" holes in the skids. +----------------------------------------------+ | | | IMPORTANT | | | | DO NOT TILT UNIT BY PUSHING AGAINST JACKET | | | | IT IS NOT NECESSARY | | | | AND BY DOING SO THE JACKET WILL BE DAMAGED | | | +----------------------------------------------+ _LEVELING UNIT_ In case floor is uneven, unit may easily be made level by inserting shims under the 4 shipping lugs. These lugs also keep the jacket 1/2" off the floor, protecting it from wet floors and dampness. _PIPING AND WIRING_ Once the unit is in its proper location with the packing carton, skids and packing material removed, it is ready for piping and connection from Room Thermostat and 110 V. 60 Cy. A.C. Current. _CONTROL SYSTEM_ The controls furnished are for a one zone Forced Water System consisting of T87F Room Thermostat, L8124A-1007 Triple Acting Aquastat and Circulator Relay, C554A-1018 Cadmium Photocell, R8184G-1005 Burner Relay and V4046A-1009 Oil Valve. Description and complete wiring diagram will be found packed with each control. _SPECIAL CONTROL SYSTEMS_ For special control systems such as multiple installations, zone controlled, unit heater, radiant panel, etc., write to factory for wiring diagrams. _CHIMNEY AND BREECHING REQUIREMENTS_ The CP boiler should be connected to a vertical vent system that will prevent: (1) positive pressure in the flue, (2) backward flow of flue gas through the unit when the burner stops, and (3) condensation in the flue. Use double-walled or insulated pipe for sections of the flue in cold areas. All outside vents, except for short extensions, must be insulated to avoid condensation in the flue. Several types of prefabricated chimneys are available providing double-walled or insulated pipe, some with ceramic and others with metallic liners. While the unit is equipped with an induced draft fan, proper size vent must be provided to remove the gases of combustion. It is recommended that a 4" to 5" increaser be used for venting the 87CPO and 108CPO and a 4" to 6" increaser be used for the 128CPO. For abnormal runs (exceeding 10 ft.), consult factory. Vent and breeching must be gas tight by sealing with asbestos or thermo-setting pressure sensitive tape. _DRAFT REGULATOR_ It is recommended that a draft regulator be installed in chimney flue _just below the flue pipe opening_, if the unit is attached to an extremely high chimney; an unlined chimney; or a chimney which is constructed on the exterior of the house. _CONTROLS AND TRIM_ Controls are installed in place at the Factory. Attach thermo-altimeter in 1/2" tapping in top front of boiler. Install 3/4" × close nipple in 3/4" top connection with 3/4" × 3/4" × 1/2" Tee. 3/4" Tee opening for installation of the relief valve and 1/2" opening for expansion tank. _WIRING_ Controls are all in place and wired at the factory except connection to circulator. _REGULATING OIL PRESSURE_ Standard nozzles furnished with the burner will produce the stamped rated capacity when used with Commercial Standard No. 2 Fuel Oil, and operated with a pressure of 100 lbs. per square inch. The standard setting of the fuel unit is 100 lbs. Due to difference in tank elevations, the pressure should be adjusted at the time of start up. _FUEL LINES_ Care should be employed when attaching the oil lines to the fuel unit. Overtightening or twisting will twist the pump-motor mounting plate and put a stress on the motor bearings. _START UP PROCEDURE_ General: 1. Make certain that correct voltage has been supplied to motor and control circuit. 2. Insure that outside air openings are provided in the boiler room for ventilation, and for admission of air for combustion. The free area of such openings should not be less than 7 square inch opening per 100,000 Btuh burner input, or more as required by local codes. 3. Check to see that flue, wiring and water level are in order. 4. Start burner fan motor to prime pump. If pump does not pick up oil within a few minutes, prime the pump with lubricating oil. Do not allow pump to run more than a few minutes without additional lubrication. 5. Check oil pressure and adjust if necessary. (See REGULATING OIL PRESSURE). 6. Set air shutters. (See ADJUSTING BURNER) Refer to Figure 1. 7. Generously lubricate the front motor bearing with SAE #20 oil. _ADJUSTING BURNER_ (See Figure 1) Positioning of the nozzle in relation to the face of the cone and the electrodes in relation to the nozzle are very important, also the face of the cone in relation to the face of the choke ring must be set according to the chart for each rate. If the air shutter openings are too large the oil may not ignite. 1. This setting will vary somewhat depending upon the grade of oil being used or if No. 1 is used instead of No. 2. 2. The approximate burner air setting may be determined by observing the fire through the observation port on the front of the boiler. If the flame is smoky, the air shutter should be opened until the fire burns clean, without any trace of smoke. The flame should be bright yellow in color with the tips of the flame turning orange. If the flame is too white, reduce the amount of air admitted; and, if too red or smoky increase the air. 3. Final adjustments should be made using a flue gas analyzer to measure the CO_2 content of the flue gas and a Bacharach model smoke meter or equivalent to determine the amount of smoke (not to exceed a "TRACE"). For checking efficiency only the stack temperature and CO_2 may be taken immediately after the fan and refer to the standard efficiency charts for the results. Readings of 5 to 8% taken after the fan correspond to 10 to 12% taken in the rear uptake of the boiler. The reduction in CO_2 reading in the flue is caused by the air being drawn in around the motor shaft for cooling purposes. The motor cooling air is at ambient temperature and, therefore, does not add energy to or subtract energy from the flue gas analysis, it only adds volume to the flue gas. Therefore, applying this data to standard efficiency charts will give a true indication of flue gas loss. +---------------------------------------------+ | | | NOTE | | | | Final adjustment should be made after | | the burner has been firing continuously | | for at least 10 minutes, as the fan pulls | | less air when the flue gases are hot. | | | +---------------------------------------------+ A. CHECK LIMIT CONTROL Run the burner long enough to bring the water temperature up to at least 190 degrees then turn the limit control setting until the burner stops. +---------------------------------------------------+ | | | NOTE | | | | The Minimum limit setting for any hot water | | boiler should be 140 degrees F. in order to | | prevent corrosion of the flues on the fire | | side. The burner should be run with the primary | | control thermostat terminals jumpered and the | | burner controlled directly from an aquastat | | keeping the boiler hot all the time, thus | | eliminating the sweating of the flues on the | | fire side caused by starting from a cold start. | | | +---------------------------------------------------+ _BELT ADJUSTMENT_ The proper tension on the fuel unit belt drive is set at the factory. However, the belt should be checked periodically to see that the setting is maintained. To check setting, first, remove the belt guard and then, using fingers, compress the belt at a point midway between the sheaves. The proper setting at this point measured between the outer edges of the belt, should be between 1-3/4" and 1-7/8". If adjustment is necessary loosen the two mounting bolts, and move the fuel unit up or down to give the necessary belt setting. Then re-tighten the mounting bolts securely and replace the belt guard. _PERFORMANCE CHECK LIST_ _QUESTION: What Causes Unit To Soot Up?_ _Answers_: 1. Nozzles 2. Flame Impingement 3. Firing Head 4. Leaks 5. Improper Burner Settings 6. Lack of Normal Maintenance 7. Poor Ignition 8. Retention Ring Cokes _Definitions of Answers_: 1. Nozzles A. Dirty B. Wrong type of nozzle, or manufacturing defect 2. Flame Impingement A. High CO_2 B. Diffuser and choke ring clearance not uniform C. Dirty nozzle, or poor patterns D. Leaks 3. Firing Head A. Diffuser and choke ring clearance not uniform B. Diffuser and choke ring face dimension out of tolerance. (See A Dimension, Figure 1) C. Dirty fuel systems 4. Leaks A. Induced fan gasket, or burner gasket improperly sealed B. Front cover assembly improperly installed or sealed 5. Improper Burner Settings A. Unit not checked out completely by the serviceman B. Flame pattern erratic (Not concentric). Burner set up by CO_2 only (Burner should be set up by CO_2, smoke and visual observation.) 6. Lack of Normal Maintenance A. Self explanatory (Recognition of the advantages of preventive maintenance). 7. Poor Ignition A. No delay in oil valve, unit flutters on start up. B. Electrodes out of position C. Too much combustion air (Air shutter open too wide) 8. Retention Ring Cokes A. Defective nozzle B. Cone, choke and nozzle out of adjustment (See Figure 1) C. Fluttering starts _DOMESTIC HOT WATER_ In order to obtain the rated capacity of the instantaneous domestic hot water coil limit control should be set to maintain 200° F boiler water temperature. Flow regulator and tempering valve should be installed on all instantaneous domestic hot water coil systems. _BURNER SETTING_ The burner is adjusted at the factory before shipment but in case of improper operation at some future date Figure 1 will show proper setting. In all cases the flame retention ring should be concentric with the choke. [Illustration: FIGURE 1] +--------+----------------+-----------------------+--------+---------+ | MODEL | NOZZLE | CHOKE RING | "A" | I. D. | | NO. | DELAVAN SIZE | NO. & DIAMETER | DIM. | VANES | +--------+----------------+-----------------------+--------+---------+ | 87CPO | 1.25 GPH 70° A | 142640-002 2-5/8 D | FLUSH | 2-25/32 | | 108CPO | 1.65 GPH 60° A | 142641 2-31/32 D | -3/16" | 2-25/32 | | 128CPO | 2.00 GPH 70° A | 142641-003 2-31/32 D | +1/4" | 2-29/32 | +--------+----------------+-----------------------+--------+---------+ [Illustration: (parts listed counter-clockwise from left side) Tubes 37CP19 08CP19 728CP19 4CP25 40624 144539 134955 144538 131798 131651 140734 142743 R8184G V4046A-16 1R111B-1BP 140611 141741 144691 141740 MM1163 141646-G03 140606] 
27286	----	GAS AND OIL ENGINES SIMPLY EXPLAINED _An Elementary Instruction Book for Amateurs and Engine Attendants_ BY WALTER C. RUNCIMAN _FULLY ILLUSTRATED_ LONDON Model Engineer Series. The "Model Engineer" Series, no. 26. 1905 CONTENTS CHAP. PAGE PREFACE 5 I. INTRODUCTORY 7 II. THE COMPONENT PARTS OF AN ENGINE 13 III. HOW A GAS ENGINE WORKS 22 IV. IGNITION DEVICES 33 V. MAGNETO IGNITION 47 VI. GOVERNING 51 VII. CAMS AND VALVE SETTINGS 63 VIII. OIL ENGINES 81 PREFACE My object in placing this handbook before the reader is to provide him with a simple and straightforward explanation of how and why a gas engine, or an oil engine, works. The main features and peculiarities in the construction of these engines are described, while the methods and precautions necessary to arrive at desirable results are detailed as fully as the limited space permits. I have aimed at supplying just that information which my experience shows is most needed by the user and by the amateur builder of small power engines. In place of giving a mere list of common engine troubles and their remedies, I have thought it better to endeavour to explain thoroughly the fundamental principles and essentials of good running, so that should any difficulty arise, the engine attendant will be able to reason out for himself the cause of the trouble, and will thus know the proper remedy to apply. This will give him a command over his engine which should render him equal to any emergency. WALTER C. RUNCIMAN. LONDON, E.C. GAS AND OIL ENGINES SIMPLY EXPLAINED CHAPTER I INTRODUCTORY The history of the gas engine goes back a long way, and the history of the internal combustion engine proper further still. It will be interesting to recount the main points in the history of the development of the class of engine we shall deal with in the following pages, in order to show what huge strides were made soon after the correct and most workable theory had been formulated. In 1678 Abbé Hautefeuille explained how a machine could be constructed to work with gunpowder as fuel. His arrangement was to explode the gunpowder in a closed vessel provided with valves, and cool the products of combustion, and so cause a partial vacuum to be formed. By the aid of such a machine, water could be raised. This inventor, however, does not seem to have carried out any experiments. In 1685 Huyghens designed another powder machine; and Papin, in 1688, described a similar machine, which was provided with regular valves, as devised by himself, in the _Proceedings of the Leipsic Academy_, 1688. From this time until 1791, when John Barber took out a patent for the production of force by the combustion of hydrocarbon in air, practically no advancement was made. The latter patent, curiously enough, comprised a very primitive form of rotary engine. Barber proposed to turn coal, oil, or other combustible stuff into gas by means of external firing, and then to mix the gases so produced with air in a vessel called the exploder. This mixture was then ignited as it issued from the vessel, and the ensuing flash caused a paddle-wheel to rotate. Mention is also made that it was an object to inject a little water into the exploder, in order to strengthen the force of the flash. Robert Street's patent of 1794 mentions a piston engine, in the cylinder of which, coal tar, spirit, or turpentine was vaporised, the gases being ignited by a light burning outside the cylinder. The piston in this engine was thrown upwards, this in turn forcing a pump piston down which did work in raising water. This was the first real gas engine, though it was crude and very imperfectly arranged. In 1801 Franzose Lebon described a machine to be driven by means of coal-gas. Two pumps were used to compress air and gas, and the mixture was fired, as recommended by the inventor, by an electric spark, and drove a piston in a double-working cylinder. The atmospheric engine of Samuel Brown, 1823, had a piston working in a cylinder into which gas was introduced, and the latter, being ignited, expanded the air in cylinder whilst burning like a flame. The fly-wheel carried the piston up to the top of its stroke, then water was used to cool the burnt gases, which also escaped through valves, the latter closing when the piston had reached the top of its stroke. A partial vacuum was formed, and the atmospheric pressure did work on the piston on its down stroke. A number of cylinders were required in this engine, three being shown in the specification all connected to the same crank-shaft. According to the _Mechanic's Magazine_, such an engine with a complete gas generating plant was fitted to a boat which ran as an experiment upon the Thames. A two-cylinder engine working on to a beam was built in Paris, but no useful results were obtained. Wright's engine of 1833 used a mixture of combustible gas and air, which operated like steam in a steam engine. This engine had a water-jacket, centrifugal governor, and flame ignition. In 1838 Barnett applied the principle of compression to a single-acting engine. He also employed a gas and air pump, which were placed respectively on either side of the engine cylinder, communication being established between the receiver into which the pumps delivered and the working cylinder as the charge was fired. The double-acting engines which Barnett devised later were not so successful. From this time to about 1860 very few practical developments are recorded. A number of French and English patents were taken out, referring to hydrogen motors, but are not of much practical value. Lenoir's patent, dating from 24th January 1860, refers to a form of engine which received considerable commercial support, and consequently became very popular. A manufacturer, named Marinoni, built several of these engines, which were set to work in Paris in a short time. Then, due to sudden demand, the Lenoir Company was formed to undertake the manufacture of these engines. It was claimed that a 4-horse-power engine could be run at a cost of 3·4 shillings per day, or just one half the cost of a steam engine using 9·9 pounds of coal per horse-power per hour. Many similar exaggerated accounts of their economy in consumption were circulated, and the public, on the strength of these figures, bought. It was understood that 17·6 cubic ft. of gas were required per horse-power per hour, but it was found that as much as 105 cubic ft. were often consumed. The discrepancy between the stated figures and the actual performance of the engine was a disappointment to the using public, and, as a result, the Lenoir engine got a bad name. Hugon, director of the Parisian gas-works, who, together with Reithmann, a watchmaker of Münich, hotly contested Lenoir's priority to this invention, brought out a modification of this engine. He cooled the cylinder by injecting water as well as using a water-jacket, and used flame instead of electric ignition. The consumption was now brought down to 87·5 cubic ft. At the second Parisian International Exhibition, 1867, an atmospheric engine, invented by Otto & Langen about this time, was shown. In this engine a free piston was used in a vertical cylinder, the former being thrown up by the force of the explosion. The only work done on the up-stroke was that to overcome the weight of the piston and piston rod, and the latter being made in the form of a rack, engaged with a toothed wheel on the axle as the piston descended, causing the fly-wheel and pulley to rotate. Barsanti and Matteucci were engaged in devising and experimenting with an engine very similar to this some years before, but Otto & Langen, no doubt, worked quite independently. Barsanti's engine never became a commercial article; while Otto & Langen's firm, it is said, held their own for ten years, and turned out about 4000 engines. In 1862 the French engineer, Beau de Rochas, laid down the necessary conditions which must prevail in order to obtain maximum efficiency. His patent says there are four conditions for perfectly utilising the force of expansion of gas in an engine. (1) Largest possible cylinder volume contained by a minimum of surface. (2) The highest possible speed of working. (3) Maximum expansion. (4) Maximum pressure at beginning of expansion. These are the conditions and principles, briefly stated, that combine to form the now well-known cycle upon which most gas engines work at the present time. It was not until 1876, fifteen years after these principles had been enumerated, that Otto carried them into practical effect when he brought out a new type of engine, with compression before ignition, higher piston speed, more rapid expansion, and a general reduction of dimensions for a given power. Due to this achievement, the cycle above referred to has always been termed the "Otto" cycle. CHAPTER II THE COMPONENT PARTS OF AN ENGINE Having recounted very briefly the chief points in the development of the gas engine from its beginning, we may proceed to deal with matters of perhaps more practical interest to those who we are assuming have had little or no actual experience in making or working internal combustion engines. The modern gas engine comprises comparatively few parts. Apart from the two main castings--the bed and cylinder--a small engine, generally speaking, consists of four fundamental members, viz., the valves and their operating mechanism, the cams and levers; the ignition device for firing the charge; and the governing mechanism for regulating the supply and admission of the explosive charge. There are innumerable designs of each one of these parts, and no two makes are precisely alike in detail, as every maker employs his own method of achieving the same end, namely, the production of an engine which comprises maximum efficiency with a minimum of wear and tear and attention. Therefore, before dealing with each of these primary parts in an arbitrary manner, and with the cycle of operations in detail, we propose to make the reader familiar with the general arrangement and method of working which usually obtains in the smaller power engines. In the following illustrations these parts are shown. A (fig. 1) is the ignition device which carries the ignition tube to fire the charge. H and I (fig. 2) are the main valves, and GC (fig. 1.) is the gas-cock. The side or cam shaft N (sometimes called the 2 to 1 shaft), the cams which move the levers M, the latter in turn operating the valves, and causing them to open and close at the proper time, are shown in fig. 11. A bracket bolted up to the side of cylinder forms a bearing for one end of the side shaft, and also carries a spindle at its lower end on which the levers oscillate, transmitting the motion imparted to them by the cams to the valves. The main cylinder casting and the bed need no description. In some cases the bed is in two portions, though now a great many makers are discarding the lower portion altogether, having found that it is cheaper, and quite as satisfactory, to use a built-up foundation instead, and, if necessary, to cut a trough for the fly-wheel to run it. This arrangement, however, only obtains where larger engines are concerned. A half-compression handle by which the exhaust cam is moved laterally on the side shaft as required is not needed on very small engines. [Illustration: FIG. 1.--General Arrangement of a Gas Engine and Accessories.] Further reference will be made to this in another chapter, and, although this is not a necessity on a _small_ engine, it is always employed on engines over 2 B.H.P. In fig. 1, HW is the cooling water outlet and CW the inlet. A small drain cock is shown at DC, through which the water in the cylinder water-jacket may be drawn off when required. The pipes leading to the inlet and outlet of this supply are connected to the cooling water tank by means of a couple of broad, flat nuts and lead washers, one inside and the other outside the tank, the latter, when clamped up well, making a perfectly water-tight joint. The outlet pipe making an acute angle with the side of tank, the washers used there should be wedge-shape in section. It is also desirable to fit a stop-cock SC, so that the pipes can be disconnected from the engine entirely, or the water-jacket emptied without running the whole of the water out of the tank. The exhaust pipe EP is made up of gas-barrel. It should lead from the engine to the silencer or exhaust box (if one is found to be necessary) as directly as possible, _i.e._, with no more bends than are needed, and what there are should not be acute. The silencer can be inside or outside the engine-room, whichever is most convenient; but both it and the exhaust piping should be kept from all direct contact with wood-work, and at the same time in a readily accessible position. Beyond the exhaust-pipe and box and the water-tank, the gas bag GB and gas meter (where small powers are concerned, the ordinary house or workshop lighting meter may be used without inconvenience) are the only other accessories which are included in a small installation. [Illustration: FIG. 2.--A Section of a Gas Engine.] Fig. 2 gives a sectional view, showing the cylinder and liner. The latter is a very desirable feature in any type of gas engine, but especially in the larger sizes; for at any future time, should it be found necessary to re-bore the liner, it can be removed with comparative ease, and is, moreover, more readily dealt with in the lathe than the whole cylinder casting would be. The liner is virtually a cast-iron tube, with a specially shaped flange at either end. At the back end the joint between it and the cylinder casting has to be very carefully made. This is a water _and_ explosion joint; hence it has not only to prevent water entering the cylinder from the water-jacket, but also to be sufficiently strong to withstand the pressure generated in the cylinder when the charge is fired. For this purpose specially prepared coppered asbestos rings are used, which will stand both water and intense heat. Sometimes a copper ring alone is employed to make the joint. At the front end the liner is just a good fit, and enters the bed easily, and a couple of bolts fitted in corresponding lugs on the liner, pass through the back end of cylinder casting, so that by tightening up these the joint at back end is made secure. A small groove is cut on a flange, and a rubber ring, of about 1/4-in. sectional diameter, is inserted here when the liner is fitted into the cylinder casting. This makes the water-jacket joint at the front end. [Illustration: FIG. 3.] [Illustration: FIG. 5.] [Illustration: FIG. 4.] Lugs are provided on the bed and cylinder castings, and are bored to receive steel bolts--three are sufficient, provided the metal in and around these lugs is not pinched. In some cases a continuous flange is provided on both bed and cylinder, and a number of bolts inserted all the way round. This, however, is unnecessary, and has a somewhat clumsy appearance. When these bolts are tightened up, the cylinder and liner are clamped firmly to the bed; but the liner being free at the open end, can expand longitudinally without causing stresses in the cylinder casting. The combustion chamber K is virtually part of the cylinder, and has approximately equal to one-fourth the total volume of the cylinder. The shape varies somewhat in different makes of engines; in some it is rectangular, with all the corners well rounded off; in others it is practically a continuation of the cylinder, _i.e._, it is circular in cross-section, with the back end more or less spherical; while, again, it is made slightly oval in cross-section; but in every case the corners should be _well_ curved and rounded off, so that there is no one part which is liable to become heated disproportionately with the rest of the casting; in fact, in the whole cylinder casting there should be no sudden change, but a uniformity in the thickness of the metal employed. This point should be carefully remembered, although it applies more particularly to those parts of the casting subjected to higher temperatures than the rest. The main bearings are usually of brass or gun-metal, and are adjusted for running in the same manner as any steam or other engines would be. The "brasses" are in halves, and are held down by the cast-iron caps, as shown in fig. 1. These bearings require extremely little attention, and do not show the wear and tear of running nearly so soon as the connecting-rod brasses. These, too, are usually of brass or gun-metal; but there are various forms of construction employed in connection with the back end or piston pin bearings. On very small engines the connecting rod is swollen at the back end in the forging, and then machined up and drilled, as shown in fig. 3. In this hole the brasses are inserted after being scraped up to a good fit on the piston pin. A flat is cut on one of the brasses, and a set screw is fitted, as shown, to prevent any movement of the latter after the final adjustment has been made. A lock nut should be used in conjunction with this set screw. Another method, and one more generally used on larger engines, is shown in fig. 4. In this case the brasses are larger than in the former, where they are virtually a split bush; here they have holes drilled in them to take the bolts, the latter usually and preferably being turned up to the shape shown in fig. 5. CHAPTER III HOW A GAS ENGINE WORKS The gas engine of the present day, although from a structural point of view is very different to the early engine, or even that of fifteen years ago, is, in respect to the principle upon which it works, very similar. The greater number of smaller power engines in use in this country work on what is known as the Otto or four-cycle principle; and it is with this class of engine we propose to deal. Reference to the various diagrams in the text will help considerably, and make it an easy matter for any reader hitherto totally unacquainted with such engines to see why and how they work. Coal-gas consists primarily of five other gases, mixed together in certain proportions, these proportions varying slightly in different parts of the country:--Hydrogen (H), 50; marsh gas (CH4), 38; carbon-monoxide, 4; olefines (C6H4), 4; nitrogen (N), 4. Gas _alone_ is not explosive; and before any practical use can be made of it, a considerable quantity of air has to be added, diluting it down to approximately ten parts air to one of pure gas. This mixture is _now_ highly explosive. The reader will do well to bear these facts constantly in mind, especially when he is repairing, adjusting, or experimenting with a gas engine. We wish to emphasise this at the outset, because a consideration of these facts will keep cropping up throughout all our dealings with the gas engine, and if once a fairly clear conception is obtained of how gas will behave under certain and various conditions, half, or even more than half, our "troubles" will disappear; the cry that the gas engine has "gone wrong" will be heard less often, and users would soon learn that the gas engine is in reality as worthy of their confidence as any other form of power generator in common use. But to revert to the explanation of the cycle of operations. The cycle is completed in four strokes of the piston, _i.e._, two revolutions of the crank shaft. At the commencement of the first out-stroke (the charging or suction stroke) gas and air are admitted to the cylinder through the respective valves (fig. 6), and continue to be drawn in by what may be termed the sucking action of the piston, until the completion of this stroke (the _precise_ position of the closing and opening of the valves will be referred to later on). The next stroke (fig. 7) is the compression stroke. All the valves are closed whilst the piston moves inwards, compressing the gases, until at the end of this stroke, and at the instant of maximum compression, the highly explosive charge is fired by means of the hot tube or an electric spark, as the case may be. The ensuing stroke--the second out-stroke of the cycle--is the result of the explosion, the expanding gases driving the piston rapidly before them; this, then, is the expansion, or working stroke (fig. 8.) [Illustration: FIG. 6.--Commencement of first out-stroke suction or charging stroke. Gas and air valve about to open.] [Illustration: FIG. 7.--Compression stroke, during which all valves remain closed.] During the last--the second inward--stroke (fig. 9) the exhaust valve is opened, and the returning piston sweeps all the burnt gases (the product of combustion) out into the exhaust pipe and so into the atmosphere. This completes the cycle, and the piston, crank, and valves are in the same relative positions as formerly, and the same series of operations is repeated again and again. Of course, it is not always the case that both air _and_ gas valve are opened on the charging stroke; that depends upon the method employed to govern the speed of the engine. Supposing it were governed on the hit and miss principle (to be explained hereafter), the gas valve would be allowed to remain closed during the charging stroke, and air alone would be drawn into the cylinder, then compressed, but not being explosive would simply expand again on the working stroke, giving back nearly all the energy which was absorbed in compressing it, and finally be exhausted in the same manner as the burnt gases are. [Illustration: FIG. 8.--Second out stroke, showing position of valves during working stroke.] [Illustration: FIG. 9.--Second inward stroke, showing position of valves during the exhaust stroke.] [Illustration: FIG. 10.--First out-stroke, showing position of valves during the charging stroke.] Fig. 10 shows diagrammatically the position of crank, piston, and valves _during_ the charging stroke. [Illustration: FIG. 11.--Cross Section of Cylinder.] In figs. 1 and 2 we gave drawings of two gas engines, which are typical examples of modern practice. Huge strides have been made in recent years in gas-engine work, as regards both workmanship and efficiency, so that to-day we have in the gas engine a machine whose mechanical efficiency compares favourably with that of any other power generator, and whose thermal efficiency is very much greater. [Illustration: FIG. 12.--Longitudinal Section of Cylinder.] Figs. 11 and 12 show respectively a sectional end and side elevation of the cylinder, from which it will not be difficult for the reader, however unacquainted he may be with gas-engine work, to see how the various requirements and peculiarities of the engine should be considered and provided for. A most important desideratum in any machine or engine is that it shall be as simple in construction as ever possible; complicated mechanism should only be introduced when such addition or complication compensates adequately for what must necessarily be a higher first cost, and incidentally the greater wear and tear and attention involved. Figs. 11 and 12 show what has been done to simplify the construction of the gas engine in recent years. The main feature in this case is the very get-at-able position of the two main valves--the air valve F and the exhaust E. These valves, as may be seen from the drawing, are capable of withdrawal after the cover of the combustion chamber has been removed. The latter is an iron casting, shaped and faced up to make an absolutely tight joint; no asbestos or any packing is used to make this joint--and is held in place by four studs, as shown. Thus, all that is necessary is to remove the four nuts, lift the cover off, then pull out the pins which keep the spiral springs in position, and withdraw the valves. The latter are seated direct on to the metal of the cylinder casting, the gun-metal bushes A and B acting as guides. Further reference to A (the mixer), which serves a twofold purpose, will be made later on. The gas valve and cock are mounted in a separate casting, which is carried by a couple of studs, the joint between this and cylinder being made with a piece of rubber insertion. The gas enters at the gas-cock, passes through the valve and port G, and round the annular space in the bush or "mixer" A, previously mentioned, and thence through a number of small holes in same, immediately below the seat of the air valve F. At the same time, pure air is drawn in _via_ the air box (as explained hereafter), through port L (fig. 11), and thence up the centre of bush A and over the small holes through which the gas is flowing. The two then thoroughly mix and enter the combustion chamber together as the air valve F is opened. This device produces a perfectly homogeneous mixture, which conduces in no small measure to perfect combustion when the explosion takes place, and upon which, to a very great extent, depends the efficiency of the engine. Besides possible loss in this direction, however, there is another source of waste which cannot be eliminated, and that is the heat taken away by the cooling water which surrounds the cylinder. As this loss is inevitable, the best thing we can do is to make it as small as possible. Theoretically, it would be no small advantage if we could work at very much higher temperatures than we do at the present time, and it is only certain mechanical difficulties which bar the way and so effectually prevent the already high thermal efficiency of the engine being greatly increased. It is no easy matter to overcome these difficulties completely, but improvements in this direction are continually being made, so that troubles which attended the gas-engine user years ago no longer exist. All that we require of the cooling water is that it shall keep certain working parts of the engine at a reasonable temperature; for instance, the cylinder must not be so hot as to deprive the lubricating oil of its property to lubricate, neither must the exhaust valve become so hot as to cause it to seize in the bush and stick up; but, beyond such considerations as these, the higher the temperature is at the commencement of each explosion the more efficient will the engine be. The object, then, is to do as little cooling as possible, and to apply the cooling effect at the right parts; hence the passages and chambers through which the cooling water circulates should be so arranged that those which require to be kept at a low temperature are in close proximity to the cooling water. On some of the engines of days gone by, the exhaust valve was carried in a large iron casting, this in turn being bolted to the cylinder casting and communicating with the combustion chamber by means of a port. Such an arrangement was found to be not only clumsy but inefficient; the water passages were small and difficult to get at; they readily furred up; and moreover, the joint between this casting and the cylinder was necessarily a water _and_ explosion joint, and the fewer we have of these the better. The method--if it may be called a method--of overcoming or preventing the exhaust valve becoming too hot is, in the case of figs. 11 and 12, simply one of judicious arrangement and design. The cooling water enters by the inlet K (fig. 11), and circulates round the exhaust valve port X and valve E immediately, before becoming heated, thus keeping the hottest of the working parts of the engine at a suitable temperature; and the valve seat, being in direct metallic communication with the cold water, does not become burnt or pitted. On the other side of the exhaust valve we have the air valve and its passages, through which cool air is continually being drawn; this also helps to keep the exhaust valve cool. From this, then, we may conclude that overheating of the cylinder will not occur under normal conditions, given an engine of good design; but, if this trouble does arise, we may safely look first of all for some defect in the cooling water circulation. Some waters contain a greater amount of impurities than others, and consequently the water space may furr up more rapidly in one district than in another. But this deposit, even under the worst conditions, accumulates very slowly, and the operation of cleaning out the water-jacket is a very infrequent necessity. The exhaust valve, however, may become overheated if it is allowed to get into bad condition, _i.e._, leaky. Its seat should be well looked after, or the hot gases will blow past when it is presumably shut; and if this defect, slight though it may be to begin with, is allowed to develop, both the seat, the valve head, and the spindle will become burnt away and pitted, perhaps badly, due to the excessive heat. CHAPTER IV IGNITION DEVICES The ignition devices commonly employed may be divided into three main classes--the metal tube, the porcelain tube, and the electric ignition. These again may be subdivided: The first being either iron or nickel (hecknum as they are sometimes called); the second are of two kinds--single-ended and double-ended; and the third takes many forms which many of my readers are possibly well acquainted with, such as the magneto, the induction coil and trembler, and the high-tension magneto ignition, the latter device having been used successfully on various occasions, though not yet universally adopted. The first-named have one or two advantages over the nickel tube. They are very inexpensive, and are easily heated to the required temperature; moreover, they can be made at home, should occasion demand. On the other hand, they are not so durable, have a very uncertain life, and consequently need renewing frequently--their average life being not more than 60 working hours. Fig. 13 gives an outline drawing of an iron tube, with its burner and chimney fixed in position. The tube is very similar to a piece of 1/4-in. gas-barrel, closed up at one end and a taper thread (1/4-in. gas) cut on the other; in fact, gas-barrel may be used for making these tubes at home--and measure about 7 or 8 in. over all It is screwed into a firing block, which in turn is screwed into the combustion chamber end, so that when right home it is in such position that the tube stands quite vertical. The section of the tube, fig. 13, shows the condition it gets into after having been in use some time. The bore, it will be seen, has become almost completely closed up, so that there is practically no communication between the hot part of the tube and the combustion chamber. This closing up of the bore is very gradual, and it is in the early stages of this process that erratic firing is likely to occur; sometimes the charge will be successfully fired and sometimes not. It may be as well to mention here that the length of the tube, although to a certain extent immaterial, should neither be excessively long nor abnormally short, the precise length varying with the size of the engine. A 1/4-in. tube, 8 ins. long, may be used successfully on engines ranging from 1/2 to 6 horse-power, provided a suitable burner is fitted enabling the tube to be heated at any required spot. After the first charge has been fired, and the exhaust takes place, practically all the burnt gases are cleared out of the cylinder, but a small amount of these will generally remain in the tube and the bore of the firing block. On the ensuing compression stroke these inert gases are compressed to the far end of the tube, thus making way for the explosive mixture to reach the hot portion, and explode, thus sending a jet of flame into the main volume of the mixture which is immediately ignited. Hence there is no advantage in having a tube too long, while, on the other hand, it _must_ not be too short. [Illustration: FIG. 13.] [Illustration: FIG. 14.] [Illustration: FIG. 15.] The asbestos lining, shown in fig. 13, may be of various thicknesses, according to the size of the chimney and the tube; the reason for this will be apparent to many; but being a most important factor in the heating of the tube, and consequently the working of the engine, it will be advisable to deal with this point more fully. Due mainly to the peculiar behaviour of iron tubes under heat and internal pressure, it is always advisable to look to them first of all when the engine shows signs of missing fire; and to always examine the bore of a fresh one, and ascertain that it is perfectly clear before putting it in. The adjustment of the ignition tube, although one of the most important and necessary to be made on the whole engine, is in itself a perfectly simple matter. It must be understood that the ignition tube cannot, with the ordinary means at our disposal, be kept at too high a temperature; but it must not be assumed that either the _size_ of the flame, or the _time_ the flame has been alight, is conclusive evidence that the tube is, or ought to be, sufficiently hot to fire the charge successfully. It is an uncommon thing to hear a man exclaim--after it has been pointed out that his tube is practically cold--"Why, it's been alight for hours!" If such is the case with you, reader, you may very rightly assume that the burner is not properly adjusted, and so does not give the _right kind of flame_. In order to get the hottest possible flame, the quantity of gas and air must be mixed in the right proportions. A common fault is that there is too much gas allowed to flow through the nipple, compared with the amount of air being drawn in at the air aperture, fig. 13. The result is, we get a flame of great length, but one which is not at all suited to our requirements; and instead of giving up its heat to the tube and the asbestos lining of the chimney, a large amount of gas we are presumably burning _in_ the chimney is not being burnt there at all, for, on applying a light just above the chimney top, a quantity of this gas we are wasting will be seen to burn with a flickering blue flame. To put matters right, it is necessary to do one of two things--either cut down the supply of gas or increase the air-supply. Providing the air aperture is normal, _i.e._, the same size as it was originally, it is better to adjust the _gas_, which may be done by tapping up the nipple N, as indicated in the enlarged sketch, fig. 14, until just the right amount of gas can flow. As a rule, if there is too much air, the flame will burn with a loud roaring noise, and is liable to fire back. The nipple should then be opened out with a small reamer--the tang of a small file, ground to a long taper point, makes an admirable tool for this purpose. Whether the burner is of the ordinary bunsen type, or the ring or stove type, the above remarks apply, as in every case the flow of gas is governed by the size of the orifice through which it flows. There is no need to use anything beyond a touch of oil when putting in a new tube, in order to make a perfectly tight joint; white or red lead are quite unnecessary, and are liable to make it a troublesome matter to remove the tube on future occasions. Neither should undue force be applied when putting in new tubes; it is liable to wear the thread in the firing block, which results in a partial stoppage of the ignition hole, as indicated in fig. 15. This is especially the case if we happen to get hold of a tube with its screwed part slightly smaller than usual. The asbestos with which the chimney is lined should be about 1/8 in. thick, and, when renewing, the same thickness should be used as originally. A thicker board will reduce the annular space round the tube, and will have a choking effect on the flame--much the same as referred to above, when there is too much gas and not enough air. A simple method of lining the chimney is to cut a block of wood to the inside dimensions of the chimney, less 1/4 in. in width and thickness, then soften the asbestos cardboard by immersing in water, and bend it round the wood, cutting off to the required size, _i.e._, till the two edges form a neat butt joint. It can be allowed to remain on the mould until dry--when it will retain its shape--or can be put into the chimney straight away, if it is wanted for use immediately. In the latter case, however, it will be some fifteen minutes or so before the tube will attain its working temperature. Asbestos linings gradually become worn and ragged, and small flakes are apt to detach themselves and fall down into the burner, which, of course, prevents the flame playing as it should around the tube. In such cases it is not always necessary to fit a new lining; if the chimney is removed, the loose flakes shaken out and the asbestos well damped and patted down with a wooden or steel foot-rule or other suitably shaped tool, it will be fit for another long spell of work. The nickel or hecknum tubes are treated in the same manner as the iron, but, as we mentioned before, are more durable, but require more heating to get them up to a workable temperature. Their greater first cost is compensated to some extent by makers in some cases guaranteeing them for six months. Of the porcelain ignition devices, we will deal with the double-ended tube first, it being the more commonly used of the two in this country. This form of tube is usually about 3 in. long, 1/2 in. diameter, and open at both ends. It may be mounted in a metal casting, in form not unlike the small gas stoves for heating soldering irons. It is heated the greater part of its length by a couple of rows of gas jets, and is frequently surrounded by an asbestos lining. The whole arrangement is in reality a tiny furnace. When in position for working, one end of the tube is open to the ignition passage leading and communicating with the combustion chamber, while the other end is sealed, through butting up against a metal cap or plate. An asbestos washer is interposed between the tube at each end and the metal it bears against, thus making a more or less flexible joint. A thumb screw is arranged at the outside end of the tube, by means of which pressure can be applied to clamp it up between the washers to the desired extent. Some care has to be exercised in adjusting this form of tube for running. When heated to the working temperature it, of course, expands, so that, if tightened up too much when cold, it is under a fairly high compression; and when the engine is started, and the explosion takes place, it not infrequently bursts, if there is not sufficient "give" in the washers to allow for the expansion. On the other hand, if not clamped up sufficiently tight to start with, when the explosion occurs, the washer at one or each end is blown out. This adjustment has to be made to a nicety, and, although a somewhat difficult matter, success may be attained after one or two trials. It is advisable, after a new tube has been put in, to start up the engine gently, _i.e._, with less than the normal supply of gas, and increase to the full amount gradually whilst running. This may be done by simply opening the gas-cock on engine partially in the first place. The single-ended porcelain tube is not so well known here as on the continent; why, we cannot say; certainly it is preferable in every way. We give a few illustrations, showing the method of using this tube. Figs. 16 and 17 show the general arrangement of tube and chimney and the manner in which they are fixed to the cylinder. The device consists primarily of three parts--the body or chimney B, the cover C, and the tube itself T. The body is a light iron casting, carried by a couple of studs SS, which are either screwed into the firing block F, or direct into the metal of the cylinder casting if no firing-block is used; the latter may very well be dispensed with in the smaller-sized engines. The tube is made of thin porcelain, slightly bell-mouthed at its open end, and is mounted in a thick metal washer W, as shown in fig. 18 in section, the joint being made with a little asbestos paper, moistened. The block F and the face of the body B (fig. 16) are recessed to take the washer W easily, but the depth of both recesses taken together must be about 1/16 in. less than the thickness of the washer W; thus, when the tube is placed in position between the body B and the block F, and the former screwed up by means of the two nuts, as shown in the figure 16, the effect is to clamp the _washer_ which carries the tube, but _not the porcelain tube itself_. [Illustration: FIG. 16.] [Illustration: FIG. 17.] [Illustration: FIG. 18.] The latter is left perfectly free to expand; and yet, owing to its particular shape, the pressure in the cylinder during the compression and explosion stroke only tends to make the joint between the tube and washer more secure. The action of this ignition device depends upon the tube heater H, which is merely a small bunsen burner, the flame of which impinges on the tube at one particular spot, raising it to a very high temperature--almost white heat. Most of my readers will know the formation of the bunsen flame. It in composed of two distinct zones. The inner one, marked A in fig. 18, is a perfectly cold part of the flame, and appears to be a pale-blue coloured cone. It is the outer zone which is the hot portion of the flame, hence this part _only_ must be allowed to play on the tube. The tip of the blue cone A must be kept about 1/4 in. below the tube, in order to ensure the hottest part of the flame impinging precisely where the heat is required. The total length of the whole flame is, to a certain extent, immaterial; but, generally speaking, it should be adjusted so that the length of the inner cone A is about 1 in. or 1-1/4 in. The same methods which we described in the early part of this chapter can be employed in the adjustment of this burner, but some care should be exercised to get the correct flame length. The result of allowing the cold part of the flame to impinge on the tube is observable in fig. 18. The black spot indicated on the drawing actually appears as a black or sooty spot when looking at the tube under these conditions; but in reality no discoloration whatever takes place, the spot disappearing immediately the cone A is made shorter, or the burner H lowered in the chimney B, so that the tip of A is just below, and does not touch the tube at all. The adjustment of the length of cone A may be accomplished in two ways--(1) by keeping the supply of gas constant, and varying the amount of air admitted at aperture K, fig. 18; (2) by keeping the supply of air constant, and varying the amount of gas admitted through nipple N. The first method is to be preferred when it is necessary to make any slight adjustment due to the variation of gas pressure during the day, and may be accomplished by fitting a small sliding shield G, as shown in the figs. 16 and 17, and moving it round so that it covers, more or less, the aperture K. Thus the length of cone A may be adjusted to a nicety in a very few seconds. This shield keeps all draughts and puffs of wind from the fly-wheel away from the aperture, and helps the flame to burn very steadily. In the first place, of course, the flame will be regulated by opening out or tapping up the nipple N (an enlarged sketch of which is given in fig. 14), so that cone A is just about 1-1/4 in. long when air aperture is full open; but once this is done, any future adjustment can be made by throttling the air-supply, or raising or lowering the burner bodily, the set screw keeping it in any desired position (see fig. 17). From the foregoing remarks it will be seen that the most noteworthy features of this form of ignition are the ease and certainty with which the tube can be fixed in a few moments; that when the two nuts on the studs SS have been tightened up there is no likelihood of the joints being "blown," for, as we said before, only the metal washer is clamped up, the porcelain tube itself being as free to expand as it was before. It is also at once obvious when any adjustment of the flame is necessary; there need be no uncertainty as to whether the tube is hot enough or not. CHAPTER V MAGNETO IGNITION The third form of ignition we have to deal with is the electric. There are a great number of different types made and used, but for gas-engine use perhaps that known as the magneto ignition is the most satisfactory. With this form, neither accumulators, dry batteries, or spark coils are required, and consequently a greater simplicity is arrived at than would otherwise be the case. In fig. 19 we show diagrammatically the ordinary form of magneto machine. Virtually it is a small dynamo which is fixed to the side of cylinder casting, and is operated in the manner shortly to be described. As we do not propose to enter into more than a brief explanation of why and how this apparatus generates current to produce the required spark, perhaps a simple analogy will make matters most intelligible to any reader not well acquainted with electrical phenomena. We know that when a current of electricity is flowing in a wire, and the wire be suddenly broken, a spark will occur at the point of breakage. This fact may be observed in an ordinary electric bell when ringing; at the tip of the contact breaker a number of tiny sparks may be seen to occur, due to the rapid make and break of the current flowing in the circuit. Precisely the same action takes place in our magneto-igniter, but, instead of a multitude of tiny sparks, we produce one at a time, at definite intervals, viz., at the commencement of each explosion stroke. [Illustration: FIG. 19.] In the later form of magneto machines there is a soft iron sleeve between the magnet poles and the armature. The former is connected to a system of levers by which a reciprocating motion is imparted to it by means of a suitably arranged cam on the side shaft. It has been found that better results are obtained by causing the magnetic field to move relative to the armature winding than to move the latter through a stationary field. Reference to the diagrams, figs. 20 and 21, will make this clear. In fig. 19 the cam C is shown just on the point of allowing the lever L to fly back into its normal position, due to the action of the springs comprising a dashpot S. As the cam rotates, it pushes the lever L to the left, the sleeve (or virtually the armature A) is also rotated through a portion of a revolution comparatively slowly; but as soon as L is released, the sleeve (or armature) flies back again almost instantaneously and for the moment is generating a current in the same manner as would any ordinary continuous current dynamo. [Illustration: FIG. 20.] [Illustration: FIG. 21.] At the instant the maximum current is being generated, the circuit is broken by means of the contact breaker D, fig. 19, which we show in detail in fig. 22. The latter is mounted on the end of the combustion chamber, and consists of two parts, D and P. [Illustration: FIG. 22.] D is an easy fit in the hole bored to receive it, and has a mushroom valve head and seating, as shown, so that it moves readily when struck by the projection E on the rod R (fig. 19); but yet, acting in the manner of a non-return valve, it allows no gas to escape when the explosion takes place in the cylinder. D is therefore in direct metallic communication with the engine frame and earth. P is a fixed metal pin, carefully insulated from all contact with the engine frame and earth. To this pin one end of the armature winding is connected, whilst the other end is connected to the engine frame. Thus a closed circuit is formed, and when the current is generated it flows from one terminal of magneto through wire to pin P, on to D, through D to earth (_i.e._, engine frame), and so back to other terminal on magneto. And as the circuit is broken between D and P, we obtain a spark, as previously explained, which may be timed to take place by adjusting the position of cam C on side shaft relatively to the position of piston. It may be said that the position of the magneto-igniter is immaterial; it will be fixed in different positions on different types of engines, and so long as the operating mechanism is simple and effective, _i.e._, as direct as is practicable, it works well, and requires little attention. The timing of the spark will be dealt with in the chapter on Cams and Valve Settings. CHAPTER VI GOVERNING The devices for governing the speed of the engine may be divided, broadly speaking, into two classes--the inertia or hit and miss governor, and the centrifugal. Of the latter type we will give an instance first. In figs. 23 and 24 the governor gear is shown diagrammatically, consisting of a couple of weights WW suspended from a vertical spindle. These fly apart when caused to revolve by the bevel wheel gearing BB, and raise the sleeve S to a greater or lesser extent. A recess in the latter engages a lever arm L, through which the vertical movement of the sleeve S is converted into a horizontal movement of the sleeve T. The latter is carried by the valve lever P, and is virtually a roller which engages with one or other of the steps of the cam C, according to the speed of the engine. The object of this arrangement is to keep the ratio of air to gas uniform throughout all variations of load. The gas and air valve are shown as both being operated by the same lever P, the accurate timing of the latter being obtained by means of set screws. [Illustration: FIG. 23.] [Illustration: FIG. 24.] Messrs Dougill & Co.'s engines are fitted with a step down cam and governor such as this. The centrifugal governor is often arranged so that instead of the charge being merely reduced in volume, the whole charge is cut out, and no explosion whatever takes place. (In this respect the same results are obtained as when a hit and miss governor is used, and the latter form therefore is to be preferred, especially on small engines, where the difference between the indicated power and the brake power is always, even under the best conditions, fairly great.) In this case the governor lever only operates the gas valve; the air valve being opened on every charging or suction stroke, whether gas is admitted or not. Another application of the centrifugal governor is to suspend a distance piece on the end of the governor lever, so that at normal speed this distance piece is interposed between the gas valve spindle and the lever operating it. In that case the gas valve will be opened. But if the speed is above the normal, the distance piece will be raised clear of the valve spindle, and the opening mechanism (driven by a cam on the side shaft) will simply move forward and recede again without ever touching the gas valve. There are any number of movements which have been, and there are many more which could be, devised to give the same result; and it depends principally upon the form of engine in question which device we adopt. The simplest and most direct action is, however, always the best; complicated mechanism is to be deprecated, especially on small engines. For this reason is the inertia governor more generally fitted to such engines. [Illustration: FIG. 25.] A simple form of this governor is shown in fig. 25. The gas valve V is shown on its seating. It is screwed into a pecker block B, and pinned as shown. The latter should be of cast steel, tempered to a straw colour; or if mild steel or iron is used, it must be well case-hardened, in order to resist wear. The pecker P (also tempered hard) is mounted on the cast-iron weight W, which in turn is pivoted on the valve lever L. It will be seen that the weight W (which is only held in the position shown by the spring S) will tend to lag behind when a sudden upward motion is imparted to the lever L. Thus it depends upon the degree of suddenness with which L moves whether the pecker P remains in the same relative position to the lever as the latter travels upwards and engages with the pecker block B, or whether it misses it and simply slides over the face of the block. The adjustment of the spring S is effected by screwing up or slacking out the milled nuts T; and on the degree to which this spring is compressed depends the sensitiveness of the governor, and consequently the speed of the engine. To obtain accurate and steady governing with this type of mechanism it is essential that the weight be perfectly free on its spindle, and that nothing but the spring S holds, or tends to hold, it in the position shown. On this account it is advisable to provide a "lip" on the pecker block, as shown, to keep the area of contact as small as possible. This effectually prevents any sticking, should a superfluity of oil happen to get on either block or pecker. For similar reasons there should be some clearance between A and the pecker, _i.e._, the latter should only bear at one point and not bed flat against A. Another form of inertia governor is shown in fig. 26 of the hit and miss type, which is employed by Messrs Capel & Co. on many of their engines. It consists of three main parts--the brass arm L carried on a stud D, on which it is free to move; the weight W, which carries the pecker P pivoted at the upper end of L; and the pecker block B, which engages the pecker when the engine requires a charge of gas. The governing action is dependent upon the shape of the operating cam from X to Y. (In the case already dealt with, the lever L serves to operate both air and gas valves, and so one cam only is necessary; but in this instance the gas valve is operated by a separate cam, and a greater nicety of adjustment is obtainable.) [Illustration: FIG. 26.] If the speed of the engine is sufficiently high, the arm L is thrust forward at such a rate that the weight W tends to lag behind, with the result that P is raised above the notch in B, as shown by the dotted lines in drawing. On the other hand, when the speed is too low, the arm L will not be thrust forward with so great a degree of suddenness, the weight W will have time to move with L, and the relative position of W and P to L will remain the same. Hence, in the first case, when a _further_ forward movement is given to L by the cam, the pecker P is clear of B, and omits to open the gas valve V; in the second case, P engages with B, and the gas valve is held open during the time the portion of cam Y to Z is passing over the roller R on arm L. The great drawback to some forms of governors is not that they fail to govern well when new, but that no provision is made to ensure them working steadily when a bit worn. The shape of the cam has everything to do with the regular working of this form of governor. Supposing our cam was of the shape shown in fig. 27, _i.e._, the governing and opening portion all in one curve, it would cause the pecker to move both _forward_ and in an _upward_ direction at the _same time_, so that at the moment of engaging B, P might still be moving in an upward direction, which would cause uncertainty of action, especially if the tips of the engaging members were at all blunt through wear; and, in all probability, P would fly off B after partially opening the gas valve. This behaviour is very undesirable, as the small quantity of gas so admitted to the cylinder is quite useless, and a sheer waste is incurred. With the governing arrangement shown in fig. 26, this trouble does not exist. The cam is so designed that the first rise from X to A determines whether or not the valve is to be opened; the curve from A to Y is struck from the centre of the side shaft; thus, during that portion of the revolution the arm L is stationary, and the pecker at the same instant takes up a definite position either in the notch in B or on top of it, and is ready to open the valve if the speed of the engine is such as to require an explosion, or simply to slide over the top of B, allowing the valve to remain closed. It is most interesting to observe the action of this governor; when an engine fitted with one is running very slowly, the three distinct movements of the pecker P may be clearly discerned as the respective portions of the cam pass over the small roller R. [Illustration: FIG. 27.] CHAPTER VII CAMS AND VALVE SETTINGS With the gas, as with any other kind of engine, the valve settings are of primary importance. On very small engines it is often the case that only the exhaust valve is operated mechanically. Again, there are several well-known makes which operate the gas and exhaust mechanically while the air valve is opened by suction alone. Though opinions differ as to which is the best course to take, there can be little doubt that, with all three valves mechanically operated, a greater nicety of adjustment is obtainable than would be otherwise possible. And provided the working parts are neatly made and finished, they will take but little power to drive them; and such loss would be compensated by the additional power and efficiency obtained from the engine, due to satisfactory and correct adjustment. In fig. 28 we give a diagram showing the exact positions of the crank when the gas, air, and exhaust valves open and close respectively, under normal conditions of working. The solid circle represents the first revolution of the crank shaft, starting from the commencement of the suction stroke, and the dotted circle the second revolution, during which the explosion and exhaust strokes take place; the dotted horizontal line shows the position of crank at the back and front dead centres. As a clear conception of why certain things happen under certain conditions is most desirable, we will first describe the operation of marking off the cams which operate the respective valve levers, and then discuss the effect of various "settings" of the valves on the running of the engine. [Illustration: FIG. 28.] Assuming that we are still dealing with the Otto cycle engine, the cam or side shaft will revolve at precisely half the speed of the crank shaft. This 2 to 1 motion is obtained by means of toothed wheels, or a screw gear. In the former case, where plain or bevel cog-wheels are employed, the one fixed on the crank shaft must be exactly half the diameter of the one on the side shaft, _i.e._, it must have one half the number of teeth. On the other hand, if a screw gear is used, the relative diameters of the two wheels may vary, but the pitch of the teeth on the one must be twice that of the other. These wheels sometimes have the teeth or thread formed in the casting, and sometimes they are cut after a plain casting has been made. The latter kind are, needless to say, better than the former, which often require filing up in order to make every tooth alike, and ensure sweet running. We know already in what positions our crank has to be at the opening and closing of the three valves, and with the aid of the diagram, fig. 28, we can determine the size of the cams. In fig. 29, S is the side shaft to which the cams have to be keyed, R the roller on valve lever, the latter being represented by the centre lines LL, as all we require to find is the motion this lever will transmit to the valve, the spindle of which is shown at V. Fig. 30 shows diagrammatically the position of crank at the opening and closing of the air valve. From this we see that the angle through which the crank travels during the time the air valve is open is equal to the obtuse angle ABC. Now, as the side shaft S revolves at half the speed of crank, it is obvious that the former will travel through only half that angle in the same space of time, _i.e._, through an angle equal to ABD. We can now transfer this angle on to S, fig. 29, and draw two lines SE, SF, cutting a circle GHJ, representing the back of the cam, which latter passes in front of the roller R without causing any movement of the lever L. [Illustration: FIG. 29.] [Illustration: FIG. 30.] [Illustration: FIG. 31.] It will be seen that by drawing a line forming a tangent to the circle GHJ at F and another at E, and producing these, they will meet at point K. Consequently, as the side shaft rotates in the direction indicated, the lever L will _begin_ to open the valve V when the cam is in the position shown in fig. 29, reach a maximum opening at K, and finally close when the cam has moved so that point E is now where F was. With a cam of this shape, however, a considerable portion of the stroke would have passed before the valve was raised any _appreciable_ distance off its seat; it would only be fully open for an instant, viz., when K was passing over R, and would begin to close again directly. Moreover, if the engine were running at even a slow speed, the motion imparted to lever L would be indefinite; and this, especially if the governor is fitted to the air valve lever, as in fig. 25, is very undesirable. Therefore, to obtain a definite opening we must set out the cam, as shown in fig. 31. In this diagram the roller is shown standing clear of the back of cam by about 1/16 in. A line MN is then drawn, forming a tangent to both roller R and circle GHJ at points F and O respectively. This gives us the opening portion of cam. Then from the centre S with radius SF describe the arc FE (shown dotted in fig. 31), and set off the angle required (ABD, fig. 30), as previously explained. Through point E draw a line forming a tangent to circle GHJ, and produce it towards P. This line gives us the closing portion of cam. The distance W is of course variable, according to the amount of lift we give the valve. By comparing these two diagrams it will be seen that in both cases the valve will be opened the same length of time, but in first case the motion will be indefinite and uncertain. In practice the corners are rounded off somewhat, in order to obtain a steady motion; and when the air cam is also the governing cam, it is advisable to round off the opening face, as indicated in fig. 32. Upon the shape of this face both the sensitiveness and the life of the governor gear depends. If it is nicely rounded off, giving a gradual rise, very little tension (or compression, as the case may be) of the controlling spring will be necessary to give the required speed to engine; whereas, if the rise is sudden, the spring will have to be screwed up tighter, and, if uneven and lumpy (_i.e._, not a fair curve), the result will, of course, be erratic governing. [Illustration: FIG. 32.] A certain amount of clearance should always be provided between the roller and the back of cam (compare figs. 29 and 31), that is, the roller should not bear against the cam, except during that portion of the stroke in which it is actually operating the valve, viz., from F to E (fig. 31). A small stop interposed between the lever and some convenient part of the engine, such as the side-shaft bracket bearing, answers this purpose. [Illustration: FIG. 33.] [Illustration: FIG. 34.] The size and shape of the exhaust cam is found in the same manner as above described; the angle through which it operates is greater than that of the air cam, and is shown in fig. 33. A fair margin should be allowed for filing or machining these castings up; the shape and sizes arrived at by the above described method being finished measurements. Fig. 34 gives the outline of an exhaust cam worked out from the setting diagram, fig. 33. [Illustration: FIG. 35.] [Illustration: FIG. 37.] [Illustration: FIG. 41.] [Illustration: FIG. 42.] We may now consider the relative positions these two cams will occupy when keyed up on the side shaft. Assuming that we have both cams finished to the proper shape and size, and the keyway cut in the side shaft, we can commence to mark off the position of keyway in the air cam. With the crank in the position shown in fig. 35, the air cam is slipped on to the side shaft and brought to the position shown in fig. 32. The keyway being already cut in the side shaft, the position for that in the cam may be scribed off, as shown by dotted lines (fig. 32), the cam removed, and the keyway cut. It is as well, however, to check this mark by turning the crank round to position shown in fig. 37, _i.e._, the closing of air valve. The side shaft will also turn through exactly half this angle, so that when the cam is again slipped on the latter, the scriber marks and keyway in shaft should be exactly in line, as they were in fig. 32, and the fall of the cam--the closing portion--should just be touching roller R, but not sufficient to keep the valve open (see fig. 38). The slightest movement of the crank from this point in a forward direction should result in a little play being felt in the lever L, assuming that the cam is also moved just enough to keep the scriber marks in line with the existing keyway. [Illustration: FIG. 36.] [Illustration: FIG. 38.] [Illustration: FIG. 39.] By these operations it will be at once evident whether the cam is too large or too small. Supposing it is too small, we will obtain two sets of marks indicating the position of keyway, as shown in fig. 39, and it is obvious that we must give the lever less play by screwing up the set screws shown in fig. 11. The effect of this is to cause the valve to open earlier and close later than it would if the play were greater; as it would were the operating portion of cam larger. A minimum amount of play must always be allowed, however. When two sets of marks are obtained, the mean must be taken and the keyway cut as shown by the thick lines in fig. 39. The exhaust cam in larger engines is usually made with a swelling on the opening portion, as shown in fig. 40, so that the valve is _very slightly_ opened some time before the crank has reached the position shown in fig. 41. Fig. 42 shows position of crank at the close of exhaust valve, and the two last-mentioned diagrams correspond with the two positions in which the exhaust cam is shown in fig. 34. The small lump on the back of exhaust cam, fig. 40, is only required on engines above 3 B.H.P. to relieve the compression on the compression stroke when starting up. By moving the roller R on valve lever longitudinally, so that it engages both parts of cam as they pass in front of it, the exhaust valve is held open during a small portion of the compression stroke, usually closing when the crank has reached the bottom centre. Referring again to fig. 26, this gas or governor cam may be set out, and the keyway marked on the same principle as already described for the air and exhaust valves. An end view of the three cams keyed up on the side shaft is given in fig. 40A. In small engines it is convenient to have the air and exhaust cams made in one casting, when one key only will be required. On some engines, instead of employing a movable roller or valve lever, the exhaust cam is fitted on side shaft with a "feather"--_i.e._, a headless key--and the cam being capable of longitudinal movement, such movement being controlled by a small lever or handle, called the half-compression lever. [Illustration: FIG. 40.] [Illustration: FIG. 40A.] Having once thoroughly grasped the important part the cams play in the working of the engine, it will be an easy matter to adjust the valve settings, and to keep them adjusted correctly. The effect of a wrong setting will then be strikingly apparent. On small engines a separate cam to operate the gas valve is not a necessity; and the practice of fitting the gas valve spindle (or the pecker, the effect would be the same) with a device for increasing or diminishing its length, is also unnecessary and unsound. The wear on a well-designed gas valve operating mechanism is practically nil; and even if there was wear, the effect would be to cause the valve to open a trifle later and close sooner than it would otherwise, _i.e._, it would remain open a shorter time during each charging stroke. This in turn (other conditions remaining the same) would give us a weaker mixture; and although too weak a mixture is preferable to a too rich one, we should have to adopt some means of increasing the richness of the mixture; otherwise the maximum power of the engine would soon be seen to diminish. To get the mixture normal again we must either enlarge the gas inlet or cut down the air-supply somewhat, and so keep the proportions the same. That is to say, the quality of the mixture is dependent upon the relative dimension of the gas and air inlets. We know by actual trial that if at the completion of the charging stroke the pressure in the cylinder is approximately that of the atmosphere, better results are obtained than when the pressure is considerably below that of the atmosphere. Thus, the larger we make the inlet ports (but still retaining correct relative dimensions) the more readily will the mixture be drawn into the cylinder as the piston moves forward, tending to create a vacuum. Of the two courses open to us to retain a good mixture it is preferable to open out the gas-supply, for by cutting down the air-supply, and sucking the gas in, due to the partial vacuum being formed, we should be keeping the proportions correct at the expense of reducing the total volume of the explosive mixture (more strictly speaking, the density of the charge) admitted to the cylinder. Under normal conditions it is not necessary to create a high vacuum to suck the gas into the cylinder, but it is as well to understand what results we would tend to produce, did we work on these lines. Of course, with small high-speed engines fitted with suction air valve, the vacuum is higher than it would be in slow-speed engines with mechanically operated valves. If we take an extreme case as an example, where, to get any gas to speak of into the cylinder the air-supply would have to be cut down or throttled to an abnormal extent, we will realise at once that such a small quantity of both air and gas would have been drawn in, and consequently the mixture would be so rarefied that on the compression stroke the pressure would possibly be extremely low and totally inadequate to produce efficient working. Moreover, working at such a high vacuum as this would not only prevent us obtaining a normal explosion in the cylinder, but would upset the working of the exhaust valve. The latter being held down on its seat during the suction stroke by means of a spiral spring would be lifted off its seat by suction (the partial vacuum in the cylinder), and any burnt gases which happened to be hanging about in the exhaust port or pipe would be drawn into the cylinder again, and tend to damp the ensuing explosion. Too early closing of the exhaust should be avoided almost as rigorously as too late. The latter will affect the working in a similar way to the exhaust being lifted on the charging stroke by suction; on the other hand, if it closes too soon, the entire volume of burnt gases will not have been swept out of the cylinder, and the effect will again be to damp the following explosion. The gas valve opens just after the crank is above the back centre and closes just before the front centre is reached, that is, opening a little after the air valve and closing a shade before it, thus every particle of gas is used in the cylinder, due to a draught of air being drawn in after the gas valve has been closed. The settings of the valve being of primary importance, no matter what size engine we are dealing with, and being also the most confusing matter for anyone unacquainted with gas engines to grasp, it will not be out of place to suggest a simple method of checking these settings. Let us begin by pulling the fly-wheel round backwards until we feel the piston is on the compression stroke, then from this point--the crank being about 45° above the front centre--pull the wheel round until the crank is in the position for the exhaust opening (see fig. 28). In this position there should be but the _slightest_ play in the exhaust lever, showing that the valve is _just_ on point of opening; and by keeping one's hand on the lever whilst the fly-wheel is pulled round _very slowly_ (it is a good plan to get some one else to do the pulling round), it is possible to ascertain the precise point at which the valve opens. Next pull round till the crank is in the position for the air valve opening, and observe that it is set correctly. Then go on to a trifle above the back centre, where the exhaust valve should close, and so on till the opening and closing of each valve has been checked. It will be noticed that the air, and sometimes the gas, valve opens before the exhaust closes. This overlap is necessary; and it will be found that the smaller the engine and the higher the speed the greater this overlap will be to obtain good results, although a good deal of individual judgment must be used in settling the exact amount of overlap, as the requisite amount may, to get the best results, vary in different engines of precisely the same dimensions and type. When dealing with engines which have no separate gas valve--the gas being admitted with the air, which is sometimes the case with very small engines--the above notes referring to the gas setting independently, will, of course, not hold good. It may be mentioned with regard to the lump on the opening side of the exhaust cam, that this if overdone is found to be detrimental on large engines, and even on small ones. If it is too large, it will cause both exhaust valve and seat to become burnt and pitted, due to the surface being exposed to the exceedingly high temperature of the expanding gases. If it is too large, it is equivalent to opening the exhaust valve too early, and the effect is the same, viz., a waste of power and damage to the valve and its seat. [Illustration: FIG. 43.] [Illustration: FIG. 44.--Brake Testing.] The method of grinding in the valves to their seats with emery powder and oil is so well known that no further description is needed here. We give, however, in fig. 43 a sketch showing a very expeditious way of dealing with very badly worn or burnt seats. The sketch explains itself. Such a tool is readily made; even the cutter could be turned and filed up to shape and then hardened at home. By lightly tapping in the taper cotter pin little by little, sufficient pressure is put on the cutter to make it an easy matter to completely re-face an old seat or form a new one. A T-wrench or "tommy" can be used to work the cutter spindle. The lower part of the latter must be the same diameter as the existing valve spindle; the bush acts as a guide; and as the bevel of the cutter should be the same as that of the valve, a very little grinding in with emery powder is required to finish the job off. In fig. 44 we give a diagram showing the method of testing for Brake H.P. of engine, as it is frequently interesting to make such a simple test after any alterations or adjustments have been made. Two spring balances and a rope or cord (according to the size of the engine), fitted with a few wood blocks as shown in section, fig. 44, to keep the rope on the rim of fly-wheel, is all that is required for this test. The following formula may be used for arriving at the B.H.P.:-- B.H.P. = (S1 - S2) 3.14 x D x R / 33000 S1 = Reading in lbs. of spring balance No. 1. S2 = Reading in lbs. of spring balance No. 2. D = Diameter of fly-wheel and diameter of brake rope in feet. R = Revolutions of fly-wheel per minute. As 3.14 x D / 33000 will always remain the same for any given engine and gear, we may call that expression C; then the B.H.P. may be written-- B.H.P. = (S1 - S2) C R CHAPTER VIII OIL ENGINES The small oil engine is practically the same as the gas engine, with the addition of a vaporiser for converting the oil into gas, or vapour, to be exploded in the cylinder; consequently the one may be converted into the other in many cases without much trouble. The difficulty of producing an efficient oil engine lies principally in devising a satisfactory and reliable vapouriser--one which will work equally well under all loads. The heat supplied to the chamber must be sufficient to vaporise the oil, but not great enough to decompose it. There are various methods of vaporising the oil, and many types of vaporisers are employed to attain the same end. There are some in which a charge of oil is drawn by suction into a hot chamber in which it is converted into vapour and at the same time mixed with a small quantity of hot air; this rich mixture is then passed into the combustion chamber of the engine, in the same manner as coal-gas would be, where it is further diluted with more air drawn in through the air valve. Other arrangements cause a jet of oil to be injected into a chamber containing hot air, in the form of spray, which immediately converts the oil into vapour, and is then passed into the cylinder, compressed, and fired. Then, again, we can pump oil through a spraying nipple into the vapouriser (which is kept at a suitable temperature) whilst the cylinder is being filled with air on the suction stroke. On the following compression stroke the air is driven into the vapouriser, which communicates with the cylinder through a narrow neck, and mixes intimately with the oil vapour. Gradually, as the pressure rises, due to compression, the charge becomes more and more explosive, until at the completion of this stroke it has attained the proper proportions of air and oil vapour, and is fired by the temperature of the vapouriser and that caused by a high compression; that is, the charge is fired automatically; and once the engine is running, no heating lamp is required to keep the vapouriser at the correct temperature. It is necessary, however, to raise it to the workable temperature at starting. This is known as the Hornsby-Akroyd method. Capel's arrangement is also simple and efficient, and has the additional advantage of being capable of being fitted to their existing gas engines, the conversion being made in a very short time. This vapouriser consists primarily of a tubular casting A, on the outside of which are formed a series of vertical ribs, shown in plan, fig. 46, running to within a short distance of the flange at one end, as shown in the section, fig. 45, thus providing an annular space C between the upper ends of the ribs and the flange. This casting is enclosed by an outer casing B, which fits well over the inner tube. It has also a number of small holes drilled near the lower end communicating with the channels between the ribs. Thus it will be seen that when the gas valve is opened and suction takes place, air is drawn in through these holes, passes up into the annular space C below the top flange, from there travels to the opposite side of vapouriser, and mixes with the oil which is also being drawn in through a small nipper at N, fig. 45. Both then pass between a series of pegs, where they become thoroughly mixed, and finally pass on to the inlet valve V, fig. 47, and so into the cylinder, where the complete charge is mixed up and compressed and fired in the usual manner. Iron ignition tubes may be used, and one heating lamp serves a double purpose in keeping the tube and vapouriser hot at the same time. This lamp is fed by means of a pump actuated from the side shaft. The plunger of the pump is loaded with a spiral spring, which may be adjusted to give any desired pressure, and is kept constant and steady by means of an air vessel. This pump is shown in fig. 48. It is actuated by means of a rod and lever from the side shaft of engine. The plunger P works in a barrel B, which is carried by a small reservoir R, the latter being in communication with the main oil tank by means of the pipe H. [Illustration: FIG. 46.] [Illustration: FIG. 45.] [Illustration: FIG. 47.] [Illustration: FIG. 48.] [Illustration: FIG. 49.] [Illustration: FIG. 50.] [Illustration: FIG. 51.] The plunger is loaded with a spiral spring, and has a ball valve, as shown. Intermediate between this small reservoir and the main oil tank is another set of valves, shown in fig. 49. It will be seen that the suction of the pump will draw the oil up, the small and lower ball valve, of course, allowing it to pass freely. On the down stroke the lower valve will be automatically closed, and the oil will be put under pressure, this being determined by the load on the plunger valve, which is adjustable by means of the screw S, fig. 48. When the required pressure in the pipe P, figs. 45 and 49, has been attained, the plunger valve lifts on each stroke and the surplus oil flows through the plunger into the small reservoir R. The latter is at about the same level as another still smaller reservoir M (shown in figs. 47 and 50), a flow of oil being established between the two by means of a pipe Q (see figs. 48 and 50). In the reservoir R is fitted an overflow pipe, so that the oil cannot rise beyond a certain level; hence the head of oil in the smaller one M is always constant. On the suction stroke a partial vacuum is formed in the engine cylinder, consequently the pressure in the vapouriser drops somewhat below that of the atmosphere, and this small difference in pressure is enough to cause the oil to rise in the small passage X, fig. 45, beyond its normal level, and overflow into the vapourising chamber, as previously described. The valve or nipper N is shown open in the diagram, fig. 45, and all that is required to stop the engine when running is to drop the small handle L, fig. 45, when the valve will close, due to the spring S. The air vessel shown in fig. 49 is in communication with the pipe leading to the blow lamp. A pressure gauge can also be fitted, although it is not in any way a necessity. The ratchet wheel and pawl shown in fig. 48 are part of the lubricator. The wheel drives a brass or gun-metal plug, producing an intermittent rotary motion. The plug has a small hole in its periphery, which becomes filled with oil when it is at the upper part of its travel, and empties the oil out into a discharge pipe T, when it is inverted, and is then led away and applied to the piston at the required spot. Fig. 51 shows this arrangement in section. 
34701	----	available by Internet Archive (http://www.archive.org) Note: Project Gutenberg also has an HTML version of this file which includes the original illustrations. See 34701-h.htm or 34701-h.zip: (http://www.gutenberg.org/files/34701/34701-h/34701-h.htm) or (http://www.gutenberg.org/files/34701/34701-h.zip) Images of the original pages are available through Internet Archive. See http://www.archive.org/details/steamengines00newyrich +----------------------------------------------------------+ | Transcriber's note: | | | | Inconsistencies have not been corrected (hyphenated | | vs non-hyphenated or spaced words), except horse-power | | changed to horsepower and cut off to cut-off. | | | | Minor typographical errors have been corrected. | | | | Text in italics is enclosed by underscore characters as | | in _italics_. | | | | Subscripts are indicated by _{...}, as in _{subscript}. | | | | In-line multi-line formulas have been changed to | | single-line formulas, where necessary with the addition | | of brackets to prevent ambiguity. | +----------------------------------------------------------+ Machinery's Reference Series Each Number Is a Unit in a Series on Electrical and Steam Engineering Drawing and Machine Design and Shop Practice NUMBER 70 STEAM ENGINES CONTENTS Action of Steam Engines 3 Rating and General Proportions of Steam Engines 11 Steam Engine Details 15 Steam Engine Economy 30 Types of Steam Engines 36 Steam Engine Testing 41 Copyright, 1911, The Industrial Press, Publishers of MACHINERY, 49-55 Lafayette Street, New York City. CHAPTER I ACTION OF STEAM ENGINES A steam engine is a device by means of which _heat_ is transformed into _work_. Work may be defined as the result produced by a force acting through space, and is commonly measured in foot-pounds; a foot-pound represents the work done in raising 1 pound 1 foot in height. The rate of doing work is called _power_. It has been found by experiment that there is a definite relation between heat and work, in the ratio of 1 thermal unit to 778 foot-pounds of work. The number 778 is commonly called the heat equivalent of work or the mechanical equivalent of heat. Heat may be transformed into mechanical work through the medium of steam, by confining a given amount in a closed chamber, and then allowing it to expand by means of a movable wall (piston) fitted into one side of the chamber. Heat is given up in the process of expansion, as shown by the lowered pressure and temperature of the steam, and work has been done in moving the wall (piston) of the closed chamber against a resisting force or pressure. When the expansion of steam takes place without the loss of heat by radiation or conduction, the relation between the pressure and volume is practically constant; that is, if a given quantity of steam expands to twice its volume in a closed chamber of the kind above described, its final pressure will be one-half that of the initial pressure before expansion took place. A pound of steam at an absolute pressure of 20 pounds per square inch has a volume of practically 20 cubic feet, and a temperature of 228 degrees. If now it be expanded so that its volume is doubled (40 cubic feet), the pressure will drop to approximately 10 pounds per square inch and the temperature will be only about 190 degrees. The drop in temperature is due to the loss of heat which has been transformed into work in the process of expansion and in moving the wall (piston) of the chamber against a resisting force, as already noted. Principle of the Steam Engine The steam engine makes use of a closed chamber with a movable wall in transforming the heat of steam into mechanical work in the manner just described. Fig. 1 shows a longitudinal section through an engine of simple design, and illustrates the principal parts and their relation to one another. The cylinder _A_ is the closed chamber in which expansion takes place, and the piston _B_, the movable wall. The cylinder is of cast iron, accurately bored and finished to a circular cross-section. The piston is carefully fitted to slide easily in the cylinder, being made practically steam tight by means of packing rings. The work generated in moving the piston is transferred to the crank-pin _H_ by means of the piston-rod _C_, and the connecting-rod _F_. The piston-rod passes out of the cylinder through a stuffing box, which prevents the leakage of steam around it. The cross-head _D_ serves to guide the piston-rod in a straight line, and also contains the wrist-pin _E_ which joins the piston-rod and connecting-rod. The cross-head slides upon the guide-plate _G_, which causes it to move in an accurate line, and at the same time takes the downward thrust from the connecting-rod. The crank-pin is connected with the main shaft _I_ by means of a crank arm, which in this case is made in the form of a disk in order to give a better balance. The balance wheel or flywheel _J_ carries the crank past the dead centers at the ends of the stroke, and gives a uniform motion to the shaft. The various parts of the engine are carried on a rigid bed _K_, usually of cast iron, which in turn is bolted to a foundation of brick or concrete. The power developed is taken off by means of a belted pulley attached to the main shaft, or, in certain cases, in the form of electrical energy from a direct-connected dynamo. [Illustration: Fig. 1. Longitudinal Section through the Ames High-speed Engine] When in action, a certain amount of steam (1/4 to 1/3 of the total cylinder volume in simple engines) is admitted to one end of the cylinder, while the other is open to the atmosphere. The steam forces the piston forward a certain distance by its direct action at the boiler pressure. After the supply is shut off, the forward movement of the piston is continued to the end of the stroke by the expansion of the steam. Steam is now admitted to the other end of the cylinder, and the operation repeated on the backward or return stroke. An enlarged section of the cylinder showing the action of the valve for admitting and exhausting the steam is shown in Fig. 2. In this case the piston is shown in its extreme backward position, ready for the forward stroke. The steam chest _L_ is filled with steam at boiler pressure, which is being admitted to the narrow space back of the piston through the valve _N_, as indicated by the arrows. The exhaust port _M_ is in communication with the other end of the cylinder and allows the piston to move forward without resistance, except that due to the piston-rod, which transfers the work done by the expanding steam to the crank-pin. The valve _N_ is operated automatically by a crank or eccentric attached to the main shaft, and opens and closes the supply and exhaust ports at the proper time to secure the results described. Work Diagram Having discussed briefly the general principle upon which an engine operates, the next step is to study more carefully the transformation of heat into work within the cylinder, and to become familiar with the graphical methods of representing it. Work has already been defined as the result of force acting through space, and the unit of work as the foot-pound, which is the work done in raising 1 pound 1 foot in height. For example, it requires 1 × 1 = 1 foot-pound to raise 1 pound 1 foot, or 1 × 10 = 10 foot-pounds to raise 1 pound 10 feet, or 10 × 1 = 10 foot-pounds to raise 10 pounds 1 foot, or 10 × 10 = 100 foot-pounds to raise 10 pounds 10 feet, etc. That is, the product of weight or force acting, times the distance moved through, represents work; and if the force is taken in pounds and the distance in feet, the result will be in foot-pounds. This result may be shown graphically by a figure called a work diagram. [Illustration: Fig. 2. Section of Cylinder, showing Slide Valve] In Fig. 3, let distances on the line _OY_ represent the force acting, and distances on _OX_ represent the space moved through. Suppose the figure to be drawn to such a scale that _OY_ is 5 feet in height, and _OX_ 10 feet long. Let each division on _OY_ represent 1 pound pressure, and each division on _OX_ 1 foot of space moved through. If a pressure of 5 pounds acts through a distance of 10 feet, then an amount of 5 × 10 = 50 foot-pounds of work has been done. Referring to Fig. 3, it is evident that the height _OY_ (the pressure acting), multiplied by the length _OX_ (the distance moved through), gives 5 × 10 = 50 square feet, which is the area of the rectangle _YCXO_; that is, the area of a rectangle may represent work done, if the height represents a force acting, and the length the distance moved through. If the diagram were drawn to a smaller scale so that the divisions were 1 inch in length instead of 1 foot, the area _YCXO_ would still represent the work done, except each square inch would equal 1 foot-pound instead of each square foot, as in the present illustration. [Illustration: Fig. 3. A Simple Work Diagram] In Fig. 4 the diagram, instead of being rectangular in form, takes a different shape on account of different forces acting at different periods over the distance moved through. In the first case (Fig. 3), a uniform force of 5 pounds acts through a distance of 10 feet, and produces 5 × 10 = 50 foot-pounds of work. In the second case (Fig. 4), forces of 5 pounds, 4 pounds, 3 pounds, 2 pounds, and 1 pound, act through distances of 2 feet each, and produce (5 × 2) + (4 × 2) + (3 × 2) + (2 × 2) + (1 × 2) = 30 foot-pounds. This is also the area, in square feet, of the figure _Y54321XO_, which is made up of the areas of the five small rectangles shown by the dotted lines. Another way of finding the total area of the figure shown in Fig. 4, and determining the work done, is to multiply the length by the average of the heights of the small rectangles. The average height is found by adding the several heights and dividing the sum by their number, as follows: 5 + 4 + 3 + 2 + 1 ----------------- = 3, and 3 × 10 = 30 square feet, as before. 5 [Illustration: Fig. 4. Another Form of Work Diagram] This, then, means that the average force acting throughout the stroke is 3 pounds, and the total work done is 3 × 10 = 30 foot-pounds. In Fig. 5 the pressure drops uniformly from 5 pounds at the beginning to 0 at the end of the stroke. In this case also the area and work done are found by multiplying the length of the diagram by the average height, as follows: 5 + 0 ----- × 10 = 25 square feet, 2 or 25 foot-pounds of work done. [Illustration: Fig. 5. Work Diagram when Pressure drops Uniformly] The object of Figs. 3, 4 and 5 is to show how foot-pounds of work may be represented graphically by the areas of diagrams, and also to make it clear that this remains true whatever the form of the diagram. It is also evident that knowing the area, the average height or pressure may be found by dividing by the length, and _vice versa_. Fig. 6 shows the form of work diagram which would be produced by the action of the steam in an engine cylinder, if no heat were lost by conduction and radiation. Starting with the piston in the position shown in Fig. 2, steam is admitted at a pressure represented by the height of the line _OY_. As the piston moves forward, sufficient steam is admitted to maintain the same pressure. At the point _B_ the valve closes and steam is cut off. The work done up to this time is shown by the rectangle _YBbO_. From the point _B_ to the end of the stroke _C_, the piston is moved forward by the expansion of the steam, the pressure falling in proportion to the distance moved through, until at the end of the stroke it is represented by the vertical line _CX_. At the point _C_ the exhaust valve opens and the pressure drops to 0 (atmospheric pressure in this case). As it is always desirable to find the work done by a complete stroke of the engine, it is necessary to find the average or mean pressure acting throughout the stroke. This can only be done by determining the area of the diagram and dividing by the length of the stroke. This gives what is called the mean ordinate, which multiplied by the scale of the drawing, will give the mean or average pressure. For example, if the area of the diagram is found to be 6 square inches, and its length is 3 inches, the mean ordinate will be 6 ÷ 3 = 2 inches. If the diagram is drawn to such a scale that 1 inch on _OY_ represents 10 pounds, then the average or mean pressure will be 2 × 10 = 20 pounds, and this multiplied by the actual length of the piston stroke will give the work done in foot-pounds. The practical application of the above, together with the method of obtaining steam engine indicator diagrams and measuring the areas of the same, will be taken up in detail under the heading of Steam Engine Testing. Definitions Relating to Engine Diagrams Before taking up the construction of an actual engine diagram, it is first necessary to become familiar with certain terms which are used in connection with it. [Illustration: Fig. 6. The Ideal Work Diagram of a Steam Engine] _Cut-off._--The cut-off is the point in the stroke at which the admission valve closes and the expansion of steam begins. _Ratio of Expansion._--This is the reciprocal of the cut-off, that is, if the cut-off is 1/4, the ratio of expansion is 4. In other words, it is the ratio of the final volume of the steam at the end of the stroke to its volume at the point of cut-off. For example, a cylinder takes steam at boiler pressure until the piston has moved one-fourth the length of its stroke; the valve now closes and expansion takes place until the stroke is completed. The one-fourth cylinderful of steam has become a cylinderful, that is, it has expanded to four times its original volume, and the ratio of expansion is said to be 4. _Point of Release._--This is the point in the stroke at which the exhaust valve opens and relieves the pressure acting on the piston. This takes place just before the end of the stroke in order to reduce the shock when the piston changes its direction of travel. _Compression._--This acts in connection with the premature release in order to reduce the shock at the end of the stroke. During the forward stroke of an engine the exhaust valve in front of the piston remains open as shown in Fig. 2. Shortly before the end of the stroke this closes, leaving a certain amount of steam in the cylinder. The continuation of the stroke compresses this steam, and by raising its pressure forms a cushion, which, in connection with the removal of the pressure back of the piston by release, brings the piston to a stop and causes it to reverse its direction without shock. High-speed engines require a greater amount of compression than those running at low speed. _Clearance_.--This is the space between the cylinder head and the piston when the latter is at the end of its stroke; it also includes that portion of the steam port between the valve and the cylinder. Clearance is usually expressed as a percentage of the piston-displacement of the cylinder, and varies in different types of engines. The following table gives approximate values for engines of different design. TABLE I. CLEARANCE OF STEAM ENGINES Type of Engine Per Cent Clearance Corliss 1.5 to 3.5 Moderate-speed 3 to 8 High-speed 4 to 10 A large clearance is evidently objectionable because it represents a space which must be filled with steam at boiler pressure at the beginning of each stroke, and from which but a comparatively small amount of work is obtained. As compression increases, the amount of steam required to fill the clearance space diminishes, but on the other hand, increasing the compression reduces the mean effective pressure. _Initial Pressure._--This is the pressure in the cylinder up to the point of cut-off. It is usually slightly less than boiler pressure owing to "wire-drawing" in the steam pipe and ports. _Terminal Pressure._--This is the pressure in the cylinder at the time release occurs, and depends upon the initial pressure, the ratio of expansion, and the amount of cylinder condensation. _Back Pressure._--This is the pressure in the cylinder when the exhaust port is open, and is that against which the piston is forced during the working stroke. For example, in Fig. 2 the small space at the left of the piston is filled with steam at initial pressure, while the space at the right of the piston is exposed to the back pressure. The working pressure varies throughout the stroke, due to the expansion of the steam, while the back pressure remains constant, except for the effect of compression at the end of the stroke. The theoretical back pressure in a non-condensing engine (one exhausting into the atmosphere) is that of the atmosphere or 14.7 pounds per square inch above a vacuum, but in actual practice it is about 2 pounds above atmospheric pressure, or 17 pounds absolute, due to the resistance of exhaust ports and connecting pipes. In the case of a condensing engine (one exhausting into a condenser) the back pressure depends upon the efficiency of the condenser, averaging about 3 pounds absolute pressure in the best practice. _Effective Pressure._--This is the difference between the pressure on the steam side of the piston and that on the exhaust side, or in other words, the difference between the working pressure and the back pressure. This value varies throughout the stroke with the expansion of the steam. _Mean Effective Pressure._--It has just been stated that the effective pressure varies throughout the stroke. The mean effective pressure (M. E. P.) is the average of all the effective pressures, and this average multiplied by the length of stroke, gives the work done per stroke. _Line of Absolute Vacuum._--In the diagram shown in Fig. 6, the line _OX_ is the line of absolute vacuum; that is, it is assumed that there is no pressure on the exhaust side of the piston. In other words, the engine is exhausting into a perfect vacuum. [Illustration: Fig. 7. Constructing a Steam Engine Work Diagram] _Atmospheric Line._--This is a line drawn parallel to the line of absolute vacuum at such a distance above it as to represent 14.7 pounds pressure per square inch, according to the scale used. Construction of Ideal Diagram One of the first steps in the design of a steam engine is the construction of an ideal diagram, and the engine is planned to produce this as nearly as possible when in operation. First assume the initial pressure, the ratio of expansion, and the percentage of clearance, for the type of engine under consideration. Draw lines _OX_ and _OY_ at right angles as in Fig. 7. Make _OR_ the same percentage of the stroke that the clearance is of the piston displacement; make _RX_ equal to the length of the stroke (on a reduced scale). Erect the perpendicular _RA_ of such a height that it shall represent, to scale, an absolute pressure per square inch equal to 0.95 of the boiler pressure. Draw in the dotted lines _AK_ and _KX_, and the atmospheric line _LH_ at a height above _OX_ to represent 14.7 pounds per square inch. Locate the point of cut-off, _B_, according to the assumed ratio of expansion. Points on the expansion curve _BC_ are found as follows: Divide the distance _BK_ into any number of equal spaces, as shown by _a_, _b_, _c_, _d_, etc., and connect them with the point _O_. Through the points of intersection with _BP_, as _a´_, _b´_, _c´_, _d´_, etc., draw horizontal lines, and through _a_, _b_, _c_, _d_, etc., draw vertical lines. The intersection of corresponding horizontal and vertical lines will be points on the theoretical expansion line. If the engine is to be non-condensing, the theoretical work, or indicator diagram, as it is called, will be bounded by the lines _ABCHG_. The actual diagram will vary somewhat from the theoretical, as shown by the shaded lines. The admission line between _A_ and _B_ will slant downward slightly, and the point of cut-off will be rounded, owing to the slow closing of the valve. The first half of the expansion line will fall below the theoretical, owing to a drop in pressure caused by cylinder condensation, but the actual line will rise above the theoretical in the latter part of the stroke on account of re-evaporation, due to heat given out by the hot cylinder walls to the low-pressure steam. Instead of the pressure dropping abruptly at _C_, release takes place just before the end of the stroke, and the diagram is rounded at _CF_ instead of having sharp corners. The back pressure line _FD_ is drawn slightly above the atmospheric line, a distance to represent about 2 pounds per square inch. At _D_ the exhaust valve closes and compression begins, rounding the bottom of the diagram up to _E_. The area of the actual diagram, as shown by the shaded lines in Fig. 7, will be smaller than the theoretical, in about the following ratio: Large medium-speed engines, 0.90 of theoretical area. Small medium-speed engines, 0.85 of theoretical area. High-speed engines, 0.75 of theoretical area. CHAPTER II RATING AND GENERAL PROPORTIONS OF STEAM ENGINES The capacity or power of a steam engine is rated in horsepower, one horsepower (H. P.) being the equivalent of 33,000 foot-pounds of work done per minute. The horsepower of a given engine may be computed by the formula: _APLN_ H. P. = ------ 33,000 in which _A_ = area of piston, in square inches, _P_ = mean effective pressure per square inch, _L_ = length of stroke, in feet, _N_ = number of strokes per minute = number of revolutions × 2. The derivation of the above formula is easily explained, as follows: The area of the piston, in square inches, multiplied by the mean effective pressure, in pounds per square inch, gives the total force acting on the piston, in pounds. The length of stroke, in feet, times the number of strokes per minute gives the distance the piston moves through, in feet per minute. It has already been shown that the pressure in pounds multiplied by the distance moved through in feet, gives the foot-pounds of work done. Hence, _A_ × _P_ × _L_ × _N_ gives the foot-pounds of work done per minute by a steam engine. If one horsepower is represented by 33,000 foot-pounds per minute, the power or rating of the engine will be obtained by dividing the total foot-pounds of work done per minute by 33,000. For ease in remembering the formula given, it is commonly written _PLAN_ H. P. = ------, 33,000 in which the symbols in the numerator of the second member spell the word "Plan." _Example_:--Find the horsepower of the following engine, working under the conditions stated below: Diameter of cylinder, 12 inches. Length of stroke, 18 inches. Revolutions per minute, 300. Mean effective pressure (M. E. P.), 40 pounds. In this problem, then, _A_ = 113 square inches; _P_ = 40 pounds; _L_ = 1.5 feet; and _N_ = 600 strokes. Substituting in the formula, 40 × 1.5 × 113 × 600 H. P. = -------------------- = 123. 33,000 The mean effective pressure may be found, approximately, for different conditions by means of the factors in the following table of ratios, covering ordinary practice. The rule used is as follows: Multiply the absolute initial pressure by the factor corresponding to the clearance and cut-off as found from Table II, and subtract the absolute back pressure from the result, assuming this to be 17 pounds for non-condensing engines, and 3 pounds for condensing. _Example 1_:--A non-condensing engine having 3 per cent clearance, cuts off at 1/3 stroke; the initial pressure is 90 pounds gage. What is the M. E. P.? The absolute initial pressure is 90 + 15 = 105 pounds. The factor for 3 per cent clearance and 1/3 cut-off, from Table II, is 0.71. Applying the rule we have: (105 × 0.71) - 17 = 57.5 pounds per square inch. _Example 2_:--A condensing engine has a clearance of 5 per cent. It is supplied with steam at 140 pounds gage pressure, and has a ratio of expansion of 6. What is the M. E. P.? The absolute initial pressure is 140 + 15 = 155. The factor for a ratio of expansion of 6 (1/6 cut-off) and 5 per cent clearance is 0.5, which gives (155 × 0.5) - 3 = 74.5 pounds per square inch. The power of an engine computed by the method just explained is called the indicated horsepower (I. H. P.), and gives the total power developed, including that required to overcome the friction of the engine itself. The delivered or brake horsepower (B. H. P.) is that delivered by the engine after deducting from the indicated horsepower the power required to operate the moving parts. The brake horsepower commonly varies from 80 to 90 per cent of the indicated horsepower at full load, depending upon the type and size of engine. In proportioning an engine cylinder for any given horsepower, the designer usually has the following data, either given or assumed, for the special type of engine under consideration: Initial pressure, back pressure, clearance, cut-off, and piston speed. These quantities vary in different types of engines, but in the absence of more specific data the values in Table III will be found useful. The back pressure may be taken as 17 pounds per square inch, absolute, for non-condensing engines, and as 3 pounds for condensing engines as previously stated. TABLE II. FACTORS FOR FINDING MEAN EFFECTIVE PRESSURE +--------------+-----------------------------------------+ | | Point of Cut-off | | Percentage +------+------+------+------+------+------+ | of Clearance | 1/10 | 1/6 | 1/4 | 1/3 | 1/2 | 3/4 | +--------------+------+------+------+------+------+------+ | 1.75 | 0.35 | 0.48 | 0.60 | 0.70 | 0.85 | 0.96 | | 3.00 | 0.37 | 0.49 | 0.61 | 0.71 | 0.85 | 0.96 | | 5.00 | 0.39 | 0.50 | 0.62 | 0.72 | 0.86 | 0.97 | | 7.00 | 0.41 | 0.52 | 0.63 | 0.73 | 0.86 | 0.97 | | 9.00 | 0.43 | 0.54 | 0.64 | 0.73 | 0.86 | 0.97 | +--------------+------+------+------+------+------+------+ The first step in proportioning the cylinder is to compute the approximate mean effective pressure from the assumed initial pressure, clearance, and cut-off, by the method already explained. Next assume the piston speed for the type of engine to be designed, and determine the piston area by the following formula: 33,000 H. P. A = -----------------------. M. E. P. × piston speed This formula usually gives the diameter of the piston in inches and fractions of an inch, while it is desirable to make this dimension an even number of inches. This may be done by taking as the diameter the nearest whole number, and changing the piston speed to correspond. This is done by the use of the following equation. First piston speed × first piston area -------------------------------------- = new piston speed. new piston area In calculating the effective piston area, the area of the piston rod upon one side must be allowed for. The effective or average piston area will then be (2_A_ - _a_)/2, in which _A_ = area of piston, _a_ = area of piston rod. This latter area must be assumed. After assuming a new piston diameter of even inches, its effective or average area must be used in determining the new piston speed. The length of stroke is commonly proportioned to the diameter of cylinder, and the piston speed divided by this will give the number of strokes per minute. _Example_:--Find the diameter of cylinder, length of stroke, and revolutions per minute for a simple high-speed non-condensing engine of 200 I. H. P., with the following assumptions: Initial pressure, 90 pounds gage; clearance, 7 per cent; cut-off, 1/4; piston speed, 700 feet per minute; length of stroke, 1.5 times cylinder diameter. TABLE III. PRESSURE, CLEARANCE, CUT-OFF AND PISTON SPEED OF STEAM ENGINES +---------------------+------------+-----------+-------------+------------+ | | Initial | Clearance,| Cut-off, | Piston | | Type of Engine | Pressure, | Per Cent | Proportion | Speed, Feet| | | (Gage) | | of Stroke | per Minute | +---------------------+------------+-----------+-------------+------------+ |Simple high-speed | 80 to 90 |4 to 10 | 1/4 to 1/3 | 600 to 800 | |Simple medium-speed | 80 to 90 |3 to 8 | 1/4 to 1/3 | 500 to 700 | |Simple Corliss | 80 to 90 |1.5 to 3.5| 1/4 to 1/3 | 400 to 600 | |Compound high-speed | 130 to 140 |4 to 10 | 1/10 to 1/8 | 600 to 800 | |Compound medium-speed| 130 to 140 |3 to 8 | 1/10 to 1/8 | 500 to 700 | |Compound Corliss | 130 to 140 |1.5 to 3.5| 1/10 to 1/8 | 400 to 600 | +---------------------+------------+-----------+-------------+------------+ By using the rules and formulas in the foregoing, we have: M. E. P. = (90 + 15) × 0.63 - 17 = 49 pounds. 33,000 × 200 _A_ = ------------ = 192.4 square inches. 49 × 700 The nearest piston diameter of even inches is 16, which corresponds to an area of 201 square inches. Assume a piston rod diameter of 2-1/2 inches, corresponding to an area of 4.9 square inches, from which the average or effective piston area is found to be ((2 × 201) - 4.9)/2 = 198.5 square inches. Determining now the new piston speed, we have: 700 × 192.4 ----------- = 678.5 feet per minute. 198.5 Assuming the length of stroke to be 1.5 times the diameter of the cylinder, it will be 24 inches, or 2 feet. This will call for 678.5 ÷ 2 = 340 strokes per minute, approximately, or 340 ÷ 2 = 170 revolutions per minute. CHAPTER III STEAM ENGINE DETAILS Some of the most important details of a steam engine are those of its valve gear. The simplest form of valve is that known as the plain slide valve, and as nearly all others are a modification of this, it is essential that the designer should first familiarize himself with this particular type of valve in all its details of operation. After this has been done, a study of other forms of valves will be found a comparatively easy matter. The so called Corliss valve differs radically from the slide valve, but the results to be obtained and the terms used in its design are practically the same. The valve gear of a steam engine is made up of the valve or valves which admit steam to and exhaust it from the cylinder, and of the mechanism which governs the valve movements, the latter usually consisting of one or more eccentrics attached to the main shaft. [Illustration: Fig. 8. Longitudinal Section of Slide Valve with Ports] The Slide Valve Fig. 8 shows a longitudinal section of a slide valve with the ports, bridges, etc. The valve is shown in mid-position in order that certain points relating to it may be more easily understood. The valve, _V_, consists of a hollow casting, with ends projecting beyond the ports as shown; the lower face is smoothly finished and fitted to the valve seat _AB_. In operation it slides back and forth, opening and closing the ports which connect the steam chest with the cylinder. Steam is admitted to the cylinder when either port _CD_ or _DC_ is opened, and is released when the ports are brought into communication with the exhaust port _MN_. This is accomplished by the movement of the valve, which brings one of the cylinder ports and the exhaust port both under the hollow arch _K_. The portions _DM_ and _ND_ of the valve seat are called the bridges. It will be seen by reference to Fig. 8 that the portions _OI_ and _IO_ are wider than the ports which they cover. This extra width is called the _lap_, _OC_ being the outside lap and _DI_ the inside or exhaust lap. The object of outside lap is that the steam may be shut off after the piston has moved forward a certain distance, and be expanded during the remainder of the stroke. If there were no outside lap, steam would be admitted throughout the entire stroke and there would be no expansion. If there were no inside lap, exhaust would take place throughout the whole stroke, and the advantages of premature release and compression would be lost. Hence, outside lap affects the cut-off, and inside lap affects release and compression. A valve has _lead_ when it begins to uncover the steam port before the end of the return stroke of the piston. This is shown in Fig. 9, where the piston _P_ is just ready to start on its forward stroke as indicated by the arrow. The valve has already opened a distance equal to the lead, and the steam has had an opportunity to enter and fill the clearance space before the beginning of the stroke. The lead varies in different engines, being greater in high-speed than in low-speed types. [Illustration: Fig. 9. Illustration showing Lead of Slide Valve] [Illustration: Fig. 10. Diagrammatical View of Eccentric] The Eccentric The slide valve is usually driven by an eccentric attached to the main shaft. A diagram of an eccentric is shown in Fig. 10. An eccentric is, in reality, a short crank with a crank-pin of such size that it surrounds the shaft. The arm of a crank is the distance between the center of the shaft, and the center of the crank-pin. The throw of an eccentric corresponds to this, and is the distance between the center of the shaft and the center of the eccentric disk, as shown at _a_ in Fig. 10. The disk is keyed to the shaft, and as the shaft revolves, the center of the disk rotates about it as shown by the dotted line, and gives a forward and backward movement to the valve rod equal to twice the throw _a_. [Illustration: Fig. 11. Relations of Crank and Eccentric] In Fig. 11 let _A_ represent the center of the main shaft, _B_ the crank-pin to which the connecting-rod is attached (see _H_, Fig. 1), and the dotted circle through _B_ the path of the crank-pin around the shaft. For simplicity, let the eccentric be represented in a similar manner by the crank _Ab_, and its path by the dotted circle through _b_. Fig. 12 shows a similar diagram with the piston _P_ and the valve in the positions corresponding to the positions of the crank and eccentric in Fig. 11, and in the diagram at the right in Fig. 12. The piston is at the extreme left, ready to start on its forward stroke toward the right. The crank-pin _B_ is at its extreme inner position. When the valve is at its mid-position, as in Fig. 8, the eccentric arm _Ab_ will coincide with the line _AC_, Fig. 11. If the eccentric is turned on the shaft sufficiently to bring the left-hand edge _O_, Fig. 8, of the valve in line with the edge _C_ of the port, the arm of the eccentric will have moved from its vertical position to that shown by the line _Ab´_ in Fig. 11. The angle through which the eccentric has been turned from the vertical to bring about this result is called the _angular advance_, and is shown by angle _CAb´_ in Fig. 11. The angular advance evidently depends upon the amount of lap. If the valve is to be given a lead, as indicated in Fig. 12, the eccentric must be turned still further on the shaft to open the valve slightly before the piston starts on its forward movement. This brings the eccentric to the position _Ab_ shown in Fig. 11. The angle through which the eccentric is turned to give the necessary lead opening to the valve is called the _angle of lead_, and is shown by angle _b´Ab_. By reference to Fig. 11, it is seen that the total angle between the crank and the eccentric is 90 degrees, plus the angular advance, plus the angle of lead. This is the total angle of advance. [Illustration: Fig. 12. Piston just beginning Forward Stroke] The relative positions of the piston and valve at different periods of the stroke are illustrated in Figs. 12 to 16. Fig. 12 shows the piston just beginning the forward stroke, the valve having uncovered the admission port an amount equal to the lead. The crank is in a horizontal position, and the eccentric has moved from the vertical an amount sufficient to move the valve toward the right a distance equal to the outside lap plus the lead. The arrows show that steam is entering the left-hand port and is being exhausted through the right-hand port. [Illustration: Fig. 13. Steam Port fully Opened] In Fig. 13 it is seen that the valve has traveled forward sufficiently to open the steam port to its fullest extent, and the piston has moved to the point indicated. The exhaust port is still wide open, and the relative positions of the crank and eccentric are shown in the diagram at the right. In Fig. 14 the eccentric has passed the horizontal position and the valve has started on its backward stroke, while the piston is still moving forward. The admission port is closed, cut-off having taken place, and the steam is expanding. The exhaust port is still partially open. [Illustration: Fig. 14. Valve has started on Backward Stroke] [Illustration: Fig. 15. Both Steam Ports Closed] In Fig. 15 both ports are closed and compression is taking place in front of the piston while expansion continues back of it. Release occurs in Fig. 16 just before the piston reaches the end of its stroke. The eccentric crank is now in a vertical position, pointing downward, and exhaust is just beginning to take place through the left-hand port. This completes the different stages of a single stroke, the same features being repeated upon the return of the piston to its original position. The conditions of lap, lead, angular advance, etc., pertain to practically all valves, whatever their design. [Illustration: Fig. 16. Exhaust Begins] Different Types of Valves In the following are shown some of the valves in common use, being, with the exception of the Corliss, modifications of the plain slide valve, and similar in their action. [Illustration: Fig. 17. Engine with Piston Valve] _Double-Ported Balanced Valve._--A valve of this type has already been shown in Fig. 2. This valve is flat in form, with two finished surfaces, and works between the valve-seat and a plate, the latter being prevented from pressing against the valve by special bearing surfaces which hold it about 0.002 inch away. The construction of the valve is such that when open the steam reaches the port through two openings as indicated by the arrows at the left. The object of this is to reduce the motion of the valve and quicken its action in admitting and cutting off steam. [Illustration: Fig. 18. Section through Cylinder of Engine of the Four-valve Type] [Illustration: Fig. 19. Different Types of Corliss Valves] _Piston Valve._--The piston valve shown in Fig. 17 is identical in its action with the plain slide valve shown in Fig. 8, except that it is circular in section instead of being flat or rectangular. The advantage claimed for this type of valve is the greater ease in fitting cylindrical surfaces as compared with flat ones. The valve slides in special bushings which may be renewed when worn. Piston valves are also made with double ports. [Illustration: Fig. 20. Longitudinal Section through Corliss Engine] [Illustration: Fig. 21. The Gridiron Valve] _Four-Valve Type._--Fig. 18 shows a horizontal section through the cylinder and valves of an engine of the four-valve type. The admission valves are shown at the top of the illustration and the exhaust valves at the bottom, although, in reality, they are at the sides of the cylinder. The advantage of an arrangement of this kind is that the valves may be set independently of each other and the work done by the two ends of the cylinder equalized. The various events, such as cut-off, compression, etc., may be adjusted without regard to each other, and in such a manner as to give the best results, a condition which is not possible with a single valve. _Gridiron Valve._--One of the principal objects sought in the design of a valve is quick action at the points of admission and cut-off. This requires the uncovering of a large port opening with a comparatively small travel of the valve. The gridiron valve shown in Fig. 21 is constructed especially for this purpose. This valve is of the four-valve type, one steam valve and one exhaust valve being shown in the section. Both the valve and its seat contain a number of narrow openings or ports, so that a short movement of the valve will open or close a comparatively large opening. For example, the steam valve in the illustration has 12 openings, so that if they are 1/4 inch in width each, a movement of 1/4 inch of the valve will open a space 12 × 1/4 = 3 inches in length. [Illustration: Fig. 22. The Monarch Engine with Corliss Valve Gear.--A, Rod to Eccentric; B, Governor; C, Reach Rod; D, Radial Arm; E, Steam Valve; F, Bell-crank; G, Wrist Plate; H, Exhaust Valve; K, Dash-pot] _Corliss Valve._--A section through an engine cylinder equipped with Corliss valves is shown in Fig. 20. There are four cylindrical valves in this type of engine, two steam valves at the top and two exhaust valves at the bottom. This arrangement is used to secure proper drainage. The action of the admission and exhaust valves is indicated by the arrows, the upper left-hand and the lower right-hand valve being open and the other two closed. Side and sectional views of different forms of this type of valve are shown in Fig. 19. They are operated by means of short crank-arms which are attached to a wrist-plate by means of radial arms or rods, as shown in Fig. 22. The wrist-plate, in turn, is given a partial backward and forward rotation by means of an eccentric attached to the main shaft and connected to the upper part of the wrist-plate by a rod as indicated. The exhaust valves are both opened and closed by the action of the wrist-plate and connecting rods. The steam valves are opened in this manner, but are closed by the suction of dash pots attached to the drop levers on the valve stems by means of vertical rods, as shown. [Illustration: Figs. 23 to 26. Action of Corliss Valve Gear] The action of the steam or admission valves is best explained by reference to Figs. 23 to 26. Referring to Fig. 23, _A_ is a bell-crank which turns loosely upon the valve stem _V_. The lower left-hand extension of _A_ carries the grab hook _H_, while the upper extension is connected with the wrist-plate as indicated. Ordinarily the hook _H_ is pressed inward by the spring _S_, so that the longer arm of the hook is always pressed against the knock-off cam _C_. The cam _C_ also turns upon the valve stem _V_ and is connected with the governor by means of a reach rod as indicated in Fig. 23 and shown in Fig. 22. The drop lever _B_ is keyed to the valve stem _V_, and is connected with the dash pot by a rod as indicated by the dotted line. This is also shown in Fig. 22. The end of the drop lever carries a steel block (shown shaded in Fig. 23), which engages with the grab hook _H_. When in operation, the bell-crank is rotated in the direction of the arrow by the action of the wrist-plate and connecting-rod. As the bell-crank rotates, the grab hook engages the steel block at the end of the drop lever _B_ and lifts it, thus causing the valve to open, and to remain so until the bell-crank has advanced so far that the longer arm of the grab hook _H_ is pressed outward by the projection on the knock-off cam, as shown in Fig. 24. The drop lever now being released, the valve is quickly closed by the suction of the dash pot, which pulls the lever down to its original position by means of the rod previously mentioned. [Illustration: Fig. 27. Governor for Corliss Engine] The governor operates by changing the point of cut-off through the action of the cam _C_. With the cam in the position shown in Fig. 25, cut-off occurs earlier than in Fig. 24. Should the cam be turned in the opposite direction (clockwise), cut-off would take place later. A detailed view of the complete valve mechanism described is shown assembled in Fig. 26, with each part properly named. A detail of the governor is shown in Fig. 27. An increase in speed causes the revolving balls _BB_ to swing outward, thus raising the weight _W_ and the sleeve _S_. This in turn operates the lever _L_ through rod _R_ and a bell-crank attachment, as shown in the right-hand view. An upward and downward movement of the balls, due to a change in speed of the engine, swings the lever _L_ backward and forward as shown by the full and dotted lines. The ends of this lever are attached by means of reach-rods to the knock-off cams, this being shown more clearly in Fig. 22. The connections between the lever _L_ and cam _C_ are such that a raising of the balls, due to increased speed, will reduce the cut-off and thus slow down the engine. On the other hand, a falling of the balls will lengthen the cut-off through the same mechanism. [Illustration: Fig. 28. Dash-pot for Corliss Engine] [Illustration: Figs. 29 and 30. Plan and Longitudinal Section of Adjustable Piston] Mention has already been made of the dash pot which is used to close the valve suddenly after being released from the grab hook. The dash-pot rod is shown in Fig. 26, and indicated by dotted lines in Figs. 23 to 25. A detailed view of one form of dash pot is shown in Fig. 28. When the valve is opened, the rod attached to lever _B_, Figs. 23 and 24, raises the piston _P_, Fig. 28, and a partial vacuum is formed beneath it which draws the piston and connecting rod down by suction as soon as the lever _B_ is released, and thus closes the valve suddenly and without shock. The strength of the suction and the air cushion for this piston are regulated by the inlet and outlet valves shown on the sides of the dash pot. Engine Details Figs. 29 to 37 show various engine details, and illustrate in a simple way some of the more important principles involved in steam engine design. [Illustration: Fig. 31. A Typical Cross-head] [Illustration: Figs. 32 and 33. Methods Commonly Used for Taking Up Wear in a Connecting-rod] A partial cross-section of an adjustable piston is shown in Fig. 29, and a longitudinal section of the same piston in Fig. 30. The principal feature to be emphasized is the method of automatic expansion employed to take up any wear and keep the piston tight. In setting up the piston a hand adjustment is made of the outer sleeve or ring _R_ by means of the set-screws _AA_. Ring _R_ is made in several sections, so that it may be expanded in the form of a true circle. Further tightness is secured without undue friction by means of the packing ring _P_ which fits in a groove in _R_ and is forced lightly against the walls of the cylinder by a number of coil springs, one of which is shown at _S_. As the cylinder and piston become worn, screws _A_ are adjusted from time to time, and the fine adjustment for tightness is cared for by the packing ring _P_ and the coil springs _S_. The points to be brought out in connection with the cross-head are the methods of alignment and adjustment. A typical cross-head is shown in cross and longitudinal sections in Fig. 31. Alignment in a straight line, longitudinally, is secured by the cylindrical form of the bearing surfaces or shoes, shown at _S_. These are sometimes made V-shaped in order to secure the same result. The wear on a cross-head comes on the surfaces _S_, and is taken up by the use of screw wedges _W_, shown in the longitudinal section. As the sliding surfaces become worn, the wedges are forced in slightly by screwing in the set-screws and clamping them in place by means of the check-nuts. [Illustration: Fig. 34. Outboard Bearing for Corliss Type Engine] [Illustration: Fig. 35. Inner Bearing and Bed of Corliss Engine] The method commonly employed in taking up the wear in a connecting-rod is shown in Figs. 32 and 33. The wear at the wrist-pin is taken by the so called brasses, shown at _B_ in the illustrations. The inner brass, in both cases, fits in a suitable groove, and is held stationary when once in place. The outer brass is adjustable, being forced toward the wrist-pin by a sliding wedge which is operated by one or more set-screws. In Fig. 32 the wedge is held in a vertical position, and is adjusted by two screws as shown. The arrangement made use of in Fig. 33 has the wedge passing through the rod in a horizontal position, and adjusted by means of a single screw, as shown in the lower view. With the arrangements shown, tightening up the brasses shortens the length of the rod. In practice the wedges at each end of the rod are so placed that tightening one shortens the rod, and tightening the other lengthens it, the total effect being to keep the connecting-rod at its original length. A common form of outboard bearing for an engine of the slow-speed or Corliss type is illustrated in Fig. 34. The various adjustments for alignment and for taking up wear are the important points considered in this case. The plate _B_ is fastened to the stone foundation by anchor bolts not shown. Sidewise movement is secured by loosening the bolts _C_, which pass through slots in the bearing, and adjusting by means of the screws _S_. Vertical adjustment is obtained by use of the wedge _W_, which is forced in by the screw _A_, as required. The inner bearing and bed piece of a heavy duty Corliss engine is shown in Fig. 35. The bearing in this case is made up of four sections, so arranged that either horizontal or vertical adjustment may be secured by the use of adjusting screws and check-nuts. Engines of the slide-valve type are usually provided either with a fly-ball throttling governor, or a shaft governor. A common form of throttling governor is shown in Fig. 36. As the speed increases the balls _W_ are thrown outward by the action of the centrifugal force, and being attached to arms hinged above them, any outward movement causes them to rise. This operates the spindle _S_, which, in turn, partially closes the balanced valve in body _B_, thus cutting down the steam supply delivered to the engine. The action of a throttling governor upon the work diagram of an engine is shown in Fig. 38. Let the full line represent the form of the diagram with the engine working at full load. Now, if a part of the load be thrown off, the engine will speed up slightly, causing the governor to act as described, thus bringing the admission and expansion lines into the lower positions, as shown in dotted lines. [Illustration: Fig. 36. Common Form of Throttling Governor] The shaft governor is used almost universally on high-speed engines, and is shown in one form in Fig. 37. It consists, in this case, of two weights _W_, hinged to the spokes of the wheel near the circumference by means of suitable arms. Attached to the arms, as shown, are coil springs _C_. The ends of the arms beyond the weights are connected by means of levers _L_ to the eccentric disk. When the engine speeds up, the weights tend to swing outward toward the rim of the wheel, the amount of the movement being regulated by the tension of the springs _C_. As the arms move outward, the levers at the ends turn the eccentric disk on the shaft, the effect of which is to change the angle of advance and shorten the cut-off. When the speed falls below the normal, the weights move toward the center and the cut-off is lengthened. The effect of this form of governor on the diagram is shown in Fig. 39. The full line represents the diagram at full load, and the dotted line when the engine is under-loaded. [Illustration: Fig. 37. Shaft Governor for High-speed Engine] CHAPTER IV STEAM ENGINE ECONOMY Under the general heading of steam engine economy, such items as cylinder condensation, steam consumption, efficiency, ratio of expansion, under- and over-loading, condensing, etc., are treated. The principal waste of steam in the operation of an engine is due to condensation during the first part of the stroke. This condensation is due to the fact that during expansion and exhaust the cylinder walls and head and the piston are in contact with comparatively cool steam, and, therefore, give up a considerable amount of heat. When fresh steam is admitted at a high temperature, it immediately gives up sufficient heat to raise the cylinder walls to a temperature approximating that of the entering steam. This results in the condensation of a certain amount of steam, the quantity depending upon the time allowed for the transfer of heat, the area of exposed surface, and the temperature of the cylinder walls. During the period of expansion the temperature falls rapidly, and the steam being wet, absorbs a large amount of heat. After the exhaust valve opens, the drop in pressure allows the moisture that has collected on the cylinder walls to evaporate into steam, so that during the exhaust period but little heat is transferred. With the admission of fresh steam at boiler pressure, a mist is condensed on the cylinder walls, which greatly increases the rapidity with which heat is absorbed. The amount of heat lost through cylinder condensation is best shown by a practical illustration. One horsepower is equal to 33,000 foot-pounds of work per minute, or 33,000 × 60 = 1,980,000 foot-pounds per hour. This is equivalent to 1,980,000 ÷ 778 = 2,550 heat units. The latent heat of steam at 90 pounds gage pressure is 881 heat units. Hence, 2,250 ÷ 881 = 2.9 pounds of steam at 90 pounds pressure is required per horsepower, provided there is no loss of steam, and all of the contained heat is changed into useful work. As a matter of fact, from 30 to 35 pounds of steam are required in the average simple non-condensing high-speed engine. There are three remedies which are used to reduce the amount of cylinder condensation. The first to be used was called steam jacketing, and consisted in surrounding the cylinder with a layer of high-pressure steam, the idea being to keep the inner walls up to a temperature nearly equal to that of the incoming steam. This arrangement is but little used at the present time, owing both to the expense of operation and to its ineffectiveness as compared with other methods. The second remedy is the use of superheated steam. It has been stated that the transfer of heat takes place much more rapidly when the interior surfaces are covered with a coating of moisture or mist. Superheated steam has a temperature considerably above the point of saturation at the given pressure; hence, it is possible to cool it a certain amount before condensation begins. This has the effect of reducing the transfer of heat for a short period following admission, and this is the time that condensation takes place most rapidly under ordinary conditions with saturated steam. This, in fact, is the principal advantage derived from the use of superheated steam, although it is also lighter for a given volume, and therefore, a less weight of steam is required, to fill the cylinder up to the point of cut-off. The economical degree of superheating is considered to be that which will prevent the condensation of any steam on the walls of the cylinder up to the point of cut-off, thus keeping them at all times free from moisture. The objections to superheated steam are its cutting effect in the passages through which it flows, and the difficulty experienced in lubricating the valves and cylinder at such a high temperature. The third and most effective remedy for condensation losses is that known as compounding, which will be treated under a separate heading in the following. Multiple Expansion Engines It has been explained that cylinder condensation is due principally to the change in temperature of the interior surfaces of the cylinder, caused by the variation in temperature of the steam at initial and exhaust pressures. Therefore, if the temperature range be divided between two cylinders which are operated in series, the steam condensed in the first or high pressure cylinder will be re-evaporated and passed into the low-pressure cylinder as steam, where it will again be condensed and re-evaporated as it passes into the exhaust pipe. Theoretically, this should reduce the condensation loss by one-half, and if three cylinders are used, the loss should be only one-third of that in a simple engine. In actual practice the saving is not as great as this, but with the proper relation between the cylinders, these results are approximated. Engines in which expansion takes place in two stages are called compound engines. When three stages are employed, they are called triple expansion engines. Compounding adds to the first cost of an engine, and also to the friction, so that in determining the most economical number of cylinders to employ, the actual relation between the condensation loss and the increased cost of the engine and the friction loss, must be considered. In the case of power plant work, it is now the practice to use compound engines for the large sizes, while triple expansion engines are more commonly employed in pumping stations. Many designs of multiple expansion engines are provided with chambers between the cylinders, called receivers. In engines of this type the exhaust is frequently reheated in the receivers by means of brass coils containing live steam. In the case of a cross-compound engine, a receiver is always used. In the tandem design it is often omitted, the piping between the two cylinders being made to answer the purpose. The ratio of cylinder volumes in compound engines varies with different makers. The usual practice is to make the volume of the low-pressure cylinder from 2.5 to 3 times that of the high-pressure. The total ratio of expansion in a multiple expansion engine is the product of the ratios in each cylinder. For example, if the ratio of expansion is 4 in each cylinder in a compound engine, the total ratio will be 4 × 4 = 16. The effect of a triple-expansion engine is sometimes obtained in a measure by making the volume of the low-pressure cylinder of a compound engine 6 or 7 times that of the high-pressure. This arrangement produces a considerable drop in pressure at the end of the high-pressure stroke, with the result of throwing a considerable increase of work on the high-pressure cylinder without increasing its ratio of expansion, and at the same time securing a large total ratio of expansion in the engine. In the case of vertical engines, the low-pressure cylinder is sometimes divided into two parts in order to reduce the size of cylinder and piston. In this arrangement a receiver of larger size than usual is employed, and the low-pressure cranks are often set at an angle with each other. Another advantage gained by compounding is the possibility to expand the steam to a greater extent than can be done in a single cylinder engine, thus utilizing, as useful work, a greater proportion of the heat contained in the steam. This also makes it possible to employ higher initial pressures, in which there is a still further saving, because of the comparatively small amount of fuel required to raise the pressure from that of the common practice of 80 or 90 pounds for simple engines, to 120 to 140 pounds, which is entirely practical in the case of compound engines. With triple expansion, initial pressures of 180 pounds or more may be used to advantage. The gain from compounding may amount to about 15 per cent over simple condensing engines, taking steam at the same initial pressure. When compound condensing engines are compared with simple non-condensing engines, the gain in economy may run from 30 to 40 per cent. TABLE IV. STEAM CONSUMPTION OF ENGINES +-------------------------+--------------------------------+ | | Pounds of Steam per Indicated | | | Horsepower per Hour | | Kind of Engine +----------------+---------------+ | | Non-condensing | Condensing | +-------------------------+----------------+---------------+ | { High-speed | 32 | 24 | | Simple { Medium-speed | 30 | 23 | | { Corliss | 28 | 22 | | | | | | { High-speed | 26 | 20 | | Compound { Medium-speed | 25 | 19 | | { Corliss | 24 | 18 | +-------------------------+----------------+---------------+ Steam Consumption and Ratio of Expansion The steam consumption is commonly called the _water rate_, and is expressed in pounds of dry steam required per indicated horsepower per hour. This quantity varies widely in different types of engines, and also in engines of the same kind working under different conditions. The water rate depends upon the "cylinder losses," which are due principally to condensation, although the effects of clearance, radiation from cylinder and steam chest, and leakage around valves and piston, form a part of the total loss. Table IV gives the average water rate of different types of engines working at full load. The most economical ratio of expansion depends largely upon the type of the engine. In the case of simple engines, the ratio is limited to 4 or 5 on account of excessive cylinder condensation in case of larger ratios. This limits the initial pressure to an average of about 90 pounds for engines of this type. In the case of compound engines, a ratio of from 8 to 10 is commonly employed to advantage, while with triple-expansion engines, ratios of 12 to 15 are found to give good results. [Illustration: Fig. 38. Action of Throttling Governor on Indicator Diagram] [Illustration: Fig. 39. Effect of Shaft Governor on Indicator Diagram] [Illustration: Fig. 40. Increasing Power of Engine by Condensing] [Illustration: Fig. 41. Decreasing Steam Consumption by Condensing] The _thermal efficiency_ of an engine is the ratio of the heat transformed into work to the total heat supplied to the engine. In order to determine this, the _absolute_ temperature of the steam at admission and exhaust pressures must be known. These pressures can be measured by a gage, and the corresponding temperatures taken from a steam table, or better, the temperatures can be measured direct by a thermometer. The absolute temperature is obtained by adding 461 to the reading in degrees Fahrenheit (F.). The formula for thermal efficiency is: _T__{1} - _T__{2} ----------------- _T__{1} in which _T__{1} = absolute temperature of steam at initial pressure. _T__{2} = absolute temperature of steam at exhaust pressure. _Example_:--The temperature of the steam admitted to the cylinder of an engine is 340 degrees F., and that of the exhaust steam 220 degrees F. What is the thermal efficiency of the engine? (340 + 461) - (220 + 461) Thermal efficiency = ------------------------- = 0.15 (340 + 461) The _mechanical efficiency_ is the ratio of the delivered or brake horsepower to the indicated horsepower, and is represented by the equation: B. H. P. Mechanical efficiency = -------- I. H. P. in which B. H. P. = brake horsepower, I. H. P. = indicated horsepower. All engines are designed to give the best economy at a certain developed indicated horsepower called full load. There must, of course, be more or less fluctuation in the load under practical working conditions, especially in certain cases, such as electric railway and rolling mill work. The losses, however, within a certain range on either side of the normal load, are not great in a well designed engine. The effect of increasing the load is to raise the initial pressure or lengthen the cut-off, depending upon the type of governor. This, in turn, raises the terminal pressure at the end of expansion, and allows the exhaust to escape at a higher temperature than before, thus lowering the thermal efficiency. The effect of reducing the load is to lower the mean effective pressure. (See Figs. 38 and 39.) This, in throttling engines, is due to a reduction of initial pressure, and in the automatic engine to a shortening of the cut-off. The result in each case is an increase in cylinder condensation, and as the load becomes lighter, the friction of the engine itself becomes a more important part of the total indicated horsepower; that is, as the load becomes lighter, the mechanical efficiency is reduced. Effect of Condensing So far as the design of the engine itself it concerned, there is no difference between a condensing and a non-condensing engine. The only difference is that in the first case the exhaust pipe from the engine is connected with a condenser instead of discharging into the atmosphere. A condenser is a device for condensing the exhaust steam as fast as it comes from the engine, thus forming a partial vacuum and reducing the back pressure. The attaching of a condenser to an engine may be made to produce two results, as shown by the work diagrams illustrated in Figs. 40 and 41. In the first case the full line represents the diagram of the engine when running non-condensing, and the area of the diagram gives a measure of the work done. The effect of adding a condenser is to reduce the back pressure on an average of 10 to 12 pounds per square inch, which is equivalent to adding the same amount to the mean effective pressure. The effect of this on the diagram, when the cut-off remains the same, is shown by the dotted line in Fig. 40. The power of the engine per stroke is increased by an amount represented by the area enclosed by the dotted line and the bottom of the original diagram. Assuming the reduction in back pressure to be 10 pounds, which is often exceeded in the best practice, the gain in power by running condensing will be proportional to the increase in mean effective pressure under these conditions. For example, if the mean effective pressure is 40 pounds when running non-condensing, it will be increased to 40 + 10 = 50 pounds when running condensing, that is, it is 50/40 = 1.25 times as great as before. Therefore, if the engine develops 100 I. H. P. under the first condition, its final power will be increased to 100 × 1.25 = 125 I. H. P. under the second condition. Fig. 41 shows the effect of adding a condenser and shortening the cut-off to keep the area of the diagram the same as before. The result in this case is a reduction in the quantity of steam required to develop the same indicated horsepower. The theoretical gain in economy under these conditions will run from about 28 to 30 per cent for simple, and from 20 to 22 per cent for compound engines. The actual gain will depend upon the cost and operation of the condenser which varies greatly in different localities. CHAPTER V TYPES OF STEAM ENGINES There are various ways of classifying steam engines according to their construction, the most common, perhaps, being according to speed. If this classification is employed, they may be grouped under three general headings: High-speed, from 300 to 400 revolutions per minute; moderate-speed, from 100 to 200 revolutions; and slow-speed, from 60 to 90 revolutions; all depending, however, upon the length of stroke. This classification is again sub-divided according to valve mechanism, horizontal and vertical, simple and compound, etc. The different forms of engines shown in the following illustrations show representative types in common use for different purposes. The Ball engine, as shown in Fig. 42, is a typical horizontal single valve high-speed engine with a direct-connected dynamo. It is very rigid in design and especially compact for the power developed. The valve is of the double-ported type shown in Fig. 2, having a cover plate for removing the steam pressure from the back of the valve. The piston is hollow with internal ribs similar to that shown in Fig. 29, and is provided with spring packing rings carefully fitted in place. The governor is of the shaft type, having only one weight instead of two, as shown in Fig. 37. [Illustration: Fig. 42. The Ball Engine] The Sturtevant engine shown in Fig. 43 is a vertical high-speed engine of a form especially adapted to electrical work. Engines of this general design are made in a variety of sizes, and are often used on account of the small floor space required. In the matter of detail, such as valves, governors, etc., they do not differ materially from the high-speed horizontal engine. Fig. 44 illustrates a moderate-speed engine of the four-valve type. These engines are built either with flat valves, or with positively driven rotary or Corliss valves, the latter being used in the engine shown. It will be noticed that the drop-lever and dash-pot arrangement is omitted, the valves being both opened and closed by means of the wrist-plate and its connecting rods. This arrangement is used on account of the higher speed at which the engine is run, the regular Corliss valve gear being limited to comparatively low speeds. All engines of this make are provided with an automatic system of lubrication. The oil is pumped through a filter to a central reservoir, seen above the center of the engine, and from here delivered to all bearings by gravity. The pump is attached to the rocker arm, and therefore easily accessible for repairs. The standard Harris Corliss engine shown in Fig. 45, is typical of its class. It is provided with the girder type of frame, and with an outboard bearing mounted upon a stone foundation. The valve gear is of the regular Corliss type, driven by a single eccentric and wrist-plate. The dash pots are mounted on cast-iron plates set in the floor at the side of the engine, where they may be easily inspected. The governor is similar in construction to the one already described, and shown in Fig. 27. The four engines so far described are simple engines, the expansion taking place in a single cylinder. Figs. 46 to 48 show three different types of the compound engine. [Illustration: Fig. 43. The Sturtevant Vertical Engine] The engine shown in Fig. 46 is of a type known as the tandem compound. In this design the cylinders are in line, the low-pressure cylinder in front of the high-pressure, as shown. There is only one piston rod, the high-pressure and low-pressure pistons being mounted on the same rod. The general appearance of an engine of this design is the same as a simple engine, except for the addition of the high-pressure cylinder. The governor is of the shaft type and operates by changing the cut-off in the high-pressure cylinder. The cut-off in the low pressure cylinder is adjusted by hand to divide the load equally between the two cylinders for the normal load which the engine is to carry. [Illustration: Fig. 44. Moderate Speed Engine of the Four-valve Type] The engine shown in Fig. 47 is known as a duplex compound. In this design the high-pressure cylinder is placed directly below the low-pressure cylinder, as indicated, and both piston rods are attached to the same cross-head. The remainder of the engine is practically the same as a simple engine of the same type. [Illustration: Fig. 45. The Harris Corliss Engine] Fig. 48 shows a cross-compound engine of heavy design, built especially for rolling mill work. In this arrangement two complete engines are used, except for the main shaft and flywheel, which are common to both. The engine is so piped that the high-pressure cylinder exhausts into the low-pressure, through a receiver, the connection being under the floor and not shown in the illustration. One of the advantages of the cross-compound engine over other forms is that the cranks may be set 90 degrees apart, so that when one is on a dead center the other is approximately at its position of greatest effort. Selection of an Engine The selection of an engine depends upon a number of conditions which vary to a considerable extent in different cases. Among these may be mentioned first cost, size and character of plant, available space, steam economy, and utilization of the exhaust steam. The question of first cost is usually considered in connection with that of operation, and items such as interest and depreciation are compared with the saving made through the saving in steam with high priced engines. [Illustration: Fig. 46. The Skinner Tandem Engine] [Illustration: Fig. 47. American Ball Duplex Compound Engine] The principal use of the stationary engine is confined to the driving of electric generators and the furnishing of motive power in shops and factories. For the first of these uses, in cases where floor space is limited, as in office buildings, and where the power does not exceed about 100 I. H. P., the simple non-condensing high-speed engine is probably employed more than any other type. For larger installations, a saving may usually be made by the substitution of the moderate-speed four-valve engine. The question of simple and compound engines in this class of work depends largely upon the use made of the exhaust steam. In winter time the exhaust is nearly always utilized in the heating system, hence steam economy is not of great importance, and the simple engine answers all purposes at a smaller first cost. In localities where the heating season is comparatively short and fuel high, there is a decided advantage in using compound engines on account of their greater steam economy when operated within their economical range as regards load. [Illustration: Fig. 48. The Monarch Corliss Engine] In large central plants where low cost of operation is always of first importance, it is common practice to use the best class of compound condensing engines of moderate or low speed. Those equipped with some form of Corliss valve gear are frequently found in this class of work. In the generation of power for shops and factories, where there is plenty of floor space, low-speed engines of the Corliss type are most commonly used. When space is limited, very satisfactory results may be obtained by using the moderate-speed four-valve engine. In deciding upon an engine for any particular case, the problem must be studied from all sides, and one be chosen which best answers the greatest number of requirements. CHAPTER VI STEAM ENGINE TESTING The principal information sought in the usual test of a steam engine is: 1. The indicated horsepower developed under certain standard conditions. 2. The friction of the engine, from which is determined the mechanical efficiency. 3. The steam consumption per indicated horsepower. 4. The general action of the valves. 5. The pressure conditions in the cylinder at different periods of the stroke. The ultimate object of an efficiency test is to determine the foot-pounds of work delivered by the engine per pound of coal burned in the boiler furnaces. The general method of finding the pounds of dry steam evaporated per pound of coal has been treated in MACHINERY'S Reference Series No. 67, "Boilers," under the head of "Boiler Testing." In the present case it is, therefore, only necessary to carry the process a step further and determine the foot-pounds of work developed per pound of steam. The apparatus used in engine testing, in addition to that used in boiler testing, consists of a steam engine _indicator_ and reducing device for taking diagrams, and a _planimeter_ for measuring them afterwards. If the test is made independently of the boiler test, a calorimeter for measuring the amount of moisture in the steam should be added to the outfit. It has already been shown how a diagram may be made to represent graphically the work done in a steam engine cylinder during one stroke of the piston. The diagrams shown thus far have been theoretical or ideal cards constructed from assumed relations of the pressure acting and the distance moved through by the piston. An indicator is a device for making a diagram of what actually takes place in an engine cylinder under working conditions. Such a diagram shows the points of admission, cut-off, and release, and indicates accurately the pressures acting upon both sides of the piston at all points of the stroke. A common form of steam engine indicator is shown in Fig. 49. It consists of a cylinder _C_ which is placed in communication at _E_ with one end of the engine cylinder by a proper pipe connection, provided with a quick opening and closing cock or valve. The cylinder _C_ contains a piston, above which is placed a coil spring of such strength that a given pressure per square inch acting upon the lower side of the piston will compress the spring a definite and known amount. Extending through the cap or head of cylinder _C_ is a stem attached to the piston below, and connected by suitable levers with a pencil point _P_. The arrangement of the levers is such that a certain rise of the piston causes the point _P_ to move upward in a vertical line a proportional amount. The springs used above the piston vary in strength, and are designated as 20-pound, 40-pound, 60-pound, etc. A 20-pound spring is of such strength that a pressure of 20 pounds per square inch, acting beneath the piston in cylinder _C_, will raise the pencil point 1 inch. With a 40-pound spring, a pressure of 40 pounds per square inch will be required to raise the pencil 1 inch, and so on for the other strengths of spring. The hollow drum _D_ rotates back and forth upon a vertical stem at its center, its motion being produced by the string _H_, which is attached by means of a suitable reducing motion to the cross-head of the engine. The return motion to the drum is obtained from a coil spring contained within it and not shown. The paper upon which the diagram is to be drawn is wound around the drum _D_, and held in place by the spring clip _F_. In taking an indicator card, the length of stroke must be reduced to come within the limits of the drum, that is, it must be somewhat less than the circumference of drum _D_. In practice, the diagram is commonly made from 3 to 4 inches in length. There are a number of devices in use for reproducing the stroke of the engine on a smaller scale. The most accurate consists of a series of pulleys over which the cord passes on its way from the cross-head to the indicator drum. The indicator is connected with the engine cylinder by means of special openings tapped close to the heads and either plugged or closed by means of stop-cocks when not in use. In some cases two indicators are used, one being connected to each end of the cylinder, while in others a single indicator is made to answer the purpose by being so piped that it can be connected with either end by means of a three-way cock. After the indicator is connected and the cord adjusted to give the proper motion to the drum, a card is attached, after which the three-way cock is opened and steam allowed to blow through the indicator to warm it up. The cock is now closed and the pencil pressed against the drum to get the so-called atmospheric line. The cock is again opened, and the pencil pressed lightly against the drum during one complete revolution of the engine. The cock is then thrown over to connect the indicator with the other end of the cylinder and the operation is repeated. [Illustration: Fig. 49. Steam Engine Indicator] The indicator card obtained in this way is shown in Fig. 50. It is sometimes preferred to take the diagrams of the two ends on separate cards, but it is simpler to take them both on the same one, and also easier to compare the working of the two ends of the cylinder. The analysis of a card for practical purposes is shown in Fig. 51. Suppose, for example, that the length of the diagram measures 3.6 inches; the distance to the point of cut-off is 1.2 inch; and the distance to the point of release is 3.3 inches. Then, by dividing 1.2 by 3.6, the cut-off is found to occur at 1.2 ÷ 3.6 = 1/3 of the stroke. Release occurs at 3.3 ÷ 3.6 = 0.92 of the stroke. Compression begins at (3.6 - 0.5) ÷ 3.6 = 0.86 of the stroke. The diagrams shown in Figs. 50 and 51 are from non-condensing engines, and the back-pressure line is therefore above the atmospheric line, as indicated. The indicator diagram gives a means of determining the mean effective pressure, from which the power of the engine can be found from the previously given equation _APLN_ I. H. P. = ------. 33,000 The method of determining the mean effective pressure is as follows: First measure the area of the card in square inches, by means of a planimeter (an instrument described later), and divide this area by the length in inches. This gives the mean ordinate; the mean ordinate, in turn, multiplied by the strength of spring used, will give the mean effective pressure in pounds per square inch. For example, suppose that the card shown in Fig. 51 is taken with a 60-pound spring, and that the area, as measured by a planimeter, is found to be 2.6 square inches. Dividing the area by the length gives 2.6 ÷ 3.6 = 0.722 inch as the mean ordinate, and this multiplied by the strength of spring gives a mean effective pressure of 0.722 × 60 = 43.3 pounds per square inch. [Illustration: Fig. 50. A Typical Indicator Diagram] In practice, diagrams taken from the two ends of the cylinder usually vary more or less, due to inequalities in the valve action. Again, the effective area of the piston on the crank end is less than that on the head end, by an amount equal to the area of the piston rod. For these reasons it is customary to compute the mean effective pressure of all the cards separately, and take, for use in the formula, the average of the various computations. The corrected value of the piston area is, as already stated, equal to (2_A_ - _a_)/2, in which _A_ is the area of the piston, and _a_ the area of the piston rod. Substituting these values for _A_ and _P_ in the formula, together with the length of stroke and average number of revolutions per minute, the indicated horsepower is easily computed. In making an ordinary test, diagrams are taken from both ends of the cylinder at 10-minute intervals for several hours, depending upon the accuracy required. The revolutions of the engine are counted for two or three-minute periods each time a pair of cards are taken, or still better, an automatic counter is used for the run, from which the average number of revolutions per minute may be determined. [Illustration: Fig. 51. Diagram for Illustrating Method of Computation] The friction of the engine is determined by taking a pair of cards while "running light," that is, with the belt thrown off, or the engine uncoupled, from the dynamo, if part of a direct-connected outfit. The friction load is then computed in horsepower from the indicator cards, and subtracted from the indicated horsepower when loaded. Thus we obtain the delivered or brake horsepower. The delivered horsepower divided by the indicated horsepower gives the mechanical efficiency. This may be expressed in the form of an equation as follows: I. H. P. - friction loss ------------------------ = mechanical efficiency. I. H. P. Planimeter The planimeter is an instrument for measuring areas in general, and especially for measuring the areas of indicator cards. Some forms give the mean effective pressure directly, without computations, by changing the scale to correspond with the spring used in the indicator. A planimeter of this type is shown in Fig. 52. The method of manipulating this instrument is as follows. Set the arm _BD_ equal to the length of the card _EF_, by means of the thumb screw _S_, and set the wheel at zero on the scale, which must correspond to the spring used in the indicator. Next, place the point _D_ at about the middle of the area to be measured, and set point _C_ so that the arm _CB_ shall be approximately at right angles with _BD_. Then move _D_ to the upper left-hand corner of the diagram, and with the left hand move _C_ either to the right or left until the wheel comes back exactly to the zero point on the scale; then press the point firmly into the paper. Now, go around the outline of the diagram with point _D_ from left to right, finishing exactly at the starting point. The mean effective pressure may now be read from the scale opposite the edge of the wheel. When very accurate results are required, the tracer point _D_ may be passed over the diagram several times, and the reading divided by the number of times it is thus passed around. With short cards, 3 inches and under in length, it is best to make the arm _BD_ twice the length of the card, and go around the diagram twice, taking the reading directly from the scale as in the first case. Determining Steam Consumption When it is desired to determine accurately the water rate of an engine, a boiler test should be carried on simultaneously with the test upon the engine, from which the pounds of dry steam supplied may be determined as described in MACHINERY'S Reference Series No. 67, "Boilers." Knowing the average weight of steam supplied per hour for the run, and the average indicated horsepower developed during the same period, the water rate of the engine is easily computed. Sometimes the average cylinder condensation for a given type and make is known for certain standard conditions. In this case an approximation may be made from an indicator diagram which represents the average operation of the engine during the test. [Illustration: Fig. 52. General Construction of Planimeter] A diagram shows by direct measurement the pressure and volume at any point of the stroke, and the weight of steam per cubic foot for any given pressure may be taken directly from a steam table. The method, then, of finding the weight of steam at any point in the stroke is to find the volume in cubic feet, including the clearance and piston displacement to the given point, which must be taken at cut-off or later, and to multiply this by the weight per cubic foot corresponding to the pressure at the given point measured on the diagram. As this includes the steam used for compression, it must be corrected, as follows, to obtain the actual weight used per stroke. Take some convenient point on the compression curve, as _Q_, in Fig. 53; measure its absolute pressure from the vacuum line _OX_ and compute the weight of steam to this point. Subtract this weight from that computed above for the given point on the expansion line, and the result will be the weight of steam used per stroke. The best point on the expansion line to use for this purpose is just before release, both because the maximum amount of leakage has taken place, and also because of the re-evaporation of a portion of the steam condensed during admission. The actual computation of the steam consumption from an indicator diagram is best shown by a practical illustration. _Example_--Let Fig. 53 represent a diagram taken from the head end of a 16 × 30-inch non-condensing engine, running at a speed of 150 revolutions per minute; the card is taken with a 60-pound spring; the clearance of the engine is 6 per cent; the average cylinder condensation is 20 per cent of the total steam consumption; the diameter of the piston rod is 3 inches. [Illustration: Fig. 53. Diagram for Calculating Steam Consumption] Measuring the card with a planimeter shows the mean effective pressure to be 48.2 pounds. The area of the piston is 201 square inches; the area of the piston rod is 7 square inches; hence, the average piston area = ((2 × 201) - 7)/2 = 198 square inches, approximately. Then 198 × 48.2 × 2.5 × 300 I. H. P. = ---------------------- = 217. 33,000 In Fig. 53, _GH_ is the atmospheric line; _OX_ is the line of vacuum or zero pressure, drawn so that _GO_ = 14.7 pounds on the scale; and _OY_ is the clearance line, so drawn that _ON_ = 0.06 _NX_. The line _PQ_ is drawn from _OX_ to some point on the compression line, as at _Q_. From _C_, a point on the expansion line, just before release, the line _CF_ is drawn perpendicular to _OX_. The following dimensions are now carefully measured from the actual diagram (not the one shown in the illustration), with the results given: _OX_ = 3.71 _OP_ = 0.42 _NX_ = 3.50 _CF_ = 0.81 _OF_ = 3.20 _QP_ = 0.81 On the indicator diagram, being taken with a 60-pound spring, all vertical distances represent pounds per square inch, in the ratio of 60 pounds per inch of height. The stroke of the engine is 30 inches or 2.5 feet. The length of the diagram _NX_ is 3.5 inches; hence, each inch in length represents 2.5/3.5 = 0.71 feet. From the above it is evident that vertical distances in Fig. 53 must be multiplied by 60 to reduce them to pounds pressure per square inch, and that horizontal distances must be multiplied by 0.71 to reduce them to feet. Making these reductions gives: _OX_ = 2.63 feet. _OP_ = 0.30 foot. _NX_ = 2.49 feet. _CF_ = 48.6 pounds. _OF_ = 2.27 feet. _QP_ = 48.6 pounds. As a card from the head end of the cylinder is taken to avoid corrections for the piston rod, the area is 201 square inches or 1.4 square foot. With the above data the volume and weight of the steam in the cylinder can be computed at any point in the stroke. When the piston is at _C_, the volume is 1.4 × 2.27 = 3.18 cubic feet. When the piston is at _Q_, the volume is 1.4 × 0.30 = 0.42 cubic foot. From a steam table the weight of a cubic foot of steam at 48.6 pounds absolute pressure is found to be 0.116 pounds. Therefore, the weight of steam present when the piston is at _C_ is 3.18 × 0.116 = 0.369 pounds. The weight of steam present when the piston is at _Q_ is 0.42 × 0.116 = 0.049 pound. That is the weight of steam in the cylinder at release is 0.369 pound, and the weight kept at exhaust closure for compression is 0.049 pound. The weight exhausted per stroke is therefore 0.369 - 0.049 = 0.32 pound. The number of strokes per hour is 150 × 2 × 60 = 18,000, from which the steam accounted for by the diagram is found to be 18,000 × 0.32 = 5760 pounds, or 5760 ÷ 217 = 26.5 pounds per indicated horsepower per hour. If the cylinder condensation for this type of engine is 20 per cent of the total steam consumption, the water rate will be 26.5 ÷ 0.8 = 33.1 pounds per indicated horsepower per hour. In the present case it has been assumed, for simplicity, that the head- and crank-end diagrams were exactly alike, except for the piston rod. Ordinarily, the above process should be carried out for both head and crank ends, and the results averaged. 
27687	----	STEAM TURBINES A BOOK OF INSTRUCTION FOR THE ADJUSTMENT AND OPERATION OF THE PRINCIPAL TYPES OF THIS CLASS OF PRIME MOVERS COMPILED AND WRITTEN BY HUBERT E. COLLINS FIRST EDITION Second Impression McGRAW-HILL BOOK COMPANY, Inc. 239 WEST 39TH STREET, NEW YORK 6 BOUVERIE STREET, LONDON, E. C. Copyright, 1909, by the Hill Publishing Company All rights reserved TRANSCRIBER'S NOTES The authors of this book used the spellings "aline," "gage," and "hight" for the conventional spellings "align," "gauge," and "height." As they are used consistently and do not affect the sense, they have been left unchanged. Obvious typos and misspellings that did not affect the sense have been silently corrected. The following substantive typographical errors have also been corrected: "being" to "bearing" (p. 68); "FIG. 50" to "FIG. 56" (p. 91), and "Fig. 2" to "Fig. 73" (p. 159). Two other likely errors have been left as transcriber queries: lead/load on p. 142 and beating/heating on p. 177. Superscript numbers are indicated with carets: B^1. Subscript numbers are indicated with curly braces: P{1} for P-sub-1. INTRODUCTION This issue of the Power Handbook attempts to give a compact manual for the engineer who feels the need of acquainting himself with steam turbines. To accomplish this within the limits of space allowed, it has been necessary to confine the work to the description of a few standard types, prepared with the assistance of the builders. Following this the practical experience of successful engineers, gathered from the columns of _Power_, is given. It is hoped that the book will prove of value to all engineers handling turbines, whether of the described types or not. Hubert E. Collins. New York, April, 1909. CONTENTS CHAP. PAGE I The Curtis Steam Turbine in Practice 1 II Setting the Valves of the Curtis Turbine 31 III Allis-Chalmers Steam Turbine 41 IV Westinghouse-Parsons Turbine 58 V Proper Method of Testing a Steam Turbine 112 VI Testing a Steam Turbine 137 VII Auxiliaries for Steam Turbines 154 VIII Trouble with Steam Turbine Auxiliaries 172 I. THE CURTIS STEAM TURBINE IN PRACTICE[1] [1] Contributed to _Power_ by Fred L. Johnson. "Of the making of books there is no end." This seems especially true of steam-turbine books, but the book which really appeals to the operating engineer, the man who may have a turbine unloaded, set up, put in operation, and the builders' representative out of reach before the man who is to operate it fully realizes that he has a new type of prime mover on his hands, with which he has little or no acquaintance, has not been written. There has been much published, both descriptive and theoretical, about the turbine, but so far as the writer knows, there is nothing in print that tells the man on the job about the details of the turbine in plain language, and how to handle these details when they need handling. The operating engineer does not care why the moving buckets are made of a certain curvature, but he does care about the distance between the moving bucket and the stationary one, and he wants to know how to measure that distance, how to alter the clearance, if necessary, to prevent rubbing. He doesn't care anything about the area of the step-bearing, but he does want to know the way to get at the bearing to take it down and put it up again, etc. The lack of literature along this line is the writer's apology for what follows. The Curtis 1500-kilowatt steam turbine will be taken first and treated "from the ground up." On entering a turbine plant on the ground floor, the attention is at once attracted by a multiplicity of pumps, accumulators and piping. These are called "auxiliaries" and will be passed for the present to be taken up later, for though of standard types their use is comparatively new in power-plant practice, and the engineer will find that more interruptions of service will come from the auxiliaries than from the turbine itself. Builders' Foundation Plans Incomplete It is impractical for the manufacturers to make complete foundation drawings, as they are not familiar with the lay-out of pipes and the relative position of other apparatus in the station. All that the manufacturers' drawing is intended to do is to show the customer where it will be necessary for him to locate his foundation bolts and opening for access to the step-bearing. [Illustration: FIG. 1] Fig. 1 shows the builders' foundation drawing, with the addition of several horizontal and radial tubes introduced to give passage for the various pipes which must go to the middle of the foundation. Entering through the sides of the masonry they do not block the passage, which must be as free as possible when any work is to be done on the step-bearing, or lower guide-bearing. Entering the passage in the foundation, a large screw is seen passing up through a circular block of cast iron with a 3/4-inch pipe passing through it. This is the step-supporting screw. It supports the lower half of the step-bearing, which in turn supports the entire revolving part of the machine. It is used to hold the wheels at a proper hight in the casing, and adjust the clearance between the moving and stationary buckets. The large block which with its threaded bronze bushing forms the nut for the screw is called the cover-plate, and is held to the base of the machine by eight 1-1/2-inch cap-screws. On the upper side are two dowel-pins which enter the lower step and keep it from turning. (See Figs. 2 and 3.) [Illustration: FIG. 2] [Illustration: FIG. 3] The step-blocks are very common-looking chunks of cast iron, as will be seen by reference to Fig. 4. The block with straight sides (the lower one in the illustration) has the two dowel holes to match the pins spoken of, with a hole through the center threaded for 3/4-inch pipe. The step-lubricant is forced up through this hole and out between the raised edges in a film, floating the rotating parts of the machine on a frictionless disk of oil or water. The upper step-block has two dowel-pins, also a key which fits into a slot across the bottom end of the shaft. [Illustration: FIG. 4] The upper side of the top block is counterbored to fit the end of the shaft. The counterbore centers the block. The dowel-pins steer the key into the key-way across the end of the shaft, and the key compels the block to turn with the shaft. There is also a threaded hole in the under side of the top block. This is for the introduction of a screw which is used to pull the top block off the end of the shaft. If taken off at all it must be pulled, for the dowel-pins, key and counterbore are close fits. Two long bolts with threads the whole length are used if it becomes necessary to take down the step or other parts of the bottom of the machine. Two of the bolts holding the cover-plate in place are removed, these long bolts put in their places and the nuts screwed up against the plate to hold it while the remaining bolts are removed. How to Lower Step-Bearings to Examine Them Now, suppose it is intended to take down the step-bearings for examination. The first thing to do is to provide some way of holding the shaft up in its place while we take its regular support from under it. In some machines, inside the base, there is what is called a "jacking ring." It is simply a loose collar on the shaft, which covers the holes into which four plugs are screwed. These are taken out and in their places are put four hexagonal-headed screws provided for the purpose, which are screwed up. This brings the ring against a shoulder on the shaft and then the cover-plate and step may be taken down. While all the machines have the same general appearance, there are some differences in detail which may be interesting. One difference is due to the sub-base which is used with the oil-lubricated step-bearings. This style of machine has the jacking ring spoken of, while others have neither sub-base nor jacking ring, and when necessary to take down the step a different arrangement is used. [Illustration: FIG. 5] A piece of iron that looks like a big horseshoe (Fig. 5) is used to hold the shaft up. The flange that covers the entrance to the exhaust base is taken off and a man goes in with the horseshoe-shaped shim and an electric light. Other men take a long-handled wrench and turn up the step-screw until the man inside the base can push the horseshoe shim between the shoulder on the shaft and the guide-bearing casing. The men on the wrench then back off and the horseshoe shim supports the weight of the machine. When the shim is in place, or the jacking ring set up, whichever the case may be, the cover-plate bolts may be taken out, the nuts on the long screws holding the cover in place. The 3/4-inch pipe which passes up through the step-screw is taken down and, by means of the nuts on the long screws, the cover-plate is lowered about 2 inches. Then through the hole in the step-screw a 3/4-inch rod with threads on both ends is passed and screwed into the top step; then the cover-plate is blocked so it cannot rise and, with a nut on the lower end of the 3/4-inch rod, the top step is pulled down as far as it will come. The cover-plate is let down by means of the two nuts, and the top step-block follows. When it is lowered to a convenient hight it can be examined, and the lower end of the shaft and guide-bearing will be exposed to view. [Illustration: FIG. 6] The lower guide-bearing (Fig. 6) is simply a sleeve flanged at one end, babbitted on the inside, and slightly tapered on the outside where it fits into the base. The flange is held securely in the base by eight 3/4-inch cap-screws. Between the cap-screw holes are eight holes tapped to 3/4-inch, and when it is desired to take the bearing down the cap-screws are taken out of the base and screwed into the threaded holes and used as jacks to force the guide-bearing downward. Some provision should be made to prevent the bearing from coming down "on the run," for being a taper fit it has only to be moved about one-half inch to be free. Two bolts, about 8 inches long, screwed into the holes that the cap-screws are taken from, answer nicely, as a drop that distance will not do any harm, and the bearing can be lowered by hand, although it weighs about 200 pounds. The lower end of the shaft is covered by a removable bushing which is easily inspected after the guide-bearing has been taken down. If it is necessary to take off this bushing it is easily done by screwing four 5/8-inch bolts, each about 2 feet long, into the tapped holes in the lower end of the bushing, and then pulling it off with a jack. (See Fig. 7.) Each pipe that enters the passage in the foundation should be connected by two unions, one as close to the machine as possible and the other close to the foundation. This allows the taking down of all piping in the passage completely and quickly without disturbing either threads or lengths. [Illustration: FIG. 7] Studying the Blueprints Fig. 8 shows an elevation and part-sectional view of a 1500-kilowatt Curtis steam turbine. If one should go into the exhaust base of one of these turbines, all that could be seen would be the under side of the lower or fourth-stage wheel, with a few threaded holes for the balancing plugs which are sometimes used. The internal arrangement is clearly indicated by the illustration, Fig. 8. It will be noticed that each of the four wheels has an upper and a lower row of buckets and that there is a set of stationary buckets for each wheel between the two rows of moving buckets. These stationary buckets are called intermediates, and are counterparts of the moving buckets. Their sole office is to redirect the steam which has passed through the upper buckets into the lower ones at the proper angle. [Illustration: FIG. 8. ELEVATION AND PART-SECTIONAL VIEW OF A 1500-KILOWATT CURTIS TURBINE] The wheels are kept the proper distance apart by the length of hub, and all are held together by the large nut on the shaft above the upper wheel. Each wheel is in a separate chamber formed by the diaphragms which rest on ledges on the inside of the wheel-case, their weight and steam pressure on the upper side holding them firmly in place and making a steam-tight joint where they rest. At the center, where the hubs pass through them, there is provided a self-centering packing ring (Fig. 9), which is free to move sidewise, but is prevented from turning, by suitable lugs. This packing is a close running fit on the hubs of the wheel and is provided with grooves (plainly shown in Fig. 9) which break up and diminish the leakage of steam around each hub from one stage to the next lower. Each diaphragm, with the exception of the top one, carries the expanding nozzles for the wheel immediately below. [Illustration: FIG. 9] The expanding nozzles and moving buckets constantly increase in size and number from the top toward the bottom. This is because the steam volume increases progressively from the admission to the exhaust and the entire expansion is carried out in the separate sets of nozzles, very much as if it were one continuous nozzle; but with this difference, not all of the energy is taken out of the steam in any one set of nozzles. The idea is to keep the velocity of the steam in each stage as nearly constant as possible. The nozzles in the diaphragms and the intermediates do not, except in the lowest stage, take up the entire circumference, but are proportioned to the progressive expansion of steam as it descends toward the condenser. Clearance While the machine is running it is imperative that there be no rubbing contact between the revolving and stationary parts, and this is provided for by the clearance between the rows of moving buckets and the intermediates. Into each stage of the machine a 2-inch pipe hole is drilled and tapped. Sometimes this opening is made directly opposite a row of moving buckets as in Fig. 10, and sometimes it is made opposite the intermediate. When opposite a row of buckets, it will allow one to see the amount of clearance between the buckets and the intermediates, and between the buckets and the nozzles. When drilled opposite the intermediates, the clearance is shown top and bottom between the buckets and intermediates. (See Fig. 11.) This clearance is not the same in all stages, but is greatest in the fourth stage and least in the first. The clearances in each stage are nearly as follows: First stage, 0.060 to 0.080; second stage, 0.080 to 0.100; third stage, 0.080 to 0.100; fourth stage, 0.080 to 0.200. These clearances are measured by what are called clearance gages, which are simply taper slips of steel about 1/2-inch wide accurately ground and graduated, like a jeweler's ring gage, by marks about 1/2-inch apart; the difference in thickness of the gage is one-thousandth of an inch from one mark to the next. [Illustration: FIG. 10] [Illustration: FIG. 11] To determine whether the clearance is right, one of the 2-inch plugs is taken out and some marking material, such as red lead or anything that would be used on a surface plate or bearing to mark the high spots is rubbed on the taper gage, and it is pushed into the gap between the buckets and intermediates as far as it will go, and then pulled out, the marking on the gage showing just how far in it went, and the nearest mark giving in thousandths of an inch the clearance. This is noted, the marking spread again, and the gage tried on the other side, the difference on the gage showing whether the wheel is high or low. Whichever may be the case the hight is corrected by the step-bearing screw. The wheels should be placed as nearly in the middle of the clearance space as possible. By some operators the clearance is adjusted while running, in the following manner: With the machine running at full speed the step-bearing screw is turned until the wheels are felt or heard to rub lightly. The screw is marked and then turned in the opposite direction until the wheel rubs again. Another mark is made on the screw and it is then turned back midway between the two marks. Either method is safe if practiced by a skilful engineer. In measuring the clearance by the first method, the gage should be used with care, as it is possible by using too much pressure to swing the buckets and get readings which could be misleading. To an inexperienced man the taper gages would seem preferable. In the hands of a man who knows what he is doing and how to do it, a tapered pine stick will give as satisfactory results as the most elaborate set of hardened and ground clearance gages. Referring back to Fig. 11, at A is shown one of the peep-holes opposite the intermediate in the third stage wheel for the inspection of clearance. The taper clearance gage is inserted through this hole both above and below the intermediate, and the distance which it enters registers the clearance on that side. This sketch also shows plainly how the shrouding on the buckets and the intermediates extends beyond the sharp edges of the buckets, protecting them from damage in case of slight rubbing. In a very few cases wheels have been known to warp to such an extent from causes that were not discovered until too late, that adjustment would not stop the rubbing. In such cases the shrouding has been turned or faced off by a cutting-off tool used through the peep-hole. Carbon Packing Used Where the shaft passes through the upper head of the wheel-case some provision must be made to prevent steam from the first stage escaping. This is provided for by carbon packing (Fig. 12), which consists of blocks of carbon in sets in a packing case bolted to the top head of the wheel-case. There are three sets of these blocks, and each set is made of two rings of three segments each. One ring of segments breaks joints with its mate in the case, and each set is separated from the others by a flange in the case in which it is held. In some cases the packing is kept from turning by means of a link, one end of which is fastened to the case and the other to the packing holder. Sometimes light springs are used to hold the packing against the shaft and in some the pressure of steam in the case does this. There is a pipe, also shown in Fig. 12, leading from the main line to the packing case, the pressure in the pipe being reduced. The space between the two upper sets of rings is drained to the third stage by means of a three-way cock, which keeps the balance between the atmosphere and packing-case pressure. The carbon rings are fitted to the shaft with a slight clearance to start with, and very soon get a smooth finish, which is not only practically steam-tight but frictionless. [Illustration: FIG. 12] The carbon ring shown in Fig. 12 is the older design. The segments are held against the flat bearing surface of the case by spiral springs set in brass ferrules. The circle is held together by a bronze strap screwed and drawn together at the ends by springs. Still other springs press the straps against the surface upon which the carbon bears, cutting off leaks through joints and across horizontal surfaces of the carbon. The whole ring is prevented from turning by a connecting-rod which engages a pin in the hole, like those provided for the springs. [Illustration: FIG. 13] [Illustration: FIG. 14] [Illustration: FIG. 15] [Illustration: FIG. 16] The Safety-stop There are several designs of safety-stop or speed-limit devices used with these turbines, the simplest being of the ring type shown in Fig. 13. This consists of a flat ring placed around the shaft between the turbine and generator. The ring-type emergencies are now all adjusted so that they normally run concentric with the shaft, but weighted so that the center of gravity is slightly displaced from the center. The centrifugal strain due to this is balanced by helical springs. But when the speed increases the centrifugal force moves the ring into an eccentric position, when it strikes a trigger and releases a weight which, falling, closes the throttle and shuts off the steam supply. The basic principle upon which all these stops are designed is the same--the centrifugal force of a weight balanced by a spring at normal speed. Figs. 14, 15, and 16 show three other types. The Mechanical Valve-Gear Fig. 17 shows plainly the operation of the mechanical valve-gear. The valves are located in the steam chests, which are bolted to the top of the casing directly over the first sets of expansion nozzles. The chests, two in number, are on opposite sides of the machine. The valve-stems extend upward through ordinary stuffing-boxes, and are attached to the notched cross-heads by means of a threaded end which is prevented from screwing in or out by a compression nut on the lower end of the cross-head. Each cross-head is actuated by a pair of reciprocating pawls, or dogs (shown more plainly in the enlarged view, Fig. 18), one of which opens the valve and the other closes it. The several pairs of pawls are hung on a common shaft which receives a rocking motion from a crank driven from a worm and worm-wheel by the turbine shaft. The cross-heads have notches milled in the side in which the pawls engage to open or close the valve, this engagement being determined by what are called shield-plates, A (Fig. 18), which are controlled by the governor. These plates are set, one a little ahead of the other, to obtain successive opening or closing of the valves. When more steam is required the shield plate allows the proper pawl to fall into its notch in the cross-head and lift the valve from its seat. If less steam is wanted the shield-plate rises and allows the lower pawl to close the valve on the down stroke. [Illustration: FIG. 17] [Illustration: FIG. 18] The valves, as can easily be seen, are very simple affairs, the steam pressure in the steam chest holding the valve either open or shut until it is moved by the pawl on the rock-shaft. The amount of travel on the rock-shaft is fixed by the design, but the proportionate travel above and below the horizontal is controlled by the length of the connecting-rods from the crank to the rock-shaft. There are besides the mechanical valve-gear the electric and hydraulic, but these will be left for a future article. The Governor The speed of the machine is controlled by the automatic opening and closing of the admission valves under the control of a governor (Fig. 19), of the spring-weighted type attached directly to the top end of the turbine shaft. The action of the governor depends on the balance of force exerted by the spring, and the centrifugal effort of the rectangular-shaped weights at the lower end; the moving weights acting through the knife-edge suspension tend to pull down the lever against the resistance of the heavy helical spring. The governor is provided with an auxiliary spring on the outside of the governor dome for varying the speed while synchronizing. The tension of the auxiliary spring is regulated by a small motor wired to the switchboard. This spring should be used only to correct slight changes in speed. Any marked change should be corrected by the use of the large hexagonal nut in the upper plate of the governor frame. This nut is screwed down to increase the speed, and upward to decrease it. [Illustration: FIG. 19] The Stage Valves Fig. 20 represents one of the several designs of stage valve, sometimes called the overload valve, the office of which is to prevent too high pressure in the first stage in case of a sudden overload, and to transfer a part of the steam to a special set of expanding nozzles over the second-stage wheel. This valve is balanced by a spring of adjustable tension, and is, or can be, set to open and close within a very small predetermined range of first-stage pressure. The valve is _intended_ to open and close instantly, and to supply or cut off steam from the second stage, without affecting the speed regulation or economy of operation. If any leaking occurs past the valve it is taken care of by a drip-pipe to the third stage. [Illustration: FIG. 20] The steam which passes through the automatic stage valves and is admitted to the extra set of nozzles above the second-stage wheel acts upon this wheel just the same as the steam which passes through the regular second-stage nozzles; i.e., all the steam which goes through the machine tends to hasten its speed, or, more accurately, does work and _maintains_ the speed of the machine. II. SETTING THE VALVES OF THE CURTIS TURBINE[2] [2] Contributed to _Power_ by F. L. Johnson. Under some conditions of service the stage valve in the Curtis turbine will not do what it is designed to do. It is usually attached to the machine in such manner that it will operate with, or a little behind, in the matter of time, the sixth valve. The machine is intended to carry full load with only the first bank of five valves in operation, with proper steam pressure and vacuum. If the steam pressure is under 150 pounds, or the vacuum is less than 28 inches, the sixth valve may operate at or near full load, and also open the stage valve and allow steam to pass to the second-stage nozzles at a much higher rate of speed than the steam which has already done some work in the first-stage wheel. The tendency is to accelerate unduly the speed of the machine. This is corrected by the governor, but the correction is usually carried too far and the machine slows down. With the stage valve in operation, at a critical point the regulation is uncertain and irregular, and its use has to be abandoned. The excess first-stage pressure will then be taken care of by the relief valve, which is an ordinary spring safety valve (not pop) which allows the steam to blow into the atmosphere. The mechanical valve-gear does not often get out of order, but sometimes the unexpected happens. The shop man may not have properly set up the nuts on the valve-stems; or may have fitted the distance bushings between the shield plates too closely; the superheat of the steam may distort the steam chest slightly and produce friction that will interfere with the regulation. If any of the valve-stems should become loose in the cross-heads they may screw themselves either in or out. If screwed out too far, the valve-stem becomes too long and the pawl in descending will, after the valve is seated, continue downward until it has broken something. If screwed in, the cross-head will be too low for the upper pawl to engage and the valve will not be opened. This second condition is not dangerous, but should be corrected. The valve-stems should be made the right length, and all check-nuts set up firmly. If for any purpose it becomes necessary to "set the valves" on a 1500-kilowatt mechanical gear, the operator should proceed in the following manner. Setting the Valves of a 1500-Kilowatt Curtis Turbine We will consider what is known as the "mechanical" valve-gear, with two sets of valves, one set of five valves being located on each side of the machine. [Illustration: FIG. 21] In setting the valves we should first "throw out" all pawls to avoid breakage in case the rods are not already of proper length, holding the pawls out by slipping the ends of the pawl springs over the points of the pawls, as seen in Fig. 21. Then turn the machine slowly by hand until the pawls on one set of valves are at their highest point of travel, then with the valves wide open adjust the drive-rods, i.e., the rods extending from the crank to the rock-shaft, so that there is 1/32 of an inch clearance (shown dotted in Fig. 17, Chap. I) at the point of opening of the pawls when they are "in." (See Fig. 22.) Then set up the check-nuts on the drive-rod. Turn the machine slowly, until the pawls are at their lowest point of travel. Then, with the valves closed, adjust each _valve-stem_ to give 1/32 of an inch clearance at the point of closing of the pawls when they are "in," securely locking the check-nut as each valve is set. Repeat this operation on the other side of the machine and we are ready to adjust the governor-rods. (Valves cannot be set on both sides of the machine at the same time, as the pawls will not be in the same relative position, due to the angularity of the drive-rods.) [Illustration: FIG. 22] Next, with the turbine running, and the synchronizing spring in mid-position, adjust the governor-rods so that the turbine will run at the normal speed of 900 revolutions per minute when working on the fifth valve, and carrying full load. The governor-rods for the other side of the turbine (controlling valves Nos. 6 to 10) should be so adjusted that the speed change between the fifth and sixth valves will not be more than three or four revolutions per minute. The valves of these turbines are all set during the shop test and the rods trammed with an 8-inch tram. Governors are adjusted for a speed range of 2 per cent. between no load and full load (1500 kilowatt), or 4 per cent. between the mean speeds of the first and tenth valves (no load to full overload capacity). The rods which connect the governor with the valve-gear have ordinary brass ends or heads and are adjusted by right-and-left threads and secured by lock-nuts. They are free fits on the pins which pass through the heads, and no friction is likely to occur which will interfere with the regulation, but too close work on the shield-plate bushings, or a slight warping of the steam chest, will often produce friction which will seriously impair the regulation. If it is noticed that the shield-plate shaft has any tendency to oscillate in unison with the rock-shaft which carries the pawls, it is a sure indication that the shield-plates are not as free as they should be, and should be attended to. The governor-rod should be disconnected, the pawls thrown out and the pawl strings hooked over the ends. The plates should then be rocked up and down by hand and the friction at different points noted. The horizontal rod at the back of the valve-gear may be loosened and the amount of end play of each individual shield-plate noticed and compared with the bushings on the horizontal rod at the back which binds the shield-plates together. If the plates separately are found to be perfectly free they may be each one pushed hard over to the right or left and wedged; then each bushing tried in the space between the tail-pieces of the plates. It will probably be found that the bushings are not of the right length, due to the alteration of the form of the steam chest by heat. It will generally be found also that the bushings are too short, and that the length can be corrected by very thin washers of sheet metal. It has been found in some instances that the thin bands coming with sectional pipe covering were of the right thickness. After the length of the bushings is corrected the shield-plates may be assembled, made fast and tested by rocking them up and down, searching for signs of sticking. If none occurs, the work has been correctly done, and there will be no trouble from poor regulation due to friction of the shield-plates. The Baffler The water which goes to the step-bearing passes through a baffler, the latest type of which is shown by Fig. 23. It is a device for restricting the flow of water or oil to the step- and guide-bearing. The amount of water necessary to float the machine and lubricate the guide-bearing having been determined by calculation and experiment, the plug is set at that point which will give the desired flow. The plug is a square-threaded worm, the length of which and the distance which it enters the barrel of the baffler determining the amount of flow. The greater the number of turns which the water must pass through in the worm the less will flow against the step-pressure. [Illustration: FIG. 23] The engineers who have settled upon the flow and the pressure decided that a flow of from 4-1/2 to 5-1/2 gallons per minute and a step-pressure of from 425 to 450 pounds is correct. These factors are so dependent upon each other and upon the conditions of the step-bearing itself that they are sometimes difficult to realize in every-day work; nor is it necessary. If the machine turns freely with a lower pressure than that prescribed by the engineers, there is no reason for raising this pressure; and there is only one way of doing it without reducing the area of the step-bearing, and that is by obstructing the flow of water in the step-bearing itself. A very common method used is that of grinding. The machine is run at about one-third speed and the step-water shut off for 15 or 20 seconds. This causes grooves and ridges on the faces of the step-bearing blocks, due to their grinding on each other, which obstruct the flow of water between the faces and thus raises the pressure. It seems a brutal way of getting a scientific result, if the result desired can be called scientific. The grooving and cutting of the step-blocks will not do any harm, and in fact they will aid in keeping the revolving parts of the machine turning about its mechanical center. The operating engineer will be very slow to see the utility of the baffler, and when he learns, as he will sometime, that the turbine will operate equally well with a plug out as with it in the baffler, he will be inclined to remove the baffler. It is true that with one machine operating on its own pump it is possible to run without the baffler, and it is also possible that in some particular case two machines having identical step-bearing pressures might be so operated. The baffler, however, serves a very important function, as described more fully as follows: It tends to steady the flow from the pump, to maintain a constant oil film as the pressure varies with the load, and when several machines are operating on the same step-bearing system it is the only means which fixes the flow to the different machines and prevents one machine from robbing the others. Therefore, even if an engineer felt inclined to remove the baffler he would be most liable to regret taking such a step. If the water supply should fail from any cause and the step-bearing blocks rub together, no great amount of damage will result. The machine will stop if operated long under these conditions, for if steam pressure is maintained the machine will continue in operation until the buckets come into contact, and if the step-blocks are not welded together the machine may be started as soon as the water is obtained. If vibration occurs it will probably be due to the rough treatment of the step-blocks, and may be cured by homeopathic repeat-doses of grinding, say about 15 seconds each. If the step-blocks are welded a new pair should be substituted and the damaged ones refaced. Some few experimental steps of spherical form, called "saucer" steps, have been installed with success (see Fig. 24). They seem to aid the lower guide-bearing in keeping the machine rotating about the mechanical center and reduce the wear on the guide-bearing. In some instances, too, cast-iron bushings have been substituted for bronze, with marked success. There seems to be much less wear between cast-iron and babbitt metal than between bronze and babbitt metal. The matter is really worth a thorough investigation. [Illustration: FIG. 24] III. ALLIS-CHALMERS COMPANY STEAM TURBINE In Fig. 25 may be seen the interior construction of the steam turbine built by Allis-Chalmers Co., of Milwaukee, Wis., which is, in general, the same as the well-known Parsons type. This is a plan view showing the rotor resting in position in the lower half of its casing. [Illustration: FIG. 25] Fig. 26 is a longitudinal cross-section cut of rotor and both lower and upper casing. Referring to Fig. 26 the steam comes in from the steam-pipe at C and passes through the main throttle or regulating valve D, which is a balanced valve operated by the governor. Steam enters the cylinder through the passage E. Turning in the direction of the bearing A, it passes through alternate stationary and revolving rows of blades, finally emerging at F and going out by way of G to the condenser or to atmosphere. H, J, and K represent three stages of blading. L, M, and Z are the balance pistons which counterbalance the thrust on the stages H, J, and K. O and Q are equalizing pipes, and for the low-pressure balance piston similar provision is made by means of passages (not shown) through the body of the spindle. [Illustration: FIG. 26] R indicates a small adjustable collar placed inside the housing of the main bearing B to hold the spindle in a position where there will be such a clearance between the rings of the balance pistons and those of the cylinder as to reduce the leakage of steam to a minimum and at the same time prevent actual contact under varying temperature. At S and T are glands which provide a water seal against the inleakage of air and the outleakage of steam. U represents the flexible coupling to the generator. V is the overload or by-pass valve used for admitting steam to intermediate stage of the turbine. W is the supplementary cylinder to contain the low-pressure balance piston. X and Y are reference letters used in text of this chapter to refer to equalizing of steam pressure on the low-pressure stage of the turbine. The first point to study in this construction is the arrangement of "dummies" L, M, and Z. These dummy rings serve as baffles to prevent steam leakage past the pistons, and their contact at high velocity means not only their own destruction, but also damage to or the wrecking of surrounding parts. A simple but effective method of eliminating this difficulty is found in the arrangement illustrated in this figure. The two smaller balance pistons, L and M, are allowed to remain on the high-pressure end; but the largest piston, Z, is placed upon the low-pressure end of the rotor immediately behind the last ring of blades, and working inside of the supplementary cylinder W. Being backed up by the body of the spindle, there is ample stiffness to prevent warping. This balance piston, which may also be plainly seen in Fig. 25, receives its steam pressure from the same point as the piston M, but the steam pressure, equalized with that on the third stage of the blading, X, is through holes in the webs of the blade-carrying rings. Entrance to these holes is through the small annular opening in the rotor, visible in Fig. 25 between the second and third barrels. As, in consequence of varying temperatures, there is an appreciable difference in the endwise expansion of the spindle and cylinder, the baffling rings in the low-pressure balance piston are so made as to allow for this difference. The high-pressure end of the spindle being held by the collar bearing, the difference in expansion manifests itself at the low-pressure end. The labyrinth packing of the high-pressure and intermediate pistons has a small axial and large radial clearance, whereas the labyrinth packing of the piston Z has, vice versa, a small radial and large axial clearance. Elimination of causes of trouble with the low-pressure balance piston not only makes it possible to reduce the diameter of the cylinder, and prevent distortion, but enables the entire spindle to be run with sufficiently small clearance to obviate any excessive leakage of steam. Detail of Blade Construction In this construction the blades are cut from drawn stock, so that at its root it is of angular dovetail shape, while at its tip there is a projection. To hold the roots of the blades firmly, a foundation ring is provided, as shown at A in Fig. 27. This foundation ring is first formed to a circle of the proper diameter, and then slots are cut in it. These slots are accurately spaced and inclined to give the right pitch and angle to the blades (Fig. 28), and are of dovetail shape to receive the roots of the blades. The tips of the blades are substantially bound together and protected by means of a channel-shaped shroud ring, illustrated in Fig. 31 and at B in Fig. 27. Fig. 31 shows the cylinder blading separate, and Fig. 27 shows both with the shrouding. In these, holes are punched to receive the projections on the tips of the blades, which are rivetted over pneumatically. [Illustration: FIG. 27] The foundation rings themselves are of dovetail shape in cross-section, and, after receiving the roots of the blades, are inserted in dovetailed grooves in the cylinder and rotor, where they are firmly held in place by keypieces, as may be seen at C in Fig. 27. Each keypiece, when driven in place, is upset into an undercut groove, indicated by D in Fig. 27, thereby positively locking the whole structure together. Each separate blade is firmly secured by the dovetail shape of the root, which is held between the corresponding dovetailed slot in the foundation ring and the undercut side of the groove. [Illustration: FIG. 28] Fig. 29, from a photograph of blading fitted in a turbine, illustrates the construction, besides showing the uniform spacing and angles of the blades. [Illustration: FIG. 29] The obviously thin flanges of the shroud rings are purposely made in that way, so that, in case of accidental contact between revolving and stationary parts, they will wear away enough to prevent the blades from being ripped out. This protection, however, is such that to rip them out a whole half ring of blades must be sheared off at the roots. The strength of the blading, therefore, depends not upon the strength of an individual blade, but upon the combined shearing strength of an entire ring of blades. [Illustration: FIG. 30] The blading is made up and inserted in half rings, and Fig. 30 shows two rings of different sizes ready to be put in place. Fig. 31 shows a number of rows of blading inserted in the cylinder of an Allis-Chalmers steam turbine, and Fig. 32 gives view of blading in the same turbine after nearly three years' running. [Illustration: FIG. 31] [Illustration: FIG. 32] The Governor Next in importance to the difference in blading and balance piston construction, is the governing mechanism used with these machines. This follows the well-known Hartung type, which has been brought into prominence, heretofore largely in connection with hydraulic turbines; and the governor, driven directly from the turbine shaft by means of cut gears working in an oil bath, is required to operate the small, balanced oil relay-valve only, while the two steam valves, main and by-pass (or overload), are controlled by an oil pressure of about 20 pounds per square inch, acting upon a piston of suitable size. In view of the fact that a turbine by-pass valve opens only when the unit is required to develop overload, or the vacuum fails, a good feature of this governing mechanism is that the valve referred to can be kept constantly in motion, thereby preventing sticking in an emergency, even though it be actually called into action only at long intervals. Another feature of importance is that the oil supply to the bearings, as well as that to the governor, can be interconnected so that the governor will automatically shut off the steam if the oil supply fails and endangers the bearings. This mechanism is also so proportioned that, while responding quickly to variations in load, its sensitiveness is kept within such bounds as to secure the best results in the parallel operation of alternators. The governor can be adjusted for speed while the turbine is in operation, thereby facilitating the synchronizing of alternators and dividing the load as may be desired. In order to provide for any possible accidental derangement of the main governing mechanism, an entirely separate safety or over-speed governor is furnished. This governor is driven directly by the turbine shaft without the intervention of gearing, and is so arranged and adjusted that, if the turbine should reach a predetermined speed above that for which the main governor is set, the safety governor will come into action and trip a valve which entirely shuts off the steam supply, bringing the turbine to a stop. Lubrication Lubrication of the four bearings, which are of the self-adjusting, ball and socket pattern, is effected by supplying an abundance of oil to the middle of each bearing and allowing it to flow out at the ends. The oil is passed through a tubular cooler, having water circulation, and pumped back to the bearings. Fig. 33 shows the entire arrangement graphically and much more clearly than can be explained in words. The oil is circulated by a pump directly operated from the turbine, except where the power-house is provided with a central oiling system. Particular stress is laid by the builders upon the fact that it is not necessary to supply the bearings with oil under pressure, but only at a head sufficient to enable it to run to and through the bearings; this head never exceeding a few feet. With each turbine is installed a separate direct-acting steam pump for circulating oil for starting up. This will be referred to again under the head of operating. [Illustration: FIG. 33] Generator The turbo-generator, which constitutes the electrical end of this unit, is totally enclosed to provide for noiseless operation, and forced ventilation is secured by means of a small fan carried by the shaft on each end of the rotor. The air is taken in at the ends of the generator, passes through the fans and is discharged over the end connections of the armature coils into the bottom of the machine, whence it passes through the ventilating ducts of the core to an opening at the top. The field core is, according to size, built up either of steel disks, each in one piece, or of steel forgings, so as to give high magnetic permeability and great strength. The coils are placed in radial slots, thereby avoiding side pressure on the slot insulation and the complex stresses resulting from centrifugal force, which, in these rotors, acts normal to the flat surface of the strip windings. Operation As practically no adjustments are necessary when these units are in operation, the greater part of the attention required by them is involved in starting up and shutting down, which may be described in detail as follows: _To Start Up_ First, the auxiliary oil pump is set going, and this is speeded up until the oil pressure shows a hight sufficient to lift the inlet valve and oil is flowing steadily at the vents on all bearings. The oil pressure then shows about 20 to 25 pounds on the "Relay Oil" gage, and 2 to 4 pounds on the "Bearing Oil" gage. Next the throttle is opened, without admitting sufficient steam to the turbine to cause the spindle to turn, and it is seen that the steam exhausts freely into the atmosphere, also that the high-pressure end of the turbine expands freely in its guides. Water having been allowed to blow out through the steam-chest drains, the drains are closed and steam is permitted to continue flowing through the turbine not less than a half an hour (unless the turbine is warm to start with, when this period may be reduced) still without turning the spindle. After this it is advisable to shut off steam and let the turbine stand ten minutes, so as to warm thoroughly, during which time the governor parts may be oiled and any air which may have accumulated in the oil cylinder above the inlet valve blown off. Then the throttle should be opened sufficiently to start the turbine spindle to revolving very slowly and the machine allowed to run in this way for five minutes. Successive operations may be mentioned briefly as admitting water to the oil cooler; bringing the turbine up to speed, at the same time slowing down the auxiliary oil pump and watching that the oil pressures are kept up by the rotary oil pump on the turbine; turning the water on to the glands very gradually and, before putting on vacuum, making sure that there is just enough water to seal these glands properly; and starting the vacuum gradually just before putting on the load. These conditions having been complied with, the operator next turns his attention to the generator, putting on the field current, synchronizing carefully and building up the load on the unit gradually. The principal precautions to be observed are not to start without warming up properly, to make sure that oil is flowing freely through the bearings, that vacuum is not put on until the water glands seal, and to avoid running on vacuum without load on the turbine. In Operation In operation all that is necessary is to watch the steam pressure at the "Throttle" and "Inlet" gages, to see that neither this pressure nor the steam temperature varies much; to keep the vacuum constant, as well as pressures on the water glands and those indicated by the "Relay Oil" and "Bearing Oil" gages; to take care that the temperatures of the oil flowing to and from the bearings does not exceed 135 degrees Fahr. (at which temperature the hand can comfortably grasp the copper oil-return pipes); to see that oil flows freely at all vents on the bearings, and that the governor parts are periodically oiled. So far as the generator is concerned, it is only essential to follow the practice common in all electric power plant operation, which need not be reviewed here. _Stopping the turbine_ is practically the reverse of starting, the successive steps being as follows: starting the auxiliary oil pump, freeing it of water and allowing it to run slowly; removing the load gradually; breaking the vacuum when the load is almost zero, shutting off the condenser injection and taking care that the steam exhausts freely into the atmosphere; shutting off the gland water when the load and vacuum are off; pulling the automatic stop to trip the valve and shut off steam and, as the speed of the turbine decreases, speeding up the auxiliary oil pump to maintain pressure on the bearings; then, when the turbine has stopped, shutting down the auxiliary oil pump, turning off the cooling water, opening the steam chest drains and slightly oiling the oil inlet valve-stem. During these operations the chief particulars to be heeded are: not to shut off the steam before starting the auxiliary oil pump nor before the vacuum is broken, and not to shut off the gland water with vacuum on the turbine. The automatic stop should also remain unhooked until the turbine is about to be started up again. General Water used in the glands of the turbine must be free from scale-forming impurities and should be delivered at the turbine under a steady pressure of not less than 15 pounds. The pressure in the glands will vary from 4 to 10 pounds. This water may be warm. In the use of water for the cooling coils and of oil for the lubricating system, nothing more is required than ordinary good sense dictates. An absolutely pure mineral oil must be supplied, of a non-foaming character, and it should be kept free through filtering from any impurities. The above refers particularly to Allis-Chalmers turbines of the type ordinarily used for power service. For turbines built to be run non-condensing, the part relating to vacuum does not, of course, apply. IV. WESTINGHOUSE-PARSONS STEAM TURBINE While the steam turbine is simple in design and construction and does not require constant tinkering and adjustment of valve gears or taking up of wear in the running parts, it is like any other piece of fine machinery in that it should receive intelligent and careful attention from the operator by inspection of the working parts that are not at all times in plain view. Any piece of machinery, no matter how simple and durable, if neglected or abused will in time come to grief, and the higher the class of the machine the more is this true. Any engineer who is capable of running and intelligently taking care of a reciprocating engine can run and take care of a turbine, but if he is to be anything more than a starter and stopper, it is necessary that he should know what is inside of the casing, what must be done and avoided to prevent derangement, and to keep the machine in continued and efficient operation. In the steam turbine the steam instead of being expanded against a piston is made to expand against and to get up velocity in itself. The jet of steam is then made to impinge against vanes or to react against the moving orifice from which it issues, in either of which cases its velocity and energy are more or less completely abstracted and appropriated by the revolving member. The Parsons turbine utilizes a combination of these two methods. [Illustration: FIG. 34] Fig. 34 is a sectional view of the standard Westinghouse-Parsons single-flow turbine. A photograph of the rotor R R R is reproduced in Fig. 35, while in Fig. 36 a section of the blading is shown upon a larger scale. Between the rows of the blading upon the rotor extend similar rows of stationary blades attached to the casing or stator. The steam entering at A (Fig. 34), fills the circular space surrounding the rotor and passes first through a row of stationary blades, 1 (Fig. 37), expanding from the initial pressure P to the slightly lower pressure P{1}, and attaining by that expansion a velocity with which it is directed upon the moving blade 2. In passing through this row of blades it is further expanded from pressure P{1} to P{2} and helps to push the moving blades along by the reaction of the force with which it issues therefrom. Impinging upon the second row of stationary blades 3, the direction of flow is diverted so as to make it impinge at a favorable angle upon the second row of revolving blades 4, and the action is continued until the steam is expanded to the pressure of the condenser or of the medium into which the turbine finally exhausts. As the expansion proceeds, the passages are made larger by increasing the length of the blades and the diameter of the drums upon which they are carried in order to accommodate the increasing volume. [Illustration: FIG. 35] [Illustration: FIG. 36] [Illustration: FIG. 37] It is not necessary that the blades shall run close together, and the axial clearance, that is the space lengthwise of the turbine between the revolving and the stationary blades, varies from 1/8 to 1/2 inch; but in order that there may not be excessive leakage over the tops of the blades, as shown, very much exaggerated, in Fig. 38, the radial clearance, that is, the clearance between the tops of the moving blades and the casing, and between the ends of the stationary blades and the shell of the rotor, must be kept down to the lowest practical amount, and varies, according to the size of the machine and length of blade, from about 0.025 to 0.125 of an inch. [Illustration: FIG. 38] In the passage A (Fig. 34) exists the initial pressure; in the passage B the pressure after the steam has passed the first section or diameter of the rotor; in the passage C after it has passed the second section. The pressure acting upon the exposed faces of the rows of vanes would crowd the rotor to the left. They are therefore balanced by pistons or "dummies" P P P revolving with the shaft and exposing in the annular spaces B^1 and C^1 the same areas as those of the blade sections which they are designed to balance. The same pressure is maintained in B^1 as in B, and in C^1 as in C by connecting them with equalizing pipes E E. The third equalizing pipe connects the back or right-hand side of the largest dummy with the exhaust passage so that the same pressure exists upon it as exists upon the exhaust end of the rotor. These dummy pistons are shown at the near end of the rotor in Fig. 35. They are grooved so as to form a labyrinth packing, the face of the casing against which they run being grooved and brass strips inserted, as shown in Fig. 39. The dummy pistons prevent leakage from A, B^1 and C^1 to the condenser, and must, of course, run as closely as practicable to the rings in the casing, the actual clearance being from about 0.005 to 0.015 of an inch, again depending on the size of the machine. [Illustration: FIG. 39] The axial adjustment is controlled by the device shown at T in Fig. 34 and on a larger scale in Fig. 40. The thrust bearing consists of two parts, T{1} T{2}. Each consists of a cast-iron body in which are placed brass collars. These collars fit into grooves C, turned in the shaft as shown. The halves of the block are brought into position by means of screws S{1} S{2} acting on levers L{1} L{2} and mounted in the bearing pedestal and cover. The screws are provided with graduated heads which permit the respective halves of the thrust bearing to be set within one one-thousandth of an inch. [Illustration: FIG. 40] The upper screw S{2} is set so that when the rotor exerts a light pressure against it through the thrust block and lever the grooves in the balance pistons are just unable to come in contact with the dummy strips in the cylinder. The lower screw S{1} is then adjusted to permit about 0.008 to 0.010 of an inch freedom for the collar between the grooves of the thrust bearing. These bearings are carefully adjusted before the machine leaves the shop, and to prevent either accidental or unauthorized changes of their adjustment the adjusting screw heads are locked by the method shown in Fig. 40. The screw cannot be revolved without sliding back the latch L{3}. To do this the pin P{4} must be withdrawn, for which purpose the bearing cover must be removed. In general this adjustment should not be changed except when there has been some wear of the collars in the thrust bearing; nevertheless, it is a wise precaution to go over the adjustment at intervals. The method of doing this is as follows: The machine should have been in operation for some time so as to be well and evenly heated and should be run at a reduced speed, say 10 per cent. of the normal, during the actual operation of making the adjustment. Adjust the upper screw which, if tightened, would push the spindle away from the thrust bearing toward the exhaust. Find a position for this so that when the other screw is tightened the balance pistons can just be heard to touch, and so the least change of position inward of the upper screw will cause the contact to cease. To hear if the balance pistons are touching, a short piece of hardwood should be placed against the cylinder casing near the balance piston. If the ear is applied to the other end of the piece of wood the contact of the balance pistons can be very easily detected. The lower screw should then be loosened and the upper screw advanced from five to fifteen one-thousandths, according to the machine, at which position the latter may be considered to be set. The lower screw should then be advanced until the under half of the thrust bearing pushes the rotor against the other half of the thrust bearing, and from this position it should be pushed back ten or more one-thousandths, to give freedom for the rotor between the thrusts, and locked. A certain amount of care should be exercised in setting the dummies, to avoid straining the parts and thus obtain a false setting. The object in view is to have the grooves of the balance pistons running as close as possible to the collars in the cylinder, but without danger of their coming in actual contact, and to allow as little freedom as possible in the thrust bearing itself, but enough to be sure that it will not heat. The turbine rotor itself has scarcely any end thrust, so that all the thrust bearing has to do is to maintain the above-prescribed adjustment. The blades are so gaged that at all loads the rotor has a very light but positive thrust toward the running face of the dummy strips, thus maintaining the proper clearance at the dummies as determined by the setting of the proper screw adjustment. Main Bearings The bearings which support the rotor are shown at F F in Fig. 34 and in detail in Fig. 41. The bearing proper consists of a brass tube B with proper oil grooves. It has a dowel arm L which fits into a corresponding recess in the bearing cover and which prevents the bearing from turning. On this tube are three concentric tubes, C D E, each fitting over the other with some clearance so that the shaft is free to move slightly in any direction. These tubes are held in place by the nut F, and this nut, in turn, is held by the small set-screw G. The bearing with the surrounding tubes is placed inside of the cast-iron shell A, which rests in the bearing pedestal on the block and liner H. The packing ring M prevents the leakage of oil past the bearing. Oil enters the chamber at one end of the bearing at the top and passes through the oil grooves, lubricating the journal, and then out into the reservoir under the bearing. The oil also fills the clearance between the tubes and forms a cushion, which dampens any tendency to vibration. [Illustration: FIG. 41] The bearings, being supported by the blocks or "pads" H, are self-alining. Under these pads are liners 5, 10, 20, and 50 thousandths in thickness. By means of these liners the rotor may be set in its proper running position relative to the stator. This operation is quite simple. Remove the liners from under one bearing pad and place them under the opposite pad until a blade touch is obtained by turning the rotor over by hand. After a touch has been obtained on the top, bottom, and both sides, the total radial blade clearance will be known to equal the thickness of the liners transferred. The position of the rotor is then so adjusted that the radial blade clearance is equalized when the turbine is at operating temperature. On turbines running at 1800 revolutions per minute or under, a split babbitted bearing is used, as shown in Figs. 42a and 42b. These bearings are self-alining and have the same liner adjustment as the concentric-sleeve bearings just described. Oil is supplied through a hole D in the lower liner pad, and is carried to the oil groove F through the tubes E E. The oil flows from the middle of this bearing to both ends instead of from one end to the other, as in the other type. [Illustration: FIG. 42A] [Illustration: FIG. 42B] Packing Glands Where the shaft passes through the casing at either end it issues from a chamber in which there exists a vacuum. It is necessary to pack the shaft at these points, therefore, against the atmospheric pressure, and this is done by means of a water-gland packing W W (Fig. 34). Upon the shaft in Fig. 35, just in front of the dummy pistons, will be seen a runner of this packing gland, which runner is shown upon a larger scale and from a different direction in Fig. 43. To get into the casing the air would have to enter the guard at A (Fig. 44), pass over the projecting rings B, the function of which is to throw off any water which may be creeping along the shaft by centrifugal force into the surrounding space C, whence it escapes by the drip pipe D, hence over the five rings of the labyrinth packing E and thence over the top of the revolving blade wheel, it being apparent from Fig. 43 that there is no way for the air to pass by without going up over the top of the blades; but water is admitted to the centrally grooved space through the pipe shown, and is revolved with the wheel at such velocity that the pressure due to centrifugal force exceeds that of the atmosphere, so that it is impossible for the air to force the water aside and leak in over the tips of the blades, while the action of the runner in throwing the water out would relieve the pressure at the shafts and avoid the tendency of the water to leak outward through the labyrinth packing either into the vacuum or the atmosphere. [Illustration: FIG. 43] [Illustration: FIG. 44] The water should come to the glands under a head of about 10 feet, or a pressure of about 5 pounds, and be connected in such a way that this pressure may be uninterruptedly maintained. Its temperature must be lower than the temperature due to the vacuum within the turbine, or it will evaporate readily and find its way into the turbine in the form of steam. [Illustration: FIG. 45] In any case a small amount of the steaming water will pass by the gland collars into the turbine, so that if the condensed steam is to be returned to the boilers the water used in the glands must be of such character that it may be safely used for feed water. But whether the water so used is to be returned to the boilers or not it should never contain an excessive amount of lime or solid matter, as a certain amount of evaporation is continually going on in the glands which will result in the deposit of scale and require frequent taking apart for cleaning. [Illustration: FIG. 46] When there is an ample supply of good, clean water the glands may be packed as in Fig. 45, the standpipe supplying the necessary head and the supply valve being opened sufficiently to maintain a small stream at the overflow. When water is expensive and the overflow must be avoided, a small float may be used as in Fig. 46, the ordinary tank used by plumbers for closets, etc., serving the purpose admirably. When the same water that is supplied to the glands is used for the oil-cooling coils, which will be described in detail later, the coils may be attached to either of the above arrangements as shown in Fig. 47. [Illustration: FIG. 47] When the only available supply of pure water is that for the boiler feed, and the condensed steam is pumped directly back to the boiler, as shown in Fig. 48, the delivery from the condensed-water pumps may be carried to an elevation 10 feet above the axis of the glands, where a tank should be provided of sufficient capacity that the water may have time to cool considerably before being used. In most of these cases, if so desired, the oil-cooling water may come from the circulating pumps of the condenser, provided there is sufficient pressure to produce circulation, as is also shown in Fig. 48. [Illustration: FIG. 48] When the turbine is required to exhaust against a back pressure of one or two pounds a slightly different arrangement of piping must be made. The water in this case must be allowed to circulate through the glands in order to keep the temperature below 212 degrees Fahrenheit. If this is not done the water in the glands will absorb heat from the main castings of the machine and will evaporate. This evaporation will make the glands appear as though they were leaking badly. In reality it is nothing more than the water in the glands boiling, but it is nevertheless equally objectionable. This may be overcome by the arrangement shown in Fig. 49, where two connections and valves are furnished at M and N, which drain away to any suitable tank or sewer. These valves are open just enough to keep sufficient circulation so that there is no evaporation going on, which is evidenced by steam coming out as though the glands were leaking. These circulating valves may be used with any of the arrangements above described. [Illustration: FIG. 49] The Governor On the right-hand end of the main shaft in Fig. 34 there will be seen a worm gear driving the governor. This is shown on a larger scale at A (Fig. 50). At the left of the worm gear is a bevel gear driving the spindle D of the governor, and at the right an eccentric which gives a vibratory motion to the lever F. The crank C upon the end of the shaft operates the oil pump. The speed of the turbine is controlled by admitting the steam in puffs of greater or less duration according to the load. The lever F, having its fulcrum in the collar surrounding the shaft, operates with each vibration of the eccentric the pilot valve. The valve is explained in detail later. [Illustration: FIG. 50] This form of governor has been superseded by an improved type, but so many have been made that it will be well to describe its construction and adjustment. The two balls W W (Fig. 50) are mounted on the ends of bell cranks N, which rest on knife edges. The other end of the bell cranks carry rollers upon which rest a plate P, which serves as a support for the governor spring S. They are also attached by links to a yoke and sleeve E which acts as a fulcrum for the lever F. The governor is regulated by means of the spring S resting on the plate P and compressed by a large nut G on the upper end of the governor spindle, which nut turns on a threaded quill J, held in place by the nut H on the end of the governor spindle and is held tight by the lock-nut K. To change the compression of the spring and thereby the speed of the turbine the lock-nut must first be loosened and the hand-nut raised to lower the speed or lowered to raise the speed as the case may be. This operation may be accomplished while the machine is either running or at rest. The plate P rests upon ball bearings so that by simply bringing pressure to bear upon the hand-wheel, which is a part of the quill J, the spring and lock-nut may be held at rest and adjusted while the rest of the turbine remains unaffected. Another lever is mounted upon the yoke E on the pin shown at I, the other end of which is fastened to the piston of a dash-pot so as to dampen the governor against vibration. Under the yoke E will be noticed a small trigger M which is used to hold the governor in the full-load position when the turbine is at rest. The throwing out of the weights elevates the sleeve E, carrying with it the collar C, which is spanned by the lever F upon the shaft H. The later turbines are provided with an improved form of governor operating on the same principle, but embodying several important features. First, the spindle sleeve is integral with the governor yoke, and the whole rotates about a vertical stationary spindle, so that two motions are encountered--a rotary motion and an up and down motion, according to the position taken by the governor. This spiral motion almost entirely eliminates the effect of friction of rest, and thereby enhances the sensitiveness of the governor. Second, the governor weights move outward on a parallel motion opposed directly by spring thrust, thus relieving the fulcrum entirely of spring thrust. Third, the lay shaft driving the governor oil pump and reciprocator is located underneath the main turbine shaft, so that the rotor may be readily removed without in the least disturbing the governor adjustment. The Valve-Gear The valve-gear is shown in section in Fig. 51, the main admission being shown at V{1} at the right, and the secondary V{2} at the left of the steam inlet. The pilot valve F receives a constant reciprocating motion from the eccentric upon the layshaft of the turbine through the lever F (Fig. 50). These reciprocations run from 150 to 180 per minute. The space beneath the piston C is in communication with the large steam chest, where exists the initial pressure through the port A; the admission of steam to the piston C being controlled by a needle valve B. The pilot valve connects the port E, leading from the space beneath the piston to an exhaust port I. [Illustration: FIG. 51] When the pilot valve is closed, the pressures can accumulate beneath the piston C and raise the main admission valve from its seat. When the pilot valve opens, the pressure beneath the piston is relieved and it is seated by the helical spring above. If the fulcrum E (Fig. 50) of the lever F were fixed the admission would be of an equal and fixed duration. But if the governor raises the fulcrum E, the pilot valve F (Fig. 51) will be lowered, changing the relations of the openings with the working edges of the ports. The seating of the main admission valve is cushioned by the dashpot, the piston of which is shown in section at G (Fig. 51). The valve may be opened by hand by means of the lever K, to see if it is perfectly free. The secondary valve is somewhat different in its action. Steam is admitted to both sides of its actuating piston through the needle valves M M, and the chamber from which this steam is taken is connected with the under side of the main admission valve, so that no steam can reach the actuating piston of the secondary valve until it has passed through the primary valve. When the pilot valve is closed, the pressures equalize above and below the piston N and the valve remains upon its seat. When the load upon the turbine exceeds its rated capacity, the pilot valve moves upward so as to connect the space above the piston with the exhaust L, relieving the pressure upon the upper side and allowing the greater pressure below to force the valve open, which admits steam to the secondary stage of the turbine. It would do no good to admit more steam to the first stage, for at the rated capacity that stage is taking all the steam for which the blade area will afford a passage. The port connecting the upper side of the piston N with the exhaust may be permanently closed by means of the hand valve Q, to be found on the side of the secondary pilot valve chest, thus cutting the secondary valve entirely out of action. No dashpot is necessary on this valve, the compression of the steam in the chamber W by the fall of the piston being sufficient to avoid shock. The timing of the secondary valve is adjusted by raising or lowering the pilot valve by means of the adjustment provided. It should open soon enough so that there will not be an appreciable drop in speed before the valve comes into play. The economy of the machine will be impaired if the valve is allowed to open too soon. Safety Stop Governor This device is mounted on the governor end of the turbine shaft, as shown in Figs. 52 and 53. When the speed reaches a predetermined limit, the plunger A, having its center of gravity slightly displaced from the center of rotation of the shaft, is thrown radially outward and strikes the lever B. It will easily be understood that when the plunger starts outward, the resistance of spring C is rapidly overcome, since the centrifugal force increases as the square of the radius, or in this case the eccentricity of the center of gravity relative to the center of rotation. Hence, the lever is struck a sharp blow. This releases the trip E on the outside of the governor casing, and so opens the steam valve F, which releases steam from beneath the actuating piston of a quick-closing throttle valve, located in the steam line. Thus, within a period of usually less than one second, the steam is entirely shut off from the turbine when the speed has exceeded 7 or 8 per cent of the normal. [Illustration: FIG. 52] [Illustration: FIG. 53] The Oiling System Mounted on the end of the bedplate is the oil pump, operated from the main shaft of the turbine as previously stated. This may be of the plunger type shown in Fig. 54, or upon the latest turbine, the rotary type shown in Fig. 55. Around the bedplate are located the oil-cooling coils, the oil strainer, the oil reservoir and the oil pipings to the bearing. [Illustration: FIG. 54] The oil reservoir, cooler, and piping are all outside the machine and easily accessible for cleaning. Usually a corrugated-steel floor plate covers all this apparatus, so that it will not be unsightly and accumulate dirt, particularly when the turbine is installed, so that all this apparatus is below the floor level; i.e., when the top of the bedplate comes flush with the floor line. In cases where the turbine is set higher, a casing is usually built around this material so that it can be easily removed, and forms a platform alongside the machine. [Illustration: FIG. 55] The oil cooler, shown in Fig. 56, is of the counter-current type, the water entering at A and leaving at B, oil entering at C (opening not shown) and leaving at D. The coils are of seamless drawn copper, and attached to the cover by coupling the nut. The water manifold F is divided into compartments by transverse ribs, each compartment connecting the inlet of each coil with the outlet of the preceding coil, thus placing all coils in series. These coils are removable in one piece with the coverplate without disturbing the rest of the oil piping. [Illustration: FIG. 56] Blading [Illustration: FIG. 57] The blades are drawn from a rod consisting of a steel core coated with copper so intimately connected with the other metal that when the bar is drawn to the section required for the blading, the exterior coating drawn with the rest of the bar forms a covering of uniform thickness as shown in Fig. 57. The bar after being drawn through the correct section is cut into suitable lengths punched as at A (Fig. 58), near the top of the blade, and has a groove shown at B (Fig. 59), near the root, stamped in its concave face, while the blade is being cut to length and punched. The blades are then set into grooves cut into the rotor drum or the concave surface of the casing, and spacing or packing pieces C (Fig. 59) placed between them. These spacing pieces are of soft iron and of the form which is desired that the passage between the blades shall take. The groove made upon the inner face of the blade is sufficiently near to the root to be covered by this spacing piece. When the groove has been filled the soft-iron pieces are calked or spread so as to hold the blades firmly in place. A wire of comma section, as shown at A (Fig. 59), is then strung through the punches near the outer ends of the blades and upset or turned over as shown at the right in Fig. 58. This upsetting is done by a tool which shears the tail of the comma at the proper width between the blades. The bent-down portion on either side of the blade holds it rigidly in position and the portion retained within the width of the blade would retain the blade in its radial position should it become loosened or broken off at the root. This comma lashing, as it is called, takes up a small proportion only of the blade length or projection and makes a job which is surprisingly stiff and rigid, and yet which yields in case of serious disturbance rather than to maintain a contact which would result in its own fusing or the destruction of some more important member. [Illustration: FIG. 58] [Illustration: FIG. 59] Starting Up the Turbine When starting up the turbine for the first time, or after any extended period of idleness, special care must be taken to see that everything is in good condition and that all parts of the machine are clean and free from injury. The oil piping should be thoroughly inspected and cleaned out if there is any accumulation of dirt. The oil reservoirs must be very carefully wiped out and minutely examined for the presence of any grit. (Avoid using cotton waste for this, as a considerable quantity of lint is almost sure to be left behind and this will clog up the oil passages in the bearings and strainer.) The pilot valves should be removed from the barrel and wiped off, and the barrels themselves cleaned out by pushing a soft cloth through them with a piece of wood. In no case should any metal be used. If the turbine has been in a place where there was dirt or where there has been much dust blowing around, the bearings should be removed from the spindle and taken apart and thoroughly cleaned. With care this can be done without removing the spindle from the cylinder, by taking off the bearing covers and very carefully lifting the weight of the spindle off the bearings, then sliding back the bearings. It is best to lift the spindle by means of jacks and a rope sling, as, if a crane is used, there is great danger of lifting the spindle too high and thereby straining it or injuring the blades. After all the parts have been carefully gone over and cleaned, the oil for the bearing lubrication should be put into the reservoirs by pouring it into the governor gear case G (Fig. 34). Enough oil should be put in so that when the governor, gear case, and all the bearing-supply pipes are full, the supply to the oil pump is well covered. Special care should be taken so that no grit gets into the oil when pouring it into the machine. Considerable trouble may be saved in this respect by pouring the oil through cloth. A very careful inspection of the steam piping is necessary before the turbine is run. If possible it should be blown out by steam from the boilers before it is finally connected to the turbine. Considerable annoyance may result by neglecting this precaution, from particles of scale, red lead, gasket, etc., out of the steam pipe, closing up the passages of the guide blades. When starting up, always begin to revolve the spindle without vacuum being on the turbine. After the spindle is turning slowly, bring the vacuum up. The reason for this is, that when the turbine is standing still, the glands do not pack and air in considerable quantity will rush through the glands and down through the exhaust pipe. This sometimes has the effect of unequal cooling. In case the turbine is used in conjunction with its own separate condenser, the circulating pump may be started up, then the turbine revolved, and afterward the air pump put in operation; then, last, put the turbine up to speed. In cases, however, where the turbine exhausts into the same condenser with other machinery and the condenser is therefore already in operation, the valve between the turbine and the condenser system should be kept closed until after the turbine is revolved, the turbine in the meantime exhausting through the relief valve to atmosphere. Care must always be taken to see that the turbine is properly warmed up before being caused to revolve, but in cases where high superheat is employed always revolve the turbine just as soon as it is moderately hot, and before it has time to become exposed to superheat. In the case of highly superheated steam, it is not undesirable to provide a connection in the steam line by means of which the turbine may be started up with saturated steam and the superheat gradually applied after the shaft has been permitted to revolve. For warming up, it is usual practice to set the governor on the trigger (see Fig. 50) and open the throttle valve to allow the entrance of a small amount of steam. It is always well to let the turbine operate at a reduced speed for a time, until there is assurance that the condenser and auxiliaries are in proper working order, that the oil pump is working properly, and that there is no sticking in the governor or the valve gear. After the turbine is up to speed and on the governor, it is well to count the speed by counting the strokes of the pump rod, as it is possible that the adjustment of the governor may have become changed while the machine has been idle. It is well at this time, while there is no load on the turbine, to be sure that the governor controls the machine with the throttle wide open. It might be that the main poppet valve has sustained some injury not evident on inspection, or was leaking badly. Should there be some such defect, steps should be taken to regrind the valve to its seat at the first opportunity. On the larger machines an auxiliary oil pump is always furnished. This should be used before starting up, so as to establish the oil circulation before the turbine is revolved. After the turbine has reached speed, and the main oil pump is found to be working properly, it should be possible to take this pump out of service, and start it again only when the turbine is about to be shut down. If possible, the load should be thrown on gradually to obviate a sudden, heavy demand upon the boiler, with its sometimes attendant priming and rush of water into the steam pipe, which is very apt to take place if the load is thrown on too suddenly. A slug of water will have the effect of slowing down the turbine to a considerable extent, causing some annoyance. There is not likely to be the danger of the damage that is almost sure to occur in the reciprocating engine, but at the same time it is well to avoid this as much as possible. A slug of water is obviously more dangerous when superheated steam is being employed, owing to the extreme temperature changes possible. Running While the turbine is running, it should have a certain amount of careful attention. This, of course, does not mean that the engineer must stand over it every minute of the day, but he must frequently inspect such parts as the lubricators, the oiling system, the water supply to the glands and the oil-cooling coil, the pilot valve, etc. He must see that the oil is up in the reservoir and showing in the gage glass provided for that purpose, and that the oil is flowing freely through the bearings, by opening the pet cocks in the top of the bearing covers. An ample supply of oil should always be in the machine to keep the suction in the tank covered. Care must be taken that the pump does not draw too much air. This can usually be discovered by the bubbling up of the air in the governor case, when more oil should be added. It is well to note from time to time the temperature of the bearings, but no alarm need be occasioned because they feel warm to the touch; in fact, a bearing is all right as long as the hand can be borne upon it even momentarily. The oil coming from the bearings should be preferably about 120 degrees Fahrenheit and never exceed 160 degrees. It should generally be seen that the oil-cooling coil is effective in keeping the oil cool. Sometimes the cooling water deposits mud on the cooling surface, as well as the oil depositing a vaseline-like substance, which interferes with the cooling effect. The bearing may become unduly heated because of this, when the coil should be taken out at the first opportunity and cleaned on the outside and blown out by steam on the inside, if this latter is possible. If this does not reduce the temperature, either the oil has been in use too long without being filtered, or the quality of the oil is not good. Should a bearing give trouble, the first symptom will be burning oil which will smoke and give off dense white fumes which can be very readily seen and smelled. However, trouble with the bearings is one of the most unlikely things to be encountered, and, if it occurs, it is due to some radical cause, such as the bearings being pinched by their caps, or grit and foreign matter being allowed to get into the oil. If a bearing gets hot, be assured that there is some very radical cause for it which should be immediately discovered and removed. Never, under any circumstances, imagine that you can nurse a bearing, that has heated, into good behavior. Turbine bearings are either all right or all wrong. There are no halfway measures. The oil strainer should also be occasionally taken apart and thoroughly cleaned, which operation may be performed, if necessary, while the turbine is in operation. The screens should be cleaned by being removed from their case and thoroughly blown out with steam. In the case of a new machine, this may have to be done every two or three hours. In course of time, this need only be repeated perhaps once a week. The amount of dirt found will be an indication of the frequency with which this cleaning is necessary. The proper water pressure, about five pounds per square inch, must be maintained at the glands. Any failure of this will mean that there is some big leak in the piping, or that the water is not flowing properly. The pilot valve must be working freely, causing but little kick on the governor, and should be lubricated from time to time with good oil. Should it become necessary, while operating, to shut down the condenser and change over to non-condensing operation, particular care should be observed that the change is not made too suddenly to non-condensing, as all the low-pressure sections of the turbine must be raised to a much higher temperature. While this may not cause an accident, it is well to avoid the stresses which necessarily result from the sudden change of temperature. The same reasons, of course, do not hold good in changing from non-condensing to condensing. Shutting Down When shutting down the turbine the load may be taken off before closing the throttle; or, as in the case of a generator operating on an independent load, the throttle may be closed first, allowing the load to act as a brake, bringing the turbine to rest quickly. In most cases, however, the former method will have to be used, as the turbine generally will have been operating in parallel with one or more other generators. When this is the case, partially close the throttle just before the load is to be thrown off, and if the turbine is to run without load for some time, shut off the steam almost entirely in order to prevent any chance of the turbine running away. There is no danger of this unless the main valve has been damaged by the water when wet steam has been used, or held open by some foreign substance, when, in either case, there may be sufficient leakage to run the turbine above speed, while running light. At the same time, danger is well guarded against by the automatic stop valve, but it is always well to avoid a possible danger. As soon as the throttle is shut, stop the condenser, or, in the case where one condenser is used for two or more turbines, close the valve between the turbine and the condenser. Also open the drains from the steam strainer, etc. This will considerably reduce the time the turbine requires to come to rest. Still more time may be saved by leaving the field current on the generator. Care should be taken, when the vacuum falls and the turbine slows down, to see that the water is shut off from the glands for fear it may leak out to such an extent as to let the water into the bearings and impair the lubricating qualities of the oil. Inspection At regular intervals thorough inspection should be made of all parts of the turbine. As often as it appears necessary from the temperature of the oil, depending on the quality of the oil and the use of the turbine, remove the oil-cooling coil and clean it both on the inside and outside as previously directed; also clean out the chamber in which it is kept. Put in a fresh supply of oil. This need not necessarily be new, but may be oil that has been in use before but has been filtered. We recommend that an oil filter be kept for this purpose. Entirely new oil need only be put into the turbine when the old oil shows marked deterioration. With a first-class oil this will probably be a very infrequent necessity, as some new oil has to be put in from time to time to make up the losses from leakage and waste. Clean out the oil strainer, blowing steam through the wire gauze to remove any accumulation of dirt. Every six months to a year take off the bearing covers, remove the bearings, and take them apart and clean out thoroughly. Even the best oil will deposit more or less solid matter upon hot surfaces in time, which will tend to prevent the free circulation of the oil through the bearings and effectively stop the cushioning effect on the bearings. Take apart the main and secondary valves and clean thoroughly, seeing that all parts are in good working order. Clean and inspect the governor and the valve-gear, wiping out any accumulation of oil and dirt that may appear. Be sure to clean out the drains from the glands so that any water that may pass out of them will run off freely and will not get into the bearings. At the end of the first three months, and after that about once a year, take off the cylinder cover and remove the spindle. When the turbine is first started up, there is very apt to be considerable foreign matter come over in the steam, such as balls of red lead or small pieces of gasket too small to be stopped by the strainer. These get into the guide blades in the cylinder and quite effectively stop them up. Therefore, the blades should be gone over very carefully, and any such additional accumulation removed. Examine the glands and equilibrium ports for any dirt or broken parts. Particularly examine the glands for any deposit of scale. All the scale should be chipped off the gland parts, as, besides preventing the glands from properly packing, this accumulation will cause mechanical contact and perhaps cause vibration of the machine due to lack of freedom of the parts. The amount of scale found after the first few inspections will be an indication of how frequently the cleaning should be done. As is discussed later, any water that is unsuitable for boiler feed should not be used in the glands. In reassembling the spindle and cover, very great care must be taken that no blades are damaged and that nothing gets into the blades. Nearly all the damage that has been done to blades has resulted from carelessness in this respect; in fact, it is impossible to be too careful. Particular care is also to be taken in assembling all the parts and in handling them, as slight injury may cause serious trouble. In no case should a damaged part be put back until the injury has been repaired. If for any reason damaged blades cannot be repaired at the time, they can be easily removed and the turbine run again without them until it is convenient to put in new ones; in fact, machines have been run at full load with only three-quarters of the total number of blades. In such an event remove the corresponding stationary blades as well as the moving blades, so as not to disturb the balance of the end thrust. Conditions Conducive to Successful Operation In the operation of the turbine and the conditions of the steam, both live and exhaust play a very important part. It has been found by expensive experimenting that moisture in the steam has a very decided effect on the economy of operation; or considerably more so than in the case of the reciprocating engine. In the latter engine, 2 per cent. of moisture will mean very close to 2 per cent. increase in the amount of water supplied to the engine for a given power. On the other hand, in the turbine 2 per cent. moisture will cause an addition of more nearly 4 per cent. It is therefore readily seen that the drier the entering steam, the better will be the appearance of the coal bill. By judicious use of first-class separators in connection with a suitable draining system, such as the Holly system which returns the moisture separated from the steam, back to the boilers, a high degree of quality may be obtained at the turbine with practically no extra expense during operation. Frequent attention should be given the separators and traps to insure their proper operation. The quality of the steam may be determined from time to time by the use of a throttling calorimeter. Dry steam, to a great extent, depends upon the good and judicious design of steam piping. Superheated steam is of great value where it can be produced economically, as even a slight degree insures the benefits to be derived from the use of dry steam. The higher superheats have been found to increase the economy to a considerable extent. When superheat of a high degree (100 degrees Fahrenheit or above) is used special care must be exercised to prevent a sudden rise of the superheat of any amount. The greatest source of trouble in this respect is when a sudden demand is made for a large increase in the amount of steam used by the engine, as when the turbine is started up and the superheater has been in operation for some time before, the full load is suddenly thrown on. It will be readily seen that with the turbine running light and the superheater operating, there is a very small amount of steam passing through; in fact, practically none, and this may become very highly heated in the superheater, but loses nearly all its superheat in passing slowly to the turbine; then, when a sudden demand is made, this very high temperature steam is drawn into the turbine. This may usually be guarded against where a separately fired superheater is used, by keeping the fire low until the load comes on, or, in the case where the superheater is part of the boiler, by either not starting up the superheater until after load comes on, or else keeping the superheat down by mixing saturated steam with that which has been superheated. After the plant has been started up there is little danger from this source, but such precautions should be taken as seem best in the particular cases. Taking up the exhaust end of the turbine, we have a much more striking departure from the conditions familiar in the reciprocating engine. Due to the limits imposed upon the volume of the cylinder of the engine, any increase in the vacuum over 23 or 24 inches, in the case, for instance, of a compound-condensing engine, has very little, if any, effect on the economy of the engine. With the turbine, on the other hand, any increase of vacuum, even up to the highest limits, increases the economy to a very considerable extent and, moreover, the higher the vacuum the greater will be the increase in the economy for a given addition to the vacuum. Thus, raising the vacuum from 27 to 28 inches has a greater effect than from 23 to 24 inches. For this reason the engineer will readily perceive the great desirability of maintaining the vacuum at the highest possible point consistent with the satisfactory and economical operation of the condenser. The exhaust pipe should always be carried downward to the condenser when possible, to keep the water from backing up from the condenser into the turbine. If the condenser must be located above the turbine, then the pipe should be carried first downward and then upward in the U form, in the manner of the familiar "entrainer," which will be found effectively to prevent water getting back when the turbine is operating. Condensers As has been previously pointed out, the successful and satisfactory operation of the turbine depends very largely on the condenser. With the reciprocating engine, if the condenser will give 25 inches vacuum, it is considered fairly good, and it is allowed to run along by itself until the vacuum drops to somewhere below 20 inches, when it is completely gone over, and in many cases practically rebuilt and the vacuum brought back to the original 25 inches. It has been seen that this sort of practice will never do in the case of the turbine condenser and, unless the vacuum can be regularly maintained at 27 or 28 inches, the condenser is not doing as well as it ought to do, or it is not of the proper type, unless perhaps the temperature and the quantity of cooling water available render a higher vacuum unattainable. On account of the great purity of the condensed steam from the turbine and its peculiar availability for boiler feed (there being no oil of any kind mixed with it to injure the boilers), the surface condenser is very desirable in connection with the turbine. It further recommends itself by reason of the high vacuum obtainable. Where a condenser system capable of the highest vacuum is installed, the need of utilizing it to its utmost capacity can hardly be emphasized too strongly. A high vacuum will, of course, mean special care and attention, and continual vigilance for air leaks in the exhaust piping, which will, however, be fully paid for by the great increase in economy. It must not be inferred that a high vacuum is essential to successful operation of this type of turbine, for excellent performance both in the matter of steam consumption and operation is obtained with inferior vacuum. The choice of a condenser, however, is a matter of special engineering, and is hardly within the province of this article. Oils There are several oils on the market that are suitable for the purpose of the turbine oiling system, but great care must be exercised in their selection. In the first place, the oil must be pure mineral, unadulterated with either animal or vegetable oils, and must have been washed free from acid. Certain brands of oil require the use of sulphuric acid in their manufacture and are very apt to contain varying degrees of free acid in the finished product. A sample from one lot may have almost no acid, while that from another lot may contain a dangerous amount. Mineral oils that have been adulterated, when heated up, will partially decompose, forming acid. These oils may be very good lubricants when first put into use, but after awhile they lose all their good qualities and become very harmful to the machine by eating the journals in which they are used. These oils must be very carefully avoided in the turbine, as the cheapness of their first cost will in no way pay for the damage they may do. A very good and simple way to test for such adulterations is to take up a quantity of the oil in a test tube with a solution of borax and water. If there is any animal or vegetable adulterant present it will appear as a white milk-like emulsion which will separate out when allowed to stand. The pure mineral oil will appear at the top as a clear liquid and the excess of the borax solution at the bottom, the emulsion being in between. A number of oils also contains a considerable amount of paraffin which is deposited in the oil-cooling coil, preventing the oil from being cooled properly, and in the pipes and bearings, choking the oil passages and preventing the proper circulation of the oil and cushioning effect in the bearing tubes. This is not entirely a prohibitive drawback, the chief objection being that it necessitates quite frequently cleaning the cooling coil, and the oil piping and bearings. Some high-class mineral oils of high viscosity are inclined to emulsify with water, which emulsion appears as a jelly-like substance. It might be added that high-grade oils having a high viscosity might not be the most suitable for turbine use. Since the consumption of oil in a turbine is so very small, being practically due only to leakage or spilling, the price paid for it should therefore be of secondary importance, the prime consideration being its suitability for the purpose. In some cases a central gravity system will be employed, instead of the oil system furnished with the turbine, which, of course, will be a special consideration. For large installations a central gravity oiling system has much to recommend it, but as it performs such an important function in the power plant, and its failure would be the cause of so much damage, every detail in connection with it should be most carefully thought out, and designed with a view that under no combination of circumstances would it be possible for the system to become inoperative. One of the great advantages of such a system is that it can be designed to contain very large quantities of oil in the settling tanks; thus the oil will have quite a long rest between the times of its being used in the turbine, which seems to be very helpful in extending the life of the oil. Where the oil can have a long rest for settling, an inferior grade of oil may be used, providing, however, that it is absolutely free of acid. V. PROPER METHOD OF TESTING A STEAM TURBINE[3] [3] Contributed to _Power_ by Thomas Franklin. The condensing arrangements of a turbine are perhaps mainly instrumental in determining the method of test. The condensed steam alone, issuing from a turbine having, for example, a barometric or jet condenser, cannot be directly measured or weighed, unless by meter, and these at present are not sufficiently accurate to warrant their use for test purposes, if anything more than approximate results are desired. The steam consumed can, in such a case, only be arrived at by measuring the amount of condensing water (which ultimately mingles with the condensed steam), and subtracting this quantity from the condenser's total outflow. Consequently, in the case of turbines equipped with barometric or jet condensers, it is often thought sufficient to rely upon the measurement taken of the boiler feed, and the boiler's initial and final contents. Turbines equipped with surface-condensing plants offer better facilities for accurate steam-consumption calculations than those plants in which the condensed exhaust steam and the circulating water come into actual contact, it being necessary with this type simply to pump the condensed steam into a weighing or measuring tank. In the case of a single-flow turbine of the Parsons type, the covers should be taken off and every row of blades carefully examined for deposits, mechanical irregularities, deflection from the true radial and vertical positions, etc. The blade clearances also should be gaged all around the circumference, to insure this clearance being an average working minimum. On no account should a test be proceeded with when any doubt exists as to the clearance dimensions. [Illustration: FIG. 60] The dummy rings of a turbine, namely, those rings which prevent excessive leakage past the balancing pistons at the high-pressure end, should have especial attention before a test. A diagrammatic sketch of a turbine cylinder and spindle is shown in Fig. 60, for the benefit of those unfamiliar with the subject. In this A is the cylinder or casing, B the spindle or rotor, and C the blades. The balancing pistons, D, E, and F, the pressure upon which counterbalances the axial thrust upon the three-bladed stages, are grooved, the brass dummy rings G G in the cylinder being alined within a few thousandths of an inch of the grooved walls, as indicated. After these rings have been turned (the turning being done after the rings have been calked in the cylinder), it is necessary to insure that each ring is perfectly bedded to its respective grooved wall so that when running the several small clearances between the groove walls and rings are equal. A capital method of thus bedding the dummy rings is to grind them down with a flour of emery or carborundum, while the turbine spindle is slowly revolving under steam. Under these conditions the operation is performed under a high temperature, and any slight permanent warp the rings may take is thus accounted for. The turbine thrust-block, which maintains the spindle in correct position relatively to the spindle, may also be ground with advantage in a similar manner. The dummy rings are shown on a large scale in Fig. 61, and their preliminary inspection may be made in the following manner: The spindle has been set and the dummy rings C are consequently within a few thousandths of an inch of the walls _d_ of the spindle dummy grooves D. The clearances allowed can be gaged by a feeler placed between a ring and the groove wall. Before a test the spindle should be turned slowly around, the feelers being kept in position. By this means any mechanical flaws or irregularities in the groove walls may be detected. [Illustration: FIG. 61] It has sometimes been found that the groove walls, under the combined action of superheated steam and friction, in cases where actual running contact has occurred, have worn very considerably, the wear taking the form of a rapid crumbling away. It is possible, however, that such deterioration may be due solely to the quality of the steel from which the spindle is forged. Good low-percentage carbon-annealed steel ought to withstand considerable friction; at all events the wear under any conditions should be uniform. If the surfaces of both rings and grooves be found in bad condition, they should be re-ground, if not sufficiently worn to warrant skimming up with a tool. As the question of dummy leakage is of very considerable importance during a test, it may not be inadvisable to describe the manner of setting the spindle and cylinder relatively to one another to insure minimum leakage, and the methods of noting their conduct during a prolonged run. In Fig. 62, showing the spindle, B is the thrust (made in halves), the rings O of which fit into the grooved thrust-rings C in the spindle. Two lugs D are cast on each half of the thrust-block. The inside faces of these lugs are machined, and in them fit the ball ends of the levers E, the latter being fulcrumed at F in the thrust-bearing cover. The screws G, working in bushes, also fit into the thrust-bearing cover, and are capable of pushing against the ends of the levers E and thus adjusting the separate halves of the block in opposite directions. [Illustration: FIG. 62] The top half of the turbine cylinder having been lifted off, the spindle is set relatively to the bottom half by means of the lower thrust-block screw G. This screw is then locked in position and the top half of the cover then lowered into place. With this method great care must necessarily be exercised when lowering the top cover; otherwise the brass dummy rings may be damaged. A safer method is to set the dummy rings in the center of the grooves of the spindle, and then to lower the cover, with less possibility of contact. There being usually plenty of side clearance between the blades of a turbine, it may be deemed quite safe to lock the thrust-block in its position, by screwing the screws G up lightly, and then to turn on steam and begin running slowly. Next, the spindle may be very carefully and gradually worked in the required direction, namely, in that direction which will tend to bring the dummy rings and groove walls into contact, until actual but very light contact takes place. The slightest noise made by the rubbing parts inside the turbine can be detected by placing one end of a metal rod onto the casing in vicinity of the dummy pistons, and letting the other end press hard against the ear. Contact between the dummy rings and spindle being thus demonstrated, the spindle must be moved back by the screws, but only by the slightest amount possible. The merest fraction of a turn is enough to break the contact, which is all that is required. In performing this operation it is important, during the axial movements of the spindle, to adjust the halves of the thrust-block so that there can exist no possible play which would leave the spindle free to move axially and probably vibrate badly. After ascertaining the condition of the dummy rings, attention might next be turned to the thrust-block, which must not on any account be tightened up too much. It is sufficient to say that the actual requirements are such as will enable a very thin film of oil to circulate between each wall of the spindle thrust-grooves and the brass thrust-blocks ring. In other words, there should be no actual pressure, irrespective of that exerted by the spindle when running, upon the thrust-block rings, due to the separate halves having been nipped too tightly. The results upon a test of considerable friction between the spindle and thrust-rings are obvious. The considerations outlined regarding balancing pistons and dummy rings can be dispensed with in connection with impulse turbines of the De Laval and Rateau types, and also with double-flow turbines of a type which does not possess any dummies. The same general considerations respecting blade conditions and thrust-blocks are applicable, especially to the latter type. With pure so-called impulse turbines, where the blade clearances are comparatively large, the preliminary blade inspection should be devoted to the mechanical condition of the blade edges and passages. As the steam velocities of these types are usually higher, the importance of minimizing the skin friction and eliminating the possibility of eddies is great. Although steam leakage through the valves of a turbine may not materially affect its steam consumption, unless it be the leakage through the overload valve during a run on normal full load, a thorough examination of all valves is advocated for many reasons. In a turbine the main steam-inlet valve is usually operated automatically from the governor; and whether it be of the pulsating type, admitting the steam in blasts, or of the non-pulsating throttling type, it is equally essential to obtain the least possible friction between all moving and stationary parts. Similar remarks apply to the main governor, and any sensitive transmitting mechanism connecting it with any of the turbine valves. If a safety or "runaway" governor is possessed by the machine to be tested, this should invariably be tried under the requisite conditions before proceeding farther. The object of this governor being automatically to shut off all steam from the turbine, should the latter through any cause rise above the normal speed, it is often set to operate at about 12 to 15 per cent. above the normal. Thus, a turbine revolving at about 3000 revolutions per minute would be closed down at, say, 3500, which would be within the limit of "safe" speed. Importance of Oiling System and Water Service The oil question, being important, should be solved in the early stages previously, if possible, to any official or unofficial consumption tests. Whether the oil be supplied to the turbine bearings by a self-contained system having the oil stored in the turbine bedplate or by gravity from a separate oil source, does not affect the question in its present aspect. The necessary points to investigate are four in number, and may be headed as follows: (a) Examination of pipes and partitions for oil leakage. (b) Determination of volume of oil flowing through each bearing per unit of time. (c) Examination for signs of water in oil. (d) Determination of temperature rise between inlet and outlet of oil bearings. The turbine supplied with oil by the gravity or any other separate system holds an advantage over the ordinary self-contained machine, inasmuch as the oil pipes conveying oil into and from the bearings can be easily approached and, if necessary, repaired. On the other hand, the machine possessing its own oil tank, cooling chamber and pump is somewhat at a disadvantage in this respect, as a part of the system is necessarily hidden from view, and, further, it is not easily accessible. The leakage taking place in any system, if there be any, must, however, be detected and stopped. Fig. 63 is given to illustrate a danger peculiar to the self-contained oil system, in which the oil and oil-cooling chambers are situated adjacently in the turbine bedplate. One end of the bedplate only is shown; B is a cast-iron partition dividing the oil chamber C from the oil-cooling chamber D. Castings of this kind have sometimes a tendency to sponginess and the trouble consequent upon this weakness would take the form of leakage between the two chambers. Of course this is only a special case, and the conditions named are hardly likely to exist in every similarly designed plant. The capacity of oil, and especially of hot oil, to percolate through the most minute pores is well known. Consequently, in advocating extreme caution when dealing with oil leakage, no apology is needed. [Illustration: FIG. 63] It may be stated without fear of contradiction that the oil in a self-contained system, namely, a system in which the oil, stored in a reservoir near or underneath the turbine, passes only through that one turbine's bearings, and immediately back to the storage compartment, deteriorates more rapidly than when circulating around an "entire" system, such as the gravity or other analogous system. In the latter, the oil tanks are usually placed a considerable distance from the turbine or turbines, with the oil-cooling arrangements in fairly close proximity. The total length of the oil circuit is thus considerably increased, incidentally increasing the relative cooling capacity of the whole plant, and thereby reducing the loss of oil by vaporization. The amount of oil passing through the bearings can be ascertained accurately by measurement. With a system such as the gravity it is only necessary to run the turbine up to speed, turn on the oil, and then, over a period, calculate the volume of oil used by measuring the fall of level in the storage tank and multiplying by its known cross-sectional area. In those cases where the return oil, after passing through the bearings, is delivered back into the same tank from which it is extracted, it is of course necessary, during the period of test, to divert this return into a separate temporary receptacle. Where the system possesses two tanks, one delivery and one return (a superior arrangement), this additional work is unnecessary. The same method can be applied to individual turbines pumping their own oil from a tank in the bedplate; the return oil, as previously described, being temporarily prevented from running back to the supply. The causes of excessive oil consumption by bearings are many. There is an economical mean velocity at which the oil must flow along the revolving spindle; also an economical mean pressure, the latter diminishing from the center of the bearing toward the ends. The aim of the economist must therefore be in the direction of adjusting these quantities correctly in relation to a minimum supply of oil per bearing; and the principal factors capable of variation to attain certain requirements are the several bearing clearances measured as annular orifices, and the bearing diameters. It is not always an easy matter to detect the presence of water in an oil system, and this difficulty is increased in large circuits, as the water, when the oil is not flowing, generally filters to the lowest members and pipes of the system, where it cannot usually be seen. A considerable quantity of water in any system, however, indicates its presence by small globular deposits on bearings and spindles, and in the worst cases the water can clearly be seen in a small sample tapped from the oil mains. There is only one effective method of ridding the oil of this water, and this is by allowing the whole mass of oil in the system to remain quiescent for a few days, after which the water, which falls to the lowest parts, can be drained off. A simple method of clearing out the system is to pump all the oil the whole circuit contains through the filters, and thence to a tank from which all water can be taken off. One of the ordinary supply tanks used in the gravity system will serve this purpose, should a temporary tank not be at hand. If necessary, the headers and auxiliary pipes of the system can be cleaned out before circulating the oil again, but as this is rather a large undertaking, it need only be resorted to in serious cases. [Illustration: FIG. 64] It is seldom possible to discover the correct and permanent temperature rise of the circulating oil in a turbine within the limited time usually alloted for a test. After a continuous run of one hundred hours it is possible that the temperature at the bearing outlets may be lower than it was after the machine had run for, say, only twenty hours. As a matter of fact an oil-temperature curve plotted from periodical readings taken over a continuous run of considerable length usually reaches a maximum early, afterward falling to a temperature about which the fluctuations are only slight during the remainder of the run. Fig. 64 illustrates an oil-temperature curve plotted from readings taken over a period of twenty-four hours. In this case the oil system was of the gravity description, the capacity of the turbine being about 6000 kilowatts. The bearings were of the ordinary white-metal spherical type. Over extended runs of hundreds and even thousands of hours, the above deductions may be scarcely applicable. Running without break for so long, a small turbine circulating its own lubricant would possibly require a renewal of the oil before the run was completed, in the main owing to excessive temperature rise and consequent deterioration of the quality of the oil. Under these conditions the probabilities are that several temperature fluctuations might occur before the final maximum, and more or less constant, temperature was reached. In this connection, however, the results obtained are to a very large extent determined by the general mechanical design and construction of the oiling system and turbine. A reference to Fig. 63 again reveals at once a weakness in that design, namely, the unnecessarily close proximity in which the oil and water tanks are placed. [Illustration: FIG. 65] A design of thermometer cup suitable for oil thermometers is given in Fig. 65 in which A is an end view of the turbine bedplate, B is a turbine bearing and C and D are the inlet and outlet pipes, respectively. The thermometer fittings, which are placed as near the bearing as is practicable, are made in the form of an angular tee fitting, the oil pipes being screwed into its ends. The construction of the oil cup and tee piece is shown in the detail at the left where A is the steel tee piece, into which is screwed the brass thermometer cup B. The hollow bottom portion of this cup is less than 1/16 of an inch in thickness. The top portion of the bored hole is enlarged as shown, and into this, around the thermometer, is placed a non-conducting material. The cup itself is generally filled with a thin oil of good conductance. Allied to the oil system of a turbine plant is the water service, of comparatively little importance in connection with single self-contained units of small capacity, where the entire service simply consists of a few coils and pipes, but of the first consideration in large installations having numerous separate units supplied by oil and water from an exterior source. The largest turbine units are often supplied with water for cooling the bearings and other parts liable to attain high temperature. Although the water used for cooling the bearings indirectly supplements the action taking place in the separate oil coolers, it is of necessity a separate auxiliary service in itself, and the complexity of the system is thus added to. A carefully constructed water service, however, is hardly likely to give trouble of a mechanical nature. The more serious deficiencies usually arise from conditions inherent to the design, and as such must be approached. Special Turbine Features to be Inquired into Before leaving the prime mover itself, and proceeding to the auxiliary plant inspection, it may be well to instance a few special features relating to the general conduct of a turbine, which it is the duty of a tester to inquire into. There are certain specified qualifications which a machine must hold when running under its commercial conditions, among these being lack of vibration of both turbine and machinery driven, be it generator or fan, the satisfactory running of auxiliary turbine parts directly driven from the turbine spindle, minimum friction between the driving mediums, such as worm-wheels, pumps, fans, etc., slight irregularities of construction, often resulting in heated parts and excessive friction and wear, and must therefore be detected and righted before the final test. Furthermore, those features of design--and they are not infrequent in many machines of recent development--which, in practice, do not fulfil theoretical expectations, must be re-designed upon lines of practical consistency. The experienced tester's opinion is often at this point invaluable. To illustrate the foregoing, Figs. 66, 67, and 68 are given, representing, respectively, three distinct phases in the evolution of a turbine part, namely, the coupling. Briefly, an ordinary coupling connecting a driving and a driven shaft becomes obstinate when the two separate spindles which it connects are not truly alined. The desire of turbine manufacturers has consequently been to design a flexible coupling, capable of accommodating a certain want of alinement between the two spindles without in any way affecting the smooth running of the whole unit. [Illustration: FIG. 66] [Illustration: FIG. 67] In Fig. 66 A is the turbine spindle end and B the generator spindle end, which it is required to drive. It will be seen from the cross-sectional end view that both spindle ends are squared, the coupling C, with a square hole running through it, fitting accurately over both spindle ends as shown. Obviously the fit between the coupling and spindle in this case must be close, otherwise considerable wear would take place; and equally obvious is the fact than any want of alinement between the two spindles A and B will be accompanied by a severe strain upon the coupling, and incidentally by many other troubles of operation of which this inability of the coupling to accommodate itself to a little want of alinement is the inherent cause. Looking at the coupling illustrated in Fig. 67, it will be seen that something here is much better adapted to dealing with troubles of alinement. The turbine and generator spindles A and B, respectively, are coned at the ends, and upon these tapered portions are shrunk circular heads C and D having teeth upon their outer circumferences. Made in halves, and fitting over the heads, is a sleeve-piece, with teeth cut into its inner bored face. The teeth of the heads and sleeve are proportioned correctly to withstand, without strain, the greatest pressure liable to be thrown upon them. There is practically no play between the teeth, but there exists a small annular clearance between the periphery of the heads and the inside bore of the sleeve, which allows a slight lack of alinement to exist between the two spindles, without any strain whatever being felt by the coupling sleeve E. The nuts F and G prevent any lateral movement of the coupling heads C and D. For all practical requirements this type of coupling is satisfactory, as the clearances allowed between sliding sleeve and coupling heads can always be made sufficient to accommodate a considerable want of alinement, far beyond anything which is likely to occur in actual practice. Perhaps the only feature against it is its lack of simplicity of construction and corresponding costliness. [Illustration: FIG. 68] The type illustrated in Fig. 68 is a distinct advance upon either of the two previous examples, because, theoretically at least, it is capable of successfully accommodating almost any amount of spindle movement. The turbine and generator spindle ends, A and B, have toothed heads C and D shrunk upon them, the heads being secured by the nuts E and F. The teeth in this case are cut in the enlarged ends as shown. A sleeve G, made in halves, fits over the heads, and the teeth cut in each half engage with those of their respective heads. All the teeth and teeth faces are cut radially, and a little side play is allowed. The Condenser To some extent, as previously remarked, the condenser and condensing arrangements are instrumental in determining the lines upon which a test ought to be carried out. In general, the local features of a plant restrict the tester more or less in the application of his general methods. A thorough inspection, including some preliminary tests if necessary, is as essential to the good conduct of the condensing plant as to the turbine above it. It may be interesting to outline the usual course this inspection takes, and to draw attention to a few of the special features of different plants. For this purpose a type of vertical condenser is depicted in Fig. 69. Its general principle will be gathered from the following description: Exhaust steam from the turbine flows down the pipe T and enters the condenser at the top as shown, where it at once comes into contact with the water tubes in W. These tubes fill an annular area, the central un-tubed portion below the baffle cap B forming the vapor chamber. The condensed steam falls upon the bottom tube-plate P and is carried away by the pipe S leading to the water pump H. The Y pipe E terminating above the level of the water in the condenser enters the dry-air pump section pipe A. Cold circulating water enters the condenser at the bottom, through the pipe I, and entering the water chamber X proceeds upward through the tubes into the top-water chamber Y, and from there out of the condenser through the exit pipe. It will be observed that the vapor extracted through the plate P passes on its journey out of the condenser through the cooling chamber D surrounded by the cold circulating water. This, of course, is a very advantageous feature. At R is the condenser relief, at U the relief valve for the water chambers. [Illustration: FIG. 69] A new condenser, especially if it embody new and untried features, generally requires a little time and patience ere the best results can be obtained from it. Perhaps the quickest and most satisfactory method of getting at the weak points of this portion of a plant is to test the various elements individually before applying a strict load test. Thus, in dealing with a condenser similar to that illustrated in Fig. 69, the careful tester would probably make, in addition to a thorough mechanical examination, three or four individual vacuum and water tests. A brief description of these will be given. The water test, the purpose of which is to discover any leakage from the tubes, tube-plates, water pipes, etc., into portions of the steam or air chambers, should be made first. Water Tests of Condenser The condenser is first thoroughly dried out, particular care being given to the outside of the tubes and the bottom tube-plate P. Water is then circulated through the tubes and chambers for an hour or two, after which the pumps are stopped, all water is allowed to drain out and a careful examination is made inside. Any water leaking from the tubes above the bottom baffle-plate will ultimately be deposited upon that plate. It is essential to stop this leakage if there be any, otherwise the condensed steam measured during the consumption test will be increased to the extent of the leakage. A slight leakage in a large condenser will obviously not affect the results to any serious extent. The safest course to adopt when a leak is discovered and it is found inopportune to effect immediate repair is to measure the actual volume of leakage over a specified period, and the quantity then being known it can be subtracted from the volume of the condensed steam at the end of the consumption test. It is equally essential that no leakage shall occur between the bottom tube-plate P and the tube ends. The soundness of the tube joints, and the joint at the periphery of the tube-plate can be tested by well covering the plate with water, the water chamber W and cooling chamber having been previously emptied, and observing the under side of the plate. It must be admitted that the practice of measuring the extent of a water leak over a period, and afterward with this knowledge adjusting the obtained quantities, is not always satisfactory. On no account should any test be made with considerable water leakage inside the condenser. The above method, however, is perhaps the most reliable to be followed, if during its conduct the conditions of temperature in the condenser are made as near to the normal test temperature as possible. There are many condensers using salt water in their tubes, and in these cases it would seem natural to turn to some analytical method of detecting the amount of saline and foreign matter leaking into the condensed steam. Unless, however, only approximate results are required, such methods are not advocated. There are many reasons why they cannot be relied upon for accurate results, among these being the variation in the percentage of saline matter in the sea-water, the varying temperature of the condenser tubes through which the water flows, and the uncertainty of such analysis, especially where the percentage leakage of pure saline matter is comparatively small. The Vacuum Test Having convinced himself of the satisfactory conduct of the condenser under the foregoing simple preparatory water tests, the tester may safely pass to considerations of vacuum. There exists a good old-fashioned method of discovering the points of leakage in a vacuum chamber, namely, that of applying the flame of a candle to all seams and other vulnerable spots, which in the location of big leaks is extremely valuable. Assuming that the turbine joints and glands have been found capable of preventing any inleak of air, with only a small absolute pressure of steam or air inside it, and, further, an extremely important condition, with the turbine casing at high and low temperatures, separately, a vacuum test can be conducted on the condenser alone. This test consists of three operations. In the first place a high vacuum is obtained by means of the air pump, upon the attainment of which communication with everything else is closed, and results noted. The second operation consists in repeating the above with the water circulating through the condenser tubes, the results in this case also being carefully tabulated. Before conducting the third test, the condensers must be thoroughly warmed throughout, by running the turbine for a short time if necessary, and after closing communication with everything, allowing the vacuum to slowly fall. A careful consideration and comparison of the foregoing tests will reveal the capabilities of the condenser in the aspect in which it is being considered, and will suggest where necessary the desirable steps to be taken. VI. TESTING A STEAM TURBINE[4] [4] Contributed to _Power_ by Thomas Franklin. Special Auxiliary Plant for Consumption Test There are one or two points of importance in the conduct of a test on a turbine and these will be briefly touched upon. Fig. 70 illustrates the general arrangement of the special auxiliary plant necessary for carrying through a consumption test, when the turbine exhaust passes through a surface condenser. The condensed steam, after leaving the condenser, passes along the pipe A to the pump, and is then forced along the pipe B (leading under ordinary circumstances to the hot-well), through the main water valve C directly to the measuring tanks. To enter these the water has to pass through the valves D and E, while the valves F and G are for quickly emptying the tanks when necessary, being of a larger bore than the inlet valves. The inlet pipes H I are placed directly above the outlet valves, and thus, when required, before any measurements are taken, the water can flow directly through the outlet valves, the pipes terminating only a short distance above them, away to an auxiliary tank or directly to the hot-well. Levers K and L fulcrumed at J and J are connected to the valve spindles by auxiliary levers. The valve arrangement is such that by pulling down the lever K the inlet valve D is opened and the inlet valve E is closed. Again, by pulling down the lever L the outlet valve F is closed, while the outlet valve G is also simultaneously closed. [Illustration: FIG. 70] During a consumption test the valves are operated in the following manner: The lever K is pulled down, which opens the inlet valve to the first tank and closes that to the second. The bottom lever L, however, is lifted, which for the time being opens the outlet valve F, and incidentally opens the valve G; the latter valve can; however, for the moment be neglected. When the turbine is started, and the condensed steam begins to accumulate in the condenser, the water is pumped along the pipes and, both the inlet and outlet valves on the first tank being open, passes through, without any being deposited in the tank, to the drain. This may be continued until all conditions are right for a consumption test and, the time being carefully noted, lever L is quickly pulled down and the valves F and G closed. The first tank now gradually fills, and after a definite period, say fifteen minutes, the lever K is pushed up, thus diverting the flow into the second tank. While the latter is filling, the water in the first tank is measured, and the tank emptied by a large sluice valve, not shown. The operation of alternately filling, measuring, and emptying the two measuring tanks is thus carried on until the predetermined time of duration of test has expired, when the total water as measured in the tanks, and representing the amount of steam condensed during that time, is easily found by adding together the quantities given at each individual measurement. All that are necessary to insure successful results from a plant similar to this are care and accuracy in its operation and construction. Undoubtedly in most cases it is preferable to weigh the condensed steam instead of measuring the volume passed, and from that to calculate the weight. If dependence is being placed upon the volumetric method, it is advisable to lengthen the duration of the test considerably, and if possible to measure the feed-water evaporated at the same time. Such a course, however, would necessitate little change, and none of a radical nature, from the arrangement described. Where, however, the measuring method is adopted, the all-important feature, requiring on the tester's part careful personal investigation, is the graduation of the tanks. It facilitates this operation very considerably when the receptacles are graduated upon a weight scale. That is to say, whether or not a vertical scale showing the actual hight of water be placed inside the tank, it is advisable to have a separate scale indicating at once to the attendant the actual contents, by weight, of the tank at any time. It is the tester's duty to himself to check the graduation of this latter scale by weighing the water with which he performs the operation of checking. Apart from the foregoing, there is little to be said about the measuring apparatus. As has been stated, accuracy of result depends in this connection, as in all others, upon careful supervision and sound and accurate construction, and this the tester can only positively insure by exhaustive inspection in the one case and careful deliberation in the conduct of the other. It will be readily understood that the procedure--and this implies some limitations--of a test is to an extent controlled by the conditions, or particular environment of the moment. This is strictly true, and as a consequence it is often impossible, in a maker's works, for example, to obtain every condition, coinciding with those specified, which are to be had on the site of final operation only. For this reason it would appear best to reserve the final and crucial test of a machine, which test usually in the operating sense restricts a prime mover in certain directions with regard to its auxiliary plant, etc., until the machine has been finally erected on its site. Obviously, unless a machine had become more or less standardized, a preliminary consumption test would be necessary, but once this primary qualification respecting consumption had been satisfactorily settled, there appears to be no reason why exhaustive tests in other directions should not all be carried out upon the site, where the conditions for them are so much more favorable. When the steam consumption of a steam turbine is so much higher than the guaranteed quantity, it usually takes little less than a reconstruction to put things right. The minor qualifications of a machine, however, which can be examined into and tested with greater ease, and usually at considerably less expense, upon the site, and consequently under specified conditions, may be advantageously left over until that site is reached, where it is obvious that any shortcomings and general deficiency in performance will be more quickly detected and diagnosed. Test Loads from the Tester's View-point Before proceeding to describe the points of actual interest in the consumption test, a few considerations respecting test loads will be dealt with from the tester's point of view. Here again we often find ourselves restricted, to an extent, by the surrounding conditions. The very first considerations, when undertaking to carry out a consumption test, should be devoted to obtaining the steadiest possible lead [Transcriber: load?]. It may be, and is in many cases, that circumstances are such as to allow a steady electrical load to be obtained at almost any time. On the other hand an electrical load of any description is sometimes not procurable at all, without the installation of a special plant for the purpose. In such cases a mechanical friction load, as, for example, that obtained by the water brake, is sometimes available, or can easily be procured. Whereas, however, this type of load may be satisfactory for small machines, it is usually quite impossible for use with large units, of, say, 5000 kilowatts and upward. It is seldom, however, that turbines are made in large sizes for directly driving anything but electrical plants, although there is every possibility of direct mechanical driving between large steam turbines and plants of various descriptions, shortly coming into vogue, so that usually there exist some facilities for obtaining an electrical load at both the maker's works and upon the site of operation. One consideration of importance is worth inquiring into, and this has relation to the largest turbo-generators supplied for power-station and like purposes. Obviously, the testing of, say, a 7000-kilowatt alternator by any standard electrical-testing method must entail considerable expense, if such a test is to be carried out in the maker's works. Nor would this expense be materially decreased by transferring the operations to the power-station, and there erecting the necessary electrical plant for obtaining a water load, or any other installation of sufficient capacity to carry the required load according to the rated full capacity of the machine. Assuming, then, that there exist no permanent facilities at either end, namely the maker's works and the power station, for adequately procuring a steady electrical-testing load of sufficient capacity, there still remains, in this instance, an alternative source of power which is usually sufficiently elastic to serve all purposes, and this is of course the total variable load procurable from the station bus-bars. It is conceivable that one out of a number of machines running in parallel might carry a perfectly steady load, the latter being a fraction of a total varying quantity, leaving the remaining machines to receive and deal with all fluctuations which might occur. Even in the event of there being only two machines, it is possible to maintain the load on one of them comparatively steady, though the percentage variation in load on either side of the normal would in the latter case be greater than in the previous one. This is accomplished by governor regulation after the machines have been paralleled. For example, assuming three turbo-alternators of similar make and capacity to be running in parallel, each machine carrying exactly one-third of the total distributed load, it is fair to regard the governor condition, allowing for slight mechanical disparities of construction, of all three machines as being similar; and even in the case of three machines of different capacity and construction, the governor conditions when the machines are paralleled are more or less relatively and permanently fixed in relation to one another. In other words, while the variation in load on each machine is the same, the relative variation in the governor condition must be constant. By a previously mentioned system of governor regulation, however, it is possible, considering again for a moment the case of three machines in parallel, by decreasing the sensitiveness of one governor only, to accommodate nearly all the total variation in load by means of the two remaining machines, the unresponsiveness of the one governor to change in speed maintaining the load on that machine fairly constant. By this method, at any rate, the variation in load on any one machine can be minimized down to, say, 3 per cent, either side of the normal full load. There is another and more positive method by which a perfectly steady load can be maintained upon one machine of several running in parallel. This may be carried out as follows: Suppose, in a station having a total capacity of 20,000 kilowatts, there are three machines, two of 6000 kilowatts each, and one of 8000 kilowatts, and it is desired to carry out a steady full-load test upon one of the 6000 kilowatts units. Assuming that the test is to be of six hours' duration, and that the conditions of load fluctuations upon the station are well known, the first step to take is to select a period for the test during which the total load upon all machines is not likely to fall below, say, 8000 kilowatts. The tension upon the governor spring of the turbine to be tested must then be adjusted so that the machine on each peak load is taxed to its utmost normal capacity; and even when the station load falls to its minimum, the load from the particular machine shall not be released sufficiently to allow it to fall below 6000 kilowatts. Under these conditions, then, it may be assumed that although the load on the test machine will vary, it cannot fall below 6000 kilowatts. Therefore, all that remains to be done to insure a perfectly steady load equal to the normal full load of the machine, or 6000 kilowatts, is to fix the main throttle or governing valve in such a position that the steam passing through at constant pressure is just capable of sustaining full speed under the load required. When this method is adopted, it is desirable to fix a simple hight-adjusting and locking mechanism to the governing-valve spindle. The load as read on the indicating wattmeter can then be very accurately varied until correct, and farther varied, if necessary, should any change occur in the general conditions which might either directly or indirectly bring about a change of load. Preparing the Turbine for Testing All preliminary labors connected with a test being satisfactorily disposed of, it only remains to place the turbines under the required conditions, and to then proceed with the test. For the benefit of those inexperienced in the operation of large turbines, we will assume that such a machine is about to be started for the purpose outlined. It is always advisable to make a strict practice of getting all the auxiliary plant under way before starting up the turbine. In handling a turbine plant the several operations might be carried through in the following order: (1) Circulating oil through all bearings and oil chambers.[5] (2) Starting of condenser circulating-water pumps, and continuous circulation of circulating water through the tubes of condenser. (3) Starting of pump delivering condensed steam from the condenser hot-well to weighing tanks. (4) Starting of air pump, vacuum being raised as high as possible within condenser. (5) Sealing of turbine glands, whether of liquid or steam type, no adjustment of the quantity of sealing fluid being necessary, however, at this point. (6) Adjustment of valves on and leading to the water-weighing tanks. (7) Opening of main exhaust valve or valves between turbine and condenser. (8) Starting up of turbine and slowly running to speed. (9) Application of load, and adjustment of gland-sealing steam. [5] In a self-contained system, where the oil pump is usually driven from the turbine spindle, this would of course be impossible. In the gravity and allied systems, however, it should always be the first operation performed. The tests for oil consumption, described previously, having been carried out, it is assumed that suitable means have been adopted to restrict the total oil flow through the bearings to a minimum quantity. The running to speed of large turbo-alternators requires considerable care, and should always be done slowly; that is to say the rate of acceleration should be slow. It is well known that the vibration of a heavy unit is accompanied by a synchronous or non-synchronous vibration of the foundation upon which it rests. The nearest approach to perfect synchronism between unit and foundation is obtained by a gradual rise in speed. A machine run up to speed too quickly might, after passing the critical speed, settle down with little visible vibration, but at a later time, even hours after, suddenly begin vibrating violently from no apparent cause. The chances of this occurring are minimized by slow and careful running to speed. Whether the machine being tested is one of a number running in parallel, or a single unit running on a steady water load, the latter should in all cases be thrown on gradually until full load is reached. A preliminary run of two or three hours--whenever possible--should then be made, during which ample opportunity is afforded for regulating the conditions in accordance with test requirements. The tester will do well during the last hour of this trial run to station his recorders at their several posts and, for a short time at least, to have a complete set of readings taken at the correct test intervals. This more particularly applies to the electrical water, superheat and vacuum readings. In the case of a turbo-alternator the steadiness obtainable in the electrical load may determine the frequency of readings taken, both electrical and otherwise. On a perfectly steady water-tank load, for example, it may be sufficiently adequate to read all wattmeters, voltmeters, and ammeters from standard instruments at from one- to two-minute intervals. Readings at half-minute intervals, however, should be taken with a varying load, even when the variation is only slight. The water-measurement readings may of course be taken at any suitable intervals, the time being to an extent determined by the size of the measuring tanks or the capacity of the weighing machine or machines. When designing the measuring apparatus, the object should be to minimize, within economical and practical range, the total number of weighings or measurements necessary. Consequently, no strict time of interval between individual weighings or measurements can be given in this case. It may be said, however, that it is not desirable to take these at anything less than five-minute intervals. Under ordinary circumstances a three- to five-minute interval is sufficient in the case of all steam-pressure, vacuum--including mercurial columns and barometer--superheat and temperature readings. Gland and Hot-Well Regulation There are two highly important features requiring more or less constant attention throughout a test, namely the gland and hot-well regulation. For the present purpose we may assume that the glands are supplied with either steam or water for sealing them. All steam supplied to the turbine obviously goes to swell the hot-well contents, and to thus increase the total steam consumption. The ordinary steam gland is in reality a pressure gland. At both ends of the turbine casing is an annular chamber, surrounding the turbine spindle at the point where it projects through the casing. A number of brass rings on either side of this chamber encircle the spindle, with only a very fine running clearance between the latter and themselves. Steam enters the gland chamber at a slight pressure, and, when a vacuum exists inside the turbine casing, tends to flow inward. The pressure, however, inside the gland is increased until it exceeds that of the atmosphere outside, and by maintaining it at this pressure it is obvious that no air can possibly enter the turbine through the glands, to destroy the vacuum. The above principle must be borne in mind during a test upon a turbine having steam-fed glands. Perhaps the best course to follow--in view of the economy of gland steam consumption necessary--is as follows: During the preliminary non-test run, full steam is turned into both glands while the vacuum is being raised, and maintained until full load has been on the turbine for some little time. The vacuum will by this time have probably reached its maximum, and perhaps fallen to a point slightly lower, at which hight it may be expected to remain, other conditions also remaining constant. The gland steam must now be gradually turned off until the amount of steam vapor issuing from the glands is almost imperceptible. This should not lower the vacuum in the slightest degree. By gradual degrees the gland steam can be still farther cut down, until no steam vapor at all can be discerned issuing from the gland boxes. This reduction should be continued until a point is reached at which the vacuum is affected, when it must be stopped and the amount of steam flowing to the gland again increased very slightly, just enough to bring the vacuum again to its original hight. The steam now passing into the glands is the minimum required under the conditions, and should be maintained as nearly constant as possible throughout the test. Practically all steam entering the glands is drawn into the turbine, and thence to the condenser, and under the circumstances it may be assumed the increase in steam consumption arising from this source is also a minimum. There is one mechanical feature which has an important bearing upon the foregoing question, and which it is one of the tester's duties to investigate. This is illustrated in Fig. 71, which shows a turbine spindle projecting through the casing. The gland box is let into the casing as shown. Brass rings A calked into the gland box encircle the shaft on either side of the annular steam space S. As the clearance between the turbine spindle and the rings A is in a measure instrumental in determining the amount of steam required to maintain a required pressure inside the chamber, it is obvious that this clearance should be minimum. An unnecessarily large clearance means a proportionally large increase in gland steam consumption and _vice versa_. [Illustration: FIG. 71] When the turbine glands are sealed with water, all water leakage which takes place into the turbine, and ultimately to the condenser hot-well, must be measured and subtracted from the hot-well contents at the end of a test. The foregoing remarks would not apply to those cases in which the gland supply is drawn from and returned to the hot-well, or a pipe leading from the hot-well. Then no correction would be necessary, as all water used for gland purposes might be assumed as being taken from the measuring tanks and returned again in time for same or next weighing or measurement. General Considerations There are a few principal elementary points which it is necessary always to keep in mind during the conduct of a test. Among these are the effects of variation in vacuum, superheat, initial steam pressure, and, as already indicated, in load. There exist many rules for determining the corrections necessitated by this variation. For example, it is often assumed that 9 degrees Fahrenheit, excess or otherwise, above or below that specified, represents an increase or reduction in efficiency of about 1 per cent. It is probable that the percentage increase or decrease in steam consumption, in the case of superheat, can be more reliably calculated than in other cases, as, for example, vacuum; but the increase cannot be said to be due solely to the variation in superheat. In other words, the individuality of the particular turbine being tested always contributes something, however small this something may be, to the results obtained. These remarks are particularly applicable where vacuum is concerned. Here again rules exist, one of these being that every additional inch of vacuum increases the economy of the turbine by something slightly under half a pound of steam per kilowatt-hour. But a moment's consideration convinces one of the utter unreliability of such rules for general application. It is, for instance, well known that many machines, when under test, have demonstrated that the total increase in the water rate is very far from constant. A machine tested, for example, gave approximately the following results, the object of the test being to discover the total increase in the water rate per inch decrease in vacuum: From 27 inches to 26 inches, 4.5 per cent. From 26.2 inches to 24.5 inches, 2.5 per cent. This illustrates to what an extent the ratio of increase can vary, and it must be borne in mind that it is very probable that the variation is different in different types and sizes of machines. There can exist, therefore, no empirical rules of a reliable nature upon which the tester can base his deductions. The only way calculated to give satisfaction is to conduct a series of preliminary tests upon the turbine undergoing observation, and from these to deduce all information of the nature required, which can be permanently recorded in a set of curves for reference during the final official tests. In conclusion, it must be admitted that many published tests outlining the performances of certain makes of turbine are unreliable. To determine honestly the capabilities of any machine in the direction of steam economy is an operation requiring time, and unbiased and accurate supervision. By means of such assets as "floating quantities," short tests during exceptionally favorable conditions, and disregard of the vital necessity of running a test under the proper specified conditions, it is comparatively easy to obtain results apparently highly satisfactory, but which under other conditions might be just the reverse. These considerations are, however, unworthy of the tester proper. VII. AUXILIARIES FOR STEAM TURBINES[6] [6] Contributed to _Power_ by Thomas Franklin. The Jet Condenser The jet condenser illustrated in Fig. 72 is singularly well adapted for the turbine installation. As the type has not been so widely adopted as the more common forms of jet condenser and the surface types, it may prove of interest to describe briefly its general construction and a few of its special features in relation to tests. [Illustration: FIG. 72] Referring to the figure, C is the main condenser body. Exhaust steam enters at the left-hand side through the pipe E, condensing water issuing through the pipe D at the opposite side. Passing through the short conical pipe P, the condensing water enters the cylindrical chamber W and falls directly upon the spraying cone S. The hight of this spraying cone is determined by the tension upon the spring T, below the piston R, the latter being connected to the cone by a spindle L. An increase of the water pressure inside the chamber W will thus compress the spring, and the spraying cone being consequently lowered increases the aperture between it and the sloping lower wall of the chamber W, allowing a greater volume of water to be sprayed. The piston R incidentally prevents water entering the top vapor chamber V. From the foregoing it can be seen that this condenser is of the contra-flow type, the entering steam coming immediately into contact with the sprayed water. The perforated diaphragm plate F allows the vapor to rise into the chamber V, from which it is drawn through the pipe A to the air pump. A relief valve U prevents an excessive accumulation of pressure in the vapor chamber, this valve being obviously of delicate construction, capable of opening upon a very slight increase of the internal pressure over that of the atmosphere. Condensed steam and circulating water are together carried down the pipe B to the well Z, from which a portion may be carried off as feed water, and the remainder cooled and passed through the condenser again. Under any circumstances, whether the air pump is working or not, a certain percentage of the vapor in the condenser is always carried down the pipe B, and this action alone creates a partial vacuum, thus rendering the work of the air pump easier. As a matter of fact, a fairly high vacuum can be maintained with the air pump closed down, and only the indirect pumping action of the falling water operating to rarify the contents of the condenser body. It is customary to place the condenser forty or more feet above the circulating-water pump, the latter usually being a few feet below the turbine. Features Demanding Attention When operating a condenser of this type, the most important features requiring preliminary inspection and regulation while running are: (a) Circulating-water regulation. (b) Freedom of all mechanical parts of spraying mechanism. (c) Relief-valve regulation. (d) Water-cooling arrangements. The tester will, however, devote his attention to a practical survey of the condenser and its auxiliaries, before running operations commence. A preliminary vacuum test ought to be conducted upon the condenser body, and the exhaust piping between the condenser and turbine. To accomplish this the circulating-water pipe D can be filled with water to the condenser level. The relief valve should also be water-sealed. Any existing leakage can thus be located and stopped. Having made the condenser as tight as possible within practical limits, vacuum might be again raised and, with the same parts sealed, allowed to fall slowly for, say, ten minutes. A similar test over an equal period may then be conducted with the relief valve not water-sealed. A comparison of the times taken for an equal fall of vacuum in inches, under the different conditions, during the above two tests, will reveal the extent of the leakage taking place through the relief valve. It seems superfluous to add that the fall of vacuum in both the foregoing tests must not be accelerated in any way, but must be a result simply of the slight inevitable leakage which is to be found in every system. On a comparatively steady load, and with consequently only small fluctuation in the volume of steam to be condensed, the conditions are most favorable for regulating the amount of circulating water necessary. Naturally, an excess of water above the required minimum will not affect the pressure conditions inside the condenser. It does, however, increase the quantity of water to be handled from the hot-well, and incidentally lowers the temperature there, which, whether the feed-water pass through economizers or otherwise, is not advisable from an economical standpoint. Thus there is an economical minimum of circulating water to be aimed at, and, as previously stated, it can best be arrived at by running the turbine under normal load and adjusting the flow of the circulating water by regulating the main valve and the tension upon the spring T. Under abnormal conditions, the breakdown of an air pump, or the sudden springing of a bad leak, for instance, the amount of circulating water can be increased by a farther opening of the main valve if necessary, and a relaxation of the spring tension by hand; or, the spring tension might be automatically changed immediately upon the vacuum falling. The absolute freedom of all moving parts of the spraying mechanism should be one of the tester's first assurances. To facilitate this, it is customary to construct the parts, with the exception of the springs, of brass or some other non-corrosive metal. The spraying cone must be thoroughly clean in every channel, to insure a well-distributed stream of water. Nor is it less important that careful attention be given to the setting and operation of the relief valve, as will be seen later. The obvious object of such a valve is to prevent the internal condenser pressure ever being maintained much higher than the atmospheric pressure. A number of carefully designed rubber flap valves, or one large one, have been found to act successfully for this purpose, although a balanced valve of more substantial construction would appear to be more desirable. Importance of Relief Valves The question of relief valves in turbine installations is an important one, and it seems desirable at this point to draw attention to another necessary relief valve and its function, namely the turbine atmospheric valve. As generally understood, this is placed between the turbine and condenser, and, should the pressure in the latter, owing to any cause, rise above that of the atmosphere, it opens automatically and allows the exhaust steam to flow through it into the atmosphere, or into another condenser. A general diagrammatic arrangement of a steam turbine, condenser, and exhaust piping is shown in Fig. 73. Connected to the exhaust pipe B, near to the condenser, is the automatic atmospheric valve D, from which leads the exhaust piping E to the atmosphere. The turbine relief valve is shown at F, and the condenser relief valve at G. The main exhaust valve between turbine and condenser is seen at H. We have here three separate relief valves: one, F, to prevent excessive pressure in the turbine: the second, D, an atmospheric valve opening a path to the air, and, in addition to preventing excessive pressure accumulating, also helping to keep the temperature of the condenser body and tubes low; the third, the condenser relief valve G, which in itself ought to be capable of exhausting all steam from the turbine, should occasion demand it. [Illustration: FIG. 73] Assuming a plant of this description to be operating favorably, the conditions would of necessity be as follows: The valves F, D, and G, all closed; the valve H open. Suppose that, owing to sudden loss of circulating water, the vacuum fell to zero. The condenser would at once fill with steam, a slight pressure would be set up, and whichever of the three valves happened to be set to blow off at the lowest pressure would do so. Now it is desirable that the first valve to open under such circumstances should be the atmospheric valve D. This being so, the condenser would remain full of steam at atmospheric pressure until the attendant had had time to close the main hand-or motor-operated exhaust valve H, which he would naturally do before attempting to regain the circulation of the condensing water. Again, assume the installation to be running under the initial conditions, with the atmospheric valve D and all remaining valves except H closed. Suppose the vacuum again fell to zero from a similar cause, and, further, suppose the atmospheric valve D failed to operate automatically. The only valves now capable of passing the exhaust steam are the turbine and condenser relief valves F and G. Inasmuch as the pressures at exhaust in the turbine proper, on varying load, vary over a considerably greater range than the small fairly constant absolute pressures inside the condenser, it is obviously necessary to allow for this factor in the respective setting of these two relief valves. In other words, the obvious deduction is to set the turbine relief valve to blow off at a higher pressure than the condenser relief valve, even when considering the question with respect to condensing conditions only. In this second hypothetical case, then, with a closed and disabled atmospheric valve, the exhaust must take place through the condenser, until the turbine can be shut down, or the circulating water regained without the former course being found necessary. There is one other remote case which may be assumed, namely, the simultaneous refusal of both atmospheric and condenser relief valves to open, upon the vacuum inside the condenser being entirely lost. The exhaust would then be blown through the turbine relief valve F, until the plant could be closed down. Although the conditions just cited are highly improbable in actual practice, it can at once be seen that to insure the safety of the condenser, absolutely, the turbine relief valve must be set to open at a comparatively low pressure, say 40 pounds by gage, or thereabouts. To set it much lower than this would create a possibility of its leaking when the turbine was making a non-condensing run, and when the pressure at the turbine exhaust end is often above that of the atmosphere. From every point of view, therefore, it is advisable to make a minute examination of all relief valves in a system, and before a test to insure that these valves are all set to open at their correct relative pressures. It must be admitted that the practice of placing a large relief valve upon a condenser in addition to the atmospheric exhausting valve is by no means common. The latter valve, where surface condensing is adopted, is often thought sufficient, working in conjunction with a quickly operated main exhaust valve. Similarly, with a barometric condenser as that illustrated in Fig. 72, the atmospheric exhaust valve D (seen in Fig. 73) is sometimes dispensed with. This course is, however, objectionable, for upon a loss of vacuum in the turbine, all exhaust steam must pass through the condenser body, or the entire plant be closed down until the vacuum is regained. The simple construction of the barometric condenser, however, is in such an event much to its advantage, and the passage of the hot steam right through it is not likely to seriously warp or strain any of its parts, as might probably happen in the case of a surface condenser. The question of the advisability of thus adding to a plant can only be fairly decided when all conditions, operating and otherwise, are fully known. For example, if we assume a large turbine to be operating on a greatly varying load, and exhausting into a condenser, as that in Fig. 72, and, further, having an adequate stand-by to back it up, one's obvious recommendation would be to equip the installation with both a condenser relief valve and an atmospheric valve, in addition, of course, to the main exhaust valve, which is always placed between the atmospheric valve and condenser. There are still other considerations, such as water supply, condition of circulating water, style of pump, etc., which must all necessarily have an obvious bearing upon the settlement of this question; so that generalization is somewhat out of place, the final design in all cases depending solely upon general principles and local conditions. Other Necessary Features of a Test In connection with the condenser, of any type, and its auxiliaries, there remain a few necessary examinations and operations to be conducted, if it is desired to obtain the very best results during the test. It will be sufficient to just outline them, the method of procedure being well known, and the requirement of any strict routine being unnecessary. These include: (1) A thorough examination of the air-pump, and, if possible, an equally careful examination of diagrams taken from it when running on full load. Also careful examination of the piping, and of any other connections between the air pump and condenser, or other auxiliaries. It will be well in this examination to note the general "lay" of the air pipes, length, hight to which they rise above condenser and air pump, facilities for drainage, etc., as this information may prove valuable in determining the course necessary to rectify deficiencies which may later be found to exist. (2) In a surface condenser, inspection of the pumps delivering condensed steam to the measuring tanks or hot-well; inspection of piping between the condenser and the pump, and also between the pump and measuring tanks. If these pumps are of the centrifugal type it is essential to insure, for the purposes of a steam-consumption test, as much regularity of delivery as possible. (3) In the case of a consumption test upon a turbine exhausting into a barometric condenser, and where the steam consumed is being measured by the evaporation in the boiler over the test period, time must be devoted to the feed-pipes between the feed-water measuring meter or tank and the boilers. Under conditions similar to those operating in a plant such as that shown in Fig. 72, the necessary boiler feed might be drawn from the hot-well, the remainder of the hot-well contents probably being pumped through water coolers, or towers, for circulating through the condenser. With the very best system, it is possible for a slight quantity of oil to leak into the exhaust steam, and thence to the hot-well. In its passage, say along wooden conduits, to the measuring tank or meter, this water would probably pass through a number of filters. The efficiency of these must be thoroughly insured. It is unusual, in those cases where a simple turbine steam-consumption test is being carried out, and not an efficiency test of a complete plant, to pass the measured feed-water through economizers. Should the latter course, owing to special conditions, become necessary, a careful examination of all economizer pipes would be necessary. (4) The very careful examination of all thermometer pockets, steam- and temperature-gage holes, etc., as to cleanliness, non-accumulation of scale, etc. Special Auxiliaries Necessary Having outlined the points of interest and importance in connection with the more permanent features of a plant, we arrive at the preparation and fitting of those special auxiliaries necessary to carry on the test. [Illustration: FIG. 74] It is customary, when carrying out a first test, upon both prime mover and auxiliaries, to place every important stage in the expansion in communication with a gage, so that the various pressures may be recorded and later compared with the figures of actual requirement. To do this, in the case of the turbine, it is necessary to bore holes in the cover leading to the various expansion chambers, and into each of these holes to screw a short length of steam pipe, having preferably a loop in its length, to the other end of which the gage is attached. Fig. 74 illustrates, diagrammatically, a complete turbine installation, and shows the various points along the course taken by the steam at which it is desirable to place pressure gages. The figure does not show the high-pressure steam pipe, nor any of the turbine valves. With regard to these, it will be desirable to place a steam gage in the pipe, immediately before the main stop-valve, and another immediately after it. Any fall of pressure between the two sides of the valve can thus be detected. To illustrate this clearly, Fig. 75 is given, showing the valves of a turbine, and the position of the gages connected to them. The two gages E and F on either side of the main stop-valve A are also shown. The steam after passing through the valve, which, in the case of small turbines, is hand-operated, goes in turn through the automatic stop-valve B, the function of which is to automatically shut steam off should the turbine attain a predetermined speed above the normal, the steam strainer C, and finally through the governing valve D into the turbine. As shown, gages G and H are also fitted on either side of the strainer, and these, in conjunction with gages E and F, will enable any fall in pressure between the first two valves and the governing valve to be found. Up to the governing-valve inlet no throttling of the steam ought to take place under normal conditions, i.e., with all valves open, and consequently any fall in pressure between the steam inlet and this point must be the result of internal wire-drawing. By placing the gages as shown, the extent to which this wire-drawing affects the pressures obtainable can be discovered. [Illustration: FIG. 75] On varying and even on normal and steady full load, the steam is more or less reduced in pressure after passing through the governing valve D; a gage I must consequently be placed between the valve, preferably on the valve itself, and the turbine. Returning to Fig. 74, the gages shown are A, B, C, D, and E, connected to the first, second, third, fourth, and fifth expansions; also F in the turbine and exhaust space, where there are no blades, G in the exhaust pipe immediately before the main exhaust valve E (see Fig. 73), and H connected to the condenser. On condensing full load it is probable that A, B, and C will all register pressures above the atmosphere, while gages D, E, F, and G will register pressures below the atmosphere, being for this purpose vacuum gages. On the other hand, with a varying load, and consequently varying initial pressures, one or two of the gages may register pressure at one moment and vacuum at another. It will therefore be necessary to place at these points compound gages capable of registering both pressure and vacuum. With the pressures in the various stages constantly varying, however, a gage is not by any means the most reliable instrument for recording such variations. The constant swinging of the finger not only renders accurate reading at any particular moment both difficult and, to an extent, unreliable, but, in addition, the accompanying sudden changes of condition, both of temperature and pressure, occurring inside the gage tube, in a comparatively short time permanently warp this part, and thus altogether destroy the accuracy of the gage. It is well known that even with the best steel-tube gages, registering comparatively steady pressures, this warping of the tube inevitably takes place. The quicker deterioration of such gage tubes, when the gage is registering quickly changing pressures, can therefore readily be conceived, and for this reason alone it is desirable to have all gages, whatever the conditions under which they work, carefully tested and adjusted at short intervals. If it is desired to obtain reliable registration of the several pressures in the different expansions of a turbine running on a varying load, it would therefore seem advisable to obtain these by some type of external spring gage (an ordinary indicator has been found to serve well for this purpose) which the sudden internal variations in pressure and temperature cannot deleteriously affect. In view of the great importance he must attach to his gage readings, the tester would do well to test and calibrate and adjust where necessary all the gages he intends using during a test. This he can do with a standard gage-testing outfit. By this means only can he have full confidence in the accuracy of his results. In like manner it is his duty personally to supervise the connecting and arrangement of the gages, and the preliminary testing for leakage which can be carried out simultaneously with the vacuum test made upon the turbine casing. Where Thermometers are Required Equally important with the foregoing is the necessity of calibrating and testing of all thermometers used during a test. Where possible it is advisable to place new thermometers which have been previously tested at all points of high temperature. Briefly running them over, the points at which it is necessary to place thermometers in the entire system of the steam and condensing plant are as follows: (1) A thermometer in the steam pipe on the boiler, where the pipe leaves the superheater. (2) In the steam pipe immediately in front of the main stop-valve, near point E in Fig. 75. (3) In the main governing valve body (see I, Fig. 75) on the inlet side. (4) In the main governing valve body on the turbine side, which will register temperatures of steam after it has passed through the valve. (5) In the steam-turbine high-pressure chamber, giving the temperature of the steam before it has passed through any blades. (6) In the exhaust chamber, giving the temperature of steam on leaving the last row of blades. (7) In the exhaust pipe near the condenser. (8) In the condenser body. (9) In the circulating-water inlet pipe close to the condenser. (10) In the circulating-water outlet pipe close to the condenser. (11) In the air-pump suction pipe close to the condenser. (12) In the air-pump suction pipe close to the air pump. It is not advisable to place at those vital points, the readings at which directly or indirectly affect the consumption, two thermometers, say one ordinary chemical thermometer and one thermometer of the gage type, thus eliminating the possibility of any doubt which might exist were only one thermometer placed there. There is no apparent reason why one should attempt to take a series of temperature readings during a consumption test on varying load. The temperatures registered under a steady load test can be obtained with great reliability, but on a varying load, with constantly changing temperatures at all points, this is impossible. This is, of course, owing to the natural sluggishness of the temperature-recording instruments, of whatever class they belong to, in responding to changes of condition. As a matter of fact, the possibility of obtaining correctly the entire conditions in a system running under greatly varying loads is very doubtful indeed, and consequently great reliance cannot be placed upon figures obtained under such conditions. A few simple calculations will reveal to the tester his special requirements in the direction of measuring tanks, piping, etc., for his steam consumption test. Thus, assuming the turbine to be tested to be of 3000 kilowatt capacity normal load, with a guaranteed steam consumption of, say, 14.5 pounds per kilowatt-hour, he calculates the total water rate per hour, which in this case would be 43,500 pounds, and designs his weighing or measuring tanks to cope with that amount, allowing, of course, a marginal tank volume for overload requirements. VIII. TROUBLES WITH STEAM TURBINE AUXILIARIES[7] [7] Contributed to _Power_ by Walter B. Gump. The case about to be described concerns a steam plant in which there were seven cross-compound condensing Corliss engines, and two Curtis steam turbines. The latter were each of 1500-kilowatt capacity, and were connected to surface condensers, dry-vacuum pumps, centrifugal, hot-well and circulating pumps, respectively. In the illustration (Fig. 76), the original lay-out of piping is shown in full lines. Being originally a reciprocating plant it was difficult to make the allotted space for the turbines suitable for their proper installation. The trouble which followed was a perfectly natural result of the failure to meet the requirements of a turbine plant, and the description herein given is but one example of a great many where the executive head of a concern insists upon controlling the situation without regard to engineering advice or common sense. [Illustration: FIG. 76. TURBINE AUXILIARIES AND PIPING] Circulating Pump Fails to Meet Guarantee Observing the plan view, it will be seen that the condensers for both turbines receive their supply of cooling water from the same supply pipe; that is, the pipes, both suction and discharge, leading to No. 1 condenser are simply branches from No. 2, which was installed first without consideration for a second unit. When No. 1 was installed there was a row of columns from the basement floor to the main floor extending in a plane which came directly in front of the condenser. The column P shown in the plan was so located as to prevent a direct connection between the centrifugal circulating pump and the condenser inlet. The centrifugal pump was direct-connected to a vertical high-speed engine, and the coupling is shown at E in the elevation. Every possible plan was contemplated to accommodate the engine and pump without removing any of the columns, and the arrangement shown was finally adopted, leaving the column P in its former place by employing an S-connection from the pump to the condenser. It should be stated that the pump was purchased under a guarantee to deliver 6000 gallons per minute under a head of 50 feet, with an impeller velocity of 285 revolutions per minute. The vertical engine to which the pump was connected proved to be utterly unfit for running at a speed beyond 225 to 230 revolutions per minute, and in addition the S-bend would obviously reduce the capacity, even at the proper speed of the impeller. Besides these factors there was another feature even more serious. It was found that when No. 2 unit was operating No. 1 could not get as great a quantity of circulating water as when No. 2 was shut down. This was because No. 2 was drawing most of the water, and No. 1 received only that which No. 2 could not pull from the suction pipe A. This will be clear from the fact that the suction and discharge pipes for No. 1 were only 16 inches, while those of No. 2 were 20 inches and 16 inches, respectively. The condenser for No. 2 had 1000 square feet less cooling surface than No. 1, which had 6000 square feet and was supplied with cooling water by means of two centrifugal pumps of smaller capacity than for No. 1 and arranged in parallel. These were each driven by an electric motor, and were termed "The Siamese Twins," due to the way in which they were connected. The load factor of the plant ranged from 0.22 to 0.30, the load being almost entirely lighting, so that for the winter season the load factor reached the latter figure. The day load was, therefore, light and not sufficient to give one turbine more than from one-fourth to one-third its rated capacity. Under these conditions No. 1 unit was able to operate much more satisfactorily than when fully loaded, because of the fact that the cooling water was more effective. This was, of course, all used by No. 1 unit when No. 2 was not operating. At best, however, it was found that the vacuum could not be made to exceed 24 inches, and during the peak, with the two turbines running, the vacuum would often drop to 12 inches. A vacuum of 16 inches or 18 inches on the peak was considered good. An Investigation Severe criticism "rained" heavily upon the engineer in charge, and complaints were made in reference to the high oil consumption. An investigation on the company's part followed, and the firm which furnished the centrifugal pump and engine was next in order to receive complaints. Repeated efforts were made to increase the speed of the vertical engine to 285 revolutions per minute, but such a speed proved detrimental to the engine, and a lower speed of about 225 revolutions per minute had to be adopted. A thorough test on the pump to ascertain its delivery at various speeds was the next move, and a notched weir, such as is shown in the elevation, was employed. The test was made on No. 2 cooling tower, not shown in the sketch, and showed that barely 3000 gallons per minute were being delivered to the cooling tower. While the firm furnishing the pump was willing to concede that the pump might not be doing all it should, attention was called to the fact that there might be some other conditions in connection with the system which were responsible for the losses. Notable among these was the hydraulic friction, and when this feature of the case was presented, the company did not seem at all anxious to investigate the matter further; obviously on account of facing a possible necessity for new piping or other apparatus which might cost something. Approximately 34 feet was the static head of water to be pumped over No. 2 cooling tower. Pressure gages were connected to the suction, discharge, and condenser inlet, as shown at G, G' and G'' respectively. When No. 1 unit was operating alone the gage G showed practically zero, indicating no vacuum in the suction pipe. Observing the same gage when No. 2 unit was running, a vacuum as high as 2 pounds was indicated, showing that No. 2 was drawing more than its share of cooling water from the main A and hence the circulating pump for No. 1 was fighting for all it received. Gage G' indicated a pressure of 21 pounds, while G'' indicated 18.5 pounds, showing a difference of 2.5 pounds pressure lost in the S-bend. This is equivalent to a loss of head of nearly 6 feet, 0.43 pound per foot head being the constant employed. The total head against which the pump worked was therefore G' + G = 21 + 2, or 23 ---- = 53 0.43 feet approximately. Since the static head was 34 feet, the head lost in friction was evidently 53-34 = 19 feet, or 1900 ---- = 36 53 per cent., approximately. Supply of Cooling Water Limited In addition to this the supply of cooling water was limited, the vacuum being extremely low at just the time when efficient operation should be had. The natural result occurred, which was this: As the load on the turbine increased, the amount of steam issuing into the condenser increased, beating [Transcriber: heating?] the circulating water to a temperature which the cooling tower (not in the best condition) was unable to decrease to any great extent. The vacuum gradually dropped off, which indicated that the condenser was being filled with vapor, and in a short time the small centrifugal tail-pump lost its prime, becoming "vapor bound," and the vacuum further decreased. The steam which had condensed would not go into the tail-pump because of the tendency of the dry-pump to maintain a vacuum. When a certain point was reached the dry-vacuum pump started to draw water in its cylinder, and the unit had to be shut down immediately. Vapor-bound Pumps As the circulating water gradually rose in temperature the circulating pump also became "vapor bound," so that the unit would be tied up for the rest of the night, as this pump could not be made to draw hot water. The reason for this condition may be explained in the following way. When the circulating pump was operating and there was a suction of 2 pounds indicated at G, the water was not flowing to the pump of its own accord, but was being pulled through by force. This water would flow through the pump until a point was reached when the water became hot enough to be converted into vapor, this occurring at a point where the pressure was sufficiently reduced to cause the water to boil. Naturally this point was in the suction pipe and vapor was thus maintained behind the pump as long as it was operating. In this case the pump was merely maintaining a partial vacuum, but not drawing water. After the vacuum was once lost, by reason of the facts given, it could not be regained, as the circulating water, piping and condenser required a considerable period of time in which to cool. Before any radical changes were made it was decided that a man should crawl in the suction pipe A, and remove such sand, dirt, or any other obstacles as were believed to cause the friction. After this had been done and considerable sand had been removed, tests were resumed with practically the same results as before. The investigation was continued and the dry-vacuum pumps were overhauled, as they had been damaged by water in the cylinders, and furthermore needed re-boring. In short, the auxiliaries were restored to the best condition that could be brought about by the individual improvement of each piece of apparatus. As this was not the seat of the trouble, however, the remedy failed to effect a "cure." It was demonstrated that the steam consumption of the turbines was greatly increased due to priming of the boilers, as well as condensation in the turbine casing; hence, the ills above mentioned were aggravated. Changes in Piping After a great deal of argument from the chief engineer, and the firm which furnished the pump, both making a strong plea for a change in the piping, the company accepted the inevitable, and the dotted portion shows the present layout. The elbow M was removed, and a tee put in its place to which the piping D was connected. The circulating pump was removed to the position shown, and a direct connection substituted for the S-bend. The discharge pipe C was carried from No. 1 unit separately, as shown in the elevation, and terminated at No. 1 cooling tower instead of No. 2, which shortened the distance about 60 feet, the total length of pipe (one way) from No. 1 unit being originally 250 feet. In this way the condensing equipment was made practically separate for each turbine, as it should have been in the first place. With the new piping a vacuum of 24 inches on the peak could be reached. While this is far from an efficient value, yet it is better than the former figure. The failure to reach a vacuum of 28 inches or better is due primarily to a lack of cooling water, but an improvement in this regard could be made by reconstructing the cooling towers, which at present do not offer the proper amount of cooling surface. The screens used were heavy galvanized wire of about 3/16-inch mesh, which became coated in a short time, and must be thoroughly cleaned to permit the water to drop through them. The supply of cooling water was taken from a 30-inch pipe line several miles long and fed from a spring. The amount of water varied considerably and was at times quite insufficient for the load on the plant. Instead of meeting this condition with the best apparatus possible, a chain of difficulties were added to it, with the results given. INDEX Acceleration, rate of, 147 Adjustment, axial, 65 making, 66 Air-pump, examining, 163 Allis-Chalmers Co. steam turbine, 41 Auxiliaries, 2, 154 special, 165 Auxiliary plant for consumption test, 137 spring on governor dome, 28 Axial adjustment, 65 Baffler, 36 functions, 39 Bearings, main, 69 Blades, construction details, 44 inspecting, 104 Blading, Allis-Chalmers turbine, 48 Westinghouse-Parsons turbine, 59, 92 Blueprints, studying, 11 Buckets, moving, 14 stationary, 14 Bushings, 36 Carbon packing, 19 ring, 20 Central gravity oiling system, 111 Circulating pump fails to meet guarantee, 172 Clearance, 15, 150 adjusting, 18 between moving and stationary buckets, 4 gages, 17 measuring, 18 radial, 63 Comma lashing, 95 Condensers, 108, 131 jet, 154 Conditions for successful operation, 105 Cooling water supply limited, 177 Coupling, 127 Cover-plate, 4 -plate, lowering, 9 Curtis turbine, 11 turbine in practice, 1 setting valves, 31, 32 De Laval turbines, 118 Draining system, 105 Dummy leakage, 115 pistons, 63, 65 rings, 43, 113, 114 Equalizing pipes, 64 Exhaust end of turbine, 107 pipe, 107 Expanding nozzles, 14 Feed-pipes, 164 Flow, rate, 38 Foundation drawings, 2 rings, 44, 46 Fourth-stage wheel, 14 Franklin, Thomas, 112, 137, 154 Gages, calibrating and adjusting, 169 clearance, 17 for test work, 165 Generator, 53 Glands, examination for scale, 104 packing, 71, 77 regulation, 148 Governor, Allis-Chalmers turbine, 48 Curtis turbine, 27, 31 improved, Westinghouse-Parsons turbine, 83 -rods, adjusting, 35 safety-stop, 86 Westinghouse-Parsons turbine, 80 Grinding, 38 Guide-bearing, lower, 9 Gump, Walter B., 172 Holly draining system, 106 Horseshoe shim, 8 Hot-well regulation, 148 Inspection, 103 Intermediate, 14 Jacking ring, 8 Jet condenser, 154 Johnson, Fred L., 1, 31 Leakage, 118 Load variation, 144 Lower guide-bearing, 9 Lubrication, 51 Measuring tanks, 171 Mechanical valve-gear, 32 Nozzles, expanding, 14 Oil, 57, 103, 109 amount passing through bearings, 122 consumption, high, 175 detecting water in, 122 pressure, 122 -temperature curve, 123 Oil, testing, 110 velocity of flow, 122 Oiling, 87 system, importance, 119 Operation, Allis-Chalmers turbine, 54, 55 successful, 105 Operations in handling turbine plant, 146 Overload valve, 28 Packing, carbon, 19 glands, 71 ring, self-centering, 14 Parsons type of turbine, 41 Passage in foundation, 2 Peep-holes, 15, 18 Piping, 171 changing, 179 inspection, 164 Pressure, 63 gages, 166 in glands, 57 Pump, circulating, fails to meet guarantee, 172 inspection, 164 Radial clearance, 63 Rateau turbines, 118 Relief valves, 31 valves, importance, 159 Ring, carbon, 20 Rotor, Westinghouse-Parsons turbine, 59 Running, 99 Safety-stop, 22 -stop governor, 86 Saucer steps, 39 Screw, step-bearing, 18 step-supporting, 4 Separators, 105 Setting spindle and cylinder for minimum leakage, 115 valves in Curtis turbine, 31, 32 Shaft, holding up while removing support, 8 Shield-plate, 26, 36 Shim, horseshoe, 8 Shroud rings, 44, 46 Shrouding on buckets and intermediates, 18 Shutting down, 101 Special turbine features, 127 Spindle, lifting, 96 removing, 104 Spraying mechanism, 158 Stage valves, 28, 31 Starting up, 54, 95 Step-bearing, lowering to examine, 8 -bearing screw, 18 -blocks, 4 -lubricant, 4 -pressure, 38 -supporting screw, 4 -water, flow, 38 Stopping turbine, 56 Sub-base, 8 Superheated steam, 105 Test loads, 141 necessary features, 163 Testing oil, 110 preparing turbine for, 145 steam turbine, 112, 137, 152 Thermometer, calibrating and testing, 169 oil, 125 Thrust-block, 118 Top block, 4 Troubles with steam turbine auxiliaries, 172 Turbine features, special, 127 Vacuum, 152 raising, 107 test, 135 Valve-gear, 83 -gear, mechanical, 22, 32 operation during consumption test, 138 overload, 28 relief, 31 importance, 159 setting in Curtis turbine, 31, 32 stage, 28,31 Vapor bound pumps, 178 Water, cooling, limited, 177 in oil, detecting, 122 -measurement readings, 148 pressure, 101 service, 126 importance, 119 tests of condenser, 133 used in glands, 57, 76 Westinghouse-Parsons steam turbine, 58 Wheels, 14 lower or fourth-stage, 14 position, 18 
17783	----	THE TRAVELING ENGINEERS' ASSOCIATION To Improve The Locomotive Engine Service of American Railroads EXAMINATION QUESTIONS AND ANSWERS For Firemen for Promotion and New Men for Employment :-: Copyrighted by W. O. Thompson, March, 1911 Revised January, 1919 * * * * * =PREFACE= It is the policy of railroads to employ firemen who will in time become competent locomotive engineers. This requires that a man should have at least a common school education, good habits and be in good physical condition. He should be alert, with good reasoning faculties and a man of sound judgment. Having these qualifications, advancement will come to those who are conscientious in discharging their duties and who devote some of their leisure hours to study. As an aid to this end, and that the railroad companies may derive the highest efficiency from the man employed as a locomotive engineman, a code of questions is given him, and it is expected that the preparation necessary to correctly answer the questions will indicate how well he has progressed. The list of questions is also intended as a guide to the matters on which he should be correctly informed, both during his term of service as a fireman and for future promotion to engineer. When a man is first employed as a fireman he will be given a list of questions on which he will be examined at the end of the first year; having passed this examination successfully he will then be given the examination questions for the following year; having passed this examination satisfactorily, he will be given a third and final set of examination questions on which he will be examined before being promoted to engineer. All these examinations will be both written and oral. The third year examination for promotion will be before the General Board of Examiners. At any of these examinations, if he fails to pass 80 per cent. of the questions asked, another trial, not less than two months and not more than six months later, will be given him to pass the same examination; if he fails to pass by a percentage of 80 per cent. he shall be dropped from the service. Where the examinations consist of both air brake and machinery, the candidate must pass 80 per cent. in each to be successful. Firemen passing the third and final series of questions will be promoted in the order of their seniority as firemen, except that those who pass on the first trials shall rank, when promoted, above those who passed on the second trials. Engineers employed who have had service on other roads, will be required to pass the third series of questions before entering the service. It is not expected that the man will pass these examinations without assistance, and in order that he will understand the use of locomotive and air brake appliances properly, he is expected to go to the Master Mechanic, General Foreman, Road Foreman or Traveling Engineer, also Air Brake Inspector or Instructor, or any other official, and ask them for such information as may be required on any of the questions or on any points in connection with the work. He is not only invited, but also urged to do this, as the more knowledge of his business a man possesses, the better will be the results obtained. He will have ample time to study each set of questions; there is no doubt that with a reasonable amount of study each week, supplemented with close observation of the working of the locomotive, the information necessary to answer satisfactorily the entire list of questions can be easily mastered in the time given. In regard to breakdowns, it is advised that he carefully inspect each breakdown or disabled engine that comes to his notice, see where the parts have given way and in what manner the work of blocking up it done. It is not expected that all the breakdowns which may happen to a locomotive will occur on the engine that he is with; therefore it is good practice to observe how other men care for these breakdowns. In connection with these examinations the work done by the fireman during the year and how the work compares with that of other firemen in the same class of service will be carefully noted; his record as to the use of coal, supplies and attention to duty will be taken into consideration. It is hoped that he will give everything in detail the consideration it merits and realize fully that it is by looking after the little things that a man succeeds. It should be borne in mind that by filling well the position he holds he becomes entitled to the confidence that makes better positions possible. It is understood that those who conduct the examination may ask any question or questions bearing on any subject of this examination, in order to determine how well the persons being examined understands the subject. A mere memorized answer will not be sufficient. The full meaning of each answer must be understood. =EXAMINATION QUESTIONS= FIRST SERIES 1. Q. What do you consider essential for your success in regard to the use of fuel A. I deem it essential to my success to be as economical in the use of fuel and supplies as is consistent with the work to be performed, exercising good judgment in my work, harmonious co-operation with my engineer, and showing a willingness to learn and practice the best methods in my work. 2. Q. What are the fireman's duties on arrival at enginehouse previous to going out on a locomotive? A. He is required to examine the bulletin board, guards on water and lubricator glasses; try gauge cocks to find true water level; then examine grates, ash-pan, flues and fire-box. Put fire in proper shape; see that a proper supply of firing tools, water, coal, oil and waste are provided, that all lamps and markers are filled, cleaned and in proper condition; and to perform such other duties as may be required by the engineer to assist him in getting the engine in readiness. 3. Q. What pressure is indicated by the steam gauge? What is meant by atmospheric pressure? A. The pressure per square inch inside of the boiler. Atmospheric pressure is the pressure represented by the density of the atmosphere in pounds per square inch, which is at sea level 14.7 pounds. 4. Q. On what principle does a steam gauge work? A. The steam gauge pointer is actuated by a flattened or bent round tube to straighten itself under the pressure of steam against the water inside of tube. The gauge pointer receives movement from suitable mechanism connected with the tube. 5. Q. What is the source of power in a steam locomotive? A. Heat is the source of power in all steam engines. It is necessary to have fuel and water. When fuel is burned, the water coming in contact with the hot sheets evaporates and becomes steam, which is then used in the cylinders to force the pistons back and forth. 6. Q. About what quantity of water should be evaporated in a locomotive boiler to the pound of coal? A. From five to seven pounds of water. For example, one gallon of water weighs eight and one-third pounds, therefore 100 pounds of coal should evaporate from sixty to eighty-four gallons of water. 7. Q. What is steam, and how is it generated? A. Steam is water in the condition of a vapor and is generated by heating the water above the boiling point. 8. Q. What is the purpose of the water gauge glass and gauge cocks? A. To indicate the level of water in the boiler. 9. Q. What would indicate to you that the boiler connections of water gauge glasses were becoming clogged? A. The up and down movement of the water in the glass would become slow and inactive, or it would not register correctly with the gauge cocks. 10. Q. At what temperature does water boil? A. At atmospheric pressure, which is 14.7 pounds at sea level, water boils at 212 degrees Fahrenheit; the temperature, however, increases as the pressure under which the water is boiled increases. At 200 pounds boiler pressure the temperature would be 388 degrees Fahrenheit. 11. Q. What is carbon? A. Carbon forms the greatest part of all kinds of coal; the higher the per cent. of carbon, the higher the grade of coal. 12. Q. What is the composition of bituminous coal? A. It is composed of carbon about 75 per cent. and many gaseous substances, as is shown by its burning with a large flame and much smoke. Anthracite, on the contrary, is nearly pure carbon and burns with a small flame. 13. Q. What is combustion? A. Combustion or burning is a chemical process, it is the action of fire on inflammable substances and is the union of the oxygen in the air with the carbon in the fuel; this is called rapid combustion. Slow combustion is the decaying of wood or iron by the elements. 14. Q. Is air necessary for combustion? A. Yes. 15. Q. About how many cubic feet of air is necessary for the combustion of a pound of coal in a locomotive fire-box? A. About 300 cubic feet of air must pass through the grates and fire for complete combustion of one pound of coal. 16. Q. Why must air be heated before combining with coal? A. Air, like coal and its gases, must be heated before they will unite to form what is known as combustion and so as not to reduce the temperature of the fire-box below the igniting point of the gases. 17. Q. Why is it necessary to provide for combustion a supply of air through the fuel in the furnace? A. In order to supply the oxygen necessary for combustion. 18. Q. What is the effect upon combustion if too little air is supplied? If too much air is supplied? A. If too little air is supplied, combustion is not complete, and only one-third as much heat is obtained. If too much air is supplied, combustion is complete; but the excess air must be heated, resulting in a lower temperature. If twice the amount of air required for complete combustion be supplied, the temperature of the fire-box will be about one-half as high. 19. Q. Give a practical definition of the igniting temperature. A. In all ordinary combustion there is a definite temperature, called the ignition or kindling temperature, to which combustible substance must be heated in order that it may unite with the gas in supporting the combustion. The burning substance must not only be heated up to the kindling temperature, but it must be kept as high as this temperature, or combustion will cease. 20. Q. State why such temperature is necessary and at what place in the fire-box it is most required. A. The center is the hottest part of the fire-box. There is a much lower temperature in the fire-box at the sides and end sheets, due to the water on the opposite sides of the sheets being of a lower temperature than the fire-box; therefore if we get as high a temperature as possible at the side and end sheets, we will increase the steam-making efficiency of the boiler. The gases which are liberated from the coal as soon as it becomes heated must attain a temperature of about 1,800 degrees Fahrenheit, known as the "temperature of ignition," before they will unite with air which must also be heated up to that point. 21. Q. How is draft created through the fire? A. Exhaust steam escaping through the stack reduces the pressure in the smoke-box below the pressure of the atmosphere outside, therefore the air tends to force itself into the smoke-box through all openings; with everything in good condition, the easiest and largest passage for it is through the grates and other openings into the fire-box and from it through the tubes into the smoke-box and up the stack. 22. Q. Is smokeless firing practicable? A. Yes, but it is necessary in order to obtain good results that boiler and fire-box be in good condition, coal broken to the proper firing size; then, with the hearty and intelligent co-operation of both engineer and fireman, smokeless firing is both economical and practicable. 23. Q. In what condition should the fire be in order that the best results may be obtained from the combustion of the coal? A. The fire should be as light as the work being done by the engine will permit, evenly distributed over the grates and free from clinkers. 24. Q. How should the blower be used? A. A blower should be used very lightly, being careful not to draw too much air into the fire-box and through the flues, especially when fire is being cleaned or thin on grates. 25. Q. What is the result of opening the fire-door when the engine is working steam? A. It will cause a cooling effect in the fire-box and is liable to start the flues leaking. 26. Q. What is the effect of putting too many scoops of coal on a bright fire? Is this a waste of fuel? A. It has the effect of temporarily deadening and cooling the fire, causes emission of quantities of black smoke, as only a limited amount of gas can be burned in a fire-box at a time; all in excess of that amount escapes from the stack and is a waste of fuel. 27. Q. What effect has the fire upon a scoopful of coal when it is placed in the fire-box? A. The heat from the fire drives the gases from the coal and they are ignited by the hot flame as they pass over the bright fire; the coke which is left burns where it is. 28. Q. In what condition should the fire be to consume these gases? A. A bright white coke fire, almost incandescent. 29. Q. What is the temperature of the fire when in this condition? A. It must not be less than 1,800 degrees Fahrenheit to consume the gases liberated from the coal, and it only requires from 750 to 900 degrees Fahrenheit to burn the coke that remains on the grate; as coke burns from the outside, less heat is required to consume it. 30. Q. How can the fire be maintained in this condition? A. By adding coal to the fire in small quantities, spreading it over the grate surface and no faster than it is burned. 31. Q. What is black smoke? Is it combustible? A. Black smoke consists of small particles of carbon suspended in the gases of combustion and indicates incomplete combustion. Black smoke is not combustible, it is like lampblack and cannot be burned after having been produced. The production of it can be prevented by suitable arrangements and manipulation. 32. Q. Should the gas not burn in the fire-box, will it burn after it enters the flues? Why? A. Gas will not burn only a short distance in the flues of a boiler, as the water absorbs the heat so quickly that the temperature of gas is lowered below the igniting point. 33. Q. What is the effect on the flow of air through the fire from opening the door? What on the burning of the gases? What on the flues and sheets of the fire-box? A. When the furnace door is opened, the flow of air through the grate is stopped in proportion to the amount that passes through the door. The vacuum will be filled from the quickest source and the door is closer than some parts of the grate. The gases mix with the air from the door and pass out through the flues; no combustion takes place, as the air is not hot enough to unite with the gas. The flues and sheets of the box will be caused to leak on account of the rapid contraction. 34. Q. Can the firing be done more effectively if the water level is observed closely? A. Yes, in order to know how much water there is in the boiler and whether it is necessary to hurry the fire; if the boiler is full, it is possible to prevent the pops opening by delaying the fire. 35. Q. How should the fire and water be handled in starting from a terminal or other station? A. The steam pressure should be near the maximum and there should be sufficient water in the boiler to last until such time as the fire is burning well so that the pressure will not be reduced when water is put into the boiler. There should be a moderately heavy bed of fire well burned and distributed evenly over the grates. After the fire is burning well, the injector should be started lightly; the feed being gradually increased so as not to cause any decrease of steam pressure. 36. Q. What is the purpose of a safety valve on a locomotive boiler? Why are more than one used? A. A safety valve is used to limit the maximum pressure in the boiler by opening and allowing steam to escape. More than one safety valve are used as additional protection against excessive pressure; one is set at the maximum pressure and the others are set at two or three pounds above the maximum pressure. 37. Q. What is usually the reason for steam being wasted from the safety valve? What can be done to prevent this waste? A. Careless firing, careless running. Both engineer and fireman work in harmony to obtain the best results. 38. Q. What is the estimated waste of coal for each minute the safety valve is open? A. About fifteen pounds. The estimated waste of steam when an engine pops equals every second all the heat obtained from a quarter pound of coal. Safety valves usually remain open about half a minute, resulting in the loss of about eight pounds of coal. 39. Q. What should be the condition of the fire on arriving at a station where a stop is to be made? A. On approaching the station where a stop is to be made, firing should be stopped far enough back to allow the carbon gases to be consumed before the throttle is closed, so there will be little or no black smoke from the stack and yet have sufficient fire that it will not be necessary to feed the fire again if a short stop is to be made until the train is started and the engine cut back or nearly to the running cut-off. 40. Q. How should you build up the fire when at stations in order to avoid black smoke? A. Put in small quantities of coal at a time, have the door slightly open and have the blower on lightly; good judgment must be exercised by the fireman. 41. Q. Why is it that if there is a thin fire with a hole in it the steam pressure will fall at once? A. Because too much cold air is drawn into the fire-box and through the tubes, retarding combustion and cooling the fire-box and tubes. 42. Q. If the injector is to be used after throttle is shut off, how should the fire be maintained? A. A sufficient quantity of coal should be placed on the grates to maintain the maximum steam pressure and the blower used to keep the fire burning brightly. 43. Q. What would be the result of starting a heavy train or allowing drivers to slip with the fire too thin on the grates? A. The fire would be pulled off the grates and into the tubes, leaving the fire bed full of holes and some of the fire remaining on the grates turned over. Large quantities of cold air would be drawn in, resulting in a rapid decrease of temperature and pressure. The tubes would possibly start leaking and the fire would be in such condition that it could not be built up properly in a long distance. Possibly the grates would become clogged up with green coal--an excellent opportunity for forming clinkers. In this condition, the engine would fail to make steam for the entire trip. 44. Q. Where should the coal, as a rule, be placed in the fire-box? A. As a rule, more coal is burned along the sides and in the corners than in the middle of the grates; the fire should consequently be kept somewhat heavier along the sides and corners than in the middle. 45. Q. How is the fire affected by and what causes clinkers? A. A clinker shuts off area of grate surface according to its size, and thereby shutting off that much of the air supply and interfering with proper combustion. Clinkers are caused by firing too heavy in spots, which prevents sufficient air passing up through these spots and allows the coal to run together, melting the ash, and sand; running a hoe or slash bar through the fire will bring the points of melted sand together, thereby causing a clinker. 46. Q. How can you best avoid their formation and dispose of them? A. Light firing and occasionally moving the grates lightly is the best preventive. When once formed, they should be removed if possible by firing around and burning them out. 47. Q. How can you explain the slower burning of the coke and how understand the proper manner of supplying fresh coal? A. The gases of coal are lighter than air and will pass away whether consumed or not. The slow burning of the coke is due to the fact that it burns from the outside only. When a fire reaches a white or incandescent heat it indicates that the gases are burned and a fresh supply of coal should be added; this is to be done as light as the service performed by the engine will permit. 48. Q. When and for what purpose is the use of a rake on the fire bed allowable? A. The rake should be used on the fire very seldom, because raking the fire bed tends to form clinkers, especially when the rake is plunged down through the fire to the grate. It may be used when necessary to rake the fire lightly when on the road for the purpose of breaking the crust, which may be found as a consequence of too heavy firing. 49. Q. Within what limits may steam pressure be allowed to vary, and why? A. Pressure should not be allowed to vary more than five pounds from the maximum for the reason that too much expansion and contraction will take place, which many times is the cause of flues leaking, cracked or broken side sheets and stay bolts. 50. Q. Has improper firing any tendency to cause the tubes to leak? How? A. Yes; if the pressure is not regularly maintained, the fluctuations of temperature cause constant contraction and expansion to take place. If the fire is not carried level, but is carried heavy in some parts of the fire-box and light in others, holes will be worked in, cold air drawn through, lowering the temperature, chilling the tubes and causing leaks. Carrying the fire too heavy in some places, causes clinkers to form. If the door is open too long, too much cold air is drawn over the fire, causing the tubes to leak. 51. Q. What do you consider abuse of a boiler? A. Careless or improperly supplying water to the boiler, improper firing or allowing steam to vary from high to low pressure, causing unnecessary expansion and contraction. 52. Q. Does the stopping up of flues affect the steaming capacity of the engine? A. Yes; obstructed flues reduce the heating surface, reduce the steaming capacity of the engine, and, as a rule, result in causing the flues to leak. They also cause an increase of speed of the gases through the remaining flues and a poor steaming engine. 53. Q. What causes honeycomb over the flues? A. Honeycomb on flues is usually caused by the draft through the fire picking up the sulphur and molten clay which is in a molten and sticky condition in the fire; as it passes on its way to the stack, some of it strikes the flue-sheet and sticks or passes through the flues, clogging up the netting in the front end. 54. Q. How would you take care of a boiler with leaky tubes or fire-box, and why? A. Keep a bright, clean fire, especially up next to the flue-sheet, and as even a pressure of steam as possible and not use the blower any stronger than is absolutely necessary. 55. Q. Why is it very important that coal should be broken so that it will not be larger than an ordinary sized apple before being put into the fire-box? A. In order to get rapid and complete combustion, coal should be broken into small pieces; this aids combustion by exposing a larger surface to the flame and can be fired more economically and better results are obtained. 56. Q. Should rapid firing be practiced? A. No; it should not be practiced for the same reason that heavy firing is wrong. A few moments should intervene between each shovelful to allow the fresh coal to get to burning and to maintain the high temperature in the fire-box. 57. Q. When and why should you wet the coal on the tender? A. Coal should be wet for the purpose of cleanliness to keep dust from flying and because moderately wet coal gives out more heat for the reason that there is not so much fine coal drawn through the tubes. It should be wet as often as necessary to accomplish these purposes. 58. Q. What are the advantages of a large grate surface? A. Greater heating surface, lighter fire and more complete combustion are possible with the larger grate surface, because a larger amount is burning at one time at a slower rate of combustion. 59. Q. Why are grates made to shake, and how, when and where should they be shaken? A. For the purpose of breaking any clinkers that might form and to shake out all refuse from the grates. The best time to shake grates is when throttle is closed, as there is no exhaust to carry the unconsumed gases and sulphur through the flues into the front end, which is liable to choke or clog up netting and cause a steam failure. Grates should not be shaken while passing over bridges, near lumber or hay yards or through prohibited territory. 60. Q. Do you understand that coal furnished represents money invested, and should be fired economically and not allowed to fall out of the gangway? A. The fuel of locomotives is property and represents money invested the same as do buildings, rolling stock, etc.; careless or inefficient firemen who waste fuel destroy property as certainly as though cars or engines were smashed up. The coal should be carefully raked off the deck and in from the gangways; it should not be allowed to fall, as it is wasted and dangerous to people near the track. The deck should be kept clean for greater comfort and convenience. 61. Q. Is is objectionable to fill the tanks too full of coal or overflow tank at standpipes or water tanks? A. It is. Tanks filled too full of coal are dangerous and a great waste of coal, as the jar when running will cause a part of it to fall off; water overflowing from tanks results in washing away the ballast and in cold weather freezes over the tracks. 62. Q. What are the duties of a fireman on arrival at the terminal? A. Different roads have different assigned duties for the firemen to perform. They should leave the cab, boiler head, oil cans and deck in a clean condition, boiler full of water, enough fire and steam, so that the hostler will not be required to put in fuel while the engine is in his charge; should know that throttle valve is securely closed, reverse lever in center of quadrant, cylinder cocks open, and if equipped with independent brake, it to be applied; in fact, it is an excellent opportunity for a mechanical officer to judge the ability of the fireman and future engineer. 63. Q. Is the engineer responsible for the fireman's conduct while on duty and for the manner in which the fireman's duties are performed? A. He is. The fireman is under the direction of the engineer, and the fireman's duties are to be performed in accordance with the engineer's instructions. 64. Q. What is the duty of the superheater damper, and how does it operate? A. The duty of the damper is to control the flow of gases through the large flues, thereby protecting the units which are contained therein from being overheated after throttle is closed. The position of damper when the engine is not working steam, is closed. 65. Q. What will be the effect on the steaming of the engine if the damper does not open properly? A. Engine will steam poorly for the reason that there will be no draft through the large flues. The steam will not be superheated because heated gases cannot come in contact with superheated units contained in the large flues. 66. Q. How may steam failure be avoided in case the damper fails to operate? A. The counterweight may be tied up, thereby opening the damper. =AIR BRAKE QUESTIONS= 1. Q. What is an air brake? A. A brake operated by compressed air. 2. Q. How is this air compressed? A. By an air compressor on the locomotive. 3. Q. Name the different parts of the air brake as applied to the locomotive. A. The air compressor, compressor governor, automatic and independent brake valves, distributing valve, triple valve, auxiliary reservoir, brake cylinders, main reservoir, air gauges, angle cocks, cut-out cocks and the necessary piping. 4. Q. What is the purpose of the main reservoir? A. It is used for storing a large volume of air for the purpose of promptly charging and recharging the brakes. Where the engine is equipped with either the E. T. or L. T. type of brakes, main reservoir air is used to supply the air to the brake cylinders on the locomotive. 5. Q. What other appliances use main reservoir air? A. It is used in the operation of the power reverse gear, sand blower, bell ringer, water scoop, air signal, fire door, water sprinkler and other devices. 6. Q. What does the red hand on each of the air gauges indicate? A. The red hand on the large gauge indicates main reservoir pressure; on the small gauge, brake cylinder pressure. 7. Q. What does the black hand on each of the air gauges indicate? A. The black hand on the large gauge indicates the equalizing reservoir pressure; on the small gauge, brake pipe pressure. 8. Q. What pressure is usually carried in the main reservoir? A. Ninety pounds in freight and 130 pounds in passenger service. But where freight engines are equipped with duplex compressor governor, the low pressure top is adjusted to ninety pounds and the high pressure top to 130 pounds. 9. Q. What pressure is usually carried in the brake pipe? A. Seventy pounds in freight and 110 pounds in passenger service. 10. Q. What must the air pass through in flowing from the main reservoir to the brake pipe? A. Through the automatic brake valve. 11. Q. Name the different positions of the automatic brake valve. A. Release, running, lap, service and emergency positions. The brake valve used with the E. T. and L. T. equipment has still another position known as holding position, which is located between running and lap positions. 12. Q. Name the different positions of the independent brake valve. A. Release, running, lap, slow application and quick application positions. 13. Q. How many kinds of triple valves are there in use? A. Two; plain and quick action. 14. Q. How is the automatic brake applied? How released? A. The automatic brake is applied by a reduction of brake pipe pressure, and is released by restoring the brake pipe pressure. 15. Q. When the independent brake valve handle is placed in application position, are the train brakes affected? A. No; only the brakes on the locomotive are applied. 16. Q. What controls the pressure in the main reservoir? A. The compressor governor. =EXAMINATION QUESTIONS= SECOND SERIES 1. Q. What, in your opinion, is the best way to fire a locomotive? A. To carry a nice, level fire on the grate, or it may be just a little heavier at the sides and front, so the air cannot come through it near the sheets as rapidly as in the center of the fire-box; always fire as light as consistent with the work required, endeavor to maintain a uniform steam pressure at all times, and avoid unnecessary black smoke and a waste of steam through the safety valves by the engine popping. 2. Q. What are the advantages of superheated steam over saturated steam in locomotive service? A. Saving in water; saving in fuel; increased boiler capacity and a more powerful locomotive. Superheated steam does away entirely with all condensation in the cylinders, while saturated steam coming in contact with passages in cylinder saddle and walls of cylinders, is immediately cooled and in cooling, a part of it is changed back into water which affects the pressure and therefore its capacity to do work. 3. Q. How is the saving in water produced? A. By the elimination of all cylinder condensation present in saturated steam locomotives and the increase in volume of a given weight of steam. 4. Q. How is the saving in coal accomplished? A. Because there is less steam used to do the same amount of work, there is less water evaporated and consequently less coal required to evaporate the water. 5. Q. How is the increased boiler capacity obtained? A. A boiler will evaporate a certain amount of water into steam and if part of the steam is lost by condensation, only that remaining is available for running the engine. Superheating eliminates the losses, thereby increasing the available useful steam. Further, superheating increases the volume of a given weight of steam, thereby reducing the consumption of steam required to develop a certain power and consequently increases the capacity. 6. Q. How is a more powerful engine obtained? A. By reason of the increased boiler capacity an engine may be worked farther down before a steam failure occurs. 7. Q. What type of fire tube superheater is in most general use in locomotive service? A. The top header fire tube type, known as the "Schmidt Superheater." A system of units located in large flues through which the steam passes on its way from the dry pipe to the steam pipes, and a damper mechanism which controls the flow of gases through the large flues. 8. Q. Describe the construction and location of the header. A. The header is a simple casting, divided by partition walls into saturated and superheated steam passages. It is located between the dry pipe and the steam pipes, the same as the nigger head in a saturated locomotive. The dry pipe is in communication with the saturated steam passages and the steam pipes with the superheated steam passages and these are in communication with each other through the superheated units. 9. Q. Describe the construction of superheater units and their connection to the header. A. The units are composed of four seamless steel pipes, connected by three return bends. Of the four pipes, two are straight and two are bent upward and connected to the header by means of a clamp and bolt; one end of the unit is in communication with the saturated steam passage and the other with the superheated steam passage in the header casting. 10. Q. Trace the flow of steam through the top header fire tube superheater. A. When the engine throttle is open, saturated steam passes through the dry pipe into the saturated steam passage of the header casting. From this passage it enters one end of the unit, passing backward toward the fire-box, forward through one of the straight pipes and the front return bend, backward through the other straight pipe to the back return bend, and forward through the bent pipe and upward into the superheater steam passage of the header, from which it enters the steam pipes and is carried to the steam chest. 11. Q. What should be the position of throttle valve when running a superheater locomotive? A. The engine should always be run with as wide open throttle as the conditions will permit, regulating the steam admission to the cylinders according to work to be performed. 12. Q. What should be the position of throttle while drifting? A. The throttle valve should be kept slightly open while drifting, so as to admit a small quantity of steam in valve chamber and cylinder above atmospheric pressure, to prevent the inrush of hot air and gases which destroy lubrication, also to prevent excessive wear to valve, cylinder and piston rod packing. 13. Q. How should the water be carried in boiler of superheater locomotives? A. As low as the conditions will permit, because this practice reduces the tendency to work water over into the dry pipe and units, as the superheater locomotive will use one-third less water than the saturated locomotive. 14. Q. What care should be exercised in lubricating a superheater locomotive? A. The supply of oil to steam chest should be watched very closely by the engineer, he to know that lubricator is feeding constantly and evenly over entire division, and according to work performed. 15. Q. Describe the general form of a locomotive boiler. A. A locomotive boiler is cylindrical in form, it usually has a rectangular shaped fire-box at one end and a smoke-box at the other, and flues extend through the cylindrical part, and, like the fire-box, are surrounded by water. 16. Q. How does the wide fire-box type of boiler differ from the ordinary boiler, and what are its advantages? A. The wide fire-box type of boiler is built so the fire-box is above the frame and extends out over the driving wheels. The advantages of this are to obtain a larger grate area in the same length of fire-box and to give a slower rate of combustion per square foot of grate surface. The deep fire-box is limited in width to the distance between the frames, while the shallow fire-box sets on top of the frames and between the driving wheels. 17. Q. Why have two fire-box doors been placed in the large type of locomotive boilers? A. For convenience of the fireman on account of the greater width of the fire-box, so that coal can easily be distributed to all parts of the fire-box. 18. Q. Describe a locomotive fire-box. A. The modern form is a rectangular shaped structure located at the back end of the boiler. It has a door and is composed of two side sheets, a crown sheet, a back sheet and a flue sheet from which the flues extend to the smoke-box at the other end of the boiler. 19. Q. To what strains is a fire-box subjected? A. To crushing strains and to those of unequal contraction and expansion. 20. Q. How are the sheets of a fire-box supported? A. They are supported by staybolts screwed through the inside and outside sheets with their ends riveted over. 21. Q. In what manner is a crown sheet supported? A. By crown bars or radial staybolts. 22. Q. What are the bad features about crown bars? A. They are hard to keep clean and frequently cause crown sheets to become mud burned. 23. Q. What are the advantages of radial stayed crown sheets? A. They are easier to keep clean and cheaper to repair. 24. Q. How are the inside and outside sheets of a fire-box secured at the bottom? A. They are riveted to a wrought iron ring called a mud-ring. 25. Q. Describe the ash-pan and its use. A. It is a receptacle secured to the fire-box and usually provided with dampers to regulate the flow of air to the fire. It collects the ashes that drop from the fire-box and prevents them from setting fire to bridges or other property along the track. Engine-men must know that ash-pan slide and hopper bottoms are closed before leaving enginehouse. 26. Q. What is a "wagon-top" boiler? A. It is a boiler that has the fire-box end made larger than the cylindrical part to provide more steam space. 27. Q. Why are boilers provided with steam domes? A. To furnish more steam space and to obtain dryer steam and to provide a place for the safety valves, steam pipes, throttle valve and whistle. 28. Q. What must be the condition of a boiler to give the best results? A. It must have good circulation and be clean and free from mud or scale. 29. Q. What is meant by "circulation" in a boiler? A. Free movement of the water, so that it may come in contact with the heating surface and after being converted into steam be immediately replaced by a fresh supply of water. 30. Q. What would be the effect if a "leg" of the fire-box became filled with mud? A. There would be no water in contact with the fire-box sheets and they would quickly become overheated and mud-burned. 31. Q. What would be the result if the fire-box sheets became overheated? A. They would be weakened and forced off the staybolts and an explosion would occur. 32. Q. Would it be advisable to put water into a boiler after the sheets had become bare and red hot? A. No. The fire should be killed at once. 33. Q. What effect has the stoppage of a large number of flues? A. The heating surface and draft are decreased by just that much area. 34. Q. Why are boiler checks placed so far away from the fire-box? A. To introduce the water into the boiler at as great a distance from the fire-box as possible. This permits the water to become heated to a high temperature before it comes in contact with the fire-box and also improves circulation. 35. Q. What part of the boiler has the greatest pressure? Why? A. The bottom, because it is subject to the weight of the water in addition to the steam pressure in the boiler. 36. Q. What are the advantages of the extension front end? A. To provide room for suitable draft and spark appliances. 37. Q. What is the purpose of a netting in a smoke-box or front end? A. To act as a crusher of all cinders and prevent large cinders from passing out of the front end to the atmosphere. 38. Q. What is the object of hollow staybolts? A. To indicate when the staybolt is broken by the escape of steam through the small hole in the bolt. 39. Q. What will cause the engine to tear holes in the fire? A. Working hard or slipping when the dampers are open and the door closed, or too thin a fire. 40. Q. Name the various adjustable appliances in the front end by which the draft may be regulated. A. The exhaust nozzle, the diaphragm and the draft pipes or petticoat pipe. 41. Q. What object is there in having the exhaust steam go through the stack? A. To create a draft through the tubes and fire-box. 42. Q. How does this affect the fire? A. The exhaust steam escaping through the stack tends to empty the smoke-box of gases and produces a partial vacuum there, atmospheric pressure then forces air through the grates and tubes to refill the smoke-box, and in this way the draft through the fire is established and maintained. 43. Q. Explain what adjustments can be made and the effect of each adjustment on the fire. A. Larger or smaller nozzle tips cause less or greater draft on the fire; raising or lowering the draft pipes and diaphragm causes the engine to burn the fire more at the rear or front end of the fire-box; the size and position of the draft pipes increase the draft through the top or bottom flues; the latter adjustments should always be attempted before reducing the nozzle. 44. Q. What does it indicate when the exhaust issues strongest from one side of the stack? A. The stack, exhaust pipe or petticoat pipe are out of plumb. 45. Q. What is the effect of leaky steam pipe joints inside the smoke-box? A. The engine will not steam freely. 46. Q. What causes "pull" on the fire-box door? A. The partial vacuum in the front end; when excessive it indicates dampers closed, fire clinkered or insufficient opening for the admission of air under the fire. 47. Q. If upon opening the fire-box door you discover there what is commonly called a red fire, what might be the cause? A. The grates may have become clogged with ashes or clinkers so that sufficient air could not pass through them to the fire. 48. Q. Is it not a waste of fuel to open the fire-box door to prevent pops from opening? How can this be prevented more economically? A. Yes. This can usually be prevented by putting the heater into the tank, or putting on the injector, or by more careful firing. 49. Q. Describe the principle upon which the injector works. A. The action of the injector is due first to the difference between "kinetic" or moving energy and "static" or standing energy; second, to the fact that steam at a pressure travels at a very high velocity and when placed in contact with a stream of water it is condensed into water, and at the same time it imparts enough velocity to the water to give it sufficient momentum to overcome a pressure even greater than the original pressure of the steam. By imparting this velocity to the water it gives it sufficient energy to throw open the check valves and enter the boiler against high pressure. 50. Q. What is the difference between a lifting and a non-lifting injector? A. A lifting injector will create sufficient vacuum to raise the water from the level of the tank. The steam tubes in a non-lifting injector are different and it will not raise the water, but merely force it into the boiler. A non-lifting injector must be placed below the level of the water in the tank so the water will flow to it by gravity. 51. Q. Will an injector work with a leak between the injector and tank? Why? Will it prime? A. A lifting injector will not work if the leak is bad. It will not prime because the air admitted through the leak destroys the vacuum necessary to raise the water to the injector level. A non-lifting injector will work, as the water will escape from the pipe instead of air being drawn into it as with the lifting injector. 52. Q. If it primes well, but breaks when the steam is turned on wide, where would you look for the trouble? A. Insufficient water supply due to tank valve partly closed, strainer stopped up or tank hose kinked, injector tubes out of line, limed up, or delivery tube cut, or wet steam from the throttle. 53. Q. If it would not prime, where would you expect to find the trouble? A. Insufficient water supply, priming valve out of order, or with the lifting injector the trouble might be caused by a leak between the injector and tank. 54. Q. Will an injector prime if the boiler check leaks badly or if it is stuck up? If the injector throttle leaks badly? A. No. 55. Q. If steam or water shows at the overflow pipe when the injector is not working, how can you tell whether it comes from the boiler check or the injector throttle? A. Close the main steam valve at the boiler, that will stop the leak if it comes from the injector throttle. 56. Q. Will an injector prime if primer valve leaks? Will that prevent its working? A. It will prime, but not as readily as with priming valve in good condition. This will not prevent its working, but it may waste some water from the overflow. 57. Q. Will an injector work if air cannot get into the tank as fast as the water is taken out? A. No. 58. Q. If you had to take down a tank hose, how would you stop the water from flowing out of the tank that has the syphon connections instead of the old-style tank valves? A. Open the pet cock at the top of the syphon before taking the hose down. 59. Q. Is any more water used when the engine foams than when the water is solid? A. Yes, very much more. 60. Q. How would you prevent injector feed pipes or tank hose from freezing in winter when not in use? A. The steam valve should be slightly open to permit a slight circulation of steam through the feed and branch pipes. The heater cock should be closed and the drip cock under the boiler check or on the branch pipe should be opened to insure a circulation of steam through the branch pipe. 61. Q. How would you prevent the overflow pipe from freezing with a lifting injector? A. The overflow valve should be opened just enough to permit a little steam to escape through the overflow pipe to prevent it from freezing. 62. Q. Name the various parts of the injector. A. The injector consists of a body supplied with a steam valve, a steam nozzle, a primer, a combining tube, a delivery tube, a line check valve, an overflow valve, a water valve, and a lifting injector has a lifting tube. 63. Q. What may be done if a combining tube is obstructed? A. The steam valve bonnet may be removed and the obstruction forced out with a piece of stiff wire, or uncouple the delivery pipe from the injector and unscrew and remove the tubes; the obstruction can then be removed and the tubes replaced. 64. Q. How is the greatest injury done to a boiler when cleaning or knocking the fire? A. By excessive use of the blower drawing cold air through the fire-box and flues. 65. Q. Why does putting a large quantity of cold water into a boiler when the throttle is closed cause the flues to leak? When is this most serious? A. When steam is not being used there is not much circulation of water in the boiler, and the water entering the boiler at about 150 degrees temperature is heavier than the water in the boiler. The cooler water will go to the bottom and reduce the temperature in that part of the boiler and causing the flues to contract in length as well as in diameter and this has a tendency to pull them out of the sheet. This will loosen them and cause them to leak. After the fire has been knocked this tendency is much greater, and for that reason cold water should not be put into a boiler after the fire has been knocked out. Always fill the boiler before the fire is knocked out. 66. Q. Is warm water in the tank of any advantage in making steam rapidly? A. Yes; careful experiments have shown that a locomotive will generate one per cent. more steam for every eleven degrees that the tank water is heated; thus by heating the feed water in the tank from 39 degrees to 94 would effect a saving of five per cent. 67. Q. Then why not heat the feed water to the boiling point (212 degrees)? A. If the feed water is heated much above 100 degrees it will not condense enough steam in the injector to cause it to work properly. Some injectors will work hotter water than others. It would also spoil the paint on the tank if heated to a much higher temperature. 68. Q. At 200 pounds pressure per square inch, what is the pressure per square foot on the sheets of a boiler? A. About fifteen tons. 69. Q. What is the total pressure on the fire-box of a large locomotive? A. Over 3,000 tons. 70. Q. Give a practical definition of heating surface. A. The heating surface of a boiler includes all parts of the boiler and tubes that are directly exposed to fire or heat from the fire and are surrounded by water. 71. Q. Should an engine be slipped to get water out of the cylinders or steam passages? A. No; the water should be worked out by opening the cylinder cocks and starting the engine slowly. 72. Q. What does it indicate when the smoke trails back over the train and into the coaches after shutting off? A. It indicates poor firing or a lack of understanding between the engineer and fireman in regard to where the engine was to be shut off. 73. Q. Before shaking grates or dumping the ash-pan, what should be observed? A. That the engine is not passing over bridges or cattle guards, crossings, switches, interlocking fixtures, or in yards. Fire on the track should be extinguished promptly at places where ash-pans are cleaned. 74. Q. Which is easier and more satisfactory on a long run, to stop and clean the fire if necessary or to continue to the end of a long, hard trip with a dirty fire? A. Stop and clean the fire if necessary. It will save fuel and labor during the remainder of the trip and may also save an engine failure. 75. Q. Should you examine the flues to see if they are stopped up and leaking, and inspect the grate and grate rigging carefully before leaving the engine at a terminal? A. Yes, so they can be reported if necessary. Clean flues and grates working well make a vast difference in the success of a fireman, and a great many engine failures could be avoided by keeping the flues and grates in proper condition. 76. Q. How should cab lamps, signal lamps, oil cans and lanterns be cared for? A. They should be kept clean, free from leaks and always filled and ready for service before leaving terminals. 77. Q. About how many drops in a pint of valve oil when fed through a lubricator? A. About 4,500 drops. 78. Q. Assuming that five drops per minute are fed to each of two valves and one drop per minute to the air pump, how many hours would be required to feed one pint of valve oil? A. About eight hours. 79. Q. Assuming that the engine is running twenty-miles per hour, how many miles per pint would be run? A. About 160 miles per pint. 80. Q. How many drops per minute should ordinarily be fed? A. This will vary with the size of the locomotive and the work to be performed. On small yard engines one drop per minute for each cylinder is usually sufficient and one drop for the air pump every two or three minutes. This depends on the condition of the pump and the service being performed. For large engines in slow freight service four to five drops per minute, and for large engines in heavy fast passenger service from five to seven drops per minute should be fed. Air pumps in freight service where the brake pipe is in moderately good condition can usually be run with one or two drops per minute when handling long trains of cars equipped with air brakes. 81. Q. Will any bad results ensue from filling the lubricator full of cold oil? A. Yes; when the oil gets hot it will expand and may break the glass or bulge or burst the lubricator. 82. Q. If a sight feed gets stopped up, how could you clean it out? A. Close the water valve and the regulating valves to the other feeds. Open drain cock and draw out a small quantity of water so as to bring the oil in top part of lubricator below the top end of oil pipe leading to feed arm, then open wide the regulating valve to feed that is stopped up and the pressure from the equalizing tube will force the obstruction out of the feed nozzle and up into the body of the lubricator. Next, close this regulating valve until the feed glass fills with water, then open water valve and start feeds. 83. Q. How would you clean out chokes? A. First, shut off boiler pressure and condenser valve; next, remove feed valve bonnet, then open main throttle valve, when the steam from steam chest will blow back through the choke plug, clearing it of any obstruction. 84. Q. What is superheated steam? A. It is the saturated steam separated from the water from which it is generated with more heat added, increasing its temperature from 100 degrees to 250 degrees Fahrenheit above the saturated steam temperature. 85. Q. What is the advantage of superheating or increasing the temperature of the steam? A. By increasing the temperature of the steam the volume of a given weight of steam is increased and all losses due to cylinder condensation are eliminated, which result in a reduced steam consumption, a saving in coal and water and increased boiler capacity. 86. Q. How is the increased temperature obtained by the use of the superheater? A. By admitting the saturated steam into a partitioned receiver which has a number of 1-1/2-inch pipes attached to it. These are located in and extend nearly the full length of the large flues, the steam having to pass through these 1-1/2-inch pipes on its way back to the receiver, absorbs the heat from the gases passing through the large tubes, causing its temperature to rise, or in other words, become superheated. 87. Q. How much is the volume of steam increased by superheating? A. For each 100 degrees of superheat added to saturated steam, at temperatures ordinarily used in locomotive practice, the volume of a given weight is increased roughly from sixteen to seventeen per cent. 88. Q. Why is the superheated steam so much more economical on coal and water than the saturated steam? A. Because for a given amount of water evaporated you can increase the volume of steam 33 per cent. by superheating. It is readily seen that the coal does not have to be burned if the steam used has 33 per cent. more volume for filling space, or in other words, only so much steam can be admitted to the cylinders for every movement of the valve, and what can not be used must remain in the boiler, so if the engine can not use all of the steam that the boiler is capable of generating, the saving must show in coal and water. If you can not use all of the steam you do not have to burn coal to make it. 89. Q. Which is the better practice, to close the feed valves or water valve while waiting on sidings, etc.? A. Close the feed valves; the water valve may leak. 90. Q. How can you tell if equalizer tubes become stopped up or broken? A. If they were stopped up the equalization would be destroyed, and when the steam-chest pressure was less than the boiler pressure the feed would work too fast, the oil would enter the feed glass in a stream instead of forming into drops. If they were broken, the lubricator could not be used. The auxiliary oilers would have to be used to lubricate the cylinders. =AIR BRAKE QUESTIONS= 1. Q. Explain how an air compressor should be started. A. A compressor should be started slowly, with the drain cocks open to allow the water of condensation to escape; and as no provision is made in the steam end to cushion the pistons at the end of their stroke, it should be allowed to work slowly until a pressure of thirty or forty pounds has accumulated in the main reservoir; the piston, having to work against this pressure, will be cushioned at the end of each stroke. After the compressor is warm, the drain cocks should be closed and the throttle opened sufficiently to run the compressor at the proper speed. The lubricator should then be started and allowed to feed freely until eight or ten drops have passed, when the feed should be reduced to an amount sufficient for proper lubrication. 2. Q. What kind of oil should be used to lubricate both the steam and air cylinders of the compressor? A. Valve oil. 3. Q. Where does the main reservoir pressure begin and end? A. Begins at the discharge valves in the compressor and ends at the engineer's brake valve. 4. Q. Where does the brake pipe pressure begin and end? A. The brake pipe pressure begins at the feed valve and ends at the brake pipe side of the triple piston, conductor's valve and at the rear angle cock. 5. Q. What is meant by excess pressure, and where is this pressure carried? A. Excess pressure is carried in the main reservoir and is the pressure above that in the brake pipe. 6. Q. Why is excess pressure necessary? A. To insure the prompt release of all brakes and quick recharge of the brake pipe and auxiliary reservoirs. 7. Q. How is the amount of excess pressure regulated? A. By the compressor governor. 8. Q. Name the different parts of the air brake as applied to a car. A. The triple valve, auxiliary reservoir, brake cylinder, brake pipe, angle cocks, cut-out cock, retaining valve, centrifugal dirt collector and strainer tee. 9. Q. What is the duty of the triple valve? A. The triple valve has three duties to perform: Charge the auxiliary reservoir; apply the brake; and release the brake. 10. Q. What is the purpose of the auxiliary reservoir? A. It is here that the air is stored that is admitted to the brake cylinder when the brake is applied; thus, each car carries its own brake power. 11. Q. What is the purpose of the brake cylinder? A. It is here where the power of the compressed air is converted into work by forcing the brake piston out, moving the brake levers, rods and brake beams, forcing the brake shoes against the wheels, applying the brake. 12. Q. What is the purpose of the brake pipe and angle cocks? A. It is through the brake pipe that all brakes in the train are placed into communication with the brake valve on the locomotive; and through the brake pipe, air from the main reservoir flows to the triple valves and auxiliary reservoirs on the different cars. The angle cocks are for the purpose of opening and closing the ends of the brake pipe. 13. Q. What is the purpose of the cut-out cock? A. To cut out any brake that is not in operating condition. 14. Q. How is a brake cut out? A. By closing the cut-out cock in the cross-over pipe and bleeding the auxiliary reservoir. 15. Q. How would you bleed an auxiliary reservoir? A. By holding open the release valve on the reservoir until all air has escaped. 16. Q. How would you bleed off a stuck brake? A. By holding open the auxiliary release valve until the brake piston starts to move toward release position. =OIL BURNING LOCOMOTIVES= 1. Q. What are the fireman's duties on arrival at the enginehouse previous to going out on an oil burning locomotive? A. In addition to the duties usually performed on any engine, the fireman should observe the condition of draft pans and arch, observe the condition of burner and dampers; try the oil regulating valve; see that the burner is properly delivering fuel oil to the fire; see that the oil heaters are in working order; that the fuel oil is heated to proper temperature; and see that proper supplies of fuel oil, sand and water have been provided as well as the necessary tools for handling an oil fire. 2. Q. How warm should the oil be at all times in the tank. A. Warm enough to flow freely at all times, usually about 112 degrees. This temperature is about that which the hand can bear on the outside of the tank. 3. Q. If the oil is too warm, what happens? A. Many of the good qualities of the oil may be lost by keeping it too warm, and the burner is more difficult to operate and does not work as well when the oil is kept at too high a temperature. Should the oil be too warm, it will give off too much gas which would be liable to cause an explosion in the oil tank. 4. Q. What tools are necessary for firing purposes on an oil burning locomotive? A. The tools necessary for firing an oil burning engine include sand horn, brick hook, and a small iron bar to be used in cleaning carbon from the mouth of the burner. 5. Q. What is liable to happen if the heater valve is open too much? A. If the heater valve is opened too much it would be liable to burst the heater hose as well as to heat the oil to a too high temperature and place an unnecessary strain on all the heater connections, causing them to leak. 6. Q. What should be done on approaching stations where additional supply of fuel oil is to be taken? A. Shut off the fire, close safety and main oil valves, remove any lamps that are so close as to be unsafe when manhole cover is open. 7. Q. What care must be exercised in the use of lamps, torches or lanterns about oil tanks whether hot or cold? A. Never permit oil lamps or oil torches to be carried within ten feet of the tank opening. Only incandescent lamps or pocket flash lights should be used around oil tank manhole when taking oil. 8. Q. How can oil in the tank be measured without taking a light to the manhole? A. By inserting a measuring stick into oil in tank and taking stick to the light for reading. 9. Q. What precautions must be taken before entering tanks that have been used for oil to clean or make repairs? A. Oil tanks, before being entered by workmen, should be thoroughly steamed and cooled before being entered. For safety they should be steamed from six to eight hours. 10. Q. How should the fire be lighted in an oil burning locomotive? A. First see that no one is working under the engine, that there is the proper amount of water in the boiler and that it will flow through the gauge cocks, that there is no accumulation of oil in the ash-pan or fire-box or existing leaks throughout. If there is no steam in the boiler, the steam connections can be made to the three-way cock at the smoke-arch that will answer for blower and atomizer. If there are twenty pounds of steam in the boiler, it can be operated with its own blower. If oil in the tank is too cold to flow into the burner readily, it must be heated. Open the front damper and put on the blower strong enough to create the necessary draft, open the atomizer valve long enough to blow out any water that might be in the steam pipe to the burner, then close the valve and throw a piece of burning waste in front of the burner and open the atomizer valve enough to carry oil to the burning waste and open the regulating valve slowly until the oil is known to be ignited. Watch the ignition through the hole in the fire-box door, then regulate the steam and oil supply to suit. Be sure that no oil is wasting below the burner or an explosion may result that will prove disastrous. 11. Q. Should the fire go out and it is desired to rekindle it while bricks are hot, is it safe to depend on the hot bricks to ignite the oil without the use of lighted waste? A. No; depending upon the heat from the firebricks to re-light the fire is dangerous and forbidden. 12. Q. What is termed an atomizer, and what does it perform? A. The atomizer is a casting containing two long ports with an extension lip; the upper port is for oil and the lower one for steam. The lip aids the steam in atomizing and spreading the oil, which, when properly mingled with the air and ignited, will produce combustion. The atomizer is located just under the mud-ring and pointed a little upward, so the stream of oil and spray of steam would strike the opposite wall a few inches above the bottom if it would pass clear across the fire-box. 13. Q. In starting or closing the throttle of the locomotive, how should the fireman regulate the fire, in advance or after the action of the engineer? A. In starting an oil burning engine the oil should gradually be brought up as the throttle is opened and the movement and amount of oil should be kept slightly in advance of the action of the engineer in order to prevent an inrush of cold air as the engine is working, which would result in injury to the fire-box and flues. When the throttle is to be closed, the fire should be reduced very slightly in advance of the closing of the throttle. This is to prevent the engine from popping off and black smoke drifting back over the train. 14. Q. Is it necessary that the engineer and fireman on an oil burning locomotive work in perfect harmony and advise each other of intended action at every change of conditions? A. Yes; they should work in harmony with each other on any locomotive. The fireman should watch every move the engineer makes, and the engineer should advise the fireman of every intended change of the throttle, so he can operate his valves accordingly and save fuel and avoid black smoke. 15. Q. What is the effect of forcing the fire on an oil burning locomotive? A. Forcing the fire is very hard on fire-box sheets and flues, and will cause them to leak. An even temperature should be maintained in the fire-box of any locomotive. 16. Q. Is a careful regulation of steam and oil valves and dampers necessary to obtain the most economical results? A. Yes; the fireman's oil valve should be opened just wide enough to permit a sufficient amount of oil to be fed to produce a good fire, but not wide enough to waste oil or produce a volume of black smoke. 17. Q. How can you judge whether the combustion is good or bad, so the valve may be regulated accordingly? A. By the color of the fire in the fire-box. When it is a dull red color, the temperature is below 1,000 degrees and combustion is incomplete, dense black smoke will issue from the stack. If it is a bright red, the temperature will be about 1,800 degrees and combustion very good, and no black smoke will appear from the stack. 18. Q. How should the flues be cleaned from soot when running, and about how often is this necessary? A. By placing a small quantity of sand in an elbow shaped funnel or horn, and by inserting same in an opening provided in fire door while engine is working hard, allowing the exhaust to draw the sand through the flues, thus cutting soot and gum from them in its passage and discharging it from the stack. It is necessary that the flues be cleaned of soot on leaving terminals or sidings where the engine has been at rest for any length of time, and also as often as found necessary to aid the engine in steaming. This depends to a great extent upon the degree of perfection with which combustion is obtained. Attention should also be given flues just prior to entering points where engine is to be put in roundhouse or otherwise detained in order to leave the flues clean, as this will aid in putting engine under steam with little delay where the blower alone is to be relied on for draft. 19. Q. Is the injudicious use of the blower particularly injurious on an oil burning locomotive? A. Yes; the injudicious use of a blower is injurious to any boiler. The cold air drawn through the fire-box is hard on the sheets and flues and will cause them to leak. 20. Q. Is the blower more injurious when a light smoke is emitting from the stack or when a dense black smoke is emitting? A. It is most injurious when a light smoke is emitting. 21. Q. In drifting down long grades should the fire be shut off or burned lightly? Why? A. The fire should be burned lightly and not permitted to get low enough to allow the fire-box to lose its temperature, as this will contract the flues and cause them to leak. 22. Q. How should the fire be handled when switching? A. The fire must be regulated to meet the requirements of the work the engine is performing on each move and to protect against any possibility of the fire being drawn out by the exhaust. 23. Q. Would not some fuel be wasted in this way? A. Not necessarily. A waste of fuel can be avoided by close attention on the part of the fireman when switching as well as when running. 24. Q. How should the fire be handled when leaving stations? A. It should be burning brightly and strong enough to prevent the draft from putting it out when the throttle is opened. And a little smoke should show up at the stack, which would indicate that the fire was being forced just a little ahead of the working of the engine. 25. Q. Which is desirable, to use as much or as little steam jet atomizer as possible? A. It is desirable to use as little atomizer as will make engine show perfect combustion and economy. 26. Q. What is the result of too little steam jet atomizer when standing at stations or when the engine is working light? A. The result of too little atomizer when standing at station or when engine is working lightly, will result in the oil not being carried far enough into the fire-box or arch and not properly atomized and the fire is liable to go out. The oil will drop from the mouth of the burner into the draft pan to the ground where it is very liable to start a fire under the engine. 27. Q. If too much steam jet atomizer is used with a light fire? A. It will create a disagreeable gas, which will cause the fire to burn with a succession of light explosions and kicks, also a waste of steam, and which would reduce the fire-box temperature. 28. Q. When the fire kicks and smokes, what should be done? A. The atomizer should be adjusted. If this does not overcome the trouble, the heater should be put in service, for, possibly, the oil is too cold to flow freely. Another cause of the fire kicking and smoking results from water being mixed with the oil. If this is the case, it should be drained out of the oil tank immediately. 29. Q. How should the dampers be used on an oil burning locomotive? A. They should be opened just enough to admit sufficient air to produce perfect combustion, but not enough to cool the fire-box. The dampers should be closed when the engine is drifting or when at rest and the fire is cut very low or is out entirely. 30. Q. About how much smoke do you consider an oil burning locomotive should make under adverse conditions, when the engine is steaming well, but is being crowded by the engineer? A. Only a light smoke should show at the stack. 31. Q. What color is most desirable at peep holes in the fire-box? A. A white color is most desirable. 32. Q. What will produce the bright red color? A. Leaky steam pipes, side seams, flues and improper combustion will produce a ruddy color in the fire-box. 33. Q. How does water in the oil affect the fire? A. Water in the oil will produce popping or kicking with the fire in the fire-box and at times the fire will die down entirely and then flash up as the water disappears and the oil reaches the burner. The most noticeable result of water in the oil is the fact that the fire will get very low. It will almost go out entirely and then will suddenly flash up again as the oil appears. Water in the oil produces a very dangerous condition and should be prevented immediately by draining the water from the fuel oil tank. 34. Q. Do you consider it advisable to keep the burners clean, and how often? A. When equipped with steam blow-out pipes, they should be blown out before commencing trip so that burners will distribute oil evenly to each side of fire-box. 35. Q. What position should burner be with reference to level and in line with center of fire-box? A. It is very essential that burners be level and throw flames just to clear floor of arch in order to derive full benefit of heating surface, as the draft has a great tendency to elevate flames, at opposite end of the fire-box. 36. Q. Are you aware that in course of time the atomizer port will become worn too large and will discharge too large a volume of steam to properly atomize, and the remedy? A. Yes; the lip or bushing should be closed to proper opening so that steam will be restricted at the nozzle and escape with a bursting effect to properly atomize the oil instead of flowing out in quantities against flash walls before it has time to ignite. 37. Q. What is the real object of having the fire-box lined with bricks, and will engine steam without them? A. Not so well as with the brick, the sheets being in contact with water are too cool to flash the oil readily and hence the use of what is called a "flash wall" built of fire brick and heated to a very high temperature aids combustion very materially. 38. Q. Do you consider it your duty to keep close inspection of brick work as to need of repairs, such as air entering between brick and side sheets? A. Yes. To see that plaster is kept between the walls and sheets to keep cold air from being drawn in. 39. Q. Will engine steam if brick falls in front of burners or in path of flame and what may be done? A. No. Remove them with the brick hook or rod by pulling them out through damper of draft pan. 40. Q. Where engine is equipped with an oil-reheater or oil line, do you consider it a help to engine's steaming qualities when used? A. Yes; at all times this heater should be used. 41. Q. Why use second heater? Why not heat it to a high temperature in oil tank with oil heater? A. Too much gas generating and boiling the oil continually destroys the higher qualities besides being hard to control the flow through regulation valve. 42. Q. Do you consider a vent hole in oil tank advisable, and why? A. Yes; to allow any accumulation of gas to escape and to admit the air so that oil will flow freely. 43. Q. Do you inspect your oil pipes and report all leaks? What other bad effect has a pipe leak aside from waste of oil? A. Yes. It will cause oil to feed irregularly. 44. Q. Are you aware that keeping the flues clean is the greatest one thing that you can do in regard to fuel economy, and how often should they be cleaned? A. Yes. At least every ten miles. 45. Q. Do you know that the engine should be working hard and at a speed not less than twenty miles per hour when sanding flues to avoid the sand falling to floor of the fire-box and accumulating in front of them? A. Yes. 46. Q. Do you realize that on first closing throttle you should not adjust fire too low? Explain best method. A. Yes. I would allow steam pressure to fall back some fifteen pounds before throttle is closed and on having closed same leave a good fire in box, allowing it to cool gradually to avoid leaky flues, broken staybolts, cracked sheets caused by sudden fall of temperature. 47. Q. How is the flow of oil controlled? A. By the valves in tank and pipe connections. 48. Q. Name these valves, their location and purpose. A. The safety valve controls the flow of oil from the fuel oil tank through an opening in bottom sheet of tank to the pipes leading to burner. This valve is forced to its seat by a heavy spring and is held off its seat by a key in the upright rod extending above the top of tank. To this key a rope or chain is attached and also attached to the cab to cause the pin in rod to be pulled in case of a separation between engine and tank and allow the valve to be seated by its spring and avoid a waste of oil. The second or main oil valve is located in oil pipe under deck leading to burner. It is usually of the plug-cock pattern connected by bell crank and this connected to some part of the engine by chain, in which case it also acts as a safety valve in case of separation between engine and tender. In other cases it is connected by an operating rod extending above deck of tender where it can be operated by hand in case of safety valves failure to shut off the flow of oil. The third or firing valve is usually located between heater box and burner, and is provided with an upright rod extending into cab where it is provided with a handle or lever in position to be conveniently handled by fireman while seated in cab. This valve regulates the flow of oil desired to reach the fire. 49. Q. When shutting out fire which valve should be closed first? Why? A. The safety valve. To allow the oil in pipes to be consumed and to see that this valve is in working order. 50. Q. Should safety valve fail to shut off the flow of oil in such cases would it be safe to rely on the firing valve to shut off the fire? A. No. The main valve should then be closed. 51. Q. Should the firing valve be depended upon to shut off the fire at any time? Why? A. No. From constant use they are frequently leaking and the trouble is not detected while in use, and again there is always danger of the handle being moved by workmen or others about the cab. 52. Q. What is a heater box? A. It is an apparatus having two passages, one for steam passing from boiler to heater pipes in tank and another passage for oil from tank before it is delivered to burner. In this manner the oil before reaching the burner is heated much higher than the temperature of that contained in tank. 53. Q. In the event of the heater pipes or connections becoming defective, how could the oil be heated in tank? A. By closing the firing valve, closing the valve on heater pipe, and opening valve on heater box, the steam from heater throttle can be passed directly through the oil feed pipe to the fuel supply. 54. Q. In the event of an objectionable quantity of water in oil, how can it be removed? A. In some instances the tanks are provided with drain pipes for this purpose, but in the absence of same, the feed hose or pipe between engine and tank can be disconnected and used as a drain to fuel oil tank. 55. Q. What effect has leaks between fuel tank and firing valve? A. A waste of oil only. 56. Q. What effect has leaks between firing valve and burner? A. In addition to a loss of oil while fire is burning low, and but little steam atomizer being used, it interferes very materially with the engine's steaming by admitting air when using considerable steam atomizer. This causes a very irregular oil feed. 57. Q. What action of the fire would indicate leaks in pipes between firing valve and burner? A. The fire-box will give off sounds similar to slight explosions, and the smoke at stack will indicate irregular fuel feeding. 58. Q. What would you consider the proper adjustment of burner? A. That which will provide for the delivery of the oil from burner to flash wall without striking arch, side walls, or floor brick while doing so. 59. Q. In case it becomes necessary to fire up an oil burning engine with wood, what parts should be given particular attention? A. The brick work. To see that same is not damaged or displaced while placing the wood in fire-box, also to protect by placing brick over that portion of burner extending into fire-box ahead of mud ring, or by so arranging the wood in fire-box as to prevent any great amount of heat from reaching the burner and melting nozzle of same. 60. Q. In case of sudden drop in steam pressure, what might be the cause? A. Loose brick perhaps fallen in front of burner and obstructed the flow of oil. The petticoat pipe may be loose and out of line or the dampers may have fallen shut. 61. Q. In case brick have fallen in front of burner, how can they be removed? A. By a hook provided for that purpose. They can usually be forced out through the vent openings, but if this cannot be done, they should be thrown against the blast wall in order to get them as far as possible out of the course of the fuel feed. 62. Q. In case a petticoat pipe becomes deranged, what can be done? A. In case it cannot be put back in proper position, it should be removed altogether. (Trips have been successfully completed in this manner.) 63. Q. Will a corroded burner mouth prevent the proper delivery of fuel to fire? A. Yes. 64. Q. What causes the mouth of burner to corrode? A. The asphaltum and sand contained in the oil. 65. Q. How can this be removed on the road? A. By having a hook or rod provided with a point that can be inserted into mouth of burner. 66. Q. Why should a fuel oil tank not be filled to its holding capacity? A. Because when heater is applied the oil would expand and overflow. 67. Q. In case of derailment or other accident that might cause the fireman to desert his position in cab, what should he do? A. Pull key out of safety valve rod, thereby allowing oil feed from tank to be shut off. =MECHANICAL EXAMINATION= THIRD SERIES 1. Q. What are the duties of an engineman before attaching a locomotive to the train? A. He should make a complete inspection of the locomotive, observing all important nuts and bolts, look for any signs of hot bearings on previous trip, see that the engine is equipped with necessary tools and supplies, test both of the injectors and the air brake equipment to be sure they are in good working order, see that headlight and signal lamps are in place and ready for service, observe water conditions in boiler, inspect the interior of the fire-box and see that the locomotive is properly lubricated. 2. Q. What tools should there be on the locomotive? A. Such as are necessary to properly operate the locomotive, care for the machinery, disconnect and block up in case of breakdown and the necessary firing tools. 3. Q. What examination should be made after any repair work has been done on valve, brasses, etc.? A. See that brasses are properly fitted, keys fastened and nuts made tight. If any repairs have been made on valves or valve gear, would see that the reverse lever could be moved freely and that all movable parts had been properly replaced; would also give especial attention with reference to lubrication of these parts. 4. Q. What attention should be given to boiler attachments, such as gauge cocks, water glasses, etc.? A. Would see that the gauge cocks can be opened to try the water and closed, so steam and water would not come out into cab. Observe the water glass and note if water is moving up and down in the glass, see that the steam valve at the top and water valve at bottom of glass could be opened and closed, and allow water and steam to circulate freely through the glass. 5. Q. What do you consider necessary to report on locomotive boilers? A. Should report all defects on boiler and its attachments while engine is in engineer's charge. 6. Q. Trace the steam from the boiler through the cylinders to the atmosphere and explain how it transmits power. A. Steam enters the throttle valve located in the highest part of the dome in order to get the driest steam, then passes through the standpipe and dry pipe out of the boiler to the steam pipe tee or nigger-head located in the front end, then through steam pipes to the steam chest. A steam valve in each steam chest distributes the steam so that it enters the cylinders at or just before the beginning of the stroke; pushing the piston to the end of its stroke; just before the piston reaches the end of the cylinder, the steam valve opens communication to the exhaust port through a cavity in its exhaust side, then through the exhaust pipes and tips up through the draft or petticoat pipe and stack to the atmosphere. When steam pushes the piston through the cylinder, its power is transmitted by the main rod to the main crank pin which causes the wheels to revolve, thus moving the engine and its train. 7. Q. Why is it important that there be no holes through the smoke-box door or front end and none in smoke-box seams or joints? A. So as to maintain as good a vacuum as possible in the smoke-box and prevent small amounts of air coming in through leaks which tend to heat and warp the smoke-box and its door. 8. Q. How should the locomotive be started to avoid jerks, and what train and other signals should be looked out for at the time of starting? A. Place the reverse lever in full gear, open the throttle valve gradually so as to start the train one car at a time and easily. Look for signals ahead to show that the track is clear and switch is in correct position, then look for signals from the rear end that the train is all coming. 9. Q. Will an engine equipped with superheat units move as quickly as a saturated steam locomotive when throttle valve is first opened? A. No. 10. Q. Why? A. Because steam must first pass through superheat units before it enters the steam pipes leading to steam chest. 11. Q. In placing engine on the turntable, at water or stand pipes, or at other similar places, what must be done? A. Close throttle valve sooner so that the steam confined in superheat units, pipes and steam chests, will have passed out to the atmosphere. 12. Q. After a locomotive has been started, how can it be run most economically? A. By regulating the supply of steam to the steam chest with the throttle and the point of cut-off with the reverse lever; so that no more steam be used than necessary to maintain the proper speed, whenever possible working the engine at short cut-off so as to use steam expansively. 13. Q. What is meant by working steam expansively? A. Hooking the reverse lever up toward the center gives the valve a shorter travel and closes the live steam port when the piston has made only a part of its stroke. This cuts off the supply of live steam coming from the steam chest. The expansion of the steam already in the cylinder pushes the piston to the end of its stroke without the use of a full cylinder of live steam. 14. Q. How rapidly should water be supplied to the boiler? A. No faster than it is evaporated into steam, unless just before a hard pull; or when shutting off with a heavy bright fire in the fire-box to prevent waste of steam at the pops. 15. Q. What is the difference between priming and foaming of a locomotive boiler? A. Priming is caused by carrying the water too high in the boiler so that when the throttle valve is opened some of it passes over with the steam in the form of a spray. Foaming is caused by the water becoming dirty from animal or alkaline matter, so that heat makes it foam like soap suds. Muddy water or certain vegetable matters will also make a boiler foam. 16. Q. What should you do in a case of foaming? What in a case of priming? A. In a case of foaming, if possible, allow the boiler to cool off a little, increase the supply of feed water to prevent water getting too low, and whenever possible blow some of the dirty water out of the boiler, replacing it with clean water. In case of priming, shut off the supply of feed water until the water level drops to the proper height in the boiler. 17. Q. What danger is there when the water foams badly? When it primes badly? A. There is danger of knocking out cylinder heads, cutting the valves, stalling on some grade or getting on some train's time because the engine cannot be worked to its proper power. When shutting off steam, the water is liable to drop below the crown sheet and thus risk burning the fire-box. When water primes badly, it is liable to break cylinder packing rings, knock out cylinder heads, break bolts in the steam chest and cut the valves. In such a case additional oil should be fed to the steam chest until the valves are properly lubricated. 18. Q. Suppose that with the water glass in good working order, immediately after closing the throttle the water disappeared from the water glass, what should be done? A. Would open the throttle and endeavor to raise water until both injectors would put enough water into the boiler to make it entirely safe to close the throttle. If unable to raise the water level to the lower gauge cock would smother the fire or put it out entirely, if necessary, keeping both injectors working. 19. Q. What work about a locomotive should be done by the engineman? A. Inspection of the engine both before and after the trip. The engineer should do any necessary work on the engine after starting out on the trip to avoid breakdowns and insure getting over the road promptly. This means tightening up any important bolts that work loose on the trip and keeping parts from working out of position, adjusting wedges and rod keys. 20. Q. How should the work of setting up the wedges be done? A. Place the engine on the upper quarter on the side with the loose wedge. Do not set the brake if brake shoe will push the driving box against the defective wedge, but block engine truck wheels so the engine cannot move, push the boxes against the shoe or dead wedge with a little steam, set the wedge up until it is a snug fit, then pull it down about one-sixteenth of an inch and fasten. Provision should be made for expansion of the box when it gets warm. 21. Q. How should rod brasses be keyed? A. If properly fitted they should be keyed brass to brass; if not so fitted, they should be keyed on the large part of the pin so they will be free enough to run without heating and snug enough to run without pounding. Do not key them so tight at either end as to prevent the lateral motion of the brass on the pins. 22. Q. How should an engine be placed for the purpose of keying the rod brasses? A. For the main rod, place the engine on the quarter or the top forward eighth, whichever place gives the largest diameter of the pin to key the brass against. After keying up, test by moving the wheel to another position and see if brasses are free on the pin. For the side or parallel rods, always place the engine on the center for the side that is to be keyed. 23. Q. How should the side rods on a mogul or consolidation locomotive be keyed? A. Place the engine on the center on that side, key up the brass on the main pin first, work each way toward the ends of the rods, being careful to keep them the proper length so they do not bind when passing either center. Be sure that wedges are properly set up before keying the side rods. 24. Q. What is the necessity for keeping the brasses keyed up properly? A. If too tight, they will surely run hot; if too loose, they will pound and injure the brasses as well as endanger the safety of the straps and rod bolts. Very loose brasses can pound enough to get hot. 25. Q. What is meant by an engine out of tram? Out of quarter? A. When corresponding wheels on opposite sides of the engine on different axes are not spaced equally apart; where the axle of any wheel is not at a right angle to the center line from front to rear of engine, so they do not run square on the rails, or where the space between the axle centers on opposite sides is not equal. This is sometimes indicated by unequal flange wear and should be reported at once. Wheels are out of quarter when the crank pin in one wheel is not exactly 90 degrees or one quarter of a turn from the pin in the wheels on the other end of the same axle. This is usually caused by slipping the engine with sand on one rail only and the condition of engine should be reported at once. 26. Q. Describe a piston valve. A. A piston valve is a cylindrical spool-shaped valve constructed with packing rings much the same as the steam piston that moves through the cylinder, except that a piston valve is double or composed of two pistons connected by center rod or spool working in a bushing of equal diameter. Steam and exhaust ports are cut through this bushing; steam ports to the cylinder and exhaust port to the exhaust pipe. There is also a steam port for live steam from the boiler. As the pressure on this valve is equal in both directions it is practically balanced. 27. Q. What is a balanced slide valve? How is it balanced, and why? For what purpose is the hole drilled through the top of the valve? A. One in which the steam pressure on the top and bottom of the valve is nearly equalized. This is done by protecting a portion of the top of the valve from the steam pressure. It is usually balanced by strips held against the pressure or balance plate by one or more springs. This is done to prevent live steam from getting on top of valve and thus relieve the valve from the top pressure which would cause excessive friction between the bottom of the valve and its seat. The hole through the top is to allow any steam which might leak by the strips to pass into the exhaust, so pressure could not accumulate on the top of the valve, also to equalize the exhaust pressure between the top of the valve and exhaust cavity as well as to assist in lubricating the balance plate. 28. Q. What is meant by inside and outside admission valves? A. With an inside admission valve (usually a piston valve), the live steam comes between the piston valve heads, the outside end of the heads being connected with and exposed to exhaust pressure, it admits steam past the inside edges of the valves. An outside admission valve has the space between the ends connected to the exhaust and a space at the ends connected with the live steam. It admits steam past its outside edges. A piston valve can be either inside or outside admission, while a slide valve is always outside admission. 29. Q. What is the relative motion of the main piston and the steam valves for inside admission, and, on the other hand, for outside admission? A. If the piston is in the front end of the cylinder, an inside admission valve must move forward in order to connect the inside of the valve with the front live steam port to admit steam against the piston. The outside end of the valve opens the exhaust port for the back end of the cylinder. In the same position of the piston an outside admission valve must move backwards to open the steam port or in the same direction as the steam piston when commencing its stroke. 30. Q. What is an Allen ported valve, and what is its object? A. An Allen ported valve is an outside admission slide valve having an extra port from one end of the valve to the other, above the exhaust cavity and through the body of the valve. This extra port is calculated to admit steam through the valve at the same time that steam passes by the end of the valve into the same steam port, thus doubling the area of opening for live steam when the port is first opened. 31. Q. What is the difference in the valve motion for outside admission valves and for inside admission valves? A. An outside admission valve must be moved in the opposite direction to an inside admission valve in relation to the movement of the steam piston when beginning its stroke; therefore either the position of the eccentric or the position of the rocker arms in relation to the rocker shaft must be opposite for a change in these valves. 32. Q. What is a direct motion valve gear? What is an indirect motion valve gear? A. A direct motion valve gear is one in which the valve moves in the same direction as the eccentric rod, that is doing the work, in many cases no rocker arm is used. In case a rocker arm is used, both arms point in the same direction like the letter U. An indirect motion valve gear is one in which the valve moves in an opposite direction to the eccentric rod doing the work. A rocker is used in which the arms point in opposite directions from the shaft connecting them. Owing to the design and construction of the Walschaert valve gear, it is a direct motion gear when the engine is running in one direction with the link block in the bottom of the link, an indirect motion when the engine is running in an opposite direction with the link block in the top of the link; usually direct motion when running forward. 33. Q. How can you detect the difference between a blow in valve or piston packing? A. A blow from the valve is more constant and has a somewhat different sound, while a blow from cylinder or piston packing will blow stronger at the beginning of the stroke and gradually decrease as the stroke is completed. 34. Q. How would you place engine to locate broken admission steam ring in piston valve? A. Would place engine on quarter, reverse lever in center so as to cover ports, then open throttle; and the steam will blow out of cylinder cock at the end of cylinder where broken valve ring is located. 35. Q. How would you locate broken exhaust ring in piston valve? A. Watch the cross-head when engine is working steam. As there will be three normal and one light exhausts, you can determine on which side of the engine the light exhaust takes place. 36. Q. What is meant by lead? What by line and line? A. Lead is the amount of port opening for live steam to cylinder ahead or back of piston when the piston is on the dead center. If the steam edge of the valve is in line with the edge of the steam port when the piston is on the center, it is said to be line and line. 37. Q. What is meant by steam lap? A. The distance that the valve overlaps the live steam edges of the steam ports when it is in the center of its travel over the seat. This distance is measured at one end only, although the valve laps equally at both ends. 38. Q. What is meant by exhaust lap? What by exhaust clearance? A. Exhaust lap is the distance that the exhaust edge of the valve overlaps the exhaust edge of the steam port when the valve is in central position. Exhaust clearance is the opening between the exhaust edge of the valve and the exhaust edge of the steam port with valve in central position. If the valve has neither exhaust lap or clearance it is said to be line and line. 39. Q. What is meant by release? What by compression? A. Release is the point in the travel of the piston when the port is opened. Compression is the distance the piston travels after exhaust port closes before the live steam port opens. During this travel of the piston the exhaust port is closed so the moving piston compresses the steam left in the cylinder. 40. Q. With an indirect valve motion and outside admission valve, what would be the position of the eccentric relative to the crank pin on that side? What with a direct valve gear? What difference between outside admission valve and inside admission valve as to this position? A. With an indirect valve motion and an outside admission valve, the go-ahead eccentric follows the crank pin with engine running ahead. Without any lap or lead it would be a quarter of a turn or 90 degrees behind the pin, but as all valves have lap and lead, the eccentric is advanced or placed toward the pin enough to move the valve the amount of the lap and lead. With a direct valve gear and an outside admission valve, the eccentric will be a quarter of a turn or 90 degrees ahead of the crank pin and advanced enough to move the valve the amount of the lap and lead. With an inside admission valve and an indirect valve motion, the eccentric will come the same as for an outside admission valve and direct motion, or more than a quarter of a turn ahead of the pin. With an inside admission valve and direct motion, as piston valves are usually put up, the eccentric will follow the pin less than a quarter of a turn. 41. Q. What effect would be produced upon the lap and lead by changing the length of the eccentric rod? A. Lap depends on the construction of the valve. A change of the eccentric rod would not effect it, but would widen the port opening at one end of the travel and reduce it at the other. It should be equal at both ends. Lead is controlled by the position of the eccentric on the axle and it must be equal at both ends. Changing the length of the eccentric rod from the proper one does not really affect the lead, because no proper measurement can be made until lead is equal at both ends. Therefore improper length of eccentric rods varies the port opening at the beginning of the stroke of the piston at both ends. 42. Q. Why are eccentric rods made adjustable? A. In order to change their length to make adjustment of the valve gear not as easily made in other ways. 43. Q. Why is it necessary to keep the cylinders free from water? A. In order to avoid damaging valves and cylinders, to insure perfect lubrication and obtain the most efficient service from the locomotive. 44. Q. Where is the piston rod packing located? Where cylinder packing? A. Piston rod packing is usually soft metallic rings located inside of a gland at the back end of cylinder and around the rod. Cylinder packing rings are usually cast iron, placed around the piston head and bearing against the walls of the cylinder. 45. Q. How are metallic packing rings on piston rods and valve stems held in place? What provisions are made for the uneven movements of the rod? A. The packing rings fit into a vibrating cup or cone located inside the gland, being held therein by means of a spring as well as by the steam pressure. Provision is made for uneven movement of the rod by making the inside of the gland larger than the vibrating cup and using a ball-joint ring between the vibrating cup and gland. 46. Q. While running under steam and there is a failure of part of the locomotive which does not seem to prevent running at full speed, how would you proceed? A. Keep the locomotive running if in your judgment it is safe. Try to ascertain what the injury is and be prepared at the next stop to do such work as the case demands, being careful to make the stop at such a place that the work can be done without interfering with the movements of main line trains. 47. Q. If one side of a locomotive is disabled, what would you do in a general way to make it possible to use steam on the other side? A. Disconnect enough parts to allow for the turning of the wheels and for reversing of the opposite side without moving the valve on the disabled side. 48. Q. In case a locomotive in your care became disabled on the road, what would you do? A. First see that the train is protected. Next examine the locomotive and see what is necessary to do to move it and if possible the train. If unable to make repairs at once to bring the engine and train forward, would advise exact condition of engine and ask for help. In the meantime endeavor to move the train so as to give other trains the use of the main line. 49. Q. Suppose a wash-out plug blew out or a blow-off cock broke off or would not close, what should be done? A. Kill the fire, get the train on a side track, if possible, and if unable to make repairs get the engine in condition to be towed in. In all cases with a disabled engine allow the train to drift to a siding, when possible, and stop between the switches so as to allow other trains to pass through siding. 50. Q. Can a locomotive boiler without steam pressure be filled by being towed by another engine? If towed, how filled? A. Yes. Close all openings where air could enter the boiler. All relief valves, cylinder cocks, gauge cocks, the whistle valve and air pump steam valve should be closed. Place the reverse lever in full gear in the direction the engine is to be towed with water supply valve and injector throttle open. Use engine oil through auxiliary oil cups to oil valves and pistons. The movement of the pistons in the cylinders will pump the air out of the boiler and atmospheric pressure on water in the tank will force water into boiler when the engine is towed. 51. Q. What should be done if grates should be burned out or broken while on the road? A. Pull the fire off the broken or burned grates, cover that section with any pieces of iron at hand (fish-plates or angle-bars are very good), then level up the fire, clean ash-pan and proceed with full train. 52. Q. What precaution should be taken to prevent locomotive throwing fire? A. The netting and smoke-arch should be kept in good condition; cinder slide and hand hole plates securely fastened, ash-pan clean and slide dampers for dumping ashes closed. Care should be exercised in working the engine, especially in the vicinity of stations or places where fire is liable to catch. Avoid working the engine hard so as to prevent throwing cinders. 53. Q. What shall be done with a badly leaking or bursted flue? A. Plug it if possible with an iron or wooden plug. If in the fire-box end, a piece of scantling or post can be sharpened and driven into the flue from the fire-box door; it will then burn off up to where the water from the bursted flue keeps it wet. If a bottom flue, would cover it with ashes or green coal so that the leakage would not put out the balance of the fire. If able to maintain steam pressure, would then proceed with a full train. 54. Q. What should be done in case the throttle valve stem became disconnected while the valve is closed? If it became disconnected leaving valve open? A. Would notify the train crew and Dispatcher and arrange to be towed in. With lubricator working, unless in very cold weather so there is danger of the water freezing in the cylinders or steam chest passages, would not disconnect. By taking out lubricator chokes and steam chest valves from the oil pipe, a larger supply of steam could be got into the cylinders. If in to clear of other trains and practicable, would take up the dome cap and connect the throttle again. If disconnected and valve stuck open, would notify the train crew and Dispatcher, reduce steam pressure until the engine could be handled with reverse lever and brake, and proceed with such a train as the engine can handle. 55. Q. In case a valve yoke or stem became broken inside of steam chest, how can the breakage be located? A. In this case the disabled valve is always pushed to the front end of the steam chest so that with a slide valve or outside admission piston valve the back port is open to live steam. When given steam, the engine will stop on the eighth, and when reversed will move over to the other eighth, being stopped there by the live steam in the back end of the cylinder having the disabled valve. Steam will blow from the back cylinder cock on the disabled side and cannot be changed by reversing the engine. If the valve is pushed far enough ahead to open the exhaust port, steam will blow through the exhaust so the engine cannot be moved. With an inside admission valve the forward steam port will be opened and steam will come out of the forward cylinder cock on the disabled side. 56. Q. After locating a breakage of this kind, how would you proceed to put the engine in safe running order? A. Would move the valve to central position so as to cover both steam ports, if possible. This may be done by taking out the relief valve if on front side of the steam chest and pushing valve back, or taking up the cover for a slide valve; or taking off front head for a piston valve. Disconnect the valve rod from rocker arm and block valve stem so it cannot blow out of the gland or let valve work back. Loosen cylinder head in order to provide for lubricating cylinder so as to leave the main rod up on the disabled side and proceed on one side. If unable to cover the open steam port it would be necessary to disconnect the main rod on the disabled side, blocking the piston at the proper end of the guides so live steam coming into the cylinder would not move it. 57. Q. If a slide valve is broken, what can be done to run the engine on one side? A. Remove the steam chest cover, place a thin board between the valve and the steam passages in the seat, replace steam chest cover, disconnect valve rod, and if able to lubricate the cylinders leave up the main rod and proceed on one side. 58. Q. If one of the bolts connecting the two parts of a built-up link on Stephenson gear breaks or is lost, how would you proceed? A. If temporary bolt cannot be supplied, take down the forward part of the link, disconnect and remove link block, fasten valve to cover ports, and proceed. If moving link will clear rocker arm or other parts of the machinery after link block is taken out, it will not be necessary to disconnect eccentrics. 59. Q. What should be done in case of link saddle pin breaking? A. Remove the broken parts and block the disabled link in such a position that the entire train could be started, using a very short block above the link block in the link slot and a longer one below it. 60. Q. With one link blocked up, what should be guarded against? A. Reversing the engine or moving the tumbling shaft arm down so the link on the disabled side can strike it. 61. Q. How can it be known if an eccentric has slipped on the axle? A. By the uneven exhaust of the engine and a thorough inspection to determine the cause. 62. Q. Having determined which eccentric has slipped, how should it be reset? A. Place the engine on the center on disabled side and if a back-up eccentric has slipped, would place the reverse lever in full forward gear and mark the valve stem flush with the gland; then place the reverse lever in full back gear and move the slipped eccentric until the mark on the stem returns to its original position, taking notice that the throw of the eccentric is on the other side of the axle from the go-ahead eccentric used as a marker, and tighten up set-screws. To set a go-ahead eccentric, use the back-up one on that side for the marker. If the eccentric had been keyed on, would move the cam until the key-way in the axle came in line with the slot in the cam. Knowing the position of the eccentric in relation to the crank pin, an inspection would show where it belongs. The eccentrics are usually opposite the third spoke in the driving wheel from the pin, sometimes ahead of the pin, in other cases back of the pin, depending on whether it is an inside or outside admission valve, a go-ahead or back-up eccentric. 63. Q. What should be done in case of a broken eccentric strap or rod? A. For a go-ahead strap or rod take down all broken parts, disconnect valve rod, cover ports, and come in on one side. It is safer to take down also the back-up strap and rod on that side. If the back-up strap and rod is broken, it is possible to secure the bottom end of the link so it will not turn over, work the engine full stroke ahead, proceeding with full train until the main line is clear. 64. Q. How should the engine be disconnected if the lower rocker arm became broken? If link block pin? A. Would remove broken parts; if moving link would strike anything connected with the rocker box or broken arm it would be necessary to take down both eccentric straps and rods. Block valve central over ports and come ahead on one side. If a link block pin was broken, it might be possible to put a bolt in there to do the work, otherwise block the valve on the center of its seat and if the link will not clear the lower end of the rocker arm take down the eccentric straps and rod. In any case where necessary to take off the eccentric rod always take off the strap also. 65. Q. For what breakdown is it necessary to take down the main rod? The side rod? A. A broken main crank pin, broken main rod or strap, broken piston rod when near the middle of the rod, broken cross-head or guide, broken valve or seat when steam cannot be kept out of the cylinder. Side rods must come down for broken side rod, broken main pin, or broken side rod pin affecting that rod. 66. Q. If it is not necessary to take down the main rod of disabled side of the engine, how would you arrange to lubricate the cylinders? A. If cylinder and piston are in good shape and it is possible to block the valve to admit a small quantity of steam into the back end of the cylinder, oil from the lubricator will go through this opening and oil the piston rod and cylinder packing. If not possible to block the valve properly, cover the ports and oil the cylinder through the indicator plug openings or relief plug holes. If not possible to do this, slack off the bolts on the front cylinder head, wedge the head open so oil can be introduced. In some cases it may be necessary to take the head off; that however, allows dust and grit to enter the cylinder. 67. Q. What is the by-pass valve, and what is its duty? A. By-pass valves are connected to the steam port leading to the cylinder. Its duty is to open when the engine is drifting with steam shut off, and close when working steam, to allow air to pass back and forth from opposite sides of the moving piston. 68. Q. What is a vacuum relief valve? What a cylinder relief valve? A. A vacuum relief valve is usually located on the steam chest or the live steam passage to the chest and opens when steam is shut off and engine drifting, allowing atmospheric pressure to pass into the steam chest, closing when working steam. A cylinder relief valve is a pop valve screwed into the cylinder head and set at high enough pressure so it does not open in ordinary service, but will open to allow water to pass out when the exhaust port is closed by valves; or on compound engines when the pressure in the low-pressure cylinder gets too high. 69. Q. What would be considered a bad engine or tender truck wheel? A. One loose on axle; having bad flat spots; very sharp flanges; bad sand spots; cracks shelled out; or other defect that would make the wheel unsafe. 70. Q. What should be done if a tender truck wheel or axle should break? A. Would place a piece of timber or rail across the tender, jack up the corner of the truck that is disabled chain it to the timber and fasten the timber at the other end to hold it so it would carry the disabled truck. If it is possible to slide the wheel or truck, place a tie across the rail and keep the wheel from turning, then slide it to a siding. 71. Q. What should be done if an engine truck wheel or axle should break? A. Would block between the engine frame and truck frame over the good wheel on disabled side, swing the disabled corner of the truck to the engine frame with a chain. Look out when crossing frogs that disabled truck does not leave the track. With a broken flange, would block the wheel to prevent its turning and skid it to a siding. 72. Q. What should be done for a broken tender truck spring? A. Jack the tender up to where it belongs and put a block in place of the broken spring. 73. Q. What should be done with a broken engine truck spring or equalizer? A. For a broken spring, raise the front end of the engine and place blocks across the equalizers under the truck spring near the spring band. For a broken equalizer, block on top of engine truck boxes and under truck frame. 74. Q. What should be done if a driving spring hanger or equalizer should break? A. Would block between the driving box affected and under the frame over it, using hardwood block or piece of iron. Would also block the equalizer up to its proper position between the disabled end and the frame, or over the other end, as the type of spring rigging requires, to hold the equalizer level. For a broken equalizer, would block on top of all boxes affected, would raise the engine by running the proper driving wheels upon an incline or wedge to lift the engine while other boxes were blocked; a re-railing frog comes handy for this work. 75. Q. How can an engine be moved if the reverse lever or reach rod were caught at short cut-off by a broken spring or hanger? A. By removing the pin at the forward end of reach rod, to free the tumbling shaft and allow it to be moved either forward or back to move the engine. A block should be placed over the link block to avoid damaging it when uncoupled, as well as to hold link in proper position to move the engine. This would allow the engine to be moved and clear the main line. 76. Q. How can the blowing of steam past cylinder packing, a valve or valve strip be distinguished or located? A. Test for a leaky slide valve, place the engine on the quarter on the suspected side with the reverse lever in center notch; the valve should be in the middle of its travel and cover both ports. If steam blows through the open cylinder cocks on that side, the valve or seat are defective. A leaky balanced valve strip will allow steam to blow through the hole on top of the valve into the exhaust port in the seat and very little steam will come out of the cylinder cock; in some cases with the valve barely opening a steam port to the exhaust, air will draw in at the cylinder cock. If there is a drip cock in the exhaust pipe under the saddle, the steam will blow out there. After testing for leaky valve, place the engine on about the forward bottom or top back eighth, block the wheels or set the brakes solid, put reverse lever in corner, open cylinder cocks and give the engine steam. If steam comes out of both cylinder cocks, and testing valve shows it is tight, then the packing is blowing. Cylinder packing should be tested with steam first on one side of the piston and then on the other. 77. Q. If engine should blow badly and be unable to start the train when on the right dead center, on which side would be the blow generally? A. On the left side. If the side standing on the quarter cannot start the train, the trouble is usually there. 78. Q. If throttle were closed and steam came out of cylinder cocks, what might be the cause? A. To test for this, first shut off steam connection to the lubricator; steam leaking into the cylinders can come from a leaky throttle or leaky dry pipe. 79. Q. Is it possible to distinguish between a leaky throttle and a leaky dry pipe? A. Yes; a leaky throttle usually leaks steam at all times. A leaky dry pipe will leak both steam and water. It will show a stream of water at the cylinder cocks when the water level in the boiler is raised above the leak in the dry pipe. 80. Q. What effect have leaky steam pipes in the smoke-arch, and how should they be tested? A. Leaky steam pipes waste steam and very seriously affect the draft in the front end. A bad leak in the back part of the joint at the bottom will blow into the tubes and make the engine smoke at the door with throttle wide open while standing still. To test them, open the front door and cover the joint with fine cinders. When the engine is given steam, the cinders will blow away from the leak; to properly test them in the shop, water under heavy pressure should be used. 81. Q. How should the test for a leaky exhaust pipe joint, or a leaky nozzle joint be made? A. About the only test that can be made on the road is to open the front end and reverse the engine with throttle partly opened, watching the suspected joint at the same time. For the bottom one with cinders around the joint, for the top one it can sometimes be detected by holding a torch near the joint. 82. Q. What should be done if a steam chest cracks? A. Would loosen up the steam chest cover to free the sides, and wedge between the studs and walls of chest, crowding the broken parts together. A brake shoe key does this nicely. Would then tighten down on steam chest cover and proceed. 83. Q. What should be done if a steam chest breaks? A. Would take off steam chest cover, place strips of boards over the steam inlets and block on top of them so that the steam chest cover would hold them in place and prevent live steam coming out of inlet. Would then make the necessary disconnection and proceed on one side. 84. Q. If a link lifter or arm were broken, what should be done? A. Take off the disabled parts, block between the top of the link and link block, having the disabled link blocked down very nearly in full strokes. For safety, both the top and bottom of the disabled link should have blocks in its slot; the good link would be held in place by the reverse lever and should under no consideration be dropped down any farther than the disabled link was. 85. Q. If the reverse lever or reach rod should break, what should be done? A. If either breaks, place an iron bar or suitable piece of material across the top of both frames, securely fastening it in position, then fasten the arm of the tumbling shaft to the bar. This will require the engine to be worked at about half cut-off; handle such part of the train as the road conditions would permit. 86. Q. What should be done if the piston, piston rod, cross-head, main rod or crank pin are broken or bent? A. If a piston should break, would remove broken parts, disconnect valve stem, clamp valve in central position, and if moving piston would not damage cylinder, leave main rod up and proceed. If a piston rod, cross-head, main rod or crank pin are broken or bent, would take down the main rod, block the valve and cross-head; if piston rod is broken off at the cross-head, leave main rod up. 87. Q. What should be done when there is a loose or lost cylinder key? A. If the cylinder key is loose, it should be tightened up; if lost, something should be substituted. In case nothing solid can be found to take the place of the key, the engine should be run in light to avoid further damage. 88. Q. What should be done if a safety valve spring or stud breaks? A. The steam pressure should be reduced. With broken spring, screw the parts down solid or clamp the stem down. This can be done by laying a piece of scantling across the top of the valve, fastening each end to the hand rail on opposite sides of the engine in case of broken stud. Would then raise steam pressure and proceed. Care should be taken to see that the other safety valves relieve the steam pressure properly. 89. Q. How can an engine be brought in with a broken front end or stack? A. By boarding up the front end to make it as near air tight as possible and using a barrel or a petticoat pipe in place of the stack, wiring it fast to the smoke-arch. Where a portion of the stack is inside the smoke-box the engine might steam without the barrel or petticoat pipe. 90. Q. What should be done if the frame is broken between the main driver and cylinder? A. Either give up the train and come in light, or disconnect the engine on that side and come in with reduced tonnage, depending on how badly the engine pounds when working steam. 91. Q. If the frame is broken back of the main driver? A. Do not disconnect and do not try to pull a heavy train; it is safer to come in with light tonnage. 92. Q. In case of broken side rods, what should be done? A. Take down the broken rod and corresponding rod on the other side of the engine. 93. Q. What can be done if the intermediate side rods were broken on a consolidation engine having the eccentric on the axle ahead of the main wheel? A. In this case the engine must be towed in. It is possible when the main pin is broken, so that all rods on one side are taken off, to leave the rods up on the other side and move the engine with her own steam, but very few roads will allow this, because engineers will be inclined to leave the main rod up on the disabled side to prevent engine catching on the center. If main rod is left up on the disabled side, the wheels will surely slip and wreck the rods on the other side. 94. Q. Should one of the forward tire, main tire, intermediate tire, back tire, or a trailer tire break, what must be done to bring the engine up? A. Would run the wheel of the broken tire on a block in order to raise the wheel clear of the rail and the box up in the driving box jaws. Remove the oil cellar and place a block between the driving journal and pedestal brace to carry the disabled wheel center clear of the rail. Would also block up on top of the box of the wheel ahead or back as the case might be, in order to take the weight from the disabled wheel. It might not be necessary to take off any of the rods, but would run the engine light to the shop, giving special attention to lubrication of the disabled wheel and using extra precaution in entering side tracks and passing over frogs and switches. With the tire of a back driver or trailer wheel broken, it is usually necessary to swing the rear end of the engine from the tender to keep the rear end on the track. With an inside radial journal, box on the trailer axle; for a broken trailer tire, both trailer wheels must be blocked and swung clear of the rail. 95. Q. What is a good method of raising a wheel when jacks are not available? A. By raising the wheel on a hardwood block or iron wedge; a re-railing frog comes very handy for this purpose. 96. Q. How can it be known when the wedges are set up too tight and the driving box sticks, and in what manner can they be pulled down? A. If wedges are set up too tight, it causes the boxes to stick and the engine to ride rough. Inspection of the engine when moving will locate the disabled box; usually this gets hot at once and the wedges should be immediately pulled down. Loosen the jam nuts on the wedge bolts and back them down; if the wedge is stuck very tight it may be necessary to run one or more of the wheels over a block; or to loosen the pedestal, brace bolt and allow the jaws to spread to release the box. 97. Q. What are some of the various causes for pounds? A. Wedges not properly adjusted, loose or worn driving box brasses, rod brasses not keyed or in need of reducing, loose side rod bushings or side rod connections, worn cross-heads, wrist pins, broken frame, loose cylinder key, loose piston on rod, or rod loose in cross-head, loose follower bolts or obstruction in the cylinder. 98. Q. How may a pound in driving boxes, wedges or rod brasses be located, and after locating what should be done? A. Place the engine at half stroke on side to be tested. Do not set brake when testing for loose wedges or defective boxes; set brake when testing for other pounds. Reverse engine from forward to back gear under steam, noting the movement of the axle in the boxes, the driving boxes between the wedges, rod brasses on the pins and movement of cross-head between the guides. If possible would adjust wedges or rod brasses at once and report repairs needed at the terminal. 99. Q. How locate loose follower bolts? A. Shut off steam and allow engine to drift; there will be a pound in the cylinder when the loose follower bolt strikes a forward cylinder-head as the engine passes the forward center on that side; give engine steam while still moving and if the pound stops it is likely to be a loose or broken follower bolt. When working steam, the compression or pre-admission takes up the lost motion in the rod and connections, so the loose bolt does not strike the head; when shut off the piston travels the extra amount of this lost motion and the bolt strikes the head. 100. Q. When should cross-heads or guides be reported to be lined? A. When there is excessive lost motion between the cross-head and the top and bottom guides, or between the cross-head and the guide at the sides, or when the piston rod is not central between the guides. 101. Q. When should driving box wedges be reported to be lined? A. When they have been set up as far as possible and the boxes are still loose between the wedge and shoe. At this time would also report any excessive flange wear on any one particular tire. 102. Q. When should rod brasses be reported to be reduced? When to be lined? A. Rod brasses should be reported reduced when they are larger than the pins and are pounding and cannot be keyed up properly. They should be reported to be lined when the key has been drawn or driven to its full length and the brasses do not close together or are too loose in the strap lengthwise of the rod. 103. Q. When should lost motion between engine and tender be taken up? A. When the lost motion becomes so great as to endanger the breaking of connections. 104. Q. How do you proceed to pack a driving box equipped with a grease cellar? A. Remove the filling plate on the inside of the cellar. Pull down the indicators and follower plates, insert the grease between the follower plate and perforated plate; when full, replace the filling plate on the inside of the cellar and allow the spring and follower plate to force the grease through the perforated plate to the journal. 105. Q. Please explain the principle on which an injector works. A. With a lifting injector the steam valve is opened a small amount to furnish steam for the priming or starting jet. This forces the air in the body of the injector and top end of suction pipe out through the overflow valve, producing a partial vacuum in the body of the injector. Atmospheric pressure in the tank then forces the water into the injector body. When it begins to come out through the overflow, a further movement of the steam valve opens the forcing valve wide, so a full supply of steam strikes the water at a high velocity and at the same time condensing. This action of the steam gives the water sufficient velocity to overcome the boiler pressure and pass into the boiler. 106. Q. Explain the passage of steam from the boiler to the steam heat pipe. A. Steam is admitted to the steam heat pipe, in which there is placed a reducing valve through which it passes at reduced pressure, into the steam heat pipe under the entire length of the train. The reducing valve is located in the cab close to the steam heat throttle. 107. Q. If the steam heat gauge shows proper pressure, but the steam heat pipe pressure appears to be low, what should be done? A. If the steam heat gauge is showing the correct pressure, there is an obstruction in the pipe somewhere, most likely in the steam heat hose, and this should be looked for and remedied; if the gauge is correct, then it is the reducing valve that is at fault and this should be readjusted, as well as the gauge. 108. Q. What is the cause of failure with the second injector, and what should be done to obviate this failure? A. Lack of attention and failure to use every day will allow joints to work loose and boiler check to fill up with mud and scale. It should be tested every day and worked regularly so as to keep it in good working order. 109. Q. If an injector stops working while on the road, what should you do? A. Would first ascertain if sufficient water was in the tender and tender valve open, and that water was cool enough in the tender so the injector would handle it. Would next see that no obstruction was in the feed pipe or strainer and that the feed pipe was free from leaks, and that the injector was getting a sufficient supply of steam. If the injector would not prime, would see whether overflow or heater valve could open wide, or if overflow pipe was obstructed. If suction pipe was very hot would blow water back into tank and let suction fill with cold water. If possible, examine for obstruction in the steam priming tube and water tubes. If it would prime and fail to deliver water to the boiler, would see that the delivery tube was not obstructed and then look for trouble at the boiler check. An obstruction in the tubes would stop the injector working at once, while wear of the tubes or filling up with scale would affect the injector gradually. 110. Q. What are the advantages of the combination boiler check and stop valve? A. A combination boiler check is fitted with a valve similar to a globe valve and can be closed at will. Its advantage is that the boiler pressure can be shut off from the check and the valve repaired without cooling the boiler. This hand-operated valve can be closed to prevent the boiler water passing back in case the check valve sticks up and allows the boiler water to pass back to the injector when not working. 111. Q. How can a disconnected tank valve be opened without stopping? A. Close the overflow or heater valve and turn steam back toward the tank; this will usually lift the valve from its seat or turn it around so it opens. 112. Q. What comprises the steam heat equipment on a locomotive? A. A globe valve throttle at the boiler, a reducing valve, a steam gauge connected to the steam heat pipe and the proper piping and hose connections. 113. Q. What pressure is carried in the steam heat pipe, and how is it controlled? A. From twenty to sixty pounds in the train pipe, depending on the length of the train, and is controlled by the regulating valve. 114. Q. What would you do in case the regulating valve failed to operate? A. In case the regulating valve would not admit sufficient steam to the train pipe, would take it apart and block the steam valve open. If the pressure ran up too high in the steam heat train pipe, would control it with the steam throttle at the boiler head. 115. Q. How does the steam heat reducing valve control the pressure? A. The inlet valve for live steam is opened and closed by the movement of a metallic diaphragm in the valve which is opened by spring pressure on one side and closed by steam pressure on the other side. To regulate this pressure, stiffen the spring to carry more, weaken it to carry less by turning the handle connected to this spring either up or down. 116. Q. If steam heat gauge showed the required pressure and cars were not being heated properly, how would you proceed to locate the trouble? A. First note where the hand on the steam heat gauge stands when steam is shut off; if it does not drop back to zero see how much it lacks of this and note the rise of pressure shown by the gauge when steam is turned on. This is to test the gauge. If gauge is not correct, pay no attention to it, but send back steam enough to heat the train. Over sixty pounds will usually make the hose couplings on the cars rise up and leak at the joints. 117. Q. When engine is detached from the train, what precaution should you take to prevent freezing of the steam heat train pipe? What to prevent damage of steam heat hose? A. Open steam throttle to allow a very little steam to pass into steam heat train pipe to prevent its freezing. If end of hose is liable to strike frogs or crossings, hang it up where it will be safe. 118. Q. What constitutes abuse of an engine? A. Improper use of injector by filling boiler at a rapid rate when drifting or standing in a siding, unless you have a heavy bright fire to heat the injected water to the boiler temperature as fast as it comes into the boiler. Excessive use of the blower, especially with a light fire or when cleaning the fire. Improper attention to machinery, such as keeping parts not properly lubricated, rods not properly keyed, wedges not adjusted, carrying too much or too little water in the boiler, working water through the cylinders, allowing engine to slip unnecessarily, use of sand on one rail only or otherwise improperly; being careless in any way where care is required and not properly reporting the necessary work so it can be done promptly. 119. Q. How are accidents and breakdown best prevented? A. By inspection both at and after leaving terminals, frequently while on the road, keeping all parts properly adjusted, water in the boiler at the proper level and using good judgment in the handling of the engine and train. It is much better to use care and prevent accidents than to make repairs after they occur. 120. Q. What are the duties of an engineman when leaving his engine at the terminal? A. Place her on the proper track to be turned over to the hostler, leave throttle closed securely, reverse lever in center notch, cylinder cocks open, and lubricator feeds to steam chest and cylinders closed. The boiler should be full of water and sufficient fire to maintain steam pressure until fire is knocked out. Call fireman's attention to anything of special importance. Inspect the engine very thoroughly, ascertain whether any tools or signals have been lost on the trip and make a full report of the condition of the entire locomotive. 121. Q. What is the most important bolt or nut on the locomotive? A. The loose one. It should be cared for immediately. 122. Q. In reporting work on an engine, is it sufficient to do it in a general way, such as saying: "Injector won't work," "lubricator won't work," "engine won't steam," "engine blows," etc.? Or would you report each special defect so it could be located after the engine was put in roundhouse or on designated track whether it had steam pressure in boiler or not? A. No. Report all defects noticed so plainly that they can be located by the repair man without unnecessary work and whether there is steam in the boiler or not at the time repairs are to be made. If the engine blows, make a test to locate the blow and report it correctly. Also report any unusual feature in the operation of the engine during the trip. =COMPOUND LOCOMOTIVES= 1. Q. Wherein do compound locomotives differ from ordinary or simple ones? A. Simple engines take live steam from the boiler and after one expansion in a single cylinder it is exhausted to the atmosphere. A compound engine has two cylinders, sometimes one on each side of the locomotive; other types have four cylinders or two on each side of the locomotive. The live steam first passes into one cylinder, expanding down for a portion of its pressure, and then being allowed to pass into the second cylinder where it expands a second time, thus getting two expansions from each volume of live steam. Both simple and compound locomotives consist of two engines coupled to the same set of driving wheels. Balanced compounds have four sets of main rods and crank pins. Mallet compounds have two complete sets of engines under one boiler. 2. Q. Why is one cylinder on a compound locomotive called the high-pressure cylinder and the other one a low-pressure cylinder? A. The high-pressure cylinder takes that name because it works live steam direct from the boiler at high pressure. The low-pressure cylinder receives the steam after the first expansion and works with a low pressure. It is always larger than its companion high-pressure cylinder in order to get the same power from the low-pressure steam. 3. Q. In the Schenectady two-cylinder compound, what is the duty of the oil dash-pot? A. It is intended to prevent the too rapid movement of the intercepting valve which might damage the valve or seat, and it is necessary that the dash-pot should be full of oil to make it work properly. 4. Q. Explain how a Schenectady two-cylinder compound may be operated as a simple engine. A. To operate the compound as a simple engine, the separate exhaust valve is opened which will cause the intercepting valve to move and stay in position to allow the high-pressure cylinder to exhaust direct to the atmosphere and admits live steam at a reduced pressure to the low-pressure cylinder. This should be done when starting a train or when moving very slowly and about to stall on a grade. The engine should not be operated simple while running except when at low speed. 5. Q. Explain how a two-cylinder compound is changed from simple to compound. A. Place the handle of the three-way cock or simpling valve in the cab so as to release the air from the cylinder of the separate exhaust valve. A coiled spring will then close this valve. This permits the exhaust steam of the high-pressure cylinder to accumulate in the receiver until sufficient pressure is obtained to force the intercepting valve into compounding position. This shuts off live steam from the low-pressure cylinder and allows exhaust steam from the high-pressure cylinder to feed through the receiver into the low-pressure steam chest. 6. Q. How should a compound engine be lubricated? A. One-third more oil should be fed to the high than the low-pressure cylinder, using more oil at high speed than at slow. 7. Q. Why feed more oil to high than to a low-pressure cylinder? A. Because some of the oil from the high-pressure cylinder follows the steam into the low-pressure cylinder. 8. Q. How would you lubricate the valve of low-pressure cylinder if the oil feed became inoperative on that side? A. Feed an increased quantity through the oil pipe to the intercepting valve. Shut the engine off occasionally and cut into simple position. Oil will then go direct from the intercepting valve into the low-pressure steam chest and cylinders. This would avoid going out on steam chest to oil by hand. 9. Q. How much water should be carried in the boiler of a compound locomotive? A. A very moderate level, never allowing it to get so high that moist steam will pass through the cylinders, because for satisfactory service a compound engine should always have dry steam. 10. Q. How should a compound locomotive be started with a long train? A. In simple position with cylinder cocks open. 11. Q. When drifting what should be the position of the separate exhaust valve, the cylinder and port cocks? A. Open position. 12. Q. What will cause two exhausts of air to blow from the three-way cock or simpling valve in the cab when the engine is being changed to compound? A. A sticky exhaust valve. It does not move when air is first discharged. The second exhaust comes when it does move. 13. Q. What does steam blowing at the three-way cock indicate? A. The separate exhaust valve not seating properly caused by stuck valves, a weak or broken spring, or the packing rings of separate exhaust valve leaking. 14. Q. What can be done if the engine will not operate compound when the air pressure on the separate exhaust valve is released by the three-way cock? A. The separate exhaust valve has failed to close. Try jarring it with a hammer on the front side, near the exhaust valve. With a bad case, take the valve out, clean it and replace, if not broken. 15. Q. If the engine stands with high-pressure side on the dead center and will not move when given steam, where is the trouble, and what may be done to start the engine? Why? A. The intercepting valve is stuck in compound position, so live steam cannot get to the low-pressure cylinder. In a case of this kind, close the throttle, open cylinder and port cocks; when all pressure is relieved, use a bar to move forward the rod that works through the oil dash-pot, thus moving the valve to simple position and steam will pass to the low-pressure cylinder as soon as throttle is open. The engine will not start, because with the low-pressure piston on the quarter, steam must be admitted to its cylinder to start the engine. 16. Q. In the event of a breakdown, how should one disconnect? A. The same as a simple engine with separate exhaust valve open, so engine will work simple instead of compound. 17. Q. What may be done to shut off steam pressure from the steam chest and low-pressure cylinder? A. To shut off steam from the low-pressure chest, pull out the rod that runs through the dash-pot as far as possible and fasten it in this position. Then open the separate exhaust valve. 18. Q. Is it important that air be pumped up on a two-cylinder compound before the engine is moved? Why? A. Yes. Because the separate exhaust valve is opened by air pressure and the engine cannot be simpled without sufficient pressure. 19. Q. How are the blows in a compound located? A. The same as in a simple engine with the exception that any blow on the high-pressure side will not be heard when the separate exhaust valve is closed. A blow on the high-pressure side will increase the pressure in the low-pressure side, so relief valves will pop on low-pressure side when working compound with full throttle. 20. Q. What should be done if high-pressure piston of a cross compound is broken off the rod, or if the high-pressure or low-pressure cylinder head is broken? A. Cover the ports on that side, open separate exhaust valve and run in; use live steam in low-pressure cylinder only, for the broken piston. With broken cylinder head, would cover ports on that side. Open separate exhaust and run in with low-pressure side. Would not take down main rod, but would take out pop valves in both cylinder heads and see that the cylinder is properly oiled. For low-pressure head broken, would cover ports on that side, open separate exhaust valve and use high-pressure side; need not take down main rod, but would see that the cylinder is well oiled. 21. Q. In the event of separate exhaust valves failing to work when throttle is wide open, what can be done to assist in opening? A. Ease throttle off very fine to reduce the receiver pressure; in a moment or two the separate exhaust valve should then move. If this did not work, would shut off entirely, even at the risk of stalling, as in that event the train could be started again with engine cut in simple. 22. Q. If a transmission bar on a cross compound is broken, what would you do for the right side? For the left side? A. For right side would cover ports on that side, take out pop from cylinder head, open separate exhaust and run in with other cylinder. For left side, cover ports and fasten valve stem same as for right side. Would leave main rods up, keep separate exhaust open in both cases and see that cylinder is well oiled. 23. Q. In the event of a cross compound beginning to jerk badly and cylinder head pops in low-pressure cylinder popping, where would you look for the trouble? A. That either the high-pressure valve or piston packing was blowing live steam into the receiver and then into low-pressure steam chest. If possible would locate trouble and report accordingly. 24. Q. If during a trip you found the piston valve rings of a cross compound were broken, what would you do? A. If nothing but rings were broken, would reduce boiler pressure about 25 per cent. and go on with my train if possible. 25. Q. If piston valve on cross compound was broken so it became necessary to remove it, what should you do? A. Remove the broken piston valve, reduce boiler pressure to 100 pounds and proceed. 26. Q. What is the difference between a Vauclain four-cylinder compound, a four-cylinder tandem, a balanced and a Mallet compound in their arrangement of cylinders? A. A Vauclain compound has two cylinders on each side, one above the other, and both piston rods connected to one cross-head. A four-cylinder tandem has four cylinders, the high pressure being ahead of the low pressure on each side, and both pistons connected to one piston rod and one cross-head. A balanced compound has four cylinders, the two high-pressure cylinders being between the frames, each having a main rod connected to a crank axle. The two low-pressure cylinders are located outside the frame, each having a main rod and crank pin connected to the driving wheel center. A Mallet compound consists of two separate and independent engines, one fixed to the boiler, the other swinging from a center and sliding back and forth under the front end of the boiler. The rear engine works steam at high pressure; steam from this engine exhausts through a receiver pipe having flexible joints to the forward engine which works the steam at low pressure, then exhausts it to the front end and stack. 27. Q. How many main steam valves has each type? A. The Vauclain has one valve on each side, distributing steam to the high and low-pressure cylinder on that side. The four-cylinder tandem has two valves on each side, one for each of the two cylinders. A Baldwin balanced compound has two valves the same as the Vauclain. The American balanced compound has four valves, one for each cylinder, the two valves for one side of the engine being connected to one valve rod. A Mallet compound has a separate valve for each cylinder the same as a simple locomotive. 28. Q. How do you test for blow in high and low-pressure cylinder packing for each type of compound engine? A. Simple the engine if a cross compound, then make test the same as for a simple engine. For Vauclain four-cylinder compounds, test low pressure first. A blow past the low-pressure piston will show the same as on a simple engine; a blow past the high-pressure piston will make the engine stronger on that side when working a full throttle and the exhaust from the low-pressure cylinder will be heavier. To test the valve on either side, cover the ports. Broken packing rings in the steam valve will show a blow in one position and be tight in another. For tandem compound, to test high-pressure piston packing, stand engine on the top quarter, lever in back gear, drivers blocked and starting valve closed; remove back indicator plug or open back cylinder cock of high-pressure cylinder. Steam coming from the back cylinder cock must get by the piston packing or by-pass or starting valve. Now put reverse lever ahead and try the other indicator plug or cylinder cock. If a leaky by-pass valve in the front end is the trouble, no steam will come through. To test the low-pressure piston packing, place the engine in the same position, lever in position to admit steam into the front end of high-pressure cylinder. Open starting valve, remove back indicator plug of low-pressure cylinder and give engine steam; if steam comes from the indicator plug opening or open back cylinder cock, either packing or by-pass is leaking. To determine which one, put reverse lever in another position, close back indicator plug and open forward one; if blow still continues, the packing rings are leaking or else both by-pass valves. Would then inspect the by-pass valves. 29. Q. How can the blow through sleeve packing between high and low-pressure cylinder of the tandem compound be located? A. Place the engine as before on the top quarter, put reverse lever in forward gear, see that starting valve is closed, block the drivers or set the brakes solid and open the throttle. Until the engine moves, unless there is a leak, no steam can get into the front side of the low-pressure cylinder. Remove the indicator plug in front end of the low-pressure cylinder for this test. 30. Q. How test for piston packing blow with balanced compound? A. For a Baldwin balanced compound to test the high-pressure piston packing, place the engine with the outside main pin on that side of the engine on the bottom quarter, the reverse lever in the forward notch, starting valve closed, set the brakes solid or block the drivers, remove the indicator plug in the front end of either the high or low-pressure cylinder. With throttle open this will admit steam to the back end of high-pressure cylinder. Steam coming out of this plug opening, will indicate a leak past the piston or the high-pressure valve. If uncertain, next test the high-pressure valve by moving the reverse lever to the center notch. This should cover the ports and if the valve is tight the blow will stop. To test the low-pressure piston, place the engine in the same position with wheels blocked, starting valve open, back indicator plug out; when throttle is opened, the leaky packing will be shown by steam issuing from the plug opening. If uncertain, the valve can be tested by bringing reverse lever to the center of quadrant, which will spot valve over port and if it is tight the blow will stop. In any compound engine a blow past the high-pressure packing tends to increase the pressure in the low-pressure cylinder. A blow past the low-pressure packing can always be heard at the exhaust, and is usually on both forward and back strokes, while a blow past the by-pass valves or valve bushings occurs at a certain part of a complete revolution only. 31. Q. In case it was necessary to disconnect on one side of a compound engine, how would you cover ports and hold valves in position? A. The easiest way is to clamp the valve stem to hold valve in mid position; this should cover all ports. It may be necessary to take off head of piston valve chest and block in there. 32. Q. Is it a disadvantage to work a compound engine in short cut-off? Why? A. Yes. If cut-off is too short the proper proportion of steam passing the throttle will not get to the low-pressure cylinder. The work should be divided between the two cylinders on same side. 33. Q. In what way do the Mallet or articulated compounds differ from other steam locomotives in the distribution of the steam? A. Mallet compounds have two separate and complete engines under one boiler. The rear engine has a rigid connection to the back end of the boiler; this engine works boiler steam direct the same as a simple locomotive. Under the front end of the boiler is another engine so constructed that the entire front engine can move from side to side under the boiler, having a hinged connection at the front end of the rear engine to allow the locomotive to pass curves more easily. The front engine takes the exhaust steam from the rear engine through a flexible pipe or receiver and works it through a larger set of cylinders and thus compounds the steam. From the low-pressure cylinders the steam is exhausted to the atmosphere through the stack. 34. Q. How do you get the use of both engines when starting a train? A. To get steam into the low-pressure cylinders before the high-pressure engine has exhausted, some types of the Mallet compound have a live steam pipe with a valve in the cab to admit boiler steam to the receiver pipe and thus get the use of the front engine in starting a train. The American Locomotive Company articulated compounds have an intercepting valve similar to the one used in the Richmond cross compound, located between the exhaust passage of the rear engine and the flexible receiving pipe of the front one. This intercepting valve when in SIMPLE position, allows the high-pressure cylinders of the rear engine to exhaust directly to the stack instead of into the receiver, and feeds boiler steam at a reduced pressure into the receiver pipe for the low-pressure cylinders without giving any back pressure on the high-pressure pistons. This increases the power of the complete locomotive about 20 per cent. When in compound position, the intercepting valve cuts off the supply of live steam to the receiver pipe and forces the exhaust steam to go to the low-pressure engine ahead. 35. Q. How is the American articulated compound changed from compound to simple, and back to compound again? A. To work the locomotive simple, place the handle of operating valve in the cab to point toward the rear. This admits steam against the piston that operates the emergency exhaust valve and opens it. Exhaust steam from the high-pressure engine can pass to the exhaust nozzle instead of to the low-pressure engine. The intercepting valve then moves over so that live steam reduced to 40 per cent. of boiler pressure goes through the receiver pipe to the low-pressure engine. To work compound, place the handle of the operating valve to point forward. This will exhaust the steam, holding the emergency exhaust valve open; a spring and the pressure of the steam exhausted from the rear engine will close the emergency exhaust valve and build up a pressure against the intercepting valve that will open it so exhaust steam from the rear engine will go to the forward one and at the same movement close the reducing valve so no more live steam goes to the receiver. 36. Q. When is it necessary to use the operating valve to change the locomotive from compound to simple, or from simple to compound? A. When giving the engines steam to start, the intercepting valve should automatically go to simple position until exhaust steam from the rear engine builds up a receiver pressure that shifts the valve to compound; if it does not, use the operating valve. When moving less than four miles an hour or when about to stall on a grade, set the engines working simple; changing to compound when the danger of stalling is over or the speed is more than four miles an hour. If there is no intercepting valve to furnish live steam to the forward engine, open the starting valve to admit live steam to the receiver pipe and low-pressure engine. 37. Q. If in starting the locomotive the forward engine does not take steam, what is the trouble? A. The reducing valve may be stuck shut on account of being dirty or stuck on the stem of the intercepting valve. In case the reducing valve is stuck shut, the head of the dash-pot can be taken off and the valve worked back and forth to loosen it. The intercepting valve should be liberally oiled just before starting and occasionally during long runs to keep it free from sticking. 38. Q. Why does the Mallet compound have more power when working simple than compound? A. If a starting valve is used to admit live steam to the receiver pipe and thence to the low-pressure engine, this gives a higher pressure to the low-pressure cylinders. If an intercepting valve is used, the open emergency exhaust valve allows exhaust steam from the rear engine to go direct to the stack; this takes away the back pressure of the receiver steam from the high-pressure pistons, about 30 per cent. of the boiler pressure, and thus adds to the power of the rear engine. The reducing valve when feeding live steam gives about 40 per cent. of boiler pressure to the low-pressure engine instead of the 30 per cent. it gets from the receiver; the added power of both engines working simple is about 20 per cent. over the compound operation. 39. Q. What is the duty of the by-pass valves on the sides of the low-pressure cylinders? Should they be kept clean of gum and grit? A. These valves are connected to the steam ports at each end of the cylinders and open to allow air and steam to pass from one end of the cylinder to the other; away from the moving piston when the engine is drifting. If not kept clean they may stick open; when working steam the engine will blow badly; if they stick shut the engine will pound when drifting. 40. Q. In what position should the reverse lever be when the steam is shut off and the engine drifting? A. Below three-quarters of full gear, so the valves will have nearly full travel. 41. Q. Why should the power reversing gear of the Mallet compound always have its dash-pot cylinder full of oil? A. To prevent the too rapid movement of the reverse gear piston and its damage. 42. Q. In what position should the engines stand to test for blows in valves and piston packing? A. Put the operating valve, or starting valve, in simple position. Spot the engine in the proper position and test each engine for blows the same as for a simple engine. 43. Q. What power is used with Ragonnet or Baldwin power reverse gear? A. Air pressure. 44. Q. Can and should steam pressure be used? A. Yes. However, steam should never be used except in an emergency when air is not available. 45. Q. What precaution should be taken regarding steam check and throttle? A. That they are tight and check working properly, to insure that steam is kept from entering main reservoir, for if it should do so it would burn out the gaskets in the air brake equipment, allow moisture to accumulate, which would result in freezing and bursting of equipment as well as being dangerous. 46. Q. What would cause the gear to fail to hold links in intended cut-off, and allow them to raise and lower without operating valve in the cab being changed? A. Leaks in main valve and piston packing. =WALSCHAERT AND BAKER-PILLIOD VALVE GEARS= 1. Q. Give a brief explanation of the Walschaert valve gear. A. The Walschaert gear has an eccentric crank attached to the end of the main pin on each side of the locomotive, with an eccentric rod from this pin to the connection at the bottom end of the link. This eccentric is located so it serves for both forward and back motion. The link swings on a center trunnion and cannot be moved up and down as the Stephenson link, but the link block can be moved from one end of the link to the other to reverse the engine; or part way toward the center of the link to change the cut-off. A radius rod connects the link block to the valve stem. There are two motions given to the valve stem, one from the link block which regulates the travel of the valve for the cut-off and reversing; the other motion is from a connection with the cross-head which gives the valve a positive motion to take care of the lap and lead. To give this motion there is used a combination lever or a lap and lead lever connected to a cross-head arm by the union link. 2. Q. Is the Walschaert gear direct or indirect? A. It is direct when the link block is below the center of the link; it is indirect when the link block is above the center of the link. 3. Q. What are the principal differences in the location of the Stephenson and Walschaert gears, and what advantages does this give the Walschaert? A. The Stephenson gear is placed between the main frames and employs two eccentrics, with straps and rods on each side of the locomotive; one for forward and one for backward motion. The Walschaert gear is placed outside the driving wheels and frame, has but one eccentric, which is a simple arm connected to the outside end of the crank pin for both forward and back motion. The links are set above the wheels on a level with the steam chest, the combination lever next to the cross-head. This gives it an advantage of a better chance to inspect all parts, the eccentric connections are much lighter and direct, which makes them less liable to wear or breakdown, and the valve has a constant lead. 4. Q. How is the lead affected by movement of the reverse lever with the two gears? A. With the Stephenson gear the lead increases as the reverse lever is hooked toward the center in both forward and back motion. With the Walschaert gear the lead is the same in all positions of the lever, so that the lever is used to reverse the engine or adjust the cut-off. 5. Q. In reversing, how do the two gears differ as to the movement of the link and link block? A. With the Stephenson gear, when reversing, the link is raised and lowered, bringing the block which is not moved by the reverse lever under control of either the forward or back-up eccentric as is desired to move the engine the proper way. With the Walschaert gear the link is not moved by the reverse lever, but the link block is raised and lowered in the link; the position of the block above or below the center of the link controlling the direction of motion. 6. Q. What would you disconnect if the eccentric crank, eccentric rod, or the arm at the bottom of the link should break? A. Would remove the broken parts, disconnect the link lifter from the radius rod and block the link block in the center of the link; the combination lever would then move the valve twice the amount of its lap and lead, which would be sufficient to provide for lubricating the cylinder. 7. Q. If the main crank pin was broken? A. Take down eccentric rod, eccentric crank, main rod and all connecting rods, block cross-head, disconnect from end of radius rod, chain it to running board and block steam valve to cover ports. 8. Q. Broken cross-head pin, main rod, strap or brasses? A. Take down main rod, block cross-head, disconnect front end of radius rod and chain to running board and block the valve to cover ports. 9. Q. With a broken combination lever, union link or cross-head arms, what would you do? A. Would disconnect the forward end of the radius rod and secure it to the running board with a small chain, wire or rope, remove all broken parts, take off the combination lever, even if not broken, secure the valve in its central position, loosen cylinder head to provide for lubrication, leave up main rod and proceed on one side. If valve was blocked to open rear port slightly, this would provide for lubrication and the cylinder head need not be loosened. 10. Q. If the radius rod on Walschaert gear is disabled, what should be done? A. If broken in front of the link block, take off the broken part by disconnecting from combination lever, take down eccentric rod, fasten valve to cover ports and proceed on one side. If broken back of the link block, block the link block in the desired position and proceed with both sides. 11. Q. What would you disconnect with a Walschaert gear if a valve yoke should break? A. Disconnect the forward end of the radius rod, suspend it from running board, block the valve, provide for lubricating the piston and proceed. 12. Q. How proceed with a broken reach rod? A. Remove the reach rod, block links on lower side to hold them in running position for proper direction. Unless radius rod lifters can be uncoupled, leave a little slack in the blocking. 13. Q. How can you tell without opening the steam chest if the valve covers the port with Stephenson gear? With Walschaert gear? A. Place the rocker shaft vertical with Stephenson gear. Place the combination lever vertical with reverse lever in mid gear so the link block is in the center of Walschaert link. 14. Q. What is the Baker-Pilliod valve gear? A. It is an outside gear with an eccentric crank, similar to the Walschaert gear, but without a reversing link. The motion is reversed by means of a reversing yoke instead of a link; the cut-off is changed in the same manner. It uses a combination lever connected with a union link to its cross-head arm. In case of breakdown remove the broken parts the same as described for Walschaert gear, blocking the reversing yoke, if necessary, in the proper position. 15. Q. Is the Baker gear a direct or an indirect motion? A. It is direct, going ahead for an inside admission and indirect backing up, and just the opposite for the outside admission type. 16. Q. What parts of the Baker gear take the place of the link which is used by the Stephenson or Walschaert motion? A. The radius bars and reverse yoke. 17. Q. What relation to the main pin is the eccentric crank set to? A. The eccentric crank always follows the main pin. 18. Q. Should the eccentric rod or eccentric crank break how is the engine put in condition to proceed? A. The disabled side can have lap and lead travel and a port opening equal to the lead for all cut-offs. First block the bell crank by using a "U" bolt (which should be provided) in the holes placed in the gear frame for this purpose. Throwing reverse lever in mid-gear will help to get bell crank in position to block. Second, take down broken parts. Third, knock out back pin of short reach rod and throw reverse yoke in forward motion against gear frame. 19. Q. What is to be done should a gear connection rod break? A. Do the same as for a broken eccentric or crank. 20. Q. What is to be done should the upper part of gear connection rod break? A. If break is close to the middle pin, do the same as for a broken eccentric rod and also tie lower end of gear connection rod to keep it from swinging. If break is near the top and below the jaw, first block the bell crank and wire the connection rod fast to radius bars. If break is through top jaw, do the same as for broken eccentric rod. 21. Q. What is to be done should a radius bar break? A. Do the same as for broken eccentric rod. 22. Q. If the horizontal arm of bell crank should break? A. Same as broken eccentric rod. 23. Q. What is to be done should the vertical arm or bell crank break? A. Take down union link combination lever and valve rod, then block valve over ports by using set-screw in valve stem cross-head provided for that purpose. 24. Q. Should you break cross-head arm or union link, what would you do? A. If rod be provided to secure lower end of the combination lever to guide yoke, remove broken parts and proceed with full train, working engine at long cut-off. Otherwise would remove broken parts, combination lever and valve rod, cover ports, and proceed on one side. 25. Q. What do you do if a union link should break? A. Same as for a broken cross-head arm. 26. Q. What is to be done if a combination lever should break? A. Tie combination lever plumb, same as for a broken cross-head arm, if it is possible. If not possible, take down the combination lever and valve rod and cover the ports. 27. Q. What is to be done if a valve rod breaks? A. Take down the broken parts and cover ports, leaving the rest of the gear intact. 28. Q. What is to be done if a reverse yoke breaks? A. If lugs for holding reach rod breaks, block yoke securely at whatever cut-off you wish to work the engine and take down the short reach rod. If break is below the lugs, do the same as for broken eccentric rod. 29. Q. What do you do if reach rod should break? A. If short reach rod breaks, block the yoke at cut-off desired and wire fast so it cannot move. If main reach rod breaks, block between tumbling shaft arm and cross-tie brace, wiring same securely. 30. Q. What is to be done if the engine breaks down other than valve gear? A. In this case do the same as for any other valve. =SOUTHERN VALVE GEAR= 1. Q. If the eccentric crank or eccentric rods fail? A. Disconnect the eccentric rod from crank, radius hanger and transmission yoke, tie up the hanger and yoke, clamp valve central position and proceed. 2. Q. If radius hanger fails? A. Disconnect the hanger from rod and take down eccentric rod, clamp valve in central position and proceed. 3. Q. If transmission yoke fails? A. Disconnect from the eccentric rod and clamp valve in central position and proceed. 4. Q. If horizontal arm of bell crank fails? A. Disconnect the yoke from the eccentric rod, tie up to clear, clamp valve in central position and proceed. 5. Q. If vertical arm to bell crank breaks? A. Clamp valve in central position and proceed. Take the broken arm down if necessary. 6. Q. If one auxiliary reach rod or reverse shaft arm fail? A. Block both link blocks in same position of links, and in such a position as to give port opening enough to start train and control speed by throttle. 7. Q. If main reach rod, or middle arm to reverse shaft fail? If both auxiliary reach rods fail? A. Block link blocks in full valve travel, controlling power and speed with the throttle. =LUBRICATION= 1. Q. What produces friction, and what is the result of excessive friction? A. Friction as considered in locomotive service is produced by one body being rubbed across the surface of another when they are held in contact by pressure, and the result of excessive friction is heat more or less intense and the destruction of the journal and its bearing or the roughening of the sliding surfaces. 2. Q. What is lubrication and its object? A. The object of lubrication is to interpose a film of oil, grease or some lubricant between the two surfaces that will prevent these rubbing surfaces from coming into too intimate contact. 3. Q. What examinations should be made by the engineer to insure successful lubrication? A. See that all oil holes are open, cups filled and in good working order, the packing in cellars evenly put in and in contact with the journal. That waste on top of driving or truck boxes is in proper shape, also that grease cups are filled, and the plugs and jam nuts in good shape, and that the grease cellars contain sufficient grease for the next trip. 4. Q. How should feeders of all oil cups be adjusted? A. To feed as small a quantity of oil as possible and regularly to give perfect lubrication. 5. Q. Why is it bad practice to keep engine oil close to boiler in warm weather? A. The oil is thinned to such a degree by the heat of the boiler that it runs off as soon as applied, and very often a hot bearing is the result. 6. Q. In what manner would you care for a hot bearing if discovered on the road? A. Use as much time as available in cooling the same, making sure that all moving parts are free and carefully lubricated before proceeding. 7. Q. What kind of oil should be used on hot bearings? A. Use engine oil unless the temperature of bearing consumes it, when a small quantity of valve oil may be used while the bearing is warm enough to make this oil flow. The valve oil must be removed as soon as the bearing cools to prevent reheating. 8. Q. At completion of trip what is necessary? A. Close all adjustable feeds and examine all lubricated parts by contact with the hand to determine that they are not above running temperature. 9. Q. How would you determine what boxes to report examined? Why not report all boxes examined? A. By placing the hand on driving box, on hub of engine truck wheel and on top of tender truck boxes nearest the brass, and would not report them examined unless the temperature of same was above running heat. It is not necessary to report all boxes examined, because they do not all give trouble at the same time. If this report was made, it would appear that a proper inspection had not been made and would result in unnecessary work and waste of material. 10. Q. Why is it bad practice to disturb the packing on top of driving and engine truck boxes with spout of oil can when oiling engine? A. This packing is put on top of boxes to assist in keeping dirt and dust out of oil holes, also to aid in gradual lubrication from the top. If this packing is disturbed it will permit dirt and grit to work into oil holes and on the bearings as well as feed the oil away too rapidly. 11. Q. How do you adjust grease cups as applied to rods? A. Screw down plug until you feel a slight resistance from the grease, stop when grease shows between brass and pin; this should be sufficient over the division. 12. Q. Is it usual for pins to run warm when using grease? A. Yes; grease does not work properly until it gets warm enough to flow readily over the bearing. 13. Q. What effect does too much pressure produce? A. Wastes grease and increases the friction until the surplus amount is worked out so the bearing runs free on its journal. 14. Q. Is it necessary to use oil with grease on crank pins? A. No. 15. Q. When an engine is equipped with Elvin driving box lubricator, how can you tell whether a sufficient amount of lubricant is in the grease receptacle? A. The indicator wire fastened to the bottom of the grease cellar indicates the amount of grease left in the cellar. 16. Q. Why should engine oil not be used on valves and cylinders? A. Engine oil loses its lubricating qualities before it gets up to the temperature of the valves and cylinders when they are working steam. 17. Q. At what temperature does engine oil lose its lubricating qualities? At what temperature for valve oil? A. Engine oil begins to separate and give off gas at 345 degrees F. The temperature of steam at 120 pounds is 350 degrees F., while valve oil has a flash test of 520 degrees F. The temperature of steam at 235 pounds is 431 degrees F., much lower than the flash test of valve oil. 18. Q. How and by what means are valves, cylinders and the steam end of air pumps lubricated? A. By a sight-feed hydrostatic lubricator. 19. Q. What is the principle on which a lubricator operates. How does the oil get from the cup to the steam chest? A. The lubricator is located in the cab so there is a gradual descent in the oil pipe from the lubricator to the steam chest. Above the oil reservoir is a condenser that is kept filled with water condensed from steam fed from the boiler. The pressure of this water comes on the oil in the oil tank below it, forcing oil through the sight-feed valves; it then passes up by the sight-feed glasses to the oil pipe and steam chest. The use of the glasses is to make the drop of oil visible as it leaves the sight-feed nipple so the amount of oil fed can be regulated. Steam from the boiler fed to the lubricator at boiler pressure through the equalizing tubes balances the pressure which comes from the steam chest when the engine is working steam. 20. Q. How should the lubricator be filled? A. First close all valves connected with the lubricator, open drain plug and remove filling plug, allowing water to escape until oil appears with it. Drain plug should then be closed. Fill the oil tank in the usual way, being careful not to overflow it; then replace filling plug. If the supply of oil is insufficient to fill the lubricator, water can be used to finish it, as the lubricator will begin feeding sooner when filled full. 21. Q. After filling lubricator, what should be done? A. Open the steam throttle to the lubricator wide, then carefully open the water valve, but do not open the feeds until sure the chamber in the glass is filled with water. 22. Q. How long before leaving terminal should the feed valves be opened? Why? A. About fifteen minutes; this time is necessary to allow oil to feed through the oil pipe and reach the steam chests. 23. Q. How many drops should be fed per minute? A. From one to seven, timed by the watch, depending on conditions. Cylinders of large size require more oil than smaller ones. 24. Q. If lubricator feeds regularly when working steam and too rapidly after shutting off, what is the trouble? A. The opening in the choke plug at the lubricator or through the steam valves at the steam chest is too large and should be reduced to the proper size by applying new chokes or valves. 25. Q. When valves appear dry while using steam and the lubricator is working all right, what would you do to relieve these conditions? A. Ease off throttle for a few seconds to reduce the steam chest pressure and drop the reverse lever a few notches to give the valve a longer travel; oil held in the pipes will then flow down. =FEDERAL REGULATIONS= =For Inspection of Locomotive Boilers and Safety Appliances= 1. Q. What is the purpose of the federal rules and regulations for inspection of locomotive boilers? A. So that all railroads operating under the laws of the United States government, would be obliged to maintain their boilers in a safe working condition. 2. Q. What is the purpose of the quarterly and monthly interstate inspection cards placed in the cab of the locomotive? A. So that the federal inspector or engineer may see that the locomotive boiler has received its monthly or quarterly inspection. 3. Q. What constitutes a safety appliance, as applied to a locomotive? A. Any appliance that is placed on a locomotive for the purpose of protecting the employees from personal injury. 4. Q. Name some of the safety appliances found on a locomotive? A. Shield for tubular glass lubricators, also shields for water glass, automatic couplers, with lever attachments, air brakes, etc. 5. Q. In what condition should safety appliances be maintained? A. They should be maintained in first class condition. 6. Q. What should be done in event of any of the safety appliances being damaged while engine is in service so as to render it unsafe? A. Warn all employees whose duties require them to work around the locomotive of its unsafe condition, then make report to those in authority so that it may be taken out of service until repairs are made. 7. Q. What effort should be made on the part of the engineer to prevent persons using a safety appliance which he knows is damaged and unsafe? A. He should use such precaution as in his judgment would protect from injury all persons who are on or around the locomotive. 8. Q. What is the duty of the engineer in event of his discovering a safety appliance which is in an unsafe condition when taking an engine from roundhouse territory? A. He should report at once to the person in authority so that necessary repairs may be made before engine goes into service. =PYLE-NATIONAL ELECTRIC HEADLIGHT= 1. Q. Why are electric headlights applied to locomotives? A. Electric headlights are applied to locomotives so that the engineer may have a clear view of the track for enough ahead of the train to enable him to protect the company's property in his charge. 2. Q. How far ahead of the engine should the arc headlight illuminate the track? A. Not less than from fifteen to twenty telegraph poles. 3. Q. State how you would focus the lamp. A. First, would adjust back of the reflector so front edge of reflector will be parallel with front edge of case. Second, adjust the lamp to have point of copper electrode as near the center of reflector as possible with carbons as near the center of the chimney holes as you can set them. Third, have the locomotive on straight track. Now move the base of the lamp around until you get a parallel beam of white light straight down the center of the track, then tighten the lamp down. 4. Q. If the light throws shadows upon the track, is it properly focused? A. No. 5. Q. If the light is properly focused, that is, if the rays are leaving the reflector in parallel lines, but the light does not strike the center of the track, what should be done? A. When the light rays are thrown out in parallel lines and they do not strike the center of the track, it denotes that the headlight case is not set straight with the engine, and the entire case on base board must be shifted until the shaft of light strikes the track as desired. 6. Q. What can you do to insure a good and unfailing light for the entire trip? A. By carefully inspecting the entire equipment before departing on each trip, and know that there are no wires with insulation charred or worn off, that all screws and connections are tight, commutator clean and brushes set in brush holder in proper manner. Carbon in lamp of sufficient length to complete trip, and that the carbon will feed through the clutch freely and rests central over the copper electrode. Copper electrode cleaned off, oil in both bearings and see that steam does not blow at stuffing box gland. 7. Q. What kind of oil and how much would you use in the bearings of the electric headlight equipment? A. Would use the best grade of black or engine oil furnished for both bearings and only enough oil in oil cellar that the revolving loose oil ring may trail through the oil. When bearings are supplied with oil cups, use a heavy oil such as good engine or valve oil. 8. Q. Why should you not use valve oil in these bearings? A. Valve oil cannot be used successfully in the main bearing because of its heavy body. Valve oil could not be carried up to shaft by the oil ring in cold weather, as the ring will not revolve. 9. Q. What is the most vital part of the dynamo? A. The commutator. 10. Q. What care or attention should be given the commutator? A. The commutator must be kept clean, free from dirt, and the mica must be kept filed a trifle below the surface of the copper bars. 11. Q. What kind of a bearing should the brush have on the commutator? A. Brushes should be fitted to have a bearing with the same contour as the commutator. 12. Q. How are the brushes fitted? A. Brushes are fitted by cutting a strip of No. 0 sandpaper about the width of the commutator surface (have the dynamo idle), place the strips of sandpaper under the brush, then pull the sandpaper from left to right; continue this process until the brush has been fitted to a true smooth bearing. Then trim about one-eighth inch off of the front edge of the brush. 13. Q. Is it advisable to ever try to fit a brush with a file or knife? A. Most emphatically no. You could not get a bearing across the brush no matter how hard you might try with either a file or a knife. 14. Q. Why is it important to clean the scale off of the point of the copper electrode each trip? A. The scale on the copper electrode after it has cooled off is a non-conductor of current, and acts as a blind gasket between the carbon and the copper electrode. Unless this scale is removed, the current cannot pass between the points of carbon and electrode and you cannot, therefore, have a light. When the dynamo fields are compound wound, it is unnecessary to clean scale from copper electrode oftener than once a week, at which time copper electrode should be removed from holder and all scale cleaned off. (With compound wound dynamo fields the cab lamps will continue to burn when head-lamp is extinguished by lifting carbon by hand.) 15. Q. How should the copper electrode be trimmed at the point? A. The copper electrode should have about one-eighth inch surface on the contact point. 16. Q. How far should the copper electrode project over the holder? A. About one inch. 17. Q. Should the electrode be raised up to one and one-half inches, what might happen? A. If the copper electrode was run at a point so near the clutch, the intense heat of the arc might do damage to the top carbon holder and clutch. 18. Q. What regulation should be given to the tension spring No. 93 of the lamp, and why? A. This tension spring, No. 93, should be regulated when the current is off the lamp and should be adjusted only tight enough to pull the magnet yoke up against the top stop lug on the side of lamp column. 19. Q. If this tension spring was tightened too tightly, what might happen? A. At usual speed between stations, the movement of the engine would impart an added resistance against the pull of the solenoid by the tension spring, which would shorten up the arc and dim down the light. 20. Q. Is there anything else that could cause the light to dim down when the engine is running fast? A. Yes; if the spring No. 92-A that hold the heel of the clutch should be too weak, the heel of the clutch would be forced up by the motion of the locomotive; this would release the carbon which would fall to the point of the copper electrode, causing the light to dim down, or, if the clutch should be used until the sharp edge that grips the carbon should have become worn smooth or round, the same would occur. 21. Q. If the light burns satisfactorily while the engine is in motion, but goes out when engine is stopped, where would you find the trouble? A. This trouble is most always found to be caused by the tension spring No. 93 being too weak, though if the dash-pot plunger has become corroded until it sticks in the dash-pot, the light will act the same as if the tension spring were too weak. 22. Q. If the dash-pot should be found stuck, would you put oil in it? A. Coal oil could be used to clean and cut the dirt out of the pot and from off the plunger, but after the dash-pot and plunger have been cleaned, all oil must be wiped off, for oil would cause the plunger to stick as well as collect dirt. 23. Q. If the carbon of lamp should "jig or pound", what can be done to stop it? A. If the carbons pound the electrode, it is evidence that the iron armature No. 64 may be too far out of the solenoid, or the speed of the turbine engine may be too slow. This trouble can be remedied by adding another link to the suspension link, which has one end connected to the magnet yoke, the other end being connected to the iron armature No. 64. If, however, when the arc is formed, it is found that the bottom end of iron armature No. 64 measures one-half inch from bottom of solenoid, the pounding is caused by the speed of turbine engine being too slow. 24. Q. If the copper electrode was fusing, how would you know it? A. When the copper electrode is fused, a green light is always given off. 25. Q. What should be done when a green light is seen? A. Immediately close off on the steam throttle until a white light re-appears. 26. Q. What is the cause of the fusing of the copper electrode? A. Usually too high speed of the armature, although should you connect the wires up wrong that the current flowing from the dynamo to the lamp should enter the lamp at the electrode instead of passing through the carbon first, you would get a green light and fuse the electrode. 27. Q. What arrangements have been made so that you cannot connect the wires wrong? A. The positive binding posts, both at the dynamo and the lamp, have been provided with a much larger hole to receive the wire than has been made in the negative binding posts, and the ends of the positive wire should always be bent or doubled back, so that they will just enter the receptacle in the positive binding posts, but cannot be connected at the negative binding posts. 28. Q. Should the copper electrode and holder become fused until no longer serviceable while on the road, what would you do? A. Would remove the damaged holder from the lamp and substitute either an iron bolt of sufficient length or a carbon, securing the improvised electrode in the bracket of lamp same as the electrode holder is held, only being sure that the end of the bolt or carbon comes up into the center of the reflector and did not rest on the base of reflector or lamp. 29. Q. What is the difference between a series wound equipment and a compound wound equipment, and what advantages are obtained from the use of the compound equipment. A. With the series wound equipment, the incandescent cab lights burn only with the arc lamp, while with the compound machine the incandescent lamps are independent of the arc and can be used as desired. 30. Q. If you were running along with your light burning steadily and nicely, then suddenly the light began to flash badly and kept it up, where would you look for the trouble? A. Trouble would usually be found at one of the binding posts, where one of the binding post screws would be found loose. 31. Q. If you were running along with light burning satisfactorily and suddenly it went out, where would you be likely to find the trouble? A. You would find that either the carbon had burned out, one of the lead wires had broken between the dynamo and the lamp, or one of the wires had gotten loose at the binding post and fallen out. 32. Q. If the light goes out while you are between stations, what course should an engineer pursue? A. If the light goes out while you are between stations and an investigation cannot be made within a few minutes thereafter to determine the cause, the steam should be shut off from the turbine and the dynamo stopped until such time when the cause of failure can be determined. 33. Q. Why is it essential to shut off steam and stop the equipment? A. For the reason that if the failure was due to a short circuit, damage might be done to the coils or armature by overheating. 34. Q. How does the equipment act when short-circuited? A. When there is short circuit, the engine will labor heavily, run slow with a large volume of steam blowing at the exhaust, there will be no light shown either at the arc or cab lamps, and the carbon point and cab lights will only show a dull red or go entirely out. 35. Q. How will the equipment act when the circuit is broken, either by a broken disconnected wire or a burned-out carbon? A. With a broken circuit the engine will run noiselessly and fast with very little steam blowing at exhaust and no light will be seen at the arc or on cab lights. 36. Q. If the insulation on the cab wires is worn off until your two wires can come together either directly or through the medium of some metallic substance, what would occur? A. A short circuit would result that would put out all of your lights. 37. Q. What should be done? A. Wrap the exposed wire, if you can locate it, with a piece of waste, or if you cannot locate the short circuit, disconnect one of your cab wires from the dynamo. This would give you the benefit of the arc lamp and you can look for the trouble at your leisure. 38. Q. If the light goes out when steam drops back fifteen to twenty pounds, what is the trouble? A. Either one of the governor valves is stuck shut, short bushing No. 18 in engine cab is worn badly, allowing wheel to drop away from the governor stand so steam passes around wheel to exhaust, or governor springs are too weak. 39. Q. In this case what should be done? A. Report of the action of the dynamo should be made upon the work book at the terminal. 40. Q. If clutch rod No. 78-B should break while on the road, what could be done to get use of the lamp? A. A piece of wire could be used by fastening one end around the end of top lever No. 59, the other end being attached to clutch through eye. 41. Q. If you should lose the clothespin holder or top carbon clutch, what could be done to get the light? A. Would fasten a wire around the carbon and top holder to keep carbon in line, being careful not to get the wire either too tight or too loose. 42. Q. If you should lose the iron armature No. 64 in solenoid, what could be done to get use of light? A. Would use a common iron bolt and suspend same by wire in magnet. 43. Q. What would be the result if any of the levers of the lamp should bind? A. All levers of the lamp must work absolutely free and must not drag, for if they are not perfectly free the carbon cannot feed properly. =Pyle-National Electric Incandescent Headlight= 44. Q. What is meant by an incandescent headlight equipment? A. A headlight having an electric incandescent lamp in the reflector in place of the usual oil or acetylene gas flame, and electric instead of oil cab lamps, the electricity being generated by a small combination steam-turbine and electric generator. Suitable wiring distributes the electric current. 45. Q. In what manner does the incandescent headlight differ from the arc headlight? A. It is not so powerful. An incandescent or bulb type of lamp takes the place of the arc lamp in the headlight reflector. The current being less than is required for an arc, is supplied by a smaller turbine. 46. Q. What type of incandescent lamp is used in the reflector? A. A low voltage, gas filled bulb, containing a very compact or concentrated fillament. 47. Q. Why cannot a standard or house type of lamp be successfully used in the reflector? A. Because the fillament or light-giving wire inside the bulb is not sufficiently compact or concentrated to reflect the light in the form of a beam. The voltage of the house lamp is also too high to be used on a locomotive installation. 48. Q. How is the lamp held in place in the reflector? A. By the usual socket, into which the lamp screws. The socket is a part of the focusing device, one type of which holds the lamp in a horizontal position, while in the other the lamp is held vertically or upright. 49. Q. Before turning the steam into the turbine, what precautions should be observed? A. The turbo-generator should be lubricated by a small amount of black or engine oil, placed in the cup on the turbine or steam end. On the generator end, the oil should be maintained within one-half inch of the top of the hinge-cover cup; using black oil. The drainage of the steam end is cared for automatically by a three-eighth inch drain pipe without a valve. The pipe should be kept open. 50. Q. How do you proceed when you wish to use the light? A. Open the globe valve in the steam pipe to the turbo-generator, at least two turns. The water-glass, steam and air gauge lamps in the cab, and the number indicator lamp in the headlight case should light up as soon as the turbo-generator reaches full speed. A double-throw knife switch in the cab controls the headlight. In one position the switch gives the full brilliancy of the headlight. The opposite or "dimmer" position reduces the brilliancy about one-half. When the switch bar is in neither position the headlight is entirely out, and only the number lamp is burning. The classification lamp, lubricator and order or reading lamp, are controlled by a small switch on the socket of each lamp. 51. Q. For what purpose is the dimmer, and how does it operate? A. It is to reduce the intensity of the headlight when locomotive is in yards or around stations. It consists of a small resistance tube in the wiring circuit, and with the cab switch in dimmer position, a portion of the current is converted into heat instead of light. 52. Q. How is an incandescent headlight focussed? A. By moving the lamp in its position in the reflector until the most brilliant and compact beam of light is obtained. If the beam does not strike the track centrally, or as high or low, the headlight case must be moved on its platform until the beam is properly directed. It is often necessary to raise the front or back of the case by shimming between the case and its platform in order to direct the beam of light the proper distance ahead of the locomotive. 53. Q. What provision is made for moving or focussing the lamp in the reflector? A. When the lamp is mounted horizontally there are thumb screws by which the lamp may be moved sidewise, up and down, and forward and backward. This mounting is called the "micrometer" device, because of the accuracy of adjustment. With the vertical mounting, a flat head thumb screw at the base of the lamp support releases the ball joint so that the lamp may be easily moved sidewise or forward and backward. To raise or lower the lamp, the thumb screw higher on the lamp stand must be loosened. 54. Q. What causes a "black spot" in the illumination ahead of the locomotive? A. The lamp is out of focus, being too far ahead or back of the proper position in the reflector. 55. Q. How would you remedy the following possible defects? A. (a) =All lamps fail to burn.= If turbine is not running the wrong steam valve in the cab may have been opened, or there may be a second valve, closed, in the steam pipe. The screen on the governor valve in the turbine may be clogged. Remove brass cap at top of turbine and unscrew screen or strainer-cap. (b) =Turbo-generator runs, but no lights.= Wires may be "short-circuited" (crossed) which will cause brushes to spark badly, and turbo-generator to pull hard. The "short" can usually be found by an occasional sparking or smoke at the point of trouble. Separate and protect wires when short is found. The brushes may be "cocked up" as left by some repair man. Open the dynamo door and see that the brushes bear on the copper commutator. A wire may be loose at the dynamo binding posts (which may be seen when the dynamo door is open), or at the main switch in the cab. A main wire may have broken. (All locomotives are not equipped with fuse plugs.) A fuse plug may have become loose or burnt out. Replace with new fuse plugs or break an incandescent lamp and twist the leads in the base together, when the base may be screwed into the fuse plug socket, answering the purpose of a fuse plug, temporarily. (c) =Headlight fails to burn.= Examine the wires between cab switch and head lamp for breaks or disconnections. Examine fuse plugs (which are sometimes in head lamp circuit only) and proceed as in (b) if trouble is found there. Headlight bulb may not be screwed in far enough to make contact in the socket, as the lock-sockets provided to prevent lamps loosening cause lamp to screw in hard. Lamp may have broken fillament. Replace with proper type of lamp or use a cab lamp. (d) =Lamps burn dim.= Steam valve not open wide enough. Boiler pressure too low. Brushes sparking badly on commutator of dynamo--due to poor contact. Governor or steam-valve of turbine improperly adjusted. (e) =Lamps burn too brightly.= Improper turbine regulation. Throttle the steam valve in cab until lamps are reduced to proper brilliancy. Report all irregularities on arriving at terminal. =SCHROEDER HEADLIGHT= 1. Q. What is the speed of a Schroeder headlight dynamo? A. About 2,800 revolutions per minute. 2. Q. How is the speed altered? A. By a governor in the turbine. 3. Q. How would you proceed to change the speed of the governor? A. Remove cover No. 3 and loosen lock nut No. 14 and turn nut No. 13 to the right to increase the speed and to the left to decrease it. 4. Q. What is a short circuit? A. A connection between the positive and negative wires of the dynamo without any resistance between. 5. Q. How does the dynamo act when short-circuited? A. It will run very slowly as it is under a heavy strain. 6. Q. What would be the result if left to run under that strain? A. The armature or fields would burn out. 7. Q. What would you do if a short circuit developed while on the road? A. Shut the steam off and remove the positive or right-hand wire of the cab circuit from the dynamo, start up and see if the headlight went to work properly; if not, replace the cab wire and remove the positive or left-hand wire and see if the cab lights burned properly. If such was the case, let it run, using the small incandescent light in the case for a headlight and report it at the roundhouse. 8. Q. What is a volt? A. The unit of pressure of electricity. 9. Q. What is an ampere? A. The unit of quantity of electricity. 10. Q. What is the proper voltage of a Schroeder headlight? A. About 28 volts. 11. Q. Can a person be injured by that voltage? A. No. 12. Q. What is the proper amperage of a Schroeder headlight? A. About 30. 13. Q. How often should the ball bearings be oiled? A. About three times a week. 14. Q. How often should the governor be oiled? A. Before leaving every trip. 15. Q. What kind of oil should be used? A. Valve oil. 16. Q. Is it necessary to clean the electrode every trip? A. No. 17. Q. Why? A. The dynamo is provided with shunt fields which build up the current regardless of the arc light. 18. Q. What are the two causes of lamp burning green? A. Speed too high, or wires to the lamp being reversed. 19. Q. If the carbons burned away too fast, but otherwise the lamp appeared to be burning properly, where would you look for the trouble? A. It would indicate that tripping spring No. 209 was too tight. 20. Q. If tripping spring No. 209 was being annealed from heat and sparks were noticed at the clutch, where would you look for the trouble? A. Flexible wire No. 251 would be broken. ="BUDA-ROSS" ELECTRIC HEADLIGHT= 1. Q. What are the three essential elements in the "Buda-Ross" electric headlight equipment? A. Steam turbine engine, dynamo directly connected on the same shaft, and self-focusing arc lamp. 2. Q. At what speed should the turbine run? A. 2,800 revolutions per minute. 3. Q. How is the speed controlled? A. By a centrifugal governing device. 4. Q. How does the steam enter the turbine? A. Through a main valve which is perfectly balanced in all steam pressures directly and impinged on the buckets directly from a nozzle. 5. Q. About how much opening should this valve have? A. About one-fourth of an inch. 6. Q. Can the lift of this valve be changed? A. Yes. 7. Q. How? A. By adjusting the inner sleeve of the valve with a common monkey wrench after removing cap nut on top of turbine. 8. Q. Can this be done while the light is burning? A. Yes. 9. Q. What is necessary to do this? A. Take a monkey wrench and screw the inner sleeve down to the right to reduce the lift, and to the left to increase the lift. In reducing the lift you reduce the speed, and by increasing the lift you increase the speed. 10. Q. Is there any other method of setting speed? A. Yes. 11. Q. How? A. By removing oil box on the turbine cap and adjusting the nuts on the governor studs on the face of wheel. 12. Q. Is any provision made for operating the light with low pressure steam? A. Yes. 13. Q. What? A. An auxiliary valve is used which operates automatically at any predetermined pressure, which is adjusted by an adjusting stem at the bottom of the engine and which can also be adjusted while the light is burning. 14. Q. What kind of oil should be used in the "Buda-Ross" bearings? A. Cylinder or valve oil. 15. Q. What style of generator is used. A. An iron-clad type with no outside magnetism. 16. Q. How many fields in this generator? A. Two. 17. Q. What style field is used? A. Compound wound. 18. Q. What kind of wire is used on these fields? A. Deltabeston wire. 19. Q. Why is Deltabeston wire used in preference to cotton-covered wire? A. So that it cannot be injured by short circuits, for if a short circuit occurs and afterwards is removed there is no danger done to the insulation on this make of wire. 20. Q. Where are the fields located? A. One on each side of the dynamo. 21. Q. Why? A. So that they cannot be injured by waste oil from the ball bearing, or by water or snow. 22. Q. How should ball bearing on dynamo end be lubricated? A. By removing oil plug in frame just back of dynamo and introducing cylinder oil. 23. Q. Is it necessary to remove the top carbon holder from the lamp to remove reflector from case? A. No. 24. Q. Why not? A. Because there is no top guide to the carbon, as the carbon is guided by the clutches. 25. Q. How many levers are there in the lamp? A. Only one. 26. Q. What regulation should be given to top lever spring No. 308 on lamp? A. Top lever spring No. 308 should be adjusted as loose as possible and not have light go out standing still. 27. Q. If this spring was tightened until the light burned steady when the locomotive was at rest, what might occur when engine was running high speed? A. It might cause the light to dim down. 28. Q. Is there anything else that would cause the light to dim down when the engine is running fast? A. If the clutches should be used until the sharp edge that grips the carbon have become worn smooth or round they would allow the carbon to feed too fast and the light would burn dim. 29. Q. If the light burns satisfactory while engine is in motion, but goes out when engine is stopped, where would you find the trouble? A. This trouble is most always found to be caused by the top lever springs No. 308 being too weak; or, an imperfect carbon, though if the dash pot plunger has become corroded until it sticks in the dash pot, the light will act the same as if the tension spring was too weak. 30. Q. Is it possible to apply the bottom electrode holder wrong? A. No 31. Q. Why not? A. For the reason that its support is on a center line with the electrode and the holder can be turned in any direction and the electrode is held central with the top carbon. 32. Q. What would you do if you had no bottom electrode holder? A. Place a piece of 5/8-inch carbon in the hole through the bottom bracket having top end in focal point of reflector and tighten with set-screw; as this carbon would burn away the light would be raised and it would therefore be necessary to raise the carbon about every hour, as the carbon would burn away about one-half inch per hour. =GENERAL QUESTIONS AND ANSWERS ON ELECTRIC HEADLIGHTS= 33. Q. Describe the passage of the current through the lamp and tell how arc light is formed? A. It enters the lamp at the binding posts with the large hole, then to the top carbon holder, carbon, then into the electrode and holder; from there to the solenoid and back to the dynamo, leaving the lamp at the binding post with the small hole in it. The magnetism from the current while passing through the solenoid attracts magnet in a downward motion, and it in turn, by the levers on the lamp, separate the carbon from the copper, thereby forming the arc. 34. Q. Why should sandpaper be used to smooth commutator instead of emery cloth? A. In using emery paper a piece of emery might lodge in the grooves between the commutator segments, and being a conductor of electricity, causes short. Will also get embedded in the copper and cut the brushes. Sand will not do this. 35. Q. State how you would go about to focus a lamp? A. (1) Would adjust back of reflector so front edge of reflector would be parallel with front edge of case. (2) Adjust lamp to have point of copper electrode as near the center of reflector as possible with carbons as near the center of chimney hole as you can set them. (3) Have the locomotive on straight track. Now move the base of the lamp around until you get a parallel beam of white light straight down the center of the track, then tighten lamp down. 36. Q. If the light throws shadows upon the track, is it properly focused? A. No. 37. Q. If the light is properly focused, that is, if the rays are leaving the reflector in parallel lines, but the light does not strike the center of the track, what should be done? A. When the light rays are thrown out in parallel lines and they do not strike the center of the track, it denotes that the headlight case is not set straight with the engine, and the entire case on baseboard must be shifted until the shaft of light strikes the track as desired. 38. Q. What can you do to insure a good and unfailing light for the entire trip? A. By carefully inspecting the entire equipment before departing on each trip and know that there are no wires with insulation chafed or worn off; that all screws and connections are tight; commutator clean; brushes set in brush holder in the proper manner; carbon in lamp of sufficient length to complete trip; copper electrode cleaned off and oil in both bearings. 39. Q. Why would you not fill the main oil cellar full of oil? A. If you should fill the main oil cellar full of oil, the oil would run out of the overflow holes on the side and all over the equipment and locomotive and could do the dynamo no good but possibly harm. 40. Q. What is the most vital part of the dynamo? A. The commutator. 41. Q. What care and attention should be given the commutator? A. The commutator must be kept clean, free from dirt and grease; the mica must be kept filed down about one-sixty-fourth of an inch below the surface of the bars. 42. Q. How should you clean the commutator, and when? A. The commutator should be cleaned before starting out on each trip by using a piece of damp waste, rubbing the bars lengthwise, then wipe dry with clean dry piece of waste. 43. Q. What kind of a bearing should the brush have on the commutator? A. Brushes should be fitted to have a bearing with the same contour as the commutator, with bearing covering no less than two of the commutator bars, nor more than three of the bars. 44. Q. How are the brushes fitted? A. Brushes are fitted by cutting a strip of No. O sandpaper about the width of the commutator surface. (Have the dynamo idle.) Place the strip of sandpaper under the brush on the commutator with the rough side towards the brush, then pull the sandpaper from right to left; continue this process until the brush has been fitted to a true smooth bearing. Then trim about one-eighth of an inch off the front edge of the brush. 45. Q. Is it advisable to ever try to fit a brush up with a file or knife? A. No. 46. Q. Why is it important to clean the scale off the point of the copper electrode each trip? A. To allow the point of the carbon and the electrode to touch to form a circuit; this scale being a non-conductor of electricity and with it on, the current would not pass from the carbon to the electrode and holder. 47. Q. How should the copper electrode be trimmed at the point? A. Copper electrode should have about 1/4-inch surface at contact point. 48. Q. How far should the copper electrode project above the holder? A. One inch. 49. Q. Should the electrode be raised up to 1-1/2 inches, what might happen? A. If the copper electrode was run at a point so near the clutch, the intense heat of the arc might do damage to the top carbon holder and clutch. 50. Q. If the dash pot should be found stuck, would you put oil in it? A. Coal oil should be used to clean and cut the dirt out of the pot and from off the plunger, but after the dash pot and plunger have been cleaned all oil should be wiped off of same, as the oil would cause the plunger to collect dirt and stick. 51. Q. If one carbon of lamp should "jig or pound", what can be done to stop it? A. If the carbon jumps or pounds the electrode, it is evident that the iron armature is too far out of the solenoid, or the speed is too low. 52. Q. Does the pounding of the lamp occur with the old series wound machines or with the new compound wound machines? A. The pounding of the lamp occurs with the new compound wound machines. 53. Q. If the copper electrode was fusing, how would you know it? A. By the fact, when copper is fused a shaft of green light will be thrown off instead of a shaft of white light. 54. Q. What should be done when a green light is seen? A. Close the throttle to turbine engine, then open slowly until a white light re-appears. 55. Q. What is the cause of the copper electrode fusing? A. The cause of the copper electrode fusing is due to too high speed of the generator, or having lead wires connected up wrong, allowing positive current to get into copper electrode first. 56. Q. What arrangements have been made so that you cannot connect your wires wrong? A. The positive binding post both at the dynamo and lamp have been provided with a much larger hole to receive the wire than has been made in the negative binding post, and the ends of the positive wire should always be bent or doubled back so they will just enter the receptacle in the positive binding posts, but cannot be connected to the negative binding post. 57. Q. Should the copper electrode and holder become fused until no longer serviceable out on the road, what would you do? A. Would remove the damaged holder from the lamp and substitute a carbon, securing the substituted electrode in the bracket of lamp same as the electrode holder is held. Be sure that the end of the carbon comes up to center of reflector and does not rest on base of reflector or lamp. 58. Q. If you were running along with your light burning steady and nice, then suddenly the light began to flash badly and kept it up, where would you look for the trouble? A. You would no doubt find one of the lead wires loose in binding post. 59. Q. If you were running along with light burning satisfactorily and suddenly your light went out, where would you be likely to find the trouble? A. You would undoubtedly find carbon burned out, or a lead wire was broken off or out of the binding posts. 60. Q. If the light goes out while between stations, what course would an engineer pursue? A. If investigation cannot be made within a few minutes thereafter to determine the cause, the steam should be shut off from the turbine engine until such time when cause of failure can be determined. 61. Q. Why is it essential to shut off steam and stop the equipment? A. If failure was due to a short circuit, damage might be done to the armature or field coils by overheating. 62. Q. How does the equipment act when short circuited? A. The engine will labor heavily and run slowly with a large volume of steam blowing at the exhaust, the carbon points and cab lights will only show a dull red light. 63. Q. How would you test for a broken circuit? A. Would test for a broken circuit or open circuit: First, by placing a carbon across the binding posts at dynamo. If the trouble was in the dynamo, no flash would be seen, but if dynamo was all right you would get a flash; this would indicate that the trouble was on towards the lamp. Second: Go to the lamp, place your carbon across binding posts. If wire was broken between dynamo and lamp you would not get a flash. If your wires were all right you would get a flash and you would find your trouble in the lamp. No doubt, it would be a burned-out carbon. 64. Q. How would you proceed to locate the point of trouble with a short circuit? A. Would remove (1) one of the lead wires from the binding post at dynamo; if trouble was in dynamo you would not note any difference in action of speed. (2) Would disconnect one of the cab wires; if the trouble is in cab circuit, speed would increase and lamp would burn. (3) If trouble is not in cab circuit, would go to lamp, disconnect one of the main wires from binding post; if short circuit is in the wires between dynamo and lamp, there would be no change in speed of dynamo, but if the wires are O. K. the speed of engine would increase and your trouble would be in the lamp. =DUPLEX LOCOMOTIVE STOKER= 1. Q. Of what does the driving mechanism of a Duplex Locomotive Stoker consist? A. It consists of a steam cylinder with reverse head and valve arrangement similar to the steam end of an eleven inch Westinghouse air pump. 2. Q. How is the power controlled? A. The speed is variable, and by turning the valve controlling the engine steam inlet, can be made greater or less according to the amount of coal needed. 3. Q. For ordinary operation, how much steam pressure is required? A. About fifteen pounds, with piston strokes varying from 10 to 15 per minute. 4. Q. How can the duplex stoker driving engine be started, stopped, or reversed? A. By means of operating and reversing rod, fastened to the back head and connected with the valve on reverse head of engine cylinder. 5. Q. How can the conveying screws be started, stopped, or reversed separately or together? A. By ratchet and pawl arrangement controlling each. 6. Q. What practice should be followed in building up the fire before leaving a terminal? A. Build up a light even fire by hand and do not bring stoker into use until the locomotive is working steam. 7. Q. How should the stoker be oiled and operated? A. It should be thoroughly oiled before leaving the terminal, then see that operating rod on back head is in center or running position, open main jet line so they register about fifteen pounds on the jet steam gauge if coal is coarse, or ten pounds if coal is small. Next, the driving engine steam valve should be opened wide and the throttle valve opened just enough to supply the proper amount of coal to the fire-box. 8. Q. How is the distribution of coal over the grate area accomplished? A. By means of a low-pressure constant steam jet located in the back and bottom portion of each distributor elbow, as indicated by its individual pointer on steam gauge. 9. Q. By increasing the jet pressure, will more coal be carried to forward end of fire-box and against the flue-sheet? A. Yes, it will, and by decreasing the jet pressure more coal will be fed at middle and back end of fire-box. [Illustration] 10. Q. Can the fireman direct the even distribution of coal in the fire-box? A. Yes; by changing position of the dividing rib located in the transfer hopper, and by moving the regulating lever to either side. 11. Q. Should the sliding plates at the bottom of the tank be closed before coal is put on tank? A. Yes, so that screw conveyor will not become clogged and inoperative. Only one slide should be opened at a time and coal fed from tank as required. 12. Q. In case the stoker becomes clogged or it is desired to reverse it for any reason, what must be done? A. The operating rod located on the back-head of the locomotive boiler--if the piston is making a power stroke--should be moved to its lower position, and if the piston is making a return stroke, it should be moved to its upper position. This moves a small valve in the auxiliary head, bolted to reverse head, and steam is admitted to opposite head of cylinder, causing the piston to change its direction. The return of the operating rod handle to a central position causes the driving engine to resume its normal operation. 13. Q. How can the fireman observe the condition of fire in fire-box? A. The elbows are provided with peep valves with swinging covers through which the coal supply and condition of fire may be seen. 14. Q. Why are two gauges necessary? [Illustration] A. The driving engine gauge on the left indicates the pressure of steam used by the driving engine. The one on the right has two indicators, the red indicator showing the steam pressure on the jet in left elbow, and the black indicator showing the pressure on the jet in the right elbow. 15. Q. When train is standing on siding for a short period, what should be done? A. Shut stoker off by throwing operating rod on back head of locomotive boiler out of running position. 16. Q. When train is to stand for a long time or engine is left at terminal, what should be done? A. The driving engine should be cut out entirely by closing main steam line inlet and main lubricator connection, and in winter time all drain cocks should be opened. 17. Q. If sufficient coal can not be supplied over front grates, what may be the cause? A. Distributors may be warped and point too low, or steam jets may be plugged with pipe scale and not blowing freely. 18. Q. How would you start and operate stoker? A. First open main valve No. 1 at steam turret. Valve 2 is then opened; this is the main valve in stoker steam line. Next open valve 3, which allows the steam to flow to the distributor jet line; open valves 4 and 5, which govern the pressure on the jets until ten pound pressure shows on the right-hand gauge. See valve 8 to the exhaust line is open, and valve 9 to the transfer hopper is closed. 19. Q. How would you start the stoker engine? A. Place operating lever 10 in horizontal or running position. Place conveyor reversing lever 12 in forward position. Open valve 6, which allows the steam to pass to the operating valve and starts stoker running. Valve 7 is to be used as an emergency valve only in case of clogging. Stoker should be run slowly at first. Do not feed too much coal and carry a light fire. 20. Q. How would you reverse conveyor screw in tank? A. Lower handle 10 on operation rod on boiler head to bottom position. Move screw conveyor, reverse lever 12 back to rear or reverse position, raise handle 10 on operating rod to center position. 21. Q. How would you stop conveyor screw in tank? A. Place conveyor reversing lever 12 in center position. 22. Q. How would you reverse right or left elevator screw? A. Raise elevator pawl shifter 26 on top of the vertical shaft to upper position. 23. Q. How would you stop right or left elevator screw? A. Raise elevator pawl shifter 26 on top of the elevator to middle position. 24. Q. How would you locate clogs in case the stoker stalls? A. First, shut off pressure to stoker engine cylinder by closing valve 6. Second, move operating valve lever 10 to its lowest position. Third, place tender conveyor reverse lever 12 in center. Fourth, place right elevator pawl shifter 26 in neutral position. Fifth, raise operating valve lever 10 to center position. Sixth, open valve 6 sufficiently to run left elevator to ascertain if it operates freely. Cut in right elevator by lowering pawl shifter 26, and if stoker stops, the obstruction is in the right elevator. If it continues to operate, then the obstruction is in the tank conveyor. 25. Q. How would you remove clogs? A. Clogs in upright elevators usually occur at the bottom. Raise the door in the engine deck and remove the obstruction if in the elevator, reverse the elevator screw forcing the obstruction back down in transfer hopper. It may be a small mine spike lodged above this point, and by removing the nut at top of elevator casing and removing the door the obstruction can be easily removed. 26. Q. If the clog is in the tank conveyor, how would it be removed? A. The clog will usually be found in the crushing zone. Reverse the tank conveyor screw, forcing the obstruction back, when it can be removed from the trough. 27. Q. How far should the conveyor screw be run backwards? A. Not more than three revolutions. [Illustration] PARTS OF DUPLEX LOCOMOTIVE STOKER 1. Conveyor Trough. 2. Conveyor Screw. 3. Angle Ring. 4. Crusher. 5. Operating Head. 6. Driving Engine Cylinder. 7. Reverse Valve. 8. Piston Rod. 9. Transfer Hopper. 10. Left Elevator Casing. 11. Left Elevator Screw. 12. End of Elevator Screw Shaft. 13. Elevator Pawl Shifter. 14. Elevator Pawl Casing. 15. Distributors. 16. Left Distributor Elbow. 17. Right Distributor Elbow. 18. Dividing Rib. 19. Right Elevator Casing. 20. Oil Box. 21. Conveyor Reverse Lever. 22. Conveyor Oil Cups. 23. Rack Housing. 24. Rack. 25. Conveyor Pawl Casing. 26. Conveyor Screw Flexible Connection Sleeve. 27. Conveyor Screw Flexible Connection. 28. Conveyor Slide Support Roller. 29. Conveyor Slide Support. 30. Conveyor End Bearing and Gear Case. 31. Conveyor Screw Gear. 32. Conveyor Screw Driving Gear. =AIR BRAKE QUESTIONS= COMPRESSOR GOVERNOR 1. Q. When steam is first turned on, what must it pass through before entering the compressor? A. The compressor governor. 2. Q. What does Fig. 1 represent? A. This shows a sectional view of the SF compressor governor in open position. 3. Q. What is the duty of the compressor governor? A. To automatically regulate the main reservoir pressure by controlling the steam to the compressor. 4. Q. How are the regulating portions of the governor designated? A. The one having two pipe connections and a light regulating spring is known as the excess pressure head; the other, with a single pipe connection and heavy regulating spring, as the maximum pressure head. 5. Q. When does the excess pressure head control the flow of steam to the compressor? A. When the automatic brake valve is in any one of its first three positions; namely, release, running and holding positions. 6. Q. With the automatic brake valve in release, running or holding position, what pressure is in chamber "f" above the diaphragm? In chamber "d" below the diaphragm? [Illustration: Fig. 1. The SF-4 Compressor Governor. Connections: FVP, Feed Valve Pipe. ABV, Automatic Brake Valve. MR, Main Reservoir. B, From Boiler. P, To Air Pump.] A. Air, at feed valve pipe pressure, enters at the connection marked "FVP" and flows to chamber "f" above the diaphragm; this pressure acts in conjunction with the regulating spring 27 in creating the total pressure on the diaphragm. Air at main reservoir pressure flows through the automatic brake valve to the connection marked "ABV" to chamber "d" under the diaphragm. 7. Q. At what pressure is the regulating spring in the excess pressure head adjusted? A. Usually twenty pounds. 8. Q. With the spring adjusted at twenty pounds, what will be the total pressure on the upper side of the diaphragm? A. Twenty pounds, plus the pressure in the feed valve pipe. 9. Q. With the feed valve adjusted at seventy pounds, and the regulating spring at twenty pounds, what pressure will be had in the main reservoir when the governor stops the compressor? A. Ninety pounds. 10. Q. Explain the operation of the governor in controlling the compressor when a main reservoir pressure of ninety pounds is reached. A. When the main reservoir pressure in chamber "d" slightly exceeds the pressure on top of the diaphragm it will move upward, carrying the pin valve with it. The air in chamber "d" passes by the unseated pin valve through port "b" into chamber "b" above the governor piston, forcing it downward, seating the steam valve 5, thus shutting off the steam to the compressor. 11. Q. How long will the governor remain in this position? A. Until the main reservoir pressure falls below ninety pounds, when the combined spring and air pressure in chamber "f" will force the diaphragm 28 down, seating the pin valve. This shuts off the supply of air from chamber "d", and the air confined in chamber "b" will escape to the atmosphere through the vent port "c". The pressure now being removed from above the governor piston, the spring 9 aided by the steam pressure under the valve 5, will force the piston upward, unseating the steam valve 5, allowing steam to pass through the governor to the compressor. 12. Q. When the steam valve is seated, is steam entirely shut off from the compressor? A. No; there is a small port drilled through the valve; its purpose is to maintain a circulation in the steam pipe and keep the compressor working slowly; thereby preventing condensation when the steam valve is closed. 13. Q. With the automatic brake valve in release, running, or holding position, does the maximum pressure head operate? A. No; as during this time the main reservoir pressure is not sufficiently high to actuate its diaphragm. 14. Q. Where does the air come from that operates the maximum pressure head? A. From the main reservoir direct. (See Fig. 1.) 15. Q. When does the maximum pressure head control the compressor? A. When the automatic brake valve is in either lap, service or emergency position, also when the main reservoir cut-out cock is closed. 16. Q. How is the pressure created on top of the diaphragm in the maximum pressure head? A. By the regulating spring 19. 17. Q. What is the adjustment of this spring? A. Spring 19 is adjusted to the maximum pressure desired in the main reservoir usually 130 pounds. 18. Q. Explain the operation of the governor when the main reservoir pressure exceeds the tension of the regulating spring 19. A. When the pressure in chamber "a" exceeds the tension of the regulating spring 19, the diaphragm 20 is forced upward, unseating the pin valve, allowing air to flow from chamber "a" to chamber "b" above the governor piston, forcing it down, shutting off steam and stopping the compressor. 19. Q. How long will the governor remain in this position? A. Until the main reservoir pressure in chamber "a" under the diaphragm becomes slightly less than the adjustment of the regulating spring 19, when the diaphragm 20 will move down, seating the pin valve, shutting off the flow of air from chamber "a" to chamber "b". The air entrapped above the governor piston will escape to the atmosphere through the relief port "c"; this will allow the governor piston to raise, unseating the steam valve 5, again allowing steam to pass through the governor to the compressor. 20. Q. Is the maximum pressure head cut out in any position of the automatic brake valve? A. No; as the air that operates this head comes direct from the main reservoir, therefore is not controlled by the brake valve. 21. Q. Is the excess pressure head cut out in any position of the brake valve? A. Yes; as the air that operates this head comes through the automatic brake valve, and when the handle is moved beyond holding position, the port in the rotary valve seat, through which the air flows to chamber "d" is closed, thereby cutting out this head, leaving the compressor under the control of the maximum pressure head. 22. Q. What is the object of the duplex or double head governor? A. By use of the duplex governor the main reservoir pressure may be controlled at two different predetermined pressures; as when running along the excess or low pressure head controls the compressor, at the low pressure--usually ninety pounds--this being sufficient to keep the brakes released and fully charged; whereas, in lap position, as following a brake application, the maximum or high pressure head controls the compressor at the maximum pressure used--generally 130 pounds--this for a prompt release and quick recharge of the brakes. From this it will be seen that the compressor has to work against the high pressure only during the time the brake is applied. 23. Q. In what position should the automatic brake valve handle be placed when adjusting the excess pressure head? The maximum pressure head? A. Running position for the excess pressure head; lap position for the maximum pressure head. 24. Q. If, with the automatic brake valve handle in running position, the brake pipe and main reservoir do not stand twenty pounds apart, where would you look for the trouble? A. Would first learn if the maximum pressure head was properly adjusted, and if it were, would then look for the trouble in the adjustment of the regulating spring in the excess pressure head. 25. Q. What should be done? A. The regulating spring should be properly adjusted. 26. Q. How should the adjustment of the regulating spring in either pressure head be made? A. By removing the cap nut 25 or 17 and screwing the regulating nut 26 or 18 up or down as may be required. DEFECTS OF THE GOVERNOR 27. Q. What would be the effect if one or both of the pin valves leaked? A. Would cause a delay in opening of the steam valve after the pin valve had seated; and if air leaks by faster than it can escape through the relief port "c", pressure will accumulate in chamber "b" and force the governor piston downward, so as to partially or wholly close the steam valve 5. 28. Q. How can you tell if the pin valves leak? A. Leakage past the pin valve in the maximum pressure head will cause a constant blow at the relief port in all positions of the brake valve; leakage past the pin valve in the excess pressure head will cause a blow in the first three positions of the brake valve only. 29. Q. What would be the effect if the relief port "c" stopped up? A. The compressor will not start promptly after the pin valve seats. 30. Q. What would be the effect if the drain port "W" were stopped up? A. Steam leaking into the chamber under the governor piston will form a pressure and prevent the piston being forced downward to close the steam valve; the compressor will therefore continue to work until the main reservoir pressure is about equal to boiler pressure. 31. Q. If the pipe leading from the feed valve pipe to the excess pressure head of the governor breaks, what effect will it have on the compressor? A. The compressor will stop when the main reservoir pressure reaches about forty-five pounds. 32. Q. If the pipe breaks, what should be done? A. Plug the end toward the feed valve and put a blind gasket in the pipe leading from the automatic brake valve to the governor, at the connection marked ABV. 33. Q. If the pipe leading from the automatic brake valve to the governor breaks, what should be done? A. Plug the pipe toward the brake valve; the compressor will now be controlled by the maximum pressure head. 34. Q. If the pipe leading from the main reservoir to the maximum head of the governor breaks, what should be done? A. Plug the main reservoir end of the pipe. The excess pressure head will now control the compressor in the first three positions of the automatic brake valve handle, but will have no control after the handle is moved as far as lap position. =PARASITE GOVERNOR= 35. Q. What is the purpose of the parasite governor, and where is this governor located? A. This governor is located in the pipe connection between the main reservoir and parasite reservoir, and its purpose is to control the flow of air from the main to the parasite reservoir. 36. Q. What is the purpose of the parasite reservoir? A. It is here that air is stored for use in all air operated devices on the locomotive, except the brake. 37. Q. Explain the operation of the parasite governor. A. The operation of this governor is much the same as the compressor governor, and differs only in that the supply valve is open when it is in its lower position. 38. Q. At what pressure is the regulating spring adjusted? A. About fifteen pounds. 39. Q. What pressure is required in the main reservoir before air is admitted to the parasite reservoir? A. At least fifteen pounds above that in the brake pipe. 40. Q. What pressure is obtained in the parasite reservoir? A. The same as that in the main reservoir, when the main reservoir pressure is fifteen pounds greater than that in the brake pipe. 41. Q. What will prevent the charging of the parasite reservoir, and what should be done? A. This may be caused by the feed valve being improperly adjusted, sticking in open position or leakage of main reservoir air past the valve to the feed valve pipe and governor top. =WESTINGHOUSE 9-1/2 OR 11-INCH COMPRESSOR= 42. Q. What is the duty of the air compressor? A. To furnish the compressed air used in the operation of the brakes, and all other air operated appliances on both locomotive and cars. 43. Q. Explain the operation of the steam end of the compressor. A. When steam is turned on at the boiler it flows through the steam pipe and governor, entering the compressor at the steam enlet, then through the steam passage "a" to the reversing valve chamber "C" also to the main valve chamber "A" between the differential pistons 77 and 79. The area of the piston at the right being greater than the one at the left, the main valve is moved to the right, (See Fig. 2) admitting steam to port "b" which leads to the lower end of the steam cylinder; steam is now free to flow under the main piston, forcing it upward. When the piston has almost completed its upward stroke, the reversing plate 69 on top of the piston 65 engages a shoulder on the reversing rod 71, moving the rod and reversing valve 72 upward (See Fig. 3). The upward movement of the reversing valve closes the ports "f" and "h" and opens port "g"; thus permitting steam to enter the chamber at the right of the large piston 77, balancing the pressure on this piston, and the pressure acting on the right side of the small piston 79--the chamber at the left being open to the exhaust--will force the main valve to the left. [Illustration: Diagrammatic View, Up Stroke Fig. 2.] When the main valve moves to the left, steam is admitted through port "c" to the upper end of the cylinder on top of the piston 65, forcing it downward. At the same time the lower end of the cylinder is connected through exhaust cavity "b" of the main valve to the exhaust port "d", allowing the steam below the piston to escape to the atmosphere. 44. Q. When the piston has about completed its downward stroke, what takes place? A. The reversing plate 69 engages the button "k" on the end of the reversing rod 71 pulling the rod and the reversing valve down. This movement of the reversing valve closes port "g" and the cavity in the face of the valve connects ports "f" and "h", which allows the steam in chamber "D" at the right of the large differential piston to escape to the exhaust, thus allowing the main valve to move to the right, exhausting the steam from the top end of the cylinder, and at the same time admitting steam to the lower end, causing an upward stroke of the piston. 45. Q. Explain the operation of the air end of the compressor. A. The movement of the steam piston 65 is imparted to the air piston 66 by means of the piston rod. When the air piston moves up, a partial vacuum is formed below it, and air from the atmosphere will enter through passage "F" thence through passage "n" to the under side of receiving valve 86b (see Fig. 2), lifting this valve from its seat, and will fill the cylinder with air at about atmosphere pressure. [Illustration: Diagrammatic View, Down Stroke Fig. 3.] In the meantime the air above the piston, being compressed, will hold the upper receiving valve 86a to its seat, and when the pressure is slightly greater than that in the main reservoir, this pressure acting under the upper discharge valve 86c, will lift this valve from its seat and now the air will be free to flow through passage "G" to the main reservoir connection. On the down stroke the action is similar, air is taken in through the upper receiving valve 86a, while the air below the piston is being compressed and forced past the lower discharge valve 86d, to the main reservoir. (See Fig. 3.) 46. Q. What lift should the air valves have? A. All valves should have a lift of three thirty-second of an inch. 47. Q. At what speed should the compressor be run to obtain the best results? A. At 100 to 120 single strokes per minute. 48. Q. What kind of oil should be used in the air end of the compressor and on the swab? A. Valve oil. 49. Q. How often should the air end of the compressor be oiled? A. No fixed rule can be given as so much depends on the condition of the compressor, as well as the amount of work required; but in any case it should be used sparingly. CROSS-COMPOUND COMPRESSOR 50. Q. What do Figures 4 and 5 represent? A. These are diagramatic views of a cross-compound compressor. 51. Q. Why is this called a cross-compound compressor? [Illustration: Diagram of 8-1/2" Cross Compound Compressor. The High Pressure Steam (Low Pressure Air) Piston on Its Upward Stroke Fig. 4.] A. Because both steam and air are compounded, that is, the steam is used the second time before it is exhausted to the atmosphere, while the air is compressed the second time before it is delivered to the main reservoir. 52. Q. How many cylinders have the cross-compound compressor? A. Four; two steam cylinders and two air cylinders. 53. Q. What is the diameter of the different cylinders? A. The high pressure steam cylinder is 8-1/2 inches; the low pressure steam cylinder 14-1/2 inches; the low pressure air cylinder 14-1/2 inches; high pressure air cylinder 9 inches. 54. Q. Explain the valve gear of this compressor. A. The valve gear is the same as that of the 9-1/2 or 11 inch compressor, only that a piston valve is used to distribute the steam instead of a slide valve. 55. Q. Where does the steam come from that is used in the high pressure steam cylinder? A. Direct from the boiler. 56. Q. Where does the steam come from that is used in the low pressure steam cylinder? A. The steam after doing work in the high pressure steam cylinder is exhausted into the low pressure steam cylinder, where it becomes the working pressure of this cylinder. 57. Q. Explain the operation of this compressor. A. When steam is first turned on, it enters the compressor at the steam inlet (see Fig. 4) and flows through passage "a" into the reversing valve chamber "C" and on to chambers "b" and "y" against the inner faces of the differential pistons, causing the main valve to move to the right. In this position of the main valve, port "g" is open to chamber "b", thus admitting live steam to the lower end of the high pressure steam cylinder, causing an upward movement of the piston 7. When the piston 7 has nearly completed its up stroke, the reversing plate 18, which is attached to the top of this piston, comes in contact with a shoulder on the reversing rod 21, forcing it upward, carrying with it the reversing valve 22, the movement of which closes port "m", at the same time opens port "n", filling chamber "D" with live steam from chamber "C" and passage "a". This balances the pressure on the two sides of the large piston of the differential pistons, and the pressure acting against the inner side of the small piston causes the main valve to move to the left (see Fig. 5). The main valve moving to the left closes port "g" to the live steam and at the same time connects this port with port "f" leading to the lower end of the low pressure steam cylinder, causing an up stroke of the low pressure steam piston 8. In the meantime port "c", which leads to the upper end of the high pressure steam cylinder, is open to chamber "y", allowing live steam to flow down on top of the high pressure steam piston 7, forcing it downward. As the high pressure steam piston about completes its downward stroke, the reversing plate 18 engages the button on the lower end of the reversing rod 21, pulling the rod and reversing valve 22 down, closing port "n" and at the same time connecting port "m" and "l" through the exhaust cavity "q", thus allowing the steam in chamber "D" to escape to the exhaust. The pressure being removed from the outer face of the large differential piston, the main valve will again move to the right, opening port "g", admitting live steam beneath the piston 7, and at the same time connecting the upper end of the high pressure steam cylinder through port "c", chamber "h" and port "d" to the upper end of the low pressure steam cylinder, causing a downward movement of the low pressure steam piston; the steam below this piston will now be free to escape to the exhaust through port "f", chamber "i" and port "e". Thus it will be seen that the steam used in the high pressure steam cylinder is live steam from the boiler, while the steam used in the low pressure steam cylinder is the exhaust steam from the high pressure steam cylinder. 58. Q. Explain the operation of the air end of the compressor. A. As the low pressure air piston 9 moves up, a partial vacuum is created beneath it and air from the atmosphere enters the air inlet and passage "r" past the lower receiving valve 38 and fills the lower end of the cylinder with air at about atmospheric pressure (see Fig. 4). In the meantime the air above the piston being compressed will hold the upper receiving valve 37 to its seat, thus preventing a back-flow of air to the atmosphere; at the same time the upper intermediate discharge valves 39 are forced from their seats, allowing the air from the low pressure air cylinder to flow through passage "u" to the high pressure air cylinder, the piston of which is now moving downward. The air beneath the high pressure air piston 10 being compressed will hold the lower intermediate discharge valves 40 to their seats, thus preventing the air in the high pressure air cylinder flowing back to the low pressure air cylinder. When the pressure in the high pressure air cylinder becomes slightly greater than the main reservoir pressure, the final discharge valve 42 will be forced from its seat and the air beneath the piston allowed to flow to the main reservoir through passage "w". On the opposite strokes of these pistons air is compressed in a similar manner, but the opposite air valves are used. [Illustration: Diagram of 8-1/2" Cross-Compound Compressor. The High Pressure Steam (Low Pressure Air) Piston on Its Downward Stroke Fig. 5.] 59. Q. How many valves are there in the air end of the compressor? A. Ten; two upper and two lower receiving valves; two upper and two lower intermediate discharge valves; one upper and one lower final discharge valves. 60. Q. Are the air valves all the same size? A. No; the receiving and final discharge valves are the same size and of the size used in the 11-inch compressor, while the intermediate valves are the same as used in the 9-1/2-inch compressor. The receiving and final discharge valves are two inches in diameter, while the intermediate valves are one and one-half inches. 61. Q. What lift is given the different air valves? A. All valves have 3/32-inch lift. DEFECTS OF THE COMPRESSOR 62. Q. What are some of the common causes for the compressor stopping? A. Lack of lubrication; bent, worn or broken reversing rod; loose or worn reversing plate; nuts on air end of piston rod coming off; defective compressor governor; and, in addition with the cross-compound compressor, final discharge valve broken or stuck open, or packing rings in main valve pistons breaking and catching in the steam ports. 63. Q. What will cause the piston to make an uneven stroke? A. This may be caused by a broken or stuck open air valve, or air valves not having proper lift. Where the piston short strokes, it is generally caused by over-lubrication of the steam end. 64. Q. What are some of the common causes for the compressor running hot? A. The overheating of the compressor may be due to any one of the following causes: Running at high speed; working against high pressure; packing rings in air piston badly worn; air cylinder worn; defective air valves; air passages or air discharge pipe partially stopped up; leaky piston rod packing; lack of lubrication. 65. Q. What will cause the compressor to run slow? A. This may be caused by leaky air piston packing rings; final discharge valves leaking, or air passages partially stopped up. A defective governor may also cause the compressor to run slow. 66. Q. What will cause the compressor to run very fast and heat, and not compress any air? A. This may be caused by the strainer becoming clogged with ice or dirt, preventing air entering the cylinder. 67. Q. If, when steam is first turned on, the piston makes a stroke up and stops, where would you look for the trouble? A. The shoulder on the reversing rod may be worn; the opening in the reversing plate too large to engage the shoulder on the reversing rod; loose reversing plate studs preventing the piston traveling far enough to reverse the compressor, or the main valve stuck in its position at the right. 68. Q. If the piston makes a stroke up and a stroke down and stops, where is the trouble? A. This may be caused by a loose reversing plate, or the button on the lower end of the reversing rod worn or broken off, or the nuts off the piston rod in the air end, or the main valve stuck in its position at the left. 69. Q. What will cause the piston to make a quick up stroke? A. This may be caused by a broken or stuck open upper receiving or lower discharge valve. 70. Q. What will cause the piston to make a quick down stroke? A. Lower receiving or upper discharge valve broken or stuck open. 71. Q. If a receiving valve breaks or sticks open, how may it be located? A. The air will flow back to the atmosphere as the piston moves toward the defective valve and may be detected by holding the hand over the strainer. 72. Q. If a receiving valve in a cross-compound compressor breaks, what may be done? A. Remove the broken valve, blocking the opening made by its removal, and as there are two upper and two lower receiving valves the compressor will now take air through the other valve. 73. Q. If an intermediate discharge valve breaks or sticks open, how may it be located? A. No air will be taken in to that end of the compressor as the piston moves from the defective valve, and may be located by holding the hand over the strainer. 74. Q. If an intermediate discharge valve breaks, what may be done? A. Remove the broken valve, blocking the opening made by its removal, and as there are two upper and two lower intermediate discharge valves the air will now pass from the low pressure cylinder to the high pressure cylinder through the other valve. 75. Q. If a final discharge valve breaks, what effect will it have on the compressor? A. Will cause the compressor to stop when the main reservoir pressure is in excess of forty pounds. 76. Q. How would you test for a defective final discharge valve? A. To test for this defect, bleed the main reservoir pressure below forty pounds, and if the compressor starts it indicates a defective discharge valve. 77. Q. If a final discharge valve breaks, what may be done? A. As the receiving valves and final discharge valves are the same size, the defective valve may be replaced by one of the receiving valves, blocking the opening made by the removal of the receiving valve. 78. Q. Where piston rod packing is blowing bad, what may be done to stop it? A. This generally indicates lack of lubrication, and by cleaning and oiling the swab the trouble may be overcome. However, there are times when leakage by the packing is so great that the oil is blown off the swab as fast as it is applied, therefore is of no value in lubricating the parts. Where this condition exists, a little hard grease wrapped up in an old flag and tied around the piston rod will ensure its being lubricated. 79. Q. If the compressor stops, how can you tell if the governor is responsible for the trouble? A. By opening the drain cock in the steam passage between the governor and the compressor; if steam flows freely, the trouble is in the compressor; if not, it is in the governor. 80. Q. How may a compressor often be started when it stops? A. By closing the steam throttle for a few seconds, then opening it quickly; if this does not start it, try tapping the main valve chamber. This will usually overcome the trouble where the compressor stops on account of lack of lubrication. 81. Q. What will cause a compressor to short-stroke or dance? A. Too much oil in the steam end; bent reversing rod; or low steam pressure, as when the governor has almost shut off the steam. ENGINEER'S BRAKE VALVE 82. Q. Name the different positions of the G-6 and H-6 brake valves. A. Release, running, lap, service, and emergency position, with the G-6; release, running, holding, lap, service, and emergency positions, with the H-6. 83. Q. What is the purpose of release position? A. To provide a large and direct opening from the main reservoir to the brake pipe, for the free flow of air, when charging and recharging the brakes. 84. Q. What pressure will be had in the brake pipe if the brake valve be left in release position? A. Main reservoir pressure. 85. Q. Can the locomotive brake be released by the automatic brake valve in release position, when using the H-6 valve? A. No; as the port in the automatic brake valve to which the distributing valve release pipe is attached is blanked in this position of the valve. 86. Q. What is the purpose of running position, and when should it be used? A. This is the proper position for the brake valve when the brakes are charged and not in use, also when it is desired to release the locomotive brake with this valve. In this position the brake pipe pressure is maintained at a predetermined amount by the feed valve, as all air that now enters the brake pipe must pass through the feed valve. 87. Q. What is the purpose of holding position? A. To hold the locomotive brake applied while recharging the brakes. The charging of the brake pipe and equalizing reservoir is the same in holding as in running position. 88. Q. What is the purpose of lap position? A. To hold both the locomotive and train brakes applied after an automatic application. 89. Q. What is the purpose of service position? A. This position of the brake valve enables the engineer to make a gradual reduction of brake pipe pressure, thus causing a service application of the brakes. 90. Q. What is the purpose of emergency position? A. In this position of the brake valve, the brake pipe is connected directly with the atmosphere through the large ports in the valve, causing a sudden reduction of brake pipe pressure, this in turn causing the distributing valve on the engine and all operating triple valves on cars in the train to move to emergency position, thus insuring a quick and full application of the brake. 91. Q. How should the brake valve be handled when making an emergency application of the brake? A. The valve should be placed in full emergency position and left there until the train stops, even though the danger may have disappeared. DEFECTS OF THE BRAKE VALVE 92. Q. What will cause a constant blow at the brake pipe exhaust port, and what may be done to overcome it? A. This indicates that the brake pipe exhaust valve is being held off its seat, due no doubt to dirt; tapping the side of the valve will sometimes stop the blow; if not, close the brake pipe cut-out cock and make a heavy service reduction; next, place the brake valve handle in release position. This will cause a strong blow at the exhaust port, which will invariably remove the trouble. 93. Q. If the pipe connecting the brake valve with the equalizing reservoir breaks, can both locomotive and train brakes be operated with the automatic brake valve? A. Yes; by placing a blind gasket in the pipe connection at the brake valve and plugging the brake pipe exhaust port. To apply the brake, move the handle carefully toward emergency position, making a gradual reduction of brake pipe pressure through the direct exhaust ports of the brake valve; when the desired reduction is made, the handle should be moved gradually back to lap position. 94. Q. What would be the effect if the handle were moved to lap quickly? A. Would cause the release of the brakes on the head end of the train. 95. Q. What will cause air to blow at the brake pipe exhaust port when the handle is moved to lap position? A. This is caused by a leak from the equalizing reservoir or its connections, which reduces the pressure in chamber "D" above the equalizing piston, allowing brake pipe pressure under the piston to force it up, unseating the brake pipe exhaust valve, permitting brake pipe air to flow to the atmosphere. 96. Q. What is the purpose of the equalizing reservoir? A. The purpose of the equalizing reservoir is to furnish a larger volume of air above the equalizing piston than is found in chamber "D", thus to enable the engineer to make a graduated reduction of the pressure above the equalizing piston. 97. Q. What defect will cause the brake pipe and main reservoir pressure to equalize when the handle is in running position? A. This may be caused by leakage past the rotary valve, defective body gasket, or leakage by the feed valve or its case gasket. To determine which part is at fault, close the cut-out cock under the brake valve and move the handle to service position, exhausting all air from chamber "D" and the brake pipe; return the handle to lap position. Leakage of air past the rotary valve is generally into the brake pipe port which allows the air to come in under the equalizing piston, thus forcing it upward, unseating the brake pipe exhaust valve, allowing this air to escape to the atmosphere at the brake pipe exhaust port. Leakage past the body gasket allows air to enter chamber "D", above the equalizing piston, holding it in its lower position, keeping the brake pipe exhaust port closed, thereby preventing the escape of this air to the atmosphere. Since the capacity of the equalizing reservoir and chamber "D" is small, such a leak will cause the black hand to quickly move up to the position of the red hand. To determine if the leakage be in the feed valve or its gasket, recharge the brake pipe to some pressure below the adjustment of the feed valve, then place the handle in lap position. If the black hand on the air gauge remains stationary, it is fair to assume that the trouble is in the feed valve or its gasket, as in this position of the brake valve the feed valve is cut out. 98. Q. With the engine alone, the brake pipe pressure will equalize with that in the main reservoir, while when coupled to a train the pressure will remain at that for which the feed valve is adjusted; where is the trouble? A. This is caused by light leakage of main reservoir air into the brake pipe, and may come past the rotary valve, body gasket, or feed valve, and with the lone engine is sufficient to raise the brake pipe pressure to that in the main reservoir; while, when coupled to a train, the brake pipe leakage of which is greater than this amount, this leakage will not be noticed. THE FEED VALVE AND ITS DEFECTS 99. Q. What do Figures 6 and 7 represent? A. These are diagrams of the B-6 feed valve in both open and closed positions. 100. Q. Name the different parts of the feed valve. A. The valve consists of the following parts: 2, valve body; 3, pipe bracket; 5, cap nut; 6, piston spring; 7, piston spring tip; 8, supply valve piston; 9, supply valve; 10, supply valve spring; 11, regulating valve cap nut; 12, regulating valve; 13, regulating valve spring; 14, diaphragm; 15, diaphragm ring; 16, diaphragm spindle; 17, regulating spring; 18, spring box; 19 and 20, stop rings; 21, clamping screw; 22, hand wheel. 101. Q. Explain the operation of the feed valve. A. The feed valve consists of two portions, the supply and regulating portions. The supply portion consists of a slide valve 9 and a piston 8 (see Fig. 6). The supply valve 9 opens and closes communication between the main reservoir and the feed valve pipe and is moved by the piston 8 which is operated by main reservoir air entering through passage "a" on one side or by the pressure of the spring 6 on the other side. The regulating portion consists of a brass diaphragm 14, on one side of which is the diaphragm spindle 16, held against the diaphragm by the regulating spring 17, and on the other side a regulating valve 12, held against the diaphragm or its seat, as the case may be, by the spring 13. Chamber "L" at the left of the diaphragm is open to the feed valve pipe through the passage "e" and "d". The feed valve is adjusted by turning the hand wheel 22 in or out, thus increasing or decreasing the pressure exerted by the spring on the diaphragm. The same results are obtained in turning the hand wheel 22 as when turning the adjusting screw in the older types of feed valves. [Illustration: Fig. 6. Diagram of B-6 Feed Valve, Closed. Connections: MR, Main Reservoir Pipe; FVP, Feed Valve Pipe.] Air from the main reservoir flowing through passage "a" into chamber "B" will force the piston 8 to the left against the tension of the spring 6; the piston in moving will take with it the supply valve 9, opening the supply port in the valve to port "c" in its seat as shown in Fig. 7. Main reservoir air will now be free to flow through passage "a", chamber "B", port "c" and passage "d" to the feed valve pipe. Air coming through port "c" also flows through passage "e" to chamber "L" at the left of the diaphragm 14, and this pressure tends toward forcing the diaphragm to the right; but the diaphragm being supported by the regulating spring 17, will remain in its position at the left, holding the regulating valve 12 off its seat, until the pressure in chamber "L" exceeds the tension of the regulating spring 17. Air, therefore, continues to flow from the main reservoir through a, B, c, d and e to the feed valve pipe and chamber "L", increasing the pressure, until the pressure on the diaphragm 14 overcomes the tension of the regulating spring 17, when the diaphragm will move to the right, allowing the spring 13 to force the regulating valve 12 to its seat, closing port "K". Chambers "G" and "H" are then no longer open to chamber "L" and the feed valve pipe, and these chambers being small, the pressure raises quickly to main reservoir pressure due to the leakage of air past the supply piston 8, which forms but a loose fit in its bushing. When the pressure in chamber "G" becomes nearly equal to that in chamber "B", the piston spring "6" forces the piston 8 and its slide valve 9 to closed position, which prevents further flow of air from the main reservoir to the feed valve pipe (see Fig. 6). The feed valve will remain in closed position until the pressure in chamber "L" is slightly reduced so that the pressure on the diaphragm 14 is no longer able to withstand the pressure of the regulating spring 17, which then forces the diaphragm to the left, lifting the regulating valve 12 from its seat and again opening port "K" to chamber "L", thus dropping the pressure at the left of piston 8 below that of the main reservoir acting on the opposite side of the piston. [Illustration: Fig. 7. Diagram of B-6 Feed Valve, Open.] Main reservoir pressure then forces the supply piston and valve over into open position, as shown in Fig. 7, and allows a further flow of air through port "c" to the feed valve pipe to again raise its pressure to the adjustment of the feed valve, when the valve will again close. 102. Q. What is the duty of the feed valve? A. To control and maintain a constant pressure in the brake pipe when the brake valve is in running or holding position. 103. Q. What defect in the feed valve will cause the brake pipe pressure to equalize with that in the main reservoir? A. This may be caused by a defective feed valve case gasket, permitting main reservoir air to leak into the feed valve pipe, or leakage past the supply valve, or the regulating valve held from its seat, or the supply valve piston too tight a fit in its cylinder. 104. Q. If the brake pipe charges too slowly when nearing the maximum pressure, where is the trouble? A. This may be caused by a loose-fitting supply valve piston 8, or the port past the regulating valve 12 partly stopped up. 105. Q. How should the feed valve be tested? A. With the brakes released, and charged to the adjustment of the feed valve, create a brake pipe leak of from seven to ten pounds and note the black hand on the brake pipe gauge. The fluctuation of this hand will indicate the opening and closing of the feed valve, which should not permit a variation of over two pounds in brake pipe pressure; if it does, it indicates a dirty condition of the valve, and should be cleaned. 106. Q. If the main reservoir pipe connection to the feed valve breaks, what should be done? A. This will cause a loss of main reservoir air, and both ends of the pipe must be plugged. As no air now comes to the feed valve to charge the brake pipe in running or holding position of the brake valve, the handle must be carried in release position. 107. Q. What must be done if the pipe between the feed valve and automatic brake valve breaks? A. Slack off on the regulating nut of the feed valve until all tension is removed from the regulating spring and plug the pipe toward the brake valve. To charge the brake pipe, the brake valve handle must be carried in release position. 108. Q. If the feed valve becomes defective so that it will not control brake pipe pressure, what may be done? A. As the reducing valve used for the independent brake, and the feed valve are practically the same, they may be changed one for the other, the reducing valve taking the place of the feed valve. INDEPENDENT BRAKE VALVE 109. Q. Name the different positions of the independent brake valve used with the E-T equipment. A. Release, running, lap, slow-application position, quick-application position. 110. Q. What is the purpose of release position? A. To release the locomotive brake when the automatic brake valve is in other than running position. 111. Q. What is the purpose of running position? A. This is the proper position for the brake valve when not in use, and to release the locomotive brake when the automatic brake valve is in running position. 112. Q. What is the purpose of lap position? A. To hold the locomotive brake applied after an independent application. 113. Q. What is the purpose of slow-application position? A. This position may be used when it is desired to make a light or gradual application of the brake, as in stretching or bunching the slack of a train. 114. Q. What is the purpose of quick-application position? A. To apply the locomotive brake quickly, as in short switching. 115. Q. What brake cylinder pressure is usually developed with this brake? A. About forty-five pounds. DEAD ENGINE FEATURE 116. Q. What is the dead engine device? A. The dead engine device is a pipe connection between the main reservoir and the brake pipe. In this pipe is found a combined strainer and check valve with a choke fitting and cut-out cock, which when open forms a connection between the brake pipe and the main reservoir. 117. Q. What is the purpose of this device? A. To provide a means of charging the main reservoir of an engine whose compressor is inoperative. 118. Q. What is the object of charging a main reservoir of an engine with a disabled compressor? A. As the air used in the locomotive brake cylinders comes from the main reservoir, for the brakes to be operated on this engine it is necessary that its main reservoir be charged. 119. Q. With a 70-pound brake pipe pressure, what pressure should be had in the main reservoir when using this device? A. About fifty pounds. 120. Q. When the dead engine feature is being used, in what position should the automatic and independent brake valves be carried? A. Running position. 121. Q. What should be the position of the brake pipe cut-out cock below the brake valve? A. It should be closed. DISTRIBUTING VALVE 122. Q. What is the duty of the distributing valve? A. To admit air from the main reservoir to the locomotive brake cylinders when applying the brake, to automatically maintain the brake cylinder pressure against leakage, to develop the proper brake cylinder pressure regardless of piston travel and to exhaust the air from the brake cylinders when releasing the brake. 123. Q. To what is the distributing valve attached? A. To the distributing valve reservoir. 124. Q. How many chambers has the distributing valve reservoir? A. Two; pressure chamber and application chamber. [Illustration: Fig. 8. Release, Automatic or Independent. Connections: MR, Main Reservoir Pipe; IV, Distributing Valve Release Pipe; II, Application Cylinder Pipe; CYLS, Brake Cylinder Pipe; BP, Brake Pipe.] 125. Q. Name the different pipe connections to the distributing valve reservoir. A. Referring to Fig. 8, the connection marked "MR" is the main reservoir supply pipe; "II", application cylinder pipe; "IV", distributing valve release pipe; "BP", brake pipe; "CYLS", brake cylinder pipe. 126. Q. To what do these different pipes connect? A. The main reservoir supply pipe connects the distributing valve with the main reservoir pipe. The application cylinder pipe connects the application cylinder of the distributing valve with the independent and automatic brake valves. The distributing valve release pipe connects the application cylinder exhaust port in the distributing valve with the independent brake valve, and through it, when in running position, to the automatic brake valve. The brake cylinder pipe connects the distributing valve with the different brake cylinders on the locomotive. The brake pipe branch pipe connects the distributing valve with the brake pipe. 127. Q. Explain the operation of the distributing valve when making an automatic service application of the brake. A. When the brakes are fully charged, the brake pipe and pressure chamber pressures are equal, and when a gradual reduction of brake pipe pressure is made it will be felt in chamber "p" at the right of the equalizing piston 26, creating a difference in pressure on the two sides of the piston, causing it to move to the right. The first movement of the piston closes the feed groove "v", also moves the graduating valve 28, uncovering the service port "z" in the equalizing slide valve 31; this movement of the piston also causes the shoulder on the end of its stem to engage the equalizing slide valve, and the continued movement of the piston moves the valve to service position, in which port "z" connects with port "h" in the seat of the valve, as shown in Fig. 9. As the equalizing slide valve chamber is at all times connected to the pressure chamber, air can now flow from this chamber to both the application cylinder and chamber through ports "z" and "h", cavity "n" and port "w" until the pressure on the left or pressure chamber side of the equalizing piston 26 becomes slightly less than that in the brake pipe, when the piston and graduating valve will move to the left until the shoulder on the piston stem strikes the slide valve; this movement of the graduating valve closes the service port "z", thus closing the communication between the pressure chamber and application chamber and cylinder, also closing port "l" which leads to the safety valve. The distributing valve is now said to be in service lap position. (See Fig. 10.) 128. Q. Upon what does the pressure in the application chamber and cylinder depend when making a service application of the brake? A. On the amount of brake pipe reduction; and as the relative volume of the pressure chamber and application cylinder and chamber is practically the same as that of an auxiliary reservoir and brake cylinder, it will be understood that one pound from the pressure chamber will make two and one-half pounds in the application chamber and cylinder; in other words, with the pressure chamber charged to seventy pounds and no pressure in the application chamber and cylinder, if they were connected and the pressure allowed to equalize it would do so at about fifty pounds; that is, twenty pounds from the pressure chamber will make fifty pounds in the application chamber and cylinder. [Illustration: Fig. 9. Automatic Service.] 129. Q. How is the application piston 10 affected by the air pressure in the application cylinder "g"? A. Pressure forming in this cylinder will force the piston to the right; the piston in moving will carry with it the exhaust valve 16, closing the exhaust ports "e" and "d", at the same time moving the application valve 5, opening the supply port "b", allowing main reservoir air from chamber "a" to flow through ports "b" and "C" to the connection marked "CYLS", and on to the different brake cylinders of the locomotive until the pressure in the brake cylinders and at the right of the application piston becomes slightly greater than that in chamber "g" when the application piston and valve will move back to lap position as shown in Figures 9 and 10. 130. Q. With the application valve in lap position, if there be brake cylinder leakage, will the locomotive brake leak off? A. No; any drop in brake cylinder pressure will be felt in chamber "b" at the right of the application piston 10, causing a difference in pressure on the two sides of the piston, thus allowing the pressure in the application cylinder to move the application piston and valve to the right, again opening the supply port "b" allowing a further flow of main reservoir air from chamber "a" to the brake cylinders until the pressure is again slightly greater than that in the application cylinder "g", when the application piston and valve will move back to lap position. Thus in this way air will be supplied to the brake cylinders of the locomotive, holding the brake applied regardless of leakage. 131. Q. What effect will piston travel have on the pressure developed in the brake cylinders? A. None; as the pressure in the brake cylinders is entirely dependent on the pressure in the application cylinder, which is not affected by piston travel. 132. Q. Explain the movement of the parts in the distributing valve when the automatic brake valve is moved to release position, after an automatic application of the brake. A. In release position of the brake valve, air from the main reservoir flows direct to the brake pipe, causing a rise of pressure which is felt in chamber "p" on the right or brake pipe side of the equalizing piston 26; this increase of pressure will cause the piston to move toward the left, carrying the graduating valve 28 and slide valve 31 to release position. [Illustration: Fig. 10. Service Lap.] This allows the air from the application chamber and cylinder to flow to the distributing valve release pipe "IV" and on through the independent brake valve to the automatic brake valve, where the port to which this pipe leads is blanked by the automatic rotary valve, thus preventing the air from leaving the application chamber and cylinder, holding the locomotive brake applied while the train brakes are being released. The movement of the parts, and the results obtained are the same where the release is made in holding position. 133. Q. Explain the movement of the parts in the distributing valve when the brake valve is moved to running position after having first been moved to release or holding position, following a brake application. A. In this position of the brake valve the port to which the distributing valve release pipe is connected is open to the exhaust, thus allowing the air to escape from the application chamber and cylinder. The reduction of pressure in chamber "g", will allow the brake cylinder pressure in chamber "b" to force the application piston and its valves to release position, thus allowing the brake cylinder air to escape to the atmosphere, through the exhaust ports "e" and "d". (See Fig. 8.) 134. Q. Explain how an independent release of the locomotive brake is obtained after an automatic application has been made. A. If the brakes have been applied throughout the train, by means of the automatic brake valve, and it is desired to release the locomotive brakes without releasing the train brakes, the handle of the independent brake valve is placed in release position. In this position of the independent brake valve, the application cylinder in the distributing valve is connected through the application cylinder pipe to the direct exhaust port of the independent brake valve; thus exhausting the air from the application cylinder, causing a release of the locomotive brake. This independent release of the locomotive brake does not cause the equalizing piston and its slide valve in the distributing valve to change their position. 135. Q. Explain what takes place when an automatic emergency application is made. A. Any sudden reduction of brake pipe pressure is felt on the brake pipe side of the equalizing piston 26 and will cause it and the slide valve 31 to move to the extreme right, compressing the graduating spring 60. (See Fig. 11.) In this position pressure chamber air can flow to the application cylinder only as the application chamber is now cut off. This will cause a quick rise of pressure in the application cylinder, forcing the application piston and its valves to full application position, admitting main reservoir air to the brake cylinders and applying the brake. In emergency position of the automatic brake valve there is a small port in the rotary valve, called the blow-down timing port, through which main reservoir air is free to flow to the application cylinder "g" through the application cylinder pipe "II", causing a rise of pressure equal to the adjustment of the safety valve. 136. Q. At what pressure is the safety valve adjusted? A. At sixty-eight pounds. 137. Q. What is the purpose of the quick action cap, and where is it located? A. Its purpose is to assist the brake valve in venting brake pipe air when an emergency application of the brake is made, and is located on the brake pipe side of the distributing valve in place of the plain cap. (See Figs. 8 and 11.) 138. Q. Explain the operation of the quick action cap. [Illustration: Fig. 11. Emergency Position of No. 6 Distributing Valve with Quick-Action Cap.] A. In an emergency application, the equalizing piston 26 moves to the extreme right, the knob on the piston strikes the graduating stem 59, causing it to compress the graduating spring 46, and move the slide valve 48 to the right, opening port "j". [Illustration: Fig. 12. Independent Application.] Brake pipe pressure in chamber "p" flows to chamber "X", pushes down check valve 53, and passes to the brake cylinders through port "m" in the cap and distributing valve body. When the brake cylinders and brake pipe pressures equalize, check valve 53 is forced to its seat by spring 54, thus preventing air in the brake cylinders from flowing back into the brake pipe. When a release of the brake occurs and piston 26 is moved back to its normal position, spring 46 forces graduating stem 59 and slide valve 48 back to release position. 139. Q. Explain the operation of the distributing valve when making an independent application of the brake. A. When the independent brake valve handle is moved to application position, air is admitted from the reducing valve pipe through the application cylinder pipe to the application chamber and cylinder. Pressure forming in the application cylinder will move the application piston 10 to the right, carrying with it the exhaust valve 16 and the application valve 5, closing the exhaust port and opening the supply port, admitting main reservoir air from chamber "a" to the brake cylinders (see Fig. 12) until the pressure in the brake cylinders and chamber "b" slightly exceeds that in chamber "g", when the application piston 10 and valve 5 will move back to lap position. By moving the brake valve handle to either release or running position, the air is exhausted from the application cylinder and chamber, thus reducing the pressure in chamber "g", allowing the pressure in chamber "b" to force the piston to the left, carrying with it the exhaust valve 16, opening the exhaust ports "e" and "d", allowing the air from the brake cylinders to escape to the atmosphere, thus releasing the brake. DISTRIBUTING VALVE DEFECTS 140. Q. If the locomotive brake released with the automatic brake valve in lap position, where would you look for the trouble? A. Would look for a leak in the application cylinder pipe or in the application cylinder cap gasket. 141. Q. If the brake remained applied in lap position, but released in release or holding position, where would you look for the trouble? A. Would look for a leak in the distributing valve release pipe. 142. Q. If the distributing valve release pipe and application cylinder pipe were crossed, what would be the effect? A. A brake application made by the automatic brake valve cannot be released by the independent brake valve. 143. Q. If the safety valve leaks, what will be the effect? A. This may prevent the brake applying, and in an independent application if the brake does apply, it will release when the brake valve is returned to lap position. BROKEN PIPES 144. Q. If the main reservoir supply pipe to the distributing valve breaks, what should be done? A. Plug the pipe toward the main reservoir. The locomotive brake is lost, but if the distributing valve is equipped with a quick action cap, when an emergency application is made, the air coming from the brake pipe, through the quick action cap, will apply the locomotive brake. 145. Q. If the application cylinder pipe breaks, what effect will it have on the locomotive brake? A. The locomotive brake cannot be applied with either automatic or independent brake valve. By plugging the pipe toward the distributing valve the automatic brake will be restored. 146. Q. If the distributing valve release pipe breaks, what will be the effect? A. The holding feature of the brake will be lost; that is, the locomotive brake will release when the automatic brake valve is moved to either release or holding position, the same as with the old G-6 equipment. 147. Q. If the release pipe is broken and not plugged, can the independent brake be applied? A. Yes, by placing the brake valve handle in quick-application position the brake will apply, but there will be a waste of air through the broken pipe, and the brake will release when the brake valve is returned to lap position. 148. Q. If the brake cylinder pipe breaks, can the locomotive brake be applied? A. This depends on where the pipe breaks; if between the cut-out cock and any one of the brake cylinders, close the cut-out cock to that cylinder, and the other cylinders may be used. But if the pipe breaks at the distributing valve, the locomotive brake will be lost. 149. Q. If the brake pipe connection to the distributing valve breaks, what should be done? A. Plug the end from the brake pipe; the locomotive brake must now be released by placing the independent valve in release position. 150. Q. If the brake pipe connection to the distributing valve breaks and is plugged, can the locomotive brake be operated? A. The independent brake may be applied and released in the usual manner, but the automatic brake will be lost for service braking. TYPE K TRIPLE VALVE 151. Q. On what is this type of triple valve designed to operate? A. On freight equipment cars only. 152. Q. Explain the operation of the "K" triple valve. [Illustration: Fig. 13. Full Release and Charging Position.] A. When air is admitted to the brake pipe it is free to enter the triple at "a" (see Fig. 13) and flow through the passage "e" to chamber "f", thence through port "g" to chamber "h" in front of the triple valve piston 4. Pressure forming in chamber "h" will force the piston to the left until its packing ring uncovers the feed groove "i" in the bushing, thus creating a communication between chamber "h" and the slide valve chamber. Brake pipe air will now be free to flow past the piston to the slide valve chamber and out at "R" to the auxiliary reservoir. Air will continue to feed through the groove "i" until the auxiliary reservoir and brake pipe pressures are equal, and it is then we say that the brake is fully charged. Brake pipe air entering chamber "a" will lift the check valve 15, and charge chamber "Y" to brake pipe pressure. When a gradual reduction of brake pipe pressure is made, as in a service application of the brakes, the pressure being reduced in chamber "h", auxiliary reservoir pressure will move the piston 4 toward service position. (See Fig. 14.) The first movement of the piston closes the feed groove "i", thus closing communication between the auxiliary reservoir and the brake pipe, preventing a back-flow of air from the auxiliary to the brake pipe, and at the same time moving the graduating valve 7, opening the service port "Z" in the slide valve. The continued movement of the piston will move the slide valve until the service port "Z" registers with the brake cylinder port "r" in the valve seat, thus creating a communication between the auxiliary reservoir and the brake cylinder. Air will now flow from the auxiliary to the brake cylinder until the pressure on the auxiliary side of the piston 4 becomes slightly less than in the brake pipe, when the piston and the graduating valve 7 will move back just far enough to close the service port "Z", thus closing communication between the auxiliary reservoir and the brake cylinder. At the same time, the first movement of the graduating valve connects the two ports "o" and "q" in the slide valve through the cavity "v" in the graduating valve, and the movement of the slide valve brings port "o" to register with port "y" in the slide valve seat, and port "q" with port "t". This permits the air in chamber "Y" to flow through port "y", "o", "v", "q", and "t", thence around the emergency piston 8, which fits loosely in its cylinder, to chamber "X" and the brake cylinder. When the pressure in chamber "Y" has reduced below the brake pipe pressure remaining in chamber "a", the check valve 15 is raised and allows brake pipe air to flow past the check valve and through the ports above mentioned to the brake cylinder. [Illustration: Fig. 14. Quick Service Position.] The size of these ports are so proportioned that the flow of air from the brake pipe to the top of the emergency piston 8, is not sufficient to force the latter downward and thus cause an emergency application, but at the same time takes enough air from the brake pipe to cause a local reduction of brake pipe pressure at that point, thus assisting the brake valve in increasing the rapidity with which the brake pipe reduction travels through the train. The triple valve is now said to be in "Quick Service" position. (See Fig. 14.) 153. Q. Will the triple valve move to quick service position whenever a gradual reduction brake pipe reduction is made? A. No; with short trains, the brake pipe volume being comparatively small, will reduce more rapidly for a certain reduction at the brake valve than with a long train. Therefore, with a short train, the brake pipe pressure reducing more quickly, the triple piston and its valves will move to "full service" position, as shown in Fig. 15. In this position the quick service port "y" is closed, so that no air flows from the brake pipe to the brake cylinder. Thus, when the brake pipe reduction is sufficiently rapid, there is no need for this quick service reduction, and the triple valve automatically cuts out this feature of the valve when not required. 154. Q. How long will the auxiliary reservoir air continue to flow to the brake cylinder? A. Air will continue to flow to the brake cylinder until the pressure on the auxiliary side of the triple piston becomes slightly less than that on the brake pipe side, when the piston 4 and the graduating valve 7 will move to the left until the shoulder on the piston stem strikes the slide valve. (See Fig. 16.) This movement has caused the graduating valve to close the service port "Z", thus cutting off any further flow of air from the auxiliary to the brake cylinder and also port "o", thus preventing any further flow of air from the brake pipe to the brake cylinder. The triple valve is now said to be in lap position. 155. Q. How is the triple valve affected by a further reduction of brake pipe pressure? [Illustration: Fig. 15. Full Service Position.] A. A further reduction of brake pipe pressure will cause the triple piston 4 and the graduating valve 7 to again move to the right, opening ports "Z" and "o", allowing a further flow of brake pipe and auxiliary air to the brake cylinder. This may be continued until the auxiliary reservoir and brake cylinder pressures become equal, after which any further reduction of brake pipe pressure is only a waste of air. With seventy pounds brake pipe pressure, and eight-inch piston travel, a twenty-pound reduction will cause equalization at about fifty pounds. [Illustration: Fig. 16. Lap Position.] 156. Q. Explain the operation of the triple valve in the release of the brake. A. To release the brakes and recharge the auxiliary reservoirs, air is admitted through the brake valve to the brake pipe. This increase of pressure on the brake pipe side of the triple valve piston 4 above that on the other side causes the piston and slide valve to move back to release position, which permits the air in the brake cylinder to flow to the atmosphere, through the exhaust port of the triple, thus releasing the brake. At the same time, air from the brake pipe flows through the feed groove "i" around the triple piston to the auxiliary reservoir, which is thus recharged. Now the "K" triple valve has two release positions: =Full Release= and =Retarded Release=. To which of these two positions the parts will move when the brakes are released, depends upon how the brake pipe pressure is increased. It is generally understood that those cars toward the head end of the train, receiving the air first, will have their brake pipe pressure raised more rapidly than those in the rear; thus the friction of the brake pipe causes the pressure to build up more rapidly in the chamber "h" of the triple valve toward the front end of the train than in those in the rear. As soon as the pressure is enough greater than the auxiliary reservoir pressure to overcome the friction of the piston, graduating valve and slide valve, all three are moved toward the left until the piston stem strikes the retarding stem 31, which is held in position by the retarding spring 33. Where the rate of increase of brake pipe pressure is slow, it will be impossible to raise the pressure in chamber "h" sufficiently to overcome the tension of the retarding spring 33, and the triple valve will remain in full release position, as shown in Fig. 13. Brake cylinder air will now be free to exhaust through port "r", large cavity "n" in the slide valve and port "p" leading to the atmosphere. If, however, the triple valve is near the head end of the train, and the brake pipe pressure builds up more rapidly than the auxiliary can recharge, an excess of pressure will be obtained in chamber "h" over that in the auxiliary reservoir, and will cause the piston 4 to compress the retarding spring 33, and move the triple valve parts to retarded release position as shown in Fig. 17. 157. Q. What effect has retarded release position of the triple valve on the release of the brakes? A. In this position of the triple valve, cavity "n" in the slide valve connects port "r" leading to the brake cylinder, with port "p" to the atmosphere, and the brake will release; but as the small "tail port" extension of cavity "n" is over exhaust port "p", the discharge of air from the brake cylinder is quite slow. [Illustration: Fig. 17. Retarded Release and Charging Position.] 158. Q. What is the object of delaying the exhaust of the brake cylinder air? A. In this way, the brakes on the front end of the train require a longer time to release than those on the rear. This feature is called =retarded release=, and although the triple valves near the locomotive commence to release before those in the rear, yet the exhaust of air from the brake cylinder is sufficiently slow to hold back the release of the brakes at the front end of the train long enough to insure a uniform release of the brakes on the train as a whole. This permits of releasing the brakes on very long trains at low speeds without danger of damaging train. [Illustration: Fig. 18. Emergency Position.] 159. Q. What other desirable feature is found in this position of the triple valve? A. In this position, the back of the piston is in contact with the end of the slide valve bush, and, as these two surfaces are ground to an accurate fit, the piston makes a tight "seal" on the end of the bush except at one point, where a feed groove is cut in the piston to allow air to pass around the end of the slide valve bush into chamber "R" and the auxiliary reservoir. This feed groove is much smaller than the feed groove "i" in the piston bush, so that when the triple valve piston is in =Retarded Release= position the recharge of the auxiliary reservoir takes place much more slowly than when it is in =Full Release= position, thus permitting a greater volume and pressure of air to flow toward the rear of the train. 160. Q. Explain the operation of the triple valve in emergency position. A. When any sudden reduction of brake pipe pressure is made below that in the auxiliary reservoir, it will be felt in chamber "h" in front of piston 4 and cause this piston to move to the extreme right, as shown in Fig. 18. This movement of the parts will open port "t" in the slide valve seat and allow air from the auxiliary reservoir to flow to the top of the emergency piston 8, forcing the latter downward and opening emergency valve 10. The unseating of the emergency valve allows the air in chamber "Y" to escape to the brake cylinder, thus permitting brake pipe pressure in chamber "a" to lift the check valve 15 and flow to the brake cylinder through chambers "Y" and "X", until brake cylinder and brake pipe pressure nearly equalize, when the check valve is forced to its seat by the check valve spring 12, preventing the air in the cylinder from escaping back into the brake pipe again. The emergency valve and piston will now return to their normal position. At the same time port "s" in the slide valve registers with port "r" in the slide valve seat, and allows air from the auxiliary reservoir to flow to the brake cylinder. This sudden discharge of brake pipe air into the brake cylinder has the effect on the next triple valve, which in turn vents brake pipe air that affects the following triple valve and so on throughout the train. NEW YORK AIR BRAKE AIR COMPRESSOR 161. Q. What do Figures 19 and 20 represent? A. These are cross-sectional views of the New York compressor. 162. Q. Of what does the valve gear of this compressor consist? A. Of two main valves, actuated by tappet rods which enter into the hollow piston rods, and are moved by tappet plates, which are fastened to the steam piston heads. 163. Q. How is the admission and exhaust of steam controlled? A. The valve under the cylinder at the right controls the flow of steam to and from the cylinder at the left; while the valve under the cylinder at the left controls the flow of steam to and from the cylinder at the right. 164. Q. Explain the operation of the steam end of the compressor. [Illustration: Low Pressure Piston Moving Upward. High Pressure Piston at Rest. Fig. 19.] A. Assuming both pistons are at the bottom of their cylinders, when the compressor throttle is opened, live steam will flow to both steam chests "B" (see Fig. 19), and through port "o" to the under side of the piston "T" and through port "g" to the upper side of piston "H". The steam under piston "T" will force it upward, and when it very nearly completes its stroke, the tappet plate "Q" will engage the button on the end of the tappet rod "P", moving the main valve "C" to its upper position. In this position the exhaust cavity "r" in the main valve connects port "g" with the exhaust port "X", thus allowing steam above the piston "H" to escape to the exhaust, at the same time steam is admitted through port "s" to the under side of piston "H", forcing it upward. As this piston very nearly completes its stroke, the tappet plate "L" (see Fig. 20) engages the button on the tappet rod "P", moving the main valve "A" to its upper position. Exhaust cavity "r" now connects port "o", which leads to the lower end of the cylinder at the right, with the exhaust port "X", thus allowing the steam under piston "T" to escape to the exhaust, at the same time steam is admitted through port "V" to the upper end of the cylinder at the right, on top of piston "T", forcing it downward; as it very nearly completes its stroke, the tappet plate "Q" engages the shoulder on the tappet rod "P", moving the main valve "C" to its lower position. The exhaust cavity "r" in the valve now connects port "s" with the exhaust port "X", allowing steam below piston "H" to escape to the exhaust, and at the same time steam is admitted to the top of this piston, forcing it down, thus completing a cycle of the compressor. 165. Q. Explain the operation of the air end of the compressor. A. As the piston in the low pressure cylinder "D" moves up (see Fig. 19), a partial vacuum is formed below it, and air flowing through the strainer passes downward through the air passage, then past the lower receiving valve "W" into the lower end of the cylinder, filling it with air at about atmospheric pressure. In the meantime the air that is being compressed above the piston holds the receiving valve "U" to its seat, and lifts the upper intermediate discharge valve "K" from its seat, allowing the air to pass from the low to the high pressure cylinder "F". The high pressure piston now moving up causes a partial vacuum to be formed below it, and air from the atmosphere flows past the lower receiving valve "N", filling this end of the cylinder with air at about atmospheric pressure. The air above the piston being compressed, holds the upper intermediate valve "K" and receiving valve "J" to their seats and lifts the upper final discharge valve "M", allowing the air to pass to the main reservoir. The action is the same on the down stroke, only air is compressed in the opposite end of the cylinders and the opposite air valves are used. 166. Q. What should be the lift of the different air valves? A. In the No. 1 and No. 2 compressors all valves should have 1/16-inch lift; in the No. 5 and No. 6 all valves should have 3/16-inch lift. 167. Q. If a receiving valve to the low pressure air cylinder breaks or sticks open, what effect will it have on the compressor, and how may it be located? A. No air will be compressed in the low pressure cylinder, as the piston moves toward the defective valve, and may be located by noting the movement of the low pressure piston, as it will be much quicker toward the defective valve than the opposite stroke. Air will blow back to the atmosphere as the piston moves toward the defective valve, and may be detected by holding the hand over the strainer. 168. Q. If an intermediate discharge valve breaks or sticks open, what effect will it have on the compressor, and how may it be located? A. If an intermediate discharge valve breaks or sticks open, no air will be compressed by that end of the compressor where is located the defective valve, as the air will simply flow back and forth from the high to the low pressure cylinders; no air will be taken in from the atmosphere through the strainer as the pistons move from the defective valve. 169. Q. If a final discharge valve breaks, what effect will it have on the compressor? A. Main reservoir air will be free to return to the high pressure cylinder as the high pressure piston moves from the defective valve; therefore, no air will be taken in through the receiving valve of the high pressure air cylinder at the end where is located the defective valve. The low pressure piston will make a slow stroke toward the defective valve and a normal stroke from it; while the high pressure piston will make a slow stroke toward the defective valve and a quick stroke from it. Defective air valves may generally be located by noting the temperature of the valve chamber in which they are located. 170. Q. What will cause the compressor to run hot? A. Running the compressor too fast; working against high pressure; air piston packing rings leaking; air cylinder worn; air passages or discharge pipe partially stopped up; air valves leaking; air valves stuck shut; or lack of lubrication. 171. Q. How should the air end of the compressor be oiled, and what grade of oil used? [Illustration: Fig. 20. High Pressureiston Moving Upward. Low Pressure Piston at Rest.] A. Oil should be used sparingly in the low pressure cylinder, but more is required in the high pressure cylinder, owing to higher temperature. A good quality of valve oil should be used. 172. Q. How is the steam end of the compressor affected by the use of too much oil? A. This may cause the compressor to short stroke, and where the piston type of valve is used, may cause the compressor to stop. L-T EQUIPMENT AUTOMATIC CONTROL VALVE 173. Q. What is the duty of the control valve? A. To admit air from the main reservoir to the locomotive brake cylinders when applying the brakes; to automatically maintain the brake cylinder pressure against leakage; to develop the proper brake cylinder pressure regardless of piston travel; and to exhaust the air from the brake cylinders when releasing the brake, in all automatic applications of the brake. 174. Q. Explain the operation of the control valve when making an automatic service application of the brake. A. Air enters the control valve at the connection marked "BP" (Fig. 21), which leads to chamber "F" above the piston 3, forcing it down, uncovering the feed groove "G" in the bushing, allowing air to feed past the piston into the slide valve chamber, and then through port "H" to the auxiliary reservoir. The air will feed through in this manner until the auxiliary reservoir and brake pipe pressure equalize. When a gradual reduction of brake pipe pressure is made, it will be felt in chamber "F", above piston 3, creating a difference in pressure on the two sides of the piston, which will cause it to move upward. [Illustration: Fig. 21. Automatic Control Valve. Full Release.] The first movement of the piston closes the feed groove "G", also moves the graduating valve 10, uncovering the service port "J" in the slide valve 4, and the continued movement of the piston moves the slide valve to service position, in which the service port "J" connects with port "E" in the valve seat. (See Fig. 22.) As the slide valve chamber and auxiliary reservoir are connected at all times, air can now flow from the auxiliary to the control cylinder "D" and control reservoir, through ports "H", "J" and "E", until the pressure on the lower or auxiliary side of piston 3 becomes slightly less than that in chamber "F" or brake pipe side, when the piston and graduating valve will move down until the shoulder on the piston strikes the slide valve; this movement of the graduating valve closes the service port "J", thus closing the communication between the auxiliary and control cylinder and reservoir, also closing port "W", which leads to the safety valve. (See Fig. 23.) 175. Q. How is piston 2 affected by the air pressure in the control cylinder "D"? A. Pressure forming in this cylinder will force the piston downward. The piston in moving down will carry the exhaust valve 7 with it, closing the exhaust port "N" and moves the preliminary admission valve "1A" from its seat against the tension of spring 8, allowing the pressure in chamber "O" to pass to the brake cylinders, thus creating a balancing effect on valve 1, which allows it to be opened against main reservoir pressure, thus allowing main reservoir air to flow from chamber "A" to chamber "B" and the brake cylinders on the locomotive (see Fig. 22) until the pressure in the brake cylinders and chamber "B", below piston 2, becomes slightly greater than that in the control cylinder "D" when the piston will move up just far enough to allow the valves "1" and "1A" to be seated, or to lap position. (See Fig. 23.) [Illustration: Automatic Control Valve. Service Position. Fig. 22.] 176. Q. With the control valve now in lap position, will the brake release on account of brake cylinder leakage? A. Any drop in brake cylinder pressure will be felt in chamber "B" below the piston 2, causing a difference in pressure on the two sides of the piston, allowing the pressure in the control cylinder "D" to move the piston 2 down, unseating the admission valves, allowing a further flow of main reservoir air from chamber "A" to chamber "B" and the brake cylinders until the pressure is again slightly greater than that in the control cylinder "D", when the piston 2 will again move up, allowing the admission valves to close. Thus in this way air will be supplied to the brake cylinders of the locomotive, holding the brakes applied regardless of leakage. 177. Q. Explain the movement of the parts in the control valve, when the automatic brake valve is moved to release position, following an automatic application of the brake. A. In release position of the brake valve, air from the main reservoir flows direct to the brake pipe, causing an increase of pressure, which is felt in chamber "F" on the upper side of piston 3; this increase of pressure will cause the piston to move down, carrying with it the graduating valve 10 and slide valve 4 to release position. This allows air from the control cylinder "D" and control reservoir to flow through the release pipe "IV" and on to the automatic brake valve, where the port to which this pipe leads is blanked by the automatic rotary valve, which prevents the air leaving the control cylinder and reservoir, thus holding the locomotive brake applied while the train brakes are being released. The movement of the parts are the same where the release is made in holding position. 178. Q. Explain the movements of the parts in the control valve when the automatic brake valve is moved to running position, after having first been moved to release or holding position. [Illustration: Automatic Control Valve. Service Lap Position. Fig. 23.] A. In this position of the brake valve the port to which the release pipe "IV" is connected is open to the exhaust, thus allowing the air in the control cylinder and reservoir to escape to the atmosphere. The reduction of pressure in the control cylinder "D" below that in chamber "B" causes the control piston 2 to move up, carrying with it the exhaust valve 7 to release position, opening the exhaust port "N", thus allowing the air to return from the brake cylinders through ports "C" and "N" to the atmosphere, releasing the brake. (See Fig. 21.) 179. Q. Explain what takes place in the control valve when an automatic emergency application of the brake is made. A. Any sudden reduction of brake pipe pressure will be felt on the brake pipe side of piston 3, and will cause it and the valve 4 to move to their extreme upper position, the knob on the piston striking the graduating stem 13, causing it to compress the spring 14, moving the emergency valve 15 upward, opening port "Q"; this allows brake pipe air to flow against valve 16, unseating it, then through port "T" to the brake cylinder. (See Fig. 24.) In the meantime auxiliary reservoir air can flow past the end of the slide valve through port "E" to the control cylinder "D" and control reservoir, forcing piston 2 downward unseating valves "I" and "IA", thus allowing main reservoir air to flow to the brake cylinders, applying the brake. 180. Q. At what pressure will the auxiliary reservoir and control reservoir equalize when using seventy pounds brake pipe pressure? A. At about fifty pounds; however, with the automatic brake valve in emergency position, there is a small port in the rotary valve (called the blow-down timing port) opened to the control reservoir pipe and control reservoir which allows main reservoir air to flow to the control reservoir and cylinder, raising the pressure to the adjustment of the safety valve. [Illustration: Fig. 24. Automatic Control Valve. Emergency Position. (With Quick Action Cylinder Cap.)] 181. Q. At what pressure is the safety valve adjusted? A. At fifty pounds. 182. Q. What types of brake valve are used with this equipment? A. The automatic brake valve is of the rotary valve type and is the same valve as used with the E-T equipment. The straight air brake valve is of the slide valve type. The control valve takes no part in the application or release of the straight air brake. What has been said of the H-6 brake valve used with the E-T equipment, applies to the automatic brake valve used with the L-T equipment. BROKEN PIPES 183. Q. If the main reservoir supply pipe to the automatic control valve breaks, what should be done? A. Plug the pipe toward the main reservoir. The locomotive brake cannot be applied in an automatic service application; but if the control valve be equipped with a quick action cap and an emergency application is made, the air vented from the brake pipe to the brake cylinder will apply the brake. The independent brake will not be affected. 184. Q. What will be the effect if the release pipe breaks? A. The holding feature of the brake will be lost; that is, the brake will release when the automatic brake valve is returned to release or holding position. 185. Q. If the brake cylinder pipe breaks, can the locomotive brake be applied with the automatic brake valve? With the independent brake valve? A. This depends on where the pipe breaks; if between the cut-out cock and any one of the brake cylinders, close the cut-out cock to that cylinder, and the other cylinders may be used. But if the pipe breaks between the control valve and the double-throw check valve, the automatic brake is lost; if the break be between the independent brake valve and double-throw check valve, the independent brake is lost. 186. Q. If the brake cylinder pipe breaks and is not plugged, what must be done? A. Close the cut-out cock in the main reservoir supply pipe, this to avoid the waste of air when a brake application is made on the train. 187. Q. If the brake pipe connection to the control valve breaks, what should be done? A. Plug the end leading from the brake pipe; the automatic brake cannot be applied on the locomotive, but the independent brake will not be affected. 188. Q. If the control cylinder pipe breaks, what effect will it have and what must be done? A. The locomotive brake cannot be applied with the automatic brake valve; by plugging the pipe, this feature of the brake will be restored, but the independent release feature will be lost. 189. Q. If any of the pipes here enumerated breaks, will it in any way affect an application of the independent brake? A. No; as the independent and automatic features are entirely separate from each other; that is, the automatic control valve is not brought into use when an independent application of the brake is made. CONTROL VALVE DEFECTS 190. Q. If there is a blow at the control valve exhaust port when the brake is released, where would you look for the trouble? A. This would indicate a leaky application valve, or a leak past the emergency valve. 191. Q. If there be a continuous blow at the control valve exhaust port when the brake is applied, where would you look for the trouble? A. This would indicate leakage past the exhaust valve 7. 192. Q. If the locomotive brake released with the automatic brake valve in lap position, where is the trouble? A. Would look for a leak in the control reservoir pipe or special release valve. 193. Q. If the brake remained applied in lap position, but released in release or holding position, where would you look for the trouble? A. This would indicate a leak in the control valve release pipe. MISCELLANEOUS 194. Q. What is meant by an application of the brake? A. The first and all following reductions, until the brake is released. 195. Q. How many applications of the brake should be made when making a stop with a passenger train, and why? A. Two; the first a heavy one to reduce the speed quickly, and the second a light one to complete the stop; thereby preventing wheel sliding and shock to the train. 196. Q. How many applications of the brake should be made when making a stop with a long freight train? A. One; this to prevent the possibility of causing damage to the train. 197. Q. Explain how a stop should be made with a freight train. A. Probably no more difficult question to answer could be asked, as the service braking of a train must be governed by the condition surrounding it; meaning, relation of brake power to weight of train; rail condition; speed and grade. To prevent breaking in two and other damage, freight trains should be stopped with one brake application, which may consist of one or more reductions, up to full service. Generally speaking, the slack should be bunched before the brakes are applied, and this may best be done by gradually closing the throttle and allow the train to drift some little distance. The first reduction should not be less than five or more than eight pounds. The brakes should be applied as soon as possible after the slack has had time to run in, the object of this being to have the train slack adjusted while the brakes are least effective, due to the high speed and light brake cylinder pressure. It is at this time that damage may be done to the train; therefore, if the slack be kept bunched or stretched, as the case may be, the possibility of train damage will be greatly reduced. To obtain this condition, complete the stop with as light a brake application as permissible. When the brake is first applied, the engineer should note if the tendency be for the train slack to bunch or stretch, and having learned that the train is inclined to stretch badly, he can keep the slack stretched by making the initial brake pipe reduction before shutting off steam, then shut off steam gradually as soon as the brake valve exhaust port closes, the object in working steam being to prevent the slack running in as the application is made, which in turn will prevent severe jerks due to the slack running out as the rear brakes become effective. Where the locomotive is equipped with an independent release feature, its brakes should be kept released while the train brakes are being applied. 198. Q. Is it considered good practice to attempt making an accurate stop with a freight train? A. It may be said to be very poor judgment to attempt making an accurate stop with a freight train, such as a spot stop for coal or water or a close-up stop for a switch. Some engineers seem to think that it is a reflection on their judgment if an accurate stop is not made, but this is not so, due to the fact that no two trains brake alike, and the same train may not brake twice alike. Therefore, aim for a smooth stop, which means a safe stop, leaving accuracy out of the question until the time comes when you are handling a passenger train. 199. Q. What precaution should be taken after a stop is made on a heavy grade? A. The air brakes should be released and a sufficient number of hand brakes applied to hold the train. Never rely on the air brake to hold the train for any length of time. 200. Q. Why is it dangerous to repeatedly apply and release the brakes without giving time for the auxiliaries to fully recharge? A. As time is required to charge the auxiliaries, the feed groove in the triple valve being small, if the brakes are repeatedly applied and released without giving time to recharge, the braking power will be lost. 201. Q. What benefits are derived from the use of the retaining valve? A. By use of the retaining valve the brake is held applied while the triple valve is in release position and the auxiliary is being recharged; thereby assisting in retarding the movement of the train down grade, also keeps the train bunched and gives a higher brake power on the second application with the same reduction of brake pipe pressure. 202. Q. With a seventy-pound brake pipe pressure how much of a reduction is necessary to set the brakes in full, and why? A. About twenty pounds. This will cause the auxiliary reservoir and brake cylinder pressures to equalize. 203. Q. What effect has piston travel on the pressure developed in the brake cylinder? A. The longer the piston travel the greater the volume or space to be filled with air; therefore the lower the pressure. 204. Q. When should brakes be tested? A. Brakes should be tested before leaving a terminal and after any change in the make-up of the train, at all designated points, also, whenever the engineer is in doubt as to his having the control of all brakes. 205. Q. How should a terminal test of the brakes be made? A. After the pressure is pumped up, a reduction of about ten pounds should be made and the length and force of the brake pipe exhaust should be noted, also the manner in which the exhaust closes; then a further reduction of ten pounds should be made and the brake held applied until signaled to release. 206. Q. If, when making a service application of the brake, the brake pipe exhaust closes suddenly and then begins to blow again, what does it indicate? A. That the brakes, or at least part of them, have applied in quick action. 207. Q. What is meant by a running test, and when should this test be made? A. A running test is made while the train is in motion, and steam is being used, when a sufficient reduction should be made to apply all brakes. After noting the efficiency of the brakes they should be released. Running tests should be made following all standing tests and at all other points on the road as required by the rules. 208. Q. When double-heading, which engineman should have full control of the brakes? A. The head engineer; the cut-out cock under the brake valve on the second engine should be closed and the compressor allowed to run. 209. Q. How may the engineman assist the trainman in finding a bursted hose? A. After the train has come to a stop, the brake valve should be placed in running position; by so doing, air will be admitted to the brake pipe and cause a blow at the point where the hose is burst. 210. Q. If the locomotive brake creeps on with the automatic and independent brake valves in running position, where would you look for the trouble? A. This is caused by the pressure chamber being overcharged or a non-sensitive feed valve allowing brake pipe pressure to vary, which in turn causes an automatic application of the brake. 211. Q. How often should the main reservoir be drained? A. The main reservoir should be drained at the beginning of each trip. * * * * * =INDEX= Page Air Brake Questions, First Series 22 Air Brake Questions, Second Series 44 Air Brake Questions, Third Series 164 Compound Locomotives 98 Examination Questions, First Series 7 Examination Questions, Second Series 25 Examination Questions, Third Series, Mechanical 62 Federal Regulations 126 Headlight, Pyle National 127 Headlight, Schroeder 141 Headlight, "Buda-Ross" Electric 143 Lubrication 120 Oil Burning Locomotives 47 Preface 3 Southern Valve Gear 119 Stoker, Duplex 154 Walschaert and Baker-Pilliod Valve Gears 113 * * * * * Transcribers Notes: Punctuation and heading format normal. Page 7, "feul" changed to "fuel" (use of fuel). Page 16, "therby" changed to "thereby" (thereby causing) Page 31, "criculation" changed to "circulation" (good circulation) Page 65, "lcomotive" changed to "locomotive" (locomotive has been started) Page 78, "reevrse" changed to "reverse" (reverse lever) Page 86, "serously" changed to "seriously" (very seriously affect) Page 108, "disadvanage" changed to "disadvantage" (disadvantage to work) Page 126, "aperating" changed to "operating" (operating under the laws) Page 129, "sucessfully" changed to "successfully" (used successfully) Page 131, "damge" changed to "damage" (might do damage) Page 139, "Tubo" changed to "Turbo" (Turbo-generator) Page 147, "direcion" changed to "direction" (in any direction) Page 149, "cummutator" changed to "commutator" (The commutator) Page 204, "distributng" changed to "distributing" (distributing valve) Page 215, "chambr" changed to "chamber" (remaining in chamber) Page 216, "slighty" changed to "slightly" (slightly less) Page 233, "releas" changed to "release" (release is made) Page 243, "the" changed to "then" (and then begins to blow). 
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22245	----	----------------------------------------------------------------------- By Sara Ware Bassett The Invention Series Paul and the Printing Press Steve and the Steam Engine ----------------------------------------------------------------------- [Illustration: "It was the conquering of this multitude of defects that gave to the world the intricate, exquisitely made machine."--Frontispiece. See page 103.] ----------------------------------------------------------------------- The Invention Series STEVE AND THE STEAM ENGINE By Sara Ware Bassett With Illustrations By A. O. Scott Boston Little, Brown, And Company 1921 ----------------------------------------------------------------------- Copyright, 1921, By Little, Brown, and Company. All rights reserved Published September, 1921 The Plimpton Press Norwood Mass U S A ----------------------------------------------------------------------- CONTENTS CHAPTER PAGE I An Unpremeditated Folly 1 II A Meeting with an Old Friend 19 III A Second Calamity 34 IV The Story of the First Railroad 51 V Steve Learns a Sad Lesson 67 VI Mr. Tolman's Second Yarn 77 VII A Holiday Journey 94 VIII New York and What Happened There 110 IX An Astounding Calamity 125 X An Evening of Adventure 145 XI The Crossing of the Country 156 XII New Problems 169 XIII Dick Makes His Second Appearance 178 XIV A Steamboat Trip by Rail 192 XV The Romance of the Clipper Ship 205 XVI Again the Magic Door Opens 216 XVII More Steamboating 224 XVIII A Thanksgiving Tragedy 238 XIX The End of the House Party 248 ----------------------------------------------------------------------- LIST OF ILLUSTRATIONS "It was the conquering of this multitude of defects that gave to the world the intricate, exquisitely made machine" Frontispiece "You've got your engine nicely warmed up, youngster," he observed casually 9 "I wish you'd tell me about this queer little old-fashioned boat" 181 He was fighting to prevent himself from being drawn beneath the jagged, crumbling edge of the hole 244 ----------------------------------------------------------------------- STEVE AND THE STEAM ENGINE CHAPTER I AN UNPREMEDITATED FOLLY Steve Tolman had done a wrong thing and he knew it. While his father, mother, and sister Doris had been absent in New York for a week-end visit and Havens, the chauffeur, was ill at the hospital, the boy had taken the big six-cylinder car from the garage without anybody's permission and carried a crowd of his friends to Torrington to a football game. And that was not the worst of it, either. At the foot of the long hill leading into the village the mighty leviathan so unceremoniously borrowed had come to a halt, refusing to move another inch, and Stephen now sat helplessly in it, awaiting the aid his comrades had promised to send back from the town. What an ignominious climax to what had promised to be a royal holiday! Steve scowled with chagrin and disappointment. The catastrophe served him right. Unquestionably he should not have taken the car without asking. He had never run it all by himself before, although many times he had driven it when either his father or Havens had been at his elbow. It had gone all right then. What reason had he to suppose a mishap would befall him when they were not by? It was infernally hard luck! Goodness only knew what was the matter with the thing. Probably something was smashed, something that might require days or even weeks to repair, and would cost a lot of money. Here was a pretty dilemma! How angry his father would be! The family were going to use the automobile Saturday to take Doris back to Northampton for the opening of college and had planned to make quite a holiday of the trip. Now it would all have to be given up and everybody would blame him for the disappointment. A wretched hole he was in! The boys had not given him much sympathy, either. They had been ready enough to egg him on into wrong-doing and had made of the adventure the jolliest lark imaginable; but the moment fun had been transformed into calamity they had deserted him with incredible speed, climbing out of the spacious tonneau and trooping jauntily off on foot to see the town. It was easy enough for them to wash their hands of the affair and leave him to the solitude of the roadside; the automobile was not theirs and when they got home they would not be confronted by irate parents. How persuasively, reflected Stephen, they had urged him on. "Oh, be a sport, Steve!" Jack Curtis had coaxed. "Who's going to be the wiser if you do take the car? Anyhow, you have run it before, haven't you? I don't believe your father will mind." "Take a chance, Stevie," his chum, Bud Taylor, pleaded. "What's the good of being such a boob? Do you think if my father had a car and it was standing idle in the garage when a bunch of kids needed it to go to a school game I would hesitate? You bet I wouldn't!" "It isn't likely your Dad would balk at your using the car if he knew the circumstances," piped another boy. "We have got that match to play off, and now that the electric cars are held up by the strike how are we to get to Torrington? Don't be a ninny, Steve." Thus they had ridiculed, cajoled, and wheedled Steve until his conscience had been overpowered and, yielding to their arguments, he had set forth for the adjoining village with the triumphant throng of tempters. At first all had gone well. The fourteen miles had slipped past with such smoothness and rapidity that Stephen, proudly enthroned at the wheel, had almost forgotten that any shadow rested on the hilarity of the day. He had been dubbed a good fellow, a true sport, a benefactor to the school--every complimentary pseudonym imaginable--and had glowed with pleasure beneath the avalanche of flattery. As the big car with its rollicking occupants had spun along the highway, many a passer-by had caught the merry mood of the cheering group and waved a smiling salutation in response to their shouts. In the meanwhile, exhilarated by the novelty of the escapade, Steve had increased the speed until the red car fairly shot over the level macadam, its blurred outlines lost in the scarlet of the autumn foliage. Then suddenly when the last half-mile was reached and Torrington village, the goal of the pilgrimage, was in sight, quite without warning the panting monster had stopped and all attempts to urge it farther were of no avail. There it stood, its motionless engine sending out odors of hot varnish and little shimmering waves of heat. Immediately a hush had descended upon the boisterous company. There was a momentary pause, followed by a clamor of advice. When, however, it became evident that there was no prospect of restoring the disabled machine to action, one after another of the frightened schoolboys had dropped out over the sides of the car and after loitering an instant or two with a sort of shamefaced indecision, at the suggestion of Bud Taylor they had all set out for the town. "Tough luck, old chap!" Bud had called over his shoulder. "Mighty tough luck! Wish we had time to wait and see what's queered the thing; but the game is called at two-thirty, you know, and we have only about time to make it. We'll try and hunt up a garage and send somebody back to help you. So long!" And away they had trooped without so much as a backward glance, leaving Stephen alone on the country road, worried, mortified, and resentful. There was no excuse for their heartless conduct, he fumed indignantly. They were not all on the eleven. Five of the team had come over in Tim Barclay's Ford, so that several of the fellows Steve had brought were merely to be spectators of the game. At least Bud Taylor, his especial crony, was not playing. He might have remained behind. How selfish people were, and what a fleeting thing was popularity! Why, half an hour ago he had been the idol of the crowd! Then Bud had shouted: "Come ahead, kids, let's hoof it to Torrington!" and in the twinkling of an eye the tide had turned, the mob had shifted its allegiance and gone tagging off at the heels of a new leader. They did not mean to have their pleasure spoiled, not they! Scornfully Stephen watched them mount the hill, their crimson sweaters making a zigzag line of color in the sunshine; even their laughter, care-free as if nothing had happened, floated back to him on the still air, demonstrating how little concern they felt for him and his refractory automobile. Well might they proceed light-heartedly to the village, spend their money on sodas and ice-cream cones, and shout themselves hoarse at the game. No thought of future punishment marred their enjoyment and the program was precisely the one he had outlined for himself before Fate had intervened and raised a prohibitory hand. The fun he had missed was, however, of scant consequence now. All he asked was to get the car safely back to his father's garage before the family returned from New York on the afternoon train. Now that his excitement had cooled into sober second thought, he marveled that he had been led into committing such a monstrous offense. He must have been mad. Often he had begged to do the very thing he had done and his father had always refused to let him, insisting that an expensive touring car was no toy for a boy of his age. Perhaps there had been some truth in the assertion, too, he now admitted. Yet were he to hang for it, he could not see why he had not run the car exactly as his elders were wont to do. Of course he had had a pretty big crowd aboard and the heavy load might have strained the machinery; and possibly--just possibly--he had speeded a bit. He certainly had made phenomenally good time for he did not want the fellows to think he was afraid to let out the engine. Well, whatever the matter was, the harm was done now and he was in a most unenviable plight. No doubt it would cost a small fortune to get the automobile into shape again, more money than he had in the world; certainly far more than he had in his pocket at the present moment. What was he to do? Even suppose the boys did remember to send back help (they probably wouldn't--but suppose they did) how was he to pay a machinist? As he pictured himself being towed to a garage and the car being left there, he felt an uncomfortable sensation in his throat. He certainly was in for it now. It would be ignominious to charge the repairs to his father but that would be the only course left him. Fortunately Mr. Tolman, who was a railroad official, was well known in the locality and therefore there would be no trouble about obtaining credit; but to ask his father to pay the bills for this escapade was anything but a manly and honorable way out and Steve wished with all his heart he had never been persuaded into the wretched affair. If there were only some escape possible, some alternative from being obliged to confess his wrong-doing! But to hope to conceal or make good the disaster was futile. And even if he could cover up what had happened, how contemptible it would be! He detested doing anything underhanded. Only sneaks and cowards resorted to subterfuge and although he had been called many names in his life these two had not been among them. No, he should make a clean breast of what he had done and bear the consequences, and once out of his miserable plight he would take care never again to be a party to such an adventure. He had learned his lesson. So absorbed was he in framing these worthy resolutions that he did not notice a tiny moving speck that appeared above the crest of the hill and now came whirling toward him. In fact the dusty truck and its yet more dusty driver were beside him before he heeded either one. Then the newcomer came to a stop and he heard a pleasant voice: "What's the matter, sonny?" Stephen glanced up, trying bravely to return his questioner's smile. The man who addressed him was white-haired, ruddy, and muscular, and he wore brown denim overalls stained with oil and grease; but although he was middle-aged there was a boyish friendliness in his face and in the frank blue eyes that peered out from under his shaggy brows. "What's the trouble with your machine?" he repeated. "I don't know," returned Stephen. "If I did, you bet I wouldn't be sitting here." The workman laughed. "Suppose you let me have a look at it," said he, climbing off the seat on which he was perched. "I wish you would." "It is a pretty fine car, isn't it?" observed the man, as he approached it. "Is it yours?" "My father's." "He lets you use it, eh?" Stephen did not answer. "Some fathers ain't that generous," went on the man as he began to examine the silent monster. "If I had an outfit like this, I ain't so sure I'd trust it to a chap of your size. Still, if you have your license, I suppose you must know how to run it." [Illustration: "You've got your engine nicely warmed up, youngster," he observed casually. Page 9.] A shiver passed through Stephen's body. A license! What if the stranger should ask to see it? There was a heavy fine, he now remembered, for driving a car unless one were in possession of this precious paper, although what the penalty was he could not at the instant recall; he had entirely forgotten there were any such legal details. Fearfully he eyed the mechanic. The man, however, did not pursue the subject but instead appeared engrossed in carefully inspecting the automobile inside and out. As he poked about, now here, now there, Stephen watched him with constantly increasing nervousness; and after the investigation had proceeded for some little time and no satisfactory result had been reached, the boy's heart sank. Something very serious must be the matter if the trouble were so hard to locate, he reasoned. In imagination he heard his father's indignant reprimands and saw the Northampton trip shrivel into nothingness. The workman in the meantime remained silent, offering no comment to relieve his anxiety. What he was thinking under the shabby visor cap pulled so low over his brows it was impossible to fathom. His hand was now unscrewing the top of the gasoline tank. "You've got your engine nicely warmed up, youngster," observed he casually. "Maybe 'twas just as well you did come to a stop. You must have covered the ground at a pretty good clip." There certainly was something very disconcerting about the stranger's conversation and again Stephen looked at him with suspicion. "Oh, I don't know," he mumbled, trying to assume an off-hand air. "Perhaps we did come along fairly fast." "You weren't alone then." "N--o," was the uncomfortable reply. "The fellows who sent you back from the village were with me." For the first time the workman evinced surprise. "Nobody sent me," he retorted. "I just thought as I was going by that you looked as if you were up against it, and as I happen to know something about engines I pulled up to give you a helping hand. The fix you are in isn't serious, though." He smiled broadly as if something amused him. "What is the matter with the car?" demanded the boy desperately, in a voice that trembled with eagerness and anxiety and defied all efforts to remain under his control. "Why, son, nothing is wrong with your car. You've got no gasoline, that's all." "Gasoline!" repeated the lad blankly. "Sure! You couldn't have had much aboard when you started, I guess. It managed to bring you as far as this, however, and here you came to a stop. The up-grade of the hill tipped the little gas you did have back in the tank so it would not run out, you see. Fill her up again and she'll sprint along as nicely as ever." The relief that came with the information almost bowled Steve over. For a moment he could not speak; then when he had caught his breath he exclaimed excitedly: "How can I get some gasoline?" His rescuer laughed at the fevered question. "Why, I happen to have a can of it here on my truck," he drawled, "and I can let you have part of it if you are so minded." "Oh, I don't want to take yours," objected the boy. "Nonsense! Why not? I am going right past a garage on my way back and can get plenty more. We'll tip enough of mine into your tank to carry you home. It won't take a minute." The suggestion was like water to the thirsty. "All right!" cried Stephen. "If you will let me pay for it I shall be mightily obliged to you. I'm mightily obliged anyway." "Pshaw! I've done nothing," protested the person in the oily jumper. "What are we in the world for if not to do one another a good turn when we can?" As he spoke he extricated from his conglomerate load of lumber, tools, and boxes a battered can, the contents of which he began to transfer into Stephen's empty tank. "There!" ejaculated he presently, as he screwed the metal top on. "That isn't all she'll hold, but it will at least get you home. You are going right back, aren't you?" The boy glanced quickly at the speaker. "Yes." "That's right. I would if I were in your place," urged the man. Furtively Stephen scrutinized the countenance opposite but although the words had contained a mingled caution and rebuke there was not the slightest trace of interest in the face of the speaker, who was imperturbably wiping off the moist nickel cap with a handful of waste from his pocket. "Yes," he repeated half-absently, "I take it that amount of gas will just about carry you back to Coventry; it won't allow for any detours, to be sure, but if you follow the straight road it ought to fetch you up there all right." Stephen started and again an interrogation rose to his lips. Who was this mysterious mechanic and why should he assume with such certainty that Coventry was the abiding place of the car? He longed to ask but a fear of lengthening the interview prevented him from doing so. If he began to ask questions might not the stranger assume the same privilege and wheel upon him with some embarrassing inquiry? No, the sooner he was clear of this wizard in the brown overalls the better. But for the sake of his peace of mind he should like to know whether the man really knew who he was or whether his comments were simply matters of chance. There certainly was something very uncanny and uncomfortable about it all, something that led him to feel that the person in the jumper was fully acquainted with his escapade, disapproved of it, and meant to prevent him from prolonging it. Yet as he took a peep into the kindly blue eyes which he did not trust himself to meet directly he wondered if this assumption were not created by a guilty conscience rather than by fact. Certainly there was nothing accusatory in the other's bearing. His face was frankness itself. In books criminals were always fearing that people suspected them, reflected Steve. The man knew nothing about him at all. It was absurd to think he did. Nevertheless the boy was eager to be gone from the presence of those searching blue eyes and therefore he climbed into his car, murmuring hurriedly: "You've been corking to help me out!" The workman held up a protesting hand. "Don't think of it again," he answered. "I was glad to do it. Good luck to you!" With nervous hands Stephen started the engine and, backing the automobile about, headed it homeward. Now that danger was past his desire to reach Coventry before his father should arrive drove every other thought from his mind, and soon the mysterious hero of the brown jumper was forgotten. Although he made wonderfully good time back over the road it seemed hours before he turned in at his own gate and brought the throbbing motor to rest in the garage. A sigh of thankfulness welled up within him. The great red leviathan that had caused him such anguish of spirit stood there in the stillness as peacefully as if it had never stirred from the spot it occupied. If only it had remained there, how glad the boy would have been. He ventured to look toward the windows fronting the avenue. No one was in sight, it was true; but to flatter himself that he had been unobserved was ridiculous for he saw by the clock that his father, mother, and Doris must already have reached home. Doubtless they were in the house now and fully acquainted with what he had done. If they had not missed the car from the garage they would at least have seen it whirl into the driveway with him at the wheel. Any moment his father might appear at his shoulder. To delay was useless. He had had his fun and now in manly fashion he must face the music and pay for it. How he dreaded the coming storm! Once, twice he braced himself, then moved reluctantly toward the house, climbed the steps, and let himself in at the front door. He could hardly expect any one would come to greet him under the circumstances. An ominous silence pervaded the great dim hall but after the glare of the white ribbon of road on which his eyes had been so intently fixed he found the darkness cool and tranquilizing. At first he could scarcely see; then as he gradually became accustomed to the faint light he espied on the silver card tray a telegram addressed to himself and with a quiver of apprehension tore it open. Telegrams were not such a common occurrence in his life that he had ceased to regard them with misgiving. The message on which his gaze rested, however, contained no ill tidings. On the contrary it merely announced that the family had been detained in New York longer than they had expected and would not return until noon to-morrow. He would have almost another day, therefore, before he would be forced to make confession to his father! The respite was a welcome one and with it his tenseness relaxed. He even gained courage on the strength of his steadier nerves to creep into the kitchen and confront Mary, the cook, whom he knew must have seen him shoot into the driveway and who, having been years in the home, would not hesitate to lecture him roundly for his conduct. But Mary was not there and neither was Julia, the waitress. In the absence of the head of the house the two had evidently ascended to the third story there to forget in sleep the cares of daily life. Stephen smiled at the discovery. It was a coincidence. Unquestionably Fate was with him. It helped his self-respect to feel that at least the servants were in ignorance of what he had done. Nobody knew--nobody at all! With an interval of rest and a dash of cold water upon his face gradually the act he had committed began to sink back into normal perspective and loom less gigantic in his memory. After all was it such a dreadful thing, he asked himself. Of course he should not have done it and he fully intended to confess his fault and accept the blame. But was the folly so terrible? He owned that he regretted it and admitted that he was somewhat troubled over the probable consequences, and every time he awoke in the night a dread of the morrow came upon him. In the morning he rushed off to school, found the team had won the game, and came home feeling even more justified than before. Why, if he had not taken the car, the school might have forfeited that victory! All the afternoon as he sat quietly at his books he tried to keep this consideration uppermost in his mind. Then at dinner time there was a stir in the hall and he knew the moment he feared had arrived. The family were back again! Slowly he stole down over the heavily carpeted stairs. Yes, there they were, just coming in at the door, laughing and chatting gaily with Julia, who had let them in. The next instant his mother had espied him on the landing and had called a greeting. There was a smile on her face that reproached him for having yielded to the temptation to deceive her even for a second. "Such a delightful trip as we have had, Steve!" she called. "We wished a dozen times that you were with us. But some vacation you shall have a holiday in New York with your father to pay for what you have missed this time. You shall not be cheated out of all the fun, dear boy!" "Everything been all right here, son?" inquired his father from the foot of the stairs. "Yes, Dad." "Havens has not showed up yet, I suppose." The boy flushed. "No, sir." "It seems to take him an interminable time to have his tonsils out. If he does not appear pretty soon I shall have to get another man to run the car. We can't be left high and dry like this," fretted the elder man irritably. "Suppose I knew nothing about it, where would we be? I wished to-day you were old enough to have a license and could have come to the station to meet us. I believe with a little more instruction you could manage that automobile all right. Not that I should let you go racing over the country with a lot of boys. But you might be very useful in taking your mother and sister about and helping when we were in a fix like this. I think you would enjoy doing it, too." "I--I'm--sure I should," replied the lad, avoiding his father's eye and studying the toe of his shoe intently. It passed through his mind as he stood there that now was the moment for confession. He had only to say, "_I had the car out yesterday_," and the dreaded ordeal would be over. But somehow he could not utter the words. Instead he descended from the landing and followed the others into the library where the conversation immediately shifted to other topics. In the jumble of narrative his chance to speak was swallowed up nor during the next few days did any suitable opportunity occur for him to make his belated confession. When Mr. Tolman was not at meetings of the railroad board he was at his office or occupied with important affairs, and by and by so many events had intervened that to go back into the past seemed to Stephen idle sentimentality. At length he had lulled his conscience into deciding that in view of the conditions it was quite unnecessary to acquaint his father and mother with his wrong-doing at all. He was safely out of the entanglement and was it not just as well to accept his escape with gratitude and let sleeping dogs lie? All the punishments in the world could not change anything now. What would be the use of telling? CHAPTER II A MEETING WITH AN OLD FRIEND The day of the excursion to Northampton was one of those clear mornings when a light frost turned the maples to vermilion and in a single night transformed the ripening summer foliage to the splendor of autumn. The Tolman family were in the highest spirits; it was not often that Mr. Tolman could be persuaded to leave his business and steal away for a week-end and when he did it was always a cause for great rejoicing. Doris, elated at the prospect of rejoining her college friends, was also in the happiest frame of mind and tripped up and down stairs, collecting her forgotten possessions and jamming them into her already bulging suitcase. As for Steve, the prickings of conscience that had at first tormented him and made him shrink from being left alone with his father had quite vanished. He had argued himself into a state of mental tranquility where further punishment for his misdemeanor seemed superfluous. After his hairbreadth escape from disaster there was no danger, he argued, of his repeating the experiment, and was not this the very lesson all punishments sought to instill? If he had achieved this result without bothering his father about the details, why so much the better. Did not the old adage say that "experience is the best teacher"? Certainly in this case the maxim held true. Having thus excused his under-handedness and stifled the protests of his better nature he felt, or tried to feel, entirely at peace with the world; and as he now sauntered out to greet the new day he did it as jauntily as if he had nothing to conceal. Already the car was at the door with the luggage aboard and its engine humming invitingly. As the boy listened to the sound he could not but rejoice that the purring monster could tell no tales. How disconcerting it would be should the scarlet devil suddenly shout aloud: "Well, Steve, don't you hope we do not get stalled to-day the way we did going to Torrington?" Mercifully there was no danger of that. The engine might puff and purr and snort but at least it could not talk, and his secret was quite safe. This reflection lighted his face with courage and when the family came out to join him no one would have suspected that the slender boy waiting on the doorstep harbored a thought of anything but anticipation in the prospect of the coming holiday. "Is everything in, Steve?" asked his father, approaching with Doris's remaining grip. "I think so, Dad," was the reply. "It certainly seems as if I had piled in almost a dozen suitcases." "Nonsense, Stevie," pouted Doris. "There were only four." "Five, Miss Sophomore!" contradicted her brother. "Five! That one Dad is bringing makes the fifth, and I would be willing to bet that it is yours." "That's where you are wrong, Smartie," the girl laughed good-humoredly, making a mischievous grimace at him from beneath the brim of her saucy little toque of blue velvet. "I am not guilty of the extra suitcase. It's mother's." "Your mother's!" ejaculated Mr. Tolman incredulously. "Mercy on us! I never knew your mother to be starting out on a short trip with such an array of gowns." Then turning toward his wife, he added in bantering fashion: "Aren't you getting a little frivolous, my dear? If it were Doris now--" "But it isn't this time!" interrupted the young lady triumphantly. Her mother exchanged a glance with her and they both laughed. "No, Henry, I am the one to blame," Mrs. Tolman admitted. "You see, if I am to keep pace with my big son and daughter I must look my best; so I have not only brought the extra suitcase but I am going to be tremendously fussy as to where it is put." "I do believe Mater's brought all her jewels with her!" Steve declared wickedly. "Well, she shall have her sunbursts, tiaras, and things where she can keep her eye on them every moment. Suppose I put them down here at your feet, Mother." Without further ado, he started to lift the basket suitcase into the car. "Don't tip it up, son. Don't tip it up!" cautioned his mother. "Your mother is afraid of knocking some of the pearls or emeralds out of their setting," chuckled Mr. Tolman. "Go easy, Steve!" A general laugh arose as the offending piece of baggage was stowed away out of sight. An instant later wraps and rugs were bundled in, everybody was cosily tucked up, and Mr. Tolman placed his hands on the wheel. "Now we're off, Dad!" cried Stephen, as he sprang in beside his father. Mr. Tolman needed no second bidding. There was a whir, a leap forward, and the automobile glided down the long avenue and out into the highway. Steve, studying the road map, was too much interested in tracing out the route they were to follow to notice that after the car had spun along smoothly for several miles its speed lessened, and it was not until it came to a complete standstill that he aroused himself from his preoccupation sufficiently to see that his father was bending forward over the starter. "What's wrong, Henry?" inquired his wife from the back seat. "I can't imagine," was the impatient reply. "Had I not left the tank with gasoline in it, I should say it was empty; but of course that cannot be the case, for I always keep enough in it to carry us to the garage. Otherwise we should be stalled at our own doorstep and not able to get anywhere." Climbing out, he began to unscrew the metal top of the tank while Stephen watched him in consternation. The boy did not need to hear the result of the investigation for already the wretched truth flashed upon him. The tank was empty; of course it was! He knew that without being told. Had not the workman who had replenished it Wednesday said quite plainly that there was only enough gas in it to get him home to Coventry? He should have remembered to stop at the garage and take on an extra supply on the way back as his father always did. How stupid he had been! In his haste to get home he had forgotten every other consideration and the present dilemma was the result of his thoughtlessness. Yet how could he have stopped at the Coventry garage even had he thought of it? All the men there knew him and his father, and if he had gone there or had even driven through the center of the town somebody would have been sure to see him and mention the incident. Why, it was to avoid this very danger that he had returned by the less frequented way. The man in the brown jeans had certainly calculated to a nicety when he measured out that gasoline. He had not meant him to do any more riding that day; that was apparent. What business was it of his, anyway, and why was he so solicitous as to where he went? There was something puzzling about that man. Steve had thought so at the time. Not that it mattered now. All that did matter was that here they were stalled at the side of the road in almost the same spot where he had been stalled the other day; and they were there because he had neglected to procure gasoline. The lad felt the hot blood throb in his cheeks. Again the chance for confession confronted him and again his tongue was tied. In a word he could have explained the whole predicament; but he did not. Instead he sat as if stunned, the heart inside him pounding violently. He saw that his father was not only deeply annoyed but baffled to solve the incident. "The gas is all out; that's the trouble!" he announced. "What are we going to do, Dad?" inquired Doris anxiously. "Oh, we can get more all right, daughter," returned her father reassuringly. "Don't worry, my dear. But what I can't understand is how we come to be in such a plight." "Doesn't gasoline evaporate, Henry?" suggested Mrs. Tolman. "To some extent, yes; but there could be no such shrinkage as this unless there was a leak in the tank. I never dreamed the supply was so low. Well, it is my own fault. I should have made sure everything was right before we started." Steve shifted his position uncomfortably. He was manly enough not to enjoy hearing his father shoulder blame that did not rightfully belong to him. "Now let me think what we had better do," went on Mr. Tolman. "Unfortunately there isn't a house in sight from which we can telephone for help; and we are fully five miles from Torrington. Our only hope is that some one bound for the town may overtake us and allow Steve to ride to the village for aid." "Couldn't I walk it, Dad?" asked the boy, with an impulse to make good the mischief he had done. "Oh, no; I wouldn't do that unless the worst befalls," his father replied kindly. "We should gain nothing. It is a long tramp and would simply be a waste of time. Let us wait like Mr. Micawber, and see if something does not turn up." Wretchedly Stephen settled back into his seat. He would rather have walked to Torrington, done almost anything rather than remain there in the quiet autumn stillness and listen to the accusations of his conscience. What a coward he was! "It is a shame for us to be tied up here!" he heard Doris complain. "I know it, daughter, and I am as sorry as you are," responded her father patiently. "In fact, probably, I am more sorry, since it is through my own carelessness that we are stranded." Again the impulse to blurt out the truth and take the blame that belonged to him took possession of Stephen; but with resolution he forced it back. Nervously he fingered the road map. If he had only spoken at the beginning! It was harder now. He should have made a clean breast of the whole affair when his father got home from New York. Then was the time to have done it. But since he had let that opportunity pass it was awkward, almost absurd, to make confession now. He would much better keep still. In the meanwhile a gradual depression fell upon the occupants of the car. Mrs. Tolman did not speak; Doris subsided into hushed annoyance; and Mr. Tolman began to pace back and forth at the side of the road and anxiously scan the stretch of macadam that narrowed away between the avenue of trees bordering the highway. Presently he uttered an exclamation of relief. "Here comes a truck!" he cried. "We will tip the driver and persuade him to let you ride on to Torrington with him, Steve. This is great luck!" Stepping into the pathway of the approaching car he held up his hand and the passer-by came to a stop beside him. Stephen looked up expectantly; then a thrill of foreboding seized him and he quickly turned his head aside. It needed no second glance to assure him that the man whom his father was addressing was none other than the workman in the brown jeans who had rescued him from his former plight. He bent lower over the road map, trying to conceal his face and decide what to do. In another moment the teamster would probably recognize him, recall the incident of their former meeting, and hailing him as an old acquaintance, relate the entire story. The possibility was appalling, but terrible as it was it did not equal the disquietude he experienced when he heard his father ejaculate with sudden surprise: "Why, if it isn't O'Malley! I did not recognize you, Jake. You are just in time to extricate us from a most inconvenient situation. We are headed for Northampton and find ourselves without gasoline. If you can take my son along to Torrington with you so he can hunt up a garage and ride back with some one on a service car I shall be very grateful to you." "I'd be glad to go myself, sir." "No, no! I shall not allow you to do that," protested Mr. Tolman. "You are on your way to work and I could not think of detaining you. All I ask is that you take my boy along to the village." "I'd really be pleased to go, sir," reiterated O'Malley. "I am in no great rush." "No, I shan't hear to it, Jake," Mr. Tolman repeated. "Nevertheless I appreciate your offer. Take the boy along and that is all I'll ask. Come, Steve, jump aboard! O'Malley, son, is one of our railroad people, whose services we value highly. He is going to be good enough to let you ride over to Torrington with him." Although the introduction compelled Stephen to give the waiting employee a nod of greeting, he did not meet his eye or evince any sign of recognition, and he sensed that the light that had flashed into the man's face at sight of him died out as quickly as it had come. The boy had an uncomfortable realization as he climbed to the seat of the truck and took his place beside its driver that O'Malley must be rating him as a snob. No one but a cad would accept a stranger's kindness and then cut him dead the next time he encountered him. It was better to endure this misjudgment, however, than to acknowledge a previous acquaintance with the mechanic and thereby arouse his father's suspicion and curiosity. Hence, without further parley, he settled himself and in silence the truck started off. For some minutes he waited, expecting that when they were well out of earshot of the family the man at the wheel would turn and with a laugh make some reference to the adventure of the past week. It certainly must have amused him to find the great red car again stalled in the same spot, and what would be more natural than that he should comment on the coincidence and perhaps make a joke of the circumstance? But to the boy's chagrin the teamster did no such thing. Instead he kept his eyes fixed on the road and gave no evidence that he had ever before seen the lad at his elbow. Stephen was aghast. It was not possible the workman had forgotten the happening. He began to feel very uncomfortable. As the landscape slipped past and the car sped on, the distance to Torrington lessened. Still there seemed to be no prospect of the stranger at the wheel breaking his silence. If it had merely been a silence perhaps Steve would not have minded so much; but there was an implied rebuke in the stillness that nettled and stung and left him with a consciousness of being ignored by a superior being. "I say!" he burst out, when he could endure the ignominy of his position no longer, "don't you remember me, Mr. O'Malley?" The man who guided the car did not turn his head but he nodded. "I remember you all right," replied he politely. "I just thought you did not remember me." "Oh, I remembered you right away," declared Steve eagerly. "Did you?" There was a subtle irony in the tone that the lad was not clever enough to detect. "Of course." "Is that so!" came dryly from O'Malley. "Yes, indeed! I remembered you right away," Steve stumbled on. "You are the man who gave me the gasoline when I was stuck here Wednesday." "I am." "I knew you the first minute I saw you," repeated Stephen. "I did not notice any sign that you did," was the terse response. "Oh--well--you see, I couldn't very well speak back there," explained Steve with confusion. "They would all have wanted to know where I--I mean I would have to--it would just have made a lot of talk," concluded he lamely. For the first time the elder man, moving his eyes from the ribbon of gleaming highway, confronted him. "So your father did not know you had the car out the other day?" said he. "N--o." The workman showed no surprise. "I guessed as much," he remarked. "But of course you have told him since." "Not yet," Steve stammered. "I was going to--honest I was; but things kept interrupting until it got to be so late that it seemed silly to rake the matter all up. Besides, I shan't do it again, so what is the use of jawing about it?" He stopped, awaiting a response from the railroad employee; but none came. "Anyhow," he argued with rising irritability, "what good does it do to discuss things that are over and done with? You can't undo them." The man at the wheel vouchsafed no answer. "It is because I forgot to stop for more gas when I went home the other day that we are in this fix now," Steve finally blurted out, finding relief in brutal confession. Still the only reply to his monologue was the chugging of the engine. At last his voice rose to a higher pitch and there was anger in it. "I'm talking to you," he shouted in exasperation. "I am listening." "Well, why don't you say something?" "What is there to say?" "Why--eh--you could tell me what you think." "I guess you know that already." Stephen's face turned scarlet. "I did intend to tell my father," repeated he, instantly on the defensive. "Straight goods, I did." The man shrugged his shoulders. "It was only that it didn't seem to come right. You know how things go sometimes." He saw the workman's lip curl. "You think I ought to have told." "Have I said so?" "No, but I know you do think so." "I wasn't aware I'd expressed any opinion." "No--but--well--hang it all--you think I am a coward for not making a clean breast of the whole thing!" cried Stephen, now thoroughly enraged. "What do you think yourself?" O'Malley suddenly inquired with disconcerting directness. "Oh, I know I've been rotten," admitted the boy. "Still, even now--" He paused. "You mean that even now it isn't too late?" put in the truckman, his face lighting to a smile. "N--o; that wasn't exactly what I was going to say," began the lad, resuming his argumentative tone. "What I mean is that--" A swift frown replaced the elder man's smile. "Here we are at the garage," he broke in. "They will do whatever you want them to." He seemed in a hurry and as Stephen could find no excuse for lingering he climbed reluctantly out of the truck and stood balancing himself on the curb that edged the sidewalk. "I'm much obliged to you for bringing me over," he observed awkwardly. "That's all right." The man in the brown jeans started his engine. "Say, Mr. O'Malley!" called Stephen desperately. "Well?" "You--you--won't tell my father about my taking the car, will you?" he pleaded wretchedly. "_I_ tell him?" Never had he heard so much scorn compressed into three words. "You need have no worries," declared the man over his shoulder, a contemptuous sneer curling his lips. "I confess my own wrong-doing but I do not tattle the sins of other people. Your father will never be the wiser about you so far as I am concerned. Whatever you want him to know you will have to tell him yourself." Baffled, mortified, and stinging with humiliation as if he had been whipped, Stephen watched him disappear round the bend of the road. O'Malley despised him, that he knew; and he did not at all relish being despised. CHAPTER III A SECOND CALAMITY While hunting up the garage and negotiating for gasoline Steve thrust resolutely from his mind his encounter with O'Malley and the galling sense of inferiority it carried with it; but once on the highroad again the smart returned and the sting lingering behind the man's scorn was not to be allayed. It required every excuse his wounded dignity could muster to bolster up his pride and make out for himself the plausible case that had previously comforted him and lulled his conscience to rest. It was now more impossible than ever for him to make any confession, he decided; for having denied in his father's presence O'Malley's acquaintance it would be ridiculous to acknowledge that he had known the truck driver all along. Of course he could not do that. Whatever he might have said or done at the time, it was entirely too late to go back on his conduct now. One event had followed on the heels of another until to slip out a single stone of the structure he had built up would topple over the whole house. If he had spoken in the beginning that would have been quite simple. All he could do now was to let bygones be bygones and in the pleasure of to-day forget the mistakes of yesterday. Consoled by this reflection he managed to recapture such a degree of his self-esteem that by the time he rejoined the family he was once more holding his head in the air and smiling with his wonted lightness of heart. "We shall get you to Northampton now, daughter, without more delay, I hope," Mrs. Tolman affirmed when the car was again skimming along. "We may be a bit behind schedule; nevertheless a late arrival by motor will be pleasanter than to have made the trip by train." "I should say so!" was the fervent ejaculation. "Come, come!" interrupted Mr. Tolman. "I shall not sit back and allow you two people to cry down the railroads. They are not perfect, I will admit, and unquestionably trains do not always go at the hours we wish they did; a touring car is, perhaps, a more comfortable and luxurious method of travel, especially in summer. But just as it is an improvement over the train, so the train was a mighty advance over the stagecoach of olden days." "Oh, I don't know, Dad," Stephen mused. "I am not so sure that I should not have liked stagecoaches better. Think what jolly sport it must have been to drive all over the country!" "In fine weather, yes--that is, if the roads had been as excellent as they are now; but you must remember that in the old coaching days road-building had not reached its present perfection. Traveling by stage over a rough highway in a conveyance that had few springs was not so comfortable an undertaking as it is sometimes pictured. Furthermore you must not forget that it was also perilous, for not only was there danger from accident on these poorly constructed, unlighted thoroughfares but there was in addition the menace from highwaymen in the less populated districts. It took a great while to make a journey of any length, too, and to sleep in a coach where one was cramped, jolted, and either none too warm or miserably hot was not an unalloyed delight, as I am sure you will agree." "I had not thought of any of those things," owned Stephen. "It just seemed on the face of it as if it must have been fun to ride on top of the coach and see the sights as one does from the Fifth Avenue or London buses." "Oh," laughed his father, "a few hours' adventure like that is quite a different affair from making a stagecoach journey. I grant that to ride on a clear morning through the streets of a great city, or bowl along the velvet roads of a picturesque countryside as one frequently does in England is very delightful. To read Dickens' descriptions of journeys up to London is to long to don a greatcoat, wind a muffler about one's neck, and amid the cracking of whips and tooting of horns dash off behind the horses for the fairy city his pen portrays. Who would not have liked, for example, to set out with Mr. Pickwick for the Christmas holidays at Dingley Dell? Why, you cannot even read about it without seeing in your mind's eye the envious throng that crowded the inn yard and watched while the stableboys loosed the heads of the leaders and the steeds galloped away! And those marvelous country taverns he depicts, with their roaring fires, their steaming roasts, their big platters of fowl deluged in gravy, and their hot puddings! Was there ever writer more tantalizing?" "You will have us all hungry in two minutes, Dad, if you keep on," exclaimed Stephen. "And Dickens has us hungry, too," declared Mr. Tolman. "Nevertheless we must not forget that he paints but one side of the picture. He fails to emphasize what such a trip meant when the weather was cold and stormy, and those outside the coach as well as those inside it were often drenched with rain or snow, and well-nigh frozen to death. Moreover, while it is true that many of the inns along the turnpike were clean and furnished excellent fare, there were others that could boast nothing better than chilly rooms, damp beds, and only a very limited hospitality." "I believe you are a realist, Henry," said his wife playfully. Her husband laughed. "Nor must we lose sight of the time consumed by making a trip by coach," he went on. "Business in those days was not such a rushing matter as it is now, of course; yet even when issues of importance were at stake, or crises of life and death were to be met, there was no hurrying things beyond a certain point. Physical impossibility prohibited it. Horses driven at their liveliest pace could cover only a comparatively small number of miles an hour; and at the points where the relays were changed, or the horses fed and rested; the mails deposited or taken aboard; and passengers left or picked up, there were unavoidable delays. In fact, the strongest argument against the stagecoach, and the one that influenced public opinion the most, was this so-called fast-mail service; for in order to make connections with other mail coaches along the route and not forfeit the money paid for doing so, horses were often driven at such a merciless rate of speed that the poor creatures became total wrecks within a very short time. Many a horse fell in its tracks in the inn yards, having been lashed along to make the necessary ten miles an hour and reach a specified town on schedule. Other horses were maimed for life. It is tragic to consider that in England before the advent of the railroad about thirty thousand horses were annually either killed outright or injured so badly that they were of little use afterward." "Great Scott, Dad!" ejaculated Stephen. "And England was no more guilty in this respect than was America, for in the early days of our own country when people were demanding quicker transportation and swifter mail service thousands of noble beasts offered up their last breath in making the required rate of speed." "I suppose nobody thought about the horses," murmured the boy. "I am sure I didn't." "If the public thought at all it was too selfish to care, I am afraid, until threatened by the possibility of the total extermination of these creatures," was his father's reply. "This danger, blended with a humane impulse which rose from the gentler-minded portion of the populace, was the decisive factor in urging men to seek out some other method of travel. Then, too, the world was waking up commercially and it was becoming imperative to find better ways for transporting the ever increasing supplies of merchandise. The quick moving of troops from one point to another was also an issue. Although the canals of England enabled the government to carry quite a large body of men, the method was a slow one. In 1806, for instance, it took exactly a week to shift troops from Liverpool to London, a distance of thirty-four miles." "Why, they could have marched it in less time than that, couldn't they?" questioned Doris derisively. "Yes, the journey might easily have been made on foot in two days," nodded her father. "But in war time a long march which exhausts the soldiers is frequently an unwise policy, for the men are in no condition when they arrive to go into immediate action, as reënforcements often must." "I see," answered Doris. "When the Liverpool and Manchester Railroad was opened in 1830 this thirty-four miles was covered in two hours," continued Mr. Tolman. "Of course the quick transportation of troops was then, as now, of very vital importance. We have had plenty of illustrations of that in our recent war against Germany. Frequently the fate of a battle has hung on large reënforcements being speedily dispatched to a weak point in the line. Moreover, by means of the railroads, vast quantities of food, ammunition and supplies of all sorts can constantly be sent forward to the men in action. During the late war our American engineers laid miles and miles of track under fire, thereby keeping open the route to the front so that there was no danger of the fighters being cut off and left unequipped. It was a service for which they, as well as our nation, won the highest praise. And not only was there a constant flow of supplies but it was by means of these railroads that hospital trains were enabled to carry to dressing stations far behind the lines thousands of wounded men whose lives might otherwise have been lost." "I suppose the slightly wounded could be made more comfortable in this way, too," Mrs. Tolman suggested. "Yes, indeed," was the reply. "Not only were the men better cared for in the roomier hospitals behind the lines, but as there was more space there the peril from contagion, always a menace when large numbers of sick are packed closely together, was greatly lessened; for there is nothing army doctors dread so much as an epidemic of disease when there is not enough room to isolate the patients." "When did England adopt railroads in place of stagecoaches, Dad?" asked Doris presently. At the question her father laughed. "See here!" he protested good-humoredly, "what do you think I am? Just because I happen to be a superintendent do you think me a volume of railroad history, young woman? The topic, I confess, is a fascinating one; but I am off for a vacation to-day." "Oh, tell us, Dad, do!" urged the girl. "Nonsense! What is the use of spoiling a fine morning like this talking business?" objected her father. "But it is not business to us," interrupted Mrs. Tolman. "It is simple a story--a sort of fairy tale." "It is not unlike a fairy tale, that's a fact," reflected her husband gravely. "Imagine yourself back, then, in 1700, before steam power was in use in England. Now you must not suppose that steam had never been heard of, for an ancient Alexandrian record dated 120 B. C. describes a steam turbine, steam fountain, and steam boiler; nevertheless, Hero, the historian who tells us of them, leaves us in doubt as to whether these wonders were actually worked out, or if they were, whether they were anything but miniature models. Still the fact that they are mentioned goes to prove that there were persons in the world who at a very early date vaguely realized the possibilities of steam as a force, whether turned to practical uses or not. For years the subject remained an alluring one which led many a scientist into experiments without number. In various parts of the world men played with the idea and wrote about it; but no one actually produced any practical steam contrivance until 1650, when the second Marquis of Worcester constructed a steam fountain that could force the water from the moat around his castle as high as the top of one of the towers. The feat was looked upon as a marvel and afterward a larger fountain, similar in principle, was constructed at Vauxhall and from that time on the future of steam as a motive power was assured." "Did the Marquis of Worcester go on with his experiments and make other things?" demanded Stephen. "Apparently not," replied his father. "He did, nevertheless, furnish a basis for others to work on. Scientists were encouraged to investigate with redoubled zeal this strange vapor which, when controlled and directed, could carry water to the top of a castle tower. When in 1698 Savery turned Worcester's crude steam fountain to draining mines and carrying a water supply, every vestige of doubt that this mighty power could be applied to practical uses vanished." "Did the steam engine come soon afterward?" queried Doris, who had become interested in the story. "No, not immediately," answered Mr. Tolman, pausing to shift the gear of the car. "Before the steam engine, as we know it, saw the light, there had to be more experimenting and improving of the steam fountain. It was not until 1705 that Thomas Newcomen and his partner, John Calley, invented and patented the first real steam engine. Of course it was not in the least like the engines we use now. Still, it was a steam device with moving parts which would pump water, a tremendous advance over the mechanisms of the past where all the power had been secured by the alternate filling and emptying of a vacuum, or vacant receptacle, attached to the pump. Now, with Newcomen's engine a complete revolution took place. The engine with moving parts, the ancestor of our modern exquisitely constructed machinery, speedily crowded out the primitive steam fountain idea. The new device was very imperfect, there can be no question about that; but just as the steam fountain furnished the inspiration for the engine with moving parts, so this forward step became the working hypothesis for the engines that followed." "What engines did follow?" Doris persisted, "and who did invent our steam engine?" "Silly! And you in college," jeered Steve disdainfully. "I am not taking a course in steam engines there," laughed his sister teasingly. "Anyway, girls are not expected to know who invented all the machines in the world, are they, Dad?" Mr. Tolman waited a moment, then said soothingly: "No, dear. Girls are not usually so much interested in scientific subjects as boys are--although why they should not be I never could quite understand. Nevertheless, I think it might be as well for even a girl to know to whom we are indebted for such a significant invention as the steam engine. "It was James Watt," Stephen asserted triumphantly. "It certainly was," his father agreed. "And since your brother has his information at his tongue's end, suppose we get him to tell us more about this remarkable person." Stephen flushed. "I'm afraid," began he lamely, "that I don't know much more. You see, I studied about him quite a long time ago and I don't remember the details. I should have to look it up. I do recall the name, though--" His father looked amused. "I don't know which of you children is the more blameworthy," remarked he in a bantering tone. "Doris, who never heard of Watt; or Stephen, who has forgotten all about him." Both the boy and the girl chuckled good-humoredly. "At least I knew his name, Dad--give me credit for that," piped Steve. "That was something, certainly," Mrs. Tolman declared, joining in the laugh. "Well, since neither of us can furnish the story, I don't see but that you will have to do it, Dad," Doris said mischievously. "It would be a terrible humiliation if I should discover that I could not do it, wouldn't it?" replied Mr. Tolman with a smile. "In point of fact, there actually is not a great deal more that it is essential for one to know. It was by perfecting the engines of the Newcomen type and adding to them first one and then another valuable device that Watt finally built up the forerunner of our present-day engine. The progression was a gradual one. Now he would better one part, then some other. He surrounded the cylinder, for example, with a jacket, or chamber, which contained steam at the same pressure as that within the boiler, thereby keeping it as hot as the steam that entered it--a very important improvement over the old idea; then he worked out a plan by which the steam could be admitted at each end of the cylinder instead of at one end, as was the case with former engines. The latter innovation resulted in the push and pull of the piston rod. So it went." "How did Watt come to know so much about engines?" asked Stephen. "Oh, Watt was an engineer by trade--or rather he was a maker of mathematical instruments for the University of Glasgow, where he came into touch with a Newcomen engine. He also made surveys of rivers, harbors, and canals. So you see it was quite a consistent thing that a man with such a bent of mind should take up the pastime of experimenting with a toy like the steam engine in his leisure hours." "Did he go so far as to patent it, Henry?" Mrs. Tolman questioned. "Yes, he did. Many of our scientists either had not the wit to do this, alas, or else they were too impractical to appreciate the value of their ideas. In consequence the glory and financial benefit of what they did was often filched from them. But Watt was a Scotchman and canny enough to realize to some extent what his invention was worth. He therefore obtained a patent on it which was good for twenty-five years; and when, in 1800, this right expired he retired from business with both fame and fortune." "It is nice to hear of one inventor who got something out of his toil," Mrs. Tolman observed. "Indeed it is. Think of the many men who have slaved day and night, forfeited health, friends, and money to give to the world an idea, and never lived to receive either gratitude or financial reward, dying unknown or entirely forgotten. There is something tragic about the injustice of it. But Watt, I am glad to say, lived long enough to witness the service he had done mankind and enjoy an honored place among the great of the world." "Is the kind of engine Watt invented now in use?" Doris inquired. "Yes, that is a double-acting or reciprocating engine of a more perfect type," her father returned. "Mechanics and engineers went on improving Watt's engine just as he had improved those that had preceded it. It is interesting, too, to notice that after thousands of years scientists have again worked around to the steam turbine described so long ago in the Alexandrian records. This engine, although it does away with many of the moving parts introduced by Newcomen, preserves the essential principles of that early engine combined with Watt's later improvements. To-day we have a number of different kinds of engines, their variety differing with the purpose to which they are applied. Their cost, weight, and the space they require have been reduced and their power increased, and in addition we have made it possible to run them not only by means of coal or wood but by gasoline, oil, or electricity. We have small, light-weight engines for navigation use; mighty engines to propel our great warships and ocean liners; stationary engines for mills and power plants; to say nothing of the wonderful locomotive engines that can draw the heaviest trains over the highest of mountains. The principle of all these engines is, however, the same and for the brain behind them we must thank James Watt." "Was it Watt who invented the locomotive, too?" ventured Doris. Her father shook his head. "The perfecting of the locomotive, my dear, is, as Kipling says, another story." "Tell it to us." "Not now, daughter," protested Mr. Tolman. "I am far too hungry; and more than that I am eager to enjoy this beautiful country and forget railroads and locomotives." "Did you say you were hungry, Henry?" asked Mrs. Tolman. "I am--starved!" her husband said apologetically. "Isn't it absurd to be hungry so early in the day?" "It is nearly noon, Dad!" said Steve, glancing down at the clock in the front of the car. "Noon! Why, I thought it was still the middle of the morning." "No, indeed! While you have been talking we have come many a mile, and the time has slipped past," his wife said. "If all goes well--" The shot from a bursting tire rent the air. "Which evidently it does not," interrupted Mr. Tolman grimly, bringing the car to a stop. "How aggravating! We were almost into Palmer, where I had planned for us to lunch. Now it may be some little time before we can get anything to eat." "Motorist's luck! Motorist's luck, my dear!" cried Mrs. Tolman gaily. "An automobilist must resign himself to taking cheerfully what comes." "That is all very well," grumbled her husband, as he clambered out of the car. "Nevertheless you must admit that this mishap on the heels of the other one is annoying." Stephen also got out and the two bent to examine the punctured tire. "I should not mind so much if I were not so hungry," murmured Mr. Tolman. "How are you, Steve? Fainting away?" The boy laughed. "Well, I could eat something if I had it," he confessed. "I wish I hadn't mentioned food," went on Mr. Tolman humorously. "It was an unfortunate suggestion." "I'm hungry, too," piped Doris. "There, you see the epidemic you have started, Henry," called Mrs. Tolman accusingly. "Here is Doris vowing she is in the last throes of starvation." Nobody noticed that in the meanwhile the mother had reached down and lifted into her lap the small suitcase hidden in the bottom of the car. She opened the cover and began to remove its contents. At length, when a remark her husband made to her went unheeded, he sensed her preoccupation and came around to the side of the car where she was sitting. Immediately he gave a cry of surprise. "My word!" he exclaimed. "Steve, come here and see what your mother has." Stephen looked. There sat Mrs. Tolman, unpacking with quiet enjoyment sandwiches, eggs, cake, cookies, and olives. A shout of pleasure rose from the famished travelers. "So it was not your jewels, after all, Mater!" cried Stephen. "No, and after the way you have slandered me and my little suitcase, none of you deserve a thing to eat," his mother replied. "However, I am going to be magnanimous if only to shame you. Now climb in and we will have our lunch. You can fix the tire afterward." The men were only too willing to obey. As with brightened faces they took their seats in the car, Stephen smiled with affection at his mother. "Well, Mater, Watt was not the only person who lived to see himself appreciated; and I don't believe people were any more grateful to him for his steam engine than we are to you right now for this luncheon. You are the best mother I ever had." CHAPTER IV THE STORY OF THE FIRST RAILROAD The new tire went on with unexpected ease and early afternoon saw the Tolmans once more bowling along the highway toward Northampton. The valley of the Connecticut was decked with harvest products as for an autumnal pageant. Stacks of corn dotted the fields and pyramids of golden pumpkins and scarlet apples made gay the verandas of the old homesteads or brightened the doorways of the great red barns flanking them. "All that is needed to transform the scene into a giant Hallowe'en festival is to have a witch whisk by on a broomstick, or a ghost bob up from behind a tombstone," declared Mrs. Tolman. "Just think! If we had come by train we would have missed all this beauty." "I see plainly that you do not appreciate the railroads, my dear," returned her husband mischievously. "This is the second time to-day that you have slandered them. You sound like the early American traveler who asserted that it was ridiculous to build railroads which did very uncomfortably in two days what could be done delightfully by coach in eight or ten." "Why, I should have thought people who had never heard of motor-cars would have welcomed the quicker transportation the railroads offered," was Mrs. Tolman's reply. "One would have thought so," answered Mr. Tolman. "Still, when we recall how primitive the first railroads were, the prejudice against them is not to be wondered at." "How did they differ from those we have now, Dad?" Doris asked. "In almost every way," answered her father, with a smile. "You see at the time Stephenson invented his steam locomotive nothing was known of this novel method of travel. As I told you, persons were accustomed to make journeys either by coach or canal. Then the steam engine was invented and immediately the notion that this power might be applied to transportation took possession of the minds of people in different parts of England. As a result, first one and then another made a crude locomotive and tried it out without scruple on the public highway, where it not only frightened horses but terrified the passers-by. Many an amusing story is told of the adventures of these amateur locomotives. A machinist named Murdock, who was one of James Watt's assistants, built a sort of grasshopper engine with very long piston rods and with legs at the back to help push it along; with this odd contrivance he ventured out into the road one night just at twilight. Unfortunately, however, his restless toy started off before he was ready to have it, and turning down an unfrequented lane encountered a timid clergyman who was taking a peaceful stroll and frightened the old gentleman almost out of his wits. The poor man had never seen a locomotive before and when the steaming object with its glowing furnace and its host of moving arms and legs came puffing toward him through the dusk he was overwhelmed with terror and screamed loudly for help." A laugh arose from the listeners. "And that is but one of the many droll experiences of the first locomotive makers," continued Mr. Tolman. "For example Trevithick, another pioneer in the field, also built a small steam locomotive which he took out on the road for a trial trip. It chanced that during the experimental journey he and his fireman came to a tollgate and puffing up to the keeper with the baby steam engine, they asked what the fee would be for it to pass. Now the gate keeper, like the minister, had had no acquaintance with locomotives, and on seeing the panting red object looming like a specter out of the darkness and hearing a man's voice intermingled with its gasps and snorts, he shouted with chattering teeth: "There is nothing to pay, my dear Mr. Devil! Just d-r-i-v-e along as f-a-s-t--as--ever--you--can." His hearers applauded the story. "Who did finally invent the railroad?" inquired Doris after the merriment had subsided. "George Stephenson, an Englishman," replied her father. "For some time he had been experimenting with steam locomotives at the Newcastle coal mines where some agency stronger than mules or horses was needed to carry the products from one place to another. He had no idea of transporting people when he began to work out the suggestion. All he thought of was a coal train which would run on short lengths of track from mine to mine. But the notion assumed unexpected proportions until the Darlington road, the most ambitious of his projects, reached the astonishing distance of thirty-seven miles. When the rails for it were laid the engineer intended it should be used merely for coal transportation, as its predecessors had been; but some of the miners who lived along the route and were daily obliged to go back and forth to work begged that some sort of a conveyance be made that could also run along the track and enable them to ride to work instead of walking. So a little log house not unlike a log cabin, with a table in the middle and some chairs around it, was mounted on a cart that fitted the rails, and a horse was harnessed to the unique vehicle." "And it was this log cabin on wheels that gave Stephenson his inspiration for a railroad train!" gasped Doris. "Yes," nodded her father. "When the engineer saw the crude object the first question that came to him was why could not a steam locomotive propel cars filled with people as well as cars filled with coal. Accordingly he set to work and had several coach bodies mounted on trucks, installing a lever brake at the front of each one beside the coachman's box. In front of the grotesque procession he placed a steam locomotive and when he had fastened the coaches together he had the first passenger train ever seen." "It must have been a funny looking thing!" Steve exclaimed, smiling with amusement at the picture the words suggested. "It certainly was," agreed his father. "If you really wish to know how funny, some time look up the prints of this great-great-grandfather of our present-day Pullman and you will be well repaid for your trouble; the contrast is laughable." "But was this absurd venture a success?" queried Mrs. Tolman incredulously. "Indeed it was!" returned her husband. "In fact, Stephenson, like Watt, was one of the few world benefactors whose gift to humanity was instantly hailed with appreciation. The railroad was, to be sure, a wretched little affair when viewed from our modern standpoint, for there were no gates at the crossings, no signals, springless cars, and every imaginable discomfort. Fortunately, however, our ancestors had not grown up amid the luxuries of this era, and being of rugged stock that was well accustomed to hardships of every variety they pronounced the invention a marvel, which in truth it was. "You've said it!" chuckled Steve in the slang of the day. "In the meantime," went on Mr. Tolman, "conditions all over England were becoming more and more congested, and from every direction a clamor arose for a remedy. You see the invention of steam spinning machinery had greatly increased the output of the Manchester cotton mills until there was no such thing as getting such a vast bulk of merchandise to those who were eager to have it. Bales of goods waiting to be transported to Liverpool not only overflowed the warehouses but were even stacked in the open streets where they were at the mercy of robbers and storms. The canals had all the business they could handle, and as is always the result in such cases their owners became arrogant under their prosperity and raised their prices, making not the slightest attempt to help the public out of its dilemma. Undoubtedly something had to be done and in desperation a committee from Parliament sent for Stephenson that they might discuss with him the feasibility of building a railroad from Manchester to Liverpool. The committee had no great faith in the enterprise. Most of its members did not believe that a railroad of any sort was practical or that it could ever attain speed enough to be of service. However, it was a possibility, and as they did not know which way to turn to quiet the exasperated populace they felt they might as well investigate this remedy. It could do no harm." Mr. Tolman paused as he stooped to change the gear of the car. "So Stephenson came before the board, and one question after another was hurled at him. When, however, he was asked, half in ridicule, whether or not his locomotive could make thirty miles an hour and he answered in the affirmative, a shout of derision arose from the Parliament members. Nobody believed such a miracle possible. Nevertheless, in spite of their sceptical attitude, it was finally decided to build the Liverpool-Manchester road and about a year before its opening a date was set for a contest of locomotives to compete for the five-hundred-pound prize offered by the directors of the road." "I suppose ever so many engines entered the lists," ventured Steve with interest. "There were four," returned his father. "And Stephenson drove one of them?" "Yes." "Oh, I hope it got the prize!" put in Doris eagerly. Her father smiled at her earnestness. "It did," was his reply. "Stephenson's engine was called the 'Rocket' and was a great improvement over the locomotive he had used at the mines, for this one had not only a steam blast but a multi-tubular boiler, a tremendous advance in engine building." "I suppose that the winner of the prize not only got the money the road offered but his engine was the one chosen as a pattern for those to be used on the new railroad," ventured Stephen. "Precisely. So you see a great deal depended on the showing each locomotive made. Unluckily in the excitement a tinder box had been forgotten, and when it came time to start, the spark to light the fires had to be obtained from a reading glass borrowed from one of the spectators. This, of course, caused some delay. But once the fires were blazing and steam up, the engines puffed away to the delight of those looking on." "I am glad Stephenson was the winner," put in Doris. "Yes," agreed her father. "He had worked hard and deserved success. It would not have seemed fair for some one else to have stolen the fruit of his toil and brain. Yet notwithstanding this, his path to fame was not entirely smooth. Few persons win out without surmounting obstacles and Stephenson certainly had his share. Not only was he forced to fight continual opposition, but the opening of the Manchester and Liverpool road, which one might naturally have supposed would be a day of great triumph, was, in spite of its success, attended by a series of catastrophes. It was on September 15, 1830, that the ceremonies took place, and long before the hour set for the gaily decorated trains to pass the route was lined with excited spectators. The cities of Liverpool and Manchester also were thronged with those eager to see the engines start or reach their destination. There were, however, mingled with the crowd many persons who were opposed to the new venture." "Opposed to it?" Steve repeated with surprise. "Yes. It seems odd, doesn't it?" "But why didn't they want a railroad?" persisted the boy. "I thought that was the very thing they were all demanding." "You must not forget the condition of affairs at the time," said his father. "Remember the advent of steam machinery had deprived many of the cotton spinners of their jobs and in consequence they felt bitterly toward all steam inventions. Then in addition there were the stagecoach drivers who foresaw that if the railroads supplanted coaches they would no longer be needed. Moreover innkeepers were afraid that a termination of stage travel would lessen their trade." "Each man had his own axe to grind, eh?" smiled Steve. "I'm afraid so," his father answered. "Human nature is very selfish, and then as now men who worked for the general welfare regardless of their own petty preferences were rare. To the side of the enemies of the infant invention flocked every one with a grievance. The gentry argued that the installation of locomotives would frighten the game out of the country and ruin the shooting. Other opposers contended that the smoke from the engines would not only kill the birds but in time kill the patrons of the railroads as well. Still others protested that the sparks from the funnels might set fire to the fields of grain or to the forests. A swarm of added opponents dwelt on the fact that the passengers would be made ill by the lurching of the trains; that the rapid inrush of air would prevent their breathing; and that every sort of people would be herded together without regard to class,--the latter a very terrible calamity in a land where democracy was unknown. Even such intelligent men as the poet Wordsworth and the famous writer Ruskin came out hotly against the innovation, seeing in it nothing but evil." "Didn't the opening of the Manchester and Liverpool Railroad convince the kickers they were wrong?" asked Steve. "Unfortunately not," was Mr. Tolman's reply. "You see several unlucky incidents marred the complete success of the occasion. As the trains trimmed with bunting and flowers started out the scene seemed gay enough. On one car was a band of music; on another the directors of the road; and on still another rode the Duke of Wellington, who at that time was Prime Minister of England and had come down from London with various other dignitaries to honor the enterprise. Church bells rang, cannon boomed, and horns and whistles raised a din of rejoicing. But everywhere among the throng moved a large group of unemployed laborers who had returned from the Napoleonic wars in a discontented frame of mind and resented the use of steam machinery. They were on edge for trouble and if there were none they were ready to make it. So strong was the resentment of this element against the government that it seemed tempting Providence for the Prime Minister to venture into the manufacturing district of Manchester. At first it was decided that he would better omit the trip altogether; but on second thought it seemed wiser for him not to add fuel to the flames by disappointing the mill workers. The audience was in too ugly a mood to be angered. Therefore Wellington bravely resolved to carry out the program and ride in one of the open cars." "I hope nothing happened to him, Dad!" gasped Doris breathlessly. "Nothing beyond a good many minor insults and indignities," responded her father. "He was, however, in constant peril, and to those who bore the responsibility of the function he was a source of unceasing anxiety. But in spite of the jeers of the mob, their crowding and pushing about his car, he kept a smiling face like the true gentleman he was. Some of the rougher element even went so far as to hurl missiles at him. You can imagine how worried his friends were for his safety and how the directors who had invited him fidgeted. And as if this worry were not enough, by and by a fine rain began to fall and those persons riding in the open coaches, as well as the decorations and the spectators, got well drenched. Then there were delays on the turnouts while one train passed another; and as a climax to these discouragements, Mr. Hickson, a member of Parliament from Liverpool, got in the path of an approaching engine, became confused and was run over; and although Stephenson himself carried him by train to Liverpool he died that evening." "I should call the fête to introduce the steam engine into England a most disastrous and forlorn one," remarked Mrs. Tolman. "Well, in reality it was not such a failure as it sounds," replied her husband, "for only those most closely connected with it sensed the misfortunes that attended it. The greater part of the people along the route were good-humored and pleased; they marveled at the trains as they passed, cheered the Duke and the authorities with him, listened with delight to the band, and made a jest of the rain. A holiday crowd, you know, is usually quite patient. Hence the delays that fretted the guests and the officials of the road did not annoy the multitudes so vitally." "Poor Stephenson really got some satisfaction out of the day then," sighed Mrs. Tolman. "Oh, yes, indeed," said her husband. "Although I fancy the death of Mr. Hickson must have overshadowed his rejoicings. Notwithstanding this, however, the railroad proved itself a practical venture, which was the main thing. Such slight obstacles as the terror of the horses and the fact that the tunnels into Liverpool were so low that the engines had to be detached and the trains hauled into the yards by mules could be remedied." A flicker of humor danced in Mr. Tolman's eyes. "And did England begin to build railroads right away?" Steve inquired. "Yes, and not only England but France also. Frenchmen who crossed the Channel took home glowing accounts of the novel invention and immediately the French Government realized that that country must also have railroads. But just as the conservative element in England had been sceptical and blocked Stephenson's progress--or tried to--so a corresponding faction in France did all it could to cry down the enterprise. Even those who upheld the introduction of the roads advocated them for only short distances out of Paris; a long trunk route they labeled as an absurdity. Iron was too expensive, they argued; furthermore the mountains of the country rendered extensive railroading impossible. France did not need railroads anyway. Nevertheless the little group of seers who favored the invention persisted and there was no stopping the march of which they were the heralds. Railroads had come to stay and they stayed." "It was a fortunate thing they did, wasn't it?" murmured Doris. "A very fortunate thing," returned Mr. Tolman heartily. "Every great invention is usually suggested by a great need and so it was with this one. By 1836 the craze for railroad building swept both hemispheres. In England the construction of lines to most out-of-the-way and undesirable places were proposed, and the wildest schemes for propelling trains suggested; some visionaries even tried sails as a medium of locomotion instead of steam. Rich and poor rushed to invest their savings in railroads and alas, in many cases the misguided enthusiasts lost every shilling of their money in the project. Great business firms failed, banking houses were ruined, and thousands of workmen were thrown out of employment. In consequence a reaction followed and it was years before wary investors could again be induced to finance a railroad. In the interim both engines and coaches underwent improvement, especially the third-class carriage which in the early days was nothing more than an open freight car and exposed its unhappy patrons to snow, rain, and freezing weather." "Great Scott!" cried Steve. "I should say there was room for improvement if that was the case." "There was indeed," echoed his father. "In fact, it was a long time before travel by train became a pleasure. Most of the engines used pitch pine or soft coal as a fuel and as there were no guards on the smokestacks to prevent it, the smoke, soot, and cinders used to blow back from the funnels and shower the passengers. On the first railroad trip from New York to Albany those sitting outside the coaches were compelled to put up umbrellas to protect themselves from these annoyances." "Imagine it!" burst out Doris, with a rippling laugh. "Nor were the umbrellas of any service for long," continued Mr. Tolman, "for the sparks soon burned their coverings until nothing but the steel ribs remained." "I don't wonder the trip was not a pleasure," smiled Mrs. Tolman. "Yet, in spite of its discomfort, it was a novelty and you must not forget that, as I said before, the public of that period was a simple and less exacting one than is the public of to-day. We make a frightful fuss if we are jolted, chilled, crowded, delayed, or made uncomfortable; but our forefathers were a hale and hearty lot--less overworked perhaps, less nervous certainly, less indulged. They had never known anything better than cold houses, draughty and crowded stagecoaches, and stony highways--plenty of obstacles, you see, and few luxuries. Therefore with naïve delight they welcomed one new invention after another, overlooking its defects and considering themselves greatly blessed to have anything as fine. Probably we, who are a thousand per cent better off than they, do more grumbling over the tiny flaws in the mechanism of our lives than they did over the mammoth ones." "Oh, come, Dad!" protested Stephen. "Aren't you putting it rather strong?" "Not a whit too strong, Steve," Mrs. Tolman interrupted. "I believe we are a fussy, pampered, ungrateful generation. It is rather pathetic, too, to think it is we who now reap the benefits of all those perfected ideas which our ancestors enjoyed only in their most primitive beginnings. It seems hardly fair that Stephenson, for example, should never have seen a modern Pullman. "He was spared something, wasn't he, Dad?" chuckled Steve mischievously. But Mr. Tolman did not heed the remark. "He had the vision," returned he softly, "the joy of seeing the marvel for the first time, imperfect as it was. Perhaps that was compensation enough. It is the reward of every inventor. Remember it is no mean privilege to stand upon the peak in Darien which Keats pictures." CHAPTER V STEVE LEARNS A SAD LESSON No more disasters attended the journey and the travelers spun swiftly on to Northampton, arriving at the old New England town late in the afternoon. What a scene of activity the college campus presented! Bevies of girls, hatless and in gay-colored sweaters, drifted hither and thither, their laughter floating through the twilight with musical clearness. Occasionally some newcomer would join a group and a shout of welcome would hail her advent. Although Steve turned away from these gushing greetings with masculine scorn nevertheless he was far more interested in the novel picture than he would have been willing to admit. More than once he caught his eyes following a slender figure in white, across whose hair the sunset slanted, turning its blowing masses to a glory of gold. With what ease and freedom the girl moved! And when, as she passed, some one unceremoniously tossed her a ball and she caught it with swift accuracy, his admiration was completely won. Steve speculated as to whether she would prove to be as pretty at close range as she was at a distance and decided not. Distance always brings a glamor with it. However, pretty or not, there was no disputing that she was a great favorite for every circle of students opened its magic ring at her approach and greeted her with a noisy clamor of affection. That she held herself with quiet reserve and was less demonstrative than those about her did not appear to lessen in the least their regard for her, and as Stephen watched he registered the wager that she was a person of more common sense than most girls. Until recently it had been his habit to condemn the entire sex; but of late he had discovered that exceptions might be made to his rule. There were girls in the world worth noticing, even some worth talking to; and he felt certain that this attractive creature in white was one of them. However, it was an absurdity to be thinking about her now and quite beneath his dignity. But he meant sometime, when he could do so in casual fashion, to find out from Doris who she was. He had a curiosity to know what this person who looked as if she could row a boat, swim, and play tennis well, was called. Doris was always raving about her roommate, Jane Harden. She had said so much about her that he fairly detested the sound of her name. Now if only Jane Harden were a girl like this one, there would be some reason and excuse for being enthusiastic over her. To have this guest brought home to spend the Christmas holidays would be a pleasure to look forward to. How well she would skate and how gracefully; and how pretty she would be, especially if she had her hat off as she had now! It was Doris who interrupted his reverie with the words: "I hate to have you dear people go but I suppose you will have to. But do just wait long enough for me to see if I can't find Jane somewhere. She is crazy to meet my family and will scold me to death if I let you get away." "I am afraid we can't stay but a moment or two, dear," objected Mrs. Tolman. "It is growing late, you know, and we must get to the hotel before it is too dark." "But I won't delay you a second, Mother--truly, I won't. I do want you to meet Jane. I'll ask the girls if they have seen her anywhere." "If you get out into that mob they'll fall all over you and you'll never get back," growled Steve, who was beginning to feel hungry and was none too graciously inclined toward the prospective stranger. "Oh, yes, I will," laughed Doris as she darted away. In spite of this sanguine prediction, however, she did not return as promptly as she had promised, and Mr. Tolman began to fidget uneasily. "We really ought to be starting on," he said at last. "Where is that child?" "I knew she'd stop to admire everybody's new hat and talk over the whole summer," grumbled Steve scornfully. "You are thinking of your dinner, son," his mother put in playfully. "You bet I am! I'm hungry as a bear." A pause followed in which visions of a big beefsteak with crisply fried potatoes blotted out every other picture from Steve's mind. "Perhaps we ought not to have waited," he heard his mother murmur. "But I had not the heart to disappoint Doris. She is so fond of Jane and has talked so much about her! I had no idea it would take her so long to--" "Here she comes!" Mr. Tolman broke in. Stephen glanced up. Yes, there was Doris hurrying across the grass and beside her, walking with the same free and buoyant swing, was the girl of the golden hair,--Jane Harden. With the same reserve and yet without a shadow of self-consciousness she came forward and in acknowledgment of the hurried introductions extended her hand with a grave smile of welcome; but both smile and gesture carried with them a sincerity very appealing. When she greeted Steve he flushed at being addressed as _Mr. Tolman_ and mentally rose six inches in his boots. Yes, she was decidedly pretty, far prettier than she had been in the distance even. In all his life he had never seen a more attractive girl. "I hope, Jane, that you are coming home with Doris for a visit sometime when your own family can spare you," he heard his mother say. "We all should like to have you." "And I should like to come," was the simple and direct answer. "Do plan on it then. Come any time that you can arrange to. We should very much enjoy having you, shouldn't we, Stephen?" Stephen, so suddenly appealed to, turned very red and answered "Yes" in a tone that seemed to come gruffly from way down inside his chest, and then to the sound of hasty farewells the car started and shot out into the village street and the campus with its rainbow-hued occupants was lost to sight. "A charming girl, isn't she?" Mrs. Tolman said to her husband. "So natural and unaffected! Doris says that she is quite the idol of the college and bids fair to be class president. I wish Doris would bring her home for the holidays." Inwardly Steve echoed the sentiment but outwardly he preserved silence. He was too human a boy to dwell long on thoughts of any girl and soon Jane Harden was quite forgotten in the satisfaction of a steaming dinner and a comfortable bed, and the fairy journey of the next day when amid a splendor of crimson and gold the glories of Jacob's Ladder and the Mohawk Trail stretched before his eyes. Within the week the big red car headed for Coventry and without a mishap rolled into the familiar main street of the town which never had seemed dearer than after the interval of absence. As the automobile sped past, friendly faces nodded from the sidewalks and hands were waved in greeting. Presently his mother called from the tonneau: "Isn't that the Taylors' car, Henry, coming toward us? If it is do stop, for I want to speak to them." Mr. Tolman nodded and slowed down the engine, at the same time putting out his hand to bring the on-coming car to a standstill. Yes, there were the Taylors, and on the front seat beside the chauffeur sat "But," the friend who had been most influential in coaxing Stephen into the dilemma of the past fortnight. It was Bud, Steve could not forget, who had been the first to drop out of the car when trouble had befallen and who had led the other boys off on foot with him to Torrington. The memory of his chum's treacherous conduct still rankled in Steve's mind. He had not spoken to him since. But now here the two boys were face to face and unless they were to betray to their parents that something was wrong they must meet with at least a semblance of cordiality. The question was which of them should be the first to make the advance. Twice Bud cleared his throat and appeared to be on the verge of uttering a greeting when he encountered Stephen's scowl and lost courage to call the customary: "Ah, there, Stevie!" And Stephen, feeling that right was on his side and being too proud to open the conversation, could not bring himself to say: "Hi, Bud!" as he always did. As a result the schoolmates simply glared at each other. Fortunately their elders were too much occupied with friendly gossip to notice them and it was not until the talk shifted abruptly into a channel that appalled both boys that their glance met with the sympathy of common danger. It was Bud's mother from whose lips the terrifying words innocently fell. "Havens ill and you in New York Wednesday!" she exclaimed incredulously. "But I certainly thought I saw your car turning into the gate that very afternoon." "I guess not, my dear," asserted Mrs. Tolman tranquilly. "The car has not been out of the garage until now. It must have been somebody else you saw." "But it was your car--I am certain of it," persisted Mrs. Taylor. "Nonsense, Mary!" laughed her husband. "If the car has been in the garage for a week how could it have been. You probably dreamed it. You want a big red car so much yourself that you see them in your sleep." "No, I don't," protested Mrs. Taylor smiling good-humoredly at her husband's banter. "Well, it may have been the Woodworths'," Mrs. Tolman said with soothing inspiration. "They have a car like ours and Mrs. Woodworth came to call while I was away. I'll ask the maid when I get home." "Y-e-s, it may have been the Woodworths'," admitted Mrs. Taylor reluctantly. It was plain, however, that she was unconvinced. "But I could have staked my oath that it was your car and Steve driving it," she added carelessly. "Steve!" Mr. Tolman ejaculated. "Oh, Steve never drives the car," put in Mrs. Tolman quickly. "He is not old enough to have a license yet, you know. That proves absolutely that you were mistaken. But Stephen has run the car now and then when Havens or his father were with him and he does very well at it. Some day he will be driving it alone, won't you, son?" Bending forward she patted the boy's shoulder affectionately. For an instant it seemed to Stephen as if every one in both cars must have heard the _pound_, _pound_, _pound_ of his heart, as if everybody from Coventry to Torrington must have heard it. Helplessly he stared at Bud and Bud stared back. No words were needed to assure the two that once again they were linked together by misdoing as they often had been in the past. Bud looked anxiously toward his chum. He was a mischievous, happy-go-lucky lad but in his homely, freckled face there was a winsome manliness. Whatever the scrapes he got into through sheer love of fun it was characteristic of him that he was always courageous enough to confess to them. This was the first inkling he had had that Stephen had not acquainted his father with the escapade of the previous week and such a course was so at variance with his own frank nature that he was aghast. Even now he waited, expecting his pal would offer the true explanation of the mystery under discussion. He was ready to bear his share of the blame,--bear more than belonged to him if he could lighten Steve's sentence of punishment. But the silence remained unbroken and the words he expected to hear did not come. A wave of surprise swept over his face, surprise followed by a growing scorn. It came to him in a flash that Stephen Tolman, the boy he had looked up to as a sort of idol, was a coward, a coward! He was afraid! It seemed impossible. Why, Steve was always in the thick of the football skirmishes, never shrinking from the roughness of the game; he was a fearless hockey player, a dauntless fighter. Coward was the last name one would have thought of applying to him. And yet here he sat cowering before the just result of his conduct. Bud was disappointed, ashamed; he turned away his head but not before the wretched lad who confronted him had caught in his glance the same contemptuous expression he had seen in O'Malley's face. Again Stephen was despised and knew it. Nevertheless it would not do to betray his secret now. He must not show that he was disconcerted. At every cost he must brazen out the affair. He had gone too far to do otherwise. He wondered as he sat there if any one suspected him; if his father, whose eye was as keen as that of an eagle, had put together any of the threads of evidence. He might be cherishing suspicions this very moment. It seemed impossible that he shouldn't. If only he would speak and have it over! Anything would be better than this suspense and uncertainty. Mr. Tolman, however, maintained unwonted stillness and save for a restless twitching of his fingers on the wheel of the car did not move. If, thought Steve miserably, he could summon the nerve to look up, he would know in a second from his father's face whether he was annoyed or angry. At last the situation became unbearable and come what might he raised his eyes. To his amazement his father was sitting there quite serenely and so was everybody else, and the pause that seemed to him to stretch into hours had glided off as harmlessly and as naturally as other pauses. Apparently nobody was thinking about him, at least nobody but Bud. With a sigh of relief his tense muscles relaxed. He could trust Bud not to betray him. Once again he was safe! CHAPTER VI MR. TOLMAN'S SECOND YARN For a day or two it seemed to Stephen that he would never cease to be haunted by the shame and regret that followed his confiscation of the big red touring car, or forget the good resolutions he made in consequence; but within an incredibly short time both considerations were thrust into the background by the rush of life's busy current. School and athletics kept him occupied so that he had little leisure for thought, and when he was in the house his father and mother smiled on him as affectionately as before, which did much to restore to him his normal poise. Long ago the boys had dropped the motor-car episode from their memories and even Bud Taylor did not refer to it when he and Steve came together to organize the hockey team for the approaching matches. In the meantime the Thanksgiving holidays were drawing near and Mr. Tolman suggested that he and Stephen should run over to New York for a short visit. With the prospect of so much pleasure was it strange the boy ceased to dwell on the unhappiness of the past or the possibility of disaster in the future? The coming journey to New York was, to be sure, no great novelty, for Stephen had often accompanied his father there on business excursions; nevertheless such an outing was a treat to which he looked forward as a sort of Arabian Nights adventure when for a short time he stayed at a large hotel, ate whatever food pleased his fancy, and went sight-seeing and to innumerable "shows" with his father. He was wont to return to Coventry after the holiday with a throng of happy memories and many a tale of marvels with which to entertain the boys. Therefore when he and his father boarded the express Thanksgiving week the lad was in the highest spirits. "Motor-cars are all very well," observed Mr. Tolman, as the porter stowed their luggage away, "but on a cold night like this a Pullman car on a well-laid track is not to be despised. Eh, son?" "I don't believe that I should want to travel to New York in a touring-car at this time of year," agreed Stephen, smiling. "It is getting too late in the season to use an open car, anyway," rejoined his father. "I have delayed putting the car up because I have been hoping we might have a little more warm weather; but I guess the warm days have gone and the winter has come to stay now." "But there is no snow yet, Dad." "No. Still it is too chilly to drive with any comfort. The Taylors shipped their car off last week and when I get home I shall do the same." Stephen looked disappointed. "I don't mind the cold when I'm wrapped up," he ventured. "You are not at the wheel, son," was his father's quick retort. "The man who is has his fingers nipped roundly, I can assure you. It is a pity we have become so soft and shrink so from discomfort. Think what our forbears endured when they went on journeys!" "Neither the English stagecoaches nor Stephenson's railroad could have been very comfortable, to judge from your descriptions of them," laughed Steve. "Oh, don't heap all the blame on the English," his father replied. "Our own modes of travel in the early days were quite as bad as were those on the other side of the water." "I wish you would tell me about the first American railroads," said the boy. "I was wondering about them the other night." Mr. Tolman settled back in his seat thoughtfully. "America," he answered presently, "went through a pioneer period of railroading not unlike England's. Many strange steam inventions were tried in different parts of the country, and many fantastic scientific notions put before the public. Even previous to Watt's steam engine Oliver Evans had astonished the quiet old city of Philadelphia by driving through its peaceful streets in a queer steam vehicle, half carriage and half boat, which he had mounted on wheels. Evans was an ingenious fellow, a born inventor if ever there was one, who worked out quite a few steam devices, some of which Watt later improved and adopted. Then in 1812 John Stevens of New York got interested in the steam idea and urged the commissioners of his state to build a railroad between Lake Erie and Albany, suggesting that a steam engine not unlike the one that propelled the Hudson River ferryboats could be used as power for the trains. He was enthusiastic over the scheme but the New York officials had no faith in the proposition, insisting that a steam locomotive could never be produced that would grip the rails with sufficient tension to keep cars on the track or draw a heavy load." "They'd better have given the plan a showdown," interrupted Steve grimly. "No doubt that is true," admitted his father. "However, it is very easy for us, with our knowledge of science, to look back and laugh at their mistakes. The world was very new in those days and probably had we lived at that time and been equally ignorant of railroads and engines we should have been just as cautious and unbelieving. The railroad was still a young invention, you must remember, and to many persons it seemed a rather mad, uncertain enterprise." "When was the first American railroad built?" inquired the lad. "If by a railroad you mean something which moved along rails like a tram-car, the first such road was built at Quincy, Mass., in 1826; but it was not a steam railroad. It was merely a train of cars drawn by horses along a track that spanned a series of stone ties. Nor was it very extensive in length. In fact, it was only three miles long and probably would not have been built at all if the question had not arisen as to how the heavy blocks of granite necessary for the construction of Bunker Hill monument were to be carried from the quarries to the Neponset River, the point from which they were to be shipped to Charlestown. Bryant, the builder of the road, had heard of Stephenson's successful use of tracks at the Newcastle coal mines and saw no reason why a road of similar pattern could not be laid from the quarries to the ship landing. If such a plan could be worked out, he argued, it would be a great saving of time and labor. Accordingly the railroad was built at a cost of more than ten thousand dollars a mile and it unquestionably performed the service required of it even if it did necessitate the expenditure of a good deal of money. Since the grade sloped toward the river the heavily loaded cars moved down the tracks very easily and as they were empty on their return the ascent was made with equal ease. All the year round this quaint railroad was in constant use, a snowplow being attached to the front car in winter to clear the deep snow from the tracks." "I suppose that was the first railroad snowplow, too," observed Stephen. "I suppose it was," his father agreed. "For some time afterward this old road with its granite ties was the model from which American engineers took their inspiration, it being many years before railroad builders realized that wooden ties were more flexible and made a better, even though less durable roadbed." "Were any more railroads like the Quincy road built in America?" questioned Steve. "Yes, a railroad very much like it was built in the Pennsylvania mining country to transport coal from the mines at Summit down to the Lehigh Valley for shipment. An amusing story is told of this railroad, too. It extended down the mountainside in a series of sharp inclines between which lay long stretches of level ground. Now you know when you coast downhill your speed will give you sufficient impetus to carry you quite a way on a flat road before you come to a stop. So it was with this railroad. But the force the cars gained on the hillside could not carry them entirely across these long levels, and therefore platform cars were built on which a number of mules could be transported and later harnessed to the cars to pull them across the flat stretches. At the end of each level the mules would be taken aboard again and carried down to the next one, where they were once more harnessed to the cars. Now the tale goes that to the chagrin of the railroad people the mules soon grew to enjoy riding so much that they had no mind to get out and walk when the level places were reached and it became almost impossible to make them. All of which proves the theory I advanced before--that too much luxury is not good for any of us and will even spoil a perfectly good mule." Steve chuckled in response. "I'm afraid with railroads like these America did not make much progress," he said. "No very rapid strides," owned his father. "Nevertheless men were constantly hammering away at the railroad idea. In out-of-the-way corners of the country were many persons who had faith that somehow, they knew not how, the railroad would in time become a practical agency of locomotion. When the Rainhill contest of engines took place in England before the opening of the Liverpool-Manchester road, and Stephenson carried off the prize, Horatio Allen, one of the engineers of the Delaware and Hudson Canal Company, was sent over to examine the locomotives competing and if possible buy one for a new railroad they hoped to put into operation. Unluckily none of the engines were for sale but he was able to purchase at Stourbridge a steam locomotive and this he shipped to New York. It reached there in 1829--a ridiculous little engine weighing only seven tons. Before its arrival a track of hemlock rails fastened to hemlock ties had been laid and as the Lackawanna River lay directly in the path of the proposed road a wooden trestle about a hundred feet high had been built across the river. This trestle was of very frail construction and calculated to sustain only a four-ton engine and therefore when the seven-ton locomotive from Stourbridge arrived and was found to weigh nearly double that specification there was great consternation." "Did they tear the trestle down and build another?" asked Steve with much interest. Mr. Tolman did not heed the question. "Now in addition to the disconcerting size of the engine," he continued, "the wooden rails which had been laid during the previous season had warped with the snows and were in anything but desirable condition. So altogether the prospect of trying out the enterprise, on which a good deal of money had already been spent, was not alone disheartening but perilous." "The inspectors or somebody else would have put an end to such a crazy scheme jolly quick if it had been in our day, wouldn't they?" grinned the boy. "Yes, nobody could get very far with anything so unsafe now," his father responded. "But all this happened before the era of inspectors, construction laws, or the _Safety First_ slogan. Hence no one interfered with Horatio Allen. If he chose to break his neck and the necks of many others as well he was free to do so. Therefore, nothing daunted, he got up steam in his baby engine, which was the more absurd for having painted at its front a fierce red lion, and off he started--along his hemlock railroad. The frail bridge swayed and bent as the locomotive rumbled over it but by sheer miracle it did not give way and Allen reached the other side without being plunged to the bottom of the river." Steve drew a long breath of relief. "Did they go on using the railroad after that?" he asked. His father shook his head. "No," he replied. "Although every one agreed that the demonstration was a success the wooden rails were not durable enough to last long and the company was not rich enough to replace them with metal ones. Therefore, in spite of Allen's pleas and his wonderful exhibition of courage, the road fell into disuse, the engine was taken apart, and the enterprise abandoned." "What a pity!" "Yes, it was, for had New York persevered in this undertaking the railroad might have made its advent in the United States much sooner than it did. As it was, once again, like a meteor, the experiment flashed into sight and disappeared with success well within reach." "And who was the next promoter?" "Peter Cooper was the next experimenter of note," Mr. Tolman answered, "and his adventure with railroading was entertaining, too. He lived in Baltimore and being of a commercial trend of mind he decided that if a railroad could be built through the Potomac Valley and across the Alleghany Mountains it might win back for his state the trade that was rapidly being snatched away by the Erie and Pennsylvania Canal. With this idea in mind Cooper built thirteen miles of track and after experimenting with a sort of tram-car and finding it a failure he had a car made that should be propelled by sails." "Sails!" gasped Steve. His father smiled at his astonishment. "Yes, sails!" he repeated. "Into this strangely equipped vehicle he invited some of the editors of the Baltimore papers, and little sensing what was before them the party set forth on its excursion." "Did the car go?" "Oh, it went all right!" chuckled Mr. Tolman. "The trouble was not with its _going_. The difficulty was that as it flew along the rails a cow suddenly loomed in its pathway and as she did not move out of the way of the approaching car she and the railroad pioneers came into collision. With a crash the car toppled over and the editors, together with the enraged Peter Cooper, were thrown out into the mud. Of course the affair caused the public no end of laughter but to Cooper and his guests it proved convincingly that sails were not a desirable substitute for steam power." "I suppose Cooper then went to work to build some other kind of a railroad," mused Steve. "That is exactly what he did," was the rejoinder. "He did not, however, do this deliberately but rather fell into a dilemma that left him no other choice. You see a group of men coaxed him to buy some land through which it was expected the new Baltimore and Ohio Railroad was to pass. These prospectors figured that as the road was already started and a portion of the wooden track laid the railroad was a sure thing, and by selling their land to the railroad authorities they would be enabled to turn quite a fortune for themselves. In all good faith Cooper had joined the company and then, after discovering that the railroad men had apparently abandoned their plan to build, in dastardly fashion, one after another of the promoters wriggled out of the enterprise and left poor Peter Cooper with a large part of his money tied up in a worthless, partially constructed railroad." "What a rotten trick!" cried Steve. "Yes; and yet perhaps Cooper deserved a little chastisement," smiled Mr. Tolman. "Instead of making money out of other people as he had intended--" "He got stung himself!" burst out the boy. "Practically so, yes," was the reply. "Well, at any rate, there he was and if he was ever to get back any of his fortune he must demonstrate that he had profound faith in the partly constructed railroad. Accordingly he bought a small engine weighing about a ton--" "One ton!" "So small that it was christened the 'Tom Thumb.' He now had his wooden rails and his pygmy engine but was confronted by still another perplexity. The railroad must pass a very abrupt curve, it was unavoidable that it should do so--a curve so dangerous that everybody who saw it predicted that to round it without the engine jumping the track and derailing the cars behind would be impossible. Poor Peter Cooper faced a very discouraging problem. There was no gainsaying that the curve was a bad one; moreover, his locomotive was not so perfect a product as he might have wished. It had been built under his direction and consisted of the wee engine he had bought in New York connected with an iron boiler about the size of an ordinary tin wash boiler; and as no iron piping was made in America at this time Cooper had taken some old steel musket barrels as a substitute for tubing. With this crude affair he was determined to convince the public that a steam railroad was a workable proposition." "He had a nerve!" "It took nerve to live and accomplish anything in those days," returned Mr. Tolman. "In the first place few persons had fortunes large enough to back big undertakings; and in addition America was still such a young country that it had not begun to produce the materials needed by inventors for furthering any very extensive projects. In fact the world of progress was, as Kipling says, 'very new and all.' Hence human ingenuity had to make what was at hand answer the required purpose, and as a result Peter Cooper's Tom Thumb engine, with its small iron boiler and its gun-barrel tubing, was set upon the wooden track, and an open car (a sort of box on wheels with seats in it) was fastened to it. Into this primitive conveyance the guests invited for the occasion clambered. Ahead lay the forbidding curve. Stephenson, the English engineer, had already stated mathematically the extreme figure at which a curve could be taken and the locomotive still remain on the track, and Peter Cooper was well aware that the curve he must make was a far worse one. However, it would never do for him to betray that he had any misgivings. Therefore, together with his guests, he set out on his eventful trip which was either to demolish them all, or convince the dignitaries of the railroad company that not only was a steam railroad practical but that the Baltimore and Ohio Road was a property valuable enough to be backed by capital." Steve leaned forward, listening eagerly to the story. "Slowly the little engine started, and nearer and nearer came the terrible curve. The train was now running at fifteen miles an hour, a speed almost unbelievable to the simple souls of that time. Round the curve it went in safety, increasing its velocity to eighteen miles an hour. The railroad officials who were Cooper's guests were frantic with enthusiasm. One man produced paper and pencil and begged those present to write their names, just to prove that it was possible to write even when flying along at such a meteoric rate of speed. Another man jotted down a few sentences to demonstrate that to think and write connected phrases were things that could be done, in spite of the fact that one was dashing through space with this unearthly rapidity." "So the railroad men were converted, were they?" "They were more than converted; they were exultant," said his father. "Of course it was some time after this before the Baltimore and Ohio Railroad became a reality. Capital had to be raised and the project stably launched." "Oh, then this was not the first railroad in the country, after all," observed the boy in a disappointed tone. "No. South Carolina boasts the first regular passenger locomotive propelled by steam," returned Mr. Tolman. "This road ran from Charleston to Hamburg and although a charter was obtained for it in 1827 it took all the first year to lay six miles of track. In fact it was not until 1830 that the railroad began to be operated to any extent. When it was, a locomotive, every part of which had been produced in this country, was employed to draw the trains. This was the first steam locomotive of American make in history. It was dubbed 'The Best Friend' and, like the engines that had preceded it, had a series of interesting adventures. Since it was the only locomotive in the possession of the road and was in use all day any repairs on the hard-worked object had to be made at night." "Humph!" ejaculated Stephen. "Nevertheless 'The Best Friend' might have gone on its way prosperously had it not been for the ignorance of those who ran it. The engineer, to be sure, understood more or less about a steam locomotive although he was none too wise; but the fireman, unfortunately, understood next to nothing, and one day, on being left alone in the cab and seeing the steam escaping from the safety valve, he conceived the notion that a leak was causing unnecessary waste. Therefore he securely screwed up the space through which the steam had been issuing, and to make prevention more certain he himself, a large and heavy man, sat down on the escape valve." "And presto!" exclaimed Steve, rubbing his hands. "Exactly so! Presto, indeed! Figuratively speaking, he blew sky-high and 'The Best Friend' with him," replied Mr. Tolman. "It was an unfortunate happening, too, for people were still ill-informed about the uses of steam and very nervous about its mysterious power and this accident only served to make them more so. For some time afterward many persons refused to patronize the railroad in spite of all the authorities could do to soothe them. In time, however, the public calmed down, although in order to reassure them it was found necessary to put a car heaped with bales of cotton between them and the engine, not only to conceal the monster from their view but also to convince them that it was some distance away. Whether they also had a vague notion that in case they went skyward the cotton might soften their fall when they came down, I do not know." "Railroading certainly had its troubles, didn't it?" Steve commented with amusement. "It certainly had, especially in our own country," was the reply. "In England Stephenson and other experimenters like him had materials at hand which to some extent served their purpose; moreover, thanks to Watt and other inventors, there were definite scientific ideas to work from. But in America the successful railroad which might serve as a model was unknown. Therefore for some time English engines continued to be shipped across the sea, and even then it was a long time before our American engineers understood much about their mechanism. Only by means of repeated experiments, first in one part of the country and then in another, did our American railroads, so marvelous in their construction, come into being." Mr. Tolman paused a moment, yawned, and then rose and beckoned to the porter. "We still have much to perfect in our modern railroad, however," he said with a touch of humor. "The sleeping car, for example, is an abomination, as you are speedily to have proved to you. Here, porter! We'd like these berths made up. I guess we'd better turn in now, son. You have had enough railroading for one day and are tired. You must get a rest and be in the pink of condition to-morrow for, remember, you are going to wake up in New York." "If it will make to-morrow come any quicker I am quite ready to go to bed," retorted Stephen, with a sleepy smile. CHAPTER VII A HOLIDAY JOURNEY The next morning, when Steve woke to the swaying of the train and a drowsy sense of confusion and smoke, he could not for an instant think where he was; but it did not take long for him to open his eyes, recollect the happenings of the previous day, smile with satisfaction, and hurriedly wriggle into his clothes. Already he could hear his father stirring in the berth below and presently the elder man called: "We shall be in New York in half-an-hour, son, so get your traps packed up. How did you sleep?" "Sound as a top!" "That is fine! I was afraid you might not rest very well. As I observed last night, a sleeping car is not all that it might be. The day will come when it will have to be improved. However, since it gets us to New York safely and economizes hours of day travel, it is a blessing for which we should be grateful." As he spoke he moved into the aisle and helped the boy down from his perch; they then sought out a distant seat where they dropped down and watched the rapidly passing landscape. "I have been thinking, as I was dressing, of the story you told me last night about our American railroads," said the lad. "It surprised me a good deal to hear that the South took the lead over the North in the introduction of the steam locomotive." Mr. Tolman smiled into the eager face. "While it is true that South Carolina took the initiative in railroading for a short time the South did not remain long in the ascendency," he answered, "for the third steam locomotive put into actual passenger service was built at Albany. This city, because of its geographical position, was a great stagecoach center, having lines that radiated from it into the interior in almost every direction. And not only was it an important coaching rendezvous but as it was also a leading commercial tributary of New York the Mohawk and Hudson Railroad had built a short track between Albany and Schenectady and supplied it with cars propelled by horse power. Now in 1831 the company decided to transform this road into a steam railroad and to this end ordered a steam locomotive called the 'DeWitt Clinton' to be constructed at West Point with the aim of demonstrating to the northern States the advantages of steam transportation. You can imagine the excitement this announcement caused. Think, if you had never seen a steam engine, how eager you would be to behold the wonder. These olden time New Yorkers felt precisely the same way. Although the route was only sixteen miles long the innovation was such a novel and tremendous one that all along the way crowds of spectators assembled to watch the passing of the magic train. At the starting point near the Hudson there was a dense throng of curious onlookers who gathered to see for the first time in all their lives the steam locomotive and its brigade of coaches,--for in those days people never spoke of a train of cars; a group of railroad carriages was always known as a brigade, and the term _coach_ was, and in many cases still is applied to the cars. This train that created so much interest was practically like Stephenson's English trains, being made up of a small locomotive, a tender, and two carriages constructed by fastening stagecoach bodies on top of railroad trucks. Stout iron chains held these vehicles together--a primitive, and as it subsequently proved, a very impractical method of coupling." "It must have been a funny enough train!" Steve exclaimed. "I doubt if it appeared so to the people of that time," his father returned, "for since the audience of that period had nothing with which to compare it, it probably seemed quite the ordinary thing. Was it not like the railroad trains used in England? How was America to know anything different? Yes, I am sure the 'DeWitt Clinton' was considered a very grand affair indeed, even though it was only a small engine without a cab, and had barely enough platform for the engineer to stand upon while he drove the engine and fed the pitch-pine logs into the furnace." "How many people did the train hold?" inquired Steve, with growing curiosity. "Each coach carried six persons inside and two outside," was Mr. Tolman's reply, "and on this first eventful trip not quite enough adventurous souls could be found to fill the seats. Perhaps could the unwary passengers who did go have foreseen the discomforts ahead of them there would have been fewer yet. But often ignorance is bliss. It certainly was so in this case for in high feather the fortunate ones took their places, the envied of many a beholder." "What happened?" asked the boy eagerly. "Was the trip a success?" "That depends on what you mean by success," laughed his father. "If you are asking whether the passengers arrived safely at Schenectady I can assure you that they did; but if you wish to know whether the journey was a comfortable one, and likely to convert the stranger to steam travel, that is quite another matter. The description of the excursion which history has handed down to us is very naïve. In the first place the pitch-pine fuel sent a smudge of smoke and cinders back over all the passengers and if it did not entirely choke them it at least encrusted them thickly with dirt, particularly the ones who sat outside. The umbrellas they opened to protect themselves were soon demolished, their coverings being blown away or burned up by the sparks. In fact, it was only by continual alertness that the clothing of the venturesome travelers was not ignited. In the meantime those inside the coaches fared little better, for as the coaches were without springs and the track was none too skilfully laid, the jolting of the cars all but sent the heads of the passengers through the roof of the coaches. Added to this the train proceeded in a series of jerks that wrenched the chains and banged one coach into another with such violence that those outside were in danger of being hurled down upon the track, and those inside were tossed hither and thither from seat to seat. You will easily comprehend that the outing was not one of unalloyed pleasure." The boy laughed heartily. "Of course," went on Mr. Tolman, "there was no help for anybody until the first stopping place was reached; but when the engine slowed down and the grimy, almost unrecognizable pilgrims had a chance to catch their breath, something had to be done by way of a remedy. The remedy fortunately was near at hand and consisted of nothing very difficult. Some of the more enterprising of the company leaped out and tore the rails from a near-by fence and after stretching the coupling chains taut, they bound them to the wooden boards. In this way the coaches were kept apart and the silk hats of the dignitaries who had been invited to participate in the opening of the road rescued from total annihilation." "I'll bet everybody was glad to disembark at Schenectady," declared Stephen. "I'll wager they were! They must have been exhausted from being jounced and jostled about. Nevertheless the novelty of the adventure probably brought its own compensations, and they were doubtless diverted from their woes by the sight of the cheering and envious spectators, the terrified horses, and the open-mouthed children that greeted them wherever they went." "But the promoters could hardly expect the public to be very keen for a steam railroad after such an exhibition," reflected Steve. "Fortunately our forefathers were not as critical as you," said his father, "and in consequence the coach line from Albany to Schenectady was speedily supplanted by a steam railroad, as were the various coach lines into the interior of the State. As a result hundreds of broken-down coach horses were turned out to pasture, a merciful thing. Gradually a series of short steam railway lines were constructed from one end of the State to the other, until in 1851 these were joined together to make a continuous route to Lake Erie. Perhaps we have only scant appreciation of the revolution that came with this advance in transportation. It meant the beginning of travel and commerce between the eastern States and those in the interior of the country; it also meant the speedy shipment of eastern products to the West, where they were greatly needed, and the reception of western commodities in the East. But more than all this, it signified a bond of fellowship between the scattered inhabitants of the same vast country who up to this time had been almost total strangers to one another, and was a mighty stride in the direction of national loyalty and sympathy. Therefore it was entirely seemly that Millard Fillmore, then President of the United States, and Daniel Webster, the Secretary of State, should be honored guests at the celebration that attended the opening of the railroad." "Did the road reach no farther than Lake Erie?" asked Stephen. "Not at first," replied his father. "From that point commerce was carried on by means of ships on the Great Lakes. But in time western railroad companies began to build short stretches of track which later on they joined together as the other railroad builders had done." "Did the line go all the way across the country?" "Oh, no, indeed. Our trans-continental railroads were a mighty project in themselves and their story is a romance which I will tell you some other time. Before such stupendous enterprises could be realities, our young, young country had a vast deal of growing to do, and its infant railroads and engineering methods had to be greatly improved. So long as we still built roads where the rails were liable to come up through the floor and injure the passengers, and where the tracks were not strongly enough constructed to resist floods and freshets, our steam locomotion could not expect any universal degree of popularity." "I don't suppose, though, that the cows continued to tip the cars over and turn the passengers out into the dirt as they did in the days of Peter Cooper," mused Steve thoughtfully. "They may not have derailed the trains," his father replied quite seriously, "but they often did delay them. Nor could the passengers be blamed for finding fault with the unheated cars, or the fact that sometimes, when it snowed hard, the engineer ran his engine under cover and refused to go on, leaving those on the train the choice of staying where they were until the storm abated or going on foot to their destination." "Not really!" "Yes, indeed. Such things happened quite frequently. Then there are stories of terrible gales when the snow piled up on the track until the engine had to be dug out, for snow plows did not keep the tracks clear then as they do now; nor was it an uncommon thing for the mud from the spring washouts to submerge the rails, in which case the engines had to be pulled out of the mire by oxen. In fact, at certain seasons of the year some trains carried oxen for this very purpose. For you must remember that the engines of that date were not powerful enough to make progress through mud, snow, or against fierce head winds. Often a strong gale would delay them for hours or bring them to a standstill altogether." "Well, I guess it is no wonder we were not equipped to build a trans-continental road under such conditions," said the lad, with a quiet smile. "Oh, these defects were only a minor part of our railroad tribulations," responded his father. "For example, when Pennsylvania started her first railroad the year after the line between New York and Schenectady was laid, there was a fresh chapter of obstacles. Strangely enough, the locomotive, 'Old Ironsides,' was built by Mr. M. W. Baldwin, whose name has since become celebrated as the founder of the Baldwin Locomotive Works. In 1832, however, the Baldwin locomotive was quite a different product from the present-day magnificently constructed steam engine. This initial attempt at locomotive building was a queer little engine with wheels so light that unless there was plenty of ballast aboard it was impossible to keep it on the track; and besides that, the poor wee thing could not get up steam enough to start itself and in consequence Mr. Baldwin and some of his machinists were obliged to give it a violent push whenever it set out and then leap aboard when it was under way in order to weigh it down and keep it on the track." "Imagine having to hold an engine down!" ejaculated Steve, with amusement. "The story simply goes to prove how much in the making locomotives really were," Mr. Tolman said. "And not only did this toy engine have to be started by a friendly push, but it was too feeble to generate steam fast enough to keep itself going after it was once on its way. Therefore every now and then the power would give out and Mr. Baldwin and his men would be forced to get out and run along beside the train, pushing it as they went that it might keep up its momentum until a supply of steam could again be acquired. Can you ask for anything more primitive than that?" "It certainly makes one realize the progress locomotive builders have made," the boy replied, with gravity. "It certainly does," agreed his father. "Think how Baldwin and his men must have struggled first with one difficulty and then with another; think how they must have experimented and worked to perfect the tiny engine with which they began! It was the conquering of this multitude of defects that gave to the world the intricate, exquisitely made machine which at this very minute is pulling you and me into New York." There was an interval of silence during which Stephen glanced out at the flying panorama framed by the window. "Where was New England all this time?" demanded he, with jealous concern. "Didn't Massachusetts do anything except build the old granite road at Quincy?" "Railroads, for various reasons, were not popular in Massachusetts," returned his father. "As usual New England was conservative and was therefore slow in waking up to the importance of steam transportation. Boston was on the coast, you see, and had its ships as well as the canal boats that connected the city with the manufacturing districts of the Merrimac. Therefore, although the question of building railroads was agitated in 1819 nothing was done about the matter. As was natural the canal company opposed the venture, and there was little enthusiasm elsewhere concerning a project that demanded a great outlay of money with only scant guarantee that any of it would ever come back to the capitalists who advanced it. Moreover, the public in general was sceptical about railroads or else totally uninterested in them. And even had a railroad been built at this time it would not have been a steam road for it was proposed to propel the cars by horse power just as those at Quincy had been." "Oh!" interjected Steve scornfully. "They might at least have tried steam." "People had little faith in it," explained Mr. Tolman. "Those who had the faith lacked the money to back the enterprise, and those who had the money lacked the faith. If a company could have gone ahead and built a steam railroad that was an unquestioned success many persons would undoubtedly have been convinced of its value and been willing to put capital into it; but as matters stood, there was so much antagonism against the undertaking that nobody cared to launch the venture. There were many business men who honestly regarded a steam railroad as a menace to property and so strong was this feeling that in 1824 the town of Dorchester, a village situated a short distance from Boston, actually took legal measures to prevent any railroad from passing through its territory." "They needn't have been so fussed," said Stephen, with a grin. "Railroads weren't plenty enough to worry them!" "Oh, the Quincy road was not the only railroad in Massachusetts," his father asserted quickly, "for in spite of opposition a railroad to Lowell, modeled to some extent after the old granite road, had been built. This railroad was constructed on stone ties, as the one at Quincy had been; for although such construction was much more costly it was thought at the time to be far more durable. Several years afterward, when experience had demonstrated that wood possessed more _give_, and that a hard, unyielding roadbed only creates jar, the granite ties that had cost so much were taken up and replaced by wooden ones." "What a shame!" "Thus do we live and learn," said his father whimsically. "Our blunders are often very expensive. The only redeeming thing about them is that we pass our experience on to others and save them from tumbling into the same pit. Thus it was with the early railroad builders. When the Boston and Providence Road was constructed this mistake was not repeated and a flexible wooden roadbed was laid. In the meantime a short steam railroad line had been built from Boston to Newton, a distance of seven miles, and gradually the road to this suburb was lengthened until it extended first to Natick and afterward to Worcester, a span of forty-four miles. Over this road, during fine weather, three trains ran daily; in winter there were but two. I presume nothing simpler or less pretentious could have been found than this early railroad whose trains were started at the ringing of a bell hung on a near-by tree. Although it took three hours to make a trip now made in one, the journey was considered very speedy, and unquestionably it was if travelers had to cover the distance by stagecoach. When we consider that in 1834 it took freight the best part of a week to get to Boston by wagons a three-hour trip becomes a miracle." "I suppose there was not so much freight in those days anyway," Steve speculated. "Fortunately not. People had less money and less leisure to travel, and therefore there were not so many trunks to be carried; I am not sure, too, but the frugal Americans of that day had fewer clothes to take with them when they did go. Then, as each town or district was of necessity more or less isolated, people knew fewer persons outside of their own communities, did a less extensive business, and had less incentive to go a-visiting. Therefore, although the Boston and Worcester Railroad could boast only two baggage cars (or burthen cars, as they were called), the supply was sufficient, which was fortunate, especially since the freight house in Boston was only large enough to shelter these two." "And out of all this grew the Boston and Albany Railroad?" questioned the boy. "Yes, although it was not until 1841, about eight years later, that the line was extended to New York State. By that time tracks had been laid through the Berkshire hills, opening up the western part of Massachusetts. The story of that first momentous fifteen-hour journey of the Boston officials to the New York capital, where they were welcomed and entertained by the Albany dignitaries, is picturesque reading indeed. One of the party who set out from Boston on that memorable day carried with him some spermaceti candles which on the delegates' arrival were burned with great ceremony at the evening dinner." "I suppose it seemed a wonderful thing to reach Albany in fifteen hours," remarked Steve. "It was like a fairy tale," his father answered. "To estimate the marvel to the full you must think how long it would have taken to drive the distance, or make the journey by water. Therefore the Boston officials burned their spermaceti candles in triumph; and the next day, when the Albany hosts returned to Boston with their guests, they symbolized the onrush of the world's progress by bringing with them a barrel of flour which had been cut, threshed, and ground only two days before, and put into a wooden barrel made from a tree which was cut down, sawed, and put together while the flour was being ground. This does not seem to us anything very astounding but it was a feat to stop the breath in those days." "And what did they do with the flour?" "Oh, that evening when they reached Boston the flour was made into some sort of bread which was served at the dinner the Boston men gave to their visitors." "I wonder what they would have said if somebody had told them then that sometime people would be going from Boston to New York in five hours?" the lad observed. "I presume they would not have believed it," was the reply. "Nor would they have been able to credit tales of the great numbers of persons who would constantly be traveling between these two great cities. At that time so few people made the trip that it was very easy to keep track of them; and that they might be identified in case of accident the company retained a list of those who went on the trains. At first this rule worked very well, the passengers being carefully tabulated, together with their place of residence; but later, when traffic began to increase and employees began to have more to do, those whose duty it was to make out these lists became hurried and careless and in the old railroad annals we read such entries as these: "'_Woman in green bonnet; boy; stranger; man with side whiskers,_' etc." A peal of laughter broke from Stephen. "Railroad officials would have some job to list passengers now, wouldn't they?" he said. "We should all just have to wear identification tags as the men did during the War." His father acquiesced whimsically. "I have sometimes feared we might have to come to that, anyway," he replied. "With the sky populated with aeroplanes and the streets filled with automobiles man stands little chance in these days of preserving either his supremacy or his identity. When we get on Fifth Avenue to-day you see if you do not agree with me," he added, as the train pulled into the big station. CHAPTER VIII NEW YORK AND WHAT HAPPENED THERE It took no very long interval to prove that there was some foundation for Mr. Tolman's last assertion, for within a short time the travelers were standing on Fifth Avenue amid the rush of traffic, and feeling of as little importance as dwarfs in a giant's country. The roar of the mighty city, its bustle and confusion, were both exhilarating and terrifying. They had left their luggage at the hotel and now, while Steve's father went to meet a business appointment, the boy was to take a ride up the Avenue on one of the busses, a diversion of which he never tired. To sit on top and look down on the throng in the streets was always novel and entertaining to one who passed his days in a quiet New England town. Therefore he stopped one of the moving vehicles and in great good humor bade his father good-by; and feeling very self-sufficient to be touring New York by himself, clambered eagerly up to a seat. There were few passengers on the top of the coach for the chill of early morning still lingered in the air; but before they reached Riverside Drive a man with a bright, ruddy countenance and iron-grey hair hailed the bus and climbed up beside the boy. As he took his place he glanced at him kindly and instantly Steve felt a sense of friendliness toward the stranger; and after they had ridden a short distance in silence the man spoke. "What a beautiful river the Hudson is!" he remarked. "Although I am an old New Yorker I never cease to delight in its charm and its fascinating history. It was on this body of water, you know, that the first steamboat was tried out." "I didn't know it," Stephen confessed, with an honest blush. "You will be learning about it some day, I fancy," said the other, with a smile. "An interesting story it is, too. All the beginnings of our great industries and inventions read like romances." "My father has just been telling me about the beginnings of some of our railroads," observed Steve shyly, "and certainly his stories were as good as fairy tales." "Is your father especially interested in railroads?" inquired the New Yorker. "Yes, sir. He is in the railroad business." "Ah, then that accounts for his filling your ears with locomotives instead of steamboats," declared the man, with a twinkle in his eyes. "Now if I were to spin a yarn for you, it would be of steamboats because that happens to be the thing I am interested in; I believe their history to be one of the most alluring tales to which a boy could listen. Sometime you get a person who knows the drama from start to finish to relate to you the whole marvelous adventure of early steamboating, and you see if it does not beat the railroad story all out." He laughed a merry laugh in which Stephen joined. "I wish you would tell it to me yourself," suggested the lad. The man turned with an expression of pleasure on his red-cheeked face. "I should like nothing better, my boy," he said quickly, "but you see it is a long story and I am getting out at the next corner. Sometime, however, we may meet again. Who knows? And if we do you shall hold me to my promise to talk steamboats to you until you cry for mercy." Bending down he took up a leather bag which he had placed between his feet. "I am leaving you here, sonny," he said. "I take it you are in New York for a holiday." "Yes, sir, I am," returned Steve with surprise. "My father and I are staying here just for a few days." "I hope you will have a jolly good time during your visit," the man said, rising. Stephen murmured his thanks and watched the erect figure descend from the coach and disappear into a side street. It was not until the New Yorker was well out of sight and the omnibus on its way that his eye was caught by the red bill book lying on the floor at his feet. None of the few scattered passengers had noticed it and stooping, he picked it up and quietly slipped it into his pocket. What should he do with it? Of course he could hand it over to the driver of the bus and tell him he had found it. But the man might not be honest and instead of turning it in to the company might keep it. There was little doubt in Steve's mind that the pocketbook belonged to the stranger who had just vacated the place and it was likely his address was inside it. If so, what a pleasure it would be to return the lost article to its rightful owner himself. By so doing he would not only be sure the pocketbook reached its destination but he might see the steamboat man again. He longed to open the bill book and investigate its contents. What was in it, he wondered. Well, the top of a Fifth Avenue coach was no place to be looking through pocketbooks, there was no question about that. Let alone the fact that persons might be watching him, there was danger that in the fresh morning breeze something might take wing, sail down to the Hudson, and never be seen again. Therefore he decided to curb his impatience and wait until he reached a more favorable spot to examine his suddenly acquired treasure. Accordingly he tucked the long red wallet farther down into the breast pocket of his ulster, and feeling assured that nothing could be done about it at present, gave himself up to the pleasure and excitement of the drive. It was not until he had rejoined his father at the hotel and the two were sitting at lunch in the great dining room that the thought of it again flashed into his mind. "Gee, Dad!" he suddenly exclaimed, looking up from his plateful of fried chicken with fork suspended in mid-air. "I meant to tell you I found a pocketbook in the bus this morning." "A pocketbook!" "Yes, sir. I think the man who had been sitting beside me must have dropped it when he stooped over to get his bag. At any rate it was lying there after he got out." "What did you do with it?" Mr. Tolman inquired with no great warmth of interest. "Gave it to the conductor, I suppose." The boy shook his head. "No, I didn't," was the answer. "I was afraid he might not turn it in, and as I liked the man who lost it I wanted to be sure he got it, so I brought it back with me." "And where is it now?" demanded Mr. Tolman, now all attention. "I hope you were not so careless as to leave it upstairs in our room." "No. I didn't leave it in the room," returned the lad. "It is out in my coat pocket. I meant to take it out and see what was in it; but so many things happened that I forgot about it until this very minute." "You don't mean that you left it in your ulster pocket and let them hang it out there on the rack?" "Yes." "You checked your coat and left it there?" "Why--yes," came the faltering reply. Mr. Tolman was on his feet. "Wait here until I come back," he said in a sharp tone. "Where are you going?" "Give me your check quickly," went on his father, without heeding the question. "Hurry!" Steve fumbled in his jacket pocket. "Be quick, son, be quick!" commanded Mr. Tolman impatiently. "Don't you know it is never safe to leave anything of value in your coat when you are staying at a large city hotel? Somebody may have taken the pocketbook already." Scarlet with consternation the lad produced the check. "If nothing has happened to that pocketbook you will be very fortunate," asserted the man severely. "Stay here! I will be right back." With beating heart the boy watched him thread his way between the tables and disappear from the dining room into the lobby. Suppose the bill book should be gone! What if there had been valuable papers in it, money--a great deal of money--and now through his carelessness it had all disappeared? How stupid he had been not to remember about it and give it to his father the instant they had met! In fact, he would much better have taken a chance and handed it to the bus conductor than to have done the foolish thing he had. He had meant so well and blundered so grievously! How often his father had cautioned him to be careful of money when he was traveling! Tensely he sat in his chair and waited with miserable anxiety, his eyes fixed on the dining-room door. Then presently, to his great relief, he saw his father returning. "Did you--" he began. "You will have to come yourself, Steve," said the elder man whose brow was wrinkled into a frown of annoyance. "The maid who checked the coats is not there, and the one who is insists that the ulster is not mine, and in spite of the check will not allow me to search the pockets of it." Stephen jumped up. "I suppose she is right, too," went on Mr. Tolman breathlessly, "but the delay is very unfortunate." They made their way into the corridor, where by this time an office clerk and another man had joined the maid who was in charge of the coat rack. Stephen presented his check and without comment the woman handed him his coat. With trembling hand he dived into the deep pocket and from it drew forth the red bill book which he gave to his father. "There it is, Dad, safe and sound!" he gasped. Instantly the clerk was in their path. "I beg pardon, sir," said he with deference, "but does that pocketbook belong to you?" Mr. Tolman wheeled about. "Eh--what did you say?" he inquired. "I asked, sir, if that pocketbook was your property?" repeated the clerk. Mr. Tolman faced his inquisitor. "What business is that of yours?" he demanded curtly. "I am sorry, sir, to appear rude," the hotel employee replied, "but we have been asked to be on the lookout for a young lad who rode this morning on one of the Fifth Avenue busses where a valuable pocketbook was lost. Your son tallies so well with the description that--" "It was I," put in Stephen eagerly, without regard for consequences. "Who wants me?" With a smile of eagerness he turned, expecting to encounter the genial face of his acquaintance of the morning. Then he would smile, hold out the pocketbook, and they would laugh together as he explained the adventure, and perhaps afterward have luncheon in company. Instead no familiar form greeted him. On the contrary the slender man who had been standing beside the clerk came forward. Mr. Tolman sensed the situation in a second. "You mean somebody thinks my son took the pocketbook?" asked he indignantly, as he confronted the clerk and his companion. "It is not my affair, sir, and I am sorry it should happen in our hotel," apologized the clerk. "Perhaps if you will just explain the whole matter to this gentleman--" he broke off, saying in an undertone to the man at his elbow. "This is your boy, Donovan." The tall man came nearer. "You are a detective?" asked Mr. Tolman bluntly. "Well, something of the sort, sir," admitted the man called Donovan. "It is occasionally my business to hunt people up." "And you have been sent to hunt my son up?" Donovan nodded. Stephen turned white and his father put a reassuring hand on his shoulder. "My son and I," he replied, addressing the detective quietly, "can explain this entire affair to you and will do so gladly. The boy did find the pocketbook but he was ignorant of its value because he has not even looked inside it. In fact, that he had the article in his possession did not come into his mind until a few moments ago. If he had known the thing was valuable, do you suppose he would have left it in his ulster pocket and checked the coat in a public place like this?" The detective made no reply. "We both shall be very glad," went on Mr. Tolman firmly, "to go with you to headquarters and straighten the matter out." "There may be no need of that, sir," Donovan responded with a pleasant smile. "If we can just talk the affair over in a satisfactory way--" "Suppose you come upstairs to our room," suggested Mr. Tolman. "That will give us more quiet and privacy. Will that be agreeable to you?" "Perfectly." As the three walked toward the elevator Steve glanced with trepidation at the plain-clothes man. The boy knew he had done nothing wrong; but would he be able to convince the detective of the truth of his story? He was thoroughly frightened and wondered whether his father was also alarmed. If, however, Mr. Tolman was worried he at least did not show it. Instead he courteously led the way from the elevator down the dim corridor and unlocked the door of Number 379. "Come in, Mr. Donovan," he said cordially. "Here is a chair and a cigar. Now, son, tell us the story of this troublesome pocketbook from beginning to end." In a trembling voice Stephen began his tale. He spoke slowly, uncertainly, for he was well scared. Gradually, however, he forgot his agitation and his voice became more positive. He recounted the details of the omnibus ride with great care, adding ingenuously when he came to the termination of the narrative: "And I hoped the man's name would be inside the pocketbook because I liked him very much and wanted to return to him what he had lost." "And wasn't it?" put in Mr. Donovan quickly. "I don't know," was the innocent retort. "Don't you remember I told you that I hadn't looked inside yet?" The detective laughed with satisfaction. "That was a shabby trick of mine, youngster," said he. "It was mean to try to trap you." "Trap me?" repeated Steve vaguely. "There, there, sonny!" went on Donovan kindly. "Don't you worry a minute more about this mix-up. Mr. Ackerman, the gentleman who lost the bill book, did not think for a second that you had taken it. He simply was so sure that he had lost it on the bus that he wanted to locate you and find out whether you knew anything about it or not. His name was not inside the pocketbook, you see, and therefore any one who found it would have no way of tracing its owner. What it contains are valuable papers and a big wad of Liberty Bonds which, as your father knows, could quickly be converted into cash. In consequence Mr. Ackerman decided that the sooner the pocketbook was found the better. The omnibus people denied any knowledge of it and you were the only remaining clue." Mr. Tolman sank back in his chair and a relaxation of his muscles betrayed for the first time that he had been much more disturbed than he had appeared to be. "Well," he said, lighting a fresh cigar, "the bill book is not only located but we can hand it back intact to its owner. If you can inform us where the gentleman lives, my boy and I will call a taxi and go to his house or office with his property." A flush of embarrassment suffused the face of the officer. "Maybe you would like to come with us, Donovan," added Mr. Tolman, who instantly interpreted the man's confusion. "I hate to be dogging your footsteps, sir, in this fashion," Mr. Donovan answered, with obvious sincerity. "Still, I--" "You have your orders, no doubt." "Well, yes, sir," admitted the plain-clothes man with reluctance. "I have." "You were to keep your eye on us until the pocketbook reached its owner." "That's about it, sir. Not that I personally have the least suspicion that a gentleman like you would--" "That is all right, my man. I perfectly understand your position," Mr. Tolman cut in. "After all, you have your duty to do and business is business. We'll just telephone Mr. Ackerman that we are coming so that we shall be sure of catching him, and then we will go right up there." "Very well, sir." Stephen's father started toward the telephone and then, as if struck by a sudden thought, paused and turned. "Steve," he said, "I believe you are the person to communicate with Mr. Ackerman. Call him up and tell him you have found his purse and that you and your father would like to come up to his house, if it will be convenient, and return it." "All right, Dad." "You will find his number on this slip of paper, sonny," the detective added, handing the lad a card. "He is not at his office. He went home to lunch in the hope that he had left the pocketbook there." After some delay Stephen succeeded in getting the number written on the card. A servant answered the summons. "May I speak to Mr. Ackerman, please?" inquired the lad. "He is at luncheon? No, it would not do the least good for me to tell you my name for he would not know who it was. Just tell him that the boy who sat beside him this morning on the Fifth Avenue bus--" there was a little chuckle. "Oh, he will be here directly, will he? I thought perhaps he would." A moment later a cheery voice which Steve at once recognized to be that of the steamboat man came over the wire: "Well, sonny?" "I found your bill book, Mr. Ackerman, and my father and I would like to bring it up to you." "Well, well! that is fine news!" cried the man at the other end of the line. "How did you know who it belonged to?" "Oh, I--we--found out--my father and I," stammered the lad. "May we come up to your house with it now?" "You would much better let me come to you; then only one person will be inconvenienced," the New Yorker returned pleasantly. "Where are you staying?" "At the Manhattan." "You must not think of taking the trouble of coming way up here. Let me join you and your father at your hotel." "Very well, Mr. Ackerman. If you'd rather--" "I certainly should rather!" was the emphatic answer. "I could not think of bringing two people so far out of their way." "There are three of us!" squeaked Stephen. "Three?" "Yes, sir. We have another person--a friend--with us," explained the boy, with quiet enjoyment. How easy it was to laugh now! "All the more reason why I should come to you, then," asserted Mr. Ackerman. "I will be at the Manhattan within half an hour. Perhaps if you and your father and your friend have the afternoon free you would like to go to some sort of a show with me after we conclude our business. Since you are here on a holiday you can't be very busy." Stephen's eyes sparkled with merriment. "I don't know whether our friend can go or not," he replied politely, "but I think perhaps Dad and I could; and if we can we should like to very much." "That will be excellent. I will come right along. Not only shall I be glad to get my pocketbook back again but I shall be glad to see you once more. I told you this morning that I had a feeling we should meet some time. Whom shall I ask for at the hotel?" "Stephen Tolman." With a click the boy hung up the receiver. "Mr. Ackerman is coming right down," said he, addressing his father and the detective with a mischievous smile. "He has invited the three of us to go to the matinee with him." "The three of us!" echoed the plain-clothes man. "Yes," returned the lad. "I told him we had a friend with us and so he said to bring him along." "Good heavens!" Donovan ejaculated. Mr. Tolman laughed heartily. "Not all the thieves you arrest take you to a theater party afterward, do they, Officer?" he asked. "I said from the first you were gentlemen," Mr. Donovan asserted with humor. "But couldn't you go?" inquired Steve, quite seriously. "Bless you, no, sonny!" replied the man. "I am from headquarters, you know, and my work is chasing up crooks--not going to matinees." Nevertheless there was an intonation of gentleness in his voice, as he added, "I am obliged to you just the same, for in spite of my calling I am a human being and I appreciate being treated like one." CHAPTER IX AN ASTOUNDING CALAMITY Mr. Ackerman was as good as his word, for within half an hour he presented himself at the hotel where he found Mr. Tolman, Mr. Donovan and Steve awaiting him in their pleasant upstairs room. As he joined them his eye traveled inquiringly from one to another of the group and lingered with curiosity on the face of the detective. The next instant he was holding out his hand to Stephen. "Well, my boy, I am glad to see you again," said he, a ring of heartiness in his voice. "And I am glad to see you, too, Mr. Ackerman," Steve replied, returning the hand-clasp with fervor. "This is my father, sir; and this"--for a second he hesitated, then continued, "is our friend, Mr. Donovan." With cordiality the New Yorker acknowledged the introductions. "Mr. Donovan," explained Mr. Tolman, scanning Mr. Ackerman's countenance with a keen, half-quizzical expression, "is from headquarters." The steamboat magnate started and shot a quick glance at those present. It was plain he was disconcerted and uncertain as to how to proceed. Mr. Donovan, however, came to his rescue, stepping tactfully into the breach: "I was not needed for anything but to supply your address, sir; but I was able to do that, so between us all we have contrived to return your pocketbook to you as good as before it left your possession." As he spoke Mr. Tolman drew forth the missing bill book and held it toward its owner. "That looks pretty good to me!" Mr. Ackerman exclaimed, as he took the article from Mr. Tolman's outstretched hand and regarded it reflectively. "I don't know when I have ever done anything so careless and stupid. You see I had got part way to the bank before I remembered that I had left my glasses, on which I am absolutely dependent, at home. Therefore, there being no taxi in sight, I hailed a passing bus and climbed up beside this youngster. How the bill book happened to slip out of my pocket I cannot explain. It seemed to me it would be safer to have the securities upon my person than in a bag that might be snatched from me; but apparently my logic was at fault. I was, however, so certain of my wisdom that I never thought to question it until I had reached the sidewalk and the bus had gone. "Your boy, Mr. Tolman, confided while we rode along this morning that he was visiting in New York for a few days; but of course I did not ask his name or address and so when I wanted his help in tracing the missing pocketbook I had no way of locating him beyond assuming that he must be staying at one of the hotels. Therefore when the omnibus company could furnish no clue, I got into touch with an agency whose business it is to hunt people up. If the pocketbook had been dropped on the bus I felt sure your boy, who was almost the only other person on top of the coach, would know about it; if, on the other hand, it had been dropped in the street, my problem would be a different one. In either case the sooner I knew my course of action the better. I hope you will believe, Mr. Tolman, that when I called in the aid of detectives I had no suspicions against your son's honesty." Mr. Tolman waved the final remark aside good-humoredly. "We have not taken the affair as a personal matter at all," he declared. "We fully appreciate your difficulty in finding Stephen, for he was also up against the problem of finding you. New York is a rather large city anyway, and for two people who do not even know one another's names to get together is like hunting a needle in a haystack. Our only recourse to discovering the owner of the pocketbook would be through the advertising columns of the papers and that is the method we should have followed had not Donovan appeared and saved us the trouble." He exchanged a smile with the detective. "The advertising column was my one hope," Mr. Ackerman replied. "I felt sure that any honest person who picked up the purse would advertise it. It was not the honest people I was worrying about. It was the thought that I had dropped the bill book in the street where any Tom-Dick-and-Harry could run away with it that concerned me. Moreover, even if your boy had found it on the bus, he might have turned it in to an employee of the coach line who was not honest enough to give it in turn to his superiors. So I wanted to know where I stood; and now that I do I cannot tell you how grateful I am both to Stephen and to this officer here for the service they have rendered me." Then, turning toward Mr. Tolman, he added in an undertone, "I hope neither you nor your son have suffered any annoyance through this unfortunate incident." "Not in the least," was the prompt response. "I confess we were a trifle disconcerted at first; but Mr. Donovan has performed his duty with such courtesy that we entertain toward him nothing but gratitude." "I am glad of that," Mr. Ackerman replied, "for I should deeply regret placing either you or your boy, even for a moment, in an uncomfortable position, or one where it might appear that I--" But Mr. Tolman cut him short. "You took the quickest, most sensible course, Ackerman," said he. "Too much was at stake for you to risk delay. When a pocketbook filled with negotiable securities disappears one must of necessity act with speed. Neither Stephen nor I cherish the least ill-will about the affair; do we, son?" "No, indeed." Then smiling ingenuously up into the face of the New York man, he said: "Don't you want to look in your pocketbook and see if everything is all right, sir?" The steamboat financier laughed. "You are a prudent young man," declared he. "No, I am quite willing to risk that the property you have so kindly guarded is intact." "It ought to be," the boy said. "I haven't even opened the pocketbook." "A better proof still that everything is safe within it," chuckled Mr. Ackerman. "No, sonny, I am not worrying. I should not worry even if you had ransacked the bill book from one end to the other. I'd take a chance on the honesty of a boy like you." Mr. Tolman, however, who had been listening, now came forward and broke into the conversation: "Stephen's suggestion is a good, businesslike one, Ackerman," he declared. "As a mere matter of form--not as a slam against our morals--I am sure that both he and I would prefer that you examined your property while we are all here together and assure yourself that it is all right." "Pooh! Pooh! Nonsense!" objected the financier. "It is a wise notion, Mr. Ackerman," rejoined Mr. Donovan. "Business is business. None of us questions the honor of Mr. Tolman or his son. They know that. Nevertheless I am sure we should all feel better satisfied if you went through the formality of an investigation." "Very well, just as you say. But I want it understood that I do it at their and your request. I am perfectly satisfied to leave things as they are." Taking the now familiar red pocketbook from his coat he opened it unconcernedly; then the three persons watching him saw a look of consternation banish the smile from his face. "What's wrong, Ackerman?" inquired the plain-clothes man quickly. Without a word the other held the bill book toward him. It was empty. Bonds, securities, money were gone! A gasp of incredulity came from Stephen. "I didn't open it--truly I didn't!" exclaimed he, in a terror-stricken voice. But Mr. Ackerman did not heed the remark. "I am afraid this looks pretty black for us, Ackerman," said Mr. Tolman slowly. "We have nothing to give you but the boy's word." Mr. Donovan, however, who had been studying the group with a hawklike scrutiny now sprang to his feet and caught up his hat. "I don't see how they dared put it over!" he exclaimed excitedly. "But they almost got away with it. Even I was fooled." "You don't mean to insinuate," Mr. Tolman burst out, "that you think we--" "Good heavens, no!" replied the detective with his hand on the door knob. "Don't go getting hot under the collar, Mr. Tolman. Nobody is slamming _you_. I have been pretty stupid about this affair, I'm afraid; but give me credit for recognizing honest people when I see them. No, somebody has tricked you--tricked you all. But the game isn't up yet. If you gentlemen will just wait here--" The sentence was cut short by the banging of the door. The detective was gone. His departure was followed by an awkward silence. Mr. Ackerman's face clouded into a frown of disappointment and anxiety; Mr. Tolman paced the floor and puffed viciously at a cigar; and Steve, his heart cold within him, looked from one to the other, chagrin, mortification and terror in his eyes. "I didn't open the pocketbook, Mr. Ackerman," he reiterated for the twentieth time. "I truly didn't." But the steamboat magnate was too deeply absorbed in his own thoughts and speculations to notice the high-pitched voice with its intonation of distress. At last Mr. Tolman could endure the situation no longer. "This is a most unfortunate happening, Ackerman," he burst out. "I am more concerned about it than I can express. My boy and I are utter strangers to you and we have no way of proving our honesty. All I can say is that we are as much amazed at the turn affairs have taken as yourself, and we regret it with quite as much poignancy--perhaps more since it reflects directly upon us. If there is anything we can do--" He stopped, awaiting a reply from the other man, but none came. "Good heavens, Ackerman," he cried. "You don't mean to say you do not believe my son and me--that you suspect us of double-dealing!" "I don't know what to believe, Tolman," owned Mr. Ackerman with candor. "I want very much to credit your story; in my heart, I do credit it. But head and heart seem to be at variance in this matter. Frankly I am puzzled to know where the contents of that pocketbook have gone. Were the things taken out before the bill book fell into your son's hands or afterward? And if afterward, who took them? Who had the chance? Donovan seems to think he has a clue, but I confess I have none." "Hadn't you looked over the bonds and stuff since you took them home?" "No," Mr. Ackerman admitted. "I got them from the broker yesterday and as it was too late to put them into the safe-deposit vault, I took them home with me instead of putting them in our office safe as I should have done. I thought it would be easier for me to stop at the bank with them this morning on my way to business. It was foolish planning but I aimed to save time." "So the pocketbook was at your house over night?" Mr. Ackerman nodded. "Yes," confessed he. "Nevertheless it did not go out of my possession. I had it in the inner pocket of my coat all the time." "You are sure no one took the things out while you were asleep last night?" "Why--I--I don't see how they could," faltered Mr. Ackerman. "My servants are honest--at least, they always have been. I have had them for years. Moreover, none of them knew I had valuable papers about me. How could they?" was the reply. Once more silence fell upon the room. "Come, Tolman," ejaculated the steamboat man presently, "you are a level-headed person. What is your theory?" "If I did not know my son and myself as well as I do," Mr. Tolman answered with deliberation, "my theory would be precisely what I fancy yours is. I should reason that during the interval between the finding of the purse and its return the contents had been extracted." He saw the New Yorker color. "That, I admit, is my logical theory," Mr. Ackerman owned with a blush, "but it is not my intuitive one. My brain tells me one thing and my heart another; and in spite of the fact that the arguments of my brain seem correct I find myself believing my heart and in consequence cherishing a groundless faith in you and your boy," concluded he, with a faint smile. "That is certainly generous of you, Ackerman!" Mr. Tolman returned, much moved by the other's confidence. "Stephen and I are in a very compromising situation with nothing but your belief between us and a great deal of unpleasantness. We appreciate your attitude of mind more than we can express. The only other explanation I can offer, and in the face of the difficulties it would involve it hardly seems a possible one, is that while the coat was hanging in the lobby--" There was a sound outside and a sharp knock at the door, and an instant later Mr. Donovan entered, his face wreathed in smiles. Following him was the woman who had checked the coats, a much frightened bell boy, and a blue-uniformed policeman. The woman was sobbing. "Indeed, sir," she wailed, approaching Steve, "I never meant to keep the pocketbook and make trouble for you. I have a boy of my own at home, a lad about your age. What is to become of him now? Oh, dear; oh, dear!" She burst into passionate weeping. "Now see here, my good woman, stop all this crying and talk quietly," cut in the policeman in a curt but not unkind tone. "If you will tell us the truth, perhaps we can help you. In any case we must know exactly what happened." "She must understand that anything she says can be used against her," cautioned the detective, who in spite of his eagerness to solve the mystery was determined the culprit should have fair play. "Indeed, I don't care, sir," protested the maid, wiping her eyes on her ridiculously small apron. "I can't be any worse off than I am now with a policeman taking me to the lock-up. I'll tell the gentlemen the truth, I swear I will." With a courtesy he habitually displayed toward all womanhood Mr. Tolman drew forward a chair and she sank gratefully into it. "I spied the bill book in the young gentleman's pocket the minute he took off his coat," began she in a low tone. "It was bright colored and as it was sticking part way out I couldn't help seeing it. Of course, I expected he would take it with him into the dining room but when he didn't I came to the conclusion that there couldn't be anything of value in it. But by and by I had more coats to hang up and one of them, a big, heavy, fur-lined one, brushed against the young gentleman's ulster and knocked the pocketbook out on to the floor so that it lay open under the coat rack. It was then that I saw it was stuffed full of papers and things." She stopped a moment to catch her breath and then went resolutely on: "It seemed to me it was no sort of a plan to put the wallet back into the lad's pocket, for when I wasn't looking somebody might take it. So I decided I much better keep it safe for him, and maybe," she owned with a blush, "get a good-sized tip for doing it. I have a big pocket in my underskirt where I carry my own money and I slipped it right in there, meaning to hand it to the young man when he came out from lunch." The corners of her mouth twitched and her tears began to fall again, but she wiped them away with her apron and proceeded steadily: "But nothing turned out as I planned, for no sooner was the bill book in my pocket than I was called away to help about the wraps at a lady's luncheon upstairs. There were so many people about the hall that I had no chance to restore the bill book to the lad's pocket without some one seeing me and thinking, perhaps, that I was stealing. There was no help but to take it with me, trusting they would not keep me long upstairs and that I would get back to my regular place before the young gentleman came out of the dining room. It was when I got out of the elevator in the upper hall that I spied Dick, one of the bell boys I knew, and I called to him; and after explaining that I couldn't get away to go downstairs I asked him to take the wallet and put it in 47's pocket. He's a good-natured little chap and always ready to do an errand, and more than that he's an honest boy. So I felt quite safe and went to work, supposing the young man had his pocketbook long ago." All eyes were turned upon the unlucky bell boy who hung his head and colored uncomfortably. "So it was the boy who took the contents of the pocketbook!" was Mr. Ackerman's comment. "Speak up, boy," commanded the officer. "The gentleman is talking to you." The lad looked up with a frightened start. He might have been sixteen years of age but he did not look it for he was pale and underfed; nor was there anything in his bearing to indicate the poise and maturity of one who was master of the occasion. On the contrary, he was simply a boy who was frankly distressed and frightened, and as unfeignedly helpless in the present emergency as if he had been six years old and been caught stealing jam from the pantry shelf. It did not take more than a glance to convince the onlookers that he was no hardened criminal. If he had done wrong it had been the result either of impulse or mischief, and the dire result of his deed was a thing he had been too unsophisticated to foresee. The plight in which he now found himself plainly amazed and overwhelmed him and he looked pleadingly at his captors. "Well, my boy, what have you to say for yourself?" repeated Mr. Ackerman more gently. "Nothin'." "Nothing?" "No, sir." "You did take the things out of the pocketbook then." "Yes, sir." "But you are not a boy accustomed to taking what does not belong to you." The culprit shot a glance of gratitude toward the speaker but made no reply. "How did you happen to do it this time?" persisted Mr. Ackerman kindly. "Come, tell me all about it." Perhaps it was the ring of sympathy in the elder man's voice that won the boy's heart. Whatever the charm, it conquered; and he met the eyes that scanned his countenance with a timid smile. "I wanted to see what was in the pocketbook," said he with naïve honesty, "and so I took the things out to look at them. I wasn't goin' to keep 'em. I dodged into one of the little alcoves in the hall and had just pulled the papers out when I heard somebody comin'. So I crammed the whole wad of stuff into my pocket, waiting for a time when I could look it over and put it back. But I got held up just like Mrs. Nolan did," he pointed toward the woman in the chair. "Some man was sick and the clerk sent me to get a bottle of medicine the minute I got downstairs, and all I had the chance to do was to stick the empty wallet in 47's pocket and beat it for the drug store. I thought there would be letters or something among the papers that would give the name of the man they belonged to, and I'd take 'em to the clerk at the desk an' say I found 'em. But no sooner had I got the medicine up to room Number 792 than the policeman nabbed me with the papers an' things on me. That's all there is to it, sir." "Have you the things now?" the officer put in quickly. "Sure! Didn't I just tell you I hadn't had the chance to hand 'em over to the clerk," the boy reiterated, pulling a wad of crumpled Liberty Bonds and documents out of his pocket, and tumbling them upon the table. There was no doubting the lad's story. Truth spoke in every line of his face and in the frankness with which he met the scrutiny of those who listened to him. If one had questioned his uprightness the facts bore out his statements, for once out of the hotel on an errand he might easily have taken to his heels and never returned; or he might have disposed of his booty during his absence. But he had done neither. He had gone to the drug store and come back with every intention of making restitution for the result of his curiosity. That was perfectly evident. "I'm sorry, sir," he declared, when no one spoke. "I know I shouldn't have looked in the pocketbook or touched the papers; but I meant no harm--honest I didn't." "I'll be bound of that, sir," the woman interrupted. "Dick was ever a lad to be trusted. The hotel people will tell you that. He's been here several years and there's never been a thing against him. I blame myself for getting him into this trouble, for without meaning to I put temptation in his way. I know that what he's told you is the living truth, and I pray you'll try and believe him and let him go. If harm was to come to the lad through me I'd never forgive myself. Let the boy go free and put the blame on me, if you must arrest somebody. I'm older and it doesn't so much matter; but it's terrible to start a child of his age in as a criminal. The name will follow him through life. He'll never get rid of it and have a fair chance. Punish me but let the little chap go, I beg of you," pleaded the woman, with streaming eyes. Mr. Ackerman cleared his throat; it was plain that the simple eloquence of the request had touched him deeply. "With your permission, officer, I am going to withdraw my charge," he said, with a tremor in his voice. "You are to let both these persons go scot free. You, my good woman, meant well but acted foolishly. As for the boy, Donovan, I will assume the responsibility for him." "You are willing to stand behind him, Mr. Ackerman?" "I am." The detective turned toward the boy who had risen and was fumbling awkwardly with the brass buttons adorning his uniform. "You hear, Dick Martin, what the gentleman says," began he impressively. "He believes you are a good boy, and as you have handed back the valuables in your possession he is going to take a chance on you and let you go." A wave of crimson swept over the face of the boy and for the first time the tension in the youthful countenance relaxed. "But Mr. Ackerman," Donovan continued, "expects you are going to behave yourself in future and never do such a thing again." "I am going to see your father, Dick," broke in Mr. Ackerman's kindly voice, "and talk with him and--" "I haven't any father," declared the lad. "Your mother then." "I've no mother either." "Who do you live with?" "Mr. Aronson." "Is he a relative?" "Oh, no, sir! I haven't any relatives. There's nobody belongin' to me. Mr. Aronson is the tailor downstairs where I sleep. When I ain't working here I do errands for him and he lets me have a cot in a room with four other boys--newsboys, bell hops and the like. We pay two dollars between us for the room and sometimes when I carry a lot of boxes round for Mr. Aronson he gives me my breakfast." "Nobody else is responsible for you?" "Nop!" returned the boy with emphasis. "No, sir, I mean." "I'll attend to all this, Donovan," murmured Mr. Ackerman in an undertone to the detective. "The lad shall not remain there. I don't know yet just what I'll do with him but I will plan something." Then addressing the lad, he continued, "In the meantime, Dick, you are to consider me your relative. Later I shall hunt you up and we will get better acquainted. Be a good boy, for I expect some day you are going to make me very proud of you." "What!" In sheer astonishment the boy regarded his benefactor. There was something very appealing in the little sharp-featured face which had now lost much of its pallor and softened into friendliness. "Why shouldn't you make me proud of you?" inquired Mr. Ackerman softly. "You can, you know, if you do what is right." "I'm goin' to try to, sir," burst out Dick with earnestness. "I'm goin' to try to with all my might." "That is all any one can ask of you, sonny," replied the steamboat magnate. "Come, shake hands. Remember, I believe in you, and shall trust you to live up to your word. The officer is going to let you go and none of us is going to mention what has happened. I will fix up everything for you and Mrs. Nolan so you can both go back to your work without interference. Now bid Mr. Tolman and his son good-by and run along. Before I leave the hotel I will look you up and you can give me Mr. Aronson's address." Master Richard Martin needed no second bidding. Eager to be gone he awkwardly put out his hand, first to Mr. Tolman and then to Steve; and afterward, with a shy smile to the detective and the policeman and a boyish duck of his head, he shot into the hall and they heard him rushing pell-mell down the corridor. Mrs. Nolan, however, was more self-controlled. She curtsied elaborately to each of the men and called down upon their heads every blessing that the sky could rain, and it was only after her breath had become quite exhausted that she consented to retire from the room and in company with the policeman and the detective proceeded downstairs in the elevator. "Well, Tolman," began the New Yorker when they were at last alone, "you see my heart was my best pilot. I put faith in it and it led me aright. Unfortunately it is now too late for the matinee but may I not renew my invitation and ask you and your son to dine with me this evening and conclude our eventful day by going to the theater afterward?" Mr. Tolman hesitated. "Don't refuse," pleaded the steamboat man. "Our acquaintance has, I confess, had an unfortunate beginning; but a bad beginning makes for a good ending, they say, and I feel sure the old adage will prove true in our case. Accept my invitation and let us try it out." "You are very kind," murmured Mr. Tolman vaguely, "but I--" "Help me to persuade your father to be generous, Stephen," interposed Mr. Ackerman. "We must not let a miserable affair like this break up what might, perhaps, have been a delightful friendship." "I don't need any further persuading, Ackerman," Mr. Tolman spoke quickly. "I accept your invitation with great pleasure." "That's right!" cried Mr. Ackerman, with evident gratification. "Suppose you come to my house at seven o'clock if that will be convenient for you. We will have a pleasant evening together and forget lost pocketbooks, detectives and policemen." Taking out a small card, he hurriedly scrawled an address upon it. "I keep a sort of bachelor's hall out on Riverside Drive," explained he, with a shade of wistfulness. "My butler looks out for me and sees that I do not starve to death. He and his son are really excellent housekeepers and make me very comfortable." He slipped into his overcoat. "At seven, then," he repeated. "Don't fail me for I should be much disappointed. Good-by!" and with a wave of his hand he departed, leaving Stephen and his father to themselves. CHAPTER X AN EVENING OF ADVENTURE That evening Steve and his father took a taxi-cab and drove to the number Mr. Ackerman had given them. It proved to be an imposing apartment house of cream brick overlooking the Hudson; and the view from the fifth floor, where their host lived, was such a fascinating one that the boy could hardly be persuaded to leave the bay window that fronted the shifting panorama before him. "So you like my moving picture, do you, Steve?" inquired the New Yorker merrily. "It is great! If I lived here I shouldn't do a bit of studying," was the lad's answer. "You think the influence of the place bad, then." "It would be for me," Stephen chuckled. Both Mr. Tolman and Mr. Ackerman laughed. "I will own," the latter confessed, "that at first those front windows demoralized me not a little. They had the same lure for me as they have for you. But by and by I gained the strength of mind to turn my back and let the Hudson River traffic look out for itself." "You might try that remedy, son," suggested Steve's father. "No, no, Tolman! Let the boy alone. If he is enjoying the ferries and steamboats so much the better." "But there seem to be plenty of steamboats here in the room to enjoy," was Mr. Tolman's quick retort. "Steamboats?" repeated Steve vaguely, turning and looking about him. Sure enough, there were steamboats galore! Wherever he looked he saw them. Not only were the walls covered with pictures of every imaginable type of steamer, but wherever there was space enough there were tiers of little ship models in glass cases. There were side-wheelers, awkwardly constructed boats with sprawling paddles, screw propellers, and twin-screw craft; ferryboats, tugs, steam yachts, and ocean liners. Every known variety of sea-going contrivance was represented. The large room was like a museum of ships and the boy gave an involuntary exclamation of delight. "Jove!" It was a laconic tribute to the marvels about him but it was uttered with so much vehemence that there was no mistaking its sincerity. Evidently, terse as it was, its ring of fervor satisfied Mr. Ackerman for he smiled to himself. "I never saw so many boats in all my life!" burst out Steve. "I told you I was in the steamboat business," put in Mr. Ackerman mischievously. "I should think you were!" was the lad's comment. "This is a wonderful collection, Ackerman," Mr. Tolman asserted, as he rose and began to walk about the room. "How did you ever get it together? Many of these prints are priceless." "Oh, I have been years doing it," Mr. Ackerman said. "It has been my hobby. I have chosen to sink my money in these toys instead of in an abandoned farm or antique furniture. It is just a matter of taste, you see." "You must have done some scouring of the country to make your collection so complete. I don't see how you ever succeeded in finding these old pictures and models. It is a genuine history lesson." "I do not deserve all the credit, by any means," the capitalist protested with modesty. "My grandfather, who was one of the owners of the first of the Hudson River steamers, began collecting pictures and drawings; and at his death they came to my father who added to them. Afterward, when the collection descended to me, I tried to fill in the gaps in order to make the sequence complete. Of course in many cases I have not been able to find what I wanted, for neither prints nor models of some of the ships I desired were to be had. Either there were no copies of them in existence, or if there were no money could tempt their owners to part with them. Still I have a well enough graded lot to show the progression." "I should think you had!" said Mr. Tolman heartily. "You have arranged them beautifully, too, from the old whalers and early American coasting ships to the clippers. Then come the first steam packets, I see, and then the development of the steamboat through its successive steps up to our present-day floating palace. It tells its own story, doesn't it?" "In certain fashion, yes," Mr. Ackerman agreed. "But the real romance of it will never be fully told, I suppose. What an era of progress through which to have lived!" "And shared in, as your family evidently did," interposed Mr. Tolman quickly. His host nodded. "Yes," he answered, "I am quite proud to think that both my father and my grandfather had their humble part in the story." "And well you may be. They were makers of history." Both men were silent an instant, each occupied with his own thoughts. Mr. Tolman moved reflectively toward the mantelpiece before which Steve was standing, gazing intently at a significant quartette of tiny models under glass. First came a ship of graceful outline, having a miniature figurehead of an angel at its prow and every sail set. Beside this was an ungainly side-wheeler with scarce a line of beauty to commend it. Next in order came an exquisite, up-to-date ocean liner; and the last in the group was a modern battleship with guns, wireless, and every detail cunningly reproduced. Stephen stood speechless before them. "What are you thinking of, son?" his father asked. "Why, I--" the boy hesitated. "Come, tell us! I'd like to know, too," echoed Mr. Ackerman. "Why, to be honest I was wondering how you happened to pick these particular four for your mantel," replied the lad with confusion. The steamboat man smiled kindly. "You think there are handsomer boats in the room than these, do you?" "Certainly there are better looking steamships than this one," Steve returned, pointing with a shrug of his shoulders at the clumsy side-wheeler. "But that rather ugly craft is the most important one of the lot, my boy," Mr. Tolman declared. "I suppose that is true," Mr. Ackerman agreed. "The fate of all the others hung on that ship." "Why?" was the boy's prompt question. "Oh, it is much too long a yarn to tell you now," laughed his host. "Were we to begin that tale we should not get to the theater to-night, say nothing of having any dinner." "I'd like to hear the story," persisted Stephen. "You will be reading it from a book some day." "I'd rather hear you tell it." "If that isn't a spontaneous compliment, Ackerman, I don't know what is," laughed Mr. Tolman. The steamboat man did not reply but he could not quite disguise his pleasure, although he said a bit gruffly: "We shall have to leave the story and go to the show to-night. I've bought the tickets and there is no escape," added he humorously. "But perhaps before you leave New York there will be some other chance for me to spin my yarn for you, and put your father's railroad romances entirely in the shade." The butler announced dinner and they passed into the dining room. If, however, Stephen thought that he was now to leave ships behind him he was mistaken, for the dining room proved to be quite as much of a museum as the library had been. Against the dull blue paper hung pictures of racing yachts, early American fighting ships, and nautical encounters on the high seas. The house was a veritable wonderland, and so distracted was the lad that he could scarcely eat. "Come, come, son," objected Mr. Tolman at last, "you will not be ready in time to go to any show unless you turn your attention to your dinner." "That's right," Mr. Ackerman said. "Fall to and eat your roast beef. We are none too early as it is." Accordingly Stephen fixed his eyes on his plate with resolution and tried his best to think no more of his alluring surroundings. With the coming of the ice-cream he had almost forgotten there were such things as ships, and when he rose from the table he found himself quite as eager to set forth to the theater as any other healthy-minded lad of his age would have been. The "show" Mr. Ackerman had selected had been chosen with much care and was one any boy would have delighted to see. The great stage had, for the time being, been transformed to a western prairie and across it came a group of canvas-covered wagons, or prairie schooners, such as were used in the early days by the first settlers of the West. Women and children were huddled beneath the arched canopy of coarse cloth and inside this shelter they passed the weary days and nights of travel. Through sun and storm the wagons rumbled on; jogging across the rough, uncharted country and jolting over rocks, sagebrush, and sand. There were streams to ford, mountains to climb on the long trip westward, but undaunted by obstacles the heroic little band of settlers who had with such determination left kin and comfort behind them passed on to that new land toward which their faces were set. It was such a company as this that Stephen now saw pictured before him. Perched on the front seat of the wagon driving the horses was the father of the family, rugged, alert, and of the woodsman type characteristic of the New England pioneer. The cavalcade halted. A fire was built and the travelers cooked their supper. Across the valley one could see the fading sunset deepen into twilight. From a little stream near-by the men brought water for the tired horses. Then the women and children clambered into the "ship of the desert" and prepared for a night's rest. In the meantime the men lingered about the dying fire and one of them, a gun in his hand, paced back and forth as if on guard. Then suddenly he turned excitedly to his comrades with his finger on his lips. He had heard a sound, the sound they all dreaded,--the cry of an Indian. Presently over the crest of the hill came stealing a stealthy band of savages. On they came, crouching against the rocks and moving forward with the lithe, gliding motion of serpents. The men sank down behind the brush, weapons in hand, and waited. On came the bloodthirsty Indians. Then, just when the destruction of the travelers seemed certain, onto the stage galloped a company of cowboys. Immediately there was a flashing of rifles and a din of battle. First it seemed as if the heroic rescuers would surely be slaughtered. But they fought bravely and soon the Indians were either killed or captured. Amid the confusion the owners of the prairie schooners leaped to the seats of their wagons, lashed forward their tired horses, and disappeared in safety with the terrified women and children. It was not until the curtain fell upon this thrilling adventure that Stephen sank back into his chair and drew a long breath. "Some show, eh, son?" said Mr. Tolman, as they put on their overcoats to leave the theater after the three long acts were over. The boy looked up, his eyes wide with excitement. "I should say!" he managed to gasp. "Did you like it, sonny?" Mr. Ackerman inquired. "You bet I did!" "Think you would have preferred to cross the continent by wagon rather than by train?" Steve hesitated. "I guess a train would have been good enough for me," he replied. "Was it really as bad as that before the railroads were built?" "Quite as bad, I'm afraid," was his father's answer. "Sometimes it was even worse, for the unfortunate settlers did not always contrive to escape. It took courage to be a pioneer and travel the country in those days. Undoubtedly there was much romance in the adventure but hand in hand with it went no little peril and discomfort. We owe a great deal to the men who settled the West; and, I sometimes think, even more to the dauntless women." Stephen did not reply. Very quietly he walked down the aisle between his father and Mr. Ackerman, and when he gave his hand to the latter and said good-night he was still thoughtful. It was evident that the scenes he had witnessed had made a profound impression on him and that he was still immersed in the atmosphere of prairie schooners, lurking Indians, and desert hold-ups. Even when he reached the hotel he was too tense and broad awake to go to bed. "I wish you'd tell me, Dad, how the first railroad across the country was built," he said. "I don't see how any track was ever laid through such a wilderness. Didn't the Indians attack the workmen? I should think they would have." His father placed a hand kindly on his shoulder. "To-morrow we'll talk trans-continental railroads, son, if by that time you still wish to," said he. "But to-night we'll go to bed and think no more about them. I am tired and am sure you must be." "I'm not!" was the prompt retort. "I rather fancy you will discover you are after you have undressed," smiled his father. "At any rate we'll have to call off railroading for to-night, for if you are not sleepy, I am." "But you won't have time to tell me anything to-morrow," grumbled Steve, rising unwillingly from his chair. "You will be busy and forget all about it and--" "I have nothing to do until eleven o'clock," interrupted Mr. Tolman, "when I have a business meeting to attend. Up to that time I shall be free. And as for forgetting it--well, you might possibly remind me if the promise passes out of my mind." In spite of himself the boy grinned. "You can bank on my reminding you all right!" he said, yawning. "Very well. Then it is a bargain. You do the reminding and I will do the story-telling. Are you satisfied and ready to go to bed and to sleep now?" "I guess so, yes." "Good-night then." "Good-night, Dad. I--I've had a bully day." CHAPTER XI THE CROSSING OF THE COUNTRY In spite of the many excitements crowded into his first day in New York Stephen found that when his head actually touched the pillow sleep was not long in coming and he awoke the next morning refreshed by a heavy and dreamless slumber. He was even dressed and ready for breakfast before his father and a-tiptoe to attack whatever program the day might present. Fortunately Mr. Tolman was of a sufficiently sympathetic nature to remember how he had felt when a boy, and with generous appreciation for the lad's impatience he scrambled up and made himself ready for a breakfast that was earlier, perhaps, than he would have preferred. "Well, son," said he, as they took their places in the large dining room, "what is the prospect for to-day? Are you feeling fit for more adventures?" "I'm primed for whatever comes," smiled the boy. "That's the proper spirit! Indians, bandits and cowboys did not haunt your pillow then." "I didn't stay awake to see." "You are a model traveler! Now we must plan something pleasant for you to do to-day. I am not sure that we can keep up the pace yesterday set us, for it was a pretty thrilling one. Robberies and arrests do not come every day, to say nothing of flotillas of ships and Wild West shows. However, we will do the best we can not to let the day go stale by contrast. But first I must dictate a few letters and glance over the morning paper. This won't take me long and while I am doing it I would suggest that you go into the writing room and send a letter to your mother. I will join you there in half an hour and we will do whatever you like before I go to my meeting. How is that?" "Righto!" Accordingly, after breakfast was finished, Steve wandered off by himself in search of paper and ink, and so sumptuous did he find the writing appointments that he not only dashed off a letter to his mother recounting some of the happenings of the previous day, but on discovering a rack of post cards he mailed to Jack Curtis, Tim Barclay, Bud Taylor and some of the other boys patronizing messages informing them that New York was "great" and he was _sorry they were not there_. In fact, it seemed at the moment that all those unfortunate persons who could not visit this magic city were to be profoundly pitied. In the purchase of stamps for these egoistic missives the remainder of the time passed, and before he realized the half-hour was gone, he saw his father standing in the doorway. "I am going up to the room now to hunt up some cigars, Steve," announced the elder man. "Do you want to come along or stay here?" "I'll come with you, Dad," was the quick reply. The elevator shot them to the ninth floor in no time and soon they were in their room looking down on the turmoil in the street below. "Some city, isn't it?" commented Mr. Tolman, turning away from the busy scene to rummage through his suit case. "It's a corker!" "I thought you would like to go out to the Zoo this morning while I am busy. What do you say?" "That would be bully." "It is a simple trip which you can easily make alone. If you like, you can start along now," Mr. Tolman suggested. "But you said last night that if I would hurry to bed, to-day you would tell me about the Western railroads," objected Stephen. He saw his father's eyes twinkle. "You have a remarkable memory," replied he. "I recall now that I did say something of the sort. But surely you do not mean that you would prefer to remain here and talk railroads than to go to the Zoo." "I can go to the Zoo after you have gone out," maintained Steve, standing his ground valiantly. "You are a merciless young beggar," grinned his father. "I plainly see that like Shylock you are determined to have your pound of flesh. Well, sit down. We will talk while I smoke." As the boy settled contentedly into one of the comfortable chintz-covered chairs, Mr. Tolman blew a series of delicate rings of smoke toward the ceiling and wrinkled his brow thoughtfully. "You got a pretty good idea at the theater last night what America was before we had trans-continental railroads," began he slowly. "You know enough of geography too, I hope, to imagine to some extent what it must have meant to hew a path across such an immense country as ours; lay a roadbed with its wooden ties; and transport all this material as well as the heavy rails necessary for the project. We all think we can picture to ourselves the enormity of the undertaking; but actually we have almost no conception of the difficulties such a mammoth work represented." He paused, half closing his eyes amid the cloud of smoke. "To begin with, the promoters of the enterprise received scant encouragement to attack the problem, for few persons of that day had much faith in the undertaking. In place of help, ridicule cropped up from many sources. It was absurd, the public said, to expect such a wild-cat scheme to succeed. Why, over six hundred miles of the area to be covered did not contain a tree and in consequence there would be nothing from which to make cross-ties. And where was the workmen's food to come from if they were plunged into a wilderness beyond the reach of civilization? The thing couldn't be done. It was impossible. Of course it was a wonderful idea. But it never could be carried out. Where were the men to be found who would be willing to take their lives in their hands and set forth to work where Indians or wild beasts were liable to devour them at any moment? Moreover, to build a railroad of such length would take a lifetime and where was the money coming from? For you must remember that the men of that period had no such vast fortunes as many of them have now, and it was no easy task to finance a scheme where the outlay was so tremendous and the probability of success so shadowy. Even as late as 1856 the whole notion was considered visionary by the greater part of the populace." "But the fun of doing it, Dad!" ejaculated Stephen, with sparkling eyes. "The fun of it!" repeated his father with a shrug. "Yes, there was fun in the adventure, there is no denying that; and fortunately for the dreamers who saw the vision, men were found who felt precisely as you do. Youth always puts romance above danger, and had there not been these romance lovers it would have gone hard with the trans-continental railroads. We might never have had them. As it was, even the men who ventured to cast in their lot with the promoters had the caution to demand their pay in advance. They had no mind to be deluded into working for a precarious wage. At length enough toilers from the east and from the west were found who were willing to take a chance with their physical safety, and the enterprise was begun." Stephen straightened up in his chair. "Had the only obstacle confronting them been the reach of uncharted country ahead that would have been discouraging enough. Fancy pushing your way through eight hundred miles of territory that had never been touched by civilization! And while you are imagining that, do not forget that the slender ribbon of track left behind was your only link with home; and your only hope of getting food, materials, and sometimes water. Ah, you would have had excitement enough to satisfy you had you been one of that company of workmen! On improvised trucks they put up bunks and here they took turns in sleeping while some of their party stood guard to warn them of night raids from Indians and wild beasts. Even in the daytime outposts had to be stationed; and more than once, in spite of every precaution, savages descended on the little groups of builders, overpowered them, and slaughtered many of the number or carried away their provisions and left them to starve. Sometimes marauders tore up the tracks, thereby breaking the connection with the camps in the rear from which aid could be summoned; and in early railroad literature we find many a tale of heroic engineers who ran their locomotives back through almost certain destruction in order to procure help for their comrades. Supply trains were held up and swept clean of their stores; paymasters were robbed, and sometimes murdered, so no money reached the employees; every sort of calamity befell the men. Hundreds of the ten thousand Chinese imported to work at a microscopic wage died of sickness or exposure to the extreme heat or cold." "Gee!" gasped Stephen, "I'd no idea it was so bad as all that!" "Most persons have but a faint conception of the price paid for our railways--paid not alone in money but in human life," answered Mr. Tolman. "The route of the western railroads, you see, did not lie solely through flat, thickly wooded country. Our great land, you must remember, is made up of a variety of natural formations, and in crossing from the Atlantic coast to that of the Pacific we get them one after another. In contrast to the forests of mighty trees, with their tangled undergrowth, there were stretches of prairie where no hills broke the level ground; another region contained miles and miles of alkali desert, dry and scorching, where the sun blazed so fiercely down on the steel rails that they became too hot to touch. Here men died of sunstroke and of fever; and some died for want of water. Then directly in the railroad's path arose the towering peaks of the Sierras and Rockies whose snowy crests must be crossed, and whose cold, storms and gales must be endured. Battling with these hardships the workmen were forced to drill holes in the rocky summits and bolt their rough huts down to the earth to prevent them from being blown away." "I don't see how the thing could have been done!" Steve exclaimed, with growing wonder. "And you must not forget to add to the chapter of tribulations the rivers that barred the way; the ravines that must either be filled in or bridged; the rocks that had to be blasted out; and the mountains that must be climbed or tunneled." "I don't see how they ever turned the trick!" the boy repeated. "It is the same old tale of progress," mused his father. "Over and over again, since time began, men have given their lives that the world might move forward and you and I enjoy the benefits of civilization. Remember it and be grateful to the past and to that vast army of toilers who offered up their all that you might, without effort, profit by the things it took their blood to procure. There is scarcely a comfort you have about you that has not cost myriad men labor, weariness, and perhaps life itself. Therefore value highly your heritage and treat the fruits of all hard work with respect; and whenever you can fit your own small stone into the structure, or advance any good thing that shall smooth the path of those who are to follow you, do it as your sacred duty to those who have so unselfishly builded for you." There was a moment of silence and the rumble of the busy street rose to their ears. "I never shall build anything that will help the men of the future," observed Stephen, in a low tone. "Every human being is building all the time," replied his father. "He is building a strong body that shall mean a better race; a clean mind that shall mean a purer race; a loyalty to country that will result in finer citizenship; and a life of service to his fellows that will bring in time a broader Christianity. Will not the world be the better for all these things? It lies with us to carry forward the good and lessen the evil of the universe, or tear down the splendid ideals for which our fathers struggled and retard the upward march of the universe. If everybody put his shoulder to the wheel and helped the forward spin of our old world, how quickly it would become a better place!" As he concluded his remarks Mr. Tolman took out his watch. "Well, well!" said he. "I had no idea it was so late. I must hurry or I shall not finish my story." "As I told you the men from the east and those from the west worked toward each other from opposite ends of the country. As soon as short lengths of track were finished they were joined together. Near the great Salt Lake of Utah a tie of polished laurel wood banded with silver marked the successful crossing of Utah's territory. Five years later Nevada contributed some large silver spikes to join her length of track to the rest. California sent spikes of solid gold, symbolic both of her cooperation and her mineral wealth; Arizona one of gold, one of silver, and one of iron. Many other States offered significant tributes of similar nature. And when at last the great day came when all the short lines were connected in one whole, what a celebration there was from sea to sea! Wires had been laid so that the hammer that drove the last spike sent the news to cities all over the land. Bells rang, whistles blew, fire alarms sounded. The cost of the Union Pacific was about thirty-nine million dollars and that of the Central Pacific about one hundred and forty million dollars. The construction of the Southern Pacific presented a different set of problems from those of the Northern, but many of the difficulties encountered were the same. Bands of robbers and Indians beset the workmen and either cut the ties and spread the rails, or tore the track up altogether for long distances. Forest fires often overtook the men before they could escape, although trains sometimes contrived to get through the burning areas by drenching their roofs and were able to bring succor to those in peril. Then there were washouts and snowstorms quite as severe as any experienced in the northern country." "I'm afraid I should have given the whole thing up!" interrupted Steve. "Many another was of your mind," returned Mr. Tolman. "The frightful heat encountered when crossing the deserts was, as I have said, the greatest handicap. Frequently the work was at a standstill for months because all the metal--rails and tools--became too hot to handle. The difficulty of getting water to the men in order to keep them alive in this arid waste was in itself colossal. Tank cars were sent forward constantly on all the railroads, northern as well as southern, and the suffering experienced when such cars were for various reasons stalled was tremendous. The sand storms along the Southern Pacific route were yet another menace. So you see an eagerness for adventure had to be balanced by a corresponding measure of bravery. Those early days of railroad building were not all romance and picturesqueness." Stephen nodded as his father rose and took up his hat and coat. "I'd like to hear Mr. Ackerman tell of the early steamboating," remarked the lad. "I'll bet the story couldn't match the one you have just told." "Perhaps not," his father replied. "Nevertheless the steamships had their full share of exciting history and you must not be positive in your opinion until you have heard both tales. Now come along, son, if you are going with me, for I must be off." Obediently Stephen slipped into his ulster and tagged at his father's heels along the corridor. What a magic country he lived in! And how had it happened that it had been his luck to be born now rather than in the pioneer days when there were not only no railroads but no great hotels like this one, and no elevators? "I suppose," observed Mr. Tolman, as they went along, "we can hardly estimate what the coming of these railroads meant to the country. All the isolated sections were now blended into one vast territory which brought the dwellers of each into a common brotherhood. It was no small matter to make a unit of a great republic like ours. The seafarer and the woodsman; easterner, westerner, northerner, and southerner exchanged visits and became more intelligently sympathetic. Rural districts were opened up and made possible for habitation. The products of the seacoast and the interior were interchanged. Crops could now be transported; material for clothing distributed; and coal, steel, and iron--on which our industries were dependent--carried wherever they were needed. Commerce took a leap forward and with it national prosperity. From now on we were no longer hampered in our inventions or industries and forced to send to England for machinery. We could make our own engines, manufacture our own rails, coal our own boilers. Distance was diminished until it was no longer a barrier. Letters that it previously took days and even weeks to get came in hours, and the cost and time for freight transportation was revolutionized. In 1804, for example, it took four days to get a letter from New York to Boston; and even as late as 1817 it cost a hundred dollars to move a ton of freight from Buffalo to New York and took twenty days to do it. In every direction the railroads made for national advancement and a more solid United States. No soldiers, no statesmen of our land deserve greater honor as useful citizens than do these men who braved every danger to build across the country our trans-continental railways." CHAPTER XII NEW PROBLEMS "I have been thinking, Dad," said Steve that evening, while they sat at dinner, "of the railroad story you told me this morning. It was some yarn." His father laughed over the top of his coffee cup. "It was, wasn't it?" replied he. "And the half was not told then. I was in too much of a hurry to give you an idea of all the trials the poor railroad builders encountered. Did it occur to you, for example, that after the roads to the Pacific coast were laid their managers were confronted by another great difficulty,--the difference in time between the east and the west?" "I never thought of that," was Steve's answer. "Of course the time must have differed a lot." "Indeed it did! Every little branch road followed the time peculiar to its own section of the country, and the task of unifying this so that a basis for a common time-table could be adopted was tremendous. A convention of scientists from every section of the country was called to see what could be done about the fifty-three different times in use by the various railroads." "Fifty-three!" ejaculated Stephen, with a grin. "Why, that was almost as many as Heinz pickles." "In this case the results of the fifty-three varieties were far more menacing, I am afraid, than those of the fifty-seven," said his father, with a smile, "for travel under such a régime was positively unsafe." "I can see that it would be. What did they do?" "Well, after every sort of suggestion had been presented it was decided to divide the country up into four immense parts, separated from one another by imaginary lines running north and south." "Degrees of longitude?" "Precisely!" returned Mr. Tolman, gratified that the boy had caught the point so intelligently. "The time of each of these sections jumped fifteen degrees, or one hour, and the railroads lying in each district were obliged to conform to the standard time of their locality. Until this movement went into effect there had been, for example, six so-called standard times to reckon with in going from Boston to Washington." "I don't see why everybody didn't get smashed up!" "I don't either; and I fancy the passengers and the railroad people didn't," declared Mr. Tolman. "But with the new state of things the snarl was successfully untangled and the roads began to be operated on a more scientific basis. Then followed gradual improvements in cars which as time went on were made more comfortable and convenient. The invention of the steam engine and the development of our steel products were the two great factors that made our American railroads possible. With the trans-continental roads to carry materials and the opening up of our coal, iron and copper mines we were at last in a position to make our railroads successful. Then science began to evolve wonderful labor-saving machinery which did away with the slow, primitive methods our pioneer engineers had been obliged to employ. The steam shovel was invented, the traveling crane, the gigantic derrick, the pile driver. The early railroad builders had few if any of these devices and were forced to do by hand the work that machinery could have performed in much less time. When one thinks back it is pathetic to consider the number of lives that were sacrificed which under present-day conditions might have been saved. Yet every great movement goes forward over the dead bodies of unnamed heroes. To an extent this is unavoidable and one of the enigmas of life. If every generation were as wise at the beginning as it is at the end there would be no progress. Nevertheless, when you reflect that ten thousand Chinese and Chilean laborers died while building one of the South American railroads it does make us wonder why we should be the ones to reap the benefits of so much that others sowed, doesn't it?" mused the boy's father. "Do you mean to say that ten thousand persons were killed while that railroad was being built?" questioned Stephen, aghast. "They were not all killed," was the reply. "Many of them died of exposure to cold, and many from the effects of the climate. Epidemics swept away hundreds of lives. This particular railroad was one of the mightiest engineering feats the world had seen for in its path lay the Andes Mountains, and there was no escape from either crossing or tunneling them. The great tunnel that pierces them at a height of 15,645 feet above sea level is one of the marvels of science. In various parts of the world there are other such monuments to man's conquest of the opposing forces of nature. Honeycombing the Alps are spiral tunnels that curve round and round like corkscrews inside the mountains, rising slowly to the peaks and making it possible to reach the heights that must be traversed. Among these marvels is the Simplon Tunnel, famous the world over. The road that crosses the Semmering Pass from Trieste to Vienna is another example of what man can do if he must. By means of a series of covered galleries it makes its way through the mountains that stretch like a wall between Italy and Austria. In the early days this territory with its many ravines and almost impassable heights would have been considered too difficult to cross. The railroad over the Brenner Pass between Innsbruck and Botzen penetrates the mountains of the Tyrol by means of twenty-three tunnels." "I learned about the St. Gothard tunnel in school," Steve interrupted eagerly. "Yes, that is yet another of the celebrated ones," his father rejoined. "In fact, there are now so many of these miracles of skilful railroading that we have almost ceased to wonder at them. Railroads thread their way up Mt. Washington, Mt. Rigi, and many another dizzy altitude; to say nothing of the cable-cars and funicular roads that take our breath away when they whirl us to the top of some mountain, either in Europe or in our own land. Man has left scarce a corner of our planet inaccessible, until now, not content with scaling the highest peaks by train, he has progressed still another stage and is flying over them. Thus do the marvels of one age become the commonplace happenings of the next. Our ancestors doubtless thought, when they had accomplished the miracles of their generation, that nothing could surpass them. In the same spirit we regard our aeroplanes and submarines with triumphant pride. But probably the time will come when those who follow us will look back on what we have done and laugh at our attempts just as you laughed when I told you of the first railroad." Stephen was thoughtful for a moment. "It's a great game--living--isn't it, Dad?" "It is a great game if you make yourself one of the team and pull on the side of the world's betterment," nodded his father. "Think what such a thing as the railroad has meant to millions and millions of people. Not only has it opened up a country which might have been shut away from civilization for centuries; but it has brought men all over the world closer together and made it possible for those of one land to visit those of another and come into sympathy with them. Japan, China, and India, to say nothing of the peoples of Europe, are almost our neighbors in these days of ships and railroads." "I suppose we should not have known much about those places, should we," reflected the boy. "Certainly not so much as we do now," was his father's answer. "Of course, travelers did go to those countries now and then; but to get far into their interior in a palanquin carried by coolies, for example, was a pretty slow business." "And uncomfortable, too," Stephen decided. "I guess the natives were mighty glad to see the railroads coming." To the lad's surprise his father shook his head. "I am afraid they weren't," observed he ruefully. "You recall how even the more civilized and better educated English and French opposed the first railroads? Well, the ignorant orientals, who were a hundred times more superstitious, objected very vehemently. The Chinese in particular feared that the innovation would put to flight the spirits which they believed inhabited the earth, air, and water. Surely, they argued, if these gods were disturbed, disaster to the nation must inevitably follow. It was almost impossible to convince even the more intelligent leaders that the railroad would be a benefit instead of a menace for before the ancient beliefs argument was helpless." "Well, the railroads were built just the same, weren't they?" "Yes. Fortunately some of the more enlightened were led to see the wisdom of the enterprise, and they converted the others to their views or else overrode their protests. They were like a lot of children who did not know what was best for them and as such they had to be treated. Nevertheless, you may be quite certain that the pioneer days of railroad building in the East were not pleasant ones. Materials had to be carried for great distances both by water and by land. In 1864, when the first locomotive was taken to Ceylon, it had to be transported on a raft of bamboo and drawn from the landing place to the track by elephants." "Humph!" chuckled Steve. "It's funny to think of, isn't it?" "More funny to think of than to do, I guess," asserted his father. "Still it is the battle against obstacles that makes life interesting, and in spite of all the hardships I doubt if those first railroad men would have missed the adventure of it all. Out of their resolution, fearlessness and vision came a wonderful fulfillment, and it must have been some satisfaction to know that they had done their share in bringing it about." "I suppose that is what Mr. Ackerman meant when he spoke of the history of steamboating," said the boy slowly. "Yes. He and his family had a hand in that great game and I do not wonder he is proud of it. And speaking of Mr. Ackerman reminds me that he called up this afternoon to ask if you would like to take a motor-ride with him to-morrow morning while I am busy." "You bet I would!" was the fervent reply. "I thought as much, so I made the engagement for you. He is coming for you at ten o'clock. And he will have quite a surprise for you, too." "What is it?" the boy asked eagerly. "It is not my secret to tell," was the provoking answer. "You will know it in good time." "To-morrow?" "I think so, yes." "Can't you tell me anything about it?" "Nothing but that you were indirectly responsible for it." "_I!_" gasped Stephen. Mr. Tolman laughed. "That will give you something to wonder and to dream about," he responded, rising from the table. "Let us see how much of a Sherlock Holmes you are." Steve's mind immediately began to speculate rapidly on his father's enigmatic remark. All the way up in the elevator he pondered over the conundrum; and all the evening he turned it over in his mind. At last, tired with the day's activities, he went to bed, hoping that dreams might furnish him with a solution of the riddle. But although he slept hard no dreams came and morning found him no nearer the answer than he had been before. He must wait patiently for Mr. Ackerman to solve the puzzle. CHAPTER XIII DICK MAKES HIS SECOND APPEARANCE When Mr. Ackerman's car rolled up to the hotel later in the morning the puzzle no longer lacked a solution for in the automobile beside the steamboat magnate sat Dick Martin, the lad of the pocketbook adventure. At first glance Steve scarcely recognized the boy, such a transformation had taken place in his appearance. He wore a new suit of blue serge, a smartly cut reefer, shiny shoes, a fresh cap, and immaculate linen. Soap and water, as well as a proper style of haircut had added their part to the miracle until now, with face glowing and eyes alight with pleasure, Dick was as attractive a boy as one would care to see. "I have brought Dick along with me, you see," the New Yorker explained, when the three were in the car and speeding up Fifth Avenue. "He and I have been shopping and now he is coming home to stay with me until we hear from one of the schools to which I have written. If they can find a place for him he will start at once. Then he is going to study hard and see what sort of a man he can make of himself. I expect to be very proud of him some day." The lad flushed. "I am going to do my best," said he, in a low tone. "That is all any one can do, sonny," declared Mr. Ackerman kindly. "You'll win out. Don't you worry! I'm not." He smiled and Dick smiled back timidly. "Have you been up to Mr. Ackerman's house yet and seen the boats?" Stephen asked, to break the pause that fell between them. "His collection, you mean? Sure! I'm--staying there." "Living there, sonny," put in the financier. "Then I suppose he's told you all about them," went on Stephen, a hint of envy in his tone. "I haven't yet," laughed their host, "for there hasn't been time. Dick only left the hotel yesterday and we have had a great deal to do since. We had to go to his lodgings and say good-by to the people there who have been kind to him and tell them why he was not coming back. And then there were errands and many other things to see to. So he has not been at home much yet," concluded Mr. Ackerman, with a kindly emphasis on the final sentence. Dick beamed but it was evident that the magnitude of his good fortune had left him too overwhelmed for words. Perhaps neither of the boys minded that there was little conversation during the drive for there was plenty to see and to Dick Martin, at least, an automobile ride was such an uncommon experience that it needed no embellishments. They rode up Morningside Drive and back again, looking down on the river as they went, and exclaiming when some unusual craft passed them. Evidently Mr. Ackerman was quite content to let matters take their natural course; but he was not unmindful of his guests and when at last he saw a shadow of fatigue circle Dick's eyes and give place to the glow of excitement that had lighted them he said: "Now suppose we go back to the house for a while. We have an hour or more before Stephen has to rejoin his father and you two chaps can poke about the suite. What do you say?" Steve was all enthusiasm. He had been quietly hoping there would be a chance for him to have another peep at the wonderful steamboats. "I'd like nothing better!" was his instant reply. "I did not see half I wanted to when I was there before, and we go home to-morrow, you know. If I don't see your ships and things to-day I never shall." "Oh, don't say that!" Mr. Ackerman said quickly. "You and Dick and I are going to be great friends. We are not going to say good-by and never see one another any more. Sometime you will be coming to New York again, I hope. However, if he wants to have a second glimpse of our boats now we'll let him, won't we, Dick?" Again the boy smiled a timid smile into his benefactor's face. [Illustration: "I wish you'd tell me about this queer little old-fashioned boat." Page 181.] It did not take long to reach the house and soon the three were in the wonderful room with its panorama of ships moving past the windows and its flotilla of still more ships decorating the walls. "Now you boys go ahead and entertain yourselves as you please," Mr. Ackerman said. "I am going to sit here and read the paper; but if there is anything you want to ask me you are welcome to do so." Stephen strolled over to the mantelpiece and stood before the model of the quaint side-wheeler that had held his attention at the time of his first visit; then he stole a furtive glance at the man in the big chair. "Did you really mean, Mr. Ackerman," he faltered, "that we could ask you questions?" "Certainly." "Then I wish you'd tell me about this queer little old-fashioned boat, and how you happened to put it between this up-to-date ocean liner and this battleship." The elder man looked up. "That boat that interests you is a model of Fulton's steamboat--or at least as near a model as I could get," explained he. "I put it there to show the progress we have made in shipbuilding since that day." Steve laughed. "I see the progress all right," replied he, "but I am afraid I do not know much about Fulton and his side-wheeler." Mr. Ackerman let the paper slip into his lap. "I assumed every boy who went to school learned about Robert Fulton," answered he, half teasingly and yet with real surprise. "I suppose I ought to have learned about him," retorted Stephen, with ingratiating honesty, "and maybe I did once. But if I did I seem to have forgotten about it. You see there are such a lot of those old chaps who did things that I get them all mixed up." Apparently the sincerity of the confession pleased the capitalist for he laughed. "I know!" returned he sympathetically. "Every year more and more things roll up to remember, don't they? Had we lived long ago, before so many battles and discoveries had taken place, and so many books been written, life would have been much simpler. Now the learning of all the ages comes piling down on our heads. But at least you can congratulate yourself that you are not so badly off as the boys will be a hundred years hence; they, poor things, will have to learn all about what _we_ have been doing, and if the world progresses as rapidly in history and in science as it is doing now, I pity them. Not only will they have to go back to Fulton but to him they will probably have to add a score of other inventors." Both boys joined in the steamboat man's hearty laugh. "Well, who was Fulton, anyway, Mr. Ackerman?" Stephen persisted. "If you want me to tell you that Robert Fulton was the first American to make a successful steamboat I can give you that information in a second," was the reply. "But if you wish to hear how he did it that is a much longer story." "I like stories," piped Dick from the corner of the couch where he was sitting. "So do I," echoed Steve. "Then I see there is no help for me!" Mr. Ackerman answered, taking off his spectacles and putting them into the case. With an anticipatory smile Stephen seated himself on the great leather divan beside the other boy. "Before the steamboat came," began Mr. Ackerman, "you must remember that paddle wheels had long been used, for both the Egyptians and the Romans had built galleys with oars that moved by a windlass turned by the hands of slaves or by oxen. Later there were smaller boats whose paddle wheels were driven by horses. So you see paddle wheels were nothing new; the world was just waiting for something that would turn them around. After the Marquis of Worcester had made his steam fountain he suggested that perhaps this power might be used to propel a boat but unfortunately he died before any experiments with the idea could be made. Various scientists, however, in Spain, France, England and Scotland caught up the plan but after struggling unsuccessfully with it for a time abandoned it as impractical. In 1802 Lord Dundas, a proprietor in one of the English canals, made an encouraging start by using a tow-boat with a paddle wheel at its stern. But alas, this contrivance kicked up such a fuss in the narrow stream that it threatened to tear the banks along the edge all to pieces and therefore it was given up and for ten years afterward there was no more steamboating in England." The boys on the couch chuckled. "In the meantime in America thoughtful men were mulling over the problem of steam navigation. Watt's engine had opened to the minds of inventors endless possibilities; and the success of the early railroads made many persons feel that a new era of science, whose wonders had only begun to unfold, was at hand. In Connecticut there lived a watchmaker by the name of John Fitch, who, although he knew little of the use of steam, knew much about machinery. Through the aid of a company that furnished him with the necessary money he built a steamboat which was tried out in 1787 and made three miles an hour. Of course it was not a boat like any of ours for it was propelled by twelve oars, or paddles, operated by a very primitive steam engine. Nevertheless, it was the forerunner of later and better devices of a similar nature, and therefore Fitch is often credited with being the inventor of the steamboat. Perhaps, had he been able to go on with his schemes, he might have given the world something really significant in this direction; but as it was he simply pointed the way. His money gave out, the company would do nothing further for him, and after building a second boat that could go eight miles an hour instead of three he became discouraged and intemperate and let his genius go to ruin, dying later in poverty--a sad end to a life that might well have been a brilliant one. After Fitch came other experimenters, among them Oliver Evans of Philadelphia who seems to have been a man of no end of inventive vision." "Wasn't he the one who tried sails on a railroad train?" inquired Steve, noting with pleasure the familiar name. "He was that very person," nodded Mr. Ackerman. "He evidently had plenty of ideas; the only trouble was that they did not work very well. He had already applied steam to mills and wagons, and now he wanted to see what he could do with it aboard a boat. Either he was very impractical or else hard luck pursued his undertakings. At any rate, he had a boat built in Kentucky, an engine installed on it, and then he had the craft floated to New Orleans from which point he planned to make a trip up the Mississippi. But alas, before his boat was fully ready, there was a drop in the river and the vessel was left high and dry on the shore." "Jove!" exclaimed Dick involuntarily. "Pretty tough, wasn't it?" remarked Mr. Ackerman. "What did he do then?" demanded Stephen. "Did he resurrect the boat?" "No, it did not seem to be any use; instead he had the engine and boiler taken out and put into a saw mill where once again hard luck pursued him, for the mill was burned not long after. That was the end of Oliver Evans's steamboating." Mr. Ackerman paused thoughtfully. "Now while Fitch and those following him were working at the steamboat idea here in America, Robert Fulton, also a native of this country, was turning the notion over in his mind. Strangely enough, he had not intended to be an inventor for he was in France, studying to be a painter. During a visit to England he had already met several men who were interested in the steam engine and through them had informed himself pretty thoroughly about the uses and action of steam. In Paris he made the acquaintance of a Mr. Barlow and the two decided to raise funds and build a steamboat to run on the Rhone. This they did, but unfortunately the boat sank before any degree of success had been achieved. Then Fulton, not a whit discouraged, told the French Government that if they would furnish the money he would build a similar boat to navigate the Seine. The French, however, had no faith in the plan and promptly refused to back it." "I'll bet they wished afterward they had!" interrupted Dick. "I presume they did," agreed Mr. Ackerman. "It is very easy to see one's mistakes after a thing is all over. Anyway, Mr. Barlow came back to America, where Fulton joined him, and immediately the latter went to building a steamboat that should be practical. On his way home he had stopped in England and purchased various parts for his engine and when he got to New York he had these set up in an American boat. You must not for a moment imagine that everything about this first steamboat of Fulton's was original. On the contrary he combined what was best in the experiments of previous inventors. He adopted the English type of engine, the side paddle, everything that seemed to him workable. Barlow and a rich New Yorker named Livingston backed the enterprise. Now some time before the State of New York, half in jest and half in irony, had granted to Livingston the sole right to navigate the New York waters by means of ships driven by steam or fire engines. At the time the privilege had caused much mirth for there were nothing but sailing ships in existence, and there was no prospect of there ever being any other kind of vessel. Hence the honor was a very empty one and nobody expected a time would arrive when it would ever be of any value to its owner. But Livingston was a shrewder and more far-seeing man than were the old legislators at Albany, and to Fulton he was an indispensable ally." The boy listened breathlessly. "How these three men managed to keep their secret so well is a mystery; but apparently they did, and when Fulton suddenly appeared on the Hudson with a steamboat named the _Clermont_ for Mr. Livingston's country seat on the Palisades, the public was amazed. A model of the boat with a miniature engine had previously been tried out so the three promoters had little doubt that their project would work, and it did. As the new craft moved along without any sails to propel it the sensation it made was tremendous. People were divided as to whether to flee from it in terror or linger and marvel at it. It is a pity that the newspapers of the period did not take the advent of this remarkable invention more seriously for it would have been interesting to know more of the impression it created. As it was little is recorded about it. Probably the very silence of the press is significant of the fact that there was scant faith in the invention, and that it was considered too visionary a scheme to dignify with any notice. However that may be, the newspapers passed this wonderful event by with almost no comment. History, however, is more generous and several amusing stories have come down to us of the fright the _Clermont_ caused as she crept along the river at dusk with a shower of vermilion sparks rising from her funnel. One man who came around a bend of the stream in his boat and encountered the strange apparition for the first time told his wife afterward that he had met the devil traveling the river in a sawmill." There was a shout of laughter from the boys. "The trial trip, to which many distinguished guests were invited, took place a few days later, and after improving some of the defects that cropped up the steamboat was advertised to run regularly between New York and Albany. Now if you think this announcement was hailed with joy you are much mistaken," continued Mr. Ackerman, smiling to himself at some memory that evidently amused him. "On the contrary the owners of the sailing ships which up to this time had had the monopoly of traffic were furious with rage. So vehemently did they maintain that the river belonged to them that at last the matter went to the courts and Daniel Webster was retained as Fulton's counsel. The case attracted wide attention throughout the country, and when it was decided in Fulton's favor there was great excitement. Every sort of force was brought to bear to thwart the new steamboat company. Angry opponents tried to blow up the boat as it lay at the dock; attempts were made to burn it. At length affairs became so serious that a clause was appended to the court's decree which made it a public crime punishable by fine or imprisonment to attempt to injure the _Clermont_." Mr. Ackerman paused to light a fresh cigar. "From the moment the law took this stand the success of the undertaking became assured and it is interesting to see how quickly the very men who jeered loudest at the enterprise now came fawning and begging to have a part in it. Other steamboats were added to the line and soon rival firms began to construct steamboats of their own and try to break up Fulton's monopoly of the waters of the State. For years costly lawsuits raged, and in defiance of the right the New York legislature had granted to Livingston, the fiercest competition took place. Sometime I should like to tell you more of this phase of the story for it is a very exciting and interesting yarn. Yet in spite of all the strife and hatred that pursued him Fulton's river-boats and ferries continued to run." "The State stuck to its bargain, then," murmured Steve, "and left Livingston the rights awarded him?" "No," replied Mr. Ackerman. "For a time they clung to their agreement; but at last the courts withdrew the right as illegal, and poor Livingston, who had sunk the greater part of his fortune in the steamboat business, lived to see the fruit of his toil wrested from him. In point of fact, I believe the decision of the courts to have been a just one for no one person or group of persons should control the waterways of the country. You can see the wisdom of this yourself. Nevertheless, the decree hit Livingston pretty hard. It was the first step in the destruction of a monopoly," added Mr. Ackerman whimsically. "Since then such decrees have become common happenings in America, monopolies being considered a menace to national prosperity. Certainly in this case it was well that the Supreme Court of the United States decided that all waters of the country should be free to navigators, no matter in what kind of vessel they chose to sail." "It was tough on Fulton and his friends, though, wasn't it?" observed Dick, who was plainly unconvinced as many another had been of the justice of the arguments. "Yes," agreed Mr. Ackerman, smiling into his troubled eyes, "I grant you it was tough on them." CHAPTER XIV A STEAMBOAT TRIP BY RAIL It was with a sense of deep regret that Stephen bade good-by to Mr. Ackerman and Dick and returned to the hotel to join his father. For the steamboat financier he had established one of those ardent admirations which a boy frequently cherishes toward a man of attractive personality who is older than himself; and for Dick he had a genuine liking. There was a quality very winning in the youthful East-sider and now that the chance for betterment had come his way Steve felt sure that the boy would make good. There was a lot of pluck and grit in that wiry little frame; a lot of honesty too, Stephen reflected, with a blush. He was not at all sure but that in the matter of fearlessness and moral courage the New York lad had the lead of him. Certainly he was not one who shrank from confessing when he had been at fault which, Steve owned with shame, could not be said of himself. For several days he had not thought of his automobile escapade but now once more it came to his mind, causing a cloud to chase the joyousness from his face. Alas, was he never to be free of the nagging mortification that had followed that single act? Was it always to lurk in the background and make him ashamed to confront the world squarely? Well, it was no use regretting it now. He had made his choice and he must abide by it. Nevertheless he was not quite so spontaneously happy when he met his father at luncheon and recounted to him the happenings of the morning. "Mr. Ackerman is taking a big chance with that boy," was Mr. Tolman's comment, when a pause came in the narrative. "I only hope he will not disappoint him. There must be a great difference between the standards of the two. However, Dick has some fine characteristics to build on--honesty and manliness. I think the fact that he showed no coward blood and was ready to stand by what he had done appealed to Ackerman. It proved that although they had not had the same opportunity in life they at least had some good stuff in common. You can't do much with a boy who isn't honest." Stephen felt the blood beating in his cheeks. Fortunately his father did not notice his embarrassment and as they soon were on their way to a picture show the memory that had so importunately raised its unwelcome head was banished by the stirring story of a Californian gold mine. Therefore by the time Stephen was ready to go to bed the ghost that haunted him was once more thrust into the background and he had gained his serenity. No, he was not troubled that night by dreams of his folly nor did he awaken with any remembrance of it. Instead he and his father chatted as they packed quite as pleasantly as if no specter stood between them. "Well, son, have you enjoyed your holiday?" inquired Mr. Tolman, as they settled themselves in the great plush chairs of the parlor car and waited for the train to start. "Yes, I've had a bully time, Dad." "I'm glad of that," was the kind reply. "It was unlucky that my business took up so much more of my time than I had expected and that I had to leave you to amuse yourself instead of going about with you, as I had planned. It was too bad. However, if you have managed to get some fun out of your visit that is the main thing. In fact, I am not sure but that you rather enjoyed going about alone," concluded he mischievously. Stephen smiled but did not reply. There was no denying that he had found being his own master a pleasant experience which had furnished him with a gratifying sense of freedom and belief in his own importance. What a tale he would have to tell the fellows at home! And how shocked his mother would be to hear that he had been turned loose in a great city in this unceremonious fashion! He could hear her now saying to his father: "I don't see what you were thinking of, Henry, to let Stephen tear about all alone in a city like New York. I should have worried every instant if I had known what he was doing. Suppose anything had happened to him!" Well, mercifully, nothing had happened,--that is, nothing worse than his falling into the hands of a detective and being almost arrested for robbery, reflected the boy with a grin. Perhaps Mr. Tolman interpreted his thoughts for presently he observed with a smile: "It is time you were branching out some for yourself, anyway, son. You are old enough now to be treated like a man, not like a little boy." As he spoke he looked toward Stephen with an expression of such pride and affection that the force of it swept over the lad as it never had done before. What a bully sort his father was, he suddenly thought; and how genuinely he believed in him! Why not speak out now and clear up the wretched deception he had practiced, and start afresh with a clean conscience? With impulsive resolve he gripped the arms of the chair and pulled himself together for his confession. But just at the crucial moment there was a stir in the aisle and a porter followed by two belated passengers hurried into the train which was on the brink of departure. That they had made their connection by a very narrow margin was evident in their appearance, for both were hot and out of breath, and the stout colored porter puffed under the stress of his haste and the heavy luggage which weighed him down. "It's these two chairs, sir," he gasped, as he tossed the new leather suit case into the rack. "Is there anything else I can do for you?" "No," replied the traveler, thrusting a bill into the darkey's hand. Already the train was moving. "Keep the change," he added quickly. "Thank you, sir! Thank you!" stammered the vanishing negro. "Well, we caught it, didn't we, Dick? It didn't look at one time as if it were possible. That block of cars on the avenue was terrible. But we are off now! It was about the closest shave I ever made." Then he turned around. "Hullo!" he cried. "Who's this? Bless my soul!" Both Mr. Tolman and Steve joined in the laugh of amazement. "Well, if this isn't a great note!" went on Mr. Ackerman, still beaming with surprise. "I thought you people were not going until the afternoon train." "I managed to finish up my business yesterday and get off earlier than I planned," Mr. Tolman explained. "But I did not know _you_ had any intention of going in this direction." "I hadn't until this morning," laughed the financier. "Then a telegram arrived saying they could take Dick at the New Haven school to which I had written if he entered right away, at the beginning of the term. So I dropped everything and here we are _en route_. It was rather short notice and things were a bit hectic; but by turning the whole apartment upside down, rushing our packing, and keeping the telephone wire hot we contrived to make the train." "It is mighty nice for us," put in Mr. Tolman cordially. "So Dick is setting forth on his education, is he?" "Yes, he is starting out to make of himself a good scholar, a good sport, a good athlete, and I hope a good man," returned the New Yorker. "A pretty big order, isn't it, Dick?" laughed Mr. Tolman. "It seems so," returned the boy. "It is not a bit too big," interrupted Mr. Ackerman. "Dick knows he hasn't got to turn the trick all in a minute. He and I understand such things take time. But they _can be done_ and we expect we are going to do them." He flashed one of his rare smiles toward his protégé and the lad smiled back frankly. "I expect so, too," echoed Mr. Tolman. "You've got plenty of backers behind you, Dick, and you have a clear path ahead. That is all any boy needs." "You're going back to school, aren't you, youngster?" Mr. Ackerman suddenly inquired of Stephen. "Yes, sir. I start in next week." "Decided yet whether you will be a railroad man like your Dad, or a steamboat man like me?" went on the New Yorker facetiously. "Not yet." "Oh, for shame! It should not take you any time at all to decide a question like that," the capitalist asserted teasingly. "What's hindering you?" Stephen gave a mischievous chuckle. "I can't decide until I have heard both sides," said he. "So far I know only half the steamboat story." "I see! In other words you think that between here and New Haven I might beguile the time by going on with the yarn I began yesterday." "That thought crossed my mind, sir,--yes." "You should go into the diplomatic service, young man. Your talents are being wasted," observed Mr. Ackerman good-humoredly. "Well, I suppose I could romance for the benefit of you two boys for part of the way, at least. It will give your father, Steve, a chance to go into the other car and smoke. Where did we break off our story? Do you remember?" "Where the United States said anybody had the right to sail anywhere he wanted to, in any kind of a boat he chose," piped Dick with promptness. "Yes, yes. I recall it all now," said Mr. Ackerman. "The courts withdrew the grant giving Livingston the sole right to navigate the waters of New York State by means of steamboats. So you want to hear more about it, do you?" "Yes!" came simultaneously from both the boys. "Then all aboard! Tolman, you can read, or run off and enjoy your cigar. We are going on a steamboat cruise." "Push off! You won't bother me," was the tolerant retort, as the elder man unfolded the morning paper. Mr. Ackerman cleared his throat. "Before this decree to give everybody an equal chance in navigating the waters of the country was handed down by the courts," he began, "various companies, in defiance of Livingston's contract, began building and running steamboats on the Hudson. Two rival boats were speedily in operation and it was only after a three years' lawsuit that they were legally condemned and handed over to Fulton to be broken up. Then the ferryboat people got busy and petitioned the New York Legislature for the right to run their boats to and fro between the New York and New Jersey sides of the river, and it is interesting to remember that it was on one of these ferry routes that Cornelius Vanderbilt, the great American financier, began his career." "I never knew that!" ejaculated Dick, intent on the story. "After the ruling of the Supreme Court in 1818 that all the waters of the country were free there was a rush to construct and launch steamers on the Hudson. The route was, you see, not only the most direct one between Albany and New York but it also lay in the line of travel between the eastern States and those of the west which were just being opened to traffic by the railroads and ships of the Great Lakes. Now you must not for a moment imagine that in those days there were any such vast numbers of persons traversing the country as there are now. Our early Americans worked hard and possessed only comparatively small fortunes so they had little money to throw away on travel simply for its own sake; moreover the War of 1812 had left the country poor. Nevertheless there were a good many persons who were obliged to travel, and it followed that each of the Hudson River lines of steamers was eager to secure their patronage. Hence a bitter competition arose between the rival steamboat companies." He paused and smiled whimsically at some memory that amused him. "Every inducement was offered the public by these battling forces. The older vessels were scrapped or reduced to tug service and finer steamboats were built; and once upon the water the engines were driven at full speed that quicker trips might lure passengers to patronize the swifter boats. Captains and firemen pitted their energies against one another and without scruple raced their ships, with the result that there were many accidents. In spite of this, however, the rivalry grew rather than diminished." "It must have been great sport," remarked Stephen. "Oh, there was sport in plenty," nodded Mr. Ackerman. "Had you lived during those first days of Hudson River transportation you would have seen all the sport you wanted to see, for the steamboat feud raged with fury, the several companies trying their uttermost to get the trade away from the Fulton people and from one another. Money became no object, the only aim being to win in the game. Fares were reduced from ten dollars to one, and frequently passengers were carried for nothing simply for the sheer spite of getting them away from other lines. Vanderbilt was in the thick of the fray, having now accumulated sufficient fortune to operate no less than fifty boats. Among the finest vessels were those of the Emerald Line; and the _Swallow_ and the _Rochester_, two of the speediest rivals, were continually racing each other. The devices resorted to in order to ensnare passengers were very amusing: some boats carried bands; others served free meals; and because there were few newspapers in those days, and only limited means for advertising, runners were hired to go about the city or waylay prospective travelers at the docks and try to coax them into making their trip by some particular steamer." "That was one way of getting business!" laughed Steve. "And often a very effective way, too," rejoined Mr. Ackerman. "In June of 1847 a tremendously exciting race took place between the _Oregon_ and the _Vanderbilt_, then a new boat, for a thousand dollars a side. The steamers left the Battery at eleven o'clock in the morning and a dense crowd turned out to see them start. For thirty miles they kept abreast; then the _Oregon_ gained half a length and in passing the other boat bumped into her, damaging her wheelhouse. It was said at the time that the disaster was not wholly an accident. Certainly there were grounds for suspicion. As you may imagine, the calamity roused the rage of the competing boat. But the commander of the _Oregon_ was undaunted by what he had done. All he wished was to win the race and that he was determined to do. He got up a higher and higher pressure of steam, and used more and more coal until, when it was time to return to New York, he discovered that his supply had given out and that he had no more fuel." "And he had to give up the race?" queried Dick breathlessly. "Not he! He wasn't the giving-up kind," said Mr. Ackerman. "Finding nothing at hand to run his boilers with he ordered all the expensive fittings of the boat to be torn up and cast into the fire--woodwork, furniture, carvings; anything that would burn. In that way he kept up his furious rate of speed and came in victorious by the rather close margin of twelve hundred feet." "Bully for him!" cried Dick. But Stephen did not echo the applause. "It was not a square race," he said, "and he had no right to win. Anyway, his steamboat must have been pretty well ruined." "I fancy it was an expensive triumph," owned Mr. Ackerman. "Without doubt it cost much more than the thousand dollars he won to repair the vessel. Still, he had the glory, and perhaps it was worth it to the company." "Were there other races like that?" Dick asked. "Yes, for years the racing went on until there were so many fires, explosions and collisions, that the steamer inspection law was put through to regulate the conditions of travel. It certainly was high time that something was done to protect the public, too, for such universal recklessness prevailed that everybody was in danger. Boats were overloaded; safety valves were plugged; boilers carried several times as much steam as they had any right to do, and many lives had been sacrificed before the government stepped in and put a stop to this strife for fame and money. Since then the traffic on the Hudson has dropped to a plane of sanity and is now carried on by fine lines of boats that conform to the rules for safety and efficient service." "And what became of Mr. Vanderbilt?" interrogated Dick, who was a New Yorker to the core and had no mind to lose sight of the name with which he was familiar. "Oh, Mr. Vanderbilt was a man who had many irons in the fire," replied Mr. Ackerman, smiling at the boy's eagerness. "He did not need to be pitied for just about this time gold was discovered in California and as the interest of the country swung in that direction Vanderbilt, ever quick to seize an opening wherever it presented itself, withdrew some of his steamers from the Hudson and headed them around to the Pacific coast instead." "And your family, Mr. Ackerman, were mixed up in all this steamboat rumpus?" commented Steve suddenly. "Yes, my grandfather was one of the Hudson River racers and quite as bad as the rest of them," the man replied. "Nevertheless he was a stanch, clever old fellow, and because he did his part toward building up the commerce and prosperity of the nation I have always regarded him with the warmest respect. I do not approve of all his methods, however, any more than I approve of many of the cut-throat business methods of to-day which sometime will be looked back upon with as much shame as these have been. There are moments, I must confess, when I wonder if we, with all our supposed enlightenment, have made any very appreciable advance over the frank and open racing done by our forefathers on the Hudson," reflected he half-humorously. "Perhaps we are a trifle more humane; and yet there is certainly much to be desired in the way we still sacrifice the public to our greed for money. An evil sometimes has to come to a climax to make us conscious of our injustice. Let us hope that our generation will not be so blind that it will not heed the warnings of its conscience, and instead delay until some such catastrophe comes upon it as pursued the racing boats of the Hudson River." CHAPTER XV THE ROMANCE OF THE CLIPPER SHIP It was with genuine regret that Mr. Tolman and Stephen parted from Mr. Ackerman and Dick when the train reached New Haven. "We shall not say good-by to Dick," Mr. Tolman declared, "for he is not to be very far away and I hope sometime he will come to Coventry and spend a holiday with us. Why don't you plan to do that too, Ackerman? Run over from New York for Thanksgiving and bring the boy with you. Why not?" "That is very kind of you." "But I mean it," persisted Mr. Tolman. "It is no perfunctory invitation. Plan to do it. We should all be delighted to have you. There is nothing in the world Mrs. Tolman loves better than a houseful of guests. Doris will be home from college and I should like you to see what a fine big daughter I have. As for Steve--" "I wish you would come, Mr. Ackerman," interrupted the boy. Mr. Ackerman hesitated. "I tell you what we'll do," replied he at length. "We'll leave it to Dick. If he makes a good record at school and earns the holiday we will accept your invitation. If he doesn't we won't come. Is that a bargain, youngster?" he concluded, turning to the lad at his side. The boy flushed. "It is a rather stiff one, sir," he answered, with a laughing glance. "I think that's playing for too high stakes, Ackerman," Mr. Tolman objected. "It is a little rough to put all the burden on Dick. Suppose we divide up the responsibility and foist half of it on Stephen? Let us say you will come if both boys make good in their studies and conduct." Dick drew a breath of relief at the words, regarding the speaker with gratitude. "That is a squarer deal, isn't it?" continued Mr. Tolman. "I think so--yes," was Dick's response. "And you, Steve--do you subscribe to the contract?" "Yes, I'll sign," grinned Stephen. "Then the agreement is clinched," exclaimed his father, "and it will be the fault of you two young persons if we do not have a jolly reunion at Thanksgiving time. Good-by Ackerman! Good-by, Dick. Good luck to you! We are pinning our faith on you, remember. Don't disappoint us." "I'll try not to," the boy answered, as he stepped to the platform. "Dick is a fine, manly young chap," observed Mr. Tolman, after the train was once more under way and he and Stephen were alone. "I have a feeling that he is going to make good, too. All he needed was a chance. He has splendid stuff in him. There isn't a mean bone in his body." Stephen moved uncomfortably in his chair and a guilty blush rose to his cheek but apparently his father did not notice it. "You liked Mr. Ackerman also, didn't you, son? Indeed there is no need to ask for he is a genius with young people and no boy could help liking a man of his type. It is a pity he hasn't a dozen children, or isn't the leader of a boy's school." "He is corking at story-telling!" was Steve's comment. "He certainly is. I caught some fragments of his Hudson River tale and did not wonder that it fascinated you. What a remarkable era that was!" he mused. "There were a lot of questions I wanted to ask him," Stephen said. "Such as?" "Well, for one thing I was curious to know what happened after the steamers on the Hudson were proved a success." "I can answer that question," replied his father promptly. "After the river boats had demonstrated their practicability steamships were built for traffic along short distances of the coast. Owing to the War of 1812 and the danger to our shipping from the British, however, the launching of these new lines did not take place immediately; but in time the routes were established. The first of these was from New York to New Haven. You see, travel by steam power was still so much of a novelty that Norwich, first proposed as a destination, was felt to be too far away. It was like taking one's life in one's hands to venture such an immense distance from land on a steamboat." Stephen smiled with amusement. "But gradually," continued Mr. Tolman, "the public as well as the steamboat companies became more daring and a line from New York to Providence, with Vanderbilt's _Lexington_ as one of the ships, was put into operation. Then in 1818 a line of steamers to sail the Great Lakes was built; and afterwards steamships to travel to points along the Maine coast. The problem of navigation on the rivers of the interior of the country followed and here a new conundrum in steamboat construction confronted the builders, for the channels of many of the streams were shallow and in consequence demanded a type of boat very long and wide in proportion to its depth of hull. After such a variety of boat had been worked out and constructed, lines were established on several of the large rivers, and immediately the same old spirit of rivalry that pervaded the Hudson years before cropped up in these other localities. Bitter competition, for example, raged between the boats that plied up and down the Mississippi; and in 1870 a very celebrated race took place between the _Natchez_ and the _Robert E. Lee_. The distance to be covered was 1218 miles and the latter ship made it in three days, eighteen hours, and thirty minutes. The test, however, was not a totally fair one since the _Natchez_ ran into a fog that held her up for six hours. But the event illustrates the keen interest with which men followed the progress of American shipping; and you can see how natural it was that after the river boats, lake steamers, coastwise vessels and tugs had had their day the next logical step (and very prodigious one) was the--" "The ocean liner!" ejaculated Stephen. "Precisely!" nodded his father. "Now there are two separate romances of our ocean-going ships. The first one is of the sailing vessels and is a chronicle of adventure and bravery as enthralling as any you could wish to read. I wish I had time to tell it to you in full and do it justice, but I fear I can only sketch in a few of the facts and leave you to read the rest by yourself some time. You probably know already that whalers went out from Gloucester, New Bedford, and various of our eastern ports and often were gone on two or three-year cruises; and when you recall that in those early days there not only was no wireless but not even the charts, lighthouses, and signals of a thoroughly surveyed coast you will appreciate that setting forth on such a voyage for whale-oil (then used almost exclusively for lighting purposes) took courage. Of course the captains of the ships had compasses for the compass came into use just before the beginning of the Fifteenth Century and was one of the things that stimulated the Portuguese and Spaniards to start out on voyages of discovery. The Spaniards built ships that were then considered the largest and finest afloat, and probably Columbus caught the enthusiasm of the period and with the newly invented compass to guide him was stirred to brave the ocean and discover other territory to add to the riches of the land he loved. It was a golden age of romance and adventure and the journeys of Columbus grew out of it quite naturally. But in America shipping had its foundation in no such picturesque beginning. The first vessel made in this country was constructed as a mere matter of necessity, being built at the mouth of the Kennebec River to carry back to England a group of disheartened, homesick settlers." He paused thoughtfully a moment. "Even the ships of later date had their birth in the same motive--that of necessity. The early colonists were forced to procure supplies from England and they had no choice but to build ships for that purpose. At first these sailing packets were very small, and as one thinks of them to-day it is to marvel that they ever made so many trips without foundering. As for our coastwise ships, up to 1812 they were nothing more than schooner-rigged hulls." "I wonder where the word _schooner_ came from," commented Steve. "The legend goes that the term _scoon_ was a colloquialism used when skipping stones. When a pebble glanced along the top of the water it was said to _scoon_," answered his father, with a smile. "After the War of 1812 was over and our American vessels were safe from possible attack, and after the country itself had recovered somewhat from the stress of this financial burden so that men had more money to invest in commerce, we began to branch out and build finer vessels; and when it came to rigging them there seemed to be no name to apply to the arrangement of the sails. The story goes that one day as one of these new ships sailed out of Gloucester harbor a fisherman watching her exclaimed with admiration, 'See her _scoon_!' The phrase not only caught the public fancy but that of the shipbuilders as well, and the word _schooner_ was quickly adopted." "I never knew that before!" announced Steve, when the narrative was concluded. "Slowly the models of ships improved," went on his father, without heeding the interruption. "Vessels became larger, faster, more graceful. Even the whalers and fishing smacks took on more delicate lines. Merchants from Salem, Gloucester, New Bedford invested their hard-earned savings in whalers and trading ships, and many of them made their fortunes by so doing. The sailing packets that went to Liverpool began to make excellent time records. Although the English were now using steamers for trans-Atlantic travel they had not perfected them to a sufficient extent to make their trips faster than those of sailing ships." "About how long did it take them to cross?" inquired Stephen. "The average time to Liverpool was from nineteen to twenty-one days," was the answer. "And for the return voyage from thirty to thirty-five." "Whew, Dad! Why, one could walk it in that time!" exclaimed the lad. "It was a long time," his father agreed. "But it is not fair to measure it by present-day standards. Think how novel a thing it was to cross the ocean at all!" "I suppose so," came reflectively from Stephen. "It was not long," continued his father, "before the English improved their engines so that their steamers made better time, and then our American sailing packets were left far behind. This, as you can imagine, did not please our proud and ambitious colonists who were anxious to increase their commerce and build up their young and growing country. Something must be done! As yet they had not mastered the enigma of steam but they could make their sailing ships swifter and finer and this they set to work to do. Out of this impetus for prosperity came the remarkable clipper-ship era. "We shall probably never see such beautiful ships again," continued Mr. Tolman, a trifle sadly. "Youth and romance go hand in hand, and our country was very young, and proud and eager in those days. Our commerce was only beginning and the far corners of the world were strange, unexplored and alluring. It is like an Arabian Night's Tale to read of those wonderful ships built to carry merchandise to China, India and other foreign ports. Speed was their aim--speed, speed, speed! They must hold their own against the English steamers if they would keep their place on the seas. For in those days the methods of packing produce were very primitive, and it was imperative that such perishable things as tea, dried fruits, spices and coffee should be rushed to the markets before the dampness spoiled them. If they mildewed they would be a dead loss to the merchants handling them. Moreover as cable and telegraph were unknown there was no way to keep in touch with the demands of the public, or be sure of prices. Therefore every merchant hurried his goods home in the hope of being the first in the field and reaping the largest profits." "More racing!" exclaimed Stephen. "It was racing, indeed!" returned his father. "Ships raced one another back from China, each trying desperately to discharge her cargo before her rival did. Like great sea-birds these beautiful boats skimmed the waves, stretching every inch of canvas to be the winner at the goal. As a result the slow merchant packets with their stale cargoes could find no patrons, the clippers commanding not only all the trade but the highest prices for produce as well. Silks, chinaware, ivory, bamboo--all the wealth of the Orient began to arrive in America where it was hungrily bought up, many a man making his fortune in the East India trade. Of this fascinating epoch Hawthorne gives us a vivid picture." "It must have been great to travel on one of those ships!" said Stephen. "It was not all pleasure, by any means, son," Mr. Tolman replied. "Often the vessels encountered hurricanes and typhoons in the treacherous Eastern waters. Sometimes ships were blown out of their course and wrecked, or cast ashore on islands where their crews became the prey of cannibals." "Jove!" "It had its outs--this cruising to distant ports," announced his father. "Moreover, the charts in use were still imperfect and lighthouse protection was either very scanty or was lacking entirely." "What became of the clipper ships?" "Well, we Americans never do anything by halves, you know. When we go in we go in all over," laughed his father. "That is what we did with our clipper ships. We were so pleased with them that we built more and more, sending them everywhere we could think of. Many went around to California to carry merchandise to the gold searchers. At last there were so many of these swift vessels that they cut into one another and freight rates dropped. Besides, steamboats were coming into general use and were now running on all the more important ocean routes. The day of the sailing ship was over and the marvelous vessels were compelled to yield their place to the heralds of progress and become things of the past. Nevertheless, their part in our American commerce will never be forgotten and we have them to thank not only for the fame they brought our country but also for much of its wealth." With a quick gesture of surprise he rose hurriedly. "See!" he exclaimed. "We are almost home. We have talked 'ships and sealing-wax' for hours." "It hasn't seemed for hours," retorted Stephen, springing to collect his luggage. "Nor to me, either." "Some time I'd like to hear about the ocean liners," ventured the boy. "You must get Mr. Ackerman to tell you that story when he comes to visit us Thanksgiving," was the reply, "if he _does_ come. That part of it seems to be up to you and Dick." "I mean to do my part to get him here," Steve announced. "I hope Dick will plug, too." "I rather think you can trust him for that," was the quiet answer. CHAPTER XVI AGAIN THE MAGIC DOOR OPENS A change of trains and a brief hour's journey brought the travelers safely to Coventry where Havens met them with the automobile. "This will be our last ride this fall," observed Mr. Tolman, as he loitered on the platform while the luggage was being lifted into the car. "We shall have to put the motor up in a day or two. It will not need much of an overhauling in the way of repairs this season, I guess, for it is comparatively new and should be in pretty good condition. There may be a few slight things necessary but nothing much. Isn't that so, Havens?" "It is badly scratched, sir." "Scratched!" "Yes, sir--both inside and out. I wonder you haven't noticed it. Still you wouldn't unless you got it in just the right light. I did not myself at first. There are terrible scratches everywhere. You would think ten men had climbed all over it. Look!" "Oh, it can't be so bad as all that," laughed Mr. Tolman good-humoredly, evidently not taking the chauffeur's comment seriously. "The car was new in the spring and we have not given it very hard wear. What little luggage we have carried has been carefully put in; I have seen to that myself. Only a short time ago I thought how splendidly fresh the varnish looked. In fact, I examined it just before you were ill. It can't have become very much defaced since then for we have not had the car out of the garage except for one short excursion." Havens' brow darkened into a puzzled frown. "I don't understand it at all, sir," he replied. "I could swear the scratches were not there when I went away. If you didn't tell me yourself the car hadn't been used much I'd stake my oath it had had a great deal of knocking about while I was gone. Look here, Mr. Tolman! Look at that, and that, and that--great digs in the paint as if people with boots on had climbed over the sides." Mr. Tolman looked and so, with a sinking heart, did Stephen. "Mercy on us! I never noticed all this before!" cried Mr. Tolman, in consternation. "What in the world--" he stopped as if he could find no words to voice his amazement. "Look at this!" He placed a finger on a broad, clearly defined line that extended from the top of the tonneau to the bottom. "You would think somebody had dug his heels in here and then slid down until he reached the ground! And this! What on earth has happened to the thing, Havens? It looks as if it had been used for a gymnasium." Hot and cold by turns, Steve listened. The marks to which his father pointed told a truthful story. Somebody had braced his heels against the side and then slid to the ground; it was Bud Taylor. And that other jagged line indicated where Tim Barclay had scrambled over the edge and made his hurried exit. The history of the whole miserable adventure was etched in the varnish as vividly as if it had been traced there in words. Stephen gasped with horror when he saw how plainly the entire story stood out in the sunlight of the November day. Why, the most stupid person alive could read it! Every moment he expected that his father or Havens would wheel on him and ask accusingly: "When was it you carried all those boys to Torrington?" He could hear his heart thumping inside him and feel the beat of the blood that scorched his cheek. He had not pictured a dilemma like this. The affair had gone off so smoothly that he had flattered himself every possibility of discovery was past, and in this comforting knowledge he had basked with serenity. And now, behold, here he was at the brink of peril, and just when he had had such a glorious holiday, too! "How do you solve the riddle, Havens?" he heard his father asking. "I ain't solvin' it, sir," was the drawling answer. "Maybe Steve could give you a hint, though," he added slyly. The lad stiffened. He and Havens had never been friends. They had been through too many battles for that. The chauffeur did not like boys and took no trouble to conceal the fact, and as a result he had been the prey of many a mischievous prank. It was through his vigilance that Stephen had more than once been brought to justice and in the punishment that followed Havens had exulted without restraint. As a retaliation the boy tormented him whenever opportunity presented, the two carrying on a half-bitter, half-humorous feud which was a source of mutual gratification. Had not this been the case the confession that trembled on Stephen's tongue would doubtless have been uttered then and there. But to speak before Havens and afford him the chance to crow and rejoice,--that was not to be thought of. Therefore, drawing in his chin and holding his head a trifle higher than was his wont, he replied with hauteur: "I've no solution at all to offer. How could I have?" For the fraction of a second Mr. Tolman looked sharply at his son as if some new thought had suddenly struck him; then the piercing scrutiny faded from his eyes and he turned away. "Well, I guess we shall have to drop the matter for the present, anyway, and be getting home," said he. "It will do no good for us to stand here in the cold and argue. We shall be no nearer an answer. Come, jump in, Steve!" With a strange sense of reluctance the boy obeyed. He felt the door to confession closing with finality behind him; and now that he saw all chance for dallying on its threshold cut off, he began to regret that it should so completely close. Once again the opportunity to clear his conscience had come about in an easy, natural manner; confession had been gently and tactfully invited and he had turned his back. Never again, probably, would he have such a chance as this. Without any ignominious preamble he could have spoken the few words necessary and been a free man! But alas, he had hesitated too long. His father followed him into the car, banged the door, and they shot homeward. Perhaps, temporized the lad as they rode along, he would say something when they reached the house. Why wasn't it better anyway to wait until he and his father were quiet and alone? Who could blame him for not wanting to confess his misdemeanors before an audience? His father would understand and forgive his reticence, he was sure. Having lulled his conscience to rest with the assurance of this future reparation he sank back against the cushions and drew the robe closer about him. There was no use in letting the ride be spoiled by worry. He did not need to speak until he got back, and he needn't speak at all if he did not wish to. If no favorable opening occurred, why, he could still remain silent and wait a better chance. He had taken no vow, made no promise; nothing actually bound him to act unless he chose. It was surprising how his spirits rose with this realization. He even ventured to talk a little and make a joke or two. These overtures received only scant response from his father, however, for Mr. Tolman's brow had settled into a frown and it needed no second glance to assure Stephen that the happenings of the past half-hour had put the elder man very much out of humor. How unfortunate, mused the boy, that this mood should have come upon his father. It would take more than an ordinary measure of courage to approach him now. Why, it would be braving the lions, actually tempting fate to go to him with a confession when he looked like this. Would it not be much wiser to wait? With a sharp swerve they turned in at the gate and rolled up the long driveway; then the front door burst open and from it issued not only Mrs. Tolman and Doris but with them the girl with the wonderful hair, Jane Harden, whom he had seen at Northampton. A hubbub of greeting ensued and in the interchange of gay conversation all thought of confession was swept from Stephen's mind. Nor in the days that followed, with their round of skating, hockey, snow-shoeing, and holiday festivities, did the inclination to revert to the follies of the past arise. The big red touring-car was sent away without further allusion to its battered condition and with its departure the last link with the misfortunes that tormented him seemed destroyed. Once, it is true, when he overheard his father telling his mother that the bill for repainting and varnishing the car was going to be very large, his conscience smote him. But what, he argued, could he do? Even were he to come forward now and shoulder the blame it would not reduce the expense of which his father complained. He had no money. Therefore he decided it was better to close his ears and try and forget the entire affair. His father had evidently accepted the calamity with resignation and made up his mind to bear the consequences without further demur. Why not let the matter rest there? At this late date it would be absurd to speak, especially when it could not alter the situation. In the meantime letters came from Mr. Ackerman and from Dick. The latter was very happy at the New Haven school and was making quite a record for himself, and it was easy to detect between the lines of the steamboat magnate's epistle that he was much gratified by the progress of his protégé. Thanksgiving would soon be here and if the Tolmans still extended their invitation for the holidays the two New Yorkers would be glad to accept it. "I'll write Ackerman to-day," announced Mr. Tolman at breakfast. "The invitation has hung on Stephen and Dick, and I am glad to say they each have made good. How fine that that little East Side chap should have turned out so well! I don't wonder Ackerman is pleased. Everybody does not get appreciation in return for kindness. I know many a parent whose children repay what is done for them only with sneaking, unworthy conduct and utter ingratitude. Dick may not have been born into prosperity but he is a thoroughbred at heart and it shows in his actions. He is every inch a gentleman." At the words Stephen's blood tingled. What would his father think of him if he knew what a mean-spirited coward he was? Well, it was impossible to tell him now. It would upset the whole Thanksgiving party. CHAPTER XVII MORE STEAMBOATING The night before Thanksgiving Mr. Ackerman and Dick arrived at Coventry and it was difficult to believe the change wrought in the New York boy. Not only was his face round, rosy and radiant with happiness but along with a new manliness had stolen a gentler bearing and a courtesy that had not been there when he had set forth to school. "Why, you must have put on ten pounds, Dick!" cried Mr. Tolman, shaking hands with his young guest after greeting the steamboat magnate. "It is eleven pounds, sir," laughed Dick. "We have bully eats at school and all you want of them." The final phrase had a reminiscent ring as if it harked back to a time when three ample meals were a mirage of the imagination. "Well, I am glad to hear you have done justice to them and encouraged the cook," was Mr. Tolman's jocular reply. "Now while you stay here you must cheer on our cook in the same fashion. If you don't we shall think you like New Haven better." "I guess there is no danger of that," put in Mr. Ackerman. "Dick seems hollow down to his ankles. There is no filling him up; is there, boy?" "I couldn't eat that third ice-cream you offered me yesterday," was the humorous retort. "I hope you've saved some room for to-morrow's dinner," Mrs. Tolman interrupted, "for there will be mince pie and plum pudding and I don't know what not. And then there is the turkey--we ordered an extra large one on purpose." Dick and Steve exchanged a sheepish grin. "Well, it is jolly to see you good people," Mr. Tolman declared, as he ushered the visitors into the living room, where a bright fire burned on the hearth. "Our boys have done well, haven't they, Ackerman? I don't know which is to win the scholarship race--the steamboats or the railroads." "We could compare marks," Stephen suggested. "That would hardly be fair," Mr. Ackerman objected quickly, "for the steamboats did not start even with the railroads in this contest. Dick has had to put in a lot of hours with a tutor to make up for the work he missed at the beginning of the year. He has been compelled to bone down like a beaver to go ahead with his class; but he has succeeded, haven't you, sonny?" "I hope I have," was the modest retort. "Furthermore," went on Mr. Ackerman, "there are other things beside scholarship to be considered in this bargain. We want fine, manly boys as well as wise ones. Conduct counts for a great deal, you know." Stephen felt himself coloring. "There have been no black marks on Dick's record thus far. How about yours, Steve?" asked the New York man. "I--er--no. I haven't had any black marks, either," responded Stephen, with a gulp of shame. "That is splendid, isn't it!" commented Mr. Ackerman. "I wasn't looking for them. You have too fine a father to be anything but a square boy." Once more Stephen knew himself to be blushing. If they would only talk about something else! "Are you going to finish your steamboat story for us while you are here?" inquired he with sudden inspiration. "Why, I had not thought of doing any steamboating down here," laughed the capitalist. "Rather I came to help the Pilgrims celebrate their first harvest." "But even they had to come to America by boat," suggested Doris mischievously. "I admit that," owned the New Yorker. "And what is more, they probably would have come in a steamboat if one had been running at the time." "What was the first American steamship to cross the Atlantic, Ackerman?" questioned Mr. Tolman when they were all seated before the library fire. "I suppose the _Savannah_ had that distinction," was the reply. "She was built in New York in 1818 to be used as a sailing packet; but she had side wheels and an auxiliary engine, and although she did not make the entire trans-Atlantic distance by steam she did cover a part of it under steam power. Her paddle wheels, it is interesting to note, were so constructed that they could be unshipped and taken aboard when they were not in use, or when the weather was rough. I believe it took her twenty-seven days to make the trip from Savannah to Liverpool and eighty hours of that time she was using her engine. Although she made several trips in safety it was quite a while before the American public was sufficiently convinced of the value of steam to build other steamships. A few small ones appeared in our harbors, it is true, but they came from Norway or England; they made much better records, too, than anything previously known, the _Sirius_ crossing in 1838 in nineteen days, and the _Great Western_ in fifteen. In the meantime shipbuilders on both sides of the Atlantic were studying the steamboat problem and busy brains in Nova Scotia and on the Clyde were working out an answer to the puzzle. One of the most alert of these brains belonged to Samuel Cunard, the founder of the steamship line that has since become world famous. In May, 1840, through his instrumentality, the _Unicorn_ set out from England for Boston arriving in the harbor June third after a voyage of sixteen days. When we reflect that she was a wooden side-wheeler, not much larger than one of our tugboats, we marvel that she ever put in her appearance. Tidings of her proposed trip had already preceded her, and when after much anxious watching she was sighted there was the greatest enthusiasm along the water front, the over-zealous populace who wished to give her a royal welcome setting off a six-pounder in her honor that shattered to atoms most of her stained glass as she tied up at the dock." His audience laughed. "You see," continued the capitalist, "the ship came in answer to a circular sent out by our government to various shipbuilders asking bids from swift and reliable boats to carry our mails to England. Cunard immediately saw the commercial advantages of such an opportunity, and not having money enough to back the venture himself the Halifax man went to Scotland where he met Robert Napier, a person who like himself had had wide experience in shipping affairs. Both men were enthusiastic over the project; before long the money necessary for the undertaking was raised, and the British and North American Royal Mail Steam Packet Company, with a line of four ships, was awarded the United States Government contract. These ships were very significantly named: the _Britannia_ in honor of England, the _Arcadia_ as a compliment to Mr. Cunard's Nova Scotia home, the _Caledonia_ in memory of Napier's Scotch ancestry, and the _Columbia_ out of regard to America. And in passing it is rather interesting to recall that in homage to these pioneer ships it has become a tradition of the Cunard Line to use names that terminate in the letter _a_ for all the ships that have followed them. For, you must remember, it was this modest group of steam packets that were the ancestors of such magnificent boats as the _Mauretania_ and _Lusitania_." "There was some difference!" interrupted Stephen. "Well, rather! Had you, however, told Samuel Cunard then that such mammoth floating hotels were possible he would probably not have believed you. He had task enough on his hands to carry the mails; transport the few venturesome souls that dared to cross the sea; and compete with the many rival steamship lines that sprang up on both sides of the ocean as soon as some one had demonstrated that trans-Atlantic travel was practical. For after Cunard had blazed the path there were plenty of less daring persons ready to steal from him the fruits of his vision and courage. From 1847 to 1857 the Ocean Steamship Company carried mails between New York and Bremen, and there was a very popular line that ran from New York to Havre, up to the period of the Civil War. Among the individual ships none, perhaps, was more celebrated than the _Great Eastern_, a vessel of tremendous length, and one that more nearly approached our present-day liners as to size. Then there was the Collins Line that openly competed with the Cunard Line; and to further increase trans-Atlantic travel, in 1855 Cornelius Vanderbilt, ever at the fore in novel projects, began operating lines of steamships not only to England and France but to Bremen." Mr. Ackerman paused a moment. "By 1871 there was an American line between Philadelphia and Liverpool. In the meantime, ever since 1861, there had been a slow but steady advance in ocean shipbuilding. Although iron ships had gradually replaced wooden ones the side-wheeler was still in vogue, no better method of locomotion having been discovered. When the change from this primitive device to the screw propeller came it was a veritable leap in naval architecture. Now revolutions in any direction seldom receive a welcome and just as the conservatives had at first hooted down the idea of iron ships, asserting they would never float, so they now decried the use of the screw propeller. Indeed there was no denying that this innovation presented to shipbuilders a multitude of new and balking problems. While the clipper ships had greatly improved the designs of vessels the stern was still their weakest point and now, in addition to this already existing difficulty, came the new conundrums presented by the pitch, or full turn of the thread, in the screw propeller; also the churning of the current produced by the rapidly whirling wheel, which was found to retard the speed of the ship very materially. Valiantly engineers wrestled with one after another of these enigmas until they conquered them and put shipbuilding on the upward path where it has been ever since. In time steel ships replaced the cruder vessels of iron; finer types of engines were worked out; the wireless and the many electrical devices which herald approaching foes and announce the presence of icebergs have been invented; until now the ocean liner is practically safe from all perils except fogs, icebergs and submarines." He stopped a moment with eyes fixed on the glowing logs that crackled on the hearth. "Meanwhile," he went on, "comfort aboard ship has progressed to luxury. Better systems of ventilation, more roomy sleeping quarters, more windows and improved lighting facilities have been installed. The general arrangement of the ship has also been vastly improved since the days when the high bulwark and long deckhouse were in use. Now iron railings allow the sea to wash back and forth in time of storm, and in consequence there is less danger of vessels being swamped by the waves. Then there are watertight doors and bulkheads, double bottoms to the hulls, and along with these more practical advances have come others of a more healthful and artistic trend. The furniture is better; the decoration of the cabins and saloons prettier and more harmonious; there has been more hygienic sanitation. When the _Oceanic_ of the White Star Line was built in 1870 she had a second deck, and this novel feature was adopted broadcast and eventually ushered in the many-deck liners now in use. The _Servia_, built in 1881, was the first steel ship and the advantage of its greater elasticity was instantly seen. Builders were wise enough to grasp the fact that with the increasing length of vessels steel ships would be able to stand a greater strain. Little by little the gain went on in every direction. Nevertheless, in spite of the intelligence of the shipbuilders, it was long before trans-Atlantic navigators had the courage to trust themselves entirely to their engines and discard masts; although they shifted to steel ones instead of those of iron or wood, they still persisted in carrying them." He smiled as he spoke. "When the twin-screw propeller made its appearance it brought with it greater speed and there was a revival of the old racing spirit. Between the various shipping lines of all nations the contest for size and swiftness has raged ever since. Before the Great War, Germany had a very extensive collection of large and rapid liners, many of them built on the Clyde, that fought to surpass the Cunard ships. The White Star Line also took a hand in the game and built others. In the contest, alas, America has been far behind until gradually she has let other countries slip in and usurp the major proportion of ocean commerce. It is a pitiful thing that we should not have applied our skill and wealth of material to building fine American steamship lines of our own instead of letting so many of our tourists turn their patronage to ships of foreign nations. Perhaps if the public were not so eager for novelty, and so constantly in search for the newest, the largest and the fastest boats, we should be content to make our crossings in the older and less gaudy ships, which after all are quite as seaworthy. But we Americans must always have the superlative, and therefore many a steamer has had to be scrapped simply because it had no palm gardens, no swimming pools, no shore luxuries. We have not, however, wholly neglected naval construction for we have many fine steamships, a praiseworthy lot of battleships and cruisers and some very fine submarines. I hope and believe that the time will come when our merchant marine will once again stand at the front as it did in the days of the clipper ships. Our commerce reaches out to every corner of the earth and why should we rely on other countries to transport our goods?" "I suppose there are no pirates now, are there, Mr. Ackerman?" asked Dick, raising his eyes expectantly to the capitalist's face. "I am afraid there are very few, Dick boy," returned the elder man kindly. "I suppose that is somewhat of a disappointment to you. You would have preferred to sail the seas in the days when every small liner carried her guns as a defence against raiders and was often forced to use them, too. But when international law began to regulate traffic on the high seas and the ocean thoroughfare ceased to be such a deserted one pirates went out of fashion, and every nation was granted equal rights to sail the seas unmolested. It was because this freedom was menaced by German submarines in the late war and our privilege to travel by water threatened that our nation refused to tolerate such conditions. A code of humane laws that had been established for the universal good was being broken and we could not permit it. For you must remember that now there are almost as many laws on the ocean as on the land. There are rules for all kinds of vessels, of which there are a far greater variety than perhaps you realize. Not only have we steamships, cruisers, and battleships but we have schooners, barques, brigs, tugboats, dredgers, oil-tankers, turret ships for freight, cargo boats, steam tramps, coalers, produce ships, ice-breakers, train ferries, steam trawlers, fire boats, river boats, harbor excursion boats, coasters, whalebacks, steam yachts, launches and lake steamers. Each of these is carefully classified and has its particular traffic rules, and in addition to these is obliged to obey certain other general marine laws to which all of them are subject, in order that travel by water may be made safe." "Don't all ships have to be inspected, too?" asked Stephen. "Yes; and not only are they inspected but to protect the lives of their passengers and crew, as well as preserve their cargo, they must adhere to specified conditions. The number of passengers and crew is regulated by law, as is the amount of the cargo. Ocean liners, for example, must have aboard a certain number of lifeboats, rafts, belts, life preservers, fire extinguishers, lines of hose; and the size of all these is carefully designated. There must be frequent drills in manning the boats; the fire hose must be tested to see that it works and is in proper condition; and in thick weather the foghorns must be sounded at regular intervals. There is no such thing now as going to sea in haphazard fashion and trusting to luck. Everything that can be done for the safety of those who travel the ocean must be done." He paused a moment, then added: "And in the meanwhile, that every protection possible shall be offered to ships, we have been as busy on the land as on the water and have established a code of laws to govern our coasts, harbors and rivers. Government surveys have charted the shores of all countries so that now there are complete maps that give not only the coast line but also the outlying islands, rocks and shoals that might be a menace to ships. It is no longer possible for a State bordering on the sea to put up a low building at the water's edge and set a few candles in the windows as was done back in the year eighteen hundred." Both the boys laughed. "We can laugh now," assented Mr. Ackerman with a smile, "but in those days I fancy it was no laughing matter. Even with all our up-to-date devices there are wrecks; and think of the ships that must have gone down before charts were available, lighthouses and bell buoys in vogue, wireless signals invented and the coast patrol in operation. I shudder to picture it. Sailing the seas was a perilous undertaking then, I assure you. Even the first devices for safety were primitive. The Argand lamp of 1812 was not at all powerful and the lenses used were far from perfect. Foghorns were operated by hand or by horse power and were not strong enough to be heard at any great distance. Bell buoys were unknown although there were such things as bell-boats which were anchored in dangerous spots and rung by the wash of the waves. There were lightships, too, but more often than not their feeble light was obscured or unnoticed and they were run down by the ships they sought to protect. Altogether there was room for improvement at every point and slowly but surely it came. After the Daboll trumpet, whistle and siren had been tried finer horns operated by steam or power engines supplanted them until now all along our coasts and inland streams signals of specified strength have been installed, a commission deciding just what size signals shall be used and where they shall be placed. There are lighthouses of prescribed candle power; automatic flashlights and whistling buoys; coastguard stations with carefully drilled crews; all regulated by law and matters of compulsion. If men and ships are lost now it is because it is beyond human power to help it." "There are facts about the water that are impossible to modify," interrupted Mr. Tolman, "and I suppose we shall never be able wholly to eliminate the dangers growing out of them. There are for example silence zones where, because of the nature of air currents or atmospheric conditions, no sounds can be heard. Often a foghorn comparatively near at hand will belch forth its warning and its voice be swallowed up in this strange stillness. Many a calamity has occurred that could only be accounted for in this way. Man is ingenious, it is true, but he is not omniscient and in the face of some of the caprices of nature he is powerless." Mr. Ackerman rose and stood with his back to the fire. "And now," went on Mr. Tolman, addressing Stephen and Dick, "I should say you two had had quite a lecture on steamboating and should move that you both go to bed." Quickly Mr. Ackerman interrupted him. "I should amend the motion by suggesting that we all go to bed," laughed he. "I am quite as tired as the boys are." The amendment was passed, the motion carried, and soon the entire Tolman family was wrapped in sleep. CHAPTER XVIII A THANKSGIVING TRAGEDY Perhaps had Stephen known what was in store for him on the morrow he might not have slept so soundly. As it was, he and Dick had to be called three times before they opened their eyes on the Thanksgiving sunshine. A heavy frost had fallen during the night, touching the trees with splendor and transforming the brown earth to a jewelled sweep of gems that flashed like brilliants in the golden light. The boys scrambled into their clothes and, ruddy from a cold shower, descended to the dining room where amid the fragrance of steaming coffee the family were just sitting down to breakfast. "Well, what is up for to-day, boys?" inquired Mrs. Tolman, after the more formal greetings were over. "What are you planning to do with Dick, Stephen?" "We're going skating over to the Hollow if the ice is any good," was the prompt response. "It was fine yesterday and unless somebody has smashed it all up it ought to be good to-day." "That plan sounds rather nice, doesn't it, Jane?" Doris suggested to her roommate. "Why don't we go, too?" "I'd like nothing better," was the answer. "The youngsters have sketched a very alluring program," Mr. Ackerman said. "If I had any skates I should be tempted to join them. I have not been on the ice in years but in my day I used to be quite a hockey player." "Oh, do come, Mr. Ackerman!" cried Steve eagerly. "If you used to skate it will all come back to you. It is like swimming, you know; once you have learned you never forget how." "But I've nothing to skate with," laughed the New Yorker. "Oh, we can fix you up with skates all right, if you really want to go," Mr. Tolman said. "I have a couple of pairs and am sure you could manage to use one of them." "So you are a skater, are you, Tolman?" the capitalist observed, with surprise. "Oh, I am nothing great," Mr. Tolman protested, "but I have always enjoyed sports and muddled along at them. Coventry is quite a distance from Broadway, you see, and therefore we must get our recreation in other ways." "It is a darn sight better than anything New York has to offer," commented the other man soberly. "Good wholesome out-of-door exercise is not to be mentioned in the same breath with a hot theater where a picture show is a makeshift for something better. Give me fresh air and exercise every time!" "Well, since that is the way you feel about it we can comply with your request," Mr. Tolman rejoined, with a smile. "If you do not mind hobbling back to New York lame as a cart-horse you can certainly have your wish, for we have the ice, the skates, plenty of coats and sweaters--everything necessary. Suppose we all start for the Hollow at ten o'clock. It is a mile walk but as we are having a late dinner we shall still have a long morning." "That will suit me all right," returned Mr. Ackerman. "By the way, Henry," interrupted Mrs. Tolman, addressing her husband, "Havens is waiting to see you. He has some message for you." "Where is he?" "In the hall." "Ask Mary to tell him to go into my den. I'll be there in a minute." What a merry party it was that chatted and laughed there in the warmth of the sunny dining room! For the time being the elders dropped their cares and became as young in spirit as the boys and girls. Jokes, stories and good-humored banter passed back and forth until with one accord everybody rose from the table and sauntered into the library where a great blaze of logs glowed and crackled. "If you will excuse me I will see what Havens wants," remarked Mr. Tolman, as he lighted his cigar. "Probably the garage people have unearthed some more repairs that must be made on that car. They seem to have a faculty for that sort of thing. Every day they discover something new the matter with it. I shall have a nice little bill by the time they finish." Shrugging his shoulders, he passed into the hall. It was more than half an hour before he returned and when he did a close observer would have noticed that his face had lost its brightness and that the gaiety with which he took up the conversation with his guests was forced and unnatural. However, he tried resolutely to banish his irritation, whatever its cause. He went up to the attic with Mr. Ackerman, where the two searched out skates, woolen gloves and sweaters; he jested with Doris and Jane Harden; he challenged Dick to a race across the frozen ground. But beneath his lightness lingered a grave depression which betokened to those who knew him best that something was wrong. Yet he was evidently determined the cloud should not obtrude itself and spoil the happiness of the day. Probably some business annoyance that could not be remedied had arisen; or possibly Havens had given notice. Such contingencies were of course to be deplored but as they could not be helped, why let them ruin the entire holiday? Therefore nobody heeded Mr. Tolman's mood which was so well controlled that his guests were unconscious of it, and the group of skaters swung along over the frosty fields with undiminished merriment. The Hollow for which they were bound lay in a deserted stone quarry where a little arm of the river had penetrated the barrier of rocks and, gradually flooding the place, made at one end a deep pool; from this point the water spread itself over the meadows in a large, shallow pond. Had the spot been nearer the town it would doubtless have been overrun with skaters; but as it was isolated, and there was a larger lake near the center of the village, few persons took the trouble to seek out this remote stretch of ice. This morning it lay desolate like a gleaming mirror, not a human being marring its solitude. "We shall have the place all to ourselves!" exclaimed Mr. Ackerman. "There will be no spectators to watch me renew my youth, thank goodness!" Quickly the skates were strapped on and the young people shot out into the sunshine and began to circle about. More cautiously Mr. Tolman and his guest followed. "I wouldn't go into the quarry," shouted Mr. Tolman, "for I doubt if it has been cold enough yet to freeze the ice very solidly there. There are liable to be air holes where the river makes in." "Oh, we fellows have skated in the quarry millions of times, Dad," Stephen protested. "It is perfectly safe." "There is no way of telling whether it is or not," was the response, "so suppose for to-day we keep away from it." "But--" "Oh, don't argue, Stevie," called Doris. "If Dad doesn't want us to go there that's enough, isn't it?" "But half the fun is making that turn around the rocks," grumbled Stephen, in a lower tone. "I don't see why Dad is such a fraid-cat. I know this pond better than he does and--" "If your father says not to skate there that ought to go with you," cut in Dick. "He doesn't want you to--see? Whether it is safe or not has nothing to do with it." "But it's so silly!" went on Stephen. "Why--" "Oh, cut it out! Can it!" ejaculated the East Side lad. "Your dad says _No_ and he's the boss." The ungracious retort Steve offered was lost amid the babel of laughter that followed, and the skaters darted away up the pond. Indeed, one could not long have cherished ill humor amid such radiant surroundings. There was too much sunshine, too much sparkle in the clear air; too much jollity and happiness. Almost before he realized it Stephen's irritation had vanished and he was speeding across the glassy surface of the ice as gay as the gayest of the company. He never could explain afterward just how it happened that he found himself around the bend of the quarry and sweeping with the wind toward its farther end. He had not actually formulated the intention of slipping away from the others and invading this forbidden spot. Nevertheless, there he was alone in the tiny cove with no one in sight. What followed was all over in a moment,--the breaking ice and the plunge into the frigid water. The next he knew he was fighting with all his strength to prevent himself from being drawn beneath the jagged, crumbling edge of the hole. To clamber out was impossible, for every time he tried the thin ice would break afresh under his hands and submerge him again in the bitter cold of the moving stream. Over and over he tried to pull himself to safety but without success. Then suddenly he felt himself becoming numb and helpless. His teeth chattered and he could no longer retain his hold on the frail support that was keeping his head above water. He was slipping back into the river. _He was not going to be able to get out!_ With a piercing scream he made one last desperate lunge forward, and again the ice that held him broke and the water dashed over his ears and mouth. When he next opened his eyes it was to find himself in his own bed with a confusion of faces bending over him. "There!" he heard some one say in a very small, far-away voice. "He is coming to himself now, thank God! It was chiefly cold and fright. He is safe now, Tolman. Don't you worry! You'd better go and get off some of your wet clothing, or you will catch your death." Mr. Ackerman was speaking. "Yes, Henry, do go!" pleaded his wife. [Illustration: He was fighting to prevent himself from being drawn beneath the jagged, crumbling edge of the hole. Page 244.] As Stephen looked about him in the vague, groping uncertainty of returning consciousness his glance fell upon his father who stood beside his pillow, shivering nervously. He put out his hand and touched the dripping coat sleeve. "What--" began he weakly. Then with a rush it all came back to him and everything was clear. He had been drowning and his father had plunged into the water to save him! A sob rose in his throat and he caught the elder man's hand between both of his. "Oh, Dad," he exclaimed, "I've been so rotten to you--so mean--so cowardly. I'm ashamed to--" "Don't talk about it now, son. I know." "You know what I did?" "Yes." "But--" the boy paused bewildered. "Don't talk any more about it now, Stevie," pleaded his mother. "But I've got to know," said the lad. "Can't you see that--" "Let me talk with him alone a moment," suggested Mr. Tolman in an undertone. "He is all upset and he won't calm down until he has this thing off his mind. Leave me here with him a little while. I'll promise that he does not tire himself." The doctor, Mr. Ackerman and Mrs. Tolman moved across the room toward the window. "You asked how I knew, son," began his father with extreme gentleness. "I didn't really know. I just put two and two together. There was the scratched machine and the gasoline gone--both of which facts puzzled me not a little. But the proof that clinched it all and made me certain of what had happened came to me this morning when Havens brought me an old red sweater and some school papers of Bud Taylor's that the men who were overhauling the car found under the seat. In an instant the whole thing was solved." "You knew before we went skating then?" "Yes." "And--and--you jumped into the water after me just the same." Mr. Tolman's voice trembled: "You are my son and I love you no matter what you may do." "Oh, Dad, I'm so sorry!" sobbed the boy. "I wanted to tell you--I meant to. It was just that I was too much of a coward. I was so ashamed of what I had done that I hadn't the nerve. After it was over it all seemed so wrong. I knew you would be angry--" "Rather say _sorry_, son." "Well, sorry. And now that you have been so white to me I'm more ashamed still." "There, there, my boy, we will say no more about it," his father declared. "You and your conscience have probably had a pretty bitter battle and I judge you have not been altogether happy since your adventure. People who do wrong never are. It is no fun to carry your fault to bed with you and find it waiting when you wake up in the morning." "You bet it isn't!" replied the lad, with fervor. "But can't I do something now to make good, Dad?" Mr. Tolman checked an impulsive protest and after a moment responded gravely: "We will see. Perhaps you would like to earn something toward doing over the car." "Yes! Yes! I would!" "Well, all that can be arranged later. We--" "Henry," broke in Mrs. Tolman, "you must go this instant and get into some dry clothes. You are chilled through. The doctor says Stephen is going to be none the worse for his ducking and that he can come down stairs to dinner after he has rested a little longer. So our Thanksgiving party is not to be spoiled, after all. In fact, I believe we shall have more to give thanks for than we expected," concluded she, making an unsteady attempt to speak lightly. "I think so, too," echoed her husband. "And so do I!" added Stephen softly, as he exchanged an affectionate smile with his father. CHAPTER XIX THE END OF THE HOUSE PARTY As they were persons of strong constitution and in good athletic training neither Mr. Tolman nor Steve were any the worse for the narrow escape of the morning, and although a trifle spent with excitement both were able to take their places at the dinner table so that no cloud rested on the festivity of the day. Certainly such a dinner never was,--or if there ever had been one like it in history at least Dick Martin had never had the luck to sit down to it. The soup steaming and hot, the celery white and crisp, the sweet potatoes browned in the oven and gleaming beneath their glaze of sugar, the cranberry sauce vivid as a bowl of rubies; to say nothing of squash, and parsnips and onions! And as for the turkey,--why, it was the size of an ostrich! With what resignation it lay upon its back, with what an abject spirit of surrender,--as if it realized that resistance was futile and that it must docilely offer itself up to make perfect the feast. And the pudding, the golden-tinted pies with their delicate crust, the nuts; the pyramid of fruit, riotous in color; the candies of every imaginable hue and flavor! Was it a wonder that Dick, who had never before beheld a real New England home Thanksgiving, regarded the novelty with eyes as large as saucers and ate until there was not room for another mouthful? "Gee!" he gasped in a whisper to Stephen, as he sank weakly back into his chair when the coffee made its appearance. "This sure is some dinner." The others who chanced to overhear the observation laughed. "Had enough, sonny?" inquired Mr. Tolman. "_Enough!_" There was more laughter. "I suppose were it not for the trains and the ships we should not be having such a meal as this to-day," remarked Mrs. Tolman. "You are right," was Mr. Ackerman's reply. "Let me see! Fruit from Florida, California and probably from Italy; flour from the Middle West; coffee from South America; sugar probably from Cuba; turkey from Rhode Island, no doubt; and vegetables from scattered New England farms. Add to this cigarettes from Egypt and Turkey and you have covered quite a portion of the globe." "It is a pity we do not consider our indebtedness to our neighbors all over the world oftener," commented Mr. Tolman. "We take so much for granted these days. To appreciate our blessings to the full we should have lived in early Colonial times when the arrival of a ship from across the ocean was such an important event that the wares she brought were advertised broadcast. Whenever such a vessel came into port a list of her cargo was issued and purchasers scrambled eagerly to secure the luxuries she carried. Pipes of wine, bolts of cloth, china, silks, tea--all were catalogued. It was no ordinary happening when such a boat docked, I assure you." "I suppose it was a great event," reflected Mrs. Tolman, "although I never half realized it." "And not only was the advent of merchandise a red-letter day but so was the advent of travelers from the other side of the water. Picture if you can the excitement that ensued when Jenny Lind, the famous singer, visited this country! And the fact that we were now to hear this celebrated woman was not the only reason for our interest. She had actually come in a ship from across the sea! Others would come also. America was no longer cut off from the culture of the old world, an isolated country bereft of the advantages of European civilization. We were near enough for distinguished persons to make trips here! Charles Dickens and the Prince of Wales came--and how cosmopolitan we felt to be entertaining guests from the mother-country! Certainly the Atlantic could not be very wide if it could be crossed so easily and if we could have the same speakers, the same readers, the same singers as did the English! Our fathers and grandfathers must have thrilled with satisfaction at the thought. The ocean was conquered and was no longer an estranging barrier." "What would they have said to crossing the water by aeroplane or bobbing up in a foreign port in a submarine?" put in Doris. "And some day I suppose the marvels of our age that cause our mouths to open wide and our eyes to bulge with amazement will become as humdrum as the ocean liner and the Pullman have," Mrs. Tolman remarked. "Yes," returned her husband. "Think of the fight every one of these innovations has had to put up before it battled its way to success. The first locomotives, you remember, were not only rated as unsafe for travel but also actually destructive to property. The major part of the public had no faith in them and predicted they would never be used for general travel. As for crossing the ocean--why, one was welcome to take his life in his hands if he chose, of course; but to cross in an iron ship--it was tempting Providence! Did not iron always sink? And how people ridiculed Darius Green and his flying machine! Most of the prophets were thought to be crazy. History is filled with stories of men who wrecked their worldly fortunes to perpetuate an idea, and but too frequently an idea they never lived to see perfected." During the pause that followed Mr. Ackerman leaned across the table and as he sipped his coffee asked mischievously: "Well, Steve, having now heard both stories, have you come to a conclusion which one you are going to vote for?" "No, sir," was the dubious response. "I'm farther away from a decision than ever. Just as I get it settled in my mind that the railroads have done the biggest things and conquered the most difficulties along come the steamships and I am certain they are six times as wonderful." "And you, Dick--what do you say?" questioned the financier, smiling. "Surely you are going to stand up for the steamboat." But to his chagrin Dick shook his head. "I feel as Steve does," replied he. "No sooner do I get settled one way than something turns me round the other." "So far as I can see we shall have to leave the matter a draw, shan't we, Tolman?" observed the New Yorker. "It would be a jolly subject for a debate, wouldn't it?" put in Stephen. "Sometimes we have discussions like that at school and the next time we do I believe I'll suggest this topic. It would be mighty interesting." "It certainly would," his father echoed. "But it also would be a very sorry event if you could not demonstrate that the railroads had the supremacy for were their prestige to be threatened I might have to move out of town." "In case Connecticut did not want you, you might come to New York where you would be sure of being appreciated," put in Mr. Ackerman. "And that is not all talk, either, for I want you and the whole family to give me a promise to-day that you will come over and join Dick and me at Christmas. I've never had a boy of my own to celebrate the holiday with before, you must remember; but this time I have a real family and I am going to have a real Christmas," he continued, smiling affectionately at the lad beside him. "So I want every one of you to come and help me to make the day a genuine landmark. And if I'm a little new at playing Santa Claus some of you who have been schooled in the rôle for many years can show me how. We can't promise to stage for you such an excitement as Stephen got up for us this morning, and we never can give you a dinner equal to this; but we can give you a royal welcome. You can come by boat or come by train," added he slyly. "No guest who patronizes the railroads will be shut out, even if he is misguided. The chief thing is for you to come, one and all, and we will renew our friendship and once again bless Stephen, Dick, and my lost pocketbook, for bringing us together." FINIS ----------------------------------------------------------------------- The first volume in "The Invention Series" PAUL AND THE PRINTING PRESS By SARA WARE BASSETT With illustrations by A. O. Scott 12mo. Cloth. 218 pages. Paul Cameron, president of the class of 1920 in the Burmingham High School, conceives the idea of establishing a school paper, to the honor and glory of his class. So _The March Hare_ comes into existence, and Paul and his schoolfellows bend all their energies to making it a success. They have their difficulties and Paul in particular bears the brunt of their troubles, but _The March Hare_ lives up to its reputation for life and liveliness and becomes not only a class success, but a town institution. This is the first volume in "The Invention Series." "It is the sort of story that boys of fourteen years and upward will enjoy and ought to enjoy, a combination that is rarely achieved."--Boston Post. "A welcome volume which will appeal to boys who want a good story that will give some information as well."--New York Evening Post. "'Paul and the Printing Press' not only has a keen story interest, but has the advantage of carrying much valuable information for all young folks for whom the mysterious and all-powerful printing press has an attraction."--Boston Herald. LITTLE, BROWN & CO., PUBLISHERS 34 Beacon Street, Boston ----------------------------------------------------------------------- 
39033	----	AN INTRODUCTION TO MACHINE DRAWING AND DESIGN BY DAVID ALLAN LOW (WHITWORTH SCHOLAR), M. INST. M.E. HEAD MASTER OF THE PEOPLE'S PALACE TECHNICAL SCHOOLS, LONDON AUTHOR OF 'A TEXT-BOOK ON PRACTICAL SOLID OR DESCRIPTIVE GEOMETRY' 'AN ELEMENTARY TEXT-BOOK OF APPLIED MECHANICS' ETC. [Illustration] _FOURTH EDITION_ LONDON LONGMANS, GREEN, AND CO. AND NEW YORK: 15 EAST 16th STREET 1890 PRINTED BY SPOTTISWOODE AND CO., NEW-STREET SQUARE LONDON PREFACE. It is now generally recognised that the old-fashioned method of teaching machine drawing is very unsatisfactory. In teaching by this method an undimensioned scale drawing, often of a very elaborate description, is placed before the student, who is required to _copy_ it. Very often the student succeeds in making a good copy of the drawing placed before him without learning very much about the object represented by it, and this state of matters is sometimes not much improved by the presence of the teacher, who is often simply an art master, knowing nothing about machine design. It is related of one school that a pupil, after making a copy of a particular drawing, had a discussion with his teacher as to whether the object represented was a sewing machine or an electrical machine. Evidently the publisher of the drawing example in this case did not adopt the precaution which a backward student used at an examination in machine design: he put on a full title above his drawing, for the information of his examiner. Now, if machine drawing is to be of practical use to any one, he must be able to understand the form and arrangement of the parts of a machine from an inspection of suitable drawings of them without seeing the parts themselves. Also he ought to be able to make suitable drawings of a machine or parts of a machine from the machine or the parts themselves. In producing this work the author has aimed at placing before young engineers and others, who wish to acquire the skill and knowledge necessary for making the simpler _working drawings_ such as are produced in engineers' drawing offices, a number of good exercises in drawing, sufficient for one session's work, and at the same time a corresponding amount of information on the design of machine details generally. The exercises set are of various kinds. In the first and simplest certain views of some machine detail are given, generally drawn to a small scale, which the student is asked to reproduce _to dimensions marked on these views_, and he is expected to keep to these dimensions, and not to measure anything from the given illustrations. In the second kind of exercise the student is asked to reproduce certain views shown _to dimensions given in words or in tabular form_. In the third kind of exercise the student is required to make, in addition to certain views shown to given dimensions, others which he can only draw correctly if he thoroughly understands the design before him. In the fourth kind of exercise the student is asked to make the necessary working drawings for some part of a machine which has been previously described and illustrated, _the dimensions to be calculated by rules given in the text_. The illustrations for this work are all new, and have been specially prepared by the author from _working drawings_, and he believes that they will be found to represent the best modern practice. As exercises in drawing, those given in this book are not numbered exactly in their order of difficulty, but unless on the recommendation of a teacher, the student should take them up in the order given, omitting the following:--26, 27, 28, 35, 40, 42, 43, 45, 49, 50, 54, 60, 61, as he comes to them, until he has been right through the book; afterwards he should work out those which he omitted on first going over the book. In addition to the exercises given in this work the student should practise making freehand sketches of machine details from actual machines or good models of them. Upon these sketches he should put the proper dimensions, got by direct measurement from the machine or model by himself. These sketches should be made in a note-book kept for the purpose, and no opportunity should be lost of inserting a sketch of any design which may be new to the student, always putting on the dimensions if possible. These sketches form excellent examples from which to make working drawings. The student should also note any rules which he may meet with for proportioning machines, taking care, however, in each case to state the source of such information for his future guidance and reference. As machine drawing is simply the application of the principles of descriptive geometry to the representation of machines, the student of the former subject, if he is not already acquainted with the latter, should commence to study it at once. D. A. L. GLASGOW: _March_ 1887. _PREFACE TO THE THIRD EDITION._ To this edition another chapter has been added, containing a number of miscellaneous exercises, which it is hoped will add to the usefulness of the work as a text-book in science classes. The latest examination paper in machine drawing by the Science and Art Department has also been added to the Appendix. D. A. L. LONDON: _August_ 1888. CONTENTS. PAGE I. INTRODUCTION 1 II. RIVETED JOINTS 6 III. SCREWS, BOLTS, AND NUTS 14 IV. KEYS 22 V. SHAFTING 24 VI. SHAFT COUPLINGS 25 VII. BEARINGS FOR SHAFTS 30 VIII. PULLEYS 36 IX. TOOTHED WHEELS 39 X. CRANKS AND CRANKED SHAFTS 43 XI. ECCENTRICS 47 XII. CONNECTING RODS 49 XIII. CROSS-HEADS 56 XIV. PISTONS 57 XV. STUFFING-BOXES 63 XVI. VALVES 68 XVII. MATERIALS USED IN MACHINE CONSTRUCTION 76 XVIII. MISCELLANEOUS EXERCISES 81 APPENDIX A 99 APPENDIX B 102 INDEX 113 AN INTRODUCTION TO MACHINE DRAWING AND DESIGN. I. INTRODUCTION. _Drawing Instruments._--For working the exercises in this book the student should be provided with the following:--A well-seasoned yellow pine _drawing-board_, 24 inches long, 17 inches wide, and 3/8 inch or 1/2 inch thick, provided with cross-bars on the back to give it strength and to prevent warping. A =T= _square_, with a blade 24 inches long attached permanently to the stock, _but not sunk into it_. One 45° and one 60° _set square_. The short edges of the former may be about 6 inches and the short edge of the latter about 5 inches long. A _pair of compasses_ with pen and pencil attachments, and having legs from 5 inches to 6 inches long. A _pair of dividers_, with screw adjustment if possible. A _pair of small steel spring pencil bows_ for drawing small circles, and a _pair of small steel spring pen bows_ for inking in the same. A _drawing pen_ for inking in straight lines. All compasses should have _round points_, and if possible _needle_ points. A piece of india-rubber will also be required, besides two pencils, one marked H or HH and one marked HB or F; the latter to be used for lining in a drawing which is not to be inked in, or for freehand work. Pencils for mechanical drawing should be sharpened with a _chisel point_, and those for freehand work with a _round point_. _Do not wet the pencil_, as the lines afterwards made with it are very difficult to rub out. Drawing-paper for working drawings may be secured to the board by _drawing-pins_, but the paper for finished drawings or drawings upon which there is to be a large amount of colouring should be _stretched_ upon the board. The student should get the best instruments he can afford to buy, and he should rather have a few good instruments than a large box of inferior ones. _Drawing-paper._--The names and sizes of the sheets of drawing paper are given in the following table:-- Inches Demy 20 × 15 Medium 22 × 17 Royal 24 × 19 Imperial 30 × 22 Atlas 34 × 26 Double Elephant 40 × 27 Antiquarian 52 × 31 The above sizes must not be taken as exact. In practice they will be found to vary in some cases as much as an inch. Cartridge-paper is made in sheets of various sizes, and also in rolls. Hand-made paper is the best, but it is expensive. Good cartridge-paper is quite suitable for ordinary drawings. _Centre Lines._--Drawings of most parts of machines will be found to be symmetrical about certain lines called _centre lines_. These lines should be drawn first with great care. On a pencil drawing centre lines should be thin continuous lines; in this book they are shown thus -- - -- - --. After drawing the centre line of any part the dimensions of that part must be marked off from the centre line, so as to insure that it really is the centre line of that part: thus in making a drawing of a rivet, such as is shown at (_a_) fig. 1, after drawing the centre line, half the diameter of the rivet would be marked off on each side of that line, in order to determine the lines for the sides of the rivet. _Inking._--For inking in drawings the best Indian ink should be used, and not common writing ink. Common ink does not dry quick enough, and rapidly corrodes the drawing pens. The pen should be filled by means of a brush or a narrow strip of paper, and not by dipping the pen into the ink. In cases where there are straight lines and arcs of circles touching one another _ink in the arcs first_, then the straight lines; in this way it is easier to hide the joints. _Colouring._--Camel's-hair or sable brushes should be used; the latter are the best, but are much more expensive than the former. The colour should be rubbed down in a dish, and the tint should be light. The mistake which a beginner invariably makes is in having the colour of too dark a tint. First go over the part to be coloured with the brush and _clean_ water for the purpose of damping it. Next dry with clean blotting-paper to take off any superfluous water. Then take another brush with the colour, and beginning at the top, work from left to right and downwards. If it is necessary to recolour any part let the first coating dry before beginning. Engineers have adopted certain colours to represent particular materials; these are given in the following table:-- _Table showing Colours used to represent Different Materials._ MATERIAL COLOUR Cast iron Payne's grey or neutral tint. Wrought iron Prussian blue. Steel Purple (mixture of Prussian blue and crimson lake). Brass Gamboge with a little sienna or a very little red added. Copper A mixture of crimson lake and gamboge, the former colour predominating. Lead Light Indian ink with a very little indigo added. Brickwork Crimson lake and burnt sienna. Firebrick Yellow and Vandyke brown. Greystones Light sepia or pale Indian ink, with a little Prussian blue added. Brown freestone Mixture of pale Indian ink, burnt sienna, and carmine. Soft woods For ground work, pale tint of sienna. Hard woods For ground work, pale tint of sienna with a little red added. For graining woods use darker tint with a greater proportion of red. _Printing._--A good drawing should have its title printed, a plain style of letter being used for this purpose, such as the following:-- [Illustration: ABCDEFGHIJKLMNOPQRST UVWXYZ 1234567890] [Illustration: ABCDEFGHIJKLMNOPQR STUVWXYZ 1234567890] The following letters look well _if they are well made_, but they are much more difficult to draw. [Illustration: ABCDEFGHIJKLMNOP QRSTUVWXYZ 1234567890] For remarks on a drawing the following style is most suitable:-- [Illustration: abcdefghijklmnopqrstuvwxyz] All printing should be done by freehand. _Border lines_ are seldom put on engineering drawings. _Working Drawings._--A good working drawing should be prepared in the following manner. It must first be carefully outlined in pencil and then inked in. After this all parts cut by planes of section should be coloured, the colours used indicating the materials of which the parts are made. Parts which are round may also be lightly shaded with the brush and colours to suit the materials. The centre lines are now inked in with _red_ or _blue ink_. The red ink may be prepared by rubbing down the cake of crimson lake, and the blue ink in like manner from the cake of Prussian blue. Next come the _distance_ or _dimension_ lines, which should be put in with _blue_ or _red ink_, depending on which colour was used for the centre lines. Dimension lines and centre lines are best put in of different colour. The arrow-heads at the ends of the dimension lines are now put in with _black ink_, and so are the figures for the dimensions. The arrow-heads and the figures should be made with a common writing pen. The dimensions should be put on neatly. Many a good drawing has its appearance spoiled through being slovenly dimensioned. We may here point out the importance of putting the dimensions on a working drawing. If the drawing is not dimensioned, the workman must get his sizes from the drawing by applying his rule or a suitable scale. Now this operation takes time, and is very liable to result in error. Time is therefore saved, and the chance of error reduced, by marking the sizes in figures. In practice it is not usual to send original drawings from the drawing office to the workshop, but copies only. The copies may be produced by various 'processes,' or they may be tracings drawn by hand. Many engineers do not ink in their original drawings, but leave them in pencil; especially is this the case if the drawings are not likely to be much used. _Scales._--The best scales are made of ivory, and are twelve inches long. Boxwood scales are much cheaper, although not so durable as those made of ivory. If the student does not care to go to the expense of ivory or boxwood scales, he can get paper ones very cheap, which will be quite sufficient for his purpose. The divisions of the scale should be marked down to its edge, so that measurements may be made by applying the scale directly to the drawing. For working such exercises as are in this book the student should be provided with the following scales:-- A scale of 1, or 12 inches to a foot. " 1/2 " 6 " " 1/3 " 4 " " 1/4 " 3 " " 1/6 " 2 " A scale of 1 is spoken of as 'full size,' and a scale of 1/2 as 'half size.' Engineers in this country state dimensions of machines in feet, inches, and fractions of an inch, the latter being the 1/2, 1/4, 1/8, 1/16, &c. In making calculations it is generally more convenient to use decimal fractions, and then substitute for the results the equivalent fractions in eighths, sixteenths, &c. The following table will be found useful for this purpose:-- _Decimal Equivalents of Fractions of an Inch._ +----------+--------------------+ | Fraction | Decimal Equivalent | +----------+--------------------+ | 1/32 | .03125 | | 1/16 | .0625 | | 3/32 | .09375 | | 1/8 | .125 | | 5/32 | .15625 | | 3/16 | .1875 | | 7/32 | .21875 | | 1/4 | .25 | | 9/32 | .28125 | | 5/16 | .3125 | | 11/32 | .34375 | | 3/8 | .375 | | 13/32 | .40625 | | 7/16 | .4375 | | 15/32 | .46875 | | 1/2 | .5 | | 17/32 | .53125 | | 9/16 | .5625 | | 19/32 | .59375 | | 5/8 | .625 | | 21/32 | .65625 | | 11/16 | .6875 | | 23/32 | .71875 | | 3/4 | .75 | | 25/32 | .78125 | | 13/16 | .8125 | | 27/32 | .84375 | | 7/8 | .875 | | 29/32 | .90625 | | 15/16 | .9375 | | 31/32 | .96875 | | 1 | 1.0 | +----------+--------------------+ Engineers use a single accent (') to denote _feet_, and a double accent (") to denote _inches_. Thus 2' 9" reads two feet nine inches. II. RIVETED JOINTS. Two plates or pieces to be riveted together have holes punched or drilled in them in such a manner that one may be made to overlap the other so that the holes in the one may be opposite the holes in the other. The rivets, which are round bars of iron, or steel, or other metal, are heated to redness and inserted in the holes; the head already formed on the rivet, and called the tail, is then held up, and the point is hammered or pressed so as to form another head. This process of forming the second head on the rivet is known as riveting, and may be done by hand-hammering or by a machine. _Forms of Rivet Heads._--In fig. 1 are shown four different forms of rivet heads: (_a_) is a _snap head_, (_b_) a _conical head_ (_c_) a _pan head_, and (_d_) _a countersunk head_. _Proportions of Rivet Heads._--The diameter of the snap head is about 1.7 times the diameter of the rivet, and its height about .6 of the diameter of the rivet. The conical head has a diameter twice and a height three quarters of the rivet diameter. The greatest diameter of the pan head is about 1.6, and its height .7 of the rivet diameter. The greatest diameter of the countersunk head may be one and a half, and its depth a half of the diameter of the rivet. [Illustration: FIG. 1.] In fig. 1 at (_a_) and (_b_) are shown geometrical constructions devised by the author for drawing the snap and conical head for any size of rivet, the proportions being nearly the same as those given above. _Geometrical Construction for Proportioning Snap Heads._--With centre A, and radius equal to half diameter of rivet, describe a circle cutting the centre line of the rivet at B and C. With centre B and radius BC describe the arc CD. Make BE equal to AD. With centre E and radius ED describe the arc DFH. _Construction for Conical Head._--With centre K, and radius equal to diameter of rivet, describe the semicircle LMN, cutting the side of the rivet at M. With centre M and radius MN describe the arc NP to cut the centre line of rivet at P. Join PL and PN. When a number of rivets of the same diameter have to be shown on the same drawing the above constructions need only be performed on one rivet. After the point E has been discovered the distance AE may be measured off on all the other rivets, and the arcs corresponding to DFH drawn with radii equal to ED. In like manner the height KP of the conical head may be marked off on all rivets of the same diameter with conical heads. _Caulking._--In order to make riveted joints steam- or water-tight the edges of the plates and the edges of the heads of the rivets are burred down by a blunt chisel or caulking tool as shown at Q and R. [Illustration: FIG. 2.] [Illustration: FIG. 3.] EXERCISE 1: _Forms of Rivets._--Draw, full size, the rivets and rivet heads shown in fig. 1. The diameter of the rivet in each case to be 1-1/8 inches, and the thickness of the plates 7/8 inch. EXERCISE 2: _Single Riveted Lap Joint._--Draw, full size, the plan and sectional elevation of the _single riveted lap joint_ shown in fig. 2. _Table showing the Proportions of Single Riveted Lap Joints for various Thicknesses of Plates._ (_Plates and Rivets Wrought Iron._) +--------------+-------------+----------+--------------+ | Thickness of | Diameter of | Pitch of | Width of lap | | plates | rivets | rivets | | +--------------+-------------+----------+--------------+ | 1/4 | 9/16 | 1-5/8 | 1-3/4 | | 5/16 | 5/8 | 1-3/4 | 2 | | 3/8 | 11/16 | 1-7/8 | 2-1/4 | | 7/16 | 3/4 | 2 | 2-1/2 | | 1/2 | 13/16 | 2-1/8 | 2-3/4 | | 9/16 | 7/8 | 2-1/4 | 2-7/8 | | 5/8 | 15/16 | 2-5/16 | 3 | | 11/16 | 1 | 2-3/8 | 3-1/8 | | 3/4 | 1-1/16 | 2-1/2 | 3-1/4 | +------------------------------------------------------+ All the dimensions are in inches. [Illustration: FIG. 4.] EXERCISE 3.--Draw, half size, a plan and section of a single riveted lap joint for plates 3/4" thick to the dimensions given in the above table. EXERCISE 4: _Double Riveted Lap Joint._--Draw, full size, the two views of the _double riveted lap joint_ shown in fig. 3. _Table showing the Proportions of Double Riveted Lap Joints for various Thicknesses of Plates._ (_Plates and Rivets Wrought Iron._) +-----------+-------------+----------+------------------+----------+ | Thickness | Diameter of | Pitch of | Distance between | Width of | | of plates | rivets | rivets | rows of rivets | lap | +-----------+-------------+----------+------------------+----------+ | 3/8 | 11/16 | 2-1/2 | 1-1/8 | 3-1/2 | | 7/16 | 3/4 | 2-5/8 | 1-1/4 | 3-3/4 | | 1/2 | 13/16 | 2-3/4 | 1-3/8 | 4 | | 9/16 | 7/8 | 2-7/8 | 1-7/16 | 4-1/4 | | 5/8 | 15/16 | 3 | 1-9/16 | 4-1/2 | | 11/16 | 1 | 3-1/8 | 1-3/4 | 4-3/4 | | 3/4 | 1-1/16 | 3-1/4 | 1-7/8 | 5 | | 13/16 | 1-1/16 | 3-3/8 | 1-7/8 | 5 | | 7/8 | 1-1/8 | 3-1/2 | 1-15/16 | 5-1/4 | | 15/16 | 1-1/8 | 3-5/8 | 1-15/16 | 5-1/4 | | 1 | 1-3/16 | 3-3/4 | 2 | 5-1/2 | +-----------+-------------+----------+------------------+----------+ [Illustration: FIG. 5.] EXERCISE 5.--Draw, half size, a plan and section of a double riveted lap joint for plates 7/8 inch thick to the dimensions given in the above table. EXERCISE 6: _Single Riveted Butt Joints._--In fig. 4 are shown _single riveted butt joints_. One of the sectional views shows a butt joint with one _cover plate_ or _butt strap_; the other sectional view shows the same joint with two cover plates; the third view is a plan of both arrangements. Draw all these views full size. EXERCISE 7.--Fig. 5 shows a plan and sectional elevation of the connection of three plates together, which are in the same plane, by means of single riveted butt joints and single cover plates. The butt straps where they overlap are forged so as to fit one another as shown, and thus form a close joint. Draw these views to the scale of 6 inches to a foot. The plates are 1/2 inch thick and the butt straps 9/16 inch thick. All other dimensions must be deduced from the table for single riveted lap joints. EXERCISE 8.--The connection of three plates by single riveted lap joints is shown in fig. 6. To make the joint close one plate has a portion of its edge thinned out, and the plate above it is set up at this part so as to lie close to the former. Draw the three views shown in fig. 6 to the same scale as the last exercise. The plates are 7/16 inch thick. All other dimensions to be obtained from table for single riveted lap joints. EXERCISE 9: _Corner of Wrought-iron Tank._--This exercise is to illustrate the connection of plates which are at right angles to one another by means of _angle irons_. Fig. 7 is a plan and elevation of the corner of a wrought-iron tank. The sides of the tank are riveted to a vertical angle iron, the cross section of which is clearly shown in the plan. Another angle iron of the same dimensions is used in the same way to connect the sides with the bottom. The sides do not come quite up to the corner of the vertical angle iron, excepting at the bottom where the horizontal angle iron comes in. At this point the vertical plates meet one another, and the edge formed is rounded over to fit the interior of the bend of the horizontal angle iron so as to make the joint tight. Draw half size. The dimensions are as follows: angle irons 2-1/2 inches × 2-1/2 inches × 3/8 inch; plates 3/8 inch thick; rivets 11/16 inch diameter and 2 inches pitch. EXERCISE 10: _Gusset Stay._--In order that the flat ends of a steam boiler may not be bulged out by the pressure of the steam they are strengthened by means of stays. One form of boiler stay, called a 'gusset stay,' is shown in fig. 8. This stay consists of a strip of wrought-iron plate which passes in a diagonal direction from the flat end of the boiler to the cylindrical shell. One end of this plate is placed between and riveted to two angle irons which are riveted to the shell of the boiler. A similar arrangement connects the other end of the stay plate to the flat end of the boiler. In this example the stay or gusset plate is 3/4 of an inch thick; the angle irons are 4 inches broad and 1/2 inch thick. The rivets are 1 inch in diameter. The same figure also illustrates the most common method of connecting the ends of a boiler to the shell. The end plates are _flanged_ or bent over at right angles and riveted to the shell as shown. The radius of the inside curve at the angle of the flange is 1-1/4 inches. Draw this example to a scale of 3 inches to 1 foot. [Illustration: FIG. 6.] [Illustration: FIG. 7.] [Illustration: FIG. 8.] III. SCREWS, BOLTS, AND NUTS. _Screw Threads._--The various forms of screw threads used in machine construction are shown in fig. 9. The _Whitworth_ =V= thread is shown at (_a_). This is the standard form of triangular thread used in this country. The angle between the sides of the =V= is 55°, and one-sixth of the total depth is rounded off both at the top and bottom. At (_b_) is shown the _Sellers_ =V= thread, which is the standard triangular thread used by engineers in America. In this form of thread the angle between the sides of the =V= is 60°, and one-eighth of the total depth is cut square off at the top and bottom. The _Square_ thread is shown at (_c_). This form is principally used for transmitting motion. [Illustration: FIG. 9.] Comparing the triangular and square threads, the former is the stronger of the two; but owing to the normal pressure on the =V= thread being inclined to the axis of the screw, that pressure must be greater than the pressure which is being transmitted by the screw; and therefore, seeing that the normal pressure on the square thread is parallel, and therefore equal to the pressure transmitted in the direction of the axis of the screw, the friction of the =V= thread must be greater than the friction of the square thread. In the case of the triangular thread there is also a tendency of the pressure to burst the nut. The _Buttress_ thread shown at (_e_) is designed to combine the advantages of the =V= and square threads, but it only has these advantages when the pressure is transmitted in one direction; if the direction of the pressure be reversed, the friction and bursting action on the nut are even greater than with the =V= thread, because of the greater inclination of the slant side of the buttress thread. The angles of the square thread are frequently rounded to a greater or less extent to render them less easily damaged. If this rounding is carried to excess we get the _Knuckle_ thread shown at (_d_). The rounding of the angles increases both the strength and the friction. EXERCISE 11: _Forms of Screw Threads._--Draw to a scale of three times full size the sections of screw threads as shown in fig. 9. The pitch for the Whitworth, Sellers, and buttress threads to be 3/8 inch, and the pitch of the square and knuckle threads to be 1/2 inch. _Dimensions of Whitworth Screws._ +-----------------------------------+ | Diameter | Number | Diameter | | of screw | of threads | at bottom | | | per inch | of thread | +----------+------------+-----------+ | 1/8 | 40 | .093 | | 3/16 | 24 | .134 | | 1/4 | 20 | .186 | | 5/16 | 18 | .241 | | 3/8 | 16 | .295 | | 7/16 | 14 | .346 | | 1/2 | 12 | .393 | | 5/8 | 11 | .508 | | 3/4 | 10 | .622 | | 7/8 | 9 | .733 | | 1 | 8 | .840 | | 1-1/8 | 7 | .942 | | 1-1/4 | 7 | 1.067 | | 1-3/8 | 6 | 1.162 | | 1-1/2 | 6 | 1.286 | | 1-5/8 | 5 | 1.369 | | 1-3/4 | 5 | 1.494 | | 1-7/8 | 4-1/2 | 1.590 | | 2 | 4-1/2 | 1.715 | | 2-1/4 | 4 | 1.930 | | 2-1/2 | 4 | 2.180 | | 2-3/4 | 3-1/2 | 2.384 | | 3 | 3-1/2 | 2.634 | | 3-1/4 | 3-1/4 | 2.856 | | 3-1/2 | 3-1/4 | 3.106 | | 3-3/4 | 3 | 3.323 | | 4 | 3 | 3.573 | | 4-1/4 | 2-7/8 | 3.805 | | 4-1/2 | 2-7/8 | 4.055 | | 4-3/4 | 2-3/4 | 4.284 | | 5 | 2-3/4 | 4.534 | | 5-1/4 | 2-5/8 | 4.762 | | 5-1/2 | 2-5/8 | 5.012 | | 5-3/4 | 2-1/2 | 5.238 | | 6 | 2-1/2 | 5.488 | +-----------------------------------+ _Gas Threads_[1] (_Whitworth Standard_). [1] Used for wrought-iron and brass tubes. +-------------------------------------------------------------+ | Diameter of Screw | 1/8 | 1/4 | 3/8 | 1/2 | 5/8 | 3/4 | 1 | +-------------------+-----+-----+-----+-----+-----+-----+------ | Number of threads | | | | | | | | | per inch | 28 | 19 | 19 | 14 | 14 | 14 | 11 | +-------------------------------------------------------------+ +-------------------------------------------------+ | Diameter of Screw | 1-1/4 | 1-1/2 | 1-3/4 | 2 | +-------------------+-------+-------+-------+-----+ | Number of threads | | | | | | per inch | 11 | 11 | 11 | 11 | +-------------------------------------------------+ _Representation of Screws._--The correct method of representing screw threads involves considerable trouble, and is seldom adopted by engineers for working drawings. For an explanation of the method see the author's Text-book on Practical Solid Geometry, Part II., problem 134. A method very often adopted on working drawings is shown in fig. 15; here the thin lines represent the points, and the thick lines the roots of the threads. At fig. 16 is shown a more complete method. The simplest method is illustrated by figs. 10, 11, 13, and 14. Here dotted lines are drawn parallel to the axis of the screw as far as it extends, and at a distance from one another equal to the diameter of the screw at the bottom of the thread. [Illustration: FIG. 10.] [Illustration: FIG. 11.] _Forms of Nuts._--The most common form of nut is the hexagonal shown in figs. 10, 13, 14, 15, and 16; next to this comes the square nut shown in fig. 11. The method of drawing these nuts will be understood by reference to the figures; the small circles indicate the centres, and the inclined lines passing through them the radii of the curves which represent the chamfered or bevelled edge of the nut. In all the figures but the first the chamfer is just sufficient to touch the middle points of the sides, and in these cases the drawing of the nut is simpler. [Illustration: FIG. 12.] [Illustration: FIG. 13.] [Illustration: FIG. 14.] _Forms of Bolts._--At (_a_), fig. 12, is shown a bolt with a square head and a square neck. If this form of bolt is passed through a square hole the square neck prevents the bolt from turning when the nut is being screwed up. Instead of a square neck a snug may be used for the same purpose, as shown on the cup-headed bolt at (_b_). The snug fits into a short groove cut in the side of the hole through which the bolt passes. At (_a_) the diagonal lines are used to distinguish the flat side of the neck from the round part of the bolt above it. At (_c_) is shown a tee-headed bolt, and at (_d_) an eye-bolt. Fig. 13 represents a hook bolt. A bolt with a countersunk head is shown in fig. 11. If the countersunk head be lengthened so as to take up the whole of the unscrewed part of the bolt, we get the taper bolt shown in fig. 14, which is often used in the couplings of the screw shafts of steamships. The taper bolt has the advantage of having no projecting head, and it may also be made a tight fit in the hole with less trouble than a parallel bolt. Bolts may also have hexagonal heads. [Illustration: FIG. 15] [Illustration: FIG. 16] _Studs_, or _stud bolts_, are shown in figs. 15 and 16; that in fig. 15 is a _plain stud_, while that in fig. 16 has an intermediate collar forged upon it, and is therefore called a _collared stud_. _Proportions of Nuts and Bolt-heads._--In the hexagonal nut the diameter D across the flats is 1-1/2_d_ + 1/8, where _d_ is the diameter of the bolt. The same rule gives the width of a square nut across the flats. A rule very commonly used in making drawings of hexagonal nuts is to make the diameter D, across the angles equal to 2_d_. H, the height of the nut, is equal to the diameter of the bolt. In square and hexagonal headed bolts the height of the head varies from _d_ to 2/3_d_; the other dimensions are the same as for the corresponding nuts. _Washers_ are flat, circular, wrought-iron plates, having holes in their centres of the same diameter as the bolts on which they are used. The object of the washer is to give a smooth bearing surface for the nut to turn upon, and it is used when the surfaces of the pieces to be connected are rough, or when the bolt passes through a hole larger than itself, as shown in fig. 10. The diameter of the washer is a little more than the diameter of the nut across the angles, and its thickness about 1/8 of the diameter of the bolt. EXERCISE 12.--Draw, full size, the views shown in fig. 10 of an hexagonal nut and washer for a bolt 1-1/4 inches in diameter. The bolt passes through a hole 1-3/4 × 1-1/4. All the dimensions are to be calculated from the rules which have just been given. EXERCISE 13.--Draw, full size, the plan and elevation of the square nut and bolt with countersunk head shown in fig. 11, to the dimensions given. EXERCISE 14.--Draw, full size, the elevation of the hook bolt with hexagonal nut shown in fig. 13 to the dimensions given, and show also a plan. EXERCISE 15.--Draw, to a scale of 4 inches to a foot, the conical bolt for a marine shaft coupling shown in fig. 14. All the parts are of wrought iron. EXERCISE 16.--Fig. 15 is a section of the mouth of a small steam-engine cylinder, showing how the cover is attached; draw this full size. EXERCISE 17.--Fig. 16 shows the central portion of the india-rubber disc valve which is described on page 68. A is the central boss of the grating, into which is screwed the stud B, upon which is forged the collar C. The upper part of the stud is screwed, and carries the guard D and an hexagonal nut E. F is the india-rubber. The grating and guard are of brass. The stud and nut are of wrought iron. Draw full size the view shown. _Lock Nuts._--In order that a nut may turn freely upon a bolt, there is always a very small clearance space between the threads of the nut and those of the bolt. This clearance is shown exaggerated at (_a_), fig. 17, where A is a portion of a bolt within a nut B. Suppose that the bolt is stretched by a force W. When the nut B is screwed up, the upper surfaces of the projecting threads of the nut will press on the under surfaces of the threads of the bolt with a force P equal and opposite to W, as shown at (_b_), fig. 17. When in this condition the nut has no tendency to slacken back, because of the friction due to the pressure on the nut. Now suppose that the tension W on the bolt is momentarily diminished, then the friction which opposes the turning of the nut may be so much diminished that a vibration may cause it to slacken back through a small angle. If this is repeated a great many times the nut may slacken back so far as to become useless. [Illustration: FIG. 17.] [Illustration: FIG. 18.] A very common arrangement for locking a nut is shown at (_a_), fig. 18. C is an ordinary nut, and B one having half the thickness of C. B is first screwed up tight so as to act on the bolt, as shown at (_b_), fig. 17. C is then screwed on top of B. When C is almost as tight as it can be made, it is held by one spanner, while B is turned back through a small angle with another. The action of the nuts upon the bolt and upon one another is now as shown at (_b_), fig. 18. It will be seen that the nuts are wedged tight on to the bolt, and that this action is independent of the tension W in the bolt. The nuts will, therefore, remain tight after the tension in the bolt is removed. It is evident that if the nuts are screwed up in the manner explained, the outer nut C will carry the whole load on the bolt; hence C should be the thicker of the two nuts. In practice, the thin nut, called the lock nut, is often placed on the outside, for the reason that ordinary spanners are too thick to act on the thin nut when placed under the other. Another very common arrangement for locking a nut is shown in fig. 19. A is the bolt and B the nut, the lower part of which is turned circular. A groove C is also turned on the nut at this part. The circular part of the nut fits into a circular recess in one of the parts connected by the bolt. Through this part passes a set screw D, the point of which can be made to press on the nut at the bottom of the groove C. D is turned back when the nut B is being moved, and when B is tightened up, the set screw is screwed up so as to press hard on the bottom of the groove C. The nut B is thus prevented from slackening back. The screw thread is turned off the set screw at the point where it enters the groove on the nut. [Illustration: FIG. 19] The use of the groove for receiving the point of the set screw is this: The point of the set screw indents the nut and raises a bur which would interfere with the free turning of the nut in the recess if the bur was not at the bottom of a groove. Additional security is obtained by drilling a hole through the point of the bolt, and fitting it with a split pin E. Locking arrangements for nuts are exceedingly numerous, and many of them are very ingenious, but want of space prevents us describing them. We may point out, however, that many very good locking arrangements have the defect of only locking the nut at certain points of a revolution, say at every 30°. It will be noticed that the two arrangements which we have described are not open to this objection. EXERCISE 18.--Draw, full size, a plan, front elevation, and side elevation of the arrangement of nuts shown in fig. 18, for a bolt 7/8 inch diameter. EXERCISE 19.--Draw the plan and elevation of the nut and locking arrangement shown in fig. 19. Make also an elevation looking in the direction of the arrow. Scale 6 inches to a foot. IV. KEYS. _Keys_ are wedges, generally rectangular in section, but sometimes circular; they are made of wrought iron or steel, and are used for securing wheels, pulleys, cranks, &c., to shafts. [Illustration: Fig. 20.] Various sections of keys are shown in fig. 20. At (_a_) is the _hollow_ or _saddle key_. With this form of key it is not necessary to cut the shaft in any way, but its holding power is small, and it is therefore only used for light work. At (_b_) is the _key on a flat_, sometimes called a _flat key_. The holding power of this key is much greater than that of the saddle key. At (_c_) is the _sunk key_, a very secure and very common form. The part of the shaft upon which a key rests is called the _key bed_ or _key way_, and the recess in the boss of the wheel or pulley into which the key fits is called the _key way_; both are also called _key seats_. With saddle, flat, and sunk keys the key bed is parallel to the axis of the shaft; but the key way is deeper at one end than the other to accommodate the taper of the key. The sides of the key are parallel. The _round key_ or taper pin shown at (_d_) is in general only used for wheels or cranks which have been previously shrunk on to their shafts or forced on by great pressure. After the wheel or crank has been shrunk on, a hole is drilled, half into the shaft and half into the wheel or crank, to receive the pin. When the point of a key is inaccessible the other end is provided with a _gib head_ as shown at (_e_), to enable the key to be withdrawn. A _sliding_ or _feather key_ secures a piece to a shaft so far as to prevent the one from rotating without the other, but allows of relative motion in the direction of the axis of the shaft. This form of key has no taper, and it is secured to the piece carried by the shaft, but is made a _sliding fit_ in the key way of the shaft. In one form of feather key the part within the piece carried by the shaft is dovetailed as shown at (_f_). In another form the key has a round projecting pin forged upon it, which enters a corresponding hole as shown at (_g_). The feather key may also be secured to the piece carried by the shaft by means of one or more screws as shown at (_h_). The key way in the shaft is made long enough to permit of the necessary sliding motion. _Cone Keys._--These are sometimes fitted to pulleys, and are shown in fig. 32, page 38. In this case the eye of the pulley is tapered and is larger than the shaft. The space between the shaft and the boss of the pulley is filled with three _saddle_ or _cone keys_. These keys are made of cast iron and are all cast together, and before being divided the casting is bored to fit the shaft and turned to fit the eye of the pulley. By this arrangement of keys the same pulley may be fixed on shafts of different diameters by using keys of different thicknesses; also the pulley may be bored out large enough to pass over any boss which may be forged on the shaft. _Proportions of Keys._--The following rules are taken from Unwin's 'Machine Design,' pp. 142-43. Diameter of eye of wheel, or boss of shaft = _d_. Width of key = 3/4_d_ + 1/8. Mean thickness of sunk key = 1/8_d_ + 1/8. " key on flat = 1/16_d_ + 1/16. The following table gives dimensions agreeing with average practice. _Dimensions of Keys._ D = diameter of shaft. B = breadth of key. T = thickness of sunk key. T_{1} = thickness of flat key, also = thickness of saddle key. Taper of key 1/8 inch per foot of length, _i.e._ 1 in 96. +---------------------------------------------------------------+ | D | 3/4 | 1 | 1-1/4 | 1-1/2 | 1-3/4 | 2 | 2-1/4 | 2-1/2 | +-----+-----+-----+-------+-------+-------+-----+-------+-------+ | B | 5/16| 3/8 | 7/16 | 1/2 | 9/16 | 5/8 | 11/16 | 11/16 | | T | 1/4 | 1/4 | 1/4 | 5/16 | 5/16 | 5/16| 3/8 | 3/8 | |T_{1}| 3/16| 3/16| 3/16 | 3/16 | 1/4 | 1/4 | 1/4 | 5/16 | +---------------------------------------------------------------+ +-------------------------------------------------------------------+ | D | 2-3/4 | 3 | 3-1/2 | 4 | 4-1/2 | 5 | 5-1/2 | 6 | +-----+-------+-----+-------+-------+-------+-------+-------+-------+ | B | 3/4 | 7/8 | 1 | 1-1/8 | 1-1/4 | 1-3/8 | 1-1/2 | 1-5/8 | | T | 3/8 | 7/16| 1/2 | 1/2 | 9/16 | 5/8 | 11/16 | 3/4 | |T_{1}| 5/16 | 5/16| 3/8 | 7/16 | 1/2 | 1/2 | 9/16 | 5/8 | +-------------------------------------------------------------------+ +-------------------------------------------------------+ | D | 7 | 8 | 9 | 10 | 11 | 12 | +-----+-------+-------+-------+--------+--------+-------+ | B | 1-7/8 | 2-1/8 | 2-3/8 | 2-5/8 | 2-7/8 | 3-1/8 | | T | 13/16 | 15/16 | 1 | 1-1/16 | 1-3/16 | 1-1/4 | |T_{1}| 11/16 | 3/4 | 7/8 | 15/16 | 1-1/16 | 1-1/8 | +-------------------------------------------------------+ V. SHAFTING. Shafting is nearly always cylindrical and made of wrought iron or steel. Cast iron is rarely used for shafting. _Axles_ are shafts which are subjected to bending without twisting. The parts of a shaft or axle which rest upon the bearings or supports are called _journals_, _pivots_, or _collars_. In journals the supporting pressure is at right angles to the axis of the shaft, while in pivots and collars the pressure is parallel to that axis. Shafts may be solid or hollow. Hollow shafts are stronger than solid shafts for the same weight of material. Thus a hollow shaft having an external diameter of 10-1/4 inches and an internal diameter of 7 inches would have about the same weight as a solid shaft of the same material 7-1/2 inches in diameter, but the former would have about double the strength of the latter. Hollow shafts are also stiffer and yield less to bending action than solid shafts, which in some cases, as in propeller shafts, is an objection. VI. SHAFT COUPLINGS. For convenience of making and handling, shafts used for transmitting power are generally made in lengths not exceeding 30 feet. These lengths are connected by couplings, of which we give several examples. [Illustration: FIGS. 21 and 22.] _Solid_, _Box_, or _Muff Couplings._--One form of box coupling is shown in fig. 21. Here the ends of the shafts to be connected butt against one another, meeting at the centre of the box, which is made of cast iron. The shafts are made to rotate as one by being secured to the box by two wrought-iron or steel keys, both driven from the same end of the box. A clearance space is left between the head of the forward key and the point of the hind one, to facilitate the driving of them out, as then only one key needs to be started at a time. Sometimes a single key the whole length of the box is used, in which case it is necessary that the key ways in the shafts be of exactly the same depth. The half-lap coupling, introduced by Sir William Fairbairn, is shown in fig. 22. In this form of box coupling the ends of the shafts overlap within the box. It is evident that one shaft cannot rotate without the other as long as the box remains over the lap. To keep the box in its place it is fitted with a saddle key. It will be noticed that the lap joint is sloped in such a way as to prevent the two lengths of shaft from being pulled asunder by forces acting in the direction of their length. Half-lap couplings are not used for shafts above 5 inches in diameter. It may here be pointed out that the half-lap coupling is expensive to make, and is now not much used. As shafts are weakened by cutting key ways in them, very often the ends which carry couplings are enlarged in diameter, as shown in fig. 21, by an amount equal to the thickness of the key. An objection to this enlargement is that wheels and pulleys require either that their bosses be bored out large enough to pass over it, or that they be split into halves, which are bolted together after being placed on the shaft. _Dimensions of Box Couplings._ D = diameter of shaft. T = thickness of metal in box. L = length of box for butt coupling. L_{1} = length of box for lap coupling. _l_ = length of lap. D_{1} = diameter of shaft at lap. +---------------------------------------------------------------+ | D | 1-1/2 | 2 | 2-1/2 | 3 | 3-1/2 | 4 | +-------+--------+--------+---------+-------+----------+--------+ | T | 1-1/8 | 1-5/16 | 1-1/2 | 1-3/4 | 1-15/16 | 2-1/8 | | L | 5-3/4 | 7 | 8-1/4 | 9-1/2 | 10-3/4 | 12 | | L_{1} | 4-1/8 | 5-1/4 | 6-3/8 | 7-1/2 | 8-5/8 | 9-3/4 | | _l_ | 1-7/16 | 1-7/8 | 2-5/16 | 2-3/4 | 3-3/16 | 3-5/8 | | D_{2} | 2-5/16 | 3 | 3-11/16 | 4-3/8 | 5-1/16 | 5-3/4 | +---------------------------------------------------------------+ +----------------------------------------------+ | D | 4-1/2 | 5 | 5-1/2 | 6 | +-------+---------+--------+--------+----------+ | T | 2-5/16 | 2-1/2 | 2-3/4 | 2-15/16 | | L | 13-1/4 | 14-1/2 | 15-3/4 | 17 | | L_{1} | 10-7/8 | 12 | -- | -- | | _l_ | 4-1/16 | 4-1/2 | -- | -- | | D_{2} | 6-7/16 | 7-1/8 | -- | -- | +----------------------------------------------+ Slope of lap 1 in 12. EXERCISE 20: _Solid Butt Coupling._--From the above table of dimensions make a longitudinal and a transverse section of a solid butt coupling for a shaft 2-1/2 inches in diameter. Scale 6 inches to a foot. EXERCISE 21: _Fairbairn's Half-Lap Coupling._--Make the same views as in the last exercise of a half-lap coupling for a 3-inch shaft to the dimensions in the above table. Scale 6 inches to a foot. _Flange Couplings._--The form of coupling used for the shafts of marine engines is shown in fig. 23. The ends of the different lengths of shaft have flanges forged on them, which are turned along with the shaft. These flanges butt against one another, and are connected by bolts. These bolts may be parallel or tapered; generally they are tapered. A parallel bolt must have a head, but a tapered bolt will act without one. In fig. 23 the bolts are tapered, and also provided with heads. In fig. 14, page 17, is shown a tapered bolt without a head. The variation of diameter in tapered bolts is 3/8 of an inch per foot of length. [Illustration: FIG. 23.] Sometimes a projection is formed on the centre of one flange which fits into a corresponding recess in the centre of the other, for the purpose of ensuring the shafts being in line. Occasionally a cross-key is fitted in between the flanges, being sunk half into each, for the purpose of diminishing the shearing action on the bolts. EXERCISE 22: _Marine Coupling._--Draw the elevation and section of the coupling shown in fig. 23; also an elevation looking in the direction of the arrow. Scale 3 inches to a foot. The following table gives the dimensions of a few marine couplings taken from actual practice. _Examples of Marine Couplings._ +--------------------------------------------------------------------+ | Diameter of shaft |2-3/8 | 9-3/4 | 12-7/8 |16-1/2 | 22-1/2 | 23 | +--------------------+------+-------+--------+-------+--------+------+ |Diameter of flange | 6 | 19 | 24 | 32 | 35 | 38 | |Thickness of flange | 1 | 2-3/4 | 3-1/8 | 4-1/4 | 6 | 5 | |Diameter of bolts | 3/4 | 2-3/4 | 2-11/16| 3-1/2 | 4-1/4 | 4-1/4| |Number of bolts | 3 | 6 | 6 | 8 | 9 | 8 | |Diameter of bolt | | | | | | | | circle |4-1/8 | 14-1/8|18-13/16| 25 | 28-3/4 |30-3/8| +--------------------------------------------------------------------+ All the above dimensions are in inches. EXERCISE 23.--Select one of the couplings from the above table, and make the necessary working drawings for it to a suitable scale. The cast-iron flange coupling is shown in fig. 24. In this kind of coupling a cast-iron centre or boss provided with a flange is secured to the end of each shaft by a sunk key driven from the face of the flange. These flanges are then connected by bolts and nuts as in the marine coupling. To ensure the shafts being in line the end of one projects into the flange of the other. In order that the face of each flange may be exactly perpendicular to the axis of the shaft they should be 'faced' in the lathe, after being keyed on to the shaft. If the coupling is in an exposed position, where the nuts and bolt-heads would be liable to catch the clothes of workmen or an idle driving band which might come in the way, the flanges should be made thicker, and be provided with recesses for the nuts and bolt-heads. [Illustration: FIG. 24.] _Dimensions of Cast-iron Flange Couplings._ +--------------------------------------------------------------------+ | |Diameter| | |Depth | |Diameter|Diameter| |Diameter| of |Thickness|Diameter| at |Number| of | of bolt| |of shaft| flange |of flange| of boss| boss | of | bolts | circle | | D | F | T | B | L | bolts| d | C | +--------|--------|---------|--------|------|------|--------|--------+ | 1-1/2 | 7-1/4 | 7/8 | 3-1/2 |2-5/8 | 3 |5/8 | 5-1/2 | | 2 | 8-7/8 | 1-1/16 | 4-3/8 |3-3/16| 4 | 3/4| 6-3/4 | | 2-1/2 | 10-5/8 | 1-1/4 | 5-5/16 |3-3/4 | 4 |7/8 | 8-1/8 | | 3 | 12-3/8 | 1-7/16 | 6-1/4 |4-5/16| 4 | 1 | 9-1/2 | | 3-1/2 | 13-1/8 | 1-5/8 | 7-1/8 |4-7/8 | 4 | 1 |10-5/16 | | 4 | 14 | 1-3/4 | 8 |5-7/16| 6 | 1 |11-1/4 | | 4-1/2 | 15-5/8 | 2 | 8-7/8 |6 | 6 |1-1/8 |12-1/2 | | 5 | 17-3/8 | 2-1/8 | 9-13/16|6-5/8 | 6 | 1-1/4|13-13/16| | 5-1/2 | 18-1/4 | 2-5/16 |10-3/4 |7-1/4 | 6 |1-1/4 |14-3/4 | | 6 | 19-7/8 | 2-1/2 |11-5/8 |7-3/4 | 6 | 1-3/8| 16 | +--------------------------------------------------------------------+ The projection of the shaft _p_ varies from 1/4 inch in the small shafts to 1/2 inch in the large ones. EXERCISE 24: _Cast-iron Flange Coupling._--Draw the views shown in fig. 24 of a cast-iron flange coupling, for a shaft 4-1/2 inches in diameter, to the dimensions given in the above table. Scale 4 inches to a foot. VII. BEARINGS FOR SHAFTS. An example of a very simple form of bearing is shown in fig. 25, which represents a brake shaft carrier of a locomotive tender. The bearing in this example is made of cast iron and in one piece. Through the oval-shaped flange two bolts pass for attaching the bearing to the wrought-iron framing of the tender. With this form of bearing there is no adjustment for wear, so that when it becomes worn it must be renewed. [Illustration: FIG. 25.] EXERCISE 25: _Brake Shaft Carrier._--Draw the elevation and sectional plan of the bearing shown in fig. 25. Draw also a vertical section through the axis. The latter view to be projected from the first elevation. Scale 6 inches to a foot. _Pillow Block_, _Plummer Block_, or _Pedestal_.--The ordinary form of plummer block is represented in fig. 26. A is the block proper, B the sole through which pass the holding-down bolts. C is the cap. Between the block and the cap is the brass bush, which is in halves, called _brasses_ or _steps_. The bed for the steps in this example is cylindrical, and is prepared by the easy process of boring. The steps are not supported throughout their whole length, but at their ends only where fitting strips are provided as shown. As the wear on a step is generally greatest at the bottom, it is made thicker there than at the sides, except where the fitting strips come in. To prevent the steps turning within the block they are generally furnished with lugs, which enter corresponding recesses in the block and cover. [Illustration: FIG. 26] In the block illustrated the journal is lubricated by a _needle lubricator_; this consists of an inverted glass bottle fitted with a wood stopper, through a hole in which passes a piece of wire, which has one end in the oil within the bottle, and the other resting on the journal of the shaft. The wire or needle does not fill the hole in the stopper, but if the needle is kept from vibrating the oil does not escape owing to capillary attraction. When, however, the shaft rotates, the needle begins to vibrate, and the oil runs down slowly on to the journal; oil is therefore only used when the shaft is running. EXERCISE 26: _Pillow Block for a Four-inch Shaft._--Draw the views shown of this block in fig. 26. Make also separate drawings, full size, of one of the steps. Scale 6 inches to a foot. _Proportions of Pillow Blocks._--The following rules may be used for proportioning pillow blocks for shafts up to 8 inches diameter. It should be remembered that the proportions used by different makers vary considerably, but the following rules represent average practice. Diameter of journal = _d_. Length of journal = _l_. Height to centre = 1.05_d_ + .5. Length of base = 3.6_d_ + 5. Width of base = .8_l_. " block = .7_l_. Thickness of base = .3_d_ + .3. " cap = .3_d_ + .4. Diameter of bolts = .25_d_ + .25. Distance between centres of cap bolts = 1.6_d_ + 1.5. " " base bolts = 2.7_d_ + 4.2. Thickness of step at bottom = _t_ = .09_d_ + .15. " " sides = 3/4 _t_. The length of the journal varies very much in different cases, and depends upon the speed of the shaft, the load which it carries, the workmanship of the journal and bearing, and the method of lubrication. For ordinary shafting one rule is to make _l_ = _d_ + 1. Some makers use the rule _l_ = 1.5_d_; others make _l_ = 2_d_. EXERCISE 27: _Design for Pillow Block._--Make the necessary working drawings for a pillow block for a shaft 5 inches in diameter, and having a journal 7 inches long. [Illustration: FIG. 27.] _Brackets._--When a pillow block has to be fixed to a wall or column a bracket such as that shown in figs. 27 and 28 may be used. The pillow block rests between the _joggles_ A A, and is bolted down to the bracket and secured in addition with keys at the ends of the base of the block, in the same manner as is shown, for the attachment of the bracket to the column. EXERCISE 28: _Pillar Bracket._--Fig. 27 shows a side elevation and part horizontal section, and fig. 28 shows an end elevation of a pillar bracket for carrying a pillow block for a 3-inch shaft. Draw these views _properly projected from one another_, showing the pillow block, which is to be proportioned by the rules given on page 32. Draw also a plan of the whole. Scale 4 inches to a foot. [Illustration: FIG. 28.] _Hangers._--When a shaft is suspended from a ceiling it is carried by hangers, one form of which is shown in fig. 29, and which will be readily understood. The cap of the bearing, it will be noticed, is secured by means of a bolt, and also by a square key. EXERCISE 29: _Shaft Hanger._--Draw the two elevations shown in fig. 29, and also a sectional plan. The section to be taken at a point 5 inches above the centre of the shaft. Scale 6 inches to a foot. _Wall Boxes._--In passing from one part of a building to another a shaft may have to pass through a wall. In that case a neat appearance is given to the opening and a suitable support obtained for a pillow block by building into the wall a _wall box_, one form of which is shown in fig. 30. EXERCISE 30: _Wall Box._--Draw the views of the wall box shown in fig. 30, and also a sectional plan; the plane of section to pass through the box a little above the joggles for the pillow block. Scale 3 inches to a foot. [Illustration: FIG. 29.] [Illustration: FIG. 30.] VIII. PULLEYS. _Velocity Ratio in Belt Gearing._--Let two pulleys A and B be connected by a belt, and let their diameters be D_{1} and D_{2}; and let their speeds, in revolutions per minute, be N_{1} and N_{2} respectively. If there is no slipping, the speeds of the rims of the pulleys will be the same as that of the belt, and will therefore be equal. Now the speed of the rim of A is evidently = D_{1} × 3.1416 × N_{1}; while the speed of the rim of B is = D_{2} × 3.1416 × N_{2}. Hence D_{1} × 3.1416 × N_{1} = D_{2} × 3.1416 × N_{2}, and therefore N_{1} D_{2} ----- = -----. N_{2} D_{1} _Pulleys for Flat Bands._--In cross section the rim of a pulley for carrying a flat band is generally curved as shown in figs. 31 and 32, but very often the cross section is straight. The curved cross section of the rim tends to keep the band from coming off as long as the pulley is rotating. Sometimes the rim of the pulley is provided with flanges which keep the band from falling off. Pulleys are generally made entirely of cast iron, but a great many pulleys are now made in which the centre or nave only is of cast iron, the arms being of wrought iron cast into the nave, while the rim is of wrought sheet iron. The arms of pulleys when made of wrought iron are invariably straight, but when made of cast iron they are very often curved. In fig. 31, which shows an arrangement of two cast-iron pulleys, the arms are straight; while in fig. 32, which shows another cast-iron pulley, the arms are curved. Through unequal cooling, and therefore unequal contraction of a cast-iron, pulley in the mould, the arms are generally in a state of tension or compression; and if the arms are straight they are very unyielding, so that the result of this initial stress is often the breaking of an arm, or of the rim where it joins an arm. With the curved arm, however, its shape permits it to yield, and thus cause a diminution of the stress due to unequal contraction. The cross section of the arms of cast-iron pulleys is generally elliptical. [Illustration: Fig. 31.] EXERCISE 31: _Fast and Loose Pulleys_.--Fig. 31 shows an arrangement of fast and loose pulleys. A is the fast pulley, secured to the shaft C by a sunk key; B is the loose pulley, which turns freely upon the shaft. The loose pulley is prevented from coming off by a collar D, which is secured to the shaft by a tapered pin as shown. The nave or boss of the loose pulley is here fitted with a brass liner, which may be renewed when it becomes too much worn. Draw the elevations shown, completing the left-hand one. Scale 6 inches to a foot. By the above arrangement of pulleys a machine may be stopped or set in motion at pleasure. When the driving band is on the loose pulley the machine is at rest, and when it is on the fast pulley the machine is in motion. The driving band is shifted from the one pulley to the other by pressing on that side of the band which is advancing towards the pulleys. [Illustration: FIG. 32.] EXERCISE 32: _Cast-iron Pulley with Curved Arms and Cone Keys_.--Draw a complete side elevation and a complete cross section of the pulley represented in fig. 32 to a scale of 3 inches to a foot. In drawing the side elevation of the arms first draw the centre lines as shown; next draw three circles for each arm, one at each end and one in the middle; the centres of these circles being on the centre line of the arm, and their diameters equal to the widths of the arm at the ends and at the middle respectively. Arcs of circles are then drawn to touch these three circles. The centres and radii of these arcs may be found by trial. The cone keys for securing the pulley to the shaft were described on p. 23. _Pulleys for Ropes_.--Ropes made of hemp are now extensively used for transmitting power. These ropes vary in diameter from 1 inch to 2 inches, and are run at a speed of about 4,500 feet per minute. The pulleys for these ropes are made of cast iron, and have their rims grooved as shown in fig. 33, which is a cross section of the rim of a pulley carrying three ropes. The angle of the V is usually 45°, and the rope rests on the sides of the groove, and not on the bottom, so that it is wedged in, and has therefore a good hold of the pulley. The diameter of the pulley should not be less than 30 times the diameter of the rope. Two pulleys connected by ropes should not be less than thirty feet apart from centre to centre, but this distance may be as much as 100 feet. [Illustration: FIG. 33.] EXERCISE 33: _Section of Rim of Rope Pulley._--Draw, half size, the section of the rim of a rope pulley shown in fig. 33. IX. TOOTHED WHEELS. _Pitch Surfaces of Spur Wheels._--Let two smooth rollers be placed in contact with their axes parallel, and let one of them rotate about its axis; then if there is no slipping the other roller will rotate in the opposite direction with the same surface velocity; and if D_{1}, D_{2} be the diameters of the rollers, and N_{1}, N_{2} their speeds in revolutions per minute, it follows as in belt gearing that-- N_{1} D_{2} ----- = -----. N_{2} D_{1} If there be considerable resistance to the motion of the follower slipping may take place, and it may stop. To prevent this the rollers may be provided with teeth; then they become _spur wheels_; and if the teeth be so shaped that the ratio of the speeds of the toothed rollers at any instant is the same as that of the smooth rollers, the surfaces of the latter are called the _pitch surfaces_ of the former. _Pitch Circle._--A section of the pitch surface of a toothed wheel by a plane perpendicular to its axis is a circle, and is called a _pitch circle_. We may also say that the pitch circle is the edge of the pitch surface. The pitch circle is generally traced on the side of a toothed wheel, and is rather nearer the points of the teeth than the roots. _Pitch of Teeth._--The distance from the centre of one tooth to the centre of the next, or from the front of one to the front of the next, _measured at the pitch circle_, is called the _pitch of the teeth_. If D be the diameter of the pitch circle of a wheel, _n_ the number of teeth, and _p_ the pitch of the teeth, then D × 3.1416 = _n_ × _p_. [Illustration: FIG. 34.] By the diameter of a wheel is meant the diameter of its pitch circle. _Form and Proportions of Teeth._--The ordinary form of wheel teeth is shown in fig. 34. The curves of the teeth should be cycloidal curves, although they are generally drawn in as arcs of circles. It does not fall within the scope of this work to discuss the correct forms of wheel teeth. The student will find the theory of the teeth of wheels clearly and fully explained in Goodeve's 'Elements of Mechanism,' and in Unwin's 'Machine Design.' The following proportions for the teeth of ordinary toothed wheels may be taken as representing average practice:-- Pitch of teeth = _p_ = arc _a b c_ (fig. 34). Thickness of tooth = _b c_ = .48_p_. Width of space = _a b_ = .52_p_. Total height of tooth = _h_ = .7_p_. Height of tooth above pitch line = _k_ = .3_p_. Depth of tooth below pitch line = _l_ = .4_p_. Width of tooth = 2_p_ to 3_p_. EXERCISE 34: _Spur Wheel._--Fig. 35 shows the elevation and sectional plan of a portion of a cast-iron spur wheel. The diameter of the pitch circle is 23-7/8 inches, and the pitch of the teeth is 1-1/2 inches, so that there will be 50 teeth in the wheel. The wheel has six arms. Draw a complete elevation of the wheel and a half sectional plan, also a half-plan without any section. Draw also a cross section of one arm. Scale 4 inches to a foot. [Illustration: FIG. 35.] _Mortise Wheels._--When two wheels gearing together run at a high speed the teeth of one are made of wood. These teeth, or cogs, as they are generally called, have tenons formed on them, which fit into mortises in the rim of the wheel. This wheel with the wooden teeth is called a _mortise wheel_. An example of a mortise wheel is shown in fig. 36. [Illustration: FIG. 36.] _Bevil Wheels._--In bevil wheels the pitch surfaces are parts of cones. Bevil wheels are used to connect shafts which are inclined to one another, whereas spur wheels are used to connect parallel shafts. In fig. 36 is shown a pair of bevil wheels in gear, one of them being a mortise wheel. At (_a_) is a separate drawing, to a smaller scale, of the pitch cones. The pitch cones are shown on the drawing of the complete wheels by dotted lines. The diameters of bevil wheels are the diameters of the bases of their pitch cones. EXERCISE 35: _Pair of Bevil Wheels._--Draw the sectional elevation of the bevil wheels shown in gear in fig. 36. Commence by drawing the centre lines of the shafts, which in this example are at right angles to one another; then draw the pitch cones shown by dotted lines. Next put in the teeth which come into the plane of the section, then complete the sections of the wheels. The pinion or smaller wheel has 25 teeth, and the wheel has 50 teeth, which makes the pitch a little over 3 inches. Each tooth of the mortise wheel is secured as shown by an iron pin 5/16 inch diameter. Scale 3 inches to a foot. X. CRANKS AND CRANKED SHAFTS. The most important application of the crank is in the steam-engine, where the reciprocating rectilineal motion of the piston is converted into the rotary motion of the crank-shaft by means of the crank and connecting rod. At one time steam-engine cranks were largely made of cast iron, now they are always made of wrought iron or steel. The crank is either forged in one piece with the shaft, or it is made separately and then keyed to it. _Overhung Crank._--Fig. 37 shows a wrought-iron overhung crank. A is the crank-shaft, B the crank arm, provided at one end with a boss C, which is bored out to fit the shaft; at the other end of the crank arm is a boss D, which is bored out to receive the crank-pin E, which works in one end of the connecting rod. The crank is secured to the shaft by the sunk key F. It is also good practice to _shrink_ the crank on to the shaft. The process of shrinking consists of boring out the crank a little smaller than the shaft, and then heating it, which causes it to expand sufficiently to go on to the shaft. As the crank cools, it shrinks and grips the shaft firmly. The crank may also be shrunk on to the crank-pin, the latter being then riveted over as shown in fig. 37. [Illustration: FIG. 37.] A good plan to adopt in preference to the shrinking process is to force the parts together by hydraulic pressure. This method is adopted for placing locomotive wheels on their axles, and for putting in crank-pins. As to the amount of pressure to be used, the practice is to allow a force of 10 tons for every inch of diameter of the pin, axle, or shaft. Instead of being riveted in, the crank pin may be prolonged and screwed, and fitted with a nut. Another plan is to put a cotter through the crank and the crank-pin. The distance from the centre of the crank-shaft to the centre of the crank-pin is called the radius of the crank. The _throw_ of the crank is twice the radius. In a direct-acting engine the throw of the crank is equal to the stroke of the piston. EXERCISE 36: _Wrought-iron Overhung Crank._--Draw the two elevations shown in fig. 37, also a plan. Scale 1-1/2 inches to a foot. _Proportions of Overhung Cranks._ D = diameter of shaft. _d_ = " crank-pin. Length of large boss = .9 D. Diameter " = 1.8 D. Length of small boss = 1.1 _d_. Diameter " = 1.8 _d_. Width of crank arm at centre of shaft = 1.3 D. " " crank-pin = 1.5 _d_. The thickness of the crank arm may be roughly taken as = .7 D. EXERCISE 37.--Design a wrought-iron crank for an engine having a stroke of 4 feet. The crank-shaft is 9 inches in diameter, and the crank-pin is 4-3/4 inches in diameter and 6-1/2 inches long. [Illustration: FIG. 38.] _Locomotive Cranked Axle._--As an example of a cranked shaft we take the cranked axle for a locomotive with inside cylinders shown in fig. 38; here the crank and shaft or axle are forged in one piece. A is the wheel seat, B the journal, C the crank-pin, and D and E the crank arms. Only one half of the axle is shown in fig. 38, but the other half is exactly the same. The cranks on the two halves are, however, at right angles to one another. The ends of the crank arms are turned in the lathe, the crank-pin ends being turned at the same time as the axle, and the other ends at the same time as the crank-pin. This consideration determines the centres for the arcs shown in the end view. EXERCISE 38.--Draw to a scale of 2 inches to a foot the side and end elevations of the locomotive cranked axle partly shown in fig. 38. The distance between the centre lines of the cylinders is 2 feet. [Illustration: FIG. 39.] _Built-up Cranks._--The form of cranked shaft shown in fig. 38 is largely used for marine engines, but for the very powerful engines now fitted in large ships this design of shaft is very unreliable, the built-up crank shown in fig. 39 being preferred, although it is much heavier than the other. It will be seen from the figure that the shaft, crank arms, and crank-pin are made separately. The arms are shrunk on to the pin and the shaft, and secured to the latter by sunk keys. These heavy shafts and cranks are generally made of steel. EXERCISE 39.--Keeping to the dimensions marked in fig. 39, draw the views there shown of a built-up crank-shaft for a marine engine. Scale 3/4 inch to a foot. XI. ECCENTRICS. The _eccentric_ is a particular form of crank, being a crank in which the crank-pin is large enough to embrace the crank-shaft. In the eccentric what corresponds to the crank-pin is called the sheave or pulley. The advantage which an eccentric possesses over a crank is that the shaft does not require to be divided at the point where the eccentric is put on. The crank, however, has this advantage over the eccentric, namely, that it can be used for converting circular into reciprocating motion, or _vice versâ_, while the eccentric can only be used for converting circular into reciprocating motion. This is owing to the great leverage at which the friction of the eccentric acts. The chief application of the eccentric is in the steam-engine, where it is used for working the valve gear. To permit of the sheave being placed on the shaft without going over the end (which could not be done at all in the case of a cranked axle, and would be a troublesome operation in most cases) it is generally made in two pieces, as shown in fig. 40, which represents one of the eccentrics of a locomotive. The two parts of the sheave are connected by two cotter bolts. The part which embraces the sheave is called the eccentric strap, and corresponds to, and is, in fact, a connecting rod end: the rod proceeding from this is called the eccentric rod. The distance from the centre of the sheave to the centre of the shaft is called the _radius_ or _eccentricity_ of the eccentric. The _throw_ is twice the eccentricity. The sheave is generally made of cast iron. The strap may be of brass, cast iron, or wrought iron; when the strap is made of wrought iron it is commonly lined with brass. [Illustration: FIG. 40.] EXERCISE 40: _Locomotive Eccentric._--In fig. 40 D E is the sheave, F H the strap, and K the eccentric rod. The sheave and strap are made of cast iron, and the eccentric rod is made of wrought iron. (_a_) is a vertical cross section through the oil-box of the strap; (_b_) is a plan of the end of the eccentric rod and part of the strap. All the nuts are locked by means of cotters. Draw first the elevation, partly in section as shown. Next draw two end elevations, one looking each way. Afterwards draw a horizontal section through the centre, and also a plan. Scale 4 inches to a foot. XII. CONNECTING RODS. The most familiar example of the use of a connecting rod is in the steam-engine, where it is used to connect the rotating crank with the reciprocating piston. The rod itself is made of wrought iron or steel, and is generally circular or rectangular in section. The ends of the rod are fitted with steps, which are held together in a variety of ways. _Strap End._--A form of connecting rod end, which is not so common as it used to be, is shown in fig. 41. At (_a_) is shown a longitudinal section with all the parts put together, while at (_b_), (_c_), _(d)_ and (_e_) the details are shown separately. A B is the end of the rod which butts against the brass bush C D, which is in two pieces. A _strap_ E passes round the bush and on to the end of the rod as shown. The arms of the strap have rectangular holes in them, which are not quite opposite a similar hole in the rod when the parts are put together. If a wedge or _cotter_ F be driven into these three holes they will tend to come into line, and the parts of the bush will be pressed together. To prevent the cotter opening out the strap, and to increase the sliding surface, a _gib_ H is introduced. The gib is provided with horns at its ends to keep it in its place. Sometimes two gibs are used, one on each side of the cotter; this makes the sliding surface on both sides of the cotter the same. The cotter is secured by a set screw K. The unsectioned portion of fig. (_a_) to the right of the gib, or to the left of the cotter, is called the _clearance_ or _draught._ [Illustration: FIG. 41.] EXERCISE 41: _Connecting Rod End._--Make the following views of the connecting rod end illustrated by fig. 41. First, a vertical section, the same as shown at (_a_). Second, a horizontal section. Third, side elevation. Fourth, a plan. Or the first and third views may be combined in a half vertical section and half elevation; and the second and fourth views may be combined in a half horizontal section and half plan. All the dimensions are to be taken from the detail drawings (_b_), (_c_), (_d_), and (_e_), _but the details need not be drawn separately_. The brass bush is shown at (_d_) by half elevation, half vertical section, half plan, and half horizontal section. The draught or clearance is 7-16ths of an inch. _Box End._--At (_a_), fig. 42, is shown what is known as a box end for a connecting rod. The part which corresponds to the loose strap in the last example is here forged in one piece with the connecting rod. In this form the brass bush is provided with a flange all round on one side, but on the opposite side the flange is omitted except at one end; this is to allow of the bush being placed within the end of the rod. The construction of the bush will be understood by reference to the sketch shown at (_b_). The bush is in two parts, which are pressed tightly together by means of a cotter. This cotter is prevented from slackening back by two set screws. Each set screw is cut off square at the point, and presses on the flat bottom of a very shallow groove cut on the side of the cotter. The top, bottom, and ends of this box end are turned in the lathe at the same time as the rod itself; this accounts for the curved sections of these parts. It is clear from the construction of a box end that it is only suitable for an overhung crank. EXERCISE 42: _Locomotive Connecting Rod._--In fig. 42 is shown a connecting rod for an outside cylinder locomotive. (_a_) is the crank-pin end, and (_c_) the cross-head end. The end (_a_) has just been described under the head 'box end.' We may just add that in this particular example the brass bush is lined with white metal as shown, and that the construction of the oil-box is the same as that on the coupling rod end shown in fig. 44. The end (_c_) is forked, and through the prongs of the fork passes the cross-head pin, of which a separate dimensioned drawing is shown at (_d_). Observe that the tapered parts A and B of this pin are parts of the same cone. The rotation of the pin is prevented by a small key as shown. The cross-head pin need not be drawn separately, and the isometric projection of the bush at (_b_) may be omitted, but all the other views shown are to be drawn to a scale of 6 inches to a foot. _Marine Connecting Rod._--The form of connecting rod shown in fig. 43 is that used in marine engines, but it is also used extensively in land engines. A B is the crank-pin end, and C the cross-head end. The end A B is forged in one piece, and after it is turned, planed, and bored it is slotted across, so as to cut off the cap A. The parts A and B are held together by two bolts as shown. This end of the rod is fitted with brass steps, which are lined with white metal. The cross-head end is forked, and through the prongs of the fork passes a pin D, which also passes through the cross-head, which is forged on to the piston rod or attached to it in some other way. [Illustration: FIG. 42.] [Illustration: FIG. 43.] EXERCISE 43: _Marine Connecting Rod._--Draw all the views shown in fig. 43 of one form of marine connecting rod. For detail drawings of the locking arrangement for the nuts see fig. 19, page 21. Scale 4 inches to a foot. _Coupling Rods._--A rod used to transmit the motion of one crank to another is called a _coupling rod_. A familiar example of the use of coupling rods will be found in the locomotive. Coupling rods are made of wrought iron or steel, and are generally of rectangular section. The ends are now generally made solid and lined with solid brass bushes, _without any adjustment for wear_. This form of coupling rod end is found to answer very well in locomotive practice where the workmanship and arrangements for lubrication are excellent. When the brass bush becomes worn it is replaced by a new one. Fig. 44 shows an example of a locomotive coupling rod end for an outside cylinder engine. In this case it is desirable to have the crank-pin bearings for the coupling rods as short as possible, for a connecting rod and coupling rod in this kind of engine work side by side on the same crank-pin, which, being overhung, should be as short as convenient for the sake of strength. The requisite bearing surface is obtained by having a pin of large diameter. The brass bush is prevented from rotating by means of the square key shown. The oil-box is cut out of the solid, and has a wrought-iron cover slightly dovetailed at the edges. This cover fits into a check round the top inner edge of the box, which is originally parallel, but is made to close on the dovetailed edges of the cover by riveting. A hole in the centre of this cover, which gives access to the oil-box, is fitted with a screwed brass plug. The brass plug has a screwed hole in the centre, through which oil may be introduced to the box. Dust is kept out of the oil-box by screwing into the hole in the brass plug a common cork. The oil is carried slowly but regularly from the oil-box over to the bearing by a piece of cotton wick. [Illustration: FIG. 44.] EXERCISE 44: _Coupling Rod End._--Draw first the side elevation and plan, each partly in section as shown in fig. 44. Then instead of the view to the left, which is an end elevation partly in section, draw a complete end elevation looking to the right, and also a complete vertical cross section through the centre of the bearing. Scale 6 inches to a foot. XIII. CROSS-HEADS. An example of a steam-engine cross-head is shown in fig. 45. A is the end of the piston rod which has forged upon it the cross-head B. The cross-head pin shown at (_d_), fig. 42, and to which the connecting rod is attached, works in the bearing C. Projecting pieces D, forged on the top and bottom of the cross-head, carry the slide blocks E which work on the slide bars, and thus guide the motion of the piston rod. [Illustration: FIG. 45.] EXERCISE 45: _Locomotive Cross-head._--In fig. 45 are shown side and end elevations, partly in section, of the cross-head and slide blocks for an outside cylinder locomotive. Draw these views half size, showing also on the end elevation the cross-head pin and a vertical section of the connecting rod end from fig. 42. The bush in the cross-head which forms the bearing for the cross-head pin is of wrought iron, case-hardened, and is prevented from rotating by the key shown. The cross-head is of wrought iron, and the slide blocks are of cast iron, and are fitted with white metal strips as shown. A short brass tube leads oil from the upper slide block into a hole in the cross-head as shown, which carries it to a slot in the bush which distributes it over the cross-head pin. XIV. PISTONS. A _piston_ is generally a cylindrical piece which slides backwards and forwards inside a hollow cylinder. The piston may be moved by the action of fluid pressure upon it as in a steam-engine, or it may be used to give motion to a fluid as in a pump. A piston is usually attached to a rod, called a _piston rod_, which passes through the end of the cylinder inside which the piston works, and which serves to transmit the motion of the piston to some piece outside the cylinder, or _vice versâ_. [Illustration: FIG. 46.] A _plunger_ is a piston made in one piece with its piston rod, the piston and the rod being of the same diameter. A piston which is provided with one or more valves which allow the fluid to pass through it from one side to the other is called a _bucket_. _Simple Piston._--The simplest form of piston is a plain cylinder fitting accurately another, inside which it moves. Such a piston works with very little friction, but as there is no adjustment for wear, such a piston is not suitable for a high fluid pressure if it has to work constantly. This simple form of piston is used in the steam-engine indicator, and also in pumps. Fig. 46 shows the piston of the circulation pump of a marine engine. A is the cast-iron casing or barrel of the pump; B is a brass liner fitting tightly into the former at its ends, and secured by eight screwed Muntz metal pins C, four at each end; D is the piston, which is made of brass, and is attached to a Muntz metal piston rod E. The liner is bored out smooth and true from end to end, and the piston is turned so as to be a sliding fit to the liner. The wear in this form of piston is diminished by making the rubbing surface large. EXERCISE 46: _Piston for Circulating Pump._--Draw the vertical sectional elevation of the piston, &c., shown in fig. 46, also a half plan and half horizontal section through the centre. Scale 4 inches to a foot. _Pump Bucket._--The next form of piston which we illustrate is shown in fig. 47. This represents the air-pump bucket of a marine engine. The bucket is made of brass, and is provided with six india-rubber disc valves. The rod is in this case made of Muntz metal. Air-pump rods for marine engines are very often made of wrought iron cased with brass. It will be observed that there is a wide groove around the bucket, which is filled with hempen rope or gasket. This gasket forms an elastic packing which prevents leakage. This is an old-fashioned form of packing, and is now only used for pump buckets. [Illustration: FIG. 47.] EXERCISE 47: _Air-pump Bucket._--Draw the sectional elevation of the air-pump bucket shown in fig. 47. Also draw a half plan looking downwards and a half plan looking upwards. Scale 4 inches to a foot. _Ramsbottom's Packing._--The form of packing used in the air-pump bucket, fig. 47, is not suitable for steam pistons. For the latter the packing is now always metallic. The simplest form of metallic packing is that known as Ramsbottom's. This form is very largely used for locomotive pistons, and for small pistons in many kinds of engines besides. A locomotive piston for an 18-inch cylinder with Ramsbottom's packing is shown in fig. 48. The particular piston there illustrated is made of brass, and is secured to a wrought-iron piston rod by a brass nut. Two circumferential grooves of rectangular section are turned out of the piston, and into these fit two corresponding rings, which may be of brass, cast iron, or steel. In this example the rings are of cast iron. These rings are first turned a little larger in diameter than the bore of the cylinder (in this example 1/2 inch), and then sprung over the piston into the groves prepared for them. Their own elasticity causes the rings to press outwards on the cylinder. At the point where a ring is split a leakage of steam will take place, but with quick-running pistons this leakage is unimportant. The points where the rings are cut should be placed diametrically opposite, so as to diminish the leakage of steam. [Illustration: FIG. 48.] EXERCISE 48: _Locomotive Piston._--A part elevation and part section of a locomotive piston, for a cylinder having a bore 18 inches in diameter, is shown in fig. 48. Draw this, and also a view looking on the nut in the direction of the axis of the piston rod. Scale 6 inches to a foot. _Note._--The reason why the part of the piston rod within the piston has such a quick taper is that the piston has to be taken off the rod while it is in the cylinder. The cross-head being forged on the end of the piston rod prevents the piston and piston rod being withdrawn together. _Large Pistons._--Pistons of large diameter are generally provided with two cast-iron packing rings placed within the same groove. These rings are pressed outwards against the cylinder, and also against the sides of the groove by one or more springs. One form of this packing (Lancaster's) is shown in fig. 49. Here one spring only is used, and it is first made a straight spiral spring, and then bent round and its ends united. The action of the spring will be clearly understood from the illustration. For the purpose of admitting the packing rings the piston is divided into two parts, one the piston proper, and the other the _junk ring_. In fig. 49, A is the junk ring, which is secured to the piston by means of bolts as shown. [Illustration: FIG. 49.] EXERCISE 49: _Marine Engine Piston._--The piston illustrated by fig. 49 is for the high-pressure cylinder of a marine engine. The piston, junk ring, and packing rings are of cast iron. The piston rod and nut are of wrought iron, so also are the junk ring bolts. The nuts for the latter are of brass. The spiral spring is made from steel wire 3/8 inch diameter. An enlarged section of one of the packing rings is shown at (_a_). A front elevation of the locking arrangement for the piston rod nut is shown at (_b_). A sectional plan of one of the nuts for the junk ring bolts is shown at (_c_). First draw the vertical section of this piston, next draw a plan, one-third of which is to show the piston complete, one-third to show the junk ring removed, and the remaining third to be a horizontal section through between the packing rings. The details (_a_) and (_c_) need not be drawn separately. Scale 3 inches to a foot. _Proportions of Marine Engine Pistons._--Mr. Seaton, in his 'Manual of Marine Engineering,' gives the following rules for designing marine engine pistons:-- D = diameter of piston in inches. _p_ = effective pressure in lbs. per square inch. _x_ = D/50 × [sqrt (_p_)] + 1. Thickness of front of piston near boss 0.2 × _x_. " " " rim 0.17 × _x_. " back of piston 0.18 × _x_. " boss around rod 0.3 × _x_. " flange inside packing ring 0.23 × _x_. " " at edge 0.25 × _x_. " junk ring at edge 0.23 × _x_. " " inside packing ring. 0.21 × _x_. " " at bolt-holes 0.35 × _x_. " metal around piston edge 0.25 × _x_. Breadth of packing ring 0.63 × _x_. Depth of piston at centre 1.4 × _x_. Lap of junk ring on piston 0.45 × _x_. Space between piston body and packing ring 0.3 × _x_. Diameter of junk-ring bolts 0.1 × _x_ + .25 inch. Pitch of junk-ring bolts 10 diameters. Number of webs in piston (D + 20)/12. Thickness " 0.18 × _x_. EXERCISE 50: _Design for Marine Engine Piston._--Calculate by Seaton's rules the dimensions for a marine engine piston 40 inches in diameter, and subjected to an effective pressure of 36 lbs. per square inch. Then make the necessary working drawings for this piston to a scale of, say, 3 inches to a foot. _Note._--Take the dimensions got by calculation to the nearest 1-16th of an inch. XV. STUFFING-BOXES. [Illustration: FIG. 50.] In fig. 50 is shown a gland and stuffing-box for the piston rod of a vertical engine. A B is the piston rod, C D a portion of the cylinder cover, and E F the _stuffing-box_. Fitting into the bottom of the stuffing-box is a brass bush H. The space K around the rod A B is filled with _packing_, of which there is a variety of kinds, the simplest being greased hempen rope. The packing is compressed by screwing down the cast-iron gland L M, which is lined with a brass bush N. In this case the gland is screwed down by means of three stud-bolts P, which are screwed into a flange cast on the stuffing-box. Surrounding the rod on the top of the gland there is a recess R for holding the lubricant. [Illustration: FIG. 51.] [Illustration: FIG. 52.] The object of the gland and stuffing-box is to allow the piston rod to move backwards and forwards freely without any leakage of steam. Fig. 51 shows a gland and stuffing-box for a horizontal rod. The essential difference between this example and the last is in the mode of lubrication. The gland flange has cast within it an oil-box which is covered by a lid; this lid is kept shut or open by the action of a small spring as shown. A piece of cotton wick (not shown in the figure) has one end trailing in the oil in the oil-box, while the other is carried over and passed down the hole A B. The wick acts as a siphon, and drops the oil gradually on to the rod. In this example only two bolts are used for screwing in the gland; and the flanges of the gland and stuffing-box are not circular, but oval-shaped. In the case of small rods the gland is made entirely of brass, and no liner is then necessary. Fig. 52 shows a form of gland and stuffing-box sometimes used for small rods. The stuffing-box is screwed externally, and carries a nut A B which moves the gland. EXERCISE 51: _Gland and Stuffing-box for a Vertical Rod._--Draw the views shown in fig. 50 to the dimensions given. Scale 6 inches to a foot. EXERCISE 52: _Gland and Stuffing-box for a Horizontal Rod._--Fig. 51 shows a plan, half in section, and an elevation half of which is a section through the gland flange. Draw these to a scale of 6 inches to a foot, using the dimensions marked in the figure. EXERCISE 53: _Screwed Gland and Stuffing-box._--Draw, full size, the views shown in fig. 52 to the given dimensions. A more elaborate form of gland and stuffing-box is shown in fig. 53. This is for a large marine engine with inverted cylinders, such as is used on board large ocean steamers. The stuffing-box is cast separate from the cylinder cover to which it is afterwards bolted. The lubricant is first introduced to the oil-boxes marked A, from which it passes to the recess B, where it comes in contact with the piston rod. To prevent the lubricant from being wasted by running down the rod, the main gland is provided with a shallow gland and stuffing-box which is filled with soft cotton packing, which soaks up the lubricant. The main gland is screwed up by means of six bolts, and to prevent the gland from locking itself in the stuffing-box, it is necessary that the nuts should be turned together. This is done in a simple and ingenious manner. One-half of each nut is provided with teeth, and these gear with a toothed wheel which has a rim only; this rim is held up by a ring C. When one nut is turned, all the rest follow in the same direction. [Illustration: FIG. 53.] EXERCISE 54: _Gland and Stuffing-box for Piston Rod of Large Inverted Cylinder Engine._--The lower view in fig. 53 is a half plan looking upwards, and a half section of the gland looking downwards. The upper view is a vertical section. Complete all these views and add an elevation. Scale 3 inches to a foot. _Note._--The large nuts, the wheel, the supporting ring, and small gland are made of brass. _Dimensions of Stuffing-boxes and Glands._ _d_ = diameter of rod. _t__{1} = thickness of _d__{1} = diameter of box (inside). stuffing-box flange. _l_ = length of stuffing-box _t__{2} = thickness of gland bush. flange. _l__{1} = length of packing space. _t__{3} = thickness of bushes in _l__{2} = length of gland. box and gland. _t_ = thickness of metal in _d__{2} = diameter of gland bolts. stuffing-box. _n_ = number of bolts. +----------------------------------------------------------+ | _d_ | _d__{1} | _l_ | _l__{1} | _l__{2} | _t_ | _t__{1} | +-----+---------+-----+---------+---------+------+---------+ |1 | 1-3/4 | 3/4| 2 | 1-1/2 | 7/16| 1/2 | |1-1/2| 2-1/2 |1-1/4| 2-5/8 | 2 | 9/16| 11/16 | |2 | 3-1/2 |1-3/4| 3-1/4 | 2-1/2 | 11/16| 7/8 | |2-1/2| 4-1/8 |2-1/4| 3-7/8 | 2-7/8 | 13/16| 1-1/16 | |3 | 4-3/4 |2-3/4| 4-1/2 | 3-1/4 | 15/16| 1-1/4 | |3-1/2| 5-1/4 | 3 | 5-1/8 | 3-5/8 |1 | 1-3/8 | |4 | 5-7/8 |3-1/4| 5-3/4 | 4 |1 | 1-3/8 | |4-1/2| 6-3/8 |3-1/2| 6-3/8 | 4-3/8 |1-1/16| 1-9/16 | |5 | 7 |3-3/4| 7 | 4-5/8 |1-1/16| 1-9/16 | |6 | 8 |4-1/4| 8-1/4 | 5 |1-1/8 | 1-11/16 | +----------------------------------------------------------+ +-------------------------------------------------+ | _d_ | _t__{2} | _t__{3} | _d__{2} | _n_ | +-----+-----------------+---------+---------+-----+ |1 | _t__{2}=_t_ | 3/16 | 7/16 | 2 | |1-1/2| when gland | 1/4 | 5/8 | 2 | |2 | flange is | 5/16 | 3/4 | 2 | |2-1/2| made of cast | 5/16 | 7/8 | 2 | |3 | iron and | 3/8 | 1 | 2 | |3-1/2| _t__{2}=_t__{1} | 3/8 | 1 | 2 | |4 | when gland | 7/16 | 1 | 2 | |4-1/2| flange is | 7/16 | 7/8 | 4 | |5 | made of | 7/16 | 1 | 4 | |6 | brass. | 1/2 | 1-1/4 | 4 | +-------------------------------------------------+ The proportions of glands and stuffing-boxes vary considerably but the above table represents average practice. EXERCISE 55:--Make the necessary working drawings for a gland and stuffing-box for a locomotive engine piston rod 2-1/2 inches in diameter, to the dimensions given in the table. XVI. VALVES. Professor Unwin divides valves, according to their construction into three classes as follows:--(1) flap valves, which bond or turn upon a hinge; (2) lift valves, which rise perpendicularly to the seat; (3) sliding valves, which move parallel to the seat. Examples of flap valves are shown in figs. 54 and 55; two forms of lift valves are shown in figs. 56 and 57, and in figs. 58 and 59 are shown two forms of slide valve. The slide valve shown in fig. 58 moves in a straight line, while that shown in fig. 59 (called a cock) moves in circle. _India-rubber Valves._--In india-rubber valves there is a grating covered by a piece of india-rubber, which may be rectangular, but is generally circular, and which is held down along one edge if rectangular, or at the centre if circular. Water or other fluid can pass freely upwards through the grating, but when it attempts to return the elasticity of the india-rubber, and the pressure of the water upon it, cause it to lie close on the grating, and thus prevent the return of the water. The india-rubber is prevented from rising too high by a perforated guard. In fig. 54 is shown an example of an india-rubber disc valve. A is the grating, B the india-rubber, C the guard secured to the grating or seat by the stud D and nut E. The grating is held in position by bolts and nuts F. The grating and guard are generally of brass. India-rubber disc valves are also shown on the air-pump bucket, fig. 47. EXERCISE 56: _India-rubber Disc Valve._--Fig. 54 shows a vertical section and a plan of an india-rubber disc valve. In the plan one-half of the guard and india-rubber are supposed to be removed so as to show the grating or seat. Draw these views, and also an elevation. A detail drawing of the central stud is shown in fig. 16, page 18. In fig. 54 the elevation of the guard is drawn as it is usually drawn in practice, but if the student has a sufficient knowledge of descriptive geometry he should draw the elevation completely showing the perforations. Scale 6 inches to a foot. [Illustration: FIG. 54.] [Illustration: FIG. 55.] _Kinghorn's Metallic Valve._--The action of this valve is the same as that of an india-rubber valve, but a thin sheet of metal (phosphor bronze) takes the place of the india-rubber. This valve is now largely used in the pumps of marine engines, and is shown in fig. 55 as applied to an air-pump bucket. Three valves like the one shown are arranged round the bucket. EXERCISE 57: _Kinghorn's Metallic Valve._--Fig. 55 shows an elevation and plan of one form of this valve. In the plan one-half of the guard and metal sheet are supposed to be removed, so as to show the grating, which in this case is part of an air-pump bucket. Draw the views shown, and also a vertical section of the guard through the centres of the bolts. All the parts are of brass except the valve proper, which is of phosphor bronze. Scale 6 inches to a foot. _Conical Disc Valves._--A very common form of valve is that shown in figs. 56 and 57. This form of valve consists of a disc, the edge of which (called the face) is conical. The conical edge of this disc fits accurately on a corresponding seat. The angle which the valve face makes with its axis is generally 45°. If the disc is raised, either by the action of the fluid as in the india-rubber valve, or by other means, an opening is formed around the disc through which the fluid can pass. The valve is guided in rising and falling either by three feathers underneath it, as in fig. 56, or by a central spindle which moves freely through a hole in the centre of a bridge which stretches across the seat, as in fig. 57. The lift of the valve is limited by a stop above it, which forms part of the casing containing the valve. The lift should in no case exceed one-fourth of the diameter of the valve, and it is generally much less than this. The guiding feathers (fig. 56) are notched immediately under the disc for the purpose of making available the full circumferential opening of the valve for the passage of the fluid. These notches also prevent the feathers from interfering with the turning or scraping of the valve face. Conical disc valves and their seats are nearly always made of brass. EXERCISE 58: _Conical Disc Valves._--Draw, half size, the plans and elevations shown in figs. 56 and 57. In fig. 57 the valve is shown open in the elevation, and in the plan it is removed altogether in order to show the seat with its guide bridge. [Illustration: Plan of Valve. FIG. 56.] [Illustration: Plan of Seat. FIG. 57.] _Simple Slide Valve._--The form of valve shown in fig. 58, often called the _locomotive slide valve_, is very largely used in all classes of steam-engines for distributing the steam in the steam cylinders. The valve is shown separately at (_d_), (_e_), and (_f_), while at (_a_), (_b_), and (_c_) is shown its connection with the steam cylinder. It will be observed that the valve itself is in the shape of a box with one side open, the edges of the open side being flanged. When the valve is in its middle position, as shown at (_a_), two of these flanged edges completely cover two rectangular openings S_{1} and S_{2}, called _steam ports_, while the hollow part of the valve is opposite to a third port E, called the _exhaust port_. As shown at (_a_) the piston P would be moving upwards and the valve downwards. By the time the piston has reached the top of its stroke the valve will have moved so far down as to partly uncover the steam port S_{1}, and admit steam from the valve casing C through S_{1} and the passage P_{1} to the top of the piston. The pressure of this steam on the top of the piston will force the latter down. While the above action has been going on, the port S_{2} will have become uncovered, and the hollow part of the valve will be opposite both the steam port S_{2} and the exhaust port E, so that the steam from the under side of the piston, and which forced the piston up, can now escape by the passage P_{2}, the steam port S_{2}, and the exhaust port E to the exhaust outlet O, and thence into the atmosphere, if it is a non-condensing engine, or into the condenser if it is a condensing engine, or into another cylinder if it is a compound engine. After the piston has performed, a certain part of its downward stroke, the valve, which has been moving downwards, will commence to move upwards, and when it has reached a certain point it will cover the port S_{1}, and shut off the supply of steam to the top of the piston. It is generally arranged that the steam shall be cut off before the piston reaches the end of the stroke. When the piston reaches the bottom of its stroke the valve has moved far enough up to uncover the port S_{2} and admit steam to the bottom of the piston, and to uncover the port S_{1} and allow the steam to escape from the top of the piston through the passage P_{1}, the port S_{1}, the port E, and outlet O. In this way the piston is moved up and down in the cylinder. The valve is attached to a valve spindle S by nuts as shown, the hole in the valve through which the spindle passes being oval-shaped to permit of the valve adjusting itself so as to always press on its seat. When the valve is in its middle position it generally more than covers the steam ports. The amount which the valve projects over the steam port on the outside, the valve being in its middle position, is called the _outside lap_ of the valve, and the amount which it projects on the inside is called the _inside lap_. When the term lap is used without any qualification, outside lap is to be understood. In fig. 58 it will be seen that the valve has no inside lap, and that the outside lap is three-eighths of an inch. The inside lap is generally small compared with the outside lap. [Illustration: FIG. 58.] When the piston is at the beginning of its stroke the steam port is generally open by a small amount called the _lead_ of the valve. The reciprocating motion of the slide valve is nearly always derived from an eccentric fixed on the crank-shaft of the engine. Slide valves are generally made of brass, bronze, or cast iron. EXERCISE 59: _Simple Slide Valve._--At (_d_), fig. 58, is shown a sectional elevation of a simple slide valve for a steam-engine, the section being taken through the centre line of the valve spindle, while at (_e_) is shown a cross section and elevation, and at (_f_) a plan of the same. Draw all these views full size, and also a sectional elevation at A B. The valve is made of brass, and the valve spindle and nuts of wrought iron. EXERCISE 60: _Slide Valve Casing, &c., for Steam-engine._--Draw, half size, the views shown at (_a_), (_b_), and (_c_), fig. 58; also a sectional plan at L M. (_b_) is an elevation of the valve casing with the cover and the valve removed. (_a_) is a sectional elevation, the section being taken through the axes of the steam cylinder and valve spindle. (_c_) is a sectional plan, the section being a horizontal one through the centre of the exhaust port. The inlet and outlet for the steam are clearly shown in the sectional plan: in the sectional elevation their positions are shown by dotted circles. The stroke of the piston is in this case 12 inches, so that from the dimensions given at (_a_) it must come within a quarter of an inch of each end of the cylinder; this is called the _cylinder clearance_. The piston has three Ramsbottom rings, a quarter of an inch wide and a quarter of an inch apart. The steam cylinder and valve casing are made of cast iron. _Cocks._--A cock consists of a slightly conical plug which fits into a corresponding casing cast on a pipe. Through the plug is a hole which may be made by turning the plug to form a continuation of the hole in the pipe, and thus allow the fluid to pass, or it may be turned round so that the solid part of the plug lies across the hole in the pipe, and thus prevent the fluid from passing. As the student will be quite familiar with the common water cock or tap such as is used in dwelling-houses we need not illustrate it here. [Illustration: FIG. 59.] Fig. 59 shows a cock of considerable size, which may be used for water or steam under high pressure. The plug in this example is hollow, and is prevented from coming out by a cover which is secured to the casing by four stud bolts. An annular ridge of rectangular section projecting from the under side of the cover, and fitting into a corresponding recess on the top of the casing, serves to ensure that the cover and plug are concentric, and prevents leakage. Leakage at the neck of the plug is prevented by a gland and stuffing-box. The top end of the plug is made square to receive a handle for turning it. The size of a cock is taken from the bore of the pipe in which it is placed; thus fig. 59 shows a 2-1/4-inch cock. EXERCISE 61: 2-1/4-_inch Steam or Water Cock._--First draw the views of this cock shown in fig. 59, then draw a half end elevation and half cross section through the centre of the plug. Scale 6 inches to a foot. Instead of drawing the parts of the pipe on the two sides of the plug in the same straight line as in fig. 59, one may be shown proceeding from the bottom of the casing, so that the fluid will have to pass through the bottom of the plug and through one side. This is a common arrangement. All the parts of the valve and casing in this example are made of brass. XVII. MATERIALS USED IN MACHINE CONSTRUCTION. _Cast Iron._--The essential constituents of cast iron are iron and carbon, the latter forming from 2 to 5 per cent. of the total weight. Cast iron, however, usually contains varying small amounts of silicon, sulphur, phosphorus, and manganese. In cast iron the carbon may exist partly in the free state and partly in chemical combination with the iron. In _white cast iron_ the whole of the carbon is in chemical combination with the iron, while in _grey cast iron_ the carbon is principally in the free state, that is, simply mixed mechanically with the iron. It is the free carbon which gives the grey iron its dark appearance. A mixture of the white and grey varieties of cast iron when melted produces _mottled cast iron_. The greater the amount of carbon chemically combined with the iron, the whiter, harder, and more brittle does it become. The white cast iron is stronger than the grey, but being more brittle it is not so suitable for resisting suddenly applied loads. White iron melts at a lower temperature than grey iron, but after melting it does not flow so well, or is not so liquid as the grey iron. White iron contracts while grey iron expands on solidifying. The grey iron, therefore, makes finer castings than the white. Castings after solidifying contract in cooling about 1/8 of an inch per foot. Castings possessing various degrees of strength and hardness are produced by melting mixtures of various proportions of white and grey cast irons. White cast iron has a higher specific gravity than grey cast iron. Cast iron gives little or no warning before breaking. The thickness of the metal throughout a casting in cast iron should be as uniform as possible, so that it may cool and therefore contract uniformly throughout; otherwise some parts may be in a state of initial strain after the casting has cooled, and will therefore be easier to fracture. Re-entrant angles should be avoided; such should be rounded out with fillets. The presence of phosphorus in cast iron makes it more fusible, and also more brittle. The presence of sulphur diminishes the strength considerably. The grey varieties of cast iron are called _foundry irons_ or _foundry pigs_, while the white varieties are called _forge irons_ or _forge pigs_, from the fact that they are used for conversion into wrought iron. Amongst iron manufacturers the different varieties of cast iron are designated by the numbers 1, 2, 3, &c., the lowest number being applied to the greyest variety. _Chilled Castings._--When grey cast iron is melted a portion of the free carbon combines chemically with the iron; this, however, separates out again if the iron is allowed to cool slowly; but if it is suddenly cooled a greater amount of the carbon remains in chemical combination, and a whiter and harder iron is produced. Advantage is taken of this in making _chilled castings_. In this process the whole or a part of the mould is lined with cast iron, which, being a comparatively good conductor of heat, chills a portion of the melted metal next to it, changing it into a hard white iron to a depth varying from 1/8 to 1/2 an inch. To protect the cast-iron lining of the mould from the molten metal it is painted with loam. _Malleable Cast Iron._--This is prepared by imbedding a casting in powdered red hematite (an oxide of iron), and keeping it at a bright red heat for a length of time varying from several hours to several days according to the size of the casting. By this process a portion of the carbon in the casting is removed, and the strength and toughness of the latter become more like the strength and toughness of wrought or malleable iron. _Wrought or Malleable Iron._--This is nearly pure iron, and is made from cast iron by the puddling process, which consists chiefly of raising the cast iron to a high temperature in a reverberatory furnace in the presence of air, which unites with the carbon and passes off as gas. In other words the carbon is burned out. The iron is removed from the puddling furnace in soft spongy masses called _blooms_, which are subjected to a process of squeezing or hammering called _shingling_. These shingled blooms still contain enough heat to enable them to be rolled into rough _puddled bars_. These puddled bars are of very inferior quality, having less than half the strength of good wrought iron. The puddled bars are cut into pieces which are piled together, reheated, and again rolled into bars, which are called _merchant bars_. This process of piling, reheating, and re-rolling may be repeated several times, depending on the quality of iron required. Up to a certain point the quality of the iron is improved by reheating and rolling or hammering, but beyond that a repetition of the process diminishes the strength of the iron. The process of piling and rolling gives wrought iron a fibrous structure. When subjected to vibrations for a long time, the structure becomes crystalline and the iron brittle. The crystalline structure induced in this way may be removed by the process of _annealing_, which consists in heating the iron in a furnace, and then allowing it to cool slowly. _Forging and Welding._--The process of pressing or hammering wrought iron when at a red or white heat into any desired shape is called _forging_. If at a white heat two pieces of wrought iron be brought together, their surfaces being clean, they may be pressed or hammered together, so as to form one piece. This is called _welding_, and is a very valuable property of wrought iron. _Steel._--This is a compound of iron with a small per-centage of carbon, and is made either by adding carbon to wrought iron, or by removing some of the carbon from cast iron. In the _cementation_ process, bars of wrought iron are imbedded in powdered charcoal in a fireclay trough, and kept at a high temperature in a furnace for several days. The iron combines with a portion of the carbon to form _blister steel_, so named because of the blisters which are found on the surface of the bars when they are removed from the furnace. The bars of blister steel are broken into pieces about 18 inches long, and tied together in bundles by strong steel wire. These bundles are raised to a welding heat in a furnace, and then hammered or rolled into bars of _shear steel_. To form _cast steel_ the bars of blister steel are broken into pieces and melted into crucibles. In the _Siemens-Martin_ process for making steel, cast and wrought iron are melted together on the hearth of a regenerative gas-furnace. _Bessemer steel_ is made by pouring melted cast iron into a vessel called a converter, through which a blast of air is then urged. By this means the carbon is burned out, and comparatively pure iron remains. To this is added a certain quantity of 'spiegeleisen,' which is a compound of iron, carbon, and manganese. _Hardening and Tempering of Steel._--Steel, if heated to redness and cooled suddenly, as by immersion in water, is hardened. The degree of hardness produced varies with the rate of cooling; the more rapidly the heated steel is cooled, the harder does it become. Hardened steel is softened by the process of _annealing_, which consists in heating the hardened steel to redness, and then allowing it to cool slowly. Hardened steel is _tempered_, or has its degree of hardness lowered, by being heated to a temperature considerably below that of a red heat, and then cooling suddenly. The higher the temperature the hardened steel is raised to, the lower does its 'temper' become. _Case-hardening._--This is the name given to the process by which the surfaces of articles made of wrought iron are converted into steel, and consists in heating the articles in contact with substances rich in carbon, such as bone-dust, horn shavings, or yellow prussiate of potash. This process is generally applied to the articles after they are completely finished by the machine tools or by hand. The coating of steel produced on the article by this process is hardened by cooling the article suddenly in water. _Copper._--This metal has a reddish brown colour, and when pure is very malleable and ductile, either when cold or hot, so that it may be rolled or hammered into thin plates, or drawn into wire. Slight traces of impurities cause brittleness, although from 2 to 4 per cent. of phosphorus increases its tenacity and fluidity. Copper is a good conductor of heat and of electricity. Copper is largely used for making alloys. _Alloys._--_Brass_ contains two parts by weight of copper to one of zinc. _Muntz metal_ consists of three parts of copper to two of zinc. Alloys consisting of copper and tin are called _bronze_ or _gun-metal_. Bronze is harder the greater the proportion of tin which it contains; five parts of copper to one of tin produce a very hard bronze, and ten of copper to one of tin is the composition of a soft bronze. _Phosphor bronze_ contains copper and tin with a little phosphorus; it has this advantage over ordinary bronze, that it may be remelted without deteriorating in quality. This alloy also has the advantage that it may be made to possess great strength accompanied with hardness, or less strength with a high degree of toughness. _Wood._--In the early days of machines wood was largely used in their construction, but it is now used to a very limited extent in that direction. _Beech_ and _hornbeam_ are used for the cogs of mortise wheels. _Yellow pine_ is much used by pattern-makers. _Box_, a heavy, hard, yellow-coloured wood, is used for the sheaves of pulley blocks, and sometimes for bearings in machines. _Lignum-vitæ_ is a very hard dark-coloured wood, and remarkable for its high specific gravity, being 1-1/3 times the weight of the same volume of water. This wood is much used for bearings of machines which are under water. XVIII. MISCELLANEOUS EXERCISES. The illustrations in this chapter are in most cases not drawn to scale; they are also in some parts incomplete, and in others some of the lines are purposely drawn wrong. The student must keep to the dimensions marked on the drawings, and where no sizes are given he must use his own judgment in proportioning the parts. All errors must be corrected, and any details required, but not shown completely in the illustrations, must be filled in. EXERCISE 62: _Single Riveted Butt Joint with Tee-iron Cover Strap._--Two views, one a side elevation and the other a sectional elevation, of a riveted joint are shown in fig. 60. Draw these views, and also a plan projected from one of them. Show the rivets completely in all the views. Scale 4 inches to a foot. [Illustration: FIG. 60.] [Illustration: FIG. 61.] EXERCISE 63: _Girder Stay for Steam Boiler._--The flat crown of the fire-box of locomotive and marine boilers is generally supported or stayed by means of girder stays, an example of which is shown in fig. 61. A B is the side elevation of a portion of one of these girders. Each girder is supported at its ends by the plates forming the vertical sides of the fire-box. The flat crown is bolted to the girders as shown. Observe that the girders are in contact with the crown only in the neighbourhood of the bolts. Consider carefully this part of the design, and then answer the following questions: (1) What objections are there to supporting the girders at the ends only without the contact pieces at the bolts? (2) What objections are there to having the girders in contact with the crown plate of the fire-box throughout their whole length? Draw the views shown in fig. 61, and from the right-hand one project a plan. Scale 4 inches to a foot. [Illustration: FIG. 62.] EXERCISE 64: _End of Bar Stay for Steam Boiler._--On page 12 one form of stay for supporting the flat end of a steam boiler is described. Another form of stay for the same purpose is shown in fig. 62. A B is a portion of the end of a steam boiler. C D is one end of a bar which extends from one end of the boiler to the other. The ends of this bar are screwed, and when the bar is of wrought iron the screwed parts are generally larger in diameter than the rest of the bar. When made of steel the bar is generally of uniform diameter throughout. In the case of wrought-iron bar stays the enlarged ends are welded on to the smaller parts. Welding is not so reliable with steel as with wrought iron. Write out answers to the following questions: (1) What is the advantage of having the screwed part of the bar larger in diameter than the rest? (2) Why are steel bar stays not generally enlarged at their screwed ends? Draw the views shown in fig. 62, and project from one of them a third view. Scale 4 inches to a foot. EXERCISE 65: _Knuckle Joint._--Draw the plan and elevation of this joint shown in fig. 63, and also draw an end elevation looking in the direction of the arrow. The parts at A and B are octagonal in cross section. Scale 4 inches to a foot. [Illustration: FIG. 63.] EXERCISE 66: _Locomotive Coupling Rod Ends._--A form of knuckle joint used on locomotive coupling rods is shown in fig. 64. In this case two rods meet and work on the same pin, as shown at (a) fig. 64. Draw, in addition to the views shown in fig. 64, a plan and a vertical section through the axis of the pin. Scale 6 inches to a foot. Would it be practicable to replace the two rods A B and B C by a single rod working on the crank pins at A, B, and C? Give reasons for your answer. [Illustration: FIG. 64.] EXERCISE 67: _Bell Crank Lever._--Draw the plan and elevation of the lever shown in fig. 65. Scale 6 inches to a foot. [Illustration: FIG. 65.] EXERCISE 68: _Back Stay for Lathe._--Draw a plan and two elevations of the stay shown in fig. 66. Make all necessary corrections and show all the details in each view. Scale full size. [Illustration: FIG. 66.] [Illustration: FIG. 67.] EXERCISE 69: _Conical Disc Valve and Casing._--Draw, half size, the views shown in fig. 67 of the conical disc valve and casing, and also add an elevation looking in the direction of the arrow. EXERCISE 70: _Connecting Rod End._--The student should carefully compare this connecting rod end (fig. 68) with those illustrated on pages 50 and 52. The lower part of fig. 68 is a half plan and half horizontal section, and the upper part is a half side elevation and half vertical section. Draw these views and also an end elevation. Scale 6 inches to a foot. [Illustration: FIG. 68.] [Illustration: FIG. 69.] [Illustration: FIG. 70.] [Illustration: FIG. 71.] [Illustration: FIG. 72.] [Illustration: FIG. 73.] [Illustration: FIG. 74.] EXERCISE 71: _Engine Cross-head._--The cross-head shown in fig. 69 is for an inverted cylinder marine engine. A is the piston rod, and B B are pins, forged in one piece with C, to which the forked end of the connecting rod is attached. Draw the upper view with the central part in section as shown. Make the right-hand half of the lower view a plan without any section, and make the left-hand half a horizontal section through the axis of the pins B B. Scale 4 inches to a foot. EXERCISE 72: _Ratchet Lever._--The lever shown in fig. 70 is used for turning the horizontal screw of a traversing screw jack. Draw the two views shown, and from one of them project a plan. Scale full size. EXERCISE 73: _Steam Whistle._--Draw, full size, the elevation and section of the steam whistle shown in fig. 71. Draw also horizontal sections at A B, C D, and E F. [Illustration: FIG. 75.] EXERCISE 74: _Screw Coupling for Railway Carriages._--Draw the three views of the screw coupling shown in fig. 72. Scale 6 inches to a foot. If the link A is fixed, through what distance will the link B move for two turns of the lever? [Illustration: FIG. 76.] EXERCISE 75: _Loose Headstock for a 6-inch Lathe._--Two views of this headstock are shown in fig. 73. On one of these views a few of the chief dimensions are marked. The details, fully dimensioned, are shown separately in figs. 74, 75, and 76. Explain clearly how the centre is moved backwards and forwards, and also how the spindle containing it is locked when it is not required to move. Draw, half-size, the views shown in fig. 73, and from the left-hand view project a plan. Draw also the detail of the locking arrangement shown in fig. 74. APPENDIX A. _SCIENCE AND ART DEPARTMENT, SOUTH KENSINGTON._ SYLLABUS. SUBJECT II.--MACHINE CONSTRUCTION AND DRAWING. It is assumed that the student has already learnt to draw to scale, and that he can draw two or more views of the same object in simple or orthographic projection. To pass in machine construction and drawing, he must be able to apply this knowledge to the representation of machinery. He must be acquainted with the form and purpose of the simpler parts of which machines are built up and must have had some practice in drawing them. To test his knowledge, rough dimensioned sketches, more or less incomplete, of simple machine details will be given him, and he will be required to produce a complete drawing in pencil to a given scale. Two or more views of at least one subject will be required, and these must be so drawn as to be properly projected one from the other, _in order to show that the student appreciates that he is producing a representation of a solid piece of machinery, and not merely copying a sketch. No credit will be given unless some knowledge of projection is shown._ The centre lines of the drawings should be shown, and parts cut by planes of section should be indicated by diagonal shading. Bolts and other fastenings should be carefully shown where required. Any indication that a candidate has merely copied the sketches given, without understanding the part represented, will invalidate his examination. FIRST STAGE OR ELEMENTARY COURSE. In the elementary stage, a knowledge is required of the simple parts only of _machines in common use_. _Some_ of these are enumerated in the following list. The student should be practised in drawing them till he recognises their forms, and the object of the arrangement should be explained to him. He should also know the simple technical terms used in describing them. A few very simple questions relating to the arrangement, proportions, and strength of the simplest machine details will be set in the examination paper. In drawing the examples set to test a student's knowledge and skill in machine drawing, it must be remembered that only a limited time is available. It is only possible to set an example to be drawn in pencil, and the points which will receive attention are (1) accuracy of scale and projection; (2) power of reading a drawing, shown by the ability to transfer portions of the mechanism and dimensions from one view to another; (3) knowledge of machines, as shown by the ability to fill in small details, such as nuts, keys, etc., omitted in the sketches given. Bearing in mind the limited time available, the student should try to make his outline clear and decisive and complete. But the diagonal lines necessary for sectional parts may be done rapidly, though neatly, by freehand if necessary. _Riveted Joints._--Forms of rivets and arrangement of rivets in lap and butt joints with single and double riveting. Junction of plates by angle and T-irons. _Bolts, Studs, and Set Screws._--Forms of these fastenings. Forms and proportions of nuts and bolt-heads. Arrangement of flanges for bolting. _Pins, Keys, and Cotters._--Form of ordinary knuckle joint. Use of split pins. Connection of parts by a key. Connection of parts by a cotter. Gib and cotter. _Pipes and Cylinders._--Forms of ordinary pipes and cylinders and their flanges and covers. _Shafting._--Forms of shafts and axles and of journals and pivots. Use of collars and bosses. Half-lap coupling. Box coupling. Flange coupling. _Pedestals and Plummer Blocks._--Simplest forms of pedestals and hangers for shafts. Form and arrangement of brass steps. Arrangements for fixing pedestals and for neutralising the effects of wear. _Toothed Gearing._--Forms of ordinary spur and bevil wheels. Meaning of the terms pitch, breadth of face, thickness of tooth, pitch line, rim, nave, arm. Mode of drawing bevil wheels in section. _Belt Pulleys._--Forms of belt pulleys for flat and round belts. Stepped speed cones. Drawing of pulleys with curved arms. _Cranks and Levers._--Forms of ordinary cast-iron and wrought-iron cranks and levers. Modes of fixing crank pin. Modes of fixing crank shaft. Double cranks. Form of eccentrics. _Links._--Most simple forms of connecting rod ends, open or closed. Use of steps in connecting rods. Use of cotters to tighten the steps. _Pistons._--Simple forms of piston. Use of piston packing. Modes of attaching piston rod. _Stuffing-Boxes._--Simple form of stuffing-box and gland. Use of packing. Mode of tightening gland. _Valves._--Simple conical of puppet valve. Simple slide valve. Cock or conical sliding valve. APPENDIX B. _EXAMINATION PAPERS SET BY THE SCIENCE AND ART DEPARTMENT._ SUBJECT II.--MACHINE CONSTRUCTION AND DRAWING. _Examiners_, PROF. T. A. HEARSON, M.Inst.C.E., and J. HARRISON, ESQ., M.Inst.M.E. GENERAL INSTRUCTIONS. _If the rules are not attended to, the paper will be cancelled._ You may take the Elementary, or the Advanced, or the Honours paper, but you must confine yourself to one of them. Put the number of the question before your answer. You are expected to prove your knowledge of machinery as well as your power of drawing neatly to scale. You are therefore to supply details omitted in the sketches, to fill in parts left incomplete, and to indicate, by diagonal lines, parts cut by planes of section. No credit will be given unless some knowledge of projection is shown, so that at least two views of one of the examples will be required properly projected one from the other. The centre lines should be clearly drawn. The figured dimensions need not be inserted. Your answers should be clearly and cleanly drawn in pencil. No extra marks will be allowed for inking in. All figures must be drawn on the single sheet of paper supplied, for no second sheet will be allowed. The value attached to each question is shown in brackets after the question. But a full and correct answer to an easy question will in all cases secure a larger number of marks than an incomplete or inexact answer to a more difficult one. Your name is not given to the Examiner, and you are forbidden to write to him about your answers. You are to confine your answers _strictly_ to the questions proposed. A single accent (') signifies _feet_; a double accent (") _inches_. _The examination in this subject lasts for four hours._ * * * * * First Stage or Elementary Examination. 1885. INSTRUCTIONS. Read the General Instructions above. Answer briefly any three, but not more than three, of the following questions, and draw two, but not more than two, of the examples. _Questions._ (_a._) Show two methods by which a cotter may be prevented from slacking back. (6.) (_b._) Sketch the brasses for a bearing, and show how they are prevented from turning in the pedestal. (6.) (_c._) Explain the object of the construction of the connecting rod end shown in fig. 78. Describe how the adjustment must be made and how it is locked. (10.) (_d._) Show the form of the Whitworth screw thread by drawing to scale a part section of two or three threads taking a pitch of 1-1/2 inches. Figure the dimensions on the sketch. How many threads to the inch are used on an inch bolt? (10.) (_e._) Make a sketch showing how the adjustment is made in the sliding parts of machine tools: as, for example, in the slide rest of a lathe. (10.) (_f._) Describe with sketches two methods by which the joints are made in connecting lengths of cast-iron pipes. (6.) _Examples to be drawn._ 1. Jaw for four-screw dog chuck for 5" lathe. Draw the two views as shown (fig. 77). Scale full size. (Note.--The other three jaws of the chuck are not to be drawn.) (35.) 2. Connecting rod end. Draw the two views as shown, partly in section (fig. 78). Draw full size. (35.) 3. Hooke's coupling. Draw the three views shown (fig. 79), adding any omitted lines where the views are incomplete. Draw to scale of 1/4 full size. (35.) [Illustration: FIGS. 77 AND 78.] [Illustration: FIG. 79.] * * * * * First Stage or Elementary Examination. 1886. INSTRUCTIONS. Read the General Instructions (page 102). Answer briefly any three, but not more than three, of the following questions, and draw two, but not more than two, of the examples. _Questions._ (_a._) Give sketches showing how the cutting tool of a lathe or other machine is secured in place. (6.) (_b._) Make a sketch of a stud, describe how it is screwed into place, and state some circumstances under which it is used in preference to a bolt. (6.) (_c._) Give sketches showing one method of attaching the valve rod to an ordinary slide valve. (6.) (_d._) Sketch a connecting rod end, with strap, gib, and cotter. Explain the use of the gib. (10.) (_e._) Explain the use of the quadrant for change wheels for a screw-cutting lathe shown in Example 1, fig. 80, by making a sketch showing it in place on a lathe with wheels in gear. (10.) (_f._) Sketch one form of hanger suitable for supporting mill-shafting. (10.) _Examples to be drawn._ 1. Quadrant for change wheels for screw-cutting lathe. Draw the two views shown (fig. 80). Scale half-size. (35.) 2. Crank-shaft. Draw the two views as shown, partly in section (fig 81). Scale 1/8 full size. (35.) 3. Ball bearing for tricycle. Draw the two views as shown, partly in section (fig. 82). Draw full size. (35.) [Illustration: FIGS. 80 AND 81.] [Illustration: FIG. 82.] * * * * * First Stage or Elementary Examination. 1887. INSTRUCTIONS. Read the General Instructions (page 102). Answer briefly any three, but not more than three, of the following questions, and draw two, but not more than two, of the examples. _Questions._ (_a._) Explain how the piston rings in Example 1, fig. 84, are made so that the piston may work steam-tight in the cylinder. How are these rings got into place? (8.) (_b._) Give two views of a double riveted lap joint for boiler-plates. (8.) (_c._) Show by sketches how a wheel is fixed on a shaft by means of a sunk key. Explain how the key may be withdrawn when it cannot be driven from the point end. (8.) (_d._) Give sketches showing the construction of a conical metal lift or puppet valve and seating. (10.) (_e._) With the aid of sketches explain how a piston rod is made to work steam-tight through the end of the cylinder. (10.) (_f._) Explain how the slotting machine ram of Example 8, fig. 85, may be made to move up and down when at work. How is the length of the stroke altered, and what is the object of the slotway in the upper part of the ram? (10.) _Examples to be drawn._ 1. Piston for steam-engine. Draw and complete the two views shown (fig. 84), the top half of the left-hand view to be in section. Scale 1/2 size. (30.) 2. Plan and sectional elevation of a footstep bearing for an upright shaft (fig. 83). Draw and complete these views. Scale 1/4 size. (35.) 3. Ram of slotting machine. Draw and complete the two elevations shown (fig. 85). The tool-holders must be drawn in their proper positions in the ram, and not separate as in the diagram. Scale 1/4 size. (35.) [Illustration: FIGS. 83 AND 84.] [Illustration: FIG. 85.] * * * * * First Stage or Elementary Examination. 1888. INSTRUCTIONS. Read the General Instructions on p. 102. Answer briefly any three, but not more than three, of the following questions, and draw two, but not more than two, of the examples. _Questions._ (_a._) Give sketches showing how the separate lengths of a line of shafting may be connected together. (8.) (_b._) What is the object of using chipping or facing strips in fitting up machine parts? Give one or two examples. (8.) (_c._) Give sketches showing how you would grip and drive a round iron bar for the purpose of turning it between the centres of a lathe. (10.) (_d._) Explain the action of the governor shown in Example 1 (fig. 86). (10.) (_e._) Describe in detail how the mud-hole door in Example 2 (fig. 88) is removed for the purpose of cleaning the boiler and how it is replaced and the joint made steam-tight. (10.) (_f._) Describe how the parts of the spur wheel in Example 3 (fig. 87) are put together, and explain why the wheel is made in segments. (10.) _Examples to be drawn._ 1. Loaded governor for small gas engine. Draw and complete the two views, partly in section as shown (fig. 86). Scale full size. (35.) 2. Mud-hole mouth-piece for Lancashire boiler. Draw and complete the two views shown (fig. 88). Scale 3/8ths. (35.) 3. Point for segments of large spur wheel. Draw and complete the views shown (fig. 87). Scale 3/16ths. _Note._--As the radius of the wheel is too large for your instruments, the circumference at the joint may be set out straight, as in a rack. (35.) [Illustration: FIGS. 86 AND 87.] [Illustration: FIG. 88.] INDEX Air-pump bucket, 58 Alloys, 80 Angle irons, 12 Annealing, 79, 80 Axles, 24 Back stay for lathe, 86 Bar stay, 83 Bearings for shafts, 30 Beech-wood, 81 Bell crank lever, 86 Bessemer steel, 79 Bevil wheels, 43 Blister steel, 79 Blooms, 78 Bolt-heads, proportions of, 18 Bolts, forms of, 17 Border lines, 4 Box couplings, 25 -- end, connecting rod, 51 Box-wood, 81 Brackets, 33 Brake shaft carrier, 30 Brass, 80 Brasses, 30 Bucket, 58 Built-up cranks, 46 Bush, 30, 49, 51, 54, 56, 63 Butt joints, 10, 11 -- strap, 10 Buttress screw thread, 15 Case-hardening, 80 Cast iron, 76 Cast iron flange coupling, 28, 29 -- steel, 79 Caulking, 8 Cementation process, 79 Centre lines, 2, 4 Chilled castings, 78 Circulating pump piston, 58 Clearance, cylinder, 74 -- of cotter, 49 Cocks, 74 Cogs, 41 -- wood for, 81 Collared stud, 18 Collars, 24 Colouring, 3 Colours for different materials, 3 Compasses, 1 Cone keys, 23, 38 Conical disc valve, 70, 71, 89 -- head, 7 Connecting rod, locomotive, 51 -- -- marine, 51 -- rods, 49, 89 Construction for rivet heads, 7 Contraction of castings, 77 Copper, 80 Cotters, 48, 49 Countersunk head, 7, 18 Coupling rod ends, 55, 84 -- rods, 54 -- screw, 96 Couplings, shaft, 25 Cover plate, 10 Cranked axle, 45 Cranks, 43 -- built-up, 46 Cross-head pin, 51 Cross-heads, 56, 89 Cross-key, 28 Cup-headed bolt, 17 Decimal equivalents, 6 Dimension lines, 5 Dimensions, 5 -- of box couplings, 26 -- cast-iron flange couplings, 29 -- keys, 24 -- stuffing-boxes and glands, 67 -- Whitworth screws, 15 Distance lines, 5 Dividers, 1 Draught of cotter, 49 Drawing board, 1 -- instruments, 1 -- paper, 2 -- pen, 1 -- pins, 2 Eccentrics, 47 Exhaust port, 71 Eye-bolt, 18 Fairbairn's coupling, 26 Fast and loose pulleys, 37 Feather key, 23 Flange couplings, 27 Flap valves, 68 Flat key, 22 Forge irons, 77 Forging, 79 Form of wheel teeth, 40 Forms of nuts, 16 -- rivet heads, 7 -- screw threads, 15 Foundry irons, 77 Gasket, 58 Gas threads, 15 Gib, 49 -- head, 23 Girder stay, 81 Gland, 64 Grey cast iron, 77 Gun-metal, 80 Gusset stay, 12 Half-lap coupling, 26 Hangers, 34 Hardening of steel, 80 Headstock lathe, 96 Hexagonal nut, 16 Hollow key, 22 Hook bolt, 18 Hornbeam, 81 India-rubber disc valves, 58, 68 Inking drawings, 2 Inside lap of valve, 72 Joggles, 33 Joint, knuckle, 84 Journals, 24 -- length of, 32 Junk ring, 61 Keys, 22 -- proportions of, 23 Kinghorn's metallic valve, 70 Knuckle joint, 84 -- screw thread, 15 Lancaster's piston packing, 61 Lap joints, 8, 9, 10, 12 -- of slide valve, 72 Lathe headstock, 96 Lead of valve, 74 Lever, bell crank, 86 -- ratchet, 96 Lignum-vitæ, 81 Locking arrangements for nuts, 21, 62 Lock nuts, 19 Locomotive connecting rod, 51 -- cranked axle, 45 -- cross-head, 56 Locomotive eccentric, 47 -- piston, 60 Lubricator, needle, 32 Malleable cast iron, 78 -- iron, 78 Marine connecting rod, 51 -- coupling, 28 -- crank-shaft, 46 -- piston, 61 Merchant bars, 78 Mortise wheels, 41 Mottled cast iron, 77 Muff couplings, 25 Muntz metal, 80 Needle lubricator, 32 Nuts, forms of, 16 -- lock, 19 -- proportions of, 18 Oil-box, 54, 65 Outside lap of slide valve, 72 Overhung crank, 43 -- cranks, proportions of, 45 Packing, 63 Pan head, 7 Pedestal, shaft, 30 Pencils, drawing, 1 Phosphor bronze, 80 Pillar bracket, 34 Pillow block, 30, 32 Pin, cross-head, 51, 54 -- split, 21 Piston rod, 57 Pistons, 57 Pitch circle, 40 -- of wheel teeth, 40 -- surfaces of wheels, 39, 43 Pivots, 24 Plummer block, 30 Plunger, 57 Printing, 4 Proportions of bolt-heads, 18 -- keys, 23 Proportions of lap joints, 9, 10 -- marine engine pistons, 62 -- nuts, 18 -- overhung cranks, 45 -- pillow blocks, 32 -- rivet heads, 7 -- wheel teeth, 40 Puddled bars, 78 Puddling process, 78 Pulley, eccentric, 47 Pulleys, 36 Pump bucket, 58 Ramsbottom's packing, 60 Ratchet lever, 96 Riveted joints, 8 Rivet heads, forms of, 7, 8 -- -- proportions of, 7 Riveting, 7 Rivets, 6 Rope pulley, 39 Round key, 23 Saddle key, 22 Scales, 5 Screw coupling, 96 Screwed gland and stuffing-box, 65 Screw threads, 14, 15 Screws, representation of, 16 Sellers =V= screw thread, 14 Set screw, 21, 49 -- squares, 1 Shaft couplings, 25 -- hanger, 34 Shafting, 24 Shear steel, 79 Sheave, eccentric, 47 Shingling, 78 Shrinking, process of, 44 Siemens-Martin steel, 79 Slide blocks, 56 -- valves, 68, 71 Sliding key, 23 Snap head, 7 Snug, 17 Spiegeleisen, 80 Spring bows, 1 Spur wheel, 41 Square nut, 16 -- screw thread, 14 Stay, back, for lathe, 86 -- bar, 83 -- girder, 81 -- gusset, 12 Steam ports, 71 -- whistle, 96 Steel, 79 Steps, 30 Strap, 49 -- eccentric, 47 -- end of connecting rod, 49 Stud bolts, 18 Studs, 18 Stuffing-boxes, 63 Sunk key, 22 Taper bolt, 18, 27 -- pin, 23 Tee-headed bolt, 18 Tee-iron cover strap, 81 Tee square, 1 Teeth of wheels, form and proportions of, 40 Teeth, pitch of, 40 Tempering of steel, 80 Throw of crank, 44 -- eccentric, 47 Toothed wheels, 39 Valve Kinghorn's metallic, 70 -- slide, 68, 71 Valves, 68 -- conical disc, 70 -- india-rubber, 58, 68 Velocity ratio in belt gearing, 36 Wall boxes, 34 Washers, 19 Welding, 79 Whistle, steam, 96 White cast iron, 77 Whitworth screws, dimensions of, 15 -- =V= screw thread, 14 Wood, 81 Working drawings, 4 Wrought iron, 78 Yellow pine, 81 PRINTED BY SPOTTISWOODE AND CO., NEW-STREET SQUARE LONDON * * * * * TEXT-BOOKS OF SCIENCE PHOTOGRAPHY. 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43375	----	MACHINERY'S REFERENCE SERIES EACH NUMBER IS ONE UNIT IN A COMPLETE LIBRARY OF MACHINE DESIGN AND SHOP PRACTICE REVISED AND REPUBLISHED FROM MACHINERY NUMBER 21 MEASURING TOOLS THIRD EDITION CONTENTS History and Development of Standard Measurements Calipers, Dividers, and Surface Gages Micrometer Measuring Instruments Miscellaneous Measuring Tools and Gages Copyright, 1910, The Industrial Press, Publishers of MACHINERY. 49-55 Lafayette Street, New York City * * * * * CHAPTER I HISTORY AND DEVELOPMENT OF STANDARD MEASUREMENTS[1] While every mechanic makes use of the standards of length every day, and uses tools graduated according to accepted standards when performing even the smallest operation in the shop, there are comparatively few who know the history of the development of the standard measurements of length, or are familiar with the methods employed in transferring the measurements from the reference standard to the working standards. We shall therefore here give a short review of the history and development of standard measurements of length, as abstracted from a paper read by Mr. W. A. Viall before the Providence Association of Mechanical Engineers. Origin of Standard Measurements By examining the ruins of the ancients it has been found that they had standard measurements, not in the sense in which we are now to consider them, but the ruins show that the buildings were constructed according to some regular unit. In many, if not all cases, the unit seems to be some part of the human body. The "foot," it is thought, first appeared in Greece, and the standard was traditionally said to have been received from the foot of Hercules, and a later tradition has it that Charlemagne established the measurement of his own foot as the standard for his country. Standards Previous to 1800 In England, prior to the conquest, the yard measured, according to later investigations, 39.6 inches, but it was reduced by Henry I in 1101, to compare with the measurement of his own arm. In 1324, under Edward II, it was enacted that "the inch shall have length of three barley corns, round and dry, laid end to end; twelve inches shall make one foot, and three feet one yard." While this standard for measurement was the accepted one, scientists were at work on a plan to establish a standard for length that could be recovered if lost, and Huygens, a noted philosopher and scientist of his day, suggested that the pendulum, which beats according to its length, should be used to establish the units of measurement. In 1758 Parliament appointed a commission to investigate and compare the various standards with that furnished by the Royal Society. The commission caused a copy of this standard to be made, marked it "Standard Yard, 1758," and laid it before the House of Commons. In 1742, members of the Royal Society of England and the Royal Academy of Science of Paris agreed to exchange standards, and two bars 42 inches long, with three feet marked off upon them, were sent to Paris, and one of these was returned later with "Toise" marked upon it. In 1760 a yard bar was prepared by Mr. Bird, which was afterwards adopted as a standard, as we shall see later. In 1774 the Royal Society offered a reward of a hundred guineas for a method that would obtain an invariable standard, and Halton proposed a pendulum with a moving weight upon it, so that by counting the beats when the weight was in one position and again when in another, and then measuring the distance between the two positions, a distance could be defined that could at any time be duplicated. The Society paid 30 guineas for the suggestion, and later the work was taken up by J. Whitehurst with the result that the distance between the positions of the weight when vibrating 42 and 84 times a minute was 59.89358 inches. The method was not further developed. How the Length of the Meter was Established In 1790, Talleyrand, then Bishop of Autun, suggested to the Constituent Assembly that the king should endeavor to have the king of England request his parliament to appoint a commission to work in unison with one to be appointed in France, the same to be composed of members of the Royal Society and Royal Academy of Science, respectively, to determine the length of a pendulum beating seconds of time. England did not respond to the invitation, and the French commission appointed considered first of all whether the pendulum beating seconds of time, the quadrant of the meridian, or the quadrant of the equator should be determined as a source of the standard. It was decided that the quadrant of the meridian should be adopted and that 0.0000001 of it should be the standard. The arc of about nine and one-half degrees, extending from Dunkirk on the English Channel to Barcelona on the Mediterranean and passing through Paris, should be the one to be measured. The actual work of measuring was done by Mechain and Delambre according to the plans laid down by the commission. Mechain was to measure about 25 per cent of the arc, the southern portion of it, and Delambre the remainder; the reason for this unequal division was that the northern division had been surveyed previously, and the territory was well-known, whereas the southern part was an unknown country, as far as the measurement of it went, and it was expected that many severe difficulties would have to be surmounted. The Revolution was in progress, and it was soon found that the perils attending the measurement of the northern part were greater than those attending the southern part of the territory. The people looked askance at all things that they did not understand, and Delambre with his instruments was looked upon as one sent to further enthrall them. He was set upon by the people at various times and although the authorities endeavored to protect him, it was only by his own bravery and tact that he was able to do his work and save his life. The Committee of Safety ordered that Mechain and Delambre close their work in 1795, and it was some time afterward before it was resumed. Having completed the field work, the results of their labors were laid before a commission composed of members of the National Institute and learned men from other nations, who had accepted the invitation that had been extended to them, and after carefully reviewing and calculating the work, the length of the meridian was determined, and from it was established the meter as we now have it. A platinum bar was made according to the figures given, and this furnishes the prototype of the meter of the present time. Notwithstanding all of the care taken in establishing the meter, from work done by Gen. Schubert, of Russia, and Capt. Clarke, of England, it has been shown that it is not 0.0000001 of the quadrant passing through Paris, but of the one passing through New York. The Standard Yard in England--Its Loss and Restoration Whether incited by the work of the French or not, we do not know, but in the early part of this century the English began to do more work upon the establishment of a standard, and in 1816 a commission was appointed by the crown to examine and report upon the standard of length. Capt. Kater made a long series of careful observations determining the second pendulum to be 39.1386 inches when reduced to the level of the sea. This measurement was made on a scale made by Troughton--who, by the way, was the first to introduce the use of the microscope in making measurements--under the direction of and for Sir Geo. Schuckburgh. In 1822, having made three reports, after many tests, it was recommended that the standard prepared by Bird in 1760, marked "Standard Yard, 1760," be adopted as the standard for Great Britain. The act of June, 1824, after declaring that this measure should be adopted as the standard, reads in Sec. III.: "And whereas it is expedient that the Standard Yard, if lost, destroyed, defaced or otherwise injured should be restored to the same length by reference to some invariable natural Standard; and whereas it has been ascertained by the Commissioners appointed by His Majesty to inquire into the Subjects of Weights and Measures, that the Yard, hereby declared to be the Imperial Standard Yard, when compared with a Pendulum vibrating Seconds of Mean Time in the latitude of London, in a Vacuum at the Level of the Sea, is in the proportion of Thirty-six Inches to Thirty-nine Inches and one thousand three hundred and ninety-three ten thousandth parts of an Inch; Be it enacted and declared, that if at any Time hereafter the said Imperial Standard Yard shall be lost, or shall be in any manner destroyed, defaced or otherwise injured, it shall and may be restored by making a new Standard Yard bearing the same proportion to such Pendulum, as aforesaid, as the said Imperial Standard Yard bears to such Pendulum." It was not long after this act had been passed, if indeed not before, that it became known that the pendulum method was an incorrect one, as it was found that errors had occurred in reducing the length obtained to that at the sea level, and despite the great pains that had been taken, it is doubtful if the method was not faulty in some of its other details. When the Houses of Parliament were burned in 1834, an opportunity was offered to try the method upon which so much time and care had been spent. A commission was appointed and to Sir Francis Baily was assigned the task of restoring the standard. He did not live to complete the task, dying in 1844. He succeeded in determining the composition of the metal that was best adapted to be used, which metal is now known as Baily's metal. Rev. R. Sheepshanks constructed a working model as a standard and compared it with two Schuckburg's scales, the yard of the Royal Society, and two iron bars that had been used in the ordnance department. Having determined to his own satisfaction and that of his associates the value of the yard, he prepared the standard imperial yard, known as Bronze No. 1, a bronze bar 38 × 1 × 1 inch, with two gold plugs dropped into holes so that the surface of the plugs passes through the center plane of the bar. Upon these plugs are three transverse lines and two longitudinal lines, the yard being the distance from the middle transverse line--the portion lying between the two longitudinal ones--of one plug, to the corresponding line on the other plug. Forty copies were made, but two of these being correct at 62 degrees Fahrenheit, and these two, together with the original and one other, are kept in England as the standards for reference. In 1855 the standard as made by Rev. Sheepshanks was legalized. Attempts to Fix a Standard in the United States The Constitution empowers Congress to fix the standards of weights and measures, but up to 1866 no legal standard length had been adopted. In his first message to Congress Washington said: "A uniformity in the weights and measures of the country is among the important objects submitted to you by the Constitution, and if it can be derived from a standard at once invariable and universal, it must be no less honorable to the public council than conducive to the public convenience." In July, 1790, Thomas Jefferson, then Secretary of State, sent a report to Congress containing two plans, both based on the length of the pendulum, in this case the pendulum to be a plain bar, the one plan to use the system then existing, referring it to the pendulum as the basis, and the other to take the pendulum and subdivide it, one-third of the pendulum to be called a foot. The whole length was that of one beating seconds of time. He made a table to read as follows: 10 Points make a Line. 10 Lines make a Foot. 10 Feet make a Decad. 10 Decads make a Rood. 10 Roods make a Furlong. 10 Furlongs make a Mile. Congress did not adopt his system, and as England was then working on the problem, it was decided to await the results of its labors. In 1816, Madison, in his inaugural address, brought the matter of standards to the attention of Congress, and a committee of the House made a report recommending the first plan of Jefferson, but the report was not acted upon. In 1821, J. Q. Adams, then Secretary of State, made a long and exhaustive report in which he favored the metric system, but still advised Congress to wait, and Congress--waited. What the Standards are in the United States The standard of length which had generally been accepted as _the_ standard, was a brass scale 82 inches long, prepared by Troughton for the Coast Survey of the United States. The yard used was the 36 inches between the 27th and 63d inch of the scale. In 1856, however "Bronze No. 11" was presented to the United States by the British government. This is a duplicate of the No. 1 Bronze mentioned before, which is the legalized standard yard in England. It is standard length at 61.79 degrees F., and is the accepted standard in the United States. A bar of Low Moor iron, No. 57, was sent at the same time, and this is correct in length at 62.58 degrees F. The expansion of Bronze No. 11 is 0.000342 inch, and that of the iron bar is 0.000221 inch for each degree Fahrenheit. While the yard is the commonly accepted standard in this country, it is not the legal standard. In 1866 Congress passed a law making legal the meter, the first and only measure of length that has been legalized by our government. Copies of the meter and kilogram, taken from the original platinum bar at Paris, referred to before, were received in this country by the President and members of the Cabinet, on Jan. 2, 1890, and were deposited with the Coast Survey. By formal order of the Secretary of the Treasury, April 5, 1893, these were denominated the "Fundamental Standards." The International Bureau of Weights and Measures After the original meter was established, it was found that copies made by various countries differed to a greater or less extent from the original, and believing that a copy could be made from which other copies could be more readily made than from the end piece meter, and that better provision could be made for the preservation of the standard, France called a convention of representatives from various States using the system, to consider the matter. The United States representatives, or commissioners, were Messrs. Henry and Hildegard, who met with the general commission in 1870. The commissioners at once set at work to solve the problem presented to them, but the Franco-Prussian war put an end to their deliberations. The deliberations were resumed later, and May 20, 1875, representatives of the various countries signed a treaty providing for the establishment and maintenance, at the common expense of the contracting nations, of a "scientific and permanent international bureau of weights and measures, the location of which should be Paris, to be conducted by a general conference for weights and measures, to be composed of the delegates of all the contracting governments." This bureau is empowered to construct and preserve the international standards, to distribute copies of the same to the several countries, and also to discuss and initiate measures necessary for the determination of the metric system. The commission adopted a form for the standard as shown in Fig. 1. The lines representing the length of the meter are drawn on the plane _A_, which is the neutral plane, and will not change in length should the bar deflect. The bar is made of 90 per cent platinum and 10 per cent iridium, about 250 kilograms having been melted when preparations were made for the first standard, so that all of the copies made from this cast represent the same coefficient of expansion and are subject to the same changes as the original. The French government presented to the bureau the pavilion Breteuil, opposite the Park of St. Cloud, which was accepted and put into order and is now the repository of the originals of the meter and the kilogram. The expense attending the first establishment of the bureau was about $10,000 to the United States, and since then its share of the annual expense has been about $900. The standards in the possession of the United States were received through the international bureau. The Commercial Value of a Standard Having at the disposal of the nation a standard of length, the question arises, "What can be made of it commercially, and how do we know when we have a copy of the standard?" [Illustration: Fig. 1. Form of Bar Adopted for International Standards of Length] In 1893, the Brown & Sharpe Mfg. Co. decided to make a new standard to replace the one they had at that date. Mr. O. J. Beale was detailed to do this work. He prepared steel bars about 40 inches long by 1¼ inch square, and after planing them, they were allowed to rest for several months. At the ends of these bars he inserted two gold plugs, the centers of which were about 36 inches apart, and a little beyond these two others about one meter apart. A bar was placed in position upon a heavy bed. This was so arranged that a tool carrier could be passed over the bar. The tool carrier consisted of a light framework, holding the marking tool. One feature of the marking was that the point of the marking tool was curved and had an angle, so that if dropped it made an impression in the form of an ellipse. In graduations, ordinarily, the line, when highly magnified, is apt to present at its ends an impression less definite than in the center, by reason of the form of the objective. The line made with the tool mentioned is short, and that portion of the line is read which passes, apparently, through the straight line in the eye-glass of the microscope. In order to make these lines as definite as possible, the point was lapped to a bright surface. After being placed in position, the microscope, which could be placed on the front of the tool carrier, was set to compare with the graduation on the standard bar from which the new bar was to be prepared. After such a setting the readings were made by three persons, and by turning the lever the marking tool was dropped, making a very fine line, so fine indeed, that when the authorities in Washington began the examination of the bar later on they declared that no line had been made upon these studs. After making the first line, the carriage was moved along to compare with the other line on the standard, and after the correction had been made by the use of the micrometer in the microscope, the marking tool was again dropped, giving the second line, which was intended to mark the limit of one yard over-all. The same operation was repeated in the marking of the meter. The whole of this work was done, of course, with the greatest care, and, while the theoretical portion of it appears very simple in detail, it required a great deal of time and patience before the last line had been made. The bar thus marked was taken to Washington, and in Mr. Beale's presence was compared by the attendants with Bronze No. 11 and later with Low Moor bar, No. 57. In comparing this standard, a method was employed very similar to that used in marking it. The bar, properly supported, was placed upon a box that rested upon rolls, and on this same box was placed the government standard with which the Brown & Sharpe standard was to be compared. The standard was placed in position under the microscope, and after being properly set to the standard, the bar to be measured was placed under the microscope, and by the micrometer screw of the microscope the variation was measured. Three comparisons were made by each of the attendants on each end before determining the reading of the microscope, and after such comparisons and many repetitions of it, the value of the standard No. 2 was found to be 36.00061 inches for the yard, and 1.0000147 meter for the meter. After this work had been done, Mr. Beale prepared a second standard which he called No. 3, and after examining, as shown above, the error was found to be 0.00002 inch for the yard, and 0.000005 meter for the meter. Observing these variations as compared with the standards originally made, we find they are very close, and it is doubtful if many repeated trials would furnish more accurate work, when we remember that out of forty original standards made, but two are correct at 62 degrees Fahrenheit. After establishing a yard, the problem of obtaining an inch comes next, and this was made by subdividing the yard into two equal parts, these into three, and the three further subdivided into six parts. It should be particularly noted that no mention has been made of a standard inch, as there is none, the standard yard only existing, the subdivision of which falls upon those undertaking standard work. There is a remarkable agreement between at least three leading gage makers of this country and abroad, and each came to the result by its own method of subdividing the standard yard. Kinds of Measurements and Measuring Tools The measurements in the shop may, in general, be divided into measurements of length and measurements of angles. The length measurements in turn may be divided into line measurements and end measurements, the former being made by placing a rule or similar instrument against the object being measured, and comparing its length with the graduations on the measuring instruments; the latter are made by comparing the object being measured with the measuring instrument, by bringing the object measured into actual contact with the measuring surfaces of the instrument. Examples of line measurements are the ordinary measurements made with the machinist's rule, and examples of end measurement are those made by the micrometer, measuring machines, and snap gages. Angular measurements can also be divided into two classes; those measured directly by graduations on the instrument, and those measured by comparison with a given angle of the instrument. Measuring instruments may also be divided into two classes, according to whether they actually are used for measuring, or whether they are principally used for comparing objects with one another. According to this classification all kinds of rules and protractors belong to the first class, whereas all gages belong to the second class. The ordinary instruments for length measurements, the regular machinists' rule, the caliper square, and the ordinary micrometer caliper, are too well known to require any additional explanation. The same is true of the regular bevel protractor for measuring angles. We shall therefore in the following chapters deal principally with special measuring tools, and with such methods in the use of tools which are likely to suggest improvements, or otherwise be valuable to the user and maker of measuring tools. * * * * * CHAPTER II CALIPERS, DIVIDERS, AND SURFACE GAGES In the present chapter we shall deal with the simpler forms of tools used for measuring, such as ordinary calipers, and their use; surface gages; special attachments for scales and squares, facilitating accurate measuring; and vernier and beam calipers. The descriptions of the tools and methods referred to have appeared in MACHINERY from time to time. The names of the persons who originally contributed these descriptions have been stated in notes at the foot of the pages, together with the month and year when their contribution appeared. Setting Inside Calipers [Illustration: Figs. 2 and 3 - Fig. 4 - Setting Inside Calipers] It is customary with most machinists, when setting inside calipers to a scale, to place one end of the scale squarely against the face of some true surface, and then, placing one leg of the caliper against the same surface, to set the other leg to the required measurement on the scale. For this purpose the faceplate of the lathe is frequently used on account of its being close at hand for the latheman. The sides of the jaws of a vise or almost anything located where the light is sufficient to read the markings on the scale are frequently used. The disadvantages of this method are, first, that a rough or untrue object is often chosen, particularly if it happens to be in a better light than a smooth and true one, and, second, that it is very hard to hold the scale squarely against an object. It is easy enough to hold it squarely crosswise, but it is not so easy a matter to keep it square edgewise. As can be readily seen, this makes quite a difference with the reading of the calipers, particularly if the scale is a thick one. Figs. 2 and 3 show this effect exaggerated. _B_ is the block against which the scale abuts. The dotted line indicates where the caliper leg should rest, but cannot do so, unless the scale is held perfectly square with the block. Fig. 4 shows a method of setting the calipers by using a small square to abut the scale and to afford a surface against which to place the leg of the caliper. The scale, lying flat on the blade of the square, is always sure to be square edgewise, and is easily held squarely against the stock of the square as shown. This method has also the advantage of being portable, and can be taken to the window or to any place where the light is satisfactory. When using a long scale, the free end may be held against the body to assist in holding it in place.[2] Shoulder Calipers [Illustration: Fig. 5. Shoulder Calipers] In Fig. 5 are shown a pair of calipers which are very handy in measuring work from shoulder to shoulder or from a shoulder to the end of the piece of work. For this purpose they are much handier, and more accurate, than the ordinary "hermaphrodites." The legs are bent at _AA_ so as to lie flat and thus bring the point of the long leg directly behind the short one which "nests" into it, as at _B_, so that the calipers may be used for short measurements as well as for long ones. Double-jointed Calipers to Fold in Tool Box In Fig. 6 are illustrated a pair of large calipers that can be folded up and put in a machinist's ordinary size tool chest. The usual large caliper supplied by the average machine shop is so cumbersome and heavy that this one was designed to fill its place. It can be carried in the chest when the usual style of large caliper cannot. It is a very light and compact tool. It is a 26-inch caliper, and will caliper up to 34 inches diameter. The top sections are made in four pieces, and the point ends fit between the top half like the blade of a knife, as shown in the engraving. Each side of the upper or top section is made of saw steel 1/16 inch thick, and the lower part or point of steel 1/8 inch thick. The double section makes the tool very stiff and light. The point section has a tongue _A_, extending between the double section, which is engaged by a sliding stud and thumb nut. The stud is a nice sliding fit in the slot, and the thumb nut clamps it firmly in place when in use. _B_, in the figure, shows the construction of the thumb nut. _C_ is a sheet copper liner put between the washers at _A_. The dotted lines in the engraving show the points folded back to close up. The large joint washers are 1¾ inch diameter, and a 5/8-inch pin with a 3/8-inch hexagon head screw tightens it up. The forward joints are the same style, but smaller. The main joint has two 1¾-inch brass distance pieces or washers between the two main washers. The top section is 12½ inches between centers, and the point sections 15 inches from center to point. Closed up, the calipers measure 16 inches over-all. [Illustration: Fig. 6. Large Double-jointed Calipers] Kinks in Inside Calipering Close measurements may be made by filing two notches in each leg of an inside caliper so as to leave a rounded projection between, as shown at _E_, Fig. 7. Then, with an outside caliper, _D_, the setting of the inside caliper, _B_, is taken from the rounded points. The inside caliper can be reset very accurately after removal by this method. A still better way is to have two short pins, _CC'_ set in the sides of the inside caliper legs, but this is not readily done as a makeshift. To measure the inside diameter of a bore having a shoulder like the piece _H_, the inside caliper _F_ may also be set as usual and then a line marked with a sharp scriber on one leg, by drawing it along the side _G_. Then the legs are closed to remove the caliper, and are reset to the scribed line. Of course, this method is not as accurate as the previous one, and can be used only for approximate measurements. [Illustration: Fig. 7. Methods of Inside Calipering] To get the thickness of a wall beyond a shoulder, as at _K_, Fig. 7, set the caliper so that the legs will pass over the shoulder freely, and with a scale measure the distance between the outside leg and the outside of the piece. Then remove the caliper and measure the distance between the caliper points. The difference between these two distances will be the thickness _M_. Inside Calipers for Close Spaces In Fig. 8 are shown a pair of inside calipers which are bent so as to be well adapted for calipering distances difficult of access, such as the keyway in a shaft and hub which does not extend beyond the hub, as indicated. With the ordinary inside calipers, having straight legs, and which are commonly used for inside work, it is generally impossible to get the exact size, as the end which is held in the hand comes in contact with the shaft before both points come into the same vertical plane. The engraving plainly shows how calipers for this purpose are made, and how used. Any mechanic can easily bend a common pair to about the shape shown to accommodate this class of work.[3] [Illustration: Fig. 8. Inside Calipers for Close Spaces] Surface Gage with Two Pointers Figs. 9 and 10 show a special surface gage, and illustrate an original idea which has been found to be a great saver of time and of milling cutters. It can also be used on the planer or shaper. By its use the operator can raise the milling machine table to the right height without testing the cut two or three times, and eliminate the danger of taking a cut that is liable to break the cutter. This tool is especially valuable on castings, as raising the table and allowing the cutter to revolve in the gritty surface while finding the lowest spot is very disastrous to the cutting edges. [Illustration: 10] To use this surface gage, the pointer marked _C_ in Fig. 9 is set to the lowest spot in the casting, and then the pointer _B_ is set from it with perhaps 1/32 inch between the points for a cut sufficient to clean up the surface. Pointer _C_ is then folded up as shown at _C'_ in Fig. 10, and the table is raised until the pointer _B_ will just touch the under side of the cutter as shown at _B'_ in Fig. 10. In this way the table is quickly adjusted to a cut that will clean the casting or other piece being machined, and with no cutting or trying whatever.[4] To Adjust the Needle of a Surface Gage [Illustration: Fig. 11. Method of Adjusting the Needle of a Surface Gage] [Illustration: Fig. 12. Scale Attachment for the Square] Fig. 11 illustrates a method of adjusting the needle of a surface gage. To set the gage 3¾ inches from the table, get somewhere within ¼ inch of the mark on the square. With the thumb and forefinger on hook _A_, turn the needle till it reaches the point desired. By turning the needle, it will travel in a circular path, on account of the bend near the point, and thus reach the desired setting. Scale Attachment for the Square Fig. 12 shows a device for attaching a scale to a square. This combination makes a very convenient tool to use when setting up work for keyseating, as is illustrated in the engraving, in which _S_ is the shaft to be splined and _C_ the milling cutter. It is also a very handy tool for truing up work on the boring mill or lathe. At the upper left-hand corner, is shown the construction of the parts, which are made of dimensions to suit the size of the scale and the square. For the combination to be successful, it is essential that the blade of the square is the same thickness as the scale.[5] Attachment for Machinist's Scale [Illustration: Fig. 13. Convenient Attachment for Machinist's Scale] Fig. 13 shows a very convenient appliance. It will be found very useful in the machine shop for setting inside calipers to any desired size. The gage is clamped over the rule wherever desired, and one leg of the calipers set against the gage, the other leg being brought flush with the end of the scale.[6] Setting Dividers Accurately To set dividers accurately, take a 1-inch micrometer and cut a line entirely around the thimble as at _A_, Fig. 14, and then, with the instrument set at zero, make a punch mark _B_ exactly one inch from the line on the thimble. If less than one inch is wanted, open out the micrometer and set the dividers to the dot and line so as to give one inch more than the distance wanted. Now with the dividers make two marks across a line, as at _a_ and _b_, Fig. 14, and then set the dividers to one inch and mark another line as at c. The distance from _c_ to _b_ is the amount desired, and the dividers can be set to it. Great care must, of course, be exercised, if accurate results are required. [Illustration: Fig. 14. Method of Setting Dividers Accurately] Combination Caliper and Divider The combination caliper and divider shown in Fig. 15 is one that is not manufactured by any of the various tool companies. It is, however, one of the handiest tools that can be in a machinist's kit, as it lends itself to so many varied uses, and often is capable of being used where only a special tool can be employed. The illustration suggests its usefulness. The tool can be used as an outside caliper, as an inside caliper, and as a divider. The common form of this tool has generally only one toe on the caliper legs, but the double toes save the reversal of the points when changing from outside to inside work. The divider points may be set at an angle, which permits of stepping off readily around the outside of a shaft at angular distances, where the ordinary dividers are useless. A number of other uses could be mentioned, but any intelligent mechanic can readily suggest them for himself. [Illustration: Fig. 15. Combination Caliper and Divider] Attachment for Vernier Calipers While vernier and slide calipers are very handy shop tools, their usefulness is much more limited than it ought to be for such expensive instruments. In order to increase the usefulness of these tools, the attachments shown in Fig. 16 may be made. In the upper left-hand part of the engraving the details of a useful addition to the caliper are shown. _A_ is made of machine steel, while the tongue _B_ is of tool steel, hardened and ground and lapped to a thickness of 0.150 inch, the top and bottom being absolutely parallel. This tongue is secured to _A_ by the two rivets _CC_. The thumb-screw _D_ is used for fastening the attachment to the sliding jaw of the vernier or slide caliper. In the upper part of the engraving is shown the base, which is of machine steel, with the slot _F_ milled for the reception of the fixed jaw of the caliper. The set-screws _GGG_ are put in at a slight angle so that the caliper will be held firmly and squarely in this base. In the figure to the left these pieces are shown in the position for forming a height gage, for which purpose the attachment is most commonly used. As a test of the accuracy of its construction when the attachment is placed in this position, the tongue _B_ should make a perfect joint with the fixed jaw of the caliper, and the vernier should give a reading of exactly 0.150. When it is desirable that the tongue _B_ should overhang, the base _E_ is pushed back even with the stationary jaw, as shown in the engraving to the right. In this position it is used for laying out and testing bushings in jigs, etc. The illustration shows the tool in use for this purpose, _K_ being the jig to be tested. All measurements are from the center line upon which the bushing No. 1 is placed. Taking this as a starting point we find the caliper to read 1 inch. Bushing No. 2, which is undergoing the test, should be 5/8 inch from this center line. It has a ¼-inch hole, and we therefore insert a plug of this diameter. Now adjust the tongue of the caliper to the bottom of this plug (as shown in the engraving) and the vernier should read 1.625 minus one-half the diameter of the plug, or 1.500, and any variation from this will show the error of the jig. In this case the top surface of _B_ was used and no allowance had to be made for its thickness. In case the bottom surface is used, 0.150 must be deducted from the reading of the caliper. [Illustration: Fig. 16. Attachment for Vernier Calipers] It is very easy to make a mistake in setting a bushing, and such a mistake is equally hard to detect unless some such means of measuring as this is at hand. It often happens that jigs and fixtures are put into use containing such errors, and the trouble is not discovered until many dollars' worth of work has been finished and found worthless. The illustration shows but one of the many uses to which this attachment may be applied. The figures given on the details are correct for making an attachment to be used upon the Brown & Sharpe vernier caliper, but for other calipers they would, of course, have to be altered to suit.[7] Improved Micrometer Beam Caliper [Illustration: Fig. 17. Improved Micrometer Beam Caliper] In a beam caliper having a sliding micrometer jaw with or without a separate clamping slide, it is necessary to have the beam divided into unit spaces, at which the jaw or slide may be accurately fixed, the micrometer screw then being used to cover the distance between the divisions; but it is difficult to construct a beam caliper of this type with holes for a taper setting pin, at exactly equal distances apart; consequently a plan that is generally followed in making such tools is to provide as many holes through the slide and beam as there are inch divisions, each hole being drilled and reamed through both the slide and beam at once. If it were attempted to drill the holes through the beam at exactly one inch apart, having only one hole in the clamping head and using it as a jig for the purpose, it would be found very difficult, if not impossible, to get the holes all of one size and exactly one inch apart. The design of the micrometer beam caliper shown in Fig. 17, which has been patented by Mr. Frank Spalding, Providence, Rhode Island, is such, however, that it is not necessary to drill more than one hole through the clamping slide. The beam _F_ is grooved longitudinally, and in the groove are fitted hardened steel adjusting blocks in which a taper hole _D_ is accurately finished. Between the blocks are filling pieces _G_, which are brazed or otherwise fastened in the groove. Holes are drilled, tapped, and countersunk between the blocks and the filling pieces _G_, in which are fitted taper head screws _EE_1_. The construction is thus obviously such that the blocks may be shifted longitudinally by loosening one screw and tightening the other. In constructing the caliper, the holes through the beam are drilled as accurately as possible, one inch apart, and centered in the longitudinal groove, but are made larger than the holes in the blocks, so as to provide for slight adjustment. Large Beam Caliper [Illustration: Fig. 18. Large Beam Caliper] Fig. 18 shows a large beam caliper designed for machinists and patternmakers. It consists of a beam _MN_ and the legs _R_ and _S_, made of cherry wood to the dimensions indicated. The legs are secured in position on the beam by means of the thumb screws _A_, which jam against the gibs _C_ at the points of the screws. The gibs have holes countersunk for the screws to enter, to hold them approximately in place, and the nuts _B_ are of brass, fitted into the filling pieces _P_ that keep them from turning. The filling pieces are riveted to the legs by means of cherry dowels _D_. One leg _S_ is provided with a fine adjustment consisting of flexible steel spring _H_, ending in a point which is adjusted by the thumb screw _E_. This screw is locked in adjustment by the check nut _G_ bearing against the brass nut _F_, which is inserted in the leg as shown.[8] * * * * * CHAPTER III MICROMETER MEASURING INSTRUMENTS Of all measuring instruments used in the shop intended for accurate measurements, those working on the principle of the ordinary micrometer calipers are the most common. In the present chapter we shall describe and illustrate a number of different designs of these tools, intended to be used for various purposes. The instruments shown in Figs. 19 to 23 were built, in leisure hours, by Mr. A. L. Monrad, of East Hartford, Conn. Micrometer for Snap Gages [Illustration: Fig. 19. Micrometer for Snap Gages] Fig. 19 shows a form of micrometer that has proved very handy for measuring snap gages, and thicknesses, and can also be used as a small height gage to measure the distance from a shoulder to the base, as shown in Fig. 20. In measuring snap gages or thicknesses, the outside and inside of the measuring disks are used, respectively. This instrument may also come in very handy when setting tools on the planer or shaper. As will be seen in the engraving, there are two sets of graduations on the sleeve _A_, thus enabling the operator to tell at a glance what measurement is obtained from the outside or the inside of the measuring disks. Each of the disks is 0.100 inch thick, so that the range of the micrometer is 0.800 and 1.000 inch for the outside and inside, respectively. The details of the instrument are as follows: The sleeve _A_ is composed of the inside measuring disk, the graduated sleeve, and the micrometer nut combined. On the disk are two projections _KK_, which are knurled, thus providing a grip when operating the tool. The sleeve is threaded on the inside of one end, which acts as a micrometer nut, and the outside of this same end is threaded to receive the adjusting nut _D_. The sleeve has two slots, each placed 90 degrees from the graduations, and these provide for compensation for wear. The disk part is hardened by heating in a lead bath, and is finished by grinding and lapping. The barrel _B_ is the same as a regular micrometer barrel, and is graduated with 25 divisions. Spindle _E_ consists of the outside disk and the micrometer screw, and the barrel _B_ fits on its end, which is tapped out to receive the speeder _C_, which serves to hold the barrel in position. The thread is ¼ inch, 40 pitch, and the disk and unthreaded parts are hardened, ground and lapped. To adjust this, instrument, loosen the speeder _C_ and turn the barrel until the proper adjustment is obtained. Then lock the barrel by tightening the speeder again.[9] [Illustration: Fig. 20. Micrometer in Fig. 19 used as Height Gage] Micrometer Caliper Square Fig. 21 shows an assembled view and the details of a micrometer caliper square which, if accurately made, is equal and often preferable to the vernier caliper now so generally used. One of its advantages over the vernier is that when the measurement is taken, it can be readily discerned without straining the eyes, and this instrument is as easy to manipulate as the regular micrometer. In the details, part _A_, which is the main body of the instrument, is made of tool steel, the forward or jaw end being solid with the body. This end is hardened, and the jaw ground and lapped. The body is bored out and two flats milled on the outside, which lighten it up and make it neat in appearance. The jaw end is counterbored out with a 45-degree counterbore to form a bearing for the forward end of the micrometer screw. A slot, 1/8 inch in width, extends from the fixed jaw to the other end, and in this slides the movable jaw _C_. There are 44 divisions along the side of this slot, each division being 0.050 inch apart, giving the tool a range of 2.000 inches for outside and 2.200 inches for inside measurements. The screw _B_ is the most essential part of this tool, its construction requiring great accuracy. Its diameter is 3/8 inch and it is cut with 20 threads per inch. On its forward end fits the cone _F_, which is hardened and ground, the round part acting as the forward bearing of the screw and fitting in the 45-degree counterbored hole in the body _A_. On its other end fits the graduated barrel _D_ and also the speeder _G_. [Illustration: Fig. 21. Micrometer Caliper Square] The barrel is graduated in fifty divisions, each division equaling 0.001 inch. On the inside of the barrel is a 45-degree bearing which rides on the cone _M_, the cone being held stationary on the end of the body. Thus it will be seen that both front and back ends of the micrometer screw are carried in cone bearings, which give a very small point of contact, thereby causing but little friction and preventing any danger of gumming up so as to run hard. The sliding jaw _C_ is made of tool steel, hardened, ground and lapped, and combined with it is the micrometer nut which is drawn to a spring temper. This nut is split and adjusted by two screws to compensate for wear. On this jaw are the two zero marks that tell at a glance the outside or inside measurements taken. The screw and washer, marked _H_ and _I_, go onto the end of the micrometer screw and take up the end play. To make a neat appearance, the cap _E_ is placed in the forward counterbored hole, being held in place by a tight fit. The adjustment of the tool is accomplished by loosening the speeder _G_ and turning the barrel on the screw; when the adjustment is made, the speeder is again tightened down and the barrel locked.[10] Micrometer Depth Gage The depth gage, shown in Fig. 22, has a ½-inch movement of the rod, and may be used with rods of any desired length. These have small 45-degree-on-a-side grooves cut into them at intervals of ½ inch. A small spiral spring, marked _I_, gives the rod a constant downward pressure, so that, when taking a measurement, the base of the tool is placed on the piece of work, and the rod always finds the bottom of the hole; then, by tightening the knurled screw _F_ the rod is clamped in position and the tool may be picked up and its measurement read from the dial. The graduations on this instrument are similar to those of the vernier caliper, only they are much plainer, as a half-inch movement of the rod turns the dial one complete revolution. The figures on the dial denote tenths of an inch, and those on the body of the tool thousandths; each graduation on the dial is therefore equal to 0.010, so that to show the depth of a hole to be 0.373 the dial would be revolved around so that the seventh division beyond the 3 mark would be near to 0, and then by looking from the 0 mark toward the left, the third graduation on the body and one on the dial would be in line, thus denoting 0.373. [Illustration: Fig. 22. Micrometer Depth Gage] The most essential part of this tool is the threaded screw _B_, which acts as a rack, and the worm-wheel, solid with the dial _C_. The upper end of the screw forms a split chuck which grips the measuring rods, while the part marked _R_ is flatted off, and against this portion bears a threaded sleeve _G_, which acts as a key to keep the screw in position. This sleeve is threaded, both inside and outside, and screws into the body of the tool, while the binding screw _F_ fits into it and binds against a small piece of copper, marked _H_, which in turn holds the screw in position. The thread on _B_ is 0.245 inch in diameter and is cut with 40 threads per inch. The worm-wheel which meshes into this screw is solid with the dial, as shown at _C_. It is 0.18 inch in diameter, and requires great accuracy in cutting; it is not hobbed, but the teeth, of which there are twenty, are milled with a circular cutter of the same diameter as the screw _B_ plus 0.002 inch. The little studs, marked _EE_, on the dial and on the body _K_, hold the coiled spring in position. Very great accuracy must be attained when locating the holes in _K_ that are to receive the screw and dial _B_ and _C_. The screw marked _J_ fits into the dial, where it serves as a bearing and also holds the dial in position. The knurled cap _D_ tightens the split chuck in order to hold the measuring rod firmly.[11] Indicator for Accuracy of Lead-screws [Illustration: Fig. 23. Indicator for Accuracy of Lead-screws] All of the tools that have been described require an accurately cut screw, and, as very few lathes are capable of producing this, it may be well to illustrate an indicator for testing the accuracy of the lead-screw, and to explain the method by which it is used. This instrument is shown in Fig. 23, where it is applied to a test screw _K_. It consists of a body _A_ on one end of which is a projection _L_ serving as the upper bearing for the pivoted lever _D_. This lever swings about a small steel pivot which can be adjusted by the screw _E_. The rear end of the lever is forked, and between the prongs is passed a thread making a double turn about the pivot _F_ that carries the pointer _J_. Any movement of this lever will, therefore, cause this pointer to revolve about the dial _C_. This dial has 20 divisions, each indicating one-half thousandth of an inch movement of the front end of the lever, so that a total revolution of the pointer about the dial would indicate a movement of the front end of the lever of 0.020 inch. The screws _I_ serve to hold the dial in place on the body of the indicator, while the spring _M_ keeps the pointer normally at the zero mark. The indicator is held in the toolpost by the arm _G_, which can be set at any angle and firmly clamped by the screw _H_. To use the indicator, remove the screw from a micrometer which is known to be accurate, and, with the aid of a brass bushing, chuck it in the lathe so that the thread end will project. Now gear the lathe to cut 40 threads per inch and apply the indicator. When the lathe is started, the point of the indicator follows along in the thread of the micrometer screw, and any variation in the lead will be noted by a movement of the pointer over the dial. If, on the other hand, no movement takes place, it is an indication that the pitch of the lead-screw is correct.[12] Micrometer Attachment for Reading Ten-thousandths of an Inch [Illustration: Fig. 24. Micrometer with Attachment for Reading Ten-thousandths of an Inch] Fig. 24 shows an attachment for micrometers designed and made for readings in tenths of thousandths of an inch. With very little fitting it is interchangeable for 1-, 2-, or 3-inch B. & S. micrometers. The idea is simple, as can be seen by the illustration. The diameter of the thimble is increased 3 to 1 by a disk which is graduated with 250 lines instead of 25, making each line represent 0.0001 inch instead of 0.001 inch. A piece of steel is then turned up and bored and cut away so as to form the index blade and a shell to clasp the micrometer frame, the whole thing being made in one piece. The thimble disk being just a good wringing fit, it can be easily adjusted 0 to 0. The attachment can be removed when fine measuring is not required.[13] Special Micrometer for Large Dimensions Fig. 25 shows a 6-inch micrometer caliper designed for measuring from 0 to 6 inches by half-thousandths. The sliding micrometer head travels on a cylinder barrel through which a hole is accurately bored to suit three plugs, one, two, and three inches long, as shown in the engraving. These plugs serve to locate the traveling head at fixed distances one inch apart. The micrometer screw itself has a travel of one inch, like any standard micrometer. A locknut is used to hold the screw in any desired position. A thumb screw at the end of the barrel bears against the end plug, and zero marks are provided to bring the screw against the plug with the same degree of pressure at each setting. When the head is clamped by means of the locking nut, it is as rigid as though it were solid with the barrel, and the faces of the measuring points are thus always parallel. [Illustration: Fig. 25. Special Micrometer for Large Dimensions] Combination Micrometer [Illustration: Fig. 26. Combined One- and Two-inch Micrometer] A combined one- and two-inch micrometer is shown in Fig. 26. One side records measurements up to one inch, and the other side up to two inches. A single knurled sleeve or nut serves to move the double-ended measuring piece one way or the other as desired, this piece having a travel of one inch. The spindle is non-rotating, so that the faces of the screw and anvil are always parallel. A locking device holds the screw in any position. This tool is convenient for use both in measuring and as a gage, since it can be conveniently held by the finger ring appearing at the back. Micrometer Stop for the Lathe Most micrometer lathe stops are limited in their use to work where only a stationary height is required. It is, however, often necessary to use the stop at different heights, to accommodate different lathes; then again, we wish to use it on the right-hand side as well as the left. The form of holder shown in Fig. 27 can be used either right or left, and for various heights, and, by simply taking out the screw _A_, the micrometer may be removed and used in any other form of holder desired. [Illustration: Fig. 27. Micrometer Stop for the Lathe] Both an assembled view and details of the holder are shown in the engraving, so that it can be easily constructed by any one desiring to do so. The micrometer and barrel may be procured from any of the manufacturers of measuring instruments. The swivel _C_ is bored out so that the axis of the micrometer screw will be parallel to the body of the holder when it is in place. The swivel is made of tool steel and is fastened to the holder by the screw _A_. It is hardened and lapped to a true bearing surface on the sides and bottom, and so adjusted that it will turn to either side and remain in the desired position without moving the screw. The holder _B_ is milled through its entire length with a 90-degree cutter so that it will fit along the ways of the lathe, and the bottom is lapped to a true surface. For a neat appearance, the tool should be color hardened. On top the holder is spotted or countersunk with a drill to form a recess for the C-clamp. A knurled ring _D_ is driven onto the micrometer sleeve so that it can be turned around to bring the graduations uppermost when the position of the barrel is changed.[14] Micrometer Surface and Height Gage [Illustration: Fig. 28. Micrometer Surface and Height Gage] Fig. 28 shows a form of surface gage that has proved very handy, and which can be used also as a height gage for measuring distances from shoulders to the base. If accurately made it is equal, and often preferable, to the vernier or slide caliper now so generally used with an attachment to the sliding jaw. One of its advantages over the vernier is the readiness with which the graduations are discerned, and it is as easy to manipulate as the ordinary micrometer. The part _B_, which forms the main body of the instrument, is made of tool steel, and one end is fitted into the base where it is held in position by the screw _D_. The remainder is milled to a thickness of 1/8 inch and has graduations of 0.025 inch for a distance of three inches. The screw _A_ is the most essential part of the tool, and its construction requires great accuracy. Its diameter is ½ inch, and it is cut with 20 threads per inch. In the upper end of the screw is driven the ball _H_ for the sake of giving a neat appearance. The top of the thread is turned off 0.010 inch to allow the scriber _F_ to slide freely on the screw. The barrel _I_ is used for raising and lowering the slide, but instead of having the graduations placed directly upon it, they are made upon the sleeve _C_, which fits over a shoulder on the barrel. This allows more easy means of adjustment than would be possible were the graduations placed on the barrel itself. The sleeve is graduated with fifty divisions each equaling a movement of the scriber of 0.001 inch. This sleeve may be turned by means of a small spanner wrench so as to bring the zero line into correct position to compensate for wear. A knurled locking nut is also provided for holding the scriber in any fixed position. The scriber itself is hardened and lapped to a finished surface, the tail end being slotted and provided with two screws to compensate for wear. On the scriber is placed the zero mark which shows at a glance the measurement that is being taken. The block _K_ is three inches in height, and by using this block and placing the gage on its top, the range of the gage is increased to six inches. The screw _E_ is used for fastening the gage to the top of the block. The center of the block is drilled out and slots cut through the sides in order to make it light and neat in appearance.[15] Micrometer of from One- to Five-inch Capacity [Illustration: Fig. 29. Micrometer of from One- to Five-inch Capacity] Fig. 29 shows a very simple and light five-inch micrometer that can be quickly set to exact position from one to five inches. The round beam is graduated by a series of angular grooves, 1 inch apart, which are of such a form and depth that the clamping fingers at the end of part _A_ spring in, allowing one inch adjustment of the beam to be quickly and positively made. The sleeve _K_ is of tool steel, being counterbored from the forward end for all but one-half inch of its length. For this half inch it is threaded on the inside and acts as a micrometer nut. The outside of the same end is threaded to receive the adjusting nut _F_, and two slots are cut in the sleeve, at 90 degrees with the graduations. These slots, by a movement of the nut _F_, provide a means for compensating for wear. The bushing _E_ is hardened and lapped, and fitted tightly in the forward counterbore of this sleeve, where it acts as a guide for the front end of the micrometer screw. The barrel _J_ is the same as that of a regular micrometer, and is graduated in 0.025 inch divisions. The most essential part of the tool is the threaded screw _I_, over the end of which fits the barrel _J_. The end is tapped out to receive the speeder _H_, which serves to hold the barrel in position. The thread is 5/16 inch in diameter, with 40 threads per inch, while the unthreaded part is hardened, ground and lapped. To adjust the instrument, loosen the speeder _H_ and turn the barrel until the proper adjustment is obtained; lock the barrel by again tightening the speeder. The beam _C_ has a ¼-inch hole drilled throughout its entire length in order to make it light. Small 90-degree grooves are cut into it at intervals of 1 inch, and a 1/8-inch slot is milled through one side to within 1¼ inch of the forward end. The back end of part _A_ forms a spring-tempered split chuck, which grips the beam and holds _A_ in position, while the exterior is threaded to receive the knurled cap _B_ by which the chuck is tightened firmly to the beam. From the front end, toward the split chuck, the body is counterbored 5/8 inch and the bushing _D_ driven in tight. This bushing has a key _G_ fitted into it, which slides in the slot of the beam and prevents the arm from turning. The projecting arm is bored and tapped to receive the sleeve _K_. This gage must be carefully and accurately made to be of value.[16] Inside Micrometer for Setting Calipers [Illustration: Fig. 30. Method of Setting Calipers from Inside Micrometers] Fig. 30 shows an application of inside micrometers which is very handy. The hole for the scriber in the scriber clamp of a surface gage is reamed out to fit the rods used with inside micrometers. This forms a convenient holder for the micrometer when used for setting outside calipers to it. The calipers can be set easily and accurately at the same time, and where extreme accuracy is not necessary this arrangement is more handy than that of using large-sized micrometers. With care and practice an accuracy of within one-quarter of 0.001 inch is obtainable in this way. Mistakes, in fact, are more easily guarded against than is the case when using the micrometers directly. Micrometer Frame [Illustration: Fig. 31. Useful and Handy Micrometer Frame] Fig. 31 shows a micrometer frame used some years ago at the Westinghouse works. The frame is an aluminum casting, and the anvil is simply a tool-steel pin, which fits well in the hole into which it is inserted, and can be clamped anywhere within the limits of its length. The micrometer end of the frame is supplied with an inside micrometer head. The tool is adjusted to a gage, either to a standard pin gage, or to an inside micrometer gage. The capacities of three of these micrometers in a set may be from about 3½ to 7 inches, 6 to 11 inches, and 10 to 15 inches. When the head is turned outward, as shown in the lower view in the cut, the tool is very handy around a horizontal boring machine where a pin gage cannot be used without removing the boring bar. Micrometer Stop for the Lathe [Illustration: Fig. 32. Micrometer Stop for the Lathe] The simple micrometer stop shown in Fig. 32 is used on the engine lathe for obtaining accurate movements of the lathe carriage. It consists of a micrometer head, which can be purchased from any micrometer manufacturer, and a machine steel body which is bored to fit the micrometer head. This tool is clamped on the front way of the lathe bed, and when the jaw of the micrometer is against the lathe carriage, it can easily be adjusted to a thousandth of an inch. Of course, care should be taken not to bump the carriage against the micrometer.[17] Use of Micrometer for Internal Thread Cutting [Illustration: Fig. 33. Method of using Micrometer for Internal Thread Cutting] Fig. 33 illustrates a means of determining the size of internally threaded work. The work shown is intended for a lathe chuck. The outside diameter of the hub on the work is turned to the same size as the hubs on small faceplates which are furnished with all new lathes. The threaded size is then taken and transferred with a micrometer, over the anvil of which is fitted a 60-degree point as shown enlarged at _A_. In connection with a graduated cross-feed screw this greatly facilitates the work over the usual cut-and-try method.[18] Inside Micrometer The inside micrometer shown in sections in Figs. 34 and 35 is adapted to measuring, by use of extension rods, from 2 inches up to any size of hole, and has one inch adjustment of the measuring screw. [Illustration: 35] Referring to the section shown in Fig. 35, the measuring screw _S_ is secured to the thimble _B_ with the screw _D_, the head of which is hardened and forms the anvil. By loosening this screw _D_, the thimble can be rotated to compensate for wear. The wear of the measuring screw and nut is taken up by screwing the bushing _A_ into the frame with the wrench shown in Fig. 37. This bushing is split in three sections for about two-thirds of its length on the threaded end. The three small lugs on the wrench fit into these slots. The handle end of the wrench is a screw driver which is used for manipulating the set screw _C_. The bushing is made an easy fit in the frame on its plain end and tapered, as shown, on its outside threaded part. This thread being the same pitch as the measuring screw, adjustment for wear does not affect the reading of the micrometer. This manner of adjustment brings the nut squarely down on the measuring screw for its whole length, presenting the same amount of wearing surface after adjustment as when new. [Illustration: Fig. 36. Handle for Inside Micrometer] [Illustration: Fig. 37. Wrench used with Inside Micrometer] The point _F_, which is hardened on its outer end, screws into the frame, and is secured by the taper-headed screw _O_, which screws into and expands the split and threaded end of the point _F_. The handle, Fig. 36, clamps over the knurled part of the frame for use in small, deep holes. The rods, six in number, running from 1 to 6 inches inclusive, are made by screwing a sleeve onto a rod with a hardened point and locking it with a taper-headed screw on its threaded and split end, the same as in the point _F_. The extension pieces, Fig. 38, are adjustable, on their socketed ends, in the same way, and run in lengths of 6, 12, 18 inches, etc.[19] [Illustration: Fig. 38. Adjustable Extension Pieces for Inside Micrometer] Direct Fractional-reading Micrometer [Illustration: Fig. 39. Direct Fractional-reading Micrometer] The direct fractional-reading micrometer shown in Fig. 39 is the result of talks with many mechanics in which all agreed that such a feature added to a micrometer would, by making it both a fractional and decimal gage, more than double its practical value. While approximate readings in 64ths, etc., may be obtained by the graduations on the barrel _B_ as on an ordinary inch scale, the exact readings of 64th, etc., may be obtained only by reference to graduations on the movable thimble _A_. There are but eight places on _A_ which coincide with the long graduation line on _B_ when any 64th, 32d, 16th, or 8th is being measured, and each of these eight places is marked with a line, and the 64th, 32d, 16th, or 8th for which that line should be used is marked thereon. (See _a_ and _b_, Fig. 40.) The line _a_ would be used for 3/32, 7/32, 11/32, etc., and the line _b_ for 1/64, 9/64, 17/64, etc. Now suppose we wish to accurately measure 15/32 inch. We first roughly read it off the inch scale on sleeve _B_ by turning out thimble _A_. Having secured it closely by drawing edge of _A_ over that graduation, we find that the line _a_ (Fig. 40) on the movable thimble very nearly or exactly coincides with the long graduation line on _B_. When these lines coincide, we have the exact measurement of 15/32 inch without reference to how many thousandths may be contained in the fraction. Thus all through the scale any fraction may be found instantly. There is no mental arithmetic, use of tables, or memory work in using the tool. The new graduations are independent of the old, and may be used equally well with or without them. [Illustration: Fig. 40. Graduations on the Fractional-reading Micrometer] Micrometers may also be graduated as in Fig. 41. Instead of using the zero line on _A_ as a base line, a point is taken one-fifth of a turn around _A_, and the graduated scale on _B_ is placed to correspond, as shown in the engraving; also, instead of making lines _a_, _b_, etc., on _A_, full length, they are made about half an inch long, and the numerators are entirely omitted and the denominators placed at the end instead of under the line. To the ordinary user of the tool, this is all that is necessary for a perfectly clear reading of the fractions.[20] [Illustration: Fig. 41. Another Method of Graduating for Fractional Reading] Sensitive Attachment for Measuring Instruments No matter how finely and accurately micrometers and verniers may be made, dependence must in all cases be placed on the sensitiveness of a man's hand to obtain the exact dimensions of the piece to be measured. In order to overcome this difficulty and eliminate the personal equation in the manufacture of duplicate and interchangeable parts, the sensitive attachment to the micrometer shown in Fig. 42 may be used, and will be found of much value. [Illustration: Fig. 42. Sensitive Micrometer Attachment] The auxiliary barrel _A_ is held to the anvil of the micrometer by means of a thumb screw _B_. At the inside end of the barrel is a secondary anvil _C_, the base of which bears against the short arm of the indicating lever _D_. The action will be clearly seen by reference to the engraving. The micrometer is so set that when a gage, _G_, of exact size, is placed between the measuring points, the long arm of the indicator stands at the 0 mark. If the pieces being calipered vary in the least from the standard size it will be readily noted by the movement of the pointer. Hard rubber shapes turned from rough casting often vary from 0.003 to 0.005 inch after having passed the inspector's test with an ordinary micrometer. With this attachment the inspector's helper can detect very minute variations from the limit size. Anything within the limits of the micrometer can be made to show to the naked eye variations as small as a ten-thousandth inch.[21] Another Sensitive Micrometer Attachment [Illustration: Fig. 43. Another Sensitive Micrometer Attachment] When testing the diameters of pieces that are handled in great quantities and are all supposed to be within certain close limits of a standard dimension, the ordinary micrometer presents the difficulty of having to be moved for each piece, and small variations in diameters have to be carefully read off from the graduations on the barrel. Not only does this take a comparatively long time, but it also easily happens that the differences from the standard diameter are not carefully noted, and pieces are liable to pass inspection that would not pass if a convenient arrangement for reading off the differences were at hand. Fig. 43 shows a regular Brown & Sharpe micrometer fitted with a sensitive arrangement for testing and inspecting the diameters of pieces which must be within certain close limits of variation. The addition to the ordinary micrometer is all at the anvil end of the instrument. The anvil itself is loose and consists of a plunger _B_, held in place by a small pin _A_. The pin has freedom to move in a slot in the micrometer body, as shown in the enlarged view in the cut. A spring _C_ holds the plunger _B_ up against the work to be measured, and a screw _D_ is provided for obtaining the proper tension in the spring. The screw and the spring are contained in an extension _E_ screwed and doweled to the body of the micrometer. A pointer or indicator is provided which is pivoted at _F_ and has one extensional arm resting against the pin _A_, which is pointed in order to secure a line contact. At the end of the indicator a small scale is graduated with the zero mark in the center, and as the indicator swings to one side or the other the variations in the size of the piece measured are easily determined. A small spring _G_ is provided for holding the pointer up against the pin _A_. The case _H_ simply serves the purpose of protecting the spring mentioned. As the plunger _B_ takes up more space than the regular anvil, the readings of the micrometer cannot be direct. The plunger _B_ can be made of such dimensions, however, that 0.100 inch deducted from the barrel and thimble reading will give the actual dimension. Such a deduction is easily done in all cases. In other words, the reading of the micrometer should be 0.100 when the face of the measuring screw is in contact with the face of the plunger; the 0.100 inch mark is thus the zero line of this measuring tool. When desiring to measure a number of pieces, a standard size piece or gage is placed between the plunger _B_ and the face _L_ of the micrometer screw, and the instrument is adjusted until the indicator points exactly to zero on the small scale provided on the body of the micrometer. After this the micrometer is locked, and the pieces to be measured are pushed one after another between the face _L_ and the plunger _B_, the indications of the pointer _M_ being meanwhile observed. Whenever the pointer shows too great a difference, the piece, of course, does not pass inspection. All deviations are easily detected, and any person of ordinary common sense can be employed for inspecting the work. Micrometer Scale [Illustration: Fig. 44. Micrometer Mounted on Machinist's Scale] A micrometer, mounted as shown in Fig. 44 is very handy. The micrometer may be used in combination with a 4-, 6-, 9-, or 12-inch scale. It can be adjusted on standard plugs, or one can make a set of gages up to 12 inches, out of 3/16-inch round tool steel wire, and use these for setting. In mounting the micrometer, before cutting it apart, mill the shoulders shown at _A_, and in milling the bottom pieces _B_, use a piece of machine steel long enough for both, cutting the piece in half after milling the slots. In this way one obtains perfect alignment. In a shop where a set of large micrometers is not kept, this arrangement is very useful.[22] * * * * * CHAPTER IV MISCELLANEOUS MEASURING TOOLS AND GAGES Among the miscellaneous measuring tools and gages dealt with in this chapter are tools and gages for measuring and comparing tapers, adjustable gages, radius gages, gages for grinding drills, sensitive gages, tools for gaging taper threaded holes, contour gages, etc. Of course, these are offered merely as examples of what can be done in the line of measuring tools for different purposes, and, while having a distinct and direct value to the mechanic, they also have a great indirect value, because they furnish suggestions for the designing and making of tools for similar purposes. Tool for Measuring Tapers [Illustration: Fig. 45. Taper Measuring Tool] Fig. 45 shows a tool which has proved very useful. It is a tool for measuring tapers on dowel pins, reamers, drill shanks, or anything to be tapered. Most machinists know that to find the taper of a shank they must use their calipers for one end and reset them for the other end; or else caliper two places, say, three inches apart, and if, for instance, the difference should be 1/16 inch, they must multiply this difference by four to get the taper per foot. With the tool above mentioned, all this trouble in calipering and figuring is saved. Simply place the shank or reamer to be measured between pins _A_, _B_, _C_, and _D_, and slide _H_ and _K_ together. Then the taper can be read at once on the graduated scale at _L_. The construction of the tool will be readily understood. The body or base _F_ has a cross piece supporting the two pins _A_ and _B_. On this slides piece _K_, which has at its right end the graduated segment. The screw _G_ is fast to piece _K_, and upon it swivels the pointer _E_, which carries the two pins _C_ and _D_. Thus these two pins can be brought into contact with a tapered piece of any diameter within the capacity of the tool, and the swivel screw _G_ allows the pins to adjust themselves to the taper of the work and the pointer _E_ to move to the left or right, showing instantly the taper per foot. As the pins _A_ and _B_ are 1½ inch apart, which is 1/8 of a foot, and the distance from _G_ to _L_ is 4½ inches, which is three times longer than the distance between _A_ and _B_, the graduations should be 3/64 inch apart, in order to indicate the taper per foot in eighths of an inch.[23] Taper Gage [Illustration: Fig. 46. Handy Taper Gage] A handy taper gage is shown in Fig. 46. The blades of the gage are made of tool steel. The edge of the blade _A_ is V-shaped, and the blade _B_ has a V-groove to correspond. The end of _B_ is offset so as to make the joint and allow the two blades to be in the same plane. A strong screw and nut are provided to hold the blades at any setting. The user of this gage looks under the edge of _A_, and is thereby enabled to tell whether the taper coincides with that set by the gage, and also where a taper piece needs touching up to make it true.[24] Test Gage for Maintaining Standard Tapers [Illustration: Fig. 47. Test Gage for Maintaining Standard Tapers] In steam injector work, accurately ground reamers of unusual tapers are commonly required, and the gage shown in Fig. 47 was designed to maintain the prevailing standard. It consists of a graduated bar, 1 inch square, with the slot _F_ running its entire length. The stationary head _A_ is secured in position flush with the end of the bar, and the sliding head _B_ is fitted with a tongue which guides it in the slot. This head may be secured in any desired position by means of a knurled thumb nut. The bushings _D_ and _D'_ are made of tool steel, hardened and ground to a knife edge on the inside flush with the face. All bushings are made interchangeable as to outside diameter. The head _B_ is fitted with an indicating edge _E_ which is set flush with the knife edge of the bushing. The reading indicates to 0.010 inch the distance the bushings are from each other, and the difference in their diameter being known, it is easy to compute the taper. With this gage it is possible to maintain the standard tapers perfectly correct, each reamer being marked with the reading as shown by the scale.[25] Inside and Outside Adjustable Gages [Illustration: Fig. 48. Adjustable Gage for Inside and Outside Measurements] Fig. 48 shows an inside and an outside adjustable gage for accurate work, used in laying out drill jigs, and in setting tools on lathes, shapers, planers, and milling machines. The outside gage is shown in the side view and in the sectional end view marked _Y_. At _X_ in the same figure is a sectional end view showing how the gage is constructed for inside work. The top and bottom edges are rounded, so that the diameters of holes may be easily measured. The gage consists of a stepped block _B_, mounted so as to slide upon the inclined edge of the block _C_. There are V-ways upon the upper edge of the latter, and the block _B_ is split and arranged to clamp over the ways by the screw shown at _S_. All parts of the gage are hardened and the faces of the steps marked _A_, are ground and finished so that at any position of the slide they are parallel to the base of the block _C_. The lower split portion of the block is spring-tempered to prevent breaking under the action of the screw, and also to cause it to spring open when loosened. The gage has the advantage that it can be quickly adjusted to any size within its limits, which does away with using blocks. In planing a piece to a given thickness, the gage may be set to that height with great accuracy by means of a micrometer caliper, and then the planer or shaper tool adjusted down to the gage. This method does away with the "cut-and-try" process, and will bring the finishing cut within 0.001 inch of the required size. If the piece being planed, or the opening to be measured, is larger than the extreme limit of the gage, parallels may be used. In fitting bushings into bushing holes, the adjustable gage may be moved out to fit the hole, and then, when the bushing is finished to the diameter given by the gage, as determined by a micrometer caliper, a driving fit is ensured.[26] Radius Gage [Illustration: Fig. 49. Radius Gage] Fig. 49 shows a radius gage which has proved to be very handy for all such work as rounding corners or grinding tools to a given radius. The blades are of thin steel, and are fastened together at the end by a rivet, thus forming a tool similar to the familiar screw pitch gage. The right-hand corner of each blade is rounded off to the given radius, while the left-hand corner is cut away to the same radius, thus providing an instrument to be used for either convex or concave surfaces. The radius to which each blade is shaped is plainly stamped upon the side.[27] Gage for Grinding Drills [Illustration: Fig. 50. Gage for Grinding Drills] Fig. 50 shows a gage for use in grinding drills, which has been found very handy and accurate. This gage enables either a large or small drill to lie solidly in the groove provided for it on top of the gage, and the lips can then be tested for their truth in width, or angle, much easier and quicker than with the gages in common use without the groove. There is a line, to set the blade _B_ by, on the stock at an angle of 59 degrees at the top of the graduated blade, and the user can easily make other lines, if needed for special work. The blade is clamped in position by the knurled nut _N_ at the back, and can be thus adjusted to any angle. The stock _A_ is cut away where the blade is pivoted on, so that one side of the blade comes directly in line with the middle of the groove.[28] Tool for Gaging Taper Threaded Holes [Illustration: Fig. 51. Tool for Gaging Taper Threaded Holes] The tool shown in Fig. 51 is used for gaging taper threaded holes in boilers when fitting studs. It is a simple, though very useful and economical tool, and it will doubtless be appreciated by those having much work of this kind to do. The hole in which the stud is to be fitted is calipered by filling the threads of the plug with chalk, and then screwing the plug in the hole. When the plug is removed the chalk will show exactly the largest diameter of the hole.[29] Contour Gage [Illustration: Fig. 52. Setting Contour Gage to Turned Sample] [Illustration: Fig. 53. End View of Contour Gage] Figs. 52, 53 and 54 illustrate a special tool which will be found of great value in certain classes of work. The need of some such device becomes apparent when patterns and core boxes are required to be accurately checked with the drawings of brass specialties, in particular. The tool is applied to the work, and the wires pressed down onto the contour by using the side of a lead pencil. Of course, patterns parted on the center could have their halves laid directly on the drawing without using the contour gage, but some patterns are cored and inseparable. Such a tool proves a relentless check upon the patternmaker, who, by making the patterns larger than necessary, can cause a considerable loss in a business where thousands of casts are made yearly from the same patterns. As a ready and universal templet it is very useful.[30] [Illustration: Fig. 54. Testing Core-box with Gage] Testing a Lead-screw [Illustration: Fig. 55. Micrometer for Testing Lathe Lead-screw] A reliable way for testing the pitch of a lead-screw, at any position of its length, is to procure a micrometer screw and barrel complete, such as can be purchased from any of the manufacturers of accurate measuring instruments, and bore out a holder so that the axis of the micrometer screw will be parallel to the holder when the screw is in place, as shown in Fig. 55. With the lathe geared for any selected pitch, the nut engaged with the lead-screw, and all backlash of screw, gears, etc., properly taken up, clamp the micrometer holder to the lathe bed, as shown in Fig. 56, so that the body of the holder is parallel to the carriage. Adjust the micrometer to one inch when the point of the screw bears against the carriage and with a surface gage scribe a line on the outer edge of the faceplate. Now rotate the lathe spindle any number of full revolutions that are required to cause the carriage to travel over the portion of the lead-screw that is being tested, bringing the line on the faceplate to the surface gage point. If the distance traveled by the carriage is not greater than one inch, the micrometer will indicate the error directly. For lengths of carriage travel greater than one inch, an end measuring rod, set to the number of even inches required, can be used between the micrometer point and lathe carriage. The error in the lead-screw is then easily determined by the adjustment that may be required to make a contact for the measuring points between the carriage and the micrometer screw. The pitch can be tested at as many points as are considered necessary by using end measuring rods, of lengths selected, set to good vernier calipers. The style of holder shown can, with the micrometer screw, be used for numerous other shop tests, and as the screw is only held by friction caused by the clamping screw, it can easily be removed and placed in any form of holder that is found necessary.[31] [Illustration: Fig. 56. Testing a Lathe Lead-screw] Simple Tool for Measuring Angles [Illustration: Fig. 57. Special Tool for Measuring Angles] Fig. 57 shows a very simple, but at the same time, a very ingenious tool for measuring angles. Strictly speaking, the tool is not intended for measuring angles, but rather for comparing angles of the same size. The illustration shows so plainly both the construction and the application of the tool, that an explanation would seem superfluous. It will be noticed that any angle conceivable can be obtained in an instant, and the tool can be clamped at this angle by means of screws passing through the joints between the straight and curved parts of which the tool consists. Linear measurements can also be taken conveniently, one of the straight arms of the tool being graduated. As both of the arms which constitute the actual angle comparator are in the same plane, it is all the easier to make accurate comparisons. This tool is of German design, and is manufactured by Carl Mahr, Esslingen a. N. Bevel Gear-testing Gage [Illustration: Fig. 58. Sensitive Gear-testing Gage] In Fig. 58 is shown a sensitive gage for inspecting small bevel gears. The special case shown to which the gage is applied in the engraving is a small brass miter gear finished on a screw machine, in which case some of the holes through the gears were not concentric with the beveled face of the gears, causing the gears to bind when running together in pairs. The gage shown is quite inexpensive, but it indicates the slightest inaccuracy. * * * * * NOTES [1] MACHINERY, October, 1897. [2] M. H. Ball, April, 1902. [3] M. H. Ball, February, 1901. [4] Harry Ash, April, 1900. [5] M. H. Ball, March, 1903. [6] Ezra F. Landis, May, 1902. [7] L. S. Brown, March, 1903. [8] C. W. Putnam, October, 1901. [9] Jos. M. Stabel, May, 1903. [10] Jos. M. Stabel, May, 1903. [11] Jos. M. Stabel, May, 1903. [12] Jos. M. Stabel, May, 1903. [13] P. L. L. Yorgensen, February, 1908. [14] A. L. Monrad, December, 1903. [15] A. L. Monrad, December, 1903. [16] A. L. Monrad, December, 1903. [17] J. L. Marshall, February, 1908. [18] Charles Sherman, November, 1905. [19] M. H. Ball, May, 1903. [20] Chas. A. Kelley, May, 1908. [21] H. J. Bachmann, December, 1902. [22] Wm. Ainscough, May, 1908. [23] John Aspenleiter, October, 1900. [24] W. W. Cowles, June, 1901. [25] I. B. Niemand, December, 1904. [26] Geo. M. Woodbury, February, 1902. [27] A. Putnam, July, 1903. [28] M. H. Ball, October, 1901. [29] F. Rattek, January, 1908. [30] Howard D. Yoder, December, 1907. [31] W. Cantelo, July, 1903. 
32677	----	SMITHSONIAN INSTITUTION UNITED STATES NATIONAL MUSEUM [Illustration] BULLETIN 254 WASHINGTON, D.C. 1968 [Illustration] THE SMITHSONIAN INSTITUTION PRESS _The Invention Of the Sewing Machine_ [Illustration] _Grace Rogers Cooper_ CURATOR OF TEXTILES MUSEUM OF HISTORY AND TECHNOLOGY SMITHSONIAN INSTITUTION WASHINGTON, D.C. 1968 _Publications of the United States National Museum_ The scholarly and scientific publications of the United States National Museum include two series, _Proceedings of the United States National Museum_ and _United States National Museum Bulletin_. In these series, the Museum publishes original articles and monographs dealing with the collections and work of its constituent museums--The Museum of Natural History and the Museum of History and Technology--setting forth newly acquired facts in the fields of anthropology, biology, history, geology, and technology. Copies of each publication are distributed to libraries, to cultural and scientific organizations, and to specialists and others interested in the different subjects. The _Proceedings_, begun in 1878, are intended for the publication, in separate form, of shorter papers from the Museum of Natural History. These are gathered in volumes, octavo in size, with the publication date of each paper recorded in the table of contents of the volume. In the _Bulletin_ series, the first of which was issued in 1875, appear longer, separate publications consisting of monographs (occasionally in several parts) and volumes in which are collected works on related subjects. _Bulletins_ are either octavo or quarto in size, depending on the needs of the presentation. Since 1902 papers relating to the botanical collections of the Museum of Natural History have been published in the _Bulletin_ series under the heading _Contributions from the United States National Herbarium_ and, since 1959, in _Bulletins_ titled "Contributions from the Museum of History and Technology," have been gathered shorter papers relating to the collections and research of that Museum. This work forms volume 254 of the _Bulletin_ series. Frank A. Taylor _Director, United States National Museum_ For sale by Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402--Price $2.75 _Contents_ Preface vii Acknowledgments viii 1. Early Efforts 1 2. Elements of a Successful Machine 17 3. The "Sewing-Machine Combination" 39 4. Less Expensive Machines 43 Appendixes 55 I. Notes on the Development and Commercial Use of the Sewing Machine 57 II. American Sewing-Machine Companies of the 19th Century 65 III. Chronological List of U.S. Sewing-Machine Patent Models in the Smithsonian Collections 125 IV. 19th-Century Sewing Machine Leaflets in the Smithsonian Collections 134 V. A Brief History of Cotton Thread 135 VI. Biographical Sketches 137 Bibliography 144 Indexes 147 Geographical Index to Companies Listed in Appendix II 149 Alphabetical Index to Patentees Listed in Appendix III 151 General Index to Chapters 1-4 155 _Preface_ It had no instrument panel with push-button controls. It was not operated electronically or jet-propelled. But to many 19th-century people the sewing machine was probably as awe-inspiring as a space capsule is to their 20th-century descendants. It was expensive, but, considering the work it could do and the time it could save, the cost was more than justified. The sewing machine became the first widely advertised consumer appliance, pioneered installment buying and patent pooling, and revolutionized the ready-made clothing industry. It also weathered the protests of those who feared the new machine was a threat to their livelihood. The practical sewing machine is not the result of one man's genius, but rather the culmination of a century of thought, work, trials, failures, and partial successes of a long list of inventors. History is too quick to credit one or two men for an important invention and to forget the work that preceded and prodded each man to contribute his share. It is no discredit to Howe to state that he _did not invent the sewing machine_. Howe's work with the sewing machine was important, and he did patent certain improvements, but his work was one step along the way. It is for the reader to decide whether it was the turning point. Since the sewing machine has been considered by some as one of the most important inventions of 19th-century America, of equal importance to this story of the invention is the history of the sewing machine's development into a practical, popular commodity. Since many new companies blossomed overnight to manufacture this very salable item, a catalog list of more than one hundred and fifty of these 19th-century companies is included in this study. Still, the list is probably incomplete. Many of the companies remained in business a very short time or kept their activities a secret to avoid payment of royalties to patent holders. Evidence of these companies is difficult to find. It is hoped that additional information will come to light as a result of this initial attempt to list and date known companies. The dating of individual machines based on their serial numbers is also a difficult task. Individual company records of this type have not survived; however, using the commercial machines in the patent collection, for which we know one limiting date--the date the machine was deposited at the patent office--and using the records that have survived, an estimated date based on the serial number can be established for many of the better known machines. _Acknowledgments_ I am greatly indebted to the late Dr. Frederick Lewton, whose interest in the history of the sewing machine initiated the collecting of information about it for the Smithsonian Institution's Division of Textiles archives and whose out-of-print booklet "A Servant in the House" prompted the writing of this work. I would also like to thank Mr. Bogart Thompson of the Singer Manufacturing Company for his cooperation in arranging for the gift of an excellent collection of 19th-century sewing machines to the Smithsonian and for allowing me to use the Singer historical files. Acknowledgment is also made of the cooperation extended by The Henry Ford Museum and Greenfield Village for permitting me to study their collection of old sewing machines. _Grace Rogers Cooper_ _Chapter One_ [Illustration: Figure 1.--AFTER ALMOST A CENTURY OF ATTEMPTS TO INVENT A MACHINE THAT WOULD SEW, the practical sewing machine evolved in the mid-19th century. This elegant, carpeted salesroom of the 1870s, with fashionable ladies and gentlemen scanning the latest model sewing machines, reflects the pinnacle reached by the new industry in just a few decades. This example, one of many of its type, is the Wheeler and Wilson sewing-machine offices and salesroom, No. 44 Fourteenth Street, Union Square, New York City. From _The Daily Graphic_, New York City, December 29, 1874. (Smithsonian photo 48091-A.)] Early Efforts To 1800 For thousands of years, the only means of stitching two pieces of fabric together had been with a common needle and a length of thread. The thread might be of silk, flax, wool, sinew, or other fibrous material. The needle, whether of bone, silver, bronze, steel, or some other metal, was always the same in design--a thin shaft with a point at one end and a hole or eye for receiving the thread at the other end. Simple as it was, the common needle (fig. 2) with its thread-carrying eye had been an ingenious improvement over the sharp bone, stick, or other object used to pierce a hole through which a lacing then had to be passed.[1] In addition to utilitarian stitching for such things as the making of garments and household furnishings, the needle was also used for decorative stitching, commonly called embroidery. And it was for this purpose that the needle, the seemingly perfect tool that defied improvement, was first altered for ease of stitching and to increase production. One of the forms that the needle took in the process of adaptation was that of the fine steel hook. Called an _aguja_ in Spain, the hook was used in making a type of lace known as _punto de aguja_. During the 17th century after the introduction of chainstitch embroideries from India, this hook was used to produce chainstitch designs on a net ground.[2] The stitch and the fine hook to make it were especially adaptable to this work. By the 18th century the hook had been reduced to needle size and inserted into a handle, and was used to chainstitch-embroider woven fabrics.[3] In France the hook was called a crochet and was sharpened to a point for easy entry into the fabric (fig. 3). For stitching, the fabric was held taut on a drum-shaped frame. The hooked needle pierced the fabric, caught the thread from below the surface and pulled a loop to the top. The needle reentered the fabric a stitch-length from the first entry and caught the thread again, pulling a second loop through the first to which it became enchained. This method of embroidery permitted for the first time the use of a continuous length of thread. At this time the chainstitch was used exclusively for decorative embroidery, and from the French name for drum--the shape of the frame that held the fabric--the worked fabric came to be called tambour embroidery. The crochet[4] or small hooked needle soon became known as a tambour needle. In 1755 a new type of needle was invented for producing embroidery stitches. This needle had to pass completely through the fabric two times (a through-and-through motion) for every stitch. The inventor was Charles F. Weisenthal, a German mechanic living in London who was granted British patent 701 for a two-pointed needle (fig. 4). The invention was described in the patent as follows: The muslin, being put into a frame, is to be worked with a needle that has two points, one at the head, and the other point as a common needle, which is to be worked by holding it with the fingers in the middle, so as not to require turning. It might be argued that Weisenthal had invented the eye-pointed needle, since he was the first inventor to put a point at the end of the needle having the eye. But, since his specifically stated use required the needle to have two points and to be passed completely through the fabric, Weisenthal had no intention of utilizing the very important advantage that the eye-pointed needle provided, that of _not_ requiring the passage of the needle through the fabric as in hand sewing. While no records can be found to establish that Weisenthal's patent was put to any commercial use during the inventor's lifetime, the two-pointed needle with eye at midpoint appeared in several 19th-century sewing-machine inventions. The earliest of the known mechanical sewing devices produced a chain or tambour stitch, but by an entirely different principle than that used with either needle just described. Although the idea was incorporated into a patent, the machine was entirely overlooked for almost a century as the patent itself was classed under wearing apparel. It was entitled "An Entire New Method of Making and Completing Shoes, Boots, Splatterdashes, Clogs, and Other Articles, by Means of Tools and Machines also Invented by Me for that Purpose, and of Certain Compositions of the Nature of Japan or Varnish, which will be very advantageous in many useful Applications." This portentously titled British patent 1,764 was issued to an English cabinetmaker, Thomas Saint, on July 17, 1790. Along with accounts of several processes for making various varnish compositions, the patent contains descriptions of three separate machines; the second of these was for "stitching, quilting, or sewing." Though far from practical, the machine incorporated several features common to a modern sewing machine. It had a horizontal cloth plate or table, an overhanging arm carrying a straight needle, and a continuous supply of thread from a spool. The motion was derived from the rotation of a hand crank on a shaft, which activated cams that produced all the actions of the machine. [Illustration: Figure 2.--PRIMITIVE NEEDLE. Bronze. Egyptian (Roman period, 30 B.C.-A.D. 642). (Smithsonian photo 1379-A.)] One cam operated the forked needle (fig. 5) that pushed the thread through a hole made by a preceding thrust of the awl. The thread was caught by a looper and detained so that it then became enchained in the next loop of thread. The patent described thread tighteners above and below the work and an adjustment to vary the stitches for different kinds of material. Other than the British patent records, no contemporary reference to Saint's machine has ever been found. The stitching-machine contents of this patent was happened on by accident in 1873.[5] Using the patent description, a Newton Wilson of London attempted to build a model of Saint's machine in 1874.[6] Wilson found, however, that it was necessary to modify the construction before the machine would stitch at all. [Illustration: Figure 3.--TAMBOUR NEEDLE AND FRAME, showing the method of forming the chainstitch, from the Diderot Encyclopedia of 1763, vol. II, _Plates Brodeur_, plate II. (Smithsonian photo 43995-C.)] This raised the question whether Saint had built even one machine. Nevertheless, the germ of an idea was there, and had the inventor followed through the sewing machine might have been classed an 18th-century rather than a 19th-century contribution. 1800-1820 There is no doubt that the successful late-18th-century improvements in spinning and weaving methods, resulting in increased production of fabrics, had a great effect in spurring inventors to ideas of stitching by machinery. Several efforts were made during the first two decades of the 19th century to produce such machines. On February 14, 1804, a French patent was issued to Thomas Stone and James Henderson for a "new mechanical principle designed to replace handwork in joining the edges of all kinds of flexible material, and particularly applicable to the manufacture of clothing."[7] The machine used a common needle and made an overcast stitch in the same manner as hand sewing. A pair of jaws or pincers, imitating the action of the fingers, alternately seized and released the needle on each side of the fabric. The pincers were attached to a pair of arms arranged to be moved backward and forward by "any suitable mechanism."[8] This machine was capable of making curved or angular as well as straight seams, but it was limited to carrying a short length of thread, necessitating frequent rethreading. The machine may have had some limited use, but it was not commercially successful. On May 30 of the same year John Duncan, a Glasgow manufacturer, was granted British patent 2,769 for "a new and improved method of tambouring, or raising flowers, figures or other ornaments upon muslins, lawns and other cottons, cloths, or stuffs." This machine made the chainstitch, using not one but many hooked needles that operated simultaneously. The needles, attached to a bar or carrier, were pushed through the vertically held fabric from the upper right side, which in this case was also the outer side. After passing through it, they were supplied with thread from spools by means of peculiarly formed hooks or thread carriers. The thread was twisted around the needle above the hook, so as to be caught by it, and drawn through to the outer surface. The shaft of the needle was grooved on the hook side and fitted with a slider. This slider closed upon the retraction of the needle from the fabric, holding the thread in place and preventing the hook from catching. The fabric was stretched between two rollers set in an upright frame capable of sliding vertically in a second frame arranged to have longitudinal motion. The combination of these two motions was sufficient to produce any required design. The principle developed by Duncan was used on embroidery machines, in a modified form, for many years. Of several early attempts, his was the first to realize any form of success. [Illustration: Figure 4.--WEISENTHAL'S two-pointed needle, 1755.] [Illustration: Figure 5.--SAINT'S SEWING MACHINE, 1790. (Smithsonian photo 42490-A.)] [Illustration: Figure 6.--CHAPMAN'S SEWING MACHINE, first eye-pointed needle, 1807. (Smithsonian photo 33299-K.)] A type of rope-stitching machine, which might be considered unimportant to this study, must be included because of its use of the eye-pointed needle, the needle that was to play a most important part in the later development of a practical sewing machine. The earliest reference to the use of a needle with an eye not being required to be passed completely through the fabric it was stitching is found in a machine invented by Edward Walter Chapman, for which he and William Chapman were granted British patent 3,078 on October 30, 1807. The machine (fig. 6) was designed to construct belting or flat banding by stitching together several strands of rope that had been laid side by side. Two needles were required and used alternately. One needle was threaded and then forced through the ropes. On the opposite side the thread was removed from the eye of the first needle before it was withdrawn. The second needle was threaded and the operation repeated. The needles could also be used to draw the thread, rather than push it, through the ropes with the same result. While being stitched, the ropes were held fast and the sewing frame and supporting carriage were moved manually as each stitch was made. Such a machine would be applicable only to the work described, since the necessity of rethreading at every stitch would make it impractical for any other type of sewing. Another early machine reported to have used the eye-pointed needle to form the chainstitch was invented about 1810 by Balthasar Krems,[9] a hosiery worker of Mayen, Germany. One knitted article produced there was a peaked cap, and Krems' machine was devised to stitch the turned edges of the cap,[10] which was suspended from wire pins on a moving wheel. The needle of the machine was attached to a horizontal shaft and carried the thread through the fabric. The loop of thread was retained by a hook-shaped pin to become enchained with the next loop at the reentry of the needle. Local history reports that this device may have been used as early as 1800, but the inventor did not patent his machine and apparently made no attempt to commercialize it. No contemporary references to the machine could be found, and use of the machine may have died with the inventor in 1813. [Illustration: Figure 7.--MADERSPERGER'S 1814 SEWING MACHINE. Illustration from a pamphlet by the inventor entitled _Beschreibung einer Nähmaschine_, Vienna, ca. 1816. (Smithsonian photo 49373.)] About the same time, Josef Madersperger, a tailor in Vienna, Austria, invented a sewing machine, which was illustrated (fig. 7) and described in a 15-page pamphlet published about 1816.[11] On May 12, 1817, a Vienna newspaper wrote of the Madersperger machine: "The approbation which his machine received everywhere has induced his Royal Imperial Majesty, in the year 1814, to give to the inventor an exclusive privilege [patent] which has already been mentioned before in these papers."[12] Madersperger's 1814 machine stitched straight or curving lines. His second machine stitched small semicircles, as shown in the illustration, and also small circles, egg-shaped figures, and angles of various degrees. The machine, acclaimed by the art experts, must therefore have been intended for embroidery stitching. From the contemporary descriptions and the illustration, the machine is judged to have made a couched stitch--one thread was laid on the surface of the fabric and stitched in place with a short thread carried by a two-pointed needle of the type invented by Weisenthal. Two fabrics could have been stitched together, but not in the manner required for tailoring. The machine must have had many deficiencies in the tension adjustment, feed, and related mechanical operations, for despite the published wishes for success the inventor did not put the machine into practical operation.[13] Years later Madersperger again attempted to invent a sewing machine using a different stitch (see p. 13). [Illustration: Figure 8.--AN ENGRAVING OF THIMONNIER and his sewing machine of 1830, from _Sewing Machine News_, 1880. (Smithsonian photo 10569-C.)] A story persists that about 1818-1819 a machine that formed a backstitch, identical to the one used in hand sewing, was invented in Monkton, Vermont. The earliest record of this machine that this author has found was in the second or 1867 edition of _Eighty Years of Progress of the United States_; the machine is not mentioned in the earlier edition. The writer of the article on sewing machines states that John Knowles invented and constructed a sewing machine, which used a single thread and a two-pointed needle with the eye in the middle to form the backstitch. This information must have come to light after the first edition was published, but from where and by whom is not known. Other sources state that two men, Adams and Dodge, produced this machine in Monkton.[14] While still others credit the Reverend John Adam Dodge, assisted by a mechanic by the name of John Knowles, with the same invention in the same location.[15] Vermont historical societies have been unable to identify the men named or to verify the story of the invention.[16] The importance of the credibility of this story, if proved, rests in the fact that it represents the first effort in the United States to produce a mechanical stitching device. 1820-1845 American records of this period are incomplete as a result of the Patent Office fire of 1836, in which most of the specific descriptions of patents issued to that date were destroyed. Patentees were asked to provide another description of their patents so that these might be copied, but comparatively few responded and only a small percentage was restored. Thus, although the printed index of patents[17] lists Henry Lye as patenting a machine for "sewing leather, and so forth" on March 10, 1826, no description of the machine has ever been located. Many patents whose original claim was for only a mechanical awl to pierce holes in leather or a clamp to hold leather for hand stitching were claimed as sewing devices once a practical machine had evolved. But no evidence has ever been found that any of these machines performed the actual stitching operation. [Illustration: Figure 9.--AN ADAPTED DRAWING of Hunt's sewing machine published by the _Sewing Machine News_, vol. 2, no. 8, 1881, to give some idea of its construction and operation. "The frame of the machine (A) rested on a base (B) that was supported by a table. The wheel (C) worked on a central shaft (E) and was set in motion by hand or foot power. On the front of the wheel (C) was a raised cam (D) into which the connecting rod (F) engaged to communicate motion to the vibrating arm (G) pivoted to the frame at (H) and carrying at the end (g) the curved needle (I). The take-up (J) served to tighten the thread after each stitch; it was connected to the vibrating arm by a rod (K). The cloth (L) was held in a vertical position between the fingers or nippers (M), which were attached to the frame. The bar (N) was toothed on one side (n) to mesh with the geared wheel (o). The lever (P) was operated by a cam (m) upon the periphery of the wheel (C), and carried the vertical pawl (S) which meshed with the ratchet (T) and moved the cloth as each stitch was made. The shuttle (U) worked in its race (V); it was operated by the vibrating lever (W), the upper end of which engaged into a groove on the face of the wheel (C)." (Smithsonian photo 42554.)] The first man known to have put a mechanical sewing device into commercial operation was Barthelemy Thimonnier,[18] a French tailor. After several years of fruitless effort he invented a machine for which he received a French patent in 1830.[19] The machine (fig. 8) made a chainstitch by means of a barbed or hooked needle. The vertically held needle worked from an overhanging arm. The needle thrust through the fabric laid on the horizontal table, caught a thread from the thread carrier and looper beneath the table, and brought a loop to the surface of the fabric. When the process was repeated the second loop became enchained in the first. The needle was moved downward by the depression of a cord-connected foot treadle and was raised by the action of a spring. The fabric was fed through the stitching mechanism manually, and a regular rate of speed had to be maintained by the operator in order to produce stitches of equal length. A type of retractable thimble or presser foot was used to hold the fabric down as required. The needle, and the entire machine, was basically an attempt to mechanize tambour embroidery, with which the inventor was quite familiar. Although this work, which served as the machine's inspiration, was always used for decorative embroidery, Thimonnier saw the possibilities of using the stitch for utilitarian purposes. By 1841 he had 80 machines stitching army clothing in a Paris shop. But a mob of tailors, fearing that the invention would rob them of a livelihood, broke into the shop and destroyed the machines. Thimonnier fled Paris, penniless. Four years later he had obtained new financial help, improved his machine to produce 200 stitches a minute, and organized the first French sewing-machine company.[20] The Revolution of 1848, however, brought this enterprise to an early end. Before new support could be found other inventors had appeared with better machines, and Thimonnier's was passed by. In addition to the two French patents Thimonnier also received a British patent with his associate Jean Marie Magnin in 1848 and one in the United States in 1850. He achieved no financial gain from either of these and died a poor man. While Thimonnier was developing his chainstitch machine in France, Walter Hunt,[21] perhaps best described as a Yankee mechanical genius, was working on a different kind of sewing machine in the United States. Sometime between 1832 and 1834 he produced at his shop in New York a machine that made a lockstitch.[22] This stitch was the direct result of the mechanical method devised to produce the stitching and represented the first occasion an inventor had not attempted to reproduce a hand stitch. The lockstitch required two threads, one passing through a loop in the other and both interlocking in the heart of the seam. At the time Hunt did not consider the sewing machine any more promising than several other inventions that he had in mind, and, after demonstrating that the machine would sew, he sold his interest in it for a small sum and did not bother to patent it. A description--one of few ever published--and sketch of a rebuilt Hunt machine (fig. 9) appeared in an article in the _Sewing Machine News_ in 1881.[23] The important element in the Hunt invention was an eye-pointed needle working in combination with a shuttle carrying a second thread. Future inventors were thus no longer hampered by the erroneous idea that the sewing machine must imitate the human hands and fingers. Though Hunt's machine stitched short, straight seams with speed and accuracy, it could not sew curved or angular work. Its stitching was not continuous, but had to be reset at the end of a short run. The validity of Hunt's claim as the inventor of the lockstitch and the prescribed method of making it was argued many times, especially during the Elias Howe patent suits of the 1850s. The decision against Hunt was not a question of invention,[24] but one of right to ownership or control. Hunt did little to promote his sewing machine and sold it together with the right to patent to George A. Arrowsmith. [Illustration: Figure 10.--MADERSPERGER'S 1839 sewing machine. Madersperger's machine consisted of two major parts: the frame, which held the material, and the stitching mechanism, called the hand. The hand shown here is an original model. (_Photo courtesy of Technisches Museum für Industrie und Gewerbe, Vienna._)] For over fifteen years, from the mid-1830s to the early 1850s, the machine dropped out of sight. When the sewing-machine litigation developed in the 1850s, the I. M. Singer company searched out the Hunt machine, had the inventor rebuild one,[25] and attempted to use this to break the Howe patent. The plan did not work. The Honorable Charles Mason, Patent Commissioner, reported: When the first inventor allows his discovery to slumber for eighteen years, with no probability of its ever being brought into useful activity, and when it is only resurrected to supplant and strangle an invention which has been given to the public, and which has been made practically useful, all reasonable presumption should be in favor of the inventor who has been the means of conferring the real benefit upon the world.[26] Hunt's machine was an invention of the 1830s, but only because of the patent litigation was it ever heard of again. During the time that a potentially successful sewing machine was being invented and forgotten in America, Josef Madersperger of Austria made a second attempt to solve the mechanical stitching problem. In 1839 he received a second patent on a machine entirely different from his 1814 effort. It was similar to Hunt's in that it used an eye-pointed needle and passed a thread through the loop of the needle-thread--the thread carried by the needle--to lock the stitch. Madersperger's machine was a multiple-needle quilting machine. The threaded needles penetrated the fabric from below and were retracted, leaving the loops on the surface. A thread was drawn through the loops to produce what the inventor termed a chain. The first two stitches were twisted before insertion into the next two, producing a type of twisted lockstitch. The mechanism for feeding the cloth was faulty, however, and the inventor himself stated in the specifications that much remained to perfect and simplify it before its general application. (This machine was illustrated [fig. 10] in the _Sewing Machine Times_, October 25, 1907, and mistakenly referred to as the 1814 model.) Madersperger realized no financial gain from either venture and died in a poorhouse in 1850. The first efforts of the 1840s reflected the work of the earlier years. In England, Edward Newton and Thomas Archbold invented and patented a machine on May 4, 1841, for tambouring or ornamenting the backs of gloves. Their machine used a hook on the upper surface to catch the loop of thread, but an eye-pointed needle from underneath was used to carry the thread up through the fabric. The machine was designed to use three needles for three rows of chainstitching, if required. Although the machine was capable of stitching two fabrics together, it was never contemplated as a sewing machine in the present use of the term. Their British patent 8,948 stated it was for "improvements in producing ornamental or tambour work in the manufacture of gloves." The earliest American patent specifically recorded as a sewing machine was U.S. patent 2,466, issued to John J. Greenough on February 21, 1842. His machine was a short-thread model that made both the running stitch and the backstitch. It used the two-pointed needle, with eye at mid-length, which was passed back and forth through the material by means of a pair of pincers on each side of the seam. The pincers opened and closed automatically. The material to be sewn was held in clamps which moved it forward between the pincers to form a running stitch or moved it alternately backward and forward to produce a backstitch. The clamps were attached to a rack that automatically fed the material at a predetermined rate according to the length of stitch required. Since the machine was designed for leather or other hard material, the needle was preceded by an awl, which pierced a hole. The machine had a weight to draw out the thread and a stop-motion to stop the machinery when a thread broke or became too short. The needle was threaded with a short length of thread and required frequent refilling. Only straight seams could be stitched. The feed was continuous to the length of the rack bar; then it had to be reset. The motions were all obtained from the revolution of a crank. It is not believed that any machines, other than the patent model (fig. 11), were ever made. Little is known of Greenough other than his name. [Illustration: Figure 11.--GREENOUGH'S PATENT MODEL, 1842. (Smithsonian photo 45525-G.)] In the succeeding year, on March 4, 1843, Benjamin W. Bean received the second American sewing-machine patent, U.S. patent 2,982. Like Greenough's, this machine made a running stitch, but by a different method. In Bean's machine the fabric was fed between the teeth of a series of gears. Held in a groove in the gears was a peculiarly shaped needle bent in two places to permit it to be held in place by the gears and with a point at one end and the eye at the opposite end, as in a common hand needle. The action of the gears caused the fabric to be forced onto and through the threaded needle. Indefinite straight seams could be stitched as the fabric was continuously forced off the needle by the turning gears (fig. 12). A screw clamp held the machine to a table or other work surface. Machines of this and similar types reportedly had some limited usage in the dyeing and bleaching mills,[27] where lengths of fabric were stitched together before processing. Improved versions of Bean's machine were to be patented in subsequent years in England and America. The same principle was also used in home machines two decades later. The third sewing-machine patent on record in the United States Patent Office is patent 3,389 issued on December 27, 1843, to George H. Corliss, better remembered as the inventor and manufacturer of the Corliss steam engine. It was his interest in the sewing machine, however, that eventually directed his attention to the steam engine. Corliss had a general store at Greenwich, New York. A customer's complaint that the boots he had purchased split at the seams made Corliss wonder why someone had not invented a machine to sew stronger seams than hand-sewn ones. He considered the problem of sewing leather, analyzing the steps required to make the saddler's stitch, one popularly used in boots and shoes. He concluded that a sewing machine to do this type of work must first perforate the leather, then draw the threads through the holes, and finally secure the stitches by pulling the threads tight. The machine Corliss invented (fig. 13) was of the same general type as Greenough's, except that two two-pointed needles were required to make the saddler's stitch. This stitch was composed of two running stitches made simultaneously, one from each side.[28] The machine used two awls to pierce the holes through which the needles passed; finger levers approached from opposite sides, seized the needles, pulled the threads firmly, and passed the needles through to repeat the operation. The working model that Corliss completed could unite two pieces of heavy leather at the rate of 20 stitches per minute. Corliss, lacking capital, went to Providence, Rhode Island, in 1844 to secure backers. After months without success, he was forced to abandon the sewing machine and accept employment as a draftsman and designer. Though he considered himself a failure, this change of employment placed him on the threshold of his more rewarding life work, improvement of the steam engine.[29] On July 22, 1844, James Rodgers was granted U.S. patent 3,672, the fourth American sewing-machine patent. The patent model is not known to be in existence, but this machine was of minor importance for it offered only a negligible change in the Bean running-stitch machine. The same corrugated gears were used but were placed in different positions so that one bend in the needle was eliminated. When Bean secured a reissue of his patent in 1849, he had adapted it to use a straight needle. Rodgers' machine is not known to have had any commercial success, although this type of machine experienced a brief period of popularity. By the early 1900s, however, the running-stitch machine was so little known that when one was illustrated in the _Sewing Machine Times_ in 1907[30] it excited more curiosity than any of the other early types. [Illustration: Figure 12.--BEAN'S PATENT MODEL, 1843. (Smithsonian photo 42490-C.)] [Illustration: Figure 13.--CORLISS' PATENT MODEL, 1843. The piece of wood in the foreground is an enlarged model of the needle. (Smithsonian photo 42490.)] On December 7, 1844, the same year that Rodgers secured his American patent, John Fisher and James Gibbons were granted British patent 10,424 for "certain improvements in the manufacture of figured or ornamental lace, or net, or other fabrics." From this superficial description of its work, the device might seem to be just another tambouring machine. It was not. Designed specifically for ornamental stitching, the machine made a two-thread stitch using an eye-pointed needle and a shuttle.[31] Several sets of needles and shuttles worked simultaneously. The needles were secured to a needlebar placed beneath the fabric. The shuttles were pointed at both ends to pass through each succeeding new loop formed by the needles. Each shuttle was activated by two vibrating arms worked by cams. Each needle was curved in the form of a bow, and in addition to the eye at the point each also had a second eye at the bottom of the curve. The shape of the needle together with the position of the eyes permitted the pointed shuttle, carrying the second thread, to pass freely through the loop in the ascending needle thread. The fabric was carried by a pair of cloth rollers, capable of sliding in a horizontal plane in both a lateral and a lengthwise direction. These combined movements were sufficient to enable the operator to produce almost every embroidered design. The ornamenting, which might be a yarn, cord, or gimp, was carried by the shuttle thread. There was no tension on the shuttle thread, which was held in place by the thread from the needle. The stitch produced was a form of couching.[32] It was in no sense a lockstitch. Fisher, who was the inventor, readily admitted at a later date that he had not had the slightest idea of producing a sewing machine, in the utilitarian meaning of the term. Although it has not been established that this machine was ever put into practical operation, Fisher's invention was to have a far-reaching effect on the development of the sewing machine in England. FOOTNOTES: [1] CHARLES M. KARCH, _Needles: Historical and Descriptive_ (12 Census U.S., vol. X, 1902), pp. 429-432. [2] FLORENCE LEWIS MAY, _Hispanic Lace and Lace Making_ (New York, 1939), pp. 267-271. [3] Diderot's _L'Encyclopédie, ou dictionnaire raisonné des sciences, des arts et des métiers ..._, vol. II (1763), Plates Brodeur, plate II. [4] The term "crochet," as used today, became the modern counterpart of the Spanish _punto de aguja_ about the second quarter of the 19th century. [5] _Sewing Machine News_ (1880), vol. 1, no. 7, p. 2. [6] This model of Saint's machine was bequeathed by Mr. Wilson to the South Kensington Museum, London, England. [7] _Sewing Machine News_ (1880), vol. 1, no. 8, p. 2. [8] Ibid. [9] ERICH LUTH, _Ein Mayener Strumpfwirker, Balthasar Krems, 1760-1813, Erfinder der Nähmaschine_, p. 10, states that the machine used an eye-pointed needle. WILHELM RENTERS, _Praktisches Wissen von der Nähmaschine_, p. 4, states that Krems used a hooked needle. Renters probably mistook the hooked retaining pin for the needle. [10] Dr. Dahmen, Burgermeister of Mayen, stated in a letter of October 8, 1963, that the original Krems machine was turned over to the officials of Mayen by Krems' descendants about the turn of the century. He verified that the machine used an eye-pointed needle. About 1920 the machine was placed in the Eifelmuseum in Genovevaburg; some of the unessential parts were restored. The machine now at this museum is the one pictured in Luth's book. A replica of the machine is in the Deutsches Museum, Munich, Germany. [11] JOSEF MADERSPERGER, _Beschreibung einer Nähmaschine_ (Vienna, ca. 1816). The exact date of this small booklet is not known. In the booklet Madersperger reports that he had received a patent in 1814 for his _first_ machine adapted to straight sewing. However, the machine described and illustrated in this booklet was one that could stitch semicircles and small figures. In _Kunst und Gewerbeblatt_, a periodical (Munich, Germany, 1817, pp. 336-338), reference is made to the Madersperger machine and a statement to the effect that the inventor had published a leaflet describing his machine. The leaflet referred to is believed to be the one under discussion. For this reason it must have been published between 1814 and 1817, therefore ca. 1816. The only copy of this booklet known to this author is in the New York Public Library. It was probably not known to authors Luth and Renters. The author wishes to thank Miss Rita J. Adrosko of her staff for her important help in translating these German publications. [12] _Sewing Machine Times_ (1907), vol. 26, no. 865, p. 1. [13] There are no known models of these early Madersperger machines in existence. Although the _Sewing Machine Times_ reported in the 1907 issue that the 1814 sewing machine was then on exhibition in the Museum of the Vienna Polytechnic, the illustration shown was of Madersperger's 1839 machine. In a letter from the director of the Technisches Museum für Industrie und Gewerbe in Vienna, received in 1962, it was stated that the original 1814 Madersperger machine was in their museum. The photographs that were sent, however, were of the 1839 machine. This machine is entirely different from the 1814-1817 machine, as can readily be seen by the reader (figs. 7 and 10). [14] JOHN P. STAMBAUGH, _A History of the Sewing Machine_ (Hartford, Conn., 1872), p. 13; _Sewing Machine News_ (July 1880), vol. 1, no. 12, p. 4. [15] "Sewing Machines," _Johnson's Universal Cyclopaedia_ (New York, 1878), vol. 4, p. 205. The 1874 edition does not include this reference to Rev. John Adam Dodge. [16] Letters to the author from the Vermont Historical Society (Nov. 13, 1953) and the Bennington Historical Museum and Art Gallery (May 2, 1953). [17] EDMUND BURKE. Commissioner of Patents, _List of Patents for Inventions and Designs Issued by the United States from 1790 to 1847_ (Washington, 1847). [18] See Barthelemy Thimonnier's biographical sketch, p. 137. [19] French patent issued to Barthelemy Thimonnier and M. Ferrand (who was a tutor at l'Ecole des Mines, Saint-Etienne, and helped finance the patent), July 17, 1830. [20] The company was located at Villefranche-sur-Saône, but no name is recorded. See J. Granger, _Thimonnier et la machine à coudre_ (1943), p. 16. [21] See Walter Hunt's biographical sketch, p. 138. [22] The earliest known reference in print to Walter Hunt's sewing machine is in _Sewing by Machinery: An Exposition of the History of Patentees of Various Sewing Machines and of the Rights of the Public_ (I. M. Singer & Co., 1853). A more detailed story of Hunt's invention is in _Sewing Machine News_ (1880-81), vol. 2, no. 2, p. 4; no. 4, p. 5; and no. 8, pp. 3 and 8. [23] Vol. 2, no. 8, p. 3. [24] In the opinion and decision of C. Mason, Commissioner of the Patent Office, offered on May 24, 1854, for the Hunt vs. Howe interference suit, Mason stated: "He [Hunt] proves that in 1834 or 1835 he contrived a machine by which he actually effected his purpose of sewing cloth with considerable success." [25] The rebuilt machine, according to a letter to the author from B. F. Thompson of the Singer company, is believed to have been one of the machines lost in a Singer factory fire at Elizabethport, N.J., in 1890. [26] Op. cit. (footnote 24). [27] EDWARD H. KNIGHT, _Sewing Machines_, vol. 3 of _Knight's American Mechanical Dictionary_. [28] A seam using the saddler's stitch appears as a neat line of touching stitches on both sides. Even when made by hand, it is sometimes misidentified by the casual observer as the lockstitch because of the uniformity of both sides. If the saddler's stitch was formed of threads of two different colors, the even stitches on one side of the seam and the odd stitches on the reverse side would be of one color, and vice versa. [29] _The Life and Works of George H. Corliss_, privately printed for Mary Corliss by the American Historical Society, 1930. The Corliss family records were turned over to the Baker Library, Harvard University. In a letter addressed to this author by Robert W. Lovett of the Manuscripts Division on August 2, 1954, it was reported that there was a record on their Corliss card to the effect that a model of his sewing machine, received with the collection, was turned over to the Massachusetts Institute of Technology; however, Mr. Lovett also stated that from a manuscript memoir of Mr. Corliss that it would seem that he developed only the one machine--the patent model. In a letter dated November 15, 1954, Stanley Backer, assistant professor of mechanical engineering, stated that after extensive inquiries they were unable to locate the model at M.I.T. In 1964, Dr. Robert Woodbury, of M.I.T., turned over to the Smithsonian Institution the official copies of the Corliss drawings and the specifications which had been awarded to the inventor by the Patent Office. It is possible that this may have been the material noted on the Harvard University card as having been transferred to M.I.T. [30] _Sewing Machine Times_ (July 10, 1907), vol. 26, no. 858, p. 1. [31] This is the earliest known patent using the combination of an eye-pointed needle and a shuttle to form a stitch. [32] In embroidery, couching is the technique of laying a decorative thread on the surface of the fabric and stitching it into place with a second less-conspicuous thread. _Chapter Two_ [Illustration: Figure 14.--HOWE'S PREPATENT MODEL of 1845, and the box used by the inventor to carry the machine to England in 1847. (Smithsonian photo 45506-B.)] Elements of a Successful Machine The requirements for producing a successful, practical sewing machine were a support for the cloth, a needle to carry the thread through the fabric and a combining device to form the stitch, a feeding mechanism to permit one stitch to follow another, tension controls to provide an even delivery of thread, and the related mechanism to insure the precise performance of each operation in its proper sequence. Weisenthal had added a point to the eye-end of the needle, Saint supported the fabric by placing it in a horizontal position with a needle entering vertically, Duncan successfully completed a chainstitch for embroidery purposes, Chapman used a needle with an eye at its point and did not pass it completely through the fabric, Krems stitched circular caps with an eye-pointed needle used with a hook to form a chainstitch, Thimonnier used the hooked needle to form a chainstitch on a fabric laid horizontally, and Hunt created a new stitch that was more readily adapted to sewing by machine than the hand stitches had been, but, although each may have had the germ of an idea, a successful machine had not evolved. There were to be hundreds of patents issued in an attempt to solve these and the numerous minor problems that would ensue. But the problems were solved. And, in spite of its Old World inception, the successful sewing machine can be credited as an American invention. Although the invention of the practical sewing machine, like most important inventions, was a many-man project, historians generally give full credit to Elias Howe, Jr. Though such credit may be overly generous, Howe's important role in this history cannot be denied. Elias Howe, Jr., was born on a farm near Spencer, Massachusetts, but he left home at an early age to learn the machinist's trade.[33] After serving an apprenticeship in Lowell, he moved to Boston. In the late 1830s, while employed in the instrument shop of Ari Davis, Howe is reported to have overheard a discussion concerning the need for a machine that would sew. In 1843, when illness kept him from his job for days at a time, he remembered the conversation and the promises of the rich reward that reputedly awaited the successful inventor. Determined to invent such a machine, he finally managed to produce sufficient results to interest George Fisher in buying a one-half interest in his proposed invention. By April 1845, Howe's machine (fig. 14) was used to sew all the seams of two woolen suits for men's clothing. He continued to demonstrate his machine but found that interest was, at best, indifferent. Nevertheless, Howe completed a second machine (fig. 15), which he submitted with his application for a patent. The fifth United States patent (No. 4,750) for a sewing machine was issued to him on September 10, 1846. The machine used a grooved and curved eye-pointed needle carried by a vibrating arm, with the needle supplied with thread from a spool. Loops of thread from the needle were locked by a thread carried by a shuttle, which was moved through the loop by means of reciprocating drivers. The cloth was suspended in a vertical position, impaled on pins projecting from a baster plate, which moved intermittently under the needle by means of a toothed wheel. The length of each stitching operation depended upon the length of the baster plate, and the seams were necessarily straight. When the end of the baster plate reached the position of the needle, the machine was stopped. The cloth was removed from the baster plate, which was moved back to its original position. The cloth was moved forward on the pins, and the seam continued. In his patent specifications, Howe claimed the following: 1. The forming of the seam by carrying a thread through the cloth by means of a curved needle on the end of a vibrating arm, and the passing of a shuttle furnished with its bobbin, in the manner set forth, between the needle and the thread which it carried, under combination and arrangement of parts substantially the same with that described. 2. The lifting of the thread that passes through the needle-eye by means of the lifting-rod, for the purpose of forming a loop of loose thread that is to be subsequently drawn in by the passage of the shuttle, as herein fully described, said lifting-rod being furnished with a lifting pin, and governed in its motion by the guide-pieces and other devices, arranged and operating substantially as described. 3. The holding of the thread that is given out by the shuttle, so as to prevent its unwinding from the shuttle-bobbin after the shuttle has passed through the loop, said thread being held by means of the lever or slipping-piece, as herein made known, or in any other manner that is substantially the same in its operation and result. 4. The manner of arranging and combining the small lever with the sliding box, in combination with the spring-piece, for the purpose of tightening the stitch as the needle is retracted. 5. The holding of the cloth to be sewed by the use of a baster-plate furnished with points for that purpose, and with holes enabling it to operate as a rack in the manner set forth, thereby carrying the cloth forward and dispensing altogether with the necessity of basting the parts together. The five claims, which were allowed Howe in his patent, have been quoted to show that he did not claim the invention of the eye-pointed needle, for which he has so often been credited. The court judgment[34] that upheld Howe's claim to his patented right to control the use of the eye-pointed needle in combination with a shuttle to form a lockstitch was mistakenly interpreted by some as verifying control of the eye-pointed needle itself. [Illustration: Figure 15.--HOWE'S PATENT MODEL, 1846. (Smithsonian photo 45525-B.)] After patenting his invention, Howe spent three discouraging years in both the United States and in England trying to interest manufacturers in building his sewing machine, under license. Finally, for £250 sterling, he sold the British patent rights to William Thomas and further agreed to adapt the machine to Thomas' manufacture of umbrellas and corsets.[35] This did not prove to be a financial success for Howe and by 1849 he was back in the United States, once again without funds. [Illustration: Figure 16.--AN ENLARGEMENT of the stitching area. (Smithsonian photo 45525-B.)] On his return, Howe was surprised to find that other inventors were engaged in the sewing-machine problem and that sewing machines were being manufactured for sale. The sixth United States sewing-machine patent (No. 5,942) had been issued to John A. Bradshaw on November 28, 1848, for a machine specifically stated as correcting the defects in the E. Howe patent. Bradshaw did not purport that his machine was a new invention. His specifications read: The curved needle used in Howe's machine will not by itself form the loop in the thread, which is necessary for the flying bobbin, with its case, to pass through, and has, therefore, to be aided in that operation by a lifting-pin, with the necessary mechanism to operate it. This is a very bungling device, and is a great incumbrance to the action of the machine, being an impediment in the way of introducing the cloth to be sewed, difficult to keep properly adjusted, and very frequently gets entangled between the thread and the needle, by which the latter is frequently broken. This accident happens very often, not withstanding all the precaution which it is possible for the most careful operator to exercise; and inasmuch as the delay occasioned thereby is very considerable, and the needles costly and difficult to replace, it is therefore very important that their breaking in this manner be prevented, which in my machine is done in the most effectual manner by dispensing with the lifting-pin altogether, the loop for the flying bobbin to pass through being made with certainty and of the proper form by means of my angular needle moved in a particular manner just before the flying-bobbin case is thrown. The shuttle and its bobbin for giving off the thread in Howe's machine are very defective ... my neat and simple bobbin-case ... gives off its thread with certainty and uniformity.... The baster-plate in the Howe machine is very inconvenient and troublesome ... in my machine ... the clamp ... is a very simple and efficient device.... The Howe machine is stationary, and the baster-plate or cloth-holder progressive. The Bradshaw machine is progressive and the cloth-holder stationary. Bradshaw's patent accurately described some of the defects of the Howe machine, but other inventors were later to offer better solutions to the problems. [Illustration: Figure 17.--MOREY AND JOHNSON sewing machine, 1849. Below: The machine is marked with the name of its maker, Safford & Williams. The number 49 is a serial number. Missing parts have been replaced with plastic. (Smithsonian photo 48400; brass plate: 48400-H.)] Although the Bradshaw machine was not in current manufacture, a machine based on it received the seventh United States sewing-machine patent. Patent 6,099 was issued to Charles Morey and Joseph B. Johnson on February 6, 1849. Their machine (fig. 17) was being offered for sale even before the patent was issued. This was the first American patent for a chainstitch machine. The stitch was made by an eye-pointed needle carrying the thread through the fabric; the thread was detained by a hook until the loop was enchained by the succeeding one. The fabric was held vertically by a baster plate in a manner similar to the Howe machine. Although not claimed in the patent description, the Morey and Johnson machine also had a bar device for stripping the cloth from the needle. This bar had a slight motion causing a yielding pressure to be exerted on the cloth. Although the patent was not granted until February 6, 1849, the application had been filed in April of the previous year. The machine was featured in the _Scientific American_ on January 27, 1849 (fig. 18): Morey and Johnson Machine--These machines are very accurately adjusted in all their parts to work in harmony, without this they would be of no use. But they are now used in most of the Print Works and Bleach Works in New England, and especially by the East Boston Flour Company. It sews about one yard per minute, and we consider it superior to the London Sewing Machine the specification of which is in our possession. It [Morey and Johnson] is more simple--and this is a great deal.... The price of a machine and right to use $135.[36] An improvement in the Morey and Johnson machine was patented by Jotham S. Conant for which he was issued a patent on May 8, 1849. Conant's machine offered a slight modification of the cloth bar and of the method of keeping the cloth taut during the stitching operation. No successful use of it is known. A second improvement of the Morey and Johnson patent was also issued on May 8, 1849; this United States patent (No. 6,439) was to John Bachelder for the first continuous, but intermittent, sewing mechanism. As shown in the patent model (fig. 19), his clothholder consisted of an endless belt supported by and running around three or any other suitable number of cylindrical rollers. A series of pointed wires projected from the surface of the belt near the edge immediately adjacent to the needle. The wires could be placed at regular or irregular distances as required. The shaft of one of the cylindrical rollers, which supported the endless clothholder, carried a ratchet wheel advanced by the action of a pawl connected to the end of the crankshaft by a small crankpin, whose position or distance from the axis of rotation of the shaft could be adjusted. [Illustration: Figure 18.--A MOREY AND JOHNSON sewing machine as illustrated in _Scientific American_, January 27, 1849. (Smithsonian photo 45771.)] By this adjustment the extent of the vertical travel of the impelling pawl was regulated to control the length of the stitch. A spring catch kept the ratchet wheel in place at the end of each forward rotation of the wheel by the pawl. A roller placed over the endless belt at its middle roller pressed the cloth onto the wire points. A curved piece of metal was bent over and down upon the top of the belt so that the cloth, as it was sewed, was carried toward and against the piece by the belt. The cloth rose upon and over the piece and was separated from the points. When the machine was in motion the cloth was carried forward, passed under the needle, was stitched, and finally, passed the separator and off the belt. A vertically reciprocating, straight, eye-pointed needle, a horizontal supporting surface, and a yielding cloth presser were all used, but none were claimed as part of the patent. These were later specifically claimed in reissues of this patent. Bachelder's one specific claim, the endless feed belt, was not limited to belt feeding only. As he explained in the patent, a revolving table or a cylinder might be substituted. [Illustration: Figure 19.--BACHELDER'S PATENT MODEL, 1849. (Smithsonian photo 45572).] Bachelder did not manufacture machines, but his patent was sold in the mid-1850s to I. M. Singer.[37] It eventually became one of the most important patents to be contributed to the "Sewing-Machine Combination," a patent pool, which is discussed in more detail on pages 41 and 42. While new ideas and inventors continued to provide the answers to some of the sewing-machine problems, Elias Howe began a series of patent suits to sustain the rights that he felt were his. Since his interest had never been in constructing machines for sale, it was absolutely essential for Howe to protect his royalty rights in order to realize any return from his patent. He was reported[38] to have supervised the construction of 14 sewing machines at a shop[39] on Gold Street in New York toward the close of 1850. Sworn contemporary testimony indicates that the machines were of no practical use.[40] Elias stated, in his application for his patent extension,[41] that he made only one machine in 1850-51. In 1852 he advertised[42] territorial rights and machines, but apparently did not realize any financial success until he sold a half interest in his patent to George Bliss in November 1852.[43] Bliss later began manufacturing machines that he initially sold as "Howe's Patent"; however, these machines were substantially different from the basic Howe machine. [Illustration: Figure 20.--BLODGETT & LEROW SEWING MACHINE, 1850, as manufactured by A. Bartholf, New York; the serial number of the machine is 19. At right, an original brass plate from the same type of machine with needle arm and presser foot and arm, serial number 119; the plate, however, does not fit the machine correctly. (Smithsonian photo 48440-D; brass plate: 48440-K.)] On May 18, 1853, Elias Howe granted his first royalty license to Wheeler, Wilson & Company. Within a few months licenses were also granted to Grover & Baker; A. Bartholf; Nichols & Bliss; J. A. Lerow; Woolridge, Keene, and Moore; and A. B. Howe, the brother of Elias. These licenses granted the manufacturer the right to use any part of the Howe patent,[44] but it did not mean that the machines were Elias Howe machines. When a royalty license was paid, the patent date and sometimes the name was stamped onto the machine. For this reason, these machines are sometimes mistakenly thought to be Elias Howe machines. They are not. Howe was also prevented from manufacturing a practical machine unless he paid a royalty to other inventors. Three of the major manufacturers and Howe resolved their differences by forming the "Sewing Machine Combination." Although Howe did not enter the manufacturing competition for many years, he profited substantially from the royalty terms of the combination. In 1860, he applied for and received a seven-year extension on his patent. [Illustration: Figure 21.--BLODGETT & LEROW SEWING MACHINE, 1850, stamped with the legend "Goddard, Rice & Co., Makers, Worcester, Mass." and the serial number 37. Below: An original brass plate marked "No. 38"; this plate fits the machine perfectly. (Smithsonian photo 48440-E; brass plate: 48440-J.)] There were Howe family machines for sale during this period, but these were the ones that Amasa Howe had been manufacturing since 1853. The machine was an excellent one and received the highest medal for sewing machines, together with many flattering testimonials, at the London International Exhibition in 1862. After the publication of this award the demand for (Amasa) Howe sewing machines was greatly increased at home and abroad. Elias took this opportunity to gain entry into the manufacturing business by persuading Amasa to let him build a factory at Bridgeport, Connecticut, and manufacture the (Amasa) Howe machines. Two years passed before the factory was completed, and Amasa's agents were discouraged. The loss could have been regained, but the machines produced at Bridgeport were not of the quality of the earlier machines. Amasa attempted to rebuild the Bridgeport machines, but finally abandoned them and resumed manufacturing machines in New York under his own immediate supervision.[45] Elias formed his own company and continued to manufacture sewing machines. In 1867 he requested a second extension of his patent, but the request was refused. Elias Howe died in October of the same year. Meanwhile, another important sewing machine of a different principle had also been patented in 1849. This was the machine of Sherburne C. Blodgett, a tailor by trade, who was supported financially by John A. Lerow. United States patent 6,766 was issued to both men on October 2, 1849. In the patent, the machine was termed as "our new 'Rotary Sewing Machine'." The shuttle movement was continuous, revolving in a circle, rather than reciprocating as in the earlier machines. Automatic tension was initiated, restraining the slack thread from interference with the point of the needle. [Illustration: Figure 22.--WILSON'S PREPATENT MODEL for his reciprocating-shuttle machine, 1850. (Smithsonian photo 45525-A.)] The Blodgett and Lerow machine was built by several shops. One of the earliest was the shop of Orson C. Phelps on Harvard Place in Boston. Phelps took the Blodgett and Lerow machine to the sixth exhibition of the Massachusetts Charitable Mechanics Association in September 1850 and won a silver medal and this praise, "This machine performed admirably; it is an exceedingly ingenious and compact machine, able to perform tailor's sewing beautifully and thoroughly."[46] Although Phelps had won the earliest known premium for a sewing machine, and although the machine was produced commercially to a considerable extent (figs. 20 and 21), one outstanding flaw in its operation could not be overlooked. As the shuttle passed around the six-inch circular shuttle race, it put a twist in the thread (or took one out if the direction was reversed) at each revolution. This caused a constant breaking of the thread, a condition that could not be rectified without changing the principle of operation. Such required changes were later to lead I. M. Singer, another well-known name, into the work of improving this machine. Also exhibited at the same 1850 mechanics fair was the machine of Allen B. Wilson. Wilson's machine received only a bronze medal, but his inventive genius was to have a far greater effect on the development of the practical sewing machine than the work of Blodgett and Lerow. A. B. Wilson[47] was one of the ablest of the early inventors in the field of mechanical stitching, and probably the most original. Wilson, a native of Willett, New York, was a young cabinetmaker at Adrian, Michigan, in 1847 when he first conceived of a machine that would sew. He was apparently unaware of parallel efforts by inventors in distant New England. After an illness, he moved to Pittsfield, Massachusetts, and pursued his idea in earnest. By November 1848 he had produced the basic drawings for a machine that would make a lockstitch. The needle, piercing the cloth, left a loop of thread below the seam. A shuttle carrying a second thread passed through the loop, and as the tension was adjusted a completed lockstitch was formed (fig. 22). Wilson's shuttle was pointed on both ends to form a stitch on both its forward and backward motion, a decided improvement over the shuttles of Hunt and Howe, which formed stitches in only one direction. After each stitch the cloth was advanced for the next stitch by a sliding bar against which the cloth was held by a stationary presser. While the needle was still in the cloth and holding it, the sliding bar returned for a fresh grip on the cloth. Wilson made a second machine, on the same principle, and applied for a patent. He was approached by the owners of the Bradshaw 1848 patent, who claimed control of the double-pointed shuttle. Although this claim was without justification, as can be seen by examining the Bradshaw patent specifications, Wilson did not have sufficient funds to fight the claim. In order to avoid a suit, he relinquished to A. P. Kline and Edward Lee, a one-half interest in his U.S. patent 7,776 which was issued on November 12, 1850 (fig. 23). [Illustration: Figure 23.--WILSON'S PATENT MODEL, 1850. (Smithsonian photo 45504-H.)] Inventor Wilson had been associated with Kline and Lee (E. Lee & Co.) for only a few months, when, on November 25, 1850, he agreed to sell his remaining interest to his partners for $2,000. He retained only limited rights for New Jersey and for Massachusetts. The sale was fruitless for the inventor, as no payment was ever made. How much money E. E. Lee & Co. realized from the Wilson machine is difficult to determine, but they ran numerous ads in the 1851 and 1852 issues of _Scientific American_. A typical one reads: A. B. Wilson's Sewing Machine, justly allowed to be the cheapest and best now in use, patented November 12, 1850; can be seen on exhibition at 195 and 197 Broadway (formerly the Franklin House, Room 23, third floor) or to E. E. Lee & Co., Earle's Hotel. Rights for territory or machines can be had by applying to George R. Chittenden, Agent.[48] [Illustration: Figure 24.--WILSON'S PREPATENT MODEL for his rotary hook, 1851. (Smithsonian photo 45506-E.)] [Illustration: Figure 25.--WILSON'S ROTARY-HOOK PATENT MODEL, 1851. (Smithsonian photo 45505-B.)] Another reads: A. B. Wilson's Sewing Machine ... the best and only practical sewing machine--not larger than a lady's work box--for the trifling sum of $35.[49] Wilson severed relations with Lee and Kline in early 1851 shortly after meeting Nathaniel Wheeler, who was to become his partner in a happier, more profitable enterprise involving the sewing machine. [Illustration: Figure 26.--WILSON'S stationary-bobbin patent model, 1852; a commercial machine was used since Wheeler, Wilson, Co. had begun manufacturing machines the previous year. (Smithsonian photo 45504-B.)] Wilson, with his two partners, was occupying a room in the old Sun Building at 128 Fulton Street, when Wheeler, on a business trip to New York City, learned of the Wilson sewing machine. Wheeler examined the machine, saw its possibilities, and at once contracted with E. Lee & Co. to make 500 of them. At the same time he engaged Wilson to go with him to Watertown, Connecticut, to perfect the machine and supervise its manufacture. Meanwhile, Wilson had been working on a substitute for the shuttle. He showed his model of the device, which became known as the rotary hook, to Wheeler who was so convinced of its superiority that he decided to develop this new machine and leave Wilson's first machine to the others, who, by degrees, had become its owners. Wilson now applied all his effort to improving the rotary hook, for which he received his second patent on August 12, 1851 (figs. 24 and 25). Wheeler, his two partners Warren and Woodruff, and Wilson now formed a new copartnership--Wheeler, Wilson, and Company. They began the manufacture of the machines under the patent, which combined the rotary hook and a reciprocating bobbin. The rotary hook extended or opened more widely the loop of the needle thread, while a reciprocating bobbin carried its thread through the extended loop. To avoid litigation which the reciprocating bobbin might have caused, Wilson contrived his third outstanding invention--the stationary bobbin. This was a feature of the first machine produced by the new company in 1851, though the patent for the stationary bobbin was not issued until June 15, 1852 (fig. 26). In all reciprocating-shuttle machines a certain loss of power is incurred in driving forward, stopping, and bringing back the shuttle at each stitch; also, the machines are rather noisy, owing to the striking of the driver against the shuttle at each stroke. These objections were removed by Wilson's rotary hook and stationary bobbin. The locking of the needle thread with the bobbin thread was accomplished, not by driving a shuttle through the loop of the needle thread, but by passing that loop under the bobbin. The driving shaft carried the circular rotary hook, one of the sewing machine's most beautiful contrivances. The success of the machine is indicated in an article that appeared in the June 1853 issue of _Scientific American_: There are 300 of these machines now in operation in various parts of the country, and the work which they can perform cannot be surpassed.... The time must soon come when every private family that has much sewing to do, will have one of these neat and perfect machines; indeed many private families have them now.... The price of one all complete is $125; every machine is made under the eye of the inventor at the company's machine shop, Watertown, Connecticut, so that every one is warranted ... agreement between Mr. Howe and Messrs. Wheeler, Wilson & Co., so every customer will be perfectly protected....[50] [Illustration: Figure 27.--WILSON'S four-motion-feed patent model, 1854, is not known to be in existence; this is a commercial machine of the period. The plate is stamped "A. B. Wilson, Patented Aug. 12, 1851, Watertown, Conn., No. 1...." (Smithsonian photo 45504.)] This agreement was important to sales, as Elias Howe was known to have sued purchasers of machines, as well as rival inventors and companies. The business was on a substantial basis by October 1853, and a stock company was formed under the name of Wheeler & Wilson Manufacturing Company.[51] A little more than a year later, on December 19, 1854, Wilson's fourth important patent (U.S. patent 12,116)--for the four-motion cloth feed--was issued to him (fig. 27). In this development, the flat-toothed surface in contact with the cloth moved forward carrying the cloth with it; then it dropped a little, so as not to touch the cloth; next it moved backward; then in the fourth motion it pushed up against the cloth and was ready to repeat the forward movements. This simple and effective feed method is still used today, with only minor modifications, in almost every sewing machine. This feed with the rotary hook and the stationary circular-disk bobbin, completed the essential features of Wilson's machine. It was original and fundamentally different from all other machines of that time. The resulting Wheeler and Wilson machine made a lockstitch by means of a curved eye-pointed needle carried by a vibrating arm projecting from a rock shaft connected by link and eccentric strap with an eccentric on the rotating hook shaft. This shaft had at its outer end the rotary hook, provided with a point adapted to enter the loop of needle thread. As the hook rotated, it passed into and drew down the loop of needle-thread, which was held by means of a loop check, while the point of the hook entered a new loop. When the first loop was cast off--the face of the hook being beveled for that purpose--it was drawn upward by the action of the hook upon the loop through which it was then passing. During the rotation of the hook each loop was passed around a disk bobbin provided with the second thread and serving the part of the shuttle in other machines. The four-motion feed was actuated in this machine by means of a spring bar and a cam in conjunction with the mandrel. From the beginning, Wheeler and Wilson had looked beyond the use of the sewing machine solely by manufacturers and had seen the demand for a light-running, lightweight machine for sewing in the home. Wilson's inventions lent themselves to this design, and Wheeler and Wilson led the way to the introduction of the machine as a home appliance. Other manufacturers followed. When the stock company was formed, Mr. Wilson retired from active participation in the business at his own request. His health had not been good, and a nervous condition made it advisable for him to be freed from the responsibility of daily routine. During this period Wilson's inventive contributions to the sewing machine continued as noted, and in addition he worked on inventions concerning cotton picking and illuminating gases. Wheeler and Wilson's foremost competitor in the early years of sewing-machine manufacture was the Singer Company, which overtook them by 1870 and finally absorbed the entire Wheeler and Wilson Manufacturing Company in 1905. The founder of this most successful 19th-century company was Isaac Singer, a native of Pittstown, New York.[52] Successively a mechanic, an actor, and an inventor, Singer came to Boston in 1850 to promote his invention of a machine for carving printers' wooden type. He exhibited the carving machine in Orson Phelps' shop, where the Blodgett and Lerow machines were being manufactured. Because the carving machine evoked but little interest, Singer turned his attention to the sewing machine as a device offering considerable opportunity for both improvement and financial reward. Phelps liked Singer's ideas and joined with George Zieber, the publisher who had been backing the carving-machine venture, to support Singer in the work of improving the sewing machine. His improvements in the Blodgett and Lerow machine included a table to hold the cloth horizontally rather than vertically (this had been used by Bachelder and Wilson also), a yielding vertical presser foot to hold the cloth down as the needle was drawn up, and a vertically reciprocating straight needle driven by a rotary, overhanging shaft. The story of the invention and first trial of the machine was told by Singer in the course of a patent suit sometime later: I explained to them how the work was to be fed over the table and under the presser-foot, by a wheel, having short pins on its periphery, projecting through a slot in the table, so that the work would be automatically caught, fed and freed from the pins, in place of attaching and detaching the work to and from the baster plate by hand, as was necessary in the Blodgett machine. Phelps and Zieber were satisfied that it would work. I had no money. Zieber offered forty dollars to build a model machine. Phelps offered his best endeavors to carry out my plan and make the model in his shop; if successful we were to share equally. I worked at it day and night, sleeping but three or four hours a day out of the twenty-four, and eating generally but once a day, as I knew I must make it for the forty dollars or not get it at all. The machine was completed in eleven days. About nine o'clock in the evening we got the parts together and tried it; it did not sew; the workmen exhausted with almost unremitting work, pronounced it a failure and left me one by one. Zieber held the lamp, and I continued to try the machine, but anxiety and incessant work had made me nervous and I could not get tight stitches. Sick at heart, about midnight, we started for our hotel. On the way we sat down on a pile of boards, and Zieber mentioned that the loose loops of thread were on the upper side of the cloth. It flashed upon me that we had forgot to adjust the tension on the needle thread. We went back, adjusted the tension, tried the machine, sewed five stitches perfectly and the thread snapped, but that was enough. At three o'clock the next day the machine was finished. I took it to New York and employed Mr. Charles M. Keller to patent it. It was used as a model in the application for the patent.[53] The first machine was completed about the last of September 1850. The partners considered naming the machine the "Jenny Lind," after the Swedish soprano who was then the toast of America. It was reported[54] to have been advertised under that name when the machine was first placed on the market, but the name was soon changed to "Singer's Perpendicular Action Sewing Machine" or simply the "Singer Sewing Machine"--a name correctly anticipated to achieve a popularity of its own. According to the contract made by the partners, the hurriedly built first machine was to be sent to the Patent Office with an application in the name of Singer and Phelps. An application was made between the end of September 1850 and March 14, 1851, as Singer refers to it briefly in the application formally filed on April 16, 1851, stating, "My present invention is of improvements on a machine heretofore invented by me and for which an application is now pending."[55] [Illustration: Figure 28.--SINGER'S PATENT MODEL, 1851; a commercial machine was used, bearing the serial number 22. (Smithsonian photo 45572-D.)] In late December 1850 Singer had bought Phelps' interest in the company. Whether the first application was later abandoned by Singer or whether it was rejected is not known,[56] but a patent on the first application was never issued. The final disposition of this first machine has remained a mystery.[57] [Illustration: Figure 29.--SINGER'S PERPENDICULAR ACTION sewing machine, an engraving from _Illustrated News_, June 25, 1853, which states: "The sewing machine has, within the last two years acquired a wide celebrity, and established its character as one of the most efficient labor saving instruments ever introduced to public notice.... We must not forget to call attention to the fact that this instrument is peculiarly calculated for female operatives. They should never allow its use to be monopolized by men." (Smithsonian photo 48091-D.)] A few machines were manufactured in late 1850 and early 1851, and these attracted considerable attention; orders began to be received in advance of production. The pending patent application did not delay the manufacture, and a number of machines were sold before August 12, 1851, when the patent was granted. The patent model is shown in figure 28.[58] It made a lockstitch by means of a straight eye-pointed needle and a reciprocating shuttle. The patent claims, as quoted from the specifications, were as follows: 1. Giving to the shuttle an additional forward motion after it has been stopped to close the loop, as described, for the purpose of drawing the stitch tight, when such additional motion is given at and in combination with the feed motion of the cloth in the reverse direction, and the final upward motion of the needle, as described, so that the two threads shall be drawn tight at the same time, as described. 2. Controlling the thread during the downward motion of the needle by the combination of a friction-pad to prevent the slack above the cloth, with the eye on the needle-carrier for drawing back the thread, for the purposes and in the manner substantially as described. 3. Placing the bobbin from which the needle is supplied with thread on an adjustable arm attached to the frame, substantially as described, when this is combined with the carrying of the said thread through an eye or guide attached to and moving with the needle-carrier, as described, whereby any desired length of thread can be given for the formation of the loop without varying the range of motion of the needle, as described. The feeding described in the Singer patent was "by the friction surface of a wheel, whose periphery is formed with very fine grooves, the edges of which are slightly serrated, against which the cloth is pressed by a spring plate or pad." Although claimed by the inventor in the handwritten specifications, it was not allowed as original. The machines manufactured by the Singer company (fig. 29) were duplicates of the patent model. These machines were quite heavy and intended for manufacturing rather than for family use in the home. [Illustration: Figure 30.--I. M. SINGER & CO. NEW YORK SHOWROOM of the mid-1850s, as illustrated in _Frank Leslie's Illustrated Newspaper_, August 29, 1857; only manufacturing machines are shown in this illustration. (Smithsonian photo 48091-B.)] [Illustration: Figure 31.--HUNT AND WEBSTER'S SEWING-MACHINE MANUFACTORY exhibition and salesroom in Boston, as illustrated in _Ballou's Pictorial_, July 5, 1856; only manufacturing machines are shown. (Smithsonian photo 45771-A.)] Singer enjoyed demonstrating the machine and showed it to church and social groups and even at circuses; this personal association then encouraged him to improve its reliability and convenience. He developed a wooden packing case which doubled as a stand for the machine and a treadle to allow it to be operated by foot. Because of the dimensions of the packing case, Singer put the pivot of the treadle toward its center, about where the instep of the foot would rest. This produced the heel-and-toe action treadle, a familiar part of the sewing machine until its replacement by the electric motor. Both hands were freed to guide and arrange the cloth that was being stitched. Singer also added a flywheel to smooth out the treadle action and later an iron stand with a treadle wide enough for both feet. The treadle had been in use for two years before a rival pointed out that it might have been patented. To Singer's chagrin it was then too late for patent laws did not permit patenting a device that had been in public use. A new obstacle appeared in the Singer company's path when Howe demanded $25,000 for infringement of his patent. Singer and Zieber decided to fight, enlisting the legal aid of Edward Clark, a lawyer and financier. Howe's action was opposed on the basis of Hunt's machine of 1834, which they stated had anticipated Howe's invention. While they were resisting, Howe sued three firms that were using and selling Singer machines. The court order required the selling firms and the purchasers to provide an account of the profits accrued from the sale and the use of the sewing machines and restrained the firms from selling the machines during the pendency of the suit.[59] As a result of this action, a number of Singer's rivals purchased licenses from Howe and advertised that anyone could sell their machines without fear of a suit. This gave them a great competitive advantage, and Singer and Clark[60] decided it was best to seek a settlement with Howe. On July 1, 1854, they paid him $15,000 and took out a license. [Illustration: Figure 32.--SINGER'S NEW FAMILY SEWING MACHINE, illustration from a brochure dating about 1858 or 1859 which states: "A few months since, we came to the conclusion that the public taste demanded a sewing machine for family purposes more exclusively; a machine of smaller size, and of a lighter and more elegant form; a machine decorated in the best style of art, so as to make a beautiful ornament in the parlor or boudoir; a machine very easily operated, and rapid in working.... To supply this public want, we have just produced, and are now prepared to receive orders for, 'Singer's new Family Sewing Machine.'" (Smithsonian photo 48091-H.)] In spite of this defeat, the Singer company could claim several important improvements to the sewing machine and the acquisition of the patents rights to the Morey and Johnson machine of 1849, which gave them control of the spring or curved arm to hold the cloth by a yielding pressure. Although this point had not been claimed in the 1849 patent, the established principle of patent law allowed that a novel device introduced and used in a patented machine could be covered by a reissue at any time during the life of the patent. Upon becoming owners of the Morey and Johnson patent, Singer applied for a reissue which covered this type of yielding pressure. It was granted on June 27, 1854. The Singer company's acquisition of the Bachelder patent had given them control of the yielding pressure bar also. [Illustration: Figure 33.--SINGER FAMILY MACHINE, 1858, head only. (Smithsonian photo 45524-F.)] Singer's aggressive selling had begun to overcome the public's suspicion of sewing machines. He pioneered in the use of lavishly decorated sewing-machine showrooms when the company offices were expanded in the mid-1850s (fig. 30). These were rich with carved walnut furniture, gilded ornaments, and carpeted floors, places in which Victorian women were not ashamed to be seen. The machines were demonstrated by pretty young women. The total effect was a new concept of selling, and Singer became the drum major of a new and coming industry that had many followers (see fig. 31). [Illustration: Figure 34.--GROVER AND BAKER'S PATENT MODEL, 1851. (Smithsonian photo 32003-G.)] The first, light, family sewing machine by the Singer company was not manufactured until 1858 (figs. 32 and 33). Comparatively few of these machines were made as they proved to be too small and light. The men in the shop dubbed the machine "The Grasshopper," but it was officially called the new Family Sewing Machine or the Family Machine.[61] Because of its shape, Singer company brochures of the 1920s referred to it as the Turtleback Machine. Since the cost of sewing machines was quite high and the average family income was low, Clark suggested the adoption of the hire-purchase plan. Into the American economy thus came the now-familiar installment buying. Singer and Clark continued to be partners until 1863 when a corporation was formed. At this time Singer decided to withdraw from active work. He received 40 percent of the stock and retired to Paris and later to England, where he died in 1875. [Illustration: Figure 35.--THIS GROVER AND BAKER CABINET-STYLE SEWING MACHINE of 1856 bears the serial number 5675 and the patent dates February 11, 1851, June 22, 1852, February 22, 1853, and May 27, 1856. (Smithsonian photo 45572-F.)] By the mid-1850s the basic elements of a successful, practical sewing machine were at hand, but the continuing court litigation over rival patent rights seemed destined to ruin the economics of the new industry. It was then that the lawyer of the Grover and Baker company, another sewing-machine manufacturer of the early 1850s, supplied the solution. Grover and Baker were manufacturing a machine that was mechanically good, for this early period. William O. Grover was another Boston tailor, who, unlike many others, was convinced that the sewing machine was going to revolutionize his chosen trade. Although the sewing machines that he had seen were not very practical, he began in 1849 to experiment with an idea based on a new kind of stitch. His design was for a machine that would take both its threads from spools and eliminate the need to wind one thread upon a bobbin. After much experimenting, he proved that it was possible to make a seam by interlocking two threads in a succession of slipknots, but he found that building a machine to do this was a much more difficult task. It is quite surprising that while he was working on this idea, he did not stumble upon a good method to produce the single-thread (as opposed to Grover and Baker's two-thread) chainstitch, later worked out by another. Grover was working so intently on the use of two threads that apparently no thought of forming a stitch with one thread had a chance to develop. At this time Grover became a partner with another Boston tailor, William E. Baker, and on February 11, 1851, they were issued U.S. patent No. 7,931 for a machine that did exactly what Grover had set out to do; it made a double chainstitch with two threads both carried on ordinary thread spools. The machine (figs. 34 and 35) used a vertical eye-pointed needle for the top thread and a horizontal needle for the underthread. The cloth was placed on the horizontal platform or table, which had a hole for the entry of the vertical needle. When this needle passed through the cloth, it formed a loop on the underside. The horizontal needle passed through this loop forming another loop beyond, which was retained until the redescending vertical needle enchained it, and the process repeated. The slack in the needle thread was controlled by means of a spring guide. The cloth was fed by feeding rolls and a band. [Illustration: Figure 36.--GROVER'S PATENT MODEL FOR THE FIRST PORTABLE CASE, 1856. The machine in the case is a commercial machine of 1854, bearing the serial number 3012 and the patent dates "Feby 11, 1851, June 22, 1852, Feby 22, 1853." Powered by a single, foot-shaped treadle that was connected by a removable wooden pitman, it also could be turned by hand. (Smithsonian photo 45525-D.)] A company was organized under the name of Grover and Baker Sewing Machine Company, and soon the partners took Jacob Weatherill, mechanic, and Orlando B. Potter, lawyer (who became the president), into the firm. Potter contributed his ability as a lawyer in lieu of a financial investment and handled the several succeeding patents of Grover and Baker. These patents were primarily for mechanical improvements such as U.S. patent No. 9,053 issued to Grover and Baker on June 22, 1852, for devising a curved upper needle and an under looper[62] to form the double-looped stitch which became known as the Grover and Baker stitch. One of the more interesting of the patents, however, was for the box or sewing case for which Grover was issued U.S. patent No. 14,956 on May 27, 1856. The inventor stated "that when open the box shall constitute the bed for the machine to be operated upon, and hanging the machine thereto to facilitate oiling, cleansing, and repairs without removing it from the box." It was the first portable sewing machine (fig. 36). Though the Grover and Baker company manufactured machines using a shuttle and producing the more common lockstitch, both under royalty in their own name and also for other smaller companies, Potter was convinced that the Grover and Baker stitch was the one that eventually would be used in both family and commercial machines. He, as president, directed the efforts of the company to that end. When the basic patents held by the "Sewing-Machine Combination" (discussed on pp. 41-42) began to run out in the mid-1870s, dissolving its purpose and lowering the selling price of sewing machines, the Grover and Baker company began a systematic curtailing of expenses and closing of branch offices. All the patents held by the company and the business itself were sold to another company.[63] But the members of the Grover and Baker company fared well financially by the strategic move. The Grover and Baker machine and its unique stitch did not have a great influence on the overall development of the mechanics of machine sewing. The merits of a double-looped stitch--its elasticity and the taking of both threads from commercial spools--were outweighed by the bulkiness of the seam and its consumption of three times as much thread as the lockstitch required. Machines making a similar type of stitch have continued in limited use in the manufacture of knit goods and other products requiring an elastic seam. But, more importantly, Grover and Baker's astute Orlando B. Potter placed their names in the annals of sewing-machine history by his work in forming the "Combination," believed to be the first "trust" of any prominence. FOOTNOTES: [33] See biographical sketch, pp. 138-141. [34] _In the Matter of the Application of Elias Howe, Jr. for an Extension of His Sewing Machine Patent Dated September 10, 1846_, New York, 1860, with attachments A and B, U.S. Patent Office. [L.C. call no. TJ 1512.H6265] [35] It is interesting to note that when William Thomas applied for the British patent of the Howe machine (issued Dec. 1, 1846), the courts would not allow the claim for the combination of the eye-pointed needle and shuttle to form a stitch, due to the Fisher and Gibbons patent of 1844. For more details on Howe's years in England see his biographical sketch, pp. 138-141. [36] The machine referred to as the London Sewing Machine is the British patent of the Thimonnier machine. This patent was applied for by Jean Marie Magnin and was published by _Newton's London Journal_, vol. 39, p. 317, as Magnin's invention. [37] The exact date is not known; however, it was prior to 1856 as the patent was included in the sewing-machine patent pool formed that year. [38] JAMES PARTON, _History of the Sewing Machine_, p. 12, (originally published in the _Atlantic Monthly_, May 1867), later reprinted by the Howe Machine Company as a separate. [39] _Sewing Machine Times_ (Feb. 25, 1907), vol. 17, no. 382, p. 1, "His [Bonata's] shop was on Gold Street, New York, near the Bartholf shop, where Howe was building some of his early machines." [40] _Sewing Machine News_, vol. 3, no. 5, p. 5, Sept. 1881-Jan. 1882. "History of the Sewing Machine." [41] Op. cit. (footnote 34). [42] _New York Daily Tribune_, Jan. 15, 1852, p. 2. [43] See Howe's biographical sketch, p. 141. [44] Op. cit. (footnote 34). Attachments A and B are copies of Judge Sprague's decisions. [45] _Sewing Machine Journal_ (July 1887), pp. 93-94. [46] _Report of the Sixth Exhibition of the Massachusetts Charitable Mechanics Association, in the City of Boston, September 1850_ (Boston, 1850). [47] See biographical sketch, pp. 141-142. [48]_Scientific American_ (Dec. 6, 1851), vol. 7, no. 12, p. 95. [49] Ibid. (Sept. 20, 1851), vol. 7, no. 1, p. 7. [50] Ibid. (June 4, 1853), vol. 7, no. 38, p. 298 [51] J. D. VAN SLYCK, _New England Manufactures and Manufactories_, vol. 2, pp. 672-682. [52] See his biographical sketch, pp. 142-143. [53] CHESTER MCNEIL, _A History of the Sewing Machine_ in Union Sales Bulletin, vol. 3, Union Special Sewing Machine Co., Chicago, Illinois, pp. 83-85. 1903. [54] _Sewing Machine Times_ (Aug. 25, 1908), vol. 18, no. 418. [55] Singer gives this limited description of the first machine, with detailed improvements for which he was then applying for a patent: "In my previous machine, to which reference has been made, the bobbin was carried by the needle-carrier, and hence the motion of the needle had to be equal to the length of thread required to form the loop, which was objectionable, as in many instances this range of motion was unnecessarily long for all other purposes...." Quoted from U.S. patent 8,294 issued to Isaac M. Singer, Aug. 12, 1851. It should be noted that in some instances there was a considerable lapse of time from the date a patent application was made until the patent was issued. In this case the handwritten specifications were dated March 14, 1851, and the formal Patent Office receipt was dated April 16, 1851. [56] If a patent was not approved, for any reason, the records were placed in an "Abandoned File." In 1930 Congress authorized the disposal of the old "Abandoned Files," requiring them to be kept for twenty years only. There are no Singer Company records giving an account of the first patent application. [57] Its whereabouts was unknown as early as 1908, as stated in the _Sewing Machine Times_ (Aug. 25, 1908), vol. 18, no. 418. Models of abandoned patents frequently remained at the Patent Office. Approximately 76,000 models were ruined in a Patent Office fire in 1877. In 1908 over 3000 models of abandoned patents were sold at auction. Either incident could account for the machine's disappearance. [58] The patent model of 8,294 is a machine that bears the serial number 22; it was manufactured before April 18, 1851, the date it was recorded as received by the Patent Office. [59] William R. Bagnall, in "Contributions to American Economic History," vol. 1 (1908), MS, Harvard School of Business Library. [60] Singer purchased Phelps' interest in the company in 1851 and sold it to Edward Clark. [61] This first, family sewing machine should not be confused in name with a model brought out in the sixties. The name of this first, family machine was in the sense of a new "family" sewing machine. In 1859 a "Letter A" family machine was introduced. Thus in 1865 when the Singer Company brought out another family machine they called it the "New" Family Sewing Machine. Both the first-style Family machine and the Letter A machine are illustrated in _Eighty Years of Progress of the United States_ (New York, 1861), vol. 2, p. 417, and discussed in an article, "The Place and Its Tenants," in the _Sewing Machine Times_ (Dec. 25, 1908), vol. 27, no. 893. [62] A looper on the underside in place of the horizontal needle. [63] Domestic Sewing Machine Company. See _Union Special Sewing Machine Co. Sales Bulletin_, vol. 3, ch. 15, pp. 58-59. _Chapter Three_ [Illustration: +----------------------------------------------------------------------------+ | A PARTIAL STATEMENT FROM RECORDS OF "THE SEWING-MACHINE COMBINATION," | | SHOWING NUMBER OF SEWING-MACHINES LICENSED ANNUALLY | | UNDER THE _ELIAS HOWE_ PATENT. | +-----+--------+---------+---------+---------+------+-------+-------+--------+ |NAME |Wheeler |I. M. |The |Grover & |A. B. |Leavitt|Ladd & |Bartholf| |OF |& |Singer |Singer |Baker |Howe |S. M. |Webster|S. M. | |MANU-|Wilson |& Co. |Manufac- |S. M. Co.|S. M. |Co. |S. M. |Co. | |FACT-|Mfg. Co.| |turing | |Co. | |Co. | | |URER.| | |Co. | | | | | | +-----+--------+---------+---------+---------+------+-------+-------+--------+ |1853 |799 |810 |.... |657 |.... |28 |100 |135 | |1854 |756 |879 |.... |2,034 |60 |217 |268 |55 | |1855 |1,171 |883 |.... |1,144 |53 |152 |73 |31 | |1856 |2,210 |2,564 |.... |1,952 |47 |235 |180 |35 | |1857 |4,591 |3,630 |.... |3,680 |133 |195 |453 |31 | |1858 |7,978 |3,594 |.... |5,070 |179 |75 |490 |203 | |1859 |21,306 |10,953 |.... |10,280 |921 |213 |1,788 |747 | |1860 |25,102 |13,000(a)|.... |(b) |(b) |(b) |(b) | | |1861 |18,556 |16,000(a)|.... |(b) |(b) |(b) |(b) |(b) | |1862 |28,202 |18,396 |.... |(b) |(b) |(b) |(b) |(b) | |1863 |29,778 |.... |20,030 |(b) |(b) |(b) |(b) |(b) | |1864 |40,062 |.... |23,632 |(b) |(b) |(b) |(b) |(b) | |1865 |39,157 |.... |26,340 |(b) |(b) |(b) |(b) |(b) | |1866 |50,132 |.... |30,960 |(b) |(b) |(b) |(b) |(b) | +-----+--------+---------+---------+---------+------+-------+-------+--------+ +-------------------------------------------------------------------------------+ | A PARTIAL STATEMENT SHOWING NUMBER OF SEWING-MACHINES LICENSED ANNUALLY | | FROM 1867 TO 1876 INCLUSIVE. | +----------------------------+----------+---------+---------+---------+---------+ | NAME OF MANUFACTURER. | 1867. | 1868. | 1869. | 1870. | 1871. | +----------------------------+----------+---------+---------+---------+---------+ |The Singer Manufacturing Co.|43,053 |59,629 |86,781 |127,833 |181,260 | |Wheeler & Wilson Mfg. Co. |38,055 |(b) |78,866 |83,208 |128,526 | |Grover & Baker S. M. Co. |32,999 |35,000(a)|35,188 |57,402 |50,838 | |Weed Sewing-Machine Co. |3,638 |12,000 |19,687 |35,002 |39,655 | |Howe Sewing-Machine Co. |11,053 |35,000(a)|45,000(a)|75,156 |134,010 | |A. B. Howe " " |.... |.... |.... |.... |20,051 | |B. P. Howe " " |.... |.... |.... |.... |.... | |Willcox & Gibbs S. M. Co. |14,152 |15,000 |17,201 |28,890 |30,127 | |Wilson (W. G.) " " |.... |.... |.... |.... |21,153 | |American B. H. & S. M. Co. |.... |.... |7,792 |14,573 |20,121 | |Florence S. M. Co. |10,534 |12,000 |13,661 |17,660 |15,947 | |Shaw & Clark S. M. Co. |2,692 |3,000 |.... |.... |.... | |Gold Medal " " " |.... |.... |.... |8,912 |13,562 | |Davis " " " |.... |.... |.... |.... |11,568 | |Domestic " " " |.... |.... |.... |.... |10,397 | |Finkle & Lyon Mfg. Co. and |2,488 |2,000 |1,339 |2,420 |7,639 | | Victor. | | | | | | |�tna Sewing-Machine Co. |2,958 |3,500 |4,548 |5,806 |4,720 | |Blees " " " |.... |.... |.... |.... |4,557 | |Elliptic " " " |3,185 |.... |.... |.... |4,555 | |Empire " " " |2,121 |5,000 |8,700 |.... |.... | |Remington Sewing-Machine Co.|.... |.... |.... |3,560 |2,965 | |Parham " " " |.... |.... |1,141 |1,766 |2,056 | |Bartram & Fanton Mfg. Co. |2,958 |.... |.... |.... |1,004 | |Bartlett Sewing-Machine Co. |.... |.... |.... |.... |614 | |J. G. Folsom |.... |.... |.... |.... |280 | |McKay Sewing-Machine Asso. |.... |.... |.... |129 |218 | |C. F. Thompson |.... |.... |.... |.... |147 | |Union Buttonhole Machine Co.|.... |.... |.... |.... |124 | |Leavitt Sewing-Machine Co. |1,051 |1,000 |771 |.... |.... | |Goodspeed & Wyman S. M. Co. |2,126 |.... |.... |.... |.... | |Keystone Sewing-Machine Co. |.... |.... |.... |.... |.... | |Secor " " " |.... |.... |.... |.... |.... | |Centennial " " " |.... |.... |.... |.... |.... | +----------------------------+----------+---------+---------+---------+---------+ | NAME OF MANUFACTURER. | 1872. | 1873. | 1874. | 1875. | 1876. | +----------------------------+----------+---------+---------+---------+---------+ |The Singer Manufacturing Co.|219,758 |232,444 |241,679 |249,852 |262,316 | |Wheeler & Wilson Mfg. Co. |174,088 |119,190 |92,827 |103,740 |108,997 | |Grover & Baker S. M. Co. |52,010 |36,179 |20,000(a)|15,000(a)|.... | |Weed Sewing-Machine Co. |42,444 |21,769 |20,495 |21,993 |14,425 | |Howe Sewing-Machine Co. |145,000(a)|90,000(a)|35,000(a)|25,000(a)|109,294 | |A. B. Howe " " |.... |.... |.... |.... |.... | |B. P. Howe " " |14,907 |13,919 |.... |.... |.... | |Willcox & Gibbs S. M. Co. |33,639 |15,881 |13,710 |14,522 |12,758 | |Wilson (W. G.) " " |22,666 |21,247 |17,525 |9,508 |.... | |American B. H. & S. M. Co. |18,930 |14,182 |13,529 |14,406 |17,937 | |Florence S. M. Co. |15,793 |8,960 |5,517 |4,892 |2,978 | |Shaw & Clark S. M. Co. |.... |.... |.... |.... |.... | |Gold Medal " " " |18,897 |16,431 |15,214 |14,262 |7,185 | |Davis " " " |11,376 |8,861 |.... |.... |.... | |Domestic " " " |49,554 |40,114 |22,700 |21,452 |23,587 | |Finkle & Lyon Mfg. Co. and |11,901 |7,446 |6,292 |6,103 |5,750 | | Victor. | | | | | | |�tna Sewing-Machine Co. |4,262 |3,081 |1,866 |1,447 |707 | |Blees " " " |6,053 |3,458 |.... |.... |.... | |Elliptic " " " |.... |.... |.... |.... |.... | |Empire " " " |.... |.... |.... |.... |.... | |Remington Sewing-Machine Co.|4,982 |9,183 |17,608 |25,110 |12,716 | |Parham " " " |.... |.... |.... |.... |.... | |Bartram & Fanton Mfg. Co. |1,000 |1,000 |250 |.... |.... | |Bartlett Sewing-Machine Co. |1,000 |.... |.... |.... |.... | |J. G. Folsom |.... |.... |.... |.... |.... | |McKay Sewing-Machine Asso. |.... |.... |128 |161 |102 | |C. F. Thompson |.... |.... |.... |.... |.... | |Union Buttonhole Machine Co.|.... |.... |.... |.... |.... | |Leavitt Sewing-Machine Co. |.... |.... |.... |.... |.... | |Goodspeed & Wyman S. M. Co. |.... |.... |.... |.... |.... | |Keystone Sewing-Machine Co. |2,665 |217 |37 |.... |.... | |Secor " " " |311 |3,430 |4,541 |1,307 |.... | |Centennial " " " |.... |514 |.... |.... |.... | +----------------------------+----------+---------+---------+---------+---------+ (a) Number estimated. (b) No data. Figure 37.--TABLE OF SEWING-MACHINE STATISTICS. From Frederick G. Bourne, "American Sewing Machines" in _One Hundred Years of American Commerce_, vol. 2. ed. Chauncey Mitchell Depew (New York: D. O. Haines, 1895), p. 530. (Smithsonian photo 42542-A.)] The "Sewing-Machine Combination" With the basic elements of a successful sewing machine assembled, the various manufacturers should have been able to produce good machines unencumbered. The court order, however, which restrained several firms from selling Singer machines while the Howe suit was pending, started a landslide; soon Wheeler, Wilson and company, Grover and Baker company, and several others[64] purchased rights from Elias Howe. This gave Howe almost absolute control of the sewing-machine business as these companies agreed to his royalty terms of $25 for every machine sold. In an attempt to improve his own machine, Howe was almost immediately caught up in another series of legal battles in which he was the defendant; the companies he had defeated were able to accuse him of infringing on patents that they owned. To compound the confusion, individual companies also were suing each other on various grounds. Because of this situation Orlando B. Potter, president of the Grover and Baker company, advanced in 1856 the idea of a "Combination" of sewing-machine manufacturers. He pointed out how the various companies were harming themselves by continuing litigation and tried to convince Howe that all would benefit by an agreement of some kind. He proposed that Elias Howe; Wheeler, Wilson and company; I. M. Singer and company; and Grover and Baker company pool their patents covering the essential features of the machine. The three companies had started production about the same time and approved of Potter's idea; Howe opposed it as he felt that he had the most to lose by joining the "Combination." He finally consented to take part in Potter's plan if the others would agree to certain stipulations. The first requirement was that at least twenty-four manufacturers were to be licensed. The second was that, in addition to sharing equally in the profits with the three companies, Howe would receive a royalty of $5 for each machine sold in the United States and $1 for each machine exported. It has been estimated that, as a result of this agreement, Howe received at least $2,000,000 as his share of the license fees between 1856 and 1867 when his patent expired.[65] The organization was called the Sewing-Machine Trust and/or the Sewing-Machine Combination. The important patents contributed to it were: 1. The grooved, eye-pointed needle used with a shuttle to form the lockstitch (E. Howe patent, held by E. Howe); 2. The four-motion feeding mechanism (A. B. Wilson patent, held by Wheeler and Wilson company); 3. The needle moving vertically above a horizontal work-plate (Bachelder patent), a continuous feeding device by belt or wheel (Bachelder patent), a yielding presser resting on the cloth (Bachelder patent), the spring or curved arm to hold the cloth by a yielding pressure (Morey and Johnson patent), the heart-shaped cam as applied to moving the needle bar (Singer patent); all these patents, held by the Singer Company.[66] The Grover and Baker company contributed several patents of relative importance, but its most important claim for admission was the fact that Potter had promoted the idea. The consent of all four member-parties was required before any license could be granted, and all were required to have a license--even the member companies. The fee was $15 per machine. A portion of this money was set aside to pay the cost of prosecuting infringers, Howe received his initial fee, and the rest was divided between the four parties. The advantage to the licensee was that he was required to pay only one fee. Most license applications were granted; only those manufacturing a machine specifically imitating the product of a licensed manufacturer were refused. The "Combination's" three company members each continued to manufacture, improve, and perfect its own machine. Other than the joint control of the patents, there was no pooling of interests, and each company competed to attract purchasers to buy its particular type of machine, as did the companies who were licensed by them. In 1860, the year Howe's patent was renewed, the general license fee was reduced from $15 to $7, and Howe's special royalty was reduced to $1 per machine. Howe remained a member until his patent ran out in 1867. The other members continued the "Combination" until 1877, when the Bachelder patent, which had been extended twice, finally expired. By that time the fundamental features of the sewing machine were no longer controlled by anyone. Open competition by the smaller manufacturers was possible, and a slight reduction in price followed. Many new companies came into being--some destined to be very short-lived. From the beginning to the end of the "Combination" there was an army of independents, including infringers and imitators, who kept up a constant complaint against it, maintaining that its existence tended to retard the improvement of the sewing machine and that the public suffered thereby. In the period immediately following the termination of the "Combination," however, only a few improvements of any importance were made, and most of these were by the member companies. FOOTNOTES: [64] These included the American Magnetic Sewing Machine Co.; A. Bartholf; Nichols and Bliss; J. A. Lerow; Woolridge, Keene, and Moore; and A. B. Howe. _New York Daily Tribune_, Sept. 3, 1853. [65] "Who Invented the Sewing-Machine," unsigned article in _The Galaxy_, vol. 4, August 31, 1867, pp. 471-481. [66] Singer has sometimes been credited as the inventor of the various improvements covered by the patents that the Singer company purchased and later contributed to the efforts of the Combination. _Chapter Four_ [Illustration: Figure 38.--GIBBS' PATENT MODEL, 1857. (Smithsonian photo 45504-E.)] Less Expensive Machines While the "Combination" was attempting to solve the problems of patent litigation, another problem faced the would-be home users of this new invention. The budget limitations of the average family caused a demand for a less expensive machine, for this first consumer appliance was a most desirable commodity.[67] There were many attempts to satisfy this demand, but one of the best and most successful grew out of a young man's curiosity. James E. A. Gibbs' first exposure to the sewing machine was in 1855 when, at the age of 24, he saw a simple woodcut illustration of a Grover and Baker machine. The woodcut represented only the upper part of the machine. Nothing in the illustration indicated that more than one thread was used, and none of the stitch-forming mechanism was visible. Gibbs assumed that the stitch was formed with one thread; he then proceeded to imagine a mechanism that would make a stitch with one thread. His solution was described in his own statement: As I was then living in a very out of the way place, far from railroads and public conveyances of all kinds, modern improvements seldom reached our locality, and not being likely to have my curiosity satisfied otherwise, I set to work to see what I could learn from the woodcut, which was not accompanied by any description. I first discovered that the needle was attached to a needle arm, and consequently could not pass entirely through the material, but must retreat through the same hole by which it entered. From this I saw that I could not make a stitch similar to handwork, but must have some other mode of fastening the thread on the underside, and among other possible methods of doing this, the chainstitch occurred to me as a likely means of accomplishing the end. I next endeavored to discover how this stitch was or could be made, and from the woodcut I saw that the driving shaft which had the driving wheel on the outer end, passed along under the cloth plate of the machine. I knew that the mechanism which made the stitch must be connected with and actuated by this driving shaft. After studying the position and relations of the needle and shaft with each other, I conceived the idea of the revolving hook on the end of the shaft, which might take hold of the thread and manipulate it into a chainstitch. My ideas were, of course, very crude and indefinite, but it will be seen that I then had the correct conception of the invention afterwards embodied in my machine.[68] [Illustration: Figure 39.--ONE OF THE FIRST COMMERCIAL MACHINES produced by the Willcox & Gibbs Sewing Machine Co. in 1857, this machine bears no serial number, although the name "James E. A. Gibbs" is inscribed in two places on the cloth plate. It was used as the patent model for Gibbs' improvement on his 1857 patent issued the following year on August 10, 1858. (Smithsonian photo P. 6393.)] Gibbs had no immediate interest in the sewing machine other than to satisfy his curiosity. He did not think of it again until January 1856 when he was visiting his father in Rockbridge County, Virginia. While in a tailor's shop there, he happened to see a Singer machine. Gibbs was very much impressed, but thought the machine entirely too heavy, complicated, and cumbersome, and the price exorbitant. It was then that he recalled the machine he had devised. Remembering how simple it was, he decided to work in earnest to produce a less-expensive type of sewing machine. Gibbs had little time to spend on this invention since his family was dependent upon him for support, but he managed to find time at night and during inclement weather. In contemporary references, Gibbs is referred to as a farmer, but since he is also reported to have had employers, it may be surmised that he was a farmhand. In any event, his decision to try to produce a less-expensive sewing machine suffered from a lack of proper tools and adequate materials. Most of the machine had to be constructed of wood, and he was forced to make his own needles. By the end of April 1856, however, his model was sufficiently completed to arouse the interest of his employers, who agreed to furnish the money necessary to patent the machine. Gibbs went to Washington, where he examined sewing-machine models in the Patent Office and other machines then on the market. Completing his investigations, Gibbs made a trip to Philadelphia and showed his invention to a builder of models of new inventions, James Willcox. Much impressed with the machine, Willcox arranged for Gibbs to work with his son, Charles Willcox, in a small room in the rear of his shop. After taking out two minor patents (on December 16, 1856, and January 20, 1857), Gibbs obtained his important one, U.S. patent No. 17,427 on June 2, 1857 (fig. 38). His association with Charles Willcox led to the formation of the Willcox & Gibbs Sewing Machine Company, and they began manufacturing chainstitch machines in 1857 (fig. 39). The machine used a straight needle to make a chainstitch. At the forward end of the main shaft was a hook which, as it rotated, carried the loop of needle-thread, elongated and held it expanded while the feed moved the cloth until the needle at the next stroke descended through the loop so held. When the needle descended through the first loop, the point of the hook was again in position to catch the second loop, at which time the first loop was cast off and the second loop drawn through it, the first loop having been drawn up against the lower edge of the cloth to form a chain. [Illustration: Figure 40.--A DOLPHIN sewing machine based on Clark's patent of 1858. This design was first used by T. J. W. Robertson in 1855, but in his patent issued on May 22 of that year no claim was made for the machine design, only for the chainstitch mechanism. The same style was used by D. W. Clark in several of his chainstitch patents, but he also made no claim for the design, stating that the machine "may be made in any desired ornamental form." The dolphin-style machines are all chainstitch models of solid brass, originally gilt. Although only about five inches long, they are full-size machines using a full-size needle. (Smithsonian photo 45505.)] A Gibbs sewing machine, on a simple iron-frame stand with treadle, sold for approximately $50 in the late 1850s,[69] while a Wheeler and Wilson[70] machine or a Grover and Baker[71] with the same type of stand sold for approximately $100. After the introduction of the Gibbs machine, the Singer company[72] brought out a light family machine in 1858 that was also first sold for $100. It was then reduced to $50, but it was not popular because it was too light (see discussion of Singer machines, pp. 34-35). In 1859, Singer brought out its second, more successful family machine, which sold for $75. Like the other companies licensed by the "Combination," Willcox and Gibbs company paid a royalty for the use of the patents it held. Although the Willcox and Gibbs machine was a single-thread chainstitch machine and the company held the Gibbs patents, the company was required to be licensed to use the basic feed, vertical needle, and other related patents held by the "Sewing-Machine Combination." With the approach of the Civil War, Gibbs returned to Virginia. Poor health prevented him from taking an active part in the war, but he worked throughout the conflict in a factory processing saltpeter for gunpowder. Afterward, Gibbs returned to Philadelphia and found that Willcox had faithfully protected his sewing-machine interests during his long absence. The firm prospered, and Gibbs finally retired to Virginia a wealthy man. Interestingly, Gibbs named the Virginia village to which he returned in later life "Raphine"--derived, somewhat incorrectly, from the Greek word "to sew." The Willcox & Gibbs Sewing Machine Company is one of the few old companies still in existence. It discontinued making and selling family-style machines many years ago and directed its energies toward specialized commercial sewing machines, many of which are based on the original chainstitch principle. There was also an ever-increasing number of other patentees and manufacturers who, in the late 1850s and 1860s, attempted to produce a sewing machine that would circumvent both the "Combination" and the high cost of manufacturing a more complicated type of machine. Some of the more interesting of these are pictured and described in figures 40 through 54. [Illustration: Figure 41.--THE CHERUB sewing machine was another Robertson first which was adopted by Clark. Robertson's patent of October 20, 1857, once again makes no claim for the design; neither does Clark's patent of January 5, 1858, illustrated here. The machine is approximately the same size as the dolphin and is made in the same manner and of the same materials. Two cherubs form the main support, one also supporting the spool and leashing a dragonfly which backs the needle mechanism. (Smithsonian photo 45504-D.)] [Illustration: Figure 42.--THE FOLIAGE SEWING MACHINE originated with D. W. Clark. Once again he did not include the design in his June 8, 1858, patent, which was aimed at improving the feeding mechanism. Like most hand-turned models, these required a clamp to fasten them to the table when in operation. (Smithsonian photo 45504-C.)] [Illustration: Figure 43.--THE SEWING SHEARS was another popular machine of unusual style. Some models were designed to both cut and sew, but most derived their names from the method of motivating power. The earliest example of the sewing-shears machine was invented by Joseph Hendrick, who stated in his patent that he was attempting to produce "a simple, portable, cheap, and efficient machine." His patent model of October 5, 1858, is illustrated. (Smithsonian photo 45504-F.)] [Illustration: Figure 44.--THE HORSE SEWING MACHINE is among the most unusual of the patents issued for mechanical improvements. Although James Perry, the patentee, made several claims for the looper, feeder, and tension, he made no mention of the unusual design of the machine, for which a patent was issued on November 23, 1858. Although it was probably one of a kind, the horse machine illustrates the extent to which the inventor's mind struggled for original design. (Smithsonian photo 45505-C.)] [Illustration: Figure 45.--MANY INVENTORS attempted to cut the cost of manufacturing a complicated machine. One of these was Albert H. Hook, whose machine is only about four inches high and two inches wide. His patent, granted November 30, 1858, simplified the construction and arrangement of the various parts. Although Hook used a barbed needle reminiscent of the one used by Thimonnier, his method of forming the stitch was entirely different. The thread was passed through the necessary guides, and when the cloth was in place the needle was thrust up from below. Passing through the fabric, the needle descended, carrying with it a loop of thread. As the process was repeated, a chainstitch was formed with the enchained loop on the under side. In spite of its simple mechanism, Hook's machine was not a commercial success. (Smithsonian photo 45505-D.)] [Illustration: Figure 46.--IN ADDITION TO MECHANICAL PATENTS, a number of design patents were also issued for sewing machines. These fall into a separate series in the Patent Office's numerical records. This unusual example featured two semidraped female figures holding the spool of thread, a mermaid holding the needle, a serpent which served as the presser foot, and a heart-shaped baster plate. The design was patented by W. N. Brown, October 25, 1859, but no examples other than the patent model are known to have been made. (Smithsonian photo 45504-A.)] [Illustration: Figure 47.--THE SQUIRREL MACHINE was another interesting design patent. S. B. Ellithorp had received a mechanical patent for a two-thread, stationary-bobbin machine on August 26, 1857. That same month he published a picture of his machine, shown here as republished in the _Sewing Machine News_, vol. 7, no. 11, November 1885. The machine was designed in the shape of "the ordinary gray squirrel so common throughout this country--an animal that is selected as a type of provident care and forethought, for its habits of frugality and for making provision for seasons of scarcity and want in times of plenty--and the different parts of the animal are each put to a useful purpose; the moving power being placed within its body, the needle stock through its head, one of its fore feet serving to guide the thread, and the other to hold down the cloth while being sewed, and the tip of its tail forming a support to the spool from which the thread is supplied." Although the design patent was not secured until June 7, 1859, the inventor was reported to have been perfecting his machine for manufacture in 1857. Ellithorp planned "to place them in market at a price that will permit families and individuals that have heretofore been deterred from purchasing a machine by the excessive and exorbitant price charged for those now in use, to possess one." Patent rights were sold under the name of Ellithorp & Fox, but the machine was never manufactured on a large scale, if at all. No squirrel machines are known to have survived. (Smithsonian photo 53112.)] [Illustration: Figure 48.--HEYER'S POCKET SEWING MACHINE patent model, November 17, 1863. This patent model is one piece, and measures about two inches in height and two inches in length. It will stitch--but only coarse, loosely woven fabrics. As can be expected, a great deal of manual dexterity is required to compensate for the omission of mechanical parts. Heyer advertised patent rights for sale, but evidence of manufactured machines of this type has yet to be discovered. (Smithsonian photo 18115-D[a].)] [Illustration: Figure 49.--HEYER'S MACHINE as illustrated in _Scientific American_, July 30, 1864. The smallest and most original of all the attempts to simplify machine sewing, Heyer's machine, which made a chainstitch, was constructed of a single strip of metal. The _Scientific American_ stated: "It is simply a steel spring ingeniously bent and arranged and it is said to sew small articles very well. The whole affair can easily be carried in the coat pocket." One method of operation, vibrating with the finger, was illustrated. The machine could be operated also by holding it in the hand and pressuring it between two fingers. Cloth was inserted at _c_, and the prongs of the spring feed _f_ carried it along after each stitch. It was stated that the needle could be cut from the same strip of metal, but it was advised also that the needle could be made as a separate piece and attached. (Smithsonian photo 48221.)] [Illustration: Figure 50.--ALTHOUGH BEAN'S AND RODGERS' running-stitch machines, the second and fourth U.S. sewing-machine patents, experienced little commercial success, small manufactured machines based on Aaron Palmer's patent of May 13, 1862, were popular in the 1860s. The patent model above is a small brass implement with crimping gears that forced the fabric onto an ordinary sewing needle. The full needle was then removed from its position, and the thread was pulled through the fabric by hand. (Smithsonian photo 45524.)] [Illustration: THE FAIRY SEWING-MACHINE. A HOLIDAY GIFT FOR THE WORK-TABLE Figure 51.--ONE OF THE EARLY COMMERCIAL MANUFACTURERS of the Palmer patent was Madame Demorest, a New York dressmaker. She advertised her Fairy sewing machine in _Godey's Lady's Book_, vol. 66, 1863, and stated: "In the first place it will attract attention from its diminutive, fairy-like size, and with the same ease with which it can be carried, an important matter to a seamstress or dressmaker employed from house to house ... What no other sewing machine attempts to do, it runs, and does not stitch, it sews the more delicate materials an ordinary sewing machine cuts or draws...." (Smithsonian photo 43690.)] [Illustration: Figure 52.--THE FAIRY SEWING MACHINE sold for five dollars and was adequate for its advertised purpose, sewing or running very lightweight fabrics. The machine was marked with the Palmer patent, the date May 13, 1862, and the name "Mme. Demorest." A machine identical to the Fairy, but bearing both Palmer patent dates, May 13, 1862, and June 19, 1863, and the name "Gold Medal," was manufactured by a less-scrupulous company. This machine was advertised as follows: "A first class sewing machine, handsomely ornamented, with all working parts silver plated. Put up in a highly polished mahogany case, packed ready for shipment. Price $10.00. This machine uses a common sewing needle, is very simple. A child can operate it. Cash with order." Some buyers felt they were swindled, as they had expected a heavy-duty machine, but no recourse could be taken against the advertiser. Another similar machine was also manufactured under the name "Little Gem." (Smithsonian photo 45525.)] [Illustration: Figures 53 and 54.--RUNNING-STITCH MACHINES were also attempted by several other inventors. Shaw & Clark, manufacturers of chainstitch machines, patented this running-stitch machine on April 21, 1863. From the appearance of the patent model, it was already in commercial production. On May 26, 1863, John D. Dale also received a patent for an improvement related to the method of holding the needle and regulating the stitches in a running-stitch machine. Dale's patent model was a commercial machine. John Heberling patented several improvements in 1878 and 1880. His machine, which was a little larger and in appearance resembled a more conventional type of sewing machine, was a commercial success. (Shaw & Clark: Smithsonian photo P. 6395; Dale: Smithsonian photo P. 6394.)] FOOTNOTES: [67] _Scientific American_ (Jan. 29, 1859), vol. 14, no. 21, p. 165. In a description of the new Willcox and Gibbs sewing machine the following observation is made: "It is astonishing how, in a few years, the sewing machine has made such strides in popular favor, and become, from being a mechanical wonder, a household necessity and extensive object of manufacture. While the higher priced varieties have such a large sale, it is no wonder that the cheaper ones sell in such tremendous quantities, and that our inventors are always trying to produce something new and cheap." [68] Op. cit. (footnote 53), pp. 129-131. [69] _Scientific American_, vol. 15, no. 21 (January 29, 1859), p. 165, and Willcox and Gibbs advertising brochure, 1864. [70] _Scientific American_, vol. 12, no. 8 (November 1, 1856), p. 62. [71] Ibid., vol. 1, no. 19 (November 5, 1859), p. 303. [72] I. M. Singer & Co.'s Gazette, vol. 5, no. 4 (March 1, 1859), p. 4, and a brochure, _Singer's New Family Sewing Machine_ (in Singer Manufacturing Company, Historic Archives). _Appendixes_ I. Notes on the Development and Commercial Use of the Sewing Machine INTRODUCTION While researching the history of the invention and the development of the sewing machine, many items of related interest concerning the machine's economic value came to light. The manufacture of the machines was in itself a boost to the economy of the emerging "industrial United States," as was the production of attachments for specialized stitching and the need for new types of needles and thread. Moreover, the machine's ability to speed up production permitted it to permeate the entire field of products manufactured by any type of stitching, from umbrellas to tents. Since this aspect of the story was not completed for this study, no attempt will be made to include any definitive statements on the economic importance of the sewing machine at home or abroad. This related information is of sufficient interest, however, to warrant inclusion in this first Appendix. Perhaps these notes will suggest areas of future research for students of American technology. READY-MADE CLOTHING Whether of the expensive or the inexpensive type, the sewing machine was much more than a popular household appliance. Its introduction had far-reaching effects on many different types of manufacturing establishments as well as on the export trade. The newly developing ready-made clothing industry was not only in a state of development to welcome the new machine but also was, in all probability, responsible for its immediate practical application and success. Until the early part of the second quarter of the 19th century, the ready-made clothing trade in the United States was confined almost entirely to furnishing the clothing required by sailors about to ship out to sea. The stores that kept these supplies were usually in the neighborhood of wharf areas. But other than the needs of these seamen, there was little market for ready-made goods. Out of necessity many of the families in the early years in this country had made their own clothing. As wealth was acquired and taste could be cultivated, professional seamstresses and tailors were in increasing demand, moved into the cities and towns, and even visited the smaller villages for as long as their services were needed. At the same time a related trade was also growing in the cities, especially in New York City, that of dealing in second-hand clothing. Industrious persons bought up old clothes, cleaned, repaired and refinished them, and sold the clothing to immigrants and transients who wished to avoid the high cost of new custom-made clothing. The repairing of this second-hand clothing led to the purchase of cheap cloth at auction--"half-burnt," "wet-goods," and other damaged yardage. When in excess of the repairing needs, this fabric was made into garments and sold with the second-hand items. Many visitors who passed through New York City were found to be potential buyers of this merchandise if a better class of ready-made clothes was made available. Manufacture began to increase. Tailors of the city began to keep an assortment of finished garments on hand. When visitors bought these, they were also very likely to buy additional garments for resale at home. The latter led to the establishment of the wholesale garment-manufacturing industry in New York about 1834-35. Most of the ready-made clothing establishments were small operations, not large factories. Large quantities of cloth were purchased; cutting was done in multiple layers with tailor's shears. Since many seamstresses were needed, the garments were farmed out to the girls in their homes. The manufacture of garments in quantity meant that the profit on each garment was larger than a tailor could make on a single custom-made item. The appeal of increased profits influenced many to enter the new industry and, due to the ensuing competition, the retail cost of each garment was lowered. Just as the new businesses were getting underway, the Panic of 1837 ruined most of them. But the lower cost and the convenience of ready-made clothing had left its mark. Not only was the garment-manufacturing business re-established soon after the Panic had subsided, but by 1841 the value of clothing sold at wholesale in New York was estimated at $2,500,000 and by 1850--a year before sewing machines were manufactured in any quantity--there were 4,278 clothing manufacturing establishments in the United States. Beside New York City, Cincinnati was also one of the important ready-made clothing centers. In 1850 the value of its products amounted to $4,427,500 and in 1860 to $6,381,190. Boston was another important center with a ready-made clothing production of $4,567,749 in 1860. Philadelphia, Baltimore, Louisville, and St. Louis all had a large wholesale clothing trade by 1860. Here was the ready market for a practical sewing machine.[73] Clothing establishments grew and began to have agencies in small towns and the sewing work was distributed throughout the countryside. The new, competing sewing-machine companies were willing to deliver a machine for a small sum and to allow the buyer to pay a dollar or two a month until the full amount of the sale was paid. This was an extension of the hire-purchase plan (buying on credit) initiated by Clark of the Singer Company. The home seamstresses were eager to buy, for they were able to produce more piecework with a sewing machine and therefore earn more money. An example of the effect that the sewing machine had on the stitching time required was interestingly established through a series of experiments conducted by the Wheeler and Wilson company. Four hand sewers and four sewing-machine operators were used to provide the average figures in this comparative time study, the results of which were published in 1861;[74] NUMBER OF STITCHES PER MINUTE _By Hand_ _By Machine_ Patent leather, fine stitching 7 175 Binding hats 33 374 Stitching vamped shoes 10 210 Stitching fine linen 23 640 Stitching fine silk 30 550 TIME FOR GARMENTS STITCHED _By Hand_ _By Machine_ Frock coats 16 hrs. 35 min. 2 hrs. 38 min. Satin vests 7 hrs. 19 min. 1 hr. 14 min. Summer pants 2 hrs. 50 min. 0 hr. 38 min. Calico dress 6 hrs. 37 min. 0 hr. 57 min. Plain apron 1 hr. 26 min. 0 hr. 9 min. Gentlemen's shirts 14 hrs. 26 min. 1 hr. 16 min. The factory manufacturer, with the sewing work done at the factory, was also developing. In 1860, Oliver F. Winchester, a shirt manufacturer of New Haven, Connecticut, stated that his factory turned out 800 dozen shirts per week, using 400 sewing machines and operators to do the work of 2,000 hand sewers. The price for hand sewing was then $3 per week, which made labor costs $6000 per week. The 400 machine operators received $4 per week, making the labor cost $1600 per week. Allowing $150 as the cost of each machine, the sewing machines more than paid for themselves in less than 14 weeks, increased the operators pay by $1 a week, and lowered the retail cost of the item.[75] The greatest savings of time, which was as much as fifty percent, was in the manufacture of light goods--such items as shirts, aprons, and calico dresses. The Commissioner of Patents weighed the monetary effect that this or any invention had on the economy against the monetary gain received by the patentee. When he found that the patentee had not been fairly compensated, he had the authority to grant a seven-year extension to the patent.[76] The sewing machine also contributed to the popularity of certain fashions. Ready-made cloaks for women were a business of a few years' standing when the sewing machine was adopted for their manufacture in 1853. Machine sewing reduced the cost of constructing the garment by about eighty percent, thereby decreasing its price and increasing its popularity. In New York City alone, the value of the "cloak and mantilla" manufacture in 1860 was $618,400.[77] Crinolines and hoopskirts were easier to stitch by machine than by hand, and these items had a spirited period of popularity due to the introduction of the sewing machine. Braiding, pleating, and tucking adorned many costume items because they could be produced by machine with ease and rapidity. In addition to using the sewing machine for the manufacture of shirts, collars, and related men's furnishings, the machine was also used in the production of men's and boy's suits and reportedly gave "a vast impetus to the trade."[78] The Army, however, was not quite convinced of the sewing machine's practical adaptation to its needs. Although a sewing machine was purchased for the Philadelphia Quartermaster Depot as early as 1851, they had only six by 1860. On March 31, 1859, General Jesup of the Philadelphia Depot wrote to a Nechard & Company stating that the machine sewing had been tried but was not used for clothing, only for stitching caps and chevrons. In another letter, on the same day, to "Messers Hebrard & Co., Louisiana Steam Clothing Factory, N. Orleans," Jesup states: "Machine sewing has been tried with us, and though it meets the requirements of a populous and civilized life, it has been found not to answer for the hard wear and tear and limited means of our frontier service. Particular attention has been paid to this subject, and we have abandoned the use of machines for coats, jackets and trousers, etc. and use them on caps and bands that are not exposed to much hard usage...."[79] At this period prior to the Civil War, the Army manufactured its own clothing. As the demands of war increased, more and more of the Army's clothing supplies were furnished on open contract--with no specifications as to stitching.[80] Machine stitching, in fact, is found in most of the Civil War uniforms. One of the problems that most probably affected the durability of the machine stitching in the 1850s was the sewing thread, a problem that was not solved until the 1860s and which is discussed later under "thread for the machine." [Illustration: Figure 55.--BLAKE'S LEATHER-STITCHING MACHINE patent model of July 6, 1858; the inventor claimed the arrangement of the mechanism used and an auxiliary arm capable of entering the shoe, which enabled the outer sole to be stitched both to the inner sole and to the upper part of the shoe. (Smithsonian photo 50361.)] SHOE MANUFACTURE Another industry that was aided by the new invention was that of shoe manufacture. Although the earliest sewing-machine patents in the United States reflect the inventors' efforts to solve the difficult task of leather stitching, and, although machines were used to a limited extent in stitching some parts of the shoe in the early and mid-1850s, it was not until 1858 that a machine was invented that could stitch the sole to the inner sole and to the upper part of the shoe. This was the invention of Lyman R. Blake and was patented by him on July 8, 1858; the patent model is shown in figure 55. Blake formed a chainstitch by using a hooked needle, which descended from above, to draw a thread through the supporting arm. Serving as the machine's bedplate, the arm was shaped to accommodate the stitching of all the parts of the shoe. [Illustration: Figure 56.--HARRIS' patent thread cutter, 1872. (Smithsonian photo P-6397.)] [Illustration: Figure 57.--WEST'S patent thread cutter, 1874. (Smithsonian photo P-63100.)] [Illustration: Figure 58.--KARR'S patent needle threader, 1871. (Smithsonian photo P-63101.)] The increased number of shoes required by the Army during the Civil War spurred the use of the sewing machine in their manufacture. The first "machine sewed bootees" were purchased by the Army in 1861. Inventors continued their efforts; the most prominent of these was Gordon McKay, who worked on an improvement of the Blake machine with Robert Mathies in 1862 and then with Blake in 1864. Reportedly, the Government at first preferred the machine-stitched shoes as they lasted eight times longer than those stitched by hand; during the war the Army purchased 473,000 pairs, but in 1871 the Quartermaster General wrote: No complaints regarding the quality of these shoes were received up to February 1867 when a Board of Survey, which convened at Hart's Island, New York Harbor reported upon the inferior quality of certain machine sewed bootees of the McKay patent, issued to the enlisted men at that post. The acting Quartermaster General, Col. D. H. Rucker, April 10, 1867, addressed a letter to all the officers in charge of depots, with instructions not to issue any more of the shoes in question, but to report to this office the quantity remaining in store. From these reports it appears that there were in store at that time 362,012 pairs M. S. Bootees, all of which were ordered to be, and have since been sold at public auction.[81] The exact complaint against the shoes was not recorded. Possibly the entire shoe was stitched by machine. It was found that although machine-stitched shoes were more durable in some respects and the upper parts of most shoes continued to be machine stitched, pegged soles for the more durable varieties remained the fashion for a decade or more, as did custom hand-stitched shoes for those who could afford them. OTHER USES The use of sewing machines in all types of manufacturing that required stitching of any type continued to grow each year. While the principal purpose for which they were utilized continued to be the manufacture of clothing items, by the year 1900 they were also used for awnings, tents, and sails; cloth bags; bookbinding and related book manufacture; flags and banners; pocketbooks, trunks, and valises; saddlery and harnesses; mattresses; umbrellas; linen and rubber belting and hose; to the aggregate sum of nearly a billion dollars--$979,988,413.[82] SEWING-MACHINE ATTACHMENTS The growing popularity of the sewing machine offered still another boost to the economy--the development of many minor, related manufacturing industries. The repetitive need for machine needles, the development of various types of attachments to simplify the many sewing tasks, and the ever-increasing need for more and better sewing thread--the sewing machine consumed from two to five times as much thread as stitching by hand--created new manufacturing establishments and new jobs. [Illustration: Figure 59.--SHANK'S patent bobbin winder, 1870. (Smithsonian photo P-6398.)] [Illustration: Figure 60.--SWEET'S patent binder, 1853. (Smithsonian photo P-6396.)] [Illustration: Figure 61.--SPOUL'S patent braid guide, 1871. (Smithsonian photo P-63102.)] [Illustration: Figure 62.--ROSE'S patent embroiderer, 1881. (Smithsonian photo P-6399.)] [Illustration: Figure 63.--HARRIS' patent buttonhole attachment, 1882. (Smithsonian photo P-63103.)] The method of manufacturing machine needles did not differ appreciably from the method used in making the common sewing needle, but the latter had never become an important permanent industry in the United States. Since the manufacture of practical sewing machines was essentially an American development and the eye-pointed needle a vital component of the machine, it followed that the manufacture of needles would also develop here. Although such a manufacture was established in 1852,[83] foreign imports still supplied much of the need in the 1870s. As more highly specialized stitching machines were developed, an ever-increasing variety of needles was required, and the industry grew. [Illustration: Figure 64.--THE TREADLE OF THE MACHINE was also used to help create music. George D. Garvie and George Wood received patent 267,874, Nov. 21, 1882, for "a cover for a sewing machine provided with a musical instrument and means for transmitting motion from the shaft of the sewing machine to the operating parts of the musical instrument." Although no patent model was submitted by the inventors, the "Musical Sewing Machine Cover" was offered for sale as early as October 1882, as shown by this advertisement that appeared in _The Sewing Machine News_ that month. (Smithsonian photo 57983.)] Soon after the sewing machine was commercially successful, special attachments for it were invented and manufactured. These ranged from the simplest devices for cutting thread to complicated ones for making buttonholes (see figs. 56 through 66). [Illustration: Figure 65.--THIS FANNING ATTACHMENT was commercially available from James Morrison & Co. in the early 1870s; it sold for one dollar as stated in the advertising brochure from which this engraving was copied. Other inventors also patented similar implements. (Smithsonian photo 45513.)] The first patent for an attachment was issued in 1853 to Harry Sweet for a binder, used to stitch a special binding edge to the fabric. Other related attachments followed; among these were the hemmer which was similar to the binder, but turned the edge of the same piece of fabric to itself as the stitching was performed. Guides for stitching braid in any pattern, as directed by the movement of the goods below, were also developed; this was followed by the embroiderer, an elaborate form of braider. The first machine to stitch buttonholes was patented in 1854 and the first buttonhole attachment in 1856, but the latter was not practical until improvements were made in the late 1860s. Special devices for refilling the bobbins were invented and patented as early as 1862, and the popularity of tucked and ruffled garments inspired inventors to provide sewing-machine attachments for these purposes also. To keep the seamstress cool, C. D. Stewart patented an attachment for fanning the operator by an action derived from the treadle (fig. 65). While electric sewing machines did not become common until the 20th century, several 19th-century inventors considered the possibility of attaching a type of motor to the machine. One was the 1871 patent of Solomon Jones, who added an "electro motor" to an 1865 Bartlett machine (fig. 66). The attachments that were developed during the latter part of the 19th century numbered in the thousands; many of these were superfluous. Most of the basic ones in use today were developed by the 1880s and remain almost unchanged. Even the recently popular home zigzag machine, an outgrowth of the buttonhole machine, was in commercial use by the 1870s. [Illustration: Figure 66.--JONES "ELECTRO MOTOR" PATENT MODEL of 1871 on a Bartlett sewing machine. (Smithsonian photo P-63104.)] Sewing-machine improvements have been made from time to time. Like other mechanical items the machine has become increasingly automatic, but the basic principles remain the same. One of the more recent developments, patented[84] in 1933 by Valentine Naftali et al., is for a manufacturing machine that imitates hand stitching. This machine uses a two-pointed "floating needle" that is passed completely through the fabric--the very idea that was attempted over one hundred years ago. The machine is currently used by commercial manufacturers to produce decorative edge-stitching that very closely resembles hand stitching. THREAD FOR THE MACHINE [Illustration: Figure 67.--SIX-CORD cabled thread.] The need for a good thread durable enough to withstand the action of machine stitching first created a problem and ultimately another new industry in this country. When the sewing machine was first developed the inventors necessarily had to use the sewing thread that was available. But, although the contemporary thread was quite suitable for hand sewing, it did not lend itself to the requirements of the machine. Cotton thread, then more commonly a three-ply variety, had a glazed finish and was wiry. Silk thread frequently broke owing to abrasion at the needle eye. For the most part linen thread was too coarse, or the fine variety was too expensive. All of the thread had imperfections that went unnoticed in the hands of a seamstress, but caused havoc in a machine. Quality silk thread that would withstand the rigors of machine stitching could be produced, but it was quite expensive also. A new type of inexpensive thread was needed; the obvious answer lay in improving the cotton thread.[85] In addition to the popular three-ply variety, cotton thread was also made by twisting together either two single yarns or more than three yarns. Increasing the number of yarns produced a more cylindrical thread. The earliest record of a six-ply cotton thread was about 1840.[86] And in 1850 C. E. Bennett of Portsmouth, New Hampshire, received a gold medal for superior six-cord, or six-ply, spool cotton at the Fair of the American Institute. But the thread was still wiry and far from satisfactory. By the mid-1860s the demonstrated need for thread manufacturers in America brought George A. Clark and William Clark, third generation cotton-thread manufacturers of Paisley, Scotland, to Newark, New Jersey, where they built a large mill. George Clark decided that a thread having both a softer finish and a different construction was needed. He produced a six-cord cabled thread, made up of three two-ply yarns (see fig. 67). The thread was called "Clark's 'Our New Thread,'" which was later shortened to O.N.T. The basic machine-thread problem was solved. When other manufacturers used the six-cord cabled construction they referred to their thread as "Best Six-Cord"[87] or "Superior Six-Cord"[88] to distinguish it from the earlier variety made up of six single yarns in a simple twist. Another new side industry of the sewing machine was successfully established. MANUFACTURE AND EXPORT, TO 1900 Sewing machines were a commodity in themselves, both at home and abroad. In 1850, there were no establishments exclusively devoted to the manufacture of sewing machines, the few constructed were made in small machine shops. The industry, however, experienced a very rapid growth during the next ten years. By 1860 there were 74 factories in 12 States,[89] mainly in the East and Midwest,[90] producing over 111,000 sewing machines a year. In addition, there were 14 factories that produced sewing-machine cases and attachments. The yearly value of these products was approximately four and a half million dollars, of which the amount exported in 1861 was $61,000. Although the number of sewing-machine factories dropped from 74 in 1860 to 69 by 1870, the value of the machines produced increased to almost sixteen million dollars. The number of sewing-machine companies fluctuated greatly from year to year as many attempted to enter this new field of manufacture. Some were not able to make a commercial success of their products. The Civil War did not seem to be an important factor in the number of companies in business in the North. Although one manufacturer ceased operations in Richmond, Virginia, and a Vermont firm converted to arms manufacture, several companies began operations during the war years. Of the 69 firms in business in 1870, only part had been in business since 1860 or before; some were quite new as a result of the expiration of the Howe patent renewal in 1867. Probably due to the termination of many of the major patents, there were 124 factories in 1880, but the yearly product value remained at sixteen million dollars. The 1890 census reports only 66 factories with a yearly production of a little less than the earlier decade. But by 1900, the yearly production of a like number of factories had reached a value of over twenty-one million, of which four and a half million dollars worth were exported annually. The total value of American sewing machines exported from 1860 to 1900 was approximately ninety million dollars. The manufacture of sewing machines made a significant contribution to the economic development of 19th-century America. FOOTNOTES: [73] _Eighth Census, 1860, Manufactures, Clothing_ (United States Census Office, published Government Printing Office: Washington, D.C., 1865). [74] _Eighty Years of Progress of the United States_ (New York, 1861), vol. 2, pp. 413-429. [75] GEORGE GIFFORD, "Argument of [George] Gifford in Favor of the Howe Application for Extension of Patent" (New York: United States Patent Office, 1860). [76] Op. cit. (footnote 34). [77] _Eighth Census, 1860, Manufactures_ (United States Census Office, published Government Printing Office: Washington, D.C., 1865), "Women's Ready-Made Clothing," p. 83. [78] Ibid., p. 64. [79] National Archives, Record Group 92, Office of the Quartermaster General, Clothing Book, Letters Sent, volume 17. [80] The author wishes to acknowledge the valuable help of Mr. Donald Kloster of the Smithsonian Institution's Division of Military History for the preceding four references and related information. [81] Letter of Nov. 4, 1871, to Col. Theo. A. Dodge, USA (Ret.), Boston, from Quartermaster General M. C. Meigs, in the National Archives, Record Group 92, Quartermaster General's Office, Letters Sent, Clothing Supplies, 1871. [82] _Twelfth Census of the United States, 1900_, vol. 10, _Manufactures_, Part 4, Special Reports on Selected Industries (United States Census Office, Washington, D.C., 1902). [83] CHARLES M. KARCH, "Needles: Historical and Descriptive," in _Twelfth Census of the United States, 1900_, vol. 10, _Manufactures_, Part 4, Special Reports on Selected Industries (United States Census Office: Washington, D.C., 1902), pp. 429-432. [84] U.S. patent 1,931,447, issued to Valentine Naftali, Henry Naftali, and Rudolph Naftali, Oct. 17, 1933. The Naftali machines are manufactured by the American Machine and Foundry Company and are called AMF Stitching Machines. [85] See Appendix V, p. 135, "A Brief History of Cotton Thread." [86] _The Story of Cotton Thread_ (New York, The Spool Cotton Company, 1933). [87] J. and P. Coats spool cotton. [88] Willimantic spool cotton. [89] New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, Pennsylvania, Delaware, Ohio, Indiana, Illinois, Kentucky. _Eighth Census, 1860, Manufactures_ (United States Census Office, published by Government Printing Office: Washington, D.C., 1865.) [90] Sewing-machine manufacture in the South was just beginning to blossom when it was curtailed by the outbreak of the Civil War. See Lester sewing machine, figure 109 on page 102. II. American Sewing-Machine Companies of the 19th Century During the latter half of the 19th century, there was a total of two hundred or more sewing-machine companies in the United States. Although a great many manufacturing-type machines were sold, this business was carried on by relatively few companies and most were primarily concerned with the family-type machines. A representative number of these family machines together with information concerning both the company and serial-number dating are found in figures 68 through 132. A great many of the companies were licensed by the "Combination," but, in addition, some companies were constructing machines that did not infringe the patents, other companies infringed the patents but managed to avoid legal action, and there were numerous companies that mushroomed into existence after the "Combination" was dissolved in 1877. Most of the latter were very short-lived. It is difficult to establish the exact dates of some of these companies as many of their records were incomplete or have since disappeared; even a great many of the "Combination" records were lost by fire. A summary of the existing records kept by the "Combination" is given in figure 37. As will be noted in the subsequent listing, only a small percentage of the companies were in business for a period longer than ten years; of those that continued longer, all but a few had disappeared by 1910. Today there are about sixty United States sewing-machine companies. Most of them manufacture highly specialized sewing machines used for specific types of commercial work; only a few produce family or home-style machines. Foreign competition has increased, and the high cost of skilled labor in this country has made competition in this consumer-product field increasingly difficult. The countless varieties of American family sewing machines, so evident in the 19th century, have passed away. First Made Discontinued Manufacturer or Earliest or Last Sewing Machine or Company Record Record Aetna Aetna Sewing Machine ca. 1867 ca. 1877 Co., Lowell, Mass. Aiken and ----, Ithaca, N.Y. ca. 1855 before 1880 Felthousen Alsop ---- -- ca. 1880 American American Sewing 1854 -- Machine Co. American Buttonhole, American Buttonhole, 1869 ca. 1874 Overseaming and Overseaming and Sewing Machine Sewing Machine Co., (fig. 68) Philadelphia, Pa. Later New American Sewing ca. 1874 ca. 1886 American Machine Co., (fig. 69) Philadelphia, Pa. American Magnetic American Magnetic 1853 1854 (fig. 70) Sewing Machine Company, Ithaca, N.Y. Atlantic (fig. 71) ---- 1869 ca. 1870 Atwater (fig. 87) ---- 1857 ca. 1860 Avery Avery Sewing Machine 1852 185- Co., New York, N.Y. Avery Avery Manufacturing 1875 1886-1900 Co., New York, N.Y. A. Bartholf Manfr. A. Bartholf, ca. 1850 185- Blodgett & Lerow manufacturer, patent 1849 New York, N.Y. (_see also_) A. Bartholf Manfr. A. Bartholf, 1853 ca. 1856 Howe's patent, manufacturer, 1846 (fig. 72) New York, N.Y. Bartholf A. Bartholf, 1857 1859 manufacturer Bartholf Sewing 1859 ca. 1865 Machine Co. Bartlett (fig. 73) Goodspeed & Wyman 1866 ca. 1870 Bartlett Sewing Machine ca. 1870 1872 Co., New York, N.Y. Baker ---- -- before 1880 Bartram & Fanton Bartram & Fanton Mfg. 1867 1874 (fig. 74) Co., Danbury, Conn. Bay State ---- -- before 1880 Beckwith (fig. 75) Barlow & Son, New York, 1871 1872 N.Y. Beckwith Sewing Machine 1872 ca. 1876 Co., New York, N.Y. Blees Blees Sewing Machine 1870 1873 Co. Blodgett & Lerow O. Phelps, Boston, 1849 1849 (fig. 21) Mass. Goddard, Rice & Co., 1849 1850 Worcester, Mass. (fig. 20) A. Bartholf, 1849 185- manufacturer, New York, N.Y. Bond ---- -- before 1880 Boston J. F. Paul & Co., 1880 -- Boston, Mass. Later New Boston Boston Sewing Machine -- after 1886 Co., Boston, Mass. Boudoir (fig. 76) Daniel Harris, 1857 ca. 1870 inventor and patentee Manufacturer--several Bradford & Barber Bradford & Barber, 1860 1861 manufacturers, Boston, Mass. Brattleboro Samuel Barker and ca. 1858 1861 Thomas White, Brattleboro, Vt. Buckeye Wilson [W.G.] Sewing ca. 1867 ca. 1876 Later New Buckeye Machine Company, (fig. 77) Cleveland, Ohio (_see_ Wilson) Buell, "E. T. A. B. Buell, ca. 1860 -- Lathbury's Patent" Westmoreland, New York Burnet & Broderick Burnet, Broderick and 1859 ca. 1860 Co. Centennial Centennial Sewing 1873 1876 (fig. 78) Machine Co. (_see_ McLean and Hooper), Philadelphia, Pa. Chamberlain Woolridge, Keene and 1853 ca. 1854 Moore, Lynn, Mass. Chicago Singer Scates, Tryber & 1879 1882 Sweetland Mfg. Co., Chicago, Ill. Later Chicago Chicago Sewing Machine 1882 ca. 1885 Co. Chicopee (_see_ Shaw & Clark) Clark (fig. 42) D. W. Clark, ca. 1858 after 1860 Bridgeport, Conn. Clark's Revolving Lamson, Goodnow & Yale, 1859 1861 Looper [double Windsor, Vt. thread] (fig. 79) (_see_ Windsor) Clinton Clinton Brothers, ca. 1861 ca. 1865 Ithaca, N.Y. Companion Thurston Mfg. Co., 1882 -- Marlboro, N.H. Crown Florence Sewing Machine 1879 after 1886 (_see_ Florence) Co., Florence, Mass. Dauntless (later Dauntless Mfg. Co., 1877 after 1882 New Dauntless) Norwalk, Ohio Davis J.A. Davis, New York, ca. 1860 -- N.Y. Davis Vertical Davis Sewing Machine 1869 after 1886 Feed Co., Watertown, N.Y. Davis Vertical Davis Sewing Machine after 1886 1924 Feed and Co., Dayton, Ohio Rotary Shuttle Decker (_also_ The Decker Mfg. Co., -- before 1881 Princess) Detroit, Mich. Demorest Demorest Mfg. Co 1882 1908 (formerly N.Y. Sewing Machine Co.) Diamond (formerly Sigwalt Sewing Machine 1880 -- Sigwalt) Co., Chicago, Ill. Domestic Wm. A. Mack & Co. and 1864 1869 N. S. Perkins, Norwalk, Ohio Domestic Domestic Sewing Machine 1869 [A] Co., Norwalk, Ohio, acquired by White Sewing Machine Co. in 1924 and maintained as a subsidiary at Cleveland, Ohio. Dorcas John P. Bowker, Boston, 1853 185- Mass. Du Laney (fig. 80) Also called Little Monitor (_see_) Durgin Charles A. Durgin, New 1853 after 1855 York, N.Y. Eldredge Eldredge Sewing Machine 1869 1890 Co., Chicago, Ill. Elliptic Sloat's Elliptic George B. Sloat and Co., ca. 1858 ca. 1860 Philadelphia, Pa. Sloat's Elliptic Union Sewing Machine 1860 1861 Co., Richmond, Va. Elliptic Wheeler & Wilson Mfg. 1861 ca. 1867 Co. Elliptic Sewing 1867 before 1880 Machine Co., N.Y., N.Y. Empire (fig. 86) Empire Sewing Machine ca. 1860 1869 Later Co., Boston, Mass. Remington-Empire Empress Manufactured on order 1877 -- through Jerome B. Secor, Bridgeport, Conn. Estey Estey Sewing Machine ca. 1880 1882 Co. Estey, Brattleboro Sewing 1883 after 1886 Fuller-Model Machine Co., Brattleboro, Vt. Eureka (fig. 81) Eureka Shuttle Sewing 1859 -- New York, N.Y. Excelsior Excelsior Sewing Machine 1854 1854 Co., New York, N.Y. Fairy (figs. 51, 52) Madame Demorest, New 1863 ca. 1865 York, N.Y. Finkle, M. (fig. 82) M. Finkle, Boston, 1856 ca. 1859 Mass. Finkle & Lyon Finkle & Lyon Sewing ca. 1859 1867 Machine Co., Boston, Mass. Later Victor First and Frost First and Frost, New ca. 1859 ca. 1861 York, N.Y. Florence (fig. 83) Florence Sewing Machine ca. 1860 after 1878 Later Crown Co., Florence, Mass. Folsom Folsom, J. G., 1865 ca. 1871 (_see_ Globe and Winchendon, Mass. New England) Fosket and Savage Fosket and Savage, 1858 1859 Meriden, Conn. Foxboro Foxboro Rotary Shuttle ca. 1882 -- Co., Foxboro, Mass. Franklin Franklin Sewing Machine 1871 1871 Co., Mason Village, N.H. Free Free Sewing Machine 1898 [A] Co., Chicago and Rockford, Ill. Gardner C. R. Gardner, 1856 -- Detroit, Mich. Globe (figs. 84, 85) J. G. Folsom, 1865 1869 Winchendon, Mass. Gold Medal Gold Medal Sewing 1863 1876 (chainstitch) Machine Co., Orange, Mass. Gold Medal ---- 1863 ca. 1865 (running stitch) Gold Hibbard Hibbard, B. S., & Co. 1875 -- Goodbody (sewing Goodbody Sewing Machine 1880 ca. 1890 shears) Co., Bridgeport, Conn. Goodes Rex & Bockius, ca. 1876 before 1881 Philadelphia, Pa. Goodrich H. B. Goodrich, Chicago, ca. 1880 ca. 1895 Ill. Grant Brothers Grant Bros. & Co., 1867 ca. 1870 (fig. 90) Philadelphia, Pa. Greenman and True Greenman and True Mfg. 1859 1860 (fig. 91) Co. Norwich, Conn. Morse and True 1860 1861 Green Mountain ---- ca. 1860 -- Griswold Variety L. Griswold, New York, ca. 1886 ca. 1890 N.Y. Grover and Baker Grover and Baker Sewing 1851 1875 (figs. 34-36, 92) Machine Co., Boston, Mass. Hancock ---- 1868 before 1881 (figs. 93, 94) Heberling Running John Heberling 1878 ca. 1885 Stitch Herron's Patent ---- 1857 -- (fig. 95) Higby Higby Sewing Machine ca. 1882 after 1886 Later Acme Co., Brattleboro, Vt. Home Johnson, Clark & Co., 1869 after 1876 Home Shuttle Orange, Mass. Homestead ---- ca. 1881 -- Household Providence Tool Co., 1880 ca. 1884 Providence, R.I. Household Sewing ca. 1885 1906 Machine Co. Howe (figs. 96, 97) Howe Sewing Machine Co., 1853 1873 New York, N.Y. (company of A. B. Howe sold to Howe Machine Co.) Howe (fig. 98) Howe Machine Co., 1867 1886 Bridgeport, Conn. Howe's Improved Nichols and Bliss, 1852 1853 Patent (fig. 107) Boston, Mass. J. B. Nichols & Co. 1853 1854 which became Nichols, Leavitt & Co., 1854 1856 Leavitt Boston, Mass. N. Hunt, which N. Hunt & Co., Boston, 1853 1854 became Hunt and Mass. Webster (figs. 99, Hunt and Webster, 1854 1857 100) Boston, Mass. Later Ladd and Webster (_see_) Improved Common ---- ca. 1870 -- Sense (fig. 102) Independent Independent Sewing 1873 -- Noiseless Machine Co., Binghamton, N.Y. Jennie June June Mfg. Co., Chicago, 1881 1890 Ill. Later Belvidere, Ill. Jewel Jewel Mfg. Co., Toledo, 1884 after 1886 Ohio Johnson (fig. 103) Emery, Houghton & Co., 1856 after 1865 Boston, Mass. Keystone Keystone Sewing Machine before 1872 ca. 1874 Co. Ladd & Webster Ladd, Webster & Co., 1858 ca. 1866 (fig. 101) Boston, Mass. Ladies Companion ---- 1858 ca. 1858 (fig. 115) (_see_ Pratt's Patent) "Lady" (fig. 104) ---- 1859 -- Landfear's Patent Parkers, Snow, Brooks 1857 -- (fig. 105) & Co., West Meriden, Conn. Langdon L.W. Langdon 1856 -- Lathrop (fig. 106) Lathrop Combination 1873 -- Sewing Machine Co. Leader Leader Sewing Machine 1882 -- Co., Springfield, Mass. Leavitt (fig. 108) Nichols, Leavitt & Co., 1855 1857 Boston, Mass. Leavitt & Co. 1857 ca. 1865 Leavitt Sewing Machine ca. 1865 1870 Co. Leslie Revolving Leslie Sewing Machine 1881 -- Shuttle Co., Cleveland, Ohio Lester (fig. 109) J.H. Lester, Brooklyn, ca. 1858 early 1860 N.Y. Lester Mfg. Co., early 1860 late 1860 Richmond, Va. Union Sewing Machine late 1860 1861 Co., Richmond, Va. Little Gem ---- -- ca. 1870 Little Giant Domestic Sewing Machine ca. 1882 -- Co., Norwalk, Ohio Little Monitor (not G.L. Du Laney, Brooklyn, ca. 1866 after 1875 associated with N.Y. Monitor) Love Love Mfg. Co., 1885 after 1886 Pittsburgh, Pa. Lyon Lyon Sewing Machine Co. 1879 ca. 1880 Macauley Thos. A. Macauley Mfg., before 1879 -- New York, N.Y. Manhattan Manhattan Sewing Machine ca. 1868 ca. 1880 Co. McKay McKay Sewing Machine 1870 1876 Assoc. McLean and Hooper B. W. Lacy & Co., ca. 1869 ca. 1873 Philadelphia, Pa. (_see_ Centennial) Meyers J. M. Meyers 1859 -- Miller's Patent ---- 1853 -- Monitor (fig. 88) Shaw & Clark Sewing 1860 1864 Machine Co., Biddeford, Me. Moore Moore Sewing Machine ca. 1860 -- Co. Morey & Johnson Safford & Williams 1849 ca. 1851 (fig. 18) Makers, Boston, Mass. Morrison Morrison, Wilkinson & 1881 -- Co., Hartford, Conn. Mower ---- ca. 1863 -- National Johnson, Clark & Co., 1874 -- Orange, Mass. National (also sold National Sewing Machine 1890 1953 under distributor's Co. (consolidation of name) the June and Eldredge Companies), Belvidere, Ill. Ne Plus Ultra O. L. Reynolds 1857 -- (fig. 110) Manufacturing Co., Dover, N.H. Nettleton & Raymond Nettleton & Raymond, ca. 1857 -- (fig. 111) Brattleboro, Vt. New England Charles Raymond (also ca. 1859 1866 (figs. 112, 113) by: Grout & White, 1862 1863 Orange, Mass.; William 1863 -- Grout, Winchendon, 1865 1865 Mass.; and J. G. Folsom, Winchendon, Mass.) Newell ---- 1881 -- New Fairbanks J. H. Drew & Co. 1878 1880 Thomas M. Cochrane 1880 -- Co., Belleville, Ill. New Home New Home Sewing Machine 1876 [A] Co., Orange, Mass. (in 1928 became affiliated with Free Sewing Machine Co.) New York ----, New York, N.Y. ca. 1855 ca. 1855 New York Shuttle N.Y. Sewing Machine Co., before 1880 1882 New York, N.Y. (later Demorest Mfg. Co.) Noble Noble Sewing Machine before 1881 after 1886 Co., Erie, Pa. Novelty C. A. French, Boston, 1869 -- Mass. Old Dominion Old Dominion Sewing ca. 1858 1860 Machine Co., Richmond, Va. Pardox ---- ca. 1865 -- Parham Parham Sewing Machine ca. 1869 ca. 1871 Co., Philadelphia, Pa. Parker Charles Parker Co., before 1860 after 1865 Meriden, Conn. Later Parker Sewing Machine Co. Pearl ---- Bennett ca. 1859 -- Philadelphia Philadelphia Sewing ca. 1872 ca. 1881 Machine Co., Philadelphia, Pa. Post Combination Post Combination Sewing before 1885 after 1886 Machine Co., Washington, D.C. Pratt's Patent ---- 1857 ca. 1858 (fig. 114) Later Ladies Companion Queen Dauntless Mfg Co., ca. 1881 -- Norwalk, Ohio Quaker City Quaker City Sewing 1859 ca. 1861 (fig. 116) Machine Co., Philadelphia, Pa. Remington Empire Remington Empire Sewing 1870 1872 Later Remington Machine Co. E. Remington & Sons, 1873 ca. 1894 Philadelphia, Pa. Robertson (dolphin T. W. Robertson, New 1855 after 1860 & cherub) (figs. York, N.Y. 40, 41) Robinson F. R. Robinson, Boston, 1853 ca. 1855 Mass. Robinson's patent Howard & Davis, Boston, 1855 -- sewing machine Mass. with Roper's improvement (fig. 117) Later Robinson same 1856 before 1860 and Roper (fig. 118) Royal St. John Royal Sewing Machine ca. 1883 1898 (formerly St. John) Co., Springfield, Ohio (later Free Co.) Ruddick ---- ca. 1860 -- Secor Secor Machine Co., 1870 1876 Bridgeport, Conn. Sewing Shears Nettleton & Raymond, ca. 1859 -- (Hendrick's patent) Bristol, Conn. (fig. 43) Sewing Shears American Hand Sewing ca. 1884 ca. 1900 Machine Co., Bridgeport, Conn. Shaw & Clark Shaw & Clark Co., ca. 1857 1866 Running Stitch Biddeford, Me. Machine (fig. 53) Chainstitch Machine (fig. 119) Chainstitch Shaw & Clark Co., 1867 1868 Machine (fig. 120) Chicopee Falls, Mass. Chicopee Sewing Machine 1868 ca. 1869 Co., Chicopee Falls, Mass. Sigwalt Sigwalt Sewing Machine ca. 1879 -- Co., Chicago, Ill. Singer (figs. 28, I. M. Singer & Co. 1851 [A] 29, 30, 32, 33, (later Singer Mfg. Co.). 121, 122) Moved from Boston to New York to Elizabethport, N.J. (factory). Springfield Springfield Sewing 1880 -- Machine Co., Springfield, Mass. Standard ---- 1870 -- (chainstitch) (fig. 123) Standard Standard Shuttle Sewing 1874 ca. 1881 (shuttle) Machine Co., New York, N.Y. Standard Standard Sewing Machine 1884 ca. 1930 Co., Cleveland, Ohio (acquired by Singer Co.) Stewart Henry Stewart & Co., 1874 1880 N.Y., N.Y. Later New Stewart Mfg Co. 1880 ca. 1883 Stewart St. John (later St. John Sewing Machine 1870 ca. 1883 Royal St. John) Co., Springfield, O. Taggart & Farr Taggart & Farr, 1858 -- (figs. 124, 125) Philadelphia, Pa. Thompson C. F. Thompson Co. 1871 1871 T. C. Thompson, Ithaca, ca. 1854 -- N.Y. Union Johnson, Clark & Co., 1876 -- Orange, Mass. Victor Finkle & Lyon Mfg. Co. 1867 ca. 1872 Victor Sewing Machine ca. 1872 ca. 1890 Co., Middletown, Conn. Wardwell Wardwell Mfg. Co., St. ca. 1876 1890 Louis, Mo. Watson (fig. 126) Jones & Lee 1850 ca. 1853 Watson & Wooster, ca. 1853 ca. 1860 Bristol, Conn. Waterbury Waterbury Co., 1853 ca. 1860 Waterbury, Conn. Weed T. E. Weed & Co. (became 1854 -- Whitney & Lyons) Weed Weed Sewing Machine Co. 1865 -- (reorganized from Whitney & Lyons), Hartford, Conn. Family Favorite 1867 -- Manu. Favorite 1868 -- General Favorite 1872 -- Hartford 1881 ca. 1900 Wesson Farmer & Gardner 1879 1880 Manufacturing Co. D. B. Wesson Sewing 1880 -- Machine Co., Springfield, Mass. West & Willson West & Willson Co., 1858 -- (fig. 127) Elyria, Ohio A. B. Wilson E. E. Lee & Co., New 1851 1852 (fig. 23) York, N.Y. A. B. Wilson's Wheeler, Wilson, Co., late 1851 1856 patent seaming Watertown, N.Y. lathe Later Wheeler Wheeler & Wilson Mfg. 1856 1905 and Wilson Co., Bridgeport, Conn. (fig. 26, 27, Singer Co., Bridgeport, 1905 1907 128, 129) Conn. White (fig. 130) White Sewing Machine 1876 [A] Co., Cleveland, Ohio Whitehill Whitehill Mfg. Co., ca. 1875 after 1886 Milwaukee, Wis. Whitney Whitney Sewing Machine ca. 1872 ca. 1880 Co., Paterson, N.J. Whitney & Lyons Whitney & Lyons (a ca. 1859 ca. 1865 machine based on the 1854 patent of T. E. Weed) Wickersham Butterfield & Stevens 1853 -- Mfg. Co., Boston, Mass. Willcox & Gibbs Willcox & Gibbs Sewing 1857 [A] (figs. 39, 131) Machine Co., New York, N.Y. Williams & Orvis Williams & Orvis Sewing ca. 1859 after 1860 Machine Co., Boston, Mass. Wilson (fig. 89) Wilson (W.G.) Sewing ca.1867 after 1885 (_see_ Buckeye) Machine Co., Cleveland, Ohio Windsor (one thread) Vermont Arms Co., 1856 1858 Windsor, Vt. Windsor Lamson, Goodnow & Yale, 1859 1861 (_see_ Clark's Windsor, Vt. Revolving Looper) Name Unknown John W. Beane 1853 -- " Henry Brind 1860 -- " Garfield Sewing Machine 1881 -- Co. " Geneva Sewing Machine 1880 -- Co. " Gove & Howard 1855 -- " Charles W. Howland, ca. 1860 -- Wilmington, Del. " Miles Greenwood & Co., ca. 1861 -- Cincinnati, Ohio " Hood, Batelle & Co. 1854 1854 " Wells & Haynes 1854 1854 " Wilson H. Smith, ca. 1860 -- Birmingham, Conn. [A] Still in existence. [Illustration: Figure 68.--AMERICAN BUTTONHOLE, Overseaming & Sewing Machine of about 1870. Using serial numbers, these machines can be dated approximately as follows: 1-7792, 1869; 7793-22366, 1870; 22367-42488, 1871; 42489-61419, 1872; 61420-75602, 1873; 75603-89132, 1874; 89133-103539, 1875; and 103540-121477, 1876. Figures are not available for the years from 1877 to 1886. (Smithsonian photo 46953-E.)] [Illustration: Figure 69.--(NEW) AMERICAN SEWING MACHINE of about 1874. Illustration is from a contemporary advertising brochure. (Smithsonian photo 33507.)] [Illustration: Figure 70.--AMERICAN MAGNETIC SEWING MACHINE, 1854. Machines of this type were manufactured for only two years under the patent of Thomas C. Thompson, March 29, 1853, and later under the patents of Samuel J. Parker, April 11, 1854, and Simon Coon, May 9, 1854. On September 30, 1853, Elias Howe listed receipts of $1000 from the American Magnetic Sewing Machine Co. for patent infringement. The machines manufactured after that date carry the Howe name and 1846 patent date to show proper licensing. Judging by Howe's usual license fee of $25 per machine, about 40 machines were manufactured prior to September 1853. The company was reported to have made about 600 machines in 1854 before it went out of business. The only American Magnetic machine known to be in existence is in the collection of the Northern Indiana Historical Society at South Bend, Indiana. (_Photo courtesy of the Northern Indiana Historical Society._)] [Illustration: Figure 71.--ATLANTIC SEWING MACHINE, 1869. This machine is typical of the many varieties manufactured for a very short time in the 1860s and 1870s. It is about the size of the average hand-turned variety, 8 by 10 inches, but lighter in weight. The frame design was the patent of L. Porter, May 11, 1869, and the mechanism was patented by Alonzo Porter, February 8, 1870. The latter patent model bears the painted legend "Atlantic" and is stamped "Aprl 1, 69," indicating that it was probably already in commercial production. This date possibly may refer also to L. Porter's design patent, since actual date of issue was usually later than date of application. (Smithsonian photo 48329-A.)] [Illustration: Figure 72.--A. BARTHOLF SEWING MACHINE, 1853. Abraham Bartholf of New York began manufacturing Blodgett & Lerow machines (see fig. 20) about 1850; the style and mechanics of these machines, however, were primarily those of the Blodgett & Lerow patent as manufactured by O. C. Phelps and Goddard, Rice & Co. For this reason they are considered Blodgett & Lerow--not Bartholf--machines. The true Bartholf machine evolved when the manufacturer substituted Howe's reciprocating shuttle for the rotary shuttle of the Blodgett & Lerow machine, continuing to manufacture the machine in his own adapted style. Bartholf manufactured reciprocating-shuttle machines as early as 1853, and his was one of the first companies licensed by Howe. All Bartholf machines licensed under Howe's patent carry the Howe name and patent date. They are sometimes mistakenly referred to as Howe machines, but they are no more Howe machines than those manufactured by Wheeler & Wilson, Singer, or many others. On April 6, 1858, Bartholf was granted a patent for an improvement of the shuttle carrier. He continued to manufacture sewing machines under the name "Bartholf Sewing Machine Co." until about 1865. Using serial numbers, Bartholf machines can be dated approximately as follows: _Serial Number_ _Year_ 1-20 1850 21-50 1851 51-100 1852 101-235 1853 236-290 1854 291-321 1855 322-356 1856 357-387 1857 388-590 1858 591-1337 1859 No record of the number of machines produced by Bartholf after 1859 is available. The Bartholf machine illustrated bears the serial number 128 and the inscription "A. Bartholf Manfr., NY--Patented Sept. 1846 E. Howe, Jr." This machine is in the collection of the Baltimore County Historical Society. Note the close similarity between it and the 1850 Blodgett & Lerow machine manufactured by Bartholf. (_Photo courtesy of the Baltimore County Historical Society._)] [Illustration: Figure 73.--BARTLETT SEWING MACHINE, 1867. The Bartlett machine was first manufactured in 1866 under the January 31, 1865, and October 10, 1865, patents of Joseph W. Bartlett. The machines were made by Goodspeed & Wyman for the Bartlett Co. and were so marked. The inventor received another patent on April 7, 1868, and later machines carry this third date also. Although the first few hundred machines did not bear the dates of patents held by the "Combination," before the end of the first year of production Bartlett was paying royalties. He continued to manufacture sewing machines until the early seventies when he converted to the manufacturing of street lamps. Using serial numbers, Bartlett's machines can be dated approximately as follows: 1-1000, 1866; 1001-3126, 1867; 3127-?, 1868. There is no record of serial numbers for the succeeding years. (Smithsonian photo 45524-G.)] [Illustration: Figure 74.--BARTRAM & FANTON SEWING MACHINE, 1867. These machines were first manufactured in 1867 under the patents of W. B. Bartram, notably his patent of January 1, 1867. Three machines were exhibited at The Eleventh Exhibition of the Massachusetts Charitable Mechanics Association in 1869 where they were awarded a bronze medal. They were compared favorably to the Willcox & Gibbs machine (see fig. 39), which they resembled. Bartram received additional patents in the early seventies and also manufactured lockstitch machines. Using serial numbers, machines may be approximately dated as follows: 1-2958, 1867; 2959-3958, 1868; 3959-4958, 1869; 4959-5958, 1870; 5959-6962, 1871; 6963-7961, 1872; 7962-8961, 1873; and 8962-9211, 1874. (Smithsonian photo P63198.)] [Illustration: Figure 75.--BECKWITH SEWING MACHINE, 1871. Among the inventors whose patent claims were "to produce a cheap and effective sewing machine" was William G. Beckwith. His machine was first manufactured by Barlow & Son, and it realized considerable success in the few years of its production. The earliest model was operated like a pair of scissors or with a cord and ring as illustrated. Beckwith later added a hand crank. The machine was purchased in Crewe, Cheshire, England; it is stamped "Pat. April 18, 71 by Wm. G. Beckwith, Foreign Pats. Secured, Barlow & Son Manuf. N.Y., [serial number] 706." By 1874 the machines were marked "Beckwith S.M. Co." and two 1872 patent dates were added. Using serial numbers, machines may be dated approximately as follows: 1-3500, 1871; 3501-7500, 1872; 7501-12500, 1873; 12501-18000, 1874; 18001-23000, 1875; 23001-?, 1876. (Smithsonian photo 46953-C.)] [Illustration: Figure 76.--BOUDOIR SEWING MACHINE, 1858. This machine, a single-thread, chainstitch model was based on the patents of Daniel Harris, dated June 9, 1857, June 16, 1857, and October 5, 1858. Manufactured primarily by Bennett in Chicago in 1859, it also may have been produced in the East, although no manufacturer's name can be found. In 1860, the Boudoir, also called Harris's Patent sewing machine, was exhibited at the Massachusetts Charitable Mechanics Association Exhibition where it won a silver medal for "its combination of parts, its beauty and simplicity, together with its ease of operation." At this time the machine was described as making a "double lock stitch" (another name for the double chainstitch). It was also described as having been before the public for some time and combining "the improvements of others for which the parties pay license." The machine head was positioned on the stand similarly to that of the West & Willson (fig. 127) and stitched from left to right. It is not known exactly how many of these machines were made or how long they were in vogue. Manufacture, although probably ceasing in the 1860s, is known to have been discontinued before 1881, when a list of obsolete sewing machines was published in _The Sewing Machine News_. (Smithsonian photo P63199.)] [Illustration: Figure 77.--(NEW) BUCKEYE SEWING MACHINE of about 1875. The Buckeye machine was one of several manufactured by W. G. Wilson of Cleveland, Ohio. It was licensed under Johnson's extended patent of April 18, 1867. Although it was small and hand turned, it used two threads and a shuttle to form a lockstitch. The machine was sufficiently popular for Wilson to introduce an improved model in the early 1870s, which he called the New Buckeye. W. G. Wilson continued to manufacture sewing machines until about the mid-eighties, although the Buckeye machines were discontinued in the seventies. (Smithsonian photo 45524-A.)] [Illustration: Figure 78.--CENTENNIAL SEWING MACHINE, 1876. The Centennial machine was basically a McLean and Hooper sewing machine which was renamed to take advantage of the coming Centennial celebration. It was based on the patents of J. N. McLean, March 30, 1869, and August 2, 1870, and made a two-thread chainstitch. Only about five hundred Centennial machines were manufactured in 1873, but by 1876 over three thousand had been constructed. The machines were advertised on white circulars which were printed in red and blue, and engraved with two women sewing, one by hand, labeled "Sewing in 1776," and one at a Centennial sewing machine, labeled "Sewing in 1876." There is no record that the machines were made after 1876. (Smithsonian photo 48216-T.)] [Illustration: Figure 79.--CLARK'S Revolving-Looper double-thread sewing machine, 1860. This machine was manufactured by Lamson, Goodnow, & Yale of Windsor, Vermont. It was an attempt to improve on the combined ideas of the Grover and Baker machine, the Nettleton & Raymond machine, and the earlier single-thread Windsor machine. The improvements were made and patented by Edwin Clark on December 6, 1859. Widely advertised, the machines sold for $35 with a foot-power table. They could also be operated by hand. Over three thousand were manufactured and sold, and preparations were being made to continue manufacture of the earlier single-thread Windsor, originally made by the company's predecessor, Vermont Arms Co., when the Civil War broke out. A flood of arms orders arrived, and the sewing-machine manufacture was discontinued early in the summer of 1861. The sewing-machine equipment and business was sold to Grout & White of Massachusetts. (Smithsonian photo 48216.)] [Illustration: Figure 80.--DU LANEY SEWING MACHINE of about 1872. Most of the small, simple, chainstitch sewing machines of this period were constructed so that they could either be turned by hand or set into a treadle-powered table. Du Laney's Little Monitor, manufactured for only a few years, was based on the patents of G.L. Du Laney, July 3, 1866, and May 2, 1871. It was a two-thread, chainstitch machine powered only by a foot treadle. By simple adjustment, the machine could also make the cablestitch and the lockstitch. (Smithsonian photo 48221-C.)] [Illustration: Figure 81.--EUREKA SEWING MACHINE, 1859. An example of the many short-lived types of which no written record can be found, this particular machine was used as a patent model for certain minor improvements in 1859. It has the name "Eureka" painted on the top and the following inscription incised on the baster plate: "Eureka Shuttle S. M. Co. 469 Broadway, N.Y." Although it is a shuttle machine, it carries no patent dates and was not included in the Howe royalty records. Neither is it listed in the obsolescence list published in 1881. The company probably could not pay its royalty fees and was forced out of business almost immediately. If this machine had not been used as a patent model, no record of the company's existence might remain. It should be noted that as in most shuttle machines the head was meant to be set into a treadle-powered table. Since most tables are very similar, they are not required for identification. (Smithsonian photo 48328-C.)] [Illustration: Figure 82.--M. FINKLE SEWING MACHINE, 1857. The M. Finkle machines were manufactured in 1856 and 1857. Sometime before or about 1859, the inventor, Milton Finkle, formed a partnership and the machines were subsequently called M. Finkle & Lyon and later simply Finkle & Lyon. In 1859 the machine was awarded a silver medal by the American Institute for producing superior manufacturing and family lockstitch sewing machines. It also won a silver medal in Boston in 1860 at the Massachusetts Charitable Mechanics Association Exhibition. Although the name of the machine was changed to Victor in 1867, the company name remained Finkle & Lyon until about 1872 when it was changed to Victor also. Victor machines were manufactured until about 1890. Machines can be dated by their serial number approximately as follows: _Serial Number_ _Year_ 1-200 1856 201-450 1857 451-700 1858 701-950 1859 951-1500 1860 1501-3000 1861 3001-5000 1862 5001-7000 1863 7001-9000 1864 9001-11000 1865 11001-13000 1866 13001-15490 1867 15491-17490 1868 17491-18830 1869 18831-21250 1870 21251-28890 1871 28891-40790 1872 40791-48240 1873 48241-53530 1874 53531-59635 1875 59636-65385 1876 No estimates are available for the years 1877 to 1890. (Smithsonian photo 48216-A.)] [Illustration] <---- [Illustration: Figure 83.--FLORENCE SEWING MACHINE. The Florence machine was based on the patents of Leander W. Langdon, whose first patent was obtained in 1855. Langdon sewing machines were manufactured by the inventor for a few years. It was his patent of March 20, 1860, that was the immediate forerunner of the Florence machine, whose name was derived from the city of manufacture, Florence, Massachusetts. The Howe royalty records of 1860 listed the Florence Sewing Machine Co. as one that took out a license that year. Langdon's patent of July 14, 1863, was incorporated into the machines manufactured after that date; however, the date is always incorrectly stamped "July 18, 1863." In 1865, the machine won a silver medal at the Tenth Exhibition of the Massachusetts Charitable Mechanics Association. Over 100,000 Florence machines were manufactured by 1870. About 1880 the company changed the name of the machine to Crown. Improvements led to the name New Crown by 1885. About this time the right to use the name Florence for a sewing machine was purchased by a midwestern firm for an entirely different machine. In 1885 the Florence company began to manufacture lamp stoves and heating stoves and shortly thereafter they discontinued the manufacture of sewing machines. Using the serial numbers, Florence machines can be dated approximately as follows: _Serial Number_ _Year_ 1-500 1860 501-2000 1861 2001-8000 1862 8001-20000 1863 20001-35000 1864 35001-50000 1865 50001-60000 1866 60001-70534 1867 70535-82534 1868 82535-96195 1869 96196-113855 1870 113856-129802 1871 129803-145592 1872 145593-154555 1873 154556-160072 1874 160073-164964 1875 164965-167942 1876 No record of the number of machines produced each year between 1877 and 1885 is available. The machine shown here, serial number 49131, was manufactured in 1865. It is stamped with the following patent dates: "Oct. 30, 1855, Mar. 20, 1860, Jan. 22, 1861, and July 18, 1863" and the Wilson patent date "Nov. 12, 1850." The machines from 1860-1863 are marked with the early Langdon patents, excluding the 1863 one, and they have the additional patent dates of Howe and others: "Sept. 10, 1846, Nov. 12, 1850, Aug. 12, 1851, May 30, 1854, Dec. 19, 1854, Nov. 4, 1856." (Smithsonian photo 45572-A.)] [Illustration: Figure 84.--GLOBE SEWING MACHINE. J. G. Folsom received two design patents in 1864, one on March 1 for a spool holder and one on May 17 for the basic style of the machine. Also in the same year, he was awarded a mechanical patent for an adjustment in the lower looper that would accommodate a change in needle size. Using these patents, he manufactured a single-thread, chainstitch machine, the Globe. Folsom also exhibited his machines at the Tenth Exhibition of the Massachusetts Charitable Mechanics Association in 1865. The Globe attracted particular attention and was awarded a silver medal.] In 1866 Folsom devised a new treadle attachment for hand-operated machines; the invention was featured in _Scientific American_, volume 14, number 17, with a Globe machine. Folsom again exhibited at the Massachusetts Mechanics exhibition in 1869. In addition to an improved single-thread Globe, he also showed a double-thread, elastic-stitch (double chainstitch) machine for which he received a silver medal. Folsom machines were manufactured until 1871; 280 machines were manufactured in that year. The Globe sewing machine illustrated is stamped "J. G. Folsom, Maker, Winchendon, Mass. Patented April 28, 1863 [Ketchum's patent], Mar. 1, 1864. May 17, 1864." The machine was manufactured before November 1864 or it would include the patent for the lower loop adjustment. (Smithsonian photo 48216-H.) NOTE: At least five sewing machines, those in figures 84 through 89, are similar enough in appearance to cause some confusion, because their basic design stems from a short pillar. [Illustration: Figure 85.--GLOBE SEWING MACHINE with treadle attachment as illustrated in _Scientific American_, April 21, 1866. (Smithsonian photo 48221-A.)] [Illustration: Figure 86.--EMPIRE SEWING MACHINE, late 1860s. Although an Empire Sewing Machine Co. existed in New York in the 1860s (the predecessor of the Remington-Empire Co.), it is not known whether this machine was manufactured by that same company, which was primarily concerned with producing shuttle machines. This chainstitch machine is marked "Empire Co., Patented April 23, 1863," the date referring again to Ketchum's patent. It is very similar to Folsom's Globe, except that it has claw feet rather than a closed base; the painted designs on the base of both are almost identical to those on the Monitor. Its spool holder, mounted in reverse, is a crude imitation of the Folsom patent. The Empire machines were probably manufactured about the same time as the Wilson machine. (_Photo courtesy of The Henry Ford Museum and Greenfield Village, Dearborn, Michigan._)] [Illustration: Figure 87.--ATWATER SEWING MACHINE, 1858. Atwater machines, based on the patent of B. Atwater, issued May 5, 1857, were manufactured from 1857 to about 1860. The machine illustrated, which is designed to be operated by a hand-turned wheel, has an upper forked dog feed, and its horizontally supported spool is directly over the stitching area. Like the others, it has a striated pillar and claw feet. The manufacturer is unknown. (Smithsonian photo P63200.)] [Illustration: Figure 88.--MONITOR SEWING MACHINE, 1860-1866. The Monitor machines of this style were not marked by their manufacturers, Shaw & Clark of Biddeford, Maine. Later the company was forced by the "Combination" to pay a royalty, so it changed the style and began marking its machines with the company name and patent dates (see fig. 119 for copy of seal). The Monitor, which employed the conventional vertical spindle to hold the spool of thread, had a top feed in the form of a walking presser. Its striated pillar was similar to that of the Atwater machine, and both featured the same claw feet and urn-like top. Unlike the Atwater, however, the Monitor had a double drive from the hand-turned wheel, which was grooved for operation with belt and treadle. (Smithsonian photo 33458.)] [Illustration: Figure 89.--WILSON SEWING MACHINE, late 1860s to early 1870s. In addition to the Buckeye (see fig. 77), W. G. Wilson manufactured several other styles of sewing machines. This one, a combination of the varying styles of the earlier pillar machine has even duplicated the general style of the spool holder patented by Folsom. The pillar is not striated, but the machine does repeat the claw feet of the Atwater and Monitor machines. Wilson machines are usually marked "Wilson Sewing Mach. Manuf'g Co. Cleveland, Ohio, Ketchum's Patent April 28, 1863." The latter name and/or patent date are found on many of the machines of this general construction. The patent is that issued to Stephen C. Ketchum for his method of converting rotary motion into reciprocal motion. (_Photo courtesy of The Henry Ford Museum and Greenfield Village, Dearborn, Michigan._)] [Illustration: Figure 90.--GRANT BROTHERS SEWING MACHINE, 1867. This machine was one of several styles that utilized Raymond's 1861 patented chainstitch method. This machine, however, used an under feed rather than a top feed. Neither a name nor a date appears on the machine. In the June 25, 1907, issue of the _Sewing Machine Times_ it was called the Common Sense machine, but detailed research has turned up no evidence to substantiate this name. However, a dated brochure advertising the Grant Brothers machine and showing a model identical to that illustrated in the _Sewing Machine Times_ has been found. The brochure states that the machine made an elastic lockstitch; this was not a true lockstitch, however, but was in fact a simple chainstitch. Grant Brothers sold their machine, which had silver-plated mountings, for $18; the price included hemmer, Barnum's self-sewer, oilcan, screwdriver, clamp, gauge, and four silver needles. An additional charge of $12 was made for a table and treadle. Compared to other chainstitch machines the price was high, and the company was short-lived. (Smithsonian photo 60794-E.)] [Illustration: Figure 91.--GREENMAN AND TRUE SEWING MACHINE. This lockstitch machine based on S. H. Roper's patent of 1857 was manufactured at Norwich, Connecticut, from 1859 to 1861 by Cyrus B. True, the inventor, and Jared F. Greenman, True's financial partner. Licensed by the "Combination" and carrying the Howe patent date, the machine had obvious merit: it was strong, well made--a good family machine. Exhibited at the Ninth Exhibition of the Massachusetts Charitable Mechanics Association in September 1860, it received a bronze medal. (At this time the company was listed as Morse and True--the inventor had obviously taken on a second financial backer.) Unfortunately, the best market for the machine lay in the South, and the outbreak of the Civil War made collections impossible. This greatly retarded business and finally drove the firm into bankruptcy. In all, it is doubtful that more than one thousand machines were produced in the three years of manufacture. The machine illustrated is marked "Greenman and True" and bears the serial number 402; it was probably manufactured early in 1860. (Smithsonian photo 48216-N.)] [Illustration: Figure 92.--GROVER AND BAKER SEWING MACHINE. The Grover and Baker machine was one of the more popular machines from the 1850s until the early 1870s. The company produced iron-frame machines, fine cabinet models, and portables (figs. 35 and 36). Their machines may be dated by serial number approximately as follows: _Serial Number_ _Year_ 1-500 1851 501-1000 1852 1001-1658 1853 1659-3893 1854 3894-5038 1855 5039-7000 1856 7001-10681 1857 10682-15752 1858 15753-26033 1859 26034-44869 1860 44870-63705 1861 63706-82641 1862 82642-101477 1863 101478-120313 1864 120314-139148 1865 139149-157886 1866 157887-190886 1867 190887-225886 1868 225887-261004 1869 261005-338407 1870 338408-389246 1871 389247-441257 1872 441258-477437 1873 477438-497438 1874 497439-512439 1875 (Smithsonian photo 45513-B, an engraving of a Grover and Baker sewing machine from an advertising brochure of about 1870.)] [Illustration: Figure 93.--HANCOCK SEWING MACHINE, 1867. One of the many inventors who turned his talents to inventing and producing a mechanically simple and cheaper machine was Henry J. Hancock. His 1867 machine is only about six inches wide; it uses a tambour-type needle, pulling a loop of thread from below the stitching surface. (Smithsonian photo P63197.)] [Illustration: Figure 94.--HANCOCK SEWING MACHINE, 1868. Hancock in 1868 received both a design patent and a mechanical patent now using the eye-pointed needle and a hook to form the chainstitch. The design was an open framework circle with a mirror mounted in front of the table clamp. The purpose of the designated "looking glass" was decorative only. The Hancock machines were only manufactured for a few years. They measure 10-1/2 inches in width, slightly larger than the earlier machine. (Smithsonian photo 48328-M.)] [Illustration: Figure 95.--[A.C.] HERRON'S PATENT SEWING MACHINE, 1858. The manufacturer of this machine is not known, but the machine was based on the patent of Abial C. Herron issued August 4, 1857. All the machines carry a small heart-shaped plate just above the needle descent bearing the patentee's name and the patent date. The patent covered an improvement in the method of making the chainstitch. The machines were provided with a hand crank, but were also meant to be operated by a belt and treadle. No records of the extent of manufacture of this machine have been found. This machine head measures 14 inches in width, about standard size. (Smithsonian photo 48329-J.)] [Illustration: Figure 96.--A. B. HOWE SEWING MACHINE of about 1860. (Smithsonian photo 45525-C.)] Figures 96, 97, and 98.--THE HOWE MACHINES. It is difficult for many to believe that the stamped legend "Elias Howe patent, Sept. 10, 1846" does not certify that a machine is an original Howe. Although Elias Howe was granted a patent for the lockstitch machine in 1846, he did not establish a sewing-machine factory for about twenty years. Early in the 1850s and later through the "Combination," however, he licensed others to make machines using his patent. These machines bore that patent date for which a royalty was being paid. Among his early licensees was his elder brother Amasa who organized the Howe Sewing Machine Co. in 1854. The Amasa Howe machines were very good ones, and in 1862 Amasa won the prize medal at the London International Exhibition. This immensely increased the popularity of the machine and Elias offered to join Amasa by building a large factory at Bridgeport, Connecticut, to fill the increasing demand for more machines. The machines produced at Bridgeport, however, although imitating the Amasa Howe machines, proved inferior in quality. Amasa found that, rather than helping his business reputation, his brother's efforts were hurting him, and he severed business relations with Elias. Because of their brief association, the 1862 prize medal awarded to A. B. Howe was sometimes credited to Elias. The latter did receive awards for his patent, but never for his manufactured machines. When the two brothers dissolved their joint venture, Elias attempted to call his new company the Howe Sewing Machine Co., but Amasa's claim that this name had been his exclusive property for many years was upheld by the courts. Elias then omitted the word "Sewing" and called his company simply the Howe Machine Co. After Elias died in 1867, the company was run by his sons-in-law, the Stockwell brothers. To distinguish their machines from those of A. B. Howe, they marked each machine with a brass medallion picturing the head and flowing locks of Elias Howe. They also continued to advertise their machine as the "original" Howe. In about 1873, B. P. Howe, Amasa's son, sold the Howe Sewing Machine Co. to the Stockwell brothers, who continued to manufacture Howe machines until 1886. The machines of the A. B. Howe Sewing Machine Co. may be dated by serial number approximately as follows: _Serial Number_ _Year_ 1-60 1854 61-113 1855 114-166 1856 167-299 1857 300-478 1858 479-1399 1859 No figures are available for 1860-1870, but 20,051 machines were manufactured in 1871. The machines of the [Elias] Howe Machine Co. are not believed to have begun with serial number 1, and no figures are available for 1865-1867. After that, the machines may be dated by serial number approximately as follows: _Serial Number_ _Year_ 11,000-46,000 1868 46,001-91,843 1869 91,844-167,000 1870 167,001-301,010 1871 301,011-446,010 1872 446,011-536,010 1873 536,011-571,010 1874 571,011-596,010 1875 596,011-705,304 1876 No figures are available for 1877-1886. [Illustration: Figure 97.--ADVERTISING BROCHURE distributed by E. Howe during the brothers' brief partnership; the machines are basically A. B. Howe machines, 1863. (Smithsonian photo 49373-A.)] [Illustration: Figure 98.--HOWE (STOCKWELL BROTHERS) MACHINE, 1870. (Smithsonian photo 45572-E.)] [Illustration: Figure 99.--PATENT MODEL OF CHRISTOPHER HODGKINS, November 2, 1852, assigned to Nehemiah Hunt. (Smithsonian photo 34551.)] Figures 99, 100, and 101.--THE N. HUNT (later, in 1856, Hunt & Webster and finally in 1858 Ladd and Webster) sewing machine was based on the patents of Christopher Hodgkins, November 2, 1852, and May 9, 1854, both of which were assigned to Nehemiah Hunt. First manufactured in 1853, the machine, which closely resembled the Hodgkins' patent, won a silver medal at the exhibition of the Massachusetts Charitable Mechanics Association that same year. In 1856 Hunt took a partner, and the company became Hunt & Webster. An interesting account of this company appeared as a feature article in _Ballou's Pictorial_, July 5, 1856, where it was reported that "the North American Shoe Company have over fifty of the latest improved machines, represented in these drawings [fig. 31], now running...." The article also estimated that a 55-million dollar increase in shoe manufacturing in Massachusetts in 1855 was due to the sewing machine. In 1856 the Hunt & Webster machine again won a silver medal at the exhibition. Very late in 1858 the company became Ladd, Webster, & Co. and continued to manufacture both family and manufacturing sewing machines until the mid-1860s. The approximate date of manufacture can be determined by serial number: _Serial Number_ _Year_ 1-100 1853 101-368 1854 369-442 1855 443-622 1856 623-1075 1857 1076-1565 1858 1566-3353 1859 No figures are available for the 1860s. [Illustration: Figure 100.--RIGHT: HUNT & WEBSTER sewing machine of about 1855, serial number 414. (Smithsonian photo 48216-V.)] [Illustration: Figure 101.--LADD, WEBSTER & CO. sewing machine of about 1858, Boston, serial number 1497. (Smithsonian photo 46953.)] [Illustration: Figure 102.--IMPROVED COMMON SENSE sewing machine of about 1870. This machine is so very similar to the New England machines in its feed, threading, looping mechanism, and in its general design, that it is sometimes mistaken for the earlier New England machines (see figs. 112 and 113). Dating from the early 1870s, the Improved Common Sense machine is about 10 inches in width, two inches larger than the New England machine. The spool holder is similar to Folsom's patented design, but is less refined. A page from an advertising brochure of the period verifies the name of the machine, but does not identify the manufacturer. There are no patent dates or identifying names or numbers on the machine illustrated. Although the Empire Co. also produced a machine of this style, their models are marked with their name and with Ketchum's patent date, April 23, 1863. Of the several styles of machine using the Raymond looper, this type seems to account for the largest volume manufactured, as evidenced by the proportionately higher number of examples still extant. (Smithsonian photo 48328-E.)] [Illustration: Figure 103.--JOHNSON SEWING MACHINE, 1857. Another of the all-but-forgotten manufacturers of the 1850s was Emery, Houghton & Co., who constructed the A.F. Johnson machines. Examination of existing machines indicates that they were manufactured in 1856 and 1857, and possibly a little longer. This one from 1857 bears the serial number 624, so we know that several hundred were manufactured. The head is ornately attractive, slightly reminiscent of Wheeler & Wilson models, and of standard size. (Smithsonian photo 48329-B.)] [Illustration: Figure 104.--"LADY" SEWING MACHINE of about 1859. The contemporary name of this machine is unknown. The unusual design of the head, or main support, is based in part on the design patent, number 216, of Isaac F. Baker, issued April 10, 1849, for a "new and useful design[,] for ornamenting furniture[,] called Cora Munro" who was a character in James Fenimore Cooper's _Last of the Mohicans_. The design shows a female figure wearing a riding dress and hat that is ornamented with a plume and a bow. Her right hand holds a riding stick and the left, her skirt. Trunks of trees and foliage complete the Baker design, which is known to have been used for girandoles of the period. A companion design was also patented by Baker, number 215, which is in the form of a man in military costume and is named "Major Heyward," for another character in _Last of the Mohicans_. The sewing machines based on the "Cora Munro" design also use branch designs as the overhanging arms. A mother bird sits in the upper branch and descends to feed a young bird as the machine is in operation. The one illustrated was used as the machine submitted with a request for patent by George Hensel of New York City for which patent 24,737 was issued on July 12, 1859. Since Hensel's patent application was for an improvement in the feed, there was no need for the highly decorative head unless such a machine was commercially available. The patent specifications merely state that the head is "ornamented." Another sewing machine of this type was used as the patent model by Sidney Parker of Sing Sing, New York, number 24,780, issued on the same date as the Hensel patent. Parker's patent also covered an improved feeding mechanism. In the patent description, however, the inventor states that "the general form of the machine is not unlike others now in use." By this he might have meant in the design, or possibly in the basic structural form. Other than the two machines described, no other examples are known to have survived, but "Lady" or "Cora Munro" sewing machines were manufactured. (Smithsonian photo 45506-D.)] [Illustration: Figure 105.--LANDFEAR'S PATENT SEWING MACHINE of about 1857. Another of the many machines that, except for isolated examples, have almost completely disappeared from the records is Landfear's machine. Fortunately, this manufacturer marked his machine--where many did not--stamping it: "Landfear's patent-Dec^r 1856, No. 262, W. H. Johnson's Patent Feb. 26th 1856, Manfrd by Parkers, Snow, Brooks & Co., West Meriden, Conn." (There was a Parker sewing machine manufactured by the Charles Parker Co. of Meriden, but his machine was a double-thread chainstitch machine and was licensed by the "Combination." The Landfear machine may have been an earlier attempt by a predecessor or closely related company.) The Landfear patent was for a shuttle machine, but it also included a mode for regulating stitch length. The name chosen for this machine may be incorrect, since the single-thread chainstitch mechanism is primarily that of W. H. Johnson, but since the Johnson patent also was used on other machines the name "Landfear" was assigned. The machine was probably another attempt to evade royalty payment to the "Combination." The serial number 262 indicates that at least that many machines were manufactured, although this model is the only one known to be in existence. The support arm of the machine head is iron, cast as a vase of flowers and painted in natural colors. The paint on the head is original, but the table has been refinished, and the iron legs, which had rusted, have been repainted. (Smithsonian photo 48440-G.)] [Illustration: Figure 106.--LATHROP SEWING MACHINE of about 1873. These machines were manufactured by the Lathrop Combination Sewing Machine Co. under the patents of Lebbeus W. Lathrop of 1869, 1870, and 1873. The machine used two threads, both taken from spools; moreover, it produced not only the double chainstitch, but it was constructed to produce also a lockstitch and a combined "lock and chain stitch." The machine illustrated bears the serial number 31 and the patent dates of Grover & Baker, and Bachelder among others, in addition to the first two Lathrop patent dates. The company lasted only a few years as it is included in the 1881 list of manufacturers that had ceased to exist. (Smithsonian photo 46953-F.)] [Illustration: Figure 107.--ILLUSTRATION FROM A BROCHURE, marked in ink: "The National Portrait Gallery, 1855." Singer Archives. (Smithsonian photo 48091-E.)] Figures 107 and 108.--THE NICHOLS AND LEAVITT sewing machines. One of Elias Howe's earliest licensees was J. B. Nichols. His machine, manufactured at first with George Bliss and later alone as J. B. Nichols & Co., was called Howe's Improved Patent Sewing Machine. It was, however, no more a Howe machine than any of the others produced under the Howe patent. In July 1855 Nichols went into partnership with Rufus Leavitt, and the company name changed to Nichols, Leavitt & Co. In 1857 it was changed again to Leavitt & Co., and finally in the mid-1860s to Leavitt Sewing Machine Co. By the 1870s, it was defunct. The Nichols-Leavitt machines can be dated by their serial numbers approximately as follows: _Serial Number_ _Year_ _Company_ 1-28 1853 Nichols & Bliss 29-245 1854 J. B. Nichols & Co. 246-397 1855 J. B. Nichols & Co.--Nichols, Leavitt & Co. 398-632 1856 Nichols, Leavitt & Co. 633-827 1857 Leavitt & Co. 828-902 1858 " 903-1115 1859 " 1116-1436 1860 " 1437-1757 1861 " 1758-2077 1862 " 2078-2400 1863 " 2401-2900 1864 " 2901-3900 1865 Leavitt Sewing Machine Co. 3901-4900 1866 " 4901-5951 1867 " 5952-6951 1868 " 6952-7722 1869 " There is no record that the company was in existence after 1869. [Illustration: Figure 108.--LEAVITT SEWING MACHINE of about 1868, serial number 6907. (Smithsonian photo 48328.)] [Illustration: Figure 109.--LESTER SEWING MACHINE of about 1858. The Lester machine was first manufactured by J. H. Lester in Brooklyn, New York. His machine was based on the patents of William Johnson, John Bradshaw and others but not on the patents held by the "Combination," although he had secured a license. When the Old Dominion Company applied for a license from the "Combination," Lester learned of this, went to Richmond, and arranged to combine his business with theirs. Since the Lester machine was the better one, it was agreed to cease the manufacture of the Old Dominion machines early in 1860 and in March the company name was changed to the Lester Mfg. Co. Late in 1860, George Sloat entered the company with his Elliptic machine; the name was changed again, this time to Union Sewing Machine Co. The manufacture of both sewing machines continued until the outbreak of the Civil War the following year, which brought a conversion to arms production. The manufacture of Lester machines was never resumed. The machine illustrated was manufactured by J. H. Lester in Brooklyn; it bears the serial number 96. The number of Lester machines manufactured from 1858 through 1861 is not known, but it was probably less than 1,000. (Smithsonian photo P63359.)] [Illustration: Figure 110.--NE PLUS ULTRA of about 1867. Another of the interesting hand-turned chainstitch machines of the late 1850s and 1860s was patented by O.L. Reynolds. The baster plates and the handle on the wheel are missing on this machine, but an interesting shield and draped-flag pattern is painted on the base. Another machine of this type has the following inscription stamped on the baster plate: "Ne Plus Ultra, Patent Applied For, 174, O.L. Reynolds, Patentee & Manufacturer, Dover N.H." Reynold's patent model, March 30, 1858, bears the serial number 110, indicating that the machine illustrated here--which bears the serial number 26--was manufactured before the patent was obtained. (Smithsonian photo 48216-F.)] [Illustration: Figure 111.--NETTLETON & RAYMOND SEWING MACHINE. One of the most ornate of the early, small, hand-turned sewing machines was patented and manufactured by Willford H. Nettleton and Charles Raymond whose first patent was received on April 14, 1857. The patent model, believed to be a commercial machine, is beautifully silver-plated. Whether this was a special one-of-a-kind model, or whether the inventors tried to make a commercial success of a silver-plated machine is not known. The machine made a two-thread chainstitch, taking both threads from commercial spools. By October 1857, the inventors had received their second patent. This time the machine was brass and gilt--brighter, but less expensive. At the same time, Nettleton & Raymond began manufacturing sewing-shears machines under the patent of J. E. Hendricks. By the latter half of 1858, Nettleton & Raymond had moved from Bristol, Connecticut, to Brattleboro, Vermont. The patented improvement of the two-thread chainstitch machine received that year was in the name of "Raymond, assignor to Nettleton," although the machines of this type bear neither name nor patent date. No record of the price for which they were sold has been found, but it would be fair to estimate that it was probably about $25. This style of machine was discontinued when the manufacture of the simpler, more profitable New England model began, a machine that Raymond had initiated just before the partners left Bristol. (Smithsonian photo 45505-E.)] [Illustration: Figure 112.--RAYMOND PATENT MODEL, March 9, 1858. (Smithsonian photo 32009-O.)] [Illustration: Figure 113.--NEW ENGLAND sewing machine of about 1860, manufactured by Nettleton & Raymond; it bears the Raymond patent date of March 9, 1858. (Smithsonian photo 45505-G.)] [Illustration: Figures 112 and 113.--NEW ENGLAND SEWING MACHINES. The small, hand-turned, sewing machines some of which were called Common Sense, were manufactured by at least three companies and possibly more. The earliest ones were those made by Nettleton & Raymond based on Charles Raymond's patent of March 9, 1858, which featured a hinged presser foot acting as the top feed. On July 30, 1861, Raymond received a patent for an improved looper; this date is found on all machines later manufactured by the inventor. In 1858 Nettleton and Raymond had moved from Bristol, Connecticut, to Brattleboro, Vermont. Also in Brattleboro at this time were Thomas H. White and Samuel Barker, who were manufacturing a small machine called the Brattleboro. White left Vermont in 1862 and went to Massachusetts. There, in partnership with William Grout, he also began to manufacture New England machines; these were basically the same as the Raymond machines. After a short time, Grout left the partnership with White and moved to Winchendon, there continuing to make New England machines for approximately one more year. In 1865, J. G. Folsom of Winchendon exhibited a New England machine at the Tenth Exhibition of the Massachusetts Charitable Mechanics Association along with his Globe machine. Whether both machines were manufactured by him or whether he might have been exhibiting one of Grout's machines is not known. There is no record that New England machines were manufactured after 1865. There is a great similarity between these machines and the Improved Common Sense sewing machines of the 1870s. It is believed that the name "Common Sense" was given by frugal New Englanders to several of the cheaper chainstitch machines of the 1860s.] [Illustration: Figure 114.--PRATT'S SECOND PATENT MODEL, March 3, 1857, probably a commercial machine. (Smithsonian photo 48328-H.)] [Illustration: Figures 114 and 115.--PRATT'S PATENT and the Ladies Companion sewing machine. The machines manufactured under the patents of Samuel F. Pratt were first sold in 1857 and 1858 as Pratt's patent. These machines carry the Pratt name and the patent dates "Feb. 3, 1857 Mar. 3;" the latter is an 1857 patent date also. In 1859 the Pratt machine was called the Ladies Companion and was so marked. It was also marked with the 1857 patent dates, the date February 16, 1858, and a serial number, and was stamped "Boston, Mass." Manufacture was discontinued after a few years.] [Illustration: Figure 115.--LADIES COMPANION, 1859. (_Photo courtesy of The Henry Ford Museum and Greenfield Village, Dearborn, Michigan._)] [Illustration: Figure 116.--QUAKER CITY SEWING MACHINE. During the first decade of sewing-machine manufacture many types of handsome wooden cases were developed to house the mechanisms. Although such cases increased the total cost, they were greatly admired and were purchased whenever family funds permitted. The machine was based on the patents of William P. Uhlinger: a mechanical patent for a double chainstitch machine on August 17, 1858 (antedated May 8), and a patent for the casing on December 28, 1858. The machine head was lowered into the casing as the lid was brought forward and closed--an idea much ahead of its time. This Quaker City machine, serial number 18, was purchased by Benjamin F. Meadows of Lafayette, Alabama, for $150 just prior to the Civil War. Relatively few machines of this type were manufactured, and the Quaker City Sewing Machine Co. existed for only a few years. Its apparent hope for a southern market was short-lived, and it was unable to compete either with the companies licensed under the "Combination" or with those producing less expensive machines. (Smithsonian photo 46953-A.)] [Illustration: Figure 117.--FROM AN ADVERTISING BROCHURE, marked in ink, "The National Portrait Gallery, 1855," in the Singer Company's archives. The brochure states "Howard & Davis, 34 Water Street, Boston, Massachusetts Sole Manufacturers of Robinson's Patent Sewing Machine with Rope[r]'s Improvements." (Smithsonian photo 48091-F.)] [Illustration: Figure 118.--SEWING MACHINE OF ABOUT 1856 with inscription "Howard & Davis Makers, Boston, Mass. Robinson & Roper Pat. Dec. 10, 1850, Aug. 15, 1854"; the drive wheel and the circular stitching plate of this machine are missing. (Smithsonian photo 48440-C.)] [Illustration: Figures 117 and 118.--ROBINSON AND ROPER sewing machines, 1855-1856. This is one of the few machines producing a backstitch or half backstitch to realize any commercial success. Manufactured a very short time by Howard & Davis, it was a short-thread machine, based on the Frederick Robinson patent of December 10, 1850, and the Samuel Roper patent of August 15, 1854. Roper produced additional improvements for which he received a patent on November 4, 1856. In the _Scientific American_, November 1, 1856, the new machine was discussed: "Robinson & Roper exhibit their new improved sewing machines, which appear to operate with great success. Two needles are employed, the points of which are furnished with hooks that alternately catch the thread and form the stitch. The finest kind of cotton thread or silk can be used. The work appears well done. Price $100."] [Illustration: Figure 119.--ILLUSTRATED PAGE in a Shaw & Clark advertising brochure, published in late 1864. (Smithsonian photo 61321.)] [Illustration: Figure 120.--SHAW & CLARK SEWING MACHINE (Page patent) of 1867, Chicopee Falls, Massachusetts. (Smithsonian photo 48216-L.)] [Illustration: Figures 119 and 120.--SHAW & CLARK SEWING MACHINES. In addition to the early style Monitor sewing machine sold by Shaw & Clark without a name or any identifying marks, the company continued to manufacture machines after a lawsuit with the "Combination" forced them to take out a license. They manufactured an adapted version of their Monitor and an entirely new design patented in 1861. Their machines were now marked with the company name and a list of patent dates including those of Howe, Wheeler and Wilson, Grover and Baker, and Singer and the Batchelder patent, together with their own design patents. In 1867 the company moved from Biddeford, Maine, to Chicopee Falls, Massachusetts. In the same year, they began manufacturing a machine of the design patented by T. C. Page. The company is believed to have become the Chicopee Sewing Machine Company which appeared the following year and remained in business only a very short time. One Chicopee sewing machine is in the Smithsonian collection.] [Illustration: Figure 121.--SINGER "Traverse Shuttle Machine--Letter A." (Smithsonian photo 58984.)] Figures 121 and 122.--SINGER SEWING MACHINES. From 1850 to 1858 the Singer company produced heavy manufacturing-type sewing machines similar to the patent model shown earlier (fig. 28). The first machine for family use, Singer's new "Family" sewing machine (fig. 33) was manufactured from 1858-1861. Their second-style family machine was called the "Traverse Shuttle Machine--Letter A;" it was manufactured from 1859 to 1865, when they introduced their third family machine and called it the "New Family" sewing machine. This style machine continued until about 1883 when the "Improved Family" machine appeared. In addition to the lockstitch machines, Singer also manufactured chainstitch machines, and many highly specialized manufacturing machines. From 1857 through the 1880s, the Singer machines were marked with two serial numbers. It is possible that the numbers were related to the "Combination" royalties paid by the Singer company. Until about 1873 there was a difference of exactly 4,000 in the two numbers, thus one machine would be marked 12163 and directly below it would be marked 16163. From 1873 the last three digits of the two numbers continued to be the same but the lower number might be much lower in value than either number used in earlier years. The larger number is believed to have been a record of total production while the lower number may have referred to a machine of a particular style. The Singer company records can shed no light on the meaning of the top (or lower of the two) serial numbers. Generally, in the earlier machines, the difference in the two numbers will not affect the dating of a machine by more than one year. Since dating by serial number can only be estimated, the two numbers do not add an appreciable variable prior to 1873. Only the larger number, however, should be considered in dating machines after 1873. _Serial Number_ _Year_ 1-100 1850 101-900 1851 901-1711 1852 1712-2521 1853 2522-3400 1854 3401-4283 1855 4284-6847 1856 6848-10477 1857 10478-14071 1858 14072-25024 1859 25025-43000 1860 43001-61000 1861 61001-79396 1862 79397-99426 1863 99427-123058 1864 123059-149399 1865 149400-180360 1866 180361-223414 1867 223415-283044 1868 283045-369826 1869 369827-497660 1870 497661-678921 1871 678922-898680 1872 898681-1121125 1873 1121126-1362805 1874 1362806-1612658 1875 1612659-1874975 1876 Since records of annual production from 1877 to the turn of the century are not complete, it is difficult to establish yearly approximations. Using the machines submitted as patent models, and thus known to have been manufactured before the date of deposit, however, has provided us with the following date guides. By 1877 there had been 2 million machines manufactured, 3 million by 1880, 4 million by 1882, 5 million by 1884, 6 million by 1886, 7 million by 1888, 8 million by 1889, 9 million by 1890, and 10 million by 1891. [Illustration: Figure 122.--SINGER "New Family" sewing machine. (Smithsonian photo 58987.)] [Illustration: Figure 123.--STANDARD SEWING MACHINE of about 1870. This chainstitch machine is believed to have been made by the company that later became the Standard Shuttle Sewing Machine Company, when they began manufacturing lockstitch machines about 1874. This machine is marked with the name, "Standard," and with the dates "Patented July 14, 1870, Patented Jan. 22, 1856, Dec. 9, 1856, Dec. 12, 1865." The dates refer to the reissue and extended reissue of the Bachelder and the A. B. Wilson patents. The number of chainstitch machines of this type that were manufactured is not known. (Smithsonian photo 45506-C.)] [Illustration: Figure 124.--TAGGART & FARR sewing machine, front view. (Smithsonian photo 48216-P.)] Figures 124 and 125.--TAGGART & FARR sewing machine, 1860. The Taggart & Farr is an almost forgotten machine. It was based on Chester Farr's patent of August 9, 1859. The machine, however, was in commercial production as early as 1858, the year the patent application was made. Using two threads--both taken directly from the spool--to form a chainstitch, the machine was operated basically by treadle but also by hand. The drive wheel is missing on this machine, but it would normally appear on the right. The name and patent date were painted on the end of the machine. This was true of many other machines of this period, which is why so many go unidentified once the paint has become worn. Several thousand Taggart & Farr machines were manufactured, but the company is believed to have had a short life, for it was among those that had disappeared by 1881. [Illustration: Figure 125.--TAGGART & FARR sewing machine, end view. (Smithsonian photo 48216-M.)] [Illustration: Figure 126.--WATSON SEWING MACHINE, 1856, illustrated in Scientific American, December 13, 1856. The earliest Watson machines were two-thread lockstitch machines, as described in the _Scientific American_, August 10, 1850. Although the magazine reported that the inventor had applied for a patent, the earliest lockstitch patent issued to William C. Watson was on March 11, 1856. A few of his machines were made in 1850, the article continued, "several of these machines are nearly finished ... persons desirous of seeing them can be gratified by calling upon Messrs. Jones & Lee." A Watson machine was exhibited by Jones & Lee at the Sixth Exhibition of the Massachusetts Charitable Mechanics Association held in Boston in September 1850. In 1853 a Watson machine was exhibited at the New York Industry of All Nations Exhibition, but this was a single-looping machine; Watson received a patent for this single-thread machine on November 25, 1856. In the December 13, 1856, issue of _Scientific American_ a machine called Watson's "Family" sewing machine was illustrated and described. It was a small machine (only 8 by 5 inches) manufactured by Watson & Wooster and selling for $10. References to the Watson single-thread machine occur as late as 1860, but no examples are known to have survived. (Smithsonian photo 48221-B.)] [Illustration: Figure 127.--WEST & WILLSON SEWING MACHINE of about 1859. The West & Willson machine, manufactured under the patent of H. B. West and H. F. Willson, enjoyed a very brief span of popularity. The patent covered the peculiar method of operating a spring-looper in combination with an eye-pointed needle to form a single chainstitch, but whether machines of this single-thread variety were manufactured is unknown. The machine illustrated here is a two-thread machine of basically the same description. It stitches from left to right and bears serial number 1544 and the inscription "West & Willson Co. patented June 29, 1858." (Smithsonian photo 49456-A.)] [Illustration: Figure 128.--WHEELER & WILSON SEWING MACHINE of about 1872. Serial number 670974. (Smithsonian photo P63149-A.)] [Illustration: Figure 129.--WHEELER AND WILSON NO. 8 sewing machine of about 1876. (Smithsonian photo 17663-C.)] [Illustration: Figures 128 and 129.--Wheeler and Wilson sewing machines. The Wheeler and Wilson company was the largest manufacturer of sewing machines in the 1850s and the 1860s. It began in 1851 as A. B. Wilson; from 1852 to 1856 it was the Wheeler, Wilson & Co., Watertown, Connecticut; and from 1856 to 1876, it was Wheeler & Wilson Mfg. Co., Bridgeport, Connecticut. The style of the head changed very little during these years (see figs. 26 and 27). Both a table style with iron legs and a cabinet model were made: the head was usually mounted to stitch from left to right. In 1861, the company introduced the famous glass presser foot, patented on March 5 of that year by J. L. Hyde. The presser foot was made of metal but shaped like an open [?] into which was slid a small glass plate, with a hole for the needle descent. The glass allowed the seamstress to observe the stitching and to produce very close-edge stitching. It remained a favorite of many women for years. In 1876, the new No. 8 machine was introduced and a new series of serial numbers was initiated. It is, therefore, imperative to know that the machine is one of the earlier style machines before using the following list of serial numbers to date the machines, approximately as follows: _Serial Number_ _Year_ 1-200 1851 201-650 1852 651-1449 1853 1450-2205 1854 2206-3376 1855 3377-5586 1856 5587-10177 1857 10178-18155 1858 18156-39461 1859 39462-64563 1860 64564-83119 1861 83120-111321 1862 111322-141099 1863 141100-181161 1864 181161-220318 1865 220319-270450 1866 270451-308505 1867 308506-357856 1868 357857-436722 1869 436723-519930 1870 519931-648456 1871 648457-822545 1872 822546-941735 1873 941736-1034563 1874 1034564-1318303 1875 1138304-1247300 1876 Records of the second series of serial numbers dating from 1876 are not available.] [Illustration: Figure 130.--WHITE SEWING MACHINE. Although the White sewing machines date from 1876, Thomas H. White had been busy in the manufacture of sewing machines for many years prior to this. White is known to have been associated with Barker in the manufacture of the Brattleboro machine and later with Grout in producing one of the several New England machines. In 1866 he moved to Cleveland, Ohio, and began manufacturing machines for sale under special trade names through selling organizations. In 1876, the White Sewing Machine Company was formed and machines were sold under the White name. The machine illustrated is a standard lockstitch machine, which would have been set into a sewing-machine table and operated by a treadle. The small handle was used to start the wheel, and thus the stitching operation, in the forward direction. This machine bears the serial number 28241 and the following patents: "Mar. 14, 1876, May 2, 1876, Oct. 24, 1876, Jan. 16, 1877, Mar. 20, 1877, Mar. 27, 1877," which are primarily the patents of D'Arcy Porter and George W. Baker. The machines of the 1870s may be dated approximately as follows: _Serial Number_ _Year_ 1-9000 1876 9000-27000 1877 27001-45000 1878 45001-63000 1879 (Smithsonian photo 48329-H.)] [Illustration: Figure 131.--WILLCOX AND GIBBS SEWING MACHINE, serial number 296572, of about 1878. From 1857 to the turn of the century, the style of the Willcox and Gibbs sewing machine changed very little (fig. 39). It was the most popular and the most reliable of the many chainstitch machines. In addition to the basic mechanical patents, Gibbs also patented the design of the sewing-machine head in 1860. In the specifications, he described it as an open ring set on a base or pedestal. The lower part of the open section supported the cloth plate. The design of the head, intentionally or not, formed a perfect letter G, the initial of the inventor. Later the machine head as a letter G was incorporated into the company's trademark. Additional patents were also granted to James Willcox for a leg and treadle design and to Charles Willcox for mechanical improvements. It has not been possible to secure information on records of serial numbers from the late 1870s through the 1920s to aid in dating machines of that period. For the preceding years, however, the machines may be dated approximately as follows: _Serial Number_ _Year_ 1-10000 1857 10001-20000 1858 20001-30000 1859 30001-40000 1860 40001-50000 1861 50001-60000 1862 60001-70000 1863 70001-80000 1864 80001-90000 1865 90001-100000 1866 100001-115000 1867 115001-130000 1868 130001-145000 1869 145001-160000 1870 160001-190127 1871 190128-223766 1872 223767-239647 1873 239648-253357 1874 253358-267879 1875 267880-279637 1876 Although the Willcox and Gibbs company is still in existence, for the past several decades the company has limited itself to the production of specialized manufacturing machines rather than family machines. (Smithsonian photo 58986.)] [Illustration] <---- [Illustration: Figure 132.--ILLUSTRATION from _Knights American Mechanical Dictionary_, vol. 3, p. 2122. The 68 sewing-machine stitches in use by 1882 are as follows: SINGLE THREAD 1. Running stitch. 2. Back stitch. 3. Fast stitch. 4. Chainstitch. 5. Coiled-loop chainstitch. 6. Knitted-loop chainstitch. 7. Knotted-loop chainstitch. 8. Loop enchained by second alternate stitch. 9. Each loop locks and enchains alternate loops. 10. Staple stitch (for waxed threads only). TWO THREADS 11. Double-needle chainstitch. 12. Double-thread chainstitch (one needle). 13. Double-looped chainstitch. 14. Chain with interlocking thread. 15. Under-thread through its own loop. 16. Two needles penetrate fabric from opposite sides. 17. Two needles working from the same side. 18. Double interlocking loop. 19. Lockstitch. 20. Twist in needle thread. 21. Double twist in needle thread. 22. Twist in shuttle thread. 23. Double twist in shuttle thread. 24. Knot stitch, shuttle thread knotted at every stitch. 25. Knot stitch, shuttle thread knotted at every other stitch. 26. Knot stitch, shuttle thread through the needle thread loop and knotted around the loop. 27. Shuttle thread pulled to the surface and interlocked with succeeding stitch to form an embroidery stitch. 28. Wire-lock stitch, thread locked in place with wire. THREE THREADS 29. Two shuttles, each locking alternate loops. 30. Double loop with interlocking third thread. 31. Two shuttle threads, both locking each loop. 32. Two shuttle threads intertwining and locking each loop. 33. Single thread; loop of needle thread drawn up over the edge and locked by needle at its next descent. 34. Two threads; loops of needle thread, above and below, extend to the edge of the fabric, and are locked by shuttle thread. 35. Two threads; needle penetrates back from edge, its loop passed to and interlocked by the needle at its next descent over the edge, and this second needle-loop locked by shuttle thread. 36. Two threads; shuttle thread drawn up over the edge of the fabric to the line of the needle thread. 37. Two threads; needle loop through the fabric locked by needle loop over the edge and second loop locked by second thread. 38. Two threads; edge of fabric covered by shuttle thread. 39. Three threads; third thread laid around the stitch at the edge of the fabric. ORNAMENTAL STITCHES 40. Zigzag; single thread chainstitch (4). 41. Zigzag; two-thread lockstitch (19). 42. Zigzag; two-thread chainstitch (13). 43. Zigzag; chain stitch with interlocking thread (14). 44. Zigzag; double loop with interlocking third thread (30). 45. Zigzag; running stitch (1). 46. Zigzag; two needles and shuttle. 47. Zigzag; variation of 46. 48-52. Zigzag stitches for sewing straw braid. 53-62. Straight straw-braid stitches. 63-67. Special embroidery stitches. 68. Saddler's stitch.] * * * * * In the _Sewing Machine News_, vol. 3, no. 5, p. 12 (1881), there were listed a number of then "defunct" machines and companies. Among these are many well-known names and little-known names for which at least one additional reference can be found. There are some, however, for which this is the only reference to date. These are: Blanchard, Babcock, Banner, Brown Rotary, Cottage, Cole, Duplex, Economist, Erie, Gutman, Hill, Hancock & Bennett, Jenks, Lockmar, La Favorite, Learned, Leggett, McCoy, McCardy, Medallion, McArthur & Co., Monopoly, Moreau, Mack, Niagra, New Cannaan, Orphean, Pride-of-the-West, Seamen & Guiness, Surprise, Stackpole, Shanks, Stanford, Troy, Utica, United States Family, Weaver, Wagner, and Williams. Some of these names may have been a "special" name given to machines manufactured by one of the known companies, but at least a few are names of machines manufactured for a very short time prior to 1881 about which we would like to know more. III. Chronological List of U.S. Sewing-Machine Patent Models in the Smithsonian Collections There are more than seven hundred sewing-machine patent models and a similar number of attachment models in the Smithsonian collections. Most of these machines were received in 1926 when the Patent Office disposed of its collection of hundreds of thousands of models. Prior to 1880, models had been required with the patent application; although the requirement was discontinued that year, patentees continued to furnish models for another decade or so. All models prior to 1836 were lost in a Patent Office fire of that year, but since the sewing-machine patent history dates from the 1840s, most of the historically important ones of this subject have been preserved. These models form a valuable part of the record of the invention, supplementing the drawings and the text of the written specifications. The early sewing-machine models were made to order, either by the inventor or a commissioned model maker. As soon as sewing machines were produced commercially, it was less expensive for the patentee to use a commercial machine of the period, to which he added his change or improvement, than to have a complete model constructed to order. Some of the commercial machines used in this way are the only examples known to be in existence, and as such, are of more interest in establishing the history of the manufactured machine than for the minor patented changes. During the period of the "Sewing Machine Combination," many patentees attempted to invent and patent "the different machine." This was either a radical change in style or an attempt to produce a far less-expensive type of machine. These machines were not always put into commercial production, but the patent models give an indication of the extent to which some inventors went to simplify or vary the mechanics of machine sewing. The following is a list of those sewing-machine patent models in the Smithsonian Institution collections: _Patentee_ |_Date_ |_Patent Number_ | | Greenough, John J. |Feb. 21, 1842 |2,466 Bean, Benjamin W. |March 4, 1843 |2,982 Corliss, George H. |Dec. 27, 1843 |3,389 Howe, Elias, Jr. |Sept. 10, 1846 |4,750 Bachelder, John |May 8, 1849 |6,439 Wilson, Allen B. |Nov. 12, 1850 |7,776 Robinson, Frederick R. |Dec. 10, 1850 |7,824 Grover & Baker |Feb. 11, 1851 |7,931 Singer, Isaac M. |Aug. 12, 1851 |8,294 Wilson, Allen B. |Aug. 12, 1851 |8,296 Wilson, Allen B. |June 15, 1852 |9,041 Miller, Charles |July 20, 1852 |9,139 Avery, Otis |Oct. 19, 1852 |9,338 Hodgkins, G. |Nov. 2, 1852 |9,365 Bradeen, J. G. |Nov. 2, 1852 |9,380 Bates, W. G. |Feb. 22, 1853 |9,592 Thompson, T. C. |March 29, 1853 |9,641 Wickersham, W. |April 19, 1853 |9,679 Johnson, W. H. |March 7, 1854 |10,597 Harrison, J., Jr. |April 11, 1854 |10,763 Avery, Otis |May 9, 1854 |10,880 Singer, Isaac |May 30, 1854 |10,975 Hunt, Walter |June 27, 1854 |11,161 Roper, S. H. |Aug. 15, 1854 |11,531 Shaw, P. |Sept. 12, 1854 |11,680 Ambler, D. C. |Nov. 1, 1854 |11,884 Robertson, T. J. W. |Nov. 28, 1854 |12,015 Lyon, W. |Dec. 12, 1854 |12,066 Stedman, G. W. |Dec. 12, 1854 |12,074 Ward, D. T. |Jan. 2, 1855 |12,146 Conant, J. S. |Jan. 16, 1855 |12,233 Smith, H. B. |Jan. 16, 1855 |12,247 Singer, I. M. |Feb. 6, 1855 |12,364 Stedman, G. W. |March 20, 1855 |12,573 Stedman, G. W. |May 1, 1855 |12,798 Chilcott, J., and Scrimgeour, J. |March 15, 1855 |12,856 Durgin, Charles A. |May 22, 1855 |12,902 Bond, J., Jr. |May 22, 1855 |12,939 Singer, Isaac |June 12, 1855 |13,065 Harrison, J., Jr. |Oct. 2, 1855 |13,616 Singer, I. M. |Oct. 9, 1855 |13,661 Singer, I. M. |Oct. 9, 1855 |13,662 Langdon, L. W. |Oct. 30, 1855 |13,727 Stedman, G. W. |Nov. 27, 1855 |13,856 Swingle, A. |Feb. 5, 1856 |14,207 Watson, Wm. C. |March 11, 1856 |14,433 Singer, I. M. |March 18, 1856 |14,475 Grover, W. O. |May 27, 1856 |14,956 Blodgett, S. C. |Aug. 5, 1856 |15,469 Roper, S. H. |Nov. 4, 1856 |16,026 Singer, Isaac M. |Nov. 4, 1856 |16,030 Gibbs, James E. A. |Dec. 16, 1856 |16,234 Jennings, L. |Dec. 16, 1856 |16,237 Johnson, A. F. |Jan. 13, 1857 |16,387 Gibbs, J. E. A. |Jan. 20, 1857 |16,434 Howe, Elias, Jr. |Jan. 20, 1857 |16,436 Alexander, Elisa |Feb. 3, 1857 |16,518 Gray, Joshua |Feb. 3, 1857 |16,566 Belcher, C. D. |March 3, 1857 |16,710 Pratt, S. F. |March 3, 1857 |16,745 Nettleton & Raymond |April 14, 1857 |17,049 Gibbs, J. E. A. |June 2, 1857 |17,427 Harris, Daniel |June 9, 1857 |17,508 Harris, Daniel |June 16, 1857 |17,571 Sage, William |June 30, 1857 |17,717 Lathbury, E. T. |July 7, 1857 |17,744 Wickersham, W. |Aug. 25, 1857 |18,068 Wickersham, W. |Aug. 25, 1857 |18,069 Behn, Henry |Aug. 25, 1857 |18,071 Nettleton, Wm. H., and |Oct. 6, 1857 |18,350 Raymond, Charles | | Roper, S. H. |Oct. 27, 1857 |18,522 Fetter, George |Dec. 1, 1857 |18,793 Watson, W. C. |Dec. 8, 1857 |18,834 Behn, H. |Dec. 15, 1857 |18,880 Hubbard, George W. |Dec. 22, 1857 |18,904 Lazelle, W. H. |Dec. 22, 1857 |18,915 Clark, David W. |Jan. 5, 1858 |19,015 Fetter, George |Jan. 5, 1858 |19,059 Clark, David W. |Jan. 12, 1858 |19,072 Clark, David W. |Jan. 19, 1858 |19,129 Dimmock, Martial, and |Jan. 19, 1858 |19,135 Rixford, Nathan | | Boyd, A. H. |Jan. 19, 1858 |19,171 Angell, Benjamin J. |Feb. 9, 1858 |19,285 Clark, David W. |Feb. 23, 1858 |19,409 Raymond, Charles |March 9, 1858 |19,612 Hendrick, Joseph E. |March 16, 1858 |19,660 Parker, Sidney |March 16, 1858 |19,662 Gray, Joshua |March 16, 1858 |19,665 Coates, F. S. |March 23, 1858 |19,684 Clark, David W. |March 23, 1858 |19,732 Reynolds, O. S. |March 30, 1858 |19,793 Bartholf, Abraham |April 6, 1858 |19,823 Savage, E. |April 6, 1858 |19,876 Atwood, J. E., J. C., and O. |April 13, 1858 |19,903 Bosworth, Chas. F. |April 20, 1858 |19,979 Clark, David W. |June 8, 1858 |20,481 Herron, A. C. |June 15, 1858 |20,557 Johnson, A. F. |June 22, 1858 |20,686 Barnes, W. T. |June 29, 1858 |20,688 Smith, E. H. |June 29, 1858 |20,739 West, H. B., and |June 29, 1858 |20,753 Willson, H. F. | | Miller, W. |June 29, 1858 |20,763 Blake, Lyman R. |July 6, 1858 |20,775 Carpenter, Lunan |July 27, 1858 |20,990 Moore, Charles |July 27, 1858 |21,015 Smith, E. H. |Aug. 3, 1858 |21,089 Wheeler and Carpenter |Aug. 3, 1858 |21,100 Gibbs, J. E. A. |Aug. 10, 1858 |21,129 Uhlinger, W. P. |Aug. 17, 1858 |21,224 Clark, David W. |Aug. 31, 1858 |21,322 Blodgett, S. C. |Sept. 7, 1858 |21,465 Hubbard, G. W. |Sept. 14, 1858 |21,537 Hendrick, J. E. |Oct. 5, 1858 |21,722 Gibbs, J. E. A. |Oct. 12, 1858 |21,751 Sangster, Amos. W. |Oct. 26, 1858 |21,929 Avery, O. and Z. W. |Nov. 9, 1858 |22,007 Spencer and Lamb |Nov. 23, 1858 |22,137 Perry, James |Nov. 23, 1858 |22,148 Burnet and Broderick |Nov. 30, 1858 |22,160 Hook, Albert H. |Nov. 30, 1858 |22,179 Raymond, Charles |Nov. 30, 1858 |22,220 Bishop, H. H. |Dec. 7, 1858 |22,226 Pratt, S. F. |Dec. 7, 1858 |22,240 Atwood, J. E. |Dec. 14, 1858 |22,273 Fosket, W. A., and |Jan. 25, 1859 |22,719 Savage, Elliot | | Snyder, W. |Feb. 15, 1859 |22,987 Clark, D. W. |May 3, 1859 |23,823 Boyd, A. H. |May 17, 1859 |24,003 Gray, Joshua |May 17, 1859 |24,022 Hook, Albert H. |May 17, 1859 |24,027 Spencer, James C. |May 17, 1859 |24,061 Carhart, Peter S. |May 24, 1859 |24,098 McCurdy, J. S. |June 14, 1859 |24,395 Goodwyn, H. H. |June 21, 1859 |24,455 Grout, William |July 5, 1859 |24,629 Hensel, George |July 12, 1859 |24,737 Parker, Sidney |July 12, 1859 |24,780 Hall, William |July 26, 1859 |24,870 Hayden, H. W. |Aug. 2, 1859 |24,937 Kelsey, D. |Aug. 2, 1859 |24,939 Emswiler, J. B. |Aug. 9, 1859 |25,002 Farr, C. N. |Aug. 9, 1859 |25,004 Harrison, James, Jr. |Aug. 9, 1859 |25,013 Tapley, G. S. |Aug. 9, 1859 |25,059 Barnes, W. T. |Aug. 16, 1859 |25,084 Booth, Ezekial |Aug. 16, 1859 |25,087 Hinkley, J. |Aug. 23, 1859 |25,231 Harrison, James, Jr. |Aug. 30, 1859 |25,262 Buell, J. S. |Sept. 13, 1859 |25,381 Vogel, Kasimir |Oct. 4, 1859 |25,692 Woodward, F. G. |Oct. 11, 1859 |25,782 Barrett, O. D. |Oct. 11, 1859 |25,785 Barnes, William T. |Oct. 25, 1859 |25,876 Sawyer, Irwin, and Alsop, T. |Oct. 25, 1859 |25,918 Budlong, William G. |Nov. 1, 1859 |25,946 Fosket, William A., |Nov. 1, 1859 |25,963 and Savage, E. | | Hicks, W. C. |Nov. 8, 1859 |26,035 Scofield, C. |Nov. 8, 1859 |26,059 Pearson, William |Nov. 22, 1859 |26,201 McCurdy, James S. |Nov. 22, 1859 |26,234 Clark, Edwin |Dec. 6, 1859 |26,336 Dickinson, C. W. |Dec. 6, 1859 |26,346 Miller, Charles |Dec. 13, 1859 |26,462 Rowe, Jas. |Dec. 27, 1859 |26,638 Johnson, A. F. |Jan. 24, 1860 |26,948 Thomson, J. |Feb. 7, 1860 |27,082 Juengst, George |Feb. 14, 1860 |27,132 Davis, Job A. |Feb. 21, 1860 |27,208 Gibbs, James E. A. |Feb. 21, 1860 |27,214 Rowe, James |Feb. 21, 1860 |27,260 Dopp, H. W. |Feb. 28, 1860 |27,279 Paine, A. R. |March 6, 1860 |27,412 Smalley, J. |March 20, 1860 |27,577 Newlove, T. |April 3, 1860 |27,761 McCurdy, J. S. |May 1, 1860 |28,097 Arnold, G. B. |May 8, 1860 |28,139 Bean, E. E. |May 8, 1860 |28,144 Holly, Birdsill |May 8, 1860 |28,176 Chamberlain, J. N. |May 29, 1860 |28,452 Ruddick, H. |May 29, 1860 |28,538 Scofield, Chas., and |June 5, 1860 |28,610 Rice, Clarke | | Smith, Wilson H. |June 19, 1860 |28,785 Rose, I. M. |June 19, 1860 |28,814 Gibbs, J. E. A. |June 26, 1860 |28,851 McCurdy, J. S. |July 3, 1860 |28,993 Mueller, H. |July 3, 1860 |28,996 Sutton, Wm. A. |July 17, 1860 |29,202 Hicks, W. C. |July 24, 1860 |29,268 Tracy, D. |Sept. 11, 1860 |30,012 Washburn, T. S. |Sept. 11, 1860 |30,031 Arnold, G. B., and A. |Sept. 25, 1860 |30,112 Leavitt, Rufus |Nov. 13, 1860 |30,634 Payne, R. S. |Nov. 13, 1860 |30,641 Heyer, Frederick |Nov. 27, 1860 |30,731 Hardie, J. W. |Dec. 4, 1860 |30,854 Earle, T. |Jan. 22, 1861 |31,156 Bruen, J. T. |Jan. 22, 1861 |31,208 Smith, J. M. |Feb. 5, 1861 |31,334 Smith, L. H. |Feb. 12, 1861 |31,411 Rice, Quartus |Feb. 12, 1861 |31,429 Rose, I. M. |March 5, 1861 |31,628 Ross, Noble G. |March 26, 1861 |31,829 Boyd, A. H. |April 2, 1861 |31,864 Mallary, G. H. |April 2, 1861 |31,897 Shaw, H. L. |April 9, 1861 |32,007 Burr, Theodore |April 9, 1861 |32,023 Jones, William, and |May 14, 1861 |32,297 Haughian, P. | | Wilder, M. G. |May 14, 1861 |32,323 Smith, Lewis H. |May 21, 1861 |32,385 Stoakes, J. W. |May 28, 1861 |32,456 Fuller, William M. |June 4, 1861 |32,496 Norton, B. F. |July 9, 1861 |32,782 Raymond, C. |July 9, 1861 |32,785 Raymond, Charles |July 30, 1861 |32,925 Case, G. F. |Aug. 13, 1861 |33,029 Hodgkins, C. |Aug. 20, 1861 |33,085 Marble, F. E. |Oct. 8, 1861 |33,439 Mann, Charles |Oct. 22, 1861 |33,556 Grover, W. O. |Nov. 26, 1861 |33,778 Hendrickson, E. M. |Feb. 4, 1862 |34,330 Derocquigny, A. C. F., |March 25, 1862 |34,748 Gance, D., and Hanzo, L. | | Thompson, R. |April 8, 1862 |34,926 Smith, John C. |April 15, 1862 |34,988 Palmer, Aaron |May 13, 1862 |35,252 Hall, W. S. |Aug. 5, 1862 |36,084 McCurdy, James S. |Aug. 19, 1862 |36,256 Grover, W. O. |Sept. 9, 1862 |36,405 Wilkins, J. N. |Sept. 30, 1862 |36,591 Humphrey, D. W. G. |Oct. 7, 1862 |36,617 House, H. A., and J. A. |Nov. 11, 1862 |36,932 Crossby, C. O., and Kellogg, H. |Dec. 2, 1862 |37,033 Shaw, A. B. |Dec. 16, 1862 |37,202 Pipo, John A. |Jan. 27, 1863 |37,550 Hollowell, J. G. |Feb. 10, 1863 |37,624 Howe, A. B. |March 17, 1863 |37,913 Weitling, W. |March 17, 1863 |37,931 Shaw & Clark |April 21, 1863 |38,246 Baldwin, Cyrus W. |April 28, 1863 |38,276 Grote, F. W. |May 5, 1863 |38,447 Palmer, C. H. |May 5, 1863 |38,450 Mack, W. A. |May 19, 1863 |38,592 Bosworth, C. F. |June 9, 1863 |38,807 McCurdy, J. S. |June 16, 1863 |38,931 Langdon, Leander W. |July 14, 1863 |39,256 House, J. A., and H.A. |Aug. 4, 1863 |39,442-39,445 (4 patents on 1 machine) | | Tracy and Hobbs |Sept. 15, 1863 |40,000 Wagener, Jeptha A. |Oct. 13, 1863 |40,296 Rehfuss, G. |Oct. 13, 1863 |40,311 Lathrop, Lebbeus W., |Oct. 27, 1863 |40,446 and de Sanno, Wm. P. | | Heyer, W. D. |Nov. 17, 1863 |40,622 Simmons, A. G., and Scofield, C. |March 1, 1864 |41,790 Guinness, W. S. |March 15, 1864 |41,916 Willcox, Charles H. |March 22, 1864 |42,036 (4 patents on 1 machine) |Aug. 9, 1864 |43,819 |Sept. 27, 1864 |44,490 |Sept. 27, 1864 |44,491 Sibley, J. J. |March 29, 1864 |42,117 Thompson, R. |April 19, 1864 |42,449 McKay & Blake |May 24, 1864 |42,916 Chittenden, H. H. |June 28, 1864 |43,289 Hall, Luther |July 5, 1864 |43,404 Planer, Louis |Aug. 23, 1864 |43,927 Atwater, B. |Sept. 6, 1864 |44,063 Dale, John D. |Oct. 11, 1864 |44,686 Gritzner, M. C. |Oct. 18, 1864 |44,720 Smith, DeWitt C. |Dec. 20, 1864 |45,528 Weitling, W. |Jan. 3, 1865 |45,777 Cadwell, C. |Jan. 24, 1865 |45,972 Bartlett, J. W. |Jan. 31, 1865 |46,064 McCurdy, James S. |Feb. 7, 1865 |46,303 Lamb, Thomas, and |Aug. 15, 1865 |49,421 Allen, John | | Humphrey, D. W. G. |Aug. 29, 1865 |49,627 Tarbox, John N. |Sept. 5, 1865 |49,803 Crosby, C. O. |Oct. 3, 1865 |50,225 Cajar, E. |Oct. 3, 1865 |50,299 Hart, William |Oct. 17, 1865 |50,469 Hecht, A. |Oct. 17, 1865 |50,473 Emerson, John |Nov. 14, 1865 |50,989 Keats, John, and Clark, Wm. S. |Nov. 14, 1865 |50,995 Rehfuss, George |Nov. 21, 1865 |51,086 Eickemeyer, Rudolf |Feb. 20, 1866 |52,698 Hanlon, John |Feb. 27, 1866 |52,847 McCurdy, J. S. |April 3, 1866 |53,743 Bartram, W. B. |May 15, 1866 |54,670 Bartram, W. B. |May 15, 1866 |54,671 Goodspeed, G. N. |May 15, 1866 |54,816 Hayes, J. |May 22, 1866 |55,029 McCloskey, John |June 19, 1866 |55,688 House, J. A. and H. A. |June 26, 1866 |55,865 Tucker, Joseph C. |July 24, 1866 |56,641 Warth, Albin |July 24, 1866 |56,646 Destouy, A. |July 31, 1866 |56,729 Schwalback, M. |July 31, 1866 |56,805 Cately, William H. |Aug. 7, 1866 |56,902 Piper, D. B. |Aug. 7, 1866 |56,990 Leyden, Austin |Aug. 14, 1866 |57,157 Clements, James M. |Aug. 21, 1866 |57,451 Davis, Job A. |Oct. 9, 1866 |58,614 Rodier, Peter |Nov. 13, 1866 |59,659 Duchemin, Wm. |Nov. 13, 1866 |59,715 Kilbourn, E. E. |Nov. 20, 1866 |59,746 Reed, T. K. |Dec. 4, 1866 |60,241 Singer, I. M. |Dec. 11, 1866 |60,433 Bartram, W. B. |Jan. 1, 1867 |60,669 Rehfuss, G. |Jan. 8, 1867 |61,102 Singer, Isaac |Jan. 15, 1867 |61,270 Cajar, Emil |Feb. 5, 1867 |61,711 Craige, E. H. |Feb. 19, 1867 |62,186 Reed, T. K. |Feb. 19, 1867 |62,287 Bartram, W. B. |March 5, 1867 |62,520 Fuller, H. W. |March 19, 1867 |63,033 Stannard, M. |April 23, 1867 |64,184 Craige, E. H. |Aug. 13, 1867 |67,635 Doll, Arnold |Sept. 3, 1867 |68,420 Bruen, L. B. |Sept. 17, 1867 |68,839 Hodgkins, C. |Oct. 8, 1867 |69,666 Baker, G. W. |Oct. 29, 1867 |70,152 Cadwell, Caleb |Nov. 19, 1867 |71,131 Fanning, J. |Dec. 31, 1867 |72,829 Warth, Albin |Jan. 7, 1868 |73,064 Rehfuss, George |Jan. 7, 1868 |73,119 Cornely, E. |Jan. 28, 1868 |73,696 Blake, L. R. |Feb. 11, 1868 |74,289 Fales, J. F. |Feb. 11, 1868 |74,328 Jencks, G. L. |Feb. 18, 1868 |74,694 Clark, Edwin E. |Feb. 25, 1868 |74,751 Halbert, A. W. |March 31, 1868 |76,076 Gritzner, M. C. |April 7, 1868 |76,323 Bartlett, Joseph W. |April 7, 1868 |76,385 Waterbury, Enos |June 16, 1868 |79,037 Cole, W. H. |June 30, 1868 |79,447 Lamson, Henry P. |July 7, 1868 |79,579 French, S. |July 28, 1868 |80,345 Stein, M. J. |Sept. 8, 1868 |81,956 Hancock, H. J. |Oct. 27, 1868 |83,492 Bartram, W. B. |Nov. 3, 1868 |83,592 Benedict, C. P. |Nov. 3, 1868 |83,596 Bonnaz, A. |Nov. 10, 1868 |83,909 Bonnaz, A. |Nov. 10, 1868 |83,910 Elliott, F. |Jan. 19, 1869 |85,918 Canfield, F. P. |Jan. 19, 1869 |86,057 Arnold B. |Jan. 26, 1869 |86,121 Jones, John |Jan. 26, 1869 |86,163 Russell, W. W. |Feb. 9, 1869 |86,695 Eldridge, G. W. |March 2, 1869 |87,331 House, J. A. and H. A. |March 2, 1869 |87,338 Gird, E. D. |March 9, 1869 |87,559 Carpenter, William |March 9, 1869 |87,633 Dunbar, C. F. |March 30, 1869 |88,282 McLean, J. N. |March 30, 1869 |88,499 Billings, C. E. |April 6, 1869 |88,603 Winter, Wm. |April 13, 1869 |88,936 Tittman, A. |April 20, 1869 |89,093 Swartwout, H. L. |April 27, 1869 |89,357 Lyons, Lucius |April 27, 1869 |89,489 Crosby, C. O. |May 25, 1869 |90,507 Gutmann, J. |May 25, 1869 |90,528 Duchemin, William |June 8, 1869 |91,101 Adams, John Q. |July 6, 1869 |92,138 Bond, Joseph, Jr. |Aug. 10, 1869 |93,588 Hoffman, Geo. W. |Aug. 24, 1869 |94,112 Brown, John H. |Aug. 31, 1869 |94,389 Heery, Luke |Sept. 14, 1869 |94,740 Gray, Joshua |Oct. 5, 1869 |95,581 Smith, E. H. |Oct. 26, 1869 |96,160 Page, Chas. |Nov. 2, 1869 |96,343 Lyon, Lucius |Nov. 9, 1869 |96,713 Clever, P. J. |Nov. 16, 1869 |96,886 Mills, Daniel |Nov. 16, 1869 |96,944 Woodruff, Geo. B., and |Nov. 16, 1869 |97,014 Browning, Geo. | | Keith, Jeremiah |Dec. 7, 1869 |97,518 Hurtu, Auguste J., and |Dec. 21, 1869 |98,064 Hautin, Victor J. | | Lamb, Thomas |Dec. 28, 1869 |98,390 Rudolph, B. |Feb. 1, 1870 |99,481 Porter, Alonzo |Feb. 8, 1870 |99,704 Smith, W. T. |Feb. 8, 1870 |99,743 Meyers, N. |Feb. 15, 1870 |99,783 Grover, W. O. |Feb. 22, 1870 |100,139 Spoehr, F. |April 12, 1870 |101,779 Kendall, George F. |April 12, 1870 |101,887 Cooney, W. |April 26, 1870 |102,226 Brown, F. H. |April 26, 1870 |102,366 Howard E., and Jackson, W. H. |May 31, 1870 |103,745 Bartram, W. B. |June 14, 1870 |104,247 Henriksen, H. P. |June 21, 1870 |104,590 Martine, Charles F. |June 21, 1870 |104,612 Nasch, Isidor |June 21, 1870 |104,630 Hall, L. |July 12, 1870 |105,329 Lyon, Lucius |July 26, 1870 |105,820 Bennor, Joseph |Aug. 9, 1870 |106,249 Barnes, M. M. |Aug. 16, 1870 |106,307 Leslie, Arthur M. |Oct. 18, 1870 |108,492 Rayer, William A.,and |Nov. 1, 1870 |108,827 Lincoln, Wm. S. | | Landfear, Wm. R. |Nov. 22, 1870 |109,427 Parham, Charles |Nov. 22, 1870 |109,443 Lamb, I. W. |Nov. 29, 1870 |109,632 Moreau, Eugene |Jan. 3, 1871 |110,669 Robinson, Charles E. |Jan. 3, 1871 |110,790 Goodyear, Charles, Jr. |Jan. 24, 1871 |111,197 Stevens, G., and Hendy, J. |Jan. 31, 1871 |111,488 Carpenter, Mary P. |Feb. 21, 1871 |112,016 Hancock, Henry J. |Feb. 21, 1871 |112,033 Sidenberg, W. |March 14, 1871 |112,745 Chase, M. |April 11, 1871 |113,498 Stein, M. J. |April 11, 1871 |113,593 Tate, Wm. J. |April 11, 1871 |113,704 House, J. A. and H. A. |May 2, 1871 |114,294 Sidenberg, W. |May 23, 1871 |115,117 Beuttels, Charles |May 23, 1871 |115,155 Thompson, G. |May 23, 1871 |115,255 Willcox and Carleton |June 27, 1871 |116,521 (3 patents on 1 machine) | |116,522 | |116,523 Willcox and Carleton |July 4, 1871 |116,783 Goodyear, Charles, Jr. |July 11, 1871 |116,947 Necker, Carl |July 18, 1871 |117,101 Pitt, James; Joseph; |July 18, 1871 |117,203 Edward; and Wm. | | Jones, John T. |Aug. 1, 1871 |117,640 West, E. P. |Aug. 1, 1871 |117,708 Jones, Solomon |Aug. 29, 1871 |118,537 (2 patents on 1 machine) | |118,538 Lamb, Thomas |Sept. 5, 1871 |118,728 Bosworth, C. F. |Jan. 9, 1872 |122,555 Smyth, D. M. |Jan. 9, 1872 |122,673 Fish, Warren L. |Feb. 13, 1872 |123,625 Palmer, C. H. |March 19, 1872 |124,694 Baker, G. W. |April 9, 1872 |125,374 Gordon and Kinert |April 16, 1872 |125,807 Howard, C. W. |April 23, 1872 |126,056 (second machine) | |126,057 Smyth, D. M. |May 14, 1872 |126,845 Beckwith, W. G. |May 21, 1872 |126,921 Bouscay, Eloi, Jr. |May 28, 1872 |127,145 Braundbeck, E. |June 11, 1872 |127,675 Heidenthal, W. |June 11, 1872 |127,765 Cleminshaw, S. |June 25, 1872 |128,363 Wardwell, S. W., Jr. |July 2, 1872 |128,684 Springer, W. A. |July 9, 1872 |128,919 Fanning, John |July 16, 1872 |129,013 Parks, Volney |July 30, 1872 |129,981 Baker, G. W. |July 30, 1872 |130,005 Smyth, D. M. |Aug. 6, 1872 |130,324 McClure, A. T. |Aug. 13, 1872 |130,385 Ashe, Robert |Aug. 20, 1872 |130,555 Bartram, W. B. |Aug. 20, 1872 |130,557 West, Elliot P. |Aug. 20, 1872 |130,674 Happe, J., and Newman, W. |Aug. 20, 1872 |130,715 Hinds, Jesse L. |Sept. 10, 1872 |131,166 Brown, F. H. |Oct. 1, 1872 |131,735 Beckwith, W. G. |Nov. 26, 1872 |133,351 Turner, S. S. |Dec. 3, 1872 |133,553 Chandler, R. |Dec. 10, 1872 |133,757 Venner, O. |Dec. 10, 1872 |133,814 Duchemin, W. |Jan. 21, 1873 |135,032 Sheffield, G. V. |Jan. 21, 1873 |135,047 Parham, Charles |Feb. 4, 1873 |135,579 Goodes, E. A. |March 11, 1873 |136,718 Tittman, A. |March 11, 1873 |136,792 Happe, J., and Newman, W. |March 25, 1873 |137,199 Ragan, Daniel |April 1, 1873 |137,321 O'Neil, John |April 8, 1873 |137,618 Kallmeyer, G. |April 8, 1873 |137,689 Ross, J. G., and Miller, T. L. |May 13, 1873 |138,764 West, Elliott P. |May 13, 1873 |138,772 Koch and Brass |May 13, 1873 |138,898 Arnold, B. |May 20, 1873 |138,981 Arnold, B. |May 20, 1873 |138,982 Lathrop, L. W. |May 20, 1873 |139,067 Chandler, Rufus |May 27, 1873 |139,368 Jones, S. H. |July 8, 1873 |140,631 Smyth, D. M. |July 22, 1873 |141,088 Wardwell, S. W., Jr. |July 29, 1873 |141,245 Stewart, J., Jr. |July 29, 1873 |141,397 Walker, William |July 29, 1873 |141,407 Blanchard, Helen A. |Aug. 19, 1873 |141,987 Springer, W. A. |Aug. 26, 1873 |142,290 Cushman, C. S. |Sept. 2, 1873 |142,442 Porter, D. A. |Nov. 25, 1873 |144,864 Koch & Brass |Dec. 2, 1873 |145,215 Richardson, E. F. |Dec. 16, 1873 |145,687 Weber, Theo. A. |Dec. 23, 1873 |145,823 Scribner, Benjamin, Jr. |Jan. 13, 1874 |146,483 Black, Samuel S. |Jan. 20, 1874 |146,642 Taylor, F. B. |Jan. 20, 1874 |146,721 Richardson, Everett P. |Jan. 27, 1874 |146,948 Muir, William |Feb. 3, 1874 |147,152 Goodes, E. A. |Feb. 10, 1874 |147,387 Springer, Wm. A. |Feb. 10, 1874 |147,441 True, C. B. |March 10, 1874 |148,336 Wardwell, S. W., Jr. |March 10, 1874 |148,339 Shorey, Samuel W. |March 17, 1874 |148,765 Smith, James H. |March 24, 1874 |148,902 Horr, Addison D. |April 21, 1874 |149,862 Page, Chas. |May 5, 1874 |150,479 Crane, Thomas |May 5, 1874 |150,532 Buhr, J. |May 26, 1874 |151,272 Smyth, D. M. |June 9, 1874 |151,801 Wensley, James |June 16, 1874 |152,055 Dinsmore, A. S., and |June 30, 1874 |152,618 Carter, John T. | | Speirs, J. |July 7, 1874 |152,813 Brewer, A. G. |July 14, 1874 |152,894 Baglin, Wm. |Aug. 18, 1874 |154,113 Howard, E. L. |Aug. 25, 1874 |154,485 Landfear, Wm. R. |Sept. 22, 1874 |155,193 Drake, Ellis |Oct. 13, 1874 |155,932 Barney, Samuel C. |Oct. 20, 1874 |156,119 Moreau, Eugene |Oct. 20, 1874 |156,171 Huntington, Thomas S. |Dec. 29, 1874 |158,214 Bartlett and Plant |Jan. 26, 1875 |159,065 Garland, H. P. |Feb. 16, 1875 |159,812 Dinsmore, Alfred S. |March 9, 1875 |160,512 McCloskey, John |March 30, 1875 |161,534 Schmidt, Albert E. |April 27, 1875 |162,697 Darling & Darling |May 25, 1875 |163,639 Richardson, Everett P. |July 13, 1875 |165,506 Whitehill, Robert |July 27, 1875 |166,172 Weber, Theodore A. |Aug. 3, 1875 |166,236 Pearson, Wm. |Aug. 17, 1875 |166,805 Beckwith, William G. |Sept. 7, 1875 |167,382 Hall, John S. |Oct. 11, 1875 |168,637 Jones, J. T. |Oct. 26, 1875 |169,106 Garland, H. P. |Oct. 26, 1875 |169,163 Wormald & Dobson |Nov. 9, 1875 |169,881 Rose, R. M. |Nov. 30, 1875 |170,596 Keith, Jeremiah |Dec. 7, 1875 |170,741 Keith, T. K. |Dec. 14, 1875 |170,955 Leavitte, Albert |Dec. 14, 1875 |171,147 Toll, Charles F. |Dec. 14, 1875 |171,193 Keats, Greenwood, & Keats |Dec. 28, 1875 |171,622 Thayer, Augustus |Jan. 11, 1876 |172,205 Frese, B. |Jan. 18, 1876 |172,308 Pearson, William |Jan. 18, 1876 |172,478 Sawyer & Esty |Feb. 29, 1876 |174,159 Porter & Baker |March 14, 1876 |174,703 Walker, William |April 11, 1876 |176,101 Upson, L. A. |April 18, 1876 |176,153 Witherspoon, S. A. |April 18, 1876 |176,211 Rice, T. M. |April 25, 1876 |176,686 Murphy, E. |May 2, 1876 |176,880 Bradford, E. F., and |May 16, 1876 |177,371 Pierce, V. R. | | Applegate & Webb |May 25, 1876 |177,784 Sullivan, John J. |June 27, 1876 |179,232 Appleton, C. J., and |July 4, 1876 |179,440 Sibley, J. J. | | Marin, Chas. |July 11, 1876 |179,709 Gullransen, P. E., and |July 25, 1876 |180,225 Rettinger, J. C. | | Butcher, Joseph |Aug. 1, 1876 |180,542 Jackson, William |Sept. 5, 1876 |181,941 Barton, Kate C. |Sept. 12, 1876 |182,096 Eickemeyer, Rudolf |Sept. 12, 1876 |182,182 Webster, W. |Sept. 12, 1876 |182,249 Knoch, C. F. |Oct. 17, 1876 |183,400 Cushman, C. S. |Nov. 21, 1876 |184,594 Harris, David |Dec. 12, 1876 |185,228 Wood, J. |Dec. 26, 1876 |185,811 Oram, Henry |Jan. 2, 1877 |185,952 Palmer, Frank L. |Jan. 2, 1877 |185,954 Hall, John S. |Feb. 6, 1877 |187,006 Palmateer, William A. |Feb. 20, 1877 |187,479 Cummins, William G. |Feb. 27, 1877 |187,822 Esty, William |Feb. 27, 1877 |187,837 Leavitt & Drew |Feb. 27, 1877 |187,874 Henriksen, H. P. |March 20, 1877 |188,515 McKay, Gordon |March 27, 1877 |188,809 Follett, J. L. |April 10, 1877 |189,446 Bond, James, Jr. |April 17, 1877 |189,599 Jacob, F. |April 24, 1877 |190,047 Beck, A. |May 1, 1877 |190,184 Hallett, H. H. |June 5, 1877 |191,584 Randel, William |June 12, 1877 |192,008 Corbett, E., and Harlow, C. F. |July 3, 1877 |192,568 Brown, F. H. |July 24, 1877 |193,477 Melhuish, R. M. |Aug. 28, 1877 |194,610 Atwood, K. C. |Sept. 4, 1877 |194,759 Macaulay, F. A. |Oct. 9, 1877 |195,939 Dimond, George H. |Oct. 16, 1877 |196,198 Sedmihradsky, A. J. |Oct. 23, 1877 |196,486 Keith, J. |Nov. 6, 1877 |196,809 Beck, August |Nov. 6, 1877 |196,863 Keith, T. H. |Nov. 6, 1877 |196,909 Keats, John |Dec. 11, 1877 |198,120 Briggs, Thomas |Jan. 1, 1878 |198,790 Corey, J. W. |Jan. 8, 1878 |198,970 Howard, T. S. L. |Jan. 15, 1878 |199,206 Bosworth, C. F. |Jan. 22, 1878 |199,500 Dancel, C. |Jan. 29, 1878 |199,802 Pearson, M. H. |Feb. 5, 1878 |199,991 Morrell, Robert W.; |April 23, 1878 |202,857 Parkinson, Thomas; and | | Parkinson, Joseph | | Barcellos, D. |April 30, 1878 |203,102 Elderfield, F. D. |June 4, 1878 |204,429 Heberling, J. |June 4, 1878 |204,604 Beukler, William |June 11, 1878 |204,704 Varicas, L. |June 11, 1878 |204,864 Stewart, W. T. |July 2, 1878 |205,698 House, Jas. A. |July 23, 1878 |206,239 Martin, W., Jr.; Dawson, D. R.; |Aug. 6, 1878 |206,743 and Orchar, R. | | Conklin, N. A. |Aug. 6, 1878 |206,774 Wollenberg, H., and Priesner, J. |Aug. 6, 1878 |206,848 Young, E. S., and Dimond, G. H. |Aug. 13, 1878 |206,992 Hoffman, Clara P., and |Aug. 13, 1878 |207,035 Meyers, Nicholas | | Wensley, Jas. |Aug. 20, 1878 |207,230 Dimond, G. H. |Aug. 27, 1878 |207,400 Steward, A. |Aug. 27, 1878 |207,454 Wood, Richard G. |Sept. 10, 1878 |207,928 McCombs, Geo. F. |Sept. 24, 1878 |208,407 Keith, Jeremiah |Oct. 22, 1878 |209,126 Wells, W. W. |Nov. 12, 1878 |209,843 Bayley, C. H. |Feb. 11, 1879 |212,122 Parmenter, Charles O. |Feb. 18, 1879 |212,495 Ingalls, N., Jr. |Feb. 25, 1879 |212,602 Cleminshaw, S. |March 18, 1879 |213,391 Webb, T., and Heartfield, C. H. |March 25, 1879 |213,537 Borton, Stockton |April 8, 1879 |214,089 Henriksen, H. P. |May 20, 1879 |215,615 Bland, Henry |June 3, 1879 |216,016 Morrison, T. W. |June 10, 1879 |216,289 Bosworth, Charles F. |June 17, 1879 |216,504 Simmons, Frederick |June 24, 1879 |216,902 Junker, Carl |July 1, 1879 |217,112 Legat, Désiré Mathurin |Aug. 12, 1879 |218,388 Willcox, C. H. |Aug. 12, 1879 |218,413 Cornely, Emile |Sept. 2, 1879 |219,225 Hamm, E. |Sept. 16, 1879 |219,578 Tuttle, J. W., and Keith, T. K. |Sept. 16, 1879 |219,782 Stackpole, G., and |Oct. 7, 1879 |220,314 Applegate, J. H. | | Otis, S. L. |Oct. 28, 1879 |221,093 Bland, H. |Nov. 11, 1879 |221,505 Bracher, T. W. |Nov. 11,1879 |221,508 Snediker, J. F. |Nov. 25, 1879 |222,089 Mooney, J. H. |Dec. 2, 1879 |222,298 Osborne, J. H. |Feb. 3, 1880 |224,219 Smith, W. M. |March 2, 1880 |225,199 Banks, C. M. |March 23, 1880 |225,784 Haberling, J. |May 4, 1880 |227,249 Haberling, J. |May 11, 1880 |227,525 Wiseman, Edmund |June 8, 1880 |228,711 Juengst, George |June 15, 1880 |228,820 Morley, J. H. |June 15, 1880 |228,918 Curtis, G. H. W. |June 22, 1880 |228,985 Lipe, C. E. |June 29, 1880 |229,322 Miller, L. B., and Diehl, P. |July 6, 1880 |229,629 Willcox, C. H. |July 20, 1880 |230,212 Shaw, E. |July 27, 1880 |230,580 Dinsmore, A. S. |Aug. 17, 1880 |231,155 Thurston, C. H. |Oct. 12, 1880 |231,300 Butcher, J. |Oct. 26, 1880 |233,657 Smyth, D. M. |Nov. 23, 1880 |234,732 Hesse, J. |Dec. 7, 1880 |235,085 Kjalman, H. N. |Dec. 21, 1880 |235,783 Morley, J. H. |Jan. 4, 1881 |236,350 Thomas, J. |Jan. 11, 1881 |236,466 Benson, G. |March 8, 1881 |238,556 Green, G. F. |March 8, 1881 |238,678 Eickemeyer, Rudolf |March 29, 1881 |239,319 Palmer, C. H. |April 26, 1881 |240,758 Campbell, D. H. |May 17, 1881 |241,612 Campbell, Duncan H. |May 17, 1881 |241,613 Leslie, A. M. |May 24, 1881 |241,808 Newell, George F. |June 7, 1881 |242,470 Gritzner, Max C. |June 28, 1881 |243,444 Keith, Jeremiah |July 5, 1881 |243,710 Choquette, A. E. |July 12, 1881 |244,033 Mooney, J. H. |July 19, 1881 |244,470 Beardslee, W. F. |Aug. 16, 1881 |245,781 Hine, Charlie M. |Aug. 23, 1881 |246,136 Willcox, C. H. |Sept. 6, 1881 |246,700 Hoefler, J. |Sept. 13, 1881 |246,883 Woodward, E. |Sept. 20, 1881 |247,285 Richards, Jean E. |Jan. 24, 1882 |252,799 Abbott, W. W. |Jan. 31, 1882 |252,984 Secor, J. B. |Feb. 14, 1882 |253,772 Deschamps, O. L. |Feb. 21, 1882 |253,915 Hull, E. H. |Feb. 28, 1882 |254,217 Roberts, William |March 7, 1882 |254,696 Willcox and Borton |March 28, 1882 |255,576 Borton and Willcox |March 28, 1882 |255,577 Borton and Willcox |March 28, 1882 |255,580 Borton and Willcox |March 28, 1882 |255,581 Veukler, W. |April 4, 1882 |255,916 Hurtu, A. J. |May 30, 1882 |258,761 Keats, Alphonso |July 11, 1882 |260,990 Ramsden, John W. |Aug. 1, 1882 |262,116 Koch, William |Aug. 8, 1882 |262,298 Bigelow, J. |Aug. 29, 1882 |263,467 Mills, Daniel |Oct. 10, 1882 |265,850 Wilkinson, Charles E. |Dec. 19, 1882 |269,251 Carlisle, W. S. |Jan. 9, 1883 |270,540 Holden, O. J., and Griswold, L. |Feb. 13, 1883 |272,050 Cameron, James W. |Feb. 20, 1883 |272,527 Miller, L. B., and Diehl, P. |March 20, 1883 |274,359 Ludeke, W. |April 10, 1883 |275,506 Bolton, J., and Petnz, A. D. |May 8, 1883 |277,106 Blodgett, John W. |June 12, 1883 |279,320 Haberling, J. |Sept. 4, 1883 |284,300 Thimonnier, E., and Vernaz, C. |Oct. 30, 1883 |287,592 Duchemin, William |Nov. 20, 1883 |288,929 Lawrence, G. H. |Dec. 25, 1883 |290,895 Clever, Peter J. |April 8, 1884 |296,529 Palmer, John H. |May 6, 1884 |298,228 Dowling, James, and |May 27, 1884 |299,118 Connolly, John | | Boecher, Adam |June 10, 1884 |300,199 Luedeke, Waldemar |June 17, 1884 |300,380 VanVechten, Orville R. |July 15, 1884 |302,063 Carr, Wm. H., and Ostrom, F. W. |Aug. 12, 1884 |303,361 Trip, J. |Dec. 2, 1884 |308,711 Farrar, Arthur |Dec. 30, 1884 |309,837 Turner, M. G. |Feb. 17, 1885 |312,306 Mills, D. |March 3, 1885 |313,359 Hurtu, August J. |April 7, 1885 |315,037 Charmbury, Henry |April 28, 1885 |316,745 Woodward & Keith |April 28, 1885 |316,927 Walker, William |June 16, 1885 |320,099 Tucker, R. D. |June 23, 1885 |320,898 Wheeler and Dial |Oct. 13, 1885 |328,165 Thomas, Joseph |Nov. 10, 1885 |330,170 Muegge, C. A. |Dec. 8, 1885 |332,207 Diehl, P. |April 13, 1886 |339,623 Diehl, P. |Aug. 24, 1886 |347,776 Helwig, Arthur |Oct. 5, 1886 |350,364 Miehling, Charles |Nov. 2, 1886 |351,992 Dieterle, H. E. |Nov. 30, 1886 |353,542 Walker, William |Dec. 7, 1886 |353,720 Rosenthal, S. A. |Dec. 7, 1886 |353,970 Temple, John |Feb. 22, 1887 |358,088 Gee, W. V. |April 19, 1887 |361,406 Lingley, John W. |Aug. 16, 1887 |368,538 Boppel, Jacob |Jan. 29, 1889 |396,979 Webster, William |April 30, 1889 |402,497 Osterhout and Hallenbeck |May 7, 1889 |402,610 Bennett and Dowling |Aug. 27, 1889 |409,728 Hine, Charles M. |Jan. 28, 1890 |420,382 Wheeler, Nathaniel |Feb. 4, 1890 |420,847 Hallenbeck, J. P. |April 8, 1890 |425,422 Lisle, Myron C. |May 20, 1890 |428,171 Walker and Bennet |May 20, 1890 |428,548 Stewart, James, Jr. |July 15, 1890 |432,449 Dewees, J. W. |July 22, 1890 |432,746 Powell, Thomas |Dec. 16, 1890 |442,695 Fletcher, James H. |Dec. 30, 1890 |443,756 Rudolph, Ernst B., deceased, |April 7, 1891 |449,927 Boulter, W. E., administrator | | Goodwin, Julius C. |April 21, 1891 |450,793 Cook, Hugo |June 23, 1891 |454,610 Bowyer, J. T. |June 23, 1891 |454,708 Willcox, C. H., and Borton, S. |April 5, 1892 |472,094 Legg and Weston |May 17, 1892 |474,840 Kern, Ferdinand |July 19, 1892 |479,369 Jackson, Francis |May 1, 1894 |519,064 Charles Abercrombi |June 5, 1892 |520,977 Taft, J. C. |Oct. 15, 1895 |547,866 IV. 19th-Century Sewing-Machine Leaflets in the Smithsonian Collections _Machine or Manufacturer_ |_Date_ |_Type_ | | American B.H.O. and Sewing Machine |1874 |Illustrated, advertising leaflet Buckeye sewing machine |ca. 1870 |Illustrated, directions for using | | the machine New Buckeye |ca. 1872 |Illustrated, directions for using | | the machine Centennial sewing machine |1876 |Illustrated, advertising leaflet Domestic sewing machine |1872 |Illustrated, advertising leaflet Florence sewing machine |1873 |Illustrated, advertising leaflet Florence sewing machine |1878 |Illustrated, directions for using | | the machine Goodes sewing machine |ca. 1876 |Advertising leaflet Grant Brothers sewing machine |1867 |Illustrated, advertising leaflet | | (Xerox copy) Grover and Baker sewing machine |1853 |Illustrated, advertising leaflet Grover and Baker sewing machine |ca. 1870 |Illustrated, advertising leaflet Home sewing machine |ca. 1870 |Illustrated, advertising leaflet Howe sewing machine, new "B" machine |1868 |Illustrated, instruction booklet Howe sewing machine |1876 |Illustrated, catalog of machines Independent Noiseless sewing machine |ca. 1874 |Illustrated, advertising leaflet Ladd, Webster sewing machine |1861 |Illustrated, advertising leaflet Little Monitor sewing machine |ca. 1872 |Illustrated, advertising leaflet Remington Family sewing machine |ca. 1874 |Illustrated, advertising leaflet Shaw and Clark sewing machine |1864 |Illustrated, advertising leaflet Singer sewing machine |1871 |Illustrated, advertising leaflet Singer sewing machine |1893 |Catalog of machines shown at the | | Columbian Exposition Standard Shuttle sewing machine |ca. 1875 |Illustrated, advertising leaflet Ten Dollar Novelty sewing machine |ca. 1870 |Illustrated, advertising leaflet Weed sewing machine |1873 |Illustrated, advertising leaflet Wheeler and Wilson sewing machine |ca. 1869 |Illustrated, instruction booklet Wheeler and Wilson sewing machine |ca. 1870-1875 |Illustrated, advertising leaflet Wheeler and Wilson no. 8 machine |ca. 1878 |Illustrated, instruction booklet Wilson sewing machine |1872 |Illustrated, advertising leaflet V. A Brief History of Cotton Thread Although Samuel Slater's wife is credited with making the first cotton sewing thread from yarns spun at the Pawtucket, Rhode Island, mill in about 1794, cotton thread did not become a manufactured item at that time. Slater turned all his interests to producing cotton-twist yarns needed for the warps of cotton fabrics. By 1809, however, the agents of Almy and Brown, partners and distributors for Slater, were advertising cotton thread as follows: Factory Cotton and Thread Store, No. 26 Court Street opposite Concert Hall. George Connell, Agent for Almy and Brown of Providence and Pawtucket Manufactories, has now for sale from eight to ten thousand weight of yarn, for weaving ... five hundred pounds cotton thread, in hanks, from No. 12 to 60 of a superior quality and very white.[91] Although it was a short hop from the spinning of cotton warps to the twisting of these cotton yarns to form a sewing thread, the general manufacture of cotton thread as an industry did not originate in the United States but rather in Scotland in the early 19th century. Napoleon's blockade, which curtailed Great Britain's importation of silk--needed not only for fabrics but also for making heddle strings for the looms--stimulated the production of cotton thread there. James and Patrick Clark, in desperation, attempted to substitute cotton for silk in their manufacture of these heddle strings. When they were successful, they considered that if cotton could be used successfully for this purpose it could also be made suitable for sewing thread. In 1812 they built a factory in Paisley, Scotland, which had long been noted for its textile industries. The thread was sold in hanks. About 1820 James' sons, James and John, who were now running J. & J. Clark & Co., began to wind the thread on spools. For this service they charged an extra halfpenny, which was refunded when the empty spool was returned. The thread was usually a three-ply or so-called three-cord thread. About 1815 James Coats, also of Paisley, started manufacturing thread at Ferguslie, Scotland. His two sons took over the company in 1826 and formed the J. & P. Coats Company. Another brother, Andrew Coats, became the selling agent in the United States about 1840. But the cotton-thread industry was not fully launched. As reported in an 1853 _Scientific American_, there was "more American thread made ten years ago than there is today."[92] It was not until the six-cord cabled cotton thread, which was suitable for both machine and hand sewing, was perfected that the industry progressed into full operation. FOOTNOTES: [91] William R. Bagnall, _Textile Industries of the United States_ (Cambridge, Mass., 1893), vol. 1, p. 164. VI. Biographical Sketches BARTHELEMY THIMONNIER The first man known to have put a sewing machine into practical operation, Barthelemy Thimonnier, was a Frenchman of obscure parentage. His father, a textile dyer of Lyon, left that city in 1793 as a result of the Revolution and journeyed with his family to l'Arbresle where Barthelemy was born in August of that year. The family resources were small, and, although the young Thimonnier was able to begin studies at the Seminaire de Saint-Jean at Lyons, he soon was forced to leave school for financial reasons and return to his home, then at Amplepuis. There he learned the tailoring trade and by 1813 was fairly well established in his own shop. At that time many of the town's inhabitants were weavers and almost every house possessed one or two looms. The noise of the shuttle echoed from these family workshops. Thimonnier noted the relatively small amount of time needed to weave a fabric compared with the slow painstaking task of sewing a garment by passing the needle in and out for each stitch of each seam. When his mind began to dwell on the idea of producing a machine to do this stitching, another of the town's occupations supplied him with a clue and an additional incentive. This village industry produced a type of embroidery work called _point de chainette_, in which a needle with a small hook was used to form the chainstitch, a popular type of decorative stitch long used in countries all over the world. It was Thimonnier's plan to use this type of hooked needle and produce the stitch by machine, employing it both as a decorative stitch and a seam-forming one. In 1825 Thimonnier moved to St. Etienne, where he became completely absorbed in the idea of inventing a sewing machine. Ignorant of any of the principles of mechanics, he worked alone and in secret for four years, neglecting his tailoring business to the extent that neighbors looked upon him as peculiar, if not crazy. By 1829 he had not only mastered the mechanical difficulties of bringing his dream to realization, but also had made the acquaintance of the man who helped him to success. Ferrand, of l'Ecole des Mines of Saint-Etienne, became interested in the machine and helped finance Thimonnier through his trials and disappointments. In 1830 Thimonnier received a patent on his machine, which produced the chainstitch by means of a needle shaped like a small crochet hook. [Illustration: Figure 133.--BARTHELEMY THIMONNIER, 1793-1857. From an engraving in the _Sewing Machine Advance_, November 15, 1880. (Smithsonian photo 10569-A.)] Thimonnier, together with Ferrand and a M. Beaunier, made attempts to introduce his machine in Paris. By 1841 they were successful in having eighty of Thimonnier's machines in use sewing army clothing in a shop in Paris. But the fears of the tailors could not be quieted. The machines were destroyed by an ignorant and infuriated mob, as had been earlier labor-saving devices such as the Jacquard attachment for the loom and Hargreaves' spinning jenny. Thimonnier was forced to flee to his home in St. Etienne, once more penniless. Soon after this, Jean Marie Magnin, an engineer from Villefranche-sur-Saône became interested in Thimonnier's machine and provided the inventor again with financial backing. In 1845 under the name of Thimonnier and Magnin the patent of 1830 was renewed, and under it they organized the first French sewing-machine company. The machines they manufactured could produce 200 stitches per minute. The Revolution of 1848 curtailed the manufacture and sale of the machines. Thimonnier, remembering his unpleasant experience in 1841, decided to go to England with Magnin, where, on February 8, 1848, they received the English patent for his chainstitch machine. He was also granted United States patent 7,622 on September 20, 1850. This later machine had some advantages over his French machine of 1830, but by this time other inventors had joined the field with machines that were more practical. Magnin entered a sewing machine (which from the description in the catalog must have been Thimonnier's invention) in the Crystal Palace Exhibition in London in 1850, but because it was late in arriving it was overlooked by the judges and not even considered in the competition. Thimonnier died in poverty at Amplepuis on July 5, 1857. WALTER HUNT Walter Hunt was born near Martinsburg, New York, on July 29, 1796. Although little is known of Hunt's early childhood, we do learn from the author of his obituary, which appeared in _Scientific American_, July 9, 1860, that even as a child he was more interested in people and what he could do for them than in what he could do to insure his own welfare. He is said to have devoted his life to his friends, frequently giving away his last cent when he did not have enough to provide for himself. There is no record that Hunt maintained a regular business other than the occupation of inventor. His interests were numerous and varied. He received his first patent on June 26, 1826, for a machine for spinning flax and hemp. During the next 33 years he patented 26 ideas. In addition he sold or dropped several more. His second patent was for a coach alarm, and through the years he also received patents for a variety of things including a knife sharpener, heating stove, ice boat, nail machine, inkwell, fountain pen, safety pin, bottle stopper, sewing machine (1854), paper collars, and a reversible metallic heel. [Illustration: Figure 134.--WALTER HUNT, 1796-1860. From a daguerreotype owned by his great-grandson, C. N. Hunt. (Smithsonian photo 32066-A.)] ELIAS HOWE, JR. Elias Howe, Jr., was born on his father's farm in Spencer, Massachusetts, on July 9, 1819. This was one of those barren New England farms with many rock-filled acres. All possible ingenuity was necessary to secure a living. The elder Howe supplemented his farming by having a small gristmill, a sawmill, and also by manufacturing cards for the fast-growing cotton industry of New England. Elias Jr.'s earliest recollections were of the latter. He worked with his brothers and sisters sticking wire teeth into strips of leather to make these cotton cards, but, not being very good at this, his family decided to let him "live out" with a neighboring farmer. (Children were leased in those days; they received their board and keep in exchange for chores they would perform.) After a few years, Elias returned home and worked in his father's mill until he was sixteen. Then, against the wishes of his family, he went to Lowell, Massachusetts. Here, he obtained a learner's place in a machine shop where cotton-spinning machinery was made and repaired. In 1837, when a financial panic hit the country, Howe lost his job. He then decided to go to Boston, and this marked a turning point in his career. In Boston he met Ari Davis, a maker of mariners' instruments and scientific apparatus. Howe began to work in Davis' shop, a place to which inventors often came to ask advice about their ideas. Davis sometimes helped them, but just as often he shouted at them in anger--he is said to have been one of the noisiest men in Boston. One day Howe overheard his employer bellowing at a man who had brought a knitting machine to the shop to seek Davis' advice. "Why are you wasting your time over a knitting machine?" said Davis, "Take my advice, try something that will pay. Make a sewing machine." "It can't be done," was the reply. "Can't be done?" shouted Davis, "Don't tell me that. Why--I can make a sewing machine myself." "If you do," interrupted the capitalist, "I can make an independent fortune for you." Davis, like most men of many words, often talked of more than he planned to do. He never attempted to invent a sewing machine. But the loud voices interested Howe, who, it is said, determined then that he would produce a sewing machine and win the fortune that the prosperous-looking man had asserted was waiting for such a deed. A kind of lameness since birth had made physical tasks painful for Howe, and he perhaps felt that this would offer an opportunity to become independent of hard physical work. After marrying on a journeyman machinist's pay of $9 a week, Howe's health worsened and by 1843 was so bad that he had to stop work for days at a time. His wife was forced to take in sewing to maintain the family. It was the sight of his wife toiling at her stitches together with the pressure of poverty that recalled to Howe his earlier interest in a machine to sew. He decided to make an earnest attempt to invent one. Watching his wife for hours at a time, he tried to visualize a machine that would duplicate the motions of the arm. After many trials, he conceived the idea of using an eye-pointed needle in combination with a shuttle to form a stitch. It is possible that, as some authors state, the solution appeared to him in a dream, a manifestation of the subconscious at work. Others have suggested that he may have learned of Hunt's machine. There is a general similarity in the two, not only in the combination of eye-pointed needle and shuttle but in the overhanging arm and vertical cloth suspension. After conceiving the idea, whatever his inspiration, Howe determined to devote all of his time to producing a working model of his machine. Elias' father, who had then started a factory for splitting palm leaves in Cambridge, gave him permission to set up a lathe and a few tools in the garret of the factory. Elias moved his family to Cambridge. Soon after his arrival, unfortunately, the building burned down, and Howe despaired of finding a place to work. He had a friend, however, in George Fisher, who had just come into a small inheritance, and Howe persuaded him to enter into partnership with him for the development of the machine. Fisher agreed to board Howe and his family, which now included two children, while Howe completed the model. Fisher also agreed to supply $500 for material and tools in exchange for a half interest in a patent if one was obtained. [Illustration: Figure 135.--ELIAS HOWE, JR., 1819-1867. From an oil painting in the Smithsonian Institution presented by the inventor's grandson, Elias Howe Stockwell. (Smithsonian photo 622.)] At long last Howe was able to spend his full time and concentration on building his machine. His family was being fed and had a roof over its head. Within a few months Howe had completed a model and by April 1845 had sewed his first seam (see fig. 14). In July of that year he sewed all the principal seams of two suits of wool clothes, one for George Fisher and one for himself. Several efforts were made to solicit public interest in the new machine. One was installed in a public hall in Boston, and a tailor was employed to operate it at three times the regular wage. The reception was similar to that of Thimonnier's: crowds came to see the "contraption," but, when Howe tried to interest large clothing establishments in using the machine, the protests of the tailors effectively blocked him. He took his sewing machine to the Quincy Hall Clothing Manufactory and offered to sew up any seams brought to him. Daily he sat in one of the rooms demonstrating his machine, and finally he challenged five of the swiftest seamstresses there to a race. Ten seams of equal length were prepared for stitching. One was given to each of the girls while the remaining five were given to Howe. Howe finished his five a little sooner than the girls each finished one, and his seams were declared the strongest and neatest. (Had any curved or angular work been brought, he could not have stitched it.) Still Howe did not receive a single order. The fear of throwing hand sewers out of work was again expressed, and, in addition, the cost of the machine was said to be too high. When it was estimated that a large shirtmaker would have to buy thirty or forty such machines, the necessary large investment was dismissed as ridiculous. Howe was not too discouraged. In the meantime, he had finished a second machine for deposit with the patent specifications, as the patent laws then required. The second was a better made machine (fig. 15) and showed several minor changes. As soon as the patent was issued on September 10, 1846, Howe and his partner returned to Cambridge. Without the inventor's enthusiasm or love of his own invention, George Fisher became thoroughly discouraged. He had boarded Howe and his family for nearly two years, had furnished the money needed to purchase the tools and materials for making the two sewing machines, had met the expense of obtaining the patent and the trip of Howe and himself to Washington; representing in all an outlay of practically $2000. Since no orders for machines had been received from either garment makers or tailors, Fisher did not see the slightest probability of the machine's becoming profitable and regarded his advances of cash as a dead loss. Howe moved back to his father's house with a plan to look elsewhere for a chance to introduce the machine. Obtaining a loan from his father, he built another machine and sent it to England by his brother Amasa. After many discouraging attempts to interest the British, Amasa met William Thomas, a manufacturer of umbrellas, corsets, and leather goods. Thomas employed many workmen, all of whom stitched by hand, and he immediately saw the possibilities of a sewing machine. He proposed that Howe sell the machine to him for £250 sterling (about $1250). Thomas further proposed to engage the inventor to adapt this machine to the making of corsets, at a salary of £3 a week. When Amasa Howe returned to Cambridge with the news, Elias was reluctant to accept Thomas' offer but had nothing better in sight. So the brothers sailed for London in February 1847, taking with them Howe's first machine and his patent papers. Thomas later advanced the passage money for Howe's wife and three children so that they could join Howe in England. At this point, historians disagree on how long Howe was in Thomas' employ and whether he succeeded in adapting the machine to meet Thomas' needs. He was in England long enough, however, to find himself without employment in a strange country, his funds nearly exhausted, and his wife ill. He hoped to profit by the notice that his work had received and began to build another machine. He sent his family home to reduce expenses while he stayed on to finish the machine. After working on it for three or four months, he was forced to sell it for five pounds and to take a note for that. To collect enough for his passage home, he sold the note for four pounds cash and pawned his precious first machine and his patent papers. He landed in New York in April 1849 with but half a crown in his pocket to show for his labors. A short time after he arrived, he learned that his wife was desperately ill. Only with a loan from his father was he able to reach her side before she died. Friends were found to look after the children, and Elias returned to work as a journeyman machinist. Howe discovered, much to his surprise, that during his absence in England the sewing machine had become recognized in the United States. Several machines made in Boston had been sold to manufacturers and were in daily operation. Upon investigating them, he felt that they utilized all or part of the invention that he had patented in 1846, and he prepared to secure just compensation for its use. The first thing he did was to regain his first machine and patent papers from the London pawnshop. It was no easy matter for Howe to raise the money, but by summer he had managed. It was sent to London with Anson Burlingame, who redeemed the loans, and by autumn of the same year the precious possessions were back in Howe's hands. Though Howe gained nothing by his English experience, William Thomas by his modest expenditure obtained all rights to the machine for Great Britain. This later proved to be a valuable property. Howe then began writing letters to those whom he considered patent infringers, requesting them to pay a fee or discontinue the manufacture of sewing machines which incorporated his patented inventions. Some at first were willing to pay the fee, but they were persuaded by the others to stand with them and resist Howe. This action forced Howe to the courts. With his father's aid he began a suit, but soon found that considerably more money than either possessed was necessary for such actions. Howe turned once more to George Fisher, but years of investing money in Howe's machine without any monetary return had cooled him to the idea. Fisher, however, agreed to sell his half interest, and in February 1851 George S. Jackson, Daniel C. Johnson, and William E. Whiting became joint owners with Howe. These men helped Howe to procure witnesses in the furtherance of numerous suits, but more money was needed than they could raise. The following year a Massachusetts man by the name of George W. Bliss was persuaded to advance the money for the heavy legal expenses needed to protect the patent. Bliss did this as a speculation and demanded additional security. Once more Elias' long-suffering parent came to the rescue and mortgaged his farm to get the necessary collateral. Only one of these suits was prosecuted to a hearing, but this one, relatively unimportant in itself, set the precedent. In it the defense relied on the earlier invention of Walter Hunt to oppose Howe's claims. The defendant succeeded in proving that Hunt invented, perfected, and sold two machines in 1834 and 1835 which contained all the essential devices in Howe's machine of 1846. But Howe showed that the defendant's machine (which was a Blodgett and Lerow) contained some features of Howe's machine which were not in Hunt's. The jury decided the case in favor of Howe. Howe later fought a vigorous battle with Isaac Singer, but after much legal controversy the ultimate decision in that case also was in Howe's favor. The suits and payments to each patent holder for the right to use his idea were choking the sewing-machine industry. Even Howe could not manufacture a practical machine without an infringement. Finally an agreement was reached and a "Combination" was formed by the major patent holders (see pp. 41-42). In the meantime, eight years of the first term of Howe's patent had expired without producing much revenue. This permitted Howe, upon the death of his partner, George Bliss, to buy Bliss' half interest for a small sum. He became, then, the sole owner of his patent just as it was to bring him a fortune. He obtained a seven-year extension for his patent in 1860 without any difficulty, and in 1867, when he applied for another extension, he stated that he had received $1,185,000 from it. Though he endeavored to show that because of the machine's great value to the public he was entitled to receive at least $150,000,000, the second application was denied. During the Civil War, Howe enlisted as a private soldier in the 17th Regiment Connecticut Volunteers. He went into the field and served as an enlisted man. On occasion when the Government was pressed for funds to pay its soldiers, he advanced the money necessary to pay his entire regiment. Howe did not establish a sewing-machine factory until just before his death in 1867. One of his early licensees had been his elder brother, Amasa, who had organized the Howe Sewing Machine Company about 1853. When Elias began manufacturing machines on his own, he sunk into the bedplate of each machine a brass medallion bearing his likeness. Elias gave his company the same name that his elder brother had used. As this had been Amasa's exclusive property for many years, he took the matter to the courts where the decision went against Elias. He then organized the Howe Machine Company and began to manufacture sewing machines. On October 3, 1867, Elias died in Brooklyn, New York, at the home of one of his sons-in-law. The company was then carried on by his two sons-in-law, who were Stockwell brothers. In 1872 the Howe Sewing Machine Company was sold by Amasa's son to the Stockwells' Howe Machine Company, which in turn went out of business in the mid-1880s. ALLEN BENJAMIN WILSON Allen B. Wilson was born in the small town of Willett, Cortlandt County, New York, in 1824. At sixteen he was apprenticed to a distant relative, a cabinetmaker. Unfortunate circumstances caused him to leave this employ, and in 1847 Wilson was in Adrian, Michigan, working as a journeyman cabinetmaker. The place and year are important, for it was at this time that he conceived his idea of a sewing machine. Because of the distant location, it is believed that he was not aware of similar efforts being made in New England. Wilson became ill and for many months could not work at his trade. By August 1848 he was able to work again and found employment at Pittsfield, Massachusetts. Resolving to develop his idea of a sewing machine, he worked diligently and by November had made full drawings of all the parts, according to his previous conceptions. In comparison to the monetary returns received by the inventors Howe and Singer, Wilson himself did not receive as great a monetary reward for his outstanding sewing-machine inventions. Because of his health Wilson retired in 1853, when the stock company was formed, but he received a regular salary and additional money from the patent renewals. Wilson petitioned for a second extension of his patents on April 7, 1874, stating that, due to his early poverty, he had been compelled to sell a half interest in a patent (his first one) for the sum of $200. Also he stated that he had not received more than his expenses during the original fourteen-year term. Wilson also stated that he had received only $137,000 during the first seven-year extension period. These figures were verified by his partner. The petition was read before both Houses of Congress and referred to the Committee on Patents.[94] There was strong feeling against the extension of the Wilson patents. The New York _Daily Graphic_, December 30, 1874, reported: [Illustration: Figure 136.--ALLEN BENJAMIN WILSON, 1824-1888. From a drawing owned by the Singer Mfg. Co. Formerly, the drawing was owned by the Wheeler & Wilson Mfg. Co. (Smithsonian photo 32066.)] So valuable has been this latter four-motion feed that few or no cloth-sewing machines are now made without it. The joint ownership of this feature of the Wilson patents has served to bind the combination of sewing-machine builders together, and enabled them to defy competition by force of the monopoly. It is this feature which the combination wishes to further monopolize for seven years by act of Congress. The inventor has probably realized millions for his invention. Singer admits that his patents, which are much less important, paid him two millions prior to 1870, since which time he has not been compelled to render an account. The Wilson patents with their extended terms were worth a much larger sum. They have been public property, so far as the feed is concerned, since June 15, 1873, and will remain so if too great a pressure is not brought to bear on Congress for their extension. A monopoly of this feed motion for seven years more would be worth from ten to thirty millions to the owner--and would cost the people four times as much. Wilson had not made the millions for he only received a small percentage of the renewals' earnings plus his salary from the patents' owner, the Wheeler and Wilson Manufacturing Company. The Congressional Committee on Patents made an adverse report in 1874 and again in 1875 and 1876, when applications for an extension were continued Wilson died on April 29, 1888. ISAAC MERRITT SINGER [Illustration: Figure 137.--- ISAAC MERRITT SINGER, 1811-1875. From a charcoal drawing owned by the Singer Mfg. Co. (Smithsonian photo 32066-B)] Isaac Singer, whose name is known around the world as a manufacturer of sewing machines, was the eighth child of poor German immigrants. Isaac was born on October 27, 1811, in Pittstown, New York, but most of his early life was spent in Oswego. He worked as a mechanic and cabinetmaker, but acquired an interest in the theater. Under the name of Isaac Merritt, he went to Rochester and became an actor. In 1839, during an absence from the theater, he completed his first invention, a mechanical excavator, which he sold for $2000. With the money Singer organized a theatrical troupe of his own, which he called "The Merritt Players." When the group failed in Fredericksburg, Ohio, Singer was stranded for lack of funds. Forced to find some type of employment, Singer took a job in a Fredericksburg plant that manufactured wooden printers' type. He quickly recognized the need for an improved type-carving machine. After inventing and patenting one, he found no financial support in Fredericksburg and decided to take the machine to New York City. Here, the firm of A. B. Taylor and Co. agreed to furnish the money and give Singer room in its Hague Street factory to build machines. A boiler explosion destroyed the first machine, and Taylor refused to advance more money. While Singer was with Taylor, George B. Zieber, a bookseller who had seen the type-carving machine, considered its value to publishers. Zieber offered to help Singer and raised $1700 to build another model. In June 1850 the machine was completed. Singer and Zieber took the machine to Boston where they rented display space in the steam-powered workshop of Orson C. Phelps at 19 Harvard Place. Only a few publishers came to look at the machine, and none wanted to buy it. Singer, contemplating his future, became interested in Phelps' work, manufacturing sewing machines for J. A. Lerow and S. C. Blodgett. Phelps welcomed Singer's interest as the design of the mechanism was faulty and purchasers kept returning the machines for repairs. Singer examined the sewing machine with the eyes of a practical machinist. He criticized the action of the shuttle, which passed around a circle, and the needle bar, which pushed a curved needle horizontally. Singer suggested that the shuttle move to and fro in a straight path and that a straight needle be used vertically. Phelps encouraged Singer to abandon the type-carving machine and turn his energies toward the improvement of the sewing machine. Convinced that he could make his ideas work, Singer sketched a rough draft of his proposed machine, and with the support of Zieber and Phelps the work began. Singer continued to be active in the sewing-machine business until 1863. He made his home in Paris for a short time and then moved to England. While living at Torquay he conceived the idea of a fabulous Greco-Roman mansion, which he planned to have built at Paignton. Singer called it "The Wigwam." Unfortunately, after all his plans, he did not live to see its completion. Singer died on July 23, 1875, of heart disease at the age of sixty-three. FOOTNOTES: [93] _The Proceedings and Debates of the 43rd Congress_, First Session, 1874 Congressional Record, vol. 2, part 3, petition read to the House by Mr. Creamer on April 7, 1874. In part 4 of the same, Mr. Buckingham read a similar petition to the Senate on May 19, 1874. Both were referred to the Committee on Patents; an extension was not granted. _Bibliography_ ADAMS, CHARLES K. Sewing machines. In vol. 7 of _Johnson's universal cyclopaedia_, New York: D. Appleton and Company, 1895. ALEXANDER, EDWIN P. Sewing, plaiting, and felting machines. Pp. 341-353 in _The Practical Mechanic's Journal's record of the great exhibition, 1862_. 1862. ----. On the sewing machine: Its history and progress. _Journal of the Royal Society of Arts_ (April 10, 1863), vol. 2, no. 542, p. 358. AMERICAN HISTORICAL SOCIETY. _The life and works of George H. Corliss._ (Privately printed for Mary Corliss by the Society.) 1930. Biography of Isaac M. Singer. _The Atlas_, New York, N.Y., March 20, 1853. BISHOP, J. LEANDER. In vol. 2 of _A history of American manufactures from 1608 to 1860_, by Bishop; Philadelphia: Edward Young and Company, 1866. BOLTON, JAMES. Sewing machines, special report on special subjects. In vol. 2 of _Report of the Committee on Awards_; Chicago: World's Columbian Exposition, 1893. BROCKETT, LINUS P. Sewing machines. In vol. 4 of _Johnson's universal cyclopaedia_; New York: D. Appleton and Company, 1874. BURR, J. B. _The great industries of the United States._ Hartford: J. B. Burr and Hyde, n.d. COOK, ROSAMOND C. _Sewing machines._ Peoria, Illinois: Manual Arts Press, 1922. DEPEW, C. M. 100 years of American commerce. In vol. 2, _American sewing machines_ by F. G. Bourne. New York: D. O. Haines, 1895. DISTRICT OF COLUMBIA CIRCUIT COURT. Case of Hunt vs. Howe. In _Federal Cases_, case 6891, book 12, 1855. DOOLITTLE, WILLIAM H. _Inventions._ Vol. in Library of modern progress. Philadelphia: Modern Progress Publishing Company, 1905. DURGIN, CHARLES A. _Digest of patents on sewing machines, Feb. 21, 1842-July 1, 1859._ New York: Livesey Brothers, 1859. FAIRFIELD, GEORGE A. Report on sewing machines. In vol. 3 of _Report of the commissioners of the United States to the international exhibition held at Vienna, 1873._ 1874. FISKE, BRADLEY A. _Invention, the master-key to progress._ New York: E. P. Dutton and Company, 1921. GIFFORD, GEORGE W. [Counsel for Elias Howe, Jr.] _Argument of Gifford in favor of Howe's application for extension of patent._ Washington: U.S. Patent Office, 1860. GRANGER, JEAN. Thimonnier et la machine à coudre. In vol. 2 of _Les publications techniques._ Paris, 1943. [Source for biographical sketch on Barthelemy Thimonnier.] GREGORY, GEORGE W. _Machines, etc., used in sewing and making clothing._ Vol. 7 of _Reports and Awards_. Philadelphia International Exhibition, 1876. U.S. Centennial Commission, Washington, D.C., 1880. HERSBERG, RUDOLPH. _The sewing machine, its history, construction and application._ Transl. Upfield Green. London: E. & F. N. Spon, 1864. HOWE, HENRY. _Adventures and achievements of Americans._ Published by the author, 1860. HOWE MACHINE COMPANY. _The Howe exhibition catalog of sewing machines._ Published by the company for the Philadelphia Centennial Exposition, 1876. HUBERT, PHILIP G., JR. _Men of achievement: inventors._ New York: Charles Scribner's Sons, 1894. HUNT, CLINTON N. _Walter Hunt, American inventor._ Published by the author, 1935. [Source for biographical sketch on Walter Hunt.] INTERNATIONAL EXHIBITION. Sewing and knitting machines. In _Reports of the Juries_, Class VII, Section A. London, 1862. JOHNSON CLARK AND COMPANY. _Sewing machines for domestic and export trade._ Published by the company, 1883. KAEMPFFERT, WALDEMAR. A popular history of American invention. _Making clothes by machine_, by John Walker Harrington, vol 2. New York: Charles Scribner's Sons, 1924. KILGARE, C. B. _Sewing-machines._ Philadelphia: J. B. Lippincott Company, 1892. KNIGHT, EDWARD H. Vol. 3 of _Knight's American mechanical dictionary_. Boston: Houghton, Mifflin and Company, 1882. LEWTON, FREDERICK L. The servant in the house: a brief history of the sewing machine. Pp. 559-583 in Annual Report of the Smithsonian Institution (1929); Washington: 1930. LUTH, ERICH. _Ein Mayener Strumpfwirker, Balthasar Krems, 1760-1813, Erfinder der Nähmaschine._ Hamburg, Germany: Verlag Herbert Luth, 1941. ----. _Josef Madersperger oder der unscheinbore Genius._ Hamburg, Germany: Reichsnerband des Deutschen Nähmaschinenhandels EV, 1933 [?]. Obituary of Isaac M. Singer. _New York Tribune_, July 26, 1875. MADERSPERGER, JOSEPH. _Beschreibung einer Nähmaschine._ Vienna, ca. 1816. O'BRIEN, WALTER. Sewing machines. _Textile American_, reprinted March 1931. [A paper read at a meeting of the Leicester Textile Society.] ORCUTT, REV. SAMUEL. _A history of the old town of Stratford and the city of Bridgeport, Connecticut._ 2 vols. Fairfield County Historical Society, 1886. PARIS UNIVERSAL EXPOSITION. _Reports of the U.S. Commissioners General Survey_, vol. 1, pp. 293-297. 1867. PARTON, JAMES. History of the sewing machine. _Atlantic Monthly_, May 1867. RAYMOND, WILLIAM CHANDLER. _Curiosities of the Patent Office._ Syracuse, N.Y.: published by the author, 1888. REID, J. A. _A monograph prepared for American industrial education conference and exposition._ Elizabethport, N.J.: Singer Manufacturing Company, 1915. RENTERS, WILHELM. _Praktisches Wissen von der Nähmaschine._ Langensalza, Berlin, and Leipzig: Verlag Julius Beltz, 1933. _Scientific American._ Issues of January 27, February 3, and November 24, 1849; July 17, 1852; July 9 and November 5, 1859; January 3 and May 16, 1863; October 19, 1867; and July 25, 1896. SCOTT, JOHN. _Genius rewarded, or the story of the sewing machine._ New York: J. J. Caulon, 1880. _Sewing Machine Advance._ Chicago. Vols. 1-35, no. 5, May 1879 to 1913. _Sewing Machine Journal._ September 1879 to December 1884. _Sewing Machine News._ New York. Vols. 1-6, 1877-1879; n.s. vols. 1-16, 1879-1893. _Sewing Machine Times._ New York. Vols. 1-9, 1882-1890; n.s. vols. 1-38 (nos. 1-725), 1891-April 1924. STAMBAUGH, JOHN P. _Sewing machines at the 22nd annual exhibition of the Maryland Institute, also a history of the sewing machine._ Hartford, Conn.: Weed Sewing Machine Company, 1872. Story of sewing machine patents. _New York Tribune_, May 23, 1862. THOMPSON, HOLLAND. The age of invention. Vol. 37 of the Chronicles of America. New Haven: Yale University Press, 1921. TOWERS, HENRY M. _Historical sketches relating to Spencer, Massachusetts._ Vol. 1. Spencer, Mass.: W. G. Heffernan, 1901. URQUHART, J. W. _Sewing machinery._ Vol. 8 in Weale's rudimentary scientific and educational series. London: Crosby Lockwood and Co., 1881. VAN SLYCK, J. D. _New England manufacturers and manufactories._ Vol. 2. Boston: Van Slyck and Company, 1879. [Source for biographical sketch on Allen Benjamin Wilson, Van Slyck, vol. 2, pp. 672-682.] WALSO, GEORGE C., JR. _History of Bridgeport and vicinity._ Vol. 2. Bridgeport, Conn.: S. J. Clarke Publishing Company, 1917. Who invented the sewing machine? _The Galaxy_ [article unsigned], vol. 4, August 1867. _Indexes_ Geographical Index to Companies listed in Appendix II CONNECTICUT Bridgeport D. W. Clark, 67 Jerome B. Secor, 68 Goodbody Sewing Machine Co., 69 Howe Machine Co., 69 Secor Machine Co., 72 American Hand Sewing Machine Co., 72 Wheeler & Wilson Mfg. Co., 74 Bristol Nettleton & Raymond, 72 Watson & Wooster, 73 Danbury Bartram & Fanton Mfg. Co., 66 Hartford Morrison, Wilkinson & Co., 71 Weed Sewing Machine Co., 74 Meriden Fosket and Savage, 68 Charles Parker Co., 72 Parker Sewing Machine Co., 72 Middletown Victor Sewing Machine Co., 73 Norwich Greenman and True Mfg. Co., 69 Waterbury Waterbury Co., 73 West Meriden Parkers, Snow, Brooks & Co., 70 DISTRICT OF COLUMBIA Washington Post Combination Sewing Machine Co., 72 ILLINOIS Belleville Thomas M. Cochrane Co., 71 J. H. Drew & Co., 71 Belvidere June Mfg. Co., 70 National Sewing Machine Co., 71 Chicago Chicago Sewing Machine Co., 67 Eldredge Sewing Machine Co., 68 Free Sewing Machine Co., 69 Scates, Tryber & Sweetland Mfg., 67 Sigwalt Sewing Machine Co., 67, 73 H. B. Goodrich, 69 June Mfg. Co., 70 Rockford Free Sewing Machine Co., 69 MAINE Biddeford Shaw & Clark Sewing Machine Co., 71, 73 MASSACHUSETTS Boston O. Phelps, 66 J. F. Paul & Co., 66 Boston Sewing Machine Co., 66 Bradford & Barber, mfgs., 66 John P. Bowker, 68 Empire Sewing Machine Co., 68 Finkle & Lyon Sewing Machine Co., 68, 73 Grover and Baker Sewing Machine Co., 69 Nichols and Bliss, 69 J. B. Nichols & Co., 69 Nichols, Leavitt & Co., 69, 70 N. Hunt & Co., 70 Hunt and Webster, 70 Emery, Houghton & Co., 70 Ladd, Webster & Co., 70 Leavitt & Co., 70 Leavitt Sewing Machine Co., 70 Safford & Williams Makers, 71 C. A. French, 72 F. R. Robinson, 72 Howard & Davis, 72 I. M. Singer & Co., 73 Butterfield & Stevens Mfg. Co., 74 Williams & Orvis Sewing Machine Co., 74 Chicopee Falls Shaw & Clark Co., 73 Chicopee Sewing Machine Co., 73 Florence Florence Sewing Machine Co., 67, 68 Foxboro Foxboro Rotary Shuttle Co., 68 Lowell Aetna Sewing Machine Co., 65 Lynn Woolridge, Keene and Moore, 67 Orange Gold Medal Sewing Machine Co., 69 Johnson, Clark & Co., 69, 71, 73 Grout & White, 71 New Home Sewing Machine Co., 71 Springfield Leader Sewing Machine Co., 70 Springfield Sewing Machine Co., 73 D. B. Wesson Sewing Machine Co.,74 Winchendon J. G. Folsom, 68, 69, 71 William Grout, 71 Worcester Goddard, Rice & Co., 66 MICHIGAN Detroit Decker Mfg. Co., 67 C. G. Gardner, 69 MISSOURI St. Louis Wardwell Mfg. Co., 73 NEW HAMPSHIRE Dover O. L. Reynolds Manufacturing Co., 71 Marlboro Thurston Mfg. Co., 67 Mason Village Franklin Sewing Machine Co., 68 NEW JERSEY Elizabethport Singer Mfg. Co. (manufactory, not office), 73 Paterson Whitney Sewing Machine Co., 74 NEW YORK Binghamton Independent Sewing Machine Co., 70 Brooklyn J. H. Lester, 70 G. L. Du Laney, 70 Ithaca Aiken and Felthousen (patentees), 65 American Magnetic Sewing Machine Co., 65 Clinton Brothers, 67 T. C. Thompson, 73 New York Avery Sewing Machine Co., 66 A. Bartholf, mfg., 66 Bartholf Sewing Machine Co., 66 Bartlett Sewing Machine Co., 66 Barlow & Son, 66 Beckwith Sewing Machine Co., 66 J. A. Davis, 67 Demorest Mfg. Co., 67 Charles A. Durgin, 68 Elliptic Sewing Machine Co., 68 Eureka Shuttle Sewing Machine Co., 68 Excelsior Sewing Machine Co., 68 Madame Demorest, 68 First and Frost, 68 L. Griswold, 69 Howe Sewing Machine Co., 69 Thos. A. Macauley Mfg., 70 New York Sewing Machine Co., 71 T. W. Robertson, 72 I. M. Singer & Co., 73 Singer Mfg. Co., 73 Standard Shuttle Sewing Machine Co., 73 Henry Stewart & Co., 73 Stewart Mfg. Co., 73 E. E. Lee & Co., 74 Willcox & Gibbs Sewing Machine Co., 74 Watertown Davis Sewing Machine Co., 67 Wheeler, Wilson & Co., 74 Westmoreland A. B. Buell, 67 OHIO Cleveland Wilson (W. G.) Sewing Machine Co., 66, 74 Domestic Sewing Machine Co. (after 1924), 67 Leslie Sewing Machine Co., 70 Standard Sewing Machine Co., 73 White Sewing Machine Co., 74 Dayton Davis Sewing Machine Co., 67 Elyria West & Willson Co., 74 Norwalk Dauntless Mfg. Co., 67, 72 Wm. A. Mack & Co., and N. S. Perkins, 67 Domestic Sewing Machine Co., 67, 70 Springfield Royal Sewing Machine Co., 72 St. John Sewing Machine Co., 73 Toledo Jewel Mfg. Co., 70 PENNSYLVANIA Erie Noble Sewing Machine Co., 72 Philadelphia American Buttonhole, Overseaming and Sewing Machine Co., 65 Centennial Sewing Machine Co., 67 George B. Sloat and Co., 68 Rex & Bockius, 69 Grant Bros. & Co., 69 B. W. Lacey & Co., 71 Parham Sewing Machine Co., 72 Philadelphia Sewing Machine Co., 72 Quaker City Sewing Machine Co., 72 E. Remington & Sons, 72 Taggart & Farr, 73 Pittsburgh Love Mfg. Co., 70 RHODE ISLAND Providence Household Sewing Machine Co., 69 Providence Tool Co., 69 VERMONT Brattleboro Samuel Barker and Thomas White, 66 Brattleboro Sewing Machine Co., 68 Estey Sewing Machine Co., 68 Higby Sewing Machine Co., 69 Nettleton & Raymond (Charles Raymond), 71 Windsor Lamson, Goodnow & Yale, 67, 74 Vermont Arms Co., 74 VIRGINIA Richmond Lester Mfg. Co., 70 Union Sewing Machine Co., 68, 70 Old Dominion Sewing Machine Co., 72 WISCONSIN Milwaukee Whitehill Mfg. Co., 74 Alphabetical Index to Patentees listed in Appendix III Abercrombi, Charles, 520977 Abbott, W. W., 252984 Adams, John Q., 92138 Alexander, Elisa, 16518 Ambler, D. C., 11884 Angell, Benjamin J., 19285 Applegate, John H., and Webb, Charles B., 177784 Appleton, C. J., and Sibley, J. J., 179440 Arnold, B., 86121, 138981, 138982 Arnold, G. B. and A., 30112 Arnold, G. B., 28139 Atwater, B., 44063 Atwood, J. E., 22273 Atwood, K. C., 194759 Atwood, J. E., J. C., and O., 19903 Avery, Otis, 9338, 10880 Avery, O. and Z. W., 22007 Bachelder, J., 6439 Baglin, William, 154113 Baker, G. W., 70152, 125374, 130005 Baldwin, Cyrus W., 38276 Banks, C. M., 225784 Barcellos, D., 203102 Barnes, M. M., 106307 Barnes, William T., 20688, 25084, 25876 Barney, Samuel C., 156119 Barrett, O. D., 25785 Bartholf, Abraham, 19823 Bartlett, Joseph W., 46064, 76385 Bartlett, Joseph W., and Plant, Frederick, 159065 Barton, Kate C., 182096 Bartram, W. B., 54670, 54671, 60669, 62520, 83592, 104247, 130557 Bates, W. G., assignor to Johnson, William H., 9592 Bayley, C. H., 212122 Bean, Benjamin W., 2982 Bean, E. E., 28144 Beardslee, W. F., 245781 Beck, August, 190184, 196863 Beckwith, William G., 126921, 133351, 167382 Behn, Henry, 18071, 18880 Belcher, C. D., 16710 Benedict, C. P., 83596 Bennett, Frank Howard, and Dowling, James, 409728 Bennor, Joseph, 106249 Benson, George, 238556 Beukler, William, 204704 Beuttel, Charles, 115155 Bigelow, J., 263467 Billings, C. E., 88603 Bishop, H. H., 22226 Black, Samuel S., 146642 Blake, Lyman R., 20775, 74289 Blanchard, Helen A., 141987 Bland, Henry, 216016, 221505 Blodgett, S. C, 15469, 21465 Blodgett, John W., 279320 Boecher, Adam, 300199 Bond, Joseph Jr., 12939, 93588, 189599 Booth, Ezekiel, 25087 Boppel, Jacob, 396979 Borton, S., 214089 Borton, Stockton, and Willcox, Charles H., 255576, 255577, 255580, 255581 Bosworth, C. F., 19979, 38807, 122555, 199500, 216504 Bounaz, A., 83909, 83910 Bouscay, Eloi, Jr., 127145 Bowyer, J. T., 454708 Boyd, A. H., 19171, 24003, 31864 Bracher, T. W., 221508 Bradeen, J. G., 9380 Bradford, E. F. and Pierce, V. R., 177371 Braundbeck, E., 127675 Brewer, A. G., 152894 Briggs, Thomas, 198790 Brown, F. H., 94389, 102366, 131735, 193477 Bruen, J. T., 31208 Bruen, L. B., 68839 Budlong, William G., 25946 Buell, J. S., 25381 Buhr, Johannes, 151272 Burnet, S. S. and Broderick, W., 22160 Burr, Theodore, 32023 Butcher, Joseph, 180542, 233657 Cadwell, Caleb, 45972, 71131 Cajar, Emil, 50299, 61711 Cameron, James W., 272527 Campbell, Duncan H., 241612, 241613 Canfield, F. P., 86057 Carhart, Peter S., 24098 Carlisle, W. S., 270540 Carpenter, Lunan, 20990 Carpenter, Mary P., 112016 Carpenter, William, 87633 Carr, William H. and Ostrom, F. W., 303361 Case, George F., 33029 Cately, William H., 56902 Chamberlain, J. N., 28452 Chandler, Rufus, 133757, 139368 Charmbury, H., 316745 Chase, M., 113498 Chilcott, J. and Scrimgeour, J., 12856 Chittenden, H. H., 43289 Choquette, A. E., 244033 Clark, David W., 19015, 19072, 19129, 19409, 19732, 20481, 21322, 23823 Clark, Edwin, 26336 Clark, Edwin E., 74751 Clements, James M., 57451 Cleminshaw, S., 128363, 213391 Clever, P. J., 96886 Clever, Peter J., 296529 Coates, F. S., 19684 Cole, W. H., 79447 Conant, J. S., 12233 Conklin, N. A., 206774 Cook, Hugo, 454610 Cooney, W., 102226 Corbett, E. and Harlow, C. F., 192568 Corey, J. W., 198970 Corliss, George H., 3389 Cornely, E., 73696 Cornely, Emile, 219225 Craige, E. H., 62186, 67635 Crane, Thomas, 150532 Crosby, C. O., 50225, 90507 Crosby, C. O. and Kellogg, H., 37033 Cummins, William G., 187822 Curtis, G. H. W., 228985 Cushman, C. S., 142442, 184594 Dale, John D., 44686 Dancel, Christian, 199802 Darling and Darling, 163639 Davis, Job A., 27208, 58614 Derocquigny, A. C. F., Gance, D., and Hanzo, L., 34748 Deschamps, O. L., 253915 Destouy, Auguste, 56729 Dewees, John W., 432746 Dickinson, C. W., 26346 Diehl, Philipp, 339623, 347776, 347777, 348113 Dieterle, H. E., 353542 Dimmock, Martial and Rixford, Nathan, 19135 Dimond, George H., 196198, 207400 Dinsmore, Alfred S., 160512, 231155 Dinsmore, A. S., and Carter, John T., 152618 Doll, Arnold, 68420 Dopp, H. W., 27279 Dowling, James, and Connolly, John, 299118 Drake, Ellis, 155932 Duchemin, William, 59715, 91101, 135032, 288929 Dunbar, C. F., 88282 Durgin, Charles A., 12902 Earle, T., 31156 Eickemeyer, Rudolf, 52698, 182182, 239319 Elderfield, F. D., 204429 Eldridge, G. W., 87331 Elliott, F., 85918 Emerson, John, 50989 Emswiler, J. B., 25002 Esty, William, 187837 Fales, J. F., 74328 Fanning, John, 72829, 129013 Farr, Chester N., 25004 Farrar, Arthur, 309837 Fetter, George, 18793, 19059 Fish, Warren L., 123625 Fletcher, James N., 443756 Follett, Joseph L., 189446 Fosket, William A., and Savage, Elliot, 22719, 25963 French, Stephen, 80345 Frese, B., 172308 Fuller, H. W., 63033 Fuller, William M., 32496 Garland, H. P., 159812, 169163 Gee, W. V., 361406 Gibbs, James E. A., 16234, 16434, 17427, 21129, 21751, 27214, 28851 Gird, E. D., 87559 Goodes, E. A., 136718, 147387 Goodspeed, G. N., 54816 Goodwin, Julius C., 450793 Goodwyn, H. H., 24455 Goodyear, Charles Jr., 111197, 116947 Gordon, James, and Kinert, William, 125807 Gray, Joshua, 16566, 19665, 24022, 95581 Green, George F., 238678 Greenough, John J., 2466 Gritzner, M. C., 44720, 76323 Gritzner, Max C., 243444 Grote, F. W., 38447 Grout, William, 24629 Grover, William O., 14956, 33778, 36405, 100139 Grover, William O., and Baker, William E., 7931 Guinness, William S., 41916 Gullrandsen, P. E., and Rettinger, J. C., 180225 Gutmann, Julius, 90528 Halbert, A. W., 76076 Hall, William, 24870 Hale, William S., 36084 Hall, Luther, 43404 Hall, L., 105329 Hall, John S., 168637, 187006 Hallenbeck, J. P., 425422 Hallett, H. H., 191584 Hamm, E., 219578 Hancock, Henry J., 83492, 112033 Hanlon, John, 52847 Happe, J., and Newman, W., 130715, 137199 Hardie, J. W., 30854 Harris, Daniel, 17508, 17571 Harris, David, 185228 Harrison, J. Jr., 10763, 13616, 25013, 25262 Hart, William, 50469 Hayes, James, 55029 Hayden, H. W., 24937 Heberling, J., 204604, 227249, 227525, 284300 Hecht, A., 50473 Heery, Luke, 94740 Heidenthal, William, 127765 Helwig, Arthur, 350364 Hendrick, Joseph E., 19660, 21722 Hendrickson, E. M., 34330 Henriksen, H. P., 104590, 188515, 215615 Hensel, George, 24737 Herron, A. C., 20557 Hesse, Joseph, 235085 Heyer, W. D., 40622 Heyer, Frederick, 30731 Hicks, William C., 26035, 29268 Hinkley, Jonas, 25231 Hinds, Jesse L., 131166 Hine, Charles M., 420382 Hine, Charlie M., 246136 Hodgkins, Christopher, 9365, 33085, 69666 Hoefler, J., 246883 Hoffman, George W., 94112 Hoffman, Clara P., and Meyers, Nicholas, 207035 Holden, O. J., and Griswold, L., 272050 Hollowell, J. G., 27624 Holly, Birdsill, 28176 Hook, Albert H., 22179, 24027 Horr, Addison D., 149862 House, James A., 206239 House, James A., and House, Henry A., 36932, 39442, 39445, 55865, 87338, 114294 Howard, C. W., 126056, 126057 Howard, T. S. L., 199206 Howard, E. L., 154485 Howard, E., and Jackson, W. H., 103745 Howe, Amasa Bemis, 37913 Howe, Elias, 4750, 16436 Hubbard, George W., 18904, 21537 Hull, E. H., 254217 Humphrey, D. W. G., 36617, 49627 Hunt, Walter, 11161 Huntington, Thomas S., 158214 Hurtu, Auguste J., 258761, 315037 Hurtu, Auguste J., and Hautin, Victor J., 98064 Ingalls, N., Jr., 212602 Jackson, Francis, 519064 Jackson, William, 181941 Jacob, Frederick, 190047 Jencks, G. L., 74694 Jennings, L., 16237 Johnson, Albert F., 16387, 20686, 26948 Johnson, W. H., 10597 Jones, John T., 86163, 117640, 169106 Jones, Samuel H., 140631 Jones, Solomon, 118537, 118538 Jones, William, and Haughian, P., 32297 Juengst, George, 27132, 228820 Junker, Carl, 217112 Kallmeyer, G., 137689 Keats, Alphonso, 260990 Keats, John, 198120 Keats, John; Greenwood, Arthur; and Keats, Alphonso, 171622 Keats, John, and Clark. Wm. S., 50995 Keith, Jeremiah, 97518, 170741, 196809, 209126, 243710 Keith, T. H., 196909 Keith, T. K., 170955 Kelsey, D., 24939 Kendall, George F., 101887 Kern, Ferdinand, 479369 Kilbourn, E. E., 59746 Kjalman, H. N., 235783 Knoch, Charles F., 183400 Koch, William, 262298 Koch, Friederich, and Brass, Robert, 138898, 145215 Lamb, Isaac W., 109632 Lamb, Thomas, 98390, 118728 Lamb, Thomas, and Allen, John, 49421 Lamson, Henry P., 79579 Landfear, William R., 109427, 155193 Langdon, Leander W., 13727, 39256 Lathbury, E. T., 17744 Lathrop, Lebbeus W., 139067 Lathrop, Lebbeus W., and de Sanno, William P., 40446 Lawrence, G. H., 290895 Lazelle, W. H., 18915 Leavitte, Albert, 171147 Leavitt, Rufus, 30634 Leavitt, Albert, and Drew, Henry L., 187874 Legat, D. M., 218388 Legg, Albert, and Weston, Charles W., 474840 Leslie, A. M., 241808 Leyden, Austin, 57157 Lingley, John W., 368538 Lipe, C. E., 229322 Lisle, Myron C., 428171 Ludeke, Waldemar, 275506, 300380 Lyon, Lucius, 89489, 96713, 105820 Lyon, W., 12066 Macauley, F. A., 195939 Mack, William A., 38592 Mallary, G. H., 31897 Mann, Charles, 33556 Marble, F. E., 33439 Marin, Charles, 179709 Martin, W., Jr.; Dawson, D. R.; and Orchar, R., 206743 Martine, Charles F., 104612 Meyers, Nicholas, 99783 Melhuish, R. M., 194610 McCloskey, John, 55688, 161534 McClure, A. T., 130385 McKay, Gordon, and Blake, Lyman, 42916 McKay, Gordon, 188809 McLean, J. N., 88499 McCombs, George F., 208407 McCurdy, James S., 24395, 26234, 28097, 28993, 36256, 38931, 46303, 53743 Miehling, Charles, 351992 Miller, Charles, 9139, 26462 Miller, Westley, 20763 Miller, Lebbens B., and Diehl, Philipp, 229629, 274359 Mills, Daniel, 96944, 265850, 313359 Mooney, John H., 222298, 244470 Moore, Charles, 21015 Moreau, Eugene, 110669, 156171 Morley, J. H., 228918, 236350 Morrell, R. W.; Parkinson, T.; Parkinson, J., 202857 Morrison, T. W., 216289 Muegge, C. A., 332207 Mueller, H., 28996 Muir, William, 147152 Murphy, E., 176880 Nasch, Isidor, 104630 Necker, Carl, 117101 Nettleton, William H., and Raymond, Charles, 17049, 18350 Newell, George F., 242470 Newlove, Thomas, 27761 Norton, B. F., 32782 O'Neil, John, 137618 Oram, Henry, 185952 Osborne, J. H., 224219 Otis, S. L., 221093 Osterhout, James A., and Hallenbeck, Joseph P., 402610 Page, Charles, 96343, 150479 Paine, A. R., 27412 Palmateer, William A., 187479 Palmer, Aaron, 35252 Palmer, C. H., 38450, 124694, 240758 Palmer, Frank L., 185954 Palmer, John H., 298228 Parham, Charles, 109443, 135579 Parker, Sidney, 19662, 24780 Parks, Volney, 129981 Parmenter, Charles O., 212495 Payne, R. S., 30641 Pearson, M. H., 199991 Pearson, William, 26201 Pearson, William, 166805, 172478 Perry, James, 22148 Piper, D. B., 56990 Pipo, John A., 37550 Pitt, James; Joseph; Edward; and William, 117203 Planer, Louis, 43927 Porter, D. A., 144864 Porter, Alonzo, 99704 Porter, D'Arcy, and Baker, George W., 174703 Powell, Thomas, 442695 Pratt, Samuel F., 16745, 22240 Ragan, Daniel, 137321 Ramsden, John W., 262116 Randel, William, 192008 Rayer, William A., and Lincoln, William S., 108827 Raymond, Charles, 19612, 22220, 32785, 32925 Reed, T. K., 60241, 62287 Rehfuss, George, 40311, 51086, 61102, 73119 Reynolds, O. S., 19793 Rice, T. M., 176686 Rice, Quartus, 31429 Richards, Jean E., 252799 Richardson, E. F., 145687 Richardson, Everett P., 146948, 165506 Roberts, William, 254696 Robertson, T. J. W., 12015 Robinson, Charles E., 110790 Robinson, Frederick R., 7824 Rodier, Peter, 59659 Roper, S. H., 11531, 16026, 18522 Rose, Israel M., 28814, 31628 Rose, Reubin M., 170596 Rosenthal, Sally Adolph, 353970 Ross, Noble G., 31829 Ross, J. G., and Miller, T. L., 138764 Rowe, James, 26638, 27260 Ruddick, H., 28538 Rudolph, Bruno, 99481 Rudolph, Ernst B. (deceased), Boulter, W. E. (administrator), 449927 Russell, W. W., 86695 Sage, William, 17717 Sangster, Amos W., 21929 Savage, Elliott, 19876 Sawyer, Irvin P., and Alsop, T., 25918 Sawyer, Sylvanus, and Esty, William, 174159 Schmidt, Albert E., 162697 Schwalback, M., 56805 Scofield, Charles, 26059 Scofield, Charles, and Rice, Clarke, 28610 Scribner, Benjamin, Jr., 146483 Secor, J. B., 253772 Sedmihradsky, A. J., 196486 Shaw, E., 230580 Shaw, Philander, 11680 Shaw, A. B., 37202 Shaw, Henry L., 32007 Shaw and Clark, 38246 Sheffield, G. V., 135047 Shorey, Samuel W., 148765 Sibley, J. J., 42117 Sidenberg, William, 112745, 115117 Simmons, Frederick, 216902 Simmons, A. G., and Scofield, C., 41790 Singer, Isaac M., 8294, 10975, 12364, 13065, 13661, 13662, 14475, 60433, 61270 Smalley, J., 27577 Smith, DeWitt C., 45528 Smith, E. H., 20739, 21089, 96160 Smith, H. B., 12247 Smith, J. M., 31334 Smith, Lewis H., 31411, 32385 Smith, John C., 34988 Smith, James H., 148902 Smith, Wilson H., 28785 Smith, W. M., 225199 Smith, William T., 99743 Smyth, D. M., 126845, 234732 Snediker, J. F., 222089 Snyder, Watson, 22987 Spencer, James C., 24061 Spencer, James H., and Lamb, Thomas, 22137 Speirs, John, 152813 Spoehr, F., 101779 Springer, William A., 128919, 142290, 147441 Stackpole, G., and Applegate, J. H., 220314 Stannard, M., 64184 Stedman, G. W., 12074, 12573, 12798, 13856 Stein, M. J., 81956, 113593 Stevens, George, and Hendy, Joshua, 111488 Steward, A., 207454 Stewart, James, Jr., 141397, 432449 Stewart, W. T., 205698 Stoakes, J. W., 32456 Sullivan, John J., 179232 Sutton, William A., 29202 Swartwout, H. L., 89357 Swingle, A., 14207 Taft, J. C., 547866 Tapley, G. S., 25059 Tarbox, John N., 49803 Tate, William J., 113704 Taylor, F. B., 146721 Temple, John, 358088 Thayer, Augustus, 172205 Thimonnier, E., and Vernaz, C., 287592 Thomas, Joseph, 330170 Thomas, J., 236466 Thompson, J., 27082 Thompson, T. C., 9641 Thompson, Rosewell, 34926, 42449 Thurston, C. H., 233300 Tittman, Alexander, 89093, 136792 Toll, Charles F., 171193 Tracy, Dwight, 30012 Tracy, Dwight, and Hobbs, George, 40000 Trip, J., 308711 True, Cyrus B., 148336 Tucker, R. D., 320898 Tucker, Joseph C., 56641 Turner, M. G., 312306 Turner, S. S., 133553 Tuttle, J. W., and Keith, T. K., 219782 Thompson, George, 115255 Uhlinger, W. P., 21224 Upson, L. A., 176153 Van Vechten, O. R., 302063 Varicas, L., 204864 Venner, O., 133814 Veukler, W., 255916 Wagener, Jeptha A., 40296 Walker, William, 141407, 176101, 320099, 353720 Walker and Bennet, 428548 Ward, D. T., 12146 Wardwell, Simon W., Jr., 128684, 141245, 148339 Warth, Albin, 56646, 73064 Washburn, T. S., 30031 Waterbury, Enos, 79037 Watson, William C., 14433, 18834 Weber, Theodore A., 145823, 166236 Webb, T., and Heartfield, C. H., 213537 Webster, W., 182249, 402497 Weitling, W., 37931, 45777 Wells, W. W., 209843 Wensley, James, 152055, 207230 West, Elliott P., 117708, 130674, 138772 West, H. B., and Willson, H. F., 20753 Wheeler, Nathaniel, 420847 Wheeler, Nathaniel, and Dial, Wilbur F., 328165 Wheeler, Darius, and Carpenter, Lunan, 21100 Whitehill, Robert, 166172 Wickersham, William, 9679, 18068, 18069 Wilder, M. G., 32323 Wilkins, J. N., 36591 Wilkinson, Charles E., 269251 Willcox, Charles H., 42036, 43819, 44490, 44491, 218413, 230212, 246700 Willcox, C. H., and Borton, S., 472094 Willcox, C. H., and Carleton, C., 116521, 116523, 116783 Wilson, Allen B., 7776, 8296, 9041 Wiseman, Edmund, 228711 Witherspoon, S. A., 176211 Winter, William, 88936 Wollenberg, H., and Priesner, J., 206848 Wood, John, 185811 Wood, Richard G., 207928 Woodruff, George B., and Browning, George, 97014 Woodward, E., 247285 Woodward, F. G., 25782 Woodward, Erastus, and Keith, Thomas K., 316927 Wormald, William, and Dobson, Edmund, 169881 Young, E. S., and Dimond, G. H., 206992 General Index to Chapters 1-4 Adams and Dodge, 9 Aetna Sewing Machine Company, 40 American Buttonhole and Sewing Machine Company, 40 Archbold, Thomas, 13 Arrowsmith, George A., 11 Bachelder, John, 22, 30, 34, 41, 42 Baker, William E., 36 (_see_ Grover & Baker) Bartholf, A., 24, 40 Bartlett Sewing Machine Company, 40 Bartram & Fanton Manufacturing Company, 40 Bean, Benjamin W., 13, 14, 15 Blees Sewing Machine Company, 40 Bliss, George, 24 Blodgett and Lerow, 24, 26, 30 Blodgett, Sherbrune C., 25 Bradshaw, John A., 21, 22, 26, 27 Brown, W. N., 50 Centennial Sewing Machine Company, 40 Chapman, Edward Walter, 7, 19 Chapman, William, 7 Clark, D. W., 47, 49 Clark, Edward, 33, 34, 35 Combination, Sewing-Machine, 23, 24, 38, 41-42, 47, 48 Conant, Jotham S., 22 Corliss, George H., 14, 15, 16 Dale, John D., 54 Davis, Ari, 19 Davis Sewing Machine Company, 40 Demorest, Madame, 53 Dodge, Rev. John Adam, 9 Domestic Sewing Machine Company, 40 Duncan, John, 6, 19 Elliptic Sewing Machine Company, 40 Ellithorp, S. B., 51 Ellithorp & Fox, 51 Empire Sewing Machine Company, 40 Fairy Sewing Machine, 53 Family Sewing Machine (Singer), 35 Finkle & Lyon Manufacturing Company, 40 Fisher, George, 19 Fisher, John, 15, 16 Florence Sewing Machine Company, 40 Folsom, J. G., 40 Gibbons, James, 15 Gibbs, James E. A., 45, 48 Goddard, Rice & Co., 25 Gold Medal Sewing Machine Company, 40, 53 Goodspeed & Wyman Sewing Machine Company, 40 Grasshopper, The, 35 Greenough, John J., 13, 14 Grover & Baker Sewing Machine Company, 24, 35, 37, 38, 40, 41 Grover, William O., 35, 38 Heberling, John, 54 Henderson, James, 6 Hendrick, Joseph, 49 Heyer, W. D., 52 Hook, Albert H., 50 Howe, Amasa B., 24 Howe, Elias, Jr., 11, 18, 19, 20, 21, 22, 23, 24, 28, 29, 33, 34, 41, 42, 138 (biographical sketch) Howe Machine Company (Elias), 25 Howe Sewing Machine Company (Amasa, then B. P.), 24, 25, 40 Hunt, Walter, 10, 11, 19, 33, 138 (biographical sketch) Jenny Lind (sewing machine), 30 Johnson, Joseph B., 22 Keystone Sewing Machine Company, 40 Kline, A. P., 27 Knowles, John, 9 Krems, Balthasar, 7, 19 Ladd & Webster Sewing Machine Company, 40 Leavitt Sewing Machine Company, 40 Lee, Edward, 27 Lee, E. & Co., 27, 28 Lerow, John A., 24, 25 Little Gem, 53 London Sewing Machine, 22 Lye, Henry, 9 McKay Sewing Machine Association, 40 Madersperger, Josef, 8, 9, 12, 13 Magnin, Jean Marie, 11, 22 Mason, The Honorable Charles, 13 Morey, Charles, 22 Morey & Johnson, 23, 34, 42 Newton, Edward, 13 Nichols and Bliss, 24 Palmer, Aaron, 52 Parham Sewing Machine Company, 40 Perry, James, 49 Phelps, Orson C., 25, 30, 31 Potter, Orlando B., 37, 38, 41 Remington Sewing Machine Company, 40 Robertson, T. J. W., 47 Rodgers, James, 15 Safford & Williams Makers, 22 Saint, Thomas, 4, 5, 19 Secor Sewing Machine Company, 40 Shaw & Clark Sewing Machine Co., 40, 54 Singer, Isaac Merritt, 23, 25, 30, 31, 33, 34, 35, 41, 142 (biographical sketch) Singer, I. M. Company, 13, 32, 34, 40 Singer Manufacturing Co., 30, 40, 42 Singer's Perpendicular Action Sewing Machine, 30, 31 Stone, Thomas, 6 Thimonnier, Barthelemy, 11, 19, 137 (biographical sketch) Thomas, William, 20 Thompson, C. F., 40 Turtleback Machine (Singer), 35 Union Buttonhole Machine Company, 40 Warren and Woodruff, 28 Weatherill, Jacob, 37 Weed Sewing Machine Company, 40 Weisenthal, Charles F., 4, 19 Wheeler & Wilson Manufacturing Company, 22, 29, 30, 40 Wheeler, Wilson and Company, 24, 28, 41 Wheeler, Nathaniel, 27, 28 Willcox and Gibbs Sewing Machine Company, 40, 46, 48 Willcox, Charles, 46, 48 Willcox, James, 46 Wilson, Allen Benjamin, 26, 27, 28, 29, 30, 141 (biographical sketch). (_See_ Wheeler & Wilson.) Wilson, Newton, 4 Wilson, (W. G.), Sewing Machine Company, 40 Woolridge, Keene, and Moore, 24 Zieber, George, 30, 33 Transcriber's Notes: Table layouts have been changed to avoid very long line lengths. Footnotes have been moved to Chapter ends. Minor punctuation errors have been corrected without note. The following typographical errors have been corrected/noted: Footnote 9 "Praktisches Wissen von der Nähmaschine."--was "Praktisches wissen von der Nähmaschine." p. 11 "a loop in the other"--was "a loop in the the other" p. 19 "chainstitch, Thimonnier used"--was "chainstitch, Thimmonier used" p. 76 "known to be in existence is"--was "known to be in eixstence is" p. 80 "7501-12500, 1873;"--was "7501-12500, 8173;" p. 119 "shaped like an open [?] into which"--A letter or symbol appears to be missing in the original between open and into. p. 119 "181161-220318"--overlaps range of previous entry. p. 130 "June 30, 1874 |152,618"--was "Jan. 30, 1874 |152,618" p. 138 "Villefranche-sur-Saône"--was "Ville-franche-sur-Saône" p. 145 "Praktisches Wissen von der Nähmaschine."--was "Praktisches wissin von der Nähmaschine." p. 153 "O'Neil, John, 137618"--was "O'Niel, John, 137618" 
39329	----	[Illustration: BALDWIN LOCOMOTIVE WORKS. [Bird's-Eye View.]] BALDWIN LOCOMOTIVE WORKS. ILLUSTRATED CATALOGUE OF LOCOMOTIVES. M. BAIRD & Co., PHILADELPHIA. MATTHEW BAIRD, GEORGE BURNHAM, CHARLES T. PARRY, EDWARD H. WILLIAMS, WILLIAM P. HENSZEY, EDWARD LONGSTRETH. PRESS OF J. B. LIPPINCOTT & CO., PHILADELPHIA. SKETCH OF THE BALDWIN LOCOMOTIVE WORKS. THE BALDWIN LOCOMOTIVE WORKS dates its origin from the inception of steam railroads in America. Called into existence by the early requirements of the railroad interests of the country, it has grown with their growth and kept pace with their progress. It has reflected in its career the successive stages of American railroad practice, and has itself contributed largely to the development of the locomotive as it exists to-day. A history of the Baldwin Locomotive Works, therefore, is, in a great measure, a record of the progress of locomotive engineering in this country, and as such cannot fail to be of interest to all who are concerned in this important element of our material progress. MATTHIAS W. BALDWIN, the founder of the establishment, learned the trade of a jeweler, and entered the service of Fletcher & Gardiner, Jewelers and Silversmiths, Philadelphia, in 1817. Two years later he opened a small shop, in the same line of business, on his own account. The demand for articles of this character falling off, however, he formed a partnership, in 1825, with David Mason, a machinist, in the manufacture of bookbinders' tools and cylinders for calico-printing. Their shop was in a small alley which runs north from Walnut Street, above Fourth. They afterwards removed to Minor Street, below Sixth. The business was so successful that steam-power became necessary in carrying on their manufactures, and an engine was bought for the purpose. This proving unsatisfactory, Mr. Baldwin decided to design and construct one which should be specially adapted to the requirements of his shop. One of these requirements was that it should occupy the least possible space, and this was met by the construction of an upright engine on a novel and ingenious plan. On a bed-plate about five feet square an upright cylinder was placed; the piston-rod connected to a cross-bar having two legs, turned downward, and sliding in grooves on the sides of the cylinder, which thus formed the guides. To the sides of these legs, at their lower ends, was connected by pivots an inverted U-shaped frame, prolonged at the arch into a single rod, which took hold of the crank of a fly-wheel carried by upright standards on the bed-plate. It will be seen that the length of the ordinary separate guide-bars was thus saved, and the whole engine was brought within the smallest possible compass. The design of the machine was not only unique, but its workmanship was so excellent, and its efficiency so great, as readily to procure for Mr. Baldwin orders for additional stationary engines. His attention was thus turned to steam engineering, and the way was prepared for his grappling with the problem of the locomotive when the time should arrive. This original stationary engine, constructed prior to 1830, has been in almost constant service since its completion, and at this day is still in use, furnishing all the power required to drive the machinery in the erecting-shop of the present works. The visitor who beholds it quietly performing its regular duty in a corner of the shop, may justly regard it with considerable interest, as in all probability the indirect foundation of the Baldwin Locomotive Works, and permitted still to contribute to the operation of the mammoth industry which it was instrumental in building up. The manufacture of stationary steam-engines thus took a prominent place in the establishment, and Mr. Mason shortly afterward withdrew from the business. In 1829-30 the use of steam as a motive power on railroads had begun to engage the attention of American engineers. A few locomotives had been imported from England, and one (which, however, was not successful) had been constructed at the West Point Foundry, in New York City. To gratify the public interest in the new motor, Mr. Franklin Peale, then proprietor of the Philadelphia Museum, applied to Mr. Baldwin to construct a miniature locomotive for exhibition in his establishment. With the aid only of the imperfect published descriptions and sketches of the locomotives which had taken part in the Rainhill competition in England, Mr. Baldwin undertook the work, and on the 25th of April, 1831, the miniature locomotive was put in motion on a circular track made of pine boards covered with hoop iron, in the rooms of the Museum. Two small cars, containing seats for four passengers, were attached to it, and the novel spectacle attracted crowds of admiring spectators. Both anthracite and pine-knot coal were used as fuel, and the exhaust steam was discharged into the chimney, thus utilizing it to increase the draught. The success of the model was such that, in the same year, Mr. Baldwin received an order for a locomotive from the Philadelphia, Germantown and Norristown Railroad Company, whose short line of six miles to Germantown was operated by horse-power. The Camden and Amboy Railroad Company had shortly before imported a locomotive from England, which was stored in a shed at Bordentown. It had not yet been put together; but Mr. Baldwin, in company with his friend, Mr. Peale, visited the spot, inspected the detached parts, and made a few memoranda of some of its principal dimensions. Guided by these figures and his experience with the Peale model, Mr. Baldwin commenced the task. The difficulties to be overcome in filling the order can hardly be appreciated at this day. There were few mechanics competent to do any part of the work on a locomotive. Suitable tools were with difficulty obtainable. Cylinders were bored by a chisel fixed in a block of wood and turned by hand. Blacksmiths able to weld a bar of iron exceeding one and one-quarter inches in thickness, were few, or not to be had. It was necessary for Mr. Baldwin to do much of the work with his own hands, to educate the workmen who assisted him, and to improvise tools for the various processes. The work was prosecuted, nevertheless, under all these difficulties, and the locomotive was finally completed, christened the "Old Ironsides," and tried on the road, November 23, 1832. The circumstances of the trial are fully preserved, and are given, further on, in the extracts from the journals of the day. Despite some imperfections, naturally occurring in a first effort, and which were afterward, to a great extent, remedied, the engine was, for that early day, a marked and gratifying success. It was put at once into service, as appears from the Company's advertisement three days after the trial, and did duty on the Germantown road and others for over a score of years. [Illustration: Fig. 1.--THE "OLD IRONSIDES," 1832.] The "Ironsides" was a four-wheeled engine, modeled essentially on the English practice of that day, as shown in the "Planet" class, and weighed, in running order, something over five tons. The rear or driving-wheels were fifty-four inches in diameter on a crank-axle placed in front of the fire-box. The cranks were thirty-nine inches from centre to centre. The front wheels, which were simply carrying wheels, were forty-five inches in diameter, on an axle placed just back of the cylinders. The cylinders were nine and one-half inches in diameter by eighteen inches stroke, and were attached horizontally to the outside of the smoke-box, which was D-shaped, with the sides receding inwardly, so as to bring the centre line of each cylinder in line with the centre of the crank. The wheels were made with heavy cast-iron hubs, wooden spokes and rims, and wrought-iron tires. The frame was of wood, placed outside the wheels. The boiler was thirty inches in diameter, and contained seventy-two copper flues, one and one-half inches in diameter and seven feet long. The tender was a four-wheeled platform, with wooden sides and back, carrying an iron box for a water-tank, inclosed in a wooden casing, and with a space for fuel in front. The engine had no cab. The valve-motion was given by a single loose eccentric for each cylinder, placed on the axle between the crank and the hub of the wheel. On the inside of the eccentric was a half-circular slot, running half-way around. A stop was fastened to the axle at the arm of the crank, terminating in a pin which projected into the slot. This pin would thus hold the eccentric at one end or the other of the half-circular slot, and the engine was reversed by moving the eccentric about the axle, by means of movable hand-levers set in sockets in the rock-shafts, until it was arrested and held by the pin at one end or the other of the slot. The rock-shafts, which were under the footboard, had arms above and below, and the eccentric-straps had each a forked rod, with a hook, or an upper and lower latch or pin, at their extremities, to engage with the upper or lower arm of the rock-shaft. The eccentric-rods were raised or lowered by a double treadle, so as to connect with the upper or lower arm of the rock-shaft, according as forward or backward gear was desired. A peculiarity in the exhaust of the "Ironsides" was that there was only a single straight pipe running across from one cylinder to the other, with an opening in the upper side of the pipe, midway between the cylinders, to which was attached at right angles the perpendicular pipe into the chimney. The cylinders, therefore, exhausted against each other; and it was found, after the engine had been put in use, that this was a serious objection. This defect was afterwards remedied by turning each exhaust-pipe upward into the chimney, substantially as is now done. The steam-joints were made with canvas and red-lead, as was the practice in English locomotives, and in consequence much trouble was caused, from time to time, by leaking. The price of the engine was to have been $4000, but some difficulty was found in procuring a settlement. The Company claimed that the engine did not perform according to contract; and objection was also made to some of the defects alluded to. After these had been corrected as far as possible, however, Mr. Baldwin finally succeeded in effecting a compromise settlement, and received from the Company $3500 for the machine. We are indebted for the sketch of the "Ironsides" from which the accompanying cut is produced, as well as for other valuable particulars in regard to the engine, to Mr. H. R. Campbell, who was the Chief Engineer of the Germantown and Norristown Railroad when the "Ironsides" was placed in service, and who is thoroughly familiar with all the facts in regard to the engine. Much of the success of the machine was due to his exertions, as, while the President of the Company was inclined to reject it as defective, Mr. Campbell was earnest in his efforts to correct its imperfections, and his influence contributed largely to retain the engine on the road. The results of the trial and the impression produced by it on the public mind may be gathered from the following extracts from the newspapers of the day: The _United States Gazette_ of Nov. 24th, 1832, remarks: "A most gratifying experiment was made yesterday afternoon on the Philadelphia, Germantown and Norristown Railroad. The beautiful locomotive engine and tender, built by Mr. Baldwin, of this city, whose reputation as an ingenious machinist is well known, were for the first time placed on the road. The engine traveled about six miles, working with perfect accuracy and ease in all its parts, and with great velocity." The _Chronicle_ of the same date noticed the trial more at length, as follows: "It gives us pleasure to state that the locomotive engine built by our townsman, M. W. Baldwin, has proved highly successful. In the presence of several gentlemen of science and information on such subjects, the engine was yesterday placed upon the road for the first time. All her parts had been previously highly finished and fitted together in Mr. Baldwin's factory. She was taken apart on Tuesday and removed to the Company's depot, and yesterday morning she was completely together, ready for travel. After the regular passenger cars had arrived from Germantown in the afternoon, the tracks being clear, preparation was made for her starting. The placing fire in the furnace and raising steam occupied twenty minutes. The engine (with her tender) moved from the depot in beautiful style, working with great ease and uniformity. She proceeded about half a mile beyond the Union Tavern, at the township line, and returned immediately, a distance of six miles, at a speed of about twenty-eight miles to the hour, her speed having been slackened at all the road crossings, and it being after dark, but a portion of her power was used. It is needless to say that the spectators were delighted. From this experiment there is every reason to believe this engine will draw thirty tons gross, at an average speed of forty miles an hour, on a level road. The principal superiority of the engine over any of the English ones known, consists in the light weight,--which is but between four and five tons,--her small bulk, and the simplicity of her working machinery. We rejoice at the result of this experiment, as it conclusively shows that Philadelphia, always famous for the skill of her mechanics, is enabled to produce steam-engines for railroads combining so many superior qualities as to warrant the belief that her mechanics will hereafter supply nearly all the public works of this description in the country." On subsequent trials, the "Ironsides" attained a speed of thirty miles per hour, with its usual train attached. So great were the wonder and curiosity which attached to such a prodigy, that people flocked to see the marvel, and eagerly bought the privilege of riding after the strange monster. The officers of the road were not slow to avail themselves of the public interest to increase their passenger receipts, and the following advertisement from _Poulson's American Daily Advertiser_ of Nov. 26, 1832, will show that as yet they regarded the new machine rather as a curiosity and a bait to allure travel than as a practical, every-day servant: "NOTICE.--The locomotive engine (built by M. W. Baldwin, of this city) will depart daily, _when the weather is fair_, with a train of passenger cars. _On rainy days horses will be attached._" This announcement did not mean that in wet weather horses _would be attached to the locomotive_ to aid if in drawing the train, but that the usual horse-cars would be employed in making the trips upon the road without the engine. Upon making the first trip to Germantown with a passenger train with the Ironsides, one of the drivers slipped upon the axle, causing the wheels to track less than the gauge of the road and drop in between the rails. It was also discovered that the valve arrangement of the pumps was defective, and they failed to supply the boiler with water. The shifting of the driving wheel upon the axle fastened the eccentric, so that it would not operate in backward motion. These mishaps caused delay, and prevented the engine from reaching its destination, to the great disappointment of all concerned. They were corrected in a few days, and the machine was used in experimenting upon its efficiency, making occasional trips with trains to Germantown. The road had an ascending grade, nearly uniform, of thirty-two feet per mile, and for the last half-mile of forty-five feet per mile, and it was found that the engine was too light for the business of the road upon these grades. Such was Mr. Baldwin's first locomotive; and it is related of him that his discouragement at the difficulties which he had undergone in building it and in finally procuring a settlement for it was such that he remarked to one of his friends, with much decision, "That is our last locomotive." It was some time before he received an order for another, but meanwhile the subject had become singularly fascinating to him, and occupied his mind so fully that he was eager to work out his new ideas in a tangible form. [Illustration: Fig. 2.--HALF-CRANK.] Shortly after the "Ironsides" had been placed on the Germantown road, Mr. E. L. Miller, of Charleston, S. C, came to Philadelphia and made a careful examination of the machine. Mr. Miller had, in 1830, contracted to furnish a locomotive to the Charleston and Hamburg Railroad Company, and accordingly the engine "Best Friend" had been built under his direction at the West Point Foundry, New York. After inspecting the "Ironsides," he suggested to Mr. Baldwin to visit the Mohawk and Hudson Railroad and examine an English locomotive which had been placed on that road in July, 1831, by Messrs. Robert Stephenson & Co., of Newcastle, England. It was originally a four-wheeled engine of the "Planet" type, with horizontal cylinders and crank-axle. The front wheels of this engine were removed about a year after the machine was put at work, and a four-wheeled swiveling or "bogie" truck substituted. The result of Mr. Baldwin's investigations was the adoption of this design, but with some important improvements. Among these was the "half-crank," which he devised on his return from this trip, and which he patented September 10, 1834. In this form of crank, shown in Figure 2, the outer arm is omitted, and the wrist is fixed in a spoke of the wheel. In other words, the wheel itself formed one arm of the crank. The result sought and gained was that the cranks were strengthened, and, being at the extremities of the axle, the boiler could be made larger in diameter and placed lower. The driving axle could also be placed back of the fire-box, the connecting rods passing by the sides of the fire-box and taking hold inside of the wheels. This arrangement of the crank also involved the placing of the cylinders outside the smoke-box, as was done on the "Ironsides." By the time the order for the second locomotive was received, Mr. Baldwin had matured this device and was prepared to embody it in practical form. The order came from Mr. E. L. Miller in behalf of the Charleston and Hamburg Railroad Company, and the engine bore his name, and was completed February 18, 1834. It was on six wheels; one pair being drivers, four and a half feet in diameter, with half-crank axle placed back of the fire-box as above described, and the four front wheels combined in a swiveling truck. The driving-wheels, it should be observed, were cast in solid bell-metal. The combined wood and iron wheels used on the "Ironsides" had proved objectionable, and Mr. Baldwin, in his endeavors to find a satisfactory substitute, had recourse to brass. June 29, 1833, he took out a patent for a cast-brass wheel, his idea being that by varying the hardness of the metal the adhesion of the drivers on the rails could be increased or diminished at will. The brass wheels on the "Miller," however, soon wore out, and the experiment with this metal was not repeated. The "E. L. Miller" had cylinders ten inches in diameter; stroke of piston, sixteen inches; and weighed, with water in the boiler, seven tons eight hundredweight. The boiler had a high dome over the fire-box, as shown in Figure 3; and this form of construction, it may be noted, was followed, with a few exceptions, for many years. The valve-motion was given by a single fixed eccentric for each cylinder. Each eccentric-strap had two arms attached to it, one above and the other below, and, as the driving-axle was back of the fire-box, these arms were prolonged backward under the footboard, with a hook on the inner side of the end of each. The rock-shaft had arms above and below its axis, and the hooks of the two rods of each eccentric were moved by hand-levers so as to engage with either arm, thus producing backward or forward gear. This form of single eccentric, peculiar to Mr. Baldwin, was in the interest of simplicity in the working parts, and was adhered to for some years. It gave rise to an animated controversy among mechanics as to whether, with its use, it was possible to get a lead on the valve in both directions. Many maintained that this was impracticable; but Mr. Baldwin demonstrated by actual experience that the reverse was the case. Meanwhile the Commonwealth of Pennsylvania had given Mr. Baldwin an order for a locomotive for the State Road, as it was then called, from Philadelphia to Columbia, which, up to that time, had been worked by horses. This engine, called the "Lancaster," was completed in June, 1834. It was similar to the "Miller," and weighed seventeen thousand pounds. After it was placed in service, the records show that it hauled at one time nineteen loaded burden cars over the highest grades between Philadelphia and Columbia. This was characterized at the time by the officers of the road as an "unprecedented performance." The success of the machine on its trial trips was such that the Legislature decided to adopt steam-power for working the road, and Mr. Baldwin received orders for several additional locomotives. Two others were accordingly delivered to the State in September and November respectively of that year, and one was also built and delivered to the Philadelphia and Trenton Railroad Company during the same season. This latter engine, which was put in service October 21, 1834, averaged twenty-one thousand miles per year to September 15, 1840. [Illustration: Fig. 3.--BALDWIN ENGINE, 1834.] Five locomotives were thus completed in 1834, and the new business was fairly under way. The building in Lodge Alley, to which Mr. Baldwin had removed from Minor Street, and where these engines were constructed, began to be found too contracted, and another removal was decided upon. A location on Broad and Hamilton Streets (the site, in part, of the present works) was selected, and a three-story L-shaped brick building, fronting on both streets, erected. This was completed and the business removed to it during the following year (1835). The original building still stands, forming the office, drawing-room, and principal machine-shops of the present works. These early locomotives, built in 1834, were the types of Mr. Baldwin's practice for some years. Their general design is shown in Figure 3. All, or nearly all of them, embraced several important devices, which were the results of his study and experiments up to that time. The devices referred to were patented September 10, 1834, and the same patent covered the four following inventions, viz.: 1. The half-crank, and method of attaching it to the driving-wheel. (This has already been described.) [Illustration: Fig. 4.--BALDWIN COMPOUND WOOD AND IRON WHEELS, 1834.] 2. A new mode of constructing the wheels of locomotive engines and cars. In this the hub and spokes were of cast-iron, cast together. The spokes were cast without a rim, and terminated in segment flanges, each spoke having a separate flange disconnected from its neighbors. By this means, it was claimed, the injurious effect of the unequal expansion of the materials composing the wheels was lessened or altogether prevented. The flanges bore against wooden felloes, made in two thicknesses, and put together so as to break joints. Tenons or pins projected from the flanges into openings made in the wooden felloes, to keep them in place. Around the whole the tire was passed and secured by bolts. The above sketch shows the device. 3. A new mode of forming the joints of steam and other tubes. This was Mr. Baldwin's invention of ground joints for steam-pipes, which was a very valuable improvement over previous methods of making joints with red-lead packing, and which rendered it possible to carry a much higher pressure of steam. 4. A new mode of forming the joints and other parts of the supply-pump, and of locating the pump itself. This invention consisted in making the single guide-bar hollow and using it for the pump-barrel. The pump-plunger was attached to the piston-rod at a socket or sleeve formed for the purpose, and the hollow guide-bar terminated in the vertical pump-chamber. This chamber was made in two pieces, joined about midway between the induction and eduction-pipes. This joint was ground steam-tight, as were also the joints of the induction-pipe with the bottom of the lower chamber, and the flange of the eduction-pipe with the top of the upper chamber. All these parts were held together by a stirrup with a set-screw in its arched top, and the arrangement was such that by simply unscrewing this set-screw the different sections of the chamber, with all the valves, could be taken apart for cleaning or adjusting. The cut below illustrates the device. [Illustration: Fig. 5.--PUMP AND STIRRUP.] It is probable that the five engines built during 1834 embodied all, or nearly all, these devices. They all had the half-crank, the ground joints for steam-pipes (which was first made by him in 1833), and the pump formed in the guide-bar, and all had the four-wheeled truck in front, and a single pair of drivers back of the fire-box. On this position of the driving-wheels, Mr. Baldwin laid great stress, as it made a more even distribution of the weight, throwing about one-half on the drivers and one-half on the four-wheeled truck. It also extended the wheel-base, making the engine much steadier and less damaging to the track. Mr. William Norris, who had established a locomotive works in Philadelphia in 1832, was at this time building a six-wheeled engine with a truck in front and the driving-wheels placed in front of the fire-box. Considerable rivalry naturally existed between the two manufacturers as to the comparative merits of their respective plans. In Mr. Norris's engine, the position of the driving-axle in front of the fire-box threw on it more of the weight of the engine, and thus increased the adhesion and the tractive power. Mr. Baldwin, however, maintained the superiority of his plan, as giving a better distribution of the weight and a longer wheel-base, and consequently rendering the machine less destructive to the track. As the iron rails then in use were generally light, and much of the track was of wood, this feature was of some importance. To the use of the ground joint for steam-pipes, however, much of the success of his early engines was due. The English builders were making locomotives with canvas and red-lead joints, permitting a steam pressure of only sixty pounds per inch to be carried, while Mr. Baldwin's machines were worked at one hundred and twenty pounds with ease. Several locomotives imported from England at about this period by the Commonwealth of Pennsylvania for the State Road (three of which were made by Stephenson) had canvas and red-lead joints, and their efficiency was so much less than that of the Baldwin engines, on account of this and other features of construction, that they were soon laid aside or sold. In June, 1834, a patent was issued to Mr. E. L. Miller, by whom Mr. Baldwin's second engine was ordered, for a method of increasing the adhesion of a locomotive by throwing a part of the weight of the tender on the rear of the engine, thus increasing the weight on the drivers. Mr. Baldwin adopted this device on an engine built for the Philadelphia and Trenton Railroad Company, May, 1835, and thereafter used it largely, paying one hundred dollars royalty for each engine. Eventually (May 6, 1839) he bought the patent for nine thousand dollars, evidently considering that the device was especially valuable, if not indispensable, in order to render his engine as powerful, when required, as other patterns having the driving-wheels in front of the fire-box, and therefore utilizing more of the weight of the engine for adhesion. In making the truck and tender wheels of these early locomotives, the hubs were cast in three pieces and afterward banded with wrought-iron, the interstices being filled with spelter. This method of construction was adopted on account of the difficulty then found in casting a chilled wheel in one solid piece. April 3, 1835, Mr. Baldwin took out a patent for certain improvements in the wheels and tubes of locomotive engines. That relating to the wheels provided for casting the hub and spokes together, and having the spokes terminate in segments of a rim, as described in his patent of September 10, 1834. Between the ends of the spokes and the tires wood was interposed, and the tire might be either of wrought-iron or of chilled cast-iron. The intention was expressed of making the tire usually of cast-iron chilled. The main object, however, was declared to be the interposition between the spokes and the rim of a layer of wood or other substance possessing some degree of elasticity. This method of making driving-wheels was followed for several years. The improvement in locomotive tubes consisted in driving a copper ferrule or thimble on the outside of the end of the tube, and soldering it in place, instead of driving a ferrule into the tube, as had previously been the practice. The object of the latter method had been to make a tight joint with the tube-sheet; but, by putting the ferrule on the outside of the tube, not only was the joint made as tight as before, but the tube was strengthened, and left unobstructed throughout to the full extent of its diameter. This method of setting flues has been generally followed in the works from that date to the present, the only difference being that, at this time, with iron tubes, the end is swedged down, the copper ferrule brazed on, and the iron end turned or riveted over against the copper thimble and the flue-sheet, to make the joint perfect. Early in 1835, the new shop on Broad Street was completed and occupied. Mr. Baldwin's attention was thenceforward given to locomotive building exclusively, except that a stationary engine was occasionally constructed. In May, 1835, his eleventh locomotive, the "Black Hawk," was delivered to the Philadelphia and Trenton Railroad Company. This was the first outside-connected engine of his build. It was also the first engine on which the Miller device of attaching part of the weight of the tender to the engine was employed. On the eighteenth engine, the "Brandywine," built for the Philadelphia and Columbia Railroad Company, brass tires were used on the driving-wheels, for the purpose of obtaining more adhesion; but they wore out rapidly and were replaced with iron. Fourteen engines were constructed in 1835; forty in 1836; forty in 1837; twenty-three in 1838; twenty-six in 1839; and nine in 1840. During all these years the general design continued the same; but, in compliance with the demand for more power, three sizes were furnished, as follows: First-class. Cylinders, 12-1/2 � 16; weight, loaded, 26,000 pounds. Second-class. " 12 � 16; " " 23,000 " Third-class. " 10-1/2 � 16; " " 20,000 " The first-class engine he fully believed, in 1838, was as heavy as would be called for, and he declared that it was as large as he intended to make. Most of the engines were built with the half-crank, but occasionally an outside-connected machine was turned out. These latter, however, failed to give as complete satisfaction as the half-crank machine. The drivers were generally four and a half feet in diameter. A patent was issued to Mr. Baldwin, August 17, 1835, for his device of cylindrical pedestals. In this method of construction, the pedestal was of cast-iron, and was bored in a lathe so as to form two concave jaws. The boxes were also turned in a lathe so that their vertical ends were cylindrical, and they were thus fitted in the pedestals. This method of fitting up pedestals and boxes was cheap and effective, and was used for some years for the driving and tender wheels. As showing the estimation in which these early engines were held, it may not be out of place to refer to the opinions of some of the railroad managers of that period. Mr. L. A. Sykes, engineer of the New Jersey Transportation Company, under date of June 12, 1838, wrote that he could draw with his engines twenty four-wheeled cars with twenty-six passengers each, at a speed of twenty to twenty-five miles per hour, over grades of twenty-six feet per mile. "As to simplicity of construction," he adds, "small liability to get out of order, economy of repairs, and ease to the road, I fully believe Mr. Baldwin's engines stand unrivalled. I consider the simplicity of the engine, the arrangement of the working-parts, and the distribution of the weight, far superior to any engine I have ever seen, either of American or English manufacture, and I have not the least hesitation in saying that Mr. Baldwin's engine will do the same amount of work with much less repairs, either to the engine or the track, than any other engine in use." L. G. Cannon, President of the Rensselaer and Saratoga Railroad Company, writes, "Your engines will, in performance and cost of repairs, bear comparison with any other engine made in this or any other country." Some of Mr. Baldwin's engines on the State Road, in 1837, cost, for repairs, only from one and two-tenths to one and six-tenths cents per mile. It is noted that the engine "West Chester," on the same road, weighing twenty thousand seven hundred and thirty-five pounds (ten thousand four hundred and seventy-five on drivers), drew fifty-one cars (four-wheeled), weighing two hundred and eighty-nine net tons, over the road, some of the track being of wood covered with strap-rail. The financial difficulties of 1836 and 1837, which brought ruin upon so many, did not leave Mr. Baldwin unscathed. His embarrassments became so great that he was unable to proceed, and was forced to call his creditors together for a settlement. After offering to surrender all his property, his shop, tools, house, and everything, if they so desired,--all of which would realize only about twenty-five per cent. of their claims,--he proposed to them that they should permit him to go on with the business, and in three years he would pay the full amount of all claims, principal and interest. This was finally acceded to, and the promise was in effect fulfilled, although not without an extension of two years beyond the time originally proposed. In May, 1837, the number of hands employed was three hundred, but this number was reducing weekly, owing to the falling off in the demand for engines. These financial troubles had their effect on the demand for locomotives, as will be seen in the decrease in the number built in 1838, 1839, and 1840; and this result was furthered by the establishment of several other locomotive works and the introduction of other patterns of engines. The changes and improvements in details made during these years may be summed up as follows: The subject of burning coal had engaged much attention. In October, 1836, Mr. Baldwin secured a patent for a grate or fireplace which could be detached from the engine at pleasure, and a new one with a fresh coal fire substituted. The intention was to have the grate with freshly ignited coal all ready for the engine on its arrival at a station, and placed between the rails over suitable levers, by which it could be attached quickly to the fire-box. It is needless to say that this was never practiced. In January, 1838, however, Mr. Baldwin was experimenting with the consumption of coal on the Germantown road, and in July of the same year the records show that he was making a locomotive to burn coal, part of the arrangement being to blow the fire with a fan. Up to 1838, Mr. Baldwin had made both driving and truck wheels with wrought tires, but during that year chilled wheels for engine and tender trucks were adopted. His tires were furnished by Messrs. S. Vail & Son, Morristown, N. J., who made the only tires then obtainable in America. They were very thin, being only one inch to one and a half inches thick; and Mr. Baldwin, in importing some tires from England at that time, insisted on their being made double the ordinary thickness. The manufacturers at first objected and ridiculed the idea, the practice being to use two tires when extra thickness was wanted, but finally they consented to meet his requirements. All his engines thus far had the single eccentric for each valve, but at about this period double eccentrics were adopted, each terminating in a straight hook, and reversed by hand-levers. At this early period, Mr. Baldwin had begun to feel the necessity of making all like parts of locomotives of the same class in such manner as to be absolutely interchangeable. Steps were taken in this direction, but it was not until many years afterward that the system of standard gauges was perfected, which has since grown to be a distinguishing feature in the establishment. In March, 1839, Mr. Baldwin's records show that he was building a number of outside-connected engines, and had succeeded in making them strong and durable. He was also making a new chilled wheel, and one which he thought would not break. On the one hundred and thirty-sixth locomotive, completed October 18, 1839, for the Philadelphia, Germantown and Norristown Railroad, the old pattern of wooden frame was abandoned, and no outside frame whatever was employed,--the machinery, as well as the truck and the pedestals of the driving-axles, being attached directly to the naked boiler. The wooden frame thenceforward disappeared gradually, and an iron frame took its place. Another innovation was the adoption of eight-wheeled tenders, the first of which was built at about this period. April 8, 1839, Mr. Baldwin associated with himself Messrs. Vail and Hufty, and the business was conducted under the firm name of Baldwin, Vail & Hufty until 1841, when Mr. Hufty withdrew, and Baldwin & Vail continued the copartnership until 1842. The time had now arrived when the increase of business on railroads demanded more powerful locomotives. It had for some years been felt that for freight traffic the engine with one pair of drivers was insufficient. Mr. Baldwin's engine had the single pair of drivers placed back of the fire-box; that made by Mr. Norris, one pair in front of the fire-box. An engine with two pairs of drivers, one pair in front and one pair behind the fire-box, was the next logical step, and Mr. Henry R. Campbell, of Philadelphia, was the first to carry this design into execution. Mr. Campbell, as has been noted, was the Chief Engineer of the Germantown Railroad when the "Ironsides" was placed on that line, and had since given much attention to the subject of locomotive construction. February 5, 1836, Mr. Campbell secured a patent for an eight-wheeled engine with four drivers connected, and a four-wheeled truck in front; and subsequently contracted with James Brooks, of Philadelphia, to build for him such a machine. The work was begun March 16, 1836, and the engine was completed May 8, 1837. This was the first eight-wheeled engine of this type, and from it the standard American locomotive of to-day takes its origin. The engine lacked, however, one essential feature; there were no equalizing beams between the drivers, and nothing but the ordinary steel springs over each journal of the driving-axles to equalize the weight upon them. It remained for Messrs. Eastwick & Harrison to supply this deficiency; and in 1837 that firm constructed at their shop in Philadelphia a locomotive on this plan, but with the driving-axles running in a separate square frame, connected to the main frame above it by a single central bearing on each side. This engine had cylinders twelve by eighteen, four coupled driving-wheels, forty-four inches in diameter, carrying eight of the twelve tons constituting the total weight. Subsequently, Mr. Joseph Harrison, Jr., of the same firm, substituted "equalizing beams" on engines of this plan afterward constructed by them, substantially in the same manner as since generally employed. In the _American Railroad Journal_ of July 30, 1836, a wood-cut showing Mr. Campbell's engine, together with an elaborate calculation of the effective power of an engine on this plan, by William J. Lewis, Esq., Civil Engineer, was published, with a table showing its performance upon grades ranging from a dead level to a rise of one hundred feet per mile. Mr. Campbell stated that his experience at that time (1835-6) convinced him that grades of one hundred feet rise per mile would, if roads were judiciously located, carry railroads over any of the mountain passes in America, without the use of planes with stationary steam power, or, as a general rule, of costly tunnels,--an opinion very extensively verified by the experience of the country since that date. A step had thus been taken toward a plan of locomotive having more adhesive power. Mr. Baldwin, however, was slow to adopt the new design. He naturally regarded innovations with distrust. He had done much to perfect the old pattern of engine, and had built over a hundred of them, which were in successful operation on various railroads. Many of the details were the subjects of his several patents, and had been greatly simplified in his practice. In fact, simplicity in all the working parts had been so largely his aim, that it was natural that he should distrust any plan involving additional machinery, and he regarded the new design as only an experiment at best. In November, 1838, he wrote to a correspondent that he did not think there was any advantage in the eight-wheeled engine. There being three points in contact, it could not turn a curve, he argued, without slipping one or the other pair of wheels sideways. Another objection was in the multiplicity of machinery and the difficulty in maintaining four driving-wheels all of exactly the same size. Some means, however, of getting more adhesion must be had, and the result of his reflections upon this subject was the project of a "geared engine." In August, 1839, he took steps to secure a patent for such a machine, and December 31, 1840, letters patent were granted him for the device. In this engine, an independent shaft or axle was placed between the two axles of the truck, and connected by cranks and coupling-rods with cranks on the outside of the driving-wheels. This shaft had a central cog-wheel engaging on each side with intermediate cog-wheels, which in turn geared into cog-wheels on each truck-axle. The intermediate cog-wheels had wide teeth, so that the truck could pivot while the main shaft remained parallel with the driving-axle. The diameters of the cog-wheels were, of course, in such proportion to the driving and truck wheels, that the latter should revolve as much oftener than the drivers as their smaller size might require. Of the success of this machine for freight service, Mr. Baldwin was very sanguine. One was put in hand at once, completed in August, 1841, and eventually sold to the Sugarloaf Coal Company. It was an outside-connected engine, weighing thirty thousand pounds, of which eleven thousand seven hundred and seventy-five pounds were on the drivers, and eighteen thousand three hundred and thirty-five on the truck. The driving-wheels were forty-four and the truck-wheels thirty-three inches in diameter. The cylinders were thirteen inches in diameter by sixteen inches stroke. On a trial of the engine upon the Philadelphia and Reading Railroad, it hauled five hundred and ninety tons from Reading to Philadelphia--a distance of fifty-four miles--in five hours and twenty-two minutes. The Superintendent of the road, in writing of the trial, remarked that this train was unprecedented in length and weight both in America and Europe. The performance was noticed in favorable terms by the Philadelphia newspapers, and was made the subject of a report by the Committee on Science and Arts of the Franklin Institute, who strongly recommended this plan of engine for freight service. The success of the trial led Mr. Baldwin at first to believe that the geared engine would be generally adopted for freight traffic; but in this he was disappointed. No further demand was made for such machines, and no more of them were built. In 1840, Mr. Baldwin received an order, through August Belmont, Esq., of New York, for a locomotive for Austria, and had nearly completed one which was calculated to do the work required, when he learned that only sixty pounds pressure of steam was admissible, whereas his engine was designed to use steam at one hundred pounds and over. He accordingly constructed another, meeting this requirement, and shipped it in the following year. This engine, it may be noted, had a kind of link-motion, agreeably to the specification received, and was the first of his make upon which the link was introduced. Mr. Baldwin's patent of December 31, 1840, already referred to as covering his geared engine, embraced several other devices, as follows: 1. A method of operating a fan, or blowing-wheel, for the purpose of blowing the fire. The fan was to be placed under the footboard, and driven by the friction of a grooved pulley in contact with the flange of the driving-wheel. 2. The substitution of a metallic stuffing, consisting of wire, for the hemp, wool, or other material which had been employed in stuffing-boxes. 3. The placing of the springs of the engine truck so as to obviate the evil of the locking of the wheels when the truck-frame vibrates from the centre-pin vertically. Spiral as well as semi-elliptic springs, placed at each end of the truck-frame, were specified. The spiral spring is described as received in two cups,--one above and one below. The cups were connected together at their centres by a pin upon one and a socket in the other, so that the cups could approach toward or recede from each other and still preserve their parallelism. 4. An improvement in the manner of constructing the iron frames of locomotives, by making the pedestals in one piece with, and constituting part of, the frames. 5. The employment of spiral springs in connection with cylindrical pedestals and boxes. A single spiral was at first used, but, not proving sufficiently strong, a combination or nest of spirals curving alternately in opposite directions was afterward employed. Each spiral had its bearing in a spiral recess in the pedestal. In the specification of this patent a change in the method of making cylindrical pedestals and boxes is noted. Instead of boring and turning them in a lathe, they were cast to the required shape in chills. This method of construction was used for a time, but eventually a return was made to the original plan, as giving a more accurate job. In 1842, Mr. Baldwin constructed, under an arrangement with Mr. Ross Winans, three locomotives for the Western Railroad of Massachusetts, on a plan which had been designed by that gentleman for freight traffic. These machines had upright boilers, and horizontal cylinders which worked cranks on a shaft bearing cog-wheels engaging with other cog-wheels on an intermediate shaft. This latter shaft had cranks coupled to four driving-wheels on each side. These engines were constructed to burn anthracite coal. Their peculiarly uncouth appearance earned for them the name of "crabs," and they were but short-lived in service. [Illustration: Fig. 6.--BALDWIN SIX-WHEELS-CONNECTED ENGINE, 1842.] [Illustration: Fig. 7.--BALDWIN FLEXIBLE-BEAM TRUCK, 1842.--ELEVATION.] [Illustration: HALF PLAN.] But, to return to the progress of Mr. Baldwin's locomotive practice. The geared engine had not proved a success. It was unsatisfactory, as well to its designer as to the railroad community. The problem of utilizing more or all of the weight of the engine for adhesion remained, in Mr. Baldwin's view, yet to be solved. The plan of coupling four or six wheels had long before been adopted in England, but on the short curves prevalent on American railroads, he felt that something more was necessary. The wheels must not only be coupled, but at the same time must be free to adapt themselves to a curve. These two conditions were apparently incompatible, and to reconcile these inconsistencies was the task which Mr. Baldwin set himself to accomplish. He undertook it, too, at a time when his business had fallen off greatly and he was involved in the most serious financial embarrassments. The problem was constantly before him, and at length, during a sleepless night, its solution flashed across his mind. The plan so long sought for, and which, subsequently, more than any other of his improvements or inventions, contributed to the foundation of his fortune, was his well-known six-wheels-connected locomotive with the four front drivers combined in a flexible truck. For this machine Mr. Baldwin secured a patent, August 25, 1842. Its principal characteristic features are now matters of history, but they deserve here a brief mention. The engine was on six wheels, all connected as drivers. The rear wheels were placed rigidly in the frames, usually behind the fire-box, with inside bearings. The cylinders were inclined, and with outside connections. The four remaining wheels had inside journals running in boxes held by two wide and deep wrought-iron beams, one on each side. These beams were unconnected, and entirely independent of each other. The pedestals formed in them were bored out cylindrically, and into them cylindrical boxes, as patented by him in 1835, were fitted. The engine-frame on each side was directly over the beam, and a spherical pin, running down from the frame, bore in a socket in the beam midway between the two axles. It will thus be seen that each side-beam independently could turn horizontally or vertically under the spherical pin, and the cylindrical boxes could also turn in the pedestals. Hence, in passing a curve, the middle pair of drivers could move laterally in one direction--say to the right--while the front pair could move in the opposite direction, or to the left; the two axles all the while remaining parallel to each other and to the rear driving-axle. The operation of these beams was, therefore, like that of the parallel-ruler. On a straight line the two beams and the two axles formed a rectangle; on curves, a parallelogram, the angles varying with the degree of curvature. The coupling-rods were made with cylindrical brasses, thus forming ball-and-socket joints, to enable them to accommodate themselves to the lateral movements of the wheels. Colburn, in his "Locomotive Engineering," remarks of this arrangement of rods as follows: "Geometrically, no doubt, this combination of wheels could only work properly around curves by a lengthening and shortening of the rods which served to couple the principal pair of driving-wheels with the hind truck-wheels. But if the coupling-rods from the principal pair of driving-wheels be five feet long, and if the beams of the truck-frame be four feet long (the radius of curve described by the axle-boxes around the spherical side bearings being two feet), then the total corresponding lengthening of the coupling-rods, in order to allow the hind truck-wheels to move one inch to one side, and the front wheels of the truck one inch to the other side of their normal position on a straight line, would be V[60^{2} + 1^{2}] - 60 + 24 - V[24^{2} - 1^{2}] = 0.0275 inch, or less than one thirty-second of an inch. And if only one pair of driving-wheels were thus coupled with a four-wheeled truck, the total wheel-base being nine feet, the motion permitted by this slight elongation of the coupling-rods (an elongation provided for by a trifling slackness in the brasses) would enable three pairs of wheels to stand without binding in a curve of only one hundred feet radius." The first engine of the new plan was finished early in December, 1842, being one of fourteen engines constructed in that year, and was sent to the Georgia Railroad, on the order of Mr. J. Edgar Thomson, then Chief Engineer and Superintendent of that line. It weighed twelve tons, and drew, besides its own weight, two hundred and fifty tons up a grade of thirty-six feet to the mile. Other orders soon followed. The new machine was received generally with great favor. The loads hauled by it exceeded anything so far known in American railroad practice, and sagacious managers hailed it as a means of largely reducing operating expenses. On the Central Railroad of Georgia, one of these twelve-ton engines drew nineteen eight-wheeled cars, with seven hundred and fifty bales of cotton, each bale weighing four hundred and fifty pounds, over maximum grades of thirty feet per mile, and the manager of the road declared that it could readily take one thousand bales. On the Philadelphia and Reading Railroad a similar engine of eighteen tons weight drew one hundred and fifty loaded cars (total weight of cars and lading, one thousand one hundred and thirty tons) from Schuylkill Haven to Philadelphia, at a speed of seven miles per hour. The regular load was one hundred loaded cars, which were hauled at a speed of from twelve to fifteen miles per hour on a level. The following extract from a letter, dated August 10, 1844, of Mr. G. A. Nicolls, then Superintendent of that line, and still connected with its management, gives the particulars of the performance of these machines, and shows the estimation in which they were held: "We have had two of these engines in operation for about four weeks. Each engine weighs about forty thousand pounds with water and fuel, equally distributed on six wheels, all of which are coupled, thus gaining the whole adhesion of the engine's weight. Their cylinders are fifteen by eighteen inches." "The daily allotted load of each of these engines is one hundred coal cars, each loaded with three and six-tenths tons of coal, and weighing two and fifteen one-hundredths tons each, empty; making a net weight of three hundred and sixty tons of coal carried, and a gross weight of train of five hundred and seventy-five tons, all of two thousand two hundred and forty pounds." "This train is hauled over the ninety-four miles of the road, half of which is level, at the rate of twelve miles per hour; and with it the engine is able to make fourteen to fifteen miles per hour on a level." "Were all the cars on the road of sufficient strength, and making the trip by daylight, nearly one-half being now performed at night, I have no doubt of these engines being quite equal to a load of eight hundred tons gross, as their average daily performance on any of the levels of our road, some of which are eight miles long." "In strength of make, quality of workmanship, finish, and proportion of parts, I consider them equal to any, and superior to most, freight engines I have seen. They are remarkably easy on the rail, either in their vertical or horizontal action, from the equalization of their weight, and the improved truck under the forward part of the engine. This latter adapts itself to all the curves of the road, including some of seven hundred and sixteen feet radius in the main track, and moves with great ease around our turning Y curves at Richmond, of about three hundred feet radius. "I consider these engines as near perfection, in the arrangement of their parts, and their general efficiency, as the present improvements in machinery and the locomotive engine will admit of. They are saving us thirty per cent, in every trip, on the former cost of motive or engine power." But the flexible-beam truck also enabled Mr. Baldwin to meet the demand for an engine with four drivers connected. Other builders were making engines with four drivers and a four-wheeled truck, of the present American standard type. To compete with this design, Mr. Baldwin modified his six-wheels-connected engine by connecting only two out of the three pairs of wheels as drivers, making the forward wheels of smaller diameter as leading wheels, but combining them with the front drivers in a flexible-beam truck. The first engine on this plan was sent to the Erie and Kalamazoo Railroad, in October, 1843, and gave great satisfaction. The Superintendent of the road was enthusiastic in its praise, and wrote to Mr. Baldwin that he doubted "if anything could be got up which would answer the business of the road so well." One was also sent to the Utica and Schenectady Railroad a few weeks later, of which the Superintendent remarked that "it worked beautifully, and there were not wagons enough to give it a full load." In this plan the leading wheels were usually made thirty-six and the drivers fifty-four inches in diameter. This machine of course came in competition with the eight-wheeled engine having four drivers, and Mr. Baldwin claimed for his plan a decided superiority. In each case about two-thirds of the total weight was carried on the four drivers, and Mr. Baldwin maintained that his engine, having only six instead of eight wheels, was simpler and more effective. At about this period Mr. Baldwin's attention was called by Mr. Levi Bissell to an "Air Spring" which the latter had devised, and which it was imagined was destined to be a cheap, effective, and perpetual spring. The device consisted of a small cylinder placed above the frame over the axle-box, and having a piston fitted air-tight into it. The piston-rod was to bear on the axle-box, and the proper quantity of air was to be pumped into the cylinder above the piston, and the cylinder then hermetically closed. The piston had a leather packing which was to be kept moist by some fluid (molasses was proposed) previously introduced into the cylinder. Mr. Baldwin at first proposed to equalize the weight between two pairs of drivers by connecting two air-springs on each side by a pipe, the use of an equalizing beam being covered by Messrs. Eastwick & Harrison's patent. The air-springs were found, however, not to work practically, and were never applied. It may be added that a model of an equalizing air-spring was exhibited by Mr. Joseph Harrison, Jr., at the Franklin Institute, in 1838 or 1839. With the introduction of the new machine, business began at once to revive, and the tide of prosperity turned once more in Mr. Baldwin's favor. Twelve engines were constructed in 1843, all but four of them of the new pattern; twenty-two engines in 1844, all of the new pattern; and twenty-seven in 1845. Three of this number were of the old type, with one pair of drivers, but from that time forward the old pattern with the single pair of drivers disappeared from the practice of the establishment, save occasionally for exceptional purposes. In 1842, the partnership with Mr. Vail was dissolved, and Mr. Asa Whitney, who had been Superintendent of the Mohawk and Hudson Railroad, became a partner with Mr. Baldwin, and the firm continued as Baldwin & Whitney until 1846, when the latter withdrew to engage in the manufacture of car-wheels, in which business he is still concerned as senior member of the firm of A. Whitney & Sons, Philadelphia. Mr. Whitney brought to the firm a railroad experience and thorough business talent. He introduced a system in many details of the management of the business, which Mr. Baldwin, whose mind was devoted more exclusively to mechanical subjects, had failed to establish or wholly ignored. The method at present in use in the establishment, of giving to each class of locomotives a distinctive designation, composed of a number and a letter, originated very shortly after Mr. Whitney's connection with the business. For the purpose of representing the different designs, sheets with engravings of locomotives were employed. The sheet showing the engine with one pair of drivers was marked B; that with two pairs, C; that with three, D; and that with four, E. Taking its rise from this circumstance, it became customary to designate as B engines those with one pair of drivers; as C engines, those with two pairs; as D engines, those with three pairs; and as E engines, those with four pairs. Shortly afterwards, a number, indicating the weight in gross tons, was added. Thus, the 12 D engine was one with three pairs of drivers, and weighing twelve tons; the 12 C, an engine of same weight, but with only four wheels connected. Substantially this system of designating the several sizes and plans has been retained to the present time. The figures, however, are no longer used to express the weight, but merely to designate the class. It will be observed that the classification as thus established began with the B engines. The letter A was reserved for an engine intended to run at very high speeds, and so designed that the driving-wheels should make two revolutions for each reciprocation of the pistons. This was to be accomplished by means of gearing. The general plan of the engine was determined in Mr. Baldwin's mind, but was never carried into execution. The adoption of the plan of six-wheels-connected engines opened the way at once to increasing their size. The weight being almost evenly distributed on six points, heavier machines were admissible, the weight on any one pair of drivers being little, if any, greater than had been the practice with the old plan of engine having a single pair of drivers; Hence engines of eighteen and twenty tons weight were shortly introduced, and in 1844 three of twenty tons weight, with cylinders sixteen and one-half inches diameter by eighteen inches stroke, were constructed for the Western Railroad of Massachusetts, and six, of eighteen tons weight, with cylinders fifteen by eighteen, and drivers forty-six inches in diameter, were built for the Philadelphia and Reading Railroad. It should be noted that three of these latter engines had iron flues. This was the first instance in which Mr. Baldwin had employed tubes of this material. The advantage found to result from the use of iron tubes, apart from their less cost, was that the tubes and boiler-shell, being of the same material, expanded and contracted alike, while in the case of copper tubes the expansion of the metal by heat varied from that of the boiler-shell, and as a consequence there was greater liability to leakage at the joints with the tube-sheets. The opinion prevailed largely at that time that some advantage resulted in the evaporation of water, owing to the superiority of copper as a conductor of heat. To determine this question, an experiment was tried with two of the six engines referred to above, one of which, the "Ontario," had copper flues, and another, the "New England," iron flues. In other respects they were precisely alike. The two engines were run from Richmond to Mount Carbon, August 27, 1844, each drawing a train of one hundred and one empty cars, and, returning, from Mount Carbon to Richmond, on the following day, each with one hundred loaded cars. The quantity of water evaporated and wood consumed was noted, with the result shown in the following table: ------------------------------------------------------------------------ | UP TRIP, | DOWN TRIP, | | AUG. 27, 1844. | AUG. 28, 1844. | ----------------------------+---------------------+----------+----------| |"Ontario."| "New |"Ontario."| "New | | | England."| | England."| | (Copper | (Iron | (Copper | (Iron | | Flues.) | Flues.) | Flues.) | Flues.) | ----------------------------+----------+----------+----------+----------| Time, running | 9h. 7m. | 7h. 41m.| 10h. 44m.| 8h. 19m.| " standing at stations. | 4h. 2m. | 3h. 7m.| 2h. 12m.| 3h. 8m.| Cords of wood burned | 6.68 | 5.50 | 6.94 | 6. | Cubic feet of water | | | | | evaporated | 925.75 | 757.26 | 837.46 | 656.39 | Ratio, cubic feet of water | | | | | to a cord of wood | 138.57 | 137.68 | 120.67 | 109.39 | ------------------------------------------------------------------------ The conditions of the experiments not being absolutely the same in each case, the results could not of course be accepted as entirely accurate. They seemed to show, however, no considerable difference in the evaporative efficacy of copper and iron tubes. The period under consideration was marked also by the introduction of the French & Baird stack, which proved at once to be one of the most successful spark-arresters thus far employed, and which was for years used almost exclusively wherever, as on the cotton-carrying railroads of the South, a thoroughly effective spark-arrester was required. This stack was introduced by Mr. Baird, then a foreman in the Works, who purchased the patent-right of what had been known as the Grimes stack, and combined with it some of the features of the stack made by Mr. Richard French, then Master Mechanic of the Germantown Railroad, together with certain improvements of his own. The cone over the straight inside pipe was made with volute flanges on its under side, which gave a rotary motion to the sparks. Around the cone was a casing about six inches smaller in diameter than the outside stack. Apertures were cut in the sides of this casing, through which the sparks in their rotary motion were discharged and thus fell to the bottom of the space between the straight inside pipe and the outside stack. The opening in the top of the stack was fitted with a series of V-shaped iron circles perforated with numerous holes, thus presenting an enlarged area, through which the smoke escaped. The patent-right for this stack was subsequently sold to Messrs. Radley & Hunter, and its essential principle is still used in the Radley & Hunter stack as at present made. In 1845, Mr. Baldwin built three locomotives for the Royal Railroad Committee of Würtemberg. They were of fifteen tons weight, on six wheels, four of them being sixty inches in diameter and coupled. The front drivers were combined by the flexible beams into a truck with the smaller leading wheels. The cylinders were inclined and outside, and the connecting-rods took hold of a half-crank axle back of the fire-box. It was specified that these engines should have the link-motion which had shortly before been introduced in England by the Stephensons. Mr. Baldwin accordingly applied a link of a peculiar character to suit his own ideas of the device. The link was made solid, and of a truncated V-section, and the block was grooved so as to fit and slide on the outside of the link. During the year 1845 another important feature in locomotive construction--the cut-off valve--was added to Mr. Baldwin's practice. Up to that time the valve-motion had been the two eccentrics, with the single flat hook for each cylinder. Since 1841 Mr. Baldwin had contemplated the addition of some device allowing the steam to be used expansively, and he now added the "half-stroke cut-off." In this device the steam-chest was separated by a horizontal plate into an upper and a lower compartment. In the upper compartment, a valve, worked by a separate eccentric, and having a single opening, admitted steam through a port in this plate to the lower steam-chamber. The valve-rod of the upper valve terminated in a notch or hook, which engaged with the upper arm of its rock-shaft. When thus working, it acted as a cut-off at a fixed part of the stroke, determined by the setting of the eccentric. This was usually at half the stroke. When it was desired to dispense with the cut-off and work steam for the full stroke, the hook of the valve-rod was lifted from the pin on the upper arm of the rock-shaft by a lever worked from the footboard, and the valve-rod was held in a notched rest fastened to the side of the boiler. This left the opening through the upper valve and the port in the partition plate open for the free passage of steam throughout the whole stroke. The first application of the half-stroke cut-off was made on the engine "Champlain" (20 D), built for the Philadelphia and Reading Railroad Company, in 1845. It at once became the practice to apply the cut-off on all passenger engines, while the six- and eight-wheels-connected freight engines were, with a few exceptions, built for a time longer with the single valve admitting steam for the full stroke. After building, during the years 1843, 1844, and 1845, ten four-wheels-connected engines on the plan above described, viz., six wheels in all, the leading wheels and the front drivers being combined into a truck by the flexible beams, Mr. Baldwin finally adopted the present design of four drivers and a four-wheeled truck. Some of his customers who were favorable to the latter plan had ordered such machines of other builders, and Colonel Gadsden, President of the South Carolina Railroad Company, called on him in 1845 to build for that line some passenger engines of this pattern. He accordingly bought the patent-right for this plan of engine of Mr. H. R. Campbell, and for the equalizing beams used between the drivers, of Messrs. Eastwick & Harrison, and delivered to the South Carolina Railroad Company, in December, 1845, his first eight-wheeled engine with four drivers and a four-wheeled truck. This machine had cylinders thirteen and three-quarters by eighteen, and drivers sixty inches in diameter, with the springs between them arranged as equalizers. Its weight was fifteen tons. It had the half-crank axle, the cylinders being inside the frame but outside the smoke-box. The inside-connected engine, counterweighting being as yet unknown, was admitted to be steadier in running, and hence more suitable for passenger service. With the completion of the first eight-wheeled "C" engine, Mr. Baldwin's feelings underwent a revulsion in favor of this plan, and his partiality for it became as great as had been his antipathy before. Commenting on the machine, he recorded himself as "more pleased with its appearance and action than any engine he had turned out." In addition to the three engines of this description for the South Carolina Railroad Company, a duplicate was sent to the Camden and Amboy Railroad Company, and a similar but lighter one to the Wilmington and Baltimore Railroad Company, shortly afterwards. The engine for the Camden and Amboy Railroad Company, and perhaps the others, had the half-stroke cut-off. From that time forward, all of his four-wheels-connected machines were built on this plan, and the six-wheeled "C" engine was abandoned, except in the case of one built for the Philadelphia, Germantown and Norristown Railroad Company in 1846, and this was afterwards rebuilt into a six-wheels-connected machine. Three methods of carrying out the general design were, however, subsequently followed. At first the half-crank was used; then horizontal cylinders inclosed in the chimney-seat and working a full-crank-axle, which form of construction had been practiced at the Lowell Works; and eventually, outside cylinders with outside connections. [Illustration: Fig. 8.--BALDWIN EIGHT-WHEELS-CONNECTED ENGINE, 1846.] Meanwhile the flexible truck machine maintained its popularity for heavy freight service. All the engines thus far built on this plan had been six-wheeled, some with the rear driving-axle back of the fire-box, and others with it in front. The next step, following logically after the adoption of the eight-wheeled "C" engine, was to increase the size of the freight machine, and distribute the weight on eight wheels all connected, the two rear pairs being rigid in the frame, and the two front pairs combined into the flexible-beam truck. This was first done in 1846, when seventeen engines on this plan were constructed on one order for the Philadelphia and Reading Railroad Company. Fifteen of these were of twenty tons weight, with cylinders fifteen and a half by twenty, and wheels forty-six inches in diameter; and two of twenty-five tons weight, with cylinders seventeen and a quarter by eighteen, and drivers forty-two inches in diameter. These engines were the first ones on which Mr. Baldwin placed sand-boxes, and they were also the first built by him with roofs. On all previous engines the footboard had only been inclosed by a railing. On these engines for the Reading Railroad, four iron posts were carried up, and a wooden roof supported by them. The engine-men added curtains at the sides and front, and Mr. Baldwin on subsequent engines added sides, with sash and glass. The cab proper, however, was of New England origin, where the severity of the climate demanded it, and where it had been used previous to this period. [Illustration: Fig. 9.--BALDWIN ENGINE FOR RACK-RAIL, 1847.] Forty-two engines were completed in 1846, and thirty-nine in 1847. The only novelty to be noted among them was the engine "M. G. Bright," built for operating the inclined plane on the Madison and Indianapolis Railroad. The rise of this incline was one in seventeen, from the bank of the Ohio River at Madison. The engine had eight wheels, forty-two inches in diameter, connected, and worked in the usual manner by outside inclined cylinders, fifteen and one-half inches diameter by twenty inches stroke. A second pair of cylinders, seventeen inches in diameter with eighteen inches stroke of piston, was placed vertically over the boiler, midway between the furnace and smoke-arch. The connecting-rods worked by these cylinders connected with cranks on a shaft under the boiler. This shaft carried a single cog-wheel at its centre, and this cog-wheel engaged with another of about twice its diameter on a second shaft adjacent to it and in the same plane. The cog-wheel on this latter shaft worked in a rack-rail placed in the centre of the track. The shaft itself had its bearings in the lower ends of two vertical rods, one on each side of the boiler, and these rods were united over the boiler by a horizontal bar which was connected by means of a bent lever and connecting-rod to the piston worked by a small horizontal cylinder placed on top of the boiler. By means of this cylinder, the yoke carrying the shaft and cog-wheel could be depressed and held down so as to engage the cogs with the rack-rail, or raised out of the way when only the ordinary drivers were required. This device was designed by Mr. Andrew Cathcart, Master Mechanic of the Madison and Indianapolis Railroad. A similar machine, the "John Brough," for the same plane, was built by Mr. Baldwin in 1850. The incline was worked with a rack-rail and these engines until it was finally abandoned and a line with easy gradients substituted. The use of iron tubes in freight engines grew in favor, and in October, 1847, Mr. Baldwin noted that he was fitting his flues with copper ends, "for riveting to the boiler." The subject of burning coal continued to engage much attention, but the use of anthracite had not as yet been generally successful. In October, 1847, the Baltimore and Ohio Railroad Company advertised for proposals for four engines to burn Cumberland coal, and the order was taken and filled by Mr. Baldwin with four of his eight-wheels-connected machines. The year 1848 showed a falling off in business, and only twenty engines were turned out. In the following year, however, there was a rapid recovery, and the production of the works increased to thirty, followed by thirty-seven in 1850, and fifty in 1851. These engines, with a few exceptions, were confined to three patterns, the eight-wheeled four-coupled engine, from twelve to nineteen tons in weight, for passengers and freight, and the six- and eight-wheels-connected engine, for freight exclusively, the six-wheeled machine weighing from twelve to seventeen tons, and the eight-wheeled, from eighteen to twenty-seven tons. The drivers of these six- and eight-wheels-connected machines were made generally forty-two, with occasional variations up to forty-eight, inches in diameter. [Illustration: Fig. 10.--BALDWIN FAST PASSENGER ENGINE, 1848.] The exceptions referred to in the practice of these years were the fast passenger engines built by Mr. Baldwin during this period. Early in 1848, the Vermont Central Railroad was approaching completion, and Governor Paine, the President of the Company, conceived the idea that the passenger service on the road required locomotives capable of running at very high velocities. Henry R. Campbell, Esq., was a contractor in building the line, and was authorized by Governor Paine to come to Philadelphia and offer Mr. Baldwin ten thousand dollars for a locomotive which could run with a passenger train at a speed of sixty miles per hour. Mr. Baldwin at once undertook to meet these conditions. The work was begun early in 1848, and in March of that year Mr. Baldwin filed a caveat for his design. The engine was completed in 1849, and was named the "Governor Paine." It had one pair of driving-wheels six and a half feet in diameter, placed back of the fire-box. Another pair of wheels, but smaller and unconnected, was placed directly in front of the fire-box, and a four-wheeled truck carried the front of the engine. The cylinders were seventeen and a quarter inches diameter and twenty inches stroke, and were placed horizontally between the frames and the boiler, at about the middle of the waist. The connecting-rods took hold of "half-cranks" inside of the driving-wheels. The object of placing the cylinders at the middle of the boiler was to lessen or obviate the lateral motion of the engine, produced when the cylinders were attached to the smoke-arch. The bearings on the two rear axles were so contrived that, by means of a lever, a part of the weight of the engine usually carried on the wheels in front of the fire-box could be transferred to the driving-axle. The "Governor Paine" was used for several years on the Vermont Central Railroad, and then rebuilt into a four-coupled machine. During its career, it was stated by the officers of the road that it could be started from a state of rest and run a mile in forty-three seconds. Three engines on the same plan, but with cylinders fourteen by twenty, and six-feet driving-wheels, the "Mifflin," "Blair," and "Indiana," were also built for the Pennsylvania Railroad Company, in 1849. They weighed each about forty-seven thousand pounds, distributed as follows: eighteen thousand on drivers, fourteen thousand on the pair of wheels in front of the fire-box, and fifteen thousand on the truck. By applying the lever, the weight on the drivers could be increased to about twenty-four thousand pounds, the weight on the wheels in front of the fire-box being correspondingly reduced. A speed of four miles in three minutes is recorded for them, and upon one occasion President Taylor was taken in a special train over the road by one of these machines at a speed of sixty miles an hour. One other engine of this pattern, the "Susquehanna," was built for the Hudson River Railroad Company, in 1850. Its cylinders were fifteen inches diameter by twenty inches stroke, and drivers six feet in diameter. All these engines, however, were short-lived, and died young, of insufficient adhesion. Eight engines with four drivers connected and half-crank-axles, were built for the New York and Erie Railroad Company in 1849, with seventeen by twenty inch cylinders; one-half of the number with six-feet and the rest with five-feet drivers. These machines were among the last on which the half-crank-axle was used. Thereafter, outside-connected engines were constructed almost exclusively. In May, 1848, Mr. Baldwin filed a caveat for a four-cylinder locomotive, but never carried the design into execution. The first instance of the use of steel axles in the practice of the establishment occurred during the same year,--a set being placed as an experiment under an engine constructed for the Pennsylvania Railroad Company. In 1850, the old form of dome boiler, which had characterized the Baldwin engine since 1834, was abandoned, and the wagon-top form substituted. The business in 1851 had reached the full capacity of the shop, and the next year marked the completion of about an equal number of engines (forty-nine). Contracts for work extended a year ahead, and, to meet the demand, the facilities in the various departments were increased, and resulted in the construction of sixty engines in 1853, and sixty-two in 1854. At the beginning of the latter year, Mr. Matthew Baird, who had been connected with the works since 1836 as one of its foremen, entered into partnership with Mr. Baldwin, and the style of the firm was made M. W. Baldwin & Co. The only novelty in the general plan of engines during this period was the addition of the ten-wheeled engine to the patterns of the establishment. The success of Mr. Baldwin's engines with all six or eight wheels connected, and the two front pairs combined by the parallel beams into a flexible truck, had been so marked that it was natural that he should oppose any other plan for freight service. The ten-wheeled engine, with six drivers connected, had, however, now become a competitor. This plan of engine was first patented by Septimus Norris, of Philadelphia, in 1846, and the original design was apparently to produce an engine which should have equal tractive power with the Baldwin six-wheels-connected machine. This the Norris patent sought to accomplish by proposing an engine with six drivers connected, and so disposed as to carry substantially the whole weight, the forward drivers being in advance of the centre of gravity of the engine, and the truck only serving as a guide, the front of the engine being connected with it by a pivot-pin, but without a bearing on the centre-plate. Mr. Norris's first engine on this plan was tried in April, 1847, and was found not to pass curves so readily as was expected. As the truck carried little or no weight, it would not keep the track. The New York and Erie Railroad Company, of which John Brandt was then Master Mechanic, shortly afterwards adopted the ten-wheeled engine, modified in plan so as to carry a part of the weight on the truck. Mr. Baldwin filled an order for this company, in 1850, of four eight-wheels-connected engines, and in making the contract he agreed to substitute a truck for the front pair of wheels if desired after trial. This, however, he was not called upon to do. In February, 1852, Mr. J. Edgar Thomson, President of the Pennsylvania Railroad Company, invited proposals for a number of freight locomotives of fifty-six thousand pounds weight each. They were to be adapted to burn bituminous coal, and to have six wheels connected and a truck in front, which might be either of two or four wheels. Mr. Baldwin secured the contract, and built twelve engines of the prescribed dimensions, viz., cylinders eighteen by twenty-two; drivers forty-four inches diameter, with chilled tires. Several of these engines were constructed with a single pair of truck-wheels in front of the drivers, but back of the cylinders. It was found, however, after the engines were put in service, that the two truck-wheels carried eighteen thousand or nineteen thousand pounds, and this was objected to by the company as too great a weight to be carried on a single pair of wheels. On the rest of the engines of the order, therefore, a four-wheeled truck in front was employed. The ten wheeled engine thereafter assumed a place in the Baldwin classification. In 1855-56, two of twenty-seven tons weight, nineteen by twenty-two cylinders, forty-eight inches drivers, were built for the Portage Railroad, and three for the Pennsylvania Railroad. In 1855, '56, and '57, fourteen, of the same dimensions, were built for the Cleveland and Pittsburg Railroad; four for the Pittsburg, Fort Wayne and Chicago Railroad; and one for the Marietta and Cincinnati Railroad. In 1858 and '59, one was constructed for the South Carolina Railroad, of the same size, and six lighter ten-wheelers, with cylinders fifteen and a half by twenty-two, and four-feet drivers, and two with cylinders sixteen by twenty-two, and four-feet drivers, were sent out to railroads in Cuba. It was some years--not until after 1860, however--before this pattern of engine wholly superseded in Mr. Baldwin's practice the old plan of freight engine on six or eight wheels, all connected. On three locomotives--the "Clinton," "Athens," and "Sparta"--completed for the Central Railroad of Georgia in July, 1852, the driving-boxes were made with a slot or cavity in the line of the vertical bearing on the journal. The object was to produce a more uniform distribution of the wear over the entire surface of the bearing. This was the first instance in which this device, which has since come into general use, was employed in the Works, and the boxes were so made by direction of Mr. Charles Whiting, then Master Mechanic of the Central Railroad of Georgia. He subsequently informed Mr. Baldwin that this method of fitting up driving-boxes had been in use on the road for several years previous to his connection with the company. As this device was subsequently made the subject of a patent by Mr. David Matthew, these facts may not be without interest. In 1853, Mr. Charles Ellet, Chief Engineer of the Virginia Central Railroad, laid a temporary track across the Blue Ridge, at Rock Fish Gap, for use during the construction of a tunnel through the mountain. This track was twelve thousand five hundred feet in length on the eastern slope, ascending in that distance six hundred and ten feet, or at the average rate of one in twenty and a half feet. The maximum grade was calculated for two hundred and ninety-six feet per mile, and prevailed for half a mile. It was found, however, in fact, that the grade in places exceeded three hundred feet per mile. The shortest radius of curvature was two hundred and thirty-eight feet. On the western slope, which was ten thousand six hundred and fifty feet in length, the maximum grade was two hundred and eighty feet per mile, and the ruling radius of curvature three hundred feet. This track was worked by two of the Baldwin six-wheels-connected flexible-beam truck locomotives constructed in 1853-54. From a description of this track, and the mode of working it, published by Mr. Ellet in 1856, the following is extracted: "The locomotives mainly relied on for this severe duty were designed and constructed by the firm of M. W. Baldwin & Company, of Philadelphia. The slight modifications introduced at the instance of the writer to adapt them better to the particular service to be performed in crossing the Blue Ridge, did not touch the working proportions or principle of the engines, the merits of which are due to the patentee, M. W. Baldwin, Esq. "These engines are mounted on six wheels, all of which are drivers, and coupled, and forty-two inches diameter. The wheels are set very close, so that the distance between the extreme points of contact of the wheels and the rail, of the front and rear drivers, is nine feet four inches. This closeness of the wheels, of course, greatly reduces the difficulty of turning the short curves of the road. The diameter of the cylinders is sixteen and a half inches, and the length of the stroke twenty inches. To increase the adhesion, and at the same time avoid the resistance of a tender, the engine carries its tank upon the boiler, and the footboard is lengthened out and provided with suspended side-boxes, where a supply of fuel may be stored. By this means the weight of wood and water, instead of abstracting from the effective power of the engine, contributes to its adhesion and consequent ability to climb the mountain. The total weight of these engines is fifty-five thousand pounds, or twenty-seven and a half tons, when the boiler and tank are supplied with water, and fuel enough for a trip of eight miles is on board. The capacity of the tank is sufficient to hold one hundred cubic feet of water, and it has storage-room on top for one hundred cubic feet of wood, in addition to what may be carried in the side-boxes and on the footboard. "To enable the engines better to adapt themselves to the flexures of the road, the front and middle pairs of drivers are held in position by wrought-iron beams, having cylindrical boxes in each end for the journal-bearings, which beams vibrate on spherical pins fixed in the frame of the engine on each side, and resting on the centres of the beams. The object of this arrangement is to form a truck, somewhat flexible, which enables the drivers more readily to traverse the curves of the road. "The writer has never permitted the power of the engines on this mountain road to be fully tested. The object has been to work the line regularly, economically, and, above all, _safely_; and these conditions are incompatible with experimental loads subjecting the machinery to severe strains. The regular daily service of each of the engines is to make four trips, of eight miles, over the mountain, drawing one eight-wheel baggage car, together with two eight-wheel passenger cars, in each direction. "In conveying freight, the regular train on the mountain is three of the eight-wheel house-cars, fully loaded, or four of them when empty or partly loaded. "These three cars, when full, weigh, with their loads, from forty to forty-three tons. Sometimes, though rarely, when the business has been unusually heavy, the loads have exceeded fifty tons. "With such trains the engines are stopped on the track, ascending or descending, and are started again, on the steepest grades, at the discretion of the engineer. "Water, for the supply of the engines, has been found difficult to obtain on the mountain; and, since the road was constructed, a tank has been established on the eastern slope, where the ascending engines stop daily on a grade of two hundred and eighty feet per mile, and are there held by the brakes while the tank is being filled, and started again at the signal and without any difficulty. "The ordinary speed of the engines, when loaded, is seven and a half miles an hour on the ascending grades, and from five and a half to six miles an hour on the descent. "When the road was first opened, it speedily appeared that the difference of forty-three feet on the western side, and fifty-eight feet on the eastern side, between the grades on curves of three hundred feet radii and those on straight lines, was not sufficient to compensate for the increased traction due to such curvature. The velocity, with a constant supply of steam, was promptly retarded on passing from a straight line to a curve, and promptly accelerated again on passing from the curve to the straight line. But, after a little experience in the working of the road, it was found advisable to supply a small amount of grease to the flange of the engine by means of a sponge, saturated with oil, which, when needed, is kept in contact with the wheel by a spring. Since the use of the oil was introduced, the difficulty of turning the curves has been so far diminished, that it is no longer possible to determine whether grades of two hundred and thirty-seven and six-tenths feet per mile on curves of three hundred feet radius, or grades of two hundred and ninety-six feet per mile on straight lines, are traversed most rapidly by the engine. "When the track is in good condition, the brakes of only two of the cars possess sufficient power to control and regulate the movement of the train,--that is to say, they will hold back the two cars and the engine. When there are three or more cars in the train, the brakes on the cars, of course, command the train so much the more easily. "But the safety of the train is not dependent on the brakes of the cars. There is also a valve or air-cock in the steam-chest, under the control of the engineer. This air-cock forms an independent brake, exclusively at the command of the engineer, and which can always be applied when the engine itself is in working order. The action of this power may be made ever so gradual, either slightly relieving the duty of the brakes on the cars, or bringing into play the entire power of the engine. The train is thus held in complete command." The Mountain Top Track, it may be added, was worked successfully for several years, by the engines described in the above extract, until it was abandoned on the completion of the tunnel. The exceptionally steep grades and short curves which characterized the line, afforded a complete and satisfactory test of the adaptation of these machines to such peculiar service. But the period now under consideration was marked by another, and a most important, step in the progress of American locomotive practice. We refer to the introduction of the link-motion. Although this device was first employed by William T. James, of New York, in 1832, and eleven years later by the Stephensons, in England, and was by them applied thenceforward on their engines, it was not until 1849 that it was adopted in this country. In that year Mr. Thomas Rogers, of the Rogers Locomotive and Machine Company, introduced it in his practice. Other builders, however, strenuously resisted the innovation, and none more so than Mr. Baldwin. The theoretical objections which confessedly apply to the device, but which practically have been proved to be unimportant, were urged from the first by Mr. Baldwin as arguments against its use. The strong claim of the advocates of the link-motion, that it gave a means of cutting off steam at any point of the stroke, could not be gainsaid, and this was admitted to be a consideration of the first importance. This very circumstance undoubtedly turned Mr. Baldwin's attention to the subject of methods for cutting off steam, and one of the first results was his "Variable Cut-off," patented April 27, 1852. This device consisted of two valves, the upper sliding upon the lower, and worked by an eccentric and rock-shaft in the usual manner. The lower valve fitted steam-tight to the sides of the steam-chest and the under surface of the upper valve. When the piston reached each end of its stroke, the full pressure of steam from the boiler was admitted around the upper valve, and transferred the lower valve instantaneously from one end of the steam-chest to the other. The openings through the two valves were so arranged that steam was admitted to the cylinder only for a part of the stroke. The effect was, therefore, to cut off steam at a given point, and to open the induction and exhaust ports substantially at the same instant and to their full extent. The exhaust port, in addition, remained fully open while the induction port was gradually closing, and after it had entirely closed. Although this device was never put in use, it may be noted in passing that it contained substantially the principle of the steam-pump, as since patented and constructed. Early in 1853, Mr. Baldwin abandoned the half-stroke cut-off, previously described, and which he had been using since 1845, and adopted the variable cut-off, which was already employed by other builders. One of his letters, written in January, 1853, states his position, as follows: "I shall put on an improvement in the shape of a variable cut-off, which can be operated by the engineer while the machine is running, and which will cut off anywhere from six to twelve inches, according to the load and amount of steam wanted, and this without the link-motion, which I could never be entirely satisfied with. I still have the independent cut-off, and the additional machinery to make it variable will be simple and not liable to be deranged." This form of cut-off was a separate valve, sliding on a partition plate between it and the main steam-valve, and worked by an independent eccentric and rock-shaft. The upper arm of the rock-shaft was curved so as to form a radius-arm, on which a sliding-block, forming the termination of the upper valve-rod, could be adjusted and held at varying distances from the axis, thus producing a variable travel of the upper valve. This device did not give an absolutely perfect cut-off, as it was not operative in backward gear, but when running forward it would cut-off with great accuracy at any point of the stroke, was quick in its movement, and economical in the consumption of fuel. After a short experience with this arrangement of the cut-off, the partition plate was omitted, and the upper valve was made to slide directly on the lower. This was eventually found objectionable, however, as the lower valve would soon cut a hollow in the valve-face. Several unsuccessful attempts were made to remedy this defect, by making the lower valve of brass, with long bearings, and making the valve-face of the cylinder of hardened steel; finally, however, the plan of one valve on the other was abandoned, and recourse was again had to an interposed partition plate, as in the original half-stroke cut-off. [Illustration: Fig. 11.--VARIABLE CUT-OFF ADJUSTMENT.] Mr. Baldwin did not adopt this form of cut-off without some modification of his own, and the modification in this instance consisted of a peculiar device, patented September 13, 1853, for raising and lowering the block on the radius-arm. A quadrant was placed so that its circumference bore nearly against a curved arm projecting down from the sliding-block, and which curved in the reverse direction from the quadrant. Two steel straps side by side were interposed between the quadrant and this curved arm. One of the straps was connected to the lower end of the quadrant and the upper end of the curved arm; the other, to the upper end of the quadrant and the lower end of the curved arm. The effect was the same as if the quadrant and arm geared into each other in any position by teeth, and theoretically the block was kept steady in whatever position placed on the radius-arm of the rock-shaft. This was the object sought to be accomplished, and was stated in the specification of the patent as follows: "The principle of varying the cut-off by means of a vibrating arm and sliding pivot-block has long been known, but the contrivances for changing the position of the block upon the arm have been very defective. The radius of motion of the link by which the sliding-block is changed on the arm, and the radius of motion of that part of the vibrating arm on which the block is placed, have, in this kind of valve gear, as heretofore constructed, been different, which produced a continual rubbing of the sliding-block upon the arm while the arm is vibrating; and as the block for the greater part of the time occupies one position on the arm, and only has to be moved toward either extremity occasionally, that part of the arm on which the block is most used soon becomes so worn that the block is loose, and jars." This method of varying the cut-off was first applied on the engine "Belle," delivered to the Pennsylvania Railroad Company, December 6, 1854, and thereafter was for some time employed by Mr. Baldwin. It was found, however, in practice, that the steel straps would stretch sufficiently to allow them to buckle and break, and hence they were soon abandoned, and chains substituted between the quadrant and curved arm of the sliding-block. These chains in turn proved little better, as they lengthened, allowing lost motion, or broke altogether, so that eventually the quadrant was wholly abandoned, and recourse was finally had to the lever and link for raising and lowering the sliding-block. As thus arranged, the cut-off was substantially what was known as the "Cuyahoga cut-off," as introduced by Mr. Ethan Rogers, of the Cuyahoga Works, Cleveland, Ohio, except that Mr. Baldwin used a partition plate between the upper and the lower valve. But while Mr. Baldwin, in common with many other builders, was thus resolutely opposing the link-motion, it was nevertheless rapidly gaining favor with railroad managers. Engineers and master mechanics were everywhere learning to admire its simplicity, and were manifesting an enthusiastic preference for engines so constructed. At length, therefore, he was forced to succumb; and the link was applied to the "Pennsylvania," one of two engines completed for the Central Railroad of Georgia, in February, 1854. The other engine of the order, the "New Hampshire," had the variable cut-off, and Mr. Baldwin, while yielding to the demand in the former engine, was undoubtedly sanguine that the working of the latter would demonstrate the inferiority of the new device. In this, however, he was disappointed, for in the following year the same company ordered three more engines, on which they specified the link-motion. In 1856, seventeen engines for nine different companies had this form of valve gear, and its use was thus incorporated in his practice. It was not, however, until 1857 that he was induced to adopt it exclusively. This step was forced upon him, at that time, by the report of Mr. Parry, then Superintendent of the Works (now a member of the present firm), who, on returning from an extended tour in the South, brought back the intelligence that the link-motion was everywhere preferred, and that the Baldwin engines were losing ground rapidly, in consequence of their lack of this feature. Mr. Baldwin's characteristic reply was, "Then they shall have link-motion hereafter." And thenceforth the independent cut-off gradually disappeared, and the link reigned in its stead. February 14, 1854, Mr. Baldwin and Mr. David Clark, Master Mechanic of the Mine Hill Railroad, took out conjointly a patent for a feed-water heater, placed at the base of a locomotive chimney, and consisting of one large vertical flue, surrounded by a number of smaller ones. The exhaust steam was discharged from the nozzles through the large central flue, creating a draft of the products of combustion through the smaller surrounding flues. The pumps forced the feed-water into the chamber around these flues, whence it passed to the boiler by a pipe from the back of the stack. This heater was applied on several engines for the Mine Hill Railroad, and on a few for other roads; but its use was exceptional, and lasted only for a year or two. In December of the same year, Mr. Baldwin filed a caveat for a variable exhaust, operated automatically, by the pressure of steam, so as to close when the pressure was lowest in the boiler, and open with the increase of pressure. The device was never put in service. The use of coal, both bituminous and anthracite, as a fuel for locomotives, had by this time become a practical success. The economical combustion of bituminous coal, however, engaged considerable attention. It was felt that much remained to be accomplished in consuming the smoke and deriving the maximum of useful effect from the fuel. Mr. Baird, who was now associated with Mr. Baldwin in the management of the business, made this matter a subject of careful study and investigation. An experiment was conducted under his direction, by placing a sheet-iron deflector in the fire-box of an engine on the Germantown and Norristown Railroad. The success of the trial was such as to show conclusively that a more complete combustion resulted. As, however, a deflector formed by a single plate of iron would soon be destroyed by the action of the fire, Mr. Baird proposed to use a water-leg projecting upward and backward from the front of the fire-box under the flues. Drawings and a model of the device were prepared, with a view of patenting it, but subsequently the intention was abandoned, Mr. Baird concluding that a fire-brick arch as a deflector to accomplish the same object was preferable. This was accordingly tried on two locomotives built for the Pennsylvania Railroad Company in 1854, and was found so valuable an appliance that its use was at once established, and it was put on a number of engines built for railroads in Cuba and elsewhere. For several years the fire-bricks were supported on side plugs; but in 1858, in the "Media," built for the West Chester and Philadelphia Railroad Company, water-pipes extending from the crown obliquely downward and curving to the sides of the fire-box at the bottom, were successfully used for the purpose. The adoption of the link-motion may be regarded as the dividing line between the present and the early and transitional stage of locomotive practice. Changes since that event have been principally in matters of detail, but it is the gradual perfection of these details which has made the locomotive the symmetrical, efficient, and wonderfully complete piece of mechanism it is to-day. In perfecting these minutiæ, the Baldwin Locomotive Works has borne its part, and it only remains to state briefly its contributions in this direction. The production of the establishment during the six years from 1855 to 1860, inclusive, was as follows: forty-seven engines in 1855; fifty-nine in 1856; sixty-six in 1857; thirty-three in 1858; seventy in 1859; and eighty-three in 1860. The greater number of these were of the ordinary type, four drivers coupled, and a four-wheeled truck, and varying in weight from fifteen ton engines, with cylinders twelve by twenty-two, to twenty-seven ton engines, with cylinders sixteen by twenty-four. A few ten-wheeled engines were built, as has been previously noted, and the remainder were the Baldwin flexible-truck six- and eight-wheels-connected engines. The demand for these, however, was now rapidly falling off, the ten-wheeled and heavy "C" engines taking their place, and by 1859 they ceased to be built, save in exceptional cases, as for some foreign roads, from which orders for this pattern were still occasionally received. A few novelties characterizing the engines of this period may be mentioned. Several engines built in 1855 had cross-flues placed in the fire-box, under the crown, in order to increase the heating surface. This feature, however, was found impracticable, and was soon abandoned. The intense heat to which the flues were exposed converted the water contained in them into highly superheated steam, which would force its way out through the water around the fire-box with violent ebullitions. Four engines were built for the Pennsylvania Railroad Company, in 1856-57, with straight boilers and two domes. The "Delano" grate, by means of which the coal was forced into the fire-box from below, was applied on four ten-wheeled engines for the Cleveland and Pittsburg Railroad, in 1857. In 1859, several engines were built with the form of boiler introduced on the Cumberland Valley Railroad in 1851 by Mr. A. F. Smith, and which consisted of a combustion-chamber in the waist of the boiler, next the fire-box. This form of boiler was for some years thereafter largely used in engines for soft coal. It was at first constructed with the "water-leg," which was a vertical water-space, connecting the top and bottom sheets of the combustion-chamber, but eventually this feature was omitted, and an unobstructed combustion-chamber employed. Several engines were built for the Philadelphia, Wilmington and Baltimore Railroad Company in 1859, and thereafter, with the "Dimpfel" boiler, in which the tubes contain water, and, starting downward from the crown-sheet, are curved to the horizontal, and terminate in a narrow water-space next the smoke-box. The whole waist of the boiler, therefore, forms a combustion-chamber, and the heat and gases, after passing for their whole length along and around the tubes, emerge into the lower part of the smoke-box. In 1860, an engine was built for the Mine Hill Railroad, with boiler of a peculiar form. The top sheets sloped upward from both ends toward the centre, thus making a raised part or hump in the centre. The engine was designed to work on heavy grades, and the object sought by Mr. Wilder, the Superintendent of the Mine Hill Railroad, was to have the water always at the same height in the space from which steam was drawn, whether going up or down grade. All these experiments are indicative of the interest then prevailing upon the subject of coal-burning. The result of experience and study had meantime satisfied Mr. Baldwin that to burn soft coal successfully required no peculiar devices; that the ordinary form of boiler, with plain fire-box, was right, with perhaps the addition of a fire-brick deflector; and that the secret of the economical and successful use of coal was in the mode of firing, rather than in a different form of furnace. The year 1861 witnessed a marked falling off in the production. The breaking out of the war at first unsettled business, and by many it was thought that railroad traffic would be so largely reduced that the demand for locomotives must cease altogether. A large number of hands were discharged from the works, and only forty locomotives were turned out during the year. It was even seriously contemplated to turn the resources of the establishment to the manufacture of shot and shell, and other munitions of war, the belief being entertained that the building of locomotives would have to be altogether suspended. So far, however, was this from being the case, that, after the first excitement had subsided, it was found that the demand for transportation by the general government, and by the branches of trade and production created by the war, was likely to tax the carrying capacity of the principal Northern railroads to the fullest extent. The government itself became a large purchaser of locomotives, and it is noticeable, as indicating the increase of travel and freight transportation, that heavier machines than had ever before been built became the rule. Seventy-five engines were sent from the works in 1862; ninety-six in 1863; one hundred and thirty in 1864; and one hundred and fifteen in 1865. During two years of this period, from May, 1862, to June, 1864, thirty-three engines were built for the United States Military Railroads. The demand from the various coal-carrying roads in Pennsylvania and vicinity was particularly active, and large numbers of ten-wheeled engines, and of the heaviest eight-wheeled four-coupled engines, were built. Of the latter class, the majority were with fifteen and sixteen inch cylinders, and of the former, seventeen and eighteen inch cylinders. The introduction of several important features in construction marks this period. Early in 1861, four eighteen inch cylinder freight locomotives, with six coupled wheels, fifty-two inches in diameter, and a Bissell pony-truck with radius-bar in front, were sent to the Louisville and Nashville Railroad Company. This was the first instance of the use of the Bissell truck in the Baldwin Works. These engines, however, were not of the regular "Mogul" type, as they were only modifications of the ten-wheeler, the drivers retaining the same position, well back, and a pair of pony-wheels on the Bissell plan taking the place of the ordinary four-wheeled truck. Other engines of the same pattern, but with eighteen and one-half inch cylinders, were built in 1862-63, for the same company, and for the Don Pedro II. Railway of Brazil. The introduction of steel in locomotive-construction was a distinguishing feature of the period. Steel tires were first used in the works in 1863, on some engines for the Don Pedro II. Railway of South America. Their general adoption on American railroads followed slowly. No tires of this material were then made in this country, and it was objected to their use that, as it took from sixty to ninety days to import them, an engine, in case of a breakage of one of its tires, might be laid up useless for several months. To obviate this objection, M. W. Baldwin & Co. imported five hundred steel tires, most of which were kept in stock, from which to fill orders. Steel fire-boxes were first built for some engines for the Pennsylvania Railroad Company in 1861. English steel, of a high temper, was used, and at the first attempt the fire-boxes cracked in fitting them in the boilers, and it became necessary to take them out and substitute copper. American homogeneous cast-steel was then tried on engines 231 and 232, completed for the Pennsylvania Railroad in January, 1862, and it was found to work successfully. The fire-boxes of nearly all engines thereafter built for that road were of this material, and in 1866 its use for the purpose became general. It may be added that while all steel sheets for fire-boxes or boilers are required to be thoroughly annealed before delivery, those which are flanged or worked in the process of boiler-construction are a second time annealed before riveting. Another feature of construction, gradually adopted, was the placing of the cylinders horizontally. This was first done in the case of an outside-connected engine, the "Ocmulgee," which was sent to the Southwestern Railroad Company of Georgia in January, 1858. This engine had a square smoke-box, and the cylinders were bolted horizontally to its sides. The plan of casting the cylinder and half-saddle in one piece and fitting it to the round smoke-box was introduced by Mr. Baldwin, and grew naturally out of his original method of construction. Mr. Baldwin was the first American builder to use an outside cylinder, and he made it for his early engines with a circular flange cast to it, by which it could be bolted to the boiler. The cylinders were gradually brought lower, and at a less angle, and the flanges prolonged and enlarged. In 1852, three six-wheels-connected engines, for the Mine Hill Railroad Company, were built with the cylinder flanges brought around under the smoke-box until they nearly met, the space between them being filled with a spark-box. This was practically equivalent to making the cylinder and half-saddle in one casting. Subsequently, on other engines on which the spark-box was not used, the half-saddles were cast so as almost to meet under the smoke-box, and, after the cylinders were adjusted in position, wedges were fitted in the interstices and the saddles bolted together. It was finally discovered that the faces of the two half-saddles might be planed and finished so that they could be bolted together and bring the cylinders accurately in position, thus avoiding the troublesome and tedious job of adjusting them by chipping and fitting to the boiler and frames. With this method of construction, the cylinders were placed at a less and less angle, until at length the truck-wheels were spread sufficiently, on all new or modified classes of locomotives in the Baldwin list, to admit of the cylinders being hung horizontally, as is the present almost universal American practice. By the year 1865, horizontal cylinders were made in all cases where the patterns would allow it. The advantages of this arrangement are manifestly in the interest of simplicity and economy, as the cylinders are thus rights or lefts, indiscriminately, and a single pattern answers for either side. A distinguishing feature in the method of construction which characterizes these Works, is the extensive use of a system of standard gauges and templets, to which all work admitting of this process is required to be made. The importance of this arrangement, in securing absolute uniformity of essential parts in all engines of the same class, is manifest, and with the increased production since 1861 it became a necessity as well as a decided advantage. It has already been noted that as early as 1839 Mr. Baldwin felt the importance of making all like parts of similar engines absolutely uniform and interchangeable. It was not attempted to accomplish this object, however, by means of a complete system of standard gauges, until many years later. In 1861 a beginning was made of organizing all the departments of manufacture upon this basis, and from it has since grown an elaborate and perfected system, embracing all the essential details of construction. An independent department of the Works, having a separate foreman and an adequate force of skilled workmen, with special tools adapted to the purpose, is organized as the Department of Standard Gauges. A system of standard gauges and templets for every description of work to be done, is made and kept by this department. The original templets are kept as "standards," and are never used on the work itself, but from them exact duplicates are made, which are issued to the foremen of the various departments, and to which all work is required to conform. The working gauges are compared with the standards at regular intervals, and absolute uniformity is thus maintained. The system is carried into every possible important detail. Frames are planed and slotted to gauges, and drilled to steel bushed templets. Cylinders are bored and planed, and steam-ports, with valves and steam-chests, finished and fitted, to gauges. Tires are bored, centres turned, axles finished, and crossheads, guides, guide-bearers, pistons, connecting- and parallel-rods planed, slotted, or finished, by the same method. Every bolt about the engine is made to a gauge, and every hole drilled and reamed to a templet. The result of the system is an absolute uniformity and interchangeableness of parts in engines of the same class, insuring to the purchaser the minimum cost of repairs, and rendering possible, by the application of this method, the large production which these Works have accomplished. Thus had been developed and perfected the various essential details of existing locomotive practice, when Mr. Baldwin died, September 7, 1866. He had been permitted, in a life of unusual activity and energy, to witness the rise and wonderful increase of a material interest which had become the distinguishing feature of the century. He had done much, by his own mechanical skill and inventive genius, to contribute to the development of that interest. His name was as "familiar as household words" wherever on the American continent the locomotive had penetrated. An ordinary ambition might well have been satisfied with this achievement. But Mr. Baldwin's claim to the remembrance of his fellow-men rests not alone on the results of his mechanical labors. A merely technical history, such as this, is not the place to do justice to his memory as a man, as a Christian, and as a philanthropist; yet the record would be manifestly imperfect, and would fail properly to reflect the sentiments of his business associates who so long knew him in all relations of life, were no reference made to his many virtues and noble traits of character. Mr. Baldwin was a man of sterling integrity and singular conscientiousness. To do right, absolutely and unreservedly, in all his relations with men, was an instinctive rule of his nature. His heroic struggle to meet every dollar of his liabilities, principal and interest, after his failure, consequent upon the general financial crash in 1837, constitutes a chapter of personal self-denial and determined effort which is seldom paralleled in the annals of commercial experience. When most men would have felt that an equitable compromise with creditors was all that could be demanded in view of the general financial embarrassment, Mr. Baldwin insisted upon paying all claims in full, and succeeded in doing so only after nearly five years of unremitting industry, close economy, and absolute personal sacrifices. As a philanthropist and a sincere and earnest Christian, zealous in every good work, his memory is cherished by many to whom his contributions to locomotive improvement are comparatively unknown. From the earliest years of his business life the practice of systematic benevolence was made a duty and a pleasure. His liberality constantly increased with his means. Indeed, he would unhesitatingly give his notes, in large sums, for charitable purposes, when money was absolutely wanted to carry on his business. Apart from the thousands which he expended in private charities, and of which, of course, little can be known, Philadelphia contains many monuments of his munificence. Early taking a deep interest in all Christian effort, his contributions to missionary enterprise and church extension were on the grandest scale, and grew with increasing wealth. Numerous church edifices in this city, of the denomination to which he belonged, owe their existence largely to his liberality, and two at least were projected and built by him entirely at his own cost. In his mental character, Mr. Baldwin was a man of remarkable firmness of purpose. This trait was strongly shown during his mechanical career, in the persistency with which he would work at a new improvement or resist an innovation. If he was led sometimes to assume an attitude of antagonism to features of locomotive-construction which after-experience showed to be valuable,--and a desire for historical accuracy has required the mention, in previous pages, of several instances of this kind,--it is at least certain that his opposition was based upon a conscientious belief in the mechanical impolicy of the proposed changes. After the death of Mr. Baldwin, the business was reorganized, in 1867, under the title of "The Baldwin Locomotive Works," M. Baird & Co., Proprietors. Messrs. George Burnham and Charles T. Parry, who had been connected with the establishment from an early period, the former in charge of the finances, and the latter as General Superintendent, were associated with Mr. Baird in the copartnership. Three years later, Messrs. Edward H. Williams, William P. Henszey, and Edward Longstreth became members of the firm. Mr. Williams had been connected with railway management on various lines since 1850. Mr. Henszey had been Mechanical Engineer, and Mr. Longstreth the General Superintendent of the Works for several years previously. The production of the Baldwin Locomotive Works from 1866 to 1871, both years inclusive, has been as follows: 1866, one hundred and eighteen locomotives. 1867, one hundred and twenty-seven " 1868, one hundred and twenty-four " 1869, two hundred and thirty-five " 1870, two hundred and eighty " 1871, three hundred and thirty-one " In July, 1866, the engine "Consolidation" was built for the Lehigh Valley Railroad, on the plan and specification furnished by Mr. Alexander Mitchell, Master Mechanic of the Mahanoy Division of that railroad. This engine was intended for working the Mahanoy plane, which rises at the rate of one hundred and thirty-three feet per mile. The "Consolidation" had cylinders twenty by twenty-four, four pairs of drivers connected, forty-eight inches in diameter, and a Bissell pony-truck in front, equalized with the front drivers. The weight of the engine, in working order, was ninety thousand pounds, of which all but about ten thousand pounds was on the drivers. This engine has constituted the first of a class to which it has given its name, and over thirty "Consolidation" engines have since been constructed. A class of engines known as "Moguls," with three pairs of drivers connected and a swing pony-truck in front equalized with the front drivers, took its rise in the practice of this establishment from the "E. A. Douglas," built for the Thomas Iron Company in 1867. These engines are fully illustrated in the Catalogue. Several sizes of "Moguls" have been built, but principally with cylinders sixteen, seventeen, and eighteen inches in diameter, respectively, and twenty-two or twenty-four inches stroke, and with drivers from forty-four to fifty-seven inches in diameter. This plan of engine has rapidly grown in favor for freight service on heavy grades or where maximum loads are to be moved, and has been adopted by several leading lines. Utilizing, as it does, nearly the entire weight of the engine for adhesion, the main and back pairs of drivers being equalized together, as also the front drivers and the pony-wheels, and the construction of the engine with swing-truck and one pair of drivers without flanges allowing it to pass short curves without difficulty, the "Mogul" is generally accepted as a type of engine especially adapted to the economical working of heavy freight traffic. In 1867, on a number of eight-wheeled four-coupled engines, for the Pennsylvania Railroad, the four-wheeled swing-bolster-truck was first applied, and thereafter nearly all the engines built in the establishment with a two- or four-wheeled truck in front have been so constructed. The two-wheeled or "pony" truck has been built both on the Bissell plan, with double inclined slides, and with the ordinary swing-bolster, and in both cases with the radius-bar pivoting from a point about four feet back from the centre of the truck. The four-wheeled truck has been made with swing-bolster exclusively and without the radius-bar. Of the engines above referred to as the first on which the swing-bolster-truck was applied, four were for express passenger service, with drivers sixty-seven inches in diameter, and cylinders seventeen by twenty-four. One of them, placed on the road September 9, 1867, was in constant service until May 14, 1871, without ever being off its wheels for repairs, making a total mileage of one hundred and fifty-three thousand two hundred and eighty miles. All of these engines have their driving-wheels spread eight and one-half feet between centres, thus increasing the adhesive weight, and with the use of the swing-truck they have been found to work readily on the shortest curves on the road. Steel flues were put in three ten-wheeled freight engines, numbers 211, 338, and 368, completed for the Pennsylvania Railroad in August, 1868, and up to the present time have been in constant use without requiring renewal. Flues of the same material have also been used in a number of engines for South American railroads. Experience with tubes of this metal, however, has not yet been sufficiently extended to show whether they give any advantages commensurate with their increased cost over iron. Steel boilers have been built, to a considerable extent, for the Pennsylvania, Lehigh Valley, Central of New Jersey, and some other railroad companies, since 1868, and with good results thus far. Where this metal is used for boilers, the plates may be somewhat thinner than if of iron, but at the same time, as shown by careful tests, giving a greater tensile strength. The thoroughly homogeneous character of the steel boiler-plate made in this country recommends it strongly for the purpose. In 1854, four engines for the Pennsylvania Railroad Company, the "Tiger," "Leopard," "Hornet," and "Wasp," were built with straight boilers and two domes each, and in 1866 this method of construction was revived. Since that date, the practice of the establishment has included both the wagon-top boiler with single dome, and the straight boiler with two domes. When the straight boiler is used, the waist is made about two inches larger in diameter than that of the wagon-top form. About equal space for water and steam is thus given in either case, and, as the number of flues is the same in both forms, more room for the circulation of water between the flues is afforded in the straight boiler, on account of its larger diameter, than in the wagon-top shape. The preference of many railroad officers for the straight boiler is based on the consideration of the greater strength which this form confessedly gives. The top and side lines being of equal length, the expansion is uniform throughout, and hence there is less liability to leak on the sides, at the junction of the waist and fire-box. The throttle-valve is placed in the forward dome, from which point drier steam can be drawn than from over the crown-sheet, where the most violent ebullitions in a boiler occur. For these reasons, as well as on account of its greater symmetry, the straight boiler with two domes is largely accepted as preferable to the wagon-top form. Early in 1870, the success of the various narrow-gauge railway enterprises in Europe aroused a lively interest in the subject, and numerous similar lines were projected on this side of the Atlantic. Several classes of engines for working railroads of this character were designed and built, and are illustrated in full in Division VII of the Catalogue. The history of the Baldwin Locomotive Works has thus been traced from its inception to the present time. Over twenty-six hundred locomotives have been built in the establishment since the completion of the "Old Ironsides," in 1832. Its capacity is now equal to the production of over four hundred locomotives annually, and it has attained the rank of the largest locomotive works in the world. It owes this position not only to the character of the work it has turned out, but largely also to the peculiar facilities for manufacture which it possesses. Situated close to the great iron and coal region of the country, the principal materials required for its work are readily available. It numbers among its managers and workmen men who have had the training of a lifetime in the various specialties of locomotive-manufacture, and whose experience has embraced the successive stages of American locomotive progress. Its location, in the largest manufacturing city of the country, is an advantage of no ordinary importance. In 1870, Philadelphia, with a total population of nearly seven hundred thousand souls, gave employment in its manufactures to over one hundred and twenty thousand persons. In other words, more than one-sixth of its population is concerned in production. The extent of territory covered by the city, embracing one hundred and twenty-seven square miles, with unsurpassed facilities for ready intercommunication by street railways, renders possible separate comfortable homes for the working population, and thus tends to elevate their condition and increase their efficiency. Such and so vast a class of skilled mechanics is therefore available from which to recruit the forces of the establishment when necessary. Under their command are special tools, which have been created from time to time with reference to every detail of locomotive-manufacture; and an organized system of production, perfected by long years of experience, governs the operation of all. With such a record for the past, and such facilities at its command for the future, the Baldwin Locomotive Works submits the following Catalogue of the principal classes of locomotives embraced in its present practice. CIRCULAR. In the following pages we present and illustrate a system of STANDARD LOCOMOTIVES, in which, it is believed, will be found designs suited to all the requirements of ordinary service. These patterns admit of modifications, to suit the preferences of railroad managers, and where machines of peculiar construction for special service are required, we are prepared to make and submit designs, or to build to specifications furnished. All the locomotives of the system herewith presented are adapted to the consumption of wood, coke, or bituminous or anthracite coal as fuel. All work is accurately fitted to gauges, which are made from a system of standards kept exclusively for the purpose. Like parts will, therefore, fit accurately in all locomotives of the same class. This system of manufacture, together with the large number of locomotives at all times in progress, and embracing the principal classes, insures unusual and especial facilities for filling at once, or with the least possible delay, orders for duplicate parts. Full specifications of locomotives will be furnished on application. M. BAIRD & CO. EXPLANATION OF TERMS. The several classes of locomotives manufactured by the Baldwin Locomotive Works have their respective distinguishing names, which are derived and applied as follows: All locomotives having one pair of driving-wheels are designated as B engines. Those having two pairs of drivers, as C engines. Those having three pairs of drivers, as D engines. Those having four pairs of drivers, as E engines. One or more figures united with one of these letters, B, C, D, or E, and preceding it, indicates the dimensions of cylinders, boiler, and other parts, and also the general plan of the locomotive: thus, 27-1/2 C designates the class of eight-wheeled locomotives (illustrated on pages 56 and 60) with two pairs of drivers and a four-wheeled truck, and with cylinders sixteen inches in diameter and twenty-two or twenty-four inches stroke. 34 E designates another class (illustrated on page 80), with four pairs of drivers and a pony truck, and with cylinders twenty inches in diameter and twenty-four inches stroke. In like manner all the other classes are designated by a combination of certain letters and figures. All corresponding important parts of locomotives of the same class are made interchangeable and exact duplicates. The following table gives a summary of the principal classes of locomotives of our manufacture: GENERAL CLASSIFICATION. ---------------------------------------------------------------------------------------------- | | | | DRIVERS. |Truck. |Weight in| Designation| SERVICE. | Gauge. |Cylinders.|-------------| No. |Working | of Class. | | | |No.|Diameter.|Wheels.|Order. | -----------+--------------------------+------------+----------+---+---------+-------+---------| | | | | | INCHES. | | POUNDS. | 8-1/2 C | Narrow Gauge | | | | | | | | Passenger and Freight. | 3 feet | 9 � 16 | 4 | 36 to 40| 2 | 25,000 | | | and over. | | | | | | 9-1/2 C | do. | " | 10 � 16 | 4 | 36 to 40| 2 | 30,000 | 12 D | Narrow Gauge Freight. | " | 11 � 16 | 6 | 36 to 40| 2 | 35,000 | 14 D | do. | " | 12 � 16 | 6 | 36 to 40| 2 | 40,000 | 8 C | Tank Switching. |4 ft. 8-1/2 | 9 � 16 | 4 | 36 | .... | 25,000 | | | and over | | | | | | 10-1/2 C | do. | " | 11 � 16 | 4 | 36 | .... | 38,000 | 11-1/2 C | do. | " | 11 � 16 | 4 | 36 | 2 | 40,000 | 12 C | do. | " | 12 � 22 | 4 | 44 | .... | 43,000 | 14 C | do. | " | 14 � 22 | 4 | 48 | .... | 48,000 | 14-1/2 C | do. | " | 14 � 22 | 4 | 48 | 2 | 50,000 | 18-1/2 C | do. | " | 15 � 22 | 4 | 48 to 54| .... | 55,000 | 15-1/2 C | do. | " | 15 � 22 | 4 | 48 to 54| 2 | 57,000 | 21 D | do. | " | 15 � 22 | 6 | 44 | .... | 60,000 | 27-1/2 D | do. | " | 16 � 22 | 6 | 44 to 48| .... | 66,000 | 8 C | Switching, | | | | | | | | with separate Tender. | " | 9 � 16 | 4 | 36 | .... | 22,000 | 10-1/2 C | do. | " | 11 � 16 | 4 | 36 | .... | 34,000 | 11-1/2 C | do. | " | 11 � 16 | 4 | 36 | 2 | 36,000 | 12 C | do. | " | 12 � 22 | 4 | 44 | .... | 38,000 | 14 C | do. | " | 14 � 22 | 4 | 48 | .... | 42,000 | 14-1/2 C | do. | " | 14 � 22 | 4 | 48 | 2 | 44,000 | 18-1/2 C | do. | " | 15 � 22 | 4 | 48 to 54| .... | 49,000 | 15-1/2 C | do. | " | 15 � 22 | 4 | 48 to 54| 2 | 51,000 | 19-1/2 C | do. | " | 16 � 22 | 4 | 48 to 54| .... | 56,000 | 21 D | do. | " | 15 � 22 | 6 | 44 | .... | 52,000 | 27-1/2 D | do. | " | 16 � 22} | 6 | 44 to 48| .... | 60,000 | | | | 24} | | | | | 25-1/2 D | do. | " | 17 � 22} | 6 | 48 to 54| .... | 66,000 | | | | 24} | | | | | 15 C | Passenger and Freight. | " | 10 � 20 | 4 | 54 | 4 | 38,000 | 16-1/2 C | do. | " | 12 � 22 | 4 | 54 to 60| 4 | 44,000 | 20-1/2 C | do. | " | 13 � 22} | 4 | 56 to 66| 4 | 50,000 | | | | 24} | | | | | 22-1/2 C | do. | " | 14 � 22} | 4 | 56 to 66| 4 | 55,000 | | | | 24} | | | | | 24-1/2 C | do. | " | 15 � 22} | 4 | 56 to 66| 4 | 60,000 | | | | 24} | | | | | 27-1/2 C | do. | " | 16 � 22} | 4 | 56 to 66| 4 | 65,000 | | | | 24} | | | | | 28 | do. | " | 17 � 22} | 4 | 56 to 66| 4 | 70,000 | | | | 24} | | | | | 24-1/2 D | Freight. | " | 16 � 22} | 6 | 48 to 54| 4 | 67,000 | | | | 24} | | | | | 26-1/2 D | do. | " | 17 � 22} | 6 | 48 to 54| 4 | 72,000 | | | | 24} | | | | | 28-1/2 D | do. | " | 18 � 22} | 6 | 48 to 54| 4 | 77,000 | | | | 24} | | | | | 27-1/2 D | Freight and pushing. | " | 16 � 22} | 6 | 48 to 54| 2 | 66,000 | | | | 24} | | | | | 25-1/2 D | do. | " | 17 � 22} | 6 | 48 to 54| 2 | 71,000 | | | | 24} | | | | | 30 D | do. | " | 18 � 22} | 6 | 48 to 54| 2 | 76,000 | | | | 24} | | | | | 34 E | Freight and Pushing. | " | 20 � 24 | 8 | 48 | 2 | 96,000 | ---------------------------------------------------------------------------------------------- PREFATORY. The dimensions given in the following Catalogue are for locomotives of four feet eight and a half inches gauge, unless otherwise stated. The _loads_ given under each class are invariably in gross tons of twenty-two hundred and forty pounds, and include both cars and lading. All the locomotives described in this Catalogue are sold with the guarantee that they will haul, on a straight track in good condition, the loads stated. Their actual performance under favorable circumstances may be relied upon largely to exceed the figures given in the guarantee. The feed-water for all locomotives specified is supplied by two pumps, or one pump and one injector. One or more injectors can also be supplied in addition to the two pumps, if desired. [Illustration: Locomotive.] DIVISION I. ROAD LOCOMOTIVES FOR PASSENGER OR FREIGHT SERVICE. CLASS 15 C. General Design Illustrated by Print on Page 52. CYLINDERS. Diameter of cylinders 10 inches. Length of stroke 20 " DRIVING-WHEELS. Diameter of drivers 54 inches. TRUCK. FOUR-WHEELED TRUCK, WITH CENTRE-BEARING BOLSTER. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 16 ft. 3-3/4 inches. TENDER. ON FOUR WHEELS. Capacity of tank 900 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 23,000 pounds. On truck 15,000 " ------ Total weight of engine, about 38,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 550 gross tons. " 20 ft. grade 250 " " " 40 " 160 " " " 60 " 115 " " " 80 " 85 " " " 100 " 65 " " DIVISION I. ROAD LOCOMOTIVES FOR PASSENGER OR FREIGHT SERVICE. CLASS 16-1/2 C. General Design Illustrated by Print on Page 52. CYLINDERS. Diameter of cylinders 12 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 54 to 60 inches. TRUCK. FOUR-WHEELED TRUCK, WITH CENTRE-BEARING BOLSTER. Diameter of wheels 24 to 26 inches. WHEEL-BASE. Total wheel-base 19 ft. 1 inch. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1200 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 28,000 pounds. On truck 16,000 " ------ Total weight of engine, about 44,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 665 gross tons. " 20 ft. grade 305 " " " 40 " 190 " " " 60 " 135 " " " 80 " 100 " " " 100 " 75 " " [Illustration: Locomotive.] DIVISION I. ROAD LOCOMOTIVES FOR PASSENGER OR FREIGHT SERVICE. CLASS 20-1/2 C General Design Illustrated by Prints on Pages 52 and 56. CYLINDERS. Diameter of cylinders 13 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. Diameter of drivers 56 to 66 inches. TRUCK. FOUR-WHEELED CENTRE-BEARING TRUCK, WITH SWING BOLSTER. Diameter of wheels 24 to 30 inches. WHEEL-BASE. Total wheel-base 20 ft. 1-3/4 inches. Rigid " (distance between driving-wheel-centres) 6 ft. 6 inches. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1400 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 30,000 pounds. On truck 20,000 " ------ Total weight of engine, about 50,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 710 gross tons. " 20 ft. grade 325 " " " 40 " 200 " " " 60 " 140 " " " 80 " 105 " " " 100 " 80 " " DIVISION I. ROAD LOCOMOTIVES FOR PASSENGER OR FREIGHT SERVICE. CLASS 22-1/2 C. General Design Illustrated by Prints on Pages 52 and 56. CYLINDERS. Diameter of cylinders 14 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. Diameter of drivers 56 to 66 inches. TRUCK. FOUR-WHEELED CENTRE-BEARING TRUCK, WITH SWING BOLSTER. Diameter of wheels 24 to 30 inches. WHEEL-BASE. Total wheel-base 20 ft. 7-3/4 inches. Rigid " (distance between driving-wheel-centres) 7 ft. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 35,000 pounds. On truck 20,000 " ------ Total weight of engine, about 55,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 835 gross tons. " 20 ft. grade 380 " " " 40 " 240 " " " 60 " 170 " " " 80 " 125 " " " 100 " 100 " " [Illustration: Locomotive.] DIVISION I. ROAD LOCOMOTIVES FOR PASSENGER OR FREIGHT SERVICE. CLASS 24-1/2 C General Design Illustrated by Prints on Pages 56 and 60. CYLINDERS. Diameter of cylinders 15 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. Diameter of drivers 56 to 66 inches. TRUCK. FOUR-WHEELED CENTRE-BEARING TRUCK, WITH SWING BOLSTER. Diameter of wheels 24 to 30 inches. WHEEL-BASE. Total wheel-base 21 ft. 3 inches. Rigid " (distance between driving-wheel-centres) 7 ft. 8 inches. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1800 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 39,000 pounds. On truck 21,000 " ------ Total weight of engine, about 60,000 " LOAD. IN ADDITION TO WEIGHT OF ENGINE AND TENDER. On a level 930 gross tons. " 20 ft. grade 430 " " " 40 " 270 " " " 60 " 190 " " " 80 " 140 " " "100 " 110 " " DIVISION I. ROAD LOCOMOTIVES FOR PASSENGER OR FREIGHT SERVICE. CLASS 27-1/2 C. General Design Illustrated by Prints on Pages 56 and 60. CYLINDERS. Diameter of cylinders 16 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. Diameter of drivers 56 to 66 inches. TRUCK. FOUR-WHEELED CENTRE-BEARING TRUCK, WITH SWING BOLSTER. Diameter of wheels 24 to 30 inches. WHEEL-BASE. Total wheel-base 21 ft. 9 inches. Rigid " (distance between driving-wheel-centres) 8 ft. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 2000 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 42,000 pounds. On truck 23,000 " ------ Total weight of engine, about 65,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1000 gross tons. " 20 ft. grade 460 " " " 40 " 290 " " " 60 " 205 " " " 80 " 150 " " " 100 " 120 " " The distance between centres of drivers (rigid wheel-base) can be made 8 ft. 6 in., if preferred to 8 ft. as given above. This greater spread of wheels, throwing more weight on the drivers, gives the engine greater adhesion, and thus adds to its efficiency for freight service. Owing to the peculiar construction of the truck, the engine is found to pass short curves without difficulty, even with this greater distance between driving-wheel-centres. [Illustration: Locomotive.] DIVISION I. ROAD LOCOMOTIVES FOR PASSENGER OR FREIGHT SERVICE. CLASS 28 C. General Design Illustrated by Prints on Pages 56, 60, and 64. CYLINDERS. Diameter of cylinders 17 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. Diameter of drivers 56 to 66 inches. TRUCK. FOUR-WHEELED CENTRE-BEARING TRUCK, WITH SWING BOLSTER. Diameter of wheels 24 to 30 inches. WHEEL-BASE. Total wheel-base 22 ft. 6-1/4 inches. Rigid " (distance between driving-wheel-centres) 8 ft. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 2200 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 45,000 pounds. On truck 25,000 " ------ Total weight of engine, about 70,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1075 gross tons. " 20 ft. grade 495 " " " 40 " 310 " " " 60 " 220 " " " 80 " 165 " " " 100 " 130 " " The distance between centres of drivers (rigid wheel-base) can be made 8 ft. 6 in., if preferred to 8 ft. as given above. This greater spread of wheels, throwing more weight on the drivers, gives the engine greater adhesion, and thus adds to its efficiency for freight service. Owing to the peculiar construction of the truck, the engine is found to pass short curves without difficulty, even with this greater distance between driving-wheel-centres. ADDENDA. ADAPTATION FOR EITHER PASSENGER OR FREIGHT SERVICE. The five preceding classes, embracing road locomotives with cylinders from thirteen to seventeen inches in diameter, admit of construction with either a twenty-two or a twenty-four inches stroke, and with driving-wheels of any diameter from fifty-six to sixty-six inches. Each class can, therefore, be adapted to either passenger or freight service, by giving the shorter stroke and the larger wheel for the former use, and the longer stroke and smaller wheel for the latter. The same cylinder pattern is used for both the twenty-two and the twenty-four inches stroke, the difference in length being made by recessing the cylinder heads. ANTHRACITE COAL BURNERS. The illustrations and figures given for engines in this Division are all for soft coal or wood burners. For anthracite coal the form of the furnace is changed, giving a longer grate and shallower fire-box. The barrel of boiler, length of connecting-rods, number and length of flues, etc., remain the same, so that no change in principal patterns results. The change in shape and dimensions of fire-box, however, alters the distribution of weight, throwing more load on the drivers and less on the truck, while the total weight of engine remains nearly the same. The hard coal burners, accordingly, having from this cause somewhat more adhesion than the soft coal burners of the same class, have proportionately more tractive power, and will haul loads from ten to fifteen per cent. greater than those given for the corresponding soft coal or wood burning engines. STRAIGHT AND WAGON-TOP BOILERS. All the engines of this division are built with wagon-top boilers or with straight boilers and two domes, as preferred. Where the latter form is made, the throttle-valve is placed in the forward dome. The wagon-top and straight boilers for the same class are so proportioned as to give equal steam space and the same number of flues in both forms of construction. [Illustration: Locomotive.] DIVISION II. TEN-WHEELED FREIGHT LOCOMOTIVES. CLASS 24-1/2 D. General Design Illustrated by Print on Page 68. CYLINDERS. Diameter of cylinders 16 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. REAR AND FRONT PAIRS WITH FLANGED TIRES 5-1/2 INCHES WIDE. MAIN PAIR WITH PLAIN TIRES 6 INCHES WIDE. Diameter of drivers 48 to 54 inches. TRUCK. FOUR-WHEELED CENTRE-BEARING TRUCK, WITH SWING BOLSTER. Diameter of wheels 24 to 26 inches. WHEEL-BASE. Total wheel-base 23 feet. Rigid " (distance between centres of rear and front drivers) 12 ft. 1 inch. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 51,000 pounds. On truck 16,000 " ------ Total weight of engine, about 67,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1230 gross tons " 20 ft. grade 570 " " " 40 " 360 " " " 60 " 260 " " " 80 " 195 " " " 100 " 155 " " DIVISION II. TEN-WHEELED FREIGHT LOCOMOTIVES. CLASS 26-1/2 D. General Design Illustrated by Print on Page 68. CYLINDERS. Diameter of cylinders 17 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. REAR AND FRONT PAIRS WITH FLANGED TIRES 5-1/2 INCHES WIDE. MAIN PAIR WITH PLAIN TIRES 6 INCHES WIDE. Diameter of drivers 48 to 54 inches. TRUCK. FOUR-WHEELED CENTRE-BEARING TRUCK, WITH SWING BOLSTER. Diameter of wheels 24 to 26 inches. WHEEL-BASE. Total wheel-base 23 ft. 2-3/4 inches. Rigid " (distance between centres of rear and front drivers) 12 ft. 8 inches. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1800 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 54,000 pounds. On truck 18,000 " ------ Total weight of engine, about 72,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1300 gross tons. " 20 ft. grade 600 " " " 40 " 380 " " " 60 " 270 " " " 80 " 205 " " " 100 " 160 " " DIVISION II. TEN-WHEELED FREIGHT LOCOMOTIVES. CLASS 28-1/2 D. General Design Illustrated by Print on Page 68. CYLINDERS. Diameter of cylinders 18 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. REAR AND FRONT PAIRS WITH FLANGED TIRES 5-1/2 INCHES WIDE. MAIN PAIR WITH PLAIN TIRES 6 INCHES WIDE. Diameter of drivers 48 to 54 inches. TRUCK. FOUR-WHEELED CENTRE-BEARING TRUCK, WITH SWING BOLSTER. Diameter of wheels 24 to 26 inches. WHEEL-BASE. Total wheel-base 23 ft. 2-3/4 inches. Rigid " (distance between centres of rear and front drivers) 12 ft. 8 inches. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 2000 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 58,000 pounds. On truck 19,000 " ------ Total weight of engine, about 77,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1400 gross tons. " 20 ft. grade 645 " " " 40 " 410 " " " 60 " 290 " " " 80 " 220 " " " 100 " 175 " " ADDENDA. HARD AND SOFT COAL BURNERS In the three classes of engines of Division II. certain differences occur between hard and soft coal burners. The print on page 68 illustrates the plan of the soft coal or wood burner. In the hard coal burner the fire-box is made longer and shallower; the rear drivers are brought farther forward, and the three pairs of drivers are arranged so that the distance between centres of rear and main drivers is the same as the distance between centres of main and front drivers. The point of suspension of the back part of the engine being thus brought forward, a greater proportion of the total weight is carried on the drivers and rendered available for adhesion, and the tractive power of the hard coal burner is accordingly somewhat greater than that of the soft coal engine. The rigid wheel-base of the hard coal burner is also lessened from 17 to 24 inches by the same modification. CURVING. All engines of this Division are built with a swing-bolster truck. The middle pair of drivers have tires without flanges. The engine is accordingly guided on the rails by the truck and the flanges of the front driving-wheels, and is found to pass curves without difficulty. If preferred, however, the front instead of the main pair of drivers can have the plain tires. Both methods are in use. STRAIGHT AND WAGON-TOP BOILERS. All the engines of this Division are built with wagon-top boilers or with straight boilers and two domes, as preferred. Where the latter form is made, the throttle-valve is placed in the forward dome. The wagon-top and straight boilers for the same class are so proportioned as to give equal steam space and the same number of flues in both forms of construction. [Illustration: Locomotive.] DIVISION III. FREIGHT OR PUSHING ENGINES.--"MOGUL" PATTERN. CLASS 27-1/2 D. General Design Illustrated by Print on Page 74. CYLINDERS. Diameter of cylinders 16 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. REAR AND FRONT PAIRS WITH FLANGED TIRES 5-1/2 INCHES WIDE. MAIN PAIR WITH PLAIN TIRES 6 INCHES WIDE. Diameter of drivers 48 to 54 inches. TRUCK. ONE PAIR OF LEADING WHEELS, WITH SWING BOLSTER AND RADIUS-BAR, EQUALIZED WITH FRONT DRIVERS. Diameter of wheels 30 inches. WHEEL-BASE. Total wheel-base 21 ft. 4 inches. Rigid " (distance between centres of rear and front drivers) 14 ft. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 57,000 pounds. On leading wheels 9,000 " ------ Total weight of engine, about 66,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1400 gross tons. " 20 ft. grade 655 " " " 40 " 415 " " " 60 " 300 " " " 80 " 230 " " " 100 " 180 " " DIVISION III. FREIGHT OR PUSHING ENGINES--"MOGUL" PATTERN. CLASS 25-1/2 D. General Design Illustrated by Print on Page 74. CYLINDERS. Diameter of cylinders 17 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. REAR AND FRONT PAIRS WITH FLANGED TIRES 5-1/2 INCHES WIDE. MAIN PAIR WITH PLAIN TIRES 6 INCHES WIDE. Diameter of drivers 48 to 54 inches. TRUCK. ONE PAIR OF LEADING WHEELS, WITH SWING BOLSTER AND RADIUS-BAR, EQUALIZED WITH FRONT DRIVERS. Diameter of wheels 30 inches. WHEEL-BASE. Total wheel-base 21 ft. 10 inches. Rigid " (distance between centres of rear and front drivers) 14 ft. 6 inches. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1800 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 62,000 pounds. On leading wheels 9,000 " ------ Total weight of engine, about 71,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1500 gross tons. " 20 ft. grade 695 " " " 40 " 445 " " " 60 " 320 " " " 80 " 245 " " " 100 " 195 " " DIVISION III. FREIGHT OR PUSHING ENGINES--"MOGUL" PATTERN. CLASS 30 D. General Design Illustrated by Print on Page 74. CYLINDERS. Diameter of cylinders 18 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. REAR AND FRONT PAIRS WITH FLANGED TIRES 5-1/2 INCHES WIDE. MAIN PAIR WITH PLAIN TIRES 6 INCHES WIDE. Diameter of drivers 48 to 54 inches. TRUCK. ONE PAIR OF LEADING WHEELS, WITH SWING BOLSTER AND RADIUS-BAR, EQUALIZED WITH FRONT DRIVERS. Diameter of wheels 30 inches. WHEEL-BASE. Total wheel-base 22 ft. 5 inches. Rigid " (distance between centres of rear and front drivers) 15 ft. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 2000 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 66,000 pounds. On leading wheels 10,000 " ------ Total weight of engine, about 76,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1600 gross tons. " 20 ft. grade 740 " " " 40 " 470 " " " 60 " 340 " " " 80 " 260 " " " 100 " 205 " " ADDENDA. ANTHRACITE COAL BURNERS. For anthracite coal, a long and shallow fire-box is constructed, and the back driving-wheels are placed at the same distance from the main pair as the latter are from the front drivers. This reduces the rigid wheel-base to some extent, but retains the same weight on drivers. CURVING. The leading wheels having a swing bolster, and the middle pair of drivers having no flanges, the engine is guided by the truck and the front drivers, and is found to pass short curves without difficulty. TRACTIVE POWER. It will be seen that in engines of this pattern nearly all the weight of the machine is utilized for adhesion, only enough load being thrown on the leading wheels to steady the engine on the track. The tractive power of these engines is accordingly greater in comparison with their total weight than that of either the eight-wheeled C or the ten-wheeled D patterns, and they are, therefore, especially suited to working steep grades and hauling heavy loads at low speeds. STRAIGHT AND WAGON-TOP BOILERS. All the engines of this Division are built with wagon-top boilers or with straight boilers and two domes, as preferred. Where the latter form is made, the throttle-valve is placed in the forward dome. The wagon-top and straight boilers for the same class are so proportioned as to give equal steam space and the same number of flues in both forms of construction. [Illustration: Locomotive.] DIVISION IV. FREIGHT OR PUSHING ENGINES.--"CONSOLIDATION" PATTERN. CLASS 34 E. Illustrated by Print on Page 80. CYLINDERS. Diameter of cylinders 20 inches. Length of stroke 24 inches. DRIVING-WHEELS. REAR AND SECOND PAIRS WITH FLANGED TIRES 5-1/2 INCHES WIDE. FRONT AND MAIN PAIRS WITH PLAIN TIRES 6 INCHES WIDE. Diameter of drivers 48 inches. TRUCK. ONE PAIR OF LEADING WHEELS, WITH SWING BOLSTER AND RADIUS-BAR, EQUALIZED WITH FRONT DRIVERS. Diameter of wheels 30 inches. WHEEL-BASE. Total wheel-base 21 ft. 10 inches. Rigid " (distance between rear and second pair of drivers) 9 ft. 10 inches. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 2400 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 87,000 pounds. On leading wheels 9,000 " ------ Total weight of engine, about 96,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 2000 gross tons. " 20 ft. grade 990 " " " 40 " 635 " " " 60 " 460 " " " 80 " 355 " " " 100 " 285 " " ADDENDA. GENERAL DESIGN. The plan of this engine admits of either straight or wagon-top boiler, and of the use, with the proper form of grate, of either anthracite or bituminous coal or of wood. WHEEL-BASE. The arrangement of the wheels is such as to permit the engine to traverse curves with nearly as much facility as an engine of the ordinary type with only four drivers. The leading wheels having a swing bolster, and the front and main drivers having no flanges, the engine is guided on the rails by the leading wheels and by the flanges of the rear and second pairs of drivers. It is, therefore, impossible for the wheels to bind on the rails. Engines of this class are run around curves of 400 feet radius and less. TRACTIVE POWER. The distribution of the total weight of the engine gives about twenty-two thousand pounds for each pair of drivers,--a weight no greater than is carried on each pair of drivers of the larger sizes of ordinary eight-wheeled C engines. The single pair of leading wheels carries only nine thousand pounds. This arrangement renders available for adhesion a total weight of 87,000 pounds. One of these engines on a recent trial hauled one hundred and fifty gross tons of cars and load up a grade of one hundred and forty-five feet with sharp curves, and two hundred and sixty-eight gross tons of cars and load up a grade of one hundred and sixteen feet to the mile. The pressure in the first case was one hundred and ten pounds, and the speed six minutes to the mile; in the second case, the pressure was one hundred and twenty pounds, and the speed seven and one-half minutes to the mile. These engines are especially adapted to the working of steep gradients or where heavy loads are to be moved. [Illustration: Locomotive.] DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 8 C. General Design Illustrated by Print on Page 84. CYLINDERS. Diameter of cylinders 9 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 inches. Distance between centres 6 feet. TENDER. ON FOUR WHEELS, 30 INCHES IN DIAMETER. Capacity of tank 750 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 22,000 pounds. LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 530 gross tons. " 20 ft. grade 245 " " " 40 " 155 " " " 60 " 110 " " " 80 " 85 " " " 100 " 70 " " DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 10-1/2 C. General Design Illustrated by Print on Page 84. CYLINDERS. Diameter of cylinders 11 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 inches. Distance between centres 6 feet. TENDER. ON FOUR WHEELS, 30 INCHES IN DIAMETER. Capacity of tank 750 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 34,000 pounds. LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 825 gross tons. " 20 ft. grade 385 " " " 40 " 250 " " " 60 " 180 " " " 80 " 140 " " " 100 " 110 " " [Illustration: Locomotive.] DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 12 C. General Design Illustrated by Print on Page 88. CYLINDERS. Diameter of cylinders 12 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 44 inches. Distance between centres 7 feet. TENDER. ON FOUR, SIX, OR EIGHT WHEELS, 30 INCHES IN DIAMETER. Capacity of tank 900 to 1400 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 38,000 pounds. LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 925 gross tons. " 20 ft. grade 435 " " " 40 " 280 " " " 60 " 200 " " " 80 " 155 " " " 100 " 125 " " DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 14 C. General Design Illustrated by Print on Page 88. CYLINDERS. Diameter of cylinders 14 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 48 inches. Distance between centres 7 feet. TENDER. ON FOUR, SIX, OR EIGHT WHEELS, 30 INCHES IN DIAMETER. Capacity of tank 900 to 1400 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 42,000 pounds. LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1020 gross tons. " 20 ft. grade 480 " " " 40 " 305 " " " 60 " 225 " " " 80 " 170 " " " 100 " 135 " " DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 18-1/2 C. General Design Illustrated by Print on Page 88. CYLINDERS. Diameter of cylinders 15 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 48 to 54 inches. Distance between centres 7 feet. TENDER. ON EIGHT WHEELS, 30 INCHES IN DIAMETER. Capacity of tank 1600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 49,000 pounds. LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1200 gross tons. " 20 ft. grade 560 " " " 40 " 360 " " " 60 " 260 " " " 80 " 200 " " " 100 " 160 " " DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 19-1/2 C. General Design Illustrated by Print on Page 88. CYLINDERS. Diameter of cylinders 16 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 48 to 54 inches. WHEEL-BASE. Total wheel-base 7 ft. 6 inches Rigid " 7 ft. 6 inches TENDER. ON EIGHT WHEELS, 30 INCHES IN DIAMETER. Capacity of tank 1600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 56,000 pounds. LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1360 gross tons. " 20 ft. grade 640 " " " 40 " 410 " " " 60 " 300 " " " 80 " 230 " " " 100 " 180 " " [Illustration: Locomotive.] DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 11-1/2 C General Design Illustrated by Print on Page 94. CYLINDERS. Diameter of cylinders 11 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 inches. TRUCK. TWO-WHEELED, WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 11 ft. 3 inches. Rigid " 4 ft. 8 inches. TENDER. ON FOUR WHEELS, 30 INCHES IN DIAMETER. Capacity of tank 750 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 30,000 pounds. On truck 5,000 " ------ Total weight of engine, about 35,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 725 gross tons. " 20 ft. grade 335 " " " 40 " 215 " " " 60 " 155 " " " 80 " 120 " " " 100 " 95 " " DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 14-1/2 C. General Design Illustrated by Print on Page 94. CYLINDERS. Diameter of cylinders 14 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 48 inches. TRUCK. TWO-WHEELED, WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 13 ft. 8-1/2 inches. Rigid " 6 ft. 6 inches. TENDER. ON FOUR WHEELS, OR TWO FOUR-WHEELED TRUCKS. Capacity of tank 1200 to 1600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 38,000 pounds. On truck 6,000 " ------ Total weight of engine, about 44,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 865 gross tons. " 20 ft. grade 400 " " " 40 " 255 " " " 60 " 180 " " " 80 " 140 " " " 100 " 110 " " DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 15-1/2 C. General Design Illustrated by Print on Page 94. CYLINDERS. Diameter of cylinders 15 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 48 to 54 inches. TRUCK. TWO-WHEELED, WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 14 ft. 9 inches. Rigid " (distance between driving-wheel centres) 7 ft. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 44,000 pounds. On truck 6,000 " ------ Total weight of engine, about 50,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1060 gross tons. " 20 ft. grade 495 " " " 40 " 315 " " " 60 " 230 " " " 80 " 170 " " " 100 " 135 " " [Illustration: Locomotive.] DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 21 D. General Design Illustrated by Print on Page 100. CYLINDERS. Diameter of cylinders 15 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 44 inches. WHEEL-BASE. Total wheel-base 9 ft. 9 inches. Rigid " 9 ft. 9 inches. TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 52,000 pounds. LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1260 gross tons. " 20 ft. grade 590 " " " 40 " 375 " " " 60 " 270 " " " 80 " 210 " " " 100 " 165 " " DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 27-1/2 D. General Design Illustrated by Print on Page 100. CYLINDERS. Diameter of cylinders 16 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. Diameter of drivers 44 to 48 inches. WHEEL-BASE. Total wheel-base 10 feet. Rigid " 10 " TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 60,000 pounds. LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1460 gross tons. " 20 ft. grade 685 " " " 40 " 440 " " " 60 " 320 " " " 80 " 245 " " " 100 " 200 " " DIVISION V. SWITCHING ENGINES WITH SEPARATE TENDERS. CLASS 25-1/2 D. General Design Illustrated by Print on Page 100. CYLINDERS. Diameter of cylinders 17 inches. Length of stroke 22 or 24 inches. DRIVING-WHEELS. Diameter of drivers 48 inches. WHEEL-BASE. Total wheel-base 10 feet. Rigid " 10 " TENDER. ON TWO FOUR-WHEELED TRUCKS. Capacity of tank 1800 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 66,000 pounds. LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 1600 gross tons. " 20 ft. grade 755 " " " 40 " 485 " " " 60 " 350 " " " 80 " 270 " " " 100 " 215 " " [Illustration: Locomotive.] DIVISION VI. TANK SWITCHING ENGINES. CLASS 8 C. General Design Illustrated by Print on Page 106. CYLINDERS. Diameter of cylinders 9 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 inches. WHEEL-BASE. Total wheel-base 6 ft. 6 inches. Rigid " 6 ft. 6 inches. TANK. Capacity 250 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 25,000 pounds. LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 565 gross tons. " 20 ft. grade 265 " " " 40 " 170 " " " 60 " 125 " " " 80 " 100 " " " 100 " 80 " " DIVISION VI. TANK SWITCHING ENGINES. CLASS 10-1/2 C. General Design Illustrated by Print on Page 106. CYLINDERS Diameter of cylinders 11 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 inches. WHEEL-BASE. Total wheel-base 6 ft. 6 inches. Rigid " 6 ft. 6 inches. TANK. Capacity 400 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 38,000 pounds. LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 855 gross tons. " 20 ft. grade 405 " " " 40 " 265 " " " 60 " 195 " " " 80 " 150 " " " 100 " 120 " " DIVISION VI. TANK SWITCHING ENGINES. CLASS 12 C. General Design Illustrated by Print on Page 106. CYLINDERS. Diameter of cylinders 12 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 44 inches. WHEEL-BASE. Total wheel-base 7 feet. Rigid " 7 " TANK. Capacity 500 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 43,000 pounds. LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 960 gross tons. " 20 ft. grade 455 " " " 40 " 295 " " " 60 " 215 " " " 80 " 170 " " " 100 " 135 " " DIVISION VI. TANK SWITCHING ENGINES. CLASS 14 C. General Design Illustrated by Print on Page 106. CYLINDERS. Diameter of cylinders 14 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 48 inches. WHEEL-BASE. Total wheel-base 7 feet. Rigid " 7 " TANK. Capacity 600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 49,000 pounds. LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 1100 gross tons. " 20 ft. grade 525 " " " 40 " 340 " " " 60 " 250 " " " 80 " 195 " " " 100 " 155 " " DIVISION VI. TANK SWITCHING ENGINES. CLASS 18-1/2 C. General Design Illustrated by Print on Page 106. CYLINDERS. Diameter of cylinders 15 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 48 inches. WHEEL-BASE. Total wheel-base 7 feet. Rigid " 7 " TANK. Capacity 700 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 56,000 pounds. LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 1230 gross tons. " 20 ft. grade 585 " " " 40 " 380 " " " 60 " 280 " " " 80 " 215 " " " 100 " 175 " " [Illustration: Locomotive.] DIVISION VI. TANK SWITCHING ENGINES. CLASS 11-1/2 C. General Design Illustrated by Print on Page 114. CYLINDERS. Diameter of cylinders 11 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 inches. TRUCK. TWO-WHEELED, WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 11 ft. 3 inches. Rigid " 4 ft. 8 inches. TANK. Capacity 400 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 35,000 pounds. On truck 5,000 " ------ Total weight of engine, about 40,000 " LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 785 gross tons. " 20 ft. grade 370 " " " 40 " 240 " " " 60 " 175 " " " 80 " 135 " " " 100 " 110 " " DIVISION VI. TANK SWITCHING ENGINES. CLASS 14-1/2 C. General Design Illustrated by Print on Page 114. CYLINDERS. Diameter of cylinders 14 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 48 inches. TRUCK. TWO-WHEELED, WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 13 ft. 8-1/2 inches. Rigid " 6 ft. 6 inches. TANK. Capacity 600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 44,000 pounds. On truck 6,000 " ------ Total weight of engine, about 50,000 " LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 980 gross tons. " 20 ft. grade 465 " " " 40 " 300 " " " 60 " 220 " " " 80 " 170 " " " 100 " 140 " " DIVISION VI. TANK SWITCHING ENGINES. CLASS 15-1/2 C. General Design Illustrated by Print on Page 114. CYLINDERS. Diameter of cylinders 15 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 48 to 54 inches. TRUCK. TWO-WHEELED, WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 14 ft. 7-1/2 inches. Rigid " 7 ft. TANK. Capacity 700 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 50,000 pounds. On truck 6,000 " ------ Total weight of engine, about 56,000 " LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 1120 gross tons. " 20 ft. grade 535 " " " 40 " 345 " " " 60 " 255 " " " 80 " 195 " " " 100 " 160 " " [Illustration: Locomotive.] DIVISION VI. TANK SWITCHING ENGINES. CLASS 21 D. General Design Illustrated by Print on Page 120. CYLINDERS. Diameter of cylinders 15 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 44 inches. WHEEL-BASE. Total wheel-base 9 ft. 9 inches. Rigid " 9 ft. 9 inches. TANK. Capacity 750 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 60,000 pounds. LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 1375 gross tons. " 20 ft. grade 650 " " " 40 " 420 " " " 60 " 310 " " " 80 " 240 " " " 100 " 195 " " DIVISION VI. TANK SWITCHING ENGINES. CLASS 27-1/2 D. General Design Illustrated by Print on Page 120. CYLINDERS. Diameter of cylinders 16 inches. Length of stroke 22 " DRIVING-WHEELS. Diameter of drivers 44 to 48 inches. WHEEL-BASE. Total wheel-base 10 feet. Rigid " 10 " TANK. Capacity 900 gallons. WEIGHT OF ENGINE IN WORKING ORDER. Total weight of engine, about 66,000 pounds. LOAD. IN ADDITION TO WEIGHT OF ENGINE. On a level 1470 gross tons. " 20 ft. grade 700 " " " 40 " 455 " " " 60 " 335 " " " 80 " 260 " " " 100 " 210 " " [Illustration: Locomotive.] DIVISION VII. NARROW-GAUGE PASSENGER AND FREIGHT LOCOMOTIVES. CLASS 8-1/2 C. General Design Illustrated by Print on Page 124. CYLINDERS. Diameter of cylinders 9 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 to 40 inches. TRUCK. TWO-WHEELED, WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 11 ft 11-1/2 inches. Rigid " 6 ft. 3 inches. TENDER. ON FOUR OR SIX WHEELS. Capacity of tank 500 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 20,000 pounds. On truck 5,000 " ------ Total weight of engine, about 25,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 480 gross tons. " 20 ft. grade 225 " " " 40 " 140 " " " 60 " 105 " " " 80 " 75 " " " 100 " 60 " " Engines of this class can be adapted to a gauge of 3 feet or upward. DIVISION VII. NARROW-GAUGE PASSENGER AND FREIGHT LOCOMOTIVES. CLASS 9-1/2 C. General Design Illustrated by Print on Page 124. CYLINDERS. Diameter of cylinders 10 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 to 40 inches. TRUCK. TWO-WHEELED-WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 12 ft. 4-1/2 inches. Rigid " 6 ft. 6 inches. TENDER. ON FOUR OR SIX WHEELS. Capacity of tank 600 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 25,000 pounds. On pony truck 5,000 " ------ Total weight of engine, about 30,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 605 gross tons. " 20 ft. grade 285 " " " 40 " 175 " " " 60 " 125 " " " 80 " 95 " " " 100 " 75 " " Engines of this class can be adapted to a gauge of 3 feet or upward. [Illustration: Locomotive.] DIVISION VIII. NARROW-GAUGE FREIGHT LOCOMOTIVES. CLASS 12 D. General Design Illustrated by Print on Page 128. CYLINDERS. Diameter of cylinders 11 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 inches. TRUCK. TWO-WHEELED, WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 14 ft. 3 inches. Rigid " 8 ft. 7 inches. TENDER. ON FOUR OR SIX WHEELS. Capacity of tank 750 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 31,000 pounds. On truck 4,000 " ------ Total weight of engine, about 35,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 730 gross tons. " 20 ft. grade 340 " " " 40 " 220 " " " 60 " 160 " " " 80 " 120 " " " 100 " 100 " " Engines of this class can be adapted to a gauge of 3 feet or upward. DIVISION VIII. NARROW-GAUGE FREIGHT LOCOMOTIVES. CLASS 14 D. General Design Illustrated by Print on Page 128. CYLINDERS. Diameter of cylinders 12 inches. Length of stroke 16 " DRIVING-WHEELS. Diameter of drivers 36 to 40 inches. TRUCK. TWO-WHEELED, WITH SWING BOLSTER AND RADIUS-BAR. Diameter of wheels 24 inches. WHEEL-BASE. Total wheel-base 15 ft. 4 inches. Rigid " 9 ft. 4 inches. TENDER. ON FOUR OR SIX WHEELS. Capacity of tank 900 gallons. WEIGHT OF ENGINE IN WORKING ORDER. On drivers 36,000 pounds. On truck 4,000 " ------ Total weight of engine, about 40,000 " LOAD. IN ADDITION TO ENGINE AND TENDER. On a level 870 gross tons. " 20 ft. grade 405 " " " 40 " 255 " " " 60 " 185 " " " 80 " 140 " " " 100 " 110 " " Engines of this class can be adapted to a gauge of 3 feet or upward. GENERAL SPECIFICATION. The following general specification of an ordinary freight or passenger locomotive is given to show principal features of construction. BOILER. Of the best Pennsylvania cold-blast charcoal iron, three-eighths inch thick, or of best homogeneous cast-steel, five-sixteenths inch thick; all horizontal seams and junction of waist and fire-box double-riveted. Boiler well and thoroughly stayed in all its parts, provided with cleaning holes, etc. Extra welt-pieces riveted to inside of side-sheets, providing double thickness of metal for studs of expansion braces. Iron sheets three-eighths inch thick riveted with three-fourths inch rivets, placed two inches from centre to centre. Steel sheets five-sixteenths inch thick riveted with five-eighths inch rivets, placed one and seven-eighths inches from centre to centre. WAIST made straight, with two domes, steam being taken from the forward dome; or with wagon-top and one dome. FLUES of iron, lap-welded, with copper ferrules on fire-box ends; or of seamless drawn copper or brass. FIRE-BOX of best homogeneous cast-steel; side- and back-sheets five-sixteenths inch thick; crown-sheet three-eighths inch thick; flue-sheet one-half inch thick. Water space three inches sides and back, four inches front. Stay bolts seven-eighths inch diameter, screwed and riveted to sheets, and not over four and one-half inches from centre to centre. Crown bars made of two pieces of wrought-iron four and one-half inches by five-eighths inch, set one and one-half inches above crown, bearing on side-sheets, placed not over four and one-half inches from centre to centre, and secured by bolts fitted to taper hole in crown-sheet, with head on under side of bolt, and nut on top bearing on crown bars. Crown stayed by braces to dome and outside shell of boiler. Fire-door opening formed by flanging and riveting together the inner and outer sheets. Blow-off cock in back or side of furnace operated from the footboard. GRATES of cast-iron, plain or rocking, for wood and soft coal; and of water tubes, for hard coal. ASH-PAN, with double dampers, operated from the footboard, for wood and soft coal; and with hopper with slide in bottom, for hard coal. SMOKE-STACK of approved pattern suitable for the fuel. CYLINDERS. Placed horizontally; each cylinder cast in one piece with half-saddle; right and left hand cylinders reversible and interchangeable; accurately planed, fitted and bolted together in the most approved manner. Oil valves to cylinders placed in cab and connected to steam-chests by pipes running under jacket. Pipes proved to two hundred pounds pressure. PISTONS. Heads and followers of cast-iron, fitted with two brass rings babbited. Piston-rods of cold-rolled iron, fitted and keyed to pistons and crossheads. GUIDES. Of steel, or iron case-hardened, fitted to guide-yoke extending across, or secured to boiler and frames. VALVE MOTION. Most approved shifting link motion, graduated to cut off equally at all points of the stroke. Links made of the best hammered iron well case-hardened. Sliding block four and one-half inches long, with flanges seven inches long. Rock shafts of wrought-iron. Reverse shaft of wrought-iron, made with arms forged on. THROTTLE-VALVE. Balanced poppet throttle-valve of cast-iron, with double seats in vertical arm of dry-pipe. DRIVING-WHEELS. CENTRES of cast-iron, with hollow spokes and rims. TIRES of cast-steel, shrunk on wheel-centres. Flanged tires five and one-half inches wide and two and three-eighths inches thick when finished. Plain tires six inches wide and two and three-eighths inches thick when finished. AXLES of hammered iron. WRIST-PINS of cast-steel, or iron case-hardened. SPRINGS of best quality of cast-steel. CONNECTING-RODS of best hammered iron, furnished with all necessary straps, keys, and brasses, well fitted and finished. EQUALIZING BEAMS of most approved arrangement, with steel bearings. Driving-boxes of cast-iron with brass bearings babbited. FRAMES. Of hammered iron, forged solid, or with pedestals separate and bolted and keyed to place. Pedestals cased with cast-iron gibs and wedges to prevent wear by boxes. Braces bolted between pedestals, or welded in. FEED WATER. Supplied by one injector and one pump, or two brass pumps, with valves and cages of best hard metal accurately fitted. Plunger of hollow iron. Cock in feed-pipe regulated from footboard. ENGINE TRUCK. SQUARE wrought-iron frame, with centre-bearing swing bolster. WHEELS of best spoke or plate pattern. AXLES of best hammered iron, with inside journals. SPRINGS of cast-steel, connected by equalizing beams. HOUSE. Of good pattern, substantially built of hard wood, fitted together with joint-bolts. Roof finished to carlines in strips of ash and walnut. Backboards with windows to raise and lower. PILOT. Of wood or iron. FURNITURE. Engine furnished with sand-box, alarm and signal bells, whistle, two safety-valves, steam and water gauges, heater and gauge cocks, oil-cans, etc. Also a complete set of tools, consisting of two jack-screws, pinch-bar, monkey, packing, and flat wrenches, hammer, chisels, etc. FINISH. Cylinders lagged with wood and cased with brass, or iron painted. Heads of cast-iron polished, or of cast-brass. Steam-chests with cast-iron tops; bodies cased with brass, or iron painted. Domes lagged with wood, with brass or iron casing on bodies, and cast-iron top and bottom rings. Boiler lagged with wood and jacketed with Russia iron secured by brass bands polished. GENERAL FEATURES OF CONSTRUCTION. All principal parts of engine accurately fitted to gauges and thoroughly interchangeable. All movable bolts and nuts and all wearing surfaces made of steel or iron case-hardened. All wearing brasses made of ingot copper and tin, alloyed in the proportion of seven parts of the former to one of the latter. All bolts and threads to U. S. standard. TENDER. On two four-wheeled trucks. Wheels of best plate pattern, thirty inches in diameter. Truck frames of square wrought-iron with equalizers between springs, or of bar-iron with wooden bolsters. Axles of best hammered iron. Oil-tight boxes with brass bearings. Tank put together with angle iron corners and strongly braced. Top and bottom plates of No. 6 iron; side plates of No. 8 iron. Tender frame of wood or iron. PAINTING. Engine and tender to be well painted and varnished. [Transcriber's notes: Obvious printer's errors have been corrected, all other inconsistencies are as in the original. The author's spelling has been maintained. V[] is used to mark square roots; e.g.: V[6 + 1] means the square root of 6 + 1.] 
44604	----	the Digital Library of the Falvey Memorial Library, Villanova University (http://digital.library.villanova.edu) Note: Project Gutenberg also has an HTML version of this file which includes the original illustrations. See 44604-h.htm or 44604-h.zip: (http://www.gutenberg.org/files/44604/44604-h/44604-h.htm) or (http://www.gutenberg.org/files/44604/44604-h.zip) Images of the original pages are available through the Digital Library of the Falvey Memorial Library, Villanova University. See http://digital.library.villanova.edu/Item/vudl:267659 Transcriber's note: Text enclosed by underscores is in italics (_italics_). Text enclosed by equal signs is in bold face (=bold=). HOW TO BECOME AN ENGINEER. Containing Full Instructions How to Proceed in Order to Become a Locomotive Engineer; Also Directions for Building a Model Locomotive; together with a Full Description of Everything an Engineer Should Know. Profusely Illustrated. BY AN OLD ENGINEER ON THE NEW YORK CENTRAL RAILROAD. New York: Frank Tousey, Publisher 29 West 26th Street. Entered according to Act of Congress, in the year 1898, by Frank Tousey, in the Office of the Librarian of Congress at Washington, D.C. CONTENTS CHAPTER I. HISTORICAL. CHAPTER II. DESCRIPTION OF THE LOCOMOTIVE. CHAPTER III. HOW TO BECOME AN ENGINEER. CHAPTER IV. DUTIES OF AN ENGINEER. CHAPTER V. HOW TO RUN A TRAIN. CHAPTER VI. HOW TO BUILD A MODEL LOCOMOTIVE. CHAPTER VII. CONCLUSION. How to Become an Engineer. CHAPTER I. HISTORICAL. To begin a subject properly you must begin at the beginning. Boys who don't like history need not read this chapter, for in it we tell how the steam engine began, and if it never had begun, you know, there would never have been any engineers, nor any necessity for writing this book. For two or three generations we have had the story of James Watt told us; how when a boy and watching his mother's tea-kettle one day he saw the steam lift the lid, and that suggested the idea that if a little steam could lift the lid of a kettle, a great deal would lift still heavier weights and revolutionize the world. Now they tell us that Watt was not the first one to have this idea by several, that it was first suggested by the Marquis of Worcester, in his book called the "Century of Inventions," as "a way to drive up water by fire," A. D. 1663. This was about a hundred years before Watt came on deck, but the marquis never put his idea into practice, and Watt did, so to the latter the credit belongs. Here are a few dates: Watt's invention of the separate condenser, 1765; Watt's first patent, 1769; Watt's first working engine introduced into a manufactory, 1775; first steam engine erected in Ireland, 1791; first steamboat run on the Hudson, 1797; first steamboat abroad, 1801. First regular steamboat ever run was from Albany to New York. The name of the boat was the North River, her builder was Robert Fulton, and she made the passage in 33 hours. The first railroad was built in England, in 1811. The first ocean steamer was the Savannah, an American craft of 350 tons, which sailed from New York for Liverpool, July 15, 1819, making the voyage in 26 days. Such were the early beginnings of steam. There are three principal kinds of engineers, locomotive, steamboat and stationary. In this little book we propose to deal mainly with the duties of a locomotive engineer. If one is a good locomotive engineer he can easily learn to manage the engine of a steamboat; and if he is skilled in either of these particulars he will have no difficulty with the biggest stationary engine ever built. [Illustration: THE FIRST LOCOMOTIVE.] The work of the different engineers differs only in detail, not in kind. Let us now glance at the history of the steam horse, which has done more than any other one thing to revolutionize the world. Be very sure that the locomotive, with its pistons, its spinning drive wheels, its polished steel and shining brass, did not come into existence all at once. By no means. Like everything else in the way of mechanical invention that attains greatness, the locomotive had an insignificant beginning to reach which we shall be obliged to get back somewhere about the middle of the last century, for then it was that the desire for faster traveling than horses can furnish seems to have had its birth. The first attempt at a railway seems to have been at Colebrook Dale, England, a spot celebrated for having the first iron bridge in the world--where a small iron road was constructed in connection with some mines; a horse furnished the motive power here. The first railroad then was without a locomotive, and, strangely enough the first locomotive was without a railroad on which to run. The first locomotive made its appearance in France. It was simply a huge tea kettle on wheels, and was built by Joseph Cugnot at Paris in the year 1769. It is the custom of English writers to ignore Cugnot's invention, and claim for themselves the origin of the locomotive; but that is only a pleasant way the English usually have. Cugnot's locomotive actually existed though, and was undoubtedly the first. It was operated by means of two bronze cylinders, into which the steam passed through a tube from the boiler--escaping through another tube. The boiler was fastened on the front of the car, which moved on three wheels--the steam acted only on the foremost wheel. The speed of Cugnot's locomotive was about three miles an hour. On the first trial it ran into a building and was broken to pieces. In 1784 the famous Watt patented a steam locomotive engine in England, which, however, never was put to use. In 1802, Trevethick and Vivian patented a locomotive, which, in 1804, traveled at the rate of five miles an hour, drawing behind it a load of ten tons of coal. Several other "traveling engines," as they were then styled, were invented by other mechanical engineers with only moderate success, it being reserved for Stephenson, in 1811, to build the first locomotive that should prove of practical use. About this time a man named Thomas Gray, of Nottingham, England, brought upon himself the contempt and ridicule of the whole English nation by pushing forward the idea of the locomotive in connection with coal mines. [Illustration: OLD NO. 1.] "It is all very well to spend money on these railway schemes," said a member of parliament about that time referring to Gray's projects, "it will do some good to the poor, but I will eat all the coals your railways will ever carry." 127,000,000 tons were carried recently in one year, on English railroads alone. What a tough time this parliamentary slow coach would have had to swallow all that! The first practical locomotive in the world--Stephenson's invention, was Old No. 1, which pulled the first regular train on the Stockton and Darlington R. R. on Tuesday, September 27, 1825. Old No. 1 cost $2,500 to build. It was a very clumsy affair; nothing better, in fact, than a big boiler on four wheels, which were moved by great levers worked by pistons from the top of the machine. [Illustration: THE ROCKET.] Old No. 1 has been preserved, and was, in the year 1859, placed upon a pedestal in that English town of Darlington as a public memorial of the beginning of the railway. No sooner had the Stockton and Darlington R. R. proved itself a success than all England was in arms against it. Here are some of the absurd objections urged against railroads, taken from the newspapers of the day. Steam horses were "contrary to nature;" they were "damaging to good morals and religion;" the smoke of the locomotive would "obscure the sun, and thereby ruin the crops." Farmyards and farmhouses would be burned by their sparks; the clanking, puffing locomotive would have such an effect on the mind as to drive people crazy (this was backed up by certificates from a dozen doctors); locomotives would cause springs to dry up and fields to become sterile; they would create great chasms by constantly running over the same ground. What twaddle! Yet all their objections were made in good faith, and we have by no means selected the most absurd. Old No. 1. proving too clumsy, a lighter locomotive was soon after built by Stephenson, called the "Rocket," which we illustrate. It won a prize of $1,500 in 1829, and is still preserved in the great locomotive works at Newcastle-on-Tyne, England. The first railroad in America was built from the granite quarries of Quincy, Mass., to the Neponset river, a few miles distant. Peter Cooper built one of the first American locomotives. It ran on the Baltimore and Ohio R. R., and was called the Tom Thumb. The boiler of the Tom Thumb was built of gun barrels and shaped like a huge bottle standing upright upon a simple platform car. Such was the beginning of the locomotive. In Great Britain alone over 600,000,000 people are annually drawn by locomotives. Add to these figures, which represent only a small island, the persons drawn by locomotives in America, Europe, and other parts of the world, and the number becomes stupendous almost beyond belief. CHAPTER II. DESCRIPTION OF THE LOCOMOTIVE. In order to become an engineer, the first thing necessary is to gain a thorough understanding of the peculiarly complicated machine which it is the duty of engineers to control. This is of the highest importance, and a careful study of this chapter and the diagrams accompanying it will be of great assistance to anybody who contemplates becoming an engineer. There are locomotives and locomotives, all built on the same general plan, but varying in details according to the ideas of their builders, and the class of work which they are expected to perform. [Illustration: AN AMERICAN LOCOMOTIVE WITH TWO DRIVING WHEELS.] Thus for elevated roads and short surface lines, devoted principally to passenger travel, locomotives of light capacity are employed; costing less at the start, and being less expensive to run. [Illustration: AMERICAN LOCOMOTIVE WITH FOUR DRIVING WHEELS.] The "dummy" is even a grade below these, being practically a stationary engine set on a car with driving wheels attached. [Illustration: OUTSIDE VIEW OF LOCOMOTIVE.] [Illustration: INSIDE VIEW OF LOCOMOTIVE.] In America our locomotives are built with long boilers and have a general trim appearance. Some have two driving wheels, others, still longer, have four. We illustrate both of them. English locomotives present a clumsy appearance alongside the American. For us to attempt to decide which is the best, would be the height of presumption. Certain it is, however, that English locomotives do run at a greater average speed than those in the United States. We will now proceed to describe by tabular arrangement, an English locomotive. This description will practically describe the American locomotive as well. We cannot enter into a detailed description of both for want of space, and select therefore the machine which has attained to the highest speed. We will first look at the outside of the locomotive. 1, 2, 3, Barrel of Boiler. 6, Smoke-box. 22, Smoke Stack. 32, Spring balance. 33, Whistle. 34, Dome. 64, Exhaust pipe. 70, Cab. 85, Brake blocks. 87, Life guards. 88, Trailing axle and wheel. 59, Heading axle and wheel. 54, Driving axle. O, Speed indicator. P, Splasher. S, Sand-box. T, Tool-box. V, Safety valve. W, Balance-wheel. Let us now take an inside view of the locomotive. Compare the numbers carefully with the cut, and take time to think what you are doing, otherwise don't read this part at all. 1, 2, 3, Rings arranged telescopically, forming barrel of boiler. 4, Solid angle-iron ring. 5, Tube plate. 6, Smoke box. 7, Shell, or covering plate. 8, Foundation ring. 9, Throat plate. 10, Back plate. 11, Fire door. 12, Covering plate of inside fire-box. 13, Tube plate. 14, Back plate. 15, Stays. 16, Mouth-piece. 17, Stays from inside fire-box to shell plate. 18, Palm stays. 19, Tubes. 20, Smoke-box door. 21, Pinching screw. 22, Chimney. 23, Chimney cap. 24, Blast pipe. 25, Top of blast pipe. 26, Balance weight. 27, Wheel spokes. 28, Front buffer. 29, Mud plug. 30, Safety valve. 31, Safety lever. 32, Spring balance. 33, Whistle. 34, Dome. 35, Regulator. 36, Steam pipes. 37, Elbow pipe. 38, Brick arch. 39, Fire bars. 40, Ash pan. 41, Front damper. 42, Back damper. 43, Frame plate. 44, Iron buffer beam (front). 45, Iron buffer beam (back). 46, (See half width plan) cylinder. 47, Cylinder posts, valve. 48, Valve chest. 49, Steel motion plate. 50, Horn blocks. 51, Axle boxes. 52, Slide bars. 53, Connecting rod. 54, Crank shaft. 55, Crank shaft, big end of. 56, Crank shaft, arm of. 57, Expansion link. 58, Weigh-bar shaft. 59, Valve spindle. 60, Valve rod guide. (See half width plan). 61, Pump. 62, Delivery pipe. 63, Field pipe. 64, Exhaust pipe. 65, Volute spring. 66, Draw-bar hook. 67, Lamp iron. 68, Oil cup. 69, Oil pipes. 70, Cab. 71, Regulator handle. 72, Reversing lever. 73, Draw-bar. 74, Draw-pin. 75, Steam-brake cylinder. 76, Hand-brake. 77, Sand-rod. 78, Front damper. 79, Back damper. 80, Trailing wheel. 81, Driving wheel. 82, Leading wheel. 83, Spring. 84, Hand rail. 85, Brake blocks. 86, Waste water-cocks. 87, Life guard. 88, Railing axle. 89, Leading axle. Z, Lead plug. 43, Frame plate from end to end of engine. 44, Iron buffer-beam. 46, Cylinders. 50, Horn block, to carry axle-box and brass. 51, Axle-box and brass. 52, Slide bars. 53, Connecting-rod. 54, Driving axle. 55, Big end of driving axle. 56, Arm of driving axle. 59, Valve-spindle. 60, Valve-rod guide. 61, Pump. 76, Hand brake. 85, Brake blocks. 88, Trailing axle. 89, Leading axle. 90, Piston rod. 91, Piston head, held on the rod by a brass nut. 92, Backway eccentric rod. 93, Frontway eccentric rod. 94, Eccentric Straps. 95, Eccentric sheaves. 96, Tire. 97, Lip on tire. 98, Brake irons. 99, Foot plating. 100, Transverse stay. A, Water space between inside and outside fire boxes. B, Slide-block with end of pump-ram screwed into the end. C, Link motion (see 57, inside view). D, Slide valve rod, working guide. H, Inside journal, showing how the axle is supported inside of frame plates. I, Cross-head, solid, with piston rod. [Illustration: UNDERNEATH THE LOCOMOTIVE--HALF WIDTH PLAN.] 15, stays in walls of fire-boxes. 18, stays from crown plate to covering plate. 19, tubes. 23, smoke-stack. 40, ash-pan. 54, crank shaft. 55, big end of crank-shaft. 56, arm of big end. 34, dome. [Illustration: IN FRONT OF THE LOCOMOTIVE CROSS-SECTION.] A, water space. F, nave of wheel. P, P, splashers over driving wheels. R, right side of engine. L, left side of engine. 75, steam brake handle. 33, whistle handle. 23, smoke stack. K, K, weather glasses. O, speed indicator. E, conductor's bell. N, oil for cylinder. X, blower handle. R, right side of engine. L, left side of engine. M, M, gauge glasses. SOME POINTS ABOUT THE LOCOMOTIVE. Here are a few interesting points about this particular locomotive which we have just been describing. It is a single engine on six wheels--which are well distributed, with a large boiler of abundant steam generating power with cylinders of great capacity, and driving wheels of moderate diameter. It is accompanied by a tender on six wheels, capable of holding a supply of 2,520 gallons of water, and 40 cwt. of coal. Notwithstanding its great capacity, this tender is so low that a tall man may stand on top of the coal without fear of being knocked down by bridges. There are over 47 tons of metal in the locomotive and tender. When they are in full working order the gross weight with water and fuel amounts to 59 tons. This locomotive drew its first train 87 miles in 1 hour and 50 minutes. DIFFERENCES IN LOCOMOTIVES. It is an old saying and a true one that no two locomotives are ever alike, any more than two men are ever alike. The difference is due not so much to the materials of which the locomotive is built as to the method in which they are put together, for no two engines were ever put together geometrically alike. They may differ in some simple matter. It may be in the casting of the cylinders, in the quality of the copper of the fire box, in the valves or in the smoke stack. Whatever the difference may be there is still always a difference which is bound to affect the running qualities either for better or for worse. CHAPTER III. HOW TO BECOME AN ENGINEER. The boy who aims to become an engineer, if he desires success, must make up his mind to two things. First, that he will, all his life, have plenty of hard work. Second, that he will, in spite of all obstacles become a good engineer. A boy who looks forward to the honorable calling should be of robust health and perfect physically. If these conditions do not exist, he should abandon the thought at once, and turn his attention to something else. There is no royal road to engineering any more than there is to any other honorable calling. A position must first be obtained in the round house as general helper. For a time the candidate must content himself with doing chores, cleaning up and any odd jobs which are given him to do. At this stage of the game he must cultivate habits of observation, be an attentive listener and try to understand and remember the "engine talk," that is going on about him. Everything he learns in this way is going to be of service later on. For the first few months, unless he is fortunate enough to gain favor in the eyes of some obliging engineer, no one is going to stop to explain matters and he need not expect it. Nevertheless there are a thousand and one little things that he can pick up if he is shrewd, all of which will come in play later on. When the locomotive is taken out watch how they do it. When it comes in keep your eyes open for points, and you will be sure to get them. When it breaks down and comes in for repairs then is the very time of all others to be on hand if you can and watch how they fix it. Every day will bring its own information--the boy's work is to watch and remember, but he must not ask too many questions, and never any at improper times, unless he desires the ill-will of everybody in the yard. By and bye he will be made an oiler, put to cleaning the big iron horse and other work of similar sort. After a time he will slip into a fireman's job, and then he must understand that his chance has come. Now all depends upon himself. Make friends with your engineer while you are acting as fireman, and learn from him all you can. The way to make friends is to be industrious, obliging and always courteous, no matter how tired you are or how badly things seem to go. The troubles and disappointments of one day should not be brought down to the next. Let every day be a new beginning in itself. Don't drink. Don't swear. Don't lose your temper and flare out under reproof. Don't shirk your work and try to do as little us you can. [Illustration: BEHIND THE LOCOMOTIVE--LOOKING IN FROM THE CAB.] Don't say to yourself so and so ain't my work and I ain't going to do it. Do whatever your hands find to do and do it with all your might. A model engineer is distinguished by the fullness of his knowledge of the engine, and this must be learned while you are a fireman--not after you become an engineer. He should love his work--the locomotive should be his hobby--and whatever contributes to enlarge his stock of information concerning it should contribute to his happiness. Unless he can feel that way, he should promptly step out of the cab and turn his attention to some other business, for he can never hope to make a good engineer. On the engine is the only place where one can learn to be an engineer. During the time the engine is under steam with a train, everything seen, heard, felt and smelt is capable of affording a lesson. On the engine the eye is trained to distinguish different colors at considerable distances. If one is color-blind he cannot be a good engineer. On the engine the ear learns to detect the slightest variation in the beats and knocks about the machinery--to distinguish the difference between the knock of an axle box and the knock of a journal. On the engine the body learns to distinguish the shocks, oscillations, etc., which are due to a defective road from those which arise from a defective engine. The olfactory nerves became very sensitive so as to detect the generation of heat from friction before any mischief is done. It is only while an engine is in steam and going at good speed that the rocks, coral-reefs and sand-banks on railways can be seen and learned, and the value of and the rank acquired by an engineer are in exact proportion to the pains he takes to find them out, and to remark their dangerous position on his chart. A model engineer can tell you all about any particular engine he happens to see merely by glancing at it. He will be able to say this was built by so and so. I know it by this crank, that piston. "Look here," he says, "that rod was built when I was a boy, it's all out of date now, consequently the engine must have been built in such a year." In short the model engineer should be familiar with the history of locomotive engines from Old No. 1 down to date. The model engineer is always a good fireman. A man may be a first-rate mechanic, he may have worked at the best class of machinery, he may have built engines and have read all the published books on the locomotive, and yet, if he is not a good hand at the coal shovel, he will never be a first-class engineer. A good fireman knows when to put on coal, how and where and just how much. A man may be the best mechanic the world ever saw and know nothing of these things which are the very all essentials of a good engineer. A model engineer is clean himself, and his engine is cleaner. Cleanliness is said to be next to godliness. Upon a railroad it may with truth be said that cleanliness is next below the highest talent and next above the length of service. A clean engineer frequently scales the ladder of progress much faster than a dirty one, although the latter may have everything else in his favor. A model engineer runs the most important trains, and he is never the man who wore the greasy, dirty cap or the coat and trousers all smeared with oil. What is the secret of constant successful engine driving? Not length of service, not because a man has served so many years on freight trains and so many more on passenger trains, for the best engineers are ever those who have been promoted over the heads of others for their smartness. Promotion according to merit should be the invariable rule on railroads. Seniority should have nothing to do with it. The position is too important, there are too many lives at stake, too much money involved to make it right or proper to push one man forward beyond another simply because of the length of his service. That sort of thing is all right for ordinary business, but for engine driving it won't do. Merit tells. To the best engineer belong the best trains. Chance never built an engine, and it should have nothing to do with running it. Yet the opposite way of doing things is the general rule. Engineer A retires, dies or is killed, and Engineer B is promoted because he happens to be next on the list. He may be a dull, stupid fellow, and Engineer C as bright as a dollar, but in the chance death of A, B gets the prize, and everybody that has any interest in the successful running of his train becomes the loser thereby. Engine driving, to be good, must be based upon rules and principles. He who strictly observes them wins; he who don't, loses. With the latter all is uncertainty; the hand trembles upon the regulator, the eye watches with painful anxiety the needle of the pressure gauge, and gazes into the fire to find out its deficiencies, but gains nothing but blindness by the attempt. With the engineer who has a reason for every act performed, either by himself or his fireman, all is different. He works by rules and principles that have proved themselves a thousand times over to be safe, practical and certain in their results. Sound rules and principles are absolutely sure in the effects of their application--not right to-day and wrong to-morrow; not right in a short trip and all astray on a long one; not right on one particular engine and wrong on another; not right on the first part of the run and wrong at the end; not right with one kind of coal and wrong with another, but _always right, every time_. Under the guidance of sound rules and principles, the mind of the driver is full, and he is enabled, under all circumstances, to handle the regulator with confidence, to travel with a boiler full of steam, and to finish with success. In a word, these are rules and principles which lead up to and make the success of an engineer. CHAPTER IV. DUTIES OF AN ENGINEER. Let us now consider in detail some of the more important duties of an engineer. THE NOTICE BOARD. Before going to his engine an engineer should, for his own safety, as well as that of the public, visit the special and general notice boards and post himself fully upon the running of the trains for the day. By neglecting this more than one engineer has lost his life. An anecdote bearing on this is related on good authority, as follows: "By incessant rain a river had become so swollen that, owing to the rush of water, the spiles of a wooden railway bridge became shifted. "The bridge was inspected, and one side of it pronounced to be dangerous. Arrangements were made to use only one track until repairs could be made, and notice of such arrangements posted in the round-house. "The engineer neglected to visit the notice board, ran his train past the man appointed to pilot him over the break, got his train off the track, and was killed." After the engineer has read the notices and made himself thoroughly acquainted with them, he may proceed to his engine--not before. INSPECTION OF THE ENGINE. When on the foot plate the first thing an engineer wants to do is to inspect his engine in every part. Begin with the water in the gauge glass and ascertain its level and find out whether it correctly indicates the height of the water in the boiler by opening the lower cock in the usual manner. Satisfied that the boiler is safe, the engineer must assume the responsibility of looking after it, for should anything prove wrong afterward, he alone can be called to account. He should also observe what pressure of steam there is in the boiler, what is the condition of the fire, how much coal there is in the tender and its quality, and lastly that the water supply is all right. If the inspection is made properly all will go well; if in a half-hearted, slip-shod fashion trouble is sure to follow. INSPECTION OF AN ENGINE OVER A PIT. It is a good and a safe rule to examine an engine over a pit before starting out. When this is done properly and regularly, the habit is unmistakably the mark of a good engineer. That an engine may be properly examined over a pit, it is necessary that it should be placed in such a position that every part of it may be seen and inspected without having the machinery moved. The examination, to be complete, should be commenced at one specified point, and continued all around the engine, until the engineer returns to the place where he began. In general, the only tools needed are wrenches. The inspection should begin at the trailing engine axle, on the engineer's side, and the best rule is to examine everything, not forgetting the fact that more engines break down in consequence of bolts and split pins working out than from any other cause. After the engineer's side has been properly examined, the under side of the engine next claims attention. The engineer should begin at the crank shaft, taking his stand, where it is possible to do so, between the shaft and the fire box, while he is testing the bolts and rivets connected with it. BIG ENDS. Big Ends require to be fitted brass and brass, to work well, and to be well-cottered or bolted up, but with sufficient slackness on the crank bearing to allow of their being easily moved sideways by hand, so that a little room may be left for the expansion of the journal by heat. Big End brasses do best, wear longest, and knock least, when tightened up a little at a time and often, instead of being allowed to run until they thump alarmingly. With proper attention they seldom run hot. LITTLE ENDS. Little Ends need scarcely any supervision excepting what is required from the oiler, provided they are fitted with steel bushes. Those fitted with brasses require the same attention as Big Ends. ECCENTRICS. When the eccentrics are being examined particular attention should be paid to the bolts, nuts, safety-cotters and set-pins. The bolts which hold the two halves of each eccentric strap together should always nip tightly, as any slackness always affects the engine's speed. Inspect carefully also the inside springs and axle boxes, specially the latter. See that the fireman oils them; if he does not, you are to blame. The ash-pan, piston rod, smoke box, etc., all need to be looked at with care, for to run right the engine must start right, and this brings us to the most important thing of all--the condition of the fire before leaving the round house, for there is no other one thing on which an engineer's good name, success and future prospects depend so much as on the condition of the fire at the beginning of the day's work. If the fire is not properly lighted at the start, no matter how good the engine or how smart the engineer, constant trouble during the trip, to say nothing of an increased consumption of coal which is bound to tell against him, will be the result. Don't get to your work late, and don't allow your fireman to be late. If the fire is to be properly built he has got to take time to it. Fires thrown together in a hurry always turn out bad. DUTIES OF A FIREMAN. As the model engineer must first have served as fireman, let us say a word on that score. Before a fireman can serve on a passenger train, he should have served awhile as freight brakeman, or in the yard shifting cars. Before going on an express train, he must have run on slow trains as fireman. All this is necessary that he may acquire a knowledge of the petty details of his work. A superintendent who puts a green hand at firing certainly exhibits a great want of good judgment, to say the least, and just this has often been the cause of serious accidents and loss of life. Here are a few things that a man must know before he can become an engineer: 1. How to make up a proper fire in a locomotive fire-box. 2. How to handle the shovel when the engine is running. 3. How to learn roads and signals. 4. How to calculate the effect of the weather on the rails. 5. How to manage an engine and train on varying grades. 6. How to have full control of an engine and train at full speed. 7. How to work the steam expansively and yet keep time. 8. How to regulate the water supply. 9. How to read the gauges at a glance and understand just what they mean. Now all these things have got to be learned while a fireman, for unless you know them you can never become an engineer. Some engineers will give no instructions. They demand certain results, and if the fireman don't do just what they expect because he does not understand what is wanted, they call him a fool, snatch the shovel out of his hand and do the work themselves. It is the engineer who is the fool in this case, and doubly so if he loses his temper and swears. Certainly it is very hard for a sensitive young man to learn of such a master, but after all it is good discipline. Never mind if you are sworn at and dubbed an idiot. No matter if you do choke a few fires and stop a few trains. Persevere! Keep your temper, watch how the engineer does it and try to do the same yourself next time. Show him that you are not the idiot he has called you, prove that you are no fool by your patience and perseverance--qualities, like enough, which he himself does not possess. A first class engineer, however, will show a new fireman just what he wants done and how to do it. Here are a few lines from an excellent manual on engineering, describing the conduct of a good engineer to his fireman. Read them with care: "With good engineers an awkward fireman soon changes his habits and appearance--he gets the knots dressed off of him, as it were. Has he been taught to come on duty dirty and late? He is sharply reproved, and very properly too. Does he throw the fire irons down anywhere after using them? He is told there is a place for everything in that engine. Is he dirty about his work? He is shown how to handle the shovel, oil feeder and everything else without blackening himself to such a degree that a boy in the street mistakes him for a chimney sweep. Thanks to such engineers, who deserve much praise for keeping their firemen in proper training, for, just as they _are_ trained so will they turn out engineers, good or bad." CHAPTER V. HOW TO RUN A TRAIN. A good engineer works his engine with direct reference to the number of cars he has to pull. It would seem as though any fool might know this, yet instances are on record where careless engineers have actually pulled out of a station without their trains, and never discovered that they were missing until they had occasion to whistle for brakes. STARTING. In starting the regulator should be opened gently, especially with a full boiler. Care is necessary when starting to keep the cylinders and valves clear of water. Half a pint of water will wash the faces of the cylinders and valves. Slip or no slip, it is better to use a little sand than to incur the risk of slipping when the rails are inclined to be slippery. When the engine begins to feel its load the regulator can be opened more. A few clear, sonorous puffs at the start do good; they rouse the fire into action at once--there is no hesitation in the matter. They also clear the tubes of loose cinders and soot left in them after being swept out. When you are well under way pull the lever up a notch or two at a time until you get it just where you want it. Don't jerk it too far, then let it out too much and have to pull it back. Feel your way as you go, and time and trouble will be saved. Nothing looks so bad as to see an engineer suddenly close the regulator, pull the lever very nearly out of gear and "smack" the steam on again. The force with which the steam may strike the piston under such circumstances is very great and often may do damage. To an attentive engineer the start is full of interest; for, although he may have made a careful and thorough examination of his engine before joining his train, he cannot feel satisfied that all is right until the full pressure of the steam is on the piston and the engine feels its load. STEAM BLOWING. Now the engineer must begin to use his ears and eyes. As the train moves on he listens. Is the steam blowing? It is. Which side? This is the way to find out. Suppose a blow is heard at each turn and only when the outside crank is nearly in a straight line with the piston rod looking from the left-hand side of the foot-plate and with the outside cranks on the same center line and on the same side of the axle as the inside crank. Then it would be discovered that a piston is blowing because the sound is intermittent, for the blowing through of a valve would be a continuous leaking. Further it would be certain that the defect was not in the left hand cylinder, there being no steam in it when the cranks were in the position above described, and therefore we must look to the right hand cylinder where the full pressure of steam must be on the piston. BEATS OF THE ENGINE. There are four beats for one revolution of the driving wheel or the crank axle. These beats tell you in emphatic language whether the engine is running right, or whether there is something out of gear. Learn what they mean and never let your attention be drawn from them. If the beats weaken--any one of them--it means trouble. Taken in time the difficulty may be easily remedied, allowed to pass unnoticed, death and disaster may result. KEEPING UP STEAM. It is scarcely necessary to state that to properly run your engine steam must be kept up. When the engine has got the train up to speed, steam should begin to issue from the safety valves. When it does not do so there has not been a full boiler, as there always should be at the start and the fireman must be made to understand how to make a starting fire in proper shape. On short runs this does not matter so much, but on express trains it is of the highest importance. On long runs if the engine is not instantly up to the mark at the start, and if the feeds must be held off to allow the fire and the engine a chance of recovery, the consequences are that the water in the boiler gets lower and less, and the uncertainty of ever getting the water up again becomes greater every minute, especially with a heavy train and against a strong side wind. MANAGEMENT OF FIRES. Of course the state of the steam depends altogether upon the way the fires are managed, but for us to give directions how to manage a locomotive fire-box to the best advantage would require pages of description which could scarcely be understood unless one had had previous practical experience. Remember one thing, the engineer is responsible for the fire, even if he does not make it. He must therefore know when a fire is good and when it is bad, _why_ and _what to do_. We shall, however, describe two styles of fire, the thoroughly bad and the thoroughly good. All intermediate grades every man must learn for himself. HOW TO BUILD A BAD FIRE. Pile your coal up in the shape of a cone, by shoveling all the coal into the middle of the fire box, and putting as little on the sides as you possibly can. Such a fire possesses the following characteristics: Uncertainty as regards steam making, positive certainty as regards the destruction of fire boxes and tubes. It generally draws air at the walls of the fire-box, and in consequence, the fire-irons are always in the fire, knocking it about and wasting the fuel. As such fires are found in the center of the grate, they weigh down the bars and burn them out in the middle in short order. Lastly, the cold air being admitted into the fire-box up the sides instead of in the middle, comes in direct contact with the heated plates and stays, doing them a great deal of damage by causing contraction and expansion. Take the best engine ever built and let an engineer run it awhile with these "haycock" fires, as they are called--and many do it--you will be sure to find the boiler subject to sudden leakage, either in the joints of the plates or in the stays, the tubes, or the foundation ring. Such engines are always in the repair shop, and because of bad firing and nothing else. HOW TO BUILD A GOOD FIRE. The good locomotive fire should maintain steam under all circumstances of load or weather, should consume its own smoke, should burn up every particle of good matter in the coal, or, in other words, capable of being worked to the highest point of economy. Such a fire requires to be made at the beginning, and maintained in a form almost resembling the inside of a saucer, shallow and concave, with its thinnest part in the center. A fire like this will make steam when other fires will make none. It is the only style of fire that should be permitted by a good engineer. FIRING. To fire properly the fireman should stand in such a position as to be able to reach the coals in the tender easily, and to work the shovel without shifting his feet, except when he turns slightly on his heels, first, toward the coal, and then toward the fire hole. If a fireman, in the act of firing, lifts his feet off the foot plate, he will roll about, and the firing will be improperly done, in consequence of the coal being knocked off the shovel by the latter catching against the fire hole ring or depletion plate. Don't jam the shovel into the fire-box--stop it dead at the fire-hole ring. Give the coals a fling, discharging them like shot right into their intended destination. Don't jam your shovel into the coal and load it down as much as possible. A few lumps of coal lying nicely on the body of the shovel can be handled better. The shovel should not be pushed into the coal by the knees, but should be worked only by the muscles of the arm. Throw the first shovelful of coal into the left hand front corner, the second shovelful in the right hand front corner, the third shovelful in the right hand back corner, the fourth shovelful in the left hand back corner, the fifth shovelful under the brick arch, close to the tube plate; the sixth and last shovelful under the door. To land this one properly the shovel must enter the fire-box and should be turned over sharp to prevent the coals falling in the center of the grate or the fire. Now comes the question when to fire. To fire properly, with the greatest effect in saving fuel, it should be done as soon as the steam begins to lift the valves, when by opening the fire-door and putting on a small quantity of coal the steam is checked sufficiently to prevent its being wasted by blowing off. Some engineers have an idea that unless the steam blows off furiously they have not done their duty by the engine. A big mistake this. When steam, water and fuel are being thrown away through the safety valves, it is a positive proof of the existence of either one or the other of the following evils: Either the engine is too small for its work or too great for its man, and both the engine and the man would do better on short runs; the former until it could be doctored, or the latter until he had learned to bottle his noise. The intervals between the rounds of firing, which should consist of six shovelfuls only each time the door is opened, is in every case regulated by the weight of the train or load, the state of the weather and the time allowed for running the trip, together with the quality of coal. The greatest possible mistake on an engine is putting on too much coal. The fire is choked, clinkers are formed, the temperature of the boiler is reduced, contraction and expansion sets in and leaks are formed--in a word everything goes wrong. The secret of good firing is to fire frequently, a little at a time. FEEDING. Having discussed fire, let us now consider the other element upon which the locomotive lives--water. The maintainance of steam in proper shape requires a knowledge of how and when to feed. The aim in feeding should be to regulate, as nearly as possible, the supply to the demand--just sufficient to keep the water at a proper level in the glass. This keeps up an even temperature in the boiler plates, tubes and fire-box, and this has much to do with the service of an engine. Many engineers always work their feed in the precise way to get the worst results. As soon as the boiler is full of steam and blowing off they turn on the pump full and keep it on until the steam is from 30 to 50 pounds below the maximum pressure before turning it off. This method is the very worst possible. What is wanted is a constant moderate supply of water, keeping the pressure as nearly even as possible. Nothing can beat this. When injectors are used one of them should be screwed down so that it will act moderately like a pump. This will save the water which is usually lost in turning injector on and off. ON THE FOOT-PLATE. When the train is under full headway the engineer should stand in his proper place on the foot-plate so as to be able to command the regulator and reversing valve at an instant's notice. Especially is this necessary at night, when the engineer's attention should always be on his engine, listening constantly to its beats to detect any irregularity which may arise from some defect in the machinery, frequently casting his eyes on the pressure gauge, and on the level of the water in the gauge glass. When the fireman puts on coal, the engineer should look round occasionally, to be sure that he is doing it right, placing the coal next to the walls of the fire-box, and not piling them in a heap in the middle. When the rails are slippery, great care is required to prevent the engine from slipping, by closing the regulator in time. When about to enter a tunnel, the sand valves should be opened, and the sand allowed to flow freely until the train emerges from the tunnel--sand is cheaper than steam. Never forget that lives and property depend upon the faithful performance of your work. CHAPTER VI. HOW TO BUILD A MODEL LOCOMOTIVE. As a preparatory step toward becoming an engineer, it is highly desirable for the boy who looks forward to that honorable calling to familiarize himself with the different parts of the locomotive engine. This we have stated before. There is no better way to accomplish it than to build a model locomotive. At first glance this may seem to be among the things impossible, but it is not so, providing the boy has a mechanical turn, and any boy who has not better not think of becoming an engineer. We now propose to give simple and accurate directions for building a model locomotive, accompanying the same with a series of illustrations, which we trust will be sufficient for the purpose intended. Before beginning we have one word of caution to offer. Don't do your work in a hurry. Don't calculate on the length of time it is going to take you to do it. Make up your mind to understand each detail before you begin, and to work slowly and carefully. If you remember this you will probably be able to build your locomotive. If you forget it you certainly will fail. HOW TO BEGIN. First of all in building a model locomotive, as in every other class of engineering work, it is necessary to get the measurements correct in spacing out the different parts to be joined together; and do not think that because it is only a model you are making that any off-hand way will do, because you will find before the engine is half finished that great accuracy is necessary if you wish your model to work. A slight mistake in the measurements of a large engine will cause so much friction as to take half its power to overcome. The same mistake with your model will stop it entirely. In soldering be careful to get the metal thoroughly heated. You will then get a firm joint--otherwise not. [Illustration: Fig. 1.] [Illustration: Fig. 3.] [Illustration: Fig. 4.] [Illustration: Fig. 6.] In giving these directions we assume that the boy who will undertake to follow them is accustomed to the use of tools to some extent. If not, he will have to learn as he advances by repeated experiments. Try your experiments on something else. In soldering, for instance, solder pieces of brass together until you learn to make a joint. Don't try your experiments on your model, or you will grow discouraged before you are half through. A word more about soldering. Do not touch the metal with the soldering-iron and then take it away. You might be able to solder in that way but the joint would not hold, but fall apart at the first pressure or slight blow. Soldering on the best work should be used very seldom, and all the fastenings should be either done by riveting, screwing or brazing, and it is hardly necessary to remark that no part of a boiler should be soldered which comes in contact with the flame of the lamp or furnace. Brazing had better not be attempted by any boy who has not been practically taught the art, unless it be on small joints. To braze the seams of a model boiler would require a forge fire, or a very powerful gas blast--too expensive for the amateur. Small things such as a broken slide valve, rod, etc., can be brazed by using a gas blowpipe. This will cost but little to make, and as it will be useful, we explain. See Fig. 1. To make a blowpipe such as is pictured in Fig. 1, first get a small piece of brass tube, A, of about half an inch diameter, and 5 inches long. Drill a hole at 2 inches from one end, and insert a piece of gas pipe, B, soldering it in place. Now take a glass tube a quarter of an inch in diameter and 7 inches long, hold one end in a gas flame, and when red-hot draw it out to a fine point, then file round and break off the tip, leaving a small hole. Now take a sound cork and squeeze it into the tube A as at C, drill a quarter inch hole through its center, insert the glass tube D, and the blow pipe is finished. To use it you connect the pipe B with a gas bracket by means of a rubber tube, and attach the glass tube D to a pair of bellows by means of another piece of rubber tubing. The bellows should have an air-bag attached. Otherwise you will have a jerky, uncertain flame. When you want to braze any article, bind the parts together with some very fine brass wire and cover with a little powdered borax and water; then lay the article on a piece of charcoal, and if it is necessary to preserve the temper of the steel you are about brazing, cut a potato in half and push each end of the steel rod into the halves, which will keep the temperature from getting too high. Then turn on the gas and start your blow pipe, at the same time working the bellows with your foot, and by either pushing in the glass tube D, or drawing it slightly out, you can regulate the shape of the flame as required. [Illustration: Fig. 2.] [Illustration: Fig. 5.] [Illustration: Fig. 7.] [Illustration: Fig. 8.] [Illustration: Fig. 11.] [Illustration: Fig. 12.] Now bring the flame to bear on the joint you wish to braze, having first supplied plenty of borax. Soon you will find the brass wire melting and running into the joint like water. It must then be neatly filled up and the joint will be scarcely visible. Here are a few tools which will be useful to you in this work. A center punch, or steel spike for mashing metal for drilling, etc., and a small riveting hammer. Three or four files of different degrees of fineness, a screw plate and taps, a small hand-drill with a set of drills to fit and a good firm vise. A lathe is of course desirable. Curves for bending metal you can easily make from pieces of bar-iron, holding them in the vise while working on them. When you have your tools ready get the material for your model. Several sheets of brass and copper, the castings and various sized screws and bolts are what will be required. All being thus prepared the time has arrived to take the FIRST STEP. The first step toward building a model locomotive is to be posted on the action of steam in the cylinder. Go to encyclopedia and read up on that point. If you have no encyclopedia go and look one up in some library. You can't build your engine until you understand this. Next draw an accurate plan of your model. Figure 2 is the idea. It is a side view of our locomotive. Let us describe. A. Boiler. B. Smoke-stack. C. Screwhead, to fill boiler with water. D. Steam chest with safety valve attached on top. E. Whistle. F. Steam tap to start the engine with. H. H. Leading and trailing wheels. I. Driving wheel. K. Cylinders. L. Frame. M. Buffers. N. Set thumbscrew to fasten on the tender. O. The lamp. P. Tap, used to ascertain the quantity of water in the boiler. R. S. Hand rail. To all locomotives there are three principal parts, the frame work, or carriage, the engine, or cylinders, and parts connected with them, and the boiler. Our model shall be a fifteen inch one. LAYING OUT MATERIALS is the next thing in order. First we want a sheet of brass for the bed plate, 1/16th of an inch thick, cut 4�14 inches, and be sure to cut the corners square. (See Figure 3.) Hammer this out flat, file it smooth and dress up, with emery cloth fastened upon a flat piece of wood. Next cut a square hole in it as at C, beginning half an inch from B, and making the opening 11 � 1-1/2 inches. Be careful to center this hole on the line A B, or your engine will be lopsided, and you must take the same care in setting the smoke stack, dome, etc. Now take Fig. 4. This represents one of the side frames. Cut these out now, thus: Drill holes at A B C for the axles to work in. Finish both sides the same way. Turn the bed plate upside down, fasten the frames on at a quarter of an inch from either side by small angle pieces (Fig. 5), or by soldering, which is easier done. Then solder a piece across each end, about half an inch deep, and the frame is ready for the wheels. These you can make if you have a lathe, but it would be better to buy your wheels ready made if you can, but if you can't do that, and have the lathe, turn your tires up to the form shown in Fig. 6. The small wheels should be about 2-1/2 inches in diameter, and the driving wheels, 4 inches. The rim, B, should project a little over 1/16th of an inch, and the rest of the edge should be beveled off rightly, as at A. The spokes should then be filed up smooth, drilling out the center hole for the axle before removing it from the lathe. Great care must be taken to turn both the driving wheels to exactly the same diameter, or one wheel would travel further in a revolution than the other, and as they ought both to be fixed rigidly on the crank shaft, the engine would never travel in a straight line, but would go round and round in a circle. Get some steel wire for the axles and fasten them to the wheels by soldering or by cutting a slot with a fine file in the center of the wheel, as at A, Fig. 7. Then file a small portion of the ends of the axle flat and drive in a brass wedge made by a piece of wire which will hold them together firmly. The crank shaft, or axle, must be hammered up to shape, making it hot occasionally in the gas flame while working it. The cranks should be at right angles to each other, and the throw of the crank half the distance of the cylinder stroke. For instance, say the cylinder being a 1-1/2 inch stroke, the distance between A B (Fig. 8) will be three-quarters of an inch, you must then ease the size of the crank at A to prevent the piston knocking the cylinder ends. [Illustration: Fig. 9.] The cylinders you had better buy ready made or have them made for you. Get a pair of oscillating cylinders of three-quarter inch bore and inch and a half stroke. These will drive your engines several miles an hour. Fig. 9 gives an underneath view of the frame work and the place to put the cylinders in. They must be supported by two lugs, A A, screwed to the bed plate B, which must have a piece cut out on either side to allow the driving wheels C, to work in, as at D; because, being larger than the others, they project beyond the top of the bed plate, as shown in Fig. 2. Next screw on by means of the hook F, the buffer beam, previously cut from a piece of mahogany, 5 inches long, half an inch thick and one inch deep, nicely squared and sand papered. Drill a hole at G, and pass the shank of the hook through the beam and piece of brass in front of the frame, screwing up tight with nut H. For buffers you may take two brass, flat-headed screws, and attach them to the beam half an inch from either end, allowing half an inch projection. Now polish everything smooth and bright. Next warm the model over the gas--don't let it get hot--and carefully lacquer it with a small brush taking care not to go over any part more than once. The spokes of the wheels must be painted, the buffer beams varnished and the cylinders painted, leaving the covers and flanges bright. Now put away your work to dry, covering carefully from dust. HOW TO MAKE THE BOILER. In making the boiler you can't be too careful. This is the part where the greatest chance for failure comes in. Buy a piece of copper tubing 11 inches long, 3 inches wide and half an inch in diameter. If you want to make it yourself bend your copper round a wooden roller and rivet or solder together--riveting is the best if you can get it tight. You must then turn two circles of brass about an eighth of an inch thick for the ends and polish all. Fig 10 gives you the idea. Now push the ends into either end of the tube about an eighth of an inch from the edge, as at A, Fig. 11, and solder in place. The projecting flange must be hammered down all around as at B, soldered and finished with a half round file. When filing solder use only an old worn file as a good one soon fills up. SMOKESTACK, TUBES, ETC. Now drill a hole at A (Fig. 10) for the smokestack, which should be three-quarters of an inch in diameter. Then cut a slot in the bottom of the boiler 6 inches long by 1-1/2 inches wide, commencing one-quarter of an inch from the forward end of the boiler. [Illustration: Fig. 10.] [Illustration: Fig. 13.] [Illustration: Fig. 14.] [Illustration: Fig. 15.] [Illustration: Fig. 16.] Next take a sheet of copper and cut a piece about 6-1/4 inches long by 6 inches wide and bend it over a wooden roller to the shape shown in Fig. 12, keeping it 1-1/2 inches apart between A and B. Cut also two other pieces of copper to the shape of your bent sheet (Fig. 12), and make it long enough to reach to the dotted line. These form the two ends, and may be placed an eighth of an inch from the edges, as in Fig. 13, and soldered in place, and the projecting rims turned over and sweated with solder from the outside, in the same manner that you did the boiler ends in Fig. 11. Then drill a three-quarter inch hole at B (Fig. 13) for the bottom of the smokestack to go into, and cut a piece of three-quarter inch brass tubing of sufficient length to pass out at top of boiler about half an inch, as shown at A, Fig. 10. You can then hammer out a rim or flange on the bottom end of the smokestack and push it up through the hole in the copper box, soldering it in place from the top as at A, Fig. 14. Then drill two small holes at each end of the box, B C, Fig. 14. These should be a little more than an eighth of an inch in diameter, to allow an eighth of an inch tube to pass through. Now get two 12-inch lengths of hard drawn steam pipe, an eighth of an inch in diameter, and with your screw plate put a thread on each end, about half an inch in length. Then make eight nuts to fit the threads on the piping, filing them up into proper shape. Now take the piping and bend it very gently, to prevent it cracking, around a bar of iron or handle of some tool held in the vise, until it is in the form shown in Fig. 15. Do each one the same, then mix a little turpentine with white lead, and smear each end, where you have formed the screws, taking care not to get any into the tubes, which can be temporarily plugged up. Next put a nut at either end, as far as the thread will take it, then smear a little white lead around the holes drilled in the ends of the box, B C, Fig. 14. Push the tubes in from the inside, and screw up firmly with the remaining nuts, in the position shown at Fig. 16. The inside nuts can then be tightened up with a wrench, and if you do all this carefully, you will never be troubled with any leakage, no matter what pressure you may get in your boiler. These tubes are immensely strong, and owing to their small size, the water in them is raised quickly to a higher temperature than that contained in the rest of the boiler, causing a continual circulation to take place, and a constant supply of steam to be found. The box can now be placed in the boiler, through the slot cut in the bottom, taking care that the top of the box is not more than half way up the boiler, as at B, Fig. 10. This will leave a portion projecting below the lower edge of boiler like C. This part protects the flame of the lamp from being blown away by the draught caused by traveling along, and which would cause you to lose steam. Solder it firmly in position from the outside to prevent the flame from touching any soldered portion. Also solder neatly round A, Fig. 10. The smoke stack can be made from another piece of three-quarter inch brass; turn it up in your lathe bright and put a collar on it at A Fig. 17, to allow it to push on to the piece of tube left projecting at A Fig. 10. The top of the smoke stack, B Fig. 17, will also require turning in the lathe and must be fitted on neatly. Get advice from some mechanic about the steam chest, which is a brass casting and will have to be turned up in the lathe, and after cutting a circular hole in the top of the boiler of about an inch in diameter it can be either screwed or soldered on, previously putting the steam pipe E in position by drilling a hole at F and after bending it as shown, pass it through at F and solder in place. The top of pipe E should be about a quarter of an inch from the top of inside of steam chest. Before soldering on the steam chest drill two holes as at G H Fig. 10, one for the small lug G to be screwed into, which holds one end of the lever of the safety valve, and that at H should be drilled conical with a rimer, and the valve H can be turned in the lathe and afterwards ground to fit the hole with a little emery and water, by means of a slot cut across the top and worked round with a screw driver. The spring case of the safety valve I, Figure 10, is easily made from a piece of one-eighth inch brass tubing, using some small, hard, brass wire to form the spring. When finished it should be hooked to the eye and screwed into the boiler at V. The manhole or screwhead, K, is used to refill the boiler when it has steamed low and will have to be turned up to shape, and the bed, L, which it screws into can be firmly soldered on the boiler, having first drilled a hole slightly larger than the diameter of the screw itself, which should be sufficiently large to allow an ordinary tin funnel to be used to refill by, and the screw ought to be long enough to hold a leather washer under the head to keep it steam-tight. The whistle, M, will require a hole drilled for it to be screwed into, and that, as also the steam-tap, N, and water-tap, O, can be bought cheap, ready to put on. The tap O should be screwed in at a slightly higher level than the top of box B, and when working the engine should steam issue from it when turned on instead of water, you ought to immediately blow off steam by safety valve H. Then unscrew K, and refill the boiler with water. [Illustration: Fig. 17.] [Illustration: Fig. 18.] [Illustration: Fig. 19.] [Illustration: Fig. 21.] [Illustration: Fig. 22.] By this time the framework will be quite dry, no doubt, so you can, after cleaning and polishing the boiler, attach it to the frame by a screw or solder at the forward end, and the steam-pipe N can be screwed on to the projecting piece of tube left at F, while you also screw a short length of pipe into the steam box of engine through a hole in the bed plate. Then bend it up to the steam tap, and solder them carefully in position; this will hold the after end of the boiler firm. Go over every soldered joint to see if any small hole is left, and resolder where necessary, as a hole in the boiler not larger than a pin's point would prevent you from getting any pressure of steam in the boiler, as the water would all blow out. Now lacquer or paint your boiler, and while it is drying turn your attention to the lamp, which we picture in Fig. 18. THE LAMP. The lamp is simply an oblong tin box, about 5 inches long by 1-1/4 inches wide and three-quarters of an inch deep. To make it cut a piece of tin 4-1/2 by 5 inches and bend it to shape. Then solder the two edges together and cut two ends to fit; push them in and solder in place. Now cut three pieces of brass quarter-inch tubing into three-quarter inch lengths; drilling holes in top of lamp, insert them, allowing a quarter of an inch to project, as at A, Fig. 17. Then solder them on four pieces of bent wire--C, C, C, C, Fig. 18--by which to hang the lamp by means of two wire pins run through them and small holes drilled in the sides of projecting piece C, Fig. 10. The screw filler B, Fig. 18, will have to be soldered in, also, and when complete the tubes A may be filled with cotton wick and the lamp about three-parts full of a methylated alcohol, which will give a clear, smokeless flame. Now you can start your locomotive by filling the boiler about three parts full of hot water, and then hooking the lamp underneath; you will soon get up a good pressure of steam. See that the taps are all turned off, and if there is no leakage from careless workmanship, you will find on turning the steam tap on, that the locomotive will run beautifully and will travel at great speed either on a smooth oil-cloth or a board floor. On rails it would run quicker still, but for this engine, if you make a small tender of the shape shown in Fig. 19, and fasten it at any angle by the set-screw on the foot-plate of the engine shown at N, Fig. 2, the model will run in any sized circle you may wish without rails, according to the angle you fix the tender to the engine. Wooden cars you can make if you wish, but each one added will reduce the speed of the engine, of course. Tin is the best material to use for the tender, as no great strength is required--indeed it should be made as light as possible. The wheels and axles you must finish in the same manner as those on the engine, and it can be made into a tank to hold an extra supply of alcohol by soldering a piece of tin round the inside and covering it in with another piece cut to shape and fitted with a screw nut to fill by as shown in Fig. 18. Such is the method of constructing a model locomotive which will run without complicated machinery. The boy who has succeeded in following these directions will no doubt be ambitious to try his hand on a more complete model on a larger scale, something like Fig. 20 for instance, which is a side view of a large model locomotive in a finished state. HOW TO BUILD A LARGE MODEL LOCOMOTIVE. In building a large model the first thing to be done is to decide how large you want it. Sketch your model carefully, or, if not able to draw plans, get some one who is to help you. Make your plan the exact size of the model you intend to build, then you can take all the measurements from it and save yourself a lot of trouble and time. Remember, however, that the larger you make the engine the more expensive the castings and materials will be. Should you persevere, however, and by good fortune succeed, you will have a model locomotive that would cost you two or three hundred dollars to buy ready made. If you have a lathe and can turn the wooden models for the castings yourself, use sheet iron for the frame-work, etc., where possible; the total expense will not be so very great. Begin your work in the same way you did on the other model. If you want a bigger engine than the one shown in Fig. 20, there would be no trouble in increasing the measurements, which we are about to give, proportionately, remembering that Fig. 20 is drawn to an eighth-inch scale. DIMENSIONS. Make your dimensions as follows: Length over all, 3 ft. 2 in. Length of bed-plate, 3.5 in. Width of bed-plate, 9 in. Diameter of driving wheels, 8-1/4 in. Diameter of leading wheels, 5-1/4 in. Gauge--that is width of track on which model can run--6-1/2 in. Cylinders, 1-3/4 in. bore by 2-1/2 in. stroke. Length of boiler, including smoke box, 28 in. Diameter of boiler, 5 in. Cylinders of the above dimensions will drive the engine at a high rate of speed, with from 30 to 50 lbs. of steam. DESCRIPTION OF LARGE MODEL LOCOMOTIVES. In Fig. 20, the different parts of the engine are lettered, and it will be well for the boy who desires to make a locomotive like it to compare the following description with the cut, before he does anything else. [Illustration: Fig. 20.] A is the smoke stack and B the steam blast used to increase the intensity of the fire worked by rod C running through the hollow hand-rail D and ending in handle F. G is the steam-dome, which with the safety valve is the same pattern previously used. H is the extra safety valve, worked from the foot-plate. I is the steam whistle, K wind guard, L starting lever, M smoke-box with door, N O spring buffers; P is the line-clearer or wheel guard. Q are the leading wheels, R R the driving wheels, S is one of the cylinders with piston rods and guides bolted to frame and showing double connecting rod at T T. U U are the springs which support the weight of the boiler, etc., on the axle bearings. The spring or rear wheel does not show, being inside the safety guard and hand-rail V. W is the back pressure valve, through which the water is thrown by the force-pump into the boiler, and X is the blow-off tap to clear the engine from all water after having used it. Y shows the side of the ash-pan. HOW TO DO THE WORK ON THE LARGE MODEL LOCOMOTIVE. First of all comes the frame work. It wants to be of eighth inch sheet iron squared up perfectly true and flat and cut as is shown in Fig. 21, beginning 4-1/2 inches from A, and leaving 6 inches at B, and cutting it 6 inches wide there by 8 inches long, and continuing it 4 inches wide for the rest of the distance. Be careful to keep it quite central on the line A B, and leave two connecting strips 1 inch wide as at C C. The side frames come next. These must be much stronger and quite different from those used in the previous model. They may be cut from the same eighth inch iron to the shape shown in Fig. 22. The center of slot B is 17 inches from one end, the center of A 10 inches from B, and the center of C 13 inches from B. In measuring, always start from a given center if you want to be accurate. That is, from B to A and from B to C; not from B to A and from C to B. The slots are each 1-1/4 inches wide by 2 inches deep, leaving 1 inch of iron at the top, as shown. The four large boles shown in Fig. 23 are only ornamental, and can be now cut out. They also serve to lighten the frame. The frames, after being smoothed up can be fastened to the bed plate in the manner described before, by angle-irons, or knees, riveted on. Two end pieces must also be prepared. Let them be 1 inch deep, with the ends hammered square, at right angles, and then riveted to the bed plate and side frames, as shown in Fig. 20. Then drill three holes in them, about an inch and a half from either end, and one in the center, by which to bolt on the buffer beams by means of a couple of screws put in at the back. The buffer beams should be mahogany, 1 inch wide by 2 deep by 10 long, squared nicely and sandpapered. A hook can then be made--Fig. 23--and a hole being drilled in the center of the beam, you can pass the hook stem through and into the central hole of framework, and screw up tight with nut at back, which will hold all firmly in place. The buffers for this model must be properly made, with springs to take the pressure in case you should run into anything. Fig. 24 shows this buffer. You will have to get it cast. Turn out in your lathe a wooden mold and get four castings in brass made from it. A Fig. 24 is cast with a square base plate 2 inches square, as in front view B, and is secured to the buffer beam by four flat-headed screws. The piece C must be turned true and just the size to slide in and out of A easily. Each part must be finished up in the lathe. A should be an inch and a half long. Drill a hole in the buffer beam to allow the head of the pin to work freely, and another hole in base plate of buffer the size of the pin, whose head prevents the spring from forcing C entirely away from A. The spring should be made of thick steel wire; the buffers can then be screwed in as just mentioned. The wheel-guard or line-clearer P (Fig. 20) can next be cut out to shape and bolted on to frame, and should just clear the line by a quarter of an inch. We will now proceed to the axle bearings and springs, U, Fig. 20. Make a wooden model like Fig. 25, and get 6 castings in brass made from it. They must then be filed up square and smooth and fitted into the slots cut at A, B, C, Fig 22, and either screwed or riveted on by the side holes. Before finally fixing them prepare 6 brass bearings, B, Fig 25, which must fit exactly and slide easily in the inner surface of A, then drilling a hole through each five-eighths of an inch in diameter. These take the axles, which in this model are all straight, and three-quarters of an inch in diameter, shouldered off to five-eighths for the bearings. Next for the springs. Take 4 pieces of either sheet iron or brass for the supports, 1-1/2 inches long by 1/4 inch wide. Drill a hole in either end as shown at C, Fig. 26. A should be three-eighths of an inch wide, drilled through, a pin put in and all riveted together loosely. [Illustration: Fig. 23.] [Illustration: Fig. 24.] [Illustration: Fig. 25.] [Illustration: Fig. 26.] Now take a clock spring and cut it into shape, as at D, Fig. 26. The top piece requires to be made hot with your blow-pipe, then the ends turned over to hold the pin B. Each piece of spring must be a little shorter than the one above it, and the ends neatly tapered, all to be inclosed in the brass band F, which has a small hole drilled at F to hold the end of the pin by which the pressure is directed on to the axle boxes, as shown in Fig. 20. A hole is also to be drilled in the bed plate over the center of each axle box to allow the pin to pass through, and also a smaller one an inch and a half on each side for the support A, Fig. 26, to screw into. Now all can be fitted into position. Next come the cylinders. These are to be an inch thick and three-quarters bore by two and a half inch stroke. They should be of the fixed slide-valve pattern, with double eccentrics fitted on the middle axle shaft, and reversing lever brought to quadrant on foot plate. They had better be bought ready made. Fig. 27 shows their working. A A are the eccentrics, B the slide-valve rod with guide G attached. C C is the bed plate and D the balance weight, F the rod leading to quadrant and lever on foot plate. The cranks are put on outside the wheels and fastened by keys as in Fig. 20. The connecting rod T should be cut to the form shown in Fig. 28, and the ends squared out and a brass band fitted in with a hole drilled from top A to oil by and a set screw B to adjust the bearings perfectly. If you wish to fit a force pump it should be placed centrally between the cylinders and be worked by an eccentric on the main shaft, but a pump on a model locomotive is next to useless unless it is also made to work by hand. In Fig. 29, we have one which can be worked either way. A is the pump; B the eccentric on main-shaft to work it by steam power. To work by hand you have only to push up hook connection C, which disconnects it from the eccentric; and then by working the handle D, which is screwed into the bottom of the plunger C, the water is forced into the boiler. An extra stuffing-box at F will be required. G is the exhaust water pipe bent up to the back-pressure valve on boiler, and H the supply pipe carried on to rear of engine. Two small blow-off cocks will be necessary on each cylinder to get rid of the condensed steam when starting. They can be connected with a tye-rod, and both worked from the foot-plate with a single handle. Now paint to suit your taste and put away to dry. Next comes the boiler, which will need extreme care. For this you will require sheet copper an eighth of an inch thick. First cut a piece 19 inches long by 16 wide and bend it round, forming a cylinder 5 inches in diameter. The cap must be closely riveted and the two ends hammered out into a flange outward, leaving the body of the boiler 17 inches long, as in Fig. 30. B is the shape of the piece to be next riveted on at after end. Now take another sheet 9 inches wide and hammer a half inch flange round it, so as to fit over the dotted line at A. Rivet them firmly together and also another piece in after end. It will then have the appearance of Fig. 31, and should be 4-1/2 inches deep from A to B, and forming a copper box 6 inches wide from B to C and 8 inches from C to D. Then rivet together another box to form the inner casing 4-1/2 inches wide by 6-1/2 inches long and 9 inches deep, the bottom to be hammered outward to the dimensions of B C C D, as shown in section Fig. 32 at A A. A hole is next to be cut out in the center of rear plate and also the rear part of inner casing which comes opposite to it, and 1-3/4 inches by 2-1/2 forming the furnace door. A casting of that shape and 3/4 of an inch thick, which is the distance between the inner and outer casing B C, must be procured and drilled with holes every 3/8 of an inch and firmly riveted in position, as shown in Fig. 32 at D. Two pins should project on either side of the inner surface to support the fire-bars and ash pan, and the bars should be made of cast iron and small enough to get out easily by tilting up one side; they should run lengthwise of the engine. For the boiler tubes some hard drawn brass tubing three-quarters of an inch in diameter will be required. Cut the pieces slightly over 17 inches long, then drill 10 holes in the inner plate as at E, Fig. 32, and in the position and arrangement shown in Fig. 33. These tubes should have a wire ring brazed on about a quarter of an inch from either end, and then being placed in their respective holes in the tube plate, the projecting portion is to be headed back with a flange, or you can fit them in as already shown in Fig. 16 by each being double screwed and nutted. These tubes allow the smoke and flame to pass through from the furnace to the smoke box, M, Fig. 20, and so away up the smoke stack, and by the large surface they expose to the fire, help to raise steam very quickly. In some engines as many as 300 tubes are fitted. The steam supply pipe and regulating lever handle should now be made and placed in position, and Fig. 34 shows the shape to make it. A B are the front and rear plates of the boiler, C is the supply pipe bent with a screw end downward, after passing plate A, and then upward into the steam dome, where it should be securely fastened into a cross-piece. D is the tap or valve which can be turned on or off from the foot-plate by means of the long rod, F, ending in the lever handle, G. The rod must be fitted with a stuffing-box, the same as those used on the cylinders, and packed with cotton wick to prevent loss of steam by leakage. When all this is complete, the forward end of the boiler can be furnished with a tube-plate riveted on and the tubes flanged over. Now the boiler must go to a practical brazier, and be properly brazed. Cut the hole for the steam dome, and let him braze it on at the same time. If the job is practically done, your boiler can be heated red-hot without fear. [Illustration: Fig. 27.] [Illustration: Fig. 28.] [Illustration: Fig. 29.] Meanwhile buy your pressure gauge--it wants to be one and a half inches in diameter--and let the brazier test your boiler to 100 pounds steam to the square inch capacity. Should it burst you will have to make another. If not you need thereafter have no fears. Now make the smoke box, which should be three inches deep and of the shape and dimensions shown in Fig. 35. This and the smoke-stack can be made of iron, hammered up to shape and finished with a brass ring. The smoke-box can be screwed on the forward flange or boiler. The door is drawn open to show the amount of bulge it should be hammered to. In the center a hole should be drilled through which to pass the screw used to close it, which is attached to the loose bar, A. The handle, B, is then screwed up tight. The door is circular and must be large enough to overlap the opening about half an inch and have a couple of bright iron or brass eyes, C, riveted on to form the hinge. Next comes the back-pressure valve, Fig 36. A is a front view with plate by which it is bolted to the boiler, as at W, Fig. 20. It is very simple to make, and consists of the casting A with top and bottom covers and the ball-valve B, which ought to be ground with a little emery and oil to fit perfectly. It acts in this manner. The water being forced up C from the pump, raises B and passes into the boiler. On the up stroke of pump, the pressure is removed from under B and the pressure of steam in the boiler causes it to fall back and close the opening entirely, preventing any water from passing away from the boiler. A small flange can be put on each outer side of the boiler near the furnace to support it on bed-plate level with smoke box. The boiler should now be covered with flannel, cut to shape and wrapped round the body part and a casing of sheet tin put over it and secured by brass bands and small nuts underneath--as shown in Fig. 20. The steam supply pipe can now be connected with the cylinders and it should be made forked as in Fig. 37. A leads from steam pipe and branches off to each cylinder, where it must be screwed up with white lead. The exhaust pipes B B should be of larger tubing and bent round up the sides of the smoke box so as to be out of the way when you have to clean the tubes. A small brass pipe, C, must also be passed through the chimney, bent upwards and fitted with a tap which should take the steam from the top of the boiler and be used as shown at D F Fig. 20. This helps to raise steam very quickly. Fig. 38 is a rear view of the foot plate and shows the necessary fittings which you must either make or buy to complete the model. The cocks you might make but the water gauge you must buy. A is the furnace door, B two gauge taps, C starting-lever handle, D spring balance safety valve, F wind-guard with two look-out holes, G steam whistle handle, H pressure gauge, N the quadrant and lever for reversing the engine, O the rear buffer beam with buffers, P the wheels showing axle, R R the springs for same and V the safety-guard rail on either side. [Illustration: Fig. 30.] [Illustration: Fig. 31.] [Illustration: Fig. 32.] [Illustration: Fig. 33.] [Illustration: Fig. 34.] [Illustration: Fig. 35.] [Illustration: Fig. 37.] [Illustration: Fig. 36.] When these fittings are all complete holes must be drilled in rear plate for each piece; they must be firmly screwed in place with white lead. The glass tube of the water gauge, the stuffing-box, and the gland of the starting lever should be closely packed with tallow and cotton wick. [Illustration: Fig. 38.] Next paint the entire model over again and let it dry. We give no directions as to colors; use your own taste. After the paint is thoroughly dry varnish with the best clear, hard varnish and let it dry again. While it is drying you can be making the rails. Get some square bar iron, cut it into six-foot lengths, if you wish the rails to be portable, and drill a hole in each end half an inch deep. The rails can be joined together at each end by means of a piece of wire and kept at a proper distance apart by being fastened to pieces of wood placed like sleepers, fastened by screws passing through holes drilled in the rails every six inches. These sections can be laid end to end, and your line be made as long as you wish. If you want a circular line, each section must be bent to a portion of a circle; one about 30 feet in diameter is suitable for this model. When finished place your locomotive on the track and get up steam. Fill the boiler with water by means of a funnel until you see it rise up three parts of the way in the glass water-gauge. Then see that all taps are turned off and start the fire. Charcoal is the best fuel, as it gives a clear, hot fire without much smoke once you start it right. Try the safety-valve occasionally to see how your steam is getting on, and when it begins to form turn on the blast-tap, which will soon draw up the fire, and you will presently see the pressure rise and show itself in the pressure-gauge. When the gauge shows 30 lbs. of steam you might start the model by turning on the cocks on cylinders until no more condensed steam issues from them. Then shut them off and turn on steam full power and watch the engine travel, gradually increasing its speed. CHAPTER VII. CONCLUSION. Let us now bear the conclusion of the whole matter, which takes us straight back to where we started, and we again repeat if you want to become an engineer make up your mind that you will be a good one or none at all. We have examined the locomotive inside and out, underneath and on top, even peering down the smoke-stack, crawling into the fire-box, and learning the true science of shoveling coal. What then remains to be told? Nothing that can be remembered long enough to be of any practical use. There are matters--dozens of them--connected with locomotive engineering which we have not even alluded to, but they are for the most part such as must be learned by actual every day experience to be of any use. We might, perhaps, under three heads speak a few closing words. First let us take up SIGNALS, and post ourselves a bit on that most important subject. The greater part of an engineer's time while on his engine must be spent in the lookout for signals. Upon this depends not only the safety of every soul on the train but his own as well. _Never jump at conclusions in the matter of signals._ Never assume that because a "distant" signal and all the other signals are off the line is clear. Every engineer should, as far as possible, not only see that each signal is off, but he should also cast his eye over the road in front of him to see whether it _should_ be off. At night caution in the matter of signals is even more necessary than in daylight. Then the only safety lies in keeping a constant lookout. You must know your road. It is not enough to know where the up grades lie and where the downs. You must know just how steep the grades are and their length. Often signals are badly placed and cannot be seen until the engine is close upon them. With this you have nothing to do. Engineers do not place signals. Doubtless if they did they would alter the position of many of them. All you have to do is to heed the signals, no matter how well or how badly they are placed. To enter into a detailed description of signals until some universal system of signaling is adopted, would be but a waste of time. You will have to learn all these things during your apprenticeship; they are matters upon which books can give you little help. Presence of mind you must always have if you expect to become a good engineer, and courage, too--plenty of it. This brings us to our second head, which we will write "BROKE DOWN." What to do when the engine has broken down? There comes the tug of war, the time when it will be definitely decided whether the engineer is good, bad or indifferent. Hundreds of lives may depend upon prompt action, thousands of dollars' worth of property are in the engineer's hands, either to waste or save when the moment of the break down comes. In Mr. S. A. Alexander's excellent treatise entitled "Broke Down" is placed in red letters over every page, "Protect Yourself from Approaching Trains." When a break-down occurs, this is the first thought which should enter the engineer's mind, and the first act should be to carry it out. There are many causes of a break-down, too many to enumerate. In the roundhouse is the place to study break-downs, for here, daily, every variety is open to inspection--broken crank-shafts, broken eccentric-rods, eccentric-straps and sheaves, broken motion and broken springs. Of course an engine may be broken, and yet able to run its train through. This is an important consideration. Some engineers hardly know when they are beaten. It is a matter of record that a certain engineer, known as "Hell-fire Jack," ran his train over a bridge after one side had been washed away by a raging flood. Thousands of such daring deeds have been accomplished by engineers, but "Cautious Jacks" will be better appreciated by the company than "Hell-fire Jacks" every time. Real heroism lies in good judgment and a cool head. Suppose that the right hand back gear eccentric-rod breaks. "Can I get along in forward gear, after having disconnected the rod and the strap?" is the question. The answer is yes, and it should be prompt, as all such answers should be when the engine breaks down. It is such readiness as this that makes break-downs but a matter of a few moments. It is also highly necessary that the engineer should ask himself "What tools have I upon the engine? What can I do with them? Can I find them in the dark? If I run off the track in what condition is my screw jack? Will it work properly? Have I a ratchet or bar to work it with?" These are things which should be continually kept in mind. AIR BRAKES. The air-brake has changed engine driving materially in the last few years, and a word or two concerning it should be said. The air-brake consists briefly of an air cylinder placed beneath each car, which can be operated by the engineer from the foot plate, the pressure of the air controlling the action of the brakes. There are two valves to an air-brake, one for ordinary stops and the other for sudden stops in case of emergency. In the first only partial pressure of the confined air is used, in the latter the full pressure is employed and the brakes brought against the wheels with all force at once. One of the most important duties of an engineer is to be well assured that the air-brakes are in proper working order. After the call for hand brakes has been given, the air brakes must not be applied until the hand brakes are released. Air and hand brakes should never be used at the same time on a car. When cars having different air pressures are coupled together the brakes will work first on that having the highest pressure. Special instruction is needed to fully comprehend the working of air brakes. Here is a speed table which may be useful. We have taken the liberty of extracting it from Alexander's "Ready-reference for Locomotive Engineers," an excellent hand-book with which all candidates for the foot-plate should provide themselves. Published by the author, S. A. Alexander, York, Pa. TIME AND SPEED TABLES. Key: M = Minutes. S = Seconds. T = 10th of a Second. M S T 10 miles per hour is 6.00 to 1 mile 11 " " " " 5.27 " 1 " 12 " " " " 5.90 " 1 " 13 " " " " 4.37 " 1 " 14 " " " " 4.17 " 1 " 15 " " " " 4.00 " 1 " 16 " " " " 3.45 " 1 " 17 " " " " 3.32 " 1 " 18 " " " " 3.20 " 1 " 19 " " " " 3.09.5 " 1 " 20 " " " " 3.00 " 1 " 21 " " " " 2.51.5 " 1 " 22 " " " " 2.43.5 " 1 " 23 " " " " 2.36.5 " 1 " 24 " " " " 2.30 " 1 " 25 " " " " 2.24 " 1 " 26 " " " " 2.18.6 " 1 " 27 " " " " 2.13.3 " 1 " 28 " " " " 2.08.5 " 1 " 29 " " " " 2.04 " 1 " 30 " " " " 2.00 " 1 " 31 " " " " 1.56 " 1 " 32 " " " " 1.52.5 " 1 " 33 " " " " 1.49 " 1 " 34 " " " " 1.45.6 " 1 " 35 " " " " 1.42.6 " 1 " 36 " " " " 1.40 " 1 " 37 " " " " 1.37.3 " 1 " 38 " " " " 1.34.7 " 1 " 39 " " " " 1.32.3 " 1 " 40 " " " " 1.30.0 " 1 " 41 " " " " 1.27.7 " 1 " 42 " " " " 1.25.7 " 1 " 43 " " " " 1.23.5 " 1 " 44 " " " " 1.21.7 " 1 " 45 " " " " 1.20.0 " 1 " 46 " " " " 1.18.2 " 1 " 47 " " " " 1.16.6 " 1 " 48 " " " " 1.15.0 " 1 " 49 " " " " 1.13.5 " 1 " 50 " " " " 1.12.0 " 1 " 51 " " " " 1.10.6 " 1 " 52 " " " " 1.09.4 " 1 " 53 " " " " 1.07.9 " 1 " 54 " " " " 1.06.6 " 1 " 55 " " " " 1.05.4 " 1 " 56 " " " " 1.04.3 " 1 " 57 " " " " 1.03.2 " 1 " 58 " " " " 1.02.2 " 1 " 60 " " " " 1.00.0 " 1 " 65 " " " " 0.55.3 " 1 " 70 " " " " 0.51.4 " 1 " 75 " " " " 0.48.0 " 1 " 80 " " " " 0.45.0 " 1 " 85 " " " " 0.42.3 " 1 " 90 " " " " 0.40.0 " 1 " 95 " " " " 0.37.9 " 1 " 100" " " " 0.36.0 " 1 " The boy who aims to become an engineer should not waste his school hours in idle dreaming or in too much sport. Improve every moment you can spare from other duties or needed exercise in studying arithmetic, geometry, algebra and mechanical engineering. A little knowledge as a draughtsman will also be a great help. Above all, get some larger manual on locomotive engineering and read and re-read it until you know its contents by heart. Remember that there is no limit to knowledge in any direction. The time can never come to any engineer when he can truthfully say to himself, "I know it all," and to his life-long study write [Illustration: THE END.] THE LARGEST AND BEST LIBRARY. PLUCK AND LUCK. Colored Covers. 32 Pages. All Kinds of Good Stories. Price 5 Cents. Issued Weekly. Read List Below. No. 1 Dick Decker, the Brave Young Fireman by Ex Fire Chief Warden 2 The Two Boy Brokers; or, From Messenger Boys to Millionaires by a Retired Banker 3 Little Lou, the Pride of the Continental Army. A Story of the American Revolution by General Jas. A. Gordon 4 Railroad Ralph, the Boy Engineer by Jas. C. 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All the above books are for sale by newsdealers throughout the United States and Canada, or they will be sent, post-paid, to your address, on receipt of 10c. each. _Send Your Name and Address for Our Latest Illustrated Catalogue._ FRANK TOUSEY, Publisher, 29 WEST 26th STREET, NEW YORK. Transcriber's note: The Table of Contents was added by the transcriber. Some inconsistent punctuation has been normalized throughout the book. Some inconsistent hyphenation (e.g. smokestack vs. smoke-stack) has been retained. Some illustrations in this book appear to have been lifted from Locomotive Engine Driving: A Practical Manual for Engineers in Charge of Locomotive Engines by Michael Reynolds (London: Crosby Lockwood, 1888). Fractions have been normalized to the form X-Y/Z. Page 5, changed "locomotiive" to "locomotive." Page 7, changed "Engilsh" to "English." Page 8, changed "clumsey" to "clumsy" and "prise" to "prize." Page 16, changed "guage" to "gauge." Page 17, changed "will came" to "will come." Page 19, changed "where on can" to "where one can." Page 21, changed "gain" to "gains." Page 22, changed "reponsibility" to "responsibility." Page 24, changed "read then" to "read them." Page 27, changed "thinest" to "thinnest." Page 29, changed "guage" to "gauge" (twice) and "at at" to "at." Page 34, changed "undestand" to "understand." Page 51, changed "shown it Fig. 35" to "shown in Fig. 35" and "llittle" to "little." Page 56, changed "definately" to "definitely." Page 57, changed "air-brakes consists" to "air-brake consists." 
476	----	None 
47187	----	STEAM SHOVELS --AND-- STEAM SHOVEL WORK. By E. A. HERMANN, M. Am. Soc. C. E. 1894. ENGINEERING NEWS PUBLISHING CO., NEW YORK. Copyright. 1894, by Engineering News Publishing Co. CONTENTS. Pages. PART 1.--Steam Shovels 1-19 " 2.--Steam Shovel Work 19-41 " 3.--Disposition of Material 41-55 " 4.--Cost of Steam Shovel Work 55-57 INDEX. Ballast, plowing, 48 Blasting, 39, 52 Brine, sprinkling earth, 52 Cars, dump, 19, 41, 47 Flat, 42 Loading, 19 Unloading, 42, 47 Cost of work, 55 Cuts, 28, 36, 39 Time for, 17 Widening, 19 Explosives, 39, 52 Fills, trestles for, 47 Grades, construction track, 34 Cutting down, 28 Grading, 25 Gravel train, 42, 45, 50 Engines for, 50 Unloading, 48 Leveling, 53 Loading cars, 19 Gangs for, 21, 22, 23 Operating, men for, 18 Plow, Barnhart, 43 Gravel, 42 Plowing, cable for, 50 Gravel train, 48 Hauling engine for, 51 Winter, brine for, 52 Railways, construction, 33 Reducing grades, 28 Widening cuts, 19 Railway work, 18, 28, 33 Rapid unloader, 51 Spreaders, 53 Steam shovels, Barnhart, 6 Boilers, 9 Bucyrus, 4 Clement, 10 Daily capacity, 41 Description, 5 Giant, 12 Invention of, 1 Little Giant, 12 Industrial Works, 10 Machinery of, 5 Marion S. S. & Dredge Co., 6 Number of men, 18 Operation, 16 Osgood, 2 Otis-Chapman, 14 Repairs, 19 Souther's, 14 Thompson, 4 Toledo F. & M. Co., 8 Types, 3 Victor, 8 Vulcan Iron Works, 12 Tools, 16, 18 Track, arrangement of, 19 Narrow gage, 47 Trains, dirt, handling, 19, 42, 45, 48, 50 Trestles for fills, 47 Widening cuts, 19 STEAM SHOVELS AND STEAM SHOVEL WORK.[1] [Footnote 1: Copyright by Engineering News Publishing Co., 1894.] By E. A. HERMANN, M. Am. Soc. C. E. Part I.--Steam Shovels. The following article originated in a short paper which was read before a local society of civil engineers, and there were so many requests made for this paper and the illustrations presented with it that the author was led to believe that there was a demand for such information. Believing that a better understanding of the capabilities of these machines will serve a useful purpose in economizing money, time and labor in the execution of work to which they are adapted, the author presents in this article the information learned by a long practical experience in this special class of work. Descriptions of the various steam shovels can readily be found in the trade catalogues of the different manufacturers, but very little has been published on the manner of using them in the execution of different classes of work, and the disposition of the excavated material after it has been loaded on cars or wagons. This part of the subject will receive most attention, and although much of it may seem very elementary to those who have had an extended experience in operating steam shovels, it may be entirely new to the much larger number who have had few or no opportunities for doing work of this kind. It has been the aim of the author to condense the reading matter as much as possible, making it a point to use many illustrations in place of lengthy explanations, thus presenting the subject more clearly than by extended descriptions. [Illustration: FIG. 1. ELEVATION AND HALF PLAN OF OSGOOD STEAM SHOVEL; Osgood Dredge Co., Albany, N. Y.] The steam shovel, or steam excavator, is a modified form of dredge adapted for excavating material on dry land. It was designed and patented by a Mr. Otis, about 1840, and like most new inventions the first machine built was a very clumsy affair, but even in this crude state it possessed many advantages for removing large masses of material. Its merits were recognized in its earliest stages, and with increased experience in its operation improvements were soon made which rendered it almost indispensable on all works requiring large quantities of excavation. It was not until 1865, however, that the machine came into general use. About this time the largely increased railway construction created an active demand for the steam shovel, which demand was quickly supplied by several manufacturers, whose machines vary in distinctive designs of various parts, but the principles of operation are essentially the same in them all. Types of Steam Shovels.--There are three types of steam shovels: First; machines mounted on trucks of standard gage, transported from place to place in freight trains (or propelled by their own power), and intended for railway work only. Second; machines mounted on wheels of other than standard gage, transported in sections by boat or wagon, or loaded complete on flat cars, and intended for both railway and other work. Third; machines mounted on wheels fitted for transportation over common roads, propelled by their own power, and intended for railway and other work. The first machines built were of the second type. As now constructed they are mounted on a wide wooden frame or car body, supported by four small wheels of 7 ft. to 8 ft. gage, thus placing the machinery close to the ground, with a wide base of support. In transporting this machine from one place to another, not on the line of a railway, it is necessary to take it apart, forward the sections and put them together again at the site of the new work. The machine is built with a view to rapid dismantling and re-erection, and for work requiring a large machine for economical excavation, located in hilly country not yet made accessible by rail, or requiring transportation by boat, it is the machine most generally used. Its ready adaptability to all kinds of work in any location has made it the favorite machine with many general contractors whose work includes large contracts for railway and other excavation. For transportation by rail this machine is run onto an ordinary flat car, only the crane being detached and loaded on a separate car. With this manner of shipment the machine can be made ready for railway work very quickly, but for exclusive railway work a machine of a later design has come into use and is now generally preferred for this class of work. [Illustration: FIG. 2.--THOMPSON STEAM SHOVEL; Bucyrus Steam Shovel & Dredge Co., South Milwaukee, Wis.] This is the machine of the first type, resting on a wooden or iron car body, supported on trucks of standard gage, with an iron or steel crane from 18 to 26 ft. high over the track when in working order, and which can be lowered to 14 ft. to permit shipment through tunnels and under low overhead bridges. Machines of the third type are generally of smaller capacity than the others; they have come into general use only within the past few years, but are now multiplying rapidly in numbers as their utility for nearly all kinds of work is better appreciated. They are especially adapted to smaller jobs and work not readily accessible by rail, but where common roads are available. These three types are shown in Figs. 1 to 9, representing the machines of seven of the principal manufacturers. Steam shovels will excavate any kind of material except solid rock, and they will load rock if it has been broken up by explosives into pieces of not more than 3-4 cu. yd. in size. The materials excavated by them are mostly sand, loose gravel, all kinds of clay, cemented gravel, hardpan, clays mixed with bowlders and other small stones, ore, phosphate rock, loose rock and thin seams of slate, shale or sandstone. These machines are used for excavating material, loading it on cars or wagons for ballasting tracks; for filling trestles, streets, roads, dams, lots and new city additions; for widening embankments for double track, side tracks, yards, shops and station grounds; for cutting down street, road and railway grades; grading lots and new city additions, railway yards, shop and station grounds; widening cuts, removing land slides, stripping coal fields, ore beds and stone quarries; digging canals and drainage ditches, loading clays for brick yards, etc. Construction of Steam Shovels.--The general plan of construction of the machines, shown in Figs. 1 to 9, is essentially the same in all, and consists of a strong frame, mounted on wheels, forming the base to which all working parts are attached. The boiler and machinery are placed near the rear end of the frame, and the mast, or post, and crane at the front end. The crane is made in two pieces connected only at the top or point, and at the foot of the mast. Between these pieces, serving as guides, is the dipper handle, carrying at its farther end the dipper or scoop. To the top of the post (or to the foot in some machines) the swinging circle is secured. [Illustration: FIG. 3.--BARNHART STEAM SHOVEL; Marion Steam Shovel Co., Marion, O.] The most used, and hence the most important part of the machinery of the steam shovel is the gearing imparting motion to the hoisting drum, actuating the chains by which the dipper is raised and lowered. It is in almost constant use, and is often subjected to severe shocks in hard digging. Of all parts of the machinery it is the most likely to break or rapidly wear out. Naturally it has received the most attention of any part of the steam shovel in all efforts to improve the design, strength and durability of the machine. There are a number of different gears in use, and essentially they are either friction clutches or positive gearing. The use of the former subjects the machinery and crane to less severe shocks, and can be thrown in and out of gear more rapidly, but it wears out quicker, often causes delay by heating, and requires frequent repairs. Positive gearing exposes the machinery and crane to more severe shocks in hard digging, and must be started slower, especially in hard material, but while these machines are a little slower than those operated with friction clutches, they are less subject to the expense of repairs and delay due to the disarrangement of the hoisting gear, so that their total output of material about equals, and sometimes exceeds, the quicker moving friction gear machine. The mechanism for thrusting the dipper into the bank is attached to the crane, and the forms most generally used are as follows: 1. A chain, one end of which is attached to the rear end of the dipper handle, and the other end wound around a drum receiving its motion by an endless chain passing over a sprocket wheel connected to the axle of the sprocket wheel at the top of the mast, over which the hoisting chain passes, thereby revolving both wheels. This drum is thrown into gear by a friction clutch, and its motion regulated by the cranesman's lever and footbrake. 2. A rack on the dipper handle operated by a pinion attached to a shaft revolved and regulated as above described. 3. A small double cylinder engine operating either a pinion and rack as above described, or revolving a drum with a chain attached to it, and the rear end of the dipper handle as described in the first case. 4. A long steam cylinder attached to the dipper handle, whose piston rod is connected to the dipper, extending or withdrawing it as desired. [Illustration: FIG. 5.--VICTOR STEAM SHOVEL; Toledo Foundry & Machine Co., Toledo, O.] The thrusting mechanism used in the last two cases imparts a rapid, steady and powerful motion, but the extra engines or steam cylinder and their connecting steam pipes involve a complication which often more than balances their advantages. Swinging the crane in a horizontal direction is generally accomplished in one of the following three ways: 1. A chain passing around the swinging circle attached to the post, and wound around drums connected to the engine by positive gearing or friction clutches. 2. A wire rope passing round the swinging circle and connected to the piston rods operated by two long steam cylinders. 3. A chain passing round the swinging circle and wound around a drum connected to a small reversible engine. The mechanisms used in the last two cases have the same advantages, but also suffer from the same objections urged against employing small engines or a steam cylinder for thrusting the dipper into the bank. The engines are either of the upright type with a single steam cylinder, or of the horizontal type, with double horizontal steam cylinders. The size of the cylinders varies for machines of different capacities, ranging from 8 by 10 ins. to 10 by 12 ins. for the upright engines, and 6 by 8 ins. to 13 by 16 ins. for the horizontal engines. The upright type of boiler with submerged flues is usually preferred, as it occupies only a small space. Horizontal boilers of the locomotive type are used in a few machines, and are more economical in the use of fuel, but occupy too large a floor space. Forced draft is used in both types of boilers, and they are generally worked to the limit of their capacity. The usual working pressure is 90 lbs. per sq. in. The safety valve is generally set to blow off at 120 lbs. per sq. in. The boiler is supplied with water either from an upright circular sheet iron tank located in a corner of the machine, behind the boiler, or from a sheet iron box tank hung under the floor. These tanks usually hold about 1,000 gallons of water, enough to run the machine half a day. The water is obtained by a pump or siphon from the tender of a locomotive on railway work, or is hauled to the machine by wagon on other work. [Illustration: FIG. 6.--CLEMENT STEAM SHOVEL; Industrial Works, Bay City, Mich.] In some machines the frame or car body is made of wood, generally oak, often incased with heavy plate iron. In others it is constructed of iron or steel I-beams and channels. In all machines it is strongly built and braced with a view to sustain the weight of the working parts and to resist the shocks to which it is subjected. The floor is usually of 3-in. oak plank. The mast or post is made of cast or wrought iron, strongly braced and guyed to the frame. It is the pivot about which the crane swings, and easy working in its bearings is of great importance for the rapid and economical operation of the machine. In order to prevent breakage or delay it should never be permitted to wabble by neglecting to promptly tighten its braces and guys in case they should work loose. The post should always stand vertical, or practically so, to insure the horizontal motion of the crane and avoid unnecessary straining of the swinging gear. For this reason the machine should be set practically level before beginning operations; and using a small mason's level is better than trusting to the eye, when blocking under the track and adjusting the jack screws for this purpose. The crane is secured to the post, and is made of wood, iron or steel, strongly and compactly built to resist the shocks to which it is often subjected. It is from 14 to 20 ft. high above the track or ground, varying with machines of different sizes and manufacture, and swings horizontally through an angle of 180 to 240 degrees, with a radius of 15 to 20 ft. In some machines it must be detached from the post for shipment, in others (mostly those made for railway use exclusively) it can be lowered to a height of 14 ft. above the track, thereby permitting shipment without detaching from the post. The dipper, scoop, or bucket is made of iron or steel, shaped somewhat like a coal scuttle. Its cutting edge is protected by four teeth made of steel or steel pointed. These teeth are easily removed for sharpening or replacement. Dippers vary in size from 1/2 cu. yd. to 2-1/2 cu. yds. capacity. They also vary somewhat in shape, according to the material to be excavated, though no special provision is made for this unless there are very large quantities of the same kind of material to be removed; or for machines working in a certain class of material only, like ore loaders. For general work in all kinds of materials the dipper is seldom changed. For soft, tenacious material, likely to adhere to the inner sides of the dipper, and not drop out promptly when the bottom door is opened for unloading, the dipper is shaped as shown in Fig. 10, with a larger bottom than mouth. In hard, or dry soft material the section shows parallel sides, as in Fig. 11. For general use the bottom of the dipper should be slightly larger than the mouth, as most materials contain more or less moisture which is likely to produce a partial clogging of the dipper by material sticking to the inner sides, especially between the teeth, necessitating frequent cleaning out whenever the machine is stopped while preparing to move forward, and sometimes oftener. For ordinary clay, cemented gravel, and hard dry materials, a dipper with a wide and shallow mouth, as shown in plan in Fig. 12, is preferred to the one shown in Fig. 13, which latter is better adapted for loose gravel, sand and other soft dry materials where a deep cut can easily be made. For hardpan, shale, loose rock and similar materials, ample strength of teeth and dipper is of greater importance than its shape. [Illustration: FIG. 7.--GIANT STEAM SHOVEL; Vulcan Iron Works Co., Toledo, O.] [Illustration: FIG. 8.--LITTLE GIANT STEAM SHOVEL; Vulcan Iron Works Co., Toledo, O.] To prevent tenacious material from sticking to the inner sides of the dipper, and to allow it to drop out freely when the bottom door is opened, it is often good economy to place a barrel of water near the head of the machine from which a bucketful can be taken and thrown into the dipper just before each cut. The water acts as a lubricant and causes the material to drop out more readily. For cleaning the dipper, the tool shown in Fig. 14 is used. [Illustration: Fig. 10. Fig. 11. Fig. 12. Fig. 13. Figs. 10 to 13.--Buckets for Steam Shovel.] The chains have links of three-quarters-inch to one-inch diameter, and are made of iron, sometimes of steel. Their constant use necessarily subjects them to great wear, and as they are also often exposed to severe shocks (especially the hoisting chain) they must be made of the very best material and in the most careful manner. At present iron chains are preferred to those made of steel: they are more durable, and less likely to break under severe shocks. Steel chains have suffered in reputation through rapid wear and frequent breakages occurring within the last few years, but with increased experience in their manufacture and use they will undoubtedly be improved, and eventually take the lead over iron chains. The propelling mechanism consists of an endless chain connecting one or more axles of the truck or supporting wheels with the shaft of the hoisting drum by means of friction clutches or positive gearing. The usual speed is five to six miles per hour. [Illustration: FIG. 9.--OTIS-CHAPMAN STEAM SHOVEL; John Souther & Co., Boston, Mass.] Steam shovels of seven of the most prominent manufacturers are shown in Figs. 1 to 9, and the general particulars of each are given in condensed form in Table I. In each case the boiler is upright. TABLE I.--GENERAL DESCRIPTION OF THE IMPORTANT PARTS OF THE MOST PROMINENT MAKES OF STEAM SHOVELS. +---Frame------+ Fig. Size, Running Gage, En- Cylin- H'st'g Shovel. Material. ft. gear. ft.ins. B'l'r gine der, gear. ins. 1. Osgood Wood 10 � 34 2 trucks 4 8-1/2 V H 2 10 �12 F " " 10 � 30 " " " " " 8-1/4�10 F " " 10 � 25 " " " " " 7 �10 F 2. Thompson {I-be'm} 10 � 32 " " " " " 10 �14 F " {and } 10 � 30 " " " " " 8 �12 F " {chan- } 10 � 28 " " " " " 8 �10 F " {nels } 10 � 24 " " " " " 6 � 8 F 3. Barnhart " 10 � 28 " " " V " 8 �10 F " " 10 � 26 " " " H 1 8 �10 F " " 10 � 24 " " " V " 8 �10 F " " 10 � 22 " " " " " 6 � 8 F 5. Victor " 10 � 30 " " " H 2 8 �10 F 6. Clement " 10 � 30 " " " " " 8 �10 P 7. Giant " 10 � 35A " " " " " 13 �16 F " " 10 � 35 " " " " " 8 �12 F " " 10 � 30 " " " " " 7 �11 F 8. Little Giant " 7 � 23{4 r'd wh 8 0 " " " 7 �11 F " " " 6 � 23{ " " 8 0 " " " 6 � 8 F 9. Otis-Ch'pm'n Wood 10 � 22{4 fl'ge wh 7 10 " V 1 10 �12 P " " 10 � 18{ " " 7 10 " " " 8 �10 P Transcriber's Note: Boiler and Engine--V=Vert., H=Hor. Hoisting Gear--F=Friction Clutch, P=Positive Fig. Thrusting Mechanism. Swinging Mechanism. { Reversible engines, 2 steam cylinders } 1. { each 6 � 8 ins. } Chains attached to { Do., do 5 � 6 ins. } circle geared } to hoisting drum 2. { Rack on dipper handle actuated by } 3. { friction clutch geared to hoisting drum. } 5. { Reversible engine, } { 2 steam cyls. 6 � 8 ins. } Wire ropes attached to } circle and pist'n rods 6. { Long st'm cyl., } in long st'm cyl. { piston rod at'ch'd to dipper } { Reversible engine, } Reversible engine, 7. { 2 steam cyls. } 2 steam cylinders { 5 � 6 ins. } 5 � 6 ins.; except A, 8. { } cylinders 7 � 9 ins. { Chains on dipper handle actuated } Chains attached to 9. { by friction clutch geared } circle geared to { to hoisting drum. } hoisting drum +--------------Crane.------------+ | +--H'ght ab've--+ | gr'nd or track. Capacity Working Shipping Swinging of Post order, order, Radius, angle, dipper, W'ht, Fig. material. Material. ft. ft. ft. deg. cu. yds. tons. 1. {Wt. iron} Wt. iron 26 14 24 240 2 40 { A } " 24 14 24 240 1-1/2 30 { frame } " 20 14 20 240 1 20 2. {Cast iron " 23 14 20 200 2-1/2 45 { " " 18 14 18 200 1-3/4 40 { " " 18 14 16 200 1-1/4 30 { " " 16 14 12 200 3/4 20 3. {Wt. iron Wood 26 14 20 200 1-1/2 37 { " " 24 14 20 200 1 26 { " " 20 14 18 200 3/4 16 { " " 18 14 18 200 1/2 12 5. {Hollow Wt. iron 19 14 20 200 2 40 {wt. ir. 6. {Cast iron " 20 14 20 200 2 40 7. {Cast steel Steel 20 14 19 200 2-1/2 70 {Cast iron " 20 14 19 200 1-3/4 45 { " " 18 14 17 200 1-1/4 30 8. { " " 16 Detach'd 15 185 1-1/4 20 { " " 15 " 15 185 3/4 18 9. { " Wood 20 " 20 200 2-1/2 26 { " " 16 " 18 200 1-1/4 15 Makers: 1 (Osgood): Osgood Dredge Co., Albany, N. Y. 2 (Thompson): Bucyrus Steam Shovel & Dredge Co., Bucyrus, O. 3, 4 (Barnhart): Marion Steam Shovel Co., Marion, O. 5 (Victor): Toledo Foundry & Machine Co., Toledo, O. 6 (Clement): Industrial Works, Bay City, Mich. 7 (Giant) and 8 (Little Giant): Vulcan Iron Works Co., Toledo, O. 9 (Otis-Chapman): John Souther & Co., Boston, Mass. Operation of Steam Shovels.--All movements of the steam shovel are controlled by two men, the engineman and the cranesman. The former is stationed near the engine, the latter on a small platform attached to the crane. The engineman directs the movements for raising and lowering the dipper, swinging it into position for unloading, and moving the machine forward or backward. The cranesman regulates the depth of the cut made by the dipper, releases it from the bank when full or near the top of the crane, and pulls the spring latch of the bottom door of the dipper when in position for unloading, thereby dumping its contents. [Illustration: Fig. 14.--Spade for Cleaning Buckets.] These motions are shown in Figs. 15 and 16. Beginning with the dipper in the position shown at A, Fig. 15, the engineman throws the hoisting drum into gear, and starting the engine pulls the dipper upward, the cranesman at the same time thrusting it forward, regulating the depth of the cut so that it will not stop the engine or tip up the rear end of the machine. When the dipper has reached the position B, near the top of the crane, the engineman throws the hoisting drum out of gear, and holds it in position with a foot brake; at the same time the cranesman by easing his foot brake, allows the dipper to fall back to the position C. The engineman then swings the dipper over the car or wagon, as shown in Fig. 16, when the cranesman pulls the latch rope, thereby opening the bottom door of the dipper and dropping the contents. The engineman then swings the crane back again to the next cut, at the same time releasing his foot brake on the hoisting drum until the dipper has fallen to a point near the ground, as at D, Fig. 15, where he holds it for an instant with the foot brake, then drops it by releasing the brake, while the cranesman (during this slight drop) regulates the length of the radius of the dipper handle by releasing his foot brake so as to bring the dipper into the position A again, and adjoining the last cut. While the dipper is being lowered, the bottom door closes and latches itself by its own weight, when all is ready again for another cut. These motions are very simple when taken separately, but when performed together by two different men, experience and quickness in both are required to carry on the work rapidly and harmoniously, without breakages or delays. In loose gravel one cut can be made in a half to three-quarters of a minute; in hard materials one and a half to two minutes, seldom more. [Illustration: Fig. 15.--Showing Series of Operations for Excavating.] [Illustration: Fig. 16.--Loading Earth from Steam Shovel Onto Cars.] After all material within reach of the dipper has been removed, an unoccupied section of track (generally about 4 ft. long) at the rear of the steam shovel is attached to the dipper by a chain and dragged around the machine to the front (by swinging the dipper horizontally) and there placed in position in line with the sections of track under the machine. The screws at the ends of the jack arm (a horizontal bar at the front end of the machine used for steadying it when cuts are taken at right angles to the steam shovel) are then released, and the machine moved forward three or four feet by throwing the propelling gear into motion. After placing the jack screws into their new position, and tightening them, and blocking the supporting wheels of the steam shovel, the machine is ready for another series of cuts. The regular employees for operating a steam shovel are the engineman, cranesman, fireman and four laborers. The latter are under the supervision of the cranesman, and their duties are to shovel forward any lumps or loose material which may roll down and lodge too close to the front of the steam shovel to be reached by the dipper, to level the surface of the ground in front of the machine, preparing it for the next section of track, to lay these sections of track, to attend to the jack screws and blocking and to act as general utility men. [Illustration: Fig. 17.--Pole for Breaking Down Edge of Excavation.] With this crew dry sand and loose gravel can readily be loaded. In harder or more tenacious materials from two to six extra men are required, depending upon the kind of material to be excavated, and also upon good management of the contractor or foreman in charge. Wet sand and fairly loose gravel requires only two extra men, whose duty is to break down the overhanging ledges of these materials which cannot be reached by the dipper, and are liable to fall when the machine has advanced, burying it or blocking the pit behind it. The implement used by these men is a pole, Fig. 17, headed by an iron point, resembling a surveyor's pole. With these poles fairly loose gravel and sand can be readily broken down, sloped at its natural angle, and fed into the pit in front of the steam shovel. In harder materials three to four extra men are usually sufficient, but in very hard or tenacious materials as many as six must be employed. These men break down overhanging material in the face of the bank which cannot be reached by the dipper, bore or drill holes for powder or dynamite when blasting becomes necessary, cut and remove trees, etc. [Illustration: Fig. 18.] On all but very small pieces of railway work there are also employed a blacksmith and helper, and two to five car repairers. The blacksmith's work consists mostly of repairs about the cars, mainly bent or broken aprons, sideboards, chains, etc. The steam shovel occupies much the smaller part of his time. His accommodation requires a small rough frame shop about 10 by 16 ft. (an old box car body is frequently used), with forge and tools. Another rough frame shed of about the same size is needed for the storage of tools, oils and supplies. The section-men of the respective sections are occasionally called on for the building and maintaining (or taking up) of the various side tracks required during the progress of the work. Part II.--Steam Shovel Work. Widening a Cut; Loading on the Main Track.--The simplest and one of the most frequent cases for the application of a steam shovel is the widening of a single track railway cut. The manner of doing this is shown in Fig. 18. A switch, A B, is put in the main track just beyond the end of the cut and far enough away to permit the steam shovel (when standing on the side track) to clear cars on the main track. Cars are then placed opposite it on the main track and the machine is ready for excavation. [Illustration: Fig. 19.] It very frequently happens that the end of the cut joins directly on an embankment, as shown in profile, Fig. 19. In cases of this kind it would be necessary to widen the embankment for the reception of the side track, near the end of the cut, if the machine were to begin work at that point, C, Fig. 18. This is very seldom done; the usual method is to remove the section, A, Figs. 19 and 20, to B by hand labor with wheelbarrows or with teams and scrapers. The excavated material is used to widen part of the embankment near the end of the cut for the reception of the side track. Section A is made barely long enough to provide a standing place for the steam shovel and clear cars on the main track; it is seldom over 50 ft. long, and averages about 30 ft. After placing the machine in this space it is ready for work. Strings of 10 to 20 cars are then drawn along the main track, and stopped opposite the machine for loading. [Illustration: Fig. 20.] [Illustration: Fig. 21.] When the machine has reached the end of the switch, it advances on short sections of track, generally 4 ft. long, which are placed in front of it, and again taken from its rear when it has moved forward one section of track more than its own length. When no more cuts are to be made for still further widening, the switch is taken up again and the machine advances on its own track sections, Fig. 21. When other cuts are to follow, however, a loading track is needed for the next cut; the side track is then extended for this purpose at convenient intervals, generally about 300 ft. at a time though often after each space of a rail length (usually 30 ft.) is clear. The latter is by far the best practice, as it permits the immediate withdrawal of the machine in case of a threatened cave-in, sidehill slip, or other unforeseen danger. After all the cars have been loaded they are taken away for unloading. Sometimes the steam shovel is left idle until the train returns, which is a very wasteful method of working, even where the haul to the dump is short, half a mile to two miles. Two engines and crews should be furnished for hauls up to ten miles; three engines and crews, or more, for longer hauls, or where the traffic on the main line is very heavy, and delays to the work trains are frequent. The material is generally utilized in filling trestles, widening embankments for side tracks, double tracks, yards, etc., thereby making two improvements at the same time. [Illustration: Fig. 22.] In widening a cut it is good policy to keep the grade of the pit from 1 to 2 ft. below the surface of the subgrade of the main track, as shown in Fig. 22, thereby providing for drainage of the ballast and also providing a receptacle for the spreading of loose material dropping off the cars and washing in from the surface of the cut; there is nearly always considerable of this loose material to roll or wash into the pit after the cut has been completed; and unless room is provided for it, the accumulation will soon reach the height of the track, washing mud on it, and choking the drainage, thus injuriously affecting the main track. Widening a Cut; Loading on a Side Track Graded by Hand or Steam.--The delays in loading on the main track of a railway in operation, due to the clearing of the track for all trains, vary from one to four hours per day of ten hours, and sometimes amount to as much as seven hours, depending upon the density of the traffic on the line. The first cut in a case such as the latter is therefore necessarily an expensive one, and where the traffic is so heavy it is often cheaper to make a narrow cut for the side track, on which the steam shovel is to load, either by wagons and wheel scrapers, Fig. 23, or by hand with wheelbarrows loading back on cars, Fig. 24. [Illustration: Fig. 23.] [Illustration: Fig. 23, a.] [Illustration: Fig. 24.] [Illustration: Fig. 24, a.] The latter plan has the great disadvantage that only one car at a time can be loaded and only a few men (six to ten) can be employed. Therefore this plan is never adopted where quick work is required, but is used only where ample time is available, and mostly as an early spring preliminary job, preparing the way for the operation of the steam shovel later in the season. From three to six flat or coal cars are used, enough to require a whole day for the gang of men employed to load; the material from the face of the excavation is loaded on wheelbarrows, and wheeled over the empty cars to the one farthest from the cut. This car is loaded first, then the one next to it, etc. At night the loaded cars are taken out of the switch by the first available freight train and hauled to the nearest yard or side track where widening of the embankment is wanted, or where the material can be otherwise used to advantage, and there unloaded by a small gang of men on the following day; the cars to be returned again the next night. Other empty cars are placed in the pit track for loading next day, by a train bound toward the pit the same night the loaded cars were taken out. The work can be carried on from either one or both ends of the cut. Coal cars should never be used if flats can possibly be obtained, as the latter can be unloaded by a gang of men one-third as large as would be necessary for unloading coal cars. [Illustration: Fig. 25.] [Illustration: Fig. 25, a.] Sometimes small dump cars are used, drawn by horses or mules, and the material unloaded at the end of the cut, thereby widening the embankment for a long side track, Fig. 25. The narrow gage track, A, is laid over the ditch adjoining the main track; the material for any slight excavation that may be necessary for this track is shoveled on the slope of the cut, as at C, on the cross section. The material is then loaded on small dump cars standing on track A, and unloaded at D. The cars are returned on track B. The cross-overs, E and F, are taken up occasionally and relaid near the advancing ends of the cut and dump. In short cuts the narrow excavation necessary for placing a side track in the cut for the steam shovel to load on is generally taken out by carts and dumped at the ends of the cut, widening the embankment for a long side track. The plan of excavation with wagons or wheel scrapers for this side track, shown in Fig. 23, is adopted where the traffic is too heavy to permit loading on the main track; when the side track is wanted at the earliest possible time; and in cuts not over 40 ft. deep. The material is dumped at the ends of the cut until the haul becomes too long, then it is taken to the top of the cut over sidehill driveways excavated for the purpose, and unloaded at a sufficient distance from the edge of the new cut to prevent its washing back by rains. These expedients are necessary only on railways where traffic is very heavy. On most railways (on all where the total delay does not exceed five hours per day) it is cheaper to load on the main track until the first cut has been made. This necessarily involves the delay due to running to and returning from the nearest side track to get out of the way of every main line train, until the pit track is long enough to contain the construction train. This, however, seldom requires more than two weeks, generally only one; the excavation of all of the first cut does not often occupy more than a month, and is only a very short time compared with the whole length of time that the steam shovel is usually in operation on all but very small jobs. [Illustration: Fig. 26.] After a side track has been laid in the first cut made by one of the methods described above, the steam shovel begins work at A, Fig. 26, loading cars standing on the side track, and some of them extending out on the main track. At first not more than ten cars should be coupled to the engine, so that the train can quickly run into the side track on the approach of a main line train, and not delay its passage. After the steam shovel has advanced a train-length, the full number of empty cars can be coupled to the engine, as they will all be on the side track while being loaded. [Illustration: Fig. 27.] Where the embankment has been previously widened by the excavated material from the cut, Fig. 27, a sufficient length to permit laying a side track long enough to hold the construction train, the full number of cars can be used at once, a great advantage in keeping the steam shovel at work without interruption by passing trains, which is unavoidable when some of the cars extend out on the main track. After the machine has reached the other end of the cut it is either withdrawn for other work, or placed on the other side of the main track for widening the cut on that side. The steam shovel begins at A, Fig. 28, loading cars standing on the main track; the main line traffic being carried over a temporary main track built in the excavation previously made by the steam shovel on the other side of the main track. Only a few cars at a time can be used for loading at first, unless the temporary main track has been extended toward B a sufficient length to clear the usual string of about 20 cars when the first car is being loaded. Grading Wide Areas.--In loading gravel for ballasting, or in widening a cut for the purpose of grading yard, shop or station grounds, the usual manner of doing the work is shown in Figs. 29 to 34. After the first cut has been made by one of the methods already described the steam shovel is started in at A, Fig. 29, for the second cut. After its completion the first side track becomes available for the storage of empty and loaded cars as in Fig. 30, greatly increasing the convenience of handling the cars and preventing delays by interferences between the strings of empty and loaded cars, then the latter cannot be taken away promptly on account of passing or shortly expected trains on the main line. After the completion of the third cut, another side track is available for cars, Fig. 31, the loaded cars are then placed on the first inside track and the empty ones on the second. The former are taken away by the road crew, and on their return placed on track No. 2. The pit crew set their loaded cars on track No. 1 for the road crew, and get their empties from track No. 2. The pit track in the rear of the steam shovel is used as a repair track for cars. [Illustration: Fig. 28.] [Illustration: Fig. 29.] [Illustration: Fig. 30.] [Illustration: Fig. 31.] After the completion of the fourth cut, Fig. 32, track No. 3 is used for a car repair and extra storage track for loads or empties, for which there may not be room in tracks 1 or 2. Enough tracks have then been built for the most efficient and economical handling of the loaded material, and if the empty cars are promptly returned the steam shovel can be kept almost constantly at work. Each pit track, on which the steam shovel advances, becomes a side track on the completion of that cut, to be used as a loading track for the next cut up to the fourth cut, after which the loading tracks are taken up on completion of the cut for which they are used, Fig. 33, and relaid in the pit of the next cut, to be used, taken up, and relaid as before for the following cuts. In pits less than one-quarter mile in length, it is sometimes necessary to retain more of these tracks to provide ample storage space for all loaded and empty cars. [Illustration: Fig. 32.] [Illustration: Fig. 33.] [Illustration: Fig. 35.] [Illustration: Fig. 36.] On all large pieces of work where the main line traffic is heavy it is important that the first side track from A to B, Fig. 32, shall be of sufficient length (usually about 700 ft.) to hold the engine and a full string of cars to avoid going on the main track when switching loads to C, and obtaining empties from D. If there is an embankment from A to B it can be widened with material taken from the cut, either by wagon or cars. [Illustration: Fig. 34.] Grading by this method for yard, shop and station grounds occurs mostly near large cities where better terminal facilities must be provided for. The width of the area excavated in this manner seldom exceeds 200 ft. (eight cuts) except in old gravel pits used for furnishing material for ballasting track, which are sometimes 300 ft. (twelve cuts) or more in width. Gravel pits and other wide areas excavated are seldom less than one-quarter mile or more than one mile in length. One-half to three-fourths of a mile is the most usual length; in exceptional cases two miles have been reached. Long and narrow pits can be worked more advantageously than short and wide ones. Cutting Down Grades.--For cutting down grades on railways where the traffic is not too heavy to prohibit loading on the main track, the usual plan of operations is shown in Figs. 35 to 42. The machine begins work at A, Figs. 35 and 36, the beginning point of the new grade, loading cars on the main track, cutting to the line of the new grade, and moving forward on the track on the surface of the pit as long as the height of the crane permits raising the dipper high enough over the cars to open the bottom door of the dipper and discharge its contents, B, Fig. 35. This point is usually about 2 ft. below the main track. The machine must then be gradually run upward on a cribwork of wooden blocking, generally pieces of pine 6 by 12 ins. by 4 ft. long, with some longer track stringers for supporting the sections of track on top of the blocking, and some thinner pieces for attaining exact heights of blocking when needed. As the machine moves forward the dipper still continues cutting to the line of the new grade, while the machine is gradually run upward on the blocking on a grade parallel to the grade of the main track, and slightly below it, maintaining a constant height between the top of the track on the blocking and the highest point to which the dipper can be raised on the crane to insure discharging its load on the cars. When the dipper has cut as low as the length of the dipper handle will permit, C, Fig. 35, the greatest depth to which the machine will cut below the level of the main track has been reached, and as the steam shovel advances the surface of the pit will be on a grade parallel to the grade of the main track, running upward to the summit, S, then downward, and continue so until it cuts the new grade line at H, when the dipper is made to cut on this grade, while the blocking under the machine is gradually lowered as it was previously raised, until the steam shovel reaches the end of the new grade at I, when it is again on the surface of the pit. [Illustration: Fig. 37.] [Illustration: Fig. 38.] [Illustration: Fig. 39.] Although the machine is gradually run upward and downward, it is always blocked level after each forward move before beginning work, to insure quick and easy swinging of the crane, as previously explained. Most machines will cut 5 ft. below the main track and load on a flat car with 18 ins. side boards. Some machines will cut as low as 8 ft., and they are preferred to others on railways where much work of this kind is done, as their use often avoids making an extra cut. [Illustration: Fig. 40.] [Illustration: Fig. 41.] [Illustration: Fig. 42.] After the first cut has been completed, the pit track, A 1, Fig. 36, becomes the temporary main and loading track; the main track is taken up from C to H, and the steam shovel run back to C to begin the second cut, Fig. 42, excavating it in the same way as the first, and loading on the temporary main track. This track again is taken up after the second cut, the machine begins at D and ends at G for the third cut and loads on the pit track in the second cut; the fourth cut is made in a similar way, the machine beginning at E and ending at F, Fig. 36. The fifth and last cut is merely a widening cut, made by loading on the track in the pit of the fourth cut. The material of each cut after the first is loaded on the track laid in the preceding cut. After the completion of the last cut, the permanent subgrade having been reached, the main track is laid on the permanent line, and the small quantity of material obtained from cutting the ditches loaded on cars by hand and taken away for unloading. The most frequent depth of cut made at the summit of grades is about 10 ft. (two cuts), Figs. 38 and 39. [Illustration: Fig. 42-1/2.] [Illustration: Fig. 43.] [Illustration: Fig. 44.] [Illustration: Fig. 45.] When the main track is on a curve, as frequently happens, an extra cut can often be avoided by slightly changing the alinement of the new main track, and at the same time reducing the degree of curvature, as shown by Figs. 42-1/2 and 43. This is particularly applicable where an odd number of cuts must be taken to reach the bottom of the new grades. The dipper will cut to a slope of about 1 to 1. When greater slopes are required, it must be done by hand or undercutting resorted to. Sloping by hand is slow and expensive work, impracticably so in all tenacious materials; it has therefore become the exception, and undercutting the rule. Cuts made in the latter manner sometimes present a rather ragged appearance when just completed, but the irregularities soon merge into a smooth surface as the action of the elements produces the natural slope of the material; the smaller cost amply compensates for the temporary lack of finished appearances. The amount of hand labor necessary where undercutting is not practiced is shown by the sections A in Figs. 38 and 41. This can be entirely avoided by undercutting the slopes, as shown in Figs. 39 and 42; the sections B will slough off within a year or two and most of the material lodge in the spaces C; a small part of this material may roll to the bottom of the cut, and can be removed by loading on cars by hand, or space may be provided for it by making the cut a few feet wider at the bottom. In most cuts for reducing grades this extra width must be cut out anyhow to provide room for both steam shovel and loading track. [Illustration: Fig. 46.] [Illustration: Fig. 47.] [Illustration: Fig. 48.] In reducing grades on railways with a traffic too heavy to permit loading on the main track, a temporary main track must first be built by one of the methods shown in Figs. 23, 24 and 25. The temporary main track, A, Figs. 44, 45 and 46, is then laid, as shown in Fig. 28, to carry the traffic of the road unobstructed. The main track then becomes the loading track for the first cut, and the following cuts are made as shown in Figs. 44, 45 and 46. The temporary main track, A, is moved to a second position, B, when the material under it must be cut away. Great care should be taken to arrange the cuts so that the temporary main track will have to be moved as few times as possible, and to attain the lowest level when it is moved. In loose gravel or sandy materials wider bermes and longer slopes must be allowed for the shelf on which the temporary main track rests than are shown in the above figures, but the method of doing the work is essentially the same. If the depth of the original cut in tenacious materials exceed the height which the dipper can reach, and break down the material above it, the cuts are arranged as shown in Figs. 47, 48 and 49. Temporary loading tracks, L, are built on the side of the slope, and the first cut on each side made by loading on them; the following cuts are then made, as shown on the figures. If the main line traffic is very heavy, it is turned over the temporary main track, A, Fig. 47, until the cut is completed. [Illustration: Fig. 49.] The original cuts are not often more than 10 ft. deep, and the section shown in Fig. 45 covers the majority of cases. On double-track railways the traffic in both directions is generally turned over one track for the length of the new cut, thereby avoiding considerable expense in providing two temporary main tracks. Each different piece of work presents different conditions; and while the same general principles apply to all, every case requires disposition according to its own special circumstances. Great care and study should be exercised in arranging the cuts, to reduce them to the fewest possible number, and avoid shifting, taking up and relaying tracks oftener than absolutely necessary. [Illustration: Fig. 50.] [Illustration: Fig. 51.] Construction Work.--On railways the steam shovel is used mostly in connection with maintenance of way work: loading gravel for ballasting the track, widening cuts, filling trestles, etc., but it is also largely used for various construction work, particularly re-alinements of the main track for reducing grades and curvature. In excavation of this class, thorough cutting should be avoided if possible, for reasons which will be subsequently explained. The work is begun by laying a temporary track, A, Figs. 50, 51 and 52, over the surface of the ground if its natural grade is not too steep to permit operating construction trains over it. Grades up to 6 per cent. (316.8 ft. per mile) can be used. A mogul engine will draw six empty flats over such a grade, a sufficient number of cars to start the work for the short cuts near the summit. The cuts are then made as indicated in Fig. 52. [Illustration: Fig. 52.] [Illustration: Fig. 53.] [Illustration: Fig. 54.] If the grade of the ground is too steep to operate a track laid on it, one of the three methods may be adopted to obtain a grade for this track: 1. The steam shovel is made to cut a trench between the points A and B, Fig. 53, where the slope of the ground is too steep to permit operating a track laid on its surface, and varying in depth from 5 to 10 ft. as may be necessary to attain the desired grade. The excavated material is dumped at D, Fig. 54, to be removed with the next cut. The length of the crane will not permit dumping at E a sufficient distance (20 ft. or more) to obtain a berme and prevent the material washing back into the new cut in the course of time; it must, therefore, be dumped at D and removed as described, unless the slope of the ground is away from the cut, as indicated by the line D F, Fig. 54; in such a case the excavated material can be dumped at F. 2. By excavating the trench with teams and scrapers. 3. By through-cutting a trench with the steam shovel, loading the material on small dump cars or wagons, and wasting it at the nearest available place. [Illustration: Fig. 55.] [Illustration: Fig. 56.] [Illustration: Fig. 57.] After the first loading track has been laid in this trench, the cuts are made as indicated in Fig. 54. When the slope of the ground is too steep to permit a track to be laid on it which can be operated, or to cut a trench for it, as frequently occurs when the excavation passes through a high spur or knoll, Figs. 55, 56 and 57, the steam shovel mounted on standard gage railway tracks cannot be used, and a machine independent of a railway track for transportation must be employed. It is started at A, Figs. 56 and 57, loading small dump cars drawn by horses, and dumping at the nearest available place outside of the lines of the new cut, as at D, Figs. 56 and 57. Sometimes wagons are used if the cuts near the top are short and not very deep, so that a temporary standard gage track can soon be run through the cut, and the material loaded on cars. The dumping track at D is changed to E F, etc., Fig. 57, as the machine cuts lower, maintaining a descending grade from the steam shovel. [Illustration: Fig. 58.] [Illustration: Fig. 59.] [Illustration: Fig. 60.] In cases of this kind it is often necessary to run the steam shovel up a very steep grade to reach the point where it is to begin work. This can readily be done by attaching one end of a one and a half inch rope to a strong tree and winding the other end around the driving axle. Then starting the running gear the machine can be drawn up grades where it could not otherwise propel itself. As a precautionary measure, it is advisable to use at least two ropes. A combination of all these methods sometimes becomes necessary, as shown in Figs. 58 and 59. The material in the knoll, K, Fig. 58, is loaded on small dump cars and unloaded at the nearest available place. When this knoll has been cut down sufficiently, and trenches cut between A B and C D, the track A B C D is built, and the excavation proceeded with, as heretofore described. The high points B, K and C are cut down first until the grade of the loading track between B and C is parallel to the grade of the proposed new main track. Cuts nearly 100 ft. in depth and a mile in length have been excavated in this manner. Two and often three steam shovels are employed at the same time, working near the ends of the cut until the through track has been laid, and then following each other, as shown in Fig. 60. As soon as possible, a through track should always be laid, as it greatly increases the capacity for the prompt and efficient handling of the cars. [Illustration: Fig. 61.] [Illustration: Fig. 62.] Enough side tracks for storing both empty and loaded cars should be built close to the work, where they can be reached without going out on the main track. Sometimes the pit tracks behind the steam shovels are utilized for this purpose, but these tracks are taken up too often, and should not be depended upon for side tracks, though they may be used as such occasionally. In through-cutting the material is loaded on small dump cars running on tracks of about 3 ft. gage, drawn by horses, and wasted on some side hill or other nearest available place; this haul seldom exceeds a quarter of a mile in length. In Fig. 61, the empty dump cars standing at A are drawn over the cross-over C by a horse, to be loaded at B; then run to D, and when from four to six cars have been loaded they are taken to the dumping place and unloaded; then returned to A. In loose materials considerable time is lost in waiting from the time the loaded car is run to D and the next empty brought from A to B. In tenacious materials not nearly so much time is lost, as the dipper cannot be filled so rapidly. This loss of time is largely avoided by arranging double loading tracks, Fig. 62, one on each side of the steam shovel, and connected to a central track for empties by the cross-over C and C´ and switches S and S´. Two horses are used, one on each side of the central track, to bring forward the empty cars from A to B, and A to B´, and return them to D and D´; these operations are alternately performed, each empty car on one loading track being brought forward while the other is being loaded. The cross-overs C and C´ should be kept close to the rear of the steam shovel, and as it advances they must be taken up and relaid; this becomes necessary about once in three days in soft materials and about once a week in hard stuff. Portable sections of tracks, switches and cross-overs are generally used between the points A and B, and can be relaid very quickly. Standard gage railway cars cannot be used in thorough cutting, as the track cannot be laid in front of a point at right angles to the post of the steam shovel, and when the track ends there the crane cannot swing back far enough to load the car. Thorough cutting should be avoided if possible, the cost due to the loss of time in switching cars, relaying tracks, extra horses and men, etc., makes it more expensive than excavating from a side cut. In excavating canals, harbor and dockwork, stripping coalfields, stone quarries, grading for new city additions, and other work not connected with a railway, as well as railway construction and re-alinement work which is inaccessible to a railway track in its early stages, the general manner of using the steam shovel is the same as for railway work; varying only in details, depending upon the means of disposing of the loaded material, by wagons, carts or dump cars, and the use or waste of this material. Although the steam shovel is employed mostly on railway work, it is not exclusively a railway machine. It is already largely used on other work, and its use in this direction is rapidly extending, especially on the increasing number of extensive public works in the vicinity of large cities. The most economical height of cut varies greatly with the nature of the material. In dry clay, loam and other dry materials which can be broken down readily with a bar or iron pointed pole (Fig. 17), cuts of 25 to 30 ft. in height are usually taken. In harder and more tenacious materials it should not exceed the height to which the dipper can be raised, 14 to 20 ft., varying with the size of the machine. In sand and loose gravel which easily falls down to the machine heights up to 60 ft. are common, and sidehill cuts in loose gravel up to 300 ft. in height have been taken. In such cases, and also in the removal of landslides, great care must be taken to avoid an avalanche of the material burying the machine when the toe of the slope is cut away. The pit track should always be kept close up to the sections of track under the steam shovel, so that it can be quickly withdrawn when necessary. As a general rule, the higher the cut the better, as the machine can then load the greatest amount of material between each advance, and lose the least possible amount of time. Each forward move of the machine requires from three to ten minutes, depending upon the height of blocking, if any, it is working on; this is a dead loss, as no cars or wagons can be loaded during that interval. Powder and dynamite are frequently used to good advantage to shatter the harder materials before excavating. When thus broken up about twice the amount of these materials can be loaded in a day. Great care must be exercised in the quantity of the explosive used, and in the location of the drill holes to prevent injury to the steam shovel. The explosives should be stored in a safe place, preferably in a vault at some distance from the place where they are to be used. The use of dynamite is confined mostly to bowlders, ledges of rock and stumps of trees, while powder is generally used for hardpan, shale, slate, cemented gravel and hard clays. For the latter materials dynamite is usually too powerful, as instead of merely lifting and loosening them, as desired, it shatters shale and slate into fragments, and compresses the other materials about it, forming a "cistern" from 3 to 5 ft. in diameter, as shown in Fig. 63. Sometimes small quantities of it are used specially for this purpose to make room for a large charge of powder at the bottom of the drill hole, where its explosion will have the most effect in loosening the superincumbent material. A charge of one-quarter to one-half of an ordinary dynamite cartridge will usually blow out a "cistern" large enough to contain from one-half to one keg of powder, Fig. 64. The depths of the drill holes in these materials vary from 4 to 20 ft.; they are made with a drill, or, in the softer materials, with an auger similar to a plank auger, generally about 2 ins. diameter, with extension pieces for deep holes, as shown in Fig. 65. Crowbars and wooden and iron wedges are also often used in breaking down overhanging material when it cannot quite be reached by the dipper. The excavation of materials for which powder or dynamite are used to loosen them requires a powerful machine, with a strongly built, medium size dipper. A small or lightly built machine giving good satisfaction in soft materials would prove an utter failure here. [Illustration: Fig. 63.] [Illustration: Fig. 64.] [Illustration: Fig. 65.] Assuming good management and a competent crew, the daily output of a steam shovel depends mostly upon the nature of the material excavated; it is also somewhat dependent upon the height and width of the face of the cutting, and largely upon the facilities for disposing of the loaded material, and keeping the machine almost constantly at work by an ample supply of empty cars and wagons. Although these varying conditions differ on each piece of work, the probable output of a machine for a given excavation can be closely estimated by good judgment based on previous experience with similar work. The average daily output in different kinds of materials, and under average, favorable and unfavorable conditions, as described above, is shown in Table II.: TABLE II. Loose Damp Capacity Delay. Sand. gravel. Dry loam. Dry clay. clay. of dipper. hours.[2] Cu. yds. Cu. yds. Cu. yds. Cu. yds. Cu.yds. 2-1/2 cu. yds. 1 Good 2,400 2,400 2,000 1,800 1,200 " 5 Poor 1,200 1,200 1,000 900 600 " 2-1/2 Avg. 1,800 1,800 1,500 1,350 900 1-3/4 cu. yds. 1 Good 1,600 1,600 1,200 1,000 800 " 5 Poor 800 800 600 500 400 " 2-1/2 Avg. 1,200 1,200 900 750 600 1 cu. yd. 1 Good 1,000 1,000 800 700 500 " 5 Poor 500 500 400 350 250 " 2-1/2 Avg. 750 750 600 525 375 [Footnote 2: The delay in hours is the time lost in moving forward and waiting for empty cars.] TABLE II.--Continued. +----- Loosened by explosives.---+ | Mixed | Stiff Hard clay and Loose Cemented Capacity Delay. blue clay. pan. boulders. rock. gravel. of dipper. hours.[3] Cu.yds. Cu.yds. Cu.yds. Cu.yds. Cu.yds. 2-1/2 cu. yds. 1 Good 800 600 600 600 600 " 5 Poor 400 300 300 300 300 " 2-1/2 Avg. 600 450 450 450 450 1-3/4 cu. yds. 1 Good 600 400 400 400 400 " 5 Poor 300 200 200 200 200 " 2-1/2 Avg. 450 300 300 300 300 1 cu. yd. 1 Good 400 300 300 300 300 " 5 Poor 200 150 150 150 150 " 2-1/2 Avg. 300 225 225 225 225 [Footnote 3: The delay in hours is the time lost in moving forward and waiting for empty cars.] Part III.--Disposition of Material. Loading the Material for Transportation.--The material excavated by a steam shovel is loaded on cars, wagons or carts. On railway work it is usually loaded on dump or flat cars. On other construction work small dump cars are most generally used, and sometimes wagons or carts. [Illustration: Fig. 66.] [Illustration: Fig. 67.] [Illustration: Fig. 68.] [Illustration: Fig. 69.] [Illustration: Fig. 73.] Standard gage railway dump cars, Figs. 66 and 67, have nearly gone out of use. They were replaced by the center ridge flat car, Figs. 68 and 69, and it in turn has been replaced by the ordinary flat car. Dump cars are of two styles, dumping either by tipping, Fig. 66, or by means of a hinged sideboard opening on an inclined floor, Fig. 67. Both are heavy, clumsy, costly and can be used for scarcely any other purpose, often standing idle from six to eight months of the year. They dump dry materials very rapidly, but are often slow in discharging damp, tenacious materials, especially in the hinged sideboard car, whose floor slope is often not sufficient to permit the material to slip out quickly, and the material must then be pushed out, thus causing much delay. The greatest objection to these cars is that they can be used for scarcely any other purpose, on most railways for no other purpose; and there is not sufficient work for them to justify keeping the necessary number on hand for the ordinary work in this line. They were replaced by the center ridge car, Figs. 68 and 69, as above noted, which is merely an ordinary flat car with a timber 4 by 6 ins. bolted on its floor along the center line, serving as a guide for a plow, Fig. 70, drawn over it by the locomotive, thereby unloading the material. The ridge timber is slightly pointed at both ends to assist in guiding the plow onto the car as it passes from one car to another. The top edges of the ridge are sometimes protected by angle irons, as in Fig. 71, and the points by cast iron caps, Fig. 72. By taking off the center ridge this car can readily be restored to general service after completing the steam shovel work. The center dump car, shown in Fig. 73, is used only for gravel ballasting where the material is wanted delivered between the rails. [Illustration: Fig. 70.] [Illustration: Fig. 71.] [Illustration: Fig. 72.] The brakes are placed on one side of the car, as shown in Figs. 74 and 75. When boulders, loose rock, etc., are to be unloaded, the brake staff is set in a socket, Fig. 76, and taken out before the plow is started. This avoids bending or breaking the staff in case any stone should be wedged between it and the moving plow. Sometimes the socket is used with the brake at its ordinary place at the end of the car; in such a case it must always be taken out before the plow reaches it. The plow, Fig. 70, is built of heavy plate and angle iron, strongly braced, and headed by a cast steel point, to which the cable is attached. The sides are curved outward at the bottom, working under the material and pushing it aside as the plow is drawn along, and held down on the car by the weight of the material and the partly downward pull of the cable at its point. Short pieces of old rails and other scrap iron are also often placed on the plow to help hold it down on the car when very tenacious materials are to be unloaded. The groove extending along the center line on the bottom fits over the ridge timber on the car, and forms the guide by which its movement is directed. Small stones, protruding bolts, slivered ridge timbers and other obstructions in the groove of the plow sometimes wedge the point fast, and before the engine can be stopped, the plow is turned up on its point, and falling to either side, tumbles off the car. The weight and elasticity of the cable is often sufficient to draw the plow half a car-length after the engine has been stopped, and it is often difficult to stop the plow quick enough to prevent upsetting when obstructions occur, although the speed is usually only two to three miles per hour. The unloading nearly always occurs on trestles or embankments, and when the plow is thrown off the car, its replacement often requires much time and labor, sometimes even making the services of the wrecking car necessary. This difficulty is very likely to occur when unloading on curves, where one side of the point of the groove presses against the ridge timber. This plow unloads the material equally on both sides of the car, as it is wanted in filling trestles, raising embankments, tracks, etc.; but it cannot be used to advantage where the material is wanted on one side only, as in widening embankments for double track, side tracks, yards, station grounds, etc. [Illustration: Fig. 74.] [Illustration: Fig. 75.] [Illustration: Fig. 76.] The many objections to the center ridge car are almost entirely avoided by the use of the Barnhart plow, Fig. 77, employing the ordinary flat car without any preparations except changing the brake staffs to one side or placing them in sockets at their ordinary places and inserting short stakes in the stake pockets, permitting the immediate use of the car for general service if necessity should so require. This plow is also built of heavy plate and angle irons, strongly braced, and headed by a cast steel point to which the cable is attached; it is preceded and followed by guiding sleds attached to it by adjustable hinges and guided over the car by the stakes in the stake pockets, which are indicated by the dotted lines. The usual speed at which it is drawn over the car is about four miles per hour, but in loose gravel it can safely be drawn at a speed of six miles per hour. On straight track it is scarcely ever thrown off the car unless carelessly handled, and it works equally well on curves when the usual means are adopted to maintain a tangential pull of the cable, as will be subsequently described. Two styles of the Barnhart plow are in use: One unloading on both sides of the car, and called the center plow, Fig. 77; and the other unloading on one side only and called the side plow, Fig. 78. [Illustration: Fig. 77.] [Illustration: Fig. 78.] [Illustration: Fig. 79.] On all but very small pieces of work the cars should be provided with hinged drop sideboards, Fig. 79, using either of the arrangements shown in Figs. 80 and 81, which will enable them to carry 12 to 14 cu. yds. instead of 6 or 7. The side boards are made in two pieces on each side of the car, Fig. 79. Those shown in Fig. 80 are used for both center and side plows; they can be quickly dropped by a man walking along the train, after arriving at the unloading place and striking the hook A an upward blow with a light hammer. The boards are hooked up again after the cars have been returned to the steam shovel pit. The side boards shown in Fig. 81 are used where the side plow only is used. Here the board on one side only (the unloading side) is hinged (or chained), and dropped by pulling out the pin B, thus leaving that side of the car entirely unobstructed for unloading the material; the board on the other side of the car is bolted to the stake pocket and is not moved. [Illustration: Fig. 80.] [Illustration: Fig. 81.] The cars should also be provided with sheet iron aprons, Figs. 82 and 83, extending from the end of one car onto the floor of the next, to prevent the material from falling on the track between the cars as the plow is drawn over them, and delaying the departure of the train until it can be shoveled out. These aprons are made either in two pieces, Fig. 82, or in one piece only, Fig. 83. The former are more easily handled, and permit access to the coupling of the cars without lifting the apron. Very little material drops on the track when the aprons and the center plow are used. The single apron is used mostly in connection with the side plow. The number of cars and engines required for each steam shovel to keep it in nearly constant operation depends upon the nature of the material excavated, the length of haul, and the density of other traffic upon the main line. This number must be determined by accompanying circumstances in each case; ordinarily, however, it averages about as given in Table III.: TABLE III. In the steam (--------------On the road up to-------------) (shovel pit.) 10 miles. 25 miles. 50 miles. 75 miles. Loco. Cars. Loco. Cars. Loco. Cars. Loco. Cars. Loco. Cars. Loose gravel 1 30 1 30 2 60 3 90 4 120 Dry clay 1 22 1 22 2 40 - - - - Damp stiff clay 1 18 1 18 2 36 - - - - Hardpan, cemented gravel, etc., loosened by explosives 1 16 1 16 2 32 - - - - The length of haul usually ranges from 2 to 15 miles; it seldom exceeds 25 miles for any material except gravel ballast, where hauls of 75 miles are frequent, and sometimes reach 200 miles. [Illustration: Fig. 82.] [Illustration: Fig. 83.] [Illustration: Fig. 84.] [Illustration: Fig. 85.] On hauls exceeding 25 miles the full number of cars and engines required can seldom be obtained, and the output of the steam shovel is correspondingly decreased. The delay in returning empty cars due to detentions from other trains is the great trouble most keenly felt in steam shovel work on railways in operation. The so-called "mud train" is generally considered an outcast, and is usually the last train to receive the dispatcher's attention for an order to the road. These delays are daily occurrences, and it is quite an exceptional case when the machine is amply supplied with empty cars. The record of most steam shovels on such work is therefore a rather poor one, when the machine really made a good showing for the crippled condition of its car service. Some of these delays can be avoided or shortened by stationing a telegraph operator at the outgoing end of the pit, and on all but very small pieces of work his wages will be many times balanced by the time gained in keeping the whole plant moving, by obtaining train orders quicker, and remaining constantly informed of the whereabouts of the construction and other trains, and regulating the work in the pit accordingly. For general construction work where the excavated material is not loaded on standard gage railway cars, small dump cars, Figs. 84 and 85, are generally used. They are more economical than wagons or carts, which are employed only in special cases, mostly in cities, where the material must be hauled some distance over several intersecting streets, and where a track will not be allowed; or for very small jobs with a long haul which would not justify building a track. The gage of these tracks is usually 2-1/2 or 3 ft., sometimes 2 ft. or even 1-1/2 ft. only; the latter gages are not often used, and the 3-ft. gage is usually preferred. The rails most generally used weigh 20 lbs. per yd. Although these tracks are only temporary their construction should be fairly substantial; but they are often built in an exceedingly careless and insecure manner, causing a great waste of power in pulling the cars over them, and resulting in frequent delays, due to derailments. The grade is usually arranged so that the loaded cars will run downhill by gravity, and only the empty cars need be drawn back to the pit. On small work, horses or mules are used to pull the cars, but on large jobs small locomotives are employed. Small dump cars vary in capacity from 1 to 3 cu. yds., the latter size being most generally used. The side dump car, Fig. 84, dumps on either side. The rotary dump car, Fig. 85, unloads on either side or end; the box can be turned around horizontally, revolving about a vertical pin in a turntable on the frame; they are used mostly in dumping off the end of a fill. In making fills it is nearly always the best plan to build a temporary trestle of round pieces of beech, cottonwood or other cheap trees, old bridge or building timber, or other second-class lumber, and then filling in with the side dump cars. By adopting this plan the unloading will progress much more rapidly than by dumping from the end of a fill, where only one car at a time can be unloaded. These trestles are inexpensive, and the saving in labor and time in making the fill will amply repay their cost. [Illustration: Fig. 86.] [Illustration: Fig. 87.] [Illustration: Fig. 88.] [Illustration: Fig. 89.] Unloading the Material.--On railways the unloading is seldom done by slow and expensive hand labor with the shovel; sometimes dump cars are employed, but in most cases flat cars and the plow are used. The trains consist of 10 to 30 cars. The car carrying the plow is attached to the rear of the train at the nearest side track to the unloading place, if it is not over 10 miles from the steam shovel pit this car is generally carried back and forth to avoid an extra stop to couple it on the train at the side track. One end of a steel wire cable is then hooked to the plow and the other end (which is attached to an ordinary car coupling link) coupled to a car or the engine. Usually this cable is about 400 ft. long and extends over 12 cars. The brakes on these cars are then set up tight and the engine started with the forward cars, Fig. 86. In very tenacious or partially frozen material the rear cars are sometimes pulled along by the plow; the wheels are then blocked with pieces of wood or with stones; sometimes it is even necessary to chain a few of these cars to the track to prevent the rear lot of cars from moving. After the plow has been started, it is drawn along slowly until it arrives on the last car, Fig. 87. The engine is then stopped and backed up a few feet to permit the cable to be thrown on one side of the track, Fig. 88. The train is then backed up again and coupled to the unloaded cars, when four to six men throw the cable on the next loaded cars, Fig. 89, coupling its forward end to a car or to the engine if the cable is long enough. The operation is then repeated until all but the car next to the engine is unloaded; this car carries the plow and is the first car to be unloaded by the next train. The ends of the cable are then detached from engine and plow, thrown to one side of the track, and left there for the next train to pick up and use in the same manner. [Illustration: Fig. 90.] [Illustration: Fig. 91.] When filling a trestle the cable cannot be thrown on one side, as described, but must be unhooked from the plow (the rear lot of cars being left standing on the trestle), dragged across the trestle, and there thrown to one side. The forward lot of cars is then backed up until its rear car is opposite the rear end of the cable, when it is loaded, the train backed up, coupled and unloaded, as before described. After unloading the train the cable must again be dragged beyond the trestle, and there thrown to one side of the track and left for the next train. The time required for unloading varies from 10 to 30 minutes, depending upon the nature of the material and the number of cars, and averages about 20 minutes, doing as much work in that time as 20 men can do in a day. When unloading on curves the operations are delayed by the necessity of using snatch blocks on the cars to insure a nearly tangential pull of the cable and avoid pulling the plow off the car. These blocks are applied as shown in Fig. 90, and at A, Fig. 91. They are hooked to long chains extending over the car and fastened to the bolster or arch bar of the truck. The number of snatch blocks required depends upon the degree of the curve and the length of the cable; generally four to six blocks, one to every third car, are enough. As the plow approaches one of these blocks it must be stopped, block and chain removed and transferred forward for use at that end of the train. The other operations of unloading are the same as when on straight track. The time required in unloading on curves varies from 20 minutes to an hour, and averages about 40 minutes, doing as much work in that time as 20 men can do in a day. The steel wire cables used vary from 1 in. to 1-1/2 ins. diameter. The former are used for unloading loose gravel and sandy material; they are light and easily handled, but cannot bear much jerking. The most usual size is 1-1/4 ins. diameter. Heavier cables require too many men (six to eight) to load them on the car preparatory to starting the plow. One of the heaviest locomotives on the road (preferably one of the consolidation type) should be used for drawing the plow over the cars. These engines are generally able to keep the plow moving with a strong steady pull, avoiding the necessity of taking a run to start the plow, and all injurious jerking of the cable, which frequently breaks it. For tenacious materials and where the haul is not more than 25 miles, it is often good policy to keep one heavy engine at this work, the other engines merely hauling the trains; this can generally be arranged so that no more engines are used than if each engine were to unload its own train. Sometimes two light engines are used for this purpose, but they can seldom move in perfect unison and more or less jerking is the result. Unfortunately the engines for the "mud trains" are not always in the best working order; they are mostly those which are about to go into the shops for turning down the tires or for general repairs, and are not in fit condition for general traffic, but still considered good enough for this service. Expensive delays due to badly working engines are frequently the result. The locomotive in the steam shovel pit should always be equipped with a steam or air driver brake to assist in quickly stopping the cars at exactly the right place when setting them for loading by the steam shovel. For the same reason the brakeman should be allowed to use short sticks in the brake-wheels to obtain a greater leverage in turning them. Both engine and train crews should be changed as little as possible and they should retain their respective trains in the pit on the road or at the dump. Most of the men dislike the "mud train" service, but some (especially the older ones) are glad to get a steady job with a full night's rest, and these are the men to be chosen. They take an interest in the success of the work, and soon acquire an expertness in handling cars, plows, etc., that makes them worth twice as much as the inexperienced or unwilling ones. The wages of these men should be equalized to average the same as the men on the road in other service, otherwise dissatisfaction and indifference are sure to result. [Illustration: Fig. 92.] The machine shown in Fig. 92 has lately come into use for pulling the plow over the cars to unload them. This is merely a double cylinder (10 by 12 ins.) reversible hoisting engine, resting on a heavy cast iron bedplate attached to the floor of a box car. Steam is supplied to the engine from the locomotive of the train, which is coupled to this car when the unloading is to begin. With this machine there is no injurious jerking of the cable, and consequently very little breakages or delays, and heavy loads of 15 cu. yds. of tenacious material are readily plowed off the cars in a more satisfactory manner than can be done by any one or two locomotives. Blocking the wheels or chaining cars to the track need not be resorted to; the cars cannot move, for the machine pulls the plow toward itself and the strain is resisted by the cars between them. If it is desired to scatter small quantities of material along the track, as it is often wanted in surfacing or raising track, both plow and train are moved in the same direction at the same or varying speeds, as may be necessary to unload the required amount of material. If a large quantity of material is wanted within a short distance, as usually happens on washouts, train and plow are moved in opposite directions. By moving them in this manner at the same speed, a whole train can be unloaded at any desired spot. Where two locomotives must be used to pull the plow over the cars, the use of this machine will dispense with one of them, and do the work in half the time. On large jobs it should not be missing. The cable is wound around the drum, A, Fig. 92, and must be long enough to extend over the whole length of the train. A steel wire cable 1-1/8 ins. diameter is generally used; but for loose gravel a 1 in. cable is amply strong enough. The steam shovel can be operated continuously throughout the year in all kinds of weather, though operations are often suspended in extremely cold weather. When working in cold weather the face of the bank sometimes freezes during the night to the depth of 3 to 6 ins., but this crust is easily broken in the morning by a few small charges of powder, and then the material can be excavated as easily as at any other season. [Illustration: Harris & Carter Spreader. Fig. 93. Fig. 94.] In freezing weather the floors of the cars should be sprinkled with brine just before loading; the brine is kept in barrels at the head of the machine, and one man using an ordinary garden sprinkling can is detailed for the work. This prevents the material from freezing to the floor of the car for three to four hours, and allows it to slip off readily when the plow is put in operation. No train should be left standing over night without unloading. The brine will not prevent freezing for this length of time, and to unload one car of the frozen stuff requires a day's labor of four to six men. Distributing the Material After Unloading.--In widening embankments for side tracks, double track, yard and station grounds, etc., the material is unloaded, as described above, forming a ridge on both sides of the track if unloaded with the center plow, or on one side of the track only if unloaded with the side plow. This material is sometimes leveled off by hand, a very slow and expensive job, but generally it is done with a leveler or spreader, Figs. 93 to 96. [Illustration: Edson Spreader. Fig. 95. Fig. 96.] In the Harris & Carter spreader, Figs. 93 and 94, the car body is cut away between the trucks to receive the two wings which level or spread the material. One or both wings can be used, and they can be raised and lowered to adjust them to any height of new embankment wanted. They will spread the material for a distance of 3 ft. from the rail. When shipping the spreader over the road the wings are drawn up by a hand windlass, revolving about hinges fixed to the braces under the floor of the car, as shown in Fig. 94. In this position the clearance is the same as that of an ordinary passenger car. The Edson spreader, Figs. 95 and 96, has only one wing, attached to an ordinary flat car, and arranged to raise and lower to adjust it to any height of new embankment wanted. The wheel, A, bears against the head of the rail, forming a brace where one is most needed, and greatly assists in preventing a derailment when hard or tenacious materials are suddenly encountered. The wing, braces, windlass, etc., are so constructed that they can be readily removed from the car, thereby restoring it to general service on completion of the work in hand. This spreader is used mostly in connection with the side plow; it will level the material for a distance of 15 ft. from the rail, wide enough to permit laying a side track from which the embankment can be further widened. Only one side at a time can be widened with this spreader. If it is desired to widen the embankment on both sides of the track, one side is completed first; the cars and spreader are then turned around on the nearest turntable or Y-track, and the other side widened by drawing the spreader in the opposite direction. If the cars are not provided with aprons they need not be turned around. This spreader is generally arranged to cut about 6 ins. below the bottom of the ties of the main track, thereby forming the subgrade for the side track, and maintaining proper drainage of the main track. The apron, B, is bolted on the spreader, and serves to remove any loose material which may fall on the track between the rail and the ends of the ties. When shipping the spreader over the road, Fig. 96, it is drawn up by a hand windlass revolving about hinges on the side sill of the car and folded down on it; in this position it will clear anything that other cars can pass. The cars of both styles of spreaders are loaded with old rails, frogs, scrap iron, etc., to hold them down and prevent derailments when hard or tenacious materials are suddenly encountered. Loads of five to ten tons are generally sufficient, though loads up to 15 tons are sometimes required. Spreaders are usually drawn at a speed of six to eight miles per hour; in loose gravel the speed often reaches 10 miles per hour. They will level off a ridge a mile in length in six to ten minutes, doing as much work in that time as 100 men can do in a day. The spreader is usually stationed in the nearest side track to the unloading place. Frequently it can be hauled between this track and the dump without raising it, or raising it only partially to clear depot platforms, switch stands and other obstructions and thereby avoid the necessity of folding it down on the car while passing between these points. Ordinarily the spreading is done by the last train before the close of the day. In cold weather or on short dumps it must be done oftener; either to prevent freezing, or to make room for the unloading material which would otherwise pile up too high for easy spreading, or be liable to roll back on the track and obstruct it for the next train. In using the spreader it is coupled to the rear of the car carrying the plow, and after the train has been unloaded it is pulled over the length of the ridge of material unloaded from its own and preceding trains, as shown in Figs. 97 and 98. Part IV.--Cost of Steam Shovel Work. The cost of steam shovel work varies greatly with the different conditions affecting each piece of work. It depends mainly upon the nature of the material, its location, the capacity and efficiency of the steam shovel, and the supply of empty cars or wagons. The efficiency of a steam shovel is not necessarily proportional to its capacity, but to the amount of work done compared to its cost; and while the amount of work done is generally larger in the machines of larger capacities, this advantage may be more than balanced by the greater cost of operation, including the cost of labor, fuel, supplies and repairs, etc. Machines of the largest capacity, with dipper of 2-1/2 cu. yds. capacity, are employed mostly in excavating soft materials, especially in loading gravel for ballasting. Machines of medium capacity are usually the most efficient for general construction work. The average daily operating expenses of a steam shovel of medium capacity are about as follows: One engineman $4.00 One cranesman 3.50 One fireman 2.00 Four pitmen at $1.50 6.00 ------- Wages of crew $15.50 ------ $15.50 One ton coal $3.00 Oil and waste .75 Water .50 ----- Fuel and supplies $4.25 ------ $19.75 Interest on capital, $6,000, at 6% $1.00 Depreciation at 10% 2.00 Repairs 1.00 ------ $4.00 ------ Total daily expense with regular crew $23.75 This will suffice for loading loose gravel; in the harder materials ordinarily occurring on construction work the following daily expenses must be met: Expenses of regular crew $23.75 Foreman $5.00 Two pole (or bank) men at $1.50 3.00 Two extra men at $1.50 3.00 One night watchman 1.50 Powder and dynamite 1.00 ------ $13.50 ------ Daily expenses on average construction work $37.25 To the above must be added the expense of transporting the machine to the work, and returning. The cost of hauling is also a variable item; it depends mostly upon the length of the haul, and on railways very largely upon the delays met with in going to and from the dumping place. On construction work it is seldom less than 3 cts. per cu. yd., and sometimes reaches 10 cts. On railways it is not often below 4 cts. for hauls up to 10 miles in length, and may reach 50 cts. or more for hauls of 75 miles or farther. [Illustration: Fig. 97.] [Illustration: Fig. 98.] Dumping is a very small item where small dump cars are used on construction work, and does not exceed 1/2 ct. per cu. yd. When wagons are used it will average about 1-1/2 cts. On railways the cost of unloading with the plow varies somewhat, depending upon the kind of material; it averages about 1/2 ct. per cu. yd. Unloading by hand averages 6 cts. On railway work, where the spreader is used, the average cost of leveling the material for widening embankments is only 0.1 ct. per cu. yd.; spreading it by hand will range from 5 to 20 cts. per cu. yd. for widths of 5 to 15 ft. from the unloading track. The total cost per cu. yd. of excavating and loading, hauling and dumping different kinds of materials with the most usual length of haul averages about as follows: Loading. Hauling. Dumping. Total. Cents. Cents. Cent. Cents. Sand and loose gravel 3 4 to 10 1/2 7-1/2 to 13-1/2 Loam 3-1/2 " " 8 to 14 Dry clay 4 " " 8-1/2 to 14-1/2 Damp clay 6 " " 10-1/2 to 16-1/2 Stiff blue clay 8 " " 12-1/2 to 18-1/2 Cemented gravel, hardpan, etc., materials loosened by explosives 10 to 16 " " 14-1/2 to 26-1/2 The steam shovel will do the work of 60 to 120 men, saving from 5 to 25 cts. per cu. yd. of material excavated and loaded. The gain is proportionally much greater in the harder, and particularly in the more tenacious materials. The machine is not adapted to small jobs, and is seldom worked in cuts of less than 8 ft. in depth; nor is it cheaper than hand and team labor on such small jobs, but on nearly all large work it is much cheaper and faster; and last, though not least, its use largely reduces the number of laborers required, and hence the probability of strikes and other labor troubles. APPENDIX. ACTUAL COST OF STEAM SHOVEL WORK. (From an article in Engineering News, June 9, 1888, we take the following particulars of reports on the actual cost of steam shovel work, and these reports show how variable is the cost of excavating, depending, as it does, upon delay, unavoidable on every line of railway, upon the weather, character of the material, length of haul, and many other conditions. When conditions are favorable as to material, prompt and short hauling, with no delays, the results show a very large increase in the output, and often a decrease in cost.--Ed. Eng. News.) From a report of the General Roadmaster of the New York Central & Hudson River R. R. of work done by two shovels on the Eastern and Western divisions, we find the largest day's work for one shovel at Yost's pit was 174 cars, the average for the month of August being 121 cars per day and for July 116 cars per day. It could have made a larger average than this with twenty more cars, as the trains making long runs could not keep cars in the pit. The largest day's work at Bergen pit with one machine was 156 carloads, the June average being 117 cars and the July 116 cars per day, and for two weeks in August 134 cars per day. At this pit they came in contact with cement, hard pan, and very coarse material. At Yost's pit they have loaded 10,511 cars in four months up to Aug. 1. Figuring these at 9 yds. per car, which is low, makes 94,599 yds. The cost of delivering on roadbed was $5,261.25, or about 5-1/2 cts. per yd. The average cost for handling by men loading and unloading is 14 cts. per yd. The report on a machine working in New Mexico on the Atchison, Topeka & Santa Fe R. R. says: "In cemented gravel, we find no difficulty, under favorable circumstances, in loading 75 to 100 cars per day, at a cost not to exceed 10 cts. per cu. yd." The engineer of the Cleveland, Mt. Vernon & Delaware R. R. gives some statements as to the cost and amount of some excavating work done under his direction. This shovel worked about 5-1/2 months in stiff clay, as follows: March loaded 1154 cars, worked 24 days. July " 955 " " 24 " Aug. " 1157 " " 22 " Sept. loaded 1556 cars, worked 23 days. Oct. " 1552 " " 23 " Nov. " 539 " " 12 " Total, 6,915 cars, 41,490 cu. yds. Greatest number of cars loaded in a single day, 97. Shovel supposed to work ten hours a day, but did not average more than 6-1/2 hours on account of waiting for cars. Carloads average 6 cu. yds. per car. Average cost of loading, 3 cts. per cu. yd., including expense of all men, shovel, oil, waste, etc. Loaded, hauled material, and unloaded at a distance of ten miles from pit, at 10 cts. per yd., including all costs, shovel, use of cars, engines and crews. A 20-mile haul on this road cost 15 cts. per yd., and a 30-mile haul about 20 cts. per yd., while on some roads a 30-mile haul costs over 75 cts. per yd., depending on the frequency of trains. The following report from the superintendent of the Sioux City & Pacific Ry. gives the operations of a shovel for nine months working in a yellow clay bank from 30 to 40 ft. in length, and with a one-mile haul: "The total number of cars loaded was 31,420 in 209 days, giving an average of 150-3/4 cars per day. The greatest number of cars loaded in one day was 275, with an average of 6 cu. yds. per car. The average cost of loading per cu. yd. is 6-1/2 cts., including expense of all men about shovel, and shifting of shovel track. Average cost of unloading with one-mile haul, 7.8 cts., including wages of all men with trains and engines, use of cars and locomotives, with all supplies and repairs of same, making a total cost of 14.3 cts. per cu. yd. or 85.8 cts. per car delivered on track." A report showing the largest amount of work, with the most complete detail as to the expense of operation was furnished by the resident engineer of the Missouri Valley & Blair Railway & Bridge Co., contractors for the Chicago & Northwestern Ry. bridge across the Missouri River at Missouri Valley, Ia., the material excavated being used in the approaches to the bridge. The work, a tabulated statement of which is given in Table IV., was done under the most favorable circumstances, with but few delays, and with but one locomotive, as the cars ran down the hill themselves while being loaded, the locomotive being employed to haul the empty cars back; the haul was short and a round trip was made in 30 minutes. The report shows that during the work of six months the average number of cars loaded per day was 205, including delays and movings, and that the average cost per cu. yd. was 7 cts., which, as shown, included labor of loading, moving shovel about once a month, moving track to suit, dynamite for caving bank, repairs of shovel, fuel, oil, waste, wages of watchman, rent of cars and locomotives, labor of engineers, firemen and wipers, labor, conductors and brakemen, and, in fact, absolutely everything connected in any way with filling the embankment. TABLE IV. Work Done by Steam Excavator in Six Months at Missouri Valley, Ia. Repairs to locomotive, shovel and cars; material $457.14 Repairs to locomotive, shovel and cars; labor 211.80 Supplies for shovel 1,760.00 Rent of locomotive and cars 1,404.75 Supplies for locomotive 1,781.52 Wages of locomotive attendants 1,508.37 Wages of all other employees 10,680.01 ----------- Total cost $17,803.59 Cars loaded 32,141 Cost per car 55.38 cts. Cost per cubic yard 7 " Hours worked by gang 2,325 Hours worked by shovel 1,926 The report of the Roadmasters' Association for 1885 gives the cost of steam shovel work as follows: Railway. Work. Cost per yd. Baltimore & Ohio Including everything, haul 5 to 25 miles 8.1 cts. Michigan Central Loading 4.5 " Michigan Central Hauling, 30 miles, labor only 4.0 " N. Y., P., & O. Loading 7.0 " Central Iowa Loading 4.75 " " " Unloading 1.9 " " " Engine service 3.1 " ---- " " Total 9.75 " The detailed statement given in Table V. was prepared by Mr. E. A. Hill, Acting Chief Engineer of the Indianapolis, Decatur & Springfield R. R., and is a record of work done under the supervision of Mr. A. J. Diddle, Roadmaster. It shows marked economy and gives an excellent idea of how the expenses are apportioned. The Otis type of excavator was used, which cuts 24 ft. wide and to a depth of 4 ft. below the track. The banks were about 15 ft. high, the average haul 4,000 ft. Twelve flat cars constituted a train. By a special cable arrangement the time of plowing off, ordinarily requiring about 15 minutes, was reduced to 5 or 6 minutes. TABLE V. Steam Shovel Work; Indianapolis, Decatur & Springfield R. R. Sangamon Montezuma Sangamon Nichol's River Gravel River Guion Hollow Trestle. Pit. Trestle. Trestle. Trestle. 1885. 1886. 1886. 1887. 1887. Total number of days 54 186 48 108 51 Number of working days 46 115 38 85 40 Days idle besides Sundays 0 45 3 7 4 Material handled light gravel. light light light clay. clay. clay. clay. Average height of bank 10 ft. 12 ft. 10 ft. 10 ft. 12 ft. Total No. cars loaded 2,899 8,631 2,771 5,254 2,528 Greatest No. load. per day 94 124 90 80 75 Least No. cars load. per day 22 16 50 30 15 Average No. loaded per day 63 75 73 61.8 63.2 Average length of haul 1 mile. 9 miles. 1 mile. 2 miles. 3/4 mile. Grade, shovel to dump, p. c. -1.00 varying. -1.00 -1.00 -1.00 Tons coal used, shov. & eng. 141 853 99 170 65 No. car loads per ton coal. 20.5 10 28 30.9 38.9 Cost of Work Per Car Load. Sangamon Montezuma Sangamon Nichol's River Gravel River Guion Hollow Trestle. Pit. Trestle. Trestle. Trestle. 1885. 1886. 1886. 1887. 1887. Cts. Cts. Cts. Cts. Cts. Foreman at $125 per month 8.86 9.67 8.00 9.01 9.88 Cranesman, $2 to $2.50 day 5.35 5.62 4.80 3.54 5.57 Fireman (shovel) $1.50 day 2.88 3.37 2.87 2.90 3.27 Laborers (4) $1.25 per day 7.86 9.92 8.77 9.80 9.80 Watchman at $1 per day 2.07 1.96 1.88 2.50 2.25 Total shovel crew 27.02 30.54 26.32 27.75 30.77 Engr. and fireman (engine) 12.00 14.50 7.44 11.00 13.10 Trainmen (conductor, $2.50; brakemen, $1.50) 5.97 14.60 5.74 5.25 5.77 Total train crew 17.97 29.10 13.18 16.25 18.87 Helpers distrb. earth, $1.10 .... 1.74 .... .... 2.72 Sec. men (track work), $1.10 0.81 1.88 1.38 1.45 .... Bridge carpenters (repairs to plant), $2.50 0.15 1.58 0.16 1.04 2.08 Sec. men (reprs plant), $1.10 .... 0.62 .... .... .... Shop bills (repairs to plant) 1.69 10.90 1.27 10.60 1.67 Total repairs to plant 1.84 13.10 1.43 11.64 1.67 Coal from $1.25 to $1.41 ton 6.31 13.30 4.47 4.31 3.28 Oil, waste, etc. 0.52 1.55 0.75 0.86 0.36 Total supplies 6.83 14.85 5.22 5.17 3.64 ----- ----- ----- ----- ----- Grand total per car load 54.47 91.19 47.53 62.26 59.75 ----- ----- ----- ----- ----- Cost, cu. yd., 8 yds. per car 6.43 11.40 5.94 7.79 7.47 Add " " for interest on cost of plant 1.00 1.00 1.00 1.00 1.00 ----- ----- ----- ----- ----- Cost per cu. yd., includ. int. 7.43 12.40 6.94 8.79 8.47 BACON'S HOISTING ENGINES For Every Possible Duty. FARREL'S--Ore and Rock CRUSHERS. Screens, Elevators, Etc. THE STANDARD FOR 25 YEARS. EARLE C. BACON, ENGINEER, Havemeyer Building, New York. WORKS: PACIFIC IRON WORKS. FARREL FOUNDRY & MACHINE CO. Steam Shovel REPAIRS. 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STEUBNER & CO., MANUFACTURERS OF HOISTING BUCKETS OF ALL KINDS AND FOR ALL PURPOSES. [Illustration] Side Dumping Cars, End Dumping Cars, Bottom Dumping Cars, Charging Cars, Special Cars, Iron Wheelbarrows, Iron Hoisting Blocks, Tar Heating Furnaces, Sheet-Iron Work, Iron Forgings, Etc. Send for Catalogue and Price List. 168-176 EAST THIRD ST., LONG ISLAND CITY, N. Y. THE BEST STEAM SHOVEL CAR. [Illustration] WRITE FOR PRICES AND CATALOGUE TO Ryan-McDonald Mfg. Co., 44 SOUTH STREET, BALTIMORE, MD., MANUFACTURERS OF Light Locomotives, Contractors' Cars, Derrick Irons and Crabs, Hoisting Engines and All Classes of Narrow Gauge Cars. CONTRACTORS' AND RAILROAD SUPPLIES. Construction, Dump and Mine Cars. CATALOGUE AND PRICES ON APPLICATION. [Illustration] HAROLD C. DAYTON & CO., 44 DEY STREET, NEW YORK. [Illustration] M. BEATTY & SONS, WELLAND, ONT. Dredges, Ditchers, Derricks and Steam Shovels OF VARIOUS STYLES AND SIZES TO SUIT ANY WORK. SUBMARINE ROCK DRILLING MACHINERY, HOISTING ENGINES, SUSPENSION CABLEWAYS, HORSE-POWER HOISTERS, GANG STONE-SAWS, CENTRIFUGAL PUMPS FOR WATER, SAND AND GOLD MINING. AND OTHER CONTRACTORS' PLANT. [Illustration] CONTRACTOR'S LOCOMOTIVES ON HAND. We Keep on hand a number of sizes both narrow and wide gauge locomotives, of best construction, for contractors' service. Catalogue mailed and prices quoted on application. [Illustration] H. K. PORTER & CO., BUILDERS OF LIGHT LOCOMOTIVES, WOOD STREET, Near 7th Ave., PITTSBURGH, PA. NO. 1 SHOVEL ON CHICAGO DRAINAGE CANAL. [Illustration] OSGOOD DREDGE CO., Albany, N. Y. MFRS. OF DREDGES AND STEAM SHOVELS. OTIS & CHAPMAN, STANDARD GRAVEL and HARDPAN EXCAVATOR MANUFACTURED EXCLUSIVELY BY JOHN SOUTHER & CO., BOSTON. Earth Displaced at ONE-QUARTER LESS EXPENSE Than by Any Other Machine [Illustration] _To Whom It May Concern_: I hereby certify that I have used the Otis patent improved Steam Excavator the past twenty years, in all kinds of earth excavation, and believe it to be the best dry land excavator in use, and the only one that will work successfully in hardpan material. I have excavated and put into cars five million yards under one contract for making land in Boston; with two of these machines I loaded from seventy to eighty thousand yards per month. N. C. MUNSON. C. P. TREAT, CONTRACTOR BANGOR & AROOSTOOK R. R. J. A. LANE, Manager. ROB'T SMITH, Ass't Manager. S. H. DOTY, Engineer. H. C. DECKER, Cashier. _Houlton, Maine, December 31, 1894._ _This is to certify that in the month of October, 1894, the bearer, Mr. John B. Shaw, with 1-3/4 yds. Souther Steam Shovel, loaded on cars 38,168 cubic yds. of ballast. Pit measurement by R. R. Co.'s Engineers._ (_Signed_) _C. P. TREAT, per S. H. Doty._ Transcriber's Notes Illustrations in this booklet are not always labelled in order of appearance, so full page diagrams may appear out of order. Fig. 4. seems to have been ommitted and is not found (or referenced) in any of the online sources. Minor corrections made to punctuation. inconsistent hyphenation and spelling. In particular: p7. "rceiving" changed to "receiving". p11. "wabble" has been left - it appears to be a variant spelling of wobble. p18. "overhanging ledges or these materials" changed to "overhanging ledges of these materials". p22. "only few men" changed to "only a few men" TABLE II. "Loose gravel 1 30 1 30 2 60 3 90 4 12" changed to "Loose gravel 1 30 1 30 2 60 3 90 4 120" p50. "steam or air driver" change to "steam or air driven" 
42369	----	Transcriber's Note Italic text is denoted by _underscores_ and bold text by =equal signs=. Whole numbers with fractional parts are denoted as 7-3/4. _Every Boy's Mechanical Library_ [Illustration] MOTORS Every Boy's Mechanical Library By J. S. ZERBE, M.E. Price, per volume, 60 cents, Net. Postage extra. AUTOMOBILES This is a subject in which every boy is interested. While few mechanics have the opportunity to actually build an automobile, it is the knowledge which he must acquire about every particular device used, that enables him to repair and put such machines in order. The aim of this book is to make the boy acquainted with each element, so that he may understand why it is made in that special way, and what the advantages and disadvantages are of the different types. To that end each structure is shown in detail as much as possible, and the parts separated so as to give a clear insight of the different functions, all of which are explained by original drawings specially prepared to aid the reader. MOTORS To the boy who wants to know the theory and the practical working of the different kinds of motors, told in language which he can understand, and illustrated with clear and explicit drawings, this volume will be appreciated. It sets forth the groundwork on which power is based, and includes steam generators, and engines, as well as wind and water motors, and thoroughly describes the Internal Combustion Engine. It has special chapters on Carbureters, Ignition, and Electrical systems used, and particularly points out the parts and fittings required with all devices needed in enginery. It explains the value of compounding, condensing, pre-heating and expansion, together with the methods used to calculate and transmit power. Numerous original illustrations. AEROPLANES This work is not intended to set forth the exploits of aviators nor to give a history of the Art. It is a book of instructions intended to point out the theories of flying, as given by the pioneers, the practical application of power to the various flying structures; how they are built; the different methods of controlling them; the advantages and disadvantages of the types now in use; and suggestions as to the directions in which improvements are required. It distinctly points out wherein mechanical flight differs from bird flight, and what are the relations of shape, form, size and weight. It treats of kites, gliders and model aeroplanes, and has an interesting chapter on the aeroplane and its uses in the great war. All the illustrations have been specially prepared for the work. CUPPLES & LEON CO., Publishers, NEW YORK [Illustration] _Every Boy's Mechanical Library_ MOTORS BY J. S. ZERBE, M.E. _Author of Aeroplanes--Automobiles_ _ILLUSTRATED_ NEW YORK CUPPLES & LEON COMPANY Copyright, 1915, by CUPPLES & LEON COMPANY CONTENTS PAGE Introductory 1 The Subject. The Inquisitive Trait. The Reasons for Doing Things. The Mystery of Mechanism. Curiosity which prompts Investigation. The Sum of Knowledge. Chapter I. Motors and Motive Power 5-21 The Water Fall. Water moves in One Direction only. What is Energy. Stored or Potential Energy. Kinetic Energy. Friction. Resistance. Inertia. The Law of Bodies. Internal and External Resistance. Momentum. Energy Indestructible. Wind Power. Rectilinear Motion. Oscillating Motion. Movements in Nature. How Man Utilizes the Various Movements. Kinds of Potential Energy. The Power in Heat. Energy in Steam. Energy from the Sun. Power from Water. The Turbine. Calculating Power of a Turbine. Horse Power. Foot Pounds. Power and Time. Gravitation. Utilizing the pull of Gravity. Taking Advantages of Forces. Pitting Forces Against each Other. Centripetal and Centrifugal Forces. Power not Created. Developing the Power of Motors. Experimenting. Chapter II. The Steam Generator 22-31 Water as an absorbent of Heat. Classification of Boilers. Mode of applying Heat. The Cylindrical Boiler. The Cornish Boiler. The Water Tube Boiler. Various Boiler Types. Compound Steam Boiler. Locomotive Steam Boiler. Vertical Steam Boiler. Chapter III. Steam Engines 32-59 The Original Turbine Engine. The Reciprocating Engine. Atmospheric Engine. The Piston. Importance of the Valve. Expanding the Steam. Balanced Valve. Rotary Valve. Engine Accessories. Efficiency of Engines. How Steam acts in a Cylinder. Indicating the Engine. Mean Efficiency. Calculating Horse Power. Condensation. Atmospheric Pressure. The Condenser. Pre-heating. Superheaters. Compounding. Triple and Quadruple Expansion Engines. The Steam Turbine. Pressure and Velocity. Form of Blades. Compounding the Jet. Chapter IV. Fuels and Combustion 60-67 Solid Fuels. Liquid Fuels. Combustion. Oxidation. The Hydro-Carbon Gases. Oxygen and the Atmosphere. Internal Combustion. Vaporizing Fuel. Explosion by Heat Compression. How Compression Heats. Elasticity of Gases. Advantages of Compression. The Necessity of Compression. Chapter V. The Internal Combustion Engine 68-82 Fixed Gases. Gas Engines. Energy of Carbon and Hydrogen. The Two-Cycle Type. Advantages of the Two-Cycle Engine. The Four-Cycle Engine. The Four Cycles. Ignition Point. Advantages of the Four-Cycle Type. The Loss in Power. Engine Construction. Valve Grinding. The Crank Shaft. The Cams. Chapter VI. Carbureters 83-101 Functions of a Carbureter. Rich Mixtures. Lean Mixtures. Types of Carbureters. The Sprayer. The Surface Type. Governing a Carbureter. Primary Air. Needle Valve. Secondary Air. Requirements in a Carbureter. Size of a Carbureter. Rule for Size of Carbureters. The Throttle. Flooding. Adjustability. Surface Carbureters. Float Chamber. Chapter VII. Ignition, Low Tension System 102-120 Electricity. Magnetism. The Armature. Characteristics of Electricity. Make and Break System. Voltage. High and Low Voltage. Low Tension method. Disadvantages of Make and Break. Amperes. Resistance. Direct Current. Alternating Current. Induction. Generating Electricity. Primary Battery. Making a Dry Cell. Energy in a cell. Wiring Methods. Series Connection. Multiple Connection. Series Multiple. Watts. Testing a Cell. Testing with Instruments. Simple Battery Make and Brake System. To Advance the Spark. The Magneto in the Circuit. Magneto Spark Plug. Chapter VIII. Ignition, High Tension 121-140 Magnetos. Alternating Current. Cutting Lines of Force. Plurality of Loops. The Electro Magnet. The Dynamo Form. The Magneto Form. Advantages of the Magneto. Induction Coil. Changing the Current. Construction of a Coil. Primary Coil. Secondary Coil. Contact Maker. High Tension with Battery and Coil. Metallic Core for Induction Coil. The Condenser. Operations of a Vibrator Coil. The Distributor. Circuiting with Distributor. Chapter IX. Mechanical Devices Utilized in Power 141-157 The Unit of Time. Horse Power. Proney Brake. Reversing Mechanism. Double Eccentric Reversing Gear. Balanced Slide Valve. Balanced Throttle Valve. Engine Governors. Injectors. Feed Water Heaters. Chapter X. Valves and Valve Fittings 158-171 Check Valve. Gate Valve. Globe Valve. The Corliss Valve. Corliss Valve-operating Mechanism. Angle Valve. Rotary Valves. Rotable Engine Valves. Throttle Valves. Blow-off Valves. Pop-Safety Valves. Chapter XI. Cams and Eccentrics 172-178 Simple Cams. Wiper Wheels. Cylindrical Cam Motion. Eccentrics. Triangularly-formed Eccentrics. Chapter XII. Gears and Gearing 179-190 Racks and Pinions. Mangle Rack. Controlling the Pinion. Dead Center. Crank Motion Substitute. Mangle Wheels. Quick Return Motion. Accelerated Motion. Quick-return Gearing. Scroll Gearing. Chapter XIII. Special Types of Engines 191-201 Temperatures. Artificial Heat. Zero. Liquids and Gases. Refrigeration. Rotary Engines. Caloric Engines. Adhesion Engines. Chapter XIV. Enginery in the Development of the Human Race 202-207 Power in Transportation. Power vs. Education and the Arts. Lack of Power in the Ancient World. The Early Days of the Republic. Lack of Cohesiveness in Countries Without Power. The Railroad as a Factor in Civilization. The Wonderful Effects of Power. England as a User of Power. The Automobile. High Character of Motor Study. The Unlimited Field of Power. Chapter XV. The Energy of the Sun, and How Heat is Measured 208-216 Fuel Economy. Direct Conversion. The Measurement of Heat. Caloric. Material Theory. Heat Transmitted in Three Ways. Conduction. Convection. Radiation. Glossary 217 LIST OF ILLUSTRATIONS FIG. PAGE 1. Undershot Wheel 13 2. Overshot Wheel 14 3. Primitive Boiler 24 4. Return Tubular Boiler 25 5. Cornish, or Scotch Boiler 25 6. Water Tube Boiler. End view 27 7. Water Tube Boiler. Side view 29 8. The Original Engine 33 9. Horizontal Section of Tube 33 10. Steam-Atmospheric Engine 35 11. Simple Valve Motion. First position 38 12. Simple Valve Motion. Second position 38 13. Effective pressure in a Cylinder 42 14. Indicating pressure line 44 15. Indicating the Engine 45 16. Compound Engine 53 16a. Relative Piston Pressures 54 17. Changing Pressure into Velocity 55 18. Reaction against Air 56 19. Reaction against Surface 56 20. Turbine. Straight Blades 57 21. Curved Blades 58 22. Compound Turbine 58 23. Two-Cycle Engine. First position 71 24. Two-Cycle Engine. Second position 73 25. Two-Cycle Engine. Third position 73 26. Four-Cycle Engine. First position 75 27. Four-Cycle Engine. Second position 75 28. Four-Cycle Engine. Third position 76 29. Four-Cycle Engine. Fourth position 76 30. Valve Grinding 81 31. Carbureter 87 32. Carbureter 95 33. Surface Carbureter 98 34. Dry Cell 108 35. Series Connection 109 36. Multiple, or Parallel Connection 110 37. Series-Multiple Connection 111 38. Circuit Testing 113 39. Make and Break, with Battery 114 40. Make and Break, with Magneto 117 41. Magneto Spark Plug 119 42. Illustrating Alternating Current 122 43. Alternating Current. Second position 122 44. Alternating Current. Third position 123 45. Alternating Current. Fourth position 124 46. Making the Circuit 125 47. The Dynamo 126 48. The Magneto 126 49. Current by Induction 128 50. Induction Coil 129 51. Typical Induction Coil 130 52. Contact Maker 131 53. Typical Circuiting, Jump spark Ignition 132 54. Metallic Core, Induction Coil 133 55. Condenser 134 56. Vibrator Coil and Connections 135 57. The Distributer 137 58. Circuiting with Distributer 138 59. Illustrating the Unit of Time 142 60. The Proney Brake 143 61. Double Eccentric Reversing Gear 146 62. Reversing Gear, Neutral 146 63. Reversing Gear, Reversed 147 64. Single Eccentric Reversing Gear 147 65. Balanced Slide Valve 148 66. Valve Chest. Double Port Exhaust 149 67. Balanced Throttle-Valve 150 68. Watt's Governor 151 69. The Original Injector 152 70. Injector with movable Combining Tube 154 71. Feed Water Heater 156 72. Check Valve 158 73. Gate Valve 159 74. Globe Valve 160 75. Corliss Valve 162 76. Corliss Valve-operating Mechanism 163 77. Angle Valve 164 78. Rotary-Valve 165 79. Two-way Rotary 165 80. Rotary Type 166 81. Two-Way Rotary Type 166 82. Butterfly Throttle 167 83. Angle Throttle 167 84. Slide Throttle 168 85. Two-slide Throttle 168 86. Blow-off Valve 169 87. Safety Pop Valve 170 88. Heart Shaped 173 89. Elliptic 173 90. Double Elliptic 173 91. Single Wiper 174 92. Double Wiper 174 93. Tilting Cam 174 94. Cam Sector 175 95. Grooved Cam 175 96. Reciprocating Motion 175 97. Pivoted Follower for Cam 176 98. Eccentric 177 99. Eccentric Cam 177 100. Triangularly-formed Eccentric 178 101. Rack and Pinion 180 102. Rack Motion 180 103. Plain Mangle Rack 181 104. Mangle Rack Motion 181 105. Alternate Circular Motion 181 106. Controlling Pinion for Mangle Rack 182 107. Illustrating Crank-pin Movement 183 108. The Dead Center 184 109. Crank Motion Substitute 184 110. Mangle Wheel 185 111. Quick Return Motion 186 112. Accelerated Circular Motion 187 113. Quick Return Gearing 188 114. Scroll Gearing 189 115. Simple Rotary Engine 196 116. Double-feed Rotary Engine 198 117. Adhesion Motor 200 INTRODUCTORY The motor is the great dominating factor in the world of industry. Every wheel and spindle; every shaft and loom, and every piece of mechanism which has motion, derives it from some sort of motor. The term _motor_ has a wider significance than any other word. A steam engine is a motor, and so, also, is a dynamo, a water wheel or a wind mill. It would be just as descriptive to call a wind mill a wind _motor_, or a steam engine a steam _motor_, as to adhere to the old terms; and, on the other hand, since it would be out of place to call a dynamo or a wind mill an engine, the word _motor_ seems best adapted to express the meaning of every type of mechanism which transforms energy into motion. In considering the subject I shall proceed on the theory that the boy knows nothing whatsoever of the subject, nor the terms used to designate the various phases, subjects and elements. It must be elementary in its character, and wholly devoid of technical terms or sentences. While it is necessary to give information in a book of this character, on the methods for figuring out power, it must be done without resorting to the formulas usually employed in engineering works, as they are of such a nature that the boy must have some knowledge of the higher mathematics to follow out the calculations employed. Indeed, every phase should be brought within the mental view of the boy, and to do this may occasionally necessitate what might appear to be long drawn out explanations, all of which, it is hoped, will be the means of more clearly presenting the subject. The opening chapters, which treat of the fundamentals, will be as nearly complete as possible, and thus lay a foundation for the work we shall be called upon to perform, when we treat of the structures of the different parts and devices in the various types of motors. The object is to explain power in its various phases, how derived, and the manner in which advantage is taken of the elements, and substances with which we are brought into contact. The reasons for each step are plainly set forth with the view of teaching the boy what power means, rather than to instruct him how to make some particular part of the machinery. _The Inquisitive Trait._--My experience has impressed me with the universality of one trait in boys, namely, that of inquisitiveness. Put a machine before a boy and allow him to dissect it, and his curiosity will prompt him to question the motive for the particular construction of each part of its make-up. _The Reasons for Doing Things._--He is interested in knowing the reason why. Every boy has the spirit of the true investigator,--that quality which seeks to go behind or delve down deeply. This is a natural instinct. _The Mystery of Mechanism._--If this taste is gratified, and he thereby learns the mystery of the machine, what a wonderful world is opened to him! The value of the lesson will depend, in a large measure, on the things which he has found out for himself. It is that which counts, because he never forgets that which he has dug out and discovered. _Curiosity Which Prompts Investigation._--I recall a farmer's boy whose curiosity led him to investigate the binding mechanism of a reaper. It was a marvel to him, as it has been to many others. He studied it day after day, and finally, unaided mastered the art. That was something which could not be taken away from him. It was a pleasure to hear him explain its operation to a group of boys, and men, too, in which he used the knot itself to explain how the various fingers and levers coöperated to perform their functions. It was an open book to him, but there was not one in the group of listeners who could repeat the explanation. _The Sum of Knowledge._--It is the self-taught boy who becomes the expert. The great inventors did not depend on explanations. A book of this character has a field of usefulness if it merely sets forth, as far as possible, the sum of useful knowledge which has been gained by others, so as to enable the boy to go forward from that point, and thus gain immensely in time. There is so much that has been developed in the past, with reference to the properties of matter, or concerning the utility of movements, and facts in the realm of weights, measures, and values of elements which he must deal with, that, as he studies the mechanical problems, the book becomes a sort of cyclopedia, more than a work designed to guide him in the building of special engines or motors. The Author. MOTORS CHAPTER I MOTORS AND MOTIVE POWER What makes the wheels turn round? This simple question is asked over and over again. To reply means pages of answers and volumes of explanations. The Water Fall.--Go with me to the little stream I have in mind, and stand on the crest of the hill where we can see the water pouring down over the falls, and watch it whirling away over the rocks below. The world was very, very old, before man thought of using the water of the falls, or the rushing stream below, to grind his corn or to render him other service. Water Moves in One Direction Only.--What the original man saw was a body of water moving in one direction only. When he wanted to grind corn he put it in the hollow of a rock, and then beat it with a stone, which he raised by hand at each stroke. In doing so two motions were required in opposite directions, and it took thousands of years for him to learn that the water rushing along in one direction, could be made to move the stone, or the pestle of his primitive grinding mill, in two directions. It took him thousands of years more to learn another thing, namely, that the water could be made to turn the stone round, or rotate it, and thus cause one stone, when turning on another, to crush and grind the grain between them. Now, as we go along with the unfolding of the great question of _motors_, we must learn something of the terms which are employed, to designate the different things we shall deal with, and we ought to have some understanding of the sources of power. What Is Energy?--The running, as well as the falling water represent energy. This is something which is in the thing, the element, or the substance itself. It does not come from without. It is not imparted to it by anything. Stored or Potential Energy.--At the top of the falls, look at that immense rock. It has been there for centuries. It, also, has energy. There is stored within it a tremendous power. You smile! Yes, the power has been there for ages, and now by a slight push it is sent crashing down the precipice. The power developed by that fall was thousands of times greater than the push which dislodged it. But, you say, the push against the stone represented an external force, and such being the case, why do you say that power is within the thing itself? The answer is, that not one iota of the power required to push the stone off its seat was added to the power of the stone when it fell. Furthermore, the power required to dislodge the stone came from within me, and not from any outside source. Here we have two different forms of energy, but both represent a moving force. The power derived from them is the same. Kinetic Energy.--The energy of the falling water or stone is called _Kinetic_ energy. In both cases the power developed came from within themselves and not from any exterior source. The difference between Potential and Kinetic Energy is therefore that Potential Energy represents the capacity to do work, while Kinetic Energy is the actual performance of work. Friction.--In every form of energy there is always something to detract from it or take away a portion of its full force, called _friction_. When a shaft turns, it rubs against the bearings, and more or less power is absorbed. When a wheel travels over the ground friction is ever present. The dislodging of the stone required ten pounds of energy, but a thousand pounds was developed by the fall. The water rushing along its rocky bed has friction all along its path. Resistance.--This friction is a resistance to the movement of a body, and is ever present. It is necessary to go back and examine the reason for this. As long as the stone was poised at the top of the precipice it had latent or potential energy, which might be termed _power at rest_. When it fell it had power in motion. In both cases gravity acted upon the stone, and in like manner on the water pouring over the falls. Inertia.--Inertia or momentum is inherent in all things and represents the resistance of any body or matter, to change its condition of rest or standing still into motion, and is then called _Inertia of Rest_, or the resistance it offers to increase or decrease its speed when moving, and is then called _Inertia of Motion_. Inertia or momentum is composed by the weight of the body and its speed and is measured by multiplying its weight by its speed. The law is, that when a body is at rest it will remain at rest eternally, and when in motion it will continue in motion forever, unless acted on by some external force or resistance. An object lying on the ground has the frictional resistance of the earth to prevent its moving. When the object is flying through space it meets the air and has also the downward pull of gravity, which seek to bring it to rest. These resisting forces are less in water, and still less in gases, and there is, therefore, a state of mobility in them which is not found in solids. Internal and External Resistance.--All bodies are subject to internal, as well as external resistance. The stone on the cliff resisted the movement to push it over. Weight was the resisting internal force, but when the stone was moving through the air, the friction with the air created external resistance. Energy Indestructible.--There is another thing which should be understood, and that is the absolute indestructibility of energy. Matter may be changed in form, or in the direction of its motion, by the change of kinetic into potential energy, or vice versa, but the sum total of the energy in the world is unalterable or constant. The tremendous power developed by the stone when it plunged through space and struck the rocks below, developed a heat at its impact. Thus the moving force which was a motion in one direction was converted into another form of energy, heat. The expansion of the material exposed to the heat also represented energy. When powder explodes and absolutely changes the form of the substance, its volume of expansion, if it should be retained within a vessel, would perform a certain amount of work, and the energy is thus transferred from one form to another without ceasing. Wind Power.--Primitive man also saw and felt the winds. He noted its tremendous power, but he could not see how a force moving in one direction only could be utilized by him. Rectilinear Motion.--This movement of the wind in one direction, like the water flowing along the bed of the river, is called _rectilinear_ motion. It required invention to convert rectilinear into circular motion. Oscillating Motion.--When he threshed his grain and winnowed it by shaking it to and fro, to rid it of the chaff, the idea of using the wind to produce an oscillating motion did not occur to him. After circular motion was produced, the crank was formed and thus the oscillating movement was brought about. Movements in Nature.--All movements in nature are simple ones, of which the following are illustrations: 1. _Rectilinear_, which, as stated, means in a straight line. 2. _Circular_, like the motion of the earth on its axis, once every twenty-four hours. 3. _Oscillatory_, like a to and fro movement, the swaying branches of trees, or the swinging of a pendulum. How Man Utilizes the Various Movements.--What man has done is to utilize the great natural forces in nature in such a way as to produce these movements at will, in either direction, with greater or less speed, at regular or irregular intervals, and at such amplitudes as are required to perform the necessary work. Kinds of Potential Energy.--Now, materials have within themselves _potential_ energy of various kinds. Thus, powder, if ignited, will burn, and in burning will expand, or explode, as we term it. This is true also of oils and gases. The expansion pressure produced from such substances depends on the speed at which they will burn, and in so confining the burning substances that a great pressure is produced. The Power in Heat.--The pressure of all such substances against the confining medium depends on heat. Any gas which has 523 degrees of heat imparted to it will expand double its volume. If one cubic inch of water is converted into steam the latter will occupy one cubic foot of space under atmospheric pressure,--that is, it will expand over 1700 times. Energy in Steam.--If the steam thus generated is now subjected to 523 degrees of heat additional, it will occupy over 3400 cubic inches of space. It will thus be seen why steam, gas, and gasoline engines are called _heat engines_, or heat _motors_. Energy From the Sun.--Many attempts have been made to utilize the heat of the sun, to turn machinery, but the difficulty has been to secure sufficient heat, on the one hand, and on the other to properly cool down the heated gases, so that the various liquid and solid fuels are required to make the heat transformations. Power From Water.--In the use of water two forms are available, one where the water is moving along or falling in a constant open stream; and the other where the flowing water is confined and where its flow can be regulated and controlled. The latter is more available for two reasons: First: Economy in the use of water. Second: Ability to control the speed or movement of the motor. With running or falling streams a large surface is required, and the wheels turn slowly. Two well-recognized forms of wheels have been employed, one called the undershot, or breast wheel, shown in Fig. 1, and the other the overshot, illustrated in Fig. 2. [Illustration: _Fig. 1. Undershot Wheel._] In both types it is difficult to so arrange them as to shut off the power or water pressure when required, or to regulate the speed. The Turbine.--Wheels which depend on the controllable pressure of the water are of the turbine type. The word is derived from the Latin word _turbo_, meaning to whirl, like a top. This is a type of wheel mounted on the lower end of a vertical or horizontal shaft, within, or at the bottom, of a penstock. The perimeter of the wheel has blades, and the whole is enclosed within a drum, so that water from the penstock will rush through the tangentially-formed conduit into the drum, and strike the blades of the wheel. [Illustration: _Fig. 2. Overshot Wheel._] A column of water one inch square and twenty-eight inches high weighs one pound,--or, to express it in another way, the pressure at the bottom of such a column is one pound, and it is a pound for each additional 28 inches. If there should be a head or height of water column of seven feet, the pressure on each square inch of water at the bottom of the penstock would be three pounds to the square inch. Assuming the opening or duct leading to the wheel blades should be 12 � 12 inches, and also the blades be 12 � 12 inches, the area would be equal to 144 square inches, and this multiplied by three pounds would equal 432 pounds pressure against the blades. Calculating Power of a Turbine Wheel.--The power of such a wheel depends principally on two things. First, the arrangement of the blades with reference to the inflowing water; and, second, the discharge port, or ability of the water to free itself from the wheel casing. Let us assume that the diameter of the wheel at the center of the blades is two feet, which would, roughly estimating, give a circumference of six feet, or a travel of each particular blade that distance at each turn of the wheel. If the wheel turns one hundred times a minute, and this is multiplied by the circumference of the wheel (six feet), the result is 600 feet. This, again, multiplied by 432 pounds (which represents the pressure of the water on the entire discharge opening), and we have a product of 259,200, which represents _foot pounds_. This means the same work as if 259,200 pounds would have been lifted through a space of one foot in one minute of time. To ascertain how much power has been developed we must know how many foot pounds there are in a horse power. Horse Power.--It is determined in this way: any force which is capable of raising 550 pounds one foot in one second of time, is developing one horse power. A man might have sufficient strength to raise such a weight once, twice, or a dozen times in succession, but if he should try to do it sixty times a minute he would find it a trying, if not impossible task. Foot Pounds.--If he should be able to lift 550 pounds sixty times within a minute, he would have lifted 33,000 pounds one foot in one minute of time (550 � 60), and thus have developed one horse power. As the water wheel, in our calculations above, raised 259,200 pounds in that period of time, this figure divided by 33,000 shows that a little more than 7-3/4 horse power was developed, assuming, of course, that we have not taken into account any waste, or loss by friction, or otherwise. This method of determining one horse power should be carefully studied. Always keep in mind the main factor, 33,000 pounds, and this multiplied by one foot, the result will be 33,000 _foot pounds_,--that is, one horse power. It would be just the same, however, if it were possible to raise one pound 550 times in one second, or one pound 33,000 times within a minute. Power and Time.--You are thus brought face to face with another thing which is just as important, namely, that, in considering power, time, as well as energy, must be considered. If a man, by superior strength, could be able to raise 550 pounds once within a second, then skip a few seconds, take another hold, and again raise it that distance, he would not be developing one horse power for a minute, but only for one second while he lifted the weight. For the whole minute he would only develop a certain number of foot pounds, and less than 33,000 foot pounds. If, within a minute, he succeeded in raising it one foot for six times, this would be six times 550, equal to 3,300 foot pounds, or just one-tenth of one horse power for one minute; so _time_ is just as important as the amount lifted at each effort. Gravitation.--Now, let us examine power from another standpoint. Every attempt which man makes to produce motion is an effort to overcome some resistance. In many cases this is "weight or gravity." While humanity unceasingly antagonizes the force of gravity it is constantly utilizing the laws of gravitation. Utilizing the Pull of Gravity.--The boy laboriously drags his sled to the top of the hill against gravity, and then depends on that force to carry him down. We have learned to set up one force in nature against the other. The running stream; the moving winds; the tides; the expansive force of all materials under heat, are brought into play to counteract the great prevailing agency which seeks to hold everything down to mother earth. Utilizing Forces.--The Bible says: Blessed is he who maketh two blades of grass grow where one grew before. To do that means the utilization of forces. Improved machinery is enabling man to make many blades grow where one grew before. New methods to force the plow through the soil; to dig it deeper; to fertilize it; and to harvest it; all require power. Pitting Forces Against Each Other.--Man has discovered how to pit the forces of nature against each other, and the laws which regulate them. Centripetal and Centrifugal Forces.--Gravity, that action which seeks to draw all matter toward the center of the earth, is termed _centripetal_ force. But as the earth rotates on its axis another force is exerted which tends to throw substances outwardly, like dirt flying from the rim of a wheel. This is called _centrifugal_ force. Man utilizes this force in many ways, one of which is illustrated in the engine governor, where the revolving balls raise the arms on which they swing, and by that means the engine valve is regulated. Power Not Created.--In taking up the study of this subject start with a correct understanding of the source of all power. It is inherent in all things. All we can do is to liberate it, or to put the various materials in such condition, that they will exert their forces for our uses. (See Page nine, "Energy Indestructible.") A ton of coal, when burned, produces a certain amount of heat, which, if allowed to escape, will not turn a wheel. But if confined, it expands the air, or it may convert water into steam which will turn ponderous machinery. Niagara Falls has sent its great volume into the chasm for untold centuries, but it has never been utilized until within the last twenty years. The energy has been there, nevertheless; and so it is with every substance of which we have knowledge. The successive steps, wherein the experimenter and the inventor have greatly improved on the original inventions, will be detailed as we go along through the different types of motors. Developing the Power of Motors.--This development in the art is a most fascinating study. It is like the explorer, forcing his way through a primeval forest. He knows not what is beyond. Often, like the traveler, he has met serious obstructions, and has had to deviate from his course, only to learn that he took the wrong direction and had to retrace his steps. The study of motors and motive power is one which calls for the highest engineering qualities. In this, as in every other of the mechanical arts, theory, while it has an important function, occupies second place. Experimenting.--The great improvements have been made by building and testing; the advance has been step by step. Sometimes a most important invention will loom up as a striking example to show how a valuable feature lies hidden and undeveloped. An illustration of this may be cited with respect to the valve of the steam engine. For four hundred years there was no striking improvement in the valve. The various types of sliding and rocking valves were modified and refined until it was assumed that they typified perfection. At one stroke the Corliss valve made such an immense improvement that the marvel was as much in its simplicity as in its performance. The reasons and the explanations will be set forth in the section which analyzes valve motion. In this, as in other matters, it shall be our aim to explain why the different improvements were regarded as epochs in the production of motors. CHAPTER II THE STEAM GENERATOR The most widely known and utilized source of power is the steam engine. Before its discovery wind and water were the only available means, except the muscular power of man, horses and other animals, which was used with the crudest sort of contrivances. In primitive days men did not value their time, so they laboriously performed the work which machinery now does for us. The steam engine, like everything else which man has devised, was a growth, and, singular as it may seem, the boiler, that vital part of the organism, was, really, the last to receive due consideration and improvement. As the boiler is depended upon to produce the steam pressure, and since the pressure depends on the rapid and economical evaporation of water, the importance of the subject will be understood in treating of the steam engine. Water as an Absorbent of Heat.--Water has the capacity to absorb a greater amount of heat than any other substance. A pewter pot, which melts at 500 degrees, will resist 2000 degrees of heat if it is filled with water, since the latter absorbs the heat so rapidly that the temperature of the metal is kept near the boiling point of water, which is 212 degrees. Notwithstanding the great heat-absorbing qualities of water, a large portion of the heat of the fuel passes through the flues and escapes from the stack. This fact has caused inventors to devise various forms of boilers, the object being to present as large an area of water as possible to the heat of the burning fuel. How that was accomplished we shall try to make plain. Classification of Boilers.--Numerous types of boilers have been devised, the object being, in all cases to evaporate the largest amount of water with the minimum quantity of fuel. All boilers may be put under two general heads, namely, those which contain a large quantity of water, and those which are intended to carry only a small charge. In the first division the boilers are designed to carry a comparatively small pressure, and in the latter high pressures are available. Mode of Applying Heat.--The most important thing to fully understand is the manner in which heat is applied to the boiler, and the different types which have been adapted to meet this requirement. The Cylindrical Boiler.--The most primitive type of boiler is a plain cylindrical shell A, shown in Fig. 3, in which the furnace B is placed below, so that the surface of the water in contact with the fire area is exceedingly limited. [Illustration: _Fig. 3. Primitive Boiler._] In such a type of boiler it would be impossible for water to extract more than quarter the heat of the fuel. Usually it was much less. The next step was to make what is called a return tubular type in which the heat of the burning gases is conveyed to the rear end of the boiler, and then returned to the front end through tubes. Fig. 4 shows this construction. The head of the shell holds the ends of a plurality of tubes, and the products of combustion pass through the conduit, below the boiler to the rear end, and are conducted upwardly to the tubes. As all the tubes are surrounded by water, it will absorb a large amount of the heat as the gases move through, and before passing out of the stack. [Illustration: _Fig. 4. Return Tubular Boiler._] [Illustration: _Fig. 5. Cornish, or Scotch Boiler._] The Cornish Boiler.--One of the most important inventions in the generation of steam was the Cornish boiler, which for many years was the recognized type for marine purposes. It had the advantage that a large amount of water could be carried and be subjected to heat at all times. Aside from that it sought to avoid the great loss due to radiation. It will be seen from an examination of Fig. 5 that the shell is made very large, and its length does not exceed its diametrical measurement. Two, and sometimes three, fire tubes are placed within the shell, these tubes being secured to the heads. Surrounding these fire tubes, are numerous small tubes, through which the products of combustion pass after leaving the rear ends of the fire tubes. In these boilers the tubes are the combustion chambers, and are provided with a grating for receiving the coal, and the rear ends of the tubes are provided with bridge walls, to arrest, in a measure, the free exit of the heated gases. These boilers would be very efficient, if they could be made of sufficient length to permit the water to absorb the heat of the fuel, but it will be seen that it would be difficult to make them of very great length. If made too small diametrically the diameter of the fire boxes would be reduced to such an extent that there would not be sufficient grate surface. It is obvious, however, that this form of boiler adds greatly to the area of the water surface contact, and in that particular is a great improvement. [Illustration: _Fig. 6. Water Tube Boiler: End View._] The Water Tube Boiler.--In the early days of the development of boilers, the universal practice was to have the products of combustion pass through the flues or the tubes. But quick generation of steam, and high pressures, necessitated a new type. This was accomplished by connecting an upper, or steam drum, with a lower, or water drum, by a plurality of small tubes, and causing the burning fuel to surround these tubes, so that the water, in passing upwardly, would thus be subjected to the action of the fuel. This form of boiler had two distinct advantages. First, an immense surface of water could be provided for; and, second, the water and steam drums could be made very small, diametrically, and thus permit of very high pressures. In Fig. 6, which is designed to show a well known type of this structure, A A, represent the water drums and B, the steam drum. The water drums are separated from each other, so as to provide for the grate bars C, and each water drum is connected with the steam drum by a plurality of tubes D. It will thus be seen that a fire box, or combustion chamber, is formed between the two sets of tubes D, and to retain the heat, or confine it as closely as possible to the tubes, a jacket E is placed around the entire structure. The ends of the water and steam drums are connected by means of tubes F, shown in side view, Fig. 7, for the return or downward flow of the water. The diagrams are made as simple as possible, to show the principal features only. The structure illustrated has been modified in many ways, principally in simplifying the construction, and in providing means whereby the products of combustion may be brought into more intimate contact with the water during its passage through the structure. [Illustration: _Fig. 7. Water Tube Boiler: Side View._] As heretofore stated, this type of boiler is designed to carry only a small quantity of water, so that it is necessary to have practically a constant inflow of feed water, and to economize in this respect the exhaust of the steam engine is used to initially heat up the water, and thus, in a measure, start the water well on its way to the evaporation point before it reaches the boiler. Various Boiler Types.--The different uses have brought forth many kinds of boilers, in order to adapt them for some particular need. It would be needless to illustrate them, but to show the diversity of structures, we may refer to some of them by their characteristics. Compound Steam-Boiler.--This is a battery of boilers having their steam and water spaces connected, and acting together to supply steam to a heating apparatus or a steam engine. These are also made by combining two or more boilers and using them as a feed water heater or a superheater, for facilitating the production of steam, or to be used for superheating steam. The terms _feed water heater and super heater_ are explained in chapter III. Locomotive Steam-Boiler.--This is a tubular boiler which has a contained furnace and ash pit, and in which the gases of combustion pass from the furnace directly into the horizontal interior tubes, and after passing through the tubes are conveyed directly into the smoke box at the opposite ends of the tubes. The name is derived from the use of such boilers on locomotive engines, but it is typical in its application to all boilers having the construction described, and used for generating steam. Vertical Steam-Boiler.--This is a form of construction in which the shell, or both the shell and the tubes, are vertical, and the tubes themselves may be used to convey the products of combustion, or serve as the means for conveying water through them, as in the well known water tube type. This form of boiler is frequently used to good advantage where it is desired to utilize ground space, and where there is sufficient head room. Properly constructed, it is economical as a steam generator. From the foregoing it will be seen that the structural features of all boilers are so arranged as to provide for the exposure of the largest possible area of water to a heated surface so that the greatest amount of heat from the fuel may be absorbed. CHAPTER III STEAM ENGINES The first steam engine was an exceedingly simple affair. It had neither eccentric, cylinder, crank, nor valves, and it did not depend upon the pressure of the steam acting against a piston to drive it back and forth, because it had no piston. It is one of the remarkable things in the history and development of mechanism, that in this day of perfected steam engines, the inventors of our time should go back and utilize the principles employed in the first recorded steam engine, namely, the turbine. Instead of pressure exerting a force against a piston, as in the reciprocating engine, the steam acted by impacting against a moving surface, and by obtaining more or less reaction from air-resistance against a freely discharging steam jet or jets. The original engine, so far as we have any knowledge, had but one moving part, namely, a vertical tubular stem, to which was attached a cross or a horizontal tube. The Original Engine.--Figure 8 is a side view of the original engine. The vertical stem A is pivoted to a frame B, and has a bore C which leads up to a cross tube D. The ends of the tube D are bent in opposite directions, as shown in the horizontal section, Fig. 9. [Illustration: _Fig. 8. The Original Engine._] [Illustration: _Fig. 9. Horizontal Section of Tube._] Steam enters the vertical stem by means of a pipe, and as it rushes up and out through the lateral tubes D, it strikes the angles E at the discharge ends, so that an impulse is given which drives the ends of the tube in opposite directions. As the fluid emerges from the ends of the tubes, it expands, and on contacting with the air, the latter, to a certain extent, resists the expansion, and this reacts on the tube. Thus, both forces, namely, impact and reaction, serve to give a turning motion to the turbine. The Reciprocating Engine.--The invention of this type of engine is wrapped in mystery. It has been attributed to several. The English maintain that it was the invention of the Marquis of Worcester, who published an account of such an engine about 1650. The French claim is that Papin discovered and applied the principle before the year 1680. In fact, the first actual working steam engine was invented and constructed by an Englishman, Captain Savery, who obtained a patent for it in 1698. This engine was so constructed as to raise water by the expansion and condensation of steam, and most engines of early times were devoted solely to the task of raising water, or were employed in mines. Atmospheric Engines.--When we examine them it is difficult to see how we can designate them as steam engines. The steam did not do the actual work, but a vacuum was depended on for the energy developed by the atmospheric pressure. A diagram is given, Fig. 10, showing how engines of this character were made and operated. A working beam A was mounted on a standard B, and one end had a chain C on which was placed heavy weights D. Near this end was also attached the upper end of a rod E, which extended down to a pump. [Illustration: Fig. 10. Steam-Atmospheric Engine.] The other end of the working beam had a chain F, which supported a piston G working within a vertically-disposed cylinder H. This cylinder was located directly above a boiler I, and a pipe J, with a valve therein, was designed to supply steam to the lower end of the cylinder. A water tank K was also mounted at a point above the cylinder, and this was supplied with water from the pump through a pipe L. Another pipe M from the tank conducted water from the tank to the bottom of the cylinder. The operation of the mechanism was as follows: The steam cock N, in the short pipe J, was opened to admit steam to the cylinder, below the piston. The stem of the steam cock also turned the cock in the water pipe M, so that during the time the steam was admitted the water was shut off. When the steam was admitted so that it filled the space below the piston, the cock N was turned to shut off the steam, and in shutting off the steam, water was also admitted. The injection of water at once condensed the steam within the cylinder so a partial vacuum was formed. It will be remembered that as steam expanded 1700 times, the condensation back into water made a very rarified area within the cylinder, and the result was that the piston was drawn down, thus raising both the weight D and also the pump rod E. This operation was repeated over and over, so long as the cock N was turned. The turning of the stem of this cock was performed manually,--that is, it had to be done by hand, and boys were usually employed for doing this. When, later on, some bright genius discovered that the valve could be turned by the machinery itself, it was regarded as a most wonderful advance. The discovery of this useful function has been attributed to Watt. Of this there is no conclusive proof. The great addition and improvements made by Watt, and which so greatly simplified and perfected the engine, were through the addition of a separate condenser and air pump, and on these improvements his fame rests. From the foregoing it will be seen that the weight D caused the piston to travel upwardly, and not the force of the steam, and the suction produced by the vacuum within the cylinder did the work of actuating the pump piston, so that it drew up the water. The Piston.--From this crude attempt to use steam came the next step, in which the steam was actually used to move the piston back and forth and thus actually do the work. In doing so the ponderous walking beam was dispensed with, and while, for a long period the pistons were vertically-placed, in time a single cylinder was used, and a crank employed to convert the reciprocating into a circular motion. Fig. 11 shows a simple diagram of a steam engine, so arranged that the operation of the valves may be readily understood. The cylinder A has a steam chest B, which contains therein a slide valve C to cover the ports at the ends of the cylinder. This figure shows the crank turning to the right, and the eccentric D on the engine shaft is so placed, that while the crank E is turning past the dead center, from 1 to 2, the slide valve C is moved to the position shown in Fig. 12, thereby covering port F and opening port G. [Illustration: _Fig. 11. Simple Valve Motion. First position._] [Illustration: _Fig. 12. Simple Valve Motion. Second position._] It will be seen that the slide valve is hollowed within, as at H, and that the exhaust port I leads from this hollowed portion while the live steam from the boiler enters through pipe J and fills the space K of the chest. In Fig. 11 live steam has been entering port F, thus driving the piston to the right. At the same time the exhaust steam at the right side of the piston is discharging through the port G and entering the hollow space within the slide valve. In Fig. 12 the conditions are reversed, and now live steam enters port G, and the exhaust passes out through port F. When the engine crank reaches the point 3, which is directly opposite 1, the reverse action takes place with the slide valve, and it is again moved to its original position, shown in Fig. 12. Importance of the Valve.--Every improvement which has been made in the engine has been directed to the valve. The importance of this should be fully understood. As the eccentric is constantly turning it is a difficult matter to so arrange the valve as to open or close it at the correct time, absolutely, and many devices have been resorted to to accomplish this. Expanding the Steam.--As all improvements were in the direction of economizing the use of steam, it was early appreciated that it would be a waste to permit the steam to enter the cylinder during the entire period that the engine traveled from end to end, so that the valve had to be constructed in such a way that while it would cut off the admission of steam at half or three-quarters stroke, the exhaust would remain on until the entire stroke was completed. Some engines do this with a fair degree of accuracy, but many of them were too complicated for general use. In the form of slide valve shown the pressure of the steam on the upper side, which is constant at all times, produces a great wearing action on its seat. This necessitated the designing of a type of valve which would have a firm bearing and be steam tight without grinding. Balanced Valve.--One of the inventions for this purpose is a valve so balanced by the steam pressure that but little wear results. This has been the subject of many patents. Another type also largely used in engines is known as the _oscillating_ valve, which is cylindrical or conical in its structure, and which revolves through less than a complete revolution in opening and closing the ports. Rotary Valve.--The rotary valve, which constantly turns, is employed where low pressures are used, but it is not effectual with high pressures. This is also cylindrical in its structure, and has one or more ports through it, which coincide with the ports through the walls of the engine, as it turns, and thus opens the port for admitting live steam and closing the discharge port at the same time or at a later period in its rotation. Engine Accessories.--While the steam engine is merely a device for utilizing the expansive force of steam, and thus push a cylinder back and forth, its successful operation, from the standpoint of economy, depends on a number of things, which are rarely ever heard of except by users and engineers. Many of these devices are understood only by those who have given the matter thorough study and application. To the layman, or the ordinary user, they are, apparently, worth but little consideration. They are the things, however, which have more than doubled the value of the steam engine as a motor. Efficiency of Engines.--When it is understood that with all the refinements referred to the actual efficiency of a steam engine is less than 30 per cent. some idea may be gained of the value which the various improvements have added to the motor. Efficiency refers to the relative amount of power which is obtained from the burning fuel. For instance, in burning petroleum about 14,000 heat units are developed from each pound. If this is used to evaporate water, and the steam therefrom drives an engine, less than 4200 heat units are actually utilized, the remaining 9800 heat units being lost in the transformation from the fuel to power. [Illustration: _Fig. 13. Effective pressure in a Cylinder._] The value of considering and providing for condensation, compression, superheating, re-heating, compounding, and radiation, and to properly arrange the clearance spaces, the steam jackets, the valve adjustments, the sizes of the ports and passages, and the governor, all form parts of the knowledge which must be gained and utilized. How Steam Acts in a Cylinder.--Reference has been made to the practice of cutting off steam before the piston has made a full stroke, and permitting the expansive power of the steam to drive the piston the rest of the way, needs some explanation. As stated in a preceding chapter the work done is estimated in foot pounds. For the purpose of more easily comprehending the manner in which the steam acts, and the value obtained by expansion, let us take a cylinder, such as is shown in Fig. 13, and assume that it has a stroke of four feet. Let the cylinder have a diameter of a little less than one foot, so that by using steam at fifty pounds pressure on every square inch of surface, we shall have a pressure of about 5000 pounds on the piston with live steam from the boiler. In the diagram the piston moves forwardly to the right from 0 to 1, which represents a distance of one foot, so that the full pressure of the steam of the boiler, representing 5000 pounds, is exerted on the piston. At 1 the steam is cut off, and the piston is now permitted to continue the stroke through the remaining three feet by the action of the steam within the cylinder, the expansive force alone being depended on. As the pressure of the steam within the cylinder is now much less and decreases as the piston moves along, we have taken a theoretical indication of the combined pressure at each six inch of the travel of the piston. The result is that we have the following figures, namely, 4000, 2700, 1750, 1000, 450 and 100. The sum of these figures is 10,000 pounds. The piston, in moving from 0 to 1, moved one foot, we will say, in one second of time, hence the work done by the direct boiler pressure was 5000 _foot pounds_; and since the piston was moved three feet more by the expansion of the steam only, after the steam pressure was shut off, the work done in the three seconds required to move the piston, was an additional 5000 foot pounds, making a total of 10,000 foot pounds for four seconds, 150,000 foot pounds per minute, or about 45 horse power. [Illustration: _Fig. 14. Indicating pressure Line._] This movement of the piston to the right, represented only a half revolution of the crank, and the same thing occurs when the piston moves back, to complete the entire revolution. Indicating the Engine.--We now come to the important part of engine testing, namely, to ascertain how much power we have obtained from the engine. To do this an indicator card must be furnished. A card to indicate the pressure, as we have shown it in the foregoing diagram would look like Fig. 14. The essential thing, however, is to learn how to take a card from a steam engine cylinder, and we shall attempt to make this plain, by a diagram of the mechanism so simplified as to be readily understood. [Illustration: _Fig. 15. Indicating the Engine._] In Fig. 15 we have shown a cylinder A, having within a piston B, and a steam inlet pipe C. Above the cylinder is a drum D, mounted on a vertical axis, and so geared up with the engine shaft that it makes one complete turn with each shaft revolution. A sheet of paper E, ruled with cross lines, is fixed around the drum. The cylinder A has a small vertical cylinder F connected therewith by a pipe A, and in this cylinder is a piston H, the stem I of which extends up alongside of the drum, and has a pointed or pencil J which presses against the paper E. Now, when the engine is set in motion the drum turns in unison with the engine shaft, and the pressure of the steam in the cylinder A, as it pushes piston B along, also pushes the piston H upwardly, so that the pencil point J traces a line on the ruled paper. It will be understood that a spring is arranged on the stem I in such a manner that it will always force the piston H downwardly against the pressure of the steam. Mean Efficiency.--We must now use a term which expresses the thing that is at the bottom of all calculations in determining how much power is developed. You will note that the pressure on the piston during the first foot of its movement was 10,000 pounds, but that from the point 1, Fig. 13, to the end of the cylinder, the pressure constantly decreased, so that the pressure was not a uniform one, but varied. Suppose we divide the cylinder into six inch spaces, as shown in Fig. 13, then the pressure of the steam at the end of each six inches will be the figures given at bottom of diagram, the sum total of which is 30,000, and the figures at the lower side show that there are eight factors. The figure 10,000 represents, of course, two six inch spaces in the first foot of travel. The result is, that, if we divide the sum total of the pressures at the eight points by 8, we will get 3750, as the mean pressure of the steam on the piston during the full stroke of the piston. In referring to the foot pounds in a previous paragraph, it was assumed that the piston moved along each foot in one second of time. That was done to simplify the statement concerning the use of foot pounds, and not to indicate the time that the piston actually travels. Calculating Horse Power.--We now have the first and most important factor in the problem,--that is, how much pressure is exerted against the piston at every half revolution of the crank shaft. The next factor to be determined is the distance that the piston travels in one minute of time. This must be calculated in feet. Let us assume that the engine turns the crank shaft at a speed of 50 revolutions a minute. As the piston travels 8 feet at each revolution, the total distance traveled is 400 feet. If, now, we have a constant pressure of 3750 pounds on the piston, and it moves along at the rate of 400 feet per minute, it is obvious that by multiplying these two together, we will get the figure which will indicate how many pounds the steam has lifted in that time. This figure is found to be 1,500,000, which means foot pounds, as we have by this means measured pressure by feet, or pounds lifted at each foot of the movement of the piston. As heretofore stated, we must now use the value of a horse power, so that we may measure the foot pounds by it. If we had a lot of wheat in bulk, and we wanted to determine how much we had, a bushel measure would be used. So with power. The measure, as we have explained, is 33,000, and 1,500,000 foot pounds should give as a result a little over 45 horse power. Condensation.--We now come to the refinements in engine construction,--that which adds so greatly to the economy of operation. The first of these is condensation. The first reciprocating engine depended on this to do the actual work. In this age it is depended upon simply as an aid. The first thing however that the engineer tries to do is to prevent condensation. This is done by jacketing the outside of the cylinder with some material which will prevent radiation of heat, or protect the steam within from being turned back into water by the cool air striking the outside of the cylinder. Atmospheric Pressure.--On the other hand, there is a time when condensation can be made available. The pressure of air on every square inch of surface is 14-3/4 pounds. When a piston moves along and steam is being exhausted from the cylinder, it must act against a pressure of 14-3/4 pounds on every square inch of its surface. The problem now is to get rid of that back pressure, and the old type engines give a hint how it may be done. Why not condense the steam discharged from the engine cylinder? In doing so a vacuum is produced on the exhaust side of the piston, at the same time a pressure is exerted on its other side. The Condenser.--Thus the condenser is brought into existence, as an aid. By jacketing condensation is prevented; it is fought as an enemy. It is also utilized as a friend. It is so with many of the forces of nature, where man for years vainly fought some principle, only to find, later on, that a friend is more valuable than a foe, and to utilize a material agency in nature is more economical than to fight it. Pre-heating.--The condenser does two things, both of which are of great value to the economical operation of the engine. For the purpose of rapidly converting the steam back into water as it issues from the engine cylinder, water is used. The steam from the cylinder has a temperature of 212 degrees and upwards, dependent on its pressure. Water, ordinarily, has a temperature of 70 degrees, or less, so that when the steam strikes a surface which is cooled down by the water, it is converted back into liquid form, but at a temperature less than boiling water. The water thus converted back from the steam gives up part of its heat to the water which cools the condenser, and the water from the condenser, as well as the water used to cool the condenser, are thus made available to be fed into the boiler, and thus assist in again converting it into a steam. The economy thus lies in helping the coal, or other fuel, do its work, or, to put it more specifically, it conserves the heat previously put out by the coal, and thus saves by using part of the heat over again. Superheaters.--Another refinement, and one which goes to the very essence of a heat motor, is the method of superheating the steam. This is a device located between the boiler and the engine, so that the steam, in its transit from the boiler to the engine, will be heated up to a high degree, and in the doing of which the pressure may be doubled, or wonderfully increased. This may be done in an economical manner in various ways, but the usual practice is to take advantage of the exhaust gases of the boiler, in the doing of which none of the heat is taken from the water in the boiler. The products of combustion escaping from the stacks of boilers vary. Sometimes the temperature will be 800 degrees and over, so that if pipes are placed within the path of the heated gases, and the supply steam from the boiler permitted to pass through them a large amount of heat is imparted to the steam from a source which is of no further use to the water being generated in the boiler. Compounding.--When reference was made to the condensation of steam as it issued from the boiler, no allusion was made to the pressure at which it emerged. If the cylinder was well jacketed, so that the amount of condensation in the cylinder was small, then the pressure would still be considerable at the exhaust. Or, the steam might be cut off before the piston had traveled very far at each stroke, in which case the exhaust would be very weak. In practice it has been found to be most economical to provide a high boiler pressure, and also to superheat the steam, but where it is not superheated, and a comparatively high boiler pressure is provided, compounding is resorted to. To compound steam means to use the exhaust to drive a piston. In such a case two cylinders are placed side by side, one, called the high pressure cylinder, being smaller than the low pressure cylinder, which takes the exhaust from the high pressure. The exhaust from the second, or low pressure cylinder may then be supplied to a condenser, and in that case the mechanism would be termed a compound condensing engine. If a condenser is not used, then it is simply a compound engine. Triple and Quadruple Expansion Engines.--Instead of using two cylinders, three, or four, are employed, each succeeding cylinder being larger than the last. As steam expands it loses its pressure, or, stated in another way, whenever it loses pressure it increases in volume. For that reason when steam enters the first cylinder at a pressure of say 250 pounds, it may exhaust therefrom into the next cylinder at a pressure of 175 pounds, with a corresponding increase in volume. To receive this increased volume, without causing a sensible back pressure on the first cylinder, the second cylinder must be larger in area than the first; in like manner when it issues from the exhaust of the second cylinder at 125 pounds pressure, there is again an increase in volume, and so on. [Illustration: _Fig. 16. Compound Engine._] Examine Fig. 16, which shows a pair of cylinders, A being the high, and B the low pressure cylinders, the exhausts of the high pressure being connected up with the inlets of the low pressure, as indicated by the pipes, C D. The diagram does not show the valve operations in detail, it being sufficient to explain that when the valve E in the pipe C is closed, the valve F, at the other end of the cylinders, in the pipe D, is closed. The same principle is employed in the triple and quadruple expansion engines, whereby the force of the steam at each exhaust is put to work immediately in the next cylinder, until it reaches such a low pressure that condensation is more effective than its pressure. The diagram, as given, is merely theoretical, and it shows the following factors: First: The diameter of each piston. Second: The area of each piston in square inches. [Illustration: Fig. 16a. Relative Piston Pressures.] Third: The steam pressure in each cylinder. Fourth: The piston pressure of each cylinder. It will be seen that an engine so arranged is able to get substantially the same pressure in each of the second, third and fourth cylinders, as in the first (see Fig. 16a), and by condensing the discharge from the fourth cylinder a most economical use of steam is provided for. The Steam Turbine.--We must now consider an entirely new use of steam as a motive power. Heretofore we have been considering steam as a matter of pressure only, in the development of power. It has been observed that when the pressure of steam decreases at the same temperature it is because it has a greater volume, or a greater volume results. [Illustration: Fig. 17. Changing Pressure into Velocity] When steam issues from the end of a pipe its velocity depends on its pressure. The higher the pressure the greater its velocity. The elastic character of steam is shown by its action when ejected from the end of a pipe, by the gradually enlarging area of the discharging column. In a reciprocating engine the power is derived from the pressure of the steam; in a turbine the power results from the impact force of the steam jet. Such being the case velocity in the movement of the steam is of first importance. Pressure and Velocity.--To show the effectiveness of velocity, as compared with pressure, examine Fig. 17. A is a pipe discharging steam at a pressure of 100 pounds. To hold the steam in the pipe would require a pressure of 100 pounds against the disk B, when held at 1, the first position. Suppose, now, the disk is moved away from the end of the pipe to position 2. The steam, in issuing forth, strikes the disk over a larger area, and in escaping it expands, with the result that its velocity from 1 to 2 is greater than the movement of the steam within the pipe that same distance. [Illustration: _Fig. 18. Reaction against Air._] [Illustration: _Fig. 19. Reaction against Surface._] The disk is now moved successively to positions 3, 4, 5, and so on. If we had a measuring device to determine the push against the disk at the various positions, it would be found that there is a point at some distance from the end of the pipe, at which the steam has the greatest striking force, which might be called the focal point. A blow pipe exhibits this same phase; the hottest point is not at the end of the pipe, but at an area some distance away, called the focal point of heat. The first feature of value, therefore, is to understand that pressure can be converted into velocity, and that to get a great impact force, the steam must be made to strike the hardest and most effective blow. When a jet of steam strikes a surface it is diverted or it glances in a direction opposite the angle at which it strikes the object. In directing a jet against the blades of a turbine it is impossible to make it strike squarely against the surface. [Illustration: Fig. 20. Turbine Straight Blades.] Let us assume that a wheel A, Fig. 20, has a set of blades B, and a steam jet is directed against it by the pipe C. It will be seen that after the first impact the steam is forced across the blades, and no further force is transferred to them. Form of Blades.--The blades are therefore so curved, that the steam after the first impact cannot freely pass along the blade, as it does on a straight blade, but imparts on every element of the curved-back blade, thereby giving up continually part of its speed to the blade. This is clearly shown in Fig. 21, where the pipe D ejects the stream of steam against the concaved blades E. Many modifications have been made in the shapes of these blades, all designed to take advantage of this action. [Illustration: _Fig. 21. Curved Blades._] [Illustration: _Fig. 22. Compound Turbine._] Compounding the Jet.--We may extend the advantages gained by this form of blades, and diverting the course of the jet, so that it will be directed through a series of wheels, each of which will get the benefit of the moving mass from the pipes. Such a structure is shown in Fig. 22, in which three bladed wheels A, B, C, are caused to rotate, a set of stationary blades D, E, being placed between the three moving wheels, but the stationary blades are disposed in reverse directions. When the steam from pipes F, F, impinges against the blades of the first wheel A, it is directed by the stationary blade D to the next wheel B, and from the stationary blade E to the blades of the next wheel C, thus, in a manner somewhat similar to the compounding effect of the steam engine, utilizes the pressure which is not used at the first impulse. CHAPTER IV FUELS AND COMBUSTION All fuels must be put into a gaseous state before they will burn. This is true of coal as well as of hydro-carbon oils. Neither coal nor petroleum will burn in its native state, without the addition of oxygen. This is absolutely necessary to support combustion. Burning is caused by the chemical union of oxygen with such substances as will burn. This burning process may be slow, and extend over a period of years, or it may be instantaneous, in which latter case the expansion of the heated gases is so great as to cause an explosion. When a sufficient amount of oxygen has been mixed with a fuel to permit it to burn, a high temperature is necessary to cause the immediate burning of the entire mass. If such a temperature is not present the course of combustion is not arrested, but it will, on its own account, start to oxydize, and eventually be reduced to the same condition that would take place if exploded by means of a flame. Solid Fuels.--The great fuels in nature are carbon and hydrogen, carbon being the substance most widely known and depended upon. Hard coal, for instance, is composed almost wholly of carbon; whereas soft coal has a considerable quantity of hydrogen. As coal was formed by wood, which, through long process of time became carbonized, it contains considerable foreign matter which will not burn, forming ash. Liquid Fuels.--The volatile oils, however, have very little non-combustible matter. Ordinary petroleum contains about 80 per cent, of carbon, and from 12 to 15 per cent. of hydrogen, the residue being foreign matter, all more or less susceptible of being consumed at high temperatures. Combustion.--The term _combustion_, in its general sense, means the act of burning; but in a larger and more correct application it refers to that change which takes place in matter when oxygen unites with it. Oxygen is a wonderful element, and will unite with all known substances, unlike all other elements in this respect. It may take years for it to form a complete unity. Thus, wood, in time, will crumble, or rot, as it is called. This is a slow process of combustion, brought about without applying heat to it, the change taking place in a gradual way, because oxygen unites with only a small portion of the wood. Oxidation.--Iron will rust. This is another instance of combustion, called oxidation. When oxygen unites with a substance it may produce an acid, or an alkali, or a neutral compound. When wood is burned it produces an ash, and this ash contains a large amount of potash, or lye, which is an alkali, or a salt. So when other substances are burnt the result may be an acid, like sulphur, or it may be unlike either acid or the alkali. The unity of oxygen with the food in the body is another instance of oxidation, which produces and maintains the heat necessary for existence. Carbon or hydrogen, as a fuel, are inert without oxygen, so that in considering the evolution of a force which is dependent on heat, we should know something of its nature, thereby enabling us to utilize it to the best advantage. The Hydro-carbon Gases.--If petroleum, or gasoline, should be put into the form of a gas, and as such be confined in a receiver, without adding any oxygen, it would be impossible to ignite it. The character of the material is such that it would instantaneously extinguish any flame. Now, to make a burning mixture, at least three parts of oxygen must be mixed with one of the hydro-carbon, before it is combustible. Oxygen and Atmosphere.--The atmosphere is not oxygen. Only one-fifth of common air is oxygen, the residue being, principally, nitrogen, which is not a fuel. To produce the proper aëration, therefore, at least fifteen parts of air must be mixed with one part of hydro-carbon gas. The term _hydro-carbon_ is applied to petroleum, and its products, because the elements carbon and hydrogen make up the largest part of the oil, whereas this is not the case with most of the other oils. We are now dealing with a fuel such as is needed in _Internal Combustion Engines_, and it is well to know some of the problems involved in the use of the fuel, as this will give a better understanding of the structure of the devices which handle and evolve the gases, and properly burn them within the engine. Vaporizing Fuel.--As the pure liquid will not burn in that state the first essential is to put it into a gaseous form, or to generate a vapor from it. The vapor thus made is not a gas, in the true sense of that term, but it is composed of minute globules of finely-divided particles of oil. Nearly all liquids will vaporize if permitted to come into contact with air. The greater the surface exposed to air the more rapidly will it turn into a vapor. By forcibly ejecting the liquid from a pipe or spraying device, and mingling air with it, evaporation is facilitated, and at the same time the proper admixture of air is provided to make a combustible substance the moment sufficient heat is brought into contact with it. This is what actually takes place in a gasoline engine, and all the mechanism is built with this end in view. It has been the universal practice to make an explosive mixture of this character, and then ignite it by means of an electric spark, but it is now known that such a fuel can be exploded by pressure, and this needs some explanation. Explosion by Compression.--The study of the compressibility of gases is an interesting one. As we have previously stated, the atoms, comprising the gases, are constantly moving among themselves with great rapidity, so that they bombard the sides of the receiver in which they are confined, and also contact with each other in their restless movements. When compression takes place the speed of the movements of the atoms is greatly accelerated, the friction of their movements is increased, and heat is evolved. As the pressure becomes greater the heat increases until it is of such intensity that the gas ignites, and an explosion follows. How Compression Heats.--The theory of the compressibility of gases may be stated as follows: Let us assume that the temperature of the air is 70 degrees Fahrenheit, and we have a receiver which holds two cubic feet of this air. If the contained air is now compressed to a volume of one cubic foot, the temperature of two cubic feet is compressed into one cubic foot, and there is now 140 degrees of heat within the receiver. If this cubic foot of air is again compressed to half its volume, the temperature is correspondingly increased. While this it not absolutely true in practice, owing to the immense loss caused by radiation, still, it will enable the mind to grasp the significance of compression, when the subject of heat is concerned. Elasticity of Gases.--The great elasticity of gases, and the perfected mechanical devices for compressing the same, afford means whereby ten or twenty atmospheres can be forced into a receiver, and thereby produce pressures of several hundred pounds, which would mean sufficiently high temperatures to ignite oils having the higher flash point. Advantages of Compression.--The compression system permits of the introduction of a larger quantity of fuel than is usually drawn into the cylinder, and thereby a greater and more efficient action is produced on the piston of the engine on account of quicker combustion and therefore higher gas pressures. The compression, however, rarely if ever exceeds six atmospheres or about 90 pounds per square inch. _The Necessity of Compression._--There are two reasons why compression is necessary before igniting it. First, because it is essential to put sufficient gas in the cylinder to make the engine efficient. To illustrate: Suppose we have a cylinder capable of drawing in 150 cubic inches of gas, and this is compressed down to 25 cubic inches, the space then occupied by the gas would represent what is called the clearance space at the head of the cylinder. To compress it to a greater degree the clearance space might be made smaller, which could be done in several ways, but whether the gas thus drawn in should be compressed to 30, or 25, or even 10 cubic inches, it is obvious that there would be no more fuel in the cylinder in one case than in the other. As however the mean effective pressure, which determines the efficiency of the motor, increases with the compression pressure, the latter should be as high as possible, but not so high that premature explosion takes place owing to the heat created by compression. Second: The more perfect the mixture of the vaporized product with the air, the more vigorous will be the explosion. The downward movement of the piston draws in the charge of air and sprayed jet of gasoline, and the only time for mixing it is during the period that it travels from the carbureter through the pipes and manifold to the cylinder. Having in mind the statement formerly made that compression causes a more rapid movement of the molecules of a gas, it is obvious that the upward movement of the piston, in the act of compressing the gas has a more positive action in causing an intimate mixture of the hydro-carbon gases than took place when the gases were traveling through the pipes on their way to the cylinder. CHAPTER V THE INTERNAL COMBUSTION ENGINE It will be observed that in a steam engine the heat is developed outside of the cylinders and the latter used solely for the purpose of taking the steam and utilizing it, by causing its expansion to push a piston to and fro. We shall now consider that type of motor which creates the heat within the cylinder itself and causes an expansion which is at once used and discharged at the reciprocating motion of the piston. The original method of utilizing what is called _Internal combustion_ Motors, was to employ a fixed gas. A _fixed_ gas is one which will remain permanently in that condition, unlike a vapor made from gasoline. The difference may be explained as follows: Fixed Gases.--If the vapor of gasoline, or petroleum, is subjected to a high heat, upwards of 1500 degrees, it is so changed chemically, that it will not again return to a liquid state. This is called _fixing_ it. Gas is made in that way from the vapor of coal, and fixed, producing what is called illuminating gas. Although the temperature of fixing it is fully three times greater than is required to explode it, the fact that it is heated in closed retorts, and oxygen is prevented from mixing with it, prevents it from burning, or exploding. Gas Engines.--Such a gas has been used for many years in engines which were usually of the horizontal type, and were made exceedingly heavy and cumbrous, and provided with enormous fly wheels. Gases thus made are not as rich as those generated direct from the hydro-carbon fuels, because, being usually made from coal they did not have a large percentage of hydrogen. Energy of Carbon and Hydrogen.--When a pound of carbon is burned, it develops 14,500 heat units, and a pound of hydrogen over 52,000 heat units. Assuming that 85 per cent. of a pound of petroleum is carbon, and 15 per cent. is hydrogen, the heat units of the carbon would be 12,225, and the heat units of the 15 per cent. of hydrogen would be 12,800. The combined value is, therefore, 25,025, which is almost double that of coal gas. This fact makes the gasoline engine so much more efficient, and for the same horse power the cylinders can be made smaller, and the whole structure much lighter in every way. Gasoline motors are of two types, one in which an explosion takes place at every revolution of the crank, called the _two-cycle_, and the other the _four-cycle_, in which the explosion occurs at every other turn of the crank. The terms _two-cycle_ is derived from the movement of the piston, as that moves downwardly during the period when the crank is making a half turn, and returns in its upward stroke when the crank completes the turn, or that two half turns of the crankshaft complete the cycle. Four-cycle engines have two such complete movements at each impulse, or require four half turns of the crankshaft to complete the cycle. The Two-Cycle Type.--In order to clearly distinguish between this and the four-cycle, it would be well to examine the diagram, Fig. 23. For a clearer understanding the drawing is explained in detail. The cylinder A, within which the piston works, has a removable cap B, and at its lower end a removable crank case C. The case is designed to entirely close the lower end of the cylinder so that it is air tight, for reasons which will be explained. The outer jacket, or casing D, at the upper end of the cylinder, is designed to provide a space E, for the circulation of water, to cool the cylinder during its working period. The crankshaft F passes through the crank case, the latter having suitable bearings G for taking care of the wear. [Illustration: _Fig. 23. Two-cycle. First Position._] The piston H is connected up with the rod I, the latter being hinged at a point within the piston, as shown. The crank case has an inlet port, provided with a valve which opens inwardly, so that when the piston moves upwardly the valve will open and air will be drawn into the crank case and space below the piston. At one side is a vertical duct K, which extends from a point directly above the crank case, to such a position that when the piston is at its lowest point gas can be discharged into the space above the piston. On the opposite side of the cylinder, and a little above the inlet port of the duct K, is a discharge port M. The inlet port and the discharge port, thus described, are both above the lower end of the piston when it is at its highest point. The spark plug is shown at N. On the upper end of the piston, and close to the side wall through which the inlet port K is formed, is an upwardly-projecting deflecting plate O, the uses of which will be explained in the description of its operation. Fig. 23 shows the piston at its highest point, and we will now assume that ignition takes place, thus driving the piston downwardly until the upper end of the piston has fully uncovered the discharge port M, as shown in Fig. 24. This permits the exhaust to commence, and as the piston proceeds down still further, so as to uncover the inlet port K, the gas, which at the down stroke has been compressed in the space below the piston, rushes in, and as it strikes the deflecting plate O, is caused to flow upwardly, and thus helps to drive out the burnt gases remaining at the upper end of the cylinder. [Illustration: Two-cycle Engine. Fig. 24. Second position. Fig. 25. Third position.] This action is called scavenging the cylinder, and the efficiency of this type of engine is largely due to the manner in which this is done. It is obvious that more or less of the unburnt gases will remain, or that some of the unburnt carbureted air will pass out at each discharge, and thus, in either case, detract from the power of the subsequent explosion. As the piston now moves upwardly to complete the cycle, the piston closes both of the ports, thus confining the gas which was previously partly compressed, and as the piston proceeds the gas is still further compressed until the piston again reaches the upward limit of its motion. Advantages of the Two-Cycle Engine.--This kind of engine has several distinct advantages. It has less weight than the four-cycle; it gives double the number of impulses for a given number of revolutions of the crankshaft; and it dispenses with valves, springs, cam-shafts, stems and push rods. More or less danger, however, attends the operation of a two-cycle engine, principally from the fact that an explosive mixture in a partially compressed condition is forced into the space which the instant before was occupied by a flame, and it is only because the expansion of the burst gases at the previous charge has its temperature decreased so far below the explosion point, that the fresh gas is not ignited, although there have been occasions when explosions have taken place during the upstroke. The Four-Cycle Engine.--The most approved type is that which is known as the _four-cycle_. This will also be fully diagrammed so as to enable us to point out the distinctive difference. [Illustration: Four-cycle Engine. Fig. 26. First position. Fig. 27. Second position.] Figs. 26 and 27 show sections of a typical four-cycle engine, in which the inlet and the exhaust valves are mechanically operated. The cylinder A is either cast with or separate from the crank case B, and has a removable head C. The upper end of the cylinder has a water space formed by the jacket D. The inlet port E and the discharge port F are both at the upper end of the cylinder. The crank shaft G passes horizontally through the crank case, and it is not necessary, as in the case of the two-cycle-engine, to have the case closed tight. The piston H is attached to the connecting rod I, which is coupled to the crank, as shown. The crank shaft has a small gear J, which meshes with two gears of double size on opposite sides of the crank shaft, one of the gears K, being designed to carry the cam L for actuating the stem L´, which opens the valve M in the port that admits the carbureted air. [Illustration: Four-cycle Engine. Fig. 28. Third position. Fig. 29. Fourth position.] The other large gear N is mounted on a shaft which carries a cam O that engages the lower end of a push rod P, to open the valve Q in the discharge port F. It should be observed that the stems L´, P, are made in two parts, with interposing springs R, so the valves may be firmly seated when the stems drop from the cams. The spark plug S is located in the head, close to the inlet port. The character of the igniting system is immaterial, as the object of the present diagrams is to show the cycle and method of operating the engine at each explosion, and to fully illustrate the manner in which it is distinguished from the two-cycle type. A fly wheel is necessary in this as in the other type, and in practice the two gear wheels, K, N, are placed outside of the case B, and only the small gear, and the cam shafts, on which the cams are mounted, are within the case. The operation is as follows: In Fig. 26 the piston is shown in a position about to commence its downward movement, and we will assume that the ignition has just taken place. Both valves M, Q, are closed, as it will be noticed that the cams L, O, are not in contact with the lower ends of the push rods. The explosion drives the piston down to the position shown in Fig. 27, when the cam O begins to raise the stem P, and thus opens the discharge valve Q, permitting the burnt gases to escape as the piston travels upwardly to the position shown in Fig. 28. At this position the valve Q closes, and the cam L opens the inlet valve M, so that as the piston descends the second revolution, the carbureted air is drawn in until the crank has just turned at its lowest limit of movement, as shown in Fig. 29. The upward stroke of the piston now performs the work of compressing the carbureted air in the cylinder, and it is ready for the ignition the moment it again reaches the position shown in Fig. 26. The Four Cycles.--The four distinct operations thus performed are as follows: First, the explosion, and downward movement of the piston. Second, the upward movement of the piston, and the discharge of the burnt gases. Third, the down stroke of the piston, and the indrawing of a fresh charge of carbureted air. Fourth, the upward movement of the piston, and the compression of the charge of carbureted air. The order of the engine performance may be designated as follows: 1. Impulse. 2. Exhaust. 3. Admission. 4. Compression. Ignition Point.--While the point of ignition, shown in the foregoing diagrams, represents them as taking place after the crank has passed the dead center, the firing, in practice, is so adjusted that the spark flashes before the crank turns past the dead center. The reason for this will be apparent on a little reflection. As the crank turns very rapidly the spark should be _advanced_, as it is called, because it takes an interval of time for the spark to take effect and start the explosion. If the sparking did not take place until the crank had actually passed the dead center, the full effect of the compression and subsequent explosion pressure would not be had. Advantage of the Four-Cycle Type.--The most marked advantage in the four-cycle type is its efficiency. As it has one full stroke within which to exhaust the burnt gases, the cylinder is in a proper condition to receive a full value of the incoming charge, and there is no liability of any of the unburnt gases escaping during the exhaust from the previous explosion. The next important advantage of this type is in the fact that it can be operated at a higher speed than the two-cycle type, and this is a great advantage, notwithstanding the less number of impulses in the four-cycle type. The Loss in Power.--The great disadvantage in all engines of this class is the great loss resulting from their action. The explosion which takes place raises the temperature to fully 2000 degrees of heat, and unless some provision is made to keep the cylinder down to a much lower temperature the engine would soon be useless. High temperatures of this character absolutely prevent lubrication, a thing which is necessary to insure proper working. For this reason a water jacket is provided, although there are engines which are cooled by the action of air. In any event, the heat imparted to the cylinder is carried away and cannot be used effectively, so that fully one-half of the power is dissipated in this direction alone. The next most serious loss is in the escape of heat through the burnt gases, which amounts to seventeen per cent. If the expansive force of the burnt gases at the time of ignition is 250 pounds per square inch, and at the time of the discharge it is fifty pounds, only four-fifths of its power is effectively used. As, however, the discharge is against the air pressure of nearly fifteen pounds per square inch, it is obvious that thirty-five pounds per inch is driven away and lost. The third loss is by conduction and radiation, which amounts to fifteen per cent. or more, so that the total loss from all sources is about eighty-four per cent., leaving not more than sixteen per cent. of the value of the fuel which is converted into power. Engine Construction.--In the construction of engines the utmost care should be exercised in making the various parts. The particular features which require special care are the valves, which should be ground to fit tightly, the proper fitting of the piston rings, crank shaft and connecting rod bearings as well as the accurate relining of these bearings. [Illustration: Fig. 30. Valve Grinding.] Valve Grinding.--Fig. 30 shows a valve and valve seat. The valve has usually a cross groove so that a screw driver in a drill stock may be used to turn it and to exert the proper pressure. The finest emery powder and a first class quality of oil should be used. The valve is seated and after the oil and emery powder are applied the drill stock is used to turn the valve. After twenty or thirty turns, wipe off the parts and examine the contact edges, to see whether the entire surfaces are bright, which will indicate that the valve fits true on its seat. Never overgrind. This is entirely unnecessary. It is better also to rock the crank of the drill stock back and forth, instead of turning it in one direction only. The Crank Shaft.--The crank shaft is the most difficult part of the engine to build. It is usually made of a single forging of special steel and the cranks and bearings are turned out of this, requiring the utmost care. Formerly these were subject to breakage, but improved methods have eliminated all danger in this direction. The Cams.--Notwithstanding the ends of the push rods are provided with rollers to make the contact with the cams, the latter will wear, and in doing so they will open the valves too late. The slightest wear will make considerable difference in the inlet valve, and it requires care and attention for this reason, in properly designing the cams, so that wear will be brought to a minimum. CHAPTER VI CARBURETERS A carbureter is a device which receives and mixes gasoline and air in proper proportions, and in which a vapor is formed for gasoline engines. The product of the carbureter is a mixture of gasoline vapor and air, not a gas. A gas, as explained, is of such a character that it remains fixed and will not stratify or condense. Functions of a Carbureter.--The function of a carbureter is to supply air and gasoline by means of its adjustable features so as to make the best mixture. The proportions of air and gasoline will vary, but generally the average is fifteen parts of air to one of gasoline vapor. If there is too much gasoline, proportionately, a waste of fuel results, as a great amount of soot is formed under those conditions. If there is an excess of air the mixture, when ignited, will not have such a high temperature, hence the expansive force is less, and the result is a decrease of power. While it is possible to get a rapid evaporation from gasoline by heating it, experience has shown that it is more economical to keep the gasoline cool, or at ordinary temperatures, provided the carbureter is properly constructed, because the vapor, if heated, when drawn into the engine, will be unduly expanded, and less fuel in that case is drawn in at each charge, and less power results. Rich Mixtures.--There are conditions under which rich mixtures are advantageous. This is a mixture in which there is a larger percentage of gasoline than is necessary for instantaneous combustion. For ordinary uses such a mixture would not be economical. At low speeds, however, or when carrying heavy loads, it is desirable, for the reasons that at a slow speed the combustion is slower. Rich mixtures are objectionable at high speeds because, as the combustion is slow, incomplete combustion within the power stroke results, the temperature of the gas at the end of the stroke is very high, and this will seriously affect the exhaust valves. Furthermore, there is likelihood of the gas continuing to burn after it is discharged from the cylinder. Lean Mixtures.--Such a mixture is one which has a less amount of gasoline than is necessary to make a perfectly explosive compound. For high speeds a lean mixture is desirable, principally because it burns more rapidly than a rich mixture. Types of Carbureters.--There are two distinct types of carbureters, one which sprays the gasoline into a conduit through which air is passing, and the other in which a large surface of gasoline is placed in the path of the moving air column, which was originally used, but has been absolutely replaced by the jet carbureters on account of their better control features. It will be remembered that reference was made to the manner in which vaporization takes place, this term being used to designate that tendency of all liquids to change into a gaseous state. All carbureters are designed with the object of mechanically presenting the largest possible area of oil to the air, so that the latter will become impregnated with the vapor. The Sprayer.--The best known type depends on dividing up the gasoline into fine globules, by ejecting it from a small pipe or jet. The spray thus formed is caught by the air column produced by the suction of the engine pistons, and during its passage through the throttle and the manifold, is in condition where a fair mixture of air and vapor is formed, which will readily ignite. The Surface Type.--This form of carbureter provides a pool of gasoline with a large surface, within the shell, so arranged that as the air is drawn past the pool it must come into contact with the oil, and thus take up the necessary quantity of evaporated gasoline for charging the air. The _surface_ type has not been used to a large extent, but the _sprayer_ is universally used, and of this kind there are many examples of construction, each having some particular merit. Governing a Carbureter.--It is a curious thing that one carbureter will work admirably with one engine, and be entirely useless in another. This is due to several factors, both in the engine design and in the carbureter itself. The quality of mixture that an engine will take depends on its speed. The suction of the pistons depends on the speed of the engine. If, at ordinary speed the carbureter gives a proper mixture, the throats and passages through the pipes and manifold, as well as the valve which discharges the gasoline, may be in a prime condition to do good work; but when the pistons work at double speed the inrush of air may not carry with it the proper amount of fuel; or, under those conditions, the air may receive too great an amount of gasoline, proportionally. The latter is usually the case, hence provision must be made for such a contingency, and we shall therefore take up the various features essential in the construction of the carbureter, so as to show what steps have been taken to meet the problems arising from varying speeds, differences in the character of the fuel, regulating the inflow and mixture of gasoline and air, and adjustments. [Illustration: _Fig. 31. Carbureter._] So many different types of carbureters have been devised, that it is difficult to select one which typifies all the best elements of construction. In Fig. 31 we have shown a well known construction, and which will illustrate the features of the sprayer type to good advantage. The body of the device, represented by A, has a flange by means of which it is secured to the pipe which carries the carbureted air to the engine. The lower end of this tubular body is contracted, as shown at B, so as to form what is called a venturi tube. Exteriorly this contracted tube is threaded, as shown at C, so as to receive thereon a threaded body D, the lower end of the body having an enlarged disk-head E, integral therewith, and an upwardly-projecting annular flange F is formed around this disk to receive and hold a cylinder G, which constitutes the float and fuel chamber. The upper end of this cylinder rests against a seat cast with the body A, and packing rings are placed at the ends of the cylinder to prevent the oil from leaking out. Within the tubular body D is a vertical tube H, integral with the disk head E, and oil is supplied to this tube through ducts I, which communicate with the chamber within the reservoir G. A drain cock is at the lower end of this tube, and an adjustable cap K screws on the tubular stem of the drain tube, around which air is admitted, the air passing upwardly through vertical ducts L, as shown, and thus mixes with air at the contracted part of the venturi tube. A ring-like float N is placed within the glass chamber, and this is adapted to engage with the inner end of a lever N´, this lever being pivoted at O, within a side extension P of the carbureter shell. The inner end of this lever has a link hinged thereto, the lower end of which serves as a needle valve to close the ejecting orifice of the tube L. The outer end of the lever N´ engages a shoulder on a vertically-disposed needle valve Q, which has its point in the inlet opening of the pipe R, through which gasoline is supplied to the glass chamber. A spring T serves to keep the valve stem normally on its seat. Directly opposite this chambered extension P is another extension U, also cast with the shell, through which is a vertical stem V. This stem carries a downwardly-opening valve W, that seats against a plug, and a spring X below the valve, serves to keep it against its seat, unless there should be an extraordinarily heavy pull or suction. This is the auxiliary air inlet, and the lower spring is actuated only when the engine is running at moderate speeds, but when running at high speed and an additional quantity of air is required the upper spring Y is compressed, and thus a much greater quantity of air is allowed to pass in and mingle with the spray at the throttle valve Z. The throttle valve is mounted in the discharge opening, and is controlled by a lever on the outside of the carbureter. The device operates as follows: Primary air enters the opening between the cup K and the disk-head E, passing up into the space around the oil tube H. As the spring T, around the needle valve Q, draws up the valve from its seat, oil is permitted to flow in through the duct R and fill the chamber, until the float engages with the inner end of the lever N, and raises it, thus uncovering the ejecting end of the tube H, and at the same time closing the inlet tube R. The suction from the engine then draws air through the primary duct, as stated, and also an additional quantity through the secondary source, by way of the valve W, this valve being so regulated as to supply the requisite quantity. The auxiliary air source serves the purpose that means should be provided to supply more than the ordinary amount of air, when running at high speeds. From the foregoing it will be observed that a carbureter must be so constructed that it will perform a variety of work. These are: First, Automatic means for filling the float chamber when the gasoline goes below a certain level. Second, Cutting off the supply of gasoline. Third, Providing a primary supply of gasoline for spraying purposes. Fourth, Furnishing an auxiliary air supply. Fifth, Throttling means in the discharge opening. It is thus a most wonderful contrivance, and considering that all the elements necessary to make it work satisfactorily are provided with adjustable devices, it may be seen that to make it perform correctly requires a perfect understanding of its various features. Requirements in a Carbureter.--In view of the foregoing it might be well to know how to select a carbureter that is ideal in its operation. First. The adjustment of the auxiliary valve should be of such a character that at the slowest speed the valve should not be lifted from its seat. Second. It must be so arranged that it is not difficult to change the relative amount of air and gasoline. Third. The floating chamber should be so arranged that the float will act on the lever which lifts the valve of the injecting pipe, even though the carbureter body should be tilted at an angle. This is particularly important when the carbureter is used in automobiles. Fourth. The valves should be in such position that they are readily accessible for cleaning or for examination. Fifth. The float should be so arranged that it is adjustable with reference to the lever that it contacts with. Sixth. A gauze strainer should be placed at the gasoline inlet, and it is also advisable to have a similar strainer above the mixing chamber, beyond the throttle. Seventh. There should be no pockets at any point in the body to hold the gasoline which might condense. Eighth. The body of the carbureter should be so constructed that every part is easily accessible, and draining means provided so that every particle of gasoline can be withdrawn. Ninth. Means for heating it, in case of cold weather. Size of the Carbureter.--The proper size of a carbureter for an engine has been the subject of considerable discussion and experimenting. If its passages are too large, difficulty will be experienced in starting the engine, because the pulling draft through the primary will not be sufficient to make a spray that will unite with the air. A carbureter too large will only waste fuel, even after the engine has been cranked up so it will start. If the carbureter is too small the engine will not develop its required output of power. While it might work satisfactorily at low speeds it would be entirely inefficient at high speeds. Rule for Size of Carbureter.--In all cases the valve opening and cylinder capacity in the engine should determine this. The size of the opening of the carbureter outlet should be the same as that of the engine valve, which is also the case where the carbureter supplies a multi-cylinder, as there is only one valve open at the same time. It was formerly the custom to use a carbureter for each cylinder but the practice has been abandoned, because it is obvious that a single carbureter will, owing to the continuous suction, supply a mixture of more nearly uniform character than two or more, even though they should supply the mixture to a common manifold. The Throttle.--Much of the economy in running an engine depends on the manipulation of the throttle. As an example, with a certain motor and carbureter it will be found that for maximum speed the throttle should be open about one-eighth of the way. The proper way, in starting the engine, is to open the throttle fully half way, and to retard the spark. As soon as the engine begins to run properly, the spark is advanced and the throttle closed down to the required point. The engine speed may always be maintained by the throttle under a constant varying load, by adjusting the throttle valve. A rich mixture may be obtained by throttling the primary air supply. The throttle may also be a most effective means of economizing fuel when the engine has a first class sparking device, as in that case the throttle can be closed down to provide a very small opening. Flooding.--One of the most prevalent troubles in carbureters is the liability to flood. This is usually caused by foreign matter getting under or in the float valve, so that it will not properly seat. Sometimes the mere moving of the float will dislodge the particle. Another cause of flooding is due, frequently, to an improperly-arranged float, which, when the engine is inclined, will prevent improper seating of the valve, and flooding follows. The greatest care should be exercised in seeing that the gasoline supply is free from all impurities when it is poured into the tank. To strain it is the best precaution, and it pays to be particular in this respect. It is surprising to see the smallest speck, either stop the flow entirely, or produce an overflow, either of which will cause a world of trouble. Water is another element which has no place in a carbureter. An indication of this is the irregular movement of the engine. The only remedy is to stop and drain the carbureter. A few drops may cause all the trouble. [Illustration: _Fig. 32. Carbureter._] Types of Carbureters.--In Fig. 32 we show another type of carbureter, which is simple in construction, and has many desirable features. The cylindrical body of the carbureter, A, has a downwardly-projecting globular extension B, at one side of which is a flange C to secure it to the pipe, and through this is the discharge opening D. This globular extension serves as the mixing chamber. Within the cylindrical shell is an upwardly-projecting circularly-formed extension E, and the top or cap F of the cylindrical body A has a downwardly-projecting cylindrical rim G which overlaps the lower circular extension E, and it is so constructed that a very thin annular slit H is thus formed between the two parts, through which fuel oil flows from the float chamber I into the space around the central tube J which passes down through the two circular extensions E, G. This central tube J is designed for the auxiliary air supply. It extends down to the globular base B, and has a valve K seated against its end. The stem L of the valve is vertically-movable within an adjustable stem M, and a helical spring N, capable of having its tension adjusted by the stem M, bears upwardly against the valve so as to keep it normally against the lower end of the tube J. The auxiliary air, therefore, passes down centrally through the tube J, while the primary air supply passes through openings O, surrounding the tube J, downwardly past the slitted opening H, and thence to the discharge port D. Surrounding the tubular projections E, G, and within the float chamber I, is the float P. This is designed to strike the bifurcated ends of a lever Q, which is hinged near its outer end, as at R, and has its short projecting end resting beneath the collar of a vertical needle valve S. This needle valve is vertically placed within a chambered extension T at the side of the shell A, and its lower end rests within the opening of the inlet U which supplies the gasoline to the chamber I. The upper end of the valve stem passes through a plug V, through which is a vent hole W. A spring X is used between the plug and the collar on the lower end of the needle valve, so that the valve is kept on its seat thereby, unless the gasoline in the chamber should fall so low as to cause the float to rest on the inner end of the lever Q, when the needle valve would be unseated thereby. All the parts of this device seem to be accessible, and it is presented as an example of construction that seems to meet pretty nearly all of the ideal requirements of a device for furnishing a perfect admixture. Surface Carbureter.--This type of carbureter also requires a float but does not have secondary air inlet mechanism. It has one striking advantage over the sprayer system, in the particular that the suction of the engine is not depended upon to draw the gasoline from the float chamber. It is much more sensitive to adjustment in the float level and needle valve than the other type. [Illustration: _Fig. 33. Surface Carbureter._] The diagram, Fig. 33, shows a body A, somewhat bowl-shaped, with a chambered extension, B, at one side, at the lower side of which is the fuel inlet duct C. Directly above this duct the upper wall of the extension has a plug D, the lower end of which carries therein the upper end of a vertically-movable needle valve, E, the lower end of the valve resting within the duct C. A float F within the bowl-shaped body is secured at one side to a lever G, which is hinged at a point near the needle valve E, and the short end of this lever connects with this needle valve in such a manner that as the float moves upwardly the valve is seated, and when the level of the fuel oil falls below a certain point the needle is lifted from its seat, and oil is permitted to flow into the float chamber. The cap H of the float chamber has cast therewith a U-shaped tube, the inlet end I being horizontally-disposed, while the discharge end J is vertical. Directly above the lowest part of the bend in this tube, the vertical dimension of the tube is contracted by a downwardly-projecting wall K, so as to form a narrow throat L. Below this contracted point, the U-shaped tube has integral therewith a downwardly-projecting stem M, the lower end of which passes through an opening in the float chamber, and is threaded, so as to receive a nut, by means of which the cap H may be firmly fixed to the float chamber. This stem M has a vertical duct N, which communicates with the float chamber, and is provided with a drain plug O. Alongside of this duct is a tube P which extends up into the U-shaped tube and is open at its lower end so that the level of the gasoline within the bent tube cannot extend above the end of this drain tube P. An adjustable valve stem Q passes through one side of the bent tube, the lower end being pointed and adapted to regulate the inflow of gasoline through the duct N, and into the U-shaped tube. A throttle valve R is placed in the discharge end of the U-shaped tube, which is susceptible of regulation by means of a lever S. The diagram shows the gasoline within the U-shaped tube, so that it is on a level with the gasoline in the float chamber. In operation a sufficient amount of gasoline is permitted to enter the float chamber so that a pool is formed in the bottom of the U-shaped tube. When suction takes place the air rushes through the tube, at I, down beneath the wall K, and in doing so it sweeps past the surface of the pool at that point, absorbing a greater or less amount of the vapor. In order to adjust the device so that a smaller amount of the liquid fuel will be exposed, the carbureter is adjusted so it will close the needle valve before the level of the liquid is so high, and thereby a less surface of oil is formed within the U-shaped tube. It is obvious that this type of carbureter, owing to the absence of the secondary air-supply mechanism, can be readily regulated and all adjustments made while running, while for automobile uses the lever S, which controls the throttle, can be connected up with a dash-board control. CHAPTER VII IGNITION. LOW TENSION SYSTEM Electricity, that subtle force, which manifests itself in so many ways, is nevertheless beyond the power of man to see. The only way in which we know of its presence is by the results produced by its movements, because it can make itself known to our senses only by some form of motion. The authorities regard light, heat and electricity as merely different forms of motion. The most that can be done with such a force is to learn the laws governing it. Magnetism.--This is a form of electricity. In fact, it is one of the most universal manifestations, for without it electricity would be useless. When the first permanent magnet was found at Magnesia, it was not considered electricity. The sciences had not arrived at that point where they were able to classify it as belonging to lightning and other manifestations of that kind which we now know to be electricity. The Armature.--But magnetism can no more be seen than electricity flowing through a wire. If a piece of metal has magnetism it will attract a piece of iron or steel placed in close proximity, and thus we are permitted to see the action. The lightning in the upper atmosphere burns the gases in its path. This enables us to see, not the current, but its action,--the result produced by its power. The electric current has many peculiar manifestations, the causes of some of them being known and utilized. In the use of this medium for igniting the fuel gas, many of the phases of electrical phenomena are brought into play, and it is necessary, therefore, to know something of the fundamentals of the science to enable us to apply it. Characteristics of Electricity.--When a current passes along a wire, it does not describe a straight path, but it moves around the conductor in the form of circles. The current is not confined wholly to the wire itself, but it extends out a certain distance from it at all points. Magnetic Field.--Every part of a wire which is carrying a current of electricity has, surrounding it, a magnetic field, of the same character, and to all intents and purposes, of the same nature as the magnetic field at the ends of a magnet. Elasticity.--This current has also something akin to elasticity. That is, it surges to and fro, particularly when a current is interrupted in the circuit. At the instant of breaking a current in an electric light circuit there is a momentary flash which is much brighter than the normal light, which is due to the regular flow of the current. This is due to the surging movement, or the elastic tension, in the current. Advantage is taken of this characteristic, in making a spark. This spark is produced at the instant that the ends of the wires are separated. The Make and Break System.--No spark is caused by putting the two ends together, or by making the connection, but only by breaking it, hence it is termed the _make_ and _break_ method of ignition. When the connection is broken the current tries to leap across the gap, and in doing so develops such an intense heat that the spark follows. As a result of the high temperature it is necessary to use such a material where the gap is formed that it will not be burned. For this purpose platinum, and other metals are now employed. Voltage.--This plays an important part in ignition. Voltage is that quality which gives pressure or intensity to a current. It is the driving force, just as a head of water gives pressure to a stream of water. High and Low Voltage.--A high tension current,--that is, one having a high voltage, will leap across a gap, whereas a low voltage must have an easy path. When the ends of a wire in a circuit are separated, air acts as a perfect insulator between them, and the slightest separation will prevent a low current from jumping across. This is not the case with a high tension current, where it will leap across and produce the flash known as the _jump spark_. Low Tension System.--Two distinct types of ignition have grown out of the voltage referred to, in which the _make_ and _break_ system uses the low tension, because of its simplicity in the electrical equipment. Disadvantages of the Make and Break.--There is one serious drawback to the extended use of this system, and that is the necessity of using a moving part within the cylinder, to make and break the contact in the conductor, as it is obvious that this part of the mechanism must be placed within the compressed mixture in order to ignite it. Amperes.--A current is also measured by amperes,--that is, the quantity flowing. A large conductor will take a greater quantity of current than a small one, just as in the case of water a large pipe will convey a greater amount of the liquid. Resistance.--All conductors offer resistance to the flow of a current, and this is measured in _Ohms_. The best conductor is silver and the next best is copper, this latter material being used universally, owing to its comparative cheapness. Iron is a relatively poor conductor. Resistance can be overcome to a certain extent, however, if a large conductor is used, but it is more economical to use a small conductor which has small resistance, like copper, than a heavy conductor, as iron, even though pound for pound the latter may be cheaper. Direct Current.--There are two kinds of current, one which flows in one direction only, called the _Direct_. It is produced in a dynamo which has a pair of commutator brushes so arranged that as the armature turns and its wires move through the magnetic fields of a magnet, and have direction of the current alternate, these brushes will change the alternations so the current will travel over the working conductors in one direction only. Primary and secondary batteries produce a direct current. These will be described in their appropriate places. Alternating Current.--This is a natural current. All dynamos originally make this kind of current, but the commutator and brushes in the direct current machine change the output method only. The movement of this current is likened to a rapid to and fro motion, first flowing, for an instant, to one pole, and then back again, from which the term _alternating_ is derived. While the sudden breaking in a circuit will produce a spark with either the direct or the alternating currents, the direct is usually employed for the make and break system, since batteries are used as the electrical source. On the other hand the jump spark method employs the alternating current, because the high tension can be most effectively produced through the use of _induction coils_, which will be explained in connection with the jump spark method of ignition. Generating Electricity.--There are two ways to produce a current for operating an ignition system, one by a primary battery, and the other by means of a magneto, a special type of dynamo, which will be fully explained in its proper place. Primary Battery.--As we are now concerned with the make and break system, the battery type of generation, and method of wiring up the same, should first be explained. Thus, in Fig. 34, a primary battery is shown, in which the zinc cell A has an upwardly-projecting wing B at one side, to which the conductor is attached; and within, centrally, is a carbon bar C. An electrolyte, which may be either acid or alkali, must be placed within the cell. [Illustration: _Fig. 34. Dry Cell._] Making a Dry Cell.--The zinc is the negative, and the carbon the positive electrode. The best material for the electrolyte is crushed coke, which is carbon, and dioxide of manganese is used for this purpose, and the interstices are filled with a solution of sal-ammoniac. The top of the cell is covered with asphaltum, so as to retain the moistened material and the liquid within the cell, and thus constituted, it is called a _dry cell_. Energy in a Cell.--A battery is made up of a number of these cells. Each cell has a certain electric energy, usually from one and a half to one and three-quarter volts, and from twenty-five to forty amperes. The amperage of a cell depends on its size, or rather by the area of the electrodes; but the voltage is a constant one, and is not increased by the change, formation, or size of the electrodes. For this reason the cells are used in groups, forming, as stated, a battery, and to get efficient results, various methods of connecting them up are employed. [Illustration: _Fig. 35. Series Connection._] Wiring Methods.--As at least six cells are required to operate a coil, the following diagrams will show that number to illustrate the different types of connections. Series Connection.--The six cells, Fig. 35, show the carbon electrodes A, of one cell, connected by means of a wire B with the zinc electrode wing C of the next cell, and so on, the cell at one end having a terminal wire D connected with the zinc, and the cell at the other end a wire E connected with the carbon electrode. The current, therefore, flows directly through the six cells, and the pressure between the terminal wires D, E, is equal to the combined pressure of the six cells, namely, 1-1/2 � 6, which is equal to 9 volts. The amperage, however, is that of one cell, which, in these diagrams, will be assumed to be 25. [Illustration: _Fig. 36. Multiple, or Parallel Connection._] Parallel Connection.--Now examine Fig. 36. In this case the carbon electrodes A are all connected up in series, that is, one following the other in a direct line, by wires B, and the zinc electrodes C, are, in like manner, connected up in series with each other by wires D. The difference in potential at these terminals B, D, is the same as that of a single cell, namely, one and a half volt. The amperage, on the other hand, is that of the six cells combined, or 150. This method of connecting the cells is also called _parallel_, since the two wires forming the connections are parallel with each other, and remembering this it may be better to so term it. Multiple Connections.--This is also designated as _series multiple_ since the two sets of cells each have the connections made like the series method, Fig. 35. The particular difference being, that the zinc terminals of the two sets of cells are connected up with one terminal wire A, and the carbon terminals of the two sets are joined to a terminal B. [Illustration: _Fig. 37. Series-Multiple Connection._] The result of this form of connection is to increase the voltage equal to that of one cell multiplied by the number of cells in one set, and the amperage is determined by that of one cell multiplied by the two sets. Each set of cells in this arrangement is called a battery, and we will designate them as No. 1, and No. 2. Each battery, therefore, being connected in series, has a voltage equal to 4-1/2 volts, and the amperage 50, since there are two batteries. Now the different arrangement of volts and amperes does not mean that the current strength is changed in the batteries or in the cells. If the pressure is increased the flow is lessened. If the current flow, or the quantity sent over the wires is increased, the voltage is comparatively less. Watts.--This brings in another element that should be understood. If the current is multiplied by the amperes a factor is obtained, called _Watts_. Thus, as each cell has 1-1/2 volts and 25 amperes, their product is 37-1/2 watts. To show that the same energy is present in each form of connection let us compare the watts derived from each: Series connection: 9 volts � 25 amperes, equal 225 watts. Parallel connection: 1-1/2 volts � 150 amperes, equal 225 watts. Series Multiple connection: 4-1/2 volts � 50 amperes, equal 225 watts. From the foregoing, it will be seen that the changes in the wiring did not affect the output, but it enables the user of the current to effect such changes that he may, for instance, in case a battery should be weak, or have but little voltage, so change connections as to temporarily increase it, although in doing so it is at the expense of the amperage, which is correspondingly decreased. It would be well to study the foregoing comparative analysis of the three forms of connections, so far as the energy is concerned, because there is an impression that increasing the voltage, is adding to the power of a current. It does nothing but increase the pressure. There is not one particle of increase in the energy by so doing. [Illustration: _Fig. 38. Circuit Testing._] _Testing a Cell._--The cells should be frequently tested, to show what loss there is in the amperage. This is done by putting an ammeter in the circuit. If a meter of this kind is not handy, a good plan is to take off one of the wire connections, and snap the wire on the terminal, and the character of the spark will show what energy there is in the cell. Testing With Instruments.--The method of testing with voltmeter and ammeter, is shown in Fig. 38. The voltmeter is placed in a short circuit between the two terminal wires, whereas the ammeter is placed in circuit with one of the wires. The reason for this is that the voltmeter registers the pressure, the power, or the difference of potential between the two sides of the cell, and the ammeter shows the quantity of current flowing over the wire. In practice batteries are not used continuously for igniting. They are temporarily employed, principally for starting, because their continued use would quickly deplete them. [Illustration: _Fig. 39. Make and Break, with Battery._] Simple Battery Make and Break System.--In order to show this method in its simplest form, examine Fig. 39, which diagrams the various parts belonging to the system. We have illustrated it with two cylinders, portions of the heads being shown by the outlines A, A. B, B represent terminals which project into the cylinders, and are insulated from the engine heads. Through the sides of the engine heads are rock shafts C, the ends within the cylinder having fingers D which are adapted to engage with the inner ends of terminals B, B. On the ends of the rock shafts outside of the cylinders, they are provided with levers E, E, one end of each being attached to a spring F, so that the tension of the spring will normally keep the upper end of the finger D in contact with the terminal B. The cut shows one finger engaging with B, and the other not in contact. The other end of the lever E rests beneath a collar or shoulder G on a vertical rod H. The lower end of this rod engages with a cam I on a shaft J, and when the cam rotates the rod drops off the elevated part of the cam, and in doing so the shoulder G strikes the end of the lever E and causes the finger to rapidly break away from the terminal B, where the spark is produced. To Advance the Spark.--For the purpose of advancing or retarding the spark, this rod has, near its lower end, a horizontally-movable bar K, which may be moved to and fro a limited distance by a lever L, this lever being the substitute in this sketch of the lever on the steering wheel of an automobile. The spark is advanced or retarded by causing the lower end of the rod H to be moved to the left or to the right, so that it will drop off of the raised portion of the cam earlier or later. The wiring up is a very simple matter. The battery M has one end connected up with one terminal of a switch N, while the other terminal of the switch has a wire connection with the terminal plugs B, B, in the cylinder heads. The other end of the battery is connected with the metal of the engine, which may be indicated by the dotted line O which runs to the rock shaft C, and thus forms a complete circuit. The operation is as follows: When the key P of the switch is moved over so that it contacts with the terminal N, the battery is thrown into the circuit, and the current then passes to the plug B of the first cylinder, as the finger D in that cylinder is in contact with that terminal, and it passes along the finger D, and rock-shaft C, to the metal of the engine, and passes thence to the battery, this course being indicated by the dotted line O. At the same time, while cylinder No. 2 is also connected up with the battery, the shoulder of the rod H has drawn the finger D from its contact with the plug B, hence the current cannot pass in that direction. As the cam I, of cylinder No. 1, turns in the direction of the arrow, the rod drops down and suddenly makes a break in the terminal of this cylinder, causing the ignition, to be followed by a like action in No. 2. The Magneto in the Circuit.--To insure the life of the battery, so that it may be in service only during that period at the starting, when the magneto is not active, the latter is so placed in the circuit, that, at the starting, when, for instance, the automobile is being cranked, it is cut out by the switch on the dash board. [Illustration: Fig. 40. Make and Break, with Magneto.] In Fig. 40, a simple two-pole switch is used. With the magneto it is necessary to have a three-point switch, R, and a plain coil S is placed between the switch and battery. One side of the magneto T is connected by wire U with one of the points of the switch R, and the other side of the magneto is connected with the metal of the engine, which is indicated by the dotted line V. In all other respects the mechanism is the same. The starting operation has been explained with reference to the preceding figure, and when the engine has picked up, and is properly started, the switch bar is thrown over so it contacts with the point connected up with the wire U leading to the magneto. This, of course, cuts out the battery, and the engine is now running on the magneto alone. The object of the coil S is to oppose a rapid change of the current at the moment of the interruption. The coil induces a counter current the moment the break is made, and as the current continues to flow for a very short period after the break a spark of greater intensity is produced than if the circuit should be permitted to go from the battery to the sparker directly, as in the previous illustration. The best spark is produced by quickly making the break between the points B, D, so that particular attention has been given to mechanism which will do this effectively. Magneto Spark Plug.--One of the devices to obviate the difficulty of providing moving mechanism outside of the engine cylinder, is shown in Fig. 41. In this the coil A is connected with a terminal B at the head of the device and the other is connected to the plug C which screws into the cylinder head. [Illustration: _Fig. 41. Magneto Spark Plug._] Within the core is a pivotally-mounted lever D, the upper end E of which is attracted by the tubular metallic core F, and the lower end having a contact point G, which is adapted to engage with a stationary point H. The pivot I, on which the lever D is mounted, provides a means whereby the lever swings, and a spring J is so arranged that when the lower end of the lever is disengaged from the contact, the spring will return it to its normal position. In its operation when a contact is formed by the timing device of the magneto, so as to give a spark, the circuit passes to the terminal B, coil A, and plug C, thus forming a complete circuit. This energizes the core A, pulling the upper end of the lever, and at the same time causes the lower end to disengage the two contacts G, H, which breaks the circuit and produces a spark. The breaking of the circuit deënergizes the core, and the spring again draws the lever back to its normal position, ready for the next completion of the circuit by the timing device. Such an arrangement is as simple as the spark plug usually employed in the use of the high tension system, although it is more expensive than the plug. CHAPTER VIII IGNITION. HIGH TENSION This system is used to the largest extent, so that we ought to have a full explanation of the devices which are required to do the work. While magnetos are used with the low tension system, for the reasons stated, they are especially necessary with the _Jump Spark_ method. Magnetos.--The most important element in this system is the magneto, so we shall try and make the subject as explicit as possible. As stated, a magneto is a special type of dynamo which will now be explained. For this purpose it will be necessary to show the elementary operation of an alternating current dynamo. Alternating Current.--In Fig. 42 A is a bar of soft iron, around which is a coil of wire B, the wire being insulated, so that it will not touch the bar. There is no magnetism in this bar, and this simple form of structure is shown, merely to represent what is called the _field_ of a dynamo. The object of the coil of wire is to make a magnet of the bar, for the moment a current is sent over the wire, a magnet is formed, and the magnetism leaves the bar the moment the current ceases to flow. If this bar should be of hard steel it would retain the magnetism. [Illustration: _Fig. 42. Illustrating Alternating Current._] [Illustration: _Fig. 43. Alternating Current. Second position._] Now, the primary difference between the magneto and the dynamo, is that this field bar is a permanent magnet in the magneto, whereas the field is only a temporary magnet in the dynamo. This should always be kept in mind. The end of a magnet, whether it is a temporary one, or permanent, has a magnetic field of force at the ends as well as at all parts of it, exterior to the surface of the bar. Such a field is indicated, and in the dynamo, no such field exists unless a current is passing over the wire B, which is called the _field winding_. The U-shaped piece of metal C represents the armature. It is shown hinged to the top of two posts, for clearness in understanding, and is adapted to turn to the right, and in turning the loop passes the end of the field bar B, and passes through the magnetic field which is indicated by the dotted lines D. [Illustration: _Fig. 44. Alternating Current. Third position._] Now, if the loop is simply permitted to remain in the position shown in Fig. 42, a current would flow through the loop, this transference of the current being called induction, and this characteristic of the flow of electricity will be explained and its utility explained. Cutting Lines of Force.--The loop will now be turned to the right so that it passes the magnetic field and goes beyond it in its revolution. This motion of passing the armature through the magnetic field is called _cutting_ the _lines of force_. While the loop was lying within the magnetic field, and also when it was moving through the field, the current set up in the loop flowed in the direction of the darts F, or to the right, through the pivots D. In Fig. 43 the loop is shown as having made a quarter turn, and it is now vertical, or at right angles to its former position. The loop in thus passing away loses its force, until it reaches the position shown in Fig. 44, when there is a surging back of the current to the opposite direction, as indicated by the arrows. [Illustration: _Fig. 45. Alternating Current. Fourth position._] When the loop reaches the lowest position, shown in Fig. 45, it again begins to get the influence of the magnetic field, and a reversal back to its former direction takes place, this surging movement back and forth being due to the reversal of the polarity in the coil brought about by the position in which it is placed relative to the magnetic field. It is now an easy matter to connect the ends of the loop with wire conductors. This is shown in Fig. 46, where a small metal wheel G is placed on each end of the spindle, and in having a strip of metal bearing H on the wheel. These are not commutator brushes, but are merely wiping brushes to take the current from the turning parts. Wires I connect with these wiping bars, and through them the current is transmitted to perform the work. [Illustration: _Fig. 46. Making the Circuit._] Plurality of Loops.--The dynamo may have a plurality of loops, which are called _coils_, and there may be a single magnet or any number of magnets. Instead of driving these coils past the face of the magnet, or magnets, the latter may be driven past the coils. In fact with most of the alternating current machines the fields are the rotating parts and the armatures, or the coils, are fixed. The voltage is increased if the coils have a large number of turns on the armature, and also if the armature, or the turning part, is speeded up. Voltage will also be higher if larger or more powerful magnets are used in the magnetos. The Electro-Magnet.--The permanent magnet, such as is used in the magneto, is distinguished by the fact that it contains a permanent charge of magnetism, but this is not an _electro-magnet_. This is a magnet made of soft iron, so it will be readily demagnetized. While not shown in the diagrams, an iron core may be placed within the loop or coil, and this is done in all dynamos, because the iron core acts as a carrier of the magnetism, concentrating it at the center, because it is a much better conductor than air. [Illustration: _Fig. 47. The Dynamo._] [Illustration: _Fig. 48. The Magneto._] The Dynamo Form.--Consult the diagram, Fig. 47. The iron heads A represent the bar in the previous diagrams, and B the wire around the bar. C is the armature, which in this case represents a number of loops, or coils, and D is the commutator, which is used in the direct current machine to correct the alternations referred to in the previous diagrams, so as to send the current in one direction only, the commutator brushes E being used to carry off the current for use. The Magneto Form.--The metal loop F, in Fig. 48, being a permanent magnet, the armature, G, formed of a plurality of loops, has no field wires to connect with it, as in the case of the dynamo. Advantage of the Magneto.--The magneto has a pronounced advantage over the dynamo, as a source of power for ignition purposes, in the particular that the strength of the magnetic field is constant. In a dynamo this varies with the output, because when used on an automobile where the speed is irregular, the voltage will vary. The voltage of the magneto is a constant one, and is thus better adapted to meet the needs of ignition. Induction Coil.--The induction coil is a device which is designed to produce a very high voltage from a low tension, so that a current from it will leap across a gap and make a hot spark. We stated in a previous section that a current leaps across from one conductor to another, so that electricity can be transferred from a wire to another not touching it, by means of induction. Look at Fig. 49, which represents two wires side by side. The current is flowing over one wire A, and by bringing wire B close to A, but not touching it, a current will be induced to leap across the gap and the wire B will be charged. If the ends of the wire B are brought together, so as to form a circuit, and a current detector is placed in the circuit it will be found that a current is actually flowing through it, but it is now moving in a direction opposite to the current flowing through A. [Illustration: _Fig. 49. Current by Induction._] Changing the Current.--But we have still another thing to learn. If the two wires are not of the same thickness it would not prevent the current from leaping across, but another astonishing thing would result. First, we shall use a wire B double the thickness of wire A. If now, we had an instrument to test the voltage and the amperage, it would be found that the voltage in B is less than that in A, and also that the amperage is greater. Second, if the conditions are reversed, and the wire A is thicker than B, the latter will have an increase of voltage, but a lower ampere flow than in A. Now this latter condition is just what is necessary to give a high tension. Voltage is necessary to make a current leap across a gap. By this simple illustration we have made an induction coil which may be used for making a high tension jump spark. Construction of a Coil.--Two wires side by side do not have the appearance of a coil, and even though such an arrangement might make a high tension current, it would be difficult to apply. To put the device in such a shape that it can be utilized, a spool is made, as shown in Fig. 50. [Illustration: Fig. 50. Induction Coil.] This spool A has a number of layers of thick, insulated wire B first wound around it, the layers being well insulated from each other, and the opposite ends brought out at one end or at the opposite ends, as shown at C, D. On this is a layer of finer wire, also insulated, this wire E having its terminals also brought out at the ends of the spool, and after the whole is thus wound, the outside of the coil is covered with a moisture proof material. The Primary Coil.--The winding of thick wire is called the _primary_ coil. The current from the battery or the electric generator is led to this inner coil. [Illustration: _Fig. 51. Typical Induction Coil._] The Secondary Coil.--The fine wire wrapping represents the secondary coil, which is raised to a high voltage, and this actuates the sparking mechanism. In the art it is customary to illustrate the various contrivances by certain conventional forms. Fig. 51 shows the manner of designating an induction coil in a diagram, in which the heavy zig-zag line indicates the primary, and the lighter zig-zag lines the secondary coil. [Illustration: _Fig. 52. Contact Maker._] Contact Maker.--A simple little device used in the primary circuit of an induction coil, is known as a _contact maker_. This, as shown in Fig. 52, is merely a case A, through which is a shaft B that carries within the shell a cam C. A spring finger D has its free end normally bearing against the cam, and when the nose on the cam moves out the spring finger, the latter is moved outwardly so it contacts with a plug E in the side wall of the case, although it is insulated therefrom. This contact establishes a current through the plug, spring finger and case. The diagram, Fig. 53, illustrates the principles of construction and arrangement of a high tension jump spark ignition, in which the electrical source is a battery actuating an induction coil. High Tension With Battery and Coil.--The battery A has one side connected up by wire B with one terminal of the primary C in the induction coil, and the other side of the battery has a wire D leading to the contact maker. A switch E is placed in the line of this wire. [Illustration: _Fig. 53. Typical Circuiting, Jump Spark Ignition._] The other terminal of the primary has a wire F leading to the insulated contact plug G of the contact maker. This completes the generating circuit. The cam H is on a shaft I, which travels one half the speed of the engine shaft. One side of the secondary coil J has a wire K leading to the spark plug, while the other terminal of the secondary has a wire L which is grounded on the engine M. When the nose of the cam pushes over the spring finger and closes the cam, the circuit through the finger flows through the primary coil and excites the secondary. When the cam again immediately breaks the circuit a high tension current is momentarily induced in the secondary, so that the current leaps the gap in the spark plug and makes the spark. [Illustration: _Fig. 54. Metallic Core, Induction Coil._] Metallic Core for Induction Coil.--In the previous description of the induction coil it was stated that the spool might be made of wood. These coils are also provided with metal cores, which can be used to make what is called a vibratory coil. The Condenser.--A necessary addition to the circuiting provided by an induction coil, is a _condenser_. This is used in the primary circuit to absorb the self-induced current of the primary and thus cause it to oppose the rapid fall of the primary current. The condenser is constructed of a number of tinfoil sheets, of suitable size, each sheet having a wing at one end, and these sheets are laid on top of each other, with the wings of the alternate sheets at opposite ends. Very thin sheets of waxed paper are placed between the tin foil sheets so that they are thus insulated from each other. The wings at the ends are used to make connections for the conducting wires. The device is not designed to conduct electricity, but to act as a sort of absorbent, if it might so be termed. The large surface affords a means where more or less of the current moves from the conductor at one end to the conductor at the other end, and as it is designed to absorb a portion of the current in the line it is merely bridged across from one side of the circuit to the other. [Illustration: _Fig. 55. Condenser._] The diagram, Fig. 55, represents the conventional form of illustrating it in sketching electrical devices. Operation of a Vibrator Coil.--The illustration, Fig. 56, shows the manner in which a vibrator coil is constructed and operated. The coil comprises a metal core A, the primary winding B being connected at one terminal, by a wire C, with a post D, and the other terminal by a wire E with one side of a battery F. A switch G is in the line of this conductor. [Illustration: _Fig. 56. Vibrator Coil and Connections._] The post D holds the end of a vibrating spring H, which has a hammer H´ on its free end, which is adapted to contact with the end of the metal core A, but is normally held out of contact, so that it rests against the end of an adjusting screw I which passes through a post J. The post J is connected up with the battery by a wire K, and a wire L also runs from the wire K to the conductor C, through a condenser M. The secondary coil N, has the outlet wires O, P, which run to the spark plug Q on the engine. The operation is as follows: When the switch G closes the circuit, the battery thus thrown in the primary coil magnetizes the core A, and the hammer H´ is attracted to the end of the core, thus breaking the circuit at the contact screw I. The result is that the core is immediately demagnetized, and the spring H draws the hammer back to be again attracted by the core which is again magnetized, so that the hammer on the vibrator arm H goes back and forth with great rapidity. From the foregoing explanations it will be understood how the primary induces a high tension current in the secondary, and in order that the spark may occur at the right time, a _timer_ for closing and opening the primary circuit must be provided. By this means an induced high tension current is caused to flow at the time the spark is needed in the cycle of the engine operation. _The Distributer._--The distributer is a timing device which controls both the primary and the secondary currents, and it also has reference to the revolving switch on the shaft of a magneto whereby the current is distributed to the various cylinders in regular order. Fig. 57 shows a form of distributer which will illustrate the construction. A is the shaft which is driven at one half the engine speed. It is usually run by suitable gearing direct from the shaft of the magneto. [Illustration: _Fig. 57. The Distributer._] Its outer end rests in a bearing plate B, of insulating material, which plate serves as the disk to hold the contact plates, 1, 2, 3, 4, to correspond with the four cylinders to which the current is to be distributed. Wires 5, 6, 7, and 8, run to the respective spark plugs C from these contact plates. The projecting end of the shaft A carries thereon a contact finger D, which is designed to contact with the respective plates, and an insulating ring E is interposed between the shaft and finger so as to prevent short circuiting of the high tension current. On the side of the finger is a hub F, integral therewith, and a wiper attached to a post bears against the hub so as to form continuous contact. A wire leads from the post to one terminal of the secondary coil. [Illustration: _Fig. 58. Circuiting with Distributer._] Circuiting With Distributer.--The diagram Fig. 58 shows the complete connections of a system which comprises a magneto, induction coil, condenser, and a distributer. The magneto A has on its armature shaft B two revolving disks C, D, one of which must be insulated from the shaft, and one end of the coil E of the armature is connected with one of these disks, and the other end of the coil is attached to the other disk. Alongside of these disks is another disk F which has projecting points G to engage with and make temporary contact with a spring finger which actuates the interrupter I, this being a contact breaker which breaks the primary current at the time a spark is required. One terminal of this interrupter is connected by a wire J with one end of the primary winding K, of the induction coil, and the other end of the primary has a wire L which runs to the disk C. The other terminal of the interrupter has a wire M leading to a condenser N, and from the other side of the condenser is a wire O leading to the wire J before described. The wiper of the other disk D has a wire connection with the wire M. The distributer shaft P is so mounted that it may receive its motion from the shaft of the magneto, and for this purpose the latter shaft has a gear Q one half the diameter of the gear R on the distributer shaft. The distributer S has been described with sufficient clearness in a preceding diagram, to show how the wires T lead therefrom and connect up with the spark plugs U. One terminal of the secondary coil V is connected by a wire W with the wiper X which contacts with the hub of the distributer finger X´, and the other terminal of the primary is grounded at Y, which represents the metal of the engine. CHAPTER IX MECHANICAL DEVICES UTILIZED IN POWER One of the most important things in enginery is the capacity to determine the power developed. Although the method of ascertaining this appears to be somewhat complicated, it is really simple, and will be comprehended the more readily if it is constantly borne in mind that a certain weight must be lifted a definite distance within a particular time. The Unit of Time.--The unit of time is either the second, or the minute, usually the latter, because it would be exceedingly difficult to make the calculations, or rather to note the periods as short as a second, and a very simple piece of mechanism to ascertain this, is to mount a horizontal shaft A, Fig. 59, in bearings B, B, and affix a crank C at one end. It will be assumed that the shaft is in anti-friction bearings so that for the present we shall not take into account any loss by way of friction. A cord, with one end attached to the shaft and the other fixed to a weight D, the latter weighing, say 550 pounds, is adapted to be wound on the shaft as it is turned by the crank. Knowing the length of the cord and the time required to wind it up, it will be an easy matter to figure out the power exerted to lift the weight, which means, the power developed in doing it. [Illustration: _Fig. 59. Illustrating the Unit of Time._] Suppose the cord is 100 feet long, and it requires one and a half minutes to raise the weight the full limit of the cord. It is thus raising 550 pounds 100 feet in 45 seconds. One horse power means that we must raise 550 pounds one foot in one second of time, hence we have developed only 1/45th of one horse power. Instead of using the crank, this shaft may be attached to the engine shaft so it will turn slowly. Then add sufficient weight so that the engine will just lift it, and wind the cord on the shaft. You can then note the time, for, say, one minute, and when the weight is lifted, make the following calculation: Weight lifted one hundred feet in one minute of time was 825 pounds. Multiply 100 by 825, which equals 82,500. This represents _foot pounds_. [Illustration: Fig. 60. The Proney Brake.] As there are 33,000 foot pounds in a horse power, 82,500 divided by this figure will show that 2-1/2 horse power were developed. The Proney Brake.--Such a device is difficult to handle, but it is illustrated merely to show the simplicity of the calculation. As a substitute for this mechanism, a device, called the _Proney brake_ has been devised, which can be used without rewinding of a cord. This is accomplished by frictional means to indicate the power, and by the use of weights to determine the lift. The following is a brief description of its construction: The engine shaft A, Fig. 60, which is giving out its power, and which we want to test, has thereon a pulley B, which turns in the direction of the arrow. Resting on the upper side of the pulley is a block C, which is attached to a horizontal lever D by means of bolts E, these bolts passing through the block C and lever D, and having their lower ends attached to the terminals of a short sprocket chain F. Block segments G are placed between the chain and pulley B, and when the bolts E are tightened the pulley is held by frictional contact between the block C and the segments G. The free end of the lever has a limited vertical movement between the stops H, and a swinging receptacle I, on this end of the lever, is designed to receive weights J. The first thing to do is to get the dimensions of the pulley, its speed, and length of the lever. By measurement, the diameter of the pulley is six inches. To get the circumference multiply this by 3.1416. The distance around, therefore, is a little over 18.84 inches. The speed of the pulley being 225 times per minute, this figure, multiplied by 18.84, gives the perimeter of the pulley 4239 inches. As we must have the figures in feet, dividing 4239 by 12, we have 353.25 feet. The length of the lever from the center of the pulley to the suspension point of the receptacle, is 4 feet, and this divided by the radius of the pulley (which is 6 inches), gives the leverage. One half of six inches, is three inches, or 1/4 of one foot, and 4 divided by this number, is 1' 4", or 1-1/3 feet, which is the _leverage_. Now, let us suppose the weight J is 1200 pounds. This must be multiplied by the leverage, 1-1/3 feet, which equals 1800, and this must be multiplied by the feet of travel in the pulley, namely, 353.25, which is equal to 635,850. This represents _foot pounds_. Now, following out the rule, as there are 33,000 foot pounds in a horse power, the foregoing figure, 635,850, divided by 33,000, equals 19 horse power within a fraction. Reversing Mechanism.--A thorough knowledge of the principles underlying the various mechanical devices, and their construction, is a part of the education belonging to motors. One of the important structures, although it is very simple, when understood, requires some study to fully master. This has reference to reversing mechanism, which is, in substance a controllable valve motion, whereby the direction of the valve is regulated at will. All motions of this character throw the valve to a neutral point which is intermediate the two extremes, and the approach to the neutral means a gradual decrease in the travel of the valve until the reciprocating motion ceases entirely at the neutral position. [Illustration: _Fig. 61. Double Eccentric Reversing Gear._] [Illustration: _Fig. 62. Reversing Gear, Neutral._] Double Eccentric Reversing Gear.--A well known form of gear is shown in Fig. 61, in which the engine shaft A has two eccentrics B, C, the upper eccentric B being connected with the upper end of a slotted segment D by means of a stem E, and the other eccentric C is connected with the lower end of the segment by the stem F. The eccentrics B, C, are mounted on the shaft so they project in opposite directions. The slotted segment carries therewith the pin G of a valve rod H, and the upper end of the segment has an eye I, to which eye is a rod J operated by a lever. [Illustration: _Fig. 63. Reversing Gear, Reversed._] [Illustration: _Fig. 64. Single Eccentric Reversing Gear._] By this arrangement the link may be raised or lowered, and as the valve rod pin has no vertical movement, either the connecting link E or F may be brought into direct line with the valve rod H. Fig. 61 shows the first position, in which the valve rod H is in direct line with the upper connecting rod E, actuated by the cam B. Fig. 62 shows the neutral position. Here the pin G serves as a fulcrum for the rocking movement of the segment; whereas in Fig. 63 the valve rod H is in line with the lower connecting rod F, so that the valve is pushed to and fro by the eccentric C. [Illustration: _Fig. 65. Balanced Slide Valve._] It is more desirable, in many cases, to use a single eccentric on the engine shaft, which can be done by pivoting the segment L, Fig. 64, to a stationary support M, and connecting one end of the segment by a link N with the single eccentric O. In this construction the valve rod P is shifted vertically by a rod Q, operated from the reversing lever, thus providing a changeable motion through one eccentric. Balanced Slide Valves.--In the chapter pertaining to the steam engine, a simple form of slide valve was shown, and it was stated therein that the pressure of the steam bearing on the valve would quickly grind it down. To prevent this various types of balanced valves have been made, a sample of which is shown in Fig. 64. The valve chest A has in its bottom two ports C, D, leading to the opposite ends of the cylinder, and within is the sliding valve E, which moves beneath an adjustable plate F connected with the top or cover G of the valve chest. [Illustration: _Fig. 66. Valve Chest. Double Port Exhaust._] This is also modified, as shown in Fig. 66, in which case the slide valve H bears against the cover I at two points, so that as there is steam on the upper surface to a slightly greater area than on the lower side, there is sufficient downward pressure to hold it firmly on its seat, and at the same time not cause any undue grinding. This valve also has double exhaust ports J, J. Balanced Throttle Valve.--Fig. 67 will give a fair idea of the construction of throttle valves, the illustration showing its connection with a simple type of governor. [Illustration: _Fig. 67. Balanced Throttle-Valve._] Engine Governors.--Probably the oldest and best known governor for regulating the inlet of steam to an engine, is what is known as the Watt design. This is shown in Fig. 68. The pedestal A which supports the mechanism, has an upwardly-projecting stem B, to the upper end of which is a collar C, to which the oppositely-projecting pendent arms D are hinged. These arms carry balls E at their free ends. [Illustration: Fig. 68. Watt's Governor.] The lower part of the stem has thereon a sliding collar F, and links G, with their lower ends hinged to the collar, have their upper ends attached to the swinging arms D. The collar has an annular groove at its lower end, to receive therein the forked end of one limb of a bell-crank lever H, the other limb of this lever being connected up with the engine throttle, by means of a link L. Centrifugal motion serves to throw out the balls, as indicated by the dotted lines J, and this action raises the bell-crank lever, and opens the throttle valve. Numerous types of governors have been constructed, some of which operate by gravity, in connection with centrifugal action. Some are made with the balls adapted to swing downwardly, and thrown back by the action of springs. Others have the balls sliding on horizontally-disposed arms, and thrown back by the action of springs; and gyroscopic governors are also made which are very effective. [Illustration: _Fig. 69. The Original Injector._] Fly wheel governors are not uncommon, which are placed directly on the engine shaft, or placed within the fly wheel itself, the latter being a well known form for engines which move slowly. Injectors.--The Injector is one of the anomalies in mechanism. It actually forces water into a boiler by the action of the steam itself, against its own pressure. It is through the agency of condensation that it is enabled to do this. The illustration, Fig. 69, which represents the original type of the device, comprises a shell A, within which is a pair of conically formed tubes, B, C, in line with each other, the small ends of the tubes being pointed towards each other, and slightly separated. The large end of the conical tube C, which points toward the pipe D, which leads to the water space of the boiler, has therein a check valve E. The steam inlet pipe F, has a contracted nozzle G, to eject steam into the large end of the conical tube B, and surrounding the nozzle F is a chamber which has a pipe H leading out at one side, through which cold water is drawn into the injector. Surrounding the conical pipes B, C, is a chamber I, which has a discharge pipe J. The action of the device is very simple. When steam is permitted to flow into the conical tube B, from the nozzle G, it passes out through the drain port J, and this produces a partial vacuum to form in the space surrounding the nozzle G. As a result water is drawn up through the pipe H, and meeting with the steam condenses the latter, thereby causing a still greater vacuum, and this vacuum finally becomes so great that, with the inrushing steam, and the rapid movement through the conical tubes, past their separated ends, a full discharge through the drain J is prevented. [Illustration: Fig. 70. Injector with Movable Combining Tube.] As it now has no other place to go the check valve E is unseated, and the cold water is forced into the boiler through the pipe D, and this action will continue as long as condensation takes place at the nozzle G. Many improvements have been made on the original form, mostly in the direction of adjusting the steam nozzle, and to provide the proper proportion of flow between the steam and water, as this must be adjusted to a nicety to be most effective. An example of a movable tube which closes the outlet to the overflow, is shown in Fig. 70. The steam inlet tube A is at one end of the shell, and the outlet tube B to the boiler, at the other end, and intermediate the two is a tube C, with its open flaring end adapted to receive the steam from the tube A. This tube is longitudinally-movable, so that the controlling lever D may move it to and fro. A chamber E surrounds the nozzle A, and has a water inlet pipe F, while the space G between the ends of the pipes B, C, has an outlet H, a single check valve I being interposed. In operation the tube C may be adjusted the proper distance from the end of the pipe B, and when the current is once established through the injector, the pipe C may be brought into contact with B, and thus entirely cut out the movement of the water to the overflow. Feed Water Heater.--An apparatus of this kind is designed to take the exhaust steam from the engine and condense it, and from the condenser it is again returned to the boiler. The water thus used over again goes into the boiler at a temperature of over 180 degrees, and thus utilizes the heat that would otherwise be required to raise the temperature of the water from the natural heat, say 70, up to that point. In Fig. 71 the illustration shows a typical heater, which comprises an outer shell A, each end having a double head, the inner head B being designed to receive the ends of a plurality of horizontally disposed pipes, and the outer heads C, separated from the inner head so as to provide chambers, one end having one, and the other head being provided with two horizontal partitions D, so the water may be diverted back and forth through the three sets of pipes within the shell. [Illustration: _Fig. 71. Feed Water Heater._] The three sets of pipes, E, F, and G, are so arranged that they carry the water back and forth from one head to the other, and for this purpose the water for cooling the steam enters the port H at one end, passes through the upper set of pipes E to the other end, then back through the same set of pipes on the other side of a partition, not shown, and back and forth through the two lower sets of pipes F, G. The steam enters at the port I at the top of the shell, and passes down, as it is condensed, being discharged at the outlet J. CHAPTER X VALVES AND VALVE FITTINGS In the use of steam, compressed gas, or any medium which must have a controllable flow, valves are a necessary element; and the important point is to know what is best adapted for the use which is required in each case. For this reason one of the best guides is to fully understand the construction of each. The following illustrations and descriptions will give a good idea of the various types in use. [Illustration: _Fig. 72. Check Valve._] Check Valve.--Fig. 72 shows a longitudinal section of a check valve, which is designed to prevent the water from returning or backing up from the pressure side. The cylindrical body A is threaded at each end, and has an inclined partition B therein which has a circular aperture. [Illustration: _Fig. 73. Gate Valve._] The upper side of the shell has an opening, adapted to be closed by a cap C, large enough to insert the valve D, which is hinged to the upper side of the partition. Water or gas is forced in through the valve in the direction of the arrow, and the hinged valve is always in position to close the opening in the partition. In case the valve should leak it may be readily ground by taking the small plug E from the opening, and with a screw driver, turning the valve, and thereby fit it snugly on its seat. [Illustration: _Fig. 74. Globe Valve._] Gate Valve.--The cylindrical shell A has its ends internally threaded, and is provided, midway between its ends, with a partition wall B, having a central aperture. The upper side of the shell has an opening to receive the bonnet C, through which the valve stem D passes. This stem carries at its lower end a gate E which rests against the partition B. The stem D is threaded to screw into the threaded bore of the gate. A packing gland F surrounds the stem D. It will thus be seen that the turning of the stem D draws the gate up or down, and thus effects an opening, which provides a direct passage for the water through the valve body. Globe Valve.--A globe valve has the advantage that the valve is forced against its seat by the pressure of the wheel, differing from the gate valve, that depends on the pressure of the fluid to keep it tight. The valve body A has therein a Z-shaped partition B, the intermediate, horizontally-disposed limb of the partition being directly below the opening through the body, which is designed to receive the bonnet C. The bonnet has a central vertical bore, the lower end of which is threaded to receive the wheel spindle. The lower end of the spindle carries the circular valve, which is seated in the opening of the Z-shaped partition. The Corliss Valve.--The valve itself is of the rotary type, as shown in Fig. 75, in which the port A goes to the cylinder, and B is the passage for the steam from the boiler. The cylindrical valve body C has within the aperture B a gate D, one edge of which rests against the abutment through which the port A is formed, and this gate has within it the bar E which is connected with the crank outside of the casing. The Corliss Valve-Operating Mechanism.--As the operation of the valves in the Corliss type of engine is so radically different from the ordinary reciprocation engine, a side view of the valve grouping and its connecting mechanism are shown in Fig. 76. [Illustration: _Fig. 75. Corliss Valve._] The cylinder has an inlet valve A at each end, and an outlet valve B at each end for the discharge of the steam. C is a valve rod from the eccentric which operates the valves, and D a wrist plate, having an oscillatory or rocking motion around its center E. The attachments F F, of the steam rods, open the inlet ports A A, and G G, are the attachments of exhaust rods which open and close the exhaust valves B B. H H are catches which can be unhooked from the stems of the valves A by the governor rods J J. The vertical links K, K are connected at their lower ends with the pistons of dash pots, and have their upper ends attached to the valve spindles, and act to close the valves A A when the catches H are released by the governor rods J by means of the weights of the pistons in the dash pots. [Illustration: _Fig. 76. Corliss Valve-operating Mechanism._] The dash pots L L act in such a manner as to cushion the descent of the links K and thus prevent undue shock. M is a wrist plate pin by which the valve rod C can be released from the wrist plate. The whole purpose of the mechanism is to provide a means for closing the valves which are at the steam inlet ports, by a sudden action. The exhaust valves, on the other hand, are not so tripped but are connected directly with the wrist plate which drives all four of the valves. The wrist plate or spider has a rocking motion, being driven by an eccentric rod from the engine-shaft. The mechanism thus described gives a variable admission as the load varies, but a constant release of the exhaust and a constant compression to act as a cushion. [Illustration: _Fig. 77. Angle Valve._] It gives a high initial pressure in the cylinder, and a sharp cut off, hence it is found to be very efficient. Angle Valve.--One of the most useful is the angle valve, which is designed to take the place of an angle bend or knee in the line of the piping. The mechanism is the same as in the well known globe valve construction, the bonnet A being on a line with one of the right-angled limbs of the body. The pressure of the fluid should always be on the lower side of the valve C, coming from the direction of the arrow B, for the reason that should the steam pressure be constant on the other side, it would be difficult to repack the gland D without cutting off the steam from the pipe line. [Illustration: _Fig. 78. Rotary Valve._] [Illustration: _Fig. 79. Two-way Rotary._] Referring back to the illustration of the globe valve, it will be noticed that the same thing, so far as it pertains to the direction of the steam, applies in that construction, and a common mistake is to permit the pressure of the steam to be exerted so that it is constantly acting against the packing of the spindle. Rotary Valves.--Two forms of rotary valves are shown, one as illustrated in Fig. 78, where the rotating part, or plug, A has one straight-way opening B, which coincides with two oppositely-projecting ports C, D. The other form, Fig. 79, has an L-shaped opening E through the rotating plug F, and the casing, in which the plug is mounted has three ports, one, G, being the inlet, and the other two H, I, at right angles for the discharge of the fluid. [Illustration: Fig. 80. Rotary Type.] [Illustration: _Fig. 81. Two-way Rotary Type._] Rotable Engine Valves.--So many different forms of the rotable valve have been made, that it is impossible to give more than a type of each. For engine purposes the plugs are usually rotated in unison with the engine shaft, and a single delivery valve of this kind is shown in Fig. 80. This has three ports in the casing, namely the inlet port A, and two outlet ports C, D. The plug has a curved cut out channel E, and this extends around the plug a distance equal to nearly one-half of the circumference, so that the steam will be diverted into, say, B, for a period equal to one-quarter turn of the plug, and then into port C, for the same length of time. Fig. 81 shows a valve which has a double action. The plug G has two oppositely-disposed curved channels, H, I, and the casing has a single inlet port J, and two oppositely-disposed outlet ports K, L. [Illustration: _Fig. 82. Butterfly Throttle._] [Illustration: _Fig. 83. Angle Throttle._] When the plug turns the port L serves to convey the live steam to the engine, while the other port K at the same time acts as the exhaust, and this condition is alternately reversed so that L acts as the discharge port. Throttle Valves.--The throttle valves here illustrated are those used in connection with gasoline engines. The best known is the _Butterfly_ valve, shown in Fig. 82, and this is also used as a damper, for regulating the draft in furnaces and stoves. This type is made in two forms, one in which the two wings of the valve are made to swing up or down in unison, and the other, as illustrated, where the disk A is in one piece, and turns with the spindle B to which it is fixed. [Illustration: _Fig. 84. Slide Throttle._] [Illustration: _Fig. 85. Two-slide Throttle._] In Fig. 83 the wing C is curved, so that by swinging it around the circle, the opening of the discharge pipe D is opened or closed. Another design of throttle is represented in Fig. 84. One side of the pipe A has a lateral extension B, which is double, so as to receive therein a sliding plate C, which is easily controllable from the outside. Fig. 85 shows a form of double sliding plate, where the double lateral extensions project out in opposite directions, as at D, D, and within these extensions are sliding plates which are secured together in such a way that as one is pushed in the other also moves in, and thus acts in unison to close or to open the space between them. It is the most perfect form of throttle valve, as it causes the gases to open directly into the center of the outgoing pipe. Blow-off Valves.--The illustration shows a type of valve which is used on steamboats and very largely on farm boilers throughout the country. The pipe A from the boiler has cast therewith, or otherwise attached, a collar B, which has a standard C projecting upwardly at one side, to the upper end of which is hinged a horizontal lever D, which has a weight at its other end. [Illustration: _Fig. 86. Blow-off Valve._] The upper end of the pipe has a conically-ground seat, to receive a conical valve E, the stem of which is hinged, as at F, to the level. The weight may be adjusted to the pressure desired before blowing out and the only feature in this type of valve is the character of the valve seat, which is liable, through rust, and other causes, to leak. Pop, or Safety Valve.--As it has been found more desirable and practical to use a form of valve which is not liable to deterioration, and also to so arrange it that it may be manually opened, the _Safety Pop_ valve was devised. [Illustration: _Fig. 87. Safety Pop Valve._] This is shown in Fig. 87, in which the valve seat base A, which is attached to the top of the boiler, has a cup-shaped outlet B, that is screwed to it, and this carries a lever C, by means of which the valve may be manually opened. A vertical shell D is attached to the cup-shaped portion, and this has a removable cap E. The valve F is seated within a socket in the base, and has a disk head, to receive the lower end of a coiled spring G. The spring is supported in position by a stem H which extends down from the head, and an adjusting nut I serves to regulate the pressure desired before the steam in the boiler can act. CHAPTER XI CAMS AND ECCENTRICS More or less confusion arises from the terms _cams_ and _eccentrics_. A cam is a wheel which may be either regular in shape, like a _heart-wheel_, or irregular, like a _wiper-wheel_. The object in all forms of cams is to change motion from a regular into an irregular, or reversely, and the motion may be accelerated or retarded at certain points, or inverted into an intermittent or reciprocating movement, dependent on the shape of the cam. A cam may be in the shape of a slotted or grooved plate, like the needle bar of a sewing machine, where a crank pin works in the slot, and this transmits an irregular vertical movement to the needle. A cam may have its edge provided with teeth, which engage with the teeth of the engaging wheel, and thus impart, not only an irregular motion but also a turning movement, such forms being largely used to give a quickly rising or falling motion. What are called _wiper-wheels_ are designed to give an abrupt motion and such types are used in trip hammers, and to operate stamp mills. In harvesters, printing presses, sewing machines, and mechanism of that type, the cam is used in a variety of forms, some of them very ingenious and complicated. [Illustration: _Fig. 88. Heart-shaped._] [Illustration: _Fig. 89. Elliptic._] [Illustration: Fig. 90. Double Elliptic.] Cams are also used for cutting machines, or in tracing apparatus where it would be impossible to use ordinary mechanism. All such forms are special, requiring care and study to make their movements co-relate with the other parts of the mechanism that they are connected up with. Simple Cams.--Fig. 88 shows a form of the most simple character, used, with some modifications, to a larger extent than any other. It is called the _heart-shaped_ cam, and is the regular type. Fig. 89 is an elliptical cam, which is also regular. What is meant by _regular_ is a form that is the same in each half portion of its rotation. Fig. 90 is a double elliptic, which gives a regular movement double the number of times of that produced by the preceding figure, and the differences between the measurements across the major and minor axes may vary, relatively, to any extent. [Illustration: _Fig. 91. Single Wiper._] [Illustration: _Fig. 92. Double Wiper._] [Illustration: _Fig. 93. Tilting Cam._] Wiper Wheels.--Wiper wheels are cams which give a quick motion to mechanism, the most common form being the single wiper, as shown in Fig. 91. The double wiper cam, Fig. 92, has, in some mechanism, a pronounced difference between the lengths of the two fingers which form the wipers. The form of cam shown in Fig. 93 is one much used in iron works for setting in motion the tilt hammer. Only three fingers are shown, and by enlarging the cam at least a dozen of these projecting points may be employed. Cam Sectors.--Fig. 94 shows a type of cam which is designed for rock shafts. The object of this form of cam is to impart a gradually increasing motion to a shaft. Assuming that A is the driving shaft, and B the driven shaft, the cam C, with its short end D, in contact with the long end E of the sector F, causes the shaft B to travel at a more accelerated speed as the other edges G, H, approach each other. [Illustration: _Fig. 94. Cam Sector._] [Illustration: _Fig. 95. Grooved Cam._] [Illustration: _Fig. 96. Reciprocating Motion._] Cylinder Cam.--Fig. 95 shows one form of cylinder A with a groove B in it, which serves as a means for moving a bar C back and forth. The bar has a projecting pin D, which travels in the groove. This form of movement may be modified in many ways, as for instance in Fig. 96, where the drum E has a sinuous groove F to reciprocate a bar G to and fro, the groove being either regular, so as to give a continuous back and forth movement of the bar; or adapted to give an irregular motion to the bar. [Illustration: _Fig. 97. Pivoted Follower for Cam._] Double Cam Motion.--Cams may also be so arranged that a single one will produce motions in different directions successively, as illustrated in Fig. 97. The horizontal bar A, hinged at B to the upper end of a link C, has its free end resting on the cam D. The arm A has also a right-angled arm E extending downwardly, and is kept in contact with the cam by means of a spring F. Connecting rods G, H, may be hinged to the arm E and bar A, respectively, so as to give motion to them in opposite directions as the cam revolves. Eccentrics.--An eccentric is one in which the cam or wheel itself is circular in form, but is mounted on a shaft out of its true center. An eccentric may be a cam, but a cam is not always eccentric in its shape. The term is one in direct contrast with the word _eccentric_. [Illustration: _Fig. 98. Eccentric._] [Illustration: _Fig. 99. Eccentric Cam._] Fig. 98 shows the wheel, or the cam, which is regular in outline, that is circular in form, but is mounted on the shaft out of its true center. In this case it is properly called an eccentric cam but in enginery parlance it is known as the eccentric, as represented in Fig. 99. Triangularly-Formed Eccentric.--Fig. 100 illustrates a form of cam which has been used on engines. The yoke A being integral with the bar B, gives a reciprocating motion to the latter, and the triangular form of the cam C, which is mounted on the shaft D, makes a stop motion at each half-revolution, then produces a quick motion, and a slight stop only, at the half turn, and the return is then as sudden as the motion in the other direction. [Illustration: Fig. 100. Triangularly-formed Eccentric.] CHAPTER XII GEARS AND GEARING For the purpose of showing how motion may be converted from a straight line or from a circular movement into any other form or direction, and how such change may be varied in speed, or made regular or irregular, the following examples are given, which may be an aid in determining other mechanical devices which can be specially arranged to do particular work. While cams and eccentrics may be relied on to a certain extent, there are numerous places where the motion must be made positive and continued. This can be done only by using gearing in some form, or such devices as require teeth to transmit the motion from one element to the other. The following illustrations do not by any means show all the forms which have been constructed and used in different machines, but they have been selected as types merely, in order to give the suggestions for other forms. Racks and Pinions.--The rack and pinion is the most universal piece of mechanism for changing motion. Fig. 101 illustrates it in its most simple form. When constructed in the manner shown in this figure it is necessary that the shaft which carries the pinion shall have a rocking motion, or the rack itself must reciprocate in order to impart a rocking motion to the shaft. [Illustration: Fig. 101. Rack and Pinion.] [Illustration: Fig. 102. Rack Motion.] This is the case also in the device shown in Fig. 102, where two rack bars are employed. A study of the cams and eccentrics will show that the transference of motion is limited, the distances being generally very small; so that the rack and pinions add considerably to the scope of the movement. The Mangle Rack.--The device called the _mangle rack_ is resorted to where a back and forth, or a reciprocating movement is to be imparted to an element by a continuous rotary motion. [Illustration: Fig. 103. Plain Mangle Rack.] [Illustration: Fig. 104. Mangle Rack Motion.] [Illustration: Fig. 105. Alternate Circular Motion.] The plain mangle racks are shown in Figs. 103 and 104, the former of which has teeth on the inside of the opposite parallel limbs, and the latter, Fig. 104, having teeth not only on the parallel sides, but also around the circular parts at the ends. This form of rack may be modified so that an alternate circular motion will be produced during the movement of the rack in either direction. Fig. 105 is such an instance. A pinion within such a rack will turn first in one direction, and then in the next in the other direction, and so on. If the rack is drawn back and forth the motion imparted to the pinion will be such as to give a continuous rocking motion to the pinion. Controlling the Pinion.--Many devices have been resorted to for the purpose of keeping the pinion in engagement with the teeth of the mangle rack. One such method is shown in Fig. 106. [Illustration: Fig. 106. Controlling Pinion for Mangle Rack.] The rack A has at one side a plate B, within which is a groove C, to receive the end of the shaft D, which carries the pinion E. As the mangle rack moves to such a position that it reaches the end of the teeth F on one limb, the groove C diverts the pinion over to the other set of teeth G. All these mangle forms are substitutes for cranks, with the advantage that the mangle gives a uniform motion to a bar, whereas the to and fro motion of the crank is not the same at all points of its travel. Examine the diagram, Fig. 107, and note the movement of the pin A which moves along the path B. The crank C in its turning movement around the circle D, moves the pin A into the different positions 1, 2, 3, etc., which correspond with the positions on the circle D. [Illustration: Fig. 107. Illustrating Crank-pin Movement.] The Dead Centers.--There is also another advantage which the rack possesses. Where reciprocating motion is converted into circular motion, as in the case of the ordinary steam engine, there are two points in the travel of a crank where the thrust of the piston is not effective, and that is at what is called the _dead centers_. In the diagram, Fig. 108, the ineffectiveness of the thrust is shown at those points. Let A represent the piston pushing in the direction of the arrow B against the crank C. When in this position the thrust is the most effective, and through the arc running from D to E, and from H to G, the cylinder does fully four-fifths of the work of the engine. [Illustration: _Fig. 108. The Dead Center._] While the crank is turning from G to D, or from I to J, and from K to L, no work is done which is of any value as power. If, therefore, a mangle bar should be used instead of the crank it would add greatly to the effectiveness of the steam used in the cylinder. [Illustration: _Fig. 109. Crank Motion Substitute._] Crank Motion Substitute.--In Fig. 109 the pinion A is mounted so that its shaft is in a vertical slot B in a frame C. The mangle rack D, in this case, has teeth on its outer edge, and is made in an elongated form. The pinion shaft moves up and down the slot and thus guides the pinion around the ends of the rack. [Illustration: Fig. 110. Mangle Wheel.] Mangle Wheels.--The form which is the most universal in its application is what is called the _mangle wheel_. In Fig. 110 is shown a type wherein the motion in both directions is uniform. Mangle wheels take their names from the ironing machines called _mangles_. In apparatus of this kind the movement back and forth is a slow one, and the particular form of wheels was made in order to facilitate the operation of such machines. In some mangles the work between the rollers is uniform back and forth. In others the work is done in one direction only, requiring a quick return. In still other machines arrangements are made to provide for short strokes, and for different speeds in the opposite directions, under certain conditions, so that this requirement has called forth the production of many forms of wheels, some of them very ingenious. [Illustration: _Fig. 111. Quick Return Motion._] The figure referred to has a wheel A, on one side of which is a peculiarly-formed continuous slot B, somewhat heart-shaped in general outline, one portion of the slot being concentric with the shaft C. Within the convolutions of the groove is a set of teeth D, concentric with the shaft C. The pinion E, which meshes with the teeth D, has the end of its shaft F resting in the groove B, and it is also guided within a vertical slotted bar G. The pinion E, therefore, travels over the same teeth in both directions, and gives a regular to and fro motion. Quick Return Motion.--In contradistinction to this is a wheel A, Fig. 111, which has a pair of curved parallel slots, with teeth surrounding the slots. When the wheel turns nearly the entire revolution, with the pinion in contact with the outer set of teeth, the movement transmitted to the mangle wheel is a slow one. [Illustration: _Fig. 112. Accelerated Circular Motion._] When the pinion arrives at the turn in the groove and is carried around so the inner teeth are in engagement with the pinion, a quick return is imparted to the wheel. Accelerated Motion.--Aside from the rack and mangle type of movement, are those which are strictly gears, one of them being a volute form, shown in Fig. 112. This gear is a face plate A, which has teeth B on one face, which are spirally-formed around the plate. These mesh with a pinion C, carried on a horizontal shaft D. This shaft is feathered, as shown at E, so that it will carry the gear along from end to end. [Illustration: _Fig. 113. Quick Return Gearing._] The gear has cheek-pieces F to guide it along the track of teeth. As the teeth approach the center of the wheel A, the latter impart a motion to the gear which is more than twice the speed that it receives at the starting point, the speed being a gradually increasing one. Quick Return Gearing.--Another much more simple type of gearing, which gives a slow forward speed and a quick return action, is illustrated in Fig. 113. A is a gear with internal teeth through one half of its circumference, and its hub B has teeth on its half which is opposite the teeth of the rim. A pinion C on a shaft D is so journaled that during one half of the rotation of the wheel A, it engages with the rim teeth, and during the other half with the hub teeth. As the hub B and gear C are the same diameter, one half turn of the pinion C will give a half turn to the wheel A. [Illustration: _Fig. 114. Scroll Gearing._] As the rim teeth of the wheel A are three times the diameter of the pinion C, the latter must turn once and a half around to make a half revolution of the wheel A. Scroll Gearing.--This is a type of gearing whereby at the close of each revolution the speed may be greater or less than at the beginning. It comprises two similarly-constructed gears A, B, each with its perimeter scroll-shaped, as shown. The diagram shows their positions at the beginning of the rotation, the short radial limb of one gear being in line with the long limb of the other gear, hence, when the gears rotate, their speeds relative to each other change, being constantly accelerated in one or decreased in the other. CHAPTER XIII SPECIAL TYPES OF ENGINES In describing various special types of motors, attention is first directed to that class which depend on the development of heat in various gases, and this also necessitates some explanation of ice-making machinery, and the principles underlying refrigeration. It is not an anomaly to say that to make ice requires heat. Ice and boiling water represent merely the opposites of a certain scale in the condition of matter, just as we speak of light and darkness, up and down, and like expressions. We are apt to think zero weather is very cold. Freezing weather is a temperature of 32 degrees. At the poles 70 degrees below have been recorded. In interstellar space,--that is, the region between the planets, it is assumed that the temperature is about 513 degrees Fahrenheit, below zero, called absolute zero. The highest heat which we are able to produce artificially, is about 10,000 degrees by means of the electric arc. We thus have a range of over 10,500 degrees of heat, but it is well known that heat extends over a much higher range. Assuming, however, that the figures given represent the limit, it will be seen that the difference between ice and boiling water, namely, 180 degrees, is a very small range compared with the temperatures referred to. In order to effect this change power is necessary, and power requires a motor of some kind. Hence it is, that to make a lower temperature, a higher degree of heat is necessary, and in the transit between a high and a low temperature, there is considerable loss in this respect, as in every other phase of power mechanism, as has been pointed out in a previous chapter. In order that we may clearly understand the phenomena of heat and cold, let us take a receiver which holds a cubic foot of gas or liquid, and exhaust all the air from it so the vacuum will be equivalent to the atmospheric pressure, namely, 14.7 pounds per square inch. Alongside is a small vessel containing one cubic inch of water, which is heated so that it is converted into steam, and is permitted to exhaust into the receiver. When all the water is converted into steam and fills the receiver we shall have the same pressure inside the receiver as on the outside. It will be assumed, of course, that there has been no loss by condensation, and that the cubic inch of water has been expanded 1700 times by its conversion into steam. In a short time the steam will condense into water, and we now have, again, a partial vacuum in the receiver, due, of course, to the change in bulk from steam to water. Each time the liquid is heated it produces a pressure, and the pressure indicates the presence of heat; and whenever it cools a loss of pressure is indicated, and that represents cold, or the opposite of heat. Now, putting these two things together, we get the starting point necessary in the development of power. Let us carry the experiment a step further. Liquids are not compressible. Gases are. The first step then is to take a gas and compress it, which gives it an increase of heat temperature, dependent on the pressure. If the same receiver is used, and say, two atmospheres are compressed within it, so that it has two temperatures, and the exterior air cools it down to the same temperature of the surrounding atmosphere, we are ready to use the air within to continue the experiment. Let us convey this compressed gas through pipes, and thus permit it to expand; in doing so the area within the pipes, which is very much greater than that of the receiver, grows colder, due to the rarefied gases within. Now bearing in mind the previous statement, that loss of pressure indicates a lowering of temperature, we can see that first expanding the gas, or air, by heat, and then allowing it to cool, or to produce the heat by compressing it, and afterwards permitting it to exhaust into a space which rarefies it, will make a lower temperature. It is this principle which is used in all refrigerating machines, whereby the cool pipes extract the heat from the surrounding atmosphere, or when making ice, from the water itself, and this temperature may be lowered to any extent desired, dependent on the degree of rarefaction produced. Let us now see how this applies to the generation of power in which we are more particularly interested. All liquids do not evaporate at the same temperature as water. Some require a great deal more than 212 degrees; others, like, for instance, dioxide-of-carbon, will evaporate at 110 degrees, or about one half the heat necessary to turn water into steam. On the other hand, all gases act alike so far as their heat absorption is concerned, so that by using a material with a low evaporative unit, less fuel will be required to get the same expansion, which means the same power. To illustrate this, let us assume that we have equal quantities of water, and of dioxide-of-carbon, and that is to be converted into a gas. It will take just double the amount of fuel to convert the water into a gaseous state. As both are now in the same condition, the law of heat absorption is the same from this time on. The dioxide-of-carbon engine is one, therefore, which uses the vapor of this material, which, after passing through the engine, is condensed and pumped back to the boiler to be used over and over. In like manner, also, ether, which has a low point of vaporization, is used in some engines, the principle being the same as the foregoing type. Rotary Engines.--Many attempts have been made to produce a rotary type of steam engine, and also to adapt it for use as an internal combustion motor. The problem is a complicated one for the following reasons: First, it is difficult to provide for cut-off and expansion. A rotating type, to be efficient, must turn at a high rate of speed, and this makes the task a more trying one. Second, the apparent impossibility of properly packing the pistons. The result is a waste of steam, or the gas used to furnish the power. Third, the difficulty in providing a suitable abutment so as to confine the steam or gas, and make it operative against the piston. [Illustration: _Fig. 115. Simple Rotary Engine._] In Fig. 115 is shown a type of rotary which is a fair sample of the characteristics of all motors of this form. It comprises an outer cylindrical shell, or casing, A, having a bore through the ends, which is above the true center of the shell, to receive a shaft B. This shaft carries a revolving drum C of such dimensions that it is in contact with the shell at its upper side only, as shown at D, leaving a channel E around the other portions of the drum. The steam inlet is at F, which is one-eighth of the distance around the cylinder, and the exhaust is at G, the same distance from the point D, on the other side. The inlet and the outlet pipes are, therefore, at the contracted parts of the channel. The drum has a pair of radially-movable blades H H´, which may move independently of each other, but usually they are connected together, thus dispensing with the use of any springs to keep their ends in contact with the shell. When steam enters the inlet F the pressure against the blade H drives the drum to the right, and the drum and shell, by contacting at D, form an abutment. Each charge of steam drives the drum a little over a half revolution. A great deal of ingenuity has been exercised to arrange this abutment so that the blades may pass and provide a steam space for a new supply of steam. In certain types a revolving abutment is formed, as shown, for instance, in Fig. 116. The shell A, in this case, has two oppositely-disposed inlet and outlet ports, B, C, respectively, and between each set of ports is a revolving gate, formed of four wings D, mounted on a shaft E, in a housing outside of the circular path F, between the drum G and shell A. The drum G is mounted on a shaft H which is centrally within the shell, and it has two oppositely-projecting rigid blades I. When steam enters either of the supply ports B, the drum is rotated, and when the blades reach the revolving gates, the latter are turned by the blades, or, they may be actuated by mechanism connected up with the driving shaft. [Illustration: _Fig. 116. Double-feed Rotary Engine._] Caloric Engine.--This is an engine which is dependent on its action upon the elastic force of air which is expanded by heat. The cylinder of such a motor has means for heating it, and thus expanding the air, and a compressor is usually employed which is operated by the engine itself, to force compressed air into the cylinder. It is not an economical engine to work, but it is frequently used in mines, in which case the compressor is located at the surface, and the engine operated within the mine, thus serving a double purpose, that of supplying power, and also furnishing the interior with fresh air. All engines of this character must run at a slow speed, for the reason that air does not absorb heat rapidly, and sufficient time must be given to heat up and expand the air, so as to make it effective. Adhesion Engine.--A curious exhibition of the action of a gas against a solid, is shown in what is called an _Adhesion Engine_. Fig. 117 shows its construction. A plurality of disks A are mounted on a shaft B, these disks being slightly separated from each other. The steam discharge pipe C is flattened at its emission end, as shown at D, so the steam will contact with all the disks. The steam merely contacts with the sides of the disks, the movement of the steam being substantially on the plane of the disks themselves, and the action sets up a rapid rotation, and develops a wonderful amount of power. [Illustration: _Fig. 117. Adhesion Motor._] It will be understood that the disks are enclosed by a suitable casing, so that the steam is carried around and discharged at a point about three quarters of the distance in the circumference. This motor is given to illustrate a phase of the subject in the application of a motor fluid, like steam, or heated gases, that shows great possibilities. It also points out a third direction in which an expansive fluid may be used. Thus the two well-known methods, namely, _pressure_, and _impact_ forces, may be supplemented by the principle of _adhesion_, in which the expansive force of a gas, passing alongside of and in contact with a plain surface, may drag along the surface in its train. Such an exhibition of force has an analogy in nature by what is known as capillary attraction, which shows _adhesion_. For instance, sap flowing up the pores of trees, or water moving along the fibers of blotting paper, illustrates movement of liquids when brought into contact with solids. CHAPTER XIV ENGINERY IN THE DEVELOPMENT OF THE HUMAN RACE The energy of a nation may be expressed by its horse power. It is not numbers, or intellect, or character, or beliefs that indicate the progress of a people in a material sense. It is curious how closely related enginery is with the advancement of a people. Nothing can be more striking to illustrate this than railroads as a feature of development in any country. Power in Transportation.--Without the construction and maintenance of mechanical power, railroads would be impossible. To be able to quickly and cheaply move from place to place, is the most important factor in human life. The ability of people to interchange commodities, and to associate with others who are not in their own intimate community, are the greatest civilizing agencies in the world. Power vs. Education and the Arts.--Education, the cultivation of the fine arts, and the desire for luxuries, without the capacity for quickly interchanging commodities and to intermingle with each other, are ineffectual to advance the interests of any nation, or to maintain its prosperity. Lack of Power in the Ancient World.--The Greeks and the Romans had a civilization which is a wonder even to the people of our day. They had the arts and architecture which are now regarded as superb and incomparable. They had schools of philosophy and academies of learning; their sculpture excites the admiration of the world; and they laid the foundation theories of government from which we have obtained the basis of our laws. The Early Days of the Republic.--When our forefathers established the Republic there were many misgivings as to the wisdom of including within its scope such a large area as the entire Atlantic seacoast. From Maine to Florida the distance is 1250 miles; and from New York to the Mississippi 900 miles, comprising an area of 1,200,000 square miles. How could such an immense country ever hold itself together? It was an area nearly as large as that controlled by Rome when at the height of her power. If it was impossible for the force of Roman arms to hold such a region within its control, how much more difficult it would be for the Colonies to expect cohesion among their scattered peoples. Lack of Cohesiveness in a Country Without Power.--Those arguments were based on the knowledge that every country in ancient times broke apart because there was no unity of interest established, and because the different parts of the same empire did not become acquainted or associated with each other. The Railroad as a Factor in Civilization.--The introduction of railroads, by virtue of motive power, changed the whole philosophy of history in this respect. Even in our own country an example of the value of railroads was shown in the binding effect which they produced between the East and the West prior to the Civil War. All railroads, before that period, ran east and west. Few extended north and south. It is popularly assumed that the antagonism between the North and the South grew out of the question of slavery. This is, no doubt, largely so, as an immediate cause, but it was the direct cause which prevented the building of railroads between the two sections. It simply reënforces the argument that the motor, the great power of enginery, was not brought into play to unite people who were antagonistic, and who could not, due to imperfect communication, understand each other. To-day the United States contains an area nearly as great as the whole of Europe, including Russia, with their twenty, or more, different governments. Here we have a united country, with similar laws, habits, customs and religions throughout. In many of those foreign countries the people of adjoining provinces are totally unlike in their characteristics. It has been shown that wherever this is the case it is due to lack of quick and cheap intercommunication. The Wonderful Effects of Power.--This remarkable similarity in the conditions of the people throughout the United States is due to the railroads, that great personification of power, notwithstanding the diverse customs and habits of the people which daily come to our shores and spread out over our vast country. It has unified the people. It has made San Francisco nearer to New York than Berlin was to Paris in the time of Napoleon. The people in Maine and Texas are neighbors. The results have been so far reaching that it has given stability to the government greater than any other force. But there is another lesson just as wonderful to contemplate. England has an area of only about 58,000 square miles, about the same size as either Florida, Illinois, or Wisconsin. England as a User of Power.--The enginery within her borders is greater than the combined energy of all the people on the globe. Through the wonderful force thus set in motion by her remarkable industries she has become the great manufacturing empire of the world, and has called into existence a carrying fleet of vessels, also controlled by motors, so stupendous as to be beyond belief. We may well contemplate the great changes which have been brought about by the fact that man has developed and is using power in every line of work which engages his activities. The Automobile.--He does not, in progressive countries, depend on the muscle of the man, or on the sinews of animals. These are too weak and too slow for his needs. Look at the changes brought about by the automobile industry within the past ten years. What will the next century bring forth? Artificial power, if we may so term it, is a late development. It is very young when compared with the history of man. High Character of Motor Study.--The study of motors requires intellect of a high order. It is a theme which is not only interesting and attractive to the boy, but the mastery of the subject in only one of its many details, opens up a field of profit and emoluments. The Unlimited Field of Power.--It is a field which is ever broadening. The student need not fear that competition will be too great, or the opportunities too limited, and if these pages will succeed, in only a small measure, in teaching the fundamental ideas, we shall be repaid for the efforts in bringing together the facts presented. CHAPTER XV THE ENERGY OF THE SUN, AND HOW HEAT IS MEASURED In the first chapter we tried to give a clear view of the prime factors necessary to develop motion. The boy must thoroughly understand the principles involved, before his mind can fully grasp the ideas essential in the undertaking. While the steam engine has been the prime motor for moving machinery, it is far from being efficient, owing to the loss of two-thirds of the energy of the fuel in the various steps from the coal pile to the turning machinery. _First_, the fuel is imperfectly consumed, the amount of air admitted to the burning mass being inadequate to produce perfect combustion. _Second_, the mechanical device, known as the boiler, is not so constructed that the water is able to completely absorb the heat of the fuel. _Third_, the engine is not able to continuously utilize the expansive force of the steam at every point in the revolution of the crankshaft. _Fourth_, radiation, the dissipation of heat, and condensation, are always at work, and thus detract from the efficiency of the engine. The gasoline motor, the next prime motor of importance, is still less efficient in point of fuel economy, since less than one-third of the fuel is actually represented in the mechanism which it turns. The production of energy, in both cases, involves the construction of a multiplicity of devices and accessories, many of them difficult to make and hard to understand. To produce power for commercial purposes, at least two things are absolutely essential. First, there must be uniformity in the character of the power produced; and, second, it must be available everywhere. Water is the cheapest prime power, but its use is limited to streams or moving bodies of water. If derived from the air currents no dependence can be placed on the regularity of the energy. Heat is the only universal power on the globe. The sun is the great source of energy. Each year it expends in heat a sufficient force to consume over sixty lumps of coal, each equal to the weight of the earth. Of that vast amount the earth receives only a small part, but the portion which does come to it is equal to about one horse power acting continuously over every thirty square feet of the surface of our globe. The great problem, in the minds of engineers, from the time the steam engine became a factor, was to find some means whereby that energy might be utilized, instead of getting it by way of burning a fuel. One of the first methods proposed was to use a lens or a series of mirrors, by means of which the rays might be focused on some object, or materials, and thus produce the heat necessary for expansion, without the use of fuel. Wonderful results have been produced by this method; but here, again, man meets with a great obstacle. The heat of the sun does not reach us uniformly in its intensity; clouds intervene and cut off the rays; the seasons modify the temperature; and the rotation of the globe constantly changes the direction of the beams which fall upon the lens. The second method consists in using boxes covered with glass, the interior being blackened to absorb the heat, and by that means transmit the energy to water, or other substances adapted to produce the expansive force. Devices of this character are so effective that temperatures much above the boiling point of water have been obtained. The system is, however, subject to the same drawbacks that are urged against the lens, namely, that the heat is irregular, and open to great variations. These defects, in time, may be overcome, in conserving the force, by using storage batteries, but to do so means the change from one form of energy to another, and every change means loss in power. The great problem of the day is this one of the conversion of heat into work. It is being done daily, but the boy should understand that the _direct conversion_ is what is required. For instance, to convert the energy, which is in coal, into the light of an electric lamp, requires at least five transformations in the form of power, which may be designated as follows: 1. The burning of the coal. 2. The conversion of the heat thus produced into steam. 3. The pressure of the steam into a continuous circular motion in the steam engine. 4. The circular motion of the steam engine into an electric current by means of a dynamo. 5. The change from the current form of energy to the production of an incandescent light in the lamp itself, by the resistance which the carbon film offers to the passage of the current. Should an inventor succeed in eliminating only one of the foregoing steps, he would be hailed as a genius, and millions would not be sufficient to compensate the fortunate one who should be able to dispense with three of the steps set forth. The Measurement of Heat.--To measure heat means something more than simply to take the temperature. As heat is work, or energy, there must be a means whereby that energy can be expressed. It has been said that the basis of all true science consists in correct definitions. The terms used, therefore, must be uniform, and should be used to express certain definite things. When those are understood then it is an easy matter for the student to grope his way along, as he meets the different obstacles, for he will know how to recognize them. Before specifically explaining the measurement it might be well to understand some of the terms used in connection with heat. The original theory of heat was, that it was composed of certain material, although that matter was supposed to be subtle, imponderable and pervading everything. This imponderable substance was called _Caloric_. It was supposed that these particles mutually attracted and repelled each other, and were also attracted and repelled by other bodies, so that they contracted and expanded. The phenomenon of heat was thus accounted for by the explanation that the expansion and contraction made the heat. This was known as the _Material Theory of Heat_. But that phase of the explanation has now been abandoned, in favor of what is known as the _dynamical_, or _mechanical_ theory, which is regarded merely as a _mode_ of _motion_, or a sort of vibration, wherein the particles move among each other, with greater or less rapidity or in some particular manner. Thus, the movements of the atoms may be accelerated, or caused to act in a certain way, by friction, by percussion, by compression, or by combustion. Heat is the universal result of either of those physical movements. Notwithstanding that the material theory of heat is now abandoned, scientists have retained, as the basis of all heat measurements, the name which was given to the imponderable substance, namely, _Caloric_. It is generally written _Calorie_, in the text books. A calorie has reference to the quantity of heat which will raise the temperature of one kilogram of water, one degree Centigrade. As one kilogram is equal to about two pounds, three and a quarter ounces, and one degree Centigrade is the same as one and two-thirds degrees Fahrenheit, it would be more clearly expressed by stating that a caloric is the quantity of heat required to raise the temperature of one and one-fifth pound of water one degree Fahrenheit. This is known as the scientific unit of the thermal or heat value of a caloric. But the engineering unit is what is called the British Thermal Unit, and designated in all books as B. T. U. This is calculated by the amount of heat which is necessary to raise a kilogram of water one degree Fahrenheit. According to Berthelot, the relative value of calorics and B. T. U. are as follows: HEATS OF COMBUSTION --------------------------------------------------- _Substance._ _Calories._ _B. T. U._ --------------------------------------------------- Hydrogen 34,500 62,100 Carbon to carbon dioxide 8,137 14,647 Carbon to carbon monoxide 2,489 4,480 Carbon monoxide 2,435 4,383 Methane 13,343 24,017 Ethylene 12,182 21,898 Cellulose 4,200 7,560 Acetylene 12,142 21,856 Peat 5,940 10,692 Naphthalene 9,690 10,842 Sulphur 2,500 4,500 When it is understood that heat is transmitted in three different ways, the value of a measuring instrument, or a unit, will become apparent. Thus, heat may be transmitted either by _conduction_, _convection_, or _radiation_. _Conduction_ is the method whereby heat is transmitted from one particle to another particle, or from one end of a rod, or other material to the other end. Some materials will conduct the heat much quicker than others, but if we have a standard, such as the calorie, then the amount of heat transmitted and also the amount lost on the way may be measured. _Convection_ applies to the transmission of heat through liquids and gases. If heat is applied to the top or surface of a liquid, the lower part will not be affected by it. If the heat is applied below, then a movement of the gas or liquid begins to take place, the heated part moving to the top, and the cooler portions going down and thus setting up what are called _convection currents_. _Radiation_ has reference to the transference of heat from one body to another, either through a vacuum, the air, or even through a solid. By means of the foregoing table, which gives the heats developed by the principal fuels, it is a comparatively easy matter to determine the calorific value of fuels, which is ascertained by making an analysis of the fuel. The elements are then taken together, and the table used to calculate the value. Suppose, for instance, that the analysis shows that the fuel has seventy-five per cent. of carbon and twenty-five per cent. of hydrogen. It is obvious that if we take seventy-five per cent. of 8,137 (which is the index for carbon), and twenty-five per cent. of 43,500 (the index of hydrogen), and adding the two together, the result, 14,727, would represent the calorific value of the fuel. GLOSSARY OF WORDS USED IN TEXT OF THIS VOLUME =Absolute.= Independent; free from all limitations. =Amplitude.= Greatness of extent; the state or quality of being sufficient. =Absorbent.= A material which will take up a liquid. =Absorbing.= Taking up, or taking in. =Absorption.= The act or process of taking up or fully occupying. =Abutment.= A wall; a stop. =Accuracy.= Correctness; positiveness. =Accession.= Added to; addition, or increase. =Accelerate.= Quickened; hurried. =Accessible.= Available; capable of being reached. =Accelerated.= A quickening, as of process or action. =Actuating.= Moved or incited by some motive. =Advance Spark.= The term applied to the movement of the mechanism in an internal combustion engine, which will cause the electric spark to act before the crank has passed the dead center. =Aeration.= To add air; to impregnate with oxygen. =Alkali.= In chemistry it is known as a compound of hydrogen and oxygen, with certain chemicals. Anything which will neutralize an acid. =Allusion.= Referring to; noticed. =Anomaly.= A deviation from an ordinary rule; irregular. =Adhesion.= To cling to; to stick together. =Adjustment.= To arrange in proper order; to set into working condition. =Alternating A current which goes back and current.= forth in opposite directions; unlike a direct current which flows continuously in one direction. =Ampere.= The unit of current; the term in which strength of current is measured. An ampere is an electromotive force of one volt through a resistance of one ohm. =Amplitude.= The state or quality of being broad, or full. =Analysis.= The separation into its primitive or original parts. =Annular.= Pertaining to or formed like a ring. =Armature.= The part of a dynamo or motor which revolves, and on which the wire coils are wound. =Assuming.= Taking on; considered to be correct or otherwise. =Asphaltum.= A bituminous composition used for pavements, properly made from natural bitumen, or from asphalt rock. =Atmospheric.= Referring to; noticed. =Available.= Capable of being employed or used. =Bearings.= The part in mechanism in which journals or spindles rest and turn. =Bifurcated.= In two parts; branching, like a fork. =Blow-off valve.= A valve so arranged that at certain pressures the valve will automatically open and allow the steam to escape from the boiler. =Bombard.= An assault; an attack by shot or shell. =Bonnet.= The cap of a valve, which is so arranged that while it permits the valve stem to turn, will also prevent leakage. =Butterfly-valve.= A form of valve which is usually flat, and adapted to open out, or turn within the throat or pipe. =Caloric.= Pertaining to heat. =Cam.= A rotating wheel, or piece, either regular or irregular, non-circular, or eccentric. =Carbon.= A material like coke, ground or crushed. It required high heat to burn it, and it is used for the burning material in electric arc lamps. =Carbureter.= The device used to mix air and gaseous fuel in an internal combustion engine. =Carbonized.= Put into a charred form; coke is carbonized coal; charcoal is carbonized wood. =Carbureted.= Air or gas to which has been added the gaseous product of petroleum, or some distillate. =Centripetal.= That which draws inwardly, or to the center, like the gravitational action of the earth. =Centrifugal.= That which throws outwardly; the opposite of centripetal. =Check valve.= A form of valve which will permit liquids to freely flow in one direction, but which will open automatically, so as to allow the liquid to flow in the opposite direction. =Chemical.= Pertaining to the composition of matter; or relating to chemistry. =Chambered.= Having compartments, or divided up into recesses. =Circumference.= Around the outside. =Circularly.= Around; about the circumference. =Circulation.= The movement of water to and fro through conduits. =Clearance.= The space at the head of a cylinder within which the steam or gases are compressed by the piston. =Classification.= To put in order in a systematic way. =Coincide.= To correspond with identity of parts. =Cohesion.= To stick together. The attraction of material substances of the same kind for each other. =Coöperate.= To work together harmoniously. =Compounding.= Composed of or produced by the union of two or more parts, or elements. =Complicated.= Very much involved; not simple. =Commutator.= The revolving part on the armature of a dynamo or motor, which is divided up into a multiplicity of insulated plates, which are connected with the coils of the wire around the armature. =Combustion.= Burning; the action of the unity of oxygen with any substance, which causes it to be destroyed or changed. =Commodity.= Any product, or kind of goods. =Concaved.= Hollowed. =Condensation.= The change from a gaseous to a liquid or solid state. =Condenser.= An apparatus which converts a gas into a liquid. =Concentric.= A line which at any point is at the same distance from a common center. =Conductor.= A substance which will convey either heat or electricity from one end to the other. =Conical.= In the form of a cone. =Conically.= In the form of a cone. =Conduit.= A trough, tube, or other contrivance, which will convey liquids or gases from place to place. =Conduction.= The capacity to transmit from one point to another. =Connecting Rod.= That part of mechanism which connects the piston rod with the crank. =Conserve.= To take care of; to use judiciously. =Constant.= Being the same thing at all times; not varying. =Contrivance.= Any mechanism, or device which will serve a certain purpose. =Contra- That which is opposite to, distinction.= comparatively; taken in conjunction with for the purpose of comparison. =Cornish.= A form of boiler which has the fire tubes within the water space. =Contact Breaker.= A device which has the current normally in circuit, and is so arranged that the circuit is broken at certain intervals, and again immediately reëstablished. =Co-relate.= Belonging to; having reference to the same order. =Conventional.= The regular manner or method. =Contact Maker.= A device for making contacts in an electric circuit at regular intervals. =Convolution.= The turns or twists taken. The changes or movement or the peculiar flow of a liquid. =Control.= Handling with regularity; The act of guiding. =Contracted.= Made smaller. =Contingency.= An event; under certain conditions. =Counteract.= To antagonize; to so act as to go against. =Converting.= Changing; to put in an opposite condition. =Cylindrical.= In the form of a cylinder; barrel-shaped. =Cyclopedia.= A work which gives, in alphabetical order, the explanations of terms and subjects. =Cycle.= A period extending over a certain time; a certain order of events. =Dead Center.= That point in the turn of a crank where the piston has no effective pull in either direction. =Deënergize.= To take power away from. =Deflecting.= To glance off; to change the regular or orderly course. =Demagnetized.= To take magnetism away from. =Deterioration.= To take away from; to grow smaller; to lessen; to depreciate in quality. =Deviate.= To avoid; to get around; not going or doing in the regular way. =Diagram.= A mechanical plan or outline, as distinguished from a perspective drawing. =Diametrically.= Across or through the object; through the center. =Dioxide.= An oxide containing two atoms of oxygen to the molecule. =Direct current.= An electric current which flows continuously in one direction. =Dissipated.= Changed, or entirely dispensed with; usually applied to a condition where materials or substances are scattered. =Distributer.= A piece of mechanism in an electric circuit, which switches the current from one part to the other. =Dissect.= To take apart. =Dominating.= Overpowering; having greatest power. =Diverse.= Different; unlike. =Dry Cell.= A battery in which the electrolyte is not in a fluid state. =Duct.= Either an open trough or conduit, or a closed path for the movement of gases or liquids. =Dynamo.= A mechanical device for the purpose of generating electricity. =Eccentric.= A wheel having its perimeter so formed that the center is not in the exact middle portion. =Economy.= Prudence; carefulness; not disposed to be excessive. =Efficiency.= Well adapted for the situation; mechanism which will do the work perfectly, or cheaply. =Effectiveness.= Well done; to the best advantage. =Ejecting.= Throwing out; sending forth. =Elastic.= That quality of material which tends to cause it to return to its original shape when distorted. =Elementary.= Primitive; the first; in the simplest state. =Electric arc.= A term applied to the current which leaps across the slightly separated ends of an electric conductor. =Electricity.= An agent, incapable of being seen, but which produces great energy. =Electrolyte.= The agent, or material in a battery, usually a liquid, which the current passes through in going from one electrode to the other. =Elliptical.= A form which might be expressed by the outline shape of an egg, measured from end to end. =Emolument.= Pay; remuneration; the amount received for employment of any kind. =Emission.= To send out from; a sending or putting out. =Energy.= Force; power. =Essential.= The main thing; the important element. =Evaporate.= To convert into vapor, usually by heat. =Exhaust.= The discharge part of an engine, or other apparatus. =Excessive.= Too much; more than is required. =Expansion.= Enlarged; the occupying of a greater space. =Explicit.= Particularly definite; carefully explained and understood. =External.= Outside; the outer surface. =Facilitating.= Helping; aiding in anything. =Factor.= An element in a problem. =Fahrenheit.= One of the standards of heat measurement. A thermometer scale, in which the freezing point of water is 32, and the boiling temperature is 212. =Fascinating.= Attractiveness; capacity to allure. =Feathered.= Applied to the shape of an article, or to a rib on the side of a shaft, which is designed to engage with a groove. =Fertilizer.= Material for enriching soil and facilitating the growth of vegetables. =Field.= A term applied to the windings and the pole pieces of a dynamo or motor, which magnetically influence the armature. =Focal.= The point; the place to which all the elements or forces tend. =Foot pounds.= The unit of mechanical work, being the work done in moving one pound through a distance of one foot. =Four-cycle.= A gasoline engine, in which the ignition of the compressed hydro-carbon gases takes place every other revolution. =Formation.= The arrangement of any mechanism, or a series of elements. =Formula.= The recipe for the doing of a certain thing; a direction. =Friction.= A retarding motion; the prevention of a free movement. =Function.= The qualities belonging to an article, machine or thing; that which a person is capable of performing. =Fundamental.= The basis; the groundwork of a thing. =Gaseous.= Of the nature of a gas. =Gearing.= Usually applied to two or more sets of toothed wheels which coöperate with each other. =Generating.= Producing; manufacturing; bringing out of. =Globules.= The small particles of liquids; or the molecules comprising fluids. =Gravitation.= The force of the earth which causes all things to move toward it; the attraction of mass for mass. =Heart Wheel.= A wheel having the outline of a heart. =Helical.= A spirally-wound form. =High Tension.= A term applied to a current of electricity, which has a very high voltage, but low amperage. =Horizontal.= Level, like the surface of water; at right angles to a line which points to the center of the earth. =Horse Power.= The unit of the rate of work, equal to 33,000 pounds lifted one foot in one minute. =Hydro-carbon.= A gas made from the vaporization of crude petroleum or of its distillates. =Hydrogen.= One of the original elements. The lightest of all gases. =Ignite.= To set on fire. =Ignition.= The term applied to the firing of a charge of gas in a gas or gasoline engine. =Impact.= A blow; a striking force. =Impregnated.= To instill; to add to. =Impulse.= A natural tendency to do a certain thing; determination to act in a certain way through some influence. =Impinge.= To strike against; usually to contact with at an angle. =Incomparable.= Too good or great to measure. =Inclined.= Not level; leaning; not horizontal. =Induction.= The peculiar capacity of an electric current to pass from one conductor to another through the air. =Indication.= That which shows; to point out. =Injector.= A device whereby the pressure of the steam in a boiler will force water into the boiler. =Initially.= At first; the original act. =Injection.= To put into; to eject from an apparatus, into some other element. =Insulated.= So covered as to prevent loss of current by contact with outside substances or materials. =Intimate.= Close to; on good terms with. =Integral.= A complete whole; containing all the parts. =Instinct.= Knowledge within; something which influences conduct or action. =Interstellar.= The space beyond the earth; that portion of the heavens occupied by the stars. =Internal.= Within; that portion of mechanism which is inside. =Interposing.= To step into; to place between, or in the midst of. =Intensity.= Fierce; strong; above the ordinary. =Interrupted.= To stop; to take advantage of. =Interstices.= The spaces in between. =Instantaneous.= Immediately; at once; without waiting. =Intricate.= Difficult; not easy. =Inquisitive.= The desire to inquire into. =Jacketing.= To coat or cover on the outside. =Jump Spark.= One of the methods of igniting hydro-carbon gases. A current of sufficiently high voltage is used to cause the current to jump across the space between the separated ends of a conductor. =Kinetic.= Consisting in or depending on motion. =Latent.= That which is within itself. =Lateral.= Branching out from the sides; usually applied as the meaning for the direction which is at right angles to a fore and aft direction. =Lines of force.= Applied to electricity, air, water, or any moving element, which has a well directed movement in a definite direction. =Low Tension.= In methods for igniting hydro-carbon charges, any circuiting which has a low voltage. =Lubrication.= The oiling of mechanical parts to reduce friction. =Mangle.= A machine for smoothing out clothing, goods, etc. =Magneto.= A dynamo which has the field pieces, or poles made of permanent magnets. =Magnetism.= That quality, or agency by virtue of which certain bodies are productive of magnetic force. =Manifestation.= Showing or explaining a state of things; an outward show. =Make and Break.= An ignition system, which provides for throwing in and cutting out an electric circuit. =Manifold.= A system of piping whereby the exhausts of a gasoline engine are brought together into one common discharge. =Manganese.= A hard, brittle, grayish white metallic element, used in the manufacture of paints and of glass, and also for alloying metals. =Manually.= Doing things by hand; muscular activity. =Material.= Substances and parts from which articles are made. =Mechanically.= Doing things by means of machinery, or in some regular order. =Mobility.= The capacity to move about. =Multiple.= A figure used a certain number of times, is said to be a multiple of a number, if it will divide the number equally. Thus 4 is a multiple of 16; 3 is a multiple of 9, and so on. =Neutral.= Neither; not in favor of any party or thing. =Normal.= As usual; in the regular way; without varying from the ordinary manner. =Ohm's Law.= In electricity, it is expressed as follows: 1. The current strength is equal to the electromotive force divided by its resistance. 2. The electromotive force is equal to the current strength multiplied by the resistance. 3. The resistance is equal to the electromotive force divided by the current strength. =Oscillating.= Moving to and fro, like a pendulum. =Orifice.= An opening; a hole. =Organism.= Any part of the body, or any small germ or animalcule. =Oxidation.= The action of air or oxygen on any material, is called oxidation. Thus rust on iron is called oxidation. =Oxygen.= A colorless, tasteless gas, the most important in nature, called the acid-maker of the universe, as it unites with all substances, and produces either an acid, an alkali, or a neutral compound. =Parallel.= Two lines are said to be parallel, when they are lying side by side and are equally distant from each other from end to end. =Pendulum.= A bar suspended at one end to a pivot pin, and having its lower end free to swing to and fro. =Penstock.= A reservoir designed to receive and discharge water into a turbine or other form of water wheel. =Permanent.= That which will last; not easily stopped. =Pestle.= An implement of stone or metal used for breaking and grinding up chemicals, and other material in a mortar. =Petroleum.= A liquid fuel product, found in many places, its component parts being about 15 per cent. hydrogen and 85 per cent. carbon. =Perimeter.= The outer rim, or circle. =Piston.= That part of an engine which is attached to the piston rod. =Pinion.= A small gear wheel driven by a larger gear wheel. =Platinum.= An exceedingly hard metal, used in places for electrical work where the current is liable to burn out ordinary conductors. =Polarity.= The quality of having opposite poles. =Pre-heating.= To heat before the ordinary process of heating commences. =Ponderous.= Large; heavy; difficult to handle. =Port.= In nautical parlance the left side of a vessel; the larboard side; also an opening, or a conduit for the transmission of gas or liquid. =Pop valve.= A valve designed to open and allow escape of the imprisoned gases when the latter reach a certain pressure. =Potential.= The power; the term used in electricity to denote the energy in a motor. =Plurality.= More than one; many. =Precipice.= A high and very steep cliff. =Pressure.= The act of one body placed in contact with another and acting against it or against each other. =Precaution.= Taking great care; being assured of safety. =Primary A cell, or a number of cells, made battery.= of pairs of metallic couples, immersed in an electrolyte of either an acid or an alkali. =Proney Brake.= A device for testing machinery and determining power, by means of friction. =Primeval.= The earliest; the first; of a low order. =Proportion.= The relation of one thing or number, to another; comparative merit. =Proximity.= Close to; near at hand. =Quadruple.= Four times. =Rack.= A bar having a number of teeth, to serve as a step or measure for a pawl, or a toothed wheel. =Radial.= Extending out from the center. =Radiation.= The property of many substances to give forth heat or cold, or to disperse it. =Rarified.= Made less than the normal pressure, as air, which is not as dense at a high as at a low altitude. =Receiver.= In telephone apparatus, that part of the mechanism which transmits the message to the ear. =Rectilinear.= A right line; a straight direction forwardly. =Reaction.= A force which is counter to a movement in another direction. =Refrigeration.= Cooling process; the art of freezing. =Refined.= Purifying; improved. =Re-heating.= The process of further heating or increasing the temperature during the progress of the work. =Requisite.= The necessary part; the requirement. =Residue.= The balance; what is left over. =Resistance.= Opposition; against. =Reciprocating.= One for the other; moving from one side to the other. =Refinement.= Chastity of thought, taste, manner, or actions. =Retort.= A vigorous answer. A receptacle adapted to stand a high heat. =Revolution.= Turning, like the earth in its orbit. =Rock Shaft.= A shaft which turns part of its rotation in one direction, and then turns in the other direction. =Rotation.= The turning of a wheel on its axle; the rotation of the earth on its axis each day. Distinguishing from revolution which is a swinging of the entire body of the earth around the sun in its orbit. =Sal-Ammoniac.= A white metallic element. =Scavenging.= To clean out; to scour. =Secondary A battery which is charged with a Battery.= current, and then gives forth an electric current of a definite amount. It is also known as an _accumulator_, since its elements continue to accumulate electric energy. =Secondary coil.= In induction coils two wire wrappings are necessary, the first winding being, usually, of heavy wire, and called the primary; the second winding is of finer wire, and is called the secondary coil. =Sector.= An A-shaped piece cut from a disk; distinguish this from a segment, which is a part cut off from a disk by a single straight line. =Secondary.= Occupying a second place; not of the first kind, or place. =Segment.= A part cut off from a disk, by a single line; the part of a circle included within a chord and its arc. =Sewerage.= The conveyance of waste matter from a building. =Sinuous.= Systematic draining by means of pipes or conduits. Characterized by bends, or curves, or a serpentine curving, or wave-like outline. =Slide Valve.= A form, which moves along a flat surface through which the duct is formed. =Solution.= A liquid having therein different substances mixed together. =Sprayer.= To eject; to send forth in small particles. =Stability.= Fixed; strength to stand without support. =Stupendous.= Immense; large; much beyond the largest of the kind. =Standard.= A sample of the measure or extent; a type or a model. =Stratify.= To deposit, form, or range in strata. =Super Heating.= To heat up beyond the ordinary or normal point. =Subtle.= Crafty; made of light material; daintily constructed. =Supersede.= In place of; to take the place of. =Susceptible.= Capable of being changed or influenced. =Suspension.= Hanging; floating of a body in fluid. =Suction.= The production of a partial vacuum in a space connected with a fluid under pressure. =Terminal.= The end; the last part. =Technical.= Specially or exclusively pertaining to some art or subject. =Theoretical.= That which is speculative, as distinguished from practical. =Throttle Valve.= A device which is designed to cut off the flow of a fluid. =Throttling.= The closing of a port; the cutting down of a supply. =Transformation.= A complete change; made over into something else. =Transmit.= To convey; to send to another part. =Transference.= To convey to another part; the change from one thing to another. =Transferred.= Put over. =Triple.= Three; thrice. =Turbine.= To turn; a form of water wheel and steam engine, where the fluid impinges against the blades arranged around the perimeter of the wheel. =Tubular.= Hollowed; like a pipe. =Two-Cycle.= A gasoline engine, in which the compressed hydro-carbon gases are fired every turn of the crank shaft. =Typical.= The nature or characteristics of a type. =Undershot.= A type of wheel in which the water shoots past and against the blades on the lower side. =Unison.= Together; conjointly; acting with each other. =Universally.= All over the world; throughout all space. =Utility.= Use; that which is valuable or of service. =Vacuum.= That part from which all material is taken; in a limited sense, air, which has less density than the normal. =Vaporizing.= To convert into gas, usually by heat. =Variable.= With differing characteristics; changeable. =Venturi Tube.= A form of tube which has a contracted part between its ends. =Vertical.= In the direction of a line which points to the center of the earth. =Vibrator Coil.= In electrical devices used in the ignition systems of certain types of gasoline engines, a winding is provided on a metallic core, which has an armature that is made so it will vibrate. =Volt.= The pressure of an electric current; the unit of electromotive force. =Voltage.= Electromotive force as expressed in volts. =Volt Meter.= An instrument for indicating the voltage of an electric circuit. =Watt.= The electrical unit of the rate of working in an electric circuit, the rate being the electromotive force of one volt, and the intensity of one ampere. =Weight.= The measure of the force toward the center of the earth, due to gravity. =Winnowed.= Taken out; sifted from. =Wiping Bar.= A metallic piece which rests against a moving wheel and designed to take a current from or to transmit it to the wheel. The Motor Boys Series (_Trade Mark, Reg. U. S. Pat. Of._) By CLARENCE YOUNG 12mo. Illustrated. Price per volume, 60 cents, postpaid. [Illustration] =The Motor Boys= _or Chums Through Thick and Thin_ =The Motor Boys Overland= _or A Lone Trip for Fun and Fortune_ =The Motor Boys in Mexico.= _or The Secret of The Buried City_ =The Motor Boys Across the Plains= _or The Hermit of Lost Lake_ [Illustration] =The Motor Boys Afloat= _or The Stirring Cruise of the Dartaway_ =The Motor Boys on the Atlantic= _or The Mystery of the Lighthouse_ =The Motor Boys in Strange Waters= _or Lost in a Floating Forest_ =The Motor Boys on the Pacific= _or The Young Derelict Hunters_ [Illustration] =The Motor Boys in the Clouds= _or A Trip for Fame and Fortune_ =The Motor Boys Over the Rockies= _or A Mystery of the Air_ =The Motor Boys Over the Ocean= _or A Marvellous Rescue in Mid-Air_ =The Motor Boys on the Wing= _or Seeking the Airship Treasure_ [Illustration] =The Motor Boys After a Fortune= _or The Hut on Snake Island_ =The Motor Boys on the Border= _or Sixty Nuggets of Gold_ =The Motor Boys Under the Sea= _or From Airship to Submarine_ =The Motor Boys on Road and River= (_new_) _or Racing to Save a Life_ CUPPLES & LEON CO., Publishers, NEW YORK Up-to-date Baseball Stories Baseball Joe Series By LESTER CHADWICK Author of "The College Sports Series" 12mo. Illustrated. Price per volume, 60 cents, postpaid. * * * * * [Illustration] Ever since the success of Mr. Chadwick's "College Sports Series" we have been urged to get him to write a series dealing exclusively with baseball, a subject in which he is unexcelled by any living American author or coach. Baseball Joe of the Silver Stars _or The Rivals of Riverside_ In this volume, the first of the series, Joe is introduced as an everyday country boy who loves to play baseball and is particularly anxious to make his mark as a pitcher. He finds it almost impossible to get on the local nine, but, after a struggle, he succeeds. A splendid picture of the great national game in the smaller towns of our country. Baseball Joe on the School Nine _or Pitching for the Blue Banner_ Joe's great ambition was to go to boarding school and play on the school team. He got to boarding school but found it harder making the team there than it was getting on the nine at home. He fought his way along, and at last saw his chance and took it, and made good. Baseball Joe at Yale _or Pitching for the College Championship_ From a preparatory school Baseball Joe goes to Yale University. He makes the freshman nine and in his second year becomes a varsity pitcher and pitches in several big games. Baseball Joe in the Central League _or Making Good as a Professional Pitcher_ In this volume the scene of action is shifted from Yale College to a baseball league of our central states. Baseball Joe's work in the box for Old Eli had been noted by one of the managers and Joe gets an offer he cannot resist. Joe accepts the offer and makes good. Baseball Joe in the Big League _or A Young Pitcher's Hardest Struggle_ From the Central League Joe is drafted into the St. Louis Nationals. At first he has little to do in the pitcher's box, but gradually he wins favor. A corking baseball story that fans, both young and old, will enjoy. * * * * * CUPPLES & LEON CO., Publishers, NEW YORK The Racer Boys Series by CLARENCE YOUNG Author of "The Motor Boys Series", "Jack Ranger Series", etc. etc. Fine cloth binding. Illustrated. Price per volume, 60c postpaid. * * * * * [Illustration] The announcement of a new series of stories by Mr. Clarence Young is always hailed with delight by boys and girls throughout the country, and we predict an even greater success for these new books, than that now enjoyed by the "Motor Boys Series." =The Racer Boys= or The Mystery of the Wreck This, the first volume of the series, tells who the Racer Boys were and how they chanced to be out on the ocean in a great storm. Adventures follow in rapid succession in a manner that only Mr. Young can describe. =The Racer Boys At Boarding School= or Striving for the Championship When the Racer Boys arrived at the school everything was at a standstill, and the students lacked ambition and leadership. The Racers took hold with a will, got their father to aid the head of the school financially, and then reorganized the football team. =The Racer Boys To The Rescue= or Stirring Days in a Winter Camp Here is a story filled with the spirit of good times in winter--skating, ice-boating and hunting. =The Racer Boys on The Prairies= or The Treasure of Golden Peak From their boarding school the Racer Boys accept an invitation to visit a ranch in the West. =The Racer Boys on Guard= or The Rebellion of Riverview Hall Once more the boys are back at boarding school, where they have many frolics, and enter more than one athletic contest. =The Racer Boys Forging Ahead= or The Rivals of the School League Once more the Racer Boys go back to Riverview Hall, to meet their many chums as well as several enemies. Athletics play an important part in this volume, and the rivalry is keen from start to finish. The Racer Boys show what they can do under the most trying circumstances. * * * * * CUPPLES & LEON CO., Publishers, NEW YORK The Dorothy Dale Series By MARGARET PENROSE Author of "The Motor Girls Series" 12mo. Illustrated. Price per volume, 60 cents, postpaid. * * * * * [Illustration] Dorothy Dale: A Girl of To-Day Dorothy is the daughter of an old Civil War veteran who is running a weekly newspaper in a small Eastern town. When her father falls sick, the girl shows what she can do to support the family. Dorothy Dale at Glenwood School More prosperous times have come to the Dale family, and Major Dale resolves to send Dorothy to a boarding school. Dorothy Dale's Great Secret A splendid story of one girl's devotion to another. How Dorothy kept the secret makes an absorbing story. Dorothy Dale and Her Chums A story of school life, and of strange adventures among the gypsies. Dorothy Dale's Queer Holidays Relates the details of a mystery that surrounded Tanglewood Park. Dorothy Dale's Camping Days Many things happen, from the time Dorothy and her chums are met coming down the hillside on a treacherous load of hay. Dorothy Dale's School Rivals Dorothy and her chum, Tavia, return to Glenwood School. A new student becomes Dorothy's rival and troubles at home add to her difficulties. Dorothy Dale in the City Dorothy is invited to New York City by her aunt. This tale presents a clever picture of life in New York as it appears to one who has never before visited the Metropolis. Dorothy Dale's Promise Strange indeed was the promise and given under strange circumstances. Only a girl as strong of purpose as was Dorothy Dale would have undertaken the task she set for herself. Dorothy Dale in the West Dorothy's father and her aunt inherited a valuable tract of land in the West. The aunt, Dorothy and Tavia, made a long journey to visit the place, where they had many adventures. * * * * * CUPPLES & LEON CO., Publishers, NEW YORK The Motor Girls Series By MARGARET PENROSE Author of the highly successful "Dorothy Dale Series" 12mo. Illustrated. Price per volume, 60 cents, postpaid. * * * * * [Illustration] The Motor Girls _or A Mystery of the Road_ When Cora Kimball got her touring car she did not imagine so many adventures were in store for her. A tale all wide awake girls will appreciate. The Motor Girls on a Tour _or Keeping a Strange Promise_ A great many things happen in this volume. A precious heirloom is missing, and how it was traced up is told with absorbing interest. The Motor Girls at Lookout Beach _or In Quest of the Runaways_ There was a great excitement when the Motor Girls decided to go to Lookout Beach for the summer. The Motor Girls Through New England _or Held by the Gypsies_ A strong story and one which will make this series more popular than ever. The girls go on a motoring trip through New England. The Motor Girls on Cedar Lake _or The Hermit of Fern Island_ How Cora and her chums went camping on the lake shore and how they took trips in their motor boat, are told in a way all girls will enjoy. The Motor Girls on the Coast _or The Waif from the Sea_ The scene is shifted to the sea coast where the girls pay a visit. They have their motor boat with them and go out for many good times. The Motor Girls on Crystal Bay _or The Secret of the Red Oar_ More jolly times, on the water and at a cute little bungalow on the shore of the bay. A tale that will interest all girls. The Motor Girls on Waters Blue _or The Strange Cruise of the Tartar_ Before the girls started on a long cruise down to the West Indies, they fell in with a foreign girl and she informed them that her father was being held a political prisoner on one of the islands. A story that is full of fun as well as mystery. * * * * * CUPPLES & LEON CO., Publishers, NEW YORK Ruth Fielding Series By ALICE B. EMERSON 12mo. Illustrated. Price per volume, 40 cents, postpaid. * * * * * [Illustration] Ruth Fielding of The Red Mill _or Jaspar Parloe's Secret_ Telling how Ruth, an orphan girl, came to live with her miserly uncle, and how the girl's sunny disposition melted the old miller's heart. Ruth Fielding at Briarwood Hall _or Solving the Campus Mystery_ Ruth was sent by her uncle to boarding school. She made many friends, also one enemy, who made much trouble for her. Ruth Fielding at Snow Camp _or Lost in the Backwoods_ A thrilling tale of adventures in the backwoods in winter, is told in a manner to interest every girl. Ruth Fielding at Lighthouse Point _or Nita, the Girl Castaway_ From boarding school the scene is shifted to the Atlantic Coast, where Ruth goes for a summer vacation with some chums. Ruth Fielding at Silver Ranch _or Schoolgirls Among the Cowboys_ A story with a western flavor. How the girls came to the rescue of Bashful Ike, the cowboy, is told in a way that is most absorbing. Ruth Fielding on Cliff Island _or The Old Hunter's Treasure Box_ Ruth and her friends go to Cliff Island, and there have many good times during the winter season. Ruth Fielding at Sunrise Farm _or What Became of the Raby Orphans_ Jolly good times at a farmhouse in the country, where Ruth rescues two orphan children who ran away. Ruth Fielding and the Gypsies _or The Missing Pearl Necklace_ This volume tells of stirring adventures at a Gypsy encampment, of a missing heirloom, and how Ruth has it restored to its owner. * * * * * CUPPLES & LEON CO., Publishers, NEW YORK The Dave Dashaway Series By ROY ROCKWOOD Author of the "Speedwell Boys Series" and the "Great Marvel Series." 12mo. Illustrated. Price per volume, 40 cents, postpaid. * * * * * Never was there a more clever young aviator than Dave Dashaway. All up-to-date lads will surely wish to read about him. * * * * * [Illustration] Dave Dashaway the Young Aviator _or In the Clouds for Fame and Fortune_ This initial volume tells how the hero ran away from his miserly guardian, fell in with a successful airman, and became a young aviator of note. Dave Dashaway and His Hydroplane _or Daring Adventures Over the Great Lakes_ Showing how Dave continued his career as a birdman and had many adventures over the Great Lakes, and how he foiled the plans of some Canadian smugglers. Dave Dashaway and His Giant Airship _or A Marvellous Trip Across the Atlantic_ How the giant airship was constructed and how the daring young aviator and his friends made the hazardous journey through the clouds from the new world to the old, is told in a way to hold the reader spellbound. Dave Dashaway Around the World _or A Young Yankee Aviator Among Many Nations_ An absorbing tale of a great air flight around the world, of adventures in Alaska, Siberia and elsewhere. A true to life picture of what may be accomplished in the near future. Dave Dashaway: Air Champion _or Wizard Work in the Clouds_ Dave makes several daring trips, and then enters a contest for a big prize. An aviation tale thrilling in the extreme. * * * * * CUPPLES & LEON CO., Publishers, NEW YORK The Speedwell Boys Series By ROY ROCKWOOD Author of "The Dave Dashaway Series," "Great Marvel Series," etc. 12mo. Illustrated. Price per volume, 40 cents, postpaid. * * * * * All boys who love to be on the go will welcome the Speedwell boys. They are clean cut and loyal lads. * * * * * [Illustration] The Speedwell Boys on Motor Cycles _or The Mystery of a Great Conflagration_ The lads were poor, but they did a rich man a great service and he presented them with their motor cycles. What a great fire led to is exceedingly well told. The Speedwell Boys and Their Racing Auto _or A Run for the Golden Cup_ A tale of automobiling and of intense rivalry on the road. There was an endurance run and the boys entered the contest. On the run they rounded up some men who were wanted by the law. The Speedwell Boys and Their Power Launch _or To the Rescue of the Castaways_ Here is an unusual story. There was a wreck, and the lads, in their power launch, set out to the rescue. A vivid picture of a great storm adds to the interest of the tale. The Speedwell Boys in a Submarine _or The Lost Treasure of Rocky Cove_ An old sailor knows of a treasure lost under water because of a cliff falling into the sea. The boys get a chance to go out in a submarine and they make a hunt for the treasure. The Speedwell Boys and Their Ice Racer _or The Perils of a Great Blizzard_ The boys had an idea for a new sort of iceboat, to be run by combined wind and motor power. How they built the craft, and what fine times they had on board of it, is well related. * * * * * CUPPLES & LEON CO., Publishers, NEW YORK * * * * * 
45932	----	Internet Archive (https://archive.org) Note: Images of the original pages are available through Internet Archive. See https://archive.org/details/gasolinemotor00slaurich Transcriber's note: Text enclosed by underscores is in italics (_italics_). Text in small capital letters has been changed to upper case. THE GASOLINE MOTOR by HAROLD WHITING SLAUSON, M. E. Author of "The Motor Boat" Outing Handbooks New York Outing Publishing Company MCMXIII Copyright, 1913, by Outing Publishing Company All rights reserved CONTENTS I. TYPES OF MOTORS 9 II. VALVES 24 III. BEARINGS 43 IV. THE IGNITION SYSTEM 62 V. MAGNETOS 83 VI. CARBURETORS AND THEIR FUEL 90 VII. LUBRICATION 112 VIII. COOLING 130 IX. TWO CYCLE MOTORS 148 THE GASOLINE MOTOR THE GASOLINE MOTOR CHAPTER I TYPES OF MOTORS There are certain events that must happen in a gasoline motor before the engine will run of its own accord. For instance, to obtain successive power impulses, the charge must first be admitted to the cylinder and compressed; it must then be ignited to form the explosion that creates the force at the flywheel; and the burned gases resulting from this explosion must be ejected in order to clear the cylinder for the new charge. To accomplish this series of events, some motors require four strokes, while others do the business in two. These are popularly called four-cycle and two-cycle motors, respectively. A cycle, of course, can be any round of events, such as a cycle of years--at the end of which time the previous happenings are scheduled to repeat themselves. But in gas engine parlance a cycle is taken to mean the round of events from, say, the explosion of one charge to the ignition of the next. Thus, it will be seen that the four-cycle motor requires four strokes of the piston to accomplish its round of events, and is, properly, a four-_stroke_ cycle motor. Likewise, the so-called two-cycle motor requires two strokes to complete its cycle and should therefore be termed a two-_stroke_ cycle motor. If this longer terminology could be adhered to, there would be less misunderstanding of the meanings of two- and four-cycle, for when taken literally, these abbreviated forms signify absolutely nothing. Usage seems to have made them acceptable, however, and if the reader will but remember that four-cycle, for instance, means four _strokes per cycle_, the term becomes almost as simple as does "four-cylinder." It is evident that there are two strokes for each revolution of the flywheel--one when the crank is forced down and the other when the crank moves up. As the piston is attached to the crank through the medium of the connecting rod, the strokes are measured by the motion of the piston. Thus, since it requires four strokes of the piston to complete the round of events in the four-cycle motor, the explosions occur only at every second revolution of the flywheel. In this connection it must be remembered that we are dealing with but one cylinder at a time, for a four-cycle engine is practically a collection of four single-cylinder units. But even though the explosion in a four-cycle motor occurs only every other revolution, the engine is by no means idle during the interval between these power impulses, for each stroke has its own work to do. The explosion exerts a force similar to a "hammer blow" of several tons on the piston, and the latter is pushed down, thus forming the first stroke of the cycle. The momentum of the flywheel carries the piston back again to the top of its travel, and during this second stroke all of the burned, or exhaust, gases are forced out and the cylinder is cleaned, or "scavenged." The piston is then carried down on its third stroke, which tends to create a partial vacuum and sucks in the charge for the next explosion. On the fourth, and final, stroke of the cycle the piston, still actuated by the momentum of the flywheel, is pushed up against the recently-admitted charge and compresses this to a point five or six times greater than that of the atmosphere. At the extreme top of this last stroke, the spark is formed, causing the next explosion, and the events of this cycle are repeated. Now, inasmuch as on one up-stroke of the piston the charge must be held tightly in place in order that it may be compressed, and on the next up-stroke a free passage must be offered so that the exhaust gases may be forced out, it is evident that a valve must be used as a sentry placed at the openings to restrain the desirable gas from escaping and also to facilitate the retreat of the objectionable exhaust. Likewise, the force of the explosion must be confined to the piston on one down-stroke in order that all of the energy may be concentrated at the crank, while on the succeeding down-stroke a free passage must be afforded to the charge so that it may be sucked in through the carburetor. Consequently a second valve must be used to control the inlet passage on the down-strokes and prevent the escape of the force of the explosion through an opening that was intended as an entrance for the fresh charge. Thus valves are a necessity on all motors in which successive similar strokes of the piston do not perform the same operations. As quadrupeds and bipeds form the two great divisions of the animal kingdom, so is the motor separated into the two main classes of four-cycle and two-cycle engines. Even though to all exterior appearances, the two types of motors may be identical, the distinction, to the engineer, at least, is as marked as is the difference between a stork and an elephant. The difference is somewhat reversed, however, in that, while the elephant has double the number of legs of the stork, the four-cycle motor has but one-half the number of power impulses of its two-cycle cousin at the same speed. In other words, there is an explosion in each cylinder of the two-cycle motor with every revolution of the flywheel,--instead of with alternate revolutions, as is the case with the four-cycle type. But the number of events necessary to produce each explosion must be the same in both types of motors, and consequently it is only by "doubling up" and performing several operations with each stroke that the two-cycle motor can obtain a power impulse with each revolution of the flywheel. Starting with the ignition of the charge, as in the four-cycle motor, let us see how the events are combined in the two-cycle type so that all will occur within the allotted two strokes. Directly after the explosion there is but one event that can happen if this force has been properly harnessed, and that is the violent downward travel of the piston. Just before the bottom of this downward stroke is reached, however, an opening is uncovered through which the exhaust gases can expend the remainder of their energy--which by this time has become greatly reduced. Immediately after this another passage is uncovered and the charge is forced into the cylinder under pressure, thus helping to clear the cylinder of the remainder of the exhaust gases. All of this takes place near the end of the down-stroke; and at the beginning of its return, the piston closes the openings previously uncovered for the passage of the exhaust gases and incoming charge, and then compresses the mixture during the remainder of its up-stroke. Thus the suction stroke and the "scavenging" stroke of the four-cycle motor are dispensed with in the two-cycle type and every downward thrust of the piston is a power stroke. The two-cycle motor has been used in several notable instances with great success on motor cars, but by far the larger majority of automobile power plants are of the four-cycle type. In view of the wonderful simplicity of the two-cycle motor, its small number of moving parts, and its more frequent power impulses, it may well be asked: "Why is this not in more popular use on the motor car?" The four-cycle motor has but one power stroke out of every four, while only alternate strokes of the two-cycle motor consume power without producing any. This would seem to indicate that, for equal sizes and weights, the two-cycle motor would produce twice as much power as the four-cycle type--and this is true theoretically. But the four-cycle motor devotes an entire stroke to forcing out the exhaust gases, or scavenging, and another entire stroke to drawing in a fresh charge, and it is evident that these operations can be done much more effectively in this manner than when combined with several other events following each other in such rapid succession as is the case with the two-cycle motor. In the two-cycle motor the incoming charge must be diluted to a certain extent with the exhaust gases which have not been entirely expelled, and the intake valve port is uncovered for so short a time that unless there has been very high compression in the base, the cylinder cannot be entirely filled with the explosive mixture at high speeds. This is described in greater detail in the last chapter of this volume. Thus, while admittedly simpler in construction and operation than the four-cycle, the two-cycle motor in its ordinary forms does not obtain quite as high an efficiency from the fuel as does its more complicated cousin. Each type has its distinct use, however, and in many instances in which low initial cost and simplicity of design are more desirable than are economy of fuel and high efficiency of operation, the two-cycle motor stands supreme. The sentries that stand guard over the passages through which the gases make their entrance and exit may appear in a variety of guises, but they determine the shape of the cylinders of a motor and divide the four-cycle engine into a number of classes. For instance, if the valves controlling the admission of the explosive mixture are placed on one side of the cylinders and those officiating over the exit of the exhaust gases are located on the opposite side, the motor is known as the "T-head" type because of the shape of its cylinders. All valves that are placed at the side of the cylinder must operate in pockets so as not to interfere with the movement of the piston. These pockets are cast with the cylinder and form a projection at its side near the top. When these projections are cast on opposite sides, a cylinder having the shape of the letter "T" is formed, while if the valves operate on the same side, the single projection forms a cylinder having the shape of the inverted letter "L." Hence cylinders having valves on opposite sides are called "T"-head motors, while "L"-head motor is synonymous for an engine having "valves on the same side." When the valves are placed in the head, there is no need of separate pockets, for these valves operate from above and do not interfere with the movement of the piston. There may be a combination of these positions, one set of valves being placed in the head and the others at the side. This is known as the "inlet in head, exhaust at side" type--or vice versa, as the case may be. The valve that has been in almost universal use in motor cars is known as the "poppet" type, as distinguished from the sliding and rotary styles. As evidenced by its name, the poppet valve is pushed or lifted from its seat, and thus the full area of the opening to the passage is made available almost immediately. The poppet valve is lifted by a cam, the shape of which determines the relative speed of operation of the valve, and is returned to its seat by a stiff spring. The nature of the contact that the valve makes with its seat depends upon the condition of the surfaces and is the deciding factor as to whether the joint is completely air-tight or not. When the exhaust valve is opened, its head is thrust directly in the path of the hot, out-rushing gases; these same gases also swirl around the edge of the seat. The excessive heat and the particles of carbon that are often found in the exhaust gases tend to corrode and build a deposit on the edges of the valve and its seat, thus eventually preventing perfect contact from taking place. This makes necessary the grinding of the valves--an operation that is familiar to the majority of motor car owners and drivers. While the poppet valve motor is still used on the majority of automobiles, a new and radical type of valve mechanism has been giving successful results. This is known as the sliding sleeve type of motor, and while it has been used for several seasons in Europe, 1912 saw its adoption for the first time in America. The sleeve motor, it must be understood, is of the four-cycle type, the events occurring in the same order as on any ordinary automobile motor, and the only difference lies in the nature of the valves that control the openings of the exhaust and inlet passages. That this difference is great, however, will be realized when it is understood that the valves consist of two concentric shells, in the inner one of which the piston reciprocates. In other words, two hollow cylinders line the interior of the cylinder casting and replace the poppet valves and pockets of the more familiar type of motor. These sleeves, or shells, or hollow cylinders--or whatever name it is chosen to give them--slide up and down in the same line of action as that of the piston. A port, or slot, is cut near the top on opposite sides of each of the shells. These four ports are so arranged that one set opens directly opposite the intake passage, while the other opens by the exhaust manifold entrance. When it is said that these ports open, it is meant that similar slots in the two sleeves come opposite each other, or "register," so that an unobstructed passage for the gas is offered. The port in one sleeve may be opposite the intake pipe entrance, but if the slot in the other sleeve does not correspond with this, the passage is effectively closed. Thus it will be seen that the ports are opened and closed by the movement of the sleeves in opposite directions. For example, just before the opening of the intake port, the inner sleeves will be traveling upward while the outer shell moves downward, and the slots in the two shells will be opposite each other at the instant that they pass the inlet pipe. This gives a much quicker opening than would be the case if one shell stood still while the other moved downward, and it is because the slots approach each other from opposite directions that this motor can be run efficiently at high speeds. Inasmuch as this is a four-cycle motor and the explosions occur in each cylinder but once during every two revolutions of the flywheel, each sleeve makes but one stroke for every two of the piston. The sleeves are operated by eccentrics attached to a shaft driven at a two-to-one speed by the crank shaft of the motor, and as they are well lubricated there is but very little friction generated between them and the piston. In fact, it has been shown that the power required to operate the sleeves, when well lubricated, is considerably less than that consumed by the springs and valve mechanism of the poppet valve motor, for the reason that the former type of valve does not open against the pressure of the exhaust, as is the case with the ordinary gas engine valve. Besides the two- and four-cycle divisions, a motor is known by the arrangement of its cylinders and is classified as "cylinders cast separately," "cast in pairs," or "triple cast," according to whether there are one, two or three cylinders to a unit. The last-named type is not as common as are the "pair-cast" cylinders and of course can only be used on six-cylinder motors. When all of the cylinders of a motor are cast in one piece, the engine is known as a "bloc" motor. This is a type that has come into popular use for small and medium-sized power plants during the past few years on account of the simplicity of its construction and the smooth and compact design that is rendered possible. Of course it may be argued that, with such a design, the entire set must be replaced if a single cylinder is damaged, but castings have been so improved that an accident or imperfection requiring the renewal of a cylinder is very rare. It is evident that, beyond a certain size of cylinder, a bloc casting becomes too bulky to be handled conveniently, and as the entire casting must be removed when it is desired to reach the connecting rods, crank shaft, or piston rings, a motor so designed will seldom be found that develops more than forty or fifty horsepower. This type of casting is found on some six-cylinder cars, however, but it is naturally only the "light sixes" that will use such a motor. Above six-cylinders, a motor is usually arranged with its power units set at an angle on either side of the vertical, thus forming the V-shaped motor. Several eight-cylinder motors are so constructed, the units being arranged four on a side and each set placed at an angle of about thirty degrees from the vertical. This gives the effect of two four-cylinder motors placed side by side and operating on the same crank shaft. In order to make the motor as compact as possible, the cylinders are "staggered;" or, in other words, the cylinders of one set are placed opposite the spaces between the units of the other. It will be seen that the V-shaped design of motor shortens the power plant and enables it to be set in a much smaller space under the bonnet than would be the case were the cylinders placed one in front of the other, as in the four- and six-cylinder types. As a rule, the two-cylinder, four-cycle motor is of a different type from its four- and six-cylinder cousins, and is known as a "horizontal opposed" engine. In such a motor, the cylinders are set lengthwise and the pistons operate opposite each other in such a manner that a "long, narrow, and thin" power plant is obtained that is especially well-suited for a location under the body of the car. In fact, this horizontal motor, which may, of course, be of the four-cylinder type, is the only shape that can well be used under the body or seat of a touring car. In some small runabouts, however, the "double-opposed" motor is used to good advantage under the forward bonnet, as in the "big fellows." There are, of course, many other features of design that serve to differentiate one automobile power plant from another, but these are details that do not serve to classify the motor, and the man who knows whether his machine is two- or four-cycle; poppet or sleeve valve; separate, pair, or en bloc cylinder castings; and "T"- or "L"-head shape will have at his fingers' ends distinctions that would have "floored" the salesman of a few years ago. CHAPTER II VALVES It has been stated in the preceding chapter that the valves of the gasoline motor are the sentinels placed on guard at the entrance to and exit from each cylinder to make certain that the mixture follows its proper course at the proper time. Therefore, if we accept the definition that a valve is a mechanical appliance for controlling the flow of a liquid or a gas, strictly speaking no such thing as a "valveless" motor exists. Two-cycle motors are sometimes said to be valveless because of the fact that the movement of the piston automatically regulates the flow of the exhaust and intake gases, but in this case the piston is in reality the valve. On the four-cycle motor, however, like events take place only on alternate strokes in the same direction, and consequently some controlling mechanism that operates but once for every four strokes of the piston is needed to time the flow of the gases. As has been stated in the previous chapter, the most common form of valve is known as the poppet type from the fact that its action is a lifting one. Such a valve may be located in a projection cast on either side of the top of each cylinder, or it may be inverted from this position and placed in the cylinder head. When in the former location, the valve is opened by an upward push on the rod to which it is attached at its center, while a valve placed in the cylinder head is forced down to allow the escape or entrance of the exhaust or intake gases. The ordinary type of poppet valve is somewhat similar in shape to a mushroom, having a very thin and flat head and a slender stem. The disc portion of the valve is known as its head, while the rod forged with the valve and by which the head is raised and lowered is called the stem. The projections cast in the cylinders of a "T"-head or "L"-head motor, and in which the valves are placed, are known as the valve pockets. Valves so located are lifted by a direct upward push caused by the rotation of a cam and are returned to their closed position by means of the extension of a stiff spiral spring surrounding each valve stem. It is only the outer edge of the lower side of the valve head that comes in contact with the surrounding surfaces of the opening which is closed when the valve is returned to its ordinary position by the spring. This surface of contact surrounding the opening is known as the valve seat, and it is this, together with the edge of the valve which rests against it, that must be ground smooth in order to insure a tight joint when the valve is closed. On the majority of poppet valves the edge of the head and the seat against which it rests are beveled to an angle of approximately forty degrees in order to conform to the natural direction taken by the gases when they are admitted or expelled. In a few cases, however, the seat angle is ninety degrees, which means that the edge of the head is ground flat, or straight, at right angles to the stem. One of the chief advantages found in the use of a poppet valve is the fact that a large opening can be obtained after the valve head has been raised but a comparatively short distance. This means that the valve stem need travel only a fraction of an inch between the full open and the full closed position of the valve and that the operating mechanism for obtaining this lift is simple. Practically every poppet valve, therefore, is lifted by means of a cam, which is a thick, irregularly-shaped piece of steel mounted on a shaft known as the cam shaft. If the end of the valve stem, or a rod connected to it, is held against the periphery of the cam while the latter is revolved by its shaft, the valve will be forced up, or away, rather, an amount corresponding to the increase in distance between the periphery of the cam at this point of contact and its axis. In other words, if the cam were a true circle with its axis passing through its center, there would be no motion of the valve, for all points of the periphery of a circle are at the same distance from the center. Consequently a portion of the periphery of the cam is extended in the shape of a "nose," the projection of this beyond the smallest diameter of the cam being the distance that the valve will be lifted when this point of the cam surface comes in contact with the stem or push rod. The broader, or more blunt, the nose of the cam, the longer will the valve remain open as the cam shaft is revolved, while the "slope" of the sides of the nose determines the rapidity with which the valve will be pushed out and back. Inasmuch as the valve should remain closed throughout two-thirds or three-quarters of every two revolutions of the flywheel, the greater part of the periphery of the cam is circular, or at the same distance from the axis at all points. As has been mentioned before, the cam serves only to lift the valve, the return of the latter to its seat being obtained by the force from a spring that is coiled around the stem. Thus the spring holds the end of the push rod at all times against the periphery of the cam. This push rod, in some instances, is a small bar of special steel that slides in guides of long-wearing bearing alloy. The upper end of the push rod is in contact with the lower end of the valve stem, while its other extremity is oftentimes designed in the form of a small steel roller that thus serves to create a rolling contact with the periphery of the cam. In other designs, the lower extremity of the push rod may be in the form of a specially-hardened steel pin with a rounded end, while still a third type consists of a flat disc slightly "offset" on the end of the push rod so that various points of its surface will come in contact with the periphery of the cam and the wear will be evenly distributed. Whatever the particular design, however, the cam is well lubricated and both it and the push rod are intended to last as long as any part of the motor. Many motors are designed with one valve at the side and the other, usually the intake, in the head. There are also many motors manufactured that have both the intake and the exhaust valves located in the head, in which case the valve pockets, or projections, are eliminated. Such valves may be operated by the same type of cams and cam shaft as those used to open the valves at the side. As the opening of a valve located in the head is downward, however, the motion produced by the cam on the push rod must be reversed in direction. This reversal of motion is obtained by means of a lever mounted at its center and placed in contact with the upper extremity of the push rod at its outer end. The other end of this lever operates in contact with the end of the valve stem, and thus an upward push on the rod is converted into a downward thrust on the stem. This lever that reverses the direction of the push rod motion is known as a rocker arm and is mounted in a yoke cast with the cylinder head. Inasmuch as a spring is used to keep the valve tightly closed when the cam is not lifting the latter, it is the contact of the valve head with its seat that must form the stop to the motion of the spring. It will be seen that the force of the spring is communicated through the valve stem to the push rod, and thence to the periphery of the cam when the latter is in a position to lift the valve. The push rod should not be forced tightly against the periphery of the cam when the valve is closed, however, for this would prevent perfect contact between the valve and its seat. Consequently there should be a certain amount of "play" between the end of the push rod and valve stem so that it will be certain that the head is forced against the seat with the full power of the spring and without the cam serving as a stop. On the other hand, this play should not be too great, for the cam and push rod will then move an appreciable distance before the valve is raised. This will cause the opening of the valve to occur late and will reduce the distance that the stem is raised, thus restricting the size of the opening. Furthermore, an undue amount of play between the ends of the push rod and stem will result in a pound or "hammer blow" between the two that is liable to wear the surfaces rapidly. The "happy medium" that will give the best results may be obtained by properly setting the small valve "tappets" that are secured to the end of the stems or push rods. By turning the nut of the tappet in one direction, the length of the push rod will be reduced, while the reverse operation will increase the length of the rod or stem. This is primarily intended for taking up any wear that may occur at the ends of the push rod or valve stem. In the case of engines having the valves in the head, the long push rod of each valve should be so loose as to move perceptibly when shoved up and down by the thumb and finger. When the rocker arm is pressed down against the valve stem, the space between the other end of the rocker arm and the push rod should be sufficiently wide to admit a piece of tissue paper. The same test may be made in connection with valves located at the side, after first ascertaining that the end of the short push rod is resting firmly against the periphery of the cam. The play will be apparent, of course, only when the valve is tightly closed, and in order to make certain that their cams are in the "inactive" position, the piston should be set at the beginning of the explosion stroke when testing the intake or exhaust valve. This is at the point of ignition and is the time at which both valves should be tightly closed. The cam shaft to which the cams that operate the valves are attached is generally placed inside the crank case. If the motor is of the "T"-head type, having valves on opposite sides of the cylinders, the cam shaft operating the exhaust valves will be found on one side of the crank case, while that for opening the inlet valves will be located on the other. If the motor is of the "L"-head type, all the cams will be placed on the one shaft. The cams are sometimes forged with their shaft in a solid piece, while in other designs they are keyed in place, but whatever type is used, the cams and their shaft may be considered as integral with each other. The cam shafts are generally driven by a gear meshing with a smaller one attached to the front end of the crank shaft of the motor, which forms one of the forward train of gears that are enclosed in an aluminum case. If the cam shaft is driven at the same speed as is the crank shaft of the motor, it will be seen that the valves will open once at every revolution of the flywheel. In a four-cycle motor, however, the explosion and other events occur but once in each cylinder for every two revolutions of the flywheel, and consequently the cam shaft must be driven at one-half the speed of the crank shaft. To obtain the proper speed ratio, each cam shaft is driven by a "two-to-one" gear, which means that the gear on the end of the crank shaft has but one-half as many teeth as have those attached to the cam shafts. There is thus one revolution of each cam shaft gear for every two of the crank shaft gear, and consequently each cam shaft is driven at the required half speed. The cam shafts may be driven by a chain, the links of which fit over teeth cut on sprocket wheels, but there must always be a constant relation between the position of the cam shaft and that of the crank shaft. This constant relation is necessary in order that the valves will open and close at the proper points during the travel of the piston. For example, the exhaust valve should open toward the end of the explosion stroke in order to allow the burned gases to be forced out, and the cam for operating this valve should always be in the lifting position at exactly the proper moment. If the cam shaft is not positively driven, this position may change and the exhaust valve might be opened at the beginning of the ignition of the charge, in which case the force of the explosion would be wasted almost entirely. On the other hand, the inlet valve should open at about the beginning of the suction stroke in order that the fresh charge may be drawn in by the downward travel of the piston; it is evident that this cannot be opened at any other time without a resulting loss in the power developed by the motor. The proper timing of the action of the valves is consequently one of the most important adjustments of a motor. When the motor is assembled and tested at the factory, the valves are properly timed and there is no possibility that they will require further adjustment in this respect until after the engine is "taken down" for the purpose of cleaning or the renewal of a broken part. If it should ever become necessary to remove one of the cam shafts or any of the gears constituting the forward train, the greatest care should be taken to make certain that all are returned to _exactly_ their original position. A difference of one tooth in the relative meshing of the gears may result in a loss of fifty per cent. of the power developed by the motor. Absolute rules for the proper timing of the valves cannot be given here, for various motors are designed with slightly different positions at which the exhaust and inlet valves should be opened and closed. A cam shaft should never be removed, however, without first marking the intermeshing teeth of its driving gear and those of its companions. This may best be done by means of a small prick punch which, when tapped lightly with a hammer, will make a permanent mark at the desired point on the surface of the gear. If the motor is of the "T"-head type, having its valves operated by two cam shafts, care should be taken to designate the right and left-hand gears so that their positions will not be reversed if both have been removed at the same time. A safe method to pursue is to indicate the right-hand gear with one punch mark, while two should be used for the gear at the left. Three teeth should be marked on each pair of intermeshing gears. That is, a tooth on one gear should be marked, and then each of the teeth between which it meshes on the other gear. The second cam shaft gear should be marked before the motor is turned. As has been stated, the cams on many motors are forged integral with their shafts, and there is consequently no possibility of the removal of one from the other. Those cams which are keyed to their shafts are accurately and rigidly set and the keyways so cut that there is slight chance of a mistake in returning a cam that has been removed. It should seldom be necessary to remove a cam from its shaft, however. Many motors are provided with timing marks on the flywheel to indicate the positions of the latter at which the valves of the various cylinders should open and close. In connection with these marks a pointer attached to the crank case and indicating the top of the flywheel is used. When the marked, for example, 4 Ex 0, is under the pointer, it indicates that the exhaust valve on the fourth cylinder should be about to open. If the motor is turned but very little beyond this point, a lifting should be felt at the proper push rod or valve stem. It is well to test the setting of the valves occasionally by means of these marks, for wear at the rocker arms, the push rods, the valve stem, or the cam travelers will result in unevenly-timed valves. It should be remembered that it is the valve itself that should open after the proper mark on the flywheel has been passed, and that the movement of a long push rod is not sufficient evidence that the valve is beginning to leave its seat. There may be so great an amount of lost motion between the push rod, cam, rocker arm, and valve stem that the flywheel may be turned several degrees beyond the proper point before this "play" will be taken up and the valve itself will begin to move. Although the timing of a motor may be given in inches of piston travel beyond a certain dead center, at which point an exhaust or inlet valve should open or close, it is generally expressed in degrees of flywheel revolution. Suppose, for example, it is said that the inlet valve should open ten degrees after the beginning of the suction stroke. This would indicate that the flywheel should be turned through an arc of ten degrees from the point at which the piston is at its upper dead center before the inlet valve for that particular cylinder should begin to open. Expressed in terms of flywheel revolution, the total travel of the piston during each stroke is 180 degrees, and as in the proximity of its dead centers the piston moves but a short distance in comparison with the size of the arc through which the flywheel swings, valves may be set very accurately by this method. Not all cam shafts for operating the valves are located in the crank case. On several designs of motors the cam shaft extends along the top of the cylinders and is driven by a vertical shaft and two sets of bevel gears. On such motors both inlet and exhaust valves are located in the cylinder heads, and owing to the proximity of the cam shaft, but short push rods and valve stems are needed. The valves are sometimes operated by means of a bell crank or rocker arm that acts directly against the cam surface and end of the valve stem. On some designs a double cam is used which serves to operate both the inlet and exhaust valves of the cylinder. The bearings and cams of such a shaft are generally enclosed in oil and dustproof casing screwed to the top of the cylinders. Such a cam shaft should never be dismounted without first marking intermeshing teeth of all spur and bevel gears that are concerned in its operation. All poppet valves must be accessible and readily removable for the purpose of cleaning and grinding the contact surfaces of the head and seat. The pockets in which the valves placed at the side of a cylinder are located are generally provided with large screw plugs at the top. Such a plug may be removed with a heavy wrench, and as the opening which it fills is larger than the head of the valve, the latter may be removed after first loosening the spiral spring surrounding its stem. It is not necessary to remove the valve entirely from its pocket in order to grind its surfaces, but the pin holding the spring stop in place must be withdrawn so that the tension of the spring on the valve will not be so great as to prevent the latter from being lifted to permit the introduction of the abrasive and turning the head with the grinding tool. Valves located in the head of the cylinder must be removed entirely before their surfaces can be ground. This, however, is not a difficult operation, as the valve and its seat are generally placed in a removable "cage" that either screws in place or is held firmly in position by means of a clamp or like device. Inasmuch as the seat is contained in this removable cage in which the valve operates, the grinding may be done at a work bench or on the bed of any convenient tool, independently of the location of the motor. If a valve seems sluggish in its action at high speeds of the motor, it is possible that its spring has become somewhat weakened. These springs are designed to be exceedingly stiff and heavy, some of them requiring a pressure of two hundred and fifty pounds to compress the coils one inch. With such a spring, a special tool is required to compress it sufficiently to enable the valve to be removed. A spiral spring that has become weakened may sometimes be strengthened by "stretching," but it is not to be supposed that this would be of great avail in the case of a spring as heavy as those used on some valves. If, however, a flat tool is introduced between the various coils and each is separated slightly so that the ultimate length of the entire spring is greater than it was formerly, it will exert a more powerful force on the valve when it is returned to its place surrounding the stem. Stiffening the spring, however, will be of but little help if the stem or push rod is tight in the guides through which it slides. These guides are often made of a special bearing bronze and are designed to withstand a large amount of wear, but the friction surfaces must be lubricated if satisfactory service is to be obtained. The lower guide is generally lubricated by the oil from the cams, while the guide near the valve may receive its oil from the engine cylinder. It is not necessary that these guides shall be packed or that they shall be particularly tight, as they are not called upon to retain any gas or air pressure, but they must hold the stem and rod sufficiently rigid to prevent any perceptible side motion and thus cause imperfect seating of the valve. In replacing valve stems and push rods, it should be made certain that each works freely in its guide before the spring is installed. If there is a slight tendency for the guide to grip the rod or stem, the latter should be smoothed with emery paper at the point at which it comes in contact with the guide and plenty of oil applied until the surfaces are well "worked down." As the distance that the rods and stems travel through the guides is comparatively short, the wear is slight and only a small amount of lubricant is needed, provided the rubbing surfaces are smooth and well-fitted to each other. The mechanism of a sleeve valve motor is slightly different from that of the poppet valve type. Each sleeve is operated by a connecting rod and eccentric mounted on a shaft driven by a chain or gears from the crank shaft of the motor. The eccentric replaces the cams of the poppet valve motor, and as it must maintain a certain relation with the position of the piston in order that the operation of the valves shall be timed correctly, the same care must be observed in replacing the eccentric shaft with the proper teeth of the sprocket or gear in mesh as has already been described in connection with the cam shaft of the poppet valve motor. CHAPTER III BEARINGS In the general meaning of the term, a bearing is any part that carries weight or pressure and at the same time rubs over another surface. According to this definition, the portion of the cylinder walls traversed by the pistons are bearings, and that is in reality the case, but the term has come to be applied more specifically to the part of the machine in which another part _revolves_, either continuously or intermittently. Thus the portions of the crank shaft on which it is supported and the parts of metal in which they revolve combine to form the crank shaft bearings. The shaft or stud on which a gear or wheel is mounted and on which it revolves is the bearing of that gear or wheel. Although they are concealed, as some six-cylinder motors may be provided with as many as three dozen, or more, bearings--if we consider those on which the cam, pump, and magneto shafts and the gears are mounted--but what descriptions, rules, and precautions apply to all hold true in the largest sense when the crank shaft, connecting rod, and wrist pin bearings only are considered. It is on this latter class that the greatest wear of the motor is concentrated, and the owner who understands and inspects these need fear no trouble from the cam shaft and gear bearings. The expert will judge of the condition of a motor by the wear that has occurred in the bearings rather than by any exhibition of temporary power that it may develop in a short test, and it is for this reason that the "general public" runs a risk whenever it buys a second-hand car that has not been thoroughly overhauled by a reputable factory or inspected by a competent engineer. The bearings are in reality the vitals of the motor, and when these are worn beyond the point of easy adjustment or renewal, the repairs necessary to place the machine in good condition would oftentimes cost more than the entire engine is worth. But even in a badly-worn motor, the bearings may be "taken up" and "doctored" so that, for a while at least, the engine will seem to run perfectly and develop its full power. This will not be for long, however, and soon the motor will begin to pound, knock, and rattle until an examination will bring to light the true condition of the bearings. In no machine are the bearings subjected to more severe usage than in the automobile motor. In order that the motor car power plant shall be light in weight and occupy but a small amount of space, the power must be transmitted at high speeds. In many an automobile motor, the pressure imparted to a single bearing during a certain portion of its revolution may frequently be well over two tons, and in this same bearing, the "speed of rubbing" may approach eight or nine hundred feet per minute. In other words, at normal speeds of the motor, about a sixth of a mile of steel surface will rub over a certain point in each crank shaft bearing during every minute that the engine is running. When properly lubricated, an iron or steel shaft will run in almost any kind of a metal bearing that is sufficiently strong to carry the weights and pressures imposed upon the shaft. The friction generated between two different metals that rub against each other, however, varies according to the composition of those metals, and consequently it is advisable to employ some material for a bearing that will offer a minimum resistance to the turning of the shaft. Friction must be reduced between all moving surfaces in order that the mechanical efficiency of the machine shall be high, and it is in the bearings that a large amount of power may be absorbed. But even between the best-lubricated surfaces, employing the most efficient metal as a bearing, some wear is bound to occur. The crank shaft of a four- or a six-cylinder motor is forged or sawed from one piece of steel, and with the accurate machining, finishing, and grinding to which it is subjected, it becomes an expensive part of the engine. Consequently it is advisable that the wear of bearings of such parts shall be restricted to the "boxes" or surrounding stationary metal in which the shaft revolves at these points. In order that all wear shall occur here, rather than in the shaft, the boxes are made of or lined with a softer metal. If the crank shaft is of hard steel, the bearing metal may be of brass or bronze, but it has been found that babbitt metals give the most satisfactory service for such conditions--particularly as a sufficiently hard crank shaft is difficult to produce commercially. Not only is a babbitt metal softer than the steel of the shaft and consequently receives practically all the wear of the bearing, but it has the added advantage of melting at comparatively low temperatures. At first thought, this may seem like a doubtful advantage, but in case of a failure of the oil supply to that bearing, this characteristic may be the means of saving the crank shaft, and possibly the crank case, cylinders, and connecting rods, from rack and ruin. The purpose of lubrication is to reduce friction between the two surfaces in contact. Friction generates heat, and consequently the temperature of a bearing to which a sufficient supply of oil is not delivered will be raised to a very high point. This high temperature will cause both parts of the bearing to expand, with the result that the fit becomes very tight and the shaft binds or "seizes" in its box. This is the familiar "hot box," so often the bane of railroad men, and if the shaft is still run under these conditions, the bearing material will be torn out and the surface of the shaft, axle, or whatever the revolving portion happens to be, will be cut and abraded, oftentimes beyond the possibility of repair. It is such accidents as these that are prevented by the use of an easily-melted babbitt metal. If the oil supply becomes insufficient so that the temperature of the bearing is raised above a certain point, the babbitt metal will be melted and will run out of its container before any damage can be done to the shaft. Efficient running cannot, of course, be obtained with the bearing "burned out" in this manner, but the babbitt is quickly and easily renewed and serves as a sort of fusible safety valve that saves many an expensive crank shaft replacement. Babbitt metals may be of various compositions and proportions and many contain lead, but those which have been found to give the best results for use on the crank shafts of automobile motors are composed only of tin, antimony, and copper. If lead is used at all for this purpose, it should not appear in proportions above one per cent of the total composition. Inasmuch as a babbitt metal will fuse at a comparatively low temperature and is much softer than steel, it is obvious that such a material will not withstand heavy pressures unless reinforced and is unsuited for structural purposes. Consequently the babbitt is placed in the bearing box in the form of a thin lining within which the shaft revolves. When the shaft is "lined up" in the box, the hot babbitt metal may be poured in until the space is entirely filled. When the babbitt cools, the shaft may be turned, and when lubricant has been introduced in the oil grooves which should have been provided for the purpose, the new bearing will be ready for use. It is not to be expected that the majority of motor car owners will rebabbitt the crank shaft bearings themselves, but it is necessary to understand the general principles of such bearing design in order to inspect the motor intelligently and to determine upon the repairs needed. The above method of renewing "burned out" bearings applies to babbitts in general, but the severe usage that automobile engine crank shaft and connecting rod bearings are called upon to withstand necessitates the exercise of a certain amount of additional care. It is necessary that the box shall fit the shaft perfectly, so that there can be no "play," and yet the shaft must be allowed to turn easily within its surrounding babbitt metal. As was stated above, the shaft may be easily loosened from the babbitt metal after the latter has cooled, and this would form a satisfactory type of bearing were it not advisable that some means be supplied by which the wear could be taken up without renewing the entire babbitt lining. The bearing boxes of the crank shaft are each made in two halves, the lower portion being cast integral with the crank case, while the upper half is in the form of a separate cap that may be held in place by two or four bolts. In this case, it is necessary that the boxes shall be in two sections, for the shape of the crank shaft prevents it from being slid into place lengthwise, and consequently it must be placed on its bearing from the top. In some designs of motors the bearing caps form the lower half of the box, but as in this case the base of the motor must be inverted in order to remove the crank shaft, the caps will still be considered as the "top" halves of the boxes. There may be dove-tail grooves cut in the inside of the halves of the boxes to retain the babbitt metal after it has been poured in place. Consequently, in order to remove the cap after renewing the babbitt lining, the babbitt metal must be cut in two at the joint between the two halves of the box. The two halves of the box, instead of fitting closely together, are separated by thin strips of copper or fiber known as "shims" that serve to relieve the shaft from the pressure of the bolts when the bearing cap is screwed in place. In other words, the two halves of the box must be held tightly in place by means of the bolts and nuts, but none of this pressure should rest on the revolving shaft, as this would bind it and prevent it from turning easily. Consequently by "building up" the space between the two halves with these thin shims the proper adjustment may be obtained. These shims provide the method of taking up the wear in the babbitt that will eventually result. By loosening the box retaining bolts and removing the required number of shims, the halves of the box will be brought closer together. When the bearing cap is screwed securely in place, the shaft should be able to revolve freely without binding, and yet the fit should be sufficiently tight to prevent any "play" at right angles to the length of the shaft. The pressure of a shaft should not be concentrated in one place, but should be distributed over as large a surface of the babbitt metal as is possible. A few years ago, when renewing or repairing a bearing, it was considered sufficient to pour in the molten metal or to remove the proper number of shims--and the bearing was then said to be ready for its work. But even though no play was apparent, it was possible that the shaft rested on only a few portions of the bearing surface; and the increased attention that is now paid to the details of automobile construction is no better exemplified than in the fact that nearly all bearings are "scraped" in. This operation is simple and consists merely in removing any slight excess babbitt metal so that the lining fits the shaft throughout its entire length and circumference. The babbitt is sufficiently soft to enable it to be peeled or scraped with a sharp tool provided for the purpose, and no great degree of skill is necessary in obtaining the required fit. In order to determine at exactly what portions of the babbitt lining the pressure is too great, a dye or paint known as "blueing" is used. The bearing portion of the crank shaft is painted with this, and the cap is then screwed in place. If the crank shaft is then turned and the cap removed, it will be found that the blueing has been transferred from the bearing to the portions of the babbitt metal on which the pressure is the greatest. These portions should then be shaved with the tool mentioned above, and the same test repeated. As the excess metal is removed, it will be found that the blueing gradually is deposited over a larger area of the babbitt, but it is not to be supposed that the fit can be made so perfect that the color will be distributed evenly over the entire surface. Care should be taken to screw the bearing cap onto the shims as tightly as possible each time the blueing test is to be made. There is nothing that will heat a bearing so quickly as a poor alignment of the shaft supported by it. For this reason gasoline engine crank shafts are made exceptionally strong and heavy, especially those that are supported only at their extremities, or at these points and in the center of their length. A shaft that is bent or twisted to even the slightest degree will soon "burn out" all of its bearings, regardless of the amount of oil that may be fed to them. This is because of the unequal pressures on the different sides of the bearing that allow no room for the admission of the film of oil or other lubricant that is necessary in all cases to prevent a "hot box." On the other hand, the bearings must all be in perfect alignment, for to set one slightly "off" would produce the same result as though the shaft were bent. It will be seen that the use of babbitt produces a "self-aligning" bearing, for the straight shaft may be set in its proper position and the molten metal poured around the interior of the boxes. As it is highly important that the cap screws or nuts holding the bearing cap in place should remain set as tightly as possible, precautions must be taken to prevent any of these from working loose. This may be done by means of a cotter pin that passes through a hole in each bolt and through a pair of corresponding notches cut in the top of opposite faces of the nut. A notch is generally cut in the top of each face of the nut in order that the latter may be held securely in place in any position. A continuous wire passing through all of the bolts and nuts is sometimes used instead of the individual cotter pins. Many modern automobile motors are designed with the crank shaft running in ball bearings. The type generally used consists of a row of balls set between the inner and outer edges of two concentric rings. The inside of the outer and the outside of the inner ring are grooved, constituting the ball "race" which forms the surface upon which the balls roll and which, at the same time, serves to hold them in place. Each ball of the same bearing must be made of exactly the same size as its companions--or at least within one or two ten-thousandths of an inch--and each one must be large enough and of sufficient strength to withstand, by itself, the entire pressure in that bearing. The inner ring slips over the bearing portion of the shaft with a comparatively tight fit, while the outer ring remains stationary in its bed in the crank case. The inner ring turns with the shaft, thus causing the balls to roll in their race. Each ball rolls about its own axis, and the entire series describes a circular motion in the same direction as that taken by the shaft, but considerably slower. Consequently there is no rubbing in such a bearing, all the motion being of the rolling type, and as this reduces friction to a minimum, the balls may be run without oil, although lubrication of the proper kind would certainly not harm the bearing. Ball bearings are adapted only for a two-bearing crank shaft, for inasmuch as the rings must be slipped over the shaft, it would be manifestly impossible to provide a ball bearing in the center, or in any other portion beyond a crank. Next in importance to the main bearings of a crank shaft are those by which the connecting rods communicate their motion to the cranks. These are known as the crank pin bearings or the "big end" of the connecting rod bearings. But inasmuch as the upper, or smaller, end of the connecting rods are termed the wrist-pin bearings, the other end may be called simply the connecting rod bearing. The connecting rod bearings are similar to the main bearings described in the foregoing pages and are renewed and adjusted in the same manner. It is probable, however, that these receive a greater amount of wear than do the main bearings, inasmuch as the former obtain the direct impact of the force of each explosion. Furthermore, the box of the connecting rod bearing describes a complete circle with each revolution of the crank shaft, in addition to the "internal rotation" of the crank, while an alternate push and pull is delivered to it by the connecting rod on its various strokes. Consequently it is the connecting rod bearings that will become loose and require "taking up" before any attention need be bestowed on the main bearings. The wear will increase in the connecting rod bearing as the play becomes greater, and if matters are not remedied, the box may eventually be broken, with the result that the end of the connecting rod thus freed will start on the "rampage" and will punch several pieces out of the bottom of the crank case. Brass or bronze bearings may be used at the big end of the connecting rods, but the large majority of motor car engines are provided with babbitted bearings at these points. It is especially necessary that these bearings should be scraped to a perfect fit and that the shims should be adjusted properly so that no side play will be apparent when the connecting rod is moved transversely to the length of the crank shaft. When renewing the babbitts of connecting rod bearings care should be taken to allow the connecting rod to swing free before the molten metal is poured in. If this is not done, the connecting rod may be forced slightly to one side or the other and will be held permanently in this position when the babbitt cools. This will induce a slight side thrust in the connecting rod, which will be communicated to the piston, with the result that the side of the latter and of the portion of the cylinder wall against which it moves will be scored and worn unduly. Inasmuch as the connecting rod bearings are subjected to such a variety of strains, and as looseness at these points will result in serious wear, it is doubly necessary that the nuts and bolts holding the bearing caps in place should be securely wired or held tightly by means of the previously-mentioned cotter pins. It is evident that the base of the large end of the connecting rod forms the upper half of the bearing box, while the cap constitutes the lower end and is attached from the bottom. The connecting rod bearings on some motors are hinged at one side so that the cap may be turned away from the crank shaft when it is desired to remove the connecting rod. In this case the hinge replaces the one or two bolts or nuts on one side of the box and is held in the proper position by those on the other side. While it may be easier to adjust a bearing provided with such a cap, the results obtained can hardly be expected to be as satisfactory for high-grade service, as is the case when the shims may be used on both sides of the two halves of the bearing. The wrist-pin bearing is located at the upper, or small, end of each connecting rod, and, although it also carries the full force of each explosion, it is not subjected to as great wear as is the bearing at the other end of the connecting rod. The reason for this is that this bearing does not revolve and its friction surface is reduced to the comparatively small arc through which the connecting rod swings. Wear can occur here, however, and because this bearing is more inaccessible than is the crank shaft or connecting rod bearing, trouble at the wrist pin is often overlooked. The wrist pin can only be reached by the removal of the piston and connecting rod. In the majority of designs the wrist pin is placed in the sides of the piston and is held stationary by small keys or by set screws. In this case, the bearing surface is formed by the wrist pin and the small end of the connecting rod, at which point the greatest wear occurs. This bearing is never babbitted, but in order to reduce the wear on the wrist pin--which is generally made of hardened steel--the circular opening in the upper end of the connecting rod is lined with a bronze or brass bushing that forms a bearing fit over the wrist pin. It is this lining, or bushing, that will wear rather than the hardened steel wrist pin, but as the former is easily removed and is not expensive to replace, the renewal of this bearing is a comparatively simple matter. In other types of wrist pin bearings, the pin is held stationary in the connecting rod opening and turns with it as the connecting rod swings through its arc on each stroke of the piston. With such a design, the bearing surface is formed by each end of the wrist pin and the openings in the sides of the piston walls in which the wrist pin rests. In order to form an easily-replaced bearing surface, these openings in the piston walls are lined with brass or bronze bushings that receive the major part of the wear, as has been described in connection with the bushings fitted to the opening at the small end of the connecting rod. There is nothing complicated or mysterious connected with the renewal or repair of bearings, but the man who makes such replacements or adjustments must be an accurate and careful worker, and while he need not be a "born machinist," he must at least possess the "knack" of handling tools properly. And he must, above all, realize that the designers and manufacturers of his motor have been dealing in measurements of the thousandth part of an inch and that too great care cannot be taken in the repair of bearings to obtain a perfect fit. If he is renewing a connecting rod or a wrist pin bearing, he must also remember that the piston has formerly been traveling over a certain area of cylinder surface that has not varied in length the ten-thousandth part of an inch between one stroke and the next. Consequently, the babbitts or bushings should be so replaced that the piston shall occupy the same position relative to the cylinder walls at the top and bottom of its stroke that it did formerly. In other words, by varying the thickness of the top of the babbitt he is replacing, he may change the "center" of the bearing so that the piston will start on its upward stroke from a different point than was previously the case. Thus, while the length of travel of the piston will be the same, it will traverse a slightly different portion of the cylinder walls under the new conditions, and this will have the effect of changing the compression and, possibly, of wearing the piston and rings unduly. CHAPTER IV THE IGNITION SYSTEM It was the application of the electric current to the ignition system of the gasoline engine that first enabled these new forms of power plants to be designed with sufficient compactness and to possess enough flexibility to render their use practical on self-propelled vehicles. Without the electric ignition system, the speed and power of the vehicle could not well be controlled, and the explosions would be uncertain and irregular, at best. Those of us who are familiar with the electric gas lighters that were in popular use a few years ago are furnished with a convincing demonstration of the operation of the first electric ignition systems. By pulling a chain, a wire, or arm was rubbed across a metal point until the contact thus formed was suddenly broken. This arm and the stationary point formed the two terminals of an electric circuit, which caused a flash of blue flame when the contact was broken as the one was "wiped" across the other. The flame thus formed at the instant the contact was broken contained sufficient heat to ignite the gas escaping from the burner to which the device was attached. Sparks will be formed in the same manner if we hold two wires, connected to the opposite poles of a set of batteries, in both hands and wipe the bare ends across each other. If an arrangement producing this effect is introduced into the gas engine cylinder at the portion in which the charge is compressed, the flash resulting when the terminals are separated will serve to ignite the explosive mixture. The movable terminal is connected to a rod which passes through the cylinder walls and is attached to a mechanism actuated by a cam revolved by the engine. This mechanism is termed the "make-and-break" ignition system for the reason that contact of these terminals is alternately made and broken to produce the flash of electricity that explodes the surrounding charge. In order to produce a flash of sufficient size when the contact is broken, the nature of the current, obtained from the dry cells or storage battery is changed somewhat by conducting it through a coil of wire surrounding a bundle of bare copper wires. This is known as a spark coil, and while it is generally used with battery ignition of the make-and-break type, magnetos may be designed which produce the proper kind of current direct, without the aid of the coil. An ordinary set of six dry cells, connected in series--or like with unlike poles--will produce a current of between twenty and twenty-five amperes at a pressure of about nine volts--assuming each battery, when new, to deliver twenty-five amperes at a pressure of one and one-half volts. The "series" wiring gives the entire set the combined voltage of all with the average amperage of one. For the benefit of those who have forgotten their elementary physics, let it be remembered that the ampere is the measure of current _amount_, or flow, while the voltage is concerned only with the _pressure_ of the current. By the use of various arrangements of windings of wires, the voltage may be raised with a corresponding decrease in the amperage--and vice versa. Thus, if a coil is used that doubles the original number of amperes produced by the battery, the voltage will be halved. The make-and-break type of ignition has been used successfully for many years, but with the perfection of the magneto, it has been largely supplanted, in automobile practice, at least, by the "jump spark," or "high-tension" system. Because of the fact that the latter system is less expensive to construct and is highly efficient, it will be found also on the majority of the older cars not equipped with a magneto. It was found, after the general adoption of the make-and-break ignition system, that a flame was not necessary for the combustion of a properly-mixed charge in the engine cylinder. In fact, a tiny spark, scarcely one-sixteenth of an inch long and no larger around than a pin, was discovered to be sufficient to produce the ignition of the charge. Although, of small volume, such a spark generates intense heat, and it is upon this quality, rather than upon area, that the charge depends for its ignition--although it is claimed that a large flame will produce more complete, rapid, and consequently more efficient, combustion. But the jump spark possesses the advantage of requiring no moving parts projecting through the cylinder walls into the combustion chamber, and its greater simplicity over that of the make-and-break system has resulted in its almost universal adoption by automobile manufacturers. It has been stated in a preceding paragraph that the voltage produced by the average battery set will not exceed nine or ten, and even the pressure generated by the ordinary magneto is not greater than this. But air is not a good conductor of electricity and forms a very high resistance to the passage of a current. It is only when the high resistance of an air gap is encountered in its circuit, however, that a spark will be formed by the current, and consequently the form of electricity used in this system must have resistance-overcoming properties. But it is only by raising the voltage of the current that even a short air gap can be bridged by the spark. In fact, a pressure of somewhat over fifty thousand volts is required to produce a spark less than an inch long in the air. Although only called upon to jump a gap about a sixteenth of an inch across, the ordinary high-tension current is capable of bridging a space eight or ten times this width in order that ample pressure will always be assured for the formation of the spark. Furthermore, the warm gases in which the spark is formed in the cylinder increase the resistance ordinarily encountered and it is consequently necessary to raise the voltage above the amount that would be needed were the plug exposed to the open air. These conditions make advisable a pressure of from twelve thousand to thirty thousand volts in the ordinary jump spark system, and it is from this voltage that the term "high tension" is obtained. The nine or ten volts delivered by the batteries are transformed to this larger amount by means of an induction coil--or what is more generally termed merely the "coil." This is in reality a "step-up" transformer, since it transforms the current from one of low voltage to another of two or three thousand times its original pressure. This transformer consists of two coils of wire, one surrounding the other. The inner coil is composed of a comparatively few number of turns of rather coarse wire wound around a soft iron core, and is termed the "primary" winding, since the current from the batteries is led directly through it. The outer coil is composed of many turns of a very fine wire, all of which are thoroughly insulated from each other and from the inner winding. This outer coil is termed the "secondary" winding and is the one from which the high-tension, or transformed, current is taken. This secondary current is "induced" from the primary winding through which the battery current passes and possesses a voltage that has increased over its original amount in the same proportion that the number of turns in the secondary winding bears to those in the primary. Therefore, if the original battery voltage is ten and there are a thousand times as many turns in the secondary winding as in the primary, the resulting high-tension current will have a pressure of ten thousand volts. The principle of the coil is dependent entirely upon that peculiar electric property known as "induction." Around every wire through which an electric current passes are invisible "lines of force" similar to those that emanate from an electro-magnet. These lines of force surround the wire throughout its length, and arrange themselves in a spiral formation. Insulation has no effect on these lines of force, and they may be collected from wires which are separated from each other by several thicknesses of current-confining material. It is, of course, necessary to use insulated wires in the construction of these coils, for otherwise the current would merely pass to adjoining turns and would not travel the entire length of the winding--and therefore as great a number of lines could not be collected. If an additional layer or layers of wire is wound around the first series of turns, the lines of force will be collected, or "induced," by this second coil, and will constitute the secondary current. The induction effect is greatly increased if the primary current is allowed to accumulate, or "pile up," and discharge, alternately, for this surging of the current creates a sort of "overflow" from the original containing wires. Ohm's Law, which states that the number of amperes in an electric circuit is equal to the voltage divided by the number of ohms of resistance encountered, shows that the current will be changed by its passage through the primary winding. The induced current is further changed, and when collected by the secondary winding and sent through its long coils, we have the high-tension circuit mentioned in the preceding paragraph. If the reader remembers that it is but one hundred and ten volts that is used to operate our electric lights and that five hundred will run a trolley car, he may wonder why it is not dangerous to handle as great a pressure as the thirty thousand volts that are used in connection with the ignition system of a motor car. But it is the combination of great voltage with high amperage that is dangerous, and if it is remembered that, as the former is increased, the latter is reduced correspondingly, it will be realized that the ordinary high-tension ignition current possesses a _quantity_, or flow, of scarcely one one-hundredth of an ampere. If we liken the electric current to a flow of water in a pipe, we have the amperes corresponding to the quantity of the flow, or the number of gallons that will be delivered at the outlet in a given time. Continuing this analogy, the voltage of the electric current will be the pressure, or "head" in the water system, and the current from the batteries before the coil is reached will correspond to a moderate flow of water at a comparatively low pressure. After the coil has transformed the current to the high voltage, we have the conditions of a very small opening in the water pipe containing a tremendous pressure. Such a stream will possess but small flow, but its high pressure will enable it to be "squirted" to a far greater distance than would be the case were its volume larger and its "head" less. Although the pressure is high, its quantity is so low that the stream can do but little damage and would scarcely more than tickle the flesh of a person against whom it is directed. Thus it is with the ignition current. It can "tickle," rather viciously, sometimes, as many persons will aver, but the _amount_ of electricity involved is so slight as to render the high pressure harmless. Nevertheless, it is well to avoid allowing the fingers or the arm to become a part of the high-tension circuit, for the result may be startling as well as annoying. But in order that the high voltage shall be induced in the secondary coil, the primary circuit must be alternately made and broken between one stroke and the next. Consequently proper "piling up," or "surging," of the current will be effected. This is accomplished by means of an "interrupter" that either vibrates rapidly or "snaps" once at the formation of each spark. The former is the more common type used with battery ignition and is known as a vibrating coil. A circuit breaker is generally incorporated in the mechanism of a magneto, and consequently when such an instrument is used, the vibrator on the coil is dispensed with. It is the vibrator on each coil that forms the "buzz" that can be heard whenever the box cover is removed, and that often furnishes a simple test for determining the condition of the ignition system of the particular cylinder with which that coil is connected. The vibrator is a flat, spring steel piece that rests near one end of the soft iron core around which the primary coil is wound. The springy nature of the vibrator ordinarily holds it against a small, adjustable contact point that should be set about an eighth of an inch from the end of the above-mentioned soft iron core. The primary coil is so wired that its current passes through the vibrator steel and the contact point against which it rests. As soon as the current travels through the coil surrounding the soft iron core, however, the latter becomes magnetized and draws the steel vibrator toward it. This breaks the circuit, the magnetism of the iron core disappears, and the vibrator returns to its original position against its contact point. But this action again forms the circuit, and the same operation is repeated as long as the current is allowed to flow toward the coil. This is the same principle on which an electric bell is rung, but the vibrator of the coil makes and breaks the circuit much more rapidly on account of the less weight of the moving parts. This vibration of the coil interrupter is so rapid--hundreds a second probably--that the resulting spark is practically continuous and shows no effect of the breaks in the circuit. Even though it is the primary current, of low voltage, that is interrupted by the vibrator, the frequency of these interruptions causes a slight sparking, or arcing, at the contact points. These are therefore subjected to rather a high degree of heat, as well as a large amount of wear, and it is necessary that they be made of a material that will resist both. Platinum has been found to be unusually suitable for this purpose, but owing to its high cost, only a small amount in the form of two points, or "buttons," is used. One of these points is placed in the vibrator steel, and the other is embedded in the end of the screw against which the first rests. Thus the actual contact is made against these heat-and-wear-resisting platinum points, and it is evident that upon their proper action depends the formation of the spark in the cylinder with which that particular vibrator is connected. Notwithstanding the fact that platinum possesses high heat-resisting properties, the constant arcing at the contact points will eventually form a sort of corrosion in which minute particles of the material are carried from one point to the other in the direction in which the current flows. If the current is reversed, the corrosion will take place in the other direction, and consequently the platinum point that formerly lost a part of its material will gradually be "built up" again. This corrosive action is known as "pitting," and while it may be reduced to a certain extent by reversing the terminals of the battery, as described, the platinum will occasionally require additional attention. A coil having badly pitted contact points on the vibrator will "stick" and will cease to form a spark regularly. It is often difficult to distinguish between trouble arising from badly-pitted contact points and that caused by weak or nearly-exhausted batteries, as either ailment produces the same symptoms of irregular running and "jerking" in the motor. For this reason, a volt and ampere meter for measuring the pressure and amount of the current delivered by the batteries should form a part of every automobile owner's tool equipment. It is the amperage, rather than the voltage, that is reduced through continued use of the batteries, and when this quantity falls below nine or ten, the cells should be discarded--or recharged, in the case of a storage battery. But if the ignition occurs irregularly when the batteries are delivering the proper amount of current, it is probable that the trouble lies in the pitted condition of the platinum contact points of the vibrator of the coil. Fine emery cloth rubbed over the surfaces of contact should serve to remedy matters. It should be made certain that the resulting surfaces on the platinum points are not only rubbed smooth, but level, as well, in order that the entire area of each will rest in contact and the current will not be concentrated at a small portion. It is probable that there will be a screw adjustment on the vibrator by means of which the force with which the latter rests against its contact point may be regulated. If the vibrator is set too tight, an undue amount of current will be required to magnetize the core of the coil sufficiently to pull the vibrator away from its contact point, and the batteries will soon "run out." On the other hand, the tension of the vibrator should be sufficient to enable it to spring away from the core of the coil as soon as the circuit is broken, for otherwise the vibrator will lag and will not be as "lively" as is necessary to obtain the best results. The contact screw should be set so that the vibrator rests _about_ three-thirty-seconds of an inch from the end of the magnetic core. After the tension of the vibrator has been set to approximately the proper amount, the ear must be trusted for the correct adjustment of the contact screw. When the switch is thrown on and the motor turned until current flows through the coil, the resulting buzz emanating from the vibrator should be decided and forceful. If this buzz is exceedingly high-pitched, it is an indication that the vibrator has been set too tight, and its tension should be loosened if unscrewing the contact point slightly does not lower the tone. It must be remembered that the tension of the vibrator can be changed by turning the contact screw. If this screw is turned down so that it forces the vibrator toward the iron core, the tension will be greater than will be the case if the contact point is turned to the left. If the buzz of the vibrator is pitched lower than was formerly the case, it is an indication that the contact point should be screwed down, or that the tension of the vibrator should be tightened. It is probable that turning the contact screw to the right will produce the proper result. While these changes in the position of the contact screw are being made, the switch should be left turned on so that the variations in the pitch of the vibrator buzz may be detected. When an evenly-pitched, vigorous buzz has been secured, the switch should be thrown on and off several times to make certain that the response of the vibrator is instant and positive. The switch should then be left on and the vibrator allowed to buzz for several seconds in order that it may be determined whether the pitch of the sound will change, or not. If there is a change noticeable, the contact screw should be readjusted until the pitch of the buzz remains constant as long as the circuit is closed. The coil and batteries or magneto by no means form the entire ignition system, although the generation of the spark depends entirely upon them. The spark must be regulated to occur at the proper point in the stroke of the piston, as a continuous spark would not only waste the current, but would cause the ignition of the charge during the upward stroke and would result in an impulse in the reverse direction that would prevent the motor from running for more than half a turn. The device by which the time of the occurrence of the spark is regulated is called the timer. This consists, in its essentials, of a hard rubber disc provided with a copper or brass segment. A metal pin, roller, or ball rests against the outer edge of the disc, and as the latter is revolved, the electrical circuit is completed whenever the two metal portions come in contact with each other. The hard rubber being a non-conductor of electricity, prevents the flow of the current at all other times. The disc of the timer, known as the "commutator," is so geared that it revolves in unison with the motor. Inasmuch as the explosion occurs in each cylinder only at every second stroke of a four-cycle motor, the commutator on this type of engine is geared to revolve at one-half the speed of the crank shaft. In the two-cycle motor, on the other hand, the explosion occurs in each cylinder at every revolution, and consequently the commutator should turn at crank shaft speed. Although the spark is intended to occur approximately at the extreme upper end of the compression stroke, a few degrees variation both above and below this point is necessary in order to obtain the desired speed and power flexibility of the gasoline motor. At high speeds, the spark should be timed to occur before the piston reaches the extreme top of its stroke, while at slower revolutions of the motor the ignition should take place, in some instances, just after the piston has started to descend. This variation In timing is obtained by swinging the contact piece of the timer--known as the brush--either forward or backward through an arc corresponding to the range of advance and retard. If this brush is swung in a direction opposite to that of the revolution of the commutator, the metal portions will meet sooner, with the result that the spark will occur earlier, or will be "advanced." If, however, the brush is swung to a point farther along in the direction of rotation of the commutator, the spark will occur later, or will be "retarded." These variations of position of the brush are generally obtained by means of a lever attached to the steering post or wheel. It is evident that the current must pass from the brush to the metal segment of the commutator in order to complete the circuit through the timer and thus form the spark. It is the primary current, or low-tension current from the battery or magneto, that passes through the timer, and as this is of low voltage and is therefore easily discouraged, it is necessary that the contact points be kept clean in order that its travel may be made easy. Timers are generally protected from dirt, but the particles that will naturally be worn off from the metal and rubber commutator and brush should be cleaned out before its accumulation becomes deposited on the contact points and interferes with perfect electrical connection. A few years ago, the majority of battery ignition systems employed a separate coil for each cylinder of the motor. Each coil in this system is connected with an individual brush that operates against the same commutator as do the brushes for the other cylinders. With such a system, the primary circuit leads from one terminal of the battery to the primary winding of the coil, through this and the vibrator to the brush of the timer reserved for that particular coil and cylinder, and thence through the switch to the other terminal of the battery. This order may be reversed, or the timer, switch, and coil may be placed in any consecutive position, provided the current passes through all in its travel from one terminal of the battery to the other. The secondary, or high-tension current is led from the terminal of the secondary winding on the coil to the spark plug of the proper cylinder. There should be a "ground" wire to serve for the return of the secondary current. This may lead from any part of the primary circuit to a clean metal connection on the motor. The multiple coil system is still used to a large extent, but an elaboration of it will be found on many of the modern cars. This consists of the use of but a single coil for all of the cylinders of the motor. This is done by means of a distributor, which is a sort of "glorified timer" consisting of a commutator provided with as many segments as there are cylinders in the motor. This distributor receives the current from a single coil and delivers it to the proper cylinder as the various connections are made. The timer still performs its function of completing the circuit from the source of current only at the proper instant, and leaves the distributor to serve the purpose of a "switch" to "sidetrack" the current and deliver it at the various cylinders in turn. If it should ever become necessary to remove any part of the timer, or to change the length of the spark control rods, the greatest care should be taken to make certain that the motor is properly timed when the various portions are replaced. This can best be done by setting the spark lever in its central position, removing a plug from one of the cylinders, and introducing a rod or long screw driver into the opening for the purpose of determining the exact top of the stroke of the piston. When the flywheel is turned, the top of the stroke should be marked on the rod or screw driver as the latter is forced upward by the piston. If the spark plug is laid with its large nut resting on the cylinder head, and the switch is thrown, the time of the occurrence of the spark can be readily observed as the motor is turned slowly by hand. This spark should occur in this particular plug just as the piston of that cylinder reaches the top of its stroke, as indicated by the change in the direction of the movement of the rod or screw driver. If the spark occurs too soon or too late, the commutator should be moved backward or forward to remedy the respective trouble. Although if the timer is set properly for one cylinder it is probable that the spark in the others is also timed correctly, it is well to test each to make certain that there has been no uneven wear in the contact segments of the commutator or the brush. CHAPTER V MAGNETOS The perfection of the magneto and its application to cars of all classes and sizes has marked the most important step in gasoline motor ignition since the introduction of the electric spark. The magneto is now considered one of the most vital parts of the car, and while it is possible for the motor to be run for many miles on the batteries that form the auxiliary ignition sources, the mechanical current generator has left the field of the desirable accessories and has become an actual, physical portion of the engine. The operation of the magneto is simple, its whys and wherefores are logical, and if one investigates the subject, even superficially, he will discover that the much-maligned machine seldom gives trouble, and that when it does, such action, or failure to act, is due to neglect, abuse, or some other perfectly legitimate reason, rather than "pure cussedness" on the part of the instrument itself. If the mere mechanical aspect is considered; if it is realized that the magneto consists mainly of a bundle of wires which, when revolved near the ends of a magnet, collects that magnetism and sends it through the circuit in the form of the electric current, and that consequently the magneto is a converter that changes part of the mechanical energy of the motor into the spark-forming fluid, the chief idea of magneto principles may be more easily grasped. To be sure, the magneto is delicate, and for that reason it should never be dissected by the amateur, but inasmuch as what few adjustments it has are readily accessible, it is seldom that the machine need to be taken apart. The platinum points of the contact breaker, usually located in the small box on the end of the armature shaft, may need to be smoothed with emery paper occasionally if they have become pitted from excessive sparking, but this is a simple operation and is not greatly different from the care given to the vibrator of the dashboard spark coil, as described in the preceding chapter. A few drops of oil should be fed to the lubricating cups or holes of the armature shaft as often as the directions call for--usually about once every five hundred miles--but aside from this, the owner can generally forget that he has a magneto, and will only be reminded of the fact by the pleasing absence of ignition trouble. If ignition trouble does occur, it is more than probable that the fault lies with the plugs, timer, or wires, rather than with the magneto. The man who drives a magneto-equipped car knows that the current producer is run by a gear connected, either directly or through the medium of other gears with the crank shaft of the motor. He knows, then, that the magneto is driven positively and that there is a constant relation between its speed and the number of revolutions of the motor. But does he know that it is absolutely necessary that a certain position of the armature shall always correspond with a similar position of the crank shaft of the motor, and that consequently the same teeth of the driving gears must always mesh? He will most assuredly be made aware of this if he disconnects his magneto and then fails to replace the gears so that exactly the same teeth are in mesh, for even the difference of a single tooth between the normal positions of the armature and crank shaft will prevent the magneto from delivering a sufficient spark to enable the motor to run. The reason for this is simple. All of these direct-driven magnetos are of the alternating current type, as this form allows of the simplest construction of armature and windings. The alternating current generator obtains its name from the fact that there are no regularly-defined north and south poles at any part of the circuit, as these keep changing continuously, or alternating. During each revolution of the armature of the alternating current magneto, there are but two positions at which a current will be formed. Now the spark in any cylinder of a motor is required at about the top of the compression stroke of the piston in that cylinder. Consequently when the piston is at the top of its compression stroke, ready for the spark that will ignite the charge, the armature of the magneto must be in one of its two current-generating positions, and there must therefore be a constant relation between the position of the crank shaft, to which each piston is connected, and that of the revolving part of the magneto. If, now, the driving gear of the magneto is returned to its place without regard to the teeth of the next gear with which it meshes, it will be seen that the proper relation between the position of the armature and that of the crank shaft will not be maintained. Under these conditions, when the piston is at the top of the compression stroke, ready for the spark, the armature will not be in a position at which a current can be generated, and there can consequently be no spark formed at the plug. Conversely, when the armature has been revolved to the position at which a current will be formed, none of the pistons will be requiring the spark, and this consequent lack of "team work" will prevent the operation of the motor. In order to maintain this team work between the armature of the magneto and the crank shaft of the motor, the intermeshing teeth of the gears should be marked with a prick punch before they are removed, so that they may be returned to their proper place without trouble. Only in this manner can accurate results be obtained, if it is at any time necessary to remove all or part of the magneto driving gear. The magnets forming the "fields" of the magneto in which the armature revolves are of the permanent kind; that is, they do not depend upon windings and a separate electric current for their excitation, as is the case with some of the larger generators. These magnets may be considered to be the most faithful part of the machine, for they generally retain their strength under all conditions of rest or work, and it is upon them that the proper operation of the magneto largely depends. A magneto in which the magnets have become weakened is useless for ignition purposes until the fields can be remagnetized, and as this can only be done at the factory, the machine in its entirety must be removed from the motor. It is a comparatively easy matter to determine whether or not the fields have lost their magnetism by placing a piece of iron or steel within close range of the base or sides of the magneto. An appreciable pull will be exerted by the magnets if they still retain their strength, although it is not to be supposed that the force thus exhibited will be very vigorous from such a small machine. If the magneto has been disconnected from its driving gear for any reason, the amount of magnetism remaining in the fields will be best determined by turning the armature shaft with the hand. A resistance should be offered to the turning at first until a certain point is reached, after which the armature should exhibit a strong tendency to fly forward to a new position, one hundred and eighty degrees beyond its former normal position of rest. This activity of the armature is one of the best guides to the amount of magnetism remaining in the fields. Many magnetos that have been installed on old motor cars not previously so equipped are of the friction-driven, direct-current type that produces a uniform spark at any point throughout the armature revolution. Current from these may be used to charge a storage battery for the operation of electric lights or to supply auxiliary ignition current for starting. The positively-driven, alternating-current magneto may also be used to operate electric lights on the car, but this type of current cannot be stored in a battery, and consequently the lights are available only when the motor is running. The magneto, however, is not primarily an electric-lighting outfit, and unless it is especially designed for the double purpose, a separate machine should generally be used for supplying illuminating current. CHAPTER VI CARBURETORS AND THEIR FUEL Although gasoline is inflammable in its liquid state, its combustion is not sufficiently rapid to approach the _explosive_ point necessary to render its energy available in the automobile engine cylinder. The proper proportion of gasoline _vapor_ and air, however, forms a mixture that is highly inflammable and that will be entirely consumed in the engine cylinder under ordinary conditions within about one-twentieth of a second after the formation of the spark. This rapid combustion so nearly approaches the instantaneous action of an explosion that it may be considered as such in all ordinary discussions of the gasoline engine. Literally, however, the gasoline engine is not an _explosion_ motor, but rather is it an engine of the _internal combustion_ type. To obtain this gasoline vapor in an easily-controlled form the carburetor was designed as one of the most important adjuncts of the automobile. The first form of carburetors, or "vaporizers," as they were called then, employed a flat, woven lamp wick over which the gasoline flowed. This spread the fuel out over a comparatively large surface and rendered evaporation rapid and simple. The chamber containing this wick was placed in the line of the intake pipe of the motor and was connected with the cylinders on the descent of the pistons on the suction stroke through the medium of the various inlet valves. In a four-cycle motor, the piston acts as a suction pump on alternate down-strokes and serves to draw the charge into the cylinder. This suction created the necessary current of air to facilitate evaporation of the gasoline on the wick, and by regulating the size of the passages, the proper proportion of air and gasoline vapor could be obtained. The modern, high-speed automobile motor, with its varying demands upon the carburetor, created the necessity for a more delicate, flexible, and compact vaporizer than was to be found in the "lamp wick" type. Consequently the wick was replaced by a small, slender, hollow tube having a cone-shaped opening at its upper end through which the gasoline from the feed pipe was made to pass. Fitting into the upper end of this tube, and pointed to the same angle, was a cone-shaped "needle" that could be moved in and out of the opening. If this needle was unscrewed slightly so that it did not form a tight fit with the end of the tube, a small ring would be formed through which the gasoline must pass when sucked by the alternate down strokes of the pistons. This tube and needle constitute, under various guises, the "needle valve" with which practically every modern carburetor is equipped. When the gasoline, rushing through the small tube, strikes the restricted opening of the needle valve, it is broken up into a fine spray which, under proper conditions, will become vaporized almost as soon as it comes in contact with a current of air. This air current is induced by the same pump-like effect of the pistons as that which sucks the gasoline through the needle valve, and thus it occurs only when the charge is desired in the cylinders. But the carburetor is not merely to provide a compact device for vaporizing the gasoline, for it must also furnish a means of regulating the proportion of gas to air. Gasoline vapor is only highly inflammable when mixed with the proper quantity of air, and if this proportion is varied above one limit or below another, ignition of the charge will not occur in the cylinders. In fact, the allowable variation in the proportion of gasoline vapor to air is restricted between very narrow limits, and should not change more than four or five per cent. from one extreme to the other. The proportion of gasoline vapor to air by weight is about one to eleven, although this will vary somewhat with the different grades of fuels. The point to be emphasized, however, is the fact that the proper proportion of air to gasoline vapor, however it may vary with different grades, should be kept constant at all speeds of the motor whenever that particular grade of fuel is used. By volume, about 97½ per cent. of the mixture should be air and the remainder gasoline vapor, and it is the device that will the most nearly maintain this proportion under all conditions of speed, temperature, and air pressure that will prove to be the most delicate and flexible carburetor. A carburetor may be adjusted for different motors, or for different operating conditions of the same motor, by means of the needle valve. The farther end of the slim rod on which the needle point is mounted terminates in a thread and finger nut that projects through the shell of the carburetor. By turning this nut in one direction, the needle valve is screwed up toward the cone-shaped end of the tube and the orifice through which the gasoline may pass is thus reduced in size. This will decrease the amount of gasoline sprayed into the air passage and will consequently change the composition of the mixture. This, however, should not be confused with throttling the motor. When the needle valve is tightened, the volume of the mixture passing to the cylinders is the same, for it is only the proportion of gasoline vapor in that mixture that is changed. Throttling consists in restricting the size of the opening through which the _mixture_ passes, and thus limits the amount of the charge that reaches the cylinders at each suction stroke of the piston. Throttling is used to reduce the power--and consequently the speed--developed by the motor, while a decrease in the amount of gasoline supplied to the air through the needle valve may serve to increase the power through an improvement in the nature of the mixture. Since the gasoline vapor, by volume, forms only about three per cent. of the explosive mixture admitted to the cylinders, a slight variation in the size of the needle valve opening will result in a marked change in the composition of the charge and may make all the difference between poor and perfect running of the motor. Consequently the needle valve nut should be moved but the small fraction of a turn for each adjustment. A motor which may refuse absolutely to run at one position of the needle valve may give perfect results if the nut is unscrewed but the eighth of a turn. In view of the marked difference in the results obtained from the use of mixtures that are "just right," and those which vary but a slight percentage in the proportion of gasoline vapor to air, it may be well to examine, superficially, the effects of "rich" and "weak" charges, and therefrom to obtain a list of "symptoms" which may aid us to diagnose motor trouble properly. We all know that air--or oxygen--is required to support combustion. "Snuffing" a candle is merely covering its end so that air cannot reach the flame. For the same reason, gasoline in a covered tank cannot burn, no matter how great the heat applied to it. The heat of the electric spark in the cylinder, although intense, does not cover a sufficiently large area to ignite any charge except that composed of the proper proportion of gasoline vapor and air. If there is too much gasoline vapor, making a "rich" mixture, there will not be sufficient air in the charge to support the entire combustion of the gas, and the burning will be slow--if it takes place at all. The same conditions will prevail if there is an insufficient supply of air for a given quantity of gasoline vapor, and consequently a rich mixture may be obtained by reducing the air flow as well as by adding to the amount of gas admitted to the mixing chamber. A rich mixture will cause irregular explosions in the cylinders, and will often emit a black, pungent smoke at the exhaust. The motor will probably overheat easily, due to the slow-burning properties of the mixture and the resulting fact that a large portion of the cylinder walls uncovered by the pistons will be exposed to the flame. In some instances, the cylinders will miss fire at regular intervals, thus changing the synchronism of the impulses with a well-defined and periodic "skip" in the sound of the explosions. While these are by no means certain symptoms of a rich mixture, the first test to be made should be to tighten the needle valve adjustment slightly when the motor is running and to note any resulting improvement in the regularity of the explosions. It may sometimes be difficult to distinguish between the symptoms of a rich and a weak mixture, but the readjustment of the needle valve as just described will at least serve to locate the trouble or to eliminate one or the other possibility from consideration. When a mixture is "starved", or when there is an insufficient supply of gasoline vapor to unite with the air admitted to the cylinders, the charge will not be highly inflammable and may not be ignited by the small spark formed at the plug. Even when ignition does take place, the resulting power impulse will be weak because of the comparatively small amount of pressure-producing gas in the mixture. The explosions may occur regularly for a while, but there will be a marked decrease in the power developed by the motor, and owing to the fact that weak mixtures may be slow-burning, "back-firing" will often result in some engines to which such a charge has been fed. On the other hand, if a motor will run at all on a weak mixture, it will produce better results than would be the case were the charge too rich in gasoline vapor. Consequently the needle valve should be closed as much as is consistent with smooth running of the motor, but the moment a loss of power or irregular explosions occur, the mixture should be enriched. At low speeds of the motor, the pumping action of the pistons is not as great as is the case at high revolutions, and consequently the suction drawing the gasoline through the needle valve is diminished. For this reason, the needle valve opening must be made larger or the air passage restricted for slow speeds of the motor, and it was consequently necessary, on the old, non-automatic vaporizers, to _increase_ the gasoline supply whenever the revolutions of the motor were to be reduced. The modern carburetor is sufficiently automatic in its action to provide the proper mixture within wide ranges of speed change of the motor, but even nowadays it is often found necessary to increase the gasoline supply or to reduce the amount of air admitted to the intake pipe whenever it is desired to throttle the motor down to a very low number of revolutions per minute. The automatic action of the ordinary carburetor is obtained by increasing the air supply at higher speeds of the motor. Consequently the motorist will realize that whenever the needle valve is to be set, such regulation should be made when the motor is well throttled, for if an ample gasoline supply is obtained at low speeds, the mixture will certainly be sufficiently rich at increased revolutions. If, on the other hand, the carburetor should be set to supply a proper mixture at high speeds, the mixture would be impoverished when the motor is throttled, and irregular running would result. The air for the operation of the motor at ordinary speeds is supplied through a fixed opening in the carburetor connected with the chamber into which the gasoline spray is introduced. In addition to this, most carburetors are supplied with an "auxiliary air opening" which serves to furnish the additional air necessary for the mixture at high speeds of the motor. The fixed opening, being restricted in size, cannot admit the increased quantity of air demanded by the higher speeds of the motor. The auxiliary opening is provided with some form of automatic valve which may consist either of a series of ball "checks," a spring-actuated "mushroom valve," or a series of special valves, each of which opens at successively increased speeds of the motor. All of these devices operate on the same principle, however, and allow the increased suction of the motor to add to the size of the air passage automatically--either by the farther opening of a single valve, or by the successive opening of different valves. Some carburetors are provided with an adjustment by means of which the "delicacy," or ease of opening, of the auxiliary air valve may be regulated. This may be done by means of a nut and screw which will increase or decrease the tension of the controlling spring. If this spring is set with a high tension, the auxiliary valve will act only when the motor is exerting great suction, or at fast speeds. The regulation of the auxiliary valve is an adjustment that should be made only after the needle valve has been set properly for slow speeds of the motor. When this condition is obtained, the throttle should be opened and the further adjustment of the carburetor for high speeds of the motor should then be made through the auxiliary air valve. In other words, the needle valve should be set so that the motor runs properly at low speeds, while the adjustment of the auxiliary air valve should be made only to secure smooth operation at a high number of revolutions. It is not to be understood that less gasoline is actually required at high speeds of the motor because the supply often needs to be cut down at the needle valve under these conditions. The actual amount required at high speeds is, of course, greater than is the case at slow, on account of the greater number of explosions in the former instance. But the suction of the motor generally increases the gasoline flow beyond the demands of the cylinders at high speeds, and it is for this reason that the automatic auxiliary air supply is provided to furnish the additional air required to support combustion. In fact, at heavy loads, when the total amount of gasoline consumed must be great, a secondary jet of fuel is brought into action in some carburetors. This is known as the "multiple-jet" type and is found on some of the large engines that must possess a speed and power variation between wide ranges. The action of these various jets is entirely automatic and is dependent upon the speed and fuel requirements of the motor. Were the gasoline fed directly from the fuel tank to the needle valve of the carburetor it is evident that the rate of flow of the liquid would depend, to a large extent, upon the amount in the tank and upon the position of the car. This would cause each charge to differ in the proportion of gasoline vapor to air, and it is hardly probable that the motor could be run at all under such conditions. In order that the pistons may suck the gasoline from a level that does not vary with the amount of fuel in the tank or the position of the car, a separate compartment is provided in the carburetor. This is known as the "float chamber," and it is from this compartment that the gasoline passes through the needle valve into the vaporizing or mixing chamber. A cork or hollow metal float is placed in this float chamber and is mounted on a lever connected with a valve located at the end of the gasoline feed pipe. As the gasoline is admitted to the chamber, the float rises and closes the valve controlling the flow of fuel. As the gasoline is sucked through the needle valve from the float chamber, the float in the latter lowers, and the fuel is again admitted by the opening of the above-described valve. The float and valve are exceedingly delicate in their operation and the gasoline is thus kept at a constant level in the chamber under all conditions of the car and tank. The stem upon which the float of some carburetors is mounted is sometimes threaded and provided with a nut by means of which the float may be raised or lowered. This furnishes an adjustment for varying the level in the float chamber and determining at what point the flow of gasoline shall be cut off by the automatic valve. The float is supposedly properly regulated when the carburetor leaves the factory, but the stem may become bent or the carburetor may be applied to a motor other than that for which it was originally designed. In either of these events, it may be found necessary to raise or lower the float before the proper level of gasoline can be maintained in the chamber. If the float is too high on its stem, the gasoline control valve may not be operated until the fuel overflows in its chamber. This is known as a "flooded" carburetor and produces a rich mixture which will ultimately prevent the proper operation of the motor. Turning down the gasoline supply at the needle valve will not remedy this, for the fuel will reach the vaporizing chamber by another route. A flooded carburetor often gives trouble, and while it may be remedied easily, the amateur may experience difficulty in locating its source. As soon as it is discovered that a carburetor has become flooded, the needle valve should be tightened so that no gasoline can pass through it, and the motor should then be cranked. This will serve to evaporate the excess gasoline in the float chamber and reduce the level to the point at which it will not overflow. The exact number of turns and fractions of turns through which the needle valve nut was moved should have been noted in order that the valve may be reset to its original position after the surplus fuel has been "cranked out." A float that is set too low on its stem will close the fuel supply valve before a sufficient amount of the fuel has flowed into the chamber, and will form a "lean" mixture at high speeds of the motor--even though the needle valve should be opened wide. The obvious remedy for such a condition is to raise the float until the gasoline will be maintained at the proper level. If there is no nut and screw adjustment by which the float may be raised, the arm to which it is attached, and which is connected with the valve, may be bent slightly. But the motorist should not "jump at conclusions" and assume that the float is improperly set the moment the carburetor begins to flood or the motor appears to "starve" at high speed. The first condition may be caused by a piece of dirt or other foreign matter that may have become lodged on the valve seat and prevented the valve from closing when the gasoline reached the proper level in the float chamber. This will produce exactly the same results as will a high float and is a trouble that will more often occur in the average carburetor. The difficulty may generally be remedied easily by draining the gasoline from the float chamber after the valve in the main supply pipe has been turned off. The offending foreign matter will generally be carried with the gasoline as the latter is drained, and the valve in the feed pipe may again be opened as soon as the drain cock is shut off. If this fails to remedy matters, it is probable that the difficulty lies with the float. A clogged gasoline pipe or dirty strainer will produce the same effect on the operation of the motor as will a float that is set too low on its stem. When the motor seems to starve at high speed, and it is evident that there is sufficient gasoline in the tank, the union should be disconnected at the point where the feed pipe joins the carburetor. If there appears to be an ample flow through this pipe when the main valve is opened, it is probable that the stoppage has occurred in the strainer. If the flow through the main feed pipe is not free, however, it is possible that the vent hole in the filler cap on the tank has become stopped or that the latter has been screwed down too tightly. In the gravity feed systems, some method must be provided to allow the air to flow into the tank to replace the gasoline fed to the carburetor. If there is no hole in the filler cap, the latter should not be screwed down so tightly that an airtight joint will be formed. Probably the simplest method of determining whether the trouble lies in a low float is to prime the carburetor and to observe the ease with which this can be done and its effect upon the engine. Nearly every carburetor is provided with a "flushing" or "priming" pin by means of which the float can be depressed so that the gasoline chamber will be filled rapidly to a point above its normal level. This is useful in starting, as the desired rich mixture is quickly obtained without an undue amount of cranking. If the carburetor flushes easily, it is evident that there is no serious stoppage in the pipe. If this easy flushing is followed by good running on the part of the motor, and if this, in turn, is succeeded by gradually-diminishing impulses indicating a weakening mixture, it is quite evident that the float is preventing the flow of the gasoline at the proper time. In addition to the flush pin found on carburetors, many are provided with other devices to render starting easy. It is well known that a "high-test" gasoline, such as a 76, will vaporize more easily than will one of a lower degree of specific gravity. Also, every motorist has had impressed upon him the fact that heat aids in the vaporization of gasoline. If we try to start a motor on a cold morning with a low-grade gasoline, such as the 60- or 62-degree fuel now generally obtained, we know that a rag dipped in hot water and wound around the carburetor will help matters. To enable low grades of fuel to be properly vaporized under all running conditions, many carburetors are provided with a water jacket surrounding the vaporizing chamber. This jacket is connected with the cooling system of the motor, and the hot water surrounding the chamber so warms the interior that vaporization is greatly facilitated. Some of these systems are provided with a shut-off cock by means of which the carburetor may be operated with hot water in the jackets, or not, as desired. Other carburetors employ a jacket surrounding the exhaust pipe of the motor and connected with the vaporizing chamber. The air is heated by the hot exhaust pipe as it is sucked into the carburetor, and this also facilitates the vaporization of the fuel. Some carburetors are provided with both jacket systems, while others have neither, but whatever design is installed, the best results will be obtained if cold air is used after the motor is once started. Cold air is more "concentrated" and contains a greater amount of oxygen per cubic foot than does air that has been expanded by heat, and consequently many carburetors are provided with a means of turning off the hot air after the motor is started. The higher the degree of specific gravity of a fuel on the Baumè scale, the more volatile will it be, and consequently a 68° gasoline will vaporize more easily and give more power than will a 60° or 62° fuel. 72° gasoline is often used in races, but the average motorist does not get better than 64°--and he is sometimes lucky to obtain fuel of that specific gravity. A hydrometer, or specific gravity tester, is a convenient instrument for the average motorist to own, and with it he may tell exactly what grade of fuel he is paying for. The Baumè scale, by which all gasoline is tested, reads in degrees, and the specific gravity is obtained by observing the depth to which the hydrometer sinks in the liquid. This instrument resembles somewhat a glass thermometer, and is so graduated that the deeper it sinks in a liquid, the higher will be the reading on its scale. Water in the fuel is an annoyance that is often encountered by the automobilist and the motor boatman, and this will make its presence known by causing the motor to skip when all adjustments and connections seem to be in perfect condition. Water is much heavier than gasoline and has no affinity for it, and consequently, as it sinks to the bottom of the tank, a few drops in a large amount of gasoline will cause trouble by passing out through the needle valve at intermittent intervals and forming an unexplosive mixture. The presence of the water in the fuel may be detected easily without the use of a hydrometer by drawing some gasoline from the bottom of the tank into a tin or white-enameled cup. If water is present, it may be seen in the form of small globules in the bottom of the cup. If the contents of the cup are poured over a flat surface so that the liquid may be allowed to spread, the gasoline will be seen to cover a large surface and evaporate quickly, while the water will seem to remain in the globules unevaporated for some time after the gasoline has disappeared. This latter test will sometimes show the presence of water when none can be discerned in the bottom of the cup before the contents are poured out on the flat surface. The practice of "doping" the fuel tank by adding to the gasoline ether or some other highly volatile liquid is not to be recommended to the average motorist. A few ounces of ether or chloroform added to the fuel will form a more volatile and consequently more powerful mixture, but unless the greatest care is taken, the motor is liable to be completely ruined by such a procedure. Numerous cases are on record in which cylinder heads have been blown off or castings cracked by the force of some of the explosions when too much "dope" has found its way into the mixture. Although the average motor gasoline obtainable nowadays is hardly all that could be desired as automobile fuel, a little care taken when filling the tank will eliminate many of the carburetor annoyances to which many cars seem to be subject. The cap of the tank should never be taken off when the air is filled with particles of dust that are liable to find their way into the fuel, and care should be taken to see that no pieces of the rubber or leather washer or packing drop into the gasoline when the cap is removed. Foreign matter and water that may be in the gasoline when purchased may be removed by straining the fuel through a chamois skin placed inside of the funnel through which the tank is filled. CHAPTER VII LUBRICATION A lubricant acts as a sort of pacifier between two surfaces that would otherwise move in contact with each other. No surface can move in direct contact with another of the same or a different material without the generation of heat; but the amount of heat generated, or resistance met with, is determined by the nature of these two rubbing surfaces. The oil, or grease, or whatever suave, slippery substance is to be used as a lubricant, interposes itself in a thin film between the two rubbing surfaces and smooths matters over, as it were. If a sufficient amount of this mechanical soothing syrup is not fed to the rubbing surfaces, the temper and temperature of each will be raised to the point where they will "clinch," and much time and effort may be required before harmony can again be restored. Thus it is actually upon a film of lubricant that a shaft rests, rather than upon the bearing, or "box," in which it turns. If the bearing is set so tight that there is no room for the interposition of an oil film, the shaft and journal will at once heat. The greater the pressure of the shaft in its box, the thicker, or heavier, should be the lubricant used, for a light oil would be squeezed out or "broken down" more easily than would one that possesses greater viscosity. The "coefficient of friction" may be termed the mechanical "amount of irritability" generated when two surfaces are rubbed together. Thus if two metals are rubbed together, this figure is high, and a large amount of friction, or heat, will be generated. A metal rubbing over oil, however--as is the case with a well-lubricated bearing--will arouse but little resentment and its pathway will be made smooth and easy, for the coefficient of friction of these two materials is low. The lower this figure can be kept, the more easily can the surfaces be rubbed over each other and the higher will be the efficiency of the bearing. Apply this to every bearing or rubbing surface of a motor, and we see that proper lubrication affects not only the length of life of the moving parts, but the ease with which the engine can be run and the consequent power development. Thus, a lubricant that will prevent wear between the moving parts may be supplied to the bearings and pistons of a motor, and under this condition the engine might "last" indefinitely; but this oil might be so viscous or possess so high a coefficient of friction that each bearing would turn with difficulty and much effort would be required to run the motor before it could begin to develop power. But the introduction of oil to a bearing not only reduces the friction between the surfaces that would otherwise move in contact with each other, but it serves another very important purpose. Every properly-lubricated portion of a motor either moves in a bath of oil or is connected with an oil reservoir so that a certain amount will be fed regularly to the rubbing surfaces. There is always _some_ heat generated in a bearing, no matter how well it may be lubricated, and the continuous flow or circulation of the oil serves to carry off this heat that would otherwise tend to dry the lubricant if there were no fresh supply. The proper lubrication of the motor is even more necessary than is the adjustment of the carburetor or the condition of the ignition system. To be sure, if either the carburetor or the ignition system is out of order, the motor will not run, but no actual harm to the mechanism will result from this fact. On the other hand, a motor may be run indefinitely with a defective lubricating system, and no apparent harm will result--until the end of that indefinite time arrives and it is found that the machine is a fit subject for a junk heap. Let us see how many parts of the motor are reached by the gallon or so of oil that we pour into the tank. A six-cylinder motor may have seven crank shaft bearings; it will certainly possess six connecting rods, each of which will be provided with a bearing at both its large and small ends--or twelve in all; there may be two cam shafts, each with five bearings and half a dozen cams; these will require, together with the magneto and pump shafts, five or six gears in the forward train; and the six pistons will demand their share of attention from the lubricating system. Here is a grand total of over fifty rubbing surfaces on a large motor, and the oil must be thoroughly and constantly distributed to each. Of course, many smaller motors, provided with but a single cam shaft and a three-bearing crank shaft, may possess but one-half of this number of lubricated parts, but at the least, the oil must reach with unfailing certainty two dozen vital places of the engine. At some of these portions, the movement is comparatively slow and the pressure is not great. Therefore such surfaces as the cams or valve stem rollers will demand less oil than will the bearings revolving at higher speed and carrying heavier loads. But it is the hardest-worked bearings that form the majority of the friction surfaces of a motor, as will be realized when it is remembered that all points on the circumference of a three-inch crank shaft bearing will travel at the approximate rate of 1,000 feet per minute--and these are the portions that also carry the heaviest load. But while the pistons can hardly be called bearings in the generally-accepted layman's definition of the term, they require the lion's share of the lubricant, and are the first portions of the motor to feel--and show--the effect of any failure of the oiling system. While in terms of miles per hour, the movement of the pistons may not seem very rapid, the thousand feet per minute at which each ordinarily travels is rather a high rate of speed when it is considered that it is entirely a rubbing or a sliding motion, and that the direction is reversed more than two thousand times during each sixty-second period. This means that each piston slides or rubs within the cylinder walls for a distance of between two and three thousand miles during an ordinary season. And remember that this is not a rolling motion, but a continuous rubbing! In addition to this high-speed rubbing, the pistons are pressed firmly against the side of the cylinders on each explosion stroke throughout a portion of their travel. This corresponds to a heavy pressure carried by the rubbing surfaces, and is caused by the side thrust induced by the angularity of the connecting rod as it overcomes the resistance of the load through the crank shaft. But this is only a small portion of the difficulties that must be overcome in cylinder lubrication. Not only must the oil pacify the rubbing surfaces and keep them well separated, but it must remain within a restricted territory of the cylinder walls. Whatever oil reaches the upper portion of the cylinder walls will be burned and will contribute to the formation of the carbon that is the mortal enemy of efficient running. Large quantities of oil burned in the cylinder will also form the dense clouds of choking blue smoke that the health authorities of many cities have been investigating, which have led to the enactment of city ordinances making the driving of a smoking automobile a misdemeanor. In view of the difficulty which has been experienced by many drivers in sufficiently lubricating the pistons without causing the car to emit clouds of smoke, it may well be asked, "Why cannot an unburnable oil be used and thereby eliminate this trouble?" This is out of the question, for the mineral oils now used are obtained from petroleum and are cousins of kerosene, gasoline, benzine, and many of the other highly-inflammable liquids that need but the touch of a match to burn almost with the rapidity of an explosion. But notwithstanding the excitable family to which the mineral oils belong, the modern motor car lubricants are removed a sufficient distance from their more inflammable relatives to enable them to withstand a temperature of between 400 and 500 degrees, Fahrenheit. This is sufficient heat-resisting ability to enable the oil to stay on the cylinder walls near the bottom of the stroke, where it is most needed; but even though its burning point could be raised to a degree double its present amount, it could not withstand the high temperature generated in the top of the cylinder at the time of the explosion. The temperature here reaches a point well above the 2000-degree mark, and were it not for the cooling system, parts of the interior of the cylinder would probably be melted by the continued application of this excessive heat. _Any_ oil, consequently, would find but small opportunity to remain in its normal state after it once reached a point at which it would be exposed to the heat of the explosions, and we must look for a preventive measure other than that of increasing the flash-point or burning-point of the lubricant. But this high temperature does not exist throughout the stroke, for as the piston descends and the gas expands, heat is given off until the oil on the lower portions of the cylinder uncovered by the piston is sometimes able to remain in comparative peace. And even though this oil remaining on the cylinder walls at the bottom of the stroke should be burned, it would not be present in sufficient volume to create the dense clouds of objectionable smoke. Consequently it is the endeavor of engineers so to design the pistons and lubricating system that excess oil will not be fed to the pistons and allowed to remain on the walls after the former have descended. But an excess amount of oil fed to the cylinders will result in so much less harm than will an insufficient supply, that we are treading on rather dangerous ground when we warn the amateur to cut down his lubricant to the point where there will be no smoke. As there are no ordinances that absolutely prohibit the slightest appearance of smoke at the exhaust, and as a faint blue trail is an excellent indication that the motor is receiving sufficient lubrication in the cylinders, it forms a satisfactory test by which the novice can determine the condition of the oiling system. By the time that the exhaust gases have passed through the pipes and have expanded in the muffler, some of the blue smoke may have disappeared, and consequently the fact that a car does not give a trace of vapor at its exhaust should not necessarily be taken as an indication that the motor is not well lubricated. If the owner would satisfy himself that the cylinders are receiving a sufficient amount of oil, he may open the individual pet cock on each, and if he finds there a faint blue trail of smoke at each explosion in that cylinder, he may rest assured that harmony exists between the rubbing surfaces of the piston and the cylinder walls. With the increase in the size and power of the automobile motors and the proportionately greater number of parts demanding lubrication, the attention required from the driver by the oiling system has been greatly lessened. Instead of the necessity of turning on individual oil cups whenever the motor is started, the modern driver merely twirls the starting crank or presses the button of the self-starter, secure in the knowledge that whenever the motor runs, the lubricating system operates--provided, of course, the reservoir is filled and there is no stoppage in the pipes. The oiling system of the modern motor is absolutely automatic, and if supplied with a sufficient quantity of a good lubricant, it will perform its work with an absence of trouble that places it among the greatest improvements of the engine of recent years. Individual oil cups such as were used formerly, have been eliminated from the cylinders, and whatever sight-feeds there may be are placed on the dash in plain view of the driver. Instead of relying upon the suction of the cylinders for the positive feed to the piston, mechanically-operated pumps are used to force the oil to the various portions of the motor. In some systems, there is a separate pump for each oil lead. This is known as a mechanical oiler, and generally consists of an oil tank located on the dashboard of the car--either in front of the driver, or under the motor hood--and connected by means of a belt or gear with some shaft of the motor. The belt or gear drives a shaft to which is connected the plungers of the various oil pumps that force the oil to the different parts of the motor. Before passing to the individual pipe, however, the oil drops through a sight-feed connected with that lead, and as all of these sight-feeds are mounted in a row within plain view of the driver, the condition of the lubricating system in part or in whole may be determined at a glance. The parts of the motor that are lubricated by an independent feed line in this manner may vary with different motors. In general, however, it may be said that it is seldom that the oil is fed directly to the piston, but that the lubricant is first distributed to the oil wells in the crank case. Here, the splash of the cranks as they revolve in the oil is depended upon to throw the lubricant upon the exposed portion of the piston as it reciprocates below the cylinder walls. The sides of the piston thus covered carry the oil to the cylinder walls. It is evident that if an excess amount of oil is continually carried up by the piston to the cylinder walls, a certain proportion of this lubricant will reach the open space in which the charge is ignited, and will there be burned--with the attendant formation of clouds of objectionable smoke. This trouble is overcome to a certain extent in some motors by the use of a type of ring set in the piston that prevents the lubricant from passing to the upper portion of the cylinder; but all the oil cannot thus be retained, and it therefore behooves the driver not to allow too great a quantity to be fed to the crank case if the "splash" system is used. The main bearings on which the crank shaft revolves are generally supplied with oil by independent leads from the oiler, and when the above-described system is used they may be regulated independently of the splash feed lubricating pipes. Excess oil at the bearings will cause no damage, but each crank shaft journal does not demand as great an amount as that supplied to a piston and connecting rod bearing. Many lubricating systems that are now in popular use employ but one pump to force the oil to the various bearings and rubbing surfaces, and regulate the supply by the size of the pipe leading to each. A satisfactory method of overcoming the possibility of excess oil in the cylinder has been adopted by some manufacturers. This consists in placing a channel, or trough, directly under the lower sweep of each connecting rod bearing. Each channel is kept filled to overflowing by a separate pipe connected with the main lead from the pump, and a constant level is consequently maintained at all speeds of the motor. An elaboration of this method consists in attaching one end of each trough to a rod operated in conjunction with the throttle, so that as the speed of the motor increases, the end of the channels may be tilted, with the result that the connecting rod scoop will dip deeper into the lubricant. After the proper level in each trough has been reached the excess oil overflows into the bottom of the crank case. From here, it is again started on its way by the pump and is distributed to the various bearings and troughs through the different pipes leading from the pump. As a further precaution against a smoking exhaust, some designers have added a baffle plate above each crank case compartment that serves to reduce the size of the opening through which the oil may be splashed. With this combination of troughs and baffle plates the possibility of a smoking motor is practically eliminated. All motors are not so equipped, however, and in the case of those provided with the bona-fide splash system, care must be taken to keep the separate crank case compartments filled to the proper level. Too high a level in the crank cases will cause the motor to smoke; while the supply should not be allowed to become so low that when the angle of the crank case is changed--as in ascending a hill--the lubricant will run toward the rear and will not be reached by the scoop on the connecting rod bearing. This latter danger makes it advisable to give this system plenty of oil when any touring is to be done through a hilly district. In some lubricating systems, the oil is supplied as it is used, and either is discharged with the exhaust, or collects in the bottom of the crank case, from which it should be drained occasionally. In the circulating systems, however, which are now used on a majority of the cars, the same oil is used continuously until it becomes "worn" or filled with sediment and particles of dirt and other foreign matter. The pump used for maintaining this circulation may be either of the plunger, centrifugal, or gear type, and is generally housed in a portion of the crank case. A strainer is usually placed in the suction end of this pump for the purpose of removing all the free foreign matter from the oil before it is again started on its mission of lubrication. In these systems, the oil well is generally located in a "secondary" bottom of the crank case. From here it may be drained when the supply is to be renewed. Another successful system by which all the bearings of the crank shaft are positively lubricated is used on many of the best cars. In this system, a continuous oil hole passes throughout the length of the crank shaft, including its "arms" and connecting rod bearings. At each bearing, one or two small oil holes connect with this main artery and extend radially to the surface. Oil is forced into the longitudinal oil hole by means of a small pump, and naturally finds its way through every radial opening to all the bearings. The excess may overflow into the individual oil wells, from which it will be splashed upon the exposed portions of the pistons as they descend. It will be seen that, no matter what modern oiling system is used, the same kind of lubricant is supplied to all parts of the motor. This feature makes matters much simpler than was the case when one oil was used for the cylinders, another, of a different thickness, supplied to the crank case, and still a third required for the gears. By the old gravity systems, the flow of oil depended largely upon its viscosity, or thickness. Therefore, in winter, a thinner oil was required than in summer, for the more a lubricant is warmed, the thinner does it become--and vice versa. With the mechanical force systems now in use, however, practically the same kind of oil may be used throughout the year--although many motorists believe that better results will be obtained if a heavier oil is used in summer than in winter. The oil will be warmed by the motor and it will not require many minutes of operation before a lubricant made thick by a low temperature will flow freely and do its work as efficiently as a thinner oil. But no matter how reliable a lubricating system may be in its operation, the driver must do his share and make certain that fresh oil of the proper quality is supplied when needed, and assure himself that all the passages are free from obstructions. Negligence on the driver's part may result in one or more "stuck" pistons that will either seriously injure the motor, or will put it out of commission until the trouble can be remedied. If a sufficient supply of oil is not fed to the rubbing surfaces between the piston and the cylinder walls, a high degree of heat is generated which will tend to expand the piston until it grips the cylinder so closely that the former cannot be moved. In this event the motor will stop "dead," and cannot be started again until the piston has cooled and contracted to its normal size. Even then, however, the motor should not be run under its own power until the burned and gummed oil has been removed and the scored surfaces have been cleaned. While this may best be done by removing the piston--at which time an examination for any badly burned rings may be made--this is not always possible, and it may be necessary to run the car home or to the nearest repair shop before the proper repairs can be made. In this case, the motor should be turned by hand until it is certain that the piston is again free in its cylinder. Liberal quantities of kerosene oil should be poured in through the spark plug opening, and if possible, the motor should be "rocked" back and forth by the flywheel to give the kerosene an opportunity to reach all parts of the piston and rings. The kerosene will serve to cut and remove much of the carbon and gummed oil and to make the way free for the fresh lubricant, which should be poured in liberal quantities into the cylinder head. The flywheel should again be moved back and forth so that the oil will reach all parts of the piston surface, and after this--if the damage has not been too great--the motor should be ready for operation. CHAPTER VIII COOLING To enable the parts of a motor to work well, there must be freedom of motion between all that move in contact with each other. This necessary freedom of motion is provided for to a certain extent by proper lubrication, but this is not all-sufficient. The necessity for some additional friction- and heat-reducing system can be better realized when it is understood that the temperature of the explosion in the cylinders of a gasoline engine is well over 2,600 degrees, Fahrenheit. The melting point of pure iron is less than 2,800 degrees. Therefore were there no escape for this heat, and could the motor be induced to run under these severe conditions, the cylinders would soon reach a temperature dangerously near the melting point. Long before this point could be reached, however, the intense heat would have expanded the pistons so that they would become stuck in their cylinders, and no more explosions could occur. An ominous knock in one or more of the cylinders, followed by a sudden laboring and final cessation of operation on the part of the motor, is sometimes the first intimation that the driver may have that his engine is over-heated; but serious as a "stuck" piston may seem, it is fortunate that the motor stops of its own accord, for to continue to run under these conditions of constantly increasing heat would be to wreak far more serious and permanent damage upon the moving parts than the broken rings or scored cylinders that usually result from a lack of lubrication or cooling medium. A large amount of the heat resulting from each explosion is carried out through the exhaust pipe in the form of the burned gases, while other portions radiate into the surrounding air. These outlets are not sufficient, however, to carry away all the heat that is necessary to enable the motor to run efficiently, for proper piston lubrication is exceedingly difficult to obtain at high temperatures. There must, therefore, be more positive and direct means for carrying off this undesired heat, and to accomplish this result every internal combustion motor is provided with a cooling system of either the air or liquid (usually water) type. Motorcycle power plants and a few of the small and medium-sized automobile engines employ the air-cooling system; the great majority of automobile engines, stationary plants, and marine motors use water as the cooling medium. Let us consider first the air-cooled system. The area presented by the outside of a smooth cylinder is not large enough to enable sufficient radiation to take place. That is, the heat is concentrated on a comparatively small surface, and this is much more difficult to keep cool than is the same amount of heat distributed over a greater area--for the cylinder will be exposed to a larger quantity of fresh air in the latter case. Therefore many air-cooled engines are provided with a series of grooves and flanges on the outer surface of the cylinder. The heat is conducted to all parts of this surface--flanges as well as grooves--and the area of the surface that is exposed to the cooling air is greatly increased thereby. These grooves and flanges may extend circumferentially around the cylinder, as is the case with many motorcycle engines, or they may extend longitudinally. Another form of air-cooling system consists of pins or spines projecting radially from the surface of the cylinder. The motion of the car through the air is generally sufficient to create a circulation of the cooling medium, but in order that this circulation may continue while the car is at rest a high-speed fan is provided that draws the air from the front toward the rear of the motor. This serves also to supplement the air circulation produced by the motion of the car, and keeps the motor much cooler than would be the case were the machine run without the fan. This fan is generally attached to a bracket at the front of the motor, and is driven either by a belt or geared shaft. In some designs, however, the fan blades are included in the flywheel at the rear of the motor and the air is thus sucked over the cylinders. One of the most effective air-cooling systems for use on an automobile motor consists of the above-mentioned longitudinal flanges and grooves enclosed in a thin jacket or casing surrounding each cylinder. These jackets are open at the top and bottom of the cylinders, and connect with large pipes, or troughs, through which air is forced. The trough into which the top of the jacket spaces open is connected with the discharge end of a large fan. The air is thus driven into the top trough, through each jacket, and into the lower trough, the farther termination of which is connected with the suction end of a fan included in the flywheel. The two fans serve to set up a rapid circulation of air which, by means of the troughs and jackets, is concentrated upon the surfaces of the grooves and flanges of each cylinder and none is wasted on parts of the motor that it is unnecessary to cool. Furthermore, the rear cylinders receive as much air as do the forward ones, for the trough serves to distribute the circulation equally along the grooves and flanges of each. Inasmuch as the heat from an air-cooled motor is radiated directly into the current of air itself, the surface is very susceptible to temperature changes from the interior. Thus, if the car is run for a great distance on the low gear, and the cylinders become hot in consequence, a larger amount of heat will immediately be radiated from the cooling surfaces than is the case when the motor is running slowly. A "coast" down a short hill, however, will serve to cool the motor rapidly, for if the engine is run from the momentum of the car with the spark turned off, cool air will be drawn into the cylinders, and this, in addition to the circulation of cold air on the outside, will reduce the temperature of the engine rapidly. This is a feature of the operation of an air-cooled motor that is not possessed to so large an extent by those of the water-cooled type. It is, perhaps, hardly accurate to apply the term "water-cooled" to the ordinary type of automobile motor. Water is merely the medium that transfers the heat from the cylinders to the cooling surface of the radiator. As air is used to cool this heated water, we see that the only difference between the two systems lies in the point of application of the actual heat-absorbing medium--which is air in both cases. Thus in the air-cooled motor the air is carried directly to the surfaces to be cooled; while in the other type, the heat is transferred by means of the water to the point where it may be effectually discharged into the air. Each cylinder of a water-cooled motor is surrounded by a space known as the water jacket. This space is generally cast with the cylinder, although in some designs of motors the jackets are formed by the subsequent application of a copper casing that serves to retain the water. The water jackets are connected with each other by means of piping and water-tight joints so that the water will pass successively from one to the other. If the water remained in these spaces, it would soon be warmed to a temperature far above the boiling point, steam would be formed, a high pressure generated, and infinite harm would result--both to motor and to passengers. The piping, however, does not end with the connections between the cylinders, but extends to and from the radiator. This radiator is a large, perforated structure placed either forward of the motor to form the end of the bonnet-covering, or in front of the dash between it and the rear cylinder of the engine. The radiator is a mass of small cellular or tubular passages, each one of which possesses an exceedingly large outer surface in proportion to the amount of water that it can contain. When the hot water reaches the radiator it is distributed to these many cells or tubes, and is thus spread over a large cooling surface. A large fan is usually located directly behind the radiator, and as this serves to draw the air rapidly through the openings between the cells or tubes, cooling is greatly facilitated. There are several types of radiators in general use. Some consist of a number of flat cells placed in such a manner that regular-shaped air openings will be formed. Each side of each flat water cell abuts on an air passage. Such a radiator is known as the honeycomb, or cellular, the former term being applied to those whose cells resemble a honeycomb. The tubular radiator consists of a number of vertical, parallel tubes through which the water passes, and which are placed a sufficient distance apart to provide ample air passages between them. Each tube is covered at frequent intervals with fluted, circular flanges that serve to increase the radiating surface in much the same manner as do the grooves and flanges on the cylinders of the air-cooled motor. All air passages in any radiator extend directly through the width of the radiator, while the water circulates from top to bottom in a vertical direction. The reason for this circulation of the water will be apparent if we call to mind a bit of our elementary physics. When water is heated, it expands and rises, and for this reason, we always find the surface of the water in a teakettle warmer than is that at the bottom--although the latter is closer to the fire. As the water is circulated through the radiator, it is cooled by the passage of the large amount of air through the openings between the cells or tubes. The water thus cooled sinks to the bottom of the radiator and is replaced by the water just heated by the motor. The cooled water is conducted to the bottom portion of the end cylinder, and passes to the others in succession, gradually rising as it is heated, until it is again forced to the radiator at the top. There are two methods of circulating the water through the cylinder jackets and radiator. The most common method consists of the introduction of a pump in the lower portion of the circulating system. In the case of automobile motors, this pump is driven by gears connected with the crank shaft of the engine. Such a pump will be either of the gear or centrifugal type, and will suck the cooled water from the lower portion of the radiator, and force it through the jackets. The second method is known as the thermo-syphon system because the circulation is automatic and depends upon the cooling of the water in the radiator. When the cooled water sinks, a syphon action is formed that tends to draw the hot water from the cylinder jackets, and the automatic circulation will thus continue as long as the successive heating and cooling take place. Inasmuch as the pump is driven by the crank shaft of the engine, its speed will be proportional to that of the motor. The same holds true of the fan that serves to draw the air through the radiator. It will thus be seen that both the water and the air are forced at a more rapid rate when the motor runs at high speed, and that therefore the extra heat generated by the more frequent explosions in the cylinders will be counteracted to a certain extent. The increased number of explosions and the higher speed at which the fan turns also cause quicker heating and cooling of the water by the thermo-syphon system, thus forming a more rapid circulation. Inasmuch as the force exerted upon the water by its cooling and heating is not as great as that formed by a high-speed and efficient pump, the pipes and connections of the thermo-syphon system must be of ample size in order to keep the resistance to the passage of the water as low as possible. Care must also be taken in the design of this system so to construct and connect the pipes and jackets that the hot water will be allowed to rise and the cool to descend, and thus to make possible the syphon conditions on which principle the circulation is based. The ability of the radiator to carry off the heat from the water depends upon the rapidity with which the air passes through the passages provided for the purpose. The amount of air passing through is determined by the speed of the suction fan and the rapidity of travel of the car itself against the wind. It has been shown that, when the motor runs at a high number of revolutions, the fan turns faster and the rapidity of circulation is increased. But if the car itself does not increase its speed in proportion to the higher revolutions of the motor, the maximum amount of air will not be forced through the radiator passages, and the excess heat will not be carried off entirely from the cylinders. This is a condition that prevails when the motor is run on low gear. The speed of the motor is increased, while that of the car is reduced; additional heat is generated in the cylinders, but the speed of the air is not increased in proportion. Therefore a motor that is driven a long distance on the low gear will have a tendency to overheat. Water under atmospheric pressure cannot be brought to a temperature above 212 degrees Fahrenheit without being converted into steam. Therefore, when the heat from a water-cooled motor cannot be carried away sufficiently fast, the water in the circulating system will begin to boil. As long as water remains in the jackets, the temperature of these spaces cannot well rise above 212 degrees, and consequently there is small danger that a water-cooled motor will become overheated to the point at which the pistons will "seize" in the cylinders. The moment the water in the circulating system begins to boil, however, exceedingly rapid evaporation naturally takes place, and the water will soon entirely disappear in the form of steam and vapor. To run the motor under these conditions will mean that pistons and rings will soon become stuck in their cylinders, although liberal quantities of oil will sometimes delay this inevitable result. But even when the cooling water is not brought to the boiling point there is a vapor that is constantly dispelled from it whenever its temperature is brought above that of the air. The water system of an automobile must therefore be replenished at irregular intervals, depending upon the amount and nature of the running to which the car has been subjected. The older cars were provided with an extra water tank, generally located under the seat, and connected directly with the water jackets and the radiator. The usual water-cooling system of the present-day car, however, is self-contained--that is, there is no separate tank for the storage of the water. The water is poured into the top of the radiator, and from this high point it reaches every part of the circulating system. Whenever the radiator will accommodate a couple of quarts, or more, it is well to fill it, for _too much_ water _cannot be used_ on the modern design of cooling system. It is true that a motor runs at its highest efficiency when its temperature is as great as that at which proper lubrication of the pistons can be obtained--for a gasoline engine is a "heat engine," and the greater its unnecessary heat losses, the less will be the power developed by it. But a motor cannot be kept at the proper temperature by reducing the amount of cooling water in its circulating system. The best method is to lessen the rapidity with which the water is cooled, and this may be accomplished by placing a leather flap, a cardboard, or other obstruction over a portion of the radiator to reduce the number of openings through which the air may pass. It should only be necessary to do this in the coldest weather, however, for the cooling system of every motor is designed to maintain the proper temperature on all except the hottest or coldest days. It has been stated in a preceding paragraph that continued running on the low gear is the most frequent cause of overheating a motor. This is true, but it is not the only cause. Obstructions in the circulating system that reduce the flow of water will have this effect, as will also deposits on the interior of the cylinders that serve to prevent the proper transfer of heat to the water in the jacket spaces. Removal of the carbon will remedy the latter trouble, but to clear out the circulating system is more or less of a complicated matter. Stoppage in the pipes or radiator cells may be caused by a lime deposit from "hard" water that may have been used in the circulating system. There are preparations intended to remove this deposit, but such should not be used without first advising with the maker of the car or an experienced repair man. A series of battered cells in the radiator may reduce the number of cooling spaces that should be traversed by the water, and thus the hot water cannot be distributed over as great an air area as is necessary to maintain the motor at the proper temperature. Such a condition will be apparent from a marked difference in temperature between the affected portion of the radiator and the remainder. If a deposit has been formed on a certain series of cells, or if they have been obstructed in any other manner, the hot water cannot circulate through this section of the radiator, and it will remain comparatively cool. Water is a liquid that remains in its fluid stage only through a temperature range of 180 degrees--at atmospheric pressure. At 212 degrees it boils and turns to vapor, while at 32 degrees it freezes and becomes a solid. In neither of these stages does it form a desirable cooling medium for a gasoline motor. Of the two, however, its solid stage is the more harmful to the motor. Not only will it cease to flow when it becomes ice, but the expansion of the water during the formation of the solid is liable to burst its retainer--whether it be the cells of the radiator, the pump, pipes, or even the cylinder walls themselves. It is the radiator that is the most liable to suffer from such a cause, however, for each cell contains so small an amount of water that the liquid will be brought to the freezing point before the larger volume in the jacket spaces approaches this temperature. Of course the water will be kept well above the freezing point when the motor is running, and it is only when the machine has stood idle for several hours that care must be taken to prevent the formation of ice in the circulating system. Aside from keeping the car in a warm place whenever the motor is to be at rest more than two hours, there is only one method of preventing the cooling water from freezing, and that is by the introduction of some chemical that lowers the point at which the liquid will turn to a solid. There are several ingenious heaters available that are attached to the circulating pipes and that serve to keep all of the jacket water warm; the use of these producing the same conditions as though the car were kept in an artificially-heated garage. One of the most common liquids used in the cooling water to prevent freezing is alcohol. If equal parts of wood alcohol and water are used in the cooling system, the resulting mixture will not freeze until it reaches a temperature colder than 25 degrees below zero. A weaker mixture--one having 25 per cent. of wood alcohol--will freeze at about zero, and it therefore depends upon the prevailing cold-weather temperature as to the proper proportion that should be used. It must be remembered that the boiling point of alcohol is much lower than is that of water, and that therefore a mixture that will not freeze in exceedingly cold weather is liable to boil away on the first moderate day on which the car is run. The above-mentioned 50 per cent. mixture of wood alcohol and water will boil at 135 degrees, while the 25 per cent. solution will withstand a temperature 40 degrees higher before it is transformed into vapor. As the lower temperature will be reached easily if the motor is run for some time in comparatively moderate weather, it will be seen that the stronger mixture should be used only where winters are very severe. It must also be borne in mind that, as alcohol boils more readily than does water, it follows that it will evaporate more easily, as well. Therefore, in order to maintain a uniform proportion of wood alcohol to water, the former should be replenished more often than is the latter. Glycerine is another substance that is often mixed with the cooling water to prevent the latter from freezing. A 50 per cent. mixture of this and water has a freezing point of about zero, or slightly lower, and boils at practically the same temperature as water--210 degrees. Combinations of wood alcohol and glycerine may be used--equal parts of each being the usual proportion--and thus various freezing and boiling points may be obtained. The radiator is one of the most delicate parts of the motor car's construction, and yet it is the most exposed to flying sticks and stones that may be thrown up by the rapid travel of the car. The car owner may do well to follow the practice of many racing drivers who place a heavy wire mesh screen in front of the radiator as a protection against obstacles that may be struck by the front of the car. It would seem that sticks and stones would be thrown toward the rear of the car, and would therefore avoid the radiator by a wide margin, but experience has proved that, at high speed, such loose pieces are frequently forced forward and are _run_ into by the front of the car. CHAPTER IX TWO-CYCLE MOTORS There has always been a strong prejudice in favor of the four-cycle motor for the power plant of the gasoline automobile. This may be due to the fact that designers have spent most of their time and energy on the development of this engine, and that therefore the two-cycle type has not yet been sufficiently "tried out" in the motor car to enable us to judge fairly as to its real merits. Certain it is that in the few instances in which the two-cycle motor has been used as an automobile power plant, the results have been highly satisfactory, and the present vogue of the four-cycle motor--with well over 98 per cent. of the automobiles now made adhering to this type--is largely due to popular prejudice in its favor. As has been described in the first chapter of the present volume, the four-cycle motor devotes a separate stroke to each of the events of expansion, scavenging or expulsion of the burned gases, suction, and compression. The two-cycle motor, on the other hand, devotes but two strokes to these four events, and there is therefore an explosion twice as often in the two-cycle engine cylinder as is the case with the four-cycle type. But in lieu of the suction stroke of the four-cycle motor, there must be some method of forcing the charge into the cylinder of the two-cycle engine. The base, or compartment below the piston, in which the crank revolves, is used for this purpose. As the piston travels upward on its compression stroke, a partial vacuum is formed in the base, and if a passage is opened between this compartment and the carburetor, the charge will be sucked in. All outside connections with the base are tightly closed on the down-stroke of the piston, and consequently the recently-inhaled charge will be compressed, ready for its entrance into the cylinder above the piston as soon as the connecting passage is opened. This passage is opened, as has already been described, at the bottom of the stroke and the compressed charge rushes in and fills the space in the cylinder that at that time is being vacated by the exhaust gases. The majority of two-cycle motors are made without any valve mechanism, the opening and closing of the passages being entirely automatic. These passages are cast with the engine and lead into the cylinder through openings in the walls called "ports." The opening leading from the cylinder to the exhaust pipe, or exhaust port, is placed near the bottom of the stroke so that it is covered by the piston, except at the lower extremity of the travel of the latter. Just below the exhaust port, and on the opposite side of the interior of the cylinder, is placed the intake port, or opening of the passage connecting the cylinder with the base. Now, as the piston is forced downward, it uncovers the exhaust port and an easy means of escape is furnished for the burned gases. Immediately after this, the intake port on the opposite side is uncovered by the still-descending piston, and the previously compressed charge, which is only awaiting the opportunity in the base, "blows" in. The exhaust gases are still escaping when this happens, and therefore it is necessary to prevent the incoming charge from passing directly across the top of the piston and out through the exhaust port before use has been made of its explosive qualities. Consequently, to keep it in its proper path, a baffle plate is attached to the top of the piston which serves to deflect the incoming charge toward the top of the cylinder, and this not only prevents the loss of the mixture, but also furnishes a blast of air that helps to blow out the burned gases. On the return of the piston to the top of its stroke, it first passes over the intake port and then covers the exhaust port, effectually closing both and preventing the escape of the charge during compression. While this is going on, it must be remembered, the piston is forming the partial vacuum in the base, which serves to draw in the charge for the succeeding explosion. If the charge is drawn directly into the base from the carburetor, a check valve must be used in the pipe connecting the two; otherwise the mixture would be forced back into the carburetor the instant the piston began its descent. A two-cycle motor drawing its charge in this manner is known as the two-port type, for there are only the exhaust and the inlet ports in the interior of the cylinder walls. The passage connecting the carburetor with the base may enter at the bottom of the cylinder, for this space and the base are the same when the piston is at the top of its stroke. Thus if this port is placed so that it is uncovered when the piston is at the top of its stroke, it will admit the charge to the base at a time when a partial vacuum has been created in this compartment by the upward movement of the piston. This port is again covered as soon as the piston starts on its downward journey, and thus the charge is prevented from escaping until the intake port connecting the base with the top of the cylinder is opened. Such a two-cycle motor is known as the three-port type, and it will be seen that not even an automatic check valve is used in its passages--and it is consequently a "valveless" motor in the liberal interpretation of the term. The high velocity of the charge recompenses for the short time that the port is uncovered, and consequently the base is filled with nearly as large an amount of charge as is the case with the two-port motor--which allows the incoming gases to enter the crank case during the entire upward stroke of the piston. It will thus be seen that the piston of the two-cycle motor acts as a pump in two ways. First, the vacuum is formed that serves to draw the charge into the crank case, or base, of the motor; and second, the return stroke of the piston compresses this recently-inhaled charge and makes it ready to be "shot" up into the cylinder as soon as the piston has uncovered the port that forms the upper terminal of the communicating passage. There can, of course, no greater amount of fresh charge enter the cylinder than is drawn into the crank case. Consequently, the amount to which the cylinder will be filled depends upon the vacuum formed and the pressure exerted upon the charge by the succeeding down-stroke of the piston. It is to be supposed that the piston rings will be tight and that none of the charge can escape by them, and therefore the vacuum formed and pressure exerted in the crank case will depend entirely upon the displacement of the piston in its travel compared with the total capacity of the crank case. In other words, if the crank case is large and the piston is small and travels but a short distance, its pump action on the entire volume will be small. But if the crank case is small and the travel of the piston alternately doubles and halves the volume, the motion of the piston will cause the pressure in the crank case to vary greatly. In a preceding paragraph it has been described in what manner the incoming charge in the two-cycle motor was used to "scavenge" the cylinder, or rid it of burned gases, by deflecting the mixture and allowing this to force out the remaining exhaust before the exhaust port was closed by the upward motion of the piston. It is evident that the greater the force, within certain limits, with which the charge enters the cylinder, the more perfect will be the scavenging action. But there is a limit to the pressure that can be attained by the mixture when it is compressed in the crank case previous to its discharge into the cylinder. This limit is determined by the size of the space required for the revolution of the crank and "big end" of the connecting rod, and by the volume displaced by the motion of the piston. The crank must have room in which to revolve, and the displacement of the piston can only be the area of its top multiplied by its length of stroke. Thus eight pounds per square inch is about the usual limit of crank case compression with this type of two-cycle motor. This may be varied slightly one way or the other by the arrangement of the ports, but it makes slight difference whether the motor is of the two- or three-port type so far as this consideration is concerned. Two-cycle motors have been designed which combine the principles of action of both the two- and three-port types. The most important departure from the generally-accepted type of two-cycle motor, however, is the design in which the charge is fed into the cylinder from a chamber that is absolutely independent of the crank case proper. This may be accomplished in several ways. There may be what is termed a "differential piston" in which a separate plunger operates in the interior of the hollow "trunk" piston, and by means of the proper connection with the crank shaft compresses the charge in the chamber thus formed at the time it is to be forced into the cylinder. Another design for obtaining intake compression independent of the crank case consists of a collar, or circular enlargement at the base of the piston. This collar reciprocates within the lower portion of the piston in a chamber which has been bored to the exact size. The collar consequently forms a variable base for this compartment, and as the piston descends, the collar travels with it, thus drawing in a charge of the fresh mixture. On the upward stroke, this mixture is compressed by the collar as it reduces the size of the compartment. It will be seen that such a motor can be designed to compress the charge to almost any amount. Inasmuch as the mixture, as mentioned above, is compressed on the up-stroke of the piston, it is evident that it cannot be discharged into that particular cylinder at that time--for the mixture should be delivered to its cylinder only when the piston is at the bottom of its stroke. In the case of a four-cylinder engine, however, one of the pistons would be in the proper position for the entrance of the charge, and it is into this cylinder, that the compressed mixture is forced. The compression space in each cylinder, therefore, works for its neighbor, rather than for itself. This interchange of courtesies is obtained through the good offices of a distributor in the form of a rotating, hollow cylinder having ports cut throughout its length that register with corresponding passages leading to the various cylinders. This distributor is timed with the crank shaft of the motor, and may be driven either by a gear or by a silent chain. As the mixture is compressed in the separate chamber of one cylinder, the passage leading to the distributor is opened by the revolution of the latter, and the charge is led through this passage, the distributor, and thence through another passage--also opened by the distributor--to the proper cylinder. The cylinders thus operate in pairs, one receiving its charge while the other is about to begin its explosion stroke--and vice versa. The force of the explosion in a gasoline engine cylinder is not only dependent upon the amount and nature of the inflammable mixture admitted, but upon the force with which it is compressed, as well. The average compression pressure of a two- or four-cycle engine of the ordinary type, is from 60 to 70 pounds per square inch. Inasmuch as this pressure, assuming that the rings and valves are tight, is proportional to the displacement of the piston stroke compared with the volume of the clearance space, the amount of compression is constant at all speeds and loads of the motor. Should it be possible to increase this compression at will, it would be found that, with a warm motor, a pressure in the neighborhood of 100 pounds per square inch would serve to generate sufficient heat to ignite the mixture before the formation of the spark--for it is one of the elementary laws of physics that a gas will become heated when compressed. It is for this reason that the compression pressure of the ordinary automobile motor is kept in the neighborhood of 70 pounds per square inch. A method of varying compression pressure to meet individual load requirements has been devised for some motors, however, and while such types are not as yet in general use in automobiles, it is probable that the near future will find much advancement along these lines. One such two-cycle motor that has been designed especially for automobile use employs a separate air compressor driven by the engine itself and used as the clutch and variable speed transmission of the car. The amount of pressure generated in the compressor is dependent upon the resistance offered to its operation--or, in other words, it increases with additional load carried by the motor. The compression, or compressed air, rather, is carried directly from the compressor to the cylinders of the motor, being admitted at the proper time by a rotary valve driven by the crank shaft. Thus the compression in each cylinder is automatically regulated by the load, and a motor of this type possesses a high "overload" capacity. The motor mentioned above operates on somewhat the same principles as those found in the Diesel engine, which will be, as many predict, the ultimate type of internal combustion motor. The Diesel motor is not necessarily a particular make of engine, but bears the name of the originator of the principles involved. These are distinct from those of the Otto cycle, which is the principle upon which practically all automobile motors operate. The Otto cycle consists of the well-known series of events in the cylinder, as follows: Ignition, followed by the explosion, or expansion of the burned charge; discharge of the exhaust gases, or scavenging; admission of the fresh charge, suction; and compression of the newly-received mixture previous to ignition and the repetition of the cycle. In speaking of the Otto and Diesel engines, it must be borne in mind that they are referred to as a class, rather than as a particular make--as one would mention poppet valve or sleeve valve engines--for there may be many manufacturers of each type. Although the Diesel principle may be applied to either the two or four-cycle type of motor, it is to the former design that it lends itself unusually well. This motor operates a two-stage air compressor in conjunction with a storage tank. At the beginning of the compression stroke, pure air under high pressure is admitted to the cylinder. In its upward travel, the piston compresses this air to a pressure approximating 500 pounds per square inch. While it has been shown that such a pressure is about five times more than enough to generate sufficient heat to cause premature ignition, it must be remembered that, unlike the ordinary type of motor, this is only pure air that is injected into the cylinder and contains none of the explosive gasoline vapor. At the top of the stroke, however, when the compression is at its maximum, the fuel is injected directly into the cylinder without having been previously vaporized. This is another feature in which the Diesel motor is entirely different from the Otto type, for the latter must employ a carburetor to vaporize the fuel before it can be admitted to the cylinder. But inasmuch as there is already a pressure approximating 500 pounds per square inch in the cylinder of the Diesel motor at the time the fuel is injected, there must be a force behind the latter of 750 or 1,000 pounds per square inch in order to enable it to overcome the resistance of the highly-compressed air in the cylinder. In short, the liquid fuel is sprayed directly into the cylinder at a pressure of 750 or 1,000 pounds per square inch. This tremendous pressure is sufficient, not only to vaporize the particles of fuel as soon as they enter the cylinder from the nozzle, or "atomizer," but to cause them to burst into flame, as well. In other words, the compression of the air previously has generated sufficient heat in the cylinder to ignite the fuel immediately on its admission. The fuel continues to be injected into the cylinder during the greater part of the down-stroke of the piston. In this respect, also, is the Diesel motor radically different from the Otto type, for the latter receives its full charge at one time and fires the entire amount in a single "explosion." In the Diesel motor, on the other hand, the ignition continues as long as fuel is admitted, and thus this engine is of the internal _combustion_ type in the strictest sense of the word. It is, after all, the expansion of the gases due to the heat of combustion that produces the power in a gasoline engine, and if the fuel can be so admitted that it can burn during the greater part of the stroke, a high efficiency will be obtained. The exhaust gases of the ordinary two-cycle motor pass out of the exhaust port as it is uncovered by the descent of the piston. Those that remain are forced out by the sudden admission of the fresh charge, which is deflected upward and is intended to scavenge the top of the cylinder. But it is claimed that thus employing the fresh mixture as a scavenging agent is wasteful of the fuel-permeated charge and does not conduce to efficient running. The system is simple in the extreme, however, and does its work well in small installations in which fuel economy is not of vital importance. But in the two-cycle Diesel type of engine, the high pressure of the pure air is used for scavenging, and as this is admitted with so large an initial force, the exhaust port may remain uncovered for a longer period than would be the case were the air to rely entirely on the up-stroke of the piston for its compression. Then too, whatever air may escape contains no fuel, and consequently efficient scavenging may be obtained without waste. At the high pressure at which the fuel is injected into the cylinder of the Diesel engine, practically any grade of gasoline, naphtha, kerosene, crude oil, or other form of petroleum can be vaporized. The compressed air employed in the compression and injection of the fuel is also used for starting the motor, for this is not a type that is amenable to hand cranking. Thus the Diesel type of engine can be run in any weather on any grade of oil fuel, and as the carburetor and electrical ignition system are absolutely eliminated, two of the great sources of trouble of the automobile motor are absent--and this feature, alone, even more than the superior economy of operation, will appeal to the average motorist. Just when this type of motor will be taken up by automobile designers is difficult to state. The Diesel type of engine has proved so wonderfully successful for large stationary power plants and for marine purposes, and its reliability is so absolute on all grades of fuel, that this motor may solve the failing-gasoline-supply problem. As yet, about 100 horsepower is the smallest unit that has been made in any quantities, but it was recently announced that this type would, in the very near future, be built for motor trucks and other commercial vehicles. Consequently, it is well for all those interested in the application of the two-cycle motor to the automobile to understand the elementary principles on which this radically-different type operates. * * * * * * Transcriber's note: Inconsistent hyphenation has been retained unless one form predominated. The following corrections have been made: p. 19 This give a much -> give changed to gives p. 34 purpose of cleanning -> cleanning changed to cleaning Everything else has been retained as printed. 
38415	----	* * * * * Transcriber's Note: The original publication has been replicated faithfully except as listed near the end of this text. Text in italics is shown like _this_. Text emphasized with bold characters or other treatment is shown like =this=. * * * * * Gas-Engines and Producer-Gas Plants A PRACTICE TREATISE SETTING FORTH THE PRINCIPLES OF GAS-ENGINES AND PRODUCER DESIGN, THE SELECTION AND INSTALLATION OF AN ENGINE, CONDITIONS OF PERFECT OPERATION, PRODUCER-GAS ENGINES AND THEIR POSSIBILITIES, THE CARE OF GAS-ENGINES AND PRODUCER-GAS PLANTS, WITH A CHAPTER ON VOLATILE HYDROCARBON AND OIL ENGINES BY R. E. MATHOT, M.E. Member of the Société des Ingénieurs Civils de France, Institution of Mechanical Engineers, Association des Ingénieurs de l'Ecole des Mines du Hainaut of Brussels TRANSLATED FROM ORIGINAL FRENCH MANUSCRIPT BY WALDEMAR B. KAEMPFFERT WITH A PREFACE BY DUGALD CLERK, M. INST. C.E., F.C.S. ILLUSTRATED NEW YORK MUNN & COMPANY OFFICE OF THE SCIENTIFIC AMERICAN 361 BROADWAY 1905 PREFACE TO "MATHOT'S GAS-ENGINES AND PRODUCER-GAS PLANTS" BY DUGALD CLERK, M. INST.C.E., F.C.S. Mr. Mathot, the author of this interesting work, is a well-known Belgian engineer, who has devoted himself to testing and reporting upon gas and oil engines, gas producers and gas plants generally for many years past. I have had the pleasure of knowing Mr. Mathot for many years, and have inspected gas-engines with him. I have been much struck with the ability and care which he has devoted to this subject. I know of no engineer more competent to deal with the many minute points which occur in the installation and running of gas and oil engines. I have read this book with much interest and pleasure, and I consider that it deals effectively and fully with all the principal detail points in the installation, operation, and testing of these engines. I know of no work which has gone so fully into the details of gas-engine installation and up-keep. The work clearly points out all the matters which have to be attended to in getting the best work from any gas-engine under the varying circumstances of different installations and conditions. In my view, the book is a most useful one, which deserves, and no doubt will obtain, a wide public recognition. DUGALD CLERK. _March, 1905._ INTRODUCTION The constantly increasing use of gas-engines in the last decade has led to the invention of a great number of types, the operation and care of which necessitate a special practical knowledge that is not exacted by other motors, such as steam-engines. Explosion-engines, driven by illuminating-gas, producer-gas, oil, benzin, alcohol and the like, exact much more care in their operation and adjustment than steam-engines. Indeed, steam-engines are regularly subjected to comparatively low pressures. The temperature in the cylinders, moreover, is moderate. On the other hand, the explosion-motor is irregularly subjected to high and low pressures. The temperature of the gases at the moment of explosion is exceedingly high. It is consequently necessary to resort to artificial means for cooling the cylinder; and the manner in which this cooling is effected has a very great influence on the operation of the motor. If the cooling be effected too rapidly, the quantity of gas consumed is considerably increased; if the cooling be effected too slowly, the motor parts will quickly deteriorate. In order to reduce the gas consumption to a minimum, a matter which is particularly important when the motor is driven by street-gas, the explosive mixture is compressed before ignition. Only if all the parts are built with joints absolutely gas-tight is it possible to obtain this compression. The slightest leakage past the valves or around the piston will sensibly increase the consumption. The mixture should be exploded at the exact moment the piston starts on its working stroke. If ignition occurs too soon or too late, the result will be a marked diminution in the useful effect produced by the expansion of the gas. All ignition devices are composed of delicate parts, which cannot be too well cared for. It follows from what has thus far been said that the causes of perturbation are more numerous in a gas than in a steam engine; that with a gas-engine, improper care will lead to a much greater increase in consumption than with a steam-engine, and will cause a waste in power which would hardly be appreciable in steam-engines, whether their joints be tight or not. It is the purpose of this manual to indicate the more elementary precautions to be taken in the care of an engine operating under normal conditions, and to explain how repairs should be made to remedy the injuries caused by accidents. Engines which are of less than 200 horse-power and which are widely used in a small way will be primarily considered. In another work the author will discuss more powerful engines. Before considering the choice, installation, and operation of a gas-engine, it will be of interest to ascertain the relative cost of different kinds of motive power. Disregarding special reasons which may favor the one or the other method of generating power, the net cost per horse-power hour will be considered in each case in order to show which is the least expensive method of generating power in ordinary circumstances. R. E. MATHOT. MARCH, 1905. TABLE OF CONTENTS CHAPTER I PAGE MOTIVE POWER AND COST OF INSTALLATION 17 CHAPTER II SELECTION OF AN ENGINE The Otto Cycle.--The First Period.--The Second Period.--The Third Period.--The Fourth Period.--Valve Mechanism.--Ignition.-- Incandescent Tubes.--Electric Ignition.--Electric Ignition by Battery and Induction-Coil.--Ignition by Magnetos.--The Piston.-- Arrangement of the Cylinder.--The Frame.--Fly-Wheels.--Straight and Curved Spoke Fly-Wheels.--The Crank-Shaft.--Cams, Rollers, etc.--Bearings.--Steadiness.--Governors.--Vertical Engines.-- Power of an Engine.--Automatic Starting 21 CHAPTER III THE INSTALLATION OF AN ENGINE Location.--Gas-Pipes.--Dry Meters.--Wet Meters.--Anti-Pulsators, Bags, Pressure-Regulators.--Precautions.--Air Suction.-- Exhaust.--Legal Authorization 69 CHAPTER IV FOUNDATION AND EXHAUST The Foundation Materials.--Vibration.--Air Vibration, etc.-- Exhaust Noises 87 CHAPTER V WATER CIRCULATION Running Water.--Water-Tanks.--Coolers 98 CHAPTER VI LUBRICATION Quality of Oils.--Types of Lubricators 111 CHAPTER VII CONDITIONS OF PERFECT OPERATION General Care.--Lubrication.--Tightness of the Cylinder.-- Valve-Regrinding.--Bearings.--Crosshead.--Governor.--Joints.-- Water Circulation.--Adjustment 121 CHAPTER VIII HOW TO START AN ENGINE.--PRELIMINARY PRECAUTIONS Care during Operation.--Stopping the Engine 128 CHAPTER IX PERTURBATIONS IN THE OPERATION OF ENGINES AND THEIR REMEDY Difficulties in Starting.--Faulty Compression.--Pressure of Water in the Cylinder.--Imperfect Ignition.--Electric Ignition by Battery or Magneto.--Premature Ignition.--Untimely Detonations.--Retarded Explosions.--Lost Motion in Moving Parts.--Overheated Bearings.--Overheating of the Cylinder.-- Overheating of the Piston.--Smoke arising from the Cylinder.-- Back Pressure to the Exhaust.--Sudden Stops 134 CHAPTER X PRODUCER-GAS ENGINES High Compression.--Cooling.--Premature Ignition.--The Governing of Engines 153 CHAPTER XI PRODUCER-GAS Street-Gas.--Composition of Producer-Gases.--Symptoms of Asphyxiation.--Gradual, Rapid Asphyxiation.--Slow, Chronic Asphyxiation.--First Aid in Cases of Carbon Monoxide Poisoning.--Sylvester Method.--Pacini Method.--Impurities of the Gases 165 CHAPTER XII PRESSURE GAS-PRODUCERS Dowson Producer.--Generators.--Air-Blast.--Blowers.--Fans.-- Compressors.--Exhausters.--Washing and Purifying.-- Gas-Holder.--Lignite and Peat Producers.--Distilling-Producers.-- Producers Using Wood Waste, Sawdust, and the like.-- Combustion-Generators.--Inverted Combustion 174 CHAPTER XIII SUCTION GAS-PRODUCERS Advantages.--Qualities of Fuel.--General Arrangement.-- Generator.--Cylindrical Body.--Refractory Lining.--Grate and Support for the Lining.--Ash-pit.--Charging-Box.-- Slide-Valve.--Cock.--Feed-Hopper.--Connection of Parts.--Air Supply.--Vaporizer.--Preheaters.--Internal Vaporizers.-- External Vaporizers.--Tubular Vaporizers.--Partition Vaporizers.--Operation of the Vaporizers.--Air-Heaters.-- Dust-Collectors.--Cooler, Washer, Scrubber.--Purifying Apparatus.--Gas-Holders.--Drier.--Pipes.--Purifying-Brush.-- Conditions of Perfect Operation of Gas-Producers.-- Workmanship and System.--Generator.--Vaporizer.--Scrubber.-- Assembling the Plant.--Fuel.--How to Keep the Plant in Good Condition.--Care of the Apparatus.--Starting the Fire for the Gas-Producer.--Starting the Engine.--Care of the Generator during Operation.--Stoppages and Cleaning 199 CHAPTER XIV OIL AND VOLATILE HYDROCARBON ENGINES Oil-Engines.--Volatile Hydrocarbon Engines.--Comparative Costs.-- Tests of High-Speed Engines.--The Manograph.--The Continuous Explosion-Recorder for High-Speed Engines.--Records 264 CHAPTER XV THE SELECTION OF AN ENGINE The Duty of a Consulting Engineer.--Specifications.--Testing the Plant.--Explosion-Recorder for Industrial Engines.--Analysis of the Gases.--Witz Calorimeter.--Maintenance of Plants.--Test of Stockport Gas-Engine with Dowson Pressure Gas-Producer.--Test of a Winterthur Engine.--Test of a Winterthur Producer-Gas Engine.--Test of a Deutz Producer-Gas Engine and Suction Gas-Producer.--Test of a 200-H.P. Deutz Suction Gas-Producer and Engine 279 CHAPTER I MOTIVE POWER--COST OF INSTALLATION The ease with which a gas-engine can be installed, compared with a steam-engine is self-evident. In places where illuminating gas can be obtained and where less than 10 to 15 horse-power is needed, street-gas is ordinarily employed.[A] The improvements which have very recently been made in the construction of suction gas-generators, however, would seem to augur well for their general introduction in the near future, even for very small powers. The installation of small street-gas-engines involves simply the making of the necessary connections with gas main and the mounting of the engine on a small base. An economical steam-engine of equal power would necessitate the installation of a boiler and its setting, the construction of a smoke-stack, and other accessories, while the engine itself would require a firm base. Without exaggeration it may be asserted that the installation of a steam-engine and of its boiler requires five times as much time and trouble as the installation of a gas-engine of equal power, without considering even the requirements imposed by storing the fuel (Fig. 1). Small steam-engines mounted on their own boilers, or portable engines, the consumption of which is generally not economical, are not here taken into account. [Illustration: FIG. 1.--30 H.P. Gas-engine and suction gas-producer.] [Illustration: FIG. 1_A_.--30 H.P. Steam-engine, boiler and smoke-stack.] So far as the question of cost is concerned, we find that a 15 to 20 horse-power steam-engine working at a pressure of 90 pounds and having a speed of 60 revolutions per minute would cost about 16-2/3 per cent. more than a 15 horse-power gas-engine, with its anti-pulsators and other accessories. The foundation of the steam-engine would likewise cost about 16-2/3 per cent. more than that of the gas-engine. Furthermore the installation of the steam-engine would mean the buying of piping, of a boiler of 100 pounds pressure, and of firebrick, and the erection of a smoke-stack having a height of at least 65 feet. Beyond a little excavating for the engine-base and the necessary piping, a gas-engine imposes no additional burdens. It may be safely accepted that the steam-engine of the power indicated would cost approximately 45 per cent. more than the gas-engine of corresponding power. The cost of running a 15 to 20 horse-power steam-engine is likewise considerably greater than that of running a gas-engine of the same size. Considering the fuel-consumption, the cost of the lubricating oil employed, the interest on the capital invested, the cost of maintenance and repair, and the salary of an engineer, it will be found that the operation of the steam-engine is more expensive by about 23 per cent. This economical advantage of the gas over the steam-engine holds good for higher power as well, and becomes even more marked when producer-gas is used instead of street-gas. Comparing, for example, a 50 horse-power steam-engine having a pressure of 90 pounds and a speed of 60 revolutions per minute, with a 50 horse-power producer-gas engine, and considering in the case of the steam-engine the cost of a boiler of suitable size, foundation, firebrick, smoke-stack, etc., and in the case of the gas-engine the cost of the producer, foundation, and the like, it will be found that the installation of a steam-engine entails an expenditure 15 per cent. greater than in the case of the producer-gas engine. However, the cost of operating and maintaining the steam-engine of 50 horse-power will be 40 per cent. greater than the operation and maintenance of the producer-gas engine. From the foregoing it follows that from 15 to 20 up to 500 horse-power the engine driven by producer-gas has considerably the advantage over the steam-engine in first cost and maintenance. For the development of horse-powers greater than 500, the employment of compound condensing-engines and engines driven by superheated steam considerably reduces the consumption, and the difference in the cost of running a steam- and gas-engine is not so marked. Still, in the present state of the art, superheated steam installations entail considerable expense for their maintenance and repair, thereby lessening their practical advantages and rendering their use rather burdensome. FOOTNOTES: [A] Recent improvements made in suction gas-producers will probably lead to the wide introduction of producer gas engines even for small power. CHAPTER II THE SELECTION OF AN ENGINE Explosion-engines are of many types. Gas-engines, of the four-cycle type, such as are industrially employed, will here be principally considered. =The Otto Cycle.=--The term "four-cycle" motor, or Otto engine, has its origin in the manner in which the engine operates. A complete cycle comprises four distinct periods which are diagrammatically reproduced in the accompanying drawings. =The First Period.=--_Suction:_ The piston is driven forward, creating a vacuum in the cylinder, and simultaneously drawing in a certain quantity of air and gas (Fig. 2). [Illustration: FIG. 2.--First cycle: Suction.] =The Second Period.=--_Compression:_ The piston returns to its initial position. All admission and exhaust valves are closed (Fig. 3). The mixture drawn in during the first period is compressed. =The Third Period.=--_Explosion and Expansion:_ When the piston has reached the end of its return stroke, the compressed mixture is ignited. Explosion takes place at the dead center. The expansion of the gas drives the piston forward (Fig. 4). [Illustration: FIG. 3.--Second cycle: Compression.] [Illustration: FIG. 4.--Third cycle: Explosion and expansion.] =The Fourth Period.=--_Exhaust:_ The piston returns a second time. The exhaust-valve is opened, and the products of combustion are discharged (Fig. 5). [Illustration: FIG. 5.--Fourth cycle: Exhaust.] These various cycles succeed one another, passing through the same phases in the same order. =Valve Mechanism.=--It is to be noted that in modern motors valves are used which are better adapted to the peculiarities of explosion-engines than were the old slide-valves used when the Otto engine was first introduced. The slide-valve may now be considered as an antiquated distributing device with which it is impossible to obtain a low consumption. In old-time gas-engines rather low compressions were used. Consequently a very low explosive power of the gaseous mixture, and low temperatures were obtained. The slide-valves were held to their seats by the pressure of external springs, and were generously lubricated. Under these conditions they operated regularly. Nowadays, the necessity of using gas-engines which are really economical has led to the use of high compressions with the result that powerful explosions and high temperatures are obtained. Under these conditions slide-valves would work poorly. They would not be sufficiently tight. To lubricate them would be difficult and ineffective. Furthermore, large engines are widely used in actual practice, and with these motors the frictional resistance of large slide-valves, moving on extensive surfaces would be considerable and would appreciably reduce the amount of useful work performed. [Illustration: FIG. 6.--Modern valve mechanism.] By reason of its peculiar operation, the slide-valve is objectionable, the gases being throttled at the time of their admission and discharge. As a result of these objections there are losses in the charge; and obnoxious counter-pressures occur. The necessity of using elements simple in their operation and free from the objections which have been mentioned, has naturally led to the adoption of the present valve. This valve is used both for the suction of the gas and of the air, as well as for the exhaust, with the result that either of these two essential phases in the operation of the motor can be independently controlled. The valves offer the following advantages: Their tightness increases with the pressure, since they always open toward the interior of the cylinder (Fig. 6). They have no rubbing surfaces, and need not, therefore, be lubricated. Their opening is controlled by levers provided with quick-acting cams; and their closure is effected by coiled springs almost instantaneous in their action (Fig. 7). Each valve, depending upon the purpose for which it is used, can be mounted in that part of the cylinder best suited for its particular function. The types of valved motors now used are many and various. In order to attain economy in consumption and regularity in operation they should meet certain essential requirements which will here be reviewed. Apart from proportioning the areas properly and from providing a suitable means of operation, it is indispensable that the valves should be readily accessible. Indeed, the valves should be regularly examined, cleaned and ground. It follows that it should be possible to take them apart easily and quickly. [Illustration: FIG. 7.--Controlling mechanism of valve.] It is necessary that the exhaust-valve be well cooled; otherwise the valve, exposed as it is to high temperatures, will suffer derangement and may cause leakage. The water-jacket should, therefore, surround the seat of the exhaust-valve, care being taken that the cooling water be admitted as near to it as possible (Fig. 8). The motor should control the air-let valve or that of the gaseous mixture. Hence these valves should not be actuated simply by springs, because springs are apt to move under the influence of the vacuum produced by suction. [Illustration: FIG. 8.--Water-jacketed valve.] The mixture of gas and air should not be admitted into the cylinder at too low a pressure; otherwise the weight of the mixture admitted would be lower than it ought to be, inasmuch as under these conditions the valve will be opened too tardily and closed prematurely. At the beginning as well as at the end of its stroke the linear velocity of the piston is quite inadequate to create a vacuum sufficient to overcome the resistance of the spring. It is, therefore, generally the practice separately to control the opening or closing of the one or the other valve (gas-valve or mixture-valve). Consequently these valves must be actuated independently of each other. Nowadays they are mechanically controlled almost exclusively,--a method which is advocated by well-known designers for industrial motors in particular. Valves which are not actuated in this manner (free valves) have only the advantage of simplicity of operation. Nevertheless, this arrangement is still to be found in certain oil and benzine engines, notably in automobile-motors. In these motors it is necessary to atomize the liquid fuel by means of aspired air, in order to produce an explosive, gaseous mixture. =Ignition.=--In the development of the gas-engine, the incandescent tube and the electric spark have taken the place of the obsolete naked flame. The last-mentioned mode of exploding the gaseous mixture will not, therefore, be discussed. The hot tube of porcelain or of metal has the indisputable merit of regularity of operation. The methods by which this operation is made as perfect as possible are many. Since certainty of ignition is obtained by means of the tube, it is important to time the ignition, so that it shall occur exactly at the moment when the piston is at the dead center. It has been previously stated that premature or belated ignition of the explosive mixture appreciably lessens the amount of useful work performed by the expansion of the gas. If ignition occur too soon, the mixture will be exploded before the piston has reached the dead center on its return stroke. As a result, the piston must overcome a considerable resistance due to the premature explosion and the consequent pressure. Furthermore, by reason of the high temperature of explosion, the gaseous products are very rapidly cooled. This rapid cooling causes a sudden drop in the pressure; and since a certain interval elapses between the moment of explosion and the moment when the piston starts on its forward stroke, the useful motive effort is the more diminished as the ignition is more premature. =Incandescent Tubes.=--In Figs. 9 and 10 two systems most commonly used are illustrated. In these two arrangements, in which no valve is used, the length or height to which the tube is heated by the outer flame is so controlled that the gaseous mixture, which has been driven into the tube after compression, reaches the incandescent zone as nearly as possible at the exact moment when ignition and explosion should take place. The temperature of the flame of the burner, the richness of the gaseous mixture, and other circumstances, however, have a marked influence on the time of ignition, so that the mixture is never fired at the exact moment mentioned. [Illustration: FIGS. 9-10.--Valveless hot tubes.] These considerations lead to the conclusion that motors in which the mixture is exploded by hot tubes provided with an ignition-valve are preferable to valveless tubes. By the use of a special valve, positively controlled by the motor itself, the chances of untimely ignition are lessened, because it is necessary simply to regulate the temperature and the position of the tube in order that ignition may be surely effected immediately upon the opening of the valve, at the very moment the cylinder gases come into contact with the incandescent portion of the tube (Fig. 11). Many manufacturers, however, do not employ the ignition-valve on motors of less than 15 to 20 horse-power, chiefly because of the cheaper construction. The total consumption is of less moment in a motor of small than of great power, and the loss due to the lack of an ignition-valve not so marked. In a high-power engine, premature explosion may be the cause of the breaking of a vital part, such as the piston-rod or the crank-shaft. For this reason, a valve is indispensable for engines of more than 20 to 25 horse-power. A breakage of this kind is less to be feared in a small motor, where the parts are comparatively stout. The gas consumption of a well-designed burner does not exceed from 3.5 to 5 cubic feet per hour. [Illustration: FIG. 11.--Ignition-tube with valve.] =Electric Ignition.=--Electric ignition consists in producing a spark in the explosion-chamber of the engine. The nicety with which it can be controlled gives it an undeniable advantage over the hot tube. But the objection has been raised, perhaps with some force, that it entails certain complications in installing the engine. Its opponents even assert that the power and the rapidity of the deflagration of the explosive mixture are greater with hot-tube ignition. This reason may have caused the hot-tube system to prevail in England, where manufacturers of gas-engines are very numerous and not lacking in experience. Electric ignition is effected in gas-engines by means of a battery and spark-coil, or by means of a small magneto machine which mechanically produces a current-breaking spark. [Illustration: FIG. 12.--Electric ignition by spark-coil and battery.] [Illustration: FIG. 13.--Spark-plug.] =Electric Ignition by Battery and Induction-Coil.=--The first system is the cheaper; but it exacts the most painstaking care in maintaining the parts in proper working condition. It comprises three essential elements--a battery, a coil, and a spark-plug (Fig. 12). The battery may be a storage-battery, which must, consequently, be recharged from time to time; or it may be a primary battery which must be frequently renewed and carefully cleaned. The induction-coil is fitted with a trembler or interrupter, which easily gets out of order and which must be regulated with considerable accuracy. The spark-plug is a particularly delicate part, subject to many possible accidents. The porcelain of which it is made is liable to crack. It is hard to obtain absolutely perfect insulation; for the terminals deteriorate as they become overheated, break, or become foul (Fig. 13). In oil-engines, especially, soot is rapidly deposited on the terminals, so that no spark can be produced. In benzine or naphtha motors, such an accident is less likely to happen. In automobile-motors, however, the spark-plug only too often fails to perform its function. The one remedy for these evils is to be found in the most painstaking care of the spark-plug and of the other elements of the ignition system. [Illustration: FIG. 14.--Magneto ignition apparatus.] [Illustration: FIG. 15.--General view and details of a magneto ignition apparatus.] =Ignition by Magnetos.=--Magneto apparatus, on the other hand, are noteworthy for the regularity of their operation. They may be used for several years without being remagnetized, and require no exceptional care. Magneto ignition devices are mechanically actuated, the necessary displacement of the coil being effected by means of a cam carried on a shaft turning with half the motor speed (Figs. 14 and 15). At the moment when it is released by the cam, the coil is suddenly returned to its initial position by means of a spring. This rapid movement generates a current that passes through terminals, which are arranged within the cylinder and which are immediately separated by mechanical means. Thus a much hotter circuit-breaking spark is produced, which is very much more energetic than that of a battery and induction-coil, and which surely ignites the gaseous mixture in the cylinder. The terminals are generally of steel, sometimes pointed with nickel or platinum (Fig. 16). The only precaution to be observed is the exclusion of moisture and occasional cleaning. For engines driven by producer-gas magneto-igniters are preferable to cells and batteries. In general, electrical ignition is to be recommended for high-pressure engines. [Illustration: FIG. 16.--Contacts of a magneto-igniter.] [Illustration: FIG. 17.--Device for regulating the moment of ignition.] In order to explain more clearly modern methods of ignition a diagram is presented, showing an electric magneto-igniter applied to the cylinder-head of a Winterthur motor, and also a sectional view of the member varying the make-and-break contacts which are mounted in the explosion-chamber (Figs. 18 and 19) 1. The magneto _A_ consists of horseshoe-magnets, between the poles of which the armature rotates. At its conically turned end, the armature-shaft carries an arm _B_, held in place by a nut. [Illustration: FIG. 18.--Winterthur electric ignition system.] 2. The igniter _C_ is a casting secured to the cylinder-head by a movable strap and provided with two axes _D_ and _M_, of which the one, _D_, made of bronze, is movable, and is fitted with a small interior contact-hammer, a percussion-lever, and an exterior recoil-spring; the other, _M_, is fixed, insulated, and arranged to receive the current from the magneto _A_, by means of an insulated copper wire _E_. 3. The spring _F_ comprises two continuous coils contained in a brass casing, and actuating a steel striking or percussion-pin. 4. The controlling devices of the magneto include a stem or rod _G_, slidable in a guide _H_, provided with a safety spring and mounted on an eccentric spindle, the position of which can be varied by means of a regulating-lever (_I_). The rod is operated from the distributing-shaft, on the conical end of which a cam _J_ carrying a spindle is secured. [Illustration: FIG. 19.--Contacts of the Winterthur system.] _Regulation of the Magneto._--The position assumed by the armature when at rest is a matter of importance in obtaining a good spark on breaking the circuit. The marks on the armature should be noted. The position of the armature may be experimentally varied, in order to obtain a spark of maximum intensity, by changing the position of the arm B on the armature-shaft. _Control of the Magneto._--The controlling gear should enable the armature to oscillate from 20 to 25 degrees. The time at which the breaking of the circuit is effected can be regulated by shifting the handle (_I_). In starting the engine, the circuit can be broken with a slight retardation, which is lessened as the engine attains its normal speed. _Igniter._--It is advisable that there should be a play of 1/2 mm. (0.0196 in.) between the lever _Z_ when at rest and the striking-pin. The axis _D_ of the circuit-breaking device should be easily movable; and the hammer which it carries at its end toward the interior of the cylinder should be in perfect contact with the stationary spindle _M_, which is electrically insulated. This spindle _M_ should be well enclosed, in order to prevent any leakage that might cause a deterioration of the insulating material. The subject of ignition is of such extreme importance that the author will recur to it from time to time in the various chapters of this book. Too much stress cannot be laid upon proper timing; otherwise there will be a needless waste of power. Cleanliness is a point that must be observed scrupulously; for spark-plugs are apt to foul only too readily, with the result that short-circuits and misfires are apt to occur. In oil and volatile hydrocarbon engines the tendency to fouling is particularly noticeable. In the chapter devoted to these forms of motors the author has dwelt upon the precautions that should be taken to forestall a possible derangement of the ignition apparatus. As a general rule the ignition apparatus installed by trustworthy manufacturers will be found best suited for the requirements of the engine. The apparatus should be fitted with a device by which the ignition can be duly timed by hand during operation (Fig. 17). [Illustration: FIG. 20.--Design of the piston.] =The Piston.=--Coming, as it does, continually in contact with the ignited gases, the piston is gradually heated to a high temperature. The rear face of the piston should preferably be plane. Curved surfaces are not to be recommended because they cool off badly. Likewise, faces having either inserted parts or bolt-heads are to be avoided, since they are liable to become red-hot and to ignite the mixture prematurely (Fig. 20). [Illustration: FIG. 21.--Piston with lubricated pin.] Among the parts of the piston which rapidly wear away because constant lubrication is difficult, is the connection with the piston-rod (Fig. 21). It is important that the bearing at the piston-pin be formed of two parts which can be adjusted to take up the wear. The pin itself should be of case-hardened steel. For large engines, some manufacturers have apparently abandoned the practice of locking the pin, by set-screws, in flanges cast in one piece with the piston. Indeed, the piston is often fractured by reason of the expansion of the pins thus held on two sides. It seems advisable to secure the pin by means of a single screw in one of the flanges, fitting it by pressure against the opposite boss. The use of wedges or of clamping-screws, introduced from without the piston to hold the pin, should be avoided. It may happen that the wedges will be loosened, will move out, and will grind the cylinder, causing injuries that cannot be detected before it is too late. The strength of the piston-pin should be so calculated that the pressure per square inch of projected surface does not exceed 1,500 to 2,850 pounds per square inch. It should be borne in mind that the initial pressure of the explosion is often equal to 400 to 425 pounds per square inch. Some manufacturers mount the pin as far to the back of the piston as possible, so as to bring it nearer the point of application of the motive force of the explosion. Other manufacturers, on the other hand, mount the pin toward the front of the piston. No great objection can be raised against either method. In the former case the position of the rings will limit that of the pin. The number of these rings ought not to be less than four or five, arranged at the rear of the piston. It is to be observed that makers of good engines use as many as 8 to 10 rings in the pistons of fair-sized motors. Piston-rings of gray pig-iron can be adjusted with the greatest nicety in such a manner that, by means of tongues fitting in their grooves, they are held from turning in the latter, whereby their openings are prevented from registering and allowing the passage of gas. As a general rule, a large number of rings may be considered a distinguishing feature of a well-built engine. In order to prevent a too rapid wear of the cylinder, several German manufacturers finish off the front of the piston with bronze or anti-friction metal in engines of more than 40 to 50 horse-power. It is to be observed, however, that this expedient is not applicable to motors the cylinders of which are comparatively cold; otherwise the bronze or anti-friction metal will deteriorate. =Arrangement of the Cylinder.=--The cylinder shell or liner, in which the piston travels, and the water-jacket should preferably be made in separate pieces and not cast of the same metal, in order to permit a free expansion (Figs. 22 and 23). If for want of care or of proper lubrication, which frequently occurs in gas-engines, the cylinder should be injured by grinding, it can be easily renewed, without the loss of all the connecting parts. [Illustration: FIG. 22.--Head, jacket and liner of cylinder, cast in one piece.] [Illustration: FIG. 23.--Cylinder with independent liner and head.] For the same reason, the cylinder and its casing should be independent of the frame. In many horizontal engines, the cylinders overhang the frame throughout the entire length, by reason of the joining of their front portions with the frames. Although such a construction is attended with no serious consequences in small engines, nevertheless in large engines it is exceedingly harmful. Indeed, in most modern single-acting engines, the pistons are directly connected with the crank-shaft by the piston-rod, without any intermediate connecting-rod or cross-head. The vertical reaction of the motive effort on the piston is, therefore, taken up entirely by the thrust of the cylinder, which is also vertical (Fig. 24). This thrust, acting against an unsupported part, may cause fractures; at any rate, it entails a rapid deterioration of the cylinder joint. [Illustration: FIG. 24.--Single-acting engines.] [Illustration: FIG. 25.--Engine with inclined bearings.] =The Frame.=--Gas-engines driven as they are, by explosions, giving rise to shocks and blows, should be built with frames, heavy, substantial, and broad-based, so as to rest solidly on the ground. This essential condition is often fulfilled at the cost of the engine's appearance; but appearance will be willingly sacrificed to meet one of the requirements of perfect operation. For engines of more than 8 to 10 horse-power, frames should be employed which can be secured to the masonry foundation without a separate pedestal or base. Some manufacturers, for the purpose of lightening the frame, attach but little importance to the foundation and to strength of construction, and employ the design illustrated in place of the crank-shaft bearing (Fig. 25); others, in order to facilitate the adjusting of the connecting-rod bearings, prefer the second form (Fig. 26). It is evident that, in the first case, a part of the effort produced by the explosion reacts on the upper portion of the connecting-rod bearing, on the cap of the crank-shaft bearing, and consequently on the fastening-bolts. In the second case, if the adjustment be not very carefully made, or if the rubbing surfaces are insufficient, the entire thrust due to the explosion will be received by the meeting parts of the two bushings, thus injuring them and causing a more rapid wear. In the construction of large engines, some manufacturers take the precaution of forming the connecting-rod bearings of four parts, adjustable to take up the wear, so that the effort is exerted against the parts disposed at right angles to each other. A form that seems rational is that shown in Fig. 27, in which the reaction of the thrust is taken up by the lower bearing, rigidly supported by the braced frame, in the direction opposite to that of the explosive effort. [Illustration: FIG. 26.--Engine with straight bearings.] [Illustration: FIG. 27.--Engine with correctly designed bearings.] The sum of the projecting surfaces of the two bearings should be so calculated that a maximum explosive pressure of 405 to 425 pounds per square inch will not subject the bearings to a pressure higher than 425 to 550 pounds per square inch. =Fly-Wheels.=--In gas-engines particularly, the fly-wheel should be secured to the crank-shaft with the utmost care. It should be mounted as near as possible to the bearings; otherwise the alinement of the shaft will be destroyed and its strength impaired. If the fly-wheel be fastened by means of a key or wedge having a projecting head, it is advisable to cover the end of the shaft by a movable sleeve. The fly-wheel should run absolutely true and straight even if the explosion be premature. In well-built engines the fly-wheels are lined up and shaped to the rim. The periphery is slightly rounded in order the better to guide the belt when applied to the wheel. [Illustration: FIG. 28.--Single fly-wheel engine with external bearing.] Furthermore, fly-wheels should be nicely balanced; those are to be preferred which have no counter-weights cast or fastened to the hub, the spokes, or the rim. The system of balancing the engine by means of two fly-wheels, mounted on opposite sides, is used chiefly for the purpose of equalizing the inertia effects. Special engines, employed for driving dynamos, and even industrial engines of high power, are preferably fitted with but a single fly-wheel, with an outer bearing, since they more readily counteract the cyclic irregularities or variations of speed occurring in a single revolution (Fig. 28). If in this case a pulley be provided, it should be mounted between the engine and the outer bearing. The following advantages may be cited in favor of the single fly-wheel, particularly in the case of dynamo-driving engines: 1. The single fly-wheel permits a more ready access to the parts to be examined. 2. It involves the employment of a third bearing, thus avoiding the overhang caused by two ordinary fly-wheels. 3. It avoids the torsional strain to which the two-wheel crank is subjected when starting, stopping, and changing the load, the peripheral resistance varying in one of the fly-wheels, while the other is subjected to a strain in the opposite direction on account of the inertia. 4. Two fly-wheels, keyed as they are to projecting ends of the shaft, will be so affected at the rims by the explosions that the belts will shake. The third bearing which characterizes the single-fly-wheel system, is but an independent support, resting solidly on the masonry bed of the engine. The bearing with its independent support is sufficiently rigid, and is not subjected to any stress from the crank at the moment of explosion, the reaction of the crank affecting only the frame bearings. With such fly-wheels, reputable firms guarantee a cyclic regularity which compares favorably with that of the best steam-engines. For a duty varying from a third of the load to the maximum load, these engines, when driving direct-current dynamos for directly supplying an electric-light circuit, will insure perfect steadiness of the light; and the effectually aperiodic measuring instruments will not indicate fluctuations greater than 2 to 3 per cent. of the tension or intensity of the current. The coefficient of the variations in the speed of a single revolution will thus be not far from 1/60. [Illustration: FIG. 29.--Curved spoke fly-wheel.] =Straight and Curved Spoke Fly-Wheels.=--The spokes of fly-wheels are either straight or curved. In assembling the motor parts it too often occurs that curved spoke fly-wheels are mounted with utter disregard of the direction in which they are to turn. It is important that curved spokes should be subjected to compression and not to traction. Hence the fly-wheels should be so mounted that the concave portions of the spokes travel in the direction of rotation, as shown in the accompanying diagram (Fig. 29). If a single fly-wheel be employed on an engine of the type in which the speed is governed by the "hit-and-miss" system, the fly-wheel should be extra heavy to counteract the irregularities of the motive impulses when the engine is not working at its full load, or in other words, when no explosion takes place at every cycle. [Illustration: FIG. 30.--Forged crank-shafts.] =The Crank-Shaft.=--The crank-shaft should be made of the best mild steel. Those shafts are to be preferred the cranks of which are not forged on (Fig. 30), but cut out of the mass of metal; furthermore, the brackets or supports should be planed and shaped so that they are square in cross-section. [Illustration: FIG. 31.--Correct design of crank-shaft.] Such a design involves fine workmanship and speaks well for the construction of the whole engine. Moreover, it enables the bearings to be brought nearer each other, reduces to a minimum that part of the crank-shaft which may be considered the weakest, and permits a rational and exact counterbalancing of the moving parts, such as the crank and the end of the connecting-rod. The best manufacturers have adopted the method of fastening to the cranks balancing weights secured to the brackets, especially for high-speed engines or for engines of high power. The projecting surface of the crank-pin should, as a rule, be calculated for a pressure of 1,400 pounds per square inch. [Illustration: FIG. 32.--Crank-shaft with balancing weight.] =Cams, Rollers, etc.=--The cams, rollers, thrust-bearings, as well as the piston-pin in particular, should be made of good steel, case-hardened to a depth of at least .08 of an inch. Their hardness and the degree of cementation may be tested by means of a file. This is the method followed by the best manufacturers. =Bearings.=--All the bearings and all guides should be adjustable to take up the wear. They are usually made of bronze or of the best anti-friction metal. =Steadiness.=--The steadiness of engines may be considered from two different standpoints. [Illustration: FIG. 33.--Inertia governor.] 1. _Variation of the Number of Revolutions at Different Loads._--This depends chiefly on the sensitiveness of the governor, which should be of the "inertia" or of the "ball" (or centrifugal) type. The first form is rarely employed, except in small engines up to 10 horse-power, and is applicable only to engines in which the "hit and miss" system is employed (Fig. 33). The second form is more widely used, and is applicable to engines having "hit-and-miss" or variable admission devices. In the first form, the governor simply displaces a very light member, whatever may be the size of the engine, for which reason the dimensions are very small. In the second form, on the other hand, the governor acts either on a conical sleeve or on some other regulating member offering resistance. Evidently, in order to overcome the reactions to which it is subjected, it must be as heavy and powerful as a steam-engine governor. Sufficient allowance is made in a good engine for variation in the number of revolutions between no load and full load, not greater than two per cent. if the admission be of the "hit-and-miss" type, and five per cent. if it be of the variable type. 2. _Cyclic Regularity._--This term means simply that the speed of the engine is constant in a single revolution. In practice this is never attained. Allowance is made in engines used for driving direct-current dynamos for a variation of about 1/60; while in industrial engines a variation of 1/25 is permissible. Cyclic variation depends only on the weight of the fly-wheel; whereas variation in the number of revolutions is determined chiefly by the governor. =Governors.=--Diagrams are here presented of the principal types of governors--the inertia governor, the ball or centrifugal governor controlling an admission-valve of the "hit-and-miss" type (Fig. 34), and the ball or centrifugal governor controlling a variable gas-admission valve (Fig. 35). In distinguishing between the operation of the two last-mentioned types, it may be stated that the former bears the same relation to the hit-and-miss gear as it does, for example, to the valve gear of a Corliss steam-engine. In other words, it is an apparatus that _indicates_ without _inducing_, admission or cut-off. The second type, on the other hand, operates by means of slides and the like, as in the Ridder type of engine, in which it controls the displacement of the cut-off or distribution slide-valve and is subjected to variable forces, depending on the pressure, lubrication, the condition of the stuffing-boxes, and the like. In gas as well as in steam engines, designs are to be commended which shield the delicate mechanism from strains and stresses that are likely to destroy its sensitiveness, as is the case in the automatic cut-off of the Corliss steam-engine. [Illustration: FIG. 34.--"Hit-and-miss" governor.] Governors should be provided with means to permit the manual variation of the speed while the engine is in operation. For small motors, one of the most widely used admission devices is that of the "hit-and-miss" type. As its name indicates, this admission arrangement allows a given quantity of gas to enter the cylinder for a number of consecutive intervals, until the engine is about to exceed its normal speed. Thereupon the governor cuts off the gas entirely. The result is that, in this system, the number of admissions is variable, but that each admitted charge is composed of a constant proportion of gas and air. The governors employed for the "hit-and-miss" type are either "inertia" or "centrifugal" governors. Inertia governors (Fig. 33) are less sensitive than those of the centrifugal type. They are generally applied only to industrial engines of small power, in which regularity of operation is a secondary consideration. Centrifugal governors employed for gas-engines with "hit-and-miss" regulation are, as a general rule, noteworthy for their small size, which is accounted for by the fact that, in most systems, merely a movable member is placed between the admission-controlling means and the valve-stem (Fig. 34). It follows that this method of operation relieves the governor of the necessity of overcoming the resistance of the weight of moving parts, more or less effectually lubricated, and subjected to the reaction of the parts which they control. In engines equipped with variable admission devices for the gas or the explosive mixture, the governor actuates a sleeve on which the admission-cam is fastened (Fig. 35). Or, the governor may displace a conical cam, the reaction of which, on contact with the lever, destroys the stability of the governor. These conditions justify the employment of powerful governors which, on account of the inertia of their parts, diminish the reactionary forces encountered. The centrifugal governor should be sufficiently effectual to prevent variations in the number of revolutions within the limits of 2 to 3 per cent. between no load and approximately full load. Under equivalent conditions, the inertia governor can hardly be relied upon for a coefficient of regularity greater than 4 to 5 per cent. [Illustration: FIG. 35.--Variable admission governor.] The manner of a governor's operation is necessarily dependent on the admission system adopted. And the admission system varies essentially with the size, the purpose of the engine, and the character of the fuel employed. [Illustration: FIG. 36.--Vertical engine.] [Illustration: FIG. 37.--Section through an engine of the vertical or "steam-hammer" type.] =Vertical Engines.=--For some years past there seems to have been a tendency in Europe to use horizontal instead of vertical engines, especially since engines of more than 10 or 15 horse-power have been extensively used for industrial purposes. The vertical type is used for 1 to 8 horse-power engines, with the cylinder in the lower part of the frame, and the shaft and its fly-wheel in the upper part (Fig. 36). The only merit to be attributed to this arrangement is a great saving of space. It is evident, however, that beyond a certain size and power, such engines are unstable. In America particularly, many manufacturers of high-power engines (50 to 100 horse-power or more) prefer the vertical or "steam-hammer" arrangement, which consists in placing the cylinder in the upper part, and the shaft in the lower part of the frame as close to the ground as possible (Figs. 37 and 38). The problem of saving space, as well as that of insuring stability, is thus solved, so that it is easily possible to run up the speed of the engine. There is also the advantage that the shaft of a dynamo can be directly coupled up with the crank-shaft of the engine, thus dispensing with a belt, which, at the least, absorbs 4 to 6 per cent. of the total power. It should, nevertheless, be borne in mind that the direct coupling of electric generators to engine-shafts implies the use of extremely large and, therefore, of extremely costly dynamos. Furthermore, by reason of this arrangement, groups of electro-generators can be disposed in a comparatively small amount of space. Some English manufacturers are also beginning to adopt the "steam-hammer" type of engine for high powers, the result being a marked saving in material and lowering of the cost of installation. [Illustration: FIG. 38.--Side and end elevations of a vertical or "steam-hammer" engine.] =Power of the Engine.=--The first thing to be considered is that the power of a gas-engine is always given in "effective" horse-power, and that the power of a steam-engine is always given in "indicated" horse-power in contracts of sale. In England and in the United States, the expression "nominal" horse-power is still employed. It may be advisable to define these various terms exactly, since unscrupulous dealers, to the buyer's loss, have done much to confuse them. "Indicated" horse-power is a designation applied to the theoretical power produced by the action of the motive agent on the piston. The work performed is measured on an indicator card, by means of which the average pressure to be considered in the computation of the theoretical power is ascertained. The "effective" or brake horse-power is equal to the "indicated" horse-power, less the energy absorbed by passive resistance, friction of the moving parts, etc. The "effective" work is an experimental term applied to the power actually developed at the shaft. This work is of interest solely to the engine user. In a well-built motor, in which the passive resistance by reason of the correct adjustment and simplicity of the parts, is reduced to a minimum, the "effective" horse-power is about 80 to 87 per cent. of the "indicated" horse-power, when the engine runs under full load. This reduced output is usually called the "mechanical efficiency" of the engine. "Nominal" horse-power is an arbitrary term in the sense in which it is used in England and America, where it is quite common. The manufacturers themselves do not seem to agree on its absolute value. A "nominal" horse-power, however, is equal to anything from 3 to 4 "effective" horse-power. The uncertainty which ensues from the use of the term should lead to its abandonment. In installing a motor, the determination of its horse-power is a matter of grave importance, which should not be considered as if the motor were a steam-engine or an engine of some other type. It must not be forgotten that, especially at full load, explosion-engines are most efficient, and that, under these conditions, it will generally be advisable to subordinate the utility of having a reserve power to the economy which follows from the employment of a motor running at a load close to its maximum capacity. On the other hand, the gas-engine user is unwilling to believe that the stipulated horse-power of the motor which is sold to him is the greatest that it is capable of developing under industrial conditions. Business competition has led some firms to sell their engines to meet these conditions. It is probably not stretching the truth too far to declare that 80 per cent. of the engines sold with no exact contract specifications are incapable of maintaining for more than a half hour the power which is attributed to them, and which the buyer expects. It follows that the power at which the engine is sold should be both industrially realized and maintained, if need be, for an entire day, without the engine's showing the slightest perturbation, or faltering in its silent and regular operation. To attain this end, it is essential that the energy developed by the engine in normal or constant operation should not exceed 90 to 95 per cent. of the maximum power which it is able to yield, and which may be termed its "utmost power". As a general rule, especially for installations in which the power fluctuates from the lowest possible to double this, as much attention must be paid to the consumption at half load as at full load; and preference should be given to the engine which, other things being equal, will operate most economically at its lowest load. In this case the consumption per effective horse-power is appreciably higher. Generally, this consumption is greater by 20 to 30 per cent. than that at full load. This is particularly true of the single-acting engines so widely used for horse-powers less than 100 to 150. In some double or triple-acting engines, according to certain writers, the diminution in the consumption will hardly be proportional to the diminution of the power, or at any rate, the difference between the consumption per B.H.P. at full load and at reduced load will be less than in other engines. It should be observed, however, that this statement is apparently not borne out by experiments which the author has had occasion to make. To a slight degree, this economy is obtained at the cost of simplicity, and consequently, at the cost of the engine. At all events, the engines have the merit of great cyclic regularity, rendering them serviceable for driving electric-light dynamos; but this regularity can also be attained by the use of the extra heavy fly-wheels which English firms, in particular, have introduced. =Automatic Starting.=--When the gas-engine was first introduced, starting was effected simply by manually turning the fly-wheel until steady running was assured. This procedure, altogether too crude in its way, is attended with some danger. In a few countries it is prohibited by laws regulating the employment of industrial machinery. If the engine be of rather large size one, moreover, which operates at high pressure--such a method of starting is very troublesome. For these reasons, among others, manufacturers have devised automatic means of setting a gas-engine in motion. Of such automatic devices, the first that shall be mentioned is a combination of pipes, provided with cocks, by the manipulation of which, a certain amount of gas, drawn from the supply pipe, is introduced into the engine-cylinder. The piston is first placed in a suitable position, and behind it a mixture is formed which is ignited by a naked flame situated near a convenient orifice. When the explosion takes place the ignition-orifice is automatically closed, and the piston is given its motive impulse. The engine thus started continues to run in accordance with the regular recurrence of the cycles. In this system, starting is effected by the explosion of a mixture, without previous compression. Some designers have devised a system of hand-pumps which compress in the cylinder a mixture of air and gas, ignited at the proper time by allowing it to come into contact with the igniter, through the manipulation of cocks (Fig. 39). These two methods are not absolutely effective. They require a certain deftness which can be acquired only after some practice. Furthermore, they are objectionable because the starting is effected too violently, and because the instantaneous explosion subjects the stationary piston, crank, and fly-wheel to a shock so sudden that they may be severely strained and may even break. Moreover, the slightest leakage in one of the valves or checks may cause the entire system to fail, and, particularly in the case of the pump, may induce a back explosion exceedingly dangerous to the man in charge of the engine. These systems are now almost generally supplanted by the compressed-air system, which is simpler, less dangerous, and more certain in its effect. The elements comprising the system in question include essentially a reservoir of thick sheet iron, capable of resisting a pressure of 180 to 225 pounds and sufficient in capacity to start an engine several times. This reservoir is connected with the engine by piping, which is disposed in one of two ways, depending upon whether the reservoir is charged by the engine itself operatively connected with the compressor, or by an independent compressor, mechanically operated. [Illustration: FIG. 39.--Tangye starter.] In the first case, the pipe is provided with a stop-cock, mounted adjacent to the cylinder, and with a check-valve. When the engine is started and the gas cut off, the air is drawn in at each cycle and driven back into the reservoir during the period of compression. When the engine, running under these conditions by reason of the inertia of the fly-wheel, begins to slow down, the check-valve is closed and the gas-admission valve opened, so as to produce several explosions and to impart a certain speed to the engine in order to continue the charging of the reservoir with compressed air. This done, the valve on the reservoir itself is tightly closed, as well as the check-valve, so as to avoid any leakage likely to cause a fall in the reservoir's pressure. In the second case, which applies particularly to engines of more than 50 horse-power, the charging pipe connected with the reservoir is necessarily independent of the pipe by means of which the motor is started. The reservoir having been filled and the decompression cam thrown into gear, starting is accomplished: 1. By placing the piston in starting position, which corresponds with a crank inclination of 10 to 20 degrees in the direction of the piston's movement, from the rear dead center, immediately after the period of compression; 2. By opening the reservoir-valve; 3. By allowing the compressed air to enter the cylinder rapidly, through the quick manipulation of the stop-cock, which is closed again when the impulse is given and reopened at the corresponding period of the following cycle, this operation being repeated several times in order to impart sufficient speed to the motor; 4. By opening the gas-valve and finally closing the two valves of the compressed-air pipe. The pipes and compressed-air reservoirs should be perfectly tight. The reservoirs should have a capacity in inverse ratio to the pressure under which they are placed, _i.e._, they increase in size as the pressure decreases. If, for example, the reservoirs should be operated normally at a pressure of 105 to 120 pounds per square inch, their capacity should be at least five or six times the volume of the engine-cylinder. If these reservoirs are charged by the engine itself, the pressure will always be less by 15 to 20 per cent. than that of the compression. CHAPTER III THE INSTALLATION OF AN ENGINE In the preceding chapter the various structural details of an engine have been summarized and those arrangements indicated which, from a general standpoint, seem most commendable. No particular system has been described in order that this manual might be kept within proper limits. Moreover, the best-known writers, such as Hutton, Hiscox, Parsell and Weed, in America; Aimé Witz, in France; Dugald Clerk, Frederick Grover, and the late Bryan Donkin, in England; Güldner, Schottler, Thering, in Germany, have published very full descriptive works on the various types of engines. We shall now consider the various methods which seem preferable in installing an engine. The directions to be given, the author believes, have not been hitherto published in any work, and are here formulated, after an experience of fifteen years, acquired in testing over 400 engines of all kinds, and in studying the methods of the leading gas-engine-building firms in the chief industrial centers of Europe and America. =Location.=--The engine should be preferably located in a well-lighted place, accessible for inspection and maintenance, and should be kept entirely free from dust. As a general rule, the engine space should be enclosed. An engine should not be located in a cellar, on a damp floor, or in badly illuminated and ventilated places. =Gas-Pipes.=--The pipes by which fuel is conducted to engines, driven by street-gas, and the gas-bags, etc., are rarely altogether free from leakage. For this reason, the engine-room should be as well ventilated as possible in the interest of safety. Long lines of pipe between the meter and the engine should be avoided, for the sake of economy, since the chances for leakage increase with the length of the pipe. It seldom happens that the leakage of a pipe 30 to 50 feet long, supplying a 30 horse-power engine, is much less than 90 cubic feet per hour. The beneficial effect of short supply pipes between meter and engine on the running of the engine is another point to be kept in mind. An engine should be supplied with gas as cool as possible, which condition is seldom realized if long pipe lines be employed, extending through workshops, the temperature of which is usually higher than that of underground piping. On the other hand, pipes should not be exposed to the freezing temperature of winter, since the frost formed within the pipe, and particularly the crystalline deposition of naphthaline, reduces the cross section and sometimes clogs the passage. Often it happens that water condenses in the pipes; consequently, the piping should be disposed so as to obviate inclines, in which the water can collect in pockets. An accumulation of water is usually manifested by fluctuations in the flame of the burner. In places where water can collect, a drain-cock should be inserted. In places exposed to frost, a cock or a plug should be provided, so that a liquid can be introduced to dissolve the naphthaline. To insure the perfect operation of the engine, as well as to avoid fluctuations in nearby lights, pipes having a large diameter should preferably be employed. The cross-section should not be less than that of the discharge-pipe of the meter, selected in accordance with the prescriptions of the following table: GAS-METERS. Table Headings-- Column A: Capacity. Column B: Normal hourly flow. Column C: Height. Column D: Width. Column E: Depth. Column F: Diameter of pipe. Column G: Power of engine to be fed. _________________________________________________________________ | | | | | Dimension in inches. | | |_______________________________________| | | | | | | A. | B. | C. | D. | E. | F. | G. ________|_________|_________|__________|__________|_______|______ | | | | | | burners | cu. ft. | | | | | h.-p. 3 | 14.726 | 13 | 11 | 9-13/16 | 0.590 | 1/2 5 | 24.710 | 18 | 13-3/4 | 10-5/8 | 0.787 | 3/4 10 | 49.420 | 21-1/4 | 18-1/2 | 12-9/16 | 0.984 | 1-2 20 | 98.840 | 23-3/16 | 19-11/16 | 15-5/16 | 1.181 | 3-4 30 | 148.260 | 25-5/8 | 21-11/16 | 18-3/16 | 1.456 | 5-6 50 | 247.100 | 29-1/2 | 24-5/16 | 20-7/16 | 1.592 | 7-10 60 | 296.520 | 30-5/16 | 25-5/8 | 25-5/8 | 1.671 | 11-14 80 | 395.360 | 33-5/16 | 30-5/16 | 27-1/8 | 1.968 | 15-19 100 | 494.200 | 35 | 33-7/16 | 29-15/16 | 1.968 | 20-25 150 | 741.300 | 40-3/16 | 40-3/16 | 33-13/16 | | 30-40 ________|_________|_________|__________|__________|_______|______ The records made are exact only when the meters (Fig. 40) are installed and operated under normal conditions. Two chief causes tend to falsify the measurements in wet meters: (1) evaporation of the water, (2) the failure to have the meter level. Evaporation occurs incessantly, owing to the flowing of the gas through the apparatus, and increases with a rise in the temperature of the atmosphere surrounding the meter. Consequently this temperature must be kept down, for which reason the meter should be placed as near the ground as possible. The evaporation also increases with the volume of gas delivered. Hence the meter should not supply more than the volume for which it was intended. In order to facilitate the return of the water of condensation to the meter and to prevent its accumulation, the pipes should be inclined as far as possible toward the meter. The lowering of the water-level in the meter benefits the consumer at the expense of the gas company. [Illustration: FIG. 40.--Wet gas-meter.] Inclination from the horizontal has an effect that varies with the direction of inclination. If the meter be inclined forward, or from left to right, the water can flow out by the lateral opening at the level, and incorrect measurements are made to the consumer's cost. During winter, the meter should be protected from cold. The simplest way to accomplish this, is to wrap substances around the meter which are poor conductors of heat, such as straw, hay, rags, cotton, and the like. Freezing of the water can also be prevented by the addition of alcohol in the proportion of 2 pints per burner. The water is thus enabled to withstand a temperature of about 5 degrees F. below zero. Instead of alcohol, glycerine in the same proportions can be employed, care being taken that the glycerine is neutral, in order that the meter may not be attacked by the acids which the liquid sometimes contains. [Illustration: FIG. 41.--Dry gas-meter.] =Dry Meters.=--Dry meters are employed chiefly in cold climates, where wet meters could be protected only with difficulty and where the water is likely to freeze. In the United States the dry meter is the type most widely employed. In Sweden and in Holland it is also generally introduced (Fig. 41). In the matter of accuracy of measurement there is little, if any, difference between wet and dry meters. The dry meter has the merit of measuring correctly regardless of the fluctuations in the water level. On the other hand, it is open to the objection of absorbing somewhat more pressure than the wet meter, after having been in operation for a certain length of time. This is an objection of no great weight; for there is always enough pressure in the mains and pipes to operate a meter. [Illustration: FIG. 42.--Section through a dry gas-meter.] In many cases, where the employment of non-freezing liquids is necessary, the dry meter may be used to advantage, since all such liquids have more or less corroding effect on sheet lead and even tin, depending upon the composition of the gas. [Illustration: FIG. 43.--Section through a dry gas-meter.] The dry meter comprises two bellows, operating in a casing divided into two compartments by a central partition. The gas is distributed on one or the other side of the bellows, by slides _B_. The slides _B_ are provided with cranks _E_, controlled by levers _M_, actuated by transmission shafts _O_, driven by the bellows. The meter is adjusted by a screw which changes the throw of the cranks _E_ and consequently affects the bellows. The movement of the crank-shaft _D_ is transmitted to the indicating apparatus. In order to obviate any leakage, this shaft passes through a stuffing-box, _G_. The diagrams (Figs. 42-43) show the construction of a dry meter, the arrows indicating the course taken by the gas. [Illustration: FIG. 44.--Rubber bag to prevent fluctuations of the ignition flame.] [Illustration: FIG. 45.--Rubber bags on gas-pipes.] Care should be taken to provide the gas-pipe with a drain-cock, at a point near the engine. By means of this cock, any air in the pipe can be allowed to escape before starting; otherwise the engine can be set in motion only with difficulty. If the engine be provided with an incandescent tube, the gas-supply pipe of the igniter should be fitted with a small rubber pouch or bag, in order to obviate fluctuations in the burner flame, caused by variations in the pressure (Fig. 44). As a general rule, the supply-pipe should be connected with the main pipe on the forward side of the bags and gas-governors. The main pipe and all other piping near the engine should extend underground, so that free access to the motor from all sides can be obtained, without possibility of injury. =Anti-pulsators, Bags, Pressure-Regulators.=--The most commonly employed means of preventing fluctuation of nearby lights, due to the sharp strokes of the engine, consists in providing the gas-supply pipe with rubber bags (Fig. 45), which form reservoirs for the gas and, by reason of their elasticity, counteract the effect produced by the suction of the engine. Nevertheless, in order to insure a supply of gas at a constant pressure, which is necessary for the perfect operation of the engine, there are generally used, in addition to the bags, devices called gas-governors, or anti-pulsators (Fig. 46). Although these devices are constructed in different ways, the underlying principle is the same in all. They comprise a metallic casing, containing a flexible diaphragm of rubber or of some fabric impermeable to gas. Suction of the engine creates a vacuum in the casing. The diaphragm bends, thereby actuating a valve, which cuts off the gas supply. During the three following periods (compression, explosion, and exhaust) the gas, by reason of its pressure on the diaphragm, opens the valve and fills the casing, ready for the next suction stroke. [Illustration: FIG. 46.--An anti-pulsator.] Other devices, which are never sold with the engine, but are rendered necessary by reason of the conditions imposed by the gas supply are sold under the name "pressure-regulators" (Fig. 47). They consist of a bell, floating in a reservoir containing water and glycerine (or mercury), and likewise actuate a valve which partially controls the flow of gas. This valve being balanced, its mechanical action is the more certain. Such devices are very effective in maintaining the steadiness of lights. On the other hand, they are often an obstacle to the operation of the engine because they reduce the flow and pressure of the gas too much. In order to obviate this difficulty, a pressure-regulator should be chosen with discrimination, and of sufficiently large size to insure the maintenance of an adequate supply of gas to the engine. Frequent examinations should be made to ascertain if the bell of the regulator is immersed in the liquid. In the case of anti-pulsators, care should be taken that they are not spattered with oil, which has a disastrous effect on rubber. Anti-pulsators are generally mounted about 4 inches from a wall, in order that the diaphragm may be actuated by hand, if need be. [Illustration: FIG. 47.--A pressure-regulator.] =Precautions.=--In order not to strain the rubber of the bags or of the anti-pulsators, it is advisable to place a stop-cock in advance of these devices so that they can not be filled while the motor is at rest. The capacity of the rubber bags that can be bought in the market being limited, it is necessary to place one, two, or three extra bags in series (Figs. 48 and 49), for large pipes; but it should be borne in mind that the total section of the branch pipes should be at least equal to that of the main pipe. It is also advisable to extend the tube completely through the bag as shown in Figs. 48 and 49. [Illustration: FIGS. 48-49.--Arrangement of rubber bags.] If there be two branch pipes the minimum diameter which meets this requirement is ascertained as follows: Draw to any scale a semicircle having a diameter equal or proportional to that of the main pipe (Fig. 50). The sides of the isosceles triangle inscribed within this semicircle give the minimum diameter of each of the branch pipes. Sometimes engines are provided with a cock having an arrangement by means of which the gas feed is permanently regulated, according to the quality and pressure of the gas and according to the load at which the engine is to run. This renders it possible to open the cock always to the same point (Fig. 51). [Illustration: FIG. 50.] [Illustration: FIG. 51.] =Air Suction.=--In a special chapter the precautions to be taken to counteract the influence of the suction of the engine in causing vibration will be treated. The manner in which the suction of air is effected necessarily has as marked an influence on the operation of the engine as the supply of gas, since air and gas constitute the explosive mixture. Resistance to the suction of air should be carefully avoided, for which reason the length of the pipe should be reduced to a minimum, and its cross-section kept at least equal to that of the air inlet of the engine. Since the quality of street-gas varies with each city, the proper proportions of gas and air are not constant. In order that these proportions may be regulated, it is a matter of some importance to fit some suitable device on the pipe. Good engines are provided with a plug or flap valve. Generally the air-pipe terminates either in the hollowed portion of the frame, or in an independent pot, or air chest. The first arrangement is not to be recommended for engines over 20 to 25 horse-power. Accidents may result, such as the breaking of the frame by reason of back firing, of which more will be said later. If an independent chest be employed, its closeness to the ground renders it possible for dust easily to pass through the air-holes in the walls at the moment of suction, and even to enter the cylinder, where its presence is particularly harmful, leading, as it does, to the rapid wear of the rubbing surfaces. This evil can be largely remedied by filling the air-chest with cocoa fiber or even wood fiber, provided the latter does not become packed down so as to prevent the air from passing freely. Such fibers act as air-filters. Regular cleaning or renewal of the fiber protects the cylinder from wear. In a general way, care should be taken, before fitting both the gas and air pipes, to tap the pipes, elbows, and joints lightly with a hammer on the outside in order to loosen whatever rust or sand may cling to the interior; otherwise this foreign matter may enter the cylinder and cause perturbations in the operation of the engine. Under all circumstances, care should be taken not to place the end of the air-pipe under the floor or in an enclosed space, because leakage may occur, due to the bad seating of the air-valve, thereby producing a mixture which may explode if the flame leaps back, as we shall see in the discussion of suction by pipes terminating in the hollow of the frame. On the other hand, sand or sawdust should not be sprinkled on the floor. =Exhaust.=--For the exhaust, cast-iron or drawn pipes as short as possible should be used. Not only the power of the engine, but also its economic consumption, can be markedly affected by the employment of long and bent pipes. Resistance to the exhaust of the products of combustion not only causes an injurious counter-pressure, but also prevents the clearing of the cylinder of burnt gases, which contaminate the aspired mixture and rob it of much of its explosiveness. The necessity of evacuating the cylinder as completely as possible is, nevertheless, not always reconcilable with local surroundings. To a certain extent, the objections to long exhaust-pipes are overcome by rigorously avoiding the use of elbows. Gradual curves are preferable. In the case of very long pipes it is advisable to increase their diameter every 16 feet from the exhaust. The exhaust-chest should be placed as near as possible to the engine; it should never be buried; for the joints of the inlet and outlet pipes of the exhaust-chest should be easily accessible, so that they may be renewed when necessary. The author recommends the placing of the exhaust-chest in a masonry pit, which can be closed with a sheet-metal cover. For engines of 20 horse-power and upward, these joints should be entirely of asbestos. Pipes screwed directly into the casting are liable to rust. Exposed as they are to the steam or water of the exhaust, they cannot be detached. [Illustration: FIG. 52.--Method of mounting pipes.] The water, which results from the combination of the hydrogen of the gas with the oxygen of the air, is deposited in most cases at the bottom of the exhaust-chest. It is advisable to fit a plug or iron cock in the base of the chest. Alkaline or acid water will always corrode a bronze cock. In order that the pipes may not also be attacked, they are not disposed horizontally, but are given a slight incline toward the point where the water is drained off. If pipes of some length be employed, they should be able to expand freely without straining the joints, as shown in the accompanying diagram (Fig. 52), in which the exhaust-chest rests on iron rollers which permit a slight displacement. For the sake of safety, at least that portion of the piping which is near the engine should be located at a proper distance from woodwork and other combustible material. By no means should the exhaust discharge into a sewer or chimney, even though the sewer or chimney be not in use; for the unburnt gases may be trapped, and dangerous explosions may ensue at the moment of discharge. The joints or threaded sleeves employed in assembling the exhaust-pipe should be tested for tightness. The combined action of the moisture and heat causes the metal to rust and to deteriorate very rapidly at leaky spots. When several engines are installed near one another, each should be provided with a special exhaust-pipe; otherwise it may happen, when the engines are all running at once, that the products of combustion discharged by the one may cause a back pressure detrimental to the exhaust of the next. It is possible to employ a pipe common to all the exhausts if the pipe starts from a point beyond the exhaust-chests, in which case Y-joints and not T-joints are to be used. The manner of securing the pipes to walls by means of detachable hangers, lined with asbestos, is shown in a general way in the accompanying Fig. 53. The object of this arrangement is to render detachment easy and to prevent the transmission of shocks to the masonry. The precautions to be taken for muffling the noise of the exhaust will be discussed later. The end of the exhaust-pipe should be slightly curved down in order to prevent the entrance of rain. Exhaust-pipes are subjected to considerable vibration, due to the sudden discharge of the gases. To protect the joints, the pipes should be rigidly fastened in place. [Illustration: FIG. 53.--Method of securing pipes to walls.] =Legal Authorization.=--In most countries gas-engines may be installed only in accordance with the provision of general or local laws, which impose certain conditions. These laws vary with different localities, for which reason they are not discussed here. CHAPTER IV FOUNDATION AND EXHAUST The reader will remember from what has already been said that a gas-engine is a motor which, more than any other, is subjected to forces, suddenly and repeatedly exerted, producing violent reactions on the foundation. It follows that the foundation must be made particularly resistant by properly determining its shape and size and by carefully selecting the material of which it is to be built. =The Foundation Materials.=--Well-hardened brick should be used. The top course of bricks should be laid on edge. It is advisable to increase the stability of the foundation by longitudinally elongating it toward the base, as shown in the accompanying diagram (Fig. 54). As a binding material, only mortar composed of coarse sand or river sand and of good cement, should be used. Instead of coarse sand, crushed slag, well-screened, may be employed. The mortar should consist of 2/3 slag and 1/3 cement. Oil should not in any way come into contact with the mortar; it may percolate through the cement and alter its resistant qualities. As in the construction of all foundations, care should be taken to excavate down to good soil and to line the bottom with concrete, in order to form a single mass of artificial stone. A day or two should be allowed for the masonry to dry out, before filling in around it. When the engine is installed on the ground floor above a vaulted cellar, the foundation should not rest directly on the vault below or on the joists, but should be built upon the very floor of the cellar, so that it passes through the planking of the ground floor without contact. [Illustration: FIG. 54.--Method of building the foundation.] When the engine is to be installed on a staging, the method of securing it in place illustrated in Fig. 55 should be adopted. Although a foundation, built in the manner described, will fulfill the usual conditions of an industrial installation, it will be inadequate for special cases in which trepidation is to be expected. Such is the case when engines are to be installed in places where, owing to the absence of factories, it is necessary to avoid all nuisance, such as noise, trepidations, odors, and the like. [Illustration: FIG. 55.--Elevated foundation.] =Vibration.=--In order to prevent the transmission of vibration, the foundation should be carefully insulated from all neighboring walls. For this purpose various insulating substances called "anti-vibratory" are to be recommended. Among these may be mentioned horsehair, felt packing, cork, and the like. The efficacy of these substances depends much on the manner in which they are applied. It is always advisable to interpose a layer of one of these substances, from one to four inches thick, between the foundation and the surrounding soil, the thickness varying with the nature of the material used and the effect to be obtained. Between the bed of concrete, mentioned previously, and the foundation-masonry and between the foundation and the engine-frame, a layer of insulating material may well be placed. Preference is to be given to substances not likely to rot or at least not likely to lose their insulating property, when acted upon by heat, moisture or pressure. Here it may not be amiss to warn against the utilization of cork for the bottom of the foundation; for water may cause the cork to swell and to dislocate the foundation or destroy its level. The employment of the various substances mentioned does not entail any great expense when the foundations are not large and the engines are light. But the cost becomes considerable when insulating material is to be employed for the foundation of a 30 to 50 horse-power engine and upwards. For an engine of such size the author recommends an arrangement as simple as it is efficient, which consists in placing the foundation of the engine in a veritable masonry basin, the bottom of which is a bed of concrete of suitable thickness. The foundation is so placed that the lateral surfaces are absolutely independent of the supporting-walls of the basin thus formed. Care should be taken to cover the bottom with a layer of dry sand, rammed down well, varying in thickness with each case. This layer of sand constitutes the anti-vibratory material and confines the trepidations of the engine to the foundation. As a result of this arrangement, it should be observed that, being unsupported laterally, the foundation should be all the more resistant, for which reason the base-area and weight should be increased by 30 to 40 per cent. The expense entailed will be largely offset by saving the cost of special anti-vibratory substances. In places liable to be flooded by water, the basin should be cemented or asphalted. When the engine is of some size and is intended for the driving of one or more dynamos which may themselves give rise to vibrations, the dynamos are secured directly to the foundation of the engine, which is extended for that purpose, so that both machines are carried solidly on a single base. The foregoing outline should not lead the proprietor of a plant to dispense with the services of experts, whose long experience has brought home to them the difficulties to be overcome in special cases. It should here be stated, as a general rule, that the bricks should be thoroughly moistened before they are laid in order that they may grip the mortar. After having been placed on the foundation and roughly trimmed with respect to the transmission devices, the engine is carefully leveled by means of hardwood wedges driven under the base. This done, the bolts are sealed by very gradually pouring a cement wash into the holes, and allowing it to set. When the holes are completely filled and the bolts securely fastened in place, a shallow rim, or edge of clay, or sand is run around the cast base, so as to form a small box or trough, in which cement is also poured for the purpose of firmly binding the engine frame and foundation together. When, as in the case of electric-light engines, single extra-heavy fly-wheels are employed, provided with bearings held in independent cast supports, the following rule should be observed to prevent the overheating due to unlevelness, which usually occurs at the bushings of these bearings: That part of the foundation which is to receive such a support should rest directly on the concrete bed and should be rigidly connected at the bottom with the main foundation. When the foundation is completely blocked up, the fly-wheel bearing with its support is hung to the crank-shaft; and not until this is effected is the masonry at the base of the support completed and rigidly fixed in its proper position. For very large engines, the foundation-bolts should be particularly well sealed into the foundation. In order to attain this end the bricks are laid around the bolt-holes, alternately projected and retracted as shown in Fig. 54. Broken stone is then rammed down around the fixed bolt; in the interstices cement wash is poured. =Air Vibration, etc.=--Vibration due chiefly to the transmission of noises and the displacement of air by the piston should not be confused with the trepidations previously mentioned. The noise of an engine is caused by two distinct phenomena. The one is due to the transmitting properties of the entire solid mass constituting the frame, the foundation, and the soil. The other is due to vibrations transmitted to the air. In both cases, in order to reduce the noise to a minimum, the moving parts should be kept nicely adjusted, and above all, shocks avoided, the more harmful of which are caused by the play between the joint at the foot of the connecting-rod and the piston-pin, and between the head of the connecting-rod and the crank-shaft. Although smooth running of the engine may be assured, there is always an inherent drawback in the rapid reciprocating movement of the piston. In large, single-acting gas-engines, a considerable displacement of air is thus produced. In the case of a forty horse-power engine having a cylinder diameter and piston-stroke respectively of 13-3/4 inches and 21-3/5 inches, it is evident that at each stroke the piston will displace about 2 cubic feet of air, the effect of which will be doubled when it is considered that on the forward stroke back pressure is created and on the return stroke suction is produced. The air motion caused by the engine is the more readily felt as the engine-room is smaller. If the room, for example, be 9 feet by 15 feet by 8 feet, the volume will be 1,080 cubic feet. From this it follows that the 2 cubic feet of air in the case supposed will be alternately displaced six times each second, which means the displacement of 12 cubic feet at short intervals with an average speed of 550 feet per minute. Such vibrations transmitted to halls or neighboring rooms are due entirely to the displacement of the air. In installations where the air-intake of the engine is located in the engine-room, a certain compensation is secured, at the period of suction, between the quantity of air expelled on the forward stroke of the piston and the quantity of air drawn into the cylinder. From this it follows that the vibration caused by the movement of the air is felt less and occurs but once for two revolutions of the engine. This phenomenon is very manifest in narrow rooms in which the engine happens to be installed near glass windows. By reason of the elasticity of the glass, the windows acquire a vibratory movement corresponding in period with half the number of revolutions of the engine. It follows from the preceding that, in order to do away with the air vibration occasioned by the piston in drawing in and forcing out air in an enclosed space, openings should be provided for the entrance of large quantities of air, or a sufficient supply of air should be forced in by means of a fan. The author ends this section with the advice that all pipes in general and the exhaust-pipe in particular be insulated from the foundation and from the walls through which they pass as well as from the ground, as metal pipes are good conductors of sound and liable to carry to some distance from the engine the sounds of the moving parts. =Exhaust Noises.=--Among the most difficult noises to muffle is that of the exhaust. Indeed, it is the exhaust above all that betrays the gas-engine by its discharge to the exterior through the exhaust-pipe. The most commonly employed means for rendering the exhaust less perceptible consists in extending the pipe upward as far as possible, even to the height of the roof. This is an easy way out of the difficulty; but it has a bad effect on the operation of the engine. It reduces the power generated and increases the consumption, as will be explained in a special paragraph. Expansion-boxes, more commonly called exhaust-mufflers, considerably deaden the noise of explosion by the use of two or three successive receptacles. But this remedy is attended with the same faults that mark the use of extremely long pipes. The best plan is to mount a single exhaust-muffler near the discharge of the engine in the engine-room itself, where it will serve at least the purpose of localizing the sound. [Illustration: FIG. 56.--Exhaust-muffler.] The employment of pipes of sufficiently large cross-section to constitute expansion-boxes in themselves will also muffle the exhaust. A more complete solution of the problem is obtained by causing the exhaust-pipe, after leaving the muffler, to discharge into a masonry trough having a volume equal to twelve times that of the engine-cylinder (Fig. 56). This trough should be divided into two parts, separated by a horizontal iron grating. Into the lower part, which is empty, the exhaust-pipe discharges; in the upper part, paving-blocks or hard stones not likely to crumble with the heat, are placed. Between this layer of stones and the cover it is advisable to leave a space equal to the first. Here the gases may expand after having been divided into many parts in passing through the spaces left between adjacent stones. The trough should not be closed by a rigid cover; for, although efficient muffling may be attained, certain disadvantages are nevertheless encountered. It may happen that in a badly regulated engine, unburnt gases may be discharged into this trough, forming an explosive mixture which will be ignited by the next explosion, causing considerable damage. Still, the explosion will be less dangerous than noisy. It may be mentioned in passing that this disadvantage occurs rarely. A second arrangement consists in superposing the end of the exhaust-pipe upon a casing of suitable size, which casing is partitioned off by several perforated baffle-plates. This casing is preferably made of wood, lined with metal, so that it will not be resonant. The size of the casing, the number of partitions and their perforations, and the manner of disposing the partitions have much to do with the result to be obtained. Here again the experience of the expert is of use. Various other systems are employed, depending upon the particular circumstances of each case. Among these systems may be mentioned those in which the pipe is forked at its end to form either a yoke (Fig. 57) or a double curve, each branch of which terminates in a muffler (Fig. 58). [Illustration: FIG. 57.] [Illustration: FIG. 58.--Two types of exhaust-mufflers.] It should be observed that, under ordinary conditions, noises heard as hissing sounds are often due to the presence of projections, or to distortion of the pipes near the discharge opening. Consequently, in connecting the pipes, care should be taken that the joints or seams have no interior projections. Occasionally, water may be injected into the exhaust-muffler in order to condense the vapors of the exhaust, the result being a deadening of the noises; but in order to be truly efficient this method should be employed with discretion, for which reason the advice of an expert is of value. CHAPTER V WATER CIRCULATION Circulation of water in explosion-engines is one of the essentials of their perfect operation. Two special cases are encountered. In the one the jacket of the engine is supplied with running water; in the other, reservoirs are employed, the circulation being effected simply by the difference in specific gravity in a thermo-siphon apparatus. Coolers are also used. =Running Water.=--A water-jacket fed from a constant source of running water, such as the water mains of a town, is certainly productive of the best results, the supply, moreover, being easily regulated; but the system is not widely used because the water runs away and is entirely lost. If running water be employed, the outlet of the jacket is so disposed that the water gushes out immediately on leaving the cylinder, and that the flow is visible and accessible, in order that the temperature may be tested by the hand. Apart from the relatively great cost of water in towns, the use of running water is objectionable on account of its chemical composition. Though it may be clear and limpid, it frequently contains lime salts, carbonates, sulphates, and silicates which are precipitated by reason of the sudden change of temperature to which the water is subjected as it comes into contact with the walls of the cylinder. That part of the water-jacket surrounding the head or explosion-chamber, where the temperature is necessarily the highest, becomes literally covered with calcareous incrustations, which are the more harmful because they are bad conductors of heat and because they reduce and even obstruct the passage exactly at the point where the water must circulate most freely to do any good. If the circulating water be pumped into the jacket, it is preferable, wherever possible, to use cistern water, which is not likely to contain lime salts in suspension. If river water be used, it should be free from the objections already mentioned, which are all the more grave if the water be muddy, as sometimes happens. The water-jacket can be easily freed from all non-adhering deposits by flushing it periodically through the medium of a conveniently placed cock. It is always preferable to pass the water through a reservoir where its impurities can settle, before it flows to the cylinder. In the case considered, the water usually has an average temperature of 54 to 60 degrees F., under which condition the hourly flow should be at least 5-1/2 gallons per horse-power per hour, the temperature rising at the outlet-pipe of the cylinder to 140 and 158 degrees F., which should not be surpassed. However, in engines working with high compression, 104 to 122 degrees F. should not be exceeded. If the water-jacket be fed by a reservoir, it is essential that the reservoir comply with the following conditions: In horizontal engines the water-inlet is always located in the base of the cylinder, while the outlet is located at the top. By providing the inlet-pipe extending to the cylinder with a cock, the circulation of water can be regulated to correspond with the work performed by the engine. Another cock at the end of the outlet-pipe near the reservoir serves, in conjunction with the first, to arrest the circulating water. When the weather is very cold or when the cylinder must be repaired, these two cocks may be closed, and the pipe and water-jacket of the cylinder drained by means of the drain-cock _V_ (Fig. 59), mounted at the inlet of the engine's water-jacket. In order that the pressure of the atmosphere may not prevent the flowing of the water, the highest part of the pipe is provided with a small tube, _T_, communicating with the atmosphere. [Illustration: FIG. 59.--Thermo-siphon cooling system.] On account of the importance of preventing losses of the charge in the pipes the author recommends the utilization of sluice-valves of the type shown in Fig. 60, instead of the usual cone or plug type. [Illustration: FIG. 60.--Vanne sluice-cock.] =Water-Tanks.=--The reservoir is mounted in such a way that its base is flush with the top of the cylinder; it should be as near as possible to the cylinder in order to obviate the use of long inlet and return pipes. This fact, however, does not necessarily render it advisable to place the reservoir in the engine-room; for such a disposition is doubly disadvantageous in so far as it does not permit a sufficiently rapid cooling of the circulating water by reason of the high temperature of the surrounding air, and in so far as it is liable to cause the formation of vapors which injuriously affect the engine. Consequently, the reservoir should be placed in as cool a place as possible, preferably even in the open air; for the water is not likely to freeze, except when it has been allowed to stand for a considerable time. The reservoir should be left uncovered so as to facilitate cooling by the liberation of the vapors formed on the surface of the water. Circulation being effected solely by the difference in specific gravity or density between the warmer water emerging from the cylinder and the cooler water which flows in from the reservoir, the slightest obstruction will impede the flow. Hence, the cross-section of the pipes should not be less than that of the inlet and outlet openings of the cylinder of the engine. Good circulation cannot be attained if the water must overcome inclines or obstacles in the pipes themselves. Instead of elbows, long curves of great radius, limited to the smallest possible number, should be employed. This is particularly true of the return-pipe extending from the cylinder back to the reservoir. For this pipe a minimum incline of 10 to 15 per cent. should be allowed, in order that the water may run up into the reservoir. The height of the water in the reservoir should be from 2 to 4 inches above the discharge of the return-pipe. In order to maintain this level it is advisable to use some automatic device such as a float-valve, in which case the reservoir should not be allowed to become too full. [Illustration: FIG. 61.--Correct arrangement of tanks and piping.] The size of a reservoir is determined by the engine; it should be large enough to enable the engine to run smoothly at its maximum load for several hours consecutively. Under these conditions, the reservoir should have a capacity of 45 to 55 gallons per horse-power for engines with "hit-and-miss" admission, and 55 to 65 gallons for engines controlled by variable admission. It is not advisable to employ reservoirs having a capacity of more than 330 to 440 gallons, the usual diameter being about 3 feet. [Illustration: FIG. 62.--Incorrect arrangement of tanks and piping.] If the power of the engine be such that several reservoirs are necessary, then the reservoirs should be connected in such a manner that the top of the first communicates with the bottom of the next and so on, the first reservoir receiving the water as it comes from the cylinder (Fig. 61). Intercommunication of the reservoirs by means of a common top tube (_a_) is objectionable; and simultaneous intercommunication at top and bottom (_a_ and _b_) is ineffective, so far as one of the reservoirs is concerned (Fig. 62). [Illustration: FIG. 63.--Tanks connected by inclined pipes.] The reservoirs are true thermo-siphons. Consequently the water should be methodically circulated; in other words, the hottest water, flowing from the engine into the top of the first reservoir and having, for example, a temperature of 104 degrees F., is cooled off to 86 degrees F. and drops to the bottom of the reservoir, thence to be driven, at a temperature sensibly equal to 86 degrees F., to the second reservoir, where a further cooling of 18 degrees F. takes place. In passing on to the following reservoirs the temperature is still further lowered, until the water finally reaches its minimum temperature, after which it flows back to the engine-cylinder. [Illustration: FIG. 64.--Circulating pump with by-pass.] In order to effect this cooling, the reservoirs can be connected in several ways. The most common method, as shown in Fig. 63, consists in connecting the reservoirs by oblique pipes. This is open to criticism, however, since leakage occurs, caused by the employment of elbows which retard the circulation. A less cumbrous and more efficient method of connection consists in joining the reservoirs by a single pipe at the top, as shown in Fig. 61; but care must be taken to extend this pipe at the point of its entrance into the adjoining reservoir by means of a downwardly projecting extension, or to fit its discharge-end with a box, closed by a single partition, open at the bottom. In order to prevent incrustation of the water-jacket surrounding the cylinder, a pound of soda per 17 cubic feet of the reservoir capacity is monthly introduced, and the jacket flushed weekly by a cock conveniently mounted near the cylinder (Fig. 59). The jacket is thus purged of calcareous sediments, which are prevented by the soda from adhering to the metal. The flushing-cock mentioned also serves to drain the water-jacket of the cylinder in case of intense or persistent cold, which would certainly freeze the water in the jacket, thereby cracking the cylinder or the exposed pipes. In order to regulate the circulation of the water in accordance with the work performed by the engine, a cock should be fitted to the water supply pipe at a convenient place. In engines of large size, driven at full load for long periods, cooling by natural circulation is often inadequate. In such cases, circulation is quickened by a small rotary or reciprocating pump, driven from the engine itself and fitted with a by-pass provided with a cock. This arrangement permits the renewal of the natural thermo-siphon circulation in case of accident to the pump (Fig. 64). [Illustration: FIG. 65.--Water-cooler in which tree branches are employed.] =Coolers.=--The arrangement which is illustrated in Fig. 65, and which has the merit of simplicity, will be found of service in cooling the water. It comprises a tank _B_ surmounted by a set of trays _E_, formed of frames to which iron rods are secured, spaced 1 to 2 feet apart, so as to form superimposed series separated by 1-1/2 to 2-1/3 feet. On these trays bundles of tree branches are placed. The cold water at the bottom of the tank is forced by the pump _P_i into the water-jacket, from which it emerges hot, and flows through the pipe _T_, which ends in a sprinkler _G_, formed of communicating tubes and perforated with a sufficient number of holes to enable the water to fall upon the trays in many drops. Thus finely divided, the water falls from one tray to another, retarded as it descends by the bundles of tree branches. It finally reaches the tank in a very cold condition and is then ready to be pumped to the engine. Birch branches are to be preferred on account of their tenuity. Great care should be taken to cover the tank with a sheet-metal closure in order to prevent twigs and foreign bodies from entering and from being drawn into the pump. [Illustration: FIG. 66.--Fan-cooler.] In the following table the dimensions of an operative apparatus of this kind are given,--an apparatus, moreover, that may be constructed of wood or of iron:-- Table Headings-- Column A: Horse-power. Column B: Volume in cubic ft. Column C: Base. Column D: Height. Column E: Height of tray-base. Column F: Pump--Capacity in gals. per min. ______________________________________________ | | | | | | Tank. | | | |____________________| | | | | | | A. | B. | C. | D. | E. | F. _____|_____|_____________|______|______|______ | | | | | 30 | 105 | 4.9' x 4.9' | 4.4' | 6.6' | 16.71 40 | 154 | 5.2' x 5.2' | 5.6' | 7.4' | 18.69 50 | 190 | 5.7' x 5.7' | 6.4' | 8.1' | 21.99 75 | 350 | 6.6' x 6.6' | 8.1' | 9.1' | 35.18 100 | 490 | 7.4' x 7.4' | 9.1' | 9.1' | 43.98 _____|_____|_____________|______|______|______ In order that the water may not drop to one side, the base of the apparatus should be made 10 to 12 inches less in width than the tank. The size of these apparatus may be considerably reduced by constructing them in the form of closed chests, into the bottom of which air maybe injected by means of fans in order to accelerate cooling (Fig. 66). CHAPTER VI LUBRICATION Lubrication is a subject that should be studied by every gas-engine user. So far as the piston is concerned it is a matter of the utmost importance. The piston does its work under very peculiar conditions. It is driven at great linear velocities; and it is, moreover, subjected to high temperatures which have nothing in common with good lubrication if care be not exercised. The piston is the essential, vital element of an engine. Upon its freedom from leakage depends the maintenance of a proper compression, and, consequently, the production of power and economical consumption. As it travels forward and as it recedes from the explosion-chamber, it uncovers more and more of the frictional surface constituting the interior wall of the cylinder. This surface, as a result, is regularly brought into contact with the ignited, expanding gases after each explosion. For this reason the oil which covers the wall is constantly subjected to high temperatures, by which it is likely to be volatilized and burned. Therefore, the first condition to be fulfilled in properly lubricating the piston is a constant and regular supply of oil. =Quality of Oils.=--For cylinder lubrication only the very best oils should be used; perfect lubrication is of such importance that cost should not be considered. Besides, the surplus oil which is usually caught in the drip-pan is by no means lost. After having been filtered it can be used for lubricating the bearings of the crank, the cam-shaft, and like parts. Cylinder-oil should be exceedingly pure, free from acids, and composed of hydrocarbons that leave no residue after combustion. Only mineral oils, therefore, are suitable for the purpose. Those oils should be selected which, with a maximum of viscosity, are capable of withstanding great heat without volatilizing or burning. The point at which a good cylinder-oil ignites should not be lower than 535 degrees F. Whether an oil possesses this essential quality is easily enough ascertained in practice without resorting to laboratory tests. All that is necessary is to heat the oil in a metal vessel or a porcelain dish. In order that the temperature may be uniform the vessel is shielded from the direct flame by interposing a piece of sheet metal or a layer of dry sand. As soon as gases begin to arise a lighted match is held over the oil. When the gases are ignited the thermometer reading is taken, the instrument being immersed in the oil. The temperature recorded is that corresponding with the point of ignition. For cylinder lubrication American mineral oil is preferable to Russian oil. The specific gravity should lie somewhere between .886 and .889 at 70 degrees F. Oil of this quality begins to evaporate at about 365 degrees F. Ignition occurs at 535 degrees F. The point of complete combustibility lies between 625 and 645 degrees F. Oil of this quality solidifies at 39 or 41 degrees F. Its color is a reddish yellow with a greenish fluorescence. Compared with water its degree of viscosity lies between 11.5 and 12.5 at a temperature of 140 degrees F. Before lubricating other parts of the engine with oil that has been used for the piston, heavy particles and foreign matter, such as dust, bearing incrustations, and the like, should be filtered out. The piston-pivot and the connecting-rod head are preferably lubricated with fresh oil, because their constant movement renders inspection difficult and the control of lubrication irksome. A good, industrial mineral oil of usual market quality will be found satisfactory. In order to bring home the importance of employing good cylinder-oil and of proper lubrication the author can only state that in his personal experience he has frequently detected losses varying from 10 to 15 per cent. in the power developed by engines poorly lubricated. =Types of Lubricators.=--Among the more common apparatus employed for automatically lubricating the cylinder, the author mentions an English oiler of the type pictured in Fig. 67 which is driven simply by a belt from the intermediary shaft, and which rotates the pulley _P_ secured on the shaft _a_ of the apparatus, at a very slow speed. The shaft _a_ is provided at its end with a small crank, from which a small iron arm _f_ is suspended, which arm dips in the oil contained in the cup _G_ of the oiler. When the shaft _a_ is turned this arm, as it sweeps through the oil-bath, collects a certain quantity of oil which it deposits on the collector _b_. From this spindle the oil passes through an outlet-pipe opening into the bottom of the oiler, and thence to the cylinder. The entire apparatus is closed by a cover _D_ which can be easily removed in order to ascertain the quantity of oil still remaining in the apparatus. Many other systems are utilized which, like the one that has been described, enable the feed to be controlled. Often small force-pumps are employed as cylinder-lubricators. Whatever may be the type selected, preference should be given to that in which the feed is visible (Fig. 68). [Illustration: FIG. 67.--An automatic English oiler.] If the oil be fed under pressure the cylinder is more constantly lubricated. Pressure-lubricators are nowadays widely used on large engines. It is advisable to add a little salt to the water contained in sight-feed lubricators so that the drop of oil is easily freed. These oil-pumps are provided with small check-valves at their outlets as well as at the inlets of cylinders. In order that pressure-lubricators may operate perfectly they should be regularly inspected and the check-valves ground from time to time. The lubrication of the crank-shaft and of the two connecting-rod heads should receive every attention. [Illustration: FIG. 68.--Sight-feed lubricating-pump.] [Illustration: FIG. 69.--Method of oiling the piston and end of the connecting-rod.] Lubricating devices should be employed which, besides being efficient, do not necessitate the stopping of the engine in order to oil the bearings. The foot of the connecting-rod at the point where it is pivoted to the piston is generally lubricated with cylinder-oil which is supplied by a tube mounted in the proper place across the piston-wall (Fig. 69). This arrangement may be adequate enough for small engines; but it is not sufficiently sure for engines of considerable size. An independent lubricating system should be employed, lubrication being effected either by a splasher mounted in front of the cylinder or by a lubricator secured to the connecting-rod by which the pivot is lubricated through the medium of a small tube supplying special oil (Fig. 21). The head of the connecting-rod where it meets the crank, must also be carefully lubricated because of the important nature of the work which it must perform, and because of the shocks to which it is subjected at each explosion. For motors of high power the system which seems to give most satisfactory results is that illustrated in Fig. 70. The arrangement there shown consists of an annular vessel secured at one side of the crank and turning concentrically on its axis; the vessel being connected with a long tube extending into a channel formed in the crank and discharging at the surface of the crank-pin within the bearing at the head of the connecting-rod. An adjustable sight-feed lubricator conducts the oil along a pipe to the vessel. Turning with the shaft, the vessel retains the oil in the periphery so that the feed in the previously mentioned channel in the connecting-rod head, is constant. [Illustration: FIG. 70.--Method of oiling the crank-shaft.] The main crank-shaft bearings are more easily lubricated. Among the systems commonly used with good results may be mentioned that shown in Fig. 71, in which the half section represents a small tube starting from the bearing and terminating in the interior of an oil recess or reservoir cast integrally with the bearing-cap. This reservoir is filled up to the level of the tube opening. A piece of cotton waste held on a small iron wire is inserted in the tube, part of the cotton being allowed to hang down in the reservoir. This cotton serves as a kind of siphon and feeds the bearing by capillary attraction with a constant quantity of oil, the supply being regulated by varying the thickness of the cotton. When the motor is stopped, the cotton should be removed in order that oil-feeding may not uselessly continue. Glass, sight-feed lubricators with stop-cocks, are very often used on crank-shafts. They are cleaner and much more easily regulated. Of all shaft-bearing lubricators, those which are most to be recommended are of the revolving-ring type (Fig. 72). They presuppose, however, bearings of large size and a special arrangement of bushings which renders their application somewhat expensive. Furthermore, the revolving-ring system can hardly be used in connection with engines of less than 20 horse-power. Since the system is applied almost exclusively to dynamo-shafts, it need not here be described in detail. As its name indicates, it consists of a metal ring having a diameter larger than that part of the shaft from which it is suspended and by which it is rotated. The lower part of the ring is immersed in an oil bath so that a certain quantity of lubricant is continually transferred to the shaft. [Illustration: FIG. 71.--Cotton-waste lubricator.] The revolving ring bearing should be fitted with a drain-cock and a glass tube in order to control the level of the oil in the bearing. Many manufacturers have adopted lubricating devices for valve-stems, and especially for exhaust-valves. The system adopted consists of a small tube curved in any convenient direction and discharging in the stem-guide. The free end is provided with a plug. A few drops of petroleum are introduced once or twice a day. [Illustration: FIG. 72.--Ring type of bearing oiler.] The lubrication of an engine entails certain difficulties which are easily overcome. One of these is the splashing of oil by the connecting-rod head. In order that this splashed oil may be collected in the base of the engine a suitably curved sheet-metal guard is mounted over the crank. A more serious difficulty is presented when the oil from a crank-bearing finds its way to the hub of the fly-wheel, whence it is driven by the centrifugal force to the rim. The oil is not only splashed against the walls of the engine-room, but it also destroys the adhesion of the belt if the fly-wheel be employed as a pulley. In order to overcome this objection the oil is prevented from spreading along the shaft by means of a circular guard (Fig. 73) mounted on that portion of the shaft toward the interior of the bearing. [Illustration: FIG. 73.--Shaft with oil-guard.] The problem of lubrication is of particular importance if the engine is driven for several days at a time without a stop. This happens in the case of mill and shop engines. Lubricators of large volume or lubricators which can be readily filled without stopping the engine should be employed. CHAPTER VII THE CONDITIONS OF PERFECT OPERATION =General Care.=--Gas-engines, as well as most machines in general, should be kept in perfect condition. Cleanliness, even in the case of parts of secondary importance, is indispensable. Unpainted and polished surfaces such as the shaft of the engine, the distributing cam-shafts, the levers, the connecting-rod and the like, should be kept in a condition equal to that when they were new. The absence of all traces of rust or corrosion in these parts affords sufficient evidence of the care taken of the invisible members such as the piston, the valves, ignition devices, and the like. =Lubrication.=--The rubbing surfaces of a gas-engine should be regularly and perfectly lubricated. The absence of lost motion and backlash in the bearings, guides, and joints is of particular importance not only because of its influence on steady and silent running, but also on the power developed and on the consumption. As we have already seen in the chapter on lubrication, a special quality of oil should be employed for the lubrication of the cylinder. The feed of the lubricator supplying this most vital part of the engine is so regulated that it meets the actual requirements with the utmost nicety possible. In a subsequent chapter, in which faulty operation will be discussed, it will be shown how too much and too little oil may cause serious trouble. =Tightness of the Cylinder.=--The amount of power developed depends principally on the degree of compression to which the explosive mixture is subjected. The economical operation of the engine depends in general upon perfect compression. It is, therefore, necessary to keep those parts in good order upon which the tightness of the cylinder depends. These parts are the piston, the valves, and their joints, and the ignition devices whether they be of the hot-tube or electrical variety. In order to prevent leakage at the piston, the rings should be protected from all wear. It is of the utmost importance that the surfaces both of the piston and of the cylinder, be highly polished so that binding cannot occur. In cleansing the cylinder, emery paper or abrasive powder should not be employed; for the slightest particle of abrasive between the surfaces in contact will surely cause leakage. The oil and dirt, which is turned black by friction and which may adhere to the piston rings, should be washed away with petroleum. Similarly the other parts of the cylinder should be cleaned to which burnt oil tends to adhere. =Valve-Regrinding.=--The valves should be regularly ground. Even in special cases where they may show no trace of rapid wear they should be removed at least every month. In order to avoid any accident, care should be taken in adjusting the valves after the cap has been unbolted not to introduce a candle or a lighted match either in the valve-chambers or in the cylinder, without first closing the gas-cock. Furthermore, a few turns should be given to the engine, in order to drive out any explosive mixture that may still remain in the cylinder or the connected passages. The exhaust-valve, by reason of the high temperature to which the disk and the seat are subjected, should receive special attention. The valve should be ground on its seat every two or three months at least, depending upon the load of the engine. =Bearings and Crosshead.=--The bushings of the engine shaft should always be held tightly in place. The looseness to which they are liable, particularly in gas-engines on account of the sharp explosions, tends to unscrew the nuts and to hasten the wear of the brass, which is the result of frequent tightening. The slightest play in the bearings of the engine-shaft as well as in the bearings of connecting-rods increases the sound that engines naturally produce. =Governor.=--The governor should receive careful attention so far as its cleanliness is concerned; for if its operation is not easy it is apt to become "lazy" and to lose its sensitiveness. If the governor be of the ball type, or of the conical pendulum type operated by centrifugal force, it is well to lubricate each joint without excess of oil. In order to prevent the accumulation and the solidification of oil, the governor should be lubricated from time to time with petroleum. If the governor is actuated by inertia, which is the case in most engines of the hit-and-miss variety, it needs less care; still, it is advisable to keep the contact at which the thrust takes place well oiled. The operation of any of these governors is usually controlled by the tension of a spring, or by a counterweight. In order to increase the speed of the engine, or in other words, to increase the number of admissions of gas in a given time, all that is usually necessary is to tighten up the spring, or to change the position of the counterweight. It should be possible to effect this adjustment while the engine is running in such a manner that the speed can be easily changed. =Joints.=--In most well-built engines the caps of the valve-chests and other removable parts are secured "metal on metal" without interposing special joints. In other words, the surfaces are themselves sufficiently cohesive to insure perfect tightness. In engines which are not of this class, asbestos joints are very frequently employed, particularly at the exhaust-valve cap and the suction-valve. In some engines, where for any reason it is necessary frequently to detach the caps, certain precautions should be taken to protect the joints so that they may not be exposed to deterioration whenever they are removed. For this purpose, they are first immersed in water in order to be softened, then dried and washed with olive or linseed oil on the side upon which they rest in the engine. On the cap side they are dusted with talcum or with graphite. Treated in this manner, the joint will adhere on one side and will be easily released on the other. Joints that are liable to come in contact with the gases in the explosion-chamber should be free from all projections toward the interior of the cylinder; for during compression these uncooled projections may become incandescent and may thus cause premature ignition. As a general rule when the cap is placed in position the joint should be retightened after a certain time, when the surfaces have become sufficiently heated. In order to tighten the joints the bolts and nuts should not be oiled; otherwise the removal of the cap becomes difficult. =Water Circulation.=--In a previous chapter, the importance of the water circulation and the necessity of keeping the cylinder-jacket hot, have been sufficiently dwelt upon. As the cylinder tends to become hotter with an increase in the load, because of the greater frequency of explosions, it is advisable to regulate the flow of the water in order to prevent its becoming more than sufficient in quantity when the engine is lightly loaded; for under these conditions the cylinder will be cold and the explosive mixture will be badly utilized. A suitable temperature of 140 to 158 degrees F. is easily maintained by adjusting the circulation of the water. This can be accomplished by providing the water-inlet pipe leading to the cylinder with a cock which can be opened more or less, as may be necessary. The temperature of 140 to 158 degrees F., which has been mentioned, may, at first blush, seem rather high because it would be impossible to keep the hand on the outlet-pipe. The cylinder, however, will not become overheated so long as it is possible to hold the hand beneath the jacket near the water-inlet. This relates only to engines having a compression of 50 to 100 lbs. per square inch. For engines of higher compression, a lower running temperature will be safer. On this matter the instructions of the engine maker should be carried out. =Adjustment.=--Gas-engines, at least those which are built by trustworthy firms, are always put to the brake test before they are sent from the shops, and are adjusted to meet the requirements of maximum efficiency. But since the nature and quality of gas necessarily vary with each city, it is evident that an engine adjusted to develop a certain horse-power with a gas of a certain richness, may not fulfil all expectations if it is fed with a gas less rich, less pure, hotter, and the like. The altitude also has some influence on the efficiency of the engine. As it increases, the density of the mixture diminishes; that is to say, for the same volume the engine is using a smaller amount. From this it follows that a gas-engine ought to be adjusted as a general rule on the spot where it is to be used. The fulfilment of this condition is particularly important in the case of explosion-engines, because an advancement or retardation of only one-half a second in igniting the explosive mixture will cause a considerable loss in useful work. From this it would follow that gas-engines should be periodically inspected in order that they may operate with the highest efficiency and economy. As in the case of steam-engines, it is advisable to take indicator records which afford conclusive evidence of the perturbations to which every engine is subject after having run for some time. Most gas-engine users either have no indicating instruments at their disposal or else are not sufficiently versed in their employment and the interpretation of their records to study perturbations by their means. For this reason the advice of experts should be sought,--men who understand the meaning of the diagrams taken and who are able by their means to effect a considerable saving in gas. CHAPTER VIII HOW TO START AN ENGINE--PRELIMINARY PRECAUTIONS The first step which is taken in starting an engine driven by street-gas is, naturally, the opening of the meter-cock and the valves between the meter and the engine. When the gas has reached the engine, the rubber bags will swell up and the anti-pulsator diaphragm will be forced out. The drain-cock of the gas-pipe is then opened. In order to ascertain whether the flow of gas is pure, a match is applied to the outlet of the cock. The flame is allowed to burn until it changes from its original blue color to a brilliant yellow. If the hot-tube system of ignition be employed, the Bunsen burner is ignited, care being taken that the flame emerging from the tube is blue in color. If necessary the admission of air to the burner is regulated by the usual adjusting-sleeve. A white or smoky flame indicates an insufficient supply of air to the burner. A characteristic sooty odor is still other evidence of the same fact. Sometimes a white flame may be produced by the ignition of the gas at the opening of the adjusting-sleeve. A blue or greenish flame is that which has the highest temperature and is the one which should, therefore, be obtained. About five or ten minutes are required to heat up the tube, owing to the material of which it is made. When the proper temperature has been attained the tube becomes a dazzling cherry red in color. While the tube is being heated up, it is well to determine whether the engine is properly lubricated and all the cups and oil reservoirs are duly filled up. The cotton waste of the lubricators should be properly immersed, and the drip lubricators examined to determine whether they are supplying their normal quantity of oil. The regulating-levers of the valves should be operated in order to ascertain whether the valves drop upon their seats as they should. The stem of the exhaust-valve should be lubricated with a few drops of petroleum. If the ignition system employed be of the electric type, with batteries and coils, tests should be made to determine whether the current passes at the proper time on completing the circuit with the contact mounted on the intermediary shaft. This contact should produce the characteristic hum caused by the operation of the coil. If a magneto be used in connection with the ignition apparatus, its inspection need not be undertaken whenever the engine is started, because it is not so likely to be deranged. Still, it is advisable, as in the case of ignition by induction-coils, to set in position the device which retards the production of the spark. This precaution is necessary in order to avoid a premature explosion, liable to cause a sharp backward revolution of the fly-wheel. After the ignition apparatus and the lubricators have been thus inspected, the engine is adjusted with the piston at the starting position, which is generally indicated by a mark on the cam-shaft. The starting position corresponds with the explosion cycle and is generally at an angle of 40 to 60 degrees formed by the crank above the horizontal and toward the rear of the engine. The gas-cock is opened to the proper mark, usually shown on a small dial. If there be no mark, the cock is slowly opened in order that no premature explosion may be caused by an excess of gas. The steps outlined in the foregoing are those which must be taken with all motors. Each system, however, necessitates peculiar precautions, which are usually given in detailed directions furnished by the builder. As a general rule the engines are provided on their intermediary shafts with a "relief" or "half-compression" cam. By means of this cam the fly-wheel can be turned several times without the necessity of overcoming the resistance due to complete compression. Care should be taken, however, not to release the cam until the engine has reached a speed sufficient to overcome this resistance. Engines of considerable size are commonly provided with an automatic starting appliance. In order to manipulate the parts of which this appliance is composed, the directions furnished by the manufacturer must be followed. Particularly is this true of automatic starters comprising a hand-pump by means of which an explosive mixture is compressed,--true because in the interests of safety great care must be taken. The tightness and free operation of the valves or clacks which are intended to prevent back firing toward the pump should be made the subject of careful investigation. Otherwise, the piston of the pump is likely to receive a sudden shock when back firing occurs. When the engine has been idle for several days, it is advisable, before starting, to give it several turns (without gas) in order to be sure that all its parts operate normally. The same precaution should be taken in starting an engine, if a first attempt has failed, in order to evacuate imperfect mixtures that may be left in the cylinder. Before this test is made, the gas-cock should, of course, be closed in order to prevent an untimely explosion. It is advisable in starting an engine not to bend the body over the ignition-tube, because the tube is likely to break and to scatter dangerous fragments. Under no condition whatever should the fly-wheel be turned by placing the foot upon the spokes. All that should be done is to set it in motion by applying the hand to the rim. =Care During Operation.=--When the engine has acquired its normal speed, the governor should be looked after in order that its free operation may be assured and that all possibility of racing may be prevented. After the engine has been running normally for a time, the cocks of the water circulation system should be manipulated in order to adjust the supply of water to the work performed by the engine. In other words the cylinder should be kept hot, but not burning, as previously explained in the paragraph in which the water-jacket is discussed. The maintenance of a suitable temperature is extremely important so far as economy is concerned. All the bearings should be inspected in order that hot boxes may be obviated. =Stopping the Engine.=--The steps to be taken in stopping the engine are the following: 1. Stopping the various machines driven by the engine,--a practice which is followed in the case of all motors; 2. Throwing out the driving-pulley of the engine itself, if there be one; 3. Closing the cock between the meter and the gas-bags in order to prevent the escape of gas and the useless stretching of the rubber of the bags or of the anti-pulsating devices; 4. Actuating the half-compression or relief cam as the motor slows down, in order to prevent the recoil due to the compression; 5. Closing the gas-admission cock; 6. Shutting off the supply of oil of free flowing lubricators, and lifting out the cotton from the others. If the engine be used to drive a dynamo, particularly a dynamo provided with metal brushes, the precaution should be taken of lifting the brushes before the engine is stopped in order to prevent their injury by a return movement of the armature-shaft; 7. Shutting off the cooling-water cock if running water is used. If the engine is exposed to great cold, the freezing of the water in the jacket is prevented while the engine is at rest, either by draining the jacket entirely, or by arranging a gas jet or a burner beneath the cylinder for the purpose of causing the water to circulate. If such a burner be used the cocks of the water supply pipe should, of course, be left open. CHAPTER IX PERTURBATIONS IN THE OPERATION OF ENGINES AND THEIR REMEDY In this chapter will be discussed certain perturbations which affect the operations of gas-engines to a more marked degree than lack of care in their construction. In previous chapters defects in operation due to various causes have been dwelt upon, such as objectionable methods in the construction of an engine, ill-advised combination of parts, defects of installation, and the like; and an attempt has been made to determine in each case the conditions which must be fulfilled by the engine in order to secure efficiency and economy at a normal load. =Difficulties in Starting.=--The preliminary precautions to be taken in starting an engine having been indicated, it is to be assumed that the advice given has been followed. Nevertheless various causes may prevent the starting of the engine. =Faulty Compression.=--Defective compression, as a general rule, prevents the ignition of the explosive mixture. Whether or not the compression be imperfect can be ascertained by moving the piston back to the period corresponding with compression, in other words, that position in which all valves are closed. If no resistance be encountered, it is evident that the air or the gaseous mixture is escaping from the cylinder by way of the admission-valve, the exhaust-valve, or the piston. The valves, ordinarily seated by springs, may remain open because their stems have become bound, or because some obstruction has dropped in between the disk and the seat. In a worn-out or badly kept engine the valves are likely to leak. If that be the case grinding is the only remedy. If a valve be clogged, which becomes sufficiently evident by manipulating the controlling levers, it is necessary simply to clean the stem and its guides in order to remove the caked oil which accumulates in time. If the engine be new, the binding of the valve-stems is often caused by insufficient play between the stems and their guides. Should this prove to be the case, the defect is remedied by rubbing the frictional surface of the stem with fine emery paper and by lubricating it with cylinder-oil. The exhaust-valve, however, should be lubricated only with petroleum. It is not unlikely that the exhaust-valve may leak for two other reasons. In the first place, the tension of the spring which serves to return the valve may have lessened and may be insufficient to prevent the valve from being unseated during suction. Again, the screw or roller serving as a contact between the lever and the valve-stem, may not have sufficient play, so that the lengthening of the stem on account of its expansion may prevent the valve from falling back on its seat. The first-mentioned defect is remedied by renewing the spring, or by the provision of an additional spring or of a counterweight in order to prevent the stoppage of the motor. The second defect can be remedied by regulating the contact. Leakage past the piston may be caused by the breaking of one or more rings, by wear or binding of the rings, or by wear or binding of the cylinder. The whistling caused by the air or the mixture as it passes back proves the existence of this fault. =Presence of Water in the Cylinder.=--It may sometimes happen that water may find its way into the cylinder with the gas by reason of the bad arrangement of the piping. It may also happen that water may enter the cylinder through the water-jacket joint. Again, the presence of water in the cylinder may be due to condensation of the steam formed by the chemical union of the hydrogen of the gas and the oxygen of the air, which condensation is caused by the cool walls of the cylinder. The water may sometimes accumulate in the exhaust pipe and box, when they have been improperly drained, and may thus return to the cylinder. Whatever may be its cause, however, the presence of water in the cylinder impedes the starting of the engine, because the gases resulting from the explosion are almost spontaneously chilled, thereby diminishing the working pressure. If electric ignition be employed, drops of water may be deposited between the contacts, thereby causing short circuits which prevent the passing of the spark. If there be no drain-cock on the cylinder, the difficulty of starting the engine can be overcome only by ceaseless attempts to set it in motion. The leaky condition of a joint as well as the presence of a particle of gravel in the cylinder-casting, through which the water can pass from the jacket, is attested by the bubbling up of gas in the water-tank at the opening of the supply tube. These bubbles are caused by the passage of the gas through the jacket after the explosion. If such bubbles be detected, the cylinder should be renewed or the defect remedied. In order to obviate any danger, the stop-cocks of the water-jacket, which have already been described in a previous chapter, should be closed while the engine is idle. =Imperfect Ignition.=--The difficulties encountered in starting an engine, and caused by imperfect ignition, vary in their nature with the character of the ignition system employed, whether that system, for example, be of the electric, or of the incandescent or hot tube type. Frequently it happens that in starting an engine a hot tube may break. If the tube be of porcelain the accident may usually be traced to improper fitting or to the presence of water in the cylinder. If the tube be of metal, its breaking is caused usually by a weakening of the metal through long use--an accident that occurs more often in starting the engine than in normal operation, because the explosions at starting are more violent, owing to the tendency of the supply-pipes to admit an excess of gas at the beginning. A misfire arising from a faulty tube in starting may be caused by an obstruction or by leaks at the joints or in the body of the tube itself, thereby allowing a certain quantity of the mixture to escape before ignition. This defect in the tube is usually disclosed by a characteristic whistling sound. A tube may leak either at the bottom or at the top. In the first case, starting is very difficult, because the part of the mixture compressed toward the tube will escape through the opening before it reaches the incandescent zone. In the second case, ignition may be simply retarded to so marked an extent that a sufficient motive effect cannot be produced. An example of this retardation, artificially produced to facilitate the starting and to obviate premature explosions, is found in a system of ignition-tubes provided with a small cock or variable valve (Figs. 74 and 75). [Illustration: FIG. 74.] [Illustration: FIG. 75.--Ignition-tubes provided with needle valves to facilitate starting.] The mere enumeration of defects caused by leakage is sufficient to indicate the remedy to be adopted. It may be well to recall in this connection the important part played by the ignition-valve. If it be leaky, or if its free operation be impeded, starting will always be difficult. =Electric Ignition by Battery or Magneto.=--If the electric ignition apparatus, whatever may be the method by which the spark is produced, be imperfect in operation, the first step to be taken is to ascertain whether the spark is produced at the proper time, in other words, slightly after the dead center in the particular position given to the admission device at starting. If a coil and a battery be employed, it is advisable to remove the plug and to place it with its armature upon a well-polished metal surface to produce an electrical contact, preventing, however, the contact of the binding post with this metallic surface. The same method of inspection is adopted with the make-and-break apparatus of an electric magneto. In both cases it should be ascertained whether or not there is any short-circuiting. The contacts should be cleaned with a little benzine if they are covered with oil or caked grease. If no spark is produced at the plug or at the make-and-break device it may be inferred that the wires are broken or that the generating apparatus is out of order. A careful examination will indicate what measures are to be taken to cure the defects. =Premature Ignition.=--It has several times been stated that the moment of ignition of the gaseous mixture has a pronounced influence on the operation of gas-engines and upon their economy. Premature ignition takes place when there is a violent shock at the moment when the piston leaps from the rear dead center to the end of the compression stroke. The violent effects produced are all the more harmful because they tend to overheat the interior of the engine and thereby to increase in intensity. Premature ignition may be due to several causes. If a valveless hot tube be employed it may happen that the incandescent zone is too near the base. If the tube be provided with a valve, it very frequently happens that the valve leaks or that it opens too soon. In the case of electric ignition, the circuit may be completed before the proper time, because of faulty regulation. The suggestions made in the preceding chapters indicate the method of remedying these defects. Faulty ignition may have its origin not only in the method of ignition employed, but also in excessive heating of the internal parts of the engine, caused by continual overloading or by inadequate circulation of water. Passing to those cases of premature ignition of a special nature which are not due to any functional defect in the engine, but which are purely accidental in origin, such as the uncleanliness of the parts within the cylinder or the presence of some projecting part which becomes heated to incandescence during compression, it should first be stated that these ignitions, usually termed spontaneous, often occur well in advance of the end of the compression stroke. They are characterized by a more marked shock than that caused by ordinary premature ignition and usually result in bringing the engine to a complete stop in a very short time. These spontaneous explosions counteract to such an extent the impulse of the compression period, during which the piston is moving back, that they have a tendency to reverse the direction in which the engine is running. In such cases a careful inspection and a scrupulous cleaning of the cylinder and of the piston should be undertaken. The bottom of the piston is particularly likely to retain grease which has become caked, and which is likely to become heated to incandescence and spontaneously to ignite the explosive mixture. =Untimely Detonations.=--The sound produced by the explosions of a normally operating engine can hardly be heard in the engine-room. Untimely detonations are produced either at the exhaust, or in the suction apparatus, near the engine itself. These detonations are noisier than they are dangerous; still, they afford evidence of some fault in the operation which should be remedied. Detonations produced at the exhaust are caused by the burning of a charge of the explosive mixture in the exhaust-pipe, which charge, for some reason, has not been ignited in the cylinder, and has been driven into the exhaust-pipe, where it catches fire on coming into contact with the incandescent gases discharged from the cylinder after the following explosion. Detonations produced in the suction apparatus of the engine, which apparatus is either arranged in the base itself or in a separate chest, are often noisier than the foregoing. They are caused by the accidental backward flowing of the explosive mixture, and by its ignition outside of the cylinder. The accident may be traced to three causes: 1. The suction-valve of the mixture may not be tight and may leak during the period of compression, allowing a certain quantity of the mixture to pass into the suction-chest or into the frame. When the explosion takes place in the cylinder that part of the mixture which has passed back is ignited, as we have just seen, thereby producing a very loud deflagration. The obvious remedy consists in making the suction-valve tight by carefully grinding it. 2. It may happen that at the end of the exhaust stroke incandescent particles may remain in the cylinder, which particles may consist of caked oil or may be retained by poorly cooled projections. The result is that the mixture is prematurely ignited during the suction period. 3. The engine is so regulated, particularly in the case of English-built engines, as to effect what is technically called "scavenging" the products of combustion. In order to obtain this result, the mixture-valve is opened before the end of the exhaust stroke of the piston and the closing of the exhaust-valve. Owing to the inertia and the speed acquired by the products of combustion shot into the exhaust-pipe after explosion, a lowering of the pressure is produced in the cylinder toward the end of the stroke, causing the entrance of air by the open admission-valve and consequently effecting the scavenging of the burnt gases, part of which would otherwise remain in the cylinder. It is evident that if a charge of the mixture has not been normally exploded, either because its constituents have not been mingled in the proper proportion, or because the ignition apparatus has missed fire, this charge at the moment of exhausting will pass out of the cylinder without any acquired speed, and will flow back in part at the end of the exhaust stroke past the prematurely opened admission-valve, thereby lodging in the air suction apparatus. Despite the suction which takes place immediately following the re-entrance of the gas into the cylinder, a certain quantity of the mixture is still confined in the suction-pipe and its branches, where it will catch fire at the end of the exhaust stroke after the opening of the mixture-valve. In order to avoid these detonations it is necessary simply to see to it that the mixture is regularly ignited. This is accomplished by mixing the gas and air in proper proportions or by correcting the ignition time. =Retarded Explosions.=--Retarded explosions considerably reduce the power which an engine should normally yield, and sensibly increase the consumption. They are due to three chief causes: (1), faulty ignition; (2), the poor quality of the mixture; (3), compression losses. The existence of the defect cannot be ascertained with any certainty without the use of an indicator or of some registering device which gives graphic records. Nevertheless, it is possible in some degree to detect retarded explosions, simply by observing whether there is a diminution in the power or an excessive consumption, despite the perfect operation and good condition of all the engine parts. In order to remedy the defect it should be ascertained if the compression is good, if the supply of gas is normal, and if the conditions under which the mixture of air and gas is produced have not been changed. Lastly, the ignition apparatus is gradually adjusted to accelerate its operation until a point is reached when, after explosion, shocks are produced which indicate an excessive advance. The ignition apparatus is then adjusted to a point slightly ahead of the corresponding position. Recalling the descriptions already given of the various systems of ignition, the manner of regulating the moment of ignition in each case may be summarized as follows: 1. For the valveless incandescent tube, provided with a burner the position of which can be varied, ignition can be accelerated by bringing the burner nearer to the base. Retardation is effected by moving the burner away from the base. 2. In the case of the incandescent tube of the fixed burner type, the moment of ignition will depend upon the length of the tube. The retardation will be greater as the tube is shorter, and _vice versa_. 3. If the tube be provided with an ignition-valve, the time of ignition having been regulated by the maker, regulation need not be undertaken except if the valve-stem be worn or the controlling-cam be distorted. If these defects should be noted, the imperfect parts should be repaired or renewed. 4. In electric igniters the controlling apparatus is generally provided with a regulating device which may be manipulated during the operation of the motor. If the manual adjustment of the regulating apparatus be unproductive of satisfactory results, it is advisable to ascertain whether the spark is being produced normally. Before the engine has come to a stop, one of the valve-casings is raised, and through the opening thus produced it is easily seen whether the spark is of sufficient strength, the engine in the meanwhile being turned by hand. Care should always be taken to purge the cylinder of the gas that it may contain, in order to prevent dangerous explosions. If the spark should prove to be too feeble, or if there be no spark at all, despite the fact that every part of the mechanism is properly adjusted, it may be inferred that the fault lies with the current and is caused by 1. Imperfect contact with the binding-posts, with the conducting wire, or with the contact-breaking members; 2. A short circuit in one of the dismembered pieces; 3. The presence of a layer of oil or of caked grease forming an insulator, injurious to induction, between the armature and the magnets; 4. A deposit of oil or moisture on the contact-breaking parts; 5. The exhaustion of the magnets, which, however, occurs only after several years of use, except when the magneto has been subjected for a long time to a high temperature. The mere discovery of any of these defects sufficiently indicates the means to be adopted in remedying them. =Lost Motion in Moving Parts.=--Lost motion of the moving parts is due to structural errors. Its cause is to be found in the insufficient size of the frictional bearing surfaces, and improper proportioning of shafts, pins, and the like. The result is a premature wear which cannot be remedied. Imperfect adjustment, lack of care, and bad lubrication, may also hasten the wear of certain parts. This wear is manifested in shocks, occurring during the operation of the engine,--shocks which are particularly noticeable at the moment of explosion. Besides the inconveniences mentioned, wearing of the gears and of the moving parts leads to derangement of the power-transmitting members. So far as the admission and exhaust valves are concerned, the wearing of the cams, rollers, and lever-pivots is evidenced by a retardation in the opening of these valves and an acceleration in their closing. The ignition, whatever may be the system employed, is affected by lost motion and is retarded. The engine appreciably loses in power, and its consumption becomes excessive. =Overheated Bearings.=--Apart from the imperfect adjustment of a member, it may happen that the bushings of the main bearings of the ends of the connecting-rod, and of the piston-pivot, may become heated because of excessive play, or of too much tightening, or of a lack of oil, or of the employment of oil of bad quality. The overheating may lead to the binding of frictional surfaces and even to the fusion of bushings if they be lined with anti-friction metal. In order to avoid the overheating of parts, it is advisable, while the engine is running, to touch them from time to time with the back of the hand. As soon as the slightest overheating is felt, the temperature may be lowered often by liberal oiling. If this be inadequate and if for special reasons it is impossible to stop the engine, the overheated part may be cooled by spraying it with soapy water. If the overheating has not been detected or reduced in time, a characteristic odor of burnt oil will be perceived, accompanied by smoke. The part overheated will then have attained a temperature so high that it cannot be touched with the hand. Should this occur, it is inadvisable to employ oil, because it would immediately burn up and would only aggravate the conditions. Cotton waste should be carefully applied to the overheated member, and gradual spraying with soapy water begun. In special cases where the lubricating openings or channels are not likely to be obstructed, a little flowers of sulphur may be added to the oil, if this be very fluid. Castor oil may also be successfully employed. If the binding of the rubbing surfaces should prevent the reduction of the overheated member's temperature, the engine must necessarily be stopped, and the parts affected detached. All causes of binding are removed by means of a steel scraper. The surfaces of the bushings and of the shaft which they receive are smoothed with a soft file and then polished with fine emery paper. Before the parts are replaced, the precaution of ascertaining whether they touch at all points should be taken. Careful inspection and copious lubrication should, of course, be undertaken when the engine is again started. =Overheating of the Cylinder.=--The overheating of the cylinder may be due to a complete lack of water in the jacket or to an accidental diminution in the quantity of water supplied. If this discovery is made too late, and if the cylinder has reached a very high temperature, the circulation of the water should not be suddenly re-established, because of the liability of breaking the casting. It is best to stop the engine and to restore the parts to their normal condition. It is well to recall at this point that if the calcareous incrustation of the water-jacket or the branch pipes should hinder the free circulation of water, cleaning is, of course, necessary. The jacket may be washed several times with a twenty per cent. solution of hydrochloric acid. After this treatment the jacket should, of course, be rinsed with fresh water before the piping of the water-circulating apparatus is again connected. =Overheating of the Piston.=--If the overheating of the piston is not due to faulty adjustment, it may be caused by lack of oil or to the employment of a lubricant not suitable for the purpose. In a previous chapter the importance of using a special oil for cylinder lubrication has been insisted upon. The overheating of the piston can also result from that of the piston-pin. Should this be the case it is advisable to stop the engine, to ascertain the condition and the degree of lubrication of this member and its bearing. Overheating of the piston is manifested by an increase of the temperature of the cylinder at the forward end. If this overheating be not checked, binding of the piston in the cylinder is likely to result. =Smoke Arising from the Cylinder.=--This is generally a sign either of overheating, which causes the oil to evaporate, or of an abnormal passage of gas, caused by the explosion. Abnormal passage of gas may result from wear or from distortion of the cylinder, or from wear or breakage of the piston-rings. The result is always the overheating of the cylinder and a reduction in compression and power. If the engine is well kept and shows no sign of wear, leakage may be caused simply by the fouling of the piston-rings, which then adhere in their grooves and have but insufficient play. This defect is obviated by cleaning the rings in the manner explained in Chapter VII. Lubrication is faulty when the quantity of lubricant supplied is either insufficient or too abundant, or when the oils employed are of bad quality. It has already been shown that insufficient lubrication and the utilization of bad oils leads to the overheating of the moving parts. Insufficient lubrication may be caused by imperfect operation of the lubricators, or, particularly during cold weather, by too great a viscosity or congelation of the oil. If a lubricator be imperfect in its operation, the condition of its regulating mechanism should be ascertained, if it has any, and an examination made to discover any obstruction in the oil-ducts. Such obstructions are very likely to occur in new devices which have been packed in cotton waste or excelsior, with the result that the particles of the packing material often find their way into openings. An oil may be bad in quality because of its very nature, or because of the presence of foreign bodies. In either case an oil of better quality should be substituted. The freezing of oil by intense cold may be retarded by the addition of ordinary petroleum to the amount of 10 to 20 per cent. An excess of oil in the bearings results simply in an unnecessary waste of lubricant, and the splashing of oil on the engine and about the room. If too much oil be used in the cylinder, grave consequences may be the result; for a certain quantity of the oil is likely to accumulate within the cylinder, where it burns and forms a caky mass that may be heated to incandescence and prematurely ignite the explosive mixture. Especially in producer-gas engines is an excess of cylinder-lubricant likely to cause such accidents. Indeed, the temperature of explosion not being as high as in street-gas engines, the excess oil cannot be so readily removed with certainty by evaporation or combustion. On the other hand, the compression of the mixture being generally higher, premature ignition is very likely to occur. =Back Pressure to the Exhaust.=--How the pipes and chests for the exhaust should be arranged in order not to exert a harmful influence on the motor has already been explained. Even if the directions given have been followed, however, the exhaust may not operate properly from accidental causes. Among these causes may be mentioned obstructions in the form of foreign bodies, such as particles of rust, which drop from the interior of the pipes after the engine has been running for some time and which, accumulating at any place in the pipe, are likely to clog the passage. Furthermore, the products of combustion may contain atomized cylinder oil which finds its way into the exhaust-pipe. This oil condenses on the walls of the elbows and bends of the pipe in a deposit which, as it carbonizes, is converted into a hard cake and which reduces the cross-section of the passage, thereby constituting a true obstacle to the free exhaust of the gases. These various defects are manifested in a loss in engine power as well as in an abnormal elevation of the temperature of the parts surrounding the exhaust opening. =Sudden Stops.=--Sudden stops are occasioned by faulty operation of the engine, and by imperfect fuel supply. Among the first class the chief causes to be mentioned are the following: 1. Overheating, which has already been discussed and which may block a moving part. 2. Defective ignition. 3. Binding of the admission-valve or of the exhaust-valve, preventing respectively suction or compression. 4. The breaking or derangement of a member of the distributing mechanism. 5. A weakening of the exhaust-valve spring, so that the valve is opened by the suction of fresh quantities of mixture. These faults are due to carelessness and improper inspection of the engine. So far as the fuel supply of the engine is concerned, the causes of stoppage will vary if street-gas or producer-gas be employed. In the former case the difficulty may be occasioned by the improper operation of the meter, by the formation of a water-pocket in the piping, by the binding of an anti-pulsator valve, by the derangement of a pressure-regulator, or by a sudden change in the gas pressure when no pressure-regulator is employed. If producer-gas be used, stoppages may be occasioned by a sudden change in the quality, quantity, or temperature of the gas. These defects will be examined in detail in the chapter on Gas-Producers. CHAPTER X PRODUCER-GAS ENGINES Thus far only street-gas or illuminating-gas engines have been discussed. If the engine employed be small--10 to 15 horse-power, for instance--street-gas is a fuel, the richness, purity and facility of employment of which offsets its comparatively high cost. But the constantly increasing necessity of generating power cheaply has led to the employment of special gases which are easily and cheaply generated. Such are the following: Blast-furnace gases, Coke-oven gases, Fuel-gas proper, Mond gas, Mixed gas, Water-gas, Wood-gas. The practical advantages resulting from the utilization of these gases in generating power were hardly known until within the last few years. The many uses to which these gases have been applied in Europe since 1900 have definitely proved the industrial value of producer-gas engines in general. The steps which have led to this gradually increasing use of producer-gas have been learnedly discussed and commented upon in the instructive works and publications of Aimé Witz, Professor in the Faculty of Sciences of Lille, in those of Dugald Clerk, of London, F. Grover, of Leeds, and Otto Güldner, of Munich, and in those of the American authors, Goldingham, Hiscox, Hutton, Parsell and Weed, etc. The new tendencies in the construction of large engines may be regarded as an interesting verification of the forecasts of these men--forecasts which coincide with the opinion long held by the author. Aimé Witz has always been an advocate of high pressures and of increased piston speed. English builders who made experiments in this direction conceded the beneficial results obtained; but while they increased the original pressure of 28 to 43 pounds per square inch employed five or six years ago to the pressure of 85 to 100 pounds per square inch nowadays advocated, the Germans, for the most part, have adopted, at least in producer-gas engines, pressures of 114 to 170 pounds per square inch and more. =High Compression.=--In actual practice, the problem of high pressures is apparently very difficult of solution, and many of the best firms still seem to cling to old ideas. The reason for their course is, perhaps, to be found in the fact that certain experiments which they made in raising the pressures resulted in discouraging accidents. The explosion-chambers became overheated; valves were distorted; and premature ignition occurred. Because the principle underlying high pressures was improperly applied, the results obtained were poor. High pressures cannot be used with impunity in cylinders not especially designed for their employment, and this is the case with most engines of the older type, among which may be included most engines of English, French, and particularly of American construction. In American engines notably, the explosion-chamber, the cylinder and its jacket, are generally cast in one piece, so that it is very difficult to allow for the free expansion of certain members with the high and unequal temperatures to which they are subjected (Fig. 22). Some builders have attempted to use high pressures without concerning themselves in the least with a modification of the explosive mixture. The result has been that, owing to the richness of the mixture, the explosive pressure was increased to a point far beyond that for which the parts were designed. Sudden starts and stops in operation, overheating of the parts, and even breaking of crank-shafts, were the results. The engines had gained somewhat in power, but no progress had been made in economy of consumption, although this was the very purpose of increasing the compression. High pressures render it possible to employ poor mixtures and still insure ignition. A quality of street-gas, for example, which yields one horse-power per hour with 17.5 cubic feet and a mixture of 1 part gas and 8 of air compressed to 78 pounds per square inch, will give the same power as 14 cubic feet of the same gas mixed with 12 parts of air and compressed to 171 pounds per square inch. "Scavenging" of the cylinder, a practice which engineers of modern ideas seem to consider of much importance, is better effected with high pressures, for the simple reason that the explosion-chamber, at the end of the return stroke, contains considerably less burnt gases when its volume is smaller in proportion to that of the cylinder. In impoverishing the mixture to meet the needs of high pressures, the explosive power is not increased and in practice hardly exceeds 365 to 427 pounds per square inch. With the higher pressures thus obtained there is consequently no reason for subjecting the moving parts to greater forces. [Illustration: FIG. 76.--Method of cooling the cylinder-head.] =Cooling.=--The increase in temperature of the cylinder-head and of the valves, due wholly to high compression, is perfectly counteracted by an arrangement which most designers seem to prefer, and which, as shown in the accompanying diagram (Fig. 76), consists in placing the mixture and exhaust-valves in a passage forming a kind of antechamber completely surrounded by water. The immediate vicinity of this water assures the perfect and equal cooling of the valve-seats. This arrangement, while it renders it possible to reduce the size of the explosion-chamber to a minimum, has the additional mechanical advantage of enabling the builder to bore the seats and valve-guides with the same tool, since they are all mounted on the same line. From the standpoint of efficiency, the design has the advantage of permitting the introduction of the explosive mixture without overheating it as it passes through the admission-valve, which obtains all the benefit of the cooling of the cylinder-head, literally surrounded as it is by water. In large engines the cooling effect is even heightened by separately supplying the jackets of the cylinder-head and of the cylinder. In engines of less power the top of the cylinder-head jacket is placed in communication with that of the cylinder, so that the coldest water enters at the base of the head and, after having there been heated, passes around the cylinder in order finally to emerge at the top toward the center. The water having been thus methodically circulated, the useful effect and regularity of the cooling process is increased. Notwithstanding the care which is devoted to water circulation, it is advisable to run the producer-gas engine "colder" than the older street-gas types, in which the more economic speed is that at which the water emerges from the jacket at about a temperature of 104 degrees F. It would seem advisable to meet the requirements of piston lubrication by reducing to a minimum the quantity of heat withdrawn by the circulating water. Indeed, the personal experiments of the author bear out this principle. For street-gas engines, however, the cylinders should be worked at the highest possible temperature consistent with the requirements of lubrication. It should not be forgotten that, in large engines fed with producer-gas, economy of consumption is a secondary consideration, because of the low quantity of fuel required. The cost, moreover, may well be sacrificed to that steadiness of operation which is of such great importance in large engines furnishing the power of factories; for in such engines sudden stops seriously affect the work to be performed. For this reason engine builders have been led to the construction of motors provided with very effective cooling apparatus. Since the circulation of the water around the explosion-chamber and the cylinder is not sufficient to counteract the rise of temperature, it has become the practice to cool separately each part likely to be subjected to heat. The seats of the exhaust-valves, the valves themselves, the piston, and sometimes the piston-rod, have been provided with water-jackets. =Premature Ignition.=--Returning to the causes of the discouragements encountered by some designers who endeavored to use high pressures, it has already been mentioned that premature ignition of the explosive mixture in cylinders not suited for high pressures is one reason for the bad results obtained. An explanation of these results is to be found in the high theoretical temperature corresponding with great pressures and in the quantity of heat which must be absorbed by the walls of the explosion-chamber. These two circumstances are in themselves sufficient to produce spontaneous ignition of excessively rich mixtures, compressed in an overheated chamber unprovided with a sufficient circulation of water. A third cause of premature ignition may also be found in the old system of ignition which, in most English engines, consists of a metallic or porcelain tube, the interior of which communicates with the explosion-chamber, an exterior flame being employed to heat the tube to incandescence. In tubes of this type which are not provided with a special ignition-valve, the time of ignition is dependent only on the moment when the explosive mixture, driven into the tube, comes into contact, at the end of the compression stroke, with the incandescent zone, thereby causing the ignition. This very empirical method leads either to an acceleration or retardation of the ignition, depending upon the temperature of the tube, the position of the red-hot zone, its dimensions, and the temperature of the mixture, which is determined by the load of the engine. Although this system, the only merit of which is its simplicity, may meet the requirements of small engines, there is not the slightest doubt that it is quite inapplicable to those of more than 20 to 25 horse-power, for in such engines greater certainty in operation is demanded. Even if only the more improved of the two types of hot-tube ignition be considered, with or without valves, it must still be held that they are inapplicable to high compression engines. The ignition-valve is the part which suffers most from the high temperature to which it is subjected. Its immediate proximity to the incandescent tube, and its contact with the burning gas when it flares up, render it almost impossible to employ any cooling arrangement. Although with the exercise of great care it may work satisfactorily in engines of normal pressure, it is evident that it cannot meet the requirements of high pressure engines, because the temperature of the compressed mixture is such that the charge is certain to catch fire by mere contact with the overheated valve. In industrial engines of small size, premature ignition has little, if any, effect except upon silent operation and economic consumption. This does not hold true, however, of large engines. Besides the inconveniences mentioned, there is also the danger of breaking the cranks or other moving parts. The inertia of these members is a matter of some concern, because of their weight and of the linear speed which they attain in large engines. Some idea of this may be obtained when it is considered that in a producer-gas or blast-furnace-gas engine having a piston diameter of 24 inches and an explosive pressure of 299 pounds per square inch, the force exerted at the moment of explosion is about 132,000 pounds. Naturally, engine builders have adopted the most certain means of avoiding premature ignition and its grave consequences. The method of ignition which at present seems to be preferred to any other for producer-gas is that employing a break-spark obtained with the magneto apparatus previously described. Some builders of large engines, particularly desirous of assuring steadiness of running, have provided the explosion-chamber with two independent igniters. It may be that they have adopted this arrangement largely for the purpose of avoiding the inconveniences resulting from a failure of one of the igniters, rather than for the purpose of igniting the mixture in several places so as to obtain a more uniform ignition and one better suited for the propagation of the flame. =The Governing of Engines.=--Various methods have been adopted for the purpose of varying the motive power of an engine between no load and full load, still preserving, however, a constant speed of rotation. These methods consist in changing either the quantity or the quality of the mixture admitted into the cylinder. Thus it may happen that an engine may be supplied: 1. With a mixture constant in quality and in quantity; 2. With a mixture variable in quality and constant in quantity; 3. With a mixture constant in quality and variable in quantity. 1. _Mixture Constant in Quality and Quantity._--This method implies the use of the hit-and-miss system of admission, in which the number of admissions and explosions varies, while the value or the composition of each admitted charge remains as constant as the compression itself (Fig. 34). This system has already been referred to and its simplicity fully set forth. By its use a comparatively low consumption is obtained, even when the engine is not running at full load. On the other hand, it has the disadvantage of necessitating the employment of heavy fly-wheel to preserve cyclic regularity. 2. _Mixture Variable in Quality and Constant in Quantity._--The governing system most commonly employed to obtain a mixture variable in quality and constant quantity is based upon the control of the gas-admission valve by means of a cam having a conical longitudinal section, as shown in Fig. 35. This cam, commonly called a "conical cam," is connected with a lever actuated from the governor. As the lever swings under the action of the governor, the cam is shifted along the half-speed shaft of the engine. The result is that the gas-admission valve is opened for a longer or shorter period. In another system a cylindrical valve is mounted between the chamber in which the mixture is formed and the gas-supply pipe, the valve being carried on the same stem as the mixture-valve itself. The cylindrical valve is displaced by the governor so as to vary the quantity of gas drawn in with relation to the quantity of air. When the engines are fed with producer-gas the parts which have just been described should be frequently inspected and cleaned; for they are only too easily fouled. Engines thus governed should be run at high pressure so as to insure the ignition of the producer-gas mixtures formed when the position of the cam corresponds with the minimum opening of the gas-valve. Powerful governors should be employed, capable of overcoming the resistance offered by the cylindrical valve or the cam. It may often happen that variations in the load of the engine render it necessary to actuate the air valve, so as to obtain a mixture which will be ignited and exploded under the best possible conditions. 3. _Mixture Constant in Quality and Variable in Quantity._--In supplying an engine with a mixture constant in quality and variable in quantity, the compression does not remain constant. The quantity of mixture drawn in by the cylinder may even be so far reduced that the pressure drops below the point at which ignition takes place. For that reason engines of this type should be run at high pressures. The variation of the quantity of mixture may be effected in various ways. The simplest arrangement consists in mounting a butterfly-valve in the mixture pipe, which valve is controlled by the governor and throttles the passage to a greater or lesser degree. A very striking solution of the problem consists in varying the opening of the mixture-valve itself. To attain this end the valve is moved by levers. The point of application of one of these levers is displaced under the action of the governor so as to vary the travel of the valve within predetermined limits. Under these conditions a mixture of constant homogeneity is introduced into the cylinder, so proportioned as to insure ignition even at low pressures. [Illustration: FIG. 76_a_.--Governing system for producer-gas engines.] In recent experiments conducted by the author it was proved that with this governing system ignition still takes place even though the pressure has dropped to 43 pounds per square inch. This system has the merit of rendering it possible to employ ordinary governors of moderate size, since the resistance to be overcome at the point of application of the lever is comparatively small. In the accompanying illustration the Otto Deutz system is illustrated. CHAPTER XI PRODUCER-GAS It may here be not amiss to point out the differences between illuminating gas and those gases which are called in English "producer" gases, and in French "poor" gases, because of their low calorific value. =Street-Gas.=--This gas, the composition of which varies with different localities, has a calorific value, which is a function of its composition, and which varies from 5,000 to 5,600 calories per cubic meter (19,841 to 24,896 B.T.U. per 35.31 cubic feet) measured at constant pressure and corrected to 0 degrees C. (32 degrees F.) at a pressure of 760 millimeters (29.9 inches of mercury, or atmospheric pressure), not including the latent heat of the water of condensation. The following table gives the average volumetric composition of illuminating gas in various cities: ____________________________________________________________________ | | Cities. |______________________________________________ | | | | | | | Manches- | New | | | London. | ter. | York. | Paris. | Berlin. _____________________|_________|__________|_______|________|________ | | | | | Hydrogen | 48 | 46 | 40 | 52 | 50 Carbon monoxide | 4 | 7 | 4 | 6 | 9 Methane | 38 | 35 | 37 | 32 | 33 Various hydrocarbons | 4 | 6 | 7 | 6 | 5 Carbon dioxide | | 4 | 3 | | 2 Nitrogen | 5 | 2 | 8 | 4 | 1 Oxygen | 1 | ... | 1 | ... | ... |_________|__________|_______|________|________ | | | | | | 100 | 100 | 100 | 100 | 100 _____________________|_________|__________|_______|________|________ Furthermore, these constituents vary within certain limits. This is also true of the calorific value. Experiments made by the author have demonstrated that in the same place at an interval of a few hours, variations of approximately ten per cent. occur. =Composition of Producer-Gases.=--The average chemical composition of producer-gases varies with the conditions under which they are generated and the nature of the fuel. The following are the proportions of its constituents expressed volumetrically: Table Headings-- A: Blast Furnace. B: Producer. C: Mond. D: Mixed (Fichet). E: Water (Stache). F: Wood (Riché). ________________________________________________________________________ | | Gas. |_________________________________________________ | | | | | | | A. | B. | C. | D. | E. | F. ______________________|_______|_______|_______|________|________|_______ | | | | | | Nitrogen and oxygen | 60 | 59 | 42 | 50 | 5 | 1 Carbon monoxide | 24 | 25 | 11 | 20 | 40 | 29 Carbon dioxide | 12 | 5 | 16 | 7 | 4 | 11 Hydrocarbons | 2 | 2 | 2 | 3 | 1 | 15 Hydrogen | 2 | 9 | 29 | 20 | 50 | 44 |_______|_______|_______|________|________|_______ | | | | | | | 100 | 100 | 100 | 100 | 100 | 100 |_______|_______|_______|________|________|_______ Calorific value | | | | | | in calories. | 950 | 1,100 | 1,400 | 1,300 | 2,400 | 2,960 Average weight of a | | | | | | cubic meter in kilos| 1.30 | 1.1 | 1.02 | 1.05 | 0.680 | 0.824 Or of a cubic foot | | | | | | in pounds | 0.008 | 0.007 | 0.006 | 0.0068 | 0.0042 | 0.0051 ______________________|_______|_______|_______|________|________|_______ Blast-furnace gas has been used for generating power by means of gas-engines for about ten years. At the present time it is used in engines of very high power, a discussion of which engines more properly belongs to a work on metallurgy, and has no place, therefore, in a manual such as this. Producer-gas, in the true sense of the term, is generated in special apparatus either under pressure or by suction in a manner to be described in the following chapters. Mond gas is produced in generators of the blowing or pressure type from bituminous coal, necessitating the employment of special purifiers and permitting the collection of the by-products of the fractional distillation of the coal. Mond gas plants are, therefore, rather complicated and can be advantageously utilized only for large engines. More exhaustive information can be obtained from the descriptions published by the builders of Mond gas generators. Mixed gas is generated in apparatus arranged so that the retort is kept at a high temperature, thereby producing a gas richer in hydrogen than that made by producers. It should be observed that in practice the generators at present used yield a producer-gas, the calorific value of which fluctuates between 1,000 and 1,400 calories per cubic meter (3,968 to 5,158 B.T.U. per 35.31 cubic feet); and the composition varies accordingly, in the manner that has already been indicated in the tables for producer-gas and mixed gas. There is no necessity, therefore, for drawing a distinction between these two qualities of gas. Water-gas should theoretically be composed of 50 per cent. carbon monoxide and 50 per cent. hydrogen, resulting from the decomposition of steam by incandescent coal. In practice, however, it contains a little nitrogen and carbon dioxide. The gas is obtained from generators in which air is alternately blown in to fan the fire and then steam to produce gas. Water-gas is employed in soldering on account of its reducing properties and of the high temperature of its flame. The great quantity of carbon monoxide which it contains renders it very poisonous and exceedingly dangerous, because it is generated under pressure. From the economical standpoint, its generation is more expensive than that of producer-gas, for which reason its employment in gas-engines is hardly of much value. Wood-gas, the composition of which has already been given, is generated in apparatus of the Riché type, the principle of which consists in heating a cast retort charged with any kind of fuel, namely wood, and vertically mounted on a masonry base. This apparatus should be of particular interest to the proprietors of sawmills, furniture factories, and the like, since it offers a means of using the waste products of their plants. The relatively high proportion of carbon monoxide in producer-gas is objectionable from a hygienic standpoint, so much so, indeed, that it has attracted the attention of manufacturers. Carbon monoxide, the specific gravity of which is 0.967, is a gas peculiarly poisonous and dangerous. It cannot be breathed without baneful effects, and is even more dangerous than carbonic-acid gas, which eventually causes asphyxiation by reducing the quantity of oxygen in the air. For this reason, it is necessary to take the utmost precaution in efficiently and continuously ventilating the rooms in which the gas-generators and their accessories are installed. This suggestion should be followed, above all, when the apparatus in question are installed in cellars and basements. As a further precaution, where the plant is rather large a workman should not be allowed to enter the generator room alone. Blowing-generators, or those in which the gas is produced under pressure, are more dangerous than suction-generators. In the former a leaky joint may cause the vitiation of the surrounding air as the producer-gas escapes; in the suction apparatus the same fault simply causes more air to be drawn in. Dr. Melotte recommends the following procedure in cases of carbon monoxide asphyxiation: CARBON MONOXIDE ASPHYXIATION Cases of poisoning by carbon monoxide are both frequent and dangerous. The gas is extremely poisonous, and all the more dangerous because it is odorless, colorless and tasteless. When it comes into contact with the blood, it forms a combination so stable that it is reacted upon by the oxygen of the air only with difficulty. It follows, therefore, that with each respiration of air charged with carbon monoxide, a certain quantity of blood is poisoned. In consequence of this, there is a possibility of poisoning in open air. =Symptoms.=--The symptoms observed will vary with the manner in which the blood has been poisoned. There are two ways in which this poisoning can occur. The one depends upon whether the atmosphere contains an excess of carbon monoxide; the other whether the air breathed contains only traces of the gas. =Gradual, Rapid Asphyxiation.=--At first a vague sickness is felt, rapidly followed by violent headaches, vertigo, anxiety, oppression, dimness of vision, beating of the pulse at the temples, hallucinations, and an irresistible desire to sleep. If at this stage the patient has a sufficient idea of danger to prompt him to open a window or door, he will escape death. In the second stage, the victim's legs are paralyzed, but he can still move his arms and his head. The mind still preserves its clearness, and in a measure assists the further process of asphyxiation because of its impotency. Then follow coma and death. =Slow, Chronic Asphyxiation.=--Slow, chronic asphyxiation is not infrequent. Its symptoms are often difficult to detect. Poisoning is manifested by weakness, cephalalgia, vomiting, pallor, general anemia, lassitude, and local paralysis. If any of these symptoms appear in the men who work in the vicinity of the producers, immediate steps should be taken to prevent the possibility of carbon monoxide asphyxiation. FIRST AID IN CASES OF CARBON MONOXIDE POISONING It has already been stated that the oxygen of the air has no oxidizing effect upon blood contaminated by carbon monoxide. Only a liberal current of pure oxygen can oxidize the combination formed and render hematosis possible. This liberal current can be obtained from an oxygen tank of the portable variety, provided with a tube carrying at its free end a mask which is held over the mouth and the nostrils. The absorption of gas takes place by artificial respiration, which is effected in several ways. The most practical of these are the Sylvester and Pacini methods. =Sylvester Method.=--The patient is laid on his back. His arms are raised over his head and then brought back on each side of the body. This operation is repeated fifteen times per minute approximately. The method is very frequently employed and is excellent in its results. =The Pacini Method.=--Four fingers are placed in the pit of the arm, with the thumb on the shoulder. The shoulder is then alternately raised and lowered, producing a marked expansion of the chest. This method is the more effective of the two. The movements described are repeated fifteen to twenty times each minute very rhythmically. One or the other of these two methods of treatment should be immediately applied in serious cases. Certain preliminary precautions should be taken in all cases, however. The patient should be carried to a well-ventilated and moderately heated room, stripped of his clothes, and warmed by water-bottles and heated linen. Reflex action should be excited, the peripheral nervous system stimulated in order to contract the heart and the respiratory muscles, and the precordial region cauterized. In addition to this treatment, the region of the diaphragm should be rubbed and pinched, the skin rubbed, cold showers given, flagellations administered, urtications (whipping with nettles) undertaken, the skin and the mucous membranes excited, the mucous membrane of the nose and of the pharynx titillated with a feather dipped in ammonia, alcohol, vinegar, or lemon juice. Rhythmic traction of the tongue is effective when carried out as follows: The tongue is seized with a forceps and kept extended by means of a coarse thread. It is then pulled out from the mouth sharply and allowed to reenter after each traction. These movements should be rhythmic and should be repeated fifteen to twenty times a minute. All these efforts should be continued for several hours. When the patient has finally been revived, he should be placed in a warm bed. Stimulants such as wine, coffee, and the like should be administered. If the head should be congested, local blood-letting should be resorted to and four or six leeches applied behind the ears. It should be borne in mind that the various steps enumerated are to be taken pending the arrival of a physician. IMPURITIES OF THE GASES Most of the coal used in generating producer-gas contains sulphur. Sulphuretted hydrogen is thus produced, which mixes with the gas and imparts to it its characteristic odor. In some gas-generators, purifiers are employed in which sawdust mixed with iron salts is utilized, with the result that a combination is formed with the sulphuretted hydrogen, thereby removing it from the producer-gas. In other forms of generators a more summary method of purification is adopted, so that traces of sulphuretted hydrogen still remain. Since this gas attacks copper, the employment of this metal is not advisable for the following apparatus: Generator (openings, cock for testing the gas); piping (gas-pressure cocks, drain and pet cocks); engine (gas-admission cock, lubricating joint in the cylinder, valves and cocks of the compressed-air starting-pipe). The distillation of coal in generators results in the formation of ammonia gas. This also has a corrosive action on copper and its alloys; but owing to its great solubility, it is eliminated by the waters of the "scrubber" and does not reach the engine. PRODUCTION AND CONSUMPTION The quantity of gas produced in most generators varies from 6.4 to 8.2 pounds per cubic foot of raw coal burnt in the generator. The engine consumes per horse-power per hour 70 to 115 cubic feet of gas, depending upon its richness. CHAPTER XII PRESSURE GAS-PRODUCERS As we have already seen, producer-gas as a fuel for engines may be generated in two kinds of apparatus, the one operating under pressure, and the other by suction. =Dowson Gas-Producers.=--The first pressure-generators were introduced by Dowson of London and necessitated installations of quite a complicated nature. Later improvements made by the designers contributed much to the general employment of their system. Many installations varying from 50 to 100 horsepower and more may be found in the United Kingdom, all of them made by Dowson. Indeed, for a long time the name of Dowson was coupled with producer-gas itself. The Dowson system necessitates the utilization of anthracite or of comparatively hard coal, such as that mined in Wales and Pennsylvania. Owing to the necessity of employing this special quality of coal the Dowson system and the systems that sprang from it were burdened with cooling, washing, and purifying apparatus, which complicated the installations to such an extent that they resembled gas works. The generator that took the place of the retort was fed with air and steam, blown in under pressure, necessitating the employment of a boiler. Furthermore, the production of the gas under pressure necessitated the use of a gasometer for its collection before it was supplied to the engine-cylinder. Such Installations were evidently costly, and were, moreover, difficult to maintain in proper working order. Nevertheless, there are many cases in which they must be industrially employed. [Illustration: FIG. 77.--A complete Dowson producer-gas plant.] [Illustration: FIG. 78.--A Simplex producer-gas plant.] Among these may be cited works in which producer-gas is employed as a furnace fuel or as a soldering or roasting medium. Still other cases are those in which the producer-gas must be piped to some distance from a central generating installation to various engines, in the manner rendered familiar in gas-lighting practice. Most pressure gas-generators have been copied from the original type invented by Dowson. These include a generator in which the gas is produced; an injector fed by a boiler; a fan or a compressor by means of which a mixture of steam and air is blown under the generator-furnace; washing apparatus termed "scrubbers"; gas-purifying apparatus; and a gas-holder (Fig. 77). =Generators.=--The generator consists of a retort made of refractory clay, vertically mounted, and cylindrical or conical in form. This retort is protected on its exterior by a metal jacket with an intermediate layer of sand which serves to reduce the heat lost by radiation. The fuel is charged through the top of the retort, which is provided with a double closure in order to prevent the entrance of air during the charging operation. The generator rests on a grid arranged at the base of the retort, upon which grid the ashes fall. The outlet of the injector-pipe opens into the ash-pit, and this injector constantly supplies a mixture of steam and air. The mixture is generally superheated by passing it through a coil arranged in the fire-box of the boiler, in the generator, or in the outlet for burnt gases. Sometimes the air is subjected to a preliminary heating by recuperating in some way the waste heat of the apparatus. The chief features in the arrangement of generators which have received the attention of manufacturers are the following: Good distribution of the fuel in charging; easy descent of the fuel; reduction of the destructive action of the clinkers on the walls; means for cleaning the grate without interfering with the generation of gas; prevention of leakage. Many devices have been employed to fulfil these requisites. A perfect distribution of the fuel during charging is attained chiefly by the form of the hopper, and of its gate, which is generally conical. In most apparatus the gate opens toward the interior of the generator, and the inclination of its walls causes a uniform scattering of the fuel in the retort. It is all the more necessary to disperse the fuel in this manner when the cross-section of the retort is small compared with its height. _The facility of the fuel's_ descent is dependent largely upon the nature and the size of the coal employed. Porous coal gives better results than dense and compact coal. It is therefore preferable to employ screened coal free from dust in pieces each the size of a hazel-nut. The various sections given to the interior, including as they do cylindrical forms, truncated at the summit or the base, partially truncated toward the base and the like, would lead to the conclusion that this question is not of the importance which some writers would have us believe. Still, it must be considered that if the fuel drops slowly, its prolonged detention within the walls of the hopper and its transformation into fusible slag may result in a disintegration of the refractory lining of the furnace. The quantity of steam injected, greater or less, according to the nature of the fuel, renders it possible to obtain friable slags and consequently to prevent grave injury to the retort. Red-ash coal is in general fusible, containing as it does some iron. Its temperature of fusion varies between 1,832 to 2,732 degrees F. _Cleanliness_ is most important so far as the operation of the generator is concerned. It should be possible to scrape the generator during operation without changing the composition of the gas, when the incandescent zone is chilled, or an excess of air is introduced, or the steam-injector be momentarily thrown out of operation. Mechanical cleaners with movable grates or revolving beds have the merit of causing the ashes to drop without interfering with the operation of the apparatus. The same meritorious feature is characteristic of ash-pits having water-sealed joints. Pressure gas-generators need not be as perfectly gas-tight as suction apparatus. Leakage of gas, which is usually manifested by a characteristic odor, results in a loss of consumption and renders the air unfit to breathe. A generator should be provided in its upper part with openings through which a poker can easily be introduced in order to shake up the fuel and to dislodge the clinkers which tend to form and which cause the principal defects in operation, particularly with fuels that tend to swell, cake, and adhere to the furnace walls when heated. Many apparatus, moreover, are provided with lateral openings having mica panes through which the progress of combustion can be observed (Fig. 79). [Illustration: FIG. 79.--Fichet-Heurtey producer with rotating bed-plate.] =Air-Blast.=--The system by which air and steam are injected necessitates the employment of a steam-boiler of 75 pounds pressure. This method of blowing, which is rather complicated, has the disadvantage of varying in feed with the pressure of the steam in the boiler, which pressure is not easily maintained at a given number of pounds per square inch. Moreover, when more or less resistance is offered by the fuel in the generator the quantity of air which is injected is likely to be diminished in quantity while the quantity of steam remains the same. The result is a change in speed which follows from the modification of the proportions of the two elements. For these reasons some manufacturers have resorted of late years to the employment of fans and blowers. [Illustration: FIG. 80.--Koerting blower.] =Blowers.=--The fans or blowers employed vary considerably in arrangement. Most of them are based on the Koerting system (Fig. 80), and comprise essentially (1) a tube through which the steam is supplied under pressure, and (2) a cylindro-conical blast-pipe. The tube is placed in the axis of the blast-pipe at its outer opening. As it escapes under pressure the steam is caught in the blast-pipe and draws with it a certain quantity of air, which can be regulated. It is important that these injection blowers should operate in such a manner that the pressure and the feed of air and steam can be controlled. =Fans.=--Mechanical blowers have the advantage of dispensing with the employment of steam under pressure and the consequent installation of a boiler (Fig. 78). Driven by the engine itself or from some separate source of power, these apparatus are easily placed in position, require no great amount of attention, and utilize but little energy. They are either of the centrifugal type or of the rotary type, exemplified in the Root blower (Fig. 81). The latter system has the advantage of high efficiency, and of enabling comparatively high pressures--19 to 27 inches of water--to be attained, which, however, are used only for special fuels, such as lignite, peat, and the like. The air supplied by the blower, before reaching the fire-box, is superheated, either before or after it is charged with steam. [Illustration: FIG. 81.--Root blower.] =Compressors.=--In some installations air is supplied by compressor under the high pressure of 70 to 90 pounds per square inch, and seem well adapted to the production of a gas of good quality. Moreover, neither tar nor ammoniacal waters are produced. The Gardie producer may be considered typical of this class of apparatus (Fig. 82). The chief feature of this producer is to be found in simple washing and purifying apparatus. It may be well to state here that the compression of air at high pressure occasions some complications, and a considerable expenditure of power. [Illustration: FIG. 82.--Gardie producer.] =Exhausters.=--Some designers have invented devices which draw gas into the generator whence it is supplied to the engines, these suction apparatus being connected with the blowers or used separately. But with the exception of a few special instances, such arrangements are not widely used--at least not for the production of motive power alone. Whatever may be the arrangement employed for the introduction of a mixture of air and steam under the grate of the generator, the blast-pipe as a general rule discharges toward the center of the apparatus. Still, in large producers it becomes desirable to provide a means for varying the quantity of air and steam within wide limits so as to regulate the heat of the fire. For that reason several outlets are symmetrically arranged below the fuel. [Illustration: FIG. 83.--Sawdust purifier.] =Washing and Purifying.=--In pressure producers the gas is generally washed and purified with much more care than in suction apparatus. Given a sufficient pressure, the gas can be driven through the different apparatus and the spaces between the material which they contain without any difficulty. The gases emerge from the generator highly heated, and this heat is used either to warm the injection water or to generate the steam fed to the furnace. The gases then enter the washing apparatus, which most frequently consists of a succession of contrivances in which the gas is washed either by causing it to bubble up through the water, or by subjecting it to superficial friction against a sheet of water, or by systematically circulating it in a mass of continuously besprinkled inert material. The object of washing is to remove the dust contained in the gas and to precipitate it in the form of a slime which can be removed by flushing. [Illustration: FIG. 84.--Moss or fiber purifier.] Physical purification thus begun is completed by passing the gas through a filtering bed consisting of fiber, sawdust, or moss (Figs. 83 and 84). Chemical purification if it is necessary, is effected by means of calcium hydrate, iron oxide, or, still better, by a mixture of lime and iron sulphate. This filtering material must necessarily be renewed after it is exhausted. [Illustration: FIG. 85.--Combined gas-holder and washer.] =Gas-Holder.=--The gas-holder is composed essentially of a tank and a bell. Sometimes, for the purpose of simplifying the apparatus, the tank is so arranged as to take the place of a washer or scrubber (Fig. 85). The bell should be provided with mechanism which, when the bell is full, automatically diminishes or stops the generation of gas. It is advisable to provide the bell with a blow or flap valve opening toward the interior. If, therefore, it should happen that the gas supply is cut off while the engine still continues to run, the suction of the engine will not draw the water from the tank of the gas-holder. When engines are employed the horse-power of which does not exceed 50, it is sometimes customary to use the water of the tank (placed at a higher elevation than the engine) to cool the cylinder. In this manner the cost of installing special reservoirs is saved. If such an arrangement be employed, however, the quantity of water contained in the tank should be at least double that ordinarily contained in reservoirs. If this precaution be not observed, the water may become excessively heated and expand the gas in the bell. The volume of the bell of the gas-holder should preferably be not less than about 3 cubic feet per effective horse-power of the engine to be supplied. Under these circumstances the bell acts as a pressure-regulator, assures a sufficient homogeneity of the remaining gas, and renders it possible to supply the engine during the short intervals in which it is necessary to stop the blast to poke the fire. But if the engine consumes 60 to 80 cubic feet of producer-gas per horse-power per hour, the bell must be very much larger in size if the generation of gas is to be checked for some time. It may be well to recall here that coal is not the only fuel which lends itself to the generation of gas suitable for driving engines, but that some generators are able to utilize lignite, peat, and the like. In others, straw, wood, shavings and sawdust, tannery waste, and other organic matter is burnt with an efficiency very much higher than that which they would give in the fireboxes of steam-boilers. [Illustration: FIG. 86.--Otto Deutz lignite-producer.] =Lignite and Peat Producers.=--Lignite and peat generators (Fig. 86) cannot operate on the suction principle because of the resistance offered to the passage of gas by the layer of fuel. This resistance is considerable and extremely variable. Consequently, lignite and peat generators must operate on the pressure principle by utilizing a blast of air or a steam injector, depending upon the amount of water contained in the lignite. As a general rule a Root blower operating at a pressure of 8 to 27 inches of water, depending upon the quality of the lignite, is employed. These generators are not to be recommended for powers less than 50 horse-power, for the cost of the apparatus becomes too great. The best lignite is that which, after combustion, leaves a fine ash and no agglomerated clinker. Lignite has the peculiarity of forming dust which ignites very easily when air is admitted into the generator. For this reason the generator should not be scraped during operation, in order to avoid the production of a flame which may escape from the apparatus. The scrubber is simply a column without coke, and is provided with an interior sprinkler. The coke is too rapidly clogged with tar. Much of this tar is deposited in a chamber which precedes the gas-holder. Several quarts of tar may be tapped from the chamber daily. The gas-holder serves merely to regulate the production of gas. The pipes leading to the engine should be cleaned several times each month, in order to remove the thin layer of tar which is deposited within them. There are many kinds of lignite, and the gas-generator should be constructed to meet the peculiar requirements of the variety employed. The layer of fuel should be such in thickness that the gas as it emerges from the generator has a temperature of about 77 degrees F. This is the temperature of the gas which leaves the scrubber in the case of anthracite-generators. If the lignite contains much water, the greater part is retained in the washer by the gas in the form of drops. Sometimes the water drips through the grate of the generator. Lignite-generators may also be operated with peat, and even with town refuse, with slight modifications. The consumption per horse-power per hour is 3.3 pounds of lignite containing 2,400 calories (9,424.9 B.T.U.). In order to generate the same power with a boiler and steam-engine, 8.8 pounds would be required. An engine driven unloaded with fuel furnished by a lignite-generator will consume 50 per cent. of the weight of the fuel required at full load. This depends upon the proportion of water contained in the lignite and on losses of heat by radiation from the generator. In street-gas engines running without load, the absorption is 20 per cent., in anthracite-generators 40 per cent. of the consumption at full load. Passing now to the utilization of wood, of which something has already been said in Chapter XI, two entirely distinct processes are successfully employed in apparatus of the Riché type, these processes depending upon the form of the wood used--whether, in other words, the wood be consumed in the form of sticks or blocks or in the form of chips, sawdust, bark, and the like, all of them the wastes of factories in which wood is used. =Distilling-Producers.=--If the wood consists of logs, it is burnt in a generator comprising a fire-box and a distilling retort. The fire-box is charged with ordinary coal which serves to heat the retort to redness. The wood is discharged through the top of the retort, and the gas, produced by the distillation, escapes through the bottom and passes to the washing apparatus. The base of the retort is heated to about 1,652 degrees F., while at the top this temperature is reduced to 752 degrees F. The wood thus treated is transformed into charcoal, which is a by-product of some value. [Illustration: FIG. 87.--Riché distilling-producer.] The lower part of this cast retort (Fig. 87) is lined with charcoal, the residue of previous distillations. The wood which is introduced in the upper part of the retort is distilled in the chamber. The retort is held by its own weight in a socket on the foot, which socket is lined with a special refractory cement, made of silicate, asbestos forming the joint. The products of combustion, issuing from the furnace, pass by way of the flue to the lower part of the casing, and raise the temperature of the retort and the charcoal it contains to that of a cherry red (1,652 degrees F.). These products of combustion then float to the upper part of the casing and heat the top of the retort to a temperature of about 752 degrees F., in which part the wood or the wooden waste to be distilled is enclosed. Thence the products of combustion pass through a horizontal flue, provided with a damper, into a collecting flue by which they are led to the smoke-stack. The products of distillation formed in the chamber, having no outlet at the top of the retort, must traverse the zone filled with incandescent carbon. The condensible products are conducted as permanent gases (carbonic-acid gas in the state of carbon monoxide) and are collected in the receptacle, after having passed the funnel and the bell of the purifying apparatus. A gas-furnace is formed by grouping in a single mass of masonry a certain number of elements of the kind just described. It is essential that the retorts should be vertically placed, that they be made only of cast metal and not of refractory clay, and, finally, that their diameter be not much more than 10 inches, which size has been found most expedient in practice. The gas collected in the bell or in one or more of the receptacles passes into the gasometer and then into the service pipes. If 2.2 pounds of wood be distilled by burning in the furnace 8/9 of a pound of coal of average quality or 2.2 pounds of wood (either sawdust or waste), 24.5 to 28 cubic feet of gas will be generated having a thermal value of 3,000 to 3,300 calories per cubic meter (11,904 to 13,094 B.T.U. per 35.31 cubic feet), and a residue 44 pounds of charcoal will be left. In practice only the wood of commerce containing in the green state 20 to 40 per cent. of water, depending upon the variety, is used. Hornbeam contains the least water (18 per cent.), while elmwood and spruce contain the most (44 to 45 per cent.). The blast apparatus of the generator being started, the gas is supplied under pressure. By reason of its permanent composition and its richness, it is an excellent substitute for street-gas in incandescent lighting, a good furnace fuel reducing agent. _Producers Using Wood Waste, Sawdust, and the Like._--If waste wood in the form of shavings, sawdust, straw, bark, and the like, should be employed, a still higher efficiency is obtained with self-reducing generators of the Riché type. _Combustion-Generators._--In combustion-generators (Fig. 88) the fuel is burnt and not distilled. The generator comprises two distinct elements. The first is the generator proper, in which the combustion takes place. Upon it is placed a hopper or fuel supply box. The Second element is the reducer, in which by an independent process the reduction of the carbonic-acid gas, the dissociation of the steam, and the transformation of the hydrocarbons takes place. The generator is provided at its base with a grate having oblique bars in tiers, which grate is furnished with a channel in which the water for the generation of hydrogen flows. On a level with this grate, at the opposite side, is a flue communicating with the reduction column of coke. The incandescent zone of the generator should not extend above the level of the grate. Instead of passing through the layers of fresh fuel and out by way of the top, the gas generated flows directly into the reduction column where it heats the coke to incandescence. The high temperature to which the coke is subjected, coupled with the injection of air, effects useful reactions. This additional air, however, is not used if the fuel is free from all products of distillation. [Illustration: FIG. 88.--Riché combustion-producer.] Experience has shown that gas of 1,000 to 1100 calories per cubic meter (3,968 to 4,365 B.T.U. per 35.31 cubic feet), which heat content is necessary to develop one horse-power per hour, can be obtained with 3.96 pounds of wood in the form of shavings and sawdust containing 30 per cent. of water. The corresponding quantity of coke consumed in the reduction column is insignificant, and may be placed at about 0.112 pounds per horse-power per hour. It has been proven in actual practice that, both in the distilling and combustion types of apparatus, the wood, either in the green state or in the form of saw-mill waste, may contain as much as 60 per cent. of water. Either of the two systems can be operated under pressure with an air-blast, in which case a gas-holder and bell must be employed. The gas as it passes from the generator to the gas-holder is conducted through a cooler and washer and through a moss filter, which removes traces of the products that may have escaped the distillation. =Inverted Combustion.=--With a few exceptions the pressure-generators which have been described, as well as suction gas-producers which will be later discussed, are fed with anthracite coal or with coke. They cannot be operated with moderately soft or bituminous coal. For this reason they limit the employment of producer-gas engines. Manufacturers have long sought generators in which any fuel whatever can be consumed. Among the producers which seem to overcome the objections cited to a certain degree, are those which are based on the principle of inverted combustion. These apparatus embody the ideas of Ebelmen, the products of distillation being decomposed by passing them over layers of incandescent fuel. [Illustration: FIG. 89.--Deschamps inverted-combustion producer.] Many writers place in the class of inverted combustion producers, apparatus of the Riché, Thwaite, and Duff type, in which this idea is also carried out. Riché employs an independent incandescent mass to reduce the products of distillation of another mass. Thwaite employs two vessels which serve alternately as distilling retorts and reducing columns. Duff draws in the products of distillation for the purpose of blowing them under the fire. All these generators can hardly be said to be of the inverted combustion type. [Illustration: FIG. 90.--Fangé-Chavanon inverted-combustion producer.] The generators of Deschamps (Fig. 89) and of Fangé and Chavanon (Fig. 90), on the other hand, are producers in which the combustion is really inverted, and which are worked continuously. The air enters at the upper part of the retort, passes through the entire mass of fuel, carrying with it the distilled volatile products, and when the mixture reaches the incandescent zone, chemical reactions occur that result in the production of a gas entirely free from tar and other impurities. CHAPTER XIII SUCTION GAS-PRODUCERS The high cost and the complicated nature of the pressure gas-generators which have just been discussed have led manufacturers to attempt in some other way the generation of producer-gas intended for operating motors. Several inventors, among whom we will mention Bénier and A. Taylor (in France), made some praiseworthy although not immediately very successful attempts to simplify the manufacture of producer-gas. =Advantages.=--In these systems the suction occasioned by the motor itself has taken the place of a forced draft, produced in the generator by an air-injector or a fan, so that the gas, instead of being stored under pressure in a gas-holder, is kept in the apparatus under a pressure below that of the atmosphere. As the device for producing a draft by means of boiler pressure or of a fan, and the gas-holder, are dispensed with, the result is a saving, first in the cost of installation, consumption, and floor space. Furthermore, the cooler and washer are supplanted by a single scrubber. Manufacturers have succeeded in devising apparatus remarkable for the simplicity of the processes employed and yielding economical results which would never be obtained with pressure-generators employing gas-holders and boilers, considering that the boiler alone calls for a consumption of from 15 to 30 per cent. of the total amount of coal used for making the gas. The best results obtained by the author with pressure gas-producers have indicated a consumption of not much less than 1 to 1-1/4 pounds of anthracite per horse-power per hour at the motor, while with suction-generators, under similar conditions and with the same grade of fuel, he has repeatedly found a consumption of from 9/10 pounds per effective horse-power per hour. In either case, the gas obtained developed between 1,100 and 1,300 calories (4,365 and 5,158 B.T.U. per 35.31 cubic feet) if produced from anthracite yielding from 7,500 to 8,000 calories (29,763 to 31,746 B.T.U.) per 2.2 pounds. The suction apparatus will also work very well with inferior coal containing up to 6 to 8 per cent. of volatile matter and from 8 to 10 per cent. of ash. This great advantage added to all the others explains the favorable reception which European manufacturers at once gave to suction-producers. The petroleum engine itself will find a serious competitor in the new system. As regards the possibility of employing suction gas generators with respect to the somewhat peculiar properties of the fuel, it may be said at the outset that coke from gas works yielding from 6,000 to 6,500 calories (22,911 to 24,995 B.T.U.) and also charcoal are perfectly available. One horse-power per hour is obtained with a consumption of 1.1 to 1.3 pounds of coke. Blast-furnace coke may be used in case of need, but its employment is not to be recommended on account of the sulphides it contains, which sulphides, being carried along by the gas, are liable to form sulphuric acid with the steam, the corrosive action of which would soon destroy the cylinder and other important parts of the engine. =Qualities of Fuel.=--Anthracite coal is, upon the whole, so far the best available fuel for generators. However, it should possess certain qualities which will now be briefly indicated. In suction gas-generators, above all, it is important that no harmful resistance should be opposed to the passage of the air and of the gas produced. It is therefore necessary to employ coal of a size that will answer the foregoing condition, without being too expensive. The size of the pieces, to a certain extent, determines the price; and with coal of the same properties, pieces 1.1 to 2 inches may cost 1.4 of the price for the ordinary size of 0.59 to 0.98 inches, which is very well adapted for gas-generators. This is the size of a hazel-nut. Moreover, it will be advisable to select the dryest coals, containing a minimum of volatile matter and having no tendency to coke or to cohere, in order that the volatilized products may not by distillation obstruct the interstices through which the gases must pass. For the same reason coal which breaks up and becomes pulverized under the action of the fire is not to be recommended. The coal should also be such as to avoid the formation of arches which would interfere with the proper settling of the fuel during its combustion. It may be stated as a rule that, with coal that does not cohere, the content of volatile matter should not exceed 5 to 8 per cent. Coal which contains more than 10 to 15 per cent. of ash should not be used, for the reason that it chokes up and obstructs generators in which the dropping and discharge of the ashes is done automatically, a fact which should not pass unnoticed. The furnace cannot be cleaned safely with a fire of this kind, where combustion takes place in an enclosed space, without hindering the production of gas. Here again a point may be raised very much in favor of suction gas-producers. In a good generator, the ash-pit can be cleaned and the fire stoked without interrupting the liberation of the gas drawn in and without appreciably impairing the quality of the gas. These considerations are of importance so far as the gas-generator itself is concerned. Other conditions which should be noticed affect the engine fed by the generator, the grade of coal used, and the purification of the gas obtained from it. Unless special chemical cleaners and purifiers are employed, thereby complicating the plant, the coal utilized should yield as little tar as possible during distillation; for the tendency of the tar to choke up the pipes and to clog the valves is one of the chief causes of defective operation of producer-gas engines. Tar changes the proper composition of the explosive mixture. When it catches fire in the cylinder it causes premature ignition, which is so dangerous in large engines. From what has been said in the foregoing, it follows that, in the present state of the art, the satisfactory operation of gas-generators depends no longer on the use of pure anthracite, such as Pennsylvania coal in America and Welsh coal in England, containing an amount of carbon as high as 90 to 94 per cent. and having a thermal value of 33,529 B.T.U. On the contrary, good dry coal yielding from 29,763 to 31,746 B.T.U. is quite suitable for the generation of producer-gas. A final, practical advantage which speaks in favor of a generator and motor plant as compared with a steam-engine, is the small amount of water required. Apart from the water used for cooling the engine, which may be used over and over again if cooled, any water, whether it forms scale or deposits, may be employed for cooling and washing the gas in the scrubber. According to the author's personal experience, an average of 3.3 gallons of water per effective horse-power per hour is sufficient for this purpose. This is about one-half of the amount required by a non-condensing slide-valve engine of from 15 to 30 horse-power. The difference in the consumption of water is quite important in city plants, where water is rather expensive as a rule. =General Arrangement.=--A suction gas-generator plant of the character we have been discussing is shown in Fig. 91. [Illustration: FIG. 91.--Engine and suction gas-producer.] The apparatus _A_ is the generator proper, in which combustion takes place. The gas produced passes into the apparatus _B_ through a series of tubes, to be conveyed to the washer _C_. In the apparatus _B_, which is the vaporizer, the water admitted at the top under atmospheric pressure is vaporized by contact with a series of tubes, heated by the gas coming from the generator. The steam, together with air, is drawn into the lower part of the generator to support combustion. This vaporizer is provided with an overflow for the outlet of the water which has not been vaporized. The producer-gas pipe which leads from the vaporizer to the washer has a branch _D_, for the temporary escape to the atmosphere of the gas produced before and after the operation of the engine. In the washer, as the drawing shows, the gas enters at the bottom and leaves at the top to pass to the gas expansion-chamber _E_ and thence to the motor. The gas thus passes through the body of coke in the opposite direction to the wash water, which then flows to the waste-pipe. The coke and the water free the gas not only from the dust carried along, but from the ammonia and other impurities contained in the gas. When firing the generator, a small hand ventilator _G_ is used for blowing in air to fan the fire. The gas obtained at first, being unsuitable for combustion, is allowed to escape through the branch _D_. After injecting air for about 10 to 15 minutes, the engine can be started after closing the branch _D_. The suction of the engine itself will then gradually bring about the proper conditions for its regular running, and after a quarter of an hour or half an hour the gas is rich enough to run the engine under a full load. The apparatus just described is the original type, upon which many improvements have been made for the purpose of securing a uniform gas production and of diminishing the interval of time elapsing between the firing of the generator and the running of the engine under a full load. Each of the elements of this apparatus--to wit, the generator, vaporizer, super-heater, and washer--have been modified and improved more or less successfully by the manufacturers; and in order that the reader may perceive the merits and the drawbacks of the various arrangements adopted, the most important ones will be separately discussed. =Generator.=--With respect to the general arrangement of parts, generators may be divided into two classes: First.--Generators with internal vaporizers, such as the Otto Deutz and Wiedenfeld generators. [Illustration: FIG. 92.--Old type of Winterthur producer.] Second.--Generators with external vaporizers, such as the Taylor, Bollinckx, Pintsch, Kinderlen, Benz, Wiedenfeld, Hille, and Goebels generators. =Cylindrical Body.=--The generator consists essentially of a mantle made of sheet-iron or cast-iron and containing a refractory lining which forms a retort, a grate, and an ash-pit. In the small size apparatus the cast-iron mantle is often used, whereas in large sizes the mantle is made of riveted sheet-iron so as to reduce its weight and its cost. In the latter case the linings are securely riveted or bolted. The Winterthur generator (Figs. 92 and 93), the Taylor generator (Fig. 94), and the Benz generator (Fig. 97), are made of cast-iron; the Wiedenfeld generator (Fig. 95), the Pintsch generator (Fig. 96), are made of sheet-iron; the Bollinckx (Fig. 98) is made partly of sheet-iron and partly of cast-iron. The different parts of a generator, if made of sheet-iron, are held together by means of angle-irons forming yokes, and a sheet of asbestos is interposed. If the parts are made of cast-iron, they are connected after the manner of pipe-joints and packed with compressed asbestos. This latter way of assembling the parts presents the advantage of allowing them to be dismembered readily. Therefore, it allows the several parts to expand freely and facilitates the securing of tight joints. This last consideration is exceedingly important, particularly for the joints which are beyond the zone in which the distillation of the fuel takes place. Any entrance of air through these joints would necessarily impair the quality of the gas, either by mingling therewith, or by combustion. The air so admitted would also be liable to form an explosive mixture which might become ignited in case of a premature ignition of the cylinder charge during suction or through some other cause. [Illustration: FIG. 93.--New type of Winterthur producer.] [Illustration: FIG. 94.--The A. Taylor producer.] [Illustration: FIG. 95.--Wiedenfeld producer.] [Illustration: FIG. 96.--Pintsch producer.] [Illustration: FIG. 97.--Benz producer.] [Illustration: FIG. 98.--Bollinckx producer.] [Illustration: FIG. 99.--Lencauchez producer.] =Refractory Lining.=--The interior lining of the generator should be made of refractory clay of the best quality. It would seem advisable, in order to facilitate repairs, to employ retorts made of pieces held together instead of retorts made of a single piece. In the first case the assembling should preferably be made by means of refractory cement, and the inner surface should be covered with a coating so as to form a practically continuous stone surface. [Illustration: FIG. 100.--Goebels producer.] Some manufacturers, in order to allow for the renewal of the part most liable to be burnt, employ at the bottom of the tank a refractory moulded ring (Lencauchez, Fig. 99). It is always advisable to place between the shell or mantle of the generator and the refractory lining a layer of a material which is a bad conductor of heat as, for instance, asbestos or sand, in order to avoid as much as possible loss of heat due to external radiation (Fig. 100). [Illustration: FIG. 101.--Pierson producer.] =Grate and Support for the Lining.=--These parts, owing to their contact with the ashes and the hot embers, are liable to deteriorate rapidly. It is therefore indispensable that they should be removable and easily accessible, so that they may be renewed in case of need. From this point of view, grates composed of independent bars would appear to be preferable. The clearance between the bars depends, of course, on the kind of ashes resulting from the different grades of fuel. It is advisable to design the grate so that the free passage for the air is about 60 to 70 per cent. of the total surface. In generators having a cup-shaped ash-pit, containing water (Fig. 95), the grate and the base of the retort are less liable to burn than in apparatus having dry ash-pits. Certain apparatus, such as those of Lencauchez (Fig. 99), Pierson (Fig. 101), and Taylor (Fig. 94), have no grates; the fuel is held in the retort by the ashes, which form a cone resting on a sheet-iron base, easy of access for cleaning and from which the fuel slides down gradually. The Pierson generator (Fig. 101) is provided with a poker comprising a central fork, which is worked with a lever, in order to stir the fire from below without entirely extinguishing the cone of ashes. In some apparatus in which a grate is used (Fig. 92), a space is left between the grate and the support of the retort. This arrangement has the merit of allowing only finely divided and completely burnt ashes to pass to the ash-pit. Moreover, a large surface grate can be employed, thus facilitating the passage of the mixture of air and steam. [Illustration: FIG. 102.--Kiderlen producer.] The space above mentioned is provided with a cleaning-door through which cinder and slag may be removed. In other apparatus the grate rests either on the support of the refractory lining, as in the old type invented by Wiedenfeld (Fig. 95), or upon a projection embedded in the lining, as, for instance, in the Kiderlen (Fig. 102) and Pintsch generators (Fig. 96). In the Riché apparatus (Fig. 103) there is, besides the ordinary grate, a grate with tiers on which the fuel spreads. This grate consists of wide, hollow bars containing water. It should be noted that the apparatus is of the blower type. [Illustration: FIG. 103.--Riché combustion-producer.] An interesting arrangement is found in Bénier's generator (Fig. 104). This consists of a grate formed of projections cast around a cylinder which can be turned about its axis. The finely divided ashes which are retained in the spaces between these projections are thus carried into the ash-pit, and those which adhere to the metal are scraped away by a metallic comb fastened to the lower part of the apparatus. The "Phoenix" generator (Fig. 105) is fitted with a grate having a mechanical cleaning device, worked by a lever from the outside. [Illustration: FIG. 104.--Bénier producer.] [Illustration: FIG. 105.--Phoenix producer.] =Ash-Pit.=--The ash-pits are exposed to the destructive effects of heat and moisture, and should preferably be constructed of cast-iron, since sheet-steel is liable to corrode quickly. [Illustration: FIG. 106.--Otto Deutz producer.] In most apparatus the ash-pit is hermetically sealed, and the air for supporting combustion enters below the grate through a pipe leading from the heater or the vaporizer. This arrangement seems best adapted to prevent the leakage of gas which tends to take place by reaction after each suction stroke of the engine. Ash-pits formed as water-cups, such as the Deutz (Fig. 106), the Wiedenfeld (Fig. 95), and the Bollinckx (Fig. 98), are fed by the overflow from the vaporizer. These ash-pits are themselves provided with an overflow consisting of a siphon-tube forming a water-seal. Besides providing protection to the grate and other parts by this sheet of water, a larger proportion of the heat radiated from the furnace is utilized for the production of steam which contributes to enrich the gas. The doors of the ash-pits and their fittings are likewise exposed to a rapid deterioration. For this reason these parts should be very strongly made, either of cast-iron or cast-steel. Furthermore, they should, at joint surfaces, be connected in an air-tight manner, which may be attained by carefully finishing the engaging surfaces of the frame and the door proper, or by cutting a dovetail groove in one of the sides of the frame which is packed with asbestos and adapted to receive a sharp edged rib on the other part. The pintles of the hinges should also be carefully adjusted so that the joint members of the door shall remain true. Hinges with horizontal axes seem to be preferable in this respect to those having vertical axes. As a means of closing the door, the arrangement here shown (Fig. 107) seems to assure a proper engagement of the joint surfaces. It consists of a yoke which straddles the door, and which, on the one hand, swings about the hinge, and on the other hand engages a movable hoop. A screw, fastened to the yoke, serves to tighten the door by pressure on its center. This screw can also be fastened to the end of the yoke (Fig. 108). [Illustration: FIGS. 107-108.--Fire-box doors.] It is very advantageous to provide in each door a hole closed by an air-tight plug, so that in case of need a tool may be introduced for cleaning the grate. In this manner the grate may be cleaned without opening doors and without causing a harmful entrance of air. The door of the furnace, particularly, should be provided with an iron counter-plate held by hinged bolts (Fig. 109); or, better still, this door should be so constructed that it can be lined with refractory material to protect it against the radiated heat of the fire. =Charging-Box.=--Like the other parts of the generator the construction of which has been discussed above, the charging-box should be absolutely air-tight. On account of their greater security, preference should be given to double closure devices, which form a sort of preliminary chamber, owing to which the filling of the generator is made in two operations. The first operation consists in filling the preliminary chamber after opening the outer door. Upon closing this outer door, the second operation is performed, which consists in moving the inner door so as to cause the fuel in the preliminary chamber to drop into the generator. Stress has been laid on the greater safety of this type of charging-box for the reason that, with devices having a single charging-door, a sudden gust of air may rush in at the time of charging the furnace, and bring about an explosion very dangerous to the workman entrusted with stoking the furnace. [Illustration: FIG. 109.--Door with refractory lining.] The closure is generally simply a removable cover, or may be a lid swinging about a hinge having a horizontal or vertical axis. As regards the inner door, which is of great importance, in order to insure an air-tight joint, there are three chief types of closure: 1. The Lift-Valve. 2. The Slide-Valve. 3. The Cock. =The Lift-Valve.=--The lift-valve is formed by a disk of conical or spherical shape moved up and down by means of a lever having a counter-weight for adjustment. The valve is used in the Winterthur (Fig. 92) and Bollinckx (Fig. 98) generators. This device serves as an automatic closure and insures a tight joint irrespective of wear. Moreover, it presents the advantage that, at the moment of opening, it distributes the fuel evenly in the generator; but on the other hand, it has the drawback of not allowing the fuel to be examined or shaken through the charging-box. In apparatus provided with this kind of valve, it is therefore advisable to furnish the upper part of the generator with agitating holes closed by an air-tight slide. =Slide-Valve.=--The slide-valve closure consists of a smooth-finished metallic plate movable below the charging-box proper. Operated as it is from the outside, it is evident that the slightest play, the wearing of the pivot, or the weight of the charge, will form spaces between the plate and its seat through which air may rush in. Furthermore, the manipulation of the slide-valve may be interfered with if too much fuel is put in the generator. The valve or damper may move parallel to itself or swing about the operating axis. The Taylor apparatus (Fig. 94) and the Bénier apparatus (Fig. 104) are provided with such valves. The Pintsch generator (Fig. 96) is provided with a device which, properly speaking, is not a damper, but which consists of two boxes movable about a vertical axis and arranged to be displaced alternately above the shaft to effect the charging. This system effects only a single closure, but explosions are scarcely to be feared with an apparatus of this kind, owing to the considerable height of fuel contained between the charging opening and the gas-producing zone. =Cock.=--The cock is applied particularly in the modern apparatus of the Otto Deutz Co. (Fig. 106) and the Pierson generator (Fig. 101). It consists of a large cast-iron cone, having an operating handle and an opening. The cone moves in a sleeve formed by the charging-box. This arrangement appears to be preferable to the others on account of its simplicity and of the ease with which it can be taken apart for cleaning. Moreover, the fuel can be poked directly through the feed-hopper. In apparatus provided with a cock, it is advisable to place on the outside cover a mica pane through which the condition of the fuel may be examined without danger. =Feed-Hopper.=--Below the charging-box is arranged, as a rule, a hopper tapered conically downward. This part of the generator should serve only as a storage chamber for fuel. It can therefore be made of cast-iron, and has the advantage of being removable, easily replaced, and of allowing ready access to the retort for the purposes of examination and repair. The annular space surrounding this feed-hopper generally forms a chamber for receiving the gas produced, as in the Winterthur (Fig. 92), the Bollinckx (Fig. 98), and the Taylor apparatus (Fig. 99). In generators having an internal vaporizing-tank, this tank itself serves as a feed-hopper, which is the case in the Deutz apparatus (Fig. 106) and Wiedenfeld generator (Fig. 95). =Connection of Parts.=--In order to facilitate the thorough cleaning of the retort, preference is given to removable charging-boxes and feed-hoppers. These are features of apparatus of the Bollinckx type (Fig. 98), in which the charging-box is secured to the generator by means of its yoke and by catches provided with knobs, and also of apparatus of the Winterthur kind (Fig. 92), having a charging-box pivoted about a vertical axis, or apparatus of the Duplex type (Fig. 110), in which the charging-box can swing about a horizontal hinge. =Air Supply.=--We have seen that, when starting the generator, the gas is produced with the aid of a fan. This fan may be operated mechanically, but is generally operated by hand. It is customary to convey the air-blast through a pipe leading to the ash-pit, as in the Winterthur apparatus (Fig. 92). Often, however, the air supply pipe is directly branched on that which leads from the vaporizer to the ash-pit, as in the Deutz apparatus (Fig. 106). In this case a set of valves or dampers permits the disconnection of the fan or its connection with the ash-pit. [Illustration: FIG. 110.--Duplex charging-hopper.] In some apparatus an air inlet is provided immediately adjacent to the ash-pit. This arrangement is faulty for the reason that it gives rise to gaseous emanations which take place by reaction after each suction stroke of the engine. Furthermore, it is advisable that the air supplied below the ash-pit be as hot as possible. For this reason the employment of preheaters is desirable. The dry air forced in by the fan stimulates combustion, and the hot gas produced and mixed with smoke escapes through a separate flue, generally arranged beyond the vaporizer and serving as a chimney. This chimney should in all cases be extended to the outside of the building, and should never terminate in a brick chimney or similar smoke-flue. The direct escape of such gas and smoke through a telescopic chimney above the charging-box has been generally abandoned in modern structures. [Illustration: FIG. 111.--Bollinckx flue and scrubber.] [Illustration: FIG. 112.--Winterthur flue and air-reheater.] The escape-pipe mentioned, being branched on the gas-pipe leading to the engine, should be capable of disconnection when desired, by a thoroughly tight system of closure. For this purpose, some employ a simple cock (Bollinckx, Fig. 111), a three-way cock, a set of cocks, or, still better, a double valve, as in the Winterthur apparatus (Fig. 112) and the Deutz apparatus (Fig. 113). A double seated valve is also used, as is the case in the Benz generator (Fig. 114). [Illustration: FIG. 113.--Otto Deutz flue.] [Illustration: FIG. 114.--Benz flue.] =Vaporizer-Preheaters.=--As has been stated before, there are vaporizers internal or external, relatively to the generator. =Internal Vaporizers.=--The Deutz apparatus (Fig. 106), for example, consists of an annular cast-iron tank mounted above the retort of the generator. The hot gases given off by the burning fuel travel around this tank and vaporize the water which it contains. The air drawn in by the suction of the engine enters through an opening located above the tank, travels over the surface of the water which is being vaporized, and thus laden with steam passes to the ash-pit. The tank in question is supplied with water by means of a cock having a sight feed, located on the outside, and the level is kept constant by means of an overflow tube leading to the ash-pit. It is well to bend this tube and to place a funnel on its lower member. The amount of overflow may thus be regulated. These vaporizers are simple and take up little room; but they are open to the apparently well-founded objection that they heat up slowly and require a considerable time to produce the steam necessary to enrich the gas, this being due to the relatively large mass of cast-iron and the amount of water contained therein. The Pierson vaporizer (Fig. 101) and the Chavanon vaporizer (Fig. 115) both consist of an annular tank forming the base of the generator. Steam is formed near the outlet of the ashes, which, as has been described above, leads to the outer air. The development of steam is regulated by mechanical means controlled by the suction of the engine. [Illustration: FIG. 115.--Chavanon producer.] =External Vaporizers.=--External vaporizers are generally formed by a cylinder with partitions constituting two series of chambers. In one of these the hot gases from the generator travel, and in the others the water to be vaporized is contained. [Illustration: FIG. 116.--Taylor vaporizer.] [Illustration: FIG. 117.--Deutz vaporizer.] =Tubular Vaporizers.=--Different types of tubular vaporizers are manufactured. The vaporizer with a series of tubes, as in Taylor's apparatus (Fig. 116), Deutz's old model (Fig. 117), or with single tube like Pintsch's generator (Fig. 118), is formed by three compartments separated by two tube sheets or by plates which are connected by tubes. In some cases the gases pass within the tubes, while the water to be vaporized surrounds them; as in the Pintsch apparatus (Fig. 118), and Taylor apparatus (Fig. 116), Benz (Fig. 119), and Koerting generators (Fig. 120). [Illustration: FIG. 118.--Pintsch vaporizer and scrubber.] In other cases, the water lies inside and the gas outside. In this latter case, a longitudinal baffle is employed to compel the gases to heat the tubes in their whole length, as in the Deutz producer (Fig. 117). In a general way it may be said that such a series of tubes presents the disadvantage of becoming clogged up rapidly by the deposit of lime salts contained in water. [Illustration: FIG. 119.--Benz vaporizer.] [Illustration: FIG. 120.--Koerting vaporizer.] If the set of tubes consists of fire-tubes, the deposit will form on the outer surface, that is, on a portion not accessible for cleaning. From this point of view, water-tubes are preferable, as they allow the deposit or scale to be removed through the tubular heads or plates. On the other hand, such water-tubes have the drawback that their exterior surfaces are readily covered with pitch and soot. The tubular vaporizers of the Field type (Bollinckx, Fig. 98) are composed of a single sheet-iron tube or shell, in which the tubes are arranged, dipping into a chamber through which the hot gases pass. This arrangement insures a rapid production of steam, but the Field tubes are even more liable than the others to become covered with deposits. It will be seen that these types of vaporizers should all present the following features: easy access, small quantity of the body of water undergoing vaporization, and large heating surface with small volume. The use of copper or brass tubes should be strictly avoided, as they would be quickly corroded by the action of the ammonia and hydrogen sulphide contained in the gas. =Partition Vaporizers.=--Partition vaporizers comprise a cylindrical shell, generally made of cast-iron and having a double wall in which the water to be vaporized circulates. The gas coming from the generator passes into the central portion, where it comes in contact with a hollow baffle, also containing water (Wiedenfeld, Fig. 121). Vaporizers of this kind are strong, simple, and easily cleaned. =Operation of the Vaporizers.=--The general purpose of vaporizers, whatever their construction may be, is to produce steam under atmospheric pressure, by utilizing the heat of the generator gases immediately after their production, or, as in the Chavanon system, by utilizing the heat radiated from the furnace. The air drawn by the engine through the generator generally passes through the vaporizers and becomes laden with a certain amount of steam which it carries along. The amount thus taken up depends chiefly upon the temperature and the amount of gases coming from the generator, so that the greater the amount drawn into the engine, the more energetic will the vaporization be, and the richer the gas will become. It will be understood that when a generator is working at its maximum production, the interior temperature is highest and most favorable to the decomposition of the largest amount of steam. [Illustration: FIG. 121.--Wiedenfeld vaporizer.] It follows that with the very simple vaporizers which have been reviewed, a practically automatic regulation is obtained. However, some manufacturers have deemed it advisable to regulate the amount of steam more accurately, and to make it exactly proportionate to the power developed by the motor. Thus in the Winterthur gas-producer (Figs. 92 and 112) the manufacturers have omitted the vaporizer proper, and use instead an air-heater and a super-heater for air and steam. The heater is formed by a cast-iron box having two compartments, through one of which the hot gases from the generator pass, while in the other the air intended to support combustion travels. At the inlet of the super-heater a pipe terminates, which feeds, drop by drop, water supplied by a feed device to be described presently. This water is vaporized immediately upon contact with the wall of the super-heater and is carried along with the air contained in it. The super-heater comprises a hollow ring-shaped cast-iron piece arranged in the chamber of the generator, in which the gases are developed, and is thus heated to a high temperature. The mixture of air and steam circulates in this super-heater before traveling to the ash-pit. The feeder of the Winterthur gas-generator (Fig. 122) is composed of a receptacle having the shape of a tank or basin containing water and located below a closed cylindrical box. In this box a piston moves, which is provided at its lower end with a needle-valve. The upper portion of the box communicates with the gas-suction pipe through a small tube. At each suction stroke of the engine, according to the force of the suction, the needle-valve piston rises more or less and thus allows a variable amount of water to pass. [Illustration: FIG. 122.--Winterthur feeders.] This apparatus--and all those based on the same principle--presents the advantage of proportioning the amount of water to the work of the engine; but in view of its rather sensitive operation it must be kept in perfect repair and carefully watched. Obviously, should the water contain impurities, the needle-valve will bind or the orifices will be obstructed, and thus the feeding of the water will be interrupted. This will not only result in the production of a poorer gas, but will lead to greater wear of the grates, which in this case are not sufficiently cooled by the introduction of steam. [Illustration: FIG. 123.--Hille producer.] =Air-Heaters.=--The preliminary heating of the air appears to be of great utility for keeping up a good fire. This heating is very easily accomplished, and is generally effected by utilizing a portion of the waste heat of the gases, a procedure which also has the advantage of cooling the gases before they pass through the washing apparatus. The heating of the air for supporting combustion takes place either before the addition of steam (Hille's generator, Fig. 123), or after the mixture as in Wiedenfeld's apparatus (Fig. 95). In the first case, the air passes through a sheet-iron shell concentric with the basin of the generator, is there heated by the radiated heat, and is conveyed to the ash-pit by a tube into which leads the steam-supply pipe extended from the vaporizer. In the second type of heater, the mixture of air and steam is super-heated during its passage through an annular piece arranged in the ash-pit of the generator. [Illustration: FIG. 124.--Benz dust-collector.] =Dust-Collectors.=--Dust-collectors are generally placed between the generator and the scrubber or washer. They may be formed of baffle-board arrangements against which the gases laden with dust impinge, causing the dust to be thrown down into a box provided with a cleaning opening (Benz, Fig. 124, and Pintsch, Fig. 118). Some collectors are formed either by the vaporizer itself, terminating at its base in a tube which dips into water and forms a water-seal, as in the Wiedenfeld generator (Fig. 121), or by a water-chamber into which the gas-supply tube slightly dips (Bollinckx, Fig. 111). With this arrangement, the gas will bubble through the water and will be partly freed of the dust suspended in it. These water-chambers are generally fed by the overflow from the spray of the scrubber. There is thus produced a continuous circulation by which the dust, in the form of slime, is carried toward the waste-pipe or sewer. =Cooler, Washer, Scrubber.=--Some manufacturers cool the gas in a tower with water circulation. Most manufacturers, however, simply cool the gas in the washer or scrubber. This apparatus comprises a cylindrical body of sheet-iron or cast-iron formed of two compartments separated by a wooden or iron grate or perforated partition. The upper compartment up to a certain level contains either coke, glass balls, stones, pieces of wood, and the like. The top of the compartment is provided with a water supply in the nature of a sprinkler or spray nozzle. The lower compartment of the scrubber serves to collect the wash-water which has passed through the substance filling the tower. An overflow in the shape of a siphon, provided with a water seal, carries the water to the waste-pipe either directly or after it has first passed through the dust collector. The gas drawn in enters the washer in the lower compartment either above the water level (Deutz, Fig. 125; Winterthur, Fig. 126), or through an elbow which dips slightly into the water (Benz, Fig. 127; Fichet and Heurtey producer, Fig. 128). The gas passes through the grate or partition which supports the material filling the tower, and travels through the interstices in a direction opposite to that of the water falling from the top. Under these conditions, the gas is cooled, gives up the ammonia and the dust which it may still contain in suspension, and is conveyed to the engine either directly or after passing through certain purifiers. Care should be taken to place the pieces of most regular shape along the walls, so that the unevenness of their surfaces may not form upward channels along the shell, through which channels the gas could pass without meeting the wash-water. [Illustration: FIG. 125.--Otto Deutz scrubber.] [Illustration: FIG. 126.--Winterthur scrubber.] [Illustration: FIG. 127.--Benz scrubber.] The material most commonly employed in washers is coke in pieces of from 2-1/2 to 3-1/2 inches in size. This material is cheap and is very well suited for retaining the impurities of the gas. The largest pieces of coke should be placed at the bottom of the washer, and smaller pieces should form at the top a layer from 6 to 8 inches deep. In this manner the water is distributed more evenly and the gas is more thoroughly washed. Blast-furnace coke is best suited for this washing, as it is more porous and less brittle than gas-works coke. It is advisable to put a baffle-board in front of the gas outlet to reduce the carrying along of water in the conduits. [Illustration: FIG. 128.--Fichet-Heurtey scrubber.] [Illustration: FIG. 129.--Scrubber-doors.] The tower of the washer should be provided with three openings having air-tight closures, easily fastened by screws (Fig. 129). One of the openings is located in the lower compartment, slightly above the water level, to allow the deposits to be removed and to permit the cleaning of the orifice of the gas-supply tube, which is particularly liable to be obstructed. The second opening is placed above the grating which supports the filtering material. The third opening is provided on the top of the apparatus to permit the examination and cleaning of the water feed device and the gas outlet without the necessity of taking the lid of the washer apart, the joint of which is kept tight with difficulty. The two openings last mentioned also serve for introducing and removing the filtering material. =Purifying Apparatus.=--In some cases, where it is necessary to have very clean gas or where coal is employed which is softer than anthracite coal, and which therefore produces an appreciable amount of tar, supplementary purifying means must be employed. The apparatus for this purpose may, like the washers, be based upon a physical action or upon a chemical action. The physical action has for its purpose chiefly to retain the pitch and the dust which may have passed through the washer. This is accomplished by means of sawdust or wood shavings arranged in a thin layer and capable of filtering the gas without opposing too great a resistance to its passage. These materials are spread on one or more shelves superposed to form successive compartments in a box closed in an air-tight manner by an ordinary lid or a water seal cover (Pintsch, Fig. 130; Fichet and Heurtey, Fig. 131). It may be well to point out that the presence of the water carried along will, in the end, destroy the efficiency of the precipitated materials, because they swell up and cease to be permeable to the gas. These materials must therefore be renewed rather frequently. To obviate this drawback, vegetable moss may be employed, which is much less affected by moisture than most filters and keeps its spongy condition for a long time. [Illustration: FIG. 130.--Pintsch purifier.] The chemical action has for its chief object to rid the gas of the carbonic acid and the hydrogen sulphide which certain fuels give off in appreciable amounts. The purifying material, in this case, is formed either by a mixture of hydrate of lime and natural iron oxide, or by the so-called Laming mass, which consists of iron sulphide, slaked lime, and sawdust, which last serves the purpose of rendering the material looser and more permeable to the gas. The Laming mass as well as other purifying materials will become exhausted in the course of chemical reactions. It can be regenerated merely by exposure to the air. [Illustration: FIG. 131.--Fichet-Heurtey purifier.] =Gas-Holders.=--The purifiers by themselves constitute, to a certain extent, storage chambers for the gas before it is supplied to the engine; but in plants for the generation of gas without purifiers it is advisable to provide a gas-holder on the suction conduit near the engine. [Illustration: FIG. 132.--Pintsch regulating-bell.] In order to save floor space the gas-holder may be placed in the basement. Preferably the capacity of the holder should be at least from 3 to 4 times the volume of the engine-cylinder. The holder should also be provided with a drain-cock and with a hand-hole located at some accessible point, so that the slimes and pitch which tend to accumulate in the holder can be removed. In some cases the gas-holder is formed by a small regulating bell, the function of which is to insure a uniform pressure. This bell is emptied during the suction period and is filled during the three succeeding periods of compression, explosion, and exhaust (Pintsch, Fig. 132). [Illustration: FIG. 133.--Types of gas-driers.] =Drier.=--Sometimes, toward the end of a producer-gas pipe, a drier is located for the purpose of keeping back the water carried along, the drier being similar to that employed in steam conduits. It will, of course, be understood that such driers are useful only in plants having no purifiers (Fig. 133). The employment of the drier is advisable to prevent the entrance of moist gas into the cylinder and the condensation of moisture on the electric igniter. [Illustration: FIG. 134.--Elbow with closure.] =Pipes.=--The pipes connecting the several parts of a gas-producing plant should be disposed with particular care to insure tightness and cleanliness. It should be borne in mind that the gas is under a pressure below that of the atmosphere, and that the least leakage will cause the entrance of air, which will impair the quality of the gas. The greatest care should therefore be taken in fitting the joints. These joints are numerous, because there are joints wherever tubes are connected with each other and with the apparatus. Furthermore, all elbows should be provided with covers held in place by a yoke and compression screw, this being done for the purpose of providing for the introduction of a brush or other implement to remove the dust and pitch (Fig. 134). For conduits of small diameter the elbows with covers may be replaced with =T= connections, or connections provided with plugs. Gas piping in the immediate neighborhood of the cock for admitting gas to the motor should be provided with a conduit of proper diameter leading to the open air and serving to clean the apparatus and to fill them, during the operation of the fan, with gas suitable for combustion. This conduit should be provided with a stop-cock. Test-cocks for the gas should be placed on the piping immediately beyond the vaporizers, the scrubber, and near the engine. It will also be well to provide water-pressure gages before and after the scrubber to enable the attendant to ascertain the vacuum in the conduits and to adjust the running of the apparatus. =Purifying-Brush.=--As an additional precaution against the carrying of tar to the engine, metallic brushes are often employed, these brushes being spiral in form and enclosed in a cast-iron box interposed in the gas-supply pipe immediately after the engine. The gas will be broken up into streams by the obstacles formed by these brushes and will be freed of the suspended tar (Fig. 135). These brushes should be carefully cleaned at regular intervals. The best way of doing this is to drop them into kerosene or some other suitable solvent. [Illustration: FIG. 135.--Metal purifying-brush.] CONDITIONS OF PERFECT OPERATION OF GAS-PRODUCERS These conditions depend upon the workmanship or upon the system of the plant, on the care with which it has been erected, on the nature of the fuel, on the condition of preservation of the apparatus, and upon the manner in which the producers have been working. =Workmanship and System.=--The workmanship itself, which term is meant to include the choice of materials and the way they have been worked, presents no difficulty. The producers which we have discussed are very simple and offer absolutely no difficulties in their mechanical execution. As regards the system, however, especially with respect to the relative dimensions of the elements, it does not seem so far that it is possible to indicate any principle or rule capable of a rigid general application. It must be taken into account that the use of suction gas-generators has become general only in the last three or four years; the problem has therefore scarcely been adequately solved. However, some hints may be given on this subject. =Generator.=--In regard to the generator, it is possible to deduce from the best existing plants the dimensions to be given to the generator relatively to those of the engine to be supplied, upon the assumption that the engine is single-acting and runs at a normal speed of from 160 to 230 revolutions per minute. The essential portion of the generator which contributes to the production of a proper gas is that which corresponds with the combustion zone. To this portion a cross-section is given varying in size between one-half and one-quarter of the surface of the engine-piston, sometimes between one-half and nine-tenths of this surface, according to the nature and the size of the fuel that is used. With small apparatus, however, ranging from 5 to 15 horse-power, the size of the base cannot be reduced below a certain limit, since otherwise the sinking of the fuel will be prevented. This danger always exists in small generators and renders their operation rather uncertain, such uncertainty being also due to the influence of the walls. It is to be noted that most modern generators are rather too large than otherwise. Many manufacturers of no wide experience have been led to make their apparatus rather large so as to insure a more plentiful production of gas. As a matter of fact, the fire in such apparatus is liable to be extinguished when the combustion is not very active. If the principles of the formation of gas in suction-generators be kept in mind, it is evident that the gas developed is the richer the "hotter" the operation of the apparatus. Such operation also permits the decomposition of the hydrogen and carbon monoxide. The "hot" operation of a generator is accomplished best with active combustion; and since this is a function of the rapidity with which the air is fed, it obviously is advantageous to reduce the area of the air-passage to a minimum as far as allowed by the amount of fuel to be treated. As to the height of the fuel in use in the apparatus, this varies as a rule between 4 and 5 times the diameter at the base. =Vaporizer.=--The size of the vaporizer varies materially according to its type. No hard-and-fast rule can therefore be adopted for determining its heating surface; but this surface should in all cases be sufficient to vaporize under atmospheric pressure from .66 to .83 pounds of water per pound of anthracite coal consumed in the generator. =Scrubber.=--For the scrubbers, the following dimensions may be deduced from constructions now used by standard manufacturers. The volume of a scrubber is generally from six to eight times the anthracite capacity of the generator. A height of from three to four times the diameter is considered sufficient in most cases. It should be understood that in this height is included the water-pan chamber located below the partition or grate, and the upper chamber through which the gas escapes. The height of these two chambers depends necessarily upon the arrangement used for leading the gas to the lower portion of the washer and for the distribution of wash-water at the top. =Assembling the Plant.=--The author has insisted strongly on the necessity of having all the apparatus and pipe connections perfectly tight. In order to ascertain if there is any leakage, the following procedure may be adopted: When starting the fire by means of wood, straw, or other fuel producing smoke, instead of allowing this smoke to escape through the flue during the operation of the fan, it may be caused to escape through the cock which generally admits the gas to the motor, the cock being opened for this purpose. The damper in the outlet flue is closed. In this manner the smoke will fill all the apparatus and connecting pipes under a certain pressure and will escape through any cracks, the presence of which will thus be revealed. Another test, which is made during the ordinary operation of the generator, consists in passing a lighted candle along the joints; if there is any leakage, this will be shown by a deviation of the flame from a vertical position. =Fuel.=--We have discussed the subject of fuel in a preceding chapter (Chapter XIII) and have indicated the conditions to be fulfilled by low grade or anthracite coal best adapted for use in suction gas-generators. It may here be added that the coal used in the generator should be as dry as possible and in pieces of from 1/2 inch to 1 inch. Very small pieces, and particularly coal dust, are injurious and should be removed by preliminary screening as far as possible. Screened coal is thrown in with an ordinary grate shovel. =How to Keep the Plant in Good Condition.=--In regard to the generator, apart from the cleaning of the grate and of the ash-pit, which may be done during operation, it is necessary to empty the apparatus entirely once a week, if possible, in order to break off the clinkers adhering to the retort. These clinkers destroy the refractory lining, form rough projections interfering with the downward movement of the fuel, bring about the formation of arches, and reduce the effective area of the retort. At the time of this cleaning, tests are also made as to the tightness of the doors of the combustion-chamber, of the charging-boxes, etc. The vaporizer should be cleaned every week or every other week, according to the more or less bituminous character of the fuel and the greater or smaller content of lime in the water used. Lime deposits may be eliminated, or the salts may be precipitated in the form of non-adhering slimes, by introducing regularly a small amount of caustic potash or soda into the feed-water. If the deposits or incrustations are very tenacious, the use of a dilute solution of hydrochloric acid may be resorted to. Tar which may adhere to the conduits, pipes or gas passages, is best removed while the apparatus is still hot, or a solvent may be employed, such as kerosene, turpentine, etc. The connections between the vaporizer and the scrubber are particularly liable to become obstructed by the accumulation of tar or dust carried along by the gas. It is advisable to examine the several parts of the plant once or twice a week by opening the covers or the cleaning-plugs. The lower compartment of the washer keeps back the greater part of the dust which has not been retained in collectors or boxes provided especially for this purpose. The dust takes the form of slime, and, in some arrangements of apparatus, tends to clog up the overflow pipe, thus arresting the passage of gas and causing the engine to stop. This portion of the washer should be thoroughly cleaned once or twice a month. If very hard blast-furnace coke is used in the washer, it may be kept in use for over a year without requiring removal. In order to free the purifying materials from dust and lime sediments carried along by the wash-water, it is well to let the wash-water flow as abundantly as possible for about a half-hour at least once a month. At the time of renewing the purifying material the precautions indicated in the section dealing with these matters should be observed, and care should be taken to have shelves or gratings on which the material is supported in layers not too thick, so as to avoid any resistance to the passage of the gas. In a general way it is advisable to test the drain-cocks on the several apparatus daily, and to keep them in perfect condition. If, when open, one of these cocks does not discharge any gas, water, or steam, a wire should be introduced into the bore to make sure it is not clogged up. =Care of the Apparatus.=--Each producer-gas plant will require special instructions for running it, according to the system, the construction, and the size of the plant. Such instructions are generally furnished by the manufacturer. However, there are some general rules which are common to the majority of suction gas-producers, and these will here be enumerated. =Starting the Fire for the Gas Generator.=--This operation calls for the presence of the engineer of the plant and an assistant. The proper procedure is as follows: First: Open the doors of the furnace and of the ash-pit. Then open the outlet flue and make sure that the grate of the generator is clear of ashes and clinkers. It should also be seen to that the parts of the charging-box work well and that the joints are tight. Second: Ascertain whether there is the proper amount of water in the vaporizer, in the scrubber, etc., and that the feed works properly. Third: Through the door of the combustion-chamber introduce straw, wood shavings, cotton waste, etc.; light them and fill the generator with dry wood up to one-quarter or one-half of its height; then add a few pailfuls of coal. Fourth: Close the doors of the ash-pit and of the combustion-chamber and start the draft by means of the fan. As soon as the draft is started, it must be kept up without interruption until the engine begins to run, which may be ten or twenty minutes after lighting the fire. Fifth: After the draft has been continued for a few minutes, the coal becomes sufficiently incandescent to start the production of gas, which may be ascertained by trying to light the gas at the test-cock near the generator. Then the opening in the outlet flue is half closed for the purpose of producing pressure in the apparatus. Sixth: Open the outlet flue adjacent to the engine for the purpose of purging the apparatus and the conduits of the air which they contain until the gas may be lighted at the test-cock placed near the motor. Seventh: Adjust the normal outflow of wash-water for the scrubber. Eighth: As soon as the gas burns continuously at the test-cock with an orange-colored flame the engine may be started. The gas at first burns with a blue flame; this color indicates that it contains a certain amount of air. The opening of the test-cock should be so regulated as to reduce the outlet pressure of the gas sufficiently to prevent the flame from going out. During the production of the draft, as well as during the ordinary running of the plant, the filling of the apparatus with fuel should be done with care to prevent explosions of gas due to the entrance of air. Particular care should be taken never to open at the same time the lid of the charging-box and the device, be it a cock, valve, or damper, which controls the connection of the charging-box with the generator. All the operations which have been mentioned above should be carried out as quickly as possible. STARTING THE ENGINE The manner of starting the engine depends on the type of the engine and on the starting device with which it is provided, as we have already explained in connection with engines working with gas from city mains. It is, however, important for the production of a good explosive mixture to regulate the amount of air supplied to the engine according to the quality of the gas employed. It is advisable to continue the operation of the fan until several explosions have taken place in the cylinder and the engine has acquired a certain speed so as to be able to draw in the normal amount of gas. Naturally the gas-outlet tube near the admission-cock should be closed after starting the engine, as well as the opening in the outlet flue of the generator. When the motor is running properly, the amount of water fed to the vaporizer and overflowing to the ash-pit is properly adjusted. The generator is then filled up to the level indicated by the manufacturer. =Care of the Generator during Operation.=--As soon as the apparatus is running under normal conditions, it presents the advantage of requiring only very slight supervision and very little manual tending. The supervision consists: First: In regulating and keeping up a proper feed of water to the vaporizer. Second: In seeing to it that in apparatus provided with an overflow leading to the ash-pit, the water should flow constantly but without exceeding the proper amount. Third: In keeping down temperature in the scrubber by properly regulating the feed of the wash-water. This apparatus may be slightly warm at its lower part, but must be quite cold at the top. The manual tending to be done is limited to the regular filling up of the generator with fuel and to the removal of ashes and clinkers. The charging is effected at regular intervals, which, according to the various types of anthracite-generators, vary from one to six hours. Charging the apparatus at short intervals entails unnecessary labor, while charging at too long intervals will often interfere with the uniform production of the gas. It will be obvious that the amount of fuel introduced will be the larger, the greater the intervals between two fillings. This fuel is cold and contains between its particles a certain amount of air; furthermore, the layer of coal which covers the incandescent zone has become relatively thin. The excess of air impoverishes the gas, and the fresh fuel lowers the temperature of the mass undergoing combustion, so that again the gas in process of formation is weakened. Experience seems to show that as a rule it is best to fill up the generator at intervals of from two to three hours, according to the work done by the engine. It should be noted that the level of the fuel in the generator should not sink below the bottom of the feed-hopper. The author wishes again to emphasize that in order to prevent the harmful entrance of air, the charging operations should be carried out as quickly as possible; and for this reason the fuel should be introduced not by means of the shovel, but by means of a pail, scuttle, or other appropriate receptacle. Care should be taken to fill the charging box to its upper edge and to adjust its cover accurately before operating the device which closes the feed-hopper (valve, cock). The removal of the ashes and clinkers should be accomplished as infrequently as possible, since opening the doors of the ash-pit and of the combustion-chamber necessarily causes an inward suction of cold air which is harmful. As a rule with generators employing anthracite coal, it is sufficient to empty the ash-pit twice daily; this should be preferably done during stoppages. However, the cleaning of the grate by means of a poker passed between the grate-bars or over them in order to bring about the falling of the ashes, should be attended to every two to four hours, according to the type of the generator and the nature of the fuel. In order that this cleaning may be done without opening the doors, the latter should be provided with apertures having closing devices. This cleaning has for its chief object to allow the free passage of the air for supporting combustion and to keep the incandescent zone in the apparatus at the proper height. The accumulation of ashes and clinkers at the bottom of the retort will shift this zone upward and impair the quality of gas. =Stoppages and Cleaning.=--After closing the gas-inlet to the engine, the damper in the gas-outlet flue of the generator should be opened and the cocks controlling the feed of water to the scrubber and to the vaporizer should be closed. If it is desired to keep up the fire of the generator during the stoppage so as to be able to start again quickly, the ash-pit door should be opened so as to produce a natural draft which will maintain combustion. While the door is open, the clinkers which have accumulated above the grate may be removed, as they are much more easily taken off the grate when they are hot. At least once a week the fire in the generator should be put out and the generator completely cleaned--that is, when ordinary fuel is employed. For this purpose, as soon as the apparatus is stopped, a portion of the incandescent fuel is withdrawn through the doors of the combustion-chamber, and the retort is allowed to cool before it is emptied entirely. Too sudden a cooling of the retort may injure its refractory lining. In order to prevent explosions caused by the entrance of air, the feed-hopper should remain hermetically closed during the removal of the incandescent fuel through the doors of the combustion-chamber. If the apparatus is placed in a room poorly ventilated, the cleaning should be attended to by two men, so that one may assist the other in case he is overcome by the gas. In all cases there should be a strict prohibition against the use of any light having an exposed flame liable to set on fire the explosive mixtures which may be formed. When the generator, after cooling, is completely open, the charging-box is taken apart, and, if necessary, the feed-hopper also; the grates are taken out, if necessary; and, by means of a poker inserted from above, the clinkers and slag adhering to the retort are broken off. In the foregoing paragraphs the author has indicated how the several apparatus, such as the vaporizer, the washer, the conduits, etc., should be attended to and maintained in good working order. CHAPTER XIV OIL AND VOLATILE HYDROCARBON ENGINES Although this book is devoted primarily to a discussion of street-gas and producer-gas engines employed in various industries, a few words on oil and volatile hydrocarbon engines may not be out of place. Oil-engines are those which use ordinary petroleum as a fuel or illuminating oil of yellowish color, having a specific gravity varying from 0.800 to 0.820 at a temperature of 15 degrees C. (59 degrees F.), and boiling between 140 and 145 degrees C. (284 to 297 degrees F.). Volatile hydrocarbon engines are those which employ light oils obtained by distilling petroleum. These oils are colorless, have a specific gravity that varies from 0.680 to 0.720, and boil between 80 degrees and 115 degrees C. (176 to 257 degrees F.). Among these "essences," as they are called in Europe, may be mentioned benzine and alcohol. In general appearance, and the way in which they are controlled, oil-engines differ but little from gas-engines. Their usual speed, however, is 20 to 30 per cent. greater than that of gas-engines. Except in some engines of the Diesel and Banki types, the compression does not exceed 43 to 71 pounds per square inch. In volatile hydrocarbon engines, on the other hand, the speed is very high, often running from 500 to 2,000 revolutions per minute, while the speed of gas or oil engines rarely exceeds 250 or 300 revolutions per minute. =Oil-Engines.=--Oil-engines are employed chiefly in Russia and in America. Because of the high price of oil in other countries they are to be found only in small installations in country regions and are used mainly for driving locomobiles and launches. The improvements which have been made of late years in the construction of gas-engines supplied by suction gas-producers for small as well as for large powers, have hindered the general introduction of oil-engines. The characteristic feature in the design of many of the oil-engines of the four-cycle type now in use (to which type we shall confine this discussion) is to be found in the controlling mechanism employed. The underlying principle of this mechanism lies not in acting upon the admission-valve, but in causing the governor to operate the exhaust-valve in such a manner that it is held open whenever the engine tends to exceed its normal speed. Some engines, however, are built on the principle of the gas-engine, with an admission-valve so controlled by the governor that it is open during normal operation and closed whenever the speed becomes excessive. The necessity of producing a mixture of air and oil capable of being ignited in the engine-cylinder has led to the invention of various contrivances, which cannot be used if illuminating-gas or producer-gas be employed. These contrivances are the atomizer, the carbureter, the oil-pump, the air-pump, the oil-tank, and the oil-lamp. In some oil-engines all of the elements may be found, but for the purpose of simplifying the construction and of avoiding unnecessary complications, manufacturers devised arrangements which rendered it possible to discard some of them, particularly those of delicate construction and operation. It is not the intention of the author to enter into a detailed description of these various devices, since the limitations of this book would be considerably surpassed. The reader is referred to books on the oil-engine, published in the United States, England, and France.[B] Most of the observations which have been made on the construction and installation of gas-engines, as well as the precautions which have been advised in the conduct of an engine, apply with equal force to oil-engines. It will therefore be unnecessary to recur to this phase of the subject so far as oil-engines are concerned. One point only should be insisted upon--the necessity of very frequently cleaning the valves and moving parts of the engine. Illuminating-oil when burnt produces sooty deposits, particularly if combustion be incomplete, which deposits foul the various parts and cause premature ignitions and faulty operation. The use of oil in atomizers, carbureters, and lamps is accompanied with the employment of pipes and openings so small in cross-section that the slightest negligence is attended with the formation of partial obstructions that inevitably affect the operation of the engine. =Volatile Hydrocarbon Engines.=--Only those engines will here be treated which have become of importance in the development of the automobile. Some designers have attempted to employ the volatile hydrocarbon engine for industrial and agricultural purposes, and have devised electro-generator groups, hydraulic groups, and so-called "industrial combinations" in which belt and pulley transmission is employed. These applications in particular will here be rapidly reviewed. The high speed at which engines of this class are driven renders it possible to operate a centrifugal pump directly and to mount both the engine and machine which it actuates on the same base. The hydrocarbon engine has the merit of being very light and of taking up but little room. Its cost is considerably less than that of an oil or producer-gas engine of corresponding power. On the other hand, its maintenance is much more expensive, and the hydrocarbons upon which it depends for fuel anything but cheap. Furthermore, the engines wear away rapidly, on account of their high speed. For this reason it is advisable to base calculations on a life of three to four years, while oil and gas engines may generally be considered to be still of service at the end of thirteen years. On the following page a comparison of costs for installation and maintenance is drawn between the oil and hydrocarbon engine on the basis of ten horse-power. =Comparative Costs.=--A 10 horse-power oil-engine, in the matter of first cost of installation, is about 35 per cent. more expensive than a volatile hydrocarbon engine of equal power. On the other hand, the operating expenses of the oil-engine are less by 25 per cent. than they are for the volatile hydrocarbon engine. The engines which are here discussed usually have their cylinders vertically arranged, as in steam-engines of the overhead cylinder type. The crank-shaft and the connecting-rods are enclosed in a hermetically sealed box filled with oil, so that the movement of the parts themselves ensures the liberal lubrication of the piston. The suction-valve is generally free, although latterly designers have shown a tendency to connect it with the cam-shaft, with the result that it has become possible to reduce the speed appreciably without stopping the engine. The carbureter is operated by the suction of the engine. If the fuel employed is alcohol, it must be heated. =Tests of High-speed Engines.=--High-speed engines present various difficulties which must be contended with in controlling their operation. Their high speed renders it impossible to take indicator records as in the case of most industrial engines. Indicator cards, moreover, at best give but very crude data, which relate to each explosion cycle only, and which are therefore inadequate in determining the exact conditions of an engine's operation. Oil, benzine, and other so-called carbureted-air engines are particularly difficult to control because of many phenomena which cannot be recorded. In order to test the operation of high-speed engines, two different types of instruments are at present employed: the manograph and the continuous explosion recorder. =The Manograph.=--The manograph, which is the invention of Hospitalier, is an optical instrument in which a series of closed diagrams are superimposed upon a polished mirror similar in form to Watt diagrams. Because the images persist in affecting the retina of the eye an absolutely continuous, but temporary, gleam is seen. Still, it is possible to obtain a photograph or a tracing of these diagrams. =The Continuous Explosion Recorder for High-speed Engines.=--The author has devised an explosion and pressure recorder, which is mounted upon the explosion chamber to be tested and which communicates with the chamber through the medium of a cock _r_ (Fig. 136). The instrument is somewhat similar in form to the ordinary indicator. Its record, however, is made on a paper tape which is continuously unwound. The cylinder _c_ is provided with a piston _p_, about the stem of which a spring _s_ is coiled. A clock train contained in the chamber _b_ unwinds the strip of paper from the roll _p'_ and draws it over the drum _p''_, where the pencil _t_ leaves its mark. The tape is then rewound on the spindle _p'''_. A small stylus or pencil _f_ traces "the atmospheric line" on the paper as it passes over the drum _p''_. In order to obviate the binding of the piston _p_ when subjected to the high temperature of the explosions, the cylinder _c_ is provided with a casing _e_ in which water is circulated by means of a small rubber tube which fits over the nipple _e'_. This recorder analyzes with absolute precision the work of all engines, whatever may be their speed. It gives a continuous graphic record from which the number of explosions, together with the initial pressure of each, can be determined, and the order of their succession. Consequently the regularity or irregularity of the variations can be observed and traced to the secondary influences producing them, such as the section of the inlet and outlet valves and the sensitiveness of the governor. It renders it possible to estimate the resistance to suction and the back pressure due to expelling the burnt gases, the chief causes of loss in efficiency in high-speed engines. Furthermore, the influence of compression is markedly shown from the diagram obtained. [Illustration: FIG. 136.--R. Mathot's continuous explosion recorder.] [Illustration: FIG. 137.--12 H.P. Oil-engine.] [Illustration: FIG. 138.--6 H.P. Volatile Hydrocarbon Engine.] [Illustration: FIG. 139.--Effect of size of section and exhaust ports.] The recorder is mounted on the engine; its piston is driven back by each of the explosions to a height corresponding with their force; and the stylus or pencil controlled by the lever _t_ records them side by side on the moving strip of paper. The speed with which this strip is unwound conforms with the number of revolutions of the engine to be tested, so that the records of the explosions are placed side by side clearly and legibly. Their succession indicates not only the number of explosions and of revolutions which occur in a given time, but also their regularity, the number of misfires. The atmospheric pressure of the explosions is measured by a scale connected with the recorder-spring. By employing a very weak spring which flexes at the bottom simply by the effect of the compression in the engine-cylinder, it is possible to ascertain the amount of the resistance to suction and to the exhaust. It is simply sufficient to compare the explosion record with the atmospheric line, traced by the stylus _f_. By means of this apparatus, and of the records which it furnishes, it is possible analytically to regulate the work of an engine, to ascertain the proportion of air, gas, or hydrocarbon, which produces the most powerful explosion, to regulate the compression, the speed, the time of ignition, the temperature, and the like (Figs. 137, 138 and 139). In order to explain the manner of using this recorder several specimen diagrams are here given. I. _Determination of the Amount of Compression._--A spring of average power is employed, the total flexion of which corresponds almost with the maximum compression so as to obtain a curve of considerable amplitude. The engine is first revolved without producing explosions, driving it from the dynamo usually employed in shops, at the different speeds to be studied. The compression of the mixture varies in inverse ratio to the number of revolutions of the shaft, owing to the resistances which are set up in the pipes and the valves and which increase with the speed. The accompanying cut (Fig. 140) shows two distinct records taken in two different cases, namely: A.--Speed of engine, 950 revolutions per minute; amount of compression, 68.9 pounds per square inch. B.--Speed of engine, 1,500 revolutions per minute; amount of compression, 61 pounds per square inch, or 11.5 per cent. less. [Illustration: FIG. 140.] II. _Determination of the Resistance to Suction and Exhaust._--Influence of the tension of the spring of the suction valve and of the section of the pipe. Effect of the section of the exhaust-valve and of the length and shape of the exhaust-pipe: A very light spring is utilized, the travel of which is limited by a stop so as to obtain on a comparatively large scale the depressions and resistance respectively represented by the position of the corresponding curve, above or below the atmospheric line (Fig. 141). [Illustration: FIG. 141.] C.--Tension of the suction-valve: 2.9 pounds. Resistance to suction: 1/7 of an atmosphere (2.7 pounds). D.--Tension of the suction-valve: 2.17 pounds. Resistance to suction: 2/7 of an atmosphere (5.4 pounds). E.--A chest is used for the exhaust. Resistance to exhaust: 2/7 of an atmosphere (5.4 pounds). F.--The exhausted gases are discharged into the air, the pipe and the chest being discarded. Resistance to the exhaust is zero (Fig. 142). [Illustration: FIG. 142.] The depression graphically recorded is partly due to the inertia of the spring of the explosion-recorder, which spring expands suddenly when the exhaust is opened. III. _Comparison of the Average Force of the Explosions by Means of Ordinates._--A powerful spring is employed. The paper band or tape of the recorder is moved with a small velocity of translation so as to approximate as closely as possible the corresponding ordinates representing the explosions (Fig. 143). [Illustration: FIG. 143.] G.--Pure alcohol. Explosive force, 369.72 to 426.6 pounds per square inch. H.--Carbureted alcohol. Explosive force, 397.6 to 510.8 pounds per square inch. I.--Volatile hydrocarbon. Explosive force, 483.48 to 531.92 pounds per square inch. IV. _Analysis of a Cycle by Means of Open Diagrams Representing the Four Periods._--A powerful spring is employed, and the paper is moved with its maximum speed of translation. The four phases of the cycle are easily distinguished as they succeed one another graphically from right to left in other words, in a direction opposite to that in which the paper is unwound. A diagram is made which reproduces exactly the values of the corresponding pressures at different points in the travel of the piston (Fig. 144). The periods of the cycle are reproduced as faithfully as if the ordinary indicator which gives a closed curved diagram had been employed. There is no difficulty in reading the record, since the paper is not in any way connected with the engine-piston. Some attempts have been made to secure open diagrams in which the motion of translation given to the paper is controlled by the engine itself; but these apparatus as well as the ordinary indicators cannot be used when the speed of the engine exceeds 400 to 500 revolutions per minute. [Illustration: FIG. 144.] J.--Speed, 1,200 revolutions; carbureted alcohol; average force of the explosions, 426.6 pounds per square inch. Average compression, 92.43 pounds per square inch. Pressure at the end of the expansion, 21.33 pounds per square inch. V. _Analysis of the Inertia of the Recorder. Selection of the Spring to be Employed._--Given the rapidity with which the explosions succeed one another in automobile engines, it is readily understood that the inertia of the moving parts of the recorder will be graphically reproduced (Fig. 144). The effect of this inertia is a function of the weight of the moving parts and of the extent of their travel. The moving masses are represented by the piston and its rod, the spring and the levers of the parallelogram stylus. The effects due to inertia have been considerably lessened by reducing the weight of the various parts to a minimum. A hollowed piston, a hollowed rod and short and light levers have been adopted. The traditional pencil has been displaced by a silver point which traces its mark upon a metallically coated paper. For the heavy springs with their long travel, light but powerful springs with small amplitudes have been substituted. Since the perfect lubrication of the recorder-cylinder is of great importance, a simple oiling device certain in its action has been adopted. The recess of the piston forms a cup that can be filled with oil whenever the spring is changed. At each explosion the violent return of the piston splashes oil against the cylinder walls and thus insures perfect lubrication. It should be observed that if the directions given are not followed, particularly in the choice of a spring suitable for each experiment, inertia effects will be produced. These can easily be detected on the record and cannot be confused with the curves which interpret the phenomena occurring in the cylinder of the engine. At a height equal to the end of the piston's stroke, the cylinder of the recorder is provided with a water-jacket which keeps the temperature down to a proper point and prevents the binding of the piston. The explosion-chamber of automobile engines being rather small in volume, should not be sensibly increased in order that the record obtained may conform as nearly as possible with actual working conditions on the road. In order to attain this end the cylinder of the recorder is so disposed that the piston travels to the height of the connecting-cock. As a result of this arrangement the field of action of the gases is reduced to a minimum. Since these gases have no winding path to follow, they are subjected neither to loss of quantity nor to cold. FOOTNOTES: [B] Hiscox, Gas and Oil Engines, Norman W. Henley Pub. Co., New York. Parsell and Weed, Gas and Oil Engines, 1900, Norman W. Henley Pub. Co., New York. Goldingham, 1900, Spon & Chamberlain, London. Dugald Clerk, 1897, Longmans, London. Grover, 1902, Heywood, Manchester. Aimé. Witz, 1904, Barnard, Paris. H. Güldner, 1903, Springer, Berlin. CHAPTER XV THE SELECTION OF AN ENGINE The conditions which must be fulfilled both by engines and gas-producers in order that they may industrially operate with regularity and economy have been dwelt upon at some length. Unfortunately it often happens that engines are not installed as they should be, with the result that they run badly and that the reputation of gas-engines suffers unjustly. The use of suction gas-producers in particular caused considerable trouble at first owing to inexperience, so that even now many hesitate to adopt them despite their great economical advantages. The reason assigned for this hesitation is the supposed danger attending their operation. The factory proprietor who intends to install a gas-engine in his plant is not usually able to appreciate the intrinsic value of one engine when compared with another, or to determine whether the plans for an installation conform with the best practice. The innumerable types of engines offered to him by manufacturers and their agents, each of whom claims to have a better engine than his rivals, plunges the purchaser into hesitation and doubt. Not knowing which engine to select, he usually buys the cheapest. Very often he learns, as time goes by, that his installation is far from being perfect. Finally he begins to believe that he ought to consult an expert. The author's personal experience has convinced him that eight times out of ten the factory owner who has picked out an engine for himself has not obtained an installation which meets the requirements which the manufacturers of gas-engines should fulfil. Many of these requirements could be complied with were it not for the fact that the manufacturer has dropped certain details which appeared superfluous, but which were in reality very important in obtaining perfect operation. The author therefore suggests that the services of a competent expert be retained by those who intend to install a gas-engine in their plants. =The Duty of a Consulting Engineer.=--An expert fills the same office as an architect, and impartially selects the engine best suited to his client's peculiar needs. His examination of the engines offered to him will proceed somewhat according to the following programme: 1. He will first study the installation from the mechanical point of view, and also the local conditions under which that installation is to operate, in order that he may not order an engine too large or too small, or a type incompatible with the foundations at his disposal, or unable to fulfil all the requirements of his client. 2. He will examine the precautions which have been taken to avoid or reduce to a minimum certain inconveniences which attend the operation of explosion-engines. 3. He will draw up specifications, with the terms of which gas-engine makers must comply, so that he can compare on the basis of these specifications the merits of the engines submitted to him. 4. He will prepare an estimate of cost and also a contract which is not couched in terms altogether in the gas-engine maker's favor, and which gives the purchaser important warranties. 5. He will supervise the technical installation of the engine or plant. 6. He will make tests after the engine is installed and see to it that the maker has fulfilled his warranties. =Specifications.=--Since engines and gas-producers are constructed for commercial ends, it naturally follows that their manufacturers seek to make the utmost possible profit in selling their installations. Prices charged will necessarily vary with the quality of material employed, the care taken in constructing the engine and generator, the number of apparatus of the same type which are manufactured, the arrangement of the parts and that of the installations. Since there is considerable rivalry among gas-engine builders, selling prices are often cut down so far that little or no profit is left. It is very difficult--indeed impossible--to convince a purchaser that it is to his interest to pay a fair price in order to obtain a good installation, especially when other manufacturers are offering the same installation at a less price with the same warranties. As a result of this state of affairs, engine builders, in order that they may not lose an order, are willing, to reduce their prices, hoping to make up in the quality of the workmanship and the material what they would otherwise lose. Often they will deliver an engine too small in size but operating at a higher speed than that ordered; or they will select an old type, or carry out certain details with no great care. This, to be sure, is not always the case; for there are a few builders of engines who place their reputation above everything else and who would rather lose an order than execute it badly. Others, unfortunately, prefer to have the order at all costs. By retaining a consulting engineer, all these difficulties are overcome. In the first place, the engineer draws up a scale of prices and specifications which must be complied with in their entirety as well as in all details. Rival engine builders are thus compelled to make their estimates according to the same standard, so that one engine can readily be compared with another with the utmost fairness. In these specifications, penalties will be provided for by the engineer which will be levied if the warranties of the maker are not fulfilled. Otherwise the warranties are worth nothing. The first consequence of engaging a consulting engineer is to render the matter of cost a secondary one. A factory owner who employs a consulting engineer and pays him for his services, is impelled chiefly by the desire to obtain a good installation which will perform what he expects of it. For that reason necessary sacrifices will be made to comply with the client's wishes. If the purchaser considers the question of cost most important to him, he need not engage an expert to supervise the installation of his engines. He has simply to pick out the cheapest engine. Unfortunately, however, the money which he will save by such a procedure will be more than compensated for by the trouble which he will later experience when his motor stops or when it breaks down, because it has been cheaply built in the first place. The advice of a consulting engineer is therefore of importance to the purchaser, because an engine will be installed which will in every way meet his requirements. The gas-engine builder will also prefer to deal with an engineer, because the engineer can appreciate at their true worth good material and good workmanship and place a fair valuation upon them. The specifications of a gas-engine and gas-producer expert are accepted by most engine builders, because an expert will not introduce conditions which cannot be fulfilled. Some manufacturers refuse to consider the conditions imposed by specifications seriously, or else they fix different prices and make tenders on the basis of these with or without specifications. In either case the purchaser may be sure that he is not receiving what he has a right to exact. =Testing the Plant.=--When the engine has been selected the consulting engineer supervises its installation, and, after this is completed, carries out tests in order to determine whether or not the guaranteed power and consumption are attained. The methods employed in testing a gas-engine are both complex and delicate. The quality of the gas, the proportions of the elements forming the mixture, the time and the method of ignition, the temperature of the cylinder-walls, the temperature and the pressure of the gas drawn into the cylinder, all these are factors which have a decided bearing upon the results of a test. If these factors be not carefully considered the conclusions to be drawn from the test may be absolutely wrong. Indicators of any type should not be indiscriminately employed; only those specially designed for gas-engine purposes should be used. Indicator cards are in themselves inadequate, and should be supplemented by the records of explosion-recorders. The calorific value of the gas should be measured either by the Witz apparatus or by means of any other calorimeter. In interpreting the diagrams and records some difficulty will be encountered. Sometimes it happens that a particular form of curve is attributed to a cause entirely different from the real one. It happens not infrequently that engineers, whose experience is confined to engines of one make and who have not had the opportunity to make sufficient comparisons, draw such erroneous conclusions from cards. To recapitulate what has already been said, the testing of gas-engines requires considerable experience and cannot be lightly undertaken. Special instruments of precision are necessary. The author has very often been called upon to contradict the results obtained by experts whose tests have consisted simply in ascertaining the engine power either by means of a Prony brake, or by means of a brake-strap on the fly-wheel. The brake gives but crude results at best; it is a means of control, and not an instrument of scientific investigation. Something more than the mere power produced by an engine should be ascertained. The tests made should throw some light upon the reasons why that power cannot be exceeded, and show that the necessary changes can be made to cause the engine to operate more economically and to yield energy of an amount which its owner has a right to expect. The indicator and the recorder are testing instruments which clearly indicate discrepancies in operation and the means by which they may be corrected. The tests made should determine whether the power developed is not obtained largely by means of controlling devices which cause premature wearing away of the engine parts. It is not the intention of the author to describe indicators of the well-known Watt type. It is simply his purpose to call attention to the explosion-recorder which he has devised to supplement the data obtained by means of the indicator. [Illustration: FIG. 145.--Mathot explosion-recorder.] =Explosion-Recorder for Industrial Engines.=--The explosion-recorder illustrated in Fig. 145 can be adapted to any ordinary indicator. It is composed of a supporting bracket _B_ upon which a drum _T_ is mounted. This drum is rotated by a clock-train, the speed of which is controlled by means of a special compensating governor. The entire system is pivotally mounted upon the supporting screw _O_, so that the drum _T_, about which a band of paper is wound, may be swung against a stylus _C_, which records upon the paper the number and power of the explosions. These explosions are measured according to scale by a spring connected with an indicator. The records obtained disclose for any given cycle the amount of compression as well as the force of the explosion, and render it possible to study the phenomena of expansion, exhaust, and suction. They are, however, inadequate in showing exactly how an engine runs in general. Indeed, in most gas-engines, as well as oil and volatile hydrocarbon engines, each explosion differs from that which follows in character and in power; and it is absolutely essential to provide some means of avoiding these variations. The explosion-recorder gives a graphic record from which the number of explosions can be read, and also the initial pressure of each explosion, the number of corresponding revolutions, the order in which the explosions succeed one another, and consequently the regularity of certain phenomena caused by secondary influences, such as the section of the distributing members, the sensitiveness of the governor, and the like. The explosion-records can be taken simultaneously with ordinary diagrams. In order to attain this end, the recorder is allowed to swing around the pivot _O_, so that the drum carrying the paper band is brought into engagement, or swung out of engagement with the stylus, as it is influenced by each explosion, thereby leaving its record on the paper. The ordinary diagram may be traced on the drum of the indicator, as it continues to operate in its usual way. Thus the explosion-recorder renders it possible to control the operation of engines, to obtain some idea of the cause of defects and to attribute them to the proper force. Improvements can then be made which will ensure a greater efficiency. A number of records herewith reproduced illustrate the defects in the controlling apparatus and in the construction of certain engines, and also the result of improvements which have been made on the basis of the records obtained. The smaller lines indicate the compression, which is usually constant in engines in which the "hit-and-miss" system of governing is employed, while the larger lines indicate the explosions. These records are only part of the complete data normally drawn on the paper in the period of 120 seconds corresponding with an entire revolution of the recorder-drum. [Illustration: FIG. 146.--Record with automatic starter.] [Illustration: FIG. 147.--Gas-engine running at one-half load.] [Illustration: FIG. 148.--Record made after correcting faults.] [Illustration: FIG. 149.--Record made after correcting faults.] The first record was taken while starting up an engine provided with an automatic starting device and supplied with explosive mixture without previous compression (Fig. 146). The gradual lessening of the distances of the ordinates or lines representing the explosions shows that the speed of the motor was slowly increasing, and also indicates the time which elapsed before the engine was running smoothly. The records that follow (Figs. 147, 148 and 149) show the results which can be obtained with the recorder by correcting the errors due to faults in installing the engine and its accessories. The fifth record is particularly interesting because it shows the influence of the ignition-tube on the power of the deflagration of the explosive mixture (Fig. 150). This record was obtained with an engine provided with two contiguous tubes. The communication of each of these tubes with the explosion-chamber could be cut off at will at any moment. The last record (Fig. 151) was obtained at a time when the effective load of the engine was changed at two different intervals. This record shows how regularly the engine was running and how constant were the initial pressures. These pressures, however, which is the case in most engines, manifestly diminish when the explosions succeed one another without idle strokes of the piston. This shows, also, the influence of "scavenging" the products of combustion and the effect it has on the efficiency of explosion-engines. =Analysis of the Gases.=--It has already been stated that one of the tests which should be made consists in measuring the calorific value of the gas. Just what the calorific value of the gas may be it is necessary to know in order to obtain some idea of the thermal efficiency of the installation. If a suction gas-producer be employed (an apparatus in which the nature of the gas generated changes at each instant), calorimetrical analyses are indispensable in appreciating the conditions under which a generator operates. These analyses are made by means of calorimeters which give the calorific value either at a constant pressure or at a constant volume. Constant-volume instruments give a somewhat weaker record than constant-pressure instruments; but according to Professor Aimé Witz, the inventor of an excellent calorimeter, the constant-volume type is almost indispensable in gaging the efficiency of explosion-engines. [Illustration: FIG. 150.] [Illustration: FIG. 150_b_.] [Illustration: FIG. 151.--Record made when effective load was changed at two different intervals.] [Illustration: FIG. 152.--The Witz calorimeter.] =The Witz Calorimeter.=--The accompanying diagram (Fig. 152) illustrates Professor Witz's instrument. Its elements are a steel cylinder having an interior diameter of 2.36 inches, about a thickness of 0.078 inch and a height of about 3.54 inches, so that its capacity is about 15.1 cubic inches, and two covers screwed on the cylinder to seal it hermetically, oiled paper being used as a washer. The upper cover carries a spark-exciter; the lower cover is provided with a valve which discharges into a cylindrical member 1.06 inches in diameter. This second cover is downwardly inclined at its circumference toward the center to insure complete drainage of the mercury used for charging the calorimeter. All surfaces are nickel plated. The proportions of nickel and of steel are fixed by the manufacturer so as to render it possible to calculate the displacement of the apparatus in water. The calorimeter having been completely filled with mercury is inverted in this liquid in the manner of a test tube. The explosive mixture is then introduced, being fed from a bell in which it has previously been prepared. A rubber tube connects the bell with the instrument. The gas is forced from the bell to the calorimeter by the pressure in the bell. The conical form of the bottom causes the calorimeter to be emptied rapidly and to be refilled completely with explosive gas at a pressure slightly above that of the atmosphere. Equilibrium is re-established by manipulating the valve, during a very short interval, so as to permit the excess gas to escape. During this operation the calorimeter must be maintained in the vertical position shown in the diagram. The atmospheric pressure is read off to one-tenth of a millimeter (0.003936 inches) on a barometer. The temperature of the gas may be taken to be that of the mercury-vessel. The explosive mixture is prepared in the water reservoir, the glass bulb shown in the accompanying illustration being employed. This bulb is closed at its upper end by means of a cock and is tapered at its lower end. The gas or air enters at the top by means of a rubber tube and gradually displaces the water through the lower end. The bulbs have a volume varying from 200 to 500 cubic centimeters (12 to 30 cubic inches), and the error resulting from each filling of a bulb is certainly less than 15 cubic millimeters (0.0009 cubic inches). The contents are emptied into a bell by lowering the bulb into the water and opening the cock. If seven bulbfuls of air be mixed with one bulbful of gas, an explosive mixture of 1 to 7 is produced, this being the proportion commonly employed for street-gas. For producer-gases the preferred proportion is 1 to 1, oxygen being often added to the air in order to insure complete combustion. The calorimeter, after having been filled, is placed in a vessel containing a liter (1.7598 pints) of water so that it is completely immersed. A spark is then allowed to pass. The explosion is not accompanied by any noise; the temperature rises a fixed number of degrees, so that the quantity of heat liberated can easily be computed. Each division of the thermometer is equal to 0.01502 C. The scale reading is minute, each interval being divided by ten, so that readings to the 1,500th part of a degree can be taken. It should be observed that the mixture generated in the reservoir is saturated with water vapor at the temperature of the reservoir. Consequently, the vapor generated by the explosion must condense in the calorimeter if the final temperature of the calorimeter is the same as that of the water reservoir. If, on the other hand, the temperature be slightly different, a correction must be made; but the error is negligible for differences in temperature of from 2 to 3 degrees C. (3.6 to 5.4 degrees F.). This, however, is never likely to occur if the operation is conducted under favorable conditions. This apparatus is exceedingly simple and practical. It does not require the manipulation of a pump. The pressure of the mixture is read off on the barometer; the calorimeter is entirely immersed in the water of the outer vessel, so that all corrections of doubtful accuracy are obviated. The method requires but a very slight correction for temperature. Air, alone or mingled with oxygen, or a mixture of air and oxygen, can be easily tested with. =Maintenance of Plants.=--If it should be necessary to retain a consulting engineer to install an engine capable of filling all requirements, it is also necessary to select a careful attendant in order that the engine may be kept in good condition. It is a rather widespread belief that a gas-engine can be operated without any care or inspection. This belief is all the more prevalent because of the employment of street-gas engines, which, by reason of their simplicity of construction and regularity of fuel supply, often run for several hours, and even for an entire day, without any attention whatever. But this negligence, particularly in the case of engines driven from producers, is likely to produce disastrous results. Although engines of this type do not require constant inspection during operation, still they require some attention in order that the speed may be kept at a fixed number of revolutions. Moreover, the care of the engine, the cleaning of the valves and of the various parts which are likely to become dirty, and the examination and cleaning of pipes, should be accomplished with great care and at regular intervals. This task should be entrusted only to a man of intelligence. A common workman who knows nothing of the care with which the parts of an engine should be handled is likely to do more harm than good. The factory owner who follows the instructions which have been given in this book will avoid most of the stoppages and the trouble incurred in engine and generator installations, and may count upon a steadiness of operation comparable with that of a steam-engine. TEST OF A "STOCKPORT" GAS-ENGINE WITH DOWSON PRESSURE GAS PLANT Made by R. Mathot at the Works of the "Union Electrique" C^{ie}, Brussels, June 27, 1901 Piston Diameter: 15-1/2". Piston stroke, 22". Normal number of revolutions, 210. 1. Calorific value of the coal 12750 B.T.U. 2. Nature and origin of fuel: Anthracite coal of Charleroi (Belgium). 3. Cost of fuel per ton at the mine $5.50 4. Cost of fuel per ton at the plant $6.39 5. Fuel consumption per hour in the generator 46.3 lbs. 6. Fuel consumption per hour in the boiler 7 lbs. 7. Proportion of ash in the coal 6 per cent. 8. Weight of steam at 66 lbs. generated per hour 42.7 lbs. 9. Average brake horse-power 53 B.H.P. 10. Fuel consumption for gas per B.H.P. per hour 0.875 lbs. 11. Fuel consumption for steam per B.H.P. per hour 0.133 lbs. 12. Total fuel consumption 1.008 lbs. 13. Steam consumption at 66 lbs. pressure 0.81 lbs. 14. Gas pressure at the engine 1-3/8 inches 15. Weight of water per B.H.P. per hour for cooling the cylinder entering at 68° F. and leaving at 105° F. 51.5 lbs. 16. Corresponding heat absorbed in cooling 1970 B.T.U. 17. Average initial explosive pressure on piston 324 lbs. 18. Average pressure on piston per square inch 72 lbs. 19. Average indicated horse-power with 85 per cent. misses 92.5 I.H.P. 20. Corresponding mechanical efficiency 84 per cent. 21. Corresponding electric load 31.950 K.W. 22. Cost of B.H.P. per hour in anthracite $0.0029 23. Cost of kilowatt per hour in anthracite $0.0048 24. Electric power generated per B.H.P. 602.8 W. 25. Thermal efficiency at 53 B.H.P. with 85 per cent. explosions 18.5 per cent. TEST OF A 20 H.P. WINTERTHUR ENGINE With Winterthur Suction-Producer made by R. Mathot at Winterthur, June 4 and 5, 1902 DATA OF TESTS WITH ILLUMINATING GAS AND WITH FUEL GAS Dimensions of Winterthur Engine--Piston diameter: 10-3/8". Stroke: 16-7/8". Compression: 177 pounds per square inch. Regulation: hit and miss. Ignition: electro-magnetic. Fly-wheel: normal, with external bearing. Lubrication of piston: with oil-pump. Of main bearings, with rings (as in dynamos). FULL LOAD WITH STREET-GAS 1. Number of revolutions per minute 200 2. Corresponding number of explosions 96 per cent. 3. Net load on brake 120 lbs. 4. Corresponding effective power 22 B.H.P. 5. Mean initial explosive pressure on piston per square inch 455 lbs. 6. Average pressure on piston per square inch 78 lbs. 7. Gas consumption per B.H.P. at 24° C. and 721 mm. mean pressure 15.5 cubic feet 8. Gas consumption per B.H.P. reduced to 0° C. and 760 mm. mean pressure 13.5 cubic feet HALF LOAD WITH STREET-GAS 9. Number of revolutions per minute 204 10. Corresponding number of explosions 60 per cent. 11. Net load on brake 60 lbs. 12. Corresponding effective power 11.6 B.H.P. 13. Gas consumption per B.H.P. per hour at 24° C. and 721 mm. mean pressure. 21 cubic feet 14. Gas consumption per B.H.P. per hour at 0° C. and 760 mm. mean pressure. 18.3 cubic feet RUNNING WITH NO LOAD WITH STREET-GAS 15. Number of revolutions per minute 206 16. Corresponding number of explosions 22 per cent. 17. Total gas consumption per hour at 24° C. and 721 mm. mean pressure. 106 cubic feet 18. Maximum calorific power of gas per cubic foot 598 B.T.U. 19. Thermal efficiency with 96 per cent. explosions 31 per cent. 20. Mechanical efficiency with 96 per cent. explosions 82 per cent. 21. Temperature of water at the jacket-inlet 75 degs. F. 22. Temperature of water at the jacket-outlet 130 degs. F. 23. Compression per square inch on piston surface 178 lbs. 24. Pressure after expansion 37 lbs. TEST OF WINTERTHUR PLANT WITH PRODUCER-GAS 1. Nature of fuel. Belgian anthracite, "Bonne Esperance et Batterie"; size, 3/4 inch. 2. Chemical composition: Carbon, 86.5 per cent.; hydrogen, 3.5 per cent.; oxygen and nitrogen, 4.65 per cent.; ash, 5.35 per cent. 3. Calorific value per pound of coal 14200 B.T.U. 4. Net calorific value per pound of fuel 15050 B.T.U. 5. Price of anthracite delivered at the plant $3.50 per ton 6. Number of revolutions of engine per minute 200 7. Corresponding number of explosions 91 per cent. 8. Load on brake 106 lbs. 9. Corresponding effective horse-power 20.2 B.H.P. 10. Fuel consumption at the generator per hour 16.4 lbs. 11. Fuel consumed per B.H.P. per hour 0.81 lbs. 12. Proportion of ash resulting from the tests 6 per cent. 13. Mean initial explosive pressure per square inch 419.5 lbs. 14. Average pressure on piston per square inch 72.5 lbs. 15. Indicated horse-power with 91 per cent. explosions 25.4 I.H.P. 16. Mechanical efficiency 79 per cent. 17. Thermal efficiency at the producer 22 per cent. 18. Water consumption per hour in the scrubber 66 gals. 19. Cost per B.H.P. per hour in anthracite 62 gals. TEST OF A 60 B.H.P. GAS-ENGINE, TYPE G 9, WITH A SUCTION-GAS PLANT OF THE GASMOTOREN FABRIK DEUTZ (Made at Cologne, March 15, 1904, by R. Mathot.) DATA OF THE TESTS Diameter of Piston = 16.5". Piston Stroke = 18.9" FULL LOAD 1. Average number of revolutions per minute 188.66 2. Corresponding effective work 65.11 B.H.P. 3. Average compression per square inch 176 lbs. 4. Average initial explosive pressure per square inch 397 lbs. 5. Average final expansion pressure 25 lbs. 6. Vacuum at suction 4.4 lbs. 7. Average pressure on piston 81 lbs. 8. Corresponding indicated horse-power 77 I.H.P. FUEL 9. Nature of fuel: Anthracite coal 0.4" to 0.8" 10. Origin: Coalpit of Zeihe, Morsbach at Aix-la-Chapelle. 11. Chemical composition of coal: Carbon 83.22% Hydrogen 3.31% Nitrogen and Oxygen 3.01% Sulphur 0.44% Ash 7.33% Water 2.69% 12. Calorific value. 13650 B.T.U. GAS 13. Chemical composition of gas: Carbonic acid 6.60% Oxygen 0.30% Hydrogen 18.90% Methane 0.57% Carbon monoxide 24.30% Nitrogen 49.33% 14. Calorific value of gas, combination water, at 59° F. constant volume reduced to 32° F. and atmospheric pressure 140 B.T.U. TEMPERATURES _Engine_ 15. Cooling water at the inlet of the cylinder-head 55.4 deg. F. Temperature at the outlet 109.5 deg. F. 16. Temperature at outlet of cylinder 127.5 deg. F. _Gas-Generator_ 17. Temperature of water in the vaporizer 158.3 deg. F. EFFICIENCIES AND CONSUMPTION 18. Mechanical efficiency 84.6% 19. Gross consumption of coal per B.H.P. per hour 0.86 lbs 20. Thermal efficiency in proportion to the effective work and the gross consumption of coal in the gas-generator 24.3% HALF LOAD WORK 1. Average number of revolutions per minute 195.5 2. Corresponding effective work 33.85 B.H.P. 3. Corresponding average compression 125 lbs. 4. Average initial explosive pressure 258 lbs. 5. Average final expansion 18 lbs. 6. Vacuum at suction 6.8 lbs. 7. Average mean pressure on piston 46.2 lbs. 8. Corresponding indicated power 45. I.H.P. 9. Speed variation between full and half load 3.5% CONSUMPTION 10. Gross consumption of coal per B.H.P. per hour 1.155 lbs. RUNNING WITH NO LOAD 1. Average number of revolutions per minute 199 2. Minimum corresponding compression 95.55 lbs. 3. Average initial explosive pressure 220 lbs. 4. Average final expansion 0 lbs. 5. Vacuum at suction 8.8 lbs. 6. Average pressure on piston 11.2 lbs. 7. Corresponding indicated horse-power. 11 I.H.P. 8. Speed variation between full load and no load 5.2% TEST OF A GAS PLANT OF A FOUR-CYCLE DOUBLE-ACTING ENGINE OF 200 H.P. AND A SUCTION-PRODUCER IN THE WORKS OF THE GASMOTOREN FABRIK DEUTZ, COLOGNE March 14 and 15, 1904, by Messrs. A. Witz, R. Mathot, and de Herbais DATA OF THE TESTS Piston Diameter: 21-1/4". Stroke: 27-9/16". Diameter of Piston-Rods: front, 4-3/4"; rear, 4-5/16" ENGINE _Full Load Tests_ 1. Average number of revolutions per minute 151.29 and 150.20 2. Corresponding effective load 214.22 B.H.P. and 222.83 B.H.P. 3. Duration of the tests 3 hours and 10 hours 4. Average temperature of water after cooling the piston 117.5 deg. F. 5. Average temperature of water after cooling the cylinder and valve-seats 135 deg. F. 6. Water consumption per hour for cooling the piston 39 gal. PRODUCER 7. Nature and Origin of Fuel: Anthracite coal "Bonne-Esperance et Batterie" Herstal, Belgium. 8. Calorific value of fuel 14650 B.T.U. 9. Consumption of fuel per hour (plus 53 lbs. on the night of the 14th for keeping the generator fired during 14 hours, the engine being stopped) 199 lbs.-160 lbs. 10. Water consumption per hour in the vaporiser 14.2 gals. 11. Water consumption per hour in the scrubbers 318 gals. 12. Average temperature of gas at the outlet of the generator 558 deg. F. 13. Average temperature of gas at the outlet of the scrubbers 62.5 deg. F. EFFICIENCIES 14. Gross consumption of coal per B.H.P. per hour 0.927 lbs.-0.720 lbs. 15. Consumption of coal per B.H.P. after deduction of the water 0.907 lbs.-0.705 lbs. 16. Thermal efficiency relating to the effective H.P. and to the dry coal consumed in the generator 19%-24.4% 17. Water consumption per B.H.P. hour: For the cylinder, stuffing-boxes and valve-seat jackets 4.65 gals. For the piston and piston-rods 1.75 gals. For the vaporizer 0.0655 gals. For washing the gas in the scrubbers 1.42 gals. 18. Water converted in steam per lb. consumed in the generator 0.193 gals. INDEX A Adjustment of gas-engine, 126 Adjustment of moving parts, imperfect, 146 Admission-valve, binding of, 152 Admission, variable, 55, 56 Air-blast, 180 Air-chest, 82 Air, displacement of, 92 Air, exclusion of, in producers, 207 Air, filtration of, 82 Air-heater, Winterthur, 236 Air-heaters, 238 Air-pipe, 82 Air-pipe, location of, 83 Air-pump, 266 Air, regulation of supply, 82 Air suction, 81 Air suction, resistance to, 82 Air supply of producer, 225 Air-valve, control by engine, 25 Air vibration, 92 Alcohol as engine fuel, 264 Anthracite, consumption of, in producers, 200 Anthracite in producers, 190, 201 Anti-pulsators, 77 Anti-pulsators, disconnection of, in stopping engine, 132 Anti-pulsators, precautions to be taken with, 79 Anti-vibratory substances, 89 Ash-pit, 214, 217 Ash-pit, Bollinckx, 220 Ash-pit, cleaning of, 261 Ash-pit, Deutz, 220 Ash-pit, door of, 220 Ash-pit, Wiedenfeld, 220 Asphyxiation, 169 Atomizer of oil-engines, 265 B Back firing, 82, 131 Back pressure to exhaust, 151 Bags, arrangement of, 80 Bags, capacity of, 79 Bags, precautions to be taken with, 79 Bags, rubber, 77 Bark as producer fuel, 193 Batteries for ignition, 31 Bearings, adjustability of, 5 Bearings, adjustment of, 44 Bearings, care of, 123 Bearings, lubrication of, 117 Bearings, material of, 51 Bearings of fly-wheels, 92 Bearings, overheated, 146 Bearings, over-lubricated, 150 Bearings, position of, 44 Bell, gas-holder, 187 Bell, Pintsch, 248 Bell, volume of, 187 Belts, prevention of adhesion by oil, 120 Bénier, E., 199 Benzin as engine fuel, 264 Binding, 147 Blast in producers, 180, 193, 225 Blower, Koerting, 181 Blower, Root, 182, 188 Blowers for producers, 181 Blowing-generators, 169 Bolts of foundation, 91 Bomb, Witz, 284, 292 Boughs for coolers, 108 Box, charging, 221 Box, double closure for charging, 222 Box, removable charging, 225 Brake tests, 284 Branch pipes, minimum diameter of, 81 Bricks for foundation, 91 Brushes, lifting of, when dynamo-engine is stopped, 132 Brush, purifying, 250 Burner of hot tube, how ignited, 128 Burner, regulation of fixed, 144 Bushings, care of, 123 Bushings, fusion of, 147 Bushings (see also Bearings) C Calorimeter, Witz, 292 Calorimeters, 284, 290 Cam, half-compression, 130, 132 Cam, relief, 130 Cams, 51 Caps of valve-chests, 124 Carbureter, 266 Care during operation of engine, 131 Casing, independence of frame, 42 Charging a producer, 221 Charging the generator, 259 Chest for exhaust, 83 Circulation of water, 98, 125 Circulation of water, how effected, 102 Circulation of water in tanks, 105 Circulation of water, regulation of, 107 Cleaning of producer, 261 Cleanliness, necessity of, 121 Cleanliness of producers, 179 Closures for charging-boxes, 223 Coal in producers, 201 Coal in producers, bituminous, 195 Coal, Pennsylvania, 203 Coal (see also Anthracite) Coal, Welsh, 203 Cock, Deutz, 224 Cock, Pierson, 224 Cock for charging-box, 223, 224 Coke in producers, 201 Coke in washers, 242 Combustion-generators, 193 Combustion, inverted, 195 Compression, determination of, 273 Compression, faulty, 134 Compression, high, 154 Compression in Banki engine, 264 Compression in Diesel engine, 264 Compression, losses in, 143 Compression period, 21 Compression, relation to power developed, 122 Compressors for producers, 182 Connecting-rod bearings, 45 Connecting-rod bearings, rational design of, 45 Connecting-rod, lubrication of, 113, 115 Consulting engineer, advisability of retaining, 282 Consumption at half load and full load, 62 Consumption at various loads, 62 Consumption in double or triple acting engines, 62 Consumption of gas, 173 Consumption of gas in burner, 30 Consumption of suction-producers, 200 Consumption per effective horse-power, 62 Cooler for gas, 199 Cooler, for producer, 240 Coolers, 107 Coolers, size of, 109 Cooling of cylinder, 98, 100, 156 Cooling of producer-gas engines, 203 Cooling, thermo-siphon, 100 Cost of oil and volatile hydrocarbon engines, 268 Crank-pin, tensile strength of, 51 Crank-shaft, 50, 51 Crank-shaft bearings, 44 Crank-shaft bearings, design of, 46 Crank-shaft, effect of premature explosion on, 30 Crank-shaft lubrication, 117 Crank-shaft, material of, 50 Crosshead, care of, 123 Cycle, analysis of, 276 Cylinder, arrangement of, 41 Cylinder, cleaning of, 122 Cylinder, cooling of, 156 Cylinder, evacuation of, 83, 131 Cylinder, gravel in, 137 Cylinder, grinding of, 42 Cylinder, incandescent particles in, 142 Cylinder, independence of casing, Compression in, 42 Cylinder-jacket (see Water-jacket) Cylinder lubrication, 112 Cylinder-oil, 112, 149 Cylinder, overhang in horizontal engines, 42 Cylinder, overheating of, 148 Cylinder, presence of water in, 136 Cylinder-shell, 41 Cylinder, smoke from, 149 Cylinder, temperature during operation of engine, 132 Cylinder, thrust of, 43 Cylinder, tightness of, 122 D Damper, Pintsch, 224 Dampers, 223 Detonations, untimely, 141 Distributing mechanism, derangement of, 152 Drain-cock in gas-pipes, 70, 75 Drain-cocks, testing of, 256 Drier for producer-gas, 248 Dust-collector, 239 Dust-collector, Benz, 239 Dust-collector, Bollinckx, 239 Dust-collector, Pintsch, 239 Dust-collector, Wiedenfeld, 239 Dynamo, lifting brushes from, in stopping engine, 132 E Ebelmen principle, 195 Engine, Banki, 264 Engine, Diesel, 264 Engine, producer-gas and steam, compared, 203 Engine, selection of, 279 Engine, starting a producer-gas, 258 Engineer, duty of a consulting, 281 Engines, governing oil, 265 Engines, oil, 264, 265 Engines, producer-gas, 153 Engines, producer-gas, temperature of, 157 Engines, specifications of, 281 Engines, speed of oil, 264 Engines, tests of, 268 Engines, volatile hydrocarbon, 264, 267 Engines, writers on oil, 266 Escape-pipes, 228 Essences, 264 Exhaust, 83 Exhaust, back pressure to, 151 Exhaust, determination of resistance to, 274 Exhaust into sewer or chimney, 85 Exhaust, noises of, 94, 141 Exhaust period, 22 Exhaust, water in, 136 Exhausters, 183 Exhaust-chest, 83 Exhaust-muffler, 86, 94 Exhaust-pipe, 83, 85 Exhaust-pipe, design of, 96, 97 Exhaust-pipe, joints for, 85 Exhaust-pipe, oil in, 151 Exhaust-valve, binding of, 152 Exhaust-valve, cooling of, 25 Expansion-boxes, 95 Expansion period, 22 Expert, necessity of an, 282, 283 Explosion, spontaneous, 140 Explosion-engines (see Gas-engines) Explosion period, 22 Explosion-recorder, analysis of inertia of, 277 Explosion-recorder for industrial engines, 285 Explosion-recorder, the continuous, 269 Explosions, comparison of average force of, 275 Explosion-records, 288 Explosions, retarded, 143 F Fans for producers, 181 Feeder, Winterthur, 236 Feed-hopper, 224 Fire-box, door of, 221 Flues, escape, 228 Fly-wheel, oil on, 120 Fly-wheel, starting the, 131 Fly-wheels, 46 Fly-wheels as pulleys, 46 Fly-wheels, balancing of, 46 Fly-wheels, curved spoke, how mounted, 49 Fly-wheels, fastening of, 46 Fly-wheels, proper mounting of, 46 Fly-wheels, rim of, 46 Fly-wheels, single, 48, 92 Fly-wheels, single, for dynamo-engines, 46 Fly-wheels, straight and curved spoke, 49 Fly-wheels with hit-and-miss system, 50 Foundation, 44, 87 Foundation, design of, 88, 89 Foundation, excavation for, 88 Foundation, insulation of, 89, 90 Foundation of dynamo-engine, 91 Frame, 43 Frame, method of securing, to foundation, 44 Fuel of producers, 178, 187, 254 Fuel, qualities of, 201 Fuel (see also Lignite, Peat, Sawdust, Wood, Coal, etc.) Fuel, size of, 201 Fuel, smoke-producing, 254 G Gas, ascertaining purity of, 128 Gas, blast-furnace, 153 Gas, calorific value of, 284 Gas, calorific value of producer, 200 Gas, coke-oven, 153 Gas consumption, 173 Gas consumption of burner, 30 Gas, effect of quality, 152 Gas-engine, balancing of, 46 Gas-engine, care during operation, 131 Gas-engine, cost of installation, 19 Gas-engine, cost of operation, 19 Gas-engine, difficulties in starting, 134 Gas-engine, how to start a, 128 Gas-engine, how to stop a, 132 Gas-engine, installation of a, 68 Gas-engine, location of a, 68 Gas-engine, selection of a, 21 Gas-engine, simplicity of installation, 17 Gas-engine, the four-cycle, 21 Gas-engines, adjustment of, 126 Gas-engines, care of, 121 Gas-engines, "Steam-Hammer," 57 Gas-engines, temperature of, 158 Gas-engines, tests of, 283 Gas-engines, vertical, 56 Gas-engines, writers on, 68 Gas, fuel, 153 Gas-holder, 186, 189 Gas-holders, 247 Gas-holder, combined with washer or scrubber, 186 Gas, illuminating (see Street-gas) Gas, impurities of, 172 Gas, Mond, 153, 167 Gasometer (see Gas-holder) Gas, producer (see Producer-gas) Gas production, 173 Gas, purification of wood, 195 Gas supply, necessity of coolness, 69 Gas-valve, necessity of independent operation of, 27 Gas, water, 153, 169 Gas, wood, 153, 168 Gases, analysis of, 290 Generator (see also Producer) Generator, Benz, 207 Generator, Bollinckx, 207 Generator, care of, 259 Generator, charging the, 259 Generator, construction of, 177, 207 Generator, dimensions of, 252 Generator, Dowson, 177 Generator, firing the, 205, 256 Generator, hot operation of, 252 Generator of suction producer, 205 Generator, operation of, 251 Generator, Pierson, 215 Generator, Pintsch, 207 Generator, Taylor, 207 Generator, Wiedenfeld, 207 Generator, Winterthur, 207 Generator with internal vaporizer, 206 Generators, blowing, 169 Generators, pressure, 169, 177 Governor, ball, 52, 53 Governor, care during operation, 131 Governor, hit-and-miss, 52, 54 Governor, inertia, 53 Governor, sensitiveness of, 52 Governors, 53 Governors, adjustment of, 124 Governors, care of, 123 Governors, centrifugal, 56 Governors, centrifugal, with hit-and-miss regulation, 55 Governors for oil-engines, 265 Governors for producer-gas engines, 161 Governors, hit-and-miss, 54 Governors, variable admission, 56 Grate, Bénier's, 216 Grate of generator-lining, 214 Grate, Kiderlen, 216 Grate, Pintsch, 216 Grate, Wiedenfeld, 216 H Heater, air, 238 Hit-and-miss regulation (see Governors) Holders, gas, 247 Hopper, Bollinckx, 225 Hopper, Deutz, 225 Hopper for generator, 224 Hopper, removable feed, 225 Hopper, Taylor, 225 Hopper, Wiedenfeld, 225 Hopper, Winterthur, 225 Horse-power, definition of, 60 Horse-power, determination of, 61 Horse-power (see also Power) Hot tubes (see Tubes) Hydrocarbons, volatile, for engine fuel, 264 I Ignition, 27, 122 Ignition, adjustment of, 144 Ignition by battery and coil, 31 Ignition by magneto, 33 Ignition, curing defects of electric, 145 Ignition, defective, 152 Ignition, disadvantages of belated, 28 Ignition, disadvantages of premature, 28 Ignition, effect of lost motion, 146 Ignition, effect of mixture composition on, 28 Ignition, effect of temperature of flame on, 28 Ignition, effect of water on, 136 Ignition, electric, 30, 139 Ignition, electric, regulation of, 145 Ignition, faulty, 143 Ignition for high-pressure engines, 35 Ignition, hot-tube, 159 Ignition, imperfect, 137 Ignition, objections to electric, 31 Ignition of producer-gas, 160 Ignition, premature, 139, 142 Ignition, premature, in high-pressure engines, 158 Ignition, prevention of, by faulty compression, 134 Ignition, proper timing of, 27 Ignition, spontaneous, 140, 159 Ignition, tests prior to starting engine, 129 Ignition-tubes (see Tubes) Incrustation of water-jacket, 98, 148 Incrustation, prevention of, 107 Incrustations, 255 Indicators, 285 Indicator-records, 127 Induction-coil, 32 Installation, laws governing gas-engine, 86 J Joints, 125 Joints, care of, 124 L Laming mass, 246 Laws governing gas-engines, 86 Leakage of pipes, 69 Lift-valve for charging-box, 223 Lignite in producers, 188 Lining, refractory, 211 Lining, support for generator, 214 Loads, consumption at half and full, 62 Location of engine, 68 Lubricate (see Oils) Lubricating-pumps, 115 Lubrication, 111, 121 Lubrication, difficulties entailed by, 119 Lubrication, faulty, 149 Lubrication of crank-shaft, 117 Lubrication of high-power engine, 116 Lubrication of valve-stem, 119 Lubricator, cotton-waste, 117 Lubricators, automatic, 113 Lubricators, disconnection of, when stopping engine, 132 Lubricators, examination of, before starting, 129 Lubricators, feed of, 121 Lubricators, revolving-ring, 118 Lubricators, sight-feed, 118 Lubricators, types of, 113 M Magneto, adaptability for producer-gas, 35 Magneto, control of, 38 Magneto, efficiency of, 34 Magneto-igniter, construction of, 35 Magneto ignition, 33 Magneto ignition, precautions to be taken, 34 Magneto, inspection of, before starting engine, 129 Magneto, mechanical control of, 33 Magneto, operation of, 33 Magneto, regulation of, 37 Maintenance of plants, 295 Manograph, 269 Mass, Laming, 246 Meters, capacity of, 70 Meters, dry, 72 Meters, evaporation in wet, 70 Meters, falsification of records, 70 Meters, inclination of, 71 Meters, size of, 71 Misfire, 137 Mixture, effect of high compression in, 155 Mixture, effect of high pressure on, 156 Mixture, governing by varying the, 161-164 Mixture, poorness of, 143 Mixture, pressure of, 26 Mixture-valve, necessity of independence of operation of, 27 Mortar for foundation, 87 Motion, lost, 146 Muffler for exhaust, 86, 94 N Naphthalene in gas-pipes, 70 Noises, cause of, 92 Noises of exhaust, 94 O Oilers (see Lubricators) Oiling (see Lubrication) Oil, addition of sulphur to, 147 Oil, cylinder, 149 Oil-engines, 264, 265 Oil-engines, governing, 265 Oil-engines, speed of, 264 Oil-engines, writers on, 266 Oil for engine fuel, 264 Oil, freezing of, 150 Oil-guard for fly-wheel, 120 Oil-lamp, 266 Oil, prevention of spreading on fly-wheel, 120 Oil-pumps, 115, 226 Oil, quality of, 150 Oil, splashing of, 119 Oil-tank, 266 Oils, how tested, 112 Oils, mineral for lubrication, 112 Oils, purification of, 113 Oils, quality of, 112 Oils, requisites of, 112 Operation, steadiness of, 52 Otto cycle, 21 Overheating, 152 Overheating, prevention of, 147 P Pacini treatment, 171 Peat in producers, 188 Perturbations, 134 Petrol (see Oil) Pipe-hangers, 86 Pipes, 69 Pipes, cross-section of, 70 Pipes, disposition of, 77 Pipes, escape, 228 Pipes, exposure to cold, 69 Pipes for exhaust, 83 Pipes for producer-gas, 249 Pipes for water-tanks, 102, 103, 105 Pipes, hanging of, 86 Pipes, insulation from foundations and walls, 94 Pipes, leakage of, 69 Pipes, minimum diameter of branch, 81 Pipes, proper size of, 70 Piston, 39, 122 Piston, avoidance of insertions or projections, 39 Piston, cleaning of, 141 Piston, curved faces inadvisable, 39 Piston, direct connection with crank-shaft, 43 Piston, finish of, 41 Piston, importance of, 111 Piston, leakage of, 136 Piston, overheating of, 148 Piston, position of, in starting, 130 Piston, rear face of, 39 Piston-pin, construction of bearing at, 40 Piston-pin, location of, 41 Piston-pin, locking of, 40 Piston-pin, lubrication of, 113 Piston-pin, material of, 40, 51 Piston-pin, strength of, 40 Piston-rings, fouling of, 149 Piston-rings, material of, 41 Piston-rings, number of, 41 Piston-rod, effect of premature explosion on, 30 Piston-wear, 40 Poisoning, carbon monoxide, 170 Porcelain of spark-plug, 32 Power, definition of, 60 Power, measuring engine, 285 Power, "Nominal," 61 Precautions to be taken in starting, 128 Pressure, back, to exhaust, 151 Pressure-generators, 169, 177 Pressure in producer-gas engines, 160 Pressure-lubricators, 114 Pressure-producers, 174 Pressure-regulator, bell as, 187 Pressure-regulators, 77 Pressure-regulators, their construction, 78 Pressures, high, in producer-gas engines, 154 Preheaters, 229 Producer, assembling, 253 Producer, Bénier, 216 Producer, Benz, 228, 239, 240 Producer, Bollinckx, 206, 220, 225, 228, 234, 239 Producer, Chavanon, 229 Producer, cleaning of, 261 Producer, Dawson, 174 Producer, Deschamps, 198 Producer, Deutz, 206, 220, 224, 225, 228, 229, 240 Producer, Deutz, 231, 232 Producer, Deutz lignite, 188 Producer, Duff, 195 Producer, Fangé-Chavanon, 198 Producer, Fichet-Heurty, 240, 245 Producer, Gardie, 183 Producer-gas, 153 Producer-gas, 165 Producer-gas as a furnace fuel, 177 Producer-gas, calorific value of, 200 Producer-gas, composition of, 166 Producer-gas plants, tests of, 297 Producer-gas, writers on, 154 Producer, general arrangement of suction, 204 Producer, Goebels, 206 Producer, Hille, 206, 239 Producer, Kiderlen, 206 Producer, Kiderlen, 216 Producer, Koerting, 232 Producer, Lencauchez, 212, 214 Producer, Phoenix, 217 Producer, Pierson, 224, 229 Producer, Pintsch, 206, 216, 224, 231, 232, 239, 245, 248 Producer, Riché, 168, 190, 193, 195, 216 Producer (see also Generator) Producer, stoppage of, 261 Producer, Taylor, 206, 214, 225, 231, 232 Producer, test by smoke, 254 Producer, test of Deutz, 298 Producer, test of Dowson, 296 Producer, tests of Winterthur, 297 Producer, Thwaite, 195 Producer, Wiedenfeld, 206, 216, 220, 225, 234, 239 Producer, Winterthur, 225, 228, 236 Producers, advantages of suction, 199 Producers, combustion, 193 Producers, conditions of perfect operation, 251 Producers, consumption of suction, 200 Producers, distilling, 190 Producers, efficiency of, 201 Producers, efficiency of lignite, 190 Producers, efficiency of wood, 194 Producers, lignite, 188 Producers, maintenance of, 254 Producers, peat, 188 Producers, pressure, 174 Producers, self-reducing, 193 Producers, specifications of, 281 Producers, suction, 199 Producers, suction (see also Suction-producers) Producers, tests of, 297 Producers with external vaporizers, 206 Production of gas, 173 Pulley, disconnection of, in stopping engine, 132 Pump, circulating with by-pass, 106 Purifier, fiber, 185 Purifier, Fichet-Heurtey, 245 Purifier, material for, 245 Purifier, moss, 185 Purifier, Pintsch, 245 Purifier, sawdust, 185 Purifiers for gas, 184 Purifiers for producer-gas, 244 R Recorder, analysis of inertia of explosion, 277 Recorder, explosion, for industrial engines, 285 Recorder, the continuous explosion, 269 Records of engines, 284 Records of explosions, 288 Records, indicator, 127 Regrinding of valves, 122 Regularity, cyclic, 48, 53 Remagnetization of magnetos, 33 Resuscitation after asphyxiation, 171 Retort, cleaning of, 225 Retort of producer, 190 Retort, support, 214 Revolutions, variations in number of, 52 Rollers, 51 Running, steadiness of, 52 S Sand for foundation, 87 Sawdust in producers, 193 Scavenging, 142, 155 Scrubber, 189, 199 Scrubber, combined with gas-holder, 186 Scrubber for producer-gas, 240 Scrubber, size of, 253 Selection of gas-engine, 21 Shavings in producers, 193 Slide-valve for charging-box, 223 Slide-valve, its disadvantages, 23 Sluice-valves, 101 Smoke from cylinder, 149 Spark-plug, 32 Specifications of engines, 281 Specifications of producers, 281 Speed, how to increase, 124 Speed of oil-engines, 264 Speed of volatile hydrocarbon engines, 264 Speed, variation of, with load, 52 Spokes of fly-wheels, 49 Spring for valves (see Valves) Springs, selection of, for explosion-recorder, 277 Starter, Tangye, 65 Starting an engine, 128 Starting, automatic, 63, 130 Starting by compressed air, 64 Starting by hand, 63 Starting by hand-pumps, 64 Starting, difficulties in, 134 Starting, how accomplished, 66 Starting of producer-gas engine, 258 Steadiness, 52 Steam-engine, cost of installation, 19 Steam-engine, cost of operation, 19 Stoppage of producer, 261 Stopping the engine, 132 Stops, sudden, 151 Straw in producers, 193, 254 Street-gas, 165 Suction, determination of resistance to, 274 Suction, noises caused by, 141 Suction of air, 81 Suction period, 21 Suction-producer, general arrangement of, 204 Suction-producers, 199 Suction-producers, advantages of, 199 Suction-producers, efficiency of, 201 Suction-valve, leakage of, 142 Super-heater, Winterthur, 236 Sylvester treatment, 171 T Tanks, connection of, 105 Tanks, design of, 103 Tanks, location of, 102 Tanks for water-jacket, how mounted, 101 Tar in producer-plants, 200 Tar, removal of, 250 Tar (see also Scrubber, Purifier, etc.) Taylor, A., 199 Terminals of magneto apparatus, 34 Tests of gas-engine plants, 283 Tests of high-speed engines, 268 Tests of producer-gas engines, 297 Thrust-bearings, 51 Tongue, traction of, in asphyxiation cases, 172 Tower, washer, 244 Town-gas (see Street-gas) Tree branches for coolers, 107 Trepidations, 92 Tube, gas-supply pipe of incandescent, 77 Tube, incandescent, 27 Tube, incandescent, adjustment of, 144 Tube, incandescent, breakage of, 137 Tube, incandescent, danger of breaking, 131 Tube, incandescent, how started, 128 Tube, incandescent, leakage of, 138 Tubes as vaporizers, 231 Tubes, incandescent, 28, 159 Tubes, incandescent, valved, 29 Tubes, use of special valves with incandescent, 29 Tubes, valveless ignition, 28 V Valve-chests, 124 Valve mechanism, slide, 23 Valve-regrinding, 122, 135 Valve-stem lubrication, 119 Valves, 122 Valves, accessibility of, 25 Valves, cooling of, 25 Valves, cooling of, in high-pressure engines, 156 Valves, defective operation of, 135 Valves, free, 27 Valves, mechanical control of, 27 Valves, modern, 24 Valves, necessity of cleanliness, 25 Valves, regulation of, before starting, 129 Valves, requisites of, 25 Valves, retardation in action of, 146 Vaporizer, Bollinckx, 234 Vaporizer, Chavanon, 229, 234 Vaporizer, Deutz, 231, 232, 229, 225 Vaporizer, Field, 233 Vaporizer, internal, 206 Vaporizer, Koerting, 232 Vaporizer, maintenance of, 255 Vaporizer, operation of, 234 Vaporizer, Pierson, 229 Vaporizer, Pintsch, 231, 232 Vaporizer-preheaters, 229 Vaporizer, size of, 253 Vaporizer, Taylor, 231, 232 Vaporizer, Wiedenfeld, 225, 234 Vaporizers, external, 206, 230 Vaporizers, internal, 229 Vaporizers, partition, 234 Vaporizers, regulation of, 236 Vaporizers, tubular, 231 Ventilation in engine-room, 69 Vibration, 89 Vibration of air, 92 Vibration, prevention of, 89, 90 W Water circulation, 98, 107, 125 Water circulation by pump, 107 Water circulation, care during operation, 132 Water circulation, how effected, 102 Water circulation, prevention of freezing, 133 Water-coolers, 106 Water-coolers, size of, 109 Water for circulation, 99 Water for producer-gas engines, 203 Water-gas, 153, 167 Water in cylinder, 136 Water in exhaust, 136 Water-jacket, 41, 98, 125, 157 Water-jacket, incrustation of, 148 Water-jacket, outlet of, 98 Water-jacket, prevention of incrustation, 107 Water-pipe, 102 Water, purification of, for circulation, 98 Water, running, for jacket, 98 Water-tanks, 101 Water-tanks, connection of, 103, 105 Water-tanks, design of, 103 Water-tanks, location of, 102 Washer, Benz, 240 Washer, combined with gas-holder, 186 Washer, Deutz, 240 Washer, Fichet-Heurtey, 240 Washer for gas, 199 Washer for producer-gas, 240 Washer, maintenance of, 256 Washer, material employed in, 242 Washer, Winterthur, 240 Washers, 184 Wear, premature, 146 Witz apparatus, 284 Wood as fuel, 254 Wood, calorific value, 194 Wood-gas, 153, 168 Wood-gas, purification of, 195 Wood in producers, 190, 192, 193 Work, definition of effective, 60 ADVERTISEMENTS THE MIETZ & WEISS OIL ENGINE STATIONARY MARINE 1 to 75 H.P. 1 to 60 H.P. 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34030	----	Transcriber's notes: words in bold and italics have been transcribed as =word= and _word_, respectively; superscripts are indicated by ^, subscripts by _. Greek letters have been transliterated as [alpha], [beta], etc. Spelling and hyphenation have been standardised (see list at end of text). TURNING AND BORING A SPECIALIZED TREATISE FOR MACHINISTS, STUDENTS IN INDUSTRIAL AND ENGINEERING SCHOOLS, AND APPRENTICES, ON TURNING AND BORING METHODS, INCLUDING MODERN PRACTICE WITH ENGINE LATHES, TURRET LATHES, VERTICAL AND HORIZONTAL BORING MACHINES BY FRANKLIN D. JONES ASSOCIATE EDITOR OF MACHINERY AUTHOR OF "PLANING AND MILLING" _FIRST EDITION_ FIFTH PRINTING NEW YORK THE INDUSTRIAL PRESS LONDON: THE MACHINERY PUBLISHING CO., LTD. 1919 COPYRIGHT, 1914 BY THE INDUSTRIAL PRESS NEW YORK PREFACE Specialization in machine-tool manufacture has been developed to such a degree that there is need also for treatises which specialize on different classes of tools and their application in modern practice. This book deals exclusively with the use of various types of turning and boring machines and their attachments, and is believed to be unusually complete. In addition to standard practice, it describes many special operations seldom or never presented in text-books. Very little space is given to mere descriptions of different types of machine tools, the principal purpose being to explain the use of the machine and the practical problems connected with its operation, rather than the constructional details. No attempt has been made to describe every machine or tool which might properly be included, but rather to deal with the more important and useful operations, especially those which illustrate general principles. Readers of mechanical literature are familiar with MACHINERY'S 25-cent Reference Books, of which one hundred and twenty-five different titles have been published during the past six years. Many subjects, however, cannot be adequately covered in all their phases in books of this size, and in response to a demand for more comprehensive and detailed treatments on the more important mechanical subjects, it has been deemed advisable to bring out a number of larger volumes, of which this is one. This work includes much of the material published in MACHINERY'S Reference Books Nos. 91, 92 and 95, together with a great amount of additional information on modern boring and turning methods. It is a pleasure to acknowledge our indebtedness to the manufacturers who generously supplied illustrations and data, including many interesting operations from actual practice. Much valuable information was also obtained from MACHINERY. F. D. J. NEW YORK, _May, 1914_. CONTENTS PAGES CHAPTER I THE ENGINE LATHE--TURNING AND BORING OPERATIONS General Description of an Engine Lathe--Example of Cylindrical Turning--Facing the Ends Square with a Side-tool--Turning Tool--Turning Work Cylindrical--Roughing and Finishing Cuts--Filing and Finishing--Aligning Centers for Cylindrical Turning--Application of Drivers or Dogs--Lathe Arbors or Mandrels--Different Types of Lathe Arbors--Mandrel or Arbor Press--Steadyrest for Supporting Flexible Parts--Application of Steadyrest when Boring--The Follow-rest--Centering Parts to be Turned--Centering Machine--Different Forms of Centers--Precaution When Centering Tool Steel--Facing the Ends of Centered Stock--Truing Lathe Centers--Universal, Independent and Combination Chucks--Application of Chucks--Example of Boring--Measuring Bored Holes--Setting Work in the Chuck--Inaccuracy from Pressure of Chuck Jaws--Drilling and Reaming--Holding Work on Faceplate--Application of Angle-plate to Faceplate--Supporting Outer End of Chucked Work--Boring Large Castings in the Lathe--Boring Holes to a Given Center Distance--Turning Brass, Bronze and Copper--Machining Aluminum 1-53 CHAPTER II LATHE TURNING TOOLS AND CUTTING SPEEDS Turning Tools for General Work--Tool-holders with Inserted Cutters--The Position of Turning Tools--Tool Grinding--Shape or Contour of Cutting Edge--Direction of Top Slope for Turning Tools--Clearance for the Cutting Edge--Angle of Tool-point and Amount of Top Slope--Grinding a Lathe Tool--Cutting Speeds and Feeds--Average Cutting Speeds for Turning--Factors which Limit the Cutting Speed--Rules for Calculating Cutting Speeds--Feed of Tool and Depth of Cut--Effect of Lubricant on Cutting Speed--Lubricants Used for Turning--Lard Oil as a Cutting Lubricant 54-79 CHAPTER III TAPER TURNING--SPECIAL OPERATIONS--FITTING Setting Tailstock Center for Taper Turning--Example of Taper Turning--Setting the Tailstock Center with a Caliper Tool--Setting the Tailstock Center with a Square--The Taper Attachment--Application of Taper Attachment--Height of Tool when Turning Tapers--Taper Turning with the Compound Rest--Accurate Measurement of Angles and Tapers--To Find Center Distance for a Given Taper--To Find Center Distance for a Given Angle--To Find Angle for Given Taper per Foot--To Find Angle for Given Disk Dimensions--Use of the Center Indicator--Locating Work by the Button Method--Eccentric Turning--Turning a Crankshaft in a Lathe--Special Crankshaft Lathe--Operation of Special Crankshaft Lathe--Spherical Turning--Spherical Turning Attachments--Turning with Front and Rear Tools--A Multiple-tool Lathe--Examples of Multiple Turning--Knurling in the Lathe--Relieving Attachment--Application of Relieving Attachment--Relieving Hobs or Taps Having Spiral Flutes--Classes of Fits Used in Machine Construction--Forced Fits--Allowance for Forced Fits--Pressure for Forced Fits--Allowance for Given Pressure-Shrinkage Fits 80-134 CHAPTER IV THREAD CUTTING IN THE LATHE Selecting the Change Gears for Thread Cutting--The Thread Tool--Cutting the Thread--Indicator or Chasing Dial for Catching Threads--Principle of the Thread Indicator--Replacing Sharpened Thread Tool--Use of Compound Rest for Thread Cutting--Threads Commonly Used--Multiple Threads--Cutting a U. S. Standard Thread--Cutting a Left-hand Thread--Cutting a Square Thread--Cutting Multiple Threads--Setting Tool When Cutting Multiple Threads--Taper Threading--Internal Threading--Stop for Thread Tools--The Acme Standard Thread--The Whitworth Thread--Worm Threads--Coarse Threading Attachment--Testing the Size of a Thread--The Thread Micrometer--Three-wire System of Measuring Threads--Rivett-Dock Threading Tool--Cutting Screws to Compensate for Shrinkage--Calculating Change Gears for Thread Cutting--Lathes with Compound Gearing--Fractional Threads--Change Gears for Metric Pitches--Quick Change-gear Type of Lathe 135-177 CHAPTER V TURRET LATHE PRACTICE General Description of a Turret Lathe--Example of Turret Lathe Work--Machining Flywheels in Turret Lathe--Finishing a Flywheel at One Setting in Turret Lathe--Finishing a Webbed Flywheel in Two Settings--Tools for Turret Lathes--Box-tools--Examples of Box-tool Turning--Hollow Mills--Releasing Die and Tap Holders--Self-opening Die Heads--Collapsing Taps--Miscellaneous Turret Lathe Tools--Turning Gasoline Engine Pistons in Turret Lathe--Turning Piston Rings in Turret Lathe--Piston Turning in Pratt and Whitney Turret Lathe--Attachment for Turning Piston Rings--Turning Worm-gear Blanks in Turret Lathe--Turning Bevel Gear Blanks--Shell Turning Operation in Flat Turret Lathe--Chuck Work in Flat Turret Lathe--Double-spindle Flat Turret Lathe--Automatic Chucking and Turning Machine--Example of Work on Automatic Turning Machine--Determining Speed and Feed Changes--Setting the Turret Slide--Setting the Cross-slide Cam--Setting the Boring Tool for Recessing--Adjustments for Automatic Feed and Speed Changes--Turning Flywheel in Automatic Chucking and Turning Machine--Automatic Multiple-spindle Chucking Machine--Selecting Type of Turning Machine 178-241 CHAPTER VI VERTICAL BORING MILL PRACTICE Boring and Turning in a Vertical Boring Mill--Holding and Setting Work on Boring Mill Table--Turning in a Boring Mill--Boring Operations--Turning Tools for the Vertical Boring Mill--Turning a Flywheel on a Vertical Mill--Convex Turning Attachment for Boring Mills--Turning Taper or Conical Surfaces--Turret-lathe Type of Vertical Boring Mill--Examples of Vertical Turret Lathe Work--Floating Reamer Holders--Multiple Cylinder Boring Machine 242-274 CHAPTER VII HORIZONTAL BORING MACHINES Horizontal Boring Machine with Vertical Table Adjustment--Drilling and Boring--Cutters Used--Cutter-heads for Boring Large Holes--Cylinder Boring--Boring a Duplex Gasoline Engine Cylinder--Examples of Boring, Radial Facing and Milling--Fixture for Cylinder Lining or Bushing--Horizontal Boring Machine of Floor Type 275-297 INDEX 299-307 TURNING AND BORING CHAPTER I THE ENGINE LATHE--TURNING AND BORING OPERATIONS The standard "engine" lathe, which is the type commonly used by machinists for doing general work, is one of the most important tools in a machine shop, because it is adapted to a great variety of operations, such as turning all sorts of cylindrical and taper parts, boring holes, cutting threads, etc. The illustration Fig. 1 shows a lathe which, in many respects, represents a typical design, and while some of the parts are arranged differently on other makes, the general construction is practically the same as on the machine illustrated. The principal parts are the bed _B_, the headstock _H_, the tailstock _T_, and the carriage _C_. The headstock contains a spindle which is rotated by a belt that passes over the cone-pulley _P_, and this spindle rotates the work, which is usually held between pointed or conical centers _h_ and _h_{1}_ in the headstock and tailstock, or in a chuck screwed onto the spindle instead of the faceplate _F_. The carriage _C_ can be moved lengthwise along the bed by turning handle _d_, and it can also be moved by power, the movement being transmitted from the headstock spindle either through gears _a_, _b_, _c_, and lead-screw _S_, or by a belt operating on pulleys _p_ and _p_{1}_, which drive the feed-rod _R_. The lead-screw _S_ is used when cutting threads, and the feed-rod _R_ for ordinary turning operations; in this way the wear on the lead-screw is reduced and its accuracy is preserved. [Illustration: Fig. 1. Bradford Belt-driven Lathe--View of Front or Operating Side] On the carriage, there is a cross-slide _D_ which can be moved at right angles to the lathe bed by handle _e_, and on _D_ there is an upper or compound slide _E_ which can be swiveled to different positions. The tool _t_, that does the turning, is clamped to the upper slide, as shown, and it can be moved with relation to the work by the movement of the carriage _C_ along the bed, or by moving slide _D_ crosswise. The lengthwise movement is used to feed the tool along the work when turning, boring or cutting a screw, and the crosswise movement for facing the ends of shafts, etc., or for radial turning. When the tool is to be fed at an angle, other than at right angles to the bed, slide _E_, which can be set to the required angle, is used. The lengthwise and crosswise feeding movements can be effected by power, the lengthwise feed being engaged by tightening knob _k_, and the cross-feed by tightening knob _l_. The direction of either of these movements can also be reversed by shifting lever _r_. Ordinarily the carriage and slide are adjusted by hand to bring the tool into the proper position for turning to the required diameter, and then the power feed (operating in the desired direction) is engaged. The tailstock _T_ can be clamped in different positions along the bed, to suit the length of the work, and its center _h_{1}_ can be moved in or out for a short distance, when adjusting it to the work, by turning handle _n_. [Illustration: Fig. 2. Plan View of Lathe Headstock showing Back-gears] [Illustration: Fig. 3. Feed Mechanism of Lathe Apron] As some metals are much harder than others, and as the diameters of parts to be turned also vary considerably, speed changes are necessary, because if the speed is excessive, the turning tool will become dull in too short a time. These speed changes (with a belt-driven lathe) are obtained by placing the driving belt on different steps of cone-pulley _P_, and also by the use of back-gears. The cone-pulley can be connected directly with the spindle or be disengaged from it by means of bolt _m_. When the pulley and spindle are connected, five speeds (with this particular lathe) are obtained by simply shifting the driving belt to different steps of the cone. When a slower speed is required than can be obtained with the belt on the largest step of the cone, the latter is disconnected from the spindle, and the back-gears _G_ and _G_{1}_ (shown in the plan view Fig. 2) are moved forward into mesh by turning handle _O_; the drive is then from cone-pulley _P_ and gear _L_ to gear _G_, and from gear _G_{1}_ to the large gear _J_ on the spindle. When driving through the back-gears, five more speed changes are obtained by shifting the position of the driving belt, as before. The fastest speed with the back-gears in mesh is somewhat slower than the slowest speed when driving direct or with the back-gears out of mesh; hence, with this particular lathe, a series of ten gradually increasing speeds is obtained. Changes of feed for the turning tool are also required, and these are obtained by shifting the belt operating on pulleys _p_ and _p_{1}_ to different-sized steps. On some lathes these feed changes are obtained through gears which can be shifted to give different ratios. Many lathes also have gears in the headstock for changing the speeds. [Illustration: Fig. 4. Rear View of Lathe Apron] Front and rear views of the carriage apron, which contains the feeding mechanism, are shown in Figs. 3 and 4, to indicate how the feeds are engaged and reversed. The feed-rod _R_ (Fig. 1) drives the small bevel gears _A_ and _A_{1}_ (Figs. 3 and 4), which are mounted on a slide _S_ that can be moved by lever _r_ to bring either bevel gear into mesh with gear _B_. Gear _B_ is attached to pinion _b_ (see Fig. 3) meshing with gear _C_, which, when knob _k_ (Fig. 1) is tightened, is locked by a friction clutch to pinion _c_. The latter pinion drives gear _D_ which rotates shaft _E_. A pinion cut on the end of shaft _E_ engages rack _K_ (Fig. 1) attached to the bed, so that the rotation of _E_ (which is controlled by knob _k_) moves the carriage along the bed. To reverse the direction of the movement, it is only necessary to throw gear _A_ into mesh and gear _A_{1}_ out, or _vice versa_, by operating lever _r_. When the carriage is traversed by hand, shaft _E_ and gear _D_ are rotated by pinion _d_{1}_ connected with handle _d_ (Fig. 1). The drive for the cross-feed is from gear _C_ to gear _F_ which can be engaged through a friction clutch (operated by knob _l_, Fig. 1) with gear _G_ meshing with a pinion _H_. The latter rotates the cross-feed screw, which passes through a nut attached to slide _D_ (Fig. 1), thus moving the latter at right angles to the ways of the bed. The cross-feed is also reversed by means of lever _r_. As previously explained, lead-screw _S_ is only used for feeding the carriage when cutting threads. The carriage is engaged with this screw by means of two half-nuts _N_ (Fig. 4) that are free to slide vertically and are closed around the screw by operating lever _u_. These half-nuts can only be closed when lever _r_ is in a central or neutral position, so that the screw feed and the regular turning feed cannot be engaged at the same time. As previously mentioned, lead-screw _S_, Fig. 1, is rotated from the lathe spindle, through gears _a_, _b_ and _c_, called change gears. An assortment of these gears, of various sizes, is provided with the lathe, for cutting screws of different pitch. The gears to use for any pitch within the range of the lathe are given on the plate _I_. =Example of Cylindrical Turning.=--Having now considered the principal features of what might be called a standard lathe, the method of using it in the production of machine parts will be explained. To begin with a simple example of work, suppose a steel shaft is to be turned to a diameter of 2-1/4 inches and a length of 14-1/2 inches, these being the finished dimensions. We will assume that the rough stock is cut off to a length of 14-5/8 inches and has a diameter of 2-5/8 inches. The first step in this operation is to form conically shaped center-holes in each end of the piece as indicated at _c_ in Fig. 5. As all work of this kind is held, while being turned, between the centers _h_ and _h_{1}_, holes corresponding in shape to these centers are necessary to keep the work in place. There are several methods of forming these center-holes, as explained later. After the work is centered, a dog _A_ is clamped to one end by tightening screw _s_; it is then placed between the centers of the lathe. The dog has a projecting end or "tail," as it is commonly called, which enters a slot in the faceplate _F_ and thereby drives or rotates the work, when power is applied to the lathe spindle onto which the faceplate is screwed. The tailstock center _h_1_, after being oiled, should be set up just tight enough to eliminate all play, without interfering with a free rotary movement of the work. This is done by turning handle _n_, and when the center is properly adjusted, the tailstock spindle containing the center is locked by tightening handle _p_. (Ordinary machine oil is commonly used for lubricating lathe centers, but a lubricant having more "body" should be used, especially when turning heavy parts. The following mixtures are recommended: 1. Dry or powdered red lead mixed with a good grade of mineral oil to the consistency of cream. 2. White lead mixed with sperm oil with enough graphite added to give the mixture a dark lead color.) [Illustration: Fig. 5. Plan View showing Work Mounted between Centers of Lathe] =Facing the Ends Square with a Side-tool.=--Everything is now ready for the turning operation. The ends of the piece should be faced square before turning the body to size, and the tool for this squaring operation is shown in Fig. 6; this is known as a side-tool. It has a cutting edge _e_ which shaves off the metal as indicated in the end view by the dotted lines. The side _f_ is ground to an angle so that when the tool is moved in the direction shown by the arrow, the cutting edge will come in contact with the part to be turned; in other words, side _f_ is ground so as to provide clearance for the cutting edge. In addition, the top surface against which the chip bears, is beveled to give the tool keenness so that it will cut easily. As the principles of tool grinding are treated separately in Chapter II we shall for the present consider the tool's use rather than its form. [Illustration: Fig. 6. Lathe Side-tool for Facing Ends of Shafts, etc.] For facing the end, the side tool is clamped in the toolpost by tightening the screw _u_, Fig. 5, and it should be set with the cutting edge slightly inclined from a right-angled position, the point being in advance so that it will first come into contact with the work. The cutting edge should also be about the same height as the center of the work. When the tool is set, the lathe (if belt-driven) is started by shifting an overhead belt and the tool is then moved in until the point is in the position shown at _A_, Fig. 7. The tool-point is then fed against the end by handle _d_, Fig. 5, until a light chip is being turned off, and then it is moved outward by handle _e_ (as indicated by the arrow at _B_, Fig. 7), the carriage remaining stationary. As the movement of the tool-point is guided by the cross-slide _D_, which is at right angles with the axis of the work, the end will be faced square. For short turning operations of this kind, the power feeds ordinarily are not used as they are intended for comparatively long cuts. If it were necessary to remove much metal from the end, a number of cuts would be taken across it; in this case, however, the rough stock is only 1/8 inch too long so that this end need only be made true. [Illustration: Fig. 7. Facing End with Side-tool and Turning Work Cylindrical] After taking a cut as described, the surface, if left rough by the tool-point, should be made smooth by a second or finishing cut. If the tool is ground slightly round at the point and the cutting edge is set almost square, as at _C_, Fig. 7, a smooth finish can be obtained; the cut, however, should be light and the outward feed uniform. The work is next reversed in the centers and the driving dog is placed on the end just finished; the other end is then faced, enough metal being removed to make the piece 14-1/2 inches long, as required in this particular case. This completes the facing operation. If the end of the work does not need to be perfectly square, the facing operation can be performed by setting the tool in a right-angled position and then feeding it sidewise, thus removing a chip equal to the width of one side. Evidently this method is confined to comparatively small diameters and the squareness of the turned end will be determined by the position of the tool's cutting edge. =Turning Tool--Turning Work Cylindrical.=--The tool used to turn the body to the required diameter is shaped differently from the side-tool, the cutting edge _E_ of most tools used for plain cylindrical turning being curved as shown in Fig. 8. A tool of this shape can be used for a variety of cylindrical turning operations. As most of the work is done by that part of the edge marked by arrow _a_, the top of the tool is ground to slope back from this part to give it keenness. The end _F_, or the flank, is also ground to an angle to provide clearance for the cutting edge. If the tool did not have this clearance, the flank would rub against the work and prevent the cutting edge from entering the metal. This type of tool is placed about square with the work, for turning, and with the cutting end a little above the center. [Illustration: Fig. 8. Tool used for Cylindrical Turning] Before beginning to turn, a pair of outside calipers or a micrometer should be set to 2-1/4 inches, which, in this case, is the finished diameter of the work. Calipers are sometimes set by using a graduated scale as at _A_, Fig. 9, or they can be adjusted to fit a standard cylindrical gage of the required size as at _B_. Very often fixed caliper gages _C_ are used instead of the adjustable spring calipers. These fixed gages, sometimes called "snap" gages, are accurately made to different sizes, and they are particularly useful when a number of pieces have to be turned to exactly the same size. The turning tool is started at the right-hand end of the work and the tool should be adjusted with the left hand when beginning a cut, as shown in Fig. 10, in order to have the right hand free for calipering. A short space is first turned by hand feeding, as at _D_, Fig. 7, and when the calipers show that the diameter is slightly greater than the finished size (to allow for a light finishing cut, either in the lathe or grinding machine) the power feed for the carriage is engaged; the tool then moves along the work, reducing it as at _E_. Evidently, if the movement is along a line _b--b_, parallel with the axis _a--a_, the diameter _d_ will be the same at all points, and a true cylindrical piece will be turned. On the other hand, if the axis _a--a_ is inclined one way or the other, the work will be made tapering; in fact, the tailstock center _h_1_ can be adjusted laterally for turning tapers, but for straight turning, both centers must be in alignment with the carriage travel. Most lathes have lines on the stationary and movable parts of the tailstock base which show when the centers are set for straight turning. These lines, however, may not be absolutely correct, and it is good practice to test the alignment of the centers before beginning to turn. This can be done by taking trial cuts, at each end of the work (without disturbing the tool's crosswise position), and then comparing the diameters, or by testing the carriage travel with a true cylindrical piece held between the centers as explained later. [Illustration: Fig. 9. Setting Calipers by Scale--Setting by Gage--Fixed Gage] If the relative positions of the lathe centers are not known, the work should be calipered as the cut progresses to see if the diameter _d_ is the same at all points. In case the diameter gradually increases, the tailstock center should be shifted slightly to the rear before taking the next cut, but if the diameter gradually diminishes, the adjustment would, of course, be made in the opposite direction. The diameter is tested by attempting to pass the calipers over the work. When the measuring points just touch the work as they are gently passed across it, the diameter being turned is evidently the same as the size to which the calipers are set. [Illustration: Fig. 10. Views showing how the Cross-slide and Carriage are Manipulated by Hand when Starting a Cut--View to Left, Feeding Tool Laterally; View to Right, Feeding Tool in a Lengthwise Direction] As the driving dog is on one end, the cut cannot be taken over the entire length, and when the tool has arrived at say position _x_, Fig. 5, it is returned to the starting point and the work is reversed in the centers, the dog being placed upon the other end. The unfinished part is then turned, and if the cross-slide is not moved, the tool will meet the first cut. It is not likely that the two cuts will be joined or blended together perfectly, however, and for this reason a cut should be continuous when this is possible. =Roughing and Finishing Cuts.=--Ordinarily in lathe work, as well as in other machine work, there are two classes of cuts, known as "roughing" and "finishing" cuts. Roughing cuts are for reducing the work as quickly as possible almost to the required size, whereas finishing cuts, as the name implies, are intended to leave the part smooth and of the proper size. When the rough stock is only a little larger than the finished diameter, a single cut is sufficient, but if there is considerable metal to turn away, one or more deep roughing cuts would have to be taken, and, finally, a light cut for finishing. In this particular case, one roughing and one finishing cut would doubtless be taken, as the diameter has to be reduced 3/8 inch. Ordinarily the roughing cut would be deep enough to leave the work about 1/32 or perhaps 1/16 inch above the finished size. When there is considerable metal to remove and a number of roughing cuts have to be taken, the depth of each cut and the feed of the tool are governed largely by the pulling power of the lathe and the strength of the work to withstand the strain of a heavy cut. The depth of roughing cuts often has to be reduced considerably because the part being turned is so flexible that a heavy cut would spring the work and cause the tool to gouge in. Of course, just as few cuts as possible should be taken in order to save time. The speed of the work should also be as fast as the conditions will allow for the same reason, but as there are many things which govern the speed, the feed of the tool, and the depth of the cut, these important points are referred to separately in Chapter II. =Filing and Finishing.=--In many cases the last or finishing cut does not leave as smooth a surface as is required and it is necessary to resort to other means. The method commonly employed for finishing in the lathe is by the use of a file and emery cloth. The work is rotated considerably faster for filing than for turning, and the entire surface is filed by a flat, single-cut file, held as shown in Fig. 11. The file is passed across the work and advanced sidewise for each forward stroke, until the entire surface is finished. The file should be kept in contact with the work continually, but on the return stroke the pressure should be relieved. The movement of the file during the forward or cutting stroke should be much slower than when filing in a vise. By moving the file slowly, the work can make a number of revolutions for each stroke, which tends to keep it round, as practically the same amount of metal is removed from the entire circumference. On the other hand, short rapid strokes tend to produce flat spots, or at least an irregular surface, especially if the work can only make part of a revolution for each cutting stroke. The pressure on the file during the forward stroke should also be kept as nearly uniform as possible. [Illustration: Fig. 11. Filing Work after Finishing Cut is taken] It is very difficult to file a part smooth and at the same time to keep it round and cylindrical, and the more filing that has to be done, the greater the chance of error. For this reason, the amount left for filing should be very small; in fact, the metal removed by filing should be just enough to take out the tool marks and give a smooth finish. Very often a satisfactory finish can be obtained with a turning tool, and filing is not necessary at all. The file generally used for lathe work is a "single-cut bastard" of "mill" section, having a length of from 12 to 14 inches. Sometimes particles of metal collect between the teeth of a file and make deep scratches as the file is passed across the work. When this occurs, the teeth should be cleaned by using a wire brush or a file card, which is drawn across the file in the direction of the teeth. This forming of tiny particles between the teeth is known as "pinning" and it can sometimes be avoided by rubbing chalk on the file. Filing is not only done to obtain a smooth finish, but also to reduce the work to an exact diameter, as a very slight reduction can be made in this way. [Illustration: Fig. 12. Two Methods of Aligning Centers for Cylindrical Turning] If a polish is desired, this can be obtained by holding a piece of emery cloth tightly around the work as it revolves. The coarseness of emery cloth is indicated by letters and numbers corresponding to the grain number of loose emery. The letters and numbers for grits ranging from fine to coarse are as follows: _FF_, _F_, 120, 100, 90, 80, 70, 60, 54, 46, 40. For large work roughly filed, use coarse cloth such as Nos. 46 or 54, and then finer grades to obtain the required polish. If the work has been carefully filed, a good polish can be obtained with Nos. 60 and 90 cloth, and a brilliant polish by finishing with No. 120 and flour-emery. Most cylindrical parts can be finished more quickly and accurately in the grinder than in the lathe, and many classes of work are, at the present time, simply rough-turned in the lathe and then ground to size in a cylindrical grinding machine. =Aligning Centers for Cylindrical Turning.=--When a rod or shaft must be turned cylindrical or to the same diameter throughout its entire length, it is good practice to test the alignment of the centers, before inserting the work. The position of the tailstock center for cylindrical turning may be indicated by the coincidence of graduation marks on the base, but if accuracy is necessary, the relative position of the two centers should be determined in a more positive way. A very simple and convenient method of testing the alignment is shown at _A_ in Fig. 12. The work is first turned for a short distance, near the dogged end, as shown, and the tool is left as set for this cut; then the tailstock center is withdrawn and the work is moved sufficiently to permit running the tool back to the tailstock end without changing its original setting. A short cut is then taken at this end and the diameters _d_ and _d_{1}_ are carefully compared. In case there is any variation, the tailstock center is adjusted laterally, other trial cuts are taken, and the test repeated. Another method is illustrated at _B_, which requires the use of a test-bar _t_. This bar should have accurately made centers and the ends finished to exactly the same diameter. The lathe centers are aligned by placing the bar between them and then testing the position of the ends. This can be done by comparing each end with a tool held in the toolpost and moved from one to the other by shifting the carriage, but a better method is to clamp a test indicator _i_ in the toolpost and bring it in contact with first one end of the bar and then the other. If the dial does not register the same at each end, it shows that the lathe centers are not in line. Even when centers are correctly set, lathes that have been in use a long time do not always turn cylindrical or straight, because if the ways that guide the carriage are worn unevenly, the tool as it moves along does not remain in the same plane and this causes a variation in the diameter of the part being turned. =Application of Drivers or Dogs.=--Work that is turned between centers is sometimes driven by a dog which is so short for the faceplate that the bent driving end bears against the bottom _a_ of the faceplate slot, as shown at _A_, Fig. 13. If the dog is nearly the right length, it may allow the headstock center to enter the center in the work part way, with the result that the turned surface is not true with the centers. When a driving dog of this type is used, care should be taken to see that it moves freely in the faceplate slot and does not bind against the bottom. By using a straight dog (_B_), which is driven by a pin _b_ bolted to the faceplate, all danger from this source is eliminated. The straight dog, however, is used more particularly to do away with the leverage _l_ of a bent dog, as this leverage tends to spring a flexible part when a cut is being taken. [Illustration: Fig. 13. (A) Dog that is too Short for Faceplate. (B) Straight Driving Dog] Straight dogs are also made with two driving ends which engage pins on opposite sides of the faceplate. This type is preferable because it applies the power required for turning, evenly to the work, which still further reduces the tendency to spring it out of shape. The principal objection to the double-ended type lies in the difficulty of adjusting the driving pins so that each bears with equal pressure against the dog. The double-ended driver is often used for large work especially if deep roughing cuts are necessary. =Lathe Arbors or Mandrels.=--When it is necessary to turn the outside of a part having a hole through it, centers cannot, of course, be drilled in the ends and other means must be resorted to. We shall assume that the bushing _B_, Fig. 14, has a finished hole through the center, and it is desired to turn the outside cylindrical and concentric with the hole. This could be done by forcing a tightly-fitted arbor _M_, having accurately-centered ends, into the bushing and inserting the mandrel and work between the lathe centers _h_ and _h_{1}_ as shown. Evidently, if the arbor runs true on its centers, the hole in the bushing will also run true and the outside can be turned the same as though the arbor and bushing were a solid piece. From this it will be seen that an arbor simply forms a temporary support for parts that are bored and therefore cannot be centered. [Illustration: Fig. 14. Bushing mounted on Arbor for Turning] Another example of work that would be turned on an arbor is shown in Fig. 15. This is a small cast-iron wheel having a finished hole through the hub, and the outer surface and sides of the rim are to be turned true with this hole. In this case, the casting would also be held by pressing a mandrel through the hub; as shown. This method, however, would only apply to comparatively small wheels because it would be difficult, if not impossible, to prevent a large wheel from turning on the arbor when taking a cut, and even if it could be driven, large work could be done to better advantage on another type of machine. (The vertical boring mill is used extensively for turning large wheels, as explained in Chapter VI.) When turning the outside of the rim, a tool similar to that shown at _t_ should be used, but for facing or turning the sides, it might be better, if not necessary, to use tools having bent ends as shown by the dotted lines; in fact, turning tools of various kinds are made with the ends bent to the right or left, as this enables them to be used on surfaces that could not be reached very well with a straight tool. If a comparatively large pulley is mounted near the end of the arbor, it can be driven directly by pins attached to the faceplate and engaging the pulley arms. This method of driving is often employed when the diameter to be turned is large and the hole for the arbor is so small that there will not be sufficient friction for driving. [Illustration: Fig. 15. Turning Pulley Held on an Arbor] =Different Types of Lathe Arbors.=--Three different types of lathe arbors are shown in Fig. 16. The kind shown at _A_ is usually made of tool steel and the body is finished to a standard size. The ends are somewhat reduced and flat spots are milled, as shown, to give the clamping screw of the dog a good grip. The body of the arbor is usually tapered about 0.006 inch per foot. This taper makes it easier to insert the arbor in a close-fitting hole, and it also permits slight variations in the diameter of different holes. As to hardening, the practice at the present time among manufacturers is to harden arbors all over, but for extremely accurate work, an arbor having hardened ends and a soft body is generally considered superior, as there is less tendency of distortion from internal stresses. Hardened arbors are "seasoned" before finish-grinding to relieve these internal stresses. The solid type _A_, Fig. 16, is used very extensively, but in shops where a great variety of work is being done and there are many odd-sized holes, some form of expanding arbor _B_ can be used to advantage. This type, instead of being solid, consists of a tapering inner arbor _M_ on which is placed a split bushing that can be expanded, within certain limits, by driving in the tapering member. The advantage of this type is that a comparatively small stock of arbors is required, as different-sized bushings can be used. This type can also be fitted to holes of odd sizes, whereas a solid arbor must be provided for each different size hole, unless the variation is very slight. The latter are, however, more accurate than the expanding type. [Illustration: Fig. 16. Different Types of Lathe Arbors] Another form of expanding arbor is shown at _C_. This type has a straight body _N_ in which four tapering grooves are cut lengthwise, as shown, and there is a sleeve _S_, containing four slots that are located to correspond with the tapering grooves. Strips s are fitted into these slots, and as the part _N_ is driven in, the strips are moved outward as they ascend the tapering grooves. By having different sets of these strips of various heights, one arbor of this type can be made to cover quite a range of sizes. It is not suited, however, to thin work, as the pressure, being concentrated in four places, would spring a flexible part out of shape. The cone arbor or mandrel shown at _A_, in Fig. 17, is convenient for holding parts having comparatively large holes, as it can be adjusted for quite a range of diameters. The work is gripped between the two cones _c_ and _c_{1}_ which are forced together by nut _n_. The cones are prevented from turning upon the arbor by keys. This style of arbor should not be used for accurate work. The threaded arbor _B_ is used for facing the sides of nuts square with the tapped hole. When a nut is first put upon the arbor, the rough side comes against an equalizing washer _w_. This washer rests against a spherical seat so that it can shift to provide a uniform bearing for the rough side of the nut, even though it is not square with the tapped hole. This feature prevents the nut from being canted on the arbor and insures an accurately faced nut. The revolving conical center shown at _C_ is often used for holding a pipe or tube while turning the outside. The cone is adjusted to fit into the hole of the pipe, by means of the tailstock spindle, and the opposite end is usually held in a chuck. [Illustration: Fig. 17. (A) Cone Arbor. (B) Nut Arbor. (C) Pipe Center] Particular care should be taken to preserve the accuracy of the centers of lathe arbors by keeping them clean and well-oiled while in use. =Mandrel or Arbor Press.=--The best method of inserting an arbor of the solid type in a hole is by using a press, Fig. 18, designed for that purpose, but if such a press is not available and it is necessary to drive the mandrel in, a "soft" hammer, made of copper, lead or other soft material, should be used to protect the centered end of the arbor. In either case, the arbor should not be forced in too tightly, for if it fits properly, this will not be necessary in order to hold the work securely. On the other hand, the work might easily be broken by attempting to force the arbor in as far and as tightly as possible. In using the arbor press, the work is placed on the base _B_ with the hole in a vertical position, and the arbor (which should be oiled slightly) is forced down into it by ram _R_, operated by lever _L_. Slots are provided in the base, as shown, so that the end of the arbor can come through at the bottom of the hole. The lever of this particular press is counter-weighted so that it rises to a vertical position when released. The ram can then be adjusted quickly to any required height by the handwheel seen at the left. [Illustration: Fig. 18. Press for Forcing Arbors into Work] Some shops are equipped with power-driven mandrel or arbor presses. This type is particularly desirable for large work, owing to the greater pressure required for inserting mandrels that are comparatively large in diameter. One well-known type of power press is driven by a belt, and the downward pressure of the ram is controlled by a handwheel. The ram is raised or lowered by turning this handwheel in one direction or the other, and a gage shows how much pressure is being applied. This type of press can also be used for other purposes, such as forcing bushings or pins into or out of holes, bending or straightening parts, or for similar work. [Illustration: Fig. 19. Steadyrest and Follow-rest for Supporting Flexible Parts] =Steadyrest for Supporting Flexible Parts.=--Occasionally long slender shafts, rods, etc., which have to be turned, are so flexible that it is necessary to support them at some point between the lathe centers. An attachment for the lathe known as a steadyrest is often used for this purpose. A steadyrest is composed of a frame containing three jaws _J_ (Fig. 19), that can be adjusted in or out radially by turning screws _S_. The frame is hinged at _h_, thus allowing the upper half to be swung back (as shown by the dotted lines) for inserting or removing the work. The bolt-clamp _c_ holds the hinged part in the closed position. The base of the frame has V-grooves in it that fit the ways of the lathe bed. When the steadyrest is in use, it is secured to the bed by clamp _C_, and the jaws _J_ are set in against the work, thus supporting or steadying it during the turning operation. The steadyrest must, of course, be located at a point where it will not interfere with the turning tool. [Illustration: Fig. 20. Application of Steadyrest to a Flexible Rod] Fig. 20 shows the application of the steadyrest to a long forged rod, having one small end, which makes it too flexible to be turned without support. As this forging is rough, a true surface _n_ a little wider than the jaws _J_ (Fig. 19) is first turned as a bearing for the jaws. This should be done very carefully to prevent the work from mounting the tool. A sharp pointed tool should be used and very light cuts taken. The steadyrest is next clamped to the lathe bed opposite the turned surface, and the jaws are adjusted in against this surface, thus forming a bearing. Care should be taken not to set up the jaws too tightly, as the work should turn freely but without play. The large part of the rod and central collar are then turned to size, this half being machined while the small part is in the rough and as stiff as possible. The rod is then reversed and the steadyrest is applied to the part just finished, as shown at _B_, thus supporting the work while the small end is being turned. That part against which the jaws bear should be kept well oiled, and if the surface is finished it should be protected by placing a strip of emery cloth beneath the jaws with the emery side out; a strip of belt leather is also used for this purpose, the object in each case being to prevent the jaws from scratching and marring the finished surface, as they tend to do, especially if at all rough. If the work were too flexible to permit turning a spot at _n_, this could be done by first "spotting" it at some point _o_, and placing the steadyrest at that point while turning another spot at _n_. Sometimes it is desirable to apply a steadyrest to a surface that does not run true and one which is not to be turned; in such a case a device called a "cat-head" is used. This is simply a sleeve _S_ (Fig. 21) which is placed over the untrue surface to serve as a bearing for the steadyrest. The sleeve is made to run true by adjusting the four set-screws at each end, and the jaws of the steadyrest are set against it, thus supporting the work. [Illustration: Fig. 21. Cat-head which is sometimes used as Bearing for Steadyrest] =Application of Steadyrest when Boring.=--Another example illustrating the use of the steadyrest is shown in Fig. 22. The rod _R_ is turned on the outside and a hole is to be bored in the end (as shown by dotted lines) true with the outer surface. If the centers used for turning the rod are still in the ends, as they would be ordinarily, this work could be done very accurately by the following method: The rod is first placed between the centers as for turning, with a driving dog _D_ attached, and the steadyrest jaws _J_ are set against it near the outer end, as shown. Before any machine work is done, means must be provided for holding the rod back against the headstock center _h_, because, for an operation of this kind, the outer end cannot be supported by the tailstock center; consequently the work tends to shift to the right. One method of accomplishing this is shown in the illustration. A hardwood piece _w_, having a hole somewhat larger than the work, is clamped against the dog, in a crosswise position, by the swinging bolts and thumb-screws shown. If the dog is not square with the work, the wood piece should be canted so that the bearing will not be all on one side. For large heavy parts a similar "bridle" or "hold-back"--as this is commonly called--is made by using steel instead of wood for the part _w_. Another very common method which requires no special equipment is illustrated in Fig. 23. An ordinary leather belt lacing _L_ is attached to the work and faceplate while the latter is screwed off a few turns as shown. Then the lacing is drawn up by hand and tied, and the faceplate is screwed onto the spindle, thus tightening the lacing and drawing the work against the headstock center. The method of applying the lacing is quite clearly indicated in the illustration. If a small driving faceplate is used, it may be necessary to drill holes for the belt lacing, as shown. [Illustration: Fig. 22. Shaft supported by Steadyrest for Drilling and Boring End] A hole is next drilled in the end of the rod by using a twist drill in the tailstock. If the hole is finished by boring, a depth mark should be made on the tool shank that will warn the workman of the cutting end's approach to the bottom. A chuck can also be used in connection with a steadyrest for doing work of this kind, as shown in Fig. 24, the end of the rod being held and driven by the chuck _C_. If the piece is centered, it can be held on these centers while setting the steadyrest and adjusting the chuck, but if the ends are without centers, a very good way is to make light centers in the ends with a punch; after these are properly located they are used for holding the work until the steadyrest and chuck jaws have been adjusted. In case it is necessary to have the end hole very accurate with the outside of the finished rod, a test indicator _I_ should be applied to the shaft as shown. This is an instrument which shows with great accuracy whether a rotating part runs true and it is also used for many other purposes in machine shops. The indicator is held in the lathe toolpost and the contact point beneath the dial is brought against the work. If the latter does not run true, the hand of the indicator vibrates and the graduations on the dial show how much the work is out in thousandths of an inch. [Illustration: Fig. 23. Hold-back used when Outer End of Work is held in Steadyrest] =The Follow-rest.=--When turning long slender parts, such as shafts, etc., a follow-rest is often used for supporting the work. The follow-rest differs from the steadyrest in that it is attached to and travels with the lathe carriage. The type illustrated to the right in Fig. 19 has two adjustable jaws which are located nearly opposite the turning tool, thus providing support where it is most needed. In using this rest, a cut is started at the end and the jaws are adjusted to this turned part. The tool is then fed across the shaft, which cannot spring away from the cut because of the supporting jaws. Some follow-rests have, instead of jaws, a bushing bored to fit the diameter being turned, different bushings being used for different diameters. The bushing forms a bearing for the work and holds it rigidly. Whether a bushing or jaws are used, the turning tool is slightly in advance of the supporting member. [Illustration: Fig. 24. Testing Work with Dial Indicator] =Centering Parts to be Turned.=--As previously mentioned, there are a number of different methods of forming center-holes in the ends of parts that have to be turned while held between lathe centers. A method of centering light work, and one that requires few special tools, is first to locate a central point on the end and then drill and ream the center-hole by using the lathe itself. Hermaphrodite dividers are useful for finding the center, as illustrated at _A_, Fig. 25, but if the work is fairly round, a center-square _B_ is preferable. A line is scribed across the end and then another line at right angles to the first by changing the position of the square; the intersection of these two lines will be the center, which should be marked by striking a pointed punch _C_ with a hammer. If a cup or bell center-punch _D_ is available, it will not be necessary to first make center lines, as the conical part shown locates the punch in a central position. This style of punch should only be used on work which is fairly round. [Illustration: Fig. 25. Centering End with Punch preparatory to Drilling] After small centers have been located in both ends, their position can be tested by placing the work between the lathe centers and rotating it rapidly by drawing the hand quickly across it. By holding a piece of chalk close to the work as it spins around, a mark will be made on the "high" side if the centers are not accurate; the centers are then shifted toward these marks. If the work is close to the finished diameter, the centers should, of course, be located quite accurately in order that the entire surface of the work will be turned true when it is reduced to the finished size. One method of forming these center-holes is indicated in Fig. 26. A chuck _C_ is screwed onto the spindle in place of the faceplate, and a combination center drill and reamer _R_ is gripped by the chuck jaws and set to run true. The center is then drilled and reamed at one end by pressing the work against the revolving drill with the tailstock spindle, which is fed out by turning handle _n_. The piece is then reversed for drilling the opposite end. The work may be kept from revolving while the centers are being drilled and reamed, by attaching a dog to it close to the tailstock end and then adjusting the cross-slide until the dog rests upon the slide. Many parts can be held by simply gripping them with one hand. From the foregoing it will be seen that the small centers made by punch _C_, Fig. 25, serve as a starting point for the drill and also as a support for the outer end of the work while the first hole is being drilled. [Illustration: Fig. 26. Drilling Centers in the Lathe] The form of center-hole produced by a combination drill and reamer is shown by the lower left-hand view in Fig. 27. A small straight hole a in the bottom prevents the point of the lathe center from coming in contact with the work and insures a good bearing on the conical surface _c_. The standard angle for lathe centers is sixty degrees, as the illustration shows, and the tapering part of all center-holes should be made to this angle. [Illustration: Fig. 27. Centers of Incorrect and Correct Form] [Illustration: Fig. 28. Special Machine for Centering Parts to be Turned] =Centering Machine.=--Many shops have a special machine for forming centers which enables the operation to be performed quickly. One type of centering machine is shown in Fig. 28. The work is gripped in a chuck _C_ that automatically locates it in a central position so that it is not necessary to lay out the end before drilling. There are two spindles _s_, one of which holds the drill and the other the countersink, and these are rotated by a belt passing over pulley _P_. Each of these spindles is advanced by lever _L_ and either of them can be moved to a position central with the work, as they are mounted in a swiveling frame. In operating this machine, a small straight hole is first made by a twist drill held in one of the spindles; the other spindle is then moved over to the center and the hole is reamed tapering. The arrangement is such that neither spindle can be advanced by the feeding lever except when in a central position. The amount that each spindle can be advanced is limited by a fixed collar inside the head, and there is also a swinging adjustable stop against which the end of the work should be placed before tightening the chuck. These two features make it possible to ream center holes of the same size or depth in any number of pieces. [Illustration: Fig. 29. The Imperfect Center Bearing is the Result of Centering before Straightening] =Different Forms of Centers.=--In some poorly equipped shops it is necessary to form centers by the use of a center-punch only, as there is no better tool. If the end of the punch has a sixty-degree taper, a fair center can be formed in this way, but it is not a method to be recommended, especially when accurate work is required. Sometimes centers are made with punches that are too blunt, producing a shallow center, such as the one shown in the upper left-hand view, Fig. 27. In this case all the bearing is on the point of the lathe center, which is the worst possible place for it. Another way is to simply drill a straight hole as in the upper view to the right; this is also bad practice in more than one respect. The lower view to the right shows a form of center which is often found in the ends of lathe arbors, the mouth of the center being rounded, at _r_, and the arbor end recessed as shown. The rounded corner prevents the point of the lathe center from catching when it is moved rapidly towards work which is not being held quite centrally (as shown by the illustration), and the end is recessed to protect the center against bruises. Stock that is bent should always be straightened before the centers are drilled and reamed. If the work is first centered and then straightened the bearing on the lathe center would be as shown in Fig. 29. The center will then wear unevenly with the result that the surfaces last turned will not be concentric with those which were finished first. [Illustration: Fig. 30. Tool Steel should be centered Concentric, in order to remove the Decarbonized Outer Surface] =Precaution When Centering Tool Steel.=--Ordinarily centers are so located that the stock runs approximately true before being turned, but when centering tool steel to be used in making tools, such as reamers, mills, etc., which need to be hardened, particular care should be taken to have the rough surface run fairly true. This is not merely to insure that the piece will "true-up," as there is a more important consideration, the disregard of which often affects the quality of the finished tool. As is well known, the degree of hardness of a piece of tool steel that has been heated and then suddenly cooled depends upon the amount of carbon that it contains, steel that is high in carbon becoming much harder than that which contains less carbon. Furthermore, the amount of carbon found at the surface, and to some little depth below the surface of a bar of steel, is less than the carbon content in the rest of the bar. This is illustrated diagrammatically in Fig. 30 by the shaded area in the view to the left. (This decarbonization is probably due to the action of the oxygen of the air on the bar during the process of manufacture.) If stock for a reamer is so centered that the tool removes the decarbonized surface only on one side, as illustrated to the right, evidently when the reamer is finished and hardened the teeth on the side _A_ will be harder than those on the opposite side, which would not have been the case if the rough bar had been centered true. To avoid any trouble of this kind, stock that is to be used for hardened tools should be enough larger than the finished diameter and so centered that this decarbonized surface will be entirely removed in turning. [Illustration: Fig. 31. Three Methods of Facing the Ends Square] =Facing the Ends of Centered Stock.=--As a piece of work is not properly centered until the ends are faced square, we will consider this operation in connection with centering. Some machinists prefer lathe centers that are cut away as shown at _A_, Fig. 31, so that the point of the side tool can be fed in far enough to face the end right up to the center hole. Others, instead of using a special center, simply loosen the regular one slightly and then, with the tool in a position as at _B_, face the projecting teat by feeding both tool and center inward as shown by the arrow. Whenever this method is employed, care should be taken to remove any chips from the center hole which may have entered. A method which makes it unnecessary to loosen the regular center, or to use a special one, is to provide clearance for the tool-point by grinding it to an angle of approximately forty-five degrees, as shown at _C_. If the tool is not set too high, it can then be fed right up to the lathe center and the end squared without difficulty. As for the special center _A_, the use of special tools and appliances should always be avoided unless they effect a saving in time or their use makes it possible to accomplish the same end with less work. =Truing Lathe Centers.=--The lathe centers should receive careful attention especially when accurate work must be turned. If the headstock center does not run true as it revolves with the work, a round surface may be turned, but if the position of the driving dog with reference to the faceplate is changed, the turned surface will not run true because the turned surface is not true with the work centers. Furthermore, if it is necessary to reverse the work for finishing the dogged or driving end, the last part turned will be eccentric to the first. Therefore, the lathe centers should be kept true in order to produce turned surfaces that are true or concentric with the centered ends, as it is often necessary to change the part being turned "end for end" for finishing, and any eccentricity between the different surfaces would, in many cases, spoil the work. [Illustration: Fig. 32. Grinder for Truing Lathe Centers] Some lathes are equipped with hardened centers in both the head-and tailstock and others have only one hardened center which is in the tailstock. The object in having a soft or unhardened headstock center is to permit its being trued by turning, but as a soft center is quite easily bruised and requires truing oftener than one that is hard, it is better to have both centers hardened. Special grinders are used for truing these hardened centers. One type that is very simple and easily applied to a lathe is shown in Fig. 32. This grinder is held in the lathe toolpost and is driven by a wheel _A_ that is held in contact with the cone-pulley. The emery wheel _B_ is moved to a position for grinding by adjusting the carriage and cross-slide, and it is traversed across the conical surface of the center by handle _C_. As the grinding proceeds, the wheel is fed inward slightly by manipulating the cross-slide. This grinder is set to the proper angle by placing the two centered ends _D_ and _D_{1}_ between the lathe centers, which should be aligned as for straight turning. The grinding spindle will then be 30 degrees from the axis of the lathe spindle. The grinder should be carefully clamped in the toolpost so that it will remain as located by the centered ends. After the tailstock center is withdrawn, the emery wheel is adjusted for grinding. As the wheel spindle is 30 degrees from the axis of the lathe spindle, the lathe center is not only ground true but to an included angle of 60 degrees, which is the standard angle for lathe centers. There are many other styles of center grinders on the market, some of which are driven by a small belt from the cone-pulley and others by electric motors which are connected with ordinary lighting circuits. The tailstock center is ground by inserting it in the spindle in place of the headstock center. Before a center is replaced in its spindle, the hole should be perfectly clean as even a small particle of dirt may affect the alignment. The center in the headstock is usually referred to as the "live center" because it turns around when the lathe is in use, and the center in the tailstock as the "dead center," because it remains stationary. =Universal, Independent and Combination Chucks.=--Many parts that are turned in the lathe are so shaped that they cannot be held between the lathe centers like shafts and other similar pieces and it is often necessary to hold them in a chuck _A_, Fig. 33, which is screwed onto the lathe spindle instead of the faceplate. The work is gripped by the jaws _J_ which can be moved in or out to accommodate various diameters. There are three classes of chucks ordinarily used on the lathe, known as the independent, universal and combination types. The independent chuck is so named because each jaw can be adjusted in or out independently of the others by turning the jaw screws S with a wrench. The jaws of the universal chuck all move together and keep the same distance from the center, and they can be adjusted by turning any one of the screws _S_, whereas with the independent type the chuck wrench must be applied to each jaw screw. The combination chuck, as the name implies, may be changed to operate either as an independent or universal type. The advantage of the universal chuck is that round and other parts of a uniform shape are located in a central position for turning without any adjustment. The independent type is, however, preferable in some respects as it is usually stronger and adapted for holding odd-shaped pieces because each jaw can be set to any required position. [Illustration: Fig. 33. (A) Lathe Chuck. (B) Faceplate Jaw] =Application of Chucks.=--As an example of chuck work, we shall assume that the sides of disk _D_, Fig. 34, are to be turned flat and parallel with each other and that an independent chuck is to be used. First the chuck is screwed onto the lathe spindle after removing the faceplate. The chuck jaws are then moved out or in, as the case may be, far enough to receive the disk and each jaw is set about the same distance from the center by the aid of concentric circles on the face of the chuck. The jaws are then tightened while the disk is held back against them to bring the rough inner surface in a vertical plane. If the work is quite heavy, it can be held against the chuck, before the jaws are tightened, by inserting a piece of wood between it and the tailstock center; the latter is then run out far enough to force the work back. The outside or periphery of the disk should run nearly true and it may be necessary to move the jaws in on one side and out on the other to bring the disk to a central position. To test its location, the lathe is run at a moderate speed and a piece of chalk is held near the outer surface. If the latter runs out, the "high" side will be marked by the chalk, and this mark can be used as a guide in adjusting the jaws. It should be remembered that the jaws are moved only one-half the amount that the work runs out. [Illustration: Fig. 34. (A) Radial Facing. (B) Boring Pulley Held in Chuck] A round-nosed tool _t_ of the shape shown can be used for radial facing or turning operations of the kind illustrated. This tool is similar to the form used when turning between centers, the principal difference being in the direction of the top slope. The radial facing tool should be ground to slope downward toward _a_ (see Fig. 35) whereas the regular turning tool slopes toward _b_, the inclination in each case being away from that part of the cutting edge which does the work. The cutting edge should be the same height as the lathe centers, and the cut is taken by feeding the tool from the outside in to the center. The cut is started by hand and then the power feed is engaged, except for small surfaces. The first cut should, if possible, be deep enough to get beneath the scale, especially if turning cast iron, as a tool which just grazes the hard outer surface will be dulled in a comparatively short time. If it were simply necessary to turn a true flat surface and the thickness of the disk were immaterial, two cuts would be sufficient, unless the surface were very uneven, the first or roughing cut being followed by a light finishing cut. For a finishing cut, the same tool could be used, but if there were a number of disks to be faced, a square-nosed tool _F_, Fig. 35, could probably be used to better advantage. This type has a broad flat cutting edge that is set parallel with the rough-turned surface and this broad edge enables a coarse feed to be taken, thus reducing the time required for the finishing cut. If a coarse feed were taken with the round tool, the turned surface would have spiral grooves in it, whereas with the broad cutting edge, a smooth surface is obtained even though the feed is coarse. The amount of feed per revolution of the work, however, should always be less than the width _w_ of the cutting edge. Very often broad tools cannot be used for finishing cuts, especially when turning steel, because their greater contact causes chattering and results in a rough surface. An old and worn lathe is more liable to chatter than one that is heavy and well-built, and as the diameter of the work also makes a difference, a broad tool cannot always be used for finishing, even though, theoretically, it would be preferable. After one side of the disk is finished, it is reversed in the chuck, the finished surface being placed against the jaws. The remaining rough side is then turned, care being taken when starting the first cut to caliper the width of the disk at several points to make sure that the two sides are parallel. [Illustration: Fig. 35. Tools Ground so that Top Slopes away from Working Part of Cutting Edge] =Example of Boring.=--Another example of chuck work is shown at _B_, Fig. 34. In this case a cast-iron pulley is to have a true hole _h_ bored through the hub. (The finishing of internal cylindrical surfaces in a lathe is referred to as boring rather than turning.) The casting should be set true by the rim instead of by the rough-cored hole in the hub; this can be done by the use of chalk as previously explained. Even though a universal type of chuck were used, the jaws of which, as will be recalled, are self-centering, it might be necessary to turn the pulley relative to the chuck as a casting sometimes runs out because of rough spots or lumps which happen to come beneath one or more of the jaws. [Illustration: Fig. 36. Boring Tool] The shape of tool _t_ for boring is quite different from one used for outside turning, as shown by Fig. 36. The cutting end of a solid type of tool is forged approximately at right angles to the body or shank, and the top surface is ground to slope away from the working part _w_ of the cutting edge, as with practically all turning tools. The front part or flank, _f_ is also ground away to give the edge clearance. This type of tool is clamped in the toolpost with the body about parallel with the lathe spindle, and ordinarily the cutting edge would be about as high as the center of the hole, or a little below, if anything. When starting a cut, the tool is brought up to the work by moving the carriage and it is then adjusted radially to get the right depth of cut, by shifting the cross-slide. The power feed for the carriage is then used, the tool feeding back through the hole as indicated by the arrow, Fig. 34. In this case, as with all turning operations, the first cut should be deep enough to remove the hard outer scale at every part of the hole. Usually a rough-cored hole is so much smaller than the finished size that several cuts are necessary; in any case, the last or finishing cut should be very light to prevent the tool from springing away from the work, so that the hole will be as true as possible. Boring tools, particularly for small holes, are not as rigid as those used for outside turning, as the tool has to be small enough to enter the hole and for this reason comparatively light cuts have to be taken. When boring a small hole, the largest tool that will enter it without interference should be used to get the greatest rigidity possible. [Illustration: Fig. 37 (A) Setting Outside Calipers. (B) Transferring Measurements to Inside Calipers. (C) Micrometer Gage] =Measuring Bored Holes.=--The diameters of small holes that are being bored are usually measured with inside calipers or standard gages. If the pulley were being bored to fit over some shaft, the diameter of the shaft would first be measured by using outside calipers, as shown at _A_, Fig. 37, the measuring points of the calipers being adjusted until they just made contact with the shaft when passed over it. The inside calipers are then set as at _B_ to correspond with the size of the shaft, and the hole is bored just large enough to admit the inside calipers easily. Very accurate measurements can be made with calipers, but to become expert in their use requires experience. Some mechanics never become proficient in the art of calipering because their hands are "heavy" and they lack the sensitiveness and delicacy of touch that is necessary. For large holes, a gage _C_ is often used, the length _l_ being adjusted to the diameter desired. Small holes are often bored to fit hardened steel plug gages (Fig. 38), the cylindrical measuring ends of which are made with great accuracy to standard sizes. This type of gage is particularly useful when a number of holes have to be bored to the same size, all holes being made just large enough to fit the gage without any perceptible play. [Illustration: Fig. 38. Standard Plug Gage] _Setting Work in the Chuck._--When setting a part in a chuck, care should be taken to so locate it that every surface to be turned will be true when machined to the finished size. As a simple illustration, let us assume that the hole through the cast-iron disk, Fig. 39, has been cored considerably out of center, as shown. If the work is set by the outside surface _S_, as it would be ordinarily, the hole is so much out of center that it will not be true when bored to the finished size, as indicated by the dotted lines. On the other hand, if the rough hole is set true, the outside cannot be finished all over, without making the diameter too small, when it is finally turned. In such a case, the casting should be shifted, as shown by the arrow, to divide the error between the two surfaces, both of which can then be turned as shown by the dotted lines in the view to the right. This principle of dividing the error when setting work can often be applied in connection with turning and boring. After a casting or other part has been set true by the most important surface, all other surfaces which require machining should be tested to make sure that they all can be finished to the proper size. =Inaccuracy from Pressure of Chuck Jaws.=--Work that is held in a chuck is sometimes sprung out of shape by the pressure of the chuck jaws so that when the part is bored or turned, the finished surfaces are untrue after the jaws are released and the work has resumed its normal shape. This applies more particularly to frail parts, such as rings, thin cylindrical parts, etc. Occasionally the distortion can be prevented by so locating the work with relation to the chuck jaws that the latter bear against a rigid part. When the work cannot be held tightly enough for the roughing cuts without springing it, the jaws should be released somewhat before taking the finishing cut, to permit the part to spring back to its natural shape. [Illustration: Fig. 39. Diagram Illustrating Importance of Setting Work with Reference to Surfaces to be Turned] [Illustration: Fig. 40. Drilling in the Lathe] =Drilling and Reaming.=--When a hole is to be bored from the solid, it is necessary to drill a hole before a boring tool can be used. One method of drilling in the lathe is to insert an ordinary twist drill in a holder or socket _S_, Fig. 40, which is inserted in the tailstock spindle in place of the center. The drill is then fed through the work by turning the handle _n_ and feeding the spindle outward as shown by the arrow. Before beginning to drill, it is well to turn a conical spot or center for the drill point so the latter will start true. This is often done by using a special tool having a point like a flat drill. This tool is clamped in the toolpost with the point at the same height as the lathe centers. It is then fed against the center of the work and a conical center is turned. If the drill were not given this true starting point, it probably would enter the work more or less off center. Drills can also be started without turning a center by bringing the square end or butt of a tool-shank held in the toolpost in contact with the drill near the cutting end. If the point starts off center, thus causing the drill to wobble, the stationary tool-shank will gradually force or bump it over to the center. [Illustration: Fig. 41. Flat Drill and Holder] Small holes are often finished in the lathe by drilling and reaming without the use of a boring tool. The form of drill that is used quite extensively for drilling cored holes in castings is shown in Fig. 41, at _A_. This drill is flat and the right end has a large center hole for receiving the center of the tailstock. To prevent the drill from turning, a holder _B_, having a slot _s_ in its end through which the drill passes, is clamped in the toolpost, as at _C_. This slot should be set central with the lathe centers, and the drill, when being started, should be held tightly in the slot by turning or twisting it with a wrench as indicated in the end view at _D_; this steadies the drill and causes it to start fairly true even though the cored hole runs out considerably. Another style of tool for enlarging cored holes is shown in Fig. 42, at _A_. This is a rose chucking reamer, having beveled cutting edges on the end and a cylindrical body, which fits closely in the reamed hole, thus supporting and guiding the cutting end. The reamer shown at _B_ is a fluted type with cutting edges that extend from _a_ to _b_; it is used for finishing holes and the drill or rose reamer preceding it should leave the hole very close to the required size. These reamers are held while in use in a socket inserted in the tailstock spindle, as when using a twist drill. [Illustration: Fig. 42. Rose and Fluted Reamers] =Holding Work on Faceplate.=--Some castings or forgings are so shaped that they cannot be held in a chuck very well, or perhaps not at all, and work of this kind is often clamped to a faceplate which is usually larger than the faceplate used for driving parts that are turned between the centers. An example of faceplate work is shown in Fig. 43. This is a rectangular-shaped casting having a round boss or projection, the end _e_ of which is to be turned parallel with the back face of the casting previously finished on a planer. A rough cored hole through the center of the boss also needs to be bored true. The best way to perform this operation in the lathe would be to clamp the finished surface of the casting directly against the faceplate by bolts and clamps _a_, _b_, _c_, and _d_, as shown; the work would then be turned just as though it were held in a chuck. By holding the casting in this way, face _e_ will be finished parallel with the back surface because the latter is clamped directly against the true-running surface of the faceplate. If a casting of this shape were small enough it could also be held in the jaws of an independent chuck, but if the surface e needs to be exactly parallel with the back face, it is better to clamp the work to the faceplate. Most lathes have two faceplates: One of small diameter used principally for driving work turned between centers, and a large one for holding heavy or irregularly shaped pieces; either of these can be screwed onto the spindle, and the large faceplate has a number of slots through which clamping bolts can be inserted. [Illustration: Fig. 43. Casting Clamped to Faceplate for Turning and Boring] The proper way to clamp a piece to the faceplate depends, of course, largely on its shape and the location of the surface to be machined, but in any case it is necessary to hold it securely to prevent any shifting after a cut is started. Sometimes castings can be held by inserting bolts through previously drilled holes, but when clamps are used in connection with the bolts, their outer ends are supported by hardwood or metal blocks which should be just high enough to make the clamp bear evenly on the work. When deep roughing cuts have to be taken, especially on large diameters, it is well to bolt a piece to the faceplate and against one side of the casting, as at _D_, to act as a driver and prevent the work from shifting; but a driver would not be needed in this particular case. Of course a faceplate driver is always placed to the rear, as determined by the direction of rotation, because the work tends to shift backward when a cut is being taken. If the surface which is clamped against the faceplate is finished as in this case, the work will be less likely to shift if a piece of paper is placed between it and the faceplate. [Illustration: Fig. 44. Cast Elbow held on Angle-plate attached to Faceplate] Work mounted on the faceplate is generally set true by some surface before turning. As the hole in this casting should be true with the round boss, the casting is shifted on the faceplate until the rough outer surface of the boss runs true; the clamps which were previously set up lightly are then tightened. The face e is first turned by using a round-nosed tool. This tool is then replaced by a boring tool and the hole is finished to the required diameter. If the hole being bored is larger than the central hole in the faceplate, the casting should be clamped against parallel pieces, and not directly against the faceplate, to provide clearance for the tool when it reaches the inner end of the hole and prevent it from cutting the faceplate. The parallel pieces should be of the same thickness and be located near the clamps to prevent springing the casting. =Application of Angle-plate to Faceplate.=--Another example of faceplate work is shown in Fig. 44. This is a cast-iron elbow _E_, the two flanges of which are to be faced true and square with each other. The shape of this casting is such that it would be very difficult to clamp it directly to the faceplate, but it is easily held on an angle-plate _P_, which is bolted to the faceplate. The two surfaces of this angle-plate are square with each other so that when one flange of the elbow is finished and bolted against the angle-plate, the other will be faced square. When setting up an angle-plate for work of this kind, the distance from its work-holding side to the center of the faceplate is made equal to the distance _d_ between the center of one flange and the face of the other, so that the flange to be faced will run about true when bolted in place. As the angle-plate and work are almost entirely on one side of the faceplate, a weight _W_ is attached to the opposite side for counterbalancing. Very often weights are also needed to counterbalance offset parts that are bolted directly to the faceplate. The necessity of counterbalancing depends somewhat upon the speed to be used for turning. If the surface to be machined is small in diameter so that the lathe can be run quite rapidly, any unbalanced part should always be counterbalanced. Sometimes it is rather difficult to hold heavy pieces against the vertical surface of the faceplate while applying the clamps, and occasionally the faceplate is removed and placed in a horizontal position on the bench; the work can then be located about right, and after it is clamped, the faceplate is placed on the lathe spindle by the assistance of a crane. Special faceplate jaws, such as the one shown to the right in Fig. 33, can often be used to advantage for holding work on large faceplates. Three or four of these jaws are bolted to the faceplate which is converted into a kind of independent chuck. These faceplate jaws are especially useful for holding irregularly shaped parts, as the different jaws can be located in any position. =Supporting Outer End of Chucked Work.=--Fig. 45 shows how the tailstock center is sometimes used for supporting the outer end of a long casting, the opposite end of which is held in a chuck. This particular casting is to be turned and bored to make a lining for the cylinder of a locomotive in order to reduce the diameter of the cylinder which has been considerably enlarged by re-boring a number of times. These bushings are rough-turned on the outside while the outer end is supported by the cross-shaped piece or "spider" which forms a center-bearing for the tailstock. This spider has set screws in the flanged ends of the arms, which are tightened against the inner surface of the casting and are adjusted one way or the other in order to locate it in a concentric position. After roughing the outside, the inside is bored to the finish size; then centered disks, which fit into the bore, are placed in the ends of the bushing and the latter is finish-turned. The object in rough turning the outside prior to boring is to avoid the distortion which might occur if this hard outer surface were removed last. [Illustration: Fig. 45. Rough Turning a Cylinder Lining--Note Method of Supporting Outer End] =Boring Large Castings in the Lathe.=--An ordinary engine lathe is sometimes used for boring engine or pump cylinders, linings, etc., which are too large to be held in the chuck or on a faceplate, and must be attached to the lathe carriage. As a rule, work of this class is done in a special boring machine (see "Horizontal Boring Machines"), but if such a machine is not available, it may be necessary to use a lathe. There are two general methods of boring. Fig. 46 shows how the lining illustrated in Fig. 45 is bored in a large engine lathe. The casting is held in special fixtures which are attached to the lathe carriage, and the boring-bar is rotated by the lathe spindle. The tool-head of this boring-bar carries two tools located 180 degrees apart and it is fed along the bar by a star-feed mechanism shown attached to the bar and the tailstock spindle. Each time the bar revolves, the star wheel strikes a stationary pin and turns the feed-screw which, as the illustration shows, extends along a groove cut in one side of the bar. This feed-screw passes through a nut attached to the tool-head so that the latter is slowly fed through the bore. When using a bar of this type, the carriage, of course, remains stationary. [Illustration: Fig. 46. Boring a Cylinder Lining in an Ordinary Engine Lathe] Cylindrical parts attached to the carriage can also be bored by using a plain solid bar mounted between the centers. The bar must be provided with a cutter for small holes or a tool-head for larger diameters (preferably holding two or more tools) and the boring is done by feeding the carriage along the bed by using the regular power feed of the lathe. A symmetrically shaped casting like a bushing or lining is often held upon wooden blocks bolted across the carriage. These are first cut away to form a circular seat of the required radius, by using the boring-bar and a special tool having a thin curved edge. The casting is then clamped upon these blocks by the use of straps and bolts, and if the curved seats were cut to the correct radius, the work will be located concentric with the boring-bar. When using a boring-bar of this type, the bar must be long enough to allow the part being bored to feed from one side of the cutter-head to the other, the cutter-head being approximately in a central location. [Illustration: Fig. 47. Method of Setting Circle on Work Concentric with Lathe Spindle] =Boring Holes to a Given Center Distance.=--In connection with faceplate work, it is often necessary to bore two or more holes at a given distance apart. The best method of doing this may depend upon the accuracy required. For ordinary work sometimes two or more circles _A_ and _B_ (Fig. 47) are drawn upon the part to be bored, in the position for the holes; the piece is then clamped to the faceplate and one of the circles is centered with the lathe spindle by testing it with a pointer C held in the toolpost; that is, when the pointer follows the circle as the work is turned, evidently the circle is concentric with the spindle. The hole is then drilled and bored. The other circle is then centered in the same way for boring the second hole. As will be seen, the accuracy of this method depends first, upon the accuracy with which the circles were laid out, and second; upon the care taken in setting them concentric. For a more accurate way of locating parts for boring, see "Use of Center Indicator" and "Locating Work by the Button Method." =Turning Brass, Bronze and Copper.=--When turning soft yellow brass, a tool should be used having very little or no slope or rake on the top surface against which the chip bears, and for plain cylindrical turning, the point of the tool is drawn out quite thin and rounded, by grinding, to a radius of about 1/8 or 3/16 inch. If a tool having very much top slope is used for brass, there is danger of its gouging into the metal, especially if the part being turned is at all flexible. The clearance angle of a brass tool is usually about 12 or 14 degrees, which is 3 or 4 degrees greater than the clearance for steel turning tools. Most brass is easily turned, as compared with steel, and for that reason this increase in clearance is desirable, because it facilitates feeding the tool into the metal, especially when the carriage and cross-slide movements are being controlled by hand as when turning irregular shapes. The speed for turning soft brass is much higher than for steel, being ordinarily between 150 and 200 feet per minute. When turning phosphor, tobin or other tough bronze compositions, the tool should be ground with rake the same as for turning steel, and lard oil is sometimes used as a lubricant. The cutting speed for bronzes varies from 35 or 40 to 80 feet per minute, owing to the difference in the composition of bronze alloys. Turning tools for copper are ground with a little more top rake than is given steel turning tools, and the point should be slightly rounded. It is important to have a keen edge, and a grindstone is recommended for sharpening copper turning tools. Milk is generally considered the best lubricant to use when turning copper. The speed can be nearly as fast as for brass. =Machining Aluminum.=--Tools for turning aluminum should have acute cutting angles. After rough-grinding the tool, it is advisable to finish sharpening the cutting edge on a grindstone or with an oilstone for fine work, as a keen edge is very essential. High speeds and comparatively light cuts are recommended. The principal difficulty in the machining of aluminum and aluminum alloys is caused by the clogging of the chips, especially when using such tools as counterbores and milling cutters. This difficulty can be avoided largely by using the right kind of cutting lubricant. Soap-water and kerosene are commonly employed. The latter enables a fine finish to be obtained, provided the cutting tool is properly ground. The following information on this subject represents the experience of the Brown-Lipe Gear Co., where aluminum parts are machined in large quantities: For finishing bored holes, a bar equipped with cutters has been found more practicable than reamers. The cutters used for machining 4-inch holes have a clearance of from 20 to 22 degrees and no rake or slope on the front faces against which the chips bear. The roughing cutters for this work have a rather sharp nose, being ground on the point to a radius of about 3/32 inch, but for securing a smooth surface, the finishing tools are rounded to a radius of about 3/4 inch. The cutting speed, as well as the feed, for machining aluminum is from 50 to 60 per cent faster than the speeds and feeds for cast iron. The lubricant used by this company is composed of one part "aqualine" and 20 parts water. This lubricant not only gives a smooth finish but preserves a keen cutting edge and enables tools to be used much longer without grinding. Formerly, a lubricant composed of one part of high-grade lard oil and one part of kerosene was used. This mixture costs approximately 30 cents per gallon, whereas the aqualine and water mixture now being used costs less than 4 cents per gallon, and has proved more effective than the lubricant formerly employed. CHAPTER II LATHE TURNING TOOLS AND CUTTING SPEEDS Notwithstanding the fact that a great variety of work can be done in the lathe, the number of turning tools required is comparatively small. Fig. 1 shows the forms of tools that are used principally, and typical examples of the application of these various tools are indicated in Fig. 2. The reference letters used in these two illustrations correspond for tools of the same type, and both views should be referred to in connection with the following description. =Turning Tools for General Work.=--The tool shown at _A_ is the form generally used for rough turning, that is for taking deep cuts when considerable metal has to be removed. At _B_ a tool of the same type is shown, having a bent end which enables it to be used close up to a shoulder or surface _s_ that might come in contact with the tool-rest if the straight form were employed. Tool _C_, which has a straight cutting end, is used on certain classes of work for taking light finishing cuts, with a coarse feed. This type of tool has a flat or straight cutting edge at the end, and will leave a smooth finish even though the feed is coarse, provided the cutting edge is set parallel with the tool's travel so as to avoid ridges. Broad-nosed tools and wide feeds are better adapted for finishing cast iron than steel. When turning steel, if the work is at all flexible, a broad tool tends to gouge into it and for this reason round-nosed tools and finer feeds are generally necessary. A little experience in turning will teach more on this point than a whole chapter on the subject. [Illustration: Fig. 1. Set of Lathe Turning Tools for General Work] [Illustration: Fig. 2. Views illustrating Use of Various Types of Lathe Tools] The side-tools shown at _D_ and _E_ are for facing the ends of shafts, collars, etc. The first tool is known as a right side-tool because it operates on the right end or side of a shaft or collar, whereas the left side-tool _E_ is used on the opposite side, as shown in Fig. 2. Side-tools are also bent to the right or left because the cutting edge of a straight tool cannot always be located properly for facing certain surfaces. A bent right side-tool is shown at _F_. A form of tool that is frequently used is shown at _G_; this is known as a parting tool and is used for severing pieces and for cutting grooves, squaring corners, etc. The same type of tool having a bent end is shown at _H_ (Fig. 2) severing a piece held in the chuck. Work that is held between centers should not be entirely severed with a parting tool unless a steadyrest is placed between the tool and faceplate, as otherwise the tool may be broken by the springing of the work just before the piece is cut in two. It should be noted that the sides of this tool slope inward back of the cutting edge to provide clearance when cutting in a narrow groove. At _I_ a thread tool is shown for cutting a U. S. standard thread. This thread is the form most commonly used in this country at the present time. A tool for cutting a square thread is shown at _J_. This is shaped very much like a parting tool except that the cutting end is inclined slightly to correspond with the helix angle of the thread, as explained in Chapter IV, which contains descriptions of different thread forms and methods of cutting them. Internal thread tools are shown at _K_ and _L_ for cutting U. S. standard and square threads in holes. It will be seen that these tools are somewhat like boring tools excepting the ends which are shaped to correspond with the thread which they are intended to cut. [Illustration: Fig. 3. Turning Tool with Inserted Cutter] A tool for turning brass is shown at _M_. Brass tools intended for general work are drawn out quite thin and they are given a narrow rounded point. The top of the brass tool is usually ground flat or without slope as otherwise it tends to gouge into the work, especially if the latter is at all flexible. The end of a brass tool is sometimes ground with a straight cutting edge for turning large rigid work, such as brass pump linings, etc., so that a coarse feed can be used without leaving a rough surface. The tools at _N_ and _O_ are for boring or finishing drilled or cored holes. Two sizes are shown, which are intended for small and large holes, respectively. The different tools referred to in the foregoing might be called the standard types because they are the ones generally used, and as Fig. 2 indicates, they make it possible to turn an almost endless variety of forms. Occasionally some special form of tool is needed for doing odd jobs, having, perhaps, an end bent differently or a cutting edge shaped to some particular form. Tools of the latter type, which are known as "form tools," are sometimes used for finishing surfaces that are either convex, concave, or irregular in shape. The cutting edges of these tools are carefully filed or ground to the required shape, and the form given the tool is reproduced in the part turned. Ornamental or other irregular surfaces can be finished very neatly by the use of such tools. It is very difficult, of course, to turn convex or concave surfaces with a regular tool; in fact, it would not be possible to form a true spherical surface, for instance, without special equipment, because the tool could not be moved along a true curve by simply using the longitudinal and cross feeds. Form tools should be sharpened by grinding entirely on the top surface, as any grinding on the end or flank would alter the shape of the tool. [Illustration: Fig. 4. Heavy Inserted-cutter Turning Tool] =Tool-holders with Inserted Cutters.=--All of the tools shown in Fig. 1 are forged from the bar, and when the cutting ends have been ground down considerably it is necessary to forge a new end. To eliminate the expense of this continual dressing of tools and also to effect a great reduction in the amount of tool steel required, tool-holders having small inserted cutters are used in many shops. A tool-holder of this type, for outside turning, is shown in Fig. 3. The cutter _C_ is held in a fixed position by the set-screw shown, and it is sharpened, principally, by grinding the end, except when it is desired to give the top of the cutter a different slope from that due to its angular position. Another inserted-cutter turning tool is shown in Fig. 4, which is a heavy type intended for roughing. The cutter in this case has teeth on the rear side engaging with corresponding teeth cut in the clamping block which is tightened by a set-screw on the side opposite that shown. With this arrangement, the cutter can be adjusted upward as the top is ground away. [Illustration: Fig. 5. Parting Tool with Inserted Blade] [Illustration: Fig. 6. Boring Tool with Inserted Cutter and Adjustable Bar] A parting tool of the inserted blade type is shown in Fig. 5. The blade _B_ is clamped by screw _S_ and also by the spring of the holder when the latter is clamped in the toolpost. The blade can, of course, be moved outward when necessary. Fig. 6 shows a boring tool consisting of a holder _H_, a bar _B_ that can be clamped in any position, and an inserted cutter _C_. With this type of boring tool, the bar can be extended beyond the holder just far enough to reach through the hole to be bored, which makes the tool very rigid. A thread tool of the holder type is shown in Fig. 7. The angular edge of the cutter _C_ is accurately ground by the manufacturers, so that the tool is sharpened by simply grinding it flat on the top. As the top is ground away, the cutter is raised by turning screw _S_, which can also be used for setting the tool to the proper height. =The Position of Turning Tools.=--The production of accurate lathe work depends partly on the condition of the lathe used and also on the care and judgment exercised by the man operating it. Even though a lathe is properly adjusted and in good condition otherwise, errors are often made which are due to other causes which should be carefully avoided. If the turning tool is clamped so that the cutting end extends too far from the supporting block, the downward spring of the tool, owing to the thrust of the cut, sometimes results in spoiled work, especially when an attempt is made to turn close to the finished size by taking a heavy roughing cut. Suppose the end of a cylindrical part is first reduced for a short distance by taking several trial cuts until the diameter _d_, Fig. 8, is slightly above the finished size and the power feed is then engaged. When the tool begins to take the full depth _e_ of the cut, the point, which ordinarily would be set a little above the center, tends to spring downward into the work, and if there were considerable springing action, the part would probably be turned below the finished size, the increased reduction beginning at the point where the full cut started. [Illustration: Fig. 7. Threading Tool] This springing action, as far as the tool is concerned, can be practically eliminated by locating the tool so that the distance _A_ between the tool-block and cutting end, or the "overhang," is as short as possible. Even though the tool has little overhang it may tilt downward because the toolslide is loose on its ways, and for this reason the slide should have a snug adjustment that will permit an easy movement without unnecessary play. The toolslides of all lathes are provided with gibs which can be adjusted by screws to compensate for wear, or to secure a more rigid bearing. [Illustration: Fig. 8. To avoid springing, Overhang A of Tool should not be Excessive] When roughing cuts are to be taken, the tool should be located so that any change in its position which might be caused by the pressure of the cut will not spoil the work. This point is illustrated at _A_ in Fig. 9. Suppose the end of a rod has been reduced by taking a number of trial cuts, until it is 1/32 inch above the finished size. If the power feed is then engaged with the tool clamped in an oblique position, as shown, when the full cut is encountered at _c_, the tool, unless very tightly clamped, may be shifted backward by the lateral thrust of the cut, as indicated by the dotted lines. The point will then begin turning smaller than the finished size and the work will be spoiled. To prevent any change of position, it is good practice, especially when roughing, to clamp the tool square with the surface being turned, or in other words, at right angles to its direction of movement. Occasionally, however, there is a decided advantage in having the tool set at an angle. For example, if it is held about as shown at _B_, when turning the flange casting _C_, the surfaces _s_ and _s_{1}_ can be finished without changing the tool's position. Cylindrical and radial surfaces are often turned in this way in order to avoid shifting the tool, especially when machining parts in quantity. =Tool Grinding.=--In the grinding of lathe tools there are three things of importance to be considered: First, the cutting edge of the tool (as viewed from the top) needs to be given a certain shape; second, there must be a sufficient amount of clearance for the cutting edge; and third, tools, with certain exceptions, are ground with a backward slope or a side slope, or with a combination of these two slopes on that part against which the chip bears when the tool is in use. [Illustration: Fig. 9. (A) The Way in which Tool is sometimes displaced by Thrust of Cut, when set at an Angle. (B) Tool Set for Finishing both Cylindrical and Radial Surfaces] In Fig. 10 a few of the different types of tools which are used in connection with lathe work are shown. This illustration also indicates the meaning of the various terms used in tool grinding. As shown, the clearance of the tool is represented by the angle [alpha], the back slope is represented by the angle [beta], and the side slope by the angle [gamma]. The angle [delta] for a tool without side slope is known as the lip angle or the angle of keenness. When, however, the tool has both back and side slopes, this lip angle would more properly be the angle between the flank _f_ and the top of the tool, measured diagonally along a line _z--z_. It will be seen that the lines _A--B_ and _A--C_ from which the angles of clearance and back slope are measured are parallel with the top and sides of the tool shank, respectively. For lathe tools, however, these lines are not necessarily located in this way when the tool is in use, as the height of the tool point with relation to the work center determines the position of these lines, so that the _effective_ angles of back slope, clearance and keenness are changed as the tool point is lowered or raised. The way the position of the tool affects these angles will be explained later. [Illustration: Fig. 10. Illustration showing the Meaning of Terms used in Tool Grinding as applied to Tools of Different Types] While tools must, of necessity, be varied considerably in shape to adapt them to various purposes, there are certain underlying principles governing their shape which apply generally; so in what follows we shall not attempt to explain in detail just what the form of each tool used on the lathe should be, as it is more important to understand how the cutting action of the tool and its efficiency is affected when it is improperly ground. When the principle is understood, the grinding of tools of various types and shapes is comparatively easy. [Illustration: Fig. 11. Plan View of Lathe Turning and Threading Tools] =Shape or Contour of Cutting Edge.=--In the first place we shall consider the shape or contour of the cutting edge of the tool as viewed from the top, and then take up the question of clearance and slope, the different elements being considered separately to avoid confusion. The contour of the cutting edge depends primarily upon the purpose for which the tool is intended. For example, the tool _A_, in Fig. 11, where a plan view of a number of different lathe tools is shown, has a very different shape from that of, say, tool _D_, as the first tool is used for rough turning, while tool _D_ is intended for cutting grooves or severing a turned part. Similarly, tool _E_ is V-shaped because it is used for cutting V-threads. Tools _A_, _B_ and _C_, however, are regular turning tools; that is, they are all intended for turning plain cylindrical surfaces, but the contour of the cutting edges varies considerably, as shown. In this case it is the characteristics of the work and the cut that are the factors which determine the shape. To illustrate, tool _A_ is of a shape suitable for rough-turning large and rigid work, while tool _B_ is adapted for smaller and more flexible parts. The first tool is well shaped for roughing because experiments have shown that a cutting edge of a large radius is capable of higher cutting speed than could be used with a tool like _B_, which has a smaller point. This increase in the cutting speed is due to the fact that the tool _A_ removes a thinner chip for a given feed than tool _B_; therefore, the speed may be increased without injuring the cutting edge to the same extent. If, however, tool _A_ were to be used for turning a long and flexible part, chattering might result; consequently, a tool _B_ having a point with a smaller radius would be preferable, if not absolutely necessary. The character of the work also affects the shape of tools. The tool shown at _C_ is used for taking light finishing cuts with a wide feed. Obviously, if the straight or flat part of the cutting edge is in line with the travel of the tool, the cut will be smooth and free from ridges, even though the feed is coarse, and by using a coarse feed the cut is taken in less time; but such a tool cannot be used on work that is not rigid, as chattering would result. Therefore, a smaller cutting point and a reduced feed would have to be employed. Tools with broad flat cutting edges and coarse feeds are often used for taking finishing cuts in cast iron, as this metal offers less resistance to cutting than steel, and is less conducive to chattering. The shape of a tool (as viewed from the top) which is intended for a more specific purpose than regular turning, can be largely determined by simply considering the tool under working conditions. This point may be illustrated by the parting tool _D_ which, as previously stated, is used for cutting grooves, squaring corners, etc. Evidently this tool should be widest at the cutting edge; that is, the sides _d_ should have a slight amount of clearance so that they will not bind as the tool is fed into a groove. As the tool at _E_ is for cutting a V-thread, the angle [alpha] between its cutting edges must equal the angle between the sides of a V-thread, or 60 degrees. The tool illustrated at _F_ is for cutting inside square threads. In this case the width _w_ should be made equal to one-half the pitch of the thread (or slightly greater to provide clearance for the screw), and the sides should be given a slight amount of side clearance, the same as with the parting tool _D_. So we see that the outline of the tool, as viewed from the top, must conform to and be governed by its use. =Direction of Top Slope for Turning Tools.=--Aside from the question of the shape of the cutting edge as viewed from the top, there remains to be determined the amount of clearance that the tool shall have, and also the slope (and its direction) of the top of the tool. By the top is meant that surface against which the chip bears while it is being severed. It may be stated, in a general way, that the direction in which the top of the tool should slope should be away from what is to be the _working part_ of the cutting edge. For example, the working edge of a roughing tool _A_ (Fig. 11), which is used for heavy cuts, would be, practically speaking, between points _a_ and _b_, or, in other words, most of the work would be done by this part of the cutting edge; therefore the top should slope back from this part of the edge. Obviously, a tool ground in this way will have both a back and a side slope. When most of the work is done on the point or nose of the tool, as, for example, with the lathe finishing tool _C_ which takes light cuts, the slope should be straight back from the point or cutting edge _a--b_. As the side tool shown in Fig. 10 does its cutting along the edge _a--b_, the top is given a slope back from this edge as shown in the end view. This point should be remembered, for when the top slopes in the right direction, less power is required for cutting. Tools for certain classes of work, such as thread tools, or those for turning brass or chilled iron, are ground flat on top, that is, without back or side slope. =Clearance for the Cutting Edge.=--In order that the cutting edge may work without interference, it must have clearance; that is, the flank _f_ (Fig. 10) must be ground to a certain angle [alpha] so that it will not rub against the work and prevent the cutting edge from entering the metal. This clearance should be just enough to permit the tool to cut freely. A clearance angle of eight or ten degrees is about right for lathe turning tools. The back slope of a tool is measured from a line _A--B_ which is parallel to the shank, and the clearance angle, from a line _A--C_ at right angles to line _A--B_. These lines do not, however, always occupy this position with relation to the tool shank when the tool is in use. As shown to the left in Fig. 12, the base line _A--B_ for a turning tool in use intersects with the point of the tool and center of the work, while the line _A--C_ remains at right angles to the first. It will be seen, then, that by raising the tool, as shown to the right, the _effective_ clearance angle [alpha] will be diminished, whereas lowering it, as shown by the dotted lines, will have the opposite effect. A turning tool for brass or other soft metal, particularly where considerable hand manipulation is required, could advantageously have a clearance of twelve or fourteen degrees, as it would then be easier to feed the tool into the metal; but, generally speaking, the clearance for turning tools should be just enough to permit them to cut freely. Excessive clearance weakens the cutting edge and may cause it to crumble under the pressure of the cut. [Illustration: Fig. 12. Illustrations showing how Effective Angles of Slope and Clearance change as Tool is raised or lowered] =Angle of Tool-point and Amount of Top Slope.=--The lip angle or the angle of keenness [delta] (Fig. 10) is another important consideration in connection with tool grinding, for it is upon this angle that the efficiency of the tool largely depends. By referring to the illustration it will be seen that this angle is governed by the clearance and the slope [beta], and as the clearance remains practically the same, it is the slope which is varied to meet different conditions. Now, the amount of slope a tool should have depends on the work for which it is intended. If, for example, a turning tool is to be used for roughing medium or soft steel, it should have a back slope of about eight degrees and a side slope ranging from fourteen to twenty degrees, while a tool for cutting very hard steel should have a back slope of about five degrees and a side slope of nine degrees. [Illustration: Fig. 13. (A) Blunt Tool for Turning Hard Steel. (B) Tool-point Ground to give Keenness] The reason for decreasing the slope and thus increasing the lip angle for harder metals is to give the necessary increased strength to the cutting edge to prevent it from crumbling under the pressure of the cut. The tool illustrated at _A_, Fig. 13, is much stronger than it would be if ground as shown at _B_, as the former is more blunt. If a tool ground as at _A_, however, were used for cutting very soft steel, there would be a greater chip pressure on the top and, consequently, a greater resistance to cutting, than if a keener tool had been employed; furthermore the cutting speed would have to be lower, which is of even greater importance than the chip pressure; therefore, the lip angle, as a general rule, should be as small as possible without weakening the tool so that it cannot do the required work. In order to secure a strong and well-supported cutting edge, tools used for turning very hard metal, such as chilled rolls, etc., are ground with practically no slope and with very little clearance. Brass tools, while given considerable clearance, as previously stated, are ground flat on top or without slope; this is not done, however, to give strength to the cutting edge, but rather to prevent the tool from gouging into the work, which it is likely to do if the part being turned is at all flexible and the tool has top slope. Experiments conducted by Mr. F. W. Taylor to determine the most efficient form for lathe roughing tools showed that the nearer the lip angle approached sixty-one degrees, the higher the cutting speed. This, however, does not apply to tools for turning cast iron, as the latter will work more efficiently with a lip angle of about sixty-eight degrees. This is doubtless because the chip pressure, when turning cast iron, comes closer to the cutting edge which should, therefore, be more blunt to withstand the abrasive action and heat. Of course, the foregoing remarks concerning lip angles apply more particularly to tools used for roughing. [Illustration: Fig. 14. Grinding the Top and Flank of a Turning Tool] =Grinding a Lathe Tool.=--The way a turning tool is held while the top surface is being ground is shown to the left in Fig. 14. By inclining the tool with the wheel face, it will be seen that both the back and side slopes may be ground at the same time. When grinding the flank of the tool it should be held on the tool-rest of the emery wheel or grindstone, as shown by the view to the right. In order to form a curved cutting edge, the tool is turned about the face of the stone while it is being ground. This rotary movement can be effected by supporting the inner end of the tool with one hand while the shank is moved to and fro with the other. Often a tool which has been ground properly in the first place is greatly misshapen after it has been sharpened a few times. This is usually the result of attempts on the part of the workman to re-sharpen it hurriedly; for example, it is easier to secure a sharp edge on the turning tool shown to the left in Fig. 12, by grinding the flank as indicated by the dotted line, than by grinding the entire flank. The clearance is, however, reduced and the lip angle changed. There is great danger when grinding a tool of burning it or drawing the temper from the fine cutting edge, and, aside from the actual shape of the cutting end, this is the most important point in connection with tool grinding. If a tool is pressed hard against an emery or other abrasive wheel, even though the latter has a copious supply of water, the temper will sometimes be drawn. When grinding a flat surface, to avoid burning, the tool should frequently be withdrawn from the stone so that the cooling water (a copious supply of which should be provided) can reach the surface being ground. A moderate pressure should also be applied, as it is better to spend an extra minute or two in grinding than to ruin the tool by burning, in an attempt to sharpen it quickly. Of course, what has been said about burning applies more particularly to carbon steel, but even self-hardening steels are not improved by being over-heated at the stone. In some shops, tools are ground to the theoretically correct shape in special machines instead of by hand. The sharpened tools are then kept in the tool-room and are given out as they are needed. =Cutting Speeds and Feeds.=--The term cutting speed as applied to turning operations is the speed in feet per minute of the surface being turned, or, practically speaking, it is equivalent to the length of a chip, in feet, which would be turned in one minute. The term cutting speed should not be confused with revolutions per minute, because the cutting speed depends not only upon the speed of the work but also upon its diameter. The feed of a tool is the amount it moves across the surface being turned for each revolution; that is, when turning a cylindrical piece, the feed is the amount that the tool moves sidewise for each revolution of the work. Evidently the time required for turning is governed largely by the cutting speed, the feed, and the depth of the cut; therefore, these elements should be carefully considered. Cutting Speeds and Feeds for Turning Tools[1] +---------------------------------++---------------------------------+ | Steel--Standard 7/8-inch Tool ||Cast Iron--Standard 7/8-inch Tool| +-----+-----+---------------------++-----+-----+---------------------+ | | | Speed in Feet per || | | Speed in Feet per | |Depth|Feed | Minute for a Tool ||Depth|Feed | Minute for a Tool | | of | in | which is to last || of | in | which is to last | | Cut | In- | 1-1/2 Hour before || Cut | In- | 1-1/2 Hour before | | in |ches | Re-grinding || in |ches | Re-grinding | | In- | +------+------+-------++ In- | +-------+------+------+ |ches | | Soft |Medium| Hard ||ches | | Soft |Medium| Hard | | | |Steel |Steel |Steel || | | Cast | Cast | Cast | | | | | | || | | Iron | Iron | Iron | +-----+-----+------+------+-------++-----+-----+-------+------+------+ | | 1/64| 476 | 238 | 108 || | 1/16| 122 | 61.2 | 35.7 | |3/32 | 1/32| 325 | 162 | 73.8 ||3/32 | 1/8 | 86.4 | 43.2 | 25.2 | | | 1/16| 222 | 111 | 50.4 || | 3/16| 70.1 | 35.1 | 20.5 | | | 3/32| 177 | 88.4| 40.2 ++-----+-----+-------+------+------+ +-----+-----+------+------+-------++ | 1/32| 156 | 77.8 | 45.4 | | | 1/64| 420 | 210 | 95.5 || 1/8 | 1/16| 112 | 56.2 | 32.8 | | 1/8 | 1/32| 286 | 143 | 65.0 || | 1/8 | 79.3 | 39.7 | 23.2 | | | 1/16| 195 | 97.6| 44.4 || | 3/16| 64.3 | 32.2 | 18.8 | | | 1/8 | 133 | 66.4| 30.2 ++-----+-----+-------+------+------+ +-----+-----+------+------+-------++ | 1/32| 137 | 68.6 | 40.1 | | | 1/64| 352 | 176 | 80.0 ||3/16 | 1/16| 99.4 | 49.7 | 29.0 | |3/16 | 1/32| 240 | 120 | 54.5 || | 1/8 | 70.1 | 35.0 | 20.5 | | | 1/16| 164 | 82 | 37.3 || | 3/16| 56.8 | 28.4 | 16.6 | | | 1/8 | 112 | 56 | 25.5 ++-----+-----+-------+------+------+ +-----+-----+------+------+-------++ | 1/32| 126 | 62.9 | 36.7 | | | 1/64| 312 | 156 | 70.9 || 1/4 | 1/16| 90.8 | 45.4 | 26.5 | | 1/4 | 1/32| 213 | 107 | 48.4 || | 1/8 | 64.1 | 32.0 | 18.7 | | | 1/16| 145 | 72.6| 33.0 || | 3/16| 52 | 26.0 | 15.2 | | | 3/32| 116 | 58.1| 26.4 ++-----+-----+-------+------+------+ +-----+-----+------+------+-------++ | 1/32| 111 | 55.4 | 32.3 | | | 1/64| 264 | 132 | 60.0 || 3/8 | 1/16| 80 | 40.0 | 23.4 | | 3/8 | 1/32| 180 | 90.2| 41.0 || | 1/8 | 56.4 | 28.2 | 16.5 | | | 1/16| 122 | 61.1| 27.8 ++-----+-----+-------+------+------+ +-----+-----+------+------+-------++ | 1/32| 104 | 52.1 | 30.4 | | 1/2 | 1/64| 237 | 118 | 53.8 || 1/2 | 1/16| 75.2 | 37.6 | 22.0 | | | 1/32| 162 | 80.8| 36.7 || | 1/8 | 43.1 | 21.6 | 12.6 | +-----+-----+------+------+-------++-----+-----+-------+------+------+ |Steel--Standard 5/8-inch Tool ||Cast Iron--Standard 5/8-inch Tool| +-----+-----+------+------+-------++-----+-----+-------+------+------+ |Depth|Feed | Soft |Medium| Hard ||Depth|Feed | Soft |Medium| Hard | | of | |Steel |Steel |Steel || of | | Cast | Cast | Cast | | Cut | | | | || Cut | | Iron | Iron | Iron | +-----+-----+------+------+-------++-----+-----+-------+------+------+ | | 1/64| 548 | 274 | 125 || | 1/32| 160 | 80.0 | 46.6 | |1/16 | 1/32| 358 | 179 | 81.6 ||3/32 | 1/16| 110 | 55.0 | 32.2 | | | 1/16| 235 | 117 | 53.3 || | 1/8 | 75.4 | 37.7 | 22.0 | +-----+-----+------+------+-------++-----+-----+-------+------+------+ | | 1/64| 467 | 234 | 106 || | 1/32| 148 | 74.0 | 43.3 | |3/32 | 1/32| 306 | 153 | 69.5 || 1/8 | 1/16| 104 | 51.8 | 32.0 | | | 1/16| 200 | 100 | 45.5 || | 1/8 | 69.6 | 34.8 | 20.3 | | | 3/32| 156 | 78 | 35.5 ++-----+-----+-------+------+------+ +-----+-----+------+------+-------++ | 1/64| 183 | 91.6 | 68.0 | | | 1/64| 417 | 209 | 94.8 ||3/16 | 1/32| 135 | 67.5 | 39.4 | | 1/8 | 1/32| 273 | 136 | 62.0 || | 1/16| 94 | 47.0 | 27.4 | | | 1/16| 179 | 89.3| 40.6 || | 1/8 | 64.3 | 32.2 | 18.8 | | | 3/32| 140 | 69.8| 31.7 ++-----+-----+-------+------+------+ +-----+-----+------+------+-------++ | 1/64| 171 | 85.7 | 50.1 | | | 1/64| 362 | 181 | 82.2 || 1/4 | 1/32| 126 | 63.2 | 36.9 | |3/16 | 1/32| 236 | 118 | 53.8 || | 1/16| 87.8 | 43.9 | 25.6 | | | 1/16| 155 | 77.4| 35.2 || | 3/32| 70.4 | 35.2 | 20.6 | +-----+-----+------+------+-------++-----+-----+-------+------+------+ | 1/4 | 1/64| 328 | 164 | 74.5 || 3/8 | 1/64| 156 | 77.8 | 45.4 | | | 1/32| 215 | 107 | 48.8 || | 1/32| 116 | 57.8 | 33.8 | +-----+-----+------+------+-------++ | 1/16| 79.7 | 39.9 | 23.3 | | 3/8 | 1/64| 286 | 143 | 65.0 || | | | | | +-----+-----+------+------+-------++-----+-----+-------+------+------+ [1] Cutting speeds for tools of a good grade of high-speed steel, properly ground and heat-treated.--From MACHINERY'S HANDBOOK. =Average Cutting Speeds for Turning.=--The cutting speed is governed principally by the hardness of the metal to be turned; the kind of steel of which the turning tool is made; the shape of the tool and its heat-treatment; the feed and depth of cut; whether or not a cooling lubricant is used on the tool; the power of the lathe and also its construction; hence it is impossible to give any definite rule for determining either the speed, feed, or depth of cut, because these must be varied to suit existing conditions. A general idea of the speeds used in ordinary machine shop practice may be obtained from the following figures: Ordinary machine steel is generally turned at a speed varying between 45 and 65 feet per minute. For ordinary gray cast iron, the speed usually varies from 40 to 50 feet per minute; for annealed tool steel, from 25 to 35 feet per minute; for soft yellow brass, from 150 to 200 feet per minute; for hard bronze, from 35 to 80 feet per minute, the speed depending upon the composition of the alloy. While these speeds correspond closely to general practice, they can be exceeded for many machining operations. The most economical speeds for a given feed and depth of cut, as determined by the experiments conducted by Mr. F. W. Taylor, are given in the table, "Cutting Speeds and Feeds for Turning Tools." The speeds given in this table represent results obtained with tools made of a good grade of high-speed steel properly heat-treated and correctly ground. It will be noted that the cutting speed is much slower for cast iron than for steel. Cast iron is cut with less pressure or resistance than soft steel, but the slower speed required for cast iron is probably due to the fact that the pressure of the chip is concentrated closer to the cutting edge, combined with the fact that cast iron wears the tool faster than steel. The speeds given are higher than those ordinarily used, and, in many cases, a slower rate would be necessary to prevent chattering or because of some other limiting condition. =Factors which limit the Cutting Speed.=--It is the durability of the turning tool or the length of time that it will turn effectively without grinding, that limits the cutting speed; and the hardness of the metal being turned combined with the quality of the tool are the two factors which largely govern the time that a tool can be used before grinding is necessary. The cutting speed for very soft steel or cast iron can be three or four times faster than the speed for hard steel or hard castings, but whether the material is hard or soft, the kind and quality of the tool used must also be considered, as the speed for a tool made of ordinary carbon steel will have to be much slower than for a tool made of modern "high-speed" steel. When the cutting speed is too high, even though high-speed steel is used, the point of the tool is softened to such an extent by the heat resulting from the pressure and friction of the chip, that the cutting edge is ruined in too short a time. On the other hand, when the speed is too slow, the heat generated is so slight as to have little effect and the tool point is dulled by being slowly worn or ground away by the action of the chip. While a tool operating at such a low speed can be used a comparatively long time without re-sharpening, this advantage is more than offset by the fact that too much time is required for removing a given amount of metal when the work is revolving so slowly. Generally speaking, the speed should be such that a fair amount of work can be done before the tool requires re-grinding. Evidently, it would not pay to grind a tool every few minutes in order to maintain a high cutting speed; neither would it be economical to use a very slow speed and waste considerable time in turning, just to save the few minutes required for grinding. For example, if a number of roughing cuts had to be taken over a heavy rod or shaft, time might be saved by running at such a speed that the tool would have to be sharpened (or be replaced by a tool previously sharpened) when it had traversed half-way across the work; that is, the time required for sharpening or changing the tool would be short as compared with the gain effected by the higher work speed. On the other hand, it might be more economical to run a little slower and take a continuous cut across the work with one tool. The experiments of Mr. Taylor led to the conclusion that, as a rule, it is not economical to use roughing tools at a speed so slow as to cause them to last more than 1-1/2 hour without being re-ground; hence the speeds given in the table previously referred to are based upon this length of time between grindings. Sometimes the work speed cannot be as high as the tool will permit, because of the chattering that often results when the lathe is old and not massive enough to absorb the vibrations, or when there is unnecessary play in the working parts. The shape of the tool used also affects the work speed, and as there are so many things to be considered, the proper cutting speed is best determined by experiment. =Rules for Calculating Cutting Speeds.=--The number of revolutions required to give any desired cutting speed can be found by multiplying the cutting speed, in feet per minute, by 12 and dividing the product by the circumference of the work in inches. Expressing this as a formula we have _C_ � 12 _R_ = -------- [pi]_d_ in which _R_ = revolutions per minute; _C_ = the cutting speed in feet per minute; [pi] = 3.1416; _d_ = the diameter in inches. For example if a cutting speed of 60 feet per minute is wanted and the diameter of the work is 5 inches, the required speed would be found as follows: 60 � 12 _R_ = ---------- = 46 revolutions per minute. 3.1416 � 5 If the diameter is simply multiplied by 3 and the fractional part is omitted, the calculation can easily be made, and the result will be close enough for practical purposes. In case the cutting speed, for a given number of revolutions and diameter, is wanted, the following formula can be used: _R_[pi]_d_ _C_ = ---------- 12 Machinists who operate lathes do not know, ordinarily, what cutting speeds, in feet per minute, are used for different classes of work, but are guided entirely by past experience. =Feed of Tool and Depth of Cut.=--The amount of feed and depth of cut also vary like the cutting speed, for different conditions. When turning soft machine steel the feed under ordinary conditions would vary between 1/32 and 1/16 inch per revolution. For turning soft cast iron the feed might be increased to from 1/16 to 1/8 inch per revolution. These feeds apply to fairly deep roughing cuts. Coarser feeds might be used in many cases especially when turning large rigid parts in a powerful lathe. The depth of a roughing cut in machine steel might vary from 1/8 to 3/8 inch, and in cast iron from 3/16 to 1/2 inch. These figures are intended simply to give the reader a general idea of feeds and cuts that are feasible under average conditions. Ordinarily coarser feeds and a greater depth of cut can be used for cast iron than for soft steel, because cast iron offers less resistance to turning, but in any case, with a given depth of cut, metal can be removed more quickly by using a coarse feed and the necessary slower speed, than by using a fine feed and the higher speed which is possible when the feed is reduced. When the turning operation is simply to remove metal, the feed should be coarse, and the cut as deep as practicable. Sometimes the cut must be comparatively light, either because the work is too fragile and springy to withstand the strain of a heavy cut, or the lathe has not sufficient pulling power. The difficulty with light slender work is that a heavy cut may cause the part being turned to bend under the strain, thus causing the tool to gouge in, which would probably result in spoiling the work. Steadyrests can often be used to prevent flexible parts from springing, as previously explained, but there are many kinds of light work to which the steadyrest cannot be applied to advantage. The amount of feed to use for a finishing cut might, properly, be either fine or coarse. Ordinarily, fine feeds are used for finishing steel, especially if the work is at all flexible, whereas finishing cuts in cast iron are often accompanied by a coarse feed. Fig. 15 illustrates the feeds that are often used when turning cast iron. The view to the left shows a deep roughing cut and the one to the right, a finishing cut. By using a broad flat cutting edge set parallel to the tool's travel, and a coarse feed for finishing, a smooth cut can be taken in a comparatively short time. Castings which are close to the finished size in the rough can often be finished to advantage by taking a single cut with a broad tool, provided the work is sufficiently rigid. It is not always practicable to use these broad tools and coarse feeds, as they sometimes cause chattering, and when used on steel, a broad tool tends to gouge or "dig in" unless the part being turned is rigid. Heavy steel parts, however, are sometimes finished in this way. The modern method of finishing many steel parts is to simply rough them out in a lathe to within, say, 1/32 inch of the required diameter and take the finishing cut in a cylindrical grinding machine. [Illustration: Fig. 15. Roughing Cut--Light Finishing Cut and Coarse Feed] =Effect of Lubricant on Cutting Speed.=--When turning iron or steel a higher cutting speed can be used, if a stream of soda water or other cooling lubricant falls upon the chip at the point where it is being removed by the tool. In fact, experiments have shown that the cutting speed, when using a large stream of cooling water and a high-speed steel tool, can be about 40 percent higher than when turning dry or without a cooling lubricant. For ordinary carbon steel tools, the gain was about 25 per cent. The most satisfactory results were obtained from a stream falling at a rather slow velocity but in large volume. The gain in cutting speed, by the use of soda water or other suitable fluids, was found to be practically the same for all qualities of steel from the softest to the hardest. Cast iron is usually turned dry or without a cutting lubricant. Experiments, however, made to determine the effect of applying a heavy stream of cooling water to a tool turning cast iron, showed the following results: Cutting speed without water, 47 feet per minute; cutting speed with a heavy stream of water, nearly 54 feet per minute; increase in speed, 15 per cent. The dirt caused by mixing the fine cast-iron turnings with a cutting lubricant is an objectionable feature which, in the opinion of many, more than offsets the increase in cutting speed that might be obtained. Turret lathes and automatic turning machines are equipped with a pump and piping for supplying cooling lubricant to the tools in a continuous stream. Engine lathes used for general work, however, are rarely provided with such equipment and a lubricant, when used, is often supplied by a can mounted at the rear of the carriage, having a spout which extends above the tool. Owing to the inconvenience in using a lubricant on an engine lathe, steel, as well as cast iron, is often turned dry especially when the work is small and the cuts light and comparatively short. =Lubricants Used for Turning.=--A good grade of lard oil is an excellent lubricant for use when turning steel or wrought iron and it is extensively used on automatic screw machines, especially those which operate on comparatively small work. For some classes of work, especially when high-cutting speeds are used, lard oil is not as satisfactory as soda water or some of the commercial lubricants, because the oil is more sluggish and does not penetrate to the cutting point with sufficient rapidity. Many lubricants which are cheaper than oil are extensively used on "automatics" for general machining operations. These usually consist of a mixture of sal-soda (carbonate of soda) and water, to which is added some ingredient such as lard oil or soft soap to thicken or give body to the lubricant. A cheap lubricant for turning, milling, etc., and one that has been extensively used, is made in the following proportions: 1 pound of sal-soda, 1 quart of lard oil, 1 quart of soft soap, and enough water to make 10 or 12 gallons. This mixture is boiled for one-half hour, preferably by passing a steam coil through it. If the solution should have an objectionable odor, this can be eliminated by adding 2 pounds of unslaked lime. The soap and soda in this solution improve the lubricating quality and also prevent the surfaces from rusting. For turning and threading operations, plain milling, deep-hole drilling, etc., a mixture of equal parts of lard oil and paraffin oil will be found very satisfactory, the paraffin being added to lessen the expense. Brass or bronze is usually machined dry, although lard oil is sometimes used for automatic screw machine work. Babbitt metal is also worked dry, ordinarily, although kerosene or turpentine is sometimes used when boring or reaming. If babbitt is bored dry, balls of metal tend to form on the tool point and score the work. Milk is generally considered the best lubricant for machining copper. A mixture of lard oil and turpentine is also used for copper. For aluminum, the following lubricants can be used: Kerosene, a mixture of kerosene and gasoline, soap-water, or "aqualine" one part, water 20 parts. =Lard Oil as a Cutting Lubricant.=--After being used for a considerable time, lard oil seems to lose some of its good qualities as a cooling compound. There are several reasons for this: Some manufacturers use the same oil over and over again on different materials, such as brass, steel, etc. This is objectionable, for when lard oil has been used on brass it is practically impossible to get the fine dust separated from it in a centrifugal separator. When this impure oil is used on steel, especially where high-speed steels are employed, it does not give satisfactory results, owing to the fact that when the cutting tool becomes dull, the small brass particles "freeze" to the cutting tool and thus produce rough work. The best results are obtained from lard oil by keeping it thin, and by using it on the same materials--that is, not transferring the oil from a machine in which brass is being cut to one where it would be employed on steel. If the oil is always used on the same class of material, it will not lose any of its good qualities. Prime lard oil is nearly colorless, having a pale yellow or greenish tinge. The solidifying point and other characteristics of the oil depend upon the temperature at which it was expressed, winter-pressed lard oil containing less solid constituents of the lard than that expressed in warm weather. The specific gravity should not exceed 0.916; it is sometimes increased by adulterants, such as cotton-seed and maize oils. CHAPTER III TAPER TURNING--SPECIAL OPERATIONS--FITTING It is often necessary, in connection with lathe work, to turn parts tapering instead of straight or cylindrical. If the work is mounted between the centers, one method of turning a taper is to set the tailstock center out of alignment with the headstock center. When both of these centers are in line, the movement of the tool is parallel to the axis of the work and, consequently, a cylindrical surface is produced; but if the tailstock _h_{1}_ is set out of alignment, as shown in Fig. 1, the work will then be turned tapering as the tool is traversed from _a_ to _b_, because the axis _x--x_ is at an angle with the movement of the tool. Furthermore the amount of taper or the difference between the diameters at the ends for a given length, will depend on how much center _h_{1}_ is set over from the central position. [Illustration: Fig. 1. Taper Turning by the Offset-center Method] [Illustration: Fig. 2. Examples of Taper Work] The amount of taper is usually given on drawings in inches per foot, or the difference in the diameter at points twelve inches apart. For example, the taper of the piece shown at _A_, Fig. 2, is 1 inch per foot, as the length of the tapering surface is just twelve inches and the difference between the diameters at the ends is 1 inch. The conical roller shown at _B_ has a total length of 9 inches and a tapering surface 6 inches long, and in this case the taper per foot is also 1 inch, there being a difference of 1/2 inch in a length of 6 inches or 1 inch in twice that length. When the taper per foot is known, the amount that the tailstock center should be set over for turning that taper can easily be estimated, but it should be remembered that the setting obtained in this way is not absolutely correct, and is only intended to locate the center approximately. When a taper needs to be at all accurate, it is tested with a gage, or by other means, after taking a trial cut, as will be explained later, and the tailstock center is readjusted accordingly. There are also more accurate methods of setting the center, than by figuring the amount of offset, but as the latter is often convenient this will be referred to first. =Setting Tailstock Center for Taper Turning.=--Suppose the tailstock center is to be set for turning part _C_, Fig. 2, to a taper of approximately 1 inch per foot. In this case the center would simply be moved toward the front of the machine 1/2 inch, or one-half the required taper per foot, because the total length of the work happens to be just 12 inches. This setting, however, would not be correct for all work requiring a taper of 1 inch per foot, as the adjustment depends not only on the _amount_ of the taper but on the _total length_ of the piece. [Illustration: Fig. 3. Detail View of Lathe Tailstock] For example, the taper roller _B_ has a taper of 1 inch per foot, but the center, in this case, would be offset less than one-half the taper per foot, because the total length is only 9 inches. For lengths longer or shorter than twelve inches, the taper per inch should be found first; this is then multiplied by the _total_ length of the work (not the length of the taper) which gives the taper for that length, and one-half this taper is the amount to set over the center. For example, the taper per inch of part _B_ equals 1 inch divided by 12 = 1/12 inch. The total length of 9 inches multiplied by 1/12 inch = 3/4 inch, and 1/2 of 3/4 = 3/8, which is the distance that the tailstock center should be offset. In this example if the taper per foot were not known, and only the diameters of the large and small ends of the tapered part were given, the difference between these diameters should first be found (2-1/2-2 = 1/2); this difference should then be divided by the length of the taper (1/2 ÷ 6 = 1/12 inch) to obtain the taper per inch. The taper per inch times the _total_ length represents what the taper would be if it extended throughout the entire length, and one-half of this equals the offset, which is 3/8 inch. =Example of Taper Turning.=--As a practical example of taper turning let us assume that the piece A, Fig. 4, which has been centered and rough-turned as shown, is to be made into a taper plug, as indicated at _B_, to fit a ring gage as at _C_. If the required taper is 1-1/2 inch per foot and the total length is 8 inches, the tailstock center would be offset 1/2 inch. [Illustration: Fig. 4. Taper Plug and Gage] To adjust the tailstock, the nuts _N_ (Fig. 3) are first loosened and then the upper part _A_ is shifted sidewise by turning screw _S_. Scales are provided on some tailstocks for measuring the amount of this adjustment; if there is no scale, draw a line across the movable and stationary parts _A_ and _B_, when the tailstock is set for straight turning. The movement of the upper line in relation to the lower will then show the offset, which can be measured with a scale. When the adjustment has been made, nuts _N_ are tightened and the part to be turned, with a dog attached, is placed between the centers the same as for straight turning. The taper end is then reduced by turning, but before it is near the finished size, the work is removed and the taper tested by inserting it in the gage. If it is much out, this can be felt, as the end that is too small can be shaken in the hole. Suppose the plug did not taper enough and only the small end came into contact with the gage, as shown somewhat exaggerated at _D_; in that case the center would be shifted a little more towards the front, whereas if the taper were too steep, the adjustment would, of course, be in the opposite direction. A light cut would then be taken, to be followed by another test. If the plug should fit the gage so well that there was no perceptible shake, it could be tested more closely as follows: Draw three or four chalk lines along the tapering surface, place the work in the gage and turn it a few times. The chalk marks will then show whether the taper of the plug corresponds to that of the gage; for example, if the taper is too great, the marks will be rubbed out on the large end, but if the taper is correct, the lines throughout their length will be partially erased. [Illustration: Fig. 5. Setting Work for Taper Turning by use of Caliper Gage] Another and more accurate method of testing tapers is to apply a thin coat of Prussian-blue to one-half of the tapering surface, in a lengthwise direction. The work is then inserted in the hole or gage and turned to mark the bearing. If the taper is correct, the bearing marks will be evenly distributed, whereas if the taper is incorrect, they will appear at one end. Tapering pieces that have to be driven tightly into a hole, such as a piston-rod, can be tested by the location of the bearing marks produced by actual contact. After the taper is found to be correct, the plug is reduced in size until it just enters the gage as at _C_. The final cut should leave it slightly above the required size, so that a smooth surface can be obtained by filing. It should be mentioned that on work of this kind, especially if great accuracy is required, the final finish is often obtained by grinding in a regular grinding machine, instead of by filing. When this method is employed, a lathe is used merely to rough-turn the part close to size. [Illustration: Fig. 6. Side View showing Relative Positions of Gage and Work] When the amount that the tailstock center should be offset is determined by calculating, as in the foregoing example, it is usually necessary to make slight changes afterward, and the work should be tested before it is too near the finished size so that in case one or more trial cuts are necessary, there will be material enough to permit this. When there are a number of tapered pieces to be turned to the same taper, the adjustment of the tailstock center will have to be changed unless the total length of each piece and the depth of the center holes are the same in each case. =Setting the Tailstock Center with a Caliper Tool.=--Another method of setting the tailstock center for taper turning is illustrated in Fig. 5. The end of an engine piston-rod is to be made tapering as at A and to dimensions _a_, _b_, _c_ and _d_. It is first turned with the centers in line as at _B_. The end _d_ is reduced to diameter _b_ up to the beginning of the taper and it is then turned to diameter _a_ as far as the taper part _c_ extends. The tailstock center is next set over by guess and a caliper tool is clamped in the toolpost. This tool, a side view of which is shown in Fig. 6, has a pointer _p_ that is free to swing about pivot _r_, which should be set to about the same height as the center of the work. The tailstock center is adjusted until this pointer just touches the work when in the positions shown by the full and dotted lines at _C_, Fig. 5; that is, until the pointer makes contact at the beginning and end of the taper part. The travel of the carriage will then be parallel to a line _x--x_, representing the taper; consequently, if a tool is started at the small end, as shown by the dotted lines at _D_, with the nose just grazing the work, it will also just graze it when fed to the extreme left as shown. Of course, if the taper were at all steep, more than one cut would be taken. [Illustration: Fig. 7. Obtaining Tailstock Center Adjustment by use of Square] If these various operations are carefully performed, a fairly accurate taper can be produced. The straight end _d_ is reduced to size after the tail-center is set back to the central position. Some mechanics turn notches or grooves at the beginning and end of the tapering part, having diameters equal to the largest and smallest part of the taper; the work is then set by these grooves with a caliper tool. The advantage of the first method is that most of the metal is removed while the centers are in alignment. [Illustration: Fig. 8. Second Step in Adjusting Tailstock Center by use of Square] =Setting the Tailstock Center with a Square.=--Still another method of adjusting the tailstock for taper turning, which is very simple and eliminates all figuring, is as follows: The part to be made tapering is first turned cylindrical or straight for 3 or 4 inches of its length, after the ends have been properly centered and faced square. The work is then removed and the tailstock is shifted along the bed until the distance _a--b_ between the extreme points of the centers is exactly 1 foot. The center is next offset a distance _b--c_ equal to one-half the required taper per foot, after which a parallel strip _D_, having true sides, is clamped in the toolpost. Part _D_ is then set at right angles to a line passing from one center point to the other. This can be done conveniently by holding a 1-foot square (preferably with a sliding head) against one side of _D_ and adjusting the latter in the toolpost until edge _E_ of the square blade is exactly in line with both center points. After part _D_ is set, it should be clamped carefully to prevent changing the position. The angle between the side of _D_ and an imaginary line which is perpendicular to axis _a--b_ is now equal to one-half the angle of the required taper. The axis of the part to be turned should be set parallel with line _E_, which can be done by setting the cylindrical surface which was previously finished, at right angles to the side of _D_. In order to do this the work is first placed between centers, the tailstock being shifted along the bed if necessary; the tail-center is then adjusted laterally until the finished cylindrical surface is square with the side of _D_. A small try-square can be used for testing the position of the work, as indicated in Fig. 8. If the length of the work is less than 1 foot, it will be necessary to move the center toward the rear of the machine, and if the length is greater than 1 foot, the adjustment is, of course, in the opposite direction. [Illustration: Fig. 9. A Lathe Taper Attachment] =The Taper Attachment.=--Turning tapers by setting over the tailstock center has some objectionable features. When the lathe centers are not in alignment, as when set for taper turning, they bear unevenly in the work centers because the axis of the work is at an angle with them; this causes the work centers to wear unevenly and results in inaccuracy. Furthermore, the adjustment of the tailstock center must be changed when turning duplicate tapers, unless the length of each piece and the depth of the center holes are the same. To overcome these objections, many modern lathes are equipped with a special device for turning tapers, known as a taper attachment, which permits the lathe centers to be kept in alignment, as for cylindrical turning, and enables more accurate work to be done. [Illustration: Fig. 10. Sectional View of Taper Attachment] Taper attachments, like lathes, vary some in their construction, but all operate on the same principle. An improved form of taper attachment is illustrated in Figs. 9 and 10. Fig. 9 shows a plan view of a lathe carriage with an attachment fitted to it, and Fig. 10 a sectional view. This attachment has an arm _A_ on which is mounted a slide _S_ that can be turned about a central pivot by adjusting screw _D_. The arm _A_ is supported by, and is free to slide on, a bracket _B_ (see also sectional view) that is fastened to the carriage, and on one end of the arm there is a clamp _C_ that is attached to the lathe bed when turning tapers. On the slide _S_ there is a shoe _F_ that is connected to bar _E_ which passes beneath the toolslide. The rear end of the cross-feed screw is connected to this bar, and the latter is clamped to the toolslide when the attachment is in use. When a taper is to be turned, the carriage is moved opposite the taper part and clamp _C_ is fastened to the bed; this holds arm _A_ and slide _S_ stationary so that the carriage, with bracket _B_ and shoe _F_, can be moved with relation to the slide. If this slide _S_ is set at an angle, as shown, the shoe as it moves along causes the toolslide and tool to move in or out, but if the slide is set parallel to the carriage travel, the toolslide remains stationary. Now if the tool, as it feeds lengthwise of the work, is also gradually moved crosswise, it will turn a taper, and as this crosswise movement is caused by the angularity of slide _S_, different tapers are obtained by setting the slide to different positions. By means of a graduated scale _G_ at the end of slide _S_, the taper that will be obtained for any angular position of the slide is shown. On some attachments there are two sets of graduations, one giving the taper in inches per foot and the other in degrees. While tapers are ordinarily given in inches per foot on drawings, sometimes the taper is given in degrees instead. The attachment is set for turning tapers by adjusting slide _S_ until pointer _p_ is opposite the division or fractional part of a division representing the taper. The whole divisions on the scale represent taper in inches per foot, and by means of the sub-divisions, the slide can be set for turning fractional parts of an inch per foot. When slide _S_ is properly set, it is clamped to arm _A_ by the nuts _N_. Bar _E_ is also clamped to the toolslide by bolt _H_, as previously stated. The attachment is disconnected for straight turning by simply loosening clamp _C_ and the bolt _H_. =Application of Taper Attachment.=--Practical examples of lathe work, which illustrate the use of the taper attachment, are shown in Figs, 11 and 12. Fig. 11 shows how a taper hole is bored in an engine piston-head, preparatory to reaming. The casting must be held either in a chuck _C_ or on a faceplate if too large for the chuck. The side of the casting (after it has been "chucked") should run true, and also the circumference, unless the cored hole for the rod is considerably out of center, in which case the work should be shifted to divide the error. The side of the casting for a short space around the hole is faced true with a round nose turning tool, after which the rough-cored hole is bored with an ordinary boring tool _t_, and then it is finished with a reamer to exactly the right size and taper. This particular taper attachment is set to whatever taper is given on the drawing, by loosening nuts _N_ and turning slide _S_ until pointer _P_ is opposite that division on the scale which represents the taper. The attachment is then ready, after bolt _H_ and nuts _N_ are tightened, and clamp _C_ is fastened to the lathe bed. The hole is bored just as though it were straight, and as the carriage advances, the tool is gradually moved inward by the attachment. If the lathe did not have a taper attachment, the taper hole could be bored by using the compound rest. [Illustration: Fig. 11. Lathe with Taper Attachment arranged for Boring Taper Hole in Engine Piston] The hole should be bored slightly less than the finish size to allow for reaming. When a reamer is used in the lathe, the outer end is supported by the tailstock center and should have a deep center-hole. The lathe is run very slowly for reaming and the reamer is fed into the work by feeding out the tailstock spindle. The reamer can be kept from revolving, either by attaching a heavy dog to the end or, if the end is squared, by the use of a wrench long enough to rest against the lathe carriage. A common method is to clamp a dog to the reamer shank, and then place the tool-rest beneath it to prevent rotation. If the shank of a tool is clamped to the toolpost so that the dog rests against it, the reamer will be prevented from slipping off the center as it tends to do; with this arrangement, the carriage is gradually moved along as the tailstock spindle is fed outward. Some reamers are provided with stop-collars which come against the finished side of the casting when the hole has been reamed to size. After the reaming operation, the casting is removed from the chuck and a taper mandrel is driven into the hole for turning the outside of the piston. This mandrel should run true on its centers, as otherwise the outside surface of the piston will not be true with the bored hole. The driving dog, especially for large work of this kind, should be heavy and stiff, because light flexible clamps or dogs vibrate and frequently cause chattering. For such heavy work it is also preferable to drive at two points on opposite sides of the faceplate, but the driving pins should be carefully adjusted to secure a uniform bearing on both sides. The foregoing method of machining a piston is one that would ordinarily be followed when using a standard engine lathe, and it would, perhaps, be as economical as any if only one piston were being made; but where such work is done in large quantities, time could be saved by proceeding in a different way. For example, the boring and reaming operation could be performed much faster in a turret lathe, which is a type designed for just such work, but a turret lathe cannot be used for as great a variety of turning operations as a lathe of the regular type. There are also many other classes of work that can be turned more quickly in special types of machines, but as more or less time is required for arranging these special machines and often special tools have to be made, the ordinary lathe is frequently indispensable when only a few parts are needed; in addition, it is better adapted to some turning operations than any other machine. Fig. 12 illustrates how a taper attachment would be used for turning the taper fitting for the crosshead end of an engine piston-rod. Even though this taper corresponds to the taper of the hole in the piston, slide _S_ would have to be reset to the corresponding division on the opposite side of the central zero mark, because the taper of the hole decreased in size during the boring operation, whereas the rod is smallest at the beginning of the cut, so that the tool must move outward rather than inward as it advances. The taper part is turned practically the same as a cylindrical part; that is, the power feed is used and, as the carriage moves along the bed, the tool is gradually moved outward by the taper attachment. [Illustration: Fig. 12. Taper Attachment Set for Turning Taper End of Piston-rod] If the rod is being fitted directly to the crosshead (as is usually the case), the approximate size of the small end of the taper could be determined by calipering, the calipers being set to the size of the hole at a distance from the shoulder or face side of the crosshead, equal to the length of the taper fitting on the rod. If the crosshead were bored originally to fit a standard plug gage, the taper on the rod could be turned with reference to this gage, but, whatever the method, the taper should be tested before turning too close to the finished size. The test is made by removing the rod from the lathe and driving it tightly into the crosshead. This shows how near the taper is to size, and when the rod is driven out, the bearing marks show whether the taper is exactly right or not. If the rod could be driven in until the shoulder is, say, 1/8 inch from the crosshead face, it would then be near enough to finish to size by filing. When filing, the lathe is run much faster than for turning, and most of the filing should be done where the bearing marks are the heaviest, to distribute the bearing throughout the length of the taper. Care should be taken when driving the rod in or out, to protect the center-holes in the ends by using a "soft" hammer or holding a piece of soft metal against the driving end. [Illustration: Fig. 13. Tool Point should be in same Horizontal Plane as Axis of Work for Taper Turning] After the crosshead end is finished, the rod is reversed in the lathe for turning the piston end. The dog is clamped to the finished end, preferably over a piece of sheet copper to prevent the surface from being marred. When turning this end, either the piston reamer or the finished hole in the piston can be calipered. The size and angle of the taper are tested by driving the rod into the piston, and the end should be fitted so that by driving tightly, the shoulder will just come up against the finished face of the piston. When the taper is finished, the attachment is disengaged and a finishing cut is taken over the body of the rod, unless it is to be finished by grinding, which is the modern and most economical method. =Height of Tool when Turning Tapers.=--The cutting edge of the tool, when turning tapers, should be at the same height as the center or axis of the work, whether an attachment is used or not. The importance of this will be apparent by referring to Fig. 13. To turn the taper shown, the tool _T_ would be moved back a distance _x_ (assuming that an attachment is used) while traversing the length _l_. As an illustration, if the tool could be placed as high as point _a_, the setting of the attachment remaining as before, the tool would again move back a distance _x_, while traversing a distance _l_, but the large end would be under-sized (as shown by the dotted line) if the diameters of the small ends were the same in each case. Of course, if the tool point were only slightly above or below the center, the resulting error would also be small. The tool can easily be set central by comparing the height of the cutting edge at the point of the tool with one of the lathe centers before placing the work in the lathe. [Illustration: Fig. 14. Plan View showing Method of Turning a Taper with the Compound Rest] =Taper Turning with the Compound Rest.=--The amount of taper that can be turned by setting over the tailstock center and by the taper attachment is limited, as the centers can only be offset a certain distance, and the slide _S_ (Fig. 9) of the attachment cannot be swiveled beyond a certain position. For steep tapers, the compound rest _E_ is swiveled to the required angle and used as indicated in Fig. 14, which shows a plan view of a rest set for turning the valve _V_. This compound rest is an upper slide mounted on the lower or main cross-slide _D_, and it can be turned to any angular position so that the tool, which ordinarily is moved either lengthwise or crosswise of the bed, can be fed at an angle. The base of the compound rest is graduated in degrees and the position of these graduations shows to what angle the upper slide is set. Suppose the seat of valve _V_ is to be turned to an angle of 45 degrees with the axis or center, as shown on the drawing at _A_, Fig. 15. To set the compound rest, nuts _n_ on either side, which hold it rigidly to the lower slide, are first loosened and the slide is then turned until the 45-degree graduation is exactly opposite the zero line; the slide is then tightened in this position. A cut is next taken across the valve by operating handle _w_ and feeding the tool in the direction of the arrow. [Illustration: Fig. 15. Example of Taper Work Turned by using Compound Rest] In this particular instance the compound rest is set to the same angle given on the drawing, but this is not always the case. If the draftsman had given the included angle of 90 degrees, as shown at _B_, which would be another way of expressing it, the setting of the compound rest would, of course, be the same as before, or to 45 degrees, but the number of degrees marked on the drawing does not correspond with the angle to which the rest must be set. As another illustration, suppose the valve were to be turned to an angle of 30 degrees with the axis as shown at _C_. In this case the compound rest would not be set to 30 degrees but to 60 degrees, because in order to turn the work to an angle of 30 degrees, the rest must be 60 degrees from its zero position, as shown. From this it will be seen that the number of degrees marked on the drawing does not necessarily correspond to the angle to which the rest must be set, as the graduations on the rest show the number of degrees that it is moved from its zero position, which corresponds to the line _a--b_. The angle to which the compound rest should be set can be found, when the drawing is marked as at _A_ or _C_, by subtracting the angle given from 90 degrees. When the included angle is given, as at _B_, subtract one-half the included angle from 90 degrees to obtain the required setting. Of course, when using a compound rest, the lathe centers are set in line as for straight turning, as otherwise the angle will be incorrect. Rules for Figuring Tapers +---------------------+---------------------+--------------------------+ | Given | To Find | Rule | +---------------------+---------------------+--------------------------+ |The taper per foot. |The taper per inch. |Divide the taper per foot | | | | by 12. | | | | | |The taper per inch. |The taper per foot. |Multiply the taper per | | | | inch by 12. | | | | | |End diameters and |The taper per foot. |Subtract small diameter | | length of taper in | | from large; divide by | | inches. | | length of taper, and | | | | multiply quotient by 12.| | | | | |Large diameter and |Diameter at small |Divide taper per foot by | | length of taper in | end in inches. | 12; multiply by length | | inches and taper | | of length of taper, and | | per foot. | | subtract result from | | | | large diameter. | | | | | |Small diameter and |Diameter at large |Divide taper per foot by | | length of taper in | end in inches. | 12; multiply by length | | inches, and taper | | of taper, and add result| | per foot. | | to small diameter. | | | | | |The taper per foot |Distance between | Subtract small diameter | | and two diameters | two given diameters| from large; divide re- | | in inches. | in inches. | mainder by taper per | | | | foot, and multiply | | | | quotient by 12. | | | | | |The taper per foot. |Amount of taper in | Divide taper per foot by | | | a certain length | 12; multiply by given | | | given in inches. | length of tapered part.| +---------------------+---------------------+--------------------------+ =Accurate Measurement of Angles and Tapers.=--When great accuracy is required in the measurement of angles, or when originating tapers, disks are commonly used. The principle of the disk method of taper measurement is that if two disks of unequal diameters are placed either in contact or a certain distance apart, lines tangent to their peripheries will represent an angle or taper, the degree of which depends upon the diameters of the two disks and the distance between them. The gage shown in Fig. 16, which is a form commonly used for originating tapers or measuring angles accurately, is set by means of disks. This gage consists of two adjustable straight-edges _A_ and _A_{1}_, which are in contact with disks _B_ and _B_{1}_. The angle [alpha] or the taper between the straight-edges depends, of course, upon the diameters of the disks and the center distance _C_, and as these three dimensions can be measured accurately, it is possible to set the gage to a given angle within very close limits. Moreover, if a record of the three dimensions is kept, the exact setting of the gage can be reproduced quickly at any time. The following rules may be used for adjusting a gage of this type. [Illustration: Fig. 16. Disk Gage for Accurate Measurement of Angles and Tapers] =To Find Center Distance for a Given Taper.=--When the taper, in inches per foot, is given, to determine center distance _C_. _Rule:_ Divide the taper by 24 and find the angle corresponding to the quotient in a table of tangents; then find the sine corresponding to this angle and divide the difference between the disk diameters by twice the sine. _Example:_ Gage is to be set to 3/4 inch per foot, and disk diameters are 1.25 and 1.5 inch, respectively. Find the required center distance for the disks. 0.75 ---- = 0.03125. 24 The angle whose tangent is 0.03125 equals 1 degree 47.4 minutes; sin 1° 47.4' = 0.03123; 1.50 - 1.25 = 0.25 inch; 0.25 ----------- = 4.002 inches = center distance C. 2 � 0.03123 =To Find Center Distance for a Given Angle.=--When straight-edges must be set to a given angle [alpha], to determine center distance _C_ between disks of known diameter. _Rule:_ Find the sine of half the angle [alpha] in a table of sines; divide the difference between the disk diameters by double this sine. _Example:_ If an angle [alpha] of 20 degrees is required, and the disks are 1 and 3 inches in diameter, respectively, find the required center distance _C_. 20 ---- = 10 degrees; sin 10° = 0.17365; 2 3 - 1 ----------- = 5.759 inches = center distance _C_. 2 � 0.17365 =To Find Angle for Given Taper per Foot.=--When the taper in inches per foot is known, and the corresponding angle [alpha] is required. _Rule:_ Divide the taper in inches per foot by 24; find the angle corresponding to the quotient, in a table of tangents, and double this angle. _Example:_ What angle [alpha] is equivalent to a taper of 1-1/2 inch per foot? 1.5 --- = 0.0625. 24 The angle whose tangent is 0.0625 equals 3 degrees 35 minutes, nearly; then, 3 deg. 35 min. � 2 = 7 deg. 10 min. =To Find Angle for Given Disk Dimensions.=--When the diameters of the large and small disks and the center distance are given, to determine the angle [alpha]. _Rule:_ Divide the difference between the disk diameters by twice the center distance; find the angle corresponding to the quotient, in a table of sines, and double the angle. _Example:_ If the disk diameters are 1 and 1.5 inch, respectively, and the center distance is 5 inches, find the included angle [alpha]. 1.5 - 1 ------- = 0.05. 2 � 5 The angle whose sine is 0.05 equals 2 degrees 52 minutes; then, 2 deg. 52 min. � 2 = 5 deg. 44 min. = angle [alpha]. [Illustration: Fig. 17. Setting Center Mark in Line with Axis of Lathe Spindle by use of Test Indicator] [Illustration: Fig. 18. Jig-plate with Buttons attached, ready for Boring] =Use of the Center Indicator.--=The center test indicator is used for setting a center-punch mark, the position of which corresponds with the center or axis of the hole to be bored, in alignment with the axis of the lathe spindle. To illustrate, if two holes are to be bored, say 5 inches apart, small punch marks having that center-to-center distance would be laid out as accurately as possible. One of these marks would then be set central with the lathe spindle by using a center test indicator as shown in Fig. 17. This indicator has a pointer _A_ the end of which is conical and enters the punch mark. The pointer is held by shank _B_ which is fastened in the toolpost. The joint _C_ by means of which the pointer is held to the shank is universal; that is, it allows the pointer to move in any direction. Now when the part being tested is rotated by running the lathe, if the center-punch mark is not in line with the axes of the lathe spindle, obviously the outer end of pointer _A_ will vibrate, and as joint _C_ is quite close to the inner end, a very slight error in the location of the center-punch mark will cause a perceptible movement of the outer end, as indicated by the dotted lines. When the work has been adjusted until the pointer remains practically stationary, the punch mark is central, and the hole is bored. The other center-punch mark is then set in the same way for boring the second hole. The accuracy of this method depends, of course, upon the location of the center-punch marks. A still more accurate way of setting parts for boring holes to a given center-to-center distance is described in the following: =Locating Work by the Button Method.=--Among the different methods employed by machinists and toolmakers for accurately locating work such as jigs, etc., on the faceplate of a lathe, the one most commonly used is known as the button method. This scheme is so named because cylindrical bushings or buttons are attached to the work in positions corresponding to the holes to be bored, after which they are used in locating the work. These buttons, which are ordinarily about 1/2 inch in diameter, are ground and lapped to the same size and the ends squared. The diameter should, preferably, be such that the radius can be determined easily, and the hole through the center should be about 1/8 inch larger than the retaining screw, so that the button can be shifted. As an illustration of the practical application of the button method, we shall consider, briefly, the way the holes would be accurately machined in the jig-plate in Fig. 18. First the centers of the seven holes should be laid off approximately correct by the usual methods, after which small holes should be drilled and tapped for the clamping screws _S_. After the buttons _B_ are clamped lightly in place, they are all set in correct relation with each other and with the jig-plate. The proper location of the buttons is very important as their positions largely determine the accuracy of the work. A definite method of procedure that would be applicable in all cases cannot, of course, be given, as the nature of the work as well as the tools available make it necessary to employ different methods. [Illustration: Fig. 19. Setting a Button True Preparatory to Boring, by use of Test Indicator] In this particular case, the three buttons _a_, _b_ and _c_ should be set first, beginning with the one in the center. As this central hole must be 2.30 and 2.65 inches from the finished sides _A_ and _A_{1}_, respectively, the work is first placed on an accurate surface-plate as shown; by resting it first on one of these sides and then on the other, and measuring with a vernier height gage, the central button can be accurately set. The buttons _a_ and _c_ are also set to the correct height from side _A_{1}_ by using the height gage, and in proper relation to the central button by using a micrometer or a vernier caliper and measuring the over-all dimension _x_. When measuring in this way, the diameter of one button would be deducted to obtain the correct center-to-center distance. After buttons _a_, _b_ and _c_ are set equidistant from side A_{1} and in proper relation to each other, the remaining buttons should be set radially from the central button _b_ and the right distance apart. By having two micrometers or gages, one set for the radial dimension _x_ and the other for the chordal distance _y_, the work may be done in a comparatively short time. [Illustration: Fig. 20. Testing Concentricity of Button with Dial Gage] After the buttons have been tightened, all measurements should be carefully checked; the work is then mounted on the faceplate of the lathe, and one of the buttons, say _b_, is set true by the use of a test indicator as shown in Fig. 19. When the end of this indicator (which is one of a number of types on the market) is brought into contact with the revolving button, the vibration of the pointer _I_ shows how much the button runs out of true. When the pointer remains practically stationary, thus showing that the button runs true, the latter should be removed. The hole is then drilled nearly to the required size, after which it is bored to the finish diameter. In a similar manner the other buttons are indicated and the holes bored, one at a time. It is evident that if each button is correctly located and set perfectly true in the lathe, the various holes will be located at the required center-to-center dimensions within very close limits. [Illustration: Fig. 21. Drilling a Bushing Hole] Fig. 20 shows how one of the buttons attached to a plate in which three holes are to be bored is set true or concentric. The particular indicator illustrated is of the dial type, any error in the location of the button being shown by a hand over a dial having graduations representing thousandths of an inch. Fig. 21 shows how the hole is drilled after the button is removed. It will be noted that the drill is held in a chuck, the taper shank of which fits into the tailstock spindle, this being the method of holding small drills. After drilling, the hole is bored as shown in Fig. 22. The boring tool should have a keen edge to avoid springing, and if the work when clamped in position, throws the faceplate out of balance, it is advisable to restore the balance, before boring, by the use of a counter-weight, because the lathe can be rotated quite rapidly when boring such a small hole. [Illustration: Fig. 22. Boring a Bushing Hole] When doing precision work of this kind, the degree of accuracy will depend upon the instruments used, the judgment and skill of the workman and the care exercised. A good general rule to follow when locating bushings or buttons is to use the method which is the most direct and which requires the least number of measurements. As an illustration of how errors may accumulate, let us assume that seven holes are to be bored in the jig-plate shown in Fig. 23, so that they are the same distance from each other and in a straight line. The buttons may be brought into alignment by the use of a straight-edge, and to simplify matters, it will be taken for granted that they have been ground and lapped to the same size. If the diameter of the buttons is first determined by measuring with a micrometer, and then this diameter is deducted from the center distance _x_, the difference will be the distance _y_ between adjacent buttons. Now if a temporary gage is made to length _y_, all the buttons can be set practically the same distance apart, the error between any two adjacent ones being very slight. If, however, the total length _z_ over the end buttons is measured by some accurate means, the chances are that this distance will not equal six times dimension _x_ plus the diameter of one button, as it should, because even a very slight error in the gage for distance _y_ would gradually accumulate as each button was set. If a micrometer were available that would span two of the buttons, the measurements could be taken direct and greater accuracy would doubtless be obtained. On work of this kind where there are a number of holes that need to have accurate over-all dimensions, the long measurements should first be taken when setting the buttons, providing, of course, there are proper facilities for so doing, and then the short ones. For example, the end buttons in this case should first be set, then the central one and finally those for the sub-divisions. [Illustration: Fig. 23. Example of Work illustrating Accumulation of Errors] =Eccentric Turning.=--When one cylindrical surface must be turned eccentric to another, as when turning the eccentric of a steam engine, an arbor having two sets of centers is commonly used, as shown in Fig. 24. The distance _x_ between the centers must equal one-half the total "throw" or stroke of the eccentric. The hub of the eccentric is turned upon the centers _a--a_, and the tongued eccentric surface, upon the offset centers, as indicated by the illustration. Sometimes eccentrics are turned while held upon special fixtures attached to the faceplate. [Illustration: Fig. 24. Special Arbor for Turning Eccentrics] When making an eccentric arbor, the offset center in each end should be laid out upon radial lines which can be drawn across the arbor ends by means of a surface gage. Each center is then drilled and reamed to the same radius _x_ as near as possible. The uniformity of the distance _x_ at each end is then tested by placing the mandrel upon the offset centers and rotating it, by hand, with a dial indicator in contact at first one end and then the other. The amount of offset can also be tested either by measuring from the point of a tool held in the toolpost, or by setting the tool to just graze the mandrel at extreme inner and outer positions, and noting the movement of the cross-slide by referring to the dial gage of the cross-feed screw. [Illustration: Fig. 25. Turning an Engine Crank-pin in an Ordinary Lathe] =Turning a Crankshaft in a Lathe.=--Another example of eccentric turning is shown in Fig. 25. The operation is that of turning the crank-pin of an engine crankshaft, in an ordinary lathe. The main shaft is first rough-turned while the forging revolves upon its centers _C_ and _C_{1}_ and the ends are turned to fit closely the center-arms _A_ and _A_{1}_. After the sides _B_ and _B_{1}_ of the crank webs have been rough-faced, the center-arms are attached to the ends of the shaft as shown in the illustration. These arms have centers at _D_ and _D_{1}_ (located at the required crank radius) which should be aligned with the rough pin, when attaching the arms, and it is advisable to insert braces _E_ between the arms and crank to take the thrust of the lathe centers. With the forging supported in this way, the crank-pin and inner sides of the webs are turned and faced, the work revolving about the axis of the pin. The turning tools must extend beyond the tool-holder far enough to allow the crank to clear as it swings around. Owing to this overhang, the tool should be as heavy as possible to make it rigid and it is necessary to take comparatively light cuts and proceed rather cautiously. After finishing the crank-pin and inside of the crank, the center-arms are removed and the main body of the shaft and the sides _B_ and _B_{1}_ are finished. This method of turning crankshafts is often used in general repair shops, etc., especially where new shafts do not have to be turned very often. It is slow and inefficient, however, and where crankshafts are frequently turned, special machines or attachments are used. [Illustration: Fig. 26. LeBlond Lathe with Special Equipment for Crankshaft Turning] =Special Crankshaft Lathe.=--A lathe having special equipment for rough-turning gas engine crankshaft pins is shown in Fig. 26. This lathe is a heavy-duty type built by the R. K. LeBlond Machine Tool Co. It is equipped with special adjustable headstock and tailstock fixtures designed to take crankshafts having strokes up to about 6 inches. The tools are held in a three-tool turret type of toolpost and there are individual cross-stops for each tool. This lathe also has a roller steadyrest for supporting the crankshaft; automatic stops for the longitudinal feed, and a pump for supplying cutting lubricant. The headstock fixture is carried on a faceplate mounted on the spindle and so arranged as to be adjustable for cranks of different throw. When the proper adjustment for a given throw has been made, the slide is secured by four T-bolts. A graduated scale and adjusting screw permit of accurate adjustments. The revolving fixture is accurately indexed for locating different crank-pins in line with the lathe centers, by a hardened steel plunger in the slide which engages with hardened bushings in the fixture. The index is so divided that the fixture may be rotated 120 or 180 degrees, making it adjustable for 2-, 4- and 6-throw cranks. After indexing, the fixture is clamped by two T-bolts which engage a circular T-slot. The revolving fixture is equipped with removable split bushings which can be replaced to fit the line bearings of different sized crankshafts. The work is driven by a V-shaped dovetail piece having a hand-nut adjustment, which also centers the pin by the cheek or web. The crank is held in position by a hinged clamp on the fixture. The tailstock fixture is also adjustable and it is mounted on a spindle which revolves in a bushing in the tailstock barrel. The adjustment is obtained in the same manner as on the headstock fixture, and removable split bushings as well as a hinged clamp are also employed. The method of chucking a four-throw crank is as follows: The two fixtures are brought into alignment by two locking pins. One of these is located in the head and enters a bushing in the large faceplate and the other is in the tailstock and engages the tailstock fixture. The crankshaft is delivered to the machine with the line bearings rough-turned and it is clamped by the hinged clamp previously referred to and centered by the V-shaped driver. The locking pins for both fixtures are then withdrawn and the machine is ready to turn two of the pins. After these have been machined, the fixtures are again aligned by the locking pins, the two T-bolts of the headstock fixture and the hinged clamp at the tailstock are released, the indexing plunger is withdrawn and the headstock fixture and crank are turned 180 degrees or until the index plunger drops into place. The crank is then clamped at the tailstock end and the revolving fixture is secured by the two T-bolts previously referred to. After the locking pins are withdrawn, the lathe is ready to turn the two opposite pins. [Illustration: Fig. 27. Diagrams showing Arrangements of Tools on LeBlond Lathe] =Operation of Special Crankshaft Lathe.=--The total equipment of this machine (see Fig. 27) is carried on a three-tool turret tool-block. The method of turning a crankshaft is as follows: A round-nosed turning tool is first fed into a cross stop as illustrated in the plan view at _A_, which gives the proper diameter. The feed is then engaged and the tool feeds across the pin until the automatic stop lever engages the first stop, which throws out the feed automatically. The carriage is then moved against a positive stop by means of the handwheel. The roller back-rest is next adjusted against the work by the cross-feed handwheel operating through a telescopic screw, and the filleting tools are brought into position as at _B_. These are run in against a stop, removing the part left by the turning tool and giving the pin the proper width and fillets of the correct radius. If the crankshaft has straight webs which must be finished, two tools seen at _b_ are used for facing the webs to the correct width. During these last two operations, the crank is supported by the roller back-rest, thus eliminating any tendency of the work to spring. [Illustration: Fig. 28. (A) Spherical Turning with Compound Rest. (B) Concave Turning] After one pin is finished in the manner described, the back-rest is moved out of the way, the automatic stop lever raised, the carriage shifted to the next pin, and the operation repeated. The tools are held in position on the turret by studs, and they can be moved and other tools quickly substituted for pins of different widths. This machine is used for rough-turning the pins close to the required size, the finishing operation being done in a grinder. It should be mentioned, in passing, that many crankshafts, especially the lighter designs used in agricultural machinery, etc., are not turned at all but are ground from the rough. =Spherical Turning.=--Occasionally it may be necessary to turn a spherical surface in the lathe. Sketch _A_, Fig. 28, shows how a small ball-shaped end can be turned on a piece held in a chuck. The lathe carriage is adjusted so that the pin around which the compound rest swivels is directly under the center a. The bolts which hold the swivel are slightly loosened to allow the top slide to be turned, as indicated by the dotted lines; this causes the tool point to move in an arc about center _a_, and a spherical surface is turned. Light cuts must be taken as otherwise it would be difficult to turn the slide around by hand. [Illustration: Fig. 29. Spherical Turning Attachment for Engine Lathe] Sketch _B_ illustrates how a concave surface can be turned. The cross-slide is adjusted until swivel pin is in line with the lathe centers, and the carriage is moved along the bed until the horizontal distance between center _b_ of the swivel, and the face of the work, equals the desired radius of the concave surface. The turning is then done by swinging the compound rest as indicated by the dotted lines. The slide can be turned more evenly by using the tailstock center to force it around. A projecting bar is clamped across the end of the slide at _d_, to act as a lever, and a centered bar is placed between this lever and the tailstock center; then by screwing out the tailstock spindle, the slide is turned about pivot _b_. The alignment between the swivel pin and the lathe centers can be tested by taking a trial cut; if the swivel pin is too far forward, the tool will not touch the turned surface if moved past center _c_, and if the pin is too far back, the tool will cut in on the rear side. =Spherical Turning Attachments.=--When spherical turning must be done repeatedly, special attachments are sometimes used. Fig. 29 shows an attachment applied to a lathe for turning the spherical ends of ball-and-socket joints. The height or radius of the cutting tool and, consequently, the diameter of the turned ball, is regulated by adjusting screw _A_. The tool is swung around in an arc, by turning handle _B_ which revolves a worm meshing with an enclosed worm-wheel. As will be seen, the work is held in a special chuck, owing to its irregular shape. [Illustration: Fig. 30. Attachment for Turning Spherical End of Gasoline Engine Piston] Another spherical turning attachment is shown in Fig. 30. This is used for machining the ends of gasoline engine pistons. The cross-slide has bolted to it a bar _A_ carrying a roller which is pressed against a forming plate _B_ by a heavy spring _C_. The forming plate _B_, which is attached to a cross-piece fastened to the ways of the lathe bed, is curved to correspond with the radius required on the piston end, and when the tool is fed laterally by moving the cross-slide, it follows the curve of plate _B_. The piston is held in a special hollow chuck which locates it in a central position and holds it rigidly. In connection with lathe work, special attachments and tools are often used, especially when considerable work of one class must be turned; however, if a certain part is required in large quantities, it is usually more economical to use some semi-automatic or automatic turning machine, especially designed for repetition work. =Turning with Front and Rear Tools.=--In ordinary engine lathe practice, one tool is used at a time, but some lathes are equipped with tool-holders at the front and rear of the carriage so that two tools can be used simultaneously. Fig. 31 shows a detail view of a lathe in which front and rear tools are being used. These tools are of the inserted cutter type and the one at the rear is inverted, as the rotary movement of the work is, of course, upward on the rear side. This particular lathe was designed for taking heavy roughing cuts and has considerable driving power. [Illustration: Fig. 31. Front and Rear Tools used for Roughing] The part shown in this illustration is a chrome-nickel steel bar which is being roughed out to form a milling machine spindle. It is necessary to reduce the diameter of the bar from 5-7/16 inches to 3-3/4 inches for a length of 27 inches, because of a collar on one end. This reduction is made in one passage of the two tools, with a feed of 1/32 inch per revolution and a speed of 60 revolutions per minute. The use of two tools for such heavy roughing cuts is desirable, especially when the parts are required in large quantities, because the thrust of the cut on one side, which tends to deflect the work, is counteracted by the thrust on the opposite side. [Illustration: Fig. 32. Lo-swing Lathe for Multiple Turning] Sometimes special tool-holders are made for the lathe, so that more than one tool can be used for turning different surfaces or diameters at the same time, the tools being set in the proper relation to each other. The advantage of this method has resulted in the design of a special lathe for multiple-tool turning. =A Multiple-tool Lathe.=--The lathe shown in Fig. 32 (which is built by the Fitchburg Machine Works and is known as the Lo-swing) is designed especially for turning shafts, pins and forgings not exceeding 3-1/2 inches in diameter. It has two carriages _A_ and _B_ which, in conjunction with special tool-holders, make it possible to turn several different diameters simultaneously. At the front of this lathe there is an automatic stop-rod _C_ for disengaging the feed when the tools have turned a surface to the required length. This stop-rod carries adjustable stops _D_ which are set to correspond with shoulders, etc., on the work. The rod itself is also adjustable axially, so that the tools, which are usually arranged in groups of two or more (depending upon the nature of the work), can be disengaged at a point nearer or farther from the headstock as may be required, owing to a variation in the depth of center holes. For example, if it were necessary to feed a group of tools farther toward the headstock after they had been automatically disengaged, the entire rod with its stops would be adjusted the required amount in that direction. [Illustration: Fig. 33. Lo-swing Lathe arranged for Turning a Steering Knuckle] The gage _G_, which is attached to a swinging arm, is used to set the stop bar with reference to a shoulder near the end of the work, when it is necessary to finish other parts to a given distance from such a shoulder or other surface. The use of this gage will be explained more fully later. Cooling lubricant for the tools is supplied through the tubes _E_. The lathe shown in the illustration is arranged for turning Krupp steel bars. A rough bar and also one that has been turned may be seen to the right. The plain cylindrical bar is turned to five different diameters, by groups of tools held on both carriages. [Illustration: Fig. 34. Plan View showing Method of driving Steering Knuckle and Arrangement of Tools] =Examples of Multiple Turning.=--Figs. 33 and 34 show how a Lo-swing lathe is used for turning the steering knuckle of an automobile. Four tools are used in this case, three cylindrical surfaces and one tapering surface being turned at the same time. For this job, the four tools are mounted on one carriage. The taper part is turned by the second tool from the headstock, which is caused to feed outward as the carriage advances by a taper attachment. This tool is held in a special holder and bears against a templet at the rear, which is tapered to correspond with the taper to be turned. This templet is attached to a bar which, in turn, is fastened to a stationary bracket seen to the extreme left in Fig. 33. This part is finished in two operations, the tool setting being identical for each operation, except for diameter adjustments. As the illustrations show, three of the four tools employed are used for straight turning on different diameters, while the fourth finishes the taper. These pieces, which are rough drop forgings, are first reduced to the approximate size. When it becomes necessary to grind the tools, they are reset and those parts which have been roughed out are turned to the finished size. The average time for the first operation, which includes starting, stopping, turning and replacing the piece, is one minute, while for the second operation with the finer feed, an average time of two minutes is required. The work is driven by sleeve _S_, which fits over the spindle and is held in position by the regular driver, as shown. This sleeve is notched to fit the knuckle, so that the latter can easily and quickly be replaced when finished. One of the interesting features of this job lies in the method of locating the shoulders on each knuckle, at the same distance from the hole _H_ which is drilled previously, and which receives the bolt on which the knuckle swivels when assembled in a car. As soon as the knuckle has been placed between the centers, a close-fitting plug _P_ (Fig. 33) is inserted in this hole and the indicator arm with its attached gage or caliper _G_ is swung up to the position shown. The stop-rod on which the stops have been previously set for the correct distance between the shoulders is next adjusted axially until the gage _G_ just touches the plug _P_. The indicator is then swung out of the way, and the piece turned. If the next knuckle were centered, say, deeper than the previous one which would, of course, cause it to be located nearer the headstock, obviously all the shoulders would be located farther from the finished hole, provided the position of the stops remained the same as before. In such a case their position would, however, be changed by shifting the stop-rod until the gage _G_ again touched the plug thus locating all the stops with reference to the hole. As the adjustment of the stop-rod changes the position of the taper templet as well as the stops, it is evident that both the shoulders and the taper are finished the same distance from the hole in each case. The connection of the bracket (to which the templet arm is attached) with the stop-rod is clearly shown in Fig. 33. This bracket can either be locked to the ways or adjusted to slide when the stop-rod is moved. [Illustration: Fig. 35. First and Second Operations on Automobile Transmission Shaft--Lo-swing Lathe] The part illustrated in Fig. 35 is an automobile transmission shaft. In this particular case, cylindrical, tapering and spherical surfaces are turned. The upper view shows, diagrammatically, the arrangement of the tools and work for the first operation. After the shaft is "spotted" at _A_ for the steadyrest, the straight part _C_ and the collar _B_ are sized with tools _S_ and _R_ which are mounted on the left-hand carriage. A concave groove is then cut in collar _B_ by tool _R_, after which spherical end _D_ is formed by a special attachment mounted on the right-hand carriage. This attachment is the same, in principle, as the regular taper-turning attachment, the substitution of a circular templet _T_ for the straight kind used on taper work being the only practical difference. [Illustration: Fig. 36. Axle End turned in One Traverse of the Five Tools shown] After the surfaces mentioned have been finished on a number of pieces, the work is reversed and the tools changed as shown by the lower view. The first step in the second operation is to turn the body _E_ of the shaft with the tool _T_ on the left-hand carriage. The taper _F_ and the straight part _G_ are then finished, which completes the turning. It will be noted that in setting up the machine for this second operation, it is arranged for taper turning by simply replacing the circular templet with the straight one shown. When this taper attachment is not in use, the swiveling arm _M_, which is attached to a bracket, is swung out of the way. The method of driving this shaft is worthy of note. A dog having two driving arms each of which bears against a pin _N_ that passes through a hole in the spindle is used. As the ends of this pin, against which the dog bears, are beveled in opposite directions, the pin turns in its hole when the dog makes contact with it and automatically adjusts itself against the two driving members of the dog. The advantage of driving by a two-tailed dog, as most mechanics know, is in equalizing the tendency to spring slender parts while they are being turned. [Illustration: Fig. 37. Lathe Knurling Tool having Three Pairs of Knurls--Coarse, Medium and Fine] In Fig. 36 another turning operation on a lathe of this type is shown, the work in this case being a rear axle for a motor truck. The turning of this part is a good example of that class of work where the rapid removal of metal is the important feature. As the engraving shows, the stock, prior to turning, is 3-1/2 inches in diameter and it is reduced to a minimum diameter of 1-1/16 inch. This metal is turned off with one traverse of the carriage or by one passage of the five tools, and the weight of the chips removed from each end of the axle is approximately 12 pounds. The time required for the actual turning is about 9 minutes, while the total time for the operation, which includes placing the heavy piece in the machine, turning, and removing the work from the lathe, is 12 minutes. The axle revolves, while being turned, at 110 revolutions per minute and a feed equivalent to 1 inch of tool travel to 60 revolutions of the work is used. It will be noticed that the taper attachment is also employed on this part, the taper being turned by the second tool from the left. As the axle is equipped with roller bearings, it was found desirable to finish the bearing part by a separate operation; therefore, in the operation shown the axle is simply roughed down rather close to the finished dimensions, leaving enough material for a light finishing cut. =Knurling in the Lathe.=--Knurling is done either to provide a rough surface which can be firmly gripped by the hand or for producing an ornamental effect. The handles of gages and other tools are often knurled, and the thumb-screws used on instruments, etc., usually have knurled edges. A knurled surface consists of a series of small ridges or diamond-shaped projections, and is produced in the lathe by the use of a tool similar to the one shown in Fig. 37, this being one of several different designs in common use. The knurling is done by two knurls _A_ and _B_ having teeth or ridges which incline to the right on one knurl and to the left on the opposite knurl, as shown by the end view. When these two knurls are pressed against the work as the latter revolves, one knurl forms a series of left-hand ridges and the other knurl right-hand ridges, which cross and form the diamond-shaped knurling which is generally used. If the surface to be knurled is wider than the knurls, the power feed of the lathe should be engaged and the knurling tool be traversed back and forth until the diamond-shaped projections are well formed. To prevent forming a double set of projections, feed the knurl in with considerable pressure at the start, then partially relieve the pressure before engaging the power feed. Use oil when knurling. The knurls commonly used for lathe work have spiral teeth and ordinarily there are three classes, known as coarse, medium and fine. The medium pitch is generally used. The teeth of coarse knurls have a spiral angle of 36 degrees and the pitch of the knurled cut (measured parallel to the axis of the work) should be about 8 per inch. For medium knurls, the spiral angle is 29-1/2 degrees and the pitch, measured as before, is 12 per inch. For fine knurls, the spiral angle is 25-3/4 degrees and the pitch 20 per inch. The knurls should be about 3/4 inch in diameter and 3/8 inch wide. When made to these dimensions, coarse knurls have 34 teeth; medium, 50 teeth; and fine knurls, 80 teeth. [Illustration: Fig. 38. Hendey Relieving Attachment applied to a Lathe] The particular tool illustrated in Fig. 37 has three pairs of knurls of coarse, medium and fine pitch. These are mounted in a revolving holder which not only serves to locate the required set of knurls in the working position, but enables each knurl to bear against the surface with equal pressure. Concave knurls are sometimes used for knurling rounded edges on screw heads, etc. =Relieving Attachment.=--Some lathes, particularly those used in toolrooms, are provided with relieving attachments which are used for "backing off" the teeth of milling cutters, taps, hobs, etc. If a milling cutter of special shape is to be made, the cutter blank is first turned to the required form with a special tool having a cutting edge that corresponds with the shape or profile of the cutter to be made. The blank is then fluted or gashed to form the teeth, after which the tops of the teeth are relieved or backed off to provide clearance for the cutting edges. The forming tool used for turning the blank is set to match the turned surface, and the teeth are backed off as the result of a reciprocating action imparted to the toolslide by the relieving attachment. The motion of the toolslide is so adjusted that the tool will meet the front of each tooth and the return movement begin promptly after the tool leaves the back end of the tooth. [Illustration: Fig. 39. Relieving a Formed Cutter] These attachments differ somewhat in their construction and arrangement but the principle of their operation is similar. Fig. 38 shows a Hendey relieving attachment applied to a lathe. A bracket carrying the gearing _A_ through which the attachment is driven is mounted upon the main gear box of the lathe, and the special slide _B_, which is used when relieving, is placed on the cross-slide after removing the regular compound rest. The gears at _A_ are changed to suit the number of flutes or gashes in the cutter, tap or whatever is to be relieved. If we assume that the work is a formed milling cutter having nine teeth, then with this particular attachment, a gear having 90 teeth would be placed on the "stud" and a 40-tooth gear on the cam-shaft, the two gears being connected by a 60-tooth intermediate gear. With this combination of gearing, the toolslide would move in and out nine times for each revolution of the work, so that the tool could back off the top of each tooth. (The gearing to use for various numbers of flutes is shown by an index plate on the attachment.) The amount of relief is varied to suit the work being done, by means of a toothed coupling which makes it possible to change the relative position between the eccentric which actuates the toolslide and the cam lever, thereby lengthening or shortening the reciprocating travel of the tool. [Illustration: Fig. 40. Relieving Side of Angular Milling Cutter] =Application of Relieving Attachment.=--Some typical examples of the kind of work for which the relieving attachment is used are shown in Figs. 39 to 42, inclusive. Fig. 39 shows how a formed milling cutter is relieved. The toolslide is set at right angles to the axis of the work, and the tool moves in as each tooth passes, and out while crossing the spaces or flutes between the teeth. As the result of this movement, the tops of the teeth are backed off eccentrically but the form or shape is the same from the front to the back of the tooth; hence, a cutter that has been relieved in this way can be ground repeatedly without changing the profile of the teeth, provided the faces are ground so as to lie in a radial plane. When relieving, the cutting speed should be much less than when turning in order to give the toolslide time to operate properly. A maximum of 180 teeth per minute is recommended, and, if wide forming tools are used, it might be advisable to reduce the speed so low that only 8 teeth per minute would be relieved. It is also essential to use a tool having a keen edge, and the toolslide should work freely but be closely adjusted to the dovetail of the lower slide. Before beginning to back off the teeth, it is a good plan to color the work either by heating it or dipping into a strong solution of copper sulphate. This will enable one to see plainly the cutting action of the tool in order to stop relieving at the proper time. [Illustration: Fig. 41. Relieving a Right-hand Tap] Fig. 40 shows a method of relieving the teeth of an angular cutter. For an operation of this kind the toolslide is swiveled around at right angles to the side that is to be relieved. By the use of an additional universal joint and bearing to permit the toolslide to be swung to a 90-degree angle, the teeth of counterbores, etc., can be relieved on the ends. When the attachment is used for relieving inside work, such as hollow mills and threading dies, the eccentric which controls the travel of the toolslide is set so that the relieving movement is away from the axis of the cutter instead of toward it. This change is made by the toothed coupling previously referred to, which connects the cam lever and oscillating shaft, the latter being turned beyond the zero mark in a clockwise direction as far as is necessary to obtain the desired amount of travel. For internal work it is also necessary to change the position of the opposing spring of the toolslide, so that it will press against the end of the slide and prevent the tool from jumping into the work. [Illustration: Fig. 42. Relieving a Hob having Spiral Flutes] Fig. 41 shows how a right-hand tap is relieved. The ordinary practice is to first set the tool the same as for cutting a thread. The motion of the toolslide is then adjusted so that the tool on the forward stroke will meet the front of each tooth, and start back as soon as the tool leaves the end of the land or top of the tooth. Taps having a left-hand thread can be relieved by two different methods. With the first method the cut starts at the cutting edge of each tooth, and ends at the "heel," the tool moving in toward the center of the work. With the second method, the cut begins at the heel and discontinues at the cutting edge, the tool being drawn away from the work during the cut. When using the first method the tap must be placed with the point toward the headstock, the shank end being supported by the tailstock center. This is done by providing an extension or blank end at the point of the tap long enough to hold the driving dog. With the second method, the tap is held between centers the same as one having a right-hand thread, but the travel of the toolslide is set the same as for inside relief. =Relieving Hobs or Taps Having Spiral Flutes.=--With this attachment, taps or hobs having "spiral" or helical flutes can also be relieved. (A spiral flute is preferable to one that is parallel to the axis, because with the former the tool has cutting edges which are square with the teeth; this is of especial importance when the lead of the hob or tap thread is considerable.) When relieving work having spiral flutes (as illustrated in Fig. 42), the lead of the spiral and the gears necessary to drive the attachment are first determined. After the attachment is geared for the number of flutes and to compensate for the spiral, the lead-screw is engaged and the backing-off operation is performed the same as though the flutes were straight. The carriage should not be disengaged from the lead-screw after starting the cut, the tool being returned by reversing the lathe. When gearing the attachment for relieving a tap or hob having spiral flutes, the gears are not selected for the actual number of flutes around the circumference but for a somewhat larger number which depends upon the lead of the hob thread and the lead of the spiral flutes. Let us assume that a hob has 6 spiral flutes and that the attachment is geared for that number. The result would be that as the tool advanced along the thread, it would not keep "in step" with the teeth because the faces of the teeth lie along a spiral (or helix which is the correct name for this curve); in other words, the tool would soon be moving in too late to begin cutting at the proper time, and to compensate for this, the attachment is geared so that the tool will make a greater number of strokes per revolution of the work than the actual number of flutes around the circumference. With this attachment, the two gears listed on the index plate for the actual number of flutes are selected, and then two compensating gears are added, thus forming a compound train of gearing. The ratio _R_ of these compensating gears is determined as follows: _r_ + 1 R = ------- _r_ in which _r_ = _L_ ÷ _l_; _L_ = lead of spiral; _l_ = lead of hob thread. For example, if a hob has a pitch circumference of 3.25, a single thread of 0.75 inch lead, and 6 spiral flutes, what compensating gears would be required? The lead _L_ of the spiral flutes is first determined by dividing the square of the circumference _C_ of the hob at the pitch line by the lead _l_ of the hob thread. Thus lead _L_ = _C^2_/_l_, or, in this case, _L_ = 3.25^2/0.75 = 14 inches, approximately. Then _r_ = 14 ÷ 0.75 = 18-2/3. Inserting these values in the formula for ratio R, 18-2/3 + 1 19-2/3 19-2/3 � 3 59 _R_ = ---------- = ------ = ---------- = -- 18-2/3 18-2/3 18-2/3 � 3 56 Hence, the compensating gears will have 56 and 59 teeth, respectively, the latter being the driver. As the gears for 6 flutes listed on the regular index plate are, stud-gear 60 teeth, cam-shaft gear 40 teeth, the entire train of gears would be as follows: Gear on stud, 60; _driven_ intermediate gear, 56; _driving_ intermediate gear, 59; cam-shaft gear, 40. It will be understood that the position of the driving gears or the driven gears can be transposed without affecting the ratio. =Classes of Fits Used in Machine Construction.=--In assembling machine parts it is necessary to have some members fit together tightly, whereas other parts such as shafts, etc., must be free to move or revolve with relation to each other. The accuracy required for a fitting varies for different classes of work. A shaft that revolves in its bearing must be slightly smaller than the bearing so that there will be room for a film of lubricant. A crank-pin that must be forced into the crank-disk is made a little larger in diameter than the hole, to secure a tight fit. When a very accurate fitting between two cylindrical parts that must be assembled without pressure is required, the diameter of the inner member is made as close to the diameter of the outer member as is possible. In ordinary machine construction, five classes of fits are used, _viz_; running fit, push fit, driving fit, forced fit and shrinkage fit. The running fit, as the name implies, is employed when parts must rotate; the push fit is not sufficiently free to rotate; the other classes referred to are used for assembling parts that must be held in fixed positions. =Forced Fits.=--This is the term used when a pin, shaft or other cylindrical part is forced into a hole of slightly smaller diameter, by the use of a hydraulic press or other means. As a rule, forced fits are restricted to parts of small and medium size, while shrinkage fits have no such limitations and are especially applicable when a maximum "grip" is desired, or when (as in the construction of ordnance) accurate results as to the intensity of stresses produced in the parts united are required. The proper allowance for a forced fit depends upon the mass of metal surrounding the hole, the size of the work, the kind and quality of the material of which the parts are composed and the smoothness and accuracy of the pin and bore. When a pin or other part is pressed into a hole a second time, the allowance for a given tonnage should be diminished somewhat because the surface of the bore is smoother and the metal more compact. The pressure required in assembling a forced fit will also vary for cast hubs of the same size, if they are not uniform in hardness. Then there is the personal factor which is much in evidence in work of this kind; hence, data and formulas for forced fit allowances must be general in their application. =Allowance for Forced Fits.=--The allowance per inch of diameter usually ranges from 0.001 inch to 0.0025 inch, 0.0015 being a fair average. Ordinarily, the allowance per inch decreases as the diameter increases; thus the total allowance for a diameter of 2 inches might be 0.004 inch, whereas for a diameter of 8 inches the total allowance might not be over 0.009 or 0.010 inch. In some shops the allowance is made practically the same for all diameters, the increased surface area of the larger sizes giving sufficient increase in pressure. The parts to be assembled by forced fits are usually made cylindrical, although sometimes they are slightly tapered. The advantages of the taper form are that the possibility of abrasion of the fitted surfaces is reduced; that less pressure is required in assembling; and that the parts are more readily separated when renewal is required. On the other hand, the taper fit is less reliable, because if it loosens, the entire fit is free with but little axial movement. Some lubricant, such as white lead and lard oil mixed to the consistency of paint, should be applied to the pin and bore before assembling, to reduce the tendency of abrasion. Allowances for Different Classes of Fits (Newall Engineering Co.) +-----+--------------------------------------------------------------+ | | Tolerances in Standard Holes[1] | |Class+------------+---------+---------+---------+---------+---------+ | | Nominal | Up to | 9/16"-1"| 1-1/16"-| 2-1/16"-| 3-1/16"-| | | Diameters | 1/2" | | 2" | 3" | 4" | +-----+------------+---------+---------+---------+---------+---------+ | | High Limit | +0.0002 | +0.0005 | +0.0007 | +0.0010 | +0.0010 | | A | Low Limit | -0.0002 | -0.0002 | -0.0002 | -0.0005 | -0.0005 | | | Tolerance | 0.0004 | 0.0007 | 0.0009 | 0.0015 | 0.0015 | +-----+------------+---------+---------+---------+---------+---------+ | | High Limit | +0.0005 | +0.0007 | +0.0010 | +0.0012 | +0.0015 | | B | Low Limit | -0.0005 | -0.0005 | -0.0005 | -0.0007 | -0.0007 | | | Tolerance | 0.0010 | 0.0012 | 0.0015 | 0.0019 | 0.0022 | +-----+------------+---------+---------+---------+---------+---------+ | Allowances for Forced Fits | +-----+------------+---------+---------+---------+---------+---------+ | | High Limit | +0.0010 | +0.0020 | +0.0040 | +0.0060 | +0.0080 | | F | Low Limit | +0.0005 | +0.0015 | +0.0030 | +0.0045 | +0.0060 | | | Tolerance | 0.0005 | 0.0005 | 0.0010 | 0.0015 | 0.0020 | +-----+------------+---------+---------+---------+---------+---------+ | Allowances for Driving Fits | +-----+------------+---------+---------+---------+---------+---------+ | | High Limit | +0.0005 | +0.0010 | +0.0015 | +0.0025 | +0.0030 | | D | Low Limit | +0.0002 | +0.0007 | +0.0010 | +0.0015 | +0.0020 | | | Tolerance | 0.0003 | 0.0003 | 0.0005 | 0.0010 | 0.0010 | +-----+------------+---------+---------+---------+---------+---------+ | Allowances for Push Fits | +-----+------------+---------+---------+---------+---------+---------+ | | High Limit | -0.0002 | -0.0002 | -0.0002 | -0.0005 | -0.0005 | | P | Low Limit | -0.0007 | -0.0007 | -0.0007 | -0.0010 | -0.0010 | | | Tolerance | 0.0005 | 0.0005 | 0.0005 | 0.0005 | 0.0005 | +-----+------------+---------+---------+---------+---------+---------+ | Allowances for Running Fits[2] | +-----+------------+---------+---------+---------+---------+---------+ | | High Limit | -0.0010 | -0.0012 | -0.0017 | -0.0020 | -0.0025 | | X | Low Limit | -0.0020 | -0.0027 | -0.0035 | -0.0042 | -0.0050 | | | Tolerance | 0.0010 | 0.0015 | 0.0018 | 0.0022 | 0.0025 | | | High Limit | -0.0007 | -0.0010 | -0.0012 | -0.0015 | -0.0020 | | Y | Low Limit | -0.0012 | -0.0020 | -0.0025 | -0.0030 | -0.0035 | | | Tolerance | 0.0005 | 0.0010 | 0.0013 | 0.0015 | 0.0015 | | | High Limit | -0.0005 | -0.0007 | -0.0007 | -0.0010 | -0.0010 | | Z | Low Limit | -0.0007 | -0.0012 | -0.0015 | -0.0020 | -0.0022 | | | Tolerance | 0.0002 | 0.0005 | 0.0008 | 0.0010 | 0.0012 | +-----+------------+---------+---------+---------+---------+---------+ [1] Tolerance is provided for holes, which ordinary standard reamers can produce, in two grades, Classes A and B, the selection of which is a question for the user's decision and dependent upon the quality of the work required; some prefer to use Class A as working limits and Class B as inspection limits. [2] Running fits, which are the most commonly required, are divided into three grades: Class X for engine and other work where easy fits are wanted; Class Y for high speeds and good average machine work; Class Z for fine tool work. =Pressure for Forced Fits.=--The pressure required for assembling cylindrical parts depends not only upon the allowance for the fit, but also upon the area of the fitted surfaces, the pressure increasing in proportion to the distance that the inner member is forced in. The approximate ultimate pressure in pounds can be determined by the use of the following formula in conjunction with the accompanying table of "Pressure Factors." =Pressure Factors= +-----+-----++-----+-----++-----+-----++------+------++------+------+ |Diam-|Pres-||Diam-|Pres-||Diam-|Pres-||Diam- |Pres- ||Diam- |Pres- | |eter,|sure ||eter,|sure ||eter,|sure ||eter, |sure ||eter, |sure | |In- |Fac- ||In- |Fac- ||In- |Fac- ||In- |Fac- ||In- |Fac- | |ches | tor ||ches | tor ||ches | tor ||ches |tor ||ches |tor | +-----+-----++-----+-----++-----+-----++------+------++------+------+ |1 | 500 ||3-1/2| 132 ||6 | 75 || 9 | 48.7 ||14 | 30.5 | |1-1/4| 395 ||3-3/4| 123 ||6-1/4| 72 || 9-1/2| 46.0 ||14-1/2| 29.4 | |1-1/2| 325 ||4 | 115 ||6-1/2| 69 ||10 | 43.5 ||15 | 28.3 | |1-3/4| 276 ||4-1/4| 108 ||6-3/4| 66 ||10-1/2| 41.3 ||15-1/2| 27.4 | |2 | 240 ||4-1/2| 101 ||7 | 64 ||11 | 39.3 ||16 | 26.5 | |2-1/4| 212 ||4-3/4| 96 ||7-1/4| 61 ||11-1/2| 37.5 ||16-1/2| 25.6 | |2-1/2| 189 ||5 | 91 ||7-1/2| 59 ||12 | 35.9 ||17 | 24.8 | |2-3/4| 171 ||5-1/4| 86 ||7-3/4| 57 ||12-1/2| 34.4 ||17-1/2| 24.1 | |3 | 156 ||5-1/2| 82 ||8 | 55 ||13 | 33.0 ||18 | 23.4 | |3-1/4| 143 ||5-3/4| 78 ||8-1/2| 52 ||13-1/2| 31.7 ||.... | .... | +-----+-----++-----+-----++-----+-----++------+------++------+------+ Assuming that _A_ = area of fitted surface; _a_ = total allowance in inches; _P_ = ultimate pressure required, in tons; _F_ = pressure factor based upon assumption that the diameter of the hub is twice the diameter of the bore, that the shaft is of machine steel, and the hub of cast iron, then, _A_ � _a_ � _F_ _P_ = --------------- 2 _Example:_--What will be the approximate pressure required for forcing a 4-inch machine steel shaft having an allowance of 0.0085 inch into a cast-iron hub 6 inches long? _A_ = 4 � 3.1416 � 6 = 75.39 square inches; _F_, for a diameter of 4 inches, = 115 (see table of "Pressure Factors"). Then, _P_ = (75.39 � 0.0085 � 115)/2 = 37 tons, approximately. =Allowance for Given Pressure.=--By transposing the preceding formula, the approximate allowance for a required ultimate tonnage can be determined. Thus, _a_ = 2_P_ ÷ _AF_. The average ultimate pressure in tons commonly used ranges from 7 to 10 times the diameter in inches. Assuming that the diameter of a machine steel shaft is 4 inches and an ultimate pressure of about 30 tons is desired for forcing it into a cast-iron hub having a length of 5-1/2 inches, what should be the allowance? _A_ = 4 � 3.1416 � 5-1/2 = 69 square inches, _F_, for a diameter of 4 inches, = 115. Then, 2 � 30 _a_ = -------- = 0.0075 inch. 69 � 115 =Shrinkage Fits.=--When heat is applied to a piece of metal, such as iron or steel, as is commonly known, a certain amount of expansion takes place which increases as the temperature is increased, and also varies somewhat with different kinds of metal, copper and brass expanding more for a given increase in temperature than iron and steel. When any part which has been expanded by the application of heat is cooled, it contracts and resumes its original size. This expansive property of metals has been taken advantage of by mechanics in assembling various machine details. A cylindrical part which is to be held in position by a shrinkage fit is first turned a few thousandths of an inch larger than the hole; the diameter of the latter is then increased by heating, and after the part is inserted, the heated outer member is cooled, causing it to grip the pin or shaft with tremendous pressure. General practice seems to favor a smaller allowance for shrinkage fits than for forced fits, although in many shops the allowances are practically the same in each case, and for some classes of work, shrinkage allowances exceed those for forced fits. In any case, the shrinkage allowance varies to a great extent with the form and construction of the part which has to be shrunk into place. The thickness or amount of metal around the hole is the most important factor. The way in which the metal is distributed also has an influence on the results. Shrinkage allowances for locomotive driving wheel tires adopted by the American Railway Master Mechanics Association are as follows: Center diameter, inches 38 44 50 56 62 66 Allowance, inches 0.040 0.047 0.053 0.060 0.066 0.070 Whether parts are to be assembled by forced or shrinkage fits depends upon conditions. For example, to press a driving wheel tire over its wheel center, without heating, would ordinarily be a rather awkward and difficult job. On the other hand, pins, etc., are easily and quickly forced into place with a hydraulic press and there is the additional advantage of knowing the exact pressure required in assembling, whereas there is more or less uncertainty connected with a shrinkage fit, unless the stresses are calculated. Tests to determine the difference in the quality of shrinkage and forced fits showed that the resistance of a shrinkage fit to slippage was, for an axial pull, 3.66 times greater than that of a forced fit, and in rotation or torsion, 3.2 times greater. In each comparative test, the dimensions and allowances were the same. The most important point to consider when calculating shrinkage fits is the stress in the hub at the bore, which depends chiefly upon the shrinkage allowance. If the allowance is excessive, the elastic limit of the material will be exceeded and permanent set will occur, or, in extreme cases, the ultimate strength of the metal will be exceeded and the hub will burst. CHAPTER IV THREAD CUTTING IN THE LATHE When threads are cut in the lathe a tool _t_ is used (see Fig. 2), having a point corresponding to the shape of the thread, and the carriage is moved along the bed a certain distance for each revolution of the work (the distance depending on the number of threads to the inch being cut) by the lead-screw _S_ which is rotated by gears _a_, _b_ and _c_, which receive their motion from the spindle. As the amount that the carriage travels per revolution of the work, and, consequently, the number of threads per inch that is cut, depends on the size of the gears _a_ and _c_ (called change gears) the latter have to be changed for cutting different threads. The proper change gears to use for cutting a given number of threads to the inch is ordinarily determined by referring to a table or "index plate" _I_ which shows what the size of gears _a_ and _c_ should be, or the number of teeth each should have, for cutting any given number of threads per inch. [Illustration: Fig. 1. Measuring Number of Threads per Inch--Setting Thread Tool] [Illustration: Fig. 2. Plan and Elevations of Engine Lathe] =Selecting the Change Gears for Thread Cutting.=--Suppose a V-thread is to be cut on the end of the bolt _B_, Fig. 2, having a diameter of 1-1/4 inch and seven threads per inch of length, as shown at _A_ in Fig. 1, which is the standard number of threads per inch for that diameter. First the change gears to use are found on plate _I_ which is shown enlarged in Fig. 3. This plate has three columns: The first contains different numbers of threads to the inch, the second the size gear to place on the "spindle" or "stud" at _a_ (Fig. 2) for different threads, and the third the size of gear _c_ for the lead-screw. As the thread selected as an example has 7 threads per inch, gear _a_ should have 48 teeth, this being the number given in the second column opposite figure 7 in the first. By referring to the last column, we find that the lead-screw gear should have 84 teeth. These gears are selected from an assortment provided with the lathe and they are placed on the spindle and lead-screw, respectively. [Illustration: Fig. 3. Index Plate showing Gear Changes for Threading] Intermediate gear _b_ does not need to be changed as it is simply an "idler" for connecting gears _a_ and _c_. Gear _b_ is mounted on a swinging yoke _Y_ so that it can be adjusted to mesh properly with different gear combinations; after this adjustment is made, the lathe is geared for cutting 7 threads to the inch. (The change gears of many modern lathes are so arranged that different combinations are obtained by simply shifting a lever. A lathe having this quick-change gear mechanism is described in the latter part of this chapter.) The work _B_ is placed between the centers just as it would be for turning, with the end to be threaded turned to a diameter of 1-1/4 inch, which is the outside diameter of the thread. =The Thread Tool.=--The form of tool used for cutting a V-thread is shown at _A_, Fig. 4. The end is ground V-shaped and to an angle of 60 degrees, which corresponds to the angle of a standard V-thread. The front or flank, _f_ of the tool is ground back at an angle to provide clearance, but the top is left flat or without slope. As it is very important to grind the end to exactly 60 degrees, a gage _G_ is used, having 60-degree notches to which the tool-point is fitted. The tool is clamped in the toolpost as shown in the plan view, Fig. 2, square with the work, so that both sides of the thread will be cut to the same angle with the axis of the work. A very convenient way to set a thread tool square is illustrated at _B_, Fig. 1. The thread gage is placed against the part to be threaded, as shown, and the tool is adjusted until the angular sides of the point bear evenly in the 60-degree notch of the gage. The top of the tool point should be at the same height as the lathe centers, as otherwise the angle of the thread will not be correct. [Illustration: Fig. 4. Thread Tools and Gage for testing Angle of End] =Cutting the Thread.=--The lathe is now ready for cutting the thread. This is done by taking several cuts, as indicated at _A_, _B_, _C_ and _D_ in Fig. 5, the tool being fed in a little farther for each successive cut until the thread is finished. When these cuts are being taken, the carriage is moved along the bed, as previously explained, by the lead-screw _S_, Fig. 2. The carriage is engaged with the lead-screw by turning lever _u_ which causes the halves of a split nut to close around the screw. The way a lathe is handled when cutting a thread is as follows: After the lathe is started, the carriage is moved until the tool-point is slightly beyond the right end of the work, and the tool is fed in far enough to take the first cut which, ordinarily, would be about 1/16 inch deep. The carriage is then engaged with the lead-screw, by operating lever _u_, and the tool moves to the left (in this case 1/7 inch for each revolution of the work) and cuts a winding groove as at _A_, Fig. 5. When the tool has traveled as far as the thread is wanted, it is withdrawn by a quick turn of cross-slide handle _e_, and the carriage is returned to the starting point for another cut. The tool is then fed in a little farther and a second cut is taken as at _B_, Fig. 5, and this operation is repeated as at _C_ and _D_ until a "full" thread is cut or until the top of the thread is sharp. The thread is then tested for size but before referring to this part of the work, the way the carriage is returned to the starting point after each cut should be explained. [Illustration: Fig. 5. Thread is formed by taking a Number of Successive Cuts] When the tool is withdrawn at the end of the first cut, if the carriage is disengaged from the lead-screw and returned by hand, the tool may or may not follow the first cut when the carriage is again engaged with the lead-screw. If the number of threads to the inch being cut is a multiple of the number on the lead-screw _S_, then the carriage can be returned by hand and engaged with the lead-screw at random and the tool will follow the first cut. For example, if the lead-screw has six threads per inch, and 6, 12, 18 or any number of threads is being cut that is a multiple of six, the carriage can be engaged at any time and the tool will always follow the original cut. This is not the case, however, when the number of threads being cut is not a multiple of the number on the lead-screw. One method of bringing the carriage back to the starting point, when cutting threads which are not multiples, is to reverse the lathe (by shifting the overhead driving belts) in order to bring the tool back to the starting point without disengaging the carriage; in this way the tool is kept in the same relation to the work, and the carriage is not disengaged from the lead-screw until the thread is finished. This is a good method when cutting short threads having a length of say two or three inches; but when they are longer, and especially when the diameter is comparatively large (which means a slower speed), it is rather slow as considerable time is wasted while the tool is moving back to its starting point. This is due to the fact that the carriage is moved slowly by the lead-screw, but when disengaged, it can be traversed quickly by turning handle _d_, Fig. 2. A method of returning the carriage by hand when the number of threads being cut is not a multiple of the number on the lead-screw is as follows: The tool is moved a little beyond the right end of the work and the carriage or split nut is engaged with the lead-screw. The lathe is then turned forward by hand to take up any lost motion, and a line is made on the lathe bed showing the position of the carriage. The positions of the spindle and lead-screw are also marked by chalking a tooth on both the spindle and lead-screw gears, which happens to be opposite a corner or other point on the bed. After a cut is taken, the carriage is returned by hand to the original starting point as shown by the line on the bed, and is again engaged when the chalk marks show that the spindle and lead-screw are in their original position; the tool will then follow the first cut. If the body of the tailstock is moved against the bridge of the carriage before starting the first cut, the carriage can be located for each following cut by moving it back against the tailstock, and it will not be necessary to have a line on the bed. [Illustration: Fig. 6. Indicator used when Cutting Threads] =Indicator or Chasing Dial for Catching Threads.=--On some lathes there is an indicator for "catching threads," as this is called in shop language. This is a simple device attached to the carriage and consists of a graduated dial _D_ and a worm-wheel _W_ (see Figs. 2 and 6) which meshes with the lead-screw, so that the dial is revolved by the lead-screw when the carriage is stationary, and when the carriage is moved by the screw, the dial remains stationary. The indicator is used by engaging the carriage when one of the graduation lines is opposite the arrow mark; after a cut is taken the carriage is returned by hand and when one of the graduation lines again moves opposite the arrow, the half-nuts are thrown into mesh, as before, and this is repeated for each successive cut, thus causing the tool to always come right with the thread. If the number of threads per inch is even, engagement can be made when any line is opposite the arrow, but for odd numbers such as 3, 7, 9, 11, etc., one of the four long or numbered lines must be used. Of course, if the thread being cut is a multiple of the number on the lead-screw, engagement can be made at any time, as previously mentioned. =Principle of the Thread Indicator.=--The principle upon which the thread indicator operates is as follows: The number of teeth in worm-wheel _W_ is some multiple of the number of threads per inch of the lead-screw, and the number of teeth in the worm-wheel, divided by the pitch of the screw, equals the number of graduations on the dial. For example, if the lead-screw has six threads per inch, the worm-wheel could have twenty-four teeth, in which case the dial would have four divisions, each representing an inch of carriage travel, and by sub-dividing the dial into eighths (as shown) each line would correspond to 1/2 inch of travel. The dial, therefore, would enable the carriage to be engaged with the lead-screw at points equal to a travel of one-half inch. To illustrate the advantage of this suppose ten threads per inch are being cut and (with the lathe stationary) the carriage is disengaged and moved 1/6 inch or one thread on the lead-screw; the tool point will also have moved 1/6 inch, but it will not be opposite the next thread groove in the work as the pitch is 1/10 inch. If the carriage is moved another thread on the lead-screw, or 2/6 inch, the tool will still be out of line with the thread on the work, but when it has moved three threads, or 1/2 inch, the tool will then coincide with the original cut because it has passed over exactly five threads. This would be true for any number of threads per inch that is divisible by 2. If the thread being cut had nine threads per inch or any other odd number, the tool would only coincide with the thread at points 1 inch apart. Therefore, the carriage can only be engaged when one of the four graduations representing an inch of travel is opposite the arrow, when cutting odd threads; whereas even numbers can be "caught" by using any one of the eight lines. This indicator can also be used for "catching" fractional threads. As an illustration, suppose 11-1/2 threads per inch are to be cut, and the carriage is engaged for the first cut when graduation line 1 is opposite the arrow; engagement would then be made for each successive cut, when either line 1 or 3 were opposite the arrow, or in other words at spaces equal to a carriage movement of 2 inches. As the use of the indicator when cutting fractional threads is liable to result in error, it is better to keep the half-nuts in engagement and return the carriage by reversing the lathe. =Replacing Sharpened Thread Tool.=--If it is necessary to sharpen the thread tool before the thread is finished, it should be reset square with the work by testing with the thread gage as at _B_, Fig. 1. The carriage is then engaged with the lead-screw and the lathe is turned forward to bring the tool opposite the partly finished thread and also to take up any backlash or lost motion in the gears or half-nut. If the tool-point is not in line with the thread groove previously cut, it can be shifted sidewise by feeding the compound rest _E_ in or out, provided the latter is set in an angular position as shown in the plan view, Fig. 2. If the thread tool is ground flat on the top as at _A_, Fig. 4, it is not a good tool for removing metal rapidly as neither of its two cutting edges has any slope. In order to give each cutting edge a backward slope, it would be necessary to grind the top surface hollow or concave, which would be impracticable. When a course thread is to be cut, a tool shaped as at _B_ can be used to advantage for rough turning the thread groove, which is afterward finished to the correct depth and angle by tool _A_. This roughing tool is ground with a backward slope from the point and the latter is rounded to make it stronger. =Use of Compound Rest for Thread Cutting.=--Another form of thread tool is shown at _A_, Fig. 7, which is very good for cutting V-threads especially of coarse pitch. When this tool is used, the compound rest _E_ is set to an angle of 30 degrees, as shown, and it is fed in for the successive cuts by handle _w_ in the direction indicated by the arrow. It will be seen that the point a of the tool moves at an angle of 60 degrees with the axis of the work, thus forming one side of the thread, and the cutting edge _a--b_, which can be set as shown at _B_, forms the opposite side and does all the cutting. As this edge is given a backward slope, as shown, it cuts easily and enables threading operations to be performed quickly. Threads cut in this way are often finished by taking a light cut with a regular thread tool. The cutting edge _a--b_ is ground to an angle of 60 degrees (or slightly less, if anything) with the side, as shown by sketch _A_. When cutting threads in steel or wrought iron, some sort of lubricant is usually applied to the tool to preserve the cutting end and give a smooth finish to the thread. Lard oil or a mixture of equal parts of lard oil and paraffin oil are often used for this purpose. If the thread is small, the lubricant may be applied from an ordinary oil can, but when cutting comparatively large threads, it is better to have a stream of oil constantly playing upon the tool-point. This constant flow may be obtained by mounting a can having a spout leading to the tool, on a bracket at the rear of the carriage. [Illustration: Fig. 7. Cutting Thread by using Compound Rest] [Illustration: Fig. 8. (A) V-thread. (B) U. S. Standard Thread. (C) Square Thread. (D) Left-hand Thread. (E) Double Square Thread. (F) Triple Square Thread] =Threads Commonly Used.=--Three forms of threads or screws which are in common use are shown in Fig. 8; these are the V-thread (_A_), the U. S. standard (_B_), and the square thread (_C_). The shapes of these threads are shown by the sectioned parts. The V-thread has straight sides which incline at an angle of 60 degrees with each other and at the same angle with the axis of the screw. The U. S. standard thread is similar to the V-thread except that the top of the thread and bottom of the groove is left flat, as shown, and the width of these flats is made equal to 1/8 of the pitch. The square thread is square in section, the width _a_, depth _b_ and space _c_ being all equal. All of these threads are right-hand, which means that the grooves wind around to the right so that a nut will have to be turned toward the right to enter it on the thread. A left-hand thread winds in the other direction, as shown at _D_, and a nut is screwed on by turning it to the left. =Multiple Threads.=--Threads, in addition to being right-and left-handed, are single, as at _A_, _B_, _C_ and _D_, double, as at _E_, and triple, as at _F_, and for certain purposes quadruple threads or those of a higher multiple are employed. A double thread is different from a single thread in that it has two grooves, starting diametrically opposite, whereas a triple thread has three grooves cut as shown at _F_. The object of these multiple threads is to obtain an increase in lead without weakening the screw. For example, the threads shown at _C_ and _E_ have the same pitch _p_ but the lead _l_ of the double-threaded screw is twice that of the one with a single thread so that a nut would advance twice as far in one revolution, which is often a very desirable feature. To obtain the same lead with a single thread, the pitch would have to be double, thus giving a much coarser thread, which would weaken the screw, unless its diameter were increased. (The lead is the distance _l_ that one thread advances in a single turn, or the distance that a nut would advance in one turn, and it should not be confused with the pitch _p_, which is the distance between the centers of adjacent threads. Obviously the lead and pitch of a single thread are the same.) =Cutting a U. S. Standard Thread.=--The method of cutting a U. S. standard thread is the same as described for a V-thread, so far as handling the lathe is concerned. The thread tool must correspond, of course, to the shape of a U. S. standard thread. This tool is first ground to an angle of 60 degrees, as it would be for cutting a V-thread, and then the point is made flat as shown in Fig. 9. As will be recalled, the width of this flat should be equal to 1/8 of the pitch. By using a gage like the one shown at _G_, the tool can easily be ground for any pitch, as the notches around the periphery of the gage are marked for different pitches and the tool-point is fitted into the notch corresponding to the pitch wanted. If such a gage is not available, the width of the flat at the point can be tested by using, as a gage, a U. S. standard tap of the same pitch as the thread to be cut. When cutting the thread, the tool is set square with the blank, and a number of successive cuts are taken, the tool being fed in until the width w of the flat at the top of the thread is equal to the width at the bottom. The thread will then be the right size provided the outside diameter _D_ is correct and the tool is of the correct form. As it would be difficult to measure the width of this flat accurately, the thread can be tested by screwing a standard nut over it if a standard thread is being cut. If it is being fitted to a tapped hole, the tap itself is a very convenient gage to use, the method being to caliper the tap and then compare its size with the work. [Illustration: Fig. 9. U. S. Standard Thread, Thread Tool, and Gage] A good method of cutting a U. S. standard thread to a given size is as follows: First turn the outside of the blank accurately to diameter _D_, and then turn a small part of the end to diameter _r_ of the thread at the root. The finishing cut for the thread is then taken with the tool point set to just graze diameter _r_. If ordinary calipers were set to diameter _r_ and measurements taken in the thread groove, the size would be incorrect owing to the angularity of the groove, which makes it necessary to hold the calipers at an angle when measuring. To determine the root diameter divide 1.299 by the number of threads per inch and subtract the quotient from the outside diameter. Expressing this rule as a formula, /1.299\ _r_ = _D_ - ( ----- ) \ _N_ / in which _D_ equals outside diameter; _N_, the number of threads per inch; and _r_, the root diameter. The number 1.299 is a constant that is always used. [Illustration: Fig. 10. End View of Lathe Headstock] =Cutting a Left-hand Thread.=--The only difference between cutting left-hand and right-hand threads in the lathe is in the movement of the tool with relation to the work. When cutting a right-hand thread, the tool moves from right to left, but this movement is reversed for left-hand threads because the thread winds around in the opposite direction. To make the carriage travel from left to right, the lead-screw is rotated backwards by means of reversing gears _a_ and _b_ (Fig. 10) located in the headstock. Either of these gears can be engaged with the spindle gear by changing the position of lever _R_. When gear _a_ is in engagement, as shown, the drive from the spindle to gear _c_ is through gears _a_ and _b_, but when lever _R_ is raised thus shifting _b_ into mesh, the drive is direct and the direction of rotation is reversed. The thread is cut by starting the tool at _a_, Fig. 8, instead of at the end. [Illustration: Fig. 11. End of Square Thread Tool, and Graphic Method of Determining Helix Angle of Thread] =Cutting a Square Thread.=--The form of tool used for cutting a square thread is shown in Fig. 11. The width _w_ is made equal to one-half the pitch of the thread to be cut and the end _E_ is at an angle with the shank, which corresponds to the inclination _x--y_ of the threads. This angle _A_ depends upon the diameter of the screw and the lead of the thread; it can be determined graphically by drawing a line _a--b_ equal in length to the circumference of the screw to be cut, and a line _b--c_, at right angles, equal in length to the lead of the thread. The angle [alpha] between lines _a--b_ and _a--c_ will be the required angle _A_. (See end view of thread tool). It is not necessary to have this angle accurate, ordinarily, as it is simply to prevent the tool from binding against the sides of the thread. The end of a square thread tool is shown in section to the right, to illustrate its position with relation to the threads. The sides _e_ and _e_{1}_ are ground to slope inward, as shown, to provide additional clearance. When cutting multiple threads, which, owing to their increased lead, incline considerably with the axis of the screw, the angles for each side of the tool can be determined independently as follows: Draw line _a--b_ equal in length to the circumference of the thread, as before, to obtain the required angle _f_ of the rear or following side _e_{1}_; the angle _l_ of the opposite or leading side is found by making _a--b_ equal to the circumference at the root of the thread. The tool illustrated is for cutting right-hand threads; if it were intended for a left-hand thread, the end, of course, would incline in the opposite direction. The square thread is cut so that the depth _d_ is equal to the width. When threading a nut for a square thread screw, it is the usual practice to use a tool having a width slightly greater than one-half the pitch, to provide clearance for the screw, and the width of a tool for threading square-thread taps to be used for tapping nuts is made slightly less than one-half the pitch. =Cutting Multiple Threads.=--When a multiple thread is to be cut, such as a double or triple thread, the lathe is geared with reference to the number of single threads to the inch. For example, the lead of the double thread, shown at _B_, Fig. 12, is one-half inch, or twice the pitch, and the number of single threads to the inch equals 1 ÷ 1/2 = 2. Therefore, the lathe is geared for cutting two threads per inch. The first cut is taken just as though a single thread were being cut, leaving the work as shown at _A_. When this cut is finished the work is turned one-half a revolution (for a double thread) without disturbing the position of the lead-screw or carriage, which brings the tool midway between the grooves of the single thread as indicated by dotted lines. The second groove is then cut, producing a double thread as shown at _B_. In the case of a triple thread, the work would be indexed one-third of a revolution after turning the first groove, and then another third revolution to locate the tool for cutting the last groove. Similarly, for a quadruple thread, it would be turned one-quarter revolution after cutting each successive groove or thread. There are different methods of indexing the work when cutting multiple threads, in order to locate the tool in the proper position for cutting another thread groove. Some machinists, when cutting a double thread, simply remove the work from the lathe and turn it one-half a revolution by placing the tail of the driving dog in the opposite slot of the faceplate. This is a very simple method, but if the slots are not directly opposite or 180 degrees apart, the last thread will not be central with the first. Another and better method is to disengage the idler gear from the gear on the stud, turn the spindle and work one-half, or one-third, of a revolution, as the case might be, and then connect the gears. For example, if the stud gear had 96 teeth, the tooth meshing with the idler gear would be marked with chalk, the gears disengaged, and the spindle turned until the chalked tooth had made the required part of a revolution, which could be determined by counting the teeth. When this method is used, the number of teeth in the stud gear must be evenly divisible by two if a double thread is being cut, or by three for a triple thread, etc. If the stud is not geared to the spindle so that each makes the same number of revolutions, the ratio of the gearing must be considered. [Illustration: Fig. 12. Views illustrating how a Double Square Thread is Cut] =Setting Tool When Cutting Multiple Threads.=--Another method, which can sometimes be used for setting the tool after cutting the first groove of a multiple thread, is to disengage the lock-nuts from the lead-screw (while the spindle is stationary) and move the carriage back whatever distance is required to locate the tool in the proper position for taking the second cut. Evidently this distance must not only locate the tool in the right place, but be such that the lock-nuts can be re-engaged with the lead-screw. Beginning with a simple illustration, suppose a double thread is being cut having a lead of 1 inch. After the first thread groove is cut, the tool can be set in a central position for taking the second cut, by simply moving the carriage back 1/2 inch (one-half the lead), or 1/2 inch plus the lead or any multiple of the lead. If the length of the threaded part were 5 inches, the tool would be moved back far enough to clear the end of the work, or say 1/2 + 5 = 5-1/2 inches. In order to disengage the lock-nuts and re-engage them after moving the carriage 5-1/2 inches (or any distance equal, in this case, to one-half plus a whole number), the lead-screw must have an even number of threads per inch. Assume that a double thread is being cut having 1-1/4 single threads per inch. The lead then would equal 1 ÷ 1-1/4 = 0.8 inch, and if the carriage is moved back 0.8 ÷ 2 = 0.4 inch, the tool will be properly located for the second cut; but the lock-nuts could not be re-engaged unless the lead-screw had ten threads per inch, which is finer than the pitch found on the lead-screws of ordinary engine lathes. However, if the movement were 0.4 + 0.8 � 2 = 2 inches, the lock-nuts could be re-engaged regardless of the number of threads per inch on the lead-screw. The rule then, is as follows: _Divide the lead of the thread by 2 for a double thread, 3 for a triple thread, 4 for a quadruple thread, etc., thus obtaining the pitch; then add the pitch to any multiple of the lead, which will give a movement, in inches, that will enable the lock-nuts to be re-engaged with the lead-screw._ Whenever the number obtained by this rule is a whole number, obviously, the movement can be obtained with a lead-screw of any pitch. If the number is fractional, the number of threads per inch on the lead-screw must be divisible by the denominator of the fraction. To illustrate the application of the foregoing rule, suppose a quadruple thread is to be cut having 1-1/2 single threads per inch (which would be the number the lathe would be geared to cut). Then the lead of the thread = 1 ÷ 1-1/2 = 0.6666 inch and the pitch = 0.6666 ÷ 4 = 0.1666 inch; adding the pitch to twice the lead we have 0.1666 + 2 � 0.6666 = 1.499 inch. Hence, if the carriage is moved 1-1/2 inch (which will require a lead-screw having an even number of threads per inch), the tool will be located accurately enough for practical purposes. When the tool is set in this way, if it does not clear the end of the part being threaded, the lathe can be turned backward to place the tool in the proper position. [Illustration: Fig. 13. Indexing Faceplate used for Multiple Thread Cutting] The foregoing rule, as applied to triple threads or those of a higher number, does not always give the only distance that the carriage can be moved. To illustrate, in the preceding example the carriage movement could be equal to 0.499, or what is practically one-half inch, instead of 1-1/2 inch, and the tool would be properly located. The rule, however, has the merit of simplicity and can be used in most cases. Special faceplates are sometimes used for multiple thread cutting, that enable work to be easily and accurately indexed. One of these is illustrated in Fig. 13; it consists of two parts _A_ and _B_, part _A_ being free to rotate in relation to _B_ when bolts _C_ are loosened. The driving pin for the lathe dog is attached to plate _A_. When one groove of a multiple thread is finished, bolts _C_ are loosened and plate _A_ is turned around an amount corresponding to the type of thread being cut. The periphery of plate _A_ is graduated in degrees, as shown, and for a double thread it would be turned one-half revolution or 180 degrees, for a triple thread, 120 degrees, etc. This is a very good arrangement where multiple thread cutting is done frequently. [Illustration: Fig. 14. Correct and Incorrect Positions of Tool for Taper Thread Cutting] =Taper Threading.=--When a taper thread is to be cut, the tool should be set square with axis _a--a_ as at _A_, Fig. 14, and not by the tapering surface as at _B_. If there is a cylindrical part, the tool can be set as indicated by the dotted lines. All taper threads should be cut by the use of taper attachments. If the tailstock is set over to get the required taper, and an ordinary bent-tail dog is used for driving, the curve of the thread will not be true, or in other words the thread will not advance at a uniform rate; this is referred to by machinists as a "drunken thread." This error in the thread is due to the angularity between the driving dog and the faceplate, which causes the work to be rotated at a varying velocity. The pitch of a taper thread that is cut with the tailstock set over will also be slightly finer than the pitch for which the lathe is geared. The amount of these errors depends upon the angle of the taper and the distance that the center must be offset. =Internal Threading.=--Internal threading, or cutting threads in holes, is an operation performed on work held in the chuck or on a faceplate, as for boring. The tool used is similar to a boring tool except that the working end is shaped to conform to the thread to be cut. The method of procedure, when cutting an internal thread, is similar to that for outside work, as far as handling the lathe is concerned. The hole to be threaded is first bored to the root diameter _D_, Fig. 15, of the screw that is to fit into it. The tool-point (of a tool for a U. S. standard or V-thread) is then set square by holding a gage _G_ against the true side of the work and adjusting the point to fit the notch in the gage as shown. The view to the right shows the tool taking the first cut. [Illustration: Fig. 15. Method of setting and using Inside Thread Tool] Very often the size of a threaded hole can be tested by using as a gage the threaded part that is to fit into it. When making such a test, the tool is, of course, moved back out of the way. It is rather difficult to cut an accurate thread in a small hole, especially when the hole is quite deep, owing to the flexibility of the tool; for this reason threads are sometimes cut slightly under size with the tool, after which a tap with its shank end held straight by the tailstock center is run through the hole. In such a case, the tap should be calipered and the thread made just small enough with the tool to give the tap a light cut. Small square-threaded holes are often finished in this way, and if a number of pieces are to be threaded, the use of a tap makes the holes uniform in size. =Stop for Thread Tools.=--When cutting a thread, it is rather difficult to feed in the tool just the right amount for each successive cut, because the tool is moved in before it feeds up to the work. A stop is sometimes used for threading which overcomes this difficulty. This stop consists of a screw _S_, Fig. 16, which enters the tool slide and passes through a block _B_ clamped in front of the slide. The hole in the block through which the stop-screw passes is not threaded, but is large enough to permit the screw to move freely. When cutting a thread, the tool is set for the first cut and the screw is adjusted until the head is against the fixed block. After taking the first cut, the stop-screw is backed out, say one-half revolution, which allows the tool to be fed in far enough for a second cut. If this cut is about right for depth, the screw is again turned about one-half revolution for the next cut and this is continued for each successive cut until the thread is finished. By using a stop of this kind, there is no danger of feeding the tool in too far as is often done when the tool is set by guess. If this form of stop is used for internal threading, the screw, instead of passing through the fixed block, is placed in the slide so that the end or head will come against the stop _B_. This change is made because the tool is fed outward when cutting an internal thread. [Illustration: Fig. 16. Cross-slide equipped with Stop for Regulating Depth of Cut when Threading] =The Acme Standard Thread.=--The Acme thread is often used, at the present time, in place of a square thread. The angle between the sides of the Acme thread is 29 degrees (see Fig. 21) and the depth is made equal to one-half the pitch plus 0.010 inch to provide clearance and insure a bearing upon the sides. The thread tool is ordinarily ground to fit a gage having notches representing different pitches. An improved form of Acme thread gage is shown in Fig. 17. The tool point is first ground to the correct angle by fitting it to the 29-degree notch in the end of the gage, as at _A_. The end is then ground to the proper width for the pitch to be cut, by testing it, as at _B_. The numbers opposite the shallow notches for gaging the width represent the number of threads per inch. With this particular gage, the tool can be set square by placing edge _D_ against the turned surface to be threaded, and adjusting the tool until the end is in line with the gage, as at _C_. By placing the tool in this position, the angle between the side and the end can also be tested. [Illustration: Fig. 17. Gage for grinding and setting Acme Thread Tools] In case it should be necessary to measure the end width of an Acme thread tool, for a pitch not on the regular gage, this can be done by using a vernier gear-tooth caliper, as indicated in Fig. 18. If we assume that the caliper jaws bear on the sides of the tool at a distance _A_ from the top, equal to 1/4 inch, then the width of the tool point equals the caliper reading (as shown by the horizontal scale) minus 0.1293 inch. For example, if the caliper reading was 0.315 inch, the width at the point would equal 0.315 - 0.1293 = 0.1857 inch, assuming that the sides were ground to the standard angle of 29 degrees. The constant to be subtracted from the caliper reading equals 2 _A_ tan 14° 30' or, in this case, 2 � 0.25 � 0.2586 = 0.1293. [Illustration: Fig. 18. Measuring Width of Acme Thread Tool with Vernier Gear-tooth Caliper] =The Whitworth Thread.=--The Whitworth (or British Standard Whitworth) thread, which is used principally in Great Britain, has an included angle of 55 degrees, and the threads are rounded at the top and at the root, as shown in Fig. 23. The shape of the tool used for cutting this thread is also shown in this illustration. The end is rounded to form the fillet at the root of the thread, and the round corners on the sides give the top of the thread the required curvature. Every pitch requires a different tool, and the cutting end is given the curved form by milling or hobbing. The hob used for this purpose is accurately threaded to correspond with the pitch for which the tool is required, and then it is fluted to form cutting edges, and is hardened. The hob is then used like a milling cutter for forming the end of the thread tool. The tool is sharpened by grinding on the top. The method of cutting a Whitworth thread is, of course, similar to that followed for a U. S. standard or V-thread, in that the tool is set square with the unthreaded blank and at the same height as the lathe centers, in order to secure a thread of the proper form. Care should be taken to turn the blank to the right diameter so that the top of the thread will be fully rounded when the screw is the required size. [Illustration: Fig. 19. United States Standard Thread] [Illustration: Fig. 20. Standard Sharp V-thread] [Illustration: Fig. 21. Acme Standard Thread] [Illustration: Fig. 22. Square Thread] [Illustration: Fig. 23. Whitworth Standard Thread] [Illustration: Fig. 24. Standard Worm Thread] =Worm Threads.=--The standard worm thread has an angle of 29 degrees between the sides, the same as an Acme thread, but the depth of a worm thread and the width of the flat at the top and bottom differ from the Acme standard, as will be seen by comparing Figs. 21 and 24. The whole depth of the thread equals the linear pitch multiplied by 0.6866, and the width of the thread tool at the end equals the linear pitch multiplied by 0.31. Gages notched for threads of different pitch are ordinarily used when grinding worm thread tools. When it is necessary to cut multiple-threaded worms of large lead in an ordinary lathe, difficulty is sometimes experienced because the lead-screw must be geared to run much faster than the spindle, thus imposing excessive strains on the gearing. This difficulty is sometimes overcome by mounting a belt pulley on the lead-screw, beside the change gear, and connecting it to the countershaft by a belt; the spindle is then driven through the change gearing from the lead-screw, instead of _vice versa_. =Coarse Threading Attachment.=--To avoid the difficulties connected with cutting threads of large lead, some lathes are equipped with a coarse screw-cutting attachment. The arrangement of this attachment, as made by the Bradford Machine Tool Co., is as follows: On the usual reversing shaft, and inside of the headstock, there is a sliding double gear, so arranged as to be engaged with either the usual gear on the spindle, or with a small pinion at the end of the cone. The gears are so proportioned that the ratio of the two engagements is as 10 to 1; that is, when engaged with the cone gear (the back-gears being thrown in) the mating gear will make ten revolutions to one of the spindle, so that when the lathe is ordinarily geared to cut one thread per inch, it will, when driven by the cone pinion, cut one thread in ten inches. This construction dispenses with the extra strain on the reverse gears due to moving the carriage at the rapid rate that would be necessary for such a large lead, when not using an attachment. These attachments are not only extensively used for the cutting of coarse screws but for cutting oil grooves on cylindrical parts. When cutting a thread of large lead or "steep pitch," the top of the thread tool should be ground so that it is at right angles to the thread; then the thread groove will be cut to the same width as the tool. =Testing the Size of a Thread.=--When the thread tool has been fed in far enough to form a complete thread, the screw is then tested for size. If we assume that a bolt is being threaded for a standard nut, it would be removed from the lathe and the test made by screwing a nut on the end. If the thread were too large, the nut might screw on very tightly or not at all; in either case, the work would again be placed in the lathe and a light cut taken over it to reduce the thread to the proper size. When replacing a threaded part between the centers, it should be put back in the original position, that is, with the "tail" of the driving dog in the same slot of the faceplate it previously occupied. [Illustration: Fig. 25. Testing Diameter of Thread with Calipers and Micrometer] As it is difficult to tell just when a thread is cut to the exact size, special thread calipers having wedge-shaped ends are sometimes used for measuring the diameter of a V-thread or a U. S. standard thread, at the bottom of the grooves or the root diameter, as shown at _A_ in Fig. 25. These calipers can be set from a tap corresponding to the size of the thread being cut, or from a previously threaded piece of the right size. =The Thread Micrometer.=--Another form of caliper for testing threads is shown at _B_. This is one of the micrometer type and is intended for very accurate work. The spindle of this micrometer has a conical end and the "anvil" is V-shaped, and these ends bear on the sides of the thread or the surfaces which form the bearing when the screw is inserted in a nut or threaded hole. The cone-shaped point is slightly rounded so that it will not bear in the bottom of the thread. There is also sufficient clearance at the bottom of the V-shaped anvil to prevent it from bearing on top of the thread. The diameter as indicated by this micrometer is the "pitch diameter" of the thread and is equal to the outside diameter minus the depth of one thread. This depth may be determined as follows: Depth of a V-thread = 0.866 ÷ No. of threads per inch; Depth of a U. S. standard thread = 0.6495 ÷ No. of threads per inch; Depth of Whitworth thread = 0.6403 ÷ No. of threads per inch. The movable point measures all pitches, but the fixed anvil is limited in its capacity, for if made large enough to measure a thread of, say, 1/4-inch pitch, it would be too wide at the top to measure a thread of 1/24-inch pitch, hence each caliper is limited in the range of threads that the anvil can measure. When measuring the "angle diameter" of a thread, the micrometer should be passed back and forth across the thread, in order to make sure that the largest dimension or the actual diameter is being measured. If the micrometer is placed over what seems to be the center of the screw and the reading is taken by simply adjusting in the anvil or point against the thread, without moving the micrometer back and forth across it, an incorrect reading may be obtained. If standard threaded reference gages are available, the size of the thread being cut can be tested by comparing it with the gage. Micrometers having small spherical measuring ends (see sketch _A_, Fig. 26) are sometimes used for this purpose. The ball points are small enough to bear against the sides of the thread and the diameter, as compared with the reference gage, can be determined with great accuracy. [Illustration: Fig. 26. (A) Testing Size of Thread with Ball-point Micrometer. (B) Testing Size of V-thread by the Three-wire System. (C) Testing the Size of a U. S. Standard Thread] =Three-wire System of Measuring Threads.=--A method of measuring threads by using an ordinary micrometer and three wires of equal diameter is illustrated at _B_ and _C_, Fig. 26. Two wires are placed between the threads on one side and one on the opposite side of the screw. The dimension _M_ over the wires is then measured with an ordinary micrometer. When the thread is cut to a standard size, the dimension _M_ for different threads is as follows: For a U. S. standard thread: _m_ = _d_ - 1.5155_p_ + 3_w_ For a sharp V-thread: _m_ = _d_ - 1.732_p_ + 3_w_ For a Whitworth standard thread: _m_ = _d_ - 1.6008_p_ + 3.1657_w_ In these formulas, _d_ = standard outside diameter of screw; _m_ = measurement over wires; _w_ = diameter of wires; _p_ = pitch of thread = 1 ÷ number of threads per inch. To illustrate the use of the formula for the U. S. standard thread, let us assume that a screw having 6 threads per inch (1/6-inch pitch) is to be cut to a diameter of 1-1/2 inch, and that wires 0.140 inch diameter are to be used in conjunction with a micrometer for measurement. Then the micrometer reading _m_ should be 1-1/2 - 1.5155 � 1/6 + 3 � 0.140 = 1.6674 inch If the micrometer reading were 1.670 inch, it would indicate that the pitch diameter of the screw was too large, the error being equal to difference between 1.667 and the actual reading. [Illustration: Fig. 27. Rivett-Dock Circular Threading Tool in Working Position] =Rivett-Dock Threading Tool.=--A special form of thread tool, which overcomes a number of disadvantages common to an ordinary single-point thread tool, is shown in Fig. 27. This tool has a circular-shaped cutter _C_, having ten teeth around its circumference, which, beginning with tooth No. 1, gradually increase in height, cutter No. 2 being higher than No. 1, etc. This cutter is mounted on a slide _S_, that is fitted to the frame _F_, and can be moved in or out by lever _L_. The hub of this lever has an eccentric stud which moves slide _S_ and locks it when in the forward or cutting position. The action of the lever in moving the slide engages the cutter with pawl _P_, thus rotating the cutter one tooth at a time and presenting a different tooth to the work for each movement of the lever. When the slide is moved forward, the heel or underside of the tooth which is in the working position rests on a stop that takes the thrust of the cut. When the tool is in use, it is mounted on the tool-block of the lathe as shown in the illustration. The cutter is set for height by placing a tooth in the working position and setting the top level with the lathe center. The cutter is also set square with the work by using an ordinary square, and it is tilted slightly from the vertical to correspond with the angle of the thread to be cut, by adjusting frame _F_. At first a light cut is taken with lever _L_ moved forward and tooth No. 1 on the stop. After this cut is completed, the lever is reversed which rotates the cutter one tooth, and the return movement places tooth No. 2 in the working position. This operation is repeated until the tenth tooth finishes the thread. It is often necessary, when using a single-point thread tool, to re-sharpen it before taking the finishing cut, but with a circular tool this is not necessary, for by using the different teeth successively, the last tooth, which only takes finishing cuts, is kept in good condition. =Cutting Screws to Compensate for Shrinkage.=--Some tool steels are liable to shrink more or less when they are hardened; consequently if a very accurate hardened screw is required, it is sometimes cut so that the pitch is slightly greater than standard, to compensate for the shrinkage due to the hardening operation. As the amount of contraction incident to hardening is very little, it is not practicable to use change gears that will give the exact pitch required. A well-known method of obtaining this increase of pitch is by the use of a taper attachment. For example, suppose a tap having 8 threads per inch is to be threaded, and, owing to the contraction of the steel, the pitch must be 0.12502 inch instead of 0.125 inch. The lathe is geared to cut 8 threads per inch or 0.125 inch pitch, and then the taper attachment is set to an angle _a_, Fig. 28, the cosine of which equals 0.125/0.12502; that is, the cosine of angle _a_ equals _the pitch required after hardening_, divided by the _pitch necessary to compensate for shrinkage_. The angle is then found by referring to a table of cosines. The tap blank is also set to the same angle a by adjusting the tailstock center, thus locating the axis of the work parallel with the slide of the taper attachment. When the carriage moves a distance _x_, the tool point will have moved a greater distance _y_ along the work, the difference between x and y depending upon angle _a_; hence the tool will cut a thread of slightly greater pitch than the lathe is geared to cut. To illustrate by using the preceding example, cosine of angle _a_ = 0.125/0.12502 = 0.99984. By referring to a table of cosines, we find that 0.99984 is the cosine of 1 degree, approximately; hence, the taper attachment slide and the work should be set to this angle. (The angle _a_ in Fig. 28 has been exaggerated in order to more clearly illustrate the principle.) [Illustration: Fig. 28. Diagram Illustrating Method of Cutting a Thread to Compensate for the Error in Pitch due to Shrinkage in Hardening] As is well known, it is objectionable to cut a thread with the tailstock center offset, because the work is not rotated at a uniform velocity, owing to the fact that the driving dog is at an angle with the faceplate. For a small angle such as 1 degree, however, the error resulting from this cause would be very small. If a thread having a pitch slightly less than standard is needed to fit a threaded part which has contracted in hardening, the taper attachment can also be used provided the lathe is equipped with special gears to cut a little less than the required pitch. Suppose a screw having a pitch of 0.198 inch is required to fit the thread of a nut the pitch of which has been reduced from 0.200 inch to 0.198 inch. If gears having 83 and 84 teeth are available, these can be inserted in a compound train, so as to reduce the 0.200 inch pitch that would be obtained with the regular gearing, to 83/84 of 0.200 or 0.19762 inch. This pitch, which is less than the 0.198 inch pitch required, is then increased by using the taper attachment as previously described. (This method was described by Mr. G. H. Gardner in MACHINERY, February, 1914.) =Calculating Change Gears for Thread Cutting.=--As previously mentioned, the change gears for cutting threads of various pitches are shown by a table or "index plate" attached to the lathe. The proper gears to be used can be calculated, but the use of the table saves time and tends to avoid mistakes. Every machinist, however, should know how to determine the size of gears used for cutting any number of threads to the inch. Before referring to any rules, let us first consider why a lathe cuts a certain number of threads to the inch and how this number is changed by the use of different gears. As the carriage _C_ and the tool are moved by the lead-screw _S_ (see Fig. 2), which is geared to the spindle, the number of threads to the inch that are cut depends, in every case, upon the number of turns the work makes while the lead-screw is moving the carriage one inch. If the lead-screw has six threads per inch, it will make six revolutions while the carriage and the thread tool travel one inch along the piece to be threaded. Now if the change gears _a_ and _c_ (see also sketch _A_, Fig. 29) are so proportioned that the spindle makes the same number of revolutions as the lead-screw, in a given time, it is evident that the tool will cut six threads per inch. If the spindle revolved twice as fast as the lead-screw, it would make twelve turns while the tool moved one inch, and, consequently, twelve threads per inch would be cut; but to get this difference in speeds it is necessary to use a combination of gearing that will cause the lead-screw to revolve once while the lathe spindle and work make two revolutions. [Illustration: Fig. 29. (A) Lathe with Simple Gearing for Thread Cutting. (B) Compound Geared Lathe] Suppose that nine threads to the inch are to be cut and the lead-screw has six threads per inch. In this case the work must make nine revolutions while the lead-screw makes six and causes the carriage and thread tool to move one inch, or in other words, one revolution of the lead-screw corresponds to one and one-half revolution of the spindle; therefore, if the lead-screw gear _c_ has 36 teeth, the gear _a_ on the spindle stud should have 24 teeth. The spindle will then revolve one and one-half times faster than the lead-screw, provided the stud rotates at the same rate of speed as the main lathe spindle. The number of teeth in the change gears that is required for a certain pitch can be found by multiplying the number of threads per inch of the lead-screw, and the number of threads per inch to be cut, by the same trial multiplier. The formula which expresses the relation between threads per inch of lead-screw, threads per inch to be cut, and the number of teeth in the change gears, is as follows: threads per inch of lead-screw teeth in gear on spindle stud ------------------------------ = ----------------------------- threads per inch to be cut teeth in gear on lead-screw Applying this to the example given, we have 6/9 = 24/36. The values of 36 and 24 are obtained by multiplying 6 and 9, respectively, by 4, which, of course, does not change the proportion. Any other number could be used as a multiplier, and if gears having 24 and 36 teeth were not available, this might be necessary. For example, if there were no gears of this size, some other multiplier as 5 or 6 might be used. Suppose the number of teeth in the change gears supplied with the lathe are 24, 28, 32, 36, etc., increasing by four teeth up to 100, and assume that the lead-screw has 6 threads per inch and that 10 threads per inch are to be cut. Then, 6 6 � 4 24 -- = ------ = -- 10 10 � 4 40 By multiplying both numerator and denominator by 4, we obtain two available gears having 24 and 40 teeth, respectively. The 24-tooth gear goes on the spindle stud and, the 40-tooth gear on the lead-screw. The number of teeth in the intermediate or "idler" gear _b_, which connects the stud and lead-screw gears, is not considered as it does not affect the ratios between gears _a_ and _c_, but is used simply to transmit motion from one gear to the other. We have assumed in the foregoing that the spindle stud (on which gear _a_ is mounted) and the main spindle of the lathe are geared in the ratio of one to one and make the same number of revolutions. In some lathes, however, these two members do not rotate at the same speed, so that if equal gears were placed on the lead-screw and spindle stud, the spindle would not make the same number of revolutions as the lead-screw. In that case if the actual number of threads per inch in the lead-screw were used when calculating the change gears, the result would be incorrect; hence, to avoid mistakes, the following general rule should be used as it gives the correct result, regardless of the ratios of the gears which connect the spindle and spindle stud: _Rule.--First find the number of threads per inch that is cut when gears of the same size are placed on the lead-screw and spindle, either by actual trial or by referring to the index plate. Then place this number as the numerator of a fraction and the number of threads per inch to be cut, as the denominator; multiply both numerator and denominator by some trial number, until numbers are obtained which correspond to numbers of teeth in gears that are available._ The product of the trial number and the numerator (or "lathe screw constant") represents the gear _a_ for the spindle stud, and the product of the trial number and the denominator, the gear for the lead-screw. =Lathes with Compound Gearing.=--When gearing is arranged as shown at _A_, Fig. 29, it is referred to as simple gearing, but sometimes it is necessary to introduce two gears between the stud and screw as at _B_, which is termed compound gearing. The method of figuring compound gearing is practically the same as that for simple gearing. To find the change gears used in compound gearing, place the "screw constant" obtained by the foregoing rule, as the numerator, and the number of threads per inch to be cut as the denominator of a fraction; resolve both numerator and denominator into two factors each, and multiply each "pair" of factors by the same number, until values are obtained representing numbers of teeth in available change gears. (One factor in the numerator and one in the denominator make a "pair" of factors.) Suppose the lathe cuts 6 threads per inch when gears of equal size are used, and that the number of teeth in the gears available are 30, 35, 40 and so on, increasing by 5 up to 100. If 24 threads per inch are to be cut, the screw constant 6 is placed in the numerator and 24 in the denominator. The numerator and denominator are then divided into factors and each pair of factors is multiplied by the same number to find the gears, thus: 6 2 � 3 (2 � 20) � (3 � 10) 40 � 30 -- = ----- = ------------------- = ------- 24 4 � 6 (4 � 20) � (6 � 10) 80 � 60 The last four numbers indicate the gears which should be used. The upper two having 40 and 30 teeth are the _driving_ gears and the lower two having 80 and 60 teeth are the _driven_ gears. The driving gears are gear _a_ on the spindle stud and gear _c_ on the intermediate stud, meshing with the lead-screw gear, and the driven gears are gears _b_ and _d_. It makes no difference which of the driving gears is placed on the spindle stud, or which of the driven is placed on the lead-screw. =Fractional Threads.=--Sometimes the lead of a thread is given as a fraction of an inch instead of stating the number of threads per inch. For example, a thread may be required to be cut, having 3/8-inch lead. The expression "3/8-inch lead" should first be transformed to "number of threads per inch." The number of threads per inch (the thread being single) equals: 1 3 8 --- = 1 ÷ - = - = 2-2/3 3/8 8 3 To find the change gears to cut 2-2/3 threads per inch in a lathe having a screw constant of 8 and change gears varying from 24 to 100 teeth, increasing by 4, proceed as follows: 8 2 � 4 (2 � 36) � (4 � 24) 72 � 96 ----- = --------- = ----------------------- = ------- 2-2/3 1 � 2-2/3 (1 � 36) � (2-2/3 � 24) 36 � 64 As another illustration, suppose we are to cut 1-3/4 thread per inch on a lathe having a screw constant of 8, and that the gears have 24, 28, 32, 36, 40 teeth, etc., increasing by four up to one hundred. Following the rule: 8 2 � 4 (2 � 36) � (4 � 16) 72 � 64 ----- = --------- = ----------------------- = ------- 1-3/4 1 � 1-3/4 (1 � 36) � (1-3/4 � 16) 36 � 28 The gears having 72 and 64 teeth are the _driving_ gears, and those with 36 and 28 teeth are the _driven_ gears. =Change Gears for Metric Pitches.=--When screws are cut in accordance with the metric system, it is the usual practice to give the lead of the thread in millimeters, instead of the number of threads per unit of measurement. To find the change gears for cutting metric threads, when using a lathe having an English lead-screw, first determine the number of threads per inch corresponding to the given lead in millimeters. Suppose a thread of 3 millimeters lead is to be cut in a lathe having an English lead-screw and a screw constant of 6. As there are 25.4 millimeters per inch, the number of threads per inch will equal 25.4 ÷ 3. Place the screw constant as the numerator, and the number of threads per inch to be cut as the denominator: 6 25.4 6 � 3 ------- = 6 ÷ ---- = ----- 25.4 3 25.4 ---- 3 The numerator and denominator of this fractional expression of the change-gear ratio are next multiplied by some trial number to determine the size of the gears. The first whole number by which 25.4 can be multiplied so as to get a whole number as the result is 5. Thus, 25.4 � 5 = 127; hence, one gear having 127 teeth is always used when cutting metric threads with an English lead-screw. The other gear required in this case has 90 teeth. Thus: 6 � 3 � 5 90 --------- = --- 25.4 � 5 127 Therefore, the following rule can be used to find the change gears for cutting metric pitches with an English lead-screw: _Rule.--Place the lathe screw constant multiplied by the lead of the required thread in millimeters multiplied by 5, as the numerator of the fraction, and 127 as the denominator. The product of the numbers in the numerator equals the number of teeth for the spindle-stud gear, and 127 is the number of teeth for the lead-screw gear._ If the lathe has a metric pitch lead-screw, and a screw having a given number of threads per inch is to be cut, first find the "metric screw constant" of the lathe or the lead of thread in millimeters that would be cut with change gears of equal size on the lead-screw and spindle stud; then the method of determining the change gears is simply the reverse of the one already explained for cutting a metric thread with an English lead-screw. _Rule.--To find the change gears for cutting English threads with a metric lead-screw, place 127 in the numerator and the threads per inch to be cut, multiplied by the metric screw constant multiplied by 5, in the denominator; 127 is the number of teeth on the spindle-stud gear and the product of the numbers in the denominator equals the number of teeth in the lead-screw gear._ =Quick Change-gear Type of Lathe.=--A type of lathe that is much used at the present time is shown in Fig. 30. This is known as the quick change-gear type, because it has a system of gearing which makes it unnecessary to remove the change gears and replace them with different sizes for cutting threads of various pitches. Changes of feed are also obtained by the same mechanism, but the feeding movement is transmitted to the carriage by the rod _R_, whereas the screw _S_{1}_ is used for screw cutting. As previously explained, the idea of using the screw exclusively for threading is to prevent it from being worn excessively, as it would be if continually used in place of rod _R_, for feeding the carriage when turning. [Illustration: Fig. 30. Lathe having Quick Change-gear Mechanism] [Illustration: Fig. 31. End and Side Views of Quick Change-gear Mechanism] The general construction of this quick change gear mechanism and the way the changes are made for cutting threads of different pitch, will be explained in connection with Figs. 30, 31 and 32, which are marked with the same reference letters for corresponding parts. Referring to Fig. 30, the movement is transmitted from gear _s_ on the spindle stud through idler gear _I_, which can be moved sidewise to mesh with either of the three gears _a_, _b_ or _c_, Fig. 31. This cone of three gears engages gears _d_, _e_ and _f_, any one of which can be locked with shaft _T_ (Fig. 32) by changing the position of knob _K_. On shaft _T_ there is a gear _S_ which can be moved along the shaft by hand lever _L_ and, owing to the spline or key _t_, both the sliding gear and shaft rotate together. Shaft _T_, carrying gears _d_, _e_ and _f_ and the sliding gear _S_, is mounted in a yoke _Y_, which can be turned about shaft _N_, thus making it possible to lower sliding gear _S_ into mesh with any one of a cone of eight gears _C_, Fig. 31. The shaft on which the eight gears are mounted has at the end a small gear _m_ meshing with gear _n_ on the feed-rod, and the latter, in turn, drives the lead-screw, unless gear _o_ is shifted to the right out of engagement, which is its position except when cutting threads. [Illustration: Fig. 32. Sectional Views of Quick Change-gear Mechanism] With this mechanism, eight changes for different threads or feeds are obtained by simply placing gear _S_ into mesh with the various sized gears in cone _C_. As the speed of shaft _T_ depends on which of the three gears _d_, _e_ and _f_ are locked to it, the eight changes are tripled by changing the position of knob _K_, making twenty-four. Now by shifting idler gear _I_, three speed changes may be obtained for gears _a_, _b_ and _c_, which rotate together, so that the twenty-four changes are also tripled, giving a total of seventy-two variations without removing any gears, and if a different sized gear _s_ were placed on the spindle stud, an entirely different range could be obtained, but such a change would rarely be necessary. As shown in Fig. 30, there are eight hardened steel buttons _B_, or one for each gear of the cone _C_, placed at different heights in the casing. When lever _L_ is shifted sidewise to change the position of sliding gear _S_, it is lowered onto one of these buttons (which enters a pocket on the under side) and in this way gear _S_ is brought into proper mesh with any gear of the cone _C_. To shift lever _L_, the handle is pulled outward against the tension of spring _r_ (Fig. 32), which disengages latch _l_ and enables the lever to be lifted clear of the button; yoke _Y_ is then raised or lowered, as the case may be, and lever _L_ with the sliding gear is shifted laterally to the required position. [Illustration: Fig. 33. Index Plate showing Position of Control Levers for Cutting Threads of Different Pitch] The position of lever _L_ and knob _K_ for cutting threads of different pitches is shown by an index plate or table attached to the lathe and arranged as shown in Fig. 33. The upper section _a_ of this table shows the different numbers of threads to the inch that can be obtained when idler gear _I_ is in the position shown by the diagram _A_. Section _b_ gives the changes when the idler gear is moved, as shown at _B_, and, similarly, section _c_ gives the changes for position _C_ of the idler. The horizontal row of figures from 1 to 8 below the word "stops" represents the eight positions for lever _L_, which has a plate _p_ (Fig. 30) just beneath it with corresponding numbers, and the column to the left shows whether knob _K_ should be out, in a central position, or in. In order to find what the position of lever _L_ and knob _K_ should be for cutting any given number of threads to the inch, find what "stop" number is directly above the number of threads to be cut, which will indicate the location of lever _L_, and also what position should be occupied by knob _K_, as shown in the column to the left. For example, suppose the lathe is to be geared for cutting eight threads to the inch. By referring to section a we see that lever _L_ should be in position 4 and knob _K_ in the center, provided the idler gear _I_ were in position _A_, as it would be ordinarily, because all standard numbers of threads per inch (U. S. standard) from 1/4 inch up to and including 4 inches in diameter can be cut with the idler gear in that position. As another illustration, suppose we want to cut twenty-eight threads per inch. This is listed in section _c_, which shows that lever _L_ must be placed in position 3 with knob _K_ pushed in and the idler gear shifted to the left as at _C_. The simplicity of this method as compared with the time-consuming operation of removing and changing gears is apparent. The diagram _D_ to the right shows an arrangement of gearing for cutting nineteen threads per inch. A 20-tooth gear is placed on the spindle stud (in place of the regular one having 16 teeth) and one with 95 teeth on the lead-screw, thus driving the latter direct as with ordinary change gears. Of course it will be understood that the arrangement of a quick change-gear mechanism varies somewhat on lathes of different make. CHAPTER V TURRET LATHE PRACTICE Turret lathes are adapted for turning duplicate parts in quantity. The characteristic feature of a turret lathe is the turret which is mounted upon a carriage and contains the tools which are successively brought into the working position by indexing or rotating the turret. In many instances, all the tools required can be held in the turret, although it is often necessary to use other tools, held on a cross-slide, for cutting off the finished part, facing a radial surface, knurling, or for some other operation. After a turret lathe is equipped with the tools needed for machining a certain part, it produces the finished work much more rapidly than would be possible by using an ordinary engine lathe, principally because each tool is carefully set for turning or boring to whatever size is required and the turret makes it possible to quickly place any tool in the working position. Turret lathes also have systems of stops or gages for controlling the travel of the turret carriage and cross-slide, in order to regulate the depth of a bored hole, the length of a cylindrical part or its diameter; hence, turning machines of this type are much more efficient than ordinary lathes for turning duplicate parts, unless the quantity is small, in which case, the advantage of the turret lathe might be much more than offset by the cost of the special tool equipment and the time required for "setting up" the machine. (See "Selecting Type of Turning Machine.") [Illustration: Fig. 1. Bardons & Oliver Turret Lathe of Motor-driven Geared-head Type] =General Description of a Turret Lathe.=--The turret lathe shown in Fig. 1 has a hexagonal shaped turret _A_ with a hole in each side in which the tools are held. This turret is mounted on a slide _B_ which is carried by a saddle _C_ that can be moved along the bed to locate the turret slide with reference to the length of the tools in the turret and the room required for indexing. The turret slide can be moved longitudinally by turning the pilot wheel or turnstile _D_, or it can be fed by power. Ordinarily, the hand adjustment is used for quickly moving the carriage when the tools are not cutting, although sometimes the hand feed is preferable to a power feed when the tools are at work, especially if the cuts are short. After a turret tool has finished its cut, the turnstile is used to return the slide to the starting point, and at the end of this backward movement the turret is automatically indexed or turned one-sixth of a revolution, thus bringing the next tool into the working position. The turret is accurately located in each of its six positions by a lock bolt which engages notches formed in a large index ring at the turret base. A binder lever _E_ at the top of the turret stud is used to clamp the turret rigidly to the slide when the tools are cutting. The forward movement of the slide for each position of the turret is controlled by stops at _F_, which are set to suit the work being turned. When parts are being turned from bar stock, the latter passes through the hollow spindle of the headstock and extends just far enough beyond the end of the spindle to permit turning one of the parts. The bar is held while the turning tools are at work, by a chuck of the collet type at _G_. This chuck is opened or closed around the bar by turning handwheel _H_. After a finished part has been cut off by a tool held in cross-slide _J_, the chuck is released and further movement of wheel _H_ causes ratchet feed dog _K_, and the bar which passes through it, to be drawn forward. This forward movement is continued until the end of the bar comes against a stop gage held in one of the turret holes, to insure feeding the bar out just the right amount for turning the next piece. On some turret lathes, the lever which operates the chuck also controls a power feed for the bar stock, the latter being pushed through the spindle against the stop. The machine illustrated has a power feed for the cross-slide as well as for the turret. The motion is obtained from the same shaft _L_ which actuates the turret slide, but the feed changes are independent. The cross-slide feed changes are varied by levers _M_ and those for the turret by levers _N_. For many turret lathe operations, such as turning castings, etc., a jawed chuck is screwed onto the spindle and the work is held the same as when a chuck is used on an engine lathe. Sometimes chucks are used having special jaws for holding castings of irregular shape, or special work-holding fixtures which are bolted to the faceplate. The small handle at _O_ is for moving the cross-slide along the bed when this is necessary in order to feed a tool sidewise. This particular machine is driven by a motor at the rear of the headstock, connection being made with the spindle through gearing. The necessary speed changes are obtained both by varying the speed of the motor and by shifting gears in the headstock. The motor is controlled by the turnstile _P_ and the gears are shifted by the vertical levers shown. While many of the features referred to are common to turret lathes in general, it will be understood that the details such as the control levers, arrangement of stops, etc., vary on turret lathes of different make. [Illustration: Figs. 2 and 3. Diagrams showing Turret Lathe Tool Equipment for Machining Automobile Hub Casting] =Example of Turret Lathe Work.=--The diagrams Figs. 2 and 3 show a turret lathe operation which is typical in many respects. The part to be turned is a hub casting for an automobile and it is machined in two series of operations. The first series is shown by the plan view, Fig. 2. The casting _A_ is held in a three-jaw chuck _B_. Tool No. 1 on the cross-slide is equipped with two cutters and rough faces the flange and end, while the inner and outer surfaces of the cylindrical part are rough bored and turned by combination boring and turning tool No. 2. This tool has, in addition to a regular boring-bar, a bracket or tool-holder which projects above the work and carries cutters that operate on the top surface. Tools Nos. 3 and 4 next come into action, No. 3 finishing the surfaces roughed out by No. 2, and No. 4 finish-facing the flange and end of the hub. The detailed side view of Tool No. 3 (which is practically the same as No. 2), shows the arrangement of the cutters _C_ and _D_, one of which turns the cylindrical surface and the other bevels the end of the hub. The hole in the hub is next finished by tool No. 5 which is a stepped reamer that machines the bore and counterbore to the required size within very close limits. The surfaces machined by the different tools referred to are indicated by the sectional view _E_ of the hub, which shows by the numbers what tools are used on each surface. For the second series of operations, the position of the hub is reversed and it is held in a spring or collet type of chuck as shown by the plan view Fig. 3. The finished cylindrical end of the hub is inserted in the split collet _F_ which is drawn back into the tapering collet ring by rod _G_ (operated by turnstile _H_, Fig. 1) thus closing the collet tightly around the casting. The first operation is that of facing the side of the flange and end of the hub with tool No. 6 on the cross-slide, which is shown in the working position. A broad cutter _H_ is used for facing the flange and finishing the large fillet, and the end is faced by a smaller cutter _I_. When these tools are withdrawn, tool No. 7 is moved up for rough turning the outside of the cylindrical end (preparatory to cutting a thread) and rough boring the hole. These same surfaces are then finished by tool No. 8. The arrangement of tools Nos. 7 and 8 is shown by the detailed view. Tool _J_ turns the part to be threaded; tool _K_ turns the end beyond the threaded part; and tool _L_ bevels the corner or edge. The reaming tool No. 9 is next indexed to the working position for finishing the hole and beveling the outer edge slightly. At the same time, the form tool No. 10, held at the rear of the cross-slide, is fed up for beveling the flange to an angle of 60 degrees. The final operation is that of threading the end, which is done with die No. 11. The boring-bars of tools Nos. 2, 3, 7 and 8 are all provided with pilots _N_ which enter close fitting bushings held in the spindle, to steady the bar while taking the cut. This is a common method of supporting turret lathe tools. The feed of the turret for both the first and second series of operations is 1/27 inch per revolution and the speeds 60 revolutions per minute for the roughing cuts and 90 revolutions per minute for the finishing cuts. The total time for machining one of these castings complete is about 7-1/2 minutes, which includes the time required for placing the work in the chuck. =Machining Flywheels in Turret Lathe.=--Figs. 4 to 6, inclusive, illustrate how a gasoline engine flywheel is finished all over in two cycles of operations. First the flywheel is turned complete on one side, the hole bored and reamed, and the outside of the rim finished; in the second cycle the other side of the flywheel is completed. [Illustration: Fig. 4. First Cycle of Operations in Finishing Gasoline Engine Flywheels on a Pond Turret Lathe] During the first operation, the work is held by the inside of the rim by means of a four-jaw chuck equipped with hard jaws. The side of the rim, the tapering circumference of the recess, the web, and the hub are first rough-turned, using tools held in the carriage toolpost. The hole is then rough-bored by bar _C_, which is supported in a bushing in the chuck, as shown in Fig. 4. The outside of the wheel rim is rough-turned at the same time by a cutter held in the extension turret tool-holder _T_ (Fig. 5), and the taper fit on the inside of the flywheel is turned by means of cutter _A_ (Fig. 4) held in a tool-holder attached to the turret. The outside of the wheel rim is next finish-turned with cutter _V_ (Fig. 5) held in an extension turret tool-holder the same as the roughing tool _T_. At the same time, the bore is finished by a cutter in boring-bar _D_ (Fig. 4). The side of the rim and the hub of the wheel are also finished at this time by two facing cutters _H_ and _K_, held in tool-holders on the face of the turret. When the finishing cuts on the rim and hub are being taken, the work is supported by a bushing on the boring-bar which enters the bore of the wheel, the boring cutter and facing tools being set in such relation to each other that the final boring of the hole is completed before the facing cuts are taken. [Illustration: Fig. 5. Elevation of Turret and Tools for Finishing Flywheels--First Operation] The web of the wheel is next finish-faced with the facing cutter held in the holder _E_, and the taper surface on the inside of the rim is finished by the tool _L_, at the same time. While these last operations are performed, the work is supported by a bushing on a supporting arbor _J_, which enters the bore of the wheel. The bore is finally reamed to size by a reamer _F_ held in a "floating" reamer-holder. When the reaming operation is completed, a clearance groove _N_ is cut on the inside of the rim, using a tool _G_ held in the carriage toolpost. The first cycle of operations on the flywheel is now completed. The flywheel is then removed from the chuck, turned around, and held in "soft" jaws for the second cycle of operations, the jaws fitting the outside of the wheel rim. (Soft unhardened jaws are used to prevent marring the finished surface of the rim.) The operations on this side are very similar to those performed on the other side. First, the side of the rim, the inside of the rim, the web, and hub are rough-turned, using tools held in the carriage toolpost. The inside of the rim and the web are then finished by a cutter held in a tool-holder at _P_, Fig. 6, which is bolted to the face of the turret. The work is supported during this operation by a bushing held on a supporting arbor _U_, having a pilot which enters a bushing in the chuck. Finally, the rim and hub are finished, by the facing cutters _R_ and _S_, the work being supported by an arbor, as before. [Illustration: Fig. 6. Second Cycle of Operations on Flywheel] These operations illustrate the methods employed in automobile factories, and other shops where large numbers of engine flywheels, etc., must be machined. =Finishing a Flywheel at One Setting in Turret Lathe.=--The plan view _A_, Fig. 7, shows an arrangement of tools for finishing a flywheel complete at one setting. The hole for the shaft has to be bored and reamed and the hub faced on both sides. The sides and periphery of the rim also have to be finished and all four corners of the rim rounded. The tools for doing this work consist of boring-bars, a reamer, facing heads on the main turret, a turret toolpost on the slide rest (carrying, in this case, three tools) and a special supplementary wing rest attached to the front of the carriage at the extreme left. The casting is held by three special hardened jaws _b_ in a universal chuck. These jaws grip the work on the inner side of the rim, leaving room for a tool to finish the rear face without striking the chuck body or jaws. Three rests _c_ are provided between the chuck jaws. The work is pressed against these rests while being tightened in the chuck, and they serve to locate it so that the arms will run true so far as sidewise movement is concerned. These rests also locate the casting with relation to the stops for the turret and carriage movements. The chuck carries a bushing _r_ of suitable diameter to support the boring-bars in the main turret, as will be described. In the first operation, boring-bar _m_ is brought in line with the spindle and is entered in bushing _r_ in the chuck. Double-ended cutter _n_ is then fed through the hub of the pulley to true up the cored hole. While boring the hole, the scale on the front face of the rim and hub is removed by tool _j_. Tool _k_ is then brought into action to rough turn the periphery, after which tool _e_, in the wing rest, is fed down to clean up the back face of the rim. As soon as the scale is removed, the hole is bored nearly to size by cutter _n_{1}_ in bar _m_{1}_, and it is finally finished with reamer _q_ mounted on a floating arbor. The cutters _f_, _g_ and _h_, in the facing head, are next brought up to rough face the hub and rim, and round the corners of the rim on the front side. This operation is all done by broad shaving cuts. The facing head in which the tools are held is provided with a pilot bar _t_ which fits the finished hole in the flywheel hub, and steadies the head during the operation. The cutters _f_, _g_ and _h_ are mounted in holders which may be so adjusted as to bring them to the proper setting for the desired dimensions. This completes the roughing operations. [Illustration: Fig. 7. Turret Lathe Tool Equipment for Machining Flywheels] The periphery of the rim is now finished by cutter _l_ in the turret toolpost which is indexed to the proper position for this operation. The rear face of the rim is finished by the same tool _e_ with which the roughing was done. Tool _e_ is then removed and replaced with _d_ which rounds the inner corner of the rim. Tool _d_ is also replaced with a third tool for rounding the outer corner of the rear side. For finishing the front faces of the rim and hub and rounding the corners of the rim, a second facing head, identical with the first one, is employed. This is shown in position in the illustration. Cutters _f_{1}_, _g_{1}_ and _h_{1}_ correspond with the cutters _f_, _g_ and _h_, previously referred to, and perform the same operations. The remaining operation of finishing the back of the hub is effected by cutter _p_. This cutter is removed from the bar, which is then inserted through the bore; the cutter is then replaced in its slot and the rear end of the hub is faced by feeding the carriage away from the headstock. This completes the operations, the flywheel being finished at one setting. =Finishing a Webbed Flywheel in Two Settings.=--The plan views _B_ and _C_, Fig. 7, show the arrangement of tools for finishing a webbed flywheel which has to be machined all over. This, of course, requires two operations. In the first of these (see sketch _B_) the rough casting is chucked on the inside of the rim with regular inside hard chuck jaws _b_. The cored hole is first rough bored with cutter _n_ attached to the end of boring-bar _m_, and guided by the drill support _d_ pivoted to the carriage. Next, the boring-bar _m_{1}_ is brought into position, the drill support being swung back out of the way. This bar is steadied by its bearing in bushing _r_ in the chuck. Two cutters, _n_{1}_ and _n_{2}_, are used to roughly shape the hole to the desired taper, the small end being finished to within 0.002 inch of the required diameter. While boring with the bar _m_{1}_, the scale is broken on the web and hub of the casting by the tool _k_ in the turret toolpost. The latter is then shifted to bring the tool _j_ into position for removing the scale on the periphery of the wheel. Next, the hole is reamed with taper reamer _q_, the pilot of which is supported by bushing _r_. The first of the facing heads is now brought into action. This facing head carries a guide _t_ which is steadied in a taper bushing _c_, driven into the taper hole of the hub for that purpose. The top cutter _f_ turns the periphery, cutter _g_ turns the hub and faces the web, and cutter _h_ faces the rim. A fourth cutter _e_ on the under side of the head faces the hub. This casting is now machined approximately to size. For finishing, similar cutters, _e_{1}_, _f_{1}_, _g_{1}_ and _h_{1}_, in the other facing head are used, the latter being supported by the taper bushing _c_ in the same way. A very light cut is taken for finishing. Tool _l_ in the carriage turret is used to round the outer and inner corners of the rim, which completes the work on this face of the casting. In the second cycle of operations, shown at _C_, the casting is chucked on the outside with the soft jaws _b_, which are bored to the exact diameter of the finished rim. The work is further supported and centered by sliding bushing _c_, which is tapered to fit the finished hole in the hub, and has an accurate bearing in bushing _r_ in the chuck. This bushing is provided with a threaded collar for forcing it into the work and withdrawing it. The scale on the web and the inside and face of the rim is first broken with the tool _k_ in the turret toolpost. These surfaces are then roughed off with cutters _f_, _g_ and _h_, in the facing head. This latter is steadied by a pilot _t_ which enters the hole in the sliding bushing _c_ on which the work is supported. A light cut is next taken with cutters _f_{1}_, _g_{1}_ and _h_{1}_, in the finishing facing head, which completes the operation. =Tools for Turret Lathes.=--The operation of a turret lathe after the tools have been properly arranged is not particularly difficult, but designing and making the tools, determining what order of operations will give the most efficient and accurate results, and setting the tools on the machine, requires both skill and experience. For some classes of work, especially if of a rather complicated nature, many of the tools must be specially designed, although there are certain standard types used on turret lathes which are adapted to general turning operations. Some of the principal types are referred to in the following. =Box-tools.=--Tools of this type are used for turning bar stock. There are many different designs, some of which are shown in Figs. 8, 9 and 10. Box-tools are held in the turret and they have back-rests opposite the turning tools, for supporting the part being turned. The box-tool shown at _A_, Fig. 8, is for roughing. The cutter _a_ is a piece of high-speed steel beveled on the cutting end to produce a keen edge. It takes a shearing tangent cut on top of the bar and the latter is kept from springing away by means of the adjustable, hardened tool-steel back-rest _b_. This tool is considered superior to a hollow mill whenever a fair amount of stock must be removed. If considerable smoothness and accuracy are necessary, the finishing box-tool shown at _B_ should follow the roughing box tool, but in most cases, especially if the part is to be threaded by a die, a finishing cut is unnecessary. [Illustration: Fig. 8. Different Types of Box-tools for Turret Lathe] The finishing box-tool _B_ is also used to follow a hollow mill if special accuracy or smoothness is desired. This tool is only intended for light finishing cuts, the allowances varying from 0.005 inch to 0.015 inch in diameter. The cutters are made of square tool steel of commercial size, and are ground and set to take a scraping end cut. This particular tool has two tool-holders which permit finishing two diameters at once. If a larger number of sizes must be turned, extra tool-holders can be applied. The single-cutter box-tool shown at _C_ is bolted directly to the face of the turret instead of being held by a shank in the turret hole, and it is adapted for heavy cuts such as are necessary when turning comparatively large bar stock. The tool-holder _a_ swivels on a stud, thus allowing the cutter to be withdrawn from the work while being returned, which prevents marring the turned surface. The high-speed steel cutter is ground to take a side cut on the end of the bar. The latter is supported by hardened and ground tool-steel rolls _b_ which revolve on hardened and ground studs. These rolls are mounted on swinging arms which have a screw adjustment for different diameters. They can also be adjusted parallel to the bar, thus enabling them to be set either in advance of or back of the cutter. The opening in the base allows the stock to pass into the turret when it is not larger than the turret hole. The box-tool shown at _D_ is similar to the one just described, except that it has two or more cutters and roller back-rests, thus enabling different diameters to be turned simultaneously. The cutters are ground to take a side cut. Ordinarily this gives a satisfactory finish, but if special accuracy and smoothness are desired, two tools should be used, one for roughing and one for finishing, the latter being ground to take a light scraping end cut. The taper-turning box-tool shown at _E_ is designed for accurately turning tapers on brass or cast-iron parts, when there is a small amount of stock to be removed. The taper is obtained by cross motion imparted to the cutter slide as the turret advances. The taper-turning box-tool shown at _F_, instead of having a single-point cutter, is provided with a wide cutter _a_. This tool is designed to turn tapering parts of small or medium diameter, requiring the use of a support which cannot be provided with a straight forming tool and holder mounted on the cut-off slide. The cutter is backed up by the screws shown, which also provide adjustment for different tapers within a limited range. The bar is supported by the three back-rests shown, which also have screw adjustment. =Examples of Box-tool Turning.=--Box-tools are not only used for cylindrical and taper turning on the end of a bar, but for many other operations. Figs. 9 and 10 show a number of box-tools of different designs, with examples of the work for which each is intended. While these tools are designed for some specific part, they can, of course, with slight modifications be adapted to other work. [Illustration: Fig. 9. Box-tools and Work for which they are Intended] A box-tool of the pilot type that is used for finishing, after the surplus stock has been removed by roughing tools, is shown at _A_, Fig. 9. The work, which is the cone for a ball bearing, is shown at _a_ by the dotted lines and also by the detail view to the right. The pilot _b_ enters the work before either of the cutters begins to operate on its respective surface. The inverted cutter _c_, which sizes the flange of the cone, is held in position by a clamp _d_, which is forced down by a collar-head screw. The cutter is further secured against a beveled shoulder at _g_ by the set-screws _f_, and it is adjusted forward by the screw _e_. By loosening the screws _f_ and the collar-head screw, the cutter may be removed for sharpening. The cutter _h_ is adjusted to cut to the proper diameter, by the screws _l_, after which the clamp _k_ is made level by the screw _j_. The collar-screw _m_ is then used to secure the tool in place. The cutter is made from drill rod and it is slightly cupped out on the cutting end to give keenness to the cutting edge. The adjusting screw _o_, which passes through plate _p_, prevents the cutter from backing away from the work. This adjusting screw plate has its screw holes slotted to avoid removing the screws when it becomes necessary to remove the plate and cutter for sharpening. Pilot _b_ is held firmly to the tool body by set-screw _r_. The hole _s_ through the shank makes it easy to remove the pilot, in case this is necessary. A pilot box-tool for finishing another type of ball bearing cone is shown at _B_. The shape of the work itself is indicated by the dotted lines _a_ and by the detail view. This tool is somewhat similar in its construction to the one just described. The cutters _b_ and _c_ are inverted and are used to face the flange at _d_ and to turn it to the proper diameter. These cutters are held by the clamp _f_ and screws _g_ and are adjusted forward by the screw _h_. The cutter _j_, which operates on top of the stock, rests on a bolster, of the proper angle and is adjusted up or down by the screws _k_. The clamp _l_, which binds against this tool, is beveled to correspond with the angle of the tool. This clamp is secured by the collar-screw shown and it is leveled by set-screws _s_. The adjusting screw _p_ prevents the cutter from slipping back. The holes in the adjusting-screw plate are also slotted in this case so that it will not be necessary to remove any screws when the cutter has to be taken out of the holder. A box-tool for finishing a treadle-rod cone for a sewing machine is shown at _C_. This tool is also of the pilot type. The cutters in it operate on opposite sides of the cone _a_. The inverted cutter _b_ sizes the cylindrical part of the cone, while the front cutter _d_ is set at the proper angle to finish the tapered part. The rear cutter _b_ is held in place by the clamp _g_ and a collar screw. It is adjusted forward by the screw _h_ in the plate _i_ which is held by screws as shown. The pilot is retained by a set-screw, and it is easily removed by inserting a small rod in the hole _l_ which passes through the shank. The cutter _d_ is held by clamp _m_ and is adjusted by screw _n_ which passes through a tapped hole in plate _o_. The screw holes in both the adjusting plates _i_ and _o_ are slotted to facilitate their removal. The box-tool illustrated at _A_, Fig. 10, is used for finishing the bushing of a double-taper cone bearing _a_. The cutters are so arranged that they all cut on the center; that is, the cutting edges lie in a horizontal plane. The inverted cutter _b_ at the rear forms the short angular surface, and the cutter _c_ in front forms the long tapering part of the bearing. The large diameter is turned, to size by cutter _d_. The pilot _e_ has a bearing in the bore nearly equal to the length of the work and it is provided with oil grooves, as shown. The taper shank of this pilot is tapped for the screw _i_ which extends the whole length of the shank and is used to draw the pilot back to its seat. It is not necessary to remove adjusting-screw plate _k_ to take out the cutter _b_, as the latter can be drawn out from the front after the collar-screw _m_ is loosened. The cutter _c_ is removed by taking off the adjusting-screw plate _s_ after loosening the collar-screw _n_. The cutter _d_ is held in a dove-tailed slot by two headless set-screws _q_. It is also backed up by an adjusting screw in the plate _s_. These adjusting screws should all have fine threads, say from 32 to 40 per inch, and be nicely fitted so they will not loosen after being adjusted. The box-tools shown at _B_ and _C_, Fig. 10, are for turning the sides of a loose pulley for a sewing machine. This pulley (shown by the dotted lines) is finished in two operations. The box-tool for finishing the side of the pulley on which the hub projects beyond the rim, is shown at _B_. The inverted cutter _a_, which faces the end of the hub, is held by a clamp _c_ (clearly shown in the end view) from the under side and it has no adjustment. The collar-screw _d_ is tapped into this clamp, which is prevented from getting out of place by the dowel-pin _f_. The pilot _g_ is made small in the shank, so that tool _a_ can be so placed as to insure the removal of all burrs around the bore of the hub. The pilot is held by a set-screw and it is provided with oil grooves. The cutter _j_ sizes the outside of the hub, and the cutter _k_ faces the side of the pulley rim. These cutters are both held by the clamp _l_ and the collar-screw _m_. No side plates are used on this tool, and the cutters are all easily removed. [Illustration: Fig. 10. Examples of Box-tool Designs] Sketch _C_ shows the box-tool used for the second operation. As the hub is flush with the rim on the side for which this tool is intended, it needs only one cutter to face both. This is done by the wide cutter _a_ which is held in a dove-tailed slot in the front of the tool and is fastened by the clamp _b_ and collar-screw _c_. The bushing _d_, in which the end of the work arbor is supported, is held by the collar-screw _e_, and to obtain the necessary compression, the body of the tool is slotted as far back as _f_. This bushing is provided with oil grooves and one side is cut away to clear the cutter _a_. The pilot end of the arbor on which the work is mounted is 1/16 inch smaller than the bore of the pulley, which allows the cutter to be set in far enough to prevent any burr which might form at the edge of the bore. A disk _i_ is inserted back of bushing _d_, so that the latter may be easily removed by passing a rod through the hollow shank. The special chuck used for this second operation on the loose pulley is screwed onto the spindle, and the work is mounted on a projecting arbor and driven by the pins engaging holes in the pulley web. The arbor is made a driving fit for the work, and the end or pilot is a running fit in the bushing of the box-tool. A counterbore in the arbor hub provides clearance for the hub of the pulley which projects beyond the rim on one side. [Illustration: Fig. 11. (A) Hollow Mill and Holder. (B) Spring Screw-threading Die and Releasing Die-holder] =Hollow Mills.=--A hollow mill such as is shown at _A_ in Fig. 11 is sometimes used in place of a box-tool (especially when turning brass) for short roughing cuts preceding a threading operation. The turning is done by the cutting edges _e_, and the turned part enters the mill and is steadied by it. If this type of tool is used for long, straight cuts, especially on square stock and when making screws with large heads from the bar, it should always be followed by a finishing box-tool to insure accurate work. A hollow mill can be sharpened readily by grinding the ends without materially changing the cutting size. A slight adjustment can be obtained by means of the clamp collar shown to the left, although this is not generally used. When making these mills, they should be reamed out tapering from the rear to give clearance to the cutting edges. For turning steel, the cutting edge should be about 1/10 of the diameter ahead of the center, whereas for brass, it should be on the center-line. [Illustration: Fig. 12. Geometric Adjustable Hollow Milling Tool] Hollow mills are also made adjustable. The design shown in Fig. 12 is especially adapted for brass finishing. It can also be used for taking light cuts on cast iron or steel but its use in place of roughing or finishing box-tools for general use is not recommended. With the exception of the cutters and screws, the complete tool consists of three parts, _viz._, the holder, cam, and ring. The cam serves to adjust the cutters for different diameters. The adjustment is made by the two screws shown, the amount being indicated by a micrometer scale. When adjusting the cutters for a given diameter, the use of a hardened steel plug of the required size is advisable, the cutters being adjusted against the plug. =Releasing Die and Tap Holders.=--Threads are cut in the turret lathe by means of dies for external threading, and taps for internal threading, the die or tap being held in a holder attached to the turret. A simple form of releasing die holder is shown at _B_, Fig. 11. This holder was designed for the spring-screw type of threading die shown to the left. The die is clamped in the holder _a_ by the set-screw shown, and the shank _b_ of the holder is inserted in the turret hole. Holder _a_ has an extension _c_ which passes through the hollow shank. When the die is pressed against the end of the work, holder _a_ and its extension moves back until lug _d_ on the holder engages lug _e_ on the shank. The die and holder are then prevented from rotating with the work and the die begins to cut a thread. It continues to screw itself onto the work with the turret following, until the thread has been cut to the required length; the turret is then stopped and as the die and holder _a_ are drawn forward, lugs _d_ and _e_ disengage so that the die simply rotates with the work without continuing to advance. The lathe spindle is then reversed and as the turret is moved back by hand, pin _f_ comes around and enters notch _g_, thus holding the die stationary; the die then backs off from the threaded end. Some tap holders are also constructed the same as this die holder, so far as the releasing mechanism is concerned. There are also many other designs in use, some of which operate on this same principle. [Illustration: Fig. 13. Geometric Self-opening and Adjustable Screw-cutting Die Head] =Self-opening Die Heads.=--The type of die holder shown at _B_ in Fig. 11 is objectionable because of the time required for backing the die off the threaded end; hence, self-opening dies are extensively used in turret lathe work. As the name implies, this type of die, instead of being solid, has several chasers which are opened automatically when the thread has been cut to the required length. The turret can then be returned without reversing the lathe spindle. The dies are opened by simply stopping the travel of the turret slide, the stop-rod for the feed of the turret being adjusted to give the proper amount of travel. [Illustration: Fig. 14. Geometric Collapsing Tap] A well-known die head of the self-opening type is shown in Fig. 13. The dies open automatically as soon as the travel of the head is retarded, or they can be opened at any point by simply holding back on the turnstile or lever by which the turret slide is moved. The die is closed again by means of the small handle seen projecting at right-angles from the side of the head. The closing may be done by hand or automatically by screwing a pin into a threaded hole opposite the handle and attaching a small piece of flat steel to the back edge of the turret slide. The latter will then engage the pin as the turret revolves, thus closing the die head. This die head has a roughing and finishing attachment which is operated by handle _A_. When this handle is moved forward, the dies are adjusted outward 0.01 inch for the roughing cut, whereas returning the handle closes and locks the dies for the finishing cut. The die head has a micrometer scale which is used when making slight adjustments to compensate for the wear of the chasers or to make either a tight-or a loose-fitting thread. =Collapsing Taps.=--The collapsing tap shown in Fig. 14 is one of many different designs that are manufactured. They are often used in turret lathe practice in place of solid taps. When using this particular style of collapsing tap, the adjustable gage _A_ is set for the length of thread required. When the tap has been fed to this depth, the gage comes into contact with the end of the work, which causes the chasers to collapse automatically. The tool is then withdrawn, after which the chasers are again expanded and locked in position by the handle seen at the side of the holder. In all threading operations, whether using taps or dies, a suitable lubricant should be used, as a better thread is obtained and there is less wear on the tools. Lard oil is a good lubricant, although cheaper compounds give satisfactory results on many classes of work. =Miscellaneous Turret Lathe Tools.=--The chamfering tool shown at _A_, Fig. 15, is used for pointing the end of a bar before running on a roughing box-tool. This not only finishes the end of the bar but provides an even surface for the box-tool to start on. The cutter is beveled on the end to form a cutting edge and it is held at an angle. The back-rest consists of a bell-mouthed, hardened tool-steel bushing which supports the bar while the cut is being taken. The stop gages _B_ and _C_ are used in the turret to govern the length of stock that is fed through the spindle. When a finished piece has been cut off, the rough bar is fed through the spindle and up against the stop gage, thus locating it for another operation. This gage may be a plain cylindrical piece of hardened steel, as at _B_, or it may have an adjusting screw as at _C_; for special work, different forms or shapes are also required. The stop gages on some machines, instead of being held in the turret, are attached to a swinging arm or bracket that is fastened to the turret slide and is swung up in line with the spindle when the stock is fed forward. The center drilling tool _D_ is designed to hold a standard combination center drill and reamer. This type of tool is often used when turning parts that must be finished afterwards by grinding, to form a center for the grinding machine. The adjustable turning tool _E_ is used for turning the outside of gear blanks, pulley hubs or the rims of small pulleys. The pilot _a_ enters the finished bore to steady the tool, and cutter _b_ is adjusted to turn to the required diameter. [Illustration: Fig. 15. Various Types of Tools for the Turret Lathe] The cutting-off tool-holder _F_ (which is held on the cross-slide of the turret lathe) is usually more convenient than a regular toolpost, as the blade can be set closer to the chuck. The blade is held in an inclined position, as shown, to provide rake for the cutting edge; the inclined blade can also be adjusted vertically, a limited amount, by moving it in or out. The multiple cutting-off tool _G_ holds two or more blades and is used for cutting off several washers, collars, etc., simultaneously. By changing the distance pieces between the cutters, the latter are spaced for work of different widths. The flat drill holder _H_ is used for drilling short holes, and also to form a true "spot" or starting point for other drills. Knurling tools are shown at _I_ and _J_. The former is intended for knurling short lengths and is sometimes clamped on top of the cut-off tool on the cross-slide, the end being swung back after knurling (as shown by the dotted lines) to prevent interference with the work when the cutting-off tool is in operation. The knurling tool _J_ has a shank and is held in the turret. The two knurls are on opposite sides of the work so that the pressure of knurling is equalized. By adjusting the arms which hold the knurls, the tool can be set for different diameters. Three styles of drill holders are shown at _K_, _L_ and _M_. Holder _K_ is provided with a split collet (seen to the left) which is tightened on the drill shank by a set-screw in the holder. This holder requires a separate collet for each size drill. The taper shank drill holder _L_ has a standard taper hole into which the shank of the drill is inserted. The adjustable type of holder _M_ is extensively used, especially on small and medium sized machines when several sizes of drills are necessary. This holder is simply a drill chuck fitted with a special shank. For large drills the plain style of holder _K_ is recommended, and if only a few sizes of drills are required, it is more satisfactory and economical than the adjustable type. The various types of small turret lathe tools referred to in the foregoing for turning, threading, tapping, knurling, etc., are a few of the many different designs of tools used in turret lathe practice. Naturally, the tool equipment for each particular job must be changed somewhat to suit the conditions governing each case. The tools referred to, however, represent in a general way, the principal types used in ordinary practice. Some of the more special tools are shown in connection with examples of turret lathe work, which are referred to in the following. =Turning Gasoline Engine Pistons in Turret Lathe.=--The making of pistons for gas engines, especially in automobile factories, is done on such a large scale that rapid methods of machining them are necessary. The plan view _A_, Fig. 16, shows the turret lathe tools used in one shop for doing this work. As is often advisable with work done in large quantities, the rough castings are made with extra projections so arranged as to assist in holding them. These projections are, of course, removed when the piece is completed. In this case the piston casting _a_ has a ring about 1-1/4 inch long and a little less in diameter than the piston, at the chucking end. The piston is held in suitable chuck jaws _b_ which are tightened against the inside of this ring. The set-screws in these special jaws are then tightened, thus clamping the casting between the points of the screws and the jaws. This method of holding permits the whole exterior of the piston to be turned, since it projects beyond the chuck jaws. This is the object in providing the piston with the projecting ring by which it is held. [Illustration: Fig. 16. (A) Method of Boring and Turning Pistons in Gisholt Lathe. (B) Special Chuck and Tools for Turning, Boring and Cutting Off Eccentric Piston Rings] The first operation consists in rough-boring the front end of the piston. The double-ended cutter _n_ is held in boring-bar _m_, which is, in turn, supported by a drill-holder, clamped to one of the faces of the turret. This bar is steadied by a bushing in the drill support _c_ which is attached to the carriage, and may be swung into or out of the operating position, as required. After this cut is completed, the turret is revolved half way around and the casting is finish-bored in a similar manner, with double-ended cutter _n_{1}_ held in bar _m_{1}_, the drill support being used as in the previous case. The support is then turned back out of the way to allow the turning tools in the turret toolpost to be used. The outside of the piston is next rough-turned with tool _k_ in the turret toolpost, which is revolved to bring this cutter into action. The toolpost is then turned to the position shown, and the outside is finish-turned by tool _j_, which takes a broad shaving cut. The turret tool-holder is again revolved to bring form tool _l_ into position. This tool cuts the grooves for the piston rings. Suitable positive stops are, of course, provided for both the longitudinal and cross movements of the turret toolpost. In the second operation, the piston _a_ is reversed and held in soft jaws, which are used in place of the hardened jaws _b_ shown in the illustration. These jaws are bored to the outside diameter of the piston, so that when closed, they hold the work true or concentric with the lathe spindle. In this operation the chucking ring by which the piston was previously held is cut off, and the end of the piston is faced true. If the crank-pin hole is to be finished, a third operation is necessary, a self-centering chuck-plate and boring and reaming tools being used. (These are not shown in the illustration.) =Turning Piston Rings in Turret Lathe.=--One method of turning piston rings is shown at _B_ in Fig. 16. The piston rings are cut from a cast-iron cylindrical piece which has three lugs _b_ cast on one end and so arranged that they may be held in a three-jawed chuck. This cylindrical casting is about 10 inches long, and when the rings are to have their inside and outside surfaces concentric, the casting is held by the lugs in the regular jaws furnished with the chuck. (The arrangement used for turning and boring eccentric rings, which is that shown in the illustration, will be described later.) The casting _a_, from which the rings are made, is first rough-bored with double-ended cutter _n_ in boring-bar _m_, after which it is finish-bored with cutter _n_{1}_ in bar _m_{1}_. While taking these cuts, the bars _m_ and _m_{1}_ are supported by their extension ends which enter bushing _r_ located in the central hole of the chuck. This furnishes a rigid support so that a heavy cut can be taken. The outside of the casting is next rough-turned with tool _k_, held in the turret toolpost. This toolpost is then revolved to bring tool _j_ into position, by which the outside is turned true to size, a broad shaving chip being taken. The toolpost is again swung around, to bring the cutting-off tool-holder _l_ into position. This holder contains four blades set the proper distance apart to give rings of the desired width. Each blade, from right to left, is set a little back of the preceding one, so that the rings are cut off one after the other, the outer rings being supported until they are completely severed. After the first four rings are cut off, the carriage is moved ahead to a second stop, and four more rings are severed, this operation being continued until the casting has been entirely cut up into rings. When the bore of the ring is to be eccentric with the outside, the holding arrangement shown in the illustration is used. The casting a is bolted to a sliding chuck-plate _c_, and the outside is rough-turned with tool _k_ in the toolpost. Finishing tool _j_ is then brought into action, and the outside diameter is turned accurately to size. Then the sliding chuck-plate _c_, carrying the work, is moved over a distance equal to the eccentricity desired, and the work is bored with cutters _n_ and _n_{1}_ as in the previous case. The turret toolpost is next revolved and the tools _l_ are used for cutting off the rings. The reason for finishing the outside first is to secure smooth rings in cutting off, as this operation should be done when the work is running concentric with the bore, rather than with the exterior surface. It will be evident that this method gives a far greater output of rings than is possible by finishing them in the more primitive way on engine lathes. The faces of the rings may be finished in a second operation if desired, or they may be ground, depending on the method used in the shop where the work is being done, and the accuracy required. [Illustration: Fig. 17. Turning Gasoline Engine Pistons in Pratt & Whitney Turret Lathe] =Piston Turning in Pratt and Whitney Turret Lathe.=--A turret lathe equipped with tools for turning, facing and grooving automobile gasoline engine pistons is shown in Fig. 17. The piston is held on an expanding pin chuck which is so constructed that all of the pins are forced outward with equal pressure and automatically conform to any irregularities on the inside of the piston. Tool _A_ rough-turns the outside, and just as this tool completes its cut, a center hole is drilled and reamed in the end of the piston by combination drill and reamer _B_. The turret is then indexed one-half a revolution and a finishing cut is taken by tool _C_. After the cylindrical body of the piston has been turned, tools held in a special holder _E_ attached to the cut-off slide are used to face the ends of the piston and cut the packing-ring grooves. While the grooves are being cut, the outer end of the piston is supported by center _D_. The center hole in the end also serves to support the piston while being ground to the required diameter in a cylindrical grinding machine. The edge at the open end of the piston may also be faced square and the inner corner beveled by a hook tool mounted on the rear cross-slide, although this is usually done in a separate operation. (This provides a true surface by which to hold this end when grinding.) [Illustration: Fig. 18. Pratt & Whitney Turret Lathe equipped with Special Attachment for Turning Eccentric Piston Rings] This illustration (Fig. 17) shows very clearly the stops which automatically disengage the turret feed. A bracket _F_ is bolted to the front of the bed and contains six stop-rods _G_ (one for each position or side of the turret). When one of these stop-rods strikes lever _H_, the feed is disengaged, the stop being adjusted to throw out the feed when the tool has completed its cut. Lever _H_ is automatically aligned with the stop-rods for different sides of the turret by a cam _J_ on the turret base. A roller _K_ bears against this cam and, through the connecting shaft and lever shown, causes lever _H_ to move opposite the stop-rod for whatever turret face is in the working position. Lever _L_ is used for engaging the feed and lever _R_ for disengaging it by hand. The indexing of the turret at the end of the backward movement of the slide is controlled by stop _M_ against which rod _N_ strikes, thus disengaging the lock bolt so that the turret can turn. This stop _M_ is adjusted along the bed to a position depending upon the length of the turret tools and the distance the turret must move back to allow the tools to clear as they swing around. [Illustration: Fig. 19. Tool Equipment for Machining Worm Gear Blanks--Davis Turret Lathe] =Attachment for Turning Piston Rings.=--Fig. 18 shows a special attachment applied to a Pratt & Whitney turret lathe for turning eccentric, gas-engine piston rings. The boring of the ring casting, turning the outside and cutting off the rings, is done simultaneously. The interior of the casting is turned concentric with the lathe spindle by a heavy boring-bar, the end of which is rigidly supported by a bushing in the spindle. The slide which carries the outside turning tool is mounted on a heavy casting which straddles the turret. The outside of the ring casting is turned eccentric to the bore as a result of an in-and-out movement imparted to the tool by a cam on shaft _A_ which is rotated from the lathe spindle through the gearing shown. For each revolution of the work, the tool recedes from the center and advances toward it an amount sufficient to give the required eccentricity. When the turning and boring tools have fed forward about 2 inches, then the cutting-off tools which are held in holder _B_ come into action. The end of each cutting-off tool, from right to left, is set a little farther away from the work than the preceding tool, so that the end rings are always severed first as the tools are fed in by the cross-slide. A number of the completed rings may be seen in the pan of the machine. [Illustration: Fig. 20. Turning Bevel Gear Blanks in Davis Turret Lathe--First Operation] =Turning Worm-gear Blanks in Turret Lathe.=--This is a second operation, the hub of worm-gear blank _G_ (Fig. 19) having previously been bored, reamed, and faced on the rear side. The casting is mounted upon a close-fitting arbor attached to a plate bolted to the faceplate of the lathe, and is driven by two pins which engage holes on the rear side. The rim is first rough-turned by a tool _A_ which operates on top, and the side is rough-faced by a toothed or serrated cutter _B_. A similar tool-holder having a tool _C_ and a smooth cutter _D_ is then used to turn the rim to the required diameter and finish the side. The end of the hub is faced by cutters mounted in the end of bars _E_ and _F_, one being the roughing cutter and the other the finishing cutter. The work arbor projects beyond the hub, as will be seen, and forms a pilot that steadies these cutter bars. The curved rim of the gear is turned to the required radius (preparatory to gashing and bobbing the worm-wheel teeth) by a formed tool _H_ held on the cross-slide. [Illustration: Fig. 21. Second Operation on Bevel Gear Blanks] =Turning Bevel Gear Blanks.=--Fig. 20 shows a plan view of the tools used for the first turning operation on bevel gear blanks (these gears are used for driving drill press spindles). The cored hole is beveled true at the end by flat drill _A_ to form a true starting surface for the three-fluted drill _B_ which follows. The hole is bored close to the required size by a tool (not shown) held in the end of bar _C_, and it is finished by reamer _D_. The cylindrical end of the gear blank or hub is rough-and finish-turned by tools held in holders _E_ and _F_, respectively. (These holders were made to set at an angle of 45 degrees, instead of being directly over the work, as usual, so that the cutters would be in view when setting up the machine.) It will be noted that the chuck is equipped with special jaws which fit the beveled part of the casting. [Illustration: Fig. 22. Sectional View of Tapering Mold Shell which is turned in Hartness Flat Turret Lathe, as illustrated in Figs. 23 to 27, Inclusive] The second and final operation on this blank is shown in Fig. 21. The work _A_ is held by a special driver plate attached to the faceplate of the machine. This driver plate has two pins which engage holes drilled in the gear blank and prevent it from rotating. The blank is also held by a bolt _B_ which forces a bushing against the cylindrical end. First, the broad beveled side which is to be the toothed part of the gear, is rough-turned by toothed cutters _C_, and a recess is formed in the end of the blank, by a turning tool in this same tool-holder. A similar tool-holder _E_, having finishing cutters, is then used to finish the bevel face and recess. The other tools seen in the turret are not used for this second operation. The rear bevel is roughed and finished by tools and held on the cross-slide. =Shell Turning Operation in Flat Turret Lathe.=--The "flat turret lathe" is so named because the turret is a flat circular plate mounted on a low carriage to secure direct and rigid support from the lathe bed. The tools, instead of being held by shanks inserted in holes in the turret, are designed so that they can be clamped firmly onto the low circular turret plate. An interesting example of flat turret lathe work is shown in Fig. 22. This is a steel shell which must be accurately finished to a slight taper, both inside and out, threaded and plain recesses are required at the ends, and, in addition, one or two minor operations are necessary. This work is done in the Hartness flat turret lathe, built by the Jones & Lamson Machine Co. The shells are turned from cold-drawn seamless steel tubing, having a carbon content of 0.20 per cent, and they are finished at the rate of one in nine minutes. The tubing comes to the machine in 12-foot lengths, and the tube being operated upon is, of course, fed forward through the hollow spindle as each successive shell is severed. [Illustration: Fig. 23. First Operation on Shell Illustrated in Fig. 22--Rough-turning and Boring] In finishing this shell, five different operations are required. During the first operation the shell is rough-bored and turned by one passage of a box-tool, Fig. 23, and the recess _A_, Fig. 22, at the outer end, is finished to size by a second cutter located in the boring-bar close to the turret. The turret is then indexed to the second station which brings the threading attachment _G_ into position, as shown in Fig. 24. After the thread is finished, the recess _B_, Fig. 22, is turned by a flat cutter _K_, Fig. 25. The inner and outer surfaces are then finished to size by a box-tool mounted on the fourth station of the turret and shown in position in Fig. 26. The final operation, Fig. 27, is performed by three tools held on an auxiliary turret cross-slide, and consists in rounding the corners at _b_ and _c_, Fig. 22, and severing the finished shell. [Illustration: Fig. 24. Second Operation--Cutting Internal Thread] One of the interesting features connected with the machining of this shell is the finishing of the inner and outer tapering surfaces. The taper on the outside is 3/32 inch Per foot, while the bore has a taper of only 1/64 inch per foot, and these surfaces are finished simultaneously. The box-tool employed is of a standard type, with the exception of an inserted boring-bar, and the taper on the outside is obtained by the regular attachment which consists of a templet _D_ (Fig. 23) of the required taper, that causes the turning tool to recede at a uniform rate as it feeds along. To secure the internal taper, the headstock of the machine is swiveled slightly on its transverse ways by the use of tapering gibs. By this simple method, the double taper is finished to the required accuracy without special tools or equipment. As those familiar with this machine know, the longitudinal movements of the turret as well as the transverse movements of the headstock are controlled by positive stops. The headstock of this machine has ten stops which are mounted in a revolving holder and are brought into position, as required, by manipulating a lever at the front. The stops for length, or those controlling the turret travel, are divided into two general groups, known as "A" and "B". Each of these groups has six stops so that there are two stops for each of the six positions or stations of the turret, and, in addition, five extra stops are available for any one tool, by the engagement of a pin at the rear of the turret. The change from the "A" to the "B" stops is made by adjusting lever _L_, Fig. 26, which also has a neutral position. [Illustration: Fig. 25. Third Operation--Turning Recess at Rear End; Tool is shown withdrawn] After the box-tool for the roughing cut, shown at work in Fig. 23, has reached the end of its travel, further movement is arrested by a stop of the "A" group. The outside turning tool is then withdrawn by operating lever _E_ and the turret is run back and indexed to the second station, thus bringing the threading attachment into position. The surface speed of 130 feet per minute which is used for turning is reduced to about 30 feet per minute for threading by manipulating levers _H_, Fig. 24. After the turret is located by another stop of the "A" group, the threading attachment is made operative by depressing a small plunger _I_, which connects a vertical driving shaft from the spindle with the splined transmission shaft _J_. A reciprocating movement is then imparted to the thread chaser _t_ which advances on the cutting stroke and then automatically retreats to clear the thread on the return. This movement is repeated until the thread is cut to the proper depth, as determined by one of the stops for the headstock. While the thread is being cut, the carriage is locked to the bed by the lever _N_, Fig. 26. It was found necessary to perform the threading operation before taking the outside finishing cut, owing to a slight distortion of the shell wall, caused by the threading operation. [Illustration: Fig. 26. Fourth Operation--Finishing the Bore and Outside] After the thread is finished, the turret is turned to the third station as shown in Fig. 25, and tool _K_ for the inner recess _B_, Fig. 22, is brought into position and fed to the proper depth, as determined by another cross-stop. The turret is also locked in position for this operation. The finishing cuts for the bore and the outside are next taken by a box-tool which is shown near the end of its cut in Fig. 26. This box-tool is similar to the one used for roughing, but it is equipped with differently shaped cutters to obtain the required finish. The outside turning tool has a straight cutting edge set tangent to the cylindrical surface and at an angle, while the boring tool has a cutting edge of large radius. An end view of this box-tool is shown in Fig. 27. A reduced feed is employed for the finishing cut, and the speed is increased to 130 feet per minute, which is the same as that used for roughing. [Illustration: Fig. 27. Fifth Operation--Rounding Ends, Scoring Large End, and Cutting Off] During the next and final operation, the turret, after being indexed to the position shown in Fig. 27, is first located by a stop of the "A" group so that the cutting-off tool _R_ in front can be used for rounding the corner _b_, Fig. 22. The stop lever _L_ is then shifted and the turret is moved to a second stop of the "B" group. The corner _c_ is then rounded and the shell is scored at _d_ by two inverted tools _S_ and _T_ at the rear, after which the finished work is severed by the cut-off tool at the front. The cross-movement of these three tools is controlled by positive stops on the cross-slide, and the latter is moved to and fro by hand lever _O_. After the shell is cut off, the stop _M_, mounted on the turret, Fig. 26, is swung into position, and the tube is automatically fed forward to the swinging stop by the roll feed, as soon as the chuck is released by operating lever _Q_. This completes the cycle of operations. A copious supply of lubricant is, of course, furnished to the tools during these operations, and the two boring-tool shanks are hollow so that lubricant can be forced through them and be made to play directly upon the cutters. =Chuck Work in Flat Turret Lathe.=--Two examples of chuck work on the Acme combination flat turret lathe are shown in Figs. 28 and 29. Fig. 28 shows the tool equipment for turning a cylindrical part _A_ which is held in a three-jaw universal chuck. The front flange is first rough-turned by a bent turning tool _B_. The diameter is regulated by one of the cross-stops at _D_ which has been previously set and controls the movement of the turret cross-slide. The longitudinal feed is disengaged when the flange has been turned, by an independent stop. This machine has twelve longitudinal stops, there being one for each turret face and six auxiliary stops, in addition to the stops for the cross-slide. [Illustration: Fig. 28. Tool Equipment for Turning Scroll Gear Blank on Acme Flat Turret Lathe] After roughing the flange, the turret carriage is locked or clamped rigidly to the bed to prevent any lengthwise movement, and the back face of the front flange is rough-turned by tool _B_ in to the diameter of the hub which is indicated by a micrometer dial on the cross-feed screw. The carriage is then unlocked and auxiliary stop No. 7 is engaged (by turning a knob at the front of the slide) and the cylindrical hub is turned back to the rear flange, the feed being disengaged by the auxiliary stop just as the tool reaches the flange. The cross-slide is now moved outward, longitudinal auxiliary stop No. 8 is engaged, the turret slide is moved against the stop, the carriage is locked and the front sides of both the front and rear flanges are rough-faced by tools _B_ and _C_. The turret is next indexed and the hole rough-bored by cutter _E_. After again indexing the turret, the hub and flanges are finish-turned and faced by tools _F_ and _G_, as described for the rough-turning operation. The final operation is that of finishing the bore by cutter _H_. [Illustration: Fig. 29. Acme Flat Turret Lathe Arranged for Turning Roller Feed Body] The operation shown in Fig. 29 is that of turning the body of a roller feed mechanism for a turret lathe. The casting is held in a three-jaw universal chuck and it is first rough-bored by tool _A_. The turret is then indexed and the side of the body and end of the hub are rough-faced by tools at _B_. The turret is again indexed for rough-turning the outside of the hub and body, by tools _C_ and _D_. Similar tools _E_ and _F_ are then used to finish these same surfaces, after which the end of the hub and side of the body are finished by tools _G_ and _H_ similar to those located at _B_. The final operation is that of finishing the bore by tool _J_ and cutting a groove in the outside of the hub by the bent tool _K_. [Illustration: Fig. 30. Turret and Head of Jones & Lamson Double-spindle Flat Turret Lathe] =Double-spindle Flat Turret Lathe.=--The extent to which modern turning machines have been developed, especially for turning duplicate parts in quantity, is illustrated by the design of turret lathe the turret and head of which is shown in Fig. 30. This machine has two spindles and a large flat turret which holds a double set of tools, so that two duplicate castings or forgings can be turned at the same time. It was designed primarily for chuck work and can be used as a single-spindle machine if desirable. When two spindles are employed for machining two duplicate parts simultaneously, considerably more time is required for setting up the machine than is necessary for the regular single-spindle type, but it is claimed that the increased rate of production obtained with the two-spindle design more than offsets this initial handicap. The manufacturers consider the single-spindle machine the best type for ordinary machine building operations, regardless of whether the work is turned from the bar or is of the chucking variety. On the other hand, the double-spindle type is preferred when work is to be produced in such quantities that the time for setting up the machine becomes a secondary consideration. [Illustration: Fig. 31. Diagram showing Tool Equipment and Successive Steps in Machining Sprocket Blanks on Double-spindle Flat Turret Lathe] When the double-spindle machine is used as a single-spindle type, a chuck 17 inches in diameter is used, and when both spindles are in operation, two 9-inch chucks are employed. The general outline of the turret is square, and the tools are rigidly held, with a minimum amount of overhang, by means of tool-blocks and binding screws connected with the clamping plates. Two duplicate sets of tools are clamped to each side of the turret and these operate simultaneously on the two pieces held in the chucks or on faceplates. Primarily the turret is used in but four positions, but when a 17-inch chuck or faceplate is employed, corner blocks may be held by the clamping plates in which tools are supported, giving, if necessary, four additional operations by indexing the turret to eight positions. A typical job to demonstrate the application of the double-spindle flat turret lathe is illustrated in Fig. 31. The parts to be turned are sprocket wheels which are held in the two 9-inch chucks. At the first position of the turret (which is the one illustrated), the inside is rough-bored by tools _A_. At the second position of the turret, tools _B_ rough-face the inner sides of the flanges; tools _C_ face the outer sides of the flanges, while tools _D_ turn the faces of the flanges. At the third position of the turret, tools _E_ finish-turn the inside of the flanges; tools _F_ finish-turn the outside of the flanges, while tools _G_ finish the faces of the flanges. At the fourth position of the turret, tools _H_ finish-bore the sprockets; tools _I_ complete the turning on the outside of the flanges, while tools _J_ accurately size the interior of the flanges. With the double-spindle flat turret lathe, each operation is a double operation, and the speeds are varied according to the nature of the cut; thus, if at one position of the turret, the tools are required to rough out the work, this may be done rapidly, for it has no bearing on the other operations that are subsequently performed. Furthermore, if the following operation has to be performed with great care, this may be done without reducing the speed of the less exacting operations. [Illustration: Fig. 32. Potter & Johnston Automatic Chucking and Turning Machine] =Automatic Chucking and Turning Machine.=--The chucking and turning machine shown in Fig. 32 is automatic in its operation, the feeding of the tools, indexing of the turret, etc., being done automatically after the machine is properly arranged, and the work is placed in the chuck. This machine is adapted to turning and boring a great variety of castings, forgings or parts from bar stock, and it is often used in preference to the hand-operated turret lathe, especially when a great many duplicate parts are required. It is provided with mechanism for operating the cross-slide, feeding the turret slide forward, returning it rapidly, rotating the turret to a new position, and feeding it forward quickly for taking a new cut. The cross-slide and turret-slide movements are effected by cams mounted on the large drum _E_ seen beneath the turret, while the various speed and feed changes are effected by dogs and pins carried on disk _D_ which is keyed to the same shaft that the cam drum is mounted upon. This shaft with the cam drum and governing disk _D_, makes one revolution for each piece of work completed. The cams for operating the turret slide are mounted upon the periphery of drum _E_. The roll which engages the angular faces of these cams and imparts movement to the turret is carried by an intermediate slide which has rack teeth engaging a pinion on the square shaft _C_. By turning this shaft with a crank, the position of the turret-slide, with relation to the cam, may be adjusted for long or short work and long or short tools, as may be required. [Illustration: Fig. 33. Rear View of Machine showing the Cross-slide Mechanism, Driving Gearing, etc.] The cams which operate the cross-slide are mounted on the right-hand end of drum _E_ and actuate the yoke _A_ (see Fig. 33) which extends diagonally upward. The rear end of this yoke has rack teeth meshing with the teeth of a segmental pinion, which is fastened to rock-shaft _B_. At the headstock end, this rock-shaft carries another segmental pinion meshing with rack teeth formed on the cross-slide. The movement imparted to the yoke by the cams is thus transmitted through the pinions and rock-shaft to the cross-slide. [Illustration: Fig. 34. The Automatic Controlling Mechanism for Feeds and Speeds] The cam drum _E_ is driven by a pinion meshing with a gear attached to its front side. This pinion is driven through a train of gearing from pulley _L_ (see Fig. 34) which is belted to the spindle. The feeds are thus always dependent on the spindle speed. By means of epicyclic gearing and suitable clutches, the motion thus derived from the spindle may be made rapid for returning the turret to be indexed and then advancing it to the cutting position again, or very slow for the forward feed when the tools are at work. These changes from slow to fast or _vice versa_ are controlled by disk _D_. This disk carries pins which strike a star wheel located back of the disk at the top, and as this star wheel is turned, the speeds are changed by operation of the gearing and clutches referred to. The first pin _M_ that strikes the star wheel advances it one-sixth of a rotation, changing the feed from fast to slow; the next pin that strikes it advances it another sixth of a rotation, changing the feed from slow to fast and so on. By adjusting the pins for each piece of work, the feed changes are made to take place at the proper time. Handwheel _E_ is geared with the cam-shaft on which the star wheel is mounted, so that the feeds may be changed by hand if desired. In addition to these feed-changing pins, disk _D_ has a dog which operates a lever by which the feed movement is stopped when the work has been completed. Four rates of feed are provided by quick change gearing of the sliding gear type, operated by handle _K_. With this handle set in the central position, the feed is disengaged. On the periphery of disk _D_ are also clamped dogs or cams _N_, which operate a horizontal swinging lever _P_ connected by a link with vertical lever _J_, which controls the two spindle speeds with which the machine is provided. Either one of these speeds can be automatically engaged at any time, by adjusting the cams _N_ on disk _D_. Lever _H_ connects or disconnects the driving pulley from the shaft on which it is mounted, thus starting or stopping the machine. The square shaft _G_ serves to operate the drums by hand and is turned with a crank. The rotation of the turret, which takes place at the rear of its travel, is, of course, effected automatically. A dog, which may be seen in Fig. 32 at the side of the bed, is set to trip the turret revolving mechanism at the proper point in the travel, to avoid interference between the tools and the work. The turret is provided with an automatic clamping device. The mechanism first withdraws the locking pin, unclamps the turret, revolves it, then throws in the locking pin and clamps the turret again. =Example of Work on Automatic Turning Machine.=--The piece selected for illustrating the "setting up" and operation of the automatic chucking and turning machine is shown in Fig. 35. This is a second operation, and a very simple one which will clearly illustrate the principles involved. In the first operation, the hole was drilled, bored and reamed, the small end of the bushing faced, and the outside diameter finished, as indicated by the sketch to the left. (The enlarged diameter at the end was used for holding the work in the chuck.) In the second operation (illustrated to the right), the enlarged chucking end is cut off and, in order to prevent wasting this piece, it is made into a collar for another part of the machine for which the bushing is intended; hence, the outside diameter is turned and the outside end faced, before cutting off the collar. In addition, the bushing is recessed in the second operation, and the outer end faced. In order to have the surfaces finished in the second operation, concentric with those machined in the first operation, the chuck is equipped with a set of soft "false jaws" which have been carefully bored to exactly the diameter of the work to be held. [Illustration: Fig. 35. Simple Example of Work done in Automatic Chucking and Turning Machine] The first thing to determine when setting up a machine of this type is the order of operations. In this particular case, the order is as follows: At the first position of the turret, the outside collar is rough-turned and the outer end rough-faced. At the second position, the collar is turned to the required diameter and the outer face is finished. The third face of the turret is not equipped with tools, this part of the cycle being taken up in cutting off the collar with a cut-off tool on the rear cross-slide. The fourth operation is that of recessing the bushing, and the fifth operation, facing the end to remove the rough surface left by the cutting-off tool. The tools _A_ and _B_, Fig. 36, used for turning the outside of the flange, are held in brackets _C_ bolted to the face of the turret. These brackets are each provided with three holes for carrying turning tool-holders. This arrangement provides for turning a number of diameters at different positions, simultaneously, but for this particular operation, a single cutting tool for each tool-holder is all that is necessary. A special device is used for recessing and will be described later. [Illustration: Fig. 36. Front View of Machine set up for the Finishing Operation on the Recessed Bushing and Collar shown in the Foreground and in Fig. 35] =Determining Speed and Feed Changes.=--As previously mentioned, the particular machine illustrated in Fig. 32 can be arranged for two automatic changes of speed to suit different diameters on the work. The change gears that will give the required spindle speeds should first be selected. These change gears for different speeds are listed on a speed and feed plate attached to the headstock of the machine (see Fig. 37). It is possible to use one speed from the list given for the fast train of gears, and one from the list for the slow train, so long as the same gears are not used in each case. The diameter of the collar on the work shown in Fig. 35 is 2-1/2 inches, and the diameter of the body is 2 inches. Assuming that the surface speed for this job should be about 40 feet per minute, a little calculation shows that the 66 revolutions per minute, given by the fast train of gears, is equivalent to a surface speed of 43 feet per minute on a diameter of 2-1/2 inches. Moreover, the 78 revolutions per minute obtained from the slow train of gearing, gives about 41 feet per minute on a diameter of 2 inches. The spindle gearing indicated for these speeds is, therefore, placed in position on the proper studs at the back of the machine. [Illustration: Fig. 37. Plate on the Headstock of Machine Illustrated in Fig. 32 giving the Speeds and Feeds] Next we have to determine on which faces of the turret to place the different tools. Each turret face is numbered to agree with the corresponding feed cam on the drum. The speed and feed plate (Fig. 37) gives the various feeds obtainable per revolution of the spindle. As will be seen, the different cams give different feeds. Cam No. 1 has a coarse feed suitable for roughing; cam No. 2 a finer feed adapted to finishing, and so on. Since the first operation consists in rough-turning, cam No. 1 is used. Cam No. 2, which gives a finer feed, is used for the finish-turning operation. Cam No. 4, which is ordinarily used for reaming, could, in this case, be used for recessing, as this recess is for clearance only and may be bored with a coarse feed. The final operation, which is that of facing, can be done with any cam and cam No. 5 may be used. It will be understood that for facing operations, the feeds given do not apply. As the roll passes over the point of the feed cam at the extreme end of the movement, the feed of the turret slide is gradually slowed down to zero; since the facing takes place in the last eighth or sixteenth inch of this movement, it is done at a feed which is gradually reduced to zero. This is, of course, as it should be, and it is not necessary to pay any attention to the tabulated feeds in facing operations. =Setting the Turret Slide.=--The next adjustment is that of setting the turret slide. In making this adjustment the turret is set in such relation to the work that the tools will have but a small amount of overhang, the cam-shaft being revolved by hand until the cam-roll is at the extreme top of the forward feeding cam, so that the turret slide is at the extreme of its forward movement. When this adjustment has been made by the means provided, set the turret index tripping dog so as to revolve the turret at the proper point. After a turning tool-holder and tool is attached to the face of the turret, cam No. 1 is placed in its operating position and is revolved by hand until the roll is on the point of the cam and the turret at the forward extreme of its motion. At this point the tool-holder is set so that the cutter will be far enough forward to complete its turning operation. The feed cam is then turned backward, thus returning the turret slide, and the cutter is set to turn the flange to the proper diameter for the roughing cut. The turret slide is fed forward and back while the cutter is adjusted, and when it is properly set, the flange is turned, the cam-drum being fed by hand. This is the first trial cut on the piece. A facing tool, shown in the working position in Fig. 36, is placed at this station of the turret, being held in the turret hole. This tool has a pilot bar and a holder which contains a facing blade. Feeding by hand, as before, the tool is adjusted lengthwise so as to rough-face the work to the dimension desired. In a similar way the finish-turning and facing tools for the second position of the turret are set, the cam-shaft being revolved by hand to bring this second face and second cam into the working position. (The finish-facing tool is not shown in place in Fig. 36.) [Illustration: Fig. 38. Diagram of Cross-slide Cams and Feeding Mechanism] =Setting the Cross-slide Cam.=--As previously mentioned, the third turret face has no tool, the cutting off of the collar being done during this part of the cycle of operations. It has been taken for granted that in setting the turret slide, room has been left between it and the chuck for the cross-slide. The cross-slide is clamped in a longitudinal position on the bed, convenient for the cutting-off operation, which is done with a tool _D_ (Fig. 36) in the rear toolpost, thus leaving the front unobstructed for the operator. When both forming and cutting off are to be done, the forming tool is generally held at the front and the cutting-off tool at the back because heavier and more accurate forming can be done with the work revolving downward toward a tool in the front toolpost, than with the tool at the rear where it is subjected to a lifting action. The arrangement of the cross-slide cams is shown in Fig. 38, which is an end view of the large drum _E_, Fig. 32. The rear feed cam is the one to be used, and since this cutting-off operation is a short one, it may be done during the return of the turret for position No. 3. The cam drum is, therefore, rotated by hand until the turret face No. 3 has begun to return. The cross-slide cams are then loosened and the rear feed cam is swung around to just touch the roller _R_ which operates arm _A_, the cross-slide having been adjusted out to nearly the limit of its forward travel, leaving approximately enough movement for cutting off the collar. The rear feed cam is then clamped in this position. A cutting-off tool is next placed in the rear toolpost at the proper height. The rear toolpost slide is then adjusted to bring the point of the cutting-off tool up to the work, and the cam drum is revolved by hand until the piece is cut off. The cross-slide tool is, of course, set in the proper position to make a collar of the required thickness. Feeding by hand is discontinued when the roll is on the point of the cam; the cutting-off tool slide is then permanently set on the cross-slide so that the point of the cutting-off tool enters the bore just far enough to completely sever the collar from the bushing. The motion of the cam drum is continued, by hand, until the roll is over the point of the feed cam. The cross-slide is then pushed back, by hand, until the cam and roll are again in contact, when the return cam is brought up and clamped in position, so that there is just room for the roll between the feed cam and the return cam. The rear return cam (as the hand feed of the cam drum is continued) brings the cross-slide back to its central position. Since there is no front tool used for this series of operations (although a tool is shown in the front toolpost, Fig. 36), the first feed and return cams are allowed to remain wherever they happen to be. These cam adjustments can all be made from the front of the machine. =Setting the Boring Tool for Recessing.=--The feeding of the turret slide is now continued to make sure that the cutting-off tool is returned to its normal position before the facing tool in the next face of the turret begins to work. The facing of the bushing, so far as the setting of the tool is concerned, is merely a repetition of the facing operation at the first position of the turret. The recessing tool is next set. This tool, which is shown diagrammatically in Fig. 39, is very simple as compared with the somewhat complex operation it has to perform. This recess is for clearance only, and accurate dimensions and fine finish are not necessary. The recessing tool consists simply of a slender boring-bar held in the turret and carrying a cutter suitably located about midway the bar. The forward end of the bar is small enough to enter a bell-mouthed bushing held in the chuck. The boring-bar is bent to one side far enough so that the cutter clears the hole as the bar enters, but is forced into the work as the rounded hole of the bushing engages the end of the bar and deflects it into the working position. The upper diagram shows the position of the bar as it enters the hole, and the lower one the position after it has entered the bushing and is engaged in turning the recess. This bar is set in the turret so that at the extreme forward travel of the turret slide, the recess will be bored to the required length. The cutter must also be adjusted to bore to the desired diameter. This completes the setting of the cutting tools. [Illustration: Fig. 39. Flexible Boring Tool used for Recessing a Bushing in Automatic Chucking and Turning Machine] =Adjustments for Automatic Feed and Speed Changes.=--The machine must now be set to perform automatically the desired changes of spindle speed and the fast and slow cam movements for the tools. After placing a new piece of work in the machine (the first one having been completed in the setting-up operation), the cam-shaft is revolved by hand until the turning tool in turret face No. 1 is just about to begin its cut. The control wheel _D_, Fig. 34, is rotated in its normal direction until the next graduation marked "slow" is in line with an index mark on the base of the machine. Then the nearest pin _M_ is moved up until it bears against a tooth of the star wheel (previously referred to) and is clamped in this position. The pin should now be in the proper location, but to test its position, rotate the cam shaft backward by hand and throw in the automatic feed; then watch the cut to see if the drum slows down just before the tool begins to work. If it does not, the pin should be adjusted a little, one way or the other, as may be required. (In going over a piece of work for the first time, it is best to have the feed set to the smallest rate, feed change handle _K_ being in position No. 1.) After the cut has been completed and the turret feed cam-roll is on the high part of the cam, the power feed should again be stopped and the handwheel revolved until the next graduation marked "fast" is opposite the index mark. The next stop pin is then moved up until it just touches the star wheel, where it is clamped in position. The feed being again thrown in, the turret will be returned rapidly, indexed, and moved forward for the second operation. After stopping the automatic movement, the pins are set for this face, and so on for all the operations, including that in which the cross-slide is used for cutting off the finished collar. As the first, second, and third operations are on comparatively large diameters, they should be done at the slow speed, handle _J_, Fig. 34, being set to give that speed. While the turret slide is being returned between operations 3 and 4, one of the spindle speed-changing dogs _N_ should be clamped to the rim of disk _D_ so as to change the spindle speed to the fast movement. This speed is continued until the last operation is completed, when a second dog is clamped in place to again throw in the slow movement. The feed knock-off dog should also be clamped in place on the disk to stop the machine at the completion of the fifth operation, when the turret is in its rear position. This completes the setting up of the machine. If the feed is finer than is necessary, the feed change handle _K_ may now be moved to a position which will give the maximum feed that can be used. It has taken considerable time to describe the setting up of the machine for this simple operation, but in the hands of a competent man it can be done quite rapidly. While a simple operation has been referred to in the foregoing, it will be understood that a great variety of work can be done on a machine of this type. It is not unusual to see as many as ten cutting tools operating simultaneously on a piece of work, the tools being carried by the turret, cross-slide and back facing attachment. The latter is operated from a separate cam applied to the cam-shaft and acting through levers on a back facing bar which passes through a hole in the spindle. In this back facing bar may be mounted drills, cutters, facing tools, etc. for machining the rear face of a casting held in the chuck jaws. Where extreme accuracy is required, a double back facing attachment may be used, arranged with cutters for taking both roughing and finishing cuts. The use of this attachment often saves a second operation. This automatic chucking and turning machine is also adapted for bar work, especially in diameters varying from 3 to 6 inches. =Turning Flywheel in Automatic Chucking and Turning Machine.=--A typical operation on the Potter & Johnston automatic chucking and turning machine is illustrated in Fig. 40, which shows the machine arranged for turning the cast-iron flywheel for the engine of a motor truck. The rim is turned and faced on both sides and the hub is bored, reamed and faced on both sides. The flywheel casting is held in a chuck by three special jaws which grip the inside of the rim. The order of the operations is as follows: The rear end of the hub is faced by the back facing bar; the cored hole is started by a four-lipped drill in the turret and the front end of the hub is rough-faced. (These tools are on the rear side of the turret when the latter is in the position shown in the illustration.) After the turret indexes, the hole is rough-bored by tool _A_ and while this is being done, the outside of the rim is rough-turned by tool _B_ held in a special bracket attached to the turret. Both sides of the rim are also rough-faced by tools _C_ and _D_ held at the front of the cross-slide, this operation taking place at the same time that the rim is turned and the hole is being bored. [Illustration: Fig. 40. Machining Flywheels in Potter & Johnston Automatic Chucking and Turning Machine] The turret again automatically recedes and indexes, thus locating bar _E_ and turning tool _G_ in the working position. The hole is then finish-bored by tool _E_ and the hub is finish-faced by blade _F_; at the same time the rim is finish-turned by tool _G_ and the sides are finish-faced to the proper width by two tools held at the rear of the cross-slide. The turret automatically recedes and indexes a third time, thus locating the flat-cutter reamer-bar _H_ in the working position and then the hole is reamed to the required diameter. This completes the cycle of operations. The total time for machining this flywheel is forty minutes. =Automatic Multiple-spindle Chucking Machine.=--An example of the specialized machines now used for producing duplicate parts, is shown in Fig. 41. This is a "New Britain" automatic multiple-spindle chucking machine of the single-head type and it is especially adapted for boring, reaming and facing operations on castings or forgings which can readily be held in chuck jaws. This particular machine has five spindles, which carry and revolve the tools. The work being machined is held stationary in the multiple chuck turret _A_ which holds each part in line with one of the spindles and automatically indexes, so that the work passes from one spindle to another until it is finished. The turret then indexes the finished piece to a sixth or "loading position" which is not opposite a spindle, where the part is removed and replaced with a rough casting. Each pair of chuck jaws is operated independently of the others by the use of a chuck wrench. These jaws are made to suit the shape of the work. [Illustration: Fig. 41. New Britain Multiple-spindle Automatic Chucking Machine of Single-head Type] When a single-head machine is in operation, the turret advances and feeds the work against the revolving tools so that a number of pieces are operated upon at the same time. The turret is fed by a cam drum _B_. Cam strips are bolted to the outside of this drum and act directly against a roller attached to the yoke _C_ which can be clamped in different positions on the spindle _D_, the position depending upon the length of the work. On the opposite end of the turret spindle is the indexing mechanism _E_. An automatically spring-operated latch _F_ engages notches in the rim of the dividing wheel, thus accurately locating the turret. The turret is locked by a steadyrest _G_, which, for each working position, automatically slides into engagement with one of the notches in the turret. This relieves the indexing mechanism of all strain. [Illustration: Fig. 42. Detail View of New Britain Double-head Eight-spindle Machine, Boring, Reaming and Facing Castings] This type of machine is also built with two spindle heads, the double-head design being used for work requiring operations on both ends. When the double-head machine is in operation, the revolving spindles and tools advance on both sides of the chuck turret, the latter remaining stationary except when indexing. The feed drums on the double-head machine are located directly beneath each group of spindles. Fig. 42 shows an example of work on a machine of the double-head design. This is an eight-spindle machine, there being two groups of four spindles on each side of the turret. The castings _E_ are for the wheel hubs of automobiles. The order of the operations on one of the castings, as it indexes around, is as follows: The hole in the hub is first rough-reamed by taper reamer _A_ and the opposite end of the hub is rough-faced and counterbored by a tool in spindle _A_{1}_. When the turret indexes, this same casting is reamed close to the finished size by reamer _B_ and the left end of the hub is rough-faced by cutter _F_, while a tool in the opposite spindle _B_{1}_ finishes the counterboring and facing operation. At the third position, reamer _C_ finishes the hole accurately to size, and when the work is indexed to the fourth position, the hub on the left side is finish-faced by a tool in spindle _D_. (The third and fourth spindles of the right-hand group are not used for this particular operation.) When the turret again indexes, the finished casting is removed and replaced with a rough one. While the successive operations on a single casting have just been described, it will be understood that all of the tools operate simultaneously and that a finished casting arrives at the unloading and loading position each time the turret indexes. Three hundred of these malleable castings are machined in nine hours. =Selecting Type of Turning Machine.=--The variety of machine tools now in use is very extensive, and as different types can often be employed for the same kind of work, the selection of the best and most efficient machine is often a rather difficult problem. To illustrate, there are many different types and designs of turning machines, such as the ordinary engine lathe, the hand-operated turret lathe, the semi-automatic turning machine, and the fully automatic type, which, after it is "set up" and started, is entirely independent. Hence, when a certain part must be turned, the question is, what kind of machine should be used, assuming that it would be possible to employ several different machines? The answer to this question usually depends principally upon the number of parts that must be turned. For example, a certain casting or forging might be turned in a lathe, which could be finished in some form of automatic or semi-automatic turning machine much more quickly. It does not necessarily follow, however, that the automatic is the best machine to use, because the lathe is designed for general work and the part referred to could doubtless be turned with the regular lathe equipment, whereas the automatic machine would require special tools and it would also need to be carefully adjusted. Therefore, if only a few parts were needed, the lathe might be the best tool to use, but if a large number were required, the automatic or semi-automatic machine would doubtless be preferable, because the saving in time effected by the latter type would more than offset the extra expense for tool equipment and setting the machine. It is also necessary, in connection with some work, to consider the degree of accuracy required, as well as the rate of production, and it is because of these varying conditions that work of the same general class is often done in machines of different types, in order to secure the most efficient results. CHAPTER VI VERTICAL BORING MILL PRACTICE All the different types of turning machines now in use originated from the lathe. Many of these tools, however, do not resemble the lathe because, in the process of evolution, there have been many changes made in order to develop turning machines for handling certain classes of work to the best advantage. The machine illustrated in Fig. 1 belongs to the lathe family and is known as a vertical boring and turning mill. This type, as the name implies, is used for boring and turning operations, and it is very efficient for work within its range. The part to be machined is held to the table _B_ either by clamps or in chuck jaws attached to the table. When the machine is in operation, the table revolves and the turning or boring tools (which are held in tool-blocks _T_) remain stationary, except for the feeding movement. Very often more than one tool is used at a time, as will be shown later by examples of vertical boring mill work. The tool-blocks _T_ are inserted in tool-bars _T_{1}_ carried by saddles _S_ which are mounted on cross-rail _C_. Each tool-head (consisting of a saddle and tool-bar) can be moved horizontally along cross-rail _C_, and the tool-bars _T_{1}_ have a vertical movement. These movements can be effected either by hand or power. When a surface is being turned parallel to the work table, the entire tool-head moves horizontally along the cross-rail, but when a cylindrical surface is being turned, the tool-bar moves vertically. The tool-heads are moved horizontally by the screws _H_ and _H_{1}_, and the vertical feed for the tool-bars is obtained from the splined shafts _V_ and _V_{1}_, there being a separate screw and shaft for each head so that the feeding movements are independent. These feed shafts are rotated for the power feed by vertical shafts _A_ and _A_{1}_ on each side of the machine. These vertical shafts connect with the feed shafts through bevel and spur gears located at the ends of the cross-rail. On most boring mills, connection is made with one of the splined shafts _V_ or screw _H_, by a movable gear, which is placed on whichever shaft will give the desired direction of feed. The particular machine illustrated is so arranged that either the right or left screw or feed shaft can be engaged by simply shifting levers _D_{1}_ or _D_. [Illustration: Fig. 1. Gisholt Vertical Boring and Turning Mill] The amount of feed per revolution of the table is varied for each tool-head by feed-changing mechanisms _F_ on each side of the machine. These feed boxes contain gears of different sizes, and by changing the combinations of these gears, the amount of feed is varied. Five feed changes are obtained on this machine by shifting lever _E_, and this number is doubled by shifting lever _G_. By having two feed boxes, the feeding movement of each head can be varied independently. The direction of either the horizontal or vertical feed can be reversed by lever _R_, which is also used for engaging or disengaging the feeds. This machine is equipped with the dials _I_ and _I_{1}_ which can be set to automatically disengage the feed at any predetermined point. There are also micrometer dials graduated to thousandths of an inch and used for adjusting the tools without the use of measuring instruments. The work table _B_ is driven indirectly from a belt pulley at the rear, which transmits the power through gearing. The speed of the table can be varied for turning large or small parts, by levers _J_ and _K_ and the table can be started, stopped or rotated part of a revolution by lever _L_ which connects with a friction clutch. There are corresponding feed and speed levers on the opposite side, so that the machine can be controlled from either position. The heads can be adjusted along the cross-rail for setting the tools by hand-cranks _N_, and the tool slides can be moved vertically by turning shafts _V_ with the same cranks. With this machine, however, these adjustments do not have to be made by hand, ordinarily, as there are rapid power movements controlled by levers _M_. These levers automatically disengage the feeds and enable the tool-heads to be rapidly shifted to the required position, the direction of the movement depending upon the position of the feed reverse lever _R_ and lever _D_. This rapid traverse, which is a feature applied to modern boring mills of medium and large size, saves time and the labor connected with hand adjustments. The cross-rail _C_ has a vertical adjustment on the faces of the right and left housings which support it, in order to locate the tool-heads at the right height for the work. This adjustment is effected by power and is controlled by levers at the sides of the housings. Normally, the cross-rail is bolted to the housings, and these bolts must be loosened before making the adjustment, and must always be tightened afterwards. The function of these different levers has been explained to show, in a general way, how a vertical boring machine is operated. It should be understood, however, that the arrangement differs considerably on machines of other makes. The construction also varies considerably on machines of the same make but of different size. [Illustration: Fig. 2. Small Boring and Turning Mill with Single Turret-head] All modern vertical boring mills of medium and large sizes are equipped with two tool-heads, as shown in Fig. 1, because a great deal of work done on a machine of this type can have two surfaces machined simultaneously. On the other hand, small mills of the type illustrated in Fig. 2 have a single head. The toolslide of this machine, instead of having a single tool-block, carries a five-sided turret _T_ in which different tools can be mounted. These tools are shifted to the working position as they are needed, by loosening binder lever _L_ and turning or "indexing" the turret. The turret is located and locked in any of its five positions by lever _I_, which controls a plunger that engages notches at the rear. Frequently, all the tools for machining a part can be held in the turret, so that little time is required for changing from one tool to the next. Some large machines having two tool-heads are also equipped with a turret on one head. =Boring and Turning in a Vertical Boring Mill.=--The vertical boring mill is, in many respects, like a lathe placed in a vertical position, the table of the mill corresponding to the faceplate or chuck of the lathe and the tool-head to the lathe carriage. Much of the work done by a vertical mill could also be machined in a lathe, but the former is much more efficient for work within its range. To begin with, it is more convenient to clamp work to a horizontal table than to the vertical surface of a lathe faceplate, or, as someone has aptly said, "It is easier to lay a piece down than to hang it up." This is especially true of the heavy parts for which the boring mill is principally used. Very deep roughing cuts can also be taken with a vertical mill. This type of machine mill is designed for turning and boring work which, generally speaking, is quite large in diameter in proportion to the width or height. The work varies greatly, especially in regard to its diameter, so that boring mills are built in a large range of sizes. The small and medium sizes will swing work varying from about 30 inches to 6 or 7 feet in diameter, whereas large machines, such as are used for turning very large flywheels, sheaves, etc., have a swing of 16 or 20 feet, and larger sizes are used in some shops. The size of a vertical mill, like any other machine tool, should be somewhat in proportion to the size of the work for which it is intended, as a very large machine is unwieldy, and, therefore, inefficient for machining comparatively small parts. =Holding and Setting Work on Boring Mill Table.=--There are three general methods of holding work to the table of a boring mill; namely, by the use of chucks, by ordinary bolts and clamps, or in special fixtures. Chucks which are built into the table (as illustrated in Fig. 2) and have both universal and independent adjustments for the jaws can be used to advantage for holding castings that are either round or irregular in shape. The universal adjustment is used for cylindrical parts, such as disks, flywheels, gear blanks, etc., and the independent adjustment, for castings of irregular shape. Chucks which have either an independent or universal movement for the jaws are known as a "combination" type and usually have three jaws. There is also a four-jaw type which has the independent adjustment only. This style is preferable for work that is not cylindrical and which must be held very securely. Chuck jaws that do not form a part of the machine table, but are bolted to it in the required position, are also employed extensively, especially on comparatively large machines. Most of the work done in a vertical mill is held in a chuck. Occasionally, however, it is preferable to clamp a part directly to the table. This may be desirable because of the shape and size of the work, or because it is necessary to hold a previously machined surface directly against the table in order to secure greater accuracy. Sometimes a casting is held in the chuck for turning one side, and then the finished side is clamped against the table for turning the opposite side. Parts which are to be machined in large quantities are often held in special fixtures. This method is employed when it enables the work to be set up more quickly than would be possible if regular clamps or chuck jaws were used. Work that is to be turned or bored should first be set so that the part to be machined is about central with the table. For example, the rim of a flywheel should be set to run true so that it can be finished by removing about the same amount of metal around the entire rim; in other words, the rim should be set concentric with the table, as shown in Fig. 3, and the sides of the rim should also be parallel to the table. [Illustration: Fig. 3. Plan View showing Flywheel Casting Chucked for Turning] A simple tool that is very useful for testing the position of any cylindrical casting consists of a wooden shank into which is inserted a piece of wire, having one end bent. This tool is clamped in the toolpost and as the work revolves the wire is adjusted close to the cylindrical surface being tested. The movement of the work with relation to the stationary wire point will, of course, show whether or not the part runs true. The advantage of using a piece of wire for testing, instead of a rigid tool, is that the wire, owing to its flexibility, will simply be bent backward if it is moved too close to a surface which is considerably out of true. The upper surface of a casting can be tested for parallelism with the table by using this same wire gage, or by comparing the surface, as the table is revolved slowly, with a tool held in the toolpost. An ordinary surface gage is also used for this purpose. The proper surface to set true, in any case, depends upon the requirements. A plain cylindrical disk would be set so that the outside ran true and the top surface was parallel with the table. When setting a flywheel, if the inside of the rim is to remain rough, the casting should be set by this surface rather than by the outside, so that the rim, when finished, will be uniform in thickness. As far as possible, chucks should be used for holding cylindrical parts, owing to their convenience. The jaws should be set against an interior cylindrical surface whenever this is feasible. To illustrate, the flywheel in Fig. 3 is gripped by the inside of the rim which permits the outside to be turned at this setting of the work. It is also advisable to set a flywheel casting in the chuck so that a spoke rests against one of the jaws as at _d_, if this is possible. This jaw will then act as a driver and prevent the casting from slipping or turning in the chuck jaws, owing to the tangential pressure of the turning tool. When a cut is being taken, the table and work rotate as shown by arrow _a_, and the thrust of the cut (taken by tool _t_) tends to move the wheel backward against the direction of rotation, as shown by arrow _b_. If one of the chuck jaws bears against one of the spokes, this movement is prevented. It is not always feasible to use a chuck jaw as a driver and then a special driver having the form of a small angle-plate or block is sometimes bolted directly to the table. Another method of driving is to set a brace between a spoke or projection on the work and a chuck jaw or strip attached to the table. Drivers are not only used when turning flywheels, but in connection with any large casting, especially when heavy cuts have to be taken. Of course, some castings are so shaped that drivers cannot be employed. =Turning in a Boring Mill.=--The vertical type of boring mill is used more for turning cylindrical surfaces than for actual boring, although a large part of the work requires both turning and boring. We shall first consider, in a general way, how surfaces are turned and then refer to some boring operations. The diagram _A_, Fig. 4, illustrates how a horizontal surface would be turned. The tool _t_ is clamped in tool-block _t_{1}_, in a vertical position, and it is fed horizontally as the table and work rotate. The tool is first adjusted by hand for the proper depth of cut and the automatic horizontal feed is then engaged. When a cylindrical surface is to be turned, the tool (provided a straight tool is used) is clamped in a horizontal position and is fed downward as indicated at _B_. The amount that the tool should feed per revolution of the work, depends upon the kind of material being turned, the diameter of the turned part and the depth of the cut. [Illustration: Fig. 4. (A) Turning a Flat Surface. (B) Turning a Cylindrical Surface] Most of the parts machined in a vertical boring mill are made of cast iron and, ordinarily, at least one roughing and one finishing cut is taken. The number of roughing cuts required in any case depends, of course, upon the amount of metal to be removed. An ordinary roughing cut in soft cast iron might vary in depth from 1/8 or 3/16 inch to 3/8 or 1/2 inch and the tool would probably have a feed per revolution of from 1/16 to 1/8 inch, although deeper cuts and coarser feeds are sometimes taken. These figures are merely given to show, in a general way, what cuts and feeds are practicable. The tool used for roughing usually has a rounded end which leaves a ridged or rough surface. To obtain a smooth finish, broad flat tools are used. The flat cutting edge is set parallel to the tool's travel and a coarse feed is used in order to reduce the time required for taking the cut. The finishing feeds for cast iron vary from 1/4 to 3/4 inch on ordinary work. The different tools used on the vertical mill will be referred to more in detail later. All medium and large sized vertical boring mills are equipped with two tool-heads and two tools are frequently used at the same time, especially on large work. Fig. 9 illustrates the use of two tools simultaneously. The casting shown is a flywheel, and the tool on the right side turns the upper side of the rim, while the tool on the left side turns the outside or cylindrical surface. As a boring mill table rotates in a counter-clockwise direction, the left-hand tool is reversed to bring the cutting edge at the rear. By turning two surfaces at once, the total time for machining the casting is, of course, greatly reduced. The turning of flywheels is a common vertical boring mill operation, and this work will be referred to in detail later on. [Illustration: Fig. 5. Tools for Boring and Reaming Holes] =Boring Operations.=--There are several methods of machining holes when using a vertical boring mill. Ordinarily, small holes are cored in castings and it is simply necessary to finish the rough surface to the required diameter. Some of the tools used for boring and finishing comparatively small holes are shown in Fig. 5. Sketch _A_ shows a boring tool consisting of a cutter _c_ inserted in a shank, which, in turn, is held in the tool slide, or in a turret attached to the tool slide. With a tool of this type, a hole is bored by taking one or more cuts down through it. The tool shown at _B_ is a four-lipped drill which is used for drilling cored holes preparatory to finishing by a cutter or reamer. This drill would probably finish a hole to within about 1/32 inch of the finish diameter, thus leaving a small amount of metal for the reamer to remove. The tool illustrated at _C_ has a double-ended flat cutter _c_, which cuts on both sides. These cutters are often made in sets for boring duplicate parts. Ordinarily, there are two cutters in a set, one being used for roughing and the other for finishing. The cutter passes through a rectangular slot in the bar and this particular style is centrally located by shoulders _s_, and is held by a taper pin _p_. Some cutter bars have an extension end, or "pilot" as it is called, which passes through a close-fitting bushing in the table to steady the bar. Sketch _D_ shows a finishing reamer. This tool takes a very light cut and is intended to finish holes that have been previously bored close to the required size. Sometimes a flat cutter _C_ is used for roughing and a reamer for finishing. The reamer is especially desirable for interchangeable work, when all holes must have a smooth finish and be of the same diameter. When a reamer is held rigidly to a turret or toolslide, it is liable to produce a hole that is either tapering or larger than the reamer diameter. To prevent this, the reamer should be held in a "floating" holder which, by means of a slight adjustment, allows the reamer to align itself with the hole. There are several methods of securing this "floating" movement. (See "Floating Reamer Holders.") [Illustration: Fig. 6. Boring with Regular Turning Tools] Large holes or interior cylindrical surfaces are bored by tools held in the regular tool-head. The tool is sometimes clamped in a horizontal position as shown at _A_, Fig. 6, or a bent type is used as at _B_. Cast iron is usually finished by a broad flat tool as at _C_, the same as when turning exterior surfaces. Obviously a hole that is bored in this way must be large enough to admit the tool-block. [Illustration: Fig. 7. Set of Boring Mill Tools] =Turning Tools for the Vertical Boring Mill.=--A set of turning tools for the vertical boring mill is shown in Fig. 7. These tools can be used for a wide variety of ordinary turning operations. When a great many duplicate parts are to be machined, special tool equipment can often be used to advantage, but as the form of this equipment depends upon the character of the work, only standard tools have been shown in this illustration. The tool shown at _A_ is a right-hand, roughing tool, and a left-hand tool of the same type is shown at _B_. Tool _C_ is an offset or bent, left-hand round nose for roughing, and _D_ is a right-hand offset roughing tool. A straight round nose is shown at _E_. Tool _F_ has a flat, broad cutting edge and is used for finishing. Left-and right-hand finishing tools of the offset type are shown at _G_ and _H_, respectively. Tool _I_ has a square end and is used for cutting grooves. Right-and left-hand parting tools are shown at _J_ and _K_, and tool _L_ is a form frequently used for rounding corners. [Illustration: Fig. 8. Diagrams Illustrating Use of Different Forms of Tools] The diagrams in Fig. 8 show, in a general way, how each of the tools illustrated in Fig. 7 are used, and corresponding tools are marked by the same reference letters in both of these illustrations. The right-and left-hand roughing tools _A_ and _B_ are especially adapted for taking deep roughing cuts. One feeds away from the center of the table, or to the right (when held in the right-hand tool-block) and the other tool is ground to feed in the opposite direction. Ordinarily, when turning plain flat surfaces, the cut is started at the outside and the tool feeds toward the center, as at _B_, although it is sometimes more convenient to feed in the opposite direction, as at _A_, especially when there is a rim or other projecting part at the outside edge. The tool shown at _A_ could also be used for turning cylindrical surfaces, by clamping it in a horizontal position across the bottom of the tool-block. The feeding movement would then be downward or at right-angles to the work table. The offset round-nose tools _C_ and _D_ are for turning exterior or interior cylinder surfaces. The shank of this tool is clamped in the tool-block in a vertical position and as the bent end extends below the tool-block, it can be fed down close to a shoulder. The straight type shown at _E_ is commonly used for turning steel or iron, and when the point is drawn out narrower, it is also used for brass, although the front is then ground without slope. Tool _F_ is for light finishing cuts and broad feeds. The amount of feed per revolution of the work should always be less than the width of the cutting edge as otherwise ridges will be left on the turned surface. The offset tools _G_ and _H_ are for finishing exterior and interior cylindrical surfaces. These tools also have both vertical and horizontal cutting edges and are sometimes used for first finishing a cylindrical and then a horizontal surface, or _vice versa_. Tool _I_ is adapted to such work as cutting packing-ring grooves in engine pistons, forming square or rectangular grooves, and similar work. The parting tools _J_ and _K_ can also be used for forming narrow grooves or for cutting off rings, etc. The sketch _K_ (Fig. 8) indicates how a tool of this kind might be used for squaring a corner under a shoulder. Tool _L_ is frequently used on boring mills for rounding the corners of flywheel rims, in order to give them a more finished appearance. It has two cutting edges so that either side can be used as when rounding the inner and outer corners of a rim. The turning tools of a vertical boring mill are similar, in many respects, to those used in a lathe, although the shanks of the former are shorter and more stocky than those of lathe tools. The cutting edges of some of the tools also differ somewhat in form, but the principles which govern the grinding of lathe and boring mill tools are identical, and those who are not familiar with tool grinding are referred to Chapter II, in which this subject is treated. =Turning a Flywheel on a Vertical Mill.=--The turning of a flywheel is a good example of the kind of work for which a vertical boring mill is adapted. A flywheel should preferably be machined on a double-head mill so that one side and the periphery of the rim can be turned at the same time. A common method of holding a flywheel is shown in Fig. 9. The rim is gripped by four chuck jaws _D_ which, if practicable, should be on the inside where they will not interfere with the movement of the tool. Two of the jaws, in this case, are set against the spokes on opposite sides of the wheel, to act as drivers and prevent any backward shifting of work when a heavy cut is being taken. The illustration shows the tool to the right rough turning the side of the rim, while the left-hand tool turns the periphery. Finishing cuts are also taken over the rim, at this setting, and the hub is turned on the outside, faced on top, and the hole bored. [Illustration: Fig. 9. Turning the Rim of a Flywheel] The three tools _A_, _B_ and _C_, for finishing the hole, are mounted in the turret. Bar _A_, which carries a cutter at its end, first rough bores the hole. The sizing cutter _B_ is then used to straighten it before inserting the finishing reamer _C_. Fig. 10 shows the turret moved over to a central position and the sizing cutter _B_ set for boring. The head is centrally located (on this particular machine) by a positive center-stop. The turret is indexed for bringing the different tools into the working position, by loosening the clamping lever _L_ and pulling down lever _I_ which disengages the turret lock-pin. When all the flywheels in a lot have been machined as described, the opposite side is finished. [Illustration: Fig. 10. Tool B set for Boring the Hub] [Illustration: Fig. 11. Diagrams showing Method of Turning and Boring a Flywheel on a Double-head Mill having one Turret Head] In order to show more clearly the method of handling work of this class, the machining of a flywheel will be explained more in detail in connection with Fig. 11, which illustrates practically the same equipment as is shown in Figs. 9 and 10. The successive order in which the various operations are performed is as follows: Tool _a_ (see sketch _A_) rough turns the side of the rim, while tool _b_, which is set with its cutting edge toward the rear, rough turns the outside. The direction of the feeding movement for each tool is indicated by the arrows. When tool _a_ has crossed the rim, it is moved over for facing the hub, as shown by the dotted lines. The side and periphery of the rim are next finished by the broad-nose finishing tools _c_ and _d_ (see sketch _B_). The feed should be increased for finishing, so that each tool will have a movement of say 1/4 or 3/8 inch per revolution of the work, and the cuts should, at least, be deep enough to remove the marks made by the roughing tools. Tool _c_ is also used for finishing the hub as indicated by the dotted lines. After these cuts are taken, the outside of the hub and inner surface of the rim are usually turned down as far as the spokes, by using offset tools similar to the ones shown at _C_ and _D_ in Fig. 7. The corners of the rim and hub are also rounded to give the work a more finished appearance, by using a tool _L_. The next operation is that of finishing the hole through the hub. The hard scale is first removed by a roughing cutter _r_ (sketch _C_), which is followed by a "sizing" cutter _s_. The hole is then finished smooth and to the right diameter by reamer _f_. The bars carrying cutters _r_ and _s_ have extensions or "pilots" which enter a close-fitting bushing in the table, in order to steady the bar and hold it in alignment. When the hole is finished, the wheel is turned over, so that the lower side of the rim and hub can be faced. The method of holding the casting for the final operation is shown at _D_. The chuck jaws are removed, and the finished side of the rim is clamped against parallels _p_ resting on the table. The wheel is centrally located for turning this side by a plug _e_ which is inserted in a hole in the table and fits the bore of the hub. The wheel is held by clamps which bear against the spokes. Roughing and finishing cuts are next taken over the top surface of the rim and hub and the corners are rounded, which completes the machining operations. If the rim needs to be a certain width, about the same amount of metal should be removed from each side, unless sandy spots or "blow-holes" in the casting make it necessary to take more from one side than from the other. That side of the rim which was up in the mold when the casting was made should be turned first, because the porous, spongy spots usually form on the "cope" or top side of a casting. =Convex Turning Attachment for Boring Mills.=--Fig. 12 shows a vertical boring mill arranged for turning pulleys having convex rims; that is, the rim, instead of being cylindrical, is rounded somewhat so that it slopes from the center toward either side. (The reason for turning a pulley rim convex is to prevent the belt from running off at one side, as it sometimes tends to do when a cylindrical pulley is used.) The convex surface is produced by a special attachment which causes the turning tool to gradually move outward as it feeds down, until the center of the rim is reached, after which the movement is inward. [Illustration: Fig. 12. Gisholt Mill equipped with Convex Turning Attachment] The particular attachment shown in Fig. 12 consists of a special box-shaped tool-head _F_ containing a sliding holder _G_, in which the tool is clamped by set-screws passing through elongated slots in the front of the tool-head. In addition, there is a radius link _L_ which swivels on a stud at the rear of the tool-head and is attached to vertical link _H_. Link _L_ is so connected to the sliding tool-block that any downward movement of the tool-bar _I_ causes the tool to move outward until the link is in a horizontal position, after which the movement is reversed. When the attachment is first set up, the turning tool is placed at the center of the rim and then link _L_ is clamped to the vertical link while in a horizontal position. The cut is started at the top edge of the rim, and the tool is fed downward by power, the same as when turning a cylindrical surface. The amount of curvature or convexity of a rim can be varied by inserting the clamp bolt _J_ in different holes in link _L_. [Illustration: Fig. 13. Turning a Taper or Conical Surface] The tools for machining the hub and sides of the rim are held in a turret mounted on the left-hand head, as shown. The special tool-holder _A_ contains two bent tools for turning the upper and lower edges of the pulley rim at the same time as the tool-head is fed horizontally. Roughing and finishing tools _B_ are for facing the hub, and the tools _C_, _D_, and _E_ rough bore, finish bore, and ream the hole for the shaft. =Turning Taper or Conical Surfaces.=--Conical or taper surfaces are turned in a vertical boring mill by swiveling the tool-bar to the proper angle as shown in Fig. 13. When the taper is given in degrees, the tool-bar can be set by graduations on the edge of the circular base _B_, which show the angle _a_ to which the bar is swiveled from a vertical position. The base turns on a central stud and is secured to the saddle _S_ by the bolts shown, which should be tightened after the tool-bar is set. The vertical power feed can be used for taper turning the same as for cylindrical work. [Illustration: Fig. 14. Turning a Conical Surface by using the Combined Vertical and Horizontal Feeds] Occasionally it is necessary to machine a conical surface which has such a large included angle that the tool-bar cannot be swiveled far enough around to permit turning by the method illustrated in Fig. 13. Another method, which is sometimes resorted to for work of this class, is to use the combined vertical and horizontal feeds. Suppose we want to turn the conical casting _W_ (Fig. 14), to an angle of 30 degrees, as shown, and that the tool-head of the boring mill moves horizontally 1/4 inch per turn of the feed-screw and has a vertical movement of 3/16 inch per turn of the upper feed-shaft. If the two feeds are used simultaneously, the tool will move a distance _h_ of say 8 inches, while it moves downward a distance _v_ of 6 inches, thus turning the surface to an angle _y_. This angle is greater (as measured from a horizontal plane) than the angle required, but, if the tool-bar is swiveled to an angle _x_, the tool, as it moves downward, will also be advanced horizontally, in addition to the regular horizontal movement. The result is that the angle _y_ is diminished and if the tool-bar is set over the right amount, the conical surface can be turned to an angle _a_ of 30 degrees. The problem, then, is to determine what the angle _x_ should be for turning to a given angle _a_. [Illustration: Fig. 15. Diagram showing Method of Obtaining Angular Position of Tool-head when Turning Conical Surfaces by using Vertical and Horizontal Feeding Movements] The way angle _x_ is calculated will be explained in connection with the enlarged diagram, Fig. 15, which shows one-half of the casting. The sine of the known angle _a_ is first found in a table of natural sines. Then the sine of angle _b_, between the taper surface and center-line of the tool-head, is determined as follows: sin_b_ = (sin_a_ � _h_) ÷ _v_, in which _h_ represents the rate of horizontal feed and _v_ the rate of vertical feed. The angle corresponding to sine _b_ is next found in a table of sines. We now have angles _b_ and _a_, and by subtracting the sum of these angles from 90 degrees, the desired angle _x_ is obtained. To illustrate: The sine of 30 degrees is 0.5; then sin _b_ = (0.5 � 1/4) ÷ 3/16 = 0.6666; hence angle _b_ = 41 degrees 49 minutes, and _x_ = 90°-(30° + 41° 49') = 18 degrees 11 minutes. Hence to turn the casting to angle _a_ in a boring mill having the horizontal and vertical feeds given, the tool-head would be set over from the vertical 18 degrees and 11 minutes which is equivalent to about 18-1/6 degrees. If the required angle _a_ were greater than angle _y_ obtained from the combined feeds with the tool-bar in a vertical position, it would then be necessary to swing the lower end of the bar to the left rather than to the right of a vertical plane. When the required angle _a_ exceeds angle _y_, the sum of angles _a_ and _b_ is greater than 90 degrees so that angle _x_ for the tool-head = (_a_ + _b_) - 90 degrees. =Turret-lathe Type of Vertical Boring Mill.=--The machine illustrated in Fig. 16 was designed to combine the advantages of the horizontal turret lathe and the vertical boring mill. It is known as a "vertical turret lathe," but resembles, in many respects, a vertical boring mill. This machine has a turret on the cross-rail the same as many vertical boring mills, and, in addition, a side-head _S_. The side-head has a vertical feeding movement, and the tool-bar _T_ can be fed horizontally. The tool-bar is also equipped with a four-sided turret for holding turning tools. This arrangement of the tool-heads makes it possible to use two tools simultaneously upon comparatively small work. When both heads are mounted on the cross-rail, as with a double-head boring mill, it is often impossible to machine certain parts to advantage, because one head interferes with the other. The drive to the table (for the particular machine illustrated) is from a belt pulley at the rear, and fifteen speed changes are available. Five changes are obtained by turning the pilot-wheel _A_ and this series of five speeds is compounded three times by turning lever _B_. Each spoke of pilot-wheel _A_ indicates a speed which is engaged only when the spoke is in a vertical position, and the three positions for _B_ are indicated, by slots in the disk shown. The number of table revolutions per minute for different positions of pilot-wheel _A_ and lever _B_ are shown by figures seen through whichever slot is at _C_. There are five rows of figures corresponding to the five spokes of the pilot-wheel and three figures in a row, and the speed is shown by arrows on the sides of the slots. The segment disk containing these figures also serves as an interlocking device which prevents moving more than one speed controlling lever at a time, in order to avoid damaging the driving mechanism. [Illustration: Fig. 16. Bullard Vertical Turret Lathe] The feeding movement for each head is independent. Lever _D_ controls the engagement or disengagement of the vertical or cross feeds for the head on the cross-rail. The feed for the side-head is controlled by lever _E_. When this lever is pushed inward, the entire head feeds vertically, but when it is pulled out, the tool-bar feeds horizontally. These two feeds can be disengaged by placing the lever in a neutral position. The direction of the feeding movement for either head can be reversed by lever _R_. The amount of feed is varied by feed-wheel _F_ and clutch-rod _G_. When lever _E_ is in the neutral position, the side-head or tool-bar can be adjusted by the hand-cranks _H_ and _I_, respectively. The cross-rail head and its turret slide have rapid power traverse movements for making quick adjustments. This rapid traverse is controlled by the key-handles _J_. The feed-screws for the vertical head have micrometer dials _K_ for making accurate adjustments. There are also large dials at _L_ which indicate vertical movements of the side head and horizontal movements of the tool slide. All of these dials have small adjustable clips _c_ which are numbered to correspond to numbers on the faces of the respective turrets. These clips or "observation stops" are used in the production of duplicate parts. For example, suppose a tool in face No. 1 for the main turret is set for a given diameter and height of shoulder on a part which is to be duplicated. To obtain the same setting of the tools for the next piece, clips No. 1, on both the vertical feed rod and screw dials, are placed opposite the graduations which are intersected by stationary pointers secured to the cross-rail. The clips are set in this way after the first part has been machined to the required size and before disturbing the final position of the tools. For turning a duplicate part, the tools are simply brought to the same position by turning the feed screws until the clips and stationary pointers again coincide. For setting tools on other faces of either turret, this operation is repeated, except that clips are used bearing numbers corresponding to the turret face in use. The main turret of this machine has five holes in which are inserted the necessary boring and turning tools, drills or reamers, as may be required. By having all the tools mounted in the turret, they can be quickly and accurately set in the working position. When the turret is indexed from one face to the next, binder lever _N_ is first loosened. The turret then moves forward, away from its seat, thus disengaging the indexing and registering pins which accurately locate it in any one of the five positions. The turret is revolved by turning crank _M_, one turn of this handle moving the turret 1/5 revolution or from one hole to the next. The side-head turret is turned by loosening lever _O_. The turret slide can be locked rigidly in any position by lever _P_ and its saddle is clamped to the cross-rail by lever _Q_. The binder levers for the saddle and toolslide of the side-head are located at _U_ and _V_, respectively. A slide that does not require feeding movements is locked in order to obtain greater rigidity. To illustrate, if the main tool slide were to feed vertically and not horizontally, it might be advisable to lock the saddle to the cross-rail, while taking the vertical cut. [Illustration: Fig. 17. Turning a Gear Blank on a Vertical Turret Lathe] The vertical slide can be set at an angle for taper turning, and the turret is accurately located over the center of the table for boring or reaming, by a positive center stop. The machine is provided with a brake for stopping the work table quickly, which is operated by lifting the shaft of pilot-wheel _A_. The side-and cross-rails are a unit and are adjusted together to accommodate work of different heights. This adjustment is effected by power on the particular machine illustrated, and it is controlled by a lever near the left end of the cross-rail. Before making this adjustment, all binder bolts which normally hold the rails rigidly to the machine column must be released, and care should be taken to tighten them after the adjustment is made. [Illustration: Fig. 18. Turning Gasoline Engine Flywheel on Vertical Turret Lathe--First Position] =Examples of Vertical Turret Lathe Work.=--In order to illustrate how a vertical turret lathe is used, one or two examples of work will be referred to in detail. These examples also indicate, in a general way, the class of work for which this type of machine is adapted. Fig. 17 shows how a cast-iron gear blank is machined. The work is gripped on the inside of the rim by three chuck jaws, and all of the tools required for the various operations are mounted in the main and side turrets. The illustration shows the first operation which is that of rough turning the hub, the top side of the blank and its periphery. The tools _A_ for facing the hub and upper surface are both held in one tool-block on the main turret, and tool _A_{1}_ for roughing the periphery is in the side turret. With this arrangement, the three surfaces can be turned simultaneously. [Illustration: Fig. 19. Turning Gasoline Engine Flywheel--Second Position] [Illustration: Fig. 20. Diagrams showing How Successive Operations are Performed by Different Tools in the Turret] The main turret is next indexed one-sixth of a revolution which brings the broad finishing tools _B_ into position, and the side turret is also turned to locate finishing tool _B_{1}_ at the front. (The indexing of the main turret on this particular machine is effected by loosening binder lever n and raising the turret lock-pin by means of lever _p_.) The hub, side and periphery of the blank are then finished. When tools _B_ are clamped in the tool-blocks, they are, of course, set for turning the hub to the required height. The third operation is performed by the tools at _C_, one of which "breaks" or chamfers the corner of the cored hole in the hub, to provide a starting surface for drill _D_, and the other turns the outside of the hub, after the chamfering tool is removed. The four-lipped shell-drill _D_ is next used to drill the cored hole and then this hole is bored close to the finished size and concentric with the circumference of the blank by boring tool _E_, which is followed by the finishing reamer _F_. When the drill, boring tool and reamer are being used, the turret is set over the center or axis of the table, by means of a positive center stop on the left-side of the turret saddle. If it is necessary to move the turret beyond the central position, this stop can be swung out of the way. Figs. 18 and 19 illustrate the turning of an automobile flywheel, which is another typical example of work for a machine of this type. The flywheel is finished in two settings. Its position for the first series of operations is shown in Fig. 18, and the successive order of the four operations for the first setting is shown by the diagrams, Fig. 20. The first operation requires four tools which act simultaneously. The three held in tool-block _A_ of the turret, face the hub, the web and the rim of the flywheel, while tool _a_ in the side-head rough turns the outside diameter. The outside diameter is also finished by broad-nosed tool _b_ which is given a coarse feed. In the second operation, the under face of the rim is finished by tool _c_, the outer corners are rounded by tool _d_ and the inner surface of the rim is rough turned by a bent tool _B_, which is moved into position by indexing the main turret. In the third operation, the side-head is moved out of the way and the inside of the rim is finished by another bent tool _B_{1}_. The final operation at this setting is the boring of the central hole, which is done with a bar _C_ having interchangeable cutters which make it possible to finish the hole at one setting of the turret. The remaining operations are performed on the opposite side of the work which is held in "soft" jaws _J_ accurately bored to fit the finished outside diameter as indicated in Fig. 19. The tool in the main turret turns the inside of the rim, and the side-head is equipped with two tools for facing the web and hub simultaneously. As the tool in the main turret operates on the left side of the rim, it is set with the cutting edge toward the rear. In order to move the turret to this position, which is beyond the center of the table, the center stop previously referred to is swung out of the way. =Floating Reamer Holders.=--If a reamer is held rigidly in the turret of a boring mill or turret lathe, it is liable to produce a hole which tapers slightly or is too large. When a hole is bored with a single-point boring tool, it is concentric with the axis of rotation, and if a reamer that is aligned exactly with the bored hole is fed into the work, the finished hole should be cylindrical and the correct size. It is very difficult, however, to locate a reamer exactly in line with a bored hole, because of slight variations in the indexing of the turret, or errors resulting from wear of the guiding ways or other important parts of the machine. To prevent inaccuracies due to this cause, reamers are often held in what is known as a "floating" holder. This type of holder is so arranged that the reamer, instead of being held rigidly, is allowed a slight free or floating movement so that it can follow a hole which has been bored true, without restraint. In this way the hole is reamed straight and to practically the same size as the reamer. [Illustration: Fig. 21. Two Types of Floating Reamer Holders] There are many different designs of floating holders but the general principle upon which they are based is illustrated by the two types shown in Fig. 21. The reamer and holder shown to the left has a ball-shank _A_ which bears against a backing-up screw _B_ inserted in the end of holder _C_ through which the driving pin passes. The lower end of the reamer shank is also spherical-shaped at _D_, and screw-pin _E_ secures the shell reamer to this end. It will be noted that the hole in the shank for pin _E_ is "bell-mouthed" on each side of the center and that there is clearance at _F_ between the shank and reamer shell; hence the reamer has a free floating action in any direction. This holder has given very satisfactory results. [Illustration: Fig. 22. Multiple-spindle Cylinder Boring Machine] The holder shown to the right is attached to the face of the turret by four fillister-head screws. Sleeve _C_ is held in plate _A_ by means of two steel pins _B_ which are tight in plate _A_ and made to fit freely in bayonet grooves _D_. Reamer holder _E_ floats on sleeve _C_, the floating motion being obtained through the four steel pins _G_ extending into driving ring _F_. Two of the pins are tight in the holder _E_ and two in sleeve _C_. The faces of sleeve _C_, driving ring _F_, and reamer holder _E_ are held tightly against each other by means of spring _H_ which insures the reamer being held perfectly true. Spring _H_ is adjusted by means of nut _I_ which is turned with a spanner wrench furnished with each holder. The reamer is so held that its axis is always maintained parallel to the center of the hole, and, at the same time, it has a slight self-adjusting tendency radially, so that the hole and reamer will automatically keep in perfect alignment with each other. =Multiple Cylinder Boring Machine.=--In automobile and other factories where a great many gasoline engine cylinders are required, multiple-spindle boring machines of the vertical type are commonly used. The machine shown in Fig. 22 is a special design for boring four cylinders which are cast _en bloc_ or in one solid casting. The work is held in a box jig which has a top plate equipped with guide bearings for holding the spindles rigidly while boring. The lower end of each spindle has attached to it a cutter-head and the boring is done by feeding the table and casting vertically. This feeding movement is effected by power and it is disengaged automatically when the cutters have bored to the required depth. The particular machine illustrated is used for rough boring only, the cylinders being finished by reaming in another similar machine. The cylinders are bored to a diameter of 3-5/8 inches, and about 3/8 inch of metal is removed by the roughing cut. The spindles have fixed center-to-center distances as the machine is intended for constant use on cylinders of one size, so that adjustment is not necessary. Of course, a special machine of this kind is only used in shops where large numbers of cylinders of one design are required continually. Some cylinder boring machines of the vertical type have spindles which can be adjusted for different center-to-center distances if this should be necessary in order to accommodate a cylinder of another size. CHAPTER VII HORIZONTAL BORING MACHINES A boring machine of the horizontal type is shown in Fig. 1. The construction and operation of this machine is very different from that of a vertical boring mill and it is also used for an entirely different class of work. The horizontal machine is employed principally for boring, drilling or milling, whereas the vertical design is especially adapted to turning and boring. The horizontal type is also used for turning or facing flanges or similar surfaces when such an operation can be performed to advantage in connection with other machine work on the same part. The type of machine illustrated in Fig. 1 has a heavy base or bed to which is bolted the column _C_ having vertical ways on which the spindle-head _H_ is mounted. This head contains a sleeve or quill in which the spindle _S_ slides longitudinally. The spindle carries cutters for boring, whereas milling cutters or the auxiliary facing arm are bolted to the end _A_ of the spindle sleeve. The work itself is attached either directly or indirectly to the table or platen _P_. When the machine is in operation, the cutter or tool revolves with the spindle sleeve or spindle and either the cutter or the part being machined is given a feeding movement, depending on the character of the work. The spindle can be moved in or out by hand for adjustment, or by power for feeding the cutter, as when boring or drilling. [Illustration: Fig. 1. Lucas Horizontal Boring, Drilling and Milling Machine] The entire spindle-head _H_ can also be moved vertically on the face of the column _C_, by hand, for setting the spindle to the proper height, or by power for feeding a milling cutter in a vertical direction. When the vertical position of the spindle-head is changed, the outboard bearing block _B_ also moves up or down a corresponding amount, the two parts being connected by shafts and gearing. Block _B_ steadies the outer end of the boring-bar and the back-rest in which this block is mounted can be shifted along the bed to suit the length of the work, by turning the squared end of shaft _D_ with a crank. The platen _P_ has a cross-feed, and the saddle _E_ on which it is mounted can be traversed lengthwise on the bed; both of these movements can also be effected by hand or power. There is a series of power feeding movements for the cutters and, in addition, rapid power movements _in a reverse direction from the feed_ for returning a cutter quickly to its starting position, when this is desirable. This machine is driven by a belt connecting pulley _G_ with an overhead shaft. When the machine is in operation, this pulley is engaged with the main driving shaft by a friction clutch _F_ controlled by lever _L_. This main shaft drives through gearing a vertical shaft _I_, which by means of other gears in the spindle-head imparts a rotary movement to the spindle. As a machine of this type is used for boring holes of various diameters and for a variety of other work, it is necessary to have a number of speed changes for the spindle. Nine speeds are obtained by changing the position of the sliding gears controlled by levers _R_ and this number is doubled by back-gears in the spindle-head and controlled by lever _J_. The amount of feed for the spindle, spindle-head, platen or saddle is varied by two levers _K_ and _K_{1}_ which control the position of sliding gears through which the feeding movements are transmitted. The direction of the feed can be reversed by shifting lever _O_. With this particular machine, nine feed changes are available for each position of the spindle back-gears, making a total of eighteen changes. The feeding movement is transmitted to the spindle-head, spindle, platen or saddle, as required, by the three distributing levers _T_, _U_ and _V_, which control clutches connecting with the transmission shafts or feed screws. When lever _T_ is turned to the left, the longitudinal power feed for the spindle is engaged, whereas turning it to the right throws in the vertical feed for the spindle-head. Lever _U_ engages the cross-feed for platen _P_ and lever _V_, the longitudinal feed for saddle _E_. These levers have a simple but ingenious interlocking device which makes it impossible to engage more than one feed at a time. For example, if lever _T_ is set for feeding the spindle, levers _U_ and _V_ are locked against movement. The feeds are started and stopped by lever _M_ which also engages the rapid power traverse when thrown in the opposite direction. This rapid traverse operates for whatever feed is engaged by the distributing levers and, as before stated, in a reverse direction. For example, if the reverse lever _O_ is set for feeding the spindle to the right, the rapid traverse would be to the left, and _vice versa_. The cross-feed for the platen can be automatically tripped at any point by setting an adjustable stop in the proper position and the feed can also be tripped by a hand lever at the side of the platen. All the different feeding movements can be effected by hand as well as by power. By means of handwheel _N_, the spindle can be moved in or out slowly, for feeding a cutter by hand. When the friction clamp _Q_ is loosened, the turnstile _W_ can be used for traversing the spindle, in case a hand adjustment is desirable. The spindle-head can be adjusted vertically by turning squared shaft _X_ with a crank, and the saddle can be shifted along the bed by turning shaft _Y_. The hand adjustment of the platen is effected by shaft _Z_. The spindle-head, platen and saddle can also be adjusted from the end of the machine, when this is more convenient. Shafts _X_, _Y_ and _Z_ are equipped with micrometer dials which are graduated to show movements of one-thousandth inch. These dials are used for accurately adjusting the spindle or work and for boring holes or milling surfaces that must be an exact distance apart. =Horizontal Boring Machine with Vertical Table Adjustment.=--Another horizontal boring machine is partly shown in Fig. 2. This machine is of the same type as that illustrated in Fig. 1, but its construction is quite different, as will be seen. The spindle cannot be adjusted vertically as with the first design described, but it is mounted and driven very much like the spindle of a lathe, and adjustment for height is obtained by raising or lowering the work table. The design is just the reverse, in this respect, of the machine shown in Fig. 1, which has a vertical adjustment for the spindle, and a work table that remains in the same horizontal plane. The raising or lowering of the table is effected by shaft _E_, which rotates large nuts engaging the screws _S_. Shaft _E_ is turned either by hand or power. [Illustration: Fig. 2. Horizontal Boring and Drilling Machine with Vertical Table Adjustment] The main spindle is driven by a cone pulley _P_, either directly, or indirectly through the back-gears shown. This arrangement gives six spindle speeds, and double this number is obtained by using a two-speed countershaft overhead. The motion for feeding the spindle longitudinally is transmitted through a cone of gears, which gives the required changes, to a pinion meshing with a rack which traverses the spindle. The large handwheel _H_ and a corresponding wheel on the opposite side are used for adjusting the spindle rapidly by hand. The yoke or outboard bearing _B_ for the boring-bars can be clamped in any position along the bed for supporting the bar as close to the work as possible. Horizontal boring machines are built in many other designs, but they all have the same general arrangement as the machines illustrated and operate on the same principle, with the exception of special types intended for handling certain classes of work exclusively. The horizontal boring, drilling and milling machine is very efficient for certain classes of work because it enables all the machining operations on some parts to be completed at one setting. To illustrate, a casting which requires drilling, boring and milling at different places, can often be finished without disturbing its position on the platen after it is clamped in place. Frequently a comparatively small surface needs to be milled after a part has been bored. If this milling operation can be performed while the work is set up for boring, accurate results will be obtained (provided the machine is in good condition) and the time saved that would otherwise be required for re-setting the part on another machine. Some examples of work on which different operations are performed at the same setting will be referred to later. The horizontal boring machine also makes it possible to machine duplicate parts without the use of jigs, which is important, especially on large work, owing to the cost of jigs. =Drilling and Boring--Cutters Used.=--Holes are drilled in a horizontal machine by simply inserting a drill of required size either directly in the spindle _S_ (see Fig. 1), or in a reducing socket, and then feeding the spindle outward either by hand or power. When a hole is to be bored, a boring-bar _B_{1}_ is inserted in the spindle and the cutter is attached to this bar. The latter is then fed through the hole as the cutter revolves. The distinction made by machinists between drilling and boring is as follows: A hole is said to be drilled when it is formed by sinking a drill into solid metal, whereas boring means the enlargement of a drilled or cored hole either by the use of a single boring tool, a double-ended cutter which operates on both sides of the hole, or a cutter-head having several tools. There are various methods of attaching cutters to boring-bars and the cutters used vary for different classes of work. A simple style of cutter which is used widely for boring small holes is shown at _A_ in Fig. 3. The cutter _c_ is made from flat stock and the cutting is done by the front edges _e_ and _e_{1}_, which are beveled in opposite directions. The cutter is held in the bar by a taper wedge _w_ and it is centered by shoulders at _s_, so that the diameter of the hole will equal the length across the cutter. The outer corners at the front should be slightly rounded, as a sharp corner would be dulled quickly. These cutters are made in different sizes and also in sets for roughing and finishing. The roughing cutter bores holes to within about 1/32 inch of the finish size and it is then replaced by the finishing cutter. A cutter having rounded ends, as shown by the detail sketch _a_, is sometimes used for light finishing cuts. These rounded ends form the cutting edges and give a smooth finish. [Illustration: Fig. 3. Boring-cutters of Different Types] Another method of holding a flat cutter is shown at _B_. The conical end of a screw bears against a conical seat in, the cutter, thus binding the latter in its slot. The conical seat also centers the cutter. A very simple and inexpensive form of cutter is shown at _C_. This is made from a piece of round steel, and it is held in the bar by a taper pin which bears against a circular recess in the side of the cutter. This form has the advantage of only requiring a hole through the boring-bar, whereas it is necessary to cut a rectangular slot for the flat cutter. [Illustration: Fig. 4. Boring with a Flat Double-ended Cutter] Fig. 4 shows how a hole is bored by cutters of the type referred to. The bar rotates as indicated by the arrow _a_ and at the same time feeds longitudinally as shown by arrow _b_. The speed of rotation depends upon the diameter of the hole and the kind of material being bored, and the feed per revolution must also be varied to suit conditions. No definite rule can be given for speed or feed. On some classes of work a long boring-bar is used, which passes through the hole to be bored and is steadied at its outer end by the back-rest _B_, Figs, 1 and 2. On other work, a short bar is inserted in the spindle having a cutter at the outer end. An inexpensive method of holding a cutter at the end of a bar is shown at _D_, Fig. 3. The cutter passes through a slot and is clamped by a bolt as shown. When it is necessary to bore holes that are "blind" or closed at the bottom, a long boring-bar which passes through the work cannot, of course, be used. Sometimes it is necessary to have a cutter mounted at the extreme end of a bar in order to bore close to a shoulder or the bottom of a hole. One method of holding a cutter so that it projects beyond the end of a bar is indicated at _E_. A screw similar to the one shown at _B_ is used, and the conical end bears in a conical hole in the cutter. This hole should be slightly offset so that the cutter will be forced back against its seat. The tool shown at _F_ has adjustable cutters. The inner end of each cutter is tapering and bears against a conical-headed screw _b_ which gives the required outward adjustment. The cutters are held against the central bolt by fillister-head screws _f_ and they are clamped by the screws _c_. Boring tools are made in many different designs and the number and form of the cutters is varied somewhat for different kinds of work. [Illustration: Fig. 5. Cutter-heads for Boring Large Holes] =Cutter-heads for Boring Large Holes.=--When large holes are to be bored, the cutters are usually held in a cast-iron head which is mounted on the boring-bar. One type of cutter-head is shown in Fig. 5. This particular head is double-ended and carries two cutters _c_. The cutter-head is bored to fit the bar closely and it is prevented from turning by a key against which a set-screw is tightened. By referring to the end view, it will be seen that each cutter is offset with relation to the center of the bar, in order to locate the front of the tool on a radial line. The number of cutters used in a cutter-head varies. By having several cutters, the work of removing a given amount of metal in boring is distributed, and holes can be bored more quickly with a multiple cutter-head, although more power is required to drive the boring-bar. The boring-bar is also steadied by a multiple cutter-head, because the tendency of any one cutter to deflect the bar is counteracted by the cutters on the opposite side. A disk-shaped head having four cutters is illustrated in Fig. 6. The cutters are inserted in slots or grooves in the face of the disk and they are held by slotted clamping posts. The shape of these posts is shown by the sectional view. The tool passes through an elongated slot and it is tightly clamped against the disk by tightening nut _n_. This head is also driven by a key which engages a keyway in the boring-bar. [Illustration: Fig. 6. Cutter-head with Four Boring Tools] Two other designs of cutter-heads are shown in Fig. 7. The one illustrated at _A_ has three equally spaced cutters which are held in an inclined position. The cutters are clamped by screws _c_ and they can be adjusted within certain limits by screws _s_. The cutters are placed at an angle so that they will extend beyond the front of the head, thus permitting the latter to be moved up close to a shoulder. The cutter-heads shown in Figs. 5 and 6 can also be moved up close to a shoulder if bent cutters are used as shown in the right-hand view, Fig. 5. The idea in bending the cutters is to bring the cutting edges in advance of the clamping posts so that they will reach a shoulder before the binding posts strike it. The arrangement of cutter-head _B_ (Fig. 7) is clearly shown by the illustration. Cutter-heads are often provided with two sets of cutters, one set being used for roughing and the other for finishing. It is a good plan to make these cutters so that the ends _e_ (Fig. 6) will rest against the bar or bottom of the slot, when the cutting edge is set to the required radius. The cutters can then be easily set for boring duplicate work. One method of making cutters in sets is to clamp the annealed stock in the cutter-head and then turn the ends to the required radius by placing the head in the lathe. After both sets of cutters have been turned in this way, they are ground to shape and then hardened. [Illustration: Fig. 7. Cutter-heads equipped with Adjustable Tools] Boring cutters intended for roughing and finishing cuts are shown in the detail view Fig. 8 at _A_ and _B_, respectively. The side of the roughing cutter _A_ is ground to a slight angle _c_ to provide clearance for the cutting edge, and the front has a backward slope _s_ to give the tool keenness. This tool is a good form to use for roughing cuts in cast iron. The finishing tool at _B_ has a broad flat edge _e_ and it is intended for coarse feeds and light cuts in cast iron. If a round cutting edge is used for finishing, a comparatively fine feed is required in order to obtain a smooth surface. The corners of tool _B_ are rounded and they should be ground to slope inward as shown in the plan view. The top or ends _d_ of both of these tools are "backed off" slightly to provide clearance. This clearance should be just enough to prevent the surface back of the cutting edge from dragging over the work. Excessive end clearance not only weakens the cutting edge, but tends to cause chattering. As a finishing tool cuts on the upper end instead of on the side, the front should slope backward as shown in the side view, rather than sidewise as with a roughing cutter. The angle of the slope should be somewhat greater for steel than cast iron, unless the steel is quite hard, thus requiring a strong blunt tool. [Illustration: Fig. 8. Boring Tools for Roughing and Finishing Cuts] =Cylinder Boring.=--Fig. 9 illustrates the use of a cutter-head for cylinder boring. After the cylinder casting is set on the platen of the machine, the boring-bar with the cutter-head mounted on it is inserted in the spindle. The bar _B_ has a taper shank and a driving tang similar to a drill shank, which fits a taper hole in the end of the spindle. The cutter-head _C_ is fastened to the bar so that it will be in the position shown when the spindle is shifted to the right, as the feeding movement (with this particular machine) is to be in the opposite direction. The casting _A_ should be set central with the bar by adjusting the work-table vertically and laterally, if necessary, and the outer support _F_ should be moved close to the work, to make the bar as rigid as possible. The cylinder is now ready to be bored. Ordinarily, one or two roughing cuts and one finishing cut would be sufficient, unless the rough bore were considerably below the finish diameter. As previously explained, the speed and feed must be governed by the kind of material being bored and the diameter of the cut. The power and rigidity of the boring machine and the quality of the steel used for making the cutters also affect the cutting speed and feed. As the finishing cut is very light, a tool having a flat cutting edge set parallel to the bar is ordinarily used when boring cast iron. The coarse feed enables the cut to be taken in a comparatively short time and the broad-nosed tool gives a smooth finish if properly ground. [Illustration: Fig. 9. Cylinder mounted on Horizontal Machine for Boring] The coarse finishing feed is not always practicable, especially if the boring machine is in poor condition, owing to the chattering of the tool, which results in a rough surface. The last or finishing cut should invariably be a continuous one, for if the machine is stopped before the cut is completed, there will be a ridge in the bore at the point where the tool temporarily left off cutting. This ridge is caused by the cooling and resulting contraction and shortening of the tool during the time that it is stationary. For this reason independent drives are desirable for boring machines. Facing arms are attached to the bar on either side of the cylinder for facing the flanges after the boring operation. The turning tool of a facing arm is fastened to a slide which is fed outward a short distance each revolution, by a star-wheel that is caused to turn as it strikes against a stationary pin. By facing the flanges in this way, they are finished square with the bore. When setting a cylinder which is to be bored it should, when the design will permit, be set true by the outside of the flange, or what is even better, by the outside of the cylinder itself, rather than by the rough bore, in order that the walls of the finished cylinder will have a uniform thickness. The position of very large cylinders, while they are being bored, is an important consideration. Such cylinders should be bored in the position which they will subsequently occupy when assembled. For example, the cylinder for a large horizontal engine should be bored while in a horizontal position, as the bore is liable to spring to a slight oval shape when the cylinder is placed horizontal after being bored while standing in a vertical position. If, however, the cylinder is bored while in the position in which it will be placed in the assembled engine, this trouble is practically eliminated. There is a difference of opinion among machinists as to the proper shape of the cutting point of a boring tool for finishing cuts, some contending that a wide cutting edge is to be preferred, while others advocate the use of a comparatively narrow edge with a reduced feed. It is claimed, that the narrow tool produces a more perfect bore, as it is not so easily affected by hard spots in the iron, and it is also pointed out that the minute ridges left by the narrow tool are an advantage rather than a disadvantage, as they form pockets for oil and aid in lubricating the cylinder. It is the modern practice, however, to use a broad tool and a coarse feed for the light finishing cut, provided the tool does not chatter. The type of machine tool used for boring cylinders, and also the method of procedure is determined largely by the size of the work and the quantity which is to be machined. The turret lathe, as well as horizontal and vertical boring mills, is used for this work, and in automobile factories or other shops where a great many cylinders are bored, special machines and fixtures are often employed. [Illustration: Fig. 10. Boring a Duplex Cylinder on a Horizontal Machine] =Boring a Duplex Gasoline Engine Cylinder.=--The method of holding work on a horizontal boring machine depends on its shape. A cylinder or other casting having a flat base can be clamped directly to the platen, but pieces of irregular shape are usually held in special fixtures. Fig. 10 shows how the cylinder casting of a gasoline engine is set up for the boring operation. The casting _W_ is placed in a fixture _F_ which is clamped to the machine table. One end of the casting rests on the adjustable screws _S_ and it is clamped by set-screws located in the top and sides of the fixture. There are two cylinders cast integral and these are bored by a short stiff bar mounted in the end of the spindle and having cutters at the outer end. A long bar of the type which passes through the work and is supported by the outboard bearing _B_, could not be used for this work, because the top of each cylinder is closed. When one cylinder is finished the other is set in line with the spindle by adjusting the work-table laterally. This adjustment is effected by screw _C_, and the required center-to-center distance between the two cylinders can be gaged by the micrometer dial _M_ on the cross-feed screw, although positive stops are often used in preference. After the first cylinder is bored, the dial is set to the zero position by loosening the small knurled screw shown, and turning the dial around. The feed screw is then rotated until the dial shows that the required lateral adjustment is made, which locates the casting for boring the second cylinder. The end of the casting is also faced true by a milling cutter. Ordinarily, milling cutters are bolted directly to the spindle sleeve _A_ on this particular machine, which gives a rigid support for the cutter and a powerful drive. [Illustration: Fig. 11. Cylinder turned around for Machining Valve Seats] The next operation is that of boring and milling the opposite end of the cylinder. This end is turned toward the spindle (as shown in Fig. 11) without unclamping the work or fixture, by simply turning the circular table _T_ half way around. This table is an attachment which is clamped to the main table for holding work that must be turned to different positions for machining the various parts. Its position is easily changed, and as the work remains fixed with relation to the table, the alignment between different holes or surfaces is assured, if the table is turned the right amount. In this case, the casting needs to be rotated one-half a revolution or 180 degrees, and this is done by means of angular graduations on the base of the table. The illustration shows the casting set for boring the inlet and exhaust valve chambers. The different cutters required for boring are mounted on one bar as shown, and the casting is adjusted crosswise to bring each valve chamber in position, by using the micrometer dial. The single-ended cutter _c_ forms a shallow circular recess or seat in the raised pad which surrounds the opening. The cover joint directly back of the cylinders is finished by milling. [Illustration: Fig. 12. Boring Differential Gear Casing] =Examples of Boring, Radial Facing and Milling.=--Another example of boring, in which the circular table is used, is shown in Fig. 12. The work _W_ is a casing for the differential gears of an automobile. It is mounted in a fixture _F_ which is bolted to the table. The casting has round ends, which are clamped in V-blocks, thus aligning the work. This fixture has a guide-bushing _G_ which is centered with the bar and cutter in order to properly locate the casting. There is a bearing at each end of the casing, and two larger ones in the center. These are bored by flat cutters similar to the style illustrated at _A_ in Fig. 3. The cutter for the inner bearings is shown at _c_. [Illustration: Fig. 13. Facing and Turning Flange of Differential Gear Casing] After the bearings are bored, the circular table is turned 90 degrees and the work is moved closer to the spindle (as shown in Fig. 13) for facing flange _F_ at right angles to the bearings. Circular flanges of this kind are faced in a horizontal boring machine by a special facing-arm or head _H_. For this particular job this head is clamped directly to the spindle sleeve, but it can also be clamped to the spindle if necessary. The turning tool is held in a slotted toolpost, and it is fed radially for turning the side or face of the flange, by the well-known star feed at _S_. When this feed is in operation the bent finger _E_ is turned downward so that it strikes one of the star wheel arms for each revolution; this turns the wheel slightly, and the movement is transmitted to the tool-block by a feed-screw. The illustration shows the tool set for turning the outside or periphery of the flange. This is done by setting the tool to the proper radius and then feeding the work horizontally by shifting the work-table along the bed. By referring to Fig. 12 it will be seen that the facing head does not need to be removed for boring, as it is attached to the spindle driving quill and does not interfere with the longitudinal adjustment of the spindle. This facing head is also used frequently for truing the flanges of cylinders which are to be bored, and for similar work. [Illustration: Fig. 14. Example of Work requiring Boring and Milling] Fig. 14 shows another example of work which requires boring and milling. This casting is mounted on a fixture which is bolted to the main table. In this case the circular table is not necessary, because the work can be finished without swiveling it around. After the boring is completed the edge _E_ is trued by the large-face milling cutter _M_ bolted to the spindle sleeve. The irregular outline of the edge is followed by moving the table crosswise and the spindle vertically, as required. =Fixture for Cylinder Lining or Bushing.=--A method of holding a cylinder lining or bushing while it is being bored is shown in Fig. 15. The lining _L_ is mounted in two cast-iron ring-shaped fixtures _F_. These fixtures are circular in shape and have flat bases which are bolted to the table of the machine. On the inside of each fixture, there are four equally spaced wedges _W_ which fit into grooves as shown in the end view. These wedges are drawn in against the work by bolts, and they prevent the lining from rotating when a cut is being taken. This form of fixture is especially adapted for holding thin bronze linings, such as are used in pump cylinders, because only a light pressure against the wedges is required, and thin work can be held without distorting it. If a very thin lining is being bored, it is well to loosen the wedges slightly before taking the finishing cut, so that the work can spring back to its normal shape. [Illustration: Fig. 15. Cylinder Lining mounted in Fixture for Boring] [Illustration: Fig. 16. Detrick & Harvey Horizontal Boring Machine of the Floor Type Boring Engine Bed Casting] =Horizontal Boring Machine of Floor Type.=--The type of horizontal boring, drilling and milling machine, shown in Fig. 16, is intended for boring heavy parts such as the cylinders of large engines or pumps, the bearings of heavy machine beds and similar work. This machine can also be used for drilling and milling, although it is intended primarily for boring, and the other operations are usually secondary. This design is ordinarily referred to as the "floor type," because the work-table is low for accommodating large heavy castings. The spindle _S_ which drives the boring-bar, and the spindle feeding mechanism, are carried by a saddle. This saddle is free to move vertically on the face of column _C_ which is mounted on transverse ways extending across the right-hand end of the main bed. This construction permits the spindle to move vertically or laterally (by traversing the column) either for adjusting it to the required position or for milling operations. The spindle also has a longitudinal movement for boring. There is an outer bearing _B_ for supporting the boring-bar, which also has lateral and vertical adjustments, so that it can be aligned with the bar. The work done on a machine of this type is either clamped directly to the large bed-plate _A_ (which has a number of T-slots for receiving the heads of the clamping bolts) or, in some cases, a special fixture may be used or an auxiliary table. Boring machines of this same general construction are built in many different sizes. The main spindle of the machine illustrated is driven by a motor located at the rear of the vertical column _C_, the motion being transmitted to the spindle through shafts and gearing. The casting _D_, shown in this particular illustration, is for a steam engine of the horizontal type, and the operation is that of boring the cylindrical guides or bearings for the crosshead. These bearings have a diameter of 15-3/4 inches and are 37-3/4 inches long. In boring them, two roughing cuts and one finishing cut are taken. The end of the casting, which in the assembled engine bears against the cylinder, is then faced by means of a regular facing arm. After removing the boring-bar the table _E_ of the special fixture on which the casting is mounted is turned one quarter of a revolution. A large milling cutter 24 inches in diameter is next mounted on the spindle of the machine, and one side of the main bearing, as well as the pads for the valve-rod guide-bar brackets, are milled. The table is then revolved and the opposite side of the main bearing is milled in the same way, the table being accurately located in the different positions by an index plunger _F_ which engages holes on the under side. The spindle is now moved upward to allow the table to be turned so as to locate the bearing end of the frame next to the headstock of the machine. The milling cutter is then used to machine the inside and top surfaces of the main bearing. By turning the fixture and not changing the position of the casting after it is bolted into place, the various surfaces are machined in the correct relation to one another without difficulty. This is a good example of the work done on horizontal boring machines of the floor type. INDEX PAGE Acme flat turret lathe, examples of chuck work 219 Acme standard thread and tool for cutting 159 Acme standard thread gage 157 Acme thread tool, measuring width with vernier caliper 157, 158 Accumulation of errors 105, 106 Aligning lathe centers for cylindrical turning 16 Allowances, average, for forced fits 130 for different classes of fits 131 for driving fits 131 for forced fits of given pressure 133 for push fits 131 for running fits 131 for shrinkage fits 133 Aluminum, lubricant for machining 53 shape of tools for turning 53 speed and feed for machining 53 Angle-plate applied to lathe faceplate 48 Angles, gage for accurate measurement of 97 Apron of lathe 4, 5 Arbor or mandrel press 22 Arbors or mandrels for lathe work, types of 19 use of 17 Attachment, application of Hendey relieving 125 convex turning for vertical boring mill 259 for coarse threading in lathe 160 for spherical turning 113 for taper turning in lathe 88 Hendey relieving 123 Automatic chucking and turning machine, Potter & Johnston 223 Potter & Johnston, method of "setting-up" 227 Potter & Johnston, turning flywheel in 236 Back-gears of lathe 3, 4 Bardons & Oliver turret lathe, general description 178 Bored holes, measuring diameter of 41 Boring and reaming tools for vertical mill 251 Boring and turning mill, vertical, general description 242 vertical, holding and setting work 247 vertical, turning in 249 Boring and turning mill, vertical, turning tools for 253 Boring-bar cutters and methods of holding 280 Boring cutters for roughing and finishing cuts 285 Boring cylinders on horizontal machine 286 Boring holes to given center distance in lathe 51 Boring in lathe, example of 39 Boring large castings in lathe 49 Boring large holes, cutter-heads used for 283 Boring machine, horizontal 275 horizontal, examples of work on 289-297 horizontal, floor type 294 vertical, multiple-spindle type 274 Boring tool, lathe 40 Box-tools, different designs and examples of work 193 for general turret lathe work 190 Bradford belt-driven lathe, general description 1 Bradford quick change-gear type of lathe 173 Brass, speed for turning 52 tool for turning in lathe 52 "Bridle" or "hold-back" for lathe 26, 27 Bullard vertical turret lathe 264 examples of work 268 Button method of locating work 101 Caliper tool for taper turning 85 Calipers, methods of setting 10, 11 "Cat-head," application in lathe work 25 Center holes, incorrect and correct forms 32 Center indicator, use of 100 Centered stock, methods of facing ends 34 Centers, lathe, aligning for cylindrical turning 16 lathe, grinder for truing 34 Centering machine 30 Centering parts to be turned 28 Centering, precaution for tool steel 33 Change gears, calculating for thread cutting 167 compound, for thread cutting 170 for cutting fractional threads 171 for cutting metric pitches 171 for thread cutting 135 Chasing dial for "catching threads" when screw cutting 141 Chuck, inaccuracy from pressure of jaws 42 lathe, application of 37 setting work in 42 universal, independent and combination 36 Chucking and turning machine, Potter & Johnston automatic 223 Potter & Johnston automatic, method of "setting-up" 227 Potter & Johnston automatic, turning flywheel in 236 Chucking machine, New Britain, multiple-spindle type 238 Clearance angle for turning tools 66 Clearance of turning tools, meaning of 62, 63 Coarse threading attachment for lathe 160 Collapsing tap, Geometric 202 Combination chuck for lathe 36 Compound rest, applied to screw or thread cutting 143 applied to taper turning 95 Convex turning attachment for vertical boring mills 259 Copper, tool for turning in lathe 52 Crankshaft lathe, description of R. K. LeBlond special 108 operation of R. K. LeBlond 110 Crankshaft turning in engine lathe 107 Cross-slide stop for threading 155 Cuts, average depth for turning 75 roughing and finishing in lathe 12, 75, 76 Cutter-heads, for boring, equipped with adjustable tools 284, 285 for horizontal boring machine 283 Cutters, boring, roughing and finishing types 285 for boring-bars 280 Cutting lubricants for turning tools 77 Cutting speeds, average for turning 72 based on Taylor's experiments 71 effect of lubricant on 76 factors which limit speeds for turning 72 rules for calculating 74 Cylinder boring machine, multiple-spindle type 274 Cylinder boring on horizontal machine 286 Cylinder lining, fixture for holding when boring 293 Cylindrical turning, simple example of 6 Davis turret lathe, turning bevel gear blanks 212 turning worm-gear blanks 211 Depth of cut for turning, average 75 Detrick & Harvey horizontal boring machine, floor type 294 Dial for "catching threads" when screw cutting 141 Dial gage, testing concentricity of button with 103, 104 Die and tap holders, releasing 199 Die-heads, self-opening type 200 Disk gage, for angles and tapers 97 rules for setting 98, 99 Dogs or drivers, lathe, application of 16 Drill, flat, for lathe 44 Drilling and reaming in lathe 43 Drivers or dogs, lathe, application of 16 Driving fits, allowances for 131 Eccentric turning in lathe 106 Engine lathe, general description 1 Errors, accumulation of 105, 106 Faceplate, indexing for multiple-thread cutting 153 lathe, application of angle-plate to 48 lathe, holding work on 45 Facing ends of centered stock, different methods 34 Feed and depth of cut for turning, average 75 Feeds and speeds for turning based on Taylor's experiments 71 Filing and polishing in lathe 13 Finishing and roughing cuts in lathe 75, 76 Fits, allowances for different classes 131 different classes used in machine construction 129 driving, allowances for 131 forced, allowances for given pressure 133 forced, average allowance for 130 forced, pressure for 132 push, allowances for 131 running, allowances for 131 shrinkage, allowances for 133 Fixture for holding thin lining when boring 293 Flat drill and holder for lathe 44 Flat turret lathe, Acme, examples of chuck work 219 Hartness, example of turning 213 Jones & Lamson double-spindle type 221 Floating reamer holders 271 Flywheel, finishing in one setting in turret lathe 186 finishing in two settings in turret lathe 189 machining in turret lathe 184 turning in Potter & Johnston automatic 236 turning in vertical boring mill 255 Follow-rest for lathe 27 Forced fits, allowances for given pressure 133 average allowance for 130 pressure generally used in assembling 132 Fractional threads, change gears for cutting 171 Gage, disk, for angles and tapers 97 disk, rules for setting 98, 99 for testing V-thread tool 138 standard plug, for holes 42 thread, Acme standard 157 Geometric collapsing tap 202 Geometric self-opening die-head 200 Gisholt convex attachment for vertical mill 259 Gisholt vertical boring mill, general description 242 Grinder for truing lathe centers 34 Grinding lathe tools 62 Hartness flat turret lathe, example of turning 213 Hendey relieving attachment 123 application of, for relieving taps, cutters and hobs 125 "Hold-back" or "bridle" for lathe 26, 27 Hollow mills for turret lathe 198 Horizontal boring machine 275 Detrick & Harvey floor type 294 examples of work 289-297 Independent chuck for lathe 36 Index plate, change gear, for lathe 137 Indicator, center, use on lathe 100 for "catching threads" when screw cutting 141 test, truing buttons with 102, 103 thread, for lathe apron, principle of 142 Inserted cutter turning tools for lathe 58 Internal threading 154 Jones & Lamson double-spindle flat turret lathe 221 Knurling in lathe and tool used 122 Lard oil as a cutting lubricant 78 Lathe, boring holes to given center distance in 51 boring large castings in 49 boring small hole with 104, 105 cutting threads in 135 drilling small hole with 104 general description of Bradford 1 LeBlond crankshaft, operation of 110 Lo-swing, general description 115 method of handling when cutting threads 138 quick change-gear type 173 R. K. LeBlond special crankshaft 108 turret type, general description 178 Lathe centers, grinder for truing 34 Lathe chucks, application of 37 universal, independent and combination 36 Lathe faceplate, holding work on 45 Lathe follow-rest 27 Lathe steadyrest 23 application of, when boring 25 Lathe taper attachment 88 practical application of 90 Lathe tool grinding 62 Lathe tools, angle of clearance 66 angle of keenness 67 application of various types 56 slope of cutting edge 66, 67 Lathe turning tools, inserted-cutter type 58 set of tools for general work 54 Lead of thread, definition of 146 LeBlond, R. K., lathe for crankshaft turning 108 Left-hand thread, method of cutting 148 Lining, fixture for holding when boring 293 Lo-swing lathe, general description 115 example of multiple-turning 117 Lubricant, effect on cutting speed 76 for cooling turning tools 77 for machining aluminum 53 lard oil as a cutting 78 Lucas horizontal boring machine 275 Mandrel or arbor press 22 Mandrels or arbors for lathe work, types of 19 for lathe work, use of 17 Metric pitches, change gears for cutting 171 Micrometer for measuring threads 162 Mills, hollow, for turret lathe 198 Multiple-spindle chucking machine, New Britain 238 Multiple-thread cutting, indexing faceplate for 153 Multiple threads 146 method of cutting 150 setting tool when cutting 152 Multiple-turning in Lo-swing lathe 117 New Britain multiple-spindle chucking machine 238 Newall Engineering Co's fit allowances 131 Pistons, gasoline engine, turning in turret lathe 204 Piston rings, attachment for turning in turret lathe 210 turning in turret lathe 206 Piston turning in Pratt & Whitney turret lathe 208 Pitch, metric, change gears for cutting 171 Pitch of thread, definition of 146 Plug gage, standard 42 Polishing and filing in lathe 13 Potter & Johnston automatic chucking and turning machine 223 method of "setting-up" 227 turning flywheel in 236 Pratt & Whitney turret lathe, arranged for piston turning 208 equipped with piston ring turning attachment 210 Press for arbors or mandrels 22 Pressure generally used in assembling forced fits 132 Push fits, allowances for 131 Quick change-gear type of lathe 173 Reamer holders, floating type 271 Reaming and drilling in lathe 43 Releasing die and tap holders 199 Relieving attachment, Hendey 123 Relieving attachment, Hendey, application of 125 Relieving hobs or taps having spiral flutes 128 Rivett-Dock threading tool 164 Roughing and finishing cuts in lathe 75, 76 Running fits, allowances for 131 Screw cutting, calculating change gears for 167 compound gearing for 170 in engine lathe 135 method of handling lathe 138 selecting change gears for 135 with compound rest 143 Screws, cutting to compensate for shrinkage 165 metric, change gears for cutting 171 testing size of 161 Selecting type of turning machine 240 Shrinkage, cutting screws to compensate for 165 Shrinkage fits, allowances for 133 Side-tool, facing with 7 Speeds for turning, average 72 based on Taylor's experiments 71 effect of lubricant 76 factors which limit 72 rules for calculating 74 Spherical turning 111 attachments for 113 "Spider" for supporting bushing while turning 48, 49 Spiral flutes, method of relieving hobs or taps with 128 Square thread and method of cutting 149, 159 Steadyrest, application of when boring 25 for engine lathe 23 Stop for lathe cross-slide when threading 155 Tap and die holders, releasing type 199 Taper attachment for lathe 88 practical application of 90 Taper boring with taper attachment 90 Taper threading, position of tool for 154 Taper turning, adjustment of tailstock center for 82 by offset-center method 80 examples of 83 height of tool for 94 in vertical boring mill 261 in vertical mill with horizontal and vertical feeds 262 setting tailstock center with caliper tool 85 setting tailstock center with square 87 with compound rest 95 with taper attachment 92, 93 Tapers, gage for accurate measurement of 97 Tapers, rules for figuring 97 Test indicator, truing buttons with 102, 103 Test or center indicator for use on lathe 100 Thread cutting, calculating change gears for 167 compound gearing for 170 cross-slide stop used for 155 indexing faceplate for multiple threads 153 in engine lathe 135 internal 154 method of handling lathe 138 selecting change gears for 135 taper, position of tool for 154 with compound rest 143 Thread gage, Acme standard 157 Thread indicator for lathe apron 141, 142 Thread micrometer 162 Thread tool, Acme, measuring width with vernier caliper 157, 158 for cutting V-thread 138 Thread tools for standard threads 159 Threads, Acme standard, and tool for cutting 159 change gears for fractional 171 cutting to compensate for shrinkage 165 different forms of 144 left-hand, method of cutting 148 metric, change gears for cutting 171 multiple 146 multiple, method of cutting 150 multiple, setting tool when cutting 152 sharp V, and tool for cutting 159 square, and method of cutting 149, 159 testing size of 161 three-wire system for measuring 163 U. S. standard, and tool for cutting 146, 159 Whitworth standard, and tool for cutting 158, 159 worm, and tool for cutting 159, 160 Threading attachment, lathe, for coarse threads 160 Threading tool, Rivett-Dock 164 Tool grinding 62 Tools for lathe, set for general turning 54 Tools for turning, angle of clearance 66 angle of keenness 67 inserted-cutter type 58 slope of cutting edge 66, 67 Tools for turret lathe 190 Tools, lathe, application of various types 56 Turning, cylindrical, simple example of 6 eccentric 106 multiple, in Lo-swing lathe 117 with front and rear tools 114 Turning speeds, average for lathe 72 based on Taylor's experiments 71 factors which limit 72 rules for calculating 74 Turning tools, angle of clearance 66 angle of keenness 67 for aluminum 53 for brass 52 for copper 52 for lathe, position of 60 for lathe, set of, for general work 54 inserted-cutter type for lathe 58 slope of cutting edge 66, 67 Turret lathe, Bardons & Oliver, general description 178 examples of chuck work in Acme flat 219 Hartness flat, example of turning 213 Jones & Lamson double-spindle type 221 machining flywheels in 184 Pratt & Whitney arranged for piston turning 208 piston ring turning attachment for 210 tools for general work 190 turning bevel gear blanks in Davis 212 turning gasoline engine pistons in 204 turning piston rings in 206 turning worm-gear blanks in Davis 211 typical example of turret lathe work 181 Turret lathe tools, miscellaneous types 202 Turret lathe type of vertical boring mill 264 Type of turning machine, factors which govern selection 240 U. S. standard thread 159 method of cutting 146 Universal chuck for lathe 36 V-thread and tool for cutting 159 Vertical boring mill, Bullard turret lathe type 264 convex turning attachment 259 general description 242 holding and setting work 247 taper turning in 261 taper turning with horizontal and vertical feeds 262 tools for boring and reaming 251 turning flywheel in 255 turning tools for 253 Vertical turret lathe, Bullard, examples of work 268 Whitworth standard thread and tool for cutting 158, 159 Wire system for measuring threads 163 Worm thread and tool for cutting 159, 160 Transcriber's notes on changes made to text: Left as in original: use of degree, deg. and °; use of minute, min. and '. Standardised to the most commonly used in the book: backgear to back-gear; camshaft to cam-shaft; crankpin to crank-pin; face-plate to faceplate; out-board to outboard; over-hang to overhang; setscrew to set-screw; steady-rest to steadyrest; subdivision(s) to sub-division(s); tail-stock to tailstock; thumbscrew to thumb-screw; tool-post to toolpost; tool-slide to toolslide; hand-wheel to handwheel; U.S. to U. S. Page 64 had a blotched (illegible) word, this has been replaced by (large and rigid) work. Table of Contents: largely re-compiled to create one-to-one links with named paragraphs and sections in text. 
10998	----	generously provided by the Digital & Multimedia Center, Michigan State University Libraries. A CATECHISM OF THE STEAM ENGINE IN ITS VARIOUS APPLICATIONS TO MINES, MILLS, STEAM NAVIGATION, RAILWAYS, AND AGRICULTURE. WITH PRACTICAL INSTRUCTIONS FOR THE MANUFACTURE AND MANAGEMENT OF ENGINES OF EVERY CLASS. BY JOHN BOURNE, C.E. _NEW AND REVISED EDITION._ [Transcriber's Note: Inconsistencies in chapter headings and numbering of paragraphs and illustrations have been retained in this edition.] PREFACE TO THE FOURTH EDITION. For some years past a new edition of this work has been called for, but I was unwilling to allow a new edition to go forth with all the original faults of the work upon its head, and I have been too much engaged in the practical construction of steam ships and steam engines to find time for the thorough revision which I knew the work required. At length, however, I have sufficiently disengaged myself from these onerous pursuits to accomplish this necessary revision; and I now offer the work to the public, with the confidence that it will be found better deserving of the favorable acceptation and high praise it has already received. There are very few errors, either of fact or of inference, in the early editions, which I have had to correct; but there are many omissions which I have had to supply, and faults of arrangement and classification which I have had to rectify. I have also had to bring the information, which the work professes to afford, up to the present time, so as to comprehend the latest improvements. For the sake of greater distinctness the work is now divided into chapters. Some of these chapters are altogether new, and the rest have received such extensive additions and improvements as to make the book almost a new one. One purpose of my emendations has been to render my remarks intelligible to a tyro, as well as instructive to an advanced student. With this view, I have devoted the first chapter to a popular description of the Steam Engine--which all may understand who can understand anything--and in the subsequent gradations of progress I have been careful to set no object before the reader for the first time, of which the nature and functions are not simultaneously explained. The design I have proposed to myself, in the composition of this work, is to take a young lad who knows nothing of steam engines, and to lead him by easy advances up to the highest point of information I have myself attained; and it has been a pleasing duty to me to smooth for others the path which I myself found so rugged, and to impart, for the general good of mankind, the secrets which others have guarded with so much jealousy. I believe I am the first author who has communicated that practical information respecting the steam engine, which persons proposing to follow the business of an engineer desire to possess. My business has, therefore, been the rough business of a pioneer; and while hewing a road through the trackless forest, along which all might hereafter travel with ease, I had no time to attend to those minute graces of composition and petty perfection of arrangement and collocation, which are the attribute of the academic grove, or the literary parterre. I am, nevertheless, not insensible to the advantages of method and clear arrangement in any work professing to instruct mankind in the principles and practice of any art; and many of the changes introduced into the present edition of this work are designed to render it less exceptionable in this respect. The woodcuts now introduced into the work for the first time will, I believe, much increase its interest and utility; and upon the whole I am content to dismiss it into circulation, in the belief that those who peruse it attentively will obtain a more rapid and more practical acquaintance with the steam engine in its various applications, than they would be likely otherwise to acquire. I have only to add that I have prepared a sequel to the present work, in the shape of a Hand-Book of the Steam Engine, containing the whole of the rules given in the present work, illustrated by examples worked out at length, and also containing such useful tables and other data, as the engineer requires to refer to constantly in the course of his practice. This work may be bound up with the "Catechism," if desired, to which it is in fact a Key. I shall thankfully receive from engineers, either abroad or at home, accounts of any engines or other machinery, with which they may become familiar in their several localities; and I shall be happy, in my turn, to answer any inquiries on engineering subjects which fall within the compass of my information. If young engineers meet with any difficulty in their studies, I shall be happy to resolve it if I can; and they may communicate with me upon any such point without hesitation, in whatever quarter of the world they may happen to be. JOHN BOURNE. 9 BILLITER STREET, LONDON, _March 1st, 1856_. PREFACE TO THE FIFTH EDITION. The last edition of the present work, consisting of 3,500 copies, having been all sold off in about ten months, I now issue another edition, the demand for the work being still unabated. It affords, certainly, some presumption that a work in some measure supplies an ascertained want, when, though addressing only a limited circle--discoursing only of technical questions, and without any accident to stimulate it into notoriety,--it attains so large a circulation as the present work has reached. Besides being reprinted in America, it has been translated into German, French, Dutch, and I believe, into some other languages, so that there is, perhaps, not too much vanity in the inference that it has been found serviceable to those perusing it. I can with truth say, that the hope of rendering some service to mankind, in my day and generation, has been my chief inducement in writing it, and if this end is fulfilled, I have nothing further to desire. I regret that circumstances have prevented me from yet issuing the "Hand-Book" which I have had for some time in preparation, and to which, in my Preface of the last year, I referred. I hope to have sufficient leisure shortly, to give that and some other of my literary designs the necessary attention. Whatever may have been the other impediments to a more prolific authorship, certainly one of them has not been the coldness of the approbation with which my efforts have been received, since my past performances seem to me to have met with an appreciation far exceeding their deserts. JOHN BOURNE. _February 2d, 1857_. PUBLISHERS' NOTICE. In offering to the American public a reprint of a work on the Steam Engine so deservedly successful, and so long considered standard, the publishers have not thought it necessary that it should be an exact copy of the English edition; there were some details in which they thought it could be improved, and better adapted to the use of American engineers. On this account, the size of the page has been increased to a full 12mo, to admit of larger illustrations, which in the English edition are often on too small a scale; and some of the illustrations themselves have been supplied by others equally applicable, more recent, and to us more familiar examples. The first part of Chapter XI, devoted in the English edition to English portable and fixed agricultural engines, in this edition gives place entirely to illustrations from American practice, of steam engines as applied to different purposes, and of appliances and machines necessary to them. But with the exception of some of the illustrations and the description of them, and the correction of a few typographical errors, this edition is a faithful transcript of the latest English edition. CONTENTS. Classification of Engines. Nature and uses of a Vacuum. Velocity of falling Bodies and Momentum of moving Bodies. Central Forces. Centres of Gravity, Gyration, and Oscillation. The Pendulum and Governor. The Mechanical Powers. Friction. Strength of materials and Strains subsisting in Machines. CHAP. I.--GENERAL DESCRIPTION OF THE STEAM ENGINE. The Boiler. The Engine. The Marine Engine. Screw Engines. The Locomotive Engine. CHAP. II.--HEAT, COMBUSTION, AND STEAM. Heat. Combustion. Steam. CHAP. III.--EXPANSION OF STEAM AND ACTION OF THE VALVES. CHAP. IV.--MODES OF ESTIMATING THE POWER AND PERFORMANCE OF ENGINES AND BOILERS. Horses Power. Duty of Engines and Boilers. The Indicator. Dynamometer, Gauges, and Cataract. CHAP. V.--PROPORTIONS OF BOILERS. Heating and Fire Grate Surface. Calorimeter and Vent. Evaporative Power of Boilers. Modern Marine and Locomotive Boilers. The Blast in Locomotives. Boiler Chimneys. Steam Room and Priming. Strength of Boilers. Boiler Explosions. CHAP. VI.--PROPORTIONS OF ENGINES. Steam Passages. Air Pump, Condenser, and Hot and Cold Water Pumps. Fly Wheel. Strengths of Land Engines. Strengths of Marine and Locomotive Engines. CHAP. VII.--CONSTRUCTIVE DETAILS OF BOILERS. Land and Marine Boilers. Incrustation and Corrosion of Boilers. Locomotive Boilers. CHAP. VIII.--CONSTRUCTIVE DETAILS OF ENGINES. Pumping Engines. Various forms of Marine Engines. Cylinders, Pistons, and Valves. Air Pump and Condenser. Pumps, Cocks, and Pipes. Details of the Screw and Screw Shaft. Details of the Paddles and Paddle Shaft. The Locomotive Engine. CHAP. IX.--STEAM NAVIGATION. Resistance of Vessels in Water. Experiments on the Resistance of Vessels. Influence of the size of Vessels upon their Speed. Structure and Operation of Paddle Wheels. Configuration and Action of the Screw. Comparative Advantages of Paddle and Screw Vessels. Comparative Advantages of different kinds of Screws. Proportions of Screws. Screw Vessels with full and auxiliary Power. Screw and Paddles combined. CHAP. X.--EXAMPLES OF ENGINES OF RECENT CONSTRUCTION. Oscillating Paddle Engines. Direct acting Screw Engine. Locomotive Engine. CHAP. XI.--ON VARIOUS FORMS AND APPLICATIONS OF THE STEAM ENGINE. Governor. Donkey Pumps. Portable Steam Engines. Stationary Engines. Steam Fire Engines. Steam Excavator. CHAP. XII.--MANUFACTURE AND MANAGEMENT OF STEAM ENGINES. Construction of Engines. Erection of Engines. Management of Marine Boilers. Management of Marine Engines. Management of Locomotives. MECHANICAL PRINCIPLES OF THE STEAM ENGINE. CLASSIFICATION OF ENGINES. 1. _Q._--What is meant by a vacuum? _A._--A vacuum means an empty space; a space in which there is neither water nor air, nor anything else that we know of. 2. _Q._--Wherein does a high pressure differ from a low pressure engine? _A._--In a high pressure engine the steam, after having pushed the piston to the end of the stroke, escapes into the atmosphere, and the impelling force is therefore that due to the difference between the pressure of the steam and the pressure of the atmosphere. In the condensing engine the steam, after having pressed the piston to the end of the stroke, passes into the condenser, in which a vacuum is maintained, and the impelling force is that due to the difference between the pressure of the steam above the piston, and the pressure of the vacuum beneath it, which is nothing; or, in other words, you have then the whole pressure of the steam urging the piston, consisting of the pressure shown by the safety-valve on the boiler, and the pressure of the atmosphere besides. 3. _Q._--In what way would you class the various kinds of condensing engines? _A._--Into single acting, rotative, and rotatory engines. Single acting engines are engines without a crank, such as are used for pumping water. Rotative engines are engines provided with a crank, by means of which a rotative motion is produced; and in this important class stand marine and mill engines, and all engines, indeed, in which the rectilinear motion of the piston is changed into a circular motion. In rotatory engines the steam acts at once in the production of circular motion, either upon a revolving piston or otherwise, but without the use of any intermediate mechanism, such as the crank, for deriving a circular from a rectilinear motion. Rotatory engines have not hitherto been very successful, so that only the single acting or pumping engine, and the double acting or rotative engine can be said to be in actual use. For some purposes, such, for example, as forcing air into furnaces for smelting iron, double acting engines are employed, which are nevertheless unfurnished with a crank; but engines of this kind are not sufficiently numerous to justify their classification as a distinct species, and, in general, those engines may be considered to be single acting, by which no rotatory motion is imparted. 4. _Q._--Is not the circular motion derived from a cylinder engine very irregular, in consequence of the unequal leverage of the crank at the different parts of its revolution? _A._--No; rotative engines are generally provided with a fly-wheel to correct such irregularities by its momentum; but where two engines with their respective cranks set at right angles are employed, the irregularity of one engine corrects that of the other with sufficient exactitude for many purposes. In the case of marine and locomotive engines, a fly-wheel is not employed; but for cotton spinning, and other purposes requiring great regularity of motion, its use with common engines is indispensable, though it is not impossible to supersede the necessity by new contrivances. 5. _Q._--You implied that there is some other difference between single acting and double acting engines, than that which lies in the use or exclusion of the crank? _A._--Yes; single acting engines act only in one way by the force of the steam, and are returned by a counter-weight; whereas double acting engines are urged by the steam in both directions. Engines, as I have already said, are sometimes made double acting, though unprovided with a crank; and there would be no difficulty in so arranging the valves of all ordinary pumping engines, as to admit of this action; for the pumps might be contrived to raise water both by the upward and downward stroke, as indeed in some mines is already done. But engines without a crank are almost always made single acting, perhaps from the effect of custom, as much as from any other reason, and are usually spoken of as such, though it is necessary to know that there are some deviations from the usual practice. NATURE AND USES OF A VACUUM. 6. _Q._--The pressure of a vacuum you have stated is nothing; but how can the pressure of a vacuum be said to be nothing, when a vacuum occasions a pressure of 15 lbs. on the square inch? _A._--Because it is not the vacuum which exerts this pressure, but the atmosphere, which, like a head of water, presses on everything immerged beneath it. A head of water, however, would not press down a piston, if the water were admitted on both of its sides; for an equilibrium would then be established, just as in the case of a balance which retains its equilibrium when an equal weight is added to each scale; but take the weight out of one scale, or empty the water from one side of the piston, and motion or pressure is produced; and in like manner pressure is produced on a piston by admitting steam or air upon the one side, and withdrawing the steam or air from the other side. It is not, therefore, to a vacuum, but rather to the existence of an unbalanced plenum, that the pressure made manifest by exhaustion is due, and it is obvious therefore that a vacuum of itself would not work an engine. 7. _Q._--How is the vacuum maintained in a condensing engine? _A._--The steam, after having performed its office in the cylinder, is permitted to pass into a vessel called the condenser, where a shower of cold water is discharged upon it. The steam is condensed by the cold water, and falls in the form of hot water to the bottom of the condenser. The water, which would else be accumulated in the condenser, is continually being pumped out by a pump worked by the engine. This pump is called the air pump, because it also discharges any air which may have entered with the water. 8. _Q._--If a vacuum be an empty space, and there be water in the condenser, how can there be a vacuum there? _A._--There is a vacuum above the water, the water being only like so much iron or lead lying at the bottom. 9. _Q._--Is the vacuum in the condenser a perfect vacuum? _A._--Not quite perfect; for the cold water entering for the purpose of condensation is heated by the steam, and emits a vapor of a tension represented by about three inches of mercury; that is, when the common barometer stands at 30 inches, a barometer with the space above the mercury communicating with the condenser, will stand at about 27 inches. 10. _Q._--Is this imperfection of the vacuum wholly attributable to the vapor in the condenser? _A._--No; it is partly attributable to the presence of a small quantity of air which enters with the water, and which would accumulate until it destroyed the vacuum altogether but for the action of the air pump, which expels it with the water, as already explained. All common water contains a certain quantity of air in solution, and this air recovers its elasticity when the pressure of the atmosphere is taken off, just as the gas in soda water flies up so soon as the cork of the bottle is withdrawn. 11. _Q._--Is a barometer sometimes applied to the condensers of steam engines? _A._--Yes; and it is called the vacuum gauge, because it shows the degree of perfection the vacuum has attained. Another gauge, called the steam gauge, is applied to the boiler, which indicates the pressure of the steam by the height to which the steam forces mercury up a tube. Gauges are also applied to the boiler to indicate the height of the water within it so that it may not be burned out by the water becoming accidentally too low. In some cases a succession of cocks placed a short distance above one another are employed for this purpose, and in other cases a glass tube is placed perpendicularly in the front of the boiler and communicating at each end with its interior. The water rises in this tube to the same height as in the boiler itself, and thus shows the actual water level. In most of the modern boilers both of these contrivances are adopted. 12. _Q._--Can a condensing engine be worked with a pressure less than that of the atmosphere? _A._--Yes, if once it be started; but it will be a difficult thing to start an engine, if the pressure of the steam be not greater than that of the atmosphere. Before an engine can be started, it has to be blown through with steam to displace the air within it, and this cannot be effectually done if the pressure of the steam be very low. After the engine is started, however, the pressure in the boiler may be lowered, if the engine be lightly loaded, until there is a partial vacuum in the boiler. Such a practice, however, is not to be commended, as the gauge cocks become useless when there is a partial vacuum in the boiler; inasmuch as, when they are opened, the water will not rush out, but air will rush in. It is impossible, also, under such circumstances, to blow out any of the sediment collected within the boiler, which, in the case of the boilers of steam vessels, requires to be done every two hours or oftener. This is accomplished by opening a large cock which permits some of the supersalted water to be forced overboard by the pressure of the steam. In some cases, in which the boiler applied to an engine is of inadequate size, the pressure within the boiler will fall spontaneously to a point considerably beneath the pressure of the atmosphere; but it is preferable, in such cases, partially to close the throttle valve in the steam pipe, whereby the issue of steam to the engine is diminished; and the pressure in the boiler is thus maintained, while the cylinder receives its former supply. 13. _Q._--If a hole be opened into a condenser of a steam engine, will air rush into it? _A._--If the hole communicates with the atmosphere, the air will be drawn in. 14. _Q._--With what Velocity does air rush into a vacuum? _A._--With the velocity which a body would acquire by falling from the height of a homogeneous atmosphere, which is an atmosphere of the same density throughout as at the earth's surface; and although such an atmosphere does not exist in nature, its existence is supposed, in order to facilitate the computation. It is well known that the velocity with which water issues from a cistern is the same that would be acquired by a body falling from the level of the head to the level of the issuing point; which indeed is an obvious law, since every particle of water descends and issues by virtue of its gravity, and is in its descent subject to the ordinary laws of falling bodies. Air rushing into a vacuum is only another example of the same general principle: the velocity of each particle will be that due to the height of the column of air which would produce the pressure sustained; and the weight of air being known, as well as the pressure it exerts on the earth's surface, it becomes easy to tell what height a column of air, an inch square, and of the atmospheric density, would require to be, to weigh 15 lbs. The height would be 27,818 feet, and the velocity which the fall of a body from such a height produces would be 1,338 feet per second. VELOCITY OF FALLING BODIES AND MOMENTUM OF MOVING BODIES. 15. _Q._--How do you determine the velocity of falling bodies of different kinds? _A._--All bodies fall with the same velocity, when there is no resistance from the atmosphere, as is shown by the experiment of letting fall, from the top of a tall exhausted receiver, a feather and a guinea, which reach the bottom at the same time. The velocity of falling bodies is one that is accelerated uniformly, according to a known law. When the height from which a body falls is given, the velocity acquired at the end of the descent can be easily computed. It has been found by experiment that the square root of the height in feet multiplied by 8.021 will give the velocity. 16. _Q._--But the velocity in what terms? _A._--In feet per second. The distance through which a body falls by gravity in one second is 16-1/12 feet; in two seconds, 64-4/12 feet; in three seconds, 144-9/12 feet; in four seconds, 257-4/12 feet, and so on. If the number of feet fallen through in one second be taken as unity, then the relation of the times to the spaces will be as follows:-- Number of seconds | 1| 2| 3| 4| 5| 6| Units of space passed through | 1| 4| 9|16|25|36| &c. so that it appears that the spaces passed through by a falling body are as the squares of the times of falling. 17. _Q._--Is not the urging force which causes bodies to fall the force of gravity? _A._--Yes; the force of gravity or the attraction of the earth. 18. _Q._--And is not that a uniform force, or a force acting with a uniform pressure? _A._--It is. 19. _Q._--Therefore during the first second of falling as much impelling power will be given by the force of gravity as during every succeeding second? _A._--Undoubtedly. 20. _Q._--How comes it, then, that while the body falls 64-4/12 feet in two seconds, it falls only 16-1/12 feet in one second; or why, since it falls only 16-1/12 feet in one second, should it fall more than twice 16-1/12 feet in two? _A._--Because 16-1/12 feet is the average and not the maximum velocity during the first second. The velocity acquired _at the end_ of the 1st second is not 16-1/12, but 32-1/6 feet per second, and at the end of the 2d second a velocity of 32-1/6 feet has to be added; so that the total velocity at the end of the 2d second becomes 64-2/6 feet; at the end of the 3d, the velocity becomes 96-3/6 feet, at the end of the 4th, 128-4/6 feet, and so on. These numbers proceed in the progression 1, 2, 3, 4, &c., so that it appears that the velocities acquired by a falling body at different points, are simply as the times of falling. But if the velocities be as the times, and the total space passed through be as the squares of the times, then the total space passed through must be as the squares of the velocity; and as the _vis viva_ or mechanical power inherent in a falling body, of any given weight, is measurable by the height through which it descends, it follows that the _vis viva_ is proportionate to the square of the velocity. Of two balls therefore, of equal weight, but one moving twice as fast as the other, the faster ball has four times the energy or mechanical force accumulated in it that the slower ball has. If the speed of a fly-wheel be doubled, it has four times the _vis viva_ it possessed before--_vis viva_ being measurable by a reference to the height through which a body must have fallen, to acquire the velocity given. 21. _Q._--By what considerations is the _vis viva_ or mechanical energy proper for the fly-wheel of an engine determined? _A._--By a reference to the power produced every half-stroke of the engine, joined to the consideration of what relation the energy of the fly-wheel rim must have thereto, to keep the irregularities of motion within the limits which are admissible. It is found in practice, that when the power resident in the fly-wheel rim, when the engine moves at its average speed, is from two and a half to four times greater than the power generated by the engine in one half-stroke--the variation, depending on the energy inherent in the machinery the engine has to drive and the equability of motion required--the engine will work with sufficient regularity for most ordinary purposes, but where great equability of motion is required, it will be advisable to make the power resident in the fly-wheel equal to six times the power generated by the engine in one half-stroke. 22. _Q._---Can you give a practical rule for determining the proper quantity of cast iron for the rim of a fly-wheel in ordinary land engines? _A._--One rule frequently adopted is as follows:--Multiply the mean diameter of the rim by the number of its revolutions per minute, and square the product for a divisor; divide the number of actual horse power of the engine by the number of strokes the piston makes per minute, multiply the quotient by the constant number 2,760,000, and divide the product by the divisor found as above; the quotient is the requisite quantity of cast iron in cubic feet to form the fly-wheel rim. 23. _Q._--What is Boulton and Watt's rule for finding the dimensions of the fly-wheel? _A._--Boulton and Watt's rule for finding the dimensions of the fly-wheel is as follows:--Multiply 44,000 times the length of the stroke in feet by the square of the diameter of the cylinder in inches, and divide the product by the square of the number of revolutions per minute multiplied by the cube of the diameter of the fly-wheel in feet. The resulting number will be the sectional area of the rim of the fly-wheel in square inches. CENTRAL FORCES. 24. _Q._--What do you understand by centrifugal and centripetal forces? _A._--By centrifugal force, I understand the force with which a revolving body tends to fly from the centre; and by centripetal force, I understand any force which draws it to the centre, or counteracts the centrifugal tendency. In the conical pendulum, or steam engine governor, which consists of two metal balls suspended on rods hung from the end of a vertical revolving shaft, the centrifugal force is manifested by the divergence of the balls, when the shaft is put into revolution; and the centripetal force, which in this instance is gravity, predominates so soon as the velocity is arrested; for the arms then collapse and hang by the side of the shaft. 25. _Q._--What measures are there of the centrifugal force of bodies revolving in a circle? _A._--The centrifugal force of bodies revolving in a circle increases as the diameter of the circle, if the number of revolutions remain the same. If there be two fly-wheels of the same weight, and making the same number of revolutions per minute, but the diameter of one be double that of the other, the larger will have double the amount of centrifugal force. The centrifugal force of the _same wheel_, however, increases as the square of the velocity; so that if the velocity of a fly-wheel be doubled, it will have four times the amount of centrifugal force. 26. _Q._--Can you give a rule for determining the centrifugal force of a body of a given weight moving with a given velocity in a circle of a given diameter? _A._--Yes. If the velocity in feet per second be divided by 4.01, the square of the quotient will be four times the height in feet from which a body must have fallen to have acquired that velocity. Divide this quadruple height by the diameter of the circle, and the quotient is the centrifugal force in terms of the weight of the body, so that, multiplying the quotient by the actual weight of the body, we have the centrifugal force in pounds or tons. Another rule is to multiply the square of the number of revolutions per minute by the diameter of the circle in feet, and to divide the product by 5,870. The quotient is the centrifugal force in terms of the weight of the body. 27. _Q._--How do you find the velocity of the body when its centrifugal force and the diameter of the circle in which it moves are given? _A._--Multiply the centrifugal force in terms of the weight of the body by the diameter of the circle in feet, and multiply the square root of the product by 4.01; the result will be the velocity of the body in feet per second. 28. _Q._--Will you illustrate this by finding the velocity at which the cast iron rim of a fly-wheel 10 feet in diameter would burst asunder by its centrifugal force? _A._--If we take the tensile strength of cast iron at 15,000 lbs. per square inch, a fly-wheel rim of one square inch of sectional area would sustain 30,000 lbs. If we suppose one half of the rim to be so fixed to the shaft as to be incapable of detachment, then the centrifugal force of the other half of the rim at the moment of rupture must be equal to 30,000 lbs. Now 30,000 lbs. divided by 49.48 (the weight of the half rim) is equal to 606.3, which is the centrifugal force in terms of the weight. Then by the rule given in the last answer 606.3 x 10 = 6063, the square root of which is 78 nearly, and 78 x 4.01 = 312.78, the velocity of the rim in feet per second at the moment of rupture. 29. _Q._--What is the greatest velocity at which it is safe to drive a cast iron fly-wheel? _A._--If we take 2,000 lbs. as the utmost strain per square inch to which cast iron can be permanently subjected with safety; then, by a similar process to that just explained, we have 4,000 lbs./49.48 = 80.8 which multiplied by 10 = 808, the square root of which is 28.4, and 28.4 x 4.01 = 113.884, the velocity of the rim in feet per second, which may be considered as the highest consistent with safety. Indeed, this limit should not be approached in practice on account of the risks of fracture from weakness or imperfections in the metal. 30. _Q._--What is the velocity at which the wheels of railway trains may run if we take 4,000 lbs. per square inch as the greatest strain to which malleable iron should be subjected? _A._--The weight of a malleable iron rim of one square inch sectional area and 7 feet diameter is 21.991 feet x 3.4 lbs. = 74.76, one half of which is 37.4 lbs. Then by the same process as before, 8,000/37.4 = 213.9, the centrifugal force in terms of the weight: 213.9 x 7, the diameter of the wheel = 1497.3, the square root of which, 38.3 x 4.01 = 155.187 feet per second, the highest velocity of the rims of railway carriage wheels that is consistent with safety. 155.187 feet per second is equivalent to 105.8 miles an hour. As 4,000 lbs. per square inch of sectional area is the utmost strain to which iron should be exposed in machinery, railway wheels can scarcely be considered safe at speed even considerably under 100 miles an hour, unless so constructed that the centrifugal force of the rim will be counteracted, to a material extent, by the centripetal action of the arms. Hooped wheels are very unsafe, unless the hoops are, by some process or other, firmly attached to the arms. It is of no use to increase the dimensions of the rim of a wheel with the view of giving increased strength to counteract the centrifugal force, as every increase in the weight of the rim will increase the centrifugal force in the same proportion. CENTRES OF GRAVITY, GYRATION, AND OSCILLATION. 31. _Q._--What do you understand by the centre of gravity of a body? _A._--That point within it, in which the whole of the weight may be supposed to be concentrated, and which continually endeavors to gain the lowest possible position. A body hung in the centre of gravity will remain at rest in any position. 32. _Q._--What is meant by the centre of gyration? _A._--The centre of gyration is that point in a revolving body in which the whole momentum may be conceived to be concentrated, or in which the whole effect of the momentum resides. If the ball of a governor were to be moved in a straight line, the momentum might be said to be concentrated at the centre of gravity of the ball; but inasmuch as, by its revolution round an axis, the part of the ball furthest removed from the axis moves more quickly than the part nearest to it, the momentum cannot be supposed to be concentrated at the centre of gravity, but at a point further removed from the central shaft, and that point is what is called the centre of gyration. 33. _Q._--What is the centre of oscillation? _A._--The centre of oscillation is a point in a pendulum or any swinging body, such, that if all the matter of the body were to be collected into that point, the velocity of its vibration would remain unaffected. It is in fact the mean distance from the centre of suspension of every atom, in a ratio which happens not to be an arithmetical one. The centre of oscillation is always in a line passing through the centre of suspension and the centre of gravity. THE PENDULUM AND GOVERNOR. 34. _Q._--By what circumstance is the velocity of vibration of a pendulous body determined? _A._--By the length of the suspending rod only, or, more correctly, by the distance between the centre of suspension and the centre of oscillation. The length of the arc described does not signify, as the times of vibration will be the same, whether the arc be the fourth or the four hundredth of a circle, or at least they will be nearly so, and would be so exactly, if the curve described were a portion of a cycloid. In the pendulum of clocks, therefore, a small arc is preferred, as there is, in that case, no sensible deviation from the cycloidal curve, but in other respects the size of the arc does not signify. 35. _Q._--If then the length of a pendulum be given, can the number of vibrations in a given time be determined? _A._--Yes; the time of vibration bears the same relation to the time in which a body would fall through a space equal to half the length of the pendulum, that the circumference of a circle bears to its diameter. The number of vibrations made in a given time by pendulums of different lengths, is inversely as the square roots of their lengths. 36. _Q._--Then when the length of the second's pendulum is known the proper length of a pendulum to make any given number of vibrations in the minute can readily be computed? _A._--Yes; the length of the second's pendulum being known, the length of another pendulum, required to perform any given number of vibrations in the minute, may be obtained by the following rule: multiply the square root of the given length by 60, and divide the product by the given number of vibrations per minute; the square of the quotient is the length of pendulum required. Thus if the length of a pendulum were required that would make 70 vibrations per minute in the latitude of London, then SQRT(39.1393) x 60/70 = (5.363)^2 = 28.75 in. which is the length required. 37. _Q._--Can you explain how it comes that the length of a pendulum determines the number of vibrations it makes in a given time? _A._--Because the length of the pendulum determines the steepness of the circle in which the body moves, and it is obvious, that a body will descend more rapidly over a steep inclined plane, or a steep arc of a circle, than over one in which there is but a slight inclination. The impelling force is gravity, which urges the body with a force proportionate to the distance descended, and if the velocity due to the descent of a body through a given height be spread over a great horizontal distance, the speed of the body must be slow in proportion to the greatness of that distance. It is clear, therefore, that as the length of the pendulum determines the steepness of the arc, it must also determine the velocity of vibration. 38. _Q._--If the motions of a pendulum be dependent on the speed with which a body falls, then a certain ratio must subsist between the distance through which a body falls in a second, and the length of the second's pendulum? _A._--And so there is; the length of the second's pendulum at the level of the sea in London, is 39.1393 inches, and it is from the length of the second's pendulum that the space through which a body falls in a second has been determined. As the time in which a pendulum vibrates is to the time in which a heavy body falls through half the length of the pendulum, as the circumference of a circle is to its diameter, and as the height through which a body falls is as the square of the time of falling, it is clear that the height through which a body will fall, during the vibration of a pendulum, is to half the length of the pendulum as the square of the circumference of a circle is to the square of its diameter; namely, as 9.8696 is to 1, or it is to the whole length of the pendulum as the half of this, namely, 4.9348 is to 1; and 4.9348 times 39.1393 in. is 16-1/12 ft. very nearly, which is the space through which a body falls by gravity in a second. 39. _Q._--Are the motions of the conical pendulum or governor reducible to the same laws which apply to the common pendulum? _A._--Yes; the motion of the conical pendulum may be supposed to be compounded of the motions of two common pendulums, vibrating at right angles to one another, and one revolution of a conical pendulum will be performed in the same time as two vibrations of a common pendulum, of which the length is equal to the vertical height of the point of suspension above the plane of revolution of the balls. 40. _Q._--Is not the conical pendulum or governor of a steam engine driven by the engine? _A._--Yes. 41. _Q._--Then will it not be driven round as any other mechanism would be at a speed proportional to that of the engine? _A._--It will. 42. _Q._--Then how can the length of the arms affect the time of revolution? [Illustration: Fig. 1.] _A._--By flying out until they assume a vertical height answering to the velocity with which they rotate round the central axis. As the speed is increased the balls expand, and the height of the cone described by the arms is diminished, until its vertical height is such that a pendulum of that length would perform two vibrations for every revolution of the governor. By the outward motion of the arms, they partially shut off the steam from the engine. If, therefore, a certain expansion of the balls be desired, and a certain length be fixed upon for the arms, so that the vertical height of the cone is fixed, then the speed of the governor must be such, that it will make half the number of revolutions in a given time that a pendulum equal in length to the height of the cone would make of vibrations. The rule is, multiply the square root of the height of the cone in inches by 0.31986, and the product will be the right time of revolution in seconds. If the number of revolutions and the length of the arms be fixed, and it is wanted to know what is the diameter of the circle described by the balls, you must divide the constant number 187.58 by the number of revolutions per minute, and the square of the quotient will be the vertical height in inches of the centre of suspension above the plane of the balls' revolution. Deduct the square of the vertical height in inches from the square of the length of the arm in inches, and twice the square root of the remainder is the diameter of the circle in which the centres of the balls revolve. 43. _Q._ Cannot the operation of a governor be deduced merely from the consideration of centrifugal and centripetal forces? _A._--It can; and by a very simple process. The horizontal distance of the arm from the spindle divided by the vertical height, will give the amount of centripetal force, and the velocity of revolution requisite to produce an equivalent centrifugal force may be found by multiplying the centripetal force of the ball in terms of its own weight by 70,440, and dividing the product by the diameter of the circle made by the centre of the ball in inches; the square root of the quotient is the number of revolutions per minute. By this rule you fix the length of the arms, and the diameter of the base of the cone, or, what is the same thing, the angle at which it is desired the arms shall revolve, and you then make the speed or number of revolutions such, that the centrifugal force will keep the balls in the desired position. 44. _Q._--Does not the weight of the balls affect the question? _A._--Not in the least; each ball may be supposed to be made up of a number of small balls or particles, and each particle of matter will act for itself. Heavy balls attached to a governor are only requisite to overcome the friction of the throttle valve which shuts off the steam, and of the connections leading thereto. Though the weight of a ball increases its centripetal force, it increases its centrifugal force in the same proportion. THE MECHANICAL POWERS. 45. _Q._--What do you understand by the mechanical powers? _A._--The mechanical powers are certain contrivances, such as the wedge, the screw, the inclined plane, and other elementary machines, which convert a small force acting through a great space into a great force acting through a small space. In the school treatises on mechanics, a certain number of these devices are set forth as the mechanical powers, and each separate device is treated as if it involved a separate principle; but not a tithe of the contrivances which accomplish the stipulated end are represented in these learned works, and there is no very obvious necessity for considering the principle of each contrivance separately when the principles of all are one and the same. Every pressure acting with a certain velocity, or through a certain space, is convertible into a greater pressure acting with a less velocity, or through a smaller space; but the quantity of mechanical force remains unchanged by its transformation, and all that the implements called mechanical powers accomplish is to effect this transformation. 46. _Q._--Is there no power gained by the lever? _A._--Not any: the power is merely put into another shape, just as the contents of a hogshead of porter are the same, whether they be let off by an inch tap or by a hole a foot in diameter. There is a greater gush in the one case than the other, but it will last a shorter time; when a lever is used there is a greater force exerted, but it acts through a shorter distance. It requires just the same expenditure of mechanical power to lift 1 lb. through 100 ft., as to lift 100 lbs. through 1 foot. A cylinder of a given cubical capacity will exert the same power by each stroke, whether the cylinder be made tall and narrow, or short and wide; but in the one case it will raise a small weight through a great height, and in the other case, a great weight through a small height. 47. _Q._--Is there no loss of power by the use of the crank? _A._--Not any. Many persons have supposed that there was a loss of power by the use of the crank, because at the top and bottom centres it is capable of exerting little or no power; but at those times there is little or no steam consumed, so that no waste of power is occasioned by the peculiarity. Those who imagine that there is a loss of power caused by the crank perplex themselves by confounding the vertical with the circumferential velocity. If the circle of the crank be divided by any number of equidistant horizontal lines, it will be obvious that there must be the same steam consumed, and the same power expended, when the crank pin passes from the level of one line to the level of the other, in whatever part of the circle it may be, those lines being indicative of equal ascents or descents of the piston. But it will be seen that the circumferential velocity is greater with the same expenditure of steam when the crank pin approaches the top and bottom centres; and this increased velocity exactly compensates for the diminished leverage, so that there is the same power given out by the crank in each of the divisions. 48. _Q._--Have no plans been projected for gaining power by means of a lever? _A._--Yes, many plans,--some of them displaying much ingenuity, but all displaying a complete ignorance of the first principles of mechanics, which teach that power cannot be gained by any multiplication of levers and wheels. I have occasionally heard persons say: "You gain a great deal of power by the use of a capstan; why not apply the same resource in the case of a steam vessel, and increase the power of your engine by placing a capstan motion between the engine and paddle wheels?" Others I have heard say: "By the hydraulic press you can obtain unlimited power; why not then interpose a hydraulic press between the engines and the paddles?" To these questions the reply is sufficiently obvious. Whatever you gain in force you lose in velocity; and it would benefit you little to make the paddles revolve with ten times the force, if you at the same time caused them to make only a tenth of the number of revolutions. You cannot, by any combination of mechanism, get increased force and increased speed at the same time, or increased force without diminished speed; and it is from the ignorance of this inexorable condition, that such myriads of schemes for the realization of perpetual motion, by combinations of levers, weights, wheels, quicksilver, cranks, and other mere pieces of inert matter, have been propounded. 49. _Q._--Then a force once called into existence cannot be destroyed? _A._--No; force is eternal, if by force you mean power, or in other words pressure acting though space. But if by force you mean mere pressure, then it furnishes no measure of power. Power is not measurable by force but by force and velocity combined. 50. _Q._--Is not power lost when two moving bodies strike one other and come to a state of rest? _A._--No, not even then. The bodies if elastic will rebound from one another with their original velocity; if not elastic they will sustain an alteration of form, and heat or electricity will be generated of equivalent value to the power which has disappeared. 51. _Q._--Then if mechanical power cannot be lost, and is being daily called into existence, must not there be a daily increase in the power existing in the world? _A._--That appears probable unless it flows back in the shape of heat or electricity to the celestial spaces. The source of mechanical power is the sun which exhales vapors that descend in rain, to turn mills, or which causes winds to blow by the unequal rarefaction of the atmosphere. It is from the sun too that the power comes which is liberated in a steam engine. The solar rays enable plants to decompose carbonic acid gas, the product of combustion, and the vegetation thus rendered possible is the source of coal and other combustible bodies. The combustion of coal under a steam boiler therefore merely liberates the power which the sun gave out thousands of years before. FRICTION. 52. _Q._--What is friction? _A._--Friction is the resistance experienced when one body is rubbed upon another body, and is supposed to be the result of the natural attraction which bodies have for one another, and of the interlocking of the impalpable asperities upon the surfaces of all bodies, however smooth. There is, no doubt, some electrical action involved in its production, not yet recognized, nor understood; and it is perhaps traceable to the disturbance of the electrical equilibrium of the particles of the body owing to the condensation or change of figure which all bodies must experience when subjected to a strain. When motion in opposite directions is given to smooth surfaces, the minute asperities of one surface must mount upon those of the other, and both will be abraded and worn away, in which act power must be expended. The friction of smooth rubbing substances is less when the composition of those substances is different, than when it is the same, the particles being supposed to interlock less when the opposite prominences or asperities are not coincident. 53. _Q._--Does friction increase with the extent of rubbing surface? _A._--No; the friction, so long as there is no violent heating or abrasion, is simply in the proportion of the pressure keeping the surfaces together, or nearly so. It is, therefore, an obvious advantage to have the bearing surfaces of steam engines as large as possible, as there is no increase of friction by extending the surface, while there is a great increase in the durability. When the bearings of an engine are made too small, they very soon wear out. 54. _Q._--Does friction increase in the same ratio as velocity? _A._--No; friction does not increase with the velocity at all, if the friction over a given amount of surface be considered; but it increases as the velocity, if the comparison be made with the time during which the friction acts. Thus the friction of each stroke of a piston is the same, whether it makes 20 strokes in the minute, or 40: in the latter case, however, there are twice the number of strokes made, so that, though the friction per stroke is the same, the friction per minute is doubled. The friction, therefore, of any machine per hour varies as the velocity, though the friction per revolution remains, at all ordinary velocities, the same. Of excessive velocities we have not sufficient experience to enable us to state with confidence whether the same law continues to operate among them. 55. _Q._--Can you give any approximate statement of the force expended in overcoming friction? _A._--It varies with the nature of the rubbing bodies. The friction of iron sliding upon iron, has generally been taken at about one tenth of the pressure, when the surfaces are oiled and then wiped again, so that no film of oil is interposed. The friction of iron rubbing upon brass has generally been taken at about one eleventh of the pressure under the same circumstances; but in machines in actual operation, where a film of some lubricating material is interposed between the rubbing surfaces, it is not more than one third of this amount or 1/33d of the weight. While this, however, is the average result, the friction is a good deal less in some cases. Mr. Southern, in some experiments upon the friction of the axle of a grindstone--an account of which may be found in the 65th volume of the Philosophical Transactions--found the friction to amount to less than 1/40th of the weight; and Mr. Wood, in some experiments upon the friction of locomotive axles, found that by ample lubrication the friction may be made as little as 1/60th of the weight. In some experiments upon the friction of shafts by Mr. G. Rennie, he found that with a pressure of from 1 to 5 cwt. the friction did not exceed 1/39th of the pressure when tallow was the unguent employed; with soft soap it became 1/34th. The fact appears to be that the amount of the resistance denominated friction depends, in a great measure, upon the nature of the unguent employed, and in certain cases the viscidity of the unguent may occasion a greater retardation than the resistance caused by the attrition. In watchwork therefore, and other fine mechanism, it is necessary both to keep the bearing surfaces small, and to employ a thin and limpid oil for the purpose of lubrication, for the resistance caused by the viscidity of the unguent increases with the amount of surface, and the amount of surface is relatively greater in the smaller class of works. 56. _Q._--Is a very thin unguent preferable also for the larger class of bearings? _A._--The nature of the unguent, proper for different bearings, appears to depend in a great measure upon the amount of the pressure to which the bearings are subjected,--the hardest unguents being best where the pressure is greatest. The function of lubricating substances is to prevent the rubbing surfaces from coming into contact, whereby abrasion would be produced, and unguents are effectual in this respect in the proportion of their viscidity; but if the viscidity of the unguent be greater than what suffices to keep the surfaces asunder, an additional resistance will be occasioned; and the nature of the unguent selected should always have reference, therefore, to the size of the rubbing surfaces, or to the pressure per square inch upon them. With oil the friction appears to be a minimum when the pressure on the surface of a bearing is about 90 lbs. per square inch. The friction from too small a surface increases twice as rapidly as the friction from too large a surface, added to which, the bearing, when the surface is too small, wears rapidly away. 57. _Q._--Has not M. Morin, in France, made some very complete experiments to determine the friction of surfaces of different kinds sliding upon one another? _A._--He has; but the result does not differ materially from what is stated above, though, upon the whole, M. Morin, found the resistance due to friction to be somewhat greater than it has been found to be by various other engineers. When the surfaces were merely wiped with a greasy cloth, but had no film of lubricating material interposed, the friction of brass upon cast iron he found to be .107, or about 1/10th of the load, which was also the friction of cast iron upon oak. But when a film of lubricating material was interposed, he found that the friction was the same whether the surfaces were wood on metal, wood on wood, metal on wood, or metal on metal; and the amount of the friction in such case depended chiefly on the nature of the unguent. With a mixture of hog's lard and olive oil interposed between the surfaces, the friction was usually from 1/12th to 1/14th of the load, but in some cases it was only 1/20th of the load. 58. _Q._--May water be made to serve for purposes of lubrication? _A._--Yes, water will answer very well if the surface be very large relatively with the pressure; and in screw vessels where the propeller shaft passes through a long pipe at the stern, the stuffing box is purposely made a little leaky. The small leakage of water into the vessel which is thus occasioned, keeps the screw shaft in this situation always wet, and this is all the lubrication which this bearing requires or obtains. 59. _Q._--What is the utmost pressure which may be employed without heating when oil is the lubricating material? _A._--That will depend upon the velocity. When the pressure exceeds 800 lbs. per square inch, however, upon the section of the bearing in a direction parallel with the axis, then the oil will be forced out and the bearing will necessarily heat. 60. _Q._--But, with, a given velocity, can you tell the limit of pressure which will be safe in practice; or with a given pressure, can you tell the limit of velocity? _A._--Yes; that may be done by the following empirical rule, which has been derived from observations made upon bearings of different sizes and moving with different velocities. Divide the number 70,000 by the velocity of the surface of the bearing in feet per minute. The quotient will be the number of pounds per square inch of section in the line of the axis that may be put upon the bearing. Or, if we divide 70,000 by the number of pounds per square inch of section, then the quotient will be the velocity in feet per minute at which the circumference of the bearing may work. 61. _Q._--The number of square inches upon which the pressure is reckoned, is not the circumference of the bearing multiplied by its length, but the diameter of the bearing multiplied by its length? _A._--Precisely so, it will be the diameter multiplied by the length of the bearing. 62. _Q._--What is the amount of friction in the case of surfaces sliding upon one another in sandy or muddy water--such surfaces, for example, as are to be found in the sluices of valves for water? _A._--Various experiments have been made by Mr. Summers of Southampton to ascertain the friction of brass surfaces sliding upon each other in salt water, with the view of finding the power required for moving sluice doors for lock gates and for other similar purposes. The surfaces were planed as true and smooth as the planing machine would make them, but were _not_ filed or scraped, and the result was as follows: Area of Slide Weight or Pressure on Power required to move the rubbing rubbing Surface. Slide _slowly_ in muddy Surface. Salt Water, kept stirred up. Sq. in. Lb. Lb. 8 56 21.5 " 112 44. " 168 65.5 " 224 88.5 " 336 140.5 " 448 170.75 [Illustration: Fig. 2. Sketch of Slide. The facing on which the slide moved was similar, but three or four times as long.] These results were the average of eight fair trials; in each case, the sliding surfaces were totally immersed in muddy salt water, and although the apparatus used for drawing the slide along was not very delicately fitted up, the power required may be considered as a sufficient approximation for practical purposes. It appears from these experiments, that rough surfaces follow the same law as regards friction that is followed by smooth, for in each case the friction increases directly as the pressure. STRENGTH OF MATERIALS AND STRAINS SUBSISTING IN MACHINES. 63. _Q._--In what way are the strengths of the different parts of a steam engine determined? _A._--By reference to the amount of the strain or pressure to which they are subjected, and to the cohesive strength of the iron or other material of which they are composed. The strains subsisting in engines are usually characterized as tensile, crushing, twisting, breaking, and shearing strains; but they may be all resolved into strains of extension and strains of compression; and by the power of the materials to resist these two strains, will their practical strength be measurable. 64. _Q._--What are the ultimate strengths of the malleable and cast iron, brass, and other materials employed in the construction of engines? _A._--The tensile and crushing strengths of any given material are by no means the same. The tensile strength, or strength when extended, of good bar iron is about 60,000 lbs., or nearly 27 tons per square inch of section; and the tensile strength of cast iron is about 15,000 lbs., or say 6 3/4 to 7 tons per square inch of section. These are the weights which are required to break them. The crushing strain of cast iron, however, is about 100,000 lbs., or 44 1/2 tons; whereas the crushing strength of malleable iron is not more than 27,000 lbs., or 12 tons, per square inch of section, and indeed it is generally less than this. The ultimate tensile strength, therefore, of malleable iron is four times greater than that of cast iron, but the crushing strength of cast iron is between three and four times greater than that of wrought iron. It may be stated, in round numbers, that the tensile strength of malleable iron is twice greater than its crushing strength; or, in other words, that it will take twice the strain to break a bar of malleable iron by drawing it asunder endways, than will cripple it by forcing it together endways like a pillar; whereas a bar of cast iron will be drawn asunder with one sixth of the force that will be required to break or cripple it when forced together endways like a pillar. 65. _Q._--What is the cohesive strength of steel? _A._--The ultimate tensile strength of good cast or blistered steel is about twice as great as that of wrought iron, being about 130,000 lbs. per square inch of section. The tensile strength of gun metal, such as is used in engines, is about 36,000 lbs. per square inch of section; of wrought copper about 33,000 lbs.; and of cast copper about 19,000 lbs. per square Inch of section. 66. _Q._--Is the crushing strength of steel greater or less than its tensile strength? _A._--It is about twice greater. A good steel punch will punch through a plate of wrought iron of a thickness equal to the diameter of the punch. A punch therefore of an inch diameter will pierce a plate an inch thick. Now it is well known, that the strain required to punch a piece of metal out of a plate, is just the same as that required to tear asunder a bar of iron of the same area of cross section as the area of the surface cut. The area of the surface cut in this case will be the circumference of the punch, 3.1416 inches, multiplied by the thickness of the plate, 1 inch, which makes the area of the cut surface 3.1416 square inches. The area of the point of the punch subjected to the pressure is .7854 square inches, so that the area cut to the area crushed is as four to one. In other words, it will require four times the strain to crush steel that is required to tear asunder malleable iron, or it will take about twice the strain to crush steel that it will require to break it by extension. 67. _Q._--What strain may be applied to malleable iron in practice? _A._--A bar of wrought iron to which a tensile or compressing strain is applied, is elongated or contracted like a very stiff spiral spring, nearly in the proportion of the amount of strain applied up to the limit at which the strength begins to give way, and within this limit it will recover its original dimensions when the strain is removed. If, however, the strain be carried beyond this limit, the bar will not recover its original dimensions, but will be permanently pulled out or pushed in, just as would happen to a spring to which an undue strain had been applied. This limit is what is called the limit of elasticity; and whenever it is exceeded, the bar, though it may not break immediately, will undergo a progressive deterioration, and will break in the course of time. The limit of elasticity of malleable iron when extended, or, in other words, the tensile strain to which a bar of malleable iron an inch square may be subjected without permanently deranging its structure, is usually taken at 17,800 lbs., or from that to 10 tons, depending on the quality of the iron. It has also been found that malleable iron is extended about one ten-thousandth part of its length for every ton of direct strain applied to it. 68. _Q._--What is the limit of elasticity of cast iron? _A._--It is commonly taken at 15,300 lbs. per square inch of section; but this is certainly much too high, as it exceeds the tensile strength of irons of medium quality. A bar of cast iron if compressed by weights will be contracted in length twice as much as a bar of malleable iron under similar circumstances; but malleable iron, when subjected to a greater strain than 12 tons per square inch of section, gradually crumples up by the mere continuance of the weight. A cast-iron bar one inch square and ten feet long, is shortened about one tenth of an inch by a compressing force of 10,000 lbs., whereas a malleable iron bar of the same dimensions would require to shorten it equally a compressing force of 20,000 lbs. As the load, however, approaches 12 tons, the compressions become nearly equal, and above that point the rate of the compression of the malleable iron rapidly increases. A bar of cast iron, when at its breaking point by the application of a tensile strain, is stretched about one six-hundredth part of its length; and an equal strain employed to compress it, would shorten it about one eight-hundredth part of its length. 69. _Q._--But to what strain may the iron used in the construction of engines be safely subjected? _A._--The most of the working parts of modern engines are made of malleable iron, and the utmost strain to which wrought iron should be subjected in machinery is 4000 lbs. per square inch of section. Cast iron should not be subjected to more than half of this. In locomotive boilers the strain of 4000 lbs. per square inch of section is sometimes exceeded by nearly one half; but such an excess of strain approaches the limits of danger. 70. _Q._--Will you explain in what way the various strains subsisting in a steam engine may be resolved into tensile and crushing strains; also in what way the magnitude of those strains may be determined? _A._--To take the case of a beam subjected to a transverse strain, such as the great beam of an engine, it is clear, if we suppose the beam broken through the middle, that the amount of strain at the upper and lower edges of the beam, where the whole strain may be supposed to be collected, will, with any given pressure on the piston, depend upon the proportion of the length to the depth of the beam. One edge of the beam breaks by extension, and the other edge by compression; and the upper and lower edges may be regarded as pillars, one of which is extended by the strain, and the other is compressed. If, to make an extreme supposition, the depth of the beam is taken as equal to its length, then the pillars answering to the edges of the beam will be compressed, and extended by what is virtually a bellcrank lever with equal arms; the horizontal distance from the main centre to the end of the beam being one of the arms, and the vertical height from the main centre to the top edge of the beam being the other arm. The distance, therefore, passed through by the fractured edge of the beam during a stroke of the engine, will be equal to the length of the stroke; and the strain it will have to sustain will consequently be equal to the pressure on the piston. If its motion were only half that of the piston, as would be the case if its depth were made one half less, the strain the beam would have to bear would be twice as great; and it may be set down as an axiom, that the strain upon any part of a steam engine or other machine is inversely equal to the strain produced by the prime mover, multiplied by the comparative velocity with which the part in question moves. If any part of an engine moves with a less velocity than the piston, it will have a greater strain on it, if resisted, than is thrown upon the piston. If it moves with a greater velocity than the piston, it will have a less strain upon it, and the difference of strain will in every case be in the inverse proportion of the difference of the velocity. 71. _Q._--Then, in computing the amount of metal necessary to give due strength to a beam, the first point is to determine the velocity with which the edge of the beam moves at that point were the strain is greatest? _A._--The web of a cast-iron beam or girder serves merely to connect the upper and lower edges or flanges rigidly together, so as to enable the extending and compressing strains to be counteracted in an effectual manner by the metal of those flanges. It is only necessary, therefore, to make the flanges of sufficient strength to resist effectually the crushing and tensile strains to which they are exposed, and to make the web of the beam of sufficient strength to prevent a distortion of its shape from taking place. 72. _Q._--Is the strain greater from being movable or intermittent than if it was stationary? _A._--Yes it is nearly twice as great from being movable. Engineers are in the habit of making girders intended to sustain a stationary load, about three times stronger than the breaking weight; but if the load be a movable one, as is the case in the girders of railway bridges, they make the strength equal to six times the breaking weight. 73. _Q._--Then the strain is increased by the suddenness with which it is applied? _A._--If a weight be placed on a long and slender beam propped up in the middle, and the prop be suddenly withdrawn, so as to allow deflection to take place, it is clear that the deflection must be greater than if the load had been gradually applied. The momentum of the weight and also of the beam itself falling through the space through which it has been deflected, has necessarily to be counteracted by the elasticity of the beam; and the beam will, therefore, be momentarily bent to a greater extent than what is due to the load, and after a few vibrations up and down it will finally settle at that point of deflection which the load properly occasions. It is obvious that a beam must be strong enough, not merely to sustain the pressure due to the load, but also that accession of pressure due to the counteracted momentum of the weight and of the beam itself. Although in steam engines the beam is not loaded by a weight, but by the pressure of the steam, yet the momentum of the beam itself must in every case be counteracted, and the momentum will be considerable in every case in which a large and rapid deflection takes place. A rapid deflection increases the amount of the deflection as well as the amount of the strain, as is seen in the cylinder cover of a Cornish pumping engine, into which the steam is suddenly admitted, and in which the momentum of the particles of the metal put into motion increases the deflection to an extent such as the mere pressure of the steam could not produce. 74. _Q._--What will be the amount of increased strain consequent upon deflection? _A._--The momentum of any moving body being proportional to the square of its velocity, it follows that the strain will be proportional to the square of the amount of deflection produced in a specified time. 75. _Q._--But will not the inertia of a beam resist deflection, as well as the momentum increase deflection? _A._--No doubt that will be so; but whether in practical cases increase of mass without reference to strength or load will, upon the whole, increase or diminish deflection, will depend very much upon the magnitude of the mass relatively with the magnitude of the deflecting pressure, and the rapidity with which that pressure is applied and removed. Thus if a force or weight be very suddenly applied to the middle of a ponderous beam, and be as suddenly withdrawn, the inertia of the beam will, as in the case of the collision of bodies, tend to resist the force, and thus obviate deflection to a considerable extent; but if the pressure be so long continued as to produce the amount of deflection due to the pressure, the effect of the inertia in that case will be to increase the deflection. 76. _Q._--Will the pressure given to the beam of an engine in different directions facilitate its fracture? _A._--Iron beams bent alternately in opposite directions, or alternately deflected and released, will be broken in the course of time with a much less strain than is necessary to produce immediate fracture. It has been found, experimentally, that a cast-iron bar, deflected by a revolving cam to only half the extent due to its breaking weight, will in no case withstand 900 successive deflections; but, if bent by the cam to only one third of its ultimate deflection, it will withstand 100,000 deflections without visible injury. Looking, however, to the jolts and vibrations to which engines are subject, and the sudden strains sometimes thrown upon them, either from water getting into the cylinder or otherwise, it does not appear that a strength answering to six times the breaking weight will give sufficient margin for safety in the case of cast-iron beams. 77. _Q._--Does the same law hold in the case of the deflection of malleable iron bars? _A._--In the case of malleable iron bars it has been found that no very perceptible damage was caused by 10,000 deflections, each deflection being such as was due to half the load that produced a large permanent deflection. 78. _Q._--The power of a rod or pillar to resist compression becomes very little when the diameter is small and the length great? _A._--The power of a rod or pillar to resist compression, varies nearly as the fourth power of the diameter divided by the square of the length. In the case of hollow cylindrical columns of cast iron, it has been found, experimentally, that the 3.55th power of the internal diameter, subtracted from the 3.55th power of the external diameter, and divided by the 1.7th power of the length, will represent the strength very nearly. In the case of hollow cylindrical columns of malleable iron, experiment shows that the 3.59th power of the internal diameter, subtracted from the 3.59th power of the external diameter, and divided by the square of the length, gives a proper expression for the strength; but this rule only holds where the strain does not exceed 8 or 9 tons on the square inch of section. Beyond 12 or 13 tons per square inch of section, the metal cannot be depended upon to withstand the strain, though hollow pillars will sometimes bear 15 or 16 tons per square inch of section. 79. _Q._--Does not the thickness of the metal of the pillars or tubes affect the question? _A._--It manifestly does; for a tube of very thin metal, such as gold leaf or tin foil, would not stand on end at all, being crushed down by its own weight. It is found, experimentally, that in malleable iron tubes of the respective thicknesses of .525, .272, and .124 inches, the resistances per square inch of section are 19.17, 14.47, and 7.47 tons respectively. The power of plates to resist compression varies nearly as the cube, or more nearly as the 2.878th power of their thickness; but this law only holds so long as the pressure applied does not exceed from 9 to 12 tons per square inch of section. When the pressure is greater than this the metal is crushed, and a new law supervenes, according to which it is necessary to employ plates of twice or three times the thickness, to obtain twice the resisting power. 80. _Q._--In a riveted tube, will the riveting be much, damaged by heavy strains? _A._--It will be most affected by percussion. Long-continued impact on the side of a tube, producing a deflection of only one fifth of that which would be required to injure it by pressure, is found to be destructive of the riveting; but in large riveted structures, such as a ship or a railway bridge, the inertia of the mass will, by resisting the effect of impact, prevent any injurious action from this cause from taking place. 81. _Q._--Will the power of iron to resist shocks be in all cases proportional to its power to resist strains? _A._--By no means. Some cast iron is very hard and brittle; and although it will in this state resist compression very strongly, it, will be easily broken by a blow. Iron which has been remelted many times generally falls into this category, as it will also do if run into very small castings. It has been found, by experiment, that iron of which the crushing weight per square inch is about 42 tons, will, if remelted twelve times, bear a crushing weight of 70 tons, and if remelted eighteen times it will bear a crushing weight of 83 tons; but taking its power to resist impact in its first state at 706, this power will be raised at the twelfth remelting to 1153, and will be sunk at the eighteenth remelting to 149. 82. _Q._--From all this it appears that a combination of cast iron and malleable iron is the best for the beams of engines? _A._--Yes, and for all beams. Engine beams should be made deeper at the middle than they are now made; the web should be lightened by holes pierced in it, and round the edge of the beam there should be a malleable iron hoop or strap securely attached to the flanges by riveting or otherwise. The flanges at the edges of engine beams are invariably made too small. It is in them that the strength of the beam chiefly resides. CHAPTER I. GENERAL DESCRIPTION OF THE STEAM ENGINE. * * * * * THE BOILER. 83. _Q._--What are the chief varieties of the steam engine in actual practical use? _A._--There is first the single-acting engine, which is used for pumping water; the rotative land engine, which is employed to drive mills and manufactories; the rotative marine engine, which is used to propel steam vessels; and the locomotive engine, which is employed on railways. The last is always a high-pressure engine; the others are, for the most part, condensing engines. 84. _Q._--Will you explain the construction and action of the single-acting engine, used for draining mines? _A._--Permit me then to begin with the boiler, which is common and necessary to all engines; and I will take the example of a wagon boiler, such as was employed by Boulton and Watt universally in their early engines, and which is still in extensive use. This boiler is a long rectangular vessel, with a rounded top, like that of a carrier's wagon, from its resemblance to which it derives its name. A fire is set beneath it, and flues constructed of brickwork encircle it, so as to keep the flame and smoke in contact with the boiler for a sufficient time to absorb the heat. [Illustration: Fig. 3] 85. _Q._--This species of boiler has not an internal furnace, but is set in brickwork, in which the furnace is formed? _A._--Precisely so. The general arrangement and configuration will be at once understood by a reference to the annexed figure (fig. 3), which is a transverse section of a wagon boiler. The line b represents the top of the grate or fire bars, which slope downward from the front at an angle of about 25°, giving the fuel a tendency to move toward the back of the grate. The supply of air ascends from the ash pit through the grate bars, and the flame passes over a low wall or bridge, and traverses the bottom of the boiler. The smoke rises up at the back of the boiler, and proceeds through the flue F along one side to the front, and returns along the other side of the boiler, and then ascends the chimney. The performance of this course by the smoke is what is termed a wheel draught, as the smoke wheels once round the boiler, and then ascends the chimney. 86. _Q._--Is the performance of this course by the smoke universal in wagon boilers? _A._--No; such boilers sometimes have what is termed a split draught. The smoke and flame, when they reach the end of the boiler, pass in this case through an iron flue or tube, reaching from end to end of the boiler; and on arriving at the front of the boiler, the smoke splits or separates--one half passing through a flue on the one side of the boiler, and the other half passing through a flue on the other side of the boiler--both of these flues having their debouch in the chimney. 87. _Q._--What are the appliances usually connected with a wagon boiler? _A._--On the top of the boiler, near the front, is a short cylinder, with a lid secured by bolts. This is the manhole door, the purpose of which is to enable a man to get into the inside of the boiler when necessary for inspection and repair. On the top of this door is a small valve opening downward, called the atmospheric valve. The intention of this valve is to prevent a vacuum from being formed accidentally in the boiler, which might collapse it; for if the pressure in the boiler subsides to a point materially below the pressure of the atmosphere, the valve will open and allow air to get in. A bent pipe, which rises up from the top of the boiler, immediately behind the position of the manhole, is the steam pipe for conducting the steam to the engine; and a bent pipe which ascends from the top of the boiler, at the back end, is the waste-steam pipe for conducting away the steam, which escapes through the safety valve. This valve is set in a chest, standing on the top of the boiler, at the foot of the waste-steam pipe, and it is loaded with iron or leaden weights to a point answerable to the intended pressure of the steam. 88. _Q._--How is the proper level of the water in the boiler maintained? _A._--By means of a balanced buoy or float. This float is attached to a rod, which in its turn is attached to a lever set on the top of a large upright pipe. The upper part of the pipe is widened out into a small cistern, through a short pipe in the middle of which a chain passes to the damper; but any water emptied into this small cistern cannot pass into the pipe, except through a small valve fixed to the lever to which the rod is attached. The water for replenishing the boiler is pumped into the small cistern on the top of the pipe; and it follows from these arrangements that when the buoy falls, the rod opens the small valve and allows the feed water to enter the pipe, which communicates with the water in the boiler; whereas, when the buoy rises, the feed cannot enter the pipe, and it has, therefore, to run to waste through an overflow pipe provided for the purpose. 89. _Q._--How is the strength of the fire regulated? _A._--The draught through the furnaces of land boilers is regulated by a plate of metal or a damper, as it is called, which slides like a sluice up and down in the flue, and this damper is closed more or less when the intensity of the fire has to be moderated. In wagon boilers this is generally accomplished by self-acting mechanism. In the small cistern pipe, which is called a stand pipe, the water rises up to a height proportional to the pressure of the steam, and the surface of the water in this pipe will rise or fall with the fluctuations in the pressure of the steam. In this pipe a float is placed, which communicates by means of a chain with the damper. If the pressure of the steam rises, the float will be raised and the damper closed, whereas, if the pressure in the boiler falls, the reverse of this action will take place. [Illustration: Fig. 4.] [Illustration: Fig. 5.] 90. _Q._--Are all land boilers of the same construction as that which you have just described? _A._--No; many land boilers are now made of a cylindrical form, with one or two internal flues in which the furnace is placed. A boiler of this kind is represented in Figs. 4 and 5, and which is the species of boiler principally used in Cornwall. In this boiler a large internal cylinder or flue runs from end to end. In the fore part of this cylinder the furnace is placed, and behind the furnace a large tube filled with water extends to the end of the boiler. This internal tube is connected to the bottom part of the boiler by a copper pipe standing vertically immediately behind the furnace bridge, and to the top part of the boiler by a bent copper pipe which stands in a vertical position near the end of the boiler. The smoke, after passing through the central flue, circulates round the sides and beneath the bottom of the boiler before its final escape into the chimney. The boiler is carefully covered over to prevent the dispersion of the heat. [Illustration: Fig. 6] 91. _Q._--Will you describe the construction of the boilers used in steam vessels? _A._--These are of two classes, flue boilers and tubular boilers, but the latter are now most used. In the flue boiler the furnaces are set within the boiler, and the flues proceeding from them wind backwards and forwards within the boiler until finally they meet and enter the chimney. Figs. 6, 7, and 8 are different views of the flue boilers of the steamer Forth. There are 4 boilers (as shown in plan, Fig. 6), with 3 furnaces in each, or 12 furnaces in all. Fig. 7 is an elevation of 2 boilers, the one to the right being the front view, and that to the left a transverse section. Fig. 8 is a longitudinal section through 2 boilers. The direction of the arrows in plan and longitudinal section, will explain the direction of the smoke current. [Illustration: Fig. 7.] [Illustration: Fig. 8.] 92. _Q._--Is this arrangement different from that obtaining in tubular boilers? _A._--In tubular boilers, the smoke after leaving the furnace just passes once through a number of small tubes and then enters the chimney. These tubes are sometimes of brass, and they are usually about 3 inches in diameter, and 6 or 7 feet long. [Illustration: Fig. 9.] [Illustration: Fig. 10.] [Illustration: Fig. 11.] Figs. 9, 10, and 11 represent a marine tubular boiler; fig. 9 being a vertical longitudinal section, fig. 10 half a front elevation and half a transverse section, and fig. 11 half a back elevation and half a transverse section near the end. There is a projecting part on the top of the boiler called the "steam chest," of which the purpose is to retain for the use of the cylinder a certain supply of steam in a quiescent state, in order that it may have time to clear itself of foam or spray. A steam chest is a usual part of all marine boilers. In fig. 9 A is the furnace, B the steam chest, and C the smoke box which opens into the chimney. The front of the smoke box is usually closed by doors which may be opened when necessary to sweep the soot out of the tubes. The following are some forms of American boilers: Figs. 12 and 13 are the transverse and longitudinal sections of a common form of American marine boiler. Figs. 14 and 15 are the front and sectional elevation of one of the boilers of the U.S. steamer Water Witch. [Illustration: Fig. 12.] [Illustration: Fig. 13.] [Illustration: Fig. 14.] [Illustration: Fig. 15.] Fig. 16 is a longitudinal section of a boiler of the drop flue variety. For land purposes the lowest range of tubes is generally omitted, and the smoke makes a last return beneath the bottom of the boiler. Figs. 17 and 18 are the transverse and longitudinal sections of a tubular boiler, built in 1837 by R.L. Stevens for the steamboat Independence. [Illustration: Fig. 16.] [Illustration: Fig. 17.] [Illustration: Fig. 18.] Fig. 19 is a longitudinal section of a common wood-burning locomotive. [Illustration: Fig. 19.] THE ENGINE. 93. _Q._--The steam passes from the boiler through, the steam pipe into the cylinder of the engine? _A._--And presses up and down the piston alternately, being admitted alternately above and below the piston by suitable valves provided for that purpose. 94. _Q._--This reciprocating motion is all that is required in a pumping engine? _A._--The prevailing form of the pumping engine consists of a great beam vibrating on a centre like the beam of a pair of scales, and the cylinder is in connection with one end of the beam and the pump stands at the other end. The pump end of the beam is usually loaded, so as to cause it to preponderate when the engine is at rest; and the whole effort of the steam is employed in overcoming this preponderance until a stroke is performed, when, the steam being shut off, the heavy end of the beam again falls and the operation is repeated. 95. _Q._--in the double-acting engine the piston is pushed by the steam both ways, whereas in the single-acting engine it is only pushed one way? _A._--The structure and action of a double-acting land engine of the kind introduced by Mr. Watt, will be understood by a reference to the annexed figure (fig. 20), where an engine of this kind is shown in section. A is the cylinder in which a movable piston, T, is forced alternately up and down by the alternate admission, to each side, of the steam from the boiler. The piston, by means of a rod called the piston rod, gives motion to the beam V W, which by means of a heavy bar, P, called the connecting rod, moves the crank, Q, and with it the fly wheel, X, from which the machinery to be driven derives its motion. 96. _Q._--Where does the steam enter from the boiler? [Illustration: Fig. 20.] _A._--At the steam pipe, B. The throttle valve in that pipe is an elliptical plate of metal swivelling on a spindle passing through its edge from side to side, and by turning which more or less the opening through the pipe will be more or less closed. The extent to which this valve is opened or closed is determined by the governor, D, the balls of which, as they collapse or expand, move up or down a collar on the governor spindle, which motion is communicated to the throttle valve by suitable rods and bell-cranks. The governor, it will be seen, consists substantially of two heavy balls attached to arms fixed upon an upright shaft, which is kept in revolution by means of a cord driven by a pulley on the fly wheel shaft. The velocity with which the balls of the governor revolve being proportional to that of the fly wheel, it will follow, that if by reason of too rapid a supply of steam, an undue speed be given to the fly wheel, and therefore to the balls, a divergence of the balls will take place to an extent corresponding to the excess of velocity, and this movement being communicated to the throttle valve it will be partly closed (see fig. 1), the supply of steam to the engine will be diminished, and the velocity of its motion will be reduced. If, on the other hand, the motion of the engine is slower than is requisite, owing to a deficient supply of steam through B, then the balls, not being sufficiently affected by centrifugal force, will fall towards the vertical spindle, and the throttle valve, C, will be more fully opened, whereby a more ample supply of steam will be admitted to the cylinder, and the speed of the engine will be increased to the requisite extent. 97. _Q._--The piston must be made to fit the cylinder accurately so as to prevent the passage of steam? _A._--The piston is accurately fitted to the cylinder, and made to move in it steam tight by a packing of hemp driven tightly into a groove or recess round the edge of the piston, and which is squeezed down by an iron ring held by screws. The piston divides the cylinder into two compartments, between which there is no communication by which steam or any other elastic fluid can pass. A casing set beside the cylinder contains the valves, by means of which the steam which impels the piston is admitted and withdrawn, as the piston commences its motion in each direction. The upper steam box B, is divided into three compartments by two valves. Above the upper steam valve V, is a compartment communicating with the steam pipe B. Below the lower valve E is another compartment communicating with a pipe called the eduction pipe, which leads downwards from the cylinder to the condenser, in which vessel the steam is condensed by a jet of cold water. By the valve V, a communication may be opened or closed between the boiler and the top of the cylinder, so as to permit or prevent a supply of steam from the one to pass to the other. By the valve E a communication may be open or closed between the top of the cylinder and the condenser, so that the steam in the top compartment of the cylinder may either be permitted to escape into the condenser, or may be confined to the cylinder. The continuation of the steam pipe leads to the lower steam box B', which, like the upper, is divided into three compartments by two valves V' and E', and the action of the lower valves is in all respects the same as that of the upper. 98. _Q._--Are all these valves connected together so that they act simultaneously? _A._--The four valves V, E, V', E' are connected by rods to a single handle H, which handle is moved alternately up and down by means of pins or tappets, placed on the rod which works the air pump. When the handle H is pressed down, the levers in connexion with it open the upper exhausting valve E, and the lower steam valve V', and close the upper steam valve V and the lower exhausting valve E'. On the other hand, when the handle H is pressed up it opens the upper steam valve V and the lower exhausting valve E', and at the same time closes the upper exhausting valve E, and the lower steam valve V'. 99. _Q._--Where is the condenser situated? _A._--The condenser K is immerged in a cistern of cold water. At its side there is a tube I, for the admission of water to condense the steam, and which is governed by a cock, by opening which to any required extent, a jet of cold water may be made to play in the condenser. From the bottom of the condenser a short pipe leads to the air pump J, and in this pipe there is a flap valve, called the foot valve, opening towards the air pump. The air pump is a pump set in the same cistern of cold water that holds the condenser, and it is fitted with a piston or bucket worked by the rod L, attached to the great beam, and fitted with a valve opening upwards in the manner of a common sucking pump. The upper part of the air pump communicates with a small cistern S, called the hot well, through a valve opening outwards and called the delivery valve. A pump M, called the hot water pump, lifts hot water out of the hot well to feed the boiler, and another pump N lifts cold water from a well or other source of supply, to maintain the supply of water to the cold water cistern, in which the condenser and air pump are placed. 100. Q.--Will you explain now the manner in which the engine acts? A.--The piston being supposed to be at the top of the cylinder, the handle H will be raised by the lower pin or tappet on the air pump rod, and the valves V and E' will be opened, and at the same time the other pair of valves V' and E will be closed. Steam will therefore be admitted above the piston and the steam or air which had previously filled the cylinder below the piston will be drawn off to the condenser. It will there encounter the jet of cold water, which is kept constantly playing there by keeping the cock I sufficiently open. It will thus be immediately condensed or reduced to water, and the cylinder below the piston will have a vacuum in it. The steam therefore admitted from the steam pipe through the open valve V to the top of the cylinder, not being resisted by pressure below, will press the piston to the bottom of the cylinder. As it approaches that position, the handle H will be struck down by the upper pin or tappet on the air pump rod, and the valves V and E', previously open, will be closed, while the valves V' and E, previously closed, will be opened. The steam which has just pressed down the piston, and which now fills the cylinder above the piston, will then flow off, through the open valve E, to the condenser, where it will be immediately condensed by the jet of cold water; and steam from the boiler, admitted through the open valve V', will fill the cylinder below the piston, and press the piston upwards. When the piston has reached the top of the cylinder, the lower pin on the air pump rod will have struck the handle upwards, and will thereby have closed the valves V' and E, and opened the valves V and E'. The piston will then be in the same situation as in the commencement, and will again descend, and so will continue to be driven up and down by the steam. 101. Q.--But what becomes of the cold water which is let into the condenser to condense the steam? A.--It is pumped out by the air pump in the shape of hot water, its temperature having been raised considerably by the admixture of the steam in it. When the air pump piston ascends it leaves behind it a vacuum; and the foot valve being relieved from all pressure, the weight of the water in the condenser forces it open, and the warm water flows from the condenser into the lower part of the air pump, from which its return to the condenser is prevented by the intervening valve. When the air pump piston descends, its pressure on the liquid under it will force open the valve in it, through which the hot water will ascend; and when the bucket descends to the bottom of the pump barrel, the warm water which was below it will all have passed above it, and cannot return. When the bucket next ascends, the water above it, not being able to return through the bucket valve, will be forced into the hot well through the delivery valve S. The hot water pump M, pumps a small quantity of this hot water into the boiler, to compensate for the abstraction of the water that has passed off in the form of steam. The residue of the hot water runs to waste. 102. _Q._--By what expedient is the piston rod enabled to pass through the cylinder cover without leaking steam out of the cylinder or air into it? _A._--The hole in the cylinder lid, through which the piston rod passes, is furnished with a recess called a stuffing box, into which a stuffing or packing of plaited hemp is forced, which, pressing on the one side against the interior of the stuffing box, and on the other side against the piston rod, which is smooth and polished, prevents any leakage in this situation. The packing of this stuffing box is forced down by a ring of metal tightened by screws. This ring, which accurately fits the piston rod, has a projecting flange, through which bolts pass for tightening the ring down upon the packing; and a similar expedient is employed in nearly every case in which packing is employed. 103. _Q._--In what way is the piston rod connected to the great beam? _A._--The piston rod is connected to the great beam by means of two links, one at each side of the beam shown at _f g_, (fig. 21.) These links are usually made of the same length as the crank, and their purpose is to enable the end of the great beam to move in the arc of a circle while the piston rod maintains the vertical position. The point of junction, therefore, of the links and the piston rod is of the form of a knuckle or bend at some parts of the stroke. 104. _Q._--But what compels the top of the piston rod to maintain the vertical position? _A._--Some engines have guide rods set on each side of the piston rod, and eyes on the top of the piston rod engage these guide rods, and maintain the piston rod in a vertical position in every part of the stroke. More commonly, however, the desired end is attained by means of a contrivance called the parallel motion. 105. _Q._--What is the parallel motion? _A._--The parallel motion is an arrangement of jointed rods, so connected together that the divergence from the vertical line at any point in the arc described by the beam is corrected by an equal and opposite divergence due to the arc performed by the jointed rods during the stroke; and as these opposite deviations mutually correct one another, the result is that the piston rod moves in a vertical direction. 106. _Q._--Will you explain the action more in detail? _A._--The pin, fig 21, which passes through the end of the beam at _f_ has a link _f g_ hung on each side of the beam, and a short cross bar, called a cross head, extends from the bottom of one of these links to the bottom of the other, which cross head is perforated with a hole in the middle for the reception of the piston rod. There are similar links _b d_ at the point of the main beam, where the air pump rod is attached. There are two rods _d g_ connecting the links _b d_ with the links _f g_, and these rods, as they always continue parallel to the main beam throughout the stroke, are called _parallel bars_. Attached to the end of these two rods at _d_ are two other rods _c d_, of which the ends at _c_ are attached to stationary pins, while the ends at _d_ follow the motion of the lower ends of the links _b d_. These rods are called the _radius bars_. Now it is obvious that the arc described by the point _d_, with _c_ as a centre, is opposite to the arc described by the point _g_ with _d_ as a centre. The rod _d g_ is, therefore, drawn back horizontally by the arc described at _d_ to an extent equal to the versed sine of the arc described at _g_, or, in other words, the line described by the point _g_ becomes a straight line instead of a curve. [Illustration: Fig. 21.] 107. _Q._--Does the air pump rod move vertically as well as the piston rod? _A._--It does. The air pump rod is suspended from a cross head, passing from the centre of one of the links _b d_ to the centre of the other link, on the opposite side of the beam. Now, as the distance from the central axis of the great beam to the point _b_ is equal to the length of the rod _c d_, it will follow that the upper end of the link will follow one arc, and the lower end an equal and opposite arc. A point in the centre of the link, therefore, where these opposite motions meet, will follow no arc at all, but will move up and down vertically in a straight line. 108. _Q._--The use of the crank is to obtain a circular motion from a reciprocating motion? _A._--That is the object of it, and it accomplishes its object in a very perfect manner, as it gradually arrests the velocity of the piston towards the end of the stroke, and thus obviates what would otherwise be an injurious shock upon the machine. When the crank approaches the lowest part of its throw, and at the same time the piston is approaching the top of the cylinder, the motion of the crank becomes nearly horizontal, or, in other words, the piston is only advanced through a very short distance, for any given distance measured on the circle described by the crank pin. Since, then, the velocity of rotation of the crank is nearly uniform, it will follow that the piston will move very slowly as it approaches the end of the stroke; and the piston is brought to a state of rest by this gradually retarded motion, both at the top and the bottom of the stroke. 109. _Q._--What causes the crank to revolve at a uniform velocity? _A._--The momentum of the machinery moved by the piston, but more especially of the fly wheel, which by its operation redresses the unequal pressures communicated by the crank, and compels the crank shaft to revolve at a nearly uniform velocity. Everyone knows that a heavy wheel if put into rapid rotation cannot be immediately stopped. At the beginning and end of the stroke when the crank is vertical, no force of torsion can be exerted on the crank shaft by the crank, but this force is at its maximum when the crank is horizontal. From the vertical point, where this force is nothing, to the horizontal point, where it is at its maximum, the force of torsion exerted on the crank shaft is constantly varying; and the fly wheel by its momentum redresses these irregularities, and carries the crank through that "dead point," as it is termed, where the piston cannot impart any rotative force. 110. _Q._--Are the configuration and structure of the steam engine, as it left the hand of Watt, materially different from those of modern engines? _A._--There is not much difference. In modern rotative land engines, the valves for admitting the steam to the cylinder or condenser, instead of being clack or pot-lid valves moved by tappets on the air pump rod, are usually sluice or sliding valves, moved by an eccentric wheel on the crank shaft. Sometimes the beam is discarded altogether, and malleable iron is more largely used in the construction of engines instead of the cast iron, which formerly so largely prevailed. But upon the whole the steam engine of the present day is substantially the engine of Watt; and he who perfectly understands the operation of Watt's engine, will have no difficulty in understanding the operation of any of the numerous varieties of engines since introduced. THE MARINE ENGINE. 111. _Q._--Will you describe the principal features of the kind of steam engine employed for the propulsion of vessels? _A._--Marine engines are of two kinds,--paddle engines and screw engines. In the one case the propelling instrument is paddle wheels kept in rotation at each side of the ship: in the other case, the propelling instrument is a screw, consisting of two or more twisted vanes, revolving beneath the water at the stern. Of each class of engines there are many distinct varieties. 112. _Q._--What are the principal varieties of the paddle engine? [Illustration: Fig. 22.] [Illustration: Fig. 23.] _A._--There is the side lever engine (fig. 26), and the oscillating engine (fig. 27), besides numerous other forms of engine which are less known or employed, such as the trunk (fig. 22), double cylinder (fig. 23), annular, Gorgon (fig. 24), steeple (fig. 25), and many others. The side lever engine, however, and the oscillating engine, are the only kinds of paddle engines which have been received with wide or general favor. [Illustration: Fig. 24.] 113. _Q._--Will you explain the main distinctive features of the side lever engine? _A._--In all paddle vessels, whatever be their subordinate characteristics, a great shaft of wrought iron, s, turned round by the engine, has to be carried from side to side of the vessel, on which shaft are fixed the paddle wheels. The paddle wheels may either be formed with fixed float boards for engaging the water, like the boards of a common undershot water wheel, or they may be formed with _feathering_ float boards as they are termed, which is float boards movable on a centre, and so governed by appropriate mechanism that they enter and leave the water in a nearly vertical position. The common fixed or radial floats, however, are the kind most widely employed, and they are attached to the arms of two or more rings of malleable iron which are fixed by appropriate centres on the paddle shaft. It is usual in steam vessels to employ two engines, the cranks of which are set at right angles with one another. When the paddle wheels are turned by the engines, the float boards engaging the water cause a forward thrust to be imparted to the shaft, which propels forward the vessel on the same principle that a boat is propelled by the action of oars. [Illustration: Fig. 25.] 114. _Q._--These remarks apply to all paddle vessels? _A._--They do. With respect to the side lever engine, it may be described to be such a modification of the land beam engine already described, as will enable it to be got below the deck of a vessel. With this view, instead of a single beam being placed overhead, two beams are used, one of which is set on each side of the engine as low down as possible. The cross head which engages the piston rod is made somewhat longer than the diameter of the cylinder, and two great links or rods proceed one from each end of the cross head to one of the side levers or beams. A similar cross bar at the other end of the beams serves to connect them together and to the connecting rod which, proceeding from thence upwards, engages the crank, and thereby turns round the paddle wheels. 115. _Q._--Will you further illustrate this general description by an example? [Illustration: Fig. 26.] _Q._--Fig. 26 is a side elevation of a side lever engine; x x represent the beams or keelsons to which the engines are attached, and on which the boilers rest. The engines are tied down by strong bolts passing through the bottom of the vessel, but the boiler keeps its position by its weight alone. The condenser and air pump are worked off the side levers by means of side rods and a cross head. A strong gudgeon, called the _main centre_, passes through the condenser at K, the projecting ends of which serve to support the side levers or beams. L is the piston rod, which, by means of the cross head and side rods, is connected to the side levers or beams, one of which is shown at H H. The line M represents the connecting rod, to which motion is imparted by the beams, through the medium of the cross tail extending between the beams, and which by means of the crank turns the paddle shaft S. The eccentric which works the slide valve is placed upon the paddle shaft. It consists of a disc of metal encircled by a hoop, to which a rod is attached, and the disc is perforated with a hole for the shaft, not in the centre, but near one edge. When, therefore, the shaft revolves, carrying the eccentric with it, the rod attached to the encircling hoop receives a reciprocating motion, just as it would do if attached to a crank in the shaft. 116. _Q._--Will you describe the mode of starting the engine? _A._--I may first mention that when the engine is at rest, the connection between the eccentric and the slide valve is broken, by lifting the end of the eccentric rod out of a notch which engages a pin on the valve shaft, and the valve is at such times free to be moved by hand by a bar of iron, applied to a proper part of the valve gear for that purpose. This being so, the engineer, when he wishes to start the engine, first opens a small valve called the _blow through valve_, which permits steam from the boiler to enter the engine both above and below the piston, and also to fill the condenser and air pump. This steam expels the air from the interior of the engine, and also any water which may have accumulated there; and when this has been done, the blow through valve is shut, and a vacuum very soon forms within the engine, by the condensation of the steam. If now the slide valve be moved by hand, the steam from the boiler will be admitted on one side of the piston, while there is a vacuum on the other side, and the piston will, therefore, be moved in the desired direction. When the piston reaches the end of the stroke, the valve has to be moved in the reverse direction, when the piston will return, and after being moved thus by hand, once or twice, the connection of the valve with the eccentric is to be restored by allowing the notch on the end of the eccentric rod to engage the pin on the valve lever, when the valve will be thereafter moved by the engine in the proper manner. It will, of course, be necessary, when the engine begins to move, to open the injection cock a little, to enable water to enter for the condensation of the steam. In the most recent marine engines, a somewhat different mechanism from this is used for giving motion to the valves, but that mechanism will be afterwards described. 117. _Q._--Are all marine engines condensing engines? _A._--Nearly all of them are so; but recently a number of gunboats have been constructed, with high pressure engines. In general, however, marine engines are low pressure or condensing engines. 118. _Q._--Will you now describe the chief features of the oscillating paddle marine engine? _A._--In the oscillating paddle marine engine, the arrangement of the paddle shaft and paddle wheels is the same as in the case already described, but the whole of the side levers, side rods, cross head, cross tail, and connecting rod are discarded. The cylinder is set immediately under the crank; the top of the piston rod is connected immediately to the crank pin; and, to enable the piston rod to accommodate itself to the movement of the crank, the cylinder is so constructed as to be susceptible of vibrating or oscillating upon two external axes or trunnions. These trunnions are generally placed about half way up on the sides of the cylinder; and through one of them steam is received from the boiler, while through the other the steam escapes to the condenser. The air pump is usually worked by means of a crank in the shaft, which crank moves the air pump bucket up and down as the shaft revolves. 119. _Q._--Will you give an example of a paddle oscillating engine? _A._--I will take as an example the oscillating engines constructed by Messrs. Ravenhill & Salked, for the Holyhead Packets. Fig. 27 is a longitudinal section of this vessel, showing an engine and boiler; and fig. 28 is a transverse section of one of the engines, showing also one of the wheels. There are two cylinders in this vessel, and one air pump, which lies in an inclined position, and is worked by a crank in the shaft which stretches between the cylinders, and which is called the _intermediate shaft_. A A, is one of the cylinders, B B the piston rod, and C C the crank. D is the crank in the intermediate shaft, which works the air pump E. There are double eccentrics fixed on the shaft, whereby the movement of the slide valves is regulated. The purpose of the double eccentrics is to enable an improved arrangement of valve gear to be employed, which is denominated the _link motion_, and which will be described hereafter. I I are the steam pipes leading to the steam trunnions K K, on which, and on the eduction trunnions connected with the pipe M, the cylinders oscillate. 120. _Q._--By what species of mechanism are the positions of the paddle floats of feathering wheels governed? _A._--The floats are supported by spurs projecting from the rim of the wheel, and they may be moved upon the points of the spurs, to which they are attached by pins, by means of short levers proceeding from the backs of the floats, and connected to rods which proceed towards the centre of the wheel. The centre, however, to which these rods proceed is not concentric with the wheel, and the rods, therefore, are moved in and out as the wheel revolves, and impart a corresponding motion to the floats. In some feathering wheels the proper motion is given to the rods by means of an eccentric on the ship's side. The action of paddle wheels, whether radial or feathering, will be more fully described in the chapter on Steam Navigation. SCREW ENGINES. 121. _Q._--What are the principal varieties of screw engines? [Illustration: Fig. 27.] [Illustration: Fig. 28.] _A._--The engines employed for the propulsion of screw vessels are divided into two great classes,--geared engines and direct acting engines; and each of these classes again has many varieties. In screw vessels, the shaft on which the screw is set requires to revolve at a much greater velocity than is required in the case of the paddle shaft of a paddle vessel; and in geared engines this necessary velocity of rotation is obtained by the intervention of toothed wheels,--the engines themselves moving with the usual velocity of paddle engines; whereas in direct acting engines the required velocity of rotation is obtained by accelerating the speed of the engines, and which are connected immediately to the screw shaft. 122. _Q._--Will you describe some of the principal varieties of geared engines? _A._--A good many of the geared engines for screw vessels are made in the same manner as land engines, with a beam overhead, which by means of a connecting rod extending downwards, gives motion to the crank shaft, on which are set the cog wheels which give motion to pinions on the screw shaft,--the teeth of the wheels being generally of wood and the teeth of the pinions of iron. There are usually several wheels on the crank shaft and several pinions on the screw shaft; but the teeth of each do not run in the same line, but are set a little in advance of one another, so as to divide the thickness of the tooth into as many parts as there are independent wheels or pinions. By this arrangement the wheels work more smoothly than they would otherwise do. 123. _Q._--What other forms are there of geared screw engines? _A._--In some cases the cylinders lie on their sides in the manner of the cylinders of a locomotive engine. In other cases vertical trunk engines are employed; and in other cases vertical oscillating engines. 124. _Q._--Will you give an example of a geared vertical oscillating engine? _A._--The engines of a geared oscillating engine are similar to the paddle wheel engines (figs. 27 and 28), but the engines are placed lengthways of the ship, and instead of a paddle wheel on the main shaft, there is a geared wheel which connects with a pinion on the screw shaft. The engines of the Great Britain are made off the same patterns as the paddle engines constructed by Messrs. John Penn & Son, for H.M.S. Sphinx. The diameter of each cylinder is 82-1/2 inches, the length of travel or stroke of the piston is 6 feet, and the nominal power is 500 horses. The Great Britain is of 3,500 tons burden, and her displacement at 16 feet draught of water is 2,970 tons. The diameter of the screw is 15-1/2 feet, length of screw in the line of the shaft, 3 feet 2 inches, and the pitch of the screw, 19 feet. 125. _Q._--What do you mean by the pitch of the screw? _A._--A screw propeller may be supposed to be a short piece cut off a screw of large diameter like a spiral stair, and the pitch of a spiral stair is the vertical height from any given step to the step immediately overhead. 126. _Q._--What is the usual number of arms? _A._--Generally a screw has two arms, but sometimes it has three or more. The Great Britain had three arms or twisted blades resembling the vanes of a windmill. The multiple of the gearing in the Great Britain is 3 to 1, and there are 17-1/2 square feet of heating surface in the boiler for each nominal horse power. The crank shaft being put into motion by the engine, carries round with it the great cog wheel, or aggregation of cog wheels, affixed to its extremity; and these wheels acting on suitable pinions on the screw shaft, cause the screw to make three revolutions for every revolution made by the engine. 127. _Q._--What are the principal varieties of direct acting screw engines? _A._--In some cases four engines have been employed instead of two, and the cylinders have been laid on their sides on each side of the screw shaft. This multiplication of engines, however, introduces needless complication, and is now but little used. In other cases two inverted cylinders are set above the screw shaft on appropriate framing; and connecting rods attached to the ends of the piston rods turn round cranks in the screw shaft. 128. _Q._--What is the kind of direct acting screw engine employed by Messrs. Penn. _A._--It is a horizontal trunk engine. In this engine a round pipe called a trunk penetrates the piston, to which it is fixed, being in fact cast in one piece with it; and the trunk also penetrates the top and bottom of the cylinder, through which it moves, and is made tight therein by means of stuffing boxes. The connecting rod is attached at one end to a pin fixed in the middle of the trunk, while the other end engages the crank in the usual manner. The air pump is set within the condenser, and is wrought by a rod which is fixed to the piston and derives its motion therefrom. The air pump is of that species which is called double-acting. The piston or bucket is formed without valves in it, but an inlet and outlet valve is fixed to each end of the pump, through the one of which the water is drawn into the pump barrel, and through the other of which it is expelled into the hot well. THE LOCOMOTIVE ENGINE. 129. _Q._--Will you describe the more important features of the locomotive engine? _A._--The locomotive employed to draw carriages upon railways, consists of a cylindrical boiler filled with brass tubes, through which the hot air passes on its progress from the furnace to the chimney, and attached to the boiler are two horizontal cylinders fitted with pistons, valves, connecting rods, and other necessary apparatus to enable the power exerted by the pistons to turn round the cranked axle to which the driving wheels are attached. There are, therefore, two independent engines entering into the composition of a locomotive, the cranks of which are set at right angles with one another, so that when one crank is at its dead point, the other crank is in a position to act with its maximum efficacy. The driving wheels, which are fixed on the crank shaft and turn round with it, propel the locomotive forward on the rails by the mere adhesion of friction, and this is found sufficient not merely to move the locomotive, but to draw a long train of carriages behind it. 130. _Q._--Are locomotive engines condensing or high pressure engines. _A._--They are invariably high pressure engines, and it would be impossible or at least highly inconvenient, to carry the water necessary for the purpose of condensation. The steam, therefore, after it has urged the piston to the end of the stroke, escapes into the atmosphere. In locomotive engines the waste steam is always discharged into the chimney through a vertical pipe, and by its rapid passage it greatly increases the intensity of the draught in the chimney, whereby a smaller fire grate suffices for the combustion of the fuel, and the evaporative power of the boiler is much increased. 131. _Q._--Can you give an example of a good locomotive engine of the usual form? _A._--To do this I will take the example of one of Hawthorn's locomotive engines with six wheels represented in fig. 29; not one of the most modern construction now in use, nor yet one of the most antiquated. M is the cylinder, R the connecting rod, C C the eccentrics by which the slide valve is moved; J J is the steam pipe by which the steam is conducted from the steam dome of the boiler to the cylinder. Near the smoke stack end of this pipe is a valve K or regulator moved by a handle _p_ at the front of the boiler, and of which the purpose is to regulate the admission of the steam to the cylinder; _f_ is a safety valve kept closed by springs; N is the eduction pipe, or, as it is commonly termed in locomotives, the _blast pipe_, by which the steam, escaping from the cylinder after the stroke has been performed, is projected up the chimney H. The water in the boiler of course covers the tubes and also the top of the furnace or fire box. It will be understood that there are two engines in each locomotive, though, from the figure being given in section, only one engine can be shown. The cylinders of this engine are each 14 inches diameter; the length of the stroke of the piston is 21 inches. There are two sets of driving wheels, 5 feet diameter, with outside connections. [Illustration: Fig. 29.] 132. _Q._--What is the tender of a locomotive? _A._--It is a carriage attached to the locomotive, of which the purpose is to contain coke for feeding the furnace, and water for replenishing the boiler. 133. _Q._--Can you give examples of modern locomotives? [Illustration: Fig. 30.] [Illustration: Fig. 31.] _A._--The most recent locomotives resemble in their material features the locomotive represented in fig. 29. I can, however, give examples of some of the most powerful engines of recent construction. Fig. 30 represents Gooch's express engine, adapted for the wide gauge of the Great Western Railway; and fig. 31 represents Crampton's express engine, adapted for the ordinary or narrow gauge railways. The cylinders of Gooch's engine are each 18 inches diameter, and 24 inches stroke; the driving wheels are 8 feet in diameter; the fire grate contains 21 square feet of area; and the heating surface of the fire box is 153 square feet. There are in all 305 tubes in the boiler, each of 2 inches diameter, giving a heating surface in the tubes of 1799 square feet. The total heating surface, therefore, is 1952 square feet. Mr. Gooch states that an engine of this class will evaporate from 300 to 360 cubic feet of water in the hour, and will convey a load of 236 tons at a speed of 40 miles an hour, or a load of 181 tons at a speed of 60 miles an hour. The weight of this engine empty is 31 tons; of the tender 8-1/2 tons; and the total weight of the engine when loaded is 50 tons. In one of Crampton's locomotives, the Liverpool, with one set more of carrying wheels than the fig., the cylinders are of 24 inches diameter and 18 inches stroke; the driving wheels are 8 feet in diameter; the fire grate contains 21-1/2 square feet of area; and the heating surface of the fire box is 154 square feet. There are in all 300 tubes in the boiler of 2-3/16 inches external diameter, giving a surface in the tubes of 2136 square feet, and a total heating surface of 2290 square feet. The weight of this engine is stated to be 35 tons when ready to proceed on a journey. Both engines were displayed at the Great Exhibition in 1851, as examples of the most powerful locomotive engines then made. The weight of such engines is very injurious to the railway; bending, crushing, and disturbing the rails, and trying very severely the whole of the railway works. No doubt the weight may be distributed upon a greater number of wheels, but if the weight resting on the driving wheels be much reduced, they will not have sufficient bite upon the rails to propel the train without slipping. This, however, is only one of the evils which the demand for high rates of speed has produced. The width of the railway, or, as it is termed, the _gauge_ of the rails, being in most of the railways in this kingdom limited to 4 feet 8-1/2 inches, a corresponding limitation is imposed on the diameter of the boiler; which in its turn restricts the number of the tubes which can be employed. As, however, the attainment of a high rate of speed requires much power, and consequently much heating surface in the boiler, and as the number of tubes cannot be increased without reducing their diameter, it has become necessary, in the case of powerful engines, to employ tubes of a small diameter, and of a great length, to obtain the necessary quantity of heating surface; and such tubes require a very strong draught in the chimney to make them effective. With a draught of the usual intensity the whole of the heat will be absorbed in the portion of the tube nearest the fire box, leaving that portion nearest the smoke box nothing to do but to transmit the smoke; and with long tubes of small diameter, therefore, a very strong draught is indispensable. To obtain such a draught in locomotives, it is necessary to contract the mouth of the blast pipe, whereby the waste steam will be projected into the chimney with greater force; but this contraction involves an increase of the pressure on the eduction side of the piston, and consequently causes a diminution in the power of the engine. Locomotives with small and long tubes, therefore, will require more coke to do the same work than locomotives in which larger and shorter tubes may be employed. CHAPTER II. HEAT, COMBUSTION, AND STEAM. HEAT. 134. _Q._--What is meant by latent heat? _A._--By latent heat is meant the heat existing in bodies which is not discoverable by the touch or by the thermometer, but which manifests its existence by producing a change of state. Heat is absorbed in the liquefaction of ice, and in the vaporization of water, yet the temperature does not rise during either process, and the heat absorbed is therefore said to become latent. The term is somewhat objectionable, as the effect proper to the absorption of heat has in each case been made visible; and it would be as reasonable to call hot water latent steam. Latent heat, in the present acceptation of the term, means sensible liquefaction or vaporization; but to produce these changes heat is as necessary as to produce the expansion of mercury in a thermometer tube, which is taken as the measure of temperature; and it is hard to see on what ground heat can be said to be latent when its presence is made manifest by changes which only heat can effect. It is the _temperature_ only that is latent, and latent temperature means sensible vaporization or liquefaction. 135. _Q._--But when you talk of the latent heat of steam, what do you mean to express? _A._--I mean to express the heat consumed in accomplishing the vaporization compared with that necessary for producing the temperature. The latent heat of steam is usually reckoned at about 1000 degrees, by which it is meant that there is as much heat in any given weight of steam as would raise its constituent water 1000 degrees if the expansion of the water could be prevented, or as would raise 1000 times that quantity of water one degree. The boiling point of water, being 212 degrees, is 180 degrees above the freezing point of water--the freezing point being 32 degrees; so that it requires 1180 times as much heat to raise 1 lb. of water into steam, as to raise 1180 lbs. of water one degree; or it requires about as much heat to raise a pound of boiling water into steam, as would raise 5-1/2 lbs. of water from the freezing to the boiling point; 5-1/2 multiplied by 180 being 990 or 1000 nearly. 136. _Q._--When it is stated that the latent heat of steam is 1000 degrees, it is only meant that this is a rough approximation to the truth? _A._--Precisely so. The latent heat, in point of fact, is not uniform at all temperatures, neither is the total amount of heat the same at all temperatures. M. Regnault has shown, by a very elaborate series of experiments on steam, which he has lately concluded, that the total heat in steam increases somewhat with the pressure, and that the latent heat diminishes somewhat with the pressure. This will be made obvious by the following numbers: Pressure. Temperature. Total Heat. Latent Heat. 15 lbs. 213.1° 1178.9° 965.8° 50 281.0 1199.6 918.6 100 327.8 1213.9 886.1 If, then, steam of 100 lbs. be expanded down to steam of 15 lbs., it will have 35 degrees of heat over that which is required for the maintenance of the vaporous state, or, in other words, it will be surcharged with heat. 137. _Q._--What do you understand by specific heat? _A._--By specific heat, I understand the relative quantities of heat in bodies at the same temperature, just as by specific gravity I understand the relative quantities of matter in bodies of the same bulk. Equal weights of quicksilver and water at the same temperature do not contain the same quantities of heat, any more than equal bulks of those liquids contain the same quantity of matter. The absolute quantity of heat in any body is not known; but the relative heat of bodies at the same temperature, or in other words their specific heats, have been ascertained and arranged in tables,-- the specific heat of water being taken as unity. 138. _Q._--In what way does the specific heat of a body enable the quantity of heat in it to be determined? _A._--If any body has only half the specific heat of water, then a pound of that body will, at any given temperature, have only half the heat in it that is in a pound of water at the same temperature. The specific heat of air is .2669, that of water being 1; or it is 3.75 times less than that of water. An amount of heat, therefore, which would raise a pound of water 1 degree would raise a pound of air 3.75 degrees. COMBUSTION. 139. _Q._--What is the nature of combustion? _A._--Combustion is nothing more than an energetic chemical combination, or, in other words, it is the mutual neutralization of opposing electricities. When coal is brought to a high temperature it acquires a strong affinity for oxygen, and combination with oxygen will produce more than sufficient heat to maintain the original temperature; so that part of the heat is rendered applicable to other purposes. 140. _Q._--Does air consist of oxygen? _A._--Air consists of oxygen and nitrogen mixed together in the proportion of 3.29 lbs. of nitrogen to 1 lb. of oxygen. Every pound of coal requires about 2.66 lbs. of oxygen for its saturation, and therefore for every pound of coal burned, 8.75 pounds of nitrogen must pass through the fire, supposing all the oxygen to enter into combination. In practice, however, this perfection of combination does not exist; from one-third to one-half of the oxygen will pass through the fire without entering into combination at all; so that from 16 to 18 lbs. of air are required for every pound of coal burned. 18 lbs. of air are about 240 cubic feet, which may be taken as the quantity of air required for the combustion of a pound of coal in practice. 141. _Q._--What are the constituents of coal? _A._--The chief constituent of coal is carbon or pure charcoal, which is associated in various proportions with volatile and earthy matters. English coal contains 80 to 90 per cent. of carbon, and from 8 to 18 per cent. of volatile and earthy matters, but sometimes more than this. The volatile matters are hydrogen, nitrogen, oxygen, and sulphur. 142. _Q._--What is the difference between anthracite and bituminous coal? _A._--Anthracite consists almost entirely of carbon, having 91 per cent. of carbon, with about 7 per cent. of volatile matter and 2 per cent. of ashes. Newcastle coal contains about 83 per cent. of carbon, 14 per cent. of volatile matter, and 3 per cent. of ashes. 143. _Q._--Will you recapitulate the steps by which you determine the quantity of air required for the combustion of coal? _A._--Looking to the quantity of oxygen required to unite chemically with the various constituents of the coal, we find for example that in 100 lbs. of anthracite coal, consisting of 91.44 lbs. of carbon, and 3.46 lbs. of hydrogen, we shall for the 91.44 lbs. of carbon require 243.84 lbs. of oxygen--since to saturate a pound of carbon by the formation of carbonic acid, requires 2-2/3 lbs. of oxygen. To saturate a pound of hydrogen in the formation of water, requires 8 lbs. of oxygen; hence 3.46 Fibs. of hydrogen will take 27.68 lbs. of oxygen for its saturation. If then we add 243.84 lbs. to 27.68 lbs. we have 271.52 lbs. of oxygen required for the combustion of 100 lbs. of coal. A given weight of air contains nearly 23.32 per cent of oxygen; hence to obtain 271.52 lbs. of oxygen, we must have about four times that quantity of atmospheric air, or more accurately, 1164 lbs. of air for the combustion of 100 lbs. of coal. A cubic foot of air at ordinary temperature weighs about .075 lbs.; so that 100 lbs. of coal require 15,524 cubic feet of air, or 1 lb. of coal requires about 155 cubic feet of air, supposing every atom of the oxygen to enter into combination. If, then, from one-third to one-half of the air passes unconsumed through the fire, an allowance of 240 cubic feet of air for each pound of coal will be a small enough allowance to answer the requirements of practice, and in some cases as much as 300 cubic feet will be required,--the difference depending mainly on the peculiar configuration of the furnace. 144. _Q._--Can you state the evaporative efficacy of a pound of coal? _A._--The evaporative efficacy of a pound of carbon has been found experimentally to be equivalent to that necessary to raise 14,000 lbs. of water through 1 degree, or 14 lbs. of water through 1000 degrees, supposing the whole heat generated to be absorbed by the water. Now, if the water be raised into steam from a temperature of 60°, then 1118.9° of heat will have to be imparted to it to convert it into steam of 15 lbs. pressure per square inch. 14,000 / 1118.9 = 12.512 Lbs. will be the number of pounds of water, therefore, which a pound of carbon can raise into steam of 15 lbs. pressure from a temperature of 60°. This, however, is a considerably larger result than can be expected in practice. 145. _Q._--Then what is the result that may be expected in practice? _A._--The evaporative powers of different coals appear to be nearly proportional to the quantity of carbon in them; and bituminous coal is, therefore, less efficacious than coal consisting chiefly of pure carbon. A pound of the best Welsh or anthracite coal is capable of raising from 9-1/2 to 10 lbs. of water from 212° into steam, whereas a pound of the best Newcastle is not capable of raising more than about 8-1/2 lbs. of water from 212° into steam; and inferior coals will not raise more than 6-1/2 lbs. of water into steam. In America it has been found that 1 lb. of the best coal is equal to 2-1/2 lbs. of pine wood, or, in some cases to 3 lbs.; and a pound of pine wood will not usually evaporate more than about 2 1/2 lbs. of water, though, by careful management, it may be made to evaporate 4 1/2 lbs. Turf will generate rather more steam than wood. Coke is equal or somewhat superior to the best coal in evaporative effect. 146. _Q._--How much water will a pound of coal raise into steam in ordinary boilers? _A._--From 6 to 8 lbs. of water in the generality of land boilers of medium quality, the difference depending on the kind of boiler, the kind of coal, and other circumstances. Mr. Watt reckoned his boilers as capable of evaporating 10.08 cubic feet of water with a bushel or 84 lbs. of Newcastle coal, which is equivalent to 7 1/2 lbs. of water evaporated by 1 lb. of coal, and this may be taken as the performance of common land boilers at the present time. In some of the Cornish boilers, however, a pound of coal raises 11.8 lbs. of boiling water into steam, or a cwt. of coal evaporates about 21 cubic feet of water from 212°. 147. _Q._--What method of firing ordinary furnaces is the best? _A._--The coals should be broken up into small pieces, and sprinkled thinly and evenly over the fire a little at a time. The thickness of the stratum of coal upon the grate should depend upon the intensity of the draught: in ordinary land or marine boilers it should be thin, whereas in locomotive boilers it requires to be much thicker. If the stratum of coal be thick while the draught is sluggish, the carbonic acid resulting from combustion combines with an additional atom of carbon in passing through the fire, and is converted into carbonic oxide, which may be defined to be invisible smoke, as it carries off a portion of the fuel: if, on the contrary, the stratum of coal be thin while the draught is very rapid, an injurious refrigeration is occasioned by the excess of air passing through the furnace. The fire should always be spread of uniform thickness over the bars of the grate, and should be without any holes or uncovered places, which greatly diminish the effect of the fuel by the refrigeratory action of the stream of cold air which enters thereby. A wood fire requires to be about 6 inches thicker than a coal one, and a turf fire requires to be 3 or 4 inches thicker than a wood one, so that the furnace bars must be placed lower where wood or turf is burned, to enable the surface of the fire to be at the same distance from the bottom of the boiler. 148. _Q._--Is a slow or a rapid combustion the most beneficial? _A._--A slow combustion is found by experiment to give the best results as regards economy of fuel, and theory tells us that the largest advantage will necessarily be obtained where adequate time has been afforded for a complete combination of the constituent atoms of the combustible, and the supporter of combustion. In many of the cases, however, which occur in practice, a slow combustion is not attainable; but the tendencies of slow combustion are both to save the fuel, and to burn the smoke. 149. _Q._--Is not the combustion in the furnaces of the Cornish boilers very slow? A.--Yes, very slow; and there is in consequence very little smoke evolved. The coal used in Cornwall is Welsh coal, which evolves but little smoke, and is therefore more favorable for the success of a smokeless furnace; but in the manufacturing districts, where the coal is more bituminous, it is found that smoke may be almost wholly prevented by careful firing and by the use of a large capacity of furnace. 150. _Q._--Do you consider slow combustion to be an advisable thing to practise in steam vessels? _A._--No, I do not. When the combustion is slow, the heat in the furnaces and flues is less intense, and a larger amount of heating surface consequently becomes necessary to absorb the heat. In locomotives, where the heat of the furnace is very intense, there will be the same economy of fuel with an allowance of 5 or 6 square feet of surface to evaporate a cubic foot of water as in common marine boilers with 10 or 12. 151. _Q._--What is the method of consuming smoke pursued in the manufacturing districts? _A._--In Manchester, where some stringent regulations for the prevention of smoke have for some time been in force, it is found that the readiest way of burning the smoke is to have a very large proportion of furnace room, whereby slow combustion may be carried on. In some cases, too, a favourable result is arrived at by raising a ridge of coal across the furnace lying against the bridge, and of the same height: this ridge speedily becomes a mass of incandescent coke, which promotes the combustion of the smoke passing over it. 152. _Q._--Is the method of admitting a stream of air into the flues to burn the smoke regarded favorably? _A._--No; it is found to be productive of injury to the boiler by the violent alternations of temperature it occasions, as at some times cold air impinges on the iron of the boiler, and at other times flame,--just as there happens to be smoke or no smoke emitted by the furnace. Boilers, therefore, operating upon this principle, speedily become leaky, and are much worn by oxidation, so that, if the pressure is considerable, they are liable to explode. It is very difficult to apportion the quantity of air admitted, to the varying wants of the fire; and as air may at some times be rushing in when there is no smoke to consume, a loss of heat, and an increased consumption of fuel may be the result of the arrangement; and, indeed, such is the result in practice, though a carefully performed experiment usually demonstrates a saving in fuel of 10 or 12 per cent. 153. _Q._--What other plans have been contrived for obviating the nuisance of smoke? _A._--They are too various for enumeration, but most of them either operate upon the principle of admitting air into the flues to accomplish the combustion of the uninflammable parts of the smoke, or seek to attain the same object by passing the smoke over or through the fire or other incandescent material. Some of the plans, indeed, profess to burn the inflammable gases as they are evolved from the coal, without permitting the admixture of any of the uninflammable products of combustion which enter into the composition of smoke; but this object has been very imperfectly fulfilled in any of the contrivances yet brought under the notice of the public, and in some cases these contrivances have been found to create weightier evils than they professed to relieve. 154. _Q._--You refer, I suppose, to Mr. Charles Wye Williams' Argand furnace? _A._--I chiefly refer to it, though I also comprehend all other schemes in which there is a continuous admission of air into the flues, with an intermittent generation of smoke. 155. _Q._--This is not so in Prideaux's furnace? _A._--No; in that furnace the air is admitted only during a certain interval, or for so long, in fact, as there is smoke to be consumed. 156. _Q._--Will you explain the chief peculiarities of that furnace? _A._--The whole peculiarity is in the furnace door. The front of the door consists of metal Venetians, which are opened when the top lever is lifted up, and shut when that lever descends to its lowest position. When the furnace door is opened to replenish the fire with coals, the top lever is raised up, and with it the piston of the small cylinder attached to the side of the furnace. The Venetians are thereby opened, and a stream of air enters the furnace, which, being heated in its passage among the numerous heated plates attached to the back of the furnace door, is in a favorable condition for effecting the combustion of the inflammable parts of the smoke. The piston in the small cylinder gradually subsides and closes the Venetians; and the rate of the subsidence of the piston may obviously be regulated by a cock, or, as in this case, a small screw valve, so that the Venetians shall just close when there is no more smoke to be consumed;--the air or other fluid within the cylinder being forced out by the piston in its descent. 157. _Q._--Had Mr. Watt any method of consuming smoke? _A._--He tried various methods, but eventually fixed upon the method of coking the coal on a dead plate at the furnace door, before pushing it into the fire. That method is perfectly effectual where the combustion is so slow that the requisite time for coking is allowed, and it is much preferable to any of the methods of admitting air at the bridge or elsewhere, to accomplish the combustion of the inflammable parts of the smoke. 158. _Q._--What are the details of Mr. Watt's arrangement as now employed? _A._--The fire bars and the dead plate are both set at a considerable inclination, to facilitate the advance of the fuel into the furnace. In Boulton and Watt's 30 horse power land boiler, the dead plate and the furnace bars are both about 4 feet long, and they are set at the angle of 30 degrees with the horizon. 159. _Q._--Is the use of the dead plate universally adopted in Boulton and Watt's land boilers? _A._--It is generally adopted, but in some cases Boulton and Watt have substituted the plan of a revolving grate for consuming the smoke, and the dead plate then becomes both superfluous and inapplicable. In this contrivance the fire is replenished with coals by a self-acting mechanism. 160. _Q._--Will you explain the arrangement of the revolving grate? _A._--The fire grate is made like a round table capable of turning horizontally upon a centre; a shower of coal is precipitated upon the grate through a slit in the boiler near the furnace mouth, and the smoke evolved from the coal dropped at the front part of the fire is consumed by passing over the incandescent fuel at the back part, from which all the smoke must have been expelled in the revolution of the grate before it can have reached that position. 161. _Q._--Is a furnace with a revolving grate applicable to a steam vessel? _A._--I see nothing to prevent its application. But the arrangement of the boiler would perhaps require to be changed, and it might be preferable to combine its use with the employment of vertical tubes, for the transmission of the smoke. The introduction of any effectual automatic contrivance for feeding the fire in steam vessels, would bring about an important economy, at the same time that it would give the assurance of the work being better done. It is very difficult to fire furnaces by hand effectually at sea, especially in rough weather and in tropical climates; whereas machinery would be unaffected by any such disturbing causes, and would perform with little expense the work of many men. 162. _Q._--The introduction of some mechanical method of feeding the fire with coals would enable a double tier of furnaces to be adopted in steam vessels without inconvenience? _A._--Yes, it would have at least that tendency; and as the space available for area of grate is limited in a steam vessel by the width of the vessel, it would be a great convenience if a double tier of furnaces could be employed without a diminished effect. It appears to me, however, that the objection would still remain of the steam raised by the lower furnace being cooled and deadened by the air entering the ash-pit of the upper fire, for it would strike upon the metal of the ash-pit bottom. 163. _Q._--Have any other plans been devised for feeding the fire by self-acting means besides that of a revolving grate? _A._--Yes, many plans, but none of them, perhaps, are free from an objectionable complication. In some arrangements the bars are made like screws, which being turned round slowly, gradually carry forward the coal; while in other arrangements the same object is sought to be attained by alternately lifting and depressing every second bar at the end nearest the mouth of the furnace. In Juckes' furnace, the fire bars are arranged in the manner of rows of endless chains working over a roller at the mouth of the furnace, and another roller at the farther end of the furnace. These rollers are put into slow revolution, and the coal which is deposited at the mouth of the furnace is gradually carried forward by the motion of the chains, which act like an endless web. The clinkers and ashes left after the combustion of the coal, are precipitated into the ash-pit, where the chain turns down over the roller at the extremity of the furnace. In Messrs. Maudslays' plan of a self-feeding furnace the fire bars are formed of round tubes, and are placed transversely across the furnace. The ends of the bars gear into endless screws running the whole length of the furnace, whereby motion is given to the bars, and the coal is thus carried gradually forward. It is very doubtful whether any of these contrivances satisfy all the conditions required in a plan for feeding furnaces of the ordinary form by self-acting means, but the problem of providing a suitable contrivance, does not seem difficult of accomplishment, and will no doubt be effected under adequate temptation. 164. _Q._--Have not many plans been already contrived which consume the smoke of furnaces very effectually? _A._--Yes, many plans; and besides those already mentioned there are Hall's, Coupland's, Godson's, Robinson's, Stevens's, Hazeldine's, Indie's, Bristow and Attwood's, and a great number of others. One plan, which promises well, consists in making the flame descend through the fire bars, and the fire bars are formed of tubes set on an incline and filled with water, which water will circulate with a rapidity proportionate to the intensity of the heat. After all, however, the best remedy for smoke appears to consist in removing from it those portions which form the smoke before the coal is brought into use. Many valuable products may be got from the coal by subjecting it to this treatment; and the residuum will be more valuable than before for the production of steam. STEAM. 165. _Q._--Have experiments been made to determine the elasticity of steam at different temperatures? _A._--Yes; very careful experiments. The following rule expresses the results obtained by Mr. Southern:--To the given temperature in degrees of Fahrenheit add 51.3 degrees; from the logarithm of the sum, subtract the logarithm of 135.767, which is 2.1327940; multiply the remainder by 5.13, and to the natural number answering to the sum, add the constant fraction .1, which will give the elastic force in inches of mercury. If the elastic force be known, and it is wanted to determine the corresponding temperature, the rule must be modified thus:--From the elastic force, in inches of mercury, subtract the decimal .1, divide the logarithm of the remainder by 5.13, and to the quotient add the logarithm 2.1327940; find the natural number answering to the sum, and subtract therefrom the constant 51.3; the remainder will be the temperature sought. The French Academy, and the Franklin Institute, have repeated Mr. Southern's experiments on a larger scale; the results obtained by them are not widely different, and are perhaps nearer the truth, but Mr. Southern's results are generally adopted by engineers, as sufficiently accurate for practical purposes. 166. _Q._--Have not some superior experiments upon this subject been lately made in France? _A._--Yes, the experiments of M. Regnault upon this subject have been very elaborate and very carefully conducted, and the results are probably more accurate than have been heretofore obtained. Nevertheless, it is questionable how far it is advisable to disturb the rules of Watt and Southern, with which the practice of engineers is very much identified, for the sake of emendations which are not of such magnitude as to influence materially the practical result. M. Regnault has shown that the total amount of heat, existing in a given weight of steam, increases slightly with the pressure, so that the sum of the latent and sensible heats do not form a constant quantity. Thus, in steam of the atmospheric pressure, or with 14.7 Lbs. upon the square inch, the sensible heat of the steam is 212 degrees, the latent heat 966.6 degrees, and the sum of the latent and sensible heats 1178.6 degrees; whereas in steam of 90 pounds upon the square inch the sensible heat is 320.2 degrees, the latent heat 891.4 degrees, and the sum of the latent and sensible heats 1211.0 degrees. There is, therefore, 33 degrees less of heat in any given weight of water, raised into steam of the atmospheric pressure, than if raised into steam of 90 Lbs.[1] pressure. 167. _Q._--What expansion does water undergo in its conversion into steam? _A._--A cubic inch of water makes about a cubic foot of steam of the atmospheric pressure. 168. _Q._--And how much at a higher pressure? _A._--That depends upon what the pressure is. But the proportion is easily ascertained, for the pressure and the bulk of a given quantity of steam, as of air or any other elastic fluid, are always inversely proportional to one another. Thus if a cubic inch of water makes a cubic foot of steam, with the pressure of one atmosphere, it will make half a cubic foot with the pressure of two atmospheres, a third of a cubic foot with the pressure of three atmospheres, and so on in all other proportions. High pressure steam indeed is just low pressure steam forced into a less space, and the pressure will always be great in the proportion in which the space is contracted. 169. _Q._--If this be so, the quantity of heat in a given weight of steam must be nearly the same, whether the steam is high or low pressure? _A._--Yes; the heat in steam is nearly a constant quantity, at all pressures, but not so precisely. Steam to which an additional quantity of heat has been imparted after leaving the boiler, or as it is called "surcharged steam," comes under a different law, for the elasticity of such steam may be increased without any addition being made to its weight; but surcharged steam is not at present employed for working engines, and it may therefore be considered in practice that a pound of steam contains very nearly the same quantity of heat at all pressures. 170. _Q._--Does not the quantity of heat in any body vary with the temperature? _A._--Other circumstances remaining the same the quantity of heat in a body increases with the temperatures. 171. _Q._--And is not high pressure steam hotter than low pressure steam? _A._--Yes, the temperature of steam rises with the pressure. 172. _Q._--How then comes it, that there is the same quantity of heat in the same weight of high and low pressure steam, when the high pressure steam has the highest temperature? _A._--Because although the temperature or sensible heat rises with the pressure, the latent heat becomes less in about the same proportion. And as has been already explained, the latent and sensible heats taken together make up nearly the same amount at all temperatures; but the amount is somewhat greater at the higher temperatures. As a damp sponge becomes wet when subjected to pressure, so warm vapor becomes hot when forced into less bulk, but in neither case does the quantity of moisture or the quantity of heat sustain any alteration. Common air becomes so hot by compression that tinder may be inflamed by it, as is seen in the instrument for producing instantaneous light by suddenly forcing air into a syringe. 173. _Q._--What law is followed by surcharged steam on the application of heat? _A._--The same as that followed by air, in which the increments in volume are very nearly in the same proportion as the increments in temperature; and the increment in volume for each degree of increased temperature is 1/490th part of the volume at 32°. A volume of air which, at the temperature of 32°, occupies 100 cubic feet, will at 212° fill a space of 136.73 cubic feet. The volume which air or steam--out of contact with water--of a given temperature acquires by being heated to a higher temperature, the pressure remaining the same, may be found by the following rule:--To each of the temperatures before and after expansion, add the constant number 458: divide the greater sum by the less, and multiply the quotient by the volume at the lower temperature; the product will give the expanded volume. 174. _Q._--If the relative volumes of steam and water are known, is it possible to tell the quantity of water which should be supplied to a boiler, when the quantity of steam expended is specified? _A._--Yes; at the atmospheric pressure, about a cubic inch of water has to be supplied to the boiler for every cubic foot of steam abstracted; at other pressures, the relative bulk of water and steam may be determined as follows:--To the temperature of steam in degrees of Fahrenheit, add the constant number 458, multiply the sum by 37.3, and divide the product by the elastic force of the steam in pounds per square inch; the quotient will give the volume required. 175. _Q._--Will this rule give the proper dimensions of the pump for feeding the boiler with water? _A._--No; it is necessary in practice that the feed pump should be able to supply the boiler with a much larger quantity of water than what is indicated by these proportions, from the risk of leaks, priming, or other disarrangements, and the feed pump is usually made capable of raising 3-1/2 times the water evaporated by the boiler. About 1/240th of the capacity of the cylinder answers very well for the capacity of the feed pump in the case of low pressure engines, supposing the cylinder to be double acting, and the pump single acting; but it is better to exceed this size. 176. _Q._--Is this rule for the size of the feed pump applicable to the case of high pressure engines? _A._--Clearly not; for since a cylinder full of high pressure steam, contains more water than the same cylinder full of low pressure steam, the size of the feed must vary in the same proportion as the density of the steam. In all pumps a good deal of the effect is lost from the imperfect action of the valves; and in engines travelling at a high rate of speed, in particular, a large part of the water is apt to return, through the suction valve of the pump, especially if much lift be permitted to that valve. In steam vessels moreover, where the boiler is fed with salt water, and where a certain quantity of supersalted water has to be blown out of the boiler from time to time, to prevent the water from reaching too high a degree of concentration, the feed pump requires to be of additional size to supply the extra quantity of water thus rendered necessary. When the feed water is boiling or very hot, as in some engines is the case, the feed pump will not draw from a depth, and will altogether act less efficiently, so that an extra size of pump has to be provided in consequence. These and other considerations which might be mentioned, show the propriety of making the feed pump very much larger than theory requires. The proper proportions of pumps, however, forms part of a subsequent chapter. [1] A table containing the results arrived at by M. Regnault is given in the Key. CHAPTER III. EXPANSION OF STEAM AND ACTION OF THE VALVES. 177. _Q._--What is meant by working engines expansively? _A._--Adjusting the valves, so that the steam is shut off from the cylinder before the end of the stroke, whereby the residue of the stroke is left to be completed by the expanding steam. 178. _Q._--And what is the benefit of that practice? _A._--It accomplishes an important saving of steam, or, what is the same thing, of fuel; but it diminishes the power of the engine, while increasing the power of the steam. A larger engine will be required to do the same work, but the work will be done with a smaller consumption of fuel. If, for example, the steam be shut off when only half the stroke is completed, there will only be half the quantity of steam used. But there will be more than half the power exerted; for although the pressure of the steam decreases after the supply entering from the boiler is shut off, yet it imparts, during its expansion, _some_ power, and that power, it is clear, is obtained without any expenditure of steam or fuel whatever. 179. _Q._--What will be the pressure of the steam, under such circumstances, at the end of the stroke? _A._--If the steam be shut off at half stroke, the pressure of the steam, reckoning the total pressure both below and above the atmosphere, will just be one-half of what it was at the beginning of the stroke. It is a well known law of pneumatics, that the pressure of elastic fluids varies inversely as the spaces into which they are expanded or compressed. For example, if a cubic foot of air of the atmospheric density be compressed into the compass of half a cubic foot, its elasticity will be increased from 15 lbs. on the square inch to 30 lbs. on the square inch; whereas, if its volume be enlarged to two cubic feet, its elasticity will be reduced to 7-1/2 lbs. on the square inch, being just half its original pressure. The same law holds in all other proportions, and with all other gases and vapors, provided their temperature remains unchanged; and if the steam valve of an engine be closed, when the piston has descended through one- fourth of the stroke, the steam within the cylinder will, at the end of the stroke, just exert one-fourth of its initial pressure. 180. _Q._--Then by computing the varying pressure at a number of stages, the average or mean pressure throughout the stroke may be approximately determined? [Illustration: Fig. 32. Diagram showing law of expansion of steam in a cylinder.] _A._--Precisely so. Thus in the accompanying figure, (fig. 32), let E be a cylinder, J the piston, _a_ the steam pipe, _c_ the upper port, _f_ the lower port, _d_ the steam pipe, prolonged to _e_ the equilibrium valve, _g_ the eduction valve, M the steam jacket, N the cylinder cover, O stuffing box, _n_ piston rod, P cylinder bottom; let the cylinder be supposed to be divided in the direction of its length into any number of equal parts, say twenty, and let the diameter of the cylinder represent the pressure of the steam, which, for the sake of simplicity, we may take at 10 lbs., so that we may divide the cylinder, in the direction of its diameter, into ten equal parts. If now the piston be supposed to descend through five of the divisions, and the steam valve then be shut, the pressure at each subsequent position of the piston will be represented by a series, computed according to the laws of pneumatics, and which, if the initial pressure be represented by 1, will give a pressure of .5 at the middle of the stroke, and .25 at the end of it. If this series be set off on the horizontal lines, it will mark out a hyperbolic curve--the area of the part exterior to which represents the total efficacy of the stroke, and the interior area, therefore, represents the diminution in the power of a stroke, when the steam is cut off at one- fourth of the descent. If the squares above the point, where the steam is cut off, be counted, they will be found to amount to 50; and if those beneath that point be counted or estimated, they will be found to amount to about 69. These squares are representative of the power exerted; so that while an amount of power represented by 50 has been obtained by the expenditure of a quarter of a cylinder full of steam, we get an amount of power represented by 69, without any expenditure of steam at all, merely by permitting the steam first used to expand into four times its original volume. 181. _Q._--Then by working an engine expansively, the power of the steam is increased, but the power of the engine is diminished? _A._--Yes. The efficacy of a given quantity of steam is more than doubled by expanding the steam four times, while the efficacy of each stroke is made nearly one-half less. And, therefore, to carry out the expansive principle in practice, the cylinder requires to be larger than usual, or the piston faster than usual, in the proportion in which the expansion is carried out. Every one who is acquainted with simple arithmetic, can compute the terminal pressure of steam in a cylinder, when he knows the initial pressure and the point at which the steam is cut off; and he can also find, by the same process, any pressure intermediate between the first and the last. By setting down these pressures in a table, and taking their mean, he can determine the effect, with tolerable accuracy, of any particular measure of expansion. It is necessary to remark, that it is the total pressure of the steam that he must take; not the pressure above the atmosphere, but the pressure above a perfect vacuum. 182. _Q._--Can you give any rule for ascertaining at one operation the amount of benefit derivable from expansion? _A._--Divide the length of stroke through which the steam expands, by the length of stroke performed with full pressure, which last call 1; the hyperbolic logarithm of the quotient is the increase of efficiency due to expansion. According to this rule it will be found, that if a given quantity of steam, the power of which working at full pressure is represented by 1, be admitted into a cylinder of such a size that its ingress is concluded when one-half the stroke has been performed, its efficacy will be raised by expansion to 1.69; if the admission of the steam be stopped at one-third of the stroke, the efficacy will be 2.10; at one- fourth, 2.39; at one-fifth, 2.61; at one-sixth, 2.79; at one-seventh, 2.95; at one-eighth, 3.08. The expansion, however, cannot be carried beneficially so far as one-eighth, unless the pressure of the steam in the boiler be very considerable, on account of the inconvenient size of cylinder or speed of piston which would require to be adopted, the friction of the engine, and the resistance of vapor in the condenser, which all become relatively greater with a smaller urging force. 183. _Q._--Is this amount of benefit actually realized in practice? _A._--Only in some cases. It appears to be indispensable to the realization of any large amount of benefit by expansion, that the cylinder should be enclosed in a steam jacket, or should in some other way be effectually protected from refrigeration. In some engines not so protected, it has been found experimentally that less benefit was obtained from the fuel by working expansively than by working without expansion--the whole benefit due to expansion being more than counteracted by the increased refrigeration due to the larger surface of the cylinder required to develop the power. In locomotive engines, with outside cylinders, this condition of the advantageous use of expansion has been made very conspicuous, as has also been the case in screw steamers with four cylinders, and in which the refrigerating surface of the cylinders was consequently large. 184. _Q._--The steam is admitted to and from the cylinder by means of a slide or sluice valve? [Illustration: Fig. 33.] _A._--Yes; and of the slide valve there are many varieties; but the kinds most in use are the D valve,--so called from its resemblance to a half cylinder or D in its cross section--and the three ported valve, shown in fig. 33, which consists of a brass or iron box set over the two ports or openings into the cylinder, and a central port which conducts away the steam to the atmosphere or condenser; but the length of the box is so adjusted that it can only cover one of the cylinder ports and the central or eduction port at the same time. The effect, therefore, of moving the valve up and down, as is done by the eccentric, is to establish a connection alternately between each cylinder port and the central passage whereby the steam escapes; and while the steam is escaping from beneath the piston, the position of the valve is such, that a free communication exists between the space above the piston and the steam in the boiler. The piston is thus urged alternately up and down--the valve so changing its position before the piston arrives at the end of the stroke, that the pressure is by that time thrown on the reverse side of the piston, so as to urge it into motion in the opposite direction. 185. _Q._--Is the motion of the valve, then, the reverse of that of the piston? _A._--No. The valve does not move down when the piston moves down, nor does it move down when the piston moves up; but it moves from its mid position, to the extremity of its throw, and back again to its mid position, while the piston makes an upward or downward movement, so that the motion is as it were at right angles to the motion of the piston; or it is the same motion that the piston of another engine, the crank of which is set at right angles with that of the first engine, would acquire. 186. _Q._--Then in a steam vessel the valve of one engine may be worked from the piston of the other? _A._--Yes, it may; or it may be worked from its own connecting rod; and in the case of locomotive engines, this has sometimes been done. 187. _Q._--What is meant by the lead of the valve? _A._--The amount of opening which the valve presents for the admission of the steam, when the piston is just beginning its stroke. It is found expedient that the valve should have opened a little to admit steam on the reverse side of the piston before the stroke terminates; and the amount of this opening, which is given by turning the eccentric more or less round upon the shaft, is what is termed the lead. 188. _Q._--And what is meant by the lap of the valve? _A._--It is an elongation of the valve face to a certain extent over the port, whereby the port is closed sooner than would otherwise be the case. This extension is chiefly effected at that part of the valve where the steam is admitted, or upon the _steam side_ of the valve, as the technical phrase is; and the intent of the extension is to close the steam passage before the end of the stroke, whereby the engine is made to operate to a certain extent expansively. In some cases, however, there is also a certain amount of lap given to the escape or eduction side, to prevent the eduction from being performed too soon when the lead is great; but in all cases there is far less lap on the eduction than on the steam side, very often there is none, and sometimes less than none, so that the valve is incapable of covering both the ports at once. 189. _Q._--What is the usual proportional length of stroke of the valve? _A._--The common stroke of the valve in rotative engines is twice the breadth or depth of the port, and the length of the valve face will then be just the breadth of the port when there is lap on neither the steam nor eduction side. Whatever lap is given, therefore, makes the valve face just so much longer. In some engines, however, the stroke of the valve is a good deal more than twice the breadth of the port; and it is to the stroke of the valve that the amount of lap should properly be referred. 190. _Q._--Can you tell what amount of lap will accomplish any given amount of expansion? _A._--Yes, when the stroke of the valve is known. From the length of the stroke of the piston subtract that part of the stroke which is intended to be accomplished before the steam is cut off; divide the remainder by the length of the stroke of the piston, and extract the square root of the quotient, which multiply by half the stroke of the valve, and from the product take half the lead; the remainder will be the lap required. 191. _Q._--Can you state how we may discover at what point of the stroke the eduction passage will be closed? _A._--To find how much before the end of the stroke the eduction passage will be closed:--to the lap on the steam side add the lead, and divide the sum by half the stroke of the valve; find the arc whose sine is equal to the quotient, and add 90° to it.; divide the lap on the eduction side by half the stroke of the valve, and find the arc whose cosine is equal to the quotient; subtract this arc from the one last obtained, and find the cosine of the remainder; subtract this cosine from 2, and multiply the remainder by half the stroke of the piston; the product is the distance of the piston from the end of the stroke when the eduction passage is closed. 192. _Q._--Can you explain how we may determine the distance of the piston from the end of the stroke, before the steam urging it onward is allowed to escape? _A._--To find how far the piston is from the end of its stroke when the steam that is propelling it by expansion is allowed to escape to the atmosphere or condenser--to the lap on the steam side add the lead; divide the sum by half the stroke of the valve, and find the arc whose sine is equal to the quotient; find the arc whose sine is equal to the lap on the eduction side, divided by half the stroke of the valve; add these two arcs together and subtract 90°; find the cosine of the residue, subtract it from 1, and multiply the remainder by half the stroke of the piston; the product is the distance of the piston from the end of its stroke when the steam that is propelling it is allowed to escape into the atmosphere or condenser. In using these rules, all the dimensions are to be taken in inches, and the answers will be found in inches also. 193. _Q._--Is it a benefit or a detriment to open the eduction passage before the end of the stroke? _A._--In engines working at a high rate of speed, such as locomotive engines, it is very important to open the exhaust passage for the escape of the steam before the end of the stroke, as an injurious amount of back pressure is thus prevented. In the earlier locomotives a great loss of effect was produced from inattention to this condition; and when lap was applied to the valves to enable the steam to be worked expansively, it was found that a still greater benefit was collaterally obtained by the earlier escape of the steam from the eduction passages, and which was incidental to the application of lap to the valves. The average consumption of coke per mile was reduced by Mr. Woods from 40 lbs. per mile to 15 lbs. per mile, chiefly by giving a free outlet to the escaping steam. 194. _Q._--To what extent can expansion be carried beneficially by means of lap upon the valve? _A._--To about one-third of the stroke; that is, the valve may be made with so much lap, that the steam will be cut off when two thirds of the stroke have been performed, leaving the residue to be accomplished by the agency of the expanding steam; but if more lap be put on than answers to this amount of expansion, a very distorted action of the valve will be produced, which may impair the efficiency of the engine. If a further amount of expansion than this is wanted, it may be accomplished by wire drawing the steam, or by so contracting the steam passage that the pressure within the cylinder must decline when the speed of the piston is accelerated, as it is about the middle of the stroke. 195. _Q._--Will you explain how this result ensues? _A._--If the valve be so made as to shut off the steam by the time two thirds of the stroke have been performed, and the steam be at the same time throttled in the steam pipe, the full pressure of the steam within the cylinder cannot be maintained except near the beginning of the stroke where the piston travels slowly; for, as the speed of the piston increases, the pressure necessarily subsides, until the piston approaches the other end of the cylinder, where the pressure would rise again but that the operation of the lap on the valve by this time has had the effect of closing the communication between the cylinder and steam pipe, so as to prevent more steam from entering. By throttling the steam, therefore, in the manner here indicated, the amount of expansion due to the lap may be doubled, so that an engine with lap enough upon the valve to cut off the steam at two-thirds of the stroke, may, by the aid of wire drawing, be virtually rendered capable of cutting off the steam at one-third of the stroke. 196. _Q._--Is this the usual way of cutting off the steam? _A._--No; the usual way of cutting off the steam is by means of a separate valve, termed an expansion valve; but such a device appears to be hardly necessary in ordinary engines. In the Cornish engines, where the steam is cut off in some cases at one-twelfth of the stroke, a separate valve for the admission of steam, other than that which permits its escape, is of course indispensable; but in common rotative engines, which may realize expansive efficacy by throttling, a separate expansion valve does not appear to be required. 197. _Q._--That is, where much expansion is required, an expansion valve is a proper appendage, but where not much is required, a separate expansion valve may be dispensed with? _A._--Precisely so. The wire drawing of the steam causes a loss of part of its power, and the result will not be quite so advantageous by throttling as by cutting off. But for moderate amounts of expansion it will suffice, provided there be lap upon the slide valve. 198. _Q._--Will you explain the structure or configuration of expansion apparatus of the usual construction? [Illustration: Fig 34.] _A._--The structure of expansion apparatus is very various; but all the kinds operate either on the principle of giving such a motion to the slide valve as will enable it to cut off the steam, at the desired point, or on the principle of shutting off the steam by a separate valve in the steam pipe or valve casing. The first class of apparatus has not been found so manageable, and is not in extensive use, except in that form known as the link motion. Of the second class, the most simple probably is the application of a cam giving motion to the throttle valve, or to a valve of the same construction, which either accurately fits the steam pipe, or which comes round to a face, which, however, it is restrained from touching by a suitable construction of the cam. A kind of expansion valve, often employed in marine engines of low speed, is the kind used in the Cornish engines, and known as the equilibrium valve. This valve is represented in fig. 34. It consists substantially of an annulus or bulging cylinder of brass, with a steam-tight face both at its upper and lower edges, at which points it fits accurately upon a stationary seat. This annulus may be raised or lowered without being resisted by the pressure of the steam, and in rotative engines it is usually worked by a cam on the shaft. The expansion cam is put on the shaft in two pieces, which are fastened to each other by means of four bolts passing through lugs, and is fixed to the shaft by keys. A roller at one end of a bell-crank lever, which is connected with the expansion valve, presses against the cam, so that the motion of the lever will work the valve. The roller is kept against the cam by a weight on a lever attached to the same shaft, but a spring is necessary for high speeds. If the cam were concentric with the shaft, the lever which presses upon it would remain stationary, and also the expansion valve; but by the projection of the cam, the end of the lever receives a reciprocating motion, which is communicated to the valve. 199. _Q._--The cam then works the valve? _A._--Yes. The position of the projection of the cam determines the point in relation to the stroke at which the valve is opened, and its circumferential length determines the length of the time during which the valve continues open. The time at which the valve should begin to open is the same under all circumstances, but the duration of its opening varies with the amount of expansion desired. In order to obtain this variable extent of expansion, there are several projections made upon the cam, each of which gives a different degree, or _grade_ as it is usually called, of expansion. These grades all begin at the same point on the cam, but are of different lengths, so that they begin to move the lever at the same time, but differ in the time of returning it to its original position. 200. _Q._--How is the degree of expansion changed? _A._--The change of expansion is effected by moving the roller on to the desired grade; which is done by slipping the lever carrying the roller endways on the shaft or pin sustaining it. 201. _Q._--Are such cams applicable in all cases? _A._--In engines moving at a high rate of speed the roller will be thrown back from the cam by its momentum, unless it be kept against it by means of springs. In some cases I have employed a spring formed of a great number of discs of India rubber to keep the roller against the cam, but a few brass discs require to be interposed to prevent the India rubber discs from being worn in the central hole. 202. _Q._--May not the percussion incident to the action of a cam at a high speed, when the roller is not kept up to the face by springs, be obviated by giving a suitable configuration to the cam itself? _A._--It may at all events be reduced. The outline of the cam should be a parabola, so that the valve may be set in motion precisely as a falling body would be; but it will, nevertheless, be necessary that the roller on which the cam presses should be forced upward by a spring rather than by a counterweight, as there will thus be less inertia or momentum in the mass that has to be moved. 203. _Q._--An additional slide valve is sometimes used for cutting off the steam? _A._--Yes, very frequently; and the slide valve is sometimes on the side or back of the valve casing, and sometimes on the back of the main or distributing valve, and moving with it. 204. _Q._--Are cams used in locomotive engines? _A._--In locomotive engines the use of cams is inadmissible, and other expedients are employed, of which those contrived by Stephenson and by Cabrey operate on the principle of accomplishing the requisite variations of expansion by altering the throw of the slide valve. 205. _Q._--What is Stephenson's arrangement? [Illustration: Fig. 35.] _A._--Stephenson connects the ends of the forward and backward eccentric rods by a link with a curved slot in which a pin upon the end of the valve rod works. By moving this link so as to bring the forward eccentric rod in the same line with the valve rod, the valve receives the motion due to that eccentric; whereas if the backward eccentric rod is brought in a line with the valve rod, the valve gets the motion proper for reversing, and if the link be so placed that the valve rod is midway between the two eccentric rods, the valve will remain nearly stationary. This arrangement, which is now employed extensively, is what is termed "the link motion." It is represented in the annexed figure, fig. 35, where _e_ is the valve rod, which is attached by a pin to an open curved link susceptible of being moved up and down by the bell-crank lever _f''_ _f''_, supported on the centre _g_, and acting on the links _f_, while the valve rod _e_ remains in the same horizontal plane; _d d'_ are the eccentric rods, and the link is represented in its lowest position. The dotted lines _h' h''_ show the position of the eccentric rods when the link is in its highest position, and _l l'_ when in mid position. 206. _Q._--What is Cabrey's arrangement? _A._--Mr. Cabrey makes his eccentric rod terminate in a pin which works into a straight slotted lever, furnished with jaws similar to the jaws on the eccentric rods of locomotives. By raising the pin of the eccentric rod in this slot, the travel of the valve will be varied, and expansive action will be the result. 207. _Q._--What other forms of apparatus are there for working steam expansively? _A._--They are too numerous for description here, but a few of them may be enumerated. Fenton seeks to accomplish the desired object by introducing a spiral feather on the crank axle, by moving the eccentric laterally against which the eccentric is partially turned round so as to cut off the steam at a different part of the stroke. Dodds seeks to attain the same end by corresponding mechanical arrangements. Farcot, Edwards, and Lavagrian cut off the steam by the application of a supplementary valve at the back of the ordinary valve, which supplementary valve is moved by tappets fixed to the valve casing. Bodmer, in 1841, and Meyer, in 1842, employed two slides or blocks fitted over apertures in the ordinary slide valve, and which blocks were approximated or set apart by a right and left handed screw passing through both.[1] Hawthorn, in 1843, employed as an expansion valve a species of frame lying on the ordinary cylinder face upon the outside of the valve, and working up against the steam side of the valve at each end so as to cut off the steam. In the same year Gonzenbach patented an arrangement which consists of an additional slide valve and valve casing placed on the back of the ordinary slide valve casing, and through this supplementary valve the steam must first pass. This supplementary valve is worked by a double ended lever, slotted at one end for the reception of a pin on the valve link, the position of which in the slot determines the throw of the supplementary valve, and the consequent degree of expansion. 208. _Q._--What is the arrangement of expansion valve used in the most approved modern engines? _A._--In modern engines, either marine or locomotive, it is found that if they are fitted with the link motion, as they nearly all are, a very good expansive action can be obtained by giving a suitable adjustment to it, without employing an expansion valve at all. Diagrams taken from engines worked in this manner show a very excellent result, and most of the modern engines trust for their expansive working to the link motion and the throttle valve. [1] In 1838 I patented an arrangement of expansion valve, consisting of two movable plates set upon the ordinary slide valve, and which might be drawn together or asunder by means of a right and left handed screw passing through both plates. The valve spindle was hollow, and a prolongation of the screw passed up through it, and was armed on the top with a small wheel, by means of which the plates might be adjusted while the engine was at work. In 1839 I fitted an expansion valve in a steam vessel, consisting of two plates, connected by a rod, and moved by tappets up against the steam edges of the valve. In another steam vessel I fitted the same species of valve, but the motion was not derived from tappets, but from a moving part of the engine, though at the moderate speed at which these engines worked I found tappets to operate well and make little noise. In 1837 I employed, as an expansion valve, a rectangular throttle valve, accurately fitting a bored out seat, in which it might be made to revolve, though it did not revolve in working. This valve was moved by a pin in a pinion, making two revolutions for every revolution of the engine, and the configuration of the seat determined the amount of the expansion. In 1855 I have again used expansion valves of this construction in engines making one hundred revolutions per minute, and with perfectly satisfactory results.-- J.B. CHAPTER IV. MODES OF ESTIMATING THE POWER AND PERFORMANCE OF ENGINES AND BOILERS. HORSES POWER. 209. _Q._--What do you understand by a horse power? _A._--An amount of mechanical force that will raise 33,000 lbs. one foot high in a minute. This standard was adopted by Mr. Watt, as the average force exerted by the strongest London horses; the object of his investigation being to enable him to determine the relation between the power of a certain size of engine and the power of a horse, so that when it was desired to supersede the use of horses by the erection of an engine, he might, from the number of horses employed, determine the size of engine that would be suitable for the work. 210. _Q._--Then when we talk of an engine of 200 horse power, it is meant that the impelling efficacy is equal to that of 200 horses, each lifting 33,000 lbs. one foot high in a minute? _A._--No, not now; such was the case in Watt's engines, but the capacity of cylinder answerable to a horse power has been increased by most engineers since his time, and the pressure on the piston has been increased also, so that what is now called a 200 horse power engine exerts, almost in every case, a greater power than was exerted in Watt's time, and a horse power, in the popular sense of the term, has become a mere conventional unit for expressing a certain size of engine, without reference to the power exerted. 211. _Q._--Then, each nominal horse power of a modern engine may raise much more than 33,000 lbs. one foot high in a minute? _A._--Yes; some raise 52,000 lbs., others 60,000 lbs., and others 66,000 lbs., one foot high in a minute by each nominal horse power. Some engines indeed work as high as five times above the nominal power, and therefore no comparison can be made between the performances of different engines, unless the power actually exerted be first discovered. 212. _Q._--How is the power actually exerted by engines ascertained? _A._--By means of an instrument called the indicator, which is a miniature cylinder and piston attached to the cylinder cover of the main engine, and which indicates, by the pressure exerted on a spring, the amount of pressure or vacuum existing within the cylinder. From this pressure, expressed in pounds per square inch, deduct a pound and a half of pressure for friction, the loss of power in working the air pump, &c.; multiply the area of the piston in square inches by this residual pressure, and by the motion of the piston, in feet per minute, and divide by 33,000; the quotient is the actual number of horses power of the engine. The same result is attained by squaring the diameter of the cylinder, multiplying by the pressure per square inch, as shown by the indicator, less a pound and a half, and by the motion of the piston, in feet per minute, and dividing by 42,017. 213. _Q._ How is the nominal power of an engine ascertained? _A._--Since the nominal power is a mere conventional expression, it is clear that it must be determined by a merely conventional process. The nominal power of ordinary condensing engines may be ascertained by the following rule: multiply the square of the diameter of the cylinder in inches, by the velocity of the piston in feet per minute, and divide the product by 6,000; the quotient is the number of nominal horses power. In using this rule, however, it is necessary to adopt the speed of piston prescribed by Mr. Watt, which varies with the length of the stroke. The speed of piston with a 2 feet stroke is, according to his system, 160 per minute; with a 2 ft. 6 in. stroke, 170; 3 ft., 180; 3 ft. 6 in., 189; 4 ft., 200; 5 ft., 215; 6 ft., 228; 7 ft., 245; 8 ft., 256 ft. 214. _Q._--Does not the speed of the piston increase with the length of the stroke? _A._--It does: the speed of the piston varies nearly as the cube root of the length of the stroke. 215. _Q._--And may not therefore some multiple of the cube root of the length of the stroke be substituted for the velocity of the piston in determining the nominal power? _A._--The substitution is quite practicable, and will accomplish some simplification, as the speed of piston proper for the different lengths of stroke cannot always be remembered. The rule for the nominal power of condensing engines when thus arranged, will be as follows: multiply the square of the diameter of the cylinder in inches by the cube root of the stroke in feet, and divide the product by 47; the quotient is the number of nominal horses power of the engine, supposing it to be of the ordinary condensing description. This rule assumes the existence of a uniform effective pressure upon the piston of 7 lbs. per square inch; Mr. Watt estimated the effective pressure upon the piston of his 4 horse power engines at 6-8 lbs. per square inch, and the pressure increased slightly with the power, and became 6.94 lbs. per square inch in engines of 100 horse power; but it appears to be more convenient to take a uniform pressure of 7 lbs. for all powers. Small engines, indeed, are somewhat less effective in proportion than large ones, but the difference can be made up by slightly increasing the pressure in the boiler; and small boilers will bear such an increase without inconvenience. 216. _Q._--How do you ascertain the power of high pressure engines? _A._--The actual power is readily ascertained by the indicator, by the same process by which the actual power of low pressure engines is ascertained. The friction of a locomotive engine when unloaded is found by experiment to be about 1 lb. per square inch on the surface of the pistons, and the additional friction caused by any additional resistance is estimated at about .14 of that resistance; but it will be a sufficiently near approximation to the power consumed by friction in high pressure engines, if we make a deduction of a pound and a half from the pressure on that account, as in the case of low pressure engines. High pressure engines, it is true, have no air pump to work; but the deduction of a pound and a half of pressure is relatively a much smaller one where the pressure is high, than where it does not much exceed the pressure of the atmosphere. The rule, therefore, for the actual horse power of a high pressure engine will stand thus: square the diameter of the cylinder in inches, multiply by the pressure of the steam in the cylinder per square inch less 1-1/2 lb., and by the speed of the piston in feet per minute, and divide by 42,017; the quotient is the actual horse power. 217. _Q._--But how do you ascertain the nominal horse power of high pressure engines? _A._--The nominal horse power of a high pressure engine has never been defined; but it should obviously hold the same relation to the actual power as that which obtains in the case of condensing engines, so that an engine of a given nominal power may be capable of performing the same work, whether high pressure or condensing. This relation is maintained in the following rule, which expresses the nominal horse power of high pressure engines: multiply the square of the diameter of the cylinder in inches by the cube root of the length of stroke in feet, and divide the product by 15.6. This rule gives the nominal power of a high pressure engine three times greater than that of a low pressure engine of the same dimensions; the average effective pressure being taken at 21 lbs. per square inch instead of 7 lbs., and the speed of the piston in feet per minute being in both rules 128 times the cube root of the length of stroke.[1] 218. _Q._--Is 128 times the cube root of the stroke in feet per minute the ordinary speed of all engines? _A._--Locomotive engines travel at a quicker speed--an innovation brought about not by any process of scientific deduction, but by the accidents and exigencies of railway transit. Most other engines, however, travel at about the speed of 128 times the cube root of the stroke in feet; but some marine condensing engines of recent construction travel at as high a rate as 700 feet per minute. To mitigate the shock of the air pump valves in cases in which a high speed has been desirable, as in the case of marine engines employed to drive the screw propeller without intermediate gearing, India rubber discs, resting on a perforated metal plate, are now generally adopted; but the India rubber should be very thick, and the guards employed to keep the discs down should be of the same diameter as the discs themselves. 219. _Q._--Can you suggest any eligible method of enabling condensing engines to work satisfactorily at a high rate of speed? _A._--The most feasible way of enabling condensing engines to work satisfactorily at a high speed, appears to lie in the application of balance weights to the engine, so as to balance the momentum of its moving parts, and the engine must also be made very strong and rigid. It appears to be advisable to perform the condensation partly in the air pump, instead of altogether in the condenser, as a better vacuum and a superior action of the air pump valves will thus be obtained. Engines constructed upon this plan may be driven at four times the speed of common engines, whereby an engine of large power may be purchased for a very moderate price, and be capable of being put into a very small compass; while the motion, from being more equable, will be better adapted for most purposes for which a rotary motion is required. Even for pumping mines and blowing iron furnaces, engines of this kind appear likely to come into use, for they are more suitable than other engines for driving the centrifugal pump, which in many cases appears likely to supersede other kinds of pumps for lifting water; and they are also conveniently applicable to the driving of fans, which, when so arranged that the air condensed by one fan is employed to feed another, and so on through a series of 4 or 5, have succeeded in forcing air into a furnace with a pressure of 2-1/2 lbs. on the square inch, and with a far steadier flow than can be obtained by a blast engine with any conceivable kind of compensating apparatus. They are equally applicable if blast cylinders be employed. 220. _Q._--Then, if by this modification of the engine you enable it to work at four times the speed, you also enable it to exert four times the power? _A._--Yes; always supposing it to be fully supplied with steam. The nominal power of this new species of engine can readily be ascertained by taking into account the speed of the piston, and this is taken into account by the Admiralty rule for power. 221. _Q._--What is the Admiralty rule for determining the power of an engine? _A._--Square the diameter of the cylinder in inches, which multiply by the speed of the piston in feet per minute, and divide by 6,000; the quotient is the power of the engine by the Admiralty rule.[2] 222. _Q._--The high speed engine does not require so heavy a fly wheel as common engines? _A._--No; the fly wheel will be lighter, both by virtue of its greater velocity of rotation, and because the impulse communicated by the piston is less in amount and more frequently repeated, so as to approach more nearly to the condition of a uniform pressure. 223. _Q._--Can nominal be transformed into actual horse power? _A._--No; that is not possible in the case of common condensing engines. The actual power exerted by an engine cannot be deduced from its nominal power, neither can the nominal power be deduced from the power actually exerted, or from anything else than the dimensions of the cylinder. The actual horse power being a dynamical unit, and the nominal horse power a measure of capacity of the cylinder, are obviously incomparable things. 224. _Q._--That is, the _nominal_ power is a commercial unit by which engines are bought and sold, and the _actual_ power a scientific unit by which the quality of their performance is determined? _A._--Yes; the nominal power is as much a commercial measure as a yard or a bushel, and is not a thing to be ascertained by any process of science, but to be fixed by authority in the same manner as other measures. The actual power, on the contrary, is a mechanical force or dynamical effort capable of raising a given weight through a given distance in a given time, and of which the amount is ascertainable by scientific investigation. 225. _Q._--Is there any other measure of an actual horse power than 33,000 lbs. raised one foot high in the minute? _A._--There cannot be any _different_ measure, but there are several equivalent measures. Thus the evaporation of a cubic foot of water in the hour, or the expenditure of 33 cubic feet of low pressure steam per minute, is reckoned equivalent to an actual horse power, or 528 cubic feet of water raised one foot high in the minute involves the same result. [1] Tables of the horse power of both high and low pressure engines are given in the Key. [2] Example.--What is the power of an engine of 42 inches diameter, 3-1/2 feet stroke, and making 85 strokes per minute? The speed of the piston will be 7 (the length of a double stroke) x 85 = 595 feet per minute. Now 42 x 42 = 1,764 x 595 = 1,049,580 / 6,000 = 175 horses power. DUTY OF ENGINES AND BOILERS. 226. _Q._--What is meant by the duty of a engine? _A._--The work done in relation to the fuel consumed. 227. _Q._--And how is the duty ascertained? _A._--In ordinary mill or marine engines it can only be ascertained by the indicator, as the load upon such engines is variable, and cannot readily be determined; but in the case of engines pumping water, where the load is constant, the number of strokes performed by the engine will represent the work done, and the amount of work done by a given quantity of coal represents the duty. In Cornwall the duty of an engine is expressed by the number of millions of pounds raised one foot high by a bushel, or 94 lbs. of Welsh coal. A bushel of Newcastle coal will only weigh 84 Lbs.; and in comparing the duty of a Cornish engine with the performance of an engine in some locality where a different kind of coal is used, it is necessary to pay regard to such variations. 228. _Q._--Can you tell the duty of an engine when you know its consumption of coal per horse power per hour? _A._--Yes, if the power given be the actual, and not the nominal, power. Divide 166.32 by the number of pounds of coal consumed per actual horse power per hour; the quotient is the duty in millions of pounds. If you already have the duty in millions of pounds, and wish to know the equivalent consumption in pounds per actual horse power per hour, divide 166.32 by the duty in millions of pounds; the quotient is the consumption per actual horse power per hour. The duty of a locomotive engine is expressed by the weight of coke it consumes in transporting a ton through the distance of one mile upon a railway; but this is a very imperfect method of representing the duty, as the tractive efficacy of a pound of coke becomes less as the speed of the locomotive becomes greater; and the law of variation is not accurately known. 229. _Q._--What amount of power is generated in good engines of the ordinary kind by a given weight of coal? _A._--The duty of different kinds of engines varies very much, and there are also great differences in the performance of different engines of the same class. In ordinary rotative condensing engines of good construction, 10 lbs. of coal per nominal horse power per hour is a common consumption; but such engines exert nearly twice their nominal power, so that the consumption per actual horse power per hour may be taken at from 5 to 6 lbs. Engines working very expansively, however, attain an economy much superior to this. The average duty of the pumping engines in Cornwall is about 60,000,000 lbs. raised 1 ft. high by a bushel of Welsh coals, which weighs 94 lbs. This is equivalent to a consumption of 3.1 lbs. of coal per actual horse power per hour; but some engines reach a duty of above 100,000,000, or 1.74 lbs. of coal per actual horse power per hour. Locomotives consume from 8 to 10 lbs. of coke in evaporating a cubic foot of water, and the evaporation of a cubic foot of water per hour may be set down as representing an actual horse power in locomotives as well as in condensing engines, if expansion be not employed. When the locomotive is worked expansively, however, there is of course a less consumption of water and fuel per horse power, or per ton per mile, than when the full pressure is used throughout the stroke; and most locomotives now operate with as much expansion as can be conveniently given by the slide valves. 230. _Q._--But is not the evaporative power of locomotives affected materially by the proportions of the boiler? _A._--Yes, but this may be said of all boilers; but in locomotive boilers, perhaps, the effect of any misproportion becomes more speedily manifest. A high temperature of the fire box is found to be conducive to economy of fuel; and this condition, in its turn, involves a small area of grate bars. The heating surface of locomotive boilers should be about 80 square feet for each square foot of grate bars, and upon each foot of grate bars about 1 cwt. of coke should be burnt in the hour. 231. _Q._--Probably the heat is more rapidly absorbed when the temperature of the furnace is high? _A._--That seems to be the explanation. The rapidity with which a hot body imparts heat to a colder, varies as the square of the difference of temperature; so that if the temperature of the furnace be very high, the larger part of the heat passes into the water at the furnace, thereby leaving little to be transmitted by the tubes. If, on the contrary, the temperature of the furnace be low, a large part of the heat will pass into the tubes, and more tube surface will be required to absorb it. About 16 cubic feet of water should be evaporated by a locomotive boiler for each, square foot of fire grate, which, with the proportion of heating surface already mentioned, leaves 5 square feet of heating surface to evaporate a cubic foot of water in the hour. This is only about half the amount of surface usual in land and marine boilers per cubic foot evaporated, and its small amount is due altogether to the high temperature of the furnace, which, by the rapidity of transmission it causes, is tantamount to an additional amount of heating surface. 232. _Q._--You have stated that the steam and vacuum gauges are generally glass tubes, up which mercury is forced by the steam or sucked by the vacuum? _A._--Vacuum gauges are very often of this construction, but steam gauges more frequently consist of a small iron tube, bent like the letter U, and into which mercury is poured. The one end of this tube communicates with the boiler, and the other end with the atmosphere; and when the pressure of the steam rises in the boiler, the mercury is forced down in the leg communicating with the boiler and rises in the other leg, and the difference of level in the legs denotes the pressure of the steam. In this gauge a rise of the mercury one inch in the one leg involves a difference of the level between the two legs of two inches, and an inch of rise is, therefore, equivalent to two inches of mercury, or a pound of pressure. A small float of wood is placed in the open leg to show the rise or fall of the mercury, and this leg is surmounted by a brass scale, graduated in inches, to the marks of which the float points. 233. _Q._--What other kinds of steam and vacuum gauges are there? _A._--There are many other kinds; but probably Bourdon's gauges are now in more extended use than, any other, and their operation has been found to be satisfactory in practice. The principle of their action may be explained to be, that a thin elliptical metal tube, if bent into a ring, will seek to coil or uncoil itself if subjected to external or internal pressure, and to an extent proportional to the pressure applied. The end of the tube is sharpened into an index, and moves to an extent corresponding to the pressure applied to the tube; but in the more recent forms of this apparatus, a dial and a hand, like those of a clock, are employed, and the hand is moved round by a toothed sector connected to the tube, and which sector acts on a pinion attached to the hand. Mr. Shank, of Paisley, has lately introduced a form of steam gauge like a thermometer, with a flattened bulb; and the pressure of the steam, by compressing the bulb, causes the mercury to rise to a point proportional to the pressure applied. THE INDICATOR. 234. _Q._--You have already stated that the actual power of an engine is ascertained by an instrument called the indicator, which consists of a small cylinder with a piston moving against a spring, and compressing it to an extent answerable to the pressure of the steam. Will you explain further the structure and mode of using that instrument? [Illustration: Fig. 36] _A._--The structure of the common form of indicator will be most readily apprehended by a reference to fig. 36, which is a McNaught's indicator. Upon a movable barrel A, a piece of paper is wound, the ends of which are secured by the slight brass clamps shown in the drawing. The barrel is supported by the bracket _b_, proceeding from the body of the indicator, and at the bottom of the barrel a watch spring is coiled with one end attached to the barrel and the other end to the bracket, so that when the barrel is drawn round by a string wound upon its lower end like a roller blind, the spring returns the barrel to its original position, when the string is relaxed. The string is attached to some suitable part of the engine, and at every stroke the string is drawn out, turning round the barrel, and the barrel is returned again by the spring on the return stroke. 235. _Q_--But in what way can these reciprocations of the barrel determine the power of the engine? _A._--They do not determine it of themselves, but are only part of the operation. In the inside of the cylinder _c_ there is a small piston moving steam tight in a cylinder of which _d_ is the piston rod, and _e_ a spiral spring of steel, which the piston, when forced upwards by the steam or sucked downwards by the vacuum, either compresses or extends; _f_ is a cock attached to the cylinder of the indicator, and which is screwed into the cylinder cover. It is obvious that, so soon as this cock is opened, the piston will be forced up when the space above the piston of the engine is opened to the boiler, and sucked down when that space is opened to the condenser--in each case to an extent proportionate to the pressure of the steam or the perfection of the vacuum, the top of the piston _c_ being open to the atmosphere. A pencil, _p_, with a knife hinge, is inserted into the piston rod, at _e_, and the point of the pencil bears upon the surface of the paper wound upon the drum A. If the drum A did not revolve, this pencil would merely trace on the paper a vertical line; but as the drum A moves round and back again every stroke of the engine, and as the pencil moves up and down again every stroke of the engine, the combined movements trace upon the paper a species of rectangle, which is called an indicator diagram; and the nature of this diagram determines the nature of the engine's performance. 236. _Q._--How does it do this? _A._--It is clear that if the pencil was moved up instantaneously to the top of its stroke, and was also moved down instantaneously to the bottom of its stroke, and if it remained without fluctuation while at the top and bottom, the figure described by the pencil would be a perfect rectangle, of which the vertical height would represent the total pressure of the steam and vacuum, and therefore the total pressure urging the piston of the engine. But in practice the pencil will neither rise nor fall instantaneously, nor will it remain at a uniform height throughout the stroke. If the steam be worked expansively the pressure will begin to fall so soon as the steam is cut off; and at the end of the stroke, when the steam comes to be discharged, the subsidence of pressure will not be instantaneous, but will occupy an appreciable time. It is clear, therefore, that in no engine can the diagram described by an indicator be a complete rectangle; but the more nearly it approaches to a rectangle, the larger will be the power produced at every stroke with any given pressure, and the area of the space included within the diagram will in every case accurately represent the power exerted by the engine during that stroke. 237. _Q._--And how is this area ascertained? _A._--It may be ascertained in various ways; but the usual mode is to take the vertical height of the diagram at a number of equidistant points on a base line, and then to take the mean of these several heights as representative of the mean pressure actually urging the piston. Now if you have the pressure on the piston per square inch, and if you know the number of square inches in its area, and the velocity with which it moves in feet per minute, you have obviously the dynamical effort of the engine, or, in other words, its actual power. 238. _Q._--How is the base line you have referred to obtained? _A._--In proceeding to take an indicator diagram, the first thing to be done is to allow the barrel to make two or three reciprocations with the pencil resting against it, before opening the cock attached to the cylinder. There will thus be traced a horizontal line, which is called the _atmospheric line_, and in condensing engines, a part of the diagram will be above and a part of it below this line; whereas, in high pressure engines the whole of the diagram will be above this line. Upon this line the vertical ordinates may be set off at equal distances, or upon any base line parallel to it; but the usual course is to erect the ordinates on the atmospheric line. 239. _Q._--Will you give an example of an indicator diagram? [Illustration: Fig. 37] _A._--Fig. 37 is an indicator diagram taken from a low pressure engine, and the waving line _a b c_, forming a sort of irregular parallelogram, is that which is described by the pencil. The atmospheric line is represented by the line o o. The scale at the side shows the pressure of the steam, which in this engine rose to about 9 lbs. per square inch, and the vacuum fell to 11 lbs. The steam begins to be cut off when, about one-fourth of the stroke has been performed, and the pressure consequently falls. 240. _Q._--Is this species of indicator which you have just described applicable to locomotive engines? _A._--It is no doubt applicable under suitable conditions; but another species of indicator has been applied by Mr. Gooch to locomotive engines, which presents several features of superiority for such a purpose. This indicator has its cylinder placed horizontally; and its piston compresses two elliptical springs; a slide valve is substituted for a cock, to open or close the communication with the engine. The top of the piston rod of this indicator is connected to the short arm of a smaller lever, to the longer arm of which the pencil is attached, and the pencil has thus a considerably larger amount of motion than the piston; but it moves in the arc of a circle instead of in a straight line. The pencil marks on a web of paper, which is unwound from one drum and wound on to another, so that a succession of diagrams are taken without the necessity of any intermediate manipulation. 241. _Q._--These diagrams being taken with a pencil moving in an arc, will be of a distorted form? _A._--They will not be of the usual form, but they may be easily translated into the usual form. It is undoubtedly preferable that the indicator should act immediately in the production of the final form of diagram. DYNAMOMETER, GAUGES, AND CATARACT. 242. _Q._--What other gauges or instruments are there for telling the state, or regulating the power of an engine? _A._--There is the counter for telling the number of strokes the engine makes, and the dynamometer for ascertaining the tractive power of steam vessels or locomotives; then there are the gauge cocks, and glass tubes, or floats, for telling the height of water in the boiler; and in pumping engines there is the cataract for regulating the speed of the engine. 243. _Q._--Will you describe the mechanism of the counter? _A._--The counter consists of a train of wheel work, so contrived that by every stroke of the engine an index hand is moved forward a certain space, whereby the number of strokes made by the engine in any given time is accurately recorded. In most cases the motion is communicated by means of a detent,--attached to some reciprocating part of the engine,--to a ratchet wheel which gives motion to the other wheels in its slow revolution; but it is preferable to derive the motion from some revolving part of the engine by means of an endless screw, as where the ratchet is used the detent will sometimes fail to carry it round the proper distance. In the counter contrived by Mr. Adie, an endless screw works into the rim of two small wheels situated on the same axis, but one wheel having a tooth more than the other, whereby a differential motion is obtained; and the difference in the velocity of the two wheels, or their motion upon one another, expresses the number of strokes performed. The endless screw is attached to some revolving part of the engine, whereby a rotatory motion is imparted to it; and the wheels into which the screws work hang down from it like a pendulum, and are kept stationary by the action of gravity. 244. _Q._--What is the nature of the dynamometer? _A._--The dynamometer employed for ascertaining the traction upon railways consists of two flat springs joined together at the ends by links, and the amount of separation of the springs at the centre indicates, by means of a suitable hand and dial, the force of traction. A cylinder of oil, with a small hole through its piston, is sometimes added to this instrument to prevent sudden fluctuations. In screw vessels the forward thrust of the screw is measured by a dynamometer constructed on the principle of a weighing machine, in which a small spring pressure at the index will balance a very great pressure where the thrust is employed; and in each case the variations of pressure are recorded by a pencil on a sheet of paper, carried forward by suitable mechanism, whereby the mean thrust is easily ascertained. The tractive force of paddle wheel steamers is ascertained by a dynamometer fixed on shore, to which the floating vessel is attached by a rope. Sometimes the power of an engine is ascertained by a friction break dynamometer applied to the shaft. 345. _Q._--What will determine the amount of thrust shown by the dynamometer? _A._--In locomotives and in paddle steamers it will be determined by the force turning the wheels, and by the smallness of the diameter of the wheels; for with small wheels the thrust will be greater than with large wheels. In screw vessels the thrust will be determined by the force turning round the screw, and by the smallness of the screw's pitch; for with any given force of torsion a fine pitch of screw will give a greater thrust than a coarse pitch of screw, just as is the case when a screw works in a solid nut. 246. _Q._--Will you explain the use of the glass gauges affixed to the boiler? _A._--The glass gauges are tubes affixed to the fronts of boilers, by the aid of which the height of the water within the boilers is readily ascertainable, for the water will stand at the same height in the tube as in the boiler, with which there is a communication maintained both at the top and bottom of the tube by suitable stopcocks. The cocks connecting the glass tube with the boiler should always be so constructed that the tube may be blown through with the steam, to clear it of any internal concretion that may impair its transparency; and the construction of the sockets in which the tube is inserted should be such, that, even when there is steam in the boiler, a broken tube may be replaced with facility. 247. _Q._--What then are the gauge cocks? _A._--The gauge cocks are cocks penetrating the boiler at different heights, and which, when opened, tell whether it is water or steam that exists at the level at which they are respectively inserted. It is unsafe to trust to the glass gauges altogether as a means of ascertaining the water level, as sometimes they become choked, and it is necessary, therefore, to have gauge cocks in addition; but if the boiler be short of steam, and a partial vacuum be produced within it, the glass gauges become of essential service, as the gauge cocks will not operate in such a case, for though opened, instead of steam and water escaping from them, the air will rush into the boiler. It is expedient to carry a pipe from the lower end of the glass tube downward into the water of the boiler, and a pipe from the upper end upward into the steam in the boiler, so as to prevent the water from boiling down through the tube, as it might otherwise do, and prevent the level of the water from being ascertainable. The average level of water in the boiler should be above the centre of the tube; and the lowest of the gauge cocks should always run water, and the highest should always blow steam. 248. _Q._--Is not a float sometimes employed to indicate the level of the water in the boiler? _A._--A float for telling the height of water in the boiler is employed only in the case of land boilers, and its action is like that of a buoy floating on the surface, which, by means of a light rod passing vertically through the boiler, shows at what height the water stands. The float is usually formed of stone or iron, and is so counterbalanced as to make its operation the same as if it were a buoy of timber; and it is generally put in connection with the feed valve, so that in proportion as the float rises, the supply of feed water is diminished. The feed water in land boilers is admitted from a small open cistern, situated at the top of an upright or stand pipe set upon the boiler, and in which there is a column of water sufficiently high to balance the pressure of the steam. 249. _Q._--What is the cataract which is employed to regulate the speed of pumping engines? [Illustration: Fig. 38. ] _A._--The cataract consists of a small pump-plunger _b_ and barrel, set in a cistern of water, the barrel being furnished on the one side with a valve, _c_, opening inwards, through which the water obtains admission to the pump chamber from the cistern, and on the other by a plug, _d_, through which, if the plunger be forced down, the water must pass out of the pump chamber. The engine in the upward stroke of the piston, which is accomplished by the preponderance of weight at the pump end of the beam, raises up the plunger of the cataract by means of a small rod,--the water entering readily through the valve already referred to; and when the engine reaches the top of the stroke, it liberates the rod by which the plunger has been drawn up, and the plunger then descends by gravity, forcing out the water through the cock, the orifice of which has previously been adjusted, and the plunger in its descent opens the injection valve, which causes the engine to make a stroke. 250. _Q._--Suppose the cock of the cataract be shut? _A._--If the cock of the cataract be shut, it is clear that the plunger cannot descend at all, and as in that case the injection valve cannot be opened, the engine must stand still; but if the cock be slightly opened, the plunger will descend slowly, the injection valve will slowly open, and the engine will make a gradual stroke as it obtains the water necessary for condensation. The extent to which the cock is open, therefore, will regulate the speed with which the engine works; so that, by the use of the cataract, the speed of the engine may be varied to suit the variations in the quantity of water requiring to be lifted from the mine. In some cases an air cylinder, and in other cases an oil cylinder, is employed instead of the apparatus just described; but the principle on which the whole of these contrivances operate is identical, and the only difference is in the detail. 251. _Q._--You have now shown that the performance of an engine is determinable by the indicator; but how do you determine the power of the boiler? _A._--By the quantity of water it evaporates. There is, however, no very convenient instrument for determining the quantity of water supplied to a boiler, and the consequence is that this element is seldom ascertained. CHAPTER V. PROPORTION OF BOILERS. HEATING AND FIRE GRATE SURFACE. 252. _Q._--What are the considerations which must chiefly be attended to in settling the proportions of boilers? _A._--In the first place there must be sufficient grate surface to enable the quantity of coal requisite for the production of the steam to be conveniently burnt, taking into account the intensity of the draught; and in the next place there must be a sufficient flue surface readily to absorb the heat thus produced, so that there may be no needless waste of heat by the chimney. The flues, moreover, must have such an area, and the chimney must be of such dimensions, as will enable a suitable draught through the fire to be maintained; and finally the boiler must be made capable of containing such supplies of water and steam as will obviate inconvenient fluctuations in the water level, and abate the risk of water being carried over into the engine with the steam. With all these conditions the boiler must be as light and compact as possible, and must be so contrived as to be capable of being cleaned and repaired with facility. 253. _Q._--Supposing, then, that you had to proportion a boiler, which should be capable of supplying steam sufficient to propel a steam vessel or railway train at a given speed, or to perform any other given work, how would you proceed? _A._--I would first ascertain the resistance which had to be overcome, and the velocity with which it was necessary to overcome it. I should then be in a position to know what pressure and volume of steam were required to overcome the resistance at the prescribed rate of motion; and, finally, I should allow a sufficient heating and fire grate surface in the boiler according to the kind of boiler it was, to furnish the requisite quantity of steam, or, in other words, to evaporate the requisite quantity of water. 254. _Q._--will you state the amount of heating surface and grate surface necessary to evaporate a given quantity of water? _A._--The number of square feet of heating or flue surface, required to evaporate a cubic foot of water per hour, is about 70 square feet in Cornish boilers, 8 to 11 square feet in land and marine boilers, and 5 or 6 square feet in locomotive boilers. The number of square feet of heating surface per square foot of fire grate, is from 13 to 15 square feet in wagon boilers; about 40 square feet in Cornish boilers; and from 50 to 90 square feet in locomotive boilers. About 80 square feet in locomotives is a very good proportion. 255. _Q._--What is the heating surface of boilers per horse power? _A._--About 9 square feet of flue and furnace surface per horse power is the usual proportion in wagon boilers, reckoning the total surface as effective surface, if the boilers be of a considerable size; but in the case of small boilers the proportion is larger. The total heating surface of a two horse power wagon boiler is, according to Boulton and Watt's proportions, 30 square feet, or 15 ft. per horse power; whereas, in the case of a 45 horse power boiler the total heating surface is 438 square feet, or 9.6 ft. per horse power. In marine boilers nearly the same proportions obtain. The original boilers of the Great Western steamer, by Messrs. Maudslay, were proportioned with about 10 square feet of flue and furnace surface per horse power, reckoning the total amount as effective; but in the boilers of the Retribution, by the same makers, but of larger size, a somewhat smaller proportion of heating surface was adopted. Boulton and Watt have found that in their marine flue boilers, 9 square feet of flue and furnace surface are requisite to boil off a cubic foot of water per hour, which is the proportion of heating surface that is allowed in their land boilers per horse power; but inasmuch as in most modern engines, and especially in marine engines, the nominal considerably exceeds the actual power, they allow 11 or 12 square feet of heating surface per nominal horse power in their marine boilers, and they reckon as effective heating surface the tops of the flues, and the whole of the sides of the flues, but hot the bottoms. For their land engines they still retain Mr. Watt's standard of power, which makes the actual and the nominal power identical; and an actual horse power is the equivalent of a cubic foot of water raised into steam every hour. 256. _Q._--What is the proper proportion of fire grate per horse power? _A._--Boulton and Watt allow 0.64 of a square foot area of grate bars per nominal horse power in their marine boilers, and a good effect arises from this proportion; but sometimes so large an area of fire grate cannot be conveniently got, and the proportion of half a square foot per horse power, which is the proportion adopted in the original boiler of the Great Western, seems to answer very well in engines working with a moderate pressure, and with some expansion; and this proportion is now very widely adopted. With this allowance, there will be 22 to 24 square feet of heating surface per square foot of fire grate; and if the consumption of fuel be taken at 6 lbs. per nominal horse power per hour, there will be about 12 lbs. of coal consumed per hour on each square foot of grate. The furnaces should not be more than 6 ft. long, as, if much longer than this, it will be impossible to work them properly for any considerable length of time, as they will become choked with clinker at the back ends. 257. _Q._--What quantity of fuel is usually consumed per hour on each square foot of fire grate? _A._--The quantity of fuel burned on each square foot of fire grate per hour, varies very much in different boilers; in wagon boilers it is from 10 to 13 lbs.; in Cornish boilers from 3-1/2 to 4 lbs.; and in locomotive boilers from 80 to 150 lbs.; but about 1 cwt. per hour is a good proportion in locomotives, as has been already explained. CALORIMETER AND VENT. 258. _Q._--In what manner are the proper sectional area and the proper capacity of the flue of a boiler determined? _A._--The proper collective area for the escape of the smoke and flame over the furnace bridges in marine boilers is 19 square inches per nominal horse power, according to Boulton and Watt's practice, and for the sectional area of the flue they allow 18 square inches per horse power. The sectional area of the flue in square inches is what is termed the _calorimeter_ of the boiler, and the calorimeter divided by the length of the flue in feet is what is termed the _vent_. In marine flue boilers of good construction the vent varies between the limits of 20 and 25, according to the size of the boiler and other circumstances--the largest boilers having generally the largest vents; and the calorimeter divided by the vent will give the length of the flue in feet. The flues of all flue boilers diminish in their calorimeter as they approach the chimney, as the smoke contracts in its volume in proportion as it parts with its heat. 259. _Q._--Is the method of determining the dimensions of a boiler flue, by a reference to its vent and calorimeter, the method generally pursued? _A._--It is Boulton and Watt's method; but some very satisfactory boilers have been made by allowing a proportion of 0.6 of a square foot of fire grate per nominal horse power, and making the sectional area of the flue at the largest part 1/7th of the area of fire grate, and at the smallest part, where it enters the chimney, 1/11th of the area of the fire grate. These proportions are retained whether the boiler is flue or tubular, and from 14 to 16 square feet of tube surface is allowed per nominal horse power. 260. _Q._--Are the proportions of vent and calorimeter, taken by Boulton and Watt for marine flue boilers, applicable also to wagon and tubular boilers? _A._--No. In wagon and tubular boilers very different proportions prevail, yet the proportions of every kind of boiler are determinable on the same general principle. In wagon boilers the proportion of the perimeter of the flue which is effective as heating surface, is to the total perimeter as 1 to 3, or, in some cases as 1 to 2.5; and with any given area of flue, therefore, the length of the flue must be from 3 to 2.5 times greater than would be necessary if the total surface were effective, else the requisite quantity of heating surface will not be obtained. If, then, the vent be the calorimeter, divided by the length, and the length be made 3 or 2.5 times greater, the vent must become 3 or 2.5 times less; and in wagon boilers accordingly, the vent varies from 8 to 11 instead of from 21 to 25, as in the case of marine flue boilers. In tubular marine boilers the calorimeter is usually made only about half the amount allowed by Boulton and Watt for marine flue boilers, or, in other words, the collective sectional area of the tubes, for the transmission of the smoke, is from 8 to 9 square inches per nominal horse power. It is better, however, to make the sectional area larger than this, and to work the boiler with the damper sufficiently closed to prevent the smoke and flame from rushing exclusively through a few of the tubes. 261. _Q._--What are the ordinary dimensions of the flue in wagon boilers? _A._--In Boulton and Watt's 45 horse wagon boiler the area of flue is 18 square inches per horse power, but the area per horse power increases very rapidly as the size of the boiler becomes less, and amounts to about 80 square inches per horse power in a boiler of 2 horse power. Some such increase is obviously inevitable, if a similar form of flue be retained in the larger and smaller powers, and at the same time the elongation of the flue in the same proportion as the increase of any other dimension is prevented; but in the smaller class of wagon boilers the consideration of facility of cleaning the flues is also operative in inducing a large proportion of sectional area. Boulton and Watt's 2 horse power wagon boiler has 30 square feet of surface, and the flue is 18 inches high above the level of the boiler bottom, by 9 inches wide; while their 12 horse wagon boiler has 118 square feet of heating surface, and the dimensions of the flue similarly measured are 36 inches by 13 inches. The width of the smaller flue, if similarly proportioned to the larger one, would be 6-1/2 inches, instead of 9 inches, and, by assuming this dimension, we should have the same proportion of sectional area per square foot of heating surface in both boilers. The length of flue in the 2 horse boiler is 19.5 ft., and in the 12 horse boiler 39 ft., so that the length and height of the flue are increased in the same proportion. 262. _Q._--Will you give an example of the proportions of a flue, in the case of a marine boiler? _A._--The Nile steamer, with engines of 110 horse power by Boulton and Watt, is supplied with steam by two boilers, which are, therefore, of 55 horses power each. The height of the flue winding within the boiler is 60 inches, and its mean width 16-1/2 inches, making a sectional area or calorimeter of 990 square inches, or 18 square inches per horse power of the boiler. The length of the flue is 39 ft., making the vent 25, which is the vent proper for large boilers. In the Dee and Solway steamers, by Scott and Sinclair, the calorimeter is only 9.72 square inches per horse power; in the Eagle, by Caird, 11.9; in the Thames and Medway, by Maudslay, 11.34, and in a great number of other cases it does not rise above 12 square inches per horse power; but the engines of most of these vessels are intended to operate to a certain extent expansively, and the boilers are less powerful in evaporating efficacy on that account. 263. _Q._--Then the chief difference in the proportions established by Boulton and Watt, and those followed by the other manufacturers you have mentioned is, that Boulton and Watt set a more powerful boiler to do the same work? _A._--That is the main difference. The proportion which one part of the boiler bears to another part is very similar in the cases cited, but the proportion of boiler relatively to the size of the engine varies very materially. Thus the calorimeter _of each boiler_ of the Dee and Solway is 1296 square inches; of the Eagle, 1548 square inches; and of the Thames and Medway, 1134 square inches; and the length of flue is 57, 60, and 52 ft. in the boilers respectively, which makes the respective vents 22-1/2, 25, and 21. Taking then the boiler of the Eagle for comparison with the boiler of the Nile, as it has the same vent, it will be seen that the proportions of the two are almost identical, for 990 is to 1548 as 39 is to 60, nearly; but Messrs. Boulton and Watt would not have set a boiler like that of the Eagle to do so much work. 264. _Q._--Then the evaporating power of the boiler varies as the sectional area of the flue? _A._--The evaporating power varies as the square root of the area of the flue, if the length of the flue remain the same; but it varies as the area simply, if the length of the flue be increased in the same proportion as its other dimensions. The evaporating power of a boiler is referable to the amount of its heating surface, and the amount of heating surface in any flue or tube is proportional to the product of the length of the tube and the square root of its sectional area, multiplied by a certain quantity that is constant for each particular form. But in similar tubes the length is proportional to the square root of the sectional area; therefore, in similar tubes, the amount of heating surface is proportional to the sectional area. On this area also depends the quantity of hot air passing through the flue, supposing the intensity of the draught to remain unaffected, and the quantity of hot air or smoke passing through the flue should vary in the same ratio as the quantity of surface. 265. _Q._--A boiler, therefore, to exert four times the power, should have four times the extent of heating surface, and four times the sectional area of flue for the transmission of the smoke? _A._--Yes; and if the same form of flue is to be retained, it should be of twice the diameter and twice the length; or twice the height and width if rectangular, and twice the length. As then the diameter or square root of the area increases in the same ratio as the length, the square root of the area divided by the length ought to be a constant quantity in each type of boiler, in order that the same proportions of flue may be retained; and in wagon boilers without an internal flue, the height in inches of the flue encircling the boiler divided by the length of the flue in feet will be 1 very nearly. Instead of the square root of the area, the effective perimeter, or outline of that part of the cross section of the flue which is effective in generating steam, may be taken; and the effective perimeter divided by the length ought to be a constant quantity in similar forms of flues and with the same velocity of draught, whatever the size of the flue may be. 266. _Q._--Will this proportion alter if the form of the flue be changed? _A._--It is clear, that with any given area of flue, to increase the perimeter by adopting a different shape is tantamount to a diminution of the length of the flue; and, if the perimeter be diminished, the length of the flue must at the same time be increased, else it will be impossible to obtain the necessary amount of heating surface. In Boulton and Watt's wagon boilers, the sectional area of the flue in square inches per square foot of heating surface is 5.4 in the two horse boiler; in the three horse it is 4.74; in the four horse, 4.35; six horse, 3.75; eight horse, 4.33; ten horse, 3.96; twelve horse, 3.63; eighteen horse, 3.17; thirty horse, 2.52; and in the forty-five horse boiler, 2.05 square inches. Taking the amount of heating surface in the 45 horse boiler at 9 square feet per horse power, we obtain 18 square inches of sectional area of flue per horse power, which is also Boulton and Watt's proportion of sectional area for marine boilers with internal flues. 267. _Q._--If to increase the perimeter of a flue is virtually to diminish the length, then a tubular boiler where the perimeter is in effect greatly extended ought to have but a short length of tube? _A._--The flue of the Nile steamer if reduced to the cylindrical form would be 35-1/2 inches in diameter to have the same area; but it would then require to be made 47-3/4 feet long, to have the same amount of heating surface, excluding the bottom as non-effective. Supposing that with these proportions the heat is sufficiently extracted from the smoke, then every tube of a tubular boiler in which the same draught existed ought to have very nearly the same proportions. 268. _Q._--But what are the best proportions of the parts of tubular boilers relatively with one another? _A._--The proper relative proportions of the parts of tubular boilers may easily be ascertained by a reference to the settled proportions of flue boilers; for the same general principles are operative in both cases. In the Nile steamer each boiler of 55 horse power has about 497 square feet of flue surface or 9 square feet per horse power, reckoning the total surface as effective. The area of the flue, which is rectangular is 990 square inches, therefore the area is equal to that of a tube 35-1/2 inches in diameter; and such a tube, to have a heating surface of 497 square feet, must be 53.4 feet or 640.8 inches in length. The length, therefore, of the tube, will be about 18 times its diameter, and with the same velocity of draught these proportions must obtain, whatever the absolute dimensions of the tube may be. With a calorimeter, therefore, of 18 square inches per horse power, the length of a tube 3 inches diameter must not exceed 4 feet 6 inches, since the heat will be sufficiently extracted from the smoke in this length, if the smoke only travels at the velocity due to a calorimeter of 18 square inches per horse power. 269. _Q._--Is this, then, the maximum length of flue which can be used in tubular boilers with advantage? _A._--By no means. The tubes of tubular boilers are almost always more than 4 feet 6 inches long, but then the calorimeter is almost always less than 18 square inches per horse power--generally about two thirds of this. Indeed, tubular boilers with a large calorimeter are not found to be so satisfactory as where the calorimeter is small, partly from the propensity of the smoke in such cases to pass through a few of the tubes instead of the whole of them, and partly from the deposit of soot which takes place when the draught is sluggish. It is a very confusing practice, however, to speak of nominal horse power in connection with boilers, since that is a quantity quite indeterminate. EVAPORATIVE POWER OF BOILERS. 270. _Q._--The main thing after all in boilers is their evaporative powers? _A._--The proportions of tubular boilers, as of all boilers, should obviously have reference to the evaporation required, whereas the demand upon the boiler for steam is very often reckoned contingent upon the nominal horse power of the engine; and as the nominal power of an engine is a conventional quantity by no means in uniform proportion to the actual quantity of steam consumed, perplexing complications as to the proper proportions of boilers have in consequence sprung up, to which most of the failures in that department of engineering may be imputed. It is highly expedient, therefore, in planning boilers for any particular engine, to consider exclusively the actual power required to be produced, and to apportion the capabilities of the boiler accordingly. 271. _Q._--In other words you would recommend the inquiry to be restricted to the mode of evaporating a given number of cubic feet of water in the hour, instead of embracing the problem how an engine of a given nominal power was to be supplied with steam? _A._--I would first, as I have already stated, consider the actual power required to be produced, and then fix the amount of expansion to be adopted. If the engine had to work up to three times its nominal power, as is now common in marine engines, I should either increase correspondingly the quantity of evaporating surface in the boiler, or adopt such an amount of expansion as would increase threefold the efficacy of the steam, or combine in a modified manner both of these arrangements. Reckoning the evaporation of a cubic foot of water in the hour as equivalent to an actual horse power, and allowing a square yard or 9 square feet as the proper proportion of flue surface to evaporate a cubic foot of water in the hour, it is clear that I must either give 27 square feet of heating surface in the boiler to have a trebled power without expansion, or I must cut off the steam at one seventh of the stroke to obtain a three-fold power without increasing the quantity of heating surface. By cutting off the steam, however, at one third of the stroke, a heating surface of 13-1/2 square feet will give a threefold power, and it will usually be the most judicious course to carry the expansion as far as possible, and then to add the proportion of heating surface necessary to make good the deficiency still found to exist. 272. _Q._--But is it certain that a cubic foot of water evaporated in the hour is equivalent to an actual horse power? _A._--An actual horse power as fixed by Watt is 33,000 lbs. raised one foot high in the minute; and in Watt's 40 horse power engine, with a 31-1/2 inch cylinder, 7 feet stroke, and making 17-1/2 strokes a minute, the effective pressure is 6.92 lbs. on the square inch clear of all deductions. Now, as a horse power is 33,000 lbs. raised one foot high, and as there are 6.92 lbs, on the square inch, it is clear that 33,000 divided by 6.92, on 4768 square inches with 6.92 lbs. on each if lifted 1 foot or 12 inches high, will also be equal to a horse power. But 4768 square inches multiplied by 12 inches in height is 57224.4 cubic inches, or 33.1 cubic feet, and this is the quantity of steam which must be expended per minute to produce an actual horse power. 273. _Q._--But are 33 cubic feet of steam expended per minute equivalent to a cubic foot of water expended in the hour? _A._.--Not precisely, but nearly so. A cubic foot of water produces 1669 cubic feet of steam of the atmospheric density of 15 lbs. per square inch, whereas a consumption of 33 cubic feet of steam in the minute is 1980 cubic feet in the hour. In Watt's engines about one tenth was reckoned as loss in filling the waste spaces at the top and bottom of the cylinder, making 1872 cubic feet as the quantity consumed per hour without this waste; and in modern engines the waste at the ends of the cylinder is inconsiderable. 274. _Q._--What power was generated by a cubic foot of water in the case of the Albion Mill engines when working without expansion? _A._--In the Albion Mill engines when working without expansion, it was found that 1 lb. of water in the shape of steam raised 28,489 lbs. 1 foot high. A cubic foot of water, therefore, or 62-1/2 lbs., if consumed in the hour, would raise 1780562.5 lbs. one foot high in the hour, or would raise 29,676 lbs. one foot high in a minute; and if to this we add one tenth for waste at the ends of the cylinder, a waste which hardly exists in modern engines, we have 32,643 lbs. raised one foot high in the minute, or a horse power very nearly. In some cases the approximation appears still nearer. Thus, in a 40 horse engine working without expansion, Watt found that .674 feet of water were evaporated from the boiler per minute, which is just a cubic foot per horse power per hour; but it is not certain in this case that the nominal and actual power were precisely identical. It will be quite safe, however, to reckon an actual horse power as producible by the evaporation of a cubic foot of water in the hour in the case of engines working without expansion; and for boiling off this quantity in flue or wagon boilers, about 8 lbs. of coal will be required and 9 square feet of flue surface. MODERN MARINE AND LOCOMOTIVE BOILERS. 275. _Q._--These proportions appear chiefly to refer to old boilers. I wish you to state what are the proportions of modern flue and tubular marine boilers. _A._--In modern marine boilers the area of fire grate is less than in Mr. Watt's original boilers, where it was one square foot to nine square feet of heating surface. The heat in the furnace is consequently more intense, and a somewhat less amount of surface suffices to evaporate a cubic foot of water. In Boulton and Watt's modern flue boilers they allow for the evaporation of a cubic foot of water 8 square feet of heating surface, 70 square inches of fire grate, 13 square inches sectional area of flues, 6 square inches sectional area of chimney, 14 square inches area over furnace bridges, ratio of area of flue to area of fire grate 1 to 5.4. To evaporate a cubic foot of water per hour in tubular boilers, the proportions are-- heating surface 9 square feet, fire grate 70 square inches, sectional area of tubes 10 square inches, sectional area of back uptake 12 square inches, sectional area of front uptake 10 square inches, sectional area of chimney 7 square inches, ratio of diameter of tube to length of tube 1/28th to 1/30th, cubical content of boiler exclusive of steam chest 6.5 cubic feet, cubical content of steam chest 1.5 cubic feet. 276. _Q._--These proportions do not apply to locomotive boilers? _A._--Not at all. In locomotive boilers the draught is maintained by the projection of the waste steam which escapes from the cylinders up the chimney, and the draught is much more powerful and the combustion much more rapid than in cases in which the combustion is maintained by the natural draught of a chimney, except indeed the chimney be of very unusual temperature and height. The proportions proper for locomotive boilers will be seen by the dimensions of a few locomotives of approved construction, which have been found to give satisfactory results in practice, and which are recorded in the following Table: Name of Engine Great Britain. Pallas. Snake. Sphinx. Diameter of cylinder 18 in. 15 in. 14-1/4 in. 18 in. Length of stroke 24 in. 20 in. 21 in. 24 in. Diameter of driving wheel 8 ft. 6 ft. 6-1/2 ft. 5 ft. Inside diameter of fire box 53 in. 55 in. 41-1/3 in. 44 in. Inside width of fire box 63 in. 42 in. 43-1/4 in. 39-1/2in. Height of fire box above bars 63 in. 52 in. 48-1/3 in. 55-1/2in. Number of fire bars 29 ... 32 16 Thickness of fire bars 3/4 in. 1-3/4 in. 5/8 in. 1 in. Number of Tubes 305 134 181 142 Outside diameter of tubes 2 in. 2 in. 1-7/8 in. 2-1/8 in. Length of tubes 11 ft 3 in 10 ft 6 in 10 ft 3-1/2 in. 14 ft 3-1/4 in. Space between tubes 1/2 in. 3/4 in. 1/2 in. Inside diameter of ferules 1-9/16 in. 1-1/2 in. 1-5/16 in. 1-5/8 in. Diameter of chimney 17 in. 15 in. 13 in. 15-1/2 in. Diameter of blast orifice 5-1/2 in. 4-5/8 in. 4-1/2 in. 4-3/4 in. Area of grate 21 sq. ft. 16.04 sqft 12.4 sq. ft. 10.56 sq. ft Area of air space of grate 11.4 sqft 4.08 sqft 5.54 sq. ft. 5 sq. ft. Area of tubes 5.46 sqft 2.40 sqft 2.8 sq. ft. 2.92 sq. ft. Area though ferules 4 sq. ft. 1.64 sqft 2 sq. ft. 2.04 sq. ft. Area of chimney 1.77 sqft 1.23 sqft .921 sq. ft. 1.31 sq. ft. Area of blast orifice 23.76 sqin 16.8 sqin 14.18 sq. in. 17.7 sq. in. Heating surface of tubes 1627 sqft 668.7 sqft 823 sq. ft. 864 sq. ft. THE BLAST IN LOCOMOTIVES. 277. _Q._--What is the amount of draught produced in locomotive boilers in comparison with that existing in other boilers? _A._--A good chimney of a land engine will produce a degree of exhaustion equal to from 1-1/2 to 2-1/2 inches of water. In locomotive boilers the exhaustion is in some cases equal to 12 or 13 inches of water, but from 3 to 6 inches is a more common proportion. 278. _Q._--And what force of blast is necessary to produce this exhaustion? _A._--The amount varies in different engines, depending on the sectional area of the tubes and other circumstances. But on the average, it may be asserted that such a pressure of blast as will support an inch of mercury, will maintain sufficient exhaustion in the smoke box to support an inch of water; and this ratio holds whether the exhaustion is little or great. To produce an exhaustion in the smoke box, therefore, of 6 inches of water, the waste steam would require to be of sufficient pressure to support a column of 6 inches of mercury, which is equivalent to a pressure of 3 lbs. on the square inch. 279. _Q._--How is the force of the blast determined? _A._--By the amount of contraction given to the mouth of the blast pipe, which is a pipe which conducts the waste steam from the cylinders and debouches at the foot of the chimney. If a strong blast be required, the mouth of this pipe requires to be correspondingly contracted, but such contraction throws a back pressure on the piston, and it is desirable to obtain the necessary draught with as little contraction of the blast pipe as possible. The blast pipe is generally a breeches pipe of which the legs join just before reaching the chimney; but it is better to join the two cylinders below, and to let a single pipe ascend to within 12 or 18 inches of the foot of the chimney. If made with too short a piece of pipe above the joining, the steam will be projected against each side of the chimney alternately, and the draught will be damaged and the chimney worn. The blast pipe should not be regularly tapered, but should be large in the body and gathered in at the mouth. 280. _Q._--Is a large and high chimney conducive to strength of draught in locomotives? _A._--It has not been found to be so. A chimney of three or four times its own diameter in height appears to answer fully as well as a longer one; and it was found that when in an engine with 17 inch cylinders a chimney of 15-1/4 inches was substituted for a chimney of 17-1/2 inches, a superior performance was the result. The chimney of a locomotive should have half the area of the tubes at the ferules, which is the most contracted part, and the blast orifice should have 1/10th of the area of the chimney. The sectional area of the tubes through the ferules should be as large as possible. Tubes without ferules it is found pass one fourth more air, and tubes with ferules only at the smoke box end pass one tenth more air than when there are ferules at both ends. 281. _Q._--Is the exhaustion produced by the blast as great in the fire box as in the smoke box? _A._--Experiments have been made to determine this, and in few cases has it been found to be more than about half as great as ordinary speeds; but much depends on the amount of contraction in the tubes. In an experiment made with an engine having 147 tubes of 1-3/4 inches external diameter, and 13 feet 10 inches long, and with a fire grate having an area of 9-1/2 square feet, the exhaustion at all speeds was found to be three times greater in the smoke box than in the fire box. The exhaustion in the smoke box was generally equivalent to 12 inches of water, while in the fire box it was equivalent to only 4 inches of water; showing that 4 inches were required to draw the air through the grate and 8 inches through the tubes. 282. _Q._--What will be the increase of evaporation in a locomotive from a given increase of exhaustion? _A._--The rate of evaporation in a locomotive or any other boiler will vary as the quantity of air passing through the fire, and the quantity of air passing through the fire will vary nearly as the square root of the exhaustion. With four times the exhaustion, therefore, there will be about twice the evaporation, and experiment shows that this theoretical law holds with tolerable accuracy in practice. 283. _Q._--But the same exhaustion will not be produced by a given strength of blast in all engines? _A._--No; engines with contracted fire grates and an inadequate sectional area of tubes, will require a stronger blast than engines of better proportions; but in any given engine the relations between the blast exhaustion and evaporation, hold which have been already defined. 284. _Q._--Is the intensity of the draught under easy regulation? _A._--The intensity of the draught may easily be diminished by partially closing the damper in the chimney, and it may be increased by contracting the orifice of the blast. A variable blast pipe, the orifice of which may be enlarged or contracted at pleasure, has been much used. There are various devices for this purpose, but the best appears to be that adopted in Stephenson's engine, where a conical nozzle is moved up or down within the blast pipe, which is made somewhat larger in diameter than the base of the cone, but with a ring projecting internally, against which the base of the cone abuts when the nozzle is pushed up. When the nozzle stands at the top of the pipe the whole of the steam has to pass through it, and the intensity of the blast is increased by the increased velocity thus given to the steam; whereas when the nozzle is moved downward the steam escapes through the annular opening left between the nozzle and the pipe, as well as through the nozzle itself, and the intensity of the blast is diminished by the enlargement of the opening for the escape of the steam thus made available. 285._Q._--What is the best diameter for the tubes of locomotive boilers? _A._--Bury's locomotive with 14 inch cylinders contains 92 tubes of 2-1/8th inches external diameter, and 10 feet 6 inches long; whereas Stephenson's locomotive with 15 inch cylinders contains 150 tubes of 1-5/8ths external diameter, 13 feet 6 inches long. In Stephenson's boiler, in order that the part of the tubes next the chimney may be of any avail for the generation of steam, the draught has to be very intense, which in its turn involves a considerable expenditure of power; and it is questionable whether the increased expenditure of power upon the blast, in Stephenson's long tubed locomotives, is compensated by the increased generation of steam consequent upon the extension of the heating surface. When the tubes are small in diameter they are apt to become partially choked with pieces of coke; but an internal diameter of 1-5/8ths may be employed without inconvenience if the draught be of medium intensity. 286. _Q._--Will you illustrate the relation between the length and diameter of locomotive tubes by a comparison with the proportion of flues in flue boilers? _A._--In most locomotives the velocity of the draught is such that it would require very long tubes to extract the heat from the products of combustion, if the heat were transmitted through the metal of the tubes with only the same facility as through the iron of ordinary flue boilers. The Nile steamer, with engines of 110 nominal horses power each, and with two boilers having two independent flues in each, of such dimensions as to make each flue equivalent to 55 nominal horses power, works at 62 per cent. above the nominal power, so that the actual evaporative efficacy of each flue would be equivalent to 89 actual horses power, supposing the engines to operate without expansion; but as the mean pressure in the cylinder is somewhat less than the initial pressure, the evaporative efficacy of each flue may be reckoned equivalent to 80 actual horses power. With this evaporative power there is a calorimeter of 990 square inches, or 12.3 square inches per actual horse power; whereas in Stephenson's locomotive with 150 tubes, if the evaporative power be taken at 200 cubic feet of water in the hour, which is a large supposition, the engine will be equal to 200 actual horses power. If the internal diameter of the tubes be taken at thirteen eighths of an inch, the calorimeter per actual horse power will only be 1.1136 square inches, or in other words the calorimeter in the locomotive boiler will be 11.11 times less than in the flue boiler for the same power, so that the draught in the locomotive must be 11.11 times stronger, and the ratio of the length of the tube to its diameter 11.11 times greater than in the flue boiler, supposing the heat to be transmitted with only the same facility. The flue of the Nile would require to be 35- 1/2 inches in diameter if made of the cylindrical form, and 47-3/4 feet long; the tubes of a locomotive if 1-3/8ths inch diameter would only require to be 22.19 inches long with the same velocity of draught; but as the draught is 11.11 times faster than in a flue boiler, the tubes ought to be 246.558 inches, or about 20-1/2 feet long according to this proportion. In practice, however, they are one third less than this, which reduces the heating surface from 9 to 6 square feet per actual horse power, and this length even is found to be inconvenient. It is greatly preferable therefore to increase the calorimeter, and diminish the intensity of the draught. BOILER CHIMNEYS. 287. _Q._--By what process do you ascertain the dimensions of the chimney of a land boiler? _A._--By a reference to the volume of air it is necessary in a given time to supply to the burning fuel, and to the velocity of motion produced by the rarefaction in the chimney; for the area of the chimney requires to be such, that with the velocity due to that rarefaction, the quantity of air requisite for the combustion of the fuel shall pass through the furnace in the specified time. Thus if 200 cubic feet of air of the atmospheric density are required for the combustion of a pound of coal,--though 250 lbs. is nearer the quantity generally required,--and 10 lbs. of coal per horse power per hour are consumed by an engine, then 2000 cubic feet of air must be supplied to the furnace per horse power per hour, and the area of the chimney must be such as to deliver this quantity at the increased bulk due to the high temperature of the chimney when moving with the velocity the rarefaction within the chimney occasions, and which, in small chimneys, is usually such as to support a column of half an inch of water. The velocity with which a denser fluid flows into a rarer one is equal to the velocity a heavy body acquires in falling through a height equal to the difference of altitude of two columns of the heavier fluid of such heights as will produce the respective pressures; and, therefore, when the difference of pressure or amount of rarefaction in the chimney is known, it is easy to tell the velocity of motion which ought to be produced by it. In practice, however, these theoretical results are not to be trusted, until they have received such modifications as will make them representative of the practice of the most experienced constructors. 288. _Q._--What then is the rule followed by the most experienced constructors? _A._--Boulton and Watt's rule for the dimensions of the chimney of a land engine is as follows:--multiply the number of pounds of coal consumed under the boiler per hour by 12, and divide the product by the square root of the height of the chimney in feet; the quotient is the area of the chimney in square inches in the smallest part. A factory chimney suitable for a 20 horse boiler is commonly made about 20 in. square inside, and 80 ft. high; and these dimensions are those which answer to a consumption of 15 lbs. of coal per horse power per hour, which is a very common consumption in factory engines. If 15 lbs. of coal be consumed per horse power per hour, the total consumption per hour in a 20 horse boiler will be 300 lbs., and 300 multiplied by 12 = 3600, and divided by 9 (the square root of the height) = 400, which is the area of the chimney in square inches. It will not answer well to increase the height of a chimney of this area to more than 40 or 50 yards, without also increasing the area, nor will it be of utility to increase the area much without also increasing the height. The quantity of coal consumed per hour in pounds, multiplied by 5, and divided by the square root of the height of the chimney, is the proper collective area of the openings between the bars of the grate for the admission of air to the fire. 289. _Q._--Is this rule applicable to the chimneys of steam vessels? _A._--In steam vessels Boulton and Watt have heretofore been in the habit of allowing 8-1/2 square inches of area of chimney per horse power, but they now allow 6 square inches to 7 square inches. In some steam vessels a steam blast like that of a locomotive, but of a smaller volume, is used in the chimney, and many of the evils of a boiler deficient in draught may be remedied by this expedient, but a steam blast in a low pressure engine occasions an obvious waste of steam; it also makes an unpleasant noise, and in steam vessels it frequently produces the inconvenience of carrying the smaller parts of the coal up the chimney, and scattering it over the deck among the passengers. It is advisable, therefore, to give a sufficient calorimeter in all low pressure boilers, and a sufficient height of chimney to enable the chimney to operate without a steam jet; but it is useful to know that a steam jet is a resource in the case of a defective boiler, or where the boiler has to be urged beyond its power. STEAM ROOM AND PRIMING. 290. _Q._--What is the capacity of steam room allowed in boilers per horse power? _A._--The capacity of steam room allowed by Boulton and Watt in their land wagon boilers is 8-3/4 cubic feet per horse power in the two horse power boiler, and 5-3/4 cubic feet in the 20 horse power boiler; and in the larger class of boilers, such as those suitable for 30 and 45 horse power engines, the capacity of the steam room does not fall below this amount, and, indeed, is nearer 6 than 5-3/4 cubic feet per horse power. The content of water is 18-1/2 cubic feet per horse power in the two horse power boiler, and 15 cubic feet per horse power in the 20 horse power boiler. 291. _Q._--Is this the proportion Boulton and Watt allow in their marine boilers? _A._--Boulton and Watt in their early steam vessels were in the habit of allowing for the capacity of the steam, space in marine boilers 16 times the content of the cylinder; but as there were two cylinders, this was equivalent to 8 times the content of both cylinders, which is the proportion commonly followed in land engines, and which agrees very nearly with the proportion of between 5 and 6 cubic feet of steam room per horse power already referred to. Taking for example an engine with 23 inches diameter of cylinder and 4 feet stroke, which will be 18.4 horse power--the area of the cylinder will be 415.476 square inches, which, multiplied by 48, the number of inches in the stroke, will give 19942.848 for the capacity of the cylinder in cubic inches; 8 times this is 159542.784 cubic inches, or 92.3 cubic feet; 92.3 divided by 18.4 is rather more than 5 cubic feet per horse power. 292. _Q._--Is the production of the steam in the boiler uniform throughout the stroke of the engine? _A._--It varies with the slight variations in the pressure within the boiler throughout the stroke. Usually the larger part of the steam is produced during the first part of the stroke of the engine, for there is then the largest demand for steam, as the steam being commonly cut off somewhat before the end of the stroke, the pressure rises somewhat in the boiler during that period, and little steam is then produced. There is less necessity that the steam space should be large when the flow of steam from the boiler is very uniform, as it will be where there are two engines attached to the boiler at right angles with one another, or where the engines work at a great speed, as in the case of locomotive engines. A high steam chest too, by rendering boiling over into the steam pipes, or priming as it is called, more difficult, obviates the necessity for so large a steam space; as does also a perforated steam pipe stretching through the length of the boiler, so as not to take the steam from one place. The use of steam of a high pressure, worked expansively, has the same operation; so that in modern marine boilers, of the tubular construction, where the whole or most of these modifying circumstances exist, there is no necessity for so large a proportion of steam room as 5 or 6 cubic feet per nominal horse power, and about one, 1-1/2, or 2 cubic feet of steam room per cubic foot of water evaporated, more nearly represents the general practice. 293. _Q._--Is this the proportion of steam room adopted in locomotive boilers? _A._--No; in locomotive boilers the proportion of steam room per cubic foot of water evaporated is considerably less even than this. It does not usually exceed 1/5 of a cubic foot per cubic foot of water evaporated; and with clean water, with a steam dome a few feet high set on the barrel of the boiler, or with a perforated pipe stretching from end to end of the barrel, and with the steam room divided about equally between the barrel and the fire box, very little priming is found to occur even with this small proportion of total steam room. About 3/4 the depth of the barrel is usually filled with water, and 1/4 with steam. 294. _Q._--What is priming? _A._--Priming is a violent agitation of the water within the boiler, in consequence of which a large quantity of water passes off with the steam in the shape of froth or spray. Such a result is injurious, both as regards the efficacy of the engine, and the safety of the engine and boiler; for the large volume of hot water carried by the steam into the condenser impairs the vacuum, and throws a great load upon the air pump, which diminishes the speed and available power of the engine; and the existence of water within the cylinder, unless there be safety valves upon the cylinder to permit its escape, will very probably cause some part of the machinery to break, by suddenly arresting the motion of the piston when it meets the surface of the water,--the slide valve being closed to the condenser before the termination of the stroke, in all engines with lap upon the valves, so that the water within the cylinder is prevented from escaping in that direction. At the same time the boiler is emptied of its water too rapidly for the feed pump to be able to maintain the supply, and the flues are in danger of being burnt from a deficiency of water above them. 295. _Q._--What are the causes of priming? _A._--The causes of priming are an insufficient amount of steam room, an inadequate area of water level, an insufficient width between the flues or tubes for the ascent of the steam and the descent of water to supply the vacuity the steam occasions, and the use of dirty water in the boiler. New boilers prime more than old boilers, and steamers entering rivers from the sea are more addicted to priming than if sea or river water had alone been used in the boilers--probably from the boiling point of salt water being higher than that of fresh, whereby the salt water acts like so much molten metal in raising the fresh water into steam. Opening the safety valve suddenly may make a boiler prime, and if the safety valve be situated near the mouth of the steam pipe, the spray or foam thus created may be mingled with the steam passing into the engine, and materially diminish its effective power; but if the safety valve be situated at a distance from the mouth of the steam pipe, the quantity of foam or spray passing into the engine may be diminished by opening the safety valve; and in locomotives, therefore, it is found beneficial to have a safety valve on the barrel of the boiler at a point remote from the steam chest, by partially opening which, any priming in that part of the boiler adjacent to the steam chest is checked, and a purer steam than before pusses to the engine. 296. _Q._--What is the proper remedy for priming? _A._--When a boiler primes, the engineer generally closes the throttle valve partially, turns off the injection water, and opens the furnace doors, whereby the generation of steam is checked, and a less violent ebullition in the boiler suffices. Where the priming arises from an insufficient amount of steam room, it may be mitigated by putting a higher pressure upon the boiler and working more expansively, or by the interposition of a perforated plate between the boiler and the steam chest, which breaks the ascending water and liberates the steam. In some cases, however, it may be necessary to set a second steam chest on the top of the existing one, and it will be preferable to establish a communication with this new chamber by means of a number of small holes, bored through the iron plate of the boiler, rather than by a single large orifice. Where priming arises from the existence of dirty water in the boiler, the evil may be remedied by the use of collecting vessels, or by blowing off largely from the surface; and where it arises from an insufficient area of water level, or an insufficient width between the flues for the free ascent of the steam and the descent of the superincumbent water, the evil may be abated by the addition of circulating pipes in some part of the boiler, which will allow the water to descend freely to the place from whence the steam rises, the width of the water spaces being virtually increased by restricting their function to the transmission of a current of steam and water to the surface. It is desirable to arrange the heating surface in such a way that the feed water entering the boiler at its lowest point is heated gradually as it ascends, until toward the superior part of the flues it is raised gradually into steam; but in all cases there will be currents in the boiler for which it is proper to provide. The steam pipe proceeding to the engine should obviously be attached to the highest point of the steam chest, in boilers of every construction. 297. _Q._--Having now stated the proportions proper to be adopted for evaporating any given quantity of water in steam boilers, will you proceed to show how you would proportion a boiler to do a given amount of work? say a locomotive boiler which will propel a train of 100 tons weight at a speed of 50 miles an hour. _A._--According to experiments on the resistance of railway trains at various rates of speed, made by Mr. Gooch, of the Great Western Railway, it appears that a train weighing, with locomotive, tender, and carriages, about 100 tons, experiences, at a speed of 50 miles an hour, a resistance of about 3,000 lbs., or about 30 lbs. per ton; which resistance includes the resistance of the engine as well as that of the train. This, therefore, is the force which must be imparted at the circumference of the driving wheels, except that small part intercepted by the engine itself, and the force exerted by the pistons must be greater than that at the circumference of the driving wheel, in the proportion of their slower motion, or in the proportion of the circumference of the driving wheel to the length of a double stroke of the engine. If the diameter of the driving wheel be 5-1/2 feet, its circumference will be 17.278 feet, and if the length of the stroke be 18 inches, the length of a double stroke will be 3 feet. The pressure on the pistons must therefore be greater than the traction at the circumference of the driving wheel, in the proportion of 17.278 to 3, or, in other words, the mean pressure on the pistons must be 17,278 lbs.; and the area of cylinders, and pressure of steam, must be such as to produce conjointly this total pressure. It thus becomes easy to tell the volume and pressure of steam required, which steam in its turn represents its equivalent of water which is to be evaporated from the boiler, and the boiler must be so proportioned, by the rules already given, as to evaporate this water freely. In the case of a steam vessel, the mode of procedure is the same, and when the resistance and speed are known, it is easy to tell the equivalent value of steam. STRENGTH OF BOILERS. 298. _Q._--What strain should the iron of boilers be subjected to in working? _A._--The iron of boilers, like the iron of machines or structures, is capable of withstanding a tensile strain of from 50,000 to 60,000 lbs. upon every square inch of section; but it will only bear a third of this strain without permanent derangement of structure, and it does not appear expedient in any boiler to let the strain exceed 4,000 lbs. upon the square inch of sectional area of metal, especially if it is liable to be weakened by corrosion. 299._Q._--Have any experiments been made to determine the strength of boilers? _A._--The question of the strength of boilers was investigated very elaborately a few years ago by a committee of the Franklin Institute, in America, and it was found that the tenacity of boiler plate increased with the temperature up to 550°, at which point the tenacity began to diminish. At 32°, the cohesive force of a square inch of section was 56,000 lbs.; at 570°, it was 66,500 lbs.; at 720°, 55,000 lbs.; at 1,050°, 32,000 lbs.; at 1,240°, 22,000 lbs.; and at 1,317°, 9,000 lbs. Copper follows a different law, and appears to be diminished in strength by every addition to the temperature. At 32° the cohesion of copper was found to be 32,800 lbs. per square inch of section, which exceeds the cohesive force at any higher temperature, and the square of the diminution of strength seems to keep pace with the cube of the increased temperature. Strips of iron cut in the direction of the fibre were found to be about 6 per cent. stronger than when cut across the grain. Repeated piling and welding was found to increase the tenacity of the iron, but the result of welding together different kinds of iron was not found to be favorable. The accidental overheating of a boiler was found to reduce the ultimate or maximum strength of the plates from 65,000 to 45,000 lbs. per square inch of section, and riveting the plates was found to occasion a diminution in their strength to the extent of one third. These results, however, are not precisely the same as those obtained by Mr. Fairbairn. 300. _Q._--What were the results obtained by him? _A._--He found that boiler plate bore a tensile strain of 23 tons per square inch before rupture, which was reduced to 16 tons per square inch when joined together by a double row of rivets, and 13 tons, or about 30,000, when joined together by a single row of rivets. A circular boiler, therefore, with the ends of its plates double riveted, will bear at the utmost about 36,000 lbs. per square inch of section, or about 12,000 lbs. per square inch of section without permanent derangement of structure. 301. _Q._--What pressure do cylindrical boilers sustain in practice? _A._--In some locomotive boilers, which are worked with a pressure of 80 lbs. upon the square inch, the thickness of the plates is only 5/16ths of an inch, while the barrel of the boiler is 39 inches in diameter. It will require a length of 3.2 inches of the boiler when the plates are 5/16ths thick to make up a sectional area of one square inch, and the separating force will be 39 times 3.2 multiplied by 80, which makes the separating force 9,984 lbs., sustained by two square inches of sectional area--one on each side; or the strain is 4,992 lbs. per square inch of sectional area, which is quite as great strain as is advisable. The accession of strength derived from the boiler ends is not here taken into account, but neither is the weakening effect counted that is caused by the rivet holes. Some locomotives of 4 feet diameter of barrel and of 3/8ths iron have been worked to as high a pressure as 200 lbs. on the inch; but such feats of daring are neither to be imitated nor commended. 302._Q._--Can you give a rule for the proper thickness of cylindrical boilers? _A._--The thickness proper for cylindrical boilers of wrought iron, exposed to an internal pressure, may be found by the following rule:--multiply 2.54 times the internal diameter of the cylinder in inches by the greatest pressure within the cylinder per circular inch, and divide by 17,800; the result is the thickness in inches. If we apply this rule to the example of the locomotive boiler just given, we have 39 x 2.54 x 62.832 (the pressure per circular inch corresponding to 80 lbs. per square inch) = 6224.1379, and this, divided by 17,800, gives 0.349 as the thickness in inches, instead of 0.3125, or 5/16ths, the actual thickness. If we take the pressure per square inch instead of per circular inch, we obtain the following rule, which is somewhat simpler:--multiply the internal diameter of the cylinder in inches by the pressure in pounds per square inch, and divide the product by 8,900; the result is the thickness in inches. Both these rules give the strain about one fourth of the elastic force, or 4,450 lbs. per square inch of sectional area of the iron; but 3,000 lbs. is enough when the flame impinges directly on the iron, as in some of the ordinary cylindrical boilers, and the rule may be adapted for that strain by taking 6,000 as a divisor instead of 8,900. 303. _Q._--In marine and wagon boilers, which are not of a cylindrical form, how do you procure the requisite strength? _A._--Where the sides of the boiler are flat, instead of being cylindrical, a sufficient number of stays must be introduced to withstand the pressure; and it is expedient not to let the strain upon these stays be more than 3,000 lbs. per square inch of section, as the strength of internal stays in boilers is generally soon diminished by corrosion. Indeed, a strain at all approaching that upon locomotive boilers would be very unsafe in the case of marine boilers, on account of the corrosion, both internal and external, to which marine boilers are subject. The stays should be small and numerous rather than large and few in number, as, when large stays are employed, it is difficult to keep them tight at the ends, and oxidation of the shell follows from leakage at the ends of the stays. All boilers should be proved, when new, to twice or three times the pressure they are intended to bear, and they should be proved occasionally by the hand pump when in use, to detect any weakness which corrosion may have occasioned. 304._ Q._--Will you describe the disposition of the stays in a marine boiler? _A._--If the pressure of steam be 20 lbs. on the square inch, which is a very common pressure in tubular boilers, there will be a pressure of 2,880 lbs. on every square foot of flat surface; so that if the strain upon the stays is not to exceed 3,000 lbs. on the square inch of section, there must be nearly a square inch of sectional area of stay for every square foot of flat surface on the top and bottom, sides, and ends of the boiler. This very much exceeds the proportion usually adopted; and in scarcely any instance are boilers stayed sufficiently to be safe when the shell is composed of flat surfaces. The furnaces should be stayed together with bolts of the best scrap iron, 1-1/4 inch in diameter, tapped through both plates of the water space with thin nuts in each furnace; and it is expedient to make the row of stays, running horizontally near the level of the bars, sufficiently low to come beneath the top of the bars, so as to be shielded from the action of the fire, with which view they should follow the inclination of the bars. The row of stays between the level of the bars and the top of the furnace should be as near the top of the furnace as will consist with the functions they have to perform, so as to be removed as far as possible from the action of the heat; and to support the furnace top, cross bars may either be adopted, to which the top is secured with bolts, as in the case of locomotives, or stays tapped into the furnace top, with a thin nut beneath, may be carried to the top of the boiler; but very little dependence can be put in such stays as stays for keeping down the top of the boiler; and the top of the boiler must, therefore, be stayed nearly as much as if the stays connecting it with the furnace crowns did not exist. The large rivets passing through thimbles, sometimes used as stays for water spaces or boiler shells, are objectionable; as, from the great amount of hammering such rivets have to receive to form the heads, the iron becomes crystalline, so that the heads are liable to come off, and, indeed, sometimes fly off in the act of being formed. If such a fracture occurs between the boilers after they are seated in their place, or in any position not accessible from the outside, it will in general be necessary to empty the faulty boiler, and repair the defect from the inside. 305. _Q._--What should be the pitch or numerical distribution of the stays? _A._--The stays, where the sides of the boiler are flat, and the pressure of the steam is from 20 to 30 lbs., should be pitched about a foot or 18 inches asunder; and in the wake of the tubes, where stays cannot be carried across to connect the boiler sides, angle iron ribs, like the ribs of a ship, should be riveted to the interior of the boiler, and stays of greater strength than the rest should pass across, above, and below the tubes, to which the angle irons would communicate the strain. The whole of the long stays within a boiler should be firmly riveted to the shell, as if built with and forming a part of it; as, by the common method of fixing them in by means of cutters, the decay or accidental detachment of a pin or cutter may endanger the safety of the boiler. Wherever a large perforation in the shell of any circular boiler occurs, a sufficient number of stays should be put across it to maintain the original strength; and where stays are intercepted by the root of the funnel, short stays in continuation of them should be placed inside. BOILER EXPLOSIONS. 306. _Q._--What is the chief cause of boiler explosions? _A._--The chief cause of boiler explosions is, undoubtedly, too great a pressure of steam, or an insufficient strength of boiler; but many explosions have also arisen from the flues having been suffered to become red hot. If the safety valve of a boiler be accidentally jammed, or if the plates or stays be much worn by corrosion, while a high pressure of steam is nevertheless maintained, the boiler necessarily bursts; and if, from an insufficiency of water in the boiler, or from any other cause, the flues become highly heated, they may be forced down by the pressure of the steam, and a partial explosion may be the result. The worst explosion is where the shell of the boiler bursts; but the collapse of a furnace or flue is also very disastrous generally to the persons in the engine room; and sometimes the shell bursts and the flues collapse at the same time; for if the flues get red hot, and water be thrown upon them either by the feed pump or otherwise, the generation of steam may be too rapid for the safety valve to permit its escape with sufficient facility, and the shell of the boiler may, in consequence, be rent asunder. Sometimes the iron of the flues becomes highly heated in consequence of the improper configuration of the parts, which, by retaining the steam in contact with the metal, prevents the access of the water: the bottoms of large flues, upon which the flame beats down, are very liable to injury from this cause; and the iron of flues thus acted upon may be so softened that the flues will collapse upward with the pressure of the steam. The flues of boilers may also become red hot in some parts from the attachment of scale, which, from its imperfect conducting power, will cause the iron to be unduly heated; and if the scale be accidentally detached, a partial explosion may occur in consequence. 307. _Q._--Does the contact of water with heated metal occasion an instantaneous generation of steam? _A._--It is found that a sudden disengagement of steam does not immediately follow the contact of water with the hot metal, for water thrown upon red hot iron is not immediately converted into steam, but assumes the spheroidal form and rolls about in globules over the surface. These globules, however high the temperature of the metal may be on which they are placed, never rise above the temperature of 205°, and give off but very little steam; but if the temperature of the metal be lowered, the water ceases to retain the spheroidal form, and comes into intimate contact with the metal, whereby a rapid disengagement of steam takes place. If water be poured into a very hot copper flask, the flask may be corked up, as there will be scarce any steam produced so long as the high temperature is maintained; but so soon as the temperature is suffered to fall below 350° or 400°, the spheroidal condition being no longer maintainable, steam is generated with rapidity, and the cork will be projected from the mouth of the flask with great force. 308. _Q._--What precautions can be taken to prevent boiler explosions? _A._--One useful precaution against the explosion of boilers from too great an internal pressure, consists in the application of a steam gauge to each boiler, which will make the existence of any undue pressure in any of the boilers immediately visible; and every boiler should have a safety valve of its own, the passage leading to which should have no connection with the passage leading to any of the stop valves used to cut off the connection between the boilers; so that the action of the safety valve may be made independent of the action of the stop valve. In some cases stop valves have jammed, or have been carried from their seats into the mouth of the pipe communicating between them, and the action of the safety valves should be rendered independent of all such accidents. Safety valves, themselves, sometimes stick fast from corrosion, from the spindles becoming bent, from a distortion of the boiler top with a high pressure, in consequence of which the spindles become jammed in the guides, and from various other causes which it would be tedious to enumerate; but the inaction of the safety valves is at once indicated by the steam gauge, and when discovered, the blow through valves of the engine and blow off cocks of the boiler should at once be opened, and the fires raked out. A cone in the ball of the waste steam pipe to send back the water carried upward by the steam, should never be inserted; as in some cases this cone has become loose, and closed up the mouth of the waste steam pipe, whereby the safety valves being rendered inoperative, the boiler was in danger of bursting. 309. _Q._--May not danger arise from excessive priming? _A._--If the water be carried out of the boiler so rapidly by priming that the level of the water cannot be maintained, and the flues or furnaces are in danger of becoming red hot, the best plan is to open every furnace door and throw in a few buckets full of water upon the fire, taking care to stand sufficiently to the one side to avoid being scalded by the rush of steam from the furnace. There is no time to begin drawing the fires in such an emergency, and by this treatment the fires, though not altogether extinguished, will be rendered incapable of doing harm. If the flues be already red hot, on no account must cold water be suffered to enter the boiler, but the heat should be maintained in the furnaces, and the blow off cocks be opened, or the mud hole doors loosened, so as to let all the water escape; but at the same time the pressure must be kept quite low in the boiler, so that there will be no danger of the hot flues collapsing with the pressure of the steam. 310. _Q._--Are plugs of fusible metal useful in preventing explosions? _A._--Plugs of fusible metal were at one time in much repute as a precaution against explosion, the metal being so compounded that it melted with the heat of high pressure steam; but the device, though ingenious, has not been found of any utility in practice. The basis of fusible metal is mercury, and it is found that the compound is not homogeneous, and that the mercury is forced by the pressure of the steam out of the interstices of the metal combined with it, leaving a porous metal which is not easily fusible, and which is, therefore, unable to perform its intended function. In locomotives, however, and also in some other boilers, a lead rivet is inserted with advantage in the crown of the fire box, which is melted out if the water becomes too low, and thus gives notice of the danger. 311. _Q._--May not explosion occur in marine boilers from the accumulation of salt on the flues? _A._--Yes, in marine boilers this is a constant source of danger, which is only to be met by attention on the part of the engineer. If the water in the boiler be suffered to become too salt, an incrustation of salt will take place on the furnaces, which may cause them to become red hot, and they may then be collapsed even by their own weight aided by a moderate pressure of steam. The expedients which should be adopted for preventing such an accumulation of salt from taking place within the boiler as will be injurious to it, properly fall under the head of the management of steam boilers, and will be explained in a subsequent chapter. CHAPTER VI. PROPORTIONS OF ENGINES. * * * * * STEAM PASSAGES. 312. _Q._--What size of orifice is commonly allowed for the escape of the steam through the safety valve in low pressure engines? _A._--About 0.8 of a circular inch per horse power, or a circular inch per 1-1/4 horse power. The following rule, however, will give the dimensions suitable for all kinds of engines, whether high or low pressure:--multiply the square of the diameter of the cylinder in inches by the speed of the piston in feet per minute, and divide the product by 375 times the pressure on the boiler per square inch; the quotient is the proper area of the safety valve in square inches. This rule of course supposes that the evaporating surface has been properly proportioned to the engine power. 313. _Q._--Is this rule applicable to locomotives? _A._--It is applicable to high pressure engines of every kind. The dimensions of safety valves, however, in practice are very variable, being in some cases greater, and in some cases less, than what the rule gives, the consideration being apparently as often what proportions will best prevent the valve from sticking in its seat, as what proportions will enable the steam to escape freely. In Bury's locomotives, the safety valve was generally 2-1/2 inches diameter for all sizes of boiler, and the valve was kept down by a lever formed in the proportion of 5 to 1, fitted at one end with a Salter's balance. As the area of the valve was 5 square inches, the number of pounds shown on the spring balance denoted the number of pounds pressure on each square inch of the boiler. 314. _Q._--Is there only one safety valve in a locomotive boiler? _A._--There are always two. 315. _Q._--And are they always pressed down by a spring balance, and never by weights? _A._--They are never pressed down by weights; in fact, weights would not answer on a locomotive at all, as they would jump up and down with the jerks or jolts of the train, and cause much of the steam to escape. In land and marine boilers, however, the safety valve is always kept down by weights; but in steam vessels a good deal of steam is lost in stormy weather by the opening of the valve, owing to the inertia of the weights when the ship sinks suddenly in the deep recess between the waves. 316. _Q._--What other sizes of safety valves are used in locomotives? _A._--Some are as large as 4 inches diameter, giving 12 square inches of area; and others are as small as 1-3/16 inch diameter, giving 1 square inch of area. 317. _Q._--And are these valves all pressed down by a Salter's spring balance? _A._--In the great majority of cases they are so, and the lever by which they are pressed down is generally graduated in the proportion of the area of the valve to unity; that is, in the case of a valve of 12 inches area, the long end of the lever to which the spring balance is attached is 12 times the length of the short end, so that the weight or pressure on the balance shows the pressure per square inch on the boiler. In some cases, however, a spiral spring, and in other cases a pile of elliptical springs, is placed directly upon the top of the valve, and it appears desirable that one of the valves at least should be loaded in this manner. It is difficult when the lever is divided in such a proportion as 12 to 1, to get sufficient lift of the valve without a large increase of pressure on the spring; and it appears expedient, therefore, to employ a shorter lever, which involves either a reduction in the area of the valve, or an increased strength in the spring. 318. _Q._--What are the proper dimensions of the steam passages? _A._--In slow working engines the common size of the cylinder passages is one twenty-fifth of the area of the cylinder, or one fifth of the diameter of the cylinder, which is the same thing. This proportion corresponds very nearly with one square inch per horse power when the length of the cylinder is about equal to its diameter; and one square inch of area per horse power for the cylinder ports and eduction passages answers very well in the case of engines working at the ordinary speed of 220 feet per minute. The area of the steam pipe is usually made less than the area of the eduction pipe, especially when the engine is worked expansively, and with a considerable pressure of steam. In the case of ordinary condensing engines, however, working with the usual pressure of from 4 to 8 lbs. above the atmosphere, the area of the steam pipe is not less than a circular inch per horse power. In such engines the diameter of the steam pipe may be found by the following rule: divide the number of nominal horse power by 0.8 and extract the square root of the quotient, which will be the internal diameter of the steam pipe. 319. _Q._--Will you explain by what process of computation these proportions are arrived at? _A._--The size of the steam pipe is so regulated that there will be no material disparity of pressure between the cylinder and boiler; and in fixing the size of the eduction passage the same object is kept in view. When the diameter of the cylinder and the velocity with which the piston travels are known, it is easy to tell what the velocity of the steam in the steam pipe will be; for if the area of the cylinder be 25 times greater than that of the steam pipe, the steam in the steam pipe must travel 25 times faster than the piston, and the difference of pressure requisite to produce this velocity of the steam can easily be ascertained, by finding what height a column of steam must be to give that velocity, and what the weight or pressure is of such a column. In practice, however, this proportion is always exceeded from the condensation of steam in the pipe. 320. _Q._--If the relation you have mentioned subsist between the area of the steam passages and the velocity of the piston, then the passages must be larger when the piston travels very rapidly? _A._--And they are so made. The area of the ports of locomotive engines is usually so proportioned as to be from 1/10th to 1/8th the area of the cylinder--in some cases even as much as 1/6th; and in all high speed engines the ports should be very large, and the valve should have a good deal of travel so as to open the port very quickly. The area of port which it appears advisable to give to modern engines of every description, is expressed by the following rule:--multiply the area of the cylinder in square inches by the speed of the piston in feet per minute, and divide the product by 4,000; the quotient is the area of each cylinder port in square inches. This rule gives rather more than a square inch of port per nominal horse power to condensing engines working at the ordinary speed; but the excess is but small, and is upon the right side. For engines travelling very fast it gives a good deal more area than the common proportion, which is too small in nearly every case. In locomotive engines the eduction pipe passes into the chimney and the force of the issuing steam has the effect of maintaining a rapid draught through the furnace as before explained. The orifice of the waste steam pipe, or the blast pipe as it is termed, is much contracted in some engines with the view of producing a fiercer draught, and an area of 1/22d of the cylinder is a common proportion; but this is as much contraction as should be allowed, and is greater than is advisable. 321. _Q._--In engines moving at a high rate of speed, you have stated that it is important to give the valve lead, or in other words to allow the steam to escape before the end of the stroke? _A._--Yes, this is very important, else the piston will have to force out the steam from the cylinder, and will be much resisted. Near the end of the stroke the piston begins to travel slowly, and if the steam be then permitted to escape, very little of the effective stroke is lost, and time is afforded to the steam, before the motion of the piston is again accelerated, to make its escape by the port. In some locomotives, from inattention to this adjustment, and from a contracted area of tube section, which involved a strong blast, about half the power of the engine has been lost; but in more recent engines, by using enlarged ports and by giving sufficient lead, this loss has been greatly diminished. 322. _Q._--What do you call sufficient lead? _A._--In fast going engines I would call it sufficient lead, when the eduction port was nearly open at the end of the stroke. 323. _Q._--Can you give any example of the benefit of increasing the lead? _A._--The early locomotives were made with very little lead, and the proportions were in fact very much the same as those previously existing in land engines. About 1832, the benefits of lap upon the valve, which had been employed by Boulton and Watt more than twenty years before, were beginning to be pretty generally apprehended; and, in the following year, this expedient of economy was applied to the steamer Manchester, in the Clyde, and to some other vessels, with very marked success. Shortly after this time, lap began to be applied to the valves of locomotives, and it was found that not only was there a benefit from the operation of expansion, but that there was a still greater benefit from the superior facility of escape given to the steam, inasmuch as the application of lap involved the necessity of turning the eccentric round upon the shaft, which caused the eduction to take place before the end of the stroke. In 1840, one of the engines of the Liverpool and Manchester Railway was altered so as to have 1 inch lap on the valve, and 1 inch opening on the eduction side at the end of the stroke, the valve having a total travel of 4-1/4 inches. The consumption of fuel per mile fell from 36.3 lbs. to 28.6 lbs, or about 25 per cent., and a softer blast sufficed. By using larger exhaust passages, larger tubes, and closer fire bars, the consumption was subsequently brought down to 15 lbs. per mile. AIR PUMP, CONDENSER, AND HOT AND COLD WATER PUMPS. 324. _Q._--Will you state the proper dimensions of the air pump and condenser in laud and marine engines? _A_--Mr. Watt made the air pump of his engine half the diameter of the cylinder and half the stroke, or one eighth of the capacity, and the condenser was usually made about the same size as the air pump; but as the pressure of the steam has been increased in all modern engines, it is better to make the air pump a little larger than this proportion. 0.6 of the diameter of the cylinder and half the stroke answers very well, and the condenser may be made as large as it can be got with convenience, though the same size as the air pump will suffice. 325. _Q._--Are air pumps now sometimes made double acting? _A._--Most of the recent direct acting marine engines for driving the screw are fitted with a double acting air pump, and when the air pump is double acting, it need only be about half the size that is necessary when it is single acting. It is single acting in nearly every case, except the case of direct acting screw engines of recent construction. 326. _Q._--What is the difference between a single and a double acting air pump? _A._--The single acting air pump expels the air and water from the condenser only in the upward stroke of the pump, whereas a double acting air pump expels the air and water both in the upward and downward stroke. It has, therefore, to be provided with inlet and outlet valves at both ends, whereas the single acting pump has only to be provided with an inlet or foot valve, as it is termed, at the bottom, and with an outlet or delivery valve, as it is termed, at the top. The single acting air pump requires to be provided with a valve or valves in the piston or bucket of the pump, to enable the air and water lying below the bucket when it begins to descend, and which have entered from the condenser during the upward stroke, to pass through the bucket into the space above it during the downward stroke, from whence they are expelled into the atmosphere on the upward stroke succeeding. But in the double acting air pump no valve is required in the piston or bucket of the pump, and all that is necessary is an inlet and outlet valve at each end. 337. _Q_--What are the dimensions of the foot and discharge valves of the air pump? _A._--The area through the foot and discharge valves is usually made equal to one fourth of the area of the air pump, and the diameter of the waste water pipe is made one fourth of the diameter of the cylinder, which gives an area somewhat less than that of the foot and discharge valve passages. But this proportion only applies in slow engines. In fast engines, with the air pump bucket moving as fast as the piston, the area through the foot and discharge valves should be equal to the area of the pump itself, and the waste water pipe should be of about the same dimensions. 328. _Q._--You have stated that double acting air pumps need only be of half the size of single acting ones. Does that relation hold at all speeds? _A._--It holds at all speeds if the velocity of the pump buckets are in each case the same; but it does not hold if the engine with the single acting pump works slowly, and the engine with the double acting pump moves rapidly, as in the case of direct acting screw engines. All pumps moving at a high rate of speed lose part of their efficiency, and such pumps should therefore be of extra size. 329. _Q._--How do you estimate the quantity of water requisite for condensation? _A._--Mr. Watt found that the most beneficial temperature of the hot well of his engines was 100 degrees. If, therefore, the temperature of the steam be 212°, and the latent heat 1,000°, then 1,212° may be taken to represent the heat contained in the steam, or 1,112° if we deduct the temperature of the hot well. If the temperature of the injection water be 50°, then 50 degrees of cold are available for the abstraction of heat; and as the total quantity of heat to be abstracted is that requisite to raise the quantity of water in the steam 1,112 degrees, or 1,112 times that quantity one degree, it would raise one fiftieth of this, or 22.24 times the quantity of water in the steam, 50 degrees. A cubic inch of water therefore raised into steam will require 22.24 cubic inches of water at 50 degrees for its condensation, and will form therewith 23.24 cubic inches of hot water at 100 degrees. Mr. Watt's practice was to allow about a wine pint (28.9 cubic inches) of injection water, for every cubic inch of water evaporated from the boiler. 330. _Q._--Is not a good vacuum in an engine conducive to increased power? _A._--It is. 331. _Q._--And is not the vacuum good in the proportion in which the temperature is low, supposing there to be no air leaks? _A._--Yes. 332. _Q._--Then how could Mr. Watt find a temperature of 100° in the water drawn from the condenser, to be more beneficial than a temperature of 70° or 80°, supposing there to be an abundant supply of cold water? 333. _A._--Because the superior vacuum due to a temperature of 70° or 80° involves the admission of so much cold water into the condenser, which has afterward to be pumped out in opposition to the pressure of the atmosphere, that the gain in the vacuum does not equal the loss of power occasioned by the additional load upon the pump, and there is therefore a clear loss by the reduction of the temperature below 100°, if such reduction be caused by the admission of an additional quantity of water. If the reduction of temperature, however, be caused by the use of colder water, there is a gain produced by it, though the gain will within certain limits be greater if advantage be taken of the lowness of the temperature to diminish the quantity of injection. 334. _Q._--How do you determine the proper area of the injection orifice? _A._--The area of the injection orifice proper for any engine can easily be told when the quantity of water requisite to condense the steam is known, and the pressure is specified under which the water enters the condenser. The vacuum in the condenser may be taken at 26 inches of mercury, which is equivalent to a column of water 29.4 ft. high, and the square root of 29.4 multiplied by 8.021 is 43.15, which is the velocity in feet per second that a heavy body would acquire in falling 29.4 ft., or with which the water would enter the condenser. Now, if a cubic foot of water evaporated per hour be equivalent to an actual horse power, and 28.9 cubic inches of water be requisite for the condensation of a cubic inch of water in the form of steam, 28.9 cubic feet of condensing water per horse power per hour, or 13.905 cubic inches per second, will be necessary for the engine, and the size of the injection orifice must be such that this quantity of water flowing with the velocity of 43.15 ft. per second, or 517.8 inches per second, will gain admission to the condenser. Dividing, therefore, 13.905, the number of cubic inches to be injected, by 517.8, the velocity of influx in inches per second, we get 0.02685 for the area of the orifice in square inches; but inasmuch as it has been found by experiment that the actual discharge of water through a hole in a thin plate is only six tenths of the theoretical discharge on account of the contracted vein, the area of the orifice must be increased in the proportion of such diminution of effect, or be made 0.04475, or 1/22d of a square inch per horse power. This, it will be remarked, is the theoretical area required per actual horse power; but as the friction and contractions in the pipe further reduce the discharge, the area is made 1/15th of a square inch per actual horse power, or rather per cubic foot of water evaporated from the boiler. 335. _Q._--Cannot the condensation of the steam be accomplished by any other means than by the admission of cold water into the condenser? _A._--It may be accomplished by the method of external cold, as it is called, which consists in the application of a large number of thin metallic surfaces to the condenser, on the one side of which the steam circulates, while on the other side there is a constant current of cold water, and the steam is condensed by coming into contact with the cold surfaces, without mingling with the water used for the purpose of refrigeration. The first kind of condenser employed by Mr. Watt was constructed after this fashion, but he found it in practice to be inconvenient from its size, and to become furred up or incrusted when the water was bad, whereby the conducting power of the metal was impaired. He therefore reverted to the use of the jet of cold water, as being upon the whole preferable. The jet entered the condenser instead of the cylinder as was the previous practice, and this method is now the one in common use. Some few years ago, a good number of steam vessels were fitted with Hall's condensers, which operated on the principle of external cold, and which consisted of a faggot of small copper tubes surrounded by water; but the use of those condensers has not been persisted in, and most of the vessels fitted with them have returned to the ordinary plan. 336. _Q._--You stated that the capacity of the feed pump was 1/240th of the capacity of the cylinder in the case of condensing engines,--the engine being double acting and the pump single acting,--and that in high pressure engines the capacity of the pump should be greater in proportion to the pressure of the steam. Can you give any rule that will express the proper capacity for the feed pump at all pressures? _A._--That will not be difficult. In low pressure engines the pressure in the boiler may be taken at 5 lbs. above the atmospheric pressure, or 20 lbs. altogether; and as high pressure steam is merely low pressure steam compressed into a smaller compass, the size of the feed pump in relation to the size of the cylinder must obviously vary in the direct proportion of the pressure; and if it be 1/240th of the capacity of the cylinder when the total pressure of the steam is 20 lbs., it must be 1/120th of the capacity of the cylinder when the pressure is 40 lbs. per square inch, or 25 lbs. per square inch above the atmospheric pressure. This law of variation is expressed by the following rule:--multiply the capacity of the cylinder in cubic inches by the total pressure of the steam in lbs. per square inch, or the pressure per square inch on the safety valve plus 15, and divide the product by 4,800; the quotient is the capacity of the feed pump in cubic inches, when the feed pump is single acting and the engine double acting. If the feed pump be double acting, or the engine single acting, the capacity of the pump must just be one half of what is given by this rule. 337. _Q._--But should not some addition be made to the size of pump thus obtained if the pump works at a high rate of speed? _A._--No; this rule makes allowance for defective action. All pumps lift much less water than is due to the size of their barrels and the number of their strokes. Moderately good pumps lose 50 per cent. of their theoretical effect, and bad pumps 80 per cent. 338. _Q._--To what is this loss of effect to be chiefly ascribed? _A._--Mainly to the inertia of the water, which, if the pump piston be drawn up very rapidly, cannot follow it with sufficient rapidity; so that there may be a vacant space between the piston and the water; and at the return stroke the momentum of the water in the pipe expends itself in giving a reverse motion to the column of water approaching the pump. Messrs. Kirchweger and Prusman, of Hanover, have investigated this subject by applying a revolving cock at the end of a pipe leading from an elevated cistern containing water, and the water escaped at every revolution of the cock in the same manner as if a pump were drawing it. With a column of water of 17 feet, they found that at 80 revolutions of the cock per minute, the water delivered per minute by the cock was 9.45 gallons; but with 140 revolutions of the cock per minute, the water delivered per minute by the cock was only 5.42 gallons. They subsequently applied an air vessel to the pipe beside the cock, when the discharge rose to 12.9 gallons per minute with 80 revolutions, and 18.28 gallons with 140 revolutions. Air vessels should therefore be applied to the suction side of fast moving pumps, and this is now done with good results. 339. _Q._--What are the usual dimensions of the cold water pump of land engines? _A._--If to condense a cubic inch of water raised into steam 28.9 cubic inches of condensing water are required, then the cold water pump ought to be 28.9 times larger than the feed pump, supposing that its losses were equally great. The feed pump, however, is made sufficiently large to compensate for leaks in the boiler and loss of steam through the safety valve, so that it will be sufficient if the cold water pump be 24 times larger than the feed pump. This ratio is preserved by the following rule:-- multiply the capacity of the cylinder in cubic inches by the total pressure of the steam per square inch, or the pressure on the safety valve plus 15, and divide the product by 200. The quotient is the proper capacity of the cold water pump in cubic inches when the engine is double acting, and the pump single acting. FLY WHEEL. 340. _Q._--By what considerations do you determine the dimensions of the fly wheel of an engine? _A._--By a reference to the power generated, each half stroke of the engine, and the number of half strokes that are necessary to give to the fly wheel its standard velocity, supposing the whole power devoted to that object. In practice the power resident in the fly varies from 2-1/2 to 6 times that generated each half stroke; and if the weight of the wheel be equal to the pressure on the piston, its velocity must be such as it would acquire by falling through a height equal to from 2-1/2 to 6 times the stroke, according to the purpose for which the engine is intended. If a very equable motion is required, a heavier or swifter fly wheel must be employed. 341. _Q._--What is Boulton and Watt's rule for fly wheels? _A._--Their rule is one which under any given circumstances fixes the sectional area of the fly wheel rim, and it is as follows:--multiply 44,000 times the square of the diameter of the cylinder in inches by the length of the stroke in feet, and divide this product by the product of the square of the number of revolutions of the fly wheel per minute, multiplied by the cube of its diameter in feet. The quotient is the area of section of the fly wheel rim in square inches. STRENGTHS OF LAND ENGINES. 342. _Q._--Can you give a rule for telling the proper thickness of the cylinders of steam engines? _A._--In low pressure engines the thickness of metal of the cylinder, in engines of a medium size, should be about 1/40th of the diameter of the cylinder, which, with a pressure of steam of 20 lbs. above the atmosphere, will occasion a strain of only 400 Lbs. per square inch of section of the metal; the thickness of the metal of the trunnion bearings of oscillating engines should be 1/32d of the diameter of the cylinder, and the breadth of the bearing should be about half its diameter. In high pressure engines the thickness of the cylinder should be about 1/16th its diameter, which, with a pressure of steam of 80 lbs. upon the square inch, will occasion a strain of 640 lbs. upon the square inch of section of the metal; and the thickness of the metal of the trunnion bearings of high pressure oscillating engines should be 1/13th of the diameter of the cylinder. The strength, however, is not the sole consideration in proportioning cylinders, for they must be made of a certain thickness, however small the pressure is within them, that they may not be too fragile, and will stand boring. While, also, an engine of 40 inches diameter would be about one inch thick, the thickness would not be quite two inches in an 80 inch cylinder. In fact there will be a small constant added to the thickness for all diameters, which will be relatively larger the smaller the cylinders become. In the cylinders of Penn's 12 horse power engines, the diameter of cylinder being 21-1/2 inches, the thickness of the metal is 9/16ths: in Penn's 40 inch cylinders, the thickness is 1 inch, and in the engines of the Ripon, Pottinger, and Indus, by Messrs. Miller, Ravenhill and Co., with cylinders 76 inches diameter, the thickness of the metal is 1-11/16. These are all oscillating engines. 343. _Q._--What is the proportion of the piston rod? _A._--The diameter of the piston rod is usually made 1/10th of the diameter of the cylinder, or the sectional area of the piston rod is 1/100th of the area of the cylinder. This proportion, however, is not applicable to locomotive, or even fast moving marine engines. In locomotive engines the piston rod is made 1/7th of the diameter of the cylinder, and it is obvious that where the pressure on the piston is great, the piston rod must be larger than when the pressure on the piston is small. 344. _Q._--What are the proper dimensions of the main links of a land beam engine? _A._--The sectional area of the main links in land beam engines is 1/113th of the area of the cylinder, and the length of the main links is usually half the length of the stroke. 345. _Q._--What are the dimensions of the connecting rod of a land engine? _A._--In land engines the connecting rod is usually of cast iron with a cruciform section: the breadth across the arms of the cross is about 1/20th of the length of the rod, the sectional area at the centre 1/28th of the area of the cylinder, and at the ends 1/35th of the area of the cylinder: the length of the rod is usually 3-1/2 times the length of the stroke. It is preferable, however, to make the connecting rod of malleable iron, and then the dimensions will be those proper for marine engines. 346. _Q._--What was Mr. Watt's rule for the connecting rod? _A._--Some of his connecting rods were of iron and some of wood. To determine the thickness when of wood, multiply the square of the diameter of the cylinder in inches by the length of the stroke in feet, and divide the product by 24. Extract the fourth root of the quotient, which is the thickness in inches. For iron the rule is the same, only the divisor was 57.6 instead of 24. 347. _Q._--What are the dimensions of the end studs of a land engine beam? _A._--In low pressure engines the diameter of the end studs of the engine beam are usually made 1/9th of the diameter of the cylinder when of cast iron, and 1/10th when of wrought iron, which gives a load with low steam of about 500 lbs. per circular inch of transverse section; but a larger size is preferable, as with large bearings the brasses do not wear so rapidly and the straps are not so likely to be burst by the bearings becoming oval. These sizes, as also those which immediately follow, suppose the pressure on the piston to be 18 lbs. per circular inch. 348. _Q._--How is the strength of a cast iron gudgeon computed? _A._--To find the proper size of a cast iron gudgeon adapted to sustain any given weight:--multiply the weight in lbs. by the intended length of bearing expressed in terms of the diameter; divide the product by 500, and extract the square root of the quotient, which is the diameter in inches. 349. _Q._--What was Mr. Watt's rule for the strength of gudgeons? _A._--Supposing the gudgeon to be square, then, to ascertain the thickness, multiply the weight resting on the gudgeon by the distance between the trunnions, and divide the product by 333. Extract the cube root of the quotient, which is the thickness in inches. 350. _Q._--How do you find the proper strength for the cast iron beam of a land engine? _A._--If the force acting at the end of an engine beam be taken at 18 lbs. per circular inch of the piston, then the force acting at the middle will be 36 lbs. per circular inch of the piston, and the proper strength of the beam at the centre will be found by the following rule:--divide the weight in lbs. acting at the centre by 250, and multiply the quotient by the distance between the extreme centres. To find the depth, the breadth being given:--divide this product by the breadth in inches, and extract the square root of the quotient, which is the depth. The depth of a land engine beam at the ends is usually made one third of the depth at the centre (the depth at the centre being equal to the diameter of the cylinder in the case of low pressure engines), while the length is made equal to three times the length of the stroke, and the mean thickness 1/108th of the length--the width of the edge bead being about three times the thickness of the web. In many modern engines the force acting at the end of the beam is more than 18 lbs. per circular inch of the piston, but the above rules are still applicable by taking an imaginary cylinder with an area larger in the proportion of the larger pressure. 351. _Q._--What was Mr. Watt's rule for the main beams of his engines? _A._--Some of those beams were of wood and some of cast iron. The wood beams were so proportioned that the thickness was 1/58th of the circumference, and the depth 1/375. The side of the beam, supposing it square, was found by multiplying the diameter of the cylinder by the length of the stroke, and extracting the cube root of the quotient, which will be the depth or thickness of the beam. This rule allows a beam 16 feet long to bend 1/8th of an inch, and a beam 32 feet long to bend 1/4 of an inch. For cast iron beams the square of the diameter of the cylinder, multiplied by the length between the centres, is equal to the square of the depth, multiplied by the thickness. 352. _Q._--What law does the strength of beams and shafts follow? _A._--In the case of beams subjected to a breaking force, the strength with any given cohesion of the material will be proportional to the breadth, multiplied by the square of the depth; and in the case of revolving shafts exposed to a twisting strain, the strength with any given cohesive power of the material will be as the cube of the diameter. 353. _Q._--How is the strength of a cast iron shaft to resist torsion determined? _A._--Experiments upon the force requisite to twist off cast iron necks show that if the cube of the diameter of neck in inches be multiplied by 880, the product will be the force of torsion which will twist them off when acting at 6 inches radius; on this fact the following rule is founded: To find the diameter of a cast iron fly wheel shaft:--multiply the square of the diameter of the cylinder in inches, by the length of the crank in inches, and extract the cube root of the product, which multiply by 0.3025, and the result will be the proper diameter of the shaft in inches at the smallest part, when of cast iron. 354. _Q._--What was Mr. Watt's rule for the necks of his crank shafts? _A._--Taking the pressure on the piston at 12 lbs. pressure on the square inch, and supposing this force to be applied at one foot radius, divide the total pressure of the piston reduced to 1 foot of radius by 31.4, and extract the cube root of the quotient, which is the diameter of the shaft: or extract the cube root of 13.7 times the number of cubic feet of steam required to make one revolution, which is also the diameter of the shaft. 355. _Q._--Can you give any rule for the strength of the teeth of wheels? _A._--To find the proper dimensions for the teeth of a cast iron wheel:-- multiply the diameter of the pitch circle in feet by the number of revolutions to be made per minute, and reserve the product for a divisor; multiply the number of _actual_ horses power to be transmitted by 240, and divide the product by the above divisor, which will give the strength. If the pitch be given to find the breadth, divide the above strength by the square of the pitch in inches; or if the breadth be given, then to find the pitch divide the strength by the breadth in inches, and extract the square root of the quotient, which is the proper pitch in inches. The length of the teeth is usually about 5/8ths of the pitch. Pinions to work satisfactorily should not have less than 30 or 40 teeth, and where the speed exceeds 220 feet in the minute, the teeth of the larger wheel should be of wood, made a little thicker, to keep the strength unimpaired. 356. _Q._--What was Mr. Watt's rule for the pitch of wheels? _A._--Multiply five times the diameter of the larger wheel by the diameter of the smaller, and extract the fourth root of the product, which is the pitch. STRENGTH OF MARINE AND LOCOMOTIVE ENGINES. 357. _Q._--Cannot you give some rules of strength which will be applicable whatever pressure may be employed? _A._--In the rules already given, the effective pressure may be reckoned at from 18 to 20 lbs. upon every square inch of the piston, as is usual in land engines; and if the pressure upon every square inch of the piston be made twice greater, the dimensions must just be those proper for an engine of twice the area of piston. It will not be difficult, however, to introduce the pressure into the rules as an element of the computation, whereby the result will be applicable both to high and low pressure engines. 358. _Q._--Will you apply this mode of computation to a marine engine, and first find the diameter of the piston rod? _A._--The diameter of the piston rod may be found by multiplying the diameter of the cylinder in inches, by the square root of the pressure on the piston in lbs. per square inch, and dividing by 50, which makes the strain 1/7th of the elastic force. 359. _Q._--What will be the rule for the connecting rod, supposing it to be of malleable iron? _A._--The diameter of the connecting rod at the ends, may be found by multiplying 0.019 times the square root of the pressure on the piston in lbs. per square inch by the diameter of the cylinder in inches; and the diameter of the connecting rod in the middle may be found by the following rule:--to 0.0035 times the length of the connecting rod in inches, add 1, and multiply the sum by 0.019 times the square root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches. The strain is equal to 1/6th of the elastic force. 360. _Q._--How will you find the diameter of the cylinder side rods of a marine engine? _A._--The diameter of the cylinder side rods at the ends may be found by multiplying 0.0129 times the square root of the pressure on the piston in lbs. per square inch by the diameter of the cylinder; and the diameter of the cylinder side rods at the middle is found by the following rule:--to 0.0035 times the length of the rod in inches, add 1, and multiply the sum by 0.0129 times the square root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches; the product is the diameter of each side rod at the centre in inches. The strain upon the side rods is by these rules equal to 1/6th of the elastic force. 361. _Q._--How do you determine the dimensions of the crank? _A._--To find the exterior diameter of the large eye of the crank when of malleable iron:--to 1.561 times the pressure of the steam upon the piston in lbs. per square inch, multiplied by the square of the length of the crank in inches, add 0.00494 times the square of the diameter of the cylinder in inches, multiplied by the square of the number of lbs. pressure per square inch on the piston; extract the square root of this quantity; divide the result by 75.59 times the square root of the length of the crank in inches, and multiply the quotient by the diameter of the cylinder in inches; square the product and extract the cube root of the square, to which add the diameter of the hole for the reception of the shaft, and the result will be the exterior diameter of the large eye of the crank when of malleable iron. The diameter of the small eye of the crank may be found by adding to the diameter of the crank pin 0.02521 times the square root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches. 362. _Q._--What will be the thickness of the crank web? _A._--The thickness of the web of the crank, supposing it to be continued to the centre of the shaft, would at that point be represented by the following rule:--to 1.561 times the square of the length of the crank in inches, add 0.00494 times the square of the diameter of the cylinder in inches, multiplied by the pressure on the piston in lbs. per square inch; extract the square root of the sum, which multiply by the diameter of the cylinder squared in inches, and by the pressure on the piston in lbs. per square inch; divide the product by 9,000, and extract the cube root of the quotient, which will be the proper thickness of the web of the crank when of malleable iron, supposing the web to be continued to the centre of the shaft. The thickness of the web at the crank pin centre, supposing it to be continued thither, would be 0.022 times the square root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder. The breadth of the web of the crank at the shaft centre should be twice the thickness, and at the pin centre 1-1/2 times the thickness of the web; the length of the large eye of the crank would be equal to the diameter of the shaft, and of the small eye 0.0375 times the square root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder. 363. _Q._--Will you apply the same method of computation to find the dimensions of a malleable iron paddle shaft? _A._--The method of computation will be as follows:--to find the dimensions of a malleable iron paddle shaft, so that the strain shall not exceed 5/6ths of the elastic force, or 5/6ths of the force iron is capable of withstanding without permanent derangement of structure, which in tensile strains is taken at 17,800 lbs. per square inch: multiply the pressure in lbs. per square inch on the piston by the square of the diameter of the cylinder in inches, and the length of the crank in inches, and extract the cube root of the product, which, multiplied by 0.08264, will be the diameter of the paddle shaft journal in inches when of malleable iron, whatever the pressure of the steam may be. The length of the paddle shaft journal should be 1-1/4 times the diameter; and the diameter of the part where the crank is put on is often made equal to the diameter over the collars of the journal or bearing. 364. _Q._--How do you find the diameter of the crank pin? _A._--The diameter of the crank pin in inches may be found by multiplying 0.02836 times the square root of the pressure on the piston in lbs. per square inch, by the diameter of the cylinder in inches. The length of the pin is usually about 9/8th times its diameter, and the strain if all thrown upon the end of the pin will be equal to the elastic force; but in ordinary working, the strain will only be equal to 1/3d of the elastic force. 365. _Q._--What are the dimensions of the cross head? _A._--If the length of the cross head be taken at 1.4 times the diameter of the cylinder, the dimensions of the cross head will be as follows:--the exterior diameter of the eye in the cross head for the reception of the piston rod, will be equal to the diameter of the hole, plus 0.02827 times the cube root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches; and the depth of the eye will be 0.0979 times the cube root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches. The diameter of each cross head journal will be 0.01716 times the square root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches--the length of the journal being 9/8ths its diameter. The thickness of the web at centre will be 0.0245 times the cube root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches; and the depth of web at centre will be 0.09178 times the cube root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches. The thickness of the web at journal will be 0.0122 times the square root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches; and the depth of the web at journal will be 0.0203 times the square root of the pressure upon the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches. In these rules for the cross head, the strain upon the web is 1/2.225 times the elastic force; the strain upon the journal in ordinary working is 1/2.33 times the elastic force; and if the outer ends of the journals are the only bearing points, the strain is 1/1.165 times the elastic force, which is very little in excess of the elastic force. 366. _Q._--How do you find the diameter of the main centre when proportioned according to this rule? _A._--The diameter of the main centre may be found by multiplying 0.0367 times the square root of the pressure upon the piston in lbs. per square inch, by the diameter of the cylinder in inches, which will give the diameter of the main centre journal in inches when of malleable iron, and the length of the main centre journal should be 1-1/2 times its diameter; the strain upon the main centre journal in ordinary working will be about 1/2 the elastic force. 367. _Q._--What are the proper dimensions of the gibs and cutters of an engine? _A._--The depth of gibs and cutters for attaching the piston rod to the cross head, is 0.0358 times the cube root of the pressure of the steam on the piston in lbs. per square inch, multiplied by the diameter of the cylinder; and the thickness of the gibs and cutters is 0.007 times the cube root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of its cylinder. The depth of the cutter through the piston is 0.017 times the square root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder in inches; and the thickness of the cutter through the piston is 0.007 times the square root of the pressure on the piston in lbs. per square inch, multiplied by the diameter of the cylinder. 368. _Q._--Are not some of the parts of an engine constructed according to these rules too weak, when compared with the other parts? _A._--It is obvious, from the varying proportions subsisting in the different parts of the engine between the strain and the elastic force, that in engines proportioned by these rules--which represent nevertheless the average practice of the best constructors--some of the parts must possess a considerable excess of strength over other parts, and it appears expedient that this disparity should be diminished, which may best be done by increasing the strength of the parts which are weakest; inasmuch as the frequent fracture of some of the parts shows that the dimensions at present adopted for those parts are scarcely sufficient, unless the iron of which they are made is of the best quality. At the same time it is quite certain, that engines proportioned by these rules will work satisfactorily where good materials are employed; but it is important to know in what parts good materials and larger dimensions are the most indispensable. In many of the parts, moreover, it is necessary that the dimensions should be proportioned to meet the wear and the tendency to heat, instead of being merely proportioned to obtain the necessary strength; and the crank pin is one of the parts which requires to be large in diameter, and as long as possible in the bearing, so as to distribute the pressure, and prevent the disposition to heat which would otherwise exist. The cross head journals also should be long and large; for as the tops of the side rods have little travel, the oil is less drawn into the bearings than if the travel was greater, and is being constantly pressed out by the punching strain. This strain should therefore be reduced as far as possible by its distribution over a large surface. In the rules which are contained in the answers to the ten preceding questions (358 to 367) the pressure on the piston in lbs. per square inch is taken as the sum of the pressure of steam in the boiler and of the vacuum; the latter being assumed to be 15 lbs. per square inch. CHAPTER VII. CONSTRUCTIVE DETAILS OF BOILERS. * * * * * LAND AND MARINE BOILERS. 369. _Q._--Will you explain the course of procedure in the construction and setting of wagon boilers? _A._--Most boilers are made of plates three eighths of an inch thick, and the rivets are from three eighths to three fourths of an inch in diameter. In the bottom and sides of a wagon boiler the heads of the rivets, or the ends formed on the rivets before they are inserted, should be large and placed next the fire, or on the outside; whereas on the top of the boiler the heads should be on the inside. The rivets should be placed about two inches distant from centre to centre, and the centre of the row of rivets should be about one inch from the edge of the plate. The edges of the plates should be truly cut, both inside and outside, and after the parts of the boiler have been riveted together, the edges of the plates should be set up or caulked with a blunt chisel about a quarter of an inch thick in the point, and struck by a hammer of about three or four pounds weight, one man holding the caulking tool while another strikes. 370. _Q._--Is this the usual mode of caulking? _A._--No, it is not the usual mode; but it is the best mode, and is the mode adopted by Mr. Watt. The usual mode now is for one man to caulk the seams with a hammer in one hand and a caulking chisel in the other, and in some of the difficult corners of marine flue boilers it is not easy for two men to get in. A good deal of the caulking has also sometimes to be done with the left hand. 371. _Q._--Should the boiler be proved after caulking? _A._--The boiler should be filled with water and caulked afresh in any leaky part. When emptied again, all the joints should be painted with a solution of sal ammoniac in urine, and so soon as the seams are well rusted they should be dried with a gentle fire, and then be painted over with a thin putty formed of whiting and linseed oil, the heat being continued until the putty becomes so hard that it cannot be readily scratched with the nail, and care must be taken neither to burn the putty nor to discontinue the fire until it has become quite dry. 372. _Q._--How should the brickwork setting of a wagon boiler be built? _A._--In building the brickwork for the setting of the boiler, the part upon which the heat acts with most intensity is to be built with clay instead of mortar, but mortar is to be used on the outside of the work. Old bars of flat iron may be laid under the boiler chime to prevent that part of the boiler from being burned out, and bars of iron should also run through the brickwork to prevent it from splitting. The top of the boiler is to be covered with brickwork laid in the best lime, and if the lime be not of the hydraulic kind, it should be mixed with Dutch terrass, to make it impenetrable to water. The top of the boiler should be well plastered with this lime, which will greatly conduce to the tightness of the seams. Openings into the flues must be left in convenient situations to enable the flues to be swept out when required, and these openings may be closed with cast iron doors jointed with clay or mortar, which may be easily removed when required. Adjacent to the chimney a slit must be left in the top of the flue with a groove in the brickwork to enable the sliding door or damper to be fixed in that situation, which by being lowered into the flue will obstruct the passage of the smoke and moderate the draught, whereby the chimney will be prevented from drawing the flame into it before the heat has acted sufficiently upon the boiler. 373. _Q._--Are marine constructed in the same way as land boilers? _A._--There is very little difference in the two cases: the whole of the shells of marine boilers, however, should be double riveted with rivets 11/16ths of an inch in diameter, and 2-3/8th inches from centre to centre, the weakening effect of double riveting being much less than that of single riveting. The furnaces above the line of bars should be of the best Lowmoor, Bowling, or Staffordshire scrap plates, and the portion of each furnace above the bars should consist only of three plates, one for the top and one for each side, the lower seam of the side plates being situated beneath the level of the bars, so as not to be exposed to the heat of the furnace. The tube plates of tubular boilers should be of the best Lowmoor, or Bowling iron, seven eighths to one inch thick: the shells should be of the best Staffordshire, or Thornycroft S crown iron, 7/16ths of an inch thick. 374. _Q._--Of what kind of iron should the angle iron or corner iron be composed? _A._--Angle iron should not be used in the construction of boilers, as in the manufacture it becomes reedy, and is apt to split up in the direction of its length: it is much the safer practice to bend the plates at the corners of the boiler; but this must be carefully done, without introducing any more sharp bends than can be avoided, and plates which require to be bent much should be of Lowmoor iron. It will usually be found expedient to introduce a ring of angle iron around the furnace mouths, though it is discarded in the other parts of the boiler; but it should be used as sparingly as possible, and any that is used should be of the best quality. 375. _Q._--Is it not important to have the holes in the plates opposite to one another? _A._--The whole of the plates of a boiler should have the holes for the rivets punched, and the edges cut straight, by means of self-acting machinery, in which a travelling table carries forward the plate with an equal progression every stroke of the punch or shears; and machinery of this kind is now extensively employed. The practice of forcing the parts of boilers together with violence, by means of screw-jacks, and drifts through the holes, should not be permitted; as a great strain may thus be thrown upon the rivets, even when there is no steam in the boiler. All rivets should be of the best Lowmoor iron. The work should be caulked both within and without wherever it is accessible, but in the more confined situations within the flues the caulking will in many cases have to be done with the hand or chipping hammer, instead of the heavy hammer previously prescribed. 376. _Q._--How is the setting of marine boilers with internal furnaces effected? _A._--In the setting of marine boilers care must be taken that no copper bolts or nails project above the wooden platform upon which they rest, and also that no projecting copper bolts in the sides of the ship touch the boiler, as the galvanic action in such a case would probably soon wear the points of contact into holes. The platform may consist of three inch planking laid across the keelsons nailed with iron, nails, the heads of which are well punched down, and caulked and puttied like a deck. The surface may then be painted over with thin putty, and fore and aft boards of half the thickness may then be laid down and nailed securely with iron nails, having the heads well punched down. This platform must then be covered thinly and evenly with mastic cement and the boiler be set down upon it, and the cement must be caulked beneath the boiler by means of wooden caulking tools, so as completely to fill every vacuity. Coomings of wood sloped on the top must next be set round the boiler, and the space between the coomings and the boiler must be caulked full of cement, and be smoothed off on the top to the slope of the coomings, so as to throw off any water that might be disposed to enter between the coomings and the boiler. 377. _Q._--How is the cement used for setting marine boilers compounded? _A._--Mastic cement proper for the setting of boilers is sold in many places ready made. Hamelin's mastic is compounded as follows:--to any given weight of sand or pulverized earthenware add two thirds such given weight of powdered Bath, Portland, or other similar stone, and to every 560 lbs. weight of the mixture add 40 lbs. weight of litharge, 2 lbs. of powdered glass or flint, 1 lb. of minium, and 2 lbs. of gray oxide of lead; pass the mixture through a sieve, and keep it in a powder for use. When wanted for use, a sufficient quantity of the powder is mixed with some vegetable oil upon a board or in a trough in the manner of mortar, in the proportion of 605 lbs. of the powder to 5 gallons of linseed, walnut, or pink oil, and the mixture is stirred and trodden upon until it assumes the appearance of moistened sand, when it is ready for use. The cement should be used on the same day as the oil is added, else it will be set into a solid mass. 378. _Q._--What is the best length of the furnaces of marine boilers? _A._--It has already been stated that furnace bars should not much exceed six feet in length, as it is difficult to manage long furnaces; but it is a frequent practice to make the furnaces long and narrow, the consequence of which is, that it is impossible to fire them effectually at the after end, especially upon long voyages and in stormy weather, and air escapes into the flues at the after end of the bars, whereby the efficacy of the boiler is diminished. Where the bars are very long it will generally be found that an increased supply of steam and a diminished consumption of coal will be the consequence of shortening them, and the bars should always lie with a considerable inclination to facilitate the distribution of the fuel over the after part of the furnace. When there are two lengths of bars in the furnace, it is expedient to make the central cross bar for bearing up the ends double, and to leave a space between the ends of the bars so that the ashes may fall through between them. The space thus left enables the bars to expand without injury on the application of heat, whereas without some such provision the bars are very liable to get burned out by bending up in the centre, or at the ends, as they must do if the elongation of the bars on the application of heat be prevented; and this must be the effect of permitting the spaces at the ends of the bars to be filled up with ashes. At each end of each bed of bars it is expedient to leave a space which the ashes cannot fill up so as to cause the bars to jam; and care must be taken that the heels of the bars do not come against any of the furnace bearers, whereby the room left at the end of the bars to permit the expansion would be rendered of no avail. 379. _Q._--Have you any remarks to offer respecting the construction and arrangement of the furnace bridges and dampers of marine boilers? _A._--The furnace bridges of marine boilers are walls or partitions built up at the ends of the furnaces to narrow the opening for the escape of heat into the flues. They are either made of fire brick or of plate iron containing water: in the case of water bridges, the top part of the bridge should be made with a large amount of slant so as to enable the steam to escape freely, but notwithstanding this precaution the plates of water bridges are apt to crack at the bend, so that fire brick bridges appear on the whole to be preferable. In shallow furnaces the bridges often come too near the furnace top to enable a man to pass over them; and it will save expense if in such bridges the upper portion is constructed of two or three fire blocks, which may be lifted off where a person requires to enter the flues to sweep or repair them, whereby the perpetual demolition and reconstruction of the upper part of the bridge will be prevented. 380. _Q._--What is the benefit of bridges? _A._--Bridges are found in practice to have a very sensible operation in increasing the production of steam, and in some boilers in which the brick bridges have been accidentally knocked down by the firemen, a very considerable diminution in the supply of steam has been experienced. Their chief operation seems to lie in concentrating the heat within the furnace to a higher temperature, whereby the heat is more rapidly transmitted from the furnace to the water, and less heat has consequently to be absorbed by the flues. In this way the bridges render the heating surface of a boiler more effective, or enable a smaller amount of heating surface to suffice. 381. _Q._--Are the bridges behind the furnaces the only bridges used in steam boilers? _A._--It is not an uncommon practice to place a hanging bridge, consisting of a plate of iron descending a certain distance into the flue, at that part of the flue where it enters the chimney, whereby the stratum of hot air which occupies the highest part of the flue is kept in protracted contact with the boiler, and the cooler air occupying the lower part of the flue is that which alone escapes. The practice of introducing a hanging bridge is a beneficial one in the case of some boilers, but is not applicable universally, as boilers with a small calorimeter cannot be further contracted in the flue without a diminution in their evaporating power. In tubular boilers a hanging bridge is not applicable, but in some cases a perforated plate is placed against the ends of the tubes, which by suitable connections is made to operate as a sliding damper which partially or totally closes up the end of every tube, and at other times a damper constructed in the manner of a venetian blind is employed in the same situation. These varieties of damper, however, have only yet been used in locomotive boilers, though applicable to tubular boilers of every description. 382. _Q._--Is it a benefit to keep the flues or tubes appertaining to each furnace distinct? _A._--In a flue boiler this cannot be done, but in a tubular boiler it is an advantage that there should be a division between the tubes pertaining to each furnace, so that the smoke of each furnace may be kept apart from the smoke of the furnace adjoining it until the smoke of both enters the chimney, as by this arrangement a furnace only will be rendered inoperative in cleaning the fires instead of a boiler, and the tubes belonging to one furnace may be swept if necessary at sea without interfering injuriously with the action of the rest. In a steam vessel it is necessary at intervals to empty out one or more furnaces every watch to get rid of the clinkers which would otherwise accumulate in them; and it is advisable that the connection between the furnaces should be such that this operation, when being performed on one furnace, shall injure the action of the rest as little as possible. 383. _Q._--Can any constructive precautions be taken to prevent the furnaces and tube plates of the boiler from being burned by the intensity of the heat? _A._--The sides of the internal furnaces or flues in all boilers should be so constructed that the steam may readily escape from their surfaces, with which view it is expedient to make the bottom of the flue somewhat wider than the top, or slightly conical in the cross section; and the upper plates should always be overlapped by the plates beneath, so that the steam cannot be retained in the overlap, but will escape as soon as it is generated. If the sides of the furnace be made high and perfectly vertical, they will speedily be buckled and cracked by the heat, as a film of steam in such a case will remain in contact with the iron which will prevent the access of the water, and the iron of the boiler will be injured by the high temperature it must in that case acquire. To moderate the intensity of the heat acting upon the furnace sides, it is expedient to bring the outside fire bars into close contact with the sides of the furnace, so as to prevent the entrance of air through the fire in that situation, by which the intensity of the heat would be increased. The tube plate nearest the furnace in tubular boilers should also be so inclined as to facilitate the escape of the steam; and the short bent plate or flange of the tube plate, connecting the tube plate with the top of the furnace, should be made with a gradual bend, as, if the bend be sudden, the iron will be apt to crack or burn away from the concretion of salt. Where the furnace mouths are contracted by bending in the sides and top of the furnace, as is the general practice, the bends should be gradual, as salt is apt to accumulate in the pockets made by a sudden bend, and the plates will then burn into holes. 384. _Q._--In what manner is the tubing of boilers performed? _A._--The tubes of marine boilers are generally iron tubes, three inches in diameter, and between six and seven feet long; but sometimes brass tubes of similar dimensions are employed. When brass tubes are employed, the use of ferules driven into the ends of the tubes is sometimes employed to keep them tight; but when the tubes are of malleable iron, of the thickness of Russell's boiler tubes, they may be made tight merely by firmly driving them into the tube plates, and the same may be done with thick brass tubes. The holes in the tube plate next the front of the boiler are just sensibly larger in diameter than the holes in the other tube plate, and the holes upon the outer surfaces of both tube plates are very slightly countersunk. The whole of the tubes are driven through both tube plates from the front of the boiler,--the precaution, however, being taken to drive them in gently at first with a light hand hammer, until the whole of the tubes have been inserted to an equal depth, and then they may be driven up by degrees with a heavy hammer, whereby any distortion of the holes from unequal driving will be prevented. Finally, the ends of the tubes should be riveted up so as to fill the countersink; the tubes should be left a little longer than the distance between the outer surfaces of the tube plates, so that the countersink at the ends may be filled by staving up the end of the tube rather than by riveting it over; and the staving will be best accomplished by means of a mandril with a collar upon it, which is driven into the tube so that the collar rests upon the end of the tube to be riveted; or a tool like a blunt chisel with a recess in its point may be used, as is the more usual practice. 385. _Q._--Should not stays be introduced in substitution of some of the tubes? _A._--It appears expedient in all cases that some of the tubes should be screwed at the ends, so as to serve as stays if the riveting at the tube ends happens to be burned away, and also to act as abutments to the riveted tube--or else to introduce very strong rods of about the same diameter as a tube, in substitution of some of the tubes; and these stays should have nuts at each end both within and without the tube plates, which nuts should be screwed up, with white lead interposed, before the tubes are inserted. If the tubes are long, their expansion when the boiler is being blown off will be apt to start them at the ends, unless very securely fixed; and it is difficult to prevent brass tubes of large diameter and proportionate length from being started at the ends, even when secured by ferules; but the brass tubes commonly employed are so small as to be susceptible of sufficient compression endways by the adhesion due to the ferules to compensate for the expansion, whereby they are prevented from starting at the ends. In some, of the early marine boilers fitted with brass tubes, a galvanic action at the ends of the tubes was found to take place, and the iron of the tube plates was wasted away in consequence, with rapidity; but further experience proved the injury to be attributable chiefly to imperfect fitting, whereby a leakage was caused that induced oxidation, and when, the tubes were well fitted any injurious action at the ends of the tubes was found to cease. 386. _Q._--What is the best mode of constructing the chimney and the parts in connection therewith? _A._--In sea-going steamers the funnel plates are usually about nine feet long and 3/16ths thick; and where different flues or boilers have their debouch in the same chimney, it is expedient to run division plates up the chimney for a considerable distance, to keep the draughts distinct. The dampers should not be in the chimney but at the end of the boiler flue, so that they may be available for use if the funnel by accident be carried away. The waste steam pipe should be of the same height as the funnel, so as to carry the waste steam clear of it, for if the waste steam strikes the funnel it will wear the iron into holes; and the waste steam pipes should be made at the bottom with a faucet joint, to prevent the working of the funnel, when the vessel rolls, from breaking the pipe at the neck. There should be two hoops round the funnel, for the attachment of the funnel shrouds, instead of one, so that the funnel may not be carried overboard if one hoop breaks, or if the funnel breaks at the upper hoop from the corrosive action of the waste steam, as sometimes happens. The deck over the steam chest should be formed of an iron plate supported by angle iron beams, and there should be a high angle iron cooming round the hole in the deck through which the chimney ascends, to prevent any water upon the deck from leaking down upon the boiler. Around the lower part of the funnel there should be a sheet iron casing to prevent any inconvenient dispersion of heat in that situation, and another short piece of casing, of a somewhat larger diameter, and riveted to the chimney, should descend over the first casing, so as to prevent the rain or spray which may beat against the chimney from being poured down within the casing upon the top of the boiler. The pipe for conducting away the waste water from the top of the safety valve should lead overboard, and not into the bilge of the ship, as inconvenience arises from the steam occasionally passing through it, if it has its termination in the engine room. 387. _Q._--Are not the chimneys of some vessels made so that they may be lowered when required? _A._--The chimneys of small river vessels which have to pass under bridges are generally formed with a hinge, so that they may be lowered backward when passing under a bridge; and the chimneys of some screw vessels are made so as to shut up like a spyglass when the fires are put out and the vessel is navigated under sails. In smaller vessels, however, two lengths of chimney suffice; and in that case there is a standing piece on deck, which, however, does not project above the bulwarks. 388. _Q._--Will you explain any further details in the construction of marine boilers which occur to you as important? _A._--The man-hole and mud-hole doors, unless put on from the outside, like a cylinder cover, with a great number of bolts, should be put on from the inside with cross bars on the outside, and the bolts should be strong, and have coarse threads and square nuts, so that the threads may not be overrun, nor the nuts become round, by the unskilful manipulations of the firemen, by whom these doors are removed or replaced. It is very expedient that sufficient space should be left between the furnace and the tubes in all tubular boilers to permit a boy to go in to clear away any scale that may have formed, and to hold on the rivets in the event of repair being wanted; and it is also expedient that a vertical row of tubes should be left out opposite to each water space to allow the ascent of the steam and descent of the water, as it has been found that the removal of the tubes in that position, even in a boiler with deficient heating surface, has increased the production of steam, and diminished the consumption of fuel. The tubes should all be kept in the same vertical line, so as to permit the introduction of an instrument to scrape them; but they may be zig-zagged in the horizontal line, whereby a greater strength of metal will be obtained around the holes in the tube plates, and the tubes should not be placed too close together, else their heating efficacy will be impaired. INCRUSTATION AND CORROSION OF BOILERS. 389. _Q._--What is the cause of the formation of scale in marine boilers? _A._--Scale is formed in all boilers which contain earthy or saline matters, just in the way in which a scaly deposit, or rock, as it is sometimes termed, is formed in a tea kettle. In sea water the chief ingredient is common salt, which exists in solution: the water admitted to the boiler is taken away in the shape of steam, and the saline matter which is not vaporizable accumulates in process of time in the boiler, until its amount is so great that the water is saturated, or unable to hold any more in solution; the salt is then precipitated and forms a deposit which hardens by heat. The formation of scale, therefore, is similar to the process of making salt from sea water by evaporation, the boiler being, in fact, a large salt pan. 390. _Q._--But is the scale soluble in fresh water like the salt in a salt pan? _A._--No, it is not; or if soluble at all, is only so to a very limited extent. The several ingredients in sea water begin to be precipitated from solution at different degrees of concentration; and the sulphate and carbonate of lime, which begin to be precipitated when a certain state of concentration is reached, enter largely into the composition of scale, and give it its insoluble character. Pieces of waste or other similar objects left within a marine boiler appear, when taken out, as if they had been petrified; and the scale deposited upon the flues of a marine boiler resembles layers of stone. 391. _Q/_--Is much inconvenience experienced in marine boilers from these incrustations upon the flues? _A._--Incrustation in boilers at one time caused much more perplexity than it does at present, as it was supposed that in some seas it was impossible to prevent the boilers of a steamer from becoming salted up; but it has now been satisfactorily ascertained that there is very little difference in the saltness of different seas, and that however salt the water may be, the boiler will be preserved from any injurious amount of incrustation by blowing off, as it is called, very frequently, or by permitting a considerable portion of the supersalted water to escape at short intervals into the sea. If blowing off be sufficiently practised, the scale upon the flues will never be much thicker than a sheet of writing paper, and _no excuse_ should be accepted from engineers for permitting a boiler to be damaged by the accumulation of calcareous deposit. 392. _Q._--What is the temperature at which sea water boils in a steam boiler? _A._--Sea water contains about 1/33rd its weight of salt, and in the open air it boils at the temperature of 213.2°; if the proportion of salt be increased to 2/33rds of the weight of the water, the boiling point will rise to 214.4°; with 3/33rds of salt the boiling point will be 215.5°; 4/33rds, 216.7°; 5/33rds, 217.9°; 6/33rds, 219°; 7/33rds, 220.2°; 8/33rds, 221.4°; 9/33rds, 222.5°; 10/33rds, 223.7°; 11/33rds, 224.9°; and 12/33rds, which is the point of saturation, 226°. In a steam boiler the boiling points of water containing these proportions of salt must be higher, as the elevation of temperature due to the pressure of the steam has to be added to that due to the saltness of the water; the temperature of steam at the atmospheric pressure being 212°, its temperature, at a pressure of 15 lbs. per square inch above the atmosphere, will be 250°, and adding to this 4.7° as the increased temperature due to the saltness of the water when it contains 4/33rds of salt, we have 254.7° as the temperature of the water in the boiler, when it contains 4/33rds of salt and the pressure of the steam is 15 lbs. on the square inch. 393. _Q._--What degree of concentration of the salt water may be safely permitted in a boiler? _A._--It is found by experience that when the concentration of the salt water in a boiler is prevented from exceeding that point at which it contains 2/33rds its weight of salt, no injurious incrustation will take place, and as sea water contains only 1/33rd of its weight of salt, it is clear that it must be reduced by evaporation to one half of its bulk before it can contain 2/33rds of salt; or, in other words, a boiler must blow out into the sea one half of the water it receives as feed, in order to prevent the water from rising above 2/33rds of concentration, or 8 ounces of salt to the gallon. 394. _Q._--How do you determine 8 ounces to the gallon to be equivalent to twice the density of salt water, or "two salt waters" as it is sometimes called? _A._--The density of the water of different seas varies somewhat. A gallon of fresh water weighs 10 lbs.; a gallon of salt water from the Baltic weighs 10.15 lbs.; a gallon of salt water from the Irish Channel weighs 10.28 lbs.; and a gallon of salt water from the Mediterranean 10.29 lbs. If we take an average saltness represented by a weight of 10.25 lbs., then a gallon of water concentrated to twice this saltness will weigh 10.5 lbs., or the salt in it will weigh .5 lbs or 8 oz., which is the proportion of 8 oz. to the gallon. However, the proportion of 2/33rds gives a greater proportion than 8 oz. to the gallon, for 2/33 = 1/16 nearly, and 1/16 of 10 lbs. = 10 oz. By keeping the density of the water in a marine boiler at the proportion of 8 or 10 oz. to the gallon, no inconvenient amount of scale will be deposited on the flues or tubes. The bulk of water, it may be remarked, is not increased by putting salt in it up to the point of saturation, but only its density is increased. 395. _Q._--Is there not a great loss of heat by blowing off so large a proportion of the heated water from the boiler? _A._--The loss is not very great. Boilers are sometimes worked at a saltness of 4/33rds, and taking this saltness and supposing the latent heat of steam to be at 1000° at the temperature of 212°, and reckoning the sum of the latent and sensible heats as forming a constant quantity, the latent heat of steam at the temperature of 250° will be 962°, and the total heat of the steam will be 1212° in the case of fresh water; but as the feed water is sent into the boiler at the temperature of 100°, the accession of heat it receives from the fuel will be 1112° in the case of fresh water, or 1112° increased by 3.98° in the case of water containing 4/33ds of salt-- the 3.98° being the 4.7° increase of temperature due to the presence of 4/33rds of salt, multiplied by 0.847 the specific heat of steam. This makes the total accession of heat received by the steam in the boiler equal to 1115.98°, or say 1116°, which multiplied by 3, as 3 parts of the water are raised into steam, gives us 3348° for the heat in the steam, while the accession of heat received in the boiler by the 1 part of residual brine will be 154.7°, multiplied by 0.85, the specific heat of the brine, or 130.495°; and 3348° divided by 130.495° is about 1/26th. It appears, therefore, that by blowing off the boiler to such an extent that the saltness shall not rise above what answers to 4/33rds of salt, about 1/25th of the heat is blown into the sea; this is but a small proportion, and as there will be a greater waste of heat, if from the existence of scale upon the flues the heat can be only imperfectly transmitted to the water, there cannot be even an economy of fuel in niggard blowing off, while it involves the introduction of other evils. The proportion of 4/33rds of saltness, however, or 16 oz. to the gallon, is larger than is advisable, especially as it is difficult to keep the saltness at a perfectly uniform point, and the working point should, therefore, be 2/33rds as before prescribed. 396. _Q._--Have no means been devised for turning to account the heat contained in the brine which is expelled from the boiler? _A._--To save a part of the heat lost by the operation of blowing off, the hot brine is sometimes passed through a number of small tubes surrounded by the feed water; but there is no very great gain from the use of such apparatus, and the tubes are apt to become choked up, whereby the safety of the boiler may be endangered by the injurious concentration of its contents. Pumps, worked by the engine for the extraction of the brine, are generally used in connection with the small tubes for the extraction of the heat from the supersalted water; and if the tubes become choked the pumps will cease to eject the water, while the engineer may consider them to be all the while in operation. 397._Q._--What is the usual mode of blowing off the supersalted water from the boiler? _A._--The general mode of blowing off the boiler is to allow the water to rise gradually for an hour or two above the lowest Working level, and then to open the cock communicating with the sea, and keep it open until the surface of the water within the boiler has fallen several inches; but in some cases a cock of smaller size is allowed to run water continuously, and in other cases brine pumps are used as already mentioned. In every case in which the supersalted water is discharged from the boiler in a continuous stream, a hydrometer or salt gauge of some convenient construction should be applied to the boiler, so that the density of the water may at all times be visible, and immediate notice be given of any interruption of the operation. Various contrivances have been devised for this purpose, the most of which operate on the principle of a hydrometer; but perhaps a more satisfactory principle would be that of a differential steam gauge, which would indicate the difference of pressure between the steam in the boiler and the steam of a small quantity of fresh water enclosed in a suitable vessel, and immerged in the water of the boiler. 398. _Q._--What is the advantage of blowing off from the surface of the water in the boiler? _A._--Blowing off from a point near the surface of the water is more beneficial than blowing off from the bottom of the boiler. Solid particles of any kind, it is well known, if introduced into boiling water, will lower the boiling point in a slight degree, and the steam will chiefly be generated on the surface of the particles, and indeed will have the appearance of coming out of them; if the particles be small the steam generated beneath and around them will balloon them to the surface of the water, where the steam will be liberated and the particles will descend; and the impalpable particles in a marine boiler, which by their subsidence upon the flues concrete into scale, are carried in the first instance to the surface of the water, so that if they be caught there and ejected from the boiler, the formation of scale will be prevented. 399. _Q._--Are there any plans in operation for taking advantage of this property of particles rising to the surface? _A._--Advantage is taken of this property in Lamb's Scale Preventer, which is substantially a contrivance for blowing off from the surface of the water that in practice is found to be very effectual; but a float in connection with a valve at the mouth of the discharging pipe is there introduced, so as to regulate the quantity of water blown out by the height of the water level, or by the extent of opening given to the feed cock. The operation, however, of the contrivance would be much the same if the float were dispensed with; but the float acts advantageously in hindering the water from rising too high in the boiler, should too much feed be admitted, and thereby obviates the risk of the water running over into the cylinder. In some boilers sheet iron vessels, called sediment collectors, are employed, which collect into them the impalpable matter, which in Lamb's apparatus is ejected from the boiler at once. One of these vessels, of about the size and shape of a loaf of sugar, is put into each boiler with the apex of the cone turned downwards into a pipe leading overboard, for conducting the sediment away from the boiler. The base of the cone stands some distance above the water line, and in its sides conical slits are cut, so as to establish a free communication between the water within the conical vessel and the water outside it. The particles of stony matter which are ballooned to the surface by the steam in every other part of the boiler, subside within the cone, where, no steam being generated, the water is consequently tranquil; and the deposit is discharged overboard by means of a pipe communicating with the sea. By blowing off from the surface of the water, the requisite cleansing action is obtained with less waste of heat; and where the water is muddy, the foam upon the surface of the water is ejected from the boiler--thereby removing one of the chief causes of priming. 400. _Q._--What is the cause of the rapid corrosion of marine boilers? _A._--Marine boilers are corroded externally in the region of the steam chest by the dripping of water from the deck; the bottom of the boiler is corroded by the action of the bilge water, and the ash pits by the practice of quenching the ashes with, salt water. These sources of injury, however, admit of easy remedy; the top of the boiler may be preserved from external corrosion by covering it with felt upon which is laid sheet lead soldered at every joint so as to be impenetrable to water; the ash pits may be shielded by guard plates which are plates fitting into the ash pits and attached to the boiler by a few bolts, so that when worn they may be removed and new ones substituted, whereby any wear upon the boiler in that part will be prevented; and there will be very little wear upon the bottom of a boiler if it be imbedded in mastic cement laid upon a suitable platform. 401. _Q._--Are not marine boilers subject to internal corrosion? _A._--Yes; the greatest part of the corrosion of a boiler takes place in the inside of the steam chest, and the origin of this corrosion is one of the obscurest subjects in the whole range of engineering. It cannot be from the chemical action of the salt water upon the iron, for the flues and other parts of the boiler beneath the water suffer very little from corrosion, and in steam vessels provided with Hall's condensers, which supply the boiler with fresh water, not much increased durability of the boiler has been experienced. Nevertheless, marine boilers seldom last more than for 5 or 6 years, whereas land boilers made of the same quality of iron often last 18 or 20 years, and it does not appear probable that land boilers would last a very much shorter time if salt water were used in them. The thin film of scale spread over the parts of a marine boiler situated beneath the water, effectually protect them from corrosion; and when the other parts are completely worn out the flues generally remain so perfect, that the hammer marks upon them are as conspicuous as at their first formation. The operation of the steam in corroding the interior of the boiler is most capricious--the parts which are most rapidly worn away in one boiler being untouched in another; and in some cases one side of a steam chest will be very much wasted away while the opposite side remains uninjured. Sometimes the iron exfoliates in the shape of a black oxide which comes away in flakes like the leaves of a book, while in other cases the iron appears as if eaten away by a strong acid which had a solvent action upon it. The application of felt to the outside of a boiler, has in several cases been found to accelerate sensibly its internal corrosion; boilers in which there is a large accumulation of scale appear to be more corroded than where there is no such deposit; and where the funnel passes through the steam chest the iron of the steam chest is invariably much more corroded than where the funnel does not pass through it. 402. _Q._--Can you suggest no reason for the rapid internal corrosion of marine boilers? _A._--The facts which I have enumerated appear to indicate that the internal corrosion of marine boilers is attributable chiefly to the existence of surcharged steam within them, which is steam to which an additional quantity of heat has been communicated subsequently to its generation, so that its temperature is greater than is due to its elastic force; and on this hypothesis the observed facts relative to corrosion become to some extent explicable. Felt, applied to the outside of a boiler, may accelerate its internal corrosion by keeping the steam in a surcharged state, when by the dispersion of a part of the heat it would cease to be in that state; boilers in which there is a large accumulation of scale must have worked with the water very salt, which necessarily produces surcharged steam; for the temperature of steam cannot be less than that of the water from which it is generated, and inasmuch as the boiling point of water, under any given pressure, rises with the saltness of the water, the temperature of the steam must rise with the saltness of the water, the pressure remaining the same; or, in other words, the steam must have a higher temperature than is due to its elastic force, or be in the state of surcharged steam. The circumstance of the chimney flue passing through the steam will manifestly surcharge the steam with heat, so that all the circumstances which are found to accelerate corrosion, are it appears such as would also induce the formation of surcharged steam. 403. _Q._--Is it the natural effect of surcharged steam to waste away iron? _A._--It is the natural effect of surcharged steam to oxidate the iron with which it is in contact, as is illustrated by the familiar process for making hydrogen gas by sending steam through a red hot tube filled with pieces of iron; and although the action of the surcharged steam in a boiler is necessarily very much weaker than where the iron is red hot, it manifestly must have _some_ oxidizing effect, and the amount of corrosion produced may be very material where the action is perpetual. Boilers with a large extent of heating surface, or with descending flues circulating through the cooler water in the bottom of the boiler before ascending the chimney, will be less corroded internally than boilers in which a large quantity of the heat passes away in the smoke; and the corrosion of the boiler will be diminished if the interior of any flue passing through the steam be coated with fire brick, so as to present the transmission of the heat in that situation. The best practice, however, appears to consist in the transmission of the smoke through a suitable passage on the outside of the boiler, so as to supersede the necessity of carrying any flue through the steam at all; or a column of water may be carried round the chimney, into which as much of the feed water may be introduced as the heat of the chimney is capable of raising to the boiling point, as under this limitation the presence of feed water around the chimney in the steam chest will fail to condense the steam. 404. _Q._--In steam vessels there are usually several boilers? _A._--Yes, in steam vessels of considerable power and size. 405. _Q._--Are these boilers generally so constructed, that any one of them may be thrown out of use? _A._--Marine boilers are now generally supplied with stop valves, whereby one boiler may be thrown out of use without impairing the efficacy of the remainder. These stop valves are usually spindle valves of large size, and they are for the most part set in a pipe which runs across the steam chests, connecting the several boilers together. The spindles of these valves should project through stuffing boxes in the covers of the valve chests, and they should be balanced by a weighted lever, and kept in continual action by the steam. If the valves be lifted up, and be suffered to remain up, as is the usual practice, they will become fixed by corrosion in that position, and it will be impossible after some time to shut them on an emergency. These valves should always be easily accessible from the engine room; and it ought not to be necessary for the coal boxes to be empty to gain access to them. 406. _Q._--Should each boiler have at least one safety valve for itself? _A._--Yes; it would be quite unsafe without this provision, as the stop valve might possibly jam. Sometimes valves jam from a distortion in the shape of the boiler when a considerable pressure is put upon it. 407. _Q._--How is the admission of the water into the boiler regulated? _A._--The admission of feed water into the boiler is regulated by hand by the engineer by means of cocks, and sometimes by spindle valves raised and lowered by a screw. Cocks appear to be the preferable expedient, as they are less liable to accident or derangement than screw valves, and in modern steam vessels they are generally employed. 408. _Q._--At what point of the boiler is the feed introduced? _A._--The feed water is usually conducted from the feed cock to a point near the bottom of the boiler by means of an internal pipe, the object of this arrangement being to prevent the rising steam from being condensed by the entering water. By being introduced near the bottom of the boiler, the water comes into contact in the first place with the bottoms of the furnaces and flues, and extracts heat from them which could not be extracted by water of a higher temperature, whereby a saving of fuel is accomplished. In some cases the feed water is introduced into a casing around the chimney, from whence it descends into the boiler. This plan appears to be an expedient one when the boiler is short of heating surface, and more than a usual quantity of heat ascends the chimney; but in well proportioned boilers a water casing round the chimney is superfluous. When a water casing is used the boiler is generally fed by a head of water, the feed water being forced up into a small tank, from whence it descends into the boiler by the force of gravity, while the surplus runs to waste, as in the feeding apparatus of land engines. 409. _Q._--Suppose that the engineer should shut off the feed water from the boilers while the engine was working, what would be the result? _A._--The result would be to burst the feed pipes, except for a safety valve placed on the feed pipe between the engine and the boilers, which safety valve opens when any undue pressure comes upon the pipes, and allows the water to escape. There is, however, generally a cock on the suction side of the feed pump, which regulates the quantity of water drawn into the pump. But there must be cocks on the boilers also to determine into which boiler the water shall be chiefly discharged, and these cocks are sometimes all shut accidentally at the same time. 410. _Q._--Is there no expedient in use in steam vessels for enabling the position of the water level in the boiler to determine the quantity of feed water admitted? _A._--In some steam vessels floats have been introduced to regulate the feed, but their action cannot be depended on in agitated water, if applied after the common fashion. Floats would probably answer if placed in a cylinder which communicates with the water in the boiler by means of small holes; and a disc of metal might be attached to the end of a rod extending beneath the water level, so as to resist irregular movements from the motion of the ship at sea, which would otherwise impair the action of the apparatus. 411. _Q._--How is the proper level of the water in the boiler of a steam vessel maintained when, the engine is stopped for some time, and the boiler is blowing off steam? _A._--By means of a separate pump worked sometimes by hand, but usually by a small separate engine called the Donkey engine. This pump, by the aid of suitable cocks, will pump from the sea into the boiler; from the sea upon deck either to wash decks or to extinguish fire; and from the bilge overboard, through a suitable orifice in the side of the ship. LOCOMOTIVE BOILERS. 412. _Q._--Will you recapitulate the general features of locomotive boilers? _A._--Locomotive boilers consist of three portions (see fig. 29): the barrel E, E, containing the tubes, the fire box B, and the smoke box F; of which the barrel smoke box, and external fire box are always of iron, but the internal fire box is generally made of copper, though sometimes also it is made of iron. The tubes are sometimes of iron, but generally of brass fixed in by ferules. The whole of the iron plates of a locomotive boiler Which are subjected to the pressure of steam, should be Lowmoor or Bowling plates of the best quality; and the copper should be coarse grained, rather than rich or soft, and be perfectly free from irregularities of structure and lamination. 413. _Q._--What are the usual dimensions of the barrel? _A._--The thickness of the plates composing the barrel of the boiler varies generally from 5/16ths to 3/8ths of an inch, and the plates should run in the direction of the circumference, so that the fibres of the iron may be in the direction of the strain. The diameter of the barrel commonly varies from 3 ft. to 3 ft. 6 inches; the diameter of the rivets should be from 11/16ths to 3/4ths of an inch, and the pitch of the rivets or distance between their centres should be from 17/8th to 2 inches. 414. _Q._--How are the fire boxes of a locomotive constructed? _A._--The space between the external and internal fire boxes forms a water space, which must be stayed every 4-1/2 or 5 inches by means of copper or iron stay bolts, screwed through the outer fire box into the metal of the inner fire box, and securely riveted within it: iron stay bolts are as durable as copper, and their superior tenacity gives them an advantage. Sometimes tubes are employed as stays. The internal and external fire boxes are joined together at the bottom by a N-shaped iron, and round the fire door they are connected by means of a copper ring 1-1/4 in. thick, and 2 in. broad,--the inner fire box being dished sufficiently outward at that point, and the outer fire box sufficiently inward, to enable a circle of rivets 3/4 of an inch in diameter passing through the copper ring and the two thicknesses of iron, to make a water-tight joint. The thickness of the plates composing the external fire box is in general 3/8ths of an inch if the fire box is circular, and from 3/8ths to 1/2 inch if the fire box is square; and the thickness of the internal fire box is in most cases 7/16ths if copper, and from 3/8ths to 7/16ths of an inch if of iron. Circular internal fire boxes, if made of iron, should be welded rather than riveted, as the rivet heads are liable to be burnt away by the action of the fire; and when the fire boxes are square each side should consist of a single plate, turned over at the edges with a radius of 3 inches, for the introduction of the rivets. 415. _Q._--Is there any provision for stiffening the crown of the furnace in a locomotive? _A._--The roof of the internal fire box, whether flat as in Stephenson's engines, or dome shaped as in Bury's, requires to be stiffened with cross stay bars, but the bars require to be stronger and more numerous when applied to a flat surface. The ends of these stay bars rest above the vertical sides of the fire box; and to the stay bars thus extending across the crown, the crown is attached at intervals by means of stay bolts. There are projecting bosses upon the stay bars encircling the bolts at every point where a bolt goes through, but in the other parts they are kept clear of the fire box crown so as to permit the access of water to the metal; and, with the view of facilitating the ascent of the steam, the bottom of each stay bar should be sharpened away in those parts where it does not touch the boiler. 416. _Q._--Is any inconvenience experienced from the intense heat in a locomotive furnace? _A._--The fire bars in locomotives have always been a source of trouble, as from the intensity of the heat in the furnace they become so hot as to throw off a scale, and to bend under the weight of the fuel. The best alleviation of these evils lies in making the bars deep and thin: 4 or 5 inches deep by five eighths of an inch thick on the upper side, and three eighths of an inch on the under side, are found in practice to be good dimensions. In some locomotives a frame carrying a number of fire bars is made so that it may be dropped suddenly by loosening a catch; but it is found that any such mechanism can rarely be long kept in working order, as the molten clinker by running down between the frame and the boiler will generally glue the frame into its place. It is therefore found preferable to fix the frame, and to lift up the bars by the dart used by the stoker, when any cause requires the fire to be withdrawn. The furnace bars of locomotives are always made of malleable iron, and indeed for every species of boiler malleable iron bars are to be preferred to bars of cast iron, as they are more durable, and may if thin be set closer together, whereby the small coal or coke is saved that would otherwise fall into the ash pit. The ash box of locomotives is made of plate iron, a quarter thick: it should not be less than 10 in. deep, and its bottom should be about 9 in. above the level of the rails. The chimney of a locomotive is made of plate iron one eighth of an inch thick: it is usually of the same diameter as the cylinder, but is better smaller, and must not stand more than 14 ft. high above the level of the rails. 417. _Q._--Are locomotive boilers provided with a steam chest? _A._--The upper portion of the external fire box is usually formed into a steam chest, which is sometimes dome shaped, sometimes semicircular, and sometimes of a pyramidical form, and from this steam chest the steam is conducted away by an internal pipe to the cylinders; but in other cases an independent steam chest is set upon the barrel of the boiler, consisting of a plate iron cylinder, 20 inches in diameter, 2 feet high, and three eighths of an inch thick, with a dome shaped top, and with the seam welded and the edge turned over to form a flange of attachment to the boiler. The pyramidical dome, of the form employed in Stephenson's locomotives, presents a considerable extent of flat surface to the pressure of the steam, and this flat surface requires to be very strongly stayed with angle irons and tension rods; whereas the semiglobular dome of the kind employed in Bury's engines requires no staying whatever. Latterly, however, these domes over the fire box have been either much reduced in size or abandoned altogether. 418. _Q._--Is any beneficial use made of the surplus steam of a locomotive? _A._--To save the steam which is formed when the engine is stationary, a pipe is usually fitted to the boiler, which on a cock being turned conducts the steam into the water in the tender, whereby the feed water is heated, and less fuel is subsequently required. This method of disposing of the surplus steam may be adopted when the locomotive is descending inclines, or on any occasion where more steam is produced than the engine can consume. 419._Q._--What means are provided to facilitate the inspection and cleaning of locomotive boilers? _A._--The man hole, or entrance into the boiler, consists of a circular or oval aperture of about 15 in. diameter, placed in Bury's locomotive at the apex of the dome, and in Stephenson's upon the front of the boiler, a few inches below the level of the rounded part; and the cover of the man hole in Bury's engine contains the safety valve seats. In whatever situation this man hole is placed, the surfaces of the ring encircling the hole, and of the internal part of the door or cover, should be accurately fitted together by scraping or grinding, so that they need only the interposition of a little red lead to make them quite tight when screwed together. Lead or canvas joints, if of any considerable thickness, will not long withstand the action of high pressure steam; and the whole of the joints about a locomotive should be such that they require nothing more than a little paint or putty, or a ring of wire gauze smeared with white or red lead to make them perfectly tight. There must be a mud hole opposite the edge of each water space, if the fire box be square, to enable the boiler to be easily cleaned out, and these holes are most conveniently closed by screwed plugs made slightly taper. A cock for emptying the boiler is usually fixed at the bottom of the fire box, and it should be so placed as to be accessible when the engine is at work, in order that the engine driver may blow off some water if necessary; but it must not be in such a position as to send the water blown off among the machinery, as it might carry sand or grit into the bearings, to their manifest injury. 420. _Q._--Will you state the dimensions of the tube plate, and the means of securing the tubes in it? _A._--The tube plates are generally made from five eighths to three fourths of an inch thick, but seven eighths of an inch thick appears to be preferable, as when the plate is thick the holes will not be so liable to change their figure during the process of feruling the tubes: the distance between the tubes should never be made less than three fourths of an inch, and the holes should be slightly tapered so as to enable the tubes to hold the tube plates together. The tubes are secured in the tube plates by means of taper ferules driven into the ends of the tubes. The ferules are for the most part made of steel at the fire box end, and of wrought iron at the smoke box end, though ferules of malleable cast iron have in some cases been used with advantage: malleable cast iron ferules are almost as easily expanded when hammered cold upon a mandrel, as the common wrought iron ones are at a working heat. Spring steel, rolled with a feather edge, to facilitate its conversion into ferules, is supplied by some of the steel-makers of Sheffield, and it appears expedient to make use of steel thus prepared when steel ferules are employed. In cases where ferules are not employed, it may be advisable to set out the tube behind the tube plate by means of an expanding mandrel. There are various forms of this instrument. One form is that known as Prosser's expanding mandrel, in which there are six or eight segments, which are forced out by means of a hexagonal or octagonal wedge, which is forced forward by a screw. When the wedge is withdrawn, the segments collapse sufficiently to enable them to enter the tube, and there is an annular protuberance on the exterior circle of the segments, which protuberance, when the mandrel is put into the tube, just comes behind the inner edge of the tube plate. When the wedge is tightened up by the screw, the protuberance on the exterior of the segments composing the mandrel causes a corresponding bulge to take place in the tube, at the back of the tube plate, and the tube is thereby brought into more intimate contact with the tube plate than would otherwise be the case. There is a steel ring indented into the segments of Prosser's mandrel, to contract the segments when the central wedge is withdrawn. A more convenient form of the instrument, however, is obtained by placing the segments in a circular box, with one end projecting; and supporting each segment in the box by a tenon, which fits into a mortise in the cylindrical box. To expand the segments, a round tapered piece of steel, like a drift, is forced into a central hole, round which the segments are arranged. A piece of steel tube, also slit up to enable a central drift to expand it, answers very well; but the thickness of that part of the tube in which there requires to be spring enough to let the mandrel expand, requires to be sufficiently reduced to prevent the pieces from cracking when the central drift is driven in by a hammer. The drift is better when made with a globular head, so that it may be struck back by the hammer, as well as be driven in. An expanding mandrel, with a central drift, is more rapid in its operation than when the expansion is produced by means of a screw. 421. _Q._--Will you explain the means that are adopted to regulate the admission of steam to the cylinders? _A._--In locomotives, the admission of the steam from the boiler to the cylinders is regulated by a valve called the regulator, which is generally placed immediately above the internal fire box, and is connected with two copper pipes;--one conducting steam from the highest point of the dome down to it, and the other conducting the steam that has passed through it along the boiler to the upper part of the smoke box. Regulators may be divided into two sorts, viz., those with, sliding valves and steam ports, and those with conical valves and seats, of which the latter kind are the best. The former kind have for the most part consisted of a circular valve and face, with radial apertures, the valve resembling the outstretched wings of a butterfly, and being made to revolve on its central pivot by connecting links between its outer edges, or by its central spindle. In some of Stephenson's engines the regulator consists of a slide valve covering a port on the top of the valve chests. A rod passes from this valve through the smoke box below the boiler, and by means of a lever parallel to the starting lever, is brought up to the engineer's reach. Cocks were at first used as regulators, but were given up, as they were found liable to stick fast. A gridiron slide valve has been used by Stephenson, which consists of a perforated square moving upon a face with an equal number of holes. This plan of a valve gives, with a small movement, a large area of opening. In Bury's engines a sort of conical plug is used, which is withdrawn by turning the handle in front of the fire box: a spiral grove of a very large pitch is made in the valve spindle, in which fits a pin fixed to the boiler, and by turning the spindle an end motion is given to it, which either shuts or opens the steam passage according to the direction in which it is turned. The best regulator would probably be a valve of the equilibrium description, such as is used in the Cornish engine: there would be no friction in such a regulator, and it could be opened or shut with a small amount of force. Such valves, indeed, are now sometimes employed for regulators in locomotives. CHAPTER VIII. CONSTRUCTIVE DETAILS OF ENGINES. PUMPING ENGINES. 422. _Q._--Will you explain the course of procedure in the erection of a pumping engine, such as Boulton and Watt introduced into Cornwall? _A._--The best instructions on this subject are those of Mr. Watt himself, which are as follows:--Having fixed on the proper situation of the pump in the pit, from its centre measure out the distance to the centre of the cylinder, from which set off all the other dimensions of the house, including the thickness of the walls, and dig out the whole of the included ground to the depth of the bottom of the cellar, so that the bottom of the cylinder may stand on a level with the natural ground of the place, or lower, if convenient, for the less the height of the house above the ground, the firmer it will be. The foundations of the walls must be laid at least two feet lower than the bottom of the cellar, unless the foundation be firm rock; and care must be taken to leave a small drain into the pit quite through the lowest part of the foundation of the lever wall, to let off any water that may be spilt in the engine house, or may naturally come into the cellar. If the foundation at that depth does not prove good, you must either go down to a better if in your reach, or make it good by a platform of wood or piles, or both. 423. _Q._--These directions refer to the foundations? _A._.--Yes; but I will now proceed to the other parts. Within the house, low walls must be built to carry the cylinder beams, so as to leave sufficient room to come at the holding down bolts, and the ends of these beams must also be lodged in the wall The lever wall must be built in the firmest manner, and run solid, course by course, with thin lime mortar, care being taken that the lime has not been long slaked. If the house be built of stone, let the stones be large and long, and let many headers be laid through the wall: it should also be a rule, that every stone be laid on the broadest bed it has, and never set on its edge. A course or two above the lintel of the door that leads to the condenser, build into the wall two parallel flat thin bars of iron equally distant from each other, and from the outside and inside of the wall, and reaching the whole breadth of the lever wall. About a foot higher in the wall, lay at every four feet of the breadth of the front, other bars of the same kind at right angles to the former course, and reaching quite through the thickness of the wall; and at each front corner lay a long bar in the middle of the side walls, and reaching quite through the front wall; if these bars are 10 feet or 12 feet long it will be sufficient. When the house is built up nearly to the bottom of the opening under the great beam another double course of bars is to be built in, as has been directed. At the level of the upper cylinder beams, holes must be left in the walls for their ends, with room to move them laterally, so that the cylinder may be got in; and smaller holes must be left quite through the walls for the introduction of iron bars, which being firmly fastened to the cylinder beams at one end, and screwed at the other or outer end, will serve, by their going through both the front and back walls, to bind the house more firmly together. The spring beams or iron bars fastened to them must reach quite through the back wall, and be keyed or screwed up tight; and they must be firmly fastened to the lever wall on each side, either by iron bars, firm pieces of wood, or long strong stones, reaching far back into the wall. They must also be bedded solidly, and the residue of the opening must be built up in the firmest manner. 424. _Q._--If there be a deficiency of water for the purpose of condensation, what course should be pursued? _A._--If there be no water in the neighborhood that can be employed for the purpose of condensation, it will be necessary to make a pond, dug in the earth, for the reception of the water delivered by the air pump, to the end that it may be cooled and used again for the engine. The pond may be three or four feet deep, and lined with turf, puddled, or otherwise made water tight. Throwing up the water into the air in the form of a jet to cool it, has been found detrimental; as the water is then charged with air which vitiates the vacuum. 425. _Q._--How is the piston of a pumping engine packed? _A._--To pack the piston, take sixty common-sized white or untarred rope-yarns, and with them plait a gasket or flat rope as close and firm as possible, tapering for eighteen inches at each end, and long enough to go round the piston, and overlapped for that length; coil this rope the thin way as hard as possible, and beat it with a sledge hammer until its breadth answers the place; put it in and beat it down with a wooden drift and a hand mallet, pour some melted tallow all around, then pack in a layer of white oakum half an inch thick, so that the whole packing may have the depth of five to six inches, depending on the size of the engine; finally, screw down the junk ring. The packing should be beat solid, but not too hard, otherwise it will create so great a friction as to prevent the easy going of the engine. Abundance of tallow should be allowed, especially at first; the quantity required will be less as the cylinder grows smooth. In some of the more modern pumping engines, the piston is provided with metallic packing, consisting for the most part of a single ring with a tongue piece to break the joint, and packed behind with hemp. The upper edge of the metallic ring is sharpened away from the inside so as to permit more conveniently the application of hemp packing behind it; and the junk ring is made much the same as if no metallic packing were employed. 426. _Q._--Will you explain the mode of putting the engine into operation? _A._--To set the engine going, the steam must be raised until the pressure in the steam pipe is at least equal to three pounds on the square inch; and when the cylinder jacket is fully warmed, and steam issues freely from the jacket cock, open all the valves or regulators; the steam will then forcibly blow out the air or water contained in the eduction pipe, and to get rid of the air in the cylinder, shut the steam valve after having blown through the engine for a few minutes. The cold water round the condenser will condense some of the steam contained in the eduction pipe, and its place will be supplied by some of the air from the cylinder. The steam valve must again be opened to blow out that air, and the operation is to be repeated until the air is all drawn out of the cylinder. When that is the case shut all the valves, and observe if the vacuum gauge shows a vacuum in the condenser; when there is a vacuum equivalent to three inches of mercury, open the injection a very little, and shut it again immediately; and if this produces any considerable vacuum, open the exhausting valve a very little way, and the injection at the same time. If the engine does not now commence its motion, it must be blown through again until it moves. If the engine be lightly loaded, or if there be no water in the pumps, the throttle valve must be kept nearly closed, and the top and exhaustion regulators must be opened only a very little way, else the engine will make its stroke with violence, and perhaps do mischief. If there is much unbalanced weight on the pump end, the plug which opens the steam valve must be so regulated, that the valve will only be opened very slightly; and if after a few strokes it is found that the engine goes out too slowly, the valve may be then so adjusted as to open wider. The engine should always be made to work full stroke, that is, until the catch pins be made to come within half an inch of the springs at each end, and the piston should stand high enough in the cylinder when the engine is at rest, to spill over into the perpendicular steam pipe any water which may be condensed above it; for if water remain upon the piston, it will increase the consumption of steam. When the engine is to be stopped, shut the injection valve and secure it, and adjust the tappets so as to prevent the exhausting valve from opening and to allow the steam valve to open and remain open, otherwise a partial vacuum may arise in the cylinder, and it may be filled with water from the injection or from leaks. A single acting engine, when it is in good order, ought to be capable of going as slow as one stroke in ten minutes, and as fast as ten strokes in one minute; and if it does not fulfil these conditions, there is some fault which should be ascertained and remedied. 427. _Q._--Your explanation has reference to the pumping engine as introduced into Cornwall by Watt: have any modifications been since made upon it? _A._--In the modern Cornish engines the steam is used very expansively, and a high pressure of steam is employed. In some cases a double cylinder engine is used, in which the steam, after having given motion to a small piston on the principle of a high pressure engine, passes into a larger cylinder, where it operates on the principle of a condensing engine; but there is no superior effect gained by the use of two cylinders, and there is greater complexity in the apparatus. Instead of the lever walls, cast iron columns are now frequently used for supporting the main beam in pumping engines, and the cylinder end of the main beam is generally made longer than the pump end in engines made in Cornwall, so as to enable the cylinder to have a long stroke, and the piston to move quickly, without communicating such a velocity to the pump buckets as will make them work with such a shock as to wear themselves out quickly. A high pressure of steam, too, can be employed where the stroke is long, without involving the necessity of making the working parts of such large dimensions as would otherwise be necessary; for the strength of the parts of a single acting engine will require to be much the same, whatever the length of the stroke may be. 428. _Q._--What kind of pump is mostly used in draining deep mines? _A._--The pump now universally preferred is the plunger pump, which admits of being packed or tightened while the engine is at work; but the lowest lift of a mine is generally supplied with a pump on the suction principle, both with the view of enabling the lowest pipe to follow the water with facility as the shaft is sunk deeper, and to obviate the inconvenience of the valves of the pump being rendered inaccessible by any flooding in the mine. The pump valves of deep mines are a perpetual source of expense and trouble, as from the pressure of water upon them it is difficult to prevent them from closing with violence; and many expedients have been contrived to mitigate the evil, of which the valve known as Harvey and West's valve has perhaps gained the widest acceptation. 429. _Q._--Will you describe Harvey and West's pump valve? _A._--This valve is a compromise between the equilibrium valve, of the kind employed for admitting the steam to and from the cylinder in single acting engines, and the common spindle valve formerly used for that purpose; and to comprehend its action, it is necessary that the action of the equilibrium valve, which has been already represented fig. 34, should first be understood. This valve consists substantially of a cylinder open at both ends, and capable of sliding upon a stationary piston fixed upon a rod the length of the cylinder, which proceeds from the centre of the orifice the valve is intended to close. It is clear, that when the cylinder is pressed down until its edge rests upon the bottom of the box containing it, the orifice of the pipe must be closed, as the steam can neither escape past the edge of the cylinder nor between the cylinder and the piston; and it is equally clear, that as the pressure upon the cylinder is equal all around it, and the whole of the downward pressure is maintained by the stationary piston, the cylinder can be raised or lowered without any further exertion of force than is necessary to overcome the friction of the piston and of the rod by which the cylinder is raised. Instead of the rubbing surface of a piston, however, a conical valve face between the cylinder and piston is employed, which is tight only when the cylinder is in its lowest position; and there is a similar face between, the edge of the cylinder and the bottom of the box in which it is placed. The moving part of the valve, too, instead of being a perfect cylinder, is bulged outward in the middle, so as to permit the steam to escape past the stationary piston when the cylindrical part of the valve is raised. It is clear, that if such a valve were applied to a pump, no pressure of water within the pump would suffice to open it, neither would any pressure of water above the valve cause it to shut with violence; and if an equilibrium valve, therefore, be used as a pump valve at all, it must be opened and shut by mechanical means. In Harvey and West's valves, however, the equilibrium principle is only partially adopted; the lower face is considerably larger in diameter than the upper face, and the difference constitutes an annulus of pressure, which will cause the valve to open or shut with the same force as a spindle valve of the area of the annulus. To deaden the shock still more effectually, the lower face of the valve is made to strike upon end wood driven into an annular recess in the pump bucket; and valves thus constructed work with very little noise or tremor; but it is found in practice, that the use of Harvey and West's valve, or any contrivance of a similar kind, adds materially to the load upon the pump, especially in low lifts where the addition of a load, to the valve makes a material addition to the total resistance which the engine has to overcome. Instead of end wood driven into a recess for the valve to strike upon, a mixture of tin and lead cast in a recess is now frequently used, and is found to be preferable to the wood. 430. _Q._--Is there any other kind of pump valve which is free from the shocks incidental to the working of common valves? _A._--In some cases canvass valves are used for pumps, with the effect of materially mitigating the shock; but they require frequent renewal, and are of inferior eligibility in their action to the slide valve, which might in many cases be applied to pumps without inconvenience. 431. _Q._--Could not a form of pump be devised capable of working without valves at all? _A._.--It appears probable, that by working a common reciprocating pump at a high speed, a continuous flow of water might be maintained through the pipes in such a way as to render the existence of any valves superfluous after once the action was begun, the momentum of the moving water acting in fact as valves. The centrifugal pump, however, threatens to supersede pumps of every other kind; and if the centrifugal pump be employed there will be no necessity for pump valves at all. There is less loss of effect by the centrifugal pump than by the common pump. 432. _Q._--What is the best form of the centrifugal pump? _A._--There are two forms in which the centrifugal pump may be applied to mines;--that in which the arms diverge from the bottom, like the letter V; and that in which revolving arms are set in a tight case near the bottom of the mine, and are turned by a shaft from the surface. Such pumps both draw and force; and either by arranging them in a succession of lifts in the shaft of the mine, or otherwise, the water may be drawn without inconvenience from any depth. The introduction of the centrifugal pump would obviously extinguish the single acting engine, as rotative engines working at a high speed would be the most appropriate form of engine where the centrifugal pump was employed. 433. _Q._--This would not be a heavy deprivation? _A._--The single acting engine is a remnant of engineering barbarism which must now be superseded by more compendious contrivances. The Cornish engines, though rudely manufactured, are very expensive in production, as a large engine does but little work; whereas by employing a smaller engine, moving with a high speed, the dimensions may be so far diminished that the most refined machinery may be obtained at less than the present cost. 434. _Q._--Are not the Cornish engines more economical in fuel than other engines? _A._--It is a mistake to suppose that there is any peculiar virtue in the existing form of Cornish engine to make it economical in fuel, or that a less lethargic engine would necessarily be less efficient. The large duty of the engines in Cornwall is traceable to the large employment of the principle of expansion, and to a few other causes which may be made of quite as decisive efficacy in smaller engines working with a quicker speed; and there is therefore no argument in the performance of the present engines against the proposed substitution. VARIOUS FORMS OF MARINE ENGINES. 435. _Q._--What species of paddle engine do you consider to be the best? _A._--The oscillating engine. 436. _Q._--Will you explain the grounds of that preference? _A._--The engine occupies little space, consists of few parts, is easily accessible for repairs, and may be both light and strong at the same time. In the case of large engines the crank in the intermediate shaft is a disadvantage, as it is difficult to obtain such a forging quite sound. But by forging it in three cranked flat bars, which are then laid together and welded into a square shaft, a sound forging will be more probable, and the bars should be rounded a little on the sides which are welded to allow the scoriae to escape during that operation. It is important in so large a forging not to let the fire be too fierce, else the surface of the iron will be burnt before the heart is brought to a welding heat. In some cases in oscillating engines the air pump has been wrought by an eccentric, and that may at any time be done where doubt of obtaining a sound intermediate shaft is entertained; but the precaution must be taken to make the eccentric very wide so as to distribute the pressure over a large surface, else the eccentric will be apt to heat. 437. _Q._--Have not objections been brought against the oscillating engine? _A._--In common with every other improvement, the oscillating engine, at the time of its introduction, encountered much opposition. The cylinder, it was said, would become oval, the trunnion bearings would be liable to heat and the trunnion joints to leak, the strain upon the trunnions would be apt to bend in or bend out the sides of the cylinder; and the circumstance of the cylinder being fixed across its centre, while the shaft requires to accommodate itself to the working of the ship, might, it was thought, be the occasion of such a strain upon the trunnions as would either break them or bend the piston rod. It is a sufficient reply to these objections to say that they are all hypothetical, and that none of them in practice have been found to exist--to such an extent at least as to occasion any inconvenience; but it is not difficult to show that they are altogether unsubstantial, even without a recourse to the disproofs afforded by experience. 438. _Q._--Is there not a liability in the cylinder to become oval from the strain thrown on it by the piston? _A._--There is, no doubt, a tendency in oscillating engines for the cylinder and the stuffing box to become oval, but after a number of years' wear it is found that the amount of ellipticity is less than that which is found to exist in the cylinders of side lever engines after a similar trial. The resistance opposed by friction to the oscillation of the cylinder is so small, that a man is capable of moving a large cylinder with one hand; whereas in the side lever engine, if the parallel motion be in the least untrue, which is, at some time or other, an almost inevitable condition, the piston is pushed with great force against the side of the cylinder, whereby a large amount of wear and friction is occasioned. The trunnion bearings, instead of being liable to heat like other journals, are kept down to the temperature of the steam by the flow of steam passing through them; and the trunnion packings are not liable to leak when the packings, before being introduced, are squeezed in a cylindrical mould. 439. _Q._--Might not the eduction trunnions be immersed in water? _A._--In some cases a hollow, or lantern brass, about one third or one fourth the length of the packing space, and supplied with steam or water by a pipe, is introduced in the middle of the packing, so that if there be any leakage through the trunnion, it will be a leakage of steam or water, which will not vitiate the vacuum; but in ordinary cases this device will not be necessary, and it is not commonly employed. It is clear that there can be no buckling of the sides of the cylinder by the strain upon the trunnions, if the cylinder be made strong enough, and in cylinders of the ordinary thickness such an action has never been experienced; nor is it the fact, that the intermediate shaft of steam vessels, to which part alone the motion is communicated by the engine, requires to adapt itself to the altering forms of the vessel, as the engine and intermediate shaft are rigidly connected, although the paddle shaft requires to be capable of such an adaptation. Even if this objection existed, however, it could easily be met by making the crank pin of the ball and socket fashion, which would permit the position of the intermediate shaft, relatively with that of the cylinder, to be slightly changed, without throwing an undue strain upon any of the working parts. 440. _Q._--Is the trunk engine inferior to the oscillating? _A._--A very elegant and efficient arrangement of trunk engine suitable for paddle vessels has latterly been employed by Messrs. Rennie, of which all the parts resemble those of Penn's oscillating engine except that the cylinders are stationary instead of being movable; and a round trunk or pipe set upon the piston, and moving steam tight through the cylinder cover, enables the connecting rod which is fixed to the piston to vibrate within it to the requisite extent. But the vice of all trunk engines is that they are necessarily more wasteful of steam, as the large mass of metal entering into the composition of the trunk, moving as it does alternately into the atmosphere and the steam, must cool and condense a part of the steam. The radiation of heat from the interior of the trunk will have the same operation, though in vertical trunk engines the loss from this cause might probably be reduced by filling the trunk with oil, so far as this could be done without the oil being spilt over the edge. 441. _Q._--What species of screw engine do you consider the best? _A._--I am inclined to give the preference to a variety of the horizontal steeple engine, such as was first used in H.M.S. Amphion. In this engine the cylinders lie on their sides, and they are placed near the side of the vessel with their mouths pointing to the keel. From each cylinder two long piston rods proceed across the vessel to a cross head working in guides; and from this cross head a connecting rod returns back to the centre of the vessel and gives motion to the crank. The piston rods are so placed in the piston that one of them passes above the crank shaft, and the other below the crank shaft. The cross head lies in the same horizontal plane as the centre of the cylinder, and a lug projects upwards from the cross head to engage one piston rod, and downwards from the cross head to engage the other piston rod. The air pump is double acting, and its piston or bucket has the same stroke as the piston of the engine. The air pump bucket derives its motion from an arm on the cross head, and a similar arm is usually employed in engines of this class to work the feed and bilge pumps. 442. _Q._--Is not inconvenience experienced in direct acting screw engines from the great velocity of their motion? _A._--Not if they are properly constructed; but they require to be much stronger, to be fitted with more care, and to have the bearing surfaces much larger than is necessary in engines moving slowly. The momentum of the reciprocating parts should also be balanced by a weight applied to the crank or crank shaft, as is done in locomotives. A very convenient arrangement for obtaining surface is to form the crank of each engine of two cast iron discs cast with heavy sides, the excess of weight upon the heavy sides being nearly equal to that of the piston and its connections. When the piston is travelling in one direction the weights are travelling in the opposite; and the momentum of the piston and its attachments, which is arrested at each reciprocation, is just balanced by the equal and opposite momentum of the weights. One advantage of the horizontal engine is, that a single engine may be employed, whereby greater simplicity of the machinery and greater economy of fuel will be obtained, since there will be less radiating surface in one cylinder than in two. CYLINDERS, PISTONS, AND VALVES, 443. _Q._--Is it a beneficial practice to make cylinders with steam jackets? _A._--In Cornwall, where great attention is paid to economy of fuel, all the engines are made with steam jackets, and in some cases a flue winds spirally round the cylinder, for keeping the steam hot. Mr. Watt, in his early practice, discarded the steam jacket for a time, but resumed it again, as he found its discontinuance occasioned a perceptible waste of fuel; and in modern engines it has been found that where a jacket is used less coal is consumed than where the use of a jacket is rejected. The cause of this diminished effect is not of very easy perception, for the jacket exposes a larger radiating surface for the escape of the heat than the cylinder; nevertheless, the fact has been established beyond doubt by repeated trials, that engines provided with a jacket are more economical than engines without one. The exterior of the cylinder, or jacket, should be covered with several plies of felt, and then be cased in timber, which must be very narrow, the boards being first dried in a stove, and then bound round the cylinder with hoops, like the staves of a cask. In many of the Cornish engines the steam is let into casings formed in the cylinder cover and cylinder bottom, for the further economisation of the heat, and the cylinder stuffing box is made very deep, and a lantern or hollow brass is introduced into the centre of the packing, into which brass the steam gains admission by a pipe provided for the purpose; so that in the event of the packing becoming leaky, it will be steam that will be leaked into the cylinder instead of air, which, being incondensable, would impair the efficiency of the engine. A lantern brass, of a similar kind, is sometimes introduced into the stuffing boxes of oscillating engines, but its use there is to receive the lateral pressure of the piston rod, and thus take any strain off the packing. 444. _Q._--Will you explain the proper course to pursue in the production of cylinders? _A._--In all engines the valve casing, if made in a separate piece from the cylinder, should be attached by means of a metallic joint, as such a barbarism as a rust joint in such situations is no longer permissible. In the case of large engines with valve casings suitable for long slides, an expansion joint in the valve casing should invariably be inserted, otherwise the steam, by gaining admission to the valve casing before it can enter the cylinder, expands the casing while the cylinder remains unaltered in its dimensions, and the joints are damaged, and in some cases the cylinder is cracked by the great strain thus introduced. The chest of the blow-through valve is very commonly cast upon the valve casing; and in engines where the cylinders are stationary this is the most convenient practice. All engines, where the valve is not of such a construction as to leave the face when a pressure exceeding that of the steam is created in the cylinder by priming or otherwise, should be provided with an escape valve to let out the water, and such valve should be so constructed that the water cannot fly out with violence over the attendants; but it should be conducted away by a suitable pipe, to a place where its discharge can occasion no inconvenience. The stuffing boxes of all engines which cannot be stopped frequently to be repacked, should be made very deep; metallic packing in the stuffing box has been used in some engines, consisting in most instances of one or more rings, cut, sprung, and slipped upon the piston rod before the cross head is put on, and packed with hemp behind. This species of packing answers very well when the parallel motion is true, and the piston rod free from scratches, and it accomplishes a material saving of tallow. In some cases a piece of sheet brass, packed behind with hemp, has been introduced with good effect, a flange being turned over on the under edge of the brass to prevent it from slipping up or down with the motion of the rod. The sheet brass speedily puts an excellent polish upon the rod, and such a packing is more easily kept, and requires less tallow than where hemp alone is employed. In side lever marine engines the attachments of the cylinder to the diagonal stay are generally made of too small an area, and the flanges are made too thick. A very thick flange cast on any part of a cylinder endangers the soundness of the cylinder, by inducing an unequal contraction of the metal; and it is a preferable course to make the flange for the attachment or the framing thin, and the surface large--the bolts being turned bolts and nicely fitted. If from malformation in this part the framing works to an inconvenient extent, the best expedient appears to be the introduction of a number of steel tapered bolts, the holes having been previously bored out; and if the flanges be thick enough, square keys may also be introduced, half into one flange and half into the other, so as to receive the strain. If the jaw cracks or breaks away, however, it will be best to apply a malleable iron hoop around the cylinder to take the strain, and this will in all cases be the preferable expedient, where from any peculiarities of structure there is a difficulty in introducing bolts and keys of sufficient strength. 445. _Q._--Which is the most eligible species of piston? _A._--For large engines, pistons with a metallic packing, consisting of a single ring, with the ends morticed into one another, and a piece of metal let in flush over the joint and riveted to one end of the ring, appears to be the best species of piston; and if the cylinder be oscillating, it will be expedient to chamfer off the upper edge of the ring on the inner side, and to pack it at the back with hemp. If the cylinder be a stationary one, springs may be substituted for the hemp packing, but in any case it will be expedient to make the vertical joints of the ends of the ring run a little obliquely, so as to prevent the joint forming a ridge in the cylinder. For small pistons two rings may be employed, made somewhat eccentric internally to give a greater thickness of metal in the centre of the ring; these rings must be set one above the other in the cylinder, and the joints, which are oblique, must be set at right angles with one another, so as to obviate any disposition of the rings, in their expansion, to wear the cylinder oval. The rings must first be turned a little larger than the diameter of the cylinder, and a piece is then to be cut out, so that when the ends are brought together the ring will just enter within the cylinder. The ring, while retained in a state of compression, is then to be put in the lathe and turned very truly, and finally it is to be hammered on the inside with the small end of the hammer, to expand the metal, and thus increase the elasticity. 446. _Q._--The rings should be carefully fitted to one another laterally? _A._--The rings are to be fitted laterally to the piston, and to one another, by scraping--a steady pin being fixed upon the flange of the piston, and fitting into a corresponding hole in the lower ring, to keep the lower ring from turning round; and a similar pin being fixed into the top edge of the lower ring to prevent the upper ring from turning round; but the holes into which these pins fit must be made oblong, to enable the rings to press outward as the rubbing surfaces wear. In most cases it will be expedient to press the packing rings out with springs where they are not packed behind with hemp, and the springs should be made very strong, as the prevailing fault of springs is their weakness. Sometimes short bent springs, set round at regular intervals between the packing rings and body of the piston, are employed, the centre of each spring being secured by a steady pin or bolt screwed into the side of the piston; but it will not signify much what kind of springs is used, provided they have sufficient tension. When pistons are made of a single ring, or of a succession of single rings, the strength of each ring should be tested previously to its introduction into the piston, by means of a lever loaded by a heavy weight. 447. _Q._--What kind of piston is employed by Messrs. Penn? _A._--Messrs. Penn's piston for oscillating engines has a single packing ring, with a tongue piece, or mortice end, made in the manner already described. The ring is packed behind with hemp packing, and the piece of metal which covers the joint is a piece of thick sheet copper or brass, and is indented into the iron of the ring, so as to offer no obstruction to the application of the hemp. The ring is fitted to the piston only on the under edge; the top edge is rounded to a point from the inside, and the junk ring does not bear upon it, but the junk ring squeezes down the hemp packing between the packing ring and the body of the piston. 448. _Q._--How should the piston rod be secured to the piston? _A._--The piston rod, where it fits into the piston, should have a good deal of taper; for if the taper be too small the rod will be drawn through the hole, and the piston will be split asunder. Small grooves are sometimes turned out of the piston rod above and below the cutter hole, and hemp is introduced in order to make the piston eye tight. Most piston rods are fixed to the piston by means of a gib and cutter, but in some cases the upper portion of the rod within the eye is screwed, and it is fixed into the piston by means of an indented nut. This nut is in some cases hexagonal, and in other cases the exterior forms a portion of a cone which completely fills a corresponding recess in the piston; but nuts made in this way become rusted into their seat after some time, and cannot be started again without much difficulty. Messrs. Miller, Ravenhill & Co. fix in their piston rods by means of an indented hexagonal nut, which may be started by means of an open box key. The thread of the screw is made flat upon the one side and much slanted on the other, whereby a greater strength is secured, without creating any disposition to split the nut. In side lever engines it is a judicious practice to add a nut to the top of the piston rod, in addition to the cutter for securing the piston rod to the cross head. In a good example of an engine thus provided, the piston rod is 7 in. in diameter, and the screw 5 in.; the part of the rod which fits into the cross head eye is 1 ft. 5-1/2 in. long, and tapers from 6-1/2 in. to 6-13/16 in. diameter. This proportion of taper is a good one; if the taper be less, or if a portion of the piston rod within the cross head eye be left untapered, as is sometimes the case, it is very difficult to detach the parts from one another. 449. _Q._--Which is the most beneficial construction of slide valve? _A._--The best construction of slide valve appears to be that adopted by Messrs. Penn for their larger engines, and which consists of a three ported valve, to the back of which a ring is applied of an area equal to that of exhaustion port, and which, by bearing steam tight against the back of the casing, so that a vacuum may be maintained within the ring, puts the valve in equilibrium, so that it may be moved with an inconsiderable exercise of force. The back of the valve casing is put on like a door, and its internal surface is made very true by scraping. There is a hole through the valve so as to conduct away any steam which may enter within the ring by leakage, and the ring is kept tight against the back of the casing by means of a ring situated beneath the bearing ring, provided with four lugs, through which bolts pass tapped into bosses on the back of the valve; and, by unscrewing these bolts,--which may be done by means of a box key which passes through holes in the casing closed with screwed plugs,--the lower ring is raised upwards, carrying the bearing ring before it. The rings must obviously be fitted over a boss upon the back of the valve; and between the rings, which are of brass, a gasket ring is interposed to compensate by its compressibility for any irregularity of pressure, and each of the bolts is provided with a ratchet collar to prevent it from turning back, so that the engineer, in tightening these bolts, will have no difficulty in tightening them equally, if he counts the number of clicks made by the ratchet. Where this species of valve is used, it is indispensable that large escape valves be applied to the cylinder, as a valve on this construction is unable to leave the face. In locomotive engines, the valve universally employed is the common three ported valve. 450. _Q._--Might not an equilibrium valve be so constructed by the interposition of springs, as to enable it to leave the cylinder face when an internal force is applied? _A._--That can no doubt be done, and in some engines has been done. In the screw steamer Azof, the valve is of the equilibrium construction, but the plate which carries the packing on which the top ring rests, is an octagon, and fits into an octagonal recess on the back of the valve. Below each side of the octagon there is a bent flat spring, which lifts up the octagonal plate, and with it the packing ring against the back of the valve casing; and should water get into the cylinder, it escapes by lifting the valve, which is rendered possible by the compressibility of the springs. An equivalent arrangement is shown in figs. 39 and 40, where the ring is lifted by spiral springs. [Illustration: Fig. 39. EQUILIBRIUM GRIDIRON SLIDE VALVE. Longitudinal Section. Scale 3/4 inch = 1 foot.] 451. _Q._--What species of valve is that shown in figs. 39 and 40? [Illustration: Fig. 40. EQUILIBRIUM GRIDIRON SLIDE VALVE. Back View with Ring removed. Scale 3/4 inch = 1 foot.] _A._--It is an equilibrium gridiron valve; so called because it lets the steam in and out by more than one port. A A are the ordinary steam passages to the top and bottom of the cylinder; B B is the ring which rubs against the back of the valve casing, and D is the eduction passage, S S S S shows the limits of the steam space, for the steam penetrates to the central chamber S S by the sides of the valve. When the valve is opened upon the steam side, the cylinder receives steam through both ports at that end of the cylinder, and both ports at the other end of the cylinder are at the same time open to the eduction. The benefit of this species of valve is, that it gives the same opening of the valve that is given in ordinary engines, with half the amount of travel; or if three ports were made instead of two, then it would give the same area of opening that is given in common engines with one third the amount of travel. For direct acting screw engines this species of valve is now extensively used. 452. _Q._--Will you describe the configuration and mode of attachment of the eccentric by which the valve is moved? _A._--In marine engines, whether paddle or screw, if moving at a slow rate of speed, the eccentric is generally loose upon the shaft, for the purpose of backing, and is furnished with a back balance and catches, so that it may stand either in the position for going ahead, or in that for going astern. The body of the eccentric is of cast iron, and it is put on the shaft in two pieces. The halves are put together with rebated joints to keep them from separating laterally, and they are prevented from sliding out by round steel pins, each ground into both halves; square keys would probably be preferable to round pins in this arrangement, as the pins tend to wedge the jaws of the eccentric asunder. In some cases the halves of the eccentric are bolted together by means of flanges, which is, perhaps, the preferable practice. The eccentric hoop in marine and land engines is generally of brass; it is expedient to cast an oil cup on the eccentric hoop, and, where practicable, a pan should be placed beneath the eccentric for the reception of the oil droppings. The notch of the eccentric rod for the reception of the pin of the valve shaft is usually steeled, to prevent inconvenient wear; for when the sides of the notch wear, the valve movement is not only disturbed, but it is very difficult to throw the eccentric rod out of gear. It is found to be preferable, however, to fit this notch with a brass bush, for the wear is then less rapid, and it is an easy thing to replace this bush with another when it becomes worn. The eccentric catches of the kind usually employed in marine engines, sometimes break off at the first bolt hole, and it is preferable to have a bolt in advance of the catch face, or to have a hoop encircling the shaft with the catches welded on it, the hoop itself being fixed by bolts or a key. This hoop may either be put on before the cranks in one piece or afterwards in two pieces. 453. _Q._--Are such eccentrics used in direct acting screw engines? _A._--No; direct acting screw engines are usually fitted with the link motion and two fixed eccentrics. AIR PUMP AND CONDENSER. 454. _Q._--What are the details of the air pump? _A._--The air pump bucket and valves are all of brass in modern marine engines, and the chamber of the pump is lined with copper, or made wholly of brass, whereby a single boring suffices. When a copper lining is used, the pump is first bored out, and a bent sheet of copper is introduced, which is made accurately to fill the place, by hammering the copper on the inside. Air pump rods of Muntz's metal or copper are much used. Iron rods covered with brass are generally wasted away where the bottom cone fits into the bucket eye, and if the casing be at all porous, the water will insinuate itself between the casing and the rod and eat away the iron. If iron rods covered with brass be used, the brass casing should come some distance into the bucket eye; the cutter should be of brass, and a brass washer should cover the under side of the eye, so as to defend the end of the rod from the salt water. Rods of Muntz's metal are probably on the whole to be preferred. It is a good practice to put a nut on the top of the rod, to secure it more firmly in the cross head eye, where that plan can be conveniently adopted. The part of the rod which fits into the cross head eye should have more taper when made of copper or brass, than when made of iron; as, if the taper be small, the rod may get staved into the eye, whereby its detachment will be difficult. 455. _Q._--What species of packing is used in air pumps? _A._--Metallic packing has in some instances been employed in air pump buckets, but its success has not been such as to lead to its further adoption. The packing commonly employed is hemp. A deep solid block of metal, however, without any packing, is often employed with a satisfactory result; but this block should have circular grooves cut round its edge to hold water. Where ordinary packing is employed, the bucket should always be made with a junk ring, whereby the packing may be easily screwed down at any time with facility. In slow moving engines the bucket valve is generally of the spindle or pot-lid kind, but butterfly valves are sometimes used. The foot and delivery valves are for the most part of the flap or hanging kind. These valves all make a considerable noise in working, and are objectionable in many ways. Valves on Belidor's construction, which is in effect that of a throttle valve hung off the centre, were some years ago proposed for the delivery and foot valves; and it appears probable that their operation would be more satisfactory than that of the valves usually employed. 456. _Q._--Where is the delivery valve usually situated? _A._--Some delivery valve seats are bolted into the mouth of the air pump, whereby access to the pump bucket is rendered difficult: but more commonly the delivery valve is a flap valve exterior to the pump. If delivery valve seats be put in the mouth of the air pump at all, the best mode of fixing them appears to be that adopted by Messrs. Maudslay. The top of the pump barrel is made quite fair across, and upon this flat surface a plate containing the delivery valve is set, there being a small ledge all round to keep it steady. Between the bottom of the stuffing box of the pump cover and the eye of the valve seat a short pipe extends encircling the pump rod, its lower end checked into the eye of the valve seat, and its upper end widening out to form the bottom of the stuffing box of the pump cover. Upon the top of this pipe some screws press, which are accessible from the top of the stuffing box gland, and the packing also aids in keeping down the pipe, the function of which is to retain the valve seat in its place. When the pump bucket has to be examined the valve seat may be slung with the cover, so as to come up with the same purchase. For the bucket valves of such pumps Messrs. Maudslay employ two or more concentric ring valves with a small lift. These valves have given a good deal of trouble in some cases, in consequence of the frequent fracture of the bolts which guide and confine the rings; but this is only a fault of detail which is easily remedied, and the principle appears to be superior to that of any of the other metallic air pump valves at present in common use. [Illustration: Fig. 41. TRUNK AIR PUMP. Scale 3/4 inch to 1 foot.] 457. _Q._--Are not air pump valves now very generally made of india rubber? _A._--They are almost invariably so made if the engines are travelling fast, as in the case of direct acting screw engines, and they are very often made of large discs or rings of india rubber, even when the engines travel slowly. A very usual and eligible arrangement for many purposes is that shown in fig. 41, where both foot and delivery valves are situated in the ends of the pump, and they, as well as the valve in the bucket are made of india rubber rings closing on a grating. The trunk in the air pump enables guide rods to be dispensed with. [Illustration: Fig. 42. PENN'S DISK VALVE FOR AIR PUMP. Section.] [Illustration: Fig. 43. PENN'S DISK VALVE FOR AIR PUMP. Ground Plan.] [Illustration: Fig. 44. MAUDSLAY'S DISC VALVE FOR AIR PUMP. Section.] 458. _Q._--The air pump, when double acting, has of course inlet and outlet valves at each end? _A._--Yes; and the general arrangement of the valves of double acting air pumps, such as are usual in direct acting screw engines, is that represented in the figure of Penn's trunk engine already described in Chapter I. Each inlet and outlet valve consists of a number of india rubber discs set over a perforated brass plate, and each disc is bound down by a bolt in the middle, which bolt also secures a brass guard set above the disc to prevent it from rising too high. The usual configuration of those valves is that represented in figs. 42, 43, and 44; figs. 42 and 43 being a section and ground plan of the species of valve used by Messrs. Penn, and fig. 44 being a section of that used by Messrs. Maudslay. It is important in these valves to have the india rubber thick,--say about an inch thick for valves eight inches in diameter. It is also advisable to make the central bolts with a nut above and a nut below, and to form the bolt with a counter sunk neck, so that it will not fall down when the top nut is removed. The lower point of the bolt should be riveted over on the nut to prevent it from unscrewing, and the top end should have a split pin through the point for the same purpose. The hole through which the bolt passes should be tapped, though the bolt is not screwed into it, so that if a bolt breaks, a temporary stud may be screwed into the hole without the necessity of taking out the whole plate. The guard should be large, else the disc may stretch in the central hole until it comes over it; but the guard should not permit too much lift of the valve, else a good deal of the water and air will return into the pump at the return stroke before the valve shuts. Penn's guard is rather small, and Maudslay's permits too much lift. 459. _Q._--What is the proper area through the valve gratings? _A._--The collective area should be at least equal to the area of the pump piston, and the lower edges of the perforations should be rounded off to afford more free ingress or egress to the water. 460. _Q._--Is there much strain thrown on the plates in which the valves are set? _A._--A good deal of strain; and in the earlier direct acting screw engines these plates were nearly in every case made too light. They should be made thick, have strong feathers upon them, and be very securely bolted down with split pins at the points of the bolts, to prevent them from unscrewing. The plate will be very apt to be broken should some of the bolts become loose. Of course all the bolts and split pins, as well as the plates and guards, must be of brass. 461. _Q._--How are the plates to be taken out should that become necessary? _A._--They are usually taken out through a door in the top of the hot well provided for that purpose, which door should be as large as the plates themselves; and it is a good precaution to cast upon this door--which will be of cast iron--six or eight stout projecting feet which will press upon the top of the outlet or delivery valve plate when the door is screwed down. The upper or delivery valve plate and the lower or foot valve plate should have similar feet. A large part of the strain will thus be transferred from the plates to the door, which can easily be made strong enough to sustain it. It is advisable that the plates should lie at an angle so that the shock of the water may not come upon the whole surface at once. 462. _Q._--Does the double acting air pump usual in direct acting screw engines, produce as good a vacuum as the single acting air pump usual in paddle engines? _A._--It will do so if properly constructed; but I do not know of any case of a double acting air pump, with india rubber valves, which has been properly constructed. 463. _Q._--What is the fault of such pumps? _A._--The pump frequently works by starts, as if at times it did not draw at all, and then again on a sudden gorged itself with water, so as to throw a great strain upon the working parts. The vacuum, moreover, is by no means so good as it should be, and it is a universal vice of direct acting screw engines that the vacuum is defective. I have been at some pains to investigate the causes of this imperfection; and in a sugar house engine fitted with pumps like those of a direct acting screw engine to maintain a vacuum in the pans, I found that a better vacuum was produced when the engine was going slowly than when it was going fast; which is quite the reverse of what was to have been expected, as the hot water which had to be removed by the condensation of the steam proceeding from the pan, was a constant quantity. In this engine, too, which was a high pressure one, the irregularities of the engine consequent upon the fitful catching of the water by the pump, was more conspicuous, as the working of this vacuum pump was the only work that the engine had to perform. 464. _Q._--And were you able to discover the cause of these irregularities? _A._--The main cause of them I found to be the largeness of the space left between the valve plates in this class of pumps, and out of which there is nothing to press the air or water which may be lying there. It consequently happens, that if there be the slightest leakage of air into the pump, this air is merely compressed, and not expelled, by the advance of the air pump piston. It expands again to its former bulk on the return of the pump piston, and prevents the water from entering until there is such an accumulation of pressure in the condenser as forces the water into the pump, when the air being expelled by the water, causes a good vacuum to be momentarily formed in the pump when it gorges itself by taking a sudden gulp of water. So soon, however, as the pressure falls in the condenser and some more air leaks into the pump, the former imperfect action recurs and is again redressed in the same violent manner. 465. _Q._--Is this irregular action of the pump the cause of the imperfect vacuum? _A._--It is one cause. Sometimes one end of the pump will alone draw and the other end will be inoperative, although it is equally open to the condenser, and this will chiefly take place at the stuffing box end, where a leakage of air is more likely to occur. I find, however, that even when both ends of the pump are acting equally and there is no leakage of air at all, the vacuum maintained by a double acting horizontal pump with india rubber valves, is not so good as that maintained by a single acting pump of the kind usual in old engines. 466. _Q._--Will you specify more precisely what were the results you obtained? _A._--When the vacuum pan was exhausted by the pumps without any boiling being carried on in the pan, but only a little cold water being let into it, and also into the pumps to enable them to act in their best manner, it was found that whereas with the old pump a vacuum of 114 on the sugar boiler's gauge could be readily obtained, equal to about 29-1/2 inches of mercury, the lowest that could possibly be got with the new horizontal pump was 122 degrees of the sugar boiler's gauge, or 29 inches of mercury, and to get that the engine must not go faster than 10 or 12 strokes per minute. The proper speed of the engine was 75 strokes per minute, but if allowed to go at that speed the vacuum fell to 130 of the sugar maker's gauge, or 28-1/2 inches of mercury. When the steam was let into the worms of the pan so as to boil the water in it, the vacuum was 134 at 75 revolutions of the engine, and went down to 132 at 40 revolutions, but rose again to 135, equal to about 28-1/4 inches of mercury, at 20 revolutions. 467. _Q._--To what do you attribute the circumstance of a better vacuum being got at low speeds than at high speeds? _A._--It is difficult to assign the precise reason, but it appears to be a consequence of the largeness of the vacant space between the valve plates. When the piston of the air pump is drawn back, the air contained in this large collection of water will cause it to boil up like soda water; and when the piston of the pump is forced forward, this air, instead of being expelled, will be again driven into the water. There will consequently be a quantity of air in the pump which cannot be got rid of at all, and which will impair the vacuum as a matter of course. 468. _Q._--What expedient did you adopt to improve the vacuum in the engine to which you have referred? _A._--I put blocks of wood on the air pump piston, which at the end of its stroke projected between the valve plates and forced the water out. I also introduced a cock of water at each end of the pump between the valve plates, to insure the presence of water at each end of the pump to force the air out. With these ameliorations the pump worked steadily, and the vacuum obtained became as good as in the old pump. I had previously introduced an injection cock into each end of the air pump in steam vessels, from which I had obtained advantageous results; and in all horizontal air pumps I would recommend the piston and valve plates to be so constructed that the whole of the water will be expressed by the piston. I would also recommend an injection cock to be introduced at each end of the pump. PUMPS, COCKS, AND PIPES. 469. _Q._--Will you explain the arrangement of the feed pump? _A._--In steam vessels, the feed pump plunger is generally of brass, and the barrel of the pump is sometimes of brass, but generally of cast iron. There should be a considerable clearance between the bottom of the plunger and the bottom of the barrel, as otherwise the bottom of the barrel may be knocked out, should coal dust or any other foreign substance gain admission, as it probably would do if the injection water were drawn at any time from the bilge of the vessel, as is usually done if the vessel springs a leak. The valves of the feed pump in marine engines are generally of the spindle kind, and are most conveniently arranged in a chest, which may be attached in any accessible position to the side of the hot well. There are two nozzles upon this chest, of which the lower one leads to the pump, and the upper one to the boiler. The pipe leading to the pump is a suction pipe when the plunger ascends, and a forcing pipe when the plunger descends. The plunger in ascending draws the water out of the hot well through the lowest of the valves, and in descending forces it through the centre valve into the space above it, which communicates with the feed pipe. Should the feed cock be shut so as to prevent any feed water from passing through it, the water will raise the topmost valve, which is loaded to a pressure considerably above the pressure of the steam, and escape into the hot well. This arrangement is neater and less expensive than that of having a separate loaded valve on the feed pipe with an overflow through the ship's side, as is the more usual practice. 470. _Q._--Will you describe what precautions are to be observed in the construction of the cocks used in engines? _A._--All the cocks about an engine should be provided with bottoms and stuffing boxes, and reliance should never be placed upon a single bolt passing through a bottom washer for keeping the plug in its place, in the case of any cock communicating with the boiler; for a great strain is thrown upon that bolt if the pressure of the steam be high, and if the plug be made with much taper; and should the bolt break, or the threads strip, the plug will fly out, and persons standing near may be scalded to death. In large cocks, it appears the preferable plan to cast the bottoms in; and the metal of which all the cocks about a marine engine are made, should be of the same quality as that used in the composition of the brasses, and should be without lead, or other deteriorating material. In some cases the bottoms of cocks are burnt in with hard solder, but this method cannot be depended upon, as the solder is softened and wasted away by the hot salt water, and in time the bottom leaks, or is forced out. The stuffing box of cocks should be made of adequate depth, and the gland should be secured by means of four strong copper bolts. The taper of blow-off cocks is an important element in their construction; as, if the taper be too great, the plugs will have a continual tendency to rise, which, if the packing be slack, will enable grit to get between the faces, while, if the taper be too little, the plug will be liable to jam, and a few times grinding will sink it so far through the shell that the waterways will no longer correspond. One eighth of an inch deviation from the perpendicular for every inch in height, is a common angle for the side of the cock, which corresponds with one quarter of an inch difference of diameter in an inch of height; but perhaps a somewhat greater taper than this, or one third of an inch difference in diameter for every inch of height, is a preferable proportion. The bottom of the plug must be always kept a small distance above the bottom of the shell, and an adequate surface must be left above and below the waterway to prevent leakage. Cocks formed according to these directions will be found to operate satisfactorily in practice, while they will occasion perpetual trouble if there be any malformation. 471. _Q._--What is the best arrangement and configuration of the blow-off cocks? _A._--The blow-off cocks of a boiler are generally placed some distance from the boiler; but it appears preferable that they should be placed quite close to it, as there are no means of shutting off the water from the pipe between the blow-off cock and the boiler, should fracture or leakage there arise. Every boiler must be furnished with a blow-off cock of its own, independently of the main blow-off cocks on the ship's sides, so that the boilers may be blown off separately, and may be shut off from one another. The preferable arrangement appears to be, to cast upon each blow-off cock a bend for attaching the cock to the bottom of the boiler, and the plug should stand about an inch in advance of the front of the boiler, so that it may be removed, or re-ground, with facility. The general arrangement of the blow-off pipes is to run a main blow-off pipe beneath the floor plates, across the ship, at the end of the engines, and into this pipe to lead a separate pipe, furnished with a cock, from each boiler. The main blow-off pipe, where it penetrates the ship's side, is furnished with a cock: and in modern steam vessels Kingston's valves are also used, which consist of a spindle or plate valve, fitted to the exterior of the ship, so that if the internal pipe or cock breaks, the external valve will still be operative. Some expedient of this kind is almost necessary, as the blow-off cocks require occasional regrinding, and the sea cocks cannot be re-ground without putting the vessel into dock, except by the use of Kingston's valves, or some equivalent expedient. 472. Q.--What is the proper construction and situation of the injection cocks, and waste water valves? A.--The sea injection cocks are usually made in the same fashion as the sea blow-off cocks, and of about the same size, or rather larger. The injection water is generally admitted to the condenser by means of a slide valve, but a cock appears to be preferable, as it is more easily opened, and has not any disposition to shut of its own accord. In paddle vessels the sea injection pipes should be put through the ship's sides in advance of the paddles, so that the water drawn in may not be injuriously charged with air. The waste water pipe passing from the hot well through the vessel's side is provided with a stop valve, called the discharge valve, which is usually made of the spindle kind, so as to open when the water coming from the air pump presses against it. In some cases this valve is a sluice valve, but the hot well is then almost sure to be split, if the engine be set on without the valve having been opened. The opening of the waste water pipe should always be above the load water line, as it will otherwise be difficult to prevent leakage through the engine into the ship when the vessel is lying in harbor. 473. Q.--What is the best arrangement of gauge cocks and glass gauges? A.--Gauge cocks are generally very inartificially made, and occasion needless annoyance. They are rarely made with bottoms, or with stuffing boxes, and are consequently, for the most part, adorned with stalactites of salt after a short period of service. The water discharged from them, too, from the want of a proper conduit, disfigures the front of the boiler, and adds to the corrosion in the ash pits. It would be preferable to combine the gauge cocks appertaining to each boiler into a single upright tube, connected suitably with the boiler, and the water flowing from them could be directed downward into a funnel tube communicating with the bilge. The cocks of the glass tubes, as well as of the gauge cocks, should be furnished with stuffing boxes and with bottoms, unless the water enters through the bottom of the plug, which in gauge cocks is sometimes the case. The glass gauge tubes should always be fitted with a cock at each neck communicating with the boiler, so that the water and steam may be shut off if the tube breaks; and the cocks should be so made as to admit of the tubes being blown through with steam to clear them, as in muddy water they will become so soiled that the water cannot be seen. The gauge cocks frequently have pipes running up within the boiler, to the end that a high water level may be made consistent with an easily accessible position of the gauge cocks themselves. With the glass tubes, however, this species of arrangement is not possible, and the glass tubes must always be placed in the position of the water level. 474. Q.--What is the proper material of the pipes in steam vessels? A.--Most of the pipes of marine engines should be made of copper. The steam pipes may be of cast iron, if made very strong, but the waste water pipes should be of copper. Cast iron blow-off pipes have in some cases been employed, but they are liable to fracture, and are dangerous. The blow-off and feed pipes should be of copper, but the waste steam pipe may be of galvanized iron. Every pipe passing through the ship's side, and every pipe fixed at both ends, and liable to be heated and cooled, should be furnished with a faucet or expansive joint; and in the case of the cast iron pipes, the part of the pipe fitting into the faucet should be turned. In the distribution of the faucets of the pipes exposed to pressure, care must be taken that they be so placed that the parts of the pipe cannot be forced asunder, or turned round by the strain, as serious accidents have occurred from the neglect of this precaution. 475. _Q._--What is the best mode of making pipes tight where they penetrate the ship's side? _A._--In wooden vessels the pipes where they pierce the ship's side, should be made tight, as follows:--the hole being cut, a short piece of lead pipe, with a broad flange at one end, should be fitted into it, the place having been previously smeared with white lead, and the pipe should then be beaten on the inside, until it comes into close contact all around with the wood. A loose flange should next be slipped over the projecting end of the lead pipe, to which it should be soldered, and the flanges should both be nailed to the timber with scupper nails, white lead having been previously spread underneath. This method of procedure, it is clear, prevents the possibility of leakage down through the timbers; and all, therefore, that has to be guarded against after this precaution, is to prevent leakage into the ship. To accomplish this object, let the pipe which it is desired to attach be put through the leaden hause, and let the space between the pipe and the lead be packed with gasket and white lead, to which a little olive oil has been added. The pipe must have a flange upon it to close the hole in the ship's side; the packing must then be driven in from the outside, and be kept in by means of a gland secured with bolts passing through the ship's side. If the pipe is below the water line the gland must be of brass, but for the waste water pipe a cast iron gland will answer. This method of securing pipes penetrating the side, however, though the best for wooden vessels, will, it is clear, fail to apply to iron ones. In the case of iron vessels, it appears to be the best practice to attach a short iron nozzle, projecting inward from the skin, for the attachment of every pipe below the water line, as the copper or brass would waste the iron of the skin if the attachment were made in the usual way. DETAILS OF THE SCREW AND SCREW SHAFT. 476. _Q._--What is the best method of fixing the screw upon the shaft? _A._--The best way is to cut two large grooves in the shaft coming up to a square end, and two corresponding grooves or key seats in the screw boss opposite the arms. Fit into the grooves on the shaft keys with heads, the length of which is equal to half the depth of the boss, and with the ends of the keys bearing against the ends of the grooves in the shaft. Then ship on the propeller, and drive other keys of an equal length from the other side of the boss, so that the points of the keys will nearly meet in the middle; next burr up the edge of the grooves upon the heads of the keys, to prevent them from working back; and finally tap a bolt into the side of the boss to penetrate the shaft. Propellers so fitted will never get slack. 477. _Q._--What is the best way of fitting in the screw pipe at the stern? _A._--It should have projecting rings, which should be turned; and cast iron pieces with holes in them, bored out to the sizes of these rings, should be secured to the stern frames, and the pipe be then shipped through all. Before this is done, however, the stern post must be bored out by a template to fit the pipe, and the pipe is to be secured at the end to the stern post either by a great external nut of cast iron, or by bolts passing through the stern post and through lugs on the pipe. The pipe should be bored throughout its entire length, and the shaft should be turned so as to afford a very long bearing which will prevent rapid wear. 478. _Q._--How is the hole formed in the deadwood of the ship in which the screw works? _A._--A great frame of malleable iron, the size of the hole, is first set up, and the plating of the ship is brought to the edge of this hole, and is riveted through the frame. It is important to secure this frame very firmly to the rest of the ship, with which view it is advisable to form a great palm, like the palm of a vice, on its inner superior corner, which, projecting into the ship, may be secured by breast-hook plates to the sides, whereby the strain which the screw causes will be distributed over the stern, instead of being concentrated on the rivets of the frame. 479. _Q._--Are there several lengths of screw shaft? _A._--There are. 480. _Q._--How then are these secured to one another? _A._--The best mode of securing the several lengths of shaft together is by forging the shafts with flanges at the ends, which are connected together by bolts, say six strong bolts in each, accurately fitted to the holes. [Illustration: Fig 44. End of the Screw Shaft of Correo, showing the mode of receiving the Thrust. A, discs; B, tightening wedge.] 481. _Q._--How is the thrust of the shaft usually received? _A._--In some cases it is received on a number of metal discs set in a box containing oil; and should one of these discs stick fast from friction, the others will be free to revolve. This arrangement, which is represented in fig. 44, is used pretty extensively and answers the purpose perfectly. It is of course necessary that the box in which the discs A are set, shall be strong enough to withstand the thrust which the screw occasions. Another arrangement still more generally used, is that represented in figs. 55 and 56, p. 331. It is a good practice to make the thrust plummer block with a very long sole in the direction of the shaft, so as to obviate any risk of canting or springing forward when the strain is applied, as such a circumstance, if occurring even to a slight extent, would be very likely to cause the bearing to heat. 482. _Q._--Are there not arrangements existing in some vessels for enabling the screw to be lifted out of the water while the vessel is at sea? _A._--There are; but such arrangements are not usual in merchant vessels. In one form of apparatus the screw is set on a short shaft in the middle of a sliding frame, which can be raised or lowered in grooves like a window and the screw shaft within the ship can be protruded or withdrawn by appropriate mechanism, so as to engage or leave free this short shaft as may be required. When the screw has to be lifted, the screw shaft is drawn into the vessel, leaving the short shaft free to be raised up by the sliding frame, and the frame is raised by long screws turned round by a winch purchase on deck. A chain or rope, however, is better for the purpose of raising this frame, than long screws; but the frame should in such case be provided with pall catches like those of a windlass, which, if the rope should break, will prevent the screw from falling. DETAILS OF THE PADDLES AND PADDLE SHAFT. 483. _Q._--What are the most important details of the construction of paddle wheels? _A._--The structure of the feathering wheel will be hereafter described in connection with an account of the oscillating engine; and it will be expedient now to restrict any account of the details to the common radial paddle, as applied to ocean steamers. The best plan of making the paddle centres is with square eyes, and each centre should be secured in its place by means of eight thick keys. The shaft should be burred up against the head of these keys with a chisel, so as to prevent the keys from coming back of their own accord. If the keys are wanted to be driven back, this burr must be cut off, and if made thick, and of the right taper, they may then be started without difficulty. The shaft must of course be forged with square projections on it, so as to be suitable for the application of centres with square eyes. Messrs. Maudslay & Co. bore out their paddle centres, and turn a seat for them on the shaft, afterward fixing them on the shaft with a single key. This plan is objectionable for the two reasons, that it is insecure when new, and when old is irremovable. The general practice among the London engineers is to fix the paddle arms at the centre to a plate by means of bolts, a projection being placed upon the plates on each side of the arm, to prevent lateral motion; but this method is inferior in durability to that adopted in the Clyde, in which each arm is fitted into a socket by means of a cutter--a small hole being left opposite to the end of each arm, whereby the arm may be forced back by a drift. 484. _Q._--How are the arms attached to the outside rings? _A._--Some engineers join the paddle arms to the outer ring by means of bolts; but unless very carefully fitted, those bolts after a time become slack sideways, and a constant working of the parts of the wheel goes on in consequence. Sometimes the part of the other ring opposite the arm is formed into a mortise, and the arms are wedged tight in these holes by wedges driven in on each side; but the plan is an expensive one, and not satisfactory, as the wedges work loose even though riveted over at the point. The best mode of making a secure attachment of the arms to the ring, consists in making the arms with long T heads, and riveting the cross piece to the outer ring with a number of rivets, not of the largest size, which would weaken the outer ring too much. The best way of securing the inner rings to the arms is by means of lugs welded on the arms, and to which the rings are riveted. 485. _Q._--What are the scantlings of the paddle floats? _A._--The paddle floats are usually made either of elm or pine; if of the former, the common thickness for large sea-going vessels is about 2-1/2 inches; if of the latter, 3 inches. The floats should have plates on both sides, else the paddle arms will be very liable to cut into the wood, and the iron of the arms will be very rapidly wasted. When the floats have been fresh put on they must be screwed up several times before they come to a bearing. If this be not done, the bolts will be sure to get slack at sea, and all the floats on the weather side may be washed off. The bolts for holding on the paddle floats are made extra strong, on account of the corrosion to which they are subject; and the nuts should be made large, and should be square, so that they may be effectually tightened up, even though their corners be worn away by corrosion. It is a good plan to give the thread of the paddle bolts a nick with a chisel, after the nut has been screwed up, which will prevent the nut from turning back. Paddle floats, when consisting of more than one board, should be bolted together edgeways, by means of bolts running through their whole breadth. The floats should not be notched to allow of their projection beyond the outer ring, as, if the sides of the notch be in contact with the outer ring, the ring is soon eaten away in that part, and the projecting part of the float, being unsupported, is liable to be broken off. 486. _Q._--Do not the wheels jolt sideways when the vessel rolls? _A._--It is usual to put a steel plate at each end of the paddle shafts tightened with a key, to prevent end play when the vessel rolls, but the arrangement is precarious and insufficient. Messrs. Maudslay make their paddle shaft bearings with very large fillets in the corner, with the view of diminishing the evil; but it would be preferable to make the bearings of the crank shafts spheroidal; and, indeed, it would probably be an improvement if most of the bearings about the engine were to be made in the same fashion. The loose end of the crank pin should be made not spheroidal, but consisting of a portion of a sphere; and a brass bush might then be fitted into the crank eye, that would completely encase the ball of the pin, and yet permit the outer end of the paddle shaft to fall without straining the pin, the bush being at the same time susceptible of a slight end motion. The paddle shaft, where it passes through the vessel's side, is usually surrounded by a lead stuffing box, which will yield if the end of the shaft falls; this stuffing box prevents leakage into the ship from the paddle wheels: but it is expedient, as a further precaution, to have a small tank on the ship's side immediately beneath the stuffing box, with a pipe leading down to the bilge to catch and conduct away any water that may enter around the shaft. 487. _Q._--How is the outer bearing of the paddle wheels supplied with tallow? _A._--The bearing at the outer end of the paddle shaft is sometimes supplied with tallow, forced into a hole in the plummer block cover, as in the case of water wheels; but for vessels intended to perform long voyages, it is preferable to have a pipe leading down to the oil cup above the journal from the top of the paddle box, through which pipe oil may at any time be supplied. 488. _Q._--Will you explain the method of putting engines into a steam vessel? _A._--As an illustration of this operation it may be advisable to take the case of a side lever engine, and the method of proceeding is as follows:-- First measure across from the inside of paddle bearers to the centre of the ship, to make sure that the central line, running in a fore and aft direction on the deck or beams, usually drawn by the carpenter, is really in the centre. Stretch a line across between the paddle bearers in the direction of the shaft; to this line, in the centre of the ship where the fore and aft mark has been made, apply a square with arms six or eight feet long, and bring a line stretched perpendicularly from the deck to the keelson, accurately to the edge of the square: the lower point of the line where it touches the keelson will be immediately beneath the marks made upon the deck. If this point does not come in the centre of the keelson, it will be better to shift it a little, so as to bring it to the centre, altering the mark upon the deck correspondingly, provided either paddle shaft will admit of this being done--one of the paddle brackets being packed behind with wood, to give it an additional projection from the side of the paddle bearer. Continue the line fore and aft upon the keelson as nearly as can be judged in the centre of the ship; stretch another line fore and aft through the mark upon the deck, and look it out of winding with the line upon the keelson. Fix upon any two points equally distant from the centre, in the line stretched transversely in the direction of the shaft; and from those points, as centres, and with any convenient radius, sweep across the fore and aft line to see that the two are at right angles; and, if not, shift the transverse line a little to make them so. From the transverse line next let fall a line upon each outside keelson, bringing the edge of the square to the line, the other edge resting on the keelson. A point will thus be got on each outside keelson, perpendicularly beneath the transverse line running in the direction of the shaft, and a line drawn between those two points will be directly below the shaft. To this line the line of the shaft marked on the sole plate has to be brought, care being taken, at the same time, that the right distance is preserved between the fore and aft line upon the sole plate, and the fore and aft line upon the central keelson. 489. _Q._--Of course the keelsons have first to be properly prepared? _A._--In a wooden vessel, before any part of the machinery is put in, the keelsons should be dubbed fair and straight, and be looked out of winding by means of two straight edges. The art of placing engines in a ship is more a piece of plain common sense than any other feat in engineering, and every man of intelligence may easily settle a method of procedure for himself. Plumb lines and spirit levels, it is obvious, cannot be employed on board a vessel, and the problem consists in so placing the sole plates, without these aids, that the paddle shaft will not stand awry across the vessel, nor be carried forward beyond its place by the framing shouldering up more than was expected. As a plumb line cannot be used, recourse must be had to a square; and it will signify nothing at what angle with the deck the keelsons run, so long as the line of the shaft across the keelsons is square down from the shaft centre. The sole plates being fixed, there is no difficulty in setting the other parts of the engine in their proper places upon them. The paddle wheels must be hung from the top of the paddle box to enable the shaft to be rove through them, and the cross stays between the engines should be fixed in when the vessel is afloat. To try whether the shafts are in a line, turn the paddle wheels, and try if the distance between the cranks is the same at the upper and under, and the two horizontal centres; if not, move the end of the paddle shaft up or down, backward or forward, until the distance between the cranks at all the four centres is the same. 490. _Q._--In what manner are the engines of a steam vessel secured to the hull? _A._--The engines of a steamer are secured to the hull by means of bolts called holding down bolts, and in wooden vessels a good deal of trouble is caused by these bolts, which are generally made of iron. Sometimes they go through the bottom of the ship, and at other times they merely go through the keelson,--a recess being made in the floor or timbers to admit of the introduction of a nut. The iron, however, wears rapidly away in both cases, even though the bolts are tinned; and it has been found the preferable method to make such of the bolts as pass through the bottom, or enter the bilge, of Muntz's metal, or of copper. In a side lever engine, four Muntz's metal bolts may be put through the bottom at the crank end of the framing of each engine, four more at the main centre, and four more at the cylinder, making twelve through bolts to each engine; and it is more convenient to make these bolts with a nut at each end, as in that case the bolts may be dropped down from the inside, and the necessity is obviated of putting the vessel on very high blocks in the dock, in order to give room to put the bolts up from the bottom. The remainder of the holding down bolts may be of iron, and may, by means of a square neck, be screwed into the timber of the keelsons as wood screws--the upper part being furnished with a nut which may be screwed down upon the sole plate, so soon as the wood screw portion is in its place. If the cylinder be a fixed one it should be bolted down to the sole plate by as many bolts as are employed to attach the cylinder cover, and they should be of copper or brass, in any situation that is not easily accessible. 491. _Q._--If the engines become loose, how do you refix them? _A._--It is difficult to fix engines effectually which have once begun to work in the ship, for in time the surface of the keelsons on which the engines bear becomes worn uneven, and the engines necessarily rock upon it. As a general rule, the bolts attaching the engines to the keelsons are too few and of too large a diameter: it would be preferable to have smaller bolts, and a greater number of them. In addition to the bolts going through the keelsons or the vessel's bottom, there should be a large number of wood screws securing the sole plate to the keelson, and a large number of bolts securing the various parts of the engine to the sole plate. In iron vessels, holding down bolts passing through the bottom are not expedient; and there the engine has merely to be secured to the iron plate of the keelsons, which are made hollow to admit of a more effectual attachment. 492. _Q._--What are the proper proportions of bolts? _A._--In well formed bolts, the spiral groove penetrates about one twelfth of the diameter of the cylinder round which it winds, so that the diameter of the solid cylinder which remains is five sixths of the diameter over the thread. If the strain to which iron may be safely subjected in machinery is one fifteenth of its utmost strength, or 4,000 lbs. on the square inch, then 2,180 lbs. may be sustained by a screw an inch in diameter, at the outside of the threads. The strength of the holding down bolts may easily be computed, when the elevating force of the piston or main centre is known; but it is expedient very much to exceed this strength in practice, on account of the elasticity of the keelsons, the liability to corrosion, and other causes. THE LOCOMOTIVE ENGINE. 493. _Q._--What is the amount of tractive force requisite to draw carriages on railways? _A._--Upon well formed railways with carriages of good construction, the average tractive force required for low speeds is about 7-1/2 lbs. per ton, or 1/300th of the load, though in some experimental cases, where particular care was taken to obtain a favorable result, the tractive force has been reduced as low as 1/500th of the load. At low speeds the whole of the tractive force is expended in overcoming the friction, which is made up partly of the friction of attrition in the axles, and partly of the rolling friction, or the obstruction to the rolling of the wheels upon the rail. The rolling friction is very small when the surfaces are smooth, and in the case of railway carriages does not exceed 1/1000th. of the load; whereas the draught on common roads of good construction, which is chiefly made up of the rolling friction, is as much as 1/36th of the load. 494._Q._--In reference to friction you have already stated that the friction of iron sliding upon brass, which has been oiled and then wiped dry, so that no film of oil is interposed, is about 1/11th of the pressure, but that in machines in actual operation, where there is a film of oil between the rubbing surfaces, the friction is only about one third of this amount, or 1/33d of the weight. How then can the tractive resistance of locomotives at low speeds, which you say is entirely made up of friction, be so little as 1/500th. of the weight? _A._--I did not state that the resistance to traction was 1/500th of the weight upon an average--to which condition the answer given to a previous question must be understood to apply--but I stated that the average traction was about 1/300th of the load, which nearly agrees with my former statement. If the total friction be 1/300th of the load, and the rolling friction be 1/1000th of the load, then the friction of attrition must be 1/429th of the load; and if the diameter of the wheels be 36 in., and the diameter of the axles be 3 in., which are common proportions, the friction of attrition must be increased in the proportion of 36 to 3, or 12 times, to represent the friction of the rubbing surface when moving with the velocity of the carriage, 12/429ths are about 1/35th of the load, which does not differ much from the proportion of 1/33d as previously determined. 495. _Q._--What is the amount of adhesion of the wheels upon the rails? _A._--The adhesion of the wheels upon the rails is about 1/5th of the weight when the rails are clean, or either perfectly wet or perfectly dry; but when the rails are half wet or greasy, the adhesion is not more than 1/10th or 1/12th of the weight or pressure upon the wheels. The weight of a locomotive of modern construction varies from 20 to 25 tons. 496. _Q._--And what is its cost and average performance? _A._--The cost of a common narrow gauge locomotive, of average power, varies from £1,900 to £2,200; it will run on an average 130 miles per day, at a cost for repairs of 2-1/2d. per mile; and the cost of locomotive power, including repairs, wages, oil, and coke, does not much exceed 6d. per mile run, on economically managed railways. This does not include a sinking fund for the renewal of the engines when worn out, which may be taken as equivalent to 10 per cent. on their original cost. 497. _Q._--Does the expense of traction increase much with an increased speed? _A._--Yes; it increases very rapidly, partly from the undulation of the earth when a heavy train passes over it at a high velocity, but chiefly from the resistance of the atmosphere and blast pipe, which constitute the greatest of the impediments to motion at high speeds. At a speed of 30 miles an hour, the atmospheric resistance has been found in some cases to amount to about 12 lbs. a ton; and in side winds the resistance even exceeds this amount, partly in consequence of the additional friction caused from the flanges of the wheels being forced against the rails, and partly because the wind catches to a certain extent the front of every carriage, whereby the efficient breadth of each carriage, in giving motion to the air in the direction of the train, is very much increased. At a speed of 30 miles an hour, an engine evaporating 200 cubic feet of water in the hour, and therefore exerting about 200 horses power, will draw a load of 110 tons. Taking the friction of the train at 7-1/2 lbs. per ton, or 825 lbs. operating at the circumference of the driving wheel--which, with 5 ft. 6 in. wheels, and 18 in. stroke, is equivalent to 4,757 lbs. upon the piston--and taking the resistance of the blast pipe at 6 lbs. per square inch of the pistons, and the friction of the engine unloaded at 1 lb. per square inch, which, with pistons 12 in. in diameter, amount together to 1,582 lbs., and reckoning the increased friction of the engine due to the load at 1/7th of the load, as in some cases it has been found experimentally to be, though a much less proportion than this would probably be a nearer average, we have 7018.4 lbs. for the total load upon the pistons. At 30 miles an hour the speed of the pistons will be 457.8 feet per minute, and 7018.4 lbs. multiplied by 457.8 ft. per minute, are equal to 3213023.5 lbs. raised one foot high in the minute, which, divided by 33,000, gives 97.3 horses power as the power which would draw 110 tons upon a railway at a speed of 30 miles an hour, if there were no atmospheric resistance. The atmospheric resistance is at the rate of 12 lbs. a ton, with a load of 110 tons, equal to 1,320 lbs., moving at a speed of 30 miles an hour, which, when reduced, becomes 105.8 horses power, and this, added to 97.3, makes 203.1, instead of 200 horses power, as ascertained by a reference to the evaporative power of the boiler. This amount of atmospheric resistance, however, exceeds the average, and in some of the experiments for ascertaining the atmospheric resistance, a part of the resistance due to the curves and irregularities of the line has been counted as part of the atmospheric resistance. 498. _Q._--Is the resistance per ton of the engine the same as the resistance per ton of the train? _A._--No; it is more, since the engine has not merely the resistance of the atmosphere and of the wheels to encounter, but the resistance of the machinery besides. According to Mr. Gooch's experiments upon a train weighing 100 tons, the resistance of the engine and tender at 13.1 miles per hour was found by the indicator to be 12.38 lbs.; the resistance per ton of the train, as ascertained by the dynamometer, was at the same speed 7.58 lbs., and the average resistance of locomotive and train was 9.04 lbs. At 20.2 miles per hour these resistances respectively became 19.0, 8.19, and 12.2 lbs. At 441 miles per hour the resistances became 34.0, 21.10, and 25.5 lbs., and at 57.4 miles an hour they became 35.5, 17.81, and 23.8 lbs. 499. _Q._--Is it not maintained that the resistance of the atmosphere to the progress of railway trains increases as the square of the velocity? _A._--The atmospheric resistance, no doubt, increases as the square of the velocity, and the power, therefore, necessary to overcome it will increase as the cube of the velocity, since in doubling the speed four times, the power must be expended in overcoming the atmospheric resistance in half the time. At low speeds, the resistance does not increase very rapidly; but at high speeds, as the rapid increase in the atmospheric resistance causes the main resistance to be that arising from the atmosphere, the total resistance will vary nearly as the square of the velocity. Thus the resistance of a train, including locomotive and tender, will, at 15 miles an hour, be about 9.3 lbs. per ton; at 30 miles an hour it will be 13.2 lbs. per ton; and at 60 miles an hour, 29 lbs. per ton. If we suppose the same law of progression to continue up to 120 miles an hour, the resistance at that speed will be 92.2 lbs. per ton, and at 240 miles an hour the resistance will be 344.8 lbs. per ton. Thus, in doubling the speed from 60 to 120 miles per hour, the resistance does not fall much short of being increased fourfold, and the same remark applies to the increase of the speed from 120 to 240 miles an hour. These deductions and other deductions from Mr. Gooch's experiments on the resistance of railway trains, are fully discussed by Mr. Clark, in his Treatise on railway machinery, who gives the following rule for ascertaining the resistance of a train, supposing the line to be in good order, and free from curves:--To find the total resistance of the engine, tender, and train in pounds per ton, at any given speed. Square the speed in miles per hour; divide it by 171, and add 8 to the quotient. The result is the total resistance at the rails in lbs. per ton. 500._Q._--How comes it, that the resistance of fluids increases as the square of the velocity, instead of the velocity simply? _A._--Because the height necessary to generate the velocity with which the moving object strikes the fluid, or the fluid strikes the object, increases as the _square_ of the velocity, and the resistance or the weight of a column of any fluid varies as the height. A falling body, as has been already explained, to have acquired twice the velocity, must have fallen through four times the height; the velocity generated by a column of any fluid is equal to that acquired by a body falling through the height of the column; and it is therefore clear, that the pressure due to any given velocity must be as the square of that velocity, the pressure being in every case as twice the altitude of the column. The work done, however, by a stream of air or other fluid in a given time, will vary as the cube of the velocity; for if the velocity of a stream of air be doubled, there will not only be four times the pressure exerted per square foot, but twice the quantity of air will be employed; and in windmills, accordingly, it is found, that the work done varies nearly as the cube of the velocity of the wind. If, however, the work done by _a given quantity_ of air moving at different speeds be considered, it will vary as the squares of the speeds. 501. _Q._--But in a case where there is no work done, and the resistance varies as the square of the speed, should not the power requisite to overcome that resistance vary as the square of the speed? _A._--It should if you consider the resistance over a given distance, and not the resistance during a given time. Supposing the resistance of a railway train to increase as the square of the speed, it would take four times the power, so far as atmospheric resistance is concerned, to accomplish a mile at the rate of 60 miles an hour, that it would take to accomplish a mile at 30 miles an hour; but in the former case there would be twice the number of miles accomplished in the same time, so that when the velocity of the train was doubled, we should require an engine that was capable of overcoming four times the resistance at twice the speed, or in other words, that was capable of exerting eight times the power, so far as regards the element of atmospheric resistance. We know by experience, however, that it is easier to attain high speeds on railways than in steam vessels, where the resistance does increase nearly as the square of the speed. 502. _Q._--Will you describe generally the arrangement of a locomotive engine? _A._--The boiler and engine are hung upon a framework set on wheels, and, together with this frame or carriage, constitute what is commonly called the locomotive. Behind the locomotive runs another carriage, called the tender, for holding coke and water. A common mode of connecting the engine and tender is by means of a rigid bar, with an eye at each end through which pins are passed. Between the engine and tender, however, buffers should always be interposed, as their pressure contributes greatly to prevent oscillation and other irregular motions of the engine. 503. _Q._--How is the framing of a locomotive usually constructed? _A._--All locomotives are now made with the framing which supports the machinery situated within the wheels; but for some years a vehement controversy was maintained respecting the relative merits of outside and inside framing, which has terminated, however, in the universal adoption of the inside framing. It is difficult, in engines intended for the narrow gauge, to get cylinders within the framing of sufficient diameter to meet the exigencies of railway locomotion; by casting both cylinders in a piece, however, a considerable amount of room may be made available to increase their diameters. It is very desirable that the cylinders of locomotives should be as large as possible, so that expansion may be adopted to a large extent; and with any given speed of piston, the power of an engine either to draw heavy loads, or achieve high velocities, will be increased with every increase of the dimensions of the cylinder. The framing of locomotives, to which the boiler and machinery are attached, and which rests upon the springs situated above the axles, is formed generally of malleable iron, but in some engines the side frames consist of oak with iron plates riveted on each side. The guard plates are in these cases generally of equal length, the frames being curved upward to pass over the driving axle. Hard cast iron blocks are riveted between the guard plates to serve as guides for the axle bushes. The side frames are connected across the ends, and cross stays are introduced beneath the boiler to stiffen the frame sideways, and prevent the ends of the connecting or eccentric rods from falling down if they should be broken. 504. _Q._--What is the nature and arrangement of the springs of locomotives? _A._--The springs are of the ordinary carriage kind, with plates connected at the centre, and allowed to slide on each other at their ends. The upper plate terminates in two eyes, through each of which passes a pin, which also passes through the jaws of the bridle, connected by a double threaded screw to another bridle, which is jointed to the framing; the centre of the spring rests upon the axle box. Sometimes the springs are placed between the guard plates, and below the framing which rests upon their extremities. One species of springs which has gained a considerable introduction, consists of a number of flat steel plates with a piece of metal or other substance interposed between them at the centre, leaving the ends standing apart. It would be preferable, perhaps, to make the plates of a common spring with different curves, so that the leaves, though in contact at the centre, would not be in contact with the ends with light loads, but would be brought into contact gradually, as the strain conies on: a spring would thus be obtained that was suitable for all loads. 505. _Q._--What is the difference between inside and outside cylinder engines? _A._--Outside cylinders are so designated when placed upon the outside of the framing, with their connecting rods operating upon pins in the driving wheels; while the inside cylinders are situated within the framing, and the connecting rods attach themselves to cranks in the driving axle. 506. _Q._--Whether are inside or outside cylinder engines to be preferred? _A._--A diversity of opinion obtains as to the relative merits of outside and inside cylinders. The chief objection to outside cylinders is, that they occasion a sinuous motion in the engine which is apt to send the train off the rails; but this action may be made less perceptible or be remedied altogether, by placing a weight upon one side of the wheels, the momentum of which will just balance the momentum of the piston and its connections. The sinuous or rocking motion of locomotives is traceable to the arrested momentum of the piston and its attachments at every stroke of the engine, and the effect of the pressure thus created will be more operative in inducing oscillation the farther it is exerted from the central line of the engine. If both cylinders were set at right angles in the centre of the carriage, and the pistons were both attached to a central crank, there would be no oscillation produced; or the same effect would be realized by placing one cylinder in the centre of the carriage, and two at the sides-- the pistons of the side cylinders moving simultaneously: but it is impossible to couple the piston of an upright cylinder direct to the axle of a locomotive, without causing the springs to work up and down with every stroke of the engine: and the use of three cylinders, though adopted in some of Stephenson's engines, involves too much complication to be a beneficial innovation. 507. _Q._--Whether are four-wheeled or six-wheeled engines preferable? _A._--Much controversial ingenuity has been expended upon the question of the relative merits of the four and six-wheeled engines; one party maintaining that four-wheeled engines are most unsafe, and the other that six-wheeled engines are unmechanical, and are more likely to occasion accidents. The four-wheeled engines, however, appear to have been charged with faults that do not really attach to them when properly constructed; for it by no means follows that if the axle of a four-wheeled engine breaks, or even altogether comes away, that the engine must fall down or run off the line; inasmuch as, if the engine be properly coupled with the tender, it has the tender to sustain it. It is obvious enough, that such a connection may be made between the tender and the engine, that either the fore or hind axle of the engine may be taken away, and yet the engine will not fall down, but will be kept up by the support which the tender affords; and the arguments hitherto paraded against the four-wheeled engines are, so far as regards the question of safety, nothing more than arguments against the existence of the suggested connection. It is no doubt the fact, that locomotive engines are now becoming too heavy to be capable of being borne on four wheels at high speeds without injury to the rails; but the objection of damage to the rails applies with at least equal force to most of the six-wheeled engines hitherto constructed, as in those engines the engineer has the power of putting nearly all the weight upon the driving wheels; and if the rail be wet or greasy, there is a great temptation to increase the bite of those wheels by screwing them down more firmly upon the rails. A greater strain is thus thrown upon the rail than can exist in the case of any equally heavy four-wheeled engine; and the engine is made very unsafe, as a pitching motion will inevitably be induced at high speeds, when an engine is thus poised upon the central driving wheels, and there will also be more of the rocking or sinuous motion. Locomotives, however, intended to achieve high speeds or to draw heavy loads, are now generally made with eight wheels, and in some cases the driving wheels are placed at the end of the engine instead of in the middle. 508. _Q._--As the question of the locomotive boiler has been already disposed of in discussing the question of boilers in general, it now only remains to inquire into the subject of the engine, and we may commence with the cylinders. Will you state the arrangement and construction of the cylinders of a locomotive and their connections? _A._--The cylinders are placed in the same horizontal plane as the axle of the driving wheels, and the connecting rod which is attached to the piston rod engages either a crank in the driving axle or a pin in the driving wheel, according as the cylinders are inside or outside of the framework. The cylinders are generally made an inch longer than the stroke, or there is half an inch of clearance at each end of the cylinder, to permit the springs of the vehicle to act without causing the piston to strike the top or bottom of the cylinder. The thickness of metal of the cylinder ends is usually about a third more than the thickness of the cylinder itself, and both ends are generally made removable. The priming of the boiler, when it occurs, is very injurious to the cylinders and valves of locomotives, especially if the water be sandy, as the grit carried over by the steam wears the rubbing surfaces rapidly away. The face of the cylinder on which the valve works is raised a little above the metal around it, both to facilitate the operation of forming the face and with the view of enabling any foreign substance deposited on the face to be pushed aside by the valve into the less elevated part, where it may lie without occasioning any further disturbance. The valve casing is sometimes cast upon the cylinder, and it is generally covered with a door which may be removed to permit the inspection of the faces. In some valve casings the top as well as the back is removable, which admits of the valve and valve bridle being removed with greater facility. A cock is placed at each end of locomotive cylinders, to allow the water to be discharged which accumulates in the cylinder from priming or condensation; and the four cocks of the two cylinders are usually connected together, so that by turning a handle the whole are opened at once. In Stephenson's engines, however, with variable expansion, there is but one cock provided for this purpose, which is on the bottom of the valve chest. 509. _Q._--What kind of piston is used in locomotives? _A._--The variety of pistons employed in locomotives is very great, and sometimes even the more complicated kinds are found to work very satisfactorily; but, in general, those pistons which consist of a single ring and tongue piece, or of two single rings set one above the other, so as to break joint, are preferable to those which consist of many pieces. In Stephenson's pistons the screws were at one time liable to work slack, and the springs to break. 510. _Q._--Will you explain the connection of the piston rod with the connecting rod? _A._--The piston rods of all engines are now generally either case hardened very deeply, or are made of steel; and in locomotive engines the diameter of the piston rod is about one seventh of the diameter of the cylinder, and it is formed of tilted steel. The cone of the piston rod, by which it is attached to the piston, is turned the reverse way to that which is adopted in common engines, with the view of making the cutter more accessible from the bottom of the cylinder, which is made to come off like a door. The top of the piston rod is secured with a cutter into a socket with jaws, through the holes of which a cross head passes, which is embraced between the jaws by the small end of the connecting rod, while the ends of the cross head move in guides. Between the piston rod clutch and the guide blocks, the feed pump rod joins the cross head in some engines. 511. _Q._--What kind of guides is employed for the end of the piston rod? _A._--The guides are formed of steel plates attached to the framing, between which work the guide blocks, fixed on the ends of the cross head, which have flanges bearing against the inner edges of the guides. Steel or brass guides are better than iron ones: Stephenson and Hawthorn attach their guides at one end to a cross stay, at the other to lugs on the cylinder cover; and they are made stronger in the middle than at the ends. Stout guide rods of steel, encircled by stuffing boxes on the ends of the cross head, would probably be found superior to any other arrangement. The stuffing boxes might contain conical bushes, cut spirally, in addition to the packing, and a ring, cut spirally, might be sprung upon the rod and fixed in advance of the stuffing box, with lateral play to wipe the rod before entering the stuffing box, to prevent it from being scratched by the adhesion of dust. 512. _Q._--Is any provision made for keeping the connecting rod always of the same length? _A._--In every kind of locomotive it is very desirable that the length of the connecting rod should remain invariable, in spite of the wear of the brasses, for there is a danger of the piston striking against the cover of the cylinder if it be shortened, as the clearance is left as small as possible in order to economize steam. In some engines the strap encircling the crank pin is fixed immovably to the connecting rod by dovetailed keys, and a bolt passes through the keys, rod, and strap, to prevent the dovetailed keys from working out. The brass is tightened by a gib and cutter, which is kept from working loose by three pinching screws and a cross pin or cutter through the point. The effect of this arrangement is to lengthen the rod, but at the cross head end of the rod the elongation is neutralized by making the strap loose, so that in tightening the brass the rod is shortened by an amount equal to its elongation at the crank pin end. The tightening here is also effected by a gib and cutter, which is kept from working loose by two pinching screws pressing on the side of the cutter. Both journals of the connecting rod are furnished with oil cups, having a small tube in the centre with siphon wicks. The connecting rod is a thick flat bar, with its edges rounded. 513. _Q._--How is the cranked axle of locomotives constructed? _A._--The cranked axle of locomotives is always made of wrought iron, with two cranks forged upon it toward the middle of its length, at a distance from each other answerable to the distance between the cylinders. Bosses are made on the axle for the wheels to be keyed upon, and bearings for the support of the framing. The axle is usually forged in two pieces, which are afterward welded together. Sometimes the pieces for the cranks are put on separately, but the cranks so made are liable to give way. In engines with outside cylinders the axles are made straight-the crank pins being inserted in the naves of the wheels. The bearings to which the connecting rods are attached are made with very large fillets in the corners, so as to strengthen the axle in that part, and to obviate side play in the connecting rod. In engines which, have been in use for some time, however, there is generally a good deal of end play in the bearings of the axles themselves, and this slackness contributes to make the oscillation of the engine more violent; but this evil may be remedied by making the bearings spheroidal, whereby end play becomes impossible. 514. _Q._--How are the bearings of the axles arranged? _A._--The axles bear only against the top of the axle boxes, which are generally of brass; but a plate extends underneath the bearing, to prevent sand from being thrown upon it. The upper part of the box in most engines has a reservoir of oil, which is supplied to the journal by tubes with siphon wicks. Stephenson uses cast iron axle boxes with brasses, and grease instead of oil; and the grease is fed upon the journal by the heat of the bearing melting it, whereby it is made to flow down through a hole in the brass. Any engines constructed with outside bearings have inside bearings also, which are supported by longitudinal bars, which serve also in some cases to support the piston guides; these bearings are sometimes made so as not to touch the shafts unless they break. 515. _Q._--How are the eccentrics of a locomotive constructed? _A._--In locomotives the body of the eccentric is of cast iron, in inside cylinder engines the eccentrics are set on the axle between the cranks, and they are put on in two pieces held together by bolts; but in straight axle engines the eccentrics are cast in a piece, and are secured on the shaft by means of a key. The eccentric, when in two pieces, is retained at its proper angle on the shaft by a pinching screw, which is provided with a jam nut to prevent it from working loose. A piece is left out of the eccentric in casting it to allow of the screw being inserted, and the void is afterward filled by inserting a dovetailed piece of metal. Stephenson and Hawthorn leave holes in their eccentrics on each side of the central arm, and they apply pinching screws in each of these holes. The method of fixing the eccentric to the shaft by a pinching screw is scarcely sufficiently substantial; and cases are perpetually occurring, when this method of attachment is adopted, of eccentrics shifting from their place. In the modern engines the eccentrics are forged on the axles. 516. _Q._--How are the eccentric straps constructed? _A._--The eccentric hoops are generally of wrought iron, as brass hoops are found liable to break. When formed of malleable iron, one half of the strap is forged with the rod, the other half being secured to it by bolts, nuts, and jam nuts. Pieces of brass are, in some cases, pinned within the malleable iron hoop; but it appears to be preferable to put brasses within the hoop to encircle the eccentric, as in the case of any other bearing. When the brass straps are used, the lugs have generally nuts on both sides, so that the length of the eccentric rod may be adjusted by their means to the proper length; but it is better for the lugs of the hoops to abut against the necks of the screws, and, if any adjustment be necessary from the wear of the straps, washers can be interposed. In some engines the adjustment is effected by screwing the valve rod, and the cross head through which it passes has a nut on either side of it, by which its position upon the valve rod is determined. 517. _Q._--Will you describe the eccentric rod and valve levers? _A._--In the engines in use before the introduction of the link motion, the forks of the eccentric rod were of steel, and the length of the eccentric rod was the distance between the centre of the crank axle and the centre of the valve shaft; but in modern engines the use of the link motion is universal. The valve lever in locomotives is usually longer than the eccentric lever, to increase the travel of the valve, if levers are employed; but it is better to connect the valve rod to the link of the link motion without the intervention of levers. The pins of the eccentric lever in the old engines used to wear quickly; Stephenson used to put a ferule of brass on these pins, which being loose, and acting like a roller, facilitated the throwing in and out of gear, and when worn could easily be replaced, so that there was no material derangement of the motion of the valve from play in this situation. 518. _Q._--What is the arrangement of a starting lever? _A._--The starting lever travels between two iron segments, and can be fixed in any desired position. This is done by a small catch or bell crank, jointed to the bottom of the handle at the end of the lever, and coming up by the side of the handle, but pressed out from it by a spring. The smaller arm of this bell crank is jointed to a bolt, which shoots into notches, made in one of the segments between which the lever moves. By pressing the bell crank against the handle of the lever the bolt is withdrawn, and the lever may be shifted to any other point, when, the spring being released, the bolt flies into the nearest notch. 519. _Q._--In what way does the starting handle act on the machinery of the engine to set it in motion? _A._--Its whole action lies in raising or depressing the link of the link motion relatively with the valve rod. If the valve rod be attached to the middle of the link, the valve will derive no motion from, it at all, and the engine will stop. If the attachment be slipped to one end of the link the engine will go ahead, and if slipped to the other end it will go astern. The starting handle merely achieves this change of position. 520. _Q._--Will you explain the operation of setting the valve of a locomotive? _A._--In setting the valves of locomotives, place the crank in the position answerable to the end of the stroke of the piston, and draw a straight line, representing the centre line of the cylinder, through the centres of the crank shaft and crank pin. From the centre of the shaft describe a circle with the diameter equal to the throw of the valve; another circle to represent the crank shaft; and a third circle to represent the path of the crank pin. From the centre of the crank shaft, draw a line perpendicular to the centre line of the cylinder and crank shaft, and draw another perpendicular at a distance from the first equal to the amount of the lap and the lead of the valve: the points in which this line intersects the circle of the eccentric are the points in which the centre of the eccentric should be placed for the forward and reverse motions. When the eccentric rod is attached directly to the valve, the radius of the eccentric, which precedes the crank in its revolution, forms with the crank an obtuse angle; but when, by the intervention of levers, the valve has a motion, opposed to that of the eccentric rod, the angle contained by the crank and the radius of the eccentric must be acute, and the eccentric must follow the crank: in other words, with a direct attachment to the valve the eccentric is set _more_ than one fourth of a revolution in advance of the crank, and with an indirect attachment the eccentric is set _less_ than one fourth of a circle behind the crank. If the valve were without lead or lap the eccentric would be exactly one fourth of a circle in advance of the crank or behind the crank, according to the nature of the valve connection; but as the valve would thus cover the port by the amount of the lap and lead, the eccentric must be set forward so as to open the port to the extent of the lap and lead, and this is effected by the plan just described. 521. _Q._--In the event of the eccentrics slipping round upon the shaft, which you stated sometimes happens, is it necessary to perform the operation of setting the valve as you have just described it? _A._--If the eccentrics shift upon the shaft, they may be easily refixed by setting the valve open the amount of the lead, setting the crank at the end of the stroke, and bringing round the eccentric upon the shaft till the eccentric rod gears with the valve. It would often be troublesome in practice to get access to the valve for the purpose of setting it, and this may be dispensed with if the amount of lap on the valve and the length of the eccentric rod be known. To this end draw upon a board two straight lines at right angles to one another, and from their point of intersection as a centre describe two circles, one representing the circle of the eccentric, the other the crank shaft; draw a straight line parallel to one of the diameters, and distant from it the amount of the lap and the lead: the points in which his parallel intersects the circle of the eccentric are the positions of the forward and backward eccentrics. Through these points draw straight lines from the centre of the circle, and mark the intersection of these lines with the circle of the crank shaft; measure with a pair of compasses the chord of the arc intercepted between either of these points, and the diameter which is at right angles with the crank, and the diameters being first marked on the shaft itself, then by transferring with the compasses the distance found in the diagram, and marking the point, the eccentric may at any time be adjusted without difficulty. [Illustration: Fig. 45.] 522. _Q._--Will you describe the structure and arrangement of the feed pumps of locomotive engines? _A._--The feed pumps of locomotives are generally made of brass, but the plungers are sometimes made of iron, and are generally attached to the piston, cross head, though in Stephenson's engines they are worked by rods attached to eyes on the eccentric hoops. There is a ball valve, fig. 45, between the pump and the tender, and two usually in the pipe leading from the pump to the boiler, besides a cock close to the boiler, by which the pump may be shut off from the boiler in case of any accident to the valves. The ball valves are guided by four branches, which rise vertically, and join together at the top in a hemispherical form. The shocks of the ball against this cap have in some cases broken it after one week's work, from the top of the cage having been flat, and the branches not having had their junction at the top properly filleted. These valve guards are attached in different ways to the pipes; when one occurs at the junction of two pieces of pipe it has a flange, which along with the flanges of the pipes and that of the valve seat are held together by a union joint. It is sometimes formed with a thread at the under end, and screwed into the pipe. The balls are cast hollow to lessen the shock, as well as to save the metal. In some cases where the feed pump plunger has been attached to the cross head, the piston rod has been bent by the strain; and that must in all cases occur, if the communication between the pump and boiler be closed when the engine is started, and there be no escape valve for the water. 523. _Q._--Are none but ball valves used in the feed pump? _A._--Spindle valves have in some cases been used instead of ball valves, but they are more subject to derangement; but piston valves, so contrived as to shut a portion of water in the cage when about to close, might be adopted with a great diminution of the shock. Slide valves might be applied, and would probably be found preferable to any of the expedients at present in use. In all spindle valves opened and shut rapidly, it is advisable to have the lower surface conical, to take off the shock of the water; and a large lift of the valve should be prevented, else much of the water during the return stroke of the pump will flow out before the valve shuts. 524. _Q._--At what part of the boiler is the feed water admitted? _A._--The feed pipe of most locomotive engines enters the boiler near the bottom and about the middle of its length. In Stephenson's engine the water is let in at the smoke box end of the boiler, a little below the water level; by this means the heat is more fully extracted from the escaping smoke, but the arrangement is of questionable applicability to engines of which the steam dome and steam pipe are at the smoke box end, as in that case the entering cold water would condense the steam. 525. _Q._--How are the pipes connecting the tender and locomotive constructed, so as to allow of play between the engine and tender without leakage? _A._--The pipes connecting the tender with the pumps should allow access to the valves and free motion to the engine and tender. This end is attained by the use of ball and socket joints; and, to allow some end play, one piece of the pipe slides into the other like a telescope, and is kept tight by means of a stuffing box. Any pipe joint between the engine and tender must be made in this fashion. 526. _Q._--Have you any suggestion to make respecting the arrangement of the feed pump? _A._--It would be a material improvement if a feed pump was to be set in the tender and worked by means of a small engine, such as that now used in steam vessels for feeding the boilers. The present action of the feed pumps of locomotives is precarious, as, if the valves leak in the slightest degree, the steam or boiling water from the boiler will prevent the pumps from drawing. It appears expedient, therefore, that at least one pump should be far from the boiler and should be set among the feed water, so that it will only have to force. If a pump was arranged in the manner suggested, the boiler could still be fed regularly, though the locomotive was standing still; but it would be prudent to have the existing pumps still wrought in the usual way by the engine, in case of derangement of the other, or in case the pump in the tender might freeze. 527. _Q._--Will you explain the construction of locomotive wheels? _A._--The wheels of a locomotive are always made of malleable iron. The driving wheels are made larger to increase the speed; the bearing wheels also are easier on the road when large. In the goods engines the driving wheels are smaller than in the passenger engines, and are generally coupled together. Wheels are made with much variety in their constructive details: sometimes they are made with cast iron naves, with the spokes and rim of wrought iron; but in the best modern wheels the nave is formed of the ends of the spokes welded together at the centre. When cast iron naves are adopted, the spokes are forged out of flat bars with T-formed heads, and are arranged radially in the founder's mould, the cast iron, when fluid, being poured among them. The ends of the T heads are then welded together to constitute the periphery of the wheel or inner tire; and little wedge-form pieces are inserted where there is any deficiency of iron. In some cases the arms are hollow, though of wrought iron; the tire of wrought iron, and the nave of cast iron; and the spokes are turned where they are fitted into the nave, and are secured in their sockets by means of cutters. Hawthorn makes his wheels with cast iron naves and wrought iron rims and arms; but instead of welding the arms together, he makes palms on their outer end, which are attached by rivets to the rim. These rivets, however, unless very carefully formed, are apt to work loose; and it would probably be found an improvement if the palms were to be slightly indented into the rim, in cases in which the palms do not meet each other at the ends. When the rim is turned it is ready for the tire, which is now made of steel. 528. _Q._--How do you find the length of bar necessary for forming a tire? _A._--To find the proper length of bar requisite for the formation of a hoop of any given diameter, add the thickness of the bar to the required diameter, and the corresponding circumference in the table of circumferences of circles is the length of the bar. If the iron be bent edgewise the breadth of the bar must be added to the diameter, for it is the thickness of the bar measured radially that is to be taken into consideration. In the tires of railway wheels, which have a flange on one edge, it is necessary to add not only the thickness of the tire, but also two thirds of the depth of the flange; generally, however, the tire bars are sent from the forge so curved that the plain edge of the tire is concave, and the flange edge convex, while the side which is afterward to be bent into contact with the cylindrical surface of the wheel is a plane. In this case the addition of the diameter of two thirds of the depth of the flange is unnecessary, for the curving of the flange edge has the effect of increasing the real length of the bar. When the tire is thus curved, it is only necessary to add the thickness of the hoop to the diameter, and then to find the circumference from a table; or the same result will be obtained by multiplying the diameter thus increased by the thickness of the hoop by 3.1416. 529. _Q._--How are the tires attached to the wheels? _A._--The materials for wheel tires are first swaged separately, and then welded together under the heavy hammer at the steel works; after which they are bent to the circle, welded, and turned to certain gauges. The tire is now heated to redness in a circular furnace; during the time it is getting hot, the iron wheel, turned to the right diameter, is bolted down upon a face plate or surface; the tire expands with the heat, and when at a cherry red, it is dropped over the wheel, for which it was previously too small, and it is also hastily bolted down to the surface plate; the whole mass is then quickly immersed by a swing crane in a tank of water five feet deep, and hauled up and down till nearly cold; the tires are not afterward tempered. The tire is attached to the rim with rivets having countersunk heads, and the wheel is then fixed on its axle. 530. _Q._--Is it necessary to have the whole tire of steel? _A._--It is not indispensable that the whole tire should be of steel; but a dovetail groove, turned out of the tire at the place where it bears most on the rail, and fitted with a band of steel, will suffice. This band may be put in in pieces, and the expedient appears to be the best way of repairing a worn tire; but particular care must be taken to attach these pieces very securely to the tire by rivets, else in the rapid revolution of the wheel the steel may be thrown out by the centrifugal force. In aid of such attachment the steel, after being introduced, is well hammered, which expands it sideways until it fills the dovetail groove. 531. _Q._--Is any arrangement adopted to facilitate the passage of the locomotive round curves? _A._--The tire is turned somewhat conical, to facilitate the passage of the engine round curves--the diameter of the outer wheel being virtually increased by the centrifugal force of the engine, and that of the inner wheel being correspondingly diminished, whereby the curve is passed without the resistance which would otherwise arise from the inequality of the spaces passed over by wheels of the same diameter fixed upon the same axle. The rails, moreover, are not set quite upright, but are slightly inclined inward, in consequence of which the wheels must be either conical or slightly dished, to bear fairly upon the rails. One benefit of inclining the rails in this way, and coning the tires, is that the flange of the wheels is less liable to bear against the sides of the rail, and with the same view the flanges of all the wheels are made with large fillets in the corners. Wheels have been placed loose upon the axle, but they have less stability, and are not now much used. Nevertheless this plan appears to be a good one if properly worked out. 532. _Q._--Are any precautions taken to prevent engines from being thrown off the rails by obstructions left upon the line? _A_.--In most engines a bar is strongly attached to the front of the carriage on each side, and projects perpendicularly downward to within a short distance of the rail, to clear away stones or other obstructions that might occasion accidents if the engine ran over them. CHAPTER IX. STEAM NAVIGATION. * * * * * RESISTANCE OF VESSELS IN WATER. 533. _Q._--How do you determine the resistance encountered by a vessel moving in water? _A._--The resistance experienced by vessels moving in water varies as the square of the velocity of their motion, or nearly so; and the power necessary to impart an increased velocity varies nearly as the cube of such increased velocity. To double the velocity of a steam vessel, therefore, will require four times the amount of tractive force, and as that quadrupled force must act through twice the distance in the same time, an engine capable of exerting eight times the original power will be required.[1] 534. _Q._--In the case of a board moving in water in the manner of a paddle float, or in the case of moving water impinging on a stationary board, what will be the pressure produced by the impact? _A._--The pressure produced upon a flat board, by striking water at right angles to the surface of the board, will be equal to the weight of a column of water having the surface struck as a base, and for its altitude twice the height due to the velocity with which the board moves through the water. If the board strike the water obliquely, the resistance will be less, but no very reliable law has yet been discovered to determine its amount. 535. _Q._--Will not the resistance of a vessel in moving through the water be much less than that of a flat board of the area of the cross section? _A._--It will be very much less, as is manifest from the comparatively small area of paddle board, and the small area of the circle described by the screw, relatively with the area of the immersed midship section of the vessel. The absolute speed of a vessel, with any given amount of power, will depend very much upon her shape. 536. _Q._--In what way is it that the shape of a vessel influences her speed, since the vessels of the same sectional area must manifestly put in motion a column of water of the same magnitude, and with the same velocity? _A._--A vessel will not strike the water with the same velocity when the bow lines are sharp as when they are otherwise; for a very sharp bow has the effect of enabling the vessel to move through a great distance, while the particles of water are moved aside but a small distance, or in other words, it causes the velocity with which the water is moved to be very small relatively with the velocity of the vessel; and as the resistance increases as the square of the velocity with which the water is moved, it is conceivable enough in what way a sharp bow may diminish the resistance. 537. _Q._--Is the whole power expended in the propulsion of a vessel consumed in moving aside the water to enable the vessel to pass? _A._--By no means; only a portion, and in well-formed vessels only a small portion, of the power is thus consumed. In the majority of cases, the greater part of the power is expended in overcoming the friction of the water upon the bottom of the vessel; and the problem chiefly claiming consideration is, in what way we may diminish the friction. 538. _Q._--Does the resistance produced by this friction increase with the velocity? _A._--It increases nearly as the square of the velocity. At two nautical miles per hour, the thrust necessary to overcome the friction varies as the 1.823 power of the velocity; and at eight nautical miles per hour, the thrust necessary to overcome the friction varies as the 1.713 power of the velocity. It is hardly proper, perhaps, to call this resistance by the name of friction; it is partly, perhaps mainly, due to the viscidity or adhesion of the water. 539. _Q._--Perhaps at high velocities this resistance may become less? _A_.--That appears very probable. It may happen that at high velocities the adhesion is overcome, so that the water is dragged off the vessel, and the friction thereafter follows the law which obtains in the case of solid bodies. But any such conclusion is mere speculation, since no experiments illustrative of this question have yet been made. 540. _Q._--Will a vessel experience more resistance in moving in salt water than in moving in fresh? _A._--If the immersion be the same in both cases a vessel will experience more resistance in moving in salt water than in moving in fresh, on account of the greater density of salt water; but as the notation is proportionably greater in the salt water the resistance will be the same with the same weight carried. 541. _Q._--Discarding for the present the subject of friction, and looking merely to the question of bow and stern resistance, in what manner should the hull of a vessel be formed so as to make these resistances a minimum? _A._--The hull should be so formed that the water, instead of being away driven forcibly from the bow, is opened gradually, so that every particle of water may be moved aside slowly at first, and then faster, like the ball of a pendulum, until it reaches the position of the midship frame, at which point it will have come to a state of rest, and then again, like a returning pendulum, vibrate back in the same way, until it comes to rest at the stern. It is not difficult to describe mechanically the line which the water should pursue. If an endless web of paper be put into uniform motion, and a pendulum carrying a pencil or brush be hung in front of it, then such pendulum will trace on the paper the proper water line of the ship, or the line which the water should pursue in order that no power may be lost except that which is lost in friction. It is found, however, in practice, that vessels formed with water lines on this principle are not much superior to ordinary vessels in the facility with which they pass through the water: and this points to the conclusion that in ordinary vessels of good form, the amount of power consumed in overcoming the resistance due to the wave at the bow and the partial vacuity at the stern is not so great as has heretofore been supposed, and that, in fact, the main resistance is that due to the friction. [1] This statement supposes that there is no difference of level between the water at the bow and the water at the stern. In the experiments on the steamer Pelican, the resistance was found to vary, as the 2.28th power of the velocity, but the deviation from the recognized law was imputed to a difference in the level of the water at the bow and stern. EXPERIMENTS ON THE RESISTANCE OF VESSELS. 542. _Q._--Have experiments been made to determine the resistance which steam vessels experience in moving through the waters? _A._--Experiments have been made both to determine the relative resistance of different classes of vessels, and also the absolute resistance in pounds or tons. The first experiments made upon this subject were conducted by Messrs. Boulton and Watt, and they have been numerous, long continued, and carefully performed. These experiments were made upon paddle vessels. 543. _Q._--Will you recount the chief results of these experiments? _A._--The purpose of the experiments was to establish a coefficient of performance, which with any given class of vessel would enable the speed, which would be obtained with any given power, to be readily predicted. This coefficient was obtained by multiplying the cube of the velocity of the vessels experimented upon, in miles per hour, by the sectional area of the immersed midship section in square feet, and dividing by the numbers of nominal horses power, and this coefficient will be large in the proportion of the goodness of the shape of the vessel. 544. _Q._--How many experiments were made altogether? _A._--There were five different sets of experiments on five different classes of vessels. The first set of experiments was made in 1828, upon the vessels Caledonia, Diana, Eclipse, Kingshead, Moordyke, and Eagle-vessels of a similar form and all with square bilges and flat floors; and the result was to establish the number 925 as the coefficient of performance of such vessels. The second set of experiments was made upon the superior vessels Venus, Swiftsure, Dasher, Arrow, Spitfire, Fury, Albion, Queen, Dart, Hawk, Margaret, and Hero-all vessels having flat floors and round bilges, where the coefficient became 1160. The third set of experiments was made upon the vessels Lightning, Meteor, James Watt, Cinderella, Navy Meteor, Crocodile, Watersprite, Thetis, Dolphin, Wizard, Escape, and Dragon-all vessels with rising floors and round bilges, and the coefficient of performance was found to be 1430. The fourth set of experiments was made in 1834, upon the vessels Magnet, Dart, Eclipse, Flamer, Firefly, Ferret, and Monarch, when the coefficient of performance was found to be 1580. The fifth set of experiments was made upon the Red Rover, City of Canterbury, Herne, Queen, and Prince of Wales, and in the case of those vessels the coefficient rose to 2550. The velocity of any of these vessels, with any power or sectional area, may be ascertained by multiplying the coefficient of its class by the nominal horse power, dividing by the sectional area in square feet, and extracting the cube root of the quotient, which will be the velocity in miles per hour; or the number of nominal horse power requisite for the accomplishment of any required speed may be ascertained by multiplying the cube of the required velocity in miles per hour, by the sectional area in square feet, and dividing by the coefficient: the quotient is the number of nominal horse power requisite to realize the speed. 545. _Q._--Seeing, however, that the nominal power does not represent an invariable amount of dynamical efficiency, would it not be better to make the comparison with reference to the actual power? _A._--In the whole of the experiments recited, except in the case of one or two of the last, the pressure of steam in the boiler varied between 2-3/4 lbs. and 4 lbs. per square inch, and the effective pressure on the piston varied between 11 lbs. and 13 lbs. per square inch, so that the average ratio of the nominal to the actual power may be easily computed; but it will be preferable to state the nominal power of some of the vessels, and their actual power as ascertained by experiment. 546. _Q._--Then state this. _A._--Of the Eclipse, the nominal power was 76, and the actual power 144.4 horses; of the Arrow, the nominal power was 60, and the actual 119.5; Spitfire, nominal 40, actual 64; Fury, nominal 40, actual 65.6; Albion, nominal 80, actual 135.4; Dart, nominal 100, actual 152.4; Hawk, nominal 40, actual 73; Hero, nominal 100, actual 171.4; Meteor, nominal 100, actual 160; James Watt, nominal 120, actual 204; Watersprite, nominal 76, actual 157.6; Dolphin, nominal 140, actual 238; Dragon, nominal 80, actual 131; Magnet, nominal 140, actual 238; Dart, nominal 120, actual 237; Flamer, nominal 120, actual 234; Firefly, nominal 52, actual 86.6; Ferret, nominal 52, actual 88; Monarch, nominal 200, actual 378. In the case of swift vessels of modern construction, such as the Red Rover, Herne, Queen, and Prince of Wales, the coefficient appears to be about 2550; but in these vessels there is a still greater excess of the actual over the nominal power than in the case of the vessels previously enumerated, and the increase in the coefficient is consequent upon the increased pressure of the steam in the boiler, as well as the superior form of the ship. The nominal power of the Red Rover, Herne, and City of Canterbury is, in each case, 120 horses, but the actual power of the Red Rover is 294, of the Herne 354, and of the City of Canterbury 306, and in some vessels the excess is still greater; so that with such variations it becomes necessary to adopt a coefficient derived from the introduction of the actual instead of the nominal power. 547. _Q._--What will be the average difference between the nominal and actual powers in the several classes of vessels you have mentioned and the respective coefficients when corrected for the actual power? _A._--In the first class of vessels experimented upon, the actual power was about 1.6 times greater than the nominal power; in the second class, 1.67 times greater; in the third class, 1.7 times greater; and in the fourth, 1.96 times greater; while in such vessels as the Red Rover and City of Canterbury, it is 2.65 times greater; so that if we adopt the actual instead of the nominal power in fixing the coefficients, we shall have 554 as the first coefficient, 694 as the second, 832 for the third, and 806 for the fourth, instead of 925, 1160, 1430, and 1580 as previously specified; while for such vessels as the Red Rover, Herne, Queen, and Prince of Wales, we shall have 962 instead of 2550. These smaller coefficients, then, express the relative merits of the different vessels without reference to any difference of efficacy in the engines, and it appears preferable, with such a variable excess of the actual over the nominal power, to employ them instead of those first referred to. From the circumstance of the third of the new coefficients being greater than the fourth, it appears that the superior result in the fourth set of experiments arose altogether from a greater excess of the actual over the nominal power. 548. _Q._--These experiments, you have already stated, were all made on paddle vessels. Have similar coefficients of performance been obtained in the case of screw vessels? _A._--The coefficients of a greater number of screw vessels have been obtained and recorded, but it would occupy too much time to enumerate them here. The coefficient of performance of the Fairy is 464.8; of the Rattler 676.8; and of the Frankfort 792.3. This coefficient, however, refers to nautical and not to statute miles. If reduced to statute miles for the purpose of comparison with the previous experiments, the coefficients will respectively become 703, 1033, and 1212; which indicate that the performance of screw vessels is equal to the performance of paddle vessels, but some of the superiority of the result may be imputed to the superior size of the screw vessels. INFLUENCE OF THE SIZE OF VESSELS UPON THEIR SPEED. 549. _Q._--Will large vessels attain a greater speed than small, supposing each to be furnished with the same proportionate power? _A._--It is well known that large vessels furnished with the same proportionate power, will attain a greater speed than small vessels, as appears from the rule usual in yacht races of allowing a certain part of the distance to be run to vessels which are of inferior size. The velocity attained by a large vessel will be greater than the velocity attained by a small vessel of the same mould and the same proportionate power, in the proportion of the square roots of the linear dimensions of the vessels. A vessel therefore with four times the sectional area and four times the power of a smaller symmetrical vessel, and consequently of twice the length, will have its speed increased in the proportion of the square root of 1 to the square root of 2, or 1.4 times. 550. _Q._--Will you further illustrate this doctrine by an example? _A._--The screw steamer Fairy, if enlarged to three times the size while retaining the same form, would have twenty-seven times the capacity, nine times the sectional area, and nine times the power. The length of such a vessel would be 434 feet; her breadth 63 feet 4-1/2 inches; her draught of water 16-1/2 feet; her area of immersed section 729 square feet; and her nominal power 1080 horses. Now as the lengths of the Fairy and of the new vessel are in the proportion of 1 to 3, the speeds will be in the proportion of the square root of 1 to the square root of 3; or, in other words, the speed of the large vessel will be 1.73 times greater than the speed of the small vessel. If therefore the speed of the Fairy be 13 knots, the speed of the new vessel will be 22.49 knots, although the proportion of power to sectional area, which is supposed to be the measure of the resistance, is in both cases precisely the same. If the speed of the Fairy herself had to be increased to 22.29 knots, the power would have to be increased in the proportion of the cube of 13 to the cube of 22.49, or 5.2 times, which makes the power necessary to propel the Fairy at that speed equal to 624 nominal horses power. STRUCTURE AND OPERATION OF PADDLE WHEELS. 551. _Q._--Will you describe the configuration and mode of action of the paddle wheels in general use? _A._--There are two kinds of paddle wheels in extensive use, the one being the ordinary radial wheel, in which the floats are fixed on arms radiating from the centre; and the other the feathering wheel, in which each float is hung upon a centre, and is so governed by suitable mechanism as to be always kept in nearly the vertical position. In the radial wheel there is some loss of power from oblique action, whereas in the feathering wheel there is little or no loss from this cause; but in every kind of paddle there is a loss of power from the recession of the water from the float boards, or the _slip_ as it is commonly called; and this loss is the necessary condition of the resistance for the propulsion of the vessel being created in a fluid. The slip is expressed by the difference between the speed of the wheel and the speed of the vessel, and the larger this difference is the greater the loss of power from slip must be--the consumption of steam in the engine being proportionate to the velocity of the wheel, and the useful effect being proportionate to the speed of the ship. 552. _Q._--The resistance necessary for propulsion will not be situated at the circumference of the wheel? _A._--In the feathering wheel, where every part of any one immerged float moves forward with the same horizontal velocity, the pressure or resistance may be supposed to be concentrated in the centre of the float; whereas, in the common radial wheel this cannot be the case, for as the outer edge of the float moves more rapidly than the edge nearest the centre of the wheel, the outer part of the float is the most effectual in propulsion. The point at which the outer and inner portions of the float just balance one another in propelling effect, is called the _centre of pressure_; and if all the resistances were concentrated in this point, they would have the same effect as before in resisting the rotation of the wheel. The resistance upon any one moving float board totally immersed in the water will, when the vessel is at rest, obviously vary as the square of its distance from the centre of motion--the resistance of a fluid varying with the square of the velocity; but, except when the wheel is sunk to the axle or altogether immersed in the water, it is impossible, under ordinary circumstances, for one float to be totally immersed without others being immersed partially, whereby the arc described by the extremity of the paddle arm will become greater than the arc described by the inner edge of the float; and consequently the resistance upon any part of the float will increase in a higher ratio than the square of its distance from the centre of motion--the position of the centre of pressure being at the same time correspondingly affected. In the feathering wheel the position of the centre of pressure of the entering and emerging floats is continually changing from the lower edge of the float--where it is when the float is entering or leaving the water--to the centre of the float, which is its position when the float is wholly immerged; but in the radial wheel the centre of pressure can never rise so high as the centre of the float. 553. _Q._--All this relates to the action of the paddle when the vessel is at rest: will you explain its action when the vessel is in motion? _A._--When the wheel of a coach rolls along the ground, any point of its periphery describes in the air a curve which is termed a cycloid; any point within the periphery traces a prolate or protracted cycloid, and any point exterior to the periphery traces a curtate or contracted cycloid--the prolate cycloid partaking more of the nature of a straight line, and the curtate cycloid more of the nature of a circle. The action of a paddle wheel in the water resembles in this respect that of the wheel of a carriage running along the ground: that point in the radius of the paddle of which the rotative speed is just equal to the velocity of the vessel will describe a cycloid; points nearer the centre, prolate cycloids, and points further from the centre, curtate cycloids. The circle described by the point whose velocity equals the velocity of the ship, is called the _rolling circle_, and the resistance due to the difference of velocity of the rolling circle and centre of pressure is that which operates in the propulsion of the vessel. The resistance upon any part of the float, therefore, will vary as the square of its distance from the rolling circle, supposing the float to be totally immerged; but, taking into account the greater length of time during which the extremity of the paddle acts, whereby the resistance will be made greater, we shall not err far in estimating the resistance upon any point at the third power of its distance from the rolling circle in the case of light immersions, and the 2.5 power in the case of deep immersions. 554. _Q._--How is the position of the centre of pressure to be determined? _A._--With the foregoing assumption, which accords sufficiently with experiment to justify its acceptation, the position of the centre of pressure may be found by the following rule:--from the radius of the wheel substract the radius of the rolling circle; to the remainder add the depth of the paddle board, and divide the fourth power of the sum by four times the depth; from the cube root of the quotient subtract the difference between the radii of the wheel and rolling circle, and the remainder will be the distance of the centre of pressure from the upper edge of the paddle. 555. _Q._--How do you find the diameter of the rolling circle? _A._--The diameter of the rolling circle is very easily found, for we have only to divide 5,280 times the number of miles per hour, by 60 times the number of strokes per minute, to get an expression for the circumference of the rolling circle, or the following rule may be adopted:--divide 88 times the speed of the vessel in statute miles per hour, by 3.1416 times the number of strokes per minute; the quotient will be the diameter in feet of the rolling circle. The diameter of the circle in which the centre of pressure moves or the effective diameter of the wheel being known, and also the diameter of the rolling circle, we at once find the excess of the velocity of the wheel over the vessel. 556. _Q._--Will you illustrate these rules by an example? _A._--A steam vessel of moderately good shape, and with engines of 200 horses power, realises, with 22 strokes per minute, a speed of 10.62 miles per hour. To find the diameter of the rolling circle, we have 88 times 10.62, equal to 934.66, and 22 times 3.1416, equal to 69.1152; then 934.66 divided by 69.1152 is equal to 13.52 feet, which is the diameter of the rolling circle. The diameter of the wheel is 19 ft. 4 in., so that the diameter of the rolling circle is about 2/3ds of the diameter of the wheel, and this is a frequent proportion. The depth of the paddle board is 2 feet, and the difference between the diameters of the wheel and rolling circle will be 5.8133, which will make the difference of their radii 2.9067; and adding to this the depth of the paddle board, we have 4.9067, the fourth power of which is 579.64, which, divided by four times the depth of the paddle board, gives us 72.455, the cube root of which is 4.1689, which, diminished by the difference of the radii of the wheel and rolling circle, leaves 1.2622 feet for the distance of the centre of pressure from the upper edge of the paddle board in the case of light immersions. The radius of the wheel being 9.6667, the distance from the centre of the wheel to the upper edge of the float is 7.6667, and adding to this 1.2622, we get 8.9299 feet as the radius, or 17.8598 feet as the diameter of the circle in which the centre of pressure revolves. With 22 strokes per minute, the velocity of the centre of pressure will be 20.573 feet per second, and with 10.62 miles per hour for the speed of the vessel, the velocity of the rolling circle will be 15.576 feet per second. The effective velocity will be the difference between these quantities, or 4.997 feet per second. Now the height from which a body must fall by gravity, to acquire a velocity of 4.997 feet per second, is about .62 feet; and twice this height, or 1.24 feet, multiplied by 62-1/2, which is the number of Lbs. weight in a cubic foot of water, gives 77-1/2 Lbs. as the pressure on each square foot of the vertical paddle boards. As each board is of 20 square feet of area, and there is a vertical board on each side of the ship, the total pressure on the vertical paddle boards will be 2900 Lbs. 557. _Q._--What pressure is this equivalent to on each square inch of the pistons? _A._--A vessel of 200 horses power will have two cylinders, each 50 inches diameter, and 5 feet stroke, or thereabout. The area of a piston of 50 inches diameter is 1963.5 square inches, so that the area of the two pistons is 3927 square inches, and the piston will move through 10 feet every revolution; and with 22 strokes per minute this will be 220 feet per minute, or 3.66 feet per second. Now, if the effective velocity of the centre of pressure and the velocity of the pistons had been the same, then a pressure of 2900 Lbs. upon the vertical paddles would have been balanced by an equal pressure on the pistons, which would have been in this case about .75 Lbs. per square inch; but as the effective velocity of the centre of pressure is 4.997 feet per second, while that of the pistons is only 3.66 feet per second, the pressure must be increased in the proportion of 4.997 to 3.66 to establish an equilibrium of pressure, or, in other words, it must be 1.02 Lbs. per square inch. It follows from this investigation, that, in radial wheels, the greater part of the engine power is distributed among the oblique floats. 558. _Q._--How comes this to be the case? _A._--To understand how it happens that more power is expended upon the oblique than upon the vertical floats, it is necessary to remember that the only resistance upon the vertical paddle is that due to the difference of velocity of the wheel and the ship; but if the wheel be supposed to be immersed to its axle, so that the entering float strikes the water horizontally, it is clear that the resistance on such float is that due to the whole velocity of rotation; and that the resistance to the entering float will be the same whether the vessel is in motion or not. The resistance opposed to the rotation of any float increases from the position of the vertical float-where the resistance is that due to the difference of velocity of the wheel and vessel--until it reaches the plane of the axis, supposing the wheel to be immersed so far, where the resistance is that due to the whole velocity of rotation; and although in any oblique float the total resistance cannot be considered operative in a horizontal direction, yet the total resistance increases so rapidly on each side of the vertical float, that the portion of it which is operative in the horizontal direction, is in all ordinary cases of immersion very considerable. In the feathering wheel, where there is little of this oblique action, the resistance will be in the proportion of the square of the horizontal velocities of the several floats, which may be represented by the horizontal distances between them; and in the feathering wheel, the vertical float having the greatest horizontal velocity will have the greatest propelling effect. 559. _Q._--Should the floats in feathering wheels enter and leave the water vertically? _A._--The floats should be so governed by the central crank or eccentric, that the entering and emerging floats have a direction intermediate between a radius and a vertical line. 560. _Q._--Can you give any practical rules for proportioning paddle wheels? _A._--A common rule for the pitch of the floats is to allow one float for every foot of diameter of the wheel; but in the case of fast vessels a pitch of 2-1/2 feet, or even less, appears preferable, as a close pitch occasions less vibration. If the floats be put too close, however, the water will not escape freely from between them, and if set too far apart the stroke of the entering paddle will occasion an inconvenient amount of vibratory motion, and there will also be some loss of power. To find the proper area of a single float:--divide the number of actual horses power of both engines by the diameter of the wheel in feet; the quotient is the area of one paddle board in square feet proper for sea going vessels, and the area multiplied by 0.6 will give the length of the float in feet. In very sharp vessels, which offer less resistance in passing through the water, the area of paddle board is usually one-fourth less than the above proportion, and the proper length of the float may in such case be found by multiplying the area by 0.7. In sea going vessels about four floats are usually immersed, and in river steamers only one or two floats. There is more slip in the latter case, but there is also more engine power exerted in the propulsion of the ship, from the greater speed of engine thus rendered possible. 561. _Q._--Then is it beneficial to use small floats? _A._--Quite the contrary. If to permit a greater speed of the engine the floats be diminished in area instead of being raised out of the water, no appreciable accession to the speed of the vessel will be obtained; whereas there will be an increased speed of vessel if the accelerated speed of the engine be caused by diminishing the diameter of the wheels. In vessels intended to be fast, therefore, it is expedient to make the wheels small, so as to enable the engine to work with a high velocity; and it is expedient to make such wheels of the feathering kind, to obviate loss of power from oblique action. In no wheel must the rolling circle fall below the water line, else the entering and emerging floats will carry masses of water before them. The slip is usually equal to about one-fourth of the velocity of the centre of pressure in well proportioned wheels; but it is desirable to have the slip as small as is possible consistently with the observance of other necessary conditions. The speed of the engine and also the speed of the vessel being fixed, the diameter of the rolling circle becomes at once ascertainable, and adding to this the slip, we have the diameter of the wheel. CONFIGURATION AND ACTION OF THE SCREW. 562. _Q._--Will you describe more in detail than you have yet done, the configuration and mode of action of the screw propeller? _A._--The ordinary form of screw propeller is represented in figs. 46 and 47; fig. 46 being a perspective view, and fig. 47 an end view, or view such as is seen when looking upon the end of the shaft. The screw here represented is one with two arms or blades. Some screws have three arms, some four and some six; but the screw with two arms is the most usual, and screws with more than three arms are not now much employed in this country. The screw on being put into revolution by the engine, preserves a spiral path in the water, in which it draws itself forward in the same way as a screw nail does when turned round in a piece of wood, whereas the paddle wheel more resembles the action of a cog wheel working in a rack. [Illustration: Fig. 46. Fig. 47. ORDINARY FORM OF SCREW PROPELLER.] 563. _Q._--But the screw of a steam vessel has no resemblance to a screw nail? _A._--It has in fact a very close resemblance if you suppose only a very short piece of the screw nail to be employed, and if you suppose, moreover, the thread of the screw to be cut nearly into the centre to prevent the wood from stripping. The original screw propellers were made with several convolutions of screw, but it was found advantageous to shorten them, until they are now only made one-sixth of a convolution in length. 564. _Q._--And the pitch you have already explained to be the distance in the line of the shaft from one convolution to the next, supposing the screw to consist of two or more convolutions? _A._--Yes, that is what is meant by the pitch. If a thread be wound upon a cylinder with an equal distance between the convolutions, it will trace a screw of a uniform pitch; and if the thread be wound upon the cylinder with an increasing distance between each convolution, it will trace a screw of an increasing pitch. But two or more threads may be wound upon the cylinder at the same time, instead of a single thread. If two threads be wound upon it they will trace a double-threaded screw; if three threads be wound upon it they will trace a treble-threaded screw; and so of any other number. Now if the thread be supposed to be raised up into a very deep and thin spiral feather, and the cylinder be supposed to become very small, like the newel of a spiral stair, then a screw will be obtained of the kind proper for propelling vessels, except that only a very short piece of such screw must be employed. Whatever be the number of threads wound upon a cylinder, if the cylinder be cut across all the threads will be cut. A slice cut out of the cylinder will therefore contain a piece of each thread. But the threads, in the case of a screw propeller, answer to the arms, so that in every screw propeller the number of threads entering into the composition of the screw will be the same as the number of arms. An ordinary screw with two blades is a short piece of a screw of two threads. 565. _Q._--In what part of the ship is the screw usually placed? [Illustration: Fig. 48] _A._--In that part of the run of the ship called the dead wood, which is a thin and unused part of the vessel just in advance of the rudder. The usual arrangement is shown in fig. 48, which represents the application to a vessel of a species of screw which has the arms bent backwards, to counteract the centrifugal motion given to the water when there is a considerable amount of slip. 566. _Q._--How is the slip in a screw vessel determined? _A._--By comparing the actual speed of the vessel with the speed due to the pitch and number of revolutions of the screw, or, what is the same thing, the speed which the vessel would attain if the screw worked in a solid nut. The difference between the actual speed and this hypothetical speed, is the slip. 567. _Q._--In well formed screw propellers what is the amount of slip found to be? _A._--If the screw be properly proportioned to the resistance that the vessel has to overcome, the slip will not be more than 10 per cent., but in some cases it amounts to 30 per cent., or even more than this. In other cases, however, the slip is nothing at all, and even less than nothing; or, in other words the vessel passes through the water with a greater velocity than if the screw were working in a solid nut. 568. _Q._--Then it must be by the aid of the wind or some other extraneous force? _A._--No; by the action of the screw alone. 569. _Q._--But how is such a result possible? _A._--It appears to be mainly owing to the centrifugal action of the screw, which interposes a film or wedge of water between the screw itself and the water on which the screw reacts. This negative slip, as it is called, chiefly occurs when the pitch of the screw is less than its diameter, and when, consequently, the velocity of rotation is greater than if a coarser pitch had been employed. There is, moreover, in all vessels passing through the water with any considerable velocity, a current of water following the vessel, in which current, in the case of a screw vessel, the screw will revolve; and in certain cases the phenomenon of negative slip may be imputable in part to the existence of this current. 570. _Q._--Is the screw propeller as effectual an instrument of propulsion as the radial or feathering paddle? _A._--In all cases of deep immersion it appears to be quite as effectual as the radial paddle, indeed, more so; but it is scarcely as effectual as the feathering paddle, with any amount of immersion, and scarcely as effectual as the common paddle in the case of light immersions. COMPARATIVE ADVANTAGES OF PADDLE AND SCREW VESSELS. 571. _Q._--Whether do you consider paddle or screw vessels to be on the whole the most advantageous? _A._--That is a large question, and can only receive a qualified answer. In some cases the use of paddles is indispensable, as, for example, in the case of river vessels of a limited draught of water, where it would not be possible to get sufficient depth below the water surface to enable a screw of a proper diameter to be got in. 572. _Q._--But how does the matter stand in the case of ocean vessels? _A._--In the case of ocean vessels, it is found that paddle vessels fitted with the ordinary radial wheels, and screw vessels fitted with the ordinary screw, are about equally efficient in calms and in fair or beam winds with light and medium immersions. If the vessels are loaded deeply, however, as vessels starting on a long voyage and carrying much coal must almost necessarily be, then the screw has an advantage, since the screw acts in its best manner when deeply immersed, and the paddles in their worst. When a screw and paddle vessel, however, of the same model and power are set to encounter head winds, the paddle vessel it is found has in all cases an advantage, not in speed, but in economy of fuel. For whereas in a paddle vessel, when her progress is resisted, the speed of the engine diminishes nearly in the proportion of the diminished speed of ship, it happens that in a screw vessel this is not so,--at least to an equal extent,--but the engines work with nearly the same rate of speed as if no increase of resistance had been encountered by the ship. It follows from this circumstance, that whereas in paddle vessels the consumption of steam, and therefore of fuel, per hour is materially diminished when head winds occur, in screw vessels a similar diminution in the consumption of steam and fuel does not take place. 573. _Q._--But perhaps under such circumstances the speed of the screw vessel will be the greater of the two? _A._--No; the speed of the two vessels will be the same, unless the strength of the head wind be so great as to bring the vessels nearly to a state of rest, and on that supposition the screw vessel will have the advantage. Such cases occur very rarely in practice; and in the case of the ordinary resistances imposed by head winds, the speed of the screw and paddle vessel will be the same, but the screw vessel will consume most coals. 574. _Q._--What is the cause of this peculiarity? _A._--The cause is, that when the screw is so proportioned in its length as to be most suitable for propelling vessels in calms, it is too short to be suitable for propelling vessels which encounter a very heavy resistance. It follows, therefore, that if it is prevented from pursuing its spiral course in the water, it will displace the water to a certain extent laterally, in the manner it does if the engine be set on when the vessel is at anchor; and a part of the engine power is thus wasted in producing a useless disturbance of the water, which in paddle vessels is not expended at all. 575. _Q._--If a screw and paddle vessel of the same mould and power be tied stern to stern, will not the screw vessel preponderate and tow the paddle vessel astern against the whole force of her engines? _A._--Yes, that will be so. 576. _Q._--And seeing that the vessels are of the same mould and power, so that neither can derive an advantage from a variation in that condition, does not the preponderance of the screw vessel show that the screw must be the most powerful propeller? _A._---No, it does not. 577. _Q._--Seeing that the vessels are the same in all respects except as regards the propellers, and that one of them exhibits a superiority, does not this circumstance show that one propeller must be more powerful than the other? _A._--That does not follow necessarily, nor is it the fact in this particular case. All steam vessels when set into motion, will force themselves forward with an amount of thrust which, setting aside the loss from friction and from other causes, will just balance the pressure on the pistons. In a paddle vessel, as has already been explained, it is easy to tell the tractive force exerted at the centre of pressure of the paddle wheels, when the pressure urging the pistons, the dimensions of the wheels and the speed of the vessel are known; and that force, whatever be its amount, must always continue the same with any constant pressure on the pistons. In a screw vessel the same law applies, so that with any given pressure on the pistons and discarding the consideration of friction, it will follow that whatever be the thrust exerted by a paddle or a screw vessel, it must remain uniform whether the vessel is in motion or at rest, and whether moving at a high or a low velocity through the water. Now to achieve an equal speed during calms in two vessels of the same model, there must be the same amount of propelling thrust in each; and this thrust, whatever be its amount, cannot afterward vary if a uniform pressure of steam be maintained. The thrusts, therefore, caused by their respective propelling instruments, when a screw and paddle vessel are tied stern to stern, must be the same as at other times; and as at other times those thrusts are equal, so must they be when the vessels are set in the antagonism supposed. 578. _Q._--How comes it then that the screw vessel preponderates? _A._--Not by virtue of a larger thrust exerted by the screw in pressing forward the shaft and with it the vessel, but by the gravitation against the stern of the wave of water which the screw raises by its rapid rotation. This wave will only be raised very high when the progress of the vessel through the water is nearly arrested, at which time the centrifugal action of the screw is very great; and the vessel under such circumstances is forced forward partly by the thrust of the screw, and partly by the hydrostatic pressure of the protuberance of water which the centrifugal action of the screw raises up at the stern. 579. _Q._--Can you state any facts in corroboration of this view? _A._--The screw vessel will not preponderate if a screw and paddle vessel be tied bow to bow and the engines of each be then reversed. In, some screw vessels the amount of thrust actually exerted by the screw under all its varying circumstances, has been ascertained by the application of a dynamometer to the end of the shaft. By this instrument--which is formed by a combination of levers like a weighing machine for carts--a thrust or pressure of several tons can be measured by the application of a small weight; and it has been found, by repeated experiment with the dynamometer, that the thrust of the screw in a screw vessel when towing a paddle vessel against the whole force of her engines, is just the same as it is when the two vessels are maintaining an equal speed in calms. The preponderance of the screw vessel must, therefore, be imputable to some other agency than to a superior thrust of the screw, which is found by experiment not to exist. 580. _Q._--Has the dynamometer been applied to paddle vessels? _A._--It has not been applied to the vessels themselves, as in the case of screw vessels, but it has been employed on shore to ascertain the amount of tractive force that a paddle vessel can exert on a rope. 581. _Q._--Have any experiments been made to determine the comparative performances of screw and paddle vessels at sea? _A._--Yes, numerous experiments; of which the best known are probably those made on the screw steamer Rattler and the paddle steamer Alecto, each vessel of the same model, size, and power,--each vessel being of about 800 tons burden and 200 horses power. Subsequently another set of experiments with the same object was made with the Niger screw steamer and the Basilisk paddle steamer, both vessels being of about 1000 tons burden and 400 horses power. The general results which were obtained in the course of these experiments are those which have been already recited. 582. _Q._--Will you recapitulate some of the main incidents of these trials? _A._--I may first state some of the chief dimensions of the vessels. The Rattler is 176 feet 6 inches long, 32 feet 8-1/2 inches broad, 888 tons burden, 200 horses power, and has an area of immersed midship section of 380 square feet at a draught of water of 11 feet 5-1/2 inches. The Alecto is of the same dimensions in every respect, except that she is only of 800 tons burden, the difference in this particular being wholly owing to the Rattler having been drawn out about 15 feet at the stern, to leave abundant room for the application of the screw. The Rattler was fitted with a dynamometer, which enabled the actual propelling thrust of the screw shaft to be measured; and the amount of this thrust, multiplied by the distance through which the vessel passed in a given time, would determine the amount of power actually utilized in propelling the ship. Both vessels were fitted with indicators applied to the cylinders, so as to determine the amount of power exerted by the engines. 583. _Q._--How many trials of the vessels were made on this occasion? _A._--Twelve trials in all; but I need not refer to those in which similar or identical results were only repeated. The first trial was made under steam only, the weather was calm and the water smooth. At 54 minutes past 4 in the morning both vessels left the Nore, and at 30-1/2 minutes past 2 the Rattler stopped her engines in Yarmouth Roads, where in 20-1/2 minutes afterward she was joined by the Alecto. The mean speed achieved by the Rattler during this trial was 9.2 knots per hour; the mean speed of the Alecto was 8.8 knots per hour. The slip of the screw was 10.2 per cent. The actual power exerted by the engines, as shown by the indicator, was in the case of the Rattler 334.6 horses, and in the case of the Alecto 281.2 horses; being a difference of 53.4 horses in favor of the Rattler. The forward thrust upon the screw shaft was 3 tons, 17 cwt., 3 qrs., and 14 lbs. The horse power of the shaft--or power actually utilized--ascertained by multiplying the thrust in pounds by the space passed through by the vessel in feet per minute, and dividing by 33,000, was 247.8 horses power. This makes the ratio of the shaft to the engine power as 1 to 1.3, or, in other words, it shows that the amount of engine power utilized in propulsion was 77 per cent. In a subsequent trial made with the vessels running before the wind, but with no sails set and the masts struck, the speed realized by the Rattler was 10 knots per hour. The slip of the screw was 11.2 per cent. The actual power exerted by the engines of the Rattler was 368.8 horses. The actual power exerted by the engines of the Alecto was 291.7 horses. The thrust of the shaft was equal to a weight of 4 tons, 4 cwt., 1 qr., 1 lb. The horse power of the shaft was 290.2 horses, and the ratio of the shaft to the engine power was 1 to 1.2. Here, therefore, the amount of the engine power utilized was 84 per cent. 584. _Q._--If in any screw vessel the power of the engine be diminished by shutting off the steam or otherwise, you will then have a larger screw relatively with the power of the engine than before? _A._--Yes. 585. _Q._--Was any experiment made to ascertain the effect of this modification? _A._--There was; but the result was not found to be better than before. The experiment was made by shutting off the steam from the engines of the Rattler until the number of strokes was reduced to 17 in the minute. The actual power was then 126.7 horses; thrust upon the shaft 2 tons, 2 cwt., 3 qrs., 14 lbs; horse power of shaft 88.4 horses; ratio of shaft to engine power 1 to 1.4; slip of the screw 18.7 per cent. In this experiment the power utilized was 71 per cent. 586. _Q._--Was any experiment made to determine the relative performances in head winds? _A._--The trial in which this relation was best determined lasted for seven hours, and was made against a strong head wind and heavy head sea. The speed of the Rattler by patent log was 4.2 knots; and at the conclusion of the trial the Alecto had the advantage by about half a mile. Owing to an accidental injury to the indicator, the power exerted by the engines of the Rattler in this trial could not be ascertained; but judging from the power exerted in other experiments with the same number of revolutions, it appears probable that the power actually exerted by the Rattler was about 300 horses. The number of strokes per minute made by the engines of the Rattler was 22, whereas in the Alecto the number of strokes per minute was only 12; so that while the engines of the Alecto were reduced, by the resistance occasioned by a strong head wind, to nearly half their usual speed, the engines of the Rattler were only lessened about one twelfth of their usual speed. The mean thrust upon the screw shaft during this experiment, was 4 tons, 7 cwt., 0 qr., 16 lbs. The horse power of the shaft was 125.9 horses, and the slip of the screw was 56 per cent. Taking the power actually exerted by the Rattler at 300 horses, the power utilized in this experiment is only 42 per cent. 587. _Q._--What are the dimensions of the screw in the Rattler? _A._--Diameter 10 feet, length 1 foot 3 inches, pitch 11 feet. The foregoing experiments show that with a larger screw a better average performance would be obtained. The best result arrived at, was when the vessel was somewhat assisted by the wind, which is equivalent to a reduction of the resistance of the hull, or to a smaller hull, which is only another expression for a larger proportionate screw. 588. _Q._--When you speak of a larger screw, what increase of dimension do you mean to express? _A._--An increase of the diameter. The amount of reacting power of the screw upon the water is hot measured by the number of square feet of surface of the arms, but by the area of the disc or circle in which the screw revolves. The diameter of the screw of the Rattler being 10 feet, the area of its disc is 78.5 square feet; and with the amount of thrust already mentioned as existing in the first experiment, viz. 8722 lbs., the reacting pressure on each square foot of the screw's disc will be 108-1/2 lbs. The immersed midship section being 380 square feet, this is equivalent to 23 lbs. per square foot of immersed midship section at a speed of 9.2 knots per hour. 589. _Q._--In smaller vessels of similar form, will the resistance per square foot of midship section be more than this? _A._--It will be considerably more. In the Pelican, a vessel of 109-3/4 square feet of midship section, I estimate the resistance per square foot of midship section at 30 lbs., when the speed of the vessel is 9.7 knots per hour. In the Minx with an immersed midship section of 82 square feet, the resistance per square foot of immersed midship section was found by the dynamometer to be 41 lbs. at a speed of 8-1/2 knots; and in the Dwarf, a vessel with 60 square feet of midship section, I estimate the resistance per square foot of midship section at 46 lbs. at a speed of 9 knots per hour, which is just double the resistance per square foot of the Rattler. The diameter of the screw of the Minx is 4-1/2 feet, so that the area of its disc is 15.9 square feet, and the area of immersed midship section is about 5 times greater than that of the screw's disc. The diameter of the screw of the Dwarf is 5 feet 8 inches, so that the area of its disc is 25.22 square feet, and the area of immersed midship section is 2.4 times greater than that of the screw's disc. The pressure per square foot of the screw's disc is 214 lbs. in the case of the Minx, and 109-1/2 lbs. in the case of the Dwarf. 590. _Q._--From the greater proportionate resistance of small vessels, will not they require larger proportionate screws than large vessels? _A._--They will. 591. _Q._--Is there any ready means of predicting what the amount of thrust of a screw will be? _A._--When we know the amount of pressure on the pistons, and the velocity of their motion relatively with the velocity of advance made by the screw, supposing it to work in a solid nut, it is easy to tell what the thrust of the screw would be if it were cleared of the effects of friction and other irregular sources of disturbance. The thrust, in fact, would be at once found by the principle of virtual velocities; and if we take this theoretical thrust and diminish it by one fourth to compensate for friction and lateral slip, we shall have a near approximation to the amount of thrust that will be actually exerted.[1] [1] See Treatise on the Screw Propeller, by J. Bourne, C. E. COMPARATIVE ADVANTAGES OF DIFFERENT SCREWS. 592. _Q._--What species of screw do you consider the best? _A._--In cases in which a large diameter of screw can be employed, the ordinary screw or helix with two blades seems to be as effective as any other, and it is the most easily constructed. If, however, the screw is restricted in diameter, or if the vessel is required to tow, or will have to encounter habitually strong head winds, it will be preferable to employ a screw with an increasing pitch, and also of such other configuration that it will recover from the water some portion of the power that has been expended in slip. 593. _Q._--How can this be done? _A._--There are screws which are intended to accomplish, this object already in actual use. When there is much slip a centrifugal velocity is given to the water, and the screw, indeed, if the engine be set on when the vessel is at rest, acts very much as a centrifugal fan would do if placed in the same situation. The water projected outward by the centrifugal force escapes in the line of least resistance, which is to the surface; and if there be a high column of water over the screw, or, in other words, if the screw is deeply immersed, then the centrifugal action is resisted to a greater extent, and there will be less slip produced. The easiest expedient, therefore, for obviating loss by slip is to sink the screw deeply in the water; but as there are obvious limits to the application of this remedy, the next best device is to recover and render available for propulsion some part of the power which has been expended in giving motion to the water. One device for doing this consists in placing the screw well forward in the dead wood, so that it shall be overhung by the stern of the ship. The water forced upward by the centrifugal action of the screw will, by impinging on the overhanging stern, press the vessel forward in the water, just in the same way as is done by the wind when acting on an oblique sail. I believe, the two revolving vanes without any twist or obliquity on them at all, would propel a vessel if set well forward in the dead wood or beneath the bottom, merely by the ascent of the water up the inclined plane of the vessel's run; and, at all events, a screw so placed would, in my judgment, aid materially in propelling the vessel when her progress was resisted by head winds. 594. _Q._--But you said there are some kinds of screws which profess to accomplish this? [Illustration: Fig. 49. THE EARL OF DUNDONALD'S PROPELLER.] _A._--There are screws which profess to counteract the centrifugal velocity given to the water by imparting to it an equal centripetal force, the consequence of which will be, that the water projected backward by the screw, instead of taking the form of the frustum of a cone, with its small end next the screw, will take the form of a cylinder. One of these forms of screw is that patented by the Earl of Dundonald in 1843, and which is represented in fig. 49. Another is the form of screw already represented in fig. 48, and which was patented by Mr. Hodgson in 1844. Mr. Hodgson bends the arms of his propellers backward, not into the form of a triangle, but into the form of a parabola, to the end that the impact of the screw on the particles of the water may cause them to converge to a focus, as the rays of light would do in a parabolic reflector. But this particular configuration is not important, seeing that the same convergence which is given to the particles of the water, with a screw of uniform pitch bent back into the form of a parabola, will be given with a screw bent back into the form of a triangle, if the pitch be suitably varied between the centre and the circumference. 595. _Q._--Then the pitch may be varied in two ways? _A._--Yes: a screw may have a pitch increasing in the direction of the length, as would happen in the case of a spiral stair, if every successive step in the ascent was thicker than the one below it; or it may increase from the centre to the circumference, as would happen in the case of a spiral stair, if every step were thinner at the centre of the lower than at its outer wall. When the pitch of a screw increases in the direction of its length, the leading edge of the screw enters the water without shock or impact, as the advance of the leading edge per revolution will not be greater than the advance of the vessel. When the pitch of a screw increases in the direction of its diameter, the central part of the screw will advance with only the same velocity as the water, so that it cannot communicate any centrifugal velocity to the water; and the whole slip, as well as the whole propelling pressure, will occur at the outer part of the screw blades. 596. _Q._--Is there any advantage derived from these forms of screws? _A._--There is a slight advantage, but it is so slight as hardly to balance the increased trouble of manufacture, and, consequently, they are not generally or widely adopted. 597. _Q._--What other kinds of screw are there proposing to themselves the same or similar objects? _A._--There is the corrugated screw, the arms of which are corrugated, so as it were to gear with the water during its revolution, and thereby prevent it from acquiring a centrifugal velocity. Then there is Griffith's screw, which has a large ball at its centre, which, by the suction it creates at its hinder part, in passing through the water, produces a converging force, which partly counteracts the divergent action of the arms. Finally, there is Holm's screw, which has now been applied to a good number of vessels with success. 598. _Q._--Will you describe the configuration and action of Holm's screw? _A._--First, then, the screw increases in the direction of its length, and this increase is very rapid at the following edge, so that, in fact, the following edge stands in the plane of the shaft, or in the vertical longitudinal plane of the vessel. Then the ends of the arms are bent over into a curved flange, the edge of which points astern, and the point where this curved flange joins the following edge of the screw is formed, not into an angle, but into a portion of a sphere, so that this corner resembles the bowl of a spoon. When the screw is put into revolution, the water is encountered by the leading edge of the screw without shock, as its advance is only equal to the advance of the vessel, and before the screw leaves the water it is projected directly astern. At the same time, the curved flange at the rim of the screw prevents the dispersion of the water in a radial direction, and it consequently assumes the form of a column or cylinder of water, projected backward from the ship. 599. _Q._--What is the nature of Beattle's screw? _A._--Beattie's screw is an arrangement of the screw propeller whereby it is projected beyond the rudder, and the main object of the arrangement is to take away the vibratory motion at the stern,--an intention which it accomplishes in practice. There is an oval eye in the rudder, to permit the screw shaft to pass through it. 600. _Q._--When the diameter of the cylinder of water projected backward by a screw, and the force urging it into motion are known, may not the velocity it will acquire be approximately determined? _A._--That will not be very difficult; and I will take for illustration the case of the Minx, already referred to, which will show how such a computation is to be conducted. The speed of this vessel, in one of the experiments made with her, was 8.445 knots; the number of revolutions of the screw per minute, 231.32; and the pressure on each square foot of area of the screw's disc, 214 lbs. If a knot be taken to be 6075.6 feet, then the distance advanced by the vessel, when the speed is 8.445 knots, will be 3.7 feet per revolution, and this advance will be made in about .26 of a second of time. Now the distance which a body will fall by gravity, in .26 of a second, is 1.087 feet; and a weight of 214 lbs. put into motion by gravity, or by a pressure of 214 lbs., would, therefore, acquire a velocity of 1.087 feet during the time one revolution of the screw is being performed. The weight to be moved, however, is 3.7 cubic feet of water, that being the new water seized by the screw each revolution for every square foot of surface in the screw's disc; and 3.7 cubic feet of water weigh 231.5 lbs., so that the urging force of 214 lbs. is somewhat less than the force of gravity, and the velocity of motion communicated to the water will be somewhat under 1.087 feet per revolution, or we may say it will be in round numbers 1 foot per revolution. This, added to the progress of the vessel, will make the distance advanced by the screw through the water 4.7 feet per revolution, leaving the difference between this and the pitch, namely 1.13 feet, to be accounted for on the supposition that the screw blades had broken laterally through the water to that extent. It would be proper to apply some correction to this computation, which would represent the increased resistance due to the immersion of the screw in the water; for a column of water cannot be moved in the direction of its axis beneath the surface, without giving motion to the superincumbent water, and the inertia of this superincumbent water must, therefore, be taken into the account. In the experiment upon the Minx, the depth of this superincumbent column was but small. The total amount of the slip was 36.53 per cent.; and there will not be much error in setting down about one half of this as due to the recession of the water in the direction of the vessel's track, and the other half as due to the lateral penetration of the screw blades. 601. _Q._--Is it not important to make the stern of screw vessels very fine, with the view of diminishing the slip, and increasing the speed? _A._--It is most important. The Rifleman, a vessel of 486 tons, had originally engines of 200 horses power, which propelled her at a speed of 8 knots an hour. The Teazer, a vessel of 296 tons, had originally engines of 100 horses power, which propelled her at a speed of 6-1/2 knots an hour. The engines of the Teazer were subsequently transferred to the Rifleman, and new engines of 40 horse power were put into the Teazer. Both vessels were simultaneously sharpened at the stern, and the result was, that the 100 horse engines drove the Rifleman, when sharpened, as fast as she had previously been driven by the 200 horse engines; and the 40 horse engines drove the Teazer, when sharpened, a knot an hour faster than she had previously been driven by the 100 horse engines. The immersion of both vessels was kept unchanged in each case; and the 100 horse engines of the Teazer, when transferred to the Rifleman, drove that vessel, after she had been sharpened, 2 knots an hour faster than they had previously driven a vessel not much more than half the size. These are important facts for every one to be acquainted with who is interested in the success of screw vessels, and who seeks to obtain the maximum of efficiency with the minimum of expense.[1] [1] See Treatise on the Screw Propeller, by John Bourne, C. E. PROPORTIONS OF SCREWS. 602. _Q._--In fixing upon the proportions of a screw proper to propel any given vessel, how would you proceed? _A._--I would first compute the probable resistance of the vessel, and I would be able to find the relative resistances of the screw and hull, and in every case it is advisable to make the screw as large in diameter as possible. The larger the screw is, the greater will be the efficiency of the engine in propelling the vessel; the larger will be the ratio of the pitch to the diameter, which produces a maximum effect; and the smaller will be the length of the screw or the fraction of a convolution to produce a maximum effect. 603. _Q._--Will you illustrate this doctrine by a practical example? _A._--The French screw steamer Pelican was fitted successively with two screws of four blades, but the diameter of the first screw was 98.42 inches, and the diameter of the second 54 inches. If the efficiency of the first screw by represented by 1, that of the second screw will be represented by .823, or, in other words, if the first screw would give a speed of 10 knots, the second would give little more than 8. The most advantageous ratio of pitch to diameter was found to be 2.2 in the case of the large screw, and 1.384 in the case of the small. The fraction of a convolution which was found to be most advantageous was .281 in the case of the large screw, and .450 in the case of the small screw. 604. _Q_--Were screws of four blades found to be more efficient than screws with two? _A_--They were found to have less slip, but not to be more efficient, the increased slip in those of two blades being balanced by the increased friction in those of four. Screws of two blades, to secure a maximum efficiency, must have a finer pitch than screws of four. 605. _Q._--Are the proportions found to be most suitable in the case of the Pelican applicable to the screws of other vessels? _A._--Only to those which have the same relative resistance of screw and hull. Taking the relative resistance to be the area of immersed midship section, divided by the square of the screw's diameter, it will in the case of the Rattler be 380/100 or 3.8. From the experiments made by MM. Bourgois and Moll on the screw steamer Pelican, they have deduced the proportions of screws proper for all other classes of vessels, whether the screws are of two, four, or six blades. 606. _Q._--Will you specify the nature of their deductions? _A._--I will first enumerate those which bear upon screws with two blades. When the relative resistance is 5.5 the ratio of pitch to diameter should be 1.006, and the fraction of the pitch or proportion of one entire convolution should be 0.454. When the relative resistance is 5, the ratio of pitch to diameter should be 1.069, and fraction of pitch 0.428; relative resistance 4.5, pitch 1.135, fraction 0.402; relative resistance 4, pitch 1.205, fraction 0.378; relative resistance 3.5, pitch 1.279, fraction 0.355; relative resistance 3, pitch 1.357, fraction 0.334; relative resistance 2.5, pitch 1.450, fraction 0.313; relative resistance 2, pitch 1.560, fraction 0.294; relative resistance 1.5, pitch 1.682, fraction 0.275. The relative resistance of 4 is that which is usual in an auxiliary line of battle ship, 3.5 in an auxiliary frigate, 3 in a high speed line of battle ship, 2.5 in a high speed frigate, 2 in a high speed corvette, and 1.5 in a high speed despatch boat. 607. _Q._--What are the corresponding proportions of screws of four blades? _A._--The ratios of the pitches to the diameter being for each of the relative resistances enumerated above, 1.342, 1.425, 1.513, 1.607, 1.705, 1.810, 1.933, 2.080, and 2.243, the respective fractions of pitch or fractions of a whole convolution will be 0.455, 0.428, 0.402, 0.378, 0.355, 0.334, 0.313, 0.294, and 0.275. 608. _Q._--And what are the corresponding proportions proper for screws of six blades? _A._--Beginning with the relative resistance of 5.5 as before, the proper ratio of pitch to diameter for that and each of the successive resistances in the case of screws with six blades, will be 1.677, 1.771, 1.891, 1.2009, 2.131, 2.262, 2.416, 2.600, 2.804; and the respective fractions of pitch will be 0.794, 0.749, 0.703, 0.661, 0.621, 0.585, 0.548, 0.515, and 0.481. These are the proportions which will give a maximum performance in every case.[1] [1] In my Treatise on the Screw Propeller I have gone into these various questions more fully than would consort with the limits of this publication. SCREW VESSELS WITH FULL AND AUXILIARY POWER. 609. _Q._--Do you consider that the screw propeller is best adapted for vessels of full power, or for vessels with auxiliary power? _A._--It is, in my opinion, best adapted for vessels with auxiliary power, and it is a worse propeller than paddle wheels for vessels which have habitually to encounter strong head winds. Screw vessels are but ill calculated--at least as constructed heretofore--to encounter head winds, and the legitimate sphere of the screw is in propelling vessels with auxiliary power. 610. _Q._--Does the screw act well in conjunction with sails? _A._--I cannot say it acts better than paddles, except in so far as it is less in the way and is less affected by the listing or heeling over of the ship. A small steam power, however, acts very advantageously in aid of sails, for not only does the operation of the sails in reducing the resistance of the hull virtually increase the screw's diameter, but the screw, by reducing the resistance which has to be overcome by the sails and by increasing the speed of the vessel, enables the sails to act with greater efficiency, as the wind will not rebound from them with as great a velocity as it would otherwise do, and a larger proportion of the power of the wind will also be used up. In the case of beam winds, moreover, the action of the screw, by the larger advance it gives to the vessel will enable the sails to intercept a larger column of wind in a given time. It appears, therefore, that the sails add to the efficiency of the screw, and that the screw also adds to the efficiency of the sails. 611. _Q._--What is the comparative cost of transporting merchandise in paddle steamers of full power, in screw steamers of auxiliary power, and in sailing ships? _A._--That will depend very much upon the locality where the comparison is made. In the case of vessels performing distant ocean voyages, in which they may reckon upon the aid of uniform and constant winds, such as the trade winds or the monsoon, sailing ships of large size will be able to carry more cheaply than any other species of vessel. But where the winds are irregular and there is not much sea room, or for such circumstances as exist in the Channel or Mediterranean trades, screw vessels with auxiliary power will constitute the cheapest instrument of conveyance. 612. _Q._--Are there any facts recorded illustrative of the accuracy of this conclusion? _A._--A full paddle vessel of 1000 tons burden and 350 horses power, will carry about 400 tons of cargo, besides coal for a voyage of 500 miles, and the expense of such a voyage, including wear and tear, depreciation, &c., will be about 190_l_. The duration of the voyage will be about 45-1/2 hours. A screw vessel of 400 tons burden and 100 horses power, will carry the same amount of cargo, besides her coals, on the same voyage, and the expense of the voyage, including wear and tear, depreciation, &c., will be not much more than 60_l_. An auxiliary screw vessel, therefore, can carry merchandise at one third of the cost of a full-powered paddle vessel. By similar comparisons made between the expense of conveying merchandise in auxiliary screw steamers and sailing ships on coasting voyages, it appears that the cost in screw steamers is about one third less than in the sailing ships; the greater expedition of the screw steamers much more than compensating for the expense which the maintenance of the machinery involves. SCREW AND PADDLES COMBINED. 613. _Q._--Would not a screw combined with paddles act in a similarly advantageous way as a screw or paddles when aided by the wind? _A._--If in any given paddle vessel a supplementary screw be added to increase her power and speed, the screw will act in a more beneficial manner than if it had the whole vessel to propel itself, and for a like reason the paddles will act in a more beneficial manner. There will be less slip both upon the paddles and upon the screw than if either had been employed alone; but the same object would be attained by giving the vessel larger paddles or a larger screw. 614. _Q._--Have any vessels been constructed with combined screw and paddles? _A._--Not any that I know of, except the great vessel built under the direction of Mr. Brunel. The Bee many years since was fitted with both screw and paddles, but this was for the purpose of ascertaining the relative efficiency of the two modes of propulsion, and not for the purpose of using both together. 615. _Q._--What would be the best means of accelerating the speed of a paddle vessel by the introduction of a supplementary screw? _A._--If the vessel requires new boilers, the best course of procedure would be to work a single engine giving motion to the screw with high pressure steam, and to let the waste steam from the high pressure engine work the paddle engines. In this way the power might be doubled without any increased expenditure of fuel per hour, and there would be a diminished expenditure per voyage in the proportion of the increased speed. 616. _Q._--What would the increased speed be by doubling the power? _A._--The increase would be in the proportion of the cube root of 1 to the cube root of 2, or it would be 1.25 times greater. If, therefore, the existing speed were 10 miles, it would be increased to 12-1/2 miles by doubling the power, and the vessel would ply with about a fourth less coals by increasing the power in the manner suggested. 617. _Q._--Is not high pressure steam dangerous in steam vessels? _A._--Not necessarily so, and it has now been introduced into a good number of steam vessels with satisfactory results. In the case of locomotive engines, where it is used so widely, very few accidents have occurred; and in steam vessels the only additional source of danger is the salting of the boiler. This may be prevented either by the use of fresh water in the boiler, or by practising a larger amount of blowing off, to insure which it should be impossible to diminish the amount of water sent into the boiler by the feed pump, and the excess should be discharged overboard through a valve near the water level of the boiler, which valve is governed by a float that will rise or fall with the fluctuating level of the water. If the float be a copper ball, a little water should be introduced into it before it is soldered or brazed up, which will insure an equality of pressure within and without the ball, and a leakage of water into it will then be less likely to take place. A stone float, however, is cheaper, and if properly balanced will be equally effective. All steam vessels should have a large excess of boiling feed water constantly flowing into the boiler, and a large quantity of water constantly blowing off through the surface valves, which being governed by floats will open and let the superfluous water escape whenever the water level rises too high. In this way the boiler will be kept from salting, and priming will be much less likely to occur. The great problem of steam navigation is the economy of fuel, since the quantity of fuel consumed by a vessel will very much determine whether she is profitable or otherwise. Notwithstanding the momentous nature of this condition, however, the consumption of fuel in steam vessels is a point to which very little attention has been paid, and no efficient means have yet been adopted in steam vessels to insure that measure of economy which is known to be attainable, and which has been attained already in other departments of engineering in which the benefits of such economy are of less weighty import. It needs nothing more than the establishment of an efficient system of registration in steam vessels, to insure a large and rapid economy in the consumption of fuel, as this quality would then become the test of an engineer's proficiency, and would determine the measure of his fame. In the case of the Cornish engines, a saving of more than half the fuel was speedily effected by the introduction of the simple expedient of registration. In agricultural engines a like economy has speedily followed from a like arrangement; yet in both of these cases the benefits of a large saving are less eminent than they would be in the case of steam navigation; and it is to be hoped that this expedient of improvement will now be speedily adopted. CHAPTER X. EXAMPLES OF ENGINES. * * * * * OSCILLATING PADDLE ENGINES. 618. _Q._--Will you describe the structure of an oscillating engine as made by Messrs. Penn? _A._--To do this it will be expedient to take an engine of a given power, and then the sizes may be given as well as an account of the configuration of the parts: we may take for an example a pair of engines of 21-1/2 inches diameter of cylinder, and 22 inches stroke, rated by Messrs. Penn at 12 horses power each. The cylinders of this oscillating engine are placed beneath the cranks, and, as in all Messrs. Penn's smaller engines, the piston rod is connected to the crank pin by means of a brass cap, provided with a socket, by means of which it is cuttered to the piston rod. There is but one air pump, which is situated within the condenser between the cylinders, and it is wrought by means of a crank in the intermediate shaft--this crank being cut out of a solid piece of metal as in the formation of the cranked axles of locomotive engines. The steam enters the cylinder through the outer trunnions, or the trunnions adjacent to the ship's sides, and enters the condenser through the two midship trunnions--a short three ported valve being placed on the front of the cylinder to regulate the flow of steam to and from the cylinder in the proper manner. The weight of this valve on one side of the cylinder is balanced by a weight hung upon the other side of the cylinder; but in the most recent engines this weight is discarded, and two valves are used, which balance one another. The framing consists of an upper and lower frame of cast iron, bound together by eight malleable iron columns: upon the lower frame the pillow blocks rest which carry the cylinder trunnions, and the condenser and the bottom frame are cast in the same piece. The upper frame supports the paddle shaft pillow blocks; and pieces are bolted on in continuation of the upper frame to carry the paddle wheels, which are overhung from the journal. 619. _Q._--What are the dimensions and arrangement of the framing? _A._--The web, or base plate of the lower frame is 3/4 of an Inch thick, and a cooming is earned all round the cylinder, leaving an opening of sufficient size to permit the necessary oscillation. The cross section of the upper frame is that of a hollow beam 6 inches deep, and about 3-1/2 inches wide, with holes at the sides to take out the core; and the thickness of the metal is 13/16ths of an inch. Both the upper and the lower frame is cast in a single piece, with the exception of the continuations of the upper frame, which support the paddle wheels. An oval ring 3 inches wide is formed in the upper frame, of sufficient size to permit the working of the air pump crank; and from this ring feathers run to the ends of the cross portions of the frame which supports the intermediate shaft journals. The columns are 1-1/2 inches in diameter; they are provided with collars at the lower ends, which rest upon bosses in the lower frame, and with collars at the upper ends for supporting the upper frame; but the upper collars of two of the corner columns are screwed on, so as to enable the columns to be drawn up when it is required to get the cylinders out. The cross section of the bottom frame is also of the form of a hollow beam, 7 inches deep, except in the region of the condenser, where it is, of course, of a different form. The depth of the boss for the reception of the columns is a little more than 7 inches deep on the lower frame, and a little more than 6 inches deep on the upper frame; and the holes through them are so cored out, that the columns only bear at the upper and lower edges of the hole, instead of all through it--a formation by which the fitting of the columns is facilitated. 620. _Q._--What are the dimensions of the condenser? _A._--The condenser, which is cast upon the lower frame, consists of an oval vessel 22-1/2 inches wide, by 2 feet 4-1/4 inches long, and 1 foot 10-1/2 inches deep; it stands 9 inches above the upper face of the bottom frame, the rest projecting beneath it; and it is enlarged at the sides by being carried beneath the trunnions. 621. _Q._--What are the dimensions of the air pump? _A._--The air pump, which is set in the centre of the condenser, is 15-1/4 inches in diameter, and has a stroke of 11 inches. The foot valve is situated in the bottom of the air pump, and its seat consists of a disc of brass, in which there is a rectangular flap valve, opening upwards, but rounded on one side to the circle of the pump, and so balanced as to enable the valve to open with facility. The balance weight, which is formed of brass cast in the same piece as the valve itself, operates as a stop, by coming into contact with the disc which constitutes the bottom of the pump; the disc being recessed opposite to the stop to enable the valve to open sufficiently. This disc is bolted to the barrel of the pump by means of an internal flange, and before it can be removed the pump must be lifted out of its place. The air pump barrel is of brass to which is bolted a cast iron mouth piece, with a port for carrying the water to the hot well; within the hot well the delivery valve, which consists of a common flap valve, is situated. The mouth piece and the air pump barrel are made tight to the condenser, and to one another, by means of metallic joints carefully scraped to a true surface, so that a little white or red lead interposed makes an air tight joint. The air pump bucket is of brass, and the valve of the bucket is of the common pot lid or spindle kind. The injection water enters through a single cock in front of the condenser--the jet striking against the barrel of the air pump. The air pump rod is maintained in its vertical position by means of guides, the lower ends of which are bolted to the mouth of the pump, and the upper to the oval in the top frame, within which the air pump crank works; and the motion is communicated from this crank to the pump rod by means of a short connected rod. The lower frame is not set immediately below the top frame, but 2-1/2 inches behind it, and the air pump and condenser are 2-1/2 inches nearer one edge of the lower frame than the other. 622. _Q._--What are the dimensions of the cylinder? _A._--The thickness of the metal of the cylinder is 9/16ths of an inch; the depth of the belt of the cylinder is 9-1/2 inches, and its greatest projection from the cylinder is 2-1/2 inches. The distance from the lower edge of the belt to the bottom of the cylinder is 11-1/2 inches, and from the upper edge of the belt to the top flange of the cylinder is 9 inches. The trunnions are 7-1/4 inches diameter in the bearings, and 3-1/2 inches in width; and the flanges to which the glands are attached for screwing in the trunnion packings are 1-1/2 inch thick, and have 7/8ths of an inch of projection. The width of the packing space round the trunnions is 5/8ths of an inch, and the diameter of the pipe passing through the trunnion 4-5/8ths, which leaves 11/16ths for the thickness of the metal of the bearing. Above and below each trunnion a feather runs from the edge of the belt or bracket between 3 and 4 inches along the cylinder, for the sake of additional support; and in large engines the feather is continued through the interior of the belt, and cruciform feathers are added for the sake of greater stiffness. The projection of the outer face of the trunnion flange from the side of the cylinder is 6-1/2 inches; the thickness of the flange round the mouth of the cylinder is 3/4 of an inch, and its projection 1-3/8 inch; the height of the cylinder stuffing box above the cylinder cover is 4-1/8 inches, and its external diameter 4-3/8 inches--the diameter of the piston rod being 2-1/8 inches. The thickness of the stuffing box flange is 1-1/8 inch. 623. _Q._--Will you describe the nature of the communication between the cylinder and condenser? _A._--The pipe leading to the condenser from the cylinder is made somewhat bell mouthed where it joins the condenser, and the gland for compressing the packing is made of a larger internal diameter in every part except at the point at which the pipe emerges from it, where it accurately fits the pipe so as to enable the gland to squeeze the packing. By this construction the gland may be drawn back without being jammed upon the enlarged part of the pipe; and the enlargement of the pipe toward the condenser prevents the air pump barrel from offering any impediment to the free egress of the steam. The gland is made altogether in four pieces: the ring which presses the packing is made distinct from the flange to which the bolts are attached which force the gland against the packing, and both ring and flange are made in two pieces, to enable them to be got over the pipe. The ring is half checked in the direction of its depth, and is introduced without any other support to keep the halves together, than what is afforded by the interior of the stuffing box; and the flange is half checked in the direction of its thickness, so that the bolts which press down the ring by passing through this half-checked part, also keep the segments of the flange together. The bottom of the trunnion packing space is contracted to the diameter of the eduction pipe, so as to prevent the packing from being squeezed into the jacket; but the eduction pipe does not fit quite tight into this contracted part, but, while in close contact on the lower side, has about 1/32nd of an inch of space between the top of the pipe and the cylinder, so as to permit the trunnions to wear to that extent without throwing a strain upon the pipe. The eduction pipe is attached to the condenser by a flange joint, and the bolt holes are all made somewhat oblong in the perpendicular direction, so as to permit the pipe to be slightly lowered, should such an operation be rendered necessary by the wear of the trunnion bearings; but in practice the wear of the trunnion bearings is found to be so small as to be almost inappreciable. 624. _Q._--Will you describe the valve and valve casing? _A._--The length of the valve casing is 16-1/2 inches, and its projection from the cylinder is 3-1/2 inches at the top, 4-1/4 inches at the centre, and 2-1/2 inches at the bottom, so that the back of the valve casing is not made flat, but is formed in a curve. The width of the valve casing is 9 inches, but there is a portion of the depth of the belt 1-1/2 inch wider, to permit the steam to enter from the belt into the casing. The valve casing is attached to the cylinder by a metallic joint; the width of the flange of this joint is 1-1/4 inch, the thickness of the flange on the casing 1/2 inch, and the thickness of the flange on the cylinder 5/8ths of an inch. The projection from the cylinder of the passage for carrying the steam upwards, and downwards, from the valve to the top and bottom of the cylinder, is 2-1/4 inches, and its width externally 8-5/8 inches. The valve is of the ordinary three ported description, and both cylinder and valve faces are of cast iron. 625. _Q._--What description of piston is used? _A._--The piston is packed with hemp, but the junk ring is made of malleable iron, as cast iron junk rings have been found liable to break: there are four plugs screwed into the cylinder cover, which, when removed, permit a box key to be introduced, to screw down the piston packing. The screws in the junk ring are each provided with a small ratchet, cut in a washer fixed upon the head, to prevent the screw from turning back; and the number of clicks given by these ratchets, in tightening up the bolts, enables the engineer to know when they have all been tightened equally. In more recent engines, and especially in those of large size, Messrs. Penn employ for the piston packing a single metallic ring with tongue piece and indented plate behind the joint; and this ring is packed behind with hemp squeezed by the junk ring as in ordinary hemp-packed pistons. 626. _Q._--Will you describe the construction of the cap for connecting the piston rod with the crank pin? _A._--The cap for attaching the piston rod to the crank pin, is formed altogether of brass, which brass serves to form the bearing of the crank pin. The external diameter of the socket by which this cap is attached to the piston rod is 3-5/16 inches. The diameter of the crank pin is 3 inches, and the length of the crank pin bearing 3-7/8 inches. The thickness of the brass around the crank pin bearing is 1 inch, and the upper portion of the brass is secured to the lower portion, by means of lugs, which are of such a depth that the perpendicular section through the centre of the bearing has a square outline measuring 7 inches in the horizontal direction, 3-7/8 inches from the centre of the pin to the level of the top of the lugs, and 2-1/2 inches from the centre of the pin to the level of the bottom of the lugs. The width of the lugs is 2 inches, and the bolts passing through them are 1-1/4 inch in diameter. The bolts are tapped into the lower portion of the cap, and are fitted very accurately by scraping where they pass through the upper portion, so as to act as steady pins in preventing the cover of the crank pin bearing from being worked sideways by the alternate thrust on each side. The distance between the centres of the bolts is 5 inches, and in the centre of the cover, where the lugs, continued in the form of a web, meet one another, an oil cup 1-5/8 inch in diameter, 1-1/8 inch high, and provided with an internal pipe, is cast upon the cover, to contain oil for the lubrication of the crank pin bearing. The depth of the cutter for attaching the cap to the piston rod is 1-1/4 inch and its thickness is 3/8ths of an inch. 627. _Q._--Will you describe the means by which the air pump rod is connected with the crank which works the air pump? [Illustration: Fig. 50. AIR PUMP CONNECTING ROD AND CROSS HEAD. Messrs. Penn.] _A._--A similar cap to that of the piston rod attaches the air pump crank to the connecting rod by which the air pump rod is moved, but in this instance the diameter of the bearing is 5 inches, and the length of the bearing is about 3 inches. The air pump connecting rod and cross head are shown in perspective in fig. 50. The thickness of the brass encircling the bearing of the shaft is three fourths of an inch upon the edge, and 1-1/8 inch in the centre, the back being slightly rounded; the width of the lugs is 1-5/8 inch, and the depth of the lugs is 2 inches upon the upper brass, and 2 inches upon the lower brass, making a total depth of 4 inches. The diameter of the bolts passing through the lugs is 1 inch, and the bolts are tapped into the lower brass, and accurately fitted into the upper one, so as to act as steady pins, as in the previous instance. The lower eye of the connecting rod is forked, so as to admit the eye of the air pump rod; and the pin which connects the two together is prolonged into a cross head, as shown in fig. 50. The ends of this cross head move in guides. The forked end of the connecting rod is fixed upon the cross head by means of a feather, so that the cross head partakes of the motion of the connecting rod, and a cap, similar to that attached to the piston rod, is attached to the air pump rod, for connecting it with the cross head. The diameter of the air pump rod is 1-1/2 inch, the external diameter of the socket encircling the rod is 2-1/8 inches, and the depth of the socket 4-1/2 inches from the centre of the cross head. The depth of the cutter for attaching the socket to the rod is 1 inch, and its thickness 5/16 inch. The breadth of the lugs is 1-3/8 inch, the depth 1-1/4 inch, making a total depth of 2-1/2 inches; and the diameter of the bolts seven eighths of an inch. The diameter of the cross head at the centre is 2 inches, the thickness of each jaw around the bearing 1 inch, and the breadth of each 9/16 inch. 628. _Q._--What are the dimensions of the crank shaft and cranks? _A._--The diameter of the intermediate shaft journal is 4-3/16 inches, and of the paddle shaft journal 4-3/8 inches; the length of the journal in each case is 5 inches. The diameter of the large eye of the crank is 7 inches, and the diameter of the hole through it is 4-3/8 inches; the diameter of the small eye of the crank is 5-1/4 inches, the diameter of the hole through it being 3 inches. The depth of the large eye is 4-1/4 inches, and of the small eye 3-3/4 inches; the breadth of the web is 4 inches at the shaft end, and 3 inches at the pin end, and the thickness of the web is 2-5/8 inches. The width of the notch forming the crank in the intermediate shaft for working the air pump is 3-1/2 inches, and the width of each of the arms of this crank is 3-15/16 inches. Both the outer and inner corners of the crank are chamfered away, until the square part of the crank meets the round of the shaft. The method of securing the cranks pins into the crank eyes of the intermediate shaft consists in the application of a nut to the end of each pin, where it passes through the eye, the projecting end of the pin being formed with a thread upon which the nut is screwed. 629. _Q._--Will you describe the eccentric and eccentric rod? [Illustration: Fig. 51. ECCENTRIC AND ROD. Messrs. Penn.] _A._--The eccentric and eccentric rod are shown in fig. 51. The eccentric is put on the crank shaft in two halves, joined in the diameter of largest eccentricity by means of a single bolt passing through lugs on the central eye, and the back balance is made in a separate piece five eighths of an inch thick, and is attached by means of two bolts, which also help to bind the halves of the eccentric together. The eccentric strap is half an inch thick, and 1-1/4 inch broad, and the flanges of the eccentric, within which the strap works, are each three eighths of an inch thick. The eccentric rod is attached to the eccentric hoop by means of two bolts passing through lugs upon the rod, and tapped into a square boss upon the hoop; and pieces of iron, of a greater or less thickness, are interposed between the surfaces in setting the valve, to make the eccentric rod of the right length. The eccentric rod is kept in gear by the push of a small horizontal rod, attached to a vertical blade spring, and it is thrown out of gear by means of the ordinary disengaging apparatus, which acts in opposition to the spring, as, in cases where the eccentric rod is not vertical, it acts in opposition to the gravity of the rod. 630. _Q._--Will you explain in detail the construction of the valve gearing, or such parts of it as are peculiar to the oscillating engine? _A._--The eccentric rod is attached by a pin, 1 inch in diameter, to an open curved link or sector with a tail projecting upward and passing through an eye to guide the link in a vertical motion. The link is formed of iron case-hardened, and is 2-3/4 inches deep at the middle, and 2-3/8 inches deep at the ends, and 1 inch broad. The opening in the link, which extends nearly its entire length, is 1-5/16 inch broad; and into this opening a brass block 2 inches long is truly fitted, there being a hole through the block 3/4 inch diameter, for the reception of the pin of the valve shaft lever. The valve shaft is 1-3/4 inch diameter at the end next the link or segment, and diminishes regularly to the other end, but its cross section assumes the form of an octagon in its passage round the cylinder, measuring mid-way 1-1/4 inch deep, by about 3/4 inch thick, and the greatest depth of the finger for moving the valve is about 1 inch. The depth of the lever for moving the valve shaft is 2 inches at the broad, and 1-1/4 inch at the narrow end. The internal breadth of the mortice in which the valve finger moves is 5/16 inch, and its external depth is 1-3/4 inch, which leaves three eighths of an inch as the thickness of metal round the hole; and the breadth, measuring in the direction of the hole, is 1-1/2 inch. The valve rod is three fourths of an inch in diameter, and the mortice is connected to the valve rod by a socket 1 inch long, and 1-1/8 inch diameter, through which a small cutter passes. A continuation of the rod, eleven sixteenths of an inch diameter, passes upward from the mortice, and works through an eye, which serves the purpose of a guide. In addition to the guide afforded to the segment by the ascending tail, it is guided at the ends upon the columns of the framing by means of thin semicircular brasses, 4 inches deep, passing round the columns, and attached to the segment by two 3/8 inch bolts at each end, passing through projecting feathers upon the brasses and segment, three eighths of an inch in thickness. The curvature of the segment is such as to correspond with the arc swept from the centre of the trunnion to the centre of the valve lever pin when the valve is at half stroke as a radius; and the operation of the segment is to prevent the valve from being affected by the oscillation of the cylinder, but the same action, would be obtained by the employment of a smaller eccentric with more lead. In some engines the segment is not formed in a single piece, but of two curved blades, with blocks interposed at the ends, which may be filed down a little, to enable the sides of the slot to be brought nearer, as the metal wears away. 631. _Q._--What kind of plummer blocks are used for the paddle shaft bearings? _A._--The paddle shaft plummer blocks are altogether of brass, and are formed in much the same manner as the cap of the piston rod, only that the sole is flat, as in ordinary plummer blocks, and is fitted between projecting lugs of the framing, to prevent side motion. In the bearings fitted on this plan, however, the upper brass will generally acquire a good deal of play after some amount of wear. The bolts are worked slack in the holes, though accurately fitted at first; and it appears expedient, therefore, either to make the bolts very large, and the sockets through which they pass very deep, or to let one brass fit into the other. 632. _Q._--How are the trunnion plummer blocks made? _A._--The trunnion plummer blocks are formed in the same manner as the crank shaft plummer blocks; the nuts are kept from turning back by means of a pinching screw passing through a stationary washer. It is not expedient to cast the trunnion plummer blocks upon the lower frame, as is sometimes done; for the cylinders, being pressed from the steam trunnions by the steam, and drawn in the direction of the condenser by the vacuum, have a continual tendency to approach one another; and as they wear slightly toward midships, there would be no power of readjustment unless the plummer blocks were movable. The flanges of the trunnions should always fit tight against the plummer block sides, but there should be a little play sideways at the necks of the trunnions, so that the cylinder may be enabled to expand when heated, without throwing an undue strain upon the trunnion supports. 633. _Q._--What kind of paddle wheel is supplied with these oscillating engines? _A._--The wheels are of the feathering kind, 9 feet 8 inches in diameter, measuring to the edges of the floats; and there are 10 floats upon each wheel, measuring 4 feet 6 inches long each, and 18-1/2 inches broad. There are two sets of arms to the wheel, which converge to a cast iron centre, formed like a short pipe with large flanges, to which the arms are affixed. The diameter of the shaft, where the centre is put on, is 4-1/2 inches, the external diameter of the pipe is 8 inches, and the diameter of the flanges is 20 inches, and their thickness 1-1/4 inch. The flanges are 12 inches asunder at the outer edge, and they partake of the converging direction of the arms. The arms are 2-1/4 inches broad and half an inch thick; the heads are made conical, and each is secured into a recess upon the side of the flange by means of three bolts. The ring which connects together the arms, runs round at a distance of 3 feet 6 inches from the centre, and the projecting ends of the arms are bent backward the length of the lever which moves the floats, and are made very wide and strong at the point where they cross the ring, to which they are attached by four rivets. The feathering action of the floats is accomplished by means of a pin fixed to the interior of the paddle box, set 3 inches in advance of the centre of the shaft, and in the same horizontal line. This pin is encircled by a cast iron collar, to which rods are attached 1-3/8 inch diameter in the centre, proceeding to the levers, 7 inches long, fixed on the back of the floats in the line of the outer arms. One of these rods, however, is formed of nearly the same dimensions as one of the arms of the wheel, and is called the driving arm, as it causes the cast iron collar to turn round with the revolution of the wheel, and this collar, by means of its attachments to the floats, accomplishes the feathering action. The eccentricity in this wheel is not sufficient to keep the floats in the vertical position, but in the position between the vertical and the radial. The diameter of the pins upon which the floats turn is 1-3/8 inch, and between the pins and paddle ring two stud rods are set between each of the projecting ends of the arms, so as to prevent the two sets of arms from being forced nearer or further apart; and thus prevent the ends of the arms from hindering the action of the floats, by being accidentally jammed upon the sides of the joints. Stays, crossing one another, proceed from the inner flange of the centre to the outer ring of the wheel, and from the outer flange of the centre to the inner ring of the wheel, with the view of obtaining greater stiffness. The floats are formed of plate iron, and the whole of the joints and joint pins are steeled, or formed of steel. For sea-going vessels the most approved practice is to make the joint pins of brass, and also to bush the eyes of the joints with brass; and the surface should be large to diminish wear. 634. _Q._--Can you give the dimensions of any other oscillating engines? _A._--In Messrs. Penn's 50 horse power oscillating engine, the diameter of the cylinder is 3 feet 4 inches, and the length of the stroke 3 feet. The thickness of the metal of the cylinder is 1 inch, and the thickness of the cylinder bottom is 1-3/4 inch, crossed with feathers, to give it additional stiffness. The diameter of the trunnion bearings is 1 foot 2 inches, and the breadth of the trunnion bearings 5-1/2 inches. Messrs. Penn, in their larger engines, generally make the area of the steam trunnion less than that of the eduction trunnion, in the proportion of 32 to 37; and the diameter of the eduction trunnion is regulated by the internal diameter of the eduction pipe, which is about 1/5th of the diameter of the cylinder. But a somewhat larger proportion than this appears to be expedient: Messrs. Rennie make the area of their eduction pipes, in oscillating engines, 1/22d of the area of the cylinder. In the oscillating engines of the Oberon, by Messrs. Rennie, the cylinder is 61 inches diameter, and 1-1/2 inch thick above and below the belt, but in the wake of the belt it is 1-1/4 inch thick, which is also the thickness of metal of the belt itself. The internal depth of the belt is 2 feet 6 inches, and its internal breadth is 4 inches. The piston rod is 6-3/4 inches in diameter, and the total depth of the cylinder stuffing box is 2 feet 4 inches, of which 18 inches consists of a brass bush--this depth of bearing being employed to prevent the stuffing box or cylinder from wearing oval. 635. _Q._--Can you give any other examples? _A._--The diameter of cylinder of the oscillating engines of the steamers Pottinger, Ripon, and Indus, by Miller & Ravenhill, is 76 inches, and the length of the stroke 7 feet. The thickness of the metal of the cylinder is 1-11/16 inch; diameter of the piston rod 8-3/4 inches; total depth of cylinder stuffing box 3 feet; depth of bush in stuffing box 4 inches; the rest of the depth, with the exception of the space for packing, being occupied with a very deep gland, bushed with brass. The internal diameter of the steam pipe is 13 inches; diameter of steam trunnion journal 25 inches; diameter of eduction trunnion journal 25 inches; thickness of metal of trunnions 2-1/4 inches; length of trunnion bearings 11 inches; projection of cylinder jacket, 8 inches; depth of packing space in trunnions, 10 inches; width of packing space in trunnions, or space round the pipes, 1-1/2 inch; diameter of crank pin 10-1/4 inches; length of bearing of crank pin 15-1/2, inches. There are six boilers on the tubular plan in each of these vessels; the length of each boiler is 10 feet 6 inches, and the breadth 8 feet; and each boiler contains 62 tubes 3 inches in diameter, and 6 feet 6 inches long, and two furnaces 6 feet 4-1/2 inches long, and 3 feet 1-1/2 inch broad. 636. _Q._--Is it the invariable practice to make the piston rod cap of brass in the way you have described? _A._--In all oscillating engines of any considerable size, the cover of the connecting brass, which attaches the crank pin to the connecting rod, is formed of malleable iron; and the socket also, which is cuttered to the end of the piston rod, is of malleable iron, and is formed with a T head, through which bolts pass up through the brass, to keep the cover of the brass in its place. 637. _Q._--Is the piston of an oscillating engine made deeper than in common engines? _A._--It is expedient, in oscillating engines, to form the piston with a projecting rim round the edge above and below, and a corresponding recess in the cylinder cover and cylinder bottom, whereby the breadth of bearing of the solid part of the metal will be increased, and in many engines this is now done. 638. _Q._--Would any difficulty be experienced in keeping the trunnions tight in a high pressure oscillating engine? _A._--It is very doubtful whether the steam trunnions of a high pressure oscillating engine will continue long tight if the packing consists of hemp; and it appears preferable to introduce a brass ring, to embrace the pipe, cut spirally, with an overlap piece to cover the cut, and packed behind with hemp. 639. _Q._--How is the packing of the trunnions usually effected? _A._--The packing of the trunnions, after being plaited as hard as possible, and cut to the length to form one turn round the pipe, is dipped into boiling tallow, and is then compressed in a mould, consisting of two concentric cylinders, with a gland forced down into the annular space by three to six screws in the case of large diameters, and one central screw in the case of small diameters. Unless the trunnion packings be well compressed, they will be likely to leak air, and it is, therefore, necessary to pay particular attention to this condition. It is also very important that the trunnions be accurately fitted into their brasses by scraping, so that there may not be the smallest amount of play left upon them; for if any upward motion is permitted, it will be impossible to prevent the trunnion packings from leaking. DIRECT ACTING SCREW ENGINE. 640. _Q._--Will you describe the configuration and construction of a direct acting screw engine? _A._--I will take as an example of this species of engine, the engine constructed by Messrs. John Bourne & Co., for the screw steamer Alma, a vessel of 500 tons burden. This engine is a single steeple engine laid on its side, and in its general features it resembles the engines of the Amphion already described, only that there is one cylinder instead of two. The cylinder is of 42 inches diameter and 42 inches stroke, and the vessel has been propelled by this single engine at the rate of fourteen miles an hour. 641. _Q._--Is not a single engine liable to stick upon the centre so that it cannot be started or reversed with facility? _A._--A single engine is no doubt more liable to stick upon the centre than two engines, the cranks of which are set at right angles with one another; but numerous paddle vessels are plying successfully that are propelled by a single engine, and the screw offers still greater facility than paddles for such a mode of construction. In the screw engine referred to, as the cylinder is laid upon its side, there is no unbalanced weight to be lifted up every stroke, and the crank, whereby the screw shaft is turned round, consists of two discs with a heavy side intended to balance the momentum of the piston and its connections; but these counter-weights by their gravitation also prevent the connecting rod and crank from continuing in the same line when the engine is stopped, and in fact they place the crank in the most advantageous position for starting again when it has to be set on. 642. _Q._--Will you explain the general arrangement of the parts of this engine? _A._--The cylinder lies on its side near one side of the vessel, and from the end of the cylinder two piston rods extend to a cross head sliding athwartships, in guides, near the other side of the vessel. To this cross head the connecting rod is attached, and one end of it partakes of the motion of the cross head or piston, while the other end is free to follow the revolution of the crank on the screw shaft. 643. _Q._--What is the advantage of two discs entering into the composition of the crank instead of one? _A._--A double crank, such as two discs form with the crank pin, is a much steadier combination than would result if only one disc were employed with an over-hung pin. Then the friction on the neck of the shaft is made one half less by being divided between the two bearings, and the short prolongation of the shaft beyond the journal is convenient for the attachment of the eccentrics to work the valves. 644. _Q._--Will you enumerate some of the principal dimensions of this engine? _A._--The bottom frame, on which also the condenser is cast, forms the base of the engine: on one end of it the cylinder is set; on the other end are the guides for the cross head, and in the middle are the bearings for the crank shaft. The part where the cylinder stands is two feet high above the engine platform, and the elevation to the centre of the guides or the centre of the shaft is 10 inches higher than this. The metal both of the side frames and bottom flange is 1-1/4 inch thick. The cylinder has flanges cast on its sides, upon which it rests on the bottom frame, and it is sunk between the sides of the frame so as to bring the centre of the cylinder in the same plane as the centre of the screw shaft. The opening left at the guides for the reception of the guide blocks is 6 inches deep, and the breadth of the bearing surface is 11 inches. The cover of the guides is 8 inches deep at the middle, and about half the depth at the ends, and holes are cored through the central web for two oil cups on each guide. The brass for each of the crank shaft bearings is cut into four pieces so that it may be tightened in the up and down direction by the bolts, which secure the plummer block cap, and tightened in the athwartship direction, which is the direction of the strain, by screwing up a wedge-formed plate against the side of the brass, a parallel plate being applied to the other side of the brass, which may be withdrawn to get out the wedge piece when the shaft requires to be lifted out of its place. The air pump is bolted to one side of the bottom frame, and a passage is cast on it conducting from the condenser to the air pump. In this passage the inlet and outlet valves at each end of the air pump are situated, and appropriate doors are formed above them to make them easily accessible. The outlet passage leading from the air pump communicates with the waste water pipe, through which the water expelled by the air pump is discharged overboard. 645. _Q._--Is the cylinder of the usual strength and configuration? _A._--The cylinder is formed of cast iron in the usual way, and is 1-1/8 inch thick in the barrel. The ends are of the same thickness, but are each stiffened with six strong feathers. The piston is cast open. The bottom of it is 5/8ths of an inch thick, and it is stiffened by six feathers 3/4 of an inch thick; but the feather connecting the piston rod eyes is 1-1/4 inch thick, and the metal round the eyes is 2 inches thick. The piston is closed by a disc or cover 5/8ths of an inch thick, secured by 15 bolts, and this cover answers also the purpose of a junk ring. The piston packing consists of a single cast iron ring 3-1/2 inches broad, and 1/2 inch thick, packed behind with hemp. This ring is formed with a tongue piece, with an indented plate behind the cut; and the cut is oblique to prevent a ridge forming in the cylinder. The total thickness of the piston is 5-1/2 inches. The piston rods are formed with conical ends for fitting into the piston, but are coned the reverse way as in locomotives, and are secured in the piston by nuts on the ends of the rods, these nuts being provided with ratchets to prevent them from unscrewing accidentally. 646. _Q._--What species of slide valve is employed? _A._--The ordinary three ported valve, and it is set on the top of the cylinder. The cylinder ports are 4-1/2 inches broad by 24 inches long; and to relieve the valve from the great friction due to the pressure on so large a surface, a balance piston is placed over the back of the valve, to which it is connected by a strong link; and the upward pressure on this piston being nearly the same as the downward pressure on the valve, it follows that the friction is extinguished, and the valve can be moved with great case with one hand. The balance piston is 21 inches in diameter. In the original construction of this balance piston two faults were committed. The passage communicating between the condenser and the top of the balance piston was too small, and the pins at the ends of the link connecting the valve and balance piston were formed with an inadequate amount of bearing surface. It followed from this misproportion that the balance piston, being adjusted to take off nearly the whole of the pressure, lifted the valve off the face at the beginning of each stroke. For the escape of the steam into the eduction passage momentarily impaired the vacuum subsisting there, and owing to the smallness of the passage leading to the space above the balance piston, the vacuum subsisting in that space could not be impaired with equal rapidity. The balance piston, therefore, rose by the upward pressure upon it momentarily predominating over the downward pressure on the valve; but this fault was corrected by enlarging the communicating passage between the top of the balance piston and the eduction pipe. The smallness of the pins at the ends of the link connecting the valve and balance piston, caused the surfaces to cut into one another, and to wear very rapidly, and the pins and eyes in this situation should be large in diameter, and as long as they can be got, as they are not so easily lubricated as the other bearings about the engine, and are moreover kept at a high temperature by the steam. The balance piston is packed in the same way as the main piston of the engine. Its cylinder, which is only a few inches in length, is set on the top of the valve casing, and a trunk projects upwards from its centre to enable the connecting link to rise up in it to attain the necessary length. [Illustration: Fig 52. CONNECTING ROD. Messrs. Bourne & Co.] 647. _Q._--What is the diameter of the piston rods and connecting rod? _A._--The piston rods, which are two in number, are 3 inches diameter, and 12 feet 10 inches long over all. They were, however, found to be rather small, and have since been made half an inch thicker. The connecting rod consists of two rods, which are prolongations of the bolts that connect the sides of the brass bushes which encircle the crank pin and cross head. The connecting rod is shown in perspective in fig. 52. The rods composing it are each 2-3/4 inches in diameter. 648. _Q._--Will you describe the configuration of the cross head. _A._--The cross head, exhibited in fig. 53, is a round piece of iron like a short shaft, with two unequal arms keyed upon it, the longer of which _b_ works the air pump, and the shorter _c_ works the feed pump. The piston rods enter these arms at _a A._ The cross head is 8 inches diameter where it is embraced by the connecting rod at _e_, and 7 inches diameter where the air pump and feed pump arms are fixed on. The ends of the cross head _d d_, for a length of 12 inches, are reduced to 3 inches diameter where they fit into round holes in the centre of the guide blocks. Those blocks are of cast iron 6 inches deep, 11 inches wide, and 14 inches long, and they are formed with flanges 1 inch thick on the inner sides of the blocks. The projection of the air pump lever from the centre of the cross head is 1 foot 9 inches, and it is bent 5-3/4 inches to one side to enable it to engage the air pump rod. The eye of this arm is 6 inches broad and about 2 inches thick. At the part where one of the piston rods passes through it, the arm is 8 inches deep and 6 inches wide; but the width thereafter narrows to 3 inches, and finally to 2 inches; and the depth of the web of the arm reduces from 8 inches at the piston rod, to 4 inches at the eye, which receives the end of the air pump rod. The feed pump arm is only 3 inches thick, and has 9 inches of projection from the centre of the cross head; but the eye attached to it on the opposite side of the cross head for the reception of the other piston rod is of the same length as that part of the air pump arm which one of the piston rods passes through. The piston rods have strong nuts on each side of each of these arms to attach them to the arms, and also to enable the length of the piston rods to be suitably adjusted, to leave equal clearance between the piston and each end of the cylinder at the termination of the stroke. [Illustration: Fig. 53. CROSS HEAD AND PUMP ARMS. Messrs. Bourne & Co.] 649. _Q._--Will you recapitulate the main particulars of the air pump? _A._--The air pump is made of brass 12-1/2 inches diameter and 42 inches stroke, and the metal of the barrel is 9/16ths of an inch thick. The air pump bucket is a solid piston of brass, 6-1/2 inches deep at the edge, and 7 inches deep at the eye; and in the edge three grooves are turned to hold water which answers the purpose of packing. The inlet and outlet valves of the air pump consist of brass plates 1/2 inch with strong feathers across them, and in each plate there are six grated perforations covered by india rubber discs 7 inches in diameter. These six perforations afford collectively an area for the passage of the water equal to the area of the pump. The air pump rod is of brass, 2-1/2 inches diameter. 650. _Q._--What are the constructive peculiarities of the discs and crank pin? _A._--The discs, which are 64 inches diameter, are formed of cast iron, and are 2-1/2 inches thick in the body, and 5 inches broad at the rim. The crank shaft is 8-1/2 inches diameter, and the central boss of the disc which receives the shaft measures 10 inches through the eye, and the metal of the eye is 3 inches thick. In the part of the disc opposite to the crank pin, the web is thickened to 10 inches for nearly the whole semicircle, with the view of making that side of the disc heavier than the other side; and when the engine is stopped, the gravitation of this heavy side raises the crank pin to the highest point it can attain, whereby it is placed in mid stroke, and cannot rest with the piston rods and connecting rod in a horizontal line. The crank pin is 8-1/2 inches diameter, and the length of the bearing or rubbing part of it is 16 inches. It is secured at the ends to the discs by flanges 18 inches diameter, and 2 inches thick. These flanges are indented into thickened parts of the discs, and are each attached to its corresponding disc by six bolts 2 inches diameter, countersunk in the back of the disc, and tapped into the malleable iron flange. Besides this attachment, each end of the pin, reduced to 4-1/2 inches diameter, passes through a hole in its corresponding disc, and the ends of the pin are then riveted over. The crank pin is perforated through the centre by a small hole about 3/4 of an inch in diameter, and three perforations proceed from this central hole to the surface of the pin. Each crank shaft bearing is similarly perforated, and pipes are cast in the discs connecting these perforations together. The result of this arrangement is, that a large part of the oil or water fed into the bearings of the shaft is driven by the centrifugal action of the discs to the surface of the crank pin, and in this way the crank pin may be oiled or cooled with water in a very effectual manner. To intercept the water or oil which the discs thus drive out by their centrifugal action, a light paddle box or splash board of thin sheet brass is made to cover the upper part of each of the discs, and an oil cup with depending wick is supported by the tops of these paddle boxes, which wick is touched at each revolution of the crank by a bridge standing in the middle of an oil cup attached to the crank pin. The oil is wiped from the wick by the projecting bridge at each revolution, and subsides into the cup from whence it proceeds to lubricate the crank pin bearing. This is the expedient commonly employed to oil the crank pins of direct acting engines; but in the engine now described, there are over and above this expedient, the communicating passages from the shaft bearings to the surface of the pin, by which means any amount of cooling or lubrication can be administered to the crank pin bearing, without the necessity of stopping or slowing the engine. [Illustration: Fig. 54. DOUBLE DISC CRANK. Messrs. Bourne & Co.] 651. _Q._--What is the diameter of the screw shaft? _A._--The screw shaft is 7-1/2 inches diameter, but the bearings on each side of the disc are 8-1/2 inches diameter, and 16 inches long. Between the side of the disc and the side of the contiguous bearings there is a short neck extending 4-3/4 inches in the length of the shaft, and hollowed out somewhat to permit the passage of the piston rod; for one piston rod passes immediately above the shaft on the one side of the discs, and the other piston rod passes immediately below the shaft on the other side of the discs. A short piece of one piston rod is shown in fig. 54. [Illustration: Fig. 55. THRUST BEARING. Messers. Bourne & Co.] [Illustration: Fig. 56. COUPLING CRANKS. Messers. Bourne & Co.] 652. _Q._--How is the thrust of the screw shaft received? _A._--The thrust of the screw shaft is received upon 7 collars, each 1 inch thick, and with 1 inch of projection above the shaft. The plummer block for receiving the thrust of the shaft is shown in fig. 55, and the coupling to enable the screw propeller to be disconnected from the engine, so that it may revolve freely when the vessel is under sail, is shown in fig. 56. When it is required to disengage the propeller from the engine, the pins passing through the opposite eyes shown fig. 56, are withdrawn by means of screws provided for that purpose, and the propeller and the engine are thenceforth independent of one another. [Illustration: Fig. 57. LINK MOTION. Messrs. Bourne & Co.] 653. _Q._--Will you describe the arrangement of the valve gearing? _A._--The end of the screw shaft, after emerging from the bearing beside the disc, is reduced to a diameter of 4 inches, and is prolonged for 4-1/2 inches to give attachment to the cam or curved plate which gives motion to the expansion valve. This plate is 3-1/2 inches thick, and a stud 3-1/2 inches diameter is fixed in the plate at a distance of 5 inches from the centre of the shaft. To this stud an arm is attached which extends to a distance of 2 inches from the centre of the shaft in the opposite direction, and the end of this arm carries a pin of 2-1/2 inches diameter. From the pin most remote from the centre of the shaft, a rod 2-1/2 inches broad and 1 inch thick extends to the upper end of the link of the link motion; and from the pin least remote from the centre of the shaft, a similar rod extends to the lower end of the link of the link motion. This link, which is represented in fig. 57, is 2-1/4 inches broad, 1 inch thick, and is capable of being raised or lowered 25 inches in all. In the open part of the link is a brass block, which, by raising or lowering the link, takes either the position in which it is represented at the centre of the link, or a position at either end of it. Through the hole in the brass block a pin passes to attach the brass to the end of a lever fixed on the valve shaft; so that whatever motion is imparted to the brass block is communicated to the valve through the medium of this lever. If the brass block be set in the middle of the link, no motion is communicated to it, and the valve being consequently kept stationary and covering both ports, the engine stops. If the link be lowered until the brass block comes to the upper end of the link, the valve receives the motion of the eccentric for going ahead, and the engine moves ahead; whereas if the link be raised until the brass block comes to the lower end of the link, the valve receives the motion of the backing eccentric, and the engine moves astern. Instead of eccentrics, however, pins at the end of the shaft are employed in this engine, the arrangement partaking of the nature of a double crank; but the backing pin has less throw than the going ahead pin, whereby the efficient length of the link for going ahead is increased; and the operation of backing, which does not require to be performed at the highest rate of speed, is sufficiently accommodated by about half the throw being given to the valve that is given in going ahead. A valve shaft extends across the end of the cylinder with two levers standing up, which engage horizontal side rods extending from a small cross head on the end of the valve rod. A lever extends downwards from the end of the valve shaft, which is connected by a pin to the brass block within the link; and the link is moved up or down by the starting handle, which, by means of a spring bolt shooting into a quadrant, holds the starting handle at any position in which it may be set. 654. _Q._--What is the diameter and pitch of the screw propeller? _A._--The diameter is 7 feet and the pitch 14 feet. The propeller is Holm's conchoidal propeller. Its diameter is smaller than is advisable, being limited by the draught of water of the vessel; and the vessel was required to have a small draught of water to go over a bar. This engine makes, under favorable circumstances, 100 strokes per minute. The speed of piston with this number of strokes is 700 feet per minute, and the engine works steadily at this speed, the shock and tremor arising from the arrested momentum of the moving parts being taken away by the counterbalance applied at the discs. LOCOMOTIVE ENGINE. 655. _Q._--Will you describe the principal features of a modern locomotive engine? _A._--I will take for this purpose the locomotive Snake, constructed by John V. Gooch for the London and South Western Railway, as an example of a modern locomotive of good construction, adapted for the narrow gauge. The length of the wheel base of this engine is 12 feet 8-1/2 inches. There are two cylinders, each 14-1/4 inches diameter and 21 inches stroke. The total weight of the engine is 19 tons; and this weight is so distributed on the wheels as to throw 8 tons on the leading wheels, 6 tons on the driving wheels, and 5 tons on the hind wheels. The engine is made with outside cylinders, and the cylinders are raised somewhat out of the horizontal line to enable them better to clear the leading wheels. 656. _Q._--What are the dimensions of the boiler? _A._--The interior of the fire box is 3 feet 7-1/4 inches wide by 3 feet 5-1/2 inches long, measuring in the direction of the rails. The area of the fire grate is consequently 12.4 square feet. The bars are somewhat lower on the side next the fire door than at the side next the tubes, and the mean height of the crown of the fire box above the bars is 3 feet 10 inches. The top edge of the fire door is about 7 inches lower than the crown of the fire box. The fire box is divided transversely by a corrugated feather or bridge of plate iron, containing water, about 3-1/2 inches wide, and of about one-third of the height of the fire box in the centre of the feather, and about two-thirds the height of the fire box at the sides where it joins the sides of the fire box. The internal shell of the fire box tapers somewhat upwards to facilitate the disengagement of the steam. It is about 2 inches narrower and shorter at the top than at the bottom; the water space between the external and internal shell of the fire box being 2 inches at the bottom and 3 inches at the top. 657. _Q._--Of what material is the fire box composed? _A._--The external shell of the fire box is formed of iron plates 3/8ths of an inch thick, and the internal shell is formed of copper plates 1/4 inch thick, but the tube plate is 3/4 inch thick. The fire grate is rectangular, and the internal and external shells are tied together by iron stay bolts 3/4 inch diameter, and pitched about 4 inches apart. The roof of the fire box is stiffened by six strong bars extending from side to side of the fire box like beams, and the top of the fire box is secured to these bars, so that it cannot be forced down without breaking or bending them. 658. _Q._--What are the dimensions of the barrel of the boiler? _A._--The barrel of the boiler is 3 feet 7-1/2 inches in diameter, and 10 feet long. It is formed of iron plates 3/8ths of an inch thick, riveted together. It is furnished with 181 brass tubes 1-7/8 inch diameter and 10 feet long, secured at the ends by ferules. The tube plate at the smoke box end is 5/8ths of an inch thick, and the tube plates above the tubes are tied together by eight iron rods 7/8ths of an inch thick, extending from end to end of the boiler. The metal of the tubes is somewhat thicker at the end next the fire, being 13 wire gauge at fire box end, and 14 wire gauge at smoke box end. The rivets of the boiler are 3/4 inch diameter and 1-1/2 inch pitch. The plating of the ash pan is 5/16ths of an inch thick, and the plating of the smoke box is 3/16ths of an inch thick. 659. _Q._--Will you describe the structure of the framework on which the boiler and its attachments rest, and in which the wheels are set? _A._--The framework or framing consists of a rectangular structure of plate iron circumscribing the boiler, with projecting lugs or arms for the reception of the axles of the wheels. In this engine the sides of the rectangle are double, or, as far as regards the sides, there are virtually two framings, one for the reception of the driving axles, and the other for the reception of the axles not connected with the engine. The whole of the parts of the outer and inner framings are connected together by knees at the corners, and the double sides are elsewhere connected by intervening brackets and stays, so as to constitute the whole into one rigid structure. The whole of the plating of the inside frame is 3/4 inch thick and 9 inches deep. The plating of the outside frame is of the same thickness and depth at the fore part, until it reaches abaft the position of the cylinders and guides, where it reduces to 1/2 inch thick. The axle guard of the leading wheels is formed of 3/4 plate bolted to the frame with angle iron guides. The axle guards of the trailing wheels are formed of two 1/2 inch plates, with cast iron blocks between them to serve as guides. The ends of the rectangular frame are formed of plates 3/4 thick, and at the front end there is a buffer beam of oak 4-1/2 inches thick and 15 inches deep. The draw bolt is 2 inches diameter. There are two strong stays on each side, joining the barrel of the boiler to the inside framing, and one angle iron on each side joining the bottom of the smoke box to the inside framing. 660. _Q._--Of what construction are the wheels? _A._--The wheels and axles are of wrought iron, and the tires of the wheels are of steel. The driving wheels are 6 feet 6-1/2 inches in diameter, and the diameter of crank pin is 3-1/2 inches. The diameter of the smaller wheels is 48-1/2 inches. The axle boxes are of cast iron with bushes of Fenton's metal, and the leading axle has four bearings. The springs are formed of steel plates, 3 feet long, 4 inches broad, and 1\2 inch thick. The axle of the driving wheel has two eccentrics, forged solid upon it, for working the pumps. 661. _Q._--Will you specify the dimensions of the principal parts of the engine? _A._--Each of the cylinders which is 14-1/4 inches diameter, has the valve casing cast upon it. The steam ports are 13 inches long and 1-5/8 inches broad, and the exhaust port is 2-1/2 inches broad. The travel of the valve is 4-1/8 inches, the lap 1 inch, and the lead 1/4 inch. The piston is 4 inches thick: its body is formed of brass with a cover of cast iron, and between the body and the cover two flanges, forged on the piston rod, are introduced to communicate the push and pull of the piston to the rod. The piston rod is of iron, 2-1/2 inches diameter. The guide bars for guiding the top of the piston rod are of steel, 4 inches broad, fixed to rib iron bearers, with hard wood 1/4 of an inch thick, interposed. The connecting rod is 6 feet long between the centres, and is fitted with bushes of white metal. The eccentrics are formed of wrought iron, and have 4-1/8 inches of throw. The link of the link motion is formed of wrought iron. It is hung by a link from a pin attached to the framing; and instead of being susceptible of upward and downward motion, as in the case of the link represented in fig. 57 a rod connecting the valve rod with the movable block in the link, is susceptible of this motion, whereby the same result is arrived at as if the link were moved and the block was stationary. One or the other expedient is preferable, according to the general nature of the arrangements adopted. The slide valve is of brass, and the regulator consists of two brass slide valves worked over ports in a chest in the steam pipe, set in the smoke box. The steam pipe is of brass, No. 14. wire gauge, perforated within the boiler barrel with holes 1/12th of an inch in diameter along its upper side. The blast pipe, which is of copper, has an orifice of 4-1/4 inches diameter. There is a damper, formed like a Venetian blind, with the plates running athwartships at the end of the tubes. [Illustration: Fig. 58. SAFETY VALVE. Gooch.] 662. _Q._--Of what construction is the safety valve? _A._--There are two safety valves, consisting of pistons 1-3/16 inch in diameter, and which are kept down by spiral springs placed immediately over them. A section of this valve is given in fig. 58. 663. _Q._--What are the dimensions of the feed pumps? _A._--The feed pumps are of brass, with plungers 4 inches diameter and 3-1/4 inches stroke. The feed pipe is of copper, 2 inches diameter. A good deal of trouble has been experienced in locomotives from the defective action of the feed pump, partly caused by the leakage of steam into the pumps, which prevented the water from entering them, and partly from the return of a large part of the water through the valves at the return stroke of the pump, in consequence of the valve lifting too high. The pet cock--a small cock communicating with the interior of the pump--will allow any steam to escape which gains admission, and the air which enters by the cock cools down the barrel of the pump, so that in a short time it will be in a condition to draw. The most ordinary species of valve in the feed pumps of locomotives, is the ball valve. Notwithstanding the excellent performance of the best examples of locomotive engines, it is quite certain that there is still much room for improvement; and indeed various sources of economy are at present visible, which, if properly developed, would materially reduce the expense of the locomotive power. In all engines the great source of expense is the fuel; and although the consumption of fuel has been greatly reduced within the last ten or fifteen years, it is capable of being still further reduced by certain easy expedients of improvement, which therefore it is important should be universally applied. One of these expedients consists in heating the feed water by the waste steam; and the feed water should in every case be sent into the boiler _boiling hot_, instead of being quite cold, as is at present generally the case. The ports of the cylinders should be as large as possible; the expansion of the steam should be carried to a greater extent; and in the case of engines with outside cylinders, the waste steam should circulate entirely round the cylinders before escaping by the blast pipe. The escape of heat from the boiler should be more carefully prevented; and the engine should be balanced by weights on the wheels to obviate a waste of power by yawing on the rails. The most important expedient of all, however, lies in the establishment of a system of registering the performance of all new engines, in order that competition may stimulate the different constructors to the attainment of the utmost possible economy; and under the stimulus of comparison and notoriety, a large measure of improvement would speedily ensue. The benefits consequent on public competition are abundantly illustrated by the rapid diminution of the consumption of fuel in the case of agricultural engines, when this stimulus was presented. CHAPTER XI OF VARIOUS FORMS, APPLICATIONS, AND APPLIANCES OF THE STEAM ENGINE. In the English edition of this work, the first part of this chapter is devoted to examples of Portable and fixed Agricultural engines, of different makers and styles of workmanship, but not in sufficient detail, nor illustrated on large enough scale to be of practical value as models, forming rather in fact an illustrated catalogue of the manufacturer, than a study for the mechanic. On this account, they have been entirely omitted, and their place supplied by a few illustrations from American workmanship, not only of Steam Engines, of various forms and applications, but also of various machines, or appliances, connected with the working of engines, as for the determination, or regulation of pressure, of the boilers; for the supply or feed of the boilers, the regulation of the speed of the engine, and the like. The Gauges used in this country to show the pressures of steam in boilers are of various constructions, but perhaps the most common is the Bourdon, or, as it is known here, the Ashcroft gauge, from the party introducing it, and holding the patent. Fig. 59 represents its interior construction. It consists of a thin metallic tube, _a_, bent into nearly a complete circle closed at one end, the steam being introduced at the other, at _b_. The effect of the pressure of the steam on the interior of the tube is to expand the circle, more or less according to the pressure, the elasticity of the metal returning the circle to its original position, when the pressure is removed. The free or closed end of the tube is connected by a link _c_ with a lever _d_, at the opposite end of which is segmental gear, in gear with a pinion, on which is a hand, which marks the pressure on a dial. The dial and hand are not shown on the cut, but are on the exterior case removed to show the construction. [Illustration: Fig. 59.] [Illustration: Fig. 60.] Fig. 60 is an elevation of a boiler with Clark's Patent Steam and Fire Regulator attached, for the control of the draft of the chimney by the pressure of steam in the boiler. It consists of a chamber, _a_, with a flexible diaphragm or cover on top, in communication with the boiler. On this diaphragm rests a plunger or piston, which is held down like a safety valve, by a lever and weight, _b_. The end of the lever is connected with a balanced damper, _c_, in the chimney. The weight, _b_, is placed at any required position on the lever, and when the pressure of steam in the boiler, exerted on the diaphragm, becomes sufficient to raise the weight, the lever rises, and the damper begins to close, and to check the draft in the chimney. When properly adjusted, the machine works on a variation of from, one to two pounds between the extremes of motion. When the dampers are very large, say 3 feet or over, they should be set on rollers, like common grindstone rollers; the regulator should be attached directly to the damper, the length of the pipe connecting the regulator with the boiler being of no account. [Illustration: Fig. 61.] Porter's Patent Governor, fig. 61, is a modification of the ordinary centrifugal governor. Very small balls are employed, from 2-1/4 to 2-5/8 inches in diameter. These swing from a single joint at the axis of the spindle, which is the most sensitive arrangement, and make from 300 to 350 revolutions per minute, at which speed their centrifugal force lifts the counterpoise. The lower arms are jointed to the upper ones at the centres of the balls, and connect with the slide by joints about two inches apart. The counterpoise may be attached to the slide in any manner; for the sake of elegance, it is put in the form of a vase rising between the arms, its stem forming the slide. The vase is hollow and filled with lead, and weighs from 60 lbs. to 175 lbs. It moves freely on the spindle, through nearly twice the vertical distances traversed by the balls, and is capable of rising from 2-1/2 to 3 inches, before its rim will touch the arms. It is represented in the figure as lifted through about one half of its range of action. The standard is bored out of the solid, forming a long and perfect bearing for the spindle; the arms and balls are of gun metal, the joint pins of steel; every part of the governor is finished bright, except the bracket carrying the lever, and the square base of the standard, which are painted. The pulley is from 3 to 10 inches in diameter, and makes in the larger sizes about 125 revolutions, and in the smaller 230 revolutions per minute; the higher speed of the governor being got up by gearing. Mr. Porter warrants the following action in this governor, operating any regulating valve or cut-off which is in reasonably good order. The engine should be run with the stop-valve wide open, and, except the usual oiling, will require no attention from the engineer, under any circumstances, after it is started, until it is to be stopped. No increase in the pressure of steam will affect its motion perceptibly. The extreme possible variation in the speed, between that at which the regulating valve will be held wide open, and that at which it will be closed, is from 3 to 5 per cent., being least in the largest governors. This is less than 1/6 of the variation required by the average of ordinary governors, and is with difficulty detected by the senses. The entire load which the engine is capable of driving may be thrown on or off at once, and one watching the revolutions cannot tell when it is done. The governor will be sensibly affected by a variation in the motion of the engine of 1 revolution in 800. Notwithstanding this extreme sensitiveness, or rather by reason of it, it will not oscillate, but when the load is uniform will stand quite, or nearly, motionless. For the supply of the water to the boiler, in many positions, it is very convenient to have a pump unconnected with the engine. On this account it is very usual in this country to have what are called donkey pumps or engines independent of the main engines, which can be used to feed the boilers, or for supplying water for many other purposes. Fig. 62 is a longitudinal section of the Worthington Steam Pump, the first of its kind, and for many years in successful operation. The general arrangement is that of a Steam Cylinder, the piston rod of which, carried through into the water cylinder and attached directly to the water plunger, works back and forth without rotary motion, and of course without using either crank or fly wheel. [Illustration: Fig. 62.] In the figures, _a_ is the Steam Cylinder--_b_, the Steam Chest--_d_, a handle for regulating the steam valve--_f_, the starting bar _g, g_, tappets attached to the valve rod, which is moved by the contact of the arm _e_, on the piston rod with said tappets--_h_, the double-acting water plunger working through a packing ring--_o, o_, force valves--_o', o'_, suction valves. The pump piston is represented as moving from right to left, the arrows indicating the course of the water through the passages. The suction valves _o'_, on the right side, and the force valves _o_, on the left side, are show open; _x_, is an air chamber made of copper; _s_, the suction pipe terminating in a vacuum chamber; made by prolonging the suction pipe, and closing it perfectly tight at the top, the connection being made to the pump by a branch as shown; _m, m_, are hand-hole plates, affording easy access to the water valves; _n, n_, small holes through the plunger, which relieve the pressure near the end of the stroke, to give momentum to throw the valves when working at slow speed. [Illustration: Fig. 63.] Fig. 63 is a perspective view of H.R. Worthington's Duplex Steam Pump. The prominent peculiarity of this pump is its valve motion. As seen in the cut, two steam pumps are placed side by side (or end to end, if desired). Each pump, by a rock shaft connected with its piston rod, gives a constant and easy motion to the steam valve of the other. Each pump therefore gives steam to and starts its neighbor, and then finishes its own stroke, pausing an instant till its own steam valve, being opened by the other pump, allows it to make the return stroke. This combined action produces a perfectly positive valve motion without dead points, great regularity and ease of motion, and entire absence of noise or shock of any kind. Both kinds of pumps are made by Mr. Worthington, of various size according to the requirements, the duplex being used for boiler feed and for the supply of cities with water. Fig. 64 is a side elevation of the Woodward Steam Pump. The pump is direct acting. The steam and water piston being on the same rod, but momentum is obtained to throw the valves by means of a fly wheel, placed beyond the pump, and connected with the piston rod by a cross head and a yoke. The machine is simple in its construction and action, and is extensively used. Giffard's Injector, both in Europe and this country, is quite extensively used to supply the place of a pump, as independent feed for all classes of boilers. It is represented in elevation and section, figs. 65 and 66. [Illustration: Fig. 64.] [Illustration: Fig. 65.] [Illustration: Fig. 66.] _A_, steam pipe leading from the boiler. _B_, a perforated tube or cylinder, through which the steam passes into the space _b_. _C_ screwed rod for regulating the passage of steam through the annular conical space _c_, and worked by the handle _d/_. _E_, suction pipe, leading from the tank or hot well to small chamber _m_. _F_, annular conical opening or discharge pipe, the size of which is regulated by the movement of the tube or cylinder _B_. _G_, hand wheel for actuating the cylinder _B_. _H_, opening, in connection with the atmosphere, intervening between discharge pipe _F_ and the receiving pipe through which the water is forced. _I_, tube through which the water passes to the boiler. _K_, valve for preventing the return of the water from the boiler when the injector is not working. _L_, waste or overflow pipe. _M_, nut to tighten the packing rings _g_ and upper packing _i_ in cylinder _B_. _N_, lock nut to hold _M_. The pipe _A_ is connected with the steam space of the boiler at its highest part, to obtain as dry steam as possible. The passage of the steam into _A_ is controlled by a cock, as is also the feed pipe to the boiler. In working, both are opened, the steam passes through _A_ into the space _b_, and issuing through the nozzle _c_ with the pressure due to its head, and a partial vacuum by its contact with the feed water, it drives this water in connection with the jet through the pipe _F_ into the pipe _I_ in connection with the water space of the boiler. _Method of Working._--Turn the wheel so as to permit a small quantity of water to flow to the instrument. Open the steam cock connecting the apparatus with the boiler. Turn slightly the handle, which will admit a small quantity of steam to the apparatus; a partial vacuum is thus produced, causing the water to enter through the supply pipe. As soon as this happens, which can be observed at the overflow pipe, the supply of steam or water may be increased as required, up to the capacity of the instrument, regulating either by means of the wheel and handle, so as to prevent any overflow. The quantity of water delivered into the boiler, may be varied by means of the stop cocks on the steam and water pipes, without altering the handles on the injector; a graduated cock on the water supply pipe is very convenient for this purpose. The machines are manufactured by Wm. Sellers & Co. Philadelphia. As an example of Portable Steam Engines, of which there are large numbers in this country of different manufacturers, we give the representation (fig. 67) of one made by J.C. Hoadley, of Lawrence, Mass. [Illustration: Fig. 67.] In these machines, the rules and proportions of the locomotive engine are adapted to the requirements of stationary power, for all purposes under forty horse power. The leading ideas are: high velocity, high pressure, good valve motion, large fire-box, numerous and short flues, and steam blast. The characteristic features are: great strength of boiler, fully adequate to bear with safety 200. lbs. pressure per sq. in., great compactness and simplicity, large and adjustable wearing surfaces, and the entire absence of all finish, or polish, for mere show. The cylinder is placed over the centre of the boiler, at the fire-box end, so that the strain due to the engine is central to the boiler (which serves as bed plate); the starting valve is under the hand of the engineer when at the fire door; and both ends of the crank shaft are available for driving pulleys. For the sake of compactness, the cylinders are set low, by means of a depression in the boiler between the stands of the crank shaft, to admit of the play of the crank and connecting rod. All the parts are attached to the boiler, which is made of sufficient strength to bear all extra strain due to the working of the engine. They have feed water heater, force pumps, Jackson's governor and valve, belt for governor, belt pulley, turned on the face, steam gauge; everything, in short, necessary to the convenient working of a steam engine. All engines are fired up and tried before they leave the shop, and they are warranted tight, safe, and complete. A strong and convenient running gear, so arranged as to be easily attached and detached at pleasure, is furnished, if desired; forming, when separate, a useful wagon. [Illustration: Fig. 68.] Fig. 68 is a compact vertical engine, as built by R. Hoe & Co., of this city. It is intended to drive printing presses, but is adapted to any kind of work, and is especially suited to such places as require economy of space. Although the value of expansion has been called in question by some of the engineers of the United States Navy, and under an appropriation from Congress is now to be made the subject of experiment; yet, in almost all the manufactories and workshops of the United States, no matter what the form of steam engine, or the purposes to which it is applied, whether stationary, locomotive, or marine, some form of cut-off, by which expansion of the steam can be availed of, is considered indispensable. Many varieties are in use, but those engines are most popular in which the cut-off is applied directly to the valves on the cylinder, opening them quickly and shutting off almost instantly, avoiding all wire drawing of the steam at the ports, and regulating the speed of the engine promptly. Of this class of engines, those manufactured by the Corliss Steam Engine Company, of Providence, R.I., are perhaps the widest known, not only for their extensive introduction, but also from having, by a long and successful litigation, established the claims of the patentee, Mr. George H. Corliss. [Illustration: Fig. 70.] Fig. 70 is a section of the cylinder and valve chests of a horizontal Corliss engine. _S_ is the steam connection, and _E_ the exhaust; there are two distinct sets of valves, the steam _s, s'_, and the exhaust _e, e'_, operated independently of each other. In their construction the valves may be considered cylindrical plugs, of which portions near the ports are cut away to admit the steam and reduce the bearing surface; the valves are fitted on the lathe and the seats by boring. The motion given to the valves is rocking, but it will be observed that the valves are not firmly connected to the rocking shaft or cylinder; in the figure the valves are shown shade lined, and the shaft or stem plain; in this way the valves are not affected by the packing of the valve stem, but always rest upon the face of the ports. In the figure the piston is just about to commence its outstroke, the movement of the steam is supposed to be represented by the arrows; the inner steam valve _s_, and the outer exhaust _e'_, are just beginning to open. It will be observed that the outer steam _s'_ is fully closed, whilst the inner exhaust valve _e_ is but barely so, showing that there has been a cut-off on the steam valve, but no lead to the exhaust, that it was left fully open till the completion of the stroke. [Illustration: Fig. 71.] Fig. 71 is a side elevation of the cylinder, with the valve connections with the governor. _S_ is the steam pipe; _s, s'_ handles to the steam valves, and _e, e'_ to the exhaust valves, shown in dotted line in fig. 70. The handles to the exhaust valves are connected directly to a rocking plate _R_, to which motion is given by a connection _x_, with an eccentric on the engine shaft. When once set, therefore the movement of the exhaust valves is constant, and they will always be opened and closed at the same point of the stroke. Connected with the rocking plate _R_, and on opposite sides of its centre, the same as the exhaust valve connections, there are two levers, vibrating on a centre _c_, of which one only is shown, as it covers the other; to the upper ends of these levers pawls are attached, one end of which rests on the stems or rods connected with the handles _s, s'_, of the steam valves; on these stems there are notches against which the pawls strike, and as the levers vibrate inward they push back the stems and thereby open the valves, and this continues for the whole length of the inward motion of the levers, or till the outer extremities of the pawls come in contact with the end of the short lever _l_, which, pushing down the outer end of the pawls, relieves the stems at the other ends, and the valve stem returns to its place through the force of springs attached to the outer extremities of the valve stems _a_, are cylindrical guides to the valve stems, at the inner extremities of which are air cushions. The lever _l_ is connected directly with the governor. As the balls rise, they depress the extremity, which comes in contact with the pawls sooner, and thereby shut the valves earlier; and on the contrary when the balls are depressed, the valves remain open longer; as the pawls come in contact with the stems always at one point, the steam valves open constantly, but are closed at any point by the relief of the pawls, according to the speed of the governor. Fig. 71 represents, partly in section and partly in plan, the cylinder, steam chests, valves, &c., of one of the Woodruff & Beach high pressure Engines, Wright's patent. Fig. 72 represents, in elevation, the cam shaft, to the upper end of which, not shown in the drawing, is attached the ordinary centrifugal governor. The cylinder, steam chests, valves, &c., being similar to those of other engines, need no special notice; but the cam for opening and closing the steam valves, fig. 72, requires particular attention, as it embodies a beautiful and simple device for cutting off the steam with certainty at any part of the stroke, the motion being produced automatically by the action of the governor on this cam, throwing it more or less out of centre with the spindle of the governor, as the rotation of the balls is less or more rapid, the eccentricity of the cam determining the amount of steam admitted to the working cylinder of the engine. To produce this effect the cam is made as follows: _C_ is a hollow cylinder or shell, with a part of one end formed into a cam proper. Throughout the whole length of this piece, upon the inside, there is a spiral groove cut to receive one end of a feather, by which its pitch or eccentricity is regulated. _C'_ is also a hollow cylinder or shell, of the same length and diameter as _C_, with a similar spiral groove cut on the inside, the outside being perfectly smooth and plain, upon which the toe (_t_) for closing the valves is fastened. The inside piece consists of two hubs _D, D'_, eccentric with each other, and made in one piece, _D_ being turned to exactly fit the inside of the shell _C_, and _D'_ to fit the shell _C'_, the hub _D'_ having a socket (_c_) into which the spindle (_s_) of the governor is screwed; the end (_d_) of the hub _D_ forming a journal or bearing, with a bevel wheel on its extremity to convey motion from the crank-shaft gearing to the governor and cut-off. There is a hole throughout the length of the inside hubs _D_ and _D'_, which is continued through the spindle of the governor, and contains the rod (_r_) that connects the cam with the governor. This hole is eccentric to the outside surface of the hub _D_, as well as to the shell _C_, and concentric with the hub _D'_ and shell _C'_, and with the governor rod (_r_). The shell _C_ and hub _D_, and shell _C'_ and hub _D'_, are connected together by feathers; one piece of each feather is of a spiral form, and the other a straight or rectangular piece, the two being connected together by a stub on the rectangular piece, which fits into a hole or bearing in the other or spiral piece, so that the latter can turn on the stub and accommodate itself to the groove in which it has to work. The spiral part of each feather works in the spiral groove on the inside of its corresponding shell _C_ and _C'_ respectively, and the rectangular pieces work in a straight groove cut in the hubs _D_ and _D'_, the inner parts of the rectangular pieces being fastened to the governor rod (_r_), so that the feathers are permanently connected with the governor. The shell _C'_ revolves inside of two yokes (_y_) and (_y'_), one attached to each steam-valve toe, (_a_) and (_a'_) respectively. On the inside of each yoke, and opposite to its valve-toe, is a raised piece, against which the closing piece (_t_) on the shell (_C'_) acts to close the valves. This shell (_C'_), as before noticed, has a spiral groove on its inside, similar in all respects to that in the cam-shell (_C_); and being acted upon in the same manner and through the same rod by the governor, it is evident that the closing piece (_t_) on its outside will always hold the same relation to the opening toe on the lower or cam-shell (_C_); and whatever alteration is made in the one, a corresponding alteration takes place in the other, thereby insuring the closing of the valves at the proper time at every point of the variation of the cut-off. When the several pieces above described are put together, the apparatus for opening and closing the valves and producing the cut-off is complete, as shown in fig. 72, and it operates as follows: [Illustration: Fig. 71.] [Illustration: Fig. 72.] Motion is communicated by gearing from the crank-shaft to the bevel wheel on the piece (_d_) on the end of the hub _D_, and is communicated to the spindle of the governor, which is screwed into the socket on _D'_. As the balls rise or fall, through change of centrifugal force due to the variation in the speed of rotation, they raise or depress the governor-rod, which passes through the spindle and the hubs _D'_ and _D_, and is attached to the feathers, thereby raising or depressing the feathers, which, acting on their respective spiral grooves, instantly alters the lift of the cam on the shell (_C_), and brings the closing toe (_t_) on the shell (_C'_) into proper position for closing, and so regulates the amount of steam admitted to the cylinder. [Illustration: Fig. 71.] Consequently, any speed may be selected at which the load of the engine is to move, and any variation from that will be instantly felt by the governor, and corrected by this simple and beautiful device. There is no jar in the working of the parts; the feathers move noiselessly in their grooves; the governor rod moves up and down through the spindle and the hubs _D_ and _D'_, and can be regulated by hand to give any required opening of the steam ports to suit the work to be done. Any change in the amount of work will then alter the speed of the engine, and so affect the governor and cam, as before said. It is unnecessary to insist on the great economy attained by using steam with a well-regulated cut-off, for practical men know now that the essential points of excellence in the steam engine are a good boiler, which generates the greatest quantity of steam for the least consumption of fuel; and, secondly, a reliable cut-off, which uses the steam to the best advantage, by admitting the proper quantity for the work required. STEAM FIRE ENGINES.--Portable engines for the extinguishment of fires, are an American invention, and to Messrs. A.B. & E. Latta, of Cincinnati, working on the right principles, is due the credit which they claim in their circular, as follows: "We claim to be the _original_ and first _projectors_ of the _first successful steam fire engine_ in the world's history. There have been many attempts at making a machine of such construction as would answer to extinguish fires; but none of them proved to be available in a sufficiently short space of time to warrant their use as a fire apparatus. We hold that a steam fire engine should be of such nature as to be brought into requisition in as short a space of time as is necessary to get the machine on the ground, and the hose laid and ready to work: that is, supposing the fire to be within one square of the place where the steamer is located. The object in locating a machine at any point is to protect that immediate vicinity; and it is therefore absolutely necessary to have it available in the shortest space of time, and that with unerring certainty. We think that reliability is of the greatest importance to the protection of a city from fire, as everything is dependent on the _working_ of such apparatus in time; and for this reason no expense should be spared on this kind of machinery." Fig. 73 is a representation of one of the Messrs. Latta's fire engines, of which there are many of different classes, according to the requirements; they say that they can furnish engines as low as $1,000, and have made some for $10,000. The first peculiar feature of this engine is the boiler; it differs entirely from all boilers now in use. [Illustration: Fig. 73.] The fire box or furnace is simply a square box or furnace of any required dimensions; it is nothing more than a water space surrounding the fire, stay-bolted as all water spaces are. It is made of boiler plate in the usual manner. The water space extends only 2/3 of the height, the balance being a single sheet. The bottom of this fire box is crossed by grate bars to support the fuel; in its rear side are fire doors, inserted for firing. The internal arrangements of the boiler are composed of a large number of tubes, lying across in a horizontal position, put together in sections with return bends resembling the coils for heating buildings. These coils are of small pipe (say one inch in diameter), and as numerous as may be necessary. They give the required amount of steam. They are secured to wrought-iron plates at each end by rivets. These plates lie close to the box, and are secured to it, top and bottom. These tubes are wrought iron, firmly screwed into the bends, so as to prevent any possible breaking. The box has a hole through both sheets, in the same manner as a hollow stay-bolt, through which the coil pipe passes, having no connection with the box. After passing into the box it divides into two pipes, then subdivides into four, and so on, until its numbers equal the number of coils in the box, and to which each limb is attached. The upper ends of these coils are the same in number, and are carried through at the top or nearly the top of the box. They then run down outside to the steam chamber, or rather water space, as the box is both steam chamber and water space. These pipes empty their contents into the box, steam and water, as it may come, all together. It will be observed that these coils of tube are sufficiently separated to allow the fire to pass between them freely, and cover their whole surface. The mode of operation of this boiler is this: The fire box is filled 2/3 full of water. The coils are dry at starting; the space for fuel being filled with good wood, the fire is lighted, and in a few moments the engineer moves his hand pump, which takes its water from the box to which it is attached, and forces it through the coils. By this means steam is generated in from 3 to 5 minutes, so as to start the engine. It will be seen that the water performs a complete circuit; it is taken from the box and passed through the coils; what is steam remains in the steam chamber, and what is not (if any) drops back into the box from where it started. Hence it will be seen that a large surface is exposed to a small quantity of water, and in a way that it is entirely controllable. All the engineer has to do to surcharge his steam, is to reduce the speed of the pump (which is independent of the main engine). By raising the heat and quantity of water, any degree of elasticity can be given to the steam, and that, too, with the least amount of waste heat in giving a natural draft. Hence the great economy of this boiler. The next feature of this engine is, it has no wood work about it to perish with the heat and roughness of the streets. All the wheels are wrought iron; and, as yet, these are the only ones that have stood a steam fire engine. The frame is wrought iron; truck, on which the front wheel is hung, wrought iron. The axles are cast steel. The engine and pump is a double-acting piston pump direct, without any rotary motion; with a perfect balance valve, it is balanced at all times, and hence the engine remains quiet without blocking, when at work. The engine is mounted on three wheels, which enables it to be turned in a very short space. Many engines have been constructed by the Messrs. Latta for the fire companies, of different cities, and have been in successful competition with other engines; the farthest throw ever made by one of their first-class engines was 310 feet from a 1-5/8 inch nozzle; steaming time, starting from cold water, 3-1/2 minutes. [Illustration: Fig. 74 AMOSKEAG STEAM FIRE ENGINE.] Fig. 74 is a representation of one class of steam fire engine, as built by the Amoskeag Manufacturing Company, at Manchester, N.H. The boiler is an upright tubular boiler, of a peculiar construction, the patent right to which is vested in the Amoskeag Manufacturing Company. This boiler is very simple in its combination, and for safety, strength, durability, and capacity for generating steam is unsurpassed. No fan or artificial blower is ever used or needed, the natural draft of the boiler being always sufficient. Starting with cold water in the boiler, a working head of steam can be generated in _less than five minutes_ from the time of kindling the fire. The engine "Amoskeag," owned by the city of Manchester, has played two streams in _three minutes and forty seconds_ after touching the match, at the same time drawing her own water. The boilers are made and proved so as to be safely run at a steam pressure of 140 to 150 lbs. to the square inch; but the engines are constructed so as to give the best streams at a pressure of about 100 lbs. to the square inch, and for service at fires a steam pressure of about 60 lbs. to the square inch is all that is required. The various styles of engine are all _vertical_ in their action, and in all the pumps and steam cylinders are firmly and directly fastened to the boiler, the steam cylinders being attached directly to the steam dome. This arrangement obviates the necessity of carrying steam to the cylinders through pipes of considerable length, and the machine has very little vibratory motion when in operation--so little that it is not necessary to block its wheels to keep it in its place, or to take the weight off the springs before commencing work. The pumps are placed on the engines as near the ground as they can be with safety, and are arranged so as to attach the suction and leading hose to either or both sides of the machine, as may be most convenient or desirable, so that less difficulty will be found in placing an engine for work, and when required to draw its own water, it has only to draw it the shortest possible distance. Each engine has two "feed pumps" for supplying the boiler, and also a connection between the main forcing pumps and the boiler, so that it can be supplied from that source if desirable. The tank which carries the water for supplying the boiler is so placed that the water in it is always above the "feed pumps," an advantage that insures the almost certain working of these pumps. These pumps are of brass, the best locomotive pattern, and one of them running with the engine, when at work, furnishes an ample supply of water to the boiler. [Illustration: Fig. 75.] The engines are exceedingly portable; they can be turned about or placed for service in as contracted a space as any hand engine, and two good horses will draw a first-class engine with the greatest ease, carrying at the same time water for the boiler, a supply of fuel sufficient to run the engine two hours, the driver, the engineer, and the fireman. Fig. 75 is a representation of the class of steam fire engine built by Silsbee, Mynderse & Co., Seneca Falls, N. Y. under Holly's patent. The boiler is vertical, with vertical water tubes passing directly through the fire. These tubes are closed at the bottom and open at the top, where they pass through a water-tight plate, and communicate with the water in the boiler. The arrangement of the tubes causes a constant current, the water rising on the outside of the tubes as they are heated, and its place being supplied by a current flowing downward through the tube to the boiler. The smoke and flame pass among the tubes up through flues. Both engine and pump are rotary, and of the same type. They consist essentially of two elliptical rotary pistons, cogged and working into one another in an air-tight case. The pistons fit close to the inside of the case, and gear into each on the line of their conjugate diameters. The action is somewhat similar to the old-fashioned rotary pump, consisting of two cog wheels in gear with, each other, the spaces at the side of the case being filled with water, which at the centre are occupied by the teeth in gear. In Holly's pump, instead of uniform teeth, and depending on the fit of the teeth with the side of the case and with each other for the packing, there are two large teeth in each piston opposite each other, which have slide pistons, and intermediate with these large teeth are small cogs, which continue the motion of the rotary pistons. The machine works very smoothly, and performs the work necessary, in ordinary service, under a pressure of 50 to 60 lbs. There are many other makers of fire engines in this country; but sufficient examples are given to illustrate the class; so successful have they been, that they are fast superseding hand engines, even in the smaller cities. Under a paid department, the following is, in the city of Boston, Mass., the comparative cost of running the two kinds of engines, viz.: STEAM FIRE ENGINE. 1 engineer........................................... $720 00 1 fireman............................................ 600 00 1 driver............................................. 600 00 1 foreman of hose.................................... 150 00 8 hosemen, at $125 each.............................. 375 00 -- -------- 7 men................................................ $2,445 00 Keeping of 2 horses.................................. 315 00 -------- Total......................................... $2,760 00 HAND ENGINE. 1 foreman............................................ $150 00 1 assistant foreman.................................. 125 00 1 clerk.............................................. 125 00 1 steward............................................ 125 00 3 leading hosemen, at $125 each...................... 375 00 33 men, at $100 each................................. 3,300 00 -- --------- 40 men............................................... $4,200 00 Here the engineer, fireman, and driver are constantly employed, the hosemen have other employment in the neighborhood, but all the company sleep in the engine house. In the city of Manchester, N.H., a steam fire engine company is composed of fourteen men, all told, one of whom, acting as driver and steward, is constantly employed, remaining at the engine house with a pair of horses always ready to run out with the engine in case of an alarm of fire. The other members of the company have other employments, and turn out only on an alarm of fire. STEAM FIRE ENGINES. "Amoskcag," Expenditures..................... $864 32 "Fire King," " ..................... 855 78 "E.W. Harrington," " ..................... 496 09 The above expense includes pay of members, team expenses, cost of gas, wood, coal, and all necessities incident to service. The "E.W. Harrington" is a second-class engine, stationed in the outskirts of the city, and was run cheaper from the fact that no horses were kept for it by the city. A first-class hand-engine company is allowed to number, all told, fifty men, and the members of the company are paid as follows: FIRST-CLASS HAND-ENGINE COMPANY. 1 foreman.......................................... $35 00 1 assistant foreman............................... 28 00 1 clerk........................................... 28 00 1 steward........................................ 68 00 46 men, at $18 each................................ 828 00 -------- 50 men. Total.............................. $987 00 By this it will be seen, that in a city like Manchester, with from twenty to twenty-five thousand inhabitants, a first-class steam fire engine can be run at an expense not to exceed that of a first-class hand engine, while in service it will do at least _four times_ the work. The cost of repairs is found by experience to be no greater on the steam fire engines than on hand engines. The Excavator, fig. 76, is the invention of the late Mr. Otis, an application of the spoon dredging machine of the docks to railway purposes, with very important modifications. The machine consists of a strong truck, _A_, _A_, mounted on railway wheels, on which is placed the boiler _C_, the crane _E_, and the requisite gearing. The excavator or shovel, _D_, is a box of wrought iron, with strong points in front to act as picks in loosening the earth, and its bottom hung by a hinge at _d_, so that, by detaching a catch, it may fly open and discharge the material raised. To operate the machine, suppose the shovel _D_ to be in the position shown in the cut; it is lowered by the chains _o_, _o_, and thrown forward or backward, if necessary, by the drum _B_, and handle _S_, till the picks in the front of the shovel are brought in proper contact with the face of the cut; motion forward is now given to the shovel by the drum _B_ and handle _S_, and at the same time it is raised by the chains _o_, _o_. These two motions can be so adjusted to each other, as to give movement to the shovel to enable it to loosen and scrape up a shovelful of earth. The handle _S_ is now left free, and the shovel _D_ is raised vertically by the chains _o_, _o_. The crane is now turned round, till the shovel comes over a rail car on a side track; the bottom of the shovel is opened, and the dirt deposited in the car. All these motions are performed by the aid of a steam engine, and are controlled by a man who stands on a platform at _f_. [Illustration: Fig 76.] 692. _Q._--Having now described the most usual and approved forms of engines applicable to numerous miscellaneous purposes for which a moderate amount of steam power is required, will you briefly recapitulate what amount of work of different kinds an engine of a given power will perform, so that any one desiring to employ an engine to perform a given amount of work, will be able to tell what the power of such engine should be? _A._--It will of course be impossible to recapitulate all the purposes to which engines are applicable, or to specify for every case the amount of power necessary for the accomplishment of a given amount of work; but some examples may be given which will be applicable to the bulk of the cases occurring in practice. 693. _Q._--Beginning, then, with the power necessary for threshing,--a 4 horse power engine, with cylinder 6 inches diameter, pressure of steam 45 lbs., per square inch, and making 140 revolutions per minute, will thresh out 40 quarters of wheat in 10 hours with a consumption of 3 cwt. of coals. _A._--Although this may be done, it is probably too much to say that it can be done on an average, and about three fourths of a quarter of wheat per horse power would probably be a nearer average. The amount of power consumed varies with the yield. Messrs. Barrett, Exall, and Andrewes give the following table as illustrative of the work done, and the fuel consumed by their portable engines; but this must be regarded as a maximum performance:-- Number of | Weight of | Quarters of | Quantity of | Quantity of Horse Power.| Engine. | Corn thrashed| Coals consumed| Water required | | in 10 Hours. | in 10 Hours. | for 10 Hours | | | | in Gallons. ------------|-----------|--------------|---------------|--------------- |Tons. Cwts.| | Cwts. | 4 | 2 0 | 40 | 3 | 360 5 | 2 5 | 50 | 4 | 380 6 | 2 10 | 60 | 5 | 460 7 | 2 15 | 70 | 6 | 540 8 | 3 0 | 80 | 7 | 620 10 | 3 10 | 100 | 9 | 780 ----------------------------------------------------------------------- 694. _Q._--In speaking of horses power, I suppose you mean indicator horse power? _A._--Yes; or rather the dynamometer horse power, which is the same, barring the friction of the engine. At the shows of the Royal Agricultural Society, the power actually exerted by the different engines is ascertained by the application of a friction wheel or dynamometer. 695. _Q._--Can you give any other examples of the power necessary for grinding corn? _A._--An engine exerting 23-1/3 horses power by the indicator works two pairs of flour stones of 4 feet 8 inches diameter, two pairs of stones grinding oatmeal of 4 feet 8 inches diameter, one dressing machine, one pair of fanners, one dust screen, and one sifting machine. One of the flour stones makes 85, and the other 90 revolutions in the minute. One of the oatmeal stones makes 120, and the other 140 revolutions in the minute. To take another case:--An engine exerting 26-1/2 indicator horses power works two pairs of flour stones, one dressing machine, two pairs of stones grinding oatmeal, and one pair of shelling stones. The flour stones, one pair of the oatmeal stones, and shelling stones, are 4 feet 8 inches diameter. The diameter of the other pair of oatmeal stones is 3 feet 8 inches. The length of the cylinder of the dressing machine is 7 feet 6 inches. The flour stones make 87 revolutions in the minute, and the larger oatmeal stone 111 revolutions, but the smaller oatmeal stone and the shelling stone revolve faster than this. At the time the indicator diagram was taken, each pair of flour stones was grinding at the rate of 5 bushels an hour; each pair of oatmeal stones about 24 bushels an hour; and the shelling stones were shelling at the rate of about 54 bushels an hour. The fanners and screen were also in operation. 696. _Q._--Have you any other case to enumerate? _A._--I may mention one in which the power of the same engine was increased by giving it a larger supply of steam. The engine when working with 8.65 horses power, gives motion to one pair of oatmeal stones of 4 feet 6 inches diameter, and one pair of flour stones 4 feet 8 inches diameter. The oatmeal stone makes 100 revolutions in the minute, and the flour stone 89. The oatmeal stones grind about 36 bushels in the hour, and the flour stones 5 bushels in the hour. The engine when working to 12 horses power drives one pair of flour stones, 4 feet 8 inches diameter, at 89 revolutions per minute and one pair of stones of the same diameter at 105 revolutions, grinding beans for cattle. The flour mill stones with this proportion of power, being more largely fed, ground 6 bushels per hour, and the other stones also ground 6 bushels per hour. When the power was increased to 18 horses, and the engine was burdened in addition with a dressing machine having a cylinder of 19 inches diameter, the speed of the flour stone fell to 85, and of the beans stone to 100 revolutions per minute, and the yield was also reduced. The dressing machine dressed 24 bushels per hour. 697. _Q._--What is the power necessary to work a sugar mill such as is used to press the juice from canes in the West Indies? _A._--Twenty horses power will work a sugar mill having rollers about 5 feet long and 28 inches diameter; the rollers making 2-1/3 turns in a minute. If the rollers be 26 inches diameter and 4-1/2 feet long, 18 horses power will suffice to work them at the same speed, and 16 horses power if the length be reduced to 3 feet 8 inches. 12 horses power will be required to work a sugar mill with rollers 24 inches diameter and 4 feet 2 inches long; and 10 horses power will suffice if the rollers be 3 feet 10 inches long and 23 inches diameter. The speed of the surface of sugar mill rollers should not be greater than 16 feet per minute, to allow time for the canes to part with their juice. In the old mills the speed was invariably too great. The quantity of juice expressed will not be increased by increasing the speed of the rollers, but more of the juice will pass away in the begass or woody refuse of the cane. 698. _Q._--What is the amount of power necessary to drive cotton mills? _A._--An indicator or actual horse power will drive 305 hand mule spindles, with proportion of preparing machinery for the same; or 230 self-acting mule spindles with preparation; or 104 throstle spindles with preparation; or 10-1/2 power looms with common sizing. The throstles referred to are the common throstles spinning 34's twist for power loom weaving, and the spindles make 4000 turns per minute. The self-acting mules are Robert's, about one half spinning 36's weft, and spindles revolving 4800 turns per minute; and the other half spinning 36's twist, with the spindles revolving 5200 times per minute. Half the hand mules were spinning 36's weft, at 4700 revolutions, and the other half 36's twist at 5000 revolutions per minute. The average breadth of the looms was 37 inches, weaving 37 inch cloth, making 123 picks per minute,--all common calicoes about 60 reed, Stockport count, and 68 picks to the inch. To take another example in the case of a mill for twisting cotton yarn into thread:--In this mill there are 27 frames with 96 common throstle spindles in each, making in all 2592 spindles. The spindles turn 2200 times in a minute; the bobbins are 1-7/8 inches diameter, and the part which holds the thread is 2-3/16 inches long. In addition to the twisting frames the steam engine works 4 turning lathes, 3 polishing lathes, 2 American machines for turning small bobbins, two circular saws, one of 22 and the other of 14 inches diameter, and 24 bobbin heads or machines for filling the bobbins with finished thread. The power required to drive the whole of this machinery is 28-1/2 horses. When all the machinery except the spindles is thrown off, the power required is 21 horses, so that 2592, the total number of spindles, divided by 21, the total power, is the number of twisting spindles worked by each actual horse power. The number is 122.84. 699. _Q._--What work will be done by a given engine in sawing timber, pressing cotton, blowing furnaces, driving piles, and dredging earth out of rivers? _A._--A high pressure cylinder 10 inches diameter, 4 feet stroke, making 35 revolutions with steam of 90 to 100 lbs. on the square inch, supplied by three cylindrical boilers 30 inches diameter and 20 feet long, works two vertical saws of 34 inches stroke, which are capable of cutting 30 feet of yellow pine, 18 inches deep, in the minute. A high pressure cylinder 14 inches diameter and 4 feet stroke, making 60 strokes per minute with steam of 40 lbs. on the square inch, supplied by three cylindrical boilers without flues, 30 inches diameter and 26 feet long, with 32 square feet of grate surface, works four cotton presses geared 6 to 1, with two screws in each, of 7-1/2 inches diameter and 1-5/8 pitch, which presses will screw 1000 bales of cotton in the twelve hours. Also one high pressure cylinder of 10 inches diameter and 3 feet stroke, making 45 to 60 revolutions per minute, with steam of 45 to 50 lbs. per square inch, with two hydraulic presses having 13 inch rams of 41 feet stroke, and force pumps 2 inches diameter and 6 inches stroke, presses 30 bales of cotton per hour. One condensing engine with cylinder 56 inches diameter, 10 feet stroke, and making 15 strokes per minute with steam of 60 lbs. pressure per square inch, cut off at 1/4th of the stroke, supplied by six boilers, each 5 feet diameter, and 24 feet long, with a 22-inch double-return flue in each, and 198 square feet of fire grate, works a blast cylinder of 126 inches diameter, and 10 feet stroke, at 15 strokes per minute. The pressure of the blast is 4 to 5 lbs. per square inch; the area of pipes 2300 square inches, and the engine blows four furnaces of 14 feet diameter, each making 100 tons of pig iron per week. Two high pressure cylinders, each of 6 inches diameter and 18 inches stroke, making 60 to 80 strokes per minute, with steam of 60 Lbs. per square inch, lift two rams, each weighing 1000 lbs., five times in a minute, the leaders for the lift being 24 feet long. One high pressure cylinder of 12 inches diameter and 5 feet stroke, making 20 strokes per minute, with steam of 60 to 70 lbs. pressure per square inch, lifts 6 buckets full of dredging per minute from a depth of 30 feet below the water, or lifts 10 buckets full of mud per minute from a depth of 18 feet below the water. CHAPTER XII. MANUFACTURE AND MANAGEMENT OF STEAM ENGINES. CONSTRUCTION OF ENGINES. 700. _Q._--What are the qualities which should be possessed by the iron of which the cylinder of steam engines are made? _A._--The general ambition in making cylinders is to make them sound and hard; but it is expedient also to make them tough, so as to approach as nearly as possible to the state of malleable iron. This may be done by mixing in the furnace as many different kinds of iron as possible; and it may be set down as a general rule in iron founding, that the greater the number of the kinds of metal entering into the composition of any casting, the denser and tougher it will be. The constituent atoms of the different kinds of iron appear to be of different sizes, and the mixture of different kinds maintains the toughness, while it adds to the density and cohesive power. Hot blast iron was at one time generally believed to be weaker than cold blast iron, but it is now questioned whether it is not the stronger of the two. The cohesive strength of unmixed iron is not in proportion to its specific gravity, and its elasticity and power to resist shocks appear to become greater as the specific gravity becomes less. Nos. 3 and 4 are the strongest irons. In most cases, iron melted in a cupola is not so strong as when remelted in an air furnace, and when run into green sand it is not reckoned so strong as when run into dry sand, or loam. The quality of the fuel, and even the state of the weather, exerts an influence on the quality of the iron: smelting furnaces, on the cold blast principle, have long been known to yield better iron in winter than in summer, probably from the existence of less moisture in the air; and it would probably be found to accomplish an improvement in the quality of the iron if the blast were made to pass through a vessel containing muriate of lime, by which the moisture of the air would be extracted. The expense of such a preparation would not be considerable, as, by subsequent evaporation, the salt might be used over and over again for the same purpose. 701. _Q._--Will you explain the process of casting cylinders? _A._--The mould into which the metal is poured is built up of bricks and loam, the loam being clay and sand ground together in a mill, with the addition of a little horse-dung to give it a fibrous structure and prevent cracks. The loam board, by which the circle of the cylinder is to be swept, is attached to an upright iron bar, at the distance of the radius of the cylinder, and a cylindrical shell of brick is built up, which is plastered on the inside with loam, and made quite smooth by traversing the perpendicular loam board round it. A core is then formed in a similar manner, but so much smaller as to leave a space between the shell and the core equal to the thickness of the cylinder, and into this space the melted metal is poured. Whatever nozzles or projections are required upon the cylinder, must be formed by means of wooden patterns, which are built into the shell, and subsequently withdrawn; but where a number of cylinders of the same kind are required, it is advisable to make these patterns of iron, which will not be liable to warp or twist while the loam is being dried. Before the iron is cast into the mould, the interior of the mould must be covered with finely powdered charcoal--or blackening, as it is technically termed; and the secret of making finely skinned castings lies in using plenty of blackening. In loam and dry sand castings the charcoal should be mixed with thick clay water, and applied until it is an eighth of an inch thick, or more; the surface should be then very carefully smoothed or sleeked, and if the metal has been judiciously mixed, and the mould thoroughly dried, the casting is sure to be a fine one. Dry sand and loam castings should be, as much as possible, made in boxes; the moulds may thereby be more rapidly and more effectually dried, and better castings will be got with a less expense. 702. _Q._--Will you explain the next operation which a cylinder undergoes? _A._--The next stage is the boring; and in boring cylinders of 74 inches diameter, the boring bar must move so as to make one revolution in about 4-1/2 minutes, at which speed the cutters will move at the rate of about 5 feet per minute. In boring brass, the speed must be slower; the common rate at which the tool moves in boring brass air pumps is about 3 feet per minute. If this speed be materially exceeded the tool will be spoiled, and the pump made taper. The speed proper for boring a cylinder will answer for boring the brass air pump of the same engine. A brass air pump of 36-1/2 inches diameter requires the bar to make one turn in about three minutes, which is also the speed proper for a cylinder 60 inches in diameter. To bore a brass air pump 36-1/2 inches in diameter requires a week, an iron one requires 48 hours, and a copper one 24 hours. In turning a malleable iron shaft 12-3/4 inches in diameter, the shaft should make about five turns per minute, which is equivalent to a speed in the tool of about 16 feet per minute; but this speed may be exceeded if soap and water be plentifully run on the point of the tool. A boring mill, of which the speed may be varied from one turn in six minutes to twenty-five turns in one minute, will be suitable for all ordinary wants that can occur in practice. 703. _Q._--Are there any precautions necessary to be observed in order that the boring may be truly effected? _A._--In fixing a cylinder into the boring mill, great care must be taken that it is not screwed down unequally; and indeed it will be impossible to bore a large cylinder in a horizontal mill without being oval, unless the cylinder be carefully gauged when standing on end, and be set up by screws when laid in the mill until it again assumes its original form. A large cylinder will inevitably become oval if laid upon its side; and if while under the tension due to its own weight it be bored round, it will become oval again when set upon end. If the bottom be cast in, the cylinder will be probably found to be round at one end and oval at the other, unless a vertical boring mill be employed, or the precautions here suggested be adopted. 704. _Q._--Does the boring tool make the cylinder sufficiently smooth for the reception of the piston? _A._--Many engine makers give no other finish to their cylinders; but Messrs. Penn grind their cylinders after they are bored, by laying them on their side, and rubbing a piece of lead, with a cross iron handle like that of a rolling stone, and smeared with emery and oil, backward and forward-- the cylinder being gradually turned round so as to subject every part successively to the operation. The lead by which this grinding is accomplished is cast in the Cylinder, whereby it is formed of the right curve; but the part of the cylinder in which it is cast should be previously heated by a hot iron, else the metal may be cracked by the sudden heat. 705. _Q._--How are the parts of a piston fitted together so as to be perfectly steam tight? _A._--The old practice was to depend chiefly upon grinding as the means of making the rings tight upon the piston or upon one another; but scraping is now chiefly relied on. Some makers, however, finish their steam surfaces by grinding them with powdered Turkey stone and oil. A slight grinding, or polishing, with powdered Turkey stone and oil, appears to be expedient in ordinary cases, and may be conveniently accomplished by setting the piston on a revolving table, and holding the ring stationary by a cross piece of wood while the table turns round. Pieces of wood may be interposed between the ring and the body of the piston, to keep the ring nearly in its right position; but these pieces of wood should be fitted so loosely as to give some side play, else the disposition would arise to wear the flange of the piston into a groove. 706. _Q._--What kind of tool is used for finishing surfaces by scraping? _A._--A flat file bent, and sharpened at the end, makes an eligible scraper for the first stages; or a flat file sharpened at the end and used like a chisel for wood. A three-cornered file, sharpened at all the corners, is the best instrument for finishing the operation. The scraping tool should be of the best steel, and should be carefully sharpened at short intervals on a Turkey stone, so as to maintain a fine edge. 707. _Q._--Will you explain the method of fitting together the valve and cylinder faces? _A._--Both faces must first be planed, then filed according to the indications of a metallic straight edge, and subsequently of a thick metallic face plate, and finally scraped very carefully until the face plate bears equally all over the surface. In planing any surface, the catches which retain the surface on the planing machine should be relaxed previously to the last cut, to obviate distortion from springing. To ascertain, whether the face plate bears equally, smear it over with a little red ochre and oil, and move the face plate slightly, which will fix the color upon the prominent points. This operation is to be repeated frequently; and as the work advances, the quantity of coloring matter is to be diminished, until finally it is spread over the face plate in a thin film, which only dims the brightness of the plate. The surfaces at this stage must be rubbed firmly together to make the points of contact visible, and the higher points will become slightly clouded, while the other parts are left more or less in shade. If too small a quantity of coloring matter be used at first, it will be difficult to form a just conception of the general state of the surface, as the prominent points will alone be indicated, whereas the use of a large quantity of coloring matter in the latter stages would destroy the delicacy of the test the face plate affords. The number of bearing points which it is desirable to establish on the surface of the work, depends on the use to which the surface is to be applied; but whether it is to be finished with great elaboration, or otherwise, the bearing points should be distributed equally over the surface. Face plates, or planometers, as they are sometimes termed, are supplied by most of the makers of engineering tools. Every factory should be abundantly supplied with them, and also with steel straight edges; and there should be a master face plate, and a master straight edge, for the sole purpose of testing, from time to time, the accuracy of those in use. 708. _Q._--Is the operation of surfacing, which you have described, necessary in the case of all slide valves? _A._--Yes; and in fitting the faces of a D valve, great care must, in addition, be taken that the valve is not made conical; for unless the back be exactly parallel with the face, it will be impossible to keep the packing from being rapidly cut away. When the valve is laid upon the face plate, the back must be made quite fair along the whole length, by draw filing, according to the indications of a straight edge; and the distance from the face to the extreme height of the back must be made identical at each extremity. 709. _Q._--When you described the operation of boring the cylinder, you stated that the cylinder, when laid upon its side, became oval; will not this change of figure distort the cylinder face? _A._--It is not only in the boring of the cylinder that it is necessary to be careful that there is no change of figure, for it will be impossible to face the valves truly in the case of large cylinders, unless the cylinder be placed on end, or internal props be introduced to prevent the collapse due to the cylinder's weight. It may be added, that the change of figure is not instantaneous, but becomes greater after some continuance of the strain than it was at first, so that in gauging a cylinder to ascertain the difference of diameter when it is placed on its side, it should have lain some days upon its side to ensure the accuracy of the operation. 710. _Q._--How is any flaw in the valve or cylinder face remedied? _A._--Should a hole occur either in the valve, in the cylinder, or any other part where the surface requires to be smooth, it may be plugged up with a piece of cast iron, as nearly as possible of the same texture. Bore out the faulty part, and afterward widen the hole with an eccentric drill, so that it will be of the least diameter at the mouth. The hole may go more than half through the iron: fit then a plug of cast iron roughly by filing, and hammer it into the hole, whereby the plug will become riveted in it, and its surface may then be filed smooth. Square pieces may be let in after the same fashion, the hole being made dovetailed, and the pieces thus fitted will never come out. 711. _Q._--When cylinders are faced with brass, how is the face attached to the cylinder? _A._--Brass faces are put upon valves or cylinders by means of small brass screws tapped into the iron, with conical necks for the retention of the brass: they are screwed by means of a square head, which, when the screw is in its place, is cut off and filed smooth. In some cases the face is made of extra thickness, and a rim not so thick runs round it, forming a step or recess for the reception of brass rivets, the heads of which are clear of the face. 712. _Q._--What is the best material for valve faces? _A._--Much trouble is experienced with every modification of valve face; but cast iron working upon cast iron is, perhaps, the best combination yet introduced. A usual practice is to pin brass faces on the cylinder, allowing the valve to retain its cast iron face. Some makers employ brass valves, and others pin brass on the valves, leaving the cylinder with a cast iron face. If brass valves are used, it is advisable to plane out two grooves across the face, and to fill them up with hard cast iron to prevent rutting. Speculum metal and steel have been tried for the cylinder faces, but only with moderate success. In some cases the brass gets into ruts; but the most prevalent affection is a degradation of the iron, owing to the action of the steam, and the face assuming a granular appearance, something like loaf sugar. This action shows itself only at particular spots, and chiefly about the angles of the port or valve face. At first the action is slow; but when once the steam has worked a passage for itself, the cutting away becomes very rapid, and, in a short time, it will be impossible to prevent the engine from heating when stopped, owing to the leakage of steam through the valve into the condenser. Copper steam pipes seem to have some galvanic action on valve faces, and malleable iron pipes have sometimes been substituted; but they are speedily worn out by oxidation, and the scales of rust which are carried on by the steam scratch the valves and cylinders, so that the use of copper pipes is the least evil. 713. _Q._--Will you explain in what manner the joints of an engine are made? _A._--Rust joints are not now much used in engines of any kind, yet it is necessary that the engineer should be acquainted with the manner of their formation. One ounce of sal-ammoniac in powder is mingled with 18 ounces or a pound of borings of cast iron, and a sufficiency of water is added to wet the mixture thoroughly, which should be done some hours before it is wanted for use. Some persons add about half an ounce of flowers of brimstone to the above proportions, and a little sludge from the grindstone trough. This cement is caulked into the joints with a caulking iron, about three quarters of an inch wide and one quarter of an inch thick, and after the caulking is finished the bolts of the joints may be tried to see if they cannot be further tightened. The skin of the iron must, in all cases, be broken where a rust joint is to be made; and, if the place be greasy, the surface must be well rubbed over with nitric acid, and then washed with water, till no grease remains. The oil about engines has a tendency to damage rust joints by recovering the oxide. Coppersmiths staunch the edges of their plates and rivets by means of a cement formed of pounded quicklime, with serum of blood, or white of egg; and in copper boilers such a substance may be useful in stopping the impalpable leaks which sometimes occur, though Roman, cement appears to be nearly as effectual. 714. _Q._--Will you explain the method of case hardening the parts of engines? _A._--The most common plan for case hardening consists in the insertion of the articles to be operated upon among horn or leather cuttings, hone dust, or animal charcoal, in an iron box provided with a tight lid, which is then put into a furnace for a period answerable to the depth of steel required. In some cases the plan pursued by the gunsmiths may be employed with convenience. The article is inserted in a sheet iron case amid bone dust, often not burned; the lid of the box is tied on with wire, and the joint luted with clay; the box is heated to redness as quickly as possible and kept half an hour at a uniform heat: its contents are then suddenly immersed in cold water. The more unwieldy portions of an engine may be case hardened by prussiate of potash--a salt made from animal substances, composed of two atoms of carbon and one of nitrogen, and which operates on the same principle as the charcoal. The iron is heated in the fire to a dull red heat, and the salt is either sprinkled upon it or rubbed on in a lump, or the iron is rubbed in the salt in powder. The iron is then returned to the fire for a few minutes, and finally immersed in water. By some persons the salt is supposed to act unequally, as if there were greasy spots upon the iron which the salt refused to touch, and the effect under any circumstances is exceedingly superficial; nevertheless, upon all parts not exposed to wear, a sufficient coating of steel may be obtained by this process. 715. _Q._--What kind of iron is most suitable for the working parts of an engine? _A._--In the malleable iron work of engines scrap iron has long been used, and considered preferable to other kinds; but if the parts are to be case hardened, as is now the usual practice, the use of scrap iron is to be reprehended, as it is almost sure to make the parts twist in the case hardening process. In case hardening, iron absorbs carbon, which causes it to swell; and as some kinds of iron have a greater capacity for carbon than other kinds, in case hardening they will swell more, and any such unequal enlargement in the constituent portions of a piece of iron will cause it to change its figure. In some cases, case hardening has caused such a twisting of the parts of an engine, that they could not afterward be fitted together; it is preferable, therefore, to make such parts as are to be case hardened to any considerable depth of Lowmoor, Bowling, or Indian iron, which being homogeneous will absorb carbon equally, and will not twist. 716. _Q._--What is the composition of the brass used for engine bearings? _A._--The brass bearings of an engine are composed principally of copper and tin. A very good brass for steam engine bearings consists of old copper 112 lbs., tin 12-1/2 lbs., zinc 2 or 3 oz.; and if new tile copper be used, there should be 13 lbs. of tin instead of 12-1/2 lbs. A tough brass for engine work consists of 1-1/2 lb. tin, 1-1/2 lb. zinc, and 10 lbs. copper; a brass for heavy bearings, 2-1/2 oz. tin, 1/2 oz. zinc, and 1 lb. copper. There is a great difference in the length of time brasses wear, as made by different manufacturers; but the difference arises as much from a different quantity of surface, as from a varying composition of the metal. Brasses should always be made strong and thick, as when thin they collapse upon the bearing and increase the friction and the wear. 717. _Q._--How is Babbitt's metal for lining the bushes of machinery compounded? _A._--Babbitt's patent lining metal for bushes has been largely employed in the bushes of locomotive axles and other machinery: it is composed of 1 lb. of copper, 1 lb. regulus of antimony, and 10 lbs. of tin, or other similar proportions, the presence of tin being the only material condition. The copper is first melted, then the antimony is added, with a small proportion of tin-charcoal being strewed over the surface of the metal in the crucible to prevent oxidation. The bush or article to be lined, having been cast with a recess for the soft metal, is to be fitted to an iron mould, formed of the shape and size of the bearing or journal, allowing a little in size for the shrinkage. Drill a hole for the reception of the soft metal, say 1/2 to 3/4 inch diameter, wash the parts not to be tinned with a clay wash to prevent the adhesion of the tin, wet the part to be tinned with alcohol, and sprinkle fine sal-ammoniac upon it; heat the article until fumes arise from the ammonia, and immerse it in a kettle of Banca tin, care being taken to prevent oxidation. When sufficiently tinned, the bush should be soaked in water, to take off any particles of ammonia that may remain upon it, as the ammonia would cause the metal to blow. Wash with pipe clay, and dry; then heat the bush to the melting point of tin, wipe it clean, and pour in the metal, giving it sufficient head as it cools; the bush should then be scoured with fine sand, to take off any dirt that may remain upon it, and it is then fit for use. This metal wears for a longer time than ordinary gun metal, and its use is attended with very little friction. If the bearing heats, however, from the stopping of the oil hole or otherwise, the metal will be melted out. A metallic grease, containing particles of tin in the state of an impalpable powder, would probably be preferable to the lining of metal just described. 718. _Q._--Can you state the composition of any other alloys that are used in engine work? _A._--The ordinary range of good yellow brass that files and turns well, is about 4-1/2 to 9 ounces of zinc to the pound of copper. Flanges to stand brazing may be made of copper 1 lb., zinc 1/2 oz., lead 3/8 oz. Brazing solders when stated in the order of their hardness are:-three parts copper and one part zinc (very hard), eight parts brass and one part zinc (hard), six parts brass, one part tin, and one part zinc (soft); a very common solder for iron, copper, and brass, consists of nearly equal parts of copper and zinc. Muntz's metal consists of forty parts zinc and sixty of copper; any proportions between the extremes of fifty parts of zinc and fifty parts copper, and thirty-seven zinc and sixty-three copper, will roll and work at a red heat, but forty zinc to sixty copper are the proportions preferred. Bell metal, such as is used for large bells, consists of 4-1/2 ounces to 5 ounces of tin to the pound of copper; speculum metal consists of from 7-1/2 ounces to 8-1/2 ounces of tin to the pound of copper. ERECTION OF ENGINES. 719. _Q._--Will you explain the operation of erecting a pair of side lever engines in the workshop? A.--In beginning the erection of side lever marine engines in the workshop, the first step is to level the bed plate lengthways and across, and strike a line up the centre, as near as possible in the middle, which indent with a chisel in various places, so that it may at any time be easily found again. Strike another line at right angles with this, either at the cylinder or crank centre, by drawing a perpendicular in the usual manner. Lay the other sole plate alongside at the right distance, and strike a line at the cylinder or crank centre of it also, shifting either sole plate a little endways until these two transverse lines come into the same line, which may be ascertained by applying a straight edge across the two sole plates. Strike the rest of the centres across, and drive a pin into each corner of each sole plate, which file down level, so as to serve for points of reference at any future stage; next, try the cylinder, or plumb it on the inside roughly, and see how it is for height, in order to ascertain whether much will be required to be chipped off the bottom, or whether more requires to be chipped off the one side than the other. Chip the cylinder bottom fair; set it in its place, plumb the cylinder very carefully with a straight edge and silk thread, and scribe it so as to bring the cylinder mouth to the right height, then chip the sole plate to suit that height. The cylinder must then be tried on again, and the parts filed wherever they bear hard, until the whole surface is well fitted. Next, chip the place for the framing; set up the framing, and scribe the horizontal part of the jaw with the scriber used for the bottom of the cylinder, the upright part being set to suit the shaft centres, and the angular flange of cylinder, where the stay is attached, having been previously chipped plumb and level. The stake wedges with which the framing is set up preparatorily to the operation of scribing, must be set so as to support equally the superincumbent weight, else the framing will spring from resting unequally, and it will be altogether impossible to fit it well. These directions obviously refer exclusively to the old description of side lever engine with cast iron framing; but there is more art in erecting an engine of that kind with accuracy, than in erecting one of the direct action engines, where it is chiefly turned or bored surfaces that have to be dealt with. 720. _Q._--How do you lay out the positions of the centres of a side lever engine? _A._--In fixing the positions of the centres in side lever engines, it appears to be the most convenient way to begin with the main centre. The height of the centre of the cross head at half stroke above the plane of the main centre is fixed by the drawing of the engine, which gives the distance from the centre of cross head at half stroke to the flange of the cylinder; and from thence it is easy to find the perpendicular distance from the cylinder flange to the plane of the main centre, merely by putting a straight edge along level, from the position of the main centre to the cylinder, and measuring from the cylinder flauge down to it, raising or lowering the straight edge until it rests at the proper measurement. The main centre is in that plane, and the fore and aft position is to be found by plumbing up from the centre line on the sole plate. To find the paddle shaft centre, plumb up from the centre line marked on the edge of the sole plate, and on this line lay off from the plane of the main centre the length of the connecting rod, if that length be already fixed, or otherwise the height fixed in the drawing of the paddle shaft above the main centre. To fix the centre for the parallel motion shaft, when the parallel bars are connected with the cross head, lay off from the plane of main centre the length of the parallel bar from the centre of the cylinder, deduct the length of the radius crank, and plumb up the central line of motion shaft; lay off on this line, measuring from the plane of main centre, the length of the side rod; this gives the centre of parallel motion shaft when the radius bars join the cross head, as is the preferable practice where parallel motions are used. The length of the connecting rod is the distance from the centre of the beam when level, or the plane of the main centre, to the centre of the paddle shaft. The length of the side rods is the distance from the centre line of the beam when level, to the centre of the cross head when the piston is at half stroke. The length of the radius rods of the parallel motion is the distance from the point of attachment on the cross head or side rod, when the piston is at half stroke, to the extremity of the radius crank when the crank is horizontal; or in engines with the parallel motion attached to the cross head, it is the distance from the centre of the pin of the radius crank when horizontal to the centre of the cylinder. Having fixed the centre of the parallel motion shaft in the manner just described, it only remains to put the parts together when the motion is attached to the cross head; but when the motion is attached to the side rod, the end of the parallel bar must not move in a perpendicular line, but in an arc, the versed sine of which bears the same ratio to that of the side lever, that the distance from the top of the side rod to the point of attachment bears to the total length of the side rod. 721. _Q._--How do you ascertain the accuracy of the parallel motion? _A._--The parallel motion when put in its place should be tested by raising and lowering the piston by means of the crane. First, set the beams level, and shift in or out the motion shaft plummer blocks or bearings, until the piston rod is upright. Then move the piston to the two extremes of its motion. If at both ends the cross head is thrown too much out, the stud in the beam to which the motion side rod is attached is too far out, and must be shifted nearer to the main centre; if at the extremities the cross head is thrown too far in, the stud in the beam is not out far enough. If the cross head be thrown in at the one end, and out equally at the other, the fault is in the motion side rod, which must be lengthened or shortened to remedy the defect. 722. _Q._--Will you describe the method pursued in erecting oscillating engines? _A._--The columns here are of wrought iron, and in the case of small engines there is a template made of wood and sheet iron, in which the holes are set in the proper positions, by which the upper and lower frames are adjusted; but in the case of large engines, the holes are set off by means of trammels. The holes for the reception of the columns are cast in the frames, and are recessed out internally: the bosses encircling the holes are made quite level across, and made very true with a face plate, and the pillars which have been turned to a gauge are then inserted. The top frame is next put on, and must bear upon the collars of the columns so evenly, that one of the columns will not be bound by it harder than another. If this point be not attained, the surfaces must be further scraped, until a perfect fit is established. The whole of the bearings in the best oscillating engines are fitted by means of scraping, and on no other mode of fitting can the same reliance be placed for exactitude. 723. _Q._--How do you set out the trunnions of oscillating engines, so that they shall be at right angles with the interior of the cylinder? _A._--Having bored the cylinder, faced the flange, and bored out the hole through which the boring bar passes, put a piece of wood across the mouth of the cylinder, and jam it in, and put a similar piece in the hole through the bottom of the cylinder. Mark the centre of the cylinder upon each of these pieces, and put into the bore of each trunnion an iron plate, with a small indentation in the middle to receive the centre of a lathe, and adjusting screws to bring the centre into any required position. The cylinder must then be set in a lathe, and hung by the centres of the trunnions, and a straight edge must be put across the cylinder mouth and levelled, so as to pass through the line in which the centre of the cylinder lies. Another similar straight edge, and similarly levelled, must be similarly placed across the cylinder bottom, so as to pass through the central line of the cylinder; and the cylinder is then to be turned round in the trunnion centres-the straight edges remaining stationary, which will at once show whether the trunnions are in the same horizontal plane as the centre of the cylinder, and if not, the screws of the plates in the trunnions must be adjusted until the central point of the cylinder just comes to the straight edge, whichever end of the cylinder is presented. To ascertain whether the trunnions stand in a transverse plane, parallel to the cylinder flange, it is only necessary to measure down from the flange to each trunnion centre; and if both these conditions are satisfied, the position of the centres may be supposed to be right. The trunnion bearings are then turned, and are fitted into blocks of wood, in which they run while the packing space is being turned out. Where many oscillating engines are made, a lathe with four centres is used, which makes the use of straight edges in setting out the trunnions superfluous. 724. _Q._--Will you explain how the slide valve of a marine engine is set? _A._--Place the crank in the position corresponding to the end of the stroke, which can easily be done in the shop with a level, or plumb line; but in a steam vessel another method becomes necessary. Draw the transverse centre line, answering to the centre line of the crank shaft, on the sole plate of the engine, or on the cylinder mouth if the engine be of the direct action kind; describe a circle of the diameter of the crank pin upon the large eye of the crank, and mark off on either side of the transverse centre line a distance equal to the semi-diameter of the crank pin. From the point thus found, stretch a line to the edge of the circle described on the large eye of the crank, and bring round the crank shaft till the crank pin touches the stretched line; the crank may thus be set at either end of its stroke. When the crank is thus placed at the end of the stroke, the valve must be adjusted so as to have the amount of lead, or opening on the steam side, which it is intended to give at the beginning of the stroke; the eccentric must then be turned round upon the shaft until the notch in the eccentric rod comes opposite the pin on the valve lever, and falls into gear: mark upon the shaft the situation of the eccentric, and put on the catches in the usual way. The same process must be repeated for going astern, shifting round the eccentric to the opposite side of the shaft, until the rod again falls into gear. In setting valves, regard must of course be had to the kind of engine, the arrangements of the levers, and the kind of valve employed; and in any general instructions it is impossible to specify every modification in the procedure that circumstances may render advisable. 725. _Q._--Is a similar method of setting the valve adopted when the link motion is employed. _A._--Each end of the link of the link motion has the kind of motion communicated to it that is due to the action of the particular eccentric with which that end is in connection. In that form of the link motion in which the link itself is moved up or down, there is a different amount of lead for each different position of the link, since to raise or lower the link is tantamount to turning the eccentric round on the shaft. In that form of the link motion in which the link itself is not raised or lowered, but is susceptible of a motion round a centre in the manner of a double ended lever, the lead continues uniform. In both forms of the link motion, as the stroke of the valve may be varied to any required extent while the lap is a constant quantity, the proportion of the lap relatively to the stroke of the valve may also be varied to any required extent, and the amount of the lap relatively with the stroke of the valve determines the amount of the expansion. In setting the valve when fitted with the link motion, the mode of procedure is much the same as when it is moved by a simple eccentric. The first thing is to determine if the eccentric rods are of the proper length, and this is done by setting the valve at half stroke and turning round the eccentric, marking each extremity of the travel of the end of the rod. The valve attachment should be midway between these extremes; and if it is not so, it must be made so by lengthening or shortening the rod. The forward and backward eccentric rods are to be adjusted in this way, and this being done, the engine is to be put to the end of the stroke, and the eccentric is to be turned round until the amount of lead has been given that is desired. The valve must be tried by turning the engine round to see that it is right at both centres, for going ahead and also for going astern. In some examples of the link motion, one of the eccentric rods is made a little longer than the other, and the position of the point of suspension or point of support powerfully influences the action of the link in certain cases, especially if the link and this point are not in the same vertical line. To reconcile all the conditions proper to the satisfactory operation of the valve in the construction of the link motion, is a problem requiring a good deal of attention and care for its satisfactory solution; and to make sure that this result is attained, the engine must be turned round a sufficient number of times to enable us to ascertain if the valve occupies the desired position, both at the top and bottom centres, whether the engine is going ahead or astern. This should also be tried with the starting handle in the different notches, or, in other words, with the sliding block in the slot or opening of the link in different positions. MANAGEMENT OF MARINE BOILERS. 726. _Q._--You have already stated that the formation of salt or scale in marine boilers is to be prevented by blowing out into the sea at frequent intervals a portion of the concentrated water. Will you now explain how the proper quantity of water to be blown out is determined? _A._--By means of the salinometer, which is an instrument for determining the density of the water, constructed on the principle of the hydrometer for telling the strength of spirits. Some of the water is drawn off from the boiler from time to time, and the salinometer is immersed in it after it has been cooled. By the graduations of the salinometer the saltness of this water is at once discovered; and if the saltness exceeds 8 ounces of salt in the gallon, more water should be blown out of the boiler to be replenished with fresher water from the sea, until the prescribed limit of freshness is attained. Should the salinometer be accidentally broken, a temporary one may be constructed of a phial weighted with a few grains of shot or other convenient weight. The weighted phial is first to be floated in fresh water, and its line of floatation marked; then to be floated in salt water, and its line of floatation marked; and another mark of an equal height above the salt water mark will be the blow off point. 727. _Q._--HOW often should boilers be blown off in order to keep them free from incrustation? _A._--Flue boilers generally require to be blown off about twice every watch, or about twice in the four hours; but tubular boilers may require to be blown off once every twenty minutes, and such an amount of blowing off should in every case be adopted, as will effectually prevent any injurious amount of incrustation. 728. _Q._--In the event of scale accumulating on the flues of a boiler, what is the best way of removing it? _A._--If the boilers require to be scaled, the best method of performing the operation appears to be the following:--Lay a train of shavings along the flues, open the safety valve to prevent the existence of any pressure within the boiler, and light the train of shavings, which, by expanding rapidly the metal of the flues, while the scale, from its imperfect conducting power, can only expand slowly, will crack off the scale; by washing down the flues with a hose, the scale will be carried to the bottom of the boiler, or issue, with the water, from the mud-hole doors. This method of scaling must be practised only by the engineer himself, and must not be intrusted to the firemen who, in their ignorance, might damage the boiler by overheating the plates. It is only where the incrustation upon the flues is considerable that this method of removing it need be practised; in partial cases the scale may be chipped off by a hatched faced hammer, and the flues may then be washed down with the hose in the manner before described. 729. _Q._--Should the steam be let out of the boiler, after it has blown out the water, when the engine is stopped? _A._--No; it is better to retain the steam in the boiler, as the heat and moisture it occasions soften any scale adhering to the boiler, and cause it to peel off. Care must, however, be taken not to form a vacuum in the boiler; and the gauge cocks, if opened, will prevent this. 730. _Q._--Are tubular boilers liable to the formation of scale in certain places, though generally free from it? _A._--In tubular boilers a good deal of care is required to prevent the ends of the tubes next the furnace from becoming coated with scale. Even when the boiler is tolerably clean in other places the scale will collect here; and in many cases where the amount of blowing off previously found to suffice for flue boilers has been adopted, an incrustation five eighths of an inch in thickness has formed in twelve months round the furnace ends of the tubes, and the stony husks enveloping them have actually grown together in some parts so as totally to exclude the water. 731. _Q._--When a tubular boiler gets incrusted in the manner you have described, what is the best course to be adopted for the removal of the scale? _A._--When a boiler gets into this state the whole of the tubes must be pulled out, which may be done by a Spanish windlass combined with a pair of blocks; and three men, when thus provided, will be able to draw out from 50 to 70 tubes per day,--those tubes with the thickest and firmest incrustations being, of course, the most difficult to remove. The act of drawing out the tubes removes the incrustation; but the tubes should afterward be scraped by drawing them backward and forward between the old files, fixed in a vice, in the form of the letter V. The ends of the tube should then be heated and dressed with the hammer, and plunged while at a blood heat into a bed of sawdust to make them cool soft, so that they may be riveted again with facility. A few of the tubes will be so far damaged at the ends by the act of drawing them out, as to be too short for reinsertion: this result might be to a considerable extent obviated by setting the tube plates at different angles, so that the several horizontal rows of tubes would not be originally of the same length, and the damaged tubes of the long rows would serve to replace the short ones; but the practice would be attended with other inconveniences. 732. _Q._--Is there no other means of keeping boilers free from scale than by blowing off? _A._--Muriatic acid, or muriate of ammonia, commonly called sal-ammoniac, introduced into a boiler, prevents scale to a great extent; but it is liable to corrode the boiler internally, and also to damage the engine, by being carried over with the steam; and the use of such intermixtures does not appear to be necessary, if blowing off from the surface of the water is largely practised. In old boilers, however, already incrusted with scale, the use of muriate of ammonia may sometimes be advantageous. 733. _Q._--Are not the tubes of tubular boilers liable to be choked up by deposits of soot? _A._--The soot which collects in the inside of the tubes of tubular boilers is removed by means of a brush, like a large bottle brush; and the carbonaceous scale, which remains adhering to the interior of the tubes, is removed by a circular scraper. Ferules in the tubes interfere with the action of this scraper, and in the case of iron tubes ferules are now generally discarded; but it will sometimes be necessary to use ferules for iron tubes, where the tubes have been drawn and reinserted, as it may be difficult to refix the tubes without such an auxiliary. Tubes one tenth of an inch in thickness are too thin: one eighth of an inch is a better thickness, and such tubes will better dispense with the use of ferules, and will not so soon wear into holes. 734. _Q._--If the furnace or flue of a boiler be injured, how do you proceed to repair it? _A._--If from any imperfection in the roof of a furnace or flue a patch requires to be put upon it, it will be better to let the patch be applied upon the upper, rather than upon the lower, surface of the plate; as if applied within the furnace a recess will be formed for the lodgment of deposit, which will prevent the rapid transmission of the heat in that part; and the iron will be very liable to be again burned away. A crack in a plate may be closed by boring holes in the direction of the crack, and inserting rivets with large heads, so as to cover up the imperfection. If the top of the furnace be bent down, from the boiler having been accidentally allowed to get short of water, it may be set up again by a screw jack,--a fire of wood having been previously made beneath the injured plate; but it will in general be nearly as expeditious a course to remove the plate and introduce a new one, and the result will be more satisfactory. 735. _Q._--In the case of the chimney being carried away by shot or otherwise, what course would you pursue? _A._--In some cases of collision, the funnel is carried away and lost overboard, and such cases are among the most difficult for which a remedy can be sought. If flame come out of the chimney when the funnel is knocked away, so as to incur the risk of setting the ship on fire, the uptake of the boiler must be covered over with an iron plate, or be sufficiently covered to prevent such injury. A temporary chimney must then be made of such materials as are on board the ship. If there are bricks and clay or lime on board, a square chimney may be built with them, or, if there be sheet iron plates on board, a square chimney may be constructed of them. In the absence of such materials, the awning stanchions may be set up round the chimney, and chain rove in through among them in the manner of wicker work, so as to make an iron wicker chimney, which may then be plastered outside with wet ashes mixed with clay, flour, or any other material that will give the ashes cohesion. War steamers should carry short spare funnels, which may easily be set up should the original funnel be shot away; and if a jet of steam be let into the chimney, a very short and small funnel will suffice for the purpose of draught. MANAGEMENT OF MARINE ENGINES. 736. _Q._--What are the most important of the points which suggest themselves to you in connection with the management of marine engines? _A._--The attendants upon engines should prepare themselves for any casualty that may arise, by considering possible cases of derangement, and deciding In what way they would act should certain accidents occur. The course to be pursued must have reference to particular engines, and no general rules can therefore be given; but every marine engineer should be prepared with the measures to be pursued in the emergencies in which he may be called upon to act, and where everything may depend upon his energy and decision. 737. _Q._--What is the first point of a marine engineer's duty? _A._--The safe custody of the boiler. He must see that the feed is maintained, being neither too high nor too low, and that blowing out the supersalted water is practised sufficiently. The saltness of the water at every half hour should be entered in the log book, together with the pressure of steam, number of revolutions of the engine, and any other particulars which have to be recorded. The economical use of the fuel is another matter which should receive particular attention. If the coal is very small, it should be wetted before being put on the fire. Next to the safety of the boiler, the bearings of the engine are the most important consideration. These points, indeed, constitute the main parts of the duty of an engineer, supposing no accident to the machinery to have taken place. 738. _Q._--If the eccentric catches or hoops were disabled, how would you work the valve? _A._--If the eccentric catches or hoops break or come off, and the damage cannot readily be repaired, the valve may be worked by attaching the end of the starting handle to any convenient part of the other engine, or to some part in connection with the connecting rod of the same engine. In side lever engines, with the starting bar hanging from the top of the diagonal stay, as is a very common arrangement, the valve might be wrought by leading a rope from the side lever of the other engine through blocks so as to give a horizontal pull to the hanging starting bar, and the bar could be brought back by a weight. Another plan would be, to lash a piece of wood to the cross tail butt of the damaged engine, so as to obtain a sufficient throw for working the valve, and then to lead a piece of wood or iron, from a suitable point in the piece of wood attached to the cross tail, to the starting handle, whereby the valve would receive its proper motion. In oscillating engines it is easy to give the required motion to the valve, by deriving it from the oscillation of the cylinder. 739. _Q._--What would you do if a crank pin broke? _A._--If the crank pin breaks in a paddle vessel with two engines, the other engine must be made to work one wheel. In a screw vessel the same course may be pursued, provided the broken crank is not the one through which the force of the other engine is communicated to the screw. In such a case the vessel will be as much disabled as if she broke the screw shaft or screw. 740. _Q._--Will the unbroken engine, in the case of disarrangement of one of the two engines of a screw or paddle vessel, be able of itself to turn the centre? _A._--It will sometimes happen, when there is much lead upon the slide valve, that the single engine, on being started, cannot be got to turn the centre if there be a strong opposing wind and sea; the piston going up to near the end of the stroke, and then coming down again without the crank being able to turn the centre. In such cases, it will be necessary to turn the vessel's head sufficiently from the wind to enable some sail to be set; and if once there is weigh got upon the vessel the engine will begin to work properly, and will continue to do so though the vessel be put head to wind as before. 741. _Q._--What should be done if a crack shows itself in any of the shafts or cranks? _A._--If the shafts or cranks crack, the engine may nevertheless be worked with moderate pressure to bring the vessel into port; but if the crack be very bad, it will be expedient to fit strong blocks of wood under the ends of the side levers, or other suitable part, to prevent the cylinder bottom or cover from being knocked out, should the damaged part give way. The same remark is applicable when flaws are discovered in any of the main parts of the engine, whether they be malleable or cast iron; but they must be carefully watched, so that the engines may be stopped if the crack is extending further. Should fracture occur, the first thing obviously to be done is to throw the engines out of gear; and should there be much weigh on the vessel, the steam should at once be thrown on the reverse side of the piston, so as to counteract the pressure of the paddle wheel. 742. _Q._--Have you any information to offer relative to the lubrication of engine bearings? _A._--A very useful species of oil cup is now employed in a number of steam vessels, and which, it is said, accomplishes a considerable saving of oil, at the same time that it more effectually lubricates the bearings. A ratchet wheel is fixed upon a little shaft which passes through the side of the oil cup, and is put into slow revolution by a pendulum attached to its outside and in revolving it lifts up little buckets of oil and empties them down a funnel upon the centre of the bearing. Instead of buckets a few short pieces of wire are sometimes hung on the internal revolving wheel, the drops of oil which adhere on rising from the liquid being deposited. upon a high part set upon the funnel, and which, in their revolution, the hanging wires touch. By this plan, however, the oil is not well supplied at slow speeds, as the drops fall before the wires are in proper position for feeding the journal. Another lubricator consists of a cock or plug inserted in the neck of the oil cup, and set in revolution by a pendulum and ratchet wheel, or any other means. There is a small cavity in one side of the plug, which is filled with oil when that side is uppermost, and delivers the oil through the bottom pipe when it comes opposite to it. 743. _Q._--What are the prevailing causes of the heating of bearings? _A._--Bad fitting, deficient surface, and too tight screwing down. Sometimes the oil hole will choke, or the syphon wick for conducting the oil from the oil cup into the central pipe leading to the bearing will become clogged with mucilage from the oil. In some cases bearings heat from the existence of a cruciform groove on the top brass for the distribution of the oil, the effect of which is to leave the top of the bearings dry. In the case of revolving journals the plan for cutting a cruciform channel for the distribution of the oil does not do much damage; but in other cases, as in beam journals, for instance, it is most injurious, and the brasses cannot wear well wherever the plan is pursued. The right way is to make a horizontal groove along the brass where it meets the upper surface of the bearing, so that the oil may be all deposited on the highest point of the journal, leaving the force of gravity to send it downward. This channel should, of course, stop short a small distance from each flange of the brass, otherwise the oil would run out at the ends. 744. _Q._--If a bearing heats, what is to be done? _A._--The first thing is to relax the screws, slow or stop the engine, and cool the bearing with water, and if it is very hot, then hot water may be first employed to cool it, and then cold. Oil with sulphur intermingled is then to be administered, and as the parts cool down, the screws may be again cautiously tightened, so as to take any jump off the engine from the bearing being too slack. The bearings of direct acting screw engines require constant watching, as, if there be any disposition to heat manifested by them, they will probably heat with great rapidity from the high velocity at which the engines work. Every bearing of a direct acting screw engine should have a cock of water laid on to it, which may be immediately opened wide should heating occur; and it is advisable to work the engine constantly, partly with water, and partly with oil applied to the bearings. The water and oil are mixed by the friction into a species of soap which both cools and lubricates, and less oil moreover is used than if water were not employed. It is proper to turn off the water some time before the engine is stopped, so as to prevent the rusting of the bearings. MANAGEMENT OF LOCOMOTIVES. 745. _Q._--What are the chief duties of the engine driver of a locomotive? _A._--His first duties are those which concern the safety of the train; his next those which concern the safety and right management of the engine and boiler. The engine driver's first solicitude should be relative to the observation and right interpretation of the signals; and it is only after these demands upon his attention have been satisfied, that he can look to the state of his engine. 746. _Q._--As regards the engine and boiler, what should his main duties be? _A._--The engineer of a locomotive should constantly be upon the foot board of the engine, so that the regulator, the whistle or the reversing handle may be used instantly, if necessary; he must see that the level of the water in the boiler is duly maintained, and that the steam is kept at a uniform pressure. In feeding the boilers with water, and the furnaces with fuel, a good deal of care and some tact are necessary, as irregularity in the production of steam will often occasion priming, even though the water be maintained at a uniform level; and an excess of water will of itself occasion priming, while a deficiency is a source of obvious danger. The engine is generally furnished with three gauge cocks, and water should always come out of the second gauge cock, and steam out of the top one when the engine is running: but when the engine is at rest, the water in the boiler is lower than when in motion, so that when the engine is at rest, the water will be high enough if it just reaches to the middle gauge cock. In all boilers which generate steam rapidly, the volume of the water is increased by the mingled steam, and in feeding with cold water the level at first falls; but it rises on opening the safety valve, which causes the steam in the water to swell to a larger volume. In locomotive boilers, the rise of the water level due to the rapid generation of steam is termed "false water." To economize fuel, the variable expansion gear, if the engine has one, should be adjusted to the load, and the blast pipe should be worked with the least possible contraction; and at stations the damper should be closed to prevent the dissipation of heat. 747. _Q._--In starting from a station, what precautions should be observed with respect to the feed? _A._--In starting from a station, and also in ascending inclined planes, the feed water is generally shut off; and therefore before stopping or ascending inclined planes, the boiler should be well filled up with water. In descending inclined planes an extra supply of water may be introduced into the boiler, and the fire may be fed, as there, is at such times a superfluity of steam. In descending inclined planes the regulator must be partially closed, and it should be entirely closed if the plane be very steep. The same precaution should be observed in the case of curves, or rough places on the line, and in passing over points or crossings. 748. _Q._--In approaching a station, how should the supply of water and fuel be regulated? _A._--The boiler should be well filled with water on approaching a station, as there is then steam to spare, and additional water cannot be conveniently supplied when the engine is stationary. The furnace should be fed with small quantities of fuel at a time, and the feed should be turned off just before a fresh supply of fuel is introduced. The regulator may, at the same time, be partially closed; and if the blast pipe be a variable one, it will be expedient to open it widely while the fuel is being introduced, to check the rush of air in through the furnace door, and then to contract it very much so soon as the furnace door is closed, in order to recover the fire quickly. The proper thickness of coke upon the grate depends upon the intensity of the draught; but in heavily loaded engines it is usually kept up to the bottom of the fire door. Care, however, must be taken that the coke does not reach up to the bottom row of tubes so as to choke them up. The fuel is usually disposed on the grate like a vault; and if the fire box be a square one, it is heaped high in the corners, the better to maintain the combustion. 749. _Q._--How can you tell whether the feed pumps are operating properly? _A._--To ascertain whether the pumps are acting well, the pet cock must be turned, and if any of the valves stick they will sometimes be induced to act again by working with the pet cock open, or alternately open and shut. Should the defect arise from a leakage of steam into the pump, which prevents the pump from drawing, the pet cock remedies the evil by permitting the steam to escape. 750. _Q._--What precautions should be taken against priming in locomotives? _A._--Should priming occur from the water in the boiler being dirty, a portion of it may be blown out; and should there be much boiling down through the glass gauge tube, the stop cock may be partially closed. The water should be wholly blown out of locomotive boilers three times a week, and at those times two mud-hole doors at opposite corners of the boiler should be opened, and the boiler be washed internally by means of a hose. If the boiler be habitually fed with dirty water, the priming will be a constant source of trouble. 751. _Q._--What measures should the locomotive engineer take, to check the velocity of the train, on approaching a station where he has to stop? _A._--On approaching a station the regulator should be gradually closed, and it should be completely shut about half a mile from the station if the train be a very heavy one: the train may then be brought to rest by means of the breaks. Too much reliance, however, must not be put upon the breaks, as they sometimes give way, and in frosty weather are nearly inoperative. In cases of urgency the steam may be thrown upon the reverse side of the piston, but it is desirable to obviate this necessity as far as possible. At terminal stations the steam should be shut off earlier than at roadside stations, as a collision will take place at terminal stations if the train overshoots the place where it ought to stop. There should always be a good supply of water when the engine stops, but the fire may be suffered gradually to burn low toward the conclusion of the journey. 752. _Q._--What is the duty of an engine man on arriving at the end of his journey? _A._--So soon as the engine stops it should be wiped down, and be then carefully examined: the brasses should be tried, to see whether they are slack or have been heating; and, by the application of a gauge, it should be ascertained occasionally whether the wheels are square on their axles, and whether the axles have end play, which should be prevented. The stuffing boxes must be tightened, and the valve gear examined, and the eccentrics be occasionally looked at to see that they have not shifted on their axles, though this defect will be generally intimated by the irregular beating of the engines. The tubes should also be examined and cleaned out, and the ashes emptied out of the smoke box through the small ash door at the end. If the engine be a six-wheeled one, with the driving wheels in the middle, it will be liable to pitch, and oscillate if too much weight be thrown upon the driving wheels; and where such faults are found to exist, the weight upon the drivings wheels should be diminished. The practice of blowing off the boiler by the steam, as is always done in marine boilers, should not be permitted as a general rule in locomotive boilers, when the tubes are of brass and the fire box of copper; but when the tubes and fire boxes are of iron, there will not be an equal risk of injury. Before starting on a journey, the engine man should take a summary glance beneath the engine--but before doing so he ought to assure himself that no other engine is coming up at the time. The regulator, when the engine is standing, should be closed and locked, and the eccentric rod be fixed out of gear, and the tender break screwed down; the cocks of the oil vessels should at the same time be shut, but should all be opened a short time before the train starts. 753. _Q._--What should be done if a tube bursts in the boiler? _A._--When a tube bursts, a wooden or iron plug must be driven into each end of it, and if the water or steam be rushing out so fiercely that the exact position of the imperfection cannot be discovered, it will be advisable to diminish the pressure by increasing the supply of feed water. Should the leak be so great that the level of the water in the boiler cannot be maintained, it will be expedient to drop the bars and quench the fire, so as to preserve the tubes and fire box from injury. 754. _Q._--If any of the working parts of a locomotive break or become deranged, what should be done? _A._--Should the piston rod or connecting rod break, or the cutters fall out or be clipped off--as sometimes happens to the piston cutter when the engine is suddenly reversed upon a heavy train--the parts should be disconnected, if the connection cannot be restored, so as to enable one engine to work; and of course the valve of the faulty engine must be kept closed. If one engine has not power enough to enable the train to proceed with the blast pipe full open, the engine may perhaps be able to take on a part of the carriages, or it may run on by itself to fetch assistance. The same course must be pursued if any of the valve gearing becomes deranged, and the defects cannot be rectified upon the spot. 755. _Q._--What are the most usual causes of railway collisions? _A._--Probably fogs and inexactness in the time kept by the trains. Collisions have sometimes occurred from carriages having been blown from a siding on to the rails by a high wind; and the slippery state of the rails, or the fracture of a break, has sometimes occasioned collisions at terminal stations. Collision has also repeatedly taken place from one engine having overtaken another, from the failure of a tube in the first engine, or from some other slight disarrangement; and collision has also taken place from the switches having been accidentally so left as to direct the train into a siding, instead of continuing it on the main line. Every train now carries fog signals, which are detonating packets, which are fixed upon the rails in advance or in the rear of a train which, whether from getting off the rails or otherwise, is stopped upon the line, and which are exploded by the wheels of any approaching train. 756. _Q._--What other duties of an engine-driver are there deserving attention? _A._--They are too various to be all enumerated here, and they also vary somewhat with the nature of the service. One rule, however, of universal application, is for the driver to look after matters himself, and not delegate to the stoker the duties which the person in charge of the engine should properly perform. Before leaving a station, the engine-driver should assure himself that he has the requisite supply of coke and water. Besides the firing tools and rakes for clearing the tubes, he should have with him in the tender a set of signal lamps and, torches, for tunnels and for night, detonating signals, screw keys, a small tank of oil, a small cask of tallow, and a small box of waste, a coal hammer, a chipping hammer, some wooden and iron plugs for the tubes, and an iron tube holder for inserting them, one or two buckets, a screw jack, wooden and iron wedges, split wire for pins, spare cutters, some chisels and files, a pinch bar, oil cans and an oil syringe, a chain, some spare bolts, and some cord, spun yarn, and rope. INDEX. Accidents in steam vessels, proper preparation for. Admiralty rule for horse power. Adhesion of wheels of locomotives to rails. Air, velocity of, entering a vacuum, required for combustion of coal; law of expansion of, by heat; Air pump, description of, action of; proper dimensions of. Air pump of marine engines, details of. Air pump of oscillating engine. Air pump of direct acting screw engines. Air pumps made both single and double acting, difference of, explained. Air pumps, double acting valves of, bad vacuum in; causes and remedy. Air pump rods, brass or copper, in marine engines. Air pump bucket, valves of. Air pump, connecting rod and cross head of oscillating engine. Air pump rod of oscillating engine. Air pump arm. Air vessels applied to suction side of pumps. "Alma," engine of, by Messrs. John Bourne & Co. "Amphion," engines of. Amoskeag steam fire engine. Angle iron in boilers, precautions respecting. Apparatus for raising screw propeller. Atmospheric valve. Atmospheric resistance to railway trains. Auxiliary power, screw vessels with. Axle bearings of locomotives. Axle guards. Axles and wheels of modern locomotives. "Azof," slide valve of. Babbitt's metal, how to compound. Balance piston to take pressure off slide valve. Ball valves. Barrel of boiler of modern locomotives. Beam, working of land engine, main or working strength proper for. Bearings of engines or other machinery, rule for determining proper surface of. Bearings, heating of, how to prevent or remedy, journals should always bottom, as, if they grip on the sides, the pressure is infinite. Beattie's screw. Belidor's valves might be used for foot and delivery valves. Bell-metal, composition of. Blast pipe of locomotives, description of. Blast in locomotives, exhaustion produced by, proper construction of the blast pipe; the blast pipe should be set below the root of the chimney so much that the cone of escaping steam shall just fill the chimney. Blast pipe with variable orifice, at one time much used. Blow-off cock of locomotives. Blow-off cocks of marine boilers, proper construction of. Blow-off cocks, description of. Blowing off supersalted water from marine boilers. Blowing off, estimate of heat lost by, mode of. Blow through valve, description of. Blowing furnaces, power necessary for. Bodies, falling, laws of. Bodmer, expansion valve by. Boilers, general description of: the wagon boiler, the Cornish boiler; the marine flue boiler; the marine tubular boiler; locomotive boiler--_see_ Locomotives. Boilers proportions of: heating surface of, fire grate, surface of; consumption of fuel on each square foot of fire bars in wagon, Cornish, and locomotive boilers; calorimmeter and vent of boilers; comparison of proportions of wagon, flue, and tubular boilers; evaporative power of boilers; power generated by evaporation of a cubic foot of water; proper proportions of modern marine boilers both flue and tubular; modern locomotive boilers; exhaustion produced by blast in locomotives; increased evaporation from increased exhaustion; strength of boilers; experiments on, by Franklin Institute; by Mr. Fairbairn; mode of computing strength of boilers; staying of. Boilers, marine, prevented from salting by blowing off, early locomotive and contemporaneous marine boilers compared; chimneys of land; rules for proportions of chimneys; chimneys of marine boilers. Boilers, constructive details of: riveting and caulking of land boilers, proving of; seams payed with mixture of whiting and linseed oil; setting of wagon boilers; riveting of marine boilers; precautions respecting angle iron; how to punch the rivet holes and shear edges of plates; setting of marine boilers in wooden vessels; mastic cement for setting marine boilers; composition of mastic cement; best length of furnace; configuration of furnace bars; advantages and construction of furnace bridges; various forms of dampers; precautions against injury to boilers from intense heat; tubing of boilers; proper mode of staying tube plates; proper mode of constructing steamboat chimneys; waste steam-pipe and funnel casing; telescope chimneys; formation of scale in marine boilers; injury of such incrustations; amount of salt in sea water; saltness permissible in boilers; amount of heat lost by blowing off; mode of discharging the supersalted water; Lamb's scale preventer; internal corrosion of marine boilers; causes of internal corrosion; surcharged steam produced from salt water; stop valves between boilers; safety or escape valve on feed pipe; locomotive boilers consist of the fire box, barrel for holding tubes, and smoke box; dimensions of the barrel and thickness of plates; mode of staying fire box and furnace crown; fire bars, ash box, and chimney; steam dome used only in old engines; manhole, mudholes, and blow-oft cock; tube plate, and mode of securing tubes; expanding mandrels; various forms of regulator. Boilers of modern locomotives. Boiler, the, proper care of, the first duty of the engineer. Bolts, proper proportions of. Boring of cylinders. Boulton and Watt's rules for fly wheel, proportions of marine flue boilers; rule for proportions of chimneys of land boilers; of marine boilers; experiments on the resistance of vessels in water. Bourdon's steam and vacuum gauges. Bourne, expansion valves by. Bourne, Messrs. J. & Co., direct acting screw engines by. Brass for bearings, composition of. Brazing solders. Bridges in furnaces, benefits of. Burning of boilers, precautions against. Bursting velocity of fly wheel, and of railway wheels. Bursting of boilers, causes of; precautions against; may be caused by accumulations of salt. Butterfly valves of air pump. Cabrey, expansion valve by. Calorimeter of boilers, definition of. Cams, proper forms of. Cast iron, strength of, proportions of cast iron beams; effects of different kinds of strains on beams; strength to resist shocks not proportional to strength to resist strains; to attain maximum strength should be combined with wrought iron. Casting of cylinders. Case-hardening, how to accomplish. Cataract, explanation of nature and uses of. Caulking of land boilers. Cement, mastic, for setting marine boilers. Central forces. Centre of pressure of paddle wheels. Centres of gravity, gyration and oscillation. Centres for fixing arms of paddle wheel. Centres of an engine, how to lay off. Centrifugal force, nature of, rule for determining; bursting velocity of fly wheel; and of railway wheels. Centrifugal pump will supersede common pump. Centripetal force, nature of. Chimney of locomotives. Chimney of steam vessels, what to do if carried away. Chimneys of land boilers, Boulton and Watt's rule for proportions of; of marine boilers. Chimneys, exhaustion produced by, high and wide chimneys in locomotives injurious. Chimneys of steamboats, telescope. Clark's patent steam fire regulator. Coal, constituents of, combustion of air required for; evaporative efficacy of; of wood, turf, and coke. Cocks, proper construction of. Cog wheels for screw engines. Coke, evaporative efficacy of. Cold water pump, description of, rule for size of. Combustion, nature of. Combustion of coal, air required for. Combustion, slow and rapid, comparative merits of, rapid combustion necessary in steam vessels, and enables less heating, surface in the boiler to suffice. Conchoidal propeller. Condensation of steam, water required for. Condenser, description of, action of; proper dimensions of. Condenser of oscillating engine. Condenser of direct acting screw engine. Condensing engine, definition of. Condensing water, how to provide when deficient. Conical pendulum or governor. Connecting rod, description of, strength proper for. Connecting rod of direct acting screw engines, of locomotives. Consumption of fuel on each square foot of fire bars in wagon, Cornish, and locomotive boilers. Copper, strength of. Corliss's steam engine. Corrosion produced by surcharged steam. Corrosion of marine boilers, causes of. Cost of locomotives. Cotton spinning, power necessary for. Counter for counting strokes of an engine. Crank, description of, unequal leverage of, corrected by fly wheel; no power lost by; action of; strength proper for. Crank of direct acting screw engines. Crank pin, strength proper for. Crank pin of direct acting screw engines. Cranked axle of locomotives. Cross head, description of, strength proper for. Cross head of direct acting screw engines. Cross tail, description of. Cylinder, description of, strength proper for. Cylinder of oscillating engine, of direct acting screw engine. Cylinders should have a steam jacket, and be felted and planted, should have escape valves. Cylinders of locomotives should be large, proper arrangement of. Cylinders, how to cast, how to bore; how to grind. Cylinder jacket, advantages of. Damper. Dampers, various forms of. Deadwood, hole in, for screw. Delivery valve, description of. Delivery or discharge valves, proper dimensions of. Delivery valves might be made on Belidor's plan. Delivery valves in mouth of air pump, of india rubber. Direct acting screw engines should be balanced. Direct acting screw engine by Messrs. John Bourne &, Co., cylinder; discs; guides; screw shaft brasses; air pump; slide valve; balance piston; connecting rod; piston rods; cross head; air pump arm; feed pump; crank pin; screw shaft; thrust plummer block; link motion; screw propeller. Discharge valves. Disc valves of india rubber for air pumps. Discs of direct acting screw engine instead of crank. Dodds, expansion valve by. Double acting engines, definition of. Double acting air pumps, valves of; faults of. Draw bolt. Dredging earth out of rivers, power necessary for. Driving wheels of locomotives. Driving piles, power necessary for. Duplex pump, Worthington's. Dundonald, Earl of, screw by. Duty of engines and boilers, how the duty is ascertainable. Dynamometer, description of. Dynamometric power of screw vessels. Eccentric, description of, sometimes made loose for backing. Eccentric and eccentric rod of oscillating engine. Eccentric notch should be fitted with a brass bush. Eccentric straps of locomotives, rods of locomotives. Eccentrics of locomotives, how to readjust. Economy of fuel in steam vessels. Edwards, expansion valve by. Elasticity, limits of. Engine, high pressure, definition of, low pressure, definition of. Engines, classification of, rotative, definition of; rotatory, definition of; single acting, definition of; double acting, definition of; mode of erecting in a vessel; how to refix if they have become loose. Engineers of steam vessels should make proper preparation for accidents. Equilibrium slide valve, grid-iron valve. Erecting engines in a vessel. Erection of engines in the workshop. Escape valve on feed pipe. Escape valves for letting water out of cylinders. Evaporative efficacy of coal, of wood, turf, and coke. Evaporative power of boilers, power generated by evaporation of a cubic foot of water; increase of evaporation due to increased exhaustion in locomotives. Excavator, Otis's. Exhaustion produced by chimneys, by the blast in locomotives; increased evaporation from increased exhaustion. Expanding mandrels for tubing boilers. Expansion of air by heat. Expansion of surcharged steam by heat. Expansion of steam, pressure of steam inversely as the space occupied; law of expansion; rule for computing the increase of efficiency produced by working expansively; necessity of efficient provisions against refrigeration in working expansively; advantages of steam jacket; Forms of apparatus for working expansively: lap on the slide valve wire drawing the steam; Cornish expansion valve, in rotative engines worked by a cam; mode of varying the degree of expansion; proper forms of cams; the link motion; expansion valves, by Cabrey, Fenton, Dodds, Farcot, Edwards, Lavagrian, Bodmer, Meyer, Hawthorn, Gonzenbach, and Bourne. Expansion joint in valve casing. Expansion valves, Cornish, the link motion; by Cabrey, Fenton, Dodds, Farcot, Edwards, Lavagrian, Bodmer, Meyer, Hawthorn, Gouzenbach, and Bourne. Explosions of boilers, causes of explosions; precautions against; dangers of accumulations of salt. Face plates or planometers. Falling bodies, laws of. Farcot, expansion valve by. Feathering paddle wheels, description of, details of. Feed pump, description of, action of; proper dimensions of; rule for proportioning. Feed pump plunger, and valves. Feed pumps of locomotives, details of. Feed pumps of direct acting screw engines. Fenton, expansion valve by. Fire bars of locomotives. Fire box of locomotives, mode of staying. Fire box of modern locomotives. Fire engines, cost of running. Fire grate surface of boilers. Fire grate in locomotives should be of small area, coke proper to be burned per hour on each square foot of bars. Firing furnaces, proper mode of. Flaws in valves or cylinders, how to remedy. Float for regulating water level in boilers. Floats of paddle. Floats of paddle wheels, increased resistance of, if oblique, floats should be large. Fly wheel corrects unequal leverage of crank, proper energy for; Boulton and Watt's rule for; bursting velocity of; description of; action of, in redressing irregularities of motion. Foot valve, description of, proper dimensions of. Foot valves might be made on Belidor's plan, of india rubber. Frame at stern for holding screw propeller. Framing of locomotives. Framing of oscillating engine. Franklin Institute, experiments on steam by. French Academy, experiments on steam by. Friction, nature of, does not vary as the rubbing surfaces, but as the retaining pressure; does not increase with the velocity per unit of distance, but increases with the velocity per unit of time; measures of friction; effect of unguents; kind of unguent should vary with the pressure; Morin's experiments; rule for determining proper surfaces of bearings; friction of rough surfaces. Friction of the water the main cause of the resistance of vessels of good shape. Fuel burnt on each square foot of fire bars in wagon, Cornish, and locomotive boilers, economy of, in steam vessels. Funnel casing. Funnel, what to do if carried away. Funnels of steam boats. _See_ Chimneys. Furnaces, proper mode of firing, smoke burning: Williams's argand; Prideaux's; Boulton and Watt's dead plate; revolving crate; Juckes's; Maudslay's; Hull's, Coupland's, Godson's, Robinson's, Stevens's, Hazeldine's, &c.. Furnaces of marine boilers, proper length of. Furnace bridges, benefits of. Fusible metal plugs useless as antidotes to explosions. Gauges, vacuum, steam; gauge cocks and glass tubes for showing level of water in boiler, description of. Gauge cocks for showing level of water in boiler. Gearing for screw engines. Gibs and cutters, strengths proper for. Giffard's injector. Glass tubes for showing water level in boilers. Glass tube cocks. Gonzeubach, expansion valve by. Gooch's indicator. Gooch's locomotive. Governor or conical pendulum, description of. Governor, Porter's patent. Gravity, centre of. "Great Western," boilers of, by Messrs. Maudslay. Gridiron valve. Griffith's screw. Grinding corn, power necessary for. Grinding of cylinders. Gudgeons, strength proper for. Guides of locomotives. Guides of direct acting screw engine. Gun metal, strength of. Gyration, centre of. Harvey and West's pump valves. Hawthorn, expansion valve by. Heat, latent, definition of. Heat, specific, definition of. Heat, Regnault's experiments on. Heat, loss of, by blowing off marine boilers. Heating surface of boilers. Heating surface per square foot of fire bars in locomotives, a cubic foot of water evaporates by five square feet of heating surface. Heating of bearings, causes of, bearings should always be slack at the sides, else the pressure is infinite. High pressure engine, definition of. High pressure engines, power of. High speed engines, arrangements proper for high speeds. Hoadley's portable engine. Hodgson's screw. Hoe & Co.'s steam engine. Holding down bolts of marine engines, or bolts for securing engines to hull. Holms's screw propeller. Horses power, definition of, nominal horse power; actual power ascertained by the indictator; Admiralty rule for. Hot water or feed pump, description of. Hot well, description of. Increasing pitch of screw. Incrustation in boilers. _See_ also Salt. India rubber valves for air pump. Indicator, description of the, by McNaught, structure and mode of using; Gooch's continuous indicator. Injection cock. Injection cocks of marine engines at ship's sides. Injection orifice, proper area of. Injector, Giffard's. Injection valve. Inside cylinder locomotives. Iron, strength of, limits of elasticity of; proper strain to be put upon iron in engines and machines; aggravation of strain by being intermittent; increase of strain due to deflection; strength of pillars and tubes, combination of malleable and cast iron. Iron, cast, strength of, cast iron beams; may be strong to resist strains, but not strong to resist shocks; should be combined with wrought iron to obtain maximum strength. Iron, if to be case hardened, should be homogeneous. Jacket of cylinder, advantages of. Joints, rust, how to make. Kingston's valves. Lamb's scale preventer. Lantern brass in stuffing boxes. Lap and lead of the valve, meaning of. Large vessels have least proportionate resistance. Latent heat, definition of. Latta's steam fire engine. Lavagrian, expansion valve by. Lead and lap of the valve, meaning of. Lead of the valve, benefits of. Lever, futility of plans for deriving power from a lever. Lifting apparatus for screw propeller. Limits of elasticity. Links, main description of. Link motion of direct acting screw engine. Link motion, how to set. Locomotive engines, general description of the locomotive; Stephenson's locomotive; Gooch's locomotive for the wide gauge; Crampton's locomotive for the narrow gauge. Locomotives, adhesion of wheels of, cost and performance of; framing of; cylinders of; springs of; outside and inside cylinders; sinuous motion of; rocking motion of; pitching motion of; pistons; piston rods; guides; cranked axle; axle bearings; eccentrics; eccentric rod; starting handle; link motion; valves, how to set; eccentrics, how to readjust; feed pumps; connection of engine and tender, driving wheels; wheel tires. Locomotive engine of modern construction, example of, fire box; barrel of boiler; tubes; tube plate; framing; axle guards; draw bolt; wheels and axles; cylinders; valve; piston; piston rod; guides; connecting rod; eccentrics; link motion; regulator; blast pipe; safety valve; feed pump; tendencies of improvement in locomotives. Locomotives, management of. Locomotive boilers, examples of modern proportions. Locomotive boilers, details of. Low pressure or condensing engine, definition of. Lubrication of rubbing surfaces, the friction depends mainly on the nature of lubricant; oil forced out of bearings, if the pressure exceeds 800 lbs. per square inch longitudinal section; water a good lubricant if the surfaces are large enough. Lubrication of engine bearings. McNaught's indicator. Main beam, strength proper for. Main centre, description of, strength proper for. Main links, description of, strength proper for. Mandrels, expanding, for tubing boilers. Manhole door. Manhole of locomotives. Marine flue boilers, proportions of. _See_ also Boilers. Marine boilers of modern construction, proper proportions of. Marine engines. _See_ Steam Engines, marine. Mastic cement for setting marine boilers. Maudslay, Messrs., boilers of "Retribution" and "Great Western," by, Mechanical powers, misconceptions respecting. Mechanical power, definition of, indestructible and eternal; the sun the source of mechanical power. Metallic packing for pistons. Metallic packing for stuffing boxes. Meyer, expansion valve by. Miller, Ravenhill & Co.'s mode of fixing piston rod to piston. Modern locomotives. Momentum, or _vis viva_. Morin, experiments on friction by. Mudholes of locomotives. Muntz's metal, composition of. "Niger" and "Basilisk," trials of. "Nile," boilers of the, by Boulton and Watt. Notch of eccentric should be fitted with brass bush. Oils for lubrication. _See_ Lubrication. Oscillation, centre of. Oscillating paddle engine, description of. Oscillating engine, advantages of, futility of objections to; details of cylinder; framing; condenser; air pump; trunnions; valve and valve casing; piston; piston rod; air pump connecting rod and cross head; air pump rod; eccentric and eccentric rod; valve gear; valve sector; shaft plummer blocks; trunnion plummer blocks; feathering paddle wheels; packing of trunnions. Oscillating engines, how to erect. Otis's excavator. Outside and inside cylinder locomotives. Packing for stuffing box of Watt's engine. Packing of piston of pumping engines, how to accomplish. Packing of trunnions. Paddle bolts, proper mode of forming. Paddle centres. Paddle floats. Paddle shaft, description of. Paddle shaft, details of. Paddle shaft plummer blocks of oscillating engines. Paddle wheels, details of, structure and operation of; slip of; centre of pressure of; rolling circle; action of oblique floats; rule for proportioning paddle wheels; benefits of large floats. Paddle wheels, feathering, description of; details of. Paddles and screw combined. Parallel motion, description of, how to lay off centres of. Pendulum, cause of vibrations of; relation of vibrations of pendulum to velocity of falling bodies; conical pendulum or governor. Penn, Messrs., engines of "Great Britain," by, direct acting screw engines by; trunk engines by. Performance of locomotives. Pillars, hollow, strength of, law of strength varies with thickness of metal. Pipe for receiving screw shaft. Pipes of marine engines. Piston, description of, how to pack with hemp. Pistons, metallic packing for. Pistons for oscillating engines. Pistons, how to fit and finish. Pistons of locomotives. Piston rod, description of, strength proper for. Piston rods of locomotives. Piston rod of oscillating engine. Piston rods of direct acting screw engine. Pitch of the screw. Pitch, increasing or expanding. Pitching motion in locomotives. Planometers, or face plates. Plummer blocks of shafts and trunnions of oscillating engines. Plummer blocks for receiving thrust of screw propeller. Plunger of feed pump. Portable engine, Hoadley's. Porter's patent governor. Ports of the cylinder, area of. Pot-lid valves of air pump. Powers, mechanical, misconception respecting. Power, horses, definition of, nominal and actual power; power of high pressure engines. Power necessary for thrashing and grinding corn, working sugar mills, spinning cotton, sawing timber, grossing cotton, blowing furnaces, driving piles, and dredging earth out of rivers. Pressing cotton, power necessary for. Priming, nature and causes of. Priming, if excessive, may occasion explosion. Propeller, screw, description of. Proportions of screws with, two, four, and six blades. Proving of boilers. Prussiate of potash for case hardening. Pumping engines, mode of erecting, mode of starting. Pumps, loss of effect in, at high speed and with hot water, causes of this loss; remedy for. Pumps used for mines. Pump, air, description, of, action of. Pumps, air, proper proportions of, single and double acting. Pump, centrifugal, better than common pump. Pump, cold water, description of. Pump, feed, description of, action of; proper dimensions of; rule for proportioning; plunger of; valves of; independent. Pump valves for mines, &c. Punching and shearing boiler plates. Railway wheels, bursting velocity of. Railway trains, resistance of. Rarefaction or exhaustion produced by chimneys. "Rattler" and "Alecto," trials of. Registration, benefits of. Regnault, experiments on heat by. Regulator, a valve for regulating the admission of steam in locomotives, description of; various forms of. Regulator, Clark's, patent steam and fire. Rennie, experiments on friction by. Resistance, experienced by railway trains. Resistance of vessels in water, mainly made up of friction; experiments on. Resistance and speed of vessels influenced by their size. "Retribution," boilers of, by Messrs. Mandslay. Riveting and caulking of land boilers. Rocking motion of locomotives. Rolling circle of paddle wheels. Rotatory engines, definition of. Rotative engines, definition of. Rust joints, how to make. Safety valve, area of, in low pressure engines, in locomotives. Salinometer, or salt gauge, how to use, how to construct. Salt, accumulation of, prevented in marine boilers by blowing off, if allowed to accumulate in boilers may occasion explosion; amount of, in sea water. Salt water produces surcharged steam. Salting of boilers, what to do if this takes place. Sawing timber, power necessary for. Scale in marine boilers. _See_ also Salt. Scale preventer, Lamb's. Scrap iron, unsuitable for case hardening. Scraping tools for metal surfaces. Screw. Screw engine, geared oscillating, description of, direct acting, description of. Screw engine, direct acting, by Messrs. John Bourne & Co. Screw engines, best forms of. Screw frame in deadwood. Screw propeller, description of. 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Setting of wagon boilers, of marine boilers. Setting the valves of locomotives. Shaft, paddle, details of. Shaft of screw propeller, details of. Shafts, strength of. Shank's steam gauge. Shocks may not be well resisted by iron that can well resist strains, effect of inertia in resisting shocks. Side levers or beams, description of. Side lever marine engines, description of. Side lever engines, how to erect. Side rods, description of, strength proper for. Silsbee, Mynderse & Co.'s steam fire engine. Single acting engines, definition of. Single acting or pumping engines, mode of erecting; mode of starting. Sinuous motion of locomotives. Slide valve, various forms of; long D and three ported valve, description of; action of the slide valve; lead and lap of the valve; rules for determining the proportions of valves; advantages of lead in swift moving engines. Slide valve, equilibrium. Slide valve with balance piston of direct acting screw engine. Slide valve, how to finish. Slide valves of marine engines, how to set. Slip of paddle wheels. Slip of the screw, positive and negative slip; lateral and retrogressive slip. Smoke, modes of consuming. Smoke burning furnaces, Williams's argand; Prideaux's; Boulton and Watt's dead plate; revolving grate; Juckes's; Maudslay's; Hall's, Coupland's, Godson's, Robinson's, Stevens's, Hazeldine's, &c. "Snake" locomotive. Southern, experiments on friction by; experiments on steam by. Specific heat, definition of. Speed of vessels influenced by their size. Spheroidal condition of water in boilers. Springs of locomotives. Stand pipe for low pressure boilers. Starting handle of locomotives. Staying of boilers. Staying tube plates, mode of. Staying fire boxes of locomotives. Steam, experiments on by Southern, French Academy, Franklin Institute, and M. Regnault. Steam pump, Worthington's; Woodward's. Steam and water, relative bulks of. 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Steam jacket, benefits of; Steam passages, area of; Steam room in boilers; Steam, surcharged, law of expansion by heat; Steel, strength of; Stephenson, link motion by; Stop valves between boilers; Straight edges; Strains subsisting in machines; Strain proper to be put upon iron in engines; Strains in machines, vary inversely as the velocity of the part to which the strain is applied. aggravated by being intermittent. increase of strain due to deflection. effects of alternate strains in opposite directions. Strength of materials. Strength of hollow pillars, law of; strength varies with thickness of metal. Strength of cast iron to resist shocks does not vary as the strength to resist strains, increase of strength by combination with cast iron. Strength of boilers, experiments on, by Franklin Institute; by Mr. Fairbairn; mode of computing; mode of staying for strength. Strength of engines: cylinder, trunnions; piston rod; main links; connecting rod; studs of the beam; gudgeons; working beam; cast iron shaft; malleable iron shaft; teeth of wheels; side rods; crank; crank pin; cross head; main centre; gibs and cutter. Studs, strength proper for. Stuffing box, description of. Stuffing boxes with metallic packing, with sheet brass packed behind with hemp; sometimes fitted with a lantern, brass. Sugar mills, power necessary to work. Summers' experiments on the friction of rough surfaces. Surcharged steam, law of expansion of, by heat. Surcharged steam produced by salt water, corrosive action of. Surfaces, how to make true. Sweeping the tubes of boilers clean of soot. Teeth of wheels. Telescope chimneys. Tender of a locomotive, description of, attachment of, to engine. Thrashing corn, power necessary for. Throttle valve, description of. Thrust of the screw propeller, modes of receiving. Thrust plummer block. Tires of locomotive wheels. Traction on railways. Trunk engine by Messrs. Rennie, disadvantages of. Trunk engines by Messrs. Penn. Trunnions of oscillating engines, description of, strength proper for; details of. Trunnion packing. Trunnion plummer blocks. Tube plates, mode of staying. Tube plates of modern locomotives. Tubes of modern locomotive boilers. Tubes of boilers, how to sweep clean of soot. Tubing of boilers. Tubing locomotive boilers. Valve, atmospheric. Valve casing, description of. Valve casing should have expansion joint. Valve and valve casing of oscillating engine. Valve delivery, description of, action of Valve, equilibrium slide. Valve, foot, description of, action of. Valve gear of Watt's engine, action of. Valve gear of oscillating engine. Valve, gridiron. Valve, slide. _See_ Slide Valve. Valve, slide, how to finish. Valves, ball, Belidor's might be used for foot and delivery valves; butterfly, of air pump; concentric ring, for air pump bucket. Valves, equilibrium. Valves, escape, for cylinders. Valves, expansion. _See_ Expansion Valves. Valves of feed pumps. Valves, india rubber, for air pump. Valves, Kingston's. Valves of locomotives, how to set. Valves, pot-lid, of air pump. Vacuum, meaning of, nature and uses of; how maintained in engines. Vacuum sometimes occurs in boilers, evils of a vacuum in boilers. Vacuum, velocity with which air rushes into a. Vacuum gauge, Bourdon's. Velocity of air entering a vacuum. Velocity of falling bodies. Vent of boilers, definition of. Vessels, resistance of, mainly made up of friction in good forms; experiments on; influence of size. _Vis viva_, or mechanical power. Waste steam pipe. Waste water pipe. Water required for condensation, pumps for supplying. Watt's double acting engine, description of. Wedge. Wheels, toothed, for screw engines. Wheels, teeth of. Wheels of locomotives, adhesion of. Wheels, driving, of locomotives. Wheel tires. Wheels and axles of modern locomotives. Wood, experiments on friction by. Wood, evaporative efficacy of. Woodman's steam pump. Woodruff & Beach's steam engine. Working beam of land engine, description of. Worthington's steam pump, duplex pump. THE END. 
47762	----	[A transcriber's note follows the text.] RECORDS OF STEAM BOILER EXPLOSIONS, BY EDWARD BINDON MARTEN, MEM. INST. OF MECHANICAL ENGINEERS; ASSOCIATE OF INSTITUTION OF CIVIL ENGINEERS, AND CHIEF ENGINEER TO THE MIDLAND STEAM BOILER INSPECTION AND ASSURANCE CO. LONDON; E. & F. N. SPON, 48, CHARING CROSS. STOURBRIDGE: R. BROOMHALL, 148, HIGH STREET. 1872. PREFACE. Accurate information as to Boiler Explosions must always be useful to those who are interested in the safe working of Steam Boilers. The following pages contain very brief abstracts of records obtained for the Midland Steam Boiler Inspection and Assurance Company, by whose permission they are now republished in a compact and convenient form. By permission of the Council of the Institution of Mechanical Engineers, the records are prefaced by a Paper on Steam Boiler Explosions and their records, and on Inspection as a means of prevention, read before that Institution at Manchester, August 1st, 1866, and a further Paper on the "Conclusions derived from the experience of recent Steam Boiler Explosions," read before the same Institution at Nottingham, August 3rd, 1870. All names of Works or Firms are omitted from the records as unnecessary. ON STEAM BOILER EXPLOSIONS AND THEIR RECORDS, AND ON INSPECTION AS A MEANS OF PREVENTION, BY EDWARD B. MARTEN, MEM. INST. M.E. A.I.C.E., EXCERPT MINUTES OF PROCEEDINGS OF THE MEETING OF THE INSTITUTION OF MECHANICAL ENGINEERS, AT MANCHESTER, 1ST AUGUST, 1866, JOSEPH WHITWORTH, ESQ., PRESIDENT, IN THE CHAIR. BY PERMISSION OF THE COUNCIL. The subject of Steam Boiler Explosions, which was brought before this Institution in June, 1848, in a paper by the late Mr. William Smith of Dudley in reference to an explosion near that place, and again in 1859 in a paper by Mr. Longridge on the economy and durability of stationary boilers, is one of great importance and is now attracting increased attention. The first public notice of the subject was by a parliamentary committee in 1817, which was appointed in consequence of a very fatal boiler explosion in London in 1815; evidence was then collected as to steamboats, and many boiler explosions were referred to. That committee recommended among other things that boilers should be made of wrought iron, instead of cast iron or copper, which had been the materials mainly used previously; that they should be inspected and tested; and that there should be two safety valves, each loaded to one third of the test pressure, under penalties for any excess. A great part of the information now existing upon the subject, especially in regard to the earlier explosions, is to be found in the records of inquests after fatal cases; and some of the careful reports of eminent engineers on those occasions have materially assisted in the formation of correct views as to the causes of explosion. Latterly also the printed reports of the inspectors of mines, and more especially the reports of the explosions of locomotives, illustrated by diagrams by the inspectors of railways, have furnished very valuable information. Since the subject has been taken up by private associations for the prevention of explosions, many more records have been published, although their usefulness is much impaired by their not containing the names of the places whereby the explosions could be identified. When the writer's attention was first directed to this subject, he met with great difficulty in obtaining correct records of boiler explosions, from which to arrive at the results of past experience; and wishing to base his own opinion on facts, rather than on the inferences of others however reliable, he followed the example of the Franklin Institute in their elaborate investigation of the subject, and collected all the records he could find; and by way of facilitating reference, arranged an index, a manuscript copy of which is presented with the present paper to the Library of this Institution. All must be agreed as to the importance of reliable information on such accidents as boiler explosions; and the writer would suggest that this Institution may materially aid in obtaining the desired records and placing them within easy access, by becoming the depository of reports on explosions, and by inducing those who have the opportunity to forward copies of reports, that these may be arranged so as to be easily found and consulted. It is very desirable that these reports should as far as possible be illustrated by sketches, as aids to the description; and also by slight models like those now shown to the meeting, by which the whole matter may be seen at a glance. So few persons comparatively have the opportunity of examining boilers after explosion, that the most erroneous ideas have prevailed, and theories have been advanced which would soon be dissipated by practical experience or by reading accurate reports. It would also very much aid in the understanding of published matter on the subject, if full descriptions of each case alluded to in illustration could be obtained. These records are as useful to the engineer as the "precedents" or "cases" to the lawyer or the surgeon. After any serious explosion, the newspapers of the neighbourhood in which it has occurred contain voluminous articles describing the disastrous result and the damage done, which, although useful as far as they go, do not in the least assist in arriving at the cause of explosion. The really important particulars, such as the description and construction of the boiler, its dimensions, and the pressure at which it worked, are in most cases omitted altogether. The record of explosions presented to the Institution contains a list of the boiler explosions in each year of the present century, as far as known to the writer, with the names of the places, and the description and sizes of the boilers, and the supposed cause of explosion, together with references to the books or papers from which further information may be obtained. Of course many of the explosions have to be put down as uncertain in some of the particulars; but every year improves the record, as fresh information is obtained, and with the assistance of the members of this Institution it might be made far more perfect and extensive. * * * * * The total number of explosions here recorded is 1046, and they caused the death of 4076 persons and the injury of 2903. The causes assigned for the several explosions are very numerous, and are no doubt incorrect in many cases; but they may be generally stated as follows: 397 are too uncertain to place under any heading; but of the rest 145 were from the boilers being worn out, or from corrosion, or from deteriorated plates or rivets. 137 from over pressure, from safety valves being wedged or overweighted, in some cases intentionally, or from other acts of carelessness. 125 from faulty construction of boiler or fittings, want of stays, or neglect of timely repair. 119 from collapse of internal tubes, generally from insufficient strength. 114 from shortness of water, or from scurf preventing the proper contact of the water with the plates; or from improper setting so as to expose the sides of the boiler to the flame above the water line. 9 from extraneous causes, such as effect of lightning striking down the stacks upon the boilers, or from fire in the building or explosion of gas in the flues. ---- 1046 total number of explosions. ==== The exploded boilers were of the following descriptions:-- 232 are not sufficiently described to place under any head; but of the rest 320 were Marine boilers of various forms. 141 were Cornish, Lancashire, or other boilers internally fired. 120 were Locomotive, or other multitubular boilers. 116 were plain Cylindrical boilers, externally fired. 64 were Balloon or haystack, wagon, Butterley, British-tube, elephant, or Trevithick boilers. 29 were Portable, agricultural, upright, or crane boilers. 14 were Heating apparatus or kitchen boilers. 10 were Upright boilers attached to puddling or mill furnaces at ironworks. ---- 1046 total number of explosions. ==== [Illustration: _Fig. 1._] The theories as to the causes of explosion have been numerous. In the early days of the steam engine, when the steam was used only as a condensing medium and the pressure in the boiler was frequently allowed to get below atmospheric pressure, many boilers were destroyed by the access of the external atmospheric pressure becoming too great, causing them to be collapsed or crumpled up; and this led to the use of the atmospheric valve still found on old boilers. Even so lately as last year, 1865, a boiler in the neighbourhood of Bury, Lancashire, has suffered in this way by collapse from external pressure; its appearance after the accident is shown in Fig. 1, which is copied from a photograph. The early explosions were so palpably due to the weakness of the boilers, which compared with those of the present day were most ill constructed, that no one thought of any other cause than the insufficient strength of the vessel to bear the expansive force of the steam contained in it. When the advantages of high-pressure steam became recognized, and the boilers were improved so as to bear the increased strain, the tremendous havoc caused by an explosion led many to think that something more must be required than the expansive force of the steam to produce such an effect; and they appear to have attributed to steam under certain conditions a detonating force, or a sudden access of expansive power that overcame all resistance. To support this somewhat natural supposition, it was asserted that the steam became partially decomposed into its constituent gases, forming an explosive mixture within the boiler. That this belief is still sometimes entertained is seen from the verdict of a jury even in the present year, 1866, in the case of the explosion of a plain cylindrical boiler at Leicester, shown in Fig. 2., the real cause of which appears to have been that the shell of the boiler was weakened by the manhole. It seems hardly necessary to point out the fallacy of imagining decomposition and recomposition of the steam to take place in succession in the same vessel without the introduction of any new element for causing a change of chemical combination; but it is necessary to refer to this supposition, as the idea is shown to be not yet extinct. [Illustration: _Fig. 2._] Again it has been asserted that the steam when remaining quite still in the boiler becomes heated much beyond the temperature due to the pressure; and that therefore when it is stirred or mixed or brought more in contact with the water by the opening of a valve or other cause, the water evaporates so rapidly as to produce an excessive pressure by accumulation of steam. In support of this view the frequency of explosions upon the starting of the engine after a short stand is adduced; but it is very doubtful whether by this means a sufficient extra pressure could be produced to cause an explosion, unless the boiler had been previously working up to within a very small margin of its strength. Explosions are seldom caused by a sudden increase of pressure, but rather by the pressure gradually mounting to the bursting point, when of course the effect is sudden enough. Nor is it necessary in many cases to look for much increase of pressure as the cause of explosion; for it is far more often the case that the strength of the boiler has gradually degenerated by wear or corrosion, until unable to bear even the ordinary working pressure. It is so very easy, when examining the scene of an explosion, for the first cause of rupture to be confounded with the causes of the subsequent mischief, that in many cases erroneous conclusions have been arrived at in this way. The most important points to find out in connection with any explosion are the condition of the boiler and all belonging to it immediately before the explosion, together with the locality of the first rent, the direction of the line of rupture, and the nature of the fracture; as everything occurring after the instant of the first rent is an effect and not a cause of explosion. As soon as the first rent has taken place, the balance of strain in the fabric is disturbed, and therefore the internal pressure has greatly increased power in continuing the rupture; and also the pressure being then removed from the surface of the water, which is already heated to the temperature of the steam, the whole body of the water gives out its heat in the form of steam at a considerable pressure, and thus supplies the volume of steam for carrying on the work of destruction. When thus quickly generated, the steam perhaps carries part of the water with it in the same way that it does in ordinary priming; and it has been thought by some that the impact of the water is thus added to that of the steam, to aid in the shock given to all surrounding obstacles. It is seldom that one out of a bed of boilers explodes without more or less injury to the others on either side of it; but sometimes two boilers in one bed, or three, or even five, have exploded simultaneously. * * * * * The causes of boiler explosions may be considered under the two general heads of-- Firstly, faults in the fabric of the boiler itself as originally constructed, such as bad shape, want of stays, bad material, defective workmanship, or injudicious setting:--and Secondly, mischief arising during working, either from wear and tear, or from overheating through shortness of water or accumulation of scurf; or from corrosion, in its several forms of general thinning, pitting, furrowing, or channelling of the plates; or from flaws or fractures in the material, or injury by the effect of repeated strain; or from undue pressure through want of adequate arrangements for escape of surplus steam. [Illustration: _Fig. 3._] [Illustration: _Fig. 4._] [Illustration: _Fig. 5._] There is no doubt that many of the early explosions were from faults of construction. The stronger materials now used were then found so difficult to manipulate that others easier to work were chosen, and often the shape of the boiler was only selected as the one easiest to make. The early boilers were made of copper or cast iron, with leaden or even wooden tops, and of the weakest possible shape. Such was the boiler used by Savery, shown in Fig. 3., and the Tun Boiler and Flange boiler, Figs. 4 and 5. The very fatal explosion in London in 1815, referred to by the parliamentary commission previously named, was of a cast-iron boiler, which failed because one side was too thin to bear the pressure, as the casting was of irregular thickness. The steam being at that time used only at or below atmospheric pressure as a means of obtaining a vacuum by condensation for working by the external pressure of the atmosphere, so little was pressure of the steam thought of, that boilers were proposed and it is believed were actually constructed with hooped wooden shells, like barrels, and internal fireplaces and flues of copper; and even a stone chamber was named as being a suitable shell for a boiler, with internal fireplace and copper flue passing three times the length of the inside and out at the top, like an ordinary stove and piping. These boilers must have been something like the sketches given in Figs. 6 and 7, and were intended to be exposed only to the external pressure of the atmosphere. [Illustration: _Fig. 6._] [Illustration: _Fig. 7._] [Illustration: _Fig. 8._] [Illustration: _Fig. 9._] [Illustration: _Fig. 10._] Cast iron was frequently used for the shell of boilers, with an internal fireplace and tubes of wrought iron, as shown in Fig. 8, and boilers of this construction are still to be found in use at some of the older works at the present day. As the outside shell and front plate are 1-1/2 inch thick and are not exposed to any wear at all, these boilers are sufficiently strong. A duplicate front plate with set of tubes attached is always kept on hand in case of need. Another form of cast-iron boiler is shown in Fig. 9., made in several parts put together with flange joints, with an internal fireplace and flue also made of cast iron. When cast iron was used for the parts exposed to the fire in boilers intended for high pressure, it was sometimes employed in the form of tubes of small diameter and proportionately thinner; as in Woolf's boiler, so much spoken of in the evidence before the parliamentary committee of 1817. This boiler, shown in Fig. 10., consisted of nine cast-iron pipes, about 1 foot diameter and 9 feet long, set in brickwork so that the flame played all round them. These small tubes were connected with another of larger size placed transversely above them, forming a steam receiver, and this again with a still larger one, which formed a steam chamber. No details of any explosions of the three last mentioned boilers have been obtained; but it is known that the cast iron was found a most treacherous material, especially when exposed to the action of the fire; and that the effect of explosion was very disastrous, because the boiler burst at once into many pieces, each of which was driven out with great velocity, and the danger was not mitigated by the circumstance of large masses holding together, as is found to be the case with wrought-iron boilers when exploded. * * * * * [Illustration: _Fig. 11._] [Illustration: _Fig. 12._] When wrought-iron boilers came into use the shapes were most varied, and the dimensions much larger than before. One of the earliest was the Wagon boiler, shown in Fig. 11, with round top and plain flat sides, which could only be made to bear even the smallest pressure by being strengthened with numerous stays. In most cases of explosion of this class of boiler the bottom was torn off, owing to the angle iron round it being weakened by the alternate bending backwards and forwards under each variation of pressure, as all the sides and the bottom must be constantly springing when at work. Such was the explosion at Chester in 1822, and many others. This shape was soon improved in its steam generating powers by making the sides concave instead of flat, as shown in Fig. 12, so that the heating surface was greater and also in a better position to receive the heat from the flame in the flues. This shape was further elaborated by rounding the ends as in Fig 13, and in some cases making the bottom convex to correspond with the top, as in Fig. 14. All these forms however still required numerous stays to retain them in shape, the safety of the boiler being dependent upon the stays; and numerous explosions show the weakness of these boilers. They generally gave way at the bottom, as in an explosion that occurred at Manchester in 1842, where the boiler had been weakened by frequent patching; they also sometimes exploded through the failure of the stays. [Illustration: _Fig. 13._] [Illustration: _Fig. 14._] [Illustration: _Fig. 15._] [Illustration: _Fig. 16._] [Illustration: _Fig. 17._] [Illustration: _Fig. 18._] A very early improvement in the right direction consisted in making the shell circular; and some few large boilers still exist that were made completely spherical, as show in Fig. 15, so that the whole of the iron was exposed to tension only, and required no assistance from stays, and the boiler had no tendency to alter its shape under varying pressure. This shape however had the great disadvantage of possessing the least amount of heating surface for its size or cubic contents; and also it was very liable to injury from sediment on the bottom, which accumulated on the most central spot. The spherical form was therefore soon modified into the shape shown in Fig. 16, by making the bottom more shallow, although still convex; and afterwards by putting flat or concave sides and a flat or concave bottom, with the angle constructed either of bent plates or angle iron, as in Figs. 17 and 18, which represent the forms known so well in the Staffordshire district as the common Balloon or Haystack boiler. Many of these have been made of very great size, measuring as much as 20 feet diameter, and containing so much water and steam as to be most formidable magazines for explosion. Perhaps no form of boiler has exploded more than this, partly because of the great number that have been used, but chiefly because of the inherent weakness of the shape. The records however have not been obtained of the great majority of these explosions, because they seldom caused sufficient damage or loss of life to attract much attention, as these boilers generally worked in isolated positions at collieries. The bottom is only prevented from blowing down into the fireplace by numerous stays from the top, and the angle iron round the bottom of the sides is much tried by the constant springing of the plates under every alternation of pressure; and the weakness thus occasioned is increased by the angle resting on the brickwork and being exposed to corrosion. The effect of this continued alternation of strain is well shown by the elastic model exhibited. [Illustration: _Fig. 19._] [Illustration: _Fig. 20._] [Illustration: _Fig. 21._] [Illustration: _Fig. 22._] Notwithstanding the dependence of these boilers upon stays for their strength, many have been made as large as 12 and 15 feet diameter without stays; and explosion sooner or later has been the consequence. Such was an explosion that took place at Smethwick in 1862, which is shown in Fig. 19. As the force of the explosion was only slight, the effect of the bottom giving way, and the consequent rolling over caused by the reaction of the issuing steam and water, is clearly seen. Another example that occurred at Wednesbury in 1862 is shown in Fig. 20, where the explosion was rather more violent, the bottom of the boiler being torn off all round and left upon the firegrate, and rent nearly into two pieces; while the top and sides were thrown some height in one mass, and were only put out of shape by the fall. The weakness of this boiler had been further increased by making the bottom angle of angle iron, as shown enlarged in Fig. 21, with a ring of flat plate A interposed between the angle-iron ring and the concave bottom of the boiler; so that all the effect of the springing of the bottom, as shown by the dotted lines, was thrown upon the angle iron, which was accordingly found cut off all round. Had the concave bottom been made to rise direct from the angle iron, as in Fig. 22, the springing could not have been so great, and the angle iron would only have had to stand the shearing strain of retaining in its place the rigid bottom; but as about one foot all round the bottom was flat, and the concavity was only in the central part, the angle-iron ring had to bear an up and down strain, as shown by the dotted lines in Fig. 21, and the bending action was more severe than it would have been if the bottom had even been made quite flat all over. [Illustration: _Fig. 23._] A further form of the Balloon boiler is shown in Fig. 23, where the heating surface of the bottom is increased by an internal central dome-shaped fireplace, with an arched and curved flue conducting the flame through one revolution within the boiler before passing again round the outside. This construction however must necessarily have diminished the strength of the boiler greatly. In the drawing the top of the boiler, as indicated by the dotted lines, is removed to show the interior. The desire to add to the strength of boilers by lessening the diameter of the shell led to the construction of the Plain Cylindrical boilers. They were made first with flat ends of cast iron, which frequently cracked and gave way when exposed to the fire, as described in many of the early American explosions. The flat ends when made of wrought iron, as shown in Fig. 24, are exposed to the same strain as the bottom of the balloon and wagon boilers, and are constantly springing with variation of pressure like drum heads, causing injury to the angle-iron joint. They also require long stays through them to hold in the ends, and these are subject to so much vibration that they seldom continue sound for long together, especially when joined with forked ends and cotters. [Illustration: _Fig. 24._] * * * * * As the flat ends of such boilers are always being sprung by each alternation of pressure into a more or less spherical shape, as shown by the elastic model exhibited, this consideration no doubt led to the ends being made hemispherical, as shown in Fig. 25; and plain cylindrical boilers with these hemispherical ends are now so commonly used that they far outnumber any other form of boiler. Their shape renders them very strong, as the whole of the iron is in simple tension, and internal pressure has no tendency to alter the shape, as is shown by the elastic model exhibited. There is one circumstance very much in favour of the plain cylindrical boilers, and that is that they can be so easily cleaned and repaired, as a man can stand properly at his work at every part and the whole of the interior surface is exposed equally to view. They are of course exposed to all the evils of boilers externally fired, the part under greatest strain being weakened by the action of the fire; and the bottom is also exposed to injury from accumulation of mud and chips of scurf, which cannot be prevented from falling there, and lying upon the part exposed to the direct action of the fire. When made of great length, such as 70 or 80 feet, as is the practice for applying the waste gas from blast furnaces, these boilers are also liable to seam-rips or "broken backs," owing to the greater expansion of the bottom exposed to the fierce flame for its whole length, than of the top which is kept cooler by exposure to the air; and it would therefore be better to have a succession of short boilers, rather than only a single one, where great length is required. [Illustration: _Fig. 25._] One boiler has been seen by the writer where extreme length was avoided by curling the boiler round until the ends met forming a Ring or Annular boiler. This boiler is shown in Fig. 26, and is 5 feet diameter with 25 feet external diameter of the ring, or a mean length of about 63 feet; it has been found to work well for some years, although exposed to the heat of six puddling furnaces. [Illustration: _Fig. 26._] [Illustration: _Fig. 27._] Explosions of plain cylindrical boilers have been very frequent indeed, although they have not caused a proportionate number of deaths, because they work usually in isolated positions at colliery and mine engines. The sketch shown in Fig. 27, represents an explosion that occurred at Darlaston in 1863, and illustrates the way in which these boilers usually explode. They generally open first at a longitudinal seam over the fire, which has become deteriorated by accumulations of scurf preventing proper contact of the water, so that the plates become overheated, their quality injured, their edges cracked or burnt, and the rivets drawn or loosened. The rent generally continues in the longitudinal direction to the sound seam beyond the bridge at the one end, and at the other end to the seam joining the front end to the shell; and then runs up each of the transverse seams, allowing the rent part of the shell to open out flat on both sides, and liberating both ends of the boiler, which fly off in opposite directions. Of course it is seldom that an explosion is quite so simple as this, as the direction of the flight of the various pieces is so much influenced by the last part that held in contact with the main body of the boiler. The want of due observation of this point has often led to erroneous conclusions. [Illustration: _Fig. 28._] In the explosion shown in Fig. 28, and in the model exhibited, which occurred at Westbromwich in 1864, the lower part of the side of an upright boiler was blown out; and the liberated part was also divided into two pieces, each of which fell some distance behind the boiler, in an opposite direction to the side from which they came. The explanation of this became obvious on examination, as the cause of the rupture had been the corrosion of the bottom, and the rent had run up the seams until it met the angle iron of the side tubes, round which it ran to the first seam above. This seam acted as a hinge on which the ruptured pieces turned, and they swung round so violently that they were wrenched off, but not before they had pulled the boiler over and received the diverting force which gave them their direction, for they flew off at a tangent, to the circle in which they had swung round on the sound upper seam as upon a hinge. [Illustration: _Fig. 29._] [Illustration: _Fig. 30._] In order to avoid having a large diameter for plain cylindrical boilers, especially where exposed to the fire, boilers have been used that have supplied the required steam power by a combination of several cylinders of small diameter. One of these known as the Elephant boiler, has been so much used in France that it is sometimes called the French boiler; it is shown in Fig. 29, and consists of two cylinders of small diameter connected by upright conical tubes to a large cylinder above. Another form called the Retort Boiler, shown in Fig. 30, has been described at a previous meeting of this Institution (see Proceedings Inst. M. E. 1855 page 191). The disadvantages of these two combinations of plain cylinders are that they are not easy to clean or examine internally, and also there is not free exit for the steam, which has to find its way along small channels, and carries the water away with it, causing priming, and also retarding the generation of steam and endangering the boiler plates. With a view to strengthen the plain cylinder made of wrought-iron plates, the seams are sometimes made to run diagonally, as shown in Fig. 31, on the principle that, as the longitudinal is the weakest seam and the transverse the strongest, a diagonal between them gives the greatest amount of strength to the boiler as a whole. [Illustration: _Fig. 31._] * * * * * [Illustration: _Fig. 32._] [Illustration: _Fig. 33._] [Illustration: _Fig. 34._] [Illustration: _Fig. 35._] Plain cylindrical and wagon boilers have for many years been made with internal tubes of various shapes and arrangement, through which the flame passes to add to the heating surface. These are shown in dotted lines on the previous drawings of wagon boilers, Figs. 11 and 12. They are also shown in Fig. 32, where a tube passes from over the fire to the front of a plain cylindrical boiler; in Fig. 33 two tubes pass from the sides to the front: in Fig. 34 the tube passes from the back, but returns over the fire and passes again to the back: and in Fig. 35 a tube from the back passes out through a cross tube in each side. The boilers in all these cases are fired externally. This addition of tubes has tended very much to increase the size of these boilers in order to make room for the tubes. These boilers are now found of 9, 10, and even 11 feet diameter; and this large shell being fired externally is exposed to the same dangers as those described in the plain cylindrical boiler, while it is not so easy to keep clean on account of the obstruction offered by the internal flues. When the flame has passed under the whole length of the bottom of these large boilers before going through any tube, it is doubtful whether the heating surface of the tube helps much in the generation of steam; but the tube is of use in reducing the quantity of water in the boiler, as it occupies a considerable space. [Illustration: _Fig. 36._] Explosions of these boilers have sometimes taken place by collapse of the tubes, but much more generally by the failure of the shell over the fire, as shown in the sketch Fig. 36, representing an explosion that occurred at Wolverhampton in 1865, in which the first rent took place in a seam over the fire where frequent repair had led to a considerable length of longitudinal seam being in one continuous line. The four plates over the fire parted and opened out until they had ripped two seams completely round the boiler; and the plates were thrown in one flat piece, as shown, upon a bank behind. The main body of the boiler with the tubes was turned over, and the front end blown away. [Illustration: _Fig. 37._] A modification or amalgamation of several of the forms of boilers already mentioned led to the construction known as the Butterley boiler, shown in Fig. 37, with a wagon-shaped end over the fire, continued in a single tube within a plain cylindrical shell beyond. This boiler has been found to generate steam very rapidly; but the extreme weakness of the construction over the fire and along the tube, especially at the part where the front end of the tube widens out in a bell mouth to meet the wagon-topped fireplace, has led to so many explosions that few boilers are now made of this form. A very early explosion that occurred at Edinburgh in 1821 was of a boiler somewhat of this shape, only that the wagon-topped fireplace was much longer. Other explosions of this form of boiler occurred at Ashton-under-Lyne in 1845, at Wolverhampton in 1854, and at Tipton in 1856. [Illustration: _Fig. 38._] [Illustration: _Fig. 39._] [Illustration: _Fig. 40._] [Illustration: _Fig. 41._] The desire to economise fuel led to placing the fire inside the boiler, in a tube running from end to end, as shown in Fig. 38, and the great number of boilers of this form used in Cornwall gave it the name of the Cornish boiler. The exceedingly good duty performed by these boilers led many to believe them the most perfect for economy and durability; but the great number of explosions, or more properly of collapsed flues, that have happened, have altered this opinion, and led to the double-flue boiler shown in Fig. 39, in which not only is the heating surface increased but the strength also, by having two tubes of smaller diameter in the same shell. There are a great many varieties of the two-tube boiler, which have been made for the purpose of obtaining various particular results. In some cases the two tubes have been made to unite into a single tube immediately behind the fires, forming what is known as the Breeches-tube boiler, as shown in Fig. 40, and in other instances the outside shell of the boiler has been made oval, as shown in Fig. 41, with the two tubes continued through from end to end. The heating surface has also been increased, and the strength of the main tubes, by placing smaller transverse tubes across them at right angles; but these advantages are gained by increased complication, leading of course to greater difficulty in examination and repair. * * * * * The frequent failure of tubes by collapse when used for high pressures, and also the results of careful experiments, led to the simple addition of strengthening rings of different makes around the exterior of these tubes, by which the shell and the tubes are rendered of equal strength. It has taken considerable time for the belief in the weakness of large tubes when exposed to external pressure to become general, and a great many boilers are still made and used having even large tubes without the strengthening rings; and in some districts such boilers are used in great numbers and at far higher pressures than can be considered judicious. In more than one bed of boilers, one boiler after another has exploded by the collapse of the tube from the want of strengthening rings, and yet these have still been believed unnecessary; and the cases of isolated boilers of this construction where the large tubes have collapsed are extremely numerous, yet any other reason than the weakness of the tube has been considered more probable as the cause of explosion. A sketch of a boiler with collapsed flue is given in Fig. 42, which exploded at Burton-on-Trent in 1865; and it is selected from many others because it was a new boiler, well made and mounted, and was a good example of the weakness of a large tube to resist high external pressure when made of great length without the support of strengthening rings. [Illustration: _Fig. 42._] There are a great many advantages in the tubular boiler internally fired. The shell which is exposed to the greatest tension is not also exposed to the first action of the fire. The fire is in the midst of the water, so that the greatest effect is obtained from it; and the heating surface immediately over the fire, from which most steam is generated, has not so great a depth of water above it for the steam to pass through as in the externally fired boilers heated from the bottom. The tubes also act as stays to the ends; and the mud in the water falls off the tubes, where it would do mischief, and settles on the bottom, where it is comparatively harmless. These tubular boilers are however subject to disadvantages peculiarly their own. It is not so easy to move about within them for cleaning and examination as in the plain cylindrical boiler, as the tubes fill up the space so much. The difference of expansion between the highly heated tube and the comparatively cool shell produces a strain, which causes the ends to bulge out; or if the ends are made rigid, the strain sets up a contortion in the tube, which causes furrowing of the plates by making the iron softer or more susceptible of corrosion in certain lines of strain. Notwithstanding these drawbacks however this form of boiler is an excellent one. Many modifications in the forms of boilers have been made to enable the manufacturers to use the waste heat from various processes, especially from the making of iron. The plain cylindrical boiler has been used in this way, with sometimes as many as eight puddling furnaces made to work upon one boiler. One of the earliest special arrangements for this purpose was the Upright boiler with central tube, shown in Fig. 43, which was originally made for two furnaces; and about 7 feet diameter and 16 feet high. The size has since been increased to 10 feet diameter and 28 feet high, as shown in Fig. 44. These boilers are made for one, two, three, or four puddling furnaces; and consist of a cylinder with spherical ends, standing upright, with a central tube from the bottom to about half the height, into which the side tubes join. The heat from each furnace plays over a portion of the shell, and then passes through the side tubes and down the centre tube into the underground flue to the chimney. [Illustration: _Fig. 43._] [Illustration: _Fig. 44._] These boilers have many good points: there is great heating surface; and the shell being heated all round does not strain the plates and seams by unequal expansion so much as in the horizontal plain cylindrical boiler heated only at the bottom; and as both ends are spherical there is no alteration of shape under internal pressure. Moreover in consequence of the upright position of the boiler a safe depth of water can easily be maintained, and yet the steam is taken off so high above its surface that there is little priming; and every part can most easily be cleaned and examined, as a man can stand upright both in the boiler and in the flues. But the great drawback to this class of boilers is that they must stand in the midst of the workmen; so that, although they are not more liable to explode than any other form of boiler, yet when they do burst they necessarily endanger more lives than is usually the case with other boilers that can be placed more away from the men employed at the works. Should anything arise with the boiler to make it desirable to withdraw the fire, this cannot be done without much delay, as the furnaces have to be stopped and the iron run out. Also an explosion can hardly happen without some of the melted iron being scattered among the men at work. [Illustration: _Fig. 45._] [Illustration: _Fig. 46._] Some of the most fatal explosions of these boilers have arisen from careless construction. Such was the case in an explosion at Dudley in 1862, shown in Fig. 45, where the crown plate forming the top of the centre tube was attached to the sides of the tube by so slight an angle iron, as shown enlarged in Fig. 46, that the pressure of steam on the flat crown plate fairly sheared the angle iron through, and allowed the plate to be blown down the centre tube into the chimney flue, whereupon the boiler was violently thrown off its seating by the reaction of the issuing steam and water thus liberated. * * * * * The double-tube horizontal boiler is also used in connection with iron-making furnaces in many places, one furnace working into each tube. Although by this arrangement the boiler can be placed a little further from the workmen, some very fatal explosions have happened to such boilers, as at Masborough in 1862. * * * * * [Illustration: _Fig. 47._] Single-furnace boilers have been much used in the form of a single-tube boiler standing on end, as shown in Fig. 47, with the flame passing up the tube, which is continued in the form of a chimney on the top of the boiler. The tube passes through the steam at the top, so that the plate is not protected from overheating by contact with water; and this has caused explosion in some instances, although the tube has been lined on the inside with firebrick to shield the plate from the flame. Another great disadvantage of this Chimney boiler is that the space between the tube and the shell is so narrow that it is almost impossible to examine or clean it internally. * * * * * A further arrangement for a single-furnace boiler is the Elbow boiler, shown in Fig. 48, where the two difficulties mentioned in the previous boiler are avoided. * * * * * Many internally fired upright boilers of various shapes have been constructed to suit various purposes. One of a large size that has been at work many years is shown in Fig. 49, with an internal fireplace and a suspended cone and cross tube for increasing the heating surface. This boiler is set in brickwork in such a way that the heat passes through the side tubes and round the exterior shell before going off to the chimney. [Illustration: _Fig. 48._] [Illustration: _Fig. 49._] A very fatal explosion at Stoke-upon-Trent, in 1863, resulted from an attempt to work a boiler of somewhat the same general form, but without the same careful attention to the details of construction. This boiler is shown in Fig. 50; the internal fireplace is of conical shape, 4 ft. 6 ins. diameter on the top and 6 ft. 10 ins. at bottom, and was joined to the external shell by a flat annular bottom. Almost the first time it was worked at high pressure the conical fireplace collapsed, breaking off at the seam at the top of the cone, and blowing down upon the grate, as shown in Fig. 51. The flat bottom was then left without the support of the cone and side tubes, and gave way all round the outside angle iron; and the top flew up a great height into the air, and fell a crumpled heap, as shown in the sketch. In this case the only wonder is that a boiler of such weak construction worked at all without explosion. [Illustration: _Fig. 50._] [Illustration: _Fig. 51._] * * * * * There yet remains to be noticed a very large and varied class of boilers that have been designed with the express object of avoiding explosion. Some of these, made of cast-iron pipes of small diameter, have already been referred to. When steam carriages were first constructed, boilers were tried made of a cluster of small pipes, set both upright and horizontally, connected with a general receiver and with each other by still smaller pipes. These were found to have such small circulation of water that they very soon burnt out, and also led to much priming. Afterwards, narrow chambers made of corrugated plates set like the cells of a battery were tried, but without much success. The multitubular boilers of the locomotive type soon superseded all others as quick steam generators, and until lately they have been considered as almost absolutely safe from explosion. It is found however that the barrel of these boilers is peculiarly liable to furrowing, owing to the strain weakening the iron in certain lines. Perhaps no boiler shows more clearly than the locomotive how necessary it is that every part should be open to examination; and also how unwise it would be to use for stationary purposes small cramped up boilers, only intended to meet the necessities of locomotion. Many explosions of locomotive boilers have taken place; but it is not necessary to give details in this paper, as they are fully given in the published official reports of the government inspectors. Among the form of boilers designed to obtain very rapid generation of steam, combined with increased safety from explosion, may be specially named that consisting of a system of small pipes within a shell with an artificial circulation of water, and also the boiler consisting of a cluster of cast-iron spheres, both of which have been described at previous meetings of the Institution (see Proceedings Inst. M. E. 1861 page 30, and 1864 page 61); but neither has been much used in this country at present. The boilers also which consist chiefly of small tubes hanging down into the fire, with smaller tubes or other arrangements within them for securing a natural circulation, deserve mention, as they appear successfully to accomplish that end. The principle of all these small boilers appears to be that only a small quantity of water should be contained in them, so that there should not be a reservoir of danger in the shape of a mass of highly heated water ready to be converted into steam if a rupture takes place: and it cannot be denied that this is an advantage. But on the other hand these boilers of small capacity, which evaporate their whole contents in a few minutes, are subject to new dangers from that very cause; and although admirably adapted for purposes where steam is wanted quickly on a sudden emergency, as in the case of fire engines, or where the generating power required varies each moment, as in the locomotive, they are for the most part ill adapted for ordinary stationary purposes, such as the mill or the colliery. They require constant firing and vigilant attention to the feed, and cannot be left for a time with safety like the ordinary stationary boilers. It has to be borne in mind also that the very reservoir of danger so much dreaded is also a reservoir of power, which assists in the steady maintenance of the machinery in motion. The large mass of water heated to the evaporating point, the heated brickwork of the flues, and the large fireplace, are so many assistances to regularity, and enable the man in charge to attend to his other duties without the risk of spoiling the boiler or letting down the steam by a few minutes' absence from the stoke hole. Steam employers are found at present to prefer the known dangers of the large boilers to the supposed safety of small boilers, which they fear are troublesome in practice. * * * * * Many of the early boilers were rendered weak by the injudicious manner of arranging the seams. The longitudinal seams were made in a continuous line from end to end, as shown in Fig. 24, page 20, with the transverse seams also continued completely round the boiler, so that at the corner of each plate there were four thicknesses of iron. The crossing of the seams, as in Fig. 25, page 21, adds much to the strength, and also often prevents a rent from continuing forward to a dangerous extent. It is scarcely requisite to mention the necessity of good material and workmanship to secure strength in a boiler, however perfect the design. If the plates are of weak and brittle iron, or imperfectly manufactured, they will never make a good boiler. Apart from the strain upon the boiler when at work, the iron has to undergo the strain of the necessary manipulation, shaping, and punching, during the construction of the boiler. If the plates forming the boiler are not well fitted to their places before the rivet holes are made, the errors have to be partially rectified by using the drift in the holes to an unwarrantable extent, and then using imperfect rivets to fill up the holes that do not correspond with each other; and the mischief is too frequently increased afterwards by excessive caulking, in the endeavour to stop the leaking which is sure to show itself. In this way a boiler is often exposed to most unequal internal strain between its several parts before it is set to work at all; and when the heat is applied to it, the mere expansion causes undue contortion, and leads to seam rips, and ultimately to disaster. Several specimens of faulty rivetting and caulking were exhibited to the meeting, and a sketch of one of them is shown in Fig. 52. [Illustration: _Fig. 52._] The strength of a boiler is often very much lessened by the injudicious manner in which the mountings are fixed upon the boiler, and many explosions are the consequence of this defect. Not only are a great many holes for fittings cut out of the boiler in one line, but these holes are made needlessly large. Steam domes are often so placed as greatly to weaken the shell of the boiler, the hole cut out of the plate being made the full diameter of the dome; and in some cases the domes or steam chests have been made square or rectangular, so as to weaken the shell still more, as shown in Fig. 53. Manholes are often a source of danger, if not properly arranged and duly strengthened. Even in very small boilers they are often placed with the longest diameter in the longitudinal direction of the boiler, so that the shell is greatly weakened, as in the sketch, Fig. 54, of an exploded boiler at Walsall in 1865. This boiler was 5 ft. 3 ins. long and 2 ft. 6 ins. diameter, and yet the manhole was 18 inches by 13 inches, and placed within a few inches of one end. The end was fastened in by angle iron, which was not welded, and consequently there was so little strength at the small portion of the shell between the end and the manhole that it gave way and liberated the end and the manhole lid, after which the main body of the boiler was thrown by the reaction across several streets to a great distance. [Illustration: _Fig. 53._] [Illustration: _Fig. 54._] A somewhat similar injudicious arrangement of the manhole is shown in Fig. 55, where a manhole 17 inches by 14 inches was cut out of the flat top of a steam dome only 2 ft. 6 ins. diameter, without any strengthening ring to compensate for it. The repeated strain of screwing up the manhole lid, combined with the pressure of the steam, caused the lid to force its way out through the plate and blow away. This explosion occurred at Birmingham in 1865. [Illustration: _Fig. 55._] The preceding examples have shown how explosions often result from faults in the construction of boilers; and the following instances illustrate the explosions caused by mischief arising during working. A boiler perhaps more than any other structure is subject to wear and tear; and let it be worked ever so carefully, it will seriously deteriorate. The wonder is, considering the work they have to perform, that so many boilers are found which have worked twenty, thirty, or even fifty years without explosion. The terms wear and tear however are too vague for this subject, and the mischief met with must be considered under distinct heads. There is no doubt that the thing most to be dreaded for boilers is corrosion; because when the plate is once thinned, it cannot be strengthened again, but must remain permanently weakened. Corrosion the more deserves attention because it is easily detected by moderate vigilance, and can generally be prevented by moderate care, or by the boilers being so arranged that they can be readily examined in every part. Corrosion has been the direct and unmistakeable cause of a very large proportion of the explosions that have happened: it occurs both inside and outside the boiler, according to circumstances, and attacks the iron in various ways and in different places. [Illustration: _Fig. 56._] [Illustration: _Fig. 57._] [Illustration: _Fig. 58._] [Illustration: _Fig. 59._] _Internal corrosion_ sometimes takes place from bad feed water, and its effects are different in extent in the different parts of the same boiler. It very seldom thins the plate over a large surface regularly, but attacks the iron in spots, pitting it in a number of holes. These are sometimes large, as if gradually increasing from a centre of action; and sometimes small, but so close together as to leave very little more space whole than that which is attacked. A very curious example of the latter was exhibited to the meeting, and shown in Figs. 56 and 57, cut from the lower part of the shell of a large tubular boiler externally fired. The corrosion was greatest along that part of the shell most exposed to heat, and was so extensive that two boilers exploded simultaneously. The boilers had been at work sixteen years, but the corrosion commenced about eight years before the explosion, when the feed water was rendered corrosive by being obtained from some iron mines. This explosion occurred at Aberaman in 1864. The corrosion had been seen going on for years, and was not considered sufficient to cause danger; but the depth to which it extended through the thickness of the metal is seen in the half size section, Fig. 57. Another sample equally curious was exhibited to the meeting, and shown in Figs. 58 and 59, taken from the sweep plate over the fire in a plain cylindrical boiler which had worked about ten years. The feed water was occasionally bad, and attacked the iron over the area DDD, where unprotected by scale. The protection afforded by scale against occasional corrosive feed water is worthy of notice. In the two specimens exhibited it is seen that the protection has been perfect where the scale has not been chipped off; and the edge of the sound part projects over the hollow, as seen in the half size sections, Figs. 57 and 59, the corrosive water having eaten away a larger area beneath than that through which it first entered the surface of the iron. Internal corrosion is frequently observed where boilers are fed from canals or streams in the neighbourhood of chemical works from which corrosive matter is discharged at intervals into the water. The corrosion takes place in isolated spots, but causes deep holes; which seems to be accounted for on the supposition that the scale previously upon the plate cracks during the cooling of the boiler for cleaning, and forms a blister, so that a piece of about 2 inches area is raised slightly from the iron. When the boiler is again put to work, this blister becomes filled with the corrosive water, which is held there without circulation and causes corrosion. When the boiler is again emptied these blisters may be seen, and if broken show the blackened water and the injured surface. In future working each of these blisters forms a constant unprotected point for attack. It is frequently seen further that such corrosion is arrested if water be used which deposits scurf; but fresh blisters and renewed corrosion will result from a return to the use of the bad water. The internal corrosion called furrowing has proved a frequent cause of explosion, especially in locomotive boilers. It differs from other corrosion by being in deep narrow continuous lines with abrupt edges. It will sometimes go completely through a plate; and is found where a sudden change of thickness occurs, either along the lines of the seams, or opposite the edge of angle-iron attachments. This effect is supposed to be due to the alternate springing of the plates under each variation of the pressure or temperature, causing the line of least resistance to receive a strain somewhat similar to that produced by bending a piece of iron backwards and forwards for the purpose of breaking it. This line of injury is exposed to constant attack from corrosion, because the scurf is always thrown off from it. * * * * * _External corrosion_ is a far more frequent cause of explosion in stationary boilers; and it arises from many causes. The most frequent cause, although the most easily detected, is leakage from the joints of the fittings on the top of the boiler, which are too frequently attached by bolts instead of rivets. This evil is much increased when the boilers are covered with brickwork, which holds the water against the plates, and hides the mischief from observation. It is astonishing to find how much damage is allowed in this way to go on without attention, until the tops of boilers are corroded so thin that little holes burst through. These are sometimes found stopped with wooden pegs or covered by screwed patches of plate, either of which cause leakage that hastens the mischief, as shown by the sample exhibited. Boilers exposed to the weather will of course become corroded like anything else made of iron and not painted; and yet so much mischief is sometimes caused by leakage beneath improper covering that exposure may almost be said to be the smaller evil of the two, as it is better to see what is going on than to rest in false security. No covering will be found cheaper, or better, in the long run, than a roof, which prevents the loss of heat by exposure, and yet allows free access to all the fittings and joints on the top of the boiler. [Illustration: _Fig. 60._] Some examples of the evils of covering can be given that have come under the writer's observation. A set of boilers had been well covered by arches of brickwork, so built as to keep out all water, and also set so as to touch the boilers only at intervals, leaving a space generally of a few inches. After about seven years' working, the whole of the tops of the boilers were discovered to be dangerously thin, and had to be renewed. The cause was leakage from the joints of fittings and seams of the boilers, and the issuing steam had been drawn along the space between the boilers and the arches, and had escaped at a place where it had not attracted notice. In another case, a somewhat similar set of boilers were covered with ashes, to prevent the loss of heat by radiation; and the rain and the leakage beneath the ashes, in conjunction with the corrosive matter from the ashes themselves, thinned the tops of the boilers to a dangerous extent in less than two years. A sketch of the corrosion caused in this instance by covering with ashes is shown in Figs. 60 and 61. [Illustration: _Fig. 61._] [Illustration: _Fig. 62._] [Illustration: _Fig. 63._] Similar mischief has been noticed in boilers covered with sand, as shown in the sketches Figs. 62 and 63, which represent an instance of corrosion after eight years' working; although nothing forms a better covering than sand for preventing loss of heat by radiation. In both these examples it will be seen that the corrosion has continued until the thickness of the plate has been so eaten away that a hole has been burst out at SS. A very good covering is formed by brickwork in cement; or various cements made for the purpose, which adhere to the surface of the plate and yet show leakage; or such materials as sacking or felt; or sheet-iron casing, leaving about 6 inches of air space all round the boiler. But all these have the great objection that they hide the boiler from inspection, except by the expensive process of removing the covering; and in this way dangers that have caused explosion have remained hidden from observation. Explosions have also taken place from general corrosion of the surface of the boilers in the flues. A new boiler which was set on sidewalls built upon a foundation of porous rock was found to have become corroded all along the bottom in less than two years, owing to the dampness which rose from the foundations causing a constant presence of vapour. The corrosion was peculiar, and more like that found on old iron left for a long time in a damp place; for the iron plate fell to pieces when touched, and large flakes could be raised from the surface, and the greater part of the thickness of the plate could be removed with the fingers. Somewhat similar corrosion had taken place in a boiler which exploded at Loughborough in 1863; the bottom of the shell became rent at the corroded part, and as the fracture continued spirally round the boiler several times, nearly all the shell was peeled off in the curious manner shown in Fig. 64. The explosion shown in Fig. 65, which occurred at Leeds in 1866, also arose from corrosion of the bottom of the boiler. [Illustration: _Fig. 64._] [Illustration: _Fig. 65._] [Illustration: _Fig. 66._] The greater part of the corrosion found in the side flues of boilers is caused by the leakage of seams. Many boilers are emptied for cleaning as soon as work is over on Saturday night, and long before the brickwork of the fireplaces and flues has cooled; and consequently, the boiler, having no water in it, is made much hotter than it ever is in working, and the seams are injured and sprung and the rivets loosened by the extra expansion so caused. This is sometimes done intentionally, in order to loosen the scale by the greater expansion of the iron than of the scurf. When the boiler is again set to work, the seams and rivets leak and cause that corrosion which is called channelling. This has been observed to occur to such an extent that all the seams in a boiler have been seen thus corroded; and the same has sometimes been found in all the boilers in a large manufactory. Specimens of this channelling were exhibited to the meeting. One in particular, shown in Figs. 66 and 67, deserves attention, as it shows the effect of a jet of steam and water from the leaking rivet R, in cutting a series of channels into the plate along the course of the dotted lines EEE, and producing a hole in the plate at S. This corrosion had been going on for about four years, but was in a part of the boiler seldom seen in ordinary examination. Many explosions have resulted from this form of corrosion; for when a rent is once made, the fracture continues along the thinned channel of the plate. [Illustration: _Fig. 67._] The corrosion most to be dreaded, because most difficult to detect, is that which takes place where the boiler is in contact with brickwork; and it is found alike in all forms of boilers set in brickwork. When found at the part where the side flues are gathered in at the top against the boiler, it is usually occasioned by the leaking of fittings or feed pipes, or by rain being allowed to run between the boiler and the brickwork. More than one explosion has been caused by the droppings from a roof being allowed to fall upon the tops of the flues. When the corrosion is found at the point where the bottom flue walls touch the boiler, it is frequently caused by the leaking of seams that have been strained by the weight of the boiler; and this often arises from want of care to replace the brickwork, after repair of the boiler or flues, in such a position as to take again its proper proportion of the weight of the boiler. Cases have been met with where the shape of the bottom of large boilers has been quite altered by such means. The brackets on the sides of heavy boilers have not only been strained so that the rivets or bolts have leaked and caused corrosion, but they have also bent or cracked the side plates of the boiler. The bracket shown at B in Fig. 53, page 40, made of only an angle iron with a piece of plate attached, is especially liable to cause injury if the brickwork is not rebuilt close up to the angle iron, as the leverage is so great. This is avoided by the better form of bracket shown at C, consisting of an elbow of flat bar-iron rivetted at top and bottom to the boiler. [Illustration: _Fig. 68._] In the old balloon and wagon boilers, the angle where the bottom joined the sides scarcely ever remained sound for long when in contact with the brickwork, and many of those that exploded have been found almost corroded through where they stood upon the brickwork. The explosion before alluded to and shown in Fig. 7, was caused by corrosion of the bottom of the boiler where it was set on the brickwork. Many boilers are so set that the brickwork of the flues is made to follow the shape of the boiler, with as little space between as possible; but the slight advantage gained in increased heating effect is far outweighed by the impossibility of getting into the flues for examination. It is only by having the flues sufficiently roomy that proper examination can be made, and that the indications on the brickwork of leaking can be seen and remedied, and corrosion arrested. A remarkable case of corrosion occurred in a boiler with an oval shell, set upon a middle wall. The flues were too narrow for a man to enter, and a leak in the bottom was only discovered by the boiler nearly running empty while the engine pumps were standing for a short time. It was subsequently found that the whole bottom where it rested on the wall was extensively corroded in a continuous line, and that explosion was only prevented by the numerous stays across the bottom to compensate for the oval shape. Fig. 68, shows the position and extent of the corrosion, and the plate was completely in holes at the parts indicated by the black marks. This corrosion was supposed to have been going on for about three years. [Illustration: _Fig. 69._] [Illustration: _Fig. 70._] It is sometimes asserted that corrosion cannot be the cause of an explosion, because the corroded place would simply give way and let off the steam harmlessly, or at least the boiler would not be displaced from its seating. When the corrosion is only local, and surrounded by sound plates of sufficient strength to arrest the extension of the fracture, this may be the case, as in an explosion at Sheffield in 1865, shown in Fig. 69, where a piece of plate was blown out on one side of the boiler, allowing the steam and water to escape without displacing the boiler; the thickness of the plate at that part had been reduced to 1/8th inch by corrosion in about 1-1/2 years, which had been caused by leakage at the seams from inefficient repair with bolts instead of rivets, and also from the moisture having been allowed to be kept against the plate by the brickwork. But even under such circumstances, if the piece blown out should be from the bottom, the whole boiler may be thrown a great distance by the reaction of the issuing steam, as in an explosion at Leeds in 1865, shown in Fig. 70. If the corrosion extends for any length, the first rent is almost sure to continue until a complete explosion is the result. Several of the small models exhibited to the meeting showed the line of fracture in various cases of explosion. One showed the appearance of a plain cylindrical boiler after explosion caused by corrosion along the whole length where it rested on brickwork; this explosion occurred at Wigan in 1865, and a sketch of it is given in Fig. 71. [Illustration: _Fig. 71._] Many explosions of boilers have been caused by accumulation of scurf. The mischief is not so much from scurf being gradually deposited all over the interior of the boiler to a dangerous thickness as from the chips off the sides falling in heaps on the bottom. The plate beneath this accumulation becomes overheated, because not in contact with the water, and softens and sinks down into a "pocket," which if unnoticed will soon burn quite through. If the scurf that has caused the mischief is thick and hard enough to resist the pressure for a little time, the hole enlarges, until the scurf suddenly gives way and allows the contents to issue so violently as to disturb the boiler, or at least to blow the fire out of the grate. Such was an explosion at Bilston in 1863, where a large plain cylindrical boiler, 9 ft. diameter, was heated by three large fires placed side by side along the bottom; and a large "pocket" burst out over the third grate, and scalded the attendant to death. A similar pocket in a boiler, 4 ft. 6 ins. diameter, which exploded at Dudley in 1864, after having been at work six weeks without cleaning, is shown in the transverse section, Fig. 72. In this case the scurf had filled up the circle of the boiler to a depth of 3 inches at the bottom, as shown in the drawing, and was of a very hard description; and the boiler plate was bent out in a gradual curve, and thinned to about 1/16 inch, the original thickness being 1/2 inch. [Illustration: _Fig. 72._] [Illustration: _Fig. 73._] The whole bottom of a boiler is sometimes injured, and the plates buckled and the seams sprung, from the accumulation of mud. One case may be mentioned where the water was very full of mud, and the boilers were worked day and night during the week but stopped for several hours on Sunday, during which time the deposit of mud was so thick that it did not get thoroughly disengaged again from the bottom when the boiler was set to work, but hardened into a mass. Although many of these pockets and injuries to the plates may occur without serious damage, they sometimes cause that first rent which destroys the equilibrium of the structure and leads to explosion. Some of the specimens of scurf exhibited to the Meeting show that their thickness is made up of small chips, carelessly left after cleaning or fallen from the sides of the boiler, as seen in Fig. 73, or from cotton waste or other matter left in the boiler and forming a nucleus for the scurf to accumulate upon. Other specimens show that foreign matter must have been put into the boiler to stop leaking. Accumulations of scurf in the feed pipes at the point of entrance into the boiler have also caused explosion by stopping the supply of water. The same result is caused by the freezing of the water in the pipes which are exposed, and each winter one or two boilers are injured or exploded from this cause, especially small household boilers placed behind kitchen grates. Scurf cannot be considered so great an evil as corrosion, since it can be removed, and if this is done in time, the boiler is restored to its original condition. The advantage of a pure water, which does not deposit scurf, is so great for the supply of boilers that it is always worth while to go to considerable expense for obtaining it; or to take some steps for purifying the feed water as much as possible. If it is only mud mechanically suspended, which would deposit by gravity on the bottom of the boiler, frequent use should be made of the blow-off apparatus. If the impurity is light enough to be carried to the surface in the form of scum, the blow-off apparatus should discharge from the surface of the water as well as from the bottom. If the impurity is chemically suspended in the water, some one of the many substances which form the refuse from various manufactures, and which may contain suitable ingredients, should be used to counteract the effect of the impurity. Common soda will answer the purpose perhaps better than anything else. It must not be forgotten however that the blow-off apparatus must afterwards be used more frequently, to rid the boiler of the foreign matter, or the mischief will be increased. In marine boilers, constant attention is necessary to get rid of the saline deposit; and in stationary boilers using impure water an equally systematic attention is needed to get rid of the earthy deposit. * * * * * Perhaps no cause of explosion is oftener mentioned than shortness of water, and this is not unfrequently coupled with turning on the feed suddenly into an overheated boiler. Many explosions have been attributed to this cause, when closer investigation would have revealed some far more probable reason. For instance, shortness of water was stated as the cause of the explosion, at Abercarn in 1865, of a single-tube boiler with a very large flue tube, which collapsed upwards from the bottom. The top of the tube and the sides of the shell had not the slightest mark of overheating, although exposed to the flame of three furnaces, one of which worked through the tube, and the others on each side of the shell. In this case the cause of explosion was clearly the weakness of the tube, and not shortness of water. It is erroneous to suppose that if a boiler runs dry, or if the feed is turned into a red-hot boiler, there must necessarily be an explosion. If a boiler unconnected with any other runs rapidly empty, from the breaking of the blow-off pipe or any such cause, it will simply get red-hot and sink out of shape upon the fire, as may often be seen, but no explosion would happen. If the water only falls gradually, as it would if the feed were turned off and evaporation continued, the parts exposed to the fire would get overheated as the water left them. If the subsidence of the water were very slow, those parts might get red-hot, and so much softened and weakened as to be incapable of bearing the pressure, when an explosion would take place, as at Smethwick, in the present year, where the flues were set above the water line, as shown in Fig. 74. [Illustration: _Fig. 74._] If however the water were turned on again before the overheating had gone so far, and the feed pipe were, as usual, carried down to nearly the bottom of the boiler, the water would gradually creep up the heated sides and cool the plates, the heat of which would not be sufficient to cause greater evaporation than the ordinary safety valves would carry off. The danger would not arise so much from the excess of steam generated by the heat accumulated in the heated plates of the boiler, as from the injury and strain that would be caused to the plates by the undue expansion and sudden contraction, especially as this action would take place on only a portion of the boiler. A singular case, bearing on this point, may be mentioned. A four-furnace upright boiler, like that shown in Fig. 44, happened to run so nearly empty, through the accidental sticking of the self-acting feed apparatus, that the level of the water sank to the top of the hemispherical end forming the bottom of the boiler. The feed apparatus then became released of itself, and, the feed being turned full on, the water gradually rose until the whole occurrence was only discovered by the leaking at the seams that had been sprung, which caused so much steam in the flues as to stop the working of the furnaces. The overheating had been sufficient to buckle the plates, and in one place a rupture had almost commenced; but there was no explosion. By way of direct experiment upon this point, boilers have been purposely made red-hot and then filled with cold water, without causing explosion. It has been supposed that boilers sometimes explode from overheating without the water level being below the usual point, or without the accumulation of scurf previously alluded to, but simply by the rapidity of the evaporation from an intensely heated surface causing such a continuous current of steam as to prevent the proper contact of the water with the heated plate. Such has been the cause assigned for the explosion of a three-furnace upright boiler at Birmingham in 1865, shown in Fig. 75. A piece of plate about 3 ft. by 1-1/2 ft. was blown out of the side, at a place where an enormous flame impinged continually. The plates had first bulged out, and then given way in the centre of the bulge, each edge being doubled back and broken off. There was no positive evidence as to the water supply; but the crown of the centre tube, which was much above the bottom of the part blown out, remained uninjured. A somewhat similar case was that of a large horizontal boiler at Kidderminster, the tube of which collapsed in 1865, as shown in Fig. 76. It was heated by four furnaces, one of which worked into the tube, one under the bottom, and one on each side; and all the furnaces worked into the same end of the boiler. The tube was found to have partially collapsed at that end, and the top had dropped 11 inches. This was repaired in the first instance, but was afterwards again found injured by overheating, although not so seriously. It is very probable that the extremely rapid ebullition from the sides and bottom, from which the steam had to pass up the narrow space between the tube and the shell, produced such a foaming that very little solid water could reach the top of the tube where it was exposed to extreme heat. [Illustration: _Fig. 75._] [Illustration: _Fig. 76._] Many explosions have been attributed to deterioration of the iron through long use, as in an explosion at Durham in 1864, and another at Haswell, near Sunderland, 1865, where the boilers had worked constantly for 25 and 30 years respectively. When an explosion arises from the failure of a plate which has not been properly welded in rolling, there is no question that it was unsound when put in, and escaped notice; but when the plate that fails is found to be brittle and of bad iron, the fault is rather attributed to the effect of working than to original bad quality. Of course this is not always the case, as the injury done to plates by overheating has been already explained. Pieces of plate have in some cases been erroneously pronounced to be deteriorated by work, which have been taken from situations in the boilers where they were not exposed to any action of fire that could cause overheating; and therefore in reality the injury could only have taken place when the boiler was being made, by burning the iron in bending it to the required shape. A frequent cause of fatal injury to boilers is injudicious repair, whereby the crossing of the seams is destroyed, as in the explosion at Wolverhampton in 1865, previously referred to and shown in Fig. 36. Moreover the edges of the old plates, already tried by the first rivetting and the subsequent cutting out of the rivets, are frequently strained again by the use of the drift to draw them up to the strong new plates; and many a seam rip is thus started which ultimately causes explosion. Many explosions have been caused by the want of proper apparatus for enabling the attendant to tell the height of the water and the pressure of the steam, and also by the want of sufficient apparatus for supply of feed water and escape of steam, or by the failure of one or other of these; but such explosions can only be referred to generally in the present paper. The mountings on a boiler are usually so open to observation, and the importance of having them good and efficient is so universally acknowledged, that much remark is not needed. Mention has already been made of the sticking of self-acting feed apparatus as a cause of mischief, and similar failures of floats and gauges have constantly happened; but this should by no means be considered to condemn self-acting apparatus, either for assisting in the steadiness of working, or for giving warning of danger. The apparatus however should be relied on for assistance only; and an attendant cannot be called careful who leaves a boiler dependent on such apparatus without watching. The self-acting principle has been seen by the writer applied in a novel and useful way in a recording pressure gauge, which proved the more interesting as it had shown the actual pressure of steam at the time of the explosion of one of the boilers with which it was connected. Among the numerous boiler explosions that have been attributed to over-pressure through deficient arrangements for escape of steam, in many cases the safety valves have been placed on the steam pipes in such a manner that the communication with them was cut off whenever the steam stop-valve was shut, which is just the time when the safety valves are most wanted. Safety valves are too often found needlessly overweighted; and it is believed that many boilers are constantly worked with safety valves so imprudently arranged and weighted, that they could not carry off all the steam the boilers would generate without a very great increase of pressure. * * * * * It is concluded that enough has now been said to show that boiler explosions do not arise from mysterious causes, but generally from some defect which could have been remedied if it had been known to exist. It only remains therefore to consider what is the most ready and efficient way to discover the true condition of a boiler. It has been maintained that this end is best accomplished by what is called the hydraulic test, in which a pressure of water is maintained in the boiler for a given time at a certain excess above the working pressure. This test is undoubtedly useful so far as it goes, and is perhaps the only one that can be applied to boilers with small internal spaces, such as locomotive boilers, not admitting of personal inspection over the whole of the interior; and it is also admirable for testing the workmanship of a new boiler. But on the other hand the conditions of a boiler at work are so different from those which exist during the hydraulic test, that this alone cannot be depended on; for old boilers have been known to stand this test to double their working pressure without apparent injury, although known to be dangerously corroded. The difficulty also of seeing or measuring the effect of the hydraulic test upon large boilers set in elaborate brickwork is so great that little practical benefit has resulted in many cases. It is believed by the writer that the surest way to ascertain the true condition of a boiler is to examine it at frequent intervals in every part, both inside and outside; and as this can only be done when both the boilers and the flues can be readily entered, it is specially important that facility for examination should be made a consideration in selecting a construction of boiler. Permanent safety should be considered as an element of economy, in addition to its still higher importance in reference to the preservation of life. ON THE CONCLUSIONS DERIVED FROM THE EXPERIENCE OF RECENT STEAM BOILER EXPLOSIONS, BY EDWARD B. MARTEN, MEM. INST. M.E., EXCERPT MINUTES OF PROCEEDINGS OF THE MEETING OF THE INSTITUTION OF MECHANICAL ENGINEERS, AT NOTTINGHAM, 3RD AUGUST, 1870, THOMAS HAWKSLEY, ESQ., VICE-PRESIDENT, IN THE CHAIR. BY PERMISSION OF THE COUNCIL. The records of Steam Boiler Explosions in recent years are very numerous, as the increased attention drawn to the subject in this and other countries has placed far more information at disposal; and the experience of the last four years, since a former paper was read by the writer on the subject of boiler explosions, has confirmed the opinion then expressed, that all boilers, however good in original construction, are liable in the course of time to get into bad order and explode. The particulars of the explosions during this period are given in the Tables appended to the present paper, which show the number of explosions due to each cause in each class of boiler, distinguishing those of the United Kingdom from those in foreign countries. An analysis is also given of the explosions in the last four years, showing the causes of explosion of each form of boiler; and also a summary of the causes of explosion under the three general heads of--(1) faults in construction or repair: (2) faults in working which creep on insidiously and unnoticed: (3) faults which might be seen and guarded against by careful attendants. Nearly all of the faults in these three classes would have been detected by periodical examination. * * * * * In the case of Cornish, Lancashire, and other boilers with internal flues, the faults of construction which have caused explosions have been weakness in the tubes, combustion chambers, ends, domes, or manholes; and explosions in these, as in other classes of boilers, have also resulted from external or internal corrosion, shortness of water, undue pressure of steam, and scale or mud on the boiler plates. In plain cylindrical boilers, and others without internal flues, explosions have resulted from the boiler ends being made flat, and also from frequent repairs producing seam rips, especially in boilers having the plates arranged lengthways instead of in rings. In marine boilers, weak flues and weak ends have also led to explosion, in addition to the other causes mentioned above. Locomotive boilers have in two cases exploded in consequence of the strains thrown upon them by their being used as a frame for the engine. Other explosions have resulted from want of stays, and from too much heat impinging on some particular part; and in domestic boilers from freezing of pipes under pressure. * * * * * Altogether the total number of explosions in this country that have been recorded during the past four years has amounted to 219, which may be classed under the following heads:-- Faults of construction or repair 95 Faults to be detected only by periodical examination 62 Faults which should be prevented by careful attendants 54 Extraneous or uncertain causes 8 --- Total 219 --- By these 219 explosions 315 persons were killed and 450 injured. The following are the particulars of the construction of the 219 exploded boilers:-- Cornish, Lancashire, or other boilers with internal flues 84 Plain Cylindrical boilers or others without internal flues 54 Marine boilers 12 Agricultural boilers 11 Locomotive boilers 10 Furnace-upright boilers 8 Crane boilers 6 Rag steamers, &c. 6 Balloon and Elephant boilers 5 Domestic boilers, &c. 16 Not sufficiently described 7 --- Total 219 --- The causes of these 219 explosions may also be classed as follows:-- Worn out, corroded, or burnt plates 89 Undue pressure, overloaded valves, intentional or from carelessness 25 Bad construction, defective fittings or stays, or want of repair 69 Shortness of water, formation of scale or mud, or external flues set too high 28 Extraneous or uncertain causes 8 --- Total 219 --- Sketches are given of the most instructive examples of boiler explosions during the last four years, which are sufficient to explain themselves, with a brief reference to their special features. * * * * * [Illustration: _Fig. 1._] Although the importance of periodical examination as the best safeguard against explosion is generally admitted, a great number of those who make or use boilers have not at present sufficient belief in its importance to adopt this course. Boilers are still constructed or set in such a manner as to render examination next to impossible; and are continued to be worked without making it the duty of those who mind them, or of any one else, to examine every part at frequent intervals; and hence such explosions have occurred as shown in Fig. 1, No. 12, 1870, in which the original position of the boiler before explosion is indicated by the dotted lines. It is thought by many steam users that all has been done which is possible, if their boilers are the best that can be procured, and are set in the most approved way; and it is taken for granted that such boilers should last for many years, under the idea that a good boiler can never explode unless the feed is neglected. Similar boilers are often referred to as having worked safely for ten or twenty years, but it is forgotten that they may be exposed to the insidious action of furrowing on the inside or channelling on the outside, such as caused the explosions of the originally good boilers shown in Figs. 2, 3, 4, and 5, Nos. 35, 1870; 50, 1866; 46, 1869; and 25, 1870. [Illustration: _Fig. 2._] [Illustration: _Fig. 3._] Much mischief arises from special classes of boilers, fittings, or apparatus, being looked upon as promising permanent safety from explosion; while the inevitable circumstance is overlooked that it is only so long as everything is maintained in good condition that safety is insured. An apparatus, for instance, for preventing explosion from shortness of water or over-pressure, however perfect for any such object, would be quite inefficient as a safeguard against explosion from corrosion, furrowing, channelling, or weak construction. It is curious to note how often it is the case that every other part of an establishment is subject to severe and perpetual scrutiny, the engines especially being overhauled with the most scrupulous regularity; while the boilers, the very source of the power and the heart of the whole business, are left to themselves for long periods, even for years, without examination; and it is too often only after bitter experience that owners have understood the need of this examination. In this, as in many other matters, experience has shown that there is no royal road to safety, and that immunity is only secured by unremitting care and constant watchfulness. It should never be forgotten that even a good boiler can explode; for however good at the outset, sooner or later the time must eventually arrive, when such wear and tear will have taken place as will result in dangerous weakness, unless the boiler is carefully and systematically attended to. Although a boiler may even last safely for ten to thirty or more years if worked slowly and with care, no confidence can be placed in a boiler which has worked so long, unless it is examined in every part. [Illustration: _Fig. 4._] [Illustration: _Fig. 5._] [Illustration: _Fig. 6._] [Illustration: _Fig. 7._] The opinion is more general than many are aware of, that explosions as a rule are caused by shortness of water and the sudden turning on of the feed water upon red-hot plates; and the appearances of injury in the plates from fire, arising in the ordinary course of working, have been frequently mistaken for signs of overheating from shortness of water at the time of explosion, as illustrated in Figs. 6 and 7, No. 24, 1867, and No. 59, 1866. Although boilers do explode from the softening of the plates by overheating in consequence of shortness of water, yet it is very doubtful whether the turning on of the cold water at such a time is ever the cause of explosion. The feed water being always introduced at the bottom of the boiler, as in Figs. 8, 9, and 10, cannot be scattered suddenly near the overheated parts, but must rise gradually up the sides; and the boiler would have gone to pieces from the giving way of the softened parts long before the water reached them, as was the case in the explosions shown in Figs. 11 and 12, end of 1868. The experiment of injecting cold water into red-hot boilers has been carefully tried more than once, without producing any explosion. [Illustration: _Fig. 8._] [Illustration: _Fig. 9._] [Illustration: _Fig. 10._] Although it may be too much to suppose that boiler explosions will ever be entirely prevented, it is important that those who have the care of boilers should understand better what are the true causes of explosion, in order that they may know what to guard against in addition to shortness of water. This better understanding of the subject has been much retarded by the supposition that the causes of boiler explosions are beyond the comprehension of the boiler minders; and still more by the important differences of opinion among those under whom they work. Much evil has resulted from the promulgation of strongly expressed views, which have been founded upon facts but of too limited extent, and such as must become modified by consideration of the facts of a large number and variety of explosions. Mysterious theories to account for explosions have been resorted to only from want of clearer explanations. [Illustration: _Fig. 11._] [Illustration: _Fig. 12._] [Illustration: _Fig. 13._] [Illustration: _Fig. 14._] Before considering in detail the causes of explosion, it is necessary to recall to mind that beyond question there is sufficient accumulated force in any working boiler to cause all the violent effects of an explosion, if this force be suddenly liberated. In Figs. 13 and 14, No. 18, 1869, and No. 63, 1866, are shown the violent effects of the rupture of vessels employed for steaming rags, which were filled with steam only. In ordinary boilers however there is present, besides the steam, a quantity of water heated much beyond the atmospheric boiling point; and when rupture takes place and the pressure is suddenly relieved, part of this water evaporates, and keeps up the supply of steam to continue the rupture and destruction. The explosion of a boiler differs from the discharge of electricity or lightning, which cleaves the air and instantly leaves a vacuum; it also differs from the discharge of detonating compounds which act suddenly and leave a vacuum; but it more nearly resembles the discharge of gunpowder, which burns sufficiently slowly to keep up a continuous pressure behind a projectile until it leaves a gun; and each cubic foot of water in a boiler working at 60 lbs. pressure has been shown to produce in steam an explosive effect equal to one pound of gunpowder. None of the elaborate but unlikely theories of decomposed steam, or of electric accumulations, suppose a force so fitted to cause destruction as that contained in the highly heated water existing in all working boilers. * * * * * The following appear to be the general results to be derived from the experience of the explosions in this country during the last four years. [Illustration: _Fig. 15._] [Illustration: _Fig. 16._] First as to faults of construction which fall under the department of the boiler maker or repairer. One of the most apparent causes of explosion in stationery boilers is the loss of strength occasioned by frequent repair, not only from the injury done to the old plates by removing rivets, but from the want of bond in the new work. This has lead to many of the explosions of the Plain Cylindrical boilers, such as are shown in Figs. 15, 16, and 17, No. 45, 1869, No. 32, 1870, and No. 20, 1870. Where the plates are arranged longitudinally instead of in rings, the danger is increased, as there is less chance of a dangerous rip being arrested by a crossed joint. So great a number of boilers with continuous longitudinal seams, especially in the North, have worked for twenty or thirty years, that it can hardly be supposed they are any weaker than the boilers made in rings; but they are more liable to explode, for if a seam rip occurs, it more easily extends along the seam, and leads to the general break up of the boiler, shown in Fig. 18, No. 59, 1869. [Illustration: _Fig. 17._] [Illustration: _Fig. 18._] Perhaps no boilers have worked for a greater number of years than the Plain Cylindrical boilers, many specimens being in existence and apparently in good order which were put to work fifty or sixty years ago. When such boilers have been too much or injudiciously repaired, they are treacherous and uncertain; but their rupture and explosion occur not so much on account of fault of shape, as from the simple reason that like willing horses they are easily overworked. The grates are usually twice as large as the fair proportion to the heating surface, producing the double evil of forcing more heat through the iron plates over the fire than they can transmit without injury, and allowing a great amount of heat to pass away to the chimney without useful effect. Careful experiment shows that nearly as good duty can be obtained with the plain cylindrical boiler as with any other form, provided the rate of combustion is in fair proportion to the extent of heating surface in the boiler. The circumstance that many plain cylindrical boilers have exploded is not sufficient to condemn this make of boiler, which is the cheapest, simplest, and most easily set. If the number of explosions alone were to be taken as the guide, it would lead to the condemnation of the Cornish and Lancashire boilers, from the experience of the past four years. But in case of both plain cylindrical and other forms of boilers, most of the dangers admit of remedy, and can be guarded against by frequent examination. [Illustration: _Fig. 19._] [Illustration: _Fig. 20._] Five very fatal explosions have occurred of boilers heated by Puddling and Mill Furnaces, leading in some cases to the supposition that this form of boiler is more liable to explosion than others. They were not adopted however in the iron-making districts without great care and consideration, and there does not seem ground for attributing special danger to them. The causes of the five explosions referred to of these boilers were manifest, and would have led to the explosion of any form of boiler; the loss of life however was great, because the situation of the boilers was among a large number of workmen. The steam power required in ironworks so far exceeds that in any other trade, that an ironwork is half composed of boilers; the workmen are necessarily within the range of explosion of many boilers, and hence the great loss of life when such an accident occurs. The explosions of such boilers shown in Figs. 19 and 20, No. 24, 1868, and No. 31, 1868, were from external and internal corrosion respectively of the bottoms, rendering them too weak to bear the ordinary pressure. [Illustration: _Fig. 21._] [Illustration: _Fig. 22._] [Illustration: _Fig. 24._] Those shown in Figs. 21 and 22, No. 23, 1870, and No. 53, 1869, were from the collapse of the central tubes, which were weakened by external and internal corrosion respectively. In Fig. 24, No. 35, 1868, the shell was in bad order from over work and receiving too much heat from four large furnaces, one of these especially causing a constant mass of flame to impinge upon a single plate, which resulted in a seam rip. [Illustration: _Fig. 23._] [Illustration: _Fig. 25._] [Illustration: _Fig. 26._] [Illustration: _Fig. 27._] The greatest number of explosions and the greatest loss of life and personal injury have been in the case of Cornish and Lancashire boilers, or others with internal flues. In the county of Cornwall itself there have been many explosions, as often from the rupture of the shell, Fig. 23, No. 58, 1869, as from the collapse of the tube, Fig. 25, No. 35, 1869. The temporary patching on some of these old boilers was most extensive, Fig. 26, No. 52, 1869, and the only wonder really was that they held together as long as they did. The belief that shortness of water is the only cause which can lead to the collapse of tubes is so strong, that the boiler minders have often been condemned almost unheard in cases of explosion, as if there were no room for doubt that their neglect was the cause. Explosions from weakness of tubes are not however confined to Cornwall, as for example in Fig. 27, No. 42, 1868, where the flue was oval and very weak: although it was supposed that shortness of water caused the accident, from the idea that nothing else could account for it. The strain caused by the varying temperature of the internal tubes in Cornish or Lancashire boilers, and the difficulty of staying their flat ends so as to make them sufficiently secure without being too rigid to allow for the expansion of the tubes, render them liable to corrosion or "furrowing" in particular lines of strain, the destructive action of which is very rapid; while the large quantity of brickwork around the outside, necessary to form the external flues, also renders them liable to corrosion in the parts most difficult of access. In this favourite form of boiler therefore careful and frequent examination in every part is more needed than in boilers of simpler form and setting; and the increasing number of explosions among these boilers seems to establish that they are only trustworthy if frequently examined and kept in perfect order. [Illustration: _Fig. 28._] [Illustration: _Fig. 29._] [Illustration: _Fig. 30._] Several instances have occurred of explosion of Portable Crane Boilers. Their small size has led to their condition being disregarded, under the idea that scarcely any pressure could burst them. In practice it is found however that they are often exposed to greater pressure than other boilers, because the fire is large and quick in proportion to their size; and they often have to stand for a considerable time with the steam up, and their exposed position and long intervals of rest add to the chances of corrosion, as shown by the example in Fig. 28, No. 14, 1869. The large manholes without strengthening rings, that are so often put in these boilers, have been the cause of explosions such as that shown in Fig 29, No. 57, 1866. [Illustration: _Fig. 31._] The same remark applies to some of the portable or agricultural boilers which have exploded, such as those shown in Figs. 30 and 31, No. 43, 1868, and No. 12, 1869. Much mischief is often caused by bad imitation of well planned boilers. Thus in boilers of the Cornish form, the ends are made sometimes so rigid as to give no allowance for the expansion of the tube, and the result is such continued strain as to cause constant leaking and the consequent risk of fracture. In furnace boilers the tops of the crowns of the inside tubes are often made flat, as in Fig. 37, instead of being domed; or the inside tube is of undue size, as in Fig. 21, No. 23, 1870, see page 73. Furnace boilers have been made with the omission of the stays that are so peculiarly necessary in that form, whereby both ends have been left free to bulge outwards with the pressure, as in Fig. 32. [Illustration: _Fig. 37._] [Illustration: _Fig. 32._] [Illustration: _Fig. 33._] [Illustration: _Fig. 34._] [Illustration: _Fig. 35._] Cornish boilers are often altered to the plain cylindrical form, without compensation being made for the loss of strength caused by the removal of the tube; this has led to such explosions as shown in Fig. 33, No. 47, 1869, where two tubes where taken out, and Fig. 34, No. 42, 1867, where one tube was taken out. One of the most frequent and serious causes of loss of strength is the repairing of externally fired boilers. Not only are the patches sometimes only bolted on in a temporary manner, as in Fig. 35, No. 29, 1869, but even where they are rivetted on there is an entire want of bond or crossed joint, as in the case of the exploded boilers shown in Figs. 15, 16, and 17, see page 70 and 71, No. 10, 1869, and Fig. 36. [Illustration: _Fig. 36._] [Illustration: _Fig. 38._] An attempt is made in Fig. 38 to show the effect of wear and tear of boiler plate in an ordinary upright furnace boiler, such as is shown in Fig. 37. The external surface is exposed to intense heat and consequently expands, while the internal surface is kept cool by contact with the water and expands to a much less degree. The continued repetition of this process produces the same effect of cracking the surface as that seen in the anvil blocks of steam hammers; and the strength of the plate is reduced in proportion to the destruction of the continuity of its surface. The deleterious effect of this process is much increased if the boiler is subject to alternate heating and streams of cold air on opening the fire-doors. To avoid it the flame should have room to spread over as large a surface as possible, without impinging on one particular point, and the firing should be as regular as possible; and hence the greater freedom from injury in boilers mechanically fired or heated by gas. The above action is quite distinct from the overheating of the plates that occurs when no water is in contact with them, which simply softens them and reduces their strength, as in Fig. 39. It is believed that many boilers suffer from overheating without being short of water: and an attempt is made to show this action in such an upright boiler as is represented in Fig. 37, page 78, by the enlarged section of the side shown in Fig. 40. The flame is shown impinging on a limited surface, as before, and the steam rises so rapidly from the inner surface as to maintain a continuous stratum of steam between the iron and the water, and the plate consequently becomes overheated at that part. When the intense flame subsides by an alteration of the working of the furnace, the stream of steam diminishes, and the water returns and suddenly cools and contracts the plate, but often not before it has commenced to get out of shape. This has perhaps led to the explosion shown in Fig. 59, No. 37, 1868, page 82. The same thing may happen to the crowns of tubes of internally fired boilers when over fired, as in Fig. 41. Success has attended the use of internal linings to boilers, arranged so as to ensure a rapid circulation over the most heated parts, and also to catch all the mud and loose scale. [Illustration: _Fig. 39._] [Illustration: _Fig. 40._] [Illustration: _Fig. 59._] [Illustration: _Fig. 41._] [Illustration: _Fig. 42._] [Illustration: _Fig. 43._] [Illustration: _Fig. 44._] In order to enable boiler minders to make proper periodical examinations, it is necessary that care should be taken to arrange both the boilers and the flues with that view; and this can be done without materially injuring the efficiency of the boiler. Ordinary plain cylindrical boilers can be entered easily, as in Fig. 42; and although the small spaces between the tubes and the shells of Cornish and Lancashire Boilers, as shown in Fig. 43, render the complete examination troublesome, there is no difficulty in seeing those parts most likely to need examination, such as the crowns of the tubes and the end plates and angle iron. It is in the external flues that greater accommodation is needed, as in many cases these are so narrow that the boiler is quite inaccessible without pulling down the brickwork, as in Figs. 44 and 45. The loss of heating effect caused by the use of wider flues is so little, that it is far outweighed by the greater security obtained from the more efficient examination that is thereby rendered practicable. The flues of the plain cylindrical boiler are easily made wide enough for a man to pass through them. The flues of Cornish and Lancashire boilers should be made as shown in Figs. 46 and 47, so that a man can enter them without such inconvenience as in Fig. 48. One point of danger being the use of wide mid-feather walls, on which corrosion is apt to take place, these should be narrowed and the weight of the boiler supported on side brackets; the top of the mid-feather and side walls can then be constructed with sight holes as at A A in Figs. 49 and 50, so as to give the means of examining the plates near each seam by simply removing loose bricks. [Illustration: _Fig. 45._] [Illustration: _Fig. 46._] [Illustration: _Fig. 47._] [Illustration: _Fig. 48._] [Illustration: _Fig. 49._] [Illustration: _Fig. 50._] [Illustration: _Fig. 51._] [Illustration: _Fig. 52._] [Illustration: _Fig. 53._] [Illustration: _Fig. 54._] [Illustration: _Fig. 55._] The explosions of fourteen Domestic or Heating-Apparatus Boilers are included in the list of explosions, Table III; and some notice is required to be taken of these, because they have led to the loss of the lives of those who could not be expected to know their construction or how to guard against accident; and as these boilers are seldom seen or examined after they are once set, they should be the more carefully constructed. In one or two cases these boilers were of a rectangular shape, as in Fig. 51, No. 41, 1868, ill adapted to bear internal pressure, and yet placed in connection with cisterns in the roofs of lofty houses, so as to expose them to a hydrostatic pressure almost up to their bursting strength without any addition of steam pressure. The most usual cause of explosion is the lighting of the fire during frosty weather in a house that has been left vacant, so that steam pressure accumulates in the boiler whilst the exit is frozen up, as was the case in Fig. 52, No. 6, 1870. The cast-iron boilers commonly used, Fig. 53, end of 1869, are capable of bearing but little pressure; and the wrought iron boilers, as in Fig. 54, No. 7, 1870, are found often so badly welded as to be but little stronger; but even if they were as strong as they could be made, the stoppage of the pipes by ice would lead to explosion. Steam pressure may be guarded against by a safety valve; but as this may become set fast in a little time, it would be far better to avoid all chance of steam accumulation by such an arrangement as that shown in Fig. 55, where the circulating boiler is placed within an open-topped boiler behind the kitchen fire, and only receives its heat through the hot water surrounding it, and therefore cannot itself become sufficiently hot to generate steam. * * * * * [Illustration: _Fig. 56._] A few remarks may be useful as to those faults arising in working which fall under the department of the boiler minders. Not a few of the explosions during the last four years have occurred from acts of simple carelessness, such as where a blow-off pipe was left open, so that the boiler was nearly emptied of water while at work; or in another case where two boilers were fed at the same time through a common pipe without a back valve, and the water from one "kicked" over into the other. Undue pressure has been allowed to accumulate by safety valves being tied down, as in the agricultural boiler, Fig. 56, No. 16, 1867; or by an extra weight being put upon the safety valve, as in an instance where three bricks were fastened to the lever and the fires were lighted earlier than usual, under the idea that an accumulation of steam could be raised during the night to make a good start in the morning. Another explosion was caused by working a boiler at more than three times its proper pressure to meet a temporary emergency. In not a few cases of explosion there was no pressure gauge on the boiler, or the gauge was out of repair in consequence of being placed on the steam pipe, so that it vibrated with every stroke of the engine; as in the examples shown in Figs. 24 and 16, No. 35, 1868, No. 32, 1870, pages 70 and 74. [Illustration: _Fig. 57._] Corrosion has been the direct cause of many of the explosions. In one or two cases the corrosion was known to exist, but the renewal of the boiler was too long delayed, as in Fig. 57, No. 8, 1869, in others it took both owners and minders by surprise, as in Fig. 1, No. 12, 1870, page 63. It is said that to produce rapid rusting of iron there must be present oxygen, water, and carbonic acid; and as all these are present in a boiler flue when there are leaks, it is not surprising that so many cases occur of explosions from corrosion. * * * * * Much mischief is often done by the injudicious use of compositions in the boiler that are designed to prevent incrustation, especially where there is no blow-off cock or where its use is neglected. A hard deposit on the boiler plates is, in the writer's opinion, not so injurious as the soft and muddy deposit produced by the use of such compositions. A hard scale is equivalent to thickening the plate; and although this is sufficiently mischievous, the injury to the plates is much more rapid when a thicker but spongy deposit entirely prevents contact of the water and impedes the transmission of the heat. An attempt to illustrate this is given in Fig. 58, which is an enlarged view of a portion of such a boiler as is shown in Fig. 37. The money spent in boiler compositions would be better applied in securing a supply of proper water, or in filtering and purifying the water before it enters the boiler. [Illustration: _Fig. 58._] The writer has had to mention only faults in boilers; but it is not to be inferred that all boilers are working in actual danger. A very small percentage perhaps are so; but without periodical examination no one can feel sure of the condition of any boiler. It is not likely that explosions in future will be from exactly the same causes as those now described, because the known faults will be avoided. For instance no new Balloon, Wagon, or Butterley boilers are now made; and the peculiar faults and the weakness of the tubes in Cornish and others of the better classes of boilers are now so well known as to be generally avoided; and as information spreads, many evils will become things of the past. As periodical examination has been so strongly advocated, it might seem natural to desire that it should be enforced by government authority; but this is by no means recommended. A select parliamentary committee has been recently investigating the subject, with a view to ascertain whether that would be desirable, but has adjourned for the session without coming to any decision on this point. Even if a perfect system of government inspection could be contrived and perfectly administered, it would have the effect of taking the responsibility from the owners, who are the natural guardians of the safety of their boilers. Although the loss of 70 lives per annum by boiler explosions is sufficiently deplorable, the deaths by railway accidents are more than three times that number; yet very little inspection of railways is held to be necessary, and that inspection takes place chiefly before the commencement of working or after accidents. A coercive system may introduce more evils than it cures, especially as at present so much difference of opinion exists respecting the causes of boiler explosions. In the opinion of the writer, far more real good arises from the calm discussion of the facts and from the spread of correct information by such societies as this Institution, than from enforcing by law any action which is not perhaps believed by the majority of steam users to be at all necessary or useful. It has been at times suggested to increase the power and responsibility of coroners in holding inquests upon those killed by boiler explosions, by requiring them to obtain scientific evidence and to insist that the causes of the explosions shall be added to the verdicts of juries. But it is believed that this would only encumber an important institution, because a jury who might well decide whether a person had been killed by any criminal carelessness would not be a suitable tribunal to decide between possibly conflicting scientific evidence; and also, as an inquest may result in a verdict of manslaughter, the eliciting of information on such an occasion is checked by the natural fear of inadvertently involving some one in so serious a charge. The public at large, and steam users generally, would gain more information and guidance from the scientific evidence itself than from the verdict of a coroner's jury; and it is believed much good has resulted in preventing locomotive boiler explosions by publishing the reports of the government inspecting engineers, who have gained their knowledge of the facts in conversation with all those concerned, and have added recommendations which have been promptly acted upon. The writer's object has been that the boilers found most convenient and best suited for the different purposes for which they are used should be made to work with safety, rather than that reliance should be placed upon the qualities of any particular kind of boiler or fittings. No form of boiler at present admits of absolute reliance upon its freedom from risk. The following general conclusions appear to arise from the consideration of the records of boiler explosions. 1. That the force accumulated in an ordinary boiler is enough to account for the violence of an explosion. 2. That no form of boiler, however well constructed and fitted, is free from the liability to explosion, if allowed to get out of order; and that boilers which bear the hydraulic test may still be dangerous. 3. That the condition of a boiler can be satisfactorily ascertained only by periodical examinations, and that no boiler should work without being thoroughly examined at short intervals. 4. That the cost of periodical examination is so little as to be far outweighed by the greater security obtained; and that the settings of all boilers should be constructed with a view to facilitate examination. 5. That the surest way to make systematic examination general is to spread as widely as possible correct information as to the facts and ascertained causes of boiler explosions, and to inform boiler owners and minders what dangers to guard against; and that this is preferable, and more likely to lessen explosions than enforcing any system of inspection by legal enactment. TABLE I. _Summary of Records of Steam Boiler Explosions_ _up to 30th June, 1870,_ _showing Description of Exploded Boilers._ +------------------++-----------------------++-----------------------+ | Description of || Explosions up to June || Explosions in the 4 | | Boiler. || 1866. || years from June 1866 | | || || to June 1870. | + |+--------+--------+-----++--------+--------+-----+ | ||English.|Foreign.|Total||English.|Foreign.|Total| +==================++========+========+=====++========+========+=====+ |Marine || 57 | 203 | 320 || 12 | 64 | 76 | +------------------++--------+--------+-----++--------+--------+-----+ |Cornish, || 140 | 1 | 141 || 84 | 3 | 87 | |Lancashire, or || | | || | | | |others with || | | || | | | |internal flues || | | || | | | +------------------++--------+--------+-----++--------+--------+-----+ |Locomotive || 91 | 29 | 120 || 10 | 68 | 78 | +------------------++--------+--------+-----++--------+--------+-----+ |Plain Cylindrical || 114 | 2 | 116 || 54 | 3 | 57 | |externally fired || | | || | | | +------------------++--------+--------+-----++--------+--------+-----+ |Balloon, || | | || | | | |Haystack, Wagon, || 62 | 2 | 64 || 5 | 2 | 7 | |Butterley, || | | || | | | |British-Tube || | | || | | | |Elephant, or || | | || | | | |Trevithick || | | || | | | +------------------++--------+--------+-----++--------+--------+-----+ |Portable, || | | || | | | |Agricultural, || 28 | 1 | 29 || 17 | 17 | 34 | |Upright, Crane, || | | || | | | |or very small || | | || | | | +------------------++--------+--------+-----++--------+--------+-----+ |Heating, Kitchen, || 14 | .. | 14 || 22 | 14 | 36 | |Domestic, Rag || | | || | | | |Steamers, &c. || | | || | | | +------------------++--------+--------+-----++--------+--------+-----+ |Furnace-upright || 10 | .. | 10 || 8 | .. | 8 | +------------------++--------+--------+-----++--------+--------+-----+ |Not sufficiently || 203 | 29 | 232 || 7 | 175 | 182 | |described to be || | | || | | | |classified || | | || | | | +==================++========+========+=====++========+========+=====+ |Totals || 719 | 327 |1046 || 219 | 346 | 565 | +------------------++--------+--------+-----++--------+--------+-----+ TABLE I (continued) +------------------++--------------------------+ | Description of || Total Explosions | | Boiler. || up to June, 1870. | | |+--------+--------+--------+ | ||English.|Foreign.| Total. | +==================++========+========+========+ |Marine || 69 | 327 | 396 | +------------------++--------+--------+--------| |Cornish, || 224 | 4 | 228 | |Lancashire, or || | | | |others with || | | | |internal flues || | | | +------------------++--------+--------+--------+ |Locomotive || 101 | 97 | 198 | +------------------++--------+--------+--------+ |Plain Cylindrical || 168 | 5 | 173 | |externally fired || | | | +------------------++--------+--------+--------| |Balloon, || | | | |Haystack, Wagon, || 67 | 4 | 71 | |Butterley, || | | | |British-Tube || | | | |Elephant, or || | | | |Trevithick || | | | +------------------++--------+--------+--------+ |Portable, || | | | |Agricultural, || 45 | 18 | 63 | |Upright, Crane, || | | | |or very small || | | | +------------------++--------+--------+--------+ |Heating, Kitchen, || 36 | 14 | 50 | |Domestic, Rag || | | | |Steamers, &c. || | | | +------------------++--------+--------+--------+ |Furnace-upright || 18 | .. | 18 | +------------------++--------+--------+--------+ |Not sufficiently || 210 | 204 | 414 | |described to be || | | | |classified || | | | +==================++========+========+========+ |Totals || 938 | 673 | 1611 | +------------------++--------+--------+--------+ TABLE II. _Summary of Records of Steam Boiler Explosions_ _up to 30th June, 1870,_ _showing Causes of Explosions._ +-----------------++------------------------++------------------------+ |Cause of || Explosions up to June || Explosions in the 4 | |explosion. || 1866. ||years from June 1866 to | | || || June 1870. | | |+--------+--------+------++--------+--------+------+ | ||English.|Foreign.|Total.||English.|Foreign.|Total.| +=================++========+========+======++========+========+======+ |Worn out, || 92 | 53 | 145 || 89 | 5 | 94 | |corroded, or || | | || | | | |burnt plates || | | || | | | +-----------------++--------+--------+------++--------+--------+------+ |Undue pressure, || 132 | 5 | 137 || 25 | 6 | 31 | |overloaded || | | || | | | |valves, || | | || | | | |intentional or || | | || | | | |from carelessness|| | | || | | | +-----------------++--------+--------+------++--------+--------+------+ |Bad || 136 | 108 | 244 || 69 | 8 | 77 | |construction, || | | || | | | |weak tubes, || | | || | | | |defective || | | || | | | |fittings or || | | || | | | |stays, or want || | | || | | | |of repair || | | || | | | +-----------------++--------+--------+------++--------+--------+------+ |Shortness of || 106 | 8 | 114 || 28 | 2 | 30 | |water, formation || | | || | | | |of scale or mud, || | | || | | | |or external || | | || | | | |flues set too || | | || | | | |high || | | || | | | +-----------------++--------+--------+------++--------+--------+------+ |Extraneous || 6 | 3 | 9 || 2 | .. | 2 | |causes, || | | || | | | |lightning, fire, || | | || | | | |gas, &c. || | | || | | | |-----------------++--------+--------+------++--------+--------+------+ |Too uncertain to || 247 | 150 | 397 || 6 | 325 | 331 | |be classified || | | || | | | |=================++========+========+======++========+========+======+ |Totals || 719 | 327 | 1046 || 219 | 346 | 565 | +-----------------++--------+--------+------++--------+--------+------+ Table II (continued) +-----------------++------------------------+ |Cause of || Total Explosions up to | |explosion. || June 1870. | | || | | |+--------+--------+------+ | ||English.|Foreign.|Total | +=================++========+========+======+ |Worn out, || 181 | 58 | 239 | |corroded, or || | | | |burnt plates || | | | +-----------------++--------+--------+------+ |Undue pressure, || 157 | 11 | 168 | |overloaded || | | | |valves, || | | | |intentional or || | | | |from carelessness|| | | | +-----------------++--------+--------+------+ |Bad || 205 | 116 | 321 | |construction, || | | | |weak tubes, || | | | |defective || | | | |fittings or || | | | |stays, or want || | | | |of repair || | | | +-----------------++--------+--------+------+ |Shortness of || 134 | 10 | 144 | |water, formation || | | | |of scale or mud, || | | | |or external || | | | |flues set too || | | | |high || | | | +-----------------++--------+--------+------+ |Extraneous || 8 | 3 | 11 | |causes, || | | | |lightning, fire, || | | | |gas, &c. || | | | |-----------------++--------+--------+------+ |Too uncertain to || 253 | 475 | 728 | |be classified || | | | |=================++========+========+======+ |Totals || 938 | 673 | 1611 | +-----------------++--------+--------+------+ TABLE III. _Analysis of Steam Boiler Explosions in the United Kingdom_ _during the Four years ending 30th June, 1870,_ _showing the Causes of Explosion of Boilers of different descriptions._ A = Faults in construction or repair. B = Faults which should be detected by periodical examination. C = Faults which should be prevented by careful attendants. D = Causes extraneous or uncertain. E = number of Explosions. K = number of persons Killed. I = number of persons injured. CORNISH, LANCASHIRE, _or other Boilers with internal flues_. _E_ _K_ _I_ {Weak Tubes 26 17 41 {Weak combustion chambers 5 8 7 A {Weak ends 3 10 10 {Weak dome 1 0 0 {Weak manhole 1 1 1 {Bad repair 3 5 2 _E_ _K_ _I_ ------------ 39 41 61 B {External Corrosion 18 42 101 {Internal Corrosion 6 4 5 ------------ 24 46 106 {Shortness of Water 14 11 23 C {Scale of mud 3 1 0 {Undue Pressure 4 14 4 ------------ 21 26 27 _E_ _K_ _I_ ------------ 84 113 194 PLAIN CYLINDRICAL, _or other Boilers without internal flues_. _E_ _K_ _I_ {Weak flat ends 8 9 12 {Weak manhole 1 0 2 {Frequent repair producing } A { seam rip in boilers with } 15 18 28 { plates arranged lengthways} {Do. with plates arranged in } { rings } 8 11 25 ------------ 32 38 67 B {External Corrosion 11 5 19 {Internal Corrosion 5 5 6 ------------ 16 10 25 {Shortness of Water 2 1 0 C {Scale 1 1 0 {Undue pressure 3 4 3 ------------ 6 6 3 ------------ 54 54 95 ------------ MARINE BOILERS. _E_ _K_ _I_ {Weak flues 3 6 3 A {Weak ends 2 6 5 {Bad material 1 3 _E_ _K_ _I_ ------------ 6 15 9 B {External Corrosion 2 10 3 {Internal Corrosion 3 1 4 ------------ 5 11 7 C Shortness of water 1 11 7 ------------ 1 11 7 ------------ 12 37 23 LOCOMOTIVE BOILERS. A Boiler used as frame for engine 2 1 2 ------------ 2 1 2 B {External Corrosion 2 1 4 {Internal Corrosion 2 0 3 ------------ 4 1 7 {Broken connecting-rod } D { pierced boiler } 1 2 1 {Dome caught by railway bridge } 1 1 0 {Uncertain causes } 2 0 4 ------------ 4 3 5 ----------- 10 5 14 AGRICULTURAL BOILERS. A Weak manhole 1 1 4 ------------ 1 1 4 B {External Corrosion 2 3 3 {Internal Corrosion 1 1 7 ------------ 3 4 10 C {Shortness of water 1 0 0 {Undue pressure 6 15 15 ------------ 7 15 15 ----------- 11 20 29 FURNACE UPRIGHT BOILERS. {Too much flame on one part 1 2 0 A {Frequent repair producing } { seam rip } 1 13 2 ------------ 2 15 2 B {External Corrosion 2 13 11 {Internal Corrosion 2 15 6 ------------ 4 28 17 C Shortness of Water 2 3 8 ------------ 2 3 8 ----------- 8 46 27 ELEPHANT BOILERS. A Weak ends or want of stays 1 2 2 ------------ 1 2 2 B External Corrosion 1 0 4 ------------ 1 0 4 ----------- 2 2 6 CRANE BOILERS. _E_ _K_ _I_ A Weak manhole 3 7 3 _E_ _K_ _I_ ------------ 3 7 3 B External Corrosion 1 4 2 ------------ 1 4 2 C Shortness of water 2 2 0 ------------ 2 2 0 ----------- 6 13 5 RAG STEAMERS, &C. {Weak manhole 3 2 5 A {Bad material 1 1 5 {Want of stays 1 1 0 ------------ 5 4 10 C Undue Pressure 1 2 6 ------------ 1 2 6 ----------- 6 6 16 FEED-WATER HEATERS. D Uncertain causes 2 0 6 ------------ 2 0 6 ----------- 2 0 6 DOMESTIC BOILERS. A Weak shape 3 4 7 ------------ 3 4 7 B Corrosion 2 0 5 ------------ 2 0 5 C Undue Pressure from } freezing of Pipes } 9 7 9 ------------ 9 7 9 ----------- 14 11 21 BALLOON BOILERS. B External Corrosion 2 1 2 ------------ 2 1 2 C Undue Pressure 1 1 0 ------------ 1 1 0 ----------- 3 2 2 BOILERS OF UNCERTAIN DESCRIPTION. A Weak manhole 1 0 0 ------------ 1 0 0 {Steam entered through blow- } { off pipe from another boiler} 1 1 2 C { while cleaning } {Steam pipes broken 2 4 3 {Shortness of Water 1 1 4 ------------ 4 6 9 D Uncertain causes 2 0 3 ------------ 2 0 3 ----------- 7 6 12 ---------- _E_ _K_ _I_ TOTALS 219 315 450 TABLE IV. _Summary of causes of the Steam Boiler Explosions comprised in Table III._ +-----------------------------------+-----------+---------+---------+ | | E | K | I | | | Number |Number of|Number of| |Causes of Explosion. | of | persons | persons | | |Explosions.| Killed. |Injured. | +-----------------------------------+-----------+---------+---------+ |A Faults in construction or repair | 95 | 128 | 167 | +-----------------------------------+-----------+---------+---------+ |B Faults which should be detected }| 62 | 105 | 185 | | by periodical examination }| | | | +-----------------------------------+-----------+---------+---------+ |C Faults which should be prevented}| 54 | 79 | 84 | | by careful attendants }| | | | +-----------------------------------+-----------+---------+---------+ |D Extraneous or uncertain causes | 8 | 3 | 14 | +===================================+===========+=========+=========+ |Totals | 219 | 315 | 450 | +-----------------------------------+-----------+---------+---------+ BRIEF ABSTRACTS FROM REPORTS ON STEAM BOILER EXPLOSIONS, PRESENTED TO THE MIDLAND STEAM BOILER INSPECTION & ASSURANCE Co., BY EDWARD BINDON MARTEN, CHIEF ENGINEER TO THE COMPANY. _Description is shortened as much as possible, and facilitated by slight sketches, showing the position of the fragments or line of fracture, and the general construction of the Boilers._ REPUBLISHED BY THE PERMISSION OF THE COMPANY. STOURBRIDGE: B. BROOMHALL, PRINTER, HIGH STREET. 1869. BOILER EXPLOSIONS IN 1866. _No. 1. Nottingham. January 1st. none injured._ Locomotive, 110 lbs., standing with steam up near a platform. All but the fire box was blown away, the main portion being thrown a distance of 400 yards. The first rent took place at a longitudinal seam of the barrel where grooving had gone on very rapidly, which was not discovered when examined and tested a short time before. _No. 2. Walsall. (Fig. 1.) January 2nd. 2 injured._ [Illustration: _Fig. 1._] Butterley, 26ft. 6in. long, and 9ft. diameter. The wagon-shaped top to the fire place was 8ft. 6in. long, and was attached to the bell-mouth of the internal tube, which then continued circular to the back of the boiler. The tube was 3ft. 6in. diameter. All the plates were about 7/16ths inch thick, and although the boiler was an old one, they were nowhere reduced in thickness by wear. The usual pressure of steam was 18 lbs., and a self-registering gauge showed that at the time of explosion it did not exceed 20 lbs. The top of the fire grate on the right side rent longitudinally, and the upper part of the shell consisting of four rings of plates, and also the top of the fire place opened out and blew away to a considerable distance. The front end also blew away. The bell-mouth of the tube was blown to the front, and the tube which remained in the back part of the shell collapsed upwards. The cause of the explosion was most likely the intrinsic weakness of boilers of this shape, especially over the fire, where the top is only retained in its shape by numerous stays. The boiler had been very frequently repaired, at this the weakest place, and its strength had been thus so reduced as to make it unable to bear even a few pounds more than the ordinary working pressure. The whistle was found to have been gagged by hemp, carefully inserted, so that there is ground for supposing there had been intentional unfair usage. _No. 3. Blyth. (Fig. 2.) January 8th. 1 killed 1 injured._ [Illustration: _Fig. 2._] Marine, 20ft. long, and 5ft. diameter, with internal fire place and return flue, 14 lbs. There were altogether three rents in the tube over the fire, as a small band was held in its place by a stay from the tube to the shell. The escaping contents scalded those near, but no damage was done to anything but the boiler. The cause was stated to be shortness of water. There was no water gauge. _No. 4. London. January 9th. 1 killed._ One tube Cornish, 28ft. long, 6ft. 6in. diameter, with one tube 3-6 diameter, 3/8 inch plates, 45 lbs. The tube collapsed in an incline direction from weakness without strengthening rings. The appearance after explosion was nearly the same as that shown in sketch given at No. 12 explosion. _No. 5. Glasgow. (Fig. 3.) January 13th. 4 killed, 4 injured._ [Illustration: _Fig. 3._] Two tube Cornish, 22ft. 3in. long, and 7ft. 7in. diameter, 3/8 inch plates, tubes 2ft. 7in. diameter, 40 lbs. About 8ft of the back portion of the shell was torn off, leaving the tubes and ends intact. The cause of the explosion was considered to be excessive pressure, but how accumulated did not transpire. It is most natural to expect that there must have been corrosion under the bottom to cause the first rent. _No. 6. Coatbridge. January 17th. 1 injured._ Cornish. No details have been obtained. _No. 7. York. (Fig. 4.) January 18th. 1 killed, 2 injured._ [Illustration: _Fig. 4._] Agricultural, 8ft. 2in. long, 3ft. 6in. diameter in the barrel, 5/16ths inch plates, internal fire box, 2ft. 4in. wide, 2ft. 4in. high, and 2ft. 10in. deep. From the back of this fire box, two 12-inch tubes passed to an internal chamber at the back of the barrel. From this again passed nine 3-3/4 inch tubes to an exterior smoke-box fixed over the fire door. The boiler was fitted with one spring safety valve, which was screwed down tight, but there was no pressure gauge. The front plate was intended to be bolted on so that the fire-box and tubes could be taken out for cleaning, but it had been rivetted, leaving no means of cleaning, and it was nearly full of scurf. The crown plate of fire-box which was too flat and unstrengthened, rent at the front and along both top edges, and was driven into the fire. The boiler was thrown backwards and reared against a wall, resting on the front right hand corner. The cause of the explosion was that the very dirty state, caused overheating where the water was not in proper contact with the plates, and the defective construction did not admit of proper cleaning. The mountings were insufficient for the proper protection of the boiler. _No. 8. Durham. (Fig. 5.) January 29th. 1 killed, 3 injured._ [Illustration: _Fig. 5._] Plain Cylinder Boiler with hemispherical ends, 30ft. long and 6ft. diameter, 3/8 inch plates, 30 lbs. It was the second from the engine in a bed of five, and had been at work three years, then remained idle for eight years, working again fourteen years. The boiler was mounted with two safety valves 3-7/8 and 4 inches diameter, a float and alarm whistle. The boiler had been more than once repaired over the fire with several new plates. One seam over the fire had been observed to leak about a week before the explosion, but not seriously, and had been caulked. The boiler had just been started after cleaning. Six months before explosion, the boiler had been tested to 69 lbs. About 5 feet of the front end of the boiler opened out flat, and was thrown to the rear about 60 yards; the front hemispherical end was liberated and thrown 20 yards also to the rear and right hand. The back part of the boiler was thrown in a mass, and after bounding twice, lodged at a distance of 230 yards. The cause of the explosion appeared to be from the failure of a seam over the fire place in a plate deteriorated by age, and overheated through a deposit of scurf and mud. _No. 9. Birmingham. (Fig. 6.) February 7th. 1 killed, 4 injured._ [Illustration: _Fig. 6._] Plain Cylindrical Boiler, with hemispherical ends, 23ft. long, and 5ft. diameter, 3/8 inch plates, 50 lbs. It was set so as to be fired under the bottom if required, but the grate was seldom used. The principal heat was supplied from a mill furnace, the neck of which was at the left hand of the back, and the flame was carried by a wheel flue round the front of the boiler to the stack on the right hand side of the back. The boiler was fitted with a 4-3/4-inch safety valve, and also a float, but it was suspected that the latter had broken from the rod. A horizontal seam about the middle of the left hand side had given way, and the upper portion of the 3rd and 4th rings of plates had spread out like a lid without being detached from the boiler. The front end became detached and was thrown some distance to the front. The cause of explosion was, that the left side of the boiler became overheated, and so much softened, that it first bulged outwards with the ordinary working pressure, and then rent open. The overheating was most likely the result of shortness of water, but it might possibly have been in consequence of the intense heat of a mill furnace impinging on a small area so near the water line, leading to such rapid ebullition as to prevent sufficient contact of the water to keep the plates cool. _No. 10. Dunse. February 14th. 1 injured._ Locomotive. It exploded while standing in a shed, but no particulars have been obtained. _No. 11. Middlesbro'. February 26th. 1 injured._ Marine, in a small tug boat, but no details have been obtained. _No. 12. Gainsbro' (Fig. 7) February 26th. 1 injured._ [Illustration: _Fig. 7._] One Tube Cornish, 21ft. long, 5ft. diameter, with one tube 2ft. 11in. diameter, plates 3/8 inch, 64 lbs. There were no strengthening rings on the tube. The boiler was second-hand, and had only worked a part of a day at its new position when it exploded. The tube collapsed from weakness without strengthening rings. _No. 13. Redruth. (Fig. 8.) March 3rd. 1 killed._ [Illustration: _Fig. 8._] One Tube Cornish, 31ft. 9in. long, and 5ft. 9in. diameter, tube 3ft. 8in. diameter, 3/8 inch plates, 40 lbs. The tube had been repaired with a bolted patch on the left side the day before the explosion, and it is presumed it was slightly out of the circular shape, as it collapsed sideways, the top being thrown up above its proper height. There was no evidence of shortness of water. The tube without strengthening rings was too weak to sustain the ordinary working pressure. _No. 14. London. March 5th. 7 injured._ Cornish, at 27 lbs., but as the boiler was not injured, it is only noticed as an explosion, because of the imprudence of placing fittings in such dangerous positions. The boiler was beneath a work room, and the lever of the safety valve became displaced, allowing the valve to blow out, and the escaping steam rushed into the room above and scalded seven men very badly. _No. 15. Manchester. March 6th. 1 killed._ This was a Boiler with two internal fireplaces, connected into one flue at the back. The crowns of both furnaces were collapsed, and slightly rent, and the escaping steam and water scalded the attendant. The water was 8 or 9 inches below its proper level, allowing the furnace crowns to become overheated and unable to bear the working pressure. Each furnace had been fitted with a fusible plug, but they proved inefficient. _No. 16. Norwich. (Fig. 9.) March 13th. 1 killed, 1 injured._ [Illustration: _Fig. 9._] This was a very small boiler, 8ft. long, and 3ft. 2-1/2in. diameter, with two small tubes. It was fired externally. The dome was blown off and the rents continuing, the top opened out on each side, and the upper portion of both back and front was bent back. The dome cut away the whole of the top plate, and so much reduced the strength that it would not bear the ordinary working pressure. _No. 17. Dudley. (Fig. 10.) March 19th. none injured._ [Illustration: _Fig. 10._] Plain Cylinder Boiler, 36ft. long, 5ft. 6in. diameter, 60 lbs. It had frequently been repaired over the fire, so that the longitudinal seams ran for several plates without break of joint. A patch had been put on a few days before explosion, and as the rivet holes had badly fitted, there had been much strain caused by drifting, and the rivets were much distorted. A longitudinal seam gave way over the fire, when two rings of plates opened out, rending the transverse seams at each side until completely separated, and fell in two parts at a distance of about 100 yards in front of the boiler. The front end was liberated and fell in one piece about 100 yards beyond the two pieces of the shell. The main body of the boiler was driven back a few yards and rolled over so as to be upside down, but was little injured. The frequent and badly executed repair over the fireplace, had so weakened the structure as to make it unable to bear the very high ordinary pressure. This frequent repair over the fireplace had been made necessary by very hard firing and deposits of scurf from muddy water, preventing the proper contact of the water with the plates. _No. 18. Liverpool. March 22nd. 1 killed._ This was a small Boiler to supply steam for some steam winches on board a steam boat, and exploded from the overheating of the upper tubes through shortness of water, or from over pressure in consequence of having only one safety valve. _No. 19. Leeds. (Fig. 11.) March 27th. 2 killed, 18 injured._ [Illustration: _Fig. 11._] Two Tube Cornish, 24ft. 6in. long, 6ft. 6in. diameter, tubes 2ft. 6in. diameter, 3/8 inch plates, 54 lbs., fitted with steam gauge, blow-off cock, 1-1/2 inch dead weight safety valve, loaded to 54 lbs., and 4-3/8 inch lever safety valve, loaded to 62 lbs., and had been at work about five years. Nearly the whole of the two back rings of the shell were torn off and opened out, and the boiler was turned partly round, and moved upon its seat sideways and forwards. There was extensive corrosion at the under side of the back of shell, where the first rent took place, caused by the leaking of the joints and seams. _No. 20. Swansea. (Fig. 12.) April 4th. 5 killed, 4 injured._ One Tube Cornish Boiler, 30ft. long, and 7ft. diameter, tube slightly oval about 4ft. diameter, 7/16 inch plates, 43 lbs., fitted with 3-1/2 inch safety valve, which is much too small for such a boiler, glass water gauge, two gauge cocks, and pressure gauge. The tube collapsed from end to end. The front end was blown out with a short length of the tube attached, and was driven against a wall about 30 yards to the front. The main body of the shell, and the back end, with the collapsed tube within it, were driven back against another wall, about the same distance away. Very great damage was done to the surrounding property. [Illustration: _Fig. 12._] The cause of the explosion was the weakness of the tube of so large a diameter, without strengthening rings, which made it unable to bear the ordinary working pressure. It is very probable, however, that at the time of the explosion, the pressure was considerably more than usual during the stoppage of the engine, and the confusion caused by a man becoming entangled in the machinery. _No. 21. Morpeth. April 10th. 1 killed._ Plain Cylinder Boiler, 34ft. long, and 5ft. diameter, 3/8 inch plates placed lengthways, 33 lbs. The explosion took place at a seam in the front part of the bottom of the boiler just over the fire. This rupture allowed the sides to expand, until the boiler was completely destroyed and torn into seven pieces. The cause of the explosion was supposed to be the defective state of the seams over the fire, which, being placed longitudinally, were in the weakest position. _No. 22. Shiffnal. (Fig. 13.) April 21st. none injured._ [Illustration: _Fig. 13._] Two Tube Cornish, 15ft. long, 6ft. diameter, tubes 1ft. 8in. diameter, 3/8 inch plates, 40 lbs. The heat was supplied by two furnaces, one of which played into each tube. The left hand tube collapsed from shortness of water, and tore away from the angle iron in the front plate, and allowed the contents to issue violently and scatter the brickwork, but the boiler was not disturbed. _No. 23. Burnley. April 26th. 2 killed, 2 injured._ Small internally fired Boiler, 5ft. high, 2ft. 4in. diameter, and was intended to work at 70 lbs. The fittings were defective, the spiral spring of the safety valve being most easily altered, so as to cause over pressure. The manhole was not strengthened by any ring, and the first rents commenced at that point. The cause of the explosion was over pressure and defective construction. The sketch at No. 57 explosion in this year, is of a similar boiler which exploded from nearly similar causes. _No. 24. Bilston. (Fig. 14.) May 13th. none injured._ Balloon or Haystack Boiler, about 16ft. diameter, 5/16 inch plates, and worked at very little above atmospheric pressure. The boiler was chiefly used to store water during the time another boiler by the side of it was emptied. When the water was required to refill the other boiler, a fire was lighted under the balloon, and sufficient steam generated to drive the water from it into the other boiler. The safety valve never being used, it had become fast, and as a little more steam than usual had accumulated, the bottom gave way, and the reaction of the issuing contents made the boiler rise from its seat, and it fell on its side at some distance away flattened by the fall. [Illustration: _Fig. 14._] _No. 25. Westbromwich. (Fig. 15.) May 25th. none injured._ [Illustration: _Fig. 15._] One Tube Cornish Boiler, 15ft. long, and 4ft. 6in. diameter, taper tube, 2ft. 9in. diameter in front, and 2ft. diameter at back, 3/8 inch plates, 40 lbs. The boiler rested on two walls forming the bottom flue. There was a safety valve, a glass water gauge, a pressure gauge, and two fusible plugs upon the tube. Two longitudinal rents took place on the under side of the shell, allowing two strips, forming the central part, to open out by the continuation of the fracture, until they were blown to a considerable distance. The tube with the front end, and one ring of the shell were thrown to the front, while the back end was thrown to the rear, the smallest end of the tube having torn away from the back. The shell was deeply corroded where it rested on the side walls of the bottom flue, and the strength of the boiler was thereby so much reduced, that it was unable to bear the ordinary working pressure. _No. 26. Halifax. (Fig. 16.)_ _May 26th. 1 killed._ [Illustration: _Fig. 16._] One Tube Cornish, 24ft. 6in. long, and 5ft. diameter, taper tube, slightly oval in the front, 2ft. 8in. diameter, and 2ft. diameter at the back, 3/8 inch plates. The boiler was fitted with glass water gauge, float, self-acting feed apparatus, and safety valve loaded to 52 lbs., and also a mercury gauge. The tube collapsed over the fire, a rent taking place in the second ring of plates. The issuing steam and water caused the death of a man in front, but the shell of the boiler was not injured or moved. The cause of the explosion was shortness of water, and as the glass gauge was set unusually low, the man in charge may have been deceived. The oval shape of the fireplace, and the laminated iron, as shown in the fracture, rendered the tube peculiarly liable to collapse. _No. 27. Durham. May 26th. 1 killed._ Plain Cylinder Boiler, 34ft. long, 5ft. diameter, 3/8 inch plates, 45 lbs., fitted with two 5-inch safety valves, and 2 floats. The boiler was torn in two pieces, that were thrown to a considerable distance. The first rent had taken place immediately over the fire. The cause of the explosion was the weakening of the shell by frequent repair over the fire, rendered necessary by the deposit from the muddy water preventing proper contact of the water with the plates. _No. 28. Durham. May 27th. 1 killed._ Plain Cylinder Boiler, 32ft. long, 6ft. diameter, 3/8 inch plates, 35 lbs., fitted with two safety valves, two floats, and two alarm whistles. The boiler was lifted from its seat, and one end was separated and thrown to a considerable distance. The cause of the explosion was weakening of the shell from repair a few days before, and perhaps over pressure, as the gauge was found some time after, and indicated that the pressure had at some time exceeded 80 lbs. _No. 29. Redruth. May 28th. 1 killed, 4 injured._ One Tube Cornish, 30ft. 8in. long, 6ft. 8in. diameter, tube, 4ft. diameter, 7/16 inch plates, 40 lbs. The tube collapsed, and rent, and the issuing steam and water scalded those near, as it was too weak to bear the ordinary working pressure. _No. 30. Leicester. (Fig. 17.) May 31st. 1 killed, 1 injured._ [Illustration: _Fig. 17._] Plain Cylinder Boiler, with dished ends, and only 4ft. 2in. long, and 2ft. 6in. diameter, 1/4 inch plates. It was most inefficiently mounted, the safety valve was only 1-5/8-inch diameter, and of such faulty construction, that it would not open under a pressure of 162 lbs. There was no steam gauge or float, and the gauge cocks were defective. There was no means of putting water in the boiler when there was a pressure of steam. The manhole was very large for so small a boiler. Four rents started from the manhole and continued along the top of the boiler and round the end seams. A tongue-shaped strip of the top plate was attached to the back end plate; two strips about a foot wide on either side were blown away. The boiler had been turned nearly round in its flight, and fell with the back about 12 feet from the original position of the front. The boiler was worked until it was nearly dry, and, during a temporary stoppage of the engine, an accumulation of steam caused a greater pressure than the boiler could bear. _No. 31. Newcastle. June 7th. none injured._ Marine Boiler in a Tug Boat. The boiler was blown completely out of the vessel, and the greater part of it fell into the water, and a large piece alighted on a crowded quay, but without doing any damage. The cause of the explosion was supposed to be over-pressure during a temporary stoppage of the engine. _No. 32. Barnard Castle. (Fig. 18.) June 11th. 2 injured._ [Illustration: _Fig. 18._] Agricultural, of about 7 horse power. The barrel of the boiler was 6ft. 1in. long, 2ft. 5in. diameter; the fire-box end was 3ft. wide, and 2ft. 4in. deep; the fire-box was 2ft. 5-1/2in. wide, and 2ft. 7in. high, and 1ft. 9-1/2in. deep, with 23 tubes passing from it through the barrel to the smoke box and chimney. The boiler was fitted with a 2in. safety valve, which was intended to blow at 45 lbs., but as there was no ferrule, it is supposed to have been screwed down to a much greater pressure. The upper portion of the shell over the fire-box rent through the manhole, and allowed the shell to open out and fall on each side. A large portion of the front plate was also torn off. The cause of the explosion was the weakness of the manhole, which was not strengthened by any ring, and also excessive pressure from want of proper safety valve. _No. 33. Breage. June 11th. 1 killed._ Cornish Boiler, 36ft. 6in. long, and 6ft. diameter, 3/8 inch plates, 45 lbs. The tube collapsed and rent, and the issuing contents caused the death of the attendant. The weak tube of such large diameter, was unable to bear the ordinary working pressure, having no strengthening rings. _No. 34. Nottingham. June 19th. 2 killed, 4 injured._ Locomotive, 1/2 inch plates, 140 lbs. The explosion occurred at the left hand side of the ring of plates in the barrel next the fire-box, and below the foot-plate. The rent tore along the edge of the lap and into the next ring of plates. The reaction of the issuing contents threw the engine off the rails. The cause of the explosion was partial corrosion at the point of rupture and strain of the plates, as the boiler itself formed part of the frame of the engine. _No. 35. Richmond. June 26th. 2 injured._ Locomotive, being tried for the first time. The funnel came in contact with a bridge, and the dome was also torn off. _No. 36. Gainsbro' June 29th. none injured._ No details have been obtained. _No. 37. Durham. July 2nd. 4 killed._ Plain Cylindrical Boiler, 30ft. long, and 6ft. diameter, 3/8 inch plates, 28 lbs. It had been repaired a short time before the explosion, with 5 new plates. The boiler was torn up into several pieces, but the main portion remained flattened out on the seating, while some smaller pieces were sent 250 yards away. The cause of the explosion was the deterioration of the boiler, and its frequent repair over the fireplace. _No. 38. Liverpool. June 12th. 4 injured._ Elephant Boiler, 20ft. long, and 4ft. diameter, 3/8 inch plates, and worked at low pressure. The bottom shell had a tube through its whole length. A rent took place in the lower part of the fireplace, and extended along the bottom, and the reaction of the issuing contents caused the top to rear up. The cause of the explosion was supposed to be that the bottom plates were worn too thin to bear the ordinary pressure. _No. 39. Sheffield. July 4th. none injured._ Two Tube Cornish Boiler, externally fired, 30ft. long, and 6ft. diameter, 3/8 inch plates, 40 lbs. The second seam over the fire gave way, and the plate sank down upon the fire. The cause of the explosion was the deterioration of the seams over the fire, in consequence of the deposit of scurf which could not be properly cleared off owing to the internal tubes. _No. 40. Oldham. July 14th. none injured._ Boiler, with two internal furnaces, 9ft. 6in. long, and 2ft. 11in. diameter, 3/8 inch plates, uniting into one tube beyond. The furnace crown collapsed near the front of the boiler. There was an extra weight upon the safety valve, and the steam valve was left closed, so that more pressure accumulated than the boiler could bear. _No. 41. Oxford. July 23rd. 3 injured._ Rag Boiler, not used for the generation of steam. It was a plain cylinder, with hemispherical ends, about 16ft. long, and 7ft. diameter. There was a neck at each end upon which the boiler revolved, and through one of these the steam was admitted to a pressure of 30 lbs., in order to assist in cleaning the rags. There was a large manhole for filling and emptying. The boiler rent in the middle, and each half was blown to some distance. The manhole was so large, that the strength of the boiler was too much reduced, and the constant strain of revolving caused a central seam to give way at the ordinary pressure. The sketch to No. 63 is of a similar boiler. _No. 42. Tunstall. (Fig. 19.) July 28th. 2 killed, 7 injured._ [Illustration: _Fig. 19._] Boiler, 36ft. 6in. long, and 8ft. 9in. diameter, 7/16 inch plates, with flat back and hemispherical front end, 36 lbs. A tube 3ft. 3in. diameter, passed from the back end nearly to the front, and returned to the back end, but of 6 inches less diameter and then passed to an iron chimney. The fire grate was beneath the hemispherical end. The angle iron of the flat back end gave way, and separated from the shell and with the tubes attached was blown to a good distance, and the reaction drove the shell far in the opposite direction. The cause of the explosion was the bad construction of the boiler, as the back end was quite unsupported, as there were no stays, and the bend of the tubes was not attached to the shell. An adjoining boiler which was being cleaned inside by two men, was rolled off its seat by the force of the explosion. _No. 43. Widnes. August 2nd. 2 killed, 6 injured._ Plain Cylindrical Boiler, with flat ends, 23ft. long, 5ft. 3in. diameter, 3/8 inch plates, 40 lbs. Both the flat ends were blown out, and the first ring of plates at the front end torn off. The cause of the explosion was the weakness of the flat ends without stays. _No. 44. Sunderland. August 7th. 1 killed, 3 injured._ Locomotive, 13ft. 4in. long, 3ft. 11in. diameter, with 140 2-in. tubes. The fire-box was 4ft. 5in. long, 3ft. 6in. broad, and 5ft. deep, and made of copper, 1/2 inch thick, 100 lbs. It was fitted with two 4-in. safety valves, and a steam gauge. The fire-box gave way about the middle of the left side, 2ft. 6in. below the water line, where corroded to 1/8 inch, and the issuing water and steam scalded those near. _No. 45. Runcorn. (Fig. 20.) August 22nd. 3 killed, 5 injured._ [Illustration: _Fig. 20._] Marine Multitubular, 5ft. 8in. long, and 6ft. 6in. diameter, with two internal tubular furnaces, which joined to an internal chamber of large size, and small tubes passed to a smoke box and chimney in the front over the fire doors. Both ends were flat. The flat back end was insufficiently stayed, and was blown completely out and torn into two pieces, the lower portion remaining in the vessel, and the upper part falling in the water, and the reaction of the issuing contents caused the boiler to be thrown on to the side of the quay. _No. 46. Hull. (Fig. 21.) August 25th. 1 injured._ [Illustration: _Fig. 21._] One Tube Cornish, 24ft. 3in. long, and 6ft. diameter, taper tube 3ft. 5in. diameter, for about 7ft. 6in. in length, and 2ft. 6in. diameter for the rest of the length, 33 lbs. The tube was much corroded, and the fireplace gave way on left side, and was so much torn, that the plates were forced out of the front. _No. 47. Morecombe. August 27th. 3 killed, 1 injured._ Marine, of the usual construction, and had been tested to 60 lbs. It gave way at the lower portion of the back, and the issuing steam and water scalded those near. A seam rent, 6ft. 6in. long, had not been detected by testing. _No. 48. Tuddenham. August 29th. 2 killed, 2 injured._ Agricultural. It burst during a temporary stoppage from accumulation of steam, causing undue pressure. _No. 49. Glasgow. August 31st. 3 killed, 6 injured._ Upright Boiler, 36ft. high, 5ft. 6in. diameter, 7/16 inch plates, 45 lbs. The bottom gave way from shortness of water, and the main bulk of the boiler was thrown straight up into the air to a great height, but descended again on its seating. _No. 50. Chatham. (Fig. 22.) September 7th. 2 killed, 30 injured._ [Illustration: _Fig. 22._] Two Tube Cornish, 22ft. long, 7ft. 6in. diameter, with tubes, 3ft. diameter, 7/16 inch plate, 60 lbs. Some rents took place at the under side of the shell, allowing the central portion to open out and blow away. The portion containing the dome was thrown to the left, and the other to the right. The front end, with 3 rings of the shell, with the tubes and back end, were but little moved from their original position. The tubes were dented in on the top and bottom, by the fall of some large coping stones upon them, but the crowns of the furnaces were uninjured, and there was no sign of shortness of water or overheating. Extensive corrosion on the under side of the shell, where it rested on the brickwork, had so reduced the strength, that it was unable to bear the working pressure. In the sketch the fragments are drawn so as to show their position when in the boiler. _No. 51. Newark. September 21st. none injured._ One tube Cornish. The tube collapsed from shortness of water, and the escape of the steam and water blew off the door frame. _No. 52. Ashton. September 23rd. 1 injured._ Plain Cylindrical Boiler, 7ft. long, and 2ft. diameter, 3/8 inch plates, 30 lbs. The upper part of the boiler at the first ring of plates was torn off, and the front end was blown out. Extensive external corrosion, where the plates rested against the brickwork, rendered the boiler too weak to bear the ordinary pressure. _No. 53. Norwich. (Fig. 23.) September 25th. 7 killed._ [Illustration: _Fig. 23._] One Tube Cornish, 20ft. long, 4ft. 6in. diameter, tube 2ft. 6in. diameter, 3/8 inch plates, 100 lbs. It was double-rivetted, and the crown of tube was strengthened with angle iron. The shell was formed of six rings, each of two plates alternately jointed top and sides. The third ring from the front had stripped off, and was thrown to the right and forwards against a wall. The line of rent was confined to the plates forming the ring, which was an outer one, and covered the two adjoining rings in the laps, the rent being from the edge of the inner lap to the nearest rivets. The first rent had taken place in the solid iron, about 1 inch from the rivets of a seam on one side, and from this the rent had extended along the seams on either side, and of course the whole ring soon tore off when the equilibrium was destroyed by the first rent. The fittings of the boiler were sufficient, except that there was only one safety valve, and that was so constructed that it could only open a very little way. The cause was a defect in the iron at the point of the first rent, and accumulated pressure during the time of standing. _No. 54. Macclesfield. September 25th. none injured._ Multitubular Boiler, with large internal fireplace, 60 lbs. The furnace crown became overheated from shortness of water, and was crushed down and torn across two seams. The boiler was lifted from its seat and thrown back against a stone wall. _No. 55. Chelmsford. October 5th. 1 killed, 7 injured._ Agricultural, 45 lbs., and had only just been set to work. The crown plate to the fire-box was so deeply corroded from long wear that it gave way, and the issuing contents scalded those near. _No. 56. Greenwich. (Fig. 24.) October 8th. 2 killed, 2 injured._ Marine, 16ft. long, slightly oval, front end flat, 8ft. 6in. wide, 7ft. 10in. high, and the dimensions of the back hemispherical end were 2ft. less each way, 3/8 inch plates, 26 lbs. There were two internal fireplaces, of irregular shape, uniting at the back into one flue of similar shape, which did not come to the front, but passed through the steam space, and out at the top of the boiler. While the vessel was waiting to start, with steam up, the wing furnace of the starboard boiler collapsed on the wing side, as shown by the dotted lines, and allowed the steam and water to escape into the stoke hole. [Illustration: _Fig. 24._] The side of the furnace next the shell was rent along the edge of a longitudinal seam in a line, which was slightly nicked in the caulking. This rent extended about 5ft. 6in. from the front, and then at a cross seam it went along the line of rivets from the crown to the bottom of the furnace. Beyond this cross seam the furnace was collapsed, until it nearly touched the other side of the furnace, and the bulge died away towards the back end. There was also a rent in the lower part of the front of the shell, as shown in dotted line. The cause of the explosion was the weakness of the shape of the flue, which was not stayed to the shell. It had evidently gradually been giving way some time before the explosion, and eventually collapsed at nearly the ordinary pressure. Symptoms of the same alteration of shape were noticed in the corresponding flue of the other boiler. _No. 57. Liverpool. (Fig. 25.) October 9th. 7 killed, 1 injured._ Crane Boiler, 5ft. 6in. high, and 2ft. 6in. diameter, with internal conical fire-box, with two cross tubes and a chimney at the top, 1/4 inch plates, 75 lbs. The outer shell of the boiler was rent into many pieces, leaving the central conical fireplace intact. The nature of the rents showed that the plate round the manhole, which was unstrengthened by a ring, had first given way, and all the other fractures had led away from that point. This is confirmed by the fact, that the manlid was thrown a good distance, with force enough to make its way through the timber walls of a cabin. The front plate divided into many pieces, and scattered right and left, while the back plate was thrown through a cabin in the opposite direction to the manhole. [Illustration: _Fig. 25._] The central flue showed a slight indication of overheating, but the construction was such that the upper portion passed through the steam space, and was always exposed to the action of the fire, without the protection of the contact of water. The manhole without a ring on its edge to strengthen the plate, and held in by two clamps, which caused additional strain when carelessly screwed up, was by far the weakest place. The engine was standing after a short time of working, and as the safety valve was very defective, and could be screwed down until tight, against almost any pressure, it is most probable that the pressure mounted much higher than usual, when the weakest part gave way, and led to the sudden tearing up and scattering of the whole fabric. Faulty construction of both boiler and fittings, rendered it unable to bear that accumulated pressure, which the safety valve ought to have made impossible. _No. 58. Durham. October 13th. 1 killed._ One Tube Cornish, 14ft. long, 6ft. diameter, internal flue 3ft. 3in., by 2ft. 10in., 3/8 inch plates, 27 lbs., standing on three saddles, with a bearing surface of 3ft. by 4 inches. A portion of plate 20in. by 18in., at the bottom of the boiler, was so corroded that it was blown out, and the issuing contents scalded a man to death. _No. 59. Bristol. (Fig. 26.) November 1st. 7 killed._ [Illustration: _Fig. 26._] Two Marine Boilers exploded simultaneously. They were 16ft. long, 6ft. 6in. diameter at the flat front ends, and somewhat less at the hemispherical back ends. Each had two internal fireplaces, united in one flue, which returned nearly to the front and passed up through the steam space, and out at the top of shell into the funnel. The central fireplaces were not circular, and the outside fireplaces and the return flues were still more distorted, but the weakness of the shape was somewhat compensated for by stays between the tubes, and from the tubes to the shell. The mountings to the boiler were of the ordinary kind and efficient. The under sides of the shells were so deeply corroded that they were rent longitudinally for their whole length, allowing the sides to open out and tear away from the front ends. Each shell fell at a considerable distance. The furnaces, with parts of the front ends attached, fell into the water, but except one of the side flues that was a little collapsed, they were uninjured. Small pieces of the front ends were thrown to a great distance. The sides of the vessel were so completely blown out that she sank. The corrosion was no doubt caused by the leakage of the vessel, keeping the shells of the boilers constantly wet. _No. 60. London. (Fig. 27.) November 3rd. none injured._ [Illustration: _Fig. 27._] Agricultural, barrel was 3ft. 9in. long, and 2ft. 6in. diameter, 70 lbs. From the internal fire-box the heat passed through a number of 1-inch tubes to the front smoke box and chimney. During a stoppage for breakfast, the fire-box end was torn from the barrel, and from the position of those fragments that could be found, the boiler appeared to have turned over. Part of the fire-box was sent through the stage upon which the boiler was travelling, and the barrel with the tubes remaining in it, first struck a rail which caused it to be dented in, and then rebounded to a point about 100 yards from its original position. Enough of the fragments were not recovered from the river to trace the cause of the explosion, but it is presumed that, although when the boiler was left, only 20 lbs. pressure was shown by the gauge; the fire door being left closed, the pressure must have risen to a point much above the working pressure, and to more than the boiler could bear. _No. 61. Bilston. (Fig. 28.) October 1st. none injured._ One Tube Cornish, 22ft. long, 6ft. diameter, tube 4ft. 6in. diameter, 3/8 inch plates, 12 lbs. There was an unusually large dome at the back end, 5ft. diameter, and the whole of the shell was cut out from under it, so that the construction was peculiarly weak. [Illustration: _Fig. 28._] The boiler had been off for cleaning, and steam was being got up in the night, and it was said that an extra pressure was caused by the stop valve being left closed, but it could not have been very great, or the large tube would have collapsed. The dome was split in two, in the line marked in the sketch, owing to the extreme weakness of the shell at the juncture of the dome, and the shell was a little ruptured on each side of it, and so large a rent was suddenly made, that the contents of the boiler passed harmlessly into the air, without moving the boiler on its seat. _No. 62. Preston. (Fig. 29.) November 11th. 1 killed, 1 injured._ [Illustration: FRONT VIEW. BACK VIEW. _Fig. 29._] One Tube Cornish, 16ft. 3in. long, and 5ft. 8in. diameter, tube 3ft. 1in. diameter, 7/16 inch plates, 60 lbs. The tube collapsed from end to end, from over-pressure, as the man in charge had fastened 3 bricks to the lever of the safety valve causing 27 lbs. extra pressure, under the impression that he could thus accumulate a quantity of steam during the night, to be available on commencing work on the morrow. _No. 63. Tamworth. (Fig. 30.) November 20th. none injured._ [Illustration: _Fig. 30._] Revolving Steam Chamber, 12ft. 6in. long, and 5ft. diameter, 12 lbs. The manhole was large, to facilitate filling and emptying, and was rectangular and unstrengthened on the edges, and measured 3ft. 6in. in length, and 1ft. 6in. in width, and the lid fitted on the inside and was held by clamps. The boiler was much out of repair, and a crack shown in sketch, from one corner of the manhole to the commencement of the hemispherical end was only temporarily prevented from leaking by a screw-patch, which did not restore the strength. The explosion happened when in revolving, the manlid was downwards, and the lid was driven nearly through the floor, and the shell was rent from opposite corners of the manhole, and blown through the roof. The large manhole cut away nearly all the strength on one side, and the fastenings of the lid were not contrived to compensate at all for the loss of strength. The constant strain when revolving, also tended to weaken it. These two causes together were sufficient to account for the explosion, at the usual working pressure of 12 lbs., although it is possible that it might have been increased to 35 lbs., as that was the pressure in the boiler supplying the steam, although the pressure was regulated by a check valve. This explosion (and also No. 41 in this year) clearly show that a mere vessel of steam not exposed to the fire, or any chance of overheating of the plates, can burst and cause very great destruction, although there could be no sudden _increase of pressure_ which is so often supposed necessary to account for the havoc caused by explosions. _No. 64. Manchester. November 26th. none injured._ This Boiler was 28ft. long, 7ft. diameter, made of 7/16 inch plates, and worked at 50 lbs. pressure, with two internal fireplaces united into one tube beyond. The sides of the oval chamber forming the junction of furnaces and tube, crushed inwards, being of such a weak shape as to be unable to resist the ordinary working pressure. _No. 65. Hull. (Fig. 31.) December 1st. 3 killed, 2 injured._ [Illustration: _Fig. 31._] Agricultural, 7ft. 6in. long, and 3ft. 8in. diameter, 1/4 inch plates, 35 lbs., fire-box 2ft. long, and 2ft. 10in. broad. Two 11-1/2-inch tubes led to an internal chamber at the other end of the boiler, and three 8-1/4-inch tubes led back again to an external smoke box and chimney fixed over the fire door. The bottom of the right hand side lower tube was forced upwards, and rent along to within 12 inches of the fire-box. The tubes were so corroded from leakage of patches, that they were unable to bear the slight increase of pressure during a short stoppage. _No. 66. Glasgow. December 4th. 2 killed, 6 injured._ Two Tube Cornish, 22ft. long, and 7ft. 6in. diameter, tubes 3ft. diameter, and strengthened with rings in the approved manner. The second from the back of the seven rings, was ruptured at the bottom and torn off by a rent through the line of rivets on each side, and the boiler was thrown from its seat, and turned completely over, so as to lie in a contrary direction to what it was before. Extensive corrosion, from leaking of the seams beneath the brickwork, where hidden from view, was the cause of explosion. _No. 67. Willenhall. December 7th. none injured._ Plain Cylinder, with hemispherical ends, 9ft. long, 3ft. 3in. diameter, 20 lbs. The boiler was rent all along one side, and the reaction of the issuing contents caused it to be thrown some yards away, and one of the ends became altogether detached, and flew to a considerable distance. The plates were so thinned by corrosion, that they gave way on a very slight increase of pressure during a temporary stoppage of the engine. _No. 68. Glasgow. December 12th. 1 killed, 1 injured._ This Boiler was 14ft. long, with hemispherical ends, and 7ft. diameter, 30 lbs. The cause of the explosion was over-pressure and thinness of plates, wasted by corrosion. _No. 69. Manchester. (Fig. 32.) December 15th. 5 injured._ [Illustration: _Fig. 32._] Two Tube Cornish, 24ft. long, 6ft. 6in. diameter, tubes 2ft. 8in. diameter, 7/16 inch plates, 50 lbs. The boiler was fired in each of the tubes in the ordinary way, and also the heat from two furnaces passed from the back, one on each side of the outside shell. Both the internal furnaces collapsed, until the crowns almost touched the fire bars, as shown in dotted lines, but without fracture. The back of the shell, on the right side, had evidently been overheated, and had rent along the centre of a bulge, and this rent had extended along the line of rivets of the transverse seam on each side, allowing two rings of the plates of the shell to open out flat as shown. There was a bulge on the plate, on the right side of shell, corresponding with the one which parted on the opposite side. The cause of the explosion was overheating of the plates from shortness of water. _No. 70. Aberdeen. December 24th. 1 injured._ No particulars have been obtained. BOILER EXPLOSIONS IN 1867. _No. 1. Hull. January 2nd. 1 killed, 1 injured._ A small Boiler to heat a bath. It exploded, causing great damage, because the connecting pipes were frozen. All such boilers should have a proper safety valve. _No. 2. Durham. (Fig. 1.) January 2nd. 3 killed, 3 injured._ [Illustration: _Fig. 1._] Plain Cylinder, 33ft. long, 6ft. diameter, 33 lbs. pressure. Only set two days, but was old and deteriorated, and had worked before at another place. It had been turned 1/4 round, and old fitting-holes stopped. First rent was supposed to be in a seam at front end, over the fire. Main portion of shell was driven back, and front end forward, and torn in its flight. The cause of explosion was, that the seam in front was overheated and injured, and also incautious working without a steam gauge. _No. 3. Sheffield. (Fig. 2.) January 2nd. 1 killed, 4 injured._ [Illustration: _Fig. 2._] One Tube externally fired, 30ft. long, 6ft. 6in. diameter, with dished ends. Tube 2ft. 9in. diameter, slightly oval. Pressure 60 lbs. Tube collapsed sideways from end to end, because it was not strengthened by hoops or other means, which were the more needed, because it was slightly oval, and the longitudinal seams were nearly in one line. _No. 4. Preston. January 3rd. 1 killed._ Boiler for heating apparatus. Fire was lighted without noticing that as there was no safety valve, and that all escape of steam was prevented by the connecting pipes being frozen. _No. 5. Westerham. January 5th. 1 killed._ Cast-iron Boiler for heating water for a horse shower bath, fixed behind an ordinary fireplace. Burst and caused great damage, owing to the pipes being frozen. There was no safety valve. _No. 6. Barr. January 9th. 1 killed, 3 injured._ Kitchen Boiler, which burst because the supply pipes were stopped by frost, and there was no safety valve. _No. 7. London. January 11th. 1 killed._ Cornish, 12ft. long, 4ft. 6in. diameter, tube 2ft. 4in. diameter, pressure 40 lbs. Small piece of plate was blown out near the bottom, and the boiler was displaced by the reaction of issuing contents. The cause of explosion was extensive external corrosion on the lower part. _No. 8. Preston. January 16th. none injured._ Kitchen Boiler. Burst and did great damage, because pipes were frozen preventing escape of steam. There was no safety valve. _No. 9. Brechin. January 23rd. 1 killed._ Kitchen Boiler. Fire had been out some days, and the boiler burst soon after re-kindling it and did much damage, because the supply pipes were stopped by frost, and there was no safety valve for escape of steam. _No. 10. Sunderland. (Fig. 3.) January 26th. 3 injured._ [Illustration: _Fig. 3._] Plain Cylinder, 30ft. long, 6ft. 2in. diameter. Pressure 30 to 35 lbs. Rent into four pieces, which were flattened out and scattered on to other boilers, but are arranged in sketch so as to show their original position in the boiler. It had worked a very long time, and was overheated and injured along the fractured line. _No. 11. Exeter. (Fig. 4.) January 30th. 2 killed, 2 injured._ Elephant Boiler, 16ft. long, 5ft. diameter, tubes 1ft. 10in. diameter, 45 lbs. pressure. Flat end blew out, throwing boiler upwards by reaction, but shell and tubes were not injured. The flat end was not sufficiently stayed, having only one stay-rod to the centre, the bolt of which was broken. [Illustration: _Fig. 4._] _No. 12. Glasgow. February 8th. 1 killed, 4 injured._ Small Boiler to 6-horse power engine. Gave way at centre of furnace, and water forced out at both ends, and it was suspected that the water was low. _No. 13. Sheffield. (Fig. 5.) February 11th. 4 injured._ [Illustration: _Fig. 5._] Cornish, about 30ft. long. Tubes 3ft. unstayed. Tube collapsed sideways, and was rent from grate bars to end, without injuring front plates or shell. It was said to be short of water, but most likely the true cause was the weakness of the tube. _No. 14. Manchester. February 15th. none injured._ Two flued, 28ft. long, 6ft. 9in. diameter, slightly oval; plates 3/8 inch; tube 2ft. 8in. diameter, pressure 45 lbs. Shell had once been externally fired. Rent along the seams which were in one line, and a large piece of the plate blew away, leaving tubes uninjured. The cause of explosion was defective form and worn out state of shell. _No. 15. Weymouth. (Fig. 6.) March 12th. 1 killed, 3 injured._ [Illustration: _Fig. 6._] Agricultural, 45 lbs. pressure. Fire-box blew off, and the outer shell separated from it. The cause of explosion was over-pressure from the safety valve being screwed down. _No. 16. Lynn. (Fig. 7.) March 19th. 8 killed, 4 injured._ [Illustration: _Fig. 7._] Agricultural, 45 lbs. pressure. Fire-box and tubes blew out. The cause of explosion was over-pressure, as the safety valve was tied down with string. _No. 17. Blackbraes. March 23rd. 3 killed, 1 injured._ Colliery Boiler, 30 lbs. pressure. Rent in two while the engine was standing, but no details obtained. _No. 18. Barnsley. (Fig. 8.) March 29th. 2 killed, 2 injured._ [Illustration: _Fig. 8._] Small plain Cylinder, with ends nearly flat, 4ft. 7in. long, 2ft. 4in. diameter, plates 3/16 inch. No emptying plug or feed-pipe, and only a very small hand-hole. Front end attached by slight angle iron, which gave way, leaving the shell unmoved. The cause of explosion was the internal corrosion of front end owing to very bad water being used. The plates were reduced to a knife edge in line of fracture. _No. 19. Cornwall. (Fig. 9.) April 10th. 1 killed, 1 injured._ [Illustration: _Fig. 9._] Cornish, one tube 32ft. long, 6ft. diameter, tube 3ft. 10in. diameter, plates 3/8 inch, pressure 25 to 40 lbs. It was 20 years old, but just repaired and reset. Furnace tube failed and collapsed from one end to the other, except about 4 feet of front, owing to its weakness, being unstrengthened by hoops or cross tubes. _No. 20. Belfast. (Fig. 10.) April 20th. 1 killed, 2 injured._ [Illustration: _Fig. 10._] Plain Cylinder, 6ft. long, 2ft. 5in. diameter, plates 1/4 inch, pressure 90 lbs. The end blew out from excessive pressure, as the escape from the safety valve was prevented by a plug in the exit pipe. _No. 21. Birmingham. (Fig. 11.) May 9th. 2 injured._ [Illustration: _Fig. 11._] Plain Cylinder, 3ft. 2in. long, 1ft. 8in. diameter, plates 5/16 inch, pressure 30 lbs. Workmanship and material very inferior. Piece of top ripped out from manhole and allowed manlid to blow out through manhole. The cause of the explosion was, the large manhole and over-pressure. The safety valve was too small, and very roughly made. _No. 22. Hartlepool. (Fig. 12.) May 10th. 1 killed, 1 injured._ [Illustration: _Fig. 12._] Locomotive, 130 lbs. pressure. Barrel blown away and broken to pieces, leaving fire and smoke boxes. The cause of explosion was supposed to be the strain on the boiler caused by its being made a stay to the frame without allowance for expansion, and thereby weakening a horizontal seam. _No. 23. Newark. (Fig. 13.) May 18th. 4 injured._ [Illustration: _Fig. 13._] Cornish, one tube 20ft. 6in. long, 5ft. 4-1/2in. diameter, tube 3ft. diameter, plates 3/8 inch, pressure 64 lbs. The ends came out and tube collapsed for its full length, every joint being broken. The cause of explosion was bad construction and workmanship, and tube too weak for pressure. _No. 24. Tamworth. (Fig. 14.) June 4th. 2 killed._ [Illustration: _Fig. 14._] Two tube, externally fired, 30ft. long, 7ft. diameter, tubes 2ft. 4in. diameter, pressure 50 lbs. Two plates lately put in bottom gave way, and shell rent along bottom and opened out, dividing into several pieces, which were scattered to great distances, but are arranged in sketch so as to show their original position. The cause of explosion was too frequent repair over the fireplace, and external firing. _No. 25. Dudley. (Fig. 15.) July 10th. 1 killed, 2 injured._ [Illustration: _Fig. 15._] Balloon, 22ft. diameter, pressure 5 lbs. Bottom blew out and was torn in pieces. Main portion of shell fell over on to another boiler. The cause of explosion was deep corrosion along the bottom where it rested on the brickwork. _No. 26. Batley. (Fig. 16.) July 11th. 3 killed, 3 injured._ [Illustration: _Fig. 16._] One tube Cornish, 26ft. long, 8ft. 10-1/2in. diameter, tube 5ft. diameter, for 8ft. 6in. of front end, tapering to 4ft. diameter at back, pressure 30 lbs. Rent along bottom, allowing central ring of plates to open out. The whole boiler was thrown some distance by the reaction of issuing contents. The cause of explosion was corrosion at mid-feather wall, the plates being little thicker than paper. _No. 27. Rotherham. (Fig. 17.) July 13th. none injured._ [Illustration: _Fig. 17._] Two tube Cornish, 31ft. long, 7ft. diameter, tube 2ft. 7in., tapering to 2ft., pressure 55 lbs. Left hand tube collapsed, and about the centre of collapse, plate was torn in two pieces from seam to seam. The cause of explosion was overheating, because the water was being let low before all the fire was out. _No. 28. Bilton. (Fig. 18.) July 24th. 1 injured._ [Illustration: _Fig. 18._] Locomotive. Side-plate in the upper part of high top fire-box blew away. The cause of explosion was most likely the boiler being made the frame of the engine without allowance for expansion. _No. 29. Ecclesfield. August 5th. 1 killed, 2 injured._ Full particulars were not obtained, but the steam and hot water were allowed to come in from a neighbouring boiler through the blow-off pipe while the men were cleaning. _No. 30. Belfast. (Fig. 19.) August 27th. 7 killed, 3 injured._ [Illustration: _Fig. 19._] Cornish, 18ft. long, 4ft. 9in. diameter, tube 1ft. 6in. diameter, plates 3/8 inch, pressure 50 lbs. There were no stays. End plate blew out while being caulked at a jump joint in back angle iron. The cause of explosion was bad construction and want of stays, and also want of proper care in working. _No. 31. Plashetts. September 2nd. 2 injured._ Locomotive, but no details obtained. _No. 32. Ashton. September 9th. none injured._ Two flued, 40 lbs. pressure. The cast-iron mouth-piece of manhole fractured from insufficient strength, and allowed lid and upper flange to blow off. _No. 33. Blackburn. October 4th. 4 injured._ Water Heater, made of large bottle-shaped pipes placed in the flue. The force of explosion caused the neighbouring boilers to be unseated. No details have been obtained as to the cause of the explosion. _No. 34. London. (Fig. 20.) October 7th. 1 killed._ [Illustration: _Fig. 20._] One tube Cornish, 11ft. long, 4ft. diameter, plates 3/8 inch, tube 2ft. 1-1/2in. diameter, pressure 50 lbs. Gave way underneath. Top thrown upwards. Front part and tube thrown to the front. The cause of the explosion was extensive corrosion at the bottom where it touched the walls. _No. 35. Preston. October 31st. none injured._ Cornish, 26ft. long, 5ft. 6in. diameter, tube 2ft. 11in. diameter, plates 3/8 inch. Pressure 30 lbs. Tube collapsed for want of proper strengthening hoops, blowing out back end, and throwing boiler forward. _No. 36. Durham. (Fig. 21.) November 3rd. 1 killed, 1 injured._ [Illustration: _Fig. 21._] Plain Cylinder, 19ft. long, 6ft. diameter, pressure 40 lbs. It was 36 years old, and iron deteriorated and also much patched. The cause of explosion was over-pressure for so old a boiler. _No. 37. Bradford. (Fig. 22.) November 6th. 2 killed, 3 injured._ [Illustration: _Fig. 22._] Agricultural, wagon-shaped, 6ft. 5in. long, 3ft. high, 2ft. 4in. wide, plates 3/8 inch, pressure 50 lbs. Upper portion of barrel blew off. The cause of the explosion was over-pressure from locked safety valve and defective construction. _No. 38. Sheffield. (Fig. 23.) November 7th. 1 injured._ [Illustration: _Fig. 23._] Plain Cylinder, 12ft. 3in. long, 3ft. 11in. diameter, pressure 20 lbs., flat front, and round back end. Main portion thrown back and front forward. Front torn all round the root of angle iron, and stay rivets drawn through flat end. The cause of explosion was weakness of construction of flat end, and bad safety valve, which could have been loaded to 60 lbs. _No. 39. Langley Mill. (Fig. 24.) November 11th. 3 killed, 10 injured._ [Illustration: _Fig. 24._] Plain Cylinder, 40ft. long, 5ft. diameter, plates 7/16 inch, pressure 45 to 50 lbs. Parted at third seam, and front thrown forward and main portion backwards. The cause of explosion was a seam-rip of old standing near patch at place of first rupture. _No. 40. Bradford. (Fig. 25.) November 14th. 4 killed, 3 injured._ [Illustration: _Fig. 25._] Breeches tube 25ft. 6in. long, 7ft. 6in. diameter, plates 7/16 inch, pressure 30 lbs. Front end and fire-grate tubes and taper junction were thrown to the front in one piece. Main shell not injured. Back part of tube remained in boiler. Bottom part of taper junction where flattened to receive the two fire tubes, collapsed upwards. The cause of explosion was the want of proper stays or strengthening tubes, and consequent weakness. There was only one safety valve of small size. _No. 41. Chippenham. (Fig. 26.) November 21st. 3 killed, 2 injured._ [Illustration: _Fig. 26._] One tube Cornish, 11ft. long, 5ft. diameter, pressure 44 lbs. Tube gave way at an old crack at back of strap-plate and partially collapsed. _No. 42. Dudley. (Fig. 27.) November 27th. 1 killed._ [Illustration: _Fig. 27._] Plain Cylinder, 25ft. long, 6ft. diameter, plates 7/16 inch, pressure 50 lbs. Had been a one tube Cornish, but tube had been taken out, leaving flat ends. Back end was blown out. Main shell thrown forwards. The cause of explosion was weakness of construction in not sufficiently strengthening the flat end to compensate for loss of tube. _No. 43. Shields. (Fig. 28.) December 7th. none injured._ [Illustration: _Fig. 28._] One tube Cornish, 28ft. long, 6ft. diameter, tube 4ft. diameter, plates 3/8 inch. Pressure 28 lbs. Tube collapsed for the whole length, but no particulars of the cause obtained. _No. 44. Belfast. December 14th. 2 killed._ Some repair had been done to a Boiler, and a blank flange used to stop off the steam was being removed without shutting the stop-valves to the other boilers, and the joint blew out when the bolts were loosened. _No. 45. Manchester. (Fig. 29.) December 23rd. 6 killed, 4 injured._ [Illustration: _Fig. 29._] One tube Cornish, 18ft. long, 6ft. diameter, tube 3ft. 2in. diameter, plates 3/8 inch. Pressure 25 lbs. Rent along bottom, and two rings of plates blown away, but tube and ends not much injured. The cause of explosion was extensive corrosion on the part resting on the mid-feather wall. _No. 46. Barnsley. (Fig. 30.) December 28th. 1 killed._ [Illustration: _Fig. 30._] Balloon, 11ft. 6in. diameter, and 11ft. 6in. high, plates 3/8 inch. Bottom domed up 3ft. 6in. over fire; ordinary pressure 8 lbs. Boiler had worked two days at 25 lbs. pressure, but safety valve loaded to 16 lbs. The cause of explosion was undue pressure for an old boiler of such weak shape. _No. 47. Leeds. (Fig. 31.) December 30th. 2 injured._ [Illustration: _Fig. 31._] Two tube Cornish, 22ft. long, 7ft. 2in. diameter, tubes 2ft. 7in. diameter, pressure 15 lbs. Rent along bottom, and shell blown away, leaving tubes and ends nearly uninjured. The cause of explosion was, that the bottom was corroded to a knife edge all along the mid-feather wall. _No. 48. Shields. (Fig. 32.) December 31st. 2 killed, 1 injured._ [Illustration: _Fig. 32._] Plain Cylinder, 30ft. long, 4ft. 6in. diameter, plates 3/8 inch, pressure 29 lbs. Rent over fire near where a new plate had lately been put in. Front part of shell opened out and rent, and back end blew away in one piece. The cause of explosion was deterioration from 20 years' wear, and bad management. BOILER EXPLOSIONS IN 1868. _No. 1. Newcastle. (Fig. 1.) January 13th. none injured._ [Illustration: _Fig. 1._] One of three. Plain Cylinder, 27ft. long, 5ft. diameter, 3/8 inch plates, 35 lbs. pressure. The boiler was much torn up, and all the fragments thrown to the front of their original position. The cause of the explosion was that the boiler was very old and much deteriorated, so that it was unable to bear the ordinary pressure. The longitudinal arrangement of the plates, and the entrance of the feed directly on the bottom, no doubt contributed to the weakness. _No. 2. Glasgow. January 27th. 1 killed, 5 injured._ One of four. Kier or steam chamber, and not used for generating steam. It was 8ft. 6in. high, 6ft. 6in. diameter, 7/16 inch plates, 40 lbs. pressure. It was rent from top to bottom, owing to inferior iron and workmanship. _No. 3. Sheffield. (Fig. 2.) January 28th. 1 killed._ [Illustration: _Fig. 2._] One of four. One tube Cornish, 26ft. 4in. long, 6ft. 6in. diameter. Tube 3ft. 9in. diameter, 3/8 inch plates, 15 lbs. pressure. The dotted line shows outside shell of boiler. The tube collapsed from end to end while the steam was being raised, owing to the weakness of so large a tube without strengthening rings. _No. 4. London. (Fig. 3.) January 29th. 1 killed._ [Illustration: _Fig. 3._] One tube Cornish, 18ft. 3in. long, 4ft. 10in. diameter, 3/8 inch plates. Tube 3ft. diameter, 5/16 inch plates. In sketch the external shell is shown in outline to allow the tube to be seen. The tube collapsed owing to shortness of water, and rent open at one seam, allowing the contents to issue violently, although the boiler itself was not disturbed. _No. 5. Bolton. (Fig. 4.) January 31st. 1 injured._ [Illustration: _Fig. 4._] Locomotive, 90 lbs. Sketch shows interior view of fire-box with front removed. The left side of the copper fire-box burst inwards owing to the plate in line of fracture being corroded to less than 1/8 inch. _No. 6. Stoke. (Fig. 5.) February 6th. none injured._ [Illustration: _Fig. 5._] One of three. One tube Cornish, with two external fire grates with a water tube over each fire. It was 30ft. 2in. long, 6ft. diameter. Tube 3ft. diameter, 3/8 inch plates, 40 lbs. pressure. External shell is shown in dotted lines to allow of the tubes being seen. The tube had formerly been placed rather higher in the boiler. The tube collapsed sideways, having become overheated from shortness of water. The boiler itself was but little disturbed. _No. 7. Kelso. (Fig. 6.) February 11th. none injured._ [Illustration: _Fig. 6._] One tube Cornish, 9ft. 9in. long, 4ft. 6in. diameter. Tube 2ft. 3in. diameter, 5/16 inch plates, 30 lbs. pressure. The boiler rent open at the bottom, and was thrown a considerable distance by the reaction of the issuing contents. The plates along the bottom were reduced by corrosion to 1/16 inch where in contact with the brickwork, so that the boiler was unable to bear the usual working pressure. _No. 8. Durham. (Fig. 7.) February 12th. 2 killed, 1 injured._ [Illustration: _Fig. 7._] One of four. External shell is shown in dotted lines in sketch, to allow the tubes to be seen. It was 20ft. long, 7ft. diameter, 40 lbs. pressure. The two internal fire grates in the flues were 2ft. 8in. diameter, which joined at the back with a central return flue to a chimney passing out of the top of the boiler. The sides of flues were flattened to allow them to be packed closer together, and especially the central return flue, which was flattened on both sides, and thus rendered so weak that the left side collapsed and allowed the contents of the boiler to issue, blowing out the grate on the left side. _No. 9. Halifax. (Fig. 8.) March 3rd. none injured._ [Illustration: _Fig. 8._] Plain Cylinder, with flat ends, 18ft. 6in. long, 3ft. 11in. diameter, 3/8 inch plates, 50 lbs. pressure. The back end gave way at the root of the angle iron all round, and was thrown 60 yards to the rear. The boiler was forced forward, and tilted up by the reaction of the issuing contents, and forced through a wall. The cause of explosion was the want of sufficient stays to the flat end. _No. 10. Newcastle. (Fig. 9.) April 4th. 1 killed, 4 injured._ [Illustration: _Fig. 9._] One of four. Plain Cylinder, 28ft. long, 6ft. diameter, 3/8 inch plates, 30 lbs. pressure. The boiler was much torn and scattered, and much damage was done. The plates were improperly arranged longitudinally. The boiler gave way at a patch lately put on, and had become so deteriorated by nearly 30 years' wear, that it was unable to bear the usual pressure. _No. 11. Aberdeen. April 7th. 1 killed._ Two tube Cornish, 6ft. diameter. Few particulars have been obtained. The upper part of front end was blown out and did considerable damage. Most likely this was for want of proper stays. _No. 12. April 15th. 1 injured._ One of four. One tube Cornish, 15ft. long, 4ft. 7in. diameter. Tube 2ft. 8in. diameter, 1/4 inch plates, 60 lbs. pressure. The tube collapsed and rent open near the bridge, owing to its weakness with such thin plates and no strengthening rings. _No. 13. Cornwall. May 1st. 1 killed._ No details obtained. One tube Cornish. Tube collapsed, owing to its weakness without strengthening rings. _No. 14. Cornwall. May 9th. none injured._ Few particulars obtained. One tube Cornish, 34ft. long. Tube 4ft. diameter, 3/8 inch plates, 40 lbs. pressure. Tube collapsed owing to its weakness without strengthening rings. _No. 15. Oldham. May 11th. 1 killed, 1 injured._ A very small plain cylinder, 3ft. 5in. long, 1ft. 8in. diameter, 1/4 inch plates, 45 lbs. pressure. It burst at a faulty place at the lower part of the back, on the left hand side, allowing the hot water to issue, but the boiler was not much disturbed. _No. 16. Bristol. May 11th. 1 killed._ Marine. Single internal fire grate, with small return tube, 7ft. 9in. long, 5ft. 4in. diameter, 3/8 inch plates, tube 2ft. 7in. diameter, 1/4 inch plates, 62 lbs. pressure. Tube collapsed and rent open owing to its weak, corroded, and deteriorated condition, and the contents issued so violently, as to cause much damage to the boat. _No. 17. Hull. (Fig. 10.) May 12th. 2 killed, 2 injured._ [Illustration: _Fig. 10._] One of two. Plain Cylinder, 4ft. 9in. long, 3ft. diameter, 1/4 inch plates, 25 lbs. pressure. This was a second-hand boiler, and rent into several pieces just after being put to work, owing to its having become thinned to 1/8 inch by corrosion. _No. 18. Coatbridge. May 15th. 1 injured._ Plain Cylinder, flat ends, 15ft. long, 5ft. diameter, 3/8 inch plates, 30 lbs. pressure. The back end blew out and caused considerable damage, and the boiler was thrown some distance. The end was very insufficiently stayed. _No. 19. Gravesend. (Fig. 11.) May 28th. 2 killed._ [Illustration: _Fig. 11._] One of two. Marine, 13ft. 5in. long, 7ft. 2in. diameter, 5/16 inch plates, 25 lbs. pressure. The fire was in two internal furnace tubes united at the back, and the flame was returned to the front by four smaller tubes. The furnace tubes were of exceedingly weak shape as the sides followed the curve of the shell, but were not attached to it by proper stays, so that the left hand tube collapsed upwards, and one seam rent open and allowed the contents to violently escape. It is probable there may have been greater pressure than usual at the time, but the furnaces without stays were unsafe, even at the ordinary pressure. _No. 20. Durham. (Fig. 12.) June 8th. 2 killed._ [Illustration: _Fig. 12._] One of eight. Plain Cylinder, 30ft. long, 6ft. diameter, 3/8 inch plates, 35 lbs. pressure. The plates were arranged longitudinally. Boiler had worked 27 years, and was much deteriorated, and gave way at an old fracture over the grate, and was torn into 4 pieces, which were thrown a great distance. _No. 21. Huddersfield. (Fig. 13.) June 20th. 1 killed, 6 injured._ [Illustration: _Fig. 13._] One tube Cornish, 24ft. long, 6ft. diameter. Tube 3ft. 3in. diameter, 3/8 inch plates, 40 lbs. pressure. The seams were arranged diagonally, but the rents had not followed the seams, but had torn the plates. The shell gave way where extensive corrosion had reduced the plates to 1/8 inch in thickness, and all the shell was blown off, and the tube thrown over and turned end for end. _No. 22. June 22nd. none injured._ Two tube Cornish, 27ft. long, 7ft. 6in. diameter. Tube 3ft. diameter, 7/16 inch plates, 70 lbs. pressure. Left hand tube collapsed from end to end owing to its weakness without strengthening rings. _No. 23. Halifax. July 9th. 6 injured._ Two tube Cornish, 20ft. long, 6ft. 3in. diameter. Tube 2ft. 3in. diameter, 3/8 inch plates, 55 lbs. pressure. The shell was blown completely off, leaving the tubes and ends intact. The bottom was extensively corroded, so that the strength of the boiler was so reduced as not to be able to bear the usual pressure. _No. 24. Wrexham. (Fig. 14.) July 9th. 2 injured._ [Illustration: _Fig. 14._] Two Furnace Upright, 22ft. high, 8ft. 10in. diameter, 3/8 inch plates, 14 lbs. pressure. Small piece was blown out of the bottom, and the issuing contents disturbed the brickwork surrounding the boiler. The plate was corroded to a knife edge in the line of fracture, from the leaking of the adjacent blow-pipe joint. _No. 25. Dundee. July 13th. 1 killed, 1 injured._ Two tube Cornish, 28ft. 6in. long, 7ft. diameter, 3/8 inch plates. Tube 2ft. 2in. diameter, 7/16 inch plates, 40 lbs. pressure. Both furnaces collapsed, and ruptured from overheating through shortness of water. _No. 26. Halifax. July 14th. 3 injured._ Locomotive, 10ft. 9in. long, 4ft. diameter, 1/2 inch plates, 130 lbs. pressure. Nearly all the barrel was blown away. The inside was very much corroded, and there was a deep furrow at the line of first rupture, caused by the alteration in form of the boiler in the strain of working. This is usually obviated by substituting butt for lap joints, so that the pressure does not tend to alter the circular shape of barrel. _No. 27. Limerick. July 21st. 2 killed, 1 injured._ Locomotive. Few particulars are obtained. The connecting rod broke, and the loose end attached to the crank pierced the boiler, and allowed the contents to issue and scald those near. _No. 28. Hanley. (Fig. 15.) July 31st. 1 killed._ [Illustration: _Fig. 15._] One of three. Plain Cylinder, 36ft. 9in. long, 5ft. diameter, 3/8 inch plates, 50 lbs. pressure. The boiler parted at a seam over the fire bridge. The front end was thrown upwards and to a considerable distance to the front. The back part of the boiler was forced backwards. The first rent took place at a seam-rip at the ruptured seam, and the boiler exploded while the fire was being drawn in order to repair the faulty place. _No. 29. Easter Ross. August 8th. 2 killed, 3 injured._ Agricultural. It exploded while travelling, by its own steam power. The engine had stuck fast, and extra pressure of steam was raised to try and extricate it. The boiler was torn in pieces, and scattered to a great distance. _No. 30. Bilston. (Fig. 16.) August 17th. 1 killed._ [Illustration: _Fig. 16._] One of two. Plain Cylinder, 30ft. long, 5ft. diameter, 3/8 inch plates, 46 lbs. pressure. The boiler gave way on the side where the plates were overheated by the water being too low, and the front part of the shell was flattened out and thrown some distance to the rear, as its course was influenced by its remaining attached to the rest of the boiler as by a hinge; while the front end was rent into several pieces, and the back end was thrown also to the rear and rolled down a declivity into a stream. _No. 31. Liverpool. (Fig. 17.) August 20th. 7 killed, 5 injured._ [Illustration: _Fig. 17._] Two Furnace Chimney Boiler, 42ft. 4in. high, 6ft. 9in. diameter, 1/2 inch plates, 50 lbs. pressure. Nearly half the bottom plate was blown out, and the issuing contents found their way into the furnace and increased the damage. The line of rupture near where it joined the shell was corroded almost to a knife edge, which so reduced its strength as to make it unable to bear the usual working pressure of steam, in addition to that of the column of water in the boiler. _No. 32. Accrington. August 31st. 1 killed._ A Kier or Steam Bleaching Chamber, somewhat like No. 2, and not used for generating steam, 9ft. high, 8ft. diameter, 1/2 inch plates, 50 lbs. pressure. The bottom blew out, and the shell was torn to pieces. The cause of explosion was weakness of the ruptured end, and want of care in working. _No. 33. Birmingham. September 11th. 1 killed, 1 injured._ Two tube Cornish. The manlid was wrongly fixed outside with internal clamps. It was being screwed up tighter to stop leaking when the bolt broke, and the lid came off and allowed the contents of the boiler to escape. _No. 34. Greatbridge. (Fig. 18.) September 21st. none injured._ [Illustration: _Fig. 18._] One of four. One tube, externally fired, 18ft. 6in. long, 6ft. 6in. diameter. Tube 3ft. diameter, 1/2 inch plates, 40 lbs. pressure. In sketch the shell is shown in dotted lines to allow the tube to be seen. The tube collapsed from end to end and ruptured at two seams, and the contents issued so violently as to knock down the brickwork and displace the boiler. The tube was in a very weak and corroded condition, and unable to bear the usual working pressure. _No. 35. Moxley. (Fig. 19.) September 28th. 13 killed, 2 injured._ [Illustration: _Fig. 19._] One of four. Four Furnace Upright, 22ft. high, 10ft. 6in. diameter, 7/16 inch plates, 40 lbs. pressure. The boiler was rent into nine pieces, one of which was not found. The dotted line in sketch shows the outline of the boiler before explosion, and the fragments are arranged as nearly as possible in their original position. The first rent was at a seam-rip opposite the largest furnace, from whence the rupture opened in every direction. This seam-rip must have existed some time before explosion, and must have extended from rivet to rivet, until the boiler was so much weakened as to be unable to bear the usual pressure. _No. 36. Winsford. September 30th. 1 killed._ Plain Cylinder. Few particulars obtained. The end over the fire burst open and allowed the contents to escape. A thick accumulation of scale on the bottom had caused the plate to become overheated by preventing proper contact of the water. _No. 37. Elsecar. (Fig. 20.) October 2nd. 2 killed._ [Illustration: _Fig. 20._] One of four. Two Furnace Upright, 21ft. high, 7ft. diameter, 7/16 inch plates, 58 lbs. pressure. A large piece of plate was blown out of the side of the boiler, and the reaction of the issuing contents threw the boiler over on to its side. The plate was said to be overheated from shortness of water, but as the centre tubes were uninjured, the ruptured plate may have become overheated from the intense heat impinging on one place, causing so rapid a generation of steam as to prevent proper contact of water. _No. 38. Glasgow. October 12th. 1 killed, 1 injured._ Plain Cylinder, 39ft. long, 5ft. diameter, 3/8 inch plates. A small piece of plate about one-and-half-feet area blew out of the bottom, and the contents issued so violently as to do much damage, although the boiler itself was not otherwise injured. The ruptured plate was corroded, to 1/16 inch thickness by the leaking of seams, caused by the feed water entering close to the bottom of the boiler. _No. 39. Swansea. October 13th. 2 killed, 1 injured._ One of twenty-four. One tube Cornish, worked by two furnaces, 23ft. long, 6ft. 6in. diameter. Tube 3ft. 9in. diameter, 1/2 inch plates, 40 lbs. pressure. The tube was divided by a wall down the middle. The tube collapsed sideways. It was said that one side was overheated through shortness of water, but it is more than probable the explosion was owing to the weakness of so large a tube without strengthening rings. _No. 40. Preston. October 16th. 2 injured._ This was an arrangement of pipes, called an "Economiser," placed in the flues of a set of boilers for heating the feed water. It was shattered into fragments, causing considerable damage. As the whole apparatus was said to be in proper order, the explosion had been attributed to coal gas in the flues, and some peculiarities in the ruptured pipes bear out the supposition. _No. 41. London. (Fig. 21.) October 19th. 6 injured._ [Illustration: _Fig. 21._] Kitchen Boiler, for supplying hot water to the top of a lofty house. It was rectangular, 3ft. 6in. wide, 2ft. 6in. high, and 1ft. deep. The front was blown out and caused considerable damage. The boiler was of most weak shape, and although no pressure of steam was intended, it appeared to have been overlooked that the column of water to the top of the house would give sufficient pressure to make such a boiler unsafe. _No. 42. London. (Fig. 22.) October 30th. 2 killed, 10 injured._ [Illustration: _Fig. 22._] One tube Cornish, 15ft. long, 5ft. diameter, 3/8 inch plates, 50 lbs. pressure. Tube oval at fire end, 2ft. 11in. wide, 2ft. 6in. high. Circular beyond bridge, tapering to 2ft. diameter at back end. In sketch outside shell is shown in dotted lines to allow tube to be seen. The front of the tube burst beneath the fire bars, and rent upwards. Tube collapsed beyond bridge and rent open at each side, but remained intact over the fire. The oval part of the tube was of so very weak a shape, that it burst open, and the collapse of the back part followed as a consequence. _No. 43. Birmingham. (Fig. 23.) December 2nd. 1 injured._ [Illustration: _Fig. 23._] Small Portable Boiler, 4ft. 9in. high, 2ft. 3in. diameter, 1/4 inch plates, 40 lbs. pressure. The shell was rent completely off. The explosion arose from the large size of the manhole, which had no guard ring on the edge, and the lid had strained it and caused several cracks, and at last forced itself through the boiler, and the rents spread in every direction, and caused the break up of the boiler. _No. 44. Newcastle. (Fig. 24.) December 11th. 3 killed, 3 injured._ [Illustration: _Fig. 24._] Marine Upright, 13ft. 3in. high, 6ft. 6in. diameter, 1/2 inch plates. Internal fire-box 8ft. 6in. high, 6ft. diameter at bottom, 5ft. 3in. diameter at the top, 3/8 inch plates, 50 lbs. pressure. In the sketch the shell is shown in dotted lines to allow the internal fire-box to be seen. The boiler was rent into many pieces, many of which were lost in a river, so that a satisfactory conclusion as to the cause of the explosion was impossible. The boiler was not very firmly stayed, and it is supposed that it was weakened by corrosion round the fire doors. _No. 45. Hartlepool. December 29th. 1 injured._ Marine, with 3 internal fireplaces joined at the back. The back of the junction tube gave way at a place deeply corroded, and allowed the contents of the boiler to escape. * * * * * NOTE.--Two more illustrations may be given which are not sufficiently important to include in the above list. * * * * * _Willenhall. (Fig. 25.) December 24th. none injured._ [Illustration: _Fig. 25._] One of two. Plain Cylinder, 25ft. 6in. long, 5ft. 6in. diameter, 3/8 inch plates, 30 lbs. pressure. The water was allowed to get low, and the overheated plates opened and allowed the steam to escape harmlessly. _Stoke. (Fig. 26.) December 9th. none injured._ [Illustration: _Fig. 26._] One of eight. Four Furnace Upright, 22ft. high, 9ft. diameter, 7/16 inch plates, 45 lbs. pressure. The water was allowed to get so low that the shell was overheated and rent, and the side tube slightly collapsed, and the injury was not discovered until the feed water had risen up to the rupture, when it ran into the furnaces without causing any violent explosion, although cold water had been put into a red hot boiler. * * * * * STOURBRIDGE: PRINTED BY R. BROOMHALL, HIGH STREET. BOILER EXPLOSIONS IN 1869. _No. 1. Chesterfield. (Fig. 1.) January 14th. 4 killed, 2 injured._ [Illustration: _Fig. 1._] One of two. One tube Cornish, 26ft. 6in. long, 6ft. diameter, tube 3ft. 3in. diameter, 3/8 inch plates, 45 lbs. pressure. The gauge glass was broken and the float was either out of order or unobserved, as the water was allowed to get 9 inches below the usual level, so that the crown of the furnace became overheated and collapsed, and rent open where a patch had been put on some little time before. _No. 2. Manchester. (Fig. 2.) January 22nd. none injured._ [Illustration: _Fig. 2._] Locomotive. The barrel was 10ft. 6in. long, 4ft. diameter, 7/16 inch plates, 130 lbs. pressure. The engine was 14 years old, and had lately been tested to 180 lbs. hydraulic pressure. The seams near the bottom were so deeply "furrowed" or corroded just above the lap joint in a continuous line that they rent open. _No. 3. Greatbridge. (Fig. 3.) January 26th. 1 killed, 1 injured._ [Illustration: _Fig. 3._] One of two. Plain Cylinder, with flat ends, 22ft. long, 4ft. 3in. diameter, 3/8 inch plates, 60 lbs. pressure. There had formerly been a tube with internal furnace, and this had been removed without sufficient stays to compensate for the loss of strength. The plates were arranged in the weakest way with seams in one line from end to end, and the strength of the boiler had been further reduced by very frequent patching. Fracture commenced about the centre of the long seam under the dome, which had gradually ripped from rivet to rivet, until unable to bear the ordinary pressure. The boiler exploded because it was completely worn out, and shows how treacherous and uncertain a boiler becomes by constant patching and alteration. See also No. 45. _No. 4. Rotherham. (Fig. 4.) January 27th. 1 injured._ One of five. Plain cylinder, with dished ends, 36ft. long, 4ft. 6in. diameter, 3/8 inch plates, 55 lbs. pressure. It had worked about 8 years, and was much patched over the fire end, and had lately been put into what was supposed to be thorough repair. As there was no need of an inquest the wreck was quickly cleared and some of the fragments cut up, but enough particulars were obtained to give some idea of the nature of the explosion. [Illustration: _Fig. 4._] The first rent must have taken place in the bottom seams over the fire, where weakened by frequent repair. _No. 5. Durham. (Fig. 5.) February 2nd. 1 killed, 4 injured._ [Illustration: _Fig. 5._] One of twelve. Plain cylinder, 13 years old, 30ft. long, 6ft. diameter, 3/8 inch plates, 35 lbs. pressure. The plates were arranged lengthways, so that the seams were in continuous lines from end to end. This has often been mentioned as giving far less strength than where the plates are placed in rings. There had been considerable repair at various times, and just previous to explosion the boiler had been placed as was supposed in thorough repair, and some new plates had been put over the fireplace. The first rent appears to have taken place where one of these plates joined the old work. The rent quickly extended along a straight seam, and the boiler was blown into three pieces. The explosion was simply caused by the boiler having been weakened by frequent repair until unable to bear the ordinary working pressure. Externally fired boilers, when so frequently patched become treacherous and uncertain, and more especially so when the seams run from end to end. See No. 59. _No. 6. South Wales. February 12th. 2 injured._ This was a colliery boiler. Very few particulars were obtained. The roof of the engine house was blown off, the boiler was torn from its fittings and turned right round, and knocked down three walls and fell in an upright position. _No. 7. Cornwall. (Fig. 6.) February 15th. none injured._ [Illustration: _Fig. 6._] One of four. One tube Cornish, 37ft. 6in. long, 7ft. diameter. Tube 4ft. 4in. diameter, 7/16 inch plates, 40 lbs. pressure. The tube collapsed for the whole length beyond the bridge, and the back end of boiler was blown out. The portion of tube over the fire was left intact, and the fusible plug was uninjured. The cause of the explosion was the weakness of the tube of such large diameter and so great length. See No. 57. _No. 8. Yarmouth. (Fig. 7.) February 23rd. 3 injured._ [Illustration: _Fig. 7._] Marine, 17ft. long, and 15ft. high, 3/8 inch plates, 15 lbs. pressure. The top was blown off, the plates having been extensively corroded. The boiler had also been much weakened by altering it from a round to a flat top without sufficient stays. _No. 9. Drogheda. March 3rd. 2 injured._ The roof of a shed was blown off, but no particulars have been obtained. _No. 10. West Bromwich. (Fig. 8.) March 9th. 3 injured._ [Illustration: _Fig. 8._] One of two. Plain cylinder, 25ft. long, 4ft. 6in. diameter, 3/8 inch plates, 42 lbs. pressure. The boiler had been very frequently repaired, and a seam gave way where a large patch had just previously been put on over the fire, in doing which the rivet holes of the old work had evidently been cracked, rendering the boiler unable to bear the usual working pressure. See No. 45. _No. 11. Cornwall. March 18th. none injured._ One tube Cornish. The tube collapsed from want of water. _No. 12. Broseley. (Fig. 9.) April 1st. 1 killed, 4 injured._ [Illustration: _Fig. 9._] Multitubular, 9 years old, 8ft. 6in. long, barrel 6ft. long, and 2ft. 4in. diameter, 5/16 inch plates, 50 lbs. pressure. The cylinder was attached to right side of the top of the boiler over the fire box, and on the other side there was a very large manhole, the edges of which were corroded, and so strained and cracked by the screwing up of the manlid, as to be unable to bear the working pressure. The rent started in all directions from the manhole allowing the boiler to split up into three pieces. See Nos. 18 and 36. _No. 13. Cornwall. April 11th. none injured._ One tube Cornish--but no particulars. _No. 14. Barking. (Fig. 10.) April 19th. 4 killed, 2 injured._ [Illustration: _Fig. 10._] Portable Crane, 8 years old, 8ft. 3in. high, 4ft. 4in. diameter, with internal fire box, 6ft. high and 3ft. 6in. diameter, and chimney passing out at the top, 5/16 inch plates, 40 lbs. pressure. The internal fire box crushed in sideways, and the shell was rent into several pieces. The attachment of the fire box to the shell was made by bending the plates, as shown in enlarged sketch, and this is not so rigid as double angle iron and had evidently strained the chimney tube. This weakness had been so increased by deep corrosion just at the bend of the plates that it had given way. The havoc and loss of life was far greater than would have been supposed possible from so small a boiler, but similar cases are mentioned in No. 43, 1868, and No. 57, 1866. _No. 15. Durham. (Fig. 11.) April 23rd. none injured._ [Illustration: _Fig. 11._] One of two. Plain cylinder, with plates arranged lengthways, 30ft. long, 6ft. diameter, 3/8 inch plates, 9 lbs. pressure. A seam gave way on the right side over the fire and immediately rent along the straight seam from end to end, and the boiler was thrown in one mass a great distance to the left. The boiler was very old and much weakened by frequent repair, and at the time of explosion was being imprudently worked at twice its usual pressure for a temporary purpose. See No. 59. _No. 16. Bury. (Fig. 12.) April 29th. none injured._ [Illustration: _Fig. 12._] Double Furnace, internally fired, 28ft. long, 7ft. diameter, 7/16 inch plates, 55 lbs. pressure. Furnace tubes 7ft. long, 3ft. diameter, 3/8 inch plates. The crown of the left hand furnace collapsed and the right hand furnace was slightly altered in shape, as if from overheating by shortness of water, although the true cause was supposed to be the thickening of the water by use of anti-incrustation composition, preventing proper contact of the water with the plates. _No. 17. Liverpool. (Fig. 13.) May 12th. 1 killed, 1 injured._ [Illustration: _Fig. 13._] Plain cylinder, 10ft. long, 3ft. diameter, 3/8 inch plates, 50 lbs. pressure. The ends were flat made of plates, with turned edges, and there was such extensive corrosion on the inside of the bend that the back end came out and was blown 30 yards to the right and rear, the rest of the boiler being thrown to the front. The front plate had been repaired with angle iron where similarly corroded, and the shell was also much patched. The fractured edges were not 1/16 inch thick, so that the boiler was not fit to carry any pressure with safety. _No. 18. Abingdon. (Fig. 14.) May 13th. 2 killed, 2 injured._ [Illustration: _Fig. 14._] Revolving Rag boiler, 16ft. long, 6ft. diameter, 7/16 in. plates. There was no fire applied to the boiler itself, but it received steam through one end from other ordinary boilers at 50 lbs. pressure. There were two large rectangular manholes for putting in and taking out the rags, with cast iron frames and lids, attached by bolts with large nuts or clamps. The explosion appeared to have taken place when, in revolving, the manlids were approaching the bottom, and the first part to give way was at one of the manholes where the frame was previously broken. The cause of the explosion was the weakness of the manholes, which were very large, and both in the same line, and the attachment of the lids was insecure, as the bolts did not go through the lids, or in any way help to compensate for the large portion of the plate cut away. The boiler was only supported at each end, and had to act as a hollow girder to bear not only its own weight but the repeated shocks of the heavy material inside falling over and over in addition to the pressure. See Nos. 41 and 63, 1866. _No. 19. Glasgow. May 19th. 1 killed, 1 injured._ Two tube Cornish. One of the tubes collapsed for a length of 8 feet having become overheated through shortness of water. _No. 20. Durham. (Fig. 15.) May 29th. 3 injured._ [Illustration: _Fig. 15._] One of ten, 16 years old, Plain Cylinder with plates arranged lengthways, 34ft. long, 5ft. 6in. diameter, 7/16 inch plates, 50 lbs. pressure. The boiler gave way at one of the long straight seams near the bottom, and rent into five pieces, which were scattered to wide distances, but are so drawn in sketch as to show whereabouts in the boiler they came from. The boiler had been weakened by frequent repair until unable to bear the ordinary pressure. See No. 59. _No. 21. South Wales. (Fig. 16.) May 31st. 5 killed, 4 injured._ [Illustration: _Fig. 16._] One of three, very old, plain Cylinder, with flat ends, 34ft. long, 6ft. diameter, 3/8 inch plates, 40 lbs. pressure. There had formerly been a tube through the boiler, and when this was taken away new flat ends had been put in without sufficient stays to compensate for the loss of the tube. The front end was blown out, and the reaction sent the boiler upwards and broke it into three pieces. See No. 47. _No. 22. Bingley. (Fig. 17.) June 9th. 15 killed, 33 injured._ [Illustration: _Fig. 17._] Two tube Cornish, 16ft. long, 6ft. 9in. diameter, 7/16 inch plates, 50 lbs. pressure. Tubes 2ft. 6in. diameter. The bottom was so much corroded that it rent open, and the boiler was torn to pieces which were scattered to wide distances. The boiler had been much neglected and badly used, and the safety valve was insufficient, of bad construction, and overloaded, and the alarm whistle was gagged. _No. 23. Cornwall. June 14th. 1 injured._ Cornish, but no particulars have been obtained. _No. 24. Durham. (Fig. 18.) June 16th. 3 killed, 1 injured._ [Illustration: _Fig. 18._] One of three. Plain Cylinder, with plates arranged lengthways, 30ft. long, 6ft. 6in. diameter, 3/8 inch plates, 28 lbs. pressure, 25 years old. A seam gave way over the fire where there had been frequent repair, and the boiler was rent into two pieces, which were thrown to some distance. See No. 59. _No. 25. Airdrie. June 23rd. 2 killed, 3 injured._ Two tube Cornish, 35ft. long, 6ft. diameter. Tube 3ft. 2in. diameter over fire, and 2ft. diameter beyond, 50 lbs. pressure. The tube collapsed over the fire, having been very much weakened by frequent repair. _No. 26. Nuneaton. (Fig. 19.) July 5th. 3 injured._ [Illustration: _Fig. 19._] Plain Cylinder, 25ft. long, 4ft. 6in. diameter, 7/16 inch plates, 25 lbs. pressure. The plates along the line of rupture were corroded to 1/16 inch, and in some places much less, so that the boiler was quite unfit for the ordinary working pressure. _No. 27. Birmingham. (Fig. 20.) July 6th. 1 injured._ [Illustration: _Fig. 20._] Small Plain Cylinder, 5ft. long, 2ft. 2in. diameter, 1/4 inch plates, 25 lbs. pressure. Both sides of the boiler were corroded nearly through so that the strength was entirely gone, and it rent in two at the ordinary pressure. _No. 28. Wishaw. July 9th. 2 killed, 2 injured._ One of six. Breeches Tube. The tube or combustion chamber collapsed, having become overheated through shortness of water. _No. 29. Kidderminster. (Fig. 21.) July 16th. 1 killed, 4 injured._ [Illustration: _Fig. 21._] Plain Cylinder, 21ft. long, 4ft. 6in. diameter, 3/8 inch plates, 50 lbs. pressure. The boiler was very old and very much corroded. It had slightly rent open at some former time, and a most wretchedly made patch, shown in enlarged sketch, had been put on to stop leaking, made of thin sheets of iron inside and out and pasteboard between, held together by 36 slight bolts. Of course this patch did not restore the strength of the boiler, and it soon leaked badly, and the leaking hastened the corrosion of the plate below, until it was nearly eaten away, and quite unfit to bear the working pressure. _No. 30. Leeds. July 19th. 4 injured._ One of three, 12 years old. Two tube Cornish, 32ft. long, 7ft. 6in. diameter. Tube 2ft. 10in. diameter, 3/8 inch plates, 45 lbs. pressure. The right hand tube collapsed from end to end sideways, and ruptured in the furnace, and part of the tube was blown out. The cause of the explosion was simply the weakness of the tube without strengthening rings. _No. 31. South Wales. (Fig. 22.) July 19th. 1 killed._ [Illustration: _Fig. 22._] One of two. Plain Cylinder, 32ft. long, 5ft. diameter, 3/8 inch plates, 40 lbs. pressure. It gave way where deeply corroded on the inside. _No. 32. Burslem. (Fig. 23.) July 22nd. 1 killed, 3 injured._ [Illustration: _Fig. 23._] One of six. Plain Cylinder, 36ft. long, 6ft. diameter, 3/8 inch plates, 50 lbs. pressure. Although the boiler was not an old one, it had been much repaired at the seams with strap plates. It was said that the water was very bad, and deposited much mud, which allowed the seams to get overheated and injured. The seam which rent was an original one, and no doubt was ripped as the others had been before repair, and that this rip extended from hole to hole until a rupture at the ordinary pressure was the result. _No. 33. Preston. August 4th. 1 killed._ Locomotive. In shunting the engine was dragged under a bridge that was not intended for locomotives to pass, and the dome was knocked off. _No. 34. London. (Fig. 24.) August 11th. 3 killed._ [Illustration: _Fig. 24._] Marine, 8ft. long, 5ft. 6in. diameter, 3/8 inch plates, 80 lbs. pressure. The flat front end gave way at the angle iron all round, allowing the front with tubes attached, and the shell to be thrown in opposite directions. The front being flat was very weak, and depended for its strength on gusset stays and small bolts connecting the back of the combustion chamber and the round end of the shell. These stays were very defective and insufficient, and the angle iron was bad and not welded into one ring, and the boiler was therefore unfit to bear the ordinary pressure, and gave way at the weakest place. _No. 35. Cornwall. (Fig. 25.) August 16th. none injured._ [Illustration: _Fig. 25._] One tube Cornish, 32ft. long, 6ft. 6in. diameter. Tube 4ft. diameter, 7/16 inch plates, 40 to 50 lbs. pressure. There was no steam gauge. The tube collapsed from end to end, both ends being torn, but the boiler was not moved from its seat. The fusible plug was uninjured. The cause of the explosion was the weakness of the large tube. See No. 57. _No. 36. Leicester. (Fig. 26.) September 1st. 1 injured._ [Illustration: _Fig. 26._] Upright, 5ft. 6in. high, 4ft. diameter, 7/16 inch plates, 40 lbs. pressure. The top of the boiler was blown out. The rent commenced in the manhole, which was unguarded by a ring, and cracks two inches long had existed before explosion. See Nos. 12 and 18. _No. 37. Preston. (Fig. 27.) September 3rd. 1 killed, 1 injured._ [Illustration: _Fig. 27._] One of two. Two tube Cornish, 30ft. long, 7ft. 2in. diameter. Tube 2ft. 8in. in furnaces, and 2ft. 4in. beyond, 3/8 inch plates, 50 lbs. pressure. The left furnace crown collapsed and ruptured, and the right furnace crown was slightly altered in shape. The two boilers were connected by one feed pipe without back valves, so that the water from this boiler was forced into the other and allowed the tubes to be overheated. _No. 38. Liverpool. (Fig. 28.) September 8th. 1 killed, 1 injured._ [Illustration: _Fig. 28._] One tube Cornish, 22ft. 6in. long, 6ft. diameter, 3ft. tube, 7/16 inch plates, 55 lbs. pressure. The tube collapsed over the fire. It was so much thinned by corrosion, and so many of the rivet heads were eaten off, that there was not strength left to bear the ordinary pressure. _No. 39. Boxmoor. (Fig. 29.) September 10th. 1 killed, 4 injured._ [Illustration: _Fig. 29._] One of three. One tube Cornish, 27ft. 3in. long, 5ft. diameter. Tube 2ft. 10in. over furnace, and 2ft. 8in. beyond, 3/8 inch plates, 40 lbs. pressure. One ring of plates was blown out of the back end of shell. There was such extensive external corrosion on the seating at the bottom that the boiler was unable to bear the working pressure. _No. 40. Hull. (Fig. 30.) September 16th. 1 killed, 1 injured._ [Illustration: _Fig. 30._] Breeches Tube, 13 years old, 30ft. long, 7ft. diameter. Furnace tube 2ft. 10in. diameter. Main tube 3ft. 5-1/2in. diameter, and originally made to work at 20 lbs. pressure, but working lately at 45 lbs. The main tube collapsed. The boiler was not adapted for the pressure at which it was worked, and the tube was much weakened by the overheating caused by a thick incrustation of scale, and was not strengthened by any rings or stays, and was of very weak construction as the plates were arranged lengthways. _No. 41. South Wales. (Fig. 31.) September 26th. 1 killed, 1 injured._ [Illustration: _Fig. 31._] One of two, 20 years old. Plain Cylinder, 36ft. long, 6ft. 6in. diameter, 9/16 inch plates, 35 lbs. pressure. The plates and rivet heads were very much reduced in thickness by internal corrosion, and in many places were only 1/8 inch or less. _No. 42. Warrington. October 6th. 2 killed, 6 injured._ One of seventeen. Two tube Cornish, 22ft. long, 7ft. 6in. diameter. Tube 2ft. 6in. diameter, 7/16 inch plates, 45 lbs. pressure. The left hand tube collapsed. The blow-off cock was left open until the water was so low as to allow the tube to be overheated. _No. 43. Rowley. (Fig. 32.) October 13th. none injured._ [Illustration: _Fig. 32._] Plain Cylinder, with flat ends, 15ft. long, 3ft. 10in. diameter, 3/8 inch plates, 25 lbs. pressure. The back end ripped all round the angle iron, and was blown out, and the rest of the boiler was thrown forward a considerable distance. There had once been an internal tube, and when this was taken out the flat end had no stay, and was unfit to bear the usual pressure. See No. 47. _No. 44. Newcastle. (Fig. 33.) October 14th. 2 killed, 5 injured._ [Illustration: _Fig. 33._] Plain Cylinder, with plates arranged lengthways, 29ft. long, 6ft. diameter, 3/8 inch plates, 25 lbs. pressure. Although only 3 years old the boiler had always given trouble, and had been very frequently repaired. Some new plates had just been put in the bottom, and as the primary rent was in the old plates adjoining them, it is most likely they had caused seam rips in the old metal. The frequent repair had reduced the strength until unequal to bear the ordinary pressure. See No. 59. _No. 45. Greatbridge. (Fig. 34.) October 18th. 2 killed, 2 injured._ [Illustration: _Fig. 34._] One of eight, 15 years old. Plain Cylinder, 40ft. long, 6ft. diameter, 1/2 inch plates. The boiler had originally carried 60 lbs., but lately only 40 lbs. The boiler had been worked very hard, and had been so often repaired, that many of the seams were continuous for a long distance without break of joint, so that its strength was reduced until unable to bear the ordinary pressure. The treacherousness and uncertainty of boilers with one patch over another has often been pointed out, as in Nos. 3, 4, 10, and 32. _No. 46. Acorington. (Fig. 35.) October 19th. 2 killed, 3 injured._ [Illustration: _Fig. 35._] One tube Cornish, 14ft. 6in. long, 5ft. diameter. Tube 2ft. 10in. diameter, 7/16 inch plates, 40 lbs. pressure usually, and sometimes 60 lbs. One ring of plates was blown out of shell. The boiler was so very badly corroded at the bottom, that the edges of the rent were quite sharp like a knife, and the boiler was therefore unable to bear the usual working pressure. The flues were too narrow to enter for proper inspection, and the bearing surfaces were too wide and retained moisture against the plates. _No. 47. Lydney. (Fig. 36.) October 28th. 1 killed._ [Illustration: _Fig. 36._] One of four. Plain Cylinder with round front and flat back end, 36ft. long, 6ft. diameter, 7/16 inch plates, 20 lbs. pressure. The flat end was blown out, the rent extending all round the angle iron. There had originally been a breeches tube in the boiler with a strong stay to the front end, but when this was taken out no stays were put to the flat end to compensate for the loss of their support. The angle iron attaching the flat end was made in four pieces instead of being welded, and it was reduced to 3/16 inch thick by external corrosion, so that it was not strong enough to bear the ordinary working pressure. The extreme imprudence of altering boilers without due care to preserve their strength has been often pointed out. See Nos. 21 and 43. _No. 48. Newcastle. (Fig. 37.) October 29th. none injured._ [Illustration: _Fig. 37._] One of six. Plain Cylinder, with plates arranged lengthways, 40ft. long, 5ft. 3in. diameter, 40 lbs. pressure. The boiler gave way at the fire end, and divided in two, and both pieces were blown to a great distance. The boiler was old and had been much repaired, and the seams running from end to end made it very weak, but the immediate cause of the rupture was supposed to be shortness of water and consequent overheating of the plates. See No. 59. _No. 49. Stockport. October 30th. 1 killed._ [Illustration: _Fig. 38._] One of eight. Two tube Cornish, 30ft. long, 7ft. 4in. diameter. Tube 2ft. 11in. diameter, 3/8 inch plates, 50 lbs. pressure. The crown of the right hand tube became overheated from shortness of water, and bulged down and rent half round at the second seam of rivets. _No. 50. Durham. (Fig. 38.) November 2nd. 1 injured._ [Illustration: _Fig. 39._] One of four. Plain Cylinder, with the plates arranged lengthways, 38ft. long, 6ft. 6in. diameter, 3/8 inch plates, 35 lbs. pressure. A seam over the fire slightly to the right side gave way where there had been frequent repair to stop leaking. At the part which gave way there had formerly been a side fire, which had perhaps damaged the seams. This boiler was known to have been in bad condition and needing repairs. See No. 59. _No. 51. Sheerness. (Fig. 39.) November 3rd. 11 killed, 7 injured._ [Illustration: _Fig. 40._] One of three. Marine, 15ft. 6in. long, 6ft. diameter. Furnace Tube 2ft. 4in. diameter, 5/8 inch plates, 80 lbs. pressure. The left hand tube collapsed and ruptured, and the contents issued at the front and scalded all near. The right hand tube was also slightly out of shape on the top. The cause of the collapse was, that the water had been allowed to get below the crowns of the furnaces. There was no means of ascertaining how the shortness of water occurred, as all were killed who had the opportunity of knowing. _No. 52. Cornwall. (Fig. 40.) November 25th. 1 injured._ [Illustration: _Fig. 41._] One of five, 30 years old. One tube Cornish, 36ft. long, 7ft. diameter. Tube 3ft. 10in. diameter, 7/16 inch plates, 40 lbs. pressure. The shell was rent into several large pieces and thrown to some distance. The tube was also thrown out and broken, chiefly by its fall and striking against walls. The boiler was corroded very badly on the seating, which must have been known, as there were numerous small screw patches to prevent leaking at the corroded places. The shell was in such bad condition, that it was quite unfit to bear the ordinary working pressure. See No. 58. _No. 53. Bilston. (Fig. 42.) December 3rd. 8 killed, 1 injured._ [Illustration: _Fig. 42._] One of three. Four Furnace Upright, 20ft. high, 10ft. diameter. Centre tube 10ft. high, 4ft. 6in. diameter, side tubes 2ft. diameter, 3/8 inch plates, 35 lbs. pressure. The central tube collapsed, and the bottom part was blown out, and allowed the contents of the boiler to issue from the bottom into the culvert leading to the stack, and into the necks of the furnaces from which it was heated. The reaction sent the boiler up to a great height, and it divided into eleven fragments, which were very widely scattered. Comparatively little damage was done to the furnaces and premises, only the brickwork surrounding the boiler being thrown down. Although it had only worked a short time at this place, it was very old, and the central tube was corroded until only 1/8 inch thick in many places, and many of the rivet heads were quite eaten away. It was altogether so worn out that it was quite unfit to work at any pressure. _No. 54. Cornwall. (Fig. 43.) December 6th. none injured._ [Illustration: _Fig. 43._] One tube Cornish, 32ft. long, 6ft. diameter. Tube 4ft. diameter, 7/16 inch plates, 40 to 50 lbs. pressure. The tube collapsed from end to end, and the front portion was blown out with the front end, and the back end was left attached to the shell, and but little moved from its seat. The cause was doubtless the weakness of such a large tube. This is the third explosion at this engine. One of the previous explosions is described at No. 35. _No. 55. Stonehaven. December 9th. 2 injured._ Locomotive, but no particulars have been obtained. _No. 56. Cornwall. (Fig. 44.) December 10th. none injured._ [Illustration: _Fig. 44._] One tube Cornish, 26ft. long, 6ft. 6in. diameter, tube 3ft. 10in. diameter, 3/8 inch plates, 40 lbs. pressure. The tube collapsed and ruptured in the central part from weakness. _No. 57. Cornwall. (Fig. 45.) December 11th. none injured._ [Illustration: _Fig. 45._] One tube Cornish, 32ft. long, 6ft. 6in. diameter. Tube 4ft. diameter, 3/8 inch plates, 60 lbs. pressure. It was an old boiler, and some of the plates of the tube were thinned by corrosion, but it had only just been put to work at this place, and burst the first day of working. The tube collapsed beyond the bridge, and the back part with the back end plate was blown out to a great distance. The front end was also ruptured, and the whole boiler was sent forwards. The tube over the fire had not collapsed. The cause of explosion was the weakness of such a large tube without strengthening rings. Many similar boilers have exploded in the same way from the same cause, as described in Nos. 28, 30, 35, 40, 54, and 56. _No. 58. Cornwall. (Fig. 46.) December 14th. 2 killed._ [Illustration: _Fig. 46._] One tube Cornish, 26ft. 8in. long, 6ft. diameter. Tube 3ft. 10in. at front end, and 3ft. beyond, 7/16 inch plates, 40 lbs. pressure. The shell was rent into several pieces, which were scattered to wide distances. The tube was also thrown to a great distance, but was uninjured. The boiler was 36 years old. The shell was very badly corroded, and temporarily repaired with screw patches to stop leaking, so that the boiler was unfit to bear the usual pressure. See No. 52. _No. 59. Durham. (Fig. 47.) December 29th. 2 killed, 1 injured._ [Illustration: _Fig. 47._] One of three. Plain Cylinder, with plates arranged lengthways, 47ft. long, 6ft. diameter, 3/8 inch plates, 30 lbs. pressure. It gave way at the seams over the fire, where the edges of the plates had been injured by injudicious and excessive repairing and caulking. The pieces were sent to great distances. The weakness of boilers with seams from end to end in continuous lines has often been pointed out. Eight of the exploded boilers this year, Nos. 5, 15, 20, 24, 44, 48, 50, and 59, and many others in former years were of the same objectionable construction. * * * * * The following, not being steam boilers, are not included in the list, but the details may be useful. * * * * * _Oldbury. March 10th. 4 killed._ [Illustration] Tar still, 10ft. high, 7ft. diameter, with round top and domed bottom, 3/8 inch plates, and not intended to work at any pressure. The vapour passing away became congealed, and stopped up the small exit pipe, and pressure accumulated sufficiently to burst the weak shaped vessel. The bottom came completely out and was left upon the fire, while the top ascended to a great height and fell a long distance away. The loss of life was owing to the material igniting and suffocating those who were thrown down by the explosion. _Greatbridge. December 29th. 2 killed._ [Illustration] Tar still, 12ft. high, 12ft. diameter, 3/8 inch plates, and not used at any pressure usually. The upper part separated from the bottom, rending in the angle iron all round. The angle iron near the outlet pipe was corroded nearly away, as shown in enlarged sketch, and the rivet heads were eaten completely off. It was supposed that the intense frost, during a long stoppage for holidays, had caused the worm to be stopped up and pressure to accumulate, as in the one previously described. But it is perhaps more probable that the vessel gave way because it was corroded so thin in so important a part as the angle iron. The explosion was very slight, the damage and loss of life being from the fierce fire which immediately succeeded it. _Darlington. August 26th. 2 injured._ Domestic. Rectangular, and made of wrought iron. The front blew out. It was said that all the communication pipes were shut, and therefore steam accumulated until the weakest part gave way. _Manchester. December 29th. 1 killed, 1 injured._ [Illustration] The sketch is to a much larger scale than the others. Domestic, 14in. wide, 11in. high, and about 10in. deep, made of cast iron 1/4 inch thick. It had close top and two circulating pipes to warm a bath about 10ft. above it. The supply cistern was about 17ft. above the boiler. The front was blown out into the kitchen. It was said that the pipes were frozen, and that steam pressure had thus accumulated. The boiler was of a treacherous material and weak shape, and unfit to bear safely the 7 lbs. pressure the column of water from the cistern would give. The fire also acted on the sides of the boiler without any intervening brickwork. If a closed top boiler is used, there should be a dead weight safety valve to prevent pressure. A far safer plan is to have the kitchen boiler with open top and the circulating heater within it, so that it can never get overheated, as it only obtains its heat from the water in the open boiler. * * * * * _R. Broomhall, Printer, Stourbridge._ BOILER EXPLOSIONS IN 1870. _No. 1. Newcastle. (Fig. 1.) January 7th. 3 killed, 1 injured._ [Illustration: _Fig. 1._] One of five. Cornish, 13 years old, 30ft. long, 6ft. 6in. diameter. Tube 3ft. 3in. diameter, 3/8 inch plates, 30 lbs. pressure. Tube collapsed sideways from weakness, and the front part and the front plate were blown out, carrying the attendants into a deep and swollen river which ran close in front of boilers. _No. 2. South Wales. (Fig. 2.) January 15th. 1 killed, 4 injured._ [Illustration: _Fig. 2._] Plain cylinder, very old, 32ft. long, 5ft. diameter, 7/16 inch plates, 30 lbs. pressure. Externally corroded to 1/16 inch, and gave way near a seam, the front being thrown forward into a house, and the back end 150 yards to the rear, carrying away the stack. It had been badly repaired with bolted patches which had hastened corrosion, and as it was known to be nearly worn out, it was to have been replaced in a few days. _No. 3. Worksop. (Fig. 3.) January 28th. 2 killed._ [Illustration: _Fig. 3._] Domestic, 2ft. wide, 1ft. 10in. high, and 7in. deep, 3/8 inch plates, with badly welded joints. The circulating pipes to cistern, 15ft. above, were frozen, and steam pressure accumulated and blew out the front. _No. 4. Ipswich. (Fig. 4.) February 4th. 1 killed._ [Illustration: _Fig. 4._] One of three. Cornish, 7 years old, 24ft. long, 5ft. diameter. Tube 3ft. diameter, 7/16 inch plates, 65 lbs. pressure. The boiler was good and well fitted, but an accumulation of salt on tube caused overheating and rupture of 3rd seam. _No. 5. Sheffield. (Fig. 5.) February 8th. 2 killed, 6 injured._ [Illustration: _Fig. 5._] One of three. Rag Boiler, 2 years old, 11ft. diameter, 9-1/2ft. deep, 7/16 inch plates. Steam was supplied from the engine exhaust, and was usually about 10 lbs. pressure, but as the boilers from which the steam was originally supplied worked at 60 lbs., it is possible this was sometimes exceeded. The vessel was of very weak shape for even 10 lbs. pressure. _No. 6. Derby. (Fig. 6.) February 14th. 1 killed, 2 injured._ [Illustration: _Fig. 6._] Domestic, 1ft. high, 1ft. wide, 8in. across top, and 12in. across bottom, made of cast-iron, 7/16 inch thick. The fire had been let out sometime, and the circulating pipes to cistern 16ft. above were frozen, and on lighting fire steam was formed for which there was no escape, and the boiler was shattered. _No. 7. Sheffield. (Fig. 7.) February 14th. 2 killed, 1 injured._ [Illustration: _Fig. 7._] Domestic, used for warming rooms above, 2ft. 6in. wide, 2ft. high, 9in. across top, and 13in. across bottom, 3/8 inch plates. The circulating pipes to cistern, 12ft. above, were frozen, and steam was formed for which there was no vent, and boiler was rent open. The joints were so badly welded that they soon gave way, and little damage was done to property. _No. 8. Walsall. (Fig. 8.) February 19th. none injured._ [Illustration: _Fig. 8._] One of two. Plain cylinder, 12 years old, 30ft. long, 7ft. diameter, 1/2 inch plates, 50 lbs. pressure. The seams and plates were overheated by shortness of water, and gave way at ordinary pressure. It is supposed the water "kicked" into the other boiler, as there was no back valve to prevent this whenever one boiler happened to be fired a little harder, and consequently at slightly higher pressure than the other. There was no damage except to the boiler. _No. 9. Birmingham. (Fig. 9.) February 25th. none injured._ [Illustration: _Fig. 9._] Cornish, 5 years old, 32ft. long, 7ft. diameter. Tube 2ft. 4in. diameter, 7/16 inch plates, 30 lbs. pressure. Cracked along the bottom of front end where internally "furrowed." The boiler was not disturbed, but as the water escaped into an iron furnace the bricks were scattered, but little damage done. The boiler was intended for two tubes, and therefore there was a large part supported only by stays, allowing of a slight movement with varying pressure which facilitates the corrosion in certain lines of strain called "furrowing." In this case they were so close to the angle iron and filled with scale that they were difficult to detect. _No. 10. Cornwall. (Fig. 10.) March 17th. 5 injured._ [Illustration: _Fig. 10._] Upright Boiler, 2 ft. high, 1ft. 9in. diameter, 1/4 inch plates. It gave way where deeply corroded externally round the bottom angle iron. The top was blown through the roof and did considerable damage, the bottom being left in the grate. _No. 11. Sheffield. (Fig. 11.) March 27th. 1 injured._ [Illustration: _Fig. 11._] Agricultural or Contractor's Engine, 9ft. 2in. long, 2ft. 6in. diameter, 3/8 inch plates, 30 lbs. pressure. The heads of stays on each side were corroded outside and drew through the holes, allowing the angles of fire box to open. Boiler was not disturbed and no damage was done. _No. 12. Portsmouth. (Fig. 12.) March 29th. 3 killed, 1 injured._ [Illustration: _Fig. 12._] One of two. Cornish, 9 years old, 22ft. long, 6ft. diameter. Tube 3ft. diameter, 3/8 inch plates, 40 lbs. pressure. Gave way at mid-feather wall where corroded to 1/32 inch, at a place where flues were too narrow to enter. Two rings of plates were torn out and blown into an adjoining street, while the reaction of the escaping contents forced the boiler into a building in a very singular manner, doing very great damage. This case is of peculiar interest, because although the cause of explosion was so plain to see, all the old theories of decomposition of steam, and ignition of hydrogen, were revived, and it was even stated that "a bad boiler could not explode, as the corroded part would give way, and allow the steam to escape harmlessly," and any cause seemed to be considered more probable than the plain and simple one, that it was corroded to the thickness of card board. Like many other examples this explosion shows that however well a boiler is tended, it should be examined in the flues to make sure that it is safe. _No. 13. Manchester. March 30th. 2 killed, 3 injured._ Underground. Some alterations were being done to some brick arching, which fell upon and broke steam pipes, and the escape of steam suffocated those near. _No. 14. Warrington. (Fig. 13.) April 13th. 6 killed, 3 injured._ [Illustration: _Fig. 13._] Lancashire, used for evaporation only, 24ft. 6in. long, 8ft. diameter, 3/8 inch plates, and usually worked with little or no pressure. The boiler was very old and much patched, and incapable of bearing the 15 lbs. pressure which was temporarily put upon it. _No. 15. Scotland. April 18th. none injured._ Plain cylinder, said to have exploded from shortness of water, but no particulars have been obtained. _No. 16. Cornwall. (Fig. 14.) April 18th. 1 killed, 1 injured._ [Illustration: _Fig. 14._] One of two. Cornish, very old, 34ft. long, 6ft. diameter. Tube 3ft. 10in. diameter, 3/8 inch plates, 50 lbs. pressure. The tube collapsed and the front part was blown out, and the boiler was forced back a little. It was said to have been short of water, but the weakness of a tube of such large diameter was most likely the true cause. _No. 17. Wellington. (Fig. 15.) April 22nd. none injured._ [Illustration: _Fig. 15._] One of two. Balloon, very old, 11ft. high, 9ft. 6in. diameter, 3/8 inch plates, 5 lbs. pressure. The bottom was corroded externally to 1/8 inch, and temporarily repaired with screw patches, and was so reduced in strength that it gave way at the ordinary pressure. The top was blown about 20 yards away, but little damage was done. _No. 18. Cornwall. May. none injured._ Cornish, 30ft. long, 6ft. diameter. Tube 3ft. 6in. diameter, 40 lbs. pressure. Boiler gave way under bottom where corroded very thin, but little damage was done. _No. 19. Darlaston. (Fig. 16.) May. none injured._ [Illustration: _Fig. 16._] Cornish, 15ft. long, 4ft. 3in. diameter. Tube 1ft. 6in. diameter, 7/16 inch plates, 40 lbs. pressure. Tube collapsed and ruptured, having been softened by overheating through shortness of water. Very little damage was done. _No. 20. Westbromwich. (Fig. 17.) May 12th. 2 killed._ [Illustration: _Fig. 17._] One of three. Plain cylinder, 5 years old, 34ft. long, 6ft. diameter, 7/16 inch plates, 45 lbs. pressure. Gave way by the rent of a ripped seam over the fire, which had been repeatedly temporarily patched without restoring the strength or stopping the rip. Three rings were torn out of the middle, while the front end was blown into the bed room of a house, and the back part of the boiler was thrown across a canal through two walls into a distant street. Great damage was done. _No. 21. Dublin. (Fig. 18.) May 18th. 3 killed, 6 injured._ [Illustration: _Fig. 18._] Cornish. Second-hand, but just started at this place, 26ft. long, 6ft. diameter. Tube 3ft. diameter, 3/8 inch plates, 40 lbs. usual pressure. Tube collapsed from end to end. The pressure at time was supposed to be 70 lbs., and as there was no evidence of shortness of water, it is presumed the tube gave way from weakness. The boiler was moved forward about 20 feet, but much damage was done to premises. _No. 22. Bury. (Fig. 19.) May 25th. none injured._ [Illustration: _Fig. 19._] Domestic Saddle, 5ft. long, 3ft. high, 2ft. 6in. wide, 3/8 inch plates, 15 lbs. pressure, the cistern being 30ft. above. There were no stays between the inner and outer shell, and the space between them was too small to allow proper circulation of water to keep the plates from overheating, so that it was hardly fit for its ordinary pressure, and the top was blown off. _No. 23. Kidsgrove. (Fig. 20.) May 26th. 13 killed, 9 injured._ [Illustration: _Fig. 20._] One of three. Four Furnace Upright, 12 years old, 17ft. 6in. high, 9ft. diameter. Centre tube 5ft. 9in. diameter, 3/8 inch plates, 40 lbs. pressure. The centre tube was much corroded on the inside and collapsed inwards from consequent weakness, allowing the contents to issue at the bottom of the boiler, and the reaction sent the whole boiler high up into the air, and on to a roof causing great damage. _No. 24. Lowestoft. (Fig. 21.) May 27th. 2 killed._ [Illustration: _Fig. 21._] Crane or Donkey boiler on board a vessel. About 6ft. high, and 3ft. diameter, 25 lbs. pressure. The internal fire box collapsed from the softening of the plates through shortness of water, the blow off pipe having been left open too long. Little or no injury was done to the ship. _No. 25. Birmingham. (Fig. 22.) June 2nd. 2 killed, 1 injured._ [Illustration: _Fig. 22._] Cornish, 6 years old, 21ft. long, 6ft. diameter. Tube 3ft. diameter, 3/8 inch plates, 40 lbs. pressure. The tube was so much weakened by cracks and by being out of true circle, that it collapsed from end to end at the ordinary working pressure. _No. 26. Wigan. (Fig. 23.) June 6th. none injured._ [Illustration: _Fig. 23._] One of two. Cornish, 28ft. 7in. long, 5ft. 4in. diameter. Tube 3ft. diameter, slightly oval, 3/8 inch plates, 50 lbs. pressure. Tube collapsed over the fire and ruptured from weakness. The boiler was not moved and the damage was not great. _No. 27. Bury. June 9th. 1 injured._ Lancashire. The plates were reduced to 1/16 inch by external corrosion, so that the boiler was not able to bear the ordinary pressure, but no details have been obtained. _No. 28. Workington. (Fig. 24.) June 9th. 7 injured._ [Illustration: _Fig. 24._] One of two. Cornish, nearly new, 16ft. long, 5ft. diameter, 3/8 inch plates, 45 lbs. pressure. Three plates over fire collapsed from overheating through shortness of water. _No. 29. Nottingham. (Fig. 25.) June 13th. 3 injured._ [Illustration: _Fig. 25._] Ten years old. Plain cylinder, with flat ends, 10ft. long, 2ft. diameter, diagonal seams, 1/4 inch plates, 25 lbs. pressure. The whole shell was blown 80 yards to the front, and the chimney and engine house much damaged. It was much corroded and badly patched, so as to be unfit to carry pressure. _No. 30. Blackburn. (Fig. 26.) June 17th. 2 killed, 1 injured._ [Illustration: _Fig. 26._] Sixteen years old. Galloway, 26ft. long, 7ft. diameter, 3/8 inch plates, 56 lbs. pressure. There was a combustion chamber between the furnace tubes and the main tube, and this had been lately repaired insecurely, and gave way and burst upwards. The boiler was not moved, but the contents issued so violently that a good deal of damage was done to surrounding premises. _No. 31. Glasgow. (Fig. 27.) June 17th. none injured._ [Illustration: _Fig. 27._] Crane Boiler, about 2 years old, 7ft. high, 4ft. diameter, 3/8 inch plates, 50 lbs. pressure. The internal fire box collapsed and the external shell was blown to pieces. There was no sign of shortness of water, but it is supposed that the fire box was not circular, and therefore too weak to bear the ordinary pressure. _No. 32. Bilston. (Fig. 28.) June 21st. 2 killed, 6 injured._ [Illustration: _Fig. 28._] One of seven. Plain cylinder, 30 years old, 30ft. long, 8ft. 3in. diameter, 1/2 inch plates, 35 lbs. pressure. It gave way over fire place, where it had been weakened by frequent repair, which had caused a seam rip near a patch. The fragments were widely scattered, and much damage was done to the premises. The insecurity of boilers so frequently repaired with patch upon patch has been often pointed out. _No. 33. Darlington. (Fig. 29.) June 24th. 2 injured._ [Illustration: _Fig. 29._] One of twelve. Two Furnace Upright, about 2 years old, 20ft. high, 8ft. diameter, 7/16 inch plates, 30 lbs. pressure. The water was allowed to run so low that the plates softened by the overheating, and a small piece was blown open and threw down the brickwork. _No. 34. Dudley. (Fig. 30.) June 25th. 2 injured._ [Illustration: _Fig. 30._] One of two. Balloon, 34 years old, 12ft. diameter, 10ft. high, 3/8 inch plates, 7 lbs. pressure. There were no stays, and the boiler was of very weak shape, and as the boiler it worked with was loaded to 15 lbs., it is presumed this also was exposed to that pressure, and burst in consequence. It gave way at the angle at front over the fire, and was thrown over the engine house. _No. 35. Manchester. (Fig. 31.) June 27th. 2 killed, 1 injured._ [Illustration: _Fig. 31._] One of four. Galloway, 4 years old, 32ft. long, 8ft. diameter, 7/16 inch plates. Tube 2ft. 10in. diameter, originally intended for 40 lbs., but worked at 65 lbs. pressure. The left hand tube collapsed sideways, having been very much weakened by internal corrosion. _No. 36. July 2nd. 1 injured._ Marine. One of the oval tubes collapsed. The boiler was worked at a higher pressure than it was capable of bearing safely, but no particulars have been obtained. _No. 37. Scotland. July 3rd. 2 killed, 3 injured._ Plain Cylinder, 3 years old, 20ft. long, 4ft. diameter, 25lbs. pressure. It was so corroded inside about the water line from bad water, that it gave way at the ordinary pressure. The boiler was thrown 160 yards from its seat. _No. 38. July 29th. none injured._ Cornish, 26ft. long, 5ft. 9in. diameter, tube 3ft. 6in. diameter, 7/16 inch plates, 35 lbs. pressure. The boiler rent open where externally corroded to 1/32 inch, and 3 widths of plates were torn away. _No. 39. Nottingham. August 12th. none injured._ Tubulous Boiler, quite new, made entirely of tubes. One tube gave way at defective weld, but no other damage was done. _No. 40. Leicester. (Fig. 32.) August 13th. 4 killed, 5 injured._ [Illustration: _Fig. 32._] Upright Boiler, nearly new, 10ft. high, 5ft. diameter, with internal fire box, 1/2 inch plates, 45 lbs. pressure. The shell was rent into many pieces, which were widely scattered, doing much damage. The safety valve was defective and incapable of relieving the pressure, and the spring indicated wrongly, so that a much higher pressure was used than the boiler could bear safely. _No. 41. Newcastle-on-Tyne. (Fig. 33.) Sep. 14th. 5 killed, 20 injured._ One of two. Plain Cylinder, with plates arranged lengthways, 17 years old, 27ft. long, 6ft. diameter, 3/8 inch plates, 30lbs. pressure, mechanically fired. It had just been extensively repaired over the fire, but it gave way at the back end, where a plate had been put in some time before, and it is supposed that a seam rip or injury to the old plate, not visible outside or in, was then set up, which was perhaps increased by the strain of late repairs and gave way as soon as steam was again raised to working pressure. See No. 55 this year and many others in past years of similar construction. [Illustration: _Fig. 33._] _No. 42. Nottingham. (Fig. 34.) September 15th. 1 killed._ [Illustration: _Fig. 34._] Tubulous, or all tubes, 1-1/2 years old, 100 lbs. pressure. Steam was being raised with too little water in the boiler, so that the tube became overheated and incapable of bearing pressure, and rent open, and as the boiler was in a small space the steam suffocated the attendant, but the boiler was not disturbed or the premises injured. _No. 43. Tunstall. (Fig. 35.) September 17th. 3 killed, 1 injured._ One of four. Plain Cylinder, 8 years old, 36ft. long, 5ft. diameter, 3/8 inch plates, 50 lbs. pressure. It gave way at fifth seam, where a seam rip, caused by bad repair, had so far weakened it that it was unable to bear the usual pressure, and the ends were blown in opposite directions. [Illustration: _Fig. 35._] _No. 44. Exeter. (Fig. 36.) September 27th. 1 killed._ [Illustration: _Fig. 36._] Lancashire, 2 years old, 31ft. long, 7ft. diameter, tube 2ft. 10in. diameter, with 56 Field tubes in each, 3/8 inch plates, 45 lbs. pressure. The right hand tube collapsed and ruptured from softening of plates through shortness of water. The fire was blown out and set the premises on fire and much damage was done. _No. 45. Cardiff. October 1st. 1 killed, 2 injured._ Locomotive, 4-1/2 years old, 14ft. long, 4ft. diameter, 7/16 inch plates, 120 lbs. pressure. The fire box was reduced to 1/32 inch by corrosion, and unable to bear the usual pressure and rent open, and the escaping contents rushed out at the fire doors and injured those near. _No. 46. Liverpool. (Fig. 37.) October 4th. 4 killed, 4 injured._ [Illustration: _Fig. 37._] Plain Cylinder, 6ft. 6in. long, 3ft. 6in. diameter, 3/8 inch plates, 80 lbs. pressure. The plates were corroded both inside and out, and in some places reduced to less than 1/16 inch in thickness, and it was quite unfit to bear the ordinary pressure. The damage to the surrounding property was very great although the boiler was so small. The shell of the boiler was thrown across a street into an upper room of the house opposite. _No. 47. Bathgate. October 14th. 2 injured._ Rag Boiler. The boiler became exposed to higher pressure than it was intended to bear. The boiler house was destroyed, but no particulars have been obtained. _No. 48. Walsall. (Fig. 38.) October 19th. 1 killed, 2 injured._ [Illustration: _Fig. 38._] Cornish, 7 years old, 13ft. 3in. long, 5ft. 6in. diameter, tube 3ft. 6in. diameter, 3/8 inch plates, and supposed to work at 30 lbs. pressure. The gauge was so out of order that it only indicated half the real pressure. The tube was not in good condition and had leaked very much and was quite unfit for the pressure of 60 lbs. to which the valve was loaded. The tube collapsed beyond the bridge, and the contents issued at the back and drove the boiler forward 30 feet and into a workshop. _No. 49. Soho. (Fig. 39.) October 19th. 1 killed, 1 injured._ [Illustration: _Fig. 39._] One of four. Lancashire, 23ft. long, 7ft. diameter, tube 2ft. 6in. diameter, 30 lbs. pressure, usually, but 15 lbs. at time of explosion. The left side of left tube collapsed and rent owing to shortness of water. _No. 50. North Wales. (Fig. 40.) October 19th. 1 killed, 8 injured._ [Illustration: _Fig. 40._] One of two. Cornish, 26ft. long, 5ft. 6in. diameter, tube 3ft. diameter, 7/16 inch plates, 23 lbs. pressure. The bottom was so thinned by external corrosion that it was not able to bear the usual pressure and rent open. The boiler was turned upside down, and the house much injured. _No. 51. Berwick. (Fig. 41.) October 21st. 1 killed._ [Illustration: _Fig. 41._] Cornish, 12ft. long, 4ft. 3in. diameter, tube 2ft. 4-1/2in. diameter, 3/8 inch plates, 32 lbs. pressure. The tube collapsed, having become overheated through shortness of water. _No. 52. Sheffield. (Fig. 42.) October 26th. 1 killed, 1 injured._ [Illustration: _Fig. 42._] Locomotive, 11 years old, 9ft. 6in. long, 4ft. diameter, 1/2 inch plates, 80 lbs. pressure. The top plate over fire box was blown off, having given way along a "furrow" caused by corrosion in a line of strain owing to position of stays. It was in a part of the boiler where it is not usual to find it, and as it could not be seen, it increased until unable to bear the usual pressure. _No. 53. Darlaston. (Fig. 43.) October 27th. 3 injured._ [Illustration: _Fig. 43._] Plain Cylinder, 22ft. long, 4ft. diameter, 7/16 inch plates, 25 lbs. pressure. The water was allowed to get so low that the sides were softened by overheating, and rent open. The boiler was not moved and only a few bricks were disturbed. _No. 54. Cornwall. (Fig. 44.) October 27th. 1 killed._ [Illustration: _Fig. 44._] One of three. Cornish, 12 years old, 36ft. long, 6ft. diameter, tube 3ft. 9in. diameter, 3/8 inch plates, 38 lbs. pressure. The tube collapsed from end to end, the front and central parts being blown out. The shell and back of tube were thrown in one piece to the rear, and much damage was done. It was supposed to have been short of water, because the tube had collapsed, but it is more likely it collapsed because of its weakness without strengthening rings. A tube in this boiler collapsed in a similar way about 5 years previously. _No. 55. Newcastle. (Fig. 45.) November 17th. 1 killed, 2 injured._ One of seven. Plain Cylinder, with plates arranged lengthways, 30 years old, 26ft. long, 6ft. diameter, 3/8 inch plates, 35 lbs. pressure, mechanically fired. Gave way at a seam on the right hand side of the fire place, where the insertion of a new plate had caused injury to the old plate, and it divided into two parts which were sent in different directions. The uncertainty and treacherousness of these straight seamed boilers has often been pointed out. See No. 41, and many examples in former years. [Illustration: _Fig. 45._] _No. 56. South Wales. November 19th. none injured._ Cornish, 7ft. diameter, tube 4ft. diameter, 40 lbs. pressure. Tube collapsed from weakness. _No. 57. Shields. (Fig. 46.) November 24th. 1 killed, 2 injured._ [Illustration: _Fig. 46._] One of two. Marine, second hand when put in 3 years since. Return tube 12ft. 4in. long, slightly oval, 6ft. diameter at front, and 5ft. 6in. at back; tube, oval, 3ft. 10in. wide, and 3ft. deep, 5/16 inch plates, 25 lbs. pressure. The tube collapsed. It was in such a corroded and cracked condition, and so badly repaired, with screw patches, that it was unable to bear the ordinary pressure. _No. 58. Manchester. (Fig 47.) December 2nd. 3 injured._ [Illustration: _Fig. 47._] One of two. Balloon, used for evaporating only, nearly new, 9ft. high, and 9ft. diameter, 1/2 inch plates, not usually worked at any pressure. The top was thrown 60 yards away, and the bottom left on furnace. The boiler was temporarily exposed to pressure which it was too weak a shape to bear. _No. 59. Bilston. (Fig. 48.) December 2nd. 1 killed, 2 injured._ [Illustration: _Fig. 48._] Plain Cylinder, 5 years old, 14ft. 9in. long, 4ft. 9in. diameter, 3/8 inch plates, 30 lbs. pressure. The water was allowed to get so low that the sides became softened by overheating and rent open, and blew the fire upon those near, but without disturbing the boiler or brickwork. _No. 60. Hanley. (Fig. 49.) December 16th. 1 killed, 5 injured._ [Illustration: _Fig. 49._] One of two. Balloon, 30 years old, 15ft. diameter, 3/8 inch plates, worked at 20 lbs. pressure. It rent in two and threw down the engine house and chimney. The boiler was not intended to work at more than 5 lbs. pressure, and was quite unable to bear the extra pressure to which it was exposed. _No. 61. Leeds. (Fig. 50.) December 24th. 1 injured._ [Illustration: _Fig. 50._] Domestic, wrought iron, welded, 13-1/2 inches wide, 12 inches high. The house had been empty, and the pipes to cistern, 26 feet above, had frozen, and when a fire was lighted the accumulated pressure, having no escape, forced out the front. _No. 62. Leamington. (Fig. 51.) December 25th. none injured._ [Illustration: _Fig. 51._] Domestic Saddle, wrought iron welded, 1ft. 9in. long, and the same width and height. The circulating pipes were stopped by ice, and the accumulated pressure forced down the underside and rent open the joint. The building was injured. _No. 63. Morley. (Fig. 52.) December 25th. none injured._ [Illustration: _Fig. 52._] Domestic Saddle, wrought iron welded, 2ft. 6in. long, 1ft. 6in. wide and high. The circulating pipes being stopped by ice the accumulated pressure forced out the plate on the under side. The building was injured. _No. 64. Liverpool. (Fig. 53.) December 25th. 2 injured._ [Illustration: _Fig. 53._] Domestic, 1ft. 8in. wide and high, 1ft. deep, 1/2 inch cast iron. The circulating pipes were stopped with ice, and the accumulated pressure forced out the front, and did great damage to the house. _No. 65. London. (Fig. 54.) December 25th. 1 killed._ [Illustration: _Fig. 54._] Domestic, wrought iron, 1ft. 3in. wide, 1ft. 4in. high, 6in. deep, 3/8 inch thick. The circulating pipes to the cistern about 30ft. above were stopped with ice, and the accumulated pressure rent the boiler in the welded joints, and did great damage to the house. _No. 66. Dukinfield. (Fig. 55.) December 26th. none injured._ [Illustration: _Fig. 55._] Domestic, cast iron, 3/8 inch thick, 1ft. 3in. wide, 1ft. deep. The circulating pipes were frozen, and the pressure accumulated and rent the boiler to fragments and did great damage to the room. _No. 67. Northallerton. (Fig. 56.) December 29th. 1 injured._ [Illustration: _Fig. 56._] Locomotive, 20 years old, 12ft. 9in. long, with plates arranged lengthways, 3ft. 8in. diameter, 3/8 inch plates, 80 lbs. pressure. The barrel appears to have given way on the under side near fire box, and opened out and rent into fragments. As the pieces containing the probable first rent were missing, nothing positive could be ascertained. It may have contributed to the rupture that the engine drew from the fire box instead of from the frame. _No. 68. London. (Fig. 57.) December 29th. none injured._ [Illustration: _Fig. 57._] Domestic, Saddle, wrought iron, welded, 1ft. 6in. long, 1ft. 2in. wide, and 1ft. high, 3/8 inch thick. The circulating pipes to cistern 25ft. above were frozen, and the accumulated pressure forced the crown out of under side of boiler, and caused great damage to premises. _No. 69. London. December 30th. none injured._ Domestic, the circulating pipes were frozen, and the accumulated pressure caused the boiler to rent open, but little damage was done. _No. 70. Burton. Date not ascertained. 1 killed._ Plain Cylinder, underground, internally corroded until too weak to bear ordinary pressure. * * * * * _R. Broomhall, Printer, Stourbridge._ BOILER EXPLOSIONS IN 1871. _No. 1. Tranmere. (Fig. 1.) January 1st. 1 injured._ [Illustration: _Fig. 1._] Domestic. Cast-iron, 1ft. 4in. wide, 1ft. high, and 11in. deep. The circulating pipes being frozen the pressure accumulated, and rent the boiler into pieces, doing great damage. _No. 2. Rochdale. (Fig. 2.) January 2nd. 1 injured._ [Illustration: _Fig. 2._] Plain cylinder, 11ft. long, 3ft. 1in. diameter, 3/8 inch plates, 25 lbs. pressure. Ruptured at a bad patch over grate, around which were many old cracks, and the rent passed along the bottom, and through the unguarded manhole, and round several of the transverse seams, dividing the boiler into 4 or 5 pieces, which were widely scattered, but are arranged in sketch near their original position. _No. 3. January 2nd. none injured._ Cornish, 32ft. long, 6ft. 6in. diameter, 3/8 inch plates, 30 lbs. pressure. Tube ruptured at first seam over the fire from weakness caused by internal corrosion. _No. 4. Middlesbro. (Fig. 3.) January 4th. 1 killed._ [Illustration: _Fig. 3._] Domestic, 1ft. 3in. wide, 1ft. high, 11in. deep, 5/16 inch thick. The circulating pipes being frozen, the pressure accumulated and rent the boiler open, doing considerable damage. _No. 5. Stirchley. (Fig. 4.) January 9th. 1 killed, 4 injured._ [Illustration: _Fig. 4._] One of five, about 30 years old. Lancashire, 18ft. 2in. long, 7ft. 6in. diameter. Tubes 2ft. diameter, 3/8 inch plates, 12 lbs. pressure. Ruptured at corroded steam pipe joint at top of front end, and the rent followed along the angle ring of shell which was also corroded, and then along the seams of some plates in the bottom, placed longitudinally, allowing the top of the boiler to open up like a lid, without moving it much out of its original position. _No. 6. Cornwall. January 12th. 1 killed._ Cornish, 30ft. long, 6ft. diameter, 7/16 inch plates, 35 lbs. pressure. The ball weight of the safety valve was unusually near the steam pipe, and it is supposed that the boy who was scalded having put his dinner on the pipe to warm, it slipped between the ball and pipe; and that in trying to extricate it he lifted the valve which was held open by the "pasty" wedged under the ball. _No. 7. Dalry. January 13th. 3 injured._ One of two, 25 years old. Plain cylinder, 24ft. long, 4ft. diameter, 5/16 inch plates, 30 lbs. pressure. Gave way at a ring seam where much corroded near the back end, which was blown to the rear, the front end being thrown considerably forwards, and the shell was torn into many fragments which damaged the engine house, and so injured the other boiler that it also was rent into pieces and thrown some distance away. One safety valve was made to serve for the two boilers, and the connecting valve being shut there was no escape from this boiler, so that the bursting pressure soon accumulated. A similar boiler attached to the same engine exploded in April, 1870, and is mentioned as No. 15 in the "records" of that year. _No. 8. S. Wales. January 15th. none injured._ Plain cylinder, 5 years old, 35ft. 6in. long, 4ft. 10in. diameter, 1/2 inch plates, 55 lbs. pressure. Some plates over the fire became red hot from the accumulation of scale some inches thick upon them and gave way, and the reaction of the issuing contents sent the boiler some distance and did much damage. _No. 9. Manchester. January 16th. 1 injured._ Plain cylinder, flat ends, very old, 8ft. 4in. long, 3ft. diameter, 3/8 inch plates, 50 lbs. pressure. The front plate was blown out, and the boiler was thrown backwards for some distance. The boiler was corroded until too weak to bear the ordinary pressure. _No. 10. Sunderland. January 17th. 1 killed, 1 injured._ Marine. The steam expansion joint was placed between two opposite curves in the pipe, and one end drew out when first under pressure. _No. 11. Leslie. January 26th. 2 killed._ Cornish, 10ft. long, 4ft. diameter. Tube 2ft. 4in. diameter, plates 5/16 inch, 40 lbs. pressure. Gave way at bottom where it rested on the brickwork, the plates being completely eaten away by external corrosion. _No. 12. Gateshead. (Fig. 5.) January 27th. none injured._ [Illustration: _Fig. 5._] Domestic, 3ft. high, 2ft. wide, and 1ft. 1in. deep, 3/8 inch plates. The circulating pipes being frozen, the pressure accumulated, and rent the boiler open doing great damage. _No. 13. Bradford. (Fig. 6.) February 1st. 1 killed._ [Illustration: _Fig. 6._] Plain cylinder, 5 years old, flat ends, 7ft. 5in. long, 3ft. 4in. diameter, 3/8 inch plates, 45 lbs. pressure. The safety valve was loaded to 70 lbs., and this pressure was too great for the insufficient stay to the flat end, which was blown out, the boiler being thrown backwards. _No. 14. Dover. February 5th. 1 killed._ Marine, 70 lbs. pressure. The boiler was not moved from its place, and the damage appeared to have been slight, but no particulars have been obtained. _No. 15. Newcastle. (Fig. 7.) Feb. 10th. none injured._ [Illustration: _Fig. 7._] One of three, 3 years old. Chimney, 27ft. high, 5ft. diameter. Tube 2ft. 9in. diameter, 3/8 inch plates, 25 lbs. pressure. Collapsed about half-way up the tube from overheating through shortness of water. _No. 16. Birmingham. (Fig. 8.) February 15th. 3 injured._ [Illustration: _Fig. 8._] One of two, 1 year old. Portable upright, 6ft. high, 3ft. diameter, 7/16 inch plates, 25 lbs. pressure. There was but one safety valve, and that was on the other boiler. The junction valve between the boilers was closed, when left for the night, without the fire being properly put out, and there being no outlet for the steam the pressure accumulated, and the boiler ruptured at the unguarded manhole and rent into fragments, much damaging the closely packed houses near. _No. 17. Stockton. March 8th. none injured._ Locomotive. The connecting rod broke and pierced the boiler, allowing contents to issue violently. A similar case was mentioned as No. 27, July 21st, 1868, and others have occurred in previous years. _No. 18. Bradford. (Fig. 9.) March 9th. 1 killed, 1 injured._ [Illustration: _Fig. 9._] One of six, 3 years old. Lancashire, 27ft. long, 7ft. diameter. Tubes 2ft. 8in. diameter, slightly oval, 7/16 inch plates, 60 lbs. pressure. The left hand tube collapsed downwards from overheating through shortness of water. The boiler was not moved, and little damage was done to premises. _No. 19. Glasgow. March 11th. 3 killed, 3 injured._ Rag Boiler. The screws of the manlid were loosened before the steam was exhausted, and the issuing contents scalded those near. _No. 20. Wootton Bassett. (Fig. 10.) March 11th. 2 killed, 1 injured._ [Illustration: _Fig. 10._] Cornish, 12ft. long, 4ft. 8in. diameter. Tube 2ft. 3in. diameter, 3/8 inch plates, 72 lbs. pressure. Tube collapsed downwards from overheating through shortness of water. This was the second time the tube had collapsed, although the boiler had only worked 18 months. _No. 21. Newcastle. (Fig. 11.) March 16th. 1 killed._ [Illustration: _Fig. 11._] Plain cylinder, flat ends, 16ft. long, 3ft. 6in. diameter, 5/16 inch plates, 25 lbs. pressure. There being no stays to support the flat ends the varying pressure caused a slight movement backward and forward (sometimes called "drum-head" motion), which facilitated corrosion in certain lines of strain, and produced a "furrow" at the front near the bottom, which rent open. The boiler was not moved, and little damage was done to the premises. _No. 22. Brigg. (Fig. 12.) March 17th. 1 killed, 1 injured._ [Illustration: _Fig. 12._] One of five, 5 years old. Plain cylinder, 68ft. long, 4ft. 4in. diameter, plates 5/16 inch full, 65 lbs. pressure. Heated by gas. Rent at fourth seam, the front end being thrown a great distance forward, and the back end to the rear, displacing the other 4 boilers. The ruptured seam was next to a patch where the cutting out of the old rivets and putting in of new had caused a seam-rip. _No. 23. S. Wales. (Fig. 13.) March 18th. none injured._ [Illustration: _Fig. 13._] One of two, 36 years old. Lancashire, 30ft. long, 9ft. diameter. Tubes 3ft. diameter, 1/2 inch plates, 22 lbs. pressure. The boiler was rent into 3 pieces. Five rings of the back part were torn off and thrown to the rear. Four rings in the middle were opened out flat and fell across the other boiler, and the remaining part of the shell with the tubes were left on the seating. The boiler was old and much patched, and was corroded too thin to bear the usual pressure. _No. 24. Lynn. (Fig. 14.) March 23rd. 2 killed._ Cornish, 10 years old, 7ft. 3in. long, 3ft. 2in. diameter. Tubes 1ft. 10in. diameter, 3/8 inch plates, 36 lbs. pressure. The tube ruptured at the last ring of plates, and was forced inwards, allowing the contents to issue at the back. The boiler was slightly thrown forward. It was only used occasionally, but was so much reduced by internal corrosion as to be unable to bear the usual pressure. [Illustration: _Fig. 14._] _No. 25. Northwich. (Fig. 15.) May 3rd. 1 killed, 1 injured._ [Illustration: _Fig. 15._] Marine, 7 years old, 9ft. 2in. long, 6ft. 1in. diameter. Furnace tube 2ft. diameter, and 3 inch small tubes, 3/8 inch plates, 81 lbs. pressure. There were two bands as clips round the outside of boiler. Gave way at a seam where some new bottom plates had been inserted, and where the old plate was so thinned by internal corrosion as to be unable to bear the usual pressure. A small plate was blown out and shattered into three pieces, and the boiler was turned end for end. _No. 26. Barnstaple. May 9th. 1 killed._ Revolving Rag boiler of plain cylindrical shape, with three filling holes. The steam was supplied from other boilers. The central lid was unscrewed, without trying, by a small hole for the purpose, whether there was any pressure, and the lid came off, and the contents issued and scalded the attendant. _No. 27. Leamington. (Fig. 16.) May 18th. 1 killed, 2 injured._ [Illustration: _Fig. 16._] Portable multitubular, 9 years old, 8ft. 6in. long, 2ft. 6in. diameter, 5/16 inch plates, 50 lbs. pressure. The safety valve was fastened down by a nail (A) between the lever and the cover, and in consequence the pressure accumulated to more than the boiler could bear, and it was rent into many pieces, which were widely scattered. [Illustration] _No. 28. May 20th. none injured._ Portable vertical, of peculiar construction, with return down flue tubes, 6ft. high, 4ft. 6in. diameter, 3/8 inch plates, 35 lbs. pressure. The shell was torn off, the bottom having given way through weakness, from want of proper stays, from the crown of the fire box to top of the boiler. _No. 29. Hull. (Fig. 17.) May 22nd. 3 killed, 1 injured._ [Illustration: _Fig. 17._] Lancashire, 22ft. 6in. long, 7ft. 6in. diameter. Tubes 2ft. 10in. diameter, 3/8 inch plates, 70 lbs. pressure. The tube was somewhat corroded on the top, and gave way over the fire from weakness. _No. 30. Bath. May 25th. 1 killed, 1 injured._ Revolving Rag boiler of plain cylindrical shape, but revolving on trunnions, in the opposite direction to No. 26, 12ft. high, 6ft. diameter, 9/16 inch plates, 50 lbs. pressure. The steam was supplied from another boiler. The cover at one end was insecurely fastened and was blown off. _No. 31. Oakengates. (Fig. 18.) June 6th. none injured._ [Illustration: _Fig. 18._] One of two, 20 years old. Balloon, 14ft. diameter, 3/8 inch plates, 6 lbs. pressure. The pressure was allowed to far exceed the proper height during a temporary stoppage of the engine, and the bottom was rent off, and the top thrown some distance, but very little damage was done. _No. 32. Wellingbro'. (Fig. 19.) June 17th. 1 killed, 2 injured._ [Illustration: _Fig. 19._] Cornish, 28ft. long, 6ft. diameter. Tube 3ft. diameter, 3/8 inch plates, 40 lbs. pressure. Tube collapsed from weakness, and partly tore away from the back end, and the reaction from the issuing contents forced the boiler back a long way. _No. 33. Tunstal (Fig. 20). June 28th. 8 killed, 20 injured._ [Illustration: _Fig. 20._] Cornish, 43ft. long, 6ft. 6in. diameter, 7/16 inch plates. Tube 3ft. diameter, 3/8 inch plates, 50 lbs. pressure. The tube collapsed sideways from end to end through weakness, being without strengthening hoops, and with continuous longitudinal seams. The back end and part of the tube were thrown to the rear, and the rest of the boiler was thrown to the front, and separated into several fragments. _No. 34. Glasgow. July 9th. 3 killed._ The lid of a steam valve was being removed while under pressure, and the steam escaped and scalded those near. _No. 35. Rotherham. (Fig. 21.) July 11th. none injured._ [Illustration: _Fig. 21._] Cornish, 10 years old, 7ft. long, 6ft. 6in. diameter. Tube 3ft. 3in. diameter, 3/8 inch plates, 45 lbs. pressure. Gave way where much corroded by the damp brickwork of the central wall, and the back ring of plates was torn out, and the boiler turned up on end, and much damage was done to the premises. _No. 36. July 17th. none injured._ Cornish, 16 years old, 12ft. long, 4ft. diameter, 7/16 inch plates, 48 lbs. pressure. Gave way at the bottom and rent open, a belt of plates being blown away to some distance. The bottom had been extensively corroded, by the boiler being left exposed to wet for many years before it was set at this place, rendering it unfit to bear the usual pressure. _No. 37. Cumnock. (Fig. 22.) July 28th. 1 injured._ [Illustration: _Fig. 22._] One of five, about 20 years old. Plain cylinder, 20ft. long, 4ft. diameter, 5/16 inch plates, 45 lbs. pressure. The boiler had been much patched and altered, and was in very poor condition, and unfit to bear safely the ordinary pressure. Rupture commenced near the feed pipe, and ran along one side and then round each end, both of which were liberated and thrown far away, the barrel of the boiler spreading out on to the neighbouring boilers, one of which was much injured. _No. 38. Shields. (Fig. 23.) August 1st. 1 killed, 7 injured._ Multitubular, 10 years old, 7ft. long, 3ft. 6in. diameter, 5/16 inch plates, 50 lbs. pressure, but valve loaded to 80 lbs. Rupture commenced at the unguarded manhole, and the shell was rent into several pieces which were much scattered. The safety valve was defective, and the boiler had been much weakened by many patches, and was in poor condition and unable to bear the pressure at which it was worked at the time of explosion. [Illustration: _Fig. 23._] _No. 39. Wakefield. August 3rd. 1 killed, 1 injured._ One of five. Rag boiler, 5 lbs. pressure from the exhaust steam of an engine. The manhole was of very large size and insecurely fastened, and was blown off. _No. 40. Cornwall. (Fig. 24.) August 17th. 2 killed._ [Illustration: _Fig. 24._] Cornish, 30ft. long, 6ft. 3in. diameter. Tube 4ft. 3in. diameter, 18 lbs. pressure. Ruptured near brickwork at the bottom where much corroded externally, and one ring of plates was rent open. The boiler was displaced, and the premises were greatly damaged. _No. 41. Shields. August 26th. none injured._ Chemical pan, 12ft. long, 5ft. 6in. diameter, 3/8 inch plates. The end was blown off, the rivets not being strong enough for the pressure of 35 lbs. as supplied from the boilers. _No. 42. Blackburn. (Fig. 25.) August 29th. 1 killed, 2 injured._ [Illustration: _Fig. 25._] Lancashire, 26ft. long, 6ft. 6in. diameter. Tubes 2ft. 9in. diameter, 3/8 inch plates, 60 lbs. pressure. The left hand tube collapsed from overheating through shortness of water, and the contents issued violently and scalded those near. _No. 43. Hereford. August. 2 injured._ Chemical boiler, Plain cylinder, 12ft. 6in. high, 4ft. 6in. diameter, 3/8 inch plates, with cast-iron hemispherical ends with manhole in each. The pressure of 34 lbs. was obtained from another boiler. The bottom end gave way where the casting was defective, a piece was blown out, and the reaction of the issuing contents projected the boiler through the roof, through which it again descended and did much damage. _No. 44. Cardiff. (Fig. 26.) September 1st. 2 killed, 2 injured._ [Illustration: _Fig. 26._] Marine. Multitubular, 6ft. long, 6ft. diameter, 60 lbs. pressure. The under side of fire box gave way at the front rivets, the heads of which were corroded, and a tongue of plate was torn upwards, allowing the contents to issue so violently, that those near were carried overboard and drowned. _No. 45. Gresley. (Fig. 27.) September 2nd. 7 injured._ [Illustration: _Fig. 27._] One of six, 2 years old. Plain cylinder, 40ft. long, 5ft. diameter, 3/8 inch plates, 50 lbs. pressure. This case was peculiar, as the back part of the boiler was found a long way to the front, and the front end in the rear. An accumulation of scale caused pocket to form, and a hole to burn through the bottom over the grate, allowing the contents to issue so violently that the boiler was sent over end for end, when the front end was knocked off and thrown to the rear, and the contents then issuing more violently, the reaction sent the rest of the boiler in one piece a great distance to the front, where it fell, and was crushed nearly flat and broken into several fragments. _No. 46. Cornwall. (Fig. 28.) September 16th. 4 injured._ [Illustration: _Fig. 28._] One of two, 18 years old. Cornish, 32ft. 9in. long, 6ft. 6in. diameter. Tube 4ft. diameter, 3/8 inch plates, 45 lbs. pressure. The tube collapsed from end to end, dropping together like an old sack, and cracking at the edges. A small piece at the front end was blown out. The cause was supposed to be shortness of water as there was no gauge glass, but it was far more likely the weakness of so large a tube without strengthening hoops. The pressure was doubtless more than usual, as the engine had made a temporary stand. A similar collapse took place in the next boiler in December, 1869, and is described as No. 57 in the "records" of that year. _No. 47. Hull. (Fig. 29.) September 22nd. 2 injured._ [Illustration: _Fig. 29._] Vertical, with fire box of peculiar corrugated construction, 7ft. 6in. high, 3ft. diameter, 50 lbs. pressure. Gave way round the bottom of fire box where much corroded and rent open, and the reaction of the issuing contents carried the whole boiler to a considerable distance. The pressure gauge had been removed, and the safety valve did not act freely, and the pressure accumulated to more than the boiler could bear. _No. 48. Grindleton. (Fig. 30.) September 26th. 1 killed._ [Illustration: _Fig. 30._] Lancashire, 3 years old, 20ft. long, 7ft. diameter. Tube 2ft. 2in. diameter, 3/8 inch plates, 60 lbs. pressure. The boiler gave way at the second ring of plates from the back end, at the side where externally corroded to a knife edge, by brickwork made damp by being next the side of a hill. The rents extended round the boiler, and it was turned nearly bottom upwards, and the shell opened out in the curious way shown in the sketch. _No. 49. Bradford. October 9th. none injured._ One of three. Portable, multitubular, 8ft. long, 2ft. 6in. diameter, 80 lbs. pressure. There was no safety valve, dependence being placed on that of the boiler to which it was connected. Steam was got up without opening the connecting steam cock, and the consequent excessive pressure forced off the front end. _No. 50. Tipton. October 17th. none injured._ One of twenty, 22 years old. One tube worked by two furnaces, 36ft. long, 6ft. 3in. diameter. Tube from end to left side 2ft. 8in. diameter, 1/2 inch plates, 30 lbs. pressure. The tube collapsed from overheating through shortness of water, and cracked at the edges and allowed the contents to escape without any violence. _No. 51. Bury. October 21st. 2 killed, 1 injured._ A wall fell upon and broke the steam pipes, and the escaping steam scalded those near. _No. 52. October 25th. 2 injured._ Chemical boiler. Plain cylinder, 9ft. 3in. long, 6ft. diameter, 3/8 inch plates. The back end was blown out, and the boiler moved forward a few yards, and the premises were much injured. The outlet pipes were choked up, and more pressure accumulated than it was capable of bearing. _No. 53. Chesterfield. (Fig. 31.) October 25th. none injured._ Plain cylinder, 6ft. 6in. long, 2ft. 2in. diameter, 5/16 inch plates, 80 to 100 lbs. pressure. The manhole was weak and unguarded with a strengthening ring, and ruptured and allowed the lid to blow out. The rents spread along a part where strength was much reduced by the rivets being countersunk to make room for attachments. The safety valve was defective and overloaded, and there was no gauge, and the boiler was unfit to bear the pressure to which it was exposed. [Illustration: _Fig. 31._] _No. 54. Northwich. October 28th. 1 killed, 1 injured._ Chemical. The cover was unscrewed before the pressure was off, and the contents blew out violently and scalded those near. _No. 55. Bowling. (Fig. 32.) October 30th. 1 killed, 1 injured._ [Illustration: _Fig. 32._] One of two, 17 years old. Marine, 12ft. 7in. long, 6ft. 3in. diameter. Tube 4ft. wide, 2ft. 9in. high, 16 lbs. pressure. The tube was much weakened by corrosion and screw-patching and collapsed upwards, with the slightly increased pressure of a temporary stoppage of the engine. _No. 56. Bilston. October. none injured._ Chemical, 9ft. long, slightly oval, 4ft. greatest diameter, 3/8 inch plates, 2 lbs. pressure. Although not at work, it is supposed that a gas was gently passing off through a small pipe, 30ft. long, to a receiver which was under repair, and that this gas being accidentally lighted, communicated through the pipe with that in the boiler and exploded it. One end was blown off, the rupture passing completely round through the solid plate. _No. 57. Newcastle. (Fig. 33.) November 5th. none injured._ [Illustration: _Fig. 33._] Cornish, 25ft. long, about 6ft. diameter. Tube 3ft. 6in. diameter, 3/8 inch plates, 30 lbs. pressure. Tube collapsed from overheating through shortness of water. _No. 58. Gravesend. (Fig. 34.) November 8th. 2 killed._ [Illustration: _Fig. 34._] One of two. Marine, 16ft. 6in. long, 8ft. 4in. diameter. Tube of irregular shape, about 2ft. 10in. high, 3/8 inch plates, 27 lbs. pressure. The gauge was so much out of order, that it only showed 24 lbs. under a real pressure of 80 lbs. The safety valve was defective and overloaded, and the pressure was sufficient to collapse and rupture the side flue, and the contents rushed out at the front. _No. 59. Bilston. (Fig. 35.) November 12th. none injured._ [Illustration: _Fig. 35._] One of four. Cornish, about 20 years old, 26ft. long, 6ft. 6in. diameter, 7/16 inch plates, 40 lbs. pressure. Tube 3ft. 9in. diameter had been made in two parts, joined in the centre by a narrow plate 3/8 inch thick, and it collapsed at this joint, so that the top met the bottom, and thus so retarded the issue of the contents after being set in motion, that a shock was produced, which blew out an end and half the tube in opposite directions. The shell was left resting in its seat, and little damage was done to premises. The tube had much the appearance of collapse from shortness of water, but the most probable cause was that it was too weak without strengthening hoops to bear the ordinary pressure with safety. _No. 60. Diss. (Fig. 36.) November 11th. 2 killed._ [Illustration: _Fig. 36._] Portable, multitubular, about 10 years old, 8ft. 3in. long, 2ft. 7in. diameter, 3/8 inch plates, 30 lbs. pressure. The bottom of the smoke box was reduced by external corrosion to less than 1/16 inch in thickness, and was consequently unable to bear the ordinary pressure, and a piece was blown out, and the reaction of issuing contents displaced the boiler a little and much damaged the premises. _No. 61. Rotherham. November 18th. 1 killed._ The screws of a manhole were loosened while the pressure remained in the boiler, and the lid was blown off. _No. 62. Newcastle. November 25th. 1 killed._ One of twelve. Chimney, 28ft. high, 6ft. diameter. Tube 2ft. 5in. diameter, 3/8 inch plates, 25 lbs. pressure. The blow pipe was left open while some men were inside repairing, and the steam and water from the blow-off of another boiler in the same pipe was forced in upon them. _No. 63. Cradley. December 8th. 1 injured._ Locomotive, 11ft. long, 3ft. diameter, 3/8 inch plates, 95 lbs. pressure. The pressure amounted to about 134 lbs. during a temporary effort to get up a steep curved incline, and the fire box was forced inwards and the outside shell outwards, and the stays drawn, but little other damage was done. _No. 64. Middlesbro'. (Fig. 37.) December 13th. 1 injured._ Locomotive, 18ft. 6in. long, 4ft. diameter, 7/16 inch plates, 120 lbs. pressure. Gave way under bottom of barrel where "furrowed" by the combined action of corrosion and the strain upon the plates, by attachment to the frame of the engine. [Illustration: _Fig. 37._] _No. 65. Westbromwich. (Fig. 38.) December 28th. 1 injured._ [Illustration: _Fig. 38._] One of five, 23 years old. Balloon, 16ft. diameter, 3/8 inch plates, 5 lbs. pressure. It ruptured at the back where the plates in contact with brickwork were reduced by external corrosion, and the bottom was forced down upon the grate, and the top rolled over on to its side. The boiler was not being used, although connected with the other at work. The strain upon the bottom was increased by the boiler being over full and nearly to the brim. Those near were drenched with nearly cold water from it when it upset. _No. 66. Glasgow. (Fig. 39.) December 30th. 11 killed, 30 injured._ Portable upright, about 8 years old, 11ft. 4in. high, 4ft. diameter, 3/8 inch plates, 100 lbs. pressure. The internal portion gave way where attached to the fire holes and collapsed inwards, and the reaction of the issuing contents forced the boiler up some distance on to the top of a house. The safety valve did not act properly, and the pressure appears to have accumulated to more than the boiler could bear, during a temporary stoppage of the engine. [Illustration: _Fig. 39._] * * * * * _R. Broomhall, Printer, Stourbridge._ [Transcriber's note: Some of the figures are out or order, as in the original. Several (apparently) missing punctuation marks have been added to improve readability. The word 'guage' appears several times. It has been changed to 'gauge' in each location. Italics are rendered between underscores e.g. _italics_. Small caps are rendered as ALL CAPS. The following table lists other changes made by the transcriber.] +-----------------------------+ | Transcriber's Change table | +----+-----------+------------+ |page|as printed | changed to | +----+-----------+------------+ | 95| Uudue | Undue | | 105| Fig. 5. | Fig. 6. | | 110| to to | to | | 110| place | placed | | 143| he | The | | 172| reqair | repair | | 195| discribed | described | | 216| reqaired | repaired | | 221| diamer | diameter | | 250|consderable|considerable| +----+-----------+------------+ 
22657	----	STEAM ITS GENERATION AND USE [Illustration] THE BABCOCK & WILCOX CO. NEW YORK Thirty-fifth Edition 4th Issue Copyright, 1919, by The Babcock & Wilcox Co. * * * * * Bartlett Orr Press New York THE BABCOCK & WILCOX CO. 85 LIBERTY STREET, NEW YORK, U. S. A. _Works_ BAYONNE NEW JERSEY BARBERTON OHIO _Officers_ W. D. HOXIE, _President_ E. H. WELLS, _Chairman of the Board_ A. G. PRATT, _Vice-President_ _Branch Offices_ ATLANTA Candler Building BOSTON 35 Federal Street CHICAGO Marquette Building CINCINNATI Traction Building CLEVELAND New Guardian Building DENVER 435 Seventeenth Street HAVANA, CUBA 104 Calle de Aguiar HOUSTON Southern Pacific Building LOS ANGELES I. N. Van Nuy's Building NEW ORLEANS Shubert Arcade PHILADELPHIA North American Building PITTSBURGH Farmers' Deposit Bank Building SALT LAKE CITY Kearns Building SAN FRANCISCO Sheldon Building SEATTLE L. C. Smith Building TUCSON, ARIZ. Santa Rita Hotel Building SAN JUAN, PORTO RICO Royal Bank Building _Export Department, New York: Alberto de Verastegni, Director_ TELEGRAPHIC ADDRESS: FOR NEW YORK, "GLOVEBOXES" FOR HAVANA, "BABCOCK" [Illustration: Works of The Babcock & Wilcox Co., at Bayonne, New Jersey] [Illustration: Works of The Babcock & Wilcox Co., at Barberton, Ohio] [Illustration: Works of Babcock & Wilcox, Limited, Renfrew, SCOTLAND] BABCOCK & WILCOX Limited ORIEL HOUSE, FARRINGDON STREET, LONDON, E. C. WORKS: RENFREW, SCOTLAND _Directors_ JOHN DEWRANCE, _Chairman_ CHARLES A. KNIGHT ARTHUR T. SIMPSON J. H. R. KEMNAL WILLIAM D. HOXIE _Managing Director_ E. H. WELLS WALTER COLLS, _Secretary_ _Branch Offices in Great Britain_ GLASGOW: 29 St. Vincent Place BIRMINGHAM: Winchester House CARDIFF: 129 Bute Street BELFAST: Ocean Buildings, Donegal Square, E. MANCHESTER: 30 Cross Street MIDDLESBROUGH: The Exchange NEWCASTLE: 42 Westgate Road SHEFFIELD: 14 Bank Chambers, Fargate _Offices Abroad_ BOMBAY: Wheeler's Building, Hornby Road, Fort BRUSSELS: 187 Rue Royal BILBAO: 1 Plaza de Albia CALCUTTA: Clive Building JOHANNESBURG: Consolidated Buildings LIMA: Peru LISBON: 84-86 Rua do Commercio MADRID: Ventura de la Vega MELBOURNE: 9 William Street MEXICO: 22-23 Tiburcio MILAN: 22 Via Principe Umberto MONTREAL: College Street, St. Henry NAPLES: 107 Via Santa Lucia SHANGHAI: 1a Jinkee Road SYDNEY: 427-429 Sussex Street TOKYO: Japan TORONTO: Traders' Bank Building _Representatives and Licensees in_ ADELAIDE, South Australia ATHENS, Greece AUCKLAND, New Zealand BAHIA, Brazil BANGKOK, Siam BARCELONA, Spain BRUNN, Austria BUCHAREST, Roumania BUDAPEST, Hungary BUENOS AYRES, Argentine Rep. CAIRO, Egypt CHILE, Valparaiso, So. America CHRISTIANIA, Norway COLOMBO, Ceylon COPENHAGEN, Denmark ESKILSTUNA, Sweden GIJON, Spain HELSINGFORS, Finland HENGELO, Holland KIMBERLEY, South Africa MOSCOW, Russia PERTH, Western Australia POLAND, Berlin RANGOON, Burma RIO DE JANEIRO, Brazil SMYRNA, Asia Minor SOURABAYA, Java ST. PETERSBURG, Russia TAMMERFORS, Finland THE HAGUE, Holland TELEGRAPHIC ADDRESS FOR ALL OFFICES EXCEPT BOMBAY AND CALCUTTA: "BABCOCK" FOR BOMBAY AND CALCUTTA: "BOILER" [Illustration: Fonderies et Ateliers de la Courneuve, Chaudières Babcock & Wilcox, Paris, France] FONDERIES ET ATELIERS DE LA COURNEUVE CHAUDIÈRES BABCOCK & WILCOX 6 RUE LAFERRIÈRE, PARIS WORKS: SEINE--LA COURNEUVE _Directors_ EDMOND DUPUIS J. H. R. KEMNAL ETIENNE BESSON IRÉNÉE CHAVANNE CHARLES A. KNIGHT JULES LEMAIRE _Branch Offices_ BORDEAUX: 30 Boulevard Antoine Gautier LILLE: 23 Rue Faidherbe LYON: 28 Quai de la Guillotier MARSEILLE: 21 Cours Devilliers MONTPELLIER: 1 Rue Boussairolles NANCY: 2 Rue de Lorraine ST. ETIENNE: 13 Rue de la Bourse REPRESENTATIVE FOR SWITZERLAND: SPOERRI & CIE, ZURICH TELEGRAPHIC ADDRESS: "BABCOCK-PARIS" [Illustration: Wrought-steel Vertical Header Longitudinal Drum Babcock & Wilcox Boiler, Equipped with Babcock & Wilcox Superheater and Babcock & Wilcox Chain Grate Stoker] THE EARLY HISTORY OF THE GENERATION AND USE OF STEAM While the time of man's first knowledge and use of the expansive force of the vapor of water is unknown, records show that such knowledge existed earlier than 150 B. C. In a treatise of about that time entitled "Pneumatica", Hero, of Alexander, described not only existing devices of his predecessors and contemporaries but also an invention of his own which utilized the expansive force of steam for raising water above its natural level. He clearly describes three methods in which steam might be used directly as a motive of power; raising water by its elasticity, elevating a weight by its expansive power and producing a rotary motion by its reaction on the atmosphere. The third method, which is known as "Hero's engine", is described as a hollow sphere supported over a caldron or boiler by two trunnions, one of which was hollow, and connected the interior of the sphere with the steam space of the caldron. Two pipes, open at the ends and bent at right angles, were inserted at opposite poles of the sphere, forming a connection between the caldron and the atmosphere. Heat being applied to the caldron, the steam generated passed through the hollow trunnion to the sphere and thence into the atmosphere through the two pipes. By the reaction incidental to its escape through these pipes, the sphere was caused to rotate and here is the primitive steam reaction turbine. Hero makes no suggestions as to application of any of the devices he describes to a useful purpose. From the time of Hero until the late sixteenth and early seventeenth centuries, there is no record of progress, though evidence is found that such devices as were described by Hero were sometimes used for trivial purposes, the blowing of an organ or the turning of a skillet. Mathesius, the German author, in 1571; Besson, a philosopher and mathematician at Orleans; Ramelli, in 1588; Battista Delia Porta, a Neapolitan mathematician and philosopher, in 1601; Decause, the French engineer and architect, in 1615; and Branca, an Italian architect, in 1629, all published treatises bearing on the subject of the generation of steam. To the next contributor, Edward Somerset, second Marquis of Worcester, is apparently due the credit of proposing, if not of making, the first useful steam engine. In the "Century of Scantlings and Inventions", published in London in 1663, he describes devices showing that he had in mind the raising of water not only by forcing it from two receivers by direct steam pressure but also for some sort of reciprocating piston actuating one end of a lever, the other operating a pump. His descriptions are rather obscure and no drawings are extant so that it is difficult to say whether there were any distinctly novel features to his devices aside from the double action. While there is no direct authentic record that any of the devices he described were actually constructed, it is claimed by many that he really built and operated a steam engine containing pistons. In 1675, Sir Samuel Moreland was decorated by King Charles II, for a demonstration of "a certain powerful machine to raise water." Though there appears to be no record of the design of this machine, the mathematical dictionary, published in 1822, credits Moreland with the first account of a steam engine, on which subject he wrote a treatise that is still preserved in the British Museum. [Illustration: 397 Horse-power Babcock & Wilcox Boiler in Course of Erection at the Plant of the Crocker Wheeler Co., Ampere, N. J.] Dr. Denys Papin, an ingenious Frenchman, invented in 1680 "a steam digester for extracting marrowy, nourishing juices from bones by enclosing them in a boiler under heavy pressure," and finding danger from explosion, added a contrivance which is the first safety valve on record. The steam engine first became commercially successful with Thomas Savery. In 1699, Savery exhibited before the Royal Society of England (Sir Isaac Newton was President at the time), a model engine which consisted of two copper receivers alternately connected by a three-way hand-operated valve, with a boiler and a source of water supply. When the water in one receiver had been driven out by the steam, cold water was poured over its outside surface, creating a vacuum through condensation and causing it to fill again while the water in the other reservoir was being forced out. A number of machines were built on this principle and placed in actual use as mine pumps. The serious difficulty encountered in the use of Savery's engine was the fact that the height to which it could lift water was limited by the pressure the boiler and vessels could bear. Before Savery's engine was entirely displaced by its successor, Newcomen's, it was considerably improved by Desaguliers, who applied the Papin safety valve to the boiler and substituted condensation by a jet within the vessel for Savery's surface condensation. In 1690, Papin suggested that the condensation of steam should be employed to make a vacuum beneath a cylinder which had previously been raised by the expansion of steam. This was the earliest cylinder and piston steam engine and his plan took practical shape in Newcomen's atmospheric engine. Papin's first engine was unworkable owing to the fact that he used the same vessel for both boiler and cylinder. A small quantity of water was placed in the bottom of the vessel and heat was applied. When steam formed and raised the piston, the heat was withdrawn and the piston did work on its down stroke under pressure of the atmosphere. After hearing of Savery's engine, Papin developed an improved form. Papin's engine of 1705 consisted of a displacement chamber in which a floating diaphragm or piston on top of the water kept the steam and water from direct contact. The water delivered by the downward movement of the piston under pressure, to a closed tank, flowed in a continuous stream against the vanes of a water wheel. When the steam in the displacement chamber had expanded, it was exhausted to the atmosphere through a valve instead of being condensed. The engine was, in fact, a non-condensing, single action steam pump with the steam and pump cylinders in one. A curious feature of this engine was a heater placed in the diaphragm. This was a mass of heated metal for the purpose of keeping the steam dry or preventing condensation during expansion. This device might be called the first superheater. Among the various inventions attributed to Papin was a boiler with an internal fire box, the earliest record of such construction. While Papin had neglected his earlier suggestion of a steam and piston engine to work on Savery's ideas, Thomas Newcomen, with his assistant, John Cawley, put into practical form Papin's suggestion of 1690. Steam admitted from the boiler to a cylinder raised a piston by its expansion, assisted by a counter-weight on the other end of a beam actuated by the piston. The steam valve was then shut and the steam condensed by a jet of cold water. The piston was then forced downward by atmospheric pressure and did work on the pump. The condensed water in the cylinder was expelled through an escapement valve by the next entry of steam. This engine used steam having pressure but little, if any, above that of the atmosphere. [Illustration: Two Units of 8128 Horse Power of Babcock & Wilcox Boilers and Superheaters at the Fisk Street Station of the Commonwealth Edison Co., Chicago, Ill., 50,400 Horse Power being Installed in this Station. The Commonwealth Edison Co. Operates in its Various Stations a Total of 86,000 Horse Power of Babcock & Wilcox Boilers, all Fitted with Babcock & Wilcox Superheaters and Equipped with Babcock & Wilcox Chain Grate Stokers] In 1711, this engine was introduced into mines for pumping purposes. Whether its action was originally automatic or whether dependent upon the hand operation of the valves is a question of doubt. The story commonly believed is that a boy, Humphrey Potter, in 1713, whose duty it was to open and shut such valves of an engine he attended, by suitable cords and catches attached to the beam, caused the engine to automatically manipulate these valves. This device was simplified in 1718 by Henry Beighton, who suspended from the bottom, a rod called the plug-tree, which actuated the valve by tappets. By 1725, this engine was in common use in the collieries and was changed but little for a matter of sixty or seventy years. Compared with Savery's engine, from the aspect of a pumping engine, Newcomen's was a distinct advance, in that the pressure in the pumps was in no manner dependent upon the steam pressure. In common with Savery's engine, the losses from the alternate heating and cooling of the steam cylinder were enormous. Though obviously this engine might have been modified to serve many purposes, its use seems to have been limited almost entirely to the pumping of water. The rivalry between Savery and Papin appears to have stimulated attention to the question of fuel saving. Dr. John Allen, in 1730, called attention to the fact that owing to the short length of time of the contact between the gases and the heating surfaces of the boiler, nearly half of the heat of the fire was lost. With a view to overcoming this loss at least partially, he used an internal furnace with a smoke flue winding through the water in the form of a worm in a still. In order that the length of passage of the gases might not act as a damper on the fire, Dr. Allen recommended the use of a pair of bellows for forcing the sluggish vapor through the flue. This is probably the first suggested use of forced draft. In forming an estimate of the quantity of fuel lost up the stack, Dr. Allen probably made the first boiler test. Toward the end of the period of use of Newcomen's atmospheric engine, John Smeaton, who, about 1770, built and installed a number of large engines of this type, greatly improved the design in its mechanical details. [Illustration: Erie County Electric Co., Erie, Pa., Operating 3082 Horse Power of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock & Wilcox Chain Grate Stokers] The improvement in boiler and engine design of Smeaton, Newcomen and their contemporaries, were followed by those of the great engineer, James Watt, an instrument maker of Glasgow. In 1763, while repairing a model of Newcomen's engine, he was impressed by the great waste of steam to which the alternating cooling and heating of the engine gave rise. His remedy was the maintaining of the cylinder as hot as the entering steam and with this in view he added a vessel separate from the cylinder, into which the steam should pass from the cylinder and be there condensed either by the application of cold water outside or by a jet from within. To preserve a vacuum in his condenser, he added an air pump which should serve to remove the water of condensation and air brought in with the injection water or due to leakage. As the cylinder no longer acted as a condenser, he could maintain it at a high temperature by covering it with non-conducting material and, in particular, by the use of a steam jacket. Further and with the same object in view, he covered the top of the cylinder and introduced steam above the piston to do the work previously accomplished by atmospheric pressure. After several trials with an experimental apparatus based on these ideas, Watt patented his improvements in 1769. Aside from their historical importance, Watt's improvements, as described in his specification, are to this day a statement of the principles which guide the scientific development of the steam engine. His words are: "My method of lessening the consumption of steam, and consequently fuel, in fire engines, consists of the following principles: "First, That vessel in which the powers of steam are to be employed to work the engine, which is called the cylinder in common fire engines, and which I call the steam vessel, must, during the whole time the engine is at work, be kept as hot as the steam that enters it; first, by enclosing it in a case of wood, or any other materials that transmit heat slowly; secondly, by surrounding it with steam or other heated bodies; and, thirdly, by suffering neither water nor any other substance colder than the steam to enter or touch it during that time. "Secondly, In engines that are to be worked wholly or partially by condensation of steam, the steam is to be condensed in vessels distinct from the steam vessels or cylinders, although occasionally communicating with them; these vessels I call condensers; and, whilst the engines are working, these condensers ought at least to be kept as cold as the air in the neighborhood of the engines, by application of water or other cold bodies. "Thirdly, Whatever air or other elastic vapor is not condensed by the cold of the condenser, and may impede the working of the engine, is to be drawn out of the steam vessels or condensers by means of pumps, wrought by the engines themselves, or otherwise. "Fourthly, I intend in many cases to employ the expansive force of steam to press on the pistons, or whatever may be used instead of them, in the same manner in which the pressure of the atmosphere is now employed in common fire engines. In cases where cold water cannot be had in plenty, the engines may be wrought by this force of steam only, by discharging the steam into the air after it has done its office.... "Sixthly, I intend in some cases to apply a degree of cold not capable of reducing the steam to water, but of contracting it considerably, so that the engines shall be worked by the alternate expansion and contraction of the steam. "Lastly, Instead of using water to render the pistons and other parts of the engine air and steam tight, I employ oils, wax, resinous bodies, fat of animals, quick-silver and other metals in their fluid state." The fifth claim was for a rotary engine, and need not be quoted here. The early efforts of Watt are typical of those of the poor inventor struggling with insufficient resources to gain recognition and it was not until he became associated with the wealthy manufacturer, Mattheu Boulton of Birmingham, that he met with the success upon which his present fame is based. In partnership with Boulton, the business of the manufacture and the sale of his engines were highly successful in spite of vigorous attacks on the validity of his patents. Though the fourth claim of Watt's patent describes a non-condensing engine which would require high pressures, his aversion to such practice was strong. Notwithstanding his entire knowledge of the advantages through added expansion under high pressure, he continued to use pressures not above 7 pounds per square inch above the atmosphere. To overcome such pressures, his boilers were fed through a stand-pipe of sufficient height to have the column of water offset the pressure within the boiler. Watt's attitude toward high pressure made his influence felt long after his patents had expired. [Illustration: Portion of 9600 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock & Wilcox Chain Grate Stokers at the Blue Island, Ill., Plant of the Public Service Co. of Northern Illinois. This Company Operates 14,580 Horse Power of Babcock & Wilcox Boilers and Superheaters in its Various Stations] In 1782, Watt patented two other features which he had invented as early as 1769. These were the double acting engine, that is, the use of steam on both sides of the piston and the use of steam expansively, that is, the shutting off of steam from the cylinder when the piston had made but a portion of its stroke, the power for the completion of the stroke being supplied by the expansive force of the steam already admitted. He further added a throttle valve for the regulation of steam admission, invented the automatic governor and the steam indicator, a mercury steam gauge and a glass water column. It has been the object of this brief history of the early developments in the use of steam to cover such developments only through the time of James Watt. The progress of the steam engine from this time through the stages of higher pressures, combining of cylinders, the application of steam vehicles and steamboats, the adding of third and fourth cylinders, to the invention of the turbine with its development and the accompanying development of the reciprocating engine to hold its place, is one long attribute to the inventive genius of man. While little is said in the biographies of Watt as to the improvement of steam boilers, all the evidence indicates that Boulton and Watt introduced the first "wagon boiler", so called because of its shape. In 1785, Watt took out a number of patents for variations in furnace construction, many of which contain the basic principles of some of the modern smoke preventing furnaces. Until the early part of the nineteenth century, the low steam pressures used caused but little attention to be given to the form of the boiler operated in connection with the engines above described. About 1800, Richard Trevithick, in England, and Oliver Evans, in America, introduced non-condensing, and for that time, high pressure steam engines. To the initiative of Evans may be attributed the general use of high pressure steam in the United States, a feature which for many years distinguished American from European practice. The demand for light weight and economy of space following the beginning of steam navigation and the invention of the locomotive required boilers designed and constructed to withstand heavier pressures and forced the adoption of the cylindrical form of boiler. There are in use to-day many examples of every step in the development of steam boilers from the first plain cylindrical boiler to the most modern type of multi-tubular locomotive boiler, which stands as the highest type of fire-tube boiler construction. The early attempts to utilize water-tube boilers were few. A brief history of the development of the boilers, in which this principle was employed, is given in the following chapter. From this history it will be clearly indicated that the first commercially successful utilization of water tubes in a steam generator is properly attributed to George H. Babcock and Stephen Wilcox. [Illustration: Copyright by Underwood & Underwood Woolworth Building, New York City, Operating 2454 Horse Power of Babcock & Wilcox Boilers] BRIEF HISTORY OF WATER-TUBE BOILERS[1] As stated in the previous chapter, the first water-tube boiler was built by John Blakey and was patented by him in 1766. Several tubes alternately inclined at opposite angles were arranged in the furnaces, the adjacent tube ends being connected by small pipes. The first successful user of water-tube boilers, however, was James Rumsey, an American inventor, celebrated for his early experiments in steam navigation, and it is he who may be truly classed as the originator of the water-tube boiler. In 1788 he patented, in England, several forms of boilers, some of which were of the water-tube type. One had a fire box with flat top and sides, with horizontal tubes across the fire box connecting the water spaces. Another had a cylindrical fire box surrounded by an annular water space and a coiled tube was placed within the box connecting at its two ends with the water space. This was the first of the "coil boilers". Another form in the same patent was the vertical tubular boiler, practically as made at the present time. [Illustration: Blakey, 1766] The first boiler made of a combination of small tubes, connected at one end to a reservoir, was the invention of another American, John Stevens, in 1804. This boiler was actually employed to generate steam for running a steamboat on the Hudson River, but like all the "porcupine" boilers, of which type it was the first, it did not have the elements of a continued success. [Illustration: John Stevens, 1804] Another form of water tube was patented in 1805 by John Cox Stevens, a son of John Stevens. This boiler consisted of twenty vertical tubes, 1¼ inches internal diameter and 40½ inches long, arranged in a circle, the outside diameter of which was approximately 12 inches, connecting a water chamber at the bottom with a steam chamber at the top. The steam and water chambers were annular spaces of small cross section and contained approximately 33 cubic inches. The illustration shows the cap of the steam chamber secured by bolts. The steam outlet pipe "A" is a pipe of one inch diameter, the water entering through a similar aperture at the bottom. One of these boilers was for a long time at the Stevens Institute of Technology at Hoboken, and is now in the Smithsonian Institute at Washington. [Illustration: John Cox Stevens, 1805] About the same time, Jacob Woolf built a boiler of large horizontal tubes, extending across the furnace and connected at the ends to a longitudinal drum above. The first purely sectional water-tube boiler was built by Julius Griffith, in 1821. In this boiler, a number of horizontal water tubes were connected to vertical side pipes, the side pipes were connected to horizontal gathering pipes, and these latter in turn to a steam drum. In 1822, Jacob Perkins constructed a flash boiler for carrying what was then considered a high pressure. A number of cast-iron bars having 1½ inches annular holes through them and connected at their outer ends by a series of bent pipes, outside of the furnace walls, were arranged in three tiers over the fire. The water was fed slowly to the upper tier by a force pump and steam in the superheated state was discharged to the lower tiers into a chamber from which it was taken to the engine. [Illustration: Joseph Eve, 1825] The first sectional water-tube boiler, with a well-defined circulation, was built by Joseph Eve, in 1825. The sections were composed of small tubes with a slight double curve, but being practically vertical, fixed in horizontal headers, which headers were in turn connected to a steam space above and a water space below formed of larger pipes. The steam and water spaces were connected by outside pipes to secure a circulation of the water up through the sections and down through the external pipes. In the same year, John M'Curdy of New York, built a "Duplex Steam Generator" of "tubes of wrought or cast iron or other material" arranged in several horizontal rows, connected together alternately at the front and rear by return bends. In the tubes below the water line were placed interior circular vessels closed at the ends in order to expose a thin sheet of water to the action of the fire. [Illustration: Gurney, 1826] In 1826, Goldsworthy Gurney built a number of boilers, which he used on his steam carriages. A number of small tubes were bent into the shape of a "U" laid sidewise and the ends were connected with larger horizontal pipes. These were connected by vertical pipes to permit of circulation and also to a vertical cylinder which served as a steam and water reservoir. In 1828, Paul Steenstrup made the first shell boiler with vertical water tubes in the large flues, similar to the boiler known as the "Martin" and suggesting the "Galloway". The first water-tube boiler having fire tubes within water tubes was built in 1830, by Summers & Ogle. Horizontal connections at the top and bottom were connected by a series of vertical water tubes, through which were fire tubes extending through the horizontal connections, the fire tubes being held in place by nuts, which also served to make the joint. [Illustration: Stephen Wilcox, 1856] Stephen Wilcox, in 1856, was the first to use inclined water tubes connecting water spaces at the front and rear with a steam space above. The first to make such inclined tubes into a sectional form was Twibill, in 1865. He used wrought-iron tubes connected at the front and rear with standpipes through intermediate connections. These standpipes carried the system to a horizontal cross drum at the top, the entrained water being carried to the rear. Clarke, Moore, McDowell, Alban and others worked on the problem of constructing water-tube boilers, but because of difficulties of construction involved, met with no practical success. [Illustration: Twibill, 1865] It may be asked why water-tube boilers did not come into more general use at an early date, that is, why the number of water-tube boilers built was so small in comparison to the number of shell boilers. The reason for this is found in the difficulties involved in the design and construction of water-tube boilers, which design and construction required a high class of engineering and workmanship, while the plain cylindrical boiler is comparatively easy to build. The greater skill required to make a water-tube boiler successful is readily shown in the great number of failures in the attempts to make them. [Illustration: Partial View of 7000 Horse-power Installation of Babcock & Wilcox Boilers at the Philadelphia, Pa., Plant of the Baldwin Locomotive Works. This Company Operates in its Various Plants a Total of 9280 Horse Power of Babcock & Wilcox Boilers] REQUIREMENTS OF STEAM BOILERS Since the first appearance in "Steam" of the following "Requirements of a Perfect Steam Boiler", the list has been copied many times either word for word or clothed in different language and applied to some specific type of boiler design or construction. In most cases, although full compliance with one or more of the requirements was structurally impossible, the reader was left to infer that the boiler under consideration possessed all the desirable features. It is noteworthy that this list of requirements, as prepared by George H. Babcock and Stephen Wilcox, in 1875, represents the best practice of to-day. Moreover, coupled with the boiler itself, which is used in the largest and most important steam generating plants throughout the world, the list forms a fitting monument to the foresight and genius of the inventors. REQUIREMENTS OF A PERFECT STEAM BOILER 1st. Proper workmanship and simple construction, using materials which experience has shown to be the best, thus avoiding the necessity of early repairs. 2nd. A mud drum to receive all impurities deposited from the water, and so placed as to be removed from the action of the fire. 3rd. A steam and water capacity sufficient to prevent any fluctuation in steam pressure or water level. 4th. A water surface for the disengagement of the steam from the water, of sufficient extent to prevent foaming. 5th. A constant and thorough circulation of water throughout the boiler, so as to maintain all parts at the same temperature. 6th. The water space divided into sections so arranged that, should any section fail, no general explosion can occur and the destructive effects will be confined to the escape of the contents. Large and free passages between the different sections to equalize the water line and pressure in all. 7th. A great excess of strength over any legitimate strain, the boiler being so constructed as to be free from strains due to unequal expansion, and, if possible, to avoid joints exposed to the direct action of the fire. 8th. A combustion chamber so arranged that the combustion of the gases started in the furnace may be completed before the gases escape to the chimney. 9th. The heating surface as nearly as possible at right angles to the currents of heated gases, so as to break up the currents and extract the entire available heat from the gases. 10th. All parts readily accessible for cleaning and repairs. This is a point of the greatest importance as regards safety and economy. 11th. Proportioned for the work to be done, and capable of working to its full rated capacity with the highest economy. 12th. Equipped with the very best gauges, safety valves and other fixtures. The exhaustive study made of each one of these requirements is shown by the following extract from a lecture delivered by Mr. Geo. H. Babcock at Cornell University in 1890 upon the subject: THE CIRCULATION OF WATER IN STEAM BOILERS You have all noticed a kettle of water boiling over the fire, the fluid rising somewhat tumultuously around the edges of the vessel, and tumbling toward the center, where it descends. Similar currents are in action while the water is simply being heated, but they are not perceptible unless there are floating particles in the liquid. These currents are caused by the joint action of the added temperature and two or more qualities which the water possesses. 1st. Water, in common with most other substances, expands when heated; a statement, however, strictly true only when referred to a temperature above 39 degrees F. or 4 degrees C., but as in the making of steam we rarely have to do with temperatures so low as that, we may, for our present purposes, ignore that exception. 2nd. Water is practically a non-conductor of heat, though not entirely so. If ice-cold water was kept boiling at the surface the heat would not penetrate sufficiently to begin melting ice at a depth of 3 inches in less than about two hours. As, therefore, the heated water cannot impart its heat to its neighboring particles, it remains expanded and rises by its levity, while colder portions come to be heated in turn, thus setting up currents in the fluid. Now, when all the water has been heated to the boiling point corresponding to the pressure to which it is subjected, each added unit of heat converts a portion, about 7 grains in weight, into vapor, greatly increasing its volume; and the mingled steam and water rises more rapidly still, producing ebullition such as we have noticed in the kettle. So long as the quantity of heat added to the contents of the kettle continues practically constant, the conditions remain similar to those we noticed at first, a tumultuous lifting of the water around the edges, flowing toward the center and thence downward; if, however, the fire be quickened, the upward currents interfere with the downward and the kettle boils over (Fig. 1). [Illustration: Fig. 1] If now we put in the kettle a vessel somewhat smaller (Fig. 2) with a hole in the bottom and supported at a proper distance from the side so as to separate the upward from the downward currents, we can force the fires to a very much greater extent without causing the kettle to boil over, and when we place a deflecting plate so as to guide the rising column toward the center it will be almost impossible to produce that effect. This is the invention of Perkins in 1831 and forms the basis of very many of the arrangements for producing free circulation of the water in boilers which have been made since that time. It consists in dividing the currents so that they will not interfere each with the other. [Illustration: Fig. 2] But what is the object of facilitating the circulation of water in boilers? Why may we not safely leave this to the unassisted action of nature as we do in culinary operations? We may, if we do not care for the three most important aims in steam-boiler construction, namely, efficiency, durability, and safety, each of which is more or less dependent upon a proper circulation of the water. As for efficiency, we have seen one proof in our kettle. When we provided means to preserve the circulation, we found that we could carry a hotter fire and boil away the water much more rapidly than before. It is the same in a steam boiler. And we also noticed that when there was nothing but the unassisted circulation, the rising steam carried away so much water in the form of foam that the kettle boiled over, but when the currents were separated and an unimpeded circuit was established, this ceased, and a much larger supply of steam was delivered in a comparatively dry state. Thus, circulation increases the efficiency in two ways: it adds to the ability to take up the heat, and decreases the liability to waste that heat by what is technically known as priming. There is yet another way in which, incidentally, circulation increases efficiency of surface, and that is by preventing in a greater or less degree the formation of deposits thereon. Most waters contain some impurity which, when the water is evaporated, remains to incrust the surface of the vessel. This incrustation becomes very serious sometimes, so much so as to almost entirely prevent the transmission of heat from the metal to the water. It is said that an incrustation of only one-eighth inch will cause a loss of 25 per cent in efficiency, and this is probably within the truth in many cases. Circulation of water will not prevent incrustation altogether, but it lessens the amount in all waters, and almost entirely so in some, thus adding greatly to the efficiency of the surface. [Illustration: Fig. 3] A second advantage to be obtained through circulation is durability of the boiler. This it secures mainly by keeping all parts at a nearly uniform temperature. The way to secure the greatest freedom from unequal strains in a boiler is to provide for such a circulation of the water as will insure the same temperature in all parts. 3rd. Safety follows in the wake of durability, because a boiler which is not subject to unequal strains of expansion and contraction is not only less liable to ordinary repairs, but also to rupture and disastrous explosion. By far the most prolific cause of explosions is this same strain from unequal expansions. [Illustration: Fig. 4] [Illustration: 386 Horse-power Installation of Babcock & Wilcox Boilers at B. F. Keith's Theatre, Boston, Mass.] Having thus briefly looked at the advantages of circulation of water in steam boilers, let us see what are the best means of securing it under the most efficient conditions We have seen in our kettle that one essential point was that the currents should be kept from interfering with each other. If we could look into an ordinary return tubular boiler when steaming, we should see a curious commotion of currents rushing hither and thither, and shifting continually as one or the other contending force gained a momentary mastery. The principal upward currents would be found at the two ends, one over the fire and the other over the first foot or so of the tubes. Between these, the downward currents struggle against the rising currents of steam and water. At a sudden demand for steam, or on the lifting of the safety valve, the pressure being slightly reduced, the water jumps up in jets at every portion of the surface, being lifted by the sudden generation of steam throughout the body of water. You have seen the effect of this sudden generation of steam in the well-known experiment with a Florence flask, to which a cold application is made while boiling water under pressure is within. You have also witnessed the geyser-like action when water is boiled in a test tube held vertically over a lamp (Fig. 3). [Illustration: Fig. 5] If now we take a U-tube depending from a vessel of water (Fig. 4) and apply the lamp to one leg a circulation is at once set up within it, and no such spasmodic action can be produced. Thus U-tube is the representative of the true method of circulation within a water-tube boiler properly constructed. We can, for the purpose of securing more heating surface, extend the heated leg into a long incline (Fig. 5), when we have the well-known inclined-tube generator. Now, by adding other tubes, we may further increase the heating surface (Fig. 6), while it will still be the U-tube in effect and action. In such a construction the circulation is a function of the difference in density of the two columns. Its velocity is measured by the well-known Torricellian formula, V = (2gh)^{½}, or, approximately V = 8(h)^{½}, h being measured in terms of the lighter fluid. This velocity will increase until the rising column becomes all steam, but the quantity or weight circulated will attain a maximum when the density of the mingled steam and water in the rising column becomes one-half that of the solid water in the descending column which is nearly coincident with the condition of half steam and half water, the weight of the steam being very slight compared to that of the water. [Illustration: Fig. 6] It becomes easy by this rule to determine the circulation in any given boiler built on this principle, provided the construction is such as to permit a free flow of the water. Of course, every bend detracts a little and something is lost in getting up the velocity, but when the boiler is well arranged and proportioned these retardations are slight. Let us take for example one of the 240 horse-power Babcock & Wilcox boilers here in the University. The height of the columns may be taken as 4½ feet, measuring from the surface of the water to about the center of the bundle of tubes over the fire, and the head would be equal to this height at the maximum of circulation. We should, therefore, have a velocity of 8(4½)^{½} = 16.97, say 17 feet per second. There are in this boiler fourteen sections, each having a 4-inch tube opening into the drum, the area of which (inside) is 11 square inches, the fourteen aggregating 154 square inches, or 1.07 square feet. This multiplied by the velocity, 16.97 feet, gives 18.16 cubic feet mingled steam and water discharged per second, one-half of which, or 9.08 cubic feet, is steam. Assuming this steam to be at 100 pounds gauge pressure, it will weigh 0.258 pound per cubic foot. Hence, 2.34 pounds of steam will be discharged per second, and 8,433 pounds per hour. Dividing this by 30, the number of pounds representing a boiler horse power, we get 281.1 horse power, about 17 per cent, in excess of the rated power of the boiler. The water at the temperature of steam at 100 pounds pressure weighs 56 pounds per cubic foot, and the steam 0.258 pound, so that the steam forms but 1/218 part of the mixture by weight, and consequently each particle of water will make 218 circuits before being evaporated when working at this capacity, and circulating the maximum weight of water through the tubes. [Illustration: A Portion of 9600 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters Being Erected at the South Boston, Mass., Station of the Boston Elevated Railway Co. This Company Operates in its Various Stations a Total of 46,400 Horse Power of Babcock & Wilcox Boilers] [Illustration: Fig. 7] It is evident that at the highest possible velocity of exit from the generating tubes, nothing but steam will be delivered and there will be no circulation of water except to supply the place of that evaporated. Let us see at what rate of steaming this would occur with the boiler under consideration. We shall have a column of steam, say 4 feet high on one side and an equal column of water on the other. Assuming, as before, the steam at 100 pounds and the water at same temperature, we will have a head of 866 feet of steam and an issuing velocity of 235.5 feet per second. This multiplied by 1.07 square feet of opening by 3,600 seconds in an hour, and by 0.258 gives 234,043 pounds of steam, which, though only one-eighth the weight of mingled steam and water delivered at the maximum, gives us 7,801 horse power, or 32 times the rated power of the boiler. Of course, this is far beyond any possibility of attainment, so that it may be set down as certain that this boiler cannot be forced to a point where there will not be an efficient circulation of the water. By the same method of calculation it may be shown that when forced to double its rated power, a point rarely expected to be reached in practice, about two-thirds the volume of mixture of steam and water delivered into the drum will be steam, and that the water will make 110 circuits while being evaporated. Also that when worked at only about one-quarter its rated capacity, one-fifth of the volume will be steam and the water will make the rounds 870 times before it becomes steam. You will thus see that in the proportions adopted in this boiler there is provision for perfect circulation under all the possible conditions of practice. [Illustration: Fig. 8 [Developed to show Circulation]] In designing boilers of this style it is necessary to guard against having the uptake at the upper end of the tubes too large, for if sufficiently large to allow downward currents therein, the whole effect of the rising column in increasing the circulation in the tubes is nullified (Fig. 7). This will readily be seen if we consider the uptake very large when the only head producing circulation in the tubes will be that due to the inclination of each tube taken by itself. This objection is only overcome when the uptake is so small as to be entirely filled with the ascending current of mingled steam and water. It is also necessary that this uptake should be practically direct, and it should not be composed of frequent enlargements and contractions. Take, for instance, a boiler well known in Europe, copied and sold here under another name. It is made up of inclined tubes secured by pairs into boxes at the ends, which boxes are made to communicate with each other by return bends opposite the ends of the tubes. These boxes and return bends form an irregular uptake, whereby the steam is expected to rise to a reservoir above. You will notice (Fig. 8) that the upward current of steam and water in the return bend meets and directly antagonizes the upward current in the adjoining tube. Only one result can follow. If their velocities are equal, the momentum of both will be neutralized and all circulation stopped, or, if one be stronger, it will cause a back flow in the other by the amount of difference in force, with practically the same result. [Illustration: 4880 Horse-power Installation of Babcock & Wilcox Boilers at the Open Hearth Plant of the Cambria Steel Co., Johnstown, Pa. This Company Operates a Total of 52,000 Horse Power of Babcock & Wilcox Boilers] [Illustration: Fig. 9] In a well-known boiler, many of which were sold, but of which none are now made and a very few are still in use, the inventor claimed that the return bends and small openings against the tubes were for the purpose of "restricting the circulation" and no doubt they performed well that office; but excepting for the smallness of the openings they were not as efficient for that purpose as the arrangement shown in Fig. 8. [Illustration: Fig. 10] Another form of boiler, first invented by Clarke or Crawford, and lately revived, has the uptake made of boxes into which a number, generally from two to four tubes, are expanded, the boxes being connected together by nipples (Fig. 9). It is a well-known fact that where a fluid flows through a conduit which enlarges and then contracts, the velocity is lost to a greater or less extent at the enlargements, and has to be gotten up again at the contractions each time, with a corresponding loss of head. The same thing occurs in the construction shown in Fig. 9. The enlargements and contractions quite destroy the head and practically overcome the tendency of the water to circulate. A horizontal tube stopped at one end, as shown in Fig. 10, can have no proper circulation within it. If moderately driven, the water may struggle in against the issuing steam sufficiently to keep the surface covered, but a slight degree of forcing will cause it to act like the test tube in Fig. 3, and the more there are of them in a given boiler the more spasmodic will be its working. The experiment with our kettle (Fig. 2) gives the clue to the best means of promoting circulation in ordinary shell boilers. Steenstrup or "Martin" and "Galloway" water tubes placed in such boilers also assist in directing the circulation therein, but it is almost impossible to produce in shell boilers, by any means the circulation of all the water in one continuous round, such as marks the well-constructed water-tube boiler. As I have before remarked, provision for a proper circulation of water has been almost universally ignored in designing steam boilers, sometimes to the great damage of the owner, but oftener to the jeopardy of the lives of those who are employed to run them. The noted case of the Montana and her sister ship, where some $300,000 was thrown away in trying an experiment which a proper consideration of this subject would have avoided, is a case in point; but who shall count the cost of life and treasure not, perhaps, directly traceable to, but, nevertheless, due entirely to such neglect in design and construction of the thousands of boilers in which this necessary element has been ignored? In the light of the performance of the exacting conditions of present day power-plant practice, a review of this lecture and of the foregoing list of requirements reveals the insight of the inventors of the Babcock & Wilcox boiler into the fundamental principles of steam generator design and construction. Since the Babcock & Wilcox boiler became thoroughly established as a durable and efficient steam generator, many types of water-tube boilers have appeared on the market. Most of them, failing to meet enough of the requirements of a perfect boiler, have fallen by the wayside, while a few failing to meet all of the requirements, have only a limited field of usefulness. None have been superior, and in the most cases the most ardent admirers of other boilers have been satisfied in looking up to the Babcock & Wilcox boiler as a standard and in claiming that the newer boilers were "just as good." Records of recent performances under the most severe conditions of services on land and sea, show that the Babcock & Wilcox boiler can be run continually and regularly at higher overloads, with higher efficiency, and lower upkeep cost than any other boiler on the market. It is especially adapted for power-plant work where it is necessary to use a boiler in which steam can be raised quickly and the boiler placed on the line either from a cold state or from a banked fire in the shortest possible time, and with which the capacity, with clean feed water, will be largely limited by the amount of coal that can be burned in the furnace. The distribution of the circulation through the separate headers and sections and the action of the headers in forcing a maximum and continuous circulation in the lower tubes, permit the operation of the Babcock & Wilcox boiler without objectionable priming, with a higher degree of concentration of salts in the water than is possible in any other type of boiler. Repeated daily performances at overloads have demonstrated beyond a doubt the correctness of Mr. Babcock's computation regarding the circulating tube and header area required for most efficient circulation. They also have proved that enlargement of the area of headers and circulating tubes beyond a certain point diminishes the head available for causing circulation and consequently limits the ability of the boiler to respond to demands for overloads. In this lecture Mr. Babcock made the prediction that with the circulating tube area proportioned in accordance with the principles laid down, the Babcock & Wilcox boiler could be continuously run at double its nominal rating, which at that time was based on 12 square feet of heating surface per horse power. This prediction is being fulfilled daily in all the large and prominent power plants in this country and abroad, and it has been repeatedly demonstrated that with clean water and clean tube surfaces it is possible to safely operate at over 300 per cent of the nominal rating. In the development of electrical power stations it becomes more and more apparent that it is economical to run a boiler at high ratings during the times of peak loads, as by so doing the lay-over losses are diminished and the economy of the plant as a whole is increased. The number and importance of the large electric lighting and power stations constructed during the last ten years that are equipped with Babcock & Wilcox boilers, is a most gratifying demonstration of the merit of the apparatus, especially in view of their satisfactory operation under conditions which are perhaps more exacting than those of any other service. Time, the test of all, results with boilers as with other things, in the survival of the fittest. When judged on this basis the Babcock & Wilcox boiler stands pre-eminent in its ability to cover the whole field of steam generation with the highest commercial efficiency obtainable. Year after year the Babcock & Wilcox boiler has become more firmly established as the standard of excellence in the boiler making art. [Illustration: South Boston Station of the Boston Elevated Ry. Co., Boston, Mass. 9600 Horse Power of Babcock & Wilcox Boilers and Superheaters Installed in this Station] [Illustration: 3600 Horse-power Installation of Babcock & Wilcox Boilers at the Phipps Power House of the Duquesne Light Company, Pittsburgh, Pa.] EVOLUTION OF THE BABCOCK & WILCOX WATER-TUBE BOILER Quite as much may be learned from the records of failures as from those of success. Where a device has been once fairly tried and found to be imperfect or impracticable, the knowledge of that trial is of advantage in further investigation. Regardless of the lesson taught by failure, however, it is an almost every-day occurrence that some device or construction which has been tried and found wanting, if not worthless, is again introduced as a great improvement upon a device which has shown by its survival to be the fittest. The success of the Babcock & Wilcox boiler is due to many years of constant adherence to one line of research, in which an endeavor has been made to introduce improvements with the view to producing a boiler which would most effectively meet the demands of the times. During the periods that this boiler has been built, other companies have placed on the market more than thirty water-tube or sectional water-tube boilers, most of which, though they may have attained some distinction and sale, have now entirely disappeared. The following incomplete list will serve to recall the names of some of the boilers that have had a vogue at various times, but which are now practically unknown: Dimpfel, Howard, Griffith & Wundrum, Dinsmore, Miller "Fire Box", Miller "American", Miller "Internal Tube", Miller "Inclined Tube", Phleger, Weigant, the Lady Verner, the Allen, the Kelly, the Anderson, the Rogers & Black, the Eclipse or Kilgore, the Moore, the Baker & Smith, the Renshaw, the Shackleton, the "Duplex", the Pond & Bradford, the Whittingham, the Bee, the Hazleton or "Common Sense", the Reynolds, the Suplee or Luder, the Babbit, the Reed, the Smith, the Standard, etc., etc. It is with the object of protecting our customers and friends from loss through purchasing discarded ideas that there is given on the following pages a brief history of the development of the Babcock & Wilcox boiler as it is built to-day. The illustrations and brief descriptions indicate clearly the various designs and constructions that have been used and that have been replaced, as experience has shown in what way improvement might be made. They serve as a history of the experimental steps in the development of the present Babcock & Wilcox boiler, the value and success of which, as a steam generator, is evidenced by the fact that the largest and most discriminating users continue to purchase them after years of experience in their operation. [Illustration: No. 1] No. 1. The original Babcock & Wilcox boiler was patented in 1867. The main idea in its design was safety, to which all other features were sacrificed wherever they conflicted. The boiler consisted of a nest of horizontal tubes, serving as a steam and water reservoir, placed above and connected at each end by bolted joints to a second nest of inclined heating tubes filled with water. The tubes were placed one above the other in vertical rows, each row and its connecting end forming a single casting. Hand-holes were placed at each end for cleaning. Internal tubes were placed within the inclined tubes with a view to aiding circulation. No. 2. This boiler was the same as No. 1, except that the internal circulating tubes were omitted as they were found to hinder rather than help the circulation. Nos. 1 and 2 were found to be faulty in both material and design, cast metal proving unfit for heating surfaces placed directly over the fire, as it cracked as soon as any scale formed. No. 3. Wrought-iron tubes were substituted for the cast-iron heating tubes, the ends being brightened, laid in moulds, and the headers cast on. The steam and water capacity in this design were insufficient to secure regularity of action, there being no reserve upon which to draw during firing or when the water was fed intermittently. The attempt to dry the steam by superheating it in the nest of tubes forming the steam space was found to be impracticable. The steam delivered was either wet, dry or superheated, according to the rate at which it was being drawn from the boiler. Sediment was found to lodge in the lowermost point of the boiler at the rear end and the exposed portions cracked off at this point when subjected to the furnace heat. [Illustration: No. 4] No. 4. A plain cylinder, carrying the water line at its center and leaving the upper half for steam space, was substituted for the nest of tubes forming the steam and water space in Nos. 1, 2 and 3. The sections were made as in No. 3 and a mud drum added to the rear end of the sections at the point that was lowest and farthest removed from the fire. The gases were made to pass off at one side and did not come into contact with the mud drum. Dry steam was obtained through the increase of separating surface and steam space and the added water capacity furnished a storage for heat to tide over irregularities of firing and feeding. By the addition of the drum, the boiler became a serviceable and practical design, retaining all of the features of safety. As the drum was removed from the direct action of the fire, it was not subjected to excessive strain due to unequal expansion, and its diameter, if large in comparison with that of the tubes formerly used, was small when compared with that of cylindrical boilers. Difficulties were encountered in this boiler in securing reliable joints between the wrought-iron tubes and the cast-iron headers. [Illustration: No. 5] No. 5. In this design, wrought-iron water legs were substituted for the cast-iron headers, the tubes being expanded into the inside sheets and a large cover placed opposite the front end of the tubes for cleaning. The tubes were staggered one above the other, an arrangement found to be more efficient in the absorption of heat than where they were placed in vertical rows. In other respects, the boiler was similar to No. 4, except that it had lost the important element of safety through the introduction of the very objectionable feature of flat stayed surfaces. The large doors for access to the tubes were also a cause of weakness. An installation of these boilers was made at the plant of the Calvert Sugar Refinery in Baltimore, and while they were satisfactory in their operation, were never duplicated. [Illustration: No. 6] No. 6. This was a modification of No. 5 in which longer tubes were used and over which the gases were caused to make three passes with a view of better economy. In addition, some of the stayed surfaces were omitted and handholes substituted for the large access doors. A number of boilers of this design were built but their excessive first cost, the lack of adjustability of the structure under varying temperatures, and the inconvenience of transportation, led to No. 7. [Illustration: No. 7] No. 7. In this boiler, the headers and water legs were replaced by T-heads screwed to the ends of the inclined tubes. The faces of these Ts were milled and the tubes placed one above the other with the milled faces metal to metal. Long bolts passed through each vertical section of the T-heads and through connecting boxes on the heads of the drums holding the whole together. A large number of boilers of this design were built and many were in successful operation for over twenty years. In most instances, however, they were altered to later types. [Illustration: No. 8] [Illustration: No. 9] Nos. 8 and 9. These boilers were known as the Griffith & Wundrum type, the concern which built them being later merged in The Babcock & Wilcox Co. Experiments were made with this design with four passages of the gases across the tubes and the downward circulation of the water at the rear of the boiler was carried to the bottom row of tubes. In No. 9 an attempt was made to increase the safety and reduce the cost by reducing the amount of steam and water capacity. A drum at right angles to the line of tubes was used but as there was no provision made to secure dry steam, the results were not satisfactory. The next move in the direction of safety was the employment of several drums of small diameter instead of a single drum. [Illustration: No. 10] This is shown in No. 10. A nest of small horizontal drums, 15 inches in diameter, was used in place of the single drum of larger diameter. A set of circulation tubes was placed at an intermediate angle between the main bank of heating tubes and the horizontal drums forming the steam reservoir. These circulators were to return to the rear end of the circulating tubes the water carried up by the circulation, and in this way were to allow only steam to be delivered to the small drums above. There was no improvement in the action of this boiler over that of No. 9. The four passages of the gas over the tubes tried in Nos. 8, 9 and 10 were not found to add to the economy of the boiler. [Illustration: No. 11] No. 11. A trial was next made of a box coil system, in which the water was made to transverse the furnace several times before being delivered to the drum above. The tendency here, as in all similar boilers, was to form steam in the middle of the coil and blow the water from each end, leaving the tubes practically dry until the steam found an outlet and the water returned. This boiler had, in addition to a defective circulation, a decidedly geyser-like action and produced wet steam. [Illustration: No. 12] All of the types mentioned, with the exception of Nos. 5 and 6, had between their several parts a large number of bolted joints which were subjected to the action of the fire. When these boilers were placed in operation it was demonstrated that as soon as any scale formed on the heating surfaces, leaks were caused due to unequal expansion. No. 12. With this boiler, an attempt was made to remove the joints from the fire and to increase the heating surface in a given space. Water tubes were expanded into both sides of wrought-iron boxes, openings being made for the admission of water and the exit of steam. Fire tubes were placed inside the water tubes to increase the heating surface. This design was abandoned because of the rapid stopping up of the tubes by scale and the impossibility of cleaning them. [Illustration: No. 13] No. 13. Vertical straight line headers of cast iron, each containing two rows of tubes, were bolted to a connection leading to the steam and water drum above. [Illustration: No. 14] No. 14. A wrought-iron box was substituted for the double cast-iron headers. In this design, stays were necessary and were found, as always, to be an element to be avoided wherever possible. The boiler was an improvement on No. 6, however. A slanting bridge wall was introduced underneath the drum to throw a larger portion of its heating surface into the combustion chamber under the bank of tubes. This bridge wall was found to be difficult to keep in repair and was of no particular benefit. [Illustration: No. 15] No. 15. Each row of tubes was expanded at each end into a continuous header, cast of car wheel metal. The headers had a sinuous form so that they would lie close together and admit of a staggered position of the tubes when assembled. While other designs of header form were tried later, experience with Nos. 14 and 15 showed that the style here adopted was the best for all purposes and it has not been changed materially since. The drum in this design was supported by girders resting on the brickwork. Bolted joints were discarded, with the exception of those connecting the headers to the front and rear ends of the drums and the bottom of the rear headers to the mud drum. Even such joints, however, were found objectionable and were superseded in subsequent construction by short lengths of tubes expanded into bored holes. [Illustration: No. 16] No. 16. In this design, headers were tried which were made in the form of triangular boxes, in each of which there were three tubes expanded. These boxes were alternately reversed and connected by short lengths of expanded tubes, being connected to the drum by tubes bent in a manner to allow them to enter the shell normally. The joints between headers introduced an element of weakness and the connections to the drum were insufficient to give adequate circulation. [Illustration: No. 17] No. 17. Straight horizontal headers were next tried, alternately shifted right and left to allow a staggering of tubes. These headers were connected to each other and to the drums by expanded nipples. The objections to this boiler were almost the same as those to No. 16. [Illustration: No. 18] [Illustration: No. 19] Nos. 18 and 19. These boilers were designed primarily for fire protection purposes, the requirements demanding a small, compact boiler with ability to raise steam quickly. These both served the purpose admirably but, as in No. 9, the only provision made for the securing of dry steam was the use of the steam dome, shown in the illustration. This dome was found inadequate and has since been abandoned in nearly all forms of boiler construction. No other remedy being suggested at the time, these boilers were not considered as desirable for general use as Nos. 21 and 22. In Europe, however, where small size units were more in demand, No. 18 was modified somewhat and used largely with excellent results. These experiments, as they may now be called, although many boilers of some of the designs were built, clearly demonstrated that the best construction and efficiency required adherence to the following elements of design: 1st. Sinuous headers for each vertical row of tubes. 2nd. A separate and independent connection with the drum, both front and rear, for each vertical row of tubes. [Illustration: No. 20A] [Illustration: No. 20B] 3rd. All joints between parts of the boiler proper to be made without bolts or screw plates. 4th. No surfaces to be used which necessitate the use of stays. 5th. The boiler supported independently of the brickwork so as to allow freedom for expansion and contraction as it is heated or cooled. 6th. Ample diameter of steam and water drums, these not to be less than 30 inches except for small size units. 7th. Every part accessible for cleaning and repairs. With these points having been determined, No. 20 was designed. This boiler had all the desirable features just enumerated, together with a number of improvements as to detail of construction. The general form of No. 15 was adhered to but the bolted connections between sections and drum and sections and mud drum were discarded in favor of connections made by short lengths of boiler tubes expanded into the adjacent parts. This boiler was suspended from girders, like No. 15, but these in turn were carried on vertical supports, leaving the pressure parts entirely free from the brickwork, the mutually deteriorating strains present where one was supported by the other being in this way overcome. Hundreds of thousands of horse power of this design were built, giving great satisfaction. The boiler was known as the "C. I. F." (cast-iron front) style, an ornamental cast-iron front having been usually furnished. [Illustration: No. 21] The next step, and the one which connects the boilers as described above to the boiler as it is built to-day, was the design illustrated in No. 21. These boilers were known as the "W. I. F." style, the fronts furnished as part of the equipment being constructed largely of wrought iron. The cast-iron drumheads used in No. 20 were replaced by wrought-steel flanged and "bumped" heads. The drums were made longer and the sections connected to wrought-steel cross boxes riveted to the bottom of the drums. The boilers were supported by girders and columns as in No. 20. [Illustration: No. 22] No. 22. This boiler, which is designated as the "Vertical Header" type, has the same general features of construction as No. 21, except that the tube sheet side of the headers is "stepped" to allow the headers to be placed vertically and at right angles to the drum and still maintain the tubes at the angle used in Nos. 20 and 21. [Illustration: No. 23] No. 23, or the cross drum design of boiler, is a development of the Babcock & Wilcox marine boiler, in which the cross drum is used exclusively. The experience of the Glasgow Works of The Babcock & Wilcox, Ltd., with No. 18 proved that proper attention to details of construction would make it a most desirable form of boiler where headroom was limited. A large number of this design have been successfully installed and are giving satisfactory results under widely varying conditions. The cross drum boiler is also built in a vertical header design. Boilers Nos. 21, 22 and 23, with a few modifications, are now the standard forms. These designs are illustrated, as they are constructed to-day, on pages 48, 52, 54, 58 and 60. The last step in the development of the water-tube boiler, beyond which it seems almost impossible for science and skill to advance, consists in the making of all pressure parts of the boiler of wrought steel, including sinuous headers, cross boxes, nozzles, and the like. This construction was the result of the demands of certain Continental laws that are coming into general vogue in this country. The Babcock & Wilcox Co. have at the present time a plant producing steel forgings that have been pronounced by the _London Engineer_ to be "a perfect triumph of the forgers' art". The various designs of this all wrought-steel boiler are fully illustrated in the following pages. [Illustration: Wrought-steel Vertical Header Longitudinal Drum Babcock & Wilcox Boiler, Equipped with Babcock & Wilcox Superheater and Babcock & Wilcox Chain Grate Stoker] THE BABCOCK & WILCOX BOILER The following brief description of the Babcock & Wilcox boiler will clearly indicate the manner in which it fulfills the requirements of the perfect steam boiler already enumerated. The Babcock & Wilcox boiler is built in two general classes, the longitudinal drum type and the cross drum type. Either of these designs may be constructed with vertical or inclined headers, and the headers in turn may be of wrought steel or cast iron dependent upon the working pressure for which the boiler is constructed. The headers may be of different lengths, that is, may connect different numbers of tubes, and it is by a change in the number of tubes in height per section and the number of sections in width that the size of the boiler is varied. The longitudinal drum boiler is the generally accepted standard of Babcock & Wilcox construction. The cross drum boiler, though originally designed to meet certain conditions of headroom, has become popular for numerous classes of work where low headroom is not a requirement which must be met. LONGITUDINAL DRUM CONSTRUCTION--The heating surface of this type of boiler is made up of a drum or drums, depending upon the width of the boiler extending longitudinally over the other pressure parts. To the drum or drums there are connected through cross boxes at either end the sections, which are made up of headers and tubes. At the lower end of the sections there is a mud drum extending entirely across the setting and connected to all sections. The connections between all parts are by short lengths of tubes expanded into bored seats. [Illustration: Forged-steel Drumhead with Manhole Plate in Position] The drums are of three sheets, of such thickness as to give the required factor of safety under the maximum pressure for which the boiler is constructed. The circular seams are ordinarily single lap riveted though these may be double lap riveted to meet certain requirements of pressure or of specifications. The longitudinal seams are properly proportioned butt and strap or lap riveted joints dependent upon the pressure for which the boilers are built. Where butt strap joints are used the straps are bent to the proper radius in an hydraulic press. The courses are built independently to template and are assembled by an hydraulic forcing press. All riveted holes are punched one-quarter inch smaller than the size of rivets as driven and are reamed to full size after the plates are assembled. All rivets are driven by hydraulic pressure and held until black. [Illustration: Forged-steel Drumhead Interior] The drumheads are hydraulic forged at a single heat, the manhole opening and stiffening ring being forged in position. Flat raised seats for water column and feed connections are formed in the forging. All heads are provided with manholes, the edges of which are turned true. The manhole plates are of forged steel and turned to fit manhole opening. These plates are held in position by forged-steel guards and bolts. The drum nozzles are of forged steel, faced, and fitted with taper thread stud bolts. [Illustration: Forged-steel Drum Nozzle] Cross boxes by means of which the sections are attached to the drums, are of forged steel, made from a single sheet. Where two or more drums are used in one boiler they are connected by a cross pipe having a flanged outlet for the steam connection. [Illustration: Forged-steel Cross Box] The sections are built of 4-inch hot finished seamless open-hearth steel tubes of No. 10 B. W. G. where the boilers are built for working pressures up to 210 pounds. Where the working pressure is to be above this and below 260 pounds, No. 9 B. W. G. tubes are supplied. [Illustration: Inside Handhole Fittings Wrought-steel Vertical Header] The tubes are expanded into headers of serpentine or sinuous form, which dispose the tubes in a staggered position when assembled as a complete boiler. These headers are of wrought steel or of cast iron, the latter being ordinarily supplied where the working pressure is not to exceed 160 pounds. The headers may be either vertical or inclined as shown in the various illustrations of assembled boilers. [Illustration: Wrought-steel Vertical Header] Opposite each tube end in the headers there is placed a handhole of sufficient size to permit the cleaning, removal or renewal of a tube. These openings in the wrought steel vertical headers are elliptical in shape, machine faced, and milled to a true plane back from the edge a sufficient distance to make a seat. The openings are closed by inside fitting forged plates, shouldered to center in the opening, their flanged seats milled to a true plane. These plates are held in position by studs and forged-steel binders and nuts. The joints between plates and headers are made with a thin gasket. [Illustration: Inside Handhole Fitting Wrought-steel Inclined Header] In the wrought-steel inclined headers the handhole openings are either circular or elliptical, the former being ordinarily supplied. The circular openings have a raised seat milled to a true plane. The openings are closed on the outside by forged-steel caps, milled and ground true, held in position by forged-steel safety clamps and secured by ball-headed bolts to assure correct alignment. With this style of fitting, joints are made tight, metal to metal, without packing of any kind. [Illustration: Wrought-steel Inclined Header] Where elliptical handholes are furnished they are faced inside, closed by inside fitting forged-steel plates, held to their seats by studs and secured by forged-steel binders and nuts. The joints between plates and header are made with a thin gasket. [Illustration: Cast-iron Vertical Header] The vertical cast-iron headers have elliptical handholes with raised seats milled to a true plane. These are closed on the outside by cast-iron caps milled true, held in position by forged-steel safety clamps, which close the openings from the inside and which are secured by ball-headed bolts to assure proper alignment. All joints are made tight, metal to metal, without packing of any kind. The mud drum to which the sections are attached at the lower end of the rear headers, is a forged-steel box 7¼ inches square, and of such length as to be connected to all headers by means of wrought nipples expanded into counterbored seats. The mud drum is furnished with handholes for cleaning, these being closed from the inside by forged-steel plates with studs, and secured on a faced seat in the mud drum by forged-steel binders and nuts. The joints between the plates and the drum are made with thin gaskets. The mud drum is tapped for blow-off connection. All connections between drums and sections and between sections and mud drum are of hot finished seamless open-hearth steel tubes of No. 9 B. W. G. Boilers of the longitudinal drum type are suspended front and rear from wrought-steel supporting frames entirely independent of the brickwork. This allows for expansion and contraction of the pressure parts without straining either the boiler or the brickwork, and also allows of brickwork repair or renewal without in any way disturbing the boiler or its connections. [Illustration: Babcock & Wilcox Wrought-steel Vertical Header Cross Drum Boiler] CROSS DRUM CONSTRUCTION--The cross drum type of boilers differs from the longitudinal only in drum construction and method of support. The drum in this type is placed transversely across the rear of the boiler and is connected to the sections by means of circulating tubes expanded into bored seats. The drums for all pressures are of two sheets of sufficient thickness to give the required factor of safety. The longitudinal seams are double riveted butt strapped, the straps being bent to the proper radius in an hydraulic press. The circulating tubes are expanded into the drums at the seams, the butt straps serving as tube seats. The drumheads, drum fittings and features of riveting are the same in the cross drum as in the longitudinal types. The sections and mud drum are also the same for the two types. Cross drum boilers are supported at the rear on the mud drum which rests on cast-iron foundation plates. They are suspended at the front from a wrought-iron supporting frame, each section being suspended independently from the cross members by hook suspension bolts. This method of support is such as to allow for expansion and contraction without straining either the boiler or the brickwork and permits of repair or renewal of the latter without in any way disturbing the boiler or its connections. The following features of design and of attachments supplied are the same for all types. FRONTS--Ornamental fronts are fitted to the front supporting frame. These have large doors for access to the front headers and panels above the fire fronts. The fire fronts where furnished have independent frames for fire doors which are bolted on, and ashpit doors fitted with blast catches. The lugs on door frames and on doors are cast solid. The faces of doors and of frames are planed and the lugs milled. The doors and frames are placed in their final relative position, clamped, and the holes for hinge pins drilled while thus held. A perfect alignment of door and frame is thus assured and the method is representative of the care taken in small details of manufacture. The front as a whole is so arranged that any stoker may be applied with but slight modification wherever boilers are set with sufficient furnace height. [Illustration: Cross Drum Boiler Front] In the vertical header boilers large wrought-iron doors, which give access to the rear headers, are attached to the rear supporting frame. [Illustration: Wrought-steel Inclined Header Longitudinal Drum Babcock & Wilcox Boiler, Equipped with Babcock & Wilcox Superheater] [Illustration: Automatic Drumhead Stop and Check Valve] FITTINGS--Each boiler is provided with the following fittings as part of the standard equipment: Blow-off connections and valves attached to the mud drum. Safety valves placed on nozzles on the steam drums. A water column connected to the front of the drum. A steam gauge attached to the boiler front. Feed water connection and valves. A flanged stop and check valve of heavy pattern is attached directly to each drumhead, closing automatically in case of a rupture in the feed line. All valves and fittings are substantially built and are of designs which by their successful service for many years have become standard with The Babcock & Wilcox Co. The fixtures that are supplied with the boilers consist of: Dead plates and supports, the plates arranged for a fire brick lining. A full set of grate bars and bearers, the latter fitted with expansion sockets for side walls. Flame bridge plates with necessary fastenings, and special fire brick for lining same. Bridge wall girder for hanging bridge wall with expansion sockets for side walls. A full set of access and cleaning doors through which all portions of the pressure parts may be reached. A swing damper and frame with damper operating rig. There are also supplied with each boiler a wrench for handhole nuts, a water-driven turbine tube cleaner, a set of fire tools and a metal steam hose and cleaning pipe equipped with a special nozzle for blowing dust and soot from the tubes. Aside from the details of design and construction as covered in the foregoing description, a study of the illustrations will make clear the features of the boiler as a whole which have led to its success. The method of supporting the boiler has been described. This allows it to be hung at any height that may be necessary to properly handle the fuel to be burned or to accommodate the stoker to be installed. The height of the nest of tubes which forms the roof of the furnace is thus the controlling feature in determining the furnace height, or the distance from the front headers to the floor line. The sides and front of the furnace are formed by the side and front boiler walls. The rear wall of the furnace consists of a bridge wall built from the bottom of the ashpit to the lower row of tubes. The location of this wall may be adjusted within limits to give the depth of furnace demanded by the fuel used. Ordinarily the bridge wall is the determining feature in the locating of the front baffle. Where a great depth of furnace is necessary, in which case, if the front baffle were placed at the bridge wall the front pass of the boiler would be relatively too long, a patented construction is used which maintains the baffle in what may be considered its normal position, and a connection made between the baffle and the bridge wall by means of a tile roof. Such furnace construction is known as a "Webster" furnace. [Illustration: Longitudinal Drum Boiler--Front View] A consideration of this furnace will clearly indicate its adaptability, by reason of its flexibility, for any fuel and any design of stoker. The boiler lends itself readily to installation with an extension or Dutch oven furnace if this be demanded by the fuel to be used, and in general it may be stated that a satisfactory furnace arrangement may be made in connection with a Babcock & Wilcox boiler for burning any fuel, solid, liquid or gaseous. The gases of combustion evolved in the furnace above described are led over the heating surfaces by two baffles. These are formed of cast-iron baffle plates lined with special fire brick and held in position by tube clamps. The front baffle leads the gases through the forward portion of the tubes to a chamber beneath the drum or drums. It is in this chamber that a superheater is installed where such an apparatus is desired. The gases make a turn over the front baffle, are led downward through the central portion of the tubes, called the second pass, by means of a hanging bridge wall of brick and the second baffle, around which they make a second turn upward, pass through the rear portion of the tubes and are led to the stack or flue through a damper box in the rear wall, or around the drums to a damper box placed overhead. The space beneath the tubes between the bridge wall and the rear boiler wall forms a pocket into which much of the soot from the gases in their downward passage through the second pass will be deposited and from which it may be readily cleaned through doors furnished for the purpose. The gas passages are ample and are so proportioned that the resistance offered to the gases is only such as will assure the proper abstraction of heat from the gases without causing undue friction, requiring excessive draft. [Illustration: Partial Vertical Section Showing Method of Introducing Feed Water] The method in which the feed water is introduced through the front drumhead of the boiler is clearly seen by reference to the illustration. From this point of introduction the water passes to the rear of the drum, downward through the rear circulating tubes to the sections, upward through the tubes of the sections to the front headers and through these headers and front circulating tubes again to the drum where such water as has not been formed into steam retraces its course. The steam formed in the passage through the tubes is liberated as the water reaches the front of the drum. The steam so formed is stored in the steam space above the water line, from which it is drawn through a so-called "dry pipe." The dry pipe in the Babcock & Wilcox boiler is misnamed, as in reality it fulfills none of the functions ordinarily attributed to such a device. This function is usually to restrict the flow of steam from a boiler with a view to avoid priming. In the Babcock & Wilcox boiler its function is simply that of a collecting pipe, and as the aggregate area of the holes in it is greatly in excess of the area of the steam outlet from the drum, it is plain that there can be no restriction through this collecting pipe. It extends nearly the length of the drum, and draws steam evenly from the whole length of the steam space. [Illustration: Cast-iron Vertical Header Longitudinal Drum Babcock & Wilcox Boiler] [Illustration: Closed Open Patented Side Dusting Doors] The large tube doors through which access is had to the front headers and the doors giving such access to the rear headers in boilers of the vertical header type have already been described and are shown clearly by the illustrations on pages 56 and 74. In boilers of the inclined header type, access to the rear headers is secured through the chamber formed by the headers and the rear boiler wall. Large doors in the sides of the setting give full access to all parts for inspection and for removal of accumulations of soot. Small dusting doors are supplied for the side walls through which all of the heating surfaces may be cleaned by means of a steam dusting lance. These side dusting doors are a patented feature and the shutters are self closing. In wide boilers additional cleaning doors are supplied at the top of the setting to insure ease in reaching all portions of the heating surface. The drums are accessible for inspection through the manhole openings. The removal of the handhole plates makes possible the inspection of each tube for its full length and gives the assurance that no defect can exist that cannot be actually seen. This is particularly advantageous when inspecting for the presence of scale. The materials entering into the construction of the Babcock & Wilcox boiler are the best obtainable for the special purpose for which they are used and are subjected to rigid inspection and tests. The boilers are manufactured by means of the most modern shop equipment and appliances in the hands of an old and well-tried organization of skilled mechanics under the supervision of experienced engineers. [Illustration: Cast-iron Vertical Header Cross Drum Babcock & Wilcox Boiler] ADVANTAGES OF THE BABCOCK & WILCOX BOILER The advantages of the Babcock & Wilcox boiler may perhaps be most clearly set forth by a consideration, 1st, of water-tube boilers as a class as compared with shell and fire-tube boilers; and 2nd, of the Babcock & Wilcox boiler specifically as compared with other designs of water-tube boilers. WATER-TUBE _VERSUS_ FIRE-TUBE BOILERS Safety--The most important requirement of a steam boiler is that it shall be safe in so far as danger from explosion is concerned. If the energy in a large shell boiler under pressure is considered, the thought of the destruction possible in the case of an explosion is appalling. The late Dr. Robert H. Thurston, Dean of Sibley College, Cornell University, and past president of the American Society of Mechanical Engineers, estimated that there is sufficient energy stored in a plain cylinder boiler under 100 pounds steam pressure to project it in case of an explosion to a height of over 3½ miles; a locomotive boiler at 125 pounds pressure from one-half to one-third of a mile; and a 60 horse-power return tubular boiler under 75 pounds pressure somewhat over a mile. To quote: "A cubic foot of heated water under a pressure of from 60 to 70 pounds per square inch has about the same energy as one pound of gunpowder." From such a consideration, it may be readily appreciated how the advent of high pressure steam was one of the strongest factors in forcing the adoption of water-tube boilers. A consideration of the thickness of material necessary for cylinders of various diameters under a steam pressure of 200 pounds and assuming an allowable stress of 12,000 pounds per square inch, will perhaps best illustrate this point. Table 1 gives such thicknesses for various diameters of cylinders not taking into consideration the weakening effect of any joints which may be necessary. The rapidity with which the plate thickness increases with the diameter is apparent and in practice, due to the fact that riveted joints must be used, the thicknesses as given in the table, with the exception of the first, must be increased from 30 to 40 per cent. In a water-tube boiler the drums seldom exceed 48 inches in diameter and the thickness of plate required, therefore, is never excessive. The thinner metal can be rolled to a more uniform quality, the seams admit of better proportioning, and the joints can be more easily and perfectly fitted than is the case where thicker plates are necessary. All of these points contribute toward making the drums of water-tube boilers better able to withstand the stress which they will be called upon to endure. The essential constructive difference between water-tube and fire-tube boilers lies in the fact that the former is composed of parts of relatively small diameter as against the large diameters necessary in the latter. The factor of safety of the boiler parts which come in contact with the most intense heat in water-tube boilers can be made much higher than would be practicable in a shell boiler. Under the assumptions considered above in connection with the thickness of plates required, a number 10 gauge tube (0.134 inch), which is standard in Babcock & Wilcox boilers for pressures up to 210 pounds under the same allowable stress as was used in computing Table 1, the safe working pressure for the tubes is 870 pounds per square inch, indicating the very large margin of safety of such tubes as compared with that possible with the shell of a boiler. TABLE 1 PLATE THICKNESS REQUIRED FOR VARIOUS CYLINDER DIAMETERS ALLOWABLE STRESS, 12000 POUNDS PER SQUARE INCH, 200 POUNDS GAUGE PRESSURE, NO JOINTS +---------+-----------+ |Diameter | Thickness | |Inches | Inches | +---------+-----------+ | 4 | 0.033 | | 36 | 0.300 | | 48 | 0.400 | | 60 | 0.500 | | 72 | 0.600 | | 108 | 0.900 | | 120 | 1.000 | | 144 | 1.200 | +---------+-----------+ A further advantage in the water-tube boiler as a class is the elimination of all compressive stresses. Cylinders subjected to external pressures, such as fire tubes or the internally fired furnaces of certain types of boilers, will collapse under a pressure much lower than that which they could withstand if it were applied internally. This is due to the fact that if there exists any initial distortion from its true shape, the external pressure will tend to increase such distortion and collapse the cylinder, while an internal pressure tends to restore the cylinder to its original shape. Stresses due to unequal expansion have been a fruitful source of trouble in fire-tube boilers. In boilers of the shell type, the riveted joints of the shell, with their consequent double thickness of metal exposed to the fire, gives rise to serious difficulties. Upon these points are concentrated all strains of unequal expansion, giving rise to frequent leaks and oftentimes to actual ruptures. Moreover, in the case of such rupture, the whole body of contained water is liberated instantaneously and a disastrous and usually fatal explosion results. Further, unequal strains result in shell or fire-tube boilers due to the difference in temperature of the various parts. This difference in temperature results from the lack of positive well defined circulation. While such a circulation does not necessarily accompany all water-tube designs, in general, the circulation in water-tube boilers is much more defined than in fire-tube or shell boilers. A positive and efficient circulation assures that all portions of the pressure parts will be at approximately the same temperature and in this way strains resulting from unequal temperatures are obviated. If a shell or fire-tubular boiler explodes, the apparatus as a whole is destroyed. In the case of water-tube boilers, the drums are ordinarily so located that they are protected from intense heat and any rupture is usually in the case of a tube. Tube failures, resulting from blisters or burning, are not serious in their nature. Where a tube ruptures because of a flaw in the metal, the result may be more severe, but there cannot be the disastrous explosion such as would occur in the case of the explosion of a shell boiler. To quote Dr. Thurston, relative to the greater safety of the water-tube boiler: "The stored available energy is usually less than that of any of the other stationary boilers and not very far from the amount stored, pound for pound, in the plain tubular boiler. It is evident that their admitted safety from destructive explosion does not come from this relation, however, but from the division of the contents into small portions and especially from those details of construction which make it tolerably certain that any rupture shall be local. A violent explosion can only come from the general disruption of a boiler and the liberation at once of large masses of steam and water." Economy--The requirement probably next in importance to safety in a steam boiler is economy in the use of fuel. To fulfill such a requirement, the three items, of proper grate for the class of fuel to be burned, a combustion chamber permitting complete combustion of gases before their escape to the stack, and the heating surface of such a character and arrangement that the maximum amount of available heat may be extracted, must be co-ordinated. Fire-tube boilers from the nature of their design do not permit the variety of combinations of grate surface, heating surface, and combustion space possible in practically any water-tube boiler. In securing the best results in fuel economy, the draft area in a boiler is an important consideration. In fire-tube boilers this area is limited to the cross sectional area of the fire tubes, a condition further aggravated in a horizontal boiler by the tendency of the hot gases to pass through the upper rows of tubes instead of through all of the tubes alike. In water-tube boilers the draft area is that of the space outside of the tubes and is hence much greater than the cross sectional area of the tubes. Capacity--Due to the generally more efficient circulation found in water-tube than in fire-tube boilers, rates of evaporation are possible with water-tube boilers that cannot be approached where fire-tube boilers are employed. Quick Steaming--Another important result of the better circulation ordinarily found in water-tube boilers is in their ability to raise steam rapidly in starting and to meet the sudden demands that may be thrown on them. In a properly designed water-tube boiler steam may be raised from a cold boiler to 200 pounds pressure in less than one-half hour. For the sake of comparison with the figure above, it may be stated that in the U. S. Government Service the shortest time allowed for getting up steam in Scotch marine boilers is 6 hours and the time ordinarily allowed is 12 hours. In large double-ended Scotch boilers, such as are generally used in Trans-Atlantic service, the fires are usually started 24 hours before the time set for getting under way. This length of time is necessary for such boilers in order to eliminate as far as possible excessive strains resulting from the sudden application of heat to the surfaces. Accessibility--In the "Requirements of a Perfect Steam Boiler", as stated by Mr. Babcock, he demonstrates the necessity for complete accessibility to all portions of the boiler for cleaning, inspection and repair. Cleaning--When the great difference is realized in performance, both as to economy and capacity of a clean boiler and one in which the heating surfaces have been allowed to become fouled, it may be appreciated that the ability to keep heating surfaces clean internally and externally is a factor of the highest importance. Such results can be accomplished only by the use of a design in boiler construction which gives complete accessibility to all portions. In fire-tube boilers the tubes are frequently nested together with a space between them often less than 1¼ inches and, as a consequence, nearly the entire tube surface is inaccessible. When scale forms upon such tubes it is impossible to remove it completely from the inside of the boiler and if it is removed by a turbine hammer, there is no way of knowing how thorough a job has been done. With the formation of such scale there is danger through overheating and frequent tube renewals are necessary. [Illustration: Portion of 29,000 Horse-power Installation of Babcock & Wilcox Boilers in the L Street Station of the Edison Electric Illuminating Co. of Boston, Mass. This Company Operates in its Various Stations a Total of 39,000 Horse Power of Babcock & Wilcox Boilers] In Scotch marine boilers, even with the engines operating condensing, complete tube renewals at intervals of six or seven years are required, while large replacements are often necessary in less than one year. In return tubular boilers operated with bad feed water, complete tube renewals annually are not uncommon. In this type of boiler much sediment falls on the bottom sheets where the intense heat to which they are subjected bakes it to such an excessive hardness that the only method of removing it is to chisel it out. This can be done only by omitting tubes enough to leave a space into which a man can crawl and the discomforts under which he must work are apparent. Unless such a deposit is removed, a burned and buckled plate will invariably result, and if neglected too long an explosion will follow. In vertical fire-tube boilers using a water leg construction, a deposit of mud in such legs is an active agent in causing corrosion and the difficulty of removing such deposit through handholes is well known. A complete removal is practically impossible and as a last resort to obviate corrosion in certain designs, the bottom of the water legs in some cases have been made of copper. A thick layer of mud and scale is also liable to accumulate on the crown sheet of such boilers and may cause the sheet to crack and lead to an explosion. The soot and fine coal swept along with the gases by the draft will settle in fire tubes and unless removed promptly, must be cut out with a special form of scraper. It is not unusual where soft coal is used to find tubes half filled with soot, which renders useless a large portion of the heating surface and so restricts the draft as to make it difficult to burn sufficient coal to develop the required power from such heating surface as is not covered by soot. Water-tube boilers in general are from the nature of their design more readily accessible for cleaning than are fire-tube boilers. Inspection--The objections given above in the consideration of the inability to properly clean fire-tube boilers hold as well for the inspection of such boilers. Repairs--The lack of accessibility in fire-tube boilers further leads to difficulties where repairs are required. In fire-tube boilers tube renewals are a serious undertaking. The accumulation of hard deposit on the exterior of the surfaces so enlarges the tubes that it is oftentimes difficult, if not impossible, to draw them through the tube sheets and it is usually necessary to cut out such tubes as will allow access to the one which has failed and remove them through the manhole. When a tube sheet blisters, the defective part must be cut out by hand-tapped holes drilled by ratchets and as it is frequently impossible to get space in which to drive rivets, a "soft patch" is necessary. This is but a makeshift at best and usually results in either a reduction of the safe working pressure or in the necessity for a new plate. If the latter course is followed, the old plate must be cut out, a new one scribed to place to locate rivet holes and in order to obtain room for driving rivets, the boiler will have to be re-tubed. The setting must, of course, be at least partially torn out and replaced. In case of repairs, of such nature in fire-tube boilers, the working pressure of such repaired boilers will frequently be lowered by the insurance companies when the boiler is again placed in service. In the case of a rupture in a water-tube boiler, the loss will ordinarily be limited to one or two tubes which can be readily replaced. The fire-tube boiler will be so completely demolished that the question of repairs will be shifted from the boiler to the surrounding property, the damage to which will usually exceed many times the cost of a boiler of a type which would have eliminated the possibility of a disastrous explosion. In considering the proper repair cost of the two types of boilers, the fact should not be overlooked that it is poor economy to invest large sums in equipment that, through a possible accident to the boiler may be wholly destroyed or so damaged that the cost of repairs, together with the loss of time while such repairs are being made, would purchase boilers of absolute safety and leave a large margin beside. The possibility of loss of human life should also be considered, though this may seem a far cry from the question of repair costs. Space Occupied--The space required for the boilers in a plant often exceeds the requirements for the remainder of the plant equipment. Any saving of space in a boiler room will be a large factor in reducing the cost of real estate and of the building. Even when the boiler plant is comparatively small, the saving in space frequently will amount to a considerable percentage of the cost of the boilers. Table 2 shows the difference in floor space occupied by fire-tube boilers and Babcock & Wilcox boilers of the same capacity, the latter being taken as representing the water-tube class. This saving in space will increase with the size of the plant for the reason that large size boiler units while common in water-tube practice are impracticable in fire-tube practice. TABLE 2 COMPARATIVE APPROXIMATE FLOOR SPACE OCCUPIED BY BABCOCK & WILCOX AND H. R. T. BOILERS +------------+----------------+---------------+ |Size of unit|Babcock & Wilcox| H. R. T. | |Horse Power |Feet and Inches |Feet and Inches| +------------+----------------+---------------+ | 100 | 7 3 × 19 9 | 10 0 × 20 0 | | 150 | 7 10 × 19 9 | 10 0 × 22 6 | | 200 | 9 0 × 19 9 | 11 6 × 23 10 | | 250 | 9 0 × 19 9 | 11 6 × 23 10 | | 300 | 10 2 × 19 9 | 12 0 × 25 0 | +------------+----------------+---------------+ BABCOCK & WILCOX BOILERS AS COMPARED WITH OTHER WATER-TUBE DESIGNS It must be borne in mind that the simple fact that a boiler is of the water-tube design does not as a necessity indicate that it is a good or safe boiler. Safety--Many of the water-tube boilers on the market are as lacking as are fire-tube boilers in the positive circulation which, as has been demonstrated by Mr. Babcock's lecture, is so necessary in the requirements of the perfect steam boiler. In boilers using water-leg construction, there is danger of defective circulation, leaks are common, and unsuspected corrosion may be going on in portions of the boiler that cannot be inspected. Stresses due to unequal expansion of the metal cannot be well avoided but they may be minimized by maintaining at the same temperature all pressure parts of the boiler. The result is to be secured only by means of a well defined circulation. The main feature to which the Babcock & Wilcox boiler owes its safety is the construction made possible by the use of headers, by which the water in each vertical row of tubes is separated from that in the adjacent rows. This construction results in the very efficient circulation produced through the breaking up of the steam and water in the front headers, the effect of these headers in producing such a positive circulation having been clearly demonstrated in Mr. Babcock's lecture. The use of a number of sections, thus composed of headers and tubes, has a distinct advantage over the use of a common chamber at the outlet ends of the tubes. In the former case the circulation of water in one vertical row of tubes cannot interfere with that in the other rows, while in the latter construction there will be downward as well as upward currents and such downward currents tend to neutralize any good effect there might be through the diminution of the density of the water column by the steam. Further, the circulation results directly from the design of the boiler and requires no assistance from "retarders", check valves and the like, within the boiler. All such mechanical devices in the interior of a boiler serve only to complicate the design and should not be used. This positive and efficient circulation assures that all portions of the pressure parts of the Babcock & Wilcox boiler will be at approximately the same temperature and in this way strains resulting from unequal temperatures are obviated. Where the water throughout the boiler is at the temperature of the steam contained, a condition to be secured only by proper circulation, danger from internal pitting is minimized, or at least limited only to effects of the water fed the boiler. Where the water in any portion of the boiler is lower than the temperature of the steam corresponding to the pressure carried, whether the fact that such lower temperatures exist as a result of lack of circulation, or because of intentional design, internal pitting or corrosion will almost invariably result. Dr. Thurston has already been quoted to the effect that the admitted safety of a water-tube boiler is the result of the division of its contents into small portions. In boilers using a water-leg construction, while the danger from explosion will be largely limited to the tubes, there is the danger, however, that such legs may explode due to the deterioration of their stays, and such an explosion might be almost as disastrous as that of a shell boiler. The headers in a Babcock & Wilcox boiler are practically free from any danger of explosion. Were such an explosion to occur, it would still be localized to a much larger extent than in the case of a water-leg boiler and the header construction thus almost absolutely localizes any danger from such a cause. Staybolts are admittedly an undesirable element of construction in any boiler. They are wholly objectionable and the only reason for the presence of staybolts in a boiler is to enable a cheaper form of construction to be used than if they were eliminated. In boilers utilizing in their design flat-stayed surfaces, or staybolt construction under pressure, corrosion and wear and tear in service tends to weaken some single part subject to continual strain, the result being an increased strain on other parts greatly in excess of that for which an allowance can be made by any reasonable factor of safety. Where the construction is such that the weakening of a single part will produce a marked decrease in the safety and reliability of the whole, it follows of necessity, that there will be a corresponding decrease in the working pressure which may be safely carried. In water-leg boilers, the use of such flat-stayed surfaces under pressure presents difficulties that are practically unsurmountable. Such surfaces exposed to the heat of the fire are subject to unequal expansion, distortion, leakage and corrosion, or in general, to many of the objections that have already been advanced against the fire-tube boilers in the consideration of water-tube boilers as a class in comparison with fire-tube boilers. [Illustration: McAlpin Hotel, New York City, Operating 2360 Horse Power of Babcock & Wilcox Boilers] Aside from the difficulties that may arise in actual service due to the failure of staybolts, or in general, due to the use of flat-stayed surfaces, constructional features are encountered in the actual manufacture of such boilers that make it difficult if not impossible to produce a first-class mechanical job. It is practically impossible in the building of such a boiler to so design and place the staybolts that all will be under equal strain. Such unequal strains, resulting from constructional difficulties, will be greatly multiplied when such a boiler is placed in service. Much of the riveting in boilers of this design must of necessity be hand work, which is never the equal of machine riveting. The use of water-leg construction ordinarily requires the flanging of large plates, which is difficult, and because of the number of heats necessary and the continual working of the material, may lead to the weakening of such plates. In vertical or semi-vertical water-tube boilers utilizing flat-stayed surfaces under pressure, these surfaces are ordinarily so located as to offer a convenient lodging place for flue dust, which fuses into a hard mass, is difficult of removal and under which corrosion may be going on with no possibility of detection. Where stayed surfaces or water legs are features in the design of a water-tube boiler, the factor of safety of such parts must be most carefully considered. In such parts too, is the determination of the factor most difficult, and because of the "rule-of-thumb" determination frequently necessary, the factor of safety becomes in reality a factor of ignorance. As opposed to such indeterminate factors of safety, in the Babcock & Wilcox boiler, when the factor of safety for the drum or drums has been determined, and such a factor may be determined accurately, the factors for all other portions of the pressure parts are greatly in excess of that of the drum. All Babcock & Wilcox boilers are built with a factor of safety of at least five, and inasmuch as the factor of the safety of the tubes and headers is greatly in excess of this figure, it applies specifically to the drum or drums. This factor represents a greater degree of safety than a considerably higher factor applied to a boiler in which the shell or any riveted portion is acted upon directly by the fire, or the same factor applied to a boiler utilizing flat-stayed surface construction, where the accurate determination of the limiting factor of safety is difficult, if not impossible. That the factor of safety of stayed surfaces is questionable may perhaps be best realized from a consideration of the severe requirements as to such factor called for by the rules and regulations of the Board of Supervising Inspectors, U. S. Government. In view of the above, the absence of any stayed surfaces in the Babcock & Wilcox boiler is obviously a distinguishing advantage where safety is a factor. It is of interest to note, in the article on the evolution of the Babcock & Wilcox boiler, that staybolt construction was used in several designs, found unsatisfactory and unsafe, and discarded. Another feature in the design of the Babcock & Wilcox boiler tending toward added safety is its manner of suspension. This has been indicated in the previous chapter and is of such nature that all of the pressure parts are free to expand or contract under variations of temperature without in any way interfering with any part of the boiler setting. The sectional nature of the boiler allows a flexibility under varying temperature changes that practically obviates internal strain. In boilers utilizing water-leg construction, on the other hand, the construction is rigid, giving rise to serious internal strains and the method of support ordinarily made necessary by the boiler design is not only unmechanical but frequently dangerous, due to the fact that proper provision is not made for expansion and contraction under temperature variations. Boilers utilizing water-leg construction are not ordinarily provided with mud drums. This is a serious defect in that it allows impurities and sediment to collect in a portion of the boiler not easily inspected, and corrosion may result. Economy--That the water-tube boiler as a class lends itself more readily than does the fire-tube boiler to a variation in the relation of grate surface, heating surface and combustion space has been already pointed out. In economy again, the construction made possible by the use of headers in Babcock & Wilcox boilers appears as a distinct advantage. Because of this construction, there is a flexibility possible, in an unlimited variety of heights and widths that will satisfactorily meet the special requirements of the fuel to be burned in individual cases. An extended experience in the design of furnaces best suited for a wide variety of fuels has made The Babcock & Wilcox Co. leaders in the field of economy. Furnaces have been built and are in successful operation for burning anthracite and bituminous coals, lignite, crude oil, gas-house tar, wood, sawdust and shavings, bagasse, tan bark, natural gas, blast furnace gas, by-product coke oven gas and for the utilization of waste heat from commercial processes. The great number of Babcock & Wilcox boilers now in satisfactory operation under such a wide range of fuel conditions constitutes an unimpeachable testimonial to the ability to meet all of the many conditions of service. The limitations in the draft area of fire-tube boilers as affecting economy have been pointed out. That a greater draft area is possible in water-tube boilers does not of necessity indicate that proper advantage of this fact is taken in all boilers of the water-tube class. In the Babcock & Wilcox boiler, the large draft area taken in connection with the effective baffling allows the gases to be brought into intimate contact with all portions of the heating surfaces and renders such surfaces highly efficient. In certain designs of water-tube boilers the baffling is such as to render ineffective certain portions of the heating surface, due to the tendency of soot and dirt to collect on or behind baffles, in this way causing the interposition of a layer of non-conducting material between the hot gases and the heating surfaces. In Babcock & Wilcox boilers the standard baffle arrangement is such as to allow the installation of a superheater without in any way altering the path of the gases from furnace to stack, or requiring a change in the boiler design. In certain water-tube boilers the baffle arrangement is such that if a superheater is to be installed a complete change in the ordinary baffle design is necessary. Frequently to insure sufficiently hot gas striking the heating surfaces, a portion is by-passed directly from the furnace to the superheater chamber without passing over any of the boiler heating surfaces. Any such arrangement will lead to a decrease in economy and the use of boilers requiring it should be avoided. Capacity--Babcock & Wilcox boilers are run successfully in every-day practice at higher ratings than any other boilers in practical service. The capacities thus obtainable are due directly to the efficient circulation already pointed out. Inasmuch as the construction utilizing headers has a direct bearing in producing such circulation, it is also connected with the high capacities obtainable with this apparatus. Where intelligently handled and kept properly cleaned, Babcock & Wilcox boilers are operated in many plants at from 200 to 225 per cent of their rated evaporative capacity and it is not unusual for them to be operated at 300 per cent of such rated capacity during periods of peak load. Dry Steam--In the list of the requirements of the perfect steam boiler, the necessity that dry steam be generated has been pointed out. The Babcock & Wilcox boiler will deliver dry steam under higher capacities and poorer conditions of feed water than any other boiler now manufactured. Certain boilers will, when operated at ordinary ratings, handle poor feed water and deliver steam in which the moisture content is not objectionable. When these same boilers are driven at high overloads, there will be a direct tendency to prime and the percentage of moisture in the steam delivered will be high. This tendency is the result of the lack of proper circulation and once more there is seen the advantage of the headers of the Babcock & Wilcox boiler, resulting as it does in the securing of a positive circulation. In the design of the Babcock & Wilcox boiler sufficient space is provided between the steam outlet and the disengaging point to insure the steam passing from the boiler in a dry state without entraining or again picking up any particles of water in its passage even at high rates of evaporation. Ample time is given for a complete separation of steam from the water at the disengaging surface before the steam is carried from the boiler. These two features, which are additional causes for the ability of the Babcock & Wilcox boiler to deliver dry steam, result from the proper proportioning of the steam and water space of the boiler. From the history of the development of the boiler, it is evident that the cubical capacity per horse power of the steam and water space has been adopted after numerous experiments. That the "dry pipe" serves in no way the generally understood function of such device has been pointed out. As stated, the function of the "dry pipe" in a Babcock & Wilcox boiler is simply that of a collecting pipe and this statement holds true regardless of the rate of operation of the boiler. In certain boilers, "superheating surface" is provided to "dry the steam," or to remove the moisture due to priming or foaming. Such surface is invariably a source of trouble unless the steam is initially dry and a boiler which will deliver dry steam is obviously to be preferred to one in which surface must be supplied especially for such purpose. Where superheaters are installed with Babcock & Wilcox boilers, they are in every sense of the word superheaters and not driers, the steam being delivered to them in a dry state. The question has been raised in connection with the cross drum design of the Babcock & Wilcox boiler as to its ability to deliver dry steam. Experience has shown the absolute lack of basis for any such objection. The Babcock & Wilcox Company at its Bayonne Works some time ago made a series of experiments to see in what manner the steam generated was separated from the water either in the drum or in its passage to the drum. Glass peepholes were installed in each end of a drum in a boiler of the marine design, at the point midway between that at which the horizontal circulating tubes entered the drum and the drum baffle plate. By holding a light at one of these peepholes the action in the drum was clearly seen through the other. It was found that with the boiler operated under three-quarter inch ashpit pressure, which, with the fuel used would be equivalent to approximately 185 per cent of rating for stationary boiler practice, that each tube was delivering with great velocity a stream of solid water, which filled the tube for half its cross sectional area. There was no spray or mist accompanying such delivery, clearly indicating that the steam had entirely separated from the water in its passage through the horizontal circulating tubes, which in the boiler in question were but 50 inches long. [Illustration: Northwest Station of the Commonwealth Edison Co., Chicago, Ill. This Installation Consists of 11,360 Horse Power of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock & Wilcox Chain Grate Stokers] These experiments proved conclusively that the size of the steam drums in the cross drum design has no appreciable effect in determining the amount of liberating surface, and that sufficient liberating surface is provided in the circulating tubes alone. If further proof of the ability of this design of boiler to deliver dry steam is required, such proof is perhaps best seen in the continued use of the Babcock & Wilcox marine boiler, in which the cross drum is used exclusively, and with which rates of evaporation are obtained far in excess of those secured in ordinary practice. Quick Steaming--The advantages of water-tube boilers as a class over fire-tube boilers in ability to raise steam quickly have been indicated. Due to the constant and thorough circulation resulting from the sectional nature of the Babcock & Wilcox boiler, steam may be raised more rapidly than in practically any other water-tube design. In starting up a cold Babcock & Wilcox boiler with either coal or oil fuel, where a proper furnace arrangement is supplied, steam may be raised to a pressure of 200 pounds in less than half an hour. With a Babcock & Wilcox boiler in a test where forced draft was available, steam was raised from an initial temperature of the boiler and its contained water of 72 degrees to a pressure of 200 pounds, in 12½ minutes after lighting the fire. The boiler also responds quickly in starting from banked fires, especially where forced draft is available. In Babcock & Wilcox boilers the water is divided into many small streams which circulate without undue frictional resistance in thin envelopes passing through the hottest part of the furnace, the steam being carried rapidly to the disengaging surface. There is no part of the boiler exposed to the heat of the fire that is not in contact with water internally, and as a result there is no danger of overheating on starting up quickly nor can leaks occur from unequal expansion such as might be the case where an attempt is made to raise steam rapidly in boilers using water leg construction. Storage Capacity for Steam and Water--Where sufficient steam and water capacity are not provided in a boiler, its action will be irregular, the steam pressure varying over wide limits and the water level being subject to frequent and rapid fluctuation. Owing to the small relative weight of steam, water capacity is of greater importance in this respect than steam space. With a gauge pressure of 180 pounds per square inch, 8 cubic feet of steam, which is equivalent to one-half cubic foot of water space, are required to supply one boiler horse power for one minute and if no heat be supplied to the boiler during such an interval, the pressure will drop to 150 pounds per square inch. The volume of steam space, therefore, may be over rated, but if this be too small, the steam passing off will carry water with it in the form of spray. Too great a water space results in slow steaming and waste of fuel in starting up; while too much steam space adds to the radiating surface and increases the losses from that cause. That the steam and water space of the Babcock & Wilcox boiler are the result of numerous experiments has previously been pointed out. Accessibility--Cleaning. That water-tube boilers are more accessible as a class than are fire-tube boilers has been indicated. All water-tube boilers, however, are not equally accessible. In certain designs, due to the arrangement of baffling used it is practically impossible to remove all deposits of soot and dirt. Frequently, in order to cheapen the product, sufficient cleaning and access doors are not supplied as part of the boiler equipment. The tendency of soot to collect on the crown sheets of certain vertical water-tube boilers has been noted. Such deposits are difficult to remove and if corrosion goes on beneath such a covering the sheet may crack and an explosion result. [Illustration: Rear View--Longitudinal Drum Vertical Header Boiler, Showing Access Doors to Rear Headers] It is almost impossible to thoroughly clean water legs internally, and in such places also is there a tendency to unsuspected corrosion under deposits that cannot be removed. In Babcock & Wilcox boilers every portion of the interior of the heating surfaces can be reached and kept clean, while any soot deposited on the exterior surfaces can be blown off while the boiler is under pressure. Inspection--The accessibility which makes possible the thorough cleaning of all portions of the Babcock & Wilcox boiler also provides a means for a thorough inspection. Drums are accessible for internal inspection by the removal of the manhole plates. Front headers may be inspected through large doors furnished for the purpose. Rear headers in the inclined header designs may be inspected from the chamber formed by such headers and the rear wall of the boiler. In the vertical header designs rear tube doors are furnished, as has been stated. In certain designs of water-tube boilers in order to assure accessibility for inspection of the rear ends of the tubes, the rear portion of the boiler is exposed to the atmosphere with resulting excessive radiation losses. In other designs the means of access to the rear ends of the tubes are of a makeshift and unworkmanlike character. By the removal of handhole plates, all tubes in a Babcock & Wilcox boiler may be inspected for their full length either for the presence of scale or for suspected corrosion. Repairs--In Babcock & Wilcox boilers the possession of great strength, the elimination of stresses due to uneven temperatures and of the resulting danger of leaks and corrosion, the protection of the drums from the intense heat of the fire, and the decreased liability of the scale forming matter to lodge on the hottest tube surfaces, all tend to minimize the necessity for repairs. The tubes of the Babcock & Wilcox boiler are practically the only part which may need renewal and these only at infrequent intervals When necessary, such renewals may be made cheaply and quickly. A small stock of tubes, 4 inches in diameter, of sufficient length for the boiler used, is all that need be carried to make renewals. Repairs in water-leg boilers are difficult at best and frequently unsatisfactory when completed. When staybolt replacements are necessary, in order to get at the inner sheet of the water leg, several tubes must in some cases be cut out. Not infrequently a replacement of an entire water leg is necessary and this is difficult and requires a lengthy shutdown. With the Babcock & Wilcox boiler, on the other hand, even if it is necessary to replace a section, this may be done in a few hours after the boiler is cool. In the case of certain staybolt failures the working pressure of a repaired boiler utilizing such construction will frequently be lowered by the insurance companies when the boiler is again placed in service. The sectional nature of the Babcock & Wilcox boiler enables it to maintain its original working pressure over long periods of time, almost regardless of the nature of any repair that may be required. [Illustration: 1456 Horse-power Installation of Babcock & Wilcox Boilers at the Raritan Woolen Mills, Raritan, N. J. The First of These Boilers were Installed in 1878 and 1881 and are still Operated at 80 Pounds Pressure] Durability--Babcock & Wilcox boilers are being operated in every-day service with entirely satisfactory results and under the same steam pressure as that for which they were originally sold that have been operated from thirty to thirty-five years. It is interesting to note in considering the life of a boiler that the length of life of a Babcock & Wilcox boiler must be taken as the criterion of what length of life is possible. This is due to the fact that there are Babcock & Wilcox boilers in operation to-day that have been in service from a time that antedates by a considerable margin that at which the manufacturer of any other water-tube boiler now on the market was started. Probably the very best evidence of the value of the Babcock & Wilcox boiler as a steam generator and of the reliability of the apparatus, is seen in the sales of the company. Since the company was formed, there have been sold throughout the world over 9,900,000 horse power. A feature that cannot be overlooked in the consideration of the advantages of the Babcock & Wilcox boiler is the fact that as a part of the organization back of the boiler, there is a body of engineers of recognized ability, ready at all times to assist its customers in every possible way. [Illustration: 2400 Horse-power Installation of Babcock & Wilcox Boilers in the Union Station Power House of the Pennsylvania Railroad Co., Pittsburgh, Pa. This Company has a Total of 28,500 Horse Power of Babcock & Wilcox Boilers Installed] HEAT AND ITS MEASUREMENT The usual conception of heat is that it is a form of energy produced by the vibratory motion of the minute particles or molecules of a body. All bodies are assumed to be composed of these molecules, which are held together by mutual cohesion and yet are in a state of continual vibration. The hotter a body or the more heat added to it, the more vigorous will be the vibrations of the molecules. As is well known, the effect of heat on a body may be to change its temperature, its volume, or its state, that is, from solid to liquid or from liquid to gaseous. Where water is melted from ice and evaporated into steam, the various changes are admirably described in the lecture by Mr. Babcock on "The Theory of Steam Making", given in the next chapter. The change in temperature of a body is ordinarily measured by thermometers, though for very high temperatures so-called pyrometers are used. The latter are dealt with under the heading "High Temperature Measurements" at the end of this chapter. [Illustration: Fig. 11] By reason of the uniform expansion of mercury and its great sensitiveness to heat, it is the fluid most commonly used in the construction of thermometers. In all thermometers the freezing point and the boiling point of water, under mean or average atmospheric pressure at sea level, are assumed as two fixed points, but the division of the scale between these two points varies in different countries. The freezing point is determined by the use of melting ice and for this reason is often called the melting point. There are in use three thermometer scales known as the Fahrenheit, the Centigrade or Celsius, and the Réaumur. As shown in Fig. 11, in the Fahrenheit scale, the space between the two fixed points is divided into 180 parts; the boiling point is marked 212, and the freezing point is marked 32, and zero is a temperature which, at the time this thermometer was invented, was incorrectly imagined to be the lowest temperature attainable. In the centigrade and the Réaumur scales, the distance between the two fixed points is divided into 100 and 80 parts, respectively. In each of these two scales the freezing point is marked zero, and the boiling point is marked 100 in the centigrade and 80 in the Réaumur. Each of the 180, 100 or 80 divisions in the respective thermometers is called a degree. Table 3 and appended formulae are useful for converting from one scale to another. In the United States the bulbs of high-grade thermometers are usually made of either Jena 58^{III} borosilicate thermometer glass or Jena 16^{III} glass, the stems being made of ordinary glass. The Jena 16^{III} glass is not suitable for use at temperatures much above 850 degrees Fahrenheit and the harder Jena 59^{III} should be used in thermometers for temperatures higher than this. Below the boiling point, the hydrogen-gas thermometer is the almost universal standard with which mercurial thermometers may be compared, while above this point the nitrogen-gas thermometer is used. In both of these standards the change in temperature is measured by the change in pressure of a constant volume of the gas. In graduating a mercurial thermometer for the Fahrenheit scale, ordinarily a degree is represented as 1/180 part of the volume of the stem between the readings at the melting point of ice and the boiling point of water. For temperatures above the latter, the scale is extended in degrees of the same volume. For very accurate work, however, the thermometer may be graduated to read true-gas-scale temperatures by comparing it with the gas thermometer and marking the temperatures at 25 or 50 degree intervals. Each degree is then 1/25 or 1/50 of the volume of the stem in each interval. Every thermometer, especially if intended for use above the boiling point, should be suitably annealed before it is used. If this is not done, the true melting point and also the "fundamental interval", that is, the interval between the melting and the boiling points, may change considerably. After continued use at the higher temperatures also, the melting point will change, so that the thermometer must be calibrated occasionally to insure accurate readings. TABLE 3 COMPARISON OF THERMOMETER SCALES +---------------+----------+----------+----------+ | |Fahrenheit|Centigrade| Réaumur | +---------------+----------+----------+----------+ |Absolute Zero | -459.64 | -273.13 | -218.50 | | | 0 | -17.78 | -14.22 | | | 10 | -12.22 | -9.78 | | | 20 | -6.67 | -5.33 | | | 30 | -1.11 | -0.89 | |Freezing Point | 32 | 0 | 0 | |Maximum Density| | | | | of Water | 39.1 | 3.94 | 3.15 | | | 50 | 10 | 8 | | | 75 | 23.89 | 19.11 | | | 100 | 37.78 | 30.22 | | | 200 | 93.33 | 74.67 | |Boiling Point | 212 | 100 | 80 | | | 250 | 121.11 | 96.89 | | | 300 | 148.89 | 119.11 | | | 350 | 176.67 | 141.33 | +---------------+----------+----------+----------+ F = 9/5C+32° = 9/4R+32° C = 5/9(F-32°) = 5/4R R = 4/9(F-32°) = 4/5C As a general rule thermometers are graduated to read correctly for total immersion, that is, with bulb and stem of the thermometer at the same temperature, and they should be used in this way when compared with a standard thermometer. If the stem emerges into space either hotter or colder than that in which the bulb is placed, a "stem correction" must be applied to the observed temperature in addition to any correction that may be found in the comparison with the standard. For instance, for a particular thermometer, comparison with the standard with both fully immersed made necessary the following corrections: _Temperature_ _Correction_ 40°F 0.0 100 0.0 200 0.0 300 +2.5 400 -0.5 500 -2.5 When the sign of the correction is positive (+) it must be added to the observed reading, and when the sign is a negative (-) the correction must be subtracted. The formula for the stem correction is as follows: Stem correction = 0.000085 × n (T-t) in which T is the observed temperature, t is the mean temperature of the emergent column, n is the number of degrees of mercury column emergent, and 0.000085 is the difference between the coefficient of expansion of the mercury and that in the glass in the stem. Suppose the observed temperature is 400 degrees and the thermometer is immersed to the 200 degrees mark, so that 200 degrees of the mercury column project into the air. The mean temperature of the emergent column may be found by tying another thermometer on the stem with the bulb at the middle of the emergent mercury column as in Fig. 12. Suppose this mean temperature is 85 degrees, then Stem correction = 0.000085 × 200 × (400 - 85) = 5.3 degrees. As the stem is at a lower temperature than the bulb, the thermometer will evidently read too low, so that this correction must be added to the observed reading to find the reading corresponding to total immersion. The corrected reading will therefore be 405.3 degrees. If this thermometer is to be corrected in accordance with the calibrated corrections given above, we note that a further correction of 0.5 must be applied to the observed reading at this temperature, so that the correct temperature is 405.3 - 0.5 = 404.8 degrees or 405 degrees. [Illustration: Fig. 12] [Illustration: Fig. 13] Fig. 12 shows how a stem correction can be obtained for the case just described. Fig. 13 affords an opportunity for comparing the scale of a thermometer correct for total immersion with one which will read correctly when submerged to the 300 degrees mark, the stem being exposed at a mean temperature of 110 degrees Fahrenheit, a temperature often prevailing when thermometers are used for measuring temperatures in steam mains. Absolute Zero--Experiments show that at 32 degrees Fahrenheit a perfect gas expands 1/491.64 part of its volume if its pressure remains constant and its temperature is increased one degree. Thus if gas at 32 degrees Fahrenheit occupies 100 cubic feet and its temperature is increased one degree, its volume will be increased to 100 + 100/491.64 = 100.203 cubic feet. For a rise of two degrees the volume would be 100 + (100 × 2) / 491.64 = 100.406 cubic feet. If this rate of expansion per one degree held good at all temperatures, and experiment shows that it does above the freezing point, the gas, if its pressure remained the same, would double its volume, if raised to a temperature of 32 + 491.64 = 523.64 degrees Fahrenheit, while under a diminution of temperature it would shrink and finally disappear at a temperature of 491.64 - 32 = 459.64 degrees below zero Fahrenheit. While undoubtedly some change in the law would take place before the lower temperature could be reached, there is no reason why the law may not be used within the range of temperature where it is known to hold good. From this explanation it is evident that under a constant pressure the volume of a gas will vary as the number of degrees between its temperature and the temperature of -459.64 degrees Fahrenheit. To simplify the application of the law, a new thermometric scale is constructed as follows: the point corresponding to -460 degrees Fahrenheit, is taken as the zero point on the new scale, and the degrees are identical in magnitude with those on the Fahrenheit scale. Temperatures referred to this new scale are called absolute temperatures and the point -460 degrees Fahrenheit (= -273 degrees centigrade) is called the absolute zero. To convert any temperature Fahrenheit to absolute temperature, add 460 degrees to the temperature on the Fahrenheit scale: thus 54 degrees Fahrenheit will be 54 + 460 = 514 degrees absolute temperature; 113 degrees Fahrenheit will likewise be equal to 113 + 460 = 573 degrees absolute temperature. If one pound of gas is at a temperature of 54 degrees Fahrenheit and another pound is at a temperature of 114 degrees Fahrenheit the respective volumes at a given pressure would be in the ratio of 514 to 573. [Illustration: Ninety-sixth Street Station of the New York Railways Co., New York City, Operating 20,000 Horse Power of Babcock & Wilcox Boilers. This Company and its Allied Companies Operate a Total of 100,000 Horse Power of Babcock & Wilcox Boilers] British Thermal Unit--The quantitative measure of heat is the British thermal unit, ordinarily written B. t. u. This is the quantity of heat required to raise the temperature of one pound of pure water one degree at 62 degrees Fahrenheit; that is, from 62 degrees to 63 degrees. In the metric system this unit is the _calorie_ and is the heat necessary to raise the temperature of one kilogram of pure water from 15 degrees to 16 degrees centigrade. These two definitions lead to a discrepancy of 0.03 of 1 per cent, which is insignificant for engineering purposes, and in the following the B. t. u. is taken with this discrepancy ignored. The discrepancy is due to the fact that there is a slight difference in the specific heat of water at 15 degrees centigrade and 62 degrees Fahrenheit. The two units may be compared thus: 1 Calorie = 3.968 B. t. u. 1 B. t. u. = 0.252 Calories. _Unit_ _Water_ _Temperature Rise_ 1 B. t. u. 1 Pound 1 Degree Fahrenheit 1 Calorie 1 Kilogram 1 Degree centigrade But 1 kilogram = 2.2046 pounds and 1 degree centigrade = 9/5 degree Fahrenheit. Hence 1 calorie = (2.2046 × 9/5) = 3.968 B. t. u. The heat values in B. t. u. are ordinarily given per pound, and the heat values in calories per kilogram, in which case the B. t. u. per pound are approximately equivalent to 9/5 the calories per kilogram. As determined by Joule, heat energy has a certain definite relation to work, one British thermal unit being equivalent from his determinations to 772 foot pounds. Rowland, a later investigator, found that 778 foot pounds were a more exact equivalent. Still later investigations indicate that the correct value for a B. t. u. is 777.52 foot pounds or approximately 778. The relation of heat energy to work as determined is a demonstration of the first law of thermo-dynamics, namely, that heat and mechanical energy are mutually convertible in the ratio of 778 foot pounds for one British thermal unit. This law, algebraically expressed, is W = JH; W being the work done in foot pounds, H being the heat in B. t. u., and J being Joules equivalent. Thus 1000 B. t. u.'s would be capable of doing 1000 × 778 = 778000 foot pounds of work. Specific Heat--The specific heat of a substance is the quantity of heat expressed in thermal units required to raise or lower the temperature of a unit weight of any substance at a given temperature one degree. This quantity will vary for different substances For example, it requires about 16 B. t. u. to raise the temperature of one pound of ice 32 degrees or 0.5 B. t. u. to raise it one degree, while it requires approximately 180 B. t. u. to raise the temperature of one pound of water 180 degrees or one B. t. u. for one degree. If then, a pound of water be considered as a standard, the ratio of the amount of heat required to raise a similar unit of any other substance one degree, to the amount required to raise a pound of water one degree is known as the specific heat of that substance. Thus since one pound of water required one B. t. u. to raise its temperature one degree, and one pound of ice requires about 0.5 degrees to raise its temperature one degree, the ratio is 0.5 which is the specific heat of ice. To be exact, the specific heat of ice is 0.504, hence 32 degrees × 0.504 = 16.128 B. t. u. would be required to raise the temperature of one pound of ice from 0 to 32 degrees. For solids, at ordinary temperatures, the specific heat may be considered a constant for each individual substance, although it is variable for high temperatures. In the case of gases a distinction must be made between specific heat at constant volume, and at constant pressure. Where specific heat is stated alone, specific heat at ordinary temperature is implied, and _mean_ specific heat refers to the average value of this quantity between the temperatures named. The specific heat of a mixture of gases is obtained by multiplying the specific heat of each constituent gas by the percentage by weight of that gas in the mixture, and dividing the sum of the products by 100. The specific heat of a gas whose composition by weight is CO_{2}, 13 per cent; CO, 0.4 per cent; O, 8 per cent; N, 78.6 per cent, is found as follows: CO_{2} : 13 × 0.217 = 2.821 CO : 0.4 × 0.2479 = 0.09916 O : 8 × 0.2175 = 1.74000 N : 78.6 × 0.2438 = 19.16268 -------- 100.0 23.82284 and 23.8228 ÷ 100 = 0.238 = specific heat of the gas. The specific heats of various solids, liquids and gases are given in Table 4. Sensible Heat--The heat utilized in raising the temperature of a body, as that in raising the temperature of water from 32 degrees up to the boiling point, is termed sensible heat. In the case of water, the sensible heat required to raise its temperature from the freezing point to the boiling point corresponding to the pressure under which ebullition occurs, is termed the heat of the liquid. Latent Heat--Latent heat is the heat which apparently disappears in producing some change in the condition of a body without increasing its temperature If heat be added to ice at freezing temperature, the ice will melt but its temperature will not be raised. The heat so utilized in changing the condition of the ice is the latent heat and in this particular case is known as the latent heat of fusion. If heat be added to water at 212 degrees under atmospheric pressure, the water will not become hotter but will be evaporated into steam, the temperature of which will also be 212 degrees. The heat so utilized is called the latent heat of evaporation and is the heat which apparently disappears in causing the substance to pass from a liquid to a gaseous state. TABLE 4 SPECIFIC HEATS OF VARIOUS SUBSTANCES +--------------------------------------------------------------------+ | SOLIDS | +-------------------------------+----------------+-------------------+ | | Temperature[2]| | | | Degrees | Specific | | | Fahrenheit | Heat | +-------------------------------+----------------+-------------------+ | Copper | 59-460 | .0951 | | Gold | 32-212 | .0316 | | Wrought Iron | 59-212 | .1152 | | Cast Iron | 68-212 | .1189 | | Steel (soft) | 68-208 | .1175 | | Steel (hard) | 68-208 | .1165 | | Zinc | 32-212 | .0935 | | Brass (yellow) | 32 | .0883 | | Glass (normal ther. 16^{III}) | 66-212 | .1988 | | Lead | 59 | .0299 | | Platinum | 32-212 | .0323 | | Silver | 32-212 | .0559 | | Tin | -105-64 | .0518 | | Ice | | .5040 | | Sulphur (newly fused) | | .2025 | +-------------------------------+----------------+-------------------+ | LIQUIDS | +-------------------------------+----------------+-------------------+ | | Temperature[2]| | | | Degrees | Specific | | | Fahrenheit | Heat | +-------------------------------+----------------+-------------------+ | Water[3] | 59 | 1.0000 | | Alcohol | 32 | .5475 | | | 176 | .7694 | | Mercury | 32 | .03346 | | Benzol | 50 | .4066 | | | 122 | .4502 | | Glycerine | 59-102 | .576 | | Lead (Melted) | to 360 | .0410 | | Sulphur (melted) | 246-297 | .2350 | | Tin (melted) | | .0637 | | Sea Water (sp. gr. 1.0043) | 64 | .980 | | Sea Water (sp. gr. 1.0463) | 64 | .903 | | Oil of Turpentine | 32 | .411 | | Petroleum | 64-210 | .498 | | Sulphuric Acid | 68-133 | .3363 | +-------------------------------+----------------+-------------------+ | GASES | +--------------------------+---------------+--------------+----------+ | | | Specific | Specific | | | Temperature[2]| Heat at | Heat at | | | Degrees | Constant | Constant | | | Fahrenheit | Pressure | Volume | +--------------------------+---------------+--------------+----------+ | Air | 32-392 | .2375 | .1693 | | Oxygen | 44-405 | .2175 | .1553 | | Nitrogen | 32-392 | .2438 | .1729 | | Hydrogen | 54-388 | 3.4090 | 2.4141 | | Superheated Steam | | See table 25 | | | Carbon Monoxide | 41-208 | .2425 | .1728 | | Carbon Dioxide | 52-417 | .2169 | .1535 | | Methane | 64-406 | .5929 | .4505 | | Blast Fur. Gas (approx.) | ... | .2277 | ... | | Flue gas (approx.) | ... | .2400 | ... | +--------------------------+---------------+--------------+----------+ Latent heat is not lost, but reappears whenever the substances pass through a reverse cycle, from a gaseous to a liquid, or from a liquid to a solid state. It may, therefore, be defined as stated, as the heat which apparently disappears, or is lost to thermometric measurement, when the molecular constitution of a body is being changed. Latent heat is expended in performing the work of overcoming the molecular cohesion of the particles of the substance and in overcoming the resistance of external pressure to change of volume of the heated body. Latent heat of evaporation, therefore, may be said to consist of internal and external heat, the former being utilized in overcoming the molecular resistance of the water in changing to steam, while the latter is expended in overcoming any resistance to the increase of its volume during formation. In evaporating a pound of water at 212 degrees to steam at 212 degrees, 897.6 B. t. u. are expended as internal latent heat and 72.8 B. t. u. as external latent heat. For a more detailed description of the changes brought about in water by sensible and latent heat, the reader is again referred to the chapter on "The Theory of Steam Making". Ebullition--The temperature of ebullition of any liquid, or its boiling point, may be defined as the temperature which exists where the addition of heat to the liquid no longer increases its temperature, the heat added being absorbed or utilized in converting the liquid into vapor. This temperature is dependent upon the pressure under which the liquid is evaporated, being higher as the pressure is greater. TABLE 5 BOILING POINTS AT ATMOSPHERIC PRESSURE +---------------------+--------------+ | | Degrees | | | Fahrenheit | +---------------------+--------------+ | Ammonia | 140 | | Bromine | 145 | | Alcohol | 173 | | Benzine | 212 | | Water | 212 | | Average Sea Water | 213.2 | | Saturated Brine | 226 | | Mercury | 680 | +---------------------+--------------+ Total Heat of Evaporation--The quantity of heat required to raise a unit of any liquid from the freezing point to any given temperature, and to entirely evaporate it at that temperature, is the total heat of evaporation of the liquid for that temperature. It is the sum of the heat of the liquid and the latent heat of evaporation. To recapitulate, the heat added to a body is divided as follows: Total heat = Heat to change the temperature + heat to overcome the molecular cohesion + heat to overcome the external pressure resisting an increase of volume of the body. Where water is converted into steam, this total heat is divided as follows: Total heat = Heat to change the temperature of the water + heat to separate the molecules of the water + heat to overcome resistance to increase in volume of the steam, = Heat of the liquid + internal latent heat + external latent heat, = Heat of the liquid + total latent heat of steam, = Total heat of evaporation. The steam tables given on pages 122 to 127 give the heat of the liquid and the total latent heat through a wide range of temperatures. Gases--When heat is added to gases there is no internal work done; hence the total heat is that required to change the temperature plus that required to do the external work. If the gas is not allowed to expand but is preserved at constant volume, the entire heat added is that required to change the temperature only. Linear Expansion of Substances by Heat--To find the increase in the length of a bar of any material due to an increase of temperature, multiply the number of degrees of increase in temperature by the coefficient of expansion for one degree and by the length of the bar. Where the coefficient of expansion is given for 100 degrees, as in Table 6, the result should be divided by 100. The expansion of metals per one degree rise of temperature increases slightly as high temperatures are reached, but for all practical purposes it may be assumed to be constant for a given metal. TABLE 6 LINEAL EXPANSION OF SOLIDS AT ORDINARY TEMPERATURES (Tabular values represent increase per foot per 100 degrees increase in temperature, Fahrenheit or centigrade) +-------------------+--------------+----------------+----------------+ | | Temperature | | | | | Conditions[4]|Coefficient per |Coefficient per | | Substance | Degrees | 100 Degrees | 100 Degrees | | | Fahrenheit | Fahrenheit | Centigrade | +-------------------+--------------+----------------+----------------+ |Brass (cast) | 32 to 212 | .001042 | .001875 | |Brass (wire) | 32 to 212 | .001072 | .001930 | |Copper | 32 to 212 | .000926 | .001666 | |Glass (English | | | | |flint) | 32 to 212 | .000451 | .000812 | |Glass (French | | | | |flint) | 32 to 212 | .000484 | .000872 | |Gold | 32 to 212 | .000816 | .001470 | |Granite (average) | 32 to 212 | .000482 | .000868 | |Iron (cast) | 104 | .000589 | .001061 | |Iron (soft forged) | 0 to 212 | .000634 | .001141 | |Iron (wire) | 32 to 212 | .000800 | .001440 | |Lead | 32 to 212 | .001505 | .002709 | |Mercury | 32 to 212 | .009984[5] | .017971 | |Platinum | 104 | .000499 | .000899 | |Limestone | 32 to 212 | .000139 | .000251 | |Silver | 104 | .001067 | .001921 | |Steel (Bessemer | | | | |rolled, hard) | 0 to 212 | .00056 | .00101 | |Steel (Bessemer | | | | |rolled, soft) | 0 to 212 | .00063 | .00117 | |Steel (cast, | | | | |French) | 104 | .000734 | .001322 | |Steel (cast | | | | |annealed, English) | 104 | .000608 | .001095 | +-------------------+--------------+----------------+----------------+ High Temperature Measurements--The temperatures to be dealt with in steam-boiler practice range from those of ordinary air and steam to the temperatures of burning fuel. The gases of combustion, originally at the temperature of the furnace, cool as they pass through each successive bank of tubes in the boiler, to nearly the temperature of the steam, resulting in a wide range of temperatures through which definite measurements are sometimes required. Of the different methods devised for ascertaining these temperatures, some of the most important are as follows: 1st. Mercurial pyrometers for temperatures up to 1000 degrees Fahrenheit. 2nd. Expansion pyrometers for temperatures up to 1500 degrees Fahrenheit. 3rd. Calorimetry for temperatures up to 2000 degrees Fahrenheit. 4th. Thermo-electric pyrometers for temperatures up to 2900 degrees Fahrenheit. 5th. Melting points of metal which flow at various temperatures up to the melting point of platinum 3227 degrees Fahrenheit. 6th. Radiation pyrometers for temperatures up to 3600 degrees Fahrenheit. 7th. Optical pyrometers capable of measuring temperatures up to 12,600 degrees Fahrenheit.[6] For ordinary boiler practice however, their range is 1600 to 3600 degrees Fahrenheit. [Illustration: 228 Horse-power Babcock & Wilcox Boiler, Installed at the Wentworth Institute, Boston, Mass.] Table 7 gives the degree of accuracy of high temperature measurements. TABLE 7 ACCURACY OF HIGH TEMPERATURE MEASUREMENTS[7] +------------------------+------------------------+ | Centigrade | Fahrenheit | +-------------+----------+-------------+----------+ | | Accuracy | | Accuracy | | Temperature | Plus or | Temperature | Plus or | | Range | Minus | Range | Minus | | | Degrees | | Degrees | +-------------+----------+-------------+----------+ | 200- 500 | 0.5 | 392- 932 | 0.9 | | 500- 800 | 2 | 932-1472 | 3.6 | | 800-1100 | 3 | 1472-2012 | 5.4 | | 1100-1600 | 15 | 2012-2912 | 27 | | 1600-2000 | 25 | 2912-3632 | 45 | +-------------+----------+-------------+----------+ Mercurial Pyrometers--At atmospheric pressure mercury boils at 676 degrees Fahrenheit and even at lower temperatures the mercury in thermometers will be distilled and will collect in the upper part of the stem. Therefore, for temperatures much above 400 degrees Fahrenheit, some inert gas, such as nitrogen or carbon dioxide, must be forced under pressure into the upper part of the thermometer stem. The pressure at 600 degrees Fahrenheit is about 15 pounds, or slightly above that of the atmosphere, at 850 degrees about 70 pounds, and at 1000 degrees about 300 pounds. Flue-gas temperatures are nearly always taken with mercurial thermometers as they are the most accurate and are easy to read and manipulate. Care must be taken that the bulb of the instrument projects into the path of the moving gases in order that the temperature may truly represent the flue gas temperature. No readings should be considered until the thermometer has been in place long enough to heat it up to the full temperature of the gases. Expansion Pyrometers--Brass expands about 50 per cent more than iron and in both brass and iron the expansion is nearly proportional to the increase in temperature. This phenomenon is utilized in expansion pyrometers by enclosing a brass rod in an iron pipe, one end of the rod being rigidly attached to a cap at the end of the pipe, while the other is connected by a multiplying gear to a pointer moving around a graduated dial. The whole length of the expansion piece must be at a uniform temperature before a correct reading can be obtained. This fact, together with the lost motion which is likely to exist in the mechanism connected to the pointer, makes the expansion pyrometer unreliable; it should be used only when its limitations are thoroughly understood and it should be carefully calibrated. Unless the brass and iron are known to be of the same temperature, its action will be anomalous: for instance, if it be allowed to cool after being exposed to a high temperature, the needle will rise before it begins to fall. Similarly, a rise in temperature is first shown by the instrument as a fall. The explanation is that the iron, being on the outside, heats or cools more quickly than the brass. Calorimetry--This method derives its name from the fact that the process is the same as the determination of the specific heat of a substance by the water calorimeter, except that in one case the temperature is known and the specific heat is required, while in the other the specific heat is known and the temperature is required. The temperature is found as follows: A given weight of some substance such as iron, nickel or fire brick, is heated to the unknown temperature and then plunged into water and the rise in temperature noted. If X = temperature to be measured, w = weight of heated body in pounds, W = weight of water in pounds, T = final temperature of water, t = difference between initial and final temperatures of water, s = known specific heat of body. Then X = T + Wt ÷ ws Any temperatures secured by this method are affected by so many sources of error that the results are very approximate. Thermo-electric Pyrometers--When wires of two different metals are joined at one end and heated, an electromotive force will be set up between the free ends of the wires. Its amount will depend upon the composition of the wires and the difference in temperature between the two. If a delicate galvanometer of high resistance be connected to the "thermal couple", as it is called, the deflection of the needle, after a careful calibration, will indicate the temperature very accurately. In the thermo-electric pyrometer of Le Chatelier, the wires used are platinum and a 10 per cent alloy of platinum and rhodium, enclosed in porcelain tubes to protect them from the oxidizing influence of the furnace gases. The couple with its protecting tubes is called an "element". The elements are made in different lengths to suit conditions. It is not necessary for accuracy to expose the whole length of the element to the temperature to be measured, as the electromotive force depends only upon the temperature of the juncture at the closed end of the protecting tube and that of the cold end of the element. The galvanometer can be located at any convenient point, since the length of the wires leading to it simply alter the resistance of the circuit, for which allowance may be made. The advantages of the thermo-electric pyrometer are accuracy over a wide range of temperatures, continuity of readings, and the ease with which observations can be taken. Its disadvantages are high first cost and, in some cases, extreme delicacy. Melting Points of Metals--The approximate temperature of a furnace or flue may be determined, if so desired, by introducing certain metals of which the melting points are known. The more common metals form a series in which the respective melting points differ by 100 to 200 degrees Fahrenheit, and by using these in order, the temperature can be fixed between the melting points of some two of them. This method lacks accuracy, but it suffices for determinations where approximate readings are satisfactory. The approximate melting points of certain metals that may be used for determinations of this nature are given in Table 8. Radiation Pyrometers--These are similar to thermo-electric pyrometers in that a thermo-couple is employed. The heat rays given out by the hot body fall on a concave mirror and are brought to a focus at a point at which is placed the junction of a thermo-couple. The temperature readings are obtained from an indicator similar to that used with thermo-electric pyrometers. Optical Pyrometers--Of the optical pyrometers the Wanner is perhaps the most reliable. The principle on which this instrument is constructed is that of comparing the quantity of light emanating from the heated body with a constant source of light, in this case a two-volt osmium lamp. The lamp is placed at one end of an optical tube, while at the other an eyepiece is provided and a scale. A battery of cells furnishes the current for the lamp. On looking through the pyrometer, a circle of red light appears, divided into distinct halves of different intensities. Adjustment may be made so that the two halves appear alike and a reading is then taken from the scale. The temperatures are obtained from a table of temperatures corresponding to scale readings. For standardizing the osmium lamp, an amylacetate lamp, is provided with a stand for holding the optical tube. TABLE 8 APPROXIMATE MELTING POINTS OF METALS[8] +-----------------+------------------+ | Metal | Temperature | | |Degrees Fahrenheit| +-----------------+------------------+ |Wrought Iron | 2737 | |Pig Iron (gray) | 2190-2327 | |Cast Iron (white)| 2075 | |Steel | 2460-2550 | |Steel (cast) | 2500 | |Copper | 1981 | |Zinc | 786 | |Antimony | 1166 | |Lead | 621 | |Bismuth | 498 | |Tin | 449 | |Platinum | 3191 | |Gold | 1946 | |Silver | 1762 | |Aluminum | 1216 | +-----------------+------------------+ Determination of Temperature from Character of Emitted Light--As a further means of determining approximately the temperature of a furnace, Table 9, compiled by Messrs. White & Taylor, may be of service. The color at a given temperature is approximately the same for all kinds of combustibles under similar conditions. TABLE 9 CHARACTER OF EMITTED LIGHT AND CORRESPONDING APPROXIMATE TEMPERATURE[9] +--------------------------------------+-----------+ | Character of Emitted Light |Temperature| | | Degrees | | | Fahrenheit| +--------------------------------------+-----------+ |Dark red, blood red, low red | 1050 | |Dark cherry red | 1175 | |Cherry, full red | 1375 | |Light cherry, bright cherry, light red| 1550 | |Orange | 1650 | |Light orange | 1725 | |Yellow | 1825 | |Light yellow | 1975 | |White | 2200 | +--------------------------------------+-----------+ THE THEORY OF STEAM MAKING [Extracts from a Lecture delivered by George H. Babcock, at Cornell University, 1887[10]] The chemical compound known as H_{2}O exists in three states or conditions--ice, water and steam; the only difference between these states or conditions is in the presence or absence of a quantity of energy exhibited partly in the form of heat and partly in molecular activity, which, for want of a better name, we are accustomed to call "latent heat"; and to transform it from one state to another we have only to supply or extract heat. For instance, if we take a quantity of ice, say one pound, at absolute zero[11] and supply heat, the first effect is to raise its temperature until it arrives at a point 492 Fahrenheit degrees above the starting point. Here it stops growing warmer, though we keep on adding heat. It, however, changes from ice to water, and when we have added sufficient heat to have made it, had it remained ice, 283 degrees hotter or a temperature of 315 degrees Fahrenheit's thermometer, it has all become water, at the same temperature at which it commenced to change, namely, 492 degrees above absolute zero, or 32 degrees by Fahrenheit's scale. Let us still continue to add heat, and it will now grow warmer again, though at a slower rate--that is, it now takes about double the quantity of heat to raise the pound one degree that it did before--until it reaches a temperature of 212 degrees Fahrenheit, or 672 degrees absolute (assuming that we are at the level of the sea). Here we find another critical point. However much more heat we may apply, the water, as water, at that pressure, cannot be heated any hotter, but changes on the addition of heat to steam; and it is not until we have added heat enough to have raised the temperature of the water 966 degrees, or to 1,178 degrees by Fahrenheit's thermometer (presuming for the moment that its specific heat has not changed since it became water), that it has all become steam, which steam, nevertheless, is at the temperature of 212 degrees, at which the water began to change. Thus over four-fifths of the heat which has been added to the water has disappeared, or become insensible in the steam to any of our instruments. It follows that if we could reduce steam at atmospheric pressure to water, without loss of heat, the heat stored within it would cause the water to be red hot; and if we could further change it to a solid, like ice, without loss of heat, the solid would be white hot, or hotter than melted steel--it being assumed, of course, that the specific heat of the water and ice remain normal, or the same as they respectively are at the freezing point. After steam has been formed, a further addition of heat increases the temperature again at a much faster ratio to the quantity of heat added, which ratio also varies according as we maintain a constant pressure or a constant volume; and I am not aware that any other critical point exists where this will cease to be the fact until we arrive at that very high temperature, known as the point of dissociation, at which it becomes resolved into its original gases. The heat which has been absorbed by one pound of water to convert it into a pound of steam at atmospheric pressure is sufficient to have melted 3 pounds of steel or 13 pounds of gold. This has been transformed into something besides heat; stored up to reappear as heat when the process is reversed. That condition is what we are pleased to call latent heat, and in it resides mainly the ability of the steam to do work. [Graph: Temperature in Fahrenheit Degrees (from Absolute Zero) against Quantity of Heat in British Thermal Units] The diagram shows graphically the relation of heat to temperature, the horizontal scale being quantity of heat in British thermal units, and the vertical temperature in Fahrenheit degrees, both reckoned from absolute zero and by the usual scale. The dotted lines for ice and water show the temperature which would have been obtained if the conditions had not changed. The lines marked "gold" and "steel" show the relation to heat and temperature and the melting points of these metals. All the inclined lines would be slightly curved if attention had been paid to the changing specific heat, but the curvature would be small. It is worth noting that, with one or two exceptions, the curves of all substances lie between the vertical and that for water. That is to say, that water has a greater capacity for heat than all other substances except two, hydrogen and bromine. In order to generate steam, then, only two steps are required: 1st, procure the heat, and 2nd, transfer it to the water. Now, you have it laid down as an axiom that when a body has been transferred or transformed from one place or state into another, the same work has been done and the same energy expended, whatever may have been the intermediate steps or conditions, or whatever the apparatus. Therefore, when a given quantity of water at a given temperature has been made into steam at a given temperature, a certain definite work has been done, and a certain amount of energy expended, from whatever the heat may have been obtained, or whatever boiler may have been employed for the purpose. A pound of coal or any other fuel has a definite heat producing capacity, and is capable of evaporating a definite quantity of water under given conditions. That is the limit beyond which even perfection cannot go, and yet I have known, and doubtless you have heard of, cases where inventors have claimed, and so-called engineers have certified to, much higher results. The first step in generating steam is in burning the fuel to the best advantage. A pound of carbon will generate 14,500 British thermal units, during combustion into carbonic dioxide, and this will be the same, whatever the temperature or the rapidity at which the combustion may take place. If possible, we might oxidize it at as slow a rate as that with which iron rusts or wood rots in the open air, or we might burn it with the rapidity of gunpowder, a ton in a second, yet the total heat generated would be precisely the same. Again, we may keep the temperature down to the lowest point at which combustion can take place, by bringing large bodies of air in contact with it, or otherwise, or we may supply it with just the right quantity of pure oxygen, and burn it at a temperature approaching that of dissociation, and still the heat units given off will be neither more nor less. It follows, therefore, that great latitude in the manner or rapidity of combustion may be taken without affecting the quantity of heat generated. But in practice it is found that other considerations limit this latitude, and that there are certain conditions necessary in order to get the most available heat from a pound of coal. There are three ways, and only three, in which the heat developed by the combustion of coal in a steam boiler furnace may be expended. 1st, and principally. It should be conveyed to the water in the boiler, and be utilized in the production of steam. To be perfect, a boiler should so utilize all the heat of combustion, but there are no perfect boilers. 2nd. A portion of the heat of combustion is conveyed up the chimney in the waste gases. This is in proportion to the weight of the gases, and the difference between their temperature and that of the air and coal before they entered the fire. 3rd. Another portion is dissipated by radiation from the sides of the furnace. In a stove the heat is all used in these latter two ways, either it goes off through the chimney or is radiated into the surrounding space. It is one of the principal problems of boiler engineering to render the amount of heat thus lost as small as possible. The loss from radiation is in proportion to the amount of surface, its nature, its temperature, and the time it is exposed. This loss can be almost entirely eliminated by thick walls and a smooth white or polished surface, but its amount is ordinarily so small that these extraordinary precautions do not pay in practice. It is evident that the temperature of the escaping gases cannot be brought below that of the absorbing surfaces, while it may be much greater even to that of the fire. This is supposing that all of the escaping gases have passed through the fire. In case air is allowed to leak into the flues, and mingle with the gases after they have left the heating surfaces, the temperature may be brought down to almost any point above that of the atmosphere, but without any reduction in the amount of heat wasted. It is in this way that those low chimney temperatures are sometimes attained which pass for proof of economy with the unobserving. All surplus air admitted to the fire, or to the gases before they leave the heating surfaces, increases the losses. We are now prepared to see why and how the temperature and the rapidity of combustion in the boiler furnace affect the economy, and that though the amount of heat developed may be the same, the heat available for the generation of steam may be much less with one rate or temperature of combustion than another. Assuming that there is no air passing up the chimney other than that which has passed through the fire, the higher the temperature of the fire and the lower that of the escaping gases the better the economy, for the losses by the chimney gases will bear the same proportion to the heat generated by the combustion as the temperature of those gases bears to the temperature of the fire. That is to say, if the temperature of the fire is 2500 degrees and that of the chimney gases 500 degrees above that of the atmosphere, the loss by the chimney will be 500/2500 = 20 per cent. Therefore, as the escaping gases cannot be brought below the temperature of the absorbing surface, which is practically a fixed quantity, the temperature of the fire must be high in order to secure good economy. The losses by radiation being practically proportioned to the time occupied, the more coal burned in a given furnace in a given time, the less will be the proportionate loss from that cause. It therefore follows that we should burn our coal rapidly and at a high temperature to secure the best available economy. [Illustration: Portion of 9880 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock & Wilcox Chain Grate Stokers at the South Side Elevated Ry. Co., Chicago, Ill.] PROPERTIES OF WATER Pure water is a chemical compound of one volume of oxygen and two volumes of hydrogen, its chemical symbol being H_{2}O. The weight of water depends upon its temperature. Its weight at four temperatures, much used in physical calculations, is given in Table 10. TABLE 10 WEIGHT OF WATER AT TEMPERATURES USED IN PHYSICAL CALCULATIONS +---------------------------+----------+----------+ | Temperature Degrees |Weight per|Weight per| | Fahrenheit |Cubic Foot|Cubic Inch| | | Pounds | Pounds | +---------------------------+----------+----------+ |At 32 degrees or freezing | | | | point at sea level | 62.418 | 0.03612 | |At 39.2 degrees or point of| | | | maximum density | 62.427 | 0.03613 | |At 62 degrees or standard | | | | temperature | 62.355 | 0.03608 | |At 212 degrees or boiling | | | | point at sea level | 59.846 | 0.03469 | +---------------------------+----------+----------+ While authorities differ as to the weight of water, the range of values given for 62 degrees Fahrenheit (the standard temperature ordinarily taken) being from 62.291 pounds to 62.360 pounds per cubic foot, the value 62.355 is generally accepted as the most accurate. A United States standard gallon holds 231 cubic inches and weighs, at 62 degrees Fahrenheit, approximately 8-1/3 pounds. A British Imperial gallon holds 277.42 cubic inches and weighs, at 62 degrees Fahrenheit, 10 pounds. The above are the true weights corrected for the effect of the buoyancy of the air, or the weight in vacuo. If water is weighed in air in the ordinary way, there is a correction of about one-eighth of one per cent which is usually negligible. TABLE 11 VOLUME AND WEIGHT OF DISTILLED WATER AT VARIOUS TEMPERATURES[12] +-----------+---------------+----------+ |Temperature|Relative Volume|Weight per| | Degrees | Water at 39.2 |Cubic Foot| | Fahrenheit| Degrees = 1 | Pounds | +-----------+---------------+----------+ | 32 | 1.000176 | 62.42 | | 39.2 | 1.000000 | 62.43 | | 40 | 1.000004 | 62.43 | | 50 | 1.00027 | 62.42 | | 60 | 1.00096 | 62.37 | | 70 | 1.00201 | 62.30 | | 80 | 1.00338 | 62.22 | | 90 | 1.00504 | 62.11 | | 100 | 1.00698 | 62.00 | | 110 | 1.00915 | 61.86 | | 120 | 1.01157 | 61.71 | | 130 | 1.01420 | 61.55 | | 140 | 1.01705 | 61.38 | | 150 | 1.02011 | 61.20 | | 160 | 1.02337 | 61.00 | | 170 | 1.02682 | 60.80 | | 180 | 1.03047 | 60.58 | | 190 | 1.03431 | 60.36 | | 200 | 1.03835 | 60.12 | | 210 | 1.04256 | 59.88 | | 212 | 1.04343 | 59.83 | | 220 | 1.0469 | 59.63 | | 230 | 1.0515 | 59.37 | | 240 | 1.0562 | 59.11 | | 250 | 1.0611 | 58.83 | | 260 | 1.0662 | 58.55 | | 270 | 1.0715 | 58.26 | | 280 | 1.0771 | 57.96 | | 290 | 1.0830 | 57.65 | | 300 | 1.0890 | 57.33 | | 310 | 1.0953 | 57.00 | | 320 | 1.1019 | 56.66 | | 330 | 1.1088 | 56.30 | | 340 | 1.1160 | 55.94 | | 350 | 1.1235 | 55.57 | | 360 | 1.1313 | 55.18 | | 370 | 1.1396 | 54.78 | | 380 | 1.1483 | 54.36 | | 390 | 1.1573 | 53.94 | | 400 | 1.167 | 53.5 | | 410 | 1.177 | 53.0 | | 420 | 1.187 | 52.6 | | 430 | 1.197 | 52.2 | | 440 | 1.208 | 51.7 | | 450 | 1.220 | 51.2 | | 460 | 1.232 | 50.7 | | 470 | 1.244 | 50.2 | | 480 | 1.256 | 49.7 | | 490 | 1.269 | 49.2 | | 500 | 1.283 | 48.7 | | 510 | 1.297 | 48.1 | | 520 | 1.312 | 47.6 | | 530 | 1.329 | 47.0 | | 540 | 1.35 | 46.3 | | 550 | 1.37 | 45.6 | | 560 | 1.39 | 44.9 | +-----------+---------------+----------+ Water is but slightly compressible and for all practical purposes may be considered non-compressible. The coefficient of compressibility ranges from 0.000040 to 0.000051 per atmosphere at ordinary temperatures, this coefficient decreasing as the temperature increases. Table 11 gives the weight in vacuo and the relative volume of a cubic foot of distilled water at various temperatures. The weight of water at the standard temperature being taken as 62.355 pounds per cubic foot, the pressure exerted by the column of water of any stated height, and conversely the height of any column required to produce a stated pressure, may be computed as follows: The pressure in pounds per square foot = 62.355 × height of column in feet. The pressure in pounds per square inch = 0.433 × height of column in feet. Height of column in feet = pressure in pounds per square foot ÷ 62.355. Height of column in feet = pressure in pounds per square inch ÷ 0.433. Height of column in inches = pressure in pounds per square inch × 27.71. Height of column in inches = pressure in ounces per square inch × 1.73. By a change in the weights given above, the pressure exerted and height of column may be computed for temperatures other than 62 degrees. A pressure of one pound per square inch is exerted by a column of water 2.3093 feet or 27.71 inches high at 62 degrees Fahrenheit. Water in its natural state is never found absolutely pure. In solvent power water has a greater range than any other liquid. For common salt, this is approximately a constant at all temperatures, while with such impurities as magnesium and sodium sulphates, this solvent power increases with an increase in temperature. TABLE 12 BOILING POINT OF WATER AT VARIOUS ALTITUDES +--------------+----------------+-------------+---------------+ |Boiling Point | Altitude Above | Atmospheric | Barometer | | Degrees | Sea Level | Pressure | Reduced | | Fahrenheit | Feet | Pounds per | to 32 Degrees | | | | Square Inch | Inches | +--------------+----------------+-------------+---------------+ | 184 | 15221 | 8.20 | 16.70 | | 185 | 14649 | 8.38 | 17.06 | | 186 | 14075 | 8.57 | 17.45 | | 187 | 13498 | 8.76 | 17.83 | | 188 | 12934 | 8.95 | 18.22 | | 189 | 12367 | 9.14 | 18.61 | | 190 | 11799 | 9.34 | 19.02 | | 191 | 11243 | 9.54 | 19.43 | | 192 | 10685 | 9.74 | 19.85 | | 193 | 10127 | 9.95 | 20.27 | | 194 | 9579 | 10.17 | 20.71 | | 195 | 9031 | 10.39 | 21.15 | | 196 | 8481 | 10.61 | 21.60 | | 197 | 7932 | 10.83 | 22.05 | | 198 | 7381 | 11.06 | 22.52 | | 199 | 6843 | 11.29 | 22.99 | | 200 | 6304 | 11.52 | 23.47 | | 201 | 5764 | 11.76 | 23.95 | | 202 | 5225 | 12.01 | 24.45 | | 203 | 4697 | 12.26 | 24.96 | | 204 | 4169 | 12.51 | 25.48 | | 205 | 3642 | 12.77 | 26.00 | | 206 | 3115 | 13.03 | 26.53 | | 207 | 2589 | 13.30 | 27.08 | | 208 | 2063 | 13.57 | 27.63 | | 209 | 1539 | 13.85 | 28.19 | | 210 | 1025 | 14.13 | 28.76 | | 211 | 512 | 14.41 | 29.33 | | 212 | Sea Level | 14.70 | 29.92 | +--------------+----------------+-------------+---------------+ Sea water contains on an average approximately 3.125 per cent of its weight of solid matter or a thirty-second part of the weight of the water and salt held in solution. The approximate composition of this solid matter will be: sodium chloride 76 per cent, magnesium chloride 10 per cent, magnesium sulphate 6 per cent, calcium sulphate 5 per cent, calcium carbonate 0.5 per cent, other substances 2.5 per cent. [Illustration: 7200 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters at the Capital Traction Co., Washington, D. C.] The boiling point of water decreases as the altitude above sea level increases. Table 12 gives the variation in the boiling point with the altitude. Water has a greater specific heat or heat-absorbing capacity than any other known substance (bromine and hydrogen excepted) and its specific heat is the basis for measurement of the capacity of heat absorption of all other substances. From the definition, the specific heat of water is the number of British thermal units required to raise one pound of water one degree. This specific heat varies with the temperature of the water. The generally accepted values are given in Table 13, which indicates the values as determined by Messrs. Marks and Davis and Mr. Peabody. TABLE 13 SPECIFIC HEAT OF WATER AT VARIOUS TEMPERATURES +----------------------+--------------------------------+ | MARKS AND DAVIS | PEABODY | | From Values of | From Values of | | Barnes and Dieterici | Barnes and Regnault | +-----------+----------+---------------------+----------+ |Temperature| Specific | Temperature | Specific | +-----------+ Heat +----------+----------+ Heat | | Degrees | | Degrees | Degrees | | |Fahrenheit | |Centigrade|Fahrenheit| | +-----------+----------+----------+----------+----------+ | 30 | 1.0098 | 0 | 32 | 1.0094 | | 40 | 1.0045 | 5 | 41 | 1.0053 | | 50 | 1.0012 | 10 | 50 | 1.0023 | | 55 | 1.0000 | 15 | 59 | 1.0003 | | 60 | 0.9990 | 16.11 | 61 | 1.0000 | | 70 | 0.9977 | 20 | 68 | 0.9990 | | 80 | 0.9970 | 25 | 77 | 0.9981 | | 90 | 0.9967 | 30 | 86 | 0.9976 | | 100 | 0.9967 | 35 | 95 | 0.9974 | | 110 | 0.9970 | 40 | 104 | 0.9974 | | 120 | 0.9974 | 45 | 113 | 0.9976 | | 130 | 0.9979 | 50 | 122 | 0.9980 | | 140 | 0.9986 | 55 | 131 | 0.9985 | | 150 | 0.9994 | 60 | 140 | 0.9994 | | 160 | 1.0002 | 65 | 149 | 1.0004 | | 170 | 1.0010 | 70 | 158 | 1.0015 | | 180 | 1.0019 | 75 | 167 | 1.0028 | | 190 | 1.0029 | 80 | 176 | 1.0042 | | 200 | 1.0039 | 85 | 185 | 1.0056 | | 210 | 1.0052 | 90 | 194 | 1.0071 | | 220 | 1.007 | 95 | 203 | 1.0086 | | 230 | 1.009 | 100 | 212 | 1.0101 | +-----------+----------+----------+----------+----------+ In consequence of this variation in specific heat, the variation in the heat of the liquid of the water at different temperatures is not a constant. Table 22[13] gives the heat of the liquid in a pound of water at temperatures ranging from 32 to 340 degrees Fahrenheit. The specific heat of ice at 32 degrees is 0.463. The specific heat of saturated steam (ice and saturated steam representing the other forms in which water may exist), is something that is difficult to define in any way which will not be misleading. When no liquid is present the specific heat of saturated steam is negative.[14] The use of the value of the specific heat of steam is practically limited to instances where superheat is present, and the specific heat of superheated steam is covered later in the book. BOILER FEED WATER All natural waters contain some impurities which, when introduced into a boiler, may appear as solids. In view of the apparent present-day tendency toward large size boiler units and high overloads, the importance of the use of pure water for boiler feed purposes cannot be over-estimated. Ordinarily, when water of sufficient purity for such use is not at hand, the supply available may be rendered suitable by some process of treatment. Against the cost of such treatment, there are many factors to be considered. With water in which there is a marked tendency toward scale formation, the interest and depreciation on the added boiler units necessary to allow for the systematic cleaning of certain units must be taken into consideration. Again there is a considerable loss in taking boilers off for cleaning and replacing them on the line. On the other hand, the decrease in capacity and efficiency accompanying an increased incrustation of boilers in use has been too generally discussed to need repetition here. Many experiments have been made and actual figures reported as to this decrease, but in general, such figures apply only to the particular set of conditions found in the plant where the boiler in question was tested. So many factors enter into the effect of scale on capacity and economy that it is impossible to give any accurate figures on such decrease that will serve all cases, but that it is large has been thoroughly proven. While it is almost invariably true that practically any cost of treatment will pay a return on the investment of the apparatus, the fact must not be overlooked that there are certain waters which should never be used for boiler feed purposes and which no treatment can render suitable for such purpose. In such cases, the only remedy is the securing of other feed supply or the employment of evaporators for distilling the feed water as in marine service. TABLE 14 APPROXIMATE CLASSIFICATION OF IMPURITIES FOUND IN FEED WATERS THEIR EFFECT AND ORDINARY METHODS OF RELIEF +-----------------------+--------------+-----------------------------+ | Difficulty Resulting | Nature of | Ordinary Method of | | from Presence of | Difficulty | Overcoming or Relieving | +-----------------------+--------------+-----------------------------+ | Sediment, Mud, etc. | Incrustation | Settling tanks, filtration, | | | | blowing down. | | | | | | Readily Soluble Salts | Incrustation | Blowing down. | | | | | | Bicarbonates of Lime, | Incrustation | Heating feed. Treatment by | | Magnesia, etc. | | addition of lime or of lime | | | | and soda. Barium carbonate. | | | | | | Sulphate of Lime | Incrustation | Treatment by addition of | | | | soda. Barium carbonate. | | | | | | Chloride and Sulphate | Corrosion | Treatment by addition of | | of Magnesium | | carbonate of soda. | | | | | | Acid | Corrosion | Alkali. | | | | | | Dissolved Carbonic | Corrosion | Heating feed. Keeping air | | Acid and Oxygen | | from feed. Addition of | | | | caustic soda or slacked | | | | lime. | | | | | | Grease | Corrosion | Filter. Iron alum as | | | | coagulent. Neutralization | | | | by carbonate of soda. Use | | | | of best hydrocarbon oils. | | | | | | Organic Matter | Corrosion | Filter. Use of coagulent. | | | | | | Organic Matter | Priming | Settling tanks. Filter in | | (Sewage) | | connection with coagulent. | | | | | | Carbonate of Soda in | Priming | Barium carbonate. New feed | | large quantities | | supply. If from treatment, | | | | change. | +-----------------------+--------------+-----------------------------+ It is evident that the whole subject of boiler feed waters and their treatment is one for the chemist rather than for the engineer. A brief outline of the difficulties that may be experienced from the use of poor feed water and a suggestion as to a method of overcoming certain of these difficulties is all that will be attempted here. Such a brief outline of the subject, however, will indicate the necessity for a chemical analysis of any water before a treatment is tried and the necessity of adapting the treatment in each case to the nature of the difficulties that may be experienced. Table 14 gives a list of impurities which may be found in boiler feed water, grouped according to their effect on boiler operation and giving the customary method used for overcoming difficulty to which they lead. Scale--Scale is formed on boiler heating surfaces by the depositing of impurities in the feed water in the form of a more or less hard adherent crust. Such deposits are due to the fact that water loses its soluble power at high temperatures or because the concentration becomes so high, due to evaporation, that the impurities crystallize and adhere to the boiler surfaces. The opportunity for formation of scale in a boiler will be apparent when it is realized that during a month's operation of a 100 horse-power boiler, 300 pounds of solid matter may be deposited from water containing only 7 grains per gallon, while some spring and well waters contain sufficient to cause a deposit of as high as 2000 pounds. The salts usually responsible for such incrustation are the carbonates and sulphates of lime and magnesia, and boiler feed treatment in general deals with the getting rid of these salts more or less completely. TABLE 15 SOLUBILITY OF MINERAL SALTS IN WATER (SPARKS) IN GRAINS PER U. S. GALLON (58,381 GRAINS), EXCEPT AS NOTED +------------------------------+------------+-------------+ |Temperature Degrees Fahrenheit| 60 Degrees | 212 Degrees | +------------------------------+------------+-------------+ |Calcium Carbonate | 2.5 | 1.5 | |Calcium Sulphate | 140.0 | 125.0 | |Magnesium Carbonate | 1.0 | 1.8 | |Magnesium Sulphate | 3.0 pounds | 12.0 pounds | |Sodium Chloride | 3.5 pounds | 4.0 pounds | |Sodium Sulphate | 1.1 pounds | 5.0 pounds | +------------------------------+------------+-------------+ CALCIUM SULPHATE AT TEMPERATURE ABOVE 212 DEGREES (CHRISTIE) +------------------------------+----+----+-------+----+---+ |Temperature degrees Fahrenheit|284 |329 |347-365| 464|482| |Corresponding gauge pressure | 38 | 87 |115-149| 469|561| |Grains per gallon |45.5|32.7| 15.7 |10.5|9.3| +------------------------------+----+----+-------+----+---+ Table 15 gives the solubility of these mineral salts in water at various temperatures in grains per U. S. gallon (58,381 grains). It will be seen from this table that the carbonates of lime and magnesium are not soluble above 212 degrees, and calcium sulphate while somewhat insoluble above 212 degrees becomes more greatly so as the temperature increases. Scale is also formed by the settling of mud and sediment carried in suspension in water. This may bake or be cemented to a hard scale when mixed with other scale-forming ingredients. Corrosion--Corrosion, or a chemical action leading to the actual destruction of the boiler metal, is due to the solvent or oxidizing properties of the feed water. It results from the presence of acid, either free or developed[15] in the feed, the admixture of air with the feed water, or as a result of a galvanic action. In boilers it takes several forms: 1st. Pitting, which consists of isolated spots of active corrosion which does not attack the boiler as a whole. 2nd. General corrosion, produced by naturally acid waters and where the amount is so even and continuous that no accurate estimate of the metal eaten away may be made. 3rd. Grooving, which, while largely a mechanical action which may occur in neutral waters, is intensified by acidity. Foaming--This phenomenon, which ordinarily occurs with waters contaminated with sewage or organic growths, is due to the fact that the suspended particles collect on the surface of the water in the boiler and render difficult the liberation of steam bubbles arising to that surface. It sometimes occurs with water containing carbonates in solution in which a light flocculent precipitate will be formed on the surface of the water. Again, it is the result of an excess of sodium carbonate used in treatment for some other difficulty where animal or vegetable oil finds its way into the boiler. Priming--Priming, or the passing off of steam from a boiler in belches, is caused by the concentration of sodium carbonate, sodium sulphate or sodium chloride in solution. Sodium sulphate is found in many southern waters and also where calcium or magnesium sulphate is precipitated with soda ash. Treatment of Feed Water--For scale formation. The treatment of feed water, carrying scale-forming ingredients, is along two main lines: 1st, by chemical means by which such impurities as are carried by the water are caused to precipitate; and 2nd, by the means of heat, which results in the reduction of the power of water to hold certain salts in solution. The latter method alone is sufficient in the case of certain temporarily hard waters, but the heat treatment, in general, is used in connection with a chemical treatment to assist the latter. Before going further into detail as to the treatment of water, it may be well to define certain terms used. _Hardness_, which is the most widely known evidence of the presence in water of scale-forming matter, is that quality, the variation of which makes it more difficult to obtain a lather or suds from soap in one water than in another. This action is made use of in the soap test for hardness described later. Hardness is ordinarily classed as either temporary or permanent. Temporarily hard waters are those containing carbonates of lime and magnesium, which may be precipitated by boiling at 212 degrees and which, if they contain no other scale-forming ingredients, become "soft" under such treatment. Permanently hard waters are those containing mainly calcium sulphate, which is only precipitated at the high temperatures found in the boiler itself, 300 degrees Fahrenheit or more. The scale of hardness is an arbitrary one, based on the number of grains of solids per gallon and waters may be classed on such a basis as follows: 1-10 grain per gallon, soft water; 10-20 grain per gallon, moderately hard water; above 25 grains per gallon, very hard water. _Alkalinity_ is a general term used for waters containing compounds with the power of neutralizing acids. _Causticity_, as used in water treatment, is a term coined by A. McGill, indicating the presence of an excess of lime added during treatment. Though such presence would also indicate alkalinity, the term is arbitrarily used to apply to those hydrates whose presence is indicated by phenolphthalein. Of the chemical methods of water treatment, there are three general processes: 1st. Lime Process. The lime process is used for waters containing bicarbonates of lime and magnesia. Slacked lime in solution, as lime water, is the reagent used. This combines with the carbonic acid which is present, either free or as carbonates, to form an insoluble monocarbonate of lime. The soluble bicarbonates of lime and magnesia, losing their carbonic acid, thereby become insoluble and precipitate. 2nd. Soda Process. The soda process is used for waters containing sulphates of lime and magnesia. Carbonate of soda and hydrate of soda (caustic soda) are used either alone or together as the reagents. Carbonate of soda, added to water containing little or no carbonic acid or bicarbonates, decomposes the sulphates to form insoluble carbonate of lime or magnesia which precipitate, the neutral soda remaining in solution. If free carbonic acid or bicarbonates are present, bicarbonate of lime is formed and remains in solution, though under the action of heat, the carbon dioxide will be driven off and insoluble monocarbonates will be formed. Caustic soda used in this process causes a more energetic action, it being presumed that the caustic soda absorbs the carbonic acid, becomes carbonate of soda and acts as above. 3rd. Lime and Soda Process. This process, which is the combination of the first two, is by far the most generally used in water purification. Such a method is used where sulphates of lime and magnesia are contained in the water, together with such quantity of carbonic acid or bicarbonates as to impair the action of the soda. Sufficient soda is used to break down the sulphates of lime and magnesia and as much lime added as is required to absorb the carbonic acid not taken up in the soda reaction. All of the apparatus for effecting such treatment of feed waters is approximately the same in its chemical action, the numerous systems differing in the methods of introduction and handling of the reagents. The methods of testing water treated by an apparatus of this description follow. When properly treated, alkalinity, hardness and causticity should be in the approximate relation of 6, 5 and 4. When too much lime is used in the treatment, the causticity in the purified water, as indicated by the acid test, will be nearly equal to the alkalinity. If too little lime is used, the causticity will fall to approximately half the alkalinity. The hardness should not be in excess of two points less than the alkalinity. Where too great a quantity of soda is used, the hardness is lowered and the alkalinity raised. If too little soda, the hardness is raised and the alkalinity lowered. Alkalinity and causticity are tested with a standard solution of sulphuric acid. A standard soap solution is used for testing for hardness and a silver nitrate solution may also be used for determining whether an excess of lime has been used in the treatment. Alkalinity: To 50 cubic centimeters of treated water, to which there has been added sufficient methylorange to color it, add the acid solution, drop by drop, until the mixture is on the point of turning red. As the acid solution is first added, the red color, which shows quickly, disappears on shaking the mixture, and this color disappears more slowly as the critical point is approached. One-tenth cubic centimeter of the standard acid solution corresponds to one degree of alkalinity. [Illustration: 2640 Horse-power Installation of Babcock & Wilcox Boilers at the Botany Worsted Mills, Passaic, N. J.] Causticity: To 50 cubic centimeters of treated water, to which there has been added one drop of phenolphthalein dissolved in alcohol to give the water a pinkish color, add the acid solution, drop by drop, shaking after each addition, until the color entirely disappears. One-tenth cubic centimeter of acid solution corresponds to one degree of causticity. The alkalinity may be determined from the same sample tested for causticity by the coloring with methylorange and adding the acid until the sample is on the point of turning red. The total acid added in determining both causticity and alkalinity in this case is the measure of the alkalinity. Hardness: 100 cubic centimeters of the treated water is used for this test, one cubic centimeter of the soap solution corresponding to one degree of hardness. The soap solution is added a very little at a time and the whole violently shaken. Enough of the solution must be added to make a permanent lather or foam, that is, the soap bubbles must not disappear after the shaking is stopped. Excess of lime as determined by nitrate of silver: If there is an excess of lime used in the treatment, a sample will become a dark brown by the addition of a small quantity of silver nitrate, otherwise a milky white solution will be formed. Combined Heat and Chemical Treatment: Heat is used in many systems of feed treatment apparatus as an adjunct to the chemical process. Heat alone will remove temporary hardness by the precipitation of carbonates of lime and magnesia and, when used in connection with the chemical process, leaves only the permanent hardness or the sulphates of lime to be taken care of by chemical treatment. TABLE 16 REAGENTS REQUIRED IN LIME AND SODA PROCESS FOR TREATING 1000 U. S. GALLONS OF WATER PER GRAIN PER GALLON OF CONTAINED IMPURITIES[16] +-----------------------+-----------+-----------+ | | Lime[17] | Soda[18] | | | Pounds | Pounds | +-----------------------+-----------+-----------+ | Calcium Carbonate | 0.098 | ... | | Calcium Sulphate | ... | 0.124 | | Calcium Chloride | ... | 0.151 | | Calcium Nitrate | ... | 0.104 | | Magnesium Carbonate | 0.234 | ... | | Magnesium Sulphate | 0.079 | 0.141 | | Magnesium Chloride | 0.103 | 0.177 | | Magnesium Nitrate | 0.067 | 0.115 | | Ferrous Carbonate | 0.169 | ... | | Ferrous Sulphate | 0.070 | 0.110 | | Ferric Sulphate | 0.074 | 0.126 | | Aluminum Sulphate | 0.087 | 0.147 | | Free Sulphuric Acid | 0.100 | 0.171 | | Sodium Carbonate | 0.093 | ... | | Free Carbon Dioxide | 0.223 | ... | | Hydrogen Sulphite | 0.288 | ... | +-----------------------+-----------+-----------+ The chemicals used in the ordinary lime and soda process of feed water treatment are common lime and soda. The efficiency of such apparatus will depend wholly upon the amount and character of the impurities in the water to be treated. Table 16 gives the amount of lime and soda required per 1000 gallons for each grain per gallon of the various impurities found in the water. This table is based on lime containing 90 per cent calcium oxide and soda containing 58 per cent sodium oxide, which correspond to the commercial quality ordinarily purchasable. From this table and the cost of the lime and soda, the cost of treating any water per 1000 gallons may be readily computed. Less Usual Reagents--Barium hydrate is sometimes used to reduce permanent hardness or the calcium sulphate component. Until recently, the high cost of barium hydrate has rendered its use prohibitive but at the present it is obtained as a by-product in cement manufacture and it may be purchased at a more reasonable figure than heretofore. It acts directly on the soluble sulphates to form barium sulphate which is insoluble and may be precipitated. Where this reagent is used, it is desirable that the reaction be allowed to take place outside of the boiler, though there are certain cases where its internal use is permissible. Barium carbonate is sometimes used in removing calcium sulphate, the products of the reaction being barium sulphate and calcium carbonate, both of which are insoluble and may be precipitated. As barium carbonate in itself is insoluble, it cannot be added to water as a solution and its use should, therefore, be confined to treatment outside of the boiler. Silicate of soda will precipitate calcium carbonate with the formation of a gelatinous silicate of lime and carbonate of soda. If calcium sulphate is also present, carbonate of soda is formed in the above reaction, which in turn will break down the sulphate. Oxalate of soda is an expensive but efficient reagent which forms a precipitate of calcium oxalate of a particularly insoluble nature. Alum and iron alum will act as efficient coagulents where organic matter is present in the water. Iron alum has not only this property but also that of reducing oil discharged from surface condensers to a condition in which it may be readily removed by filtration. Corrosion--Where there is a corrosive action because of the presence of acid in the water or of oil containing fatty acids which will decompose and cause pitting wherever the sludge can find a resting place, it may be overcome by the neutralization of the water by carbonate of soda. Such neutralization should be carried to the point where the water will just turn red litmus paper blue. As a preventative of such action arising from the presence of the oil, only the highest grades of hydrocarbon oils should be used. Acidity will occur where sea water is present in a boiler. There is the possibility of such an occurrence in marine practice and in stationary plants using sea water for condensing, due to leaky condenser tubes, priming in the evaporators, etc. Such acidity is caused through the dissociation of magnesium chloride into hydrochloride acid and magnesia under high temperatures. The acid in contact with the metal forms an iron salt which immediately upon its formation is neutralized by the free magnesia in the water, thereby precipitating iron oxide and reforming magnesium chloride. The preventive for corrosion arising from such acidity is the keeping tight of the condenser. Where it is unavoidable that some sea water should find its way into a boiler, the acidity resulting should be neutralized by soda ash. This will convert the magnesium chloride into magnesium carbonate and sodium chloride, neither of which is corrosive but both of which are scale-forming. The presence of air in the feed water which is sucked in by the feed pump is a well recognized cause of corrosion. Air bubbles form below the water line and attack the metal of the boiler, the oxygen of the air causing oxidization of the boiler metal and the formation of rust. The particle of rust thus formed is swept away by the circulation or is dislodged by expansion and the minute pit thus left forms an ideal resting place for other air bubbles and the continuation of the oxidization process. The prevention is, of course, the removing of the air from the feed water. In marine practice, where there has been experienced the most difficulty from this source, it has been found to be advantageous to pump the water from the hot well to a filter tank placed above the feed pump suction valves. In this way the air is liberated from the surface of the tank and a head is assured for the suction end of the pump. In this same class of work, the corrosive action of air is reduced by introducing the feed through a spray nozzle into the steam space above the water line. Galvanic action, resulting in the eating away of the boiler metal through electrolysis was formerly considered practically the sole cause of corrosion. But little is known of such action aside from the fact that it does take place in certain instances. The means adopted as a remedy is usually the installation of zinc plates within the boiler, which must have positive metallic contact with the boiler metal. In this way, local electrolytic effects are overcome by a still greater electrolytic action at the expense of the more positive zinc. The positive contact necessary is difficult to maintain and it is questionable just what efficacy such plates have except for a short period after their installation when the contact is known to be positive. Aside from protection from such electrolytic action, however, the zinc plates have a distinct use where there is the liability of air in the feed, as they offer a substance much more readily oxidized by such air than the metal of the boiler. Foaming--Where foaming is caused by organic matter in suspension, it may be largely overcome by filtration or by the use of a coagulent in connection with filtration, the latter combination having come recently into considerable favor. Alum, or potash alum, and iron alum, which in reality contains no alumina and should rather be called potassia-ferric, are the coagulents generally used in connection with filtration. Such matter as is not removed by filtration may, under certain conditions, be handled by surface blowing. In some instances, settling tanks are used for the removal of matter in suspension, but where large quantities of water are required, filtration is ordinarily substituted on account of the time element and the large area necessary in settling tanks. Where foaming occurs as the result of overtreatment of the feed water, the obvious remedy is a change in such treatment. Priming--Where priming is caused by excessive concentration of salts within a boiler, it may be overcome largely by frequent blowing down. The degree of concentration allowable before priming will take place varies widely with conditions of operation and may be definitely determined only by experience with each individual set of conditions. It is the presence of the salts that cause priming that may result in the absolute unfitness of water for boiler feed purposes. Where these salts exist in such quantities that the amount of blowing down necessary to keep the degree of concentration below the priming point results in excessive losses, the only remedy is the securing of another supply of feed, and the results will warrant the change almost regardless of the expense. In some few instances, the impurities may be taken care of by some method of water treatment but such water should be submitted to an authority on the subject before any treatment apparatus is installed. [Illustration: 3000 Horse-power Installation of Cross Drum Babcock & Wilcox Boilers and Superheaters Equipped with Babcock & Wilcox Chain Grate Stokers at the Washington Terminal Co., Washington, D. C.] Boiler Compounds--The method of treatment of feed water by far the most generally used is by the use of some of the so-called boiler compounds. There are many reliable concerns handling such compounds who unquestionably secure the promised results, but there is a great tendency toward looking on the compound as a "cure all" for any water difficulties and care should be taken to deal only with reputable concerns. The composition of these compounds is almost invariably based on soda with certain tannic substances and in some instances a gelatinous substance which is presumed to encircle scale particles and prevent their adhering to the boiler surfaces. The action of these compounds is ordinarily to reduce the calcium sulphate in the water by means of carbonate of soda and to precipitate it as a muddy form of calcium carbonate which may be blown off. The tannic compounds are used in connection with the soda with the idea of introducing organic matter into any scale already formed. When it has penetrated to the boiler metal, decomposition of the scale sets in, causing a disruptive effect which breaks the scale from the metal sometimes in large slabs. It is this effect of boiler compounds that is to be most carefully guarded against or inevitable trouble will result from the presence of loose scale with the consequent danger of tube losses through burning. When proper care is taken to suit the compound to the water in use, the results secured are fairly effective. In general, however, the use of compounds may only be recommended for the prevention of scale rather than with the view to removing scale which has already formed, that is, the compounds should be introduced with the feed water only when the boiler has been thoroughly cleaned. FEED WATER HEATING AND METHODS OF FEEDING Before water fed into a boiler can be converted into steam, it must be first heated to a temperature corresponding to the pressure within the boiler. Steam at 160 pounds gauge pressure has a temperature of approximately 371 degrees Fahrenheit. If water is fed to the boiler at 60 degrees Fahrenheit, each pound must have 311 B. t. u. added to it to increase its temperature 371 degrees, which increase must take place before the water can be converted into steam. As it requires 1167.8 B. t. u. to raise one pound of water from 60 to 371 degrees and to convert it into steam at 160 pounds gauge pressure, the 311 degrees required simply to raise the temperature of the water from 60 to 371 degrees will be approximately 27 per cent of the total. If, therefore, the temperature of the water can be increased from 60 to 371 degrees before it is introduced into a boiler by the utilization of heat from some source that would otherwise be wasted, there will be a saving in the fuel required of 311 ÷ 1167.8 = 27 per cent, and there will be a net saving, provided the cost of maintaining and operating the apparatus for securing this saving is less than the value of the heat thus saved. The saving in the fuel due to the heating of feed water by means of heat that would otherwise be wasted may be computed from the formula: 100 (t - t_{i}) Fuel saving per cent = --------------- (1) H + 32 - t_{i} where, t = temperature of feed water after heating, t_{i} = temperature of feed water before heating, and H = total heat above 32 degrees per pound of steam at the boiler pressure. Values of H may be found in Table 23. Table 17 has been computed from this formula to show the fuel saving under the conditions assumed with the boiler operating at 180 pounds gauge pressure. TABLE 17 SAVING IN FUEL, IN PER CENT, BY HEATING FEED WATER GAUGE PRESSURE 180 POUNDS +-----------+-----------------------------------------+ | Initial | Final Temperature--Degrees Fahrenheit | |Temperature|-----+-----+-----+-----+-----+-----+-----| | Fahrenheit| 120 | 140 | 160 | 180 | 200 | 250 | 300 | +-----------+-----+-----+-----+-----+-----+-----+-----+ | 32 | 7.35| 9.02|10.69|12.36|14.04|18.20|22.38| | 35 | 7.12| 8.79|10.46|12.14|13.82|18.00|22.18| | 40 | 6.72| 8.41|10.09|11.77|13.45|17.65|21.86| | 45 | 6.33| 8.02| 9.71|11.40|13.08|17.30|21.52| | 50 | 5.93| 7.63| 9.32|11.02|12.72|16.95|21.19| | 55 | 5.53| 7.24| 8.94|10.64|12.34|16.60|20.86| | 60 | 5.13| 6.84| 8.55|10.27|11.97|16.24|20.52| | 65 | 4.72| 6.44| 8.16| 9.87|11.59|15.88|20.18| | 70 | 4.31| 6.04| 7.77| 9.48|11.21|15.52|19.83| | 75 | 3.90| 5.64| 7.36| 9.09|10.82|15.16|19.48| | 80 | 3.48| 5.22| 6.96| 8.70|10.44|14.79|19.13| | 85 | 3.06| 4.80| 6.55| 8.30|10.05|14.41|18.78| | 90 | 2.63| 4.39| 6.14| 7.89| 9.65|14.04|18.43| | 95 | 2.20| 3.97| 5.73| 7.49| 9.25|13.66|18.07| | 100 | 1.77| 3.54| 5.31| 7.08| 8.85|13.28|17.70| | 110 | .89| 2.68| 4.47| 6.25| 8.04|12.50|16.97| | 120 | .00| 1.80| 3.61| 5.41| 7.21|11.71|16.22| | 130 | | .91| 2.73| 4.55| 6.37|10.91|15.46| | 140 | | .00| 1.84| 3.67| 5.51|10.09|14.68| | 150 | | | .93| 2.78| 4.63| 9.26|13.89| | 160 | | | .00| 1.87| 3.74| 8.41|13.09| | 170 | | | | .94| 2.83| 7.55|12.27| | 180 | | | | .00| 1.91| 6.67|11.43| | 190 | | | | | .96| 5.77|10.58| | 200 | | | | | .00| 4.86| 9.71| | 210 | | | | | | 3.92| 8.82| +-----------+-----+-----+-----+-----+-----+-----+-----+ Besides the saving in fuel effected by the use of feed water heaters, other advantages are secured. The time required for the conversion of water into steam is diminished and the steam capacity of the boiler thereby increased. Further, the feeding of cold water into a boiler has a tendency toward the setting up of temperature strains, which are diminished in proportion as the temperature of the feed approaches that of the steam. An important additional advantage of heating feed water is that in certain types of heaters a large portion of the scale forming ingredients are precipitated before entering the boiler, with a consequent saving in cleaning and losses through decreased efficiency and capacity. In general, feed water heaters may be divided into closed heaters, open heaters and economizers; the first two depend for their heat upon exhaust, or in some cases live steam, while the last class utilizes the heat of the waste flue gases to secure the same result. The question of the type of apparatus to be installed is dependent upon the conditions attached to each individual case. In closed heaters the feed water and the exhaust steam do not come into actual contact with each other. Either the steam or the water passes through tubes surrounded by the other medium, as the heater is of the steam-tube or water-tube type. A closed heater is best suited for water free from scale-forming matter, as such matter soon clogs the passages. Cleaning such heaters is costly and the efficiency drops off rapidly as scale forms. A closed heater is not advisable where the engines work intermittently, as is the case with mine hoisting engines. In this class of work the frequent coolings between operating periods and the sudden heatings when operation commences will tend to loosen the tubes or even pull them apart. For this reason, an open heater, or economizer, will give more satisfactory service with intermittently operating apparatus. Open heaters are best suited for waters containing scale-forming matter. Much of the temporary hardness may be precipitated in the heater and the sediment easily removed. Such heaters are frequently used with a reagent for precipitating permanent hardness in the combined heat and chemical treatment of feed water. The so-called live steam purifiers are open heaters, the water being raised to the boiling temperature and the carbonates and a portion of the sulphates being precipitated. The disadvantage of this class of apparatus is that some of the sulphates remain in solution to be precipitated as scale when concentrated in the boiler. Sufficient concentration to have such an effect, however, may often be prevented by frequent blowing down. Economizers find their largest field where the design of the boiler is such that the maximum possible amount of heat is not extracted from the gases of combustion. The more wasteful the boiler, the greater the saving effected by the use of the economizer, and it is sometimes possible to raise the temperature of the feed water to that of high pressure steam by the installation of such an apparatus, the saving amounting in some cases to as much as 20 per cent. The fuel used bears directly on the question of the advisability of an economizer installation, for when oil is the fuel a boiler efficiency of 80 per cent or over is frequently realized, an efficiency which would leave a small opportunity for a commercial gain through the addition of an economizer. From the standpoint of space requirements, economizers are at a disadvantage in that they are bulky and require a considerable increase over space occupied by a heater of the exhaust type. They also require additional brickwork or a metal casing, which increases the cost. Sometimes, too, the frictional resistance of the gases through an economizer make its adaptability questionable because of the draft conditions. When figuring the net return on economizer investment, all of these factors must be considered. When the feed water is such that scale will quickly encrust the economizer and throw it out of service for cleaning during an excessive portion of the time, it will be necessary to purify water before introducing it into an economizer to make it earn a profit on the investment. From the foregoing, it is clearly indicated that it is impossible to make a definite statement as to the relative saving by heating feed water in any of the three types. Each case must be worked out independently and a decision can be reached only after an exhaustive study of all the conditions affecting the case, including the time the plant will be in service and probable growth of the plant. When, as a result of such study, the possible methods for handling the problem have been determined, the solution of the best apparatus can be made easily by the balancing of the saving possible by each method against its first cost, depreciation, maintenance and cost of operation. Feeding of Water--The choice of methods to be used in introducing feed water into a boiler lies between an injector and a pump. In most plants, an injector would not be economical, as the water fed by such means must be cold, a fact which makes impossible the use of a heater before the water enters the injector. Such a heater might be installed between the injector and the boiler but as heat is added to the water in the injector, the heater could not properly fulfill its function. TABLE 18 COMPARISON OF PUMPS AND INJECTORS _________________________________________________________________________ | | | | | Method of Supplying | | | | Feed-water to Boiler | Relative amount of | Saving of fuel over| | Temperature of feed-water as | coal required per | the amount required| | delivered to the pump or to | unit of time, the | when the boiler is | | injector, 60 degrees Fahren- | amount for a direct-| fed by a direct- | | heit. Rate of evaporation of | acting pump, feeding| acting pump without| | boiler, to pounds of water | water at 60 degrees | heater | | per pound of coal from and | without a heater, | Per Cent | | at 212 degrees Fahrenheit | being taken as unity| | |______________________________|_____________________|____________________| | | | | | Direct-acting Pump feeding | | | | water at 60 degrees without | | | | a heater | 1.000 | .0 | | | | | | Injector feeding water at | | | | 150 degrees without a heater | .985 | 1.5 | | Injector feeding through a | | | | heater in which the water is | | | | heated from 150 to 200 | | | | degrees | .938 | 6.2 | | | | | | Direct-acting Pump feeding | | | | water through a heater in | | | | which it is heated from 60 | | | | to 200 degrees | .879 | 12.1 | | | | | | Geared Pump run from the | | | | engine, feeding water | | | | through a heater in which it | | | | is heated from 60 to 200 | | | | degrees | .868 | 13.2 | |______________________________|_____________________|____________________| The injector, considered only in the light of a combined heater and pump, is claimed to have a thermal efficiency of 100 per cent, since all of the heat in the steam used is returned to the boiler with the water. This claim leads to an erroneous idea. If a pump is used in feeding the water to a boiler and the heat in the exhaust from the pump is imparted to the feed water, the pump has as high a thermal efficiency as the injector. The pump has the further advantage that it uses so much less steam for the forcing of a given quantity of water into the boiler that it makes possible a greater saving through the use of the exhaust from other auxiliaries for heating the feed, which exhaust, if an injector were used, would be wasted, as has been pointed out. In locomotive practice, injectors are used because there is no exhaust steam available for heating the feed, this being utilized in producing a forced draft, and because of space requirements. In power plant work, however, pumps are universally used for regular operation, though injectors are sometimes installed as an auxiliary method of feeding. Table 18 shows the relative value of injectors, direct-acting steam pumps and pumps driven from the engine, the data having been obtained from actual experiment. It will be noted that when feeding cold water direct to the boilers, the injector has a slightly greater economy but when feeding through a heater, the pump is by far the more economical. Auxiliaries--It is the general impression that auxiliaries will take less steam if the exhaust is turned into the condensers, in this way reducing the back pressure. As a matter of fact, vacuum is rarely registered on an indicator card taken from the cylinders of certain types of auxiliaries unless the exhaust connection is short and without bends, as long pipes and many angles offset the effect of the condenser. On the other hand, if the exhaust steam from the auxiliaries can be used for heating the feed water, all of the latent heat less only the loss due to radiation is returned to the boiler and is saved instead of being lost in the condensing water or wasted with the free exhaust. Taking into consideration the plant as a whole, it would appear that the auxiliary machinery, under such conditions, is more efficient than the main engines. [Illustration: Portion of 4160 Horse-power Installation of Babcock & Wilcox Boilers at the Prudential Life Insurance Co. Building, Newark, N. J.] STEAM When a given weight of a perfect gas is compressed or expanded at a constant temperature, the product of the pressure and volume is a constant. Vapors, which are liquids in aeriform condition, on the other hand, can exist only at a definite pressure corresponding to each temperature if in the saturated state, that is, the pressure is a function of the temperature only. Steam is water vapor, and at a pressure of, say, 150 pounds absolute per square inch saturated steam can exist only at a temperature 358 degrees Fahrenheit. Hence if the pressure of saturated steam be fixed, its temperature is also fixed, and _vice versa_. Saturated steam is water vapor in the condition in which it is generated from water with which it is in contact. Or it is steam which is at the maximum pressure and density possible at its temperature. If any change be made in the temperature or pressure of steam, there will be a corresponding change in its condition. If the pressure be increased or the temperature decreased, a portion of the steam will be condensed. If the temperature be increased or the pressure decreased, a portion of the water with which the steam is in contact will be evaporated into steam. Steam will remain saturated just so long as it is of the same pressure and temperature as the water with which it can remain in contact without a gain or loss of heat. Moreover, saturated steam cannot have its temperature lowered without a lowering of its pressure, any loss of heat being made up by the latent heat of such portion as will be condensed. Nor can the temperature of saturated steam be increased except when accompanied by a corresponding increase in pressure, any added heat being expended in the evaporation into steam of a portion of the water with which it is in contact. Dry saturated steam contains no water. In some cases, saturated steam is accompanied by water which is carried along with it, either in the form of a spray or is blown along the surface of the piping, and the steam is then said to be wet. The percentage weight of the steam in a mixture of steam and water is called the quality of the steam. Thus, if in a mixture of 100 pounds of steam and water there is three-quarters of a pound of water, the quality of the steam will be 99.25. Heat may be added to steam not in contact with water, such an addition of heat resulting in an increase of temperature and pressure if the volume be kept constant, or an increase in temperature and volume if the pressure remain constant. Steam whose temperature thus exceeds that of saturated steam at a corresponding pressure is said to be superheated and its properties approximate those of a perfect gas. As pointed out in the chapter on heat, the heat necessary to raise one pound of water from 32 degrees Fahrenheit to the point of ebullition is called the _heat of the liquid_. The heat absorbed during ebullition consists of that necessary to dissociate the molecules, or the _inner latent heat_, and that necessary to overcome the resistance to the increase in volume, or the _outer latent heat_. These two make up the _latent heat of evaporation_ and the sum of this latent heat of evaporation and the heat of the liquid make the _total heat_ of the steam. These values for various pressures are given in the steam tables, pages 122 to 127. The specific volume of saturated steam at any pressure is the volume in cubic feet of one pound of steam at that pressure. The density of saturated steam, that is, its weight per cubic foot, is obviously the reciprocal of the specific volume. This density varies as the 16/17 power over the ordinary range of pressures used in steam boiler work and may be found by the formula, D = .003027p^{.941}, which is correct within 0.15 per cent up to 250 pounds pressure. The relative volume of steam is the ratio of the volume of a given weight to the volume of the same weight of water at 39.2 degrees Fahrenheit and is equal to the specific volume times 62.427. As vapors are liquids in their gaseous form and the boiling point is the point of change in this condition, it is clear that this point is dependent upon the pressure under which the liquid exists. This fact is of great practical importance in steam condenser work and in many operations involving boiling in an open vessel, since in the latter case its altitude will have considerable influence. The relation between altitude and boiling point of water is shown in Table 12. The conditions of feed temperature and steam pressure in boiler tests, fuel performances and the like, will be found to vary widely in different trials. In order to secure a means for comparison of different trials, it is necessary to reduce all results to some common basis. The method which has been adopted for the reduction to a comparable basis is to transform the evaporation under actual conditions of steam pressure and feed temperature which exist in the trial to an equivalent evaporation under a set of standard conditions. These standard conditions presuppose a feed water temperature of 212 degrees Fahrenheit and a steam pressure equal to the normal atmospheric pressure at sea level, 14.7 pounds absolute. Under such conditions steam would be generated _at_ a temperature of 212 degrees, the temperature corresponding to atmospheric pressure at sea level, _from_ water at 212 degrees. The weight of water which _would_ be evaporated under the assumed standard conditions by exactly the amount of heat absorbed by the boiler under actual conditions existing in the trial, is, therefore, called the equivalent evaporation "from and at 212 degrees." The factor for reducing the weight of water actually converted into steam from the temperature of the feed, at the steam pressure existing in the trial, to the equivalent evaporation under standard conditions is called the _factor of evaporation._ This factor is the ratio of the total heat added to one pound of steam under the standard conditions to the heat added to each pound of steam in heating the water from the temperature of the feed in the trial to the temperature corresponding to the pressure existing in the trial. This heat added is obviously the difference between the total heat of evaporation of the steam at the pressure existing in the trial and the heat of the liquid in the water at the temperature at which it was fed in the trial. To illustrate by an example: In a boiler trial the temperature of the feed water is 60 degrees Fahrenheit and the pressure under which steam is delivered is 160.3 pounds gauge pressure or 175 pounds absolute pressure. The total heat of one pound of steam at 175 pounds pressure is 1195.9 B. t. u. measured above the standard temperature of 32 degrees Fahrenheit. But the water fed to the boiler contained 28.08 B. t. u. as the heat of the liquid measured above 32 degrees Fahrenheit. Therefore, to each pound of steam there has been added 1167.82 B. t. u. To evaporate one pound of water under standard conditions would, on the other hand, have required but 970.4 B. t. u., which, as described, is the latent heat of evaporation at 212 degrees Fahrenheit. Expressed differently, the total heat of one pound of steam at the pressure corresponding to a temperature of 212 degrees is 1150.4 B. t. u. One pound of water at 212 degrees contains 180 B. t. u. of sensible heat above 32 degrees Fahrenheit. Hence, under standard conditions, 1150.4 - 180 = 970.4 B. t. u. is added in the changing of one pound of water into steam at atmospheric pressure and a temperature of 212 degrees. This is in effect the definition of the latent heat of evaporation. Hence, if conditions of the trial had been standard, only 970.4 B. t. u. would be required and the ratio of 1167.82 to 970.4 B. t. u. is the ratio determining the factor of evaporation. The factor in the assumed case is 1167.82 ÷ 970.4 = 1.2034 and if the same amount of heat had been absorbed under standard conditions as was absorbed in the trial condition, 1.2034 times the amount of steam would have been generated. Expressed as a formula for use with any set of conditions, the factor is, H - h F = ----- (2) 970.4 Where H = the total heat of steam above 32 degrees Fahrenheit from steam tables, h = sensible heat of feed water above 32 degrees Fahrenheit from Table 22. In the form above, the factor may be determined with either saturated or superheated steam, provided that in the latter case values of H are available for varying degrees of superheat and pressures. Where such values are not available, the form becomes, H - h + s(t_{sup} - t_{sat}) F = ---------------------------- (3) 970.4 Where s = mean specific heat of superheated steam at the pressure existing in the trial from saturated steam to the temperature existing in the trial, t_{sup} = final temperature of steam, t_{sat} = temperature of saturated steam, corresponding to pressure existing, (t_{sup} - t_{sat}) = degrees of superheat. The specific heat of superheated steam will be taken up later. Table 19 gives factors of evaporation for saturated steam boiler trials to cover a large range of conditions. Except for the most refined work, intermediate values may be determined by interpolation. Steam gauges indicate the pressure above the atmosphere. As has been pointed out, the atmospheric pressure changes according to the altitude and the variation in the barometer. Hence, calculations involving the properties of steam are based on _absolute_ pressures, which are equal to the gauge pressure plus the atmospheric pressure in pounds to the square inch. This latter is generally assumed to be 14.7 pounds per square inch at sea level, but for other levels it must be determined from the barometric reading at that place. Vacuum gauges indicate the difference, expressed in inches of mercury, between atmospheric pressure and the pressure within the vessel to which the gauge is attached. For approximate purposes, 2.04 inches height of mercury may be considered equal to a pressure of one pound per square inch at the ordinary temperatures at which mercury gauges are used. Hence for any reading of the vacuum gauge in inches, G, the absolute pressure for any barometer reading in inches, B, will be (B - G) ÷ 2.04. If the barometer is 30 inches measured at ordinary temperatures and not corrected to 32 degrees Fahrenheit and the vacuum gauge 24 inches, the absolute pressure will be (30 - 24) ÷ 2.04 = 2.9 pounds per square inch. TABLE 19 FACTORS OF EVAPORATION CALCULATED FROM MARKS AND DAVIS TABLES ______________________________________________________________________ | | | |Feed | | |Temp- | | |erature| | |Degrees| Steam Pressure by Gauge | |Fahren-| | |heit | | |_______|______________________________________________________________| | | | | | | | | | | | 50 | 60 | 70 | 80 | 90 | 100 | 110 | |_______|________|________|________|________|________|________|________| | | | | | | | | | | 32 | 1.2143 | 1.2170 | 1.2194 | 1.2215 | 1.2233 | 1.2233 | 1.2265 | | 40 | 1.2060 | 1.2087 | 1.2111 | 1.2131 | 1.2150 | 1.2168 | 1.2181 | | 50 | 1.1957 | 1.1984 | 1.2008 | 1.2028 | 1.2047 | 1.2065 | 1.2079 | | 60 | 1.1854 | 1.1881 | 1.1905 | 1.1925 | 1.1944 | 1.1961 | 1.1976 | | 70 | 1.1750 | 1.1778 | 1.1802 | 1.1822 | 1.1841 | 1.1859 | 1.1873 | | 80 | 1.1649 | 1.1675 | 1.1699 | 1.1720 | 1.1738 | 1.1756 | 1.1770 | | 90 | 1.1545 | 1.1572 | 1.1596 | 1.1617 | 1.1636 | 1.1653 | 1.1668 | | 100 | 1.1443 | 1.1470 | 1.1493 | 1.1514 | 1.1533 | 1.1550 | 1.1565 | | 110 | 1.1340 | 1.1367 | 1.1391 | 1.1411 | 1.1430 | 1.1448 | 1.1462 | | 120 | 1.1237 | 1.1264 | 1.1288 | 1.1309 | 1.1327 | 1.1345 | 1.1359 | | 130 | 1.1134 | 1.1161 | 1.1185 | 1.1206 | 1.1225 | 1.1242 | 1.1257 | | 140 | 1.1031 | 1.1058 | 1.1082 | 1.1103 | 1.1122 | 1.1139 | 1.1154 | | 150 | 1.0928 | 1.0955 | 1.0979 | 1.1000 | 1.1019 | 1.1036 | 1.1051 | | 160 | 1.0825 | 1.0852 | 1.0876 | 1.0897 | 1.0916 | 1.0933 | 1.0948 | | 170 | 1.0722 | 1.0749 | 1.0773 | 1.0794 | 1.0813 | 1.0830 | 1.0845 | | 180 | 1.0619 | 1.0646 | 1.0670 | 1.0691 | 1.0709 | 1.0727 | 1.0741 | | 190 | 1.0516 | 1.0543 | 1.0567 | 1.0587 | 1.0606 | 1.0624 | 1.0638 | | 200 | 1.0412 | 1.0439 | 1.0463 | 1.0484 | 1.0503 | 1.0520 | 1.0535 | | 210 | 1.0309 | 1.0336 | 1.0360 | 1.0380 | 1.0399 | 1.0417 | 1.0432 | |_______|________|________|________|________|________|________|________| ______________________________________________________________________ | | | |Feed | | |Temp- | | |erature| | |Degrees| Steam Pressure by Gauge | |Fahren-| | |heit | | |_______|______________________________________________________________| | | | | | | | | | | | 120 | 130 | 140 | 150 | 160 | 170 | 180 | |_______|________|________|________|________|________|________|________| | | | | | | | | | | 32 | 1.2280 | 1.2292 | 1.2304 | 1.2314 | 1.2323 | 1.2333 | 1.2342 | | 40 | 1.2196 | 1.2209 | 1.2221 | 1.2231 | 1.2241 | 1.2250 | 1.2259 | | 50 | 1.2093 | 1.2106 | 1.2117 | 1.2128 | 1.2137 | 1.2147 | 1.2156 | | 60 | 1.1990 | 1.2003 | 1.2014 | 1.2025 | 1.2034 | 1.2044 | 1.2053 | | 70 | 1.1887 | 1.1900 | 1.1911 | 1.1922 | 1.1931 | 1.1941 | 1.1950 | | 80 | 1.1785 | 1.1797 | 1.1809 | 1.1819 | 1.1828 | 1.1838 | 1.1847 | | 90 | 1.1682 | 1.1695 | 1.1706 | 1.1717 | 1.1725 | 1.1735 | 1.1744 | | 100 | 1.1579 | 1.1592 | 1.1603 | 1.1614 | 1.1623 | 1.1633 | 1.1642 | | 110 | 1.1477 | 1.1489 | 1.1500 | 1.1511 | 1.1520 | 1.1530 | 1.1539 | | 120 | 1.1374 | 1.1386 | 1.1398 | 1.1408 | 1.1418 | 1.1427 | 1.1436 | | 130 | 1.1271 | 1.1284 | 1.1295 | 1.1305 | 1.1315 | 1.1324 | 1.1333 | | 140 | 1.1168 | 1.1181 | 1.1192 | 1.1203 | 1.1212 | 1.1221 | 1.1230 | | 150 | 1.1065 | 1.1078 | 1.1089 | 1.1099 | 1.1109 | 1.1118 | 1.1127 | | 160 | 1.0962 | 1.0975 | 1.0986 | 1.0997 | 1.1006 | 1.1015 | 1.1024 | | 170 | 1.0859 | 1.0872 | 1.0883 | 1.0893 | 1.0903 | 1.0912 | 1.0921 | | 180 | 1.0756 | 1.0768 | 1.0780 | 1.0790 | 1.0800 | 1.0809 | 1.0818 | | 190 | 1.0653 | 1.0665 | 1.0676 | 1.0687 | 1.0696 | 1.0706 | 1.0715 | | 200 | 1.0549 | 1.0562 | 1.0573 | 1.0584 | 1.0593 | 1.0602 | 1.0611 | | 210 | 1.0446 | 1.0458 | 1.0469 | 1.0480 | 1.0489 | 1.0499 | 1.0508 | |_______|________|________|________|________|________|________|________| ______________________________________________________________________ | | | |Feed | | |Temp- | | |erature| | |Degrees| Steam Pressure by Gauge | |Fahren-| | |heit | | |_______|______________________________________________________________| | | | | | | | | | | | 190 | 200 | 210 | 220 | 230 | 240 | 250 | |_______|________|________|________|________|________|________|________| | | | | | | | | | | 32 | 1.2350 | 1.2357 | 1.2364 | 1.2372 | 1.2378 | 1.2384 | 1.2390 | | 40 | 1.2267 | 1.2274 | 1.2282 | 1.2289 | 1.2295 | 1.2301 | 1.2307 | | 50 | 1.2164 | 1.2171 | 1.2178 | 1.2186 | 1.2192 | 1.2198 | 1.2204 | | 60 | 1.2061 | 1.2068 | 1.2075 | 1.2083 | 1.2089 | 1.2095 | 1.2101 | | 70 | 1.1958 | 1.1965 | 1.1972 | 1.1980 | 1.1986 | 1.1992 | 1.1998 | | 80 | 1.1855 | 1.1863 | 1.1869 | 1.1877 | 1.1883 | 1.1889 | 1.1895 | | 90 | 1.1750 | 1.1760 | 1.1766 | 1.1774 | 1.1780 | 1.1786 | 1.1792 | | 100 | 1.1650 | 1.1657 | 1.1664 | 1.1671 | 1.1678 | 1.1684 | 1.1690 | | 110 | 1.1547 | 1.1554 | 1.1562 | 1.1569 | 1.1575 | 1.1581 | 1.1587 | | 120 | 1.1444 | 1.1452 | 1.1459 | 1.1466 | 1.1472 | 1.1478 | 1.1484 | | 130 | 1.1341 | 1.1349 | 1.1356 | 1.1363 | 1.1369 | 1.1375 | 1.1381 | | 140 | 1.1239 | 1.1246 | 1.1253 | 1.1260 | 1.1266 | 1.1272 | 1.1278 | | 150 | 1.1136 | 1.1143 | 1.1150 | 1.1157 | 1.1163 | 1.1169 | 1.1176 | | 160 | 1.1033 | 1.1040 | 1.1047 | 1.1054 | 1.1060 | 1.1066 | 1.1073 | | 170 | 1.0930 | 1.0937 | 1.0944 | 1.0951 | 1.0957 | 1.0963 | 1.0969 | | 180 | 1.0826 | 1.0834 | 1.0841 | 1.0848 | 1.0854 | 1.0860 | 1.0866 | | 190 | 1.0723 | 1.0730 | 1.0737 | 1.0745 | 1.0751 | 1.0757 | 1.0763 | | 200 | 1.0620 | 1.0627 | 1.0634 | 1.0641 | 1.0647 | 1.0653 | 1.0660 | | 210 | 1.0516 | 1.0523 | 1.0530 | 1.0538 | 1.0544 | 1.0550 | 1.0556 | |_______|________|________|________|________|________|________|________| The temperature, pressure and other properties of steam for varying amounts of vacuum and the pressure above vacuum corresponding to each inch of reading of the vacuum gauge are given in Table 20. TABLE 20 PROPERTIES OF SATURATED STEAM FOR VARYING AMOUNTS OF VACUUM CALCULATED FROM MARKS AND DAVIS TABLES ______________________________________________________________________ | | | | | | | | | | | | Heat of | Latent | Total | | | | | Temp- | the Liquid| Heat | Heat | | | | | erature | Above | Above | Above |Density or| | | Absolute | Degrees | 32 De- | 32 De- | 32 De- |Weight per| | Vacuum | Pressure | Fahren- | grees | grees | grees |Cubic Foot| |Ins. Hg.| Pounds | heit | B. t. u. |B. t. u.|B. t. u.| Pounds | |________|__________|_________|___________|________|________|__________| | | | | | | | | | 29.5 | .207 | 54.1 | 22.18 | 1061.0 | 1083.2 | 0.000678 | | 29 | .452 | 76.6 | 44.64 | 1048.7 | 1093.3 | 0.001415 | | 28.5 | .698 | 90.1 | 58.09 | 1041.1 | 1099.2 | 0.002137 | | 28 | .944 | 99.9 | 67.87 | 1035.6 | 1103.5 | 0.002843 | | 27 | 1.44 | 112.5 | 80.4 | 1028.6 | 1109.0 | 0.00421 | | 26 | 1.93 | 124.5 | 92.3 | 1022.0 | 1114.3 | 0.00577 | | 25 | 2.42 | 132.6 | 100.5 | 1017.3 | 1117.8 | 0.00689 | | 24 | 2.91 | 140.1 | 108.0 | 1013.1 | 1121.1 | 0.00821 | | 22 | 3.89 | 151.7 | 119.6 | 1006.4 | 1126.0 | 0.01078 | | 20 | 4.87 | 161.1 | 128.9 | 1001.0 | 1129.9 | 0.01331 | | 18 | 5.86 | 168.9 | 136.8 | 996.4 | 1133.2 | 0.01581 | | 16 | 6.84 | 175.8 | 143.6 | 992.4 | 1136.0 | 0.01827 | | 14 | 7.82 | 181.8 | 149.7 | 988.8 | 1138.5 | 0.02070 | | 12 | 8.80 | 187.2 | 155.1 | 985.6 | 1140.7 | 0.02312 | | 10 | 9.79 | 192.2 | 160.1 | 982.6 | 1142.7 | 0.02554 | | 5 | 12.24 | 202.9 | 170.8 | 976.0 | 1146.8 | 0.03148 | |________|__________|_________|___________|________|________|__________| From the steam tables, the condensed Table 21 of the properties of steam at different pressures may be constructed. From such a table there may be drawn the following conclusions. TABLE 21 VARIATION IN PROPERTIES OF SATURATED STEAM WITH PRESSURE ___________________________________________________ | | | | | | | Pressure |Temperature | Heat of | Latent | Total | | Pounds | Degrees | Liquid | Heat | Heat | | Absolute | Fahrenheit |B. t. u. |B. t. u.|B. t. u.| |__________|____________|_________|________|________| | | | | | | | 14.7 | 212.0 | 180.0 | 970.4 | 1150.4 | | 20.0 | 228.0 | 196.1 | 960.0 | 1156.2 | | 100.0 | 327.8 | 298.3 | 888.0 | 1186.3 | | 300.0 | 417.5 | 392.7 | 811.3 | 1204.1 | |__________|____________|_________|________|________| As the pressure and temperature increase, the latent heat decreases. This decrease, however, is less rapid than the corresponding increase in the heat of the liquid and hence the total heat increases with an increase in the pressure and temperature. The percentage increase in the total heat is small, being 0.5, 3.1, and 4.7 per cent for 20, 100, and 300 pounds absolute pressure respectively above the total heat in one pound of steam at 14.7 pounds absolute. The temperatures, on the other hand, increase at the rates of 7.5, 54.6, and 96.9 per cent. The efficiency of a perfect steam engine is proportional to the expression (t - t_{1})/t in which t and t_{1} are the absolute temperatures of the saturated steam at admission and exhaust respectively. While actual engines only approximate the ideal engine in efficiency, yet they follow the same general law. Since the exhaust temperature cannot be lowered beyond present practice, it follows that the only available method of increasing the efficiency is by an increase in the temperature of the steam at admission. How this may be accomplished by an increase of pressure is clearly shown, for the increase of fuel necessary to increase the pressure is negligible, as shown by the total heat, while the increase in economy, due to the higher pressure, will result directly from the rapid increase of the corresponding temperature. TABLE 22 HEAT UNITS PER POUND AND WEIGHT PER CUBIC FOOT OF WATER BETWEEN 32 DEGREES FAHRENHEIT AND 340 DEGREES FAHRENHEIT _________________________________ | | | | |Temperature|Heat Units| Weight | | Degrees | per | per | | Fahrenheit| Pound |Cubic Foot| |___________|__________|__________| | | | | | 32 | 0.00 | 62.42 | | 33 | 1.01 | 62.42 | | 34 | 2.01 | 62.42 | | 35 | 3.02 | 62.43 | | 36 | 4.03 | 62.43 | | 37 | 5.04 | 62.43 | | 38 | 6.04 | 62.43 | | 39 | 7.05 | 62.43 | | 40 | 8.05 | 62.43 | | 41 | 9.05 | 62.43 | | 42 | 10.06 | 62.43 | | 43 | 11.06 | 62.43 | | 44 | 12.06 | 62.43 | | 45 | 13.07 | 62.42 | | 46 | 14.07 | 62.42 | | 47 | 15.07 | 62.42 | | 48 | 16.07 | 62.42 | | 49 | 17.08 | 62.42 | | 50 | 18.08 | 62.42 | | 51 | 19.08 | 62.41 | | 52 | 20.08 | 62.41 | | 53 | 21.08 | 62.41 | | 54 | 22.08 | 62.40 | | 55 | 23.08 | 62.40 | | 56 | 24.08 | 62.39 | | 57 | 25.08 | 62.39 | | 58 | 26.08 | 62.38 | | 59 | 27.08 | 62.37 | | 60 | 28.08 | 62.37 | | 61 | 29.08 | 62.36 | | 62 | 30.08 | 62.36 | | 63 | 31.07 | 62.35 | | 64 | 32.07 | 62.35 | | 65 | 33.07 | 62.34 | | 66 | 34.07 | 62.33 | | 67 | 35.07 | 62.33 | | 68 | 36.07 | 62.32 | | 69 | 37.06 | 62.31 | | 70 | 38.06 | 62.30 | | 71 | 39.06 | 62.30 | | 72 | 40.05 | 62.29 | | 73 | 41.05 | 62.28 | | 74 | 42.05 | 62.27 | | 75 | 42.05 | 62.26 | | 76 | 44.04 | 62.26 | | 77 | 45.04 | 62.25 | | 78 | 46.04 | 62.24 | | 79 | 47.04 | 62.23 | | 80 | 48.03 | 62.22 | | 81 | 49.03 | 62.21 | | 82 | 50.03 | 62.20 | | 83 | 51.02 | 62.19 | | 84 | 52.02 | 62.18 | | 85 | 53.02 | 62.17 | | 86 | 54.01 | 62.16 | | 87 | 55.01 | 62.15 | | 88 | 56.01 | 62.14 | | 89 | 57.00 | 62.13 | | 90 | 58.00 | 62.12 | | 91 | 59.00 | 62.11 | | 92 | 60.00 | 62.09 | | 93 | 60.99 | 62.08 | | 94 | 61.99 | 62.07 | | 95 | 62.99 | 62.06 | | 96 | 63.98 | 62.05 | | 97 | 64.98 | 62.04 | | 98 | 65.98 | 62.03 | | 99 | 66.97 | 62.02 | | 100 | 67.97 | 62.00 | | 101 | 68.97 | 61.99 | | 102 | 69.96 | 61.98 | | 103 | 70.96 | 61.97 | | 104 | 71.96 | 61.95 | | 105 | 72.95 | 61.94 | | 106 | 73.95 | 61.93 | | 107 | 74.95 | 61.91 | | 108 | 75.95 | 61.90 | | 109 | 76.94 | 61.88 | | 110 | 77.94 | 61.86 | | 111 | 78.94 | 61.85 | | 112 | 79.93 | 61.83 | | 113 | 80.93 | 61.82 | | 114 | 81.93 | 61.80 | | 115 | 82.92 | 61.79 | | 116 | 83.92 | 61.77 | | 117 | 84.92 | 61.75 | | 118 | 85.92 | 61.74 | | 119 | 86.91 | 61.72 | | 120 | 87.91 | 61.71 | | 121 | 88.91 | 61.69 | | 122 | 89.91 | 61.68 | | 123 | 90.90 | 61.66 | | 124 | 91.90 | 61.65 | | 125 | 92.90 | 61.63 | | 126 | 93.90 | 61.61 | | 127 | 94.89 | 61.59 | | 128 | 95.89 | 61.58 | | 129 | 96.89 | 61.56 | | 130 | 97.89 | 61.55 | | 131 | 98.89 | 61.53 | | 132 | 99.88 | 61.52 | | 133 | 100.88 | 61.50 | | 134 | 101.88 | 61.49 | | 135 | 102.88 | 61.47 | | 136 | 103.88 | 61.45 | | 137 | 104.87 | 61.43 | | 138 | 105.87 | 61.41 | | 139 | 106.87 | 61.40 | | 140 | 107.87 | 61.38 | | 141 | 108.87 | 61.36 | | 142 | 109.87 | 61.34 | | 143 | 110.87 | 61.33 | | 144 | 111.87 | 61.31 | | 145 | 112.86 | 61.29 | | 146 | 113.86 | 61.27 | | 147 | 114.86 | 61.25 | | 148 | 115.86 | 61.24 | | 149 | 116.86 | 61.22 | | 150 | 117.86 | 61.20 | | 151 | 118.86 | 61.18 | | 152 | 119.86 | 61.16 | | 153 | 120.86 | 61.14 | | 154 | 121.86 | 61.12 | | 155 | 122.86 | 61.10 | | 156 | 123.86 | 61.08 | | 157 | 124.86 | 61.06 | | 158 | 125.86 | 61.04 | | 159 | 126.86 | 61.02 | | 160 | 127.86 | 61.00 | | 161 | 128.86 | 60.98 | | 162 | 129.86 | 60.96 | | 163 | 130.86 | 60.94 | | 164 | 131.86 | 60.92 | | 165 | 132.86 | 60.90 | | 166 | 133.86 | 60.88 | | 167 | 134.86 | 60.86 | | 168 | 135.86 | 60.84 | | 169 | 136.86 | 60.82 | | 170 | 137.87 | 60.80 | | 171 | 138.87 | 60.78 | | 172 | 139.87 | 60.76 | | 173 | 140.87 | 60.73 | | 174 | 141.87 | 60.71 | | 175 | 142.87 | 60.69 | | 176 | 143.87 | 60.67 | | 177 | 144.88 | 60.65 | | 178 | 145.88 | 60.62 | | 179 | 146.88 | 60.60 | | 180 | 147.88 | 60.58 | | 181 | 148.88 | 60.56 | | 182 | 149.89 | 60.53 | | 183 | 150.89 | 60.51 | | 184 | 151.89 | 60.49 | | 185 | 152.89 | 60.47 | | 186 | 153.89 | 60.45 | | 187 | 154.90 | 60.42 | | 188 | 155.90 | 60.40 | | 189 | 156.90 | 60.38 | | 190 | 157,91 | 60.36 | | 191 | 158.91 | 60.33 | | 192 | 159.91 | 60.31 | | 193 | 160.91 | 60.29 | | 194 | 161.92 | 60.27 | | 195 | 162.92 | 60.24 | | 196 | 163.92 | 60.22 | | 197 | 164.93 | 60.19 | | 198 | 165.93 | 60.17 | | 199 | 166.94 | 60.15 | | 200 | 167.94 | 60.12 | | 201 | 168.94 | 60.10 | | 202 | 169.95 | 60.07 | | 203 | 170.95 | 60.05 | | 204 | 171.96 | 60.02 | | 205 | 172.96 | 60.00 | | 206 | 173.97 | 59.98 | | 207 | 174.97 | 59.95 | | 208 | 175.98 | 59.93 | | 209 | 176.98 | 59.90 | | 210 | 177.99 | 59.88 | | 211 | 178.99 | 59.85 | | 212 | 180.00 | 59.83 | | 213 | 181.0 | 59.80 | | 214 | 182.0 | 59.78 | | 215 | 183.0 | 59.75 | | 216 | 184.0 | 59.73 | | 217 | 185.0 | 59.70 | | 218 | 186.1 | 59.68 | | 219 | 187.1 | 59.65 | | 220 | 188.1 | 59.63 | | 221 | 189.1 | 59.60 | | 222 | 190.1 | 59.58 | | 223 | 191.1 | 59.55 | | 224 | 192.1 | 59.53 | | 225 | 193.1 | 59.50 | | 226 | 194.1 | 59.48 | | 227 | 195.2 | 59.45 | | 228 | 196.2 | 59.42 | | 229 | 197.2 | 59.40 | | 230 | 198.2 | 59.37 | | 231 | 199.2 | 59.34 | | 232 | 200.2 | 59.32 | | 233 | 201.2 | 59.29 | | 234 | 202.2 | 59.27 | | 235 | 203.2 | 59.24 | | 236 | 204.2 | 59.21 | | 237 | 205.3 | 59.19 | | 238 | 206.3 | 59.16 | | 239 | 207.3 | 59.14 | | 240 | 208.3 | 59.11 | | 241 | 209.3 | 59.08 | | 242 | 210.3 | 59.05 | | 243 | 211.4 | 59.03 | | 244 | 212.4 | 59.00 | | 245 | 213.4 | 58.97 | | 246 | 214.4 | 58.94 | | 247 | 215.4 | 58.91 | | 248 | 216.4 | 58.89 | | 249 | 217.4 | 58.86 | | 250 | 218.5 | 58.83 | | 260 | 228.6 | 58.55 | | 270 | 238.8 | 58.26 | | 280 | 249.0 | 57.96 | | 290 | 259.3 | 57.65 | | 300 | 269.6 | 57.33 | | 310 | 279.9 | 57.00 | | 320 | 290.2 | 56.66 | | 330 | 300.6 | 56.30 | | 340 | 311.0 | 55.94 | |___________|__________|__________| The gain due to superheat cannot be predicted from the formula for the efficiency of a perfect steam engine given on page 119. This formula is not applicable in cases where superheat is present since only a relatively small amount of the heat in the steam is imparted at the maximum or superheated temperature. The advantage of the use of high pressure steam may be also indicated by considering the question from the aspect of volume. With an increase of pressure comes a decrease in volume, thus one pound of saturated steam at 100 pounds absolute pressure occupies 4.43 cubic feet, while at 200 pounds pressure it occupies 2.29 cubic feet. If then, in separate cylinders of the same dimensions, one pound of steam at 100 pounds absolute pressure and one pound at 200 pounds absolute pressure enter and are allowed to expand to the full volume of each cylinder, the high-pressure steam, having more room and a greater range for expansion than the low-pressure steam, will thus do more work. This increase in the amount of work, as was the increase in temperature, is large relative to the additional fuel required as indicated by the total heat. In general, it may be stated that the fuel required to impart a given amount of heat to a boiler is practically independent of the steam pressure, since the temperature of the fire is so high as compared with the steam temperature that a variation in the steam temperature does not produce an appreciable effect. The formulae for the algebraic expression of the relation between saturated steam pressures, temperatures and steam volumes have been up to the present time empirical. These relations have, however, been determined by experiment and, from the experimental data, tables have been computed which render unnecessary the use of empirical formulae. Such formulae may be found in any standard work of thermo-dynamics. The following tables cover all practical cases. Table 22 gives the heat units contained in water above 32 degrees Fahrenheit at different temperatures. Table 23 gives the properties of saturated steam for various pressures. Table 24 gives the properties of superheated steam at various pressures and temperatures. These tables are based on those computed by Lionel S. Marks and Harvey N. Davis, these being generally accepted as being the most correct. TABLE 23 PROPERTIES OF SATURATED STEAM REPRODUCED BY PERMISSION FROM MARKS AND DAVIS "STEAM TABLES AND DIAGRAMS" (Copyright, 1909, by Longmans, Green & Co.) ____________________________________________________________________ |Pressure,| Temper- |Specific Vol-|Heat of |Latent Heat|Total Heat| | Pounds |ature De-| ume Cu. Ft. |the Liquid,| of Evap., |of Steam, | |Absolute |grees F. | per Pound | B. t. u. | B. t. u. | B. t. u. | |_________|_________|_____________|___________|___________|__________| | 1 | 101.83 | 333.0 | 69.8 | 1034.6 | 1104.4 | | 2 | 126.15 | 173.5 | 94.0 | 1021.0 | 1115.0 | | 3 | 141.52 | 118.5 | 109.4 | 1012.3 | 1121.6 | | 4 | 153.01 | 90.5 | 120.9 | 1005.7 | 1126.5 | | 5 | 162.28 | 73.33 | 130.1 | 1000.3 | 1130.5 | | 6 | 170.06 | 61.89 | 137.9 | 995.8 | 1133.7 | | 7 | 176.85 | 53.56 | 144.7 | 991.8 | 1136.5 | | 8 | 182.86 | 47.27 | 150.8 | 988.2 | 1139.0 | | 9 | 188.27 | 42.36 | 156.2 | 985.0 | 1141.1 | | 10 | 193.22 | 38.38 | 161.1 | 982.0 | 1143.1 | | 11 | 197.75 | 35.10 | 165.7 | 979.2 | 1144.9 | | 12 | 201.96 | 32.36 | 169.9 | 976.6 | 1146.5 | | 13 | 205.87 | 30.03 | 173.8 | 974.2 | 1148.0 | | 14 | 209.55 | 28.02 | 177.5 | 971.9 | 1149.4 | | 15 | 213.0 | 26.27 | 181.0 | 969.7 | 1150.7 | | 16 | 216.3 | 24.79 | 184.4 | 967.6 | 1152.0 | | 17 | 219.4 | 23.38 | 187.5 | 965.6 | 1153.1 | | 18 | 222.4 | 22.16 | 190.5 | 963.7 | 1154.2 | | 19 | 225.2 | 21.07 | 193.4 | 961.8 | 1155.2 | | 20 | 228.0 | 20.08 | 196.1 | 960.0 | 1156.2 | | 22 | 233.1 | 18.37 | 201.3 | 956.7 | 1158.0 | | 24 | 237.8 | 16.93 | 206.1 | 953.5 | 1159.6 | | 26 | 242.2 | 15.72 | 210.6 | 950.6 | 1161.2 | | 28 | 246.4 | 14.67 | 214.8 | 947.8 | 1162.6 | | 30 | 250.3 | 13.74 | 218.8 | 945.1 | 1163.9 | | 32 | 254.1 | 12.93 | 222.6 | 942.5 | 1165.1 | | 34 | 257.6 | 12.22 | 226.2 | 940.1 | 1166.3 | | 36 | 261.0 | 11.58 | 229.6 | 937.7 | 1167.3 | | 38 | 264.2 | 11.01 | 232.9 | 935.5 | 1168.4 | | 40 | 267.3 | 10.49 | 236.1 | 933.3 | 1169.4 | | 42 | 270.2 | 10.02 | 239.1 | 931.2 | 1170.3 | | 44 | 273.1 | 9.59 | 242.0 | 929.2 | 1171.2 | | 46 | 275.8 | 9.20 | 244.8 | 927.2 | 1172.0 | | 48 | 278.5 | 8.84 | 247.5 | 925.3 | 1172.8 | | 50 | 281.0 | 8.51 | 250.1 | 923.5 | 1173.6 | | 52 | 283.5 | 8.20 | 252.6 | 921.7 | 1174.3 | | 54 | 285.9 | 7.91 | 255.1 | 919.9 | 1175.0 | | 56 | 288.2 | 7.65 | 257.5 | 918.2 | 1175.7 | | 58 | 290.5 | 7.40 | 259.8 | 916.5 | 1176.4 | | 60 | 292.7 | 7.17 | 262.1 | 914.9 | 1177.0 | | 62 | 294.9 | 6.95 | 264.3 | 913.3 | 1177.6 | | 64 | 297.0 | 6.75 | 266.4 | 911.8 | 1178.2 | | 66 | 299.0 | 6.56 | 268.5 | 910.2 | 1178.8 | | 68 | 301.0 | 6.38 | 270.6 | 908.7 | 1179.3 | | 70 | 302.9 | 6.20 | 272.6 | 907.2 | 1179.8 | | 72 | 304.8 | 6.04 | 274.5 | 905.8 | 1180.4 | | 74 | 306.7 | 5.89 | 276.5 | 904.4 | 1180.9 | | 76 | 308.5 | 5.74 | 278.3 | 903.0 | 1181.4 | | 78 | 310.3 | 5.60 | 280.2 | 901.7 | 1181.8 | | 80 | 312.0 | 5.47 | 282.0 | 900.3 | 1182.3 | | 82 | 313.8 | 5.34 | 283.8 | 899.0 | 1182.8 | | 84 | 315.4 | 5.22 | 285.5 | 897.7 | 1183.2 | | 86 | 317.1 | 5.10 | 287.2 | 896.4 | 1183.6 | | 88 | 318.7 | 5.00 | 288.9 | 895.2 | 1184.0 | | 90 | 320.3 | 4.89 | 290.5 | 893.9 | 1184.4 | | 92 | 321.8 | 4.79 | 292.1 | 892.7 | 1184.8 | | 94 | 323.4 | 4.69 | 293.7 | 891.5 | 1185.2 | | 96 | 324.9 | 4.60 | 295.3 | 890.3 | 1185.6 | | 98 | 326.4 | 4.51 | 296.8 | 889.2 | 1186.0 | | 100 | 327.8 | 4.429 | 298.3 | 888.0 | 1186.3 | | 105 | 331.4 | 4.230 | 302.0 | 885.2 | 1187.2 | | 110 | 334.8 | 4.047 | 305.5 | 882.5 | 1188.0 | | 115 | 338.1 | 3.880 | 309.0 | 879.8 | 1188.8 | | 120 | 341.3 | 3.726 | 312.3 | 877.2 | 1189.6 | | 125 | 344.4 | 3.583 | 315.5 | 874.7 | 1190.3 | | 130 | 347.4 | 3.452 | 318.6 | 872.3 | 1191.0 | | 135 | 350.3 | 3.331 | 321.7 | 869.9 | 1191.6 | | 140 | 353.1 | 3.219 | 324.6 | 867.6 | 1192.2 | | 145 | 355.8 | 3.112 | 327.4 | 865.4 | 1192.8 | | 150 | 358.5 | 3.012 | 330.2 | 863.2 | 1193.4 | | 155 | 361.0 | 2.920 | 332.9 | 861.0 | 1194.0 | | 160 | 363.6 | 2.834 | 335.6 | 858.8 | 1194.5 | | 165 | 366.0 | 2.753 | 338.2 | 856.8 | 1195.0 | | 170 | 368.5 | 2.675 | 340.7 | 854.7 | 1195.4 | | 175 | 370.8 | 2.602 | 343.2 | 852.7 | 1195.9 | | 180 | 373.1 | 2.533 | 345.6 | 850.8 | 1196.4 | | 185 | 375.4 | 2.468 | 348.0 | 848.8 | 1196.8 | | 190 | 377.6 | 2.406 | 350.4 | 846.9 | 1197.3 | | 195 | 379.8 | 2.346 | 352.7 | 845.0 | 1197.7 | | 200 | 381.9 | 2.290 | 354.9 | 843.2 | 1198.1 | | 205 | 384.0 | 2.237 | 357.1 | 841.4 | 1198.5 | | 210 | 386.0 | 2.187 | 359.2 | 839.6 | 1198.8 | | 215 | 388.0 | 2.138 | 361.4 | 837.9 | 1199.2 | | 220 | 389.9 | 2.091 | 363.4 | 836.2 | 1199.6 | | 225 | 391.9 | 2.046 | 365.5 | 834.4 | 1199.9 | | 230 | 393.8 | 2.004 | 367.5 | 832.8 | 1200.2 | | 235 | 395.6 | 1.964 | 369.4 | 831.1 | 1200.6 | | 240 | 397.4 | 1.924 | 371.4 | 829.5 | 1200.9 | | 245 | 399.3 | 1.887 | 373.3 | 827.9 | 1201.2 | | 250 | 401.1 | 1.850 | 375.2 | 826.3 | 1201.5 | |_________|_________|_____________|___________|___________|__________| [Illustration: Portion of 6100 Horse-power Installation of Babcock & Wilcox Boilers Equipped with Babcock & Wilcox Chain Grate Stokers at the Campbell Street Plant of the Louisville Railway Co., Louisville, Ky. This Company Operates a Total of 14,000 Horse Power of Babcock & Wilcox Boilers] TABLE 24 PROPERTIES OF SUPERHEATED STEAM REPRODUCED BY PERMISSION FROM MARKS AND DAVIS "STEAM TABLES AND DIAGRAMS" (Copyright, 1909, by Longmans, Green & Co.) __________________________________________________________________ | | | | | | | Degrees of Superheat | |Pressure| |_______________________________________________| | Pounds |Saturated| | | | | | | |Absolute| Steam | 50 | 100 | 150 | 200 | 250 | 300 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 162.3 | 212.3 | 262.3 | 312.3 | 362.3 | 412.3 | 462.3 | | 5 v| 73.3 | 79.7 | 85.7 | 91.8 | 97.8 | 103.8 | 109.8 | | h| 1130.5 |1153.5 |1176.4 |1199.5 |1222.5 |1245.6 |1268.7 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 193.2 | 243.2 | 293.2 | 343.2 | 393.2 | 443.2 | 493.2 | | 10 v| 38.4 | 41.5 | 44.6 | 47.7 | 50.7 | 53.7 | 56.7 | | h| 1143.1 |1166.3 |1189.5 |1212.7 |1236.0 |1259.3 |1282.5 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 213.0 | 263.0 | 313.0 | 363.0 | 413.0 | 463.0 | 513.0 | | 15 v| 26.27 | 28.40| 30.46| 32.50| 34.53| 36.56| 38.58| | h| 1150.7 |1174.2 |1197.6 |1221.0 |1244.4 |1267.7 |1291.1 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 228.0 | 278.0 | 328.0 | 378.0 | 428.0 | 478.0 | 528.0 | | 20 v| 20.08 | 21.69| 23.25| 24.80| 26.33| 27.85| 29.37| | h| 1156.2 |1179.9 |1203.5 |1227.1 |1250.6 |1274.1 |1297.6 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 240.1 | 290.1 | 340.1 | 390.1 | 440.1 | 490.1 | 540.1 | | 25 v| 16.30 | 17.60| 18.86| 20.10| 21.32| 22.55| 23.77| | h| 1160.4 |1184.4 |1208.2 |1231.9 |1255.6 |1279.2 |1302.8 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 250.4 | 300.4 | 350.4 | 400.4 | 450.4 | 500.4 | 550.4 | | 30 v| 13.74 | 14.83| 15.89| 16.93| 17.97| 18.99| 20.00| | h| 1163.9 |1188.1 |1212.1 |1236.0 |1259.7 |1283.4 |1307.1 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 259.3 | 309.3 | 359.3 | 409.3 | 459.3 | 509.3 | 559.3 | | 35 v| 11.89 | 12.85| 13.75| 14.65| 15.54| 16.42| 17.30| | h| 1166.8 |1191.3 |1215.4 |1239.4 |1263.3 |1287.1 |1310.8 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 267.3 | 317.3 | 367.3 | 417.3 | 467.3 | 517.3 | 567.3 | | 40 v| 10.49 | 11.33| 12.13| 12.93| 13.70| 14.48| 15.25| | h| 1169.4 |1194.0 |1218.4 |1242.4 |1266.4 |1290.3 |1314.1 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 274.5 | 324.5 | 374.5 | 424.5 | 474.5 | 524.5 | 574.5 | | 45 v| 9.39 | 10.14| 10.86| 11.57| 12.27| 12.96| 13.65| | h| 1171.6 |1196.6 |1221.0 |1245.2 |1269.3 |1293.2 |1317.0 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 281.0 | 331.0 | 381.0 | 431.0 | 481.0 | 531.0 | 581.0 | | 50 v| 8.51 | 9.19| 9.84| 10.48| 11.11| 11.74| 12.36| | h| 1173.6 |1198.8 |1223.4 |1247.7 |1271.8 |1295.8 |1319.7 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 287.1 | 337.1 | 387.1 | 437.1 | 487.1 | 537.1 | 587.1 | | 55 v| 7.78 | 8.40| 9.00| 9.59| 10.16| 10.73| 11.30| | h| 1175.4 |1200.8 |1225.6 |1250.0 |1274.2 |1298.1 |1322.0 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 292.7 | 342.7 | 392.7 | 442.7 | 492.7 | 542.7 | 592.7 | | 60 v| 7.17 | 7.75| 8.30| 8.84| 9.36| 9.89| 10.41| | h| 1177.0 |1202.6 |1227.6 |1252.1 |1276.4 |1300.4 |1324.3 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 298.0 | 348.0 | 398.0 | 448.0 | 498.0 | 548.0 | 598.0 | | 65 v| 6.65 | 7.20| 7.70| 8.20| 8.69| 9.17| 9.65| | h| 1178.5 |1204.4 |1229.5 |1254.0 |1278.4 |1302.4 |1326.4 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 302.9 | 352.9 | 402.9 | 452.9 | 502.9 | 552.9 | 602.9 | | 70 v| 6.20 | 6.71| 7.18| 7.65| 8.11| 8.56| 9.01| | h| 1179.8 |1205.9 |1231.2 |1255.8 |1280.2 |1304.3 |1328.3 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 307.6 | 357.6 | 407.6 | 457.6 | 507.6 | 557.6 | 607.6 | | 75 v| 5.81 | 6.28| 6.73| 7.17| 7.60| 8.02| 8.44| | h| 1181.1 |1207.5 |1232.8 |1257.5 |1282.0 |1306.1 |1330.1 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 312.0 | 362.0 | 412.0 | 462.0 | 512.0 | 562.0 | 612.0 | | 80 v| 5.47 | 5.92| 6.34| 6.75| 7.17| 7.56| 7.95| | h| 1182.3 |1208.8 |1234.3 |1259.0 |1283.6 |1307.8 |1331.9 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 316.3 | 366.3 | 416.3 | 466.3 | 516.3 | 566.3 | 616.3 | | 85 v| 5.16 | 5.59| 6.99| 6.38| 6.76| 7.14| 7.51| | h| 1183.4 |1210.2 |1235.8 |1260.6 |1285.2 |1309.4 |1333.5 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 320.3 | 370.3 | 420.3 | 470.3 | 520.3 | 570.3 | 620.3 | | 90 v| 4.89 | 5.29| 5.67| 6.04| 6.40| 6.76| 7.11| | h| 1184.4 |1211.4 |1237.2 |1262.0 |1286.6 |1310.8 |1334.9 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 324.1 | 374.1 | 424.1 | 474.1 | 524.1 | 574.1 | 624.1 | | 95 v| 4.65 | 5.03| 5.39| 5.74| 6.09| 6.43| 6.76| | h| 1185.4 |1212.6 |1238.4 |1263.4 |1288.1 |1312.3 |1336.4 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 327.8 | 377.8 | 427.8 | 477.8 | 527.8 | 577.8 | 627.8 | | 100 v| 4.43 | 4.79| 5.14| 5.47| 5.80| 6.12| 6.44| | h| 1186.3 |1213.8 |1239.7 |1264.7 |1289.4 |1313.6 |1337.8 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 331.4 | 381.4 | 431.4 | 481.4 | 531.4 | 581.4 | 631.4 | | 105 v| 4.23 | 4.58| 4.91| 5.23| 5.54| 5.85| 6.15| | h| 1187.2 |1214.9 |1240.8 |1265.9 |1290.6 |1314.9 |1339.1 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 334.8 | 384.8 | 434.8 | 484.8 | 534.8 | 584.8 | 634.8 | | 110 v| 4.05 | 4.38| 4.70| 5.01| 5.31| 5.61| 5.90| | h| 1188.0 |1215.9 |1242.0 |1267.1 |1291.9 |1316.2 |1340.4 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 338.1 | 388.1 | 438.1 | 488.1 | 538.1 | 588.1 | 638.1 | | 115 v| 3.88 | 4.20| 4.51| 4.81| 5.09| 5.38| 5.66| | h| 1188.8 |1216.9 |1243.1 |1268.2 |1293.0 |1317.3 |1341.5 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 341.3 | 391.3 | 441.3 | 491.3 | 541.3 | 591.3 | 641.3 | | 120 v| 3.73 | 4.04| 4.33| 4.62| 4.89| 5.17| 5.44| | h| 1189.6 |1217.9 |1244.1 |1269.3 |1294.1 |1318.4 |1342.7 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 344.4 | 394.4 | 444.4 | 494.4 | 544.4 | 594.4 | 644.4 | | 125 v| 3.58 | 3.88| 4.17| 4.45| 4.71| 4.97| 5.23| | h| 1190.3 |1218.8 |1245.1 |1270.4 |1295.2 |1319.5 |1343.8 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 347.4 | 397.4 | 447.4 | 497.4 | 547.4 | 597.4 | 647.4 | | 130 v| 3.45 | 3.74| 4.02| 4.28| 4.54| 4.80| 5.05| | h| 1191.0 |1219.7 |1246.1 |1271.4 |1296.2 |1320.6 |1344.9 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 350.3 | 400.3 | 450.3 | 500.3 | 550.3 | 600.3 | 650.3 | | 135 v| 3.33 | 3.61| 3.88| 4.14| 4.38| 4.63| 4.87| | h| 1191.6 |1220.6 |1247.0 |1272.3 |1297.2 |1321.6 |1345.9 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 353.1 | 403.1 | 453.1 | 503.1 | 553.1 | 603.1 | 653.1 | | 140 v| 3.22 | 3.49| 3.75| 4.00| 4.24| 4.48| 4.71| | h| 1192.2 |1221.4 |1248.0 |1273.3 |1298.2 |1322.6 |1346.9 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 355.8 | 405.8 | 455.8 | 505.8 | 555.8 | 605.8 | 655.8 | | 145 v| 3.12 | 3.38| 3.63| 3.87| 4.10| 4.33| 4.56| | h| 1192.8 |1222.2 |1248.8 |1274.2 |1299.1 |1323.6 |1347.9 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 358.5 | 408.5 | 458.5 | 508.5 | 558.5 | 608.5 | 658.5 | | 150 v| 3.01 | 3.27| 3.50| 3.75| 3.97| 4.19| 4.41| | h| 1193.4 |1223.0 |1249.6 |1275.1 |1300.0 |1324.5 |1348.8 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 361.0 | 411.0 | 461.0 | 511.0 | 561.0 | 611.0 | 661.0 | | 155 v| 2.92 | 3.17| 3.41| 3.63| 3.85| 4.06| 4.28| | h| 1194.0 |1223.6 |1250.5 |1276.0 |1300.8 |1325.3 |1349.7 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 363.6 | 413.6 | 463.6 | 513.6 | 563.6 | 613.6 | 663.6 | | 160 v| 2.83 | 3.07| 3.30| 3.53| 3.74| 3.95| 4.15| | h| 1194.5 |1224.5 |1251.3 |1276.8 |1301.7 |1326.2 |1350.6 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 366.0 | 416.0 | 466.0 | 516.0 | 566.0 | 616.0 | 666.0 | | 165 v| 2.75 | 2.99| 3.21| 3.43| 3.64| 3.84| 4.04| | h| 1195.0 |1225.2 |1252.0 |1277.6 |1302.5 |1327.1 |1351.5 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 368.5 | 418.5 | 468.5 | 518.5 | 568.5 | 618.5 | 668.5 | | 170 v| 2.68 | 2.91| 3.12| 3.34| 3.54| 3.73| 3.92| | h| 1195.4 |1225.9 |1252.8 |1278.4 |1303.3 |1327.9 |1352.3 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 370.8 | 420.8 | 470.8 | 520.8 | 570.8 | 620.8 | 670.8 | | 175 v| 2.60 | 2.83| 3.04| 3.24| 3.44| 3.63| 3.82| | h| 1195.9 |1226.6 |1253.6 |1279.1 |1304.1 |1328.7 |1353.2 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 373.1 | 423.1 | 473.1 | 523.1 | 573.1 | 623.1 | 673.1 | | 180 v| 2.53 | 2.75| 2.96| 3.16| 3.35| 3.54| 3.72| | h| 1196.4 |1227.2 |1254.3 |1279.9 |1304.8 |1329.5 |1353.9 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 375.4 | 425.4 | 475.4 | 525.4 | 575.4 | 625.4 | 675.4 | | 185 v| 2.47 | 2.68| 2.89| 3.08| 3.27| 3.45| 3.63| | h| 1196.8 |1227.9 |1255.0 |1280.6 |1305.6 |1330.2 |1354.7 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 377.6 | 427.6 | 477.6 | 527.6 | 577.6 | 627.6 | 677.6 | | 190 v| 2.41 | 2.62| 2.81| 3.00| 3.19| 3.37| 3.55| | h| 1197.3 |1228.6 |1255.7 |1281.3 |1306.3 |1330.9 |1355.5 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 379.8 | 429.8 | 479.8 | 529.8 | 579.8 | 629.8 | 679.8 | | 195 v| 2.35 | 2.55| 2.75| 2.93| 3.11| 3.29| 3.46| | h| 1197.7 |1229.2 |1256.4 |1282.0 |1307.0 |1331.6 |1356.2 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 381.9 | 431.9 | 481.9 | 531.9 | 581.9 | 631.9 | 681.9 | | 200 v| 2.29 | 2.49| 2.68| 2.86| 3.04| 3.21| 3.38| | h| 1198.1 |1229.8 |1257.1 |1282.6 |1307.7 |1332.4 |1357.0 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 384.0 | 434.0 | 484.0 | 534.0 | 584.0 | 634.0 | 684.0 | | 205 v| 2.24 | 2.44| 2.62| 2.80| 2.97| 3.14| 3.30| | h| 1198.5 |1230.4 |1257.7 |1283.3 |1308.3 |1333.0 |1357.7 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 386.0 | 436.0 | 486.0 | 536.0 | 586.0 | 636.0 | 686.0 | | 210 v| 2.19 | 2.38| 2.56| 2.74| 2.91| 3.07| 3.23| | h| 1198.8 |1231.0 |1258.4 |1284.0 |1309.0 |1333.7 |1358.4 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 388.0 | 438.0 | 488.0 | 538.0 | 588.0 | 638.0 | 688.0 | | 215 v| 2.14 | 2.33| 2.51| 2.68| 2.84| 3.00| 3.16| | h| 1199.2 |1231.6 |1259.0 |1284.6 |1309.7 |1334.4 |1359.1 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 389.9 | 439.9 | 489.9 | 539.9 | 589.9 | 639.9 | 689.9 | | 220 v| 2.09 | 2.28| 2.45| 2.62| 2.78| 2.94| 3.10| | h| 1199.6 |1232.2 |1259.6 |1285.2 |1310.3 |1335.1 |1359.8 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 391.9 | 441.9 | 491.9 | 541.9 | 591.9 | 641.9 | 691.9 | | 225 v| 2.05 | 2.23| 2.40| 2.57| 2.72| 2.88| 3.03| | h| 1199.9 |1232.7 |1260.2 |1285.9 |1310.9 |1335.7 |1360.3 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 393.8 | 443.8 | 493.8 | 543.8 | 593.8 | 643.8 | 693.8 | | 230 v| 2.00 | 2.18| 2.35| 2.51| 2.67| 2.82| 2.97| | h| 1200.2 |1233.2 |1260.7 |1286.5 |1311.6 |1336.3 |1361.0 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 395.6 | 445.6 | 495.6 | 545.6 | 595.6 | 645.6 | 695.6 | | 235 v| 1.96 | 2.14| 2.30| 2.46| 2.62| 2.77| 2.91| | h| 1200.6 |1233.8 |1261.4 |1287.1 |1312.2 |1337.0 |1361.7 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 397.4 | 447.4 | 497.4 | 547.4 | 597.4 | 647.4 | 697.4 | | 240 v| 1.92 | 2.09| 2.26| 2.42| 2.57| 2.71| 2.85| | h| 1200.9 |1234.3 |1261.9 |1287.6 |1312.8 |1337.6 |1362.3 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 399.3 | 449.3 | 499.3 | 549.3 | 599.3 | 649.3 | 699.3 | | 245 v| 1.89 | 2.05| 2.22| 2.37| 2.52| 2.66| 2.80| | h| 1201.2 |1234.8 |1262.5 |1288.2 |1313.3 |1338.2 |1362.9 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 401.0 | 451.0 | 501.0 | 551.0 | 601.0 | 651.0 | 701.0 | | 250 v| 1.85 | 2.02| 2.17| 2.33| 2.47| 2.61| 2.75| | h| 1201.5 |1235.4 |1263.0 |1288.8 |1313.9 |1338.8 |1363.5 | |________|_________|_______|_______|_______|_______|_______|_______| | t| 402.8 | 452.8 | 502.8 | 552.8 | 602.8 | 652.8 | 702.8 | | 255 v| 1.81 | 1.98| 2.14| 2.28| 2.43| 2.56| 2.70| | h| 1201.8 |1235.9 |1263.6 |1289.3 |1314.5 |1339.3 |1364.1 | |________|_________|_______|_______|_______|_______|_______|_______| t = Temperature, degrees Fahrenheit. v = Specific volume, in cubic feet, per pound. h = Total heat from water at 32 degrees, B. t. u. [Graph: Temperature of Steam--Degrees Fahr. against Temperature in Calorimeter--Degrees Fahr. Fig. 15. Graphic Method of Determining Moisture Contained in Steam from Calorimeter Readings] MOISTURE IN STEAM The presence of moisture in steam causes a loss, not only in the practical waste of the heat utilized to raise this moisture from the temperature of the feed water to the temperature of the steam, but also through the increased initial condensation in an engine cylinder and through friction and other actions in a steam turbine. The presence of such moisture also interferes with proper cylinder lubrication, causes a knocking in the engine and a water hammer in the steam pipes. In steam turbines it will cause erosion of the blades. The percentage by weight of steam in a mixture of steam and water is called the _quality of the steam_. The apparatus used to determine the moisture content of steam is called a calorimeter though since it may not measure the heat in the steam, the name is not descriptive of the function of the apparatus. The first form used was the "barrel calorimeter", but the liability of error was so great that its use was abandoned. Modern calorimeters are in general of either the throttling or separator type. Throttling Calorimeter--Fig. 14 shows a typical form of throttling calorimeter. Steam is drawn from a vertical main through the sampling nipple, passes around the first thermometer cup, then through a one-eighth inch orifice in a disk between two flanges, and lastly around the second thermometer cup and to the atmosphere. Thermometers are inserted in the wells, which should be filled with mercury or heavy cylinder oil. [Illustration: Fig. 14. Throttling Calorimeter and Sampling Nozzle] The instrument and all pipes and fittings leading to it should be thoroughly insulated to diminish radiation losses. Care must be taken to prevent the orifice from becoming choked with dirt and to see that no leaks occur. The exhaust pipe should be short to prevent back pressure below the disk. When steam passes through an orifice from a higher to a lower pressure, as is the case with the throttling calorimeter, no external work has to be done in overcoming a resistance. Hence, if there is no loss from radiation, the quantity of heat in the steam will be exactly the same after passing the orifice as before passing. If the higher steam pressure is 160 pounds gauge and the lower pressure that of the atmosphere, the total heat in a pound of dry steam at the former pressure is 1195.9 B. t. u. and at the latter pressure 1150.4 B. t. u., a difference of 45.4 B. t. u. As this heat will still exist in the steam at the lower pressure, since there is no external work done, its effect must be to superheat the steam. Assuming the specific heat of superheated steam to be 0.47, each pound passing through will be superheated 45.4/0.47 = 96.6 degrees. If, however, the steam had contained one per cent of moisture, it would have contained less heat units per pound than if it were dry. Since the latent heat of steam at 160 pounds gauge pressure is 852.8 B. t. u., it follows that the one per cent of moisture would have required 8.5 B. t. u. to evaporate it, leaving only 45.4 - 8.5 = 36.9 B. t. u. available for superheating; hence, the superheat would be 36.9/0.47 = 78.5 degrees, as against 96.6 degrees for dry steam. In a similar manner, the degree of superheat for other percentages of moisture may be determined. The action of the throttling calorimeter is based upon the foregoing facts, as shown below. Let H = total heat of one pound of steam at boiler pressure, L = latent heat of steam at boiler pressure, h = total heat of steam at reduced pressure after passing orifice, t_{1} = temperature of saturated steam at the reduced pressure, t_{2} = temperature of steam after expanding through the orifice in the disc, 0.47 = the specific heat of saturated steam at atmospheric pressure, x = proportion by weight of moisture in steam. The difference in B. t. u. in a pound of steam at the boiler pressure and after passing the orifice is the heat available for evaporating the moisture content and superheating the steam. Therefore, H - h = xL + 0.47(t_{2} - t_{1}) H - h - 0.47(t_{2} - t_{1}) or x = --------------------------- (4) L Almost invariably the lower pressure is taken as that of the atmosphere. Under such conditions, h = 1150.4 and t_{1} = 212 degrees. The formula thus becomes: H - 1150.4 - 0.47(t_{2} - 212) x = ------------------------------ (5) L For practical work it is more convenient to dispense with the upper thermometer in the calorimeter and to measure the pressure in the steam main by an accurate steam pressure gauge. A chart may be used for determining the value of x for approximate work without the necessity for computation. Such a chart is shown in Fig. 15 and its use is as follows: Assume a gauge pressure of 180 pounds and a thermometer reading of 295 degrees. The intersection of the vertical line from the scale of temperatures as shown by the calorimeter thermometer and the horizontal line from the scale of gauge pressures will indicate directly the per cent of moisture in the steam as read from the diagonal scale. In the present instance, this per cent is 1.0. Sources of Error in the Apparatus--A slight error may arise from the value, 0.47, used as the specific heat of superheated steam at atmospheric pressure. This value, however is very nearly correct and any error resulting from its use will be negligible. There is ordinarily a larger source of error due to the fact that the stem of the thermometer is not heated to its full length, to an initial error in the thermometer and to radiation losses. With an ordinary thermometer immersed in the well to the 100 degrees mark, the error when registering 300 degrees would be about 3 degrees and the true temperature be 303 degrees.[19] The steam is evidently losing heat through radiation from the moment it enters the sampling nipple. The heat available for evaporating moisture and superheating steam after it has passed through the orifice into the lower pressure will be diminished by just the amount lost through radiation and the value of t_{2}, as shown by the calorimeter thermometer, will, therefore, be lower than if there were no such loss. The method of correcting for the thermometer and radiation error recommended by the Power Test Committee of the American Society of Mechanical Engineers is by referring the readings as found on the boiler trial to a "normal" reading of the thermometer. This normal reading is the reading of the lower calorimeter thermometer for dry saturated steam, and should be determined by attaching the instrument to a horizontal steam pipe in such a way that the sampling nozzle projects upward to near the top of the pipe, there being no perforations in the nozzle and the steam taken only through its open upper end. The test should be made with the steam in a quiescent state and with the steam pressure maintained as nearly as possible at the pressure observed in the main trial, the calorimeter thermometer to be the same as was used on the trial or one exactly similar. With a normal reading thus obtained for a pressure approximately the same as existed in the trial, the true percentage of moisture in the steam, that is, with the proper correction made for radiation, may be calculated as follows: Let T denote the normal reading for the conditions existing in the trial. The effect of radiation from the instrument as pointed out will be to lower the temperature of the steam at the lower pressure. Let x_{1} represent the proportion of water in the steam which will lower its temperature an amount equal to the loss by radiation. Then, H - h - 0.47(T - t_{1}) x_{1} = ----------------------- L This amount of moisture, x_{1} was not in the steam originally but is the result of condensation in the instrument through radiation. Hence, the true amount of moisture in the steam represented by X is the difference between the amount as determined in the trial and that resulting from condensation, or, X = x - x_{1} H - h - 0.47(t_{2} - t_{1}) H - h - 0.47(T - t_{1}) = --------------------------- - ----------------------- L L 0.47(T - t_{2}) = --------------- (6) L As T and t_{2} are taken with the same thermometer under the same set of conditions, any error in the reading of the thermometers will be approximately the same for the temperatures T and t_{2} and the above method therefore corrects for both the radiation and thermometer errors. The theoretical readings for dry steam, where there are no losses due to radiation, are obtainable from formula (5) by letting x = 0 and solving for t_{2}. The difference between the theoretical reading and the normal reading for no moisture will be the thermometer and radiation correction to be applied in order that the correct reading of t_{2} may be obtained. For any calorimeter within the range of its ordinary use, such a thermometer and radiation correction taken from one normal reading is approximately correct for any conditions with the same or a duplicate thermometer. The percentage of moisture in the steam, corrected for thermometer error and radiation and the correction to be applied to the particular calorimeter used, would be determined as follows: Assume a gauge pressure in the trial to be 180 pounds and the thermometer reading to be 295 degrees. A normal reading, taken in the manner described, gives a value of T = 303 degrees; then, the percentage of moisture corrected for thermometer error and radiation is, 0.47(303 - 295) x = ---------------- 845.0 = 0.45 per cent. The theoretical reading for dry steam will be, 1197.7 - 1150.4 - 0.47(t_{2} - 212) 0 = ------------------------------------ 845.0 t_{2} = 313 degrees. The thermometer and radiation correction to be applied to the instrument used, therefore over the ordinary range of pressure is Correction = 313 - 303 = 10 degrees The chart may be used in the determination of the correct reading of moisture percentage and the permanent radiation correction for the instrument used without computation as follows: Assume the same trial pressure, feed temperature and normal reading as above. If the normal reading is found to be 303 degrees, the correction for thermometer and radiation will be the theoretical reading for dry steam as found from the chart, less this normal reading, or 10 degrees correction. The correct temperature for the trial in question is, therefore, 305 degrees. The moisture corresponding to this temperature and 180 pounds gauge pressure will be found from the chart to be 0.45 per cent. [Illustration: Fig. 16. Compact Throttling Calorimeter] There are many forms of throttling calorimeter, all of which work upon the same principle. The simplest one is probably that shown in Fig. 14. An extremely convenient and compact design is shown in Fig. 16. This calorimeter consists of two concentric metal cylinders screwed to a cap containing a thermometer well. The steam pressure is measured by a gauge placed in the supply pipe or other convenient location. Steam passes through the orifice A and expands to atmospheric pressure, its temperature at this pressure being measured by a thermometer placed in the cup C. To prevent as far as possible radiation losses, the annular space between the two cylinders is used as a jacket, steam being supplied to this space through the hole B. The limits of moisture within which the throttling calorimeter will work are, at sea level, from 2.88 per cent at 50 pounds gauge pressure and 7.17 per cent moisture at 250 pounds pressure. Separating Calorimeter--The separating calorimeter mechanically separates the entrained water from the steam and collects it in a reservoir, where its amount is either indicated by a gauge glass or is drained off and weighed. Fig. 17 shows a calorimeter of this type. The steam passes out of the calorimeter through an orifice of known size so that its total amount can be calculated or it can be weighed. A gauge is ordinarily provided with this type of calorimeter, which shows the pressure in its inner chamber and the flow of steam for a given period, this latter scale being graduated by trial. The instrument, like a throttling calorimeter, should be well insulated to prevent losses from radiation. While theoretically the separating calorimeter is not limited in capacity, it is well in cases where the percentage of moisture present in the steam is known to be high, to attach a throttling calorimeter to its exhaust. This, in effect, is the using of the separating calorimeter as a small separator between the sampling nozzle and the throttling instrument, and is necessary to insure the determination of the full percentage of moisture in the steam. The sum of the percentages shown by the two instruments is the moisture content of the steam. The steam passing through a separating calorimeter may be calculated by Napier's formula, the size of the orifice being known. There are objections to such a calculation, however, in that it is difficult to accurately determine the areas of such small orifices. Further, small orifices have a tendency to become partly closed by sediment that may be carried by the steam. The more accurate method of determining the amount of steam passing through the instrument is as follows: [Illustration: Fig. 17. Separating Calorimeter] A hose should be attached to the separator outlet leading to a vessel of water on a platform scale graduated to 1/100 of a pound. The steam outlet should be connected to another vessel of water resting on a second scale. In each case, the weight of each vessel and its contents should be noted. When ready for an observation, the instrument should be blown out thoroughly so that there will be no water within the separator. The separator drip should then be closed and the steam hose inserted into the vessel of water at the same instant. When the separator has accumulated a sufficient quantity of water, the valve of the instrument should be closed and the hose removed from the vessel of water. The separator should be emptied into the vessel on its scale. The final weight of each vessel and its contents are to be noted and the differences between the final and original weights will represent the weight of moisture collected by the separator and the weight of steam from which the moisture has been taken. The proportion of moisture can then be calculated from the following formula: 100 w x = ----- (7) W - w Where x = per cent moisture in steam, W = weight of steam condensed, w = weight of moisture as taken out by the separating calorimeter. Sampling Nipple--The principle source of error in steam calorimeter determinations is the failure to obtain an average sample of the steam delivered by the boiler and it is extremely doubtful whether such a sample is ever obtained. The two governing features in the obtaining of such a sample are the type of sampling nozzle used and its location. The American Society of Mechanical Engineers recommends a sampling nozzle made of one-half inch iron pipe closed at the inner end and the interior portion perforated with not less than twenty one-eighth inch holes equally distributed from end to end and preferably drilled in irregular or spiral rows, with the first hole not less than one-half inch from the wall of the pipe. Many engineers object to the use of a perforated sampling nipple because it ordinarily indicates a higher percentage of moisture than is actually present in the steam. This is due to the fact that if the perforations come close to the inner surface of the pipe, the moisture, which in many instances clings to this surface, will flow into the calorimeter and cause a large error. Where a perforated nipple is used, in general it may be said that the perforations should be at least one inch from the inner pipe surface. A sampling nipple, open at the inner end and unperforated, undoubtedly gives as accurate a measure as can be obtained of the moisture in the steam passing that end. It would appear that a satisfactory method of obtaining an average sample of the steam would result from the use of an open end unperforated nipple passing through a stuffing box which would allow the end to be placed at any point across the diameter of the steam pipe. Incidental to a test of a 15,000 K. W. steam engine turbine unit, Mr. H. G. Stott and Mr. R. G. S. Pigott, finding no experimental data bearing on the subject of low pressure steam quality determinations, made a investigation of the subject and the sampling nozzle illustrated in Fig. 18 was developed. In speaking of sampling nozzles in the determination of the moisture content of low pressure steam, Mr. Pigott says, "the ordinary standard perforated pipe sampler is absolutely worthless in giving a true sample and it is vital that the sample be abstracted from the main without changing its direction or velocity until it is safely within the sample pipe and entirely isolated from the rest of the steam." [Illustration: Fig. 18. Stott and Pigott Sampling Nozzle] It would appear that the nozzle illustrated is undoubtedly the best that has been developed for use in the determination of the moisture content of steam, not only in the case of low, but also in high pressure steam. Location of Sampling Nozzle--The calorimeter should be located as near as possible to the point from which the steam is taken and the sampling nipple should be placed in a section of the main pipe near the boiler and where there is no chance of moisture pocketing in the pipe. The American Society of Mechanical Engineers recommends that a sampling nipple, of which a description has been given, should be located in a vertical main, rising from the boiler with its closed end extending nearly across the pipe. Where non-return valves are used, or where there are horizontal connections leading from the boiler to a vertical outlet, water may collect at the lower end of the uptake pipe and be blown upward in a spray which will not be carried away by the steam owing to a lack of velocity. A sample taken from the lower part of this pipe will show a greater amount of moisture than a true sample. With goose-neck connections a small amount of water may collect on the bottom of the pipe near the upper end where the inclination is such that the tendency to flow backward is ordinarily counterbalanced by the flow of steam forward over its surface; but when the velocity momentarily decreases the water flows back to the lower end of the goose-neck and increases the moisture at that point, making it an undesirable location for sampling. In any case, it should be borne in mind that with low velocities the tendency is for drops of entrained water to settle to the bottom of the pipe, and to be temporarily broken up into spray whenever an abrupt bend or other disturbance is met. [Illustration: Fig. 19. Illustrating the Manner in which Erroneous Calorimeter Readings may be Obtained due to Improper Location of Sampling Nozzle Case 1--Horizontal pipe. Water flows at bottom. If perforations in nozzle are too near bottom of pipe, water piles against nozzle, flows into calorimeter and gives false reading. Case 2--If nozzle located too near junction of two horizontal runs, as at a, condensation from vertical pipe which collects at this point will be thrown against the nozzle by the velocity of the steam, resulting in a false reading. Nozzle should be located far enough above junction to be removed from water kept in motion by the steam velocity, as at b. Case 3--Condensation in bend will be held by velocity of the steam as shown. When velocity is diminished during firing intervals and the like moisture flows back against nozzle, a, and false reading is obtained. A true reading will be obtained at b provided condensation is not blown over on nozzle. Case 4--Where non-return valve is placed before a bend, condensation will collect on steam line side and water will be swept by steam velocity against nozzle and false readings result.] Fig. 19 indicates certain locations of sampling nozzles from which erroneous results will be obtained, the reasons being obvious from a study of the cuts. Before taking any calorimeter reading, steam should be allowed to flow through the instrument freely until it is thoroughly heated. The method of using a throttling calorimeter is evident from the description of the instrument given and the principle upon which it works. [Illustration: Babcock & Wilcox Superheater] SUPERHEATED STEAM Superheated steam, as already stated, is steam the temperature of which exceeds that of saturated steam at the same pressure. It is produced by the addition of heat to saturated steam which has been removed from contact with the water from which it was generated. The properties of superheated steam approximate those of a perfect gas rather than of a vapor. Saturated steam cannot be superheated when it is in contact with water which is also heated, neither can superheated steam condense without first being reduced to the temperature of saturated steam. Just so long as its temperature is above that of saturated steam at a corresponding pressure it is superheated, and before condensation can take place that superheat must first be lost through radiation or some other means. Table 24[20] gives such properties of superheated steam for varying pressures as are necessary for use in ordinary engineering practice. Specific Heat of Superheated Steam--The specific heat of superheated steam at atmospheric pressure and near saturation point was determined by Regnault, in 1862, who gives it the value of 0.48. Regnault's value was based on four series of experiments, all at atmospheric pressure and with about the same temperature range, the maximum of which was 231.1 degrees centigrade. For fifty years after Regnault's determination, this value was accepted and applied to higher pressures and temperatures as well as to the range of his experiments. More recent investigations have shown that the specific heat is not a constant and varies with both pressure and the temperature. A number of experiments have been made by various investigators and, up to the present, the most reliable appear to be those of Knoblauch and Jacob. Messrs. Marks and Davis have used the values as determined by Knoblauch and Jacob with slight modifications. The first consists in a varying of the curves at low pressures close to saturation because of thermodynamic evidence and in view of Regnault's determination at atmospheric pressure. The second modification is at high degrees of superheat to follow Holborn's and Henning's curve, which is accepted as authentic. For the sake of convenience, the mean specific heat of superheated steam at various pressures and temperatures is given in tabulated form in Table 25. These values have been calculated from Marks and Davis Steam Tables by deducting from the total heat of one pound of steam at any pressure for any degree of superheat the total heat of one pound of saturated steam at the same pressure and dividing the difference by the number of degrees of superheat and, therefore, represent the average specific heat starting from that at saturation to the value at the particular pressure and temperature.[21] Expressed as a formula this calculation is represented by H_{sup} - H_{sat} Sp. Ht. = ----------------- (8) S_{sup} - S_{sat} Where H_{sup} = total heat of one pound of superheated steam at any pressure and temperature, H_{sat} = total heat of one pound of saturated steam at same pressure, S_{sup} = temperature of superheated steam taken, S_{sat} = temperature of saturated steam corresponding to the pressure taken. TABLE 25 MEAN SPECIFIC HEAT OF SUPERHEATED STEAM CALCULATED FROM MARKS AND DAVIS TABLES _______________________________________________________________ |Gauge | | |Pressure | Degree of Superheat | | |_____________________________________________________| | | 50 | 60 | 70 | 80 | 90 | 100 | 110 | 120 | 130 | |_________|_____|_____|_____|_____|_____|_____|_____|_____|_____| | 50 | .518| .517| .514| .513| .511| .510| .508| .507| .505| | 60 | .528| .525| .523| .521| .519| .517| .515| .513| .512| | 70 | .536| .534| .531| .529| .527| .524| .522| .520| .518| | 80 | .544| .542| .539| .535| .532| .530| .528| .526| .524| | 90 | .553| .550| .546| .543| .539| .536| .534| .532| .529| | 100 | .562| .557| .553| .549| .544| .542| .539| .536| .533| | 110 | .570| .565| .560| .556| .552| .548| .545| .542| .539| | 120 | .578| .573| .567| .561| .557| .554| .550| .546| .543| | 130 | .586| .580| .574| .569| .564| .560| .555| .552| .548| | 140 | .594| .588| .581| .575| .570| .565| .561| .557| .553| | 150 | .604| .595| .587| .581| .576| .570| .566| .561| .557| | 160 | .612| .603| .596| .589| .582| .576| .571| .566| .562| | 170 | .620| .612| .603| .595| .588| .582| .576| .571| .566| | 180 | .628| .618| .610| .601| .593| .587| .581| .575| .570| | 190 | .638| .627| .617| .608| .599| .592| .585| .579| .574| | 200 | .648| .635| .624| .614| .605| .597| .590| .584| .578| | 210 | .656| .643| .631| .620| .611| .602| .595| .588| .583| | 220 | .664| .650| .637| .626| .616| .607| .600| .592| .586| | 230 | .672| .658| .644| .633| .622| .613| .605| .597| .591| | 240 | .684| .668| .653| .640| .629| .619| .610| .602| .595| | 250 | .692| .675| .659| .645| .633| .623| .614| .606| .599| |_________|_____|_____|_____|_____|_____|_____|_____|_____|_____| |Gauge | | |Pressure | Degree of Superheat | | |-----------------------------------------------------| | | 140 | 150 | 160 | 170 | 180 | 190 | 200 | 225 | 250 | |---------+-----+-----+-----+-----+-----+-----+-----+-----+-----| | 50 | .504| .503| .502| .501| .500| .500| .499| .497| .496| | 60 | .511| .509| .508| .507| .506| .504| .504| .502| .500| | 70 | .516| .515| .513| .512| .511| .510| .509| .506| .504| | 80 | .522| .520| .518| .516| .515| .514| .513| .511| .508| | 90 | .527| .525| .523| .521| .519| .518| .517| .514| .510| | 100 | .531| .529| .527| .525| .523| .522| .521| .517| .513| | 110 | .536| .534| .532| .529| .528| .526| .525| .520| .517| | 120 | .540| .537| .535| .533| .531| .529| .528| .523| .519| | 130 | .545| .542| .539| .537| .535| .533| .531| .527| .523| | 140 | .550| .547| .544| .541| .539| .536| .534| .530| .526| | 150 | .554| .550| .547| .544| .542| .539| .537| .533| .529| | 160 | .558| .554| .551| .548| .545| .543| .541| .536| .531| | 170 | .562| .558| .555| .552| .549| .546| .544| .538| .533| | 180 | .566| .561| .558| .555| .552| .549| .546| .540| .536| | 190 | .569| .565| .562| .558| .555| .552| .549| .543| .538| | 200 | .574| .569| .566| .562| .558| .555| .552| .546| .541| | 210 | .578| .573| .569| .565| .561| .558| .555| .549| .543| | 220 | .581| .577| .572| .568| .564| .561| .558| .551| .545| | 230 | .585| .580| .575| .572| .567| .564| .561| .554| .548| | 240 | .589| .584| .579| .575| .571| .567| .564| .556| .550| | 250 | .593| .587| .582| .577| .574| .570| .567| .559| .553| |_________|_____|_____|_____|_____|_____|_____|_____|_____|_____| Factor of Evaporation with Superheated Steam--When superheat is present in the steam during a boiler trial, where superheated steam tables are available, the formula for determining the factor of evaporation is that already given, (2),[22] namely, H - h Factor of evaporation = ----- L Here H = total heat in one pound of superheated steam from the table, h and L having the same values as in (2). Where no such tables are available but the specific heat of superheat is known, the formula becomes: H - h + Sp. Ht.(T - t) Factor of evaporation = ---------------------- L Where H = total heat in one pound of saturated steam at pressure existing in trial, h = sensible heat above 32 degrees in one pound of water at the temperature entering the boiler, T = temperature of superheated steam as determined in the trial, t = temperature of saturated steam corresponding to the boiler pressure, Sp. Ht. = mean specific heat of superheated steam at the pressure and temperature as found in the trial, L = latent heat of one pound of saturated steam at atmospheric pressure. Advantages of the Use of Superheated Steam--In considering the saving possible by the use of superheated steam, it is too often assumed that there is only a saving in the prime movers, a saving which is at least partially offset by an increase in the fuel consumption of the boilers generating steam. This misconception is due to the fact that the fuel consumption of the boiler is only considered in connection with a definite weight of steam. It is true that where such a definite weight is to be superheated, an added amount of fuel must be burned. With a properly designed superheater where the combined efficiency of the boiler and superheater will be at least as high as of a boiler alone, the approximate increase in coal consumption for producing a given weight of steam will be as follows: _Superheat_ _Added Fuel_ _Degrees_ _Per Cent_ 25 1.59 50 3.07 75 4.38 100 5.69 150 8.19 200 10.58 These figures represent the added fuel necessary for superheating a definite weight of steam to the number of degrees as given. The standard basis, however, of boiler evaporation is one of heat units and, considered from such a standpoint, again providing the efficiency of the boiler and superheater is as high, as of a boiler alone, there is no additional fuel required to generate steam containing a definite number of heat units whether such units be due to superheat or saturation. That is, if 6 per cent more fuel is required to generate and superheat to 100 degrees, a definite weight of steam, over what would be required to produce the same weight of saturated steam, that steam when superheated, will contain 6 per cent more heat units above the fuel water temperature than if saturated. This holds true if the efficiency of the boiler and superheater combined is the same as of the boiler alone. As a matter of fact, the efficiency of a boiler and superheater, where the latter is properly designed and located, will be slightly higher for the same set of furnace conditions than would the efficiency of a boiler in which no superheater were installed. A superheater, properly placed within the boiler setting in such way that products of combustion for generating saturated steam are utilized as well for superheating that steam, will not in any way alter furnace conditions. With a given set of such furnace conditions for a given amount of coal burned, the fact that additional surface, whether as boiler heating or superheating surface, is placed in such a manner that the gases must sweep over it, will tend to lower the temperature of the exit gases. It is such a lowering of exit gas temperatures that is the ultimate indication of added efficiency. Though the amount of this added efficiency is difficult to determine by test, that there is an increase is unquestionable. Where a properly designed superheater is installed in a boiler the heating surface of the boiler proper, in the generation of a definite number of heat units, is relieved of a portion of the work which would be required were these heat units delivered in saturated steam. Such a superheater needs practically no attention, is not subject to a large upkeep cost or depreciation, and performs its function without in any way interfering with the operation of the boiler. Its use, therefore from the standpoint of the boiler room, results in a saving in wear and tear due to the lower ratings at which the boiler may be run, or its use will lead to the possibility of obtaining the same number of boiler horse power from a smaller number of boilers, with the boiler heating surface doing exactly the same amount of work as if the superheaters were not installed. The saving due to the added boiler efficiency that will be obtained is obvious. Following the course of the steam in a plant, the next advantage of the use of superheated steam is the absence of water in the steam pipes. The thermal conductivity of superheated steam, that is, its power to give up its heat to surrounding bodies, is much lower than that of saturated steam and its heat, therefore, will not be transmitted so rapidly to the walls of the pipes as when saturated steam is flowing through the pipes. The loss of heat radiated from a steam pipe, assuming no loss in pressure, represents the equivalent condensation when the pipe is carrying saturated steam. In well-covered steam mains, the heat lost by radiation when carrying superheated steam is accompanied only by a reduction of the superheat which, if it be sufficiently high at the boiler, will enable a considerable amount of heat to be radiated and still deliver dry or superheated steam to the prime movers. It is in the prime movers that the advantages of the use of superheated steam are most clearly seen. In an engine, steam is admitted into a space that has been cooled by the steam exhausted during the previous stroke. The heat necessary to warm the cylinder walls from the temperature of the exhaust to that of the entering steam can be supplied only by the entering steam. If this steam be saturated, such an adding of heat to the walls at the expense of the heat of the entering steam results in the condensation of a portion. This initial condensation is seldom less than from 20 to 30 per cent of the total weight of steam entering the cylinder. It is obvious that if the steam entering be superheated, it must be reduced to the temperature of saturated steam at the corresponding pressure before any condensation can take place. If the steam be superheated sufficiently to allow a reduction in temperature equivalent to the quantity of heat that must be imparted to the cylinder walls and still remain superheated, it is clear that initial condensation is avoided. For example: assume one pound of saturated steam at 200 pounds gauge pressure to enter a cylinder which has been cooled by the exhaust. Assume the initial condensation to be 20 per cent. The latent heat of the steam is given up in condensation; hence, .20 × 838 = 167.6 B. t. u. are given up by the steam. If one pound of superheated steam enters the same cylinder, it would have to be superheated to a point where its total heat is 1199 + 168 = 1367 B. t. u. or, at 200 pounds gauge pressure, superheated approximately 325 degrees if the heat given up to the cylinder walls were the same as for the saturated steam. As superheated steam conducts heat less rapidly than saturated steam, the amount of heat imparted will be less than for the saturated steam and consequently the amount of superheat required to prevent condensation will be less than the above figure. This, of course, is the extreme case of a simple engine with the range of temperature change a maximum. As cylinders are added, the range in each is decreased and the condensation is proportionate. The true economy of the use of superheated steam is best shown in a comparison of the "heat consumption" of an engine. This is the number of heat units required in developing one indicated horse power and the measure of the relative performance of two engines is based on a comparison of their heat consumption as the measure of a boiler is based on its evaporation from and at 212 degrees. The water consumption of an engine in pounds per indicated horse power is in no sense a true indication of its efficiency. The initial pressures and corresponding temperatures may differ widely and thus make a difference in the temperature of the exhaust and hence in the temperature of the condensed steam returned to the boiler. For example: suppose a certain weight of steam at 150 pounds absolute pressure and 358 degrees be expanded to atmospheric pressure, the temperature then being 212 degrees. If the same weight of steam be expanded from an initial pressure of 125 pounds absolute and 344 degrees, to enable it to do the same amount of work, that is, to give up the same amount of heat, expansion then must be carried to a point below atmospheric pressure to, say, 13 pounds absolute, the final temperature of the steam then being 206 degrees. In actual practice, it has been observed that the water consumption of a compound piston engine running on 26-inch vacuum and returning the condensed steam at 140 degrees was approximately the same as when running on 28-inch vacuum and returning water at 90 degrees. With an equal water consumption for the two sets of conditions, the economy in the former case would be greater than in the latter, since it would be necessary to add less heat to the water returned to the boiler to raise it to the steam temperature. The lower the heat consumption of an engine per indicated horse power, the higher its economy and the less the number of heat units must be imparted to the steam generated. This in turn leads to the lowering of the amount of fuel that must be burned per indicated horse power. With the saving in fuel by the reduction of heat consumption of an engine indicated, it remains to be shown the effect of the use of superheated steam on such heat consumption. As already explained, the use of superheated steam reduces condensation not only in the mains but especially in the steam cylinder, leaving a greater quantity of steam available to do the work. Furthermore, a portion of the saturated steam introduced into a cylinder will condense during adiabatic expansion, this condensation increasing as expansion progresses. Since superheated steam cannot condense until it becomes saturated, not only is initial condensation prevented by its use but also such condensation as would occur during expansion. When superheated sufficiently, steam delivered by the exhaust will still be dry. In the avoidance of such condensation, there is a direct saving in the heat consumption of an engine, the heat given up being utilized in the developing of power and not in changing the condition of the working fluid. That is, while the number of heat units lost in overcoming condensation effects would be the same in either case, when saturated steam is condensed the water of condensation has no power to do work while the superheated steam, even after it has lost a like number of heat units, still has the power of expansion. The saving through the use of superheated steam in the heat consumption of an engine decreases demands on the boiler and hence the fuel consumption per unit of power. Superheated Steam for Steam Turbines--Experience in using superheated steam in connection with steam turbines has shown that it leads to economy and that it undoubtedly pays to use superheated steam in place of saturated steam. This is so well established that it is standard practice to use superheated steam in connection with steam turbines. Aside from the economy secured through using superheated steam, there is an important advantage arising through the fact that it materially reduces the erosion of the turbine blades by the action of water that would be carried by saturated steam. In using saturated steam in a steam turbine or piston engine, the work done on expanding the steam causes condensation of a portion of the steam, so that even were the steam dry on entering the turbine, it would contain water on leaving the turbine. By superheating the steam the water that exists in the low pressure stages of the turbine may be reduced to an amount that will not cause trouble. Again, if saturated steam contains moisture, the effect of this moisture on the economy of a steam turbine is to reduce the economy to a greater extent than the proportion by weight of water, one per cent of water causing approximately a falling off of 2 per cent in the economy. The water rate of a large economical steam turbine with superheated steam is reduced about one per cent, for every 12 degrees of superheat up to 200 degrees Fahrenheit of superheat. To superheat one pound of steam 12 degrees requires about 7 B. t. u. and if 1050 B. t. u. are required at the boiler to evaporate one pound of the saturated steam from the temperature of the feed water, the heat required for the superheated steam would be 1057 degrees. One per cent of saving, therefore, in the water consumption would correspond to a net saving of about one-third of one per cent in the coal consumption. On this basis 100 degrees of superheat with an economical steam turbine would result in somewhat over 3 per cent of saving in the coal for equal boiler efficiencies. As a boiler with a properly designed superheater placed within the setting is more economical for a given capacity than a boiler without a superheater, the minimum gain in the coal consumption would be, say, 4 or 5 per cent as compared to a plant with the same boilers without superheaters. The above estimates are on the basis of a thoroughly dry saturated steam or steam just at the point of being superheated or containing a few degrees of superheat. If the saturated steam is moist, the saving due to superheat is more and ordinarily the gain in economy due to superheated steam, for equal boiler efficiencies, as compared with commercially dry steam is, say, 5 per cent for each 100 degrees of superheat. Aside from this gain, as already stated, superheated steam prevents erosion of the turbine buckets that would be caused by water in the steam, and for the reasons enumerated it is standard practice to use superheated steam for turbine work. The less economical the steam motor, the more the gain due to superheated steam, and where there are a number of auxiliaries that are run with superheated steam, the percentage of gain will be greater than the figures given above, which are the minimum and are for the most economical type of large steam turbines. An example from actual practice will perhaps best illustrate and emphasize the foregoing facts. In October 1909, a series of comparable tests were conducted by The Babcock & Wilcox Co. on the steam yacht "Idalia" to determine the steam consumption both with saturated and superheated steam of the main engine on that yacht, including as well the feed pump, circulating pump and air pump. These tests are more representative than are most tests of like character in that the saving in the steam consumption of the auxiliaries, which were much more wasteful than the main engine, formed an important factor. A résumé of these tests was published in the Journal of the Society of Naval Engineers, November 1909. The main engines of the "Idalia" are four cylinder, triple expansion, 11-1/2 × 19 inches by 22-11/16 × 18 inches stroke. Steam is supplied by a Babcock & Wilcox marine boiler having 2500 square feet of boiler heating surface, 340 square feet of superheating surface and 65 square feet of grate surface. The auxiliaries consist of a feed pump 6 × 4 × 6 inches, an independent air pump 6 × 12 × 8 inches, and a centrifugal pump driven by a reciprocating engine 5-7/16 × 5 inches. Under ordinary operating conditions the superheat existing is about 100 degrees Fahrenheit. Tests were made with various degrees of superheat, the amount being varied by by-passing the gases and in the tests with the lower amounts of superheat by passing a portion of the steam from the boiler to the steam main without passing it through the superheater. Steam temperature readings were taken at the engine throttle. In the tests with saturated steam, the superheater was completely cut out of the system. Careful calorimeter measurements were taken, showing that the saturated steam delivered to the superheater was dry. The weight of steam used was determined from the weight of the condensed steam discharge from the surface condenser, the water being pumped from the hot well into a tank mounted on platform scales. The same indicators, thermometers and gauges were used in all the tests, so that the results are directly comparable. The indicators used were of the outside spring type so that there was no effect of the temperature of the steam. All tests were of sufficient duration to show a uniformity of results by hours. A summary of the results secured is given in Table 26, which shows the water rate per indicated horse power and the heat consumption. The latter figures are computed on the basis of the heat imparted to the steam above the actual temperature of the feed water and, as stated, these are the results that are directly comparable. TABLE 26 RESULTS OF "IDALIA" TESTS _______________________________________________________________________ | | | | | | | |Date 1909 |Oct. 11|Oct. 14|Oct. 14|Oct. 12|Oct. 13| |_______________________________|_______|_______|_______|_______|_______| |Degrees of superheat Fahrenheit| 0 | 57 | 88 | 96 | 105 | |Pressures, pounds per} Throttle| 190 | 196 | 201 | 198 | 203 | |square inch above } First | | | | | | |Atmospheric Pressure } Receiver| 68.4 | 66.0 | 64.3 | 61.9 | 63.0 | | } Second | | | | | | | } Receiver| 9.7 | 9.2 | 8.7 | 7.8 | 8.4 | |Vacuum, inches | 25.5 | 25.9 | 25.9 | 25.4 | 25.2 | |Temperature, Degrees Fahrenheit| | | | | | | } Feed | 201 | 206 | 205 | 202 | 200 | | } Hot Well | 116 | 109.5 | 115 | 111.5 | 111 | | | | | | | | |Revolutions per minute | | | | | | | {Air Pump | 57 | 56 | 53 | 54 | 45 | | {Circulating Pump| 196 | 198 | 196 | 198 | 197 | | {Main Engine | 194.3 | 191.5 | 195.1 | 191.5 | 193.1 | |Indicated Horse Power, | | | | | | | Main Engine | 512.3 | 495.2 | 521.1 | 498.3 | 502.2 | |Water per hour, total pounds |9397 |8430 |8234 |7902 |7790 | |Water per indicated | | | | | | | Horse Power, pounds | 18.3 | 17.0 | 15.8 | 15.8 | 15.5 | |B. t. u. per minute per | | | | | | | indicated Horse Power | 314 | 300 | 284 | 286 | 283 | |Per cent Saving of Steam | ... | 7.1 | 13.7 | 13.7 | 15.3 | |Percent Saving of Fuel | | | | | | | (computed) | ... | 4.4 | 9.5 | 8.9 | 9.9 | |_______________________________|_______|_______|_______|_______|_______| The table shows that the saving in steam consumption with 105 degrees of superheat was 15.3 per cent and in heat consumption about 10 per cent. This may be safely stated to be a conservative representation of the saving that may be accomplished by the use of superheated steam in a plant as a whole, where superheated steam is furnished not only to the main engine but also to the auxiliaries. The figures may be taken as conservative for the reason that in addition to the saving as shown in the table, there would be in an ordinary plant a saving much greater than is generally realized in the drips, where the loss with saturated steam is greatly in excess of that with superheated steam. The most conclusive and most practical evidence that a saving is possible through the use of superheated steam is in the fact that in the largest and most economical plants it is used almost without exception. Regardless of any such evidence, however, there is a deep rooted conviction in the minds of certain engineers that the use of superheated steam will involve operating difficulties which, with additional first cost, will more than offset any fuel saving. There are, of course, conditions under which the installation of superheaters would in no way be advisable. With a poorly designed superheater, no gain would result. In general, it may be stated that in a new plant, properly designed, with a boiler and superheater which will have an efficiency at least as high as a boiler without a superheater, a gain is certain. Such a gain is dependent upon the class of engine and the power plant equipment in general. In determining the advisability of making a superheater installation, all of the factors entering into each individual case should be considered and balanced, with a view to determining the saving in relation to cost, maintenance, depreciation etc. In highly economical plants, where the water consumption for an indicated horse power is low, the gain will be less than would result from the use of superheated steam in less economical plants where the water consumption is higher. It is impossible to make an accurate statement as to the saving possible but, broadly, it may vary from 3 to 5 per cent for 100 degrees of superheat in the large and economical plants using turbines or steam engines, in which there is a large ratio of expansion, to from 10 to 25 per cent for 100 degrees of superheat for the less economical steam motors. Though a properly designed superheater will tend to raise rather than to decrease the boiler efficiency, it does not follow that all superheaters are efficient, for if the gases in passing over the superheater do not follow the path they would ordinarily take in passing over the boiler heating surface, a loss may result. This is noticeably true where part of the gases are passed over the superheater and are allowed to pass over only a part or in some cases none of the boiler heating surface. With moderate degrees of superheat, from 100 to 200 degrees, where the piping is properly installed, there will be no greater operating difficulties than with saturated steam. Engine and turbine builders guarantee satisfactory operation with superheated steam. With high degrees of superheat, say, over 250 degrees, apparatus of a special nature must be used and it is questionable whether the additional care and liability to operating difficulties will offset any fuel saving accomplished. It is well established, however, that the operating difficulties, with the degrees of superheat to which this article is limited, have been entirely overcome. The use of cast-iron fittings with superheated steam has been widely discussed. It is an undoubted fact that while in some instances superheated steam has caused deterioration of such fittings, in others cast-iron fittings have been used with 150 degrees of superheat without the least difficulty. The quality of the cast iron used in such fittings has doubtless a large bearing on the life of such fittings for this service. The difficulties that have been encountered are an increase in the size of the fittings and eventually a deterioration great enough to lead to serious breakage, the development of cracks, and when flanges are drawn up too tightly, the breaking of a flange from the body of the fitting. The latter difficulty is undoubtedly due, in certain instances, to the form of flange in which the strain of the connecting bolts tended to distort the metal. The Babcock & Wilcox Co. have used steel castings in superheated steam work over a long period and experience has shown that this metal is suitable for the service. There seems to be a general tendency toward the use of steel fittings. In European practice, until recently, cast iron was used with apparently satisfactory results. The claim of European engineers was to the effect that their cast iron was of better quality than that found in this country and thus explained the results secured. Recently, however, certain difficulties have been encountered with such fittings and European engineers are leaning toward the use of steel for this work. The degree of superheat produced by a superheater placed within the boiler setting will vary according to the class of fuel used, the form of furnace, the condition of the fire and the rate at which the boiler is being operated. This is necessarily true of any superheater swept by the main body of the products of combustion and is a fact that should be appreciated by the prospective user of superheated steam. With a properly designed superheater, however, such fluctuations would not be excessive, provided the boilers are properly operated. As a matter of fact the point to be guarded against in the use of superheated steam is that a maximum should not be exceeded. While, as stated, there may be a considerable fluctuation in the temperature of the steam as delivered from individual superheaters, where there are a number of boilers on a line the temperature of the combined flow of steam in the main will be found to be practically a constant, resulting from the offsetting of various furnace conditions of one boiler by another. [Illustration: 8400 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters at the Butler Street Plant of the Georgia Railway and Power Co., Atlanta, Ga. This Company Operates a Total of 15,200 Horse Power of Babcock & Wilcox Boilers] PROPERTIES OF AIR Pure air is a mechanical mixture of oxygen and nitrogen. While different authorities give slightly varying values for the proportion of oxygen and nitrogen contained, the generally accepted values are: By volume, oxygen 20.91 per cent, nitrogen 79.09 per cent. By weight, oxygen 23.15 per cent, nitrogen 76.85 per cent. Air in nature always contains other constituents in varying amounts, such as dust, carbon dioxide, ozone and water vapor. Being perfectly elastic, the density or weight per unit of volume decreases in geometric progression with the altitude. This fact has a direct bearing in the proportioning of furnaces, flues and stacks at high altitudes, as will be shown later in the discussion of these subjects. The atmospheric pressures corresponding to various altitudes are given in Table 12. The weight and volume of air depend upon the pressure and the temperature, as expressed by the formula: Pv = 53.33 T (9) Where P = the absolute pressure in pounds per square foot, v = the volume in cubic feet of one pound of air, T = the absolute temperature of the air in degrees Fahrenheit, 53.33 = a constant for air derived from the ratio of pressure, volume and temperature of a perfect gas. The weight of one cubic foot of air will obviously be the reciprocal of its volume, that is, 1/v pounds. TABLE 27 VOLUME AND WEIGHT OF AIR AT ATMOSPHERIC PRESSURE AT VARIOUS TEMPERATURES _______________________________________ | | | | | | Volume | | | Temperature | One Pound | Weight One | | Degrees | in | Cubic Foot | | Fahrenheit | Cubic Feet | in Pounds | |_____________|____________|____________| | | | | | 32 | 12.390 | .080710 | | 50 | 12.843 | .077863 | | 55 | 12.969 | .077107 | | 60 | 13.095 | .076365 | | 65 | 13.221 | .075637 | | 70 | 13.347 | .074923 | | 75 | 13.473 | .074223 | | 80 | 13.599 | .073535 | | 85 | 13.725 | .072860 | | 90 | 13.851 | .072197 | | 95 | 13.977 | .071546 | | 100 | 14.103 | .070907 | | 110 | 14.355 | .069662 | | 120 | 14.607 | .068460 | | 130 | 14.859 | .067299 | | 140 | 15.111 | .066177 | | 150 | 15.363 | .065092 | | 160 | 15.615 | .064041 | | 170 | 15.867 | .063024 | | 180 | 16.119 | .062039 | | 190 | 16.371 | .061084 | | 200 | 16.623 | .060158 | | 210 | 16.875 | .059259 | | 212 | 16.925 | .059084 | | 220 | 17.127 | .058388 | | 230 | 17.379 | .057541 | | 240 | 17.631 | .056718 | | 250 | 17.883 | .055919 | | 260 | 18.135 | .055142 | | 270 | 18.387 | .054386 | | 280 | 18.639 | .053651 | | 290 | 18.891 | .052935 | | 300 | 19.143 | .052238 | | 320 | 19.647 | .050898 | | 340 | 20.151 | .049625 | | 360 | 20.655 | .048414 | | 380 | 21.159 | .047261 | | 400 | 21.663 | .046162 | | 425 | 22.293 | .044857 | | 450 | 22.923 | .043624 | | 475 | 23.554 | .042456 | | 500 | 24.184 | .041350 | | 525 | 24.814 | .040300 | | 550 | 25.444 | .039302 | | 575 | 26.074 | .038352 | | 600 | 26.704 | .037448 | | 650 | 27.964 | .035760 | | 700 | 29.224 | .034219 | | 750 | 30.484 | .032804 | | 800 | 31.744 | .031502 | | 850 | 33.004 | .030299 | |_____________|____________|____________| Example: Required the volume of air in cubic feet under 60.3 pounds gauge pressure per square inch at 115 degrees Fahrenheit. P = 144 (14.7 + 60.3) = 10,800. T = 115 + 460 = 575 degrees. 53.33 × 575 Hence v = ----------- = 2.84 cubic feet, and 10,800 1 1 Weight per cubic foot = - = ---- = 0.352 pounds. v 2.84 Table 27 gives the weights and volumes of air under atmospheric pressure at varying temperatures. Formula (9) holds good for other gases with the change in the value of the constant as follows: For oxygen 48.24, nitrogen 54.97, hydrogen 765.71. The specific heat of air at constant pressure varies with its temperature. A number of determinations of this value have been made and certain of those ordinarily accepted as most authentic are given in Table 28. TABLE 28 SPECIFIC HEAT OF AIR AT CONSTANT PRESSURE AND VARIOUS TEMPERATURES ______________________________________________________________ | | | | | Temperature Range | | | |_________________________|_______________|____________________| | | | | | | Degrees | Degrees | Specific Heat | Authority | | Centigrade | Fahrenheit | | | |____________|____________|_______________|____________________| | | | | | | -30- 10 | -22- 50 | 0.2377 | Regnault | | 0-100 | 32- 212 | 0.2374 | Regnault | | 0-200 | 32- 392 | 0.2375 | Regnault | | 20-440 | 68- 824 | 0.2366 | Holborn and Curtis | | 20-630 | 68-1166 | 0.2429 | Holborn and Curtis | | 20-800 | 68-1472 | 0.2430 | Holborn and Curtis | | 0-200 | 32- 392 | 0.2389 | Wiedemann | |____________|____________|_______________|____________________| This value is of particular importance in waste heat work and it is regrettable that there is such a variation in the different experiments. Mallard and Le Chatelier determined values considerably higher than any given in Table 28. All things considered in view of the discrepancy of the values given, there appears to be as much ground for the use of a constant value for the specific heat of air at any temperature as for a variable value. Where this value is used throughout this book, it has been taken as 0.24. Air may carry a considerable quantity of water vapor, which is frequently 3 per cent of the total weight. This fact is of importance in problems relating to heating drying and the compressing of air. Table 29 gives the amount of vapor required to saturate air at different temperatures, its weight, expansive force, etc., and contains sufficient information for solving practically all problems of this sort that may arise. TABLE 29 WEIGHTS OF AIR, VAPOR OF WATER, AND SATURATED MIXTURES OF AIR AND VAPOR AT DIFFERENT TEMPERATURES, UNDER THE ORDINARY ATMOSPHERIC PRESSURE OF 29.921 INCHES OF MERCURY Column Headings: 1: Temperature Degrees Fahrenheit 2: Volume of Dry Air at Different Temperatures, the Volume at 32 Degrees being 1.000 3: Weight of Cubic Foot of Dry Air at the Different Temperatures Pounds 4: Elastic Force of Vapor in Inches of Mercury (Regnault) 5: Elastic Force of the Air in the Mixture of Air and Vapor in Inches of Mercury 6: Weight of the Air in Pounds 7: Weight of the Vapor in Pounds 8: Total Weight of Mixture in Pounds 9: Weight of Vapor Mixed with One Pound of Air, in Pounds 10: Weight of Dry Air Mixed with One Pound of Vapor, in Pounds 11: Cubic Feet of Vapor from One Pound of Water at its own Pressure in Column 4 ____________________________________________________________________________ | | | | | | | | | | | | Mixtures of Air Saturated | | | | | | | with Vapor | | |___|_____|_____|______|______________________________________________|______| | | | | | |Weight of Cubic Foot | | | | | | | | | | of the Mixture of | | | | | | | | | | Air and Vapor | | | | | | | | | |_____________________| | | | | | | | | | | | | | | | | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | |___|_____|_____|______|______|_____|_______|_______|________|________|______| | | | | | | | | | | | | | 0| .935|.0864| .044|29.877|.0863|.000079|.086379| .00092|1092.4 | | | 12| .960|.0842| .074|29.849|.0840|.000130|.084130| .00155| 646.1 | | | 22| .980|.0824| .118|29.803|.0821|.000202|.082302| .00245| 406.4 | | | 32|1.000|.0807| .181|29.740|.0802|.000304|.080504| .00379| 263.81 |3289 | | 42|1.020|.0791| .267|29.654|.0784|.000440|.078840| .00561| 178.18 |2252 | | | | | | | | | | | | | | 52|1.041|.0776| .388|29.533|.0766|.000627|.077227| .00810| 122.17 |1595 | | 62|1.061|.0761| .556|29.365|.0747|.000881|.075581| .01179| 84.79 |1135 | | 72|1.082|.0747| .785|29.136|.0727|.001221|.073921| .01680| 59.54 | 819 | | 82|1.102|.0733| 1.092|28.829|.0706|.001667|.072267| .02361| 42.35 | 600 | | 92|1.122|.0720| 1.501|28.420|.0684|.002250|.070717| .03289| 30.40 | 444 | | | | | | | | | | | | | |102|1.143|.0707| 2.036|27.885|.0659|.002997|.068897| .04547| 21.98 | 334 | |112|1.163|.0694| 2.731|27.190|.0631|.003946|.067046| .06253| 15.99 | 253 | |122|1.184|.0682| 3.621|26.300|.0599|.005142|.065042| .08584| 11.65 | 194 | |132|1.204|.0671| 4.752|25.169|.0564|.006639|.063039| .11771| 8.49 | 151 | |142|1.224|.0660| 6.165|23.756|.0524|.008473|.060873| .16170| 6.18 | 118 | | | | | | | | | | | | | |152|1.245|.0649| 7.930|21.991|.0477|.010716|.058416| .22465| 4.45 | 93.3| |162|1.265|.0638|10.099|19.822|.0423|.013415|.055715| .31713| 3.15 | 74.5| |172|1.285|.0628|12.758|17.163|.0360|.016682|.052682| .46338| 2.16 | 59.2| |182|1.306|.0618|15.960|13.961|.0288|.020536|.049336| .71300| 1.402| 48.6| |192|1.326|.0609|19.828|10.093|.0205|.025142|.045642| 1.22643| .815| 39.8| | | | | | | | | | | | | |202|1.347|.0600|24.450| 5.471|.0109|.030545|.041445| 2.80230| .357| 32.7| |212|1.367|.0591|29.921| 0.000|.0000|.036820|.036820|Infinite| .000| 27.1| |___|_____|_____|______|______|_____|_______|_______|________|________|______| Column 5 = barometer pressure of 29.921, minus the proportion of this due to vapor pressure from column 4. COMBUSTION Combustion may be defined as the rapid chemical combination of oxygen with carbon, hydrogen and sulphur, accompanied by the diffusion of heat and light. That portion of the substance thus combined with the oxygen is called combustible. As used in steam engineering practice, however, the term combustible is applied to that portion of the fuel which is dry and free from ash, thus including both oxygen and nitrogen which may be constituents of the fuel, though not in the true sense of the term combustible. Combustion is perfect when the combustible unites with the greatest possible amount of oxygen, as when one atom of carbon unites with two atoms of oxygen to form carbon dioxide, CO_{2}. The combustion is imperfect when complete oxidation of the combustible does not occur, or where the combustible does not unite with the maximum amount of oxygen, as when one atom of carbon unites with one atom of oxygen to form carbon monoxide, CO, which may be further burned to carbon dioxide. Kindling Point--Before a combustible can unite with oxygen and combustion takes place, its temperature must first be raised to the ignition or kindling point, and a sufficient time must be allowed for the completion of the combustion before the temperature of the gases is lowered below that point. Table 30, by Stromeyer, gives the approximate kindling temperatures of different fuels. TABLE 30 KINDLING TEMPERATURE OF VARIOUS FUELS ____________________________________ | | | | | Degrees | | | Fahrenheit | |_________________|__________________| | | | | Lignite Dust | 300 | | Dried Peat | 435 | | Sulphur | 470 | | Anthracite Dust | 570 | | Coal | 600 | | Coke | Red Heat | | Anthracite | Red Heat, 750 | | Carbon Monoxide | Red Heat, 1211 | | Hydrogen | 1030 or 1290 | |_________________|__________________| Combustibles--The principal combustibles in coal and other fuels are carbon, hydrogen and sulphur, occurring in varying proportions and combinations. Carbon is by far the most abundant as is indicated in the chapters on fuels. Hydrogen in a free state occurs in small quantities in some fuels, but is usually found in combination with carbon, in the form of hydrocarbons. The density of hydrogen is 0.0696 (Air = 1) and its weight per cubic foot, at 32 degrees Fahrenheit and under atmospheric pressure, is 0.005621 pounds. Sulphur is found in most coals and some oils. It is usually present in combined form, either as sulphide of iron or sulphate of lime; in the latter form it has no heat value. Its presence in fuel is objectionable because of its tendency to aid in the formation of clinkers, and the gases from its combustion, when in the presence of moisture, may cause corrosion. Nitrogen is drawn into the furnace with the air. Its density is 0.9673 (Air = 1); its weight, at 32 degrees Fahrenheit and under atmospheric pressure, is 0.07829 pounds per cubic foot; each pound of air at atmospheric pressure contains 0.7685 pounds of nitrogen, and one pound of nitrogen is contained in 1.301 pounds of air. Nitrogen performs no useful office in combustion and passes through the furnace without change. It dilutes the air, absorbs heat, reduces the temperature of the products of combustion, and is the chief source of heat losses in furnaces. Calorific Value--Each combustible element of gas will combine with oxygen in certain definite proportions and will generate a definite amount of heat, measured in B. t. u. This definite amount of heat per pound liberated by perfect combustion is termed the calorific value of that substance. Table 31, gives certain data on the reactions and results of combustion for elementary combustibles and several compounds. TABLE 31 OXYGEN AND AIR REQUIRED FOR COMBUSTION AT 32 DEGREES AND 29.92 INCHES Column headings: 1: Oxidizable Substance or Combustible 2: Chemical Symbol 3: Atomic or Combining Weight 4: Chemical Reaction 5: Product of Combustion 6: Oxygen per Pound of Column 1 Pounds 7: Nitrogen per Pound of Column 1. 3.32[23] × O Pounds 8: Air per Pound of Column 1. 4.32[24] × O Pounds 9: Gaseous Product per Pound of Column 1[25] + Column 8 Pounds 10: Heat Value per Pound of Column 1 B. t. u. 11: Volumes of Column 1 Entering Combination Volume 12: Volumes of Oxygen Combining with Column 11 Volume 13: Volumes of Product Formed Volume 14: Volume per Pound of Column 1 in Gaseous Form Cubic Feet 15: Volume of Oxygen per Pound of Column 1 Cubic Feet 16: Volume of Products of Combustion per Pound of Column 1 Cubic Feet 17: Volume of Nitrogen per Pound of Column 1 3.782[26] × Column 15 Cubic Feet 18: Volume of Gas per pound of Column 1 = Column 10 ÷ Column 17 Cubic Feet BY WEIGHT ________________________________________________________________________ | | | | | | | | 1 | 2 | 3 | 4 | 5 | 6 | |________________|_______|____|________________|_________________|_______| | | | | | | | | Carbon | C | 12 | C+2O = CO_{2} | Carbon Dioxide | 2.667 | | Carbon | C | 12 | C+O = CO | Carbon Monoxide | 1.333 | | Carbon Monoxide| CO | 28 | CO+O = CO_{2} | Carbon Dioxide | .571 | | Hydrogen | H | 1 | 2H+O = H_{2}O | Water | 8 | | | | / CH_{4}+4O = | Carbon Dioxide \ | | Methane | CH_{4}| 16 | | | 4 | | | | \ CO_{2}+2H_{2}O | and Water / | | Sulphur | S | 32 | S+2O = SO_{2} | Sulphur Dioxide | 1 | |________________|_______|____|________________|_________________|_______| ________________________________________________________ | | | | | | | | 1 | 2 | 7 | 8 | 9 | 10 | |________________|_______|_______|_______|_______|_______| | | | | | | | | Carbon | C | 8.85 | 11.52 | 12.52 | 14600 | | Carbon | C | 4.43 | 5.76 | 6.76 | 4450 | | Carbon Monoxide| CO | 1.90 | 2.47 | 3.47 | 10150 | | Hydrogen | H | 26.56 | 34.56 | 35.56 | 62000 | | | | | | | | | Methane | CH_{4}| 13.28 | 17.28 | 18.28 | 23550 | | | | | | | | | Sulphur | S | 3.32 | 4.32 | 5.32 | 4050 | |________________|_______|_______|_______|_______|_______| BY VOLUME ________________________________________________________________ | | | | | | | | 1 | 2 | 11 | 12 | 13 | 14 | |_________________|________|______|____|________________|________| | | | | | | | | Carbon | C | 1C | 2 | 2CO_{2} | 14.95 | | Carbon | C | 1C | 1 | 2CO | 14.95 | | Carbon Monoxide | CO | 2CO | 1 | 2CO_{2} | 12.80 | | Hydrogen | H | 2H | 1 | 2H_{2}O | 179.32 | | Methane | CH_{4} | 1C4H | 4 | 1CO_{2} 2H_{2}O| 22.41 | | Sulphur | S | 1S | 2 | 1SO_{2} | 5.60 | |_________________|________|______|____|________________|________| _____________________________________________________________ | | | | | | | | 1 | 2 | 15 | 16 | 17 | 18 | |_________________|________|_______|________|________|________| | | | | | | | | Carbon | C | 29.89 | 29.89 | 112.98 | 142.87 | | Carbon | C | 14.95 | 29.89 | 56.49 | 86.38 | | Carbon Monoxide | CO | 6.40 | 12.80 | 24.20 | 37.00 | | Hydrogen | H | 89.66 | 179.32 | 339.09 | 518.41 | | Methane | CH_{4} | 44.83 | 67.34 | 169.55 | 236.89 | | Sulphur | S | 11.21 | 11.21 | 42.39 | 53.60 | |_________________|________|_______|________|________|________| It will be seen from this table that a pound of carbon will unite with 2-2/3 pounds of oxygen to form carbon dioxide, and will evolve 14,600 B. t. u. As an intermediate step, a pound of carbon may unite with 1-1/3 pounds of oxygen to form carbon monoxide and evolve 4450 B. t. u., but in its further conversion to CO_{2} it would unite with an additional 1-1/3 times its weight of oxygen and evolve the remaining 10,150 B. t. u. When a pound of CO burns to CO_{2}, however, only 4350 B. t. u. are evolved since the pound of CO contains but 3/7 pound carbon. Air Required for Combustion--It has already been shown that each combustible element in fuel will unite with a definite amount of oxygen. With the ultimate analysis of the fuel known, in connection with Table 31, the theoretical amount of air required for combustion may be readily calculated. Let the ultimate analysis be as follows: _Per Cent_ Carbon 74.79 Hydrogen 4.98 Oxygen 6.42 Nitrogen 1.20 Sulphur 3.24 Water 1.55 Ash 7.82 ------ 100.00 When complete combustion takes place, as already pointed out, the carbon in the fuel unites with a definite amount of oxygen to form CO_{2}. The hydrogen, either in a free or combined state, will unite with oxygen to form water vapor, H_{2}O. Not all of the hydrogen shown in a fuel analysis, however, is available for the production of heat, as a portion of it is already united with the oxygen shown by the analysis in the form of water, H_{2}O. Since the atomic weights of H and O are respectively 1 and 16, the weight of the combined hydrogen will be 1/8 of the weight of the oxygen, and the hydrogen available for combustion will be H - 1/8 O. In complete combustion of the sulphur, sulphur dioxide SO_{2} is formed, which in solution in water forms sulphuric acid. Expressed numerically, the theoretical amount of air for the above analysis is as follows: 0.7479 C × 2-2/3 = 1.9944 O needed ( 0.0642 ) ( 0.0498 - -------) H × 8 = 0.3262 O needed ( 8 ) 0.0324 S × 1 = 0.0324 O needed ------ Total 2.3530 O needed One pound of oxygen is contained in 4.32 pounds of air. The total air needed per pound of coal, therefore, will be 2.353 × 4.32 = 10.165. The weight of combustible per pound of fuel is .7479 + .0418[27] + .0324 + .012 = .83 pounds, and the air theoretically required per pound of combustible is 10.165 ÷ .83 = 12.2 pounds. The above is equivalent to computing the theoretical amount of air required per pound of fuel by the formula: ( O) Weight per pound = 11.52 C + 34.56 (H - -) + 4.32 S (10) ( 8) where C, H, O and S are proportional parts by weight of carbon, hydrogen, oxygen and sulphur by ultimate analysis. In practice it is impossible to obtain perfect combustion with the theoretical amount of air, and an excess may be required, amounting to sometimes double the theoretical supply, depending upon the nature of the fuel to be burned and the method of burning it. The reason for this is that it is impossible to bring each particle of oxygen in the air into intimate contact with the particles in the fuel that are to be oxidized, due not only to the dilution of the oxygen in the air by nitrogen, but because of such factors as the irregular thickness of the fire, the varying resistance to the passage of the air through the fire in separate parts on account of ash, clinker, etc. Where the difficulties of drawing air uniformly through a fuel bed are eliminated, as in the case of burning oil fuel or gas, the air supply may be materially less than would be required for coal. Experiment has shown that coal will usually require 50 per cent more than the theoretical net calculated amount of air, or about 18 pounds per pound of fuel either under natural or forced draft, though this amount may vary widely with the type of furnace, the nature of the coal, and the method of firing. If less than this amount of air is supplied, the carbon burns to monoxide instead of dioxide and its full heat value is not developed. An excess of air is also a source of waste, as the products of combustion will be diluted and carry off an excessive amount of heat in the chimney gases, or the air will so lower the temperature of the furnace gases as to delay the combustion to an extent that will cause carbon monoxide to pass off unburned from the furnace. A sufficient amount of carbon monoxide in the gases may cause the action known as secondary combustion, by igniting or mingling with air after leaving the furnace or in the flues or stack. Such secondary combustion which takes place either within the setting after leaving the furnace or in the flues or stack always leads to a loss of efficiency and, in some instances, leads to overheating of the flues and stack. Table 32 gives the theoretical amount of air required for various fuels calculated from formula (10) assuming the analyses of the fuels given in the table. The process of combustion of different fuels and the effect of variation in the air supply for their combustion is treated in detail in the chapters dealing with the various fuels. TABLE 32 CALCULATED THEORETICAL AMOUNT OF AIR REQUIRED PER POUND OF VARIOUS FUELS ____________________________________________________________ | |Weight of Constituents in One |Air Required| | Fuel |Pound Dry Fuel |per Pound | | |______________________________|of Fuel | | | Carbon | Hydrogen| Oxygen |Pounds | | | Per Cent| Per Cent| Per Cent | | |________________|_________|_________|__________|____________| |Coke | 94.0 | . | . | 10.8 | |Anthracite Coal | 91.5 | 3.5 | 2.6 | 11.7 | |Bituminous Coal | 87.0 | 5.0 | 4.0 | 11.6 | |Lignite | 70.0 | 5.0 | 20.0 | 8.9 | |Wood | 50.0 | 6.0 | 43.5 | 6.0 | |Oil | 85.0 | 13.0 | 1.0 | 14.3 | |________________|_________|_________|__________|____________| [Illustration: 4064 HORSE-POWER Installation of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock & Wilcox Chain Grate Stokers, at the Cosmopolitan Electric Co., Chicago, Ill.] ANALYSIS OF FLUE GASES The object of a flue gas analysis is the determination of the completeness of the combustion of the carbon in the fuel, and the amount and distribution of the heat losses due to incomplete combustion. The quantities actually determined by an analysis are the relative proportions by volume, of carbon dioxide (CO_{2}), oxygen (O), and carbon monoxide (CO), the determinations being made in this order. The variations of the percentages of these gases in an analysis is best illustrated in the consideration of the complete combustion of pure carbon, a pound of which requires 2.67 pounds of oxygen,[28] or 32 cubic feet at 60 degrees Fahrenheit. The gaseous product of such combustion will occupy, when cooled, the same volume as the oxygen, namely, 32 cubic feet. The air supplied for the combustion is made up of 20.91 per cent oxygen and 79.09 per cent nitrogen by volume. The carbon united with the oxygen in the form of carbon dioxide will have the same volume as the oxygen in the air originally supplied. The volume of the nitrogen when cooled will be the same as in the air supplied, as it undergoes no change. Hence for complete combustion of one pound of carbon, where no excess of air is supplied, an analysis of the products of combustion will show the following percentages by volume: _Actual Volume_ _for One Pound Carbon_ _Per Cent_ _Cubic Feet_ _by Volume_ Carbon Dioxide 32 = 20.91 Oxygen 0 = 0.00 Nitrogen 121 = 79.09 --- ------ Air required for one pound Carbon 153 = 100.00 For 50 per cent excess air the volume will be as follows: 153 × 1½ = 229.5 cubic feet of air per pound of carbon. _Actual Volume_ _for One Pound Carbon_ _Per Cent_ _Cubic Feet_ _by Volume_ Carbon Dioxide 32 = 13.91 } Oxygen 16 = 7.00 } = 20.91 per cent Nitrogen 181.5 = 79.09 ----- ------ 229.5 = 100.00 For 100 per cent excess air the volume will be as follows: 153 × 2 = 306 cubic feet of air per pound of carbon. _Actual Volume_ _for One Pound Carbon_ _Per Cent_ _Cubic Feet_ _by Volume_ Carbon Dioxide 32 = 10.45 } Oxygen 32 = 10.45 } = 20.91 per cent Nitrogen 242 = 79.09 --- ------ 306 = 100.00 In each case the volume of oxygen which combines with the carbon is equal to (cubic feet of air × 20.91 per cent)--32 cubic feet. It will be seen that no matter what the excess of air supplied, the actual amount of carbon dioxide per pound of carbon remains the same, while the percentage by volume decreases as the excess of air increases. The actual volume of oxygen and the percentage by volume increases with the excess of air, and the percentage of oxygen is, therefore, an indication of the amount of excess air. In each case the sum of the percentages of CO_{2} and O is the same, 20.9. Although the volume of nitrogen increases with the excess of air, its percentage by volume remains the same as it undergoes no change while combustion takes place; its percentage for any amount of air excess, therefore, will be the same after combustion as before, if cooled to the same temperature. It must be borne in mind that the above conditions hold only for the perfect combustion of a pound of pure carbon. Carbon monoxide (CO) produced by the imperfect combustion of carbon, will occupy twice the volume of the oxygen entering into its composition and will increase the volume of the flue gases over that of the air supplied for combustion in the proportion of 100 + ½ the per cent CO 1 to ----------------------- 100 When pure carbon is the fuel, the sum of the percentages by volume of carbon dioxide, oxygen and one-half of the carbon monoxide, must be in the same ratio to the nitrogen in the flue gases as is the oxygen to the nitrogen in the air supplied, that is, 20.91 to 79.09. When burning coal, however, the percentage of nitrogen is obtained by subtracting the sum of the percentages by volume of the other gases from 100. Thus if an analysis shows 12.5 per cent CO_{2}, 6.5 per cent O, and 0.6 per cent CO, the percentage of nitrogen which ordinarily is the only other constituent of the gas which need be considered, is found as follows: 100 - (12.5 + 6.5 + 0.6) = 80.4 per cent. The action of the hydrogen in the volatile constituents of the fuel is to increase the apparent percentage of the nitrogen in the flue gases. This is due to the fact that the water vapor formed by the combustion of the hydrogen will condense at a temperature at which the analysis is made, while the nitrogen which accompanied the oxygen with which the hydrogen originally combined maintains its gaseous form and passes into the sampling apparatus with the other gases. For this reason coals containing high percentages of volatile matter will produce a larger quantity of water vapor, and thus increase the apparent percentage of nitrogen. Air Required and Supplied--When the ultimate analysis of a fuel is known, the air required for complete combustion with no excess can be found as shown in the chapter on combustion, or from the following approximate formula: Pounds of air required per pound of fuel = (C O S) 34.56 (- + (H - -) + -)[29] (11) (3 8 8) where C, H and O equal the percentage by weight of carbon, hydrogen and oxygen in the fuel divided by 100. When the flue gas analysis is known, the total, amount of air supplied is: Pounds of air supplied per pound of fuel = N 3.036 (-----------) × C[30] (12) CO_{2} + CO where N, CO_{2} and CO are the percentages by volume of nitrogen, carbon dioxide and carbon monoxide in the flue gases, and C the percentage by weight of carbon which is burned from the fuel and passes up the stack as flue gas. This percentage of C which is burned must be distinguished from the percentage of C as found by an ultimate analysis of the fuel. To find the percentage of C which is burned, deduct from the total percentage of carbon as found in the ultimate analysis, the percentage of unconsumed carbon found in the ash. This latter quantity is the difference between the percentage of ash found by an analysis and that as determined by a boiler test. It is usually assumed that the entire combustible element in the ash is carbon, which assumption is practically correct. Thus if the ash in a boiler test were 16 per cent and by an analysis contained 25 per cent of carbon, the percentage of unconsumed carbon would be 16 × .25 = 4 per cent of the total coal burned. If the coal contained by ultimate analysis 80 per cent of carbon the percentage burned, and of which the products of combustion pass up the chimney would be 80 - 4 = 76 per cent, which is the correct figure to use in calculating the total amount of air supplied by formula (12). The weight of flue gases resulting from the combustion of a pound of dry coal will be the sum of the weights of the air per pound of coal and the combustible per pound of coal, the latter being equal to one minus the percentage of ash as found in the boiler test. The weight of flue gases per pound of dry fuel may, however, be computed directly from the analyses, as shown later, and the direct computation is that ordinarily used. The ratio of the air actually supplied per pound of fuel to that theoretically required to burn it is: N 3.036(---------)×C CO_{2}+CO ------------------ (13) C O 34.56(- + H - -) 3 8 in which the letters have the same significance as in formulae (11) and (12). The ratio of the air supplied per pound of combustible to the amount theoretically required is: N ------------------ (14) N - 3.782(O - ½CO) which is derived as follows: The N in the flue gas is the content of nitrogen in the whole amount of air supplied. The oxygen in the flue gas is that contained in the air supplied and which was not utilized in combustion. This oxygen was accompanied by 3.782 times its volume of nitrogen. The total amount of excess oxygen in the flue gases is (O - ½CO); hence N - 3.782(O - ½CO) represents the nitrogen content in the air actually required for combustion and N ÷ (N - 3.782[O - ½CO]) is the ratio of the air supplied to that required. This ratio minus one will be the proportion of excess air. The heat lost in the flue gases is L = 0.24 W (T - t) (15) Where L = B. t. u. lost per pound of fuel, W = weight of flue gases in pounds per pound of dry coal, T = temperature of flue gases, t = temperature of atmosphere, 0.24 = specific heat of the flue gases. The weight of flue gases, W, per pound of carbon can be computed directly from the flue gas analysis from the formula: 11 CO_{2} + 8 O + 7 (CO + N) ---------------------------- (16) 3 (CO_{2} + CO) where CO_{2}, O, CO, and N are the percentages by volume as determined by the flue gas analysis of carbon dioxide, oxygen, carbon monoxide and nitrogen. The weight of flue gas per pound of dry coal will be the weight determined by this formula multiplied by the percentage of carbon in the coal from an ultimate analysis. [Graph: Temperature of Escaping Gases--Deg. Fahr. against Heat carried away by Chimney Gases--In B.t.u. per pound of Carbon burned.[31] Fig. 20. Loss Due to Heat Carried Away by Chimney Gases for Varying Percentages of Carbon Dioxide. Based on Boiler Room Temperature = 80 Degrees Fahrenheit. Nitrogen in Flue Gas = 80.5 Per Cent. Carbon Monoxide in Flue Gas = 0. Per Cent] Fig. 20 represents graphically the loss due to heat carried away by dry chimney gases for varying percentages of CO_{2}, and different temperatures of exit gases. The heat lost, due to the fact that the carbon in the fuel is not completely burned and carbon monoxide is present in the flue gases, in B. t. u. per pound of fuel burned is: ( CO ) L' = 10,150 × (-----------) (17) (CO + CO_{2}) where, as before, CO and CO_{2} are the percentages by volume in the flue gases and C is the proportion by weight of carbon which is burned and passes up the stack. Fig. 21 represents graphically the loss due to such carbon in the fuel as is not completely burned but escapes up the stack in the form of carbon monoxide. [Graph: Loss in B.T.U. per Pound of Carbon Burned[32] against Per Cent CO_{2} in Flue Gas Fig. 21. Loss Due to Unconsumed Carbon Contained in the CO in the Flue Gases] Apparatus for Flue Gas Analysis--The Orsat apparatus, illustrated in Fig. 22, is generally used for analyzing flue gases. The burette A is graduated in cubic centimeters up to 100, and is surrounded by a water jacket to prevent any change in temperature from affecting the density of the gas being analyzed. For accurate work it is advisable to use four pipettes, B, C, D, E, the first containing a solution of caustic potash for the absorption of carbon dioxide, the second an alkaline solution of pyrogallol for the absorption of oxygen, and the remaining two an acid solution of cuprous chloride for absorbing the carbon monoxide. Each pipette contains a number of glass tubes, to which some of the solution clings, thus facilitating the absorption of the gas. In the pipettes D and E, copper wire is placed in these tubes to re-energize the solution as it becomes weakened. The rear half of each pipette is fitted with a rubber bag, one of which is shown at K, to protect the solution from the action of the air. The solution in each pipette should be drawn up to the mark on the capillary tube. The gas is drawn into the burette through the U-tube H, which is filled with spun glass, or similar material, to clean the gas. To discharge any air or gas in the apparatus, the cock G is opened to the air and the bottle F is raised until the water in the burette reaches the 100 cubic centimeters mark. The cock G is then turned so as to close the air opening and allow gas to be drawn through H, the bottle F being lowered for this purpose. The gas is drawn into the burette to a point below the zero mark, the cock G then being opened to the air and the excess gas expelled until the level of the water in F and in A are at the zero mark. This operation is necessary in order to obtain the zero reading at atmospheric pressure. The apparatus should be carefully tested for leakage as well as all connections leading thereto. Simple tests can be made; for example: If after the cock G is closed, the bottle F is placed on top of the frame for a short time and again brought to the zero mark, the level of the water in A is above the zero mark, a leak is indicated. [Illustration: Fig. 22. Orsat Apparatus] Before taking a final sample for analysis, the burette A should be filled with gas and emptied once or twice, to make sure that all the apparatus is filled with the new gas. The cock G is then closed and the cock I in the pipette B is opened and the gas driven over into B by raising the bottle F. The gas is drawn back into A by lowering F and when the solution in B has reached the mark in the capillary tube, the cock I is closed and a reading is taken on the burette, the level of the water in the bottle F being brought to the same level as the water in A. The operation is repeated until a constant reading is obtained, the number of cubic centimeters being the percentage of CO_{2} in the flue gases. The gas is then driven over into the pipette C and a similar operation is carried out. The difference between the resulting reading and the first reading gives the percentage of oxygen in the flue gases. The next operation is to drive the gas into the pipette D, the gas being given a final wash in E, and then passed into the pipette C to neutralize any hydrochloric acid fumes which may have been given off by the cuprous chloride solution, which, especially if it be old, may give off such fumes, thus increasing the volume of the gases and making the reading on the burette less than the true amount. The process must be carried out in the order named, as the pyrogallol solution will also absorb carbon dioxide, while the cuprous chloride solution will also absorb oxygen. As the pressure of the gases in the flue is less than the atmospheric pressure, they will not of themselves flow through the pipe connecting the flue to the apparatus. The gas may be drawn into the pipe in the way already described for filling the apparatus, but this is a tedious method. For rapid work a rubber bulb aspirator connected to the air outlet of the cock G will enable a new supply of gas to be drawn into the pipe, the apparatus then being filled as already described. Another form of aspirator draws the gas from the flue in a constant stream, thus insuring a fresh supply for each sample. The analysis made by the Orsat apparatus is volumetric; if the analysis by weight is required, it can be found from the volumetric analysis as follows: Multiply the percentages by volume by either the densities or the molecular weight of each gas, and divide the products by the sum of all the products; the quotients will be the percentages by weight. For most work sufficient accuracy is secured by using the even values of the molecular weights. The even values of the molecular weights of the gases appearing in an analysis by an Orsat are: Carbon Dioxide 44 Carbon Monoxide 28 Oxygen 32 Nitrogen 28 Table 33 indicates the method of converting a volumetric flue gas analysis into an analysis by weight. TABLE 33 CONVERSION OF A FLUE GAS ANALYSIS BY VOLUME TO ONE BY WEIGHT Column Headings: A: Analysis by Volume Per Cent B: Molecular Weight C: Volume times Molecular Weight D: Analysis by Weight Per Cent _____________________________________________________________________ | | | | | | | Gas | A | B | C | D | |________________________|_______|___________|________|_______________| | | | | | | | | | | | | | | | | | 536.8 | | Carbon Dioxide CO_{2} | 12.2 | 12+(2×16) | 536.8 | ------ = 17.7 | | | | | | 3022.8 | | | | | | | | | | | | 11.2 | | Carbon Monoxide CO | .4 | 12+16 | 11.2 | ------ = .4 | | | | | | 3022.8 | | | | | | | | | | | | 220.8 | | Oxygen O | 6.9 | 2×16 | 220.8 | ------ = 7.3 | | | | | | 3022.8 | | | | | | | | | | | | 2254.0 | | Nitrogen N | 80.5 | 2×14 | 2254.0 | ------ = 74.6 | | | | | | 3022.8 | |________________________|_______|___________|________|_______________| | | | | | | | Total | 100.0 | | 3022.8 | 100.0 | |________________________|_______|___________|________|_______________| Application of Formulae and Rules--Pocahontas coal is burned in the furnace, a partial ultimate analysis being: _Per Cent_ Carbon 82.1 Hydrogen 4.25 Oxygen 2.6 Sulphur 1.6 Ash 6.0 B. t. u., per pound dry 14500 The flue gas analysis shows: _Per Cent_ CO_{2} 10.7 O 9.0 CO 0.0 N (by difference) 80.3 Determine: The flue gas analysis by weight (see Table 33), the amount of air required for perfect combustion, the actual weight of air per pound of fuel, the weight of flue gas per pound of coal, the heat lost in the chimney gases if the temperature of these is 500 degrees Fahrenheit, and the ratio of the air supplied to that theoretically required. Solution: The theoretical weight of air required for perfect combustion, per pound of fuel, from formula (11) will be, (.821 .026 .016) W = 34.56 (---- + (.0425 - ----) + ----) = 10.88 pounds. ( 3 8 8 ) If the amount of carbon which is burned and passes away as flue gas is 80 per cent, which would allow for 2.1 per cent of unburned carbon in terms of the total weight of dry fuel burned, the weight of dry gas per pound of carbon burned will be from formula (16): 11 × 10.7 + 8 × 9.0 + 7(0 + 80.3) W = --------------------------------- = 23.42 pounds 3(10.7 + 0) and the weight of flue gas per pound of coal burned will be .80 × 23.42 = 18.74 pounds. The heat lost in the flue gases per pound of coal burned will be from formula (15) and the value 18.74 just determined. Loss = .24 × 18.74 × (500 - 60) = 1979 B. t. u. The percentage of heat lost in the flue gases will be 1979 ÷ 14500 = 13.6 per cent. The ratio of air supplied per pound of coal to that theoretically required will be 18.74 ÷ 10.88 = 1.72 per cent. The ratio of air supplied per pound of combustible to that required will be from formula (14): .803 ------------------------- = 1.73 .803 - 3.782(.09 - ½ × 0) The ratio based on combustible will be greater than the ratio based on fuel if there is unconsumed carbon in the ash. Unreliability of CO_{2} Readings Taken Alone--It is generally assumed that high CO_{2} readings are indicative of good combustion and hence of high efficiency. This is true only in the sense that such high readings do indicate the small amount of excess air that usually accompanies good combustion, and for this reason high CO_{2} readings alone are not considered entirely reliable. Wherever an automatic CO_{2} recorder is used, it should be checked from time to time and the analysis carried further with a view to ascertaining whether there is CO present. As the percentage of CO_{2} in these gases increases, there is a tendency toward the presence of CO, which, of course, cannot be shown by a CO_{2} recorder, and which is often difficult to detect with an Orsat apparatus. The greatest care should be taken in preparing the cuprous chloride solution in making analyses and it must be known to be fresh and capable of absorbing CO. In one instance that came to our attention, in using an Orsat apparatus where the cuprous chloride solution was believed to be fresh, no CO was indicated in the flue gases but on passing the same sample into a Hempel apparatus, a considerable percentage was found. It is not safe, therefore, to assume without question from a high CO_{2} reading that the combustion is correspondingly good, and the question of excess air alone should be distinguished from that of good combustion. The effect of a small quantity of CO, say one per cent, present in the flue gases will have a negligible influence on the quantity of excess air, but the presence of such an amount would mean a loss due to the incomplete combustion of the carbon in the fuel of possibly 4.5 per cent of the total heat in the fuel burned. When this is considered, the importance of a complete flue gas analysis is apparent. Table 34 gives the densities of various gases together with other data that will be of service in gas analysis work. TABLE 34 DENSITY OF GASES AT 32 DEGREES FAHRENHEIT AND ATMOSPHERIC PRESSURE ADAPTED FROM SMITHSONIAN TABLES +----------+----------+--------+---------+----------+---------------+ | | | | | | Relative | | | | | Weight | | Density, | | | | | of | Volume | Hydrogen = 1 | | | |Specific|One Cubic| of +-------+-------+ | Gas | Chemical |Gravity | Foot |One Pound | |Approx-| | | Symbol | Air=1 | Pounds |Cubic Feet| Exact | imate | +----------+----------+--------+---------+----------+-------+-------+ |Oxygen | O | 1.053 | .08922 | 11.208 | 15.87 | 16 | |Nitrogen | N | 0.9673 | .07829 | 12.773 | 13.92 | 14 | |Hydrogen | H | 0.0696 | .005621 | 177.90 | 1.00 | 1 | |Carbon | | | | | | | | Dioxide | CO_{2} | 1.5291 | .12269 | 8.151 | 21.83 | 22 | |Carbon | | | | | | | | Monoxide | CO | 0.9672 | .07807 | 12.809 | 13.89 | 14 | |Methane | CH_{4} | 0.5576 | .04470 | 22.371 | 7.95 | 8 | |Ethane |C_{2}H_{6}| 1.075 | .08379 | 11.935 | 14.91 | 15 | |Acetylene |C_{2}H_{2}| 0.920 | .07254 | 13.785 | 12.91 | 13 | |Sulphur | | | | | | | | Dioxide | SO_{2} | 2.2639 | .17862 | 5.598 | 31.96 | 32 | |Air | ... | 1.0000 | .08071 | 12.390 | ... | ... | +----------+----------+--------+---------+----------+-------+-------+ [Illustration: 1942 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters in the Singer Building, New York City] CLASSIFICATION OF FUELS (WITH PARTICULAR REFERENCE TO COAL) Fuels for steam boilers may be classified as solid, liquid or gaseous. Of the solid fuels, anthracite and bituminous coals are the most common, but in this class must also be included lignite, peat, wood, bagasse and the refuse from certain industrial processes such as sawdust, shavings, tan bark and the like. Straw, corn and coffee husks are utilized in isolated cases. The class of liquid fuels is represented chiefly by petroleum, though coal tar and water-gas tar are used to a limited extent. Gaseous fuels are limited to natural gas, blast furnace gas and coke oven gas, the first being a natural product and the two latter by-products from industrial processes. Though waste gases from certain processes may be considered as gaseous fuels, inasmuch as the question of combustion does not enter, the methods of utilizing them differ from that for combustible gaseous fuel, and the question will be dealt with separately. Since coal is by far the most generally used of all fuels, this chapter will be devoted entirely to the formation, composition and distribution of the various grades, from anthracite to peat. The other fuels will be discussed in succeeding chapters and their combustion dealt with in connection with their composition. Formation of Coal--All coals are of vegetable origin and are the remains of prehistoric forests. Destructive distillation due to great pressures and temperatures, has resolved the organic matter into its invariable ultimate constituents, carbon, hydrogen, oxygen and other substances, in varying proportions. The factors of time, depth of beds, disturbance of beds and the intrusion of mineral matter resulting from such disturbances have produced the variation in the degree of evolution from vegetable fiber to hard coal. This variation is shown chiefly in the content of carbon, and Table 35 shows the steps of such variation. TABLE 35 APPROXIMATE CHEMICAL CHANGES FROM WOOD FIBER TO ANTHRACITE COAL +----------------------+-------+--------+-------+ |Substance |Carbon |Hydrogen|Oxygen | +----------------------+-------+--------+-------+ |Wood Fiber | 52.65 | 5.25 | 42.10 | |Peat | 59.57 | 5.96 | 34.47 | |Lignite | 66.04 | 5.27 | 28.69 | |Earthy Brown Coal | 73.18 | 5.68 | 21.14 | |Bituminous Coal | 75.06 | 5.84 | 19.10 | |Semi-bituminous Coal | 89.29 | 5.05 | 5.66 | |Anthracite Coal | 91.58 | 3.96 | 4.46 | +----------------------+-------+--------+-------+ Composition of Coal--The uncombined carbon in coal is known as fixed carbon. Some of the carbon constituent is combined with hydrogen and this, together with other gaseous substances driven off by the application of heat, form that portion of the coal known as volatile matter. The fixed carbon and the volatile matter constitute the combustible. The oxygen and nitrogen contained in the volatile matter are not combustible, but custom has applied this term to that portion of the coal which is dry and free from ash, thus including the oxygen and nitrogen. The other important substances entering into the composition of coal are moisture and the refractory earths which form the ash. The ash varies in different coals from 3 to 30 per cent and the moisture from 0.75 to 45 per cent of the total weight of the coal, depending upon the grade and the locality in which it is mined. A large percentage of ash is undesirable as it not only reduces the calorific value of the fuel, but chokes up the air passages in the furnace and through the fuel bed, thus preventing the rapid combustion necessary to high efficiency. If the coal contains an excessive quantity of sulphur, trouble will result from its harmful action on the metal of the boiler where moisture is present, and because it unites with the ash to form a fusible slag or clinker which will choke up the grate bars and form a solid mass in which large quantities of unconsumed carbon may be imbedded. Moisture in coal may be more detrimental than ash in reducing the temperature of a furnace, as it is non-combustible, absorbs heat both in being evaporated and superheated to the temperature of the furnace gases. In some instances, however, a certain amount of moisture in a bituminous coal produces a mechanical action that assists in the combustion and makes it possible to develop higher capacities than with dry coal. Classification of Coal--Custom has classified coals in accordance with the varying content of carbon and volatile matter in the combustible. Table 36 gives the approximate percentages of these constituents for the general classes of coals with the corresponding heat values per pound of combustible. TABLE 36 APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF GENERAL GRADES OF COAL ON BASIS OF COMBUSTIBLE +-------------------+----------------------------+--------------+ | Kind of Coal | Per Cent of Combustible | B. t. u. | | +------------+---------------+ Per Pound of | | |Fixed Carbon|Volatile Matter| Combustible | +-------------------+------------+---------------+--------------+ |Anthracite |97.0 to 92.5| 3.0 to 7.5 |14600 to 14800| |Semi-anthracite |92.5 to 87.5| 7.5 to 12.5 |14700 to 15500| |Semi-bituminous |87.5 to 75.0| 12.5 to 25.0 |15500 to 16000| |Bituminous--Eastern|75.0 to 60.0| 25.0 to 40.0 |14800 to 15300| |Bituminous--Western|65.0 to 50.0| 35.0 to 50.0 |13500 to 14800| |Lignite | Under 50 | Over 50 |11000 to 13500| +-------------------+------------+---------------+--------------+ Anthracite--The name anthracite, or hard coal, is applied to those dry coals containing from 3 to 7 per cent volatile matter and which do not swell when burned. True anthracite is hard, compact, lustrous and sometimes iridescent, and is characterized by few joints and clefts. Its specific gravity varies from 1.4 to 1.8. In burning, it kindles slowly and with difficulty, is hard to keep alight, and burns with a short, almost colorless flame, without smoke. Semi-anthracite coal has less density, hardness and luster than true anthracite, and can be distinguished from it by the fact that when newly fractured it will soot the hands. Its specific gravity is ordinarily about 1.4. It kindles quite readily and burns more freely than the true anthracites. Semi-bituminous coal is softer than anthracite, contains more volatile hydrocarbons, kindles more easily and burns more rapidly. It is ordinarily free burning, has a high calorific value and is of the highest order for steam generating purposes. Bituminous coals are still softer than those described and contain still more volatile hydrocarbons. The difference between the semi-bituminous and the bituminous coals is an important one, economically. The former have an average heating value per pound of combustible about 6 per cent higher than the latter, and they burn with much less smoke in ordinary furnaces. The distinctive characteristic of the bituminous coals is the emission of yellow flame and smoke when burning. In color they range from pitch black to dark brown, having a resinous luster in the most compact specimens, and a silky luster in such specimens as show traces of vegetable fiber. The specific gravity is ordinarily about 1.3. Bituminous coals are either of the caking or non-caking class. The former, when heated, fuse and swell in size; the latter burn freely, do not fuse, and are commonly known as free burning coals. Caking coals are rich in volatile hydrocarbons and are valuable in gas manufacture. Bituminous coals absorb moisture from the atmosphere. The surface moisture can be removed by ordinary drying, but a portion of the water can be removed only by heating the coal to a temperature of about 250 degrees Fahrenheit. Cannel coal is a variety of bituminous coal, rich in hydrogen and hydrocarbons, and is exceedingly valuable as a gas coal. It has a dull resinous luster and burns with a bright flame without fusing. Cannel coal is seldom used for steam coal, though it is sometimes mixed with semi-bituminous coal where an increased economy at high rates of combustion is desired. The composition of cannel coal is approximately as follows: fixed carbon, 26 to 55 per cent; volatile matter, 42 to 64 per cent; earthy matter, 2 to 14 per cent. Its specific gravity is approximately 1.24. Lignite is organic matter in the earlier stages of its conversion into coal, and includes all varieties which are intermediate between peat and coal of the older formation. Its specific gravity is low, being 1.2 to 1.23, and when freshly mined it may contain as high as 50 per cent of moisture. Its appearance varies from a light brown, showing a distinctly woody structure, in the poorer varieties, to a black, with a pitchy luster resembling hard coal, in the best varieties. It is non-caking and burns with a bright but slightly smoky flame with moderate heat. It is easily broken, will not stand much handling in transportation, and if exposed to the weather will rapidly disintegrate, which will increase the difficulty of burning it. Its composition varies over wide limits. The ash may run as low as one per cent and as high as 50 per cent. Its high content of moisture and the large quantity of air necessary for its combustion cause large stack losses. It is distinctly a low-grade fuel and is used almost entirely in the districts where mined, due to its cheapness. Peat is organic matter in the first stages of its conversion into coal and is found in bogs and similar places. Its moisture content when cut is extremely high, averaging 75 or 80 per cent. It is unsuitable for fuel until dried and even then will contain as much as 30 per cent moisture. Its ash content when dry varies from 3 to 12 per cent. In this country, though large deposits of peat have been found, it has not as yet been found practicable to utilize it for steam generating purposes in competition with coal. In some European countries, however, the peat industry is common. Distribution--The anthracite coals are, with some unimportant exceptions, confined to five small fields in Eastern Pennsylvania, as shown in the following list. These fields are given in the order of their hardness. Lehigh or Eastern Middle Field Green Mountain District Black Creek District Hazelton District Beaver Meadow District Panther Creek District[33] Mahanoy or Western Field[34] East Mahanoy District West Mahanoy District Wyoming or Northern Field Carbondale District Scranton District Pittston District Wilkesbarre District Plymouth District Schuylkill or Southern Field East Schuylkill District West Schuylkill District Louberry District Lykens Valley or Southwestern Field Lykens Valley District Shamokin District[35] Anthracite is also found in Pulaski and Wythe Counties, Virginia; along the border of Little Walker Mountain, and in Gunnison County, Colorado. The areas in Virginia are limited, however, while in Colorado the quality varies greatly in neighboring beds and even in the same bed. An anthracite bed in New Mexico was described in 1870 by Dr. R. W. Raymond, formerly United States Mining Commissioner. Semi-anthracite coals are found in a few small areas in the western part of the anthracite field. The largest of these beds is the Bernice in Sullivan County, Pennsylvania. Mr. William Kent, in his "Steam Boiler Economy", describes this as follows: "The Bernice semi-anthracite coal basin lies between Beech Creek on the north and Loyalsock Creek on the south. It is six miles long, east and west, and hardly a third of a mile across. An 8-foot vein of coal lies in a bed of 12 feet of coal and slate. The coal of this bed is the dividing line between anthracite and semi-anthracite, and is similar to the coal of the Lykens Valley District. Mine analyses give a range as follows: moisture, 0.65 to 1.97; volatile matter, 3.56 to 9.40; fixed carbon, 82.52 to 89.39; ash, 3.27 to 9.34; sulphur, 0.24 to 1.04." Semi-bituminous coals are found on the eastern edge of the great Appalachian Field. Starting with Tioga and Bradford Counties of northern Pennsylvania, the bed runs southwest through Lycoming, Clearfield, Centre, Huntingdon, Cambria, Somerset and Fulton Counties, Pennsylvania; Allegheny County, Maryland; Buchannan, Dickinson, Lee, Russell, Scott, Tazewell and Wise Counties, Virginia; Mercer, McDowell, Fayette, Raleigh and Mineral Counties, West Virginia; and ending in northeastern Tennessee, where a small amount of semi-bituminous is mined. The largest of the bituminous fields is the Appalachian. Beginning near the northern boundary of Pennsylvania, in the western portion of the State, it extends southwestward through West Virginia, touching Maryland and Virginia on their western borders, passing through southeastern Ohio, eastern Kentucky and central Tennessee, and ending in western Alabama, 900 miles from its northern extremity. The next bituminous coal producing region to the west is the Northern Field, in north central Michigan. Still further to the west, and second in importance to the Appalachian Field, is the Eastern Interior Field. This covers, with the exception of the upper northern portion, nearly the entire State of Illinois, southwest Indiana and the western portion of Kentucky. The Western Field extends through central and southern Iowa, western Missouri, southwestern Kansas, eastern Oklahoma and the west central portion of Arkansas. The Southwestern Field is confined entirely to the north central portion of Texas, in which State there are also two small isolated fields along the Rio Grande River. The remaining bituminous fields are scattered through what may be termed the Rocky Mountain Region, extending from Montana to New Orleans. A partial list of these fields and their location follows: Judith Basin Central Montana Bull Mountain Field Central Montana Yellowstone Region Southwestern Montana Big Horn Basin Region Southern Montana Big Horn Basin Region Northern Wyoming Black Hills Region Northeastern Wyoming Hanna Field Southern Wyoming Green River Region Southwestern Wyoming Yampa Field Northwestern Colorado North Park Field Northern Colorado Denver Region North Central Colorado Uinta Region Western Colorado Uinta Region Eastern Utah Southwestern Region Southwestern Utah Raton Mountain Region Southern Colorado Raton Mountain Region Northern New Mexico San Juan River Region Northwestern New Mexico Capitan Field Southern New Mexico Along the Pacific Coast a few small fields are scattered in western California, southwestern Oregon, western and northwestern Washington. Most of the coals in the above fields are on the border line between bituminous and lignite. They are really a low grade of bituminous coal and are known as sub-bituminous or black lignites. Lignites--These resemble the brown coals of Europe and are found in the western states, Wyoming, New Mexico, Arizona, Utah, Montana, North Dakota, Nevada, California, Oregon and Washington. Many of the fields given as those containing bituminous coals in the western states also contain true lignite. Lignite is also found in the eastern part of Texas and in Oklahoma. Alaska Coals--Coal has been found in Alaska and undoubtedly is of great value, though the extent and character of the fields have probably been exaggerated. Great quantities of lignite are known to exist, and in quality the coal ranges in character from lignite to anthracite. There are at present, however, only two fields of high-grade coals known, these being the Bering River Field, near Controllers Bay, and the Matanuska Field, at the head of Cooks Inlet. Both of these fields are known to contain both anthracite and high-grade bituminous coals, though as yet they cannot be said to have been opened up. Weathering of Coal--The storage of coal has become within the last few years to a certain extent a necessity due to market conditions, danger of labor difficulties at the mines and in the railroads, and the crowding of transportation facilities. The first cause is probably the most important, and this is particularly true of anthracite coals where a sliding scale of prices is used according to the season of the year. While market conditions serve as one of the principal reasons for coal storage, most power plants and manufacturing plants feel compelled to protect their coal supply from the danger of strikes, car shortages and the like, and it is customary for large power plants, railroads and coal companies themselves, to store bituminous coal. Naval coaling stations are also an example of what is done along these lines. Anthracite is the nearest approach to the ideal coal for storing. It is not subject to spontaneous ignition, and for this reason is unlimited in the amount that may be stored in one pile. With bituminous coals, however, the case is different. Most bituminous coals will ignite if placed in large enough piles and all suffer more or less from disintegration. Coal producers only store such coals as are least liable to ignite, and which will stand rehandling for shipment. The changes which take place in stored coal are of two kinds: 1st, the oxidization of the inorganic matter such as pyrites; and 2nd, the direct oxidization of the organic matter of the actual coal. The first change will result in an increased volume of the coal, and sometimes in an increased weight, and a marked disintegration. The changes due to direct oxidization of the coal substances usually cannot be detected by the eye, but as they involve the oxidization of the carbon and available hydrogen and the absorption of the oxygen by unsaturated hydrocarbons, they are the chief cause of the weathering losses in heat value. Numerous experiments have led to the conclusion that this is also the cause for spontaneous combustion. Experiments to show loss in calorific heat values due to weathering indicate that such loss may be as high as 10 per cent when the coal is stored in the air, and 8.75 per cent when stored under water. It would appear that the higher the volatile content of the coal, the greater will be the loss in calorific value and the more subject to spontaneous ignition. Some experiments made by Messrs. S. W. Parr and W. F. Wheeler, published in 1909 by the Experiment Station of the University of Illinois, indicate that coals of the nature found in Illinois and neighboring states are not affected seriously during storage from the standpoint of weight and heating value, the latter loss averaging about 3½ per cent for the first year of storage. They found that the losses due to disintegration and to spontaneous ignition were of greater importance. Their conclusions agree with those deduced from the other experiments, viz., that the storing of a larger size coal than that which is to be used, will overcome to a certain extent the objection to disintegration, and that the larger sizes, besides being advantageous in respect to disintegration, are less liable to spontaneous ignition. Storage under water will, of course, entirely prevent any fire loss and, to a great extent, will stop disintegration and reduce the calorific losses to a minimum. To minimize the danger of spontaneous ignition in storing coal, the piles should be thoroughly ventilated. Pulverized Fuels--Considerable experimental work has been done with pulverized coal, utilizing either coal dust or pulverizing such coal as is too small to be burned in other ways. If satisfactorily fed to the furnace, it would appear to have several advantages. The dust burned in suspension would be more completely consumed than is the case with the solid coals, the production of smoke would be minimized, and the process would admit of an adjustment of the air supply to a point very close to the amount theoretically required. This is due to the fact that in burning there is an intimate mixture of the air and fuel. The principal objections have been in the inability to introduce the pulverized fuel into the furnace uniformly, the difficulty of reducing the fuel to the same degree of fineness, liability of explosion in the furnace due to improper mixture with the air, and the decreased capacity and efficiency resulting from the difficulty of keeping tube surfaces clean. Pressed Fuels--In this class are those composed of the dust of some suitable combustible, pressed and cemented together by a substance possessing binding and in most cases inflammable properties. Such fuels, known as briquettes, are extensively used in foreign countries and consist of carbon or soft coal, too small to be burned in the ordinary way, mixed usually with pitch or coal tar. Much experimenting has been done in this country in briquetting fuels, the government having taken an active interest in the question, but as yet this class of fuel has not come into common use as the cost and difficulty of manufacture and handling have made it impossible to place it in the market at a price to successfully compete with coal. Coke is a porous product consisting almost entirely of carbon remaining after certain manufacturing processes have distilled off the hydrocarbon gases of the fuel used. It is produced, first, from gas coal distilled in gas retorts; second, from gas or ordinary bituminous coals burned in special furnaces called coke ovens; and third, from petroleum by carrying the distillation of the residuum to a red heat. Coke is a smokeless fuel. It readily absorbs moisture from the atmosphere and if not kept under cover its moisture content may be as much as 20 per cent of its own weight. Gas-house coke is generally softer and more porous than oven coke, ignites more readily, and requires less draft for its combustion. [Illustration: 16,000 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters at the Brunot's Island Plant of the Duquesne Light Co., Pittsburgh, Pa.] THE DETERMINATION OF HEATING VALUES OF FUELS The heating value of a fuel may be determined either by a calculation from a chemical analysis or by burning a sample in a calorimeter. In the former method the calculation should be based on an ultimate analysis, which reduces the fuel to its elementary constituents of carbon, hydrogen, oxygen, nitrogen, sulphur, ash and moisture, to secure a reasonable degree of accuracy. A proximate analysis, which determines only the percentage of moisture, fixed carbon, volatile matter and ash, without determining the ultimate composition of the volatile matter, cannot be used for computing the heat of combustion with the same degree of accuracy as an ultimate analysis, but estimates may be based on the ultimate analysis that are fairly correct. An ultimate analysis requires the services of a competent chemist, and the methods to be employed in such a determination will be found in any standard book on engineering chemistry. An ultimate analysis, while resolving the fuel into its elementary constituents, does not reveal how these may have been combined in the fuel. The manner of their combination undoubtedly has a direct effect upon their calorific value, as fuels having almost identical ultimate analyses show a difference in heating value when tested in a calorimeter. Such a difference, however, is slight, and very close approximations may be computed from the ultimate analysis. Ultimate analyses are given on both a moist and a dry fuel basis. Inasmuch as the latter is the basis generally accepted for the comparison of data, it would appear that it is the best basis on which to report such an analysis. When an analysis is given on a moist fuel basis it may be readily converted to a dry basis by dividing the percentages of the various constituents by one minus the percentage of moisture, reporting the moisture content separately. _Moist Fuel_ _Dry Fuel_ C 83.95 84.45 H 4.23 4.25 O 3.02 3.04 N 1.27 1.28 S .91 .91 Ash 6.03 6.07 ------ 100.00 Moisture .59 .59 ------ 100.00 Calculations from an Ultimate Analysis--The first formula for the calculation of heating values from the composition of a fuel as determined from an ultimate analysis is due to Dulong, and this formula, slightly modified, is the most commonly used to-day. Other formulae have been proposed, some of which are more accurate for certain specific classes of fuel, but all have their basis in Dulong's formula, the accepted modified form of which is: Heat units in B. t. u. per pound of dry fuel = O 14,600 C + 62,000(H - -) + 4000 S (18) 8 where C, H, O and S are the proportionate parts by weight of carbon, hydrogen, oxygen and sulphur. Assume a coal of the composition given. Substituting in this formula (18), Heating value per pound of dry coal ( .0304) = 14,600 × .8445 + 62,000 (.0425 - -----) + 4000 × .0091 = 14,765 B. t. u. ( 8 ) This coal, by a calorimetric test, showed 14,843 B. t. u., and from a comparison the degree of accuracy of the formula will be noted. The investigation of Lord and Haas in this country, Mabler in France, and Bunte in Germany, all show that Dulong's formula gives results nearly identical with those obtained from calorimetric tests and may be safely applied to all solid fuels except cannel coal, lignite, turf and wood, provided the ultimate analysis is correct. This practically limits its use to coal. The limiting features are the presence of hydrogen and carbon united in the form of hydrocarbons. Such hydrocarbons are present in coals in small quantities, but they have positive and negative heats of combination, and in coals these appear to offset each other, certainly sufficiently to apply the formula to such fuels. High and Low Heat Value of Fuels--In any fuel containing hydrogen the calorific value as found by the calorimeter is higher than that obtainable under most working conditions in boiler practice by an amount equal to the latent heat of the volatilization of water. This heat would reappear when the vapor was condensed, though in ordinary practice the vapor passes away uncondensed. This fact gives rise to a distinction in heat values into the so-called "higher" and "lower" calorific values. The higher value, _i. e._, the one determined by the calorimeter, is the only scientific unit, is the value which should be used in boiler testing work, and is the one recommended by the American Society of Mechanical Engineers. There is no absolute measure of the lower heat of combustion, and in view of the wide difference in opinion among physicists as to the deductions to be made from the higher or absolute unit in this determination, the lower value must be considered an artificial unit. The lower value entails the use of an ultimate analysis and involves assumptions that would make the employment of such a unit impracticable for commercial work. The use of the low value may also lead to error and is in no way to be recommended for boiler practice. An example of its illogical use may be shown by the consideration of a boiler operated in connection with a special economizer where the vapor produced by hydrogen is partially condensed by the economizer. If the low value were used in computing the boiler efficiency, it is obvious that the total efficiency of the combined boiler and economizer must be in error through crediting the combination with the heat imparted in condensing the vapor and not charging such heat to the heat value of the coal. Heating Value of Gaseous Fuels--The method of computing calorific values from an ultimate analysis is particularly adapted to solid fuels, with the exceptions already noted. The heating value of gaseous fuels may be calculated by Dulong's formula provided another term is added to provide for any carbon monoxide present. Such a method, however, involves the separating of the constituent gases into their elementary gases, which is oftentimes difficult and liable to simple arithmetical error. As the combustible portion of gaseous fuels is ordinarily composed of hydrogen, carbon monoxide and certain hydrocarbons, a determination of the calorific value is much more readily obtained by a separation into their constituent gases and a computation of the calorific value from a table of such values of the constituents. Table 37 gives the calorific value of the more common combustible gases, together with the theoretical amount of air required for their combustion. TABLE 37 WEIGHT AND CALORIFIC VALUE OF VARIOUS GASES AT 32 DEGREES FAHRENHEIT AND ATMOSPHERIC PRESSURE WITH THEORETICAL AMOUNT OF AIR REQUIRED FOR COMBUSTION +---------------+----------+------+-----+------+----------+-----------+ | Gas | Symbol |Cubic |B.t.u|B.t.u.|Cubic Feet|Cubic Feet | | | | Feet | per | per | of Air | of Air | | | |of Gas|Pound|Cubic | Required | Required | | | | per | | Foot |per Pound | Per Cubic | | | |Pound | | | of Gas |Foot of Gas| +---------------+----------+------+-----+------+----------+-----------+ |Hydrogen | H |177.90|62000| 349 | 428.25 | 2.41 | |Carbon Monoxide| CO | 12.81| 4450| 347 | 30.60 | 2.39 | |Methane |CH_{4} | 22.37|23550| 1053 | 214.00 | 9.57 | |Acetylene |C_{2}H_{2}| 13.79|21465| 1556 | 164.87 | 11.93 | |Olefiant Gas |C_{2}H_{4}| 12.80|21440| 1675 | 183.60 | 14.33 | |Ethane |C_{2}H_{6}| 11.94|22230| 1862 | 199.88 | 16.74 | +---------------+----------+------+-----+------+----------+-----------+ In applying this table, as gas analyses may be reported either by weight or volume, there is given in Table 33[36] a method of changing from volumetric analysis to analysis by weight. Examples: 1st. Assume a blast furnace gas, the analysis of which in percentages by weight is, oxygen = 2.7, carbon monoxide = 19.5, carbon dioxide = 18.7, nitrogen = 59.1. Here the only combustible gas is the carbon monoxide, and the heat value will be, 0.195 × 4450 = 867.75 B. t. u. per pound. The _net_ volume of air required to burn one pound of this gas will be, 0.195 × 30.6 = 5.967 cubic feet. 2nd. Assume a natural gas, the analysis of which in percentages by volume is oxygen = 0.40, carbon monoxide = 0.95, carbon dioxide = 0.34, olefiant gas (C_{2}H_{4}) = 0.66, ethane (C_{2}H_{6}) = 3.55, marsh gas (CH_{4}) = 72.15 and hydrogen = 21.95. All but the oxygen and the carbon dioxide are combustibles, and the heat per cubic foot will be, From CO = 0.0095 × 347 = 3.30 C_{2}H_{4} = 0.0066 × 1675 = 11.05 C_{2}H_{6} = 0.0355 × 1862 = 66.10 CH_{4} = 0.7215 × 1050 = 757.58 H = 0.2195 × 349 = 76.61 ------ B. t. u. per cubic foot 914.64 The _net_ air required for combustion of one cubic foot of the gas will be, CO = 0.0095 × 2.39 = 0.02 C_{2}H_{4} = 0.0066 × 14.33 = 0.09 C_{2}H_{6} = 0.0355 × 16.74 = 0.59 CH_{4} = 0.7215 × 9.57 = 6.90 H = 0.2195 × 2.41 = 0.53 ---- Total net air per cubic foot 8.13 Proximate Analysis--The proximate analysis of a fuel gives its proportions by weight of fixed carbon, volatile combustible matter, moisture and ash. A method of making such an analysis which has been found to give eminently satisfactory results is described below. From the coal sample obtained on the boiler trial, an average sample of approximately 40 grams is broken up and weighed. A good means of reducing such a sample is passing it through an ordinary coffee mill. This sample should be placed in a double-walled air bath, which should be kept at an approximately constant temperature of 105 degrees centigrade, the sample being weighed at intervals until a minimum is reached. The percentage of moisture can be calculated from the loss in such a drying. For the determination of the remainder of the analysis, and the heating value of the fuel, a portion of this dried sample should be thoroughly pulverized, and if it is to be kept, should be placed in an air-tight receptacle. One gram of the pulverized sample should be weighed into a porcelain crucible equipped with a well fitting lid. This crucible should be supported on a platinum triangle and heated for seven minutes over the full flame of a Bunsen burner. At the end of such time the sample should be placed in a desiccator containing calcium chloride, and when cooled should be weighed. From the loss the percentage of volatile combustible matter may be readily calculated. The same sample from which the volatile matter has been driven should be used in the determination of the percentage of ash. This percentage is obtained by burning the fixed carbon over a Bunsen burner or in a muffle furnace. The burning should be kept up until a constant weight is secured, and it may be assisted by stirring with a platinum rod. The weight of the residue determines the percentage of ash, and the percentage of fixed carbon is easily calculated from the loss during the determination of ash after the volatile matter has been driven off. Proximate analyses may be made and reported on a moist or dry basis. The dry basis is that ordinarily accepted, and this is the basis adopted throughout this book. The method of converting from a moist to a dry basis is the same as described in the case of an ultimate analysis. A proximate analysis is easily made, gives information as to the general characteristics of a fuel and of its _relative_ heating value. Table 38 gives the proximate analysis and calorific value of a number of representative coals found in the United States. TABLE 38 APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS ____________________________________________________________________________ | | | | | | | | | | | | No. | State | County | Field, Bed | Mine | Size | | | | or Vein | | | | | | | | | | | | | | | ____|_______|________________|________________|_______________|_____________| | | | | | | ANTHRACITES | | ____|_______|_________________________________________________|_____________| | | | | | | 1 | Pa. | Carbon | Lehigh | Beaver Meadow | | 2 | Pa. | Dauphin | Schuylkill | | Buckwheat | 3 | Pa. | Lackawanna | Wyoming | Belleview | No. 2 Buck. | 4 | Pa. | Lackawanna | Wyoming | Johnson | Culm. | 5 | Pa. | Luzerne | Wyoming | Pittston | No. 2 Buck. | 6 | Pa. | Luzerne | Wyoming | Mammoth | Large | 7 | Pa. | Luzerne | Wyoming | Exeter | Rice | 8 | Pa. | Northumberland | Schuylkill | Treverton | | 9 | Pa. | Schuylkill | Schuylkill | Buck Mountain | | 10 | Pa. | Schuylkill | | York Farm | Buckwheat | 11 | Pa. | | | Victoria | Buckwheat | 12 | Pa. | Carbon | Lehigh | Lehigh & | Buck. & Pea | | | | | Wilkes C. Co. | | 13 | Pa. | Carbon | Lehigh | | Buckwheat | 14 | Pa. | Lackawanna | |Del. & Hud. Co.| No. 1 Buck. | ____|_______|________________|________________|_______________|_____________| | | | | | | SEMI-ANTHRACITES | | ____|_______|_________________________________________________|_____________| | | | | | | 15 | Pa. | Lycoming | Loyalsock | | | 16 | Pa. | Sullivan | | Lopez | | 17 | Pa. | Sullivan | Bernice | | | ____|_______|________________|________________|_______________|_____________| | | | | | | SEMI-BITUMINOUS | | ____|_______|_________________________________________________|_____________| | | | | | | 18 | Md. | Alleghany | Big Vein, | | | | | | George's Crk. | | | 19 | Md. | Alleghany | George's Creek | | | 20 | Md. | Alleghany | George's Creek | | | 21 | Md. | Alleghany | George's Creek | Ocean No. 7 | Mine run | 22 | Md. | Alleghany | Cumberland | | | 23 | Md. | Garrett | | Washington | Mine run | | | | | No. 3 | | 24 | Pa. | Bradford | | Long Valley | | 25 | Pa. | Tioga | | Antrim | | 26 | Pa. | Cambria | "B" or Miller | Soriman Shaft | | | | | | C. Co. | | 27 | Pa. | Cambria | "B" or Miller | Henrietta | | 28 | Pa. | Cambria | "B" or Miller | Penker | | 29 | Pa. | Cambria | "B" or Miller | Lancashire | | 30 | Pa. | Cambria | Lower | Penn. C. & C. | Mine run | | | | Kittanning | Co. No. 3 | | 31 | Pa. | Cambria | Upper | Valley | Mine run | | | | Kittanning | | | 32 | Pa. | Clearfield | Lower | Eureka | Mine run | | | | Kittanning | | | 33 | Pa. | Clearfield | | Ghem | Mine run | 34 | Pa. | Clearfield | | Osceola | | 35 | Pa. | Clearfield | Reynoldsville | | | 36 | Pa. | Clearfield | Atlantic- | | Mine run | | | | Clearfield | | | 37 | Pa. | Huntington | Barnet & Fulton| Carbon | Mine run | 38 | Pa. | Huntington | | Rock Hill | Mine run | 39 | Pa. | Somerset | Lower | Kimmelton | Mine run | | | | Kittanning | | | 40 | Pa. | Somerset | "C" Prime Vein | Jenner | Mine run | ____|_______|________________|________________|_______________|_____________| _____________________________________________________________________ | | | | | Proximate Analysis (Dry Coal) |B. t. u.| | No. |________________________________________| Per | | | | | | | Pound | Authority | | Moisture | Volatile | Fixed | Ash | Dry | | | | Matter | Carbon | | Coal | | ____|__________|__________|________|_________|________|______________| | | | | | | | | | | | | | | ____|__________|__________|________|_________|________|______________| | | | | | | | 1 | 1.50 | 2.41 | 90.30 | 7.29 | | Gale | 2 | 2.15 | 12.88 | 78.23 | 8.89 | 13137 | Whitham | 3 | 8.29 | 7.81 | 77.19 | 15.00 | 12341 | Sadtler | 4 | 13.90 | 11.16 | 65.96 | 22.88 | 10591 | B. & W. Co. | 5 | 3.66 | 4.40 | 78.96 | 16.64 | 12865 | B. & W. Co. | 6 | 4.00 | 3.44 | 90.59 | 5.97 | 13720 | Carpenter | 7 | 0.25 | 8.18 | 79.61 | 12.21 | 12400 | B. & W. Co. | 8 | 0.84 | 6.73 | 86.39 | 6.88 | | Isherwood | 9 | | 3.17 | 92.41 | 4.42 | 14220 | Carpenter | 10 | 0.81 | 5.51 | 75.90 | 18.59 | 11430 | | 11 | 4.30 | 0.55 | 86.73 | 12.72 | 12642 | B. & W. Co. | 12 | 1.57 | 6.27 | 66.53 | 27.20 | 12848 | B. & W. Co. | | | | | | | | 13 | | 5.00 | 81.00 | 14.00 | 11800 | Carpenter | 14 | 6.20 | | | 11.60 | 12100 | Denton | ____|__________|__________|________|_________|________|______________| | | | | | | | | | | | | | | ____|__________|__________|________|_________|________|______________| | | | | | | | 15 | 1.30 | 8.72 | 84.44 | 6.84 | | | 16 | 5.48 | 7.53 | 81.00 | 11.47 | 13547 | B. & W. Co. | 17 | 1.29 | 8.21 | 84.43 | 7.36 | | | ____|__________|__________|________|_________|________|______________| | | | | | | | | | | | | | | ____|__________|__________|________|_________|________|______________| | | | | | | | 18 | 3.50 | 21.33 | 72.47 | 6.20 | 14682 | B. & W. Co. | | | | | | | | 19 | 3.63 | 16.27 | 76.93 | 6.80 | 14695 | B. & W. Co. | 20 | 2.28 | 19.43 | 77.44 | 6.13 | 14793 | B. & W. Co. | 21 | 1.13 | | | | 14451 | B. & W. Co. | 22 | 1.50 | 17.26 | 76.65 | 6.09 | 14700 | | 23 | 2.33 | 14.38 | 74.93 | 10.49 | 14033 | U. S. Geo. S.| | | | | | | [37] | 24 | 1.55 | 20.33 | 68.38 | 11.29 | 12965 | | 25 | 2.19 | 18.43 | 71.87 | 9.70 | 13500 | | 26 | 3.40 | 20.70 | 71.84 | 7.46 | 14484 | N. Y. Ed. Co.| | | | | | | | 27 | 1.23 | 18.37 | 75.28 | 6.45 | 14770 | So. Eng. Co. | 28 | 3.64 | 21.34 | 70.48 | 8.18 | 14401 | B. & W. Co. | 29 | 4.38 | 21.20 | 70.27 | 8.53 | 14453 | B. & W. Co. | 30 | 3.51 | 17.43 | 75.69 | 6.88 | 14279 | U. S. Geo. S.| | | | | | | | 31 | 3.40 | 14.89 | 75.03 | 10.08 | 14152 | B. & W. Co. | | | | | | | | 32 | 5.90 | 16.71 | 77.22 | 6.07 | 14843 | U. S. Geo. S.| | | | | | | | 33 | 3.43 | 17.53 | 69.67 | 12.80 | 13744 | B. & W. Co. | 34 | 1.24 | 25.43 | 68.56 | 6.01 | 13589 | B. & W. Co. | 35 | 2.91 | 21.55 | 69.03 | 9.42 | 14685 | B. & W. Co. | 36 | 1.55 | 23.36 | 71.15 | 5.94 | 13963 | Whitham | | | | | | | | 37 | 4.50 | 18.34 | 73.06 | 8.60 | 13770 | B. & W. Co. | 38 | 5.91 | 17.58 | 73.44 | 8.99 | 14105 | B. & W. Co. | 39 | 3.09 | 17.84 | 70.47 | 11.69 | 13424 | U. S. Geo. S.| | | | | | | | 40 | 9.37 | 16.47 | 75.76 | 7.77 | 14507 | P. R. R. | ____|__________|__________|________|_________|________|______________| APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS--Continued ____________________________________________________________________________ | | | | | | | | | | | | No. | State | County | Field, Bed | Mine | Size | | | | or Vein | | | | | | | | | | | | | | | ____|_______|________________|________________|_______________|_____________| | | | | | | 41 | W. Va.| Fayette | New River | Rush Run | Mine run | 42 | W. Va.| Fayette | New River | Loup Creek | | 43 | W. Va.| Fayette | New River | | Slack | 44 | W. Va.| Fayette | New River | | Mine run | 45 | W. Va.| Fayette | New River | Rush Run | Mine run | 46 | W. Va.| McDowell | Pocahontas | Zenith | Mine run | | | | No. 3 | | | 47 | W. Va.| McDowell | Tug River | Big Sandy | Mine run | 48 | W. Va.| Mercer | Pocahontas | Mora | Lump | 49 | W. Va.| Mineral | Elk Garden | | | 50 | W. Va.| McDowell | Pocahontas | Flat Top | Mine run | 51 | W. Va.| McDowell | Pocahontas | Flat Top | Slack | 52 | W. Va.| McDowell | Pocahontas | Flat Top | Lump | ____|_______|________________|________________|_______________|_____________| | | | | | | BITUMINOUS | | ____|_______|_________________________________________________|_____________| | | | | | | 53 | Ala. | Bibb | Cahaba | Hill Creek | Mine run | 54 | Ala. | Jefferson | Pratt | Pratt No. 13 | | 55 | Ala. | Jefferson | Pratt | Warner | Mine run | 56 | Ala. | Jefferson | | Coalburg | Mine run | 57 | Ala. | Walker | Horse Creek | Ivy C. & I. | Nut | | | | | Co. No. 8 | | 58 | Ala. | Walker | Jagger | Galloway C. | Mine run | | | | | Co. No. 5 | | 59 | Ark. | Franklin | Denning | Western No. 4 | Nut | 60 | Ark. | Sebastian | Jenny Lind | Mine No. 12 | Lump | 61 | Ark. | Sebastian | Huntington | Cherokee | Mine run | 62 | Col. | Boulder | South Platte | Lafayette | Mine run | 63 | Col. | Boulder | Laramie | Simson | Mine run | 64 | Col. | Fremont | Canon City | Chandler | Nut and | | | | | | Slack | 65 | Col. | Las Animas | Trinidad | Hastings | Nut | 66 | Col. | Las Animas | Trinidad | Moreley | Slack | 67 | Col. | Routt | Yampa | Oak Creek | | 68 | Ill. | Christian | Pana | Penwell Col. | Lump | 69 | Ill. | Franklin | No. 6 | Benton | Egg | 70 | Ill. | Franklin | Big Muddy | Zeigler | ¾ inch | 71 | Ill. | Jackson | Big Muddy | | | 72 | Ill. | La Salle | Streator | | | 73 | Ill. | La Salle | Streator | Marseilles | Mine run | 74 | Ill. | Macoupin | Nilwood | Mine No. 2 | Screenings | 75 | Ill. | Macoupin | Mt. Olive | Mine No. 2 | Mine run | 76 | Ill. | Madison | Belleville | Donk Bros. | Lump | 77 | Ill. | Madison | Glen Carbon | | Mine run | 78 | Ill. | Marion | | Odin | Lump | 79 | Ill. | Mercer | Gilchrist | | Screenings | 80 | Ill. | Montgomery | Pana or No. 5 | Coffeen | Mine run | 81 | Ill. | Peoria | No. 5 | Empire | | 82 | Ill. | Perry | Du Quoin | Number 1 | Screenings | ____|_______|________________|________________|_______________|_____________| APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS--Continued _____________________________________________________________________ | | | | | Proximate Analysis (Dry Coal) |B. t. u.| | No. |________________________________________| Per | | | | | | | Pound | Authority | | Moisture | Volatile | Fixed | Ash | Dry | | | | Matter | Carbon | | Coal | | ____|__________|__________|________|_________|________|______________| | | | | | | | 41 | 2.14 | 22.87 | 71.56 | 5.57 | 14959 | U. S. Geo. S.| 42 | 0.55 | 19.36 | 78.48 | 2.16 | 14975 | Hill | 43 | 6.66 | 20.94 | 73.16 | 5.90 | 14412 | B. & W. Co. | 44 | 2.16 | 17.82 | 75.66 | 6.52 | 14786 | B. & W. Co. | 45 | 0.94 | 22.16 | 75.85 | 1.99 | 15007 | B. & W. Co. | 46 | 4.85 | 17.14 | 76.54 | 6.32 | 14480 | U. S. Geo. S.| | | | | | | | 47 | 1.58 | 18.55 | 76.44 | 4.91 | 15170 | U. S. Geo. S.| 48 | 1.74 | 18.55 | 75.15 | 6.30 | 15015 | U. S. Geo. S.| 49 | 2.10 | 15.70 | 75.40 | 8.90 | 14195 | B. & W. Co. | 50 | 0.52 | 24.02 | 74.59 | 1.39 | 14490 | B. & W. Co. | 51 | 3.24 | 15.33 | 77.60 | 7.07 | 14653 | B. & W. Co. | 52 | 3.63 | 16.03 | 78.04 | 5.93 | 14956 | B. & W. Co. | ____|__________|__________|________|_________|________|______________| | | | | | | | | | | | | | | ____|__________|__________|________|_________|________|______________| | | | | | | | 53 | 6.19 | 28.58 | 55.60 | 15.82 | 12576 | B. & W. Co. | 54 | 4.29 | 25.78 | 67.68 | 6.54 | 14482 | B. & W. Co. | 55 | 2.51 | 27.80 | 61.50 | 10.70 | 13628 | U. S. Geo. S.| 56 | 0.94 | 31.34 | 65.65 | 3.01 | 14513 | B. & W. Co. | 57 | 2.56 | 31.82 | 53.89 | 14.29 | 12937 | U. S. Geo. S.| | | | | | | | 58 | 4.83 | 34.65 | 51.12 | 14.03 | 12976 | U. S. Geo. S.| | | | | | | | 59 | 2.22 | 12.83 | 75.35 | 11.82 | | U. S. Geo. S.| 60 | 1.07 | 17.04 | 74.45 | 8.51 | 14252 | U. S. Geo. S.| 61 | 0.97 | 19.87 | 70.30 | 9.83 | 14159 | U. S. Geo. S.| 62 | 19.48 | 38.80 | 49.00 | 12.20 | 11939 | B. & W. Co. | 63 | 19.78 | 44.69 | 48.62 | 6.69 | 12577 | U. S. Geo. S.| 64 | 9.37 | 38.10 | 51.75 | 10.15 | 11850 | B. & W. Co. | | | | | | | | 65 | 2.15 | 31.07 | 53.40 | 15.53 | 12547 | B. & W. Co. | 66 | 1.88 | 28.47 | 55.58 | 15.95 | 12703 | B. & W. Co. | 67 | 6.67 | 42.91 | 55.64 | 1.45 | | Hill | 68 | 8.05 | 43.67 | 49.97 | 6.36 | 10900 | Jones | 69 | 8.31 | 34.52 | 54.05 | 11.43 | 11727 | U. S. Geo. S.| 70 | 13.28 | 31.97 | 57.37 | 10.66 | 12857 | U. S. Geo. S.| 71 | 4.85 | 31.55 | 62.19 | 6.26 | 11466 | Breckenridge | 72 | 8.40 | 41.76 | 51.42 | 6.82 | 11727 | Breckenridge | 73 | 12.98 | 43.73 | 49.13 | 7.14 | 10899 | B. & W. Co. | 74 | 13.34 | 34.75 | 44.55 | 20.70 | 10781 | B. & W. Co. | 75 | 13.54 | 41.28 | 46.30 | 12.42 | 10807 | U. S. Geo. S.| 76 | 13.47 | 38.69 | 48.07 | 13.24 | 12427 | U. S. Geo. S.| 77 | 9.78 | 38.18 | 51.52 | 10.30 | 11672 | Bryan | 78 | 6.20 | 42.91 | 49.06 | 8.03 | 11880 | Breckenridge | 79 | 8.50 | 36.17 | 41.64 | 22.19 | 10497 | Breckenridge | 80 | 11.93 | 34.05 | 49.85 | 16.10 | 10303 | U. S. Geo. S.| 81 | 17.64 | 31.91 | 46.17 | 21.92 | 10705 | B. & W. Co. | 82 | 9.81 | 33.67 | 48.36 | 17.97 | 11229 | B. & W. Co. | ____|__________|__________|________|_________|________|______________| APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS--Continued ____________________________________________________________________________ | | | | | | | | | | | | No. | State | County | Field, Bed | Mine | Size | | | | or Vein | | | | | | | | | | | | | | | |_______|________________|________________|_______________|_____________| | | | | | | 83 | Ill. | Perry | Du Quoin | Willis | Mine run | 84 | Ill. | Sangamon | | Pawnee | Slack | 85 | Ill. | St. Clair | Standard | Nigger Hollow | Mine run | 86 | Ill. | St. Clair | Standard | Maryville | Mine run | 87 | Ill. | Williamson | Big Muddy | Daws | Mine run | 88 | Ill. | Williamson | Carterville | Carterville | | | | | or No. 7 | | | 89 | Ill. | Williamson | Carterville | Burr | Nut, Pea | | | | or No. 7 | | and Slack | 90 | Ind. | Brazil | Brazil | Gartside | Block | 91 | Ind. | Clay | | Louise | Block | 92 | Ind. | Green | Island City | | Mine run | 93 | Ind. | Knox | Vein No. 5 | Tecumseh | Mine run | 94 | Ind. | Parke | Vein No. 6 | Parke Coal Co.| Lump | 95 | Ind. | Sullivan | Sullivan No. 6 | Mildred | Washed | 96 | Ind. | Vigo | Number 6 | Fontanet | Mine run | 97 | Ind. | Vigo | Number 7 | Red Bird | Mine run | 98 | Iowa | Appanoose | Mystic | Mine No. 3 | Lump | 99 | Iowa | Lucas | Lucas | Inland No. 1 | Mine run | 100 | Iowa | Marion | Big Vein | Liberty No. 5 | Mine run | 101 | Iowa | Polk | Third Seam | Altoona No. 4 | Lump | 102 | Iowa | Wapello | Wapello | | Lump | 103 | Kan. | Cherokee | Weir Pittsburgh| Southwestern | Lump | | | | | Dev. Co. | | 104 | Kan. | Cherokee | Cherokee | | Screenings | 105 | Kan. | Cherokee | Cherokee | | Lump | 106 | Kan. | Linn | Boicourt | | Lump | 107 | Ky. | Bell | Straight Creek | Str. Ck. C. & | Mine run | | | | | C. Co. | | 108 | Ky. | Hopkins | Bed No. 9 | Earlington | Lump | 109 | Ky. | Hopkins | Bed No. 9 | Barnsley | Mine run | 110 | Ky. | Hopkins | Vein No. 14 | Nebo |Pea and Slack| 111 | Ky. | Johnson | Vein No. 1 | Miller's Creek| Mine run | 112 | Ky. | Mulenburg | Bed No. 9 | Pierce |Pea and Slack| 113 | Ky. | Pulaski | | Greensburg | | 114 | Ky. | Webster | Bed No. 9 | |Pea and Slack| 115 | Ky. | Whitley | | Jellico |Nut and Slack| 116 | Mo. | Adair | | Danforth | Mine run | 117 | Mo. | Bates | Rich Hill | New Home | Mine run | 118 | Mo. | Clay | Lexington | Mo. City Coal | | | | | | Co. | | 119 | Mo. | Lafayette | Waverly | Buckthorn | | 120 | Mo. | Lafayette | Waverly | Higbee | | 121 | Mo. | Linn | Bevier | Marceline | | 122 | Mo. | Macon | Bevier | Northwest | | | | | | Coal Co. | | 123 | Mo. | Morgan | Morgan Co. | Morgan Co. | Mine run | | | | | Coal Co. | | 124 | Mo. | Putnam | Mendotta | Mendotta No. 8| | 125 | N.Mex.| McKinley | Gallup | Gibson |Pea and Slack| ____|_______|________________|________________|_______________|_____________| ______________________________________________________________________ | | | | | Proximate Analysis (Dry Coal) |B. t. u.| | No. |________________________________________| Per | | | | | | | Pound | Authority | | Moisture | Volatile | Fixed | Ash | Dry | | | | Matter | Carbon | | Coal | | ____|__________|__________|________|_________|________|______________| | | | | | | | 83 | 7.22 | 33.06 | 53.97 | 12.97 | 11352 | U. S. Geo. S.| 84 | 4.81 | 41.53 | 39.62 | 18.85 | 10220 | Jones | 85 | 14.39 | 32.90 | 44.84 | 22.26 | 11059 | B. & W. Co. | 86 | 15.71 | 38.10 | 41.10 | 20.80 | 10999 | B. & W. Co. | 87 | 8.17 | 34.33 | 52.50 | 13.17 | 12643 | U. S. Geo. S.| 88 | 4.66 | 35.65 | 56.86 | 7.49 | 12286 | Univ. of Ill.| | | | | | | | 89 | 11.91 | 33.70 | 55.90 | 10.40 | 12932 | B. & W. Co. | | | | | | | | 90 | 2.83 | 40.03 | 51.97 | 8.00 | 13375 | Stillman | 91 | 0.83 | 39.70 | 52.28 | 8.02 | 13248 | Jones | 92 | 6.17 | 35.42 | 53.55 | 11.03 | 11916 | Dearborn | 93 | 10.73 | 35.75 | 54.46 | 9.79 | 12911 | B. & W. Co. | 94 | 10.72 | 44.02 | 46.33 | 9.65 | 11767 | U. S. Geo. S.| 95 | 16.59 | 42.17 | 48.44 | 9.59 | 13377 | U. S. Geo. S.| 96 | 2.28 | 34.95 | 50.50 | 14.55 | 11920 | Dearborn | 97 | 11.62 | 41.17 | 46.76 | 12.07 | 12740 | U. S. Geo. S.| 98 | 13.48 | 39.40 | 43.09 | 17.51 | 11678 | U. S. Geo. S.| 99 | 16.01 | 37.82 | 46.24 | 15.94 | 11963 | U. S. Geo. S.| 100 | 14.88 | 41.53 | 39.63 | 18.84 | 11443 | U. S. Geo. S.| 101 | 12.44 | 41.27 | 40.86 | 17.87 | 11671 | U. S. Geo. S.| 102 | 8.69 | 36.23 | 43.68 | 20.09 | 11443 | U. S. Geo. S.| 103 | 4.31 | 33.88 | 53.67 | 12.45 | 13144 | U. S. Geo. S.| | | | | | | | 104 | 6.16 | 35.56 | 46.90 | 17.54 | 10175 | Jones | 105 | 1.81 | 34.77 | 52.77 | 12.46 | 12557 | Jones | 106 | 4.74 | 36.59 | 47.07 | 16.34 | 10392 | Jones | 107 | 2.89 | 36.67 | 57.24 | 6.09 | 14362 | U. S. Geo. S.| | | | | | | | 108 | 6.89 | 40.30 | 55.16 | 4.54 | 13381 | St. Col. Ky. | 109 | 7.92 | 40.53 | 48.70 | 10.77 | 13036 | U. S. Geo. S.| 110 | 8.02 | 31.91 | 54.02 | 14.07 | 12448 | B. & W. Co. | 111 | 5.12 | 38.46 | 58.63 | 2.91 | 13743 | U. S. Geo. S.| 112 | 9.22 | 33.94 | 52.18 | 13.88 | 12229 | B. & W. Co. | 113 | 2.80 | 26.54 | 63.58 | 9.88 | 14095 | N. Y. Ed. Co.| 114 | 7.30 | 31.08 | 60.72 | 8.20 | 13600 | B. & W. Co. | 115 | 3.82 | 31.82 | 58.78 | 9.40 | 13175 | B. & W. Co. | 116 | 9.00 | 30.55 | 46.26 | 23.19 | 9889 | B. & W. Co. | 117 | 7.28 | 37.62 | 43.83 | 18.55 | 12109 | U. S. Geo. S.| 118 | 12.45 | 39.39 | 48.47 | 12.14 | 12875 | Univ. of Mo. | | | | | | | | 119 | 8.58 | 41.78 | 45.99 | 12.23 | 12735 | Univ. of Mo. | 120 | 10.84 | 31.72 | 55.29 | 12.99 | 12500 | Univ. of Mo. | 121 | 9.45 | 36.72 | 52.20 | 11.08 | 13180 | Univ. of Mo. | 122 | 13.09 | 37.83 | 42.95 | 19.22 | 11500 | U. S. Geo. S.| | | | | | | | 123 | 12.24 | 45.69 | 47.98 | 6.33 | 14197 | U. S. Geo. S.| | | | | | | | 124 | 20.78 | 39.36 | 50.00 | 10.64 | 12602 | U. S. Geo. S.| 125 | 12.17 | 36.31 | 51.17 | 12.52 | 12126 | B. & W. Co. | ____|__________|__________|________|_________|________|______________| APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS--Continued ____________________________________________________________________________ | | | | | | | | | | | | No. | State | County | Field, Bed | Mine | Size | | | | or Vein | | | | | | | | | | | | | | | |_______|________________|________________|_______________|_____________| | | | | | | 126 | Ohio | Athens | Hocking Valley | Sunday Creek | Slack | 127 | Ohio | Belmont | Pittsburgh | Neff Coal Co. | Mine run | | | | No. 8 | | | 128 | Ohio | Columbiana | Middle | Palestine | | | | | Kittanning | | | 129 | Ohio | Coshocton | Middle | Morgan Run | Mine run | | | | Kittanning | | | 130 | Ohio | Guernsey | Vein No. 7 | Little Kate | | 131 | Ohio | Hocking | Hocking Valley | | Lump | 132 | Ohio | Hocking | Hocking Valley | | | 133 | Ohio | Jackson | Brookville | Superior | Mine run | | | | | Coal Co. | | 134 | Ohio | Jackson | Lower | Superior | Mine run | | | | Kittanning | Coal Co. | | 135 | Ohio | Jackson | Quakertown | Wellston | | 136 | Ohio | Jefferson | Pittsburgh | Crow Hollow | ¾ inch | | | | or No. 8 | | | 137 | Ohio | Jefferson | Pittsburgh | Rush Run No. 1| ¾ inch | | | | or No. 8 | | | 138 | Ohio | Perry | Hocking | Congo | | 139 | Ohio | Stark | Massillon | | Slack | 140 | Ohio | Vinton | Brookville | Clarion | Nut and | | | | or No. 4 | | Slack | 141 | Okla. | Choctaw | McAlester | Edwards No. 1 | Mine run | 142 | Okla. | Choctaw | McAlester | Adamson | Slack | 143 | Okla. | Creek | | Henrietta | Lump and | | | | | | Slack | 144 | Pa. | Allegheny | Pittsburgh | | Slack | | | | 3rd Pool | | | 145 | Pa. | Allegheny | Monongahela | Turtle Creek | | 146 | Pa. | Allegheny | Pittsburgh | Bertha | ¾ inch | 147 | Pa. | Cambria | | Beach Creek | Slack | 148 | Pa. | Cambria | Miller | Lincoln | Mine run | 149 | Pa. | Clarion | Lower Freeport | | | 150 | Pa. | Fayette | Connellsville | | Slack | 151 | Pa. | Greene | Youghiogheny | | Lump | 152 | Pa. | Greene | Westmoreland | | Screenings | 153 | Pa. | Indiana | | Iselin | Mine run | 154 | Pa. | Jefferson | | Punxsutawney | Mine run | 155 | Pa. | Lawrence | Middle | | | | | | Kittanning | | | 156 | Pa. | Mercer | Taylor | | | 157 | Pa. | Washington | Pittsburgh | Ellsworth | | 158 | Pa. | Washington | Youghiogheny | Anderson | ¾ inch | 159 | Pa. | Westmoreland | Pittsburgh | Scott Haven | Lump | 160 | Tenn. | Campbell | Jellico | | | 161 | Tenn. | Claiborne | Mingo | | | 162 | Tenn. | Marion | | Etna | | 163 | Tenn. | Morgan | Brushy Mt. | | | 164 | Tenn. | Scott | Glen Mary No. 4| Glen Mary | | 165 | Tex. | Maverick | | Eagle Pass | | 166 | Tex. | Paolo Pinto | | Thurber | Mine run | 167 | Tex. | Paolo Pinto | | Strawn | Mine run | 168 | Va. | Henrico | | Gayton | | ____|_______|________________|________________|_______________|_____________| _____________________________________________________________________ | | | | | Proximate Analysis (Dry Coal) |B. t. u.| | No. |________________________________________| Per | | | | | | | Pound | Authority | | Moisture | Volatile | Fixed | Ash | Dry | | | | Matter | Carbon | | Coal | | ____|__________|__________|________|_________|________|______________| | | | | | | | 126 | 12.16 | 34.64 | 53.10 | 12.26 | 12214 | | 127 | 5.31 | 38.78 | 52.22 | 9.00 | 12843 | U. S. Geo. S.| | | | | | | | 128 | 2.15 | 37.57 | 51.80 | 10.63 | 13370 | Lord & Haas | | | | | | | | 129 | | 41.76 | 45.24 | 13.00 | 13239 | B. & W. Co. | | | | | | | | 130 | 6.19 | 33.02 | 59.96 | 7.02 | 13634 | B. & W. Co. | 131 | 6.45 | 39.12 | 50.08 | 10.80 | 12700 | Lord & Haas | 132 | 2.60 | 40.80 | 47.60 | 11.60 | 12175 | Jones | 133 | 7.59 | 38.45 | 43.99 | 17.56 | 11704 | U. S. Geo. S.| | | | | | | | 134 | 8.99 | 41.43 | 50.06 | 8.51 | 13113 | U. S. Geo. S.| | | | | | | | 135 | 3.38 | 35.26 | 54.18 | 7.56 | 12506 | Hill | 136 | 4.04 | 40.08 | 52.27 | 9.65 | 13374 | U. S. Geo. S.| | | | | | | | 137 | 4.74 | 36.08 | 54.81 | 9.11 | 13532 | U. S. Geo. S.| | | | | | | | 138 | 6 41 | 38.33 | 46.71 | 14.96 | 12284 | B. & W. Co. | 139 | 6.67 | 40.02 | 46.46 | 13.52 | 11860 | B. & W. Co. | 140 | 2.47 | 42.38 | 50.39 | 6.23 | 13421 | U. S. Geo. S.| | | | | | | | 141 | 4.79 | 39.18 | 49.97 | 10.85 | 13005 | U. S. Geo. S.| 142 | 4.72 | 28.54 | 58.17 | 13.29 | 12105 | B. & W. Co. | 143 | 7.65 | 36.77 | 50.14 | 13.09 | 12834 | U. S. Geo. S.| | | | | | | | 144 | 1.77 | 32.06 | 57.11 | 10.83 | 13205 | Carpenter | | | | | | | | 145 | 1.75 | 36.85 | 53.94 | 9.21 | 13480 | Lord & Haas | 146 | 2.61 | 35.86 | 57.81 | 6.33 | 13997 | U. S. Geo. S.| 147 | 3.01 | 32.87 | 55.86 | 11.27 | 13755 | B. & W. Co. | 148 | 5.39 | 30.83 | 61.05 | 8.12 | 13600 | B. & W. Co. | 149 | 0.54 | 35.93 | 57.66 | 6.41 | 13547 | | 150 | 1.85 | 28.73 | 63.22 | 7.95 | 13775 | Whitham | 151 | 1.25 | 32.60 | 54.70 | 12.70 | 13100 | B. & W. Co. | 152 | 11.12 | 31.67 | 55.61 | 12.72 | 13100 | P. R. R. | 153 | 2.70 | 29.33 | 63.56 | 7.11 | 14220 | B. & W. Co. | 154 | 3.38 | 29.33 | 64.93 | 5.73 | 14781 | B. & W. Co. | 155 | 0.70 | 37.06 | 56.24 | 6.70 | 13840 | Lord & Haas | | | | | | | | 156 | 4.18 | 32.19 | 55.55 | 12.26 | 12820 | B. & W. Co. | 157 | 2.46 | 35.35 | 58.46 | 6.19 | 14013 | U. S. Geo. S.| 158 | 1.00 | 39.29 | 54.80 | 5.91 | 13729 | Jones | 159 | 4.06 | 32.91 | 59.78 | 7.31 | 13934 | B. & W. Co. | 160 | 1.80 | 37.76 | 62.12 | 1.12 | 13846 | U. S. Navy | 161 | 4.40 | 34.31 | 59.22 | 6.47 | | U. S. Geo. S.| 162 | 3.16 | 32.98 | 56.59 | 10.43 | | | 163 | 1.77 | 33.46 | 54.73 | 11.87 | 13824 | B. & W. Co. | 164 | 1.53 | 40.80 | 56.78 | 2.42 | 14625 |Ky. State Col.| 165 | 5.42 | 33.73 | 44.89 | 21.38 | 10945 | B. & W. Co. | 166 | 1.90 | 36.01 | 49.09 | 14.90 | 12760 | B. & W. Co. | 167 | 4.19 | 35.40 | 52.98 | 11.62 | 13202 | B. & W. Co. | 168 | 0.82 | 17.14 | 74.92 | 7.94 | 14363 | B. & W. Co. | ____|__________|__________|________|_________|________|______________| APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS--Continued ____________________________________________________________________________ | | | | | | | | | | | | No. | State | County | Field, Bed | Mine | Size | | | | or Vein | | | | | | | | | | | | | | | |_______|________________|________________|_______________|_____________| | | | | | | 169 | Va. | Lee | Darby | Darby | 1½ inch | 170 | Va. | Lee | McConnel | Wilson | Mine run | 171 | Va. | Wise | Upper Banner | Coburn | 3½ inch | 172 | Va. | Rockingham | | Clover Hill | | 173 | Va. | Russel | Clinchfield | | | 174 | Va. | | Monongahela | Bernmont | | 175 | W. Va.| Harrison | Pittsburgh | Ocean | Mine run | 176 | W. Va.| Harrison | | Girard | Nut, Pea | | | | | | and Slack | 177 | W. Va.| Kanawha | Winifrede | Winifrede | | 178 | W. Va.| Kanawha | Keystone | Keystone | Mine run | 179 | W. Va.| Logan | Island Creek | |Nut and Slack| 180 | W. Va.| Marion | Fairmont | Kingmont | | 181 | W. Va.| Mingo | Thacker | Maritime | | 182 | W. Va.| Mingo | Glen Alum | Glen Alum | Mine run | 183 | W. Va.| Preston | Bakerstown | | | 184 | W. Va.| Putnam | Pittsburgh | Black Betsy | Bug dust | 185 | W. Va.| Randolph | Upper Freeport | Coalton | Lump and Nut| ____|_______|________________|________________|_______________|_____________| | | | | | | LIGNITES AND LIGNITIC COALS | | ____|_______|_________________________________________________|_____________| | | | | | | 186 | Col. | Boulder | | Rex | | 187 | Col. | El Paso | | Curtis | | 188 | Col. | El Paso | | Pike View | | 189 | Col. | Gunnison | South Platte | Mt. Carbon | | 190 | Col. | Las Animas | | Acme | | 191 | Col. | | Lehigh | | | 192 |N. Dak.| McLean | | Eckland | Mine run | 193 |N. Dak.| McLean | | Wilton | Lump | 194 |N. Dak.| McLean | | Casino | | 195 |N. Dak.| Stark | Lehigh | Lehigh | Mine run | 196 |N. Dak.| William | Williston | | Mine run | 197 |N. Dak.| William | Williston | | Mine run | 198 | Tex. | Bastrop | Bastrop | Glenham | | 199 | Tex. | Houston | Crockett | | | 200 | Tex. | Houston | | Houston C. & | | | | | | C. Co. | | 201 | Tex. | Milam | Rockdale | Worley | | 202 | Tex. | Robertson | Calvert | Coaling No. 1 | | 203 | Tex. | Wood | Hoyt | Consumer's | | | | | | Lig. Co. | | 204 | Tex. | Wood | Hoyt | | | 205 | Wash. | King | | Black Diamond | | 206 | Wyo. | Carbon | Hanna | | Mine run | 207 | Wyo. | Crook | Black Hills | Stilwell Coal | | | | | | Co. | | 208 | Wyo. | Sheridan | Sheridan | Monarch | | 209 | Wyo. | Sweetwater | Rock Spring | | Screenings | 210 | Wyo. | Uinta | Adaville | Lazeart | | ____|_______|________________|________________|_______________|_____________| _____________________________________________________________________ | | | | | Proximate Analysis (Dry Coal) |B. t. u.| | No. |________________________________________| Per | | | | | | | Pound | Authority | | Moisture | Volatile | Fixed | Ash | Dry | | | | Matter | Carbon | | Coal | | ____|__________|__________|________|_________|________|______________| | | | | | | | 169 | 4.35 | 38.46 | 56.91 | 4.63 | 13939 | U. S. Geo. S.| 170 | 3.35 | 36.35 | 57.88 | 5.77 | 13931 | U. S. Geo. S.| 171 | 3.05 | 32.65 | 62.73 | 4.62 | 14470 | U. S. Geo. S.| 172 | | 31.77 | 57.98 | 10.25 | 13103 | | 173 | 2.00 | 35.72 | 56.12 | 8.16 | 14200 | | 174 | | 32.00 | 59.90 | 8.10 | 13424 | Carpenter | 175 | 2.47 | 39.35 | 52.78 | 7.87 | 14202 | U. S. Geo. S.| 176 | | 36.66 | 57.49 | 5.85 | 14548 | B. & W. Co. | | | | | | | | 177 | 1.05 | 32.74 | 64.38 | 2.88 | 14111 | Hill | 178 | 2.21 | 33.29 | 58.61 | 8.10 | 14202 | U. S. Geo. S.| 179 | 1.12 | 38.61 | 55.91 | 5.48 | 14273 | Hill | 180 | 1.90 | 35.31 | 57.34 | 7.35 | 14198 | U. S. Geo. S.| 181 | 0.68 | 31.89 | 63.48 | 4.63 | 14126 | Hill | 182 | 3.02 | 33.81 | 59.45 | 6.74 | 14414 | U. S. Geo. S.| 183 | 4.14 | 29.09 | 63.50 | 7.41 | 14546 | U. S. Geo. S.| 184 | 7.41 | 32.84 | 53.96 | 13.20 | 12568 | B. & W. Co. | 185 | 2.11 | 29.57 | 59.93 | 10.50 | 13854 | U. S. Geo. S.| ____|__________|__________|________|_________|________|______________| | | | | | | | | | | | | | | ____|__________|__________|________|_________|________|______________| | | | | | | | 186 | 16.05 | 42.12 | 47.97 | 9.91 | 10678 | B. & W. Co. | 187 | 23.25 | 42.11 | 49.38 | 8.51 | 11090 | B. & W. Co. | 188 | 23.77 | 48.70 | 41.47 | 9.83 | 10629 | B. & W. Co. | 189 | 20.38 | 46.38 | 47.50 | 6.12 | | | 190 | 16.74 | 47.90 | 44.60 | 7.50 | |Col. Sc. of M.| 191 | 18.30 | 45.29 | 44.67 | 10.04 | | | 192 | 29.65 | 45.56 | 47.05 | 7.39 | 10553 | Lord | 193 | 35.96 | 49.84 | 38.05 | 12.11 | 11036 | U. S. Geo. S.| 194 | 29.65 | 46.56 | 38.70 | 14.74 | | Lord | 195 | 35.84 | 43.84 | 39.59 | 16.57 | 10121 | U. S. Geo. S.| 196 | 41.76 | 39.37 | 48.09 | 12.54 | 10121 | B. & W. Co. | 197 | 42.74 | 40.83 | 47.79 | 11.38 | 10271 | B. & W. Co. | 198 | 32.77 | 42.76 | 36.88 | 20.36 | 8958 | B. & W. Co. | 199 | 23.27 | 40.95 | 38.37 | 20.68 | 10886 | U. S. Geo. S.| 200 | 31.48 | 46.93 | 34.40 | 18.87 | 10176 | B. & W. Co. | | | | | | | | 201 | 32.48 | 43.04 | 41.14 | 15.82 | 10021 | B. & W. Co. | 202 | 32.01 | 43.70 | 43.08 | 13.22 | 10753 | B. & W. Co. | 203 | 33.98 | 46.97 | 41.40 | 11.63 | 10600 | U. S. Geo. S.| | | | | | | | 204 | 30.25 | 43.27 | 41.46 | 15.27 | 10597 | | 205 | 3.71 | 48.72 | 46.56 | 4.72 | | Gale | 206 | 6.44 | 51.32 | 43.00 | 5.68 | 11607 | B. & W. Co. | 207 | 19.08 | 45.21 | 46.42 | 8.37 | 12641 | U. S. Geo. S.| | | | | | | | 208 | 21.18 | 51.87 | 40.43 | 7.70 | 12316 | U. S. Geo. S.| 209 | 7.70 | 38.57 | 56.99 | 4.44 | 12534 | B. & W. Co. | 210 | 19.15 | 45.50 | 48.11 | 6.39 | 9868 | U. S. Geo. S.| ____|__________|__________|________|_________|________|______________| [Illustration: Portion of 12,080 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters at the Potomac Electric Co., Washington, D. C.] TABLE 39 SHOWING RELATION BETWEEN PROXIMATE AND ULTIMATE ANALYSES OF COAL ========================================================================= | | | | Common in | | | | |Proximate &| | | Proximate | | Ultimate | | | Analysis | Ultimate Analysis | Analysis | |--------------------|-----------|--------------------------|-----------| | | | | V | | | H | | N | | | M | | | | | o | | | y | | i | S | | o | | | | | l M | C | C | d | O | t | u | | i | | S | | | a a | F a | a | r | x | r | l | | s | | t | | | t t | i r | r | o | y | o | p | | t | | a | Field | | i t | x b | b | g | g | g | h | A | u | | t | or | | l e | e o | o | e | e | e | e | s | r | | e | Bed | Mine | e r | d n | n | n | n | n | r | h | e | |---|-------|--------|-----|-----|-----|----|-----|----|----|-----|-----| | | |Icy Coal| | | | | | | | | | | | | & Iron | | | | | | | | | | | | Horse | Co. | | | | | | | | | | |Ala| Creek | No. 8 |31.81|53.90|72.02|4.78| 6.45|1.66| .80|14.29| 2.56| |---|----------------|-----|-----|-----|----|-----|----|----|-----|-----| | | |Central | | | | | | | | | | | | |C. & C. | | | | | | | | | | | | Hunt- | Co. | | | | | | | | | | |Ark|ington | No. 3 |18.99|67.71|76.37|3.90| 3.71|1.49|1.23|13.30| 1.99| |---|-------|--------|-----|-----|-----|----|-----|----|----|-----|-----| | | Pana | Clover | | | | | | | | | | | | or | Leaf, | | | | | | | | | | |Ill| No. 5 | No. 1 |37.22|45.64|63.04|4.49|10.04|1.28|4.01|17.14|13.19| |---|-------|--------|-----|-----|-----|----|-----|----|----|-----|-----| | |No. 5, | | | | | | | | | | | | |Warrick| | | | | | | | | | | |Ind| Co. |Electric|41.85|44.45|68.08|4.78| 7.56|1.35|4.53|13.70| 9.11| |---|-------|--------|-----|-----|-----|----|-----|----|----|-----|-----| | |No. 11,| St. | | | | | | | | | | | |Hopkins|Bernard,| | | | | | | | | | |Ky | Co. | No. 11 |41.10|49.60|72.22|5.06| 8.44|1.33|3.65| 9.30| 7.76| |---|-------|--------|-----|-----|-----|----|-----|----|----|-----|-----| | |"B" or | | | | | | | | | | | | |Lower | | | | | | | | | | | | |Kittan-| Eureka,| | | | | | | | | | |Pa | ning | No. 31 |16.71|77.22|84.45|4.25| 3.04|1.28| .91| 6.07| .56| |---|-------|--------|-----|-----|-----|----|-----|----|----|-----|-----| | |Indiana| | | | | | | | | | | |Pa | Co. | |29.55|62.64|79.86|5.02| 4.27|1.86|1.18| 7.81| 2.90| |---|-------|--------|-----|-----|-----|----|-----|----|----|-----|-----| |W. | Fire | Rush | | | | | | | | | | |Va | Creek | Run |22.87|71.56|83.71|4.64| 3.67|1.70| .71| 5.57| 2.14| ========================================================================= Table 39 gives for comparison the ultimate and proximate analyses of certain of the coals with which tests were made in the coal testing plant of the United States Geological Survey at the Louisiana Purchase Exposition at St. Louis. The heating value of a fuel cannot be directly computed from a proximate analysis, due to the fact that the volatile content varies widely in different fuels in composition and in heating value. Some methods have been advanced for estimating the calorific value of coals from the proximate analysis. William Kent[38] deducted from Mahler's tests of European coals the approximate heating value dependent upon the content of fixed carbon in the combustible. The relation as deduced by Kent between the heat and value per pound of combustible and the per cent of fixed carbon referred to combustible is represented graphically by Fig. 23. Goutal gives another method of determining the heat value from a proximate analysis, in which the carbon is given a fixed value and the heating value of the volatile matter is considered as a function of its percentage referred to combustible. Goutal's method checks closely with Kent's determinations. All the formulae, however, for computing the calorific value of coals from a proximate analysis are ordinarily limited to certain classes of fuels. Mr. Kent, for instance, states that his deductions are correct within a close limit for fuels containing more than 60 per cent of fixed carbon in the combustible, while for those containing a lower percentage, the error may be as great as 4 per cent, either high or low. While the use of such computations will serve where approximate results only are required, that they are approximate should be thoroughly understood. Calorimetry--An ultimate or a proximate analysis of a fuel is useful in determining its general characteristics, and as described on page 183, may be used in the calculation of the approximate heating value. Where the efficiency of a boiler is to be computed, however, this heating value should in all instances be determined accurately by means of a fuel calorimeter. [Graph: B.T.U. per Pound of Combustible against Per Cent of Fixed Carbon in Combustible Fig. 23. Graphic Representation of Relation between Heat Value Per Pound of Combustible and Fixed Carbon in Combustible as Deduced by Wm. Kent.] In such an apparatus the fuel is completely burned and the heat generated by such combustion is absorbed by water, the amount of heat being calculated from the elevation in the temperature of the water. A calorimeter which has been accepted as the best for such work is one in which the fuel is burned in a steel bomb filled with compressed oxygen. The function of the oxygen, which is ordinarily under a pressure of about 25 atmospheres, is to cause the rapid and complete combustion of the fuel sample. The fuel is ignited by means of an electric current, allowance being made for the heat produced by such current, and by the burning of the fuse wire. A calorimeter of this type which will be found to give satisfactory results is that of M. Pierre Mahler, illustrated in Fig. 24 and consisting of the following parts: A water jacket A, which maintains constant conditions outside of the calorimeter proper, and thus makes possible a more accurate computation of radiation losses. The porcelain lined steel bomb B, in which the combustion of the fuel takes place in compressed oxygen. [Illustration: Fig. 24. Mahler Bomb Calorimeter] The platinum pan C, for holding the fuel. The calorimeter proper D, surrounding the bomb and containing a definite weighed amount of water. An electrode E, connecting with the fuse wire F, for igniting the fuel placed in the pan C. A support G, for a water agitator. A thermometer I, for temperature determination of the water in the calorimeter. The thermometer is best supported by a stand independent of the calorimeter, so that it may not be moved by tremors in the parts of the calorimeter, which would render the making of readings difficult. To obtain accuracy of readings, they should be made through a telescope or eyeglass. A spring and screw device for revolving the agitator. A lever L, by the movement of which the agitator is revolved. A pressure gauge M, for noting the amount of oxygen admitted to the bomb. Between 20 and 25 atmospheres are ordinarily employed. An oxygen tank O. A battery or batteries P, the current from which heats the fuse wire used to ignite the fuel. This or a similar calorimeter is used in the determination of the heat of combustion of solid or liquid fuels. Whatever the fuel to be tested, too much importance cannot be given to the securing of an average sample. Where coal is to be tested, tests should be made from a portion of the dried and pulverized laboratory sample, the methods of obtaining which have been described. In considering the methods of calorimeter determination, the remarks applied to coal are equally applicable to any solid fuel, and such changes in methods as are necessary for liquid fuels will be self-evident from the same description. Approximately one gram of the pulverized dried coal sample should be placed directly in the pan of the calorimeter. There is some danger in the using of a pulverized sample from the fact that some of it may be blown out of the pan when oxygen is admitted. This may be at least partially overcome by forming about two grams into a briquette by the use of a cylinder equipped with a plunger and a screw press. Such a briquette should be broken and approximately one gram used. If a pulverized sample is used, care should be taken to admit oxygen slowly to prevent blowing the coal out of the pan. The weight of the sample is limited to approximately one gram since the calorimeter is proportioned for the combustion of about this weight when under an oxygen pressure of about 25 atmospheres. A piece of fine iron wire is connected to the lower end of the plunger to form a fuse for igniting the sample. The weight of iron wire used is determined, and if after combustion a portion has not been burned, the weight of such portion is determined. In placing the sample in the pan, and in adjusting the fuse, the top of the calorimeter is removed. It is then replaced and carefully screwed into place on the bomb by means of a long handled wrench furnished for the purpose. The bomb is then placed in the calorimeter, which has been filled with a definite amount of water. This weight is the "water equivalent" of the apparatus, _i. e._, the weight of water, the temperature of which would be increased one degree for an equivalent increase in the temperature of the combined apparatus. It may be determined by calculation from the weights and specific heats of the various parts of the apparatus. Such a determination is liable to error, however, as the weight of the bomb lining can only be approximated, and a considerable portion of the apparatus is not submerged. Another method of making such a determination is by the adding of definite weights of warm water to definite amounts of cooler water in the calorimeter and taking an average of a number of experiments. The best method for the making of such a determination is probably the burning of a definite amount of resublimed naphthaline whose heat of combustion is known. The temperature of the water in the water jacket of the calorimeter should be approximately that of the surrounding atmosphere. The temperature of the weighed amount of water in the calorimeter is made by some experimenters slightly greater than that of the surrounding air in order that the initial correction for radiation will be in the same direction as the final correction. Other experimenters start from a temperature the same or slightly lower than the temperature of the room, on the basis that the temperature after combustion will be slightly higher than the room temperature and the radiation correction be either a minimum or entirely eliminated. While no experiments have been made to show conclusively which of these methods is the better, the latter is generally used. After the bomb has been placed in the calorimeter, it is filled with oxygen from a tank until the pressure reaches from 20 to 25 atmospheres. The lower pressure will be sufficient in all but exceptional cases. Connection is then made to a current from the dry batteries in series so arranged as to allow completion of the circuit with a switch. The current from a lighting system should not be used for ignition, as there is danger from sparking in burning the fuse, which may effect the results. The apparatus is then ready for the test. Unquestionably the best method of taking data is by the use of co-ordinate paper and a plotting of the data with temperatures and time intervals as ordinates and abscissae. Such a graphic representation is shown in Fig. 25. [Graph: Temperature--° C. against Time--Hours and Minutes Fig. 25. Graphic Method of Recording Bomb Calorimeter Results] After the bomb is placed in the calorimeter, and before the coal is ignited, readings of the temperature of the water should be taken at one minute intervals for a period long enough to insure a constant rate of change, and in this way determine the initial radiation. The coal is then ignited by completing the circuit, the temperature at the instant the circuit is closed being considered the temperature at the beginning of the combustion. After ignition the readings should be taken at one-half minute intervals, though because of the rapidity of the mercury's rise approximate readings only may be possible for at least a minute after the firing, such readings, however, being sufficiently accurate for this period. The one-half minute readings should be taken after ignition for five minutes, and for, say, five minutes longer at minute intervals to determine accurately the final rate of radiation. Fig. 25 shows the results of such readings, plotted in accordance with the method suggested. It now remains to compute the results from this plotted data. The radiation correction is first applied. Probably the most accurate manner of making such correction is by the use of Pfaundler's method, which is a modification of that of Regnault. This assumes that in starting with an initial rate of radiation, as represented by the inclination of the line AB, Fig. 25, and ending with a final radiation represented by the inclination of the line CD, Fig. 25, that the rate of radiation for the intermediate temperatures between the points B and C are proportional to the initial and final rates. That is, the rate of radiation at a point midway between B and C will be the mean between the initial and final rates; the rate of radiation at a point three-quarters of the distance between B and C would be the rate at B plus three-quarters of the difference in rates at B and C, etc. This method differs from Regnault's in that the radiation was assumed by Regnault to be in each case proportional to the difference in temperatures between the water of the calorimeter and the surrounding air plus a constant found for each experiment. Pfaundler's method is more simple than that of Regnault, and the results by the two methods are in practical agreement. Expressed as a formula, Pfaundler's method is, though not in form given by him: _ _ | R' - R | C = N|R + ------ (T" - T)| (19) |_ T' - T _| Where C = correction in degree centigrade, N = number of intervals over which correction is made, R = initial radiation in degrees per interval, R' = final radiation in degrees per interval, T = average temperature for period through which initial radiation is computed, T" = average temperature over period of combustion[39], T' = average temperature over period through which final radiation is computed.[39] The application of this formula to Fig. 25 is as follows: As already stated, the temperature at the beginning of combustion is the reading just before the current is turned on, or B in Fig. 25. The point C or the temperature at which combustion is presumably completed, should be taken at a point which falls well within the established final rate of radiation, and not at the maximum temperature that the thermometer indicates in the test, unless it lies on the straight line determining the final radiation. This is due to the fact that in certain instances local conditions will cause the thermometer to read higher than it should during the time that the bomb is transmitting heat to the water rapidly, and at other times the maximum temperature might be lower than that which would be indicated were readings to be taken at intervals of less than one-half minute, _i. e._, the point of maximum temperature will fall below the line determined by the final rate of radiation. With this understanding AB, Fig. 25, represents the time of initial radiation, BC the time of combustion, and CD the time of final radiation. Therefore to apply Pfaundler's correction, formula (19), to the data as represented by Fig. 25. N = 6, R = 0, R' = .01, T = 20.29, T' = 22.83, 20.29 + 22.54 + 22.84 + 22.88 + 22.87 + 22.86 T" = --------------------------------------------- = 22.36 6 _ _ | .01 - 0 | C = 6|0 + -------------(22.36 - 20.29)| |_ 22.85 - 20.29 _| = 6 × .008 = .048 Pfaundler's formula while simple is rather long. Mr. E. H. Peabody has devised a simpler formula with which, under proper conditions, the variation from correction as found by Pfaundler's method is negligible. It was noted throughout an extended series of calorimeter tests that the maximum temperature was reached by the thermometer slightly over one minute after the time of firing. If this period between the time of firing and the maximum temperature reported was exactly one minute, the radiation through this period would equal the radiation per one-half minute _before firing_ plus the radiation per one-half minute _after the maximum temperature is reached_; or, the radiation through the one minute interval would be the average of the radiation per minute before firing and the radiation per minute after the maximum. A plotted chart of temperatures would take the form of a curve of three straight lines (B, C', D) in Fig. 25. Under such conditions, using the notation as in formula (19) the correction would become, 2R + 2R' C = ------- + (N - 2)R', or R + (N - 1)R' (20) 2 This formula may be generalized for conditions where the maximum temperature is reached after a period of more than one minute as follows: Let M = the number of intervals between the time of firing and the maximum temperature. Then the radiation through this period will be an average of the radiation for M intervals before firing and for M intervals after the maximum is recorded, or MR + MR' M M C = ------- + (N - M)R' = - R + (N - -)R' (21) 2 2 2 In the case of Mr. Peabody's deductions M was found to be approximately 2 and formula (21) becomes directly, C = R + (N - 1)R' or formula (20). The corrections to be made, as secured by the use of this formula, are very close to those secured by Pfaundler's method, where the point of maximum temperature is not more than five intervals later than the point of firing. Where a longer period than this is indicated in the chart of plotted temperatures, the approximate formula should not be used. As the period between firing and the maximum temperature is increased, the plotted results are further and further away from the theoretical straight line curve. Where this period is not over five intervals, or two and a half minutes, an approximation of the straight line curve may be plotted by eye, and ordinarily the radiation correction to be applied may be determined very closely from such an approximated curve. Peabody's approximate formula has been found from a number of tests to give results within .003 degrees Fahrenheit for the limits within which its application holds good as described. The value of M, which is not necessarily a whole number, should be determined for each test, though in all probability such a value is a constant for any individual calorimeter which is properly operated. The correction for radiation as found on page 188 is in all instances to be added to the range of temperature between the firing point and the point chosen from which the final radiation is calculated. This corrected range multiplied by the water equivalent of the calorimeter gives the heat of combustion in calories of the coal burned in the calorimeter together with that evolved by the burning of the fuse wire. The heat evolved by the burning of the fuse wire is found from the determination of the actual weight of wire burned and the heat of combustion of one milligram of the wire (1.7 calories), _i. e._, multiply the weight of wire used by 1.7, the result being in gram calories or the heat required to raise one gram of water one degree centigrade. Other small corrections to be made are those for the formation of nitric acid and for the combustion of sulphur to sulphuric acid instead of sulphur dioxide, due to the more complete combustion in the presence of oxygen than would be possible in the atmosphere. To make these corrections the bomb of the calorimeter is carefully washed out with water after each test and the amount of acid determined from titrating this water with a standard solution of ammonia or of caustic soda, all of the acid being assumed to be nitric acid. Each cubic centimeter of the ammonia titrating solution used is equivalent to a correction of 2.65 calories. As part of acidity is due to the formation of sulphuric acid, a further correction is necessary. In burning sulphuric acid the heat evolved per gram of sulphur is 2230 calories in excess of the heat which would be evolved if the sulphur burned to sulphur dioxide, or 22.3 calories for each per cent of sulphur in the coal. One cubic centimeter of the ammonia solution is equivalent to 0.00286 grams of sulphur as sulphuric acid, or to 0.286 × 22.3 = 6.38 calories. It is evident therefore that after multiplying the number of cubic centimeters used in titrating by the heat factor for nitric acid (2.65) a further correction of 6.38 - 2.65 = 3.73 is necessary for each cubic centimeter used in titrating sulphuric instead of nitric acid. This correction will be 3.73/0.297 = 13 units for each 0.01 gram of sulphur in the coal. The total correction therefore for the aqueous nitric and sulphuric acid is found by multiplying the ammonia by 2.65 and adding 13 calories for each 0.01 gram of sulphur in the coal. This total correction is to be deducted from the heat value as found from the corrected range and the amount equivalent to the calorimeter. After each test the pan in which the coal has been burned must be carefully examined to make sure that all of the sample has undergone complete combustion. The presence of black specks ordinarily indicates unburned coal, and often will be found where the coal contains bone or slate. Where such specks are found the tests should be repeated. In testing any fuel where it is found difficult to completely consume a sample, a weighed amount of naphthaline may be added, the total weight of fuel and naphthaline being approximately one gram. The naphthaline has a known heat of combustion, samples for this purpose being obtainable from the United States Bureau of Standards, and from the combined heat of combustion of the fuel and naphthaline that of the former may be readily computed. The heat evolved in burning of a definite weight of standard naphthaline may also be used as a means of calibrating the calorimeter as a whole. COMBUSTION OF COAL The composition of coal varies over such a wide range, and the methods of firing have to be altered so greatly to suit the various coals and the innumerable types of furnaces in which they are burned, that any instructions given for the handling of different fuels must of necessity be of the most general character. For each kind of coal there is some method of firing which will give the best results for each individual set of conditions. General rules can be suggested, but the best results can be obtained only by following such methods as experience and practice show to be the best suited to the specific conditions. The question of draft is an all important factor. If this be insufficient, proper combustion is impossible, as the suction in the furnace will not be great enough to draw the necessary amount of air through the fuel bed, and the gases may pass off only partially consumed. On the other hand, an excessive draft may cause losses due to the excess quantities of air drawn through holes in the fire. Where coal is burned however, there are rarely complaints from excessive draft, as this can be and should be regulated by the boiler damper to give only the draft necessary for the particular rate of combustion desired. The draft required for various kinds of fuel is treated in detail in the chapter on "Chimneys and Draft". In this chapter it will be assumed that the draft is at all times ample and that it is regulated to give the best results for each kind of coal. TABLE 40 ANTHRACITE COAL SIZES _________________________________________________________________ | | | | | | | Testing Segments | | | Round Mesh | Standard Square | | | | Mesh | | Trade Name |__________________|__________________| | | | | | | | | Through | Over | Through | Over | | | Inches | Inches | Inches | Inches | |___________________________|_________|________|_________|________| | | | | | | | Broken | 4-1/2 | 3-1/4 | 4 | 2-3/4 | | Egg | 3-1/4 | 2-3/8 | 2-3/4 | 2 | | Stove | 2-3/8 | 1-5/8 | 2 | 1-3/8 | | Chestnut | 1-5/8 | 7/8 | 1-3/8 | 3/4 | | Pea | 7/8 | 5/8 | 3/4 | 1/2 | | No. 1 Buckwheat | 5/8 | 3/8 | 1/2 | 1/4 | | No. 2 Buckwheat or Rice | 3/8 | 3/16 | 1/4 | 1/8 | | No. 3 Buckwheat or Barley | 3/16 | 3/32 | 1/8 | 1/16 | |___________________________|_________|________|_________|________| Anthracite--Anthracite coal is ordinarily marketed under the names and sizes given in Table 40. The larger sizes of anthracite are rarely used for commercial steam generating purposes as the demand for domestic use now limits the supply. In commercial plants the sizes generally found are Nos. 1, 2 and 3 buckwheat. In some plants where the finer sizes are used, a small percentage of bituminous coal, say, 10 per cent, is sometimes mixed with the anthracite and beneficial results secured both in economy and capacity. Anthracite coal should be fired evenly, in small quantities and at frequent intervals. If this method is not followed, dead spots will appear in the fire, and if the fire gets too irregular through burning in patches, nothing can be done to remedy it until the fire is cleaned as a whole. After this grade of fuel has been fired it should be left alone, and the fire tools used as little as possible. Owing to the difficulty of igniting this fuel, care must be taken in cleaning fires. The intervals of cleaning will, of course, depend upon the nature of the coal and the rate of combustion. With the small sizes and moderately high combustion rates, fires will have to be cleaned twice on each eight-hour shift. As the fires become dirty the thickness of the fuel bed will increase, until this depth may be 12 or 14 inches just before a cleaning period. In cleaning, the following practice is usually followed: The good coal on the forward half of the grate is pushed to the rear half, and the refuse on the front portion either pulled out or dumped. The good coal is then pulled forward onto the front part of the grate and the refuse on the rear section dumped. The remaining good coal is then spread evenly over the whole grate surface and the fire built up with fresh coal. A ratio of grate surface to heating surface of 1 to from 35 to 40 will under ordinary conditions develop the rated capacity of a boiler when burning anthracite buckwheat. Where the finer sizes are used, or where overloads are desirable, however, this ratio should preferably be 1 to 25 and a forced blast should be used. Grates 10 feet deep with a slope of 1½ inches to the foot can be handled comfortably with this class of fuel, and grates 12 feet deep with the same slope can be successfully handled. Where grates over 8 feet in depth are necessary, shaking grates or overlapping dumping grates should be used. Dumping grates may be applied either for the whole grate surface or to the rear section. Air openings in the grate bars should be made from 3/16 inch in width for No. 3 buckwheat to 5/16 inch for No. 1 buckwheat. It is important that these air openings be uniformly distributed over the whole surface to avoid blowing holes in the fire, and it is for this reason that overlapping grates are recommended. No air should be admitted over the fire. Steam is sometimes introduced into the ashpit to soften any clinker that may form, but the quantity of steam should be limited to that required for this purpose. The steam that may be used in a steam jet blower for securing blast will in certain instances assist in softening the clinker, but a much greater quantity may be used by such an apparatus than is required for this purpose. Combustion arches sprung above the grates have proved of advantage in maintaining a high furnace temperature and in assisting in the ignition of fresh coal. Stacks used with forced blast should be of such size as to insure a slight suction in the furnace under any conditions of operation. A blast up to 3 inches of water should be available for the finer sizes supplied by engine driven fans, automatically controlled by the boiler pressure. The blast required will increase as the depth of the fuel bed increases, and the slight suction should be maintained in the furnace by damper regulation. The use of blast with the finer sizes causes rapid fouling of the heating surfaces of the boiler, the dust often amounting to over 10 per cent of the total fuel fired. Economical disposal of dust and ashes is of the utmost importance in burning fuel of this nature. Provision should be made in the baffling of the boiler to accommodate and dispose of this dust. Whenever conditions permit, the ashes can be economically disposed of by flushing them out with water. Bituminous Coals--There is no classification of bituminous coal as to size that holds good in all localities. The American Society of Mechanical Engineers suggests the following grading: _Eastern Bituminous Coals_-- (A) Run of mine coal; the unscreened coal taken from the mine. (B) Lump coal; that which passes over a bar-screen with openings 1¼ inches wide. (C) Nut coal; that which passes through a bar-screen with 1¼-inch openings and over one with ¾-inch openings. (D) Slack coal; that which passes through a bar-screen with ¾-inch openings. _Western Bituminous Coals_-- (E) Run of mine coal; the unscreened coal taken from the mine. (F) Lump coal; divided into 6-inch, 3-inch and 1¼-inch lump, according to the diameter of the circular openings over which the respective grades pass; also 6 × 3-inch lump and 3 × 1¼-inch lump, according as the coal passes through a circular opening having the diameter of the larger figure and over that of the smaller diameter. (G) Nut coal; divided into 3-inch steam nut, which passes through an opening 3 inches diameter and over 1¼ inches; 1¼ inch nut, which passes through a 1¼-inch diameter opening and over a ¾-inch diameter opening; ¾-inch nut, which passes through a ¾-inch diameter opening and over a 5/8-inch diameter opening. (H) Screenings; that which passes through a 1¼-inch diameter opening. As the variation in character of bituminous coals is much greater than in the anthracites, any rules set down for their handling must be the more general. The difficulties in burning bituminous coals with economy and with little or no smoke increases as the content of fixed carbon in the coal decreases. It is their volatile content which causes the difficulties and it is essential that the furnaces be designed to properly handle this portion of the coal. The fixed carbon will take care of itself, provided the volatile matter is properly burned. Mr. Kent, in his "Steam Boiler Economy", described the action of bituminous coal after it is fired as follows: "The first thing that the fine fresh coal does is to choke the air spaces existing through the bed of coke, thus shutting off the air supply which is needed to burn the gases produced from the fresh coal. The next thing is a very rapid evaporation of moisture from the coal, a chilling process, which robs the furnace of heat. Next is the formation of water-gas by the chemical reaction, C + H_{2}O = CO + 2H, the steam being decomposed, its oxygen burning the carbon of the coal to carbonic oxide, and the hydrogen being liberated. This reaction takes place when steam is brought in contact with highly heated carbon. This also is a chilling process, absorbing heat from the furnaces. The two valuable fuel gases thus generated would give back all the heat absorbed in their formation if they could be burned, but there is not enough air in the furnace to burn them. Admitting extra air through the fire door at this time will be of no service, for the gases being comparatively cool cannot be burned unless the air is highly heated. After all the moisture has been driven off from the coal, the distillation of hydrocarbons begins, and a considerable portion of them escapes unburned, owing to the deficiency of hot air, and to their being chilled by the relatively cool heating surfaces of the boiler. During all this time great volumes of smoke are escaping from the chimney, together with unburned hydrogen, hydrocarbons, and carbonic oxide, all fuel gases, while at the same time soot is being deposited on the heating surface, diminishing its efficiency in transmitting heat to the water." To burn these gases distilled from the coal, it is necessary that they be brought into contact with air sufficiently heated to cause them to ignite, that sufficient space be allowed for their mixture with the air, and that sufficient time be allowed for their complete combustion before they strike the boiler heating surfaces, since these surfaces are comparatively cool and will lower the temperature of the gases below their ignition point. The air drawn through the fire by the draft suction is heated in its passage and heat is added by radiation from the hot brick surfaces of the furnace, the air and volatile gases mixing as this increase in temperature is taking place. Thus in most instances is the first requirement fulfilled. The element of space for the proper mixture of the gases with the air, and of time in which combustion is to take place, should be taken care of by sufficiently large combustion chambers. Certain bituminous coals, owing to their high volatile content, require that the air be heated to a higher temperature than it is possible for it to attain simply in its passage through the fire and by absorption from the side walls of the furnace. Such coals can be burned with the best results under fire brick arches. Such arches increase the temperature of the furnace and in this way maintain the heat that must be present for ignition and complete combustion of the fuels in question. These fuels too, sometimes require additional combustion space, and an extension furnace will give this in addition to the required arches. As stated, the difficulty of burning bituminous coals successfully will increase with the increase in volatile matter. This percentage of volatile will affect directly the depth of coal bed to be carried and the intervals of firing for the most satisfactory results. The variation in the fuel over such wide ranges makes it impossible to definitely state the thickness of fires for all classes, and experiment with the class of fuel in use is the best method of determining how that particular fuel should be handled. The following suggestions, which are not to be considered in any sense hard and fast rules, may be of service for general operating conditions for hand firing: Semi-bituminous coals, such as Pocahontas, New River, Clearfield, etc., require fires from 10 to 14 inches thick; fresh coal should be fired at intervals of 10 to 20 minutes and sufficient coal charged at each firing to maintain a uniform thickness. Bituminous coals from Pittsburgh Region require fires from 4 to 6 inches thick, and should be fired often in comparatively small charges. Kentucky, Tennessee, Ohio and Illinois coals require a thickness from 4 to 6 inches. Free burning coals from Rock Springs, Wyoming, require from 6 to 8 inches, while the poorer grades of Montana, Utah and Washington bituminous coals require a depth of about 4 inches. In general as thin fires are found necessary, the intervals of firing should be made more frequent and the quantity of coal fired at each interval smaller. As thin fires become necessary due to the character of the coal, the tendency to clinker will increase if the thickness be increased over that found to give the best results. There are two general methods of hand firing: 1st, the spreading method; and 2nd, the coking method. [Illustration: Babcock & Wilcox Chain Grate Stoker] In the spreading method but little fuel is fired at one time, and is spread evenly over the fuel bed from front to rear. Where there is more than one firing door the doors should be fired alternately. The advantage of alternate firing is the whole surface of the fire is not blanketed with green coal, and steam is generated more uniformly than if all doors were fired at one time. Again, a better combustion results due to the burning of more of the volatile matter directly after firing than where all doors are fired at one time. In the coking method, fresh coal is fired at considerable depth at the front of the grate and after it is partially coked it is pushed back into the furnace. The object of such a method is the preserving of a bed of carbon at the rear of the grate, in passing over which the volatile gases driven off from the green coal will be burned. This method is particularly adaptable to a grate in which the gases are made to pass horizontally over the fire. Modern practice for hand firing leans more and more toward the spread firing method. Again the tendency is to work bituminous coal fires less than formerly. A certain amount of slicing and raking may be necessary with either method of firing, but in general, the less the fire is worked the better the results. Lignites--As the content of volatile matter and moisture in lignite is higher than in bituminous coal, the difficulties encountered in burning them are greater. A large combustion space is required and the best results are obtained where a furnace of the reverberatory type is used, giving the gases a long travel before meeting the tube surfaces. A fuel bed from 4 to 6 inches in depth can be maintained, and the coal should be fired in small quantities by the alternate method. Above certain rates of combustion clinker forms rapidly, and a steam jet in the ashpit for softening this clinker is often desirable. A considerable draft should be available, but it should be carefully regulated by the boiler damper to suit the condition of the fire. Smokelessness with hand firing with this class of fuel is a practical impossibility. It has a strong tendency to foul the heating surfaces rapidly and these surfaces should be cleaned frequently. Shaking grates, intelligently handled, aid in cleaning the fires, but their manipulation must be carefully watched to prevent good coal being lost in the ashpit. Stokers--The term "automatic stoker" oftentimes conveys the erroneous impression that such an apparatus takes care of itself, and it must be thoroughly understood that any stoker requires expert attention to as high if not higher degree than do hand-fired furnaces. Stoker-fired furnaces have many advantages over hand firing, but where a stoker installation is contemplated there are many factors to be considered. It is true that stokers feed coal to the fire automatically, but if the coal has first to be fed to the stoker hopper by hand, its automatic advantage is lost. This is as true of the removal of ash from a stoker. In a general way, it may be stated that a stoker installation is not advantageous except possibly for diminishing smoke, unless the automatic feature is carried to the handling of the coal and ash, as where coal and ash handling apparatus is not installed there is no saving in labor. In large plants, however, stokers used in conjunction with the modern methods of coal storage and coal and ash handling, make possible a large labor saving. In small plants the labor saving for stokers over hand-fired furnaces is negligible, and the expense of the installation no less proportionately than in large plants. Stokers are, therefore, advisable in small plants only where the saving in fuel will be large, or where the smoke question is important. Interest on investment, repairs, depreciation and steam required for blast and stoker drive must all be considered. The upkeep cost will, in general, be higher than for hand-fired furnaces. Stokers, however, make possible the use of cheaper fuels with as high or higher economy than is obtainable under operating conditions in hand-fired furnaces with a better grade of fuel. The better efficiency obtainable with a good stoker is due to more even and continuous firing as against the intermittent firing of hand-fired furnaces; constant air supply as against a variation in this supply to meet varying furnace conditions in hand-fired furnaces; and the doing away to a great extent with the necessity of working the fires. Stokers under ordinary operating conditions will give more nearly smokeless combustion than will hand-fired furnaces and for this reason must often be installed regardless of other considerations. While a constant air supply for a given power is theoretically secured by the use of a stoker, and in many instances the draft is automatically governed, the air supply should, nevertheless, be as carefully watched and checked by flue gas analyses as in the case of hand-fired furnaces. There is a tendency in all stokers to cause the loss of some good fuel or siftings in the ashpit, but suitable arrangements may be made to reclaim this. In respect to efficiency of combustion, other conditions being equal, there will be no appreciable difference with the different types of stokers, provided that the proper type is used for the grade of fuel to be burned and the conditions of operation to be fulfilled. No stoker will satisfactorily handle all classes of fuel, and in making a selection, care should be taken that the type is suited to the fuel and the operating conditions. A cheap stoker is a poor investment. Only the best stoker suited to the conditions which are to be met should be adopted, for if there is to be a saving, it will more than cover the cost of the best over the cheaper stoker. Mechanical Stokers are of three general types: 1st, overfeed; 2nd, underfeed; and 3rd, traveling grate. The traveling grate stokers are sometimes classed as overfeed but properly should be classed by themselves as under certain conditions they are of the underfeed rather than the overfeed type. Overfeed Stokers in general may be divided into two classes, the distinction being in the direction in which the coal is fed relative to the furnaces. In one class the coal is fed into hoppers at the front end of the furnace onto grates with an inclination downward toward the rear of about 45 degrees. These grates are reciprocated, being made to take alternately level and inclined positions and this motion gradually carries the fuel as it is burned toward the rear and bottom of the furnace. At the bottom of the grates flat dumping sections are supplied for completing the combustion and for cleaning. The fuel is partly burned or coked on the upper portion of the grates, the volatile gases driven off in this process for a perfect action being ignited and burned in their passage over the bed of burning carbon lower on the grates, or on becoming mixed with the hot gases in the furnace chamber. In the second class the fuel is fed from the sides of the furnace for its full depth from front to rear onto grates inclined toward the center of the furnace. It is moved by rocking bars and is gradually carried to the bottom and center of the furnace as combustion advances. Here some type of a so-called clinker breaker removes the refuse. Underfeed Stokers are either horizontal or inclined. The fuel is fed from underneath, either continuously by a screw, or intermittently by plungers. The principle upon which these stokers base their claims for efficiency and smokelessness is that the green fuel is fed under the coked and burning coal, the volatile gases from this fresh fuel being heated and ignited in their passage through the hottest portion of the fire on the top. In the horizontal classes of underfeed stokers, the action of a screw carries the fuel back through a retort from which it passes upward, as the fuel above is consumed, the ash being finally deposited on dead plates on either side of the retort, from which it can be removed. In the inclined class, the refuse is carried downward to the rear of the furnace where there are dumping plates, as in some of the overfeed types. Underfeed stokers are ordinarily operated with a forced blast, this in some cases being operated by the same mechanism as the stoker drive, thus automatically meeting the requirements of various combustion rates. Traveling Grates are of the class best illustrated by chain grate stokers. As implied by the name these consist of endless grates composed of short sections of bars, passing over sprockets at the front and rear of the furnace. Coal is fed by gravity onto the forward end of the grates through suitable hoppers, is ignited under ignition arches and is carried with the grate toward the rear of the furnace as its combustion progresses. When operated properly, the combustion is completed as the fire reaches the end of the grate and the refuse is carried over this rear end by the grate in making the turn over the rear sprocket. In some cases auxiliary dumping grates at the rear of the chain grates are used with success. Chain grate stokers in general produce less smoke than either overfeed or underfeed types, due to the fact that there are no cleaning periods necessary. Such periods occur with the latter types of stokers at intervals depending upon the character of the fuel used and the rate of combustion. With chain grate stokers the cleaning is continuous and automatic, and no periods occur when smoke will necessarily be produced. In the earlier forms, chain grates had an objectionable feature in that the admission of large amounts of excess air at the rear of the furnace through the grates was possible. This objection has been largely overcome in recent models by the use of some such device as the bridge wall water box and suitable dampers. A distinct advantage of chain grates over other types is that they can be withdrawn from the furnace for inspection or repairs without interfering in any way with the boiler setting. This class of stoker is particularly successful in burning low grades of coal running high in ash and volatile matter which can only be burned with difficulty on the other types. The cost of up-keep in a chain grate, properly constructed and operated, is low in comparison with the same cost for other stokers. The Babcock & Wilcox chain grate is representative of this design of stoker. Smoke--The question of smoke and smokelessness in burning fuels has recently become a very important factor of the problem of combustion. Cities and communities throughout the country have passed ordinances relative to the quantities of smoke that may be emitted from a stack, and the failure of operators to live up to the requirements of such ordinances, resulting as it does in fines and annoyance, has brought their attention forcibly to the matter. The whole question of smoke and smokelessness is to a large extent a comparative one. There are any number of plants burning a wide variety of fuels in ordinary hand-fired furnaces, in extension furnaces and on automatic stokers that are operating under service conditions, practically without smoke. It is safe to say, however, that no plant will operate smokelessly under any and all conditions of service, nor is there a plant in which the degree of smokelessness does not depend largely upon the intelligence of the operating force. [Illustration: Fig. 26. Babcock & Wilcox Boiler and Superheater Equipped with Babcock & Wilcox Chain Grate Stoker. This Setting has been Particularly Successful in Minimizing Smoke] When a condition arises in a boiler room requiring the fires to be brought up quickly, the operatives in handling certain types of stokers will use their slice bars freely to break up the green portion of the fire over the bed of partially burned coal. In fact, when a load is suddenly thrown on a station the steam pressure can often be maintained only in this way, and such use of the slice bar will cause smoke with the very best type of stoker. In a certain plant using a highly volatile coal and operating boilers equipped with ordinary hand-fired furnaces, extension hand-fired furnaces and stokers, in which the boilers with the different types of furnaces were on separate stacks, a difference in smoke from the different types of furnaces was apparent at light loads, but when a heavy load was thrown on the plant, all three stacks would smoke to the same extent, and it was impossible to judge which type of furnace was on one or the other of the stacks. In hand-fired furnaces much can be accomplished by proper firing. A combination of the alternate and spreading methods should be used, the coal being fired evenly, quickly, lightly and often, and the fires worked as little as possible. Smoke can be diminished by giving the gases a long travel under the action of heated brickwork before they strike the boiler heating surfaces. Air introduced over the fires and the use of heated arches, etc., for mingling the air with the gases distilled from the coal will also diminish smoke. Extension furnaces will undoubtedly lessen smoke where hand firing is used, due to the increase in length of gas travel and the fact that this travel is partially under heated brickwork. Where hand-fired grates are immediately under the boiler tubes, and a high volatile coal is used, if sufficient combustion space is not provided the volatile gases, distilled as soon as the coal is thrown on the fire, strike the tube surfaces and are cooled below the burning point before they are wholly consumed and pass through as smoke. With an extension furnace, these volatile gases are acted upon by the radiant heat from the extension furnace arch and this heat, together with the added length of travel causes their more complete combustion before striking the heating surfaces than in the former case. Smoke may be diminished by employing a baffle arrangement which gives the gases a fairly long travel under heated brickwork and by introducing air above the fire. In many cases, however, special furnaces for smoke reduction are installed at the expense of capacity and economy. From the standpoint of smokelessness, undoubtedly the best results are obtained with a good stoker, properly operated. As stated above, the best stoker will cause smoke under certain conditions. Intelligently handled, however, under ordinary operating conditions, stoker-fired furnaces are much more nearly smokeless than those which are hand fired, and are, to all intents and purposes, smokeless. In practically all stoker installations there enters the element of time for combustion, the volatile gases as they are distilled being acted upon by ignition or other arches before they strike the heating surfaces. In many instances too, stokers are installed with an extension beyond the boiler front, which gives an added length of travel during which, the gases are acted upon by the radiant heat from the ignition or supplementary arches, and here again we see the long travel giving time for the volatile gases to be properly consumed. To repeat, it must be emphatically borne in mind that the question of smokelessness is largely one of degree, and dependent to an extent much greater than is ordinarily appreciated upon the handling of the fuel and the furnaces by the operators, be these furnaces hand fired or automatically fired. [Illustration: 3520 Horse-power Installation of Babcock & Wilcox Boilers at the Portland Railway, Light and Power Co., Portland, Ore. These Boilers are Equipped with Wood Refuse Extension Furnaces at the Front and Oil Burning Furnaces at the Mud Drum End] SOLID FUELS OTHER THAN COAL AND THEIR COMBUSTION Wood--Wood is vegetable tissue which has undergone no geological change. Usually the term is used to designate those compact substances familiarly known as tree trunks and limbs. When newly cut, wood contains moisture varying from 30 per cent to 50 per cent. When dried for a period of about a year in the atmosphere, the moisture content will be reduced to 18 or 20 per cent. TABLE 41 ULTIMATE ANALYSES AND CALORIFIC VALUES OF DRY WOOD (GOTTLIEB) _______________________________________________________ | | | | | | | | | Kind | | | | | | B. t. u.| | of | C | H | N | O | Ash | per | | Wood | | | | | | Pound | |________|_______|______|______|_______|______|_________| | | | | | | | | | Oak | 50.16 | 6.02 | 0.09 | 43.36 | 0.37 | 8316 | | Ash | 49.18 | 6.27 | 0.07 | 43.91 | 0.57 | 8480 | | Elm | 48.99 | 6.20 | 0.06 | 44.25 | 0.50 | 8510 | | Beech | 49.06 | 6.11 | 0.09 | 44.17 | 0.57 | 8391 | | Birch | 48.88 | 6.06 | 0.10 | 44.67 | 0.29 | 8586 | | Fir | 50.36 | 5.92 | 0.05 | 43.39 | 0.28 | 9063 | | Pine | 50.31 | 6.20 | 0.04 | 43.08 | 0.37 | 9153 | | Poplar | 49.37 | 6.21 | 0.96 | 41.60 | 1.86 | 7834[40]| | Willow | 49.96 | 5.96 | 0.96 | 39.56 | 3.37 | 7926[40]| |________|_______|______|______|_______|______|_________| Wood is usually classified as hard wood, including oak, maple, hickory, birch, walnut and beech; and soft wood, including pine, fir, spruce, elm, chestnut, poplar and willow. Contrary to general opinion, the heat value per pound of soft wood is slightly greater than the same value per pound of hard wood. Table 41 gives the chemical composition and the heat values of the common woods. Ordinarily the heating value of wood is considered equivalent to 0.4 that of bituminous coal. In considering the calorific value of wood as given in this table, it is to be remembered that while this value is based on air-dried wood, the moisture content is still about 20 per cent of the whole, and the heat produced in burning it will be diminished by this amount and by the heat required to evaporate the moisture and superheat it to the temperature of the gases. The heat so absorbed may be calculated by the formula giving the loss due to moisture in the fuel, and the net calorific value determined. In designing furnaces for burning wood, the question resolves itself into: 1st, the essential elements to give maximum capacity and efficiency with this class of fuel; and 2nd, the construction which will entail the least labor in handling and feeding the fuel and removing the refuse after combustion. Wood, as used commercially for steam generating purposes, is usually a waste product from some industrial process. At the present time refuse from lumber and sawmills forms by far the greater part of this class of fuel. In such refuse the moisture may run as high as 60 per cent and the composition of the fuel may vary over wide ranges during different portions of the mill operation. The fuel consists of sawdust, "hogged" wood and slabs, and the percentage of each of these constituents may vary greatly. Hogged wood is mill refuse and logs that have been passed through a "hogging machine" or macerator. This machine, through the action of revolving knives, cuts or shreds the wood into a state in which it may readily be handled as fuel. Table 42 gives the moisture content and heat value of typical sawmill refuse from various woods. TABLE 42 MOISTURE AND CALORIFIC VALUE OF SAWMILL REFUSE _____________________________________________________________________ | | | | | | | | Per Cent | B. t. u. | | Kind of Wood | Nature of Refuse | Moisture | per Pound | | | | | Dry Fuel | |_____________________|_______________________|__________|____________| | | | | | | Mexican White Pine | Sawdust and Hog Chips | 51.90 | 9020 | | Yosemite Sugar Pine | Sawdust and Hog Chips | 62.85 | 9010 | | Redwood 75%, | Sawdust, Box Mill | | | | Douglas Fir 25% | Refuse and Hog | 42.20 | 8977[41] | | Redwood | Sawdust and Hog Chips | 52.98 | 9040[41] | | Redwood | Sawdust and Hog Chips | 49.11 | 9204[41] | | Fir, Hemlock, | | | | | Spruce and Cedar | Sawdust | 42.06 | 8949[41] | |_____________________|_______________________|__________|____________| It is essential in the burning of this class of fuel that a large combustion space be supplied, and on account of the usually high moisture content there should be much heated brickwork to radiate heat to the fuel bed and thus evaporate the moisture. Extension furnaces of the proper size are usually essential for good results and when this fuel is used alone, grates dropped to the floor line with an ashpit below give additional volume for combustion and space for maintaining a thick fuel bed. A thick fuel bed is necessary in order to avoid excessive quantities of air passing through the boiler. Where the fuel consists of hogged wood and sawdust alone, it is best to feed it automatically into the furnace through chutes on the top of the extension. The best results are secured when the fuel is allowed to pile up in the furnace to a height of 3 or 4 feet in the form of a cone under each chute. The fuel burns best when not disturbed in the furnace. Each fuel chute, when a proper distance from the grates and with the piles maintained at their proper height, will supply about 30 or 35 square feet of grate surface. While large quantities of air are required for burning this fuel, excess air is as harmful as with coal, and care must be taken that such an excess is not admitted through fire doors or fuel chutes. A strong natural draft usually is preferable to a blast with this fuel. The action of blast is to make the regulation of the furnace conditions more difficult and to blow over unconsumed fuel on the heating surfaces and into the stack. This unconsumed fuel settling in portions of the setting out of the direct path of the gases will have a tendency to ignite provided any air reaches it, with results harmful to the setting and breeching connection. This action is particularly objectionable if these particles are carried over into the base of a stack, where they will settle below the point at which the flue enters and if ignited may cause the stack to become overheated and buckle. Whether natural draft or blast is used, much of the fuel is carried onto the heating surfaces and these should be cleaned regularly to maintain a good efficiency. Collecting chambers in various portions of the setting should be provided for this unconsumed fuel, and these should be kept clean. With proper draft conditions, 150 pounds of this fuel containing about 30 to 40 per cent of moisture can be burned per square foot of grate surface per hour, and in a properly designed furnace one square foot of grate surface can develop from 5 to 6 boiler horse power. Where the wood contains 50 per cent of moisture or over, it is not usually safe to figure on obtaining more than 3 to 4 horse power per square foot of grate surface. Dry sawdust, chips and blocks are also used as fuel in many wood-working industries. Here, as with the wet wood, ample combustion space should be supplied, but as this fuel is ordinarily kiln dried, large brickwork surfaces in the furnace are not necessary for the evaporation of moisture in the fuel. This fuel may be burned in extension furnaces though these are not required unless they are necessary to secure an added furnace volume, to get in sufficient grate surface, or where such an arrangement must be used to allow for a fuel bed of sufficient thickness. Depth of fuel bed with the dry fuel is as important as with the moist fuel. If extension furnaces are used with this dry wood, care must be taken in their design that there is no excessive throttling of the gases in the furnace, or brickwork trouble will result. In Babcock & Wilcox boilers this fuel may be burned without extension furnaces, provided that the boilers are set at a sufficient height to provide ample combustion space and to allow for proper depth of fuel bed. Sometimes this is gained by lowering the grates to the floor line and excavating for an ashpit. Where the fuel is largely sawdust, it may be introduced over the fire doors through inclined chutes. The old methods of handling and collecting sawdust by means of air suction and blast were such that the amount of air admitted through such chutes was excessive, but with improved methods the amount of air so admitted may be reduced to a negligible quantity. The blocks and refuse which cannot be handled through chutes may be fired through fire doors in the front of the boiler, which should be made sufficiently large to accommodate the larger sizes of fuel. As with wet fuel, there will be a quantity of unconsumed wood carried over and the heating surfaces must be kept clean. In a few localities cord wood is burned. With this as with other classes of wood fuel, a large combustion space is an essential feature. The percentage of moisture in cord wood may make it necessary to use an extension furnace, but ordinarily this is not required. Ample combustion space is in most cases secured by dropping the grates to the floor line, large double-deck fire doors being supplied at the usual fire door level through which the wood is thrown by hand. Air is admitted under the grates through an excavated ashpit. The side, front and rear walls of the furnace should be corbelled out to cover about one-third of the total grate surface. This prevents cold air from laneing up the sides of the furnace and also reduces the grate surface. Cord wood and slabs form an open fire through which the frictional loss of the air is much less than in the case of sawdust or hogged material. The combustion rate with cord wood is, therefore, higher and the grate surface may be considerably reduced. Such wood is usually cut in lengths of 4 feet or 4 feet 6 inches, and the depth of the grates should be kept approximately 5 feet to get the best results. Bagasse--Bagasse is the refuse of sugar cane from which the juice has been extracted by pressure between the rolls of the mill. From the start of the sugar industry bagasse has been considered the natural fuel for sugar plantations, and in view of the importance of the industry a word of history relative to the use of this fuel is not out of place. When the manufacture of sugar was in its infancy the cane was passed through but a single mill and the defecation and concentration of the saccharine juice took place in a series of vessels mounted one after another over a common fire at one end and connected to a stack at the opposite end. This primitive method was known in the English colonies as the "Open Wall" and in the Spanish-American countries as the "Jamaica Train". The evaporation and concentration of the juice in the open air and over a direct fire required such quantities of fuel, and the bagasse, in fact, played such an important part in the manufacture of sugar, that oftentimes the degree of extraction, which was already low, would be sacrificed to the necessity of obtaining a bagasse that might be readily burned. The furnaces in use with these methods were as primitive as the rest of the apparatus, and the bagasse could be burned in them only by first drying it. This naturally required an enormous quantity of handling of the fuel in spreading and collecting and frequently entailed a shutting down of the mill, because a shower would spoil the supply which had been dried. The difficulties arising from the necessity of drying this fuel caused a widespread attempt on the part of inventors to the turning out of a furnace which would successfully burn green bagasse. Some of the designs were more or less clever, and about the year 1880 several such green bagasse furnaces were installed. These did not come up to expectations, however, and almost invariably they were abandoned and recourse had to be taken to the old method of drying in the sun. From 1880 the new era in the sugar industry may be dated. Slavery was almost universally abolished and it became necessary to pay for labor. The cost of production was thus increased, while growing competition of European beet sugar lowered the prices. The only remedy for the new state of affairs was the cheapening of the production by the increase of extraction and improvement in manufacture. The double mill took the place of the single, the open wall method of extraction was replaced by vacuum evaporative apparatus and centrifugal machines were introduced to do the work of the great curing houses. As opposed to these improvements, however, the steam plants remained as they started, consisting of double flue boilers externally fired with dry bagasse. On several of the plantations horizontal multitubular boilers externally fired were installed and at the time were considered the acme of perfection. Numerous attempts were made to burn the bagasse green, among others the step grates imported from Louisiana and known as the Leon Marie furnaces, but satisfactory results were obtained in none of the appliances tried. The Babcock & Wilcox Co. at this time turned their attention to the problem with the results which ultimately led to its solution. Their New Orleans representative, Mr. Frederick Cook, invented a hot forced blast bagasse furnace and conveyed the patent rights to this company. This furnace while not as efficient as the standard of to-day, and expensive in its construction, did, nevertheless, burn the bagasse green and enabled the boilers to develop their normal rated capacity. The first furnace of this type was installed at the Southwood and Mt. Houmas plantations and on a small plantation in Florida. About the year 1888 two furnaces were erected in Cuba, one on the plantation Senado and the other at the Central Hormiguero. The results obtained with these furnaces were so remarkable in comparison with what had previously been accomplished that the company was overwhelmed with orders. The expense of auxiliary fuel, usually wood, which was costly and indispensable in rainy weather, was done away with and as the mill could be operated on bagasse alone, the steam production and the factory work could be regulated with natural increase in daily output. Progress and improvement in the manufacture itself was going on at a remarkable rate, the single grinding had been replaced by a double grinding, this in turn by a third grinding, and finally the maceration and dilution of the bagasse was carried to the extraction of practically the last trace of sugar contained in it. The quantity of juice to be treated was increased in this way 20 or 30 per cent but was accompanied by the reduction to a minimum of the bagasse available as a fuel, and led to demands upon the furnace beyond its capacity. With the improvements in the manufacture, planters had been compelled to make enormous sacrifices to change radically their systems, and the heavy disbursement necessary for mill apparatus left few in a financial position to make costly installations of good furnaces. The necessity of turning to something cheap in furnace construction but which was nevertheless better than the early method of burning the fuel dry led to the invention of numerous furnaces by all classes of engineers regardless of their knowledge of the subject and based upon no experience. None of the furnaces thus produced were in any sense inventions but were more or less barefaced infringements of the patents of The Babcock & Wilcox Co. As the company could not protect its rights without hurting its clients, who in many cases against their own will were infringing upon these patents, and as on the other hand they were anxious to do something to meet the wants of the planters, a series of experiments were started, at their own rather than at their customers' expense, with a view to developing a furnace which, without being as expensive, would still fulfill all the requirements of the manufacturer. The result was the cold blast green bagasse furnace which is now offered, and it has been adopted as standard for this class of work after years of study and observation in our installations in the sugar countries of the world. Such a furnace is described later in considering the combustion of bagasse. Composition and Calorific Value of Bagasse--The proportion of fiber contained in the cane and density of the juice are important factors in the relation the bagasse fuel will have to the total fuel necessary to generate the steam required in a mill's operation. A cane rich in wood fiber produces more bagasse than a poor one and a thicker juice is subject to a higher degree of dilution than one not so rich. Besides the percentage of bagasse in the cane, its physical condition has a bearing on its calorific value. The factors here entering are the age at which the cane must be cut, the locality in which it is grown, etc. From the analysis of any sample of bagasse its approximate calorific value may be calculated from the formula, 8550F + 7119S + 6750G - 972W B. t. u. per pound bagasse = ---------------------------- (22) 100 Where F = per cent of fiber in cane, S = per cent sucrose, G = per cent glucose, W = per cent water. This formula gives the total available heat per pound of bagasse, that is, the heat generated per pound less the heat required to evaporate its moisture and superheat the steam thus formed to the temperature of the stack gases. Three samples of bagasse in which the ash is assumed to be 3 per cent give from the formula: F = 50 S and G = 4.5 W = 42.5 B. t. u. = 4183 F = 40 S and G = 6.0 W = 51.0 B. t. u. = 3351 F = 33.3 S and G = 7.0 W = 56.7 B. t. u. = 2797 A sample of Java bagasse having F = 46.5, S = 4.50, G = 0.5, W = 47.5 gives B. t. u. 3868. These figures show that the dryer the bagasse is crushed, the higher the calorific value, though this is accompanied by a decrease in sucrose. The explanation lies in the fact that the presence of sucrose in an analysis is accompanied by a definite amount of water, and that the residual juice contains sufficient organic substance to evaporate the water present when a fuel is burned in a furnace. For example, assume the residual juice (100 per cent) to contain 12 per cent organic matter. From the constant in formula, 12×7119 (100-12)×972 ------- = 854.3 and ------------ = 855.4. 100 100 That is, the moisture in a juice containing 12 per cent of sugar will be evaporated by the heat developed by the combustion of the contained sugar. It would, therefore, appear that a bagasse containing such juice has a calorific value due only to its fiber content. This is, of course, true only where the highest products of oxidization are formed during the combustion of the organic matter. This is not strictly the case, especially with a bagasse of a high moisture content which will not burn properly but which smoulders and produces a large quantity of products of destructive distillation, chiefly heavy hydrocarbons, which escape unburnt. The reasoning, however, is sufficient to explain the steam making properties of bagasse of a low sucrose content, such as are secured in Java, as when the sucrose content is lower, the heat value is increased by extracting more juice, and hence more sugar from it. The sugar operations in Java exemplify this and show that with a high dilution by maceration and heavy pressure the bagasse meets all of the steam requirements of the mills without auxiliary fuel. A high percentage of silica or salts in bagasse has sometimes been ascribed as the reason for the tendency to smoulder in certain cases of soft fiber bagasse. This, however, is due to the large moisture content of the sample resulting directly from the nature of the cane. Soluble salts in the bagasse has also been given as the explanation of such smouldering action of the fire, but here too the explanation lies solely in the high moisture content, this resulting in the development of only sufficient heat to evaporate the moisture. TABLE 43 ANALYSES AND CALORIFIC VALUES OF BAGASSE +---------------------------------------------------------------------+ |+----------+--------+-------+-------+-------+-------+-------+-------+| || | | | | | | |B.t.u. || || | | | | | | | per || || Source |Moisture| C | H | O | N | Ash | Pound || || | | | | | | | Dry || || | | | | | | |Bagasse|| |+----------+--------+-------+-------+-------+-------+-------+-------+| ||Cuba | 51.50 | 43.15 | 6.00 | 47.95 | | 2.90 | 7985 || ||Cuba | 49.10 | 43.74 | 6.08 | 48.61 | | 1.57 | 8300 || ||Cuba | 42.50 | 43.61 | 6.06 | 48.45 | | 1.88 | 8240 || ||Cuba | 51.61 | 46.80 | 5.34 | 46.35 | | 1.51 | || ||Cuba | 52.80 | 46.78 | 5.74 | 45.38 | | 2.10 | || ||Porto Rico| 41.60 | 44.28 | 6.66 | 47.10 | 0.41 | 1.35 | 8359 || ||Porto Rico| 43.50 | 44.21 | 6.31 | 47.72 | 0.41 | 1.35 | 8386 || ||Porto Rico| 44.20 | 44.92 | 6.27 | 46.50 | 0.41 | 1.90 | 8380 || ||Louisiana | 52.10 | | | | | 2.27 | 8230 || ||Louisiana | 54.00 | | | | | | 8370 || ||Louisiana | 51.80 | | | | | | 8371 || ||Java | | 46.03 | 6.56 | 45.55 | 0.18 | 1.68 | 8681 || |+----------+--------+-------+-------+-------+-------+-------+-------+| +---------------------------------------------------------------------+ Table 43 gives the analyses and heat values of bagasse from various localities. Table 44 gives the value of mill bagasse at different extractions, which data may be of service in making approximations as to its fuel value as compared with that of other fuels. TABLE 44 VALUE OF ONE POUND OF MILL BAGASSE AT DIFFERENT EXTRACTIONS 1: Per Cent Extraction of Weight of Cane 2: Per Cent Moisture in Bagasse 3: Per Cent in Bagasse 4: Fuel Value, B. t. u. 5: Per Cent in Bagasse 6: Fuel Value, B. t. u. 7: Per Cent in Bagasse 8: Fuel Value, B. t. u. 9: Total Heat Developed per Pound of Bagasse 10: Heat Required to Evaporate Moisture[42] 11: Heat Available for Steam Generation 12: Pounds of Bagasse Equivalent to one Pound of Coal of 14,000 B. t. u. +----------------------------------------------------------------+ |+---+-----+----------+---------+---------+----------------+----+| || | | | | |B.t.u. Value per| || || | | Fiber | Sugar |Molasses |Pound of Bagasse| || || | +-----+----+----+----+----+----+-----+----+-----+ || || | | | | | | | | | | | || || 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 || |+---+-----+-----+----+----+----+----+----+-----+----+-----+----+| || BASED UPON CANE OF 12 PER CENT FIBER AND JUICE CONTAINING || ||18 PER CENT OF SOLID MATTER. REPRESENTING TROPICAL CONDITIONS || |+---+-----+-----+----+----+----+----+----+-----+----+-----+----+| ||75 |42.64|48.00|3996|6.24|451 |3.12|217 |4664 |525 |4139 |3.38|| ||77 |39.22|52.17|4343|5.74|414 |2.87|200 |4958 |483 |4475 |3.13|| ||79 |35.15|57.14|4757|5.14|371 |2.57|179 |5307 |433 |4874 |2.87|| ||81 |30.21|63.16|5258|4.42|319 |2.21|154 |5731 |372 |5359 |2.61|| ||83 |24.12|70.59|5877|3.53|256 |1.76|122 |6255 |297 |5958 |2.35|| ||85 |16.20|80.00|6660|2.40|173 |1.20| 83 |6916 |200 |6716 |2.08|| |+---+-----+-----+----+----+----+----+----+-----+----+-----+----+| || BASED UPON CANE OF 10 PER CENT FIBER AND JUICE CONTAINING || ||15 PER CENT OF SOLID MATTER. REPRESENTING LOUISIANA CONDITIONS|| |+---+-----+-----+----+----+----+----+----+-----+----+-----+----+| ||75 |51.00|40.00|3330|6.00|433 |3.00|209 |3972 |678 |3294 |4.25|| ||77 |48.07|43.45|3617|5.66|409 |2.82|196 |4222 |592 |3630 |3.86|| ||79 |44.52|47.62|3964|5.24|378 |2.62|182 |4524 |548 |3976 |3.52|| ||81 |40.18|52.63|4381|4.73|342 |2.36|164 |4887 |495 |4392 |3.19|| ||83 |35.00|58.82|4897|4.12|298 |2.06|143 |5436 |431 |5005 |2.80|| ||85 |28.33|66.67|5550|3.33|241 |1.67|116 |5907 |349 |5558 |2.52|| |+---+-----+-----+----+----+----+----+----+-----+----+-----+----+| +----------------------------------------------------------------+ Furnace Design and the Combustion of Bagasse--With the advance in sugar manufacture there came, as described, a decrease in the amount of bagasse available for fuel. As the general efficiency of a plant of this description is measured by the amount of auxiliary fuel required per ton of cane, the relative importance of the furnace design for the burning of this fuel is apparent. In modern practice, under certain conditions of mill operation, and with bagasse of certain physical properties, the bagasse available from the cane ground will meet the total steam requirements of the plant as a whole; such conditions prevail, as described, in Java. In the United States, Cuba, Porto Rico and like countries, however, auxiliary fuel is almost universally a necessity. The amount will vary, depending to a great extent upon the proportion of fiber in the cane, which varies widely with the locality and with the age at which it is cut, and to a lesser extent upon the degree of purity of the manufactured sugar, the use of the maceration water and the efficiency of the mill apparatus as a whole. [Illustration: Fig. 27. Babcock & Wilcox Boiler Set with Green Bagasse Furnace] Experience has shown that this fuel may be burned with the best results in large quantities. A given amount of bagasse burned in one furnace between two boilers will give better results than the same quantity burned in a number of smaller furnaces. An objection has been raised against such practice on the grounds that the necessity of shutting down two boiler units when it is necessary for any reason to take off a furnace, requires a larger combined boiler capacity to insure continuity of service. As a matter of fact, several small furnaces will cost considerably more than one large furnace, and the saving in original furnace cost by such an installation, taken in conjunction with the added efficiency of the larger furnace over the small, will probably more than offset the cost of additional boiler units for spares. The essential features in furnace design for this class of fuel are ample combustion space and a length of gas travel sufficient to enable the gases to be completely burned before the boiler heating surfaces are encountered. Experience has shown that better results are secured where the fuel is burned on a hearth rather than on grates, the objection to the latter method being that the air for combustion enters largely around the edges, where the fuel pile is thinnest. When burned on a hearth the air for combustion is introduced into the furnace through several rows of tuyeres placed above and symmetrically around the hearth. An arrangement of such tuyeres over a grate, and a proper manipulation of the ashpit doors, will overcome largely the objection to grates and at the same time enable other fuel to be burned in the furnace when necessary. This arrangement of grates and tuyeres is probably the better from a commercially efficient standpoint. Where the air is admitted through tuyeres over the grate or hearth line, it impinges on the fuel pile as a whole and causes a uniform combustion. Such tuyeres connect with an annular space in which, where a blast is used, the air pressure is controlled by a blower. All experience with this class of fuel indicates that the best results are secured with high combustion rates. With a natural draft in the furnace of, say, three-tenths inch of water, a combustion rate of from 250 to 300 pounds per square foot of grate surface per hour may be obtained. With a blast of, say, five-tenths inch of water, this rate can be increased to 450 pounds per square foot of grate surface per hour. These rates apply to bagasse as fired containing approximately 50 per cent of moisture. It would appear that the most economical results are secured with a combustion rate of approximately 300 pounds per square foot per hour which, as stated, may be obtained with natural draft. Where a natural draft is available sufficient to give such a rate, it is in general to be preferred to a blast. Fig. 27 shows a typical bagasse furnace with which very satisfactory results have been obtained. The design of this furnace may be altered to suit the boilers to which it is connected. It may be changed slightly in its proportions and in certain instances in its position relative to the boiler. The furnace as shown is essentially a bagasse furnace and may be modified somewhat to accommodate auxiliary fuel. The fuel is ignited in a pit A on a hearth which is ordinarily elliptical in shape. Air for combustion is admitted through the tuyeres B connected to an annular space C through which the amount of air is controlled. Above the pit the furnace widens out to form a combustion space D which has a cylindrical or spherical roof with its top ordinarily from 11 to 13 feet above the floor. The gases pass from this space horizontally to a second combustion chamber E from which they are led through arches F to the boiler. The arrangement of such arches is modified to suit the boiler or boilers with which the furnace is operated. A furnace of such design embodies the essential features of ample combustion space and long gas travel. The fuel should be fed to the furnace through an opening in the roof above the pit by some mechanical means which will insure a constant fuel feed and at the same time prevent the inrush of cold air into the furnace. This class of fuel deposits a considerable quantity of dust, which if not removed promptly will fuse into a hard glass-like clinker. Ample provision should be made for the removal of such dust from the furnace, the gas ducts and the boiler setting, and these should be thoroughly cleaned once in 24 hours. Table 45 gives the results of several tests on Babcock & Wilcox boilers using fuel of this character. TABLE 45 TESTS OF BABCOCK & WILCOX BOILERS WITH GREEN BAGASSE ____________________________________________________________________ | Duration of Test | Hours | 12 | 10 | 10 | 10 | | Rated Capacity of Boiler |Horse Power| 319 | 319 | 319 | 319 | | Grate Surface |Square Feet| 33 | 33 | 16.5 | 16.5 | | Draft in Furnace | Inches | .30 | .28 | .29 | .27 | | Draft at Damper | Inches | .47 | .45 | .46 | .48 | | Blast under Grates | Inches | ... | ... | ... | .34 | | Temperature of Exit Gases | Degrees F.| 536 | 541 | 522 | 547 | | /CO_{2} | Per Cent | 13.8 | 12.6 | 11.7 | 12.8 | | Flue Gas Analysis { O | Per Cent | 5.9 | 7.6 | 8.2 | 6.9 | | \CO | Per Cent | 0.0 | 0.0 | 0.0 | 0.0 | | Bagasse per Hour as Fired | Pounds | 4980 | 4479 | 5040 | 5586 | | Moisture in Bagasse | Per Cent |52.39 |52.93 |51.84 |51.71 | | Dry Bagasse per Hour | Pounds | 2371 | 2108 | 2427 | 2697 | | Dry Bagasse per Square Foot| | | | | | | of Grate Surface per Hour| Pounds | 71.9 | 63.9 |147.1 |163.4 | | Water per Hour from and at | | | | | | | 212 Degrees | Pounds |10141 | 9850 |10430 |11229 | | Per Cent of Rated Capacity | | | | | | | Developed | Per Cent | 92.1 | 89.2 | 94.7 |102.0 | |____________________________|___________|______|______|______|______| Tan Bark--Tan bark, or spent tan, is the fibrous portion of bark remaining after use in the tanning industry. It is usually very high in its moisture content, a number of samples giving an average of 65 per cent or about two-thirds of the total weight of the fuel. The weight of the spent tan is about 2.13 times as great as the weight of the bark ground. In calorific value an average of 10 samples gives 9500 B. t. u. per pound dry.[43] The available heat per pound as fired, owing to the great percentage of moisture usually found, will be approximately 2700 B. t. u. Since the weight of the spent tan as fired is 2.13 as great as the weight of the bark as ground at the mill, one pound of ground bark produces an available heat of approximately 5700 B. t. u. Relative to bituminous coal, a ton of bark is equivalent to 0.4 ton of coal. An average chemical analysis of the bark is, carbon 51.8 per cent, hydrogen 6.04, oxygen 40.74, ash 1.42. Tan bark is burned in isolated cases and in general the remarks on burning wet wood fuel apply to its combustion. The essential features are a large combustion space, large areas of heated brickwork radiating to the fuel bed, and draft sufficient for high combustion rates. The ratings obtainable with this class of fuel will not be as high as with wet wood fuel, because of the heat value and the excessive moisture content. Mr. D. M. Meyers found in a series of experiments that an average of from 1.5 to 2.08 horse power could be developed per square foot of grate surface with horizontal return tubular boilers. This horse power would vary considerably with the method in which the spent tan was fired. [Illustration: 686 Horse-power Babcock & Wilcox Boiler and Superheater in Course of Erection at the Quincy, Mass., Station of the Bay State Street Railway Co.] LIQUID FUELS AND THEIR COMBUSTION Petroleum is practically the only liquid fuel sufficiently abundant and cheap to be used for the generation of steam. It possesses many advantages over coal and is extensively used in many localities. There are three kinds of petroleum in use, namely those yielding on distillation: 1st, paraffin; 2nd, asphalt; 3rd, olefine. To the first group belong the oils of the Appalachian Range and the Middle West of the United States. These are a dark brown in color with a greenish tinge. Upon their distillation such a variety of valuable light oils are obtained that their use as fuel is prohibitive because of price. To the second group belong the oils found in Texas and California. These vary in color from a reddish brown to a jet black and are used very largely as fuel. The third group comprises the oils from Russia, which, like the second, are used largely for fuel purposes. The light and easily ignited constituents of petroleum, such as naphtha, gasolene and kerosene, are oftentimes driven off by a partial distillation, these products being of greater value for other purposes than for use as fuel. This partial distillation does not decrease the value of petroleum as a fuel; in fact, the residuum known in trade as "fuel oil" has a slightly higher calorific value than petroleum and because of its higher flash point, it may be more safely handled. Statements made with reference to petroleum apply as well to fuel oil. In general crude oil consists of carbon and hydrogen, though it also contains varying quantities of moisture, sulphur, nitrogen, arsenic, phosphorus and silt. The moisture contained may vary from less than 1 to over 30 per cent, depending upon the care taken to separate the water from the oil in pumping from the well. As in any fuel, this moisture affects the available heat of the oil, and in contracting for the purchase of fuel of this nature it is well to limit the per cent of moisture it may contain. A large portion of any contained moisture can be separated by settling and for this reason sufficient storage capacity should be supplied to provide time for such action. A method of obtaining approximately the percentage of moisture in crude oil which may be used successfully, particularly with lighter oils, is as follows. A burette graduated into 200 divisions is filled to the 100 mark with gasolene, and the remaining 100 divisions with the oil, which should be slightly warmed before mixing. The two are then shaken together and any shrinkage below the 200 mark filled up with oil. The mixture should then be allowed to stand in a warm place for 24 hours, during which the water and silt will settle to the bottom. Their percentage by volume can then be correctly read on the burette divisions, and the percentage by weight calculated from the specific gravities. This method is exceedingly approximate and where accurate results are required it should not be used. For such work, the distillation method should be used as follows: Gradually heat 100 cubic centimeters of the oil in a distillation flask to a temperature of 150 degrees centigrade; collect the distillate in a graduated tube and measure the resulting water. Such a method insures complete removal of water and reduces the error arising from the slight solubility of the water in gasolene. Two samples checked by the two methods for the amount of moisture present gave, _Distillation_ _Dilution_ _Per Cent_ _Per Cent_ 8.71 6.25 8.82 6.26 TABLE 46 COMPOSITION AND CALORIFIC VALUE OF VARIOUS OILS +-------------------------+-----+-----+----+--------+----+---+--------+-----+------------------------+ | Kind of Oil | %C | %H | %S | %O |S.G.|FP | %H2O |Btu |Authority | +-------------------------+-----+-----+----+--------+----+---+--------+-----+------------------------+ |California, Coaling | | | | |.927|134| |17117|Babcock & Wilcox Co. | |California, Bakersfield | | | | |.975| | |17600|Wade | |California, Bakersfield | | |1.30| |.992| | |18257|Wade | |California, Kern River | | | | |.950|140| |18845|Babcock & Wilcox Co. | |California, Los Angeles | | |2.56| | | | |18328|Babcock & Wilcox Co. | |California, Los Angeles | | | | |.957|196| |18855|Babcock & Wilcox Co. | |California, Los Angeles | | | | |.977| | .40 |18280|Babcock & Wilcox Co. | |California, Monte Christo| | | | |.966|205| |18878|Babcock & Wilcox Co. | |California, Whittier | | | .98| |.944| |1.06 |18507|Wade | |California, Whittier | | | .72| |.936| |1.06 |18240|Wade | |California |85.04|11.52|2.45| .99[44]| | |1.40 |17871|Babcock & Wilcox Co. | |California |81.52|11.51| .55|6.92[44]| |230| |18667|U.S.N. Liquid Fuel Board| |California | | | .87| | | | .95 |18533|Blasdale | |California | | | | |.891|257| |18655|Babcock & Wilcox Co. | |California | | |2.45| |.973| |1.50[45]|17976|O'Neill | |California | | |2.46| |.975| |1.32 |18104|Shepherd | |Texas, Beaumont |84.6 |10.9 |1.63|2.87 |.924|180| |19060|U.S.N. Liquid Fuel Board| |Texas, Beaumont |83.3 |12.4 | .50|3.83 |.926|216| |19481|U.S.N. Liquid Fuel Board| |Texas, Beaumont |85.0 |12.3 |1.75| .92[44]| | | |19060|Denton | |Texas, Beaumont |86.1 |12.3 |1.60| |.942| | |20152|Sparkes | |Texas, Beaumont | | | | |.903|222| |19349|Babcock & Wilcox Co. | |Texas, Sabine | | | | |.937|143| |18662|Babcock & Wilcox Co. | |Texas |87.15|12.33|0.32| |.908|370| |19338|U. S. N. | |Texas |87.29|12.32|0.43| |.910|375| |19659|U. S. N. | |Ohio |83.4 |14.7 |0.6 |1.3 | | | |19580| | |Pennsylvania |84.9 |13.7 | |1.4 |.886| | |19210|Booth | |West Virginia |84.3 |14.1 | |1.6 |.841| | |21240| | |Mexico | | | | |.921|162| |18840|Babcock & Wilcox Co. | |Russia, Baku |86.7 |12.9 | | |.884| | |20691|Booth | |Russia, Novorossick |84.9 |11.6 | |3.46 | | | |19452|Booth | |Russia, Caucasus |86.6 |12.3 | |1.10 |.938| | |20138| | |Java |87.1 |12.0 | | .9 |.923| | |21163| | |Austria, Galicia |82.2 |12.1 |5.7 | |.870| | |18416| | |Italy, Parma |84.0 |13.4 |1.8 | |.786| | | | | |Borneo |85.7 |11.0 | |3.31 | | | |19240|Orde | +-------------------------+-----+-----+----+--------+----+---+--------+-----+------------------------+ %C = Per Cent Carbon %H = Per Cent Hydrogen %S = Per Cent Sulphur %O = Per Cent Oxygen S.G. = Specific Gravity FP = Degrees Flash Point %H_{2}O = Per Cent Moisture Btu = B. t. u. Per Pound Calorific Value--A pound of petroleum usually has a calorific value of from 18,000 to 22,000 B. t. u. If an ultimate analysis of an average sample be, carbon 84 per cent, hydrogen 14 per cent, oxygen 2 per cent, and assuming that the oxygen is combined with its equivalent of hydrogen as water, the analysis would become, carbon 84 per cent, hydrogen 13.75 per cent, water 2.25 per cent, and the heat value per pound including its contained water would be, Carbon .8400 × 14,600 = 12,264 B. t. u. Hydrogen .1375 × 62,100 = 8,625 B. t. u. ------[**Should be .1375 x 62,000 = 8,525] Total 20,889 B. t. u.[**Would be Total = 20,789] The nitrogen in petroleum varies from 0.008 to 1.0 per cent, while the sulphur varies from 0.07 to 3.0 per cent. Table 46, compiled from various sources, gives the composition, calorific value and other data relative to oil from different localities. The flash point of crude oil is the temperature at which it gives off inflammable gases. While information on the actual flash points of the various oils is meager, it is, nevertheless, a question of importance in determining their availability as fuels. In general it may be stated that the light oils have a low, and the heavy oils a much higher flash point. A division is sometimes made at oils having a specific gravity of 0.85, with a statement that where the specific gravity is below this point the flash point is below 60 degrees Fahrenheit, and where it is above, the flash point is above 60 degrees Fahrenheit. There are, however, many exceptions to this rule. As the flash point is lower the danger of ignition or explosion becomes greater, and the utmost care should be taken in handling the oils with a low flash point to avoid this danger. On the other hand, because the flash point is high is no justification for carelessness in handling those fuels. With proper precautions taken, in general, the use of oil as fuel is practically as safe as the use of coal. Gravity of Oils--Oils are frequently classified according to their gravity as indicated by the Beaume hydrometer scale. Such a classification is by no means an accurate measure of their relative calorific values. Petroleum as Compared with Coal--The advantages of the use of oil fuel over coal may be summarized as follows: 1st. The cost of handling is much lower, the oil being fed by simple mechanical means, resulting in, 2nd. A general labor saving throughout the plant in the elimination of stokers, coal passers, ash handlers, etc. 3rd. For equal heat value, oil occupies very much less space than coal. This storage space may be at a distance from the boiler without detriment. 4th. Higher efficiencies and capacities are obtainable with oil than with coal. The combustion is more perfect as the excess air is reduced to a minimum; the furnace temperature may be kept practically constant as the furnace doors need not be opened for cleaning or working fires; smoke may be eliminated with the consequent increased cleanliness of the heating surfaces. 5th. The intensity of the fire can be almost instantaneously regulated to meet load fluctuations. 6th. Oil when stored does not lose in calorific value as does coal, nor are there any difficulties arising from disintegration, such as may be found when coal is stored. 7th. Cleanliness and freedom from dust and ashes in the boiler room with a consequent saving in wear and tear on machinery; little or no damage to surrounding property due to such dust. The disadvantages of oil are: 1st. The necessity that the oil have a reasonably high flash point to minimize the danger of explosions. 2nd. City or town ordinances may impose burdensome conditions relative to location and isolation of storage tanks, which in the case of a plant situated in a congested portion of the city, might make use of this fuel prohibitive. 3rd. Unless the boilers and furnaces are especially adapted for the use of this fuel, the boiler upkeep cost will be higher than if coal were used. This objection can be entirely obviated, however, if the installation is entrusted to those who have had experience in the work, and the operation of a properly designed plant is placed in the hands of intelligent labor. TABLE 47 RELATIVE VALUE OF COAL AND OIL FUEL +------+--------+-------+-----------------------------------------------+ |Gross | Net | Net | Water Evaporated from and at | |Boiler| Boiler |Evap- | 212 Degrees Fahrenheit per Pound of Coal | |Effic-|Effici- |oration+-----+-----+-----+-----+-----+-----+-----+-----+ | iency|ency[46]| from | | | | | | | | | | with | with |and at | | | | | | | | | | Oil | Oil | 212 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | | Fuel | Fuel |Degrees| | | | | | | | | | | |Fahren-| | | | | | | | | | | | heit +-----+-----+-----+-----+-----+-----+-----+-----+ | | | per | | | | | Pound | Pounds of Oil Equal to One Pound of Coal | | | |of Oil | | +------+--------+-------+-----+-----+-----+-----+-----+-----+-----+-----+ | 73 | 71 | 13.54 |.3693|.4431|.5170|.5909|.6647|.7386|.8124|.8863| | 74 | 72 | 13.73 |.3642|.4370|.5099|.5827|.6556|.7283|.8011|.8740| | 75 | 73 | 13.92 |.3592|.4310|.5029|.5747|.6466|.7184|.7903|.8621| | 76 | 74 | 14.11 |.3544|.4253|.4961|.5670|.6378|.7087|.7796|.8505| | 77 | 75 | 14.30 |.3497|.4196|.4895|.5594|.6294|.6993|.7692|.8392| | 78 | 76 | 14.49 |.3451|.4141|.4831|.5521|.6211|.6901|.7591|.8281| | 79 | 77 | 14.68 |.3406|.4087|.4768|.5450|.6131|.6812|.7493|.8174| | 80 | 78 | 14.87 |.3363|.4035|.4708|.5380|.6053|.6725|.7398|.8070| | 81 | 79 | 15.06 |.3320|.3984|.4648|.5312|.5976|.6640|.7304|.7968| | 82 | 80 | 15.25 |.3279|.3934|.4590|.5246|.5902|.6557|.7213|.7869| | 83 | 81 | 15.44 |.3238|.3886|.4534|.5181|.5829|.6447|.7125|.7772| +------+--------+-------+-----+-----+-----+-----+-----+-----+-----+-----+ | | | Net | | | | |Evap- | | | | |oration| | | | | from | | | | |and at | | | | | 212 | Barrels of Oil Equal to One Ton of Coal | | | |Degrees| | | | |Fahren-| | | | | heit | | | | | per | | | | |Barrel | | | | |of Oil | | +------+--------+-------+-----+-----+-----+-----+-----+-----+-----+-----+ | 73 | 71 | 4549 |2.198|2.638|3.077|3.516|3.955|4.395|4.835|5.275| | 74 | 72 | 4613 |2.168|2.601|3.035|3.468|3.902|4.335|4.769|5.202| | 75 | 73 | 4677 |2.138|2.565|2.993|3.420|3.848|4.275|4.703|5.131| | 76 | 74 | 4741 |2.110|2.532|2.954|3.376|3.798|4.220|4.642|5.063| | 77 | 75 | 4807 |2.082|2.498|2.914|3.330|3.746|4.162|4.578|4.994| | 78 | 76 | 4869 |2.054|2.465|2.876|3.286|3.697|4.108|4.518|4.929| | 79 | 77 | 4932 |2.027|2.433|2.838|3.243|3.649|4.054|4.460|4.865| | 80 | 78 | 4996 |2.002|2.402|2.802|3.202|3.602|4.003|4.403|4.803| | 81 | 79 | 5060 |1.976|2.371|2.767|3.162|3.557|3.952|4.348|4.743| | 82 | 80 | 5124 |1.952|2.342|2.732|3.122|3.513|3.903|4.293|4.683| | 83 | 81 | 5187 |1.927|2.313|2.699|3.085|3.470|3.856|4.241|4.627| +------+--------+-------+-----+-----+-----+-----+-----+-----+-----+-----+ [Illustration: City of San Francisco, Cal., Fire Fighting Station. No. 1. 2800 Horse Power of Babcock & Wilcox Boilers, Equipped for Burning Oil Fuel] Many tables have been published with a view to comparing the two fuels. Such of these as are based solely on the relative calorific values of oil and coal are of limited value, inasmuch as the efficiencies to be obtained with oil are higher than that obtainable with coal. Table 47 takes into consideration the variation in efficiency with the two fuels, but is based on a constant calorific value for oil and coal. This table, like others of a similar nature, while useful as a rough guide, cannot be considered as an accurate basis for comparison. This is due to the fact that there are numerous factors entering into the problem which affect the saving possible to a much greater extent than do the relative calorific values of two fuels. Some of the features to be considered in arriving at the true basis for comparison are the labor saving possible, the space available for fuel storage, the facilities for conveying the oil by pipe lines, the hours during which a plant is in operation, the load factor, the quantity of coal required for banking fires, etc., etc. The only exact method of estimating the relative advantages and costs of the two fuels is by considering the operating expenses of the plant with each in turn, including the costs of every item entering into the problem. Burning Oil Fuel--The requirements for burning petroleum are as follows: 1st. Its atomization must be thorough. 2nd. When atomized it must be brought into contact with the requisite quantity of air for its combustion, and this quantity must be at the same time a minimum to obviate loss in stack gases. 3rd. The mixture must be burned in a furnace where a refractory material radiates heat to assist in the combustion, and the furnace must stand up under the high temperatures developed. 4th. The combustion must be completed before the gases come into contact with the heating surfaces or otherwise the flame will be extinguished, possibly to ignite later in the flue connection or in the stack. 5th. There must be no localization of the heat on certain portions of the heating surfaces or trouble will result from overheating and blistering. The first requirement is met by the selection of a proper burner. The second requirement is fulfilled by properly introducing the air into the furnace, either through checkerwork under the burners or through openings around them, and by controlling the quantity of air to meet variations in furnace conditions. The third requirement is provided for by installing a furnace so designed as to give a sufficient area of heated brickwork to radiate the heat required to maintain a proper furnace temperature. The fourth requirement is provided for by giving ample space for the combustion of the mixture of atomized oil and air, and a gas travel of sufficient length to insure that this combustion be completed before the gases strike the heating surfaces. The fifth requirement is fulfilled by the adoption of a suitable burner in connection with the furnace meeting the other requirements. A burner must be used from which the flame will not impinge directly on the heating surface and must be located where such action cannot take place. If suitable burners properly located are not used, not only is the heat localized with disastrous results, but the efficiency is lowered by the cooling of the gases before combustion is completed. Oil Burners--The functions of an oil burner is to atomize or vaporize the fuel so that it may be burned like a gas. All burners may be classified under three general types: 1st, spray burners, in which the oil is atomized by steam or compressed air; 2nd, vapor burners, in which the oil is converted into vapor and then passed into the furnace; 3rd, mechanical burners, in which the oil is atomized by submitting it to a high pressure and passing it through a small orifice. Vapor burners have never been in general use and will not be discussed. Spray burners are almost universally used for land practice and the simplicity of the steam atomizer and the excellent economy of the better types, together with the low oil pressure and temperature required makes this type a favorite for stationary plants, where the loss of fresh water is not a vital consideration. In marine work, or in any case where it is advisable to save feed water that otherwise would have to be added in the form of "make-up", either compressed air or mechanical means are used for atomization. Spray burners using compressed air as the atomizing agent are in satisfactory operation in some plants, but their use is not general. Where there is no necessity of saving raw feed water, the greater simplicity and economy of the steam spray atomizer is generally the most satisfactory. The air burners require blowers, compressors or other apparatus which occupy space that might be otherwise utilized and require attention that is not necessary where steam is used. Steam spray burners of the older types had disadvantages in that they were so designed that there was a tendency for the nozzle to clog with sludge or coke formed from the oil by the heat, without means of being readily cleaned. This has been overcome in the more modern types. Steam spray burners, as now used, may be divided into two classes: 1st, inside mixers; and 2nd, outside mixers. In the former the steam and oil come into contact within the burner and the mixture is atomized in passing through the orifice of the burner nozzle. [Illustration: Fig. 28. Peabody Oil Burner] In the outside mixing class the steam flows through a narrow slot or horizontal row of small holes in the burner nozzle; the oil flows through a similar slot or hole above the steam orifice, and is picked up by the steam outside of the burner and is atomized. Fig. 28 shows a type of the Peabody burner of this class, which has given eminent satisfaction. The construction is evident from the cut. It will be noted that the portions of the burner forming the orifice may be readily replaced in case of wear, or if it is desired to alter the form of the flame. Where burners of the spray type are used, heating the oil is of advantage not only in causing it to be atomized more easily, but in aiding economical combustion. The temperature is, of course, limited by the flash point of the oil used, but within the limit of this temperature there is no danger of decomposition or of carbon deposits on the supply pipes. Such heating should be done close to the boiler to minimize radiation loss. If the temperature is raised to a point where an appreciable vaporization occurs, the oil will flow irregularly from the burner and cause the flame to sputter. On both steam and air atomizing types, a by-pass should be installed between the steam or air and the oil pipes to provide for the blowing out of the oil duct. Strainers should be provided for removing sludge from the fuel and should be so located as to allow for rapid removal, cleaning and replacing. Mechanical burners have been in use for some time in European countries, but their introduction and use has been of only recent occurrence in the United States. Here as already stated, the means for atomization are purely mechanical. The most successful of the mechanical atomizers up to the present have been of the round flame type, and only these will be considered. Experiments have been made with flat flame mechanical burners, but their satisfactory action has been confined to instances where it is only necessary to burn a small quantity of oil through each individual burner. This system of oil burning is especially adapted for marine work as the quantity of steam for putting pressure on the oil is small and the condensed steam may be returned to the system. The only method by which successful mechanical atomization has been accomplished is one by which the oil is given a whirling motion within the burner tip. This is done either by forcing the oil through a passage of helical form or by delivering it tangentially to a circular chamber from which there is a central outlet. The oil is fed to these burners under a pressure which varies with the make of the burner and the rates at which individual burners are using oil. The oil particles fly off from such a burner in straight lines in the form of a cone rather than in the form of a spiral spray, as might be supposed. With burners of the mechanical atomizing design, the method of introducing air for combustion and the velocity of this air are of the greatest importance in securing good combustion and in the effects on the character and shape of the flame. Such burners are located at the front of the furnace and various methods have been tried for introducing the air for combustion. Where, in the spray burners, air is ordinarily admitted through a checkerwork under the burner proper, with the mechanical burner, it is almost universally admitted around the burner. Early experiments with these air distributors were confined largely to single or duplicate cones used with the idea of directing the air to the axis of the burner. A highly successful method of such air introduction, developed by Messrs. Peabody and Irish of The Babcock & Wilcox Co., is by means of what they term an "impeller plate". This consists of a circular metal disk with an opening at the center for the oil burner and with radial metal strips from the center to the periphery turned at an angle which in the later designs may be altered to give the air supply demanded by the rate of combustion. The air so admitted does not necessarily require a whirling motion, but experiments show that where the air is brought into contact with the oil spray with the right "twist", better combustion is secured and lower air pressures and less refinement of adjustment of individual burners are required. Mechanical burners have a distinct advantage over those in which steam is used as the atomizing agent in that they lend themselves more readily to adjustment under wider variations of load. For a given horse power there will ordinarily be installed a much greater number of mechanical than steam atomizing burners. This in itself is a means to better regulation, for with the steam atomizing burner, if one of a number is shut off, there is a marked decrease in efficiency. This is due to the fact that with the air admitted under the burner, it is ordinarily passing through the checkerwork regardless of whether it is being utilized for combustion or not. With a mechanical burner, on the other hand, where individual burners are shut off, air that would be admitted for such burner, were it in operation, may also be shut off and there will be no undue loss from excess air. Further adjustment to meet load conditions is possible by a change in the oil pressure acting on all burners at once. A good burner will atomize moderately heavy oil with an oil pressure as low as 30 pounds per square inch and from that point up to 200 pounds or above. The heating of the oil also has an effect on the capacity of individual burners and in this way a third method of adjustment is given. Under working conditions, the oil pressure remaining constant, the capacity of each burner will decrease as the temperature of the oil is increased though at low temperatures the reverse is the case. Some experiments with a Texas crude oil having a flash point of 210 degrees showed that the capacity of a mechanical atomizing burner of the Peabody type increased from 80 degrees Fahrenheit to 110 degrees Fahrenheit, from which point it fell off rapidly to 140 degrees and then more slowly to the flash point. The above methods, together with the regulation possible through manipulation of the boiler dampers, indicate the wide range of load conditions that may be handled with an installation of this class of burners. As has already been stated, results with mechanical atomizing burners that may be considered very successful have been limited almost entirely to cases where forced blast of some description has been used, the high velocity of the air entering being of material assistance in securing the proper mixture of air with the oil spray. Much has been done and is being done in the way of experiment with this class of apparatus toward developing a successful mechanical atomizing burner for use with natural draft, and there appears to be no reason why such experiments should not eventually produce satisfactory results. Steam Consumption of Burners--The Bureau of Steam Engineering, U. S. Navy, made in 1901 an exhaustive series of tests of various oil burners that may be considered as representing, in so far as the performance of the burners themselves is concerned, the practice of that time. These tests showed that a burner utilizing air as an atomizing agent, required for compressing the air from 1.06 to 7.45 per cent of the total steam generated, the average being 3.18 per cent. Four tests of steam atomizing burners showed a consumption of 3.98 to 5.77 per cent of the total steam, the average being 4.8 per cent. Improvement in burner design has largely reduced the steam consumption, though to a greater degree in steam than in air atomizing burners. Recent experiments show that a good steam atomizing burner will require approximately 2 per cent of the total steam generated by the boiler operated at or about its rated capacity. This figure will decrease as the capacity is increased and is so low as to be practically negligible, except in cases where the question of loss of feed water is all important. There are no figures available as to the actual steam consumption of mechanical atomizing burners but apparently this is small if the requirement is understood to be entirely apart from the steam consumption of the apparatus producing the forced blast. Capacity of Burners--A good steam atomizing burner properly located in a well-designed oil furnace has a capacity of somewhat over 400 horse power. This question of capacity of individual burners is largely one of the proper relation between the number of burners used and the furnace volume. In some recent tests with a Babcock & Wilcox boiler of 640 rated horse power, equipped with three burners, approximately 1350 horse power was developed with an available draft of .55 inch at the damper or 450 horse power per burner. Four burners were also tried in the same furnace but the total steam generated did not exceed 1350 horse power or in this instance 338 horse power per burner. From the nature of mechanical atomizing burners, individual burners have not as large a capacity as the steam atomizing class. In some tests on a Babcock & Wilcox marine boiler, equipped with mechanical atomizing burners, the maximum horse power developed per burner was approximately 105. Here again the burner capacity is largely one of proper relation between furnace volume and number of burners. Furnace Design--Too much stress cannot be laid on the importance of furnace design for the use of this class of fuel. Provided a good type of burner is adopted the furnace arrangement and the method of introducing air for combustion into the furnace are the all important factors. No matter what the type of burner, satisfactory results cannot be secured in a furnace not suited to the fuel. The Babcock & Wilcox Co. has had much experience with the burning of oil as fuel and an extended series of experiments by Mr. E. H. Peabody led to the development and adoption of the Peabody furnace as being most eminently suited for this class of work. Fig. 29 shows such a furnace applied to a Babcock & Wilcox boiler, and with slight modification it can be as readily applied to any boiler of The Babcock & Wilcox Co. manufacture. In the description of this furnace, its points of advantage cover the requirements of oil-burning furnaces in general. The atomized oil is introduced into the furnace in the direction in which it increases in height. This increase in furnace volume in the direction of the flame insures free expansion and a thorough mixture of the oil with the air, and the consequent complete combustion of the gases before they come into contact with the tube heating surfaces. In such a furnace flat flame burners should be used, preferably of the Peabody type, in which the flame spreads outward toward the sides in the form of a fan. There is no tendency of the flames to impinge directly on the heating surfaces, and the furnace can handle any quantity of flame without danger of tube difficulties. The burners should be so located that the flames from individual burners do not interfere nor impinge to any extent on the side walls of the furnace, an even distribution of heat being secured in this manner. The burners are operated from the boiler front and peepholes are supplied through which the operator may watch the flame while regulating the burners. The burners can be removed, inspected, or cleaned and replaced in a few minutes. Air is admitted through a checkerwork of fire brick supported on the furnace floor, the openings in the checkerwork being so arranged as to give the best economic results in combustion. [Illustration: Fig. 29. Babcock & Wilcox Boiler, Equipped with a Peabody Oil Furnace] With steam atomizing burners introduced through the front of the boiler in stationary practice, it is usually in the direction in which the furnace decreases in height and it is with such an arrangement that difficulties through the loss of tubes may be expected. With such an arrangement, the flame may impinge directly upon the tube surfaces and tube troubles from this source may arise, particularly where the feed water has a tendency toward rapid scale formation. Such difficulties may be the result of a blowpipe action on the part of the burner, the over heating of the tube due to oil or scale within, or the actual erosion of the metal by particles of oil improperly atomized. Such action need not be anticipated, provided the oil is burned with a short flame. The flames from mechanical atomizing burners have a less velocity of projection than those from steam atomizing burners and if introduced into the higher end of the furnace, should not lead to tube difficulties provided they are properly located and operated. This class of burner also will give the most satisfactory results if introduced so that the flames travel in the direction of increase in furnace volume. This is perhaps best exemplified by the very good results secured with mechanical atomizing burners and Babcock & Wilcox marine boilers in which, due to the fact that the boilers are fired from the low end, the flames from burners introduced through the front are in this direction. Operation of Burners--When burners are not in use, or when they are being started up, care must be taken to prevent oil from flowing and collecting on the floor of the furnace before it is ignited. In starting a burner, the atomized fuel may be ignited by a burning wad of oil-soaked waste held before it on an iron rod. To insure quick ignition, the steam supply should be cut down. But little practice is required to become an adept at lighting an oil fire. When ignition has taken place and the furnace brought to an even heat, the steam should be cut down to the minimum amount required for atomization. This amount can be determined from the appearance of the flame. If sufficient steam is not supplied, particles of burning oil will drop to the furnace floor, giving a scintillating appearance to the flame. The steam valves should be opened just sufficiently to overcome this scintillating action. Air Supply--From the nature of the fuel and the method of burning, the quantity of air for combustion may be minimized. As with other fuels, when the amount of air admitted is the minimum which will completely consume the oil, the results are the best. The excess or deficiency of air can be judged by the appearance of the stack or by observing the gases passing through the boiler settings. A perfectly clear stack indicates excess air, whereas smoke indicates a deficiency. With properly designed furnaces the best results are secured by running near the smoking point with a slight haze in the gases. A slight variation in the air supply will affect the furnace conditions in an oil burning boiler more than the same variation where coal is used, and for this reason it is of the utmost importance that flue gas analysis be made frequently on oil-burning boilers. With the air for combustion properly regulated by adjustment of any checkerwork or any other device which may be used, and the dampers carefully set, the flue gas analysis should show, for good furnace conditions, a percentage of CO_{2} between 13 and 14 per cent, with either no CO or but a trace. In boiler plant operation it is difficult to regulate the steam supply to the burners and the damper position to meet sudden and repeated variations in the load. A device has been patented which automatically regulates by means of the boiler pressure the pressure of the steam to the burners, the oil to the burners and the position of the boiler damper. Such a device has been shown to give good results in plant operation where hand regulation is difficult at best, and in many instances is unfortunately not even attempted. Efficiency with Oil--As pointed out in enumerating the advantages of oil fuel over coal, higher efficiencies are obtainable with the former. With boilers of approximately 500 horse power equipped with properly designed furnaces and burners, an efficiency of 83 per cent is possible or making an allowance of 2 per cent for steam used by burners, a net efficiency of 81 per cent. The conditions under which such efficiencies are to be secured are distinctly test conditions in which careful operation is a prime requisite. With furnace conditions that are not conductive to the best combustion, this figure may be decreased by from 5 to 10 per cent. In large properly designed plants, however, the first named efficiency may be approached for uniform running conditions, the nearness to which it is reached depending on the intelligence of the operating crew. It must be remembered that the use of oil fuel presents to the careless operator possibilities for wastefulness much greater than in plants where coal is fired, and it therefore pays to go carefully into this feature. Table 48 gives some representative tests with oil fuel. TABLE 48 TESTS OF BABCOCK AND WILCOX BOILERS WITH OIL FUEL _______________________________________________________________________ | | | | | | |Pacific Light|Pacific Light|Miami Copper | | | and Power | and Power | Company | | Plant | Company | Company | | | |Los Angeles, | | Miami, | | | Cal. |Redondo, Cal.| Arizona | |_____________________________|_____________|_____________|_____________| | | | | | | | Rated Capacity | Horse | | | | | of Boiler | Power | 467 | 604 | 600 | |__________________|__________|_____________|_____________|_____________| | | | | | | | | | | Duration of Test | Hours | 10 | 10 | 7 | 7 | 10 | 4 | | | | | | | | | | | Steam Pressure | | | | | | | | | by Gauge | Pounds | 156.4| 156.9| 184.7| 184.9| 183.4| 189.5| | | | | | | | | | | Temperature of | Degrees | | | | | | | | Feed Water | F. | 62.6| 61.1| 93.4| 101.2| 157.7| 156.6| | | | | | | | | | | Degrees of | Degrees | | | | | | | | Superheat | F. | | | 83.7| 144.3| 103.4| 139.6| | | | | | | | | | | Factor of | | | | | | | | | Evaporation | |1.2004|1.2020|1.2227|1.2475|1.1676|1.1886| | | | | | | | | | | Draft in Furnace | Inches | .02 | .05 | .014| .19 | .12 | .22 | | | | | | | | | | | Draft at Damper | Inches | .08 | .15 | .046| .47 | .19 | .67 | | | | | | | | | | | Temperature of | Degrees | | | | | | | | Exit Gases | F. | 438 | 525 | 406 | 537 | 430 | 612 | | _ | | | | | | | | | Flue | CO_{2} | Per Cent | | | 14.3 | 12.1 | | | | Gas | O | Per Cent | | | 3.8 | 6.8 | | | | Analysis|_CO | Per Cent | | | 0.0 | 0.0 | | | | | | | | | | | | | Oil Burned | | | | | | | | | per Hour | Pounds | 1147 | 1837 | 1439 | 2869 | 1404 | 3214 | | | | | | | | | | | Water Evaporated | | | | | | | | | per Hour from | | | | | | | | | from and at | Pounds | 18310| 27855| 22639| 40375| 21720| 42863| | 212 Degrees | | | | | | | | | | | | | | | | | | Evaporation from | | | | | | | | | and at 212 | | | | | | | | | Degrees per | Pounds | 15.96| 15.16| 15.73| 14.07| 15.47| 13.34| | Pound of Oil | | | | | | | | | | | | | | | | | | Per Cent of | | | | | | | | | Rated Capacity | Pounds | 113.6| 172.9| 108.6| 193.8| 104.9| 207.1| | Developed | | | | | | | | | | | | | | | | | | B. t. u. per | | | | | | | | | Pound of Oil | B. t. u. | 18626| 18518| 18326| 18096| 18600| 18600| | | | | | | | | | | Efficiency | Per Cent | 83.15| 79.46| 83.29| 76.02| 80.70| 69.6 | |__________________|__________|______|______|______|______|______|______| Burning Oil in Connection with Other Fuels--Considerable attention has been recently given to the burning of oil in connection with other fuels, and a combination of this sort may be advisable either with the view to increasing the boiler capacity to assist over peak loads, or to keep the boiler in operation where there is the possibility of a temporary failure of the primary fuel. It would appear from experiments that such a combination gives satisfactory results from the standpoint of both capacity and efficiency, if the two fuels are burned in separate furnaces. Satisfactory results cannot ordinarily be obtained when it is attempted to burn oil fuel in the same furnace as the primary fuel, as it is practically impossible to admit the proper amount of air for combustion for each of the two fuels simultaneously. The Babcock & Wilcox boiler lends itself readily to a double furnace arrangement and Fig. 30 shows an installation where oil fuel is burned as an auxiliary to wood. [Illustration: Fig. 30. Babcock & Wilcox Boiler Set with Combination Oil and Wood-burning Furnace] Water-gas Tar--Water-gas tar, or gas-house tar, is a by-product of the coal used in the manufacture of water gas. It is slightly heavier than crude oil and has a comparatively low flash point. In burning, it should be heated only to a temperature which makes it sufficiently fluid, and any furnace suitable for crude oil is in general suitable for water-gas tar. Care should be taken where this fuel is used to install a suitable apparatus for straining it before it is fed to the burner. [Illustration: Babcock & Wilcox Boilers Fired with Blast Furnace Gas at the Bethlehem Steel Co., Bethlehem, Pa. This Company Operates 12,900 Horse Power of Babcock & Wilcox Boilers] GASEOUS FUELS AND THEIR COMBUSTION Of the gaseous fuels available for steam generating purposes, the most common are blast furnace gas, natural gas and by-product coke oven gas. Blast furnace gas, as implied by its name, is a by-product from the blast furnace of the iron industry. This gasification of the solid fuel in a blast furnace results, 1st, through combustion by the oxygen of the blast; 2nd, through contact with the incandescent ore (Fe_{2}O_{3} + C = 2 FeO + CO and FeO + C = Fe + CO); and 3rd, through the agency of CO_{2} either formed in the process of reduction or driven from the carbonates charged either as ore or flux. Approximately 90 per cent of the fuel consumed in all of the blast furnaces of the United States is coke. The consumption of coke per ton of iron made varies from 1600 to 3600 pounds per ton of 2240 pounds of iron. This consumption depends upon the quality of the coal, the nature of the ore, the quality of the pig iron produced and the equipment and management of the plant. The average consumption, and one which is approximately correct for ordinary conditions, is 2000 pounds of coke per gross ton (2240 pounds) of pig iron. The gas produced in a gas furnace per ton of pig iron is obtained from the weight of fixed carbon gasified, the weight of the oxygen combined with the material of charge reduced, the weight of the gaseous constituents of the flux and the weight of air delivered by the blowing engine and the weight of volatile combustible contained in the coke. Ordinarily, this weight of gas will be found to be approximately five times the weight of the coke burned, or 10,000 pounds per ton of pig iron produced. With the exception of the small amount of carbon in combination with hydrogen as methane, and a very small percentage of free hydrogen, ordinarily less than 0.1 per cent, the calorific value of blast furnace gas is due to the CO content which when united with sufficient oxygen when burned under a boiler, burns further to CO_{2}. The heat value of such gas will vary in most cases from 85 to 100 B. t. u. per cubic foot under standard conditions. In modern practice, where the blast is heated by hot blast stoves, approximately 15 per cent of the total amount of gas is used for this purpose, leaving 85 per cent of the total for use under boilers or in gas engines, that is, approximately 8500 pounds of gas per ton of pig iron produced. In a modern blast furnace plant, the gas serves ordinarily as the only fuel required. Table 49 gives the analyses of several samples of blast furnace gas. TABLE 49 TYPICAL ANALYSES OF BLAST FURNACE GAS +----------------------------------------------------------------+ |+-----------------------+------+----+-----+----+------+--------+| || |CO_{2}| O | CO | H |CH_{4}| N || |+-----------------------+------+----+-----+----+------+--------+| ||Bessemer Furnace | 9.85|0.36|32.73|3.14| .. |53.92 || ||Bessemer Furnace | 11.4 | .. |27.7 |1.9 | 0.3 |58.7 || ||Bessemer Furnace | 10.0 | .. |26.2 |3.1 | 0.2 |60.5 || ||Bessemer Furnace | 9.1 | .. |28.7 |2.7 | 0.2 |59.3 || ||Bessemer Furnace | 13.5 | .. |25.2 |1.43| .. |59.87 || ||Bessemer Furnace[47] | 10.9 | .. |27.8 |2.8 | 0.2 |58.3 || ||Ferro Manganese Furnace| 7.1 | .. |30.1 | .. | .. |62.8[48]|| ||Basic Ore Furnace | 16.0 |0.2 |23.6 | .. | .. |60.2[48]|| |+-----------------------+------+----+-----+----+------+--------+| +----------------------------------------------------------------+ Until recently, the important consideration in the burning of blast furnace gas has been the capacity that can be developed with practically no attention given to the aspect of efficiency. This phase of the question is now drawing attention and furnaces especially designed for good efficiency with this class of fuel are demanded. The essential feature is ample combustion space, in which the combustion of gases may be practically completed before striking the heating surfaces. The gases have the power of burning out completely after striking the heating surfaces, provided the initial temperature is sufficiently high, but where the combustion is completed before such time, the results secured are more satisfactory. A furnace volume of approximately 1 to 1.5 cubic feet per rated boiler horse power will give a combustion space that is ample. Where there is the possibility of a failure of the gas supply, or where steam is required when the blast furnace is shut down, coal fired grates of sufficient size to get the required capacity should be installed. Where grates of full size are not required, ignition grates should be installed, which need be only large enough to carry a fire for igniting the gas or for generating a small quantity of steam when the blast furnace is shut down. The area of such grates has no direct bearing on the size of the boiler. The grates may be placed directly under the gas burners in a standard position or may be placed between two bridge walls back of the gas furnace and fired from the side of the boiler. An advantage is claimed for the standard grate position that it minimizes the danger of explosion on the re-ignition of gas after a temporary stoppage of the supply and also that a considerable amount of dirt, of which there is a good deal with this class of fuel and which is difficult to remove, deposits on the fire and is taken out when the fires are cleaned. In any event, regardless of the location of the grates, ample provision should be made for removing this dust, not only from the furnace but from the setting as a whole. Blast furnace gas burners are of two general types: Those in which the air for combustion is admitted around the burner proper, and those in which this air is admitted through the burner. Whatever the design of burner, provision should be made for the regulation of both the air and the gas supply independently. A gas opening of .8 square inch per rated horse power will enable a boiler to develop its nominal rating with a gas pressure in the main of about 2 inches. This pressure is ordinarily from 6 to 8 inches and in this way openings of the above size will be good for ordinary overloads. The air openings should be from .75 to .85 square inch per rated horse power. Good results are secured by inclining the gas burners slightly downward toward the rear of the furnace. Where the burners are introduced over coal fired grates, they should be set high enough to give headroom for hand firing. Ordinarily, individual stacks of 130 feet high with diameters as given in Kent's table for corresponding horse power are large enough for this class of work. Such a stack will give a draft sufficient to allow a boiler to be operated at 175 per cent of its rated capacity, and beyond this point the capacity will not increase proportionately with the draft. When more than one boiler is connected with a stack, the draft available at the damper should be equivalent to that which an individual stack of 130 feet high would give. The draft from such a stack is necessary to maintain a suction under all conditions throughout all parts of the setting. If the draft is increased above that which such a stack will give, difficulties arise from excess air for combustion with consequent loss in efficiency. A poor mixing or laneing action in the furnace may result in a pulsating effect of the gases in the setting. This action may at times be remedied by admitting more air to the furnace. On account of the possibility of a pulsating action of the gases under certain conditions and the puffs or explosions, settings for this class of work should be carefully constructed and thoroughly buckstayed and tied. Natural Gas--Natural gas from different localities varies considerably in composition and heating value. In Table 50 there is given a number of analyses and heat values for natural gas from various localities. This fuel is used for steam generating purposes to a considerable extent in some localities, though such use is apparently decreasing. It is best burned by employing a large number of small burners, each being capable of handling 30 nominal rated horse power. The use of a large number of burners obviates the danger of any laneing or blowpipe action, which might be present where large burners are used. Ordinarily, such a gas, as it enters the burners, is under a pressure of about 8 ounces. For the purpose of comparison, all observations should be based on gas reduced to the standard conditions of temperature and pressure, namely 32 degrees Fahrenheit and 14.7 pounds per square inch. When the temperature and pressure corresponding to meter readings are known, the volume of gas under standard conditions may be obtained by multiplying the meter readings in cubic feet by 33.54 P/T, in which P equals the absolute pressure in pounds per square inch and T equals the absolute temperature of the gas at the meter. In boiler testing work, the evaporation should always be reduced to that per cubic foot of gas under standard conditions. TABLE 50 TYPICAL ANALYSES (BY VOLUME) AND CALORIFIC VALUES OF NATURAL GAS FROM VARIOUS LOCALITIES +----------------+-----+-----+-----+-----+-----+----+-------+------+--------+ |Locality of Well| H |CH_{4}| CO |CO_{2}| N | O | Heavy |H_{2}S|B. t. u.| | | | | | | | |Hydro- | | per | | | | | | | | |carbons| | Cubic | | | | | | | | | | | Foot | | | | | | | | | | |Calcul- | | | | | | | | | | |ated[49]| |----------------+-----+-----+-----+-----+-----+----+-------+------+--------+ |Anderson, Ind. | 1.86|93.07| 0.73| 0.26| 3.02|0.42| 0.47 | 0.15 | 1017 | |Marion, Ind. | 1.20|93.16| 0.60| 0.30| 3.43|0.55| 0.15 | 0.20 | 1009 | |Muncie, Ind. | 2.35|92.67| 0.45| 0.25| 3.53|0.35| 0.25 | 0.15 | 1004 | |Olean, N. Y. | |96.50| 0.50| | |2.00| 1.00 | | 1018 | |Findlay, O. | 1.64|93.35| 0.41| 0.25| 3.41|0.39| 0.35 | 0.20 | 1011 | |St. Ive, Pa. | 6.10|75.54|Trace| 0.34| | | 18.12 | | 1117 | |Cherry Tree, Pa.|22.50|60.27| | 2.28| 7.32|0.83| 6.80 | | 842 | |Grapeville, Pa. |24.56|14.93|Trace|Trace|18.69|1.22| 40.60 | | 925 | |Harvey Well, | | | | | | | | | | | Butler Co., Pa.|13.50|80.00|Trace| 0.66| | | 5.72 | | 998 | |Pittsburgh, Pa. | 9.64|57.85| 1.00| |23.41|2.10| 6.00 | | 748 | |Pittsburgh, Pa. |20.02|72.18| 1.00| 0.80| |1.10| 4.30 | | 917 | |Pittsburgh, Pa. |26.16|65.25| 0.80| 0.60| |0.80| 6.30 | | 899 | +----------------+-----+-----+-----+-----+-----+----+-------+------+--------+ [Illustration: 1600 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters at the Carnegie Natural Gas Co., Underwood, W. Va. Natural Gas is the Fuel Burned under these Boilers] When natural gas is the only fuel, the burners should be evenly distributed over the lower portion of the boiler front. If the fuel is used as an auxiliary to coal, the burners may be placed through the fire front. A large combustion space is essential and a volume of .75 cubic feet per rated horse power will be found to give good results. The burners should be of a design which give the gas and air a rotary motion to insure a proper mixture. A checkerwork wall is sometimes placed in the furnace about 3 feet from the burners to break up the flame, but with a good design of burner this is unnecessary. Where the gas is burned alone and no grates are furnished, good results are secured by inclining the burner downward to the rear at a slight angle. By-product Coke Oven Gas--By-product coke oven gas is a product of the destructive distillation of coal in a distilling or by-product coke oven. In this class of apparatus the gases, instead of being burned at the point of their origin, as in a beehive or retort coke oven, are taken from the oven through an uptake pipe, cooled and yield as by-products tar, ammonia, illuminating and fuel gas. A certain portion of the gas product is burned in the ovens and the remainder used or sold for illuminating or fuel purposes, the methods of utilizing the gas varying with plant operation and locality. Table 51 gives the analyses and heat value of certain samples of by-product coke oven gas utilized for fuel purposes. This gas is nearer to natural gas in its heat value than is blast furnace gas, and in general the remarks as to the proper methods of burning natural gas and the features to be followed in furnace design hold as well for by-product coke oven gas. TABLE 51 TYPICAL ANALYSES OF BY-PRODUCT COKE OVEN GAS +----------------------------------------------+ |+------+-------------------------------------+| ||CO_{2}| O |CO |CH_{4}| H | N |B.t.u. per|| || | | | | | |Cubic Foot|| |+------+-----+---+------+----+----+----------+| || 0.75 |Trace|6.0|28.15 |53.0|12.1| 505 || || 2.00 |Trace|3.2|18.80 |57.2|18.0| 399 || || 3.20 | 0.4 |6.3|29.60 |41.6|16.1| 551 || || 0.80 | 1.6 |4.9|28.40 |54.2|10.1| 460 || |+------+-----+---+------+----+----+----------+| +----------------------------------------------+ The essential difference in burning the two fuels is the pressure under which it reaches the gas burner. Where this is ordinarily from 4 to 8 ounces in the case of natural gas, it is approximately 4 inches of water in the case of by-product coke oven gas. This necessitates the use of larger gas openings in the burners for the latter class of fuel than for the former. By-product coke oven gas comes to the burners saturated with moisture and provision should be made for the blowing out of water of condensation. This gas too, carries a large proportion of tar and hydrocarbons which form a deposit in the burners and provision should be made for cleaning this out. This is best accomplished by an attachment which permits the blowing out of the burners by steam. UTILIZATION OF WASTE HEAT While it has been long recognized that the reclamation of heat from the waste gases of various industrial processes would lead to a great saving in fuel and labor, the problem has, until recently, never been given the attention that its importance merits. It is true that installations have been made for the utilization of such gases, but in general they have consisted simply in the placing of a given amount of boiler heating surface in the path of the gases and those making the installations have been satisfied with whatever power has been generated, no attention being given to the proportioning of either the heating surface or the gas passages to meet the peculiar characteristics of the particular class of waste gas available. The Babcock & Wilcox Co. has recently gone into the question of the utilization of what has been known as waste heat with great thoroughness, and the results secured by their installations with practically all operations yielding such gases are eminently successful. TABLE 52 TEMPERATURE OF WASTE GASES FROM VARIOUS INDUSTRIAL PROCESSES +-----------------------------------------------------+ |+-----------------------------------+---------------+| ||Waste Heat From |Temperature[50]|| || | Degrees || |+-----------------------------------+---------------+| ||Brick Kilns | 2000-2300 || ||Zinc Furnaces | 2000-2300 || ||Copper Matte Reverberatory Furnaces| 2000-2200 || ||Beehive Coke Ovens | 1800-2000 || ||Cement Kilns | 1200-1600[51]|| ||Nickel Refining Furnaces | 1500-1750 || ||Open Hearth Steel Furnaces | 1100-1400 || |+-----------------------------------+---------------+| +-----------------------------------------------------+ The power that can be obtained from waste gases depends upon their temperature and weight, and both of these factors vary widely in different commercial operations. Table 52 gives a list of certain processes yielding waste gases the heat of which is available for the generation of steam and the approximate temperature of such gases. It should be understood that the temperatures in the table are the average of the range of a complete cycle of the operation and that the minimum and maximum temperatures may vary largely from the figures given. The maximum available horse power that may be secured from such gases is represented by the formula: W(T-t)s H. P. = ------- (23) 33,479 Where W = the weight of gases passing per hour, T = temperature of gases entering heating surface, t = temperature leaving heating surface, s = specific heat of gases. The initial temperature and the weight or volume of gas will depend, as stated, upon the process involved. The exit temperature will depend, to a certain extent, upon the temperature of the entering gases, but will be governed mainly by the efficiency of the heating surfaces installed for the absorption of the heat. Where the temperature of the gas available is high, approaching that found in direct fired boiler practice, the problem is simple and the question of design of boiler becomes one of adapting the proper amount of heating surface to the volume of gas to be handled. With such temperatures, and a volume of gas available approximately in accordance with that found in direct fired boiler practice, a standard boiler or one but slightly modified from the standard will serve the purpose satisfactorily. As the temperatures become lower, however, the problem is more difficult and the departure from standard practice more radical. With low temperature gases, to obtain a heat transfer rate at all comparable with that found in ordinary boiler practice, the lack of temperature must be offset by an added velocity of the gases in their passage over the heating surfaces. In securing the velocity necessary to give a heat transfer rate with low temperature gases sufficient to make the installation of waste heat boilers show a reasonable return on the investment, the frictional resistance to the gases through the boiler becomes greatly in excess of what would be considered good practice in direct fired boilers. Practically all operations yielding waste gases require that nothing be done in the way of impairing the draft at the furnace outlet, as this might interfere with the operation of the primary furnace. The installation of a waste heat boiler, therefore, very frequently necessitates providing sufficient mechanical draft to overcome the frictional resistance of the gases through the heating surfaces and still leave ample draft available to meet the maximum requirements of the primary furnace. Where the temperature and volume of the gases are in line with what are found in ordinary direct fired practice, the area of the gas passages may be practically standard. With the volume of gas known, the draft loss through the heating surfaces may be obtained from experimental data and this additional draft requirement met by the installation of a stack sufficient to take care of this draft loss and still leave draft enough for operating the furnace at its maximum capacity. Where the temperatures are low, the added frictional resistance will ordinarily be too great to allow the draft required to be secured by additional stack height and the installation of a fan is necessary. Such a fan should be capable of handling the maximum volume of gas that the furnace may produce, and of maintaining a suction equivalent to the maximum frictional resistance of such volume through the boiler plus the maximum draft requirement at the furnace outlet. Stacks and fans for this class of work should be figured on the safe side. Where a fan installation is necessary, the loss of draft in the fan connections should be considered, and in figuring conservatively it should be remembered that a fan of ample size may be run as economically as a smaller fan, whereas the smaller fan, if overloaded, is operated with a large loss in efficiency. In practically any installation where low temperature gas requires a fan to give the proper heat transfer from the gases, the cost of the fan and of the energy to drive it will be more than offset by the added power from the boiler secured by its use. Furthermore, the installation of such a fan will frequently increase the capacity of the industrial furnace, in connection with which the waste heat boilers are installed. In proportioning heating surfaces and gas passages for waste heat work there are so many factors bearing directly on what constitutes the proper installation that it is impossible to set any fixed rules. Each individual installation must be considered by itself as well as the particular characteristics of the gases available, such as their temperature and volume, and the presence of dust or tar-like substances, and all must be given the proper weight in the determination of the design of the heating surfaces and gas passages for the specific set of conditions. [Graph: Per Cent of Water Heating Surface passed over by Gases/Per Cent of the Total Amount of Steam Generated in the Boiler against Temperature in Degrees Fahrenheit of Hot Gases Sweeping Heating Surface Fig. 31. Curve Showing Relation Between Gas Temperature, Heating Surface passed over, and Amount of Steam Generated. Ten Square Feet of Heating Surface are Assumed as Equivalent to One Boiler Horse Power] Fig. 31 shows the relation of gas temperatures, heating surface passed over and work done by such surface for use in cases where the temperatures approach those found in direct fired practice and where the volume of gas available is approximately that with which one horse power may be developed on 10 square feet of heating surface. The curve assumes what may be considered standard gas passage areas, and further, that there is no heat absorbed by direct radiation from the fire. Experiments have shown that this curve is very nearly correct for the conditions assumed. Such being the case, its application in waste heat work is clear. Decreasing or increasing the velocity of the gases over the heating surfaces from what might be considered normal direct fired practice, that is, decreasing or increasing the frictional loss through the boiler will increase or decrease the amount of heating surface necessary to develop one boiler horse power. The application of Fig. 31 to such use may best be seen by an example: Assume the entering gas temperatures to be 1470 degrees and that the gases are cooled to 570 degrees. From the curve, under what are assumed to be standard conditions, the gases have passed over 19 per cent of the heating surface by the time they have been cooled 1470 degrees. When cooled to 570 degrees, 78 per cent of the heating surface has been passed over. The work done in relation to the standard of the curve is represented by (1470 - 570) ÷ (2500 - 500) = 45 per cent. (These figures may also be read from the curve in terms of the per cent of the work done by different parts of the heating surfaces.) That is, 78 per cent - 19 per cent = 59 per cent of the standard heating surface has done 45 per cent of the standard amount of work. 59 ÷ 45 = 1.31, which is the ratio of surface of the assumed case to the standard case of the curve. Expressed differently, there will be required 13.1 square feet of heating surface in the assumed case to develop a horse power as against 10 square feet in the standard case. The gases available for this class of work are almost invariably very dirty. It is essential for the successful operation of waste-heat boilers that ample provision be made for cleaning by the installation of access doors through which all parts of the setting may be reached. In many instances, such as waste-heat boilers set in connection with cement kilns, settling chambers are provided for the dust before the gases reach the boiler. By-passes for the gases should in all cases be provided to enable the boiler to be shut down for cleaning and repairs without interfering with the operation of the primary furnace. All connections from furnace to boilers should be kept tight to prevent the infiltration of air, with the consequent lowering of gas temperatures. Auxiliary gas or coal fired grates must be installed to insure continuity in the operation of the boiler where the operation of the furnace is intermittent or where it may be desired to run the boiler with the primary furnace not in operation. Such grates are sometimes used continuously where the gases available are not sufficient to develop the required horse power from a given amount of heating surface. Fear has at times been expressed that certain waste gases, such as those containing sulphur fumes, will have a deleterious action on the heating surface of the boiler. This feature has been carefully watched, however, and from plants in operation it would appear that in the absence of water or steam leaks within the setting, there is no such harmful action. [Illustration: Fig. 32. Babcock & Wilcox Boiler Arranged for Utilizing Waste Heat from Open Hearth Furnace. This Setting may be Modified to Take Care of Practically any Kind of Waste Gas] CHIMNEYS AND DRAFT The height and diameter of a properly designed chimney depend upon the amount of fuel to be burned, its nature, the design of the flue, with its arrangement relative to the boiler or boilers, and the altitude of the plant above sea level. There are so many factors involved that as yet there has been produced no formula which is satisfactory in taking them all into consideration, and the methods used for determining stack sizes are largely empirical. In this chapter a method sufficiently comprehensive and accurate to cover all practical cases will be developed and illustrated. Draft is the difference in pressure available for producing a flow of the gases. If the gases within a stack be heated, each cubic foot will expand, and the weight of the expanded gas per cubic foot will be less than that of a cubic foot of the cold air outside the chimney. Therefore, the unit pressure at the stack base due to the weight of the column of heated gas will be less than that due to a column of cold air. This difference in pressure, like the difference in head of water, will cause a flow of the gases into the base of the stack. In its passage to the stack the cold air must pass through the furnace or furnaces of the boilers connected to it, and it in turn becomes heated. This newly heated gas will also rise in the stack and the action will be continuous. The intensity of the draft, or difference in pressure, is usually measured in inches of water. Assuming an atmospheric temperature of 62 degrees Fahrenheit and the temperature of the gases in the chimney as 500 degrees Fahrenheit, and, neglecting for the moment the difference in density between the chimney gases and the air, the difference between the weights of the external air and the internal flue gases per cubic foot is .0347 pound, obtained as follows: Weight of a cubic foot of air at 62 degrees Fahrenheit = .0761 pound Weight of a cubic foot of air at 500 degrees Fahrenheit = .0414 pound ------------------------ Difference = .0347 pound Therefore, a chimney 100 feet high, assumed for the purpose of illustration to be suspended in the air, would have a pressure exerted on each square foot of its cross sectional area at its base of .0347 × 100 = 3.47 pounds. As a cubic foot of water at 62 degrees Fahrenheit weighs 62.32 pounds, an inch of water would exert a pressure of 62.32 ÷ 12 = 5.193 pounds per square foot. The 100-foot stack would, therefore, under the above temperature conditions, show a draft of 3.47 ÷ 5.193 or approximately 0.67 inches of water. The method best suited for determining the proper proportion of stacks and flues is dependent upon the principle that if the cross sectional area of the stack is sufficiently large for the volume of gases to be handled, the intensity of the draft will depend directly upon the height; therefore, the method of procedure is as follows: 1st. Select a stack of such height as will produce the draft required by the particular character of the fuel and the amount to be burned per square foot of grate surface. 2nd. Determine the cross sectional area necessary to handle the gases without undue frictional losses. The application of these rules follows: Draft Formula--The force or intensity of the draft, not allowing for the difference in the density of the air and of the flue gases, is given by the formula: / 1 1 \ D = 0.52 H × P |--- - -----| (24) \ T T_{1}/ in which D = draft produced, measured in inches of water, H = height of top of stack above grate bars in feet, P = atmospheric pressure in pounds per square inch, T = absolute atmospheric temperature, T_{1} = absolute temperature of stack gases. In this formula no account is taken of the density of the flue gases, it being assumed that it is the same as that of air. Any error arising from this assumption is negligible in practice as a factor of correction is applied in using the formula to cover the difference between the theoretical figures and those corresponding to actual operating conditions. The force of draft at sea level (which corresponds to an atmospheric pressure of 14.7 pounds per square inch) produced by a chimney 100 feet high with the temperature of the air at 60 degrees Fahrenheit and that of the flue gases at 500 degrees Fahrenheit is, / 1 1 \ D = 0.52 × 100 × 14.7 | --- - --- | = 0.67 \ 521 961 / Under the same temperature conditions this chimney at an atmospheric pressure of 10 pounds per square inch (which corresponds to an altitude of about 10,000 feet above sea level) would produce a draft of, / 1 1 \ D = 0.52 × 100 × 10 | --- - --- | = 0.45 \ 521 961 / For use in applying this formula it is convenient to tabulate values of the product / 1 1 \ 0.52 × 14.7|--- - -----| \ T T_{1}/ which we will call K, for various values of T_{1}. With these values calculated for assumed atmospheric temperature and pressure (24) becomes D = KH. (25) For average conditions the atmospheric pressure may be considered 14.7 pounds per square inch, and the temperature 60 degrees Fahrenheit. For these values and various stack temperatures K becomes: _Temperature Stack Gases_ _Constant K_ 750 .0084 700 .0081 650 .0078 600 .0075 550 .0071 500 .0067 450 .0063 400 .0058 350 .0053 Draft Losses--The intensity of the draft as determined by the above formula is theoretical and can never be observed with a draft gauge or any recording device. However, if the ashpit doors of the boiler are closed and there is no perceptible leakage of air through the boiler setting or flue, the draft measured at the stack base will be approximately the same as the theoretical draft. The difference existing at other times represents the pressure necessary to force the gases through the stack against their own inertia and the friction against the sides. This difference will increase with the velocity of the gases. With the ashpit doors closed the volume of gases passing to the stack are a minimum and the maximum force of draft will be shown by a gauge. As draft measurements are taken along the path of the gases, the readings grow less as the points at which they are taken are farther from the stack, until in the boiler ashpit, with the ashpit doors open for freely admitting the air, there is little or no perceptible rise in the water of the gauge. The breeching, the boiler damper, the baffles and the tubes, and the coal on the grates all retard the passage of the gases, and the draft from the chimney is required to overcome the resistance offered by the various factors. The draft at the rear of the boiler setting where connection is made to the stack or flue may be 0.5 inch, while in the furnace directly over the fire it may not be over, say, 0.15 inch, the difference being the draft required to overcome the resistance offered in forcing the gases through the tubes and around the baffling. One of the most important factors to be considered in designing a stack is the pressure required to force the air for combustion through the bed of fuel on the grates. This pressure will vary with the nature of the fuel used, and in many instances will be a large percentage of the total draft. In the case of natural draft, its measure is found directly by noting the draft in the furnace, for with properly designed ashpit doors it is evident that the pressure under the grates will not differ sensibly from atmospheric pressure. Loss in Stack--The difference between the theoretical draft as determined by formula (24) and the amount lost by friction in the stack proper is the available draft, or that which the draft gauge indicates when connected to the base of the stack. The sum of the losses of draft in the flue, boiler and furnace must be equivalent to the available draft, and as these quantities can be determined from record of experiments, the problem of designing a stack becomes one of proportioning it to produce a certain available draft. The loss in the stack due to friction of the gases can be calculated from the following formula: f W² C H [Delta]D = -------- (26) A³ in which [Delta]D = draft loss in inches of water, W = weight of gas in pounds passing per second, C = perimeter of stack in feet, H = height of stack in feet, f = a constant with the following values at sea level: .0015 for steel stacks, temperature of gases 600 degrees Fahrenheit. .0011 for steel stacks, temperature of gases 350 degrees Fahrenheit. .0020 for brick or brick-lined stacks, temperature of gases 600 degrees Fahrenheit. .0015 for brick or brick-lined stacks, temperature of gases 350 degrees Fahrenheit. A = Area of stack in square feet. [Illustration: 24,420 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock & Wilcox Chain Grate Stokers in the Quarry Street Station of the Commonwealth Edison Co., Chicago, Ill.] This formula can also be used for calculating the frictional losses for flues, in which case, C = the perimeter of the flue in feet, H = the length of the flue in feet, the other values being the same as for stacks. The available draft is equal to the difference between the theoretical draft from formula (25) and the loss from formula (26), hence: f W² C H d^{1} = available draft = KH - -------- (27) A³ Table 53 gives the available draft in inches that a stack 100 feet high will produce when serving different horse powers of boilers with the methods of calculation for other heights. TABLE 53 AVAILABLE DRAFT CALCULATED FOR 100-FOOT STACK OF DIFFERENT DIAMETERS ASSUMING STACK TEMPERATURE OF 500 DEGREES FAHRENHEIT AND 100 POUNDS OF GAS PER HORSE POWER FOR OTHER HEIGHTS OF STACK MULTIPLY DRAFT BY HEIGHT ÷ 100 +-----+-------------------------------------------------------------------+ |Horse| | |Power| Diameter of Stack in Inches | +-----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | |36 |42 |48 |54 |60 |66 |72 |78 |84 |90 |96 |102|108|114|120|132|144| +-----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | 100 |.64| | | | | | | | | | | | | | | | | | 200 |.55|.62| | | | | | | | | | | | | | | | | 300 |.41|.55|.61| | | | | | | | | | | | | | | | 400 |.21|.46|.56|.61| | | | | | | | | | | | | | | 500 | |.34|.50|.57|.61| | | | | | | | | | | | | | 600 | |.19|.42|.53|.59| | | | | | | | | | | | | | 700 | | |.34|.48|.56|.60|.63| | | | | | | | | | | | 800 | | |.23|.43|.52|.58|.61|.63| | | | | | | | | | | 900 | | | |.36|.49|.56|.60|.62|.64| | | | | | | | | |1000 | | | |.29|.45|.53|.58|.61|.63|.64| | | | | | | | |1100 | | | | |.40|.50|.56|.60|.62|.63|.64| | | | | | | |1200 | | | | |.35|.47|.54|.58|.61|.63|.64|.65| | | | | | |1300 | | | | |.29|.44|.52|.57|.60|.62|.63|.64|.65| | | | | |1400 | | | | | |.40|.49|.55|.59|.61|.63|.64|.65|.65| | | | |1500 | | | | | |.36|.47|.53|.58|.60|.62|.63|.64|.65|.65| | | |1600 | | | | | |.31|.43|.52|.56|.59|.62|.63|.64|.65|.65| | | |1700 | | | | | | |.41|.50|.55|.58|.61|.62|.64|.64|.65| | | |1800 | | | | | | |.37|.47|.54|.57|.60|.62|.63|.64|.65| | | |1900 | | | | | | |.34|.45|.52|.56|.59|.61|.63|.64|.64| | | |2000 | | | | | | | |.43|.50|.55|.59|.61|.62|.63|.64| | | |2100 | | | | | | | |.40|.49|.54|.58|.60|.62|.63|.64| | | |2200 | | | | | | | |.38|.47|.53|.57|.59|.61|.62|.64| | | |2300 | | | | | | | |.35|.45|.52|.56|.59|.61|.62|.63| | | |2400 | | | | | | | |.32|.43|.50|.55|.58|.60|.62|.63| | | |2500 | | | | | | | | |.41|.49|.54|.57|.60|.61|.63| | | |2600 | | | | | | | | | |.47|.53|.56|.59|.61|.62|.64|.65| |2700 | | | | | | | | | |.45|.52|.55|.58|.60|.62|.64|.65| |2800 | | | | | | | | | |.44|.59|.55|.58|.60|.61|.64|.65| |2900 | | | | | | | | | |.42|.49|.54|.57|.59|.61|.63|.65| |3000 | | | | | | | | | |.40|.48|.53|.56|.59|.61|.63|.64| |3100 | | | | | | | | | |.38|.47|.52|.56|.58|.60|.63|.64| |3200 | | | | | | | | | | |.45|.51|.55|.58|.60|.63|.64| |3300 | | | | | | | | | | |.44|.50|.54|.57|.59|.62|.64| |3400 | | | | | | | | | | |.42|.49|.53|.56|.59|.62|.64| |3500 | | | | | | | | | | |.40|.48|.52|.56|.58|.62|.64| |3600 | | | | | | | | | | | |.47|.52|.55|.58|.61|.63| |3700 | | | | | | | | | | | |.45|.51|.55|.57|.61|.63| |3800 | | | | | | | | | | | |.44|.50|.54|.57|.61|.63| |3900 | | | | | | | | | | | |.43|.49|.53|.56|.60|.63| |4000 | | | | | | | | | | | |.42|.48|.52|.56|.60|.62| |4100 | | | | | | | | | | | |.40|.47|.52|.55|.60|.62| |4200 | | | | | | | | | | | |.39|.46|.51|.55|.59|.62| |4300 | | | | | | | | | | | | |.45|.50|.54|.59|.62| |4400 | | | | | | | | | | | | |.44|.49|.53|.59|.62| |4500 | | | | | | | | | | | | |.43|.49|.53|.58|.61| |4600 | | | | | | | | | | | | |.42|.48|.52|.58|.61| |4700 | | | | | | | | | | | | |.41|.47|.51|.57|.61| |4800 | | | | | | | | | | | | |.40|.46|.51|.57|.60| |4900 | | | | | | | | | | | | | |.45|.50|.57|.60| |5000 | | | | | | | | | | | | | |.44|.49|.56|.60| +-----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ FOR OTHER STACK TEMPERATURES ADD OR DEDUCT BEFORE MULTIPLYING BY HEIGHT ÷ 100 AS FOLLOWS[52] For 750 Degrees F. Add .17 inch. For 700 Degrees F. Add .14 inch. For 650 Degrees F. Add .11 inch. For 600 Degrees F. Add .08 inch. For 550 Degrees F. Add .04 inch. For 450 Degrees F. Deduct .04 inch. For 400 Degrees F. Deduct .09 inch. For 350 Degrees F. Deduct .14 inch. [Graph: Horse Power of Boilers against Diameter of Stack in Inches Fig. 33. Diameter of Stacks and Horse Power they will Serve Computed from Formula (28). For brick or brick-lined stacks, increase the diameter 6 per cent] Height and Diameter of Stacks--From this formula (27) it becomes evident that a stack of certain diameter, if it be increased in height, will produce the same available draft as one of larger diameter, the additional height being required to overcome the added frictional loss. It follows that among the various stacks that would meet the requirements of a particular case there must be one which can be constructed more cheaply than the others. It has been determined from the relation of the cost of stacks to their diameters and heights, in connection with the formula for available draft, that the minimum cost stack has a diameter dependent solely upon the horse power of the boilers it serves, and a height proportional to the available draft required. Assuming 120 pounds of flue gas per hour for each boiler horse power, which provides for ordinary overloads and the use of poor coal, the method above stated gives: For an unlined steel stack-- diameter in inches = 4.68 (H. P.)^{2/5} (28) For a stack lined with masonry-- diameter in inches = 4.92 (H. P.)^{2/5} (29) In both of these formulae H. P. = the rated horse power of the boiler. From this formula the curve, Fig. 33, has been calculated and from it the stack diameter for any boiler horse power can be selected. For stoker practice where a large stack serves a number of boilers, the area is usually made about one-third more than the above rules call for, which allows for leakage of air through the setting of any idle boilers, irregularities in operating conditions, etc. Stacks with diameters determined as above will give an available draft which bears a constant ratio of the theoretical draft, and allowing for the cooling of the gases in their passage upward through the stack, this ratio is 8. Using this factor in formula (25), and transposing, the height of the chimney becomes, d^{1} H = ----- (30) .8 K Where H = height of stack in feet above the level of the grates, d^{1} = available draft required, K = constant as in formula. Losses in Flues--The loss of draft in straight flues due to friction and inertia can be calculated approximately from formula (26), which was given for loss in stacks. It is to be borne in mind that C in this formula is the actual perimeter of the flue and is least, relative to the cross sectional area, when the section is a circle, is greater for a square section, and greatest for a rectangular section. The retarding effect of a square flue is 12 per cent greater than that of a circular flue of the same area and that of a rectangular with sides as 1 and 1½, 15 per cent greater. The greater resistance of the more or less uneven brick or concrete flue is provided for in the value of the constants given for formula (26). Both steel and brick flues should be short and should have as near a circular or square cross section as possible. Abrupt turns are to be avoided, but as long easy sweeps require valuable space, it is often desirable to increase the height of the stack rather than to take up added space in the boiler room. Short right-angle turns reduce the draft by an amount which can be roughly approximated as equal to 0.05 inch for each turn. The turns which the gases make in leaving the damper box of a boiler, in entering a horizontal flue and in turning up into a stack should always be considered. The cross sectional areas of the passages leading from the boilers to the stack should be of ample size to provide against undue frictional loss. It is poor economy to restrict the size of the flue and thus make additional stack height necessary to overcome the added friction. The general practice is to make flue areas the same or slightly larger than that of the stack; these should be, preferably, at least 20 per cent greater, and a safe rule to follow in figuring flue areas is to allow 35 square feet per 1000 horse power. It is unnecessary to maintain the same size of flue the entire distance behind a row of boilers, and the areas at any point may be made proportional to the volume of gases that will pass that point. That is, the areas may be reduced as connections to various boilers are passed. [Illustration: 6000 Horse-power Installation of Babcock & Wilcox Boilers at the United States Navy Yard, Washington, D. C.] With circular steel flues of approximately the same size as the stacks, or reduced proportionally to the volume of gases they will handle, a convenient rule is to allow 0.1 inch draft loss per 100 feet of flue length and 0.05 inch for each right-angle turn. These figures are also good for square or rectangular steel flues with areas sufficiently large to provide against excessive frictional loss. For losses in brick or concrete flues, these figures should be doubled. Underground flues are less desirable than overhead or rear flues for the reason that in most instances the gases will have to make more turns where underground flues are used and because the cross sectional area of such flues will oftentimes be decreased on account of an accumulation of dirt or water which it may be impossible to remove. In tall buildings, such as office buildings, it is frequently necessary in order to carry spent gases above the roofs, to install a stack the height of which is out of all proportion to the requirements of the boilers. In such cases it is permissible to decrease the diameter of a stack, but care must be taken that this decrease is not sufficient to cause a frictional loss in the stack as great as the added draft intensity due to the increase in height, which local conditions make necessary. In such cases also the fact that the stack diameter is permissibly decreased is no reason why flue sizes connecting to the stack should be decreased. These should still be figured in proportion to the area of the stack that would be furnished under ordinary conditions or with an allowance of 35 square feet per 1000 horse power, even though the cross sectional area appears out of proportion to the stack area. Loss in Boiler--In calculating the available draft of a chimney 120 pounds per hour has been used as the weight of the gases per boiler horse power. This covers an overload of the boiler to an extent of 50 per cent and provides for the use of poor coal. The loss in draft through a boiler proper will depend upon its type and baffling and will increase with the per cent of rating at which it is run. No figures can be given which will cover all conditions, but for approximate use in figuring the available draft necessary it may be assumed that the loss through a boiler will be 0.25 inch where the boiler is run at rating, 0.40 inch where it is run at 150 per cent of its rated capacity, and 0.70 inch where it is run at 200 per cent of its rated capacity. Loss in Furnace--The draft loss in the furnace or through the fuel bed varies between wide limits. The air necessary for combustion must pass through the interstices of the coal on the grate. Where these are large, as is the case with broken coal, but little pressure is required to force the air through the bed; but if they are small, as with bituminous slack or small sizes of anthracite, a much greater pressure is needed. If the draft is insufficient the coal will accumulate on the grates and a dead smoky fire will result with the accompanying poor combustion; if the draft is too great, the coal may be rapidly consumed on certain portions of the grate, leaving the fire thin in spots and a portion of the grates uncovered with the resulting losses due to an excessive amount of air. [Graph: Force of Draft between Furnace and Ash Pit--Inches of Water against Pounds of Coal burned per Square Foot of Grate Surface per Hour Fig. 34. Draft Required at Different Combustion Rates for Various Kinds of Coal] Draft Required for Different Fuels--For every kind of fuel and rate of combustion there is a certain draft with which the best general results are obtained. A comparatively light draft is best with the free burning bituminous coals and the amount to use increases as the percentage of volatile matter diminishes and the fixed carbon increases, being highest for the small sizes of anthracites. Numerous other factors such as the thickness of fires, the percentage of ash and the air spaces in the grates bear directly on this question of the draft best suited to a given combustion rate. The effect of these factors can only be found by experiment. It is almost impossible to show by one set of curves the furnace draft required at various rates of combustion for all of the different conditions of fuel, etc., that may be met. The curves in Fig. 34, however, give the furnace draft necessary to burn various kinds of coal at the combustion rates indicated by the abscissae, for a general set of conditions. These curves have been plotted from the records of numerous tests and allow a safe margin for economically burning coals of the kinds noted. Rate of Combustion--The amount of coal which can be burned per hour per square foot of grate surface is governed by the character of the coal and the draft available. When the boiler and grate are properly proportioned, the efficiency will be practically the same, within reasonable limits, for different rates of combustion. The area of the grate, and the ratio of this area to the boiler heating surface will depend upon the nature of the fuel to be burned, and the stack should be so designed as to give a draft sufficient to burn the maximum amount of fuel per square foot of grate surface corresponding to the maximum evaporative requirements of the boiler. Solution of a Problem--The stack diameter can be determined from the curve, Fig. 33. The height can be determined by adding the draft losses in the furnace, through the boiler and flues, and computing from formula (30) the height necessary to give this draft. Example: Proportion a stack for boilers rated at 2000 horse power, equipped with stokers, and burning bituminous coal that will evaporate 8 pounds of water from and at 212 degrees Fahrenheit per pound of fuel; the ratio of boiler heating surface to grate surface being 50:1; the flues being 100 feet long and containing two right-angle turns; the stack to be able to handle overloads of 50 per cent; and the rated horse power of the boilers based on 10 square feet of heating surface per horse power. The atmospheric temperature may be assumed as 60 degrees Fahrenheit and the flue temperatures at the maximum overload as 550 degrees Fahrenheit. The grate surface equals 400 square feet. 2000 × 34½ The total coal burned at rating = ---------- = 8624 pounds. 8 The coal per square foot of grate surface per hour at rating = 8624 ---- = 22 pounds. 400 For 50 per cent overload the combustion rate will be approximately 60 per cent greater than this or 1.60 × 22 = 35 pounds per square foot of grate surface per hour. The furnace draft required for the combustion rate, from the curve, Fig. 34, is 0.6 inch. The loss in the boiler will be 0.4 inch, in the flue 0.1 inch, and in the turns 2 × 0.05 = 0.1 inch. The available draft required at the base of the stack is, therefore, _Inches_ Boiler 0.4 Furnace 0.6 Flues 0.1 Turns 0.1 --- Total 1.2 Since the available draft is 80 per cent of the theoretical draft, this draft due to the height required is 1.2 ÷ .8 = 1.5 inch. The chimney constant for temperatures of 60 degrees Fahrenheit and 550 degrees Fahrenheit is .0071 and from formula (30), 1.5 H = ----- = 211 feet. .0071 Its diameter from curve in Fig. 33 is 96 inches if unlined, and 102 inches inside if lined with masonry. The cross sectional area of the flue should be approximately 70 square feet at the point where the total amount of gas is to be handled, tapering to the boiler farthest from the stack to a size which will depend upon the size of the boiler units used. Correction in Stack Sizes for Altitudes--It has ordinarily been assumed that a stack height for altitude will be increased inversely as the ratio of the barometric pressure at the altitude to that at sea level, and that the stack diameter will increase inversely as the two-fifths power of this ratio. Such a relation has been based on the assumption of constant draft measured in inches of water at the base of the stack for a given rate of operation of the boilers, regardless of altitude. If the assumption be made that boilers, flues and furnace remain the same, and further that the increased velocity of a given weight of air passing through the furnace at a higher altitude would have no effect on the combustion, the theory has been advanced[53] that a different law applies. Under the above assumptions, whenever a stack is working at its maximum capacity at any altitude, the entire draft is utilized in overcoming the various resistances, each of which is proportional to the square of the velocity of the gases. Since boiler areas are fixed, all velocities may be related to a common velocity, say, that within the stack, and all resistances may, therefore, be expressed as proportional to the square of the chimney velocity. The total resistance to flow, in terms of velocity head, may be expressed in terms of weight of a column of external air, the numerical value of such head being independent of the barometric pressure. Likewise the draft of a stack, expressed in height of column of external air, will be numerically independent of the barometric pressure. It is evident, therefore, that if a given boiler plant, with its stack operated with a fixed fuel, be transplanted from sea level to an altitude, assuming the temperatures remain constant, the total draft head measured in height of column of external air will be numerically constant. The velocity of chimney gases will, therefore, remain the same at altitude as at sea level and the weight of gases flowing per second with a fixed velocity will be proportional to the atmospheric density or inversely proportional to the normal barometric pressure. To develop a given horse power requires a constant weight of chimney gas and air for combustion. Hence, as the altitude is increased, the density is decreased and, for the assumptions given above, the velocity through the furnace, the boiler passes, breeching and flues must be correspondingly greater at altitude than at sea level. The mean velocity, therefore, for a given boiler horse power and constant weight of gases will be inversely proportional to the barometric pressure and the velocity head measured in column of external air will be inversely proportional to the square of the barometric pressure. For stacks operating at altitude it is necessary not only to increase the height but also the diameter, as there is an added resistance within the stack due to the added friction from the additional height. This frictional loss can be compensated by a suitable increase in the diameter and when so compensated, it is evident that on the assumptions as given, the chimney height would have to be increased at a ratio inversely proportional to the square of the normal barometric pressure. In designing a boiler for high altitudes, as already stated, the assumption is usually made that a given grade of fuel will require the same draft measured in inches of water at the boiler damper as at sea level, and this leads to making the stack height inversely as the barometric pressures, instead of inversely as the square of the barometric pressures. The correct height, no doubt, falls somewhere between the two values as larger flues are usually used at the higher altitudes, whereas to obtain the ratio of the squares, the flues must be the same size in each case, and again the effect of an increased velocity of a given weight of air through the fire at a high altitude, on the combustion, must be neglected. In making capacity tests with coal fuel, no difference has been noted in the rates of combustion for a given draft suction measured by a water column at high and low altitudes, and this would make it appear that the correct height to use is more nearly that obtained by the inverse ratio of the barometric readings than by the inverse ratio of the squares of the barometric readings. If the assumption is made that the value falls midway between the two formulae, the error in using a stack figured in the ordinary way by making the height inversely proportional to the barometric readings would differ about 10 per cent in capacity at an altitude of 10,000 feet, which difference is well within the probable variation of the size determined by different methods. It would, therefore, appear that ample accuracy is obtained in all cases by simply making the height inversely proportional to the barometric readings and increasing the diameter so that the stacks used at high altitudes have the same frictional resistance as those used at low altitudes, although, if desired, the stack may be made somewhat higher at high altitudes than this rule calls for in order to be on the safe side. The increase of stack diameter necessary to maintain the same friction loss is inversely as the two-fifths power of the barometric pressure. Table 54 gives the ratio of barometric readings of various altitudes to sea level, values for the square of this ratio and values of the two-fifths power of this ratio. TABLE 54 STACK CAPACITIES, CORRECTION FACTORS FOR ALTITUDES _______________________________________________________________________ | | | | | | | Altitude | | R | | R^{2/5} | | Height in Feet | Normal | Ratio Barometer | | Ratio Increase | | Above | Barometer | Reading | R² | in Stack | | Sea Level | | Sea Level to | | Diameter | | | | Altitude | | | |________________|___________|_________________|_______|________________| | | | | | | | 0 | 30.00 | 1.000 | 1.000 | 1.000 | | 1000 | 28.88 | 1.039 | 1.079 | 1.015 | | 2000 | 27.80 | 1.079 | 1.064 | 1.030 | | 3000 | 26.76 | 1.121 | 1.257 | 1.047 | | 4000 | 25.76 | 1.165 | 1.356 | 1.063 | | 5000 | 24.79 | 1.210 | 1.464 | 1.079 | | 6000 | 23.87 | 1.257 | 1.580 | 1.096 | | 7000 | 22.97 | 1.306 | 1.706 | 1.113 | | 8000 | 22.11 | 1.357 | 1.841 | 1.130 | | 9000 | 21.28 | 1.410 | 1.988 | 1.147 | | 10000 | 20.49 | 1.464 | 2.144 | 1.165 | |________________|___________|_________________|_______|________________| These figures show that the altitude affects the height to a much greater extent than the diameter and that practically no increase in diameter is necessary for altitudes up to 3000 feet. For high altitudes the increase in stack height necessary is, in some cases, such as to make the proportion of height to diameter impracticable. The method to be recommended in overcoming, at least partially, the great increase in height necessary at high altitudes is an increase in the grate surface of the boilers which the stack serves, in this way reducing the combustion rate necessary to develop a given power and hence the draft required for such combustion rate. TABLE 55 STACK SIZES BY KENT'S FORMULA ASSUMING 5 POUNDS OF COAL PER HORSE POWER ____________________________________________________________________ | | | | | | | | Height of Stack in Feet |Side of| | | |______________________________________________|Equiva-| | Dia- | Area | | | | | | | | | | | lent | | meter|Square| 50| 60| 70| 80 | 90 | 100| 110| 125| 150| 175|Square | |Inches| Feet |___|___|___|____|____|____|____|____|____|____| Stack | | | | |Inches | | | | Commercial Horse Power | | |______|______|______________________________________________|_______| | | | | | | | | | | | | | | | 33 | 5.94|106|115|125| 133| 141| 149| | | | | 30 | | 36 | 7.07|129|141|152| 163| 173| 182| | | | | 32 | | 39 | 8.30|155|169|183| 196| 208| 219| 229| 245| | | 35 | | 42 | 9.62|183|200|216| 231| 245| 258| 271| 289| 316| | 38 | | 48 | 12.57|246|269|290| 311| 330| 348| 365| 389| 426| 460| 43 | | 54 | 15.90|318|348|376| 402| 427| 449| 472| 503| 551| 595| 48 | | 60 | 19.64|400|437|473| 505| 536| 565| 593| 632| 692| 748| 54 | | 66 | 23.76|490|537|580| 620| 658| 694| 728| 776| 849| 918| 59 | | 72 | 28.27|591|646|698| 747| 792| 835| 876| 934|1023|1105| 64 | | 78 | 33.18|700|766|828| 885| 939| 990|1038|1107|1212|1310| 70 | | 84 | 38.48|818|896|968|1035|1098|1157|1214|1294|1418|1531| 75 | |______|______|___|___|___|____|____|____|____|____|____|____|_______| | | | | | | | | Height of Stack in Feet |Side of| | | |______________________________________________|Equiva-| | Dia- | Area | | | | | | | | | lent | | meter|Square| 100| 110 | 125 | 150 | 175 | 200 | 225 | 250 |Square | |Inches| Feet |____|_____|_____|_____|_____|_____|_____|_____| Stack | | | | |Inches | | | | Commercial Horse Power | | |______|______|______________________________________________|_______| | | | | | | | | | | | | | 90 | 44.18|1338| 1403| 1496| 1639| 1770| 1893| 2008| 2116| 80 | | 96 | 50.27|1532| 1606| 1713| 1876| 2027| 2167| 2298| 2423| 86 | | 102 | 56.75|1739| 1824| 1944| 2130| 2300| 2459| 2609| 2750| 91 | | 108 | 63.62|1959| 2054| 2190| 2392| 2592| 2770| 2939| 3098| 98 | | 114 | 70.88|2192| 2299| 2451| 2685| 2900| 3100| 3288| 3466| 101 | | 120 | 78.54|2438| 2557| 2726| 2986| 3226| 3448| 3657| 3855| 107 | | 126 | 86.59|2697| 2829| 3016| 3303| 3568| 3814| 4046| 4265| 112 | | 132 | 95.03|2970| 3114| 3321| 3637| 3929| 4200| 4455| 4696| 117 | | 144 |113.10|3554| 3726| 3973| 4352| 4701| 5026| 5331| 5618| 128 | | 156 |132.73|4190| 4393| 4684| 5131| 5542| 5925| 6285| 6624| 138 | | 168 |153.94|4878| 5115| 5454| 5974| 6454| 6899| 7318| 7713| 150 | |______|______|____|_____|_____|_____|_____|_____|_____|_____|_______| Kent's Stack Tables--Table 55 gives, in convenient form for approximate work, the sizes of stacks and the horse power of boilers which they will serve. This table is a modification of Mr. William Kent's stack table and is calculated from his formula. Provided no unusual conditions are encountered, it is reliable for the ordinary rates of combustion with bituminous coals. It is figured on a consumption of 5 pounds of coal burned per hour per boiler horse power developed, this figure giving a fairly liberal allowance for the use of poor coal and for a reasonable overload. When the coal used is a low grade bituminous of the Middle or Western States, it is strongly recommended that these sizes be increased materially, such an increase being from 25 to 60 per cent, depending upon the nature of the coal and the capacity desired. For the coal burned per hour for any size stack given in the table, the values should be multiplied by 5. A convenient rule for large stacks, 200 feet high and over, is to provide 30 square feet of cross sectional area per 1000 rated horse power. Stacks for Oil Fuel--The requirements of stacks connected to boilers under which oil fuel is burned are entirely different from those where coal is used. While more attention has been paid to the matter of stack sizes for oil fuel in recent years, there has not as yet been gathered the large amount of experimental data available for use in designing coal stacks. In the case of oil-fired boilers the loss of draft through the fuel bed is partially eliminated. While there may be practically no loss through any checkerwork admitting air to the furnace when a boiler is new, the areas for the air passage in this checkerwork will in a short time be decreased, due to the silt which is present in practically all fuel oil. The loss in draft through the boiler proper at a given rating will be less than in the case of coal-fired boilers, this being due to a decrease in the volume of the gases. Further, the action of the oil burner itself is to a certain extent that of a forced draft. To offset this decrease in draft requirement, the temperature of the gases entering the stack will be somewhat lower where oil is used than where coal is used, and the draft that a stack of a given height would give, therefore, decreases. The factors as given above, affecting as they do the intensity of the draft, affect directly the height of the stack to be used. As already stated, the volume of gases from oil-fired boilers being less than in the case of coal, makes it evident that the area of stacks for oil fuel will be less than for coal. It is assumed that these areas will vary directly as the volume of the gases to be handled, and this volume for oil may be taken as approximately 60 per cent of that for coal. In designing stacks for oil fuel there are two features which must not be overlooked. In coal-firing practice there is rarely danger of too much draft. In the burning of oil, however, this may play an important part in the reduction of plant economy, the influence of excessive draft being more apparent where the load on the plant may be reduced at intervals. The reason for this is that, aside from a slight decrease in temperature at reduced loads, the tendency, due to careless firing, is toward a constant gas flow through the boiler regardless of the rate of operation, with the corresponding increase of excess air at light loads. With excessive stack height, economical operation at varying loads is almost impossible with hand control. With automatic control, however, where stacks are necessarily high to take care of known peaks, under lighter loads this economical operation becomes less difficult. For this reason the question of designing a stack for a plant where the load is known to be nearly a constant is easier than for a plant where the load will vary over a wide range. While great care must be taken to avoid excessive draft, still more care must be taken to assure a draft suction within all parts of the setting under any and all conditions of operation. It is very easily possible to more than offset the economy gained through low draft, by the losses due to setting deterioration, resulting from such lack of suction. Under conditions where the suction is not sufficient to carry off the products of combustion, the action of the heat on the setting brickwork will cause its rapid failure. [Illustration: 7800 Horse-power Installation of Babcock & Wilcox Boilers, Equipped with Babcock & Wilcox Chain Grate Stokers at the Metropolitan West Side Elevated Ry. Co., Chicago, Ill.] It becomes evident, therefore, that the question of stack height for oil-fired boilers is one which must be considered with the greatest of care. The designer, on the one hand, must guard against the evils of excessive draft with the view to plant economy, and, on the other, against the evils of lack of draft from the viewpoint of upkeep cost. Stacks for this work should be proportioned to give ample draft for the maximum overload that a plant will be called upon to carry, all conditions of overload carefully considered. At the same time, where this maximum overload is figured liberally enough to insure a draft suction within the setting under all conditions, care must be taken against the installation of a stack which would give more than this maximum draft. TABLE 56 STACK SIZES FOR OIL FUEL ADAPTED FROM C. R. WEYMOUTH'S TABLE (TRANS. A. S. M. E. VOL. 34) +----------------------------------------------------+ |+--------+-----------------------------------------+| || | Height in Feet Above Boiler Room Floor || ||Diameter+------+------+------+-----+--------------+| || Inches | 80 | 90 | 100 | 120 | 140 | 160 || |+--------+------+------+------+------+------+------+| || 33 | 161 | 206 | 233 | 270 | 306 | 315 || || 36 | 208 | 253 | 295 | 331 | 363 | 387 || || 39 | 251 | 303 | 343 | 399 | 488 | 467 || || 42 | 295 | 359 | 403 | 474 | 521 | 557 || || 48 | 399 | 486 | 551 | 645 | 713 | 760 || || 54 | 519 | 634 | 720 | 847 | 933 | 1000 || || 60 | 657 | 800 | 913 | 1073 | 1193 | 1280 || || 66 | 813 | 993 | 1133 | 1333 | 1480 | 1593 || || 72 | 980 | 1206 | 1373 | 1620 | 1807 | 1940 || || 84 | 1373 | 1587 | 1933 | 2293 | 2560 | 2767 || || 96 | 1833 | 2260 | 2587 | 3087 | 3453 | 3740 || || 108 | 2367 | 2920 | 3347 | 4000 | 4483 | 4867 || || 120 | 3060 | 3660 | 4207 | 5040 | 5660 | 6160 || |+--------+------+------+------+------+------+------+| +----------------------------------------------------+ Figures represent nominal rated horse power. Sizes as given good for 50 per cent overloads. Based on centrally located stacks, short direct flues and ordinary operating efficiencies. Table 56 gives the sizes of stacks, and horse power which they will serve for oil fuel. This table is, in modified form, one calculated by Mr. C. R. Weymouth after an exhaustive study of data pertaining to the subject, and will ordinarily give satisfactory results. Stacks for Blast Furnace Gas Work--For boilers burning blast furnace gas, as in the case of oil-fired boilers, stack sizes as suited for coal firing will have to be modified. The diameter of stacks for this work should be approximately the same as for coal-fired boilers. The volume of gases would be slightly greater than from a coal fire and would decrease the draft with a given stack, but such a decrease due to volume is about offset by an increase due to somewhat higher temperatures in the case of the blast furnace gases. Records show that with this class of fuel 175 per cent of the rated capacity of a boiler can be developed with a draft at the boiler damper of from 0.75 inch to 1.0 inch, and it is well to limit the height of stacks to one which will give this draft as a maximum. A stack of proper diameter, 130 feet high above the ground, will produce such a draft and this height should ordinarily not be exceeded. Until recently the question of economy in boilers fired with blast furnace gas has not been considered, but, aside from the economical standpoint, excessive draft should be guarded against in order to lower the upkeep cost. Stacks should be made of sufficient height to produce a draft that will develop the maximum capacity required, and this draft decreased proportionately for loads under the maximum by damper regulation. The amount of gas fed to a boiler for any given rating is a fixed quantity and if a draft in excess of that required for that particular rate of operation is supplied, economy is decreased and the wear and tear on the setting is materially increased. Excess air which is drawn in, either through or around the gas burners by an excessive draft, will decrease economy, as in any other class of work. Again, as in oil-fired practice, it is essential on the other hand that a suction be maintained within all parts of the setting, in this case not only to provide against setting deterioration but to protect the operators from leakage of gas which is disagreeable and may be dangerous. Aside from the intensity of the draft, a poor mixture of the gas and air or a "laneing" action may lead to secondary combustion with the possibility of dangerous explosions within the setting, may cause a pulsating action within the setting, may increase the exit temperatures to a point where there is danger of burning out damper boxes, and, in general, is hard on the setting. It is highly essential, therefore, that the furnace be properly constructed to meet the draft which will be available. Stacks for Wood-fired Boilers--For boilers using wood as fuel, there is but little data upon which to base stack sizes. The loss of draft through the bed of fuel will vary over limits even wider than in the case of coal, for in this class of fuel the moisture may run from practically 0.0 per cent to over 60 per cent, and the methods of handling and firing are radically different for the different classes of wood (see chapter on Wood-burning Furnaces). As economy is ordinarily of little importance, high stack temperatures may be expected, and often unavoidably large quantities of excess air are supplied due to the method of firing. In general, it may be stated that for this class of fuel the diameter of stacks should be at least as great as for coal-fired boilers, while the height may be slightly decreased. It is far the best plan in designing a stack for boilers using wood fuel to consider each individual set of conditions that exist, rather than try to follow any general rule. One factor not to be overlooked in stacks for wood burning is their location. The fine particles of this fuel are often carried unconsumed through the boiler, and where the stack is not on top of the boiler, these particles may accumulate in the base of the stack below the point at which the flue enters. Where there is any air leakage through the base of such a stack, this fuel may become ignited and the stack burned. Where there is a possibility of such action taking place, it is well to line the stack with fire brick for a portion of its height. Draft Gauges--The ordinary form of draft gauge, Fig. 35, which consists of a U-tube, containing water, lacks sensitiveness in measuring such slight pressure differences as usually exist, and for that reason gauges which multiply the draft indications are more convenient and are much used. [Illustration: Fig. 35. U-tube Draft Gauge] [Illustration: Fig. 36. Barrus Draft Gauge] An instrument which has given excellent results is one introduced by Mr. G. H. Barrus, which multiplies the ordinary indications as many times as desired. This is illustrated in Fig. 36, and consists of a U-tube made of one-half inch glass, surmounted by two larger tubes, or chambers, each having a diameter of 2½ inches. Two different liquids which will not mix, and which are of different color, are used, usually alcohol colored red and a certain grade of lubricating oil. The movement of the line of demarcation is proportional to the difference in the areas of the chambers and the U-tube connecting them. The instrument is calibrated by comparison with the ordinary U-tube gauge. In the Ellison form of gauge the lower portion of the ordinary U-tube has been replaced by a tube slightly inclined to the horizontal, as shown in Fig. 37. By this arrangement any vertical motion in the right-hand upright tube causes a very much greater travel of the liquid in the inclined tube, thus permitting extremely small variation in the intensity of the draft to be read with facility. [Illustration: Fig. 37. Ellison Draft Gauge] The gauge is first leveled by means of the small level attached to it, both legs being open to the atmosphere. The liquid is then adjusted until its meniscus rests at the zero point on the left. The right-hand leg is then connected to the source of draft by means of a piece of rubber tubing. Under these circumstances, a rise of level of one inch in the right-hand vertical tube causes the meniscus in the inclined tube to pass from the point 0 to 1.0. The scale is divided into tenths of an inch, and the sub-divisions are hundredths of an inch. The makers furnish a non-drying oil for the liquid, usually a 300 degrees test refined petroleum. A very convenient form of the ordinary U-tube gauge is known as the Peabody gauge, and it is shown in Fig. 38. This is a small modified U-tube with a sliding scale between the two legs of the U and with connections such that either a draft suction or a draft pressure may be taken. The tops of the sliding pieces extending across the tubes are placed at the bottom of the meniscus and accurate readings in hundredths of an inch are obtained by a vernier. [Illustration: Fig. 38. Peabody Draft Gauge] EFFICIENCY AND CAPACITY OF BOILERS Two of the most important operating factors entering into the consideration of what constitutes a satisfactory boiler are its efficiency and capacity. The relation of these factors to one another will be considered later under the selection of boilers with reference to the work they are to accomplish. The present chapter deals with the efficiency and capacity only with a view to making clear exactly what is meant by these terms as applied to steam generating apparatus, together with the methods of determining these factors by tests. Efficiency--The term "efficiency", specifically applied to a steam boiler, is the ratio of heat absorbed by the boiler in the generation of steam to the total amount of heat available in the medium utilized in securing such generation. When this medium is a solid fuel, such as coal, it is impossible to secure the complete combustion of the total amount fed to the boiler. A portion is bound to drop through the grates where it becomes mixed with the ash and, remaining unburned, produces no heat. Obviously, it is unfair to charge the boiler with the failure to absorb the portion of available heat in the fuel that is wasted in this way. On the other hand, the boiler user must pay for such waste and is justified in charging it against the combined boiler and furnace. Due to this fact, the efficiency of a boiler, as ordinarily stated, is in reality the combined efficiency of the boiler, furnace and grate, and Efficiency of boiler,} Heat absorbed per pound of fuel furnace and grate } = ------------------------------- (31) Heat value per pound of fuel The efficiency will be the same whether based on dry fuel or on fuel as fired, including its content of moisture. For example: If the coal contained 3 per cent of moisture, the efficiency would be Heat absorbed per pound of dry coal × 0.97 ------------------------------------------ Heat value per pound of dry coal × 0.97 where 0.97 cancels and the formula becomes (31). The heat supplied to the boiler is due to the combustible portion of fuel which is actually burned, irrespective of what proportion of the total combustible fired may be.[54] This fact has led to the use of a second efficiency basis on combustible and which is called the efficiency of boiler and furnace[55], namely, Efficiency of boiler and furnace[55] Heat absorbed per pound of combustible[56] = -------------------------------------- (32) Heat value per pound of combustible The efficiency so determined is used in comparing the relative performance of boilers, irrespective of the type of grates used under them. If the loss of fuel through the grates could be entirely overcome, the efficiencies obtained by (31) and (32) would obviously be the same. Hence, in the case of liquid and gaseous fuels, where there is practically no waste, these efficiencies are almost identical. As a matter of fact, it is extremely difficult, if not impossible, to determine the actual efficiency of a boiler alone, as distinguished from the combined efficiency of boiler, grate and furnace. This is due to the fact that the losses due to excess air cannot be correctly attributed to either the boiler or the furnace, but only to a combination of the complete apparatus. Attempts have been made to devise methods for dividing the losses proportionately between the furnace and the boiler, but such attempts are unsatisfactory and it is impossible to determine the efficiency of a boiler apart from that of a furnace in such a way as to make such determination of any practical value or in a way that might not lead to endless dispute, were the question to arise in the case of a guaranteed efficiency. From the boiler manufacturer's standpoint, the only way of establishing an efficiency that has any value when guarantees are to be met, is to require the grate or stoker manufacturer to make certain guarantees as to minimum CO_{2}, maximum CO, and that the amount of combustible in the ash and blown away with the flue gases does not exceed a certain percentage. With such a guarantee, the efficiency should be based on the combined furnace and boiler. General practice, however, has established the use of the efficiency based upon combustible as representing the efficiency of the boiler alone. When such an efficiency is used, its exact meaning, as pointed out on opposite page, should be realized. The computation of the efficiencies described on opposite page is best illustrated by example. Assume the following data to be determined from an actual boiler trial. Steam pressure by gauge, 200 pounds. Feed temperature, 180 degrees. Total weight of coal fired, 17,500 pounds. Percentage of moisture in coal, 3 per cent. Total ash and refuse, 2396 pounds. Total water evaporated, 153,543 pounds. Per cent of moisture in steam, 0.5 per cent. Heat value per pound of dry coal, 13,516. Heat value per pound of combustible, 15,359. The factor of evaporation for such a set of conditions is 1.0834. The actual evaporation corrected for moisture in the steam is 152,775 and the equivalent evaporation from and at 212 degrees is, therefore, 165,516 pounds. The total dry fuel will be 17,500 × .97 = 16,975, and the evaporation per pound of dry fuel from and at 212 degrees will be 165,516 ÷ 16,975 = 9.75 pounds. The heat absorbed per pound of dry fuel will, therefore, be 9.75 × 970.4 = 9461 B. t. u. Hence, the efficiency by (31) will be 9461 ÷ 13,516 = 70.0 per cent. The total combustible burned will be 16,975 - 2396 = 14,579, and the evaporation from and at 212 degrees per pound of combustible will be 165,516 ÷ 14,579 = 11.35 pounds. Hence, the efficiency based on combustible from (32) will be (11.35 × 97.04) ÷ 15,359 = 71.79.[**should be 71.71] For approximate results, a chart may be used to take the place of a computation of efficiency. Fig. 39 shows such a chart based on the evaporation per pound of dry fuel and the heat value per pound of dry fuel, from which efficiencies may be read directly to within one-half of one per cent. It is used as follows: From the intersection of the horizontal line, representing the evaporation per pound of fuel, with the vertical line, representing the heat value per pound, the efficiency is read directly from the diagonal scale of efficiencies. This chart may also be used for efficiency based upon combustible when the evaporation from and at 212 degrees and the heat values are both given in terms of combustible. [Graph: Evaporation from and at 212° per Pound of Dry Fuel against B.T.U. per Pound of Dry Fuel Fig. 39. Efficiency Chart. Calculated from Marks and Davis Tables Diagonal Lines Represent Per Cent Efficiency] Boiler efficiencies will vary over a wide range, depending on a great variety of factors and conditions. The highest efficiencies that have been secured with coal are in the neighborhood of 82 per cent and from that point efficiencies are found all the way down to below 50 per cent. Table 59[57] of tests of Babcock & Wilcox boilers under varying conditions of fuel and operation will give an idea of what may be obtained with proper operating conditions. The difference between the efficiency secured in any boiler trial and the perfect efficiency, 100 per cent, includes the losses, some of which are unavoidable in the present state of the art, arising in the conversion of the heat energy of the coal to the heat energy in the steam. These losses may be classified as follows: 1st. Loss due to fuel dropped through the grate. 2nd. Loss due to unburned fuel which is carried by the draft, as small particles, beyond the bridge wall into the setting or up the stack. 3rd. Loss due to the utilization of a portion of the heat in heating the moisture contained in the fuel from the temperature of the atmosphere to 212 degrees; to evaporate it at that temperature and to superheat the steam thus formed to the temperature of the flue gases. This steam, of course, is first heated to the temperature of the furnace but as it gives up a portion of this heat in passing through the boiler, the superheating to the temperature of the exit gases is the correct degree to be considered. 4th. Loss due to the water formed and by the burning of the hydrogen in the fuel which must be evaporated and superheated as in item 3. 5th. Loss due to the superheating of the moisture in the air supplied from the atmospheric temperature to the temperature of the flue gases. 6th. Loss due to the heating of the dry products of combustion to the temperature of the flue gases. 7th. Loss due to the incomplete combustion of the fuel when the carbon is not completely consumed but burns to CO instead of CO_{2}. The CO passes out of the stack unburned as a volatile gas capable of further combustion. 8th. Loss due to radiation of heat from the boiler and furnace settings. Obviously a very elaborate test would have to be made were all of the above items to be determined accurately. In ordinary practice it has become customary to summarize these losses as follows, the methods of computing the losses being given in each instance by a typical example: (A) Loss due to the heating of moisture in the fuel from the atmospheric temperature to 212 degrees, evaporate it at that temperature and superheat it to the temperature of the flue gases. This in reality is the total heat above the temperature of the air in the boiler room, in one pound of superheated steam at atmospheric pressure at the temperature of the flue gases, multiplied by the percentage of moisture in the fuel. As the total heat above the temperature of the air would have to be computed in each instance, this loss is best expressed by: Loss in B. t. u. per pound = W(212-t+970.4+.47(T-212)) (33) Where W = per cent of moisture in coal, t = the temperature of air in the boiler room, T = temperature of the flue gases, .47 = the specific heat of superheated steam at the atmospheric pressure and at the flue gas temperature, (212-t) = B. t. u. necessary to heat one pound of water from the temperature of the boiler room to 212 degrees, 970.4 = B. t. u. necessary to evaporate one pound of water at 212 degrees to steam at atmospheric pressure, .47(T-212) = B. t. u. necessary to superheat one pound of steam at atmospheric pressure from 212 degrees to temperature T. [Illustration: Portion of 15,000 Horse-power Installation of Babcock & Wilcox Boilers, Equipped with Babcock & Wilcox Chain Grate Stokers at the Northumberland, Pa., Plant of the Atlas Portland Cement Co. This Company Operates a Total of 24,000 Horse Power of Babcock & Wilcox Boilers in its Various Plants] (B) Loss due to heat carried away in the steam produced by the burning of the hydrogen component of the fuel. In burning, one pound of hydrogen unites with 8 pounds of oxygen to form 9 pounds of steam. Following the reasoning of item (A), therefore, this loss will be: Loss in B. t. u. per pound = 9H((212-t)+970.4+.47(T-212)) (34) where H = the percentage by weight of hydrogen. This item is frequently considered as a part of the unaccounted for loss, where an ultimate analysis of the fuel is not given. (C) Loss due to heat carried away by dry chimney gases. This is dependent upon the weight of gas per pound of coal which may be determined by formula (16), page 158. Loss in B. t. u. per pound = (T-t)×.24×W. Where T and t have values as in (33), .24 = specific heat of chimney gases, W = weight of dry chimney gas per pound of coal. (D) Loss due to incomplete combustion of the carbon content of the fuel, that is, the burning of the carbon to CO instead of CO_{2}. 10,150 CO Loss in B. t. u. per pound = C×--------- (35) CO_{2}+CO C = per cent of carbon in coal by ultimate analysis, CO and CO_{2} = per cent of CO and CO_{2} by volume from flue gas analysis. 10,150 = the number of heat units generated by burning to CO_{2} one pound of carbon contained in carbon monoxide. (E) Loss due to unconsumed carbon in the ash (it being usually assumed that all the combustible in the ash is carbon). Loss in B. t. u. per pound = per cent C × per cent ash × B. t. u. per pound of combustible in the ash (usually taken as 14,600 B. t. u.) (36) The loss incurred in this way is, directly, the carbon in the ash in percentage terms of the total dry coal fired, multiplied by the heat value of carbon. To compute this item, which is of great importance in comparing the relative performances of different designs of grates, an analysis of the ash must be available. The other losses, namely, items 2, 5 and 8 of the first classification, are ordinarily grouped under one item, as unaccounted for losses, and are obviously the difference between 100 per cent and the sum of the heat utilized and the losses accounted for as given above. Item 5, or the loss due to the moisture in the air, may be readily computed, the moisture being determined from wet and dry bulb thermometer readings, but it is usually disregarded as it is relatively small, averaging, say, one-fifth to one-half of one per cent. Lack of data may, of course, make it necessary to include certain items of the second and ordinary classification in this unaccounted for group. TABLE 57 DATA FROM WHICH HEAT BALANCE (TABLE 58) IS COMPUTED +------------------------------------------------------+ |+----------------------------------------------------+| ||Steam Pressure by Gauge, Pounds | 192 || ||Temperature of Feed, Degrees Fahrenheit | 180 || ||Degrees of Superheat, Degrees Fahrenheit |115.2|| ||Temperature of Boiler Room, Degrees Fahrenheit| 81 || ||Temperature of Exit Gases, Degrees Fahrenheit | 480 || ||Weight of Coal Used per Hour, Pounds | 5714|| ||Moisture, Per Cent | 1.83|| ||Dry Coal Per Hour, Pounds | 5609|| ||Ash and Refuse per Hour, Pounds | 561|| ||Ash and Refuse (of Dry Coal), Per Cent |10.00|| ||Actual Evaporation per Hour, Pounds |57036|| || .- C, Per Cent |78.57|| || | H, Per Cent | 5.60|| ||Ultimate | O, Per Cent | 7.02|| ||Analysis -+ N, Per Cent | 1.11|| ||Dry Coal | Ash, Per Cent | 6.52|| || '- Sulphur, Per Cent | 1.18|| ||Heat Value per Pound Dry Coal, B. t. u. |14225|| ||Heat Value per Pound Combustible, B. t. u. |15217|| ||Combustible in Ash by Analysis, Per Cent | 17.9|| || .- CO_{2}, Per Cent |14.33|| ||Flue Gas -+ O, Per Cent | 4.54|| ||Analysis | CO, Per Cent | 0.11|| || '- N, Per Cent |81.02|| |+----------------------------------------------+-----+| +------------------------------------------------------+ A schedule of the losses as outlined, requires an evaporative test of the boiler, an analysis of the flue gases, an ultimate analysis of the fuel, and either an ultimate or proximate analysis of the ash. As the amount of unaccounted for losses forms a basis on which to judge the accuracy of a test, such a schedule is called a "heat balance". A heat balance is best illustrated by an example: Assume the data as given in Table 57 to be secured in an actual boiler test. From this data the factor of evaporation is 1.1514 and the evaporation per hour from and at 212 degrees is 65,671 pounds. Hence the evaporation from and at 212 degrees per pound of dry coal is 65,671÷5609 = 11.71 pounds. The efficiency of boiler, furnace and grate is: (11.71×970.4)÷14,225 = 79.88 per cent. The heat losses are: (A) Loss due to moisture in coal, = .01831 ((212-81)+970.4+.47(480-212)) = 22. B. t. u., = 0.15 per cent. (B) The loss due to the burning of hydrogen: = 9×.0560((212-81)+970.4+.47(480-212)) = 618 B. t. u., = 4.34 per cent. (C) To compute the loss in the heat carried away by dry chimney gases per pound of coal the weight of such gases must be first determined. This weight per pound of coal is: (11CO_{2}+8O+7(CO+N)) (-------------------)C ( 3(CO_{2}+CO) ) where CO_{2}, O, CO and H are the percentage by volume as determined by the flue gas analysis and C is the percentage by weight of carbon in the dry fuel. Hence the weight of gas per pound of coal will be, (11×14.33+8×4.54+7(0.11+81.02)) (-----------------------------)×78.57 = 13.7 pounds. ( 3(14.33+0.11) ) Therefore the loss of heat in the dry gases carried up the chimney = 13.7×0.24(480-81) = 1311 B. t. u., = 9.22 per cent. (D) The loss due to incomplete combustion as evidenced by the presence of CO in the flue gas analysis is: 0.11 ----------×.7857×10,150 = 61. B. t. u., 14.33+0.11 = .43 per cent. (E) The loss due to unconsumed carbon in the ash: The analysis of the ash showed 17.9 per cent to be combustible matter, all of which is assumed to be carbon. The test showed 10.00 of the total dry fuel fired to be ash. Hence 10.00×.179 = 1.79 per cent of the total fuel represents the proportion of this total unconsumed in the ash and the loss due to this cause is 1.79 per cent × 14,600 = 261 B. t. u., = 1.83 per cent. The heat absorbed by the boilers per pound of dry fuel is 11.71×970.4 = 11,363 B. t. u. This quantity plus losses (A), (B), (C), (D) and (E), or 11,363+22+618+1311+61+261 = 13,636 B. t. u. accounted for. The heat value of the coal, 14,225 B. t. u., less 13,636 B. t. u., leaves 589 B. t. u., unaccounted for losses, or 4.15 per cent. The heat balance should be arranged in the form indicated by Table 58. TABLE 58 HEAT BALANCE B. T. U. PER POUND DRY COAL 14,225 +----------------------------------------------------------------------+ |+--------------------------------------------------------------------+| || |B. t. u.|Per Cent|| |+--------------------------------------------------+--------+--------+| ||Heat absorbed by Boiler | 11,363 | 79.88 || ||Loss due to Evaporation of Moisture in Fuel | 22 | 0.15 || ||Loss due to Moisture formed by Burning of Hydrogen| 618 | 4.34 || ||Loss due to Heat carried away in Dry Chimney Gases| 1311 | 9.22 || ||Loss due to Incomplete Combustion of Carbon | 61 | 0.43 || ||Loss due to Unconsumed Carbon in the Ash | 261 | 1.83 || ||Loss due to Radiation and Unaccounted Losses | 589 | 4.15 || |+--------------------------------------------------+--------+--------+| ||Total | 14,225 | 100.00 || |+--------------------------------------------------+--------+--------+| +----------------------------------------------------------------------+ Application of Heat Balance--A heat balance should be made in connection with any boiler trial on which sufficient data for its computation has been obtained. This is particularly true where the boiler performance has been considered unsatisfactory. The distribution of the heat is thus determined and any extraordinary loss may be detected. Where accurate data for computing such a heat balance is not available, such a calculation based on certain assumptions is sometimes sufficient to indicate unusual losses. The largest loss is ordinarily due to the chimney gases, which depends directly upon the weight of the gas and its temperature leaving the boiler. As pointed out in the chapter on flue gas analysis, the lower limit of the weight of gas is fixed by the minimum air supplied with which complete combustion may be obtained. As shown, where this supply is unduly small, the loss caused by burning the carbon to CO instead of to CO_{2} more than offsets the gain in decreasing the weight of gas. The lower limit of the stack temperature, as has been shown in the chapter on draft, is more or less fixed by the temperature necessary to create sufficient draft suction for good combustion. With natural draft, this lower limit is probably between 400 and 450 degrees. Capacity--Before the capacity of a boiler is considered, it is necessary to define the basis to which such a term may be referred. Such a basis is the so-called boiler horse power. The unit of motive power in general use among steam engineers is the "horse power" which is equivalent to 33,000 foot pounds per minute. Stationary boilers are at the present time rated in horse power, though such a basis of rating may lead and has often led to a misunderstanding. _Work_, as the term is used in mechanics, is the overcoming of resistance through space, while _power_ is the _rate_ of work or the amount done per unit of time. As the operation of a boiler in service implies no motion, it can produce no power in the sense of the term as understood in mechanics. Its operation is the generation of steam, which acts as a medium to convey the energy of the fuel which is in the form of heat to a prime mover in which that heat energy is converted into energy of motion or work, and power is developed. If all engines developed the same amount of power from an equal amount of heat, a boiler might be designated as one having a definite horse power, dependent upon the amount of engine horse power its steam would develop. Such a statement of the rating of boilers, though it would still be inaccurate, if the term is considered in its mechanical sense, could, through custom, be interpreted to indicate that a boiler was of the exact capacity required to generate the steam necessary to develop a definite amount of horse power in an engine. Such a basis of rating, however, is obviously impossible when the fact is considered that the amount of steam necessary to produce the same power in prime movers of different types and sizes varies over very wide limits. To do away with the confusion resulting from an indefinite meaning of the term boiler horse power, the Committee of Judges in charge of the boiler trials at the Centennial Exposition, 1876, at Philadelphia, ascertained that a good engine of the type prevailing at the time required approximately 30 pounds of steam per hour per horse power developed. In order to establish a relation between the engine power and the size of a boiler required to develop that power, they recommended that an evaporation of 30 pounds of water from an initial temperature of 100 degrees Fahrenheit to steam at 70 pounds gauge pressure be considered as _one boiler horse power_. This recommendation has been generally accepted by American engineers as a standard, and when the term boiler horse power is used in connection with stationary boilers[58] throughout this country,[59] without special definition, it is understood to have this meaning. Inasmuch as an equivalent evaporation from and at 212 degrees Fahrenheit is the generally accepted basis of comparison[60], it is now customary to consider the standard boiler horse power as recommended by the Centennial Exposition Committee, in terms of equivalent evaporation from and at 212 degrees. This will be 30 pounds multiplied by the factor of evaporation for 70 pounds gauge pressure and 100 degrees feed temperature, or 1.1494. 30 × 1.1494 = 34.482, or approximately 34.5 pounds. Hence, _one boiler horse power is equal to an evaporation of 34.5 pounds of water per hour from and at 212 degrees Fahrenheit_. The term boiler horse power, therefore, is clearly a measure of evaporation and not of power. A method of basing the horse power rating of a boiler adopted by boiler manufacturers is that of heating surfaces. Such a method is absolutely arbitrary and changes in no way the definition of a boiler horse power just given. It is simply a statement by the manufacturer that his product, under ordinary operating conditions or conditions which may be specified, will evaporate 34.5 pounds of water from and at 212 degrees per definite amount of heating surface provided. The amount of heating surface that has been considered by manufacturers capable of evaporating 34.5 pounds from and at 212 degrees per hour has changed from time to time as the art has progressed. At the present time 10 square feet of heating surface is ordinarily considered the equivalent of one boiler horse power among manufacturers of stationary boilers. In view of the arbitrary nature of such rating and of the widely varying rates of evaporation possible per square foot of heating surface with different boilers and different operating conditions, such a basis of rating has in reality no particular bearing on the question of horse power and should be considered merely as a convenience. The whole question of a unit of boiler capacity has been widely discussed with a view to the adoption of a standard to which there would appear to be a more rational and definite basis. Many suggestions have been offered as to such a basis but up to the present time there has been none which has met with universal approval or which would appear likely to be generally adopted. With the meaning of boiler horse power as given above, that is, a measure of evaporation, it is evident that the capacity of a boiler is a measure of the power it can develop expressed in boiler horse power. Since it is necessary, as stated, for boiler manufacturers to adopt a standard for reasons of convenience in selling, the horse power for which a boiler is sold is known as its normal rated capacity. The efficiency of a boiler and the maximum capacity it will develop can be determined accurately only by a boiler test. The standard methods of conducting such tests are given on the following pages, these methods being the recommendations of the Power Test Committee of the American Society of Mechanical Engineers brought out in 1913.[61] Certain changes have been made to incorporate in the boiler code such portions of the "Instructions Regarding Tests in General" as apply to boiler testing. Methods of calculation and such matter as are treated in other portions of the book have been omitted from the code as noted. [Illustration: Portion of 2600 Horse-power Installation of Babcock & Wilcox Boilers, Equipped with Babcock & Wilcox Chain Grate Stokers at the Peter Schoenhofen Brewing Co., Chicago, Ill.] 1. OBJECT Ascertain the specific object of the test, and keep this in view not only in the work of preparation, but also during the progress of the test, and do not let it be obscured by devoting too close attention to matters of minor importance. Whatever the object of the test may be, accuracy and reliability must underlie the work from beginning to end. If questions of fulfillment of contract are involved, there should be a clear understanding between all the parties, preferably in writing, as to the operating conditions which should obtain during the trial, and as to the methods of testing to be followed, unless these are already expressed in the contract itself. Among the many objects of performance tests, the following may be noted: Determination of capacity and efficiency, and how these compare with standard or guaranteed results. Comparison of different conditions or methods of operation. Determination of the cause of either inferior or superior results. Comparison of different kinds of fuel. Determination of the effect of changes of design or proportion upon capacity or efficiency, etc. 2. PREPARATIONS _(A) Dimensions:_ Measure the dimensions of the principal parts of the apparatus to be tested, so far as they bear on the objects in view, or determine these from correct working drawings. Notice the general features of the same, both exterior and interior, and make sketches, if needed, to show unusual points of design. The dimensions of the heating surfaces of boilers and superheaters to be found are those of surfaces in contact with the fire or hot gases. The submerged surfaces in boilers at the mean water level should be considered as water-heating surfaces, and other surfaces which are exposed to the gases as superheating surfaces. _(B) Examination of Plant:_ Make a thorough examination of the physical condition of all parts of the plant or apparatus which concern the object in view, and record the conditions found, together with any points in the matter of operation which bear thereon. In boilers, examine for leakage of tubes and riveted or other metal joints. Note the condition of brick furnaces, grates and baffles. Examine brick walls and cleaning doors for air leaks, either by shutting the damper and observing the escaping smoke or by candle-flame test. Determine the condition of heating surfaces with reference to exterior deposits of soot and interior deposits of mud or scale. See that the steam main is so arranged that condensed and entrained water cannot flow back into the boiler. If the object of the test is to determine the highest efficiency or capacity obtainable, any physical defects, or defects of operation, tending to make the result unfavorable should first be remedied; all foul parts being cleaned, and the whole put in first-class condition. If, on the other hand, the object is to ascertain the performance under existing conditions, no such preparation is either required or desired. _(C) General Precautions against Leakage:_ In steam tests make sure that there is no leakage through blow-offs, drips, etc., or any steam or water connections of the plant or apparatus undergoing test, which would in any way affect the results. All such connections should be blanked off, or satisfactory assurance should be obtained that there is leakage neither out nor in. This is a most important matter, and no assurance should be considered satisfactory unless it is susceptible of absolute demonstration. 3. FUEL Determine the character of fuel to be used.[62] For tests of maximum efficiency or capacity of the boiler to compare with other boilers, the coal should be of some kind which is commercially regarded as a standard for the locality where the test is made. In the Eastern States the standards thus regarded for semi-bituminous coals are Pocahontas (Va. and W. Va.) and New River (W. Va.); for anthracite coals those of the No. 1 buckwheat size, fresh-mined, containing not over 13 per cent ash by analysis; and for bituminous coals, Youghiogheny and Pittsburgh coals. In some sections east of the Allegheny Mountains the semi-bituminous Clearfield (Pa.) and Cumberland (Md.) are also considered as standards. These coals when of good quality possess the essentials of excellence, adaptability to various kinds of furnaces, grates, boilers, and methods of firing required, besides being widely distributed and generally accessible in the Eastern market. There are no special grades of coal mined in the Western States which are widely and generally considered as standards for testing purposes; the best coal obtainable in any particular locality being regarded as the standard of comparison. A coal selected for maximum efficiency and capacity tests, should be the best of its class, and especially free from slagging and unusual clinker-forming impurities. For guarantee and other tests with a specified coal containing not more than a certain amount of ash and moisture, the coal selected should not be higher in ash and in moisture than the stated amounts, because any increase is liable to reduce the efficiency and capacity more than the equivalent proportion of such increase. The size of the coal, especially where it is of the anthracite class, should be determined by screening a suitable sample. 4. APPARATUS AND INSTRUMENTS[63] The apparatus and instruments required for boiler tests are: (A) Platform scales for weighing coal and ashes. (B) Graduated scales attached to the water glasses. (C) Tanks and platform scales for weighing water (or water meters calibrated in place). Wherever practicable the feed water should be weighed, especially for guarantee tests. The most satisfactory and reliable apparatus for this purpose consists of one or more tanks each placed on platform scales, these being elevated a sufficient distance above the floor to empty into a receiving tank placed below, the latter being connected to the feed pump. Where only one weighing tank is used the receiving tank should be of larger size than the weighing tank, to afford sufficient reserve supply to the pump while the upper tank is filling. If a single weighing tank is used it should preferably be of such capacity as to require emptying not oftener than every 5 minutes. If two or more are used the intervals between successive emptyings should not be less than 3 minutes. (D) Pressure gauges, thermometers, and draft gauges. (E) Calorimeters for determining the calorific value of fuel and the quality of steam. (F) Furnaces pyrometers. (G) Gas analyzing apparatus. 5. OPERATING CONDITIONS Determine what the operating conditions and method of firing should be to conform to the object in view, and see that they prevail throughout the trial, as nearly as possible. Where uniformity in the rate of evaporation is required, arrangement can be usually made to dispose of the steam so that this result can be attained. In a single boiler it may be accomplished by discharging steam through a waste pipe and regulating the amount by means of a valve. In a battery of boilers, in which only one is tested, the draft may be regulated on the remaining boilers to meet the varying demands for steam, leaving the test boiler to work under a steady rate of evaporation. 6. DURATION The duration of tests to determine the efficiency of a hand-fired boiler, should be 10 hours of continuous running, or such time as may be required to burn a total of 250 pounds of coal per square foot of grate. In the case of a boiler using a mechanical stoker, the duration, where practicable, should be at least 24 hours. If the stoker is of a type that permits the quantity and condition of the fuel bed at beginning and end of the test to be accurately estimated, the duration may be reduced to 10 hours, or such time as may be required to burn the above noted total of 250 pounds per square foot. In commercial tests where the service requires continuous operation night and day, with frequent shifts of firemen, the duration of the test, whether the boilers are hand fired or stoker fired, should be at least 24 hours. Likewise in commercial tests, either of a single boiler or of a plant of several boilers, which operate regularly a certain number of hours and during the balance of the day the fires are banked, the duration should not be less than 24 hours. The duration of tests to determine the maximum evaporative capacity of a boiler, without determining the efficiency, should not be less than 3 hours. 7. STARTING AND STOPPING The conditions regarding the temperature of the furnace and boiler, the quantity and quality of the live coal and ash on the grates, the water level, and the steam pressure, should be as nearly as possible the same at the end as at the beginning of the test. To secure the desired equality of conditions with hand-fired boilers, the following method should be employed: The furnace being well heated by a preliminary run, burn the fire low, and thoroughly clean it, leaving enough live coal spread evenly over the grate (say 2 to 4 inches),[64] to serve as a foundation for the new fire. Note quickly the thickness of the coal bed as nearly as it can be estimated or measured; also the water level,[65] the steam pressure, and the time, and record the latter as the starting time. Fresh coal should then be fired from that weighed for the test, the ashpit throughly cleaned, and the regular work of the test proceeded with. Before the end of the test the fire should again be burned low and cleaned in such a manner as to leave the same amount of live coal on the grate as at the start. When this condition is reached, observe quickly the water level,[65] the steam pressure, and the time, and record the latter as the stopping time. If the water level is not the same as at the beginning a correction should be made by computation, rather than by feeding additional water after the final readings are taken. Finally remove the ashes and refuse from the ashpit. In a plant containing several boilers where it is not practicable to clean them simultaneously, the fires should be cleaned one after the other as rapidly as may be, and each one after cleaning charged with enough coal to maintain a thin fire in good working condition. After the last fire is cleaned and in working condition, burn all the fires low (say 4 to 6 inches), note quickly the thickness of each, also the water levels, steam pressure, and time, which last is taken as the starting time. Likewise when the time arrives for closing the test, the fires should be quickly cleaned one by one, and when this work is completed they should all be burned low the same as the start, and the various observations made as noted. In the case of a large boiler having several furnace doors requiring the fire to be cleaned in sections one after the other, the above directions pertaining to starting and stopping in a plant of several boilers may be followed. To obtain the desired equality of conditions of the fire when a mechanical stoker other than a chain grate is used, the procedure should be modified where practicable as follows: Regulate the coal feed so as to burn the fire to the low condition required for cleaning. Shut off the coal-feeding mechanism and fill the hoppers level full. Clean the ash or dump plate, note quickly the depth and condition of the coal on the grate, the water level,[66] the steam pressure, and the time, and record the latter as the starting time. Then start the coal-feeding mechanism, clean the ashpit, and proceed with the regular work of the test. When the time arrives for the close of the test, shut off the coal-feeding mechanism, fill the hoppers and burn the fire to the same low point as at the beginning. When this condition is reached, note the water level, the steam pressure, and the time, and record the latter as the stopping time. Finally clean the ashplate and haul the ashes. In the case of chain grate stokers, the desired operating conditions should be maintained for half an hour before starting a test and for a like period before its close, the height of the throat plate and the speed of the grate being the same during both of these periods. 8. RECORDS A log of the data should be entered in notebooks or on blank sheets suitably prepared in advance. This should be done in such manner that the test may be divided into hourly periods, or if necessary, periods of less duration, and the leading data obtained for any one or more periods as desired, thereby showing the degree of uniformity obtained. Half-hourly readings of the instruments are usually sufficient. If there are sudden and wide fluctuations, the readings in such cases should be taken every 15 minutes, and in some instances oftener. The coal should be weighed and delivered to the firemen in portions sufficient for one hour's run, thereby ascertaining the degree of uniformity of firing. An ample supply of coal should be maintained at all times, but the quantity on the floor at the end of each hour should be as small as practicable, so that the same may be readily estimated and deducted from the total weight. The records should be such as to ascertain also the consumption of feed water each hour and thereby determine the degree of uniformity of evaporation. 9. QUALITY OF STEAM[67] If the boiler does not produce superheated steam the percentage of moisture in the steam should be determined by the use of a throttling or separating calorimeter. If the boiler has superheating surface, the temperature of the steam should be determined by the use of a thermometer inserted in a thermometer well. For saturated steam construct a sampling pipe or nozzle made of one-half inch iron pipe and insert it in the steam main at a point where the entrained moisture is likely to be most thoroughly mixed. The inner end of the pipe, which should extend nearly across to the opposite side of the main, should be closed and interior portion perforated with not less than twenty one-eighth inch holes equally distributed from end to end and preferably drilled in irregular or spiral rows, with the first hole not less than half an inch from the wall of the pipe. The sampling pipe should not be placed near a point where water may pocket or where such water may effect the amount of moisture contained in the sample. Where non-return valves are used, or there are horizontal connections leading from the boiler to a vertical outlet, water may collect at the lower end of the uptake pipe and be blown upward in a spray which will not be carried away by the steam owing to a lack of velocity. A sample taken from the lower part of this pipe will show a greater amount of moisture than a true sample. With goose-neck connections a small amount of water may collect on the bottom of the pipe near the upper end where the inclination is such that the tendency to flow backward is ordinarily counterbalanced by the flow of steam forward over its surface; but when the velocity momentarily decreases the water flows back to the lower end of the goose-neck and increases the moisture at that point, making it an undesirable location for sampling. In any case it must be borne in mind that with low velocities the tendency is for drops of entrained water to settle to the bottom of the pipe, and to be temporarily broken up into spray whenever an abrupt bend or other disturbance is met. If it is necessary to attach the sampling nozzle at a point near the end of a long horizontal run, a drip pipe should be provided a short distance in front of the nozzle, preferably at a pocket formed by some fitting and the water running along the bottom of the main drawn off, weighed, and added to the moisture shown by the calorimeter; or, better, a steam separator should be installed at the point noted. In testing a stationary boiler the sampling pipe should be located as near as practicable to the boiler, and the same is true as regards the thermometer well when the steam is superheated. In an engine or turbine test these locations should be as near as practicable to throttle valve. In the test of a plant where it is desired to get complete information, especially where the steam main is unusually long, sampling nozzles or thermometer wells should be provided at both points, so as to obtain data at either point as may be required. 10. SAMPLING AND DRYING COAL During the progress of test the coal should be regularly sampled for the purpose of analysis and determination of moisture. Select a representative shovelful from each barrow-load as it is drawn from the coal pile or other source of supply, and store the samples in a cool place in a covered metal receptacle. When all the coal has thus been sampled, break up the lumps, thoroughly mix the whole quantity, and finally reduce it by the process of repeated quartering and crushing to a sample weighing about 5 pounds, the largest pieces being about the size of a pea. From this sample two one-quart air-tight glass fruit jars, or other air-tight vessels, are to be promptly filled and preserved for subsequent determinations of moisture, calorific value, and chemical composition. These operations should be conducted where the air is cool and free from drafts. [Illustration: 3460 Horse-power Installation of Babcock & Wilcox Boilers at the Chicago, Ill., Shops of the Chicago and Northwestern Ry. Co.] When the sample lot of coal has been reduced by quartering to, say, 100 pounds, a portion weighing, say, 15 to 20 pounds should be withdrawn for the purpose of immediate moisture determination. This is placed in a shallow iron pan and dried on the hot iron boiler flue for at least 12 hours, being weighed before and after drying on scales reading to quarter ounces. The moisture thus determined is approximately reliable for anthracite and semi-bituminous coals, but not for coals containing much inherent moisture. For such coals, and for all absolutely reliable determinations the method to be pursued is as follows: Take one of the samples contained in the glass jars, and subject it to a thorough air drying, by spreading it in a thin layer and exposing it for several hours to the atmosphere of a warm room, weighing it before and after, thereby determining the quantity of surface moisture it contains.[68] Then crush the whole of it by running it through an ordinary coffee mill or other suitable crusher adjusted so as to produce somewhat coarse grains (less than 1/16 inch), thoroughly mix the crushed sample, select from it a portion of from 10 to 50 grams,[69] weigh it in a balance which will easily show a variation as small as 1 part in 1000, and dry it for one hour in an air or sand bath at a temperature between 240 and 280 degrees Fahrenheit. Weigh it and record the loss, then heat and weigh again until the minimum weight has been reached. The difference between the original and the minimum weight is the moisture in the air-dried coal. The sum of the moisture thus found and that of the surface moisture is the total moisture. 11. ASHES AND REFUSE The ashes and refuse withdrawn from the furnace and ashpit during the progress of the test and at its close should be weighed so far as possible in a dry state. If wet the amount of moisture should be ascertained and allowed for, a sample being taken and dried for this purpose. This sample may serve also for analysis and the determination of unburned carbon and fusing temperature. The method above described for sampling coal may also be followed for obtaining a sample of the ashes and refuse. 12. CALORIFIC TESTS AND ANALYSES OF COAL The quality of the fuel should be determined by calorific tests and analysis of the coal sample above referred to.[70] 13. ANALYSES OF FLUE GASES For approximate determinations of the composition of the flue gases, the Orsat apparatus, or some modification thereof, should be employed. If momentary samples are obtained the analyses should be made as frequently as possible, say, every 15 to 30 minutes, depending on the skill of the operator, noting at the time the sample is drawn the furnace and firing conditions. If the sample drawn is a continuous one, the intervals may be made longer. 14. SMOKE OBSERVATIONS[71] In tests of bituminous coals requiring a determination of the amount of smoke produced, observations should be made regularly throughout the trial at intervals of 5 minutes (or if necessary every minute), noting at the same time the furnace and firing conditions. 15. CALCULATION OF RESULTS The methods to be followed in expressing and calculating those results which are not self-evident are explained as follows: (A) _Efficiency._ The "efficiency of boiler, furnace and grate" is the relation between the heat absorbed per pound of coal fired, and the calorific value of one pound of coal. The "efficiency of boiler and furnace" is the relation between the heat absorbed per pound of combustible burned, and the calorific value of one pound of combustible. This expression of efficiency furnishes a means for comparing one boiler and furnace with another, when the losses of unburned coal due to grates, cleanings, etc., are eliminated. The "combustible burned" is determined by subtracting from the weight of coal supplied to the boiler, the moisture in the coal, the weight of ash and unburned coal withdrawn from the furnace and ashpit, and the weight of dust, soot, and refuse, if any, withdrawn from the tubes, flues, and combustion chambers, including ash carried away in the gases, if any, determined from the analysis of coal and ash. The "combustible" used for determining the calorific value is the weight of coal less the moisture and ash found by analysis. The "heat absorbed" per pound of coal, or combustible, is calculated by multiplying the equivalent evaporation from and at 212 degrees per pound of coal or combustible by 970.4. Other items in this section which have been treated elsewhere are: (B) Corrections for moisture in steam. (C) Correction for live steam used. (D) Equivalent evaporation. (E) Heat balance. (F) Total heat of combustion of coal. (G) Air for combustion and the methods recommended for calculating these results are in accordance with those described in different portions of this book. 16. DATA AND RESULTS The data and results should be reported in accordance with either the short form or the complete form, adding lines for data not provided for, or omitting those not required, as may conform to the object in view. 17. CHART In trials having for an object the determination and exposition of the complete boiler performance, the entire log of readings and data should be plotted on a chart and represented graphically. 18. TESTS WITH OIL AND GAS FUELS Tests of boilers using oil or gas for fuel should accord with the rules here given, excepting as they are varied to conform to the particular characteristics of the fuel. The duration in such cases may be reduced, and the "flying" method of starting and stopping employed. The table of data and results should contain items stating character of furnace and burner, quality and composition of oil or gas, temperature of oil, pressure of steam used for vaporizing and quantity of steam used for both vaporizing and for heating. TABLE DATA AND RESULTS OF EVAPORATIVE TEST SHORT FORM, CODE OF 1912 1 Test of.................boiler located at................................ to determine...............conducted by.............................. 2 Kind of furnace.......................................................... 3 Grate surface.................................................square feet 4 Water-heating surface.........................................square feet 5 Superheating surface..........................................square feet 6 Date..................................................................... 7 Duration............................................................hours 8 Kind and size of coal.................................................... AVERAGE PRESSURES, TEMPERATURES, ETC. 9 Steam pressure by gauge............................................pounds 10 Temperature of feed water entering boiler.........................degrees 11 Temperature of escaping gases leaving boiler......................degrees 12 Force of draft between damper and boiler...........................inches 13 Percentage of moisture in steam, or number degrees of superheating..................per cent or degrees TOTAL QUANTITIES 14 Weight of coal as fired[72]........................................pounds 15 Percentage of moisture in coal...................................per cent 16 Total weight of dry coal consumed..................................pounds 17 Total ash and refuse...............................................pounds 18 Percentage of ash and refuse in dry coal.........................per cent 19 Total weight of water fed to the boiler[73]........................pounds 20 Total water evaporated, corrected for moisture in steam............pounds 21 Total equivalent evaporation from and at 212 degrees...............pounds HOURLY QUANTITIES AND RATES 22 Dry coal consumed per hour.........................................pounds 23 Dry coal per square feet of grate surface per hour.................pounds 24 Water evaporated per hour corrected for quality of steam...........pounds 25 Equivalent evaporation per hour from and at 212 degrees............pounds 26 Equivalent evaporation per hour from and at 212 degrees per square foot of water-heating surface........................pounds CAPACITY 27 Evaporation per hour from and at 212 degrees (same as Line 25).....pounds 28 Boiler horse power developed (Item 27÷34½).............boiler horse power 29 Rated capacity, in evaporation from and at 212 degrees per hour....pounds 30 Rated boiler horse power...............................boiler horse power 31 Percentage of rated capacity developed...........................per cent ECONOMY RESULTS 32 Water fed per pound of coal fired (Item 19÷Item 14)................pounds 33 Water evaporated per pound of dry coal (Item 20÷Item 16)...........pounds 34 Equivalent evaporation from and at 212 degrees per pound of dry coal (Item 21÷Item 16)...................................pounds 35 Equivalent evaporation from and at 212 degrees per pound of combustible [Item 21÷(Item 16-Item 17)]......................pounds EFFICIENCY 36 Calorific value of one pound of dry coal.........................B. t. u. 37 Calorific value of one pound of combustible......................B. t. u. ( Item 34×970.4) 38 Efficiency of boiler, furnace and grate (100 × -------------)....per cent ( Item 36 ) ( Item 35×970.4) 39 Efficiency of boiler and furnace (100 × -------------)...........per cent ( Item 37 ) COST OF EVAPORATION 40 Cost of coal per ton of......pounds delivered in boiler room......dollars 41 Cost of coal required for evaporating 1000 pounds of water from and at 212 degrees........................................dollars [Illustration: Portion of 3600 Horse-power Installation of Babcock & Wilcox Boilers, Equipped with Babcock & Wilcox Chain Grate Stokers at the Loomis Street Plant of the Peoples Gas Light & Coke Co., Chicago, Ill. This Company has Installed 7780 Horse Power of Babcock & Wilcox Boilers] THE SELECTION OF BOILERS WITH A CONSIDERATION OF THE FACTORS DETERMINING SUCH SELECTION The selection of steam boilers is a matter to which the most careful thought and attention may be well given. Within the last twenty years, radical changes have taken place in the methods and appliances for the generation and distribution of power. These changes have been made largely in the prime movers, both as to type and size, and are best illustrated by the changes in central station power-plant practice. It is hardly within the scope of this work to treat of power-plant design and the discussion will be limited to a consideration of the boiler end of the power plant. As stated, the changes have been largely in prime movers, the steam generating equipment having been considered more or less of a standard piece of apparatus whose sole function is the transfer of the heat liberated from the fuel by combustion to the steam stored or circulated in such apparatus. When the fact is considered that the cost of steam generation is roughly from 65 to 80 per cent of the total cost of power production, it may be readily understood that the most fruitful field for improvement exists in the boiler end of the power plant. The efficiency of the plant as a whole will vary with the load it carries and it is in the boiler room where such variation is largest and most subject to control. The improvements to be secured in the boiler room results are not simply a matter of dictation of operating methods. The securing of perfect combustion, with the accompanying efficiency of heat transfer, while comparatively simple in theory, is difficult to obtain in practical operation. This fact is perhaps best exemplified by the difference between test results and those obtained in daily operation even under the most careful supervision. This difference makes it necessary to establish a standard by which operating results may be judged, a standard not necessarily that which might be possible under test conditions but one which experiment shows can be secured under the very best operating conditions. The study of the theory of combustion, draft, etc., as already given, will indicate that the question of efficiency is largely a matter of proper relation between fuel, furnace and generator. While the possibility of a substantial saving through added efficiency cannot be overlooked, the boiler design of the future must, even more than in the past, be considered particularly from the aspect of reliability and simplicity. A flexibility of operation is necessary as a guarantee of continuity of service. In view of the above, before the question of the selection of boilers can be taken up intelligently, it is necessary to consider the subjects of boiler efficiency and boiler capacity, together with their relation to each other. The criterion by which the efficiency of a boiler plant is to be judged is the cost of the production of a definite amount of steam. Considered in this sense, there must be included in the efficiency of a boiler plant the simplicity of operation, flexibility and reliability of the boiler used. The items of repair and upkeep cost are often high because of the nature of the service. The governing factor in these items is unquestionably the type of boiler selected. The features entering into the plant efficiency are so numerous that it is impossible to make a statement as to a means of securing the highest efficiency which will apply to all cases. Such efficiency is to be secured by the proper relation of fuel, furnace and boiler heating surface, actual operating conditions, which allow the approaching of the potential efficiencies made possible by the refinement of design, and a systematic supervision of the operation assisted by a detailed record of performances and conditions. The question of supervision will be taken up later in the chapter on "Operation and Care of Boilers". The efficiencies that may be expected from the combination of well-designed boilers and furnaces are indicated in Table 59 in which are given a number of tests with various fuels and under widely different operating conditions. It is to be appreciated that the results obtained as given in this table are practically all under test conditions. The nearness with which practical operating conditions can approach these figures will depend upon the character of the supervision of the boiler room and the intelligence of the operating crew. The size of the plant will ordinarily govern the expense warranted in securing the right sort of supervision. The bearing that the type of boiler has on the efficiency to be expected can only be realized from a study of the foregoing chapters. Capacity--Capacity, as already defined, is the ability of a definite amount of boiler-heating surface to generate steam. Boilers are ordinarily purchased under a manufacturer's specification, which rates a boiler at a nominal rated horse power, usually based on 10 square feet of heating surface per horse power. Such a builders' rating is absolutely arbitrary and implies nothing as to the limiting amount of water that this amount of heating surface will evaporate. It does not imply that the evaporation of 34.5 pounds of water from and at 212 degrees with 10 square feet of heating surface is the limit of the capacity of the boiler. Further, from a statement that a boiler is of a certain horse power on the manufacturer's basis, it is not to be understood that the boiler is in any state of strain when developing more than its rated capacity. Broadly stated, the evaporative capacity of a certain amount of heating surface in a well-designed boiler, that is, the boiler horse power it is capable of producing, is limited only by the amount of fuel that can be burned under the boiler. While such a statement would imply that the question of capacity to be secured was simply one of making an arrangement by which sufficient fuel could be burned under a definite amount of heating surface to generate the required amount of steam, there are limiting features that must be weighed against the advantages of high capacity developed from small heating surfaces. Briefly stated, these factors are as follows: 1st. Efficiency. As the capacity increases, there will in general be a decrease in efficiency, this loss above a certain point making it inadvisable to try to secure more than a definite horse power from a given boiler. This loss of efficiency with increased capacity is treated below in detail, in considering the relation of efficiency to capacity. 2nd. Grate Ratio Possible or Practicable. All fuels have a maximum rate of combustion, beyond which satisfactory results cannot be obtained, regardless of draft available or which may be secured by mechanical means. Such being the case, it is evident that with this maximum combustion rate secured, the only method of obtaining added capacity will be through the addition of grate surface. There is obviously a point beyond which the grate surface for a given boiler cannot be increased. This is due to the impracticability of handling grates above a certain maximum size, to the enormous loss in draft pressure through a boiler resulting from an attempt to force an abnormal quantity of gas through the heating surface and to innumerable details of design and maintenance that would make such an arrangement wholly unfeasible. 3rd. Feed Water. The difficulties that may arise through the use of poor feed water or that are liable to happen through the use of practically any feed water have already been pointed out. This question of feed is frequently the limiting factor in the capacity obtainable, for with an increase in such capacity comes an added concentration of such ingredients in the feed water as will cause priming, foaming or rapid scale formation. Certain waters which will give no trouble that cannot be readily overcome with the boiler run at ordinary ratings will cause difficulties at higher ratings entirely out of proportion to any advantage secured by an increase in the power that a definite amount of heating surface may be made to produce. Where capacity in the sense of overload is desired, the type of boiler selected will play a large part in the successful operation through such periods. A boiler must be selected with which there is possible a furnace arrangement that will give flexibility without undue loss in efficiency over the range of capacity desired. The heating surface must be so arranged that it will be possible to install in a practical manner, sufficient grate surface at or below the maximum combustion rate to develop the amount of power required. The design of boiler must be such that there will be no priming or foaming at high overloads and that any added scale formation due to such overloads may be easily removed. Certain boilers which deliver commercially dry steam when operated at about their normal rated capacity will prime badly when run at overloads and this action may take place with a water that should be easily handled by a properly designed boiler at any reasonable load. Such action is ordinarily produced by the lack of a well defined, positive circulation. Relation of Efficiency and Capacity--The statement has been made that in general the efficiency of a boiler will decrease as the capacity is increased. Considering the boiler alone, apart from the furnace, this statement may be readily explained. Presupposing a constant furnace temperature, regardless of the capacity at which a given boiler is run; to assure equal efficiencies at low and high ratings, the exit temperature in the two instances would necessarily be the same. For this temperature at the high rating, to be identical with that at the low rating, the rate of heat transfer from the gases to the heating surfaces would have to vary directly as the weight or volume of such gases. Experiment has shown, however, that this is not true but that this rate of transfer varies as some power of the volume of gas less than one. As the heat transfer does not, therefore, increase proportionately with the volume of gases, the exit temperature for a given furnace temperature will be increased as the volume of gases increases. As this is the measure of the efficiency of the heating surface, the boiler efficiency will, therefore, decrease as the volume of gases increases or the capacity at which the boiler is operated increases. Further, a certain portion of the heat absorbed by the heating surface is through direct radiation from the fire. Again, presupposing a constant furnace temperature; the heat absorbed through radiation is solely a function of the amount of surface exposed to such radiation. Hence, for the conditions assumed, the amount of heat absorbed by radiation at the higher ratings will be the same as at the lower ratings but in proportion to the total absorption will be less. As the added volume of gas does not increase the rate of heat transfer, there are therefore two factors acting toward the decrease in the efficiency of a boiler with an increase in the capacity. TABLE 59 TESTS OF BABCOCK & WILCOX BOILERS WITH VARIOUS FUELS ______________________________________________________________________ |Number| | | | Rated | | of | Name and Location | Kind of Coal | Kind of | Horse | | Test | of Plant | | Furnace |Power of| | | | | | Boiler | | | | | | | |______|___________________________|________________|_________|________| | |Susquehanna Coal Co., |No. 1 Anthracite|Hand | | | 1 |Shenandoah, Pa. |Buckwheat |Fired | 300 | |______|___________________________|________________|_________|________| | |Balbach Smelting & |No. 2 Buckwheat |Wilkenson| | | 2 |Refining Co., Newark, N. J.|and Bird's-eye | Stoker | 218 | |______|___________________________|________________|_________|________| | |H. R. Worthington, |No. 2 Anthracite|Hand | | | 3 |Harrison N. J. |Buckwheat |Fired | 300 | |______|___________________________|________________|_________|________| | |Raymond Street Jail, |Anthracite Pea |Hand | | | 4 |Brooklyn, N. Y. | |Fired | 155 | |______|___________________________|________________|_________|________| | |R. H. Macy & Co., |No. 3 Anthracite|Hand | | | 5 |New York, N. Y. |Buckwheat |Fired | 293 | |______|___________________________|________________|_________|________| | |National Bureau of |Anthracite Egg |Hand | | | 6 |Standards, Washington, D.C.| |Fired | 119 | |______|___________________________|________________|_________|________| | |Fred. Loeser & Co., |No. 1 Anthracite|Hand | | | 7 |Brooklyn, N. Y. |Buckwheat |Fired | 300 | |______|___________________________|________________|_________|________| | |New York Edison Co., |No. 2 Anthracite|Hand | | | 8 |New York City |Buckwheat |Fired | 374 | |______|___________________________|________________|_________|________| | |Sewage Pumping Station, |Hocking Valley |Hand | | | 9 |Cleveland, O. |Lump, O. |Fired | 150 | |______|___________________________|________________|_________|________| | |Scioto River Pumping Sta., |Hocking Valley, |Hand | | | 10 |Cleveland, O. |O. |Fired | 300 | |______|___________________________|________________|_________|________| | |Consolidated Gas & Electric|Somerset, Pa. |Hand | | | 11 |Co., Baltimore, Md. | |Fired | 640 | |______|___________________________|________________|_________|________| | |Consolidated Gas & Electric|Somerset, Pa. |Hand | | | 12 |Co., Baltimore, Md. | |Fired | 640 | |______|___________________________|________________|_________|________| | |Merrimac Mfg. Co., |Georges Creek, |Hand | | | 13 |Lowell, Mass. |Md. |Fired | 321 | |______|___________________________|________________|_________|________| | |Great West'n Sugar Co., |Lafayette, Col.,|HandFired| | | 14 |Ft. Collins, Col. |Mine Run |Extension| 351 | |______|___________________________|________________|_________|________| | |Baltimore Sewage Pumping |New River |Hand | | | 15 | Station | |Fired | 266 | |______|___________________________|________________|_________|________| | |Tennessee State Prison, |Brushy Mountain,|Hand | | | 16 |Nashville, Tenn. |Tenn. |Fired | 300 | |______|___________________________|________________|_________|________| | |Pine Bluff Corporation, |Arkansas Slack |Hand | | | 17 |Pine Bluff, Ark. | |Fired | 298 | |______|___________________________|________________|_________|________| | |Pub. Serv. Corporation |Valley, Pa., |Roney | | | 18 |of N. J., Hoboken |Mine Run |Stoker | 520 | |______|___________________________|________________|_________|________| | |Pub. Serv. Corporation |Valley, Pa., |Roney | | | 19 |of N. J., Hoboken |Mine Run |Stoker | 520 | |______|___________________________|________________|_________|________| | |Frick Building, |Pittsburgh Nut |American | | | 20 |Pittsburgh, Pa. |and Slack |Stoker | 300 | |______|___________________________|________________|_________|________| | |New York Edison Co., |Loyal Hanna, Pa.|Taylor | | | 21 |New York City | |Stoker | 604 | |______|___________________________|________________|_________|________| | |City of Columbus, O., |Hocking Valley, |Detroit | | | 22 |Dept. Lighting |O. |Stoker | 300 | |______|___________________________|________________|_________|________| | |Edison Elec. Illum. Co., |New River |Murphy | | | 23 |Boston, Mass. | |Stoker | 508 | |______|___________________________|________________|_________|________| | |Colorado Springs & |Pike View, Col.,|Green Chn| | | 24 |Interurban Ry., Col. |Mine Run |Grate | 400 | |______|___________________________|________________|_________|________| | |Pub. Serv. Corporation |Lancashire, Pa. |B&W.Chain| | | 25 |of N. J., Marion | |Grate | 600 | |______|___________________________|________________|_________|________| | |Pub. Serv. Corporation |Lancashire, Pa. |B&W.Chain| | | 26 |of N. J., Marion | |Grate | 600 | |______|___________________________|________________|_________|________| | |Erie County Electric Co., |Mercer County, |B&W.Chain| | | 27 |Erie, Pa. |Pa. |Grate | 508 | |______|___________________________|________________|_________|________| | |Union Elec. Lt. & Pr. Co., |Mascouth, Ill. |B&W.Chain| | | 28 |St. Louis, Mo. | |Grate | 508 | |______|___________________________|________________|_________|________| | |Union Elec. Lt. & Pr. Co., |St. Clair |B&W.Chain| | | 29 |St. Louis, Mo. |County, Ill. |Grate | 508 | |______|___________________________|________________|_________|________| | |Commonwealth Edison Co., |Carterville, |B&W.Chain| | | 30 |Chicago, Ill. |Ill., Screenings|Grate | 508 | |______|___________________________|________________|_________|________| ________________________________________________________________ |Number|Grate |Dura-|Steam |Temper-|Degrees|Factor| Draft | | of |Surf. | tion|Pres. | ature | Super | of | In | At | | Test |Square|Test | By | Water | -heat |Evapo-|Furnace|Boiler| | | Feet |Hours|Gauge |Degrees|Degrees|ration|Inches |Damper| | | | |Pounds| Fahr. | Fahr. | |Upr/Lwr|Inches| |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 1 | 84 | 8 | 68 | 53.9 | |1.1965| +.41 | .21 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | +.65 | | | 2 | 51.6 | 7 | 136.3| 203 | 150 |1.1480| .47 | .56 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 3 | 67.6 | 8 | 139 | 139.6 | 139 |1.1984| .70 | .96 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 4 | 40 | 8 | 110.2| 137 | |1.1185| .33 | .43 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 5 | 59.5 | 10 | 133.2| 75.2 | |1.1849| .19 | .40 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 6 | 26.5 | 18 | 132.1| 70.5 | |1.1897| .33 | | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | +.51 | | | 7 | 48.9 | 7 | 101. | 121.3 | |1.1333| -.20 | .30 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 8 | 59.5 | 6 | 191.8| 88.3 | |1.1771| .50 | | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 9 | 27 | 24 | 156.3| 58 | |1.2051| .10 | .24 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 10 | | 24 | 145 | 75 | |1.1866| .26 | .46 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 11 | 118 | 8 | 170 | 186.1 | 66.7 |1.1162| .34 | .42 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 12 | 118 | 7.92| 173 | 180.2 | 75.2 |1.1276| .44 | .58 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 13 | 52 | 24 | 75 | 53.3 | |1.1987| .25 | .35 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 14 | 59.5 | 8 | 105 | 35.8 | |1.2219| .17 | .38 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 15 | 59.5 | 24 | 170.1| 133 | |1.1293| .12 | .43 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 16 | 51.3 | 10 | 105 | 75.1 | |1.1814| .21 | .42 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 17 | 59.5 | 8 | 149.2| 71 | |1.1910| .35 | .59 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 18 | 103.2| 10 | 133.2| 65.3 | 65.9 |1.2346| .05 | .49 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 19 | 103.2| 9 | 139 | 64 | 80.2 |1.2358| .18 | .57 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 20 | 53 | 9 | 125 | 76.6 | |1.1826| +1.64 | .64 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 21 | 75 | 8 | 198.5| 165.1 | 104 |1.1662| +3.05 | .60 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 22 | | 9 | 140 | 67 | 180 |1.2942| .22 | .35 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 23 | 90 |16.25| 199 | 48.4 | 136.5 |1.2996| .23 | 1.27 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 24 | 103 | 8 | 129 | 56 | |1.2002| .23 | .30 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | +.52 | | | 25 | 132 | 8 | 200 | 57.2 | 280.4 |1.3909| +.19 | .52 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | +.15 | | | 26 | 132 | 8 | 199 | 60.7 | 171.0 |1.3191| .04 | .52 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 27 | 90 | 8 | 120 | 69.9 | |1.1888| .31 | .58 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 28 | 103.5| 8 | 180 | 46 | 113 |1.2871| .62 | 1.24 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 29 | 103.5| 8 | 183 | 53.1 | 104 |1.2725| .60 | 1.26 | |______|______|_____|______|_______|_______|______|_______|______| | | | | | | | | | | | 30 | 90 | 7 | 184 | 127.1 | 180 |1.2393| .68 | 1.15 | |______|______|_____|______|_______|_______|______|_______|______| ______________________________________________________________ |Number|Temper-| Coal | | of | ature | Total | Moist-| Total |Ash and| Total |DryCoal| | Test |FlueGas|Weight:| ure | dry | Refuse|Combus-|/sq.ft.| | |Degrees| Fired | Per | Coal | Per | tible | Grate | | | Fahr. |Pounds | Cent | Pounds| Cent | Pounds|/Hr.Lb.| |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 1 | | 11670 | 4.45 | 11151 | 26.05 | 8248 | 16.6 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 2 | 487 | 8800 | 7.62 | 8129 | 29.82 | 5705 | 19.71 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 3 | 559 | 10799 | 6.42 | 10106 | 20.02 | 8081 | 21.77 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 4 | 427 | 5088 | 4.00 | 4884 | 19.35 | 3939 | 15.26 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 5 | 414 | 9440 | 2.14 | 9238 | 11.19 | 8204 | 15.52 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 6 | 410 | 8555 | 3.62 | 8245 | 15.73 | 6948 | 17.28 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 7 | 480 | 7130 | 7.38 | 6604 | 18.35 | 5392 | 19.29 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 8 | 449 | 7500 | 2.70 | 7298 | 27.94 | 5259 | 14.73 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 9 | 410 | 15087 | 7.50 | 13956 | 11.30 | 12379 | 21.5 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 10 | 503 | 29528 | 7.72 | 27248 | | | 24.7 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 11 | 487 | 20400 | 2.84 | 19821 | 7.83 | 18269 | 21.00 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 12 | 494 | 21332 | 2.29 | 20843 | 8.23 | 19127 | 22.31 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 13 | 516 | 24584 | 4.29 | 23529 | 7.63 | 21883 | 18.85 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 14 | 523 | 15540 | 18.64 | 12643 | | | 28.59 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 15 | 474 | 18330 | 2.03 | 17958 | 16.36 | 16096 | 12.57 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 16 | 536 | 12243 | 2.14 | 11981 | | | 23.40 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 17 | 534 | 10500 | 3.04 | 10181 | | | 21.40 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 18 | 458 | 18600 | 3.40 | 17968 | 18.38 | 14665 | 17.41 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 19 | 609 | 23400 | 2.56 | 22801 | 16.89 | 18951 | 24.55 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 20 | 518 | 10500 | 1.83 | 10308 | 12.22 | 9048 | 21.56 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 21 | 536 | 25296 | 2.20 | 24736 | | | 41.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 22 | 511 | 14263 | 8.63 | 13032 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 23 | 560 | 39670 | 4.22 | 37996 | 4.32 | 36355 | 25.98 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 24 | 538 | 23000 | 23.73 | 17542 | | | 21.36 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 25 | 590 | 32205 | 4.03 | 30907 | 15.65 | 26070 | 29.26 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 26 | 529 | 24243 | 4.09 | 23251 | 12.33 | 20385 | 22.01 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 27 | 533 | 22328 | 4.42 | 21341 | 16.88 | 17739 | 29.64 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 28 | 523 | 32163 | 13.74 | 27744 | | | 33.50 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 29 | 567 | 36150 | 14.62 | 30865 | | | 37.28 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 30 | | 30610 | 11.12 | 27206 | 14.70 | 23198 | 43.20 | |______|_______|_______|_______|_______|_______|_______|_______| ______________________________________________________________ |Number| Water | | Flue Gas Analysis | | of |Actual | Equiv.|ditto /|% Rated|CO_{2} | O | CO | | Test |Evapor-|Evap. @|sq.ft. |Cap'ty.| Per | Per | Per | | | ation |>=212° |Heating|Develpd| Cent | Cent | Cent | | |/Hr.Lb.|/Hr.Lb.|Surface|PerCent| | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 1 | 10268 | 12286 | 4.10 | 118.7 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 2 | 8246 | 9466 | 4.34 | 125.7 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 3 | 9145 | 10959 | 3.65 | 105.9 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 4 | 5006 | 5599 | 3.61 | 104.7 | 12.26 | 7.88 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 5 | 7434 | 8809 | 3.06 | 87.2 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 6 | 2903 | 3454 | 2.91 | 84.4 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 7 | 7464 | 8459 | 2.82 | 81.7 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 8 | 9164 | 10787 | 2.88 | 83.5 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 9 | 4374 | 5271 | 3.51 | 101.8 | 11.7 | 7.3 | 0.07 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 10 | 8688 | 10309 | 3.44 | 99.6 | 12.9 | 5.0 | 0.2 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 11 | 24036 | 26829 | 4.19 | 121.5 | 12.5 | 6.4 | 0.5 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 12 | 25313 | 28544 | 4.46 | 129.3 | 13.3 | 5.1 | 0.5 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 13 | 9168 | 10990 | 3.42 | 99.3 | 9.6 | 8.8 | 0.4 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 14 | 11202 | 13689 | 3.91 | 113.5 | 9.1 | 9.9 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 15 | 7565 | 8543 | 3.21 | 93.1 | 10.71 | 9.10 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 16 | 9512 | 11237 | 3.74 | 108.6 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 17 | 9257 | 11025 | 3.70 | 107.2 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 18 | 15887 | 19614 | 3.77 | 108.7 | 11.7 | 7.7 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 19 | 21320 | 26347 | 5.06 | 146.7 | 11.9 | 7.8 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 20 | 9976 | 11978 | 3.93 | 112.0 | 11.3 | 7.5 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 21 | 28451 | 33066 | 5.47 | 158.6 | 12.3 | 6.4 | 0.7 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 22 | 10467 | 13526 | 4.51 | 130.7 | 11.9 | 7.2 | 0.04 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 23 | 20700 | 26902 | 5.30 | 153.5 | 11.1 | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 24 | 14650 | 17583 | 4.40 | 127.4 | | | | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 25 | 28906 | 40205 | 6.70 | 194.2 | 10.5 | 8.3 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 26 | 23074 | 30437 | 5.07 | 147.0 | 10.1 | 9.0 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 27 | 20759 | 24678 | 4.85 | 140.8 | 10.1 | 9.1 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 28 | 21998 | 28314 | 5.67 | 161.5 | 8.7 | 10.6 | 0.0 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 29 | 24386 | 31031 | 6.11 | 177.1 | 8.9 | 10.7 | 0.2 | |______|_______|_______|_______|_______|_______|_______|_______| | | | | | | | | | | 30 | 30505 | 37805 | 7.43 | 215.7 | 10.4 | 9.4 | 0.2 | |______|_______|_______|_______|_______|_______|_______|_______| _______________________________________________________ |Number| Proximate Analysis Dry Coal | Equiv.|Combnd.| | of |Volatl.| Fixed | Ash |B.t.u./|Evap. @|Efficy.| | Test |Matter |Carbon | Per | Pound |>=212°/|Boiler | | | Per | Per | Cent | Dry | Pound |& Grate| | | Cent | Cent | | Coal |DryCoal|PerCent| |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 1 | | | 26.05 | 11913 | 8.81 | 71.8 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 2 | | | | 11104 | 8.15 | 72.1 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 3 | 5.55 | 80.60 | 13.87 | 12300 | 8.67 | 68.4 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 4 | 7.74 | 77.48 | 14.78 | 12851 | 9.17 | 69.2 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 5 | | | | 13138 | 9.53 | 69.6 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 6 | 6.13 | 84.86 | 9.01 | 13454 | 9.57 | 69.0 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 7 | | | | 12224 | 8.97 | 71.2 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 8 | 0.55 | 86.73 | 12.72 | 12642 | 8.87 | 68.1 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 9 | 39.01 | 48.08 | 12.91 | 12292 | 9.06 | 71.5 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 10 | 38.33 | 46.71 | 14.96 | 12284 | 9.08 | 71.7 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 11 | 19.86 | 73.02 | 7.12 | 14602 | 10.83 | 72.0 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 12 | 20.24 | 72.26 | 7.50 | 14381 | 10.84 | 73.2 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 13 | | | | 14955 | 11.21 | 72.7 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 14 | 39.60 | 54.46 | 5.94 | 11585 | 8.66 | 72.5 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 15 | 17.44 | 76.42 | 5.84 | 15379 | 11.42 | 72.1 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 16 | 33.40 | 54.73 | 11.87 | 12751 | 9.38 | 71.4 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 17 | 15.42 | 62.48 | 22.10 | 12060 | 8.66 | 69.6 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 18 | 14.99 | 75.13 | 9.88 | 14152 | 10.92 | 74.88 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 19 | 14.40 | 74.33 | 11.27 | 14022 | 10.40 | 71.97 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 20 | 32.44 | 56.71 | 10.85 | 13510 | 10.30 | 74.6 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 21 | 19.02 | 72.09 | 8.89 | 14105 | 10.69 | 73.5 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 22 | 32.11 | 53.93 | 13.96 | 12435 | 9.41 | 73.4 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 23 | 19.66 | 75.41 | 4.93 | 14910 | 11.51 | 74.9 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 24 | 43.57 | 46.22 | 10.21 | 11160 | 8.02 | 69.7 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 25 | 22.84 | 69.91 | 7.25 | 13840 | 10.41 | 72.6 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 26 | 32.36 | 60.67 | 6.97 | 14027 | 10.47 | 72.1 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 27 | 33.26 | 54.03 | 12.71 | 12742 | 9.25 | 70.4 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 28 | 28.96 | 46.88 | 24.16 | 10576 | 8.16 | 74.9 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 29 | 36.50 | 41.20 | 22.30 | 10849 | 8.04 | 71.9 | |______|_______|_______|_______|_______|_______|_______| | | | | | | | | | 30 | | | 10.24 | 13126 | 9.73 | 71.9 | |______|_______|_______|_______|_______|_______|_______| [Illustration: 15400 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock & Wilcox Chain Grate Stokers at the Plant of the Twin City Rapid Transit Co., Minneapolis, Minn.] This increase in the efficiency of the boiler alone with the decrease in the rate at which it is operated, will hold to a point where the radiation of heat from the boiler setting is proportionately large enough to be a governing factor in the total amount of heat absorbed. The second reason given above for a decrease of boiler efficiency with increase of capacity, viz., the effect of radiant heat, is to a greater extent than the first reason dependent upon a constant furnace temperature. Any increase in this temperature will affect enormously the amount of heat absorbed by radiation, as this absorption will vary as the fourth power of the temperature of the radiating body. In this way it is seen that but a slight increase in furnace temperature will be necessary to bring the proportional part, due to absorption by radiation, of the total heat absorbed, up to its proper proportion at the higher ratings. This factor of furnace temperature more properly belongs to the consideration of furnace efficiency than of boiler efficiency. There is a point, however, in any furnace above which the combustion will be so poor as to actually reduce the furnace temperature and, therefore, the proportion of heat absorbed through radiation by a given amount of exposed heating surface. Since it is thus true that the efficiency of the boiler considered alone will increase with a decreased capacity, it is evident that if the furnace conditions are constant regardless of the load, that the combined efficiency of boiler and furnace will also decrease with increasing loads. This fact was clearly proven in the tests of the boilers at the Detroit Edison Company.[74] The furnace arrangement of these boilers and the great care with which the tests were run made it possible to secure uniformly good furnace conditions irrespective of load, and here the maximum efficiency was obtained at a point somewhat less than the rated capacity of the boilers. In some cases, however, and especially in the ordinary operation of the plant, the furnace efficiency will, up to a certain point, increase with an increase in power. This increase in furnace efficiency is ordinarily at a greater rate as the capacity increases than is the decrease in boiler efficiency, with the result that the combined efficiency of boiler and furnace will to a certain point increase with an increase in capacity. This makes the ordinary point of maximum combined efficiency somewhat above the rated capacity of the boiler and in many cases the combined efficiency will be practically a constant over a considerable range of ratings. The features limiting the establishing of the point of maximum efficiency at a high rating are the same as those limiting the amount of grate surface that can be installed under a boiler. The relative efficiency of different combinations of boilers and furnaces at different ratings depends so largely upon the furnace conditions that what might hold for one combination would not for another. In view of the above, it is impossible to make a statement of the efficiency at different capacities of a boiler and furnace which will hold for any and all conditions. Fig. 40 shows in a general form the relation of efficiency to capacity. This curve has been plotted from a great number of tests, all of which were corrected to bring them to approximately the same conditions. The curve represents test conditions. The efficiencies represented are those which may be secured only under such conditions. The general direction of the curve, however, will be found to hold approximately correct for operating conditions when used only as a guide to what may be expected. [Graph: Combined Efficiency of Boiler and Furnace Per Cent against Per Cent of Boiler's Rated Capacity Developed Fig. 40. Approximate Variation of Efficiency with Capacity under Test Conditions] Economical Loads--With the effect of capacity on economy in mind, the question arises as to what constitutes the economical load to be carried. In figuring on the economical load for an individual plant, the broader economy is to be considered, that in which, against the boiler efficiency, there is to be weighed the plant first cost, returns on such investment, fuel cost, labor, capacity, etc., etc. This matter has been widely discussed, but unfortunately such discussion has been largely limited to central power station practice. The power generated in such stations, while representing an enormous total, is by no means the larger proportion of the total power generated throughout the country. The factors determining the economic load for the small plant, however, are the same as in a large, and in general the statements made relative to the question are equally applicable. The economical rating at which a boiler plant should be run is dependent solely upon the load to be carried by that individual plant and the nature of such load. The economical load for each individual plant can be determined only from the careful study of each individual set of conditions or by actual trial. The controlling factor in the cost of the plant, regardless of the nature of the load, is the capacity to carry the maximum peak load that may be thrown on the plant under any conditions. While load conditions, do, as stated, vary in every individual plant, in a broad sense all loads may be grouped in three classes: 1st, the approximately constant 24-hour load; 2nd, the steady 10 or 12-hour load usually with a noonday period of no load; 3rd, the 24-hour variable load, found in central station practice. The economical load at which the boiler may be run will vary with these groups: 1st. For a constant load, 24 hours in the day, it will be found in most cases that, when all features are considered, the most economical load or that at which a given amount of steam can be produced the most cheaply will be considerably over the rated horse power of the boiler. How much above the rated capacity this most economic load will be, is dependent largely upon the cost of coal at the plant, but under ordinary conditions, the point of maximum economy will probably be found to be somewhere between 25 and 50 per cent above the rated capacity of the boilers. The capital investment must be weighed against the coal saving through increased thermal efficiency and the labor account, which increases with the number of units, must be given proper consideration. When the question is considered in connection with a plant already installed, the conditions are different from where a new plant is contemplated. In an old plant, where there are enough boilers to operate at low rates of capacity, the capital investment leads to a fixed charge, and it will be found that the most economical load at which boilers may be operated will be lower than where a new plant is under consideration. 2nd. For a load of 10 or 12 hours a day, either an approximately steady load or one in which there is a peak, where the boilers have been banked over night, the capacity at which they may be run with the best economy will be found to be higher than for uniform 24-hour load conditions. This is obviously due to original investment, that is, a given amount of invested capital can be made to earn a larger return through the higher overload, and this will hold true to a point where the added return more than offsets the decrease in actual boiler efficiency. Here again the determining factors of what is the economical load are the fuel and labor cost balanced against the thermal efficiency. With a load of this character, there is another factor which may affect the economical plant operating load. This is from the viewpoint of spare boilers. That such added capacity in the way of spares is necessary is unquestionable. Since they must be installed, therefore, their presence leads to a fixed charge and it is probable that for the plant, as a whole, the economical load will be somewhat lower than if the boilers were considered only as spares. That is, it may be found best to operate these spares as a part of the regular equipment at all times except when other boilers are off for cleaning and repairs, thus reducing the load on the individual boilers and increasing the efficiency. Under such conditions, the added boiler units can be considered as spares only during such time as some of the boilers are not in operation. Due to the operating difficulties that may be encountered at the higher overloads, it will ordinarily be found that the most economical ratings at which to run boilers for such load conditions will be between 150 and 175 per cent of rating. Here again the maximum capacity at which the boilers may be run for the best plant economy is limited by the point at which the efficiency drops below what is warranted in view of the first cost of the apparatus. 3rd. The 24-hour variable load. This is a class of load carried by the central power station, a load constant only in the sense that there are no periods of no load and which varies widely with different portions of the 24 hours. With such a load it is particularly difficult to make any assertion as to the point of maximum economy that will hold for any station, as this point is more than with any other class of load dependent upon the factors entering into the operation of each individual plant. The methods of handling a load of this description vary probably more than with any other kind of load, dependent upon fuel, labor, type of stoker, flexibility of combined furnace and boiler etc., etc. In general, under ordinary conditions such as appear in city central power station work where the maximum peaks occur but a few times a year, the plant should be made of such size as to enable it to carry these peaks at the maximum possible overload on the boilers, sufficient margin of course being allowed for insurance against interruption of service. With the boilers operating at this maximum overload through the peaks a large sacrifice in boiler efficiency is allowable, provided that by such sacrifice the overload expected is secured. [Illustration: Portion of 4890 Horse-power Installation of Babcock & Wilcox Boilers at the Billings Sugar Co., Billings, Mont. 694 Horse Power of these Boilers are Equipped with Babcock and Wilcox Chain Grate Stokers] Some methods of handling a load of this nature are given below: Certain plant operating conditions make it advisable, from the standpoint of plant economy, to carry whatever load is on the plant at any time on only such boilers as will furnish the power required when operating at ratings of, say, 150 to 200 per cent. That is, all boilers which are in service are operated at such ratings at all times, the variation in load being taken care of by the number of boilers on the line. Banked boilers are cut in to take care of increasing loads and peaks and placed again on bank when the peak periods have passed. It is probable that this method of handling central station load is to-day the most generally used. Other conditions of operation make it advisable to carry the load on a definite number of boiler units, operating these at slightly below their rated capacity during periods of light or low loads and securing the overload capacity during peaks by operating the same boilers at high ratings. In this method there are no boilers kept on banked fires, the spares being spares in every sense of the word. A third method of handling widely varying loads which is coming somewhat into vogue is that of considering the plant as divided, one part to take care of what may be considered the constant plant load, the other to take care of the floating or variable load. With such a method that portion of the plant carrying the steady load is so proportioned that the boilers may be operated at the point of maximum efficiency, this point being raised to a maximum through the use of economizers and the general installation of any apparatus leading to such results. The variable load will be carried on the remaining boilers of the plant under either of the methods just given, that is, at the high ratings of all boilers in service and banking others, or a variable capacity from all boilers in service. The opportunity is again taken to indicate the very general character of any statements made relative to the economical load for any plant and to emphasize the fact that each individual case must be considered independently, with the conditions of operations applicable thereto. With a thorough understanding of the meaning of boiler efficiency and capacity and their relation to each other, it is possible to consider more specifically the selection of boilers. The foremost consideration is, without question, the adaptability of the design selected to the nature of the work to be done. An installation which is only temporary in its nature would obviously not warrant the first cost that a permanent plant would. If boilers are to carry an intermittent and suddenly fluctuating load, such as a hoisting load or a reversing mill load, a design would have to be selected that would not tend to prime with the fluctuations and sudden demand for steam. A boiler that would give the highest possible efficiency with fuel of one description, would not of necessity give such efficiency with a different fuel. A boiler of a certain design which might be good for small plant practice would not, because of the limitations in practicable size of units, be suitable for large installations. A discussion of the relative value of designs can be carried on almost indefinitely but enough has been said to indicate that a given design will not serve satisfactorily under all conditions and that the adaptability to the service required will be dependent upon the fuel available, the class of labor procurable, the feed water that must be used, the nature of the plant's load, the size of the plant and the first cost warranted by the service the boiler is to fulfill. TABLE 60 ACTUAL EVAPORATION FOR DIFFERENT PRESSURES AND TEMPERATURES OF FEED WATER CORRESPONDING TO ONE HORSE POWER (34½ POUNDS PER HOUR FROM AND AT 212 DEGREES FAHRENHEIT) ----------------------------------------------------------------------------------------------------------------------------------------- Temperature| | of | Pressure by Gauge--Pounds per Square Inch | Feed | | Degrees | | Fahrenheit | 50 | 60 | 70 | 80 | 90 | 100 | 110 | 120 | 130 | 140 | 150 | 160 | 170 | 180 | 190 | 200 | 210 | 220 | 230 | 240 | 250 | -----------+-----------------------------------------------------------------------------------------------------------------------------| 32 |28.41|28.36|28.29|28.24|28.20|28.16|28.13|28.09|28.07|28.04|28.02|27.99|27.97|27.95|27.94|27.92|27.90|27.89|27.87|27.86|27.83| 40 |28.61|28.54|28.49|28.44|28.40|28.35|28.32|28.29|28.26|28.23|28.21|28.18|28.16|28.14|28.12|28.11|28.09|28.07|28.06|28.05|28.03| 50 |28.85|28.79|28.73|28.68|28.64|28.60|28.56|28.53|28.50|28.47|28.45|28.43|28.40|28.38|28.36|28.35|28.33|28.31|28.30|28.28|28.27| 60 |29.10|29.04|28.98|28.93|28.88|28.84|28.81|28.77|28.74|28.72|28.69|28.67|28.65|28.62|28.60|28.59|28.57|28.55|28.54|28.52|28.51| 70 |29.36|29.29|29.23|29.18|29.14|29.09|29.06|29.02|28.99|28.96|28.94|28.92|28.89|28.87|28.85|28.83|28.82|28.80|28.78|28.77|28.76| 80 |29.62|29.55|29.49|29.44|29.39|29.35|29.31|29.27|29.24|29.22|29.19|29.17|29.14|29.12|29.10|29.08|29.07|29.05|29.03|29.02|29.00| 90 |29.88|29.81|29.75|29.70|29.65|29.61|29.57|29.53|29.50|29.47|29.45|29.42|29.40|29.38|29.36|29.34|29.32|29.30|29.29|29.27|29.25| 100 |30.15|30.08|30.02|29.96|29.91|29.87|29.83|29.80|29.76|29.73|29.71|29.68|29.66|29.63|29.61|29.60|29.58|29.56|29.54|29.53|29.51| 110 |30.42|30.35|30.29|30.23|30.18|30.14|30.10|30.06|30.03|30.00|29.97|29.95|29.92|29.90|29.88|29.86|29.84|29.82|29.81|29.79|29.77| 120 |30.70|30.63|30.56|30.51|30.46|30.41|30.37|30.33|30.30|30.27|30.24|30.22|30.19|30.17|30.15|30.13|30.11|30.09|30.07|30.06|30.04| 130 |30.99|30.91|30.84|30.79|30.73|30.69|30.65|30.61|30.57|30.54|30.52|30.49|30.47|30.44|30.42|30.40|30.38|30.36|30.35|30.33|30.31| 140 |31.28|31.20|31.13|31.07|31.02|30.97|30.93|30.89|30.86|30.83|30.80|30.77|30.75|30.72|30.70|30.68|30.66|30.64|30.62|30.61|30.59| 150 |31.58|31.49|31.42|31.36|31.31|31.26|31.22|31.18|31.14|31.11|31.08|31.06|31.03|31.01|30.98|30.96|30.94|30.92|30.91|30.89|30.87| 160 |31.87|31.79|31.72|31.66|31.61|31.56|31.51|31.47|31.44|31.40|31.37|31.35|31.32|31.29|31.27|31.25|31.23|31.21|31.19|31.18|31.16| 170 |32.18|32.10|32.02|31.96|31.91|31.86|31.81|31.77|31.73|31.70|31.67|31.64|31.62|31.59|31.57|31.54|31.52|31.50|31.49|31.47|31.46| 180 |32.49|32.41|32.33|32.27|32.22|32.16|32.12|32.08|32.04|32.00|31.97|31.95|31.92|31.89|31.87|31.84|31.82|31.80|31.79|31.77|31.75| 190 |32.81|32.72|32.65|32.59|32.53|32.47|32.43|32.38|32.35|32.32|32.29|32.26|32.23|32.20|32.17|32.15|32.13|32.11|32.09|32.07|32.05| 200 |33.13|33.05|32.97|32.91|32.85|32.79|32.75|32.70|32.66|32.63|32.60|32.57|32.54|32.51|32.49|32.46|32.44|32.42|32.40|32.38|32.36| 210 |33.47|33.38|33.30|33.24|33.18|33.13|33.08|33.03|32.99|32.95|32.92|32.89|32.86|32.83|32.81|32.79|32.76|32.74|32.72|32.70|32.68| ----------------------------------------------------------------------------------------------------------------------------------------- The proper consideration can be given to the adaptability of any boiler for the service in view only after a thorough understanding of the requirements of a good steam boiler, with the application of what has been said on the proper operation to the special requirements of each case. Of almost equal importance to the factors mentioned are the experience, the skill and responsibility of the manufacturer. With the design of boiler selected that is best adapted to the service required, the next step is the determination of the boiler power requirements. The amount of steam that must be generated is determined from the steam consumption of the prime movers. It has already been indicated that such consumption can vary over wide limits with the size and type of the apparatus used, but fortunately all types have been so tested that manufacturers are enabled to state within very close limits the actual consumption under any given set of conditions. It is obvious that conditions of operation will have a bearing on the steam consumption that is as important as the type and size of the apparatus itself. This being the case, any tabular information that can be given on such steam consumption, unless it be extended to an impracticable size, is only of use for the most approximate work and more definite figures on this consumption should in all cases be obtained from the manufacturer of the apparatus to be used for the conditions under which it will operate. To the steam consumption of the main prime movers, there is to be added that of the auxiliaries. Again it is impossible to make a definite statement of what this allowance should be, the figure depending wholly upon the type and the number of such auxiliaries. For approximate work, it is perhaps best to allow 15 or 20 per cent of the steam requirements of the main engines, for that of auxiliaries. Whatever figure is used should be taken high enough to be on the conservative side. When any such figures are based on the actual weight of steam required, Table 60, which gives the actual evaporation for various pressures and temperatures of feed corresponding to one boiler horse power (34.5 pounds of water per hour from and at 212 degrees), may be of service. With the steam requirements known, the next step is the determination of the number and size of boiler units to be installed. This is directly affected by the capacity at which a consideration of the economical load indicates is the best for the operating conditions which will exist. The other factors entering into such determination are the size of the plant and the character of the feed water. The size of the plant has its bearing on the question from the fact that higher efficiencies are in general obtained from large units, that labor cost decreases with the number of units, the first cost of brickwork is lower for large than for small size units, a general decrease in the complication of piping, etc., and in general the cost per horse power of any design of boiler decreases with the size of units. To illustrate this, it is only necessary to consider a plant of, say, 10,000 boiler horse power, consisting of 40-250 horse-power units or 17-600 horse-power units. The feed water available has its bearing on the subject from the other side, for it has already been shown that very large units are not advisable where the feed water is not of the best. The character of an installment is also a factor. Where, say, 1000 horse power is installed in a plant where it is known what the ultimate capacity is to be, the size of units should be selected with the idea of this ultimate capacity in mind rather than the amount of the first installation. Boiler service, from its nature, is severe. All boilers have to be cleaned from time to time and certain repairs to settings, etc., are a necessity. This makes it necessary, in determining the number of boilers to be installed, to allow a certain number of units or spares to be operated when any of the regular boilers must be taken off the line. With the steam requirements determined for a plant of moderate size and a reasonably constant load, it is highly advisable to install at least two spare boilers where a continuity of service is essential. This permits the taking off of one boiler for cleaning or repairs and still allows a spare boiler in the event of some unforeseen occurrence, such as the blowing out of a tube or the like. Investment in such spare apparatus is nothing more nor less than insurance on the necessary continuity of service. In small plants of, say, 500 or 600 horse power, two spares are not usually warranted in view of the cost of such insurance. A large plant is ordinarily laid out in a number of sections or panels and each section should have its spare boiler or boilers even though the sections are cross connected. In central station work, where the peaks are carried on the boilers brought up from the bank, such spares are, of course, in addition to these banked boilers. From the aspect of cleaning boilers alone, the number of spare boilers is determined by the nature of any scale that may be formed. If scale is formed so rapidly that the boilers cannot be kept clean enough for good operating results, by cleaning in rotation, one at a time, the number of spares to take care of such proper cleaning will naturally increase. In view of the above, it is evident that only a suggestion can be made as to the number and size of units, as no recommendation will hold for all cases. In general, it will be found best to install units of the largest possible size compatible with the size of the plant and operating conditions, with the total power requirements divided among such a number of units as will give proper flexibility of load, with such additional units for spares as conditions of cleaning and insurance against interruption of service warrant. In closing the subject of the selection of boilers, it may not be out of place to refer to the effect of the builder's guarantee upon the determination of design to be used. Here in one of its most important aspects appears the responsibility of the manufacturer. Emphasis has been laid on the difference between test results and those secured in ordinary operating practice. That such a difference exists is well known and it is now pretty generally realized that it is the responsible manufacturer who, where guarantees are necessary, submits the conservative figures, figures which may readily be exceeded under test conditions and which may be closely approached under the ordinary plant conditions that will be met in daily operation. OPERATION AND CARE OF BOILERS The general subject of boiler room practice may be considered from two aspects. The first is that of the broad plant economy, with a suggestion as to the methods to be followed in securing the best economical results with the apparatus at hand and procurable. The second deals rather with specific recommendations which should be followed in plant practice, recommendations leading not only to economy but also to safety and continuity of service. Such recommendations are dictated from an understanding of the nature of steam generating apparatus and its operation, as covered previously in this book. It has already been pointed out that the attention given in recent years to steam generating practice has come with a realization of the wide difference existing between the results being obtained in every-day operation and those theoretically possible. The amount of such attention and regulation given to the steam generating end of a power plant, however, is comparatively small in relation to that given to the balance of the plant, but it may be safely stated that it is here that there is the greatest assurance of a return for the attention given. In the endeavor to increase boiler room efficiency, it is of the utmost importance that a standard basis be set by which average results are to be judged. With the theoretical efficiency obtainable varying so widely, this standard cannot be placed at the highest efficiency that has been obtained regardless of operating conditions. It is better set at the best obtainable results for each individual plant under its conditions of installation and daily operation. With an individual standard so set, present practice can only be improved by a systematic effort to approach this standard. The degree with which operating results will approximate such a standard will be found to be directly proportional to the amount of intelligent supervision given the operation. For such supervision to be given, it is necessary to have not only a full realization of what the plant can do under the best operating conditions but also a full and complete knowledge of what it is doing under all of the different conditions that may arise. What the plant is doing should be made a matter of continuous record so arranged that the results may be directly compared for any period or set of conditions, and where such results vary from the standard set, steps must be taken immediately to remedy the causes of such failings. Such a record is an important check in the losses in the plant. As the size of the plant and the fuel consumption increase, such a check of losses and recording of results becomes a necessity. In the larger plants, the saving of but a fraction of one per cent in the fuel bill represents an amount running into thousands of dollars annually, while the expense of the proper supervision to secure such saving is small. The methods of supervision followed in the large plants are necessarily elaborate and complete. In the smaller plants the same methods may be followed on a more moderate scale with a corresponding saving in fuel and an inappreciable increase in either plant organization or expense. There has been within the last few years a great increase in the practicability and reliability of the various types of apparatus by which the records of plant operation may be secured. Much of this apparatus is ingenious and, considering the work to be done, is remarkably accurate. From the delicate nature of some of the apparatus, the liability to error necessitates frequent calibration but even where the accuracy is known to be only within limits of, say, 5 per cent either way, the records obtained are of the greatest service in considering relative results. Some of the records desirable and the apparatus for securing them are given below. [Illustration: 2400 Horse-power Installation of Cross Drum Babcock & Wilcox Boilers and Superheaters at the Westinghouse Electric and Manufacturing Co., East Pittsburgh, Pa.] Inasmuch as the ultimate measure of the efficiency of the boiler plant is the cost of steam generation, the important records are those of steam generated and fuel consumed Records of temperature, analyses, draft and the like, serve as a check on this consumption, indicating the distribution of the losses and affording a means of remedying conditions where improvement is possible. Coal Records--There are many devices on the market for conveniently weighing the coal used. These are ordinarily accurate within close limits, and where the size or nature of the plant warrants the investment in such a device, its use is to be recommended. The coal consumption should be recorded by some other method than from the weights of coal purchased. The total weight gives no way of dividing the consumption into periods and it will unquestionably be found to be profitable to put into operation some scheme by which the coal is weighed as it is used. In this way, the coal consumption, during any specific period of the plant's operation, can be readily seen. The simplest of such methods which may be used in small plants is the actual weighing on scales of the fuel as it is brought into the fire room and the recording of such weights. Aside from the actual weight of the fuel used, it is often advisable to keep other coal records, coal and ash analyses and the like, for the evaporation to be expected will be dependent upon the grade of fuel used and its calorific value, fusibility of its ash, and like factors. The highest calorific value for unit cost is not necessarily the indication of the best commercial results. The cost of fuel is governed by this calorific value only when such value is modified by local conditions of capacity, labor and commercial efficiency. One of the important factors entering into fuel cost is the consideration of the cost of ash handling and the maintenance of ash handling apparatus if such be installed. The value of a fuel, regardless of its calorific value, is to be based only on the results obtained in every-day plant operation. Coal and ash analyses used in connection with the amount of fuel consumed, are a direct indication of the relation between the results being secured and the standard of results which has been set for the plant. The methods of such analyses have already been described. The apparatus is simple and the degree of scientific knowledge necessary is only such as may be readily mastered by plant operatives. The ash content of a fuel, as indicated from a coal analysis checked against ash weights as actually found in plant operation, acts as a check on grate efficiency. The effect of any saving in the ashes, that is, the permissible ash to be allowed in the fuel purchased, is determined by the point at which the cost of handling, combined with the falling off in the evaporation, exceeds the saving of fuel cost through the use of poorer coal. Water Records--Water records with the coal consumption, form the basis for judging the economic production of steam. The methods of securing such records are of later introduction than for coal, but great advances have been made in the apparatus to be used. Here possibly, to a greater extent than in any recording device, are the records of value in determining relative evaporation, that is, an error is rather allowable provided such an error be reasonably constant. The apparatus for recording such evaporation is of two general classes: Those measuring water before it is fed to the boiler and those measuring the steam as it leaves. Of the first, the venturi meter is perhaps the best known, though recently there has come into considerable vogue an apparatus utilizing a weir notch for the measuring of such water. Both methods are reasonably accurate and apparatus of this description has an advantage over one measuring steam in that it may be calibrated much more readily. Of the steam measuring devices, the one in most common use is the steam flow meter. Provided the instruments are selected for a proper flow, etc., they are of inestimable value in indicating the steam consumption. Where such instruments are placed on the various engine room lines, they will immediately indicate an excessive consumption for any one of the units. With a steam flow meter placed on each boiler, it is possible to fix relatively the amount produced by each boiler and, considered in connection with some of the "check" records described below, clearly indicate whether its portion of the total steam produced is up to the standard set for the over-all boiler room efficiency. Flue Gas Analysis--The value of a flue gas analysis as a measure of furnace efficiency has already been indicated. There are on the market a number of instruments by which a continuous record of the carbon dioxide in the flue gases may be secured and in general the results so recorded are accurate. The limitations of an analysis showing only CO_{2} and the necessity of completing such an analysis with an Orsat, or like apparatus, and in this way checking the automatic device, have already been pointed out, but where such records are properly checked from time to time and are used in conjunction with a record of flue temperatures, the losses due to excess air or incomplete combustion and the like may be directly compared for any period. Such records act as a means for controlling excess air and also as a check on individual firemen. Where the size of a plant will not warrant the purchase of an expensive continuous CO_{2} recorder, it is advisable to make analyses of samples for various conditions of firing and to install an apparatus whereby a sample of flue gas covering a period of, say, eight hours, may be obtained and such a sample afterwards analyzed. Temperature Records--Flue gas temperatures, feed water temperatures and steam temperatures are all taken with recording thermometers, any number of which will, when properly calibrated, give accurate results. A record of flue temperatures is serviceable in checking stack losses and, in general, the cleanliness of the boiler. A record of steam temperatures, where superheaters are used, will indicate excessive fluctuations and lead to an investigation of their cause. Feed temperatures are valuable in showing that the full benefit of the exhaust steam is being derived. Draft Regulation--As the capacity of a boiler varies with the combustion rate and this rate with the draft, an automatic apparatus satisfactorily varying this draft with the capacity demands on the boiler will obviously be advantageous. As has been pointed out, any fuel has some rate of combustion at which the best results will be obtained. In a properly designed plant where the load is reasonably steady, the draft necessary to secure such a rate may be regulated automatically. Automatic apparatus for the regulation of draft has recently reached a stage of perfection which in the larger plants at any rate makes its installation advisable. The installation of a draft gauge or gauges is strongly to be recommended and a record of such drafts should be kept as being a check on the combustion rates. An important feature to be considered in the installing of all recording apparatus is its location. Thermometers, draft gauges and flue gas sampling pipes should be so located as to give as nearly as possible an average of the conditions, the gases flowing freely over the ends of the thermometers, couples and sampling pipes. With the location permanent, there is no security that the samples may be considered an average but in any event comparative results will be secured which will be useful in plant operation. The best permanent location of apparatus will vary considerably with the design of the boiler. It may not be out of place to refer briefly to some of the shortcomings found in boiler room practice, with a suggestion as to a means of overcoming them. 1st. It is sometimes found that the operating force is not fully acquainted with the boilers and apparatus. Probably the most general of such shortcomings is the fixed idea in the heads of the operatives that boilers run above their rated capacity are operating under a state of strain and that by operating at less than their rated capacity the most economical service is assured, whereas, by determining what a boiler will do, it may be found that the most economical rating under the conditions of the plant will be considerably in excess of the builder's rating. Such ideas can be dislodged only by demonstrating to the operatives what maximum load the boilers can carry, showing how the economy will vary with the load and the determining of the economical load for the individual plant in question. 2nd. Stokers. With stoker-fired boilers, it is essential that the operators know the limitations of their stokers as determined by their individual installation. A thorough understanding of the requirements of efficient handling must be insisted upon. The operatives must realize that smokeless stacks are not necessarily the indication of good combustion for, as has been pointed out, absolute smokelessness is oftentimes secured at an enormous loss in efficiency through excess air. Another feature in stoker-fired plants is in the cleaning of fires. It must be impressed upon the operatives that before the fires are cleaned they should be put into condition for such cleaning. If this cleaning is done at a definite time, regardless of whether the fires are in the best condition for cleaning, there will be a great loss of good fuel with the ashes. 3rd. It is necessary that in each individual plant there be a basis on which to judge the cleanliness of a boiler. From the operative's standpoint, it is probably more necessary that there be a thorough understanding of the relation between scale and tube difficulties than between scale and efficiency. It is, of course, impossible to keep boilers absolutely free from scale at all times, but experience in each individual plant determines the limit to which scale can be allowed to form before tube difficulties will begin or a perceptible falling off in efficiency will take place. With such a limit of scale formation fixed, the operatives should be impressed with the danger of allowing it to be exceeded. 4th. The operatives should be instructed as to the losses resulting from excess air due to leaks in the setting and as to losses in efficiency and capacity due to the by-passing of gases through the setting, that is, not following the path of the baffles as originally installed. In replacing tubes and in cleaning the heating surfaces, care must be taken not to dislodge baffle brick or tile. [Illustration: 2000 Horse-power Installation of Babcock & Wilcox Boilers, Equipped with Babcock & Wilcox Chain Grate Stokers at the Sunnyside Plant of the Pennsylvania Tunnel and Terminal Railroad Co., Long Island City, N. Y.] 5th. That an increase in the temperature of the feed reduces the amount of work demanded from the boiler has been shown. The necessity of keeping the feed temperature as high as the quantity of exhaust steam will allow should be thoroughly understood. As an example of this, there was a case brought to our attention where a large amount of exhaust steam was wasted simply because the feed pump showed a tendency to leak if the temperature of feed water was increased above 140 degrees. The amount wasted was sufficient to increase the temperature to 180 degrees but was not utilized simply because of the slight expense necessary to overhaul the feed pump. The highest return will be obtained when the speed of the feed pumps is maintained reasonably constant for should the pumps run very slowly at times, there may be a loss of the steam from other auxiliaries by blowing off from the heaters. 6th. With a view to checking steam losses through the useless blowing of safety valves, the operative should be made to realize the great amount of steam that it is possible to get through a pipe of a given size. Oftentimes the fireman feels a sense of security from objections to a drop in steam simply because of the blowing of safety valves, not considering the losses due to such a cause and makes no effort to check this flow either by manipulation of dampers or regulation of fires. The few of the numerous shortcomings outlined above, which may be found in many plants, are almost entirely due to lack of knowledge on the part of the operating crew as to the conditions existing in their own plants and the better performances being secured in others. Such shortcomings can be overcome only by the education of the operatives, the showing of the defects of present methods, and instruction in better methods. Where such instruction is necessary, the value of records is obvious. There is fortunately a tendency toward the employment of a better class of labor in the boiler room, a tendency which is becoming more and more marked as the realization of the possible saving in this end of the plant increases. The second aspect of boiler room management, dealing with specific recommendations as to the care and operation of the boilers, is dictated largely by the nature of the apparatus. Some of the features to be watched in considering this aspect follow. Before placing a new boiler in service, a careful and thorough examination should be made of the pressure parts and the setting. The boiler as erected should correspond in its baffle openings, where baffles are adjustable, with the prints furnished for its erection, and such baffles should be tight. The setting should be so constructed that the boiler is free to expand without interfering with the brickwork. This ability to expand applies also to blow-off and other piping. After erection all mortar and chips of brick should be cleaned from the pressure parts. The tie rods should be set up snug and then slacked slightly until the setting has become thoroughly warm after the first firing. The boiler should be examined internally before starting to insure the absence of dirt, any foreign material such as waste, and tools. Oil and paint are sometimes found in the interior of a new boiler and where such is the case, a quantity of soda ash should be placed within it, the boiler filled with water to its normal level and a slow fire started. After twelve hours of slow simmering, the fire should be allowed to die out, the boiler cooled slowly and then opened and washed out thoroughly. Such a proceeding will remove all oil and grease from the interior and prevent the possibility of foaming and tube difficulties when the boiler is placed in service. The water column piping should be examined and known to be free and clear. The water level, as indicated by the gauge glass, should be checked by opening the gauge cocks. The method of drying out a brick setting before placing a boiler in operation is described later in the discussion of boiler settings. A boiler should not be cut into the line with other boilers until the pressure within it is approximately that in the steam main. The boiler stop valve should be opened very slowly until it is fully opened. The arrangement of piping should be such that there can be no possibility of water collecting in a pocket between the boiler and the main, from which it can be carried over into the steam line when a boiler is cut in. In regular operation the safety valve and steam gauge should be checked daily. In small plants the steam pressure should be raised sufficiently to cause the safety valves to blow, at which time the steam gauge should indicate the pressure at which the valve is known to be set. If it does not, one is in error and the gauge should be compared with one of known accuracy and any error at once rectified. In large plants such a method of checking would result in losses too great to be allowed. Here the gauges and valves are ordinarily checked at the time a boiler is cut out, the valves being assured of not sticking by daily instantaneous opening through manipulation by hand of the valve lever. The daily blowing of the safety valve acts not only as a check on the gauge but insures the valve against sticking. The water column should be blown down thoroughly at least once on every shift and the height of water indicated by the glass checked by the gauge cocks. The bottom blow-offs should be kept tight. These should be opened at least once daily to blow from the mud drum any sediment that may have collected and to reduce the concentration. The amount of blowing down and the frequency is, of course, determined by the nature of the feed water used. In case of low water, resulting either from carelessness or from some unforeseen condition of operation, the essential object to be obtained is the extinguishing of the fire in the quickest possible manner. Where practicable, this is best accomplished by the playing of a heavy stream of water from a hose on the fire. Another method, perhaps not so efficient, but more generally recommended, is the covering of the fire with wet ashes or fresh fuel. A boiler so treated should be cut out of line after such an occurrence and a thorough inspection made to ascertain what damage, if any, has been done before it is again placed in service. The efficiency and capacity depend to an extent very much greater than is ordinarily realized upon the cleanliness of the heating surfaces, both externally and internally, and too much stress cannot be put upon the necessity for systematic cleaning as a regular feature in the plant operation. The outer surfaces of the tubes should be blown free from soot at regular intervals, the frequency of such cleaning periods being dependent upon the class of fuel used. The most efficient way of blowing soot from the tubes is by means of a steam lance with which all parts of the surfaces are reached and swept clean. There are numerous soot blowing devices on the market which are designed to be permanently fixed within the boiler setting. Where such devices are installed, there are certain features that must be watched to avoid trouble. If there is any leakage of water of condensation within the setting coming into contact with the boiler tubes, it will tend toward corrosion, or if in contact with the heated brickwork will cause rapid disintegration of the setting. If the steam jets are so placed that they impinge directly against the tubes, erosion may take place. Where such permanent soot blowers are installed, too much care cannot be taken to guard against these possibilities. Internally, the tubes must be kept free from scale, the ingredients of which a study of the chapter on the impurities of water indicates are present in varying quantities in all feed waters. Not only has the presence of scale a direct bearing on the efficiency and capacity to be obtained from a boiler but its absence is an assurance against the burning out of tubes. In the absence of a blow-pipe action of the flames, it is impossible to burn a metal surface where water is in intimate contact with that surface. In stoker-fired plants where a blast is used, and the furnace is not properly designed, there is a danger of a blow-pipe action if the fires are allowed to get too thin. The rapid formation of steam at such points of localized heat may lead to the burning of the metal of the tubes. Any formation of scale on the interior surface of a boiler keeps the water from such a surface and increases its tendency to burn. Particles of loose scale that may become detached will lodge at certain points in the tubes and localize this tendency at such points. It is because of the danger of detaching scale and causing loose flakes to be present that the use of a boiler compound is not recommended for the removal of scale that has already formed in a boiler. This question is covered in the treatment of feed waters. If oil is allowed to enter a boiler, its action is the same as that of scale in keeping the water away from the metal surfaces. [Illustration: Fig. 41] It has been proven beyond a doubt that a very large percentage of tube losses is due directly to the presence of scale which, in many instances, has been so thin as to be considered of no moment, and the importance of maintaining the boiler heating surfaces in a clean condition cannot be emphasized too strongly. The internal cleaning can best be accomplished by means of an air or water-driven turbine, the cutter heads of which may be changed to handle various thicknesses of scale. Fig. 41 shows a turbine cleaner with various cutting heads, which has been found to give satisfactory service. Where a water-driven turbine is used, it should be connected to a pump which will deliver at least 120 gallons per minute per cleaner at 150 pounds pressure. This pressure should never be less than 90 pounds if satisfactory results are desired. Where an air-driven turbine is used, the pressure should be at least 100 pounds, though 150 pounds is preferable, and sufficient water should be introduced into the tube to keep the cutting head cool and assist in washing down the scale as it is chipped off. Where scale has been allowed to accumulate to an excessive thickness, the work of removal is difficult and tedious. Where such a heavy scale is of sulphate formation, its removal may be assisted by filling the boiler with water to which there has been added a quantity of soda ash, a bucketful to each drum, starting a low fire and allowing the water to boil for twenty-four hours with no pressure on the boiler. It should be cooled slowly, drained, and the turbine cleaner used immediately, as the scale will tend to harden rapidly under the action of the air. Where oil has been allowed to get into a boiler, it should be removed before placing the boiler in service, as described previously where reference is made to its removal by boiling out with soda ash. Where pitting or corrosion is noted, the parts affected should be carefully cleaned and the interior of the drums should be painted with white zinc if the boiler is to remain idle. The cause of such action should be immediately ascertained and steps taken to apply the proper remedy. When making an internal inspection of a boiler or when cleaning the interior heating surfaces, great care must be taken to guard against the possibility of steam entering the boiler in question from other boilers on the same line either through the careless opening of the boiler stop valve or some auxiliary valve or from an open blow-off. Bad accidents through scalding have resulted from the neglect of this precaution. Boiler brickwork should be kept pointed up and all cracks filled. The boiler baffles should be kept tight to prevent by-passing of any gases through the heating surfaces. Boilers should be taken out of service at regular intervals for cleaning and repairs. When this is done, the boiler should be cooled slowly, and when possible, be allowed to stand for twenty-four hours after the fire is drawn before opening. The cooling process should not be hurried by allowing cold air to rush through the setting as this will invariably cause trouble with the brickwork. When a boiler is off for cleaning, a careful examination should be made of its condition, both external and internal, and all leaks of steam, water and air through the setting stopped. If water is allowed to come into contact with brickwork that is heated, rapid disintegration will take place. If water is allowed to come into contact with the metal of the boiler when out of service, there is a likelihood of corrosion. If a boiler is to remain idle for some time, its deterioration may be much more rapid than when in service. If the period for which it is to be laid off is not to exceed three months, it may be filled with water while out of service. The boiler should first be cleaned thoroughly, internally and externally, all soot and ashes being removed from the exterior of the pressure parts and any accumulation of scale removed from the interior surfaces. It should then be filled with water, to which five or six pails of soda ash have been added, a slow fire started to drive the air from the boiler, the fire drawn and the boiler pumped full. In this condition it may be kept for some time without bad effects. If the boiler is to be out of service for more than three months, it should be emptied, drained and thoroughly dried after being cleaned. A tray of quick lime should be placed in each drum, the boiler closed, the grates covered and a quantity of quick lime placed on top of the covering. Special care should be taken to prevent air, steam or water leaks into the boiler or onto the pressure parts to obviate danger of corrosion. [Illustration: 3000 Horse-power Installation of Babcock & Wilcox Boilers in the Main Power Plant, Chicago & Northwestern Ry. Depot, Chicago, Ill.] BRICKWORK BOILER SETTINGS A consideration of the losses in boiler efficiency, due to the effects of excess air, clearly indicates the necessity of maintaining the brick setting of a boiler tight and free from air leaks. In view of the temperatures to which certain portions of such a setting are subjected, the material to be used in its construction must be of the best procurable. Boiler settings to-day consist almost universally of brickwork--two kinds being used, namely, red brick and fire brick. The red brick should only be used in such portions of the setting as are well protected from the heat. In such location, their service is not so severe as that of fire brick and ordinarily, if such red brick are sound, hard, well burned and uniform, they will serve their purpose. The fire brick should be selected with the greatest care, as it is this portion of the setting that has to endure the high temperatures now developed in boiler practice. To a great extent, the life of a boiler setting is dependent upon the quality of the fire brick used and the care exercised in its laying. The best fire brick are manufactured from the fire clays of Pennsylvania. South and west from this locality the quality of fire clay becomes poorer as the distance increases, some of the southern fire clays containing a considerable percentage of iron oxide. Until very recently, the important characteristic on which to base a judgment of the suitability of fire brick for use in connection with boiler settings has been considered the melting point, or the temperature at which the brick will liquify and run. Experience has shown, however, that this point is only important within certain limits and that the real basis on which to judge material of this description is, from the boiler man's standpoint, the quality of plasticity under a given load. This tendency of a brick to become plastic occurs at a temperature much below the melting point and to a degree that may cause the brick to become deformed under the stress to which it is subjected. The allowable plastic or softening temperature will naturally be relative and dependent upon the stress to be endured. With the plasticity the determining factor, the perfect fire brick is one whose critical point of plasticity lies well above the working temperature of the fire. It is probable that there are but few brick on the market which would not show, if tested, this critical temperature at the stress met with in arch construction at a point less than 2400 degrees. The fact that an arch will stand for a long period under furnace temperatures considerably above this point is due entirely to the fact that its temperature as a whole is far below the furnace temperature and only about 10 per cent of its cross section nearest the fire approaches the furnace temperature. This is borne out by the fact that arches which are heated on both sides to the full temperature of an ordinary furnace will first bow down in the middle and eventually fall. A method of testing brick for this characteristic is given in the Technologic Paper No. 7 of the Bureau of Standards dealing with "The testing of clay refractories with special reference to their load carrying capacity at furnace temperatures." Referring to the test for this specific characteristic, this publication recommends the following: "When subjected to the load test in a manner substantially as described in this bulletin, at 1350 degrees centigrade (2462 degrees Fahrenheit), and under a load of 50 pounds per square inch, a standard fire brick tested on end should show no serious deformation and should not be compressed more than one inch, referred to the standard length of nine inches." In the Bureau of Standards test for softening temperature, or critical temperature of plasticity under the specified load, the brick are tested on end. In testing fire brick for boiler purposes such a method might be criticised, because such a test is a compression test and subject to errors from unequal bearing surfaces causing shear. Furthermore, a series of samples, presumably duplicates, will not fail in the same way, due to the mechanical variation in the manufacture of the brick. Arches that fail through plasticity show that the tensile strength of the brick is important, this being evidenced by the fact that the bottom of a wedge brick in an arch that has failed is usually found to be wider than the top and the adjacent bricks are firmly cemented together. A better method of testing is that of testing the brick as a beam subjected to its own weight and not on end. This method has been used for years in Germany and is recommended by the highest authorities in ceramics. It takes into account the failure by tension in the brick as well as by compression and thus covers the tension element which is important in arch construction. The plastic point under a unit stress of 100 pounds per square inch, which may be taken as the average maximum arch stress, should be above 2800 degrees to give perfect results and should be above 2400 degrees to enable the brick to be used with any degree of satisfaction. The other characteristics by which the quality of a fire brick is to be judged are: Fusion point. In view of the fact that the critical temperature of plasticity is below the fusion point, this is only important as an indication from high fusion point of a high temperature of plasticity. Hardness. This is a relative quality based on an arbitrary scale of 10 and is an indication of probable cracking and spalling. Expansion. The lineal expansion per brick in inches. This characteristic in conjunction with hardness is a measure of the physical movement of the brick as affecting a mass of brickwork, such movement resulting in cracked walls, etc. The expansion will vary between wide limits in different brick and provided such expansion is not in excess of, say, .05 inch in a 9-inch brick, when measured at 2600 degrees, it is not particularly important in a properly designed furnace, though in general the smaller the expansion the better. Compression. The strength necessary to cause crushing of the brick at the center of the 4½ inch face by a steel block one inch square. The compression should ordinarily be low, a suggested standard being that a brick show signs of crushing at 7500 pounds. Size of Nodules. The average size of flint grains when the brick is carefully crushed. The scale of these sizes may be considered: Small, size of anthracite rice; large, size of anthracite pea. Ratio of Nodules. The percentage of a given volume occupied by the flint grains. This scale may be considered: High, 90 to 100 per cent; medium, 50 to 90 per cent; low, 10 to 50 per cent. The statement of characteristics suggested as desirable, are for arch purposes where the hardest service is met. For side wall purposes the compression and hardness limit may be raised considerably and the plastic point lowered. Aside from the physical properties by which a fire brick is judged, it is sometimes customary to require a chemical analysis of the brick. Such an analysis is only necessary as determining the amount of total basic fluxes (K_{2}O, Na_{2}O, CaO, MgO and FeO). These fluxes are ordinarily combined into one expression, indicated by the symbol RO. This total becomes important only above 0.2 molecular equivalent as expressed in ceramic empirical formulae, and this limit should not be exceeded.[75] From the nature of fire brick, their value can only be considered from a relative standpoint. Generally speaking, what are known as first-grade fire brick may be divided into three classes, suitable for various conditions of operation, as follows: Class A. For stoker-fired furnaces where high overloads are to be expected or where other extreme conditions of service are apt to occur. Class B. For ordinary stoker settings where there will be no excessive overloads required from the boiler or any hand-fired furnaces where the rates of driving will be high for such practice. Class C. For ordinary hand-fired settings where the presumption is that the boilers will not be overloaded except at rare intervals and for short periods only. Table 61 gives the characteristics of these three classes according to the features determining the quality. This table indicates that the hardness of the brick in general increases with the poorer qualities. Provided the hardness is sufficient to enable the brick to withstand its load, additional hardness is a detriment rather than an advantage. TABLE 61 APPROXIMATE CLASSIFICATION OF FIRE BRICK ________________________________________________________________________ | | | | | | Characteristics | Class A | Class B | Class C | |_____________________|________________|________________|________________| | | | | | | Fuse Point, Degrees | Safe at Degrees| Safe at Degrees| Safe at Degrees| | Fahrenheit | 3200-3300 | 2900-3200 | 2900-3000 | | | | | | | Compression Pounds | 6500-7500 | 7500-11,000 | 8500-15,000 | | | | | | | Hardness Relative | 1-2 | 2-4 | 4-6 | | | | | | | Size of Nodules | Medium | Medium to |Medium to Large | | | | Medium Large | | | | | | | | Ratio of Nodules | High | Medium to High | Medium Low | | | | | to Medium | |_____________________|________________|________________|________________| An approximate determination of the quality of a fire brick may be made from the appearance of a fracture. Where such a fracture is open, clean, white and flinty, the brick in all probability is of a good quality. If this fracture has the fine uniform texture of bread, the brick is probably poor. In considering the heavy duty of brick in boiler furnaces, experience shows that arches are the only part that ordinarily give trouble. These fail from the following causes: Bad workmanship in laying up of brick. This feature is treated below. The tendency of a brick to become plastic at a temperature below the fusing point. The limits of allowable plastic temperature have already been pointed out. Spalling. This action occurs on the inner ends of combustion arches where they are swept by gases at a high velocity at the full furnace temperature. The most troublesome spalling arises through cold air striking the heated brickwork. Failure from this cause is becoming rare, due to the large increase in number of stoker installations in which rapid temperature changes are to a great degree eliminated. Furthermore, there are a number of brick on the market practically free from such defects and where a new brick is considered, it can be tried out and if the defect exists, can be readily detected and the brick discarded. Failures of arches from the expansive power of brick are also rare, due to the fact that there are a number of brick in which the expansion is well within the allowable limits and the ease with which such defects may be determined before a brick is used. Failures through chemical disintegration. Failure through this cause is found only occasionally in brick containing a high percentage of iron oxide. With the grade of brick selected best suited to the service of the boiler to be set, the other factor affecting the life of the setting is the laying. It is probable that more setting difficulties arise from the improper workmanship in the laying up of brick than from poor material, and to insure a setting which will remain tight it is necessary that the masonry work be done most carefully. This is particularly true where the boiler is of such a type as to require combustion arches in the furnace. Red brick should be laid in a thoroughly mixed mortar composed of one volume of Portland cement, 3 volumes of unslacked lime and 16 volumes of clear sharp sand. Not less than 2½ bushels of lime should be used in the laying up of 1000 brick. Each brick should be thoroughly embedded and all joints filled. Where red brick and fire brick are both used in the same wall, they should be carried up at the same time and thoroughly bonded to each other. All fire brick should be dry when used and protected from moisture until used. Each brick should be dipped in a thin fire clay wash, "rubbed and shoved" into place, and tapped with a wooden mallet until it touches the brick next below it. It must be recognized that fire clay is not a cement and that it has little or no holding power. Its action is that of a filler rather than a binder and no fire-clay wash should be used which has a consistency sufficient to permit the use of a trowel. All fire-brick linings should be laid up four courses of headers and one stretcher. Furnace center walls should be entirely of fire brick. If the center of such walls are built of red brick, they will melt down and cause the failure of the wall as a whole. Fire-brick arches should be constructed of selected brick which are smooth, straight and uniform. The frames on which such arches are built, called arch centers, should be constructed of batten strips not over 2 inches wide. The brick should be laid on these centers in courses, not in rings, each joint being broken with a bond equal to the length of half a brick. Each course should be first tried in place dry, and checked with a straight edge to insure a uniform thickness of joint between courses. Each brick should be dipped on one side and two edges only and tapped into place with a mallet. Wedge brick courses should be used only where necessary to keep the bottom faces of the straight brick course in even contact with the centers. When such contact cannot be exactly secured by the use of wedge brick, the straight brick should lean away from the center of the arch rather than toward it. When the arch is approximately two-thirds completed, a trial ring should be laid to determine whether the key course will fit. When some cutting is necessary to secure such a fit, it should be done on the two adjacent courses on the side of the brick away from the key. It is necessary that the keying course be a true fit from top to bottom, and after it has been dipped and driven it should not extend below the surface of the arch, but preferably should have its lower ledge one-quarter inch above this surface. After fitting, the keys should be dipped, replaced loosely, and the whole course driven uniformly into place by means of a heavy hammer and a piece of wood extending the full length of the keying course. Such a driving in of this course should raise the arch as a whole from the center. The center should be so constructed that it may be dropped free of the arch when the key course is in place and removed from the furnace without being burned out. [Illustration: A Typical Steel Casing for a Babcock & Wilcox Boiler Built by The Babcock & Wilcox Co.] Care of Brickwork--Before a boiler is placed in service, it is essential that the brickwork setting be thoroughly and properly dried, or otherwise the setting will invariably crack. The best method of starting such a process is to block open the boiler damper and the ashpit doors as soon as the brickwork is completed and in this way maintain a free circulation of air through the setting. If possible, such preliminary drying should be continued for several days before any fire is placed in the furnace. When ready for the drying out fire, wood should be used at the start in a light fire which may be gradually built up as the walls become warm. After the walls have become thoroughly heated, coal may be fired and the boiler placed in service. As already stated, the life of a boiler setting is dependent to a large extent upon the material entering into its construction and the care with which such material is laid. A third and equally important factor in the determining of such life is the care given to the maintaining of the setting in good condition after the boiler is placed in operation. This feature is discussed more fully in the chapter dealing with general boiler room management. Steel Casings--In the chapter dealing with the losses operating against high efficiencies as indicated by the heat balance, it has been shown that a considerable portion of such losses is due to radiation and to air infiltration into the boiler setting. These losses have been variously estimated from 2 to 10 per cent, depending upon the condition of the setting and the amount of radiation surface, the latter in turn being dependent upon the size of the boiler used. In the modern efforts after the highest obtainable plant efficiencies much has been done to reduce such losses by the use of an insulated steel casing covering the brickwork. In an average size boiler unit the use of such casing, when properly installed, will reduce radiation losses from one to two per cent., over what can be accomplished with the best brick setting without such casing and, in addition, prevent the loss due to the infiltration of air, which may amount to an additional five per cent., as compared with brick settings that are not maintained in good order. Steel plate, or steel plate backed by asbestos mill-board, while acting as a preventative against the infiltration of air through the boiler setting, is not as effective from the standpoint of decreasing radiation losses as a casing properly insulated from the brick portion of the setting by magnesia block and asbestos mill-board. A casing which has been found to give excellent results in eliminating air leakage and in the reduction of radiation losses is clearly illustrated on page 306. Many attempts have been made to use some material other than brick for boiler settings but up to the present nothing has been found that may be considered successful or which will give as satisfactory service under severe conditions as properly laid brickwork. BOILER ROOM PIPING In the design of a steam plant, the piping system should receive the most careful consideration. Aside from the constructive details, good practice in which is fairly well established, the important factors are the size of the piping to be employed and the methods utilized in avoiding difficulties from the presence in the system of water of condensation and the means employed toward reducing radiation losses. Engineering opinion varies considerably on the question of material of pipes and fittings for different classes of work, and the following is offered simply as a suggestion of what constitutes good representative practice. All pipe should be of wrought iron or soft steel. Pipe at present is made in "standard", "extra strong"[76] and "double extra strong" weights. Until recently, a fourth weight approximately 10 per cent lighter than standard and known as "Merchants" was built but the use of this pipe has largely gone out of practice. Pipe sizes, unless otherwise stated, are given in terms of nominal internal diameter. Table 62 gives the dimensions and some general data on standard and extra strong wrought-iron pipe. TABLE 62 DIMENSIONS OF STANDARD AND EXTRA STRONG[76] WROUGHT-IRON AND STEEL PIPE _______________________________________________________________ | | | | | | Diameter | Circumference | | |__________________________|__________________________| | | | | | | | |External| Internal |External| Internal | | |Standard|_________________|Standard|_________________| | | and | | | and | | | | Nominal | Extra |Standard| Extra | Extra |Standard| Extra | | Size | Strong | | Strong | Strong | | Strong | |_________|________|________|________|________|________|________| | | | | | | | | | 1/8 | .405 | .269 | .215 | 1.272 | .848 | .675 | | 1/4 | .540 | .364 | .302 | 1.696 | 1.144 | .949 | | 3/8 | .675 | .493 | .423 | 2.121 | 1.552 | 1.329 | | 1/2 | .840 | .622 | .546 | 2.639 | 1.957 | 1.715 | | 3/4 | 1.050 | .824 | .742 | 3.299 | 2.589 | 2.331 | | 1 | 1.315 | 1.049 | .957 | 4.131 | 3.292 | 3.007 | | 1-1/4 | 1.660 | 1.380 | 1.278 | 5.215 | 4.335 | 4.015 | | 1-1/2 | 1.900 | 1.610 | 1.500 | 5.969 | 5.061 | 4.712 | | 2 | 2.375 | 2.067 | 1.939 | 7.461 | 6.494 | 6.092 | | 2-1/2 | 2.875 | 2.469 | 2.323 | 9.032 | 7.753 | 7.298 | | 3 | 3.500 | 3.068 | 2.900 | 10.996 | 9.636 | 9.111 | | 3-1/2 | 4.000 | 3.548 | 3.364 | 12.566 | 11.146 | 10.568 | | 4 | 4.500 | 4.026 | 3.826 | 14.137 | 12.648 | 12.020 | | 4-1/2 | 5.000 | 4.506 | 4.290 | 15.708 | 14.162 | 13.477 | | 5 | 5.563 | 5.047 | 4.813 | 17.477 | 15.849 | 15.121 | | 6 | 6.625 | 6.065 | 5.761 | 20.813 | 19.054 | 18.099 | | 7 | 7.625 | 7.023 | 6.625 | 23.955 | 22.063 | 20.813 | | 8 | 8.625 | 7.981 | 7.625 | 27.096 | 25.076 | 23.955 | | 9 | 9.625 | 8.941 | 8.625 | 30.238 | 28.089 | 27.096 | | 10 | 10.750 | 10.020 | 9.750 | 33.772 | 31.477 | 30.631 | | 11 | 11.750 | 11.000 | 10.750 | 36.914 | 34.558 | 33.772 | | 12 | 12.750 | 12.000 | 11.750 | 40.055 | 37.700 | 36.914 | |_________|________|________|________|________|________|________| __________________________________________________________ | | | | | | | | Length | | | | Internal | of | Nominal Weight | | | Transverse |Pipe in | Pounds per | | | Area |Feet per| Foot | | |_____________________| Square |_________________| | | | |Foot of | | | | Nominal | Standard | Extra |External|Standard| Extra | | Size | | Strong |Surface | | Strong | |_________|__________|__________|________|________|________| | | | | | | | | 1/8 | .0573 | .0363 | 9.440 | .244 | .314 | | 1/4 | .1041 | .0716 | 7.075 | .424 | .535 | | 3/8 | .1917 | .1405 | 5.657 | .567 | .738 | | 1/2 | .3048 | .2341 | 4.547 | .850 | 1.087 | | 3/4 | .5333 | .4324 | 3.637 | 1.130 | 1.473 | | 1 | .8626 | .7193 | 2.904 | 1.678 | 2.171 | | 1-1/4 | 1.496 | 1.287 | 2.301 | 2.272 | 2.996 | | 1-1/2 | 2.038 | 1.767 | 2.010 | 2.717 | 3.631 | | 2 | 3.356 | 2.953 | 1.608 | 3.652 | 5.022 | | 2-1/2 | 4.784 | 4.238 | 1.328 | 5.793 | 7.661 | | 3 | 7.388 | 6.605 | 1.091 | 7.575 | 10.252 | | 3-1/2 | 9.887 | 8.888 | .955 | 9.109 | 12.505 | | 4 | 12.730 | 11.497 | .849 | 10.790 | 14.983 | | 4-1/2 | 15.961 | 14.454 | .764 | 12.538 | 17.611 | | 5 | 19.990 | 18.194 | .687 | 14.617 | 20.778 | | 6 | 28.888 | 26.067 | .577 | 18.974 | 28.573 | | 7 | 38.738 | 34.472 | .501 | 23.544 | 38.048 | | 8 | 50.040 | 45.664 | .443 | 28.544 | 43.388 | | 9 | 62.776 | 58.426 | .397 | 33.907 | 48.728 | | 10 | 78.839 | 74.662 | .355 | 40.483 | 54.735 | | 11 | 95.033 | 90.763 | .325 | 45.557 | 60.075 | | 12 | 113.098 | 108.43 | .299 | 49.562 | 65.415 | |_________|__________|__________|________|________|________| Dimensions are nominal and except where noted are in inches. In connection with pipe sizes, Table 63, giving certain tube data may be found to be of service. TABLE 63 TUBE DATA, STANDARD OPEN HEARTH OR LAP WELDED STEEL TUBES +-----+--+----+-----+------+------+------+------+-------+-------+-------+ |S E D|B | T | I D |Circumference| Transverse |Square |Length |Nominal| |i x i|. | h | n i | | Area | Feet |in Feet|Weight | |z t a|W | i | t a | |Square Inches| of | per |Pounds | |e e m|. | c | e m +------+------+------+------+ Exter |Square | per | | r e| | k | r e |Exter-|Inter-|Exter-|Inter-| -nal |Foot of| Foot | | n t|G | n | n t | nal | nal | nal | nal |Surface| Exter | | | a e|a | e | a e | | | | | per | -nal | | | l r|u | s | l r | | | | |Foot of|Surface| | | |g | s | | | | | |Length | | | | |e | | | | | | | | | | +-----+--+----+-----+------+------+------+------+-------+-------+-------+ |1-1/2|10|.134|1.232| 4.712| 3.870|1.7671|1.1921| .392 | 2.546 | 1.955 | |1-1/2| 9|.148|1.204| 4.712| 3.782|1.7671|1.1385| .392 | 2.546 | 2.137 | |1-1/2| 8|.165|1.170| 4.712| 3.676|1.7671|1.0751| .392 | 2.546 | 2.353 | | 2 |10|.134|1.732| 6.283| 5.441|3.1416|2.3560| .523 | 1.909 | 2.670 | | 2 | 9|.148|1.704| 6.283| 5.353|3.1416|2.2778| .523 | 1.909 | 2.927 | | 2 | 8|.165|1.670| 6.283| 5.246|3.1416|2.1904| .523 | 1.909 | 3.234 | |3-1/4|11|.120|3.010|10.210| 9.456|8.2958|7.1157| .850 | 1.175 | 4.011 | |3-1/4|10|.134|2.982|10.210| 9.368|8.2958|6.9840| .850 | 1.175 | 4.459 | |3-1/4| 9|.148|2.954|10.210| 9.280|8.2958|6.8535| .850 | 1.175 | 4.903 | | 4 |10|.134|3.732|12.566|11.724|12.566|10.939| 1.047 | .954 | 5.532 | | 4 | 9|.148|3.704|12.566|11.636|12.566|10.775| 1.047 | .954 | 6.000 | | 4 | 8|.165|3.670|12.566|11.530|12.566|10.578| 1.047 | .954 | 6.758 | +-----+--+----+-----+------+------+------+------+-------+-------+-------+ Dimensions are nominal and except where noted are in inches. Pipe Material and Thickness--For saturated steam pressures not exceeding 160 pounds, all pipe over 14 inches should be 3/8 inch thick O. D. pipe. All other pipe should be standard full weight, except high pressure feed[77] and blow-off lines, which should be extra strong. For pressures above 150 pounds up to 200 pounds with superheated steam, all high pressure feed and blow-off lines, high pressure steam lines having threaded flanges, and straight runs and bends of high pressure steam lines 6 inches and under having Van Stone joints should be extra strong. All piping 7 inches and over having Van Stone joints should be full weight soft flanging pipe of special quality. Pipe 14 inches and over should be 3/8 inch thick O. D. pipe. All pipes for these pressures not specified above should be full weight pipe. Flanges--For saturated steam, 160 pounds working pressure, all flanges for wrought-iron pipe should be cast-iron threaded. All high pressure threaded flanges should have the diameter thickness and drilling in accordance with the "manufacturer's standard" for "extra heavy" flanges. All low pressure flanges should have diameter, thickness and drilling in accordance with "manufacturer's standard" for "standard flanges." The flanges on high pressure lines should be counterbored to receive pipe and prevent the threads from shouldering. The pipe should be screwed through the flange at least 1/16 inch, placed in machine and after facing off the end one smooth cut should be taken over the face of the flange to make it square with the axis of the pipe. [Illustration: 2000 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock & Wilcox Chain Grate Stokers at the Kentucky Electric Co., Louisville, Ky.] For pressures above 160 pounds, where superheated steam is used, all high pressure steam lines 4 inches and over should have solid rolled steel flanges and special upset lapped joints. In the manufacture of such joints, the ends of the pipe are heated and upset against the face of a holding mandrel conforming to the shape of the flange, the lapped portion of the pipe being flattened out against the face of the mandrel, the upsetting action maintaining the desired thickness of the lap. When cool, both sides of the lap are faced to form a uniform thickness and an even bearing against flange and gasket. The joint, therefore, is a strictly metal to metal joint, the flanges merely holding the lapped ends of the pipe against the gasket. A special grade of soft flanging pipe is selected to prevent breaking. The bending action is a severe test of the pipe and if it withstands the bending process and the pressure tests, the reliability of the joint is assured. Such a joint is called a Van Stone joint, though many modifications and improvements have been made since the joint was originally introduced. The diameter and thickness of such flanges should be special extra heavy. Such flanges should be turned to diameter, their fronts faced and the backs machined in lieu of spot facing. In lines other than given for pressures over 150 pounds, all flanges for wrought-iron pipe should be threaded. All threaded flanges for high pressure superheated lines 3½ inches and under should be "semi-steel" extra heavy. Flanges for other than steam lines should be manufacturer's standard extra heavy. Welded flanges are frequently used in place of those described with satisfactory results. Fittings--For saturated steam under pressures up to 160 pounds, all fittings 3½ inches and under should be screwed. Fittings 4 inches and over should have flanged ends. Fittings for this pressure should be of cast iron and should have heavy leads and full taper threads. Flanged fittings in high pressure lines should be extra heavy, and in low pressure lines standard weight. Where possible in high pressure flanges and fittings, bolt surfaces should be spot faced to provide suitable bearing for bolt heads and nuts. Fittings for superheated steam up to 70 degrees at pressures above 160 pounds are sometimes of cast iron.[78] For superheat above 70 degrees such fittings should be "steel castings" and in general these fittings are recommended for any degree of superheat. Fittings for other than high pressure work may be of cast iron, except where superheated steam is carried, where they should be of "wrought steel" or "hard metal". Fittings 3½ inches and under should be screwed, 4 inches and over flanged. Flanges for pressures up to 160 pounds in pipes and fittings for low pressure lines, and any fittings for high pressure lines should have plain faces, smooth tool finish, scored with V-shaped grooves for rubber gaskets. High pressure line flanges should have raised faces, projecting the full available diameter inside the bolt holes. These faces should be similarly scored. All pipe ½ inch and under should have ground joint unions suitable for the pressure required. Pipe ¾ inch and over should have cast-iron flanged unions. Unions are to be preferred to wrought-iron couplings wherever possible to facilitate dismantling. Valves--For 150 pounds working pressure, saturated steam, all valves 2 inches and under may have screwed ends; 2½ inches and over should be flanged. All high pressure steam valves 6 inches and over should have suitable by-passes. All valves for use with superheated steam should be of special construction. For pressures above 160 pounds, where the superheat does not exceed 70 degrees, valve bodies, caps and yokes are sometimes made of cast iron, though ordinarily semi-steel will give better satisfaction. The spindles of such valves should be of bronze and there should be special necks with condensing chambers to prevent the superheated steam from blowing through the packing. For pressures over 160 pounds and degrees of superheat above 70, all valves 3 inches and over should have valve bodies, caps and yokes of steel castings. Spindles should be of some non-corrosive metal, such as "monel metal". Seat rings should be removable of the same non-corrosive metal as should the spindle seats and plug faces. All salt water valves should have bronze spindles, sleeves and packing seats. The suggestions as to flanges for different classes of service made on page 311 hold as well for valve flanges, except that such flanges are not scored. Automatic stop and check valves are coming into general use with boilers and such use is compulsory under the boiler regulations of certain communities. Where used, they should be preferably placed directly on the boiler nozzle. Where two or more boilers are on one line, in addition to the valve at the boiler, whether this be an automatic valve or a gate valve, there should be an additional gate valve on each boiler branch at the main steam header. Relief valves should be furnished at the discharge side of each feed pump and on the discharge side of each feed heater of the closed type. Feed Lines--Feed lines should in all instances be made of extra strong pipe due to the corrosive action of hot feed water. While it has been suggested above that cast-iron threaded flanges should be used in such lines, due to the sudden expansion of such pipe in certain instances cast-iron threaded flanges crack before they become thoroughly heated and expand, and for this reason cast-steel threaded flanges will give more satisfactory results. In some instances, wrought-steel and Van Stone joints have been used in feed lines and this undoubtedly is better practice than the use of cast-steel threaded work, though the additional cost is not warranted in all stations. Feed valves should always be of the globe pattern. A gate valve cannot be closely regulated and often clatters owing to the pulsations of the feed pump. Gaskets--For steam and water lines where the pressure does not exceed 160 pounds, wire insertion rubber gaskets 1/16 inch thick will be found to give good service. For low pressure lines, canvas insertion black rubber gaskets are ordinarily used. For oil lines special gaskets are necessary. For pressure above 160 pounds carrying superheated steam, corrugated steel gaskets extending the full available diameter inside of the bolt holes give good satisfaction. For high pressure water lines wire inserted rubber gaskets are used, and for low pressure flanged joints canvas inserted rubber gaskets. Size of Steam Lines--The factors affecting the proper size of steam lines are the radiation from such lines and the velocity of steam within them. As the size of the steam line increases, there will be an increase in the radiation.[79] As the size decreases, the steam velocity and the pressure drop for a given quantity of steam naturally increases. There is a marked tendency in modern practice toward higher steam velocities, particularly in the case of superheated steam. It was formerly considered good practice to limit this velocity to 6000 feet per minute but this figure is to-day considered low. In practice the limiting factor in the velocity advisable is the allowable pressure drop. In the description of the action of the throttling calorimeter, it has been demonstrated that there is no loss accompanying a drop in pressure, the difference in energy between the higher and lower pressures appearing as heat, which, in the case of steam flowing through a pipe, may evaporate any condensation present or may be radiated from the pipe. A decrease in pipe area decreases the radiating surface of the pipe and thus the possible condensation. As the heat liberated by the pressure drop is utilized in overcoming or diminishing the tendency toward condensation and the heat loss through radiation, the steam as it enters the prime mover will be drier or more highly superheated where high steam velocities are used than where they are lower, and if enough excess pressure is carried at the boilers to maintain the desired pressure at the prime mover, the pressure drop results in an actual saving rather than a loss. The whole is analogous to standard practice in electrical distributing systems where generator voltage is adjusted to suit the loss in the feeder lines. In modern practice, with superheated steam, velocities of 15,000 feet per minute are not unusual and this figure is very frequently exceeded. Piping System Design--With the proper size of pipe to be used determined, the most important factor is the provision for the removal of water of condensation that will occur in any system. Such condensation cannot be wholly overcome and if the water of condensation is carried to the prime mover, difficulties will invariably result. Water is practically incompressible and its effect when traveling at high velocities differs little from that of a solid body of equal weight, hence impact against elbows, valves or other obstructions, is the equivalent of a heavy hammer blow that may result in the fracture of the pipe. If there is not sufficient water in the system to produce this result, it will certainly cause knocking and vibration in the pipe, resulting eventually in leaky joints. Where the water reaches the prime mover, its effect will vary from disagreeable knocking to disruption. Too frequently when there are disastrous results from such a cause the boilers are blamed for delivering wet steam when, as a matter of fact, the evil is purely a result of poor piping design, the most common cause of such an action being the pocketing of the water in certain parts of the piping from whence it is carried along in slugs by the steam. The action is particularly severe if steam is admitted to a cold pipe containing water, as the water may then form a partial vacuum by condensing the steam and be projected at a very high velocity through the pipes producing a characteristic sharp metallic knock which often causes bursting of the pipe or fittings. The amount of water present through condensation may be appreciated when it is considered that uncovered 6-inch pipe 150 feet long carrying 3600 pounds of high pressure steam per hour will condense approximately 6 per cent of the total steam carried through radiation. It follows that efficient means of removing condensation water are absolutely imperative and the following suggestions as to such means may be of service: The pitch of all pipe should be in the direction of the flow of steam. Wherever a rise is necessary, a drain should be installed. All main headers and important branches should end in a drop leg and each such drop leg and any low points in the system should be connected to the drainage pump. A similar connection should be made to every fitting where there is danger of a water pocket. Branch lines should never be taken from the bottom of a main header but where possible should be taken from the top. Each engine supply pipe should have its own separator placed as near the throttle as possible. Such separators should be drained to the drainage system. Check valves are frequently placed in drain pipes to prevent steam from entering any portion of the system that may be shut off. Valves should be so located that they cannot form water pockets when either open or closed. Globe valves will form a water pocket in the piping to which they are connected unless set with the stem horizontal, while gate valves may be set with the spindle vertical or at an angle. Where valves are placed directly on the boiler nozzle, a drain should be provided above them. High pressure drains should be trapped to both feed heaters and waste headers. Traps and meters should be provided with by-passes. Cylinder drains, heater blow-offs and drains, boiler blow-offs and similar lines should be led to waste. The ends of cylinder drains should not extend below the surface of water, for on starting up or on closing the throttle valve with the drains open, water may be drawn back into the cylinders. TABLE 64 RADIATION FROM COVERED AND UNCOVERED STEAM PIPES CALCULATED FOR 160 POUNDS PRESSURE AND 60 DEGREES TEMPERATURE +---------------------------------------------------------------------+ |+------+---------------------------+----+----+----+-----+-----+-----+| || | | | | | | | || || Pipe | |1/2 |3/4 | 1 |1-1/4|1-1/2| || ||Inches| Thickness of Covering |inch|inch|inch|inch |inch |Bare || |+------+---------------------------+----+----+----+-----+-----+-----+| || |B. t. u. per lineal foot | | | | | | || || | per hour |149 |118 | 99 | 86 | 79 | 597 || || |B. t. u. per square foot | | | | | | || || | per hour |240 |190 |161 | 138 | 127 | 959 || || 2 |B. t. u. per square foot | | | | | | || || | per hour per one degree | | | | | | || || | difference in temperature|.770|.613|.519|.445 |.410 |3.198|| |+------+---------------------------+----+----+----+-----+-----+-----+| || |B. t. u. per lineal foot | | | | | | || || | per hour |247 |193 |160 | 139 | 123 |1085 || || |B. t. u. per square foot | | | | | | || || | per hour |210 |164 |136 | 118 | 104 | 921 || || 4 |B. t. u. per square foot | | | | | | || || | per hour per one degree | | | | | | || || | difference in temperature|.677|.592|.439|.381 |.335 |2.970|| |+------+---------------------------+----+----+----+-----+-----+-----+| || |B. t. u. per lineal foot | | | | | | || || | per hour |352 |269 |221 | 190 | 167 |1555 || || |B. t. u. per square foot | | | | | | || || | per hour |203 |155 |127 | 110 | 96 | 897 || || 6 |B. t. u. per square foot | | | | | | || || | per hour per one degree | | | | | | || || | difference in temperature|.655|.500|.410|.355 |.310 |2.89 || |+------+---------------------------+----+----+----+-----+-----+-----+| || |B. t. u. per lineal foot | | | | | | || || | per hour |443 |337 |276 | 235 | 207 |1994 || || |B. t. u. per square foot | | | | | | || || | per hour |196 |149 |122 | 104 | 92 | 883 || || 8 |B. t. u. per square foot | | | | | | || || | per hour per one degree | | | | | | || || | difference in temperature|.632|.481|.394|.335 |.297 |2.85 || |+------+---------------------------+----+----+----+-----+-----+-----+| || |B. t. u. per lineal foot | | | | | | || || | per hour |549 |416 |337 | 287 | 250 |2468 || || |B. t. u. per square foot | | | | | | || || | per hour |195 |148 |120 | 102 | 89 | 877 || || 10 |B. t. u. per square foot | | | | | | || || | per hour per one degree | | | | | | || || | difference in temperature|.629|.477|.387|.329 |.287 |2.83 || |+------+---------------------------+----+----+----+-----+-----+-----+| +---------------------------------------------------------------------+ Covering--Magnesia, canvas covered. For calculating radiation for pressure and temperature other than 160 pounds, and 60 degrees, use B. t. u. figures for one degree difference. Radiation from Pipes--The evils of the presence of condensed steam in piping systems have been thoroughly discussed above and in some of the previous articles. Condensation resulting from radiation, while it cannot be wholly obviated, can, by proper installation, be greatly reduced. Bare pipe will radiate approximately 3 B. t. u. per hour per square foot of exposed surface per one degree of difference in temperature between the steam contained and the external air. This figure may be reduced to from 0.3 to 0.4 B. t. u. for the same conditions by a 1½ inch insulating covering. Table 64 gives the radiation losses for bare and covered pipes with different thicknesses of magnesia covering. Many experiments have been made as to the relative efficiencies of different kinds of covering. Table 65 gives some approximately relative figures based on one inch covering from experiments by Paulding, Jacobus, Brill and others. TABLE 65 APPROXIMATE EFFICIENCIES OF VARIOUS COVERINGS REFERRED TO BARE PIPES +--------------------------------+ |+-------------------+----------+| || Covering |Efficiency|| |+-------------------+----------+| ||Asbestocel | 76.8 || ||Gast's Air Cell | 74.4 || ||Asbesto Sponge Felt| 85.0 || ||Magnesia | 83.5 || ||Asbestos Navy Brand| 82.0 || ||Asbesto Sponge Hair| 86.0 || ||Asbestos Fire Felt | 73.5 || |+-------------------+----------+| +--------------------------------+ Based on one-inch covering. The following suggestions may be of service: Exposed radiating surfaces of all pipes, all high pressure steam flanges, valve bodies and fittings, heaters and separators, should be covered with non-conducting material wherever such covering will improve plant economy. All main steam lines, engine and boiler branches, should be covered with 2 inches of 85 per cent carbonate of magnesia or the equivalent. Other lines may be covered with one inch of the same material. All covering should be sectional in form and large surfaces should be covered with blocks, except where such material would be difficult to install, in which case plastic material should be used. In the case of flanges the covering should be tapered back from the flange in order that the bolts may be removed. All surfaces should be painted before the covering is applied. Canvas is ordinarily placed over the covering, held in place by wrought-iron or brass bands. Expansion and Support of Pipe--It is highly important that the piping be so run that there will be no undue strains through the action of expansion. Certain points are usually securely anchored and the expansion of the piping at other points taken care of by providing supports along which the piping will slide or by means of flexible hangers. Where pipe is supported or anchored, it should be from the building structure and not from boilers or prime movers. Where supports are furnished, they should in general be of any of the numerous sliding supports that are available. Expansion is taken care of by such a method of support and by the providing of large radius bends where necessary. It was formerly believed that piping would actually expand under steam temperatures about one-half the theoretical amount due to the fact that the exterior of the pipe would not reach the full temperature of the steam contained. It would appear, however from recent experiments that such actual expansion will in the case of well-covered pipe be very nearly the theoretical amount. In one case noted, a steam header 293 feet long when heated under a working pressure of 190 pounds, the steam superheated approximately 125 degrees, expanded 8¾ inches; the theoretical amount of expansion under the conditions would be approximately 9-35/64 inches. [Illustration: Bankers Trust Building, New York City, Operation 900 Horse Power of Babcock & Wilcox Boilers] FLOW OF STEAM THROUGH PIPES AND ORIFICES Various formulae for the flow of steam through pipes have been advanced, all having their basis upon Bernoulli's theorem of the flow of water through circular pipes with the proper modifications made for the variation in constants between steam and water. The loss of energy due to friction in a pipe is given by Unwin (based upon Weisbach) as f 2 v² W L E_{f} = ---------- (37) gd where E is the energy loss in foot pounds due to the friction of W units of weight of steam passing with a velocity of v feet per second through a pipe d feet in diameter and L feet long; g represents the acceleration due to gravity (32.2) and f the coefficient of friction. Numerous values have been given for this coefficient of friction, f, which, from experiment, apparently varies with both the diameter of pipe and the velocity of the passing steam. There is no authentic data on the rate of this variation with velocity and, as in all experiments, the effect of change of velocity has seemed less than the unavoidable errors of observation, the coefficient is assumed to vary only with the size of the pipe. Unwin established a relation for this coefficient for steam at a velocity of 100 feet per second, / 3 \ f = K| 1 + --- | (38) \ 10d / where K is a constant experimentally determined, and d the internal diameter of the pipe in feet. If h represents the loss of head in feet, then f 2 v² W L E_{f} = Wh = ---------- (39) gd f 2 v² L and h = -------- (40) gd If D represents the density of the steam or weight per cubic foot, and p the loss of pressure due to friction in pounds per square inch, then hD p = --- (41) 144 and from equations (38), (40) and (41), D v² L / 3 \ p = -------- × K | 1 + --- | (42) 72 g d \ 10d / To convert the velocity term and to reduce to units ordinarily used, let d_{1} the diameter of pipe in inches = 12d, and w = the flow in pounds per minute; then [pi] / d_{1}\ w = 60v × --- | ---- |^{2} D 4 \ 12 / 9.6 w and v = -------------- [pi] d_{1}^2 D Substituting this value and that of d in formula (42) / 3.6 \ w^{2} L p = 0.04839 K | 1 + ----- | ----------- (43) \ d_{1} / D d_{1}^{5} Some of the experimental determinations for the value of K are: K = .005 for water (Unwin). K = .005 for air (Arson). K = .0028 for air (St. Gothard tunnel experiments). K = .0026 for steam (Carpenter at Oriskany). K = .0027 for steam (G. H. Babcock). The value .0027 is apparently the most nearly correct, and substituting in formula (43) gives, / 3.6 \ w^{2} L p = 0.000131 | 1 + ---- | ----------- (44) \ d_{1}/ D d_{1}^{5} / pDd_{1}^{5} \ w = 87 | -------------- |^{½} (45) | / 3.6 \ | | | 1 + ---- | L | \ \ d_{1}/ / Where w = the weight of steam passing in pounds per minute, p = the difference in pressure between the two ends of the pipe in pounds per square inch, D = density of steam or weight per cubic foot,[80] d_{1} = internal diameter of pipe in inches, L = length of pipe in feet. TABLE 66 FLOW OF STEAM THROUGH PIPES +---------------------------------------------------------------------------------------+ |Initl|Diameter[81] of Pipe in Inches, Length of Pipe = 240 Diameters | |Gauge|---------------------------------------------------------------------------------+ |Press| ¾ | 1 | 1½ | 2 | 2½ | 3 | 4 | 5 | 6 | 8 | 10 | 12 | 15 | 18 | |Pound|---------------------------------------------------------------------------------+ |/SqIn| Weight of Steam per Minute, in Pounds, With One Pound Loss of Pressure | +-----+---------------------------------------------------------------------------------+ | 1 |1.16|2.07| 5.7|10.27|15.45|25.38| 46.85| 77.3|115.9|211.4| 341.1| 502.4| 804|1177| | 10 |1.44|2.57| 7.1|12.72|19.15|31.45| 58.05| 95.8|143.6|262.0| 422.7| 622.5| 996|1458| | 20 |1.70|3.02| 8.3|14.94|22.49|36.94| 68.20|112.6|168.7|307.8| 496.5| 731.3|1170|1713| | 30 |1.91|3.40| 9.4|16.84|25.35|41.63| 76.84|126.9|190.1|346.8| 559.5| 824.1|1318|1930| | 40 |2.10|3.74|10.3|18.51|27.87|45.77| 84.49|139.5|209.0|381.3| 615.3| 906.0|1450|2122| | 50 |2.27|4.04|11.2|20.01|30.13|49.48| 91.34|150.8|226.0|412.2| 665.0| 979.5|1567|2294| | 60 |2.43|4.32|11.9|21.38|32.19|52.87| 97.60|161.1|241.5|440.5| 710.6|1046.7|1675|2451| | 70 |2.57|4.58|12.6|22.65|34.10|56.00|103.37|170.7|255.8|466.5| 752.7|1108.5|1774|2596| | 80 |2.71|4.82|13.3|23.82|35.87|58.91|108.74|179.5|269.0|490.7| 791.7|1166.1|1866|2731| | 90 |2.83|5.04|13.9|24.92|37.52|61.62|113.74|187.8|281.4|513.3| 828.1|1219.8|1951|2856| | 100 |2.95|5.25|14.5|25.96|39.07|64.18|118.47|195.6|293.1|534.6| 862.6|1270.1|2032|2975| | 120 |3.16|5.63|15.5|27.85|41.93|68.87|127.12|209.9|314.5|573.7| 925.6|1363.3|2181|3193| | 150 |3.45|6.14|17.0|30.37|45.72|75.09|138.61|228.8|343.0|625.5|1009.2|1486.5|2378|3481| +---------------------------------------------------------------------------------------+ This formula is the most generally accepted for the flow of steam in pipes. Table 66 is calculated from this formula and gives the amount of steam passing per minute that will flow through straight smooth pipes having a length of 240 diameters from various initial pressures with one pound difference between the initial and final pressures. To apply this table for other lengths of pipe and pressure losses other than those assumed, let L = the length and d the diameter of the pipe, both in inches; l, the loss in pounds; Q, the weight under the conditions assumed in the table, and Q_{1}, the weight for the changed conditions. For any length of pipe, if the weight of steam passing is the same as given in the table, the loss will be, L l = ---- (46) 240d If the pipe length is the same as assumed in the table but the loss is different, the quantity of steam passing per minute will be, Q_{1} = Ql^{½} (47) For any assumed pipe length and loss of pressure, the weight will be, /240dl\ Q_{1} = Q|-----|^{½} (48) \ L / TABLE 67 FLOW OF STEAM THROUGH PIPES LENGTH OF PIPE 1000 FEET +--------------------------------------------------++----------------------------------------+ | Discharge in Pounds per Minute corresponding to || Drop in Pressure in | | Drop in Pressure on Right for Pipe Diameters || Pounds per Square Inch corresponding | | in Inches in Top Line || to Discharge on Left: Densities | | || and corresponding Absolute Pressures | | || per Square Inch in First Two Lines | +--------------------------------------------------++----------------------------------------+ | Diameter[82]--Discharge || Density--Pressure--Drop | +--------------------------------------------------++----------------------------------------+ | 12 | 10 | 8 | 6 | 4 | 3 | 2½| 2 | 1½| 1 ||.208 |.230|.284|.328|.401|.443|.506|.548| | In | In | In | In | In | In | In | In | In | In || 90 | 100| 125| 150| 180| 200| 230| 250| +--------------------------------------------------++-------+--------------------------------+ |2328|1443| 799| 371|123. |55.9|28.8|18.1|6.81|2.52||18.10|16.4|13.3|11.1|9.39|8.50|7.44|6.87| |2165|1341| 742| 344|114.6|51.9|27.6|16.8|6.52|2.34||15.60|14.1|11.4|9.60|8.09|7.33|6.41|5.92| |1996|1237| 685| 318|106.0|47.9|26.4|15.5|6.24|2.16||13.3 |12.0|9.74|8.18|6.90|6.24|5.47|5.05| |1830|1134| 628| 292| 97.0|43.9|25.2|14.2|5.95|1.98||11.1 |10.0|8.13|6.83|5.76|5.21|4.56|4.21| |1663|1031| 571| 265| 88.2|39.9|24.0|12.9|5.67|1.80|| 9.25|8.36|6.78|5.69|4.80|4.34|3.80|3.51| |1580| 979| 542| 252| 83.8|37.9|22.8|12.3|5.29|1.71|| 8.33|7.53|6.10|5.13|4.32|3.91|3.42|3.16| |1497| 928| 514| 239| 79.4|35.9|21.6|11.6|5.00|1.62|| 7.48|6.76|5.48|4.60|3.88|3.51|3.07|2.84| |1414| 876| 485| 226| 75.0|33.9|20.4|10.9|4.72|1.53|| 6.67|6.03|4.88|4.10|3.46|3.13|2.74|2.53| |1331| 825| 457| 212| 70.6|31.9|19.2|10.3|4.43|1.44|| 5.91|5.35|4.33|3.64|3.07|2.78|2.43|2.24| |1248| 873| 428| 199| 66.2|23.9|18.0|9.68|4.15|1.35|| 5.19|4.69|3.80|3.19|2.69|2.44|2.13|1.97| |1164| 722| 400| 186| 61.7|27.9|16.8|9.03|3.86|1.26|| 4.52|4.09|3.31|2.78|2.34|2.12|1.86|1.72| |1081| 670| 371| 172| 57.3|25.9|15.6|8.38|3.68|1.17|| 3.90|3.53|2.86|2.40|2.02|1.83|1.60|1.48| | 998| 619| 343| 159| 52.9|23.9|14.4|7.74|3.40|1.08|| 3.32|3.00|2.43|2.04|1.72|1.56|1.36|1.26| | 915| 567| 314| 146| 48.5|21.9|13.2|7.10|3.11|0.99|| 2.79|2.52|2.04|1.72|1.45|1.31|1.15|1.06| | 832| 516| 286| 132| 44.1|20.0|12.0|6.45|2.83|0.90|| 2.31|2.09|1.69|1.42|1.20|1.08|.949|.877| | 748| 464| 257| 119| 39.7|18.0|10.8|5.81|2.55|0.81|| 1.87|1.69|1.37|1.15| .97|.878|.769|.710| | 665| 412| 228| 106| 35.3|16.0| 9.6|5.16|2.26|0.72|| 1.47|1.33|1.08|.905|.762|.690|.604|.558| | 582| 361| 200|92.8| 30.9|14.0| 8.4|4.52|1.98|0.63|| 1.13|1.02|.828|.695|.586|.531|.456|.429| +--------------------------------------------------++----------------------------------------+ To get the pressure drop for lengths other than 1000 feet, multiply by lengths in feet ÷ 1000. Example: Find the weight of steam at 100 pounds initial gauge pressure, which will pass through a 6-inch pipe 720 feet long with a pressure drop of 4 pounds. Under the conditions assumed in the table, 293.1 pounds would flow per minute; hence, Q = 293.1, and _ _ | 240×6×4 | Q_{1} = 293.1 | ------- |^{½} = 239.9 pounds |_ 720×12_| Table 67 may be frequently found to be of service in problems involving the flow of steam. This table was calculated by Mr. E. C. Sickles for a pipe 1000 feet long from formula (45), except that from the use of a value of the constant K = .0026 instead of .0027, the constant in the formula becomes 87.45 instead of 87. In using this table, the pressures and densities to be considered, as given at the top of the right-hand portion, are the mean of the initial and final pressures and densities. Its use is as follows: Assume an allowable drop of pressure through a given length of pipe. From the value as found in the right-hand column under the column of mean pressure, as determined by the initial and final pressures, pass to the left-hand portion of the table along the same line until the quantity is found corresponding to the flow required. The size of the pipe at the head of this column is that which will carry the required amount of steam with the assumed pressure drop. The table may be used conversely to determine the pressure drop through a pipe of a given diameter delivering a specified amount of steam by passing from the known figure in the left to the column on the right headed by the pressure which is the mean of the initial and final pressures corresponding to the drop found and the actual initial pressure present. For a given flow of steam and diameter of pipe, the drop in pressure is proportional to the length and if discharge quantities for other lengths of pipe than 1000 feet are required, they may be found by proportion. TABLE 68 FLOW OF STEAM INTO THE ATMOSPHERE __________________________________________________________________ | | | | | | | Absolute | Velocity | Actual | Discharge | Horse Power | | Initial | of Outflow | Velocity | per Square | per Square | | Pressure | at Constant | of Outflow | Inch of | Inch of | | per Square | Density | Expanded | Orifice | Orifice if | | Inch | Feet per | Feet per | per Minute | Horse Power | | Pounds | Second | Second | Pounds | = 30 Pounds | | | | | | per Hour | |____________|_____________|____________|____________|_____________| | | | | | | | 25.37 | 863 | 1401 | 22.81 | 45.6 | | 30. | 867 | 1408 | 26.84 | 53.7 | | 40. | 874 | 1419 | 35.18 | 70.4 | | 50. | 880 | 1429 | 44.06 | 88.1 | | 60. | 885 | 1437 | 52.59 | 105.2 | | 70. | 889 | 1444 | 61.07 | 122.1 | | 75. | 891 | 1447 | 65.30 | 130.6 | | 90. | 895 | 1454 | 77.94 | 155.9 | | 100. | 898 | 1459 | 86.34 | 172.7 | | 115. | 902 | 1466 | 98.76 | 197.5 | | 135. | 906 | 1472 | 115.61 | 231.2 | | 155. | 910 | 1478 | 132.21 | 264.4 | | 165. | 912 | 1481 | 140.46 | 280.9 | | 215. | 919 | 1493 | 181.58 | 363.2 | |____________|_____________|____________|____________|_____________| Elbows, globe valves and a square-ended entrance to pipes all offer resistance to the passage of steam. It is customary to measure the resistance offered by such construction in terms of the diameter of the pipe. Many formulae have been advanced for computing the length of pipe in diameters equivalent to such fittings or valves which offer resistance. These formulae, however vary widely and for ordinary purposes it will be sufficiently accurate to allow for resistance at the entrance of a pipe a length equal to 60 times the diameter; for a right angle elbow, a length equal to 40 diameters, and for a globe valve a length equal to 60 diameters. The flow of steam of a higher toward a lower pressure increases as the difference in pressure increases to a point where the external pressure becomes 58 per cent of the absolute initial pressure. Below this point the flow is neither increased nor decreased by a reduction of the external pressure, even to the extent of a perfect vacuum. The lowest pressure for which this statement holds when steam is discharged into the atmosphere is 25.37 pounds. For any pressure below this figure, the atmospheric pressure, 14.7 pounds, is greater than 58 per cent of the initial pressure. Table 68, by D. K. Clark, gives the velocity of outflow at constant density, the actual velocity of outflow expanded (the atmospheric pressure being taken as 14.7 pounds absolute, and the ratio of expansion in the nozzle being 1.624), and the corresponding discharge per square inch of orifice per minute. Napier deduced an approximate formula for the outflow of steam into the atmosphere which checks closely with the figures just given. This formula is: pa W = ---- (49) 70 Where W = the pounds of steam flowing per second, p = the absolute pressure in pounds per square inch, and a = the area of the orifice in square inches. In some experiments made by Professor C. H. Peabody, in the flow of steam through pipes from ¼ inch to 1½ inches long and ¼ inch in diameter, with rounded entrances, the greatest difference from Napier's formula was 3.2 per cent excess of the experimental over the calculated results. For steam flowing through an orifice from a higher to a lower pressure where the lower pressure is greater than 58 per cent of the higher, the flow per minute may be calculated from the formula: W = 1.9AK ((P - d)d)^{½} (50) Where W = the weight of steam discharged in pounds per minute, A = area of orifice in square inches, P = the absolute initial pressure in pounds per square inch, d = the difference in pressure between the two sides in pounds per square inch, K = a constant = .93 for a short pipe, and .63 for a hole in a thin plate or a safety valve. [Illustration: Vesta Coal Co., California, Pa., Operating at this Plant 3160 Horse Power of Babcock & Wilcox Boilers] HEAT TRANSFER The rate at which heat is transmitted from a hot gas to a cooler metal surface over which the gas is flowing has been the subject of a great deal of investigation both from the experimental and theoretical side. A more or less complete explanation of this process is necessary for a detailed analysis of the performance of steam boilers. Such information at the present is almost entirely lacking and for this reason a boiler, as a physical piece of apparatus, is not as well understood as it might be. This, however, has had little effect in its practical development and it is hardly possible that a more complete understanding of the phenomena discussed will have any radical effect on the present design. The amount of heat that is transferred across any surface is usually expressed as a product, of which one factor is the slope or linear rate of change in temperature and the other is the amount of heat transferred per unit's difference in temperature in unit's length. In Fourier's analytical theory of the conduction of heat, this second factor is taken as a constant and is called the "conductivity" of the substance. Following this practice, the amount of heat absorbed by any surface from a hot gas is usually expressed as a product of the difference in temperature between the gas and the absorbing surface into a factor which is commonly designated the "transfer rate". There has been considerable looseness in the writings of even the best authors as to the way in which the gas temperature difference is to be measured. If the gas varies in temperature across the section of the channel through which it is assumed to flow, and most of them seem to consider that this would be the case, there are two mean gas temperatures, one the mean of the actual temperatures at any time across the section, and the other the mean temperature of the entire volume of the gas passing such a section in any given time. Since the velocity of flow will of a certainty vary across the section, this second mean temperature, which is one tacitly assumed in most instances, may vary materially from the first. The two mean temperatures are only approximately equal when the actual temperature measured across the section is very nearly a constant. In what follows it will be assumed that the mean temperature measured in the second way is referred to. In English units the temperature difference is expressed in Fahrenheit degrees and the transfer rate in B. t. u.'s per hour per square foot of surface. Pecla, who seems to have been one of the first to consider this subject analytically, assumed that the transfer rate was constant and independent both of the temperature differences and the velocity of the gas over the surface. Rankine, on the other hand, assumed that the transfer rate, while independent of the velocity of the gas, was proportional to the temperature difference, and expressed the total amount of heat absorbed as proportional to the square of the difference in temperature. Neither of these assumptions has any warrant in either theory or experiment and they are only valuable in so far as their use determine formulae that fit experimental results. Of the two, Rankine's assumption seems to lead to formulae that more nearly represent actual conditions. It has been quite fully developed by William Kent in his "Steam Boiler Economy". Professor Osborne Reynolds, in a short paper reprinted in Volume I of his "Scientific Papers", suggests that the transfer rate is proportional to the product of the density and velocity of the gas and it is to be assumed that he had in mind the mean velocity, density and temperature over the section of the channel through which the gas was assumed to flow. Contrary to prevalent opinion, Professor Reynolds gave neither a valid experimental nor a theoretical explanation of his formula and the attempts that have been made since its first publication to establish it on any theoretical basis can hardly be considered of scientific value. Nevertheless, Reynolds' suggestion was really the starting point of the scientific investigation of this subject and while his formula cannot in any sense be held as completely expressing the facts, it is undoubtedly correct to a first approximation for small temperature differences if the additive constant, which in his paper he assumed as negligible, is given a value.[83] Experimental determinations have been made during the last few years of the heat transfer rate in cylindrical tubes at comparatively low temperatures and small temperature differences. The results at different velocities have been plotted and an empirical formula determined expressing the transfer rate with the velocity as a factor. The exponent of the power of the velocity appearing in the formula, according to Reynolds, would be unity. The most probable value, however, deduced from most of the experiments makes it less than unity. After considering experiments of his own, as well as experiments of others, Dr. Wilhelm Nusselt[84] concludes that the evidence supports the following formulae: _ _ [lambda]_{w} | w c_{p} [delta] | a = b ------------ | --------------- |^{u} d^{1-u} |_ [lambda] _| Where a is the transfer rate in calories per hour per square meter of surface per degree centigrade difference in temperature, u is a physical constant equal to .786 from Dr. Nusselt's experiments, b is a constant which, for the units given below, is 15.90, w is the mean velocity of the gas in meters per second, c_{p} is the specific heat of the gas at its mean temperature and pressure in calories per kilogram, [delta] is the density in kilograms per cubic meter, [lambda] is the conductivity at the mean temperature and pressure in calories per hour per square meter per degree centigrade temperature drop per meter, [lambda]_{w} is the conductivity of the steam at the temperature of the tube wall, d is the diameter of the tube in meters. If the unit of time for the velocity is made the hour, and in the place of the product of the velocity and density is written its equivalent, the weight of gas flowing per hour divided by the area of the tube, this equation becomes: _ _ [lambda]_{w} | Wc_{p} | a = .0255 ------------ | --------- |^{.786} d^{.214} |_ A[lambda] _| where the quantities are in the units mentioned, or, since the constants are absolute constants, in English units, a is the transfer rate in B. t. u. per hour per square foot of surface per degree difference in temperature, W is the weight in pounds of the gas flowing through the tube per hour, A is the area of the tube in square feet, d is the diameter of the tube in feet, c_{p} is the specific heat of the gas at constant pressure, [lambda] is the conductivity of the gas at the mean temperature and pressure in B. t. u. per hour per square foot of surface per degree Fahrenheit drop in temperature per foot, [lambda]_{w} is the conductivity of the steam at the temperature of the wall of the tube. The conductivities of air, carbonic acid gas and superheated steam, as affected by the temperature, in English units, are: Conductivity of air .0122 (1 + .00132 T) Conductivity of carbonic acid gas .0076 (1 + .00229 T) Conductivity of superheated steam .0119 (1 + .00261 T) where T is the temperature in degrees Fahrenheit. Nusselt's formulae can be taken as typical of the number of other formulae proposed by German, French and English writers.[85] Physical properties, in addition to the density, are introduced in the form of coefficients from a consideration of the physical dimensions of the various units and of the theoretical formulae that are supposed to govern the flow of the gas and the transfer of heat. All assume that the correct method of representing the heat transfer rate is by the use of one term, which seems to be unwarranted and probably has been adopted on account of the convenience in working up the results by plotting them logarithmically. This was the method Professor Reynolds used in determining his equation for the loss in head in fluids flowing through cylindrical pipes and it is now known that the derived equation cannot be considered as anything more than an empirical formula. It, therefore, is well for anyone considering this subject to understand at the outset that the formulae discussed are only of an empirical nature and applicable to limited ranges of temperature under the conditions approximately the same as those surrounding the experiments from which the constants of the formula were determined. It is not probable that the subject of heat transfer in boilers will ever be on any other than an experimental basis until the mathematical expression connecting the quantity of fluid which will flow through a channel of any section under a given head has been found and some explanation of its derivation obtained. Taking the simplest possible section, namely, a circle, it is found that at low velocities the loss of head is directly proportional to the velocity and the fluid flows in straight stream lines or the motion is direct. This motion is in exact accordance with the theoretical equations of the motion of a viscous fluid and constitutes almost a direct proof that the fundamental assumptions on which these equations are based are correct. When, however, the velocity exceeds a value which is determinable for any size of tube, the direct or stream line motion breaks down and is replaced by an eddy or mixing flow. In this flow the head loss by friction is approximately, although not exactly, proportional to the square of the velocity. No explanation of this has ever been found in spite of the fact that the subject has been treated by the best mathematicians and physicists for years back. It is to be assumed that the heat transferred during the mixing flow would be at a much higher rate than with the direct or stream line flow, and Professors Croker and Clement[86] have demonstrated that this is true, the increase in the transfer being so marked as to enable them to determine the point of critical velocity from observing the rise in temperature of water flowing through a tube surrounded by a steam jacket. The formulae given apply only to a mixing flow and inasmuch as, from what has just been stated, this form of motion does not exist from zero velocity upward, it follows that any expression for the heat transfer rate that would make its value zero when the velocity is zero, can hardly be correct. Below the critical velocity, the transfer rate seems to be little affected by change in velocity and Nusselt,[87] in another paper which mathematically treats the direct or stream line flow, concludes that, while it is approximately constant as far as the velocity is concerned in a straight cylindrical tube, it would vary from point to point of the tube, growing less as the surface passed over increased. It should further be noted that no account in any of this experimental work has been taken of radiation of heat from the gas. Since the common gases absorb very little radiant heat at ordinary temperatures, it has been assumed that they radiate very little at any temperature. This may or may not be true, but certainly a visible flame must radiate as well as absorb heat. However this radiation may occur, since it would be a volume phenomenon rather than a surface phenomenon it would be considered somewhat differently from ordinary radiation. It might apply as increasing the conductivity of the gas which, however independent of radiation, is known to increase with the temperature. It is, therefore, to be expected that at high temperatures the rate of transfer will be greater than at low temperatures. The experimental determinations of transfer rates at high temperatures are lacking. Although comparatively nothing is known concerning the heat radiation from gases at high temperatures, there is no question but what a large proportion of the heat absorbed by a boiler is received direct as radiation from the furnace. Experiments show that the lower row of tubes of a Babcock & Wilcox boiler absorb heat at an average rate per square foot of surface between the first baffle and the front headers equivalent to the evaporation of from 50 to 75 pounds of water from and at 212 degrees Fahrenheit per hour. Inasmuch as in these experiments no separation could be made between the heat absorbed by the bottom of the tube and that absorbed by the top, the average includes both maximum and minimum rates for those particular tubes and it is fair to assume that the portion of the tubes actually exposed to the furnace radiations absorb heat at a higher rate. Part of this heat was, of course absorbed by actual contact between the hot gases and the boiler heating surface. A large portion of it, however, must have been due to radiation. Whether this radiant heat came from the fire surface and the brickwork and passed through the gases in the furnace with little or no absorption, or whether, on the other hand, the radiation were absorbed by the furnace gases and the heat received by the boiler was a secondary radiation from the gases themselves and at a rate corresponding to the actual gas temperature, is a question. If the radiations are direct, then the term "furnace temperature", as usually used has no scientific meaning, for obviously the temperature of the gas in the furnace would be entirely different from the radiation temperature, even were it possible to attach any significance to the term "radiation temperature", and it is not possible to do this unless the radiations are what are known as "full radiations" from a so-called "black body". If furnace radiation takes place in this manner, the indications of a pyrometer placed in a furnace are hard to interpret and such temperature measurements can be of little value. If the furnace gases absorb the radiations from the fire and from the brickwork of the side walls and in their turn radiate heat to the boiler surface, it is scientifically correct to assume that the actual or sensible temperature of the gas would be measured by a pyrometer and the amount of radiation could be calculated from this temperature by Stefan's law, which is to the effect that the rate of radiation is proportional to the fourth power of the absolute temperature, using the constant with the resulting formula that has been determined from direct experiment and other phenomena. With this understanding of the matter, the radiations absorbed by a boiler can be taken as equal to that absorbed by a flat surface, covering the portion of the boiler tubes exposed to the furnace and at the temperature of the tube surface, when completely exposed on one side to the radiations from an atmosphere at the temperature in the furnace. With this assumption, if S^{1} is the area of the surface, T the absolute temperature of the furnace gases, t the absolute temperature of the tube surface of the boiler, the heat absorbed per hour measured in B. t. u.'s is equal to _ _ | / T \ / t \ | 1600 | |----|^{4} - |----|^{4}| S^{1} |_\1000/ \1000/ _| In using this formula, or in any work connected with heat transfer, the external temperature of the boiler heating surface can be taken as that of saturated steam at the pressure under which the boiler is working, with an almost negligible error, since experiments have shown that with a surface clean internally, the external surface is only a few degrees hotter than the water in contact with the inner surface, even at the highest rates of evaporation. Further than this, it is not conceivable that in a modern boiler there can be much difference in the temperature of the boiler in the different parts, or much difference between the temperature of the water and the temperature of the steam in the drums which is in contact with it. If the total evaporation of a boiler measured in B. t. u.'s per hour is represented by E, the furnace temperature by T_{1}, the temperature of the gas leaving the boiler by T_{2}, the weight of gas leaving the furnace and passing through the setting per hour by W, the specific heat of the gas by C, it follows from the fact that the total amount of heat absorbed is equal to the heat received from radiation plus the heat removed from the gases by cooling from the temperature T_{1} to the temperature T_{2}, that _ _ | / T \ / t \ | E = 1600 | |----|^{4} - |----|^{4}| S^{1} + WC(T_{1} - T_{2}) |_\1000/ \1000/ _| This formula can be used for calculating the furnace temperature when E, t and T_{2} are known but it must be remembered that an assumption which is probably, in part at least, incorrect is implied in using it or in using any similar formula. Expressed in this way, however, it seems more rational than the one proposed a few years ago by Dr. Nicholson[88] where, in place of the surface exposed to radiation, he uses the grate surface and assumes the furnace gas temperature as equal to the fire temperature. If the heat transfer rate is taken as independent of the gas temperature and the heat absorbed by an element of the surface in a given time is equated to the heat given out from the gas passing over this surface in the same time, a single integration gives Rs (T - t) = (T_{1} - t) e^{- --} WC where s is the area of surface passed over by the gases from the furnace to any point where the gas temperature T is measured, and the rate of heat transfer is R. As written, this formula could be used for calculating the temperature of the gas at any point in the boiler setting. Gas temperatures, however, calculated in this way are not to be depended upon as it is known that the transfer rate is not independent of the temperature. Again, if the transfer rate is assumed as varying directly with the weight of the gases passing, which is Reynolds' suggestion, it is seen that the weight of the gases entirely disappears from the formula and as a consequence if the formula was correct, as long as the temperature of the gas entering the surface from the furnace was the same, the temperatures throughout the setting would be the same. This is known also to be incorrect. If, however, in place of T is written T_{2} and in place of s is written S, the entire surface of the boiler, and the formula is re-arranged, it becomes: _ _ WC | T_{1} - t | R = --- Log[89]| --------- | S |_ T_{2} - t _| This formula can be considered as giving a way of calculating an average transfer rate. It has been used in this way for calculating the average transfer rate from boiler tests in which the capacity has varied from an evaporation of a little over 3 pounds per square foot of surface up to 15 pounds. When plotted against the gas weights, it was found that the points were almost exactly on a line. This line, however, did not pass through the zero point but started at a point corresponding to approximately a transfer rate of 2. Checked out against many other tests, the straight line law seems to hold generally and this is true even though material changes are made in the method of calculating the furnace temperature. The inclination of the line, however, varied inversely as the average area for the passage of the gas through the boiler. If A is the average area between all the passes of the boiler, the heat transfer rate in Babcock & Wilcox type boilers with ordinary clean surfaces can be determined to a rather close approximation from the formula: W R = 2.00 + .0014 - A The manner in which A appears in this formula is the same as it would appear in any formula in which the heat transfer rate was taken as depending upon the product of the velocity and the density of the gas jointly, since this product, as pointed out above, is equivalent to W/A. Nusselt's experiments, as well as those of others, indicate that the ratio appears in the proper way. While the underlying principles from which the formula for this average transfer rate was determined are questionable and at best only approximately correct, it nevertheless follows that assuming the transfer rate as determined experimentally, the formula can be used in an inverse way for calculating the amount of surface required in a boiler for cooling the gases through a range of temperature covered by the experiments and it has been found that the results bear out this assumption. The practical application of the theory of heat transfer, as developed at present, seems consequently to rest on these last two formulae, which from their nature are more or less empirical. Through the range in the production of steam met with in boilers now in service which in the marine type extends to the average evaporation of 12 to 15 pounds of water from and at 212 degrees Fahrenheit per square foot of surface, the constant 2 in the approximate formula for the average heat transfer rate constitutes quite a large proportion of the total. The comparative increase in the transfer rate due to a change in weight of the gases is not as great consequently as it would be if this constant were zero. For this reason, with the same temperature of the gases entering the boiler surface, there will be a gradual increase in the temperature of the gases leaving the surface as the velocity or weight of flow increases and the proportion of the heat contained in the gases entering the boiler which is absorbed by it is gradually reduced. It is, of course, possible that the weight of the gases could be increased to such an amount or the area for their passage through the boiler reduced by additional baffles until the constant term in the heat transfer formula would be relatively unimportant. Under such conditions, as pointed out previously, the final gas temperature would be unaffected by a further increase in the velocity of the flow and the fraction of the heat carried by the gases removed by the boiler would be constant. Actual tests of waste heat boilers in which the weight of gas per square foot of sectional area for its passage is many times more than in ordinary installations show, however, that this condition has not been attained and it will probably never be attained in any practical installation. It is for this reason that the conclusions of Dr. Nicholson in the paper referred to and of Messrs. Kreisinger and Ray in the pamphlet "The Transmission of Heat into Steam Boilers", published by the Department of the Interior in 1912, are not applicable without modification to boiler design. In superheaters the heat transfer is effected in two different stages; the first transfer is from the hot gas to the metal of the superheater tube and the second transfer is from the metal of the tube to the steam on the inside. There is, theoretically, an intermediate stage in the transfer of the heat from the outside to the inside surface of the tube. The conductivity of steel is sufficient, however, to keep the temperatures of the two sides of the tube very nearly equal to each other so that the effect of the transfer in the tube itself can be neglected. The transfer from the hot gas to the metal of the tube takes place in the same way as with the boiler tubes proper, regard being paid to the temperature of the tube which increases as the steam is heated. The transfer from the inside surface of the tube to the steam is the inverse of the process of the transfer of the heat on the outside and seems to follow the same laws. The transfer rate, therefore, will increase with the velocity of the steam through the tube. For this reason, internal cores are quite often used in superheaters and actually result in an increase in the amount of superheat obtained from a given surface. The average transfer rate in superheaters based on a difference in mean temperature between the gas on the outside of the tubes and the steam on the inside of the tubes is if R is the transfer rate from the gas to the tube and r the rate from the tube to the steam: Rr ----- R + r and is always less than either R or r. This rate is usually greater than the average transfer rate for the boiler as computed in the way outlined in the preceding paragraphs. Since, however, steam cannot, under any imagined set of conditions, take up more heat from a tube than would water at the same average temperature, this fact supports the contention made that the actual transfer rate in a boiler must increase quite rapidly with the temperatures. The actual transfer rates in superheaters are affected by so many conditions that it has not so far been possible to evolve any formula of practical value. [Illustration: Iron City Brewery of the Pittsburgh Brewing Co., Pittsburgh, Pa, Operating in this Plant 2000 Horse Power of Babcock & Wilcox Boilers] INDEX PAGE Absolute pressure 117 Absolute zero 80 Accessibility of Babcock & Wilcox boiler 59 Acidity in boiler feed water 106 Actual evap. corresponding to boiler horse power 288 Advantages of Babcock & Wilcox boilers 61 Stoker firing 195 Water tube over fire tube boilers 61 Air, composition of 147 In boiler feed water 106 Properties of 147 Required for combustion 152, 156 Specific heat of 148 Supplied for combustion 157 Vapor in 149 Volume of 147 Weight of 147 Alkalinity in boiler feed water 103 Testing feed for 103 Altitude, boiling point of water at 97 Chimney sizes corrected for 248 Alum in feed water treatment 106 A. S. M. E. code for boiler testing 267 Analyses, comparison of proximate and ultimate 183 Proximate coal, and heating values 177 Analysis, coal, proximate, methods of 176 Coal, ultimate 173 Determination of heating value from 173 Analysis, Flue gas 155 Flue gas, methods of 160 Flue gas, object of 155 Anthracite coal 166 Combustion rates with 246 Distribution of 167 Draft required for 246 Firing 190 Grate ratio for 191 Semi 166 Sizes of 190 Steam as aid to burning 191 Thickness of fires with 191 Arches, fire brick, as aid to combustion 190 Fire brick, for 304 Fire brick, laying 305 Automatic stokers, advantages of 195 Overfeed 196 Traveling grate 197 Traveling grate, Babcock & Wilcox 194 Underfeed 196 Auxiliaries, exhaust from, in heating feed water 113 Superheated steam with 142 Auxiliary grates, with blast furnace gas 228 With oil fuel 225 With waste heat 235 Babcock, G. H., lecture on circulation of water in Boilers 28 Lecture on theory of steam making 92 Babcock & Wilcox Co., Works at Barberton, Ohio 7 Works at Bayonne, N. J. 6 Babcock & Wilcox boiler, accessibility of 59 Advantages of 61 Circulation of water in 57, 66 Construction of 49 Cross boxes 50 Cross drum 53 Cross drum, dry steam with 71 Drumheads 49 Drums 49 Durability 75 Evolution of 39 Fittings 55 Fixtures 55 Fronts 53 Handhole fittings 50, 51 Headers 50, 51 Inclined header, wrought steel 54 Inspection 75 Life of 76 Materials entering into the construction of 59 Mud drums 51 Path of gases in 57 Path of water in 57 Rear tube doors of 53, 74 Repairs 75 Safety of 66 Sections 50 Set for utilizing waste heat 236 Set with Babcock & Wilcox chain grate stoker 12 Set with bagasse furnace 208 Set with Peabody oil furnace 222 Supports, cross drum 53 Supports, longitudinal drum 52 Tube doors 53 Vertical header, cast iron 58 Vertical header, wrought steel 48 Babcock & Wilcox chain grate stoker 194 Babcock & Wilcox superheater 136 Bagasse, composition of 206 Furnace 209 Heat, value of 206 Tests of Babcock & Wilcox boilers with 210 Value of diffusion 207 Barium carbonate in feed water treatment 106 Barium hydrate in feed water treatment 106 Barrus draft gauge 254 Bituminous coal, classification of 167 Combustion rates with 246 Composition of 177 Distribution of 168 Firing methods 193 Semi 166 Sizes of 191 Thickness of fire with 193 Blast furnace gas, burners for 228 Combustion of 228 Composition of 227 Stacks for 228 Boiler, Blakey's 23 Brickwork, care of 307 Circulation of water in steam 28 Compounds 109 Development of water tube 23 Eve's 24 Evolution of Babcock & Wilcox 39 Fire tube, compared with water tube 61 Guerney's 24 Horse power 263 Loads, economical 283 Perkins' 24 Room piping 108 Room practice 297 Rumsey's 23 Stevens', John 23 Stevens', John Cox 23 Units, number of 289 Units, size of 289 Wilcox's 25 Woolf's 23 Boilers, capacity of 278 Care of 291 Efficiency of 256 Horse power of 265 Operation of 291 Requirements of steam 27 Testing 267 Boiling point 86 Of various substances 86 Of water as affected by altitude 97 Brick, fire 304 Arches 305 Classification of 304 Compression of 303 Expansion of 303 Hardness of 303 Laying up 305 Nodules, ratio of 303 Nodules, size of 303 Plasticity of 302 Brick, red 302 Brickwork, care of 307 British thermal unit 83 Burners, blast furnace gas 228 By-product coke oven gas 231 Natural gas 231 Oil 217 Oil, capacity of 221 Oil, mechanical atomizing 219 Oil, operation of 223 Oil, steam atomizing 218 Oil, steam consumption of 220 Burning hydrogen, loss due to moisture formed in 261 By-product coke oven gas burners 231 By-product coke oven gas, combustion of 231 By-product coke oven gas, composition and heat value of 231 Calorie 83 Calorific value (see Heat value). Calorimeter, coal, Mahler bomb 184 Mahler bomb, method of correction 187 Mahler bomb, method of operation of 185 Calorimeter, steam, compact type of throttling 132 Correction for 131 Location of nozzles for 134 Normal reading 131 Nozzles 134 Separating 133 Throttling 129 Capacity of boilers 264, 278 As affecting economy 276 Economical loads 283 With bagasse 210 With blast furnace gas 228 With coal 280 With oil fuel 224 Capacity of natural gas burners 229 Capacity of oil burners 221 Carbon dioxide in flue gases 154 Unreliability of readings taken alone 162 Carbon, fixed 165 Incomplete combustion of, loss due to 158 Monoxide, heat value of 151 Monoxide, in flue gases 155 Unconsumed in ash, loss due to 261 Care of boilers when out of service 300 Casings, boilers 307 Causticity of feed water 103 Testing for 105 Celsius thermometer scale 79 Centigrade thermometer scale 79 Chain grate stoker, Babcock & Wilcox 194 Chemicals required in feed water treatment 105 Chimney gases, losses in 158, 159 Chimneys (see Draft). Correction in dimensions for altitude 248 Diameter of 243 Draft available from 241 Draft loss in 239 For blast furnace gas 253 For oil fuel 251 For wood fuel 254 Height of 243 Horse power they will serve 250 Circulation of water in Babcock & Wilcox boilers 57, 66 Of water in steam boilers 28 Results of defective 62, 66, 67 Classification of coals 166 Fire brick 304 Feed water difficulties 100 Fuels 165 Cleaners, turbine tube 299 Cleaning, ease of, Babcock & Wilcox boilers 73 Closed feed water heaters 111 Coal, Alaska 169 Analyses and heat value 177 Analysis, proximate 176 Analysis, ultimate 173 Anthracite 166 Bituminous 167 Cannel 167 Classification of 165, 166 Combustion of 190 Comparison with oil 214 Consumption, increase due to superheat 139 Distribution of 167 Formation of 165 Lignite 167 Records 293 Semi-anthracite 166 Semi-bituminous 166 Sizes of anthracite 190 Sizes of bituminous 191 Code of A. S. M. E. for boiler testing 267 Coefficient of expansion of various substances 87 Coke 171 Oven gas, by-product, burners 231 Oven gas, by-product, combustion of 231 Oven gas, by-product, composition and heat value of 231 Coking method of firing 195 Color as indication of temperature 91 Combination furnaces 224 Combustible in fuels 150 Combustion 150 Air required for 152, 156 Air supplied for 157 Combustion of coal 190 Of gaseous fuels 227 Of liquid fuels 212 Of solid fuels other than coal 201 Composition of bagasse 205 Blast furnace gas 227 By-product coke oven gas 231 Coals 177 Natural gas 229 Oil 213 Wood 201 Compounds, boiler 109 Compressibility of water 97 Compression of fire brick 303 Condensation, effect of superheated steam on 140 In steam pipes 313 Consumption, heat, of engines 141 Correction, stem, for thermometers 80 For normal reading in steam calorimeter 131 For radiation, bomb calorimeter 187 Corrosion 101, 106 Coverings, pipe 315 Cross drum, Babcock & Wilcox boiler 52, 53, 60 Dry steam with 71 Draft area as affecting economy in Babcock & Wilcox boilers 70 Available from chimneys 241 Draft loss in chimneys 239 Loss in boilers 245 Loss in flues 243 Loss in furnaces 245 Draft required for anthracite 246 Required for various fuels 246 Drums, Babcock & Wilcox, cross 53 Cross, boxes 50 Heads 49 Longitudinal 49 Manholes 49 Nozzles on 50 Dry steam in Babcock & Wilcox boilers 71 Density of gases 147 Steam 115 Dulong's formula for heating value 173 Ebullition, point of 86 Economizers 111 Efficiency of boilers, chart of 258 Combustible basis 256 Dry coal basis 256 Increase in, due to superheaters 139 Losses in (see Heat balance) 259 Testing 267 Test _vs._ operating 278 Variation in, with capacity 284 With coal 288 With oil 224 Ellison draft gauge 254 Engine, Hero's 13 Engines, superheated steam with 141 Equivalent evaporation from and at 212 degrees 116 Eve's boiler 24 Evolution of Babcock & Wilcox boiler 39 Exhaust steam from auxiliaries 113 Expansion, coefficient of 87 Of fire brick 303 Of pipe 315 Pyrometer 89 Factor of evaporation 117 Fahrenheit thermometer scale 79 Fans, use of, in waste heat work 233 Feed water, air in 106 As affecting capacity 279 Boiler 100 Feed water heaters, closed 111 Economizers 111 Open 111 Feed water heating, methods of 111 Saving by 110 Feed water, impurities in 100 Lines 312 Method of feeding 110 Feed water treatment 102 Chemical 102 Chemical, lime and soda process 102 Chemical, lime process 102 Chemical, soda process 102 Chemicals used in lime and soda process 105 Combined heat and chemical 105 Heat 102 Less usual reagents 106 Firing, advantages of stoker 195 Methods for anthracite 190 Bituminous 193 Lignite 195 Fittings, handhole in Babcock & Wilcox boilers 50, 51 Pipe 311 Superheated steam 145 With Babcock & Wilcox boilers 55 Fixtures with Babcock & Wilcox boilers 55 Flanges, pipe 309 Flow of steam into pressure above atmosphere 317 Into the atmosphere 328 Through orifices 317 Through pipes 317 Flue gas analysis 155 Conversion of volumetric to weight 161 Methods of making 160 Object of 155 Orsat apparatus 159 Flue gas, composition of 155 Losses in 158, 159 Weight per pound of carbon in fuel 158 Weight per pound of fuel 158 Weight resulting from combustion 157 Foaming 102, 107 Fuel analysis, proximate 176 Ultimate 173 Fuel calorimeter, Mabler bomb 184 Tests, method of making 186 Fuels, classification of 165 Gaseous, and their combustion 227 Fuels, liquid, and their combustion 212 Solid, coal 190 Solid, other than coal 201 Furnace, bagasse 209 Blast furnace gas 228 By-product coke oven gas 231 Combination wood and oil 225 Efficiency of 283 Natural gas 229 Peabody oil 222 Webster 55 Wood burning 201, 202 Galvanic action 107 Gas, blast furnace, burners 228 Combustion of 228 Composition of 227 Gas, by-product coke oven, burners 231 Combustion of 231 Composition of and heat value 231 Gas, natural, burners 229 Combustion of 229 Composition and heat value of 229 Gases, chimney, losses in 158, 159 Density of 163 Flue (see Flue gases). Path of in Babcock & Wilcox boilers 57 Waste (see Waste heat) 232 Gaskets 312 Gauges, draft, Barrus 254 Ellison 255 Peabody 255 U-tube 254 Gauges, vacuum 117 Grate ratio for anthracite 191 Gravity of oils 214 Grooving 102 Guerney's boiler 24 Handhole fittings for Babcock & Wilcox boilers 50, 51 Handholes in Babcock & Wilcox boilers 50, 51 Hardness of boiler feed water 102 Permanent 102 Temporary 102 Testing for 105 Hardness of fire brick 303 Heat and chemical methods of treating feed water 105 And its measurement 79 Balance 262 Consumption of engines 141 Latent 84 Of liquid 120 Sensible 84 Specific (see Specific heat) 83 Total 86 Transfer 323 Heat value of bagasse 205 By-product coke oven gas 231 Coal 177 Heat value of fuels, determination of 173 Determination of Kent's approximate method 183 High and low 174 Heat value of natural gas 229 Oil 215 Wood 201 Heat waste (see Waste heat) 232 Heaters, feed water, closed 111 Economizers 111 Open 111 Heating feed water, saving by 110 Hero's engine 13 High and low heat value of fuels 174 High pressure steam, advantages of use of 119 High temperature measurements, accuracy of 89 Horse power, boiler 265 Evaporation (actual) corresponding to 288 Rated boiler 265 Stacks for various, of boilers 250 Hydrogen in flue gases 156 Ice, specific heat of 99 "Idalia", tests with superheated steam on yacht 143 Impurities in boiler feed water 100 Incomplete combustion of carbon, loss due to 158 Injectors, efficiency of 112 Relative efficiency of, and pumps 112 Iron alum in feed water treatment 106 Kent, Wm., determination of heat value from analysis 183 Stack table 250 Kindling point 150 Latent heat 84, 115 Laying of fire brick 305 Red brick 305 Lignite, analyses of 181 Combustion of 195 Lime and soda treatment of boiler feed 102 Used in chemical treatment of feed 105 Lime treatment of boiler feed water 102 Liquid fuels and their combustion 212 Loads, economical boiler 283 Losses due to excess air 158 Due to unburned carbon 158 Due to unconsumed carbon in the ash 261 Losses in efficiency (see Heat balance). In flue gases 158, 159 Low water in boilers 298 Melting points of metals 91 Mercurial pyrometers 89 Moisture in coal, determination of 176 In fuels, losses due to 259 In steam, determination of 129 Mud drum of Babcock & Wilcox boiler 51 Napier's formula for flow of steam 321 Natural gas, burners for 229 Combustion of 229 Composition and heat value of 229 Nitrate of silver in testing feed water 105 Nitrogen, as indication of excess air 157 In air 147 In flue gases 157 Nodules, fire brick, ratio of 303 Size of 303 Normal reading, throttling calorimeter 131 Nozzles, steam sampling for calorimeter 134 Location of 134 Oil fuel, burners (see Burners). Capacity with 224 Combustion of 217 Comparison with coal 214 Composition and heat value of 213 Efficiency with 224 Furnaces for 221 Gravity of 214 In combination with other fuels 224 Stacks for 251 Tests with 224 Open hearth furnace, Babcock & Wilcox boiler set for utilizing waste heat from 236 Open heaters, feed water 111 Operation of boilers 291 Optical pyrometers 91 Orsat apparatus 160 Oxalate of soda in feed water treatment 106 Oxygen in air 147 Flue gases 155 Peabody draft gauge 255 Formulae for coal calorimeter correction 188 Furnace for oil fuel 221, 222 Oil burner 218 Peat 167 Perkins' boiler 24 Pfaundler's method of coal calorimeter radiation correction 187 Pipe coverings 315 Data 308 Expansion of 315 Pipe fittings 311 Flanges 309 Flow of steam through 317 Radiation from bare and covered 314 Sizes 312 Supports for 315 Piping, boiler room 308 Pitting 102 Plant records, coal 293 Draft 294 Temperature 294 Water 293 Plasticity of fire brick 302 Pressed fuels 171 Priming in boilers 102 Methods of treating for 107 Properties of water 96 Proximate analyses of coal 177 Proximate analysis 173 Method of making 176 Pulverized fuels 170 Pump, efficiency of feed 112 Pyrometers, expansion 89 Mercurial 89 Optical 91 Radiation 90 Thermo-electric 90 Quality of steam 129 Radiation correction for coal calorimeter 187, 188 Correction for steam calorimeter 131 Effect of superheated steam on 140 From pipes 314 Losses in efficiency due to 307 Pyrometers 90 Ratio of air supplied to that required for combustion 157 Reagents, less usual in feed treatment 106 Records, plant, coal 293 Draft 294 Temperature 294 Water 293 Requirements of steam boilers 27 As indicated by evolution of Babcock & Wilcox 45 Rumsey's boiler 23 Safety of Babcock & Wilcox boilers 66 Salts responsible for scale 101 Solubility of 101 Sampling coal 271 Nozzles for steam 134 Nozzles for steam, location of 134 Steam 134 Steam, errors in 135 Saturated air 149 Saving by heating feed 110 With superheat in "Idalia" tests 143 With superheat in prime movers 140, 142 Scale (see Thermometers) 101 Sea water, composition of 97 Sections, Babcock & Wilcox boiler 50 Selection of boilers 277 Sensible heat 84 Separating steam calorimeter 132 Sizes of anthracite coal 190 Bituminous coal 191 Smoke, methods of eliminating 197 Smokelessness, relative nature of 197 With hand-fired furnaces 199 With stoker-fired furnaces 199 Soda, lime and, treatment of feed 103 Oxalate of, in treatment of feed 106 Removal of scale aided by 300 Silicate of, in treatment of feed 106 Treatment of boiler feed 103 Space occupied by Babcock & Wilcox boilers 66 Specific heat 83 Specific heat of air 148 Ice 99 Saturated steam 99 Specific heat of superheated steam 137 Various solids, liquids and gases 85 Water 99 Spreading method of firing 193 Stacks and draft (see Chimneys) 237 Stacks for blast furnace gas 228 Oil fuel 251 Wood 202, 254 Stayed surfaces, absence of, in Babcock & Wilcox boilers 69 Difficulties arising from use of 67 Steam 115 As aid to combustion of anthracite 191 As aid to combustion of lignite 195 Consumption of prime movers 289 Density of 115 Flow of, into atmosphere 320 Flow of, into pressure above atmosphere 318 Flow of, through pipes 317 High pressure, advantage of 119 History of generation and use of 13 Making, theory of 92 Moisture in 129 Properties of, for vacuum 119 Properties of saturated 122 Properties of superheated 125 Quality of 129 Saturated 115 Specific heat of saturated 99 Specific heat of superheated 137 Specific volume of 115 Superheated 137 Superheaters (see Superheated steam). Steaming, quick, with Babcock & Wilcox boilers 73 Stem Correction, thermometer 80 Stevens, John, boiler 23 Stevens, John Cox, boiler 23 Stokers, automatic, advantages of 195 Babcock & Wilcox chain grate 194 Overfeed 196 Smokelessness with 199 Traveling grate 197 Underfeed 196 Superheated steam 137 Additional fuel for 139 Effect on condensation 140 Effect on radiation 140 Fittings for use with 145 "Idalia" tests with 143 Specific heat of 137 Variation in temperature of 145 With turbines 142 Superheater, Babcock & Wilcox 136 Effect of on boiler efficiency 139 Supports, Babcock & Wilcox boiler 52, 53 Tan bark 210 Tar, water gas 225 Temperature, accuracy of high, measurements 89 As indicated by color 91 Of waste gases 232 Records 294 Test conditions _vs._ operating conditions 278 Testing, boiler, A. S. M. E. code for 267 Tests of Babcock & Wilcox boilers with bagasse 210 Coal 280 Oil 224 Theory of steam making 92 Thermo-electric pyrometers 90 Thermometer scale, celsius 79 Thermometer scale, centigrade 76 Fahrenheit 79 Réaumur 79 Thermometer scales, comparison of 80 Conversion of 80 Thermometer stem correction for 80 Thermometers, glass for 79 Throttling calorimeter 129 Total heat 86, 115 Treatment of boiler feed water (see Feed water) 102 Chemicals used in 105 Less usual reagents in 106 Tube data 309 Doors in Babcock & Wilcox boilers 53 Tubes in Babcock & Wilcox boilers 50 Ultimate analyses of coal 183 Analysis of fuels 173 Unaccounted losses in efficiency 261 Unconsumed carbon in ash 261 Units, boiler, number of 289 Size of 289 Units, British thermal 83 Unreliability of CO_{2} readings alone 162 Vacuum gauges 117 Properties of steam for 119 Valves used with superheated steam 312 Variation in properties of saturated steam 119 Superheat from boilers 145 Volume of air 147 Water 96 Volume, specific, of steam 115 Waste heat, auxiliary grates with boilers for 235 Babcock & Wilcox boilers set for use with 236 Boiler design for 233 Curve of temperature, heat absorption, and heating surface 235 Draft for 233 Fans for use with 233 Power obtainable from 232 Temperature of, from various processes 232 Utilization of 232 Water, air in boiler feed 106 Boiling points of 97 Compressibility of 97 Water feed, impurities in 100 Methods of feeding to boiler 132 Saving by heating 110 Treatment (see Feed water). Water-gas tar 225 Heat of the liquid 120 Path of, in Babcock & Wilcox boilers 57 Properties of 96 Records 293 Specific heat of 99 Volume of 96 Weight of 96, 120 Watt, James 17 Weathering of coal 169 Webster furnace 55 Weight of air 147 Wilcox boiler 25 Wood, combustion of dry 202 Wet 203 Composition and heat value of 201 Furnace design for 201 Moisture in 201 Sawmill refuse 202 Woolf s boiler 24 Zero, absolute 81 FOOTNOTES [Footnote 1: See discussion by George H. Babcock, of Stirling's paper on "Water-tube and Shell Boilers", in Transactions, American Society of Mechanical Engineers, Volume VI., Page 601.] [Footnote 2: When one temperature alone is given the "true" specific heat is given; otherwise the value is the "mean" specific heat for the range of temperature given.] [Footnote 3: For variation, see Table 13.] [Footnote 4: Where range of temperature is given, coefficient is mean over range.] [Footnote 5: Coefficient of cubical expansion.] [Footnote 6: Le Chatelier's Investigations.] [Footnote 7: Burgess-Le Chatelier.] [Footnote 8: For accuracy of high temperature measurements, see Table 7.] [Footnote 9: Messrs. White & Taylor Trans. A. S. M. E., Vol. XXI, 1900.] [Footnote 10: See Scientific American Supplement, 624, 625, December, 1887.] [Footnote 11: 460 degrees below the zero of Fahrenheit. This is the nearest approximation in whole degrees to the latest determinations of the absolute zero of temperature] [Footnote 12: Marks and Davis] [Footnote 13: See page 120.] [Footnote 14: See Trans., A. S. M. E., Vol. XIV., Page 79.] [Footnote 15: Some waters, not naturally acid, become so at high temperatures, as when chloride of magnesia decomposes with the formation of free hydrochloride acid; such phenomena become more serious with an increase in pressure and temperature.] [Footnote 16: L. M. Booth Company.] [Footnote 17: Based on lime containing 90 per cent calcium oxide.] [Footnote 18: Based on soda containing 58 per cent sodium oxide.] [Footnote 19: See Stem Correction, page 80.] [Footnote 20: See pages 125 to 127.] [Footnote 21: The actual specific heat at a particular temperature and pressure is that corresponding to a change of one degree one way or the other and differs considerably from the average value for the particular temperature and pressure given in the table. The mean values given in the table give correct results when employed to determine the factor of evaporation whereas the actual values at the particular temperatures and pressures would not.] [Footnote 22: See page 117.] [Footnote 23: Ratio by weight of O to N in air.] [Footnote 24: 4.32 pounds of air contains one pound of O.] [Footnote 25: Per pound of C in the CO.] [Footnote 26: Ratio by volume of O to N in air.] [Footnote 27: Available hydrogen.] [Footnote 28: See Table 31, page 151.] [Footnote 29: This formula is equivalent to (10) given in chapter on combustion. 34.56 = theoretical air required for combustion of one pound of H (see Table 31).] [Footnote 30: For degree of accuracy of this formula, see Transactions, A. S. M. E., Volume XXI, 1900, page 94.] [Footnote 31: For loss per pound of coal multiply by per cent of carbon in coal by ultimate analysis.] [Footnote 32: For loss per pound of coal multiply by per cent of carbon in coal by ultimate analysis.] [Footnote 33: The Panther Creek District forms a part of what is known as the Southern Field; in the matter of hardness, however, these coals are more nearly akin to Lehigh coals.] [Footnote 34: Sometimes called Western Middle or Northern Schuylkill Field.] [Footnote 35: Geographically, the Shamokin District is part of the Western Middle Mahanoy Field, but the coals found in this section resemble more closely those of the Wyoming Field.] [Footnote 36: See page 161.] [Footnote 37: U. S. Geological Survey.] [Footnote 38: See "Steam Boiler Economy", page 47, First Edition.] [Footnote 39: To agree with Pfaundler's formula the end ordinates should be given half values in determining T", _i. e._, T" = ((Temp. at B + Temp. at C) ÷ 2 + Temp. all other ordinates) ÷ N] [Footnote 40: B. t. u. calculated.] [Footnote 41: Average of two samples.] [Footnote 42: Assuming bagasse temperature = 80 degrees Fahrenheit and exit gas temperature = 500 degrees Fahrenheit.] [Footnote 43: Dr. Henry C. Sherman. Columbia University.] [Footnote 44: Includes N.] [Footnote 45: Includes silt.] [Footnote 46: Net efficiency = gross efficiency less 2 per cent for steam used in atomizing oil. Heat value of oil = 18500 B. t. u. One ton of coal weighs 2000 pounds. One barrel of oil weighs 336 pounds. One gallon of oil weighs 8 pounds.] [Footnote 47: Average of 20 samples.] [Footnote 48: Includes H and CH_{4}.] [Footnote 49: B. t. u. approximate. For method of calculation, see page 175.] [Footnote 50: Temperatures are average over one cycle of operation and may vary widely as to maximum and minimum.] [Footnote 51: Dependant upon length of kiln.] [Footnote 52: Results secured by this method will be approximately correct.] [Footnote 53: See "Chimneys for Crude Oil", C. R. Weymouth, Trans. A. S. M. E., Dec. 1912.] [Footnote 54: To determine the portion of the fuel which is actually burned, the weight of ashes should be computed from the total weight of coal burned and the coal and ash analyses in order to allow for any ash that may be blown away with the flue gases. In many cases the ash so computed is considerably higher than that found in the test.] [Footnote 55: As distinguished from the efficiency of boiler, furnace and grate.] [Footnote 56: To obtain the efficiency of the boiler as an absorber of the heat contained in the hot gases, this should be the heat generated per pound of combustible corrected so that any heat lost through incomplete combustion will not be charged to the boiler. This, however, does not eliminate the furnace as the presence of excess air in the gases lowers the efficiency and the ability to run without excess air depends on the design and operation of the furnace. The efficiency based on the total heat value per pound of combustible is, however, ordinarily taken as the efficiency of the boiler notwithstanding the fact that it necessarily involves the furnace.] [Footnote 57: See pages 280 and 281.] [Footnote 58: Where the horse power of marine boilers is stated, it generally refers to and is synonymous with the horse power developed by the engines which they serve.] [Footnote 59: In other countries, boilers are ordinarily rated not in horse power but by specifying the quantity of water they are capable of evaporating from and at 212 degrees or under other conditions.] [Footnote 60: See equivalent evaporation from and at 212 degrees, page 116.] [Footnote 61: The recommendations are those made in the preliminary report of the Committee on Power Tests and at the time of going to press have not been finally accepted by the Society as a whole.] [Footnote 62: This code relates primarily to tests made with coal.] [Footnote 63: The necessary apparatus and instruments are described elsewhere. No definite rules can be given for location of instruments. For suggestions on location, see A. S. M. E. Code of 1912, Appendix 24. For calibration of instruments, see Code, Vol. XXXIV, Trans., A. S. M. E., pages 1691-1702 and 1713-14.] [Footnote 64: One to two inches for small anthracite coals.] [Footnote 65: Do not blow down the water-glass column for at least one hour before these readings are taken. An erroneous indication may otherwise be caused by a change of temperature and density of the water within the column and connecting pipe.] [Footnote 66: Do not blow down the water-glass column for at least one hour before these readings are taken. An erroneous indication may otherwise be caused by a change of temperature and density of the water within the column and connecting pipe.] [Footnote 67: For calculations relating to quality of steam, see page 129.] [Footnote 68: Where the coal is very moist, a portion of the moisture will cling to the walls of the jar, and in such case the jar and fuel together should be dried out in determining the total moisture.] [Footnote 69: Say ½ ounce to 2 ounces.] [Footnote 70: For methods of analysis, see page 176.] [Footnote 71: For suggestions relative to Smoke Observations, see A. S. M. E. Code of 1912, Appendix 16 and 17.] [Footnote 72: The term "as fired" means actual condition including moisture, corrected for estimated difference in weight of coal on the grate at beginning and end.] [Footnote 73: Corrected for inequality of water level and steam pressure at beginning and end.] [Footnote 74: See Transactions, A. S. M. E., Volume XXXIII, 1912.] [Footnote 75: For methods of determining, see Technologic Paper No. 7, Bureau of Standards, page 44.] [Footnote 76: Often called extra heavy pipe.] [Footnote 77: See Feed Piping, page 312.] [Footnote 78: See Superheat Chapter, page 145.] [Footnote 79: See Radiation from Steam Lines, page 314.] [Footnote 80: D, the density, is taken as the mean of the density at the initial and final pressures.] [Footnote 81: Diameters up to 5 inches, inclusive, are _actual_ diameters of standard pipe, see Table 62, page 308.] [Footnote 82: Diameters up to 4 inches, inclusive, are _actual_ internal diameters, see Table 62, page 308.] [Footnote 83: H. P. Jordan, "Proceedings of the Institute of Mechanical Engineers", 1909.] [Footnote 84: "Zeitschrift des Vereines Deutscher Ingenieur", 1909, page 1750.] [Footnote 85: Heinrich Gröber--Zeit. d. Ver. Ing., March 1912, December 1912. Leprince-Ringuet--Revue de Mecanique. July 1911. John Perry--"The Steam Engine". T. E. Stanton--Philosophical Transactions, 1897. Dr. J. T. Nicholson--Proceedings Institute of Engineers & Shipbuilders in Scotland, 1910. W. E. Dally--Proceedings Institute of Mechanical Engineers, 1909.] [Footnote 86: Proceedings Royal Society, Vol. LXXI.] [Footnote 87: Zeitschrift des Vereines Deutscher Ingenieur, 1910, page 1154.] [Footnote 88: Proceedings Institute of Engineers and Shipbuilders, 1910.] [Footnote 89: Natural or Hyperbolic Logarithm.] 
35916	----	+-------------------------------------------------------------------+ | | | TRANSCRIBER'S NOTES: | | | | | |Formatting and coding information: | | - Text in italics is marked with underscores as in _text_. | | - Bold-face text is marked =text=. | | - Superscript x and subscript x are represented as ^{x} and _{x},| | respectively. | | - sqrt(x) represents the square root of x. | | - [oe] and [OE] represent the oe-ligatures. | | - Greek letters are written between square brackets, as in [tau] | | or [theta]. | | - Overlined 1 is represented as [=1]. | | - [<] represents a 'rotated [Delta]'. | | | |General remarks: | | - Footnotes have been moved to directly below the paragraph they | | refer to. | | - In-line multiple line formulas have been changed to in-line | | single-line formulas, with brackets added when needed. | | - The Table of Contents has been corrected to conform to the text| | rather than to the original Table of Contents. | | - The table on operating costs of trains gives 'Other expenses | | per square mile.' This has been changed to 'Per mile' the same | | as the other expenses. | | - The table on dimensions of farm and road locomotives gives the | | diameter of the boiler shell as 30 feet, which seems unlikely. | | - Feet are sometimes used as unit of area, both knots and knots | | per hour as unit of speed. | | | |Changes in text: | | - Reference letters in the text have in several cases been | | changed to conform to the letters used in the illustrations. | | - Minor typographical errors have been corrected. | | - Except when mentioned here, inconsistencies in spelling | | and hyphenation have not been corrected. Exceptions: | | 'Desagulier' to 'Desaguliers' | | 'Séguin' to 'Seguin' | | 'Goldworthy Gurney' to 'Goldsworthy Gurney' | | 'Ctesibus' to 'Ctesibius' | | 'i.e.' to 'i. e.' | | 'Warmetheorie' to 'Wärmetheorie' | | 'tour a tour' to 'tour à tour' | | 'the beam passes to the' to 'the steam passes to the' | | 'Desagulier' to 'Desaguliers' | | 'éléver' to 'élever'. | | - 'As early as 1743' moved to new paragraph. | | - 'A = 6.264035' changed to 'a = 6.264035.' | | | +-------------------------------------------------------------------+ THE INTERNATIONAL SCIENTIFIC SERIES. VOLUME XXIV. THE INTERNATIONAL SCIENTIFIC SERIES. EACH BOOK COMPLETE IN ONE VOLUME, 12MO, AND BOUND IN CLOTH. 1. FORMS OF WATER: A Familiar Exposition of the Origin and Phenomena of Glaciers. By J. TYNDALL, LL. D., F. R. S. With 25 Illustrations. $1.50. 2. PHYSICS AND POLITICS; Or, Thoughts on the Application of the Principles of "Natural Selection" and "Inheritance" to Political Society. By WALTER BAGEHOT. $1.50. 3. FOODS. 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E., PROFESSOR OF ENGINEERING STEVENS INSTITUTE OF TECHNOLOGY, PAST PRESIDENT AMERICAN SOCIETY MECHANICAL ENGINEERS, MEMBER OF SOCIETY OF CIVIL ENGINEERS, SOCIÉTÉ DES INGÉNIEURS CIVILS, VEREIN DEUTSCHE INGENIEURE, OESTERREICHISCHER INGENIEUR- UND ARCHITEKTEN-VEREIN; ASSOCIATE BRITISH INSTITUTION OF NAVAL ARCHITECTS, ETC., ETC. _SECOND REVISED EDITION._ NEW YORK: D. APPLETON AND COMPANY, 1, 3, AND 5 BOND STREET. 1886. COPYRIGHT, 1878, 1884, BY ROBERT H. THURSTON. PREFACE. This little work embodies the more generally interesting portions of lectures first written for delivery at the STEVENS INSTITUTE OF TECHNOLOGY, in the winter of 1871-'72, to a mixed audience, composed, however, principally of engineers by profession, and of mechanics; it comprises, also, some material prepared for other occasions. These lectures have been rewritten and considerably extended, and have been given a form which is more appropriate to this method of presentation of the subject. The account of the gradual development of the philosophy of the steam-engine has been extended and considerably changed, both in arrangement and in method. That part in which the direction of improvement during the past history of the steam-engine, the course which it is to-day taking, and the direction and limitation of that improvement in the future, are traced, has been somewhat modified to accord with the character of the revised work. The author has consulted a large number of authors in the course of his work, and is very greatly indebted to several earlier writers. Of these, Stuart[1] is entitled to particular mention. His "History" is the earliest deserving the name; and his "Anecdotes" are of exceedingly great interest and of equally great historical value. The artistic and curious little sketches at the end of each chapter are from John Stuart, as are, usually, the drawings of the older forms of engines. [1] "History of the Steam-Engine," London, 1824. "Anecdotes of the Steam-Engine," London, 1829. Greenwood's excellent translation of Hero, as edited by Bennett Woodcroft (London, 1851), can be consulted by those who are curious to learn more of that interesting old Greek treatise. Some valuable matter is from Farey,[2] who gives the most extended account extant of Newcomen's and Watt's engines. The reader who desires to know more of the life of Worcester, and more of the details of his work, will find in the very complete biography of Dircks[3] all that he can wish to learn of that great but unfortunate inventor. Smiles's admirably written biography of Watt[4] gives an equally interesting and complete account of the great mechanic and of his partners; and Muirhead[5] furnishes us with a still more detailed account of his inventions. [2] "Treatise on the Steam-Engine," London, 1827. [3] "Life, Times, and Scientific Labors of the Second Marquis of Worcester," London, 1865. [4] "Lives of Boulton and Watt," London, 1865. [5] "Life of James Watt," D. Appleton & Co., New York, 1859. "Mechanical Inventions of James Watt," London, 1854. For an account of the life and work of John Elder, the great pioneer in the introduction of the now standard double-cylinder, or "compound," engine, the student can consult a little biographical sketch by Prof. Rankine, published soon after the death of Elder. The only published sketch of the history of the science of thermo-dynamics, which plays so large a part of the philosophy of the steam-engine, is that of Prof. Tait--a most valuable monograph. The section of this work which treats of the causes and the extent of losses of heat in the steam-engine, and of the methods available, or possibly available, to reduce the amount of this now immense waste of heat, is, in some respects, quite new, and is equally novel in the method of its presentation. The portraits with which the book is well furnished are believed to be authentic, and, it is hoped, will lend interest, if not adding to the real value of the work. Among other works which have been of great assistance to the author, and will be found, perhaps, equally valuable to some of the readers of this little treatise, are several to which reference has not been made in the text. Among them the following are deserving of special mention: Zeuner's "Wärmetheorie," the treatises of Stewart and of Maxwell, and McCulloch's "Mechanical Theory of Heat," a short but thoroughly logical and exact mathematical treatise; Cotterill's "Steam-Engine considered as a Heat-Engine," a more extended work on the same subject, which will be found an excellent companion to, and commentary upon, Rankine's "Steam-Engine and Prime Movers," which is the standard treatise on the theory of the steam-engine. The works of Bourne, of Holley, of Clarke, and of Forney, are standards on the practical every-day matters of steam-engine construction and management. The author is almost daily in receipt of inquiries which indicate that the above remarks will be of service to very many young engineers, as well as to many to whom the steam-engine is of interest from a more purely scientific point of view. CONTENTS. CHAPTER I. THE STEAM-ENGINE AS A SIMPLE MACHINE. PAGE SECTION I.--THE PERIOD OF SPECULATION--FROM HERO TO WORCESTER, B. C. 200 TO A. D. 1650 1 Introduction--the Importance of the Steam-Engine, 1; Hero and his Treatise on Pneumatics, 4; Hero's Engines, B. C. 200, 8; William of Malmesbury on Steam, A. D. 1150, 10; Hieronymus Cardan on Steam and the Vacuum, 10; Malthesius on the Power of Steam, A. D. 1571, 10; Jacob Besson on the Generation of Steam, A. D. 1578, 11; Ramelli's Work on Machines, A. D. 1588, 11; Leonardo da Vinci on the Steam-Gun, 12; Blasco de Garay's Steamer, A. D. 1543, 12; Battista della Porta's Steam-Engine, A. D. 1601, 13; Florence Rivault on the Force of Steam, A. D. 1608, 15; Solomon de Caus's Apparatus, A. D. 1615, 16; Giovanni Branca's Steam-Engine, A. D. 1629, 16; David Ramseye's Inventions, A. D. 1630, 17; Bishop John Wilkins's Schemes, A. D. 1648, 18; Kircher's Apparatus, 19. SECTION II.--THE PERIOD OF APPLICATION--WORCESTER, PAPIN, AND SAVERY 19 Edward Somerset, Marquis of Worcester, A. D. 1663, 19; Worcester's Steam Pumping-Engines, 21; Jean Hautefeuille's Alcohol and Gunpowder Engines, A. D. 1678, 24; Huyghens's Gunpowder-Engine, A. D. 1680, 25; Invention in Great Britain, 26; Sir Samuel Morland, A. D. 1683, 27; Thomas Savery and his Engine, A. D. 1698, 31; Desaguliers's Savery Engines, A. D. 1718, 41; Denys Papin and his Work, A. D. 1675, 45; Papin's Engines, A. D. 1685-1695, 50; Papin's Steam-Boilers, 51. CHAPTER II. THE STEAM-ENGINE AS A TRAIN OF MECHANISM. THE MODERN TYPE AS DEVELOPED BY NEWCOMEN, BEIGHTON, AND SMEATON 55 Defects of the Savery Engine, 55; Thomas Newcomen, A. D. 1705, 57; the Newcomen Steam Pumping-Engine, 59; Advantages of Newcomen's Engine, 60; Potter's and Beighton's Improvements, A. D. 1713-'18, 61; Smeaton's Newcomen Engines, A. D. 1775, 64; Operation of the Newcomen Engine, 65; Power and Economy of the Engine, 69; Introduction of the Newcomen Engine, 70. CHAPTER III. THE DEVELOPMENT OF THE MODERN STEAM-ENGINE. JAMES WATT AND HIS CONTEMPORARIES. SECTION I.--JAMES WATT AND HIS INVENTIONS 79 James Watt, his Birth and Parentage, 79; his Standing in School, 81; he learns his Trade in London, 81; Return to Scotland and Settlement in Glasgow, 82; the Newcomen Engine Model, 83; Discovery of Latent Heat, 84; Sources of Loss in the Newcomen Engine, 85; Facts experimentally determined by Watt, 86; Invention of the Separate Condenser, 87; the Steam-Jacket and other Improvements, 90; Connection with Dr. Roebuck, 91; Watt meets Boulton, 93; Matthew Boulton, 93; Boulton's Establishment at Soho, 95; the Partnership of Boulton and Watt, 97; the Kinneil Engine, 97; Watt's Patent of 1769, 98; Work of Boulton and Watt, 101; the Rotative Engine, 103; the Patent of 1781, 104; the Expansion of Steam--its Economy, 105; the Double-Acting Engine, 110; the "Compound" Engine, 110; the Steam-Hammer, 111; Parallel Motions, the Counter, 112; the Throttle-Valve and Governor, 114; Steam, Vacuum, and Water Gauges, 116; Boulton & Watt's Mill-Engine, 118; the Albion Mill and its Engine, 119; the Steam-Engine Indicator, 123; Watt in Social Life, 125; Discovery of the Composition of Water, 126; Death of James Watt, 128; Memorials and Souvenirs, 128. SECTION II.--THE CONTEMPORARIES OF JAMES WATT 132 William Murdoch and his Work, 132; Invention of Gas-Lighting, 134; Jonathan Hornblower and the Compound Engine, 135; Causes of the Failure of Hornblower, 137; William Bull and Richard Trevithick, 138; Edward Cartwright and his Engine, 140. CHAPTER IV. THE MODERN STEAM-ENGINE. THE SECOND PERIOD OF APPLICATION--1800-1850--STEAM-LOCOMOTION ON RAILROADS 144 Introduction, 144; the Non-Condensing Engine and the Locomotive, 147; Newton's Locomotive, 1680, 149; Nathan Read's Steam-Carriage, 150; Cugnot's Steam-Carriage, 1769, 151; the Model Steam-Carriage of Watt and Murdoch, 1784, 153; Oliver Evans and his Plans, 1786, 153; Evans's Oruktor Amphibolis, 1804, 157; Richard Trevithick's Steam-Carriage, 1802, 159; Steam-Carriages of Griffiths and others, 160; Steam-Carriages of Goldsworthy Gurney, 1827, 161; Steam-Carriages of Walter Hancock, 1831, 165; Reports to the House of Commons, 1831, 170; the Introduction of the Railroad, 172; Richard Trevithick's Locomotives, 1804, 174; John Stevens and the Railroad, 1812, 178; William Hedley's Locomotives, 1812, 181; George Stephenson, 183; Stephenson's Killingworth Engine, 1813, 186; Stephenson's Second Locomotive, 1815, 187; Stephenson's Safety-Lamp, 1815, 187; Robert Stephenson & Co., 1824, 190; the Stockton & Darlington Engine, 1825, 191; the Liverpool & Manchester Railroad, 1826, 193; Trial of Competing Engines at Rainhill, 1829, 195; the Rocket and the Novelty, 198; Atmospheric Railways, 201; Character of George Stephenson, 204; the Locomotive of 1833, 204; Introduction of Railroads in Europe, 206; Introduction of Railroads in the United States, 207; John Stevens's Experimental Railroad, 1825, 207; Horatio Allen and the "Stourbridge Lion," 1829, 208; Peter Cooper's Engine, 1829, 209; E. L. Miller and the S. C. Railroad, 1830, 210; the "American" Type of Engine of John B. Jervis, 1832, 212; Robert L. Stevens and the T-rail, 1830, 214; Matthias W. Baldwin and his Engine, 1831, 215; Robert Stephenson on the Growth of the Locomotive, 220. CHAPTER V. THE MODERN STEAM-ENGINE. THE SECOND PERIOD OF APPLICATION--1800-1850 (CONTINUED)--THE STEAM-ENGINE APPLIED TO SHIP-PROPULSION 221 Introduction, 221; Ancient Prophecies, 223; the Earliest Paddle-Wheel, 223; Blasco de Garay's Steam-Vessel, 1543, 224; Experiments of Dionysius Papin, 1707, 214; Jonathan Hulls's Steamer, 1736, 225; Bernouilli and Gauthier, 228; William Henry, 1782, 230; the Comte d'Auxiron, 1772, 232; the Marquis de Jouffroy, 1776, 233; James Rumsey, 1774, 234; John Fitch, 1785, 285; Fitch's Experiments on the Delaware, 1787, 237; Fitch's Experiments at New York, 1796, 240; the Prophecy of John Fitch, 241; Patrick Miller, 1786-'87, 241; Samuel Morey, 1793, 243; Nathan Read, 1788, 244; Dundas and Symmington, 1801, 246; Henry Bell and the Comet, 1811, 248; Nicholas Roosevelt, 1798, 250; Robert Fulton, 1802, 251; Fulton's Torpedo-Vessels, 1801, 252; Fulton's First Steamboat, 1803, 253; the Clermont, 1807, 257; Voyage of the Clermont to Albany, 259; Fulton's Later Steamboats, 260; Fulton's War-Steamer Fulton the First, 1815, 261; Oliver Evans, 1804, 263; John Stevens's Screw-Steamer, 1804, 264; Stevens's Steam-Boilers, 1804, 264; Stevens's Iron-Clad, 1812, 268; Robert L. Stevens's Improvements, 270; the "Stevens Cut-off," 1841, 276; the Stevens Iron-Clad, 1837, 277; Robert L. Thurston and John Babcock, 1821, 280; James P. Allaire and the Messrs. Copeland, 281; Erastus W. Smith's Compound Engine, 283; Steam-Navigation on Western Rivers, 1811, 283; Ocean Steam-Navigation, 1808, 285; the Savannah, 1819, 286; the Sirius and the Great Western, 1838, 289; the Cunard Line, 1840, 290; the Collins Line, 1851, 291; the Side-Lever Engine, 292; Introduction of Screw-Steamers, 293; John Ericsson's Screw-Vessels, 1836, 294; Francis Pettit Smith, 1837, 296; the Princeton, 1841, 297; Advantages of the Screw, 299; the Screw on the Ocean, 300; Obstacles to Improvement, 301; Changes in Engine-Construction, 302; Conclusion, 303. CHAPTER VI. THE STEAM-ENGINE OF TO-DAY. THE PERIOD OF REFINEMENT--1850 TO DATE 303 Condition of the Steam-Engine at this Time, 303; the Later Development of the Engine, 304; Stationary Steam-Engines, 307; the Steam-Engine for Small Powers, 307; the Horizontal Engine with Meyer Valve-Gear, 311; the Allen Engine, 314; its Performance, 316; the Detachable Valve-Gear, 316; the Sickels Cut-off, 317; Expansion adjusted by the Governor, 318; the Corliss Engine, 319; the Greene Engine, 321; Perkins's Experiments, 323; Dr. Alban's Work, 325; the Perkins Compound Engine, 327; the Modern Pumping-Engine, 328; the Cornish Engine, 328; the Steam-Pump, 331; the Worthington Pumping-Engine, 333; the Compound Beam and Crank Engine, 335; the Leavitt Pumping-Engine, 336; the Stationary Steam-Boiler, 338; "Sectional" Steam-Boilers, 343; "Performance" of Boilers, 344. SECTION II.--PORTABLE AND LOCOMOTIVE ENGINES. 347 The Semi-Portable Engine, 348; Performance of Portable Engines, 350; their Efficiency, 352; the Hoadley Engine, 354; the Mills Farm and Road Engine, 356; Fisher's Steam-Carriage, 356; Performance of Road-Engines, 357; Trial of Road-Locomotives by the Author, 358; Conclusions, 358; the Steam Fire-Engine, 360; the Rotary Steam-Engine and Pump, 365; the Modern Locomotive, 368; Dimensions and Performance, 373; Compound Engines for Locomotives, 376; Extent of Modern Railroads, 378; SECTION III.--MARINE ENGINES. 379 The Modern Marine Engine, 379; the American Beam Engine, 379; the Oscillating Engine and Feathering Wheel, 381; the two "Rhode Islands," 382; River-Boat Engines on the Mississippi, 384; Steam Launches and Yachts, 386; Marine Screw-Engines, 389; the Marine Compound Engine, 390; its Introduction by John Elder and others, 393; Comparison with the Single-Cylinder Engine, 395; its Advantages, 396; the Surface Condenser, 397; Weight of Machinery, 398; Marine Engine Performance, 398; Relative Economy of Simple and Compound Engines, 399; the Screw-Propeller, 399; Chain-Propulsion, or Wire-Rope Towage, 402; Marine Steam-Boilers, 403; the Modern Steamship, 405; Examples of Merchant Steamers, 406; Naval Steamers--Classification, 409; Examples of Iron-Clad Steamers, 412; Power of the Marine Engine, 415; Conclusion, 417. CHAPTER VII. THE PHILOSOPHY OF THE STEAM-ENGINE. THE HISTORY OF ITS GROWTH; ENERGETICS AND THERMO-DYNAMICS 419 General Outline, 419; Origin of its Power, 419; Scientific Principles involved in its Operation, 420; the Beginnings of Modern Science, 421; the Alexandrian Museum, 422; the Aristotelian Philosophy, 424; the Middle Ages, 426; Galileo's Work, 428; Da Vinci and Stevinus, 429; Kepler, Hooke, and Huyghens, 429; Newton and the New Mechanical Philosophy, 430; the Inception of the Science of Energetics, 483; the Persistence of Energy, 433; Rumford's Experiments, 434; Fourier, Carnot, Seguin, 437; Mayer and the Mechanical Equivalent of Heat, 438; Joule's Determination of its Value, 438; Prof. Rankine's Investigations, 442; Clausius-Thompson's Principles, 444; Experimental Work of Boyle, Black, and Watt, 446; Robison's, Dalton's, Ure's, and Biot's Study of Pressures and Temperatures of Steam, 447; Arago's and Dulong's Researches, 447; Franklin Institute Investigation, 447; Cagniard de la Tour--Faraday, 447; Dr. Andrews and the Critical Point, 448; Donny's and Dufour's Researches, 448; Regnault's Determination of Temperatures and Pressures of Steam, 449; Hirn's Experiments, 450; Résumé of the Philosophy of the Steam-Engine, 451; Energy--Definitions and Principles, 451; its Measure, 452; the Laws of Energetics, 453; Thermo-dynamics, 453; its Beginnings, 454; its Laws, 454; Rankine's General Equation, 455; Rankine's Treatise on the Theory of Heat-Engines, 456; Merits of the Great Philosopher, 456. CHAPTER VIII. THE PHILOSOPHY OF THE STEAM-ENGINE. ITS APPLICATION; ITS TEACHINGS RESPECTING THE CONSTRUCTION OF THE ENGINE AND ITS IMPROVEMENT 457 Origin of all Energy, 457; the Progress of Energy through Boiler and Engine, 458; Conditions of Heat-Development in the Boiler, 458; the Steam in the Engine, 458; the Expansion of Steam, 459; Conditions of Heat-Utilization, 460; Loss of Power in the Engine, 462; Conditions affecting the Design of the Steam-Engine, 466; the Problem stated, 466; Economy as affected by Pressure and Temperature, 467; Changes which have already occurred, 468; Direction of Changes now in Progress, 470; Summary of Facts, 471; Characteristics of a Good Steam-Engine, 473; Principles of Steam-Boiler Construction, 476. LIST OF ILLUSTRATIONS. FRONTISPIECE: The Grecian Idea of the Steam-Engine. FIG. PAGE 1. Opening Temple-Doors by Steam, B. C. 200 6 2. Steam Fountain, B. C. 200 7 3. Hero's Engine, B. C. 200 8 4. Porta's Apparatus, A. D. 1601 14 5. De Caus's Apparatus, A. D. 1605 15 6. Branca's Steam-Engine, A. D. 1629 17 7. Worcester's Steam-Fountain, A. D. 1650 21 8. Worcester's Engine, A. D. 1665 22 9. Wall of Raglan Castle 22 10. Huyghens's Engine, 1680 26 11. Savery's Model, 1698 34 12. Savery's Engine, 1698 35 13. Savery's Engine, A. D. 1702 37 14. Papin's Two-Way Cock 42 15. Engine Built by Desaguliers in 1718 43 16. Papin's Digester, 1680 48 17. Papin's Engine 50 18. Papin's Engine and Water-Wheel, A. D. 1707 53 19. Newcomen's Engine, A. D. 1705 59 20. Beighton's Valve-Gear, A. D. 1718 63 21. Smeaton's Newcomen Engine 65 22. Boiler of Newcomen Engine, 1763 67 23. Smeaton's Portable-Engine Boiler, 1765 73 24. The Newcomen Model 84 25. Watt's Experiment 89 26. Watt's Engine, 1774 98 27. Watt's Engine, 1781 104 28. Expansion of Steam 108 29. The Governor 115 30. Mercury Steam-Gauge and Glass Water-Gauge 117 31. Boulton & Watt's Double-Acting Engine, 1784 119 32. Valve-Gear of the Albion Mills Engine 121 33. Watt's Half-Trunk Engine, 1784 122 34. The Watt Hammer, 1784 123 35. James Watt's Workshop 129 36. Murdoch's Oscillating Engine, 1785 134 37. Hornblower's Compound Engine, 1781 136 38. Bull's Pumping-Engine, 1798 139 39. Cartwright's Engine, 1798 141 40. The First Railroad-Car, 1825 144 41. Leupold's Engine, 1720 148 42. Newton's Steam-Carriage, 1680 149 43. Read's Steam-Carriage, 1790 150 44. Cugnot's Steam-Carriage, 1770 151 45. Murdoch's Model, 1784 153 46. Evans's Non-Condensing Engine, 1800 156 47. Evans's "Oruktor Amphibolis," 1804 157 48. Gurney's Steam-Carriage 163 49. Hancock's "Autopsy", 1833 168 50. Trevithick's Locomotive, 1804 175 51. Stephenson's Locomotive of 1815. Section 187 52. Stephenson's No. 1 Engine, 1825 191 53. Opening of the Stockton and Darlington Railroad, 1815 192 54. The "Novelty," 1829 197 55. The "Rocket," 1829 198 56. The Atmospheric Railroad 202 57. Stephenson's Locomotive, 1833 203 58. The Stephenson Valve-Gear, 1833 206 59. The "Atlantic," 1832 210 60. The "Best Friend," 1830 211 61. The "West Point," 1831 212 62. The "South Carolina," 1831 213 63. The "Stevens" Rail and Enlarged Section 215 64. "Old Ironsides," 1832 216 65. The "E. L. Miller," 1834 217 66. Hulls's Steamboat, 1736 226 67. Fitch's Model, 1785 236 68. Fitch & Voight's Boiler, 1787 238 69. Fitch's First Boat, 1787 238 70. John Fitch, 1788 239 71. John Fitch, 1796 240 72. Miller, Taylor & Symmington, 1788 242 73. Read's Boiler in Section, 1788 245 74. Read's Multi-Tubular Boiler, 1788 245 75. The "Charlotte Dundas," 1801 247 76. The "Comet," 1812 248 77. Fulton's Experiments 253 78. Fulton's Table of Resistances 254 79. Barlow's Water-Tube Boiler, 1793 256 80. The "Clermont," 1807 258 81. Engine of the "Clermont," 1808 258 82. Launch of the "Fulton the First," 1804 262 83. Section of Steam-Boiler, 1804 264 84. Engine, Boiler, and Screw-Propellers used by Stevens, 1804 265 85. Stevens's Screw Steamer, 1804 265 86. John Stevens's Twin-Screw Steamer, 1805 269 87. The Feathering Paddle-Wheel 272 88. The "North America" and "Albany," 1827-'30 274 89. Stevens's Return Tubular Boiler, 1832 275 90. Stevens's Valve-Motion 276 91. The "Atlantic," 1851 290 92. The Side-Lever Engine, 1849 291 93. Vertical Stationary Steam-Engine 308 94. Vertical Stationary Steam-Engine. Section 309 95. Horizontal Stationary Steam-Engine 312 96. Horizontal Stationary Steam-Engine 313 97. Corliss Engine 319 98. Corliss Engine Valve-Motion 320 99. Greene Engine 321 100. Thurston's Greene-Engine Valve-Gear 322 101. Cornish Pumping-Engine, 1880 329 102. Steam-Pump 331 103. The Worthington Pumping-Engine, 1876. Section 333 104. The Worthington Pumping-Engine 334 105. Double-Cylinder Pumping-Engine, 1878 335 106. The Lawrence Water-Works Engine 336 107. The Leavitt Pumping-Engine 337 108. Babcock & Wilcox's Vertical Boiler 341 109. Stationary "Locomotive" Boiler 342 110. Galloway Tube 343 111. Harrison's Sectional Boiler 345 112. Babcock and Wilcox's Sectional Boiler 346 113. Root Sectional Boiler 347 114. Semi-Portable Engine, 1878 348 115. Semi-Portable Engine, 1878 349 116. The Portable Steam-Engine, 1878 354 117. The Thrashers' Road-Engine, 1878 355 118. Fisher's Steam-Carriage 356 119. Road and Farm Locomotive 357 120. The Latta Steam Fire-Engine 361 121. The Amoskeag Engine. Section 363 122. The Silsby Rotary Steam Fire-Engine 364 123. Rotary Steam-Engine 365 124. Rotary Pump 366 125. Tank Engine, New York Elevated Railroad 369 126. Forney's Tank-Locomotive 370 127. British Express Engine 371 128. The Baldwin Locomotive. Section 372 129. The American Type of Express Engine, 1878 374 130. Beam Engine 380 131. Oscillating Steam-Engine and Feathering Paddle-Wheel 381 132. The Two "Rhode Islands," 1836-1876 383 133. A Mississippi Steamboat 384 134. Steam-Launch, New York Steam-Power Company 386 135. Launch-Engine 387 136. Horizontal, Direct-acting Naval Screw Engine 389 137. Compound Marine Engine. Side Elevation 390 138. Compound Marine Engine. Front Elevation and Section 391 139. Screw-Propeller 400 140. Tug-Boat Screw 401 141. Hirsch Screw 401 142. Marine Fire-Tubular Boiler. Section 403 143. Marine High-Pressure Boiler. Section 404 144. The Modern Steamship 407 145. Modern Iron-Clads 410 146. The "Great Eastern" 415 147. The "Great Eastern" at Sea 416 PORTRAITS. NO. PAGE 1. Edward Somerset, the Second Marquis of Worcester 20 2. Thomas Savery 31 3. Denys Papin 46 4. James Watt 80 5. Matthew Boulton 94 6. Oliver Evans 154 7. Richard Trevithick 174 8. Colonel John Stevens 178 9. George Stephenson 183 10. Robert Fulton 251 11. Robert L. Stevens 270 12. John Elder 393 13. Benjamin Thompson, Count Rumford 434 14. James Prescott Joule 439 15. Prof. W. J. M. Rankine 443 ["A Machine, receiving at distant times and from many hands new combinations and improvements, and becoming at last of signal benefit to mankind, may be compared to a rivulet swelled in its course by tributary streams, until it rolls along a majestic river, enriching, in its progress, provinces and kingdoms. "In retracing the current, too, from where it mingles with the ocean, the pretensions of even ample subsidiary streams are merged in our admiration of the master-flood, glorying, as it were, in its expansion. But as we continue to ascend, those waters which, nearer the sea, would have been disregarded as unimportant, begin to rival in magnitude and share our attention with the parent stream; until, at length, on our approaching the fountains of the river, it appears trickling from the rock, or oozing from among the flowers of the valley. "So, also, in developing the rise of a machine, a coarse instrument or a toy may be recognized as the germ of that production of mechanical genius, whose power and usefulness have stimulated our curiosity to mark its changes and to trace its origin. The same feelings of reverential gratitude which attached holiness to the spot whence mighty rivers sprang, also clothed with divinity, and raised altars in honor of, inventors of the saw, the plough, the potter's wheel, and the loom."--STUART.] THE GROWTH OF THE STEAM-ENGINE. CHAPTER I. _THE STEAM-ENGINE AS A SIMPLE MACHINE._ SECTION I.--THE PERIOD OF SPECULATION--FROM HERO TO WORCESTER, B. C. 200 TO A. D. 1650. One of the greatest of modern philosophers--the founder of that system of scientific philosophy which traces the processes of evolution in every department, whether physical or intellectual--has devoted a chapter of his "First Principles" of the new system to the consideration of the multiplication of the effects of the various forces, social and other, which are continually modifying this wonderful and mysterious universe of which we form a part. Herbert Spencer, himself an engineer, there traces the wide-spreading, never-ceasing influences of new inventions, of the introduction of new forms of mechanism, and of the growth of industrial organization, with a clearness and a conciseness which are so eminently characteristic of his style. His illustration of this idea by reference to the manifold effects of the introduction of steam-power and its latest embodiment, the locomotive-engine, is one of the strongest passages in his work. The power of the steam-engine, and its inconceivable importance as an agent of civilization, has always been a favorite theme with philosophers and historians as well as poets. As Religion has always been, and still is, the great _moral_ agent in civilizing the world, and as Science is the great _intellectual_ promoter of civilization, so the Steam-Engine is, in modern times, the most important _physical_ agent in that great work. It would be superfluous to attempt to enumerate the benefits which it has conferred upon the human race, for such an enumeration would include an addition to every comfort and the creation of almost every luxury that we now enjoy. The wonderful progress of the present century is, in a very great degree, due to the invention and improvement of the steam-engine, and to the ingenious application of its power to kinds of work that formerly taxed the physical energies of the human race. We cannot examine the methods and processes of any branch of industry without discovering, somewhere, the assistance and support of this wonderful machine. Relieving mankind from manual toil, it has left to the intellect the privilege of directing the power, formerly absorbed in physical labor, into other and more profitable channels. The intelligence which has thus conquered the powers of Nature, now finds itself free to do head-work; the force formerly utilized in the carrying of water and the hewing of wood, is now expended in the God-like work of THOUGHT. What, then, can be more interesting than to trace the history of the growth of this wonderful machine?--the greatest among the many great creations of one of God's most beneficent gifts to man--the power of invention. While following the records and traditions which relate to the steam-engine, I propose to call attention to the fact that its history illustrates the very important truth: _Great inventions are never, and great discoveries are seldom, the work of any one mind_. Every great invention is really either an aggregation of minor inventions, or the final step of a progression. It is not a creation, but _a growth_--as truly so as is that of the trees in the forest. Hence, the same invention is frequently brought out in several countries, and by several individuals, simultaneously. Frequently an important invention is made before the world is ready to receive it, and the unhappy inventor is taught, by his failure, that it is as unfortunate to be in advance of his age as to be behind it. Inventions only become successful when they are not only needed, but when mankind is so far advanced in intelligence as to appreciate and to express the necessity for them, and to at once make use of them. More than half a century ago, an able New England writer, in a communication to an English engineering periodical, described the new machinery which was built at Newport, R. I., by John Babcock and Robert L. Thurston, for one of the first steamboats that ever ran between that city and New York. He prefaced his description with a frequently-quoted remark to the effect that, as Minerva sprang, mature in mind, in full stature of body, and completely armed, from the head of Jupiter, so the steam-engine came forth, perfect at its birth, from the brain of James Watt. But we shall see, as we examine the records of its history, that, although James Watt was _an_ inventor, and probably the greatest of the inventors of the steam-engine, he was still but one of the many men who have aided in perfecting it, and who have now made us so familiar with it, and its tremendous power and its facile adaptations, that we have almost ceased to admire it, or to wonder at the workings of the still more admirable intelligence that has so far perfected it. Twenty-one centuries ago, the political power of Greece was broken, although Grecian civilization had risen to its zenith. Rome, ruder than her polished neighbor, was growing continually stronger, and was rapidly gaining territory by absorbing weaker states. Egypt, older in civilization than either Greece or Rome, fell but two centuries later before the assault of the younger states, and became a Roman province. Her principal city was at this time Alexandria, founded by the great soldier whose name it bears, when in the full tide of his prosperity. It had now become a great and prosperous city, the centre of the commerce of the world, the home of students and of learned men, and its population was the wealthiest and most civilized of the then known world. It is among the relics of that ancient Egyptian civilization that we find the first records in the early history of the steam-engine. In Alexandria, the home of Euclid, the great geometrician, and possibly contemporary with that talented engineer and mathematician, Archimedes, a learned writer, called Hero, produced a manuscript which he entitled "Spiritalia seu Pneumatica." It is quite uncertain whether Hero was the inventor of any number of the contrivances described in his work. It is most probable that the apparatus described are principally devices which had either been long known, or which were invented by Ctesibius, an inventor who was famous for the number and ingenuity of the hydraulic and pneumatic machines that he devised. Hero states, in his Introduction, his intention to describe existing machines and earlier inventions, and to add his own. Nothing in the text, however, indicates to whom the several machines are to be ascribed.[6] [6] The British Museum contains four manuscript copies of Hero's "Pneumatics," which were written in the fifteenth and sixteenth centuries. These manuscripts have been examined with great care, and a translation from them prepared by Prof. J. G. Greenwood, and published at the desire of Mr. Bennett Woodcroft, the author of a valuable little treatise on "Steam Navigation." This is, so far as the author is aware, the only existing English translation of any portion of Hero's works. The first part of Hero's work is devoted to applications of the syphon. The 11th proposition is the first application of heat to produce motion of fluids. An altar and its pedestal are hollow and air-tight. A liquid is poured into the pedestal, and a pipe inserted, of which the lower end passes beneath the surface of the liquid, and the upper extremity leads through a figure standing at the altar, and terminates in a vessel inverted above this altar. When a fire is made on the altar, the heat produced expands the confined air, and the liquid is driven up the tube, issuing from the vessel in the hand of the figure standing by the altar, which thus seems to be offering a libation. This toy embodies the essential principle of all modern heat-engines--the change of energy from the form known as heat-energy into mechanical energy, or work. It is not at all improbable that this prototype of the modern wonder-working machine may have been known centuries before the time of Hero. Many forms of hydraulic apparatus, including the hand fire-engine, which is familiar to us, and is still used in many of our smaller cities, are described, the greater number of which are probably attributable to Ctesibius. They demand no description here. A hot-air engine, however, which is the subject of his 37th proposition, is of real interest. Hero sketches and describes a method of opening temple-doors by the action of fire on an altar, which is an ingenious device, and contains all the elements of the machine of the Marquis of Worcester, which is generally considered the first real steam-engine, with the single and vital defect that the expanding fluid is air instead of steam. The sketch, from Greenwood's translation, exhibits the device very plainly. Beneath the temple-doors, in the space _A B C D_, is placed a spherical vessel, _H_, containing water. A pipe, _F G_, connects the upper part of this sphere with the hollow and air-tight shell of the altar above, _D E_. Another pipe, _K L M_, leads from the bottom of the vessel, _H_, over, in syphon-shape, to the bottom of a suspended bucket, _N X_. The suspending cord is carried over a pulley and led around two vertical barrels, _O P_, turning on pivots at their feet, and carrying the doors above. Ropes led over a pulley, _R_, sustain a counterbalance, _W_. [Illustration: FIG. 1.--Opening Temple-Doors by Steam, B. C. 200.] On building a fire on the altar, the heated air within expands, passes through the pipe, _F G_, and drives the water contained in the vessel, _H_, through the syphon, _K L M_, into the bucket, _N X_. The weight of the bucket, which then descends, turns the barrels, _O P_, raises the counterbalance, and opens the doors of the temple. On extinguishing the fire, the air is condensed, the water returns through the syphon from the bucket to the sphere, the counterbalance falls, and the doors are closed. Another contrivance is next described, in which the bucket is replaced by an air-tight bag, which, expanding as the heated air enters it, contracts vertically and actuates the mechanism, which in other respects is similar to that just described. In these devices the spherical vessel is a perfect anticipation of the vessels used many centuries later by several so-called inventors of the steam-engine. Proposition 45 describes the familiar experiment of a ball supported aloft by a jet of fluid. In this example steam is generated in a close cauldron, and issues from a pipe inserted in the top, the ball dancing on the issuing jet. No. 47 is a device subsequently reproduced--perhaps reinvented by the second Marquis of Worcester. [Illustration: FIG. 2.--Steam Fountain, B. C. 200.] A strong, close vessel, _A B C D_, forms a pedestal, on which are mounted a spherical vessel, _E F_, and a basin. A pipe, _H K_, is led from the bottom of the larger vessel into the upper part of the sphere, and another pipe from the lower part of the latter, in the form of a syphon, over to the basin, _M_. A drain-pipe, _N O_, leads from the basin to the reservoir, _A D_. The whole contrivance is called "A fountain which is made to flow by the action of the sun's rays." It is operated thus: The vessel, _E F_, being filled nearly to the top with water, or other liquid, and exposed to the action of the sun's rays, the air above the water expands, and drives the liquid over, through the syphon, _G_, into the basin, _M_, and it will fall into the pedestal, _A B C D_. Hero goes on to state that, on the removal of the sun's rays, the air in the sphere will contract, and that the water will be returned to the sphere from the pedestal. This can, evidently, only occur when the pipe _G_ is closed previous to the commencement of this cooling. No such cock is mentioned, and it is not unlikely that the device only existed on paper. Several steam-boilers are described, usually simple pipes or cylindrical vessels, and the steam generated in them by the heat of the fire on the altar forms a steam-blast. This blast is either directed into the fire, or it "makes a blackbird sing," blows a horn for a triton, or does other equally useless work. In one device, No. 70, the steam issues from a reaction-wheel revolving in the horizontal plane, and causes dancing images to circle about the altar. A more mechanical and more generally-known form of this device is that which is frequently described as the "First Steam Engine." The sketch from Stuart is similar in general form, but more elaborate in detail, than that copied by Greenwood, which is here also reproduced, as representing more accurately the simple form which the mechanism of the "Æolipile," or Ball of Æolus, assumed in those early times. [Illustration: FIG. 3.--Hero's Engine, B. C. 200.] The cauldron, _A B_, contains water, and is covered by the steam-tight cover, _C D_. A globe is supported above the cauldron by a pair of tubes, terminating, the one, _C M_, in a pivot, _L_, and the other, _E F_, opening directly into the sphere at _G_. Short, bent pipes, _H_ and _K_, issue from points diametrically opposite each other, and are open at their extremities. A fire being made beneath the cauldron, steam is formed and finds exit through the pipe, _E F G_, into the globe, and thence rushes out of the pipes, _H K_, turning the globe on its axis, _G L_, by the unbalanced pressure thus produced. The more elaborate sketch which forms the frontispiece represents a machine of similar character. Its design and ornamentation illustrate well the characteristics of ancient art, and the Greek idea of the steam-engine. This "Æolipile" consisted of a globe, _X_, suspended between trunnions, _O S_, through one of which steam enters from the boiler, _P_, below. The hollow, bent arms, _W_ and _Z_, cause the vapor to issue in such directions that the reaction produces a rotary movement of the globe, just as the rotation of reaction water-wheels is produced by the outflowing water. It is quite uncertain whether this machine was ever more than a toy, although it has been supposed by some authorities that it was actually used by the Greek priests for the purpose of producing motion of apparatus in their temples. It seems sufficiently remarkable that, while the power of steam had been, during all the many centuries that man has existed upon the globe, so universally displayed in so many of the phenomena of natural change, that mankind lived almost up to the Christian era without making it useful in giving motion even to a toy; but it excites still greater surprise that, from the time of Hero, we meet with no good evidence of its application to practical purposes for many hundreds of years. Here and there in the pages of history, and in special treatises, we find a hint that the knowledge of the force of steam was not lost; but it is not at all to the credit of biographers and of historians, that they have devoted so little time to the task of seeking and recording information relating to the progress of this and other important inventions and improvements in the mechanic arts. Malmesbury states[7] that, in the year A. D. 1125, there existed at Rheims, in the church of that town, a clock designed or constructed by Gerbert, a professor in the schools there, and an organ blown by air escaping from a vessel in which it was compressed "by heated water." [7] Stuart's "Anecdotes." Hieronymus Cardan, a wonderful mathematical genius, a most eccentric philosopher, and a distinguished physician, about the middle of the sixteenth century called attention, in his writings, to the power of steam, and to the facility with which a vacuum can be obtained by its condensation. This Cardan was the author of "Cardan's Formula," or rule for the solution of cubic equations, and was the inventor of the "smoke-jack." He has been called a "philosopher, juggler, and madman." He was certainly a learned mathematician, a skillful physician, and a good mechanic. Many traces are found, in the history of the sixteenth century, of the existence of some knowledge of the properties of steam, and some anticipation of the advantages to follow its application. Matthesius, A. D. 1571, in one of his sermons describes a contrivance which may be termed a steam-engine, and enlarges on the "tremendous results which may follow the volcanic action of a small quantity of confined vapor;"[8] and another writer applied the steam æolipile of Hero to turn the spit, and thus rivaled and excelled Cardan, who was introducing his "smoke-jack." [8] "Berg-Postilla, oder Sarepta von Bergwerk und Metallen." Nuremberg, 1571. As Stuart says, the inventor enumerated its excellent qualities with great minuteness. He claimed that it would "eat nothing, and giving, withal, an assurance to those partaking of the feast, whose suspicious natures nurse queasy appetites, that the haunch has not been pawed by the turnspit in the absence of the housewife's eye, for the pleasure of licking his unclean fingers."[9] [9] "History of the Steam-Engine," 1825. Jacob Besson, a Professor of Mathematics and Natural Philosophy at Orleans, and who was in his time distinguished as a mechanician, and for his ingenuity in contriving illustrative models for use in his lecture-room, left evidence, which Beroaldus collected and published in 1578,[10] that he had found the spirit of his time sufficiently enlightened to encourage him to pay great attention to applied mechanics and to mechanism. There was at this time a marked awakening of the more intelligent men of the age to the value of practical mechanics. A scientific tract, published at Orleans in 1569, and probably written by Besson, describes very intelligently the generation of steam by the communication of heat to water, and its peculiar properties. [10] "Theatrum Instrumentorum et Machinarum, Jacobi Bessoni, cum Franc Beroaldus, figuarum declaratione demonstrativa." Lugduni, 1578. The French were now becoming more interested in mechanics and the allied sciences, and philosophers and literati, of native birth and imported by the court from other countries, were learning more of the nature and importance of such studies as have a bearing upon the work of the engineer and of the mechanic. Agostino Ramelli, an Italian of good family, a student and an artist when at leisure, a soldier and an engineer in busier times, was born and educated at Rome, but subsequently was induced to make his home in Paris. He published a book in 1588,[11] in which he described many machines, adapted to various purposes, with a skill that was only equaled by the accuracy and general excellence of his delineations. This work was produced while its author was residing at the French capital, supported by a pension which had been awarded him by Henry III. as a reward for long and faithful services. [11] "Le diverse et artificiose machine del Capitano Agostino Ramelli, del Ponte della Prefia." Paris, 1588. The books of Besson and of Ramelli are the first treatises of importance on general machinery, and were, for many years, at once the sources from which later writers drew the principal portion of their information in relation to machinery, and wholesome stimulants to the study of mechanism. These works contain descriptions of many machines subsequently reinvented and claimed as new by other mechanics. Leonardo da Vinci, well known as a mathematician, engineer, poet, and painter, of the sixteenth century, describes, it is said, a steam-gun, which he calls the "Architonnerre," and ascribes to Archimedes. It was a machine composed of copper, and seems to have had considerable power. It threw a ball weighing a talent. The steam was generated by permitting water in a closed vessel to fall on surfaces heated by a charcoal fire, and by its sudden expansion to eject the ball. In the year 1825, the superintendent of the royal Spanish archives at Simancas furnished an account which, it was said, had been there discovered of an attempt, made in 1543 by Blasco de Garay, a Spanish navy-officer under Charles V., to move a ship by paddle-wheels, driven, as was inferred from the account, by a steam-engine. It is impossible to say to how much credit the story is entitled, but, if true, it was the first attempt, so far as is now known, to make steam useful in developing power for practical purposes. Nothing is known of the form of the engine employed, it only having been stated that a "vessel of boiling water" formed a part of the apparatus. The account is, however, in other respects so circumstantial, that it has been credited by many; but it is regarded as apocryphal by the majority of writers upon the subject. It was published in 1826 by M. de Navarrete, in Zach's "Astronomical Correspondence," in the form of a letter from Thomas Gonzales, Director of the Royal Archives at Simancas, Spain. In 1601, Giovanni Battista della Porta, in a work called "Spiritali," described an apparatus by which the pressure of steam might be made to raise a column of water. It included the application of the condensation of steam to the production of a vacuum into which the water would flow. Porta is described as a mathematician, chemist, and physicist, a gentleman of fortune, and an enthusiastic student of science. His home in Naples was a rendezvous for students, artists, and men of science distinguished in every branch. He invented the magic lantern and the camera obscura, and described it in his commentary on the "Pneumatica." In his work,[12] he described this machine for raising water, as shown in Fig. 4, which differs from one shown by Hero in the use of steam pressure, instead of the pressure of heated air, for expelling the liquid. [12] "Pneumaticorum libri tres," etc., 4to. Naples, 1601. "I Tre Libri de' Spiritali." Napoli, 1606. The retort, or boiler, is fitted to a tank from which the bent pipe leads into the external air. A fire being kindled under the retort, the steam generated rises to the upper part of the tank, and its pressure on the surface of the water drives it out through the pipe, and it is then led to any desired height. This was called by Porta an improved "Hero's Fountain," and was named his "Steam Fountain." He described with perfect accuracy the action of condensation in producing a vacuum, and sketched an apparatus in which the vacuum thus secured was filled by water forced in by the pressure of the external atmosphere. His contrivances were not apparently ever applied to any practically useful purpose. We have not yet passed out of the age of speculation, and are just approaching the period of application. Porta is, nevertheless, entitled to credit as having proposed an essential change in this succession, which begins with Hero, and which did not end with Watt. [Illustration: FIG. 4.--Porta's Apparatus, A. D. 1601.] The use of steam in Hero's fountain was as necessary a step as, although less striking than, any of the subsequent modifications of the machine. In Porta's contrivance, too, we should note particularly the separation of the boiler from the "forcing vessel"--a plan often claimed as original with later inventors, and as constituting a fair ground for special distinction. The rude engraving (Fig. 4) above is copied from the book of Porta, and shows plainly the boiler mounted above a furnace, from the door of which the flame is seen issuing, and above is the tank containing water. The opening in the top is closed by the plug, as shown, and the steam issuing from the boiler into the tank near the top, the water is driven out through the pipe at the left, leading up from the bottom of the tank. [Illustration: FIG. 5.--De Caus's Apparatus, A. D. 1605.] Florence Rivault, a Gentleman of the Bedchamber to Henry IV., and a teacher of Louis XIII., is stated by M. Arago, the French philosopher, to have discovered, as early as 1605, that water confined in a bomb-shell and there heated would explode the shell, however thick its walls might be made. The fact was published in Rivault's treatise on artillery in 1608. He says: "The water is converted into air, and its vaporization is followed by violent explosion." In 1615, Salomon de Caus, who had been an engineer and architect under Louis XIII. of France, and later in the employ of the English Prince of Wales, published a work at Frankfort, entitled "Les Raisons des Forces Mouvantes, avec diverses machines tant utile que plaisante," in which he illustrated his proposition, "Water will, by the aid of fire, mount higher than its source," by describing a machine designed to raise water by the expanding power of steam. In the sketch here given (Fig. 5), and which is copied from the original in "Les Raisons des Forces Mouvantes," etc., _A_ is the copper ball containing water; _B_, the cock at the extremity of the pipe, taking water from the bottom, _C_, of the vessel; _D_, the cock through which the vessel is filled. The sketch was probably made by De Caus's own hand. The machine of De Caus, like that of Porta, thus consisted of a metal vessel partly filled with water, and in which a pipe was fitted, leading nearly to the bottom, and open at the top. Fire being applied, the steam formed by its elastic force drove the water out through the vertical pipe, raising it to a height limited only by either the desire of the builder or the strength of the vessel. In 1629, Giovanni Branca, of the Italian town of Loretto, described, in a work[13] published at Rome, a number of ingenious mechanical contrivances, among which was a steam-engine (Fig. 6), in which the steam, issuing from a boiler, impinged upon the vanes of a horizontal wheel. This it was proposed to apply to many useful purposes. [13] "Le Machine deverse del Signior Giovanni Branca, cittadino Romano, Ingegniero, Architetto della Sta. Casa di Loretto." Roma, MDCXXIX. At this time experiments were in progress in England which soon resulted in the useful application of steam-power to raising water. [Illustration: FIG. 6.--Branca's Steam-Engine, A. D. 1629.] A patent, dated January 21, 1630, was granted to David Ramseye[14] by Charles I., which covered a number of distinct inventions. These were: "1. To multiply and make saltpeter in any open field, in fower acres of ground, sufficient to serve all our dominions. 2. To raise water from low pitts by fire. 3. To make any sort of mills to goe on standing waters by continual motion, without help of wind, water, or horse. 4. To make all sortes of tapistrie without any weaving-loom, or waie ever yet in use in this kingdome. 5. To make boats, shippes, and barges to goe against strong wind and tide. 6. To make the earth more fertile than usual. 7. To raise water from low places and mynes, and coal pitts, by a new waie never yet in use. 8. To make hard iron soft, and likewise copper to be tuffe and soft, which is not in use in this kingdome. 9. To make yellow waxe white verie speedilie." [14] Rymer's "F[oe]dera," Sanderson. Ewbank's "Hydraulics," p. 419. This seems to have been the first authentic reference to the use of steam in the arts which has been found in English literature. The patentee held his grant fourteen years, on condition of paying an annual fee of £3 6_s._ 8_d._ to the Crown. The second claim is distinct as an application of steam, the language being that which was then, and for a century and a half subsequently, always employed in speaking of its use. The steam-engine, in all its forms, was at that time known as the "fire-engine." It would seem not at all improbable that the third, fifth, and seventh claims are also applications of steam-power. Thomas Grant, in 1632, and Edward Ford, in 1640, also patented schemes, which have not been described in detail, for moving ships against wind and tide by some new and great force. Dr. John Wilkins, Bishop of Chester, an eccentric but learned and acute scholar, described, in 1648, Cardan's smoke-jack, the earlier æolipiles, and the power of the confined steam, and suggested, in a humorous discourse, what he thought to be perfectly feasible--the construction of a flying-machine. He says: "Might not a 'high pressure' be applied with advantage to move wings as large as those of the 'ruck's' or the 'chariot'? The engineer might probably find a corner that would do for a coal-station near some of the 'castles'" (castles in the air). The reverend wit proposed the application of the smoke-jack to the chiming of bells, the reeling of yarn, and to rocking the cradle. Bishop Wilkins writes, in 1648 ("Mathematical Magic"), of æolipiles as familiar and useful pieces of apparatus, and describes them as consisting "of some such material as may endure the fire, having a small hole at which they are filled with water, and out of which (when the vessels are heated) the air doth issue forth with a strong and lasting violence." "They are," the bishop adds, "frequently used for the exciting and contracting of heat in the melting of glasses or metals. They may also be contrived to be serviceable for sundry other pleasant uses, as for the moving of sails in a chimney-corner, the motion of which sails may be applied to the turning of a spit, or the like." Kircher gives an engraving ("Mundus Subterraneus") showing the last-named application of the æolipile; and Erckern ("Aula Subterranea," 1672) gives a picture illustrating their application to the production of a blast in smelting ores. They seem to have been frequently used, and in all parts of Europe, during the seventeenth century, for blowing fires in houses, as well as in the practical work of the various trades, and for improving the draft of chimneys. The latter application is revived very frequently by the modern inventor. SECTION II.--THE PERIOD OF APPLICATION--WORCESTER, PAPIN, AND SAVERY. We next meet with the first instance in which the expansive force of steam is supposed to have actually been applied to do important and useful work. In 1663, Edward Somerset, second Marquis of Worcester, published a curious collection of descriptions of his inventions, couched in obscure and singular language, and called "A Century of the Names and Scantlings of Inventions by me already Practised." One of these inventions is an apparatus for raising water by steam. The description was not accompanied by a drawing, but the sketch here given (Fig. 7) is thought probably to resemble one of his earlier contrivances very closely. Steam is generated in the boiler _a_, and thence is led into the vessel _e_, already nearly filled with water, and fitted up like the apparatus of De Caus. It drives the water in a jet out through the pipe _f_. The vessel _e_ is then shut off from the boiler _a_, is again filled through the pipe _h_, and the operation is repeated. Stuart thinks it possible that the marquis may have even made an engine with a piston, and sketches it.[15] The instruments of Porta and of De Caus were "steam fountains," and were probably applied, if used at all, merely to ornamental purposes. That of the Marquis of Worcester was actually used for the purpose of elevating water for practical purposes at Vauxhall, near London. [15] "Anecdotes of the Steam-Engine," vol. i., p. 61. [Illustration: Edward Somerset, the Second Marquis of Worcester.] How early this invention was introduced at Raglan Castle by Worcester is not known, but it was probably not much later than 1628. In 1647 Dircks shows the marquis probably to have been engaged in getting out parts of the later engine which was erected at Vauxhall, obtaining his materials from William Lambert, a brass-founder. His patent was issued in June, 1663. [Illustration: FIG. 7.--Worcester's Steam Fountain, A. D. 1650.] We nowhere find an illustrated description of the machine, or such an account as would enable a mechanic to reproduce it in all its details. Fortunately, the cells and grooves (Fig. 9) remaining in the wall of the citadel of Raglan Castle indicate the general dimensions and arrangement of the engine; and Dircks, the biographer of the inventor, has suggested the form of apparatus shown in the sketch (Fig. 8) as most perfectly in accord with the evidence there found, and with the written specifications. The two vessels, _A A´_, are connected by a steam-pipe, _B B´_, with the boiler, _C_, behind them. _D_ is the furnace. A vertical water-pipe, _E_, is connected with the cold-water vessels, _A A´_, by the pipes, _F F´_, reaching nearly to the bottom. Water is supplied by the pipes, _G G´_, with valves, _a a´_, dipping into the well or ditch, _H_. Steam from the boiler being admitted to each vessel, _A_ and _A´_, alternately, and there condensing, the vacuum formed permits the pressure of the atmosphere to force the water from the well through the pipes, _G_ and _G´_. While one is filling, the steam is forcing the charge of water from the other up the discharge-pipe, _E_. As soon as each is emptied, the steam is shut off from it and turned into the other, and the condensation of the steam remaining in the vessel permits it to fill again. As will be seen presently, this is substantially, and almost precisely, the form of engine of which the invention is usually attributed to Savery, a later inventor. [Illustration: FIG. 8.--Worcester's Engine, A. D. 1665.] [Illustration: FIG. 9.--Wall of Raglan Castle.] Worcester never succeeded in forming the great company which he hoped would introduce his invention on a scale commensurate with its importance, and his fate was that of nearly all inventors. He died poor and unsuccessful. His widow, who lived until 1681, seemed to have become as confident as was Worcester himself that the invention had value, and, long after his death, was still endeavoring to secure its introduction, but with equal non-success. The steam-engine had taken a form which made it inconceivably valuable to the world, at a time when no more efficient means of raising water was available at the most valuable mines than horse-power; but the people, greatly as it was needed, were not yet sufficiently intelligent to avail themselves of the great boon, the acceptance of which was urged upon them with all the persistence and earnestness which characterizes every true inventor. Worcester is described by his biographer as having been a learned, thoughtful, studious, and good man--a Romanist without prejudice or bigotry, a loyal subject, free from partisan intolerance; as a public man, upright, honorable, and humane; as a scholar, learned without being pedantic; as a mechanic, patient, skillful, persevering, and of wonderful ingenuity, and of clear, almost intuitive, apprehension. Yet, with all these natural advantages, reinforced as they were by immense wealth and influence in his earlier life, and by hardly lessened social and political influence when a large fortune had been spent in experiment, and after misfortune had subdued his spirits and left him without money or a home, the inventor failed to secure the introduction of a device which was needed more than any other. Worcester had attained practical success; but the period of speculation was but just closing, and that of the application of steam had not quite yet arrived. The second Marquis of Worcester stands on the record as the first steam-engine builder, and his death marks the termination of the first of those periods into which we have divided the history of the growth of the steam-engine. The "water-commanding engine," as its inventor called it, was the first instance in the history of the steam-engine in which the inventor is known to have "reduced his invention to practice." It is evident, however, that the invention of the separate boiler, important as it was, had been anticipated by Porta, and does not entitle the marquis to the honor, claimed for him by many English authorities, of being _the_ inventor of the steam-engine. Somerset was simply _one_ of those whose works collectively made the steam-engine. After the time of Worcester, we enter upon a stage of history which may properly be termed a period of application; and from this time forward steam continued to play a more and more important part in social economy, and its influence on the welfare of mankind augmented with a rapidly-increasing growth. The knowledge then existing of the immense expansive force of steam, and the belief that it was destined to submit to the control of man and to lend its immense power in every department of industry, were evidently not confined to any one nation. From Italy to Northern Germany, and from France to Great Britain, the distances, measured in time, were vastly greater then than now, when this wonderful genius has helped us to reduce weeks to hours; but there existed, notwithstanding, a very perfect system of communication, and the learning of every centre was promptly radiated to every other. It thus happened that, at this time, the speculative study of the steam-engine was confined to no part of Europe; inventors and experimenters were busy everywhere developing this promising scheme. Jean Hautefeuille, the son of a French _boulanger_, born at Orleans, adopted by the Duchess of Bouillon at the suggestion of De Sourdis, profiting by the great opportunities offered him, entered the Church, and became one of the most learned men and greatest mechanicians of his time. He studied the many schemes then brought forward by inventors with the greatest interest, and was himself prolific of new ideas. In 1678, he proposed the use of alcohol in an engine, "in such a manner that the liquid should evaporate and be condensed, _tour à tour_, without being wasted"[16]--the first recorded plan, probably, for surface-condensation and complete retention of the working-fluid. He proposed a gunpowder-engine, of which[17] he described three varieties. [16] Stuart's "Anecdotes." [17] "Pendule Perpetuelle, avec la manière d'élever d'eau par le moyen de la poudre à canon," Paris, 1678. In one of these engines he displaced the atmosphere by the gases produced by the explosion, and the vacuum thus obtained was utilized in raising water by the pressure of the air. In the second machine, the pressure of the gases evolved by the combustion of the powder acted directly upon the water, forcing it upward; and in the third design, the pressure of the vapor drove a piston, and this engine was described as fitted to supply power for many purposes. There is no evidence that he constructed these machines, however, and they are here referred to simply as indicating that all the elements of the machine were becoming well known, and that an ingenious mechanic, combining known devices, could at this time have produced the steam-engine. Its early appearance should evidently have been anticipated. Hautefeuille, if we may judge from evidence at hand, was the first to propose the use of a piston in a heat-engine, and his gunpowder-engine seems to have been the first machine which would be called a heat-engine by the modern mechanic. The earlier "machines" or "engines," including that of Hero and those of the Marquis of Worcester, would rather be denominated "apparatus," as that term is used by the physicist or the chemist, than a machine or an engine, as the terms are used by the engineer. Huyghens, in 1680, in a memoir presented to the Academy of Sciences, speaks of the expansive force of gunpowder as capable of utilization as a convenient and portable mechanical power, and indicates that he had designed a machine in which it could be applied. This machine of Huyghens is of great interest, not simply because it was the first gas-engine and the prototype of the very successful modern explosive gas-engine of Otto and Langen, but principally as having been the first engine which consisted of a cylinder and piston. The sketch shows its form. It consisted of a cylinder, _A_, a piston, _B_, two relief-pipes, _C C_, fitted with check-valves and a system of pulleys, _F_, by which the weight is raised. The explosion of the powder at _H_ expels the air from the cylinder. When the products of combustion have cooled, the pressure of the atmosphere is no longer counterbalanced by that of air beneath, and the piston is forced down, raising the weight. The plan was never put in practice, although the invention was capable of being made a working and possibly useful machine. [Illustration: FIG. 10.--Huyghens's Engine, 1680.] At about this period the English attained some superiority over their neighbors on the Continent in the practical application of science and the development of the useful arts, and it has never since been lost. A sudden and great development of applied science and of the useful arts took place during the reign of Charles II., which is probably largely attributable to the interest taken by that monarch in many branches of construction and of science. He is said to have been very fond of mathematics, mechanics, chemistry, and natural history, and to have had a laboratory erected, and to have employed learned men to carry on experiments and lines of research for his satisfaction. He was especially fond of the study and investigation of the arts and sciences most closely related to naval architecture and navigation, and devoted much attention to the determination of the best forms of vessels, and to the discovery of the best kinds of ship-timber. His brother, the Duke of York, was equally fond of this study, and was his companion in some of his work. Great as is the influence of the monarch, to-day, in forming the tastes and habits and in determining the direction of the studies and labors of the people, his influence was vastly more potent in those earlier days; and it may well be believed that the rapid strides taken by Great Britain from that time were, in great degree, a consequence of the well-known habits of Charles II., and that the nation, which had an exceptional natural aptitude for mechanical pursuits, should have been prompted by the example of its king to enter upon such a course as resulted in the early attainment of an advanced position in all branches of applied science. The appointment, under Sir Robert Moray, the superintendent of the laboratory of the king, of Master Mechanic, was conferred upon Sir Samuel Morland, a nobleman who, in his practical knowledge of mechanics and in his ingenuity and fruitfulness of invention, was apparently almost equal to Worcester. He was the son of a Berkshire clergyman, was educated at Cambridge, where he studied mathematics with great interest, and entered public life soon after. He served the Parliament under Cromwell, and afterward went to Geneva. He was of a decidedly literary turn of mind, and wrote a history of the Piedmont churches, which gave him great repute with the Protestant party. He was induced subsequently, on the accession of Charles II., to take service under that monarch, whose gratitude he had earned by revealing a plot for his assassination. He received his appointment and a baronetcy in 1660, and immediately commenced making experiments, partly at his own expense and partly at the cost of the royal exchequer, which were usually not at all remunerative. He built hand fire-engines of various kinds, taking patents on them, which brought him as small profits as did his work for the king, and invented the speaking-trumpet, calculating machines, and a capstan. His house at Vauxhall was full of curious devices, the products of his own ingenuity. He devoted much attention to apparatus for raising water. His devices seem to have usually been modifications of the now familiar force-pump. They attracted much attention, and exhibitions were made of them before the king and queen and the court. He was sent to France on business relating to water-works erected for King Charles, and while in Paris he constructed pumps and pumping apparatus for the satisfaction of Louis XIV. In his book,[18] published in Paris in 1683, and presented to the king, and an earlier manuscript,[19] still preserved in the British Museum, Morland shows a perfect familiarity with the power of steam. He says, in the latter: "Water being evaporated by fire, the vapors require a greater space (about two thousand times) than that occupied by the water; and, rather than submit to imprisonment, it will burst a piece of ordnance. But, being controlled according to the laws of statics, and, by science, reduced to the measure of weight and balance, it bears its burden peaceably (like good horses), and thus may be of great use to mankind, especially for the raising of water, according to the following table, which indicates the number of pounds which may be raised six inches, 1,800 times an hour, by cylinders half-filled with water, and of the several diameters and depths of said cylinders." [18] "Elevation des Eaux par toute sorte de Machines réduite à la Mesure au Poids et à la Balance, présentée a Sa Majesté Très Chrétienne, par le Chevalier Morland, Gentilhomme Ordinaire de la Chambre Privée et Maistre de Mechaniques du Roy de la Grande Bretagne, 1683." [19] "Les Principes de la Nouvelle Force de Feu, inventée par le Chevalier Morland, l'an 1682, et présentée a Sa Majesté Très Chrétienne, 1683." He then gives the following table, a comparison of which with modern tables proves Morland to have acquired a very considerable and tolerably accurate knowledge of the volume and pressure of saturated steam: -------------------------+------------------------ CYLINDERS. | POUNDS. -----------+-------------+---------------------- Diameter | Depth | Weight in Feet. | in Feet. | to be Raised. -----------+-------------+---------------------- 1 | 2 | 15 2 | 4 | 120 3 | 6 | 405 4 | 8 | 960 5 | 10 | 1,876 6 | 10 | 3,240 -----------+-------------+---------------------- Number of cylinders having a diameter of 6 feet and a depth of 12 feet. | | 1 | 12 | 3,240 2 | 12 | 6,480 3 | 12 | 9,720 4 | 12 | 12,960 5 | 12 | 16,200 6 | 12 | 19,440 7 | 12 | 22,680 8 | 12 | 25,920 9 | 12 | 29,190 10 | 12 | 32,400 20 | 12 | 64,800 30 | 12 | 97,200 40 | 12 | 129,600 50 | 12 | 162,000 60 | 12 | 194,400 70 | 12 | 226,800 80 | 12 | 259,200 90 | 12 | 291,600 -----------+-------------+---------------------- The rate of enlargement of volume in the conversion of water into steam, as given in Morland's book, appears remarkably accurate when compared with statements made by other early experimenters. Desaguliers gave the ratio of volumes at 14,000, and this was accepted as correct for many years, and until Watt's experiments, which were quoted by Dr. Robison as giving the ratio at between 1,800 and 1,900. Morland also states the "duty" of his engines in the same manner in which it is stated by engineers to-day. Morland must undoubtedly have been acquainted with the work of his distinguished contemporary, Lord Worcester, and his apparatus seems most likely to have been a modification--perhaps improvement--of Worcester's engine. His house was at Vauxhall, and the establishment set up for the king was in the neighborhood. It may be that Morland is to be credited with greater success in the introduction of his predecessor's apparatus than the inventor himself. Dr. Hutton considered this book to have been the earliest account of the steam-engine, and accepts the date--1682--as that of the invention, and adds, that "the project seems to have remained obscure in both countries till 1699, when Savery, who probably knew more of Morland's invention than he owned, obtained a patent," etc. We have, however, scarcely more complete or accurate knowledge of the extent of Morland's work, and of its real value, than of that of Worcester. Morland died in 1696, at Hammersmith, not far from London, and his body lies in Fulham church. From this time forward the minds of many mechanicians were earnestly at work on this problem--the raising of water by aid of steam. Hitherto, although many ingenious toys, embodying the principles of the steam-engine separately, and sometimes to a certain extent collectively, had been proposed, and even occasionally constructed, the world was only just ready to profit by the labors of inventors in this direction. But, at the end of the seventeenth century, English miners were beginning to find the greatest difficulty in clearing their shafts of the vast quantities of water which they were meeting at the considerable depths to which they had penetrated, and it had become a matter of vital importance to them to find a more powerful aid in that work than was then available. They were, therefore, by their necessities stimulated to watch for, and to be prepared promptly to take advantage of, such an invention when it should be offered them. The experiments of Papin, and the practical application of known principles by Savery, placed the needed apparatus in their hands. [Illustration: Thomas Savery.] THOMAS SAVERY was a member of a well-known family of Devonshire, England, and was born at Shilston, about 1650. He was well educated, and became a military engineer. He exhibited great fondness for mechanics, and for mathematics and natural philosophy, and gave much time to experimenting, to the contriving of various kinds of apparatus, and to invention. He constructed a clock, which still remains in the family, and is considered an ingenious piece of mechanism, and is said to be of excellent workmanship. He invented and patented an arrangement of paddle-wheels, driven by a capstan[20] for propelling vessels in calm weather, and spent some time endeavoring to secure its adoption by the British Admiralty and the Navy Board, but met with no success. The principal objector was the Surveyor of the Navy, who dismissed Savery, with a remark which illustrates a spirit which, although not yet extinct, is less frequently met with in the public service now than then: "What have interloping people, that have no concern with us, to do to pretend to contrive or invent things for us?"[21] Savery then fitted his apparatus into a small vessel, and exhibited its operation on the Thames. The invention was never introduced into the navy, however. [20] Harris, "Lexicon Technicum," London, 1710. [21] "Navigation Improved; or, The Art of Rowing Ships of all rates in Calms, with a more Easy, Swift, and Steady Motion, than Oars can," etc., etc. By Thomas Savery, Gent. London, 1698. It was after this time that Savery became the inventor of a steam-engine. It is not known whether he was familiar with the work of Worcester, and of earlier inventors. Desaguliers[22] states that he had read the book of Worcester, and that he subsequently endeavored to destroy all evidence of the anticipation of his own invention by the marquis by buying up all copies of the century that he could find, and burning them. The story is scarcely credible. A comparison of the drawings given of the two engines exhibits, nevertheless, a striking resemblance; and, assuming that of the marquis's engine to be correct, Savery is to be given credit for the finally successful introduction of the "semi-omnipotent" "water-commanding" engine of Worcester. [22] "Experimental Philosophy," vol. ii., p. 465. The most important advance in actual construction, therefore, was made by Thomas Savery. The constant and embarrassing expense, and the engineering difficulties presented by the necessity of keeping the British mines, and particularly the deep pits of Cornwall, free from water, and the failure of every attempt previously made to provide effective and economical pumping-machinery, were noted by Savery, who, July 25, 1698, patented the design of the first engine which was ever actually employed in this work. A working-model was submitted to the Royal Society of London in 1699, and successful experiments were made with it. Savery spent a considerable time in planning his engine and in perfecting it, and states that he expended large sums of money upon it. Having finally succeeded in satisfying himself with its operation, he exhibited a model "Fire-Engine," as it was called in those days, before King William III. and his court, at Hampton Court, in 1698, and obtained his patent without delay. The title of the patent reads: "A grant to Thomas Savery, Gentl., of the sole exercise of a new invention by him invented, for raising of water, and occasioning motion to all sorts of mill-works, by the impellant force of fire, which will be of great use for draining mines, serving towns with water, and for the working of all sorts of mills, when they have not the benefit of water nor constant winds; to hold for 14 years; with usual clauses." Savery now went about the work of introducing his invention in a way which is in marked contrast with that usually adopted by the inventors of that time. He commenced a systematic and successful system of advertisement, and lost no opportunity of making his plans not merely known, but well understood, even in matters of detail. The Royal Society was then fully organized, and at one of its meetings he obtained permission to appear with his model "fire-engine" and to explain its operation; and, as the minutes read, "Mr. Savery entertained the Society with showing his engine to raise water by the force of fire. He was thanked for showing the experiment, which succeeded, according to expectation, and was approved of." He presented to the Society a drawing and specifications of his machine, and "The Transactions"[23] contain a copperplate engraving and the description of his model. It consisted of a furnace, _A_, heating a boiler, _B_, which was connected by pipes, _C C_, with two copper receivers, _D D_. There were led from the bottom of these receivers branch pipes, _F F_, which turned upward, and were united to form a rising main, or "forcing-pipe," _G_. From the top of each receiver was led a pipe, which was turned downward, and these pipes united to form a suction-pipe, which was led down to the bottom of the well or reservoir from which the water was to be drawn. The maximum lift allowable was stated at 24 feet. [23] "Philosophical Transactions, No. 252." Weld's "Royal Society," vol. i., p. 357. Lowthorp's "Abridgment," vol. i. [Illustration: FIG. 11.--Savery's Model, 1698.] The engine was worked as follows: Steam is raised in the boiler, _B_, and a cock, _C_, being opened, a receiver, _D_, is filled with steam. Closing the cock, _C_, the steam condensing in the receiver, a vacuum is created, and the pressure of the atmosphere forces the water up, through the supply-pipe, from the well into the receiver. Opening the cock, _C_, again, the check-valve in the suction-pipe at _E_ closes, the steam drives the water out through the forcing-pipe, _G_, the clack-valve, _E_, on that pipe opening before it, and the liquid is expelled from the top of the pipe. The valve, _C_, is again closed; the steam again condenses, and the engine is worked as before. While one of the two receivers is discharging, the other is filling, as in the machine of the Marquis of Worcester, and thus the steam is drawn from the boiler with tolerable regularity, and the expulsion of water takes place with similar uniformity, the two systems of receivers and pipes being worked alternately by the single boiler. In another and still simpler little machine,[24] which he erected at Kensington (Fig. 12), the same general plan was adopted, combining a suction-pipe, _A_, 16 feet long and 3 inches in diameter; a single receiver, _B_, capable of containing 13 gallons; a boiler, _C_, of about 40 gallons capacity; a forcing-pipe, _D_, 42 feet high, with the connecting pipe and cocks, _E F G_; and the method of operation was as already described, except that _surface-condensation_ was employed, the cock, _F_, being arranged to shower water from the rising main over the receiver, as shown. Of the first engine Switzer says: "I have heard him say myself, that the very first time he played, it was in a potter's house at Lambeth, where, though it was a small engine, yet it (the water) forced its way through the roof, and struck off the tiles in a manner that surprised all the spectators." [24] Bradley, "New Improvements of Planting and Gardening." Switzer, "Hydrostatics," 1729. [Illustration: FIG. 12.--Savery's Engine, 1698.] The Kensington engine cost £50, and raised 3,000 gallons per hour, filling the receiver four times a minute, and required a bushel of coal per day. Switzer remarks: "It must be noted that this engine is but a small one in comparison with many others that are made for coal-works; but this is sufficient for any reasonable family, and other uses required of it in watering all middling gardens." He cautions the operator: "When you have raised water enough, and you design to leave off working the engine, take away all the fire from under the boiler, and open the cock (connected to the funnel) to let out the steam, which would otherwise, were it to remain confined, perhaps burst the engine." With the intention of making his invention more generally known, and hoping to introduce it as a pumping-engine in the mining districts of Cornwall, Savery wrote a prospectus for general circulation, which contains the earliest account of the later and more effective form of engine. He entitled his pamphlet "The Miner's Friend; or, A Description of an Engine to raise Water by Fire described, and the Manner of fixing it in Mines, with an Account of the several Uses it is applicable to, and an Answer to the Objections against it." It was printed in London in 1702, for S. Crouch, and was distributed among the proprietors and managers of mines, who were then finding the flow of water at depths so great as, in some cases, to bar further progress. In many cases, the cost of drainage left no satisfactory margin of profit. In one mine, 500 horses were employed raising water, by the then usual method of using horse-gins and buckets. The approval of the King and of the Royal Society, and the countenance of the mine-adventurers of England, were acknowledged by the author, who addressed his pamphlet to them. The engraving of the engine was reproduced, with the description, in Harris's "Lexicon Technicum," 1704; in Switzer's "Hydrostatics," 1729; and in Desaguliers's "Experimental Philosophy," 1744. The sketch which here follows is a neater engraving of the same machine. Savery's engine is shown in Fig. 13, as described by Savery himself, in 1702, in "The Miner's Friend." _L_ is the boiler in which steam is raised, and through the pipes _O O_ it is alternately let into the vessels _P P_. [Illustration: FIG. 13.--Savery's Engine, A. D. 1702.] Suppose it to pass into the left-hand vessel first. The valve _M_ being closed, and _R_ being opened, the water contained in _P_ is driven out and up the pipe _S_ to the desired height, where it is discharged. The valve _R_ is then closed, and the valve in the pipe _O_; the valve _M_ is next opened, and condensing water is turned upon the exterior of _P_ by the cock _Y_, leading water from the cistern _X_. As the steam contained in _P_ is condensed, forming a vacuum there, a fresh charge of water is driven by atmospheric pressure up the pipe _T_. Meantime, steam from the boiler has been let into the right-hand vessel _P_, the cock _W_ having been first closed, and _R_ opened. The charge of water is driven out through the lower pipe and the cock _R_, and up the pipe _S_ as before, while the other vessel is refilling preparatory to acting in its turn. The two vessels are thus alternately charged and discharged, as long as is necessary. Savery's method of supplying his boiler with water was at once simple and ingenious. The small boiler, _D_, is filled with water from any convenient source, as from the stand-pipe, _S_. A fire is then built under it, and, when the pressure of steam in _D_ becomes greater than in the main boiler, _L_, a communication is opened between their lower ends, and the water passes, under pressure, from the smaller to the larger boiler, which is thus "fed" without interrupting the work. _G_ and _N_ are _gauge-cocks_, by which the height of water in the boilers is determined; they were first adopted by Savery. Here we find, therefore, the first really practicable and commercially valuable steam-engine. Thomas Savery is entitled to the credit of having been the first to introduce a machine in which the power of heat, acting through the medium of steam, was rendered generally useful. It will be noticed that Savery, like the Marquis of Worcester, used a boiler separate from the water-reservoir. He added to the "water-commanding engine" of the marquis the system of _surface-condensation_, by which he was enabled to charge his vessels when it became necessary to refill them; and added, also, the secondary boiler, which enabled him to supply the working-boiler with water without interrupting its work. The machine was thus made capable of working uninterruptedly for a period of time only limited by its own decay. Savery never fitted his boilers with safety-valves, although it was done earlier by Papin; and in deep mines he was compelled to make use of higher pressures than his rudely-constructed boilers could safely bear. Savery's engine was used at a number of mines, and also for supplying water to towns; some large estates, country houses, and other private establishments, employed them for the same purpose. They did not, however, come into general use among the mines, because, according to Desaguliers, they were apprehensive of danger from the explosion of the boilers or receivers. As Desaguliers wrote subsequently: "Savery made a great many experiments to bring this machine to perfection, and did erect several which raised water very well for gentlemen's seats, but could not succeed for mines, or supplying towns, where the water was to be raised very high and in great quantities; for then the steam required being boiled up to such a strength as to be ready to tear all the vessels to pieces." "I have known Captain Savery, at York's buildings, to make steam eight or ten times stronger than common air; and then its heat was so great that it would melt common soft solder, and its strength so great as to blow open several joints of the machine; so that he was forced to be at the pains and charge to have all his joints soldered with spelter or hard solder." Although there were other difficulties in the application of the Savery engine to many kinds of work, this was the most serious one, and explosions did occur with fatal results. The writer just quoted relates, in his "Experimental Philosophy," that a man who was ignorant of the nature of the engine undertook to work a machine which Desaguliers had provided with a safety-valve to avoid this very danger, "and, having hung the weight at the further end of the steelyard, in order to collect more steam in order to make his work the quicker, he hung also a very heavy plumber's iron upon the end of the steelyard; the consequence proved fatal; for, after some time, the steam, not being able, with the safety-cock, to raise up the steelyard loaded with all this unusual weight, burst the boiler with a great explosion, and killed the poor man." This is probably the earliest record of a steam-boiler explosion. Savery proposed to use his engine for driving mills; but there is no evidence that he actually made such an application of the machine, although it was afterward so applied by others. The engine was not well adapted to the drainage of surface-land, as the elevation of large quantities of water through small heights required great capacity of receivers, or compelled the use of several engines for each case. The filling of the receivers, in such cases, also compelled the heating of large areas of cold and wet metallic surfaces by the steam at each operation, and thus made the work comparatively wasteful of fuel. Where used in mines, they were necessarily placed within 30 feet or less of the lowest level, and were therefore exposed to danger of submergence whenever, by any accident, the water should rise above that level. In many cases this would result in the loss of the engine, and the mine would remain "drowned," unless another engine should be procured to pump it out. Where the mine was deep, the water was forced by the pressure of steam from the level of the engine-station to the top of the lift. This compelled the use of pressures of several atmospheres in many cases; and a pressure of three atmospheres, or about 45 pounds per square inch, was considered, in those days, as about the maximum pressure allowable. This difficulty was met by setting a separate engine at every 60 or 80 feet, and pumping the water from one to the other. If any one engine in the set became disabled, the pumping was interrupted until that one machine could be repaired. The size of Savery's largest boilers was not great, their maximum diameter not exceeding two and a half feet. This made it necessary to provide several of his engines, usually, for a single mine, and at each level. The first cost and the expense of repairs were exceedingly serious items. The expense and danger, either real or apparent, were thus sufficient to deter many from their use, and the old method of raising water by horse-power was adhered to. The consumption of fuel with these engines was very great. The steam was not generated economically, as the boilers used were of such simple forms as only could then be produced, and presented too little heating surface to secure a very complete transfer of heat from the gases of combustion to the water within the boiler. This waste in the generation of steam in these uneconomical boilers was followed by still more serious waste in its application, without expansion, to the expulsion of water from a metallic receiver, the cold and wet sides of which absorbed heat with the greatest avidity. The great mass of the liquid was not, however, heated by the steam, and was expelled at the temperature at which it was raised from below. Savery quaintly relates the action of his machine in "The Miner's Friend," and so exactly, that a better description could scarcely be asked: "The steam acts upon the surface of the water in the receiver, which surface only being heated by the steam, it does not condense, but the steam gravitates or presses with an elastic quality like air, and still increasing its elasticity or spring, until it counterpoises, or rather exceeds, the weight of the column of water in the force-pipe, which then it will necessarily drive up that pipe; the steam then takes some time to recover its power, but it will at last discharge the water out at the top of the pipe. You may see on the outside of the receiver how the water goes out, as well as if it were transparent; for, so far as the steam is contained within the vessel, it is dry without, and so hot as scarcely to endure the least touch of the hand; but so far as the water is inside the vessel, it will be cold and wet on the outside, where any water has fallen on it; which cold and moisture vanish as fast as the steam takes the place of the water in its descent." After Savery's death, in 1716, several of these engines were erected in which some improvements were introduced. Dr. Desaguliers, in 1718, built a Savery engine, in which he avoided some defects which he, with Dr. Gravesande, had noted two years earlier. They had then proposed to adopt the arrangement of a single receiver which had been used by Savery himself, as already described, finding, by experiment on a model which they had made for the purpose, that one could be discharged three times, while the same boiler would empty two receivers but once each. In their arrangement, the steam was shut back in the boiler while the receiver was filling with water, and a high pressure thus accumulated, instead of being turned into the second receiver, and the pressure thus kept comparatively low. [Illustration: FIG. 14.--Papin's Two-Way Cock.] In the engine built in 1718, Desaguliers used a spherical boiler, which he provided with the lever safety-valve already applied by Papin, and adopted a comparatively small receiver--one-fifth the capacity of the boiler--of slender cylindrical form, and attached a pipe leading the water for condensation into the vessel, and effected its distribution by means of the "rose," or a "sprinkling-plate," such as is still frequently used in modern engines having jet-condensers. This substitution of jet for surface-condensation was of very great advantage, securing great promptness in the formation of a vacuum and a rapid filling of the receiver. A "two-way cock" admitted steam to the receiver, or, being turned the other way, admitted the cold condensing water. The dispersion of the water in minute streams or drops was a very important detail, not only as securing great rapidity of condensation, but enabling the designer to employ a comparatively small receiver or condenser. The engine is shown in Fig. 15, which is copied from the "Experimental Philosophy" of Desaguliers. [Illustration: FIG. 15.--Engine built by Desaguliers in 1718.] The receiver, _A_, is connected to the boiler, _B_, by a steam-pipe, _C_, terminating at the two-way cock, _D_; the "forcing-pipe," _E_, has at its foot a check-valve, _F_, and the valve _G_ is a similar check at the head of the suction-pipe. _H_ is a strainer, to prevent the ingress of chips or other bodies carried to the pipe by the current; the cap above the valves is secured by a bridle, or stirrup, and screw, _I_, and may be readily removed to clear the valves or to renew them; _K_ is the handle of the two-way cock; _M_ is the injection-cock, and is kept open during the working of the engine; _L_ is the chimney-flue; _N_ and _O_ are gauge-cocks fitted to pipes leading to the proper depths within the boiler, the water-line being somewhere between the levels of their lower ends; _P_ is a lever safety-valve, as first used on the "Digester" of Papin; _R_ is the reservoir into which the water is pumped; _T_ is the flue, leading spirally about the boiler from the furnace, _V_, to the chimney; _Y_ is a cock fitted in a pipe through which the rising-main may be filled from the reservoir, should injection-water be needed when that pipe is empty. Seven of these engines were built, the first of which was made for the Czar of Russia. Its boiler had a capacity of "five or six hogsheads," and the receiver, "holding one hogshead," was filled and emptied four times a minute. The water was raised "by suction" 29 feet, and forced by steam pressure 11 feet higher. Another engine built at about this time, to raise water 29 feet "by suction," and to force it 24 feet higher, made 6 "strokes" per minute, and, when forcing water but 6 or 8 feet, made 8 or 9 strokes per minute. Twenty-five years later a workman overloaded the safety-valve of this engine, by placing the weight at the end and then adding "a very heavy plumber's iron." The boiler exploded, killing the attendant. Desaguliers says that one of these engines, capable of raising ten tons an hour 38 feet, in 1728 or 1729, cost £80, exclusive of the piping. Blakely, in 1766, patented an improved Savery engine, in which he endeavored to avoid the serious loss due to condensation of the steam by direct contact with the water, by interposing a cushion of oil, which floated upon the water and prevented the contact of the steam with the surface of the water beneath it. He also used air for the same purpose, sometimes in double receivers, one supported on the other. These plans did not, however, prove satisfactory. Rigley, of Manchester, England, soon after erected Savery engines, and applied them to the driving of mills, by pumping water into reservoirs, from whence it returned to the wells or ponds from which it had been raised, turning water-wheels as it descended. Such an arrangement was in operation many years at the works of a Mr. Kiers, St. Pancras, London. It is described in detail, and illustrated, in Nicholson's "Philosophical Journal," vol. i., p. 419. It had a "wagon-boiler" 7 feet long, 5 wide, and 5 deep; the wheel was 18 feet in diameter, and drove the lathes and other machinery of the works. In this engine Blakely's plan of injecting air was adopted. The injection-valve was a clack, which closed automatically when the vacuum was formed. The engine consumed 6 or 7 bushels of good coals, and made 10 strokes per minute, raising 70 cubic feet of water 14 feet, and developing nearly 3 horse-power. Many years after Savery's death, in 1774, Smeaton made the first duty-trials of engines of this kind. He found that an engine having a cylindrical receiver 16 inches in diameter and 22 feet high, discharging the water raised 14 feet above the surface of the water in the well, making 12 strokes, and raising 100 cubic feet per minute, developed 2-2/3 horse-power, and consumed 3 hundredweight of coals in four hours. Its duty was, therefore, 5,250,000 pounds raised one foot per bushel of 84 pounds of coals, or 62,500 "foot-pounds" of work per pound of fuel. An engine of slightly greater size gave a duty about 5 per cent. greater. When Louis XIV. revoked the edict of Nantes, by which Henry IV. had guaranteed protection to the Protestants of France, the terrible persecutions at once commenced drove from the kingdom some of its greatest men. Among these was Denys Papin. It was at about this time that the influence of the atmospheric pressure on the boiling-point began to be observed, Dr. Hooke having found that the boiling-point was a fixed temperature under the ordinary pressure of the atmosphere, and the increase in temperature and pressure of steam when confined having been shown by Papin with his "Digester." Denys Papin was of a family which had attached itself to the Protestant Church; but he was given his education in the school of the Jesuits at Blois, and there acquired his knowledge of mathematics. His medical education was given him at Paris, although he probably received his degree at Orleans. He settled in Paris in 1672, with the intention of practising his profession, and devoted all his spare time, apparently, to the study of physics. [Illustration: Denys Papin.] Meantime, that distinguished philosopher, Huyghens, the inventor of the clock and of the gunpowder-engine, had been induced by the linen-draper's apprentice, Colbert, now the most trusted adviser of the king, to take up his residence in Paris, and had been made one of the earliest members of the Academy of Science, which was founded at about that time. Papin became an assistant to Huyghens, and aided him in his experiments in mechanics, having been introduced by Madame Colbert, who was also a native of Blois. Here he devised several modifications of the instruments of Guericke, and printed a description of them.[25] This little book was presented to the Academy, and very favorably noticed. Papin now became well known among contemporary men of science at Paris, and was well received everywhere. Soon after, in the year 1675, as stated by the _Journal des Savants_, he left Paris and took up his residence in England, where he very soon made the acquaintance of Robert Boyle, the founder, and of the members of the Royal Society. Boyle speaks of Papin as having gone to England in the hope of finding a place in which he could satisfactorily pursue his favorite studies. [25] "Nouvelles Expériences du Vuide, avec la description des Machines qui servent à le faire." Paris, 1674. Boyle himself had already been long engaged in the study of pneumatics, and had been especially interested in the investigations which had been original with Guericke. He admitted young Papin into his laboratory, and the two philosophers worked together at these attractive problems. It was while working with Boyle that Papin invented the double air-pump and the air-gun. Papin and his work had now become so well known, and he had attained so high a position in science, that he was nominated for membership in the Royal Academy, and was elected December 16, 1680. He at once took his place among the most talented and distinguished of the great men of his time. He probably invented his "Digester" while in England, and it was first described in a brochure written in English, under the title, "The New Digester." It was subsequently published in Paris.[26] This was a vessel, _B_ (Fig. 16), capable of being tightly closed by a screw, _D_, and a lid, _C_, in which food could be cooked in water raised by a furnace, _A_, to the temperature due to any desired safe pressure of steam. The pressure was determined and limited by a weight, _W_, on the safety-valve lever, _G_. It is probable that this essential attachment to the steam-boiler had previously been used for other purposes; but Papin is given the credit of having first made use of it to control the pressure of steam. [26] "La manière d'amollir les os et de faire cuire toutes sortes de viandes," etc. [Illustration: FIG. 16.--Papin's Digester, 1680.] From England, Papin went to Italy, where he accepted membership and held official position in the Italian Academy of Science. Papin remained in Venice two years, and then returned to England. Here, in 1687, he announced one of his inventions, which is just becoming of great value in the arts. He proposed to transmit power from one point to another, over long distances, by the now well-known "pneumatic" method. At the point where power was available, he exhausted a chamber by means of an air-pump, and, leading a pipe to the distant point at which it was to be utilized, there withdrew the air from behind a piston, and the pressure of the air upon the latter caused it to recede into the cylinder, in which it was fitted, raising a weight, of which the magnitude was proportionate to the size of the piston and the degree of exhaustion. Papin was not satisfactorily successful in his experiments; but he had created the germ of the modern system of pneumatic transmission of power. His disappointment at the result of his efforts to utilize the system was very great, and he became despondent, and anxious to change his location again. In 1687 he was offered the chair of Mathematics at Marburg by Charles, the Landgrave of Upper Hesse, and, accepting the appointment, went to Germany. He remained in Germany many years, and continued his researches with renewed activity and interest. His papers were published in the "Acta Eruditorum" at Leipsic, and in the "Philosophical Transactions" at London. It was while at Marburg that his papers descriptive of his method of pneumatic transmission of power were printed.[27] [27] "Recueil des diverses Pieces touchant quelques Nouvelles Machines et autres Sujets Philosophiques," M. D. Papin. Cassel, 1695. In the "Acta Eruditorum" of 1688 he exhibited a practicable plan, in which he exhausted the air from a set of engines or pumps by means of pumps situated at a long distance from the point of application of the power, and at the place where the prime mover--which was in this case a water-wheel--was erected. After his arrival at the University of Marburg, Papin exhibited to his colleagues in the faculty a modification of Huyghens's gunpowder-engine, in which he had endeavored to obtain a more perfect vacuum than had Huyghens in the first of these machines. Disappointed in this, he finally adopted the expedient of employing steam to displace the air, and to produce, by its condensation, the perfect vacuum which he sought; and he thus produced _the first steam-engine with a piston_, and the first piston steam-engine, in which condensation was produced to secure a vacuum. It was described in the "Acta" of Leipsic,[28] in June, 1690, under the title, "Nova Methodus ad vires motrices validissimas leri pretio comparandeo" ("A New Method of securing cheaply Motive Power of considerable Magnitude"). He describes first the gunpowder-engine, and continues by stating that, "until now, all experiments have been unsuccessful; and after the combustion of the exploded powder, there always remains in the cylinder about one-fifth its volume of air." He says that he has endeavored to arrive by another route at the same end; and "as, by a natural property of water, a small quantity of this liquid, vaporized by the action of heat, acquires an elasticity like that of the air, and returns to the liquid state again on cooling, without retaining the least trace of its elastic force," he thought that it would be easy to construct machines in which, "by means of a moderate heat, and without much expense," a more perfect vacuum could be produced than could be secured by the use of gunpowder. [28] "Acta Eruditorum," Leipsic, 1690. [Illustration: FIG. 17.--Papin's Engine.] The first machine of Papin (Fig. 17) was very similar to the gunpowder-engine already described as the invention of Huyghens. In place of gunpowder, a small quantity of water is placed at the bottom of the cylinder, _A_; a fire is built beneath it, "the bottom being made of very thin metal," and the steam formed soon raises the piston, _B_, to the top, where a latch, _E_, engaging a notch in the piston-rod, _H_, holds it up until it is desired that it shall drop. The fire being removed, the steam condenses, and a vacuum is formed below the piston, and the latch, _E_, being disengaged, the piston is driven down by the superincumbent atmosphere and raises the weight which has been, meantime, attached to a rope, _L_, passing from the piston-rod over pulleys, _T T_. The machine had a cylinder two and a half inches in diameter, and raised 60 pounds once a minute; and Papin calculated that a machine of a little more than two feet diameter of cylinder and of four feet stroke would raise 8,000 pounds four feet per minute--i. e., that it would yield about one horse-power. The inventor claimed that this new machine would be found useful in relieving mines from water, in throwing bombs, in ship-propulsion, attaching revolving paddles--i. e., paddle-wheels--to the sides of the vessel, which wheels were to be driven by several of his engines, in order to secure continuous motion, the piston-rods being fitted with racks which were to engage ratchet-wheels on the paddle-shafts. "The principal difficulty," he says, answering anticipated objections, "is that of making these large cylinders." In a reprint describing his invention, in 1695, Papin gives a description of a "newly-invented furnace," a kind of fire-box steam-boiler, in which the fire, completely surrounded by water, makes steam so rapidly that his engine could be driven at the rate of four strokes per minute by the steam supplied by it. Papin also proposed the use of a peculiar form of furnace with this engine, which, embodying as it does some suggestions that very probably have since been attributed to later inventors, deserves special notice. In this furnace, Papin proposed to burn his fuel on a grate within a furnace arranged with a _down-draught_, the air entering above the grate, passing _down_ through the fire, and from the ash-pit through a side flue to the chimney. In starting the fire, the coal was laid on the grate, covered with wood, and the latter was ignited, the flame, passing downward through the coal, igniting that in turn, and, as claimed by Papin, the combustion was complete, and the formation of smoke was entirely prevented. He states, in "Acta Eruditorum," that the heat was intense, the saving of fuel very great, and that the only difficulty was to find a refractory material which would withstand the high temperature attained. This is the first fire-box and flue boiler of which we have record. The experiment is supposed to have led Papin to suggest the use of a hot-blast, as practised by Neilson more than a century later, for reducing metals from their ores. Papin made another boiler having a flue winding through the water-space, and presenting a heating surface of nearly 80 square feet. The flue had a length of 24 feet, and was about 10 inches square. It is not stated what were the maximum pressures carried on these boilers; but it is known that Papin had used very high pressures in his digesters--probably between 1,200 and 1,500 pounds per square inch. In the year 1705, Leibnitz, then visiting England, had seen a Savery engine, and, on his return, described it to Papin, sending him a sketch of the machine. Papin read the letter and exhibited the sketch to the Landgrave of Hesse, and Charles at once urged him to endeavor to perfect his own machine, and to continue the researches which he had been intermittently pursuing since the earlier machine had been exhibited in public. In a small pamphlet printed at Cassel in 1707,[29] Papin describes a new form of engine, in which he discards the original plan of a modified Huyghens engine, with tight-fitting piston and cylinder, raising its load by indirect action, and makes a modified Savery engine, which he calls the "Elector's Engine," in honor of his patron. This is the engine shown in the engraving, and as proposed to be used by him in turning a water-wheel. [29] "Nouvelle manière d'élever l'Eau par la Force du Feu, mis en Lumière," par D. Papin. Cassel, 1707. The sketch is that given by the inventor in his memoir. It consists (Fig. 18) of a steam-boiler, _a_, from which steam is led through the cock, _c_, to the working cylinder, _n n_. The water beneath the floating-piston, _h_, which latter serves simply as a cushion to protect the steam from sudden condensation or contact with the water, is forced into the vessel _r r_, which is a large air-chamber, and which serves to render the outflow of water comparatively uniform, and the discharge occurs by means of the pipe _q_, from which the water rises to the desired height. A fresh supply of water is introduced through the funnel _k_, after condensation of the steam in _n n_, and the operation of expulsion is repeated. [Illustration: FIG. 18.--Papin's Engine and Water-Wheel, A. D. 1707.] This machine is evidently a retrogression, and Papin, after having earned the honor of having invented the first steam-engine of the typical form which has since become so universally applied, forfeited that credit by his evident ignorance of its superiority over existing devices, and by attempting unsuccessfully to perfect the inferior device of another inventor. Subsequently, Papin made an attempt to apply the steam-engine to the propulsion of vessels, the account of which will be given in the chapter on Steam-Navigation. Again disappointed, Papin once more visited England, to renew his acquaintance with the _savans_ of the Royal Society; but Boyle had died during the period which Papin had spent in Germany, and the unhappy and disheartened inventor and philosopher died in 1810, without having seen any one of his many devices and ingenious inventions a practical success. [Illustration] CHAPTER II. _THE STEAM-ENGINE AS A TRAIN OF MECHANISM._ "The introduction of new Inventions seemeth to be the very chief of all human Actions. The Benefits of new Inventions may extend to all Mankind universally; but the Good of political Achievements can respect but some particular Cantons of Men; these latter do not endure above a few Ages, the former forever. Inventions make all Men happy, without either Injury or Damage to any one single Person. Furthermore, new Inventions are, as it were, new Erections and Imitations of God's own Works."--BACON. THE MODERN TYPE, AS DEVELOPED BY NEWCOMEN, BEIGHTON, AND SMEATON. At the beginning of the eighteenth century every element of the modern type of steam-engine had been separately invented and practically applied. The character of atmospheric pressure, and of the pressure of gases, had become understood. The nature of a vacuum was known, and the method of obtaining it by the displacement of the air by steam, and by the condensation of the vapor, was understood. The importance of utilizing the power of steam, and the application of condensation in the removal of atmospheric pressure, was not only recognized, but had been actually and successfully attempted by Morland, Papin, and Savery. Mechanicians had succeeded in making steam-boilers capable of sustaining any desired or any useful pressure, and Papin had shown how to make them comparatively safe by the attachment of the safety-valve. They had made steam-cylinders fitted with pistons, and had used such a combination in the development of power. It now only remained for the engineer to combine known forms of mechanism in a practical machine which should be capable of economically and conveniently utilizing the power of steam through the application of now well-understood principles, and by the intelligent combination of physical phenomena already familiar to scientific investigators. Every essential fact and every vital principle had been learned, and every one of the needed mechanical combinations had been successfully effected. It was only requisite that an inventor should appear, capable of perceiving that these known facts and combinations of mechanism, properly illustrated in a working machine, would present to the world its greatest physical blessing. The defects of the simple engines constructed up to this time have been noted as each has been described. None of them could be depended upon for safe, economical, and continuous work. Savery's was the most successful of all. But the engine of Savery, even with the improvements of Desaguliers, was unsafe where most needed, because of the high pressures necessarily carried in its boilers when pumping from considerable depths; it was uneconomical, in consequence of the great loss of heat in its forcing-cylinders when the hot steam was surrounded at its entrance by colder bodies; it was slow in operation, of great first cost, and expensive in first cost and in repairs, as well as in its operation. It could not be relied upon to do its work uninterruptedly, and was thus in many respects a very unsatisfactory machine. The man who finally effected a combination of the elements of the modern steam-engine, and produced a machine which is unmistakably a true engine--i. e., a train of mechanism consisting of several elementary pieces combined in a train capable of transmitting a force applied at one end and of communicating it to the resistance to be overcome at the other end--was THOMAS NEWCOMEN, an "iron-monger" and blacksmith of Dartmouth, England. The engine invented by him, and known as the "Atmospheric Steam-Engine," is the first of an entirely new type. The old type of engine--the steam-engine as a simple machine--had been given as great a degree of perfection, by the successive improvements of Worcester, Savery, and Desaguliers, as it was probably capable of attaining by any modification of its details. The next step was necessarily a complete change of type; and to effect such a change, it was only necessary to combine devices already known and successfully tried. But little is known of the personal history of Newcomen. His position in life was humble, and the inventor was not then looked upon as an individual of even possible importance in the community. He was considered as one of an eccentric class of schemers, and of an order which, concerning itself with mechanical matters, held the lowest position in the class. It is supposed that Savery's engine was perfectly well known to Newcomen, and that the latter may have visited Savery at his home in Modbury, which was but fifteen miles from the residence of Newcomen. It is thought, by some biographers of these inventors, that Newcomen was employed by Savery in making the more intricate forgings of his engine. Harris, in his "Lexicon Technicum," states that drawings of the engine of Savery came into the hands of Newcomen, who made a model of the machine, set it up in his garden, and then attempted its improvement; but Switzer says that Newcomen "was as early in his invention as Mr. Savery was in his." Newcomen was assisted in his experiments by John Calley, who, with him, took out the patent. It has been stated that a visit to Cornwall, where they witnessed the working of a Savery engine, first turned their attention to the subject; but a friend of Savery has stated that Newcomen was as early with his general plans as Savery. After some discussion with Calley, Newcomen entered into correspondence with Dr. Hooke, proposing a steam-engine to consist of a _steam-cylinder containing a piston similar to that of Papin's, and to drive a separate pump_, similar to those generally in use where water was raised by horse or wind power. Dr. Hooke advised and argued strongly against their plan, but, fortunately, the obstinate belief of the unlearned mechanics was not overpowered by the disquisitions of their distinguished correspondent, and Newcomen and Calley attempted an engine on their peculiar plan. This succeeded so well as to induce them to continue their labors, and, in 1705, to patent,[30] in combination with Savery--who held the exclusive right to practise surface-condensation, and who induced them to allow him an interest with them--an engine combining a steam-cylinder and piston, surface-condensation, a separate boiler, and separate pumps. [30] It has been denied that a patent was issued, but there is no doubt that Savery claimed and received an interest in the new engine. In the atmospheric-engine, as first designed, the slow process of condensation by the application of the condensing water to the exterior of the cylinder, to produce the vacuum, caused the strokes of the engine to take place at very long intervals. An improvement was, however, soon effected, which immensely increased the rapidity of condensation. A jet of water was thrown directly _into_ the cylinder, thus effecting for the Newcomen engine just what Desaguliers had done for the Savery engine previously. As thus improved, the Newcomen engine is shown in Fig. 19. Here _b_ is the boiler. Steam passes from it through the cock, _d_, and up into the cylinder, _a_, equilibrating the pressure of the atmosphere, and allowing the heavy pump-rod, _k_, to fall, and, by the greater weight acting through the beam, _i i_, to raise the piston, _s_, to the position shown. The rod _m_ carries a counterbalance, if needed. The cock _d_ being shut, _f_ is then opened, and a jet of water from the reservoir, _g_, enters the cylinder, producing a vacuum by the condensation of the steam. The pressure of the air above the piston now forces it down, again raising the pump-rods, and thus the engine works on indefinitely. [Illustration: FIG. 19.--Newcomen's Engine, A. D. 1705.] The pipe _h_ is used for the purpose of keeping the upper side of the piston covered with water, to prevent air-leaks--a device of Newcomen. Two gauge-cocks, _c c_, and a safety-valve, _N_, are represented in the figure, but it will be noticed that the latter is quite different from the now usual form. Here, the pressure used was hardly greater than that of the atmosphere, and the weight of the valve itself was ordinarily sufficient to keep it down. The condensing water, together with the water of condensation, flows off through the open pipe _p_. Newcomen's first engine made 6 or 8 strokes a minute; the later and improved engines made 10 or 12. The steam-engine has now assumed a form that somewhat resembles the modern machine. The Newcomen engine is seen at a glance to have been a combination of earlier ideas. It was the engine of Huyghens, with its cylinder and piston as improved by Papin, by the substitution of steam for the gases generated by the explosion of gunpowder; still further improved by Newcomen and Calley by the addition of the method of condensation used in the Savery engine. It was further modified, with the object of applying it directly to the working of the pumps of the mines by the introduction of the overhead beam, from which the piston was suspended at one end and the pump-rod at the other. The advantages secured by this combination of inventions were many and manifest. The piston not only gave economy by interposing itself between the impelling and the resisting fluid, but, by affording opportunity to make the area of piston as large as desired, it enabled Newcomen to use any convenient pressure and any desired proportions for any proposed lift. The removal of the water to be lifted from the steam-engine proper and handling it with pumps, was an evident cause of very great economy of steam. The disposal of the water to be raised in this way also permitted the operations of condensation of steam, and the renewal of pressure on the piston, to be made to succeed each other with rapidity, and enabled the inventor to choose, unhampered, the device for securing promptly the action of condensation. Desaguliers, in his account of the introduction of the engine of Newcomen, says that, with his coadjutor Calley, he "made several experiments in private about the year 1710, and in the latter end of the year 1711 made proposals to drain the water of a colliery at Griff, in Warwickshire, where the proprietors employed 500 horses, at an expense of £900 a year; but, their invention not meeting with the reception they expected, in March following, through the acquaintance of Mr. Potter, of Bromsgrove, in Worcestershire, they bargained to draw water for Mr. Back, of Wolverhampton, where, after a great many laborious attempts, they did make the engine work; but, not being either philosophers to understand the reason, or mathematicians enough to calculate the powers and proportions of the parts, they very luckily, by accident, found what they sought for. "They were at a loss about the pumps, but, being so near Birmingham, and having the assistance of so many admirable and ingenious workmen, they came, about 1712, to the method of making the pump-valves, clacks, and buckets, whereas they had but an imperfect notion of them before. One thing is very remarkable: as they were at first working, they were surprised to see the engine go several strokes, and very quick together, when, after a search, they found a hole in the piston, which let the cold water in to condense the steam in the inside of the cylinder, whereas, before, they had always done it on the outside. They used before to work with a buoy to the cylinder, inclosed in a pipe, which buoy rose when the steam was strong and opened the injection, and made a stroke; thereby they were only capable of giving 6, 8, or 10 strokes in a minute, till a boy, named Humphrey Potter, in 1713, who attended the engine, added (what he called a _scoggan_) a catch, that the beam always opened, and then it would go 15 or 16 strokes a minute. But, this being perplexed with catches and strings, Mr. Henry Beighton, in an engine he had built at Newcastle-upon-Tyne in 1718, took them all away but the beam itself, and supplied them in a much better manner." In illustration of the application of the Newcomen engine to the drainage of mines, Farey describes a small machine, of which the pump is 8 inches in diameter, and the lift 162 feet. The column of water to be raised weighed 3,535 pounds. The steam-piston was made 2 feet in diameter, giving an area of 452 square inches. The net working-pressure was assumed at 10-3/4 pounds per square inch; the temperature of the water of condensation and of uncondensed vapor after the entrance of the injection-water being usually about 150° Fahr. This gave an excess of pressure on the steam-side of 1,324 pounds, the total pressure on the piston being 4,859 pounds. One-half of this excess is counterweighted by the pump-rods, and by weight on that end of the beam; and the weight, 662 pounds, acting on each side alternately as a surplus, produced the requisite rapidity of movement of the machine. This engine was said to make 15 strokes per minute, giving a speed of piston of 75 feet per minute, and the power exerted usefully was equivalent to 265,125 pounds raised one foot high per minute. As the horse-power is equivalent to 33,000 "foot-pounds" per minute, the engine was of 265125/33000 = 8.034--almost exactly 8 horse-power. It is instructive to contrast this estimate with that made for a Savery engine doing the same work. The latter would have raised the water about 26 feet in its "suction-pipe," and would then have forced it, by the direct pressure of steam, the remaining distance of 136 feet; and the steam-pressure required would have been nearly 60 pounds per square inch. With this high temperature and pressure, the waste of steam by condensation in the forcing-vessels would have been so great that it would have compelled the adoption of two engines of considerable size, each lifting the water one-half the height, and using steam of about 25 pounds pressure. Potter's rude valve-gear was soon improved by Henry Beighton, in an engine which that talented engineer erected at Newcastle-upon-Tyne in 1718, and in which he substituted substantial materials for the cords, as in Fig. 20. In this sketch, _r_ is a plug-tree, plug-rod, or plug-frame, as it is variously called, suspended from the great beam, with which it rises and falls, bringing the pins _p_ and _k_, at the proper moment, in contact with the handles _k k_ and _n n_ of the valves, moving them in the proper direction and to the proper extent. A lever safety-valve is here used, at the suggestion, it is said, of Desaguliers. The piston was packed with leather or with rope, and lubricated with tallow. [Illustration: FIG. 20.--Beighton's Valve-Gear, A. D. 1718.] After the death of Beighton, the atmospheric engine of Newcomen retained its then standard form for many years, and came into extensive use in all the mining districts, particularly in Cornwall, and was also applied occasionally to the drainage of wet lands, to the supply of water to towns, and it was even proposed by Hulls to be used for ship-propulsion. The proportions of the engines had been determined in a hap-hazard way, and they were in many cases very unsafe. John Smeaton, the most distinguished engineer of his time, finally, in 1769, experimentally determined proper proportions, and built several of these engines of very considerable size. He built his engines with steam-cylinders of greater length of stroke than had been customary, and gave them such dimensions as, by giving a greater excess of pressure on the steam-side, enabled him to obtain a greatly-increased speed of piston. The first of his new style of engine was erected at Long Benton, near Newcastle-upon-Tyne, in 1774. Fig. 21[31] illustrates its principal characteristic features. The boiler is not shown. [31] A fac-simile of a sketch in Galloway's "On the Steam-Engine," etc. The steam is led to the engine through the pipe, _C_, and is regulated by turning the cock in the receiver, _D_, which connects with the steam-cylinder by the pipe, _E_, which latter pipe rises a little way above the bottom of the cylinder, _F_, in order that it may not drain off the injection-water into the steam-pipe and receiver. The steam-cylinder, about ten feet in length, is fitted with a carefully-made piston, _G_, having a flanch rising four or five inches and extending completely around its circumference, and nearly in contact with the interior surface of the cylinder. Between this flanch and the cylinder is driven a "packing" of oakum, which is held in place by weights; this prevents the leakage of air, water, or steam, past the piston, as it rises and falls in the cylinder at each stroke of the engine. The chain and piston-rod connect the piston to the beam, _I I_. The arch-heads at each end of the beam keep the chains of the piston-rod and the pump-rods perpendicular and in line. [Illustration: FIG. 21.--Smeaton's Newcomen Engine.] A "jack-head" pump, _N_, is driven by a small beam deriving its motion from the plug-rod at _g_, raises the water required for condensing the steam, and keeps the cistern, _O_, supplied. This "jack-head cistern" is sufficiently elevated to give the water entering the cylinder the velocity requisite to secure prompt condensation. A waste-pipe carries away any surplus water. The injection-water is led from the cistern by the pipe, _P P_, which is two or three inches in diameter, and the flow of water is regulated by the injection-cock, _r_. The cap at the end, _d_, is pierced with several holes, and the stream thus divided rises in jets when admitted, and, striking the lower side of the piston, the spray thus produced very rapidly condenses the steam, and produces a vacuum beneath the piston. The valve, _e_, on the upper end of the injection-pipe, is a check-valve, to prevent leakage into the engine when the latter is not in operation. The little pipe, _f_, supplies water to the upper side of the piston, and, keeping it flooded, prevents the entrance of air when the packing is not perfectly tight. The "working-plug," or plug-rod, _Q_, is a piece of timber slit vertically, and carrying pins which engage the handles of the valves, opening and closing them at the proper times. The steam-cock, or regulator, has a handle, _h_, by which it is moved. The iron rod, _i i_, or spanner, gives motion to the handle, _h_. The vibrating lever, _k l_, called the _Y_, or the "tumbling-bob," moves on the pins, _m n_, and is worked by the levers, _o p_, which in turn are moved by the plug-tree. When _o_ is depressed, the loaded end, _k_, is given the position seen in the sketch, and the leg _l_ of the _Y_ strikes the spanner, _i i_, and, opening the steam-valve, the piston at once rises as steam enters the cylinder, until another pin on the plug-rod raises the piece, _P_, and closes the regulator again. The lever, _q r_, connects with the injection-cock, and is moved, when, as the piston rises, the end, _q_, is struck by a pin on the plug-rod, and the cock is opened and a vacuum produced. The cock is closed on the descent of the plug-tree with the piston. An eduction-pipe, _R_, fitted with a clock, conveys away the water in the cylinder at the end of each down-stroke; the water thus removed is collected in the hot-well, _S_, and is used as feed-water for the boiler, to which it is conveyed by the pipe _T_. At each down-stroke, while the water passes out through _R_, the air which may have collected in the cylinder is driven out through the "snifting-valve," _s_. The steam-cylinder is supported on strong beams, _t t_; it has around its upper edge a guard, _v_, of lead, which prevents the overflow of the water on the top of the piston. The excess of this water flows away to the hot-well through the pipe _W_. Catch-pins, _x_, are provided, to prevent the beam descending too far should the engine make too long a stroke; two wooden springs, _y y_, receive the blow. The great beam is carried on sectors, _z z_, to diminish losses by friction. The boilers of Newcomen's earlier engines were made of copper where in contact with the products of combustion, and their upper parts were of lead. Subsequently, sheet-iron was substituted. The steam-space in the boiler was made of 8 or 10 times the capacity of the cylinder of the engine. Even in Smeaton's time, a chimney-damper was not used, and the supply of steam was consequently very variable. In the earlier engines, the cylinder was placed on the boiler; afterward, they were placed separately, and supported on a foundation of masonry. The injection or "jack-head" cistern was placed from 12 to 30 feet above the engine, the velocity due the greater altitude being found to give the most perfect distribution of the water and the promptest condensation. [Illustration: FIG. 22.--Boiler of Newcomen's Engine, 1768.] Smeaton covered the lower side of his steam-pistons with wooden plank about 2-1/4 inches thick, in order that it should absorb and waste less heat than when the iron was directly exposed to the steam. Mr. Beighton was the first to use the water of condensation for feeding the boiler, taking it directly from the eduction-pipe, or the "hot-well." Where only a sufficient amount of pure water could be obtained for feeding the boiler, and the injection-water was "hard," Mr. Smeaton applied a heater, immersed in the hot-well, through which the feed passed, absorbing heat from the water of condensation _en route_ to the boiler. Farey first proposed the use of the "coil-heater"--a pipe, or "worm," which, forming a part of the feed-pipe, was set in the hot-well. As early as 1743, the metal used for the cylinders was cast-iron. The earlier engines had been fitted with brass cylinders. Desaguliers recommended the iron cylinders, as being smoother, thinner, and as having less capacity for heat than those of brass. In a very few years after the invention of Newcomen's engine it had been introduced into nearly all large mines in Great Britain; and many new mines, which could not have been worked at all previously, were opened, when it was found that the new machine could be relied upon to raise the large quantities of water to be handled. The first engine in Scotland was erected in 1720 at Elphinstone, in Stirlingshire. One was put up in Hungary in 1723. The first mine-engine, erected in 1712 at Griff, was 22 inches in diameter, and the second and third engines were of similar size. That erected at Ansthorpe was 23 inches in diameter of cylinder, and it was a long time before much larger engines were constructed. Smeaton and others finally made them as large as 6 feet in diameter. In calculating the lifting-power of his engines, Newcomen's method was "to square the diameter of the cylinder in inches, and, cutting off the last figure, he called it 'long hundredweights;' then writing a cipher on the right hand, he called the number on that side 'odd pounds;' this he reckoned tolerably exact at a mean, or rather when the barometer was above 30 inches, and the air heavy." In allowing for frictional and other losses, he deducted from one-fourth to one-third. Desaguliers found the rule quite exact. The usual mean pressure resisting the motion of the piston averaged, in the best engines, about 8 pounds per square inch of its area. The speed of the piston was from 150 to 175 feet per minute. The temperature of the hot-well was from 145° to 175° Fahr. Smeaton made a number of test-trials of Newcomen engines to determine their "duty"--i. e., to ascertain the expenditure of fuel required to raise a definite quantity of water to a stated height. He found an engine 10 inches in diameter of cylinder, and of 3 feet stroke, could do work equal to raising 2,919,017 pounds of water one foot high, with a bushel of coals weighing 84 pounds. One of Smeaton's larger engines, erected at Long Benton, was 52 inches in diameter of cylinder and of 7 feet stroke of piston, and made 12 strokes per minute. Its load was equal to 7-1/2 pounds per square inch of piston-area, and its effective capacity about 40 horse-power. Its duty was 9-1/2 millions of pounds raised one foot high per bushel of coals. Its boiler evaporated 7.88 pounds of water per pound of fuel consumed. It had 35 square feet of grate-surface and 142 square feet of heating-surface beneath the boilers, and 317 square feet in the flues--a total of 459 square feet. The moving parts of this engine weighed 8-1/2 tons. Smeaton erected one of these engines at the Chasewater mine, in Cornwall, in 1775, which was of very considerable size. It was 6 feet in diameter of steam-cylinder, and had a maximum stroke of piston of 9-1/2 feet. It usually worked 9 feet. The pumps were in three lifts of about 100 feet each, and were 16-3/4 inches in diameter. Nine strokes were made per minute. This engine replaced two others, of 64 and of 62 inches diameter of cylinder respectively, and both of 6 feet stroke. One engine at the lower lift supplied the second, which was set above it. The lower one had pumps 18-1/2 inches in diameter, and raised the water 144 feet; the upper engine raised the water 156 feet, by pumps 17-1/2 inches in diameter. The later engine replacing them exerted 76-1/2 horse-power. There were three boilers, each 15 feet in diameter, and having each 23 square feet of grate-surface. The chimney was 22 feet high. The great beam, or "lever," of this engine was built up of 20 beams of fir in two sets, placed side by side, and ten deep, strongly bolted together. It was over 6 feet deep at the middle and 5 feet at the ends, and was 2 feet thick. The "main centres," or journals, on which it vibrated were 8-1/2 inches in diameter and 8-1/2 inches long. The cylinder weighed 6-1/2 tons, and was paid for at the rate of 28 shillings per hundredweight. By the end of the eighteenth century, therefore, the engine of Newcomen, perfected by the ingenuity of Potter and of Beighton, and by the systematic study and experimental research of Smeaton, had become a well-established form of steam-engine, and its application to raising water had become general. The coal-mines of Coventry and of Newcastle had adopted this method of drainage; and the tin and the copper mines of Cornwall had been deepened, using, for drainage, engines of the largest size. Some engines had been set up in and about London, the scene of Worcester's struggles and disappointments, where they were used to supply water to large houses. Others were in use in other large cities of England, where water-works had been erected. Some engines had also been erected to drive mills indirectly by raising water to turn water-wheels. This is said by Farey to have been first practised in 1752, at a mill near Bristol, and became common during the next quarter of a century. Many engines had been built in England and sent across the channel, to be applied to the drainage of mines on the Continent. Belidor[32] stated that the manufacture of these "fire-engines" was exclusively confined to England; and this remained true many years after his time. When used for the drainage of mines, the engine usually worked the ordinary lift or bucket pump; when employed for water-supply to cities, the force or plunger pump was often employed, the engine being placed below the level of the reservoir. Dr. Rees states that this engine was in common use among the collieries of England as early as 1725. [32] "Architecture Hydraulique," 1734. The Edmonstone colliery was licensed, in 1725, to erect an engine, not to exceed 28 inches diameter of cylinder and 9 feet stroke of piston, paying a royalty of £80 per annum for eight years. This engine was built in Scotland, by workmen sent from England, and cost about £1,200. Its "great cost" is attributed to an extensive use of brass. The workmen were paid their expenses and 15_s._ per week as wages. The builders were John and Abraham Potter, of Durham. An engine built in 1775, having a steam-cylinder 48 inches in diameter and of 7 feet stroke, cost about £2,000. Smeaton found 57 engines at work near Newcastle in 1767, ranging in size from 28 to 75 inches in diameter of cylinder, and of, collectively, about 1,200 horse-power. Fifteen of these engines gave an average of 98 square inches of piston to the horse-power, and the average duty was 5,590,000 pounds raised 1 foot high by 1 bushel (84 pounds) of coal. The highest duty noted was 7.44 millions; the lowest was 3.22 millions. The most efficient engine had a steam-cylinder 42 inches in diameter; the load was equivalent to 9-1/4 pounds per square inch of piston-area, and the horse-power developed was calculated to be 16.7. Price, writing in 1778, says, in the Appendix to his "Mineralogia Cornubiensis:" "Mr. Newcomen's invention of the fire-engine enabled us to sink our mines to twice the depth we could formerly do by any other machinery. Since this invention was completed, most other attempts at its improvement have been very unsuccessful; but the vast consumption of fuel in these engines is an immense drawback on the profit of our mines, for every fire-engine of magnitude consumes £3,000 worth of coals per annum. This heavy tax amounts almost to a prohibition." Smeaton was given the description, in 1773, of a _stone_ boiler, which was used with one of these engines at a copper mine at Camborne, in Cornwall. It contained three copper flues 22 inches in diameter. The gases were passed through these flues successively, finally passing off to the chimney. This boiler was cemented with hydraulic mortar. It was 20 feet long, 9 feet wide, and 8-1/2 feet deep. It was heated by the waste heat from the roasting-furnaces. This was one of the earliest flue-boilers ever made. In 1780, Smeaton had a list of 18 large engines working in Cornwall. The larger number of them were built by Jonathan Hornblower and John Nancarron. At this time, the largest and best-known pumping-engine for water-works was at York Buildings, in Villiers Street, Strand, London. It had been in operation since 1752, and was erected beside one of Savery's engines, built in 1710. It had a steam-cylinder 45 inches in diameter, and a stroke of piston of 8 feet, making 7-1/2 strokes per minute, and developing 35-1/2 horse-power. Its boiler was dome-shaped, of copper, and contained a large central fire-box and a spiral flue leading outward to the chimney. Another somewhat larger machine was built and placed beside this engine, some time previous to 1775. Its cylinder was 49 inches in diameter, and its stroke 9 feet. It raised water 102 feet. This engine was altered and improved by Smeaton in 1777, and continued in use until 1813. Smeaton, as early as 1765, designed a _portable_ engine,[33] in which he supported the machinery on a wooden frame mounted on short legs and strongly put together, so that the whole machine could be transported and set at work wherever convenient. [33] Smeaton's "Reports," vol. i., p. 223. [Illustration: FIG. 23.--Smeaton's Portable-Engine Boiler, 1765.] In place of the beam, a large pulley was used, over which a chain was carried, connecting the piston with the pump-rod, and the motion was similar to that given by the discarded beam. The wheel was supported on A-frames, resembling somewhat the "gallows-frames" still used with the beam-engines of American river-boats. The sills carrying the two A's supported the cylinder. The injection-cistern was supported above the great pulley-wheel. The valve-gearing and the injection-pump were worked by a smaller wheel, mounted on the same axis with the larger one. The boiler was placed apart from the engine, with which it was connected by a steam-pipe, in which was placed the "regulator," or throttle-valve. The boiler (Fig. 23) "was shaped like a large tea-kettle," and contained a fire-box, _B_, or internal furnace, of which the sides were made of cast-iron. The fire-door, _C_, was placed on one side and opposite the flue, _D_, through which the products of combustion were led to the chimney, _E_; a short, large pipe, _F_, leading downward from the furnace to the outside of the boiler, was the ash-pit. The shell of the boiler, _A_, was made of iron plate one-quarter of an inch thick. The steam-cylinder of the engine was 18 inches in diameter, the stroke of piston 6 feet, the great wheel 6-1/2 feet in diameter, and the A-frames 9 feet high. The boiler was made 6 feet, the furnace 34 inches, and the grate 18 inches in diameter. The piston was intended to make 10 strokes per minute, and the engine to develop 4-1/8 horse-power. In 1773, Smeaton prepared plans for a pumping-engine to be set up at Cronstadt, the port of St. Petersburg, to empty the great dry dock constructed by Peter the Great and Catherine, his successor. This great dock was begun in 1719. It was large enough to dock ten of the ships of that time, and had previously been imperfectly drained by two great windmills 100 feet high. So imperfectly did they do their work, that a _year_ was required to empty the dock, and it could therefore only be used once in each summer. The engine was built at the Carron Iron Works, in England. It had a cylinder 66 inches in diameter, and a stroke of piston of 8-1/2 feet. The lift varied from 33 feet when the dock was full to 53 feet when it was cleared of water. The load on the engine averaged about 8-1/3 pounds per square inch of piston-area. There were three boilers, each 10 feet in diameter, and 16 feet 4 inches high to the apex of its hemispherical dome. They contained internal fire-boxes with grates of 20 feet area, and were surrounded by flues helically traversing the masonry setting. The engine was started in 1777, and worked very successfully. The lowlands of Holland were, before the time of Smeaton, drained by means of windmills. The uncertainty and inefficiency of this method precluded its application to anything like the extent to which steam-power has since been utilized. In 1440, there were 150 inland lakes, or "_meers_," in that country, of which nearly 100, having an extent of over 200,000 acres, have since been drained. The "Haarlemmer Meer" alone covers nearly 50,000 acres, and forms the basin of a drainage-area of between 200,000 and 300,000 acres, receiving a rainfall of 54,000,000 tons, which must be raised 16 feet in discharging it. The beds of these lakes are from 10 to 20 feet lower than the water-level in the adjacent canals. In 1840, 12,000 windmills were still employed in this work. In the following year, William II., at the suggestion of a commission, decreed that only steam-engines should be employed to do this immense work. Up to this time the average consumption of fuel for the pumping-engines in use is said to have been 20 pounds per hour per horse-power. The first engine used was erected in 1777 and 1778, on the Newcomen plan, to assist the 34 windmills employed to drain a lake near Rotterdam. This lake covered 7,000 acres, and its bed was 12 feet below the surface of the river Meuse, which passes it, and empties into the sea in the immediate neighborhood. The iron parts of the engine were built in England, and the machine was put together in Holland. The steam-cylinder was 52 inches in diameter, and the stroke of piston 9 feet. The boiler was 18 feet in diameter, and contained a double flue. The main beam was 27 feet long. The pumps were 6 in number, 3 cylindrical and 3 having a square cross-section; 3 were of 6 feet and 3 of 2-1/2 feet stroke. Two pumps only were worked at high-tide, and the others were added one at a time, as the tide fell, until, at low-tide, all 6 were at work. The size of this engine, and the magnitude of its work, seem insignificant when compared with the machinery installed 60 years later to drain the Haarlemmer Meer, and with the work done by the last. These engines are 12 feet in diameter of cylinder and 10 feet stroke of piston, and work--they are 3 in number--the one 11 pumps of 63 inches diameter and 10 feet stroke, the others 8 pumps of 73 inches diameter and of the same length of stroke. The modern engines do a "duty" of 75,000,000 to 87,000,000 with 94 pounds of coal, consuming 2-1/4 pounds of coal per hour and per horse-power. The first steam-engine applied to working the blowing-machinery of a blast-furnace was erected at the Carron Iron-Works, in Scotland, near Falkirk, in 1765, and proved very unsatisfactory. Smeaton subsequently, in 1769 or 1770, introduced better machinery into these works and improved the old engine, and this use of the steam-engine soon became usual. This engine did its work indirectly, furnishing water, by pumping, to drive the water-wheels which worked the blowing-cylinders. Its steam-cylinder was 6 feet in diameter, and the pump-cylinder 52 inches. The stroke was 9 feet. A direct-acting engine, used as a blowing-engine, was not constructed until about 1784, at which time a single-acting blowing-cylinder, or air-pump, was placed at the "out-board" end of the beam, where the pump-rod had been attached. The piston of the air-cylinder was loaded with the weights needed to force it down, expelling the air, and the engine did its work in raising the loaded piston, the air-cylinder filling as the piston rose. A large "accumulator" was used to equalize the pressure of the expelled air. This consisted of another air-cylinder, having a loaded piston which was left free to rise and fall. At each expulsion of air by the blowing-engine this cylinder was filled, the loaded piston rising to the top. While the piston of the former was returning, and the air-cylinder was taking in its charge of air, the accumulator would gradually discharge the stored air, the piston slowly falling under its load. This piston was called the "floating piston," or "fly-piston," and its action was, in effect, precisely that of the upper portion of the common blacksmith's bellows. Dr. Robison, the author of "Mechanical Philosophy," one of the very few works even now existing deserving such a title, describes one of these engines[34] as working in Scotland in 1790. It had a steam-cylinder 40 or 44 inches in diameter, a blowing-cylinder 60 inches in diameter, and the stroke of piston was 6 feet. The air-pressure was 2.77 pounds per square inch as a maximum in the blowing-cylinder; and the floating piston in the regulating-cylinder was loaded with 2.63 pounds per square inch. Making 15 or 18 strokes per minute, this engine delivered about 1,600 cubic feet of air, or 120-1/2 pounds in weight, per minute, and developed 20 horse-power. [34] "Encyclopædia Britannica," 1st edition. At about the same date a change was made in the blowing-cylinder. The air entered at the bottom, as before, but was forced out at the top, the piston being fitted with valves, as in the common lifting-pump, and the engine thus being arranged to do the work of expulsion during the down-stroke of the steam-piston. Four years later, the regulating-cylinder, or accumulator, was given up, and the now familiar "water-regulator" was substituted for it. This consists of a tank, usually of sheet-iron, set open-end downward in a large vessel containing water. The lower edge of the inner tank is supported on piers a few inches above the bottom of the large one. The pipe carrying air from the blowing-engine passes above this water-regulator, and a branch-pipe is led down into the inner tank. As the air-pressure varies, the level of the water within the inverted tank changes, rising as pressure falls at the slowing of the motion of the piston, and falling as the pressure rises again while the piston is moving with an accelerated velocity. The regulator, thus receiving surplus air to be delivered when needed, greatly assists in regulating the pressure. The larger the regulator, the more perfectly uniform the pressure. The water-level outside the inner tank is usually five or six feet higher than within it. This apparatus was found much more satisfactory than the previously-used regulator, and, with its introduction, the establishment of the steam-engine as a blowing-engine for iron-works and at blast-furnaces may be considered as having been fully established. Thus, by the end of the third quarter of the eighteenth century, the steam-engine had become generally introduced, and had been applied to nearly all of the purposes for which a single-acting engine could be used. The path which had been opened by Worcester had been fairly laid out by Savery and his contemporaries, and the builders of the Newcomen engine, with such improvements as they had been able to effect, had followed it as far as they were able. The real and practical introduction of the steam-engine is as fairly attributable to Smeaton as to any one of the inventors whose names are more generally known in connection with it. As a mechanic, he was unrivaled; as an engineer, he was head and shoulders above any constructor of his time engaged in general practice. There were very few important public works built in Great Britain at that time in relation to which he was not consulted; and he was often visited by foreign engineers, who desired his advice with regard to works in progress on the Continent. [Illustration] CHAPTER III. _THE DEVELOPMENT OF THE MODERN STEAM-ENGINE. JAMES WATT AND HIS CONTEMPORARIES._ The world is now entering upon the Mechanical Epoch. There is nothing in the future more sure than the great triumphs which that epoch is to achieve. It has already advanced to some glorious conquests. What miracles of invention now crowd upon us! Look abroad, and contemplate the infinite achievements of the steam-power. And yet we have only begun--we are but on the threshold of this epoch.... What is it but the setting of the great distinctive seal upon the nineteenth century?--an advertisement of the fact that society has risen to occupy a higher platform than ever before?--a proclamation from the high places, announcing honor, honor immortal, to the workmen who fill this world with beauty, comfort, and power--honor to be forever embalmed in history, to be perpetuated in monuments, to be written in the hearts of this and succeeding generations!--KENNEDY. SECTION I.--JAMES WATT AND HIS INVENTIONS. The success of the Newcomen engine naturally attracted the attention of mechanics, and of scientific men as well, to the possibility of making other applications of steam-power. The best men of the time gave much attention to the subject, but, until James Watt began the work that has made him famous, nothing more was done than to improve the proportions and slightly alter the details of the Newcomen and Calley engine, even by such skillful engineers as Brindley and Smeaton. Of the personal history of the earlier inventors and improvers of the steam-engine, very little is ascertained; but that of Watt has become well known. [Illustration: James Watt.] JAMES WATT was of an humble lineage, and was born at Greenock, then a little Scotch fishing village, but now a considerable and a busy town, which annually launches upon the waters of the Clyde a fleet of steamships whose engines are probably, in the aggregate, far more powerful than were all the engines in the world at the date of Watt's birth, January 19, 1736. His grandfather, Thomas Watt, of Crawfordsdyke, near Greenock, was a well-known mathematician about the year 1700, and was for many years a schoolmaster at that place. His father was a prominent citizen of Greenock, and was at various times chief magistrate and treasurer of the town. James Watt was a bright boy, but exceedingly delicate in health, and quite unable to attend school regularly, or to apply himself closely to either study or play. His early education was given by his parents, who were respectable and intelligent people, and the tools borrowed from his father's carpenter-bench served at once to amuse him and to give him a dexterity and familiarity with their use that must undoubtedly have been of inestimable value to him in after-life. M. Arago, the eminent French philosopher, who wrote one of the earliest and most interesting biographies of Watt, relates anecdotes of him which, if correct, illustrate well his thoughtfulness and his intelligence, as well as the mechanical bent of the boy's mind. He is said, at the age of six years, to have occupied himself during leisure hours with the solution of geometrical problems; and Arago discovers, in a story in which he is described as experimenting with the tea-kettle,[35] his earliest investigations of the nature and properties of steam. [35] The same story is told of Savery and of Worcester. When finally sent to the village school, his ill health prevented his making rapid progress; and it was only when thirteen or fourteen years of age that he began to show that he was capable of taking the lead in his class, and to exhibit his ability in the study, particularly, of mathematics. His spare time was principally spent in sketching with his pencil, in carving, and in working at the bench, both in wood and metal. He made many ingenious pieces of mechanism, and some beautiful models. His favorite work seemed to be the repairing of nautical instruments. Among other pieces of apparatus made by the boy was a very fine barrel-organ. In boyhood, as in after-life, he was a diligent reader, and seemed to find something to interest him in every book that came into his hands. At the age of eighteen, Watt was sent to Glasgow, there to reside with his mother's relatives, and to learn the trade of a mathematical-instrument maker. The mechanic with whom he was placed was soon found too indolent, or was otherwise incapable of giving much aid in the project, and Dr. Dick, of the University of Glasgow, with whom Watt became acquainted, advised him to go to London. Accordingly, he set out in June, 1755, for the metropolis, where, on his arrival, he arranged with Mr. John Morgan, in Cornhill, to work a year at his chosen business, receiving as compensation 20 guineas. At the end of the year he was compelled, by serious ill-health, to return home. Having become restored to health, he went again to Glasgow in 1756, with the intention of pursuing his calling there. But, not being the son of a burgess, and not having served his apprenticeship in the town, he was forbidden by the guilds, or trades-unions, to open a shop in Glasgow. Dr. Dick came to his aid, and employed him to repair some apparatus which had been bequeathed to the college. He was finally allowed the use of three rooms in the University building, its authorities not being under the municipal rule. He remained here until 1760, when, the trades no longer objecting, he took a shop in the city; and in 1761 moved again, into a shop on the north side of the Trongate, where he earned a scanty living without molestation, and still kept up his connection with the college. He did some work as a civil engineer in the neighborhood of Glasgow, but soon gave up all other employment, and devoted himself entirely to mechanics. He spent much of his leisure time--of which he had, at first, more than was desirable--in making philosophical experiments and in the manufacture of musical instruments, in making himself familiar with the sciences, and in devising improvements in the construction of organs. In order to pursue his researches more satisfactorily, he studied German and Italian, and read Smith's "Harmonics," that he might become familiar with the principles of construction of musical instruments. His reading was still very desultory; but the introduction of the Newcomen engine in the neighborhood of Glasgow, and the presence of a model in the college collections, which was placed in his hands, in 1763, for repair, led him to study the history of the steam-engine, and to conduct for himself an experimental research into the properties of steam, with a set of improvised apparatus. Dr. Robison, then a student of the University, who found Watt's shop a pleasant place in which to spend his leisure, and whose tastes affiliated so strongly with those of Watt that they became friends immediately upon making acquaintance, called the attention of the instrument-maker to the steam-engine as early as 1759, and suggested that it might be applied to the propulsion of carriages. Watt was at once interested, and went to work on a little model, having tin steam-cylinders and pistons connected to the driving-wheels by an intermediate system of gearing. The scheme was afterwards given up, and was not revived by Watt for a quarter of a century. Watt studied chemistry, and was assisted by the advice and instruction of Dr. Black, who was then making the researches which resulted in the discovery of "latent heat." His proposal to repair the model Newcomen engine in the college collections led to his study of Desaguliers's treatise, and of the works of Switzer and others. He thus learned what had been done by Savery and by Newcomen, and by those who had improved the engine of the latter. In his own experiments he used, at first, apothecaries' phials and hollow canes for steam reservoirs and pipes, and later a Papin's digester and a common syringe. The latter combination made a non-condensing engine, in which he used steam at a pressure of 15 pounds per square inch. The valve was worked by hand, and Watt saw that an automatic valve-gear only was needed to make a working machine. This experiment, however, led to no practical result. He finally took hold of the Newcomen model, which had been obtained from London, where it had been sent for repairs, and, putting it in good working order, commenced experiments with that. The Newcomen model, as it happened, had a boiler which, although made to a scale from engines in actual use, was quite incapable of furnishing steam enough to work the engine. It was about nine inches in diameter; the steam-cylinder was two inches in diameter, and of six inches stroke of piston, arranged as in Fig. 24, which is a picture of the model as it now appears. It is retained among the most carefully-preserved treasures of the University of Glasgow. [Illustration: FIG. 24.--The Newcomen Model.] Watt made a new boiler for the experimental investigation on which he was about to enter, and arranged it in such a manner that he could measure the quantity of water evaporated and of steam used at every stroke of the engine. He soon discovered that it required but a very small quantity of steam to heat a very large quantity of water, and immediately attempted to determine with precision the relative weights of steam and water in the steam-cylinder when condensation took place at the down-stroke of the engine, and thus independently proved the existence of that "latent heat," the discovery of which constitutes, also, one of the greatest of Dr. Black's claims to distinction. Watt at once went to Dr. Black and related the remarkable fact which he had thus detected, and was, in turn, taught by Black the character of the phenomenon as it had been explained to his classes by the latter some little time previously. Watt found that, at the boiling-point, his steam, condensing, was capable of heating six times its weight of water such as was used for producing condensation. Perceiving that steam, weight for weight even, was a vastly greater absorbent and reservoir of heat than water, Watt saw plainly the importance of taking greater care to economize it than had previously been customary. He first attempted to economize in the boiler, and made boilers with wooden "shells," in order to prevent losses by conduction and radiation, and used a larger number of flues to secure more complete absorption of the heat from the furnace-gases. He also covered his steam-pipes with non-conducting materials, and took every precaution that his ingenuity could devise to secure complete utilization of the heat of combustion. He soon found, however, that he was not working at the most important point, and that the great source of loss was to be found in defects which he noted in the action of the steam in the cylinder. He soon concluded that the sources of loss of heat in the Newcomen engine--which would be greatly exaggerated in a small model--were: First, the dissipation of heat by the cylinder itself, which was of brass, and was both a good conductor and a good radiator. Secondly, the loss of heat consequent upon the necessity of cooling down the cylinder at every stroke, in producing the vacuum. Thirdly, the loss of power due to the pressure of vapor beneath the piston, which was a consequence of the imperfect method of condensation. He first made a cylinder of non-conducting material--wood soaked in oil and then baked--and obtained a decided advantage in economy of steam. He then conducted a series of very accurate experiments upon the temperature and pressure of steam at such points on the scale as he could readily reach, and, constructing a curve with his results, the abscesses representing temperatures and the pressures being represented by the ordinates, he ran the curve backward until he had obtained closely-approximate measures of temperatures less than 212°, and pressures less than atmospheric. He thus found that, with the amount of injection-water used in the Newcomen engine, bringing the temperature of the interior, as he found, down to from 140° to 175° Fahr., a very considerable back-pressure would be met with. Continuing his examination still further, he measured the amount of steam used at each stroke, and, comparing it with the quantity that would just fill the cylinder, he found that at least _three-fourths was wasted_. The quantity of cold water necessary to produce the condensation of a given weight of steam was next determined; and he found that one pound of steam contained enough heat to raise about six pounds of cold water, as used for condensation, from the temperature of 52° to the boiling-point; and, going still further, he found that he was compelled to use, at each stroke of the Newcomen engine, _four times as much injection-water as should suffice to condense a cylinder full of steam_. This confirmed his previous conclusion that three-fourths of the heat supplied to the engine was wasted. Watt had now, therefore, determined by his own researches, as he himself enumerates them,[36] the following facts: [36] Robison's "Mechanical Philosophy," edited by Brewster. "1. The capacities for heat of iron, copper, and of some sorts of wood, as compared with water. "2. The bulk of steam compared with that of water. "3. The quantity of water evaporated in a certain boiler by a pound of coal. "4. The elasticities of steam at various temperatures greater than that of boiling water, and an approximation to the law which it follows at other temperatures. "5. How much water in the form of steam was required every stroke by a small Newcomen engine, with a wooden cylinder 6 inches in diameter and 12 inches stroke. "6. The quantity of cold water required in every stroke to condense the steam in that cylinder, so as to give it a working-power of about 7 pounds on the square inch." After these well-devised and truly scientific investigations, Watt was enabled to enter upon his work of improving the steam-engine with an intelligent understanding of its existing defects, and with a knowledge of their cause. Watt soon saw that, in order to reduce the losses in the working of the steam in the steam-cylinder, it would be necessary to find some means, as he said, to keep the cylinder "always as hot as the steam that entered it," notwithstanding the great fluctuations of temperature and pressure of the steam during the up and the down strokes. He has told us how, finally, the happy thought occurred to him which relieved him of all difficulty, and led to the series of modifications which at last gave to the world the modern type of steam-engine. He says:[37] "I had gone to take a walk on a fine Sabbath afternoon. I had entered the Green by the gate at the foot of Charlotte street, and had passed the old washing-house. I was thinking upon the engine at the time, and had gone as far as the herd's house, when the idea came into my mind that, as steam was an elastic body, it would rush into a vacuum, and, if a communication were made between the cylinder and an exhausted vessel, it would rush into it, and might be there condensed without cooling the cylinder. I then saw that I must get rid of the condensed steam and injection-water if I used a jet, as in Newcomen's engine. Two ways of doing this occurred to me: First, the water might be run off by a descending pipe, if an offlet could be got at the depth of 35 or 36 feet, and any air might be extracted by a small pump. The second was, to make the pump large enough to extract both water and air." "I had not walked farther than the Golf-house, when the whole thing was arranged in my mind." [37] "Reminiscences of James Watt," Robert Hart; "Transactions of the Glasgow Archæological Society," 1859. Referring to this invention, Watt said to Prof. Jardine:[38] "When analyzed, the invention would not appear so great as it seemed to be. In the state in which I found the steam-engine, it was no great effort of mind to observe that the quantity of fuel necessary to make it work would forever prevent its extensive utility. The next step in my progress was equally easy--to inquire what was the cause of the great consumption of fuel. This, too, was readily suggested, viz., the waste of fuel which was necessary to bring the whole cylinder, piston, and adjacent parts from the coldness of water to the heat of steam, no fewer than from 15 to 20 times in a minute." It was by pursuing this train of thought that he was led to devise the separate condenser. [38] "Lives of Boulton and Watt," Smiles. On Monday morning Watt proceeded to make an experimental test of his new invention, using for his steam-cylinder and piston a large brass surgeon's-syringe, 1-3/4-inch diameter and 10 inches long. At each end was a pipe leading steam from the boiler, and fitted with a cock to act as a steam-valve. A pipe led also from the top of the cylinder to the condenser, the syringe being inverted and the piston-rod hanging downward for convenience. The condenser was made of two pipes of thin tin plate, 10 or 12 inches long, and about one-sixth of an inch in diameter, standing vertically, and having a connection at the top with a horizontal pipe of larger size, and fitted with a "snifting-valve." Another vertical pipe, about an inch in diameter, was connected to the condenser, and was fitted with a piston, with a view to using it as an "air-pump." The whole was set in a cistern of cold water. The piston-rod of the little steam-cylinder was drilled from end to end to permit the water to be removed from the cylinder. This little model (Fig. 25) worked very satisfactorily, and the perfection of the vacuum was such that the machine lifted a weight of 18 pounds hung upon the piston-rod, as in the sketch. A larger model was immediately afterward constructed, and the result of its test confirmed fully the anticipations which had been awakened by the first experiment. [Illustration: FIG. 25.--Watt's Experiment.] Having taken this first step and made such a radical improvement, the success of this invention was no sooner determined than others followed in rapid succession, as consequences of the exigencies arising from the first change in the old Newcomen engine. But in the working out of the forms and proportions of the details of the new engine, even Watt's powerful mind, stored as it was with happily-combined scientific and practical information, was occupied for years. In attaching the separate condenser, he first attempted surface-condensation; but this not succeeding well, he substituted the jet. Some provision became at once necessary for preventing the filling of the condenser with water. Watt at first intended adopting the expedient which had worked satisfactorily with the less effective condensation of Newcomen's engine--i. e., leading a pipe from the condenser to a depth greater than the height of a column of water which could be counterbalanced by the pressure of the atmosphere; but he subsequently employed the air-pump, which relieves the condenser not only of the water, but of the air which also usually collects in considerable volume in the condenser, and vitiates the vacuum. He next substituted oil and tallow for water in the lubrication of the piston and keeping it steam-tight, in order to avoid the cooling of the cylinder incident to the use of the latter. Another cause of refrigeration of the cylinder, and consequent waste of power in its operation, was seen to be the entrance of the atmosphere, which followed the piston down the cylinder at each stroke, cooling its interior by its contact. This the inventor concluded to prevent by covering the top of the cylinder, allowing the piston-rod to play through a "stuffing-box"--which device had long been known to mechanics. He accordingly not only covered the top, but surrounded the whole cylinder with an external casing, or "steam-jacket," and allowed the steam from the boiler to pass around the steam-cylinder and to press upon the upper surface of the piston, where its pressure was variable at pleasure, and therefore more manageable than that of the atmosphere. It also, besides keeping the cylinder hot, could do comparatively little harm should it leak by the piston, as it could be condensed, and thus readily disposed of. When he had concluded to build the larger experimental engine, Watt determined to give his whole time and attention to the work, and hired a room in an old deserted pottery near the Broomielaw. Here he worked with a mechanic--John Gardiner, whom he had taken into his employ--uninterruptedly for many weeks. Meantime, through his friend Dr. Black, probably, he had made the acquaintance of Dr. Roebuck, a wealthy physician, who had, with other Scotch capitalists, just founded the celebrated Carron Iron-Works, and had opened a correspondence with him, in which he kept that gentleman informed of the progress of his work on the new engine. This engine had a steam-cylinder, Watt tells us, of "five or six" inches diameter, and of two feet stroke. It was of copper, smooth-hammered, but not bored out, and "not very true." This was encased in another cylinder of wood. In August, 1765, he tried the small engine, and wrote Dr. Roebuck that he had had "good success," although the machine was very imperfect. "On turning the exhausting-cock, the piston, when not loaded, ascended as quick as the blow of a hammer, and as quick when loaded with 18 pounds (being 7 pounds on the inch) as it would have done if it had had an injection as usual." He then tells his correspondent that he was about to make the larger model. In October, 1765, he finished the latter. The engine, when ready for trial, was still very imperfect. It nevertheless did good work for so rude a machine. Watt was now reduced to poverty, and, after borrowing considerable sums from friends, he was finally compelled to give up his scheme for the time, and to seek employment in order to provide for his family. During an interval of about two years he supported himself by surveying, and by the work of exploring coal-fields in the neighborhood of Glasgow for the magistrates of the city. He did not, however, entirely give up his invention. In 1767, Dr. Roebuck assumed Watt's liabilities to the amount of £1,000, and agreed to provide capital for the prosecution of his experiments and to introduce his invention; and, on the other hand, Watt agreed to surrender to Dr. Roebuck two-thirds of the patent. Another engine was next built, having a steam-cylinder seven or eight inches in diameter, which was finished in 1768. This worked sufficiently well to induce the partners to ask for a patent, and the specifications and drawings were completed and presented in 1769. Watt also built and set up several Newcomen engines, partly, perhaps, to make himself thus thoroughly familiar with the practical details of engine-building. Meantime, also, he prepared the plans for, and finally had built, a moderately large engine of his own new type. Its steam-cylinder was 18 inches in diameter, and the stroke of piston was 5 feet. This engine was built at Kinneil, and was finished in September, 1769. It was not all satisfactory in either its construction or its operation. The condenser was a surface-condenser composed of pipes somewhat like that used in his first little model, and did not prove to be satisfactorily tight. The steam-piston leaked seriously, and repeated trials only served to make more evident its imperfections. He was assisted in this time of need by both Dr. Black and Dr. Roebuck; but he felt strongly the risks which he ran of involving his friends in serious losses, and became very despondent. Writing to Dr. Black, he says: "Of all things in life, there is nothing more foolish than inventing;" and probably the majority of inventors have been led to the same opinion by their own experiences. "Misfortunes never come singly;" and Watt was borne down by the greatest of all misfortunes--the loss of a faithful and affectionate wife--while still unable to see a successful issue of his schemes. Only less disheartening than this was the loss of fortune of his steadfast friend, Dr. Roebuck, and the consequent loss of his aid. It was at about this time, in the year 1769, that negotiations were commenced which resulted in the transfer of the capitalized interest in Watt's engine to the wealthy manufacturer whose name, coupled with that of Watt, afterward became known throughout the civilized world, as the steam-engine in its new form was pushed into use by his energy and business tact. Watt met Mr. Boulton, who next became his partner, in 1768, on his journey to London to procure his patent, and the latter had then examined Watt's designs, and, at once perceiving their value, proposed to purchase an interest. Watt was then unable to reply definitely to Boulton's proposition, pending his business arrangements with Dr. Roebuck; but, with Roebuck's consent, afterwards proposed that Boulton should take a one-third interest with himself and partner, paying Roebuck therefor one-half of all expenses previously incurred, and whatever he should choose to add to compensate "for the risk he had run." Subsequently, Dr. Roebuck proposed to transfer to Boulton and to Dr. Small, who was desirous of taking interest with Boulton, one-half of his proprietorship in Watt's inventions, on receiving "a sum not less than one thousand pounds," which should, after the experiments on the engine were completed, be deemed "just and reasonable." Twelve months were allowed for the adjustment of the account. This proposal was accepted in November, 1769. [Illustration: Matthew Boulton.] MATTHEW BOULTON, who now became a partner with James Watt, was the son of a Birmingham silver stamper and piecer, and succeeded to his father's business, building up a great establishment, which, as well as its proprietor, was well known in Watt's time. Watt, writing to Dr. Roebuck before the final arrangement had been made, urged him to close with Boulton for "the following considerations: "1st. From Mr. Boulton's own character as an ingenious, honest, and rich man. 2dly. From the difficulty and expense there would be of procuring accurate and honest workmen and providing them with proper utensils, and getting a proper overseer or overseers. If, to avoid this inconvenience, you were to contract for the work to be done by a master-workman, you must give up a great share of the profit. 3dly. The success of the engine is far from being verified. If Mr. Boulton takes his chance of success from the account I shall write Dr. Small, and pays you any adequate share of the money laid out, it lessens your risk, and in a greater proportion than I think it will lessen your profits. 4thly. The assistance of Mr. Boulton's and Dr. Small's ingenuity (if the latter engage in it) in improving and perfecting the machine may be very considerable, and may enable us to get the better of the difficulties that might otherwise damn it. Lastly, consider my uncertain health, my irresolute and inactive disposition, my inability to bargain and struggle for my own with mankind: all which disqualify me for any great undertaking. On our side, consider the first outlay and interest, the patent, the present engine, about £200 (though there would not be much loss in making it into a common engine), two years of my time, and the expense of models." Watt's estimate of the value of Boulton's ingenuity and talent was well-founded. Boulton had shown himself a good scholar, and had acquired considerable knowledge of the languages and of the sciences, particularly of mathematics, after leaving the school from which he graduated into the shop when still a boy. In the shop he soon introduced a number of valuable improvements, and he was always on the lookout for improvements made by others, with a view to their introduction in his business. He was a man of the modern style, and never permitted competitors to excel him in any respect, without the strongest efforts to retain his leading position. He always aimed to earn a reputation for good work, as well as to make money. His father's workshop was at Birmingham; but Boulton, after a time, found that his rapidly-increasing business would compel him to find room for the erection of a more extensive establishment, and he secured land at Soho, two miles distant from Birmingham, and there erected his new manufactory, about 1762. The business was, at first, the manufacture of ornamental metal-ware, such as metal buttons, buckles, watch-chains, and light filigree and inlaid work. The manufacture of gold and silver plated-ware was soon added, and this branch of business gradually developed into a very extensive manufacture of works of art. Boulton copied fine work wherever he could find it, and often borrowed vases, statuettes, and bronzes of all kinds from the nobility of England, and even from the queen, from which to make copies. The manufacture of inexpensive clocks, such as are now well known throughout the world as an article of American trade, was begun by Boulton. He made some fine astronomical and valuable ornamental clocks, which were better appreciated on the Continent than in England. The business of the Soho manufactory in a few years became so extensive, that its goods were known to every civilized nation, and its growth, under the management of the enterprising, conscientious, and ingenious Boulton, more than kept pace with the accumulation of capital; and the proprietor found himself, by his very prosperity, often driven to the most careful manipulation of his assets, and to making free use of his credit. Boulton had a remarkable talent for making valuable acquaintances, and for making the most of advantages accruing thereby. In 1758 he made the acquaintance of Benjamin Franklin, who then visited Soho; and in 1766 these distinguished men, who were then unaware of the existence of James Watt, were corresponding, and, in their letters, discussing the applicability of steam-power to various useful purposes. Between the two a new steam-engine was designed, and a model was constructed by Boulton, which was sent to Franklin and exhibited by him in London. Dr. Darwin seems to have had something to do with this scheme, and the enthusiasm awakened by the promise of success given by this model may have been the origin of the now celebrated prophetic rhymes so often quoted from the works of that eccentric physician and poet. Franklin contributed, as his share in the plan, an idea of so arranging the grate as to prevent the production of smoke. He says: "All that is necessary is to make the smoke of fresh coals pass descending through those that are already ignited." His idea has been, by more recent schemers, repeatedly brought forward as new. Nothing resulted from these experiments of Boulton, Franklin, and Darwin, and the plan of Watt soon superseded all less well-developed plans. In 1767, Watt visited Soho and carefully inspected Boulton's establishment. He was very favorably impressed by the admirable arrangement of the workshops and the completeness of their outfit, as well as by the perfection of the organization and administration of the business. In the following year he again visited Soho, and this time met Boulton, who had been absent at the previous visit. The two great mechanics were mutually gratified by the meeting, and each at once acquired for the other the greatest respect and esteem. They discussed Watt's plans, and Boulton then definitely decided not to continue his own experiments, although he had actually commenced the construction of a pumping-engine. With Dr. Small, who was also at Soho, Watt discussed the possibility of applying his engine to the propulsion of carriages, and to other purposes. On his return home, Watt continued his desultory labors on his engines, as already described; and the final completion of the arrangement with Boulton, which immediately followed the failure of Dr. Roebuck, took place some time later. Before Watt could leave Scotland to join his partner at Soho, it was necessary that he should finish the work which he had in hand, including the surveys of the Caledonian canal, and other smaller works, which he had had in progress some months. He reached Birmingham in the spring of 1774, and was at once domiciled at Soho, where he set at work upon the partly-made engines which had been sent from Scotland some time previously. They had laid, unused and exposed to the weather, at Kinneil three years, and were not in as good order as might have been desired. The _block-tin_ steam-cylinder was probably in good condition, but the iron parts were, as Watt said, "perishing," while he had been engaged in his civil engineering work. At leisure moments, during this period, Watt had not entirely neglected his plans for the utilization of steam. He had given much thought, and had expended some time, in experiments upon the plan of using it in a rotary or "wheel" engine. He did not succeed in contriving any plan which seemed to promise success. It was in November, 1774, that Watt finally announced to his old partner, Dr. Roebuck, the successful trial of the Kinneil engine. He did not write with the usual enthusiasm and extravagance of the inventor, for his frequent disappointments and prolonged suspense had very thoroughly extinguished his vivacity. He simply wrote: "The fire-engine I have invented is now going, and answers much better than any other that has yet been made; and I expect that the invention will be very beneficial to me." The change of the "atmospheric engine" of Newcomen into the modern steam-engine was now completed in its essential details. The first engine which was erected at Kinneil, near Boroughstoness, had a steam-cylinder 18 inches in diameter. It is seen in the accompanying sketch. [Illustration: FIG. 26.--Watt's Engine, 1774.] In Fig. 26, the steam passes from the boiler through the pipe _d_ and the valve _c_ to the cylinder-casing or steam-jacket, _Y Y_, and above the piston, _b_, which it follows in its descent in the cylinder, _a_, the valve _f_ being at this time open, to allow the exhaust into the condenser, _h_. The piston now being at the lower end of the cylinder, and the pump-rods at the opposite end of the beam, _y_, being thus raised and the pumps filled with water, the valves _c_ and _f_ close, while _e_ opens, allowing the steam which remains above the piston to flow beneath it, until, the pressures becoming equal above and below, the weight of the pump-rods overbalancing that of the piston, the latter is rapidly drawn to the top of the cylinder, while the steam is displaced above, passing to the under-side of the piston. The valve _e_ is next closed, and _c_ and _f_ are again opened; the down-stroke is repeated. The water and air entering the condenser are removed at each stroke by the air-pump, _i_, which communicates with the condenser by the passage _s_. The pump _q_ supplies condensing-water, and the pump _A_ takes away a part of the water of condensation, which is thrown by the air-pump into the "hot-well," _k_, and from it the feed-pump supplies the boiler. The valves are moved by valve-gear very similar to Beighton's and Smeaton's, by the pins, _m m_, in the "plug-frame" or "tappet-rod," _n n_. The engine is mounted upon a substantial foundation, _B B_. _F_ is an opening out of which, before starting the engine, the air is driven from the cylinder and condenser. The inventions covered by the patent of 1769 were described as follows: "My method of lessening the consumption of steam, and consequently fuel, in fire-engines, consists in the following principles: "1st. That the vessel in which the powers of steam are to be employed to work the engine--which is called 'the cylinder' in common fire-engines, and which I call 'the steam-vessel'--must, during the whole time that the engine is at work, be kept as hot as the steam which enters it; first, by inclosing it in a case of wood, or any other materials that transmit heat slowly; secondly, by surrounding it with steam or other heated bodies; and thirdly, by suffering neither water nor other substances colder than the steam to enter or touch it during that time. "2dly. In engines that are to be worked, wholly or partially, by condensation of steam, the steam is to be condensed in vessels distinct from the steam-vessel or cylinder, though occasionally communicating with them. These vessels I call condensers; and while the engines are working, these _condensers_ ought at least to be kept as cold as the air in the neighborhood of the engines, by application of water or other cold bodies. "3dly. Whatever air or other elastic vapor is not condensed by the cold of the condenser, and may impede the working of the engine, is to be drawn out of the steam-vessels or condensers by means of pumps, wrought by the engines themselves, or otherwise. "4thly. I intend in many cases to employ the expansive force of steam to press on the pistons, or whatever may be used instead of them, in the same manner as the pressure of the atmosphere is now employed in common fire-engines. In cases where cold water cannot be had in plenty, the engines may be wrought by this force of steam only, by discharging the steam into the open air after it has done its office. "5thly. Where motions round an axis are required, I make the steam-vessels in form of hollow rings or circular channels, with proper inlets and outlets for the steam, mounted on horizontal axles like the wheels of a water-mill. Within them are placed a number of valves that suffer any body to go round the channel in one direction only. In these steam-vessels are placed weights, so fitted to them as to fill up a part or portion of their channels, yet rendered capable of moving freely in them by the means hereinafter mentioned or specified. When the steam is admitted in these engines between these weights and the valves, it acts equally on both, so as to raise the weight on one side of the wheel, and, by the reaction of the valves successively, to give a circular motion to the wheel, the valves opening in the direction in which the weights are pressed, but not in the contrary. As the vessel moves round, it is supplied with steam from the boiler, and that which has performed its office may either be discharged by means of condensers, or into the open air. "6thly. I intend in some cases to apply a degree of cold not capable of reducing the steam to water, but of contracting it considerably, so that the engines shall be worked by the alternate expansion and contraction of the steam. "Lastly, instead of using water to render the piston or other parts of the engine air or steam-tight, I employ oils, wax, resinous bodies, fat of animals, quicksilver, and other metals, in their fluid state." In the construction and erection of his engines, Watt still had great difficulty in finding skillful workmen to make the parts with accuracy, to fit them with care, and to erect them properly when once finished. And the fact that both Newcomen and Watt met with such serious trouble, indicates that, even had the engine been designed earlier, it is quite unlikely that the world would have seen the steam-engine a success until this time, when mechanics were just acquiring the skill requisite for its construction. But, on the other hand, it is not at all improbable that, had the mechanics of an earlier period been as skillful and as well-educated in the manual niceties of their business, the steam-engine might have been much earlier brought into use. In the time of the Marquis of Worcester it would have probably been found impossible to obtain workmen to construct the steam-engine of Watt, had it been then invented. Indeed, Watt, upon one occasion, congratulated himself that one of his steam-cylinders only lacked _three-eighths_ of an inch of being truly cylindrical. The history of the steam-engine is from this time a history of the work of the firm of Boulton & Watt. Newcomen engines continued to be built for years after Watt went to Soho, and by many builders. A host of inventors still worked on the most attractive of all mechanical combinations, seeking to effect further improvements. Some inventions were made by contemporaries of Watt, as will be seen hereafter, which were important as being the germs of later growths; but these were nearly all too far in advance of the time, and nearly every successful and important invention which marked the history of steam-power for many years originated in the fertile brain of James Watt. The defects of the Newcomen engine were so serious, that it was no sooner known that Boulton of Soho had become interested in a new machine for raising water by steam-power, than inquiries came to him from all sides, from mine-owners who were on the point of being drowned out, and from proprietors whose profits were absorbed by the expense of pumping, and who were glad to pay the £5 per horse-power per year finally settled upon as royalty. The London municipal water-works authorities were also ready to negotiate for pumping-engines for raising water to supply the metropolis. The firm was therefore at once driven to make preparations for a large business. The first and most important matter, however, was to secure an extension of the patent, which was soon to expire. If not renewed, the 15 years of study and toil, of poverty and anxiety, through which Watt had toiled, would prove profitless to the inventor, and the fruits of his genius would have become the unearned property of others. Watt saw, at one time, little hope of securing the necessary act of Parliament, and was greatly tempted to accept a position tendered him by the Russian Government, upon the solicitation of his old friend, Dr. Robison, then a Professor of Mathematics at the Naval School at Cronstadt. The salary was £1,000--a princely income for a man in Watt's circumstances, and a peculiar temptation to the needy mechanic. Watt, however, went to London, and, with the help of his own and of Boulton's influential friends, succeeded in getting his bill through. His patent was extended 24 years, and Boulton & Watt set about the work of introducing their engines with the industry and enterprise which characterized their every act. In the new firm, Boulton took charge of the general business, and Watt superintended the design, construction, and erection of their engines. Boulton's business capacity, with Watt's wonderful mechanical ability--Boulton's physical health, and his vigor and courage, offsetting Watt's feeble health and depression of spirits--and, more than all, Boulton's pecuniary resources, both in his own purse and in those of his friends, enabled the firm to conquer all difficulties, whether in finance, in litigation, or in engineering. It was only after the successful erection and operation of several engines that Boulton and Watt became legally partners. The understood terms were explicitly stated by Watt to include an assignment to Boulton of two-thirds the patent-right; Boulton paying all expenses, advancing stock in trade at an appraised valuation, on which it was to draw interest; Watt making all drawings and designs, and drawing one-third net profits. As soon as Watt was relieved of the uncertainties regarding his business connections, he married a second wife, who, as Arago says, by "her various talent, soundness of judgment, and strength of character," made a worthy companion to the large-hearted and large-brained engineer. Thenceforward his cares were only such as every business-man expects to be compelled to sustain, and the next ten years were the most prolific in inventions of any period in Watt's life. From 1775 to 1785 the partners acquired five patents, covering a large number of valuable improvements upon the steam-engine, and several independent inventions. The first of these patents covered the now familiar and universally-used copying-press for letters, and a machine for drying cloth by passing it between copper rollers filled with steam of sufficiently high temperature to rapidly evaporate the moisture. This patent was issued February 14, 1780. [Illustration: FIG. 27.--Watt's Engine, 1781.] In the following year, October 25, 1781, Watt patented five devices by which he obtained the rotary motion of the engine-shaft without the use of a crank. One of these was the arrangement shown in Fig. 27, and known as the "sun-and-planet" wheels. The crank-shaft carries a gear-wheel, which is engaged by another securely fixed upon the end of the connecting-rod. As the latter is compelled to revolve about the axis of the shaft by a tie which confines the connecting-rod end at a fixed distance from the shaft, the shaft-gear is compelled to revolve, and the shaft with it. Any desired velocity-ratio was secured by giving the two gears the necessary relative diameters. A fly-wheel was used to regulate the motion of the shaft.[39] Boulton & Watt used the sun-and-planet device on many engines, but finally adopted the crank, when the expiration of the patent held by Matthew Wasborough, and which had earlier date than Watt's patent of 1781, permitted them. Watt had proposed the use of a crank, it is said, as early as 1771, but Wasborough anticipated him in securing the patent. Watt had made a model of an engine with a crank and fly-wheel, and he has stated that one of his workmen, who had seen the model, described it to Wasborough, thus enabling the latter to deprive Watt of his own property. The proceeding excited great indignation on the part of Watt; but no legal action was taken by Boulton & Watt, as the overthrow of the patent was thought likely to do them injury by permitting its use by more active competitors and more ingenious men. [39] For the privilege of using the fly-wheel to regulate the motion of the engine, Boulton & Watt paid a royalty to Matthew Wasborough, who had patented it, and who held also the patent for its combination with a crank, as invented by Pickard and Steed. The next patent issued to Watt was an exceedingly important one, and of especial interest in a history of the development of the economical application of steam. This patent included: 1. The expansion of steam, and six methods of applying the principle and of equalizing the expansive power. 2. The double-acting steam-engine, in which the steam acts on each side of the piston alternately, the opposite side being in communication with the condenser. 3. The double or coupled steam-engine--two engines capable of working together, or independently, as may be desired. 4. The use of a rack on the piston-rod, working into a sector on the end of the beam, thus securing a perfect rectilinear motion of the rod. 5. A rotary engine, or "steam-wheel." The efficiency to be secured by the expansion of steam had long been known to Watt, and he had conceived the idea of economizing some of that power, the waste of which was so plainly indicated by the violent rushing of the exhaust-steam into the condenser, as early as 1769. This was described in a letter to Dr. Small, of Birmingham, in May of that year. When experimenting at Kinneil, he had tried to determine the real value of the principle by trial on his small engine. Boulton had also recognized the importance of this improved method of working steam, and their earlier Soho engines were, as Watt said, made with cylinders "double the size wanted, and cut off the steam at half-stroke." But, though "this was a great saving of steam, so long as the valves remained as at first," the builders were so constantly annoyed by alterations of the valves by proprietors and their engineers, that they finally gave up that method of working, hoping ultimately to be able to resume it when workmen of greater intelligence and reliability could be found. The patent was issued July 17, 1782. Watt specified a cut-off at one-quarter stroke as usually best. Watt's explanation of the method of economizing by expansive working, as given to Dr. Small,[40] is worthy of reproduction. He says: "I mentioned to you a method of still doubling the effect of steam, and that tolerably easy, by using the power of steam rushing into a vacuum, at present lost. This would do a little more than double the effect, but it would too much enlarge the vessels to use it all. It is peculiarly applicable to wheel-engines, and may supply the want of a condenser where force of steam is only used; for, open one of the steam-valves and admit steam, until one-fourth of the distance between it and the next valve is filled with steam, shut the valve, and the steam will continue to expand and to pass round the wheel with a diminishing power, ending in one-fourth its first exertion. The sum of this series you will find greater than one-half, though only one-fourth steam was used. The power will indeed be unequal, but this can be remedied by a fly, or in several other ways." [40] "Lives of Boulton and Watt," Smiles. It will be noticed that Watt suggests, above, the now well-known non-condensing engine. He had already, as has been seen, described it in his patent of 1769, as also the rotary engine. Watt illustrates and explains his idea very neatly, by a sketch similar to that here given (Fig. 28). Steam, entering the cylinder at _a_, is admitted until one-fourth the stroke has been made, when the steam-valve is closed, and the remainder of the stroke is performed without further addition of steam. The variation of steam-pressure is approximately inversely proportional to the variation of its volume. Thus, at half-stroke, the pressure becomes one-half that at which the steam was supplied to the cylinder. At the end of the stroke it has fallen to one-fourth the initial pressure. The pressure is always nearly equal to the product of the initial pressure and volume divided by the volume at the given instant. In symbols, _PV_ _P´_ = ----. _V´_ It is true that the condensation of steam doing work changes this law in a marked manner; but the condensation and reëvaporation of steam, due to the transfer of heat to and from the metal of the cylinder, tends to compensate the first variation by a reverse change of pressure with change of volume. [Illustration: FIG. 28.--Expansion of Steam.] The sketch shows this progressive variation of pressure as expansion proceeds. It is seen that the work done per unit of volume of steam as taken from the boiler is much greater than when working without expansion. The product of the mean pressure by the volume of the cylinder is less, but the quotient obtained by dividing this quantity by the volume or weight of steam taken from the boiler, is much greater with than without expansion. For the case assumed and illustrated, the work done during expansion is one and two-fifths times that done previous to cutting off the steam, and the work done per pound of steam is 2.4 times that done without expansion. Were there no losses to be met with and to be exaggerated by the use of steam expansively, the gain would become very great with moderate expansion, amounting to twice the work done when "following" full stroke, when the steam is cut off at one-seventh. The estimated gain is, however, never realized. Losses by friction, by conduction and radiation of heat, and by condensation and reëvaporation in the cylinder--of which losses the latter are most serious--after passing a point which is variable, and which is determined by the special conditions in each case, augment with greater rapidity than the gain by expansion. In actual practice, it is rarely found, except where special precautions are taken to reduce these losses, that economy follows expansion to a greater number of volumes than about one-half the square root of the steam-pressure; i. e., about twice for 15 or 20 pounds pressure, three times for about 30 pounds, and four and five times for 60 or 65 and for 100 to 125 pounds respectively. Watt very soon learned this general principle; but neither he, nor even many modern engineers, seem to have learned that too great expansion often gives greatly-reduced economy. The inequality of pressure due to expansion, to which he refers, was a source of much perplexity to Watt, as he was for a long time convinced that he must find some method of "equalizing" the consequent irregular effort of the steam upon the piston. The several methods of "equalizing the expansive power" which are referred to in the patent were attempts to secure this result. By one method, he shifted the centre as the beam vibrated, thus changing the lengths of the arms of that great lever, to compensate the change of moment consequent upon the change of pressure. He finally concluded that a fly-wheel, as first proposed by Fitzgerald, who advised its use on Papin's engine, would be the best device on engines driving a crank, and trusted to the inertia of a balance-weight in his pumping-engines, or to the weight of the pump-rods, and permitted the piston to take its own speed so far as it was not thus controlled. The double-acting engine was a modification of the single-acting engine, and was very soon determined upon after the successful working of the latter had become assured. Watt had covered in the top of his single-acting engine, to prevent cooling the interior of the cylinder by contact with the comparatively cold atmosphere. When this had been done, there was but a single step required to convert the machine into the double-acting engine. This alteration, by which the steam was permitted to act upon the upper and the lower sides of the piston alternately, had been proposed by Watt as early as 1767, and a drawing of the engine was laid before a committee of the House of Commons in 1774-'75. By this simple change Watt doubled the power of his engine. Although invented much earlier, the plan was not patented until he was, as he states, driven to take out the patent by the "plagiarists and pirates" who were always ready to profit by his ingenuity. This form of engine is now almost universally used. The single-acting pumping-engine remains in use in Cornwall, and in a few other localities, and now and then an engine is built for other purposes, in which steam acts only on one side of the piston; but these are rare exceptions to the general rule. The subject of his next invention was not less interesting. The double-cylinder or "compound" engine has now, after the lapse of nearly a century, become an important and usual type of engine. It is impossible to determine precisely to whom to award the credit of its first conception. Dr. Falk, in 1779, had proposed a double-acting engine, in which there were two single-acting cylinders, acting in opposite directions and alternately on opposite sides of a wheel, with which a rack on the piston-rod of each geared. Watt claimed that Hornblower, the patentee of the "compound engine," was an infringer upon his patents; and, holding the patent on the separate condenser, he was able to prevent the engine of his competitor taking such form as to be successfully introduced. The Hornblower engine was soon given up. Watt stated that this form of engine had been invented by him as early as 1767, and that he had explained its peculiarities to Smeaton and others several years before Hornblower attempted to use it. He wrote to Boulton: "It is no less than our double-cylinder engine, worked upon our principle of expansion." He never made use of the plan, however; and the principal object sought, apparently, in patenting this, as well as many other devices, was to secure himself against competition. The rack and sector patented at this time was soon superseded by the parallel-motion; and the last claim, the "steam-wheel" or rotary engine, although one was built of considerable size, was not introduced. After the patent of 1782 had been secured, Watt turned his attention, when not too hard-pressed by business, to other schemes, and to experimenting with still other modifications and applications of his engine. He had, as early as 1777, proposed to make a steam-hammer for Wilkinson's forge; but he was too closely engaged with more important matters to take hold of the project with much earnestness until late in the year 1782, when, after some preliminary trials, he reported, December 13th: "We have tried our little tilting-forge hammer at Soho with success. The following are some of the particulars: Cylinder, 15 inches in diameter; 4 feet stroke; strokes per minute, 20. The hammer-head, 120 pounds weight, rises 8 inches, and strikes 240 blows per minute. The machine goes quite regularly, and can be managed as easily as a water-mill. It requires a very small quantity of steam--not above half the contents of the cylinder per stroke. The power employed is not more than one-fourth of what would be required to raise the quantity of water which would enable a water-wheel to work the same hammer with the same velocity." He immediately set about making a much heavier hammer, and on April 26, 1783, he wrote that he had done "a thing never done before"--making his hammer strike 300 blows a minute. This hammer weighed 7-1/2 hundredweight, and had a drop of 2 feet. The steam-cylinder had a diameter of 42 inches and 6 feet stroke of piston, and was calculated to have sufficient power to drive four hammers weighing 7 hundredweight each. The engine made 20 strokes per minute, the hammer giving 90 blows in the same time. This new application of steam-power proving successful, Watt next began to develop a series of minor inventions, which were finally secured by his patent of April 27, 1784, together with the steam tilt-hammer, and a steam-carriage, or "locomotive engine." The contrivance previously used for guiding the head of the piston-rod--the sectors and chains, or rack--had never given satisfaction. The rudeness of design of the contrivance was only equalled by its insecurity. Watt therefore contrived a number of methods of accomplishing the purpose, the most beautiful and widely-known of which is the "parallel-motion," although it has now been generally superseded by one of the other devices patented at the same time--the cross-head and guides. As originally proposed, a rod was attached to the head of the piston-rod, standing vertically when the latter was at quarter-stroke. The upper end of this rod was pivoted to the end of the beam, and the lower end to the extremity of a horizontal rod having a length equal to one-half the length of the beam. The other end of the horizontal rod was coupled to the frame of the engine. As the piston rose and fell, the upper and lower ends of the vertical rod were swayed in opposite directions, and to an equal extent, by the beam and the lower horizontal rod, the middle point at which the piston-rod was attached preserving its position in the vertical line. This form was objectionable, as the whole effort of the engine was transmitted through the parallel-motion rods. Another form is shown in the sketch given of the double-acting engine in Fig. 31, which was free from this defect. The head of the piston-rod, _g_, was guided by rods connecting it with the frame at _c_, and forming a "parallelogram," _g d e b_, with the beam. Many varieties of "parallel-motion" have been devised since Watt's invention was attached to his engines at Soho. They usually are more or less imperfect, guiding the piston-rod in a line only approximately straight. The cross-head and guides are now generally used, very much as described by Watt in this patent as his "second principle." This device will be seen in the engravings given hereafter of more modern engines. The head of the piston-rod is fitted into a transverse bar, or cross-head, which carries properly-shaped pieces at its extremities, to which are bolted "gibs," so made as to fit upon guides secured to the engine-frame. These guides are adjusted to precise parallelism with the centre line of the cylinder. The cross-head, sliding in or on these guides, moves in a perfectly straight line, and, compelling the piston-rod to move with it, the latter is even more perfectly guided than by a parallel-motion. This arrangement, where properly proportioned, is not necessarily subject to great friction, and is much more easily adjusted and kept in line than the parallel-motion when wear occurs or maladjustment takes place. By the same patent, Watt secured the now common "puppet-valve" with beveled seat, and the application of the steam-engine to driving rolling-mills and hammers for forges, and to "wheel-carriages for removing persons or goods, or other matters, from place to place." For the latter purpose he proposes to use boilers "of wood, or of thin metal, strongly secured by hoops or otherwise," and containing "internal fire-boxes." He proposed to use a condenser cooled by currents of air. It would require too much space to follow Watt in all his schemes for the improvement and for the application of the steam-engine. A few of the more important and more ingenious only can be described. Many of the contracts of Boulton & Watt gave them, as compensation for their engines, a fraction--usually one-third--of the value of the fuel saved by the use of the Watt engine in place of the engine of Newcomen, the amount due being paid annually or semiannually, with an option of redemption on the part of the purchaser at ten years' purchase. This form of agreement compelled a careful determination, often, of the work done and fuel consumed by both the engine taken out and that put in its place. It was impossible to rely upon any determination by personal observation of the number of strokes made by the engine. Watt therefore made a "counter," like that now familiar to every one as used on gas-meters. It consists of a train of wheels moving pointers on several dials, the first dial showing tens, the second hundreds, the third thousands, etc., strokes or revolutions. Motion was communicated to the train by means of a pendulum, the whole being mounted on the beam of the engine, where every vibration produced a swing of the pendulum. Eight dials were sometimes used, the counter being set and locked, and only opened once a year, when the time arrived for determining the work done during the preceding twelve-month. The application of his engine to purposes for which careful adjustment of speed was requisite, or where the load was subject to considerable variation, led to the use of a controlling-valve in the steam-pipe, called the "throttle-valve," which was adjustable by hand, and permitted the supply of steam to the engine to be adjusted at any instant and altered to any desired extent. It is now given many forms, but it still is most usually made just as originally designed by Watt. It consists of a circular disk, which just closes up the steam-pipe when set directly across it, or of an elliptical disk, which closes the pipe when standing at an angle of somewhat less than 90° with the line of the pipe. This disk is carried on a spindle extending through the pipe at one side, and carrying on its outer end an arm by means of which it may be turned into any position. When placed with its face in line with the pipe, it offers very little resistance to the flow of steam to the engine. When set in the other position, it shuts off steam entirely and stops the engine. It is placed in such position at any time, that the speed of the engine is just that required at the time. In the engraving of the double-acting engine with fly-wheel (Fig. 31), it is shown at _T_, as controlled by the governor. [Illustration: FIG. 29.--The Governor.] The governor, or "fly-ball governor," as it is often distinctively called, was another of Watt's minor but very essential inventions. Two heavy iron or brass balls, _B B´_, were suspended from pins, _C C´_, in a little cross-piece carried on the head of a vertical spindle, _A A´_, driven by the engine. The speed of the engine varying, that of the spindle changed correspondingly, and the faster the balls were swung the farther they separated. When the engine's speed decreased, the period of revolution of the balls was increased, and they fell back toward the spindle. Whenever the velocity of the engine was uniform, the balls preserved their distance from the spindle and remained at the same height, their altitude being determined by the relation existing between the force of gravity and centrifugal force in the temporary position of equilibrium. The distance from the point of suspension down to the level of the balls is always equal to 9.78 inches divided by the square of the number of revolutions per second--i. e., _h_ = 9.78 (1/_N_^2) = 0.248 (1/_N_^2) meters. The arms carrying the balls, or the balls themselves, are pinned to rods, _M M´_, which are connected to a piece, _N N´_, sliding loosely on the spindle. A score, _T_, cut in this piece engages a lever, _V_, and, as the balls rise and fall, a rod, _W_, is moved, closing and opening the throttle-valve, and thus adjusting the supply of steam in such a way as to preserve a nearly fixed speed of engine. The connection with the throttle-valve and with the cut-off valve-gear is seen not only in the engraving of the double-acting Watt engine, but also in those of the Greene and the Corliss engines. This contrivance had previously been used in regulating water-wheels and windmills. Watt's invention consisted in its application to the regulation of the steam-engine. Still another useful invention of Watt's was his "mercury steam-gauge"--a barometer in which the height of the mercury was determined by the pressure of the steam instead of that of the atmosphere. This simple instrument consisted merely of a bent tube containing a portion of mercury. One leg, _B D_, of this U-tube was connected with the steam-pipe, or with the boiler by a small steam-pipe; the other end, _C_, was open to the atmosphere. The pressure of the steam on the mercury in _B D_ caused it to rise in the other "leg" to a height exactly proportioned to the pressure, and causing very nearly two inches difference of level to the pound, or one inch to the pound actual rise in the outer leg. The rude sketch from Farey, here given (Fig. 30), indicates sufficiently well the form of this gauge. It is still considered by engineers the most reliable of all forms of steam-gauge. Unfortunately, it is not conveniently applicable at high pressure. The scale, _A_, is marked with numbers indicating the pressure, which numbers are indicated by the head of a rod floating up with the mercury. A similar gauge was used to determine the degree of perfection of vacuum attained in the condenser, the mercury falling in the outer leg as the vacuum became more complete. A perfect vacuum would cause a depression of level in that leg to 30 inches below the level of the mercury in the leg connected with the condenser. In a more usual form, it consisted of a simple glass tube having its lower end immersed in a cistern of mercury, as in the ordinary barometer, the top of the tube being connected with a pipe leading to the condenser. With a perfect vacuum in the condenser, the mercury would rise in the tube very nearly 30 inches. Ordinarily, the vacuum is not nearly perfect, and, a back pressure remaining in the condenser of one or two pounds per square inch, the atmospheric pressure remaining unbalanced is only sufficient to raise the mercury 26 or 28 inches above the level of the liquid metal in the cistern. [Illustration: FIG. 30. Mercury Steam Gauge. Glass Water Gauge.] To determine the height of water in his boiler, Watt added to the gauge-cocks already long in use the "glass water-gauge," which is still seen in nearly every well-arranged boiler. This was a glass tube, _a a´_ (Fig. 30), mounted on a standard attached to the front of the boiler, and at such a height that its middle point was very little below the proposed water-level. It was connected by a small pipe, _r_, at the top to the steam-space, and another little pipe, _r´_, led into the boiler from its lower end below the water-line. As the water rose and fell within the boiler, its level changed correspondingly in the glass. This little instrument is especially liked, because the position of the water is at all times shown to the eye of the attendant. If carefully protected against sudden changes of temperature, it answers perfectly well with even very high pressures. The engines built by Boulton & Watt were finally fitted with the crank and fly-wheel for application to the driving of mills and machinery. The accompanying engraving (Fig. 31) shows the engine as thus made, combining all of the essential improvements designed by its inventor. In the engraving, _C_ is the steam-cylinder, _P_ the piston, connected to the beam by the link, _g_, and guided by the parallel-motion, _g d c_. At the opposite end of the beam a connecting-rod, _O_, connects with the crank and fly-wheel shaft. _R_ is the rod of the air-pump, by means of which the condenser is kept from being flooded by the water used for condensation, which water-supply is regulated by an "injection-handle," _E_. A pump-rod, _N_, leads down from the beam to the cold-water pump, by which water is raised from the well or other source to supply the needed injection-water. The air-pump rod also serves as a "plug-rod," to work the valves, the pins at _m_ and _R_ striking the lever, _m_, at either end of the stroke. When the piston reaches the top of the cylinder, the lever, _m_, is raised, opening the steam-valve, _B_, at the top, and the exhaust-valve, _E_, at the bottom, and at the same time closing the exhaust at the top and the steam at the bottom. When the entrance of steam at the top and the removal of steam-pressure below the piston has driven the piston to the bottom, the pin, _R_, strikes the lever, _m_, opening the steam and closing the exhaust valve at the bottom, and similarly reversing the position of the valves at the top. The position of the valves is changed in this manner with every reversal of the motion of the piston as the crank "turns over the centre." [Illustration: FIG. 31.--Boulton & Watt's Double-Acting Engine, 1784.] The earliest engines of the double-acting kind, and of any considerable size, which were built to turn a shaft, were those which were set up in the Albion Mills, near Blackfriars' Bridge, London, in 1786, and destroyed when the mills burned down in 1791. There were a pair of these engines (shown in Fig. 27), of 50 horse-power each, and geared to drive 20 pairs of stones, making fine flour and meal. Previous to the erection of this mill the power in all such establishments had been derived from windmills and water-wheels. This mill was erected by Boulton & Watt, and capitalists working with them, not only to secure the profit anticipated from locating a flour-mill in the city of London, but also with a view to exhibiting the capacity of the new double-acting "rotating" engine. The plan was proposed in 1783, and work was commenced in 1784; but the mill was not set in operation until the spring of 1786. The capacity of the mill was, in ordinary work, 16,000 bushels of wheat ground into fine flour per week. On one occasion, the mill turned out 3,000 bushels in 24 hours. In the construction of the machinery of the mill, many improvements upon the then standard practice were introduced, including cast-iron gearing with carefully-formed teeth and iron framing. It was here that John Rennie commenced his work, after passing through his apprenticeship in Scotland, sending his chief assistant, Ewart, to superintend the erection of the milling machinery. The mill was a success as a piece of engineering, but a serious loss was incurred by the capitalists engaged in the enterprise, as it was set on fire a few years afterward and entirely destroyed. Boulton and Watt were the principal losers, the former losing £6,000, and the latter £3,000. The valve-gear of this engine, a view of which is given in Fig. 27, was quite similar to that used on the Watt pumping-engine. The accompanying illustration (Fig. 32) represents this valve-motion as attached to the Albion Mills engine. [Illustration: FIG. 32.--Valve-Gear of the Albion Mills Engine.] The steam-pipe, _a b d d e_, leads the steam from the boiler to the chambers, _b_ and _e_. The exhaust-pipe, _g g_, leads from _h_ and _i_ to the condenser. In the sketch, the upper steam and the lower exhaust valves, _b_ and _f_, are opened, and the steam-valve, _e_, and exhaust-valve, _c_, are closed, the piston being near the upper end of the cylinder and descending. _l_ represents the plug-frame, which carries tappets, 2 and 3, which engage the lever, _s_, at either end of its throw, and turn the shaft, _u_, thus opening and closing _c_ and _e_ simultaneously by means of the connecting-links, 13 and 14. A similar pair of tappets on the opposite side of the plug-rod move the valves, _b_ and _f_, by means of the rods, 10 and 11, the arm, _r_, when struck by those tappets, turning the shaft, _t_, and thus moving the arms to which those rods are attached. Counterbalance-weights, carried on the ends of the arms, 4 and 15, retain the valves on their seats when closed by the action of the tappets. When the piston nearly reaches the lower end of the cylinder, the tappet, 1, engages the arm, _r_, closing the steam-valve, _b_, and the next instant shutting the exhaust-valve, _f_. At the same time, the tappet, 3, by moving the arm, _s_, downward, opens the steam-valve, _e_, and the exhaust-valve, _c_. Steam now no longer issues from the steam-pipe into the space, _c_, and thence into the engine-cylinder (not shown in the sketch); but it now enters the engine through the valve, _e_, forcing the piston upwards. The exhaust is simultaneously made to occur at the upper end, the rejected steam passing from the engine into the space, _c_, and thence through _c_ and the pipe, _g_, into the condenser. This kind of valve-gear was subsequently greatly improved by Murdoch, Watt's ingenious and efficient foreman, but it is now entirely superseded on engines of this class by the eccentric, and the various forms of valve-gear driven by it. [Illustration: FIG. 33.--Watt's Half-Trunk Engine, 1784.] The "trunk-engine" was still another of the almost innumerable inventions of Watt. A half-trunk engine is described in his patent of 1784, as shown in the accompanying sketch (Fig. 33), in which _A_ is the cylinder, _B_ the piston, and _C_ its rod, encased in the half-trunk, _D_. The plug-rod, _G_, moves the single pair of valves by striking the catches, _E_ and _F_, as was usual with Watt's earlier engines. Watt's steam-hammer was patented at the same time. It is seen in Fig. 34, in which _A_ is the steam-cylinder and _B_ its rod, the engine being evidently of the form just described. It works a beam, _C C_, which in turn, by the rod, _M_, works the hammer-helve, _L J_, and the hammer, _L_. The beam, _F G_, is a spring, and the block, _N_, the anvil. [Illustration: FIG. 34.--The Watt Hammer, 1784.] Watt found it impossible to determine the duty of his engines at all times by measurement of the work itself, and endeavored to find a way of ascertaining the power produced, by ascertaining the pressure of steam within the cylinder. This pressure was so variable, and subject to such rapid as well as extreme fluctuations, that he found it impossible to make use of the steam-gauge constructed for use on the boiler. He was thus driven to invent a special instrument for this work, which he called the "steam-engine indicator." This consisted of a little steam-cylinder containing a nicely-fitting piston, which moved without noticeable friction through a range which was limited by the compression of a helical spring, by means of which the piston was secured to the top of its cylinder. The distance through which the piston rose was proportional to the pressure exerted upon it, and a pointer attached to its rod traversed a scale upon which the pressure per square inch could be read. The lower end of the instrument being connected with the steam-cylinder of the engine by a small pipe fitted with a cock, the opening of the latter permitted steam from the engine-cylinder to fill the indicator-cylinder, and the pressure of steam was always the same in both cylinders. The indicator-pointer therefore traversed the pressure-scale, always exhibiting the pressure existing at the instant in the cylinder of the engine. When the engine was at rest and steam off, the indicator-piston stood at the same level as when detached from the engine, and the pointer stood at 0 on the scale. When steam entered, the piston rose and fell with the fluctuations of pressure; and when the exhaust-valve opened, discharging the steam and producing a vacuum in the steam-cylinder, the pointer of the indicator dropped below 0, showing the degree of exhaustion. Mr. Southern, one of Watt's assistants, fitted the instrument with a sliding board, moved horizontally backward and forward by a cord or link-work connecting directly or indirectly with the engine-beam, and thus giving it a motion coincident with that of the piston. This board carried a piece of paper, upon which a pencil attached to the indicator piston-rod drew a curve. The vertical height of any point on this curve above the base-line measured the pressure in the cylinder at the moment when it was made, and the horizontal distance of the point from either end of the diagram determined the position, at the same moment, of the engine-piston. The curve thus inscribed, called the "indicator card," or indicator diagram, exhibiting every minute change in the pressure of steam in the engine, not only enabled the mean pressure and the power of the engine to be determined by its measurement, but, to the eye of the expert engineer, it was a perfectly legible statement of the position of the valves of the engine, and revealed almost every defect in the action of the engine which could not readily be detected by external examination. It has justly been called the "engineers' stethoscope," opening the otherwise inaccessible parts of the steam-engine to the inspection of the engineer even more satisfactorily than the stethoscope of the physician gives him a knowledge of the condition and working of organs contained within the human body. This indispensable and now familiar engineers' instrument has since been modified and greatly improved in detail. The Watt engine had, by the construction of the improvements described in the patents of 1782-'85, been given its distinctive form, and the great inventor subsequently did little more than improve it by altering the forms and proportions of its details. As thus practically completed, it embodied nearly all the essential features of the modern engine; and, as we have seen, the marked features of our latest practice--the use of the double cylinder for expansion, the cut-off valve-gear, and surface-condensation--had all been proposed, and to a limited extent introduced. The growth of the steam-engine has here ceased to be rapid, and the changes which followed the completion of the work of James Watt have been minor improvements, and rarely, if ever, real developments. Watt's mind lost none of its activity, however, for many years. He devised and patented a "smoke-consuming furnace," in which he led the gases produced on the introduction of fresh fuel over the already incandescent coal, and thus burned them completely. He used two fires, which were coaled alternately. Even when busiest, also, he found time to pursue more purely scientific studies. With Boulton, he induced a number of well-known scientific men living near Birmingham to join in the formation of a "Lunar Society," to meet monthly at the houses of its members, "at the full of the moon." The time was thus fixed in order that those members who came from a distance should be able to drive home, after the meetings, by moonlight. Many such societies were then in existence in England; but that at Birmingham was one of the largest and most distinguished of them all. Boulton, Watt, Drs. Small, Darwin, and Priestley, were the leaders, and among their occasional visitors were Herschel, Smeaton, and Banks. Watt called these meetings "Philosophers' meetings." It was during the period of most active discussion at the "philosophers' meetings" that Cavendish and Priestley were experimenting with mixtures of oxygen and hydrogen, to determine the nature of their combustion. Watt took much interest in the subject, and, when informed by Priestley that he and Cavendish had both noticed a deposit of moisture invariably succeeding the explosion of the mixed gases, when contained in a cold vessel, and that the weight of this water was approximately equal to the weight of the mixed gases, he at once came to the conclusion that the union of hydrogen with oxygen produced water, the latter being a chemical compound, of which the former were constituents. He communicated this reasoning, and the conclusions to which it had led him, to Boulton, in a letter written in December, 1782, and addressed a letter some time afterward to Priestley, which was to have been read before the Royal Society in April, 1783. The letter was not read, however, until a year later, and, three months after, a paper by Cavendish, making the same announcement, had been laid before the Society. Watt stated that both Cavendish and Lavoisier, to whom also the discovery is ascribed, received the idea from him. The action of chlorine in bleaching organic coloring-matters, by (as since shown) decomposing them and combining with their hydrogen, was made known to Watt by M. Berthollet, the distinguished French chemist, and the former immediately introduced its use into Great Britain, by inducing his father-in-law, Mr. Macgregor, to make a trial of it. The copartnership of Boulton & Watt terminated by limitation, and with the expiration of the patents under which they had been working, in the first year of the present century; and both partners, now old and feeble, withdrew from active business, leaving their sons to renew the agreement and to carry on the business under the same firm-style. Boulton, however, still interested himself in some branches of manufacture, especially in his mint, where he had coined many years and for several nations. Watt retired, a little later, to Heathfield, where he passed the remainder of his life in peaceful enjoyment of the society of his friends, in studies of all current matters of interest in science, as well as in engineering. One by one his old friends died--Black in 1799, Priestley, an exile to America, in 1803, and Robison a little later. Boulton died, at the age of eighty-one, August 17, 1809, and even the loss of this nearest and dearest of his friends outside the family was a less severe blow than that of his son Gregory, who died in 1804. Yet the great engineer and inventor was not depressed by the loneliness which was gradually coming upon him. He wrote: "I know that all men must die, and I submit to the decrees of Nature, I hope, with due reverence to the Disposer of events;" and neglected no opportunity to secure amusement or instruction, and kept body and mind constantly occupied. He still attended the weekly meetings of the club, meeting Rennie and Telford, and other distinguished men of his own and the succeeding generation. He lost nothing of his fondness for invention, and spent many months in devising a machine for copying statuary, which he had not perfected to his own satisfaction at the time of his death, ten years later. This machine was a kind of pentagraph, which could be worked in any plane, and in which the marking-pencil gave place to a cutting-tool. The tracing-point followed the surface of the pattern, while the cutting-point, following its motion precisely, formed a fac-simile in the material operated upon. In the year 1800 he invented the water-main which was laid down by the Glasgow Water-Works Company across the Clyde. The joints were spherical and articulated, like those of the lobster's tail. His workshop, of which a sketch is hereafter given, as drawn by the artist Skelton, was in the garret of his house, and was well supplied with tools and all kinds of laboratory material. His lathe and his copying-machine were placed before the window, and his writing-desk in the corner. Here he spent the greater part of his leisure time, often even taking his meals in the little shop, rather than go to the table for them. Even when very old, he occasionally made a journey to London or Glasgow, calling on his old friends and studying the latest engineering devices and inspecting public works, and was everywhere welcomed by young and old as the greatest living engineer, or as the kind and wise friend of earlier days. He died August 19, 1819, in the eighty-third year of his age, and was buried in Handsworth Church. The sculptor Chantrey was employed to place a fitting monument above his grave, and the nation erected a statue of the great man in Westminster Abbey. This sketch of the greatest of all the inventors of the steam-engine has been given no greater length than its subject justifies. Whether we consider Watt as the inventor of the standard steam-engine of the nineteenth century, as the scientific investigator of the physical principles upon which the invention is based, or as the builder and introducer of the most powerful known instrument by which the "great sources of power in Nature are converted, adapted, and applied for the use and convenience of man," he is fully entitled to preëminence. His character as a man was no less admirable than as an engineer. Smiles, Watt's most conscientious and indefatigable biographer, writes:[41] [41] "Life of Watt," p. 512. [Illustration: FIG. 35.--James Watt's Workshop. (From Smiles's "Lives of Boulton and Watt.")] "Some months since, we visited the little garret at Heathfield in which Watt pursued the investigations of his later years. The room had been carefully locked up since his death, and had only once been swept out. Everything lay very much as he left it. The piece of iron which he was last employed in turning, lay on the lathe. The ashes of the last fire were in the grate; the last bit of coal was in the scuttle. The Dutch oven was in its place over the stove, and the frying-pan in which he cooked his meals was hanging on its accustomed nail. Many objects lay about or in the drawers, indicating the pursuits which had been interrupted by death--busts, medallions, and figures, waiting to be copied by the copying-machine--many medallion-moulds, a store of plaster-of-Paris, and a box of plaster casts from London, the contents of which do not seem to have been disturbed. Here are Watt's ladles for melting lead, his foot-rule, his glue-pot, his hammer. Reflecting mirrors, an extemporized camera with the lenses mounted on pasteboard, and many camera-glasses laid about, indicate interrupted experiments in optics. There are quadrant-glasses, compasses, scales, weights, and sundry boxes of mathematical instruments, once doubtless highly prized. In one place a model of the governor, in another of the parallel-motion, and in a little box, fitted with wooden cylinders mounted with paper and covered with figures, is what we suppose to be a model of his calculating-machine. On the shelves are minerals and chemicals in pots and jars, on which the dust of nearly half a century has settled. The moist substances have long since dried up; the putty has been turned to stone, and the paste to dust. On one shelf we come upon a dish in which lies a withered bunch of grapes. On the floor, in a corner, near to where Watt sat and worked, is a hair-trunk--a touching memorial of a long-past love and a long-dead sorrow. It contains all poor Gregory's school-books, his first attempts at writing, his boy's drawings of battles, his first school-exercises down to his college-themes, his delectuses, his grammars, his dictionaries, and his class-books--brought into this retired room, where the father's eye could rest upon them. Near at hand is the sculpture-machine, on which he continued working to the last. Its wooden frame is worm-eaten, and dropping into dust, like the hands that made it. But though the great workman is gone to rest, with all his griefs and cares, and his handiwork is fast crumbling to decay, the spirit of his work, the thought which he put into his inventions, still survives, and will probably continue to influence the destinies of his race for all time to come." The visitor to Westminster Abbey will find neither monarch, nor warrior, nor statesman, nor poet, honored with a nobler epitaph than that which is inscribed on the pedestal of Chantrey's monument to Watt: NOT TO PERPETUATE A NAME, WHICH MUST ENDURE WHILE THE PEACEFUL ARTS FLOURISH, BUT TO SHOW THAT MANKIND HAVE LEARNT TO HONOR THOSE WHO BEST DESERVE THEIR GRATITUDE, THE KING, HIS MINISTERS, AND MANY OF THE NOBLES AND COMMONERS OF THE REALM, RAISED THIS MONUMENT TO JAMES WATT, WHO, DIRECTING THE FORCE OF AN ORIGINAL GENIUS, EARLY EXERCISED IN PHILOSOPHIC RESEARCH, TO THE IMPROVEMENT OF THE STEAM-ENGINE, ENLARGED THE RESOURCES OF HIS COUNTRY, INCREASED THE POWER OF MAN, AND ROSE TO AN EMINENT PLACE AMONG THE MOST ILLUSTRIOUS FOLLOWERS OF SCIENCE AND THE REAL BENEFACTORS OF THE WORLD. BORN AT GREENOCK, MDCCXXXVI. DIED AT HEATHFIELD, IN STAFFORDSHIRE, MDCCCXIX. [Illustration: Tomb of James Watt.] SECTION II.--THE CONTEMPORARIES OF JAMES WATT. In the chronology of the steam-engine, the contemporaries of Watt have been so completely overshadowed by the greater and more successful inventor, as to have been almost forgotten by the biographer and by the student of history. Yet, among the engineers and engine-builders, as well as among the inventors of his day, Watt found many enterprising rivals and keen competitors. Some of these men, had they not been so completely fettered by Watt's patents, would have probably done work which would have entitled them to far higher honor than has been accorded them. WILLIAM MURDOCH was one of the men to whom Watt, no less than the world, was greatly indebted. For many years he was the assistant, friend, and coadjutor of Watt; and it is to his ingenuity that we are to give credit for not only many independent inventions, but also for the suggestions and improvements which were often indispensable to the formation and perfection of some of Watt's own inventions. Murdoch was employed by Boulton & Watt in 1776, and was made superintendent of construction in the engine department, and given general charge of the erection of engines. He was sent into Cornwall, and spent in that district much of the time during which he served the firm, erecting pumping-engines, the construction of which for so many years constituted a large part of the business of the Soho establishment. He was looked upon by both Boulton and Watt as a sincere friend, as well as a loyal adherent, and from 1810 to 1830 was given a partner's share of the income of the firm, and a salary of £1,000. He retired from business at the last of the two dates named, and, dying in 1839, was buried near the two partners in Handsworth Church. Murdoch made a model, in 1784, of the locomotive patented by Watt in that year. He devised the arrangement of "sun-and-planet wheels," adopted for a time in all of Watt's "rotative" engines, and invented the oscillating steam-engine (Fig. 36) in 1785, using the "D-slide valves," _G_, moved by the gear, _E_, which was driven by an eccentric on the shaft, without regard to the oscillation of the cylinder, _A_. He was the inventor of a rotary engine and of many minor machines for special purposes, and of many machine-tools used at Soho in building engines and machines. He seems, like Watt, to have had special fondness for the worm-gear, and introduced it wherever it could properly take the place of ordinary gearing. Some of the machines designed by Watt and Murdoch, who always worked well together, were found still in use and in good working condition by the author when visiting the works at Soho in 1873. The old mint in which, from 1797 to 1805, Boulton had coined 4,000 tons of copper, had then been pulled down, and a new mint had been erected in 1860. Many old machines still remained about the establishment as souvenirs of the three great mechanics. [Illustration: FIG. 36.--Murdoch's Oscillating Engine, 1785.] Outside of Soho, Murdoch also found ample employment for his inventive talent. In 1792, while at Redruth, his residence before finally returning to Soho, he was led to speculate upon the possibility of utilizing the illuminating qualities of coal-gas, and, convinced of its practicability, he laid the subject before the Royal Society in 1808, and was awarded the Rumford gold medal. He had, ten years earlier, lighted a part of the Soho works with coal-gas, and in 1803 Watt authorized him to extend his pipes throughout all the buildings. Several manufacturers promptly introduced the new light, and its use extended very rapidly. Still another of Murdoch's favorite schemes was the transmission of power by the use of compressed air. He drove the pattern-shop engine at Soho by means of air from the blowing-engine in the foundery, and erected a pneumatic lift to elevate castings from the foundery-floor to the canal-bank. He made a steam-gun, introduced the heating of buildings by the circulation of hot water, and invented the method of transmitting packages through tubes by the impulse of compressed air, as now practised by the "pneumatic dispatch" companies. He died at the age of eighty-five years. Among the most active and formidable of Watt's business rivals was JONATHAN HORNBLOWER, the patentee of the "compound" or double-cylinder engine. A sketch of this engine, as patented by Hornblower in 1781, is here given (Fig. 37). It was first described by the inventor in the "Encyclopædia Britannica." It consists, as is seen by reference to the engraving, of two steam-cylinders, _A_ and _B_--_A_ being the low and _B_ the high pressure cylinder--the steam leaving the latter being exhausted into the former, and, after doing its work there, passing into the condenser, as already described. The piston-rods, _C_ and _D_, are both connected to the same part of the beam by chains, as in the other early engines. These rods pass through stuffing-boxes in the cylinder-heads, which are fitted up like those seen on the Watt engine. Steam is led to the engine through the pipe, _G Y_, and cocks, _a_, _b_, _c_, and _d_, are adjustable, as required, to lead steam into and from the cylinders, and are moved by the plug-rod, _W_, which actuates handles not shown. _K_ is the exhaust-pipe leading to the condenser. _V_ is the engine feed-pump rod, and _X_ the great rod carrying the pump-buckets at the bottom of the shaft. The cocks _c_ and _a_ being open and _b_ and _d_ shut, the steam passes from the boiler into the upper part of the steam-cylinder, _B_; and the communication between the lower part of _B_ and the top of _A_ is also open. Before starting, steam being shut off from the engine, the great weight of the pump-rod, _X_, causes that end of the beam to preponderate, the pistons standing, as shown, at the top of their respective steam-cylinders. The engine being freed from all air by opening all the valves and permitting the steam to drive it through the engine and out of the condenser through the "snifting-valve," _O_, the valves _b_ and _d_ are closed, and the cock in the exhaust-pipe opened. [Illustration: FIG. 37.--Hornblower's Compound Engine, 1781.] The steam beneath the piston of the large cylinder is immediately condensed, and the pressure on the upper side of that piston causes it to descend, carrying that end of the beam with it, and raising the opposite end with the pump-rods and their attachments. At the same time, the steam from the lower end of the small high-pressure cylinder being let into the upper end of the larger cylinder, the completion of the stroke finds a cylinder full of steam transferred from the one to the other with corresponding increase of volume and decrease of pressure. While expanding and diminishing in pressure as it passes from the smaller into the larger cylinder, this charge of steam gradually resists less and less the pressure of the steam from the boiler on the upper side of the piston of the small cylinder, _B_, and the net result is the movement of the engine by pressures exerted on the upper sides of both pistons and against pressures of less intensity on the under sides of both. The pressures in the lower part of the small cylinder, in the upper part of the large cylinder, and in the communicating passage, are evidently all equal at any given time. When the pistons have reached the bottoms of their respective cylinders, the valves at the top of the small cylinder, _B_, and at the bottom of the large cylinder, _A_, are closed, and the valves _c_ and _d_ are opened. Steam from the boiler now enters beneath the piston of the small cylinder; the steam in the larger cylinder is exhausted into the condenser, and the steam already in the small cylinder passes over into the large cylinder, following up the piston as it rises. Thus, at each stroke a small cylinder full of steam is taken from the boiler, and the same weight, occupying the volume of the larger cylinder, is exhausted into the condenser from the latter cylinder. Referring to the method of operation of this engine, Prof. Robison demonstrated that the effect produced was the same as in Watt's single-cylinder engine--a fact which is comprehended in the law enunciated many years later by Rankine, that, "so far as the theoretical action of the steam on the piston is concerned, it is immaterial whether the expansion takes place in one cylinder, or in two or more cylinders." It was found, in practice, that the Hornblower engine was no more economical than the Watt engine; and that erected at the Tin Croft Mine, Cornwall, in 1792, did even less work with the same fuel than the Watt engines. Hornblower was prosecuted by Boulton & Watt for infringement. The suit was decided against him, and he was imprisoned in default of payment of the royalty, and fine demanded. He died a disappointed and impoverished man. The plan thus unsuccessfully introduced by Hornblower was subsequently modified and adopted by others among the contemporaries of Watt; and, with higher steam and the use of the Watt condenser, the "compound" gradually became a standard type of steam-engine. Arthur Woolf, in 1804, re-introduced the Hornblower or Falck engine, with its two steam-cylinders, using steam of higher tension. His first engine was built for a brewery in London, and a considerable number were subsequently made. Woolf expanded his steam from six to nine times, and the pumping-engines built from his plans were said to have raised about 40,000,000 pounds one foot high per bushel of coals, when the Watt engine was raising but little more than 30,000,000. In one case, a duty of 57,000,000 was claimed. The most successful of those competitors of Watt who endeavored to devise a peculiar form of pumping-engine, which should have the efficiency of that of Boulton & Watt, and the necessary advantage in first cost, were WILLIAM BULL and RICHARD TREVITHICK.[42] The accompanying illustration shows the design, which was then known as the "Bull Cornish Engine." [42] For an exceedingly interesting and very faithful account of their work, _see_ "Life of Richard Trevithick," by F. Trevithick, London, 1872. [Illustration: FIG. 88.--Bull's Pumping-Engine, 1798.] The steam-cylinder, _a_, is carried on wooden beams, _b_, extending across the engine-house directly over the pump-well. The piston-rod, _c_, is secured to the pump-rods, _d d_, the cylinder being inverted, and the pumps, _e_, in the shaft, _f_, are thus operated without the intervention of the beam invariably seen in Watt's engines. A connecting-rod, _g_, attached to the pump-rod and to the end of a balance-beam, _h_, operates the latter, and is counterbalanced by a weight, _i_. The rod, _j_, serves both as a plug-rod and as an air-pump connecting-rod. A snifting-valve, _k_, opens when the engine is blown through, and relieves the condenser and air-pump, _l_, of all air. The rod, _m_, operates a solid air-pump piston, the valves of the pump being placed on either side at the base, instead of in the pump-bucket, as in Watt's engines. The condensing-water cistern was a wooden tank, _n_. A jet "pipe-condenser," _o_, was used instead of a jet condenser of the form adopted by other makers, and was supplied with water through the cock, _p_. The plug-rod, _q_, as it rises and falls with the pump-rods and balance-beam, operates the "gear-handles," _r r_, and opens and closes the valves, _s s_, at the required points in the stroke. The attendant works these valves by hand, in starting, from the floor, _t_. The operation of the engine is similar to that of a Watt engine. It is still in use, with a few modifications and improvements, and is a very economical and durable machine. It has not been as generally adopted, however, as it would probably have been had not the legal proscription of Watt's patents so seriously interfered with its introduction. Its simplicity and lightness are decided advantages, and its designers are entitled to great credit for their boldness and ingenuity, as displayed in their application of the minor devices which distinguish the engine. The design is probably to be credited to Bull originally; but Trevithick built some of these engines, and is supposed to have greatly improved them while working with Edward Bull, the son of the inventor, William Bull. One of these engines was erected by them at the Herland Mine, Cornwall, in 1798, which had a steam-cylinder 60 inches in diameter, and was built on the plan just described. Another of the contemporaries of James Watt was a clergyman, EDWARD CARTWRIGHT, the distinguished inventor of the power-loom, and of the first machine ever used in combing wool, who revived Watt's plan of surface-condensation in a somewhat modified form. Watt had made a "pipe-condenser," similar in plan to those now often used, but had simply immersed it in a tank of water, instead of in a constantly-flowing stream. Cartwright proposed to use two concentric cylinders or spheres, between which the steam entered when exhausted from the cylinder of the engine, and was condensed by contact with the metal surfaces. Cold water within the smaller and surrounding the exterior vessel kept the metal cold, and absorbed the heat discharged by the condensing vapor. Cartwright's engine is best described in the _Philosophical Magazine_ of June, 1798, from which the accompanying sketch is copied. [Illustration: FIG. 39.--Cartwright's Engine, 1798.] The object of the inventor is stated to have been to remedy the defects of the Watt engine--imperfect vacuum, friction, and complication. In the figure, the steam-cylinder takes steam through the pipe, _B_. The piston, _R_, has a rod extending downward to the smaller pump-piston, _G_, and upward to the cross-head, which, in turn, drives the cranks above, by means of connecting-rods. The shafts thus turned are connected by a pair of gears, _M L_, of which one drives a pinion on the shaft of the fly-wheel. _D_ is the exhaust-pipe leading to the condenser, _F_; and the pump, _G_, removes the air and water of condensation, forcing it into the hot-well, _H_, whence it is returned to the boiler through the pipe, _I_. A float in _H_ adjusts an air-valve, so as to keep a supply of air in the chamber, to serve as a cushion and to make an air-chamber of the reservoir, and permits the excess to escape. The large tank contains the water supplied for condensing the steam. The piston, _R_, is made of metal, and is packed with two sets of cut metal rings, forced out against the sides of the cylinder by steel springs, the rings being cut at three points in the circumference, and kept in place by the springs. The arrangement of the two cranks, with their shafts and gears, is intended to supersede Watt's plan for securing a perfectly rectilinear movement of the head of the piston-rod, without friction. In the accounts given of this engine, great stress is laid upon the supposed important advantage here offered, by the introduction of the surface-condenser, of permitting the employment of a working-fluid other than steam--as, for example, alcohol, which is too valuable to be lost. It was proposed to use the engine in connection with a still, and thus to effect great economy by making the fuel do double duty. The only part of the plan which proved both novel and valuable was the metallic packing and piston, which has not yet been superseded. The engine itself never came into use. At this point, the history of the steam-engine becomes the story of its applications in several different directions, the most important of which are the raising of water--which had hitherto been its only application--the locomotive-engine, the driving of mill-machinery, and steam-navigation. Here we take leave of James Watt and of his contemporaries, of the former of whom a French author[43] says: "The part which he played in the mechanical applications of the power of steam can only be compared to that of Newton in astronomy and of Shakespeare in poetry." Since the time of Watt, improvements have been made principally in matters of mere detail, and in the extension of the range of application of the steam-engine. [43] Bataille. "Traité des Machines à Vapeur," Paris, 1847. [Illustration] CHAPTER IV. _THE MODERN STEAM-ENGINE._ "Those projects which abridge distance have done most for the civilization and happiness of our species."--MACAULAY. THE SECOND PERIOD OF APPLICATION--1800-'40. STEAM-LOCOMOTION ON RAILROADS. [Illustration: FIG. 40.--The First Railroad-Car, 1825.] Introductory.--The commencement of the nineteenth century found the modern steam-engine fully developed in all its principal features, and fairly at work in many departments of industry. The genius of Worcester, and Morland, and Savery, and Desaguliers, had, in the first period of the application of the power of steam to useful work, effected a beginning which, looked upon from a point of view which exhibits its importance as the first step toward the wonderful results to-day familiar to every one, appears in its true light, and entitles those great men to even greater honor than has been accorded them. The results actually accomplished, however, were absolutely insignificant in comparison with those which marked the period of development just described. Yet even the work of Watt and of his contemporaries was but a mere prelude to the marvellous advances made in the succeeding period, to which we are now come, and, in extent and importance, was insignificant in comparison with that accomplished by their successors in the development of all mechanical industries by the application of the steam-engine to the movement of every kind of machine. The first of the two periods of application saw the steam-engine adapted simply to the elevation of water and the drainage of mines; during the second period it was adapted to every variety of useful work, and introduced wherever the muscular strength of men and animals, or the power of wind and of falling water, which had previously been the only motors, had found application. A history of the development of industries by the introduction of steam-power during this period, would be no less extended and hardly less interesting than that of the steam-engine itself. The way had been fairly opened by Boulton and Watt; and the year 1800 saw a crowd of engineers and manufacturers entering upon it, eager to reap the harvest of distinction and of pecuniary returns which seemed so promising to all. The last year of the eighteenth century was also the last of the twenty-five years of partnership of Boulton & Watt, and, with it, the patents under which that firm had held the great monopoly of steam-engine building expired. The right to manufacture the modern steam-engine was common to all. Watt had, at the commencement of the new century, retired from active business-life. Boulton remained in business; but he was not the inventor of the new engine, and could not retain, by the exercise of all his remaining power, the privileges previously held by legal authorization. The young Boulton and the young Watt were not the Boulton & Watt of earlier years; and, had they possessed all of the business talent and all of the inventive genius of their fathers, they could not have retained control of a business which was now growing far more rapidly than the facilities for manufacturing could be extended in any single establishment. All over the country, and even on the Continent of Europe, and in America, thousands of mechanics, and many men of mechanical tastes in other professions, were familiar with the principles of the new machine, and were speculating upon its value for all the purposes to which it has since been applied; and a multitude of enthusiastic mechanics, and a larger multitude of visionary and ignorant schemers, were experimenting with every imaginable device, in the vain hope of attaining perpetual motion, and other hardly less absurd results, by its modification and improvement. Steam-engine building establishments sprang up wherever a mechanic had succeeded in erecting a workshop and in acquiring a local reputation as a worker in metal, and many of Watt's workmen went out from Soho to take charge of the work done in these shops. Nearly all of the great establishments which are to-day most noted for their extent and for the importance and magnitude of the work done in them, not only in Great Britain, but in Europe and the United States, came into existence during this second period of the application of the steam-engine as a prime mover. The new establishments usually grew out of older shops of a less pretentious character, and were managed by men who had been trained by Watt, or who had had a still more awakening experience with those who vainly strove to make up, by their ingenuity and by great excellence of workmanship, the advantages possessed at Soho in a legal monopoly and greater experience in the business. It was exceedingly difficult to find expert and conscientious workmen, and machine-tools had not become as thoroughly perfected as had the steam-engine itself. These difficulties were gradually overcome, however, and thenceforward the growth of the business was increasingly rapid. Every important form of engine had now been invented. Watt had perfected, with the aid of Murdoch, both the pumping-engine and the rotative steam-engine for application to mills. He had invented the trunk engine, and Murdoch had devised the oscillating engine and the ordinary slide-valve, and had made a model locomotive-engine, while Hornblower had introduced the compound engine. The application of steam to navigation had been often proposed, and had sometimes been attempted, with sufficient success to indicate to the intelligent observer an ultimate triumph. It only remained to extend the use of steam as a motor into all known departments of industry, and to effect such improvements in details as experience should prove desirable. The engines of Hero, of Porta, and of Branca were, it will be remembered, non-condensing; but the first plan of a non-condensing engine that could be made of any really practical use is given in the "Theatrum Machinarum" of Leupold, published in 1720. This sketch is copied in Fig. 41. It is stated by Leupold that this plan was suggested by Papin. It consists of two single-acting cylinders, _r s_, receiving steam alternately from the same steam-pipe through a "four-way cock," _x_, and exhausting into the atmosphere. Steam is furnished by the boiler, _a_, and the pistons, _c d_, are alternately raised and depressed, depressing and raising the pump-rods, _k l_, to which they are attached by the beams, _h g_, vibrating on the centres, _i i_. The water from the pumps, _o p_, is forced up the stand-pipe, _q_, and discharged at its top. The alternate action of the steam-pistons is secured by turning the "four-way cock," _x_, first into the position shown, and then, at the completion of the stroke, into the reverse position, by which change the steam from the boiler is then led into the cylinder, _s_, and the steam in _r_ is discharged into the atmosphere.[44] [44] _Vide_ "Theatrum Machinarum," vol. iii., Tab. 30. [Illustration: FIG. 41.--Leupold's Engine, 1720.] Leupold states that he is indebted to Papin for the suggestion of the peculiar valve here used. He also proposed to use a Savery engine without condensation in raising water. We have no evidence that this engine was ever built. The first rude scheme for applying steam to locomotion on land was probably that of Isaac Newton, who, in 1680, proposed the machine shown in the accompanying figure (42), which will be recognized as representing the scientific toy which is found in nearly every collection of illustrative philosophical apparatus. As described in the "Explanation of the Newtonian Philosophy," it consists of a spherical boiler, _B_, mounted on a carriage. Steam issuing from the pipe, _C_, seen pointing directly backward, by its reaction upon the carriage, drives the latter ahead. The driver, sitting at _A_, controls the steam by the handle, _E_, and cock, _F_. The fire is seen at _D_. [Illustration: FIG. 42.--Newton's Steam-Carriage, 1680.] When, at the end of the eighteenth century, the steam-engine had been so far perfected that the possibility of its successful application to locomotion had become fully and very generally recognized, the problem of adapting it to locomotion on land was attacked by many inventors. Dr. Robison had, as far back as in 1759, proposed it to James Watt during one of their conferences, at a time when the latter was even more ignorant than the former of the principles which were involved in the construction of the steam-engine, and this suggestion may have had some influence in determining Watt to pursue his research; thus setting in operation that train of thoughtful investigation and experiment which finally earned for him his splendid fame. In 1765, that singular genius, Dr. Erasmus Darwin, whose celebrity was acquired by speculations in poetry and philosophy as well as in medicine, urged Matthew Boulton--subsequently Watt's partner, and just then corresponding with our own Franklin in relation to the use of steam-power--to construct a steam-carriage, or "fiery chariot," as he poetically styled it, and of which he sketched a set of plans. A young man named Edgeworth became interested in the scheme, and, in 1768, published a paper which had secured for him a gold medal from the Society of Arts. In this paper he proposed railroads on which the carriages were to be drawn by horses, _or by ropes from steam-winding engines_. [Illustration: FIG. 43.--Read's Steam-Carriage, 1790.] Nathan Read, of whom an account will be given hereafter, when describing his attempt to introduce steam-navigation, planned, and in 1790 obtained a patent for, a steam-carriage, of which the sketch seen in Fig. 43 is copied from the rough drawing accompanying his application. In the figure, _A A A A_ are the wheels; _B B_, pinions on the hubs of the rear wheels, which are driven by a ratchet arrangement on the racks, _G G_, connected with the piston-rods; _C o_ is the boiler; _D D_, the steam-pipes carrying steam to the steam-cylinder, _E E_; _F F_ are the engine-frames; _H_ is the "tongue" or "pole" of the carriage, and is turned by a horizontal steering-wheel, with which it is connected by the ropes or chains, _I K_, _I K_; _W W_ are the cocks, which serve to shut off steam from the engine when necessary, and to determine the amount of steam to be admitted. The pipes _a a_ are exhaust-pipes, which the inventor proposed to turn so that they should point backward, in order to secure the advantage of the effort of reaction of the expelled steam. (!) Read made a model steam-carriage, which he exhibited when endeavoring to secure assistance in furtherance of his schemes, but seems to have given more attention to steam-navigation, and nothing was ever accomplished by him in this direction. These were merely promising schemes, however. The first actual experiment was made, as is supposed, by a French army-officer, NICHOLAS JOSEPH CUGNOT, who in 1769 built a steam-carriage, which was set at work in presence of the French Minister of War, the Duke de Choiseul. The funds required by him were furnished by the Compte de Saxe. Encouraged by the partial success of the first locomotive, he, in 1770, constructed a second (Fig. 44), which is still preserved in the Conservatoire des Arts et Métiers, Paris. [Illustration: FIG. 44.--Cugnot's Steam-Carriage, 1770.] This machine, when recently examined by the author, was still in an excellent state of preservation. The carriage and its machinery are substantially built and well-finished, and exceedingly creditable pieces of work in every respect. It surprises the engineer to find such evidence of the high character of the work of the mechanic Brezin a century ago. The steam-cylinders were 13 inches in diameter, and the engine was evidently of considerable power. This locomotive was intended for the transportation of artillery. It consists of two beams of heavy timber extending from end to end, supported by two strong wheels behind, and one still heavier but smaller wheel in front. The latter carries on its rim blocks which cut into the soil as the wheel turns, and thus give greater holding power. The single wheel is turned by two single-acting engines, one on each side, supplied with steam by a boiler (seen in the sketch) suspended in front of the machine. The connection between the engines and the wheels was effected by means of pawls, as first proposed by Papin, which could be reversed when it was desired to drive the machine backward. A seat is mounted on the carriage-body for the driver, who steers the machine by a train of gearing, which turns the whole frame, carrying the machinery 15 or 20 degrees either way. This locomotive was found to have been built on a tolerably satisfactory general plan; but the boiler was too small, and the steering apparatus was incapable of handling the carriage with promptness. The death of one of Cugnot's patrons, and the exile of the other, put an end to Cugnot's experiments. Cugnot was a mechanic by choice, and exhibited great talent. He was a native of Vaud, in Lorraine, where he was born in 1725. He served both in the French and the German armies. While under the Maréchal de Saxe, he constructed his first steam locomotive-engine, which only disappointed him, as he stated, in consequence of the inefficiency of the feed-pumps. The second was that built under the authority of the Minister Choiseul, and cost 20,000 livres. Cugnot received from the French Government a pension of 600 livres. He died in 1804, at the age of seventy-nine years. Watt, at a very early period, proposed to apply his own engine to locomotion, and contemplated using either a non-condensing engine or an air-surface condenser. He actually included the locomotive-engine in his patent of 1784; and his assistant, Murdoch, in the same year, made a working-model locomotive (Fig. 45), which was capable of running at a rapid rate. This model, now deposited in the Patent Museum at South Kensington, London, had a flue-boiler, and its steam-cylinder was three-fourths of an inch in diameter, and the stroke of piston 2 inches. The driving-wheels were 9-1/2 inches diameter. [Illustration: FIG. 45.--Murdoch's Model, 1784.] Nothing was, however, done on a larger scale by either Watt or Murdoch, who both found more than enough to claim their attention in the construction and introduction of other engines. Murdoch's model is said to have run from 6 to 8 miles an hour, its little driving-wheels making from 200 to 275 revolutions per minute. As is seen in the sketch, this model was fitted with the same form of engine, known as the "grasshopper-engine," which was used in the United States by Oliver Evans. "To Oliver Evans," says Dr. Ernest Alban, the distinguished German engineer, "was it reserved to show the true value of a long-known principle, and to establish thereon a new and more simple method of applying the power of steam--a method that will remain an eternal memorial to its introducer." Dr. Alban here refers to the earliest permanently successful introduction of the non-condensing high-pressure steam-engine. OLIVER EVANS, one of the most ingenious mechanics that America has ever produced, was born at Newport, Del., in 1755 or 1756, the son of people in very humble circumstances. [Illustration: Oliver Evans.] He was, in his youth, apprenticed to a wheelwright, and soon exhibited great mechanical talent and a strong desire to acquire knowledge. His attention was, at an early period, drawn to the possible application of the power of steam to useful purposes by the boyish pranks of one of his comrades, who, placing a small quantity of water in a gun-barrel, and ramming down a tight wad, put the barrel in the fire of a blacksmith's forge. The loud report which accompanied the expulsion of the wad was an evidence to young Evans of great and (as he supposed) previously undiscovered power. Subsequently meeting with a description of a Newcomen engine, he at once noticed that the elastic force of confined steam was not there utilized. He then designed the non-condensing engine, in which the power was derived exclusively from the tension of high-pressure steam, and proposed its application to the propulsion of carriages. About the year 1780, Evans joined his brothers, who were millers by occupation, and at once employed his inventive talent in improving the details of mill-work, and with such success as to reduce the cost of attendance one-half, and also to increase the fineness of the flour made. He proved himself a very expert millwright. In 1786 he applied to the Pennsylvania Legislature for a patent for the application of the steam-engine to driving mills, and to the steam-carriage, but was refused it. In 1800 or 1801, Evans, after consultation with Professor Robert Patterson, of the University of Pennsylvania, and getting his approval of the plans, commenced the construction of a steam-carriage to be driven by a non-condensing engine. He soon concluded, however, that it would be a better scheme, pecuniarily, to adapt his engine, which was novel in form and of small first cost, to driving mills; and he accordingly changed his plans, and built an engine of 6 inches diameter of cylinder and 18 inches stroke of piston, which he applied with perfect success to driving a plaster-mill. This engine, which he called the "Columbian Engine," was of a peculiar form, as seen in Fig. 46. The beam is supported at one end by a rocking column; at the other, it is attached directly to the piston-rod, while the crank lies beneath the beam, the connecting-rod, 1, being attached to the latter at the extreme end. The head of the piston-rod is compelled to rise and fall in a vertical line by the "Evans's parallelogram"--a kind of parallel-motion very similar to one of those designed by Watt. In the sketch (Fig. 46), 2 is the crank, 3 the valve-motion, 4 the steam-pipe from the boiler, _E_, 5 6 7 the feed-pipe leading from the pump, _F_. _A_ is the boiler. The flame from the fire on the grate, _H_, passes under the boiler between brick walls, and back through a central flue to the chimney, _I_. [Illustration: FIG. 46.--Evans's Non-condensing Engine, 1800.] Subsequently, Evans continued to extend the applications of his engine and to perfect its details; and, others following in his track, the non-condensing engine is to-day fulfilling the predictions which he made 70 years ago, when he said: "I have no doubt that my engines will propel boats against the current of the Mississippi, and wagons on turnpike roads, with great profit...." "The time will come when people will travel in stages moved by steam-engines from one city to another, almost as fast as birds can fly, 15 or 20 miles an hour.... A carriage will start from Washington in the morning, the passengers will breakfast at Baltimore, dine at Philadelphia, and sup in New York the same day.... "Engines will drive boats 10 or 12 miles an hour, and there will be hundreds of steamers running on the Mississippi, as predicted years ago."[45] [45] Evans's prediction is less remarkable than that of Darwin, elsewhere quoted. In 1804, Evans applied one of his engines in the transportation of a large flat-bottomed craft, built on an order of the Board of Health of Philadelphia, for use in clearing some of the docks along the water-front of the city. Mounting it on wheels, he placed in it one of his 5-horse power engines, and named the odd machine (Fig. 47) "Oruktor Amphibolis." This steam dredging-machine, weighing about 40,000 pounds, was then propelled very slowly from the works, up Market Street, around to the Water-Works, and then launched into the Schuylkill. The engine was then applied to the paddle-wheel at the stern, and drove the craft down the river to its confluence with the Delaware. [Illustration: FIG. 47.--Evans's "Oruktor Amphibolis," 1804.] In September of the same year, Evans laid before the Lancaster Turnpike Company a statement of the estimated expenses and profits of steam-transportation on the common road, assuming the size of the carriage used to be sufficient for transporting 100 barrels of flour 50 miles in 24 hours, and placed in competition with 10 wagons drawn by 5 horses each. In the sketch above given of the "Oruktor Amphibolis," the engine is seen to resemble that previously described. The wheel, _A_, is driven by a rod depending from the end of a beam, _B´ B_, the other end of which is supported at _E_ by the frame, _E F G_. The body of the machine is carried on wheels, _K K_, driven by belts, _M M_, from the pulley on the shaft carrying _A_. The paddle-wheel is seen at _W_. Evans had some time previously sent Joseph Sampson to England with copies of his plans, and by him they were shown to Trevithick, Vivian, and other British engineers. Among other devices, the now familiar Cornish boiler, having a single internal flue, and the Lancashire boiler, having a pair of internal flues, were planned and used by Evans. At about the time that he was engaged on his steam dredging-machine, Evans communicated with Messrs. McKeever & Valcourt, who contracted with him to build an engine for a steam-vessel to ply between New Orleans and Natchez on the Mississippi, the hull of the vessel to be built on the river, and the machinery to be sent to the first-named city to be set up in the boat. Financial difficulties and low water combined to prevent the completion of the steamer, and the engine was set at work driving a saw-mill, where, until the mill was destroyed by fire, it sawed lumber at the rate of 250 feet of boards per hour. Evans never succeeded in accomplishing in America as great a success as had rewarded Watt in Great Britain; but he continued to build steam-engines to the end of his life, April 19, 1819, and was succeeded by his sons-in-law, James Rush and David Muhlenberg. He exhibited equal intelligence and ingenuity in perfecting the processes of milling, and in effecting improvements in his own business, that of the millwright. When but twenty-four years old, he invented a machine for making the wire teeth used in cotton and woolen cards, turning them out at the rate of 3,000 per minute. A little later he invented a card-setting machine, which cut the wire from the reel, bent the teeth, and inserted them. In milling, he invented a whole series of machines and attachments, including the elevator, the "conveyor," the "hopper-box," the "drill," and the "descender," and enabled the miller to make finer flour, gaining over 20 pounds to the barrel, and to do this at half the former cost of attendance. The introduction of his improvements into Ellicott's mills, near Baltimore, where 325 barrels of flour were made per day, was calculated to have saved nearly $5,000 per year in cost of labor, and over $30,000 by increasing the production. He wrote "The Young Steam-Engineer's Guide," and a work which remained standard many years after his death, "The Young Millwright's Guide." Less fortunate than his transatlantic rival, he was nevertheless equally deserving of fame. He has sometimes been called "The Watt of America." The application of steam to locomotion on the common road was much more successful in Great Britain than in the United States. As early as 1786, William Symmington, subsequently more successful in his efforts to introduce steam for marine propulsion, assisted by his father, made a working model of a steam-carriage, which did not, however, lead to important results. In 1802, Richard Trevithick, a pupil of Murdoch's, who afterward became well known in connection with the introduction of railroads, made a model steam-carriage, which was patented in the same year. The model may still be seen in the Patent Museum at South Kensington.[46] [46] _See_ "Life of Trevithick." In this engine, high-pressure steam was employed, and the condenser was dispensed with. The boiler was of the form devised by Evans, and was subsequently generally used in Cornwall, where it was called the "Trevithick Boiler." The engine had but one cylinder, and the piston-rod drove a "cross-tail," working in guides, which was connected with a "cross-head" on the opposite side of the shaft by two "side-rods." The connecting-rod was attached to the cross-head and the crank, "returning" toward the cylinder as the shaft lay between the latter and the cross-head. This was probably the first example of the now common "return connecting-rod engine." The connection between the crank-shaft and the wheels of the carriage was effected by gearing. The valve-gear and the feed-pumps were worked from the engine-shaft. The inventor proposed to secure his wheels against slipping by projecting bolts, when necessary, through the rim of the wheel into the ground. The first carriage of full size was built by Trevithick and Vivian at Camborne, in 1803, and, after trial, was taken to London, where it was exhibited to the public. _En route_, it was driven by its own engines to Plymouth, 90 miles from Camborne, and then shipped by water. It is not known whether the inventor lost faith in his invention; but he very soon dismantled the machine, sold the engine and carriage separately, and returned to Cornwall, where he soon began work on a railroad-locomotive. In 1821, Julius Griffiths, of Brompton, Middlesex, England, patented a steam-carriage for the transportation of passengers on the highway. His first road-locomotive was built in the same year by Joseph Bramah, one of the ablest mechanics of his time. The frame of the carriage carried a large double coach-body between the two axles, and the machinery was mounted over and behind the rear axle. One man was stationed on a rear platform, to manage the engine and to attend to the fire, and another, stationed in front of the body of the coach, handled the steering-wheel. The boiler was composed of horizontal water-tubes and steam-tubes, the latter being so situated as to receive heat from the furnace-gases _en route_ to the chimney, and thus to act as a superheater. The wheels were driven, by means of intermediate gearing, by two steam-engines, which, with their attachments, were suspended on helical springs, to prevent injury by jars and shocks. An air-surface condenser was used, consisting of flattened thin metal tubes, cooled by the contact of the external air, and discharging the water of condensation, as it accumulated within them, into a feed-pump, which, in turn, forced it into the lowest row of tubes in the boiler. The boiler did not prove large enough for continuous work; but the carriage was used experimentally, now and then, for a number of years. During the succeeding ten years the adaptation of the steam-engine to land-transportation continued to attract more and more attention, and experimental road-engines were built with steadily-increasing frequency. The defects of these engines revealing themselves on trial, they were one by one remedied, and the road-locomotive gradually assumed a shape which was mechanically satisfactory. Their final introduction into general use seemed at one time only a matter of time; their non-success was due to causes over which the legislator and the general public, and not the engineer, had control, as well as to the development of steam-transportation on a rival plan. In 1822, David Gordon patented a road-engine, but it is not known whether it was ever built. At about the same time, Mr. Goldsworthy Gurney, who subsequently took an active part in their introduction, stated, in his lectures, that "elementary power is capable of being applied to propel carriages along common roads with great political advantage, and the floating knowledge of the day places the object within reach." He made an ammonia-engine--probably the first ever made--and worked it so successfully, that he made use of it in driving a little locomotive. Two years later, Gordon patented a curious arrangement, which, however, had been proposed twelve years earlier by Brunton, and was again proposed afterward by Gurney, and others. This consisted in fitting to the engine a set of jointed legs, imitating, as nearly as the inventor could make them, the action of a horse's legs and feet. Such an arrangement was actually experimented with until it was found that they could not be made to work satisfactorily, when it was also found that they were not needed. During the same season, Burstall & Hill made a steam-carriage, and made many unsuccessful attempts to introduce their plan. The engine used was like that of Evans, except that the steam-cylinder was placed at the end of the beam, and the crank-shaft under the middle. The front and rear wheels were connected by a longitudinal shaft and bevel gearing. The boiler was found to have the usual defect, and would only supply steam for a speed of three or four miles an hour. The result was a costly failure. W. H. James, of London, in 1824-'25, proposed several devices for placing the working parts, as well as the body of the carriage, on springs, without interfering with their operation, and the Messrs. Seaward patented similar devices. Samuel Brown, in 1826, introduced a gas-engine, in which the piston was driven by the pressure produced by the combustion of gas, and a vacuum was secured by the condensation of the resulting vapor. Brown built a locomotive which he propelled by this engine. He ascended Shooter's Hill, near London, and the principal cause of his ultimate failure seems to have been the cost of operating the engine. From this date forward, during several years, a number of inventors and mechanics seem to have devoted their whole time to this promising scheme. Among them, Burstall & Hill, Gurney, Ogle & Summers, Sir Charles Dance, and Walter Hancock, were most successful. Gurney, in the year 1827, built a steam-carriage, which he kept at work nearly two years in and about London, and sometimes making long journeys. On one occasion he made the journey from Meksham to Cranford Bridge, a distance of 85 miles, in 10 hours, including all stops. He used the mechanical legs previously adopted by Brunton and by Gordon, but omitted this rude device in those engines subsequently built. Gurney's engine of 1828 is of interest to the engineer as exhibiting a very excellent arrangement of machinery, and as having one of the earliest of "sectional boilers." The latter was of peculiar form, and differed greatly in design from the sectional boiler invented a quarter of a century earlier by John Stevens, in the United States. [Illustration: FIG. 48.--Gurney's Steam-Carriage.] In the sketch (Fig. 48) this boiler is seen at the right. It was composed of bent [<]-shaped tubes, _a a_, connected to two cylinders, _b b_, the upper one of which was a steam-chamber. Vertical tubes connected these two chambers, and permitted a complete and regular circulation of the water. A separate reservoir, called a separator, _d_, was connected with these chambers by pipes, as shown. From the top of this separator a steam-pipe, _e e e_, conveyed steam to the engine-cylinders at _f_. The cranks, _g_, on the rear axle were turned by the engines, and the eccentric, _h_, on the axle drove the valve-gearing and the valve, _i_. The link, _k l_, being moved by a line, _l l_, led from the driver's seat, the carriage was started, stopped, or reversed, by throwing the upper end of the link into gear with the valve-stem, by setting the link midway between its upper and lower positions, or by raising it until the lower end, coming into action on the valve-stem, produced a reverse motion of the valve. The pin on which this link vibrated is seen at the centre of its elliptical strap. The throttle-valve, _o_, by which the supply of steam to the engine was adjusted, was worked by the lever, _n_. The exhaust-pipe, _p_, led to the tank, _q_, and the uncondensed vapor passed to the chimney, _s s_, by the pipe, _r r_. The force-pump, _u_, taking feed-water from the tank, _t_, supplied it to the boiler by the pipe, _x x x_, which, _en route_, was coiled up to form a "heater" directly above the boiler. The supply was regulated by the cock, _y_. The attendant had a seat at _z_. A blast-apparatus, 1, was driven by an independent engine, 2 3, and produced a forced blast, which was led to the boiler-furnace through the air-duct, 5 5; 4 4 represents the steam-pipe to the little blowing-engine. The steering-wheel, 6, was directed by a lever, 7, and the change of direction of the perch, 8, which turned about a king-bolt at 9, gave the desired direction to the forward wheels and to the carriage. This seems to have been one of the best designs brought out at that time. The boiler, built to carry 70 pounds, was safe and strong, and was tested up to 800 pounds pressure. A forced draught was provided. The engines were well placed, and of good design. The valve was arranged to work the steam with expansion from half-stroke. The feed-water was heated, and the steam slightly superheated. The boiler here used has been since reproduced under new names by later inventors, and is still used with satisfactory results. Modifications of the "pipe-boiler" were made by several other makers of steam-carriages also. Anderson & James made their boilers of lap-welded iron tubes of one inch internal diameter and one-fifth inch thick, and claimed for them perfect safety. Such tubes should have sufficient strength to sustain a pressure of 20,000 pounds per square inch. If made of such good iron as the makers claimed to have put into them, "which worked like lead," they would, as was also claimed, when ruptured, open by tearing, and discharge their contents without producing the usual disastrous consequences of boiler explosions. The primary principle of the sectional boiler was then well understood. The boilers of Ogle & Summers were made up of pairs of upright tubes, set one within the other, the intervening space being filled with water and steam, and the flame passing through the inner and around the outer tube of each pair. One of the engines of Sir James Anderson and W. H. James was built in 1829. It had two 3-1/2-inch steam-cylinders, driving the rear wheels independently. In James's earlier plan of 1824-'25, a pair of cylinders was attached to each of the two halves into which the rear axle was divided, and were arranged to drive cranks set at right-angles with each other. The later machine weighed 3 tons, and carried 15 passengers, on a rough graveled road across the Epping Forest, at the rate of from 12 to 15 miles per hour. Steam was carried at 300 pounds. Several tubes gave way in the welds, but the carriage returned, carrying 24 passengers at the rate of 7 miles per hour. On a later trial, with new boilers, the carriage again made 15 miles per hour. It was, however, subject to frequent accidents, and was finally withdrawn. WALTER HANCOCK was the most successful and persevering of all those who attempted the introduction of steam on the common road. He had, in 1827, patented a boiler of such peculiar form, that it deserves description. It consisted of a collection of flat chambers, of which the walls were of boiler-plate. These chambers were arranged side by side, and connected laterally by tubes and stays, and all were connected by short vertical tubes to a horizontal large pipe placed across the top of the boiler-casing, and serving as a steam-drum or separator. This earliest of "sheet flue-boilers" did excellent service on Hancock's steam-carriages, where experience showed that there was little or no danger of disruptive explosions. Hancock's first steam-carriage was mounted on three wheels, the leading-wheel arranged to swivel on a king-bolt, and driven by a pair of oscillating cylinders connected with its axle, which was "cranked" for the purpose. The engines turned with the steering-wheel. This carriage was by no means satisfactory, but it was used for a long time, and traveled many hundreds of miles without once failing to do the work assigned it. By this time there were a half-dozen steam-carriages under construction for Hancock, for Ogle & Summers, and for Sir Charles Dance. In 1831, Hancock placed a new carriage on a route between London and Stratford, where it ran regularly for hire. Dance, in the same season, started another on the line between Cheltenham and Gloucester, where it ran from February 21st to June 22d, traveling 3,500 miles and carrying 3,000 passengers, running the 9 miles in 55 minutes usually, and sometimes in three-quarters of an hour, and never meeting with an accident, except the breakage of an axle in running over heaps of stones which had been purposely placed on the road by enemies of the new system of transportation. Ogle & Summers's carriage attained a speed, as testified by Ogle before a committee of the House of Commons, of from 32 to 35 miles an hour, and on a rising grade, near Southampton, at 24-1/2 miles per hour. They carried 250 pounds of steam, ran 800 miles, and met with no accident. Colonel Macerone, in 1833, ran a steam-carriage of his own design from London to Windsor and back, with 11 passengers, a distance of 23-1/2 miles, in 2 hours. Sir Charles Dance, in the same year, ran his carriage 16 miles an hour, and made long excursions at the rate of 9 miles an hour. Still another experimenter, Heaton, ascended Lickey Hill, between Worcester and Birmingham, on gradients of one in eight and one in nine, in places; this was considered one of the worst pieces of road in England. The carriage towed a coach containing 20 passengers. Of all these, and many others, Hancock, however, had most marked success. His coach, called the "Infant," which was set at work in February, 1831, was, a year later, plying between London "City" and Paddington. Another, called the "Era," was built for the London and Greenwich Steam-Carriage Company, which was mechanically a success. The company, however, was financially unsuccessful. In October, 1832, the "Infant" ran to Brighton from London, carrying a party of 11, at the rate of 9 miles per hour, ascending Redhill at a speed of 5 miles. They steamed 38 miles the first day, stopping at night at Hazledean, and reached Brighton next day, running 11 miles per hour. Returning with 15 passengers, the coach ran 1 mile in less than 4 minutes, and made 10 miles in 55 minutes. A run from Stratford to Brighton was made in less than 10 hours, at an average speed of 12 miles an hour running time, the actual running time being less than 6 hours. The next year another carriage, the "Enterprise," was put on the road to Paddington by Hancock for another company, and ran regularly over two weeks; but this company was also unsuccessful. In the summer of 1833 he brought out still another steam-coach, the "Autopsy" (Fig. 49), which he ran to Brighton, and then, returning to London, man[oe]uvred the carriage in the crowded streets without difficulty or accident. He went about the streets of London at all times, and without hesitation. The coach next ran between Finsbury Square and Pentonville regularly for four weeks, without accident or delay. In the sketch, a part of the side is broken away to show the machinery. The boiler, _A B_, supplies steam through the steam-pipe, _H K_, to the steam-engine, _C D_, which is coupled to the crank-shaft, _F_. _E_ is the feed-pump. The rear axle is turned by the endless chain seen connecting it with the engine-shaft, and the rear wheels, _S_, are thus driven. A blower, _T_, gives a forced draught. The driver sits at _M_, steering by the wheel, _N_, which is coupled to the larger wheel, _P_, and thus turns the forward axle into any desired position. In 1834, Hancock built a steam "drag" on an Austrian order, which, carrying 10 persons and towing a coach containing 6 passengers, was driven through the city beyond Islington, making 14 miles an hour on a level, and 8 miles or more on rising ground. In the same year he built the "Era," and, in August, put the "Autopsy" on with it, to make a steam-line to Paddington. These coaches ran until the end of November, carrying 4,000 passengers, at a usual rate of speed of 12 miles per hour. He then sent the "Era" to Dublin, where, on one occasion, it ran 18 miles per hour. [Illustration: FIG. 49.--Hancock's "Autopsy," 1833.] In 1835 a large carriage, the "Erin," was completed, which was intended to carry 20 passengers. It towed three omnibuses and a stage-coach, with 50 passengers, on a level road, at the speed of 10 miles an hour. It drew an omnibus with 18 passengers through Whitehall, Charing Cross, and Regent Street, and out to Brentford, running 14 miles an hour. It ran also to Reading, making 38 miles, with the same load, in 3 hours and 8 minutes running time. The stops _en route_ occupied a half-hour. The same carriage made 75 miles to Marlborough in 7-1/2 hours running time, stopping 4-1/2 hours on the road, in consequence of having left the tender and supplies behind. In May, 1836, Hancock put all his carriages on the Paddington road, and ran regularly for over five months, running 4,200 miles in 525 trips to Islington, 143 to Paddington, and 44 to Stratford, passing through the city over 200 times. The carriages averaged 5 hours and 17 or 18 minutes daily running time. A light steam-phaeton, built in 1838, for his own use, made 20 miles an hour, and was driven about the city, and among horses and carriages, without causing annoyance or danger. Its usual speed was about 10 miles an hour. Altogether, Hancock built nine steam-carriages, capable of carrying 116 passengers in addition to the regular attendants.[47] [47] For a detailed account of the progress of steam on the highway, _see_ "Steam on Common Roads," etc., by Young, Holley, & Fisher, London, 1861. In December, 1833, about 20 steam-carriages and traction road-engines were running, or were in course of construction, in and near London. In our own country, the roughness of roads discouraged inventors; and in Great Britain even, the successful introduction of road-locomotives, which seemed at one time almost an accomplished fact, finally met with so many obstacles, that even Hancock, the most ingenious, persistent, and successful constructor, gave up in despair. Hostile legislation procured by opposing interests, and the rapid progress of steam-locomotion on railroads, caused this result. In consequence of this interruption of experiment, almost nothing was done during the succeeding quarter of a century, and it is only within a few years that anything like a business success has been founded upon the construction of road-locomotives, although the scheme seems to have been at no time entirely given up. The opposition of coach-proprietors, and of all classes having an interest in the old lines of coaches, was most determined, and the feeling evinced by them was intensely bitter; but the advocates of the new system of transportation were equally determined and persevering, and, having right on their side, and the pecuniary advantage of the public as their object, they would probably have succeeded ultimately, except for the introduction of the still better method of transportation by rail. In the summer of 1831, when the war between the two parties was at its height, a committee of the British House of Commons made a very complete investigation of the subject. This committee reported that they had become convinced that "the substitution of inanimate for animal power, in draught on common roads, is one of the most important improvements in the means of internal communication ever introduced." They considered its practicability to have been "fully established," and predicted that its introduction would "take place more or less rapidly, in proportion as the attention of scientific men shall be drawn, by public encouragement, to further improvement." The success of the system had, as they stated, been retarded by prejudice, adverse interests, and prohibitory tolls; and the committee remark: "When we consider that these trials have been made under the most unfavorable circumstances, at great expense, in total uncertainty, without any of those guides which experience has given to other branches of engineering; that those engaged in making them are persons looking solely to their own interests, and not theorists attempting the perfection of ingenious models; when we find them convinced, after long experience, that they are introducing such a mode of conveyance as shall tempt the public, by its superior advantages, from the use of the admirable lines of coaches which have been generally established, it surely cannot be contended that the introduction of steam-carriages on common roads is, as yet, an uncertain experiment, unworthy of legislative attention." Farey, one of the most distinguished mechanical engineers of the time, testified that he considered the practicability of such a system as fully established, and that the result would be its general adoption. Gurney had run his carriage between 20 and 30 miles an hour; Hancock could sustain a speed of 10 miles; Ogle had run his coach 32 to 35 miles an hour, and ascended a hill rising 1 in 6 at the speed of 24-1/2 miles. Summers had traveled up a hill having a gradient of 1 in 12, with 19 passengers, at the rate of speed of 15 miles per hour; he had run 4-1/2 hours at 30 miles an hour. Farey thought that steam-coaches would be found to cost one-third as much as the stage-coaches in use. The steam-carriages were reported to be safer than those drawn by horses, and far more manageable; and the construction of boilers adopted--the "sectional" boiler, as it is now called--completely insured against injury by explosion, and the dangers and inconveniences arising from the frightening of horses had proved to be largely imaginary. The wear and tear of roads were found to be less than with horses, while with broad wheel-tires the carriages acted beneficially as road-rollers. The committee finally concluded: "1. That carriages can be propelled by steam on common roads at an average rate of 10 miles per hour. "2. That at this rate they have conveyed upward of 14 passengers. "3. That their weight, including engine, fuel, water, and attendants, may be under three tons. "4. That they can ascend and descend hills of considerable inclination with facility and safety. "5. That they are perfectly safe for passengers. "6. That they are not (or need not be, if properly constructed) nuisances to the public. "7. That they will become a speedier and cheaper mode of conveyance than carriages drawn by horses. "8. That, as they admit of greater breadth of tire than other carriages, and as the roads are not acted on so injuriously as by the feet of horses in common draught, such carriages will cause less wear of roads than coaches drawn by horses. "9. That rates of toll have been imposed on steam-carriages, which would prohibit their being used on several lines of road, were such charges permitted to remain unaltered." THE RAILROAD, which now, by the adaptation of steam to the propulsion of its carriages, became the successful rival of the system of transportation of which an account has just been given, was not a new device. It, like all other important changes of method and great inventions, had been growing into form for ages. The ancients were accustomed to lay down blocks of stone as a way upon which their heavily-loaded wagons could be drawn with less resistance than on the common road. This practice was gradually so modified as to result in the adoption of the now universally-practised methods of paving and road-making. The old tracks, bearing the marks of heavy traffic, are still seen in the streets of the unearthed city of Pompeii. In the early days of mining in Great Britain, the coal or the ore was carried from the mine to the vessel in which it was to be embarked in sacks on the backs of horses. Later, the miners laid out wagon-roads, and used carts and wagons drawn by horses, and the roads were paved with stone along the lines traversed by the wheels of the vehicles. Still later (about 1630), heavy planks or squared timber took the place of the stone, and were introduced into the north of England by a gentleman of the name of Beaumont, who had transferred his property there from the south. A half century later, the system had become generally introduced. By the end of the eighteenth century the construction of these "tram-ways" had become well-understood, and the economy which justified the expenditure of considerable amounts of money in making cuts and in filling, to bring the road to a uniform grade, had become well-recognized. Arthur Young, writing at this time, says the coal wagon-roads were "great works, carried over all sorts of inequalities of ground, so far as the distance of nine or ten miles," and that, on these tram-ways of timber, "one horse is able to draw, and that with ease, fifty or sixty bushels of coals." The wagon-wheels were of cast-iron, and made with grooved rims, which fitted the rounded tops of the wooden rails. But these wooden rails were found subject to rapid decay, and at Whitehaven, in 1738, they were protected from wear by cast-iron plates laid upon them, and this improvement rapidly became known and adopted. A tram-road, laid down at Sheffield for the Duke of Norfolk, in 1776, was made by laying angle-bars of cast-iron on longitudinal sleepers of timber; another, built by William Jessup in Leicestershire, in 1789, had an edge-rail, and the wheels were made with flanges, like those used to-day. The coned "tread" of the wheel, which prevents wear of flanges and reduces resistance, was the invention of James Wright, of Columbia, Pa., 40 years later. The modern railroad was simply the result of this gradual improvement of the permanent way, and the adaptation of the steam-engine to the propulsion of its wagons. At the beginning of the nineteenth century, therefore, the steam-engine had been given a form which permitted its use, and the railroad had been so far perfected that there were no difficulties to be anticipated in the construction of the permanent way, and inventors were gradually preparing, as has been seen, to combine these two principal elements into one system. Railroads had been introduced in all parts of Great Britain, some of them of considerable length, and involving the interests of so many private individuals that they were necessarily constructed under the authorization of legal enactments. In the year 1805 the Merstham Railway was opened to traffic, and it is stated that on that occasion one horse drew a train of 12 wagons, carrying 38 tons of stone, on a "down gradient" of 1 in 120, at the rate of 6 miles per hour. [Illustration: Richard Trevithick.] [Illustration: FIG. 50.--Trevithick's Locomotive, 1804.] RICHARD TREVITHICK was the first engineer to apply steam-power to the haulage of loads on the railroad. Trevithick was a Cornishman by birth, a native of Redruth. He was naturally a skillful mechanic, and was placed by his father with Watt's assistant, Murdoch, who was superintending the erection of pumping-engines in Cornwall; and from that ingenious and accomplished engineer young Trevithick probably acquired both the skill and the knowledge which, with his native talent, enterprise, and industry, enabled him to accomplish the work which has made him famous. He was soon intrusted with the erection and management of large pumping-engines, and subsequently went into the business of constructing steam-engines with another engineer, Edward Bull, who took an active part, with the Hornblowers and others, in opposing the Boulton & Watt patents. The termination of the suits which established the validity of Watt's patent put an end to their business, and Trevithick looked about for other work, and, not long after, entered into partnership with a relative, Andrew Vivian, who was also a skillful mechanic; they together designed and patented the steam-carriage already referred to. Its success was sufficiently satisfactory to awaken strong confidence of a perfect success on the now common tram-roads; and Trevithick, in February, 1804, had completed a "locomotive" engine to work on the Welsh Pen-y-darran road. This engine (Fig. 50) had a cylindrical flue-boiler, _A_, like that designed by Oliver Evans, and a single steam-cylinder, _B_, set vertically into the steam-space of the boiler, and driving the outside cranks, _L_, on the rear axle of the engine by very long connecting-rods, _D_, attached to its cross-head at _E_. The guide-bars, _I_, were stayed by braces leading to the opposite end of the boiler. No attempt was made to condense the exhaust-steam, which was discharged into the smoke-pipe. The pressure of steam adopted was 40 pounds per square inch; but Trevithick had already made a number of non-condensing engines on which he carried from 50 to 145 pounds pressure. In the year 1808, Trevithick built a railroad in London, on what was known later as Torrington Square, or Euston Square, and set at work a steam-carriage, which he called "Catch-me-who-can." This was a very plain and simple machine. The steam-cylinder was set vertically in the after-end of the boiler, and the cross-head was connected to two rods, one on either side, driving the hind pair of wheels. The exhaust-steam entered the chimney, aiding the draught. This engine, weighing about 10 tons, made from 12 to 15 miles an hour on the circular railway in London, and was said by its builder to be capable of making 20 miles an hour. The engine was finally thrown from the track, after some weeks of work, by the breaking of a rail, and, Trevithick's funds having been expended, it was never replaced. This engine had a steam-cylinder 14-1/2 inches in diameter, and a stroke of piston of 4 feet. Trevithick used no device to aid the friction of the wheels on the rails in giving pulling-power, and seems to have understood that none was needed. This plan of working a locomotive-engine without such complications as had been proposed by other engineers was, however, subsequently patented, in 1813, by Blackett & Hedley. The latter was at one time Trevithick's agent, and was director of Wylam Colliery, of which Mr. Blackett was proprietor. Trevithick applied his high-pressure non-conducting engine not only to locomotives, but to every purpose that opportunity offered him. He put one into the Tredegar Iron-Works, to drive the puddle-train, in 1801. This engine had a steam-cylinder 28 inches in diameter, and 6 feet stroke of piston; a boiler of cast-iron, 6-3/4 feet in diameter and 20 feet long, with a wrought-iron internal tube, 3 feet in diameter at the furnace-end and 24 inches beyond the furnace. The steam-pressure ranged from 50 to 100 pounds per square inch. The valve was a four-way cock. The exhaust-steam was carried into the chimney, passing through a feed-water heater _en route_. This engine was taken down in 1856.[48] [48] "Life of Trevithick." In 1803, Trevithick applied his engine to driving rock-drills, and three years later made a large contract with the Trinity Board for dredging in the Thames, and constructed steam dredging-machines for the work, of the form which is still most generally used in Great Britain, although rarely seen in the United States--the "chain-and-bucket dredger." A little later, Trevithick was engaged upon the first and unsuccessful attempt to carry a tunnel under the Thames, at London; but no sooner had that costly scheme been given up, than he returned to his favorite pursuits, and continued his work on interrupted schemes for ship-propulsion. Trevithick at last left England, spent some years in South America, and finally returned home and died in extreme poverty, April, 1833, at the age of sixty-two, without having succeeded in accomplishing the general introduction of any of his inventions. Trevithick was characteristically an inventor of the typical sort. He invented many valuable devices, but brought but few into even experimental use, and reaped little advantage from any of them. He was ingenious, a thorough mechanic, bold, active, and indefatigable; but his lack of persistence made his whole life, as Smiles has said, "but a series of beginnings." It is at about this period that we find evidence of the intelligent labors of another of our own countrymen--one who, in consequence of the unobtrusive manner in which his work was done, has never received the full credit to which he is entitled. COLONEL JOHN STEVENS, of Hoboken, as he is generally called, was born in the city of New York, in 1749; but throughout his business-life he was a resident of New Jersey. [Illustration: Colonel John Stevens.] His attention is said to have been first called to the application of steam-power by seeing the experiments of John Fitch with his steamer on the Delaware, and he at once devoted himself to the introduction of steam-navigation with characteristic energy, and with a success that will be indicated when we come to the consideration of that subject. But this far-sighted engineer and statesman saw plainly the importance of applying the steam-engine to land-transportation as well as to navigation; and not only that, but he saw with equal distinctness the importance of a well-devised and carefully-prosecuted scheme of internal communication by a complete system of railroads. In 1812 he published a pamphlet containing "Documents tending to prove the superior advantages of Railways and Steam-Carriages over Canal-Navigation."[49] At this time, the only locomotive in the world was that of Trevithick and Vivian, at Merthyr Tydvil, and the railroad itself had not grown beyond the old wooden tram-roads of the collieries. Yet Colonel Stevens says, in this paper: "I can see nothing to hinder a steam-carriage moving on its ways with a velocity of 100 miles an hour;" adding, in a foot-note: "This astonishing velocity is considered here merely possible. It is probable that it may not, in practise, be convenient to exceed 20 or 30 miles per hour. Actual experiment can only determine this matter, and I should not be surprised at seeing steam-carriages propelled at the rate of 40 or 50 miles an hour." [49] Printed by T. & J. Swords, 160 Pearl Street, New York, 1812. At a yet earlier date he had addressed a memoir to the proper authorities, urging his plans for railroads. He proposed rails of timber, protected, when necessary, by iron plates, or to be made wholly of iron; the car-wheels were to be of cast-iron, with inside flanges to keep them on the track. The steam-engine was to be driven by steam of 50 pounds pressure and upward, and to be non-condensing. Answering the objections of Robert R. Livingston and of the State Commissioners of New York, he goes further into details. He gives 500 to 1,000 pounds as the maximum weight to be placed on each wheel; shows that the trains, or "suits of carriages," as he calls them, will make their journeys with as much certainty and celerity in the darkest night as in the light of day; shows that the grades of proposed roads would offer but little resistance; and places the whole subject before the public with such accuracy of statement and such evident appreciation of its true value, that every one who reads this remarkable document will agree fully with President Charles King, who said[50] that "whosoever shall attentively read this pamphlet, will perceive that the political, financial, commercial, and military aspects of this great question were all present to Colonel Stevens's mind, and that he felt that he was fulfilling a patriotic duty when he placed at the disposal of his native country these fruits of his genius. The offering was not then accepted. The 'Thinker' was ahead of his age; but it is grateful to know that he lived to see his projects carried out, though not by the Government, and that, before he finally, in 1838, closed his eyes in death, at the great age of eighty-nine, he could justly feel assured that the name of Stevens, in his own person and in that of his sons, was imperishably enrolled among those which a grateful country will cherish." [50] "Progress of the City of New York." Without having made any one superlatively great improvement in the mechanism of the steam-engine, like that which gave Watt his fame--without having the honor even of being the first to propose the propulsion of vessels by the modern steam-engine, or steam-transportation on land--he exhibited a far better knowledge of the science and the art of engineering than any man of his time; and he entertained and urged more advanced opinions and more statesmanlike views in relation to the economical importance of the improvement and the application of the steam-engine, both on land and water, than seem to be attributable to any other leading engineer of that time. Says Dr. King: "Who can estimate if, at that day, acting upon the well-considered suggestion of President Madison, 'of the signal advantages to be derived to the United States from a general system of internal communication and conveyance,' Congress had entertained Colonel Stevens's proposal, and, after verifying by actual experiment upon a small scale the accuracy of his plan, had organized such a 'general system of internal communication and conveyance;' who can begin to estimate the inappreciable benefits that would have resulted therefrom to the comfort, the wealth, the power, and, above all, to the absolutely impregnable union of our great Republic and all its component parts? All this Colonel Stevens embraced in his views, for he was a statesman as well as an experimental philosopher; and whoever shall attentively read his pamphlet, will perceive that the political, financial, commercial, and military aspects of this great question were all present to his mind, and he felt that he was fulfilling a patriotic duty when he placed at the disposal of his native country these fruits of his genius." WILLIAM HEDLEY, who has already been referred to, seems to have been the first to show, by carefully-conducted experiment, how far the adhesion of the wheels of the locomotive-engine could be relied upon for hauling-power in the transportation of loads. His employer, Blackett, had applied to Trevithick for a locomotive-engine to haul coal-trains at the Wylam collieries; but Trevithick was unable, or was disinclined, to build him one, and in October, 1812, Hedley was authorized to attempt the construction of an engine. It was at about this time that Blenkinsop (1811) was trying the toothed rail or rack, the Messrs. Chapman (December, 1812) were experimenting with a towing-chain, and (May, 1813) Brunton with movable legs. Hedley, who had known of the success met with in the experiments of Trevithick with smooth wheels hauling loads of considerable weight, in Cornwall, was confident that equal success might be expected in the north-country, and built a carriage to be moved by men stationed at four handles, by which its wheels were turned. This carriage was loaded with heavy masses of iron, and attached to trains of coal-wagons on the railway. By repeated experiment, varying the weight of the traction-carriage and the load hauled, Hedley ascertained the proportion of the weight required for adhesion to that of the loads drawn. It was thus conclusively proven that the weight of his proposed locomotive-engine would be sufficient to give the pulling-power necessary for the propulsion of the coal-trains which it was to haul. When the wheels slipped in consequence of the presence of grease, frost, or moisture on the rail, Hedley proposed to sprinkle ashes on the track, as sand is now distributed from the sand-box of the modern engine. This was in October, 1812. Hedley now went to work building an engine with smooth wheels, and patented his design March 13, 1813, a month after he had put his engine at work. The locomotive had a cast-iron boiler, and a single steam-cylinder 6 inches in diameter, with a small fly-wheel. This engine had too small a boiler, and he soon after built a larger engine, with a return-flue boiler made of wrought-iron. This hauled 8 loaded coal-wagons 5 miles an hour at first, and a little later 10, doing the work of 10 horses. The steam-pressure was carried at about 50 pounds, and the exhaust, led into the chimney, where the pipe was turned upward, thus secured a blast of considerable intensity in its small chimney. Hedley also contracted the opening of the exhaust-pipe to intensify the blast, and was subjected to some annoyance by proprietors of lands along his railway, who were irritated by the burning of their grass and hedges, which were set on fire by the sparks thrown out of the chimney of the locomotive. The cost of Hedley's experiment was defrayed by Mr. Blackett. Subsequently, Hedley mounted his engine on eight wheels, the four-wheeled engines having been frequently stopped by breaking the light rails then in use. Hedley's engines continued in use at the Wylam collieries many years. The second engine was removed in 1862, and is now preserved at the South Kensington Museum, London. GEORGE STEPHENSON, to whom is generally accorded the honor of having first made the locomotive-engine a success, built his first engine at Killingworth, England, in 1814. [Illustration: George Stephenson.] At this time Stephenson was by no means alone in the field, for the idea of applying the steam-engine to driving carriages on common roads and on railroads was beginning, as has been seen, to attract considerable attention. Stephenson, however, combined, in a very fortunate degree, the advantages of great natural inventive talent and an excellent mechanical training, reminding one strongly of James Watt. Indeed, Stephenson's portrait bears some resemblance to that of the earlier great inventor. George Stephenson was born June 9, 1781, at Wylam, near Newcastle-upon-Tyne, and was the son of a "north-country miner." When still a child, he exhibited great mechanical talent and unusual love of study. When set at work about the mines, his attention to duty and his intelligence obtained for him rapid promotion, until, when but seventeen years of age, he was made engineer, and took charge of the pumping-engine at which his father was fireman. When a mere child, and employed as a herd-boy, he amused himself making model engines in clay, and, as he grew older, never lost an opportunity to learn the construction and management of machinery. After having been employed at Newburn and Callerton, where he first became "engine-man," he began to study with greater interest than ever the various steam-engines which were then in use; and both the Newcomen engine and the Watt pumping-engine were soon thoroughly understood by him. After having become a brakeman, he removed to Willington Quay, where he married, and commenced his wedded life on 18 or 20 shillings per week. It was here that he became an intimate friend of the distinguished William Fairbairn, who was then working as an apprentice at the Percy Main Colliery, near by. The "father of the railroad" and the future President of the British Association were accustomed, at times, to "change works," and were frequently seen in consultation over their numerous projects. It was at Willington Quay that his son Robert, who afterward became a distinguished civil engineer, was born, October 16, 1803. In the following year Stephenson removed to Killingworth, and became brakeman at that colliery; but his wife soon died, and he gladly accepted an invitation to become engine-driver at a spinning-mill near Montrose, Scotland. At the end of a year he returned, on foot, to Killingworth with his savings (about £28), expended over one-half of the amount in paying his father's debts and in making his parents comfortable, and then returned to his old station as brakeman at the pit. Here he made some useful improvements in the arrangement of the machinery, and spent his spare hours in studying his engine and planning new machines. He a little later distinguished himself by altering and repairing an old Newcomen engine at the High Pit, which had failed to give satisfaction, making it thoroughly successful after three days' work. The engine cleared the pit, at which it had been vainly laboring a long time, in two days after Stephenson started it up. In the year 1812, Stephenson was made engine-wright of the Killingworth High Pit, receiving £100 a year, and it was made his duty to supervise the machinery of all the collieries under lease by the so-called "Grand Allies." It was here, and at this period, that he commenced a systematic course of self-improvement and the education of his son, and here he first began to be recognized as an inventor. He was full of life and something of a wag, and often made most amusing applications of his inventive powers: as when he placed the watch, which a comrade had brought him as out of repairs, in the oven "to cook," his quick eye having noted the fact that the difficulty arose simply from the clogging of the wheels by the oil, which had been congealed by cold. Smiles,[51] his biographer, describes his cottage as a perfect curiosity-shop, filled with models of engines, machines of various kinds, and novel apparatus. He connected the cradles of his neighbors' wives with the smoke-jacks in their chimneys, and thus relieved them from constant attendance upon their infants; he fished at night with a submarine lamp, which attracted the fish from all sides, and gave him wonderful luck; he also found time to give colloquial instruction to his fellow-workmen. [51] "Lives of George and Robert Stephenson," by Samuel Smiles. New York and London, 1868. He built a self-acting inclined plane for his pit, on which the wagons, descending loaded, drew up the empty trains; and made so many improvements at the Killingworth pit, that the number of horses employed underground was reduced from 100 to 16. Stephenson now had more liberty than when employed at the brakes, and, hearing of the experiments of Blackett and Hedley at Wylam, went over to their colliery to study their engine. He also went to Leeds to see the Blenkinsop engine draw, at a trial, 70 tons at the rate of 3 miles an hour, and expressed his opinion in the characteristic remark, "I think I could make a better engine than that to go upon legs." He very soon made the attempt. Having laid the subject before the proprietors of the lease under which the collieries were worked, and convinced Lord Ravensworth, the principal owner, of the advantages to be secured by the use of a "traveling engine," that nobleman advanced the money required. Stephenson at once commenced his first locomotive-engine, building it in the workshops at West Moor, assisted mainly by John Thirlwall, the colliery blacksmith, during the years 1813 and 1814, completing it in July of the latter year. This engine had a wrought-iron boiler 8 feet long and 2 feet 10 inches in diameter, with a single flue 20 inches in diameter. The cylinders were vertical, 8 inches in diameter and of 2 feet stroke of piston, set in the boiler, and driving a set of wheels which geared with each other and with other cogged wheels on the two driving-axles. A feed-water heater surrounded the base of the chimney. This engine drew 30 tons on a rising gradient of 10 or 12 feet to the mile at the rate of 4 miles an hour. This engine proved in many respects defective, and the cost of its operation was found to be about as great as that of employing horse-power. Stephenson determined to build another engine on a somewhat different plan, and patented its design in February, 1815. It proved a much more efficient machine than the "Blücher," the first engine. [Illustration: FIG. 51.--Stephenson's Locomotive of 1815. Section.] This second engine (Fig. 51) was also fitted with two vertical cylinders, _C c_, but the connecting-rods were attached directly to the four driving-wheels, _W W´_. To permit the necessary freedom of motion, "ball-and-socket" joints were adopted, to unite the rods with the cross-heads, _R r_, and with the cranks, _R´ Y´_; and the two driving-axles were connected by an endless chain, _T t´_. The cranked axle and the outside connection of the wheels, as specified in the patent, were not used until afterward, it having been found impossible to get the cranked axles made. In this engine the forced draught obtained by the impulse of the exhaust-steam was adopted, doubling the power of the machine and permitting the use of coke as a fuel, and making it possible to adopt the multi-tubular boiler. Small steam-cylinders, _S S S_, took the weight of the engine and served as springs. It was at about this time that George Stephenson and Sir Humphry Davy, independently and almost simultaneously, invented the "safety-lamp," without which few mines of bituminous coal could to-day be worked. The former used small tubes, the latter fine wire gauze, to intercept the flame. Stephenson proved the efficiency of his lamp by going with it directly into the inflammable atmosphere of a dangerous mine, and repeatedly permitting the light to be extinguished when the lamp became surcharged with the explosive mixture which had so frequently proved fatal to the miners. This was in October and November, 1815, and Stephenson's work antedates that of the great philosopher.[52] The controversy which arose between the supporters of the rival claims of the two inventors was very earnest, and sometimes bitter. The friends of the young engineer raised a subscription, amounting to above £1,000, and presented it to him as a token of their appreciation of the value of his simple yet important contrivance. Of the two forms of lamp, that of Stephenson is claimed to be safest, the Davy lamp being liable to produce explosions by igniting the explosive gas when, by its combustion within the gauze cylinder, the latter is made red-hot. Under similar conditions, the Stephenson lamp is simply extinguished, as was seen at Barnsley, in 1857, at the Oaks Colliery, where both kinds of lamp were in use, and elsewhere. [52] _Vide_ "A Description of the Safety-Lamp invented by George Stephenson," etc., London, 1817. Stephenson continued to study and experiment, with a view to the improvement of his locomotive and the railroad. He introduced better methods of track-laying and of jointing the rails, adopting a half-lap, or peculiar scarf-joint, in place of the then usual square-butt joint. He patented, with these modifications of the permanent way, several of his improvements of the engine. He had substituted forged for the rude cast wheels previously used,[53] and had made many minor changes of detail. The engines built at this time (1816) continued in use many years. Two years later, with a dynamometer which he designed for the purpose, he made experimental determinations of the resistance of trains, and showed that it was made up of several kinds, as the sliding friction of the axle-journals in their bearings, the rolling friction of the wheels on the rails, the resistance due to gravity on gradients, and that due to the resistance of the air. [53] The American chilled wheel of cast-iron, a better wheel than that above described, has never been generally and successfully introduced in Europe. These experiments seemed to him conclusive against the possibility of the competition of engines on the common highway with locomotives hauling trains on the rail. Finding that the resistance, with his rolling-stock, and at all the speeds at which he made his experiments, was approximately invariable, and equivalent to about 10 pounds per ton, and estimating that a gradient rising but 1 foot in 100 would decrease the hauling power of the engine 50 per cent., he saw at once the necessity of making all railroads as nearly absolutely level as possible, and, consequently, the radically distinctive character of this branch of civil engineering work. He persistently condemned the "folly" of attempting the general introduction of steam on the common road, where great changes of level and an impressible road-bed were certain to prove fatal to success, and was most strenuous in his advocacy of the policy of securing level tracks, even at very great expense. Taking part in the contest, which now became a serious one, between the advocates of steam on the common road and those urging the introduction of locomotives and their trains on an iron track, he calculated that a road-engine capable of carrying 20 or 30 passengers at 10 miles per hour, could, on the rail, carry ten times as many people at three or four times that speed. The railway-engine finally superseded its predecessor--the engine of the common road--almost completely. In 1817, Stephenson built an engine for the Duke of Portland, to haul coal from Kilmarnock to Troon, which cost £750, and, with some interruptions, this engine worked on that line until 1848, when it was broken up. On November 18, 1822, the Hetton Railway, near Sunderland, was opened. George Stephenson was the engineer of the line--a short track, 8 miles long, built from the Hetton Colliery to the docks on the bank of the river Wear. On this line he put in five of the "self-acting inclines"--two inclines worked by stationary engines, the gradients being too heavy for locomotives--and used five locomotive-engines of his own design, which were called by the people of the neighborhood, possibly for the first time, "the iron horses." These engines were quite similar to the Killingworth engine. They drew a train of 17 coal-cars--a total load of 64 tons--about 4 miles an hour. Meantime, also, in 1823, Stephenson had been made engineer of the Stockton & Darlington Railroad, which had been projected for the purpose of securing transportation to tide-water for the valuable coal-lands of Durham. This road was built without an expectation on the part of any of its promoters, Stephenson excepted, that steam would be used as a motor to the exclusion of horses. Mr. Edward Pearse, however, one of the largest holders of stock in the road, and one of its most earnest advocates, became so convinced, by an examination of the Killingworth engines and their work, of the immense advantage to be derived by their use, that he not only supported Stephenson's arguments, but, with Thomas Richardson, advanced £1,000 for the purpose of assisting Stephenson to commence the business of locomotive-engine construction at Newcastle. This workshop, which subsequently became a great and famous establishment, was commenced in 1824. For this road Stephenson recommended wrought-iron rails, which were then costing £12 per ton--double the price of cast rails. The directors, however, stipulated that he should only buy one-half the rails required from the dealers in "malleable" iron. These rails weighed 20 pounds to the yard. After long hesitation, in the face of a serious opposition, the directors finally concluded to order three locomotives of Stephenson. The first, or "No. 1," engine (Fig. 52) was delivered in time for the opening of the road, September 27, 1825. It weighed 8 tons. Its boiler contained a single straight flue, one end of which was the furnace. The cylinders were vertical, like those of the earlier engines, and coupled directly to the driving-wheels. The crank-pins were set in the wheels at right angles, in order that, while one engine was "turning the centre," the other might exert its maximum power. The two pairs of drivers were coupled by horizontal rods, as seen in the figure, which represents this engine as subsequently mounted on a pedestal at the Darlington station. A steam-blast in the chimney gave the requisite strength of draught. These engines were built for slow and heavy work, but were capable of making what was then thought the satisfactorily high speed of 16 miles per hour. The inclines on the road were worked by fixed engines. [Illustration: FIG. 52.--Stephenson's No. 1 Engine, 1825.] On the opening day, which was celebrated as a holiday by the people far and near, the No. 1 engine drew 90 tons at the rate of 12, and at times 15, miles an hour. [Illustration: FIG. 58.--Opening of the Stockton and Darlington Railroad, 1815. (After an old engraving.)] Stephenson's engines were kept at work hauling coal-trains, but the passenger-coaches were all drawn for some time by horses, and the latter system was a rude forerunner, in most respects, of modern street-railway transportation. Mixed passenger and freight trains were next introduced, and, soon after, separate passenger-trains drawn by faster engines were placed on the line, and the present system of railroad transportation was now fairly inaugurated. A railroad between Manchester and Liverpool had been projected at about the time that the Stockton & Darlington road was commenced. The preliminary surveys had been made in the face of strong opposition, which did not always stop at legal action and verbal attack, but in some instances led to the display of force. The surveyors were sometimes driven from their work by a mob armed with sticks and stones, urged on by land-proprietors and those interested in the lines of coaches on the highway. Before the opening of the Stockton & Darlington Railroad, the Liverpool & Manchester bill had been carried through Parliament, after a very determined effort on the part of coach-proprietors and landholders to defeat it, and Stephenson urged the adoption of the locomotive to the exclusion of horses. It was his assertion, made at this time, that he could build a locomotive to run 20 miles an hour, that provoked the celebrated rejoinder of a writer in the _Quarterly Review_, who was, however, in favor of the construction of the road and of the use of the locomotive upon it: "What can be more palpably absurd and ridiculous, than the prospect held out of locomotives traveling _twice as fast_ as stage-coaches? We would as soon expect the people of Woolwich to suffer themselves to be fired off upon one of Congreve's ricochet-rockets, as trust themselves to the mercy of such a machine going at such a rate." It was during his examination before a committee of the House of Commons, during this contest, that Stephenson, when asked, "Suppose, now, one of your engines to be going at the rate of 9 or 10 miles an hour, and that a cow were to stray upon the line and get in the way of the engine, would not that be a very awkward circumstance?" replied, "Yes, _very_ awkward--_for the coo!_" And when asked if men and animals would not be frightened by the red-hot smoke-pipe, answered, "But how would they know that it was not _painted?_" The line was finally built, with George Rennie as consulting, and Stephenson as principal constructing engineer. His work on this road became one of the important elements of the success, and one of the great causes of the distinction, which marked the life of these rising engineers. The successful construction of that part of the line which lay across "Chat Moss," an unfathomable swampy deposit of peat, extending over an area of 12 square miles, and the building of which had been repeatedly declared an impossibility, was in itself sufficient to prove that the engineer who had accomplished it was no common man. Stephenson adopted the very simple yet bold expedient of using, as a filling, compacted turf and peat, and building a road-bed of materials lighter than water, or the substance composing the bog, and thus forming a _floating_ embankment, on which he laid his rails. To the surprise of every one but Stephenson himself, the plan proved perfectly successful, and even surprisingly economical, costing but little more than one-tenth the estimate of at least one engineer. Among the other great works on this remarkable pioneer-line were the tunnel, a mile and a half long, from the station at Liverpool to Edgehill; the Olive Mount deep-cut, two miles long, and in some places 100 feet deep, through red sandstone, of which nearly 500,000 yards were removed; the Sankey Viaduct, a brick structure of nine arches, of 50 feet span each, costing £45,000; and a number of other pieces of work which are noteworthy in even these days of great works. Stephenson planned all details of the line, and even designed the bridges, machinery, engines, turn-tables, switches, and crossings, and was responsible for every part of the work of their construction. Finally, the work of building the line approached completion, and it became necessary promptly to settle the long-deferred question of a method of applying motive-power. Some of the directors and their advisers still advocated the use of horses; many thought stationary hauling-engines preferable; and the remainder were, almost to a man, undecided. The locomotive had no outspoken advocate, and few had the slightest faith in it. George Stephenson was almost alone, and the opponents of steam had secured a provision in the Newcastle & Carlisle Railroad concession, stipulating expressly that horses should there be exclusively employed. The directors did, however, in 1828, permit Stephenson to put on the line a locomotive, to be used, during its construction, in hauling gravel-trains. A committee was sent, at Stephenson's request, to see the Stockton & Darlington engines, but no decided expression of opinion seems to have been made by them. Two well-known professional engineers reported in favor of fixed engines, and advised the division of the line into 19 stages of about a mile and a half each, and the use of 21 fixed engines, although they admitted the excessive first-cost of that system. The board was naturally strongly inclined to adopt their plan. Stephenson, however, earnestly and persistently opposed such action, and, after long debate, it was finally determined "to give the traveling engine a chance." The board decided to offer a reward of £500 for the best locomotive-engine, and prescribed the following conditions: 1. The engine must consume its own smoke. 2. The engine, if of 6 tons weight, must be able to draw after it, day by day, 20 tons weight (including the tender and water-tank) at 10 miles an hour, with a pressure of steam on the boiler not exceeding 50 pounds to the square inch. 3. The boiler must have two safety-valves, neither of which must be fastened down, and one of them completely out of the control of the engine-man. 4. The engine and boiler must be supported on springs, and rest on 6 wheels, the height of the whole not exceeding 15 feet to the top of the chimney. 5. The engine, with water, must not weigh more than 6 tons; but an engine of less weight would be preferred, on its drawing a proportionate load behind it; if of only 4-1/2 tons, then it might be put only on 4 wheels. The company to be at liberty to test the boiler, etc., by a pressure of 150 pounds to the square inch. 6. A mercurial gauge must be affixed to the machine, showing the steam-pressure above 45 pounds to the square inch. 7. The engine must be delivered, complete and ready for trial, at the Liverpool end of the railway, not later than the 1st of October, 1829. 8. The price of the engine must not exceed £550. This circular was printed and published throughout the kingdom, and a considerable number of engines were constructed to compete at the trial, which was proposed to take place October 1, 1829, but which was deferred to the 6th of that month. Only four engines, however, were finally entered on the day of the trial. These were the "Novelty," constructed by Messrs. Braithwaite & Ericsson, the latter being the distinguished engineer who subsequently came to the United States to introduce screw-propulsion, and, later, the monitor system of iron-clads; the "Rocket," built from Stephenson's plans; and the "Sanspareil" and the "Perseverance," built by Hackworth and Burstall, respectively. The "Sanspareil," which was built under the direction of Timothy Hackworth, one of Stephenson's earlier foremen, resembled the engine built by the latter for the Stockton & Darlington road, but was heavier than had been stipulated, was not ready for work when called, and, when finally set at work, proved to be very extravagant in its use of fuel, partly in consequence of the extreme intensity of its blast, which caused the expulsion of unconsumed coals from the furnace. The "Perseverance" could not attain the specified speed, and was withdrawn. [Illustration: FIG. 54.--The "Novelty," 1829.] The "Novelty" was apparently a well-designed and for that time a remarkably well-proportioned machine. _A_, in Fig. 54, is the boiler, _D_ the steam-cylinders, _E_ a heater. Its weight but slightly exceeded three tons, and it was a "tank engine," carrying its own fuel and water at _B_. A forced draught was obtained by means of the bellows, _C_. This engine was run over the line at the rate of about 28 miles an hour at times, but its blowing apparatus failed, and the "Rocket" held the track alone. A later trial still left the "Rocket" alone in the field. The "Rocket" (Fig. 55) was built at the works of Robert Stephenson & Co., at Newcastle-upon-Tyne. The boiler was given considerable heating-surface by the introduction of 25 3-inch copper tubes, at the suggestion of Henry Booth, secretary of the railroad company. The blast was altered by gradually closing in the opening at the extremity of the exhaust-pipe, and thus "sharpening" it until it was found to have the requisite intensity. The effect of this modification of the shape of the pipe was observed carefully by means of syphon water-gauges attached to the chimney. The draft was finally given such an intensity as to raise the water 3 inches in the tube of the draught-gauge. The total length of the boiler was 6 feet, its diameter 40 inches. The fire-box was attached to the rear of the boiler, and was 3 feet high and 2 feet wide, with water-legs to protect its side-sheets from injury by overheating. The cylinders, as seen in the sketch, were inclined, and coupled to a single pair of driving-wheels. A tender, attached to the engine, carried the fuel and water. The engine weighed less than 4-1/2 tons. [Illustration: FIG. 55.--The "Rocket," 1829.] The little engine does not seem to have been very prepossessing in appearance, and the "Novelty" is said to have been the general favorite, the Stephenson engine having few, if any, backers among the spectators. On its first trial, it ran 12 miles in less than an hour. After the accident which disabled the "Novelty," the "Rocket" came forward again, and ran at the rate of from 25 to 30 miles an hour, drawing a single carriage carrying 30 passengers. Two days later, on the 8th of October, steam was raised in a little less than an hour from cold water, and it then, with 13 tons of freight in the train, ran 35 miles in 1 hour and 48 minutes, including stops, and attained a speed of 29 miles an hour. The average of all runs for the trial was 15 miles an hour. This success, far exceeding the expectation of the most sanguine of the advocates of the system, and greatly exceeding what had been asserted by opponents to be the bounds of possibility, settled completely the whole question, and the Manchester & Liverpool road was at once equipped with locomotive engines. The "Rocket" remained on the line until 1837, when it was sold, and set at work by the purchasers on the Midgeholme Railway, near Carlisle. On one occasion, on this road, it was driven 4 miles in 4-1/2 minutes. It is now in the Patent Museum at South Kensington, London. In January, 1830, a single line of rails had been carried across Chat Moss, and, six months later, the first train, drawn by the "Arrow," ran through, June 14th, from Liverpool to Manchester, making the trip in an hour and a half, and attaining a maximum speed of over 27 miles an hour. The line was formally opened to traffic September 15, 1830. This was one of the most notable occasions in the history of the railroad, and the successful termination of the great work was celebrated, as so important an event should be, by impressive ceremonies. Among the distinguished spectators were Sir Robert Peel and the Duke of Wellington. Mr. Huskisson, a Member of Parliament for Liverpool, was also present. There had been built for the line, by Robert Stephenson & Co., 7 locomotives besides the "Rocket," and a large number of carriages. These were all brought out in procession, and 600 passengers entered the train, which started for Manchester, and ran at times, on smooth portions of the road, at the rate of 20 and 25 miles an hour. Crowds of people along the line cheered at this strange and to them incomprehensible spectacle, and the story of the wonderful performances of that day on the new railroad was repeated in every corner of the land. A sad accident, the precursor of thousands to follow the introduction of the new method of transportation, while it repressed the rising enthusiasm of the people and dampened the ardor of the most earnest of the advocates of the railroad, occurring during this trip, assisted in making known the power of the new motor and the danger attending its use as well. The trains stopped for water at Parkside, and occasion was taken to send the "Northumbrian," an engine driven by George Stephenson himself, on a side track, with the carriage containing the Duke of Wellington, and the other engines and trains were all directed to be sent along the main track in view of the Duke and his party. While this movement was in process of execution, Mr. Huskisson, who had carelessly stood on the main line until the "Rocket," which led the column, had nearly reached him, attempted to enter the carriage of the Duke. He was too late, and was struck by the "Rocket," thrown down across the rail, and the advancing engine crushed a leg so seriously that he died the same evening. Immediately after the accident, he was placed on the "Northumbrian," and Stephenson made the 15 miles to the destination of the wounded man in 25 minutes--a speed of 36 miles an hour. The news of this accident, and the statement of the velocity of the engine, were published throughout the kingdom and Europe; and the misfortune of this first victim of a railroad accident was one of the causes of the immediate adoption and rapid spread of the modern railway system. This road, which was built in the hope of securing 400 passengers per day, almost immediately averaged 1,200, and in five years reported 500,000 passengers for the year.[54] The success of this road insured the general introduction of railroads, and from this time forward there was never a doubt of their ultimate adoption to the exclusion of every other system of general internal communication and transportation. [54] Smiles. For some years after this his first great triumph, George Stephenson gave his whole time to the building of railroads and the improvement of the engine. He was assisted by his son Robert, to whom he gradually surrendered his business, and retired to Tapton House, on the Midland Railway, and led a busy but pleasant life during the remaining years of his existence. Even as early as 1840, he seems to have projected many improvements which were only generally adopted many years later. He proposed self-acting and continuous systems of brake, and considered a good system of brake of so great importance, that he advocated their compulsory introduction by State legislation. He advised moderate speeds, from considerations both of safety and of expense. A few years after the opening of the Liverpool & Manchester road, great numbers of schemes were proposed by ignorant or designing men, which had for their object the filling of the pockets of their proposers rather than the benefit of the stockholders and the public; and the Stephensons were often called upon to combat these crude and ill-digested plans. Among these was the pneumatic system of propulsion, already referred to as first proposed by Papin, in combination with his double-acting air-pump, in 1687. It had been again proposed in the early part of the present century by Medhurst, who proposed a method of pneumatic transmission of small parcels and of letters, which is now in use, and, 15 years later, a railroad to take the place of that of Stephenson and his coadjutors. The most successful of several attempts to introduce this method was that of Clegg & Samuda, at West London, and on the London & Croydon road, and again in Ireland, between Kingstown and Dalkey. A line of pipe, _B B_, seen in Fig. 56, two feet in diameter, was laid between the rails, _A A_, of the road. This pipe was fitted with a nicely-packed piston, carrying a strong arm, which rose through a slit made along the top of the pipe, and covered by a flexible strip of leather, _E E_. This arm was attached to the carriage, _C C_, to be propelled. The pressure of the atmosphere being removed, by the action of a powerful pump, from the side toward which the train was to advance, the pressure of the atmosphere on the opposite side drove the piston forward, carrying the train with it. Stephenson was convinced, after examining the plans of the projectors, that the scheme would fail, and so expressed himself. Those who favored it, however, had sufficient influence with capitalists to secure repeated trials, although each was followed by failure, and it was several years before the last was heard of this system. [Illustration: FIG. 56.--The Atmospheric Railroad.] A considerable portion of several of the later years of Stephenson's life was spent in traveling in Europe, partly on business and partly for pleasure. During a visit to Belgium in 1845, he was received everywhere, and by all classes, from the king down to the humblest of his subjects, with such distinction as is rarely accorded even to the greatest men. He soon after visited Spain with Sir Joshua Walmsley, to report on a proposed railway from the capital to the Bay of Biscay. On this journey he was taken ill, and his health was permanently impaired. Thenceforward he devoted himself principally to the direction of his own property, which had become very considerable, and spent much of his time at the collieries and other works in which he had invested it. His son had now entirely relieved him of all business connected with railroads, and he had leisure to devote to self-improvement and social amusement. Among his friends he claimed Sir Robert Peel, his old acquaintance, now Sir William, Fairbairn, Dr. Buckland, and many others of the distinguished men of that time. In August, 1848, Stephenson was attacked with intermittent fever, succeeded by hæmorrhage from the lungs, and died on the 12th of that month, at the age of sixty-six years, honored of all men, and secure of an undying fame. Soon after his death, statues were erected at Liverpool, London, and Newcastle, the cost of the second of which was defrayed by private subscriptions, including a contribution of about $1,500 by 3,150 workingmen--one of the finest tributes ever offered to the memory of a great man. But the noblest monument is that which he himself erected by the establishment of a system of education and protection of his working-people at Clay Cross. He made it a condition of employment that every employé should contribute from five to twelve pence each fortnight to a fund, to which the works also made liberal contributions. From that fund it was directed that the expenses of free education of the children of the work-people, night-schools for those employed in the works, a reading-room and library, medical treatment, and a benevolent fund were to be defrayed. Music and cricket-clubs, and prize funds for the best garden, were also founded. The school, public hall, and the church of Clay Cross, and this noble system of support, are together a nobler monument than any statue or similar structure could be. The character of George Stephenson was in every way admirable. Simple, earnest, and honorable; courageous, indomitable, and industrious; humorous, kind, and philanthropic, his memory will long be cherished, and will long prove an incentive to earnest effort and to the pursuit of an honorable fame with hundreds of the youth who, reading his simple yet absorbing story, as told by his biographer, shall in later years learn to know him. [Illustration: FIG. 57.--Stephenson's Locomotive, 1833.] After the death of his father, Robert Stephenson continued, as he had already done for several years, to conduct the business of building locomotives, as well as of constructing railroads. The work of locomotive engine-building was done at Newcastle, and for many years those works were the principal engine-building establishment of the world. After their introduction on the Liverpool & Manchester road, the engines of the firm of Robert Stephenson & Co. were rapidly modified, until they assumed the form shown in Fig. 57, which remained standard until their gradual increase in weight compelled the builders to place a larger number of wheels beneath them, and make those other changes which finally resulted in the creation of distinct types for special kinds of work. In the engine of 1833, as shown above, the cylinders, _A_, are carried at the extreme forward end of the boiler, and the driving-wheels, _B_, are coupled directly to the connecting-rod of the engine and to each other. A buffer, _C_, extends in front, and the rear end of the boiler is formed into a rectangular fire-box, _D_, continuous with the shell, _E_, and the flame and gases pass to the connection and smoke-pipe, _F_, _G_, through a large number of small tubes, _a_. Steam is led to the cylinders by a steam-pipe, _H H_, to which it is admitted by the throttle-valve, _b_. A steam-dome, _I_, from which the steam is taken, assists by giving more steam-space far above the water-line, and thus furnishing dry steam. The exhaust steam issues with great velocity into the chimney from the pipe, _J_, giving great intensity of draught. The engine-driver stands on the platform, _K_, from which all the valves and handles are accessible. Feed-pumps, _L_, supply the boiler with water, which is drawn from the tender through the pipes, _e_, _f_. The valve-gear was then substantially what it is to-day, the "Stephenson link" (Fig. 58). On the driving-axle were keyed two eccentrics, _E_, so set that the motion of the one was adapted to driving the valve when the engine was moving forward, and the other was arranged to move the valve when running backward. The former was connected, through its strap and the rod, _B_, to the upper end of a "strap-link," _A_, while the second was similarly connected with the lower end. By means of a handle, _L_, and the link, _n_, and its connections, including the counterweighted bell-crank, _M_, this link could be raised or depressed, thus bringing the pin on the link-block, to which the valve-stem was connected, into action with either eccentric. Or, the link being set in mid-gear, the valve would cover both steam-ports of the cylinder, and the engine could move neither way. As shown, the engine is in position to run backward. A series of notches, _Z_, into either of which a catch on _L_ could be dropped, enabled the driver to place the link where he chose. In intermediate positions, between mid-gear and full-gear, the motion of the valve is such as to produce expansion of the steam, and some gain in economy of working, although reducing the power of the engine. [Illustration: FIG. 58.--The Stephenson Valve-Gear, 1833.] The success of the railroad and the locomotive in Great Britain led to its rapid introduction in other countries. In France, as early as 1823, M. Beaunier was authorized to construct a line of rails from the coal-mines of St. Étienne to the Loire, using horses for the traction of his trains; and in 1826, MM. Seguin began a road from St. Étienne to Lyons. In 1832, engines built at Lyons were substituted for horses on these roads, but internal agitations interrupted the progress of the new system in France, and, for 10 years after the opening of the Manchester & Liverpool road, France remained without steam-transportation on land. In Belgium the introduction of the locomotive was more promptly accomplished. Under the direction of Pierre Simon, an enterprising and well-informed young engineer, who had become known principally as an advocate of the even then familiar project of a canal across the Isthmus of Darien, very complete plans of railroad communication for the kingdom were prepared, in compliance with a decree dated July 31, 1834, and were promptly authorized. The road between Brussels and Mechlin was opened May 6, 1837, and other roads were soon built; and the railway system of Belgium was the first on the Continent of Europe. The first German railroad worked with locomotive steam-engines was that between Nuremberg and Fürth, built under the direction of M. Denis. The other European countries soon followed in this rapid march of improvement. In the United States, public attention had been directed to this subject, as has already been stated, very early in the present century, by Evans and Stevens. At that time the people of the United States, as was natural, closely watched every important series of events in the mother-country; and so remarkable and striking a change as that which was taking place in the time of Stephenson, in methods of communication and transportation, could not fail to attract general attention and awaken universal interest. Notwithstanding the success of the early experiments of Evans and others, and in spite of the statesmanlike arguments of Stevens and Dearborn, and the earnest advocacy of the plan by all who were familiar with the revelations which were daily made of the power and capabilities of the steam-engine, it was not until after the opening of the Manchester & Liverpool road that any action was taken looking to the introduction of the locomotive. Colonel John Stevens, in 1825, had built a small locomotive, which he had placed on a circular railway before his house--now Hudson Terrace--at Hoboken, to prove that his statements had a basis of fact. This engine had two "lantern" tubular boilers, each composed of small iron tubes, arranged vertically in circles about the furnaces.[55] This exhibition had no other effect, however, than to create some interest in the subject, which aided in securing a rapid adoption of the railroad when once introduced. [55] One of these sectional boilers is still preserved in the lecture-room of the author, at the Stevens Institute of Technology. The first line of rails in the New England States is said to have been laid down at Quincy, Mass., from the granite quarry to the Neponset River, three miles away, in 1826 and 1827. That between the coal-mines of Mauch Chunk, Pa., and the river Lehigh, nine miles distant, was built in 1827. In the following year the Delaware & Hudson Canal Company built a railroad from their mines to the termination of the canal at Honesdale. These roads were worked either by gravity or by horses and mules. The competition at Rainhill, on the Liverpool and Manchester Railroad, had been so widely advertised, and promised to afford such conclusive evidence relative to the value of the locomotive steam-engine and the railroad, that engineers and others interested in the subject came from all parts of the world to witness the trial. Among the strangers present were Mr. Horatio Allen, then chief-engineer of the Delaware & Hudson Canal Company, and Mr. E. L. Miller, a resident of Charleston, S. C., who went from the United States for the express purpose of seeing the new machines tested. Mr. Allen had been authorized to purchase, for the company with which he was connected, three locomotives and the iron for the road, and had already shipped one engine to the United States, and had set it at work on the road. This engine was received in New York in May, 1829, and its trial took place in August at Honesdale, Mr. Allen himself driving the engine. But the track proved too light for the locomotive, and it was laid up and never set at regular work. This engine was called the "Stourbridge Lion"; it was built by Foster, Rastrick & Co., of Stourbridge, England. During the summer of the next year, a small experimental engine, which was built in 1829 by Peter Cooper, of New York, was successfully tried on the Baltimore & Ohio Railroad, at Baltimore, making 13 miles in less than an hour, and moving, at some points on the road, at the rate of 18 miles an hour. One carriage carrying 36 passengers was attached. This was considered a working-model only, and was rated at one horse-power. Ross Winans, writing of this trial of Cooper's engine, makes a comparison with the work done by Stephenson's "Rocket," and claims a decided superiority for the former. He concluded that the trial established fully the practicability of using locomotives on the Baltimore & Ohio road at high speeds, and on all its curves and heavy gradients, without inconvenience or danger. This engine had a vertical tubular boiler, and the draught was urged, like that of the "Novelty" at Liverpool, by mechanical means--a revolving fan. The single steam-cylinder was 3-1/4 inches in diameter, and the stroke of piston 14-1/2 inches. The wheels were 30 inches in diameter, and connected to the crank-shaft by gearing. The engine, on the trial, worked up to 1.43 horse-power, and drew a gross weight of 4-1/2 tons. Mr. Cooper, unable to find such tubes as he needed for his boiler, used gun-barrels. The whole machine weighed less than a ton. Messrs. Davis & Gartner, a little later, built the "York" for this road--a locomotive having also a vertical boiler, of very similar form to the modern steam fire-engine boiler, 51 inches in diameter, and containing 282 fire-tubes, 16 inches long, and tapering from 1-1/2 inches diameter at the bottom to 1-1/4 at the top, where the gases were discharged through a combustion-chamber into a steam-chimney. This engine weighed 3-1/2 tons. They subsequently built several "grasshopper" engines (Fig. 59), some of which ran many years, doing good work, and one or two of which are still in existence. The first--the "Atlantic"--was set at work in September, 1832, and hauled 50 tons from Baltimore 40 miles, over gradients having a maximum rise of 37 feet to the mile, and on curves having a minimum radius of 400 feet, at the rate of 12 to 15 miles an hour. This engine weighed 6-1/2 tons, carried 50 pounds of steam--a pressure then common on both continents --and burned a ton of anthracite coal on the round trip. The blast was secured by a fan, and the valve-gear was worked by cams instead of eccentrics. This engine made the round trip at a cost of $16, doing the work of 42 horses, which had cost $33 per trip. The engine cost $4,500, and was designed by Phineas Davis, assisted by Ross Winans. [Illustration: FIG. 59.--The "Atlantic," 1882.] Mr. Miller, on his return from the Liverpool & Manchester trial, ordered a locomotive for the Charleston & Hamburg Railroad from the West Point Foundery. This engine was guaranteed by Mr. Miller to draw three times its weight at the rate of 10 miles an hour. It was built during the summer of 1830, from the plans of Mr. Miller, and reached Charleston in October. The trials were made in November and December. [Illustration: FIG. 60.--The "Best Friend," 1830.] This engine (Fig. 60) had a vertical tubular boiler, in which the gases rose through a very high fire-box, into which large numbers of rods projected from the sides and top, and passed out through tubes leading them laterally outward into an outside jacket, through which they rose to the chimney. The steam-cylinders were two in number, 8 inches in diameter and of 16 inches stroke, inclined so as to connect with the driving-axle. The four wheels were all of the same size, 4-1/2 feet in diameter, and connected by coupling-rods. The engine weighed 4-1/2 tons. The "Best Friend," as it was called, did excellent work until June, 1831, when the explosion of the boiler, in consequence of the recklessness of the fireman, unexpectedly closed its career. A second engine (Fig. 61) was built for this road, at the West Point Foundery, from plans furnished by Horatio Allen, and was received and set at work early in the spring of 1831. The engine, called the "West Point," had a horizontal tubular boiler, but was in other respects very similar to the "Best Friend." It is said to have done very good work. [Illustration: FIG. 61.--The "West Point," 1831.] The Mohawk & Hudson Railroad ordered an engine at about this time, also, of the West Point Foundery, and the trials, made in July and August, 1831, proved thoroughly successful. This engine, the "De Witt Clinton," was contracted for by John B. Jervis, and fitted up by David Matthew. It had two steam-cylinders, each 5-1/2 inches in diameter and 16 inches stroke of piston. The connecting-rods were directly attached to a cranked axle, and turned four coupled wheels 4-1/2 feet in diameter. These wheels had cast-iron hubs and wrought-iron spokes and tires. The tubes were of copper, 2-1/2 inches in diameter and 6 feet long. The engine weighed 3-1/2 tons, and hauled 5 cars at the rate of 30 miles an hour. Another engine, the "South Carolina" (Fig. 62), was designed by Horatio Allen for the South Carolina Railroad, and completed late in the year 1831. This was the first eight-wheeled engine, and the prototype, also, of a peculiar and lately-revived form of engine. In the summer of 1832, an engine built by Messrs. Davis & Gartner, of York, Pa., was put on the Baltimore & Ohio road, which at times attained a speed, unloaded, of 30 miles an hour. The engine weighed 3-1/2 tons, and drew, usually, 4 cars, weighing altogether 14 tons, from Baltimore to Ellicott's Mills, a distance of 13 miles, in the schedule-time, one hour. [Illustration: FIG. 62.--The "South Carolina," 1831.] Horatio Allen's engine on the South Carolina Railroad is said to have been the first eight-wheeled engine ever built. It was at about the time of which we are now writing that the first locomotive was built of what is now distinctively known as the American type--an engine with a "truck" or "bogie" under the forward end of the boiler. This was the "American" No. 1, built at the West Point Foundery, from plans furnished by John B. Jervis, Chief Engineer, for the Mohawk & Hudson Railroad. Ross Winans had already (1831) introduced the passenger-car with swiveling trucks.[56] It was completed in August, 1832, and is said by Mr. Matthew to have been an extremely fast and smooth-running engine. A mile a minute was repeatedly attained, and it is stated by the same authority,[57] that a speed of 80 miles an hour was sometimes made over a single mile. This engine had cylinders 9-1/2 inches diameter, 16 inches stroke of piston, two pairs of driving-wheels, coupled, 5 feet in diameter each; and the truck had four 33-inch wheels. The boiler contained tubes 3 inches in diameter, and its fire-box was 5 feet long and 2 feet 10 inches wide. Robert Stephenson & Co. subsequently built a similar engine, from the plans of Mr. Jervis, and for the same road. It was set at work in 1833. In both engines the driving-wheels were behind the fire-box. This engine is another illustration of the fact--shown by the description already given of other and earlier engines--that the independence of the American mechanic, and the boldness and self-confidence which have to the present time distinguished him, were among the earliest of the fruits of our political independence and freedom. [56] "History of the First Locomotives in America," Brown. [57] "Ross Winans _vs._ The Eastern Railroad Company--Evidence." Boston, 1854. These American engines were all designed to burn anthracite coal. The English locomotives all burned bituminous coal. Robert L. Stevens, the President and Engineer of the Camden & Amboy Railroad, and a distinguished son of Colonel John Stevens, of Hoboken, was engaged, at the time of the opening of the Liverpool & Manchester Railroad, in the construction of the Camden & Amboy Railroad. It was here that the first of the now standard form of _T_-rail was laid down. It was of malleable iron, and of the form shown in the accompanying figure. It was designed by Mr. Stevens, and is known in the United States as the "Stevens" rail. In Europe, where it was introduced some years afterward, it is sometimes called the "Vignolles" rail. He purchased an engine of the Stephensons soon after the trial at Rainhill, and this engine, the "John Bull," was set up on the then uncompleted road at Bordentown, in the year 1831. Its first public trial was made in November of that year. The road was opened for traffic, from end to end, two years later. This engine had steam-cylinders 9 inches in diameter, 2 feet stroke of piston, one pair of drivers 4-1/2 feet in diameter, and weighed 10 tons. This engine, and that built by Phineas Davis for the Baltimore & Ohio Railroad, were exhibited at the Centennial Exhibition at Philadelphia, in the year 1876. [Illustration: FIG. 63.--The "Stevens" Rail. Enlarged Section.] [Illustration: FIG. 64.--"Old Ironsides," 1832.] Engines supplied to the Camden & Amboy Railroad subsequent to 1831 were built from the designs of Robert L. Stevens, in the shop of the Messrs. Stevens, at Hoboken. The other principal roads of the country, at first, very generally purchased their engines of the Baldwin Locomotive Works, then a small shop owned by Matthias W. Baldwin. Baldwin's first engine was a little model built for Peale's Museum, to illustrate to the visitors of that then well-known place of entertainment the character of the new motor, the success of which, at Rainhill, had just then excited the attention of the world. This was in 1831, and the successful working of this little model led to his receiving an order for an engine from the Philadelphia & Germantown Railroad. Mr. Baldwin, after studying the new engine of the Camden & Amboy road, made his plans, and built an engine (Fig. 64), completing it in the autumn of 1832, and setting it in operation November 23d of that year. It was kept at work on that line of road for a period of 20 years or more. This engine was of Stephenson's "Planet" class, mounted on two driving-wheels 4-1/2 feet in diameter each, and two separate wheels of the same size, uncoupled. The steam-cylinders were 9-1/2 inches in diameter, 18 inches stroke of piston, and were placed horizontally on each side of the smoke-box. The boiler, 2-1/2 feet in diameter, contained 72 copper tubes 1-1/2 inches in diameter and 7 feet long. The engine cost the railroad company $3,500. On the trial, steam was raised in 20 minutes, and the maximum speed noted was 28 miles an hour. The engine subsequently attained a speed of over 30 miles. In 1834, Mr. Baldwin completed for Mr. E. L. Miller, of Charleston, a six-wheeled engine, the "E. L. Miller" (Fig. 65), with cylinders 10 inches in diameter and 16 inches stroke of piston. He made the boiler of this engine of a form which remained standard many years, with a high dome over the fire-box. At about the same time, he built the "Lancaster," an engine resembling the "Miller," for the State road to Columbia, and several others were soon contracted for and built. By the end of 1834, 5 engines had been built by him, and the construction of locomotive-engines had become one of the leading and most promising industries of the United States. Mr. William Norris established a shop in Philadelphia in 1832, which he gradually enlarged until it, like the Baldwin Works, became a large establishment. He usually built a six-wheeled engine, with a leading-truck or bogie, and placed his driving-wheels in front of the fire-box. [Illustration: FIG. 65.--The "E. L. Miller," 1834.] At this time the English locomotives were built to carry 60 pounds of steam. The American builders adopted pressures of 120 to 130 pounds per square inch, the now generally standard pressures throughout the world. In the years 1836 and 1837, Baldwin built 80 engines. They were of three classes: 1st, with cylinders 12-1/2 inches in diameter and of 16 inches stroke, weighing 12 tons; 2d, with cylinders 12 by 16, and a weight of 10-1/2 tons; and 3d, engines weighing 9 tons, and having steam-cylinders of 10-1/2 inches diameter and of the same stroke. The driving-wheels were usually 4-1/2 feet in diameter, and the cylinder "inside-connected" to cranked axles. A few "outside-connected" engines were made, this plan becoming generally adopted at a later period. The railroads of the United States were very soon supplied with locomotive-engines built in America. In the year 1836, William Norris, who had two years before purchased the interest of Colonel Stephen H. Long, an army-officer who patented and built locomotives of his own design, built the "George Washington," and set it at work. This engine, weighing 14,400 pounds, drew 19,200 pounds up an incline 2,800 feet long, rising 369 feet to the mile, at the speed of 15-1/2 miles an hour. This showed an adhesion not far from one-third the weight on the driving-wheels. This was considered a very wonderful performance, and it produced such an impression at the time, that several copies of the "George Washington" were made, on orders from British railroads, and the result was the establishment of the reputation of the locomotive-engine builders of the United States upon a foundation which has never since failed them. The engine had Jervis's forward-truck, now always seen under standard engines, which had already been placed under railroad-cars by Ross Winans. In New England, the Locks & Canals Company, of Lowell, began building engines as early as 1834, copying the Stephenson engine. Hinckley & Drury, of Boston, commenced building an outside-connected engine in 1840, and their successors, the Boston Locomotive Works, became the largest manufacturing establishment of the kind in New England. Two years later, Ross Winans, the Baltimore builder, introduced some of his engines upon Eastern railroads, fitting them with upright boilers, and burning anthracite coal. The changes which have been outlined produced the now typical American locomotive. It was necessarily given such form that it would work safely and efficiently on rough, ill-ballasted, and often sharply-winding tracks; and thus it soon became evident that the two pairs of coupled driving-wheels, carrying two-thirds the weight of the whole engine, the forward-truck, and the system of "equalizing" suspension-bars, by which the weight is distributed fairly among all the wheels, whatever the position of the engine, or whatever the irregularity of the track, made it the very best of all known types of locomotive for the railroads of a new country. Experience has shown it equally excellent on the smoothest and best of roads. The "cow-catcher," placed in front to remove obstacles from the track, the bell, and the heavy whistle, are characteristics of the American engine also. The severity of winter-storms compelled the adoption of the "cab," or house, and the use of wood for fuel led to the invention of the "spark-arrester" for that class of engines. The heavy grades on many roads led to the use of the "sand-box," from which sand was sprinkled on the track, to prevent the slipping of the wheels. In the year 1836, the now standard chilled wheel was introduced for cars and trucks; the single eccentric, which had been, until then, used on Baldwin engines, was displaced by the double eccentric, with hooks in place of the link; and, a year later, the iron frame took the place of the previously-used wooden frame on all engines. The year 1837 introduced a period of great depression in all branches of industry, which continued until the year 1840, or later, and seriously checked all kinds of manufacturing, including the building of locomotives. On the revival of business, numbers of new locomotive-works were started, and in these establishments originated many new types of engine, each of the more successful of which was adapted to some peculiar set of conditions. This variety of type is still seen on nearly all of the principal roads. The direction of change in the construction of locomotive-engines at the period at which this division of the subject terminates is very well indicated in a letter from Robert Stephenson to Robert L. Stevens, dated 1833, which is now preserved at the Stevens Institute of Technology. He writes: "I am sorry that the feeling in the United States in favor of light railways is so general. In England we are making every succeeding railway stronger and more substantial." He adds: "Small engines are losing ground, and large ones are daily demonstrating that powerful engines are the most economical." He gives a sketch of his latest engine, weighing _nine tons_, and capable, as he states, of "taking 100 tons, gross load, at the rate of 16 or 17 miles an hour on a level." To-day there are engines built weighing 70 tons, and our locomotive-builders have standard sizes guaranteed to draw over 2,000 tons on a good and level track. [Illustration] CHAPTER V. _THE MODERN STEAM-ENGINE._ "Voilà la plus merveilleuse de toutes les Machines; le Mécanisme ressemble à celui des animaux. La chaleur est le principe de son mouvement; il se fait dans ses différens tuyaux une circulation, comme celle du sang dans les veines, ayant des valvules qui s'ouvrent et se ferment à propos; elles se nourrit, s'évacue d'elle même dans les temps réglés, et tire de son travail tout ce qu'il lui faut pour subsister. Cette Machine a pris sa naissance en Angleterre, et toutes les Machines à feu qu'on a construites ailleurs que dans la Grande Brétagne ont été exécutées par des Anglais."--BELIDOR. THE SECOND PERIOD OF APPLICATION--1800-1850 (CONTINUED). THE STEAM-ENGINE APPLIED TO SHIP-PROPULSION. Among the most obviously important and most inconceivably fruitful of all the applications of steam which marked the period we are now studying, is that of the steam-engine to the propulsion of vessels. This direction of application has been that which has, from the earliest period in the history of the steam-engine, attracted the attention of the political economist and the historian, as well as the mechanician, whenever a new improvement, or the revival of an old device, has awakened a faint conception of the possibilities attendant upon the introduction of a machine capable of making so great a force available. The realization of the hopes, the prophecies, and the aspirations of earlier times, in the modern marine steam-engine, may be justly regarded as the greatest of all the triumphs of mechanical engineering. Although, as has already been stated, attempts were made at a very early period to effect this application of steam-power, they were not successful, and the steamship is a product of the present century. No such attempts were commercially successful until after the time of Newcomen and Watt, and at the commencement of the nineteenth century. It is, indeed, but a few years since the passage across the Atlantic was frequently made in sailing-vessels, and the dangers, the discomforts, and the irregularities of their trips were most serious. Now, hardly a day passes that does not see several large and powerful steamers leaving the ports of New York and Liverpool to make the same voyages, and their passages are made with such regularity and safety, that travelers can anticipate with confidence the time of their arrival at the termination of their voyage to a day, and can cross with safety and with comparative comfort even amid the storms of winter. Yet all that we to-day see of the extent and the efficiency of steam-navigation has been the work of the present century, and it may well excite our wonder and our admiration. The history of this development of the use of steam-power illustrates most perfectly that process of growth of this invention which has been already referred to; and we can here trace it, step by step, from the earliest and rudest devices up to those most recent and most perfect designs which represent the most successful existing types of the heat-engine--whether considered with reference to its design and construction, or as the highest application of known scientific principles--that have yet been seen in even the present advanced state of the mechanic arts. The paddle-wheel was used as a substitute for oars at a very early date, and a description of paddle-wheels applied to vessels, curiously illustrated by a large wood-cut, may be found in the work of Fammelli, "De l'artificioses machines," published in old French in 1588. Clark[58] quotes from Ogilby's edition of the "Odyssey" a stanza which reads like a prophecy, and almost awakens a belief that the great poet had a knowledge of steam-vessels in those early times--a thousand years before the Christian era. The prince thus addresses Ulysses: [58] "Steam and the Steam-Engine." "We use nor Helm nor Helms-man. Our tall ships Have Souls, and plow with Reason up the deeps; All cities, Countries know, and where they list, Through billows glide, veiled in obscuring Mist; Nor fear they Rocks, nor Dangers on the way." Pope's translation[59] furnishes the following rendering of Homer's prophecy: [59] "Odyssey," Book VIII., p. 175. "So shalt thou instant reach the realm assigned, In wondrous ships, self-moved, instinct with mind; ... Though clouds and darkness veil the encumbered sky, Fearless, through darkness and through clouds they fly. Though tempests rage, though rolls the swelling main, The seas may roll, the tempests swell in vain; E'en the stern god that o'er the waves presides, Safe as they pass and safe repass the tide, With fury burns; while, careless, they convey Promiscuous every guest to every bay." It is stated that the Roman army under Claudius Caudex was taken across to Sicily in boats propelled by paddle-wheels turned by oxen. Vulturius gives pictures of such vessels. This application of the force of steam was very possibly anticipated 600 years ago by Roger Bacon, the learned Franciscan monk, who, in an age of ignorance and intellectual torpor, wrote: "I will now mention some wonderful works of art and nature, in which there is nothing of magic, and which magic could not perform. Instruments may be made by which the largest ships, with only one man guiding them, will be carried with greater velocity than if they were full of sailors," etc., etc. Darwin's poetical prophecy was published long years before Watt's engine rendered its partial fulfillment a possibility; and thus, for many years before even the first promising effort had been made, the minds of the more intelligent had been prepared to appreciate the invention when it should finally be brought forward. The earliest attempt to propel a vessel by steam is claimed by Spanish authorities, as has been stated, to have been made by Blasco de Garay, in the harbor of Barcelona, Spain, in 1543. The record, claimed as having been extracted from the Spanish archives at Simancas, states the vessel to have been of 200 tons burden, and to have been moved by paddle-wheels; and it is added that the spectators saw, although not allowed closely to inspect the apparatus, that one part of it was a "vessel of boiling water"; and it is also stated that objection was made to the use of this part of the machine, because of the danger of explosion. The account seems somewhat apocryphal, and it certainly led to no useful results. In an anonymous English pamphlet, published in 1651, which is supposed by Stuart to have been written by the Marquis of Worcester, an indefinite reference to what may probably have been the steam-engine is made, and it is there stated to be capable of successful application to propelling boats. In 1690, Papin proposed to use his piston-engine to drive paddle-wheels to propel vessels; and in 1707 he applied the steam-engine, which he had proposed as a pumping-engine, to driving a model boat on the Fulda at Cassel. In this trial he used the arrangement of which a sketch has been shown, his pumping-engine forcing up water to turn a water-wheel, which, in turn, was made to drive the paddles. An account of his experiments is to be found in manuscript in the correspondence between Leibnitz and Papin, preserved in the Royal Library at Hanover. Professor Joy found there the following letter:[60] "Dionysius Papin, Councillor and Physician to his Royal Highness the Elector of Cassel, also Professor of Mathematics at Marburg, is about to dispatch a vessel of singular construction down the river Weser to Bremen. As he learns that all ships coming from Cassel, or any point on the Fulda, are not permitted to enter the Weser, but are required to unload at Münden, and as he anticipates some difficulty, although those vessels have a different object, his own not being intended for freight, he begs most humbly that a gracious order be granted that his ship may be allowed to pass unmolested through the Electoral domain; which petition I most humbly support. G. W. LEIBNITZ. "HANOVER, _July 13, 1707_." This letter was returned to Leibnitz, with the following indorsement: "The Electoral Councillors have found serious obstacles in the way of granting the above petition, and, without giving their reasons, have directed me to inform you of their decision, and that, in consequence, the request is not granted by his Electoral Highness. H. REICHE. "HANOVER, _July 25, 1707_." [60] _Scientific American_, February 24, 1877. This failure of Papin's petition was the death-blow to his effort to establish steam-navigation. A mob of boatmen, who thought they saw in the embryo steamship the ruin of their business, attacked the vessel at night, and utterly destroyed it. Papin narrowly escaped with his life, and fled to England. In the year 1736, Jonathan Hulls took out an English patent for the use of a steam-engine for ship-propulsion, proposing to employ his steamboat in towing. In 1737 he published a well-written pamphlet, describing this apparatus, which is shown in Fig. 66, a reduced fac-simile of the plate accompanying his paper. [Illustration: FIG. 66.--Hulls's Steamboat, 1736.] He proposed using the Newcomen engine, fitted with a counterpoise-weight and a system of ropes and grooved wheels, which, by a peculiar ratchet-like action, gave a continuous rotary motion. His vessel was to have been used as a tow-boat. He says, in his description: "In some convenient part of the Tow-boat there is placed a Vessel about two-3rds full of water, with the Top closed; and this Vessel being kept Boiling, rarifies the Water into a Steam, this Steam being convey'd thro' a large pipe into a cylindrical Vessel, and there condensed, makes a Vacuum, which causes the weight of the atmosphere to press down on this Vessel, and so presses down a Piston that is fitted into this Cylindrical Vessel, in the same manner as in Mr. Newcomen's Engine, with which he raises Water by Fire. "_P_, the Pipe coming from the Furnace to the Cylinder. _Q_, the Cylinder wherein the steam is condensed. _R_, the Valve that stops the Steam from coming into the Cylinder, whilst the Steam within the same is condensed. _S_, the Pipe to convey the condensing Water into the Cylinder. _T_, a cock to let in the condensing Water when the Cylinder is full of Steam and the Valve, _P_, is shut. _U_, a Rope fixed to the Piston that slides up and down in the Cylinder. "_Note._ This Rope, _U_, is the same Rope that goes round the wheel, _D_, in the machine." In the large division of his plate, _A_ is the chimney; _B_ is the tow-boat; _C C_ is the frame carrying the engine; _Da_, _D_, and _Db_ are three wheels carrying the ropes _M_, _Fb_, and _Fa_, _M_ being the rope _U_ of his smaller figure, 30. _Ha_ and _Hb_ are two wheels on the paddle-shafts, _I I_, arranged with pawls so that the paddle-wheel, _I I_, always turns the same way, though the wheels _Ha_ and _Hb_ are given a reciprocating motion; _Fb_ is a rope connecting the wheels in the vessel, _Db_, with the wheels at the stern. Hulls says: "When the Weight, _G_, is so raised, while the wheels _Da_, _D_, and _Db_ are moving backward, the Rope _Fa_ gives way, and the Power of the Weight, _G_, brings the Wheel _Ha_ forward, and the Fans with it, so that the Fans always keep going forward, notwithstanding the Wheels _Da_, _D_, and _Db_ move backward and forward as the Piston moves up and down in the Cylinder. _L L_ are Teeth for a Catch to drop in from the Axis, and are so contrived that they catch in an alternate manner, to cause the Fan to move always forward, for the Wheel _Ha_, by the power of the weight, _G_, is performing his Office while the other wheel, _Hb_, goes back in order to fetch another stroke. "_Note._ The weight, _G_, must contain but half the weight of the Pillar of Air pressing on the Piston, because the weight, _G_, is raised at the same time as the Wheel _Hb_ performs its Office, so that it is in effect two Machines acting alternately, by the weight of one Pillar of Air, of such a Diameter as the Diameter of the Cylinder is." The inventor suggests the use of timber guards to protect the wheels from injury, and, in shallow water, the attachment to the paddle-shafts of cranks "to strike a Shaft to the Bottom of the River, which will drive the Vessel forward with the greater Force." He concludes: "Thus I have endeavoured to give a clear and satisfactory Account of my New-invented Machine, for carrying Vessels out of and into any Port, Harbour, or River, against Wind and Tide, or in a Calm; and I doubt not but whoever shall give himself the Trouble to peruse this Essay, will be so candid as to excuse or overlook any Imperfections in the diction or manner of writing, considering the Hand it comes from, if what I have imagined may only appear as plain to others as it has done to me, viz., That the Scheme I now offer is Practicable, and if encouraged will be Useful." There is no positive evidence that Hulls ever put his scheme to the test of experiment, although tradition does say that he made a model, which he tried with such ill success as to prevent his prosecution of the experiment further; and doggerel rhymes are still extant which were sung by his neighbors in derision of his folly, as they considered it. A prize was awarded by the French Academy of Sciences, in 1752, for the best essay on the manner of impelling vessels without wind. It was given to Bernouilli, who, in his paper, proposed a set of vanes like those of a windmill--a screw, in fact--one to be placed on each side of the vessel, and two more behind. For a vessel of 100 tons, he proposed a shaft 14 feet long and 2 inches in diameter, carrying "eight wheels, for acting on the water, to each of which it" (the shaft) "is perpendicular, and forms an axis for them all; the wheels should be at equal distances from each other. Each wheel consists of 8 arms of iron, each 3 feet long, so that the whole diameter of the wheel is 6 feet. Each of these arms, at the distance of 20 inches from the centre, carries a sheet-iron plane (or paddle) 16 inches square, which is inclined so as to form an angle of 60 degrees, both with the arbor and keel of the vessel, to which the arbor is placed parallel. To sustain this arbor and the wheels, two strong bars of iron, between 2 and 3 inches thick, proceed from the side of the vessel at right angles to it, about 2-1/2 feet below the surface of the water." He proposed similar screw-propellers at the stern, and suggested that they could be driven by animal or by steam-power. But a more remarkable essay is quoted by Figuier[61]--the paper of l'Abbé Gauthier, published in the "Mémoires de la Société Royale des Sciences et Lettres de Nancy." Bernouilli had expressed the belief that the best steam-engine then known--that of Newcomen--was not superior to some other motors. Gauthier proposed to use that engine in the propulsion of paddle-wheels placed at the side of the vessel. His plan was not brought into use, but his paper embodied a glowing description of the advantages to be secured by its adoption. He states that a galley urged by 26 oars on a side made but 4,320 toises (8,420 meters), or about 5 miles, an hour, and required a crew of 260 men. A steam-engine, doing the same work, would be ready for action at all times, could be applied, when not driving the vessel, to raising the anchor, working the pumps, and to ventilating the ship, while the fire would also serve to cook with. The engine would occupy less space and weight than the men, would require less aliment, and that of a less expensive kind, etc. He would make the boiler safe against explosions by bands of iron; would make the fire-box of iron, with a water-filled ash-pit and base-plate. His injection-water was to come from the sea, and return by a delivery-pipe placed above the water-line. The chains, usually leading from the end of the beam to the pump-rods, were to be carried around wheels on the paddle-shaft, which were to be provided with pawls entering a ratchet, and thus the paddles, having been given several revolutions by the descent of the piston and the unwinding of the chain, were to revolve freely while the return-stroke was made, the chain being hauled down and rewound by the wheel on the shaft, the latter being moved by a weight. The engine was proposed to be of 6 feet stroke, and to make 15 strokes per minute, with a force of 11,000 pounds. [61] "Les Merveilles de la Science." A little later (1760), a Swiss clergyman, J. A. Genevois, published in London a paper relating to the improvement of navigation,[62] in which his plan was proposed of compressing springs by steam or other power, and applying their effort while recovering their form to ship-propulsion. [62] "Some New Enquiries tending to the Improvement of Navigation." London, 1760. It was at this time that the first attempts were made in the United States to solve this problem, which had begun to be recognized as one of the greatest which had presented itself to the mechanic and the engineer. WILLIAM HENRY was a prominent citizen of the then little village of Lancaster, Pa., and was noted as an ingenious and successful mechanic.[63] He was still living at the beginning of the present century. Mr. Henry was the first to make the "rag" carpet, and was the inventor of the screw-auger. He was of a Scotch and North-of-Ireland family, his father, John Henry, and his two older brothers, Robert and James, having come to the United States about 1720. Robert settled, finally, in Virginia, and it is said that Patrick Henry, the patriot and orator, was of his family. The others remained in Chester County, Pa., where William was born, in 1729. He learned the trade of a gunsmith, and, driven from his home during the Indian war (1755 to 1760), settled in Lancaster. [63] _Lancaster Daily Express_, December 10, 1872. This account is collated from various manuscripts and letters in the possession of the author. In the year 1760 he went to England on business, where his attention was attracted to the invention--then new, and the subject of discussion in every circle--of James Watt. He saw the possibility of its application to navigation and to driving carriages, and, on his return home, commenced the construction of a steam-engine, and finished it in 1763. Placing it in a boat fitted with paddle-wheels, he made a trial of the new machine on the Conestoga River, near Lancaster, where the craft, by some accident, sank,[64] and was lost. He was not discouraged by this failure, but made a second model, adding some improvements. Among the records of the Pennsylvania Philosophical Society is, or was, a design, presented by Henry in 1782, of one of his steamboats. The German traveler Schöpff visited the United States in 1783, and at Mr. Henry's house, at Lancaster, was shown "a machine by Mr. Henry, intended for the propelling of boats, etc.; 'but,' said Mr. Henry, 'I am doubtful whether such a machine would find favor with the public, as every one considers it impracticable against wind and tide;' but that such a Boat _will_ come into use and navigate on the waters of the Ohio and Mississippi, he had not the least doubt of, but the time had not yet arrived of its being appreciated and applied." [64] Bowen's "Sketches," p. 56. John Fitch, whose experiments will presently be referred to, was an acquaintance and frequent visitor to the house of Mr. Henry, and may probably have there received the earliest suggestions of the importance of this application of steam. About 1777, when Henry was engaged in making mathematical and philosophical instruments, and the screw-auger, which at that time could only be obtained of him, Robert Fulton, then twelve years old, visited him, to study the paintings of Benjamin West, who had long been a friend and protégé of Henry. He, too, not improbably received there the first suggestion which afterward led him to desert the art to which he at first devoted himself, and which made of the young portrait-painter a successful inventor and engineer. West's acquaintance with Henry had no such result. The young painter was led by his patron and friend to attempt historical pictures,[65] and probably owes his fame greatly to the kindly and discerning mechanic. Says Galt, in his "Memoirs of Sir Benjamin West" (London, 1816): "Towards his old friend, William Henry, of Lancaster City, he always cherished the most grateful affection; he was the first who urged him to attempt historical composition." [65] Some of West's portraits, including those of Mr. and Mrs. Henry, were lately in the possession of Mr. John Jordan, of Philadelphia. When, after the invention of Watt, the steam-engine had taken such shape that it could really work the propelling apparatus of a paddle or screw vessel, a new impetus was given to the work of its adaptation. In France, the Marquis de Jouffroy was one of the earliest to perceive that the improvements of Watt, rendering the engine more compact, more powerful, and, at the same time, more regular and positive in its action, had made it, at last, readily applicable to the propulsion of vessels. The brothers Périer had imported a Watt engine from Soho, and this was attentively studied by the marquis,[66] and its application to the paddle-wheels of a steam-vessel seemed to him a simple problem. Comte d'Auxiron and Chevalier Charles Mounin, of Follenai, friends and companions of Jouffroy, were similarly interested, and the three are said to have often discussed the scheme together, and to have united in devising methods of applying the new motor. [66] Figuier. In the year 1770, D'Auxiron determined to attempt the realization of the plans which he had conceived. He resigned his position in the army, prepared his plans and drawings, and presented them to M. Bertin, the Prime Minister, in the year 1771 or 1772. The Minister was favorably impressed, and the King (May 22, 1772) granted D'Auxiron a monopoly of the use of steam in river-navigation for 15 years, provided he should prove his plans practicable, and they should be so adjudged by the Academy. A company had been formed, the day previous, consisting of D'Auxiron, Jouffroy, Comte de Dijon, the Marquis d'Yonne, and Follenai, which advanced the requisite funds. The first vessel was commenced in December, 1772. When nearly completed, in September, 1774, the boat sprung a leak, and, one night, foundered at the wharf. After some angry discussion, during which D'Auxiron was rudely, and probably unjustly, accused of bad faith, the company declined to advance the money needed to recover and complete the vessel. They were, however, compelled by the court to furnish it; but, meantime, D'Auxiron died of apoplexy, the matter dropped, and the company dissolved. The cost of the experiment had been something more than 15,000 francs. The heirs of D'Auxiron turned the papers of the deceased inventor over to Jouffroy, and the King transferred to him the monopoly held by the former. Follenai retained all his interest in the project, and the two friends soon enlisted a powerful adherent and patron, the Marquis Ducrest, a well-known soldier, courtier, and member of the Academy, who took an active part in the prosecution of the scheme. M. Jacques Périer, the then distinguished mechanic, was consulted, and prepared plans, which were adopted in place of those of Jouffroy. The boat was built by Périer, and a trial took place in 1774, on the Seine. The result was unsatisfactory. The little craft could hardly stem the sluggish current of the river, and the failure caused the immediate abandonment of the scheme by Périer. Still undiscouraged, Jouffroy retired to his country home, at Baume-les-Dames, on the river Doubs. There he carried on his experiments, getting his work done as best he could, with the rude tools and insufficient apparatus of a village blacksmith. A Watt engine and a chain carrying "duck-foot" paddles were his propelling apparatus. The boat, which was about 14 feet long and 6 wide, was started in June, 1776. The duck's-foot system of paddles proved unsatisfactory, and Jouffroy gave it up, and renewed his experiments with a new arrangement. He placed on the paddle-wheel shaft a ratchet-wheel, and on the piston-rod of his engine, which was placed horizontally in the boat, a double rack, into the upper and the lower parts of which the ratchet-wheel geared. Thus the wheels turned in the same direction, whichever way the piston was moving. The new engine was built at Lyons in 1780, by Messrs. Frères-Jean. The new boat was about 140 feet long and 14 feet wide; the wheels were 14 feet in diameter, their floats 6 feet long, and the "dip," or depth to which they reached, was about 2 feet. The boat drew 3 feet of water, and had a total weight of about 150 tons. At a public trial of the vessel at Lyons, July 15, 1783, the little steamer was so successful as to justify the publication of the fact by a report and a proclamation. The fact that the experiment was not made at Paris was made an excuse on the part of the Academy for withholding its indorsement, and on the part of the Government for declining to confirm to Jouffroy the guaranteed monopoly. Impoverished and discouraged, Jouffroy gave up all hope of prosecuting his plans successfully, and reëntered the army. Thus France lost an honor which was already within her grasp, as she had already lost that of the introduction of the steam-engine, in the time of Papin. About 1785, John Fitch and James Rumsey were engaged in experiments having in view the application of steam to navigation. Rumsey's experiments began in 1774, and in 1786 he succeeded in driving a boat at the rate of four miles an hour against the current of the Potomac at Shepherdstown, W. Va., in presence of General Washington. His method of propulsion has often been reinvented since, and its adoption urged with that enthusiasm and persistence which is a peculiar characteristic of inventors. Rumsey employed his engine to drive a great pump which forced a stream of water aft, thus propelling the boat forward, as proposed earlier by Bernouilli. This same method has been recently tried again by the British Admiralty, in a gunboat of moderate size, using a centrifugal pump to set in motion the propelling stream, and with some other modifications which are decided improvements upon Rumsey's rude arrangements, but which have not done much more than his toward the introduction of "Hydraulic or Jet Propulsion," as it is now called. In 1787 he obtained a patent from the State of Virginia for steam-navigation. He wrote a treatise "On the Application of Steam," which was printed at Philadelphia, where a Rumsey society was organized for the encouragement of attempts at steam-navigation. Rumsey died of apoplexy, while explaining some of his schemes before a London society a short time later, December 23, 1793, at the age of fifty years. A boat, then in process of construction from his plans, was afterward tried on the Thames, in 1793, and steamed at the rate of four miles an hour. The State of Kentucky, in 1839, presented his son with a gold medal, commemorative of his father's services "in giving to the world the benefit of the steamboat." JOHN FITCH was an unfortunate and eccentric, but very ingenious, Connecticut mechanic. After roaming about until forty years of age, he finally settled on the banks of the Delaware, where he built his first steamboat. In April, 1785, as Fitch himself states, at Neshamony, Bucks County, Pa., he suddenly conceived the idea that a carriage might be driven by steam. After considering the subject a few days, his attention was led to the plan of using steam to propel vessels, and from that time to the day of his death he was a persistent advocate of the introduction of the steamboat. At this time, Fitch says, "I did not know that there was a steam-engine on the earth;" and he was somewhat disappointed when his friend, the Rev. Mr. Irwin, of Neshamony, showed him a sketch of one in "Martin's Philosophy." Fitch's first model was at once built, and was soon after tried on a small stream near Davisville. The machinery was made of brass, and the boat was impelled by paddle-wheels. A rough model of his steamboat was shown to Dr. John Ewing, Provost of the University of Pennsylvania, who, August 20, 1785, addressed a commendatory letter to an ex-Member of Congress, William C. Houston, asking him to assist Fitch in securing the aid of the General Government. The latter referred the inventor, by a letter of recommendation, to a delegate from New Jersey, Mr. Lambert Cadwalader. With this, and other letters, Fitch proceeded to New York, where Congress then met, and made his application in proper form. He was unsuccessful, and equally so in attempting to secure aid from the Spanish minister, who desired that the profits should be secured, by a monopoly of the invention, to the King of Spain. Fitch declined further negotiation, determined that, if successful at all, the benefit should accrue to his own countrymen. In September, 1785, Fitch presented to the American Philosophical Society, at Philadelphia, a model in which he had substituted an endless chain and floats for the paddle-wheels, with drawings and a descriptive account of his scheme. This model is shown in the accompanying figure. [Illustration: FIG. 67.--Fitch's Model, 1785.] In March, 1786, Fitch was granted a patent by the State of New Jersey, for the exclusive right to the navigation of the waters of the State by steam, for 14 years. A month later, he was in Philadelphia, seeking a similar patent from the State of Pennsylvania. He did not at once succeed, but in a few days he had formed a company, raised $300, and set about finding a place in which to construct his engine. Henry Voight, a Dutch watchmaker, a good mechanic, and a very ingenious man, took an interest in the company, and with him Fitch set about his work with great enthusiasm. After making a little model, having a steam-cylinder but one inch in diameter, they built a model boat and engine, the latter having a diameter of cylinder of three inches. They tried the endless chain, and other methods of propulsion, without success, and finally succeeded with a set of oars worked by the engine. In August, 1786, it was determined by the company to authorize the construction of a larger vessel; but the money was not readily obtained. Meantime, Fitch continued his efforts to secure a patent from the State, and was finally, March 28, 1787, successful. He also obtained a similar grant from the State of Delaware, in February of the same year, and from New York, March 19. Money was now subscribed more freely, and the work on the boat continued uninterruptedly until May, 1787, when a trial was made, which revealed many defects in the machinery. The cylinder-heads were of wood, and leaked badly; the piston leaked; the condenser was imperfect; the valves were not tight. All these defects were remedied, and a condenser invented by Voight--the "pipe-condenser"--was substituted for that defective detail as previously made. The steamboat was finally placed in working order, and was found capable, on trial, of making three or four miles an hour. But now the boiler proved to be too small to furnish steam steadily in sufficient quantity to sustain the higher speed. After some delay, and much distress on the part of the sanguine inventor, who feared that he might be at last defeated when on the very verge of success, the necessary changes were finally made, and a trial took place at Philadelphia, in presence of the members of the Convention--then in session at Philadelphia framing the Federal Constitution--August 22, 1787. Many of the distinguished spectators gave letters to Fitch certifying his success. Fitch now went to Virginia, where he succeeded in obtaining a patent, November 7, 1787, and then returned to ask a patent of the General Government. A controversy with Rumsey now followed, in which Fitch asserted his claims to the invention of the steamboat, and denied that Rumsey had done more than to revive the scheme which Bernouilli, Franklin, Henry, Paine, and others, had previously proposed, and that Rumsey's _steamboat_ was not made until 1786. The boiler adopted in Fitch's boat of 1787 was a "pipe-boiler," which he had described in a communication to the Philosophical Society, in September, 1785. It consisted (Fig. 68) of a small water-pipe, winding backward and forward in the furnace, and terminating at one end at the point at which the feed-water was introduced, and at the other uniting with the steam-pipe leading to the engine. Voight's condenser was similarly constructed. Rumsey claimed that this boiler was copied from his designs. Fitch brought evidence to prove that Rumsey had not built such a boiler until after his own. [Illustration: FIG. 68.--Fitch and Voight's Boiler, 1787.] [Illustration: FIG. 69.--Fitch's First Boat, 1787.] Fitch's first boat-engine had a steam-cylinder 12 inches in diameter. A second engine was now built (1788) with a cylinder 18 inches in diameter, and a new boat. The first vessel was 45 feet long and 12 feet wide; the new boat was 60 feet long and of but 8 feet breadth of beam. The first boat (Fig. 69) had paddles worked at the sides, with the motion given the Indian paddle in propelling a canoe; in the second boat (Fig. 70) they were similarly worked, but were placed at the stern. There were three of these paddles. The boat was finally finished in July, 1788, and made a trip to Burlington, 20 miles from Philadelphia. When just reaching their destination, their boiler gave out, and they made their return-trip to Philadelphia floating with the tide. Subsequently, the boat made a number of excursions on the Delaware River, making three or four miles an hour. [Illustration: FIG. 70.--John Fitch, 1788.] Another of Fitch's boats, in April, 1790, made seven miles an hour. Fitch, writing of this boat, says that "on the 16th of April we got our work completed, and tried our boat again; and, although the wind blew very fresh at the east, we reigned lord high admirals of the Delaware, and no boat on the river could hold way with us." In June of that year it was placed as a passenger-boat on a line from Philadelphia to Burlington, Bristol, Bordentown, and Trenton, occasionally leaving that route to take excursions to Wilmington and Chester. During this period, the boat probably ran between 2,000 and 3,000 miles,[67] and with no serious accident. During the winter of 1790-'91, Fitch commenced another steamboat, the "Perseverance," and gave considerable time to the prosecution of his claim for a patent from the United States. The boat was never completed, although he received his patent, after a long and spirited contest with other claimants, on the 26th of August, 1791, and Fitch lost all hope of success. He went to France in 1793, hoping to obtain the privilege of building steam-vessels there, but was again disappointed, and worked his passage home in the following year. [67] "Life of John Fitch," Westcott. [Illustration: FIG. 71.--John Fitch, 1796.] In the year 1796, Fitch was again in New York City, experimenting with a little _screw_ steamboat on the "Collect" Pond, which then covered that part of the city now occupied by the "Tombs," the city prison. This little boat was a ship's yawl fitted with a screw, like that adopted later by Woodcroft, and driven by a rudely-made engine. Fitch, while in the city of Philadelphia at about this time, met Oliver Evans, and discussed with him the probable future of steam-navigation, and proposed to form a company in the West, to promote the introduction of steam on the great rivers of that part of the country. He settled at last in Kentucky, on his land-grant, and there amused himself with a model steamboat, which he placed in a small stream near Bardstown. His death occurred there in July, 1798, and his body still lies in the village cemetery, with only a rough stone to mark the spot. Both Rumsey and Fitch endeavored to introduce their methods in Great Britain; and Fitch, while urging the importance and the advantages of his plan, confidently stated his belief that the ocean would soon be crossed by steam-vessels, and that the navigation of the Mississippi would also become exclusively a steam-navigation. His reiterated assertion, "The day will come when some more powerful man will get fame and riches from my invention; but no one will believe that poor John Fitch can do anything worthy of attention," now almost sounds like a prophecy. During this period, an interest which had never diminished in Great Britain had led to the introduction of experimental steamboats in that country. PATRICK MILLER, of Dalswinton, had commenced experimenting, in 1786-'87, with boats having double or triple hulls, and propelled by paddle-wheels placed between the parts of the compound vessel. James Taylor, a young man who had been engaged as tutor for Mr. Miller's sons, suggested, in 1787, the substitution of steam for the manual power which had been, up to that time, relied upon in their propulsion. Mr. Miller, in 1787, printed a description of his plan of propelling apparatus, and in it stated that he had "reason to believe that the power of the Steam-Engine may be applied to work the wheels." In the winter of 1787-'88, William Symmington, who had planned a new form of steam-engine, and made a successful working-model, was employed by Mr. Miller to construct an engine for a new boat. This was built; the little engine, having two cylinders of but four inches in diameter, was placed on board, and a trial was made October 14, 1788. The vessel (Fig. 72) was 25 feet long, of 7 feet beam, and made 5 miles an hour. [Illustration: FIG. 72.--Miller, Taylor, and Symmington, 1788.] In the year 1789, a large vessel was built, with an engine having a steam-cylinder 18 inches in diameter, and this vessel was ready for trial in November of that year. On the first trial, the paddle-wheels proved too slight, and broke down; they were replaced by stronger wheels, and, in December, the boat, on trial, made seven miles an hour. Miller, like many other inventors, seems to have lost his interest in the matter as soon as success seemed assured, and dropped it to take up other incomplete plans. More than a quarter of a century later, the British Government gave Taylor a pension of £50 per annum, and, in 1837, his four daughters were each given a similar annuity. Mr. Miller received no reward, although he is said to have expended over £30,000. The engine of Symmington was condemned by Miller as "the most improper of all steam-engines for giving motion to a vessel." Nothing more was done in Great Britain until early in the succeeding century. In the United States, several mechanics were now at work besides Fitch. Samuel Morey and Nathan Read were among these. Nicholas Roosevelt was another. It had just been found that American mechanics were able to do the required shop-work. The first experimental steam-engine built in America is stated to have been made in 1773 by Christopher Colles, a lecturer before the American Philosophical Society at Philadelphia. The first steam-cylinder of any considerable size is said[68] to have been made by Sharpe & Curtenius, of New York City. [68] _Rivington's Gazette_, February 16, 1775. SAMUEL MOREY was the son of one of the first settlers of Orford, N. H. He was naturally fond of science and mechanics, and became something of an inventor. He began experimenting with the steamboat in 1790 or earlier, building a small vessel, and fitting it with paddle-wheels driven by a steam-engine of his own design, and constructed by himself.[69] He made a trial-trip one Sunday morning in the summer of 1790, a friend to accompany him, from Oxford, up the Connecticut River, to Fairlee, Vt., a distance of several miles, and returned safely. He then went to New York, and spent the summer of each year until 1793 in experimenting with his boat and modifications of his engine. In 1793 he made a trip to Hartford, returning to New York the next summer. His boat was a "stern-wheeler," and is stated to have been capable of steaming five miles an hour. He next went to Bordentown, N. J., where he built a larger boat, which is said to have been a side-wheel boat, and to have worked satisfactorily. His funds finally gave out, and he gave up his project after having, in 1797, made a trip to Philadelphia. Fulton, Livingston, and Stevens met Morey at New York, inspected his boat, and made an excursion to Greenwich with him.[70] Livingston is said[71] to have offered to assist Morey if he should succeed in attaining a speed of eight miles an hour. [69] _Providence Journal_, May 7, 1874. Coll., N. H. Antiquar. Soc., No. 1; "Who invented the Steamboat?" William A. Mowry, 1874. [70] Rev. Cyrus Mann, in the _Boston Recorder_, 1858. [71] Westcott. Morey's experiments seem to have been conducted very quietly, however, and almost nothing is known of them. The author has not been able to learn any particulars of the engines used by him, and nothing definite is known of the dimensions of either boat or machinery. Morey never, like Fitch and Rumsey, sought publicity for his plans or notoriety for himself. NATHAN READ, who has already been mentioned, a native of Warren, Mass., where he was born in the year 1759, and a graduate of Harvard College, was a student of medicine, and subsequently a manufacturer of chain-cables and other iron-work for ships. He invented, and in 1798 patented, a nail-making machine. He was at one time (1800-1803) a Member of Congress, and, later, a Justice of the Court of Common Pleas, and Chief Justice in Hancock County, Me., after his removal to that State in 1807. He died in Belfast, Me., in 1849, at the age of ninety years. In the year 1788 he became interested in the problem of steam-navigation, and learned something of the work of Fitch. He first attempted to design a boiler that should be strong, light, and compact, as well as safe. His first plan was that of the "Portable Furnace-Boiler," as he called it; it was patented August 26, 1791. As designed, it consisted, as seen in Figs. 73 and 74, which are reduced from his patent drawings, of a shell of cylindrical form, like the now common vertical tubular boiler. _A_ is the furnace-door, _B_ a heater and feed-water reservoir, _D_ a pipe leading the feed-water into the boiler,[72] _E_ the smoke-pipe, and _F_ the steam-pipe leading to the engine. _G_ is the "shell" of the boiler, and _H_ the fire-box. The crown-sheet, _I I_, has depending from it, in the furnace, a set of water-tubes, _b b_, closed at their lower ends, and another set, _a a_, which connect the water-space above the furnace with the water-bottom, _K K_. _L_ is the furnace, and _M_ the draught-space between the boiler and the ash-pit, in which the grates are set. [72] This is substantially an arrangement that has recently become common. It has been repatented by later inventors. [Illustration: FIG. 73.--Read's Boiler in Section, 1788.] [Illustration: FIG. 74.--Read's Multi-Tubular Boiler, 1788.] This boiler was intended to be used in both steamboats and steam-carriages. The first drawings were made in 1788 or 1789, as were those of a peculiar form of steam-engine which also resembled very closely that afterward constructed in Great Britain by Trevithick.[73] He built a boat in 1789, which he fitted with paddle-wheels and a crank, which was turned by hand, and, by trial, satisfied himself that the system would work satisfactorily. [73] "Nathan Read and the Steam-Engine." He then applied for his patent, and spent the greater part of the winter of 1789-'90 in New York, where Congress then met, endeavoring to secure it. In January, 1791, Read withdrew his petitions for patents, proposing to incorporate accounts of new devices, and renewed them a few months later. His patents were finally issued, dated August 26, 1791. John Fitch, James Rumsey, and John Stevens, also, all received patents at the same date, for various methods of applying steam to the propulsion of vessels. Read appears to have never succeeded in even experimentally making his plans successful. He deserves credit for his early and intelligent perception of the importance of the subject, and for the ingenuity of his devices. As the inventor of the vertical multi-tubular fire-box boiler, he has also entitled himself to great distinction. This boiler is now in very general use, and is a standard form. In 1792, Elijah Ormsbee, a Rhode Island mechanic, assisted pecuniarily by David Wilkinson, built a small steamboat at Winsor's Cove, Narragansett Bay, and made a successful trial-trip on the Seekonk River. Ormsbee used an "atmospheric engine" and "duck's-foot" paddles. His boat attained a speed of from three to four miles an hour. In Great Britain, Lord Dundas and William Symmington, the former as the purveyor of funds and the latter as engineer, followed by Henry Bell, were the first to make the introduction of the steam-engine for the propulsion of ships so completely successful that no interruption subsequently took place in the growth of the new system of water-transportation. Thomas, Lord Dundas, of Kerse, had taken great interest in the experiments of Miller, and had hoped to be able to apply the new motor on the Forth and Clyde Canal, in which he held a large interest. After the failure of the earlier experiments, he did not forget the matter; but subsequently, meeting with Symmington, who had been Miller's constructing engineer, he engaged him to continue the experiments, and furnished all required capital, about £7,000. This was ten years after Miller had abandoned his scheme. Symmington commenced work in 1801. The first boat built for Lord Dundas, which has been claimed to have been the "first practical steamboat," was finished ready for trial early in 1802. The vessel was called the "Charlotte Dundas," in honor of a daughter of Lord Dundas, who became Lady Milton. [Illustration: FIG. 75.--The "Charlotte Dundas," 1801.] The vessel (Fig. 75) was driven by a Watt double-acting engine, turning a crank on the paddle-wheel shaft. The sectional sketch below exhibits the arrangement of the machinery. _A_ is the steam-cylinder, driving, by means of the connecting-rod, _B C_, a stern-wheel, _E E_. _F_ is the boiler, and _G_ the tall smoke-pipe. An air-pump and condenser, _H_, is seen under the steam-cylinder. In March, 1802, the boat was brought to Lock No. 20 on the Forth and Clyde Canal, and two vessels of 70 tons burden each taken in tow. Lord Dundas, William Symmington, and a party of invited guests, were taken on board, and the boat steamed down to Port Glasgow, a distance of about 20 miles, against a strong head-wind, in six hours. The proprietors of the canal were now urged to adopt the new plan of towing; but, fearing injury to the banks of the canal, they declined to do so. Lord Dundas then laid the matter before the Duke of Bridgewater, who gave Symmington an order for eight boats like the Charlotte Dundas, to be used on his canal. The death of the Duke, however, prevented the contract from being carried into effect, and Symmington again gave up the project in despair. A quarter of a century later, Symmington received from the British Government £100, and, a little later, £50 additional, as an acknowledgment of his services. The Charlotte Dundas was laid up, and we hear nothing more of that vessel. [Illustration: FIG. 76.--The "Comet," 1812.] Among those who saw the Charlotte Dundas, and who appreciated the importance of the success achieved by Symmington, was HENRY BELL, who, 10 years afterward, constructed the Comet (Fig. 76), the first passenger-vessel built in Europe. This vessel was built in 1811, and completed January 18, 1812. The craft was of 30 tons burden, 40 feet in length, and 10-1/2 feet breadth of beam. There were _two_ paddle-wheels on each side, driven by engines rated at three horse-power. Bell had, it is said, been an enthusiastic believer in the advantages to be secured by this application of steam, from about 1786. In 1800, and again in 1803, he applied to the British Admiralty for aid in securing those advantages by experimentally determining the proper form and proportions of machinery and vessel; but was not able to convince the Admiralty of "the practicability and great utility of applying steam to the propelling of vessels against winds and tides, and every obstruction on rivers and seas where there was depth of water." He also wrote to the United States Government, urging his views in a similar strain. Bell's boat was, when finished, advertised as a passenger-boat, to leave Greenock, where the vessel was built, on Mondays, Wednesdays, and Fridays, for Glasgow, 24 miles distant, returning Tuesdays, Thursdays, and Saturdays. The fare was made "four shillings for the best cabin, and three shillings for the second." It was some months before the vessel became considered a trustworthy means of conveyance. Bell, on the whole, was at first a heavy loser by his venture, although his boat proved itself a safe, stanch vessel. Bell constructed several other boats in 1815, and with his success steam-navigation in Great Britain was fairly inaugurated. In 1814 there were five steamers, all Scotch, regularly working in British waters; in 1820 there were 34, one-half of which were in England, 14 in Scotland, and the remainder in Ireland. Twenty years later, at the close of the period to which this chapter is especially devoted, there were about 1,325 steam-vessels in that kingdom, of which 1,000 were English and 250 Scotch. But we must return to America, to witness the first and most complete success, commercially, in the introduction of the steamboat. The Messrs. Stevens, Livingston, Fulton, and Roosevelt were there the most successful pioneers. The latter is said to have built the "Polacca," a small steamboat launched on the Passaic River in 1798. The vessel was 60 feet long, and had an engine of 20 inches diameter of cylinder and 2 feet stroke, which drove the boat 8 miles an hour, carrying a party of invited guests, which included the Spanish Minister. Livingston and John Stevens had induced Roosevelt to try their plans still earlier,[74] paying the expense of the experiments. The former adopted the plan of Bernouilli and Rumsey, using a centrifugal pump to force a jet of water from the stern; the latter used the screw. Livingston going to France as United States Minister, Barlow carried over the plans of the "Polacca," and Roosevelt's friends state that a boat built by them, in conjunction with Fulton, was a "sister-ship" to that vessel. In 1798, Roosevelt patented a double engine, having cranks set at right angles. As late as 1814 he received a patent for a steam-vessel, fitted with paddle-wheels having adjustable floats. His boat of 1798 is stated by some writers to have been made by him on joint account of himself, Livingston, and Stevens. Roosevelt, some years later, was again at work, associating himself with Fulton in the introduction of steam-navigation of the rivers of the West.[75] [74] "Encyclopædia Americana." [75] "A Lost Chapter in the History of the Steamboat," J. H. B. Latrobe, 1871. In 1798, the Legislature of New York passed a law giving Chancellor Livingston the exclusive right to steam-navigation in the waters of the State for a period of 20 years, _provided_ that he should succeed, within a twelve-month, in producing a boat that should steam four miles an hour. Livingston did not succeed in complying with the terms of the act, but, in 1803, he procured the reënactment of the law in favor of himself and Robert Fulton, who was then experimenting in France, after having, in England, watched the progress of steam-navigation there, and then taken a patent in this country. [Illustration: Robert Fulton.] ROBERT FULTON was a native of Little Britain, Lancaster County, Pa., born 1765. He commenced experimenting with paddle-wheels when a mere boy, in 1779, visiting an aunt living on the bank of the Conestoga.[76] During his youth he spent much of his time in the workshops of his neighborhood, and learned the trade of a watchmaker; but he adopted, finally, the profession of an artist, and exhibited great skill in portrait-painting. While his tastes were at this time taking a decided bent, he is said to have visited frequently the house of William Henry, already mentioned, to see the paintings of Benjamin West, who in his youth had been a kind of protégé of Mr. Henry; and he may probably have seen there the model steamboats which Mr. Henry exhibited, in 1783 or 1784, to the German traveler Schöpff. In later years, Thomas Paine, the author of "Common Sense," at one time lived with Mr. Henry, and afterward, in 1788, proposed that Congress take up the subject for the benefit of the country. [76] _Vide_ "Life of Fulton," Reigart. Fulton went to England when he came of age, and studied painting with Benjamin West. He afterward spent two years in Devonshire, where he met the Duke of Bridgewater, who afterward so promptly took advantage of the success of the "Charlotte Dundas." While in England and in France--where he went in 1797, and resided some time--he may have seen something of the attempts which were beginning to be made to introduce steam-navigation in both of those countries. At about this time--perhaps in 1793--Fulton gave up painting as a profession, and became a civil engineer. In 1797 he went to Paris, and commenced experimenting with submarine torpedoes and torpedo-boats. In 1801 he had succeeded so well with them as to create much anxiety in the minds of the English, then at war with France. He had, as early as 1793, proposed plans for steam-vessels, both to the United States and the British Governments, and seems never entirely to have lost sight of the subject.[77] While in France he lived with Joel Barlow, who subsequently became known as a poet, and as Embassador to France from the United States, but who was then engaged in business in Paris. [77] _Vide_ "Life of Fulton," Colden. When about leaving the country, Fulton met Robert Livingston (Chancellor Livingston, as he is often called), who was then (1801) Embassador of the United States at the court of France. Together they discussed the project of applying steam to navigation, and determined to attempt the construction of a steamboat on the Seine; and in the early spring of the year 1802, Fulton having attended Mrs. Barlow to Plombières, where she had been sent by her physician, he there made drawings and models, which were sent or described to Livingston. In the following winter Fulton completed a model side-wheel boat. [Illustration: FIG. 77.--Fulton's Experiments.] January 24, 1803, he delivered this model to MM. Molar, Bordel, and Montgolfier, with a descriptive memoir, in which he stated that he had, by experiment, proven that side-wheels were better than the "chaplet" (paddle-floats set on an endless chain).[78] These gentlemen were then building for Fulton and Livingston their first boat, on L'Isle des Cygnes, in the Seine. In planning this boat, Fulton had devised many different methods of applying steam to its propulsion, and had made some experiments to determine the resistance of fluids. He therefore had been able to calculate, more accurately than had any earlier inventor, the relative size and proportions of boat and machinery. [78] A French inventor, a watchmaker of Trévoux, named Desblancs, had already deposited at the Conservatoire a model fitted with "chaplets." [Illustration: FIG. 78.--Fulton's Table of Resistances.] The author has examined a large collection of Fulton's drawings, among which are sketches, very neatly executed, of many of these plans, including the chaplet, side-wheel, and stern-wheel boats, driven by various forms of steam-engine, some working direct, and some geared to the paddle-wheel shaft. Figs. 77 and 78 are engraved from two of these sheets. The first represents the method adopted by Fulton to determine the resistance of masses of wood of various forms and proportions, when towed through water. The other is "A Table of the resistance of bodies moved through water, taken from experiments made in England by a society for improving Naval architecture, between the years 1793 and 1798" (Fig. 78). This latter is from a certified copy of "The Original Drawing on file in the Office of the Clerk of the New York District, making a part of the Demonstration of the patent granted to Robert Fulton, Esqr., on the 11th day of February, 1809. Dated this 3rd March, 1814," and is signed by Theron Rudd, Clerk of the New York District. Resistances are given in pounds per square foot. Guided by these experiments and calculations, therefore, Fulton directed the construction of his vessel. It was completed in the spring of 1803. But, unfortunately, the hull of the little vessel was too weak for its heavy machinery, and it broke in two and sank to the bottom of the Seine. Undiscouraged, Fulton at once set about repairing damages. He was compelled to direct the rebuilding of the hull. The machinery was little injured. In June, 1803, the reconstruction was completed, and the vessel was set afloat in July. The hull was 66 feet long, of 8 feet beam, and of light draught. August 9, 1803, this boat was cast loose, and steamed up the Seine, in presence of an immense concourse of spectators. A committee of the National Academy, consisting of Bougainville, Bossuet, Carnot, and Périer, were present to witness the experiment. The boat moved but slowly, making only between 3 and 4 miles an hour against the current, the speed through the water being about 4-1/2 miles; but this was, all things considered, a great success. The experiment was successful, but it attracted little attention, notwithstanding the fact that its success had been witnessed by the committee of the Academy and by many well-known savants and mechanics, and by officers on Napoleon's staff. The boat remained a long time on the Seine, near the palace. The water-tube boiler of this vessel (Fig. 79) is still preserved at the Conservatoire des Arts et Métiers at Paris, where it is known as Barlow's boiler. Barlow patented it in France as early as 1793, as a steamboat-boiler, and states that the object of his construction was to obtain the greatest possible extent of heating-surface. Fulton endeavored to secure the pecuniary aid and the countenance of the First Consul, but in vain. Livingston wrote home, describing the trial of this steamboat and its results, and procured the passage of an act by the Legislature of the State of New York, extending a monopoly granted him in 1798 for the term of 20 years from April 5, 1803, the date of the new law, and extending the time allowed for proving the practicability of driving a boat four miles an hour by steam to two years from the same date. A later act further extended the time to April, 1807. [Illustration: FIG. 79.--Barlow's Water-Tube Boiler, 1793.] In May, 1804, Fulton went to England, giving up all hope of success in France with either his steamboats or his torpedoes. Fulton had already written to Boulton & Watt, ordering an engine to be built from plans which he furnished them; but he had not informed them of the purpose to which it was to be applied. This engine was to have a steam-cylinder 2 feet in diameter and of 4 feet stroke. The engine of the Charlotte Dundas was of very nearly the same size; and this fact, and the visit of Fulton to Symmington in 1801, as described by the latter, have been made the basis of a claim that Fulton was a copyist of the plans of others. The general accordance of the dimensions of his boat on the Seine with those of the "Polacca" of Roosevelt is also made the basis of similar claims by the friends of the latter. It would appear, however, that Symmington's statement is incorrect, as Fulton was in France, experimenting with torpedoes, at the time (July, 1801[79]) when he is accused of having obtained from the English engineer the dimensions and a statement of the performance of his vessel. Yet a fireman employed by Symmington has made an affidavit to the same statement. It is evident, however, from what has preceded, that those inventors and builders who were at that time working with the object of introducing the steamboat were usually well acquainted with what had been done by others, and with what was being done by their contemporaries; and it is undoubtedly the fact that each profited, so far as he was able, by the experience of others. [79] Woodcroft, p. 64. While in England, however, Fulton was certainly not so entirely absorbed in the torpedo experiments with which he was occupied in the years 1804-'6 as to forget his plans for a steamboat; and he saw the engine ordered by him in 1804 completed in the latter year, and preceded it to New York, sailing from Falmouth in October, 1806, and reaching the United States December 13, 1806. The engine was soon received, and Fulton immediately contracted for a hull in which to set it up. Meantime, Livingston had also returned to the United States, and the two enthusiasts worked together on a larger steamer than any which had yet been constructed. In the spring of 1807, the "Clermont" (Fig. 80), as the new boat was christened, was launched from the ship-yard of Charles Brown, on the East River, New York. In August the machinery was on board and in successful operation. The hull of this boat was 133 feet long, 18 wide, and 9 deep. The boat soon made a trip to Albany, running the distance of 150 miles in 32 hours running time, and returning in 30 hours. The sails were not used on either occasion. [Illustration: FIG. 80.--The Clermont, 1807.] This was the first voyage of considerable length ever made by a steam-vessel; and Fulton, though not to be classed with James Watt as an inventor, is entitled to the great honor of having been the first to make steam-navigation an every-day commercial success, and of having thus made the first application of the steam-engine to ship-propulsion, which was not followed by the retirement of the experimenter from the field of his labors before success was permanently insured. [Illustration: FIG. 81.--Engine of the Clermont, 1808.] The engine of the Clermont (Fig. 81) was of rather peculiar form, the piston, _E_, being coupled to the crank-shaft, _O_, by a bell-crank, _I H P_, and a connecting-rod, _P Q_, the paddle-wheel shaft, _M N_, being separate from the crank-shaft, and connected with the latter by gearing, _O O_. The cylinders were 24 inches in diameter by 4 feet stroke. The paddle-wheels had buckets 4 feet long, with a dip of 2 feet. Old drawings, made by Fulton's own hand, and showing the engine as it was in 1808, and the engine of a later steamer, the Chancellor Livingston, are in the lecture-room of the author at the Stevens Institute of Technology. The voyage of the Clermont to Albany was attended by some ludicrous incidents, which found their counterparts wherever, subsequently, steamers were for the first time introduced. Mr. Colden, the biographer of Fulton, says that she was described, by persons who had seen her passing by night, "as a monster moving on the waters, defying wind and tide, and breathing flames and smoke." This first steamboat used dry pine wood for fuel, and the flames rose to a considerable distance above the smoke-pipe. When the fires were disturbed, mingled smoke and sparks would rise high in the air. "This uncommon light," says Colden, "first attracted the attention of the crews of other vessels. Notwithstanding the wind and tide were averse to its approach, they saw with astonishment that it was rapidly coming toward them; and when it came so near that the noise of the machinery and paddles was heard, the crews (if what was said in the newspapers of the time be true), in some instances, shrank beneath their decks from the terrific sight, and left their vessels to go on shore; while others prostrated themselves, and besought Providence to protect them from the approach of the horrible monster which was marching on the tides, and lighting its path by the fires which it vomited." In the Clermont, Fulton used several of the now characteristic features of the American river steamboat, and subsequently introduced others. His most important and creditable work, aside from that of the introduction of the steamboat into every-day use, was the experimental determination of the magnitude and the laws of ship-resistance, and the systematic proportioning of vessel and machinery to the work to be done by them. The success of the Clermont on the trial-trip was such that Fulton soon after advertised the vessel as a regular passenger-boat between New York and Albany.[80] [80] A newspaper-slip in the scrap-book of the author has the following: "The traveler of today, as he goes on board the great steamboats St. John or Drew, can scarcely imagine the difference between such floating palaces and the wee-bit punts on which our fathers were wafted 60 years ago. We may, however, get some idea of the sort of thing then in use by a perusal of the steamboat announcements of that time, two of which are as follows: ["_Copy of an Advertisement taken from the Albany Gazette, dated September, 1807._] "The North River Steamboat will leave Pauler's Hook Ferry [now Jersey City] on Friday, the 4th of September, at 9 in the morning, and arrive at Albany on Saturday, at 9 in the afternoon. Provisions, good berths, and accommodations are provided. "The charge to each passenger is as follows: "To Newburg dols. 3, time 14 hours. " Poughkeepsie " 4, " 17 " " Esopus " 5, " 20 " " Hudson " 5-1/2, " 30 " " Albany " 7, " 36 " "For places, apply to William Vandervoort, No. 48 Courtlandt Street, on the corner of Greenwich Street. "_September 2, 1807._ ["_Extract from the New York Evening Post, dated October 2, 1807._] "Mr. Fulton's new-invented _Steamboat_, which is fitted up in a neat style for passengers, and is intended to run from New York to Albany as a Packet, left here this morning with 90 passengers, against a strong head-wind. Notwithstanding which, it was judged she moved through the waters at the rate of six miles an hour." During the next winter the Clermont was repaired and enlarged, and in the summer of 1808 was again on the route to Albany; and, meantime, two new steamboats--the Raritan and the Car of Neptune--had been built by Fulton. In the year 1811 he built the Paragon. Both of the two vessels last named were of nearly double the size of the Clermont. A steam ferry-boat was built to ply between New York and Jersey City in 1812, and the next year two others, to connect the metropolis with Brooklyn. These were "twin-boats," the two parallel hulls being connected by a "bridge" or deck common to both. The Jersey ferry was crossed in fifteen minutes, the distance being a mile and a half. To-day, the time occupied at the same ferry is about ten minutes. Fulton's ferry-boat carried, at one load, 8 carriages, and about 30 horses, and still had room for 300 or 400 foot-passengers. Fulton also designed steam-vessels for use on the Western rivers, and, in 1815, some of his boats were started as "packets" on the line between New York and Providence, R. I. Meantime, the War of 1812 was in progress, and Fulton designed a steam vessel-of-war, which was then considered a wonderfully formidable craft. His plans were submitted to a commission of experienced naval officers, among whom were Commodores Decatur and Perry, Captain John Paul Jones, Captain Evans, and others whose names are still familiar, and were favorably commended. Fulton proposed to build a steam-vessel capable of carrying a heavy battery, and of steaming four miles an hour. The ship was to be fitted with furnaces for red-hot shot. Some of her guns were to be discharged below the water-line. The estimated cost was $320,000. The construction of the vessel was authorized by Congress in March, 1814; the keel was laid June 20, 1814, and the vessel was launched October 29th of the same year. [Illustration: FIG. 82.--Launch of the "Fulton the First," 1804.] The "Fulton the First," as she was called, was considered an enormous vessel at that time. The hull was double, 156 feet long, 56 feet wide, and 20 feet deep, measuring 2,475 tons. In the following May the ship was ready for her engine, and in July was so far completed as to steam, on a trial-trip, to the ocean at Sandy Hook and back--53 miles--in 8 hours and 20 minutes. In September of the same year, with armament and stores on board, the same route was traversed again, the vessel making 5-1/2 miles an hour. The vessel, as thus completed, had a double hull, each about 20 feet longer than the Clermont, and separated by a space 15 feet across. Her engine, having a steam-cylinder 48 inches in diameter and of 5 feet stroke of piston, was furnished with steam by a copper boiler 22 feet long, 12 feet wide, and 8 feet high, and turned a wheel between the two hulls which was 16 feet in diameter, and carried "floats" or "buckets" 14 feet long, and with a dip of 4 feet. The engine was in one of the two hulls, and the boiler in the other. The sides, at the gun-deck, were 4 feet 10 inches thick, and her spar-deck was surrounded by heavy musket-proof bulwarks. The armament consisted of 30 32-pounders, which were intended to discharge red-hot shot. There was one heavy mast for each hull, fitted with large latteen sails. Each end of each hull was fitted with a rudder. Large pumps were carried, which were intended to throw heavy streams of water upon the decks of the enemy, with a view to disabling the foe by wetting his ordnance and ammunition. A submarine gun was to have been carried at each bow, to discharge shot weighing 100 pounds, at a depth of 10 feet below the water-line. This was the first application of the steam-engine to naval purposes, and, for the time, it was an exceedingly creditable one. Fulton, however, did not live to see the ship completed. He was engaged in a contest with Livingston, who was then endeavoring to obtain permission from the State of New Jersey to operate a line of steamboats in the waters of the Hudson River and New York Bay, and, while returning from attending a session of the Legislature at Trenton, in January, 1815, was exposed to the weather on the bay at a time when he was ill prepared to withstand it. He was taken ill, and died February 24th of that year. His death was mourned as a national calamity. From the above brief sketch of this distinguished man and his work, it is seen that, although Robert Fulton is not entitled to distinction as an inventor, he was one of the ablest, most persistent, and most successful of those who have done so much for the world by the introduction of the inventions of others. He was an intelligent engineer and an enterprising business-man, whose skill, acuteness, and energy have given the world the fruits of the inventive genius of all who preceded him, and have thus justly earned for him a fame that can never be lost. Fulton had some active and enterprising rivals. Oliver Evans had, in 1801 or 1802, sent one of his engines, of about 150 horse-power, to New Orleans, for the purpose of using it to propel a vessel owned by Messrs. McKeever and Valcourt, which was there awaiting it. The engine was actually set up in the boat, but at a low stage of the river, and no trial could be made until the river should again rise, some months later. Having no funds to carry them through so long a period, Evans's agents were induced to remove the engine again, and to set it up in a saw-mill, where it created great astonishment by its extraordinary performance in sawing lumber. Livingston and Roosevelt were also engaged in experiments quite as early as Fulton, and perhaps earlier. The prize gained by Fulton was, however, most closely contested by Colonel JOHN STEVENS, of Hoboken, who has been already mentioned in connection with the early history of railroads, and who had been since 1791 engaged in similar experiments. In 1789 he had petitioned the Legislature of the State of New York for a grant similar to that accorded to Livingston, and he then stated that his plans were complete, and on paper. [Illustration: FIG. 83.--Section of Steam-Boiler, 1804.] In 1804, while Fulton was in Europe, Stevens had completed a steamboat, 68 feet long and of 14 feet beam, which combined novelties and merits of design in a manner that exhibited the best possible evidence of remarkable inventive talent, as well as of the most perfect appreciation of the nature of the problem which he had proposed to himself to solve. Its boiler (Fig. 83) was of what is now known as the water-tubular variety. It was quite similar to some now known as sectional boilers, and contained 100 tubes 2 inches in diameter and 18 inches long, each fastened at one end to a central water-leg and steam-drum, and plugged at the other end. The flames from the furnace passed around and among the tubes, the water being inside them. The engine (Fig. 84) was a _direct-acting high-pressure_ condensing engine, having a 10-inch cylinder, 2 feet stroke of piston, and drove a _screw_ having four blades, and of a form which, even to-day, appears quite good. The whole is a most remarkable piece of early engineering. [Illustration: FIG. 84.--Engine, Boiler, and Screw-Propellers used by Stevens, 1804.] A model of this little steamer, built in 1804, is preserved in the lecture-room of the Department of Mechanical Engineering at the Stevens Institute of Technology; and the machinery itself, consisting of the high-pressure "sectional" or "safety" tubular boiler, as it would be called to-day, the high-pressure condensing engine, with rotating valves, and twin screw-propellers, as just described, is given a place of honor in the model-room, or museum, where it contrasts singularly with the mechanism contributed to the collection by manufacturers and inventors of our own time. The hub and blade of a single screw, also used with the same machinery, is likewise to be seen there. [Illustration: FIG. 85.--Stevens's Screw Steamer, 1804.] Stevens seems to have been the first to fully recognize the importance of the principle involved in the construction of the sectional steam-boiler. His eldest son, John Cox Stevens, was in Great Britain in the year 1805, and, while there, patented another modification of this type of boiler. In his specification, he details both the method of construction and the principles which determine its form. He says that he describes this invention as it was made known to him by his father, and adds: "From a series of experiments made in France, in 1790, by M. Belamour, under the auspices of the Royal Academy of Sciences, it has been found that, within a certain range the elasticity of steam is nearly doubled by every addition of temperature equal to 30° of Fahrenheit's thermometer. These experiments were carried no higher than 280°, at which temperature the elasticity of steam was found equal to about four times the pressure of the atmosphere. By experiments which have lately been made by myself, the elasticity of steam at the temperature of boiling oil, which has been estimated at about 600°, was found to equal 40 times the pressure of the atmosphere. "To the discovery of this principle or law, which obtains when water assumes a state of vapor, I certainly can lay no claim; but to the application of it, upon certain principles, to the improvement of the steam-engine, I do claim exclusive right. "It is obvious that, to derive advantage from an application of this principle, it is absolutely necessary that the vessel or vessels for generating steam should have strength sufficient to withstand the great pressure from an increase of elasticity in the steam; but this pressure is increased or diminished in proportion to the capacity of the containing vessel. The principle, then, of this invention consists in forming a boiler by means of a system, or combination of a number of small vessels, instead of using, as in the usual mode, one large one; the relative strength of the materials of which these vessels are composed increasing in proportion to the diminution of capacity. It will readily occur that there are an infinite variety of possible modes of effecting such combinations; but, from the nature of the case, there are certain limits beyond which it becomes impracticable to carry on improvement. In the boiler I am about to describe, I apprehend that the improvement is carried to the utmost extent of which the principle is capable. Suppose a plate of brass of one foot square, in which a number of holes are perforated; into each of which holes is fixed one end of a copper tube, of about an inch in diameter and two feet long; and the other ends of these tubes inserted in like manner into a similar piece of brass; the tubes, to insure their tightness, to be cast in the plates; these plates are to be inclosed at each end of the pipes by a strong cap of cast-iron or brass, so as to leave a space of an inch or two between the plates or ends of the pipes and the cast-iron cap at each end; the caps at each end are to be fastened by screw-bolts passing through them into the plates; the necessary supply of water is to be injected by means of a forcing-pump into the cap at one end, and through a tube inserted into the cap at the other end the steam is to be conveyed to the cylinder of the steam-engine; the whole is then to be encircled in brickwork or masonry in the usual manner, placed either horizontally or perpendicularly, at option. "I conceive that the boiler above described embraces the most eligible mode of applying the principle before mentioned, and that it is unnecessary to give descriptions of the variations in form and construction that may be adopted, especially as these forms may be diversified in many different modes." Boilers of the character of those described in the specification given above were used on the locomotive built by John Stevens in 1824-'25, and one of them remains in the collections of the Stevens Institute of Technology. The use of such a boiler 70 years ago is even more remarkable than the adoption of the screw-propeller, in such excellent proportions, 30 years before the labors of Smith and of Ericsson brought the screw into general use; and we have, in this strikingly original combination, as good evidence of the existence of unusual engineering talent in this great engineer as we found of his political and statesmanlike ability in his efforts to forward the introduction of railways. Colonel John Stevens designed a peculiar form of iron-clad in the year 1812, which has been since reproduced by no less distinguished and successful an engineer than the late John Elder, of Glasgow, Scotland. It consisted of a saucer-shaped hull, carrying a heavy battery, and plated with iron of ample thickness to resist the shot fired from the heaviest ordnance then known. This vessel was secured to a swivel, and was anchored in the channel to be defended. A set of screw-propellers, driven by steam-engines, and situated beneath the vessel, where they were safe against injury by shot, were so arranged as to permit the vessel to be rapidly revolved about its centre. As each gun was brought into line of fire, it was discharged, and was then reloaded before coming around again. This was probably the earliest embodiment of the now well-established "Monitor" principle. It was probably the first iron-clad ever designed. It has recently been again brought out and introduced into the Russian navy, and is there called the "Popoffka." The first of Stevens's boats performed so well, that he immediately built another one, using the same engine as before, but employing a larger boiler, and propelling the vessel by _twin screws_, the latter being another instance of his use of a device brought forward long afterward as new, and frequently adopted. This boat was sufficiently successful to prove the practicability of making steam-navigation a commercial success; and Stevens, assisted by his sons, built a boat which he named the "Ph[oe]nix," and made the first trial in 1807, but just too late to anticipate Fulton. This boat was driven by paddle-wheels. [Illustration: FIG. 86.--Stevens's Twin-Screw Steamer, 1805.] The Ph[oe]nix, being shut out of the waters of the State of New York by the monopoly held by Fulton and Livingston, was used for a time between New York and New Brunswick, and then, anticipating a better pecuniary return, it was concluded to send her to Philadelphia, to ply on the Delaware. At that time no canal offered the opportunity to make an inland passage; and in June, 1808, Robert L. Stevens, a son of John, started with her to make the passage by sea. Although meeting a gale of wind, he arrived at Philadelphia safely, having been the first to trust himself on the open sea in a vessel relying entirely upon steam-power. From this time forward the Stevenses, father and sons, continued to construct steam-vessels; and, after the breaking down of the Fulton monopoly by the courts, they built the most successful steamboats that ran on the Hudson River. After Fulton and Stevens had thus led the way, steam-navigation was introduced very rapidly on both sides of the ocean; and on the Mississippi the number of boats set afloat was soon large enough to fulfill Evans's prediction that the navigation of that river would ultimately be effected by steam-vessels. The changes and improvements which, during the 20 years succeeding the time of Fulton and of John Stevens, gradually led to the adoption of the now recognized type of "American river-boat" and its steam-engine, were principally made by that son of the senior Stevens, who has already been mentioned--ROBERT L. STEVENS--and who became known later as the designer and builder of the first well-planned iron-clad ever constructed, the Stevens Battery. Much of his best work was done during his father's lifetime. [Illustration: Robert L. Stevens.] He made many extended and most valuable, as well as interesting, experiments on ship-propulsion, expending much time and large sums of money upon them; and many years before they became generally understood, he had arrived at a knowledge not only of the laws governing the variation of resistance at excessive speeds, but he had determined, and had introduced into his practice, those forms of least resistance and those graceful water-lines which have only recently distinguished the practice of other successful naval architects. Referring to his invaluable services, President King, who seems to have been the first to thoroughly appreciate the immense amount of original invention and the surprising excellence of the engineering of this family, in a lecture delivered in New York in 1851, gave, for the first time, a connected and probably accurate description of their work, upon which nearly all later accounts have been based. Young Stevens began working in his father's machine-shop in 1804 or 1805, when a mere boy, and thus acquired at a very early age that familiarity with practical details of work and of business which is essential to perfect success. It was he who introduced the now common "hollow water-line" in the Ph[oe]nix, and thus anticipated the claims of the builders of the once famous "Baltimore clippers," and of the inventors of the "wave-line" form of vessels. In the same vessel he adopted a feathering paddle-wheel and the guard-beam now universally seen in our river steamboats. As usually constructed, this arrangement of float is as shown in Fig. 87. The rods, _F F_, connect the eccentrically-set collar, _G_, carried on _H_, a pin mounted on the paddle-beam outside the wheel, or an eccentric secured to the vessel, with the short arms, _D D_, by which the paddles are turned upon the pins, _E E_. _A_ is the centre of the paddle-wheel, and _C C_ are arms. Circular hoops, or bands, connect all of the arms, each of which carries a float. They are all thus tied together, forming a very firm and powerful combination to resist external forces. [Illustration: FIG. 87.--The Feathering Paddle-Wheel.] The steamboat Philadelphia was built in the year 1813, and the young naval architect took advantage of the opportunity to introduce several new devices, including screw-bolts in place of tree-nails, and diagonal knees of wood and of iron. Two years later he altered the engines of this boat, and arranged them to work steam expansively. A little later he commenced using anthracite coal, which had been discovered in 1791 by Philip Ginter, and introduced at Wilkesbarre, Pa., in the smith-shops, some years before the Revolution. It had been used in a peculiar grate devised by Judge Fell, of that town, in 1808. Oliver Evans also had used it in stoves even earlier than the latter date, and at about the same time it had been used in the blast-furnace[81] at Kingston. Stevens was the first of whom we have record who was thoroughly successful in using, as a steam-coal, the new and almost unmanageable fuel. He fitted up the boiler of the steamboat Passaic for it in 1818, and adopted anthracite as a steaming-coal. He used it in a cupola-furnace in the same year, and its use then rapidly became general in the Eastern States. [81] Bishop. Stevens continued his work of improving the beam-engine for many years. He designed the now universally-used "skeleton-beam," which is one of the characteristic features of the American engine, and placed the first example of this light and elegant, yet strong, construction on the steamer Hoboken in the year 1822. He built the Trenton, which was then considered an extraordinarily powerful, fast, and handsome vessel, two years afterward, and placed the two boilers on the guards--a custom which is still general on the river steamboats of the Eastern States. In this vessel he also adopted the plan of making the paddle-wheel floats in two parts, placing one above the other, and securing the upper half on the forward and the lower half on the after side of the arm, thus obtaining a smoother action of the wheel, and less loss by oblique pressures. In 1827 he built the North America (Fig. 88), one of his largest and most successful steamers, a vessel fitted with a pair of engines each 44-1/2 inches in diameter of cylinder and 8 feet stroke of piston, making 24 revolutions per minute, driving the boat 15 to 16 miles an hour. Anticipating difficulty in keeping the long, light, shallow vessel in shape when irregularly laden, and when steaming at the high speed expected to be obtained when her powerful engine was exerting its maximum effort, he adopted the expedient of stiffening the hull by means of a truss of simple form. This proved thoroughly satisfactory, and the "hog-frame," as it has since been inelegantly but universally called, is still one of the peculiar features of every American river-steamer of any considerable size. It was in the North America, also, that he first introduced the artificial blast for forcing the fires, which is still another detail of now usual practice. [Illustration: FIG. 88.--The North America and Albany, 1827-'30.] Stevens next turned his attention to the engine again, and adopted spring bearings under the paddle-shaft of the New Philadelphia in 1828, and fitted the steam-cylinder with the "double-poppet" valve, which is now universally used on beam-engines. This consists of two disk-valves, connected by the valve-spindle. The disks are of unequal sizes, the smaller passing through the seat of the larger. When seated, the pressure of the steam is, in the steam-valve, taken on the upper side of the larger and the lower side of the smaller disk, thus producing a partial balancing of the valve, and rendering it easy to work the heaviest engine by the hand-gear. The two valve-seats are formed in the top and the bottom, respectively, of the steam-passage leading to the cylinder; and when the valve is raised, the steam enters at the top and the bottom at the same time, and the two currents, uniting, flow together into the steam-cylinder. The same form of valve is used as an exhaust-valve. At about the same time he built the now standard form of return tubular boilers for moderate pressures. In the figure, _S_ is the steam and _W_ the water space, and _F_ the furnace. The direction of the currents of smoke and gas are shown by the arrows. [Illustration: FIG. 89.--Stevens's Return Tubular Boiler, 1832.] Some years later (1840), Stevens commenced using steam-packed pistons on the Trenton, in which steam was admitted by self-adjusting valves behind the metallic packing-rings, setting them out more effectively than did the steel springs then (and still) usually employed. His pistons, thus fitted, worked well for many years. A set of the small brass check-valves used in a piston of this kind, built by Stevens, and preserved in the cabinets of the Stevens Institute of Technology, are good evidence of the ingenuity and excellent workmanship which distinguished the machinery constructed under the direction of this great engineer. [Illustration: FIG. 90.--Stevens's Valve-Motion.] The now familiar "Stevens cut-off," a peculiar device for securing the expansion of steam in the steam-cylinder, was the invention (1841) of Robert L. Stevens and a nephew, who inherited the same constructive talent which distinguished the first of these great men--Mr. Francis B. Stevens. In this form of valve-gear, the steam and exhaust valves are independently worked by separate eccentrics, the latter being set in the usual manner, opening and closing the exhaust-passages just before the crank passes its centre. The steam-eccentric is so placed that the steam-valve is opened as usual, but closed when but about one-half the stroke has been made. This result is accomplished by giving the eccentric a greater throw than is required by the motion of the valve, and permitting it to move through a portion of its path without moving the valve. Thus, in Fig. 90, if _A B_ be the direction of motion of the eccentric-rod, the valve would ordinarily open the steam-port when the eccentric assumes the position _O C_, closing when the eccentric has passed around to _O D_. With the Stevens valve-gear, the valve is opened when the eccentric reaches _O E_, and closes when it arrives at _O F_. The steam-valve of the opposite end of the cylinder is open while the eccentric is moving from _O M_ to _O K_. Between _K_ and _E_, and between _F_ and _M_, both valves are seated. _H B_ is proportional to the lift of the valve, and _O H_ to the motion of the valve-gear when out of contact with the valve-lifters. While the crank is moving through an arc, _E F_, steam is entering the cylinder; from _F_ to _M_ the steam is expanding. At _M_ the stroke is completed, and the other steam-valve opens. The ratio (E M)/(E L) is the ratio of expansion. This form of cut-off motion is still a very usual one, and can be seen in nearly all steamers in the United States not using the device of Sickles. It was at about this time, also, that Stevens, having succeeded his father in the business of introducing the steam-engine in land-transportation, as well as on the water, adopted the use of steam expansively on the locomotives of the Camden & Amboy Railroad, which was controlled and built by capital furnished principally by the Messrs. Stevens. He at the same time constructed eight-wheeled engines for heavy work, and adopted anthracite coal as fuel. In the latter change he was thoroughly successful, and the same improvement was made with engines built for fast traffic in 1848. The most remarkable of all the applications of steam-power proposed by Robert L. Stevens was that known as the Stevens Steam Iron-Clad Battery. As has already been stated, Colonel John Stevens had proposed, as early as 1812, to build a circular or saucer-shaped iron-clad, like those built 60 years later for the Russian Navy. Nothing was done, however, although the son revived the idea in a modified form 20 years afterward. In the years 1813-'14, the war with England being then in progress, he invented, after numerous and hazardous experiments, an _elongated shell_, to be fired from ordinary smooth-bored cannon. Having perfected this invention, he sold the secret to the United States, after making experiments to prove their destructiveness so decisive as to leave no doubt of the efficacy of such projectiles. As early as 1837 he had perfected a plan of an iron-clad war-vessel, and in August, 1841, his brothers, James C. and Edwin A. Stevens, representing Robert L., addressed a letter to the Secretary of the Navy, proposing to build an iron-clad vessel of high speed, with all its machinery below the water-line, and having submerged screw-propellers. The armament was to consist of the most powerful rifled guns, loading at the breech, and provided with elongated shot and shell. In the year 1842, having contracted to build for the United States Government a large war-steamer on this plan, which should be shot and shell proof, Robert L. Stevens built a steamboat at Bordentown, for the sole purpose of experimenting on the forms and curves of propeller-blades, as compared with side-wheels, and continued his experiments for many months. After some delay, during which Mr. Stevens and his brothers were engaged with their experiments and in perfecting their plans, the keel of an iron-clad was laid down in a dry-dock which had been constructed for the purpose at great cost. This vessel was to have been 250 feet long, of 40 feet beam, and 28 feet deep. The machinery was designed to furnish 700 indicated horse-power. The plating was proposed to be 4-1/2 inches thick--the same thickness of armor as was adopted 10 years later by the French for their comparatively rude constructions. In 1854, such marked progress had been made in the construction of ordnance that Mr. Stevens was no longer willing to proceed with the original plans, fearing that, were the ship completed, it might prove not invulnerable, and might throw some discredit upon its designer, as well as upon the navy of which it was to form a part. The work, which had, in those years of peace, progressed very slowly and intermittently, was therefore stopped entirely, the vessel given up, and in 1854 the keel of a ship of vastly greater size and power was laid down. The new design was 415 feet long, of 45 feet beam, and of something over 5,000 tons displacement. The thickness of armor proposed was 6-3/4 inches--2-1/4 inches thicker than that of the first French and British iron-clads--and the machinery was designed by Mr. Stevens to be of 8,624 indicated horse-power, driving twin-screws, and propelling the vessel 20 miles or more an hour. As with the preceding design, the progress of construction was intermittent and very slow. Government advanced funds, and then refused to continue the work; successive administrations alternately encouraged and discouraged the engineer; and he finally, cutting loose entirely from all official connections, went on with the work at his own expense. The remarkable genius of the elder Stevens was well reflected in the character of his son, and is in no way better exemplified than by the accuracy with which, in this great ship, those forms and proportions, both of hull and machinery, were adopted which are now, twenty-five years later, recognized as most correct under similar conditions. The lines of the vessel are beautifully fair and fine, and are what J. Scott Russell has called "wave-lines," or trochoidal lines, such as Rankine has shown to be the best possible for easy propulsion. The proportion of length to midship dimensions is such as to secure the speed proposed with a minimum resistance, and to accord closely with the proportions arrived at and adopted by common consent in present transoceanic navigation by the best--not to say radical--builders. The death of Robert L. Stevens occurred in April, 1856, when this larger vessel had advanced so far toward completion that the hull and machinery were practically finished, and it only remained to add the armor-plating, and to decide upon the form of fighting-house and upon the number and size of guns. The construction of the vessel, which had proceeded slowly and intermittently during the years of peace, as successive administrations had considered it necessary to continue the payment of appropriations, or had stopped temporarily in the absence of any apparent immediate necessity for continuance of the work, was again interrupted by his death. The name of Robert L. Stevens will be long remembered as that of one of the greatest of American mechanics, the most intelligent of naval architects, and as the first, and one of the greatest, of those to whom we are indebted for the commencement of the mightiest of revolutions in the methods and implements of modern naval warfare. American mechanical genius and engineering skill have rarely been too promptly recognized, and no excuse will be required for an attempt (which it is hoped may yet be made) to place such splendid work as that of the Messrs. Stevens in a light which shall reveal both its variety and extent and its immense importance. While Fulton was introducing the steamboat upon the waters of New York Bay and the Hudson River, and while the Stevenses, father and sons, were rapidly bringing out a fleet of steamers on the Delaware River and Bay, other mechanics were preparing to contest the field with them as opportunity offered, and as legislative acts authorizing monopoly expired by limitation or were repealed. About 1821, Robert L. Thurston, John Babcock, and Captain Stephen T. Northam, of Newport, R. I., commenced building steamboats, beginning with a small craft intended for use at Slade's Ferry, on an arm of Narragansett Bay, near Fall River. They afterward built vessels to ply on Long Island Sound. One of their earliest boats was the Babcock, built at Newport in 1826. The engine was built by Thurston and Babcock, at Portsmouth, R. I. They were assisted in their work by Richard Sanford, and with funds by Northam. The engine was of 10 or 12 inches diameter of cylinder, and 3 or 4 feet stroke of piston. The boiler was a form of "pipe-boiler," subsequently (1824) patented by Babcock. The water used was injected into the hot boiler as fast as required to furnish steam, no water being retained in the steam-generator. This boat was succeeded, in 1827-'28, by a larger vessel, the Rushlight, for which the engine was built by James P. Allaire, at New York, while the boat was built at Newport. The boilers of both vessels had tubes of cast-iron. The smaller of these boats was of 80 tons burden; it steamed from Newport to Providence, 30 miles, in 3-1/2 hours, and to New York, a distance of 175 miles, in 25 hours, using 1-3/4 cord of wood.[82] Thurston and Babcock subsequently removed to Providence, where the latter soon died. Thurston continued to build steam-engines at this place until nearly a half-century later, dying in 1874.[83] The establishment founded by him, after various changes, became the Providence Steam-Engine Works. [82] _American Journal of Science_, March, 1827; _London Mechanics' Magazine_, June 16, 1827. [83] "New Universal Cyclopædia," vol. iv., 1878. James P. Allaire, of New York, the West Point Iron Foundery, at West Point, on the Hudson River, and Daniel Copeland and his son, Charles W. Copeland, on the Connecticut River, were also early builders of engines for steam-vessels. Daniel Copeland was probably the first (1850) to adopt a slide-valve working with a lap to secure the expansion of steam. His steamboats were then usually stern-wheel vessels, and were built to ply on several routes on the Connecticut River and Long Island Sound. The son, Charles W. Copeland, went to West Point, and while there designed some heavy marine steam-machinery, and subsequently designed several steam vessels-of-war for the United States Navy. He was the earliest designer of iron steamers in the United States, building the Siamese in 1838. This steamer was intended for use on Lake Pontchartrain and the canal to New Orleans. It had two hulls, was 110 feet long, and drew but 22 inches of water, loaded. The two horizontal non-condensing engines turned a single paddle-wheel placed between the two hulls, driving the boat 10 miles an hour. The hull was constructed of plates of iron 10 feet long, formed on blocks after having been heated in a furnace constructed especially for the purpose. The frames were of T-iron, which was probably here used for the first time. The same engineer, associated with Samuel Hart, a well-known naval constructor, built, in 1841, for the United States Navy, the iron steamer Michigan, a war-vessel intended for service on the great northern lakes. This vessel is still in service, and in good order. The hull is 162-1/2 feet in length, 27 feet in breadth, and 12-1/2 feet in depth, measuring 500 tons. The frames were made of T-iron, stiffened by reverse bars of L-iron. The keel-plate was 5/8 inch thick, the bottom plates 3/8, and the sides 3/16 inch. The deck-beams were of iron, and the vessel, as a whole, was a good specimen of iron-ship building. During the period from 1830 to 1840, a considerable number of the now standard details of steam-engine and steamboat construction were devised or introduced by Copeland. He was probably the first to use (on the Fulton, 1840) an independent engine to drive the blowing-fans where an artificial draught was required. He made a practice of fitting his steamers with a "bilge-injection," by means of which the vessel could be freed of water, through the condenser and air-pump, when leaking seriously; the condensing-water is, in such a case, taken from inside the vessel, instead of from the sea. This is probably an American device. It was in use in the United States previously to 1835, as was the use of anthracite coal on steamers, which was continued by Copeland in manufacturing and in air-furnaces, as well as on steamboats. He also modified the form of Stevens's double-poppet valve, giving it such shape that it was comparatively easy to grind it tight and to keep it in order. In 1825, James P. Allaire, of New York, built compound engines for the Henry Eckford, and subsequently constructed similar engines for several other steamers, one of which, the Sun, made the trip from New York to Albany in 12 hours 18 minutes. He used steam at 100 pounds pressure. Erastus W. Smith afterward introduced this form of engine on the Great Lakes, and still later they were introduced into British steamers. The machinery of the steamer Buckeye State was constructed at the Allaire Works, New York, in 1850, from the designs of John Baird and Erastus W. Smith, the latter being the designing and constructing engineer. The steamer was placed on the route between Buffalo, Cleveland, and Detroit, in 1851, and gave most satisfactory results, consuming less than two-thirds the fuel required by a similar vessel of the same line fitted with the single-cylinder engine. The steam-cylinders of this engine were placed one within the other, the low-pressure exterior cylinder being annular. They were 37 and 80 inches in diameter respectively, and the stroke was 11 feet. Both pistons were connected to one cross-head, and the general arrangement of the engine was similar to that of the common form of beam-engine. The steam-pressure was from 70 to 75 pounds--about the maximum pressure adopted a quarter of a century later on transatlantic lines. This steamer was of high speed, as well as economical of fuel. In the year 1830, there were 86 steamers on the Hudson River and in Long Island Sound. During the early part of the nineteenth century, the introduction of the steamboat upon the waters of the great rivers of the interior of the United States was one of the most notable details of its history. Inaugurated by the unsuccessful experiment of Evans, the building of steamboats on those waters, once commenced, never ceased; and a generation after Fitch's burial on the shore of the Ohio, his last wish--that he might lie "where the song of the boatman would enliven the stillness of his resting-place, and the music of the steam-engine soothe his spirit"--was fulfilled day by day unceasingly. Nicholas J. Roosevelt was, as has been already stated, the first to take a steamboat down the great rivers. His boat was built at Pittsburgh in 1811, under an arrangement with Fulton and Livingston, from Fulton's plans. It was called the "New Orleans," was of about 200 tons burden, and was propelled by a stern-wheel, assisted, when the winds were favorable, by sails carried on two masts. The hull was 138 feet long, 30 feet beam, and the cost of the whole, including engines, was about $40,000. The builder, with his family, an engineer, a pilot, and six "deck-hands," left Pittsburgh in October, 1811, reaching Louisville in 70 hours (steaming about 10 miles an hour), and New Orleans in 14 days, steaming from Natchez. The next steamers built on Western waters were probably the Comet and the Vesuvius, both of which were in service some time. The Comet was finally laid aside, and the engine used to drive a mill, and the Vesuvius was destroyed by the explosion of her boilers. As early as 1813 there were two shops at Pittsburgh building steam-engines. Steamboat-building now became an important and lucrative business in the West; and it is stated that as early as 1840 there were a thousand steamers on the Mississippi and its tributaries. In the Washington, built at Wheeling, Va., in 1816, under the direction of Captain Henry M. Shreve, the boilers, which had previously been placed in the hold, were carried on the main-deck, and a "hurricane-deck" was built over them. Shreve substituted two horizontal direct-acting engines for the single upright engine used by Fulton, drove them by high-pressure steam without condensation, and attached them, one on each side the boat, to cranks placed at right angles. He adopted a cam cut-off expanding the steam considerably, and the flue-boiler of Evans. At that time the voyage from New Orleans to Louisville occupied three weeks, and Shreve was made the subject of many witticisms when he predicted that the time would ultimately be shortened to ten days. It is now made in four days. The Washington was seized at New Orleans, in 1817, by order of Livingston, who claimed that his rights included the monopoly of the navigation of the Mississippi and its tributaries. The courts decided adversely on this claim, and the release of the Washington was the act which removed every obstacle to the introduction of steam-navigation throughout the United States. The first steamer on the Great Lakes was the Ontario, built in 1816, at Sackett's Harbor. Fifteen years later, Western steamboats had taken the peculiar form which has since usually distinguished them. The use of the steam-engine for ocean-navigation kept pace with its introduction on inland waters. Begun by Robert L. Stevens in the United States, in the year 1808, and by his contemporaries, Bell and Dodd, in Great Britain, it steadily and rapidly advanced in effectiveness and importance, and has now nearly driven the sailing fleet from the ocean. Transatlantic steam-navigation began with the voyage of the American steamer Savannah from Savannah, Ga., to St. Petersburg, Russia, _via_ Great Britain and the North-European ports, in the year 1819. Fulton, not long before his death, planned a vessel, which it was proposed to place in service in the Baltic Sea; but circumstances compelled a change of plan finally, and the steamer was placed on a line between Newport, R. I., and the city of New York; and the Savannah, several years later, made the voyage then proposed for Fulton's ship. The Savannah measured 350 tons, and was constructed by Crocker & Fickett, at Corlears Hook, N. Y. She was purchased by Mr. Scarborough, of Savannah, who placed Captain Moses Rogers, previously in command of the Clermont and of Stevens's boat, the Ph[oe]nix, in charge. The ship was fitted with steam-machinery and paddle-wheels, and sailed for Savannah April 27, 1819, making the voyage successfully in seven days. From Savannah, the vessel sailed for Liverpool May 26th, and arrived at that port June 20th. During this trip the engines were used 18 days, and the remainder of the voyage was made under sail. From Liverpool the Savannah sailed, July 23d, for the Baltic, touching at Copenhagen, Stockholm, St. Petersburg, and other ports. At St. Petersburg, Lord Lyndock, who had been a passenger, was landed; and, on taking leave of the commander of the steamer, the distinguished guest presented him with a silver tea-kettle, suitably inscribed with a legend referring to the importance of the event which afforded him the opportunity. The Savannah left St. Petersburg in November, passing New York December 9th, and reaching Savannah in 50 days from the date of departure, stopping four days at Copenhagen, Denmark, and an equal length of time at Arundel, Norway. Several severe gales were met in the Atlantic, but no serious injury was done to the ship. The Savannah was a full-rigged ship. The wheels were turned by an inclined direct-acting low-pressure engine, having a steam-cylinder 40 inches in diameter and 6 feet stroke of piston. The paddle-wheels were of wrought-iron, and were so attached that they could be detached and hoisted on board when it was desired. After the return of the ship to the United States, the machinery was removed and was sold to the Allaire Works, of New York. The steam-cylinder was exhibited by the purchasers at the "World's Fair" at New York thirty years later. The vessel was employed, as a sailing-vessel, on a line between New York and Savannah, and was finally lost in the year 1822. Under sail, with a moderate breeze, this ship is said to have sailed about three knots, and to have steamed five knots. Pine-wood was used as the fuel, which fact accounts for the necessity of making the transatlantic voyage partly under sail. Renwick states that another vessel, ship-rigged and fitted with a steam-engine, was built at New York in 1819, to ply between New York and Charleston, and to New Orleans and Havana, and that it proved perfectly successful as a steamer, having good speed, and proving an excellent sea-boat. The enterprise was, however, pecuniarily a failure, and the vessel was sold to the Brazilian Government after the removal of the engine. In 1825 the steamer Enterprise made a voyage to India, sailing and steaming as the weather and the supply of fuel permitted. The voyage occupied 47 days. Notwithstanding these successful passages across the ocean, and the complete success of the steamboat in rivers and harbors, it was asserted, as late as 1838, by many who were regarded as authority, that the passage of the ocean by steamers was quite impracticable, unless possibly they could steam from the coasts of Europe to Newfoundland or to the Azores, and, replenishing their coal-bunkers, resume their voyages to the larger American ports. The voyage was, however, actually accomplished by two steamers in the year just mentioned. These were the Sirius, a ship of 700 tons and of 250 horse-power, and the Great Western, of 1,340 tons and 450 horse-power. The latter was built for this service, and was a large ship for that time, measuring 236 feet in length. Her wheels were 28 feet in diameter, and 10 feet in breadth of face. The Sirius sailed from Cork April 4, 1838, and the Great Western from Bristol April 8th, both arriving at New York on the same day--April 23d--the Sirius in the morning, and the Great Western in the afternoon. The Great Western carried out of Bristol 660 tons of coal. Seven passengers chose to take advantage of the opportunity, and made the voyage in one-half the time usually occupied by the sailing-packets of that day. Throughout the voyage the wind and sea were nearly ahead, and the two vessels pursued the same course, under very similar conditions. Arriving at New York, they were received with the greatest possible enthusiasm. They were saluted by the forts and the men-of-war in the harbor; the merchant-vessels dipped their flags, and the citizens assembled on the Battery, and, coming to meet them in boats of all kinds and sizes, cheered heartily. The newspapers of the time were filled with the story of the voyage and with descriptions of the steamers themselves and of their machinery. A few days later the two steamers started on their return to Great Britain, the Sirius reaching Falmouth safely in 18 days, and the Great Western making the voyage to Bristol in 15 days, the latter meeting with head-winds and working, during a part of the time, against a heavy gale and in a high sea, at the rate of but two knots an hour. The Sirius was thought too small for this long and boisterous route, and was withdrawn and replaced on the line between London and Cork, where the ship had previously been employed. The Great Western continued several years in the transatlantic trade. Thus these two voyages inaugurated a transoceanic steam-service, which has steadily grown in extent and in importance. The use of steam-power for this work of extended ocean-transportation has never since been interrupted. During the succeeding six years the Great Western made 70 passages across the Atlantic, occupying on the voyages to the westward an average of 15-1/2 days, and eastward 13-1/2. The quickest passage to New York was made in May, 1843, in 12 days and 18 hours, and the fastest steaming was logged 12 months earlier, when the voyage from New York was made in 12 days and 7 hours. Meantime, several other steamers were built and placed in the transatlantic trade. Among these were the Royal William, the British Queen, the President, the Liverpool, and the Great Britain. The latter, the finest of the fleet, was launched in 1843. This steamer was 300 feet long, 50 feet beam, and of 1,000 horse-power. The hull was of iron, and the whole ship was an example of the very best work of that time. After several voyages, this vessel went ashore on the coast of Ireland, and there remained several weeks, but was finally got off, without having suffered serious injury--a remarkable illustration of the stanchness of an iron hull when well built and of good material. The vessel was repaired, and many years afterward was still afloat, and engaged in the transportation of passengers and merchandise to Australia. The "Cunard Line" of transatlantic steamers was established in the year 1840. The first of the line--the Britannia--sailed from Liverpool for New York, July 4th of that year, and was followed, on regular sailing-days, by the other three of the four ships with which the company commenced business. These four vessels had an aggregate tonnage of 4,600 tons, and their speed was less than eight knots. To-day, the tonnage of a single vessel of the fleet exceeds that of the four; the total tonnage has risen to many times that above given. There are 50 steamers in the line, aggregating nearly 50,000 horse-power. The speed of the steamships of the present time is double that of the vessels of that date, and passages are not infrequently made in eight days. The form of steam-engine in most general use at this time, on transatlantic steamers, was that known as the "side-lever engine." It was first given the standard form by Messrs. Maudsley & Co., of London, about 1835, and was built by them for steamers supplied to the British Government for general mail service. The steam-vessels of the time are well represented in the accompanying engraving (Fig. 91) of the steamship Atlantic--a vessel which was shortly afterward (1851) built as the pioneer steamer of the American "Collins Line." This steamship was one of several which formed the earliest of American steamship-lines, and is one of the finest examples of the type of paddle-steamers which was finally superseded by the later screw-fleets. The "Collins Line" existed but a very few years, and its failure was probably determined as much by the evident and inevitable success of screw-propulsion as by the difficulty of securing ample capital, complete organization, and efficient general management. This steamer was built at New York--the hull by William Brown, and the machinery by the Novelty Iron-Works. The length of the hull was 276 feet, its breadth 45 feet, and the depth of hold 31-1/2 feet. The width over the paddle-boxes was 75 feet. The ship measured 2,860 tons. The form of the hull was then peculiar in the fineness of its lines; the bow was sharp, and the stern fine and smooth, and the general outline such as best adapted the ship for high speed. The main saloon was about 70 feet long, and the dining-room was 60 feet in length and 20 feet wide. The state-rooms were arranged on each side the dining "saloon," and accommodated 150 passengers. These vessels were beautifully fitted up, and with them was inaugurated that wonderful system of passenger-transportation which has since always been distinguished by those comforts and conveniences which the American traveler has learned to consider his by right. [Illustration: FIG. 91.--The Atlantic, 1851.] The machinery of these ships was, for that time, remarkably powerful and efficient. The engines were of the side-lever type, as illustrated in Fig. 92, which represents the engine of the Pacific, designed by Mr. Charles W. Copeland, and built by the Allaire Works. [Illustration: FIG. 92.--The Side-Lever Engine, 1849.] In this type of engine, as is seen, the piston-rod was attached to a cross-head working vertically, from which, at each side, links, _B C_, connected with the "side-lever," _D E F_. The latter vibrated about a "main centre" at _E_, like the overhead beam of the more common form of engine; from its other end, a "connecting-rod," _H_, led to the "cross-tail," _W_, which was, in turn, connected to the crank-pin, _I_. The condenser, _M_, and air-pump, _Q_, were constructed in the same manner as those of other engines, their only peculiarities being such as were incident to their location between the cylinder, _A_, and the crank, _I J_. The paddle-wheels were of the common "radial" form, covered in by paddle-boxes so strongly built that they were rarely injured by the heaviest seas. These vessels surpassed, for a time, all other sea-going steamers in speed and comfort, and made their passages with great regularity. The minimum length of voyage of the Baltic and Pacific, of this line, was 9 days 19 hours. During the latter part of the period the history of which has been here given, the marine steam-engine became subject to very marked changes in type and in details, and a complete revolution was effected in the method of propulsion. This change has finally resulted in the universal adoption of a new propelling instrument, and in driving the whole fleet of paddle-steamers from the ocean. The Great Britain was a screw-steamer. The screw-propeller, which, as has been stated, was probably first proposed by Dr. Hooke in 1681, and by Dr. Bernouilli, of Groningen, at about the middle of the eighteenth century, and by Watt in 1784, was, at the end of the century, tried experimentally in the United States by David Bushnell, an ingenious American, who was then conducting the experiments with torpedoes which were the cause of the incident which originated that celebrated song by Francis Hopkinson, the "Battle of the Kegs," using the screw to propel one of his submarine boats, and by John Fitch, and by Dallery in France. Joseph Bramah, of Great Britain, May 9, 1785, patented a screw-propeller identical in general arrangement with those used to-day. His sketch exhibits a screw, apparently of very fair shape, carried on an horizontal shaft, which passes out of the vessel through a stuffing-box, the screw being wholly submerged. Bramah does not seem to have put his plan in practice. It was patented again in England, also, by Littleton in 1794, and by Shorter in 1800. John Stevens, however, first gave the screw a practically useful form, and used it successfully, in 1804 and 1805, on the single and the twin screw boats which he built at that time. This propelling instrument was also tried by Trevithick, who planned a vessel to be propelled by a steam-engine driving a screw, at about this time, and his scheme was laid before the Navy Board in the year 1812. His plans included an iron hull. Francis Pettit Smith tried the screw also in the year 1808, and subsequently. Joseph Ressel, a Bohemian, proposed to use a screw in the propulsion of balloons, about 1812, and in the year 1826 proposed its use for marine propulsion. He is said to have built a screw-boat in the year 1829, at Trieste, which he named the Civetta. The little craft met with an accident on the trial-trip, and nothing more was done. The screw was finally brought into general use through the exertions of John Ericsson, a skillful Swedish engineer, who was residing in England in the year 1836, and of Mr. F. P. Smith, an English farmer. Ericsson patented a peculiar form of screw-propeller, and designed a steamer 40 feet in length, of 8 feet beam, and drawing 3 feet of water. The screw was double, two shafts being placed the one within the other, revolving in opposite directions, and carrying the one a right-hand and the other a left-hand screw. These screws were 5-1/4 feet in diameter. On her trial-trip this little steamer attained a speed of 10 miles an hour. Its power as a "tug" was found to be very satisfactory; it towed a schooner of 140 tons burden at the rate of 7 miles, and the large American packet-ship Toronto was towed on the Thames at a speed of 5 miles an hour. Ericsson endeavored to interest the British Admiralty in his improvements, and succeeded only so far as to induce the Lords of the Admiralty to make an excursion with him on the river. No interest was awakened in the new system, and nothing was done by the naval authorities. A note to the inventor from Captain Beaufort--one of the party--was received shortly afterward, in which it was stated that the excursionists had not found the performance of the little vessel to equal their hopes and expectations. All the interests of the then existing engine-building establishments were opposed to the innovation, and the proverbial conservatism of naval men and naval administrations aided in procuring the rejection of Ericsson's plans. Fortunately for the United States, it happened, at that time, that we had in Great Britain both civil and naval representatives of greater intelligence, or of greater boldness and enterprise. The consul at Liverpool was Mr. Francis B. Ogden, of New Jersey, a gentleman who was somewhat familiar with the steam-engine and with steam-navigation. He had seen Ericsson's plans at an earlier period, and had at once seen their probable value. He was sufficiently confident of success to place capital at the disposal of the inventor. The little screw-boat just described was built with funds of which he furnished a part, and was named, in his honor, the Francis B. Ogden. Captain Robert F. Stockton, an officer of the United States Navy, and also a resident of New Jersey, was in London at the time, and made an excursion with Ericsson on the Ogden. He was also at once convinced of the value of the new method of application of steam-power to ship-propulsion, and gave the engineer an order to build two iron screw-steamboats for use in the United States. Ericsson was induced, by Messrs. Ogden and Stockton, to take up his residence in the United States.[84] The Stockton was sent over to the United States in April, 1839, under sail, and was sold to the Delaware & Raritan Canal Company. Her name was changed, and, as the New Jersey, she remained in service many years. [84] This distinguished inventor is still a resident of New York (1878). The success of the boat built by Ericsson was so evident that, although the naval authorities remained inactive, a private company was formed, in 1839, to work the patents of F. P. Smith, and this "Ship-Propeller Company" built an experimental craft called the Archimedes, and its trial-trip was made October 14th of the same year. The speed attained was 9.64 miles an hour. The result was in every respect satisfactory, and the vessel, subsequently, made many voyages from port to port, and finally circumnavigated the island of Great Britain. The proprietors of the ship were not pecuniarily successful in their venture, however, and the sale of the vessel left the company a heavy loser. The Archimedes was 125 feet long, of 21 feet 10 inches beam, and 10 feet draught, registering 232 tons. The engines were rated at 80 horse-power. Smith's earlier experiments (1837) were made with a little craft of 6 tons burden, driven by an engine having a steam-cylinder 6 inches in diameter and 15 inches stroke of piston. The funds needed were furnished by a London banker--Mr. Wright. Bennett Woodcroft had also used the screw experimentally as early as 1832, on the Irwell, near Manchester, England, in a boat of 55 tons burden. Twin-screws were used, right and left handed respectively; they were each two feet in diameter, and were given an expanding pitch. The boat attained a speed of four miles an hour. Experiments made subsequently (1843) with this form of screw, and in competition with the "true" screw of Smith, brought out very distinctly the superiority of the former, and gave some knowledge of the proper proportions for maximum efficiency. In later examples of the Woodcroft screw, the blades were made detachable and adjustable--a plan which is still a usual one, and which has proved to be, in some respects, very convenient. When Ericsson reached the United States, he was almost immediately given an opportunity to build the Princeton--a large screw-steamer--and at about the same time the English and French Governments also had screw-steamers built from his plans, or from those of his agent in England, the Count de Rosen. In these latter ships--the Amphion and the Pomona--the first horizontal direct-acting engines ever built were used, and they were fitted with double-acting air-pumps, having canvas valves and other novel features. The great advantages exhibited by these vessels over the paddle-steamers of the time did for screw-propulsion what Stephenson's locomotive--the Rocket--did for railroad locomotion ten years earlier. Congress, in 1839, had authorized the construction of three war-vessels, and the Secretary of the Navy ordered that two be at once built in the succeeding year. Of these, one was the Princeton, the screw-steamer of which the machinery was designed by Ericsson. The length of this vessel was 164 feet, beam 30-1/2 feet, and depth 21-1/2 feet. The ship drew from 16-1/2 to 18 feet of water, displacing at those draughts 950 and 1,050 tons. The hull had a broad, flat floor, with sharp entrance and fine run, and the lines were considered at that time remarkably fine. The screw was of gun-bronze, six-bladed, and was 14 feet in diameter and of 35 feet pitch; i. e., were there no slip, the screw working as if in a solid nut, the ship would have been driven forward 35 feet at each revolution. The engines were two in number, and very peculiar in form; the cylinder was, in fact, a _semi_-cylinder, and the place of the piston-rod, as usually built, was taken by a vibrating shaft, or "rock-shaft," which carried a piston of rectangular form, and which vibrated like a door on its hinges as the steam was alternately let into and exhausted from each side of it. The great rock-shaft carried, at the outer end, an arm from which a connecting-rod led to the crank, thus forming a "direct-acting engine." The draught in the boilers was urged by blowers. Ericsson had adopted this method of securing an artificial draught ten years before, in one of his earlier vessels, the Corsair. The Princeton carried a XII-inch wrought-iron gun. This gun exploded after a few trials, with terribly disastrous results, causing the death of several distinguished men, including members of the President's cabinet. The Princeton proved very successful as a screw-steamer, attaining a speed of 13 knots, and was then considered very remarkably fast. Captain Stockton, who commanded the vessel, was most enthusiastic in praise of her. Immediately there began a revolution in both civil and naval ship-building, which progressed with great rapidity. The Princeton was the first of the screw-propelled navy which has now entirely displaced the older type of steam-vessel. The introduction of the screw now took place with great rapidity. Six steamers were fitted with Ericsson's screw in 1841, 9 in 1842, and nearly 30 in the year 1843. In Great Britain, France, Germany, and other European countries, the revolution was also finally effected, and was equally complete. Nearly all sea-going vessels built toward the close of the period here considered were screw-steamers, fitted with direct-acting, quick-working engines. It was, however, many years before the experience of engineers in the designing and in the construction and management of this new machinery enabled them to properly proportion it for the various kinds of service to which they were called upon to adapt it. Among other modifications of earlier practice introduced by Ericsson was the surface-condenser with a circulating pump driven by a small independent engine. The screw was found to possess many advantages over the paddle-wheel as an instrument for ship-propulsion. The cost of machinery was greatly reduced by its use; the expense of maintenance in working order was, however, somewhat increased. The latter disadvantage was, nevertheless, much more than compensated by an immense increase in the economy of ship-propulsion, which marked the substitution of the new instrument and its impelling machinery. When a ship is propelled by paddles, the motion of the vessel creates, in consequence of the friction of the fluid against the sides and bottom, a current of water which flows in the direction in which the ship is moving, and forms a current following the ship for a time, and finally losing all motion by contact with the surrounding mass of water. All the power expended in the production of this great stream is, in the case of the paddle-steamer, entirely lost. In screw-steamers, however, the propelling instrument works in this following current, and the tendency of its action is to bring the agitated fluid to rest, taking up and thus restoring, usefully, a large part of that energy which would otherwise have been lost. The screw is also completely covered by the water, and acts with comparative efficiency in consequence of its submersion. The rotation of the screw is comparatively rapid and smooth, also, and this permits the use of small, light, fast-running engines. The latter condition leads to economy of weight and space, and consequently saves not only the cost of transportation of the excess of weight of the larger kind of engine, but, leaving so much more room for paying cargo, the gain is found to be a double one. Still further, the quick-running engine is, other things being equal, the most economical of steam; and thus some expense is saved not only in the purchase of fuel, but in its transportation, and some still additional gain is derived from the increased amount of paying cargo which the vessel is thus enabled to carry. The change here described was thus found to be productive of enormous direct gain. Indirectly, also, some advantage was derived from the greater convenience of a deck clear from machinery and the great paddle-shaft, in the better storage of the lading, the greater facility with which the masts and sails could be fitted and used; and directly, again, in clear sides unencumbered by great paddle-boxes which impeded the vessel by catching both sea and wind. The screw was, for some years, generally regarded as simply auxiliary in large vessels, assisting the sails. Ultimately the screw became the essential feature, and vessels were lightly sparred and were given smaller areas of sail, the latter becoming the auxiliary power. In November of the year 1843, the screw-steamer Midas, Captain Poor, a small schooner-rigged craft, left New York for China, on probably the first voyage of such length ever undertaken by a steamer; and in the following January the Edith, Captain Lewis, a bark-rigged screw-vessel, sailed from the same port for India and China. The Massachusetts, Captain Forbes, a screw-steamship of about 800 tons, sailed for Liverpool September 15, 1845, the first voyage of an American transatlantic passenger-steamer since the Savannah's pioneer adventure a quarter of a century before. Two years later, American enterprise had placed both screw and paddle steamers on the rivers of China--principally through the exertions of Captain R. B. Forbes--and steam-navigation was fairly established throughout the world. On comparing the screw-steamer of the present time with the best examples of steamers propelled by paddle-wheels, the superiority of the former is so marked that it may cause some surprise that the revolution just described should have progressed no more rapidly. The reason of this slow progress, however, was probably that the introduction of the rapidly-revolving screw, in place of the slow-moving paddle-wheel, necessitated a complete revolution in the design of their steam-engines; and the unavoidable change from the heavy, long-stroked, low-speed engines previously in use, to the light engines, with small cylinders and high piston-speed, called for by the new system of propulsion, was one that necessarily occurred slowly, and was accompanied by its share of those engineering blunders and accidents that invariably take place during such periods of transition. Engineers had first to learn to design such engines as should be reliable under the then novel conditions of screw-propulsion, and their experience could only be gained through the occurrence of many mishaps and costly failures. The best proportions of engines and screws, for a given ship, were determined only by long experience, although great assistance was derived from the extensive series of experiments made with the French steamer Pelican. It also became necessary to train up a body of engine-drivers who should be capable of managing these new engines; for they required the exercise of a then unprecedented amount of care and skill. Finally, with the accomplishment of these two requisites to success must simultaneously occur the enlightenment of the public, professional as well as non-professional, in regard to their advantages. Thus it happens that it is only after a considerable time that the screw attained its proper place as an instrument of propulsion, and finally drove the paddle-wheel quite out of use, except in shoal water. Now our large screw-steamers are of higher speed than any paddle-steamers on the ocean, and develop their power at far less cost. This increased economy is due not only to the use of a more efficient propelling instrument, and to changes already described, but also, in a great degree, to the economy which has followed as a consequence of other changes in the steam-engine driving it. The earliest days of screw-propulsion witnessed the use of steam of from 5 to 15 pounds pressure, in a geared engine using jet-condensation, and giving a horse-power at an expense of perhaps 7 to 10, or even more, pounds of coal per hour. A little later came direct-acting engines with jet-condensation and steam at 20 pounds pressure, costing about 5 or 6 pounds per horse-power per hour. The steam-pressure rose a little higher with the use of greater expansion, and the economy of fuel was further improved. The introduction of the surface-condenser, which began to be generally adopted some ten years ago, brought down the cost of power to from 3 to 4 pounds in the better class of engines. At about the same time, this change to surface-condensation helping greatly to overcome those troubles arising from boiler-incrustation which had prevented the rise of steam-pressure above about 25 pounds per square inch, and as, at the same time, it was learned by engineers that the deposit of lime-scale in the marine boiler was determined by temperature rather than by the degree of concentration, and that all the lime entering the boiler was deposited at the pressure just mentioned, a sudden advance took place. Careful design, good workmanship, and skillful management, made the surface-condenser an efficient apparatus; and, the dangers of incrustation being thus lessened, the movement toward higher pressures recommenced, and progressed so rapidly that now 75 pounds per square inch is very usual, and more than 125 pounds has since been attained. The close of this period was marked by the construction of the most successful types of paddle-steamers, the complete success of transoceanic steam-transportation, the introduction of the screw-propeller and the peculiar engine appropriate to it, and, finally, a general improvement, which had finally become marked both in direction and in rapidity of movement, leading toward the use of higher steam-pressure, greater expansion, lighter and more rapidly-working machinery, and decidedly better design and construction, and the use of better material. The result of these changes was seen in economy of first cost and maintenance, and the ability to attain greater speed, and to assure greater safety to passengers and less risk to cargo. The introduction of the changes just noted finally led to the last great change in the form of the marine steam-engine, and a revolution was inaugurated, which, however, only became complete in the succeeding period. The non-success of Hornblower and of Wolff, and others who had attempted to introduce the "compound" or double-cylinder engine on land, had not convinced all engineers that it might not yet be made a successful rival of the then standard type; and the three or four steamers which were built for the Hudson River at the end of the first quarter of the nineteenth century are said to have been very successful vessels. Carrying 75 to 100 pounds of steam in their boilers, the Swiftsure and her contemporaries were by that circumstance well fitted to make that form of engine economically a success. This form of engine was built occasionally during the succeeding quarter of a century, but only became a recognized standard type after the close of the epoch to the history of which this chapter is devoted. That latest and greatest advance in the direction of increased efficiency in the marine steam-engine was, however, commenced very soon after Watt's death, and its completion was the work of nearly a half-century. [Illustration] CHAPTER VI. _THE STEAM-ENGINE OF TO-DAY._ ... "And, last of all, with inimitable power, and 'with whirlwind sound,' comes the potent agency of steam. In comparison with the past, what centuries of improvement has this single agent comprised in the short compass of fifty years! Everywhere practicable, everywhere efficient, it has an arm a thousand times stronger than that of Hercules, and to which human ingenuity is capable of fitting a thousand times as many hands as belonged to Briareus. Steam is found in triumphant operation on the seas; and, under the influence of its strong propulsion, the gallant ship-- 'Against the wind, against the tide, Still steadies with an upright keel.' It is on the rivers, and the boatman may repose on his oars; it is on highways, and exerts itself along the courses of land-conveyance; it is at the bottom of mines, a thousand feet below the earth's surface; it is in the mills, and in the workshops of the trades. It rows, it pumps, it excavates, it carries, it draws, it lifts, it hammers, it spins, it weaves, it prints. It seems to say to men, at least to the class of artisans: 'Leave off your manual labor; give over your bodily toil; bestow but your skill and reason to the directing of my power, and I will bear the toil, with no muscle to grow weary, no nerve to relax, no breast to feel faintness!' What further improvement may still be made in the use of this astonishing power it is impossible to know, and it were vain to conjecture. What we do know is, that it has most essentially altered the face of affairs, and that no visible limit yet appears beyond which its progress is seen to be impossible."--DANIEL WEBSTER. THE PERIOD OF REFINEMENT--1850 TO DATE. By the middle of the present century, as we have now seen, the steam-engine had been applied, and successfully, to every great purpose for which it was fitted. Its first application was to the elevation of water; it next was applied to the driving of mills and machinery; and it finally became the great propelling power in transportation by land and by sea. At the beginning of the period to which we are now come, these applications of steam-power had become familiar both to the engineer and to the public. The forms of engine adapted to each purpose had been determined, and had become usually standard. Every type of the modern steam-engine had assumed, more or less closely, the form and proportions which are now familiar; and the most intelligent designers and builders had been taught--by experience rather than by theory, for the theory of the steam-engine had then been but little investigated, and the principles and laws of thermo-dynamics had not been traced in their application to this engine--the principles of construction essential to successful practice, and were gradually learning the relative standing of the many forms of steam-engine, from among which have been preserved a few specially fitted for certain specific methods of utilization of power. During the years succeeding the date 1850, therefore, the growth of the steam-engine had been, not a change of standard type, or the addition of new parts, but a gradual improvement in forms, proportions, and arrangements of details; and this period has been marked by the dying out of the forms of engine least fitted to succeed in competition with others, and the retention of the latter has been an example of "the survival of the fittest." This has therefore been a Period of Refinement. During this period invention has been confined to details; it has produced new forms of parts, new arrangements of details; it has devised an immense variety of valves, valve-motions, regulating apparatus, and a still greater variety of steam-boilers and of attachments, essential and non-essential, to both engines and boilers. The great majority of these peculiar devices have been of no value, and very many of the best of them have been found to have about equal value. All the well-known and successful forms of engine, when equally well designed and constructed and equally well managed, are of very nearly equal efficiency; all of the best-known types of steam-boiler, where given equal proportions of grate to heating-surface and equally well designed, with a view to securing a good draught and a good circulation of water, have been found to give very nearly equally good results; and it has become evident that a good knowledge of principles and of practice, on the part of the designer, the constructor, and the manager of the boiler, is essential in the endeavor to achieve economical success; that good engineering is demanded, rather than great ingenuity. The inventor has been superseded here by the engineer. The knowledge acquired in the time of Watt, of the essential principles of steam-engine construction, has since become generally familiar to the better class of engineers. It has led to the selection of simple, strong, and durable forms of engine and boiler, to the introduction of various kinds of valves and of valve-gearing, capable of adjustment to any desired range of expansive working, and to the attachment of efficient forms of governor to regulate the speed of the engine, by determining automatically the point of cut-off which will, at any instant, best adjust the energy exerted by the expanding steam to the demand made by the work to be done. The value of high pressures and considerable expansion was recognized as long ago as in the early part of the present century, and Watt, by combining skillfully the several principal parts of the steam-engine, gave it very nearly the shape which it has to-day. The compound engine, even, as has been seen, was invented by contemporaries of Watt, and the only important modifications since his time have occurred in details. The introduction of the "drop cut-off," the attachment of the governor to the expansion-apparatus in such a manner as to determine the degree of expansion, the improvement of proportions, the introduction of higher steam and greater expansion, the improvement of the marine engine by the adoption of surface-condensation, in addition to these other changes, and the introduction of the double-cylinder engine, after the elevation of steam-pressure and increase of expansion had gone so far as to justify its use, are the changes, therefore, which have taken place during this last quarter-century. It began then to be generally understood that expansion of steam produced economy, and mechanics and inventors vied with each other in the effort to obtain a form of valve-gear which should secure the immense saving which an abstract consideration of the expansion of gases according to Marriotte's law would seem to promise. The counteracting phenomena of internal condensation and reëvaporation, of the losses of heat externally and internally, and of the effect of defective vacuum, defective distribution of steam, and of back-pressure, were either unobserved or were entirely overlooked. It was many years, therefore, before engine-builders became convinced that no improvement upon existing forms of expansion-gear could secure even an approximation to theoretical efficiency. The fact thus learned, that the benefit of expansive working has a limit which is very soon reached in ordinary practice, was not then, and has only recently become, generally known among our steam-engine builders, and for several years, during the period upon which we now enter, there continued the keenest competition between makers of rival forms of expansion-gear, and inventors were continually endeavoring to produce something which should far excel any previously-existing device. In Europe, as in the United States, efforts to "improve" standard designs have usually resulted in injuring their efficiency, and in simply adding to the first cost and running expense of the engines, without securing a marked increase in economy in the consumption of steam. SECTION I.--STATIONARY ENGINES. "STATIONARY ENGINES" had been applied to the operation of mill-machinery, as has been seen, by Watt and by Murdoch, his assistant and pupil; and Watt's competitors, in Great Britain and abroad, had made considerable progress before the death of the great engineer, in its adaptation to its work. In the United States, Oliver Evans had introduced the non-condensing high-pressure stationary engine, which was the progenitor of the standard engine of that type which is now used far more generally than any other form. These engines were at first rude in design, badly proportioned, rough and inaccurate as to workmanship, and uneconomical in their consumption of fuel. Gradually, however, when made by reputable builders, they assumed neat and strong shapes, good proportions, and were well made and of excellent materials, doing their work with comparatively little waste of heat or of fuel. One of the neatest and best modern designs of stationary engine for small powers is seen in Fig. 93, which represents a "vertical direct-acting engine," with base-plate--a form which is a favorite with many engineers. The engine shown in the engraving consists of two principal parts, the cylinder and the frame, which is a tapering column having openings in the sides, to allow free access to all the working parts within. The slides and pillow-blocks are cast with the column, so that they cannot become loose or out of line; the rubbing surfaces are large and easily lubricated. Owing to the vertical position, there is no tendency to side wear of cylinder or piston. The packing-rings are self-adjusting, and work free but tight. The crank is counterbalanced; the crank-pin, cross-head pin, piston-rod, valve-stem, etc., are made of steel; all the bearing surfaces are made extra large, and are accurately fitted; and the best quality of Babbitt-metal only used for the journal-bearings. [Illustration: FIG. 93.--Vertical Stationary Steam-Engine.] The smaller sizes of these engines, from 2 to 10 horse-power, have both pillow-blocks cast in the frame, giving a bearing each side of the double cranks. They are built by some constructors in quantities, and parts duplicated by special machinery (as in fire-arms and sewing-machines), which secures great accuracy and uniformity of workmanship, and allows of any part being quickly and cheaply replaced, when worn or broken by accident. The next figure is a vertical section through the same engine. [Illustration: FIG. 94.--Vertical Stationary Steam-Engine. Section.] Engines fitted with the ordinary rigid bearings require to be erected on a firm foundation, and to be kept in perfect line. If, by the settling of the foundation, or from any other cause, they get out of line, heating, cutting, and thumping result. To obviate this, modern engines are often fitted with self-adjusting bearings throughout; this gives the engine great flexibility and freedom from friction. The accompanying cuts show clearly how this is accomplished. The pillow-block has a spherical shell turned and fitted into the spherically-bored pillow-block, thus allowing a slight angular motion in any direction. The connecting-rod is forged in a single piece, without straps, gibs, or key, and is mortised through at each end for the reception of the brass boxes, which are curved on their backs, and fit the cheek-pieces, between which they can turn to adjust themselves to the pins, in the plane of the axis of the rod. The adjustment for wear is made by wedge-blocks and set screws, as shown, and they are so constructed that the parts cannot get loose and cause a break-down. The cross-head has adjustable gibs on each side, turned to fit the slides, which are cast solidly in the frame, and bored out exactly in the line with the cylinder. This permits it freely to turn on its axis, and, in connection with the adjustable boxes in the connecting-rod, allows a perfect self-adjustment to the line of the crank-pin. The out-board bearing may be moved an inch or more out of position in any direction, without detriment to the running of the engine, all bearings accommodating themselves perfectly to whatever position the shaft may assume. The ports and valve-passages are proportioned as in locomotive practice. The valve-seat is adapted to the ordinary plain slide or D-valve, should it be preferred, but the balanced piston slide-valve works with equal ease whether the steam-pressure is 10 or 100 pounds, and at the same time gives double steam and exhaust openings, which greatly facilitates the entrance of the steam to, and its escape from, the cylinder, thus securing a nearer approach to boiler-pressure and a less back-pressure, saving the power required to work an ordinary valve, and reducing the wear of valve-gear. This is a type of engine frequently seen in the United States, but more rarely in Europe. It is an excellent form of engine. The vertical direct-acting engine is sometimes, though rarely, built of very considerable size, and these large engines are more frequently seen in rolling-mills than elsewhere. Where much power is required, the stationary engine is usually an horizontal direct-acting engine, having a more or less effective cut-off valve-gear, according to the size of engine and the cost of fuel. A good example of the simpler form of this kind of engine is the small horizontal slide-valve engine, with independent cut-off valve riding on the back of the main valve--a combination generally known among engineers as the Meyer system of valve-gear. This form of steam-engine is a very effective machine, and does excellent work when properly proportioned to yield the required amount of power. It is well adapted to an expansion of from four to five times. Its disadvantages are the difficulty which it presents in the attachment of the regulator, to determine the point of cut-off by the heavy work which it throws upon the governor when attached, and the rather inflexible character of the device as an expansive valve-gear. The best examples of this class of engine have neat heavy bed-plates, well-designed cylinders and details, smooth-working valve-gear, the expansion-valve adjusted by a right and left hand screw, and regulation secured by the attachment of the governor to the throttle-valve. The engine shown in the accompanying illustration (Fig. 95) is an example of an excellent British stationary steam-engine. It is simple, strong, and efficient. The frame, front cylinder-head, cross-head guides, and crank-shaft "plumber-block," are cast in one piece, as has so generally been done in the United States for a long time by some of our manufacturers. The cylinder is secured against the end of the bed-plate, as was first done by Corliss. The crank-pin is set in a counterbalanced disk. The valve-gear is simple, and the governor effective, and provided with a safety-device to prevent injury by the breaking of the governor-belt. An engine of this kind of 10 inches diameter of cylinder, 20 inches stroke of piston, is rated by the builders at about 25 horse-power; a similar engine 30 inches in diameter of cylinder would yield from 225 to 250 horse-power. In this example, all parts are made to exact size by gauges standardized to Whitworth's sizes. [Illustration: FIG. 95.--Horizontal Stationary Steam-Engine.] [Illustration: FIG. 96.--Horizontal Stationary Steam-Engine.] In American engines (as is seen in Fig. 96), usually, two supports are placed--the one under the latter bearing, and the other under the cylinder--to take the weight of the engine; and through them it is secured to the foundation. As in the vertical engine already described, a valve is sometimes used, consisting of two pistons connected by a rod, and worked by an ordinary eccentric. By a simple arrangement these pistons have always the same pressure inside as out, which prevents any leakage or blowing through; and they are said always to work equally as well and free from friction under 150 pounds pressure as under 10 pounds per square inch, and to require no adjustment. It is more usual, however, to adopt the three-ported valve used on locomotives, with (frequently) a cut-off valve on the back of this main valve, which cut-off valve is adjusted either by hand or by the governor. Engines of the class just described are especially well fitted, by their simplicity, compactness, and solidity, to work at the high piston-speeds which are gradually becoming generally adopted in the effort to attain increased economy of fuel by the reduction of the immense losses of heat which occur in the expansion of steam in the metallic cylinders through which we are now compelled to work it. One of the best known of recent engines is the Allen engine, a steam-engine having the same general arrangement of parts seen in the above illustration, but fitted with a peculiar valve-gear, and having proportions of parts which are especially calculated to secure smoothness of motion and uniformity of pressure on crank-pin and journals, at speeds so high that the inertia of the reciprocating parts becomes a seriously-important element in the calculation of the distribution of stresses and their effect on the dynamics of the machine. In the Allen engine,[85] the cylinder and frame are connected as in the engine seen above, and the crank-disk, shaft-bearings, and other principal details, are not essentially different. The valve-gear[86] differs in having four valves, one at each end on the steam as well as on the exhaust side, all of which are balanced and work with very little resistance. These valves are not detachable, but are driven by a link attached to and moved by an eccentric on the main shaft, the position of the valve-rod attachment to which link is determined by the governor, and the degree of expansion is thus adjusted to the work of the engine. The engine has usually a short stroke, not exceeding twice the diameter of cylinder, and is driven at very high speed, generally averaging from 600 to 800 feet per minute.[87] This high piston-speed and short stroke give very great velocity of rotation. The effect is, therefore, to produce an exceptional smoothness of motion, while permitting the use of small fly-wheels. Its short stroke enables entire solidity to be attained in a bed of rigid form, making it a very completely self-contained engine, adapted to the heaviest work, and requiring only a small foundation. [85] The invention of Messrs. Charles T. Porter and John F. Allen. [86] Invented by Mr. John F. Allen. [87] Or not far from 600 times the cube root of the length of stroke, measured in feet. The journals of the shaft, and all cylindrical wearing surfaces, are finished by grinding in a manner that leaves them perfectly round. The crank-pin and cross-head pin are hardened before being ground. The joints of the valve-gear consist of pins turning in solid ferrules in the rod-ends, both hardened and ground. After years of constant use thus, no wear occasioning lost time in the valve-movements has been detected. High speed and short strokes are essential elements of economy. It is now well understood that all the surfaces with which the steam comes in contact condense it. Obviously, one way to diminish this loss is to reduce the extent of surface to which the steam is exposed. In engines of high speed and short stroke, the surfaces with which the steam comes in contact, while doing a given amount of work, present less area than in ordinary engines running at low speed. Where great steadiness of motion is desired, the expense of coupled engines is often incurred. Quick-running engines do not require to be coupled; a single engine may give greater uniformity of motion than is usually obtained with coupled engines at ordinary speeds. The ports and valve-movements, the weight of the reciprocating parts, and the size and weight of the fly-wheels, should be calculated expressly for the speeds chosen. The economy of the engine here described is unexcelled by the best of the more familiar "drop cut-off" engines. An engine reported upon by a committee of the American Institute, of which Dr. Barnard was chairman, was non-condensing, 16 inches in diameter of cylinder, 30 inches stroke, making 125 revolutions per minute, and developed over 125 horse-power with 75 pounds of steam in the boiler, using 25-3/4 pounds of steam per indicated horse-power, and 2.87 pounds of coal--an extraordinarily good performance for an engine of such small power. The governor used on this engine is known as the Porter governor. It is given great power and delicacy by weighting it down, and thus obtaining a high velocity of rotation, and by suspending the balls from forked arms, which are given each two bearing-pins separated laterally so far as to permit considerable force to be exerted in changing speeds without cramping those bearings sufficiently to seriously impair the sensitiveness of the governor. This engine as a whole may be regarded as a good representative of the high-speed engine of to-day. Since this change in the direction of high speeds has already gone so far that the "drop cut-off" is sometimes inapplicable, in consequence of the fact that the piston would, were such a valve-gear adopted, reach the end of its stroke before the detached valve could reach its seat; and since this progress is only limited by our attainments in mechanical skill and accuracy, it seems probable that the "positive-motion expansion-gear" type of engine will ultimately supersede the now standard "drop cut-off engine." The best known and most generally used class of stationary engines at the present time is, however, that which has the so-called "drop cut-off," or "detachable valve-gear." The oldest well-known form of valve-motion of this description now in use is that known as the Sickels cut-off, patented by Frederick E. Sickels, an American mechanic, about the year 1841, and also built by Hogg, of New York, who placed it upon the engine of the steamer South America. The invention is claimed for both Hogg and Sickels. It was introduced by the inventor in a form which especially adapted it to use with the beam-engine used on the Eastern waters of the United States, and was adapted to stationary engines by Messrs. Thurston, Greene & Co., of Providence, R. I., who made use of it for some years before any other form of "drop cut-off" came into general use. The Sickels cut-off consisted of a set of steam-valves, usually independent of the exhaust-valves, and each raised by a catch, which could be thrown out, at the proper moment, by a wedge with which it came in contact as it rose with the opening valve. This wedge, or other equivalent device, was so adjusted that the valve should be detached and fall to its seat when the piston reached that point in its movement, after taking steam, at which expansion was to commence. From this point, no steam entering the cylinder, the piston was impelled by the expanding vapor. The valve was usually the double-poppet. Sickels subsequently invented what was called the "beam-motion," to detach the valve at any point in the stroke. As at first arranged, the valve could only be detached during the earlier half-stroke, since at mid-stroke the direction of motion of the eccentric rod was reversed and the valve began to descend. By introducing a "wiper" having a motion transverse to that of the valve and its catch, and by giving this wiper a motion coincident with that of the piston by connecting it with the beam or other part of the engine moving with the piston, he obtained a kinematic combination which permitted the valve to be detached at any point in the stroke, adding a very simple contrivance which enabled the attendant to set the wiper so that it should strike the catch at any time during the forward movement of the "beam-motion." On stationary engines, the point of cut-off was afterward determined by the governor, which was made to operate the detaching mechanism, the combination forming what is sometimes called an "automatic" cut-off. The attachment of the governor so as to determine the degree of expansion had been proposed before Sickels's time. One of the earliest of these contrivances was that of Zachariah Allen, in 1834, using a cut-off valve independent of the steam-valve. The first to so attach the governor to a _drop cut-off_ valve-motion was George H. Corliss, who made it a feature of the Corliss valve-gear in 1849. In the year 1855, N. T. Greene introduced a form of expansion-gear, in which he combined the range of the Sickels beam-motion device with the expansion-adjustment gained by the attachment of the governor, and with the advantages of flat slide-valves at all ports--both steam and exhaust. Many other ingenious forms of expansion valve-gear have been invented, and several have been introduced, which, properly designed and proportioned to well-planned engines, and with good construction and management, should give economical results little if at all inferior to those just named. Among the most ingenious of these later devices is that of Babcock & Wilcox, in which a very small auxiliary steam-cylinder and piston is employed to throw the cut-off valve over its port at the instant at which the steam is to be cut off. A very beautiful form of isochronous governor is used on this engine, to regulate the speed of the engine by determining the point of cut-off. In Wright's engine, the expansion is adjusted by the movement, by the regulator, of cams which operate the steam-valves so that they shall hold the valve open a longer or shorter time, as required. Since compactness and lightness are not as essential as in portable, locomotive, and marine engines, the parts are arranged, in stationary engines, with a view simply to securing efficiency, and the design is determined by circumstances. It was formerly usual to adopt the condensing engine in mills, and wherever a stationary engine was required. In Europe generally, and to some extent in the United States, where a supply of condensing water is obtainable, condensing engines and moderate steam-pressures are still employed. But this type of engine is gradually becoming superseded by the high-pressure condensing engine, with considerable expansion, and with an expansion-gear in which the point of cut-off is determined by the governor. [Illustration: FIG. 97.--Corliss Engine.] [Illustration: FIG. 98--Corliss Engine Valve-Motion.] The best-known engine of this class is the Corliss engine, which is very extensively used in the United States, and which has been copied very generally by European builders. Fig. 97 represents the Corliss engine. The horizontal steam-cylinder is bolted firmly to the end of the frame, which is so formed as to transmit the strain to the main journal with the greatest directness. The frame carries the guides for the cross-head, which are both in the same vertical plane. The valves are four in number, a steam and an exhaust valve being placed at each end of the steam-cylinder. Short steam-passages are thus secured, and this diminution of clearance is a source of some economy. Both sets of valves are driven by an eccentric operating a disk or wrist-plate, _E_ (Fig. 98), which vibrates on a pin projecting from the cylinder. Short links reaching from this wrist-plate to the several valves, _D D_, _F F_, move them with a peculiarly varying motion, opening and closing them rapidly, and moving them quite slowly when the port is either nearly open or almost closed. This effect is ingeniously secured by so placing the pins on the wrist-plate that their line of motion becomes nearly transverse to the direction of the valve-links when the limit of movement is approached. The links connecting the wrist-plate with the arms moving the steam-valves have catches at their extremities, which are disengaged by coming in contact, as the arm swings around with the valve-stem, with a cam adjusted by the governor. This adjustment permits the steam to follow the piston farther when the engine is caused to "slow down," and thus tends to restore the proper speed. It disengages the steam-valve earlier, and expands the steam to a greater extent, when the engine begins to run above the proper speed. When the catch is thrown out, the valve is closed by a weight or a strong spring. To prevent jar when the motion of the valve is checked, a "dash-pot" is used, invented originally by F. E. Sickels. This is a vessel having a nicely-fitted piston, which is received by a "cushion" of water or air when the piston suddenly enters the cylinder at the end of the valve-movement. In the original water dash-pot of Sickels, the cylinder is vertical, and the plunger or piston descends upon a small body of water confined in the base of the dash-pot. Corliss's air dash-pot is now often set horizontally. [Illustration: FIG. 99.--Greene Engine.] In the Greene steam-engine (Fig. 99), the valves are four in number, as in the Corliss. The cut-off gear consists of a bar, _A_, moved by the steam-eccentric in a direction parallel with the centre-line of the cylinder and nearly coincident as to time with the piston. On this bar are tappets, _C C_, supported by springs and adjustable in height by the governor, _G_. These tappets engage the arms _B B_, on the ends of rock-shafts, _E E_, which move the steam-valves and remain in contact with them a longer or shorter time, and holding the valve open during a greater or less part of the piston-stroke, as the governor permits the tappets to rise with diminishing engine-speed, or forces them down as speed increases. The exhaust-valves are moved by an independent eccentric rod, which is itself moved by an eccentric set, as is usual with the Corliss and with other engines generally, at right angles with the crank. This engine, in consequence of the independence of the steam-eccentric, and of the contemporary movement of steam valve-motion and steam-piston, is capable of cutting off at any point from beginning to nearly the end of the stroke. The usual arrangement, by which steam and exhaust valves are moved by the same eccentric, only permits expansion with the range from the beginning to half-stroke. In the Corliss engine the latter construction is retained, with the object, in part, of securing a means of closing the valve by a "positive motion," should, by any accident, the closing not be effected by the weight or spring usually relied upon. [Illustration: FIG. 100.--Thurston's Greene-Engine Valve-Gear.] The steam-valve of the Greene engine, as designed by the author, is seen in Fig. 100, where the valve, _G H_, covering the port, _D_, in the steam-cylinder, _A B_, is moved by the rod, _J J_, connected to the rock-shaft, _M_, by the arm, _L K_. The line, _K I_, should, when carried out, intersect the valve-face at its middle point, under _G_. The characteristics of the American stationary engine, therefore, are high steam-pressure without condensation, an expansion valve-gear with drop cut-off adjustable by the governor, high piston-speed, and lightness combined with strength of construction. The pressure most commonly adopted in the boilers which furnish steam to this type of engine is from 75 to 80 pounds per square inch; but a pressure of 100 pounds is not infrequently carried, and the latter pressure may be regarded as a "mean maximum," corresponding to a pressure of 60 pounds at about the commencement of the period here considered--1850. Very much greater pressures have, however, been adopted by some makers, and immensely "higher steam" has been experimented with by several engineers. As early as 1823, Jacob Perkins[88] commenced experimenting with steam of very great tension. As has already been stated, the usual pressure at the time of Watt was but a few pounds--5 or 7--in excess of that of the atmosphere. Evans, Trevithick, and Stevens, had previously worked steam at pressures of from 50 to 75 pounds per square inch, and pressures on the Western rivers and elsewhere in the United States had already been raised to 100 or 150 pounds, and explosions were becoming alarmingly frequent. [88] Perkins was a native of Newburyport, Mass. He was born July 9, 1766, and died in London, July 30, 1849. He went to England when fifty-two years of age, to introduce his inventions. Perkins's experimental apparatus consisted of a copper boiler, of a capacity of about one cubic foot, having sides 3 inches in thickness. It was closed at the bottom and top, and had five small pipes leading from the upper head. This was placed in a furnace kept at a high temperature by a forced combustion. Safety-valves loaded respectively to 425 and 550 pounds per square inch were placed on each of two of the steam-pipes. Perkins used the steam generated under these great pressures in a little engine having a piston 2 inches in diameter and a stroke of 1 foot. It was rated at 10 horse-power.[89] [89] It was when writing of this engine that Stuart wrote, in 1824: "Judging from the rapid strides the steam-engine has made _during the last forty years_ to become a universal first-mover, and from the experience that has arisen from that extension, we feel convinced that every invention which diminishes its size without impairing its power brings it a step nearer to the assistance of the 'world's great laborers,' the husbandman and the peasant, for whom, as yet, it performs but little. At present, it is made occasionally to tread out the corn. What honors await not that man who may yet direct its mighty power to plough, to sow, to harrow, and to reap!" The progress of the steam-engine during those forty years does not to-day appear so astounding. The sentiment here expressed has lost none of its truth, nevertheless. In the year 1827, Perkins had attained working pressures, in a single-acting, single-cylinder engine, of upward of 800 pounds per square inch. At pressures exceeding 200 pounds, he had much trouble in securing effective lubrication, as all oils charred and decomposed at the high temperatures then unavoidably encountered, and he finally succeeded in evading this seemingly insurmountable obstacle by using for rubbing parts a peculiar alloy which required no lubrication, and which became so beautifully polished, after some wear, that the friction was less than where lubricants were used. At these high pressures Perkins seems to have met with no other serious difficulty. He condensed the exhaust-steam and returned it to the boiler, but did not attempt to create a vacuum in his condenser, and therefore needed no air-pump. Steam was cut off at one-eighth stroke. In the same year, Perkins made a compound engine on the Woolf plan, and adopted a pressure of 1,400 pounds, expanding eight times. In still another engine, intended for a steam-vessel, Perkins adopted, or proposed to adopt, 2,000 pounds pressure, cutting off the admission at one-sixteenth, in single-acting engines of 6 inches diameter of cylinder and 20 inches stroke of piston. The steam did not retain boiler-pressure at the cylinder, and this engine was only rated at 30 horse-power.[90] [90] Galloway and Hebert, on the Steam-Engine. London, 1836. Stuart follows a description of Perkins's work in the improvement of the steam-engine and the introduction of steam-artillery by the remark: " ... No other mechanic of the day has done more to illustrate an obscure branch of philosophy by a series of difficult, dangerous, and expensive experiments; no one's labors have been more deserving of cheering encouragement, and no one has received less. Even in their present state, his experiments are opening new fields for philosophical research, and his mechanism bids fair to introduce a new style into the proportions, construction, and form, of steam-machinery." Perkins's experience was no exception to the general rule, which denies to nearly all inventors a fair return for the benefits which they confer upon mankind. Another engineer, a few years later, was also successful in controlling and working steam under much higher pressures than are even now in use. This was Dr. Ernst Alban, a distinguished German engine-builder, of Plau, Mecklenburg, and an admirer of Oliver Evans, in whose path he, a generation later, advanced far beyond that great pioneer. Writing in 1843, he describes a system of engine and boiler construction, with which he used steam under pressures about equal to those experimentally worked by Jacob Perkins, Evans's American successor. Alban's treatise was translated and printed in Great Britain,[91] four years later. [91] "The High-Pressure Steam-Engine," etc. By Dr. Ernst Alban. Translated by William Pole, F. R. A. S. London, 1847. Alban, on one occasion, used steam of 1,000 pounds pressure. His boilers were similar in general form to the boiler patented by Stevens in 1805, but the tubes were horizontal instead of vertical. He evaporated from 8 to 10 pounds of water into steam of 600 to 800 pounds pressure with each pound of coal. He states that the difficulty met by Perkins--the decomposition of lubricants in the steam-cylinder--did not present itself in his experiments, even when working steam at a pressure of 600 pounds on the square inch, and he found that less lubrication was needed at such high pressures than in ordinary practice. Alban expanded his steam about as much as Evans, in his usual practice, carrying a pressure of 150 pounds, and cutting off at one-third; he adopted greatly increased piston-speed, attaining 300 feet per minute, at a time when common practice had only reached 200 feet. He usually built an oscillating engine, and rarely attached a condenser. The valve was the locomotive-slide.[92] The stroke was made short to secure strength, compactness, cheapness, and high speed of rotation; but Alban does not seem to have understood the principles controlling the form and proportions of the expansive engine, or the necessity of adopting considerable expansion in order to secure economy in working steam of great tension, and therefore was, apparently, not aware of the advantages of a long stroke in reducing losses by "dead-space," in reducing risk of annoyance by hot journals, or in enabling high piston-speeds to be adopted. He seems never to have attained a sufficiently high speed of piston to become aware that the oscillating cylinder cannot be used at speeds perfectly practicable with the fixed cylinder. [92] Invented by Joseph Maudsley, of London, 1827. Alban states that one of his smallest engines, having a cylinder 4-1/2 inches in diameter and 1 foot stroke of piston, with a piston-speed of but 140 to 160 feet per minute, developed 4 horse-power, with a consumption of 5.3 pounds of coal per hour. This is a good result for so small an amount of work, and for an engine working at so low a speed of piston. An engine of 30 horse-power, also working very slowly, required but 4.1 pounds of coal per hour per horse-power. The work of Perkins and of Alban, like that of their predecessors, Evans, Stevens, and Trevithick, was, however, the work of engineers who were far ahead of their time. The general practice, up to the time which marked the beginning of the modern "period of refinement," had been but gradually approximating that just described. Higher pressures were slowly approached; higher piston-speeds came slowly into use; greater expansion was gradually adopted; the causes of losses of heat were finally discovered, and steam-jacketing and external non-conducting coverings were more and more generally applied as builders became more familiar with their work. The "compound engine" was now and then adopted; and each experiment, made with higher steam and greater expansion, was more nearly successful than the last. Finally, all these methods of securing economy became recognized, and the reasons for their adoption became known. It then remained, as the final step in this progression, to combine all these requisites of economical working in a double-cylinder engine, steam-jacketed, well protected by non-conducting coverings, working steam of high pressure, and with considerable expansion at high piston-speed. This is now done by the best builders. One of the best examples of this type of engine is that constructed by the sons of Jacob Perkins, who continued the work of their father after his death. Their engines are single-acting, and the small or high-pressure cylinder is placed on the top of the larger or low-pressure cylinder. The valves are worked by rotating stems, and the loss of heat and burning of packing incident to the use of the common method are thus avoided. The stuffing-boxes are placed at the end of long sleeves, closely surrounding the vertical valve-stems also, and the water of condensation which collects in these sleeves is an additional and thorough protection against excessively high temperature at the packing. The piston-rings are made of the alloy which has been found to require no lubrication. Steam is usually worked at from 250 to 450 pounds, and is generated in boilers composed of small tubes three inches in diameter and three-eighths of an inch thick, which are tested under a pressure of 2,500 pounds per square inch. The safety-valve is usually loaded to 400 pounds. The boiler is fed with distilled water, obtained principally by condensation of the exhaust-steam, any deficiency being made up by the addition of water from a distilling apparatus. Under these conditions, but 1-1/4 pound of coal is consumed per hour and per horse-power. THE PUMPING-ENGINE in use at the present time has passed through a series of changes not differing much from that which has been traced with the stationary mill-engine. The Cornish engine is still used to some extent for supplying water to towns, and is retained at deep mines. The modern Cornish engine differs very little from that of the time of Watt, except in the proportions of parts and the form of its details. Steam-pressures are carried which were never reached during the preceding period, and, by careful adjustment of well-set and well-proportioned valves and gearing, the engine has been made to work rather more rapidly, and to do considerably more work. It still remains, however, a large, costly, and awkward contrivance, requiring expensive foundations, and demanding exceptional care, skill, and experience in management. It is gradually going out of use. This engine, as now constructed by good builders, is shown in section in Fig. 101. A comparison with the Watt engine of a century earlier will at once enable any one to appreciate the extent to which changes may be made in perfecting a machine, even after it has become complete, so far as supplying it with all essential parts can complete it. [Illustration: FIG. 101.--Cornish Pumping-Engine, 1880.] In the figure, _A_ is the cylinder, taking steam from the boiler through the steam-passage, _M_. The steam is first admitted above the piston, _B_, driving it rapidly downward and raising the pump-rod, _E_. At an early period in the stroke the admission of steam is checked by the sudden closing of the induction-valve at _M_, and the stroke is completed under the action of expanding steam assisted by the inertia of the heavy parts already in motion. The necessary weight and inertia is afforded, in many cases, where the engine is applied to the pumping of deep mines, by the immensely long and heavy pump-rods. Where this weight is too great, it is counterbalanced, and where too small, weights are added. When the stroke is completed, the "equilibrium valve" is opened, and the steam passes from above to the space below the piston, and an equilibrium of pressure being thus produced, the pump-rods descend, forcing the water from the pumps and raising the steam-piston. The absence of the crank, or other device which might determine absolutely the length of stroke, compels a very careful adjustment of steam-admission to the amount of load. Should the stroke be allowed to exceed the proper length, and should danger thus arise of the piston striking the cylinder-head, _N_, the movement is checked by buffer-beams. The valve-motion is actuated by a plug-rod, _J K_, as in Watt's engine. The regulation is effected by a "cataract," a kind of hydraulic governor, consisting of a plunger-pump, with a reservoir attached. The plunger is raised by the engine, and then automatically detached. It falls with greater or less rapidity, its velocity being determined by the size of the eduction-orifice, which is adjustable by hand. When the plunger reaches the bottom of the pump-barrel, it disengages a catch, a weight is allowed to act upon the steam-valve, opening it, and the engine is caused to make a stroke. When the outlet of the cataract is nearly closed, the engine stands still a considerable time while the plunger is descending, and the strokes succeed each other at long intervals. When the opening is greater, the cataract acts more rapidly, and the engine works faster. This has been regarded until recently as the most economical of pumping-engines, and it is still generally used in freeing mines of water, and in situations where existing heavy pump-rods may be utilized in counterbalancing the steam-pressure, and, by their inertia, in continuing the motion after the steam, by its expansion, has become greatly reduced in pressure. In this engine a gracefully-shaped and strong beam, _D_, has taken the place of the ruder beam of the earlier period, and is carried on a well-built wall of masonry, _R_. _F_ is the exhaust-valve, by which the steam passes to the condenser, _G_, beside which is the air-pump, _H_, and the hot-well, _I_. The cylinder is steam-jacketed, _P_, and protected against losses of heat by radiation by a brick wall, _O_, the whole resting on a heavy foundation, _Q_. The Bull Cornish engine is also still not infrequently seen in use. The Cornish engine of Great Britain averages a duty of about 45,000,000 pounds raised one foot high per 100 pounds of coal. More than double this economy has sometimes been attained. [Illustration: FIG. 102.--Steam-Pump.] A vastly simpler form of pumping-engine without fly-wheel is the now common "direct-acting steam-pump." This engine is generally made use of in feeding steam-boilers, as a forcing and fire pump, and wherever the amount of water to be moved is not large, and where the pressure is comparatively great. The steam-cylinder, _A R_, and feed-pump, _B Q_ (Fig. 102), are in line, and the two pistons have usually one rod, _D_, in common. The two cylinders are connected by a strong frame, _N_, and two standards fitted with lugs carry the whole, and serve as a means of bolting the pump to the floor or to its foundation. The method of working the steam-valve of the modern steam-pump is ingenious and peculiar. As shown, the pistons are moving toward the left; when they reach the end of their stroke, the face of the piston strikes a pin or other contrivance, and thus moves a small auxiliary valve, _I_, which opens a port, _E_, and causes steam to be admitted behind a piston, or permits steam to be exhausted, as in the figure, from before the auxiliary piston, _F_, and the pressure within the main steam-chest then forces that piston over, moving the main steam-valve, _G_, to which it is attached, admitting steam to the left-hand side of the main piston, and exhausting on the right-hand side, _A_. Thus the motion of the engine operates its own valves in such a manner that it is never liable to stop working at the end of the stroke, notwithstanding the absence of the crank and fly-wheel, or of independent mechanism, like the cataract of the Cornish engine. There is a very considerable variety of pumps of this class, all differing in detail, but all presenting the distinguishing feature of auxiliary valve and piston, and a connection by which it and the main engine each works the valve of the other combination. [Illustration: FIG. 103.--The Worthington Pumping-Engine, 1876. Section.] [Illustration: FIG. 104.--The Worthington Pumping-Engine.] In some cases these pumps are made of considerable size, and are applied to the elevation of water in situations to which the Cornish engine was formerly considered exclusively applicable. The accompanying figure illustrates such a pumping-engine, as built for supplying cities with water. This is a "compound" direct-acting pumping-engine. The cylinders, _A B_, are placed in line, working one pump, _F_, and operating their own air-pumps, _D D_, by a bell-crank lever, _L H_, connected to the pump-buckets by links, _I K_. Steam exhausted from the small cylinder, _A_, is further expanded in the large cylinder, _B_, and thence goes to the condenser, _C_. The valves, _N M_, are moved by the valve-gear, _L_, which is actuated by the piston-rod of a similar pair of cylinders placed by the side of the first. These valves are balanced, and the balance-plates, _R Q_, are suspended from the rods, _O P_, which allow them to move with the valves. By connecting the valves of each engine with the piston-rod of the other, it is seen that the two engines must work alternately, the one making a stroke while the other is still, and then itself stopping a moment while the latter makes its stroke. Water enters the pump through the induction-pipe, _E_, passes into the pump-barrel through the valves, _V V_, and issues through the eduction-valves, _T T_, and goes on to the "mains" by the pipe, _G_, above which is seen an air-chamber, which assists to preserve a uniform pressure on that side the pump. This engine works very smoothly and quietly, is cheap and durable, and has done excellent duty. Beam pumping-engines are now almost invariably built with crank and fly-wheel, and very frequently are compound engines. The accompanying illustration represents an engine of the latter form. [Illustration: FIG. 105.--Double-Cylinder Pumping-Engine, 1878.] [Illustration: FIG. 106.--The Lawrence Water-Works Engine.] _A_ and _B_ are the two steam-cylinders, connected by links and parallel motion, _C D_, to the great cast-iron beam, _E F_. At the opposite end of the beam, the connecting-rod, _G_, turns a crank, _H_, and fly-wheel, _L M_, which regulates the motion of the engine and controls the length of stroke, averting all danger of accident occurring in consequence of the piston striking either cylinder-head. The beam is carried on handsomely-shaped iron columns, which, with cylinders, pump, and fly-wheel, are supported by a substantial stone foundation. The pump-rod, _I_, works a double-acting pump, _J_, and the resistance to the issuing water is rendered uniform by an air-chamber, _K_, within which the water rises and falls when pressures tend to vary greatly. A revolving shaft, _N_, driven from the fly-wheel shaft, carries cams, _O P_, which move the lifting-rods seen directly over them and the valves which they actuate. Between the steam-cylinders and the columns which carry the beams is a well, in which are placed the condenser and air-pump. Steam is carried at 60 or 80 pounds pressure, and expanded from 6 to 10 times. [Illustration: FIG. 107.--The Leavitt Pumping-Engine.] A later form of double-cylinder beam pumping-engine is that invented and designed by E. D. Leavitt, Jr., for the Lawrence Water-Works, and shown in Figs. 106 and 107. The two cylinders are placed one on each side the centre of the beam, and are so inclined that they may be coupled to opposite ends of it, while their lower ends are placed close together. At their upper ends a valve is placed at each end of the connecting steam-pipe. At their lower ends a single valve serves as exhaust-valve to the high-pressure and as steam-valve to the low-pressure cylinder. The pistons move in opposite directions, and steam is exhausted from the high-pressure cylinder directly into the nearer end of the low-pressure cylinder. The pump, of the "Thames-Ditton" or "bucket-and-plunger" variety, takes a full supply of water on the down-stroke, and discharges half when rising and half when descending again. The duty of this engine is reported by a board of engineers as 103,923,215 foot-pounds for every 100 pounds of coal burned. The duty of a moderately good engine is usually considered to be from 60 to 70 millions. This engine has steam-cylinders of 17-1/2 and 36 inches diameter respectively, with a stroke of 7 feet. The pump had a capacity of about 195 gallons, and delivered 96 per cent. Steam was carried at a pressure of 75 pounds above the atmosphere, and was expanded about 10 times. Plain horizontal tubular boilers were used, evaporating 8.58 pounds of water from 98° Fahr. per pound of coal. STEAM-BOILERS.--The steam supplied to the forms of stationary engine which have been described is generated in steam-boilers of exceedingly varied forms. The type used is determined by the extent to which their cost is increased in the endeavor to economize fuel by the pressure of steam carried, by the greater or less necessity of providing against risk of explosion, by the character of the feed-water to be used, by the facilities which may exist for keeping in good repair, and even by the character of the men in whose hands the apparatus is likely to be placed. As has been seen, the changes which have marked the growth and development of the steam-engine have been accompanied by equally marked changes in the forms of the steam-boiler. At first, the same vessel served the distinct purposes of steam-generator and steam-engine. Later, it became separated from the engine, and was then specially fitted to perform its own peculiar functions; and its form went through a series of modifications under the action of the causes already stated. When steam began to be usefully applied, and considerable pressures became necessary, the forms given to boilers were approximately spherical, ellipsoidal, or cylindrical. Thus the boilers of De Caus (1615) and of the Marquis of Worcester (1663) were spherical and cylindrical; those of Savery (1698) were ellipsoidal and cylindrical. After the invention of the steam-engine of Newcomen, the pressures adopted were again very low, and steam-boilers were given irregular forms until, at the beginning of the present century, they were again of necessity given stronger shapes. The material was at first frequently copper; it is now usually wrought-iron, and sometimes steel. The present forms of steam-boilers may be classified as plain, flue, and tubular boilers. The plain cylindrical or common cylinder boiler is the only representative of the first class in common use. It is perfectly cylindrical, with heads either flat or hemispherical. There is usually attached to the boiler a "steam-drum" (a small cylindrical vessel), from which the steam is taken by the steam-pipe. This enlargement of the steam-space permits the mist, held in suspension by the steam when it first rises from the surface of the water, to separate more or less completely before the steam is taken from the boiler. [Illustration: FIG. 108.--Babcock & Wilcox's Vertical Boiler.] Flue-boilers are frequently cylindrical, and contain one or more cylindrical flues, which pass through from end to end, beneath the water-line, conducting the furnace-gases, and affording a greater area of heating-surface than can be obtained in the plain boiler. They are usually from 30 to 48 inches in diameter, and one foot or less in length for each inch of diameter. Some are, however, made 100 feet and more in length. The boiler is made of iron 1/4 to 3/8 of an inch in thickness, with hemispherical or carefully stayed flat heads, and without flues. The whole is placed in a brickwork setting. These boilers are used where fuel is inexpensive, where the cost of repairing would be great, or where the feed-water is impure. A cylindrical boiler, having one flue traversing it longitudinally, is called a Cornish boiler, as it is generally supposed to have been first used in Cornwall. It was probably first invented by Oliver Evans in the United States, previous to 1786, at which time he had it in use. The flue has usually a diameter 0.5 or 0.6 the diameter of the boiler. A boiler containing two longitudinal flues is called the Lancashire boiler. This form was also introduced by Oliver Evans. The flues have one-third the diameter of the boiler. Several flues of smaller diameter are often used, and when a still greater proportional area of heating-surface is required, tubes of from 1-1/4 inch to 4 or 5 inches in diameter are substituted for flues. The flues are usually constructed by riveting sheets together, as in making the shell or outer portion. They are sometimes welded by British manufacturers, but rarely if ever in the United States. Tubes are always "lap-welded" in the process of rolling them. Small tubes were first used in the United States, about 1785. In portable, locomotive, and marine steam-boilers, the fire must be built within the boiler itself, instead of (as in the above described stationary boilers) in a furnace of brickwork exterior to the boiler. The flame and gases from the furnace or fire-box in these kinds of boiler are never led through brick passages en route to the chimney, as often in the preceding case, but are invariably conducted through flues or tubes, or both, to the smoke-stack. These boilers are also sometimes used as stationary boilers. Fig. 108 represents such a steam-boiler in section, as it is usually exhibited in working drawings. Provision is made to secure a good circulation of water in these boilers by means of the "baffle-plates," seen in the sketch, which compel the water to flow as indicated by the arrows. The tubes are frequently made of brass or of copper, to secure rapid transmission of heat to the water, and thus to permit the use of a smaller area of heating-surface and a smaller boiler. The steam-space is made as large as possible, to secure immunity from "priming" or the "entrainment" of water with the steam. This type of steam-boiler, invented by Nathan Read, of Salem, Mass., in 1791, and patented in April of that year, was the earliest of the tubular boilers. In the locomotive boiler (Fig. 109), as in the preceding, the characteristics are a fire-box at one end of the shell and a set of tubes through which the gases pass directly to the smoke-stack. Strength, compactness, great steaming capacity, fair economy, moderate cost, and convenience of combination with the running parts, are secured by the adoption of this form. It is frequently used also for portable and stationary engines. It was invented in France by M. Seguin, and in England by Booth, and used by George Stephenson at about the same time--1828 or 1829. [Illustration: FIG. 109.--Stationary "Locomotive" Boiler.] Since the efficiency of a steam-boiler depends upon the extent of effective heating-surface per unit of weight of fuel burned in any given time--or, ordinarily, upon the ratio of the areas of heating and grate surface--peculiar expedients are sometimes adopted, having for their object the increase of heating-surface, without change of form of boiler and without proportionate increase of cost. One of these methods is that of the use of Galloway conical tubes (Fig. 110). These are very largely used in Great Britain, but are seldom if ever seen in the United States. The Cornish boiler, to which they are usually applied, consists of a large cylindrical shell, 6 feet or more in diameter, containing one tube of about one-half as great dimensions, or sometimes two of one-third the diameter of the shell each. Such boilers have a very small ratio of heating to grate surface, and their large tubes are peculiarly liable to collapse. To remove these objections, the Messrs. Galloway introduced stay-tubes into the flues, which tubes are conical in form, and are set in either a vertical or an inclined position, the larger end uppermost. The area of heating-surface is thus greatly increased, and, at the same time, the liability to collapse is reduced. The same results are obtained by another device of Galloway, which is sometimes combined with that just described in the same boiler. Several sheets in the flue have "pockets" worked into them, which pockets project into the flue-passage. [Illustration: FIG. 110.] Another device is that of an American engineer, Miller, who surrounds the furnace of cylindrical and other boilers with water-tubes. The "fuel-economizers" of Greene and others consist of similar collections of tubes set in the flues, between the boiler and the chimney. "_Sectional_" boilers are gradually coming into use with high pressures, on account of their greater safety against disastrous explosions. The earliest practicable example of a boiler of this class was probably that of Colonel John Stevens, of Hoboken, N. J. Dr. Alban, who, forty years later, attempted to bring this type into general use, and constructed a number of such boilers, did not succeed. Their introduction, like that of all radical changes in engineering, has been but slow, and it has been only recently that their manufacture has become an important branch of industry. A committee of the American Institute, of which the author was chairman, in 1871, examined several boilers of this and the ordinary type, and tested them very carefully. They reported that they felt "confident that the introduction of this class of steam-boilers will do much toward the removal of the cause of that universal feeling of distrust which renders the presence of a steam-boiler so objectionable in every locality. The difficulties in thoroughly inspecting these boilers, in regulating their action, and other faults of the class, are gradually being overcome, and the committee look forward with confidence to the time when their use will become general, to the exclusion of older and more dangerous forms of steam-boilers." The economical performance of these boilers with a similar ratio of heating to grate surface is equal to that of other kinds. In fact, they are usually given a somewhat higher ratio, and their economy of fuel frequently exceeds that of the other types. Their principal defect is their small capacity for steam and water, which makes it extremely difficult to obtain steady steam-pressure. Where they are employed, the feed and draught should be, if possible, controlled by automatic attachments, and the feed-water heated to the highest attainable temperature. Their satisfactory working depends, more than in other cases, on the ability of the fireman, and can only be secured by the exercise of both care and skill. Many forms of these boilers have been devised. Walter Hancock constructed boilers for his steam-carriage of flat plates connected by stay-bolts, several such sections composing the boiler; and about the same time (1828) Sir Goldsworthy Gurney constructed for a similar purpose boilers consisting of a steam and a water reservoir, placed one above the other, and connected by triangularly-bent water-tubes exposed to the heat of the furnace-gases. Jacob Perkins made many experiments looking to the employment of very high steam-pressures, and in 1831 patented a boiler of this class, in which the heating-surfaces nearest the fire were composed of iron tubes, which tubes also served as grate-bars. The steam and water space was principally comprised within a comparatively large chamber, of which the walls were secured by closely distributed stay-bolts. For extremely high pressures, boilers composed only of tubes were used. Dr. Ernst Alban described the boiler already referred to, and its construction and operation, and stated that he had experimented with pressures as high as 1,000 pounds to the square inch. The Harrison steam-boiler, which has been many years in use in the United States, consists of several sections, each of which is made up of hollow globes of cast-iron, communicating with each other by necks cast upon the spheres, and fitted together with faced joints. Long bolts, extending from end to end of each row, bind the spheres together. (_See_ Fig. 111.) [Illustration: FIG. 111.--Harrison's Sectional Boiler.] An example of another modern type in extensive use is given in Fig. 112, a semi-sectional boiler, which consists of a series of inclined wrought-iron tubes, connected by T-heads, which form the vertical water-channels, at each end. The joints are faced by milling them, and then ground so perfectly tight that a pressure of 500 pounds to the square inch is insufficient to produce leakage. No packing is used. The fire is made under the front and higher end of the tubes, and the products of combustion pass up between the tubes into a combustion-chamber under the steam and water drum; hence they pass down between the tubes, then once more up through the space between the tubes, and off to the chimney. The steam is taken out at the top of the steam-drum near the back end of the boiler. The rapid circulation prevents to some extent the formation of deposits or incrustations upon the heating-surfaces, sweeping them away and depositing them in the mud-drum, whence they are blown out. Rapid circulation of water, as has been shown by Prof. Trowbridge, also assists in the extraction of the heat from the gases, by the presentation of fresh water continually, as well as by the prevention of incrustation. [Illustration: FIG. 112.--Babcock and Wilcox's Sectional Boiler.] Attempts have been made to adapt sectional boilers to marine engines; but very little progress has yet been made in their introduction. The Root sectional boiler (Fig. 113), an American design, which is in extensive use in the United States and Europe, has also been experimentally placed in service on shipboard. Its heating-surface consists wholly of tubes, which are connected by a peculiarly formed series of caps; the joints are made tight with rubber "grummets." [Illustration: FIG. 113.--Root Sectional Boiler.] SECTION II.--PORTABLE AND LOCOMOTIVE ENGINES. Engines and boilers, when of small size, are now often combined in one structure which may be readily transported. Where they have a common base-plate simply, as in Fig. 114, they are called, usually, "semi-portable engines." These little engines have some decided advantages. Being attached to one base, the combined engine and boiler is easily transported, occupies little space, and may very readily be mounted upon wheels, rendering it peculiarly well adapted for agricultural purposes. [Illustration: FIG. 114.--Semi-Portable Engine, 1878.] The example here shown differs in its design from those usually seen in the market. The engine is not fastened to or upon the boiler, and is therefore not affected by expansion, nor are the bearings overheated by conduction or by ascending heat from the boiler. The fly-wheel is at the base, which arrangement secures steadiness at the high speed which is a requisite for economy of fuel. The boilers are of the upright tubular style, with internal fire-box, and are intended to be worked at 150 pounds pressure per inch. They are fitted with a baffle-plate and circulating-pipe, to prevent priming, and also with a fusible plug, which will melt and prevent the crown-sheet of the boiler burning, if the water gets low. [Illustration: FIG. 115.--Semi-Portable Engine, 1878.] Another illustration of this form of engine, as built in small sizes, is seen below. The peculiarity of this engine is, that the cylinder is placed in the top of the boiler, which is upright. By this arrangement the engine is constantly drawing from the boiler the hottest and driest steam, and there is thus no liability of serious loss by condensation, which is rapid, even in a short pipe, when the engine is separate from the boiler. The engine illustrated is rated at 10 horse-power, and makers are always expected to guarantee their machines to work up to the rated power. The cylinder is 7 by 7 inches, and the main shaft is directly over it. On this shaft are three eccentrics, one working the pump, one moving the valves, and the third one operating the cut-off. The driving-pulley is 20 inches in diameter, and the balance-wheel 30 inches. The boiler has 15 1-1/4-inch flues. It is furnished with a heater in its lower portion. The boiler of this engine is tested up to 200 pounds, and is calculated to carry 100 pounds working pressure, though that is not necessary to develop the full power of the engine. The compactness of the whole machine is exceptional. It can be set up in a space 5 feet square and 8 feet high. The weight of the 10 horse-power engine is 1,540 pounds, and of the whole machine 4,890 pounds, boxed for shipment. Every part of the mechanism usually fits and works with the exactness of a gun-lock, as each piece is carefully made to gauge. Portable engines are those which are especially intended to be moved conveniently from place to place. The engine is usually attached to the boiler, and the feed-pump is generally attached to the engine. The whole machine is carried on wheels, and is moved from one place to another, usually by horses, but sometimes by its own engine, which is coupled by an engaging and disengaging apparatus to the rear-wheels. English builders have usually excelled in the construction of this class of steam-engine, although it is probable that the best American engines are fully equal to them in design, material, and construction. The later work of the best-known English builders has given economical results that have surprised engineers. The annual "shows" of the Royal Agricultural Society have elicited good evidence of skill in management as well as of excellence of design and construction. Some little portable engines have exhibited an economical efficiency superior to that of the largest marine engines of any but the compound type, and even closely competing with that form. The causes of this remarkable economy are readily learned by an inspection of these engines, and by observation of the method of managing them at the test-trial. The engines are usually very carefully designed. The cylinders are nicely proportioned to their work, and their pistons travel at high speed. Their valve-gear consists usually of a plain slide-valve, supplemented by a separate expansion-slide, driven by an independent eccentric, and capable of considerable variation in the point of cut-off. This form of expansion-gear is very effective--almost as much so as a drop cut-off--at the usual grade of expansion, which is not far from four times. The governor is usually attached to a throttle-valve in the steam-pipe, an arrangement which is not the best possible under variable loads, but which produces no serious loss of efficiency when the engine is driven, as at competitive trials, under the very uniform load of a Prony strap-brake and at very nearly the maximum capacity of the machine. The most successful engines have had steam-jacketed cylinders--always an essential to maximum economy--with high steam and a considerable expansion. The boilers are strongly made, and are, as are also all other heated surfaces, carefully clothed with non-conducting material, and well lagged over all. The details are carefully proportioned, the rods and frames are strong and well secured together, and the bearings have large rubbing-surfaces. The connecting-rods are long and easy-working, and every part is capable of doing its work without straining and with the least friction. In handling the engines at the competitive trial, most experienced and skillful drivers are selected. The difference between the performances of the same engine in different hands has been found to amount to from 10 to 15 per cent., even where the competitors were both considered exceptionally skillful men. In manipulating the engine, the fires are attended to with the utmost care; coal is thrown upon them at regular and frequent intervals, and a uniform depth of fuel and a perfectly clean fire are secured. The sides and corners of the fire are looked after with especial care. The fire-doors are kept open the least possible time; not a square inch of grate-surface is left unutilized, and every pound of coal gives out its maximum of calorific power, and in precisely the place where it is needed. Feed-water is supplied as nearly as possible continuously, and with the utmost regularity. In some cases the engine-driver stands by his engine constantly, feeding the fire with coal in handfuls, and supplying the water to the heater by hand by means of a cup. Heaters are invariably used in such cases. The exhaust is contracted no more than is absolutely necessary for draught. The brake is watched carefully, lest irregularity of lubrication should cause oscillation of speed with the changing resistance. The load is made the maximum which the engine is designed to drive with economy. Thus all conditions are made as favorable as possible to economy, and they are preserved as invariable as the utmost care on the part of the attendant can make them. These trials are usually of only three or five hours' duration, and thus terminate before it becomes necessary to clean fires. The following are results obtained at the trial of engines which took place in July, 1870, at the Oxford Agricultural Fair: KEY: A: Number. B: Diameter. C: Stroke. D: Nominal. E: Dynamometric. F: Point of cut off. G: Revolutions per minute. H: Pounds coal per horse-power per hour. ---------------+-------------+-----+--------------+------+------+---- MAKERS' NAME | CYLINDERS. | | HORSE-POWER. | | | AND +-----+-------+ +-------+------+ | | RESIDENCE. | A | B | C | D | E | F | G | H ---------------+-----+-------+-----+-------+------+------+------+---- | |Inches.| In. | | | | | Clayton, | | | | | | | | Shuttleworth | 1 | 7 | 12 | 4 | 4.42 | ... |121.65|3.73 & Co., Lincoln | | | | | | | | | | | | | | | | Brown & May, | | | | | | | | Devizes | 1 | 7-3/16| 12 | 4 | 4.19 | 11.48|125.65|4.44 | | | | | | | | Reading Iron- | | | | | | | | Works Company, | 1 | 5-3/4 | 14 | 4 | 4.16 | ... |145.7 |4.65 Reading | | | | | | | | ---------------+-----+-------+-----+-------+------+------+------+---- These were horizontal engines, attached to locomotive boilers. At a similar exhibition held at Bury, in 1867, considerably better results even than these were reported, as below, from engines of similar size and styles: KEY: A: Number. B: Diameter. C: Stroke. D: Nominal. E: Dynamometric. F: Point of cut off. G: Revolutions per minute. H: Pounds coal per horse-power per hour. ---------------+-------------+-----+--------------+------+------+---- MAKERS' NAME | CYLINDERS. | | HORSE-POWER. | | | AND +-----+-------+ +-------+------+ | | RESIDENCE. | A | B | C | D | E | F | G | H ---------------+-----+-------+-----+-------+------+------+------+---- | |Inches.| In. | | | | | Clayton, | | | | | | | | Shuttleworth | 1 |10 | 20 | 10 | 11.00| 3.10 | 71.5 | 4.13 & Co., Lincoln | | | | | | | | | | | | | | | | Reading Iron- | | | | | | | | Works Company, | 1 | 8-5/8 | 20 | 10 | 10.43| 1.4 |109.4 | 4.22 Reading | | | | | | | | ---------------+-----+-------+-----+-------+------+------+------+---- With all these engines steam-jackets were used; the feed-water was highly and uniformly heated by exhaust-steam; the coal was selected, finely broken, and thrown on the fire with the greatest care; the velocity of the engines, the steam-pressure, and the amount of feed-water, were very carefully regulated, and all bearings were run quite loose; the engine-drivers were usually expert "jockeys." The next illustration represents the portable steam-engine as built by one of the oldest and most experienced manufacturers of such engines in the United States. In the boilers of these engines the heating-surface is given less extent than in the stationary engine-boiler, but much greater than in the locomotive, and varies from 10 to 20 square feet per horse-power. The boilers are made very strong, to enable them to withstand the strains due to the attached engine, which are estimated as equivalent to from one-tenth to one-fifth that due to the steam-pressure. The boiler is sometimes given even double the strength usual with stationary boilers of similar capacity. The engine is mounted, in this example, directly over the boiler, and all parts are in sight and readily accessible to the engineer. [Illustration: FIG. 116.--The Portable Steam-Engine, 1878.] One of these engines, of 20 horse-power, has a steam-cylinder 10 inches in diameter and 18 inches stroke of piston, making 125 revolutions per minute, and has 9 square feet of grate-surface and 288 feet of heating-surface. It weighs about 4-1/2 tons. Steam is carried at 125 pounds. In the class of engines just described, the draught is obtained by the blast of the exhaust-steam which is led into the chimney. Such engines are now sold at from $120 to $150 per horse-power, according to size and quality, the smaller engines costing most. The usual consumption of fuel is from 4 to 6 pounds per hour and per horse-power, burning from 15 to 20 pounds on each square foot of grate, and each pound evaporating about 8 pounds of water. A usual weight is, for the larger sizes, 500 pounds per horse-power. [Illustration: FIG. 117.--The Thrashers' Road-Engine, 1878.] These engines are sometimes arranged to propel themselves, as in the Mills "Thrashers'" road-engine or locomotive, of which the accompanying engraving is a good representation. This engine is proportioned for hauling a tank containing 10 barrels, or more, of water and a grain-separator over all ordinary roads, and to drive a thrashing-machine or saw-mill, developing 20 or 25 horse-power. This example of the road-engine has a boiler built to work at 250 pounds of steam; the engine is designed for a maximum power of 30 horses. This engine has a balanced valve and automatic cut-off, and is fitted with a reversing-gear for use on the road. The driving-wheels are of wrought-iron, 56 inches diameter and 8 inches wide, with cast-iron driving-arms. Both wheels are drivers on curves as well as on straight lines. The engine is guided and fired by one man, and the total weight is so small that it will pass safely over any good country bridge. A brake is attached, to insure safety when going down-hill. Although designed to move at a speed of about three miles per hour, the velocity of the piston may be increased so that four miles per hour may be accomplished when necessary. [Illustration: FIG. 118.--Fisher's Steam-Carriage.] This is an excellent example of this kind of engine as constructed at the present time. The strongly-built boiler, with its heater, the jacketed cylinder, and light, strong frame of the engine, the steel running-gear, the carefully-covered surfaces of cylinder and boiler, and excellent proportions of details, are illustrations of good modern engineering, and are in curious contrast with the first of the class, built a century earlier by Smeaton. Steam-carriages for passengers are now rarely built. Fig. 118 represents that designed by Fisher about 1870 or earlier. It was only worked experimentally. [Illustration: FIG. 119.--Road and Farm Locomotive.] The above is an engraving of a road and farm locomotive as built by one of the most successful among several British firms engaged in this work. The capacity of these engines has been determined by experiment by the author in the United States, and abroad by several distinguished engineers. The author made a trial of one of these engines at South Orange, N. J., to determine its power, speed, and convenience of working and man[oe]uvring. The following were the principal dimensions: Weight of engine, complete, 5 tons 4 cwt. 11,648 pounds. Steam-cylinder--diameter 7-3/4 inches. Stroke of piston 10 inches. Revolution of crank to one of driving-wheels 17 Driving-wheels--diameter 60 inches. " breadth of tire 10 inches. " weight, each 450 pounds. Boiler--length over all 8 feet. " diameter of shell 30 feet. " thickness of shell 7/16 inch. " fire-box sheets, outside, thickness 1/2 inch. Load on driving-wheels, 4 tons 10 cwt. 10,080 pounds. The boiler was of the ordinary locomotive type, and the engine was mounted upon it, as is usual with portable engines. The steam-cylinder was steam-jacketed, in accordance with the most advanced practice here and abroad. The crank-shaft and other wrought-iron parts subjected to heavy strains were strong and plainly finished. The gearing was of malleableized cast-iron, and all bearings, from crank-shaft to driving-wheel, on each side, were carried by a single sheet of half-inch plate, which also formed the sides of the fire-box exterior. The following is a summary of the conclusions deduced by the author from the trial, and published in the _Journal of the Franklin Institute_: A traction-engine may be so constructed as to be easily and rapidly man[oe]uvred on the common road; and an engine weighing over 5 tons may be turned continuously without difficulty on a circle of 18 feet radius, or even on a road but little wider than the length of the engine. A locomotive of 5 tons 4 hundredweight has been constructed, capable of drawing on a good road 23,000 pounds up a grade of 533 feet to the mile, at the rate of four miles an hour; and one might be constructed to draw more than 63,000 pounds up a grade of 225 feet to the mile, at the rate of two miles an hour. It was further shown that the coefficient of traction with heavily-laden wagons on a good macadamized road is not far from .04; the traction-power of this engine is equal to that of 20 horses; the weight, exclusive of the weight of the engine, that could be drawn on a level road, was 163,452 pounds; and the amount of fuel required is estimated at 500 pounds a day. The advantages claimed for the traction-engine over horse-power are: no necessity for a limitation of working-hours; a difference in first cost in favor of steam; and in heavy work on a common road the expense by steam is less than 25 per cent. of the average cost of horse-power, a traction-engine capable of doing the work of 25 horses being worked at as little expense as 6 or 8 horses. The cost of hauling heavy loads has been estimated at 7 cents per ton per mile. Such engines are gradually becoming useful in steam-ploughing. Two systems are adopted. In the one the engine is stationary, and hauls a "gang" of ploughs by means of a windlass and wire rope; in the other the engine traverses a field, drawing behind it a plough or a gang of ploughs. The latter method has been proposed for breaking up prairie-land. Thus, thirty years after the defeat of the intelligent, courageous, and persistent Hancock and his coworkers in the scheme of applying the steam-engine usefully on the common road, we find strong indications that, in a new form, the problem has been again attacked, and at least partially solved. One of the most important of the prerequisites to ultimate success in the substitution of steam for animal power on the highway is that our roads shall be well made. As the greatest care and judgment are exercised, and an immense outlay of capital is considered justifiable, in securing easy grades and a smooth track on our railroad routes, we may readily believe that similar precaution and outlay will be found advisable in adapting the common road to the road-locomotive. It would seem to the engineer that the natural obstacles generally supposed to stand in the way have, after all, no real existence. The principal inconvenience that may be anticipated will probably arise from the carelessness or avarice of proprietors, which may sometimes cause them to appoint ignorant and inefficient engine-drivers, giving them charge of what are always excellent servants, but terrible masters. Nevertheless, as the transportation of passengers on railroads is found to be attended with less liability to loss of life or injury of person than their carriage by stage-coach, it will be found, very probably, that the general use of steam in transporting freight on common roads may be attended with less risk to life or property than to-day attends the use of horse-power. The STEAM FIRE-ENGINE is still another form of portable engine. It is also one of the latest of all applications of steam-power. The steam fire-engine is peculiarly an American production. Although previously attempted, their permanently successful introduction has only occurred within the last fifteen years. [Illustration: FIG. 120.--The Latta Steam Fire-Engine.] As early as 1830, Braithwaite and Ericsson, of London, England, built an engine with steam and pump cylinders of 7 and 6-1/2 inches diameter, respectively, with 16 inches stroke of piston. This machine weighed 2-1/2 tons, and is said to have thrown 150 gallons of water per minute to a height of between 80 and 100 feet. It was ready for work in about 20 minutes after lighting the fire. Braithwaite afterward supplied a more powerful engine to the King of Prussia, in 1832. The first attempt made in the United States to construct a steam fire-engine was probably that of Hodge, who built one in New York in 1841. It was a strong and very effective machine, but was far too heavy for rapid transportation. The late J. K. Fisher, who throughout his life persistently urged the use of steam-carriages and traction-engines, designing and building several, also planned a steam fire-engine. Two were built from his design by the Novelty Works, New York, about 1860, for Messrs. Lee & Larned. They were "self-propellers," and one of them, built for the city of Philadelphia, was sent to that city over the highway, driven by its own engines. The other was built for and used by the New York Fire Department, and did good service for several years. These engines were heavy, but very powerful, and were found to move at good speed under steam and to man[oe]uvre well. The Messrs. Latta, of Cincinnati, soon after succeeded in constructing comparatively light and very effective engines, and the fire department of that city was the first to adopt steam fire-engines definitely as their principal reliance. This change has now become general. The steam fire-engine has now entirely displaced the old hand-engine in all large cities. It does its work at a fraction of the cost of the latter. It can force its water to a height of 225 feet, and to a distance of more than 300 feet horizontally, while the hand-engine can seldom throw it one-third these distances; and the "steamer" may be relied upon to work at full power many hours if necessary, while the men at the hand-engine soon become fatigued, and require frequent relief. The city of New York has 40 steam fire-engines. One engine to every 10,000 inhabitants is a proper proportion. In the standard steam fire-engine (Fig. 120) reciprocating engines and pumps are adopted, as seen in section in Fig. 121, in which _A_ is the furnace, and _B_ the set of closely-set vertical fire-tubes in the boiler. _C_ is the combustion-chamber, _D_ the smoke-pipe, and _R_ the steam-space. _E_ is the steam-cylinder, and _F_ the pump, which is seen to be double-acting. There are two pairs of engines and pumps, working on cranks, set at right angles, and turning a balance-wheel seen behind them. _G_ is the feed-pump which supplies water to the boiler, _H_ the air-chamber which equalizes the water-pressure, which reaches it through the pipe, _I J_. _K_ is the feed-water tank, under the driver's seat, _L_, which, with the engines and boiler, are carried on the frame, _M M_. The fireman stands on the platform, _N_. When it is necessary to move the machine, an endless chain connects the crank-shaft with the rear-wheels, and the engine, with pumps shut off, is thus made to drive the wheels at any desired speed. [Illustration: FIG. 121.--The Amoskeag Engine. Section.] [Illustration: FIG. 122.--The Silsby Rotary Steam Fire-Engine.] A self-propelling engine by the Amoskeag Company had the following dimensions and performance: Weight, 4 tons; speed, 8 miles per hour; steam-pressure, 75 pounds per square inch; height of stream from 1-1/4-inch nozzle, 225 feet; 1-3/4-inch nozzle, 150 feet; distance horizontally, 1-1/4-inch nozzle, 300 feet; 1-3/4-inch, 250 feet--a performance which contrasts wonderfully with that of the hand-worked fire-engine which these engines have now superseded. It has recently become common to construct the steam fire-engine with rotary engine and pump (Fig. 122). The superiority of a rotary motion for a steam-engine is apparently so evident that many attempts have been made to overcome the practical difficulties to which it is subject. One of these difficulties, and the principal one, has been the packing of the part which performs the office of the piston in the straight cylinder. Robert Stephenson once expressed the opinion that a rotary engine would never be made to work successfully, on account of this difficulty of packing. The most palpable of the advantages of the rotary engine are the reduction in the size of the engine, claimed to result from the great velocity of the piston; the avoidance of great accidental strains, especially noticed in propelling ships; and a great saving of the power which is asserted to be expended in the reciprocating engine in overcoming the inertia while changing the direction of the motions. These advantages adapt the rotary engine, in an especial manner, to the driving of a locomotive or steam fire-engine. [Illustration: FIG. 123.--Rotary Steam-Engine.] [Illustration: FIG. 124.--Rotary Pump.] In the Holly rotary engine, seen in Fig. 123, eccentrics and sliding-cams, which are frequently used in rotary engines, and which are objectionable on account of their great friction, are avoided. Corrugated pistons, or irregular cams, _C D_, are adopted, forming chambers within the cases. In the engine the steam enters at _A_, at the bottom of the case, and presses the cams apart. The only packing used is in the ends of the long metal cogs, which are ground to fit the case and are kept out by the momentum of the cams, assisted by a slight spring back of the packing-pieces. The friction on the pump (Fig. 124) is said to be less than in the engine. This is the reason given in support of the claim that the rotary engine forces water to a given distance with from one-fourth to one-third the steam-pressure necessary to drive all reciprocating engines. The smaller amount of power necessary to do the work, the less strain and consequent wear and tear upon the whole machine, are said to make it more durable and reliable. The pump being chambered, its liability to injury by the use of dirty or gritty water is lessened, and it is stated that it will last for years, pumping gritty water that would soon cut out a piston-pump. The pump used with this engine is, as shown in the above illustration, somewhat similar to the rotary engine driving it. Each of the revolving pistons has three long teeth bearing against the cylinder, and packed, to prevent leakage, like the engine-cams. They are carried on steel shafts coupled to the engine-shafts. The water enters at _E_ and is discharged at _F_, and the passages are purposely made large in order that sand, chips, and dirt, which may enter with the water, may pass through. The rotary engine is gradually coming into use for various special purposes, where small power is called for, and where economy of fuel is not important; but it has never yet competed, and may perhaps never in the future compete, with the reciprocating-piston engine where large engines are required, or where even moderate economy of fuel is essential. This form of engine has assumed so little importance, in fact, in the application of the steam-engine, that comparatively little is known of its history. Watt invented a rotary engine, and Yule many years afterward (1836) constructed such engines at Glasgow. Lamb patented another in 1842, Behrens still another in 1847. Napier, Hall, Massey, Holly, La France, and others, have built engines of this class in later times. Nearly all consist either of cams rotating in gear, as in those above sketched, or of a piston set radially in a cylinder of small diameter, which turns on its axis within a much larger cylinder set eccentrically, the piston, as the former turns, sliding in and out of the smaller cylinder as its outer edge slides in contact with the inner surface of the larger. In some forms of rotary engine, a piston revolves on a central shaft, and a sliding abutment in the external cylinder serves to separate the steam from the exhaust side and to confine the steam expanding while doing work. Nearly all of these combinations are also used as pumps. Fire-engines, made by the best-known American builders of engines, with reciprocating engines and pumps, such as are in general use in the United States, have become standard in general plan and arrangement of details. These are probably the best illustrations of extreme lightness, combined with strength of parts and working power, which have ever been produced in any branch of mechanical engineering. By using a small boiler crowded with heating-surface, very carefully proportioned and arranged, and with small water-spaces; by adopting steel for running-gear and working parts wherever possible; by working at high piston-speed and with high steam-pressure; by selecting fuel with extreme care--by all these expedients, the steam fire-engine has been brought, in this country, to a state of efficiency far superior to anything seen elsewhere. Steam is raised with wonderful promptness, even from cold water, and water is thrown from the nozzle at the end of long lines of hose to great distances. But this combination of lightness with power is only attained at the expense of a certain regularity of action which can only be secured by greater water and steam capacity in the boiler. The small quantity of water contained within the boiler makes it necessary to give constant attention to the feed, and the tendency, almost invariably observed, to serious foaming and priming not only compels unintermitted care while running, but even introduces an element of danger which is not to be despised, even though the machine be in charge of the most experienced and skillful attendants. Even the greatest care, directed by the utmost skill, would not avail to prevent frequent explosions, were it not for the fact that it rarely, if ever, happens that accidents to such boilers occur from low water, unless the boiler is actually completely emptied of water. In driving them at fires, they frequently foam so violently that it is utterly impossible to obtain any clew to the amount of water present, and the attendant usually keeps his feed-pump on and allows the foaming to go on. As long as water is passing into the boiler it is very unlikely that any portion will become overheated and that accident will occur. Such management appears very reckless, and yet accident from such a cause is exceedingly rare. The changes which have been made in LOCOMOTIVE-CONSTRUCTION during the past few years have also been in the direction of the refinement of the earlier designs, and have been accompanied by corresponding changes in all branches of railroad-work. The adjustment of parts to each other and proportioning them to their work, the modification of the minor details to suit changes of general dimensions, the improvement of workmanship, and the use of better material, have signalized this latest period. Special forms of engine have been devised for special kinds of work. Small, light tank-engines (Fig. 125), carrying their own fuel and water without "tenders," are used for moving cars about terminal stations and for making up trains; powerful, heavy, slow-moving engines, of large boiler-capacity and with small wheels, are used on steep gradients and for hauling long trains laden with coal and heavy merchandise; and hardly less powerful but quite differently proportioned "express"-engines are used for passenger and mail service. [Illustration: FIG. 125.--Tank-Engine, New York Elevated Railroad.] [Illustration: FIG. 126.--Forney's Tank-Locomotive.] A peculiar form of engine (Fig. 126) has been designed by Forney, in which the whole weight of engine, tender, coal, and water, is carried by one frame and on one set of wheels, the permanent weight falling on the driving-wheels and the variable load on the truck. These engines have also a comparatively short wheel-base and high pulling-power. The lightest tank-engines of the first class mentioned weigh 8 or 10 tons; but engines much lighter than these, even, are built for mines, where they are sent into the galleries to bring out the coal-laden wagons. The heaviest engines of this class attain weights of 20 or 30 tons. The heaviest engine yet constructed in the United States is said to be one in use on the Philadelphia & Reading Railroad, having a weight of about 100,000 pounds, which is carried on 12 driving-wheels. [Illustration: FIG. 127.--British Express Engine.] [Illustration: FIG. 128.--The Baldwin Locomotive. Section.] [Illustration: FIG. 129.--The American Type of Express-Engine, 1878.] A locomotive has two steam-cylinders, either side by side within the frame, and immediately beneath the forward end of the boiler, or on each side and exterior to the frame. The engines are non-condensing, and of the simplest possible construction. The whole machine is carried upon strong but flexible steel springs. The steam-pressure is usually more than 100 pounds. The pulling-power is generally about one-fifth the weight under most favorable conditions, and becomes as low as one-tenth on wet rails. The fuel employed is wood in new countries, coke in bituminous coal districts, and anthracite coal in the eastern part of the United States. The general arrangement and the proportions of locomotives differ somewhat in different localities. In Fig. 127, a British express-engine, _O_ is the boiler, _N_ the fire-box, _X_ the grate, _G_ the smoke-box, and _P_ the chimney. _S_ is a spring and _R_ a lever safety-valve, _T_ is the whistle, _L_ the throttle or regulator valve, _E_ the steam-cylinder, and _W_ the driving-wheel. The force-pump, _B C_, is driven from the cross-head, _D_. The frame is the base of the whole system, and all other parts are firmly secured to it. The boiler is made fast at one end, and provision is made for its expansion when heated. Adhesion is secured by throwing a proper proportion of the weight upon the driving-wheel, _W_. This is from about 6,000 pounds on standard freight-engines, having several pairs of drivers, to 10,000 pounds on passenger-engines, per axle. The peculiarities of the American type (Fig. 128) are the truck, _I J_, or bogie, supporting the forward part of the engine, the system of equalizers, or beams which distribute the weight of the machine equally over the several axles, and minor differences of detail. The cab or house, _r_, protecting the engine-driver and fireman, is an American device, which is gradually coming into use abroad also. The American locomotive is distinguished by its flexibility and ease of action upon even roughly-laid roads. In the sketch, which shows a standard American engine in section, _A B_ is the boiler, _C_ one of the steam-cylinders, _D_ the piston, _E_ the cross-head, connected to the crank-shaft, _F_, by the connecting-rod, _G H_ the driving-wheels, _I J_ the truck-wheels, carrying the truck, _K L_; _N N_ is the fire-box, _O O_ the tubes, of which but four are shown. The steam-pipe, _R S_, leads the steam to the valve-chest, _T_, in which is seen the valve, moved by the valve-gear, _U V_, and the link, _W_. The link is raised or depressed by a lever, _X_, moved from the cab. The safety-valve is seen at the top of the dome, at _Y_, and the spring-balance by which the load is adjusted is shown at _Z_. At _a_ is the cone-shaped exhaust-pipe, by which a good draught is secured. The attachments _b_, _c_, _d_, _e_, _f_, _g_--whistle, steam-gauge, sand-box, bell, head-light, and "cow-catcher"--are nearly all peculiar, either in construction or location, to the American locomotive. The cost of passenger-locomotives of ordinary size is about $12,000; heavier engines sometimes cost $20,000. The locomotive is usually furnished with a tender, which carries its fuel and water. The standard passenger-engine on the Pennsylvania Railroad has four driving-wheels, 5-1/2 feet diameter; steam-cylinders, 17 inches diameter and 2 feet stroke; grate-surface 15-1/2 square feet, and heating-surface 1,058 square feet. It weighs 63,100 pounds, of which 39,000 pounds are on the drivers and 24,100 on the truck. The freight-engine has six driving-wheels, 54-5/8 inches in diameter. The steam-cylinders are 18 inches in diameter, stroke 22 inches, grate-surface 14.8 square feet, heating-surface 1,096 feet. It weighs 68,500 pounds, of which 48,000 are on the drivers and 20,500 on the truck. The former takes a train of five cars up an average grade of 90 feet to the mile. The latter is attached to a train of 11 cars. On a grade of 50 feet to the mile, the former takes 7 and the latter 17 cars. Tank-engines for very heavy work, such as on grades of 320 feet to the mile, which are found on some of the mountain lines of road, are made with five pairs of driving-wheels, and with no truck. The steam-cylinders are 20-1/8 inches in diameter, 2 feet stroke; grate-area, 15-3/4 feet; heating-surface, 1,380 feet; weight with tank full, and full supply of wood, 112,000 pounds; average weight, 108,000 pounds. Such an engine has hauled 110 tons up this grade at the speed of 5 miles an hour, the steam-pressure being 145 pounds. The adhesion was about 23 per cent. of the weight. In checking a train in motion, the inertia of the engine itself absorbs a seriously large portion of the work of the brakes. This is sometimes reduced by reversing the engine and allowing the steam-pressure to act in aid of the brakes. To avoid injury by abrasion of the surfaces of piston, cylinder, and the valves and valve-seats, M. Le Chatelier introduces a jet of steam into the exhaust-passages when reversing, and thus prevents the ingress of dust-laden air and the drying of the rubbing surfaces. This method of checking a train is rarely resorted to, however, except in case of danger. The introduction of the "continuous" or "air" brake, which can be thrown into action in an instant on every car of the train by the engine-driver, is so efficient that it is now almost universally adopted. It is one of the most important safeguards which American ingenuity has yet devised. In drawing a train weighing 150 tons at the rate of 60 miles an hour, about 800 effective horse-power is required. A speed of 80 miles an hour has been often attained, and 100 miles has probably been reached. The American locomotive-engine has a maximum life which may be stated at about 30 years. The annual cost of repairs is from 10 to 15 per cent. of its first cost. On moderately level roads, the engine requires a pint of oil to each 25 miles, and a ton of coal to each 40 or 50 miles run. One of the best-managed railroads in the United States reports expenses as follows for one month: Number "train-miles" run per ton of coal burned 53.95 " " " " quart of oil used 34.44 Passenger-cars hauled 1 mile per ton of coal 275.7 Other " " " " " 634.8 Cost repairs per mile run $2 43 " fuel " " 3 64 " oil and waste per mile run 62 " wages of engine-men per mile run 6 22 All other expenses per mile 1 91 Total cost per "train-mile" run 14 82 Although the above sketch and description represent the construction and performance of the standard locomotive of the present time, there are indications that the compound arrangement of engines will ultimately be adopted. This will involve a considerable change of proportions, greatly increasing the volume and weight of steam-cylinders, but enabling the designer to more than proportionally decrease the weight of boiler and the quantity of fuel carried. There is no serious objection to their use, however, and no insuperable difficulty in the construction of the "double-cylinder" type of engine for the locomotive. A few such engines have already been put in service. In these engines the high-pressure cylinder is placed on one side and the larger low-pressure cylinder on the other side of the locomotive, thus having but two cylinders, as in the older plan. The valve-gear is the Stephenson link, as in the ordinary engine. At starting, the steam is allowed to act on both pistons; but after a few revolutions the course of the steam is changed, and the exhaust from the smaller cylinder, instead of passing into the chimney, is sent to the larger cylinder, which is at the same time cut off from the main steam-pipe. When the engine is ascending a steep gradient the steam may, if necessary, be taken from the boiler into both cylinders, as when starting. Compound engines of this kind have been used on the French line of railroad from Bayonne to Biarritz. They were designed by Mallet and built at Le Creuzot. The steam-cylinders are of 9-1/2 and 15-3/4 inches diameter, and of 17-3/4 inches stroke of piston. The four driving-wheels are 4 feet in diameter, and the total weight of engine is 20 tons. The boiler has 484-1/2 square feet of heating-surface, and is built to carry 10 atmospheres pressure. When hauling trains of 50 tons at 25 miles an hour, these engines require about 15 pounds of good coal per mile. The total length of the railways in operation in the United States on the 1st day of January, 1877, was 76,640 miles,[93] being an average of one mile of railway for every 600 inhabitants. The railways are as follows: [93] January, 1884, over 120,000 miles. Miles. Alabama 1,722 Alaska 0 Arizona 0 Arkansas 787 California 1,854 Colorado 950 Connecticut 925 Dakota 290 Delaware 285 Florida 484 Georgia 2,308 Idaho 0 Illinois 6,980 Indiana 4,072 Indian Territory 281 Iowa 3,937 Kansas 3,226 Kentucky 1,464 Louisiana 539 Maine 987 Maryland 1,092 Massachusetts 1,825 Michigan 3,437 Minnesota 2,024 Mississippi 1,028 Missouri 3,016 Montana 0 Nebraska 1,181 Nevada 714 New Hampshire 942 New Jersey 1,594 New Mexico 0 New York 5,520 North Carolina 1,371 Ohio 4,680 Oregon 251 Pennsylvania 5,896 Rhode Island 182 South Carolina 1,352 Tennessee 1,638 Texas 2,072 Utah 486 Vermont 810 Virginia 1,648 Washington 110 West Virginia 576 Wisconsin 2,575 Wyoming 459 ------ Total 76,640 In 1873 came the great financial crisis, with its terrible results of interrupted production, poverty, and starvation, and an almost total cessation of the work of building new railroads. The largest number of miles ever built in any one year were constructed in 1872. The greatest mileage is in Illinois, reaching 6,589; the smallest in Rhode Island, 136, and in Washington Territory, 110. The State of Massachusetts has one mile of railroad to 4.86 miles of territory, this ratio being the greatest in the country. The longest road in operation is the Chicago & Northwestern, extending 1,500 miles; the shortest, the Little Saw-Mill Run Road in Pennsylvania, which is but three miles in length. The total capital of railways in the country is $6,000,000,000, or an average of $100,000 per mile. The earnings for the year 1872 amounted to $454,969,000, or $7,500 per mile. The largest net earnings recorded as made on any road were gained by the New York Central & Hudson River, $8,260,827; the smallest on several roads which not only earned nothing, but incurred a loss. The catastrophe of 1873-'74 revealed the fact that the latter condition of railroad finances was vastly more common than had been suspected; and it is still doubtful whether the existing immense network of railroads which covers the United States can be made, as a whole, to pay even a moderate return on the money invested in their construction. At the period of maximum rate of extension of railroads in the United States--1873--the reported lengths of the railroads of Europe and America were as follows:[94] [94] _Railroad Gazette._ RAILROADS IN EUROPE AND AMERICA IN 1873. ----------------------------+------------+-------------+------------ COUNTRIES. | Railroads, | Population. | Area, | Miles. | | Sq. Miles. ----------------------------+------------+-------------+------------ United States | 71,565 | 40,232,000 | 2,492,316 Germany | 12,207 | 40,111,265 | 212,091 Austria | 5,865 | 35,943,592 | 227,234 France | 10,333 | 36,469,875 | 201,900 Russia in Europe | 7,044 | 71,207,794 | 1,992,574 Great Britain, 1872 | 15,814 | 31,817,108 | 120,769 Belgium | 1,301 | 4,839,094 | 11,412 Netherlands | 886 | 3,858,055 | 13,464 Switzerland | 820 | 2,669,095 | 15,233 Italy | 3,667 | 26,273,776 | 107,961 Denmark | 420 | 1,784,741 | 14,453 Spain | 3,401 | 16,301,850 | 182,758 Portugal | 453 | 3,987,867 | 36,510 Sweden and Norway | 1,049 | 5,860,122 | 188,771 Greece | 100 | 1,332,508 | 19,941 ----------------------------+------------+-------------+------------ The railroads in Great Britain comprise over 15,000 miles of track now being worked in the United Kingdom, on which have been expended $2,800,000,000. This sum is equal to five times the amount of the annual value of all the real property in Great Britain, and two-thirds of the national debt. After deducting all the working expenses, the gross net annual revenue of all the roads exceeds by $110,000,000 the total revenue from all sources of Belgium, Holland, Portugal, Denmark, Sweden and Norway. An army of 100,000 officers and servants is in the employ of the companies, and the value of the rolling-stock exceeds $150,000,000. SECTION III.--MARINE ENGINES. The changes which have now become completed in the marine steam-engine have been effected at a later date than those which produced the modern locomotive. On the American rivers the modification of the beam-engine since the time of Robert L. Stevens has been very slight. The same general arrangement is retained, and the details are little, if at all, altered. The pressure of steam is sometimes as high as 60 pounds per square inch. [Illustration: FIG. 130.--Beam-Engine.] The valves are of the disk or poppet variety, rising and falling vertically. They are four in number, two steam and two exhaust valves being placed at each end of the steam-cylinder. The beam-engine is a peculiarly American type, seldom if ever seen abroad. Fig. 130 is an outline sketch of this engine as built for a steamer plying on the Hudson River. This class of engine is usually adopted in vessels of great length, light draught, and high speed. But one steam-cylinder is commonly used. The cross-head is coupled to one end of the beam by means of a pair of links, and the motion of the opposite end of the beam is transmitted to the crank by a connecting-rod of moderate length. The beam has a cast-iron centre surrounded by a wrought-iron strap of lozenge shape, in which are forged the bosses for the end-centres, or for the pins to which the connecting-rod and the links are attached. The main centre of the beam is supported by a "gallows-frame" of timbers so arranged as to receive all stresses longitudinally. The crank and shaft are of wrought-iron. The valve-gear is usually of the form already mentioned as the Stevens valve-gear, the invention of Robert L. and Francis B. Stevens. The condenser is placed immediately beneath the steam-cylinder. The air-pump is placed close beside it, and worked by a rod attached to the beam. Steam-vessels on the Hudson River have been driven by such engines at the rate of 20 miles an hour. This form of engine is remarkable for its smoothness of operation, its economy and durability, its compactness, and the latitude which it permits in the change of shape of the long, flexible vessels in which it is generally used, without injury by "getting out of line." [Illustration: FIG. 131.--Oscillating Engine and Feathering Paddle-Wheel.] For paddle-engines of large vessels, the favorite type, which has been the side-lever engine, is now rarely built. For smaller vessels, the oscillating engine with feathering paddle-wheels is still largely employed in Europe. This style of engine is shown in Fig. 131. It is very compact, light, and moderately economical, and excels in simplicity. The usual arrangement is such that the feathering-wheel has the same action upon the water as a radial wheel of double diameter. This reduction of the diameter of the wheel, while retaining maximum effectiveness, permits a high speed of engine, and therefore less weight, volume, and cost. The smaller wheel-boxes, by offering less resistance to the wind, retard the progress of the vessel less than those of radial wheels. Inclined engines are sometimes used for driving paddle-wheels. In these the steam-cylinder lies in an inclined position, and its connecting-rod directly connects the crank with the cross-head. The condenser and air-pump usually lie beneath the cross-head guides, and are worked by a bell-crank driven by links on each side the connecting-rod, attached to the cross-head. Such engines are used to some extent in Europe, and they have been adopted in the United States navy for side-wheel gunboats. They are also used on the ferry-boats plying between New York and Brooklyn. [Illustration: FIG. 132.--The Two Rhode Islands, 1836-1876.] Among the finest illustrations of recent practice in the construction of side-wheel steamers are those built for the several routes between New York and the cities of New England which traverse Long Island Sound. Our illustration exhibits the form of these vessels, and also shows well the modifications in structure and size which have been made during this generation. The later vessel is 325 feet long, 45 feet beam, 80 feet wide over the "guards," and 16 feet deep, drawing 10 feet of water. The "frames" upon which the planking of the hull is fastened are of white-oak, and the lighter and "top" timbers of cedar and locust. The engine has a steam-cylinder 90 inches in diameter and 12 feet stroke of piston.[95] On each side the great saloons which extend from end to end of the upper deck are state-rooms, containing each two berths and elegantly furnished. The engine of this vessel is capable of developing about 2,500 horse-power. The great wheels, of which the paddle-boxes are seen rising nearly to the height of the hurricane-deck, are 37-1/2 feet in diameter and 12 in breadth. The hull of this vessel, including all wood-work, weighs over 1,200 tons. The weight of the machinery is about 625 tons. The steamer makes 16 knots an hour when the engine is at its best speed--about 17 revolutions per minute--and its average speed is about 14 knots on its route of 160 miles. The coal required to supply the furnaces of such a vessel and with such machinery would be about 3 tons per hour. or a little over 2-1/2 pounds per horse-power. The construction of such a vessel occupies, usually, about a year, and costs a quarter of a million dollars. [95] The steam-cylinders of the engines of steamers Bristol and Providence are 110 inches in diameter and of 12 feet stroke. [Illustration: FIG. 133.--A Mississippi Steamboat.] The non-condensing direct-acting engine is used principally on the Western rivers, driven by steam of from 100 to 150 pounds pressure, and exhausts its steam into the atmosphere. It is the simplest possible form of direct-acting engine. The valves are usually of the "poppet" variety, and are operated by cams which act at the ends of long levers having their fulcra on the opposite side of the valve, the stem of which latter is attached at an intermediate point. The engine is horizontal, and the connecting-rod directly attached to cross-head and crank-pin without intermediate mechanism. The paddle-wheel is used, sometimes as a stern-wheel, as in the plan of Jonathan Hulls of one and a half century ago, sometimes as a side-wheel, as is most usual elsewhere. One of the most noted of these steamers, plying on the Mississippi, is shown in the preceding sketch. One of the largest of these steamers was the Grand Republic,[96] a vessel 340 feet long, 56 feet beam, and 10-1/4 feet depth. The draught of water of this great craft was 3-1/2 feet forward and 4-1/2 aft. The two sets of compound engines, 28 and 56 inches diameter and of 10 feet stroke, drive wheels 38-1/2 feet in diameter and 18 feet wide. The boilers were steel. A steamer built still later on the Ohio has the following dimensions: Length, 225 feet; breadth, 35-1/2 feet; depth, 5 feet; cylinders, 17-3/8 inches in diameter, 6 feet stroke; three boilers. The hull and cabin were built at Jeffersonville, Ind. She has 40 large state-rooms. The cost of the steamer was $40,000. [96] Burned in 1877. These vessels have now opened to commerce the whole extent of the great Mississippi basin, transporting a large share of the products of a section of country measuring a million and a half square miles--an area equal to many times that of New York State, and twelve times that of the island of Great Britain--an area exceeding that of the whole of Europe, exclusive of Russia and Turkey, and capable, if as thoroughly cultivated as the Netherlands, of supporting a population of between three and four hundred millions of people. The steam-engine and propelling apparatus of the modern ocean-steamer have now become almost exclusively the compound or double-cylinder engine, driving the screw. The form and the location of the machinery in the vessel vary with the size and character of the ship which it drives. Very small boats are fitted with machinery of quite a different kind from that built for large steamers, and war-vessels have usually been supplied with engines of a design radically different from that adopted for merchant-steamers. [Illustration: FIG. 134.--Steam-Launch, New York Steam-Power Company.] The introduction of _Steam-Launches_ and small pleasure-boats driven by steam-power is of comparatively recent date, but their use is rapidly increasing. Those first built were heavy, slow, and complicated; but, profiting by experience, light and graceful boats are now built, of remarkable swiftness, and having such improved and simplified machinery that they require little fuel and can be easily managed. Such boats have strong, carefully-modeled hulls, light and strong boilers, capable of making a large amount of dry steam with little fuel, and a light, quick-running engine, working without shake or jar, and using steam economically. [Illustration: FIG. 135.--Launch-Engine.] The above sketch represents the engine built by a New York firm for such little craft. This is the smallest size made for the market. It has a steam-cylinder 3 inches in diameter and a stroke of piston of 5 inches, driving a screw 26 inches in diameter and of 3 feet pitch. The maximum power of the engine is four or five times the nominal power. The boiler is of the form shown in the illustrations of semi-portable engines, and has a heating-surface, in this case, of 75 square feet. The boat itself is like that seen on page 386, and is 25 feet long, of 5 feet 8 inches beam, and draws 2-1/4 feet of water. These little machines weigh about 150 pounds per nominal horse-power, and the boilers about 300. Some of these little vessels have attained wonderful speed. A British steam-yacht, the Miranda, 45-1/2 feet in length, 5-3/4 feet wide, and drawing 2-1/2 feet of water, with a total weight of 3-3/4 tons, has steamed nearly 18-1/2 miles an hour for short runs. The boat was driven by an engine of 6 inches diameter of cylinder and 8 inches stroke of piston, making 600 revolutions per minute, driving a two-bladed screw 2-1/2 feet in diameter and of 3-1/3 feet pitch. Its machinery had a total weight of two tons. Another English yacht, the Firefly, is said to have made 18.94 miles an hour. A little French yacht, the Hirondelle, has attained a speed of 16 knots, equal to about 18-1/2 miles, an hour. This was, however, a much larger vessel than the preceding. One of the most remarkable of these little steamers is a torpedo-boat built for the United States navy. This vessel is 60 feet long, 6 feet wide, and 5 feet deep; its screw is 38 inches in diameter and of 5 feet pitch, two-bladed, and is driven, by a very light engine and boiler, 400 revolutions per minute, the boat attaining a speed of 19 to 20 miles an hour. Another little vessel, the Vision, made nearly as great speed, developing 20 horse-power with engine and boiler weighing but about 400 pounds. Yachts of high speed require such weight and bulk of engine that but little space is left for cabins, and they are usually exceedingly uncomfortable vessels. In the Miranda the weight of machinery is more than one-half the total weight of the whole. An illustration of the more comfortable and more generally liked pleasure-yacht is the Day Dream. The length is 105 feet, and the boat draws 5-1/2 feet of water. There are two engines, having steam-cylinders 14 inches in diameter and of the same length of stroke, direct-acting, condensing, and driving a screw, of 7 feet diameter and of 10-1/2 feet pitch, 135 revolutions a minute, giving the yacht a speed of 13-1/2 knots an hour. [Illustration: FIG. 136.--Horizontal, Direct-acting Naval Screw-Engine.] In larger vessels, as in yachts, in nearly all cases, the ordinary screw-engine is direct-acting. Two engines are placed side by side, with cranks on the shaft at an angle of 90° with each other. In merchant-steamers the steam-cylinders are usually vertical and directly over the crank-pins, to which the cross-heads are coupled. The condenser is placed behind the engine-frame, or, where a jet-condenser is used, the frame itself is sometimes made hollow, and serves as a condenser. The air-pump is worked by a beam connected by links with the cross-head. The general arrangement is like that shown in Figs. 137 and 138. For naval purposes such a form is objectionable, since its height is so great that it would be exposed to injury by shot. In naval engineering the cylinder is placed horizontally, as in Fig. 136, which is a sectional view, representing an horizontal, direct-acting naval screw-engine, with jet-condenser and double-acting air and circulating pumps. _A_ is the steam-cylinder, _B_ the piston, which is connected to the crank-pin by the piston-rod, _D_, and connecting-rod, _E_. _F_ is the cross-head guide. The eccentrics, _G_, operate the valve, which is of the "three-ported variety," by a Stephenson link. Reversing is effected by the hand-wheel, _C_, which, by means of a gear, _m_, and a rack, _k_, elevates and depresses the link, and thus reverses the valve. [Illustration: FIG. 137.--Compound Marine Engine. Side Elevation.] The trunk-engine, in which the connecting-rod is attached directly to the piston and vibrates within a trunk or cylinder secured to the piston, moving with it, and extending outside the cylinder, like an immense hollow piston-rod, is frequently used in the British navy. It has rarely been adopted in the United States. [Illustration: FIG. 138.--Compound Marine Engine. Front Elevation and Section.] In nearly all steam-vessels which have been built for the merchant service recently, and in some naval vessels, the compound engine has been adopted. Figs. 137 and 138 represent the usual form of this engine. Here _A A_, _B B_ are the small and the large, or the high-pressure and the low-pressure cylinders respectively. _C C_ are the valve-chests. _G G_ is the condenser, which is invariably a surface-condenser. The condensing water is sometimes directed around the tubes contained within the casing, _G G_, while the steam is exhausted around them and among them, and sometimes the steam is condensed within the tubes, while the injection-water which is sent into the condenser to produce condensation passes around the exterior of the tubes. In either case, the tubes are usually of small diameter, varying from five-eighths to half an inch, and in length from four to seven feet. The extent of heating-surface is usually from one-half to three-fourths that of the heating-surface of the boilers. The air and circulating pumps are placed on the lower part of the condenser-casting, and are operated by a crank on the main shaft at _N_; or they are sometimes placed as in the style of engine last described, and driven by a beam worked by the cross-head. The piston-rods, _T S_, are guided by the cross-heads, _V V_, working in slipper-guides, and to these cross-heads are attached the connecting-rods, _X X_, driving the cranks, _M M_. The cranks are now usually set at right angles; in some engines this angle is increased to 120°, or even 180°. Where it is arranged as here shown, an intermediate reservoir, _P O_, is placed between the two cylinders to prevent the excessive variations of pressure that would otherwise accompany the varying relative motions of the pistons, as the steam passes from the high-pressure to the low-pressure cylinder. Steam from the boilers enters the high-pressure steam-chest, _X_, and is admitted by the steam-valve alternately above and below the piston as usual. The exhaust steam is conducted through the exhaust passage around into the reservoir, _P_, whence it it is taken by the low-pressure cylinder, precisely as the smaller cylinder drew its steam from the boiler. From the large or low-pressure cylinder the steam is exhausted into the condenser. The valve-gear is usually a Stephenson link, _g e_, the position of which is determined, and the reversal of which is accomplished, by a hand-wheel, _o_, and screw, _m n p_, which, by the bell-crank, _k i_, are attached to the link, _g e_. The "box-framing" forms also the hot-well. The surface-condenser is cleared by a single-acting air-pump, inside the frame, at _T_. The feed-pump and the bilge-pumps are driven from the cross-head of the air-pump. [Illustration: John Elder.] The successful introduction of the double-cylinder engine was finally accomplished by the exertions of a few engineers, who were at once intelligent enough to understand its advantages, and energetic and enterprising enough to push it forward in spite of active opposition, and powerful enough, pecuniarily and in influence, to succeed. The most active and earnest of these eminent men was John Elder, of the firm of Randolph, Elder & Co., subsequently John Elder & Co., of Glasgow.[97] [97] _Vide_ "Memoir of John Elder," W. J. M. Rankine, Glasgow, 1871. Elder was of Scotch descent. His ancestors had, for generations, shown great skill and talent in construction, and had always been known as successful millwrights. John Elder was born at Glasgow, March 8, 1824, and died in London, September 17, 1869. He was educated at the Glasgow High-School and in the College of Engineering at the University of Glasgow, where, however, his attendance was but for a short time. He learned the trade under his father in the workshops of the Messrs. Napier, and became an unusually expert draughtsman. After spending three years in charge of the drawing-office at the engine-building works of Robert Napier, where his father had been manager, Elder became a partner in the firm which had previously been known as Randolph, Elliott & Co., in the year 1852. The firm commenced building iron vessels in 1860. In the mean time, the experiments of Hornblower and Wolff, of Allaire and Smith, and of McNaught, Craddock, and Nicholson, together with the theoretical investigations of Thompson, Rankine, Clausius, and others, had shown plainly in what direction to look for improvement upon then standard engines, and what direction practice was taking with all types. The practical deductions which were becoming evident were recognized very early by Elder, and he promptly began to put in practice the principles which his knowledge of thermo-dynamics and of mechanics enabled him to appreciate. He adopted the compound engine, and coupled his cranks at angles of 180°, in order to avoid losses due to the friction of the crank-shaft in its bearings, by effecting a partial counterbalancing of pressures on the journals. Elder was one of the first to point out the fact that the compound engine had proved itself more efficient than the single-cylinder engine, only when the pressure of steam carried and the extent to which expansion was adopted exceeded the customary practice of his time. His own practice was, from the first, successful, and from 1853 to 1867 he and his partners were continually engaged in the construction of steamers and fitting them with compound engines. The engines of their first vessel, the Brandon, required but 3-1/4 pounds of coal per hour and per horse-power, in 1854, when the usual consumption was a third more. Five years later, they had built engines which consumed a third less than those of the Brandon; and thenceforward, for many years, their engines, when of large size, exhibited what was then thought remarkable economy, running on a consumption of from 2-1/4 to 2-1/2 pounds. In the year 1865 the British Government ordered a competitive trial of three naval vessels, which only differed in the form of their engines. The Arethusa was fitted with trunk-engines of the ordinary kind; the Octavia had three steam-cylinders, coupled to three cranks placed at angles of 120° with each other; and the Constance was fitted with compound engines, two sets of three cylinders each, and each taking steam from the boiler into one cylinder, passing it through the other two with continuous expansion, and finally exhausting from the third into the condenser. These vessels, during one week's steaming at sea, averaged, respectively, 3.64, 3.17, and 2.51 pounds of coal per hour and per horse-power, and the Constance showed a marked superiority in the efficiency of the mechanism of her engines, when the losses by friction were compared. The change from the side-lever single-cylinder engine, with jet-condenser and paddle-wheels, to the direct-acting compound engine, with surface-condenser and screw-propellers, has occurred within the memory and under the observation of even young engineers, and it may be considered that the revolution has not been completely effected. This change in the design of engine is not as great as it at first seemed likely to become. Builders have but slowly learned the principles stated above in reference to expansion in one or more cylinders, and the earlier engines were made with a high and low pressure cylinder working on the same connecting-rod, and each machine consisted of four steam-cylinders. It was at last discovered that a high-pressure single-cylinder engine exhausting into a separate larger low-pressure engine might give good results, and the compound engine became as simple as the type of engine which it displaced. This independence of high and low pressure engines is not in itself novel, for the plan of using the exhaust of a high-pressure engine to drive a low-pressure condensing engine was one of the earliest of known combinations. The advantage of introducing double engines at sea is considerably greater than on land. The coal carried by a steam-vessel is not only an item of great importance in consequence of its first cost, but, displacing its weight or bulk of freight which might otherwise be carried, it represents so much non-paying cargo, and is to be charged with the full cost of transportation in addition to first cost. The best of steam-coal is therefore usually chosen for steamers making long voyages, and the necessity of obtaining the most economical engines is at once seen, and is fully appreciated by steamship proprietors. Again, an economy of one-fourth of a pound per horse-power per hour gives, on a large transatlantic steamer, a saving of about 100 tons of coal for a single voyage. To this saving of cost is to be added the gain in wages and sustenance of the labor required to handle that coal, and the gain by 100 tons of freight carried in place of the coal. For many years the change which has here been outlined, in the forms of engine and the working of steam expansively, was retarded by the inefficiency of methods and tools used in construction. With gradual improvement in tools and in methods of doing work, it became possible to control higher steam and to work it successfully; and the change in this direction has been steadily going on up to the present time with all types of steam-engine. At sea this rise of pressure was for a considerable time retarded by the serious difficulty encountered in the tendency of the sulphate of lime to deposit in the boiler. When steam-pressure had risen to 25 pounds per square inch, it was found that no amount of "blowing out" would prevent the deposition of seriously large quantities of this salt, while at the lower pressures at first carried at sea no troublesome precipitation occurred, and the only precaution necessary was to blow out sufficient brine to prevent the precipitation of common salt from a supersaturated solution. The introduction of surface-condensation was promptly attempted as the remedy for this evil, but for many years it was extremely doubtful whether its disadvantages were not greater than its advantages. It was found very difficult to keep the condensers tight, and boilers were injured by some singular process of corrosion, evidently due to the presence of the surface-condenser. The simple expedient of permitting a very thin scale to form in the boiler was, after a time, hit upon as a means of overcoming this difficulty, and thenceforward the greatest obstacle to the general introduction was the conservative disposition found among those who had charge of marine machinery, which conservatism regarded with suspicion every innovation. Another trouble arose from the difficulty of finding men neither too indolent nor too ignorant to take charge of the new condenser, which, more complicated and more readily disarranged than the old, demanded a higher class of attendants. Once introduced, however, the surface-condenser removed the obstacle to further elevation of steam-pressure, and the rise from 20 to 60 pounds pressure soon occurred. Elder and his competitors on the Clyde were the first to take advantage of the fact when these higher pressures became practicable. The lightness of engine and the smaller weight of boiler secured when the simpler type of "compound" engine is used are great advantages, and, when coupled with the fact that by no other satisfactory device can great expansion and consequent economy of fuel be obtained at sea, the advantages are such as to make the adoption of this style of engine imperative for ship-propulsion. This extreme lightness in machinery has been largely, also, the result of very careful and skillful designing, of intelligent construction, and of care in the selection and use of material. British builders had, until after the introduction of these later types of vessels-of-war, been distinguished rather by the weight of their machinery than for nice calculation and proportioning of parts. Now the engines of the heavy iron-clads are models of good proportions, excellence in materials, and of workmanship, which are well worthy of study. The weight per indicated horse-power has been reduced from 400 or 500 pounds to less than half that amount within the last ten years. This has been accomplished by forcing the boilers--although thus, to some extent, losing economy--by higher steam-pressure, a very much higher piston-speed, reduction of friction of parts, reduction of capacity for coal-stowage, and exceedingly careful proportioning. The reduction of coal-bunker capacity is largely compensated by the increase of economy secured by superheating, by increased expansion, elevation of piston-speed, and the introduction of surface-condensation. A good marine steam-engine of the form which was considered standard 15 or 20 years ago, having low-pressure boilers carrying steam at 20 or 25 pounds pressure as a maximum, expanding twice or three times, and having a jet-condenser, would require about 30 or 35 pounds of feed-water per horse-power per hour; substituting surface-condensation for that produced by the jet brought down the weight of steam used to from 25 to 30 pounds; increasing steam-pressure to 60 pounds, expanding from five to eight times, and combining the special advantages of the superheater and the compound engine with surface-condensation, has reduced the consumption of steam to 20, or even, in some cases, 15 pounds of steam per horse-power per hour. Messrs. Perkins, of London, guarantee, as has already been stated, to furnish engines capable of giving a horse-power with a consumption of but 1-1/4 pound of coal. Mr. C. E. Emery reports the United States revenue-steamer Hassler, designed by him, to have given an ordinary sea-going performance which is probably fully equal to anything yet accomplished. The Hassler is a small steamer, of but 151 feet in length, 24-1/2 feet beam, and 10 feet draught. The engines have steam-cylinders 18.1 and 28 inches diameter, respectively, and of 28 inches stroke of piston, indicating 125 horse-power; with steam at 75 pounds pressure, and at a speed of but 7 knots, the coal consumed was but 1.87 pound per horse-power per hour. The committee of the British Admiralty on designs of ships-of-war have reported recently: "The carrying-power of ships may certainly be to some extent increased by the adoption of compound engines in her Majesty's service. Its use has recently become very general in the mercantile marine, and the weight of evidence in favor of the large economy of fuel thereby gained is, to our minds, overwhelming and conclusive. We therefore beg earnestly to recommend that the use of compound engines may be generally adopted in ships-of-war hereafter to be constructed, and applied, whenever it can be done with due regard to economy and to the convenience of the service, to those already built." The forms of screws now employed are exceedingly diverse, but those in common use are not numerous. In naval vessels it is common to apply screws of two blades, that they may be hoisted above water into a "well" when the vessel is under sail, or set with the two blades directly behind the stern-post, when their resistance to the forward motion of the vessel will be comparatively small. In other vessels, and in the greater number of full-power naval vessels, screws of three or four blades are used. The usual form of screw (Fig. 139) has blades of nearly equal breadth from the hub to the periphery, or slightly widening toward their extremities, as is seen in an exaggerated degree in Fig. 140, representing the form adopted for tug-boats, where large surface near the extremity is more generally used than in vessels of high speed running free. In the Griffith screw, which has been much used, the hub is globular and very large. The blades are secured to the hub by flanges, and are bolted on in such a manner that their position may be changed slightly if desired. The blades are shaped like the section of a pear, the wider part being nearest the hub, and the blades tapering rapidly toward their extremities. A usual form is intermediate between the last, and is like that shown in Fig. 141, the hub being sufficiently enlarged to permit the blades to be attached as in the Griffith screw, but more nearly cylindrical, and the blades having nearly uniform width from end to end. [Illustration: FIG. 139.--Screw-Propeller.] [Illustration: FIG. 140.--Tug-boat Screw.] [Illustration: FIG. 141.--Hirsch Screw.] The pitch of a screw is the distance which would be traversed by the screw in one revolution were it to move through the water without slip; i. e., it is double the distance _C D_, Fig. 140. _C D´_ represents the helical path of the extremity of the blade _B_, and _O E F H K_ is that of the blade _A_. The proportion of diameter to the pitch of the screw is determined by the speed of the vessel. For low speed the pitch may be as small as 1-1/4 the diameter. For vessels of high speed the pitch is frequently double the diameter. The diameter of the screw is made as great as possible, since the slip decreases with the increase of the area of screw-disk. Its length is usually about one-sixth of the diameter. A greater length produces loss by increase of surface causing too great friction, while a shorter screw does not fully utilize the resisting power of the cylinder of water within which it works, and increased slip causes waste of power. An empirical value for the probable slip in vessels of good shape, which is closely approximate usually, is _S_ = 4(_M_/_A_), in which _S_ is the slip per cent., and _M_ and _A_ are the areas of the midship section and of the screw-disk in square feet. The most effective screws have slightly greater pitch at the periphery than at the hub, and an increasing pitch from the forward to the rear part of the screw. The latter method of increasing pitch is more generally adopted alone. The thrust of the screw is the pressure which it exerts in driving the vessel forward. In well-formed vessels, with good screws, about two-thirds of the power applied to the screw is utilized in propulsion, the remainder being wasted in slip and other useless work. Its efficiency is in such a case, therefore, 66 per cent. Twin screws, one on each side of the stern-post, are sometimes used in vessels of light draught and considerable breadth, whereby decreased slip is secured. As has already been stated, the introduction of the compound engine has been attempted, but with less success than in Europe, by several American engineers. The most radical change in the methods of ship-propulsion which has been successfully introduced in some localities has been the adoption of a system of "wire-rope towage." It is only well adapted for cases in which the steamer traverses the same line constantly, moving backward and forward between certain points, and is never compelled to deviate to any considerable extent from the path selected. A similar system is in use in Canada, but it has not yet come into use in the United States, notwithstanding the fact that, wherever its adoption is practicable, it has a marked superiority in economy over the usual methods of propulsion. With chain or rope traction there is no loss by slip or oblique action, as in both screw and paddle-wheel propulsion. In the latter methods these losses amount to an important fraction of the total power; they rarely, if ever, fall below a total of 25 per cent., and probably in towage exceed 50 per cent. The objection to the adoption of chain-propulsion, as it is also often called, is the necessity of following closely the line along which the chain or the rope is laid. There is, however, much less difficulty than would be anticipated in following a sinuous route or in avoiding obstacles in the channel or passing other vessels. The system is particularly well adapted for use on canals. The steam-boilers in use in the later and best marine engineering practice are of various forms, but the standard types are few in number. That used on river-steamers in the United States has already been described. [Illustration: FIG. 142.--Marine Fire-tubular Boiler. Section.] Fig. 142 is a type of marine tubular boiler which is in most extensive use in sea-going steamers for moderate pressure, and particularly for naval vessels. Here the gases pass directly into the back connection from the fire, and thence forward again, through horizontal tubes, to the front connection and up the chimney. In naval vessels the steam-chimney is omitted, as it is there necessary to keep all parts of the boiler as far below the water-line as possible. Steam is taken from the boiler by pipes which are carried from end to end of the steam-space, near the top of the boiler, the steam entering these pipes through small holes drilled on the other side. Steam is thus taken from the boiler "wet," but no large quantity of water can usually be "entrained" by the steam. A marine boiler has been quite extensively introduced into the United States navy, in which the gases are led from the back connection through a tube-box around and among a set of upright water-tubes, which are filled with water, circulation taking place freely from the water-space immediately above the crown-sheet of the furnace up through these tubes into the water-space above them. These "water-tubular" boilers have a slight advantage over the "fire-tubular" boilers already described in compactness, in steaming capacity, and in economical efficiency. They have a very marked advantage in the facility with which the tubes may be scraped or freed from the deposit when a scale of sulphate of lime or other salt has formed within them by precipitation from the water. The fire-tubular boiler excels in convenience of access for plugging up leaking tubes, and is much less costly than the water-tubular. The water-tube class of boilers still remain in extensive use in the United States naval steamers. They have never been much used in the merchant service, although introduced by James Montgomery in the United States and by Lord Dundonald in Great Britain twenty years earlier. Opinion still remains divided among engineers in regard to their relative value. They are gradually reassuming prominence by their introduction in the modified form of sectional boilers. [Illustration: FIG. 143.--Marine High-Pressure Boiler. Section.] Marine boilers are now usually given the form shown in section in Fig. 143. This form of boiler is adopted where steam-pressures of 60 pounds and upward are carried, as in steam-vessels supplied with compound engines, cylindrical forms being considered the best with high pressures. The large cylindrical flues, therefore, form the furnaces as shown in the transverse sectional view. The gases rise, as shown in the longitudinal section, through the connection, and pass back to the end of the boiler through the tubes, and thence, instead of entering a steam-chimney, they are conducted by a smoke-connection, not shown in the sketch, to the smoke funnel or stack. In merchant-steamers, a steam-drum is often mounted horizontally above the boiler. In other cases a separator is attached to the steam-pipe between boilers and engines. This usually consists of an iron tank, divided by a vertical partition extending from the top nearly to the bottom. The steam, entering the top at one side of this partition, passes underneath it, and up to the top on the opposite side, where it issues into a steam-pipe leading directly to the engine. The sudden reversal of its course at the bottom causes it to leave the suspended water in the bottom of the separator, whence it is drained off by pipes. The most interesting illustrations of recent practice in marine engineering and naval architecture are found in the steamers which are now seen on transoceanic routes for the merchant service, and, in the naval service, in the enormous iron-clads which have been built in Great Britain. The City of Peking is one of the finest examples of American practice. This vessel was constructed for the Pacific Mail Company. The hull is 423 feet long, of 48 feet beam, and 38-1/2 feet deep. Accommodations are furnished for 150 cabin and 1,800 steerage passengers, and the coal-bunkers "stow" 1,500 tons of coal. The iron plates of which the sides and bottom are made are from 11/16 to one inch in thickness. The weight of iron used in construction was about 5,500,000 pounds. The machinery weighed nearly 2,000,000 pounds, with spare gear and accessory apparatus. The engines are compound, with two steam-cylinders of 51 inches and two of 88 inches diameter, and a stroke of piston of 4-1/2 feet. The condensing water is sent through the surface-condensers by circulating-pumps driven by their own engines. Ten boilers furnish steam to these engines, each having a diameter of 13 feet, a length of 13-1/2 feet, and a thickness of "shell" of 13/16 inch. Each has three furnaces, and contains 204 tubes of an outside diameter of 3-1/4 inches. All together, they have 520 square feet of grate-surface and 17,000 square feet of heating-surface. The area of cooling-surface in the condensers is 10,000 square feet. The City of Rome, a ship of later design, is 590 feet long, "over all," 52 feet beam, 52 feet deep, and measures 8,300 tons. The engines, of 8,500 horse-power, will drive the vessel 18 knots (21 miles) an hour; they have six steam-cylinders (three high and three low pressure), and are supplied with steam by 8 boilers heated by 48 furnaces. The hull is of steel, the bottom double, and the whole divided into ten compartments by transverse bulkheads. Two longitudinal bulkheads in the engine and boiler compartments add greatly to the safety of the vessel. The most successful steam-vessels in general use are these screw-steamers of transoceanic lines. Those of the transatlantic lines are now built from 350 to 550 feet long, generally propelled from 12 to 18 knots (14 to 21 miles) an hour, by engines of from 3,000 to 8,000 horse-power, consuming from 70 to 250 tons of coal a day, and crossing the Atlantic in from eight to ten days. These vessels are now invariably fitted with the compound engine and surface-condensers. One of these vessels, the Germanic, has been reported at Sandy Hook, the entrance to New York Harbor, in 7 days 11 hours 37 minutes from Queenstown--a distance, as measured by the log and by observation, of 2,830 miles. Another steamer, the Britannic, has crossed the Atlantic in 7 days 10 hours and 53 minutes. These vessels are of 5,000 tons burden, of 750 "nominal" horse-power (probably 5,000 actual). [Illustration: FIG. 144.--The Modern Steamship.] The modern steamship is as wonderful an illustration of ingenuity and skill in all interior arrangements as in size, power, and speed. The size of sea-going steamers has become so great that it is unsafe to intrust the raising of the anchor or the steering of the vessel to manual power and skill; and these operations, as well as the loading and unloading of the vessel, are now the work of the same great motor--steam. The now common form of auxiliary engine for controlling the helm is one of the inventions of the American engineer F. E. Sickels, who devised the "Sickels cut-off," and was first invented about 1850. It was exhibited at London at the International Exhibition of 1851. It consists[98] principally of two cylinders working at right angles upon a shaft geared into a large wheel fastened by a friction-plate lined with wood, and set by a screw to any desired pressure on the steering-apparatus. The wheel turned by the steersman is connected with the valve-gear of the cylinders, so that the steam, or other motor, will move the rudder precisely as the helmsman moves the wheel adjusting the steam-valves. This wheel thus becomes the steering-wheel. The apparatus is usually so arranged that it may be connected or disconnected in an instant, and hand-steering adopted if the smoothness of the sea and the low speed of the vessel make it desirable or convenient. This method was first adopted in the United States on the steamship Augusta. [98] "Official Catalogue," 1862, vol. iv., Class viii., p. 123. The same inventor and others have contrived "steam-windlasses," some of which are in general use on large vessels. The machinery of these vessels is also often fitted with a steam "reversing-gear," by means of which the engines are as easily man[oe]uvred as are those of the smallest vessels, to which hand-gear is always fitted. In one of these little auxiliary engines, as devised by the author, a small handle being adjusted to a marked position, as to the point marked "stop" on an index-plate, the auxiliary engine at once starts, throws the valve-gear into the proper position--as, if a link-motion, into "middle-gear"--thus stopping the large engines, and then it itself stops. Setting the handle so that its pointer shall point to "ahead," the little engine starts again, sets the link in position to go ahead, thus starting the large engines, and again stops itself. If set at "back," the same series of operations occurs, leaving the main engines backing and the little "reversing engine" stopped. A number of forms of reversing engine are in use, each adapted to some one type of engine. The hull of the transatlantic steamer is now always of iron, and is divided into a number of "compartments," each of which is water-tight and separated from the adjacent compartments by iron "bulkheads," in which are fitted doors which, when closed, are also water-tight. In some cases these doors close automatically when the water rises in the vessel, thus confining it to the leaking portion. Thus we have already seen a change in transoceanic lines from steamers like the Great Western (1837), 212 feet in length, of 35-1/2 feet beam, and 23 feet depth, driven by engines of 450 horse-power, and requiring 15 days to cross the Atlantic, to steamships over 550 feet long, 55 feet beam, and 55 feet deep, with engines of 10,000 horse-power, crossing the Atlantic in 7 days; iron substituted for wood in construction, the cost of fuel reduced one-half, and the speed raised from 8 to 18 knots and over. In the earlier days of steamships they were given a proportion of length to breadth of from 5 to 6 to 1; in forty years the proportion increased until 11 to 1 was reached. The whole naval establishment of every country has been greatly modified by the recent changes in methods of attack and defense; but the several classes of ships which still form the naval marine are all as dependent upon their steam-machinery as ever. [Illustration: H. B. M. Iron-Clad Captain. H. B. M. Iron-Clad Thunderer. U. S. Iron-Clad Dictator. U. S. Iron-Clad Monitor. H. B. M. Iron-Clad Giatton. French Iron-Clad Dunderberg. FIG. 145.--Modern Iron-Clads.] It is only recently that the attempt seems to have been made to determine a classification of war-vessels and to plan a naval establishment which shall be likely to meet fully the requirements of the immediate future. It has hitherto been customary simply to make each ship a little stronger, faster, or more powerful to resist or to make attack than was the last. The fact that the direction of progress in naval science and architecture is plainly perceivable, and that upon its study may be based a fair estimate of the character and relative distribution of several classes of vessels, seems to have been appreciated by very few. In the year 1870 the writer proposed[99] a classification of vessels other than torpedo-vessels, which has since been also proposed in a somewhat modified form by Mr. J. Scott Russell.[100] The author then remarked that the increase so rapidly occurring in weight of ordnance and of armor, and in speed of war-vessels, would probably soon compel a division of the vessels of every navy into three classes of ships, exclusive of torpedo-vessels, one for general service in time of peace, the others for use only in time of war. [99] _Journal Franklin Institute_, 1870. H. B. M. S. Monarch. [100] London _Engineering_, 1875. "The first class may consist of unarmored vessels of moderate size, fair speed under steam, armed with a few tolerably heavy guns, and carrying full sail-power. "The second class may be vessels of great speed under steam, unarmored, carrying light batteries and as great spread of canvas as can readily be given them; very much such vessels as the Wampanoag class of our own navy were intended to be--calculated expressly to destroy the commerce of an enemy. "The third class may consist of ships carrying the heaviest possible armor and armament, with strongly-built bows, the most powerful machinery that can be given them, of large coal-carrying capacity, and unencumbered by sails, everything being made secondary to the one object of obtaining victory in contending with the most powerful of possible opponents. Such vessels could never go to sea singly, but would cruise in couples or in squadrons. It seems hardly doubtful that attempts to combine the qualities of all classes in a single vessel, as has hitherto been done, will be necessarily given up, although the classification indicated will certainly tend largely to restrict naval operations." The introduction of the stationary, the floating, and the automatic classes of torpedoes, and of torpedo-vessels, has now become accomplished, and this element, which it was predicted by Bushnell and by Fulton three-quarters of a century ago would at some future time become important in warfare, is now well recognized by all nations. How far it may modify future naval establishments cannot be yet confidently stated, but it seems sufficiently evident that the attack, by any navy, of stationary defenses protected by torpedoes is now quite a thing of the past. It may be perhaps looked upon as exceedingly probable that torpedo-ships of very high speed will yet drive all heavily-armored vessels from the ocean, thus completing the historic parallel between the man-in-armor of the middle ages and the armored man-of-war of our own time.[101] [101] _Vide_ "Report on Machinery and Manufactures, etc., at Vienna," by the author, Washington, 1875. Of these classes, the third is of most interest, as exhibiting most perfectly the importance and variety of the work which the steam-engine is made to perform. On the later of these vessels, the anchor is raised by a steam anchor-hoisting apparatus; the heavier spars and sails are handled by the aid of a steam-windlass; the helm is controlled by a steering-engine, and the helmsman, with his little finger, sets in motion a steam-engine, which adjusts the rudder with a power which is unimpeded by wind or sea, and with an exactness that could not be exceeded by the hand-steering gear of a yacht; the guns are loaded by steam, are elevated or depressed, and are given lateral training, by the same power; the turrets in which the guns are incased are turned, and the guns are whirled toward every point of the compass, in less time than is required to sponge and reload them; and the ship itself is driven through the water by the power of ten thousand horses, at a speed which is only excelled on land by that of the railroad-train. The British Minotaur was one of the earlier iron-clads. The great length and consequent difficulty of man[oe]uvring, the defect of speed, and the weakness of armor of these vessels have led to the substitution of far more effective designs in later constructions. The Minotaur is a four-masted screw iron-clad, 400 feet long, of 59 feet beam and 26-1/2 feet draught of water. Her speed at sea is about 12-1/2 knots, and her engines develop, as a maximum, nearly 6,000 indicated horse-power. Her heaviest armor-plates are but 6 inches in thickness. Her extreme length and her unbalanced rudder make it difficult to turn rapidly. With _eighteen men at the steering-wheel_ and sixty others on the tackle, the ship, on one occasion, was 7-1/2 minutes in turning completely around. These long iron-clads were succeeded by the shorter vessels designed by Mr. E. J. Reed, of which the first, the Bellerophon, was of 4,246 tons burden, 300 feet long by 56 feet beam, and 24-1/2 feet draught, of the 14-knot speed, with 4,600 horse-power; and having the "balanced rudder" used many years earlier in the United States by Robert L. Stevens,[102] it can turn in four minutes with eight men at the wheel. The cost of construction was some $600,000 less than that of the Minotaur. A still later vessel, the Monarch, was constructed on a system quite similar to that known in the United States as the Monitor type, or as a turreted iron-clad. This vessel is 330 feet long, 57-1/2 feet wide, and 36 feet deep, drawing 24-1/2 feet of water. The total weight of ship and contents is over 8,000 tons, and the engines are of over 8,500 horse-power. The armor is 6 and 7 inches thick on the hull, and 8 inches on the two turrets, over a heavy teak backing. The turrets contain each two 12-inch rifled guns, weighing 25 tons each, and, with a charge of 70 pounds of powder, throwing a shot of 600 pounds weight with a velocity of 1,200 feet per second, and giving it a _vis viva_ equivalent to the raising of over 6,100 tons one foot high, and equal to the work of penetrating an iron plate 13-1/2 inches thick. This immense vessel is driven by a pair of "single-cylinder" engines having steam-cylinders _ten feet_ in diameter and of 4-1/2 feet stroke of piston, driving a two-bladed Griffith screw of 23-1/2 feet diameter and 26-1/2 feet pitch, 65 revolutions, at the maximum speed of 14.9 knots, or about 17-1/2 miles, an hour. To drive these powerful engines, boilers having an aggregate of about 25,000 square feet (or more than a half-acre) of heating-surface are required, with 900 square feet of grate-surface. The refrigerating surface in the condensers has an area of 16,500 square feet--over one-third of an acre. The cost of these engines and boilers was £66,500. [102] Still in use on the Hoboken ferry-boats. Were all this vast steam-power developed, giving the vessel a speed of 15 knots, the ship, if used as a "ram," would strike an enemy at rest with the tremendous "energy" of 48,000 foot-tons--equal to the shock of the projectiles of eight or nine such guns as are carried by the iron-clad itself, simultaneously discharged upon one spot. But even this great vessel is less formidable than later vessels. One of the latter, the Inflexible, is a shorter but wider and deeper ship than the Monarch, measuring 320 feet long, 75 feet beam, and 25 draught, displacing over 10,000 tons. The great rifles carried by this vessel weigh 81 tons each, throwing shot weighing a half-ton from behind iron-plating two feet in thickness. The steam-engines are of about the same power as those of the Monarch, and give this enormous hull a speed of 14 knots an hour. The navy of the United States does not to-day possess iron-clads of power even approximating that of either of several classes of British and other foreign naval vessels. The largest vessel of any class yet constructed is the Great Eastern (Fig. 146), begun in 1854 and completed in 1859, by J. Scott Russell, on the Thames, England. This ship is 680 feet long, 83 feet wide, 58 feet deep, 28 feet draught, and of 24,000 tons measurement. There are four paddle and four screw engines, the former having steam-cylinders 74 inches in diameter, with 14 feet stroke, the latter 84 inches in diameter and 4 feet stroke. They are collectively of 10,000 actual horse-power. The paddle-wheels are 56 feet in diameter, the screw 24 feet. The steam-boilers supplying the paddle-engines have 44,000 square feet (more than an acre) of heating-surface. The boilers supplying the screw-engines are still larger. At 30 feet draught, this great vessel displaces 27,000 tons. The engines were designed to develop 10,000 horse-power, driving the ship at the rate of 16-1/2 statute miles an hour. [Illustration: FIG. 146.--The Great Eastern.] The figures quoted in the descriptions of these great steamships do not enable the non-professional reader to form a conception of the wonderful power which is concentrated within so small a space as is occupied by their steam-machinery. The "horse-power" of the engines is that determined by James Watt as the maximum obtainable for eight hours a day from the strongest London draught-horses. The ordinary average draught-horse would hardly be able to exert two-thirds as much during the eight hours' steady work of a working-day. The working-day of the steam-engine, on the other hand, is twenty-four hours in length. [Illustration: FIG. 147.--The Great Eastern at Sea.] The work of the 10,000 horse-power engines of the Great Eastern could be barely equaled by the efforts of 15,000 horses; but to continue their work uninterruptedly, day in and day out, for weeks together, as when done by steam, would require at least three relays, or 45,000 horses. Such a stud would weigh 25,000 tons, and if harnessed "tandem" would extend thirty miles. It is only by such a comparison that the mind can begin to comprehend the utter impossibility of accomplishing by means of animal power the work now done for the world by steam. The cost of the greater power is but about one-tenth that of horse-power, and by its means tasks are accomplished with ease which are absolutely impossible of accomplishment by animal power. It is estimated that the total steam-power of the world is about 15,000,000 horse-power, and that, were horses actually employed to do the work which these engines would be capable of doing were they kept constantly in operation, the number required would exceed 60,000,000. Thus, from the small beginnings of the Comte d'Auxiron and the Marquis de Jouffroy in France, of Symmington in Great Britain, and of Henry, Rumsey, and Fitch, and of Fulton and Stevens, in the United States, steam-navigation has grown into a great and inestimable aid and blessing to mankind. We to-day cross the ocean with less risk, and transport ourselves and our goods at as little cost in either time or money as, at the beginning of the century, our parents experienced in traveling one-tenth the distance. It is largely in consequence of this ingenious application of a power that reminds one of the fabled genii of Eastern romance, that the mechanic and the laborer of to-day enjoy comforts and luxuries that were denied to wealth, and to royalty itself, a century ago. The magnitude of our modern steamships excites the wonder and admiration of even the people of our own time; and there is certainly no creation of art that can be grander in appearance than a transatlantic steamer a hundred and fifty yards in length, and weighing, with her stores, five or six thousand tons, as she starts on her voyage, moved by engines equal in power to the united strength of thousands of horses; none can more fully awaken a feeling of awe than an immense structure like the great modern iron-clads (Fig. 145), vessels having a total weight of 8,000 to 10,000 tons, and propelled by steam-engines of as many horse-power, carrying guns whose shot penetrate solid iron 20 inches thick, and having a power of impact, when steaming at moderate speed, sufficient to raise 35,000 tons a foot high. Far more huge than the Monarch among the iron-clads even is that prematurely-built monster, the Great Eastern (Fig. 147), already described, an eighth of a mile long, and with steam doing the work of a stud of 45,000 horses. Thus we are to-day witnessing the literal fulfillment of the predictions of Oliver Evans and of John Stevens, and almost that contained in the couplets written by the poet Darwin, who, more than a century ago, before even the earliest of Watt's improvements had become generally known, sang: "Soon shall thy arm, unconquered Steam, afar Drag the slow barge, or drive the rapid car; Or, on wide-waving wings expanded, bear The flying chariot through the fields of air." [Illustration] CHAPTER VII. _THE PHILOSOPHY OF THE STEAM-ENGINE._ THE HISTORY OF ITS GROWTH; ENERGETICS AND THERMO-DYNAMICS. "Of all the features which characterize this progressive economical movement of civilized nations, that which first excites attention, through its intimate connection with the phenomena of production, is the perpetual and, so far as human foresight can extend, the unlimited growth of man's power over Nature. Our knowledge of the properties and laws of physical objects shows no sign of approaching its ultimate boundaries; it is advancing more rapidly, and in a greater number of directions at once, than in any previous age or generation, and affording such frequent glimpses of unexplored fields beyond as to justify the belief that our acquaintance with Nature is still almost in its infancy."--MILL. The growth of the philosophy of the steam-engine presents as interesting a study as that of the successive changes which have occurred in its mechanism. In the operation of the steam-engine we find illustrated many of the most important principles and facts which constitute the physical sciences. The steam-engine is an exceedingly ingenious, but, unfortunately, still very imperfect, machine for transforming the heat-energy obtained by the chemical combination of a combustible with the supporter of combustion into mechanical energy. But the original source of all this energy is found far back of its first appearance in the steam-boiler. It had its origin at the beginning, when all Nature came into existence. After the solar system had been formed from the nebulous chaos of creation, the glowing mass which is now called the sun was the depository of a vast store of heat-energy, which was thence radiated into space and showered upon the attendant worlds in inconceivable quantity and with unmeasured intensity. During the past life of the globe, the heat-energy received from the sun upon the earth's surface was partly expended in the production of great forests, and the storage, in the trunks, branches, and leaves of the trees of which they were composed, of an immense quantity of carbon, which had previously existed in the atmosphere, combined with oxygen, as carbonic acid. The great geological changes which buried these forests under superincumbent strata of rock and earth resulted in the formation of coal-beds, and the storage, during many succeeding ages, of a vast amount of carbon, of which the affinity for oxygen remained unsatisfied until finally uncovered by the hand of man. Thus we owe to the heat and light of the sun, as was pointed out by George Stephenson, the incalculable store of potential energy upon which the human race is so dependent for life and all its necessaries, comforts, and luxuries. This coal, thrown upon the grate in the steam-boiler, takes fire, and, uniting again with the oxygen, sets free heat in precisely the same quantity that it was received from the sun and appropriated during the growth of the tree. The actual energy thus rendered available is transferred, by conduction and radiation, to the water in the steam-boiler, converts it into steam, and its mechanical effect is seen in the expansion of the liquid into vapor against the superincumbent pressure. Transferred from the boiler to the engine, the steam is there permitted to expand, doing work, and the heat-energy with which it is charged becomes partly converted into mechanical energy, and is applied to useful work in the mill or to driving the locomotive or the steamboat. Thus we may trace the store of energy received from the sun and contained in our coal through its several changes until it is finally set at work; and we might go still further and observe how, in each case, it is again usually re-transformed and again set free as heat-energy. The transformation which takes place in the furnace is a chemical change; the transfer of heat to the water and the subsequent phenomena accompanying its passage through the engine are physical changes, some of which require for their investigation abstruse mathematical operations. A thorough comprehension of the principles governing the operation of the steam-engine, therefore, can only be attained after studying the phenomena of physical science with sufficient minuteness and accuracy to be able to express with precision the laws of which those sciences are constituted. The study of the philosophy of the steam-engine involves the study of chemistry and physics, and of the new science of energetics, of which the now well-grown science of thermo-dynamics is a branch. This sketch of the growth of the steam-engine may, therefore, be very properly concluded by an outline of the growth of the several sciences which together make up its philosophy, and especially of the science of thermo-dynamics, which is peculiarly the science of the steam-engine and of the other heat-engines. These sciences, like the steam-engine itself, have an origin which antedates the commencement of the Christian era; but they grew with an almost imperceptible growth for many centuries, and finally, only a century ago, started onward suddenly and rapidly, and their progress has never since been checked. They are now fully-developed and well-established systems of natural philosophy. Yet, like that of the steam-engine and of its companion heat-engines, their growth has by no means ceased; and, while the student of science cannot do more than indicate the direction of their progress, he can readily believe that the beginning of the end is not yet reached in their movement toward completeness, either in the determination of facts or in the codification of their laws. When Hero lived at Alexandria, the great "Museum" was a most important centre, about which gathered the teachers of all then known philosophies and of all the then recognized but unformed sciences, as well as of all those technical branches of study which had already been so far developed as to be capable of being systematically taught. Astronomical observations had been made regularly and uninterruptedly by the Chaldean astrologers for two thousand years, and records extending back many centuries had been secured at Babylon by Calisthenes and given to Aristotle, the father of our modern scientific method. Ptolemy had found ready to his hand the records of Chaldean observers of eclipses extending back nearly 650 years, and marvelously accurate.[103] [103] Their estimate of the length of the Saros, or cycle of eclipses--over 19 years--was "within 19-1/2 minutes of the truth."--DRAPER. A rude method of printing with an engraved roller on plastic clay, afterward baked, thus making up ceramic libraries, was practised long previous to this time; and in the alcoves in which Hero worked were many of these books of clay. This great Library and Museum of Alexandria was founded three centuries before the birth of Christ, by Ptolemy Soter, who established as his capital that great Egyptian city when the death of his brother, the youthful but famous conqueror whose name he gave it, placed him upon the throne of the colossal successor of the then fallen Persian Empire. The city itself, embellished with every ornament and provided with every luxury that the wealth of a conquered world or the skill, taste, and ingenuity of the Greek painters, sculptors, architects, and engineers could provide, was full of wonders; it was a wonder in itself. This rich, populous, and magnificent city was the metropolis of the then civilized world. Trade, commerce, manufactures, and the fine arts were all represented in this splendid exchange, and learning found its most acceptable home and noblest field within the walls of Ptolemy's Museum; its disciples found themselves welcomed and protected by its founder and his successors, Philadelphus and the later Ptolemies. The Alexandrian Museum was founded with the declared object of collecting all written works of authority, of promoting the study of literature and art, and of stimulating and assisting experimental and mathematical scientific investigation and research. The founders of modern libraries, colleges, and technical schools have their prototype in intelligence, public spirit, and liberality, in the first of the Ptolemies, who not only spent an immense sum in establishing this great institution, but spared no expense in sustaining it. Agents were sent out into all parts of the world, purchasing books. A large staff of scribes was maintained at the museum, whose duty it was to multiply copies of valuable works, and to copy for the library such works as could not be purchased. The faculty of the museum was as carefully organized as was the plan of its administration. The four principal faculties of astronomy, literature, mathematics, and medicine were subdivided into sections devoted to the several branches of each department. The collections of the museum were as complete as the teachers of the undeveloped sciences of the time could make them. Lectures were given in all branches of study, and the number of students was sometimes as great as twelve or thirteen thousand. The number of books which were collected here, when the barbarian leaders of the Roman troops under Cæsar burned the greater part of it, was stated to be 700,000. Of these, 400,000 were within the museum itself, and were all destroyed; the rest were in the temple of Serapis, and, for the time, escaped destruction. The greatest of all the great men who lived at Alexandria at the time of the establishment of the museum was Aristotle, the teacher of Alexander and the friend of Ptolemy. It is to Aristotle that we owe the systematization of the philosophical ideas of Plato and the creation of the inductive method, in which has originated all modern science. It is to the learned men of Alexandria that we are indebted for so effective an application of the Aristotelian philosophy that all the then known sciences were given form, and were so thoroughly established that the work of modern science has been purely one of development. The inductive method, which built up all the older sciences, and which has created all those of recent development, consists, first, in the discovery and quantitative determination of facts; secondly, when a sufficient number of facts have been thus observed and defined, in the grouping of those facts, and the detection, by a study of their mutual relations, of the natural laws which give rise to or regulate them. This simple method is that--and the only--method by which science advances. By this method, and by it only, do we acquire connected and systematic knowledge of all the phenomena of Nature of which the physical sciences are cognizant. It is only by the application of this Aristotelian method and philosophy that we can hope to acquire exact scientific knowledge of existing phenomena, or to become able to anticipate the phenomena which are to distinguish the future. The Aristotelian method of observing facts, and of inductive reasoning with those facts as a basis, has taught the chemist the properties of the known elementary substances and their characteristic behavior under ascertained conditions, and has taught him the laws of combination and the effects of their union, enabling him to predict the changes and the phenomena, chemical and physical, which inevitably follow their contact under any specified set of conditions. It is this process which has enabled the physicist to ascertain the methods of molecular motion which give us light, heat, or electricity, and the range of action and the laws which govern the transfer of energy from one of these modes of motion to another. It was this method of study which enabled James Watt to detect and to remedy the defects of the Newcomen engine, and it is by the Aristotelian philosophy that the engineer of to-day is taught to construct the modern steamship, and to predict, before the keel is laid or a blow struck in the workshop or the ship-yard, what will be the weight of the vessel, its cargo-carrying capacity, the necessary size and power of its engines, the quantity of coal which they will require per day while crossing the ocean, the depth at which the great hull will float in the water, and the exact speed that the vessel will attain when the engines are exerting their thousand or their ten thousand horse-power. It was at Alexandria that this mighty philosophy was first given a field in which to work effectively. Here Ptolemy studied astronomy and "natural philosophy;" Archimedes applied himself to the studies which attract the mathematician and engineer; Euclid taught his royal pupil those elements of geometry which have remained standard twenty-two centuries; Eratosthenes and Hipparchus studied and taught astronomy, and inaugurated the existing system of quantitative investigation, proving the spherical form of the earth; and Ctesibius and Hero studied pneumatics and experimented with the germs of the steam-engine and of less important machines. When, seven centuries later, the destruction of this splendid institution was signalized by the death of that brilliant scholar and heathen teacher of philosophy, Hypatia, at the hands of the more heathenish fanatics who tore her in pieces at the foot of the cross, and by the dispersion of the library left by Cæsar's soldiers in the Serapeum, a true philosophy had been created, and the inductive method was destined to live and to overcome every obstacle in the path of enlightenment and civilization. The fall of the Alexandrian Museum, sad as was the event, could not destroy the new philosophical method. Its fruits ripened slowly but surely, and we are to-day gathering a plentiful harvest. Science, literature, and the arts, all remained dormant for several centuries after the catastrophe which deprived them of the light in which they had flourished so many centuries. The armies of the caliphs made complete the shameful work of destruction begun by the armies of Cæsar, and the Alexandrian Library, partly destroyed by the Romans, was completely dispersed by the Patriarchs and their ignorant and fanatical followers; and finally all the scattered remnants were burned by the Saracens. But when the thirst for conquest had become satiated or appeased, the followers of the caliphs turned their attention to intellectual pursuits, and the ninth century of the Christian era saw once more such a collection of philosophical writings, collected at Bagdad, as could only be gathered by the power and wealth of the later conquerors of the world. Philosophy once again resumed its empire, and another race commenced the study of the mathematics of India and of Greece, the astronomy of Chaldea, and of all the sciences which originated in Greece and in Egypt. By the conquest of Spain by the Saracens, the new civilization was imported into Western Europe and libraries were gathered together under the Moorish rulers, one of which numbered more than a half-million volumes. Wherever Saracen armies had extended Mohammedan rule, schools and colleges, libraries and collections of philosophical apparatus, were scattered in strange profusion; and students, teachers, philosophers, of all--the speculative as well as the Aristotelian--schools, gathered together at these intellectual ganglia, as enthusiastic in their work as were their Alexandrian predecessors. The endowment of colleges, that truest gauge of the intelligence of the wealthy classes of any community, became as common--perhaps more so--as at the present time, and provision was made for the education of rich and poor alike. The mathematical sciences, and the wonderful and beautiful phenomena which--but a thousand years later--were afterward grouped into a science and called chemistry, were especially attractive to the Arabian scholars, and technical applications of discovered facts and laws assisted in a wonderfully rapid development of arts and manufactures. When, a thousand years after Christ, the centre of intellectual activity and of material civilization had drifted westward into Andalusia, the foundation of every modern physical science except that now just taking shape--the all-grasping science of energetics--had been laid with experimentally derived facts; and in mathematics there had been erected a symmetrical and elegant superstructure. Even that underlying principle of all the sciences, the principle of the persistence of energy, had been, perhaps unwittingly, enunciated. Distinguished historians have shown how the progress of civilization in Europe resulted in the creation, during the middle ages, of the now great middle class, which, holding the control of political power, governs every civilized nation, and has come into power so gradually that it was only after centuries that its influence was seen and felt. This, which Buckle[104] calls the intellectual class, first became active, independently of the military and of the clergy, in the fourteenth century. In the two succeeding centuries this class gained power and influence; and in the seventeenth century we find a magnificent advance in all branches of science, literature, and art, marking the complete emancipation of the intellect from the artificial conditions which had so long repressed its every effort at advancement. [104] "History of Civilization in England," vol. i., p. 208. London, 1868. Another great social revolution thus occurred, following another period of centuries of intellectual stagnation. The Saracen invaders were driven from Europe; the Crusaders invaded Palestine, in the vain effort to recover from the hands of the infidels the Holy Sepulchre and the Holy Land; and intestine broils and inter-state conflicts, as well as these greater social movements, withdrew the minds of men once more from the arts of peace and the pursuits of scholars. It is not, then, until the beginning of the seventeenth century--the time of Galileo and of Newton--that we find the nations of Europe sufficiently quiet and secure to permit general attention to intellectual vocations, although it was a half-century earlier (1543) that Copernicus left to the world that legacy which revolutionized the theories of the astronomers and established as correct the hypothesis which made the sun the centre of the solar system. Galileo now began to overturn the speculations of the deductive philosophers, and to proclaim the still disputed principle that the book of Nature is a trustworthy commentary in the study of theological and revealed truths, so far as they affect or are affected by science; he suffered martyrdom when he proclaimed the fact that God's laws, as they now stand, had been instituted without deference to the preconceived notions of the most ignorant of men. Bruno had a few years earlier (1600) been burned at the stake for a similar offense. Galileo was perhaps the first, too, to combine invariably in application the idea of Plato, the philosophy of Aristotle, and the methods of modern experimentation, to form the now universal scientific method of experimental philosophy. He showed plainly how the grouping of ascertained facts, in natural sequence, leads to the revelation of the law of that sequence, and indicated the existence of a principle which is now known as the law of continuity--the law that in all the operations of Nature there is to be seen an unbroken chain of effect leading from the present back into a known or an unknown past, toward a cause which may or may not be determinable by science or known to history. Galileo, the Italian, was worthily matched by Newton, the prince of English philosophers. The science of theoretical mechanics was hardly beginning to assume the position which it was afterward given among the sciences; and the grand work of collating facts already ascertained, and of definitely stating principles which had previously been vaguely recognized, was splendidly done by Newton. The needs of physical astronomy urged this work upon him. Da Vinci had, in the latter half of the fifteenth century, summarized as much of the statics of mechanical philosophy as had, up to his time, been given shape; he also rewrote and added very much to what was known on the subject of friction, and enunciated its laws. He had evidently a good idea of the principle of "virtual velocities," that simple case of equivalence of work, in a connected system, which has done such excellent service since; and with his mechanical philosophy this versatile engineer and artist curiously mingled much of physical science. Then Stevinus, the "brave engineer of Bruges," a hundred years later (1586), alternating office and field work, somewhat after the manner of the engineer of to-day, wrote a treatise on mechanics, which showed the value of practical experience and judgment in even scientific work. And thus the path had been cleared for Newton. Meantime, also, Kepler had hit upon the true relations of the distances of the planets and their periodic times, after spending half a generation in blindly groping for them, thus furnishing those great landmarks of fact in the mechanics of astronomy; and Galileo had enunciated the laws of motion. Thus the foundation of the science of dynamics, as distinguished from statics, was laid, and the beginning was made of that later science of energetics, of which the philosophy of the steam-engine is so largely constituted. Hooke, Huyghens, and others, had already seen some of the principal consequences of these laws; but it remained for Newton to enunciate them with the precision of a true mathematician, and to base upon them a system of dynamical laws, which, complemented by his announcement of the existence of the force of gravitation, and his statement of its laws, gave a firm basis for all that the astronomer has since done in those quantitative determinations of size, weight, and distance, and of the movements of the heavenly bodies, which compel the wonder and admiration of mankind. The Arabians and Greeks had noticed that the direction taken by a body falling under the action of gravitation was directly toward the centre of the earth, wherever its fall might occur; Galileo had shown, by his experiments at Pisa, that the velocity of fall, second after second, varied as the numbers 1, 3, 5, 7, 9, etc., and that the distances varied as the squares of the total periods of time during which the body was falling, and that it was, in British feet, very nearly sixteen times the square of that time in seconds. Kepler had proved that the movements of the heavenly bodies were just such as would occur under the action of central attractive forces and of centrifugal force. Putting all these things together, Newton was led to believe that there existed a "force of gravity," due to the attraction, by the great mass of the earth, of its own particles and of neighboring bodies, like the moon, of which force the influence extended as far, at least, as the latter. He calculated the motion of the earth's satellite, on the assumption that his theory and the then accepted measurements of the earth's dimensions were correct, and obtained a roughly approximate result. Later, in 1679, he revised his calculations, using Picard's more accurate determination of the dimensions of the earth, and obtained a result which precisely tallied with careful measurements, made by the astronomers, of the moon's motion. The science of mechanics had now, with the publication of Newton's "Principia," become thoroughly consistent and logically complete, so far as was possible without a knowledge of the principles of energetics; and Newton's enunciations of the laws of motion, concise and absolutely perfect as they still seem, were the basis of the whole science of dynamics, as applied to bodies moving freely under the action of applied forces, either constant or variable. They are as perfect a basis for that science as are the primary principles of geometry for the whole beautiful structure which is built up on them. The three perfect qualitative expressions of dynamical law are: 1. Every free body continues in the state in which it may be, whether of rest or of rectilinear uniform motion, until compelled to deviate from that state by impressed forces. 2. Change of motion is proportional to the force impressed, and in the direction of the right line in which that force acts. 3. Action is always opposed by reaction; action and reaction are equal, and in directly contrary directions. We may add to these principles a definition of a force, which is equally and absolutely complete: _Force_ is that which produces, or tends to produce, motion, or change of motion, in bodies. It is measured statically by the weight that will counterpoise it, or by the pressure which it will produce, and dynamically by the velocity which it will produce, acting in the unit of time on the unit of mass. The quantitative determinations of dynamic effects of forces are always readily made when it is remembered that the effect of a force equal to its own weight, when the body is free to move, is to produce in one second a velocity of 32.2 feet per second, which quantity is the unit of dynamic measurement. _Work_ is the product of the resistance met in any instance of the exertion of a force, into the distance through which that force overcomes the resistance. _Energy_ is the work which a body is capable of doing, by its weight or inertia, under given conditions. The energy of a falling body, or of a flying shot, is about 1/64 its weight multiplied by the square of its velocity, or, which is the same thing, the product of its weight into the height of fall or height due its velocity. These principles and definitions, with the long-settled definitions of the primary ideas of space and time, were all that were needed to lead the way to that grandest of all physical generalizations, the doctrine of the persistence or conservation of all energy, and to its corollary declaring the equivalence of all forms of energy, and also to the experimental demonstration of the transformability of energy from one mode of existence to another, and its universal existence in the various modes of motion of bodies and of their molecules. Experimental physical science had hardly become acknowledged as the only and the proper method of acquiring knowledge of natural phenomena at the time of Newton; but it soon became a generally accepted principle. In physics, Gilbert had made valuable investigations before Newton, and Galileo's experiments at Pisa had been examples of similarly useful research. In chemistry, it was only when, a century later, Lavoisier showed by his splendid example what could be done by the skillful and intelligent use of quantitative measurements, and made the balance the chemist's most important tool, that a science was formed comprehending all the facts and laws of chemical change and molecular combination. We have already seen how astronomy and mathematics together led philosophers to the creation and the study of what finally became the science of mechanics, when experiment and observation were finally brought to their aid. We can now see how, in all these physical sciences, four primitive ideas are comprehended: matter, force, motion, and space--which latter two terms include all relations of position. Based on these notions, the science of mechanics comprehends four sections, which are of general application in the study of all physical phenomena. These are: _Statics_, which treats of the action and effect of forces. _Kinematics_, which treats of relations of motion simply. _Dynamics_, or kinetics, which treats of simple motion as an effect of the action of forces. _Energetics_, which treats of modifications of energy under the action of forces, and of its transformation from one mode of manifestation to another, and from one body to another. Under the latter of these four divisions of mechanical philosophy is comprehended that latest of the minor sciences, of which the heat-engines, and especially the steam-engine, illustrate the most important applications--_Thermo-dynamics_. This science is simply a wider generalization of principles which, as we have seen, have been established one at a time, and by philosophers widely separated both geographically and historically, by both space and time, and which have been slowly aggregated to form one after another of the sciences, and out of which, as we now are beginning to see, we are slowly evolving wider generalizations, and thus tending toward a condition of scientific knowledge which renders more and more probable the truth of Cicero's declaration: "One eternal and immutable law embraces all things and all times." At the basis of the whole science of energetics lies a principle which was enunciated before Science had a birthplace or a name: _All that exists, whether matter or force, and in whatever form, is indestructible, except by the Infinite Power which has created it._ That matter is indestructible by finite power became admitted as soon as the chemists, led by their great teacher Lavoisier, began to apply the balance, and were thus able to show that in all chemical change there occurs only a modification of form or of combination of elements, and no loss of matter ever takes place. The "persistence" of energy was a later discovery, consequent largely upon the experimental determination of the convertibility of heat-energy into other forms and into mechanical work, for which we are indebted to Rumford and Davy, and to the determination of the quantivalence anticipated by Newton, shown and calculated approximately by Colding and Mayer, and measured with great probable accuracy by Joule. [Illustration: Benjamin Thompson, Count Rumford.] The great fact of the conservation of energy was loosely stated by Newton, who asserted that the work of friction and the _vis viva_ of the system or body arrested by friction were equivalent. In 1798, Benjamin Thompson, Count Rumford, an American who was then in the Bavarian service, presented a paper[105] to the Royal Society of Great Britain, in which he stated the results of an experiment which he had recently made, proving the immateriality of heat and the transformation of mechanical into heat energy. This paper is of very great historical interest, as the now accepted doctrine of the persistence of energy is a generalization which arose out of a series of investigations, the most important of which are those which resulted in the determination of the existence of a definite quantivalent relation between these two forms of energy and a measurement of its value, now known as the "mechanical equivalent of heat." His experiment consisted in the determination of the quantity of heat produced by the boring of a cannon at the arsenal at Munich. [105] "Philosophical Transactions," 1798. Rumford, after showing that this heat could not have been derived from any of the surrounding objects, or by compression of the materials employed or acted upon, says: "It appears to me extremely difficult, if not impossible, to form any distinct idea of anything capable of being excited and communicated in the manner that heat was excited and communicated in these experiments, except it be motion."[106] He then goes on to urge a zealous and persistent investigation of the laws which govern this motion. He estimates the heat produced by a power which he states could easily be exerted by one horse, and makes it equal to the "combustion of nine wax candles, each three-quarters of an inch in diameter," and equivalent to the elevation of "25.68 pounds of ice-cold water" to the boiling-point, or 4,784.4 heat-units.[107] The time was stated at "150 minutes." Taking the actual power of Rumford's Bavarian "one horse" as the most probable figure, 25,000 pounds raised one foot high per minute,[108] this gives the "mechanical equivalent" of the foot-pound as 783.8 heat-units, differing but 1.5 per cent. from the now accepted value. [106] This idea was not by any means original with Rumford. Bacon seems to have had the same idea; and Locke says, explicitly enough: "Heat is a very brisk agitation of the insensible parts of the object ... so that what in our sensation is heat, in the object is nothing but motion." [107] The British heat-unit is the quantity of heat required to heat one pound of water 1° Fahr. from the temperature of maximum density. [108] Rankine gives 25,920 foot-pounds per minute--or 432 per second--for the average draught-horse in Great Britain, which is probably too high for Bavaria. The engineer's "horse-power"--33,000 foot-pounds per minute--is far in excess of the average power of even a good draught-horse, which latter is sometimes taken as two-thirds the former. Had Rumford been able to eliminate all losses of heat by evaporation, radiation, and conduction, to which losses he refers, and to measure the power exerted with accuracy, the approximation would have been still closer. Rumford thus made the experimental discovery of the real nature of heat, proving it to be a form of energy, and, publishing the fact a half-century before the now standard determinations were made, gave us a very close approximation to the value of the heat-equivalent. Rumford also observed that the heat generated was "exactly proportional to the force with which the two surfaces are pressed together, and to the rapidity of the friction," which is a simple statement of equivalence between the quantity of work done, or energy expended, and the quantity of heat produced. This was the first great step toward the formation of a Science of Thermo-dynamics. Rumford's work was the corner-stone of the science. Sir Humphry Davy, a little later (1799), published the details of an experiment which conclusively confirmed these deductions from Rumford's work. He rubbed two pieces of ice together, and found that they were melted by the friction so produced. He thereupon concluded: "It is evident that ice by friction is converted into water.... Friction, consequently, does not diminish the capacity of bodies for heat." Bacon and Newton, and Hooke and Boyle, seem to have anticipated--long before Rumford's time--all later philosophers, in admitting the probable correctness of that modern dynamical, or vibratory, theory of heat which considers it a mode of motion; but Davy, in 1812, for the first time, stated plainly and precisely the real nature of heat, saying: "The immediate cause of the phenomenon of heat, then, is motion, and the laws of its communication are precisely the same as the laws of the communication of motion." The basis of this opinion was the same that had previously been noted by Rumford. So much having been determined, it became at once evident that the determination of the exact value of the mechanical equivalent of heat was simply a matter of experiment; and during the succeeding generation this determination was made, with greater or less exactness, by several distinguished men. It was also equally evident that the laws governing the new science of thermo-dynamics could be mathematically expressed. Fourier had, before the date last given, applied mathematical analysis in the solution of problems relating to the transfer of heat without transformation, and his "Théorie de la Chaleur" contained an exceedingly beautiful treatment of the subject. Sadi Carnot, twelve years later (1824), published his "Réflexions sur la Puissance Motrice du Feu," in which he made a first attempt to express the principles involved in the application of heat to the production of mechanical effect. Starting with the axiom that a body which, having passed through a series of conditions modifying its temperature, is returned to "its primitive physical state as to density, temperature, and molecular constitution," must contain the same quantity of heat which it had contained originally, he shows that the efficiency of heat-engines is to be determined by carrying the working fluid through a complete cycle, beginning and ending with the same set of conditions. Carnot had not then accepted the vibratory theory of heat, and consequently was led into some errors; but, as will be seen hereafter, the idea just expressed is one of the most important details of a theory of the steam-engine. Seguin, who has already been mentioned as one of the first to use the fire-tubular boiler for locomotive engines, published in 1839 a work, "Sur l'Influence des Chemins de Fer," in which he gave the requisite data for a rough determination of the value of the mechanical equivalent of heat, although he does not himself deduce that value. Dr. Julius R. Mayer, three years later (1842), published the results of a very ingenious and quite closely approximate calculation of the heat-equivalent, basing his estimate upon the work necessary to compress air, and on the specific heats of the gas, the idea being that the work of compression is the equivalent of the heat generated. Seguin had taken the converse operation, taking the loss of heat of expanding steam as the equivalent of the work done by the steam while expanding. The latter also was the first to point out the fact, afterward experimentally proved by Hirn, that the fluid exhausted from an engine should heat the water of condensation less than would the same fluid when originally taken into the engine. A Danish engineer, Colding, at about the same time (1843), published the results of experiments made to determine the same quantity; but the best and most extended work, and that which is now almost universally accepted as standard, was done by a British investigator. James Prescott Joule commenced the experimental investigations which have made him famous at some time previous to 1843, at which date he published, in the _Philosophical Magazine_, his earliest method. His first determination gave 770 foot-pounds. During the succeeding five or six years Joule repeated his work, adopting a considerable variety of methods, and obtaining very variable results. One method was to determine the heat produced by forcing air through tubes; another, and his usual plan, was to turn a paddle-wheel by a definite power in a known weight of water. He finally, in 1849, concluded these researches. [Illustration: James Prescott Joule.] The method of calculating the mechanical equivalent of heat which was adopted by Dr. Mayer, of Heilbronn, is as beautiful as it is ingenious: Conceive two equal portions of atmospheric air to be inclosed, at the same temperature--as at the freezing-point--in vessels each capable of containing one cubic foot; communicate heat to both, retaining the one portion at the original volume, and permitting the other to expand under a constant pressure equal to that of the atmosphere. In each vessel there will be inclosed 0.08073 pound, or 1.29 ounce, of air. When, at the same temperature, the one has doubled its pressure and the other has doubled its volume, each will be at a temperature of 525.2° Fahr., or 274° C, and each will have double the original temperature, as measured on the absolute scale from the zero of heat-motion. But the one will have absorbed but 6-3/4 British thermal units, while the other will have absorbed 9-1/2. In the first case, all of this heat will have been employed in simply increasing the temperature of the air; in the second case, the temperature of the air will have been equally increased, and, besides, a certain amount of work--2,116.3 foot-pounds--must have been done in overcoming the resistance of the air; it is to this latter action that we must debit the additional heat which has disappeared. Now, 2,116.3/(2-3/4) = 770 foot-pounds per heat-unit--almost precisely the value derived from Joule's experiments. Had Mayer's measurement been absolutely accurate, the result of his calculation would have been an exact determination of the heat-equivalent, provided no heat is, in this case, lost by internal work. Joule's most probably accurate measure was obtained by the use of a paddle-wheel revolving in water or other fluid. A copper vessel contained a carefully weighed portion of the fluid, and at the bottom was a step, on which stood a vertical spindle carrying the paddle-wheel. This wheel was turned by cords passing over nicely-balanced grooved wheels, the axles of which were carried on friction-rollers. Weights hung at the ends of these cords were the moving forces. Falling to the ground, they exerted an easily and accurately determinable amount of work, _W_ × _H_, which turned the paddle-wheel a definite number of revolutions, warming the water by the production of an amount of heat exactly equivalent to the amount of work done. After the weight had been raised and this operation repeated a sufficient number of times, the quantity of heat communicated to the water was carefully determined and compared with the amount of work expended in its development. Joule also used a pair of disks of iron rubbing against each other in a vessel of mercury, and measured the heat thus developed by friction, comparing it with the work done. The average of forty experiments with water gave the equivalent 772.692 foot-pounds; fifty with mercury gave 774.083; twenty with cast-iron gave 774.987--the temperature of the apparatus being from 55° to 60° Fahr. Joule also determined, by experiment, the fact that the expansion of air or other gas without doing work produces no change of temperature, which fact is predicable from the now known principles of thermo-dynamics. He stated the results of his researches relating to the mechanical equivalent of heat as follows: 1. The heat produced by the friction of bodies, whether solid or liquid, is always proportional to the quantity of work expended. 2. The quantity required to increase the temperature of a pound of water (weighed _in vacuo_ at 55° to 60° Fahr.) by one degree requires for its production the expenditure of a force measured by the fall of 772 pounds from a height of one foot. This quantity is now generally called "Joule's equivalent." During this series of experiments, Joule also deduced the position of the "absolute zero," the point at which heat-motion ceases, and stated it to be about 480° Fahr. below the freezing-point of water, which is not very far from the probably true value,-493.2° Fahr. (-273° C.), as deduced afterward from more precise data. The result of these, and of the later experiments of Hirn and others, has been the admission of the following principle: Heat-energy and mechanical energy are mutually convertible and have a definite equivalence, the British thermal unit being equivalent to 772 foot-pounds of work, and the metric _calorie_ to 423.55, or, as usually taken, 424 kilogrammetres. The exact measure is not fully determined, however. It has now become generally admitted that all forms of energy due to physical forces are mutually convertible with a definite quantivalence; and it is not yet determined that even vital and mental energy do not fall within the same great generalization. This quantivalence is the sole basis of the science of Energetics. The study of this science has been, up to the present time, principally confined to that portion which comprehends the relations of heat and mechanical energy. In the study of this department of the science, thermo-dynamics, Rankine, Clausius, Thompson, Hirn, and others have acquired great distinction. In the investigations which have been made by these authorities, the methods of transfer of heat and of modification of physical state in gases and vapors, when a change occurs in the form of the energy considered, have been the subjects of especial study. According to the law of Boyle and Marriotte, the expansion of such fluids follows a law expressed graphically by the hyperbola, and algebraically by the expression PV^{_x_} = A, in which, with unchanging temperature, _x_ is equal to 1. One of the first and most evident deductions from the principles of the equivalence of the several forms of energy is that the value of x must increase as the energy expended in expansion increases. This change is very marked with a vapor like steam--which, expanded without doing work, has an exponent less than unity, and which, when doing work by expanding behind a piston, partially condenses, the value of _x_ increases to, in the case of steam, 1.111 according to Rankine, or, probably more correctly, to 1.135 or more, according to Zeuner and Grashof. This fact has an important bearing upon the theory of the steam-engine, and we are indebted to Rankine for the first complete treatise on that theory as thus modified. Prof. Rankine began his investigations as early as 1849, at which time he proposed his theory of the molecular constitution of matter, now well known as the theory of molecular vortices. He supposes a system of whirling rings or vortices of heat-motion, and bases his philosophy upon that hypothesis, supposing sensible heat to be employed in changing the velocity of the particles, latent heat to be the work of altering the dimensions of the orbits, and considering the effort of each vortex to enlarge its boundaries to be due to centrifugal force. He distinguished between real and apparent specific heat, and showed that the two methods of absorption of heat, in the case of the heating of a fluid, that due to simple increase of temperature and that due to increase of volume, should be distinguished; he proposed, for the latter quantity, the term heat-potential, and for the sum of the two, the name of thermo-dynamic function. [Illustration: Prof. W. J. M. Rankine.] Carnot had stated, a quarter of a century earlier, that the efficiency of a heat-engine is a function of the two limits of temperature between which the machine is worked, and not of the nature of the working substance--an assertion which is quite true where the material does not change its physical state while working. Rankine now deduced that "general equation of thermo-dynamics" which expresses algebraically the relations between heat and mechanical energy, when energy is changing from the one state to the other, in which equation is given, for any assumed change of the fluids, the quantity of heat transformed. He showed that steam in the engine must be partially liquefied by the process of expanding against a resistance, and proved that the total heat of a perfect gas must increase with rise of temperature at a rate proportional to its specific heat under constant pressure. Rankine, in 1850, showed the inaccuracy of the then accepted value, 0.2669, of the specific heat of air under constant pressure, and calculated its value as 0.24. Three years later, the experiments of Regnault gave the value 0.2379, and Rankine, recalculating it, made it 0.2377. In 1851, Rankine continued his discussion of the subject, and, by his own theory, corroborated Thompson's law giving the efficiency of a perfect heat-engine as the quotient of the range of working temperature to the temperature of the upper limit, measured from the absolute zero. During this period, Clausius, the German physicist, was working on the same subject, taking quite a different method, studying the mechanical effects of heat in gases, and deducing, almost simultaneously with Rankine (1850), the general equation which lies at the beginning of the theory of the equivalence of heat and mechanical energy. He found that the probable zero of heat-motion is at such a point that the Carnot function must be approximately the reciprocal of the "absolute" temperature, as measured with the air thermometer, or, stated exactly, that quantity as determined by a perfect gas thermometer. He confirmed Rankine's conclusion relative to the liquefaction of saturated vapors when expanding against resistance, and, in 1854, adapted Carnot's principle to the new theory, and showed that his idea of the reversible engine and of the performance of a cycle in testing the changes produced still held good, notwithstanding Carnot's ignorance of the true nature of heat. Clausius also gave us the extremely important principle: It is impossible for a self-acting machine, unaided, to transfer heat from one body at a low temperature to another having a higher temperature. Simultaneously with Rankine and Clausius, Prof. William Thomson was engaged in researches in thermo-dynamics (1850). He was the first to express the principle of Carnot as adapted to the modern theory by Clausius in the now generally quoted propositions:[109] [109] _Vide_ Tait's admirable "Sketch of Thermodynamics," second edition, Edinburgh, 1877. 1. When equal mechanical effects are produced by purely thermal action, equal quantities of heat are produced or disappear by transformation of energy. 2. If, in any engine, a reversal effects complete inversion of all the physical and mechanical details of its operation, it is a perfect engine, and produces maximum effect with any given quantity of heat and with any fixed limits of range of temperature. William Thomson and James Thompson showed, among the earliest of their deductions from these principles, the fact, afterward confirmed by experiment, that the melting-point of ice should be lowered by pressure 0.0135° Fahr, for each atmosphere, and that a body which contracts while being heated will always have its temperature decreased by sudden compression. Thomson applied the principles of energetics in extended investigations in the department of electricity, while Helmholtz carried some of the same methods into his favorite study of acoustics. The application of now well-settled principles to the physics of gases led to many interesting and important deductions: Clausius explained the relations between the volume, density, temperature, and pressure of gases, and their modifications; Maxwell reëstablished the experimentally determined law of Dalton and Charles, known also as that of Gay-Lussac (1801), which asserts that all masses of equal pressure, volume, and temperature, contain equal numbers of molecules. On the Continent of Europe, also, Hirn, Zeuner, Grashof, Tresca, Laboulaye, and others have, during the same period and since, continued and greatly extended these theoretical researches. During all this time, a vast amount of experimental work has also been done, resulting in the determination of important data without which all the preceding labor would have been fruitless. Of those who have engaged in such work, Cagniard de la Tour, Andrews, Regnault, Hirn, Fairbairn and Tate, Laboulaye, Tresca, and a few others have directed their researches in this most important direction with the special object of aiding in the advancement of the new-born sciences. By the middle of the present century, the time which we are now studying, this set of data was tolerably complete. Boyle had, two hundred years before, discovered and published the law, which is now known by his name[110] and by that of Marriotte,[111] that the pressure of a gas varies inversely as its volume and directly as its density; Dr. Black and James Watt discovered, a hundred years later (1760), the latent heat of vapors, and Watt determined the method of expansion of steam; Dalton, in England, and Gay-Lussac, in France, showed, at the beginning of the nineteenth century, that all gaseous fluids are expanded by equal fractions of their volume by equal increments of temperature; Watt and Robison had given tables of the elastic force of steam, and Gren had shown that, at the temperature of boiling water, the pressure of steam was equal to that of the atmosphere; Dalton, Ure, and others proved (1800-1818) that the law connecting temperatures and pressures of steam was expressed by a geometrical ratio; and Biot had already given an approximate formula, when Southern introduced another, which is still in use. [110] "New Experiments, Physico-Mechanical, etc., touching the Spring of Air," 1662. [111] "De la Nature de l'Air," 1676. The French Government established a commission in 1823 to experiment with a view to the institution of legislation regulating the working of steam-engines and boilers; and this commission, MM. de Prony, Arago, Girard, and Dulong, determined quite accurately the temperatures of steam under pressures running up to twenty-four atmospheres, giving a formula for the calculation of the one quantity, the other being known. Ten years later, the Government of the United States instituted similar experiments under the direction of the Franklin Institute. The marked distinction between gases, like oxygen and hydrogen, and condensible vapors, like steam and carbonic acid, had been, at this time, shown by Cagniard de la Tour, who, in 1822, studied their behavior at high temperatures and under very great pressures. He found that, when a vapor was confined in a glass tube in presence of the same substance in the liquid state, as where steam and water were confined together, if the temperature was increased to a certain definite point, the whole mass suddenly became of uniform character, and the previously existing line of demarkation vanished, the whole mass of fluid becoming, as he inferred, gaseous. It was at about this time that Faraday made known his then novel experiments, in which gases which had been before supposed permanent were liquefied, simply by subjecting them to enormous pressures. He then also first stated that, above certain temperatures, liquefaction of vapors was impossible, however great the pressure. Faraday's conclusion was justified by the researches of Dr. Andrews, who has since most successfully extended the investigation commenced by Cagniard de la Tour, and who has shown that, at a certain point, which he calls the "critical point," the properties of the two states of the fluid fade into each other, and that, at that point, the two become continuous. With carbonic acid, this occurs at 75 atmospheres, about 1,125 pounds per square inch, a pressure which would counterbalance a column of mercury 60 yards, or nearly as many metres, high. The temperature at this point is about 90° Fahr., or 31° Cent. For ether, the temperature is 370° Fahr., and the pressure 38 atmospheres; for alcohol, they are 498° Fahr., and 120 atmospheres; and for bisulphide of carbon, 505° Fahr., and 67 atmospheres. For water, the pressure is too high to be determined; but the temperature is about 775° Fahr., or 413° Cent. Donny and Dufour have shown that these normal properties of vapors and liquids are subject to modification by certain conditions, as previously (1818) noted by Gay-Lussac, and have pointed out the bearing of this fact upon the safety of steam-boilers. It was discovered that the boiling-point of water could be elevated far above its ordinary temperature of ebullition by expedients which deprive the liquid of the air usually condensed within its mass, and which prevent contact with rough or metallic surfaces. By suspension in a mixture of oils which is of nearly the same density, Dufour raised drops of water under atmospheric pressure to a temperature of 356° Fahr.--180° Cent.--the temperature of steam of about 150 pounds per square inch. Prof. James Thompson has, on theoretical grounds, indicated that a somewhat similar action may enable vapor, under some conditions, to be cooled below the normal temperature of condensation, without liquefaction. Fairbairn and Tate repeated the attempt to determine the volume and temperature of water at pressures extending beyond those in use in the steam-engine, and incomplete determinations have also been made by others. Regnault is the standard authority on these data. His experiments (1847) were made at the expense of the French Government, and under the direction of the French Academy. They were wonderfully accurate, and extended through a very wide range of temperatures and pressures. The results remain standard after the lapse of a quarter of a century, and are regarded as models of precise physical work.[112] [112] _See_ Porter on the Steam-Engine Indicator for the best set of Regnault's tables generally accessible. Regnault found that the total heat of steam is not constant, but that the latent heat varies, and that the sum of the latent and sensible heats, or the total heat, increases 0.305 of a degree for each degree of increase in the sensible heat, making 0.305 the specific heat of saturated steam. He found the specific heat of superheated steam to be 0.4805. Regnault promptly detected the fact that steam was not subject to Boyle's law, and showed that the difference is very marked. In expressing his results, he not only tabulated them but also laid them down graphically; he further determined exact constants for Biot's algebraic expression, log. _p_ = _a_ - _b_A^{_x_} - _c_B^{_x_}; making _x_ = 20 + _t_° Cent.; _a_ = 6.264035; log. _b_ = 0.1397743; log. _c_ = 0.6924351; log. A = [=1].9940493, and log. B = [=1].9983439; _p_ is the pressure in atmospheres. Regnault, in the expression for the total heat, H = A + _bt_, determined on the centigrade scale [theta] = 606.5 + 0.305 _t_ Cent. For the Fahrenheit scale, we have the following equivalent expressions: H = 1,113.44° + 0.305 _t_° Fahr., if measured from 0° Fahr. = 1,091.9° + 0.305 (_t_° - 32) Fahr.,; } if measured from = 1,081.94° + 0.305 _t_° Fahr., } the freezing-point. For latent heat, we have: L = 606.5° - 0.695 _t_° Cent. = 1,091.7°- 0.695 (_t_° - 32) Fahr. = 1,113.94°- 0.695 _t_° Fahr. Since Regnault's time, nothing of importance has been done in this direction. There still remains much work to be done in the extension of the research to higher pressures, and under conditions which obtain in the operation of the steam-engine. The volumes and densities of steam require further study, and the behavior of steam in the engine is still but little known, otherwise than theoretically. Even the true value of Joule's equivalent is not undisputed. Some of the most recent experimental work bearing directly upon the philosophy of the steam-engine is that of Hirn, whose determination of the value of the mechanical equivalent was less than two per cent. below that of Joule. Hirn tested by experiment, in 1853, and repeatedly up to 1876, the analytical work of Rankine, which led to the conclusion that steam doing work by expansion must become gradually liquefied. Constructing a glass steam-engine cylinder, he was enabled to see plainly the clouds of mist which were produced by the expansion of steam behind the piston, where Regnault's experiments prove that the steam should become drier and superheated, were no heat transformed into mechanical energy. As will be seen hereafter, this great discovery of Rankine is more important in its bearing upon the theory of the steam-engine than any made during the century. Hirn's confirmation stands, in value, beside the original discovery. In 1858 Hirn confirmed the work of Mayer and Joule by determining the work done and the carbonic acid produced, as well as the increased temperature due to their presence, where men were set at work in a treadmill; he found the elevation of temperature to be much greater in proportion to gas produced when the men were resting than when they were at work. He thus proved conclusively the conversion of heat-energy into mechanical work. It was from these experiments that Helmholtz deduced the "modulus of efficiency" of the human machine at one-fifth, and concluded that the heart works with eight times the efficiency of a locomotive-engine, thus confirming a statement of Rumford, who asserted the higher efficiency of the animal. Hirn's most important experiments in this department were made upon steam-engines of considerable size, including simple and compound engines, and using steam sometimes saturated and sometimes superheated to temperatures as high, on some occasions, as 340° Cent. He determined the work done, the quantity of heat entering, and the amount rejected from, the steam-cylinder, and thus obtained a coarse approximation to the value of the heat-equivalent. His figure varied from 296 to 337 kilogrammetres. But, in all cases, the loss of heat due to work done was marked, and, while these researches could not, in the nature of the case, give accurate quantitative results, they are of great value as qualitatively confirming Mayer and Joule, and proving the transformation of energy. Thus, as we have seen, experimental investigation and analytical research have together created a new science, and the philosophy of the steam-engine has at last been given a complete and well-defined form, enabling the intelligent engineer to comprehend the operation of the machine, to perceive the conditions of efficiency, and to look forward in a well-settled direction for further advances in its improvement and in the increase of its efficiency. A very concise _résumé_ of the principal facts and laws bearing upon the philosophy of the steam-engine will form a fitting conclusion to this historical sketch. The term "energy" was first used by Dr. Young as the equivalent of the work of a moving body, in his hardly yet obsolete "Lectures on Natural Philosophy." Energy is the capacity of a moving body to overcome resistance offered to its motion; it is measured either by the product of the mean resistance into the space through which it is overcome, or by the half-product of the mass of the body into the square of its velocity. Kinetic energy is the actual energy of a moving body; potential energy is the measure of the work which a body is capable of doing under certain conditions which, without expending energy, may be made to affect it, as by the breaking of a cord by which a weight is suspended, or by firing a mass of explosive material. The British measure of energy is the foot-pound; the metric measure is the kilogrammetre. Energy, whether kinetic or potential, may be observable and due to mass-motion; or it may be invisible and due to molecular movements. The energy of a heavenly body or of a cannon-shot, and that of heat or of electrical action, are illustrations of the two classes. In Nature we find utilizable potential energy in fuel, in food, in any available head of water, and in available chemical affinities. We find kinetic energy in the motion of the winds and the flow of running water, in the heat-motion of the sun's rays, in heat-currents on the earth, and in many intermittent movements of bodies acted on by applied forces, natural or artificial. The potential energy of fuel and of food has already been seen to have been derived, at an earlier period, from the kinetic energy of the sun's rays, the fuel or the food being thus made a storehouse or reservoir of energy. It is also seen that the animal system is simply a "mechanism of transmission" for energy, and does not create but simply diverts it to any desired direction of application. All the available forms of energy can be readily traced back to a common origin in the potential energy of a universe of nebulous substance (chaos), consisting of infinitely diffused matter of immeasurably slight density, whose "energy of position" had been, since the creation, gradually going through a process of transformation into the several forms of kinetic and potential energy above specified, through intermediate methods of action which are usually still in operation, such as the potential energy of chemical affinity, and the kinetic forms of energy seen in solar radiation, the rotation of the earth, and the heat of its interior. The _measure_ of any given quantity of energy, whatever may be its form, is the product of the resistance which it is capable of overcoming into the space through which it can move against that resistance, i. e., by the product RS. Or it is measured by the equivalent expressions (MV^{2})/2, or WV^{2}/2_g_, in which W is the weight, M is the "mass" of matter in motion, V the velocity, and _g_ the dynamic measure of the force of gravity, 32-1/6 feet, or 9.8 metres, per second. There are three great laws of energetics: 1. The sum total of the energy of the universe is invariable. 2. The several forms of energy are interconvertible, and possess an exact quantitative equivalence. 3. The tendency of all forms of kinetic energy is continually toward reduction to forms of molecular motion, and to their final dissipation uniformly throughout space. The history of the first two of these laws has already been traced. The latter was first enunciated by Prof. Sir William Thomson in 1853. Undissipated energy is called "Entrophy." The science of thermo-dynamics is, as has been stated, a branch of the science of energetics, and is the only branch of that science in the domain of the physicist which has been very much studied. This branch of science, which is restricted to the consideration of the relations of heat-energy to mechanical energy, is based upon the great fact determined by Rumford and Joule, and considers the behavior of those fluids which are used in heat-engines as the media through which energy is transferred from the one form to the other. As now accepted, it assumes the correctness of the hypothesis of the dynamic theory of fluids, which supposes their expansive force to be due to the motion of their molecules. This idea is as old as Lucretius, and was distinctly expressed by Bernouilli, Le Sage and Prévost, and Herapath. Joule recalled attention to this idea, in 1848, as explaining the pressure of gases by the impact of their molecules upon the sides of the containing vessels. Helmholtz, ten years later, beautifully developed the mathematics of media composed of moving, frictionless particles, and Clausius has carried on the work still further. The general conception of a gas, as held to-day, including the vortex-atom theory of Thomson and Rankine, supposes all bodies to consist of small particles called molecules, each of which is a chemical aggregation of its ultimate parts or atoms. These molecules are in a state of continual agitation, which is known as heat-motion. The higher the temperature, the more violent this agitation; the total quantity of motion is measured as _vis viva_ by the half-product of the mass into the square of the velocity of molecular movement, or in heat-units by the same product divided by Joule's equivalent. In solids, the range of motion is circumscribed, and change of form cannot take place. In fluids, the motion of the molecules has become sufficiently violent to enable them to break out of this range, and their motion is then no longer definitely restricted. The laws of thermo-dynamics are, according to Rankine: 1. Heat-energy and mechanical energy are mutually convertible, one British thermal unit being the equivalent in heat-energy of 772 foot-pounds of mechanical energy, and one metric _calorie_ equal to 423.55 kilogrammetres of work. 2. The energy due to the heat of each of the several equal parts into which a uniformly hot substance may be divided is the same; and the total heat-energy of the mass is equal to the sum of the energies of its parts.[113] [113] This uniformity is not seen where a substance is changing its physical state while developing its heat-energy, as occurs with steam doing work while expanding. It follows that the work performed by the transformation of the energy of heat, during any indefinitely small variation of the state of a substance as respects temperature, is measured by the product of the absolute temperature into the variation of a "function," which function is the rate of variation of the work so done with temperature. This function is the quantity called by Rankine the "heat-potential" of the substance for the given kind of work. A similar function, which comprehends the total heat-variation, including both heat transformed and heat needed to effect accompanying physical changes, is called the "thermo-dynamic function." Rankine's expression for the general equation of thermo-dynamics includes the latter, and is given by him as follows: J_dh_ = _d_H = _kd_[tau] + [tau]_d_F = [tau]_d_[phi], in which J is Joule's equivalent, _dh_ the variation of total heat in the substance, _kd_[tau] the product of the "dynamic specific heat" into the variation of temperature, or the total heat demanded to produce other changes than a transformation of energy, and [tau]_d_F is the work done by the transformation of heat-energy, or the product of the absolute temperature, [tau], into the differential of the heat-potential. [phi] is the thermo-dynamic function, and [tau]_d_[phi] measures the whole heat needed to produce, simultaneously, a certain amount of work or of mechanical energy, and, at the same time, to change the temperature of the working substance. Studying the behavior of gases and vapors, it is found that the work done when they are used, like steam, in heat-engines, consists of three parts: (_a._) The change effected in the total actual heat-motion of the fluid. (_b._) That heat which is expended in the production of internal work. (_c._) That heat which is expended in doing the external work of expansion. In any case in which the total heat expended exceeds that due the production of work on external bodies, the excess so supplied is so much added to the intrinsic energy of the substance absorbing it. The application of these laws to the working of steam in the engine is a comparatively recent step in the philosophy of the steam-engine, and we are indebted to Rankine for the first, and as yet only, extended and in any respect complete treatise embodying these now accepted principles. It was fifteen years after the publication of the first logical theory of the steam-engine, by Pambour,[114] before Rankine, in 1859, issued the most valuable of all his works, "The Steam-Engine and other Prime Movers." The work is far too abstruse for the general reader, and is even difficult reading for many accomplished engineers. It is excellent beyond praise, however, as a treatise on the thermo-dynamics of heat-engines. It will be for his successors the work of years to extend the application of the laws which he has worked out, and to place the results of his labors before students in a readily comprehended form. [114] "Théorie de la Machine à Vapeur," par le Chevalier F. M. G. de Pambour, Paris, 1844. William J. Macquorn Rankine, the Scotch engineer and philosopher, will always be remembered as the author of the modern philosophy of the steam-engine, and as the greatest among the founders of the science of thermo-dynamics. His death, while still occupying the chair of engineering at the University of Glasgow, December 24, 1872, at the early age of fifty-two, was one of the greatest losses to science and to the profession which have occurred during the century. CHAPTER VIII. _THE PHILOSOPHY OF THE STEAM-ENGINE._ ITS APPLICATION; ITS TEACHINGS RESPECTING THE CONSTRUCTION OF THE ENGINE AND ITS IMPROVEMENT. "Oftentimes an Uncertaintie hindered our going on so merrily, but by persevering the Difficultie was mastered, and the new Triumph gave stronger Heart unto us."--RALEIGH. "If everything which we cannot comprehend is to be called an impossibility, how many are daily presented to our eyes! and in contemning as false that which we consider to be impossible, may we not be depreciating a giant's effort to give an importance to our own weakness?"--MONTAIGNE. "They who aim vigorously at perfection will come nearer to it than those whose laziness or despondency makes them give up its pursuit from the feeling of its being unattainable."--CHESTERFIELD. As has been already stated, the steam-engine is a machine which is especially designed to transform energy, originally dormant or potential, into active and usefully available kinetic energy. When, millions of years ago, in that early period which the geologists call the carboniferous, the kinetic energy of the sun's rays, and of the glowing interior of the earth, was expended in the decomposition of the vast volumes of carbonic acid with which air was then charged, and in the production of a life-sustaining atmosphere and of the immense forests which then covered the earth with their almost inconceivably luxuriant vegetation, there was stored up for the benefit of the human race, then uncreated, an inconceivably great treasure of potential energy, which we are now just beginning to utilize. This potential energy becomes kinetic and available wherever and whenever the powerful chemical affinity of oxygen for carbon is permitted to come into play; and the fossil fuel stored in our coal-beds or the wood of existing forests is, by the familiar process of combustion, permitted to return to the state of combination with oxygen in which it existed in the earliest geological periods. The philosophy of the steam-engine, therefore, traces the changes which occur from this first step, by which, in the furnace of the steam-boiler, this potential energy which exists in the tendency of carbon and oxygen to combine to form carbonic acid is taken advantage of, and the utilizable kinetic energy of heat is produced in equivalent amount, to the final application of resulting mechanical energy to machinery of transmission, through which it is usefully applied to the elevation of water, to the driving of mills and machinery of all kinds, or to the hauling of "lightning" trains on our railways, or to the propulsion of the Great Eastern. The kinetic heat-energy developed in the furnace of the steam-boiler is partly transmitted through the metallic walls which inclose the steam and water within the boiler, there to evaporate water, and to assume that form of energy which exists in steam confined under pressure, and is partly carried away into the atmosphere in the discharged gaseous products of combustion, serving, however, a useful purpose, _en route_, by producing the draught needed to keep up combustion. The steam, with its store of heat-energy, passes through tortuous pipes and passages to the steam-cylinder of the engine, losing more or less heat on the way, and there expands, driving the piston before it, and losing heat by the transformation of that form of energy while doing mechanical work of equivalent amount. But this steam-cylinder is made of metal, a material which is one of the best conductors of heat, and therefore one of the very worst possible substances with which to inclose anything as subtile and difficult of control as the heat pervading a condensible vapor like steam. The process of internal condensation and reëvaporation, which is the great enemy of economical working, thus has full play, and is only partly checked by the heat from the steam-jacket, which, penetrating the cylinder, assists by keeping up the temperature of the internal surface and checking the first step, condensation, which is an essential preliminary to the final waste by reëvaporation. The piston, too, is of metal, and affords a most excellent way of exit for the heat escaping to the exhaust side. Finally, all unutilized heat rejected from the steam-cylinder is carried away from the machine, either by the water of condensation, or, in the non-condensing engine, by the atmosphere into which it is discharged. Having traced the method of operation of the steam-engine, it is easy to discover what principles are comprehended in its philosophy, to learn what are known facts bearing upon its operation, and to determine what are the directions in which improvement must take place, what are the limits beyond which improvement cannot possibly be carried, and, in some directions, to determine what is the proper course to pursue in effecting improvements. The general direction of change in the past, as well as at present, is easily seen, and it may usually be assumed that there will be no immediate change of direction in a course which has long been preserved, and which is well defined. We may, therefore, form an idea of the probable direction in which to look for improvement in the near future. Reviewing the operations which go on in this machine during the process of transformation of energy which has been outlined, and studying it more in detail, we may deduce the principles which govern its design and construction, guide us in its management, and determine its efficiency. In the furnace of the boiler, the quantity of heat developed in available form is proportional to the amount of fuel burned. It is available in proportion to the temperature attained by the products of combustion; were this temperature no higher than that of the boiler, the heat would all pass off unutilized. But the temperature produced by a given quantity of heat, measured in heat-units, is greater as the volume of gas heated is less. It follows that, at this point, therefore, the fuel should be perfectly consumed with the least possible air-supply, and the least possible abstraction of heat before combustion is complete. High temperature of furnace, also, favors complete combustion. We hence conclude that, in the steam-boiler furnace, fuel should be burned completely in a chamber having non-conducting walls, and with the smallest air-supply compatible with thorough combustion; and, further, that the air should be free from moisture, that greatest of all absorbents of heat, and that the products of combustion should be removed from the furnace before beginning to drain their heat into the boiler. A fire-brick furnace, a large combustion-chamber with thorough intermixture of gases within it, good fuel, and a restricted and carefully-distributed supply of air, seem to be the conditions which meet these requisites best. The heat generated by combustion traverses the walls which separate the gases of the furnace from the steam and water confined within the boiler, and is then taken up by those fluids, raising their temperature from that of the entering "feed-water" to that due the steam-pressure, and expanding the liquid into steam occupying a greatly-increased volume, thus doing a certain amount of work, besides increasing temperature. The extent to which heat may thus be usefully withdrawn from the furnace-gases depends upon the conductivity of the metallic wall, the rate at which the water will take heat from the metal, and the difference of temperature on the two sides of the metal. Extended "heating-surface," therefore, a metal of high conducting power, and a maximum difference of temperature on the two sides of the separating wall of metal, are the essential conditions of economy here. The heating-surface is sometimes made of so great an area that the temperature of the escaping gases is too low to give good chimney-draught, and a "mechanical draught" is resorted to, revolving "fan-blowers" being ordinarily used for its production. It is most economical to adopt this method. The steam-boiler is generally constructed of iron--sometimes, but rarely, of cast-iron, although "steel," where not hard enough to harden or temper, is better in consequence of its greater strength and homogeneousness of structure, and its better conductivity. The maximum conductivity of flow of heat for any given material is secured by so designing the boiler as to secure rapid, steady, and complete circulation of the water within it. The maximum rapidity of transfer throughout the whole area of heating-surface is secured, usually, by taking the feed-water into the boiler as nearly as possible at the point where the gases are discharged into the chimney-flue, withdrawing the steam nearer the point of maximum temperature of flues, and securing opposite directions of flow for the gases on the one side and the water on the other. Losses of heat from the boiler, by conduction and radiation to surrounding bodies, are checked as far as possible by non-conducting coverings. The mechanical equivalent of the heat generated in the boiler is easily calculated when the conditions of working are known. A pound of pure carbon has been found to be capable of liberating by its perfect combustion, resulting in the formation of carbonic acid, 14,500 British thermal units, equivalent to 14,500 × 772 = 11,194,000 foot-pounds of work, and, if burned in one hour, to 11194000/1980000 = 5.6 horse-power. In other words, with perfect utilization, but 10/56 = 0.177, or about one-sixth, of a pound of carbon would be needed per hour for each horse-power of work done. But even good coal is not nearly all carbon, and has but about nine-tenths this heat-producing power, and it is usually rated as yielding about 10,000,000 foot-pounds of work per pound. The evaporative power of pure carbon being rated at 15 pounds of water, that of good coal may be stated at 13-1/2. In metric measures, one gramme of good coal should evaporate about 13-1/2 grammes of water from the boiling-point, producing the equivalent of about 3,000,000 kilogrammetres of work from the 7,272 _calories_ of heat thus generated. A gramme of pure carbon generates in its combustion 8,080 _calories_ of heat. Per hour and per horse-power, 0.08, or less than one-twelfth, of a kilogram of carbon burned per hour evolves heat-energy equal to one horse-power. Of the coal burned in a steam-boiler, it rarely happens that more than three-fourths is utilized in making steam; 7,500,000 foot-pounds (1,036,898 kilogrammetres) is, therefore, as much energy as is usually sent to the engine per pound of good coal burned in the steam-boiler. The "efficiency" of a good steam-boiler is therefore usually not far from 0.75 as a maximum. Rankine estimates this quantity for ordinary boilers of good design and with chimney-draught at 0.92 E = ------------; 1 + 0.5(F/S) in which F/S is the ratio of weight of fuel burned per square foot of grate to the ratio of heating to grate surface; this is a formula of fairly close approximation for general practice. The steam in the engine first drives the piston some distance before the induction or steam valve is closed, and it then expands, doing work, and condensing in proportion to work done as the expansion proceeds, until it is finally released by the opening of the exhaust or eduction valve. Saturated steam is modified in its action by a process which has already been described, condensing at the beginning and reëvaporating at the end of the stroke, thus carrying into the condenser considerable quantities of heat which should have been utilized in the development of power. Whether this operation takes place in one cylinder or in several is only of importance in so far as it modifies the losses due to conduction and radiation of heat, to condensation and reëvaporation of steam, and to the friction of the machine. It has already been seen how these losses are modified by the substitution of the compound for the single-cylinder engine. The laws of thermo-dynamics teach, as has been stated, that the proportion of the heat-energy contained in the steam or other working fluid which may be transformed into mechanical energy is a fraction (H_{1} - H_{2})/H_{1}, of the total, in which H_{1} and H_{2} are the quantities of heat contained in the steam at the beginning and at the end of its operation, measuring from the absolute zero of heat-motion. In perfect gases, H_{1} - H_{2} [tau]_{1} - [tau]_{2} T_{1} - T_{2} ------------- = --------------------- = -------------------- H_{1} [tau]_{1} T_{1} + 461.2° Fahr. but in imperfect gases, and especially in vapors which, like steam, condense, or otherwise change their physical state, this equality may still exist, (H_{1} - H_{2})/H_{1} = ([tau]_{1} - [tau]_{2})/[tau]_{1}; and the fluid is equally efficient with the perfect gas as a working substance in a heat-engine. In any case it is seen that the efficiency is greatest when the whole of the heat is received at the maximum and rejected at the minimum attainable temperatures. Assuming this expression strictly accurate, a hot-air engine working from 413.6° Fahr, or 874.8° absolute temperature, down to 122° Fahr, or 583.2° absolute, should have an efficiency of 0.263, transforming that proportion of available heat into mechanical work. The engines of the steamer Ericsson closely approached this figure, and gave a horse-power for each 1.87 pound of coal burned per hour. Steam expands in the steam-cylinder quite differently under different circumstances. If no heat is either communicated to it or abstracted from it, however, it expands in an hyperbolic curve, losing its tension much more rapidly than when expanded without doing work, in consequence both of its change of volume and its condensation. The algebraic expression for this method of expansion is, according to Rankine, PV^{1.111} = C, a constant, or, according to other authorities, from PV^{1.135} = C to PV^{1.140} = C. The greater the value of the exponent of V, the greater the efficiency of the fluid between any two temperatures. The maximum value has been found to be given where the steam is saturated, but perfectly dry, at the commencement of its expansion. The loss due to condensation on the cooled interior surface of the cylinder at the commencement of the stroke and the subsequent reëvaporation as expansion progresses is least when the cylinder is kept hot by its steam-jacket and when least time is given during the stroke for this transfer of heat between the metal and the vapor. It may be said that, all things considered, therefore, losses of heat in the steam-cylinder are least when the steam enters dry, or moderately superheated, where the interior surfaces are kept hottest by the steam-jacket or by the hot-air jacket sometimes used, and where piston-speed and velocity of rotation are highest.[115] The best of compound engines, using steam of seventy-five pounds pressure and condensing, usually require about two pounds of coal per hour--20,000,000 foot-pounds of energy at the furnace--to develop a horse-power, i. e., about ten times the heat-equivalent of the mechanical work which they accomplish. Were the steam to expand like the permanent gases, they would have a theoretical efficiency of about one-quarter; actually, the efficiency is only one-tenth. The steam-engine, therefore, utilizes about two-fifths the heat-energy theoretically available with the best type of engine in general use. By far the greater part, nearly all, in fact, of the nine-tenths wasted is rejected in the exhaust steam, and can only be saved by some such method as is hereafter to be suggested of retaining that heat and returning it to the boiler. [115] In some cases, as in the Allen engine, the speed of piston has become very high, approaching 800((stroke)^{1/3}). The mechanical power which has now been communicated to the mechanism of the engine by the transfer of the kinetic energy of the hot steam to the piston is finally usefully applied to whatever "mechanism of transmission" forms the connection with the machinery driven by the engine. In this transfer, there is some loss in the engine itself, by friction. This is an extremely variable amount, and it can be made very small by skillful design and good workmanship and management. It may be taken at one-half pound per square inch of piston for good engines of 100 horse-power and upward, but is often several pounds in very small engines. It is least when the rubbing surfaces are of different materials, but both of smooth, hard, close-grained metal, well lubricated, and where advantage is taken of any arrangement of parts which permits the equilibration of pressure, as on the shaft-bearings of double and triple engines. The friction of a steam-engine of large size and good design is usually between five and seven per cent. of its total power. It increases rapidly as the size of engine decreases. Having now traced somewhat minutely the growth of the steam-engine from the beginning of the Christian era to the present time, having rapidly outlined the equally gradual, though intermittent, growth of its philosophy, and having shown how the principles of science find application in the operation of this wonderful machine, we are now prepared to study the conditions which control the intelligent designer, and to endeavor to learn what are the lessons taught us by science and by experience in regard to the essential requisites of efficient working of steam and economy in the consumption of fuel. We may even venture to point out definitely the direction in which improvement is now progressing as indicated by a study of these requisites, and may be able to perceive the natural limits to such progress, and possibly to conjecture what must be the character of that change of type which only can take the engineer beyond the limit set to his advance so long as he is confined to the construction of the present type of engine. First, we must consider the question: _What is the problem, stated precisely and in its most general form, that engineers have been here attempting to solve?_ After stating the problem, we will examine the record with a view to determine what direction the path of improvement has taken hitherto, to learn what are the conditions of efficiency which should govern the construction of the modern steam-engine, and, so far as we may judge the future by the past, by inference, to ascertain what appears to be the proper course for the present and for the immediate future. Still further, we will inquire, what are the conditions, physical and intellectual, which best aid our progress in perfecting the steam-engine. This most important problem may be stated in its most general, yet definite, form as follows: _To construct a machine which shall, in the most perfect manner possible, convert the kinetic energy of heat into mechanical power, the heat being derived from the combustion of fuel, and steam being the receiver and the conveyer of that heat._ The problem, as we have already seen, embodies two distinct and equally important inquiries: The first: What are the scientific principles involved in the problem as stated? The second: How shall a machine be constructed that shall most efficiently embody, and accord with, not only those scientific principles, but also all of those principles of engineering practice that so vitally affect the economical value of every machine? The one question is addressed to the man of science, the other to the engineer. They can be satisfactorily answered, even so far as our knowledge at present permits, after studying with care the scientific principles involved in the theory of the steam-engine under the best light that science can afford us, and by a careful study of the various steps of improvement that have taken place and of accompanying variations of structure, analyzing the effect of each change, and tracing the reasons for them. The theory of the steam-engine is too important and too extensive a subject to be satisfactorily treated here in even the most concise possible manner. I can only attempt a plain statement of the course which seems to be pointed out by science as the proper one to pursue in the endeavor to increase the economical efficiency of steam-engines. The teachings of science indicate that _success in economically deriving mechanical power from the energy of heat-motion will, in all cases, be the greater as we work between more widely separated limits of temperature, and as we more perfectly provide against losses by dissipation of heat in directions in which it is unavailable for the production of power_. Scientific research, as we have seen, has proved that, in all known varieties of heat-engine, a large loss of effect is unavoidable from the fact that we cannot, in the ordinary steam-engine, reduce the lower limit of temperature, in working, below a point which is far above the absolute zero of temperature--far above that point at which bodies have no heat-motion. The point corresponding to the mean temperature of the surface of the earth is above the ordinary lower limit. The higher the temperature of the steam when it enters the steam cylinder, and the lower that which it reaches before the exhaust occurs, the greater, science tells us, will be our success, provided we at the same time avoid waste of heat and power. Now, looking back over the history of the steam-engine, we may briefly note the prominent improvements and the most striking changes of form, and may thus endeavor to obtain some idea of the general direction in which we are to look for further advance. Beginning with the machine of Porta, at which point we may first take up an unbroken thread, it will be remembered that we there found a single vessel performing the functions of all the parts of a modern pumping-engine; it was, at once, boiler, steam-cylinder, and condenser, as well as both a lifting and a forcing pump. The Marquis of Worcester divided the engine into two parts, using a separate boiler. Savery duplicated that part of the engine of Worcester which performed the several parts of pump, steam-cylinder, and condenser, and added the use of water to effect rapid condensation, perfecting, so far as it was ever perfected, the steam-engine as a simple machine. Newcomen and Calley next separated the pump from the steam-engine proper, producing the modern steam-engine--the engine as a train of mechanism; and in their engine, as in Savery's, we noticed the use of surface condensation first, and subsequently that of the jet thrown into the midst of the steam to be condensed. Watt finally effected the crowning improvements, and completed the movement o£ "differentiation" by separating the condenser from the steam-cylinder. Here this process of change ceased, the several important operations of the steam-engine now being conducted each in a separate vessel. The boiler furnished the steam, the cylinder derived from it mechanical power, and it was finally condensed in a separate vessel, while the power which had been obtained from it in the steam-cylinder was transmitted through still other parts, to the pumps, or wherever work was to be done. Watt, also, took the initiative in another direction. He continually increased the efficiency of the machine by improving the proportions of its parts and the character of its workmanship, thus making it possible to render available many of those improvements in detail upon which effectiveness is so greatly dependent and which are only useful when made by a skillful workman. Watt and his contemporaries also commenced that movement toward higher pressures of steam and greater expansion which has been the most striking feature noticed in the progress of steam-engineering since his time. Newcomen used steam of barely more than atmospheric pressure and raised 105,000 pounds of water one foot high with a pound of coal consumed. Smeaton raised the pressure somewhat and increased the duty considerably. Watt started with a duty double that of Newcomen and raised it to 320,000 foot-pounds per pound of coal, with steam at 10 pounds pressure. To-day, Cornish engines of the same general plan as those of Watt, but worked with 40 to 60 pounds of steam and expanding three or four times, do a duty probably averaging, with the better class of engines, 600,000 foot-pounds per pound of coal. The compound pumping-engine runs the figure up to above 1,000,000. The increase in steam-pressure and in expansion since Watt's time has been accompanied by a very great improvement in workmanship--a consequence, very largely, of the rapid increase in perfection, and in the wide range of adaptation of machine-tools--by higher skill and intelligence in designing engines and boilers, by increased piston-speed, greater care in obtaining dry steam, and in keeping it dry until thrown out of the cylinder, either by steam-jacketing or by superheating, or both combined; it has further been accompanied by a greater attention to the important matter of providing carefully against losses by radiation and conduction of heat. We use, finally, the compound or double-cylinder engine for the purpose of saving some of the heat usually lost in internal condensation and reëvaporation, and precipitation of condensed vapor from great expansion. It is evident that, although there is a limit, tolerably well defined, in the scale of temperature, below which we cannot expect to pass, a degree gained in approaching this lower limit is more remunerative than a degree gained in the range of temperature available by increasing temperatures.[116] [116] The fact here referred to is easily seen if it is supposed that an engine is supplied with steam at a temperature of 400° above absolute zero and works it, without waste, down to a temperature of 200°. Suppose one inventor to adapt the engine to the use of steam of a range from 500° down to 200°, while another works his engine, with equally effective provision against losses, between the limits of 400° and 100°, an equal range with a lower mean. The first case gives an efficiency of one-half, the second three-fifths, and the third three-fourths, the last giving the highest effect. Hence the attempt made by the French inventor, Du Trembly, about the year 1850, and by other inventors since, to utilize a larger proportion of heat by approaching more closely the lower limit, was in accordance with known scientific principles. We may summarize the result of our examination of the growth of the steam-engine thus: _First._ The process of improvement has been one, primarily, of "differentiation;"[117] the number of parts has been continually increased; while the work of each part has been simplified, a separate organ being appropriated to each process in the cycle of operations. [117] This term, though perhaps not familiar to engineers, expresses the idea perfectly. _Secondly._ A kind of secondary process of differentiation has, to some extent, followed the completion of the primary one, in which secondary process one operation is conducted partly in one and partly in another portion of the machine. This is illustrated by the two cylinders of the compound engine and by the duplication noticed in the binary engine. _Thirdly._ The direction of improvement has been marked by a continual increase of steam-pressure, greater expansion, provision for obtaining dry steam, high piston-speed, careful protection against loss of heat by conduction or radiation, and, in marine engines, by surface condensation. The direction which improvement seems now to be taking, and the proper direction, as indicated by an examination of the principles of science, as well as by our review of the steps already taken, would seem to be: working between the widest attainable limits of temperature. Steam must enter the machine at the highest possible temperature, must be protected from waste, and must retain, at the moment before exhaust, the least possible amount of heat. He whose inventive genius, or mechanical skill, contributes to effect either the use of higher steam with safety and without waste, or the reduction of the temperature of discharge, confers a boon upon mankind. In detail: In the engine, the tendency is, and may probably be expected to continue, in the near future at least, toward higher steam-pressure, greater expansion in more than one cylinder, steam-jacketing, superheating, a careful use of non-conducting protectors against waste, and the adoption of still higher piston-speeds. In the boiler: more complete combustion without excess of air passing through the furnace, and more thorough absorption of heat from the furnace-gases. The latter will probably be ultimately effected by the use of a mechanically produced draught, in place of the far more wasteful method of obtaining it by the expenditure of heat in the chimney. In construction we may anticipate the use of better materials, and more careful workmanship, especially in the boiler, and much improvement in forms and proportions of details. In management, there is a wide field for improvement, which improvement we may feel assured will rapidly take place, as it has now become well understood that great care, skill, and intelligence are important essentials to the economical management of the steam-engine, and that they repay, liberally, all of the expense in time and money that is requisite to secure them. In attempting improvements in the directions indicated, it would be the height of folly to assume that we have reached a limit in any one of them, or even that we have approached a limit. If further progress seems checked by inadequate returns for efforts made, in any case, to advance beyond present practice, it becomes the duty of the engineer to detect the cause of such hinderance, and, having found it, to remove it. A few years ago, the movement toward the expansive working of high steam was checked by experiments seeming to prove positive disadvantage to follow advance beyond a certain point. A careful revision of results, however, showed that this was true only with engines built, as was then common, in utter disregard of all the principles involved in such a use of steam, and of the precautions necessary to be taken to insure the gain which science taught us should follow. The hinderances are mechanical, and it is for the engineer to remove them. The last remark is especially applicable to the work of the engineer who is attempting to advance in the direction in which, as already intimated, an unmistakable revolution is now progressing, the modification of the modern steam-engine to adapt it safely and successfully to run at the high piston-speed, and great velocity of rotation which have been already attained and which must undoubtedly be greatly exceeded in the future. As there is no known and definite limit to the economical increase of speed, and as the limit set by practical conditions is continually being set farther back as the builder acquires greater skill and attains greater accuracy of workmanship and the power to insure greater rigidity of parts and durability of wearing surfaces, we must anticipate a continued and indefinite progress in this direction--a progress which must evidently be of advantage, whatever may be the direction that other changes may take. It is evident that this adaptation of the steam-engine to great speed of piston is the work now to be done by the engineer. The requisites to success are obvious, and may be concisely stated as follows: 1. Extreme accuracy in proportions. 2. Perfect accuracy in fitting parts to each other. 3. Absolute symmetry of journals. 4. Ample area and maximum durability of rubbing surfaces. 5. Perfect certainty of an ample and continuous lubrication. 6. A nicely calculated and adjusted balance of reciprocating parts. 7. Security against injury by shock, whether due to the presence of water in the cylinder or to looseness of running parts. 8. A "positive-motion" cut-off gear. 9. A powerful but sensitive and accurately-working governor determining the degree of expansion.[118] [118] The author is not absolutely confident on the latter point. It may be found more economical and satisfactory, ultimately, to determine the point of cut-off by an automatic apparatus adjusting the expansion-gear _by reference to the steam-pressure_, regulating the speed by attaching the governor elsewhere. The author has devised several forms of apparatus of the kind referred to. 10. Well-balanced valves and an easy-working valve-gear. 11. Small volume of "dead-space," or "clearance," and properly adjusted "compression." It would seem sufficiently evident that the engine with detachable ("drop") cut-off valve-gear must, sooner or later, become an obsolete type, although the substitution of springs or of steam-pressure for gravity in the closing of the detached valve may defer greatly this apparently inevitable change. The "engine of the future" will not probably be a "drop cut-off engine." As regards the construction of the engine as a piece of mechanism, the principles and practice of good engineering are precisely the same, whether applied in the designing of the compound or of the ordinary type of steam-engine. The proportioning of the two machines to each other in such manner as to form an effective whole, by procuring approximately equal amounts of work from both, is the only essential peculiarity of compound-engine design which calls for especial care, and the method of securing success in practice may be stated to be, for both forms of engines, as follows: 1. A good design, by which is meant-- _a._ Correct proportions, both in general dimensions and in arrangement of parts, and proper forms and sizes of details to withstand safely the forces which may be expected to come upon them. _b._ A general plan which embodies the recognized practice of good engineering. _c._ Adaptation to the specific work which it is intended to perform, in size and in efficiency. It sometimes happens that good practice dictates the use of a comparatively uneconomical design. 2. Good construction, by which is meant-- _a._ The use of good material. _b._ Accurate workmanship. _c._ Skillful fitting and a proper "assemblage" of parts. 3. Proper connection with its work, that it may do that work under the conditions assumed in its design. 4. Skillful management by those in whose hands it is placed. _In general_, it may be stated that, to secure maximum economical efficiency, steam should be worked at as high a pressure as possible, and the expansion should be fixed as nearly as possible at the point of maximum economy for that pressure. In general, the number of times which the volume of steam may be expanded in the standard single-cylinder, high-pressure engine with maximum economy, is not far from 1/2 sqrt(P), where P is the pressure in pounds per square inch; it rarely exceeds 0.75 sqrt(P). This may be exceeded in double-cylinder engines. It is even more disadvantageous to cut off too short than to "'follow' too far." With considerable expansion, steam-jacketing and moderate superheating should be adopted, to prevent excessive losses by internal condensation and reëvaporation; and expansion should take place in double cylinders, to avoid excessive weight of parts, irregularity of motion, and great loss by friction. To secure this vitally important economy, it is advisable to seek some practicable method of lining the cylinder with a non-conducting material. This plan, as has been seen, was adopted by Smeaton, in constructing Newcomen engines a century ago. Smeaton used wood on his pistons, and Watt tried wood as a material for steam-cylinder linings. That material is too perishable at temperatures now common, and no metal has yet been substituted, or even discovered, which answers the same purpose. The loss will also be reduced by increasing the speed of rotation and velocity of piston. Where no effectual means can be found of preventing contact of the steam with a good absorbent and conductor of heat, it will be found best to sacrifice some of the efficiency due to the change of state of the vapor, by superheating it and sending it into the cylinder at a temperature considerably exceeding that of saturation. With low steam and slowly-moving pistons, it is better to pursue the latter course than to attempt to increase the efficiency of the engine by greater expansion. External surfaces should be carefully covered by non-conductors and non-radiators, to prevent losses by conduction and radiation of heat. It is especially necessary to reduce back-pressure and to obtain the most perfect vacuum possible without overloading the air-pump, if it is desired to obtain the maximum efficiency by expansion, and it then becomes also very necessary to reduce losses by "dead-spaces" and by badly-adjusted valves. The piston-speed should be as great as can be sustained with safety. Good engines should not require more than W = (200/sqrt(P)) where W = the weight of steam per hour and per horse-power; the best practice gives about W = (180/sqrt(P)) in large engines with dry steam, high piston-speed, and good design, construction, and management. The expansion-valve gear should be simple. The point of cut-off is perhaps best determined by the governor. The valve should close rapidly, but without shock, and should be balanced, or some other device should be adopted to make it easy to move and free from liability to cutting or rapid wear. The governor should act promptly and powerfully, and should be free from liability to oscillate, and to thus introduce irregularities which are sometimes not less serious than those which the instrument is intended to prevent. Friction should be reduced as much as possible, and careful provision should be made to economize lubricants as well as fuel. The Principles of Steam-Boiler Construction are exceedingly simple; and although attempts are almost daily made to obtain improved results by varying the design and arrangement of heating-surface, the best boilers of nearly all makers of acknowledged standing are practically equal in merit, although of very diverse forms. In making boilers, the effort of the engineer should evidently be: 1. To secure complete combustion of the fuel without permitting dilution of the products of combustion by excess of air. 2. To secure as high temperature of furnace as possible. 3. To so arrange heating-surfaces that, without checking draught, the available heat shall be most completely taken up and utilized. 4. To make the form of boiler such that it shall be constructed without mechanical difficulty or excessive expense. 5. To give it such form that it shall be durable, under the action of the hot gases and of the corroding elements of the atmosphere. 6. To make every part accessible for cleaning and repairs. 7. To make every part as nearly as possible uniform in strength, and in liability to loss of strength by wear and tear, so that the boiler when old shall not be rendered useless by local defects. 8. To adopt a reasonably high "factor of safety" in proportioning parts. 9. To provide efficient safety-valves, steam-gauges, and other appurtenances. 10. To secure intelligent and very careful management. In securing complete combustion, the first of these desiderata, an ample supply of air and its thorough intermixture with the combustible elements of the fuel are essential; for the second--high temperature of furnace--it is necessary that the air-supply shall not be in excess of that absolutely needed to give complete combustion. The efficiency of a furnace in making heat available is measured by T - T´ E = -------; T - _t_ in which E represents the ratio of heat utilized to the whole calorific value of the fuel, T is the furnace-temperature, T´ the temperature of the chimney, and _t_ that of the external air. The higher the furnace-temperature and the lower that of the chimney, the greater the proportion of heat available. It is further evident that, however perfect the combustion, no heat can be utilized if either the temperature of the chimney approximates to that of the furnace, or if the temperature of the furnace is reduced by dilution approximately to that of the boiler. Concentration of heat in the furnace is secured, in some cases, by special expedients, as by heating the entering air, or as in the Siemens gas-furnace, heating both the combustible gases and the supporter of combustion. Detached fire-brick furnaces have an advantage over the "fire-boxes" of steam-boilers in their higher temperature; surrounding the fire with non-conducting and highly heated surfaces is an effective method of securing high furnace-temperature. In arranging heating-surface, the effort should be to impede the draught as little as possible, and so to place them that the circulation of water within the boiler should be free and rapid at every part reached by the hot gases. The directions of circulation of water on the one side and of gas on the other side of the sheet should, whenever possible, be opposite. The cold water should enter where the cooled gases leave, and the steam should be taken off farthest from that point. The temperature of chimney-gases has thus been reduced in practice to less than 300° Fahr., and an efficiency equal to 0.75 to 0.80 the theoretical has been attained. The extent of heating-surface simply, in all of the best forms of boiler, determines the efficiency, and in them the disposition of that surface seldom affects it to any great extent. The area of heating-surface may also be varied within very wide limits without very greatly modifying efficiency. A ratio of 25 to 1 in flue and 30 to 1 in tubular boilers represents the relative area of heating and grate surfaces as chosen in the practice of the best-known builders. The material of the boiler should be tough and ductile iron, or, better, a soft steel containing only sufficient carbon to insure melting in the crucible or on the hearth of the melting-furnace, and so little that no danger may exist of hardening and cracking under the action of sudden and great changes of temperature. Where iron is used, it is necessary to select a somewhat hard, but homogeneous and tough, quality for the fire-box sheets or any part exposed to flames. The factor of safety is invariably too low in this country, and is never too high in Europe. Foreign builders are more careful in this matter than our makers in the United States. The boiler should be built strong enough to bear a pressure at least six times the proposed working-pressure; as the boiler grows weak with age, it should be occasionally tested to a pressure far above the working-pressure, which latter should be reduced gradually to keep within the bounds of safety. In the United States, the factor of safety is seldom more than four in the new boilers, frequently much less, and even this is reduced practically to one and a third by the operation of our inspection-laws. The principles just enunciated are those generally, perhaps universally, accepted principles which are stated in all text-books of science and of steam-engineering, and are accepted by both engineers and men of science. These principles are correct, and the deductions which have been here formulated are rigidly exact, as applied to all types of heat-engine in use; and they lead us to the determination, in all cases, of the "modulus" of efficiency of the engine, i. e., to the calculation of the ratio of its actual efficiency to that efficiency which it would have, were it absolutely free from loss of heat by conduction or radiation, or other method of loss of heat or waste of power, by friction of parts or by shock. The best modern marine compound engines sometimes, as we have seen, consume as little as two pounds of coal per horse-power and per hour; but this is but about one-tenth the power derivable from the fuel, were all its heat thoroughly utilized. This loss may be divided thus: 70 per cent. rejected in exhausted steam; 20 per cent. lost by conduction and radiation and by faults of mechanism and design; and only the 10 per cent. remaining is utilized. Thirty per cent. of the heat generated in the furnace is usually lost in the chimney, and of the remainder, which enters the engine, 20 per cent. at most is all which we can hope to save any portion of by improvements effected in our best existing type of steam-engine. It has already been shown how the engineer can best proceed in attempting this economy. The direction in which further improvement must take place in the standard type of engine is plainly that which shall most efficiently check losses by internal condensation and reëvaporation by the transfer of heat to and from the metal of the steam-cylinder. The condensation of steam doing work is evidently not a disadvantage, but, on the contrary, a decided advantage. A new type of engine can, if at all, probably only supersede the common form when engineers can employ steam of very high pressure, and adopt much greater range of expansion than is now usual. Great velocity of piston and high speed of rotation are also essential in the attempt to make any revolution in steam-engine construction a success. When a new form of steam-engine is likely to be introduced, if at all, can be scarcely even conjectured. It seems evident that its success is to be secured, if a revolution is ever to occur, by the adoption of high steam-pressures, of great piston speeds, by care and skill in design, by the use of exceptionally excellent materials of construction, by great perfection of workmanship, and by intelligence in its management. Experiment and experience will probably lead gradually to the general and safe employment of much higher steam-pressures and very greatly increased piston-speeds, and may ultimately reveal and remove all those difficulties which must invariably be expected to be met here, as in all other attempts to effect radical changes, however important they may be. [Illustration] * * * * * _Scientific Publications._ =THE HUMAN SPECIES.= By A. DE QUATREFAGES, Professor of Anthropology in the Museum of Natural History, Paris. 12mo, cloth, $2.00. The work treats of the unity, origin, antiquity, and original localization of the human species, peopling of the globe, acclimatization, primitive man, formation of the human races, fossil human races, present human races, and the physical and psychological characters of mankind. =STUDENTS' TEXT-BOOK OF COLOR; or, MODERN CHROMATICS.= With Applications to Art and Industry. With 130 Original Illustrations, and Frontispiece in Colors. By OGDEN N. ROOD, Professor of Physics in Columbia College. 12mo, cloth, $2.00. "In this interesting book Professor Rood, who, as a distinguished Professor of Physics in Columbia College, United States, must be accepted as a competent authority on the branch of science of which he treats, deals briefly and succinctly with what may be termed the scientific _rationale_ of his subject. But the chief value of his work is to be attributed to the fact that he is himself an accomplished artist as well as an authoritative expounder of science."--_Edinburgh Review, October, 1879, in an article on "The Philosophy of Color._" =EDUCATION AS A SCIENCE.= By ALEXANDER BAIN, LL. D. 12mo, cloth, $1.75. "This work must be pronounced the most remarkable discussion of educational problems which has been published in our day. We do not hesitate to bespeak for it the widest circulation and the most earnest attention. It should be in the hands of every school-teacher and friend of education throughout the land."--_New York Sun._ =A HISTORY OF THE GROWTH OF THE STEAM-ENGINE.= By ROBERT H. THURSTON, A. M., C. E., Professor of Mechanical Engineering in the Stevens Institute of Technology, Hoboken, N. J., etc. With 163 Illustrations, including 15 Portraits. 12mo, cloth, $2.50. "Professor Thurston almost exhausts his subject; details of mechanism are followed by interesting biographies of the more important inventors. If, as is contended, the steam-engine is the most important physical agent in civilizing the world, its history is a desideratum, and the readers of the present work will agree that it could have a no more amusing and intelligent historian than our author."--_Boston Gazette._ =STUDIES IN SPECTRUM ANALYSIS.= By J. NORMAN LOCKYER, F. R. S., Correspondent of the Institute of France, etc. With 60 Illustrations. 12mo, cloth, $2.50. "The study of spectrum analysis is one fraught with a peculiar fascination, and some of the author's experiments are exceedingly picturesque in their results. They are so lucidly described, too, that the reader keeps on, from page to page, never flagging in interest in the matter before him, nor putting down the book until the last page is reached."--_New York Evening Express._ =GENERAL PHYSIOLOGY OF MUSCLES AND NERVES.= By Dr. I. ROSENTHAL, Professor of Physiology at the University of Erlangen. With seventy-five Woodcuts. ("International Scientific Series.") 12mo, cloth, $1.50. "The attempt at a connected account of the general physiology of muscles and nerves is, as far as I know, the first of its kind. The general data for this branch of science have been gained only within the past thirty years."--_Extract from Preface._ =SIGHT=: An Exposition of the Principles of Monocular and Binocular Vision By JOSEPH LE CONTE, LL. D., author of "Elements of Geology"; "Religion and Science"; and Professor of Geology and Natural History in the University of California. With numerous Illustrations. 12mo, cloth, $1.50. "It is pleasant to find an American book which can rank with the very best of foreign works on this subject. Professor Le Conte has long been known as an original investigator in this department; all that he gives us is treated with a master-hand."--_The Nation._ =ANIMAL LIFE=, as affected by the Natural Conditions of Existence. By KARL SEMPER, Professor of the University of Würzburg. With 2 Maps and 106 Woodcuts, and Index. 12mo, cloth, $2.00. "This is in many respects one of the most interesting contributions to zoölogical literature which has appeared for some time."--_Nature._ =THE ATOMIC THEORY.= By AD. WURTZ, Membre de l'Institut; Doyen Honoraire de la Faculté de Médecine; Professeur à la Faculté des Sciences de Paris. Translated by E. CLEMINSHAW, M. A., F. C. S., F. I. C., Assistant Master at Sherborne School. 12mo, cloth, $1.50. "There was need for a book like this, which discusses the atomic theory both in its historic evolution and in its present form. And perhaps no man of this age could have been selected so able to perform the task in a masterly way as the illustrious French chemist, Adolph Wurtz. It is impossible to convey to the reader, in a notice like this, any adequate idea of the scope, lucid instructiveness, and scientific interest of Professor Wurtz's book. The modern problems of chemistry, which are commonly so obscure from imperfect exposition, are here made wonderfully clear and attractive."--_The Popular Science Monthly._ =THE CRAYFISH.= An Introduction to the Study of Zoölogy. By Professor T. H. HUXLEY, F. R. S. With 82 Illustrations. 12mo, cloth, $1.75. "Whoever will follow these pages, crayfish in hand, and will try to verify for himself the statements which they contain, will find himself brought face to face, with all the great zoölogical questions which excite so lively an interest at the present day." "The reader of this valuable monograph will lay it down with a feeling of wonder at the amount and variety of matter which has been got out of so seemingly slight and unpretending a subject."--_Saturday Review._ =SUICIDE=: An Essay In Comparative Moral Statistics. By HENRY MORSELLI, Professor of Psychological Medicine in Royal University, Turin. 12mo, Cloth, $1.75. "Suicide" is a scientific inquiry, on the basis of the statistical method, into the laws of suicidal phenomena. Dealing with the subject as a branch of social science, it considers the increase of suicide in different countries, and the comparison of nations, races, and periods in its manifestation. The influences of age, sex, constitution, climate, season, occupation, religion, prevailing ideas, the elements of character, and the tendencies of civilization, are comprehensively analyzed in their bearing upon the propensity to self-destruction. Professor Morselli is an eminent European authority on this subject. It is accompanied by colored maps illustrating pictorially the results of statistical inquiries. =VOLCANOES: What they Are and what they Teach.= By J. W. JUDD, Professor of Geology in the Royal School of Mines (London). With Ninety-six Illustrations. 12mo. Cloth, $2.00. "In no field has modern research been more fruitful than in that of which Professor Judd gives a popular account in the present volume. The great lines of dynamical, geological, and meteorological inquiry converge upon the grand problem of the interior constitution of the earth, and the vast influence of subterranean agencies.... His book is very far from being a mere dry description of volcanoes and their eruptions; it is rather a presentation of the terrestrial facts and laws with which volcanic phenomena are associated."--_Popular Science Monthly._ "The volume before us is one of the pleasantest science manuals we have read for some time."--_Athenæum._ "Mr. Judd's summary is so full and so concise that it is almost impossible to give a fair idea in a short review."--_Pall Mall Gazette._ =THE SUN.= By C. A. YOUNG, Ph. D., LL. D., Professor of Astronomy in the College of New Jersey. With numerous Illustrations. 12mo. Cloth, $2.00. "Professor Young is an authority on 'The Sun,' and writes from intimate knowledge. He has studied that great luminary all his life, invented and improved instruments for observing it, gone to all quarters of the world in search of the best places and opportunities to watch it, and has contributed important discoveries that have extended our knowledge of it. "It would take a cyclopædia to represent all that has been done toward clearing up the solar mysteries. Professor Young has summarized the information, and presented it in a form completely available for general readers. There is no rhetoric in his book; he trusts the grandeur of his theme to kindle interest and impress the feelings. His statements are plain, direct, clear, and condensed, though ample enough for his purpose, and the substance of what is generally wanted will be found accurately given in his pages."--_Popular Science Monthly._ =ILLUSIONS: A Psychological Study.= By JAMES SULLY, author of "Sensation and Intuition," etc. 12mo. Cloth. $1.50. This volume takes a wide survey of the field of error, embracing in its view not only the illusions commonly regarded as of the nature of mental aberrations or hallucinations, but also other illusions arising from that capacity for error which belongs essentially to rational human nature. The author has endeavored to keep to a strictly scientific treatment--that is to say, the description and classification of acknowledged errors, and the exposition of them by a reference to their psychical and physical conditions. "This is not a technical work, but one of wide popular interest, in the principles and results of which every one is concerned. The illusions of perception of the senses and of dreams are first considered, and then the author passes to the illusions of introspection, errors of insight, illusions of memory, and illusions of belief. The work is a noteworthy contribution to the original progress of thought, and may be relied upon as representing the present state of knowledge on the important subject to which it is devoted."--_Popular Science Monthly._ =THE BRAIN AND ITS FUNCTIONS.= By J. LUYS, Physician to the Hospice de la Salpêtrière. With Illustrations. 12mo. Cloth, $1.50. "No living physiologist is better entitled to speak with authority upon the structure and functions of the brain than Dr. Luys. His studies on the anatomy of the nervous system are acknowledged to be the fullest and most systematic ever undertaken. Dr. Luys supports his conclusions not only by his own anatomical researches, but also by many functional observations of various other physiologists, including of course Professor Ferrier's now classical experiments."--_St. James's Gazette._ "Dr. Luys, at the head of the great French Insane Asylum, is one of the most eminent and successful investigators of cerebral science now living; and he has given unquestionably the clearest and most interesting brief account yet made of the structure and operations of the brain. We have been fascinated by this volume more than by any other treatise we have yet seen on the machinery of sensibility and thought; and we have been instructed not only by much that is new, but by many sagacious practical hints such as it is well for everybody to understand."--_The Popular Science Monthly._ =THE CONCEPTS AND THEORIES OF MODERN PHYSICS.= By J. B. STALLO. 12mo. Cloth, $1.75. "Judge Stallo's work is an inquiry into the validity of those mechanical conceptions of the universe which are now held as fundamental in physical science. He takes up the leading modern doctrines which are based upon this mechanical conception, such as the atomic constitution of matter, the kinetic theory of gases, the conservation of energy, the nebular hypothesis, and other views, to find how much stands upon solid empirical ground, and how much rests upon metaphysical speculation. Since the appearance of Dr. Draper's 'Religion and Science,' no book has been published in the country calculated to make so deep an impression on thoughtful and educated readers as this volume.... The range and minuteness of the author's learning, the acuteness of his reasoning, and the singular precision and clearness of his style, are qualities which very seldom have been jointly exhibited in a scientific treatise."--_New York Sun._ =THE FORMATION OF VEGETABLE MOULD, THROUGH THE ACTION OF WORMS, WITH OBSERVATIONS ON THEIR HABITS.= By CHARLES DARWIN, LL. D., F. R. S., author of "On the Origin of Species," etc., etc. With Illustrations. 12mo, cloth. Price, $1.50. "Mr. Darwin's little volume on the habits and instincts of earth-worms is no less marked than the earlier or more elaborate efforts of his genius by freshness of observation, unfailing power of interpreting and correlating facts, and logical vigor in generalizing upon them. The main purpose of the work is to point out the share which worms have taken in the formation of the layer of vegetable mould which covers the whole surface of the land in every moderately humid country. All lovers of nature will unite in thanking Mr. Darwin for the new and interesting light he has thrown upon a subject so long overlooked, yet so full of interest and instruction, as the structure and the labors of the earth-worm."--_Saturday Review._ "Respecting worms as among the most useful portions of animate nature, Dr. Darwin relates, in this remarkable book, their structure and habits, the part they have played in the burial of ancient buildings and the denudation of the land, in the disintegration of rocks, the preparation of soil for the growth of plants, and in the natural history of the world."--_Boston Advertiser._ =ANTS, BEES, AND WASPS.= A Record of Observations on the Habits of the Social Hymenoptera. By Sir JOHN LUBBOCK, Bart., M. P., F. R. S., etc., author of "Origin of Civilization, and the Primitive Condition of Man," etc., etc. With Colored Plates. 12mo, cloth, $2.00. "This volume contains the record of various experiments made with ants, bees, and wasps during the last ten years, with a view to test their mental condition and powers of sense. The principal point in which Sir John's mode of experiment differs from those of Huber, Forel, McCook, and others, is that he has carefully watched and marked particular insects, and has had their nests under observation for long periods--one of his ants' nests having been under constant inspection ever since 1874. His observations are made principally upon ants because they show more power and flexibility of mind; and the value of his studies is that they belong to the department of original research." "We have no hesitation in saying that the author has presented us with the most valuable series of observations on a special subject that has ever been produced, charmingly written, full of logical deductions, and, when we consider his multitudinous engagements, a remarkable illustration of economy of time. As a contribution to insect psychology, it will be long before this book finds a parallel."--_London Athenæum._ =DISEASES OF MEMORY=: An Essay in the Positive Psychology. By TH. RIBOT, author of "Heredity," etc. Translated from the French by William Huntington Smith. 12mo, cloth, $1.50. "M. Ribot reduces diseases of memory to law, and his treatise is of extraordinary interest."--_Philadelphia Press._ "Not merely to scientific, but to all thinking men, this volume will prove intensely interesting."--_New York Observer._ "M. Ribot has bestowed the most painstaking attention upon his theme, and numerous examples of the conditions considered greatly increase the value and interest of the volume."--_Philadelphia North American._ "To the general reader the work is made entertaining by many illustrations connected with such names as Linnæus, Newton, Sir Walter Scott, Horace Vernet, Gustave Doré, and many others."--_Harrisburg Telegraph._ "The whole subject is presented with a Frenchman's vivacity of style."--_Providence Journal._ "It is not too much to say that in no single work have so many curious cases been brought together and interpreted in a scientific manner."--_Boston Evening Traveller._ =MYTH AND SCIENCE.= By TITO VIGNOLI. 12mo, cloth, price, $1.50. "His book is ingenious; ... his theory of how science gradually differentiated from and conquered myth is extremely well wrought out, and is probably in essentials correct."--_Saturday Review._ "The book is a strong one, and far more interesting to the general reader than its title would indicate. The learning, the acuteness, the strong reasoning power, and the scientific spirit of the author, command admiration."--_New York Christian Advocate._ "An attempt made, with much ability and no small measure of success, to trace the origin and development of the myth. The author has pursued his inquiry with much patience and ingenuity, and has produced a very readable and luminous treatise."--_Philadelphia North American._ "It is a curious if not startling contribution both to psychology and to the early history of man's development."--_New York World._ =MAN BEFORE METALS.= By N. JOLY, Professor at the Science Faculty of Toulouse; Correspondent of the Institute. With 148 Illustrations, 12mo. Cloth, $1.75. "The discussion of man's origin and early history, by Professor De Quatrefages, formed one of the most useful volumes in the 'International Scientific Series,' and the same collection is now further enriched by a popular treatise on paleontology, by M. N. Joly, Professor in the University of Toulouse. The title of the book, 'Man before Metals,' indicates the limitations of the writer's theme. His object is to bring together the numerous proofs, collected by modern research, of the great age of the human race, and to show us what man was, in respect of customs, industries, and moral or religious ideas, before the use of metals was known to him."--_New York Sun._ "An interesting, not to say fascinating volume."--_New York Churchman._ =ANIMAL INTELLIGENCE.= By GEORGE J. ROMANES, F. R. S., Zoölogical Secretary of the Linnæan Society, etc. 12mo. Cloth, $1.75. "My object in the work as a whole is twofold: First, I have thought it desirable that there should be something resembling a text-book of the facts of Comparative Psychology, to which men of science, and also metaphysicians, may turn whenever they have occasion to acquaint themselves with the particular level of intelligence to which this or that species of animal attains. My second and much more important object is that of considering the facts of animal intelligence in their relation to the theory of descent."--_From the Preface._ "Unless we are greatly mistaken, Mr. Romanes's work will take its place as one of the most attractive volumes of the 'International Scientific Series.' Some persons may, indeed, be disposed to say that it is too attractive, that it feeds the popular taste for the curious and marvelous without supplying any commensurate discipline in exact scientific reflection; but the author has, we think, fully justified himself in his modest preface. The result is the appearance of a collection of facts which will be a real boon to the student of Comparative Psychology for this is the first attempt to present systematically well-assured observations on the mental life of animals."--_Saturday Review._ "The author believes himself, not without ample cause, to have completely bridged the supposed gap between instinct and reason by the authentic proofs here marshaled of remarkable intelligence in some of the higher animals. It is the seemingly conclusive evidence of reasoning; powers furnished by the adaptation of means to ends in cases which can not be explained on the theory of inherited aptitude or habit."--_New York Sun._ =THE SCIENCE OF POLITICS.= By SHELDON AMOS, M. A., author of "The Science of Law," etc. 12mo. Cloth, $1.75. "To the political student and the practical statesman it ought to be of great value."--_New York Herald._ "The author traces the subject from Plato and Aristotle in Greece, and Cicero in Rome, to the modern schools in the English field, not slighting the teachings of the American Revolution or the lessons of the French Revolution of 1793. Forms of government, political terms, the relation of law, written and unwritten, to the subject, a codification from Justinian to Napoleon in France and Field in America, are treated as parts of the subject in hand. Necessarily the subjects of executive and legislative authority, police, liquor, and land laws are considered, and the question ever growing in importance in all countries, the relations of corporations to the state."--_New York Observer._ =THE FUNDAMENTAL CONCEPTS OF MODERN PHILOSOPHIC THOUGHT, CRITICALLY AND HISTORICALLY CONSIDERED.= By RUDOLPH EUCKEN, Ph. D., Professor in Jena. With an Introduction by NOAH PORTER, President of Yale College. One vol., 12mo, 304 pages. Cloth. Price, $1.75. President Porter declares of this work that "there are few books within his knowledge which are better fitted to aid the student who wishes to acquaint himself with the course of modern speculation and scientific thinking, and to form an intelligent estimate of most of the current theories." =MIND IN THE LOWER ANIMALS IN HEALTH AND DISEASE.= By W. LAUDER LINDSAY, M. D., F. R. S. E., etc. 2 vols., 8vo. Cloth, $4.00. "The author of this work, which, regarded merely as an accumulation of verified and classified facts, is a unique and precious contribution to the data of comparative psychology, claims that he entered on his inquiry without any theory to defend, support, or illustrate. We are bound to say that, while his general conclusions are boldly and continually avowed, his claim of fairness and caution is justified by his method of examining particular phenomena; that he seems willing at all times to renounce any impression or belief which is shown to be scientifically untenable."--_New York Sun._ "In this work--two volumes of over 500 pages--Dr. Lindsay marshals a proportionately large number of facts against those philosophers who maintain that the intelligence of man differs in kind and not simply in degree from that of the lower animals. It is one purpose of his book to show that the main differences between man and the lower animals exist rather in their physical than in their mental structure. In this way of thinking, all animals possess not the semblance of, but the true substance of mind and will."--_New York World._ "So far as we are aware there has been no treatise upon the subject of animal intelligence so broad in its foundations, so well considered, or so scientific in its methods of inquiry, as that which has been prepared by Dr. W. Lauder Lindsay in two large volumes, the first being devoted to a study of animal mind in health, and the second to animal mind in disease. We may safely say that his work is, in some respects, the most important essay of the kind that has yet been undertaken. His observations have been supplemented by a thorough mastery of the history and literature of the subject, and hence his conclusions rest upon the broadest possible foundation of safe induction. There is a good analytical index to the book, as there ought to be to every work of the kind."--_New York Evening Post._ =THE ELEMENTARY PRINCIPLES OF SCIENTIFIC AGRICULTURE.= By N. T. LUPTON, LL. D., Professor of Chemistry in Vanderbilt University, Nashville, Tenn. 18mo. Cloth. Price, 45 cents. =A GLOSSARY OF BIOLOGICAL, ANATOMICAL, AND PHYSIOLOGICAL TERMS.= By THOMAS DUNMAN. Small 8vo. Cloth. 161 pages. Price, $1.00. "It has been the author's task to furnish here a small and convenient but very complete glossary of those terms; and he has done this so well, both in his choice of terms for definition and in his clear exposition of their etymological and technical meaning, as to leave nothing to be desired in this direction."--_New York Evening Post._ _For sale by all booksellers, or any work sent by mail, post-paid, on receipt of price._ D. APPLETON & CO., Publishers, 1, 3, & 5 Bond Street, New York. SCIENTIFIC LECTURES AND ESSAYS. =Popular Lectures on Scientific Subjects.= By H. HELMHOLTZ, Professor of Physics in the University of Berlin. First Series. Translated by E. ATKINSON, Ph. D., F. C. S. With an Introduction by Professor TYNDALL. With 51 Illustrations. 12mo. Cloth, $2.00. _CONTENTS._--On the Relation of Natural Science to Science in General.--On Goethe's Scientific Researches.--On the Physiological Causes of Harmony in Music--Ice and Glaciers.--Interaction of the Natural Forces.--The Recent Progress of the Theory of Vision.--The Conservation of Force.--Aim and Progress of Physical Science. =Popular Lectures on Scientific Subjects.= By H. HELMHOLTZ. Second Series. 12mo. Cloth, $1.50. _CONTENTS._--Gustav Magnus.--In Memoriam.--The Origin and Significance of Geometrical Axioms.--Relation of Optics to Painting.--Origin of the Planetary System.--On Thought in Medicine.--Academic Freedom in German Universities. "Professor Helmholtz's second series of 'Popular Lectures on Scientific Subjects' forms a volume of singular interest and value. He who anticipates a dry record of facts or a sequence of immature generalization will find himself happily mistaken. In style and method these discourses are models of excellence, and, since they come from a man whose learning and authority are beyond dispute, they may be accepted as presenting the conclusions of the best thought of the times in scientific fields."--_Boston Traveler._ =Science and Culture, and other Essays.= By Professor T. H. HUXLEY, F. R. S. 12mo. Cloth, $1.50. "Of the essays that have been collected by Professor Huxley in this volume, the first four deal with some aspect of education. Most of the remainder are expositions of the results of biological research, and, at the same time, illustrations of the history of scientific ideas. 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"But in most centers of education," writes Professor Cooke, "the old traditions so far survive that the great end of scientific culture is lost in attempting to conform even laboratory instruction to the old academic methods of recitations and examinations. To point out this error, and to claim for science-teaching its appropriate methods, was one object of writing these essays." _For sale by all booksellers; or sent by mail, post-paid, on receipt of price._ New York: D. APPLETON & CO., 1, 3, & 5 Bond Street. 
60819	----	file was produced from scans of public domain works at the University of Michigan's Making of America collection.) [Illustration: FIRST-CLASS 5-IN. CENTRE LATHE, WITH TRAVERSING MANDREL AND OVERHEAD APPARATUS, BY JAMES MUNRO, LAMBETH.] THE LATHE & ITS USES; OR, INSTRUCTION IN THE ART OF TURNING WOOD AND METAL. INCLUDING A DESCRIPTION OF THE MOST MODERN APPLIANCES FOR THE ORNAMENTATION OF PLANE AND CURVED SURFACES. With an Appendix, IN WHICH IS DESCRIBED AN ENTIRELY NOVEL FORM OF LATHE FOR ECCENTRIC AND ROSE ENGINE TURNING; A LATHE AND PLANING MACHINE COMBINED; _And other Valuable Matter relating to the Art_. COPIOUSLY ILLUSTRATED. NEW YORK: JOHN WILEY & SON, PUBLISHERS, NO. 2, CLINTON PLACE. 1868. PREFACE Although the title of this work is sufficient to declare its contents, a few prefatory remarks may not be superfluous as to its design and the manner in which that design has been carried out. It has ever been to the writer a matter of surprise and regret, that although the art of turning has been so long and so successfully pursued in this country, both by artisans and amateurs, no work has appeared in the English language treating upon the subject, except one or two sketches and imperfect treatises. Some years since Mr. Holtzapffel advertised a forthcoming series of seven volumes, intended to supply this manifest deficiency in our scientific and mechanical literature, and the subject would have been handled by him in a thoroughly exhaustive and masterly manner. The untimely death of that gentleman occurred after the publication of the first three volumes, which are indeed complete in themselves, and of immeasurable value to the mechanic and amateur; but which are unfortunately only introductory, "simple turning by hand-tools" being the special subject of the proposed fourth volume. The present proprietors of the firm of Holtzapffel & Co. having, in their catalogue even up to the time of the most recent edition, continued to advertise the seven volumes, amateurs especially have anxiously hoped for the publication of some part at least of the remainder of the series. That expectation is, it is to be feared, little likely to be rewarded; and, not until that fact had been ascertained with something bordering upon certainty, did the author of the present work venture to take up the pen and endeavour to set forth the principles and practice of an art which, like so many others, he has found so absorbing and attractive, and withal so delightful a source of recreation to mind and body. Several things, however, contributed to make the writer hesitate to undertake such a work. In the first place he was aware that a number of _possible_ readers would probably be more competent than himself for such a task, especially those whose means might have enabled them to procure a large amount of the most modern and approved apparatus connected with the Lathe, and whose occupations might allow of more leisure for their extensive use than falls to the lot of the writer. In the next place the risk of publication was such as he felt himself hardly justified in encountering. Just at this time, however, chance placed in his hand two or three numbers of the "English Mechanic," in which some one else had begun, but speedily resigned, a series of papers "On the Lathe and its Uses," compiled from American journals. The author of the present work at once put himself in communication with the editor and proprietor of the above periodical with a result now well known to the readers. The following pages are not, strictly speaking, a mere reprint from the "English Mechanic." The papers have been carefully revised and re-arranged; some statements, the correctness of which appeared doubtful, modified or wholly withdrawn; while, in one or two instances, whole chapters have been re-written, and the suggestions and inventions relating to the Lathe, furnished by other correspondents, embodied (when they appeared of real value) in the work. But, in addition, a valuable Appendix is now published, containing matter of great importance, contributed by one or two gentlemen, who most kindly placed their papers at the service of the author. Foremost among them stands a paper on the angles of tools, by Dodsworth Haydon, Esq., of Guildford. A clever arrangement of Lathe for Rose Engine Work, by the aid of the Eccentric Chuck without Rosettes, is also added from the pen of Mr. Elias Taylor, of Brighton; and one or two matters, which did not appear so fully treated as they deserved in the body of the work, have been resumed and more fully discussed in the Appendix. The author gratefully acknowledges the suggestions of various correspondents, amateurs and working men, from whom, as a rule, he has not failed to obtain any required assistance. That the work, in its present form, is entirely satisfactory or complete, the writer cannot pretend; that many errors have crept in is highly probable; but, if it is acknowledged to be the best work _yet_ produced on the Lathe, and should prove in any degree serviceable to amateur or artisan in the pursuit of this most delightful art--aye, if it should stir up some abler pen to write a better and more complete series, it will afford real pleasure and lasting gratification to THE AUTHOR. CONTENTS PREFACE. Introduction. Chucks. Hand Turning of Wood. Hollowed Work. Cutting Screws. Hollowing Out Soft Wood. American Scroll Chuck. Metal Turning by Hand Tools. Overhead Apparatus. Self-acting and Screw-cutting Lathes. Wheel Cutting in the Lathe. Fret Saws to Mount upon the Lathe Bed. Turning Spheres. Hoblyn's Compound Slide-Rest. Chucks with Slides and Compound Movements. Turning Ovals, etc., by Means of a Template. Eccentric Chuck. Curiosities. Grooving and Mortising Small Work. Ornamental Turning. The Eccentric Cutter Frame. Segment Engine. Holtzapffel's Rose Cutter Frame. Universal Cutter Frame. Rose Engine. Rectilineal Chuck. Epicycloidal Chuck. The Spiral Chuck. APPENDIX. Professor Willis's Tool Holder for the Slide Rest. Munro's Planing Machine to be attached to the Lathe, and worked with the foot. Hicks' Expanding Mandrel. Turning Spheres by means of Templates. Plant's Geometric Chuck. A Paper on the Principles which Govern the Formation and Application of Acute Edges, with special reference to Fixed Turning-tools, contributed by Mr. Dodsworth Haydon. Detached-cutter Holders. New form of Rose Engine by E. Taylor. Oval Turning and Rose Cutting with Templates with my Apparatus. THE LATHE AND ITS USES. The Lathe has now for many years been steadily making its way from the workshops of our leading artisans to those of the amateur and lesser stars of the mechanical world. This is but the natural result of the various additions and improvements which have been introduced into its construction from time to time. The unworkmanlike and clumsy tool of olden days has long since been superseded by one of admirable finish and perfect aptitude for its designed uses; and now that its construction is no longer dependent upon the skill of the workman alone, but upon machinery moving with the precision of clockwork, the fitting of the various parts is accomplished with the greatest ease and certainty. The sale being thus extended, the price has considerably diminished--the monopoly enjoyed by one or two makers no longer exists; and there are few of a mechanical turn of mind who cannot now provide themselves with a lathe suited to their requirements. Nevertheless, the adepts in the art of turning are by no means so numerous as might be expected, and, among amateurs especially, it is rare to find work executed in first-rate style by simple hand tools requiring skill and practice in their use, so that it not unfrequently happens that a workman who can turn out exquisite specimens of ivory carving and ornamental lathe work, is but a fourth-rate hand with the gouge and chisel. But however beautifully executed such ornamental work may be, the _credit_ is rather due to the tool than the workman, and a well turned box with accurately fitting cover may bespeak more skill in handiwork than the above elaborately designed specimen. Moreover the one requires lathe fittings, which are not always to be had unless the purse is well filled, whereas the general mechanic (amateur or professional) can provide the tools needed for the other; hence we propose first of all to give some practical hints on plain hand turning of wood and metal. The ordinary form of foot lathe is well known and requires no special description, it is represented in the frontispiece of this volume. There are, however, certain points of detail in its construction, to which it is necessary to direct the reader's attention. First and foremost comes the mandrel, of which there are several patterns, according to the special purpose for which the lathe may be intended. Now of whatever form it may be made this is the essential part of the lathe, and must run with the utmost truth in its bearings. Imperfection here will be imparted to all work executed upon it, and accuracy in this part alone will make up for any slight defects that may occur in less important parts of the machine. For ordinary work in wood alone or in brass the best form is represented in Fig. 1. [Illustration: FIG. 1.] [Illustration: FIG. 3.] [Illustration: FIG. 2.] The part _a, b_, should be cylindrical, with a feather let in to fit a slot in the pulley shown in Fig. 2. This pulley, whether of hard wood or metal, is thus slipped on the mandrel as far as the collar _d, d_, and a nut _e_, screwed up tightly at the back of it, fixes it securely in its place, from which it may be moved if requisite and replaced without fear of being out of truth. This cannot be done if the mandrel is squared at _a, b_, and the pulley driven on with a hammer, as commonly done by inferior workmen. The part _c_, is made conical, to fit a hardened steel collar of similar shape. The angle of this conical part is of some importance, as if it is too small the mandrel is apt to jam and stick tight in its bearings. 35° will be found to work well. With regard to the length of this conical part, opinions differ considerably, but it must be remembered that friction is independent of the _extent_ of the bearing surfaces and depends on the force with which they are pressed together (in the present case it depends on the tension of the lathe cord and the weight of the material to be turned), so that a tolerably wide margin may be allowed in this matter. Practically the question is decided by the thickness of the casting of the poppet head, _which_ is regulated by the required strength and size of the lathe. The collar is sometimes of hardened steel, sometimes of brass. The latter would theoretically cause less friction than the former, but practically nothing can beat a well finished collar of hard steel. Collars of this material made by the original Holtzapffel two generations back are now as good as ever, perhaps even better. The centre, which screws up against the left-hand end of the mandrel, should be of the form shown in Fig. 3--a plain cylinder with a screw cut at each end to receive clamping nuts. The central part is rather larger than the screwed parts, and passes truly through the poppet head. This form is much better than a simple screw with points, as the latter is not likely to keep the line of centres in being screwed up into its place. It will be found of great convenience to have the screw on the nose of the mandrel (and indeed _all_ screws about the lathe) of standard Whit worth pitch, as taps for the chucks are thus readily obtained, and nuts and screws of the various sizes may be also procured to remedy breakages and losses. Upon this subject, however, we shall have occasion to treat more fully when we pass from the description of the lathe itself to the work that is to be accomplished by its aid. The only form of back poppet that need be particularised is that made with cylinder and leading screw. The simple pointed screw passing through the lathe head tapped to receive it, not only requires no special description, but it is only calculated for lathes of the commonest design, as it is seldom that the line of centres is accurately maintained by the point at every part of the revolution of the screw. Moreover, the latter soon works loose in the poppet, and for anything like accurate work becomes speedily useless. The cylinder and _pushing_ screw is indeed far superior to the form just alluded to, and where cheapness is an object it has its advantages over the first-named and best form. It is represented in Fig. 4. The cylindrical part is shown at B, and may have at one end the usual point, and at the other a small conical hole or hollow centre. It may then be reversed in its bearings at pleasure, or other cylinders with different shaped ends can be substituted, as may be found convenient. Of course the pushing screw A is for the purpose of advancing the cylinder, which is clamped by the small screw at C. The cylinder and leading screw are shown in detail in Fig. 5, which is the poppet head bored throughout to receive the spindle or cylinder A. At the right hand this bore is enlarged to form a recess, B, to receive the head of the leading screw, C. This screw is generally made with a left-handed thread, so as to withdraw the back centre when turned from right to left. The spindle A, A is bored, and a left-handed female thread is cut from end to end--this however is turned off at the place destined to receive the movable point or centre, and a hole slightly tapering is cut, or if preferred a cylindrical hole is made and tapped for the same purpose. The spindle has also a slot cut from end to end, into which a screw enters from the poppet, preventing the spindle from turning round while the internal screw is revolving by means of the small wheel and handle fixed to its right hand end. The spindle is now put in its place, the screw inserted and turned till the head or flange, C, rests in the recess before mentioned--a flat plate, F, is then attached to the back of the poppet by three or four screws, the head of the leading screw passing through its centre; the small wheel is then attached and the whole is complete. [Illustration: FIG. 4.] [Illustration: FIG. 5.] It is evident that by turning the wheel the internal screw is put in revolution, and as it is prevented by its flange from assuming any motion in the direction of its length, the movable cylinder will instead be withdrawn or thrust forward. This form of poppet is the best that can be adopted and is of general use in all first-class lathes. In addition to the movable point _g_, a flange similar to H should be fitted. This will be found of great use when the lathe is used for drilling, the piece of work resting against it, while the pressure is regulated by the leading screw. There are, in addition to the flange and pointed centre, other pieces of apparatus that can be substituted, as occasion may require, and these will be hereafter described in this series. With regard to the common rest for hand turning a lengthened description is unnecessary. The T or tee should for wood turning be of the form shown in Fig. 6 at A. It is often made as B, which is a very inconvenient pattern, as the cross piece on which the tool rests cannot be advanced sufficiently close to the work if the latter exceeds a diameter of two or three inches. For metal turning the top of the rest should be flat, and about one inch broad, as the heel of the hook tools used for turning iron must be able to take a firm bearing upon its surface. Sometimes a plate of brass is riveted on the flat top, as the tool takes a firmer hold on this metal, and when the latter becomes defaced and channelled it can be renewed without the cost of a new casting in iron. The turner should be provided with two or three tees for metal and for wood,--one may be long enough to have two legs and require two sockets, as shown at C. This is convenient in turning long pieces of wood,--a very short tee, not more than an inch in length, should also be provided, and if one tee is specially kept with a very level and smooth edge, it will be found of great advantage in chasing screws--indeed the latter work can hardly be managed at all if the top of the rest is damaged and uneven. The next part requiring description is the boring collar, without which even a hand turning lathe can hardly be considered complete. This boring collar is intended so to support one end of the work, instead of its being held by the back centre, as to enable the workman to get at the end of it for the purpose of drilling it. Suppose for instance the work in hand is a tool handle, and that it is so far finished as only to require the hole for the reception of the tang of the tool. If this is bored by hand with a gimlet, it is seldom that the hole will be truly in the axis of the piece, but when this is done in the lathe by the help of the boring collar the bore will be truly central, and the tool when in place will fall in the same line with the handle. This will conduce to the correctness of the work in hand more than the amateur or other workman might suppose, and a row of tools thus truly handled and in good condition generally bespeaks an efficient and careful artisan. There are several plans for boring collar of nearly equal efficiency, and we shall describe one or two of the most common, and also one invented by the author, and which, if carefully made, is of great service. Fig. 7 represents a poppet head, B, which is but half the height of the other poppets of the lathe--a side view of this is shown at B, Fig. 8. Near the top of this poppet is a hole through which passes a bolt C, by which and its nut the circular plate A can be securely clamped in any desired position, as it revolves freely on the bolt as a centre pin. This plate is bored with a series of conical holes, which are so arranged that their respective centres will be in a line with the centres of the mandrel when any one of them is brought into a position corresponding with the line _c, c_. The hole thus brought into position for use (having been selected according to the size of the work to be bored), takes the place of the back centre; the end of the work rests in the cone, which is greased or soaped to reduce friction, and the rest being fixed at the other side of the boring collar, the drill can be readily used, and the bore afterwards enlarged if necessary with any convenient tool. This boring collar is generally made of iron, but a substitute of hard wood will frequently serve the purpose, and can be made by the amateur, who may be unable to obtain one of more durable material. If made of wood the best unguent will be soap or black lead, such as is used for grates, or a mixture of the two. This black lead or plumbago (it has no lead in its composition) will always be found serviceable where wood works upon wood, and also to give a smooth surface to wooden patterns for casting. [Illustration: FIG. 6.] [Illustration: FIG. 7.] [Illustration: FIG. 8.] Where cost is an object, a simple substitute for the boring collar is frequently made by the ordinary workman by a piece of board one inch thick, shaped like Fig. 9, with a single hole of the size most generally required; and the work is then fitted to the boring collar, instead of the latter to the work. In turning tool handles, for instance, where a few dozen are required all of the same size, or nearly so, a device of this kind, which can be made in a few minutes, is sufficiently effective. This form has been modified in two ways, and either will be found convenient. In the first, the conical hole is made of the largest size likely to be required, a set of boxwood plugs are then turned to fit this hole and are themselves bored in a similar way to suit various sizes of work. The form of these plugs is shown in Fig. 10, which is a side sectional view, and at B, where the same is shown in perspective. Two small screws or pins _b, c_, Fig. 10, fitting into the holes _a, a_, Fig. 9, prevent these flange-shaped plugs from turning round in the board as the work revolves. The pattern of A, Fig. 9, may be varied, and is better made of hard wood, and of a form which will afford a good bearing upon the lathe bed. [Illustration: FIG. 9.] [Illustration: FIG. 10.] The second modification is more difficult to make, but equally effective. It is shown complete in Fig. 11. This form, arranged by the writer, has many advantages over the two last-named, and is very serviceable. A is the poppet, of the full height of the ordinary lathe heads, or a couple of inches higher. B, the slide forming the support of the piece to be bored. The form of the poppet without this attachment is shown in Fig. 12. If for nice work it should be made of metal and the face of it planed, but for general purposes hard wood will suffice. _b, b_, Fig. 11, are two pieces of brass forming a groove or guide in which a slide B, with dovetailed edges is fitted to work. This slide is bored, like the ordinary collar, with conical holes of different sizes, and should be made of metal and planed on back and edges. Over each hole is a mark, and this is to be brought to a similar mark on the face of the poppet. The plate is then clamped in position by a screw at the back of the poppet. One or more of such slides may be fitted at pleasure, and in case of wear or damage these are the only parts requiring to be renewed. [Illustration: FIG. 11.] [Illustration: FIG. 12.] It is a good plan to arrange a socket and tee of a rest as _b, c_, Fig. 13, at the back of this boring collar, especially as the position of the tool will be always the same, so that the rest may be a permanent part of the poppet. There is sometimes a difficulty with the ordinary form of boring collar in advancing the rest T sufficiently near the work (the foot of the poppet, and that of the rest preventing it, by coming in contact.) There is another modification of boring collar, forming at the same time a guide for the drill, which in slender work, where the tool is long and fine, becomes almost a matter of necessity. [Illustration: FIG. 13.] This consists in making such a guide cone as mentioned and shown in Fig. 10, B, but with a continuation containing a smaller hole for the drill, as Fig. 14. Both this and the other shorter cones above-mentioned may be made to screw into the poppet A, Fig. 9, instead of being kept in place by the pins at _a, a_, of that figure. In that case however the hole in the poppet must be cylindrical and only used as a support for the cones themselves. In addition to the use of these boring collars already alluded to, they serve for the purpose of turning up the points of screws like those of lathe centres. These are first formed between centres with carrier chuck, the back poppet is then removed and the extreme point fitted through one of the holes of the boring collar and the marks of the centre turned off. [Illustration: FIG. 14.] Another useful adjunct to the lathe is the back rest for supporting long and slender articles, which would otherwise bend under the pressure of the tool. The ordinary and simplest form is shown in Fig. 15, and this is of general use with brush handle makers and others whose work is confined to a few sizes and shapes only. A better form is shown in Fig. 16. A support of wood or metal shaped like A is clamped to the lathe bed. Through the upper part the slide B passes and is wedged up so as to support the work--or the socket of a lathe rest may be arranged to take the upright part A, which must then be rounded, as shown at C. [Illustration: FIG. 15.] [Illustration: FIG. 16.] A modification of the latter, communicated to the _English Mechanic_, is shown in Fig. 16A. Its construction and mode of application is sufficiently evident without a detailed description. Fig. 16B is another form made in metal. It consists of two similar plates with a triangular opening A, through which the work is passed, and which has an oval slot D, by which the apparatus is secured to the short poppet of the boring collar. Between the two plates slides a third, partly visible at C, which can be clamped by a screw at B, this screw also serving as a stud by which the plate may be moved. The work is allowed to take up its own bearing in the triangular opening as it revolves in the lathe. The clamping screw of the poppet is then secured, and the centering thus made certain. The plate C is then made to descend so as to touch the work, and clamped in that position. This is a very good central support for long slender articles. [Illustration: FIG. 16A.] [Illustration: FIG. 16B.] There is a plan practised by German turners by which the back rest is in a measure superseded, and which may be mentioned here. It is simply the peculiar method of using the left hand. This is placed on the piece to be turned so that the fingers partly encircle the work while the thumb rests in the hollow of the gouge, or upon the end of the tool. The fingers thus form a back rest and keep the work pressed against the cutting edge, which is further steadied by the thumb. As the tool traverses the work the left-hand accompanies it, and with a little practice a ramrod or similar long and slender article may be readily and accurately turned. This position is shown in Fig. 17, and though the novice will find it difficult to work thus, it is well worth the trouble of mastering, as the method once acquired will be found of very great service. [Illustration: FIG. 17.] We have now described more or less in detail the principal parts of the lathe as adapted for hand turning. Before we dismiss this part of the subject, however, it will be necessary to say a few words respecting the bed and lower fittings, the flywheel, treadle, and their adjuncts. Beyond question the iron bed, planed as it now is at a moderate price, by machinery, is the best that can be adopted, especially if it is intended eventually to fit up the simple tool with slide rest and superior apparatus. Nevertheless, the pocket must in this case also frequently decide the question of material. If wood is preferred by necessity or otherwise, it should be _hard_ wood, beech, or Spanish mahogany, unless it is proposed to plate the surface with iron. This latter plan costs little and, besides stiffening the bed, it prevents the wear and tear caused by the constant shifting of the back poppet and rest. A flat strip of iron one inch or an inch and a half wide can be picked out from the stores of any village blacksmith straight and level as it came from the rolls of the manufacturer. Selecting a piece of the required length and breadth, the eighth of an inch thick or rather more, the purchaser will have holes drilled and countersunk at intervals of nine or ten inches, to receive 3/4-inch screws. These strips will have to be laid upon the top of the bed, at its inner edges; they need not be let in flush with the surface unless appearance is studied. They must then be screwed down firmly, and by means of a file worked by both hands up and down their length (not across them) a good surface may be readily obtained. If the iron is let into the bed this filing will abrade the wood work, which is the reason why we prefer screwing it on the surface. This method produces a very excellent and durable lathe bed, and it will be free from much of the tremor which is so disagreeable while working upon a lathe entirely of cast iron unless the bed of the latter and the standards are more substantial than is usual with small lathes. The standards supporting the axle of the fly wheel and bed may in like manner be of wood or iron. Even when the bed is of iron these may be of hard wood, although it is customary to make them of the same material as the bed. If of beech, oak, or mahogany, as in some of Holtzapffel's best lathes with iron beds, the tremor before alluded to will be considerably lessened. Iron is nevertheless very neat, and is quite the fashion with the majority of makers, but is too often faulty in respect of solidity. The standards as a rule are too slight, an elegant pattern being studied to the sacrifice of substance and weight, The bed and stand of a lathe cannot be too strong and stiff. Respecting this matter of stiffness and solidity we seldom find it sufficiently considered, and, even with practical workmen, a defect in this particular is more frequently acknowledged and put up with than remedied, although the _comfort_ of a steady lathe is beyond question, to say nothing of its superiority when good workmanship is studied (as it always should be). The old French lathes made in the form of a thick table with four stout legs, forming the bed and back-board, are by no means to be despised as patterns; and instead of the usual method of making but one standard at end of the bed, there can be no question that two additional ones add considerably to the stability of the machine. The fly wheel should be sufficiently heavy and have three speed grooves on the rim and two additional ones to produce a slow motion, which is required for turning metal. The latter may be worked with ease in this way when the article to be turned is small, but if heavy work is likely to be encountered the back geared lathe, to be hereafter described, must be substituted, and the slide rest will then also replace the hand tools. The crank axle is generally supported by two centre screws, the points being hardened, and also the ends of the axles, which are accordingly made of steel, and the holes for the centre screws neatly drilled and countersunk. This is however not the most perfect method, and as we are speaking of better class lathes, as well as those of more common and cheaper make, we must by no means omit to speak of a very superior way of fitting the crank axle. The latter must be turned at both ends, the wheel bored and slipped on, and keyed in its place. Two wheels of brass about two inches diameter, must then take the place of the centre screws. These are called friction wheels, and they must be placed sufficiently near each other to support the end of the axle between them, as shown in Fig. 17B, _a_ and _b_. A pair of these must be thus fitted to each standard, and after the axle is placed in position a third may be placed above it to prevent the lathe cord from lifting the axle out of place by its tension. The axle and friction wheels will thus work together with an exquisitely smooth rolling motion--there will be no tendency to thrust the lathe standards apart as must result from tightening the ordinary centre screws, and the friction of the axle on its bearings will be reduced to a minimum. Any person acquainted with the use of the lathe may readily fit up these friction wheels, and the time and trouble so expended will be amply repaid by the superior ease with which the lathe can be used. We may say the same of the chain and eccentric, which can replace with similar advantage the crank and hook in ordinary use. [Illustration: FIG. 17B.] [Illustration: FIG. 18.] For the latter the following arrangements are necessary. A is the eccentric keyed to the crank axle, and may be either in the middle of the same or, as in Muir's patent lathes, at one end outside the standard. Around it passes the endless flat chain B (known as crank chain). This also passes round a roller in the treadle shown at C. This chain does not act as a mere link, but when the lathe is in action it moves round and over the eccentric and treadle roller. The motion of the whole is smooth and regular, and, what is almost as important, _noiseless_. In Muir's and other lathes the crank chain is used without the eccentric, being applied to the crank instead. Perhaps there is not much to choose between the two, but no one who has studied the eccentric and observed its exquisitely gentle and smooth motion in an ordinary engine can have failed to be struck by these valuable qualities. It must however be remembered that its throw is half that of a crank of the same eccentricity and the latter will have the advantage in power size for size. In whatever position the lathe may be set up let the rise of the treadle be moderate. It is exceedingly disagreeable to work at a lathe where the rise of the foot board is so great as to bring the knee into contact with the lathe bed, a consummation not infrequent in country made ones. This is only to be escaped by giving up a certain portion of power. Let A, B, Fig. 19, be the line of the treadle when at rest; _c_, the crank. To gain power we should let part A, E, be longer than E, B, as in the sketch. But let this arrangement be made, and when the crank is at its highest point, the line G, B, will show the position of the treadle and foot board. Hence this kind of leverage is not practicably available to any extent, and the length taken from foot board to link may with advantage be even less than that from link to the axle on which the treadle works. In lathes, of all machine tools, it is essential that the workman should be able to stand easily, that the movements of the leg and body should not be communicated to the tool, the play of the treadle and such items of detail being of more consequence than might at first sight appear, and any method tending to diminish friction, vibration, and noise is well worth consideration in planning this machine. [Illustration: FIG. 19.] We may now suppose the reader the happy possessor of a well made foot lathe, long or short in bed, high or low in poppet, according to his need, but, of whatever size, carefully made and firmly fixed in a well-lighted place, and if possible on the basement floor--an upstairs workshop is objectionable owing to the certain vibration of a boarded floor. He will now require certain chucks and tools, many of the former of which he will have to make for himself. CHUCKS. No lathe can be considered well fitted until it is supplied with a large number of chucks, by which strange term are signified the various appliances for fixing to the mandrel the article to be turned. When it is considered how varied are the forms which present themselves to the turner, it may readily be conceived that much ingenuity has to be exercised in contriving methods for mounting his work in the lathe; and when in addition to variety of _form_, variety of _size_ has to be taken into consideration, it is plain that a large assortment of chucks is a necessary item in the workshop of the turner. A vast number of these chucks are of necessity made of wood, as required, and such wooden ones are altered from time to time to suit different-sized work, till they eventually become so completely used up as to be only fit for the fire. In addition, however, to these, there are certain chucks of metal (chiefly brass or gun metal) which should always be ordered with a lathe, or fitted to it before any work (even the making of wooden chucks) can be satisfactorily accomplished. The first of these, is represented in Fig. 20, the part A, screws to the mandrel; while the work is attached to the taper screw B. The use of this chuck is to hold short pieces or flat discs, which allow of a hole in the centre and require to be turned on the face. It is only used for wood-work. This is the chuck to be selected when it is desired to make a wooden chuck. A piece of sound wood being chosen of the requisite size, and roughly rounded by the axe or chisel, a hole is made in one face by a gimlet rather smaller than the tapering screw. The piece is then firmly screwed to the latter, the opposite end dressed with gouge and chisel, and the rest being placed across the end, a hand-drill for wood is brought to bear upon the piece. The hole thus made in the centre is then enlarged by any convenient tool until its diameter is only a little less than that of the screw cut on the lathe mandrel. An inside screw tool is then made use of to cut a thread of the same pitch as that of the mandrel, or a tap of similar size and pitch screwed into it (the former is the best but most difficult method to a novice), the piece detached from the taper screw chuck, which is removed, and the wood attached to the nose of the mandrel on which it may now be accurately fitted and finished to the requisite form and hollowed out or otherwise, as may be necessary. Numberless articles may be in a similar manner turned upon the above chuck such as the bottoms of candlesticks, ring or other stands, bread-platters, small wheels, and so forth; it may therefore stand as number one of these adjuncts to the lathe. [Illustration: FIG 20.] Fig. 21 is the face plate, another most serviceable chuck of almost universal application in such work as surface-turning and boring, and where a hole in the centre is inadmissible. To this belong various dogs or cramps, a few forms of which are shown at _a_, _b_, _c_, _d_. These hold the work firmly down to the surface of the plate, being tightened from behind by screw nuts. It will be seen that there are four slots and numbers of holes in the face plate, some of the latter being tapped for screws. These slots and holes may be increased in number, and some of the latter may be square instead of round, and the cramps may be of all shapes and sizes, because sometimes it may be required to hold down a flat piece of brass the eighth of an inch thick only, and the next job may be to hollow an irregular block of wood of three or four inches in thickness, or it may be necessary to bore out the boss of a wheel, or to turn the rim--all of which, and a hundred others, are cases in which the aid of the face plate will be in requisition. [Illustration: FIG. 21.] Fig. 22 is the chuck specially used for turning rods of metal. It consists of two parts, the body A, which screws to the mandrel, and the piece B, which passes through a slot and is clamped by a small screw at one side _c_. To these must be added the carrier which is of such forms as A1, B1, C1. Above is shown a rod of metal to be turned with this chuck in position for use. Of this we shall have to speak again when we arrive at the subject of metal-turning. There should be several sizes of carriers kept in stock, from 1/4in. in the largest part of the ring to 2in. or 3in., or even much larger for heavy work. The amateur will, however, scarcely need these larger ones. The usual method of making the wood-holding chuck for work that is to be also supported by the back centre, is to have a socket cast like Fig. 23, C, with a central hole to take the fork A, which is held in place by a set screw. This socket is useful for other purposes as it will hold short pieces of iron to be turned, but the fork is far inferior for general work to the piece _b_; this is made of iron, and the end of the cross (against which the wood to be turned comes) is sharpened but must not be _too_ sharp. The end of the piece of wood has then two saw-cuts made at right angles to each other into which the sharpened edges of the cross fall, Fig. 23 D, and the whole will turn together without any chance of slipping. It often happens, when the ordinary fork is used, that if the tool chances to hitch in the work, the latter is either thrown quite out of the lathe, or the centre of the fork retains its place, while the other two points slip and score the work. This can never happen with the form B, which is the most reliable pattern that can be devised for work of this nature. [Illustration: FIG. 22.] [Illustration] [Illustration: FIG. 23.] Fig. 24 is to some extent self-centering. A piece of wood hollowed out conically has three nails, or three-square saw-files so placed within the cone as to present three sharp edges inwards. Any piece of wood, if not too hard, will, if placed with one end in the chuck, while the back centre is screwed against the other, centre itself in some part of this cone, and, being at the same time held by the three sharp edges, will necessarily revolve in the chuck. There are many cases in which even in this rough form such a chuck will prove useful; but if it were cast in metal and the three edges formed by slips of steel, and the whole accurately turned, it would be a very efficient and good self-centering chuck. In its more common form it is largely used by the turners of mop and broom handles, who work rapidly and cannot afford to waste time in chucking their work. With the above, the lathe, if worked by steam or water power, is not even stopped,--the screw of the back centre has a quick thread, so that a single turn to or fro fixes or releases the work; and thus, one handle being finished, another piece takes its place in the chuck, is fixed by a half-turn of the back screw, and being set in rapid motion is turned and completed by a practised hand in a couple of minutes or less. [Illustration: FIG. 24.] Fig. 25 represents another useful chuck, generally of boxwood, called the barrel stave chuck. It is turned conical, the largest part being towards the mandrel; it is then wholly or partially drilled through, after which saw-cuts are made longitudinally, as in the drawing. These allow a certain degree of expansion when a piece of work is fitted into it, and it is tightened round the latter by driving on a ring of iron or brass. This ring is sometimes cut with a coarse thread inside, and a similar thread being chased on the outside of the chuck, it is screwed upon the cone instead of requiring to be driven by blows of a hammer. One important use of this chuck is to re-mount in the lathe, for ornamentation by the eccentric cutter or other apparatus, any finished work that could not be readily chucked in any other manner, or to hold rings requiring (like curtain rings) to be turned on the inside. Such articles will, from the nature of this chuck, be truly centred at once; and their exterior parts will not be liable to injury, as they would be by being driven into an ordinary chuck hollowed out to receive them. [Illustration: FIG. 25.] Another useful chuck for turning short pieces of metal such as bolts and binding screws, and which is in a great measure self centering is made of cast iron, and is usually called the dog-nose chuck, represented in Fig. 26. This is made with movable jaw hinged, as more plainly seen in B. The screw clamps these jaws firmly together, and any small piece of work is thus securely held. The centering, however, is not accurate, though sufficiently so for many purposes. The die chuck (Fig. 27) is accurately self-centering, and although somewhat expensive, is a valuable addition to the lathe. This chuck consists, first of all, of a socket for screw to fit the mandrel, and round flat plate of brass cast in one piece, as in Fig. 28. This must be carefully turned and faced in the lathe. Two pieces of iron or brass are then screwed to the face, as B, B, 28A, leaving a space between, the sides of which are to be truly parallel. These pieces may either be chamfered to form V-pieces, or may be rectangular on their inner edges; at C, C, a part of each is cut away, and the outer or back plate is also filed down to receive the small plates D, D. E shows a groove in which a screw lies, half of which has a right and half a left handed thread; this is shown in Fig. 29. It will be evident that if this screw is placed in the groove of the bottom plate, and its ends pass through the pieces D, D, which are screwed to the plates, it can revolve in its bearings, but will have no endwise motion; the collar F resting in a recess under the top plate D. This screw passes through a projection in the back of the pair of dies, which projection also goes into the same slot in the back plate in which the screw works when turned by the key (Fig. 27, B). The above being nicely fitted, the dies moving evenly but stiffly in their places, the plain top is screwed on, keeping all firmly together. This plate has a long opening or slot (Fig. 27), through which the jaws of the dies and part of the screw are visible. The ends of the screw should not project, as any such projection is calculated to bring to grief the knuckles of the turner--a consideration worth attention in every form of chuck--the squared ends of the screw lie in a recess in the small plates, as shown in the section of one of these plates (Fig. 28X). Into this recess the key fits over the screw end; and by turning this the dies are simultaneously moved asunder, or closer together so as to grasp centrally as in the jaws of a vice, any small article, such as a screw or short rod of metal placed between them, A similarly contrived chuck is often used under the name of a universal chuck, for holding pieces of large diameter, and is very useful for taking pieces of ivory which have to be hollowed or otherwise worked, as will hereafter be detailed. In this case the jaws may be semicircular in form, as Fig. 30. [Illustration: FIG. 26.] [Illustration: FIG. 27.] [Illustration: FIG. 28.] [Illustration: FIG. 28A.] [Illustration: FIG. 29.] [Illustration: FIG. 30.] It is however, evident that these two chucks have a rather limited range. The first can only be used for small work, and the only case in which the latter can take firm hold all round the work is when the jaws are just so far apart as that they form portions of the circumference of one and the same circle. Practically they will hold the work tightly under an extended range of sizes, and they are thus of great use to the turner. The following is however more perfect in operation, from the fact that it has four jaws instead of two which meet concentrically. This may be made either with two long screws at right angles to each other, with right and left-handed threads to each, as in the die chucks, or more simply and, in some respects more satisfactorily, with four distinct screws, all of the same pitch, and all with squared ends of equal size, to allow of the same key being used to turn them. It is possible to use such a chuck as an eccentric chuck if desired, which is certainly a recommendation in its favour over those which work always concentrically. The face of this chuck is shown in Fig. 31. The ends of the four screws have a bearing in the small centre plate _b_, whilst the collars or flanges rest in a recess under the several plates _c, c_. The face of this chuck is graduated by each die, so that it is easy to set the jaws concentrically or to place one or more eccentrically to take in work of other shape than round or square. The jaws of this form of chuck are used for two purposes, either to hold work inside them like a vice, or externally. A ring, for instance, requiring to be chased on the outside is slipped over the jaws, which are then caused to recede from the centre so as to hold the work securely. If the latter does not run truly, one or more of the screws can be slackened, and the opposite ones tightened, or if the eccentricity appears to be in an intermediate part, two adjacent screws will have to be thus slackened and the others tightened. On the whole this is a most useful pattern of chuck. [Illustration: FIG. 31.] The following is a very excellent self-centering chuck now coming into extensive use. It has been noticed in more than one periodical. The description annexed is extracted from the pages of the _English Mechanic_. "The chuck hereby illustrated seems to be a very convenient form, easily adjusted and holding the drill securely. It is also well adapted for holding wire to be threaded. Every piece of which it is composed is of cast steel well hardened. It can be furnished with a shank to fit the hole for the centre, screwed on the spindle, or slipped on the centre. No wrench is necessary, the gripe of the fingers being sufficient to secure the shank of any drill. The inventor claims that he has used a one-inch drill, in tenacious wrought iron in one of them, receiving a shank of only three-eighths of an inch diameter without using a wrench." Fig. 31A represents the shell of the chuck with milled bosses for the fingers. The core, B, is threaded and receives a steel wire spring which is inserted into the rear of each jaw, so that when relieved from pressure, the jaws open automatically. [Illustration: FIG. 31A.] With this brief explanation, the operation of the chuck can be easily comprehended. These chucks are made of two sizes, one with an opening of three-eighths of an inch, and the other of three-sixteenths of an inch, and they can be made of larger sizes. Patented by L. H. Olmsted, Stamford, Connecticut, United States America. Another chuck of self centering design, has likewise appeared in the periodical above named, into which it appears to have been copied from an American paper. The accompanying engravings illustrate some improvements in the arrangement of chucks which have been recently patented in this country, the inventors being Messrs. Smith and Haight, both of New York, U.S. The first part of the invention refers to an arrangement of adjustable chuck, by means of which tools and other articles of different diameters may be held firmly in the jaws of the chuck. Fig. 31B is a longitudinal view of the chuck, partly in section. The spindle, _a_, is fitted so that it may be inserted tightly in the mandrel of the lathe. On the front end of the spindle is a conical screw on which is fitted the cap, _b_; this part is formed with an opening at the front end, having three longitudinal slots in it. In each of these slots an adjustable jaw, _c_, is fitted, the inner part of which is threaded with a female screw, to fit the conical screw on the spindle, _a_. An outer casing _d_, encloses the front part of the chuck, and behind this is fitted a loose collar, which is screwed into the casing _d_, so as to connect the parts firmly together. By turning the cap, _b_, with the casing, _d_, and collar, in one direction, the jaws, _c_, are moved forward and project out through the openings, and they may thus be adjusted to grip a tool or other article of small diameter. The opposite motion of the cap causes the jaws to recede, and in this way they may be adjusted to grasp articles of different diameters. [Illustration: FIG. 31B.] Another arrangement of the adjustable chuck is shown in Fig. 31C, which is a front view, and Fig. 31D, a longitudinal section of the same. A, is the body of the chuck, the front part of which is formed with a rim or flange, in which are three radial recesses having fitted therein the sliding jaws, B. In the rear of each jaw is a bearing, in which is fitted a pin carrying a small lever, C, the front end of which is rounded, as shown in the section, and enters a slot made in the jaw, B; so that when the levers are moved outwards they cause the jaws to contract or move towards the centre. The back part of the body, A, of the chuck is threaded, and on this part is fitted a collar, D, and in front of this is a sliding collar, E, which is connected to the collar, D, by means of a pin which enters a groove formed in the latter. The sliding collar is prevented from turning round on the body, A, by means of a feather, which works in a longitudinal groove formed in the inner circumference of the collar. Three inclined planes, F, are formed on the periphery of the collar, E, which extend to the backward ends of the levers, C, so that by moving the collar to and fro, the jaws, B, are caused to contract or expand, according to the size of the article to be grasped. A short cylindrical block, G, made of a conical figure internally is fitted loosely within the chuck, A, and serves to centre the end of a drill or other short article, but may be removed when it is desired to pass a rod or other article through the body of the chuck. To provide for the easy turning of the collar, D, it is shown as fitted with a hand wheel, H. With this arrangement of the several parts, the jaws of the chuck readily adapt themselves to drill or bit shanks as well as to articles of parallel form, or of a tapered or irregular figure. [Illustration: FIG. 31C.] [Illustration: FIG. 31D.] The chucks last named belong to the class of compound or mechanical tools; and though their usefulness is beyond question, they need not be considered absolutely necessary, as the work which they are designed to facilitate can be and often is done without their aid. Indeed, success in the art of turning by no means depends absolutely upon the possession of expensive apparatus, and the amateur or mechanic will find the advantage of ransacking his own brain for the devising of divers makeshifts and off-hand contrivances--especially in this chuck-making department. Among the simple expedients the following will be found well worthy of adoption. A, Fig. 32, is a simple flange or flat brass plate with a boss behind, similar to a small face plate, and is to be turned up, drilled, and tapped to fit the mandrel. If the latter has a diameter of 3/4 of an inch, a few of these brass pieces should be cast from a set of wooden patterns ranging from two to three or four inches across the diameter of the plate, and, after having been fitted to the mandrel and turned, four holes, countersunk for wood screws, should be made, as shown in the sketch. These are intended to do away with the necessity of boring out and tapping each individual wooden chuck. They can be readily attached to any piece of wood by four screws, and a few minutes will be sufficient to adapt the same to any required purpose. A flat piece of board, for instance, itself too thin, or of too soft substance to permit of its being attached to the mandrel in the ordinary way, can thus be made into a temporary face plate, or a ring cut out of it, or any desired operation performed upon it. Indeed, these socket pieces will be found serviceable on many occasions, and will do away with the necessity of a large set of cup chucks. [Illustration: FIG. 32.] A few of the latter, however, are very useful and will cost but little. The castings are sold by weight, and the turner will experience no difficulty in fitting and finishing them for himself. Fig. 33 is the form of these, and needs no description. The substance may be from 1/8 to 1/4 of an inch, and need not be more, as that thickness will stand any reasonable shock caused by driving a piece of wood into the chuck, and it is always well not to overweight the mandrel with chucks of undue size or substance. The addition of three to six screws to one or two sizes of the cup chuck extends its usefulness. This form is represented in Fig. 34, A and B. In this case, the casting may be rather more substantial (1/4 to �3/8 of an inch in thickness). The screws _must be strictly radial_, pointing to the centre of the circle, and their ends must be turned off or filed flat. Their heads may be squared to enable a key or pair of pincers to be applied, or round with a hole through them. It is better to make this kind of chuck with six screws--three in one plane, and three again _between_ these in another plane behind them. In fitting a piece of work into the chuck, it will not at first be found an easy matter to make it run truly. The best way is to centre it as nearly as can be guessed, by means of the three screws nearest to the open end of the chuck, and then, placing the latter on the mandrel, set the lathe in slow motion and correct the eccentricity of the piece by means of the three inner screws. Even after this it is probable that a little alternate slackening and tightening of the different screws may be necessary; but a little practice will quickly enable the turner to set a piece of work in the true axial line of the mandrel without much difficulty, and the work will then be held very securely. Any short piece, such as the ring of an eccentric to be bored truly inside, may be held by the outer set of screws alone; but if such a piece of work as a small cylinder is to be bored, the six screws must be brought into action. Here let the hint given when speaking of projecting screws, be repeated, _Beware of the knuckles_, which are peculiarly liable to be damaged in making use of these chucks. The shirt sleeve or coat, moreover, does not always enjoy perfect immunity from similar danger, and both should be kept out of harm's way, not for their own sake only, but because the arm may be brought into violent contact with the rest if the sleeve should get entangled (the momentum of the flywheel being great, and therefore not to be checked entirely at any given moment). A single rap of the above nature is not a _delightful_ even if _salutary_ lesson to the novice. [Illustration: FIG. 33.] [Illustration: FIG. 34.] To hold rings and washers a tapering mandrel, Fig. 35, is used; and of these it is necessary to keep a few different sizes to suit different diameters. These may be made of iron or brass if for permanent use, but box or other hard wood is a ready substitute, and may be turned down for smaller work when the surface gets spoiled by use. The expanding mandrel, "Hicks' patent," which will be treated of hereafter, is a convenient substitute for the simple conical form here spoken of; and in manufactories where large numbers of mandrels have to be kept of various sizes, a great saving of time, money, and labour is effected by their use. For amateurs and artisans in a smaller way of business the simpler form is generally sufficient. A slight modification is here appended, by which the common form may sometimes be made more efficient in the holding a ring tightly while undergoing the operation of turning, and this can be made applicable to metal mandrels, though specially intended for wooden ones. Fig. 36. [Illustration: FIG. 35.] [Illustration: FIG. 36.] The mandrel having been turned conical (N.B., the angle of the cone must be small, so that the size will diminish very gradually from the largest end), the wood is divided by a fine saw, just as the chuck already described with the outside rings was sawn into segments, a conical hole having been first made at the smallest end, as shown in the section _b, b_. Into this a short cone of larger angle is to be fitted, against the end of which the point of the back centre will press, tending to drive it into the mandrel, which will thus be made to expand. The ring to be turned will prevent the mandrel from splitting by the wedge-like action of the plug, unless the said ring is of light substance, in which case this form must not be used. The work will, by the above method, be securely and centrally held and not liable to slip towards the small end of the chuck. In the Fig. 36, a groove, _c, c_, is shown at the bottom of the saw-cuts. This should also be made round the boxwood spring chucks with rings, as it gives more freedom of expansion to the segments. With such a groove and the chuck itself completely hollowed out, the pressure of a _strong_ india-rubber ring will be sufficient to hold work whilst being polished: and this will, when the latter is delicate, be even superior to the screwed rings, as the pressure will be more gentle and equable. India-rubber rings for this purpose must not be thin and flat, like those used for bundles of papers or letters, but made of round material, the thickness of a quill or even larger. They may be had of all sizes at an india-rubber warehouse in Holborn, at the bottom of the hill on the left hand side going eastward, and not far from Negretti and Zambra's shop. The writer is not acquainted with the name of the proprietor. Having had occasion to speak of tapping chucks of metal to fit the mandrel, it will be as well to speak here of the requisite tools for effecting this. In the case of iron chucks it is not likely, as a general rule, that the amateur or workman will obtain access to a screw-cutting lathe, and to cut an internal thread by hand with the chasing tool is hardly feasible, though readily accomplished in the case of brass chucks. When, therefore, a lathe is purchased, a set of taps of the diameter and pitch of the screw on the mandrel should be provided. Of these there must be three--an entering taper tap, an intermediate one rather less tapering, and a plug tap, which is cylindrical. And here we must enter a caution. Do not let the tapering taps be too long. For instance, let it be required to tap the boss of a face plate in which the hole cannot be drilled through the plate. It is first bored out to the size of the _bottom_ of the mandrel threads, or rather less. Tap number one must then be screwed into it; but if this is too long, so that it cannot enter to the end of the threads cut upon it, the second tap will be too large and will not enter properly, but will most likely start a new thread for itself and spoil the first. Fig. 37, _a_, _b_, _c_, shows the form required; _d_, the form to be avoided, except in cases where, as in the cup chucks, a hole can be made quite through the article, so that the tapering tap can be worked to the line _x, y_, or nearly so. The long tap, _gradually_ tapering as it does from end to end, is of course the easiest to use, and for nuts and such like is far the best; the conical tap of larger angle requires more power, but in the case named it is a matter of necessity to use it; and, if preferred, a set of four taps instead of three will remedy any difficulty. The novice must take great care to place the tap perpendicular to the face of the chuck, or the shoulder will not fit close to that on the mandrel. If much difficulty is experienced, such an arrangement as Fig. 38 may be of service. A represents the standard of an upright drill-post, of which B is the bench, C the screw by which to depress the drill and keep it to the cut. For the latter, and brace by which it is worked, substitute the tap, and place a spanner or wrench round the head of it. In the centre mark, which is generally left from the turning, place screw point _c_. By means of a plumb line or square, D, test the perpendicularity of the tap; and as the latter penetrates, keep it to its work by the screw C; oil the tap freely, and the chuck will be easily and accurately cut with the required thread. Some kind of clamp will of course be required to secure the chuck to B, while it is being tapped. [Illustration: FIG. 37.] [Illustration: FIG. 38.] The upright drill should always have a place in the workshop. It is much easier to drill with it than in the lathe, and the mandrel will thus be saved considerably. The latter should never be used except for light work. A variety of drilling apparatus will hereafter be described in this series, so that we need not now write more upon this part of our subject. Somewhat akin to the chuck described as the cup chuck with six screws, is a chuck mentioned in an old French work,[1] the purpose of which is to turn up a cylinder, with a point at the end, so as to insure the axial line being kept. In the ordinary course, the cylinder would be turned up with the point and carrier, or driver, chuck already described; the conical point would be then turned down as far as possible, and the mark of the back centre afterwards turned off by means of the boring collar. It is by help of a miniature lathe and boring collar in one piece that the pivots of the balance of a watch are finished. In both cases the work may be well done by the same process. The chuck now to be described requires no boring collar, but at the same time it does not seem to be well suited for any but light work; in which latter case however it would be advantageous, and must therefore have a place in our present paper. The body of the chuck is shown in section, in Fig. 39. A is the socket with screw to fit on the mandrel of the lathe. It will be seen that the chuck itself is hollowed out cylindrically, and in this cylindrical cavity slides a plug, _c_, bored conically, which can be fixed by a thumb-screw, _h_, traversing a slot in the body of the chuck. This cone is destined to receive one end of the cylinder to be pointed, which will, according to its diameter, centre itself in some part of the conical hole in the plug. The latter is made movable, so as to be adapted to the length of the article to be turned. At the outer end of the chuck is a groove dovetailed to receive a slide, shown clearly in the cross section B. The slide must be of sufficient substance to allow a clamping screw, _f_, to be tapped into it at one end, which screw must be long enough to reach when fully advanced nearly to the apex of the triangular opening seen in the slide. The action of the whole contrivance is as follows:--The cylinder to be pointed is placed in the conical cavity of the plug--the latter slid to or fro till the point to be turned projects a short distance beyond the mouth of the chuck through the triangular opening in the front slide; when it is fixed by a turn of the screw, _f_, which forms the third point of resistance, the sides of the triangular opening forming the other two. As the point or apex of the triangle is always in the diameter of the cylindrical chuck, it will only be necessary to move the slide itself in order to bring the axis of the cylinder to be turned in a line with that of the mandrel. As soon as this is accomplished so that the piece runs truly, the screw, _g_, is turned, and the slide fixed in position. A good deal of ingenuity is displayed by the inventor of this chuck, a description of which was published twenty years ago, and there are very many cases in which it will be called into requisition by the mechanic. With a little care, moreover, the amateur might make one for himself--the body of brass or gun metal, the plug and sliding part of iron or steel. [1] Manuel de Tourneur par H. Bergeron. [Illustration: FIG. 39.] Amongst the various devices connected with the lathe, many of which, even as makeshifts, are valuable to the turner, is one not generally known for keeping up the tension of the lathe cord in whatever groove of the fly wheel or pulley it may be placed. The plan is not more ingenious than practical, and the writer is acquainted with one workman, a gasfitter by trade, who has had it in constant use for many years. Directly over the mandrel pulley is another of larger diameter, in which are two grooves of equal depth, fig. 40. This upper pulley is suspended on a movable arm, D, which is pivoted at E, and kept up by an india-rubber spring, F, or, as in the original plan (before these rubber cumulators were known), by a cord passing over a pulley, and having a heavy weight attached, as shown by the dotted lines. In the fig. A represents the fly wheel, B the mandrel, C the upper pulley. The lathe cord is very long, and passes upwards from A, over the upper pulley in groove 1, down again and round the mandrel, a second time over groove 2 of the upper pulley and down to the fly wheel. The tension of the cord is thus always the same, and is regulated by the spring or weight. If the cord is slipped to a smaller part of the lathe pulley, the slack is instantaneously taken up by the descent of the weight, and rising of the arm D, which in like manner yields to allow the cord to be slipped to the larger groove of the mandrel pulley. [Illustration: FIG. 40.] There are many other useful contrivances for chucking work in the lathe, a few of which will be noticed on a future page. The main thing to be attended to is the holding securely as well as centrally the object to be turned. If this is attained, the precise form of chuck is of little importance, and it matters not whether it be made of metal or wood. The latter has indeed, in some respects, an advantage resulting from its elasticity and the ease with which its form is modified. HAND TURNING OF WOOD. We have now described the simple foot-lathe and chucks adapted for hand turning, but of the latter a great number may be provided, and will, in fact, accumulate as the turner proceeds to work upon objects of varied form and size. No chuck once made should be thrown away until it has become so reduced, from repeated alterations, as to be no longer serviceable. And now, before we commence actual turning, it will be well to offer a few concluding remarks upon the selection of a lathe. It will be evident from our previous remarks and illustrations that there is room for great diversity in the size and quality of this machine, and it is astonishing what excellent work is often turned out by an experienced hand from a lathe of the worst description. The simple pole-lathe, which is so out of date that we did not deem it worthy of notice in this series, with its reciprocating motion, like the little tool of the watchmaker, has, before now, supplied the cabinet maker with first-class work, and not many years since we ourselves stood before just such a clumsy tool, taking first lessons in the art. Our next step was to a lathe with wooden poppets, and flywheel of the same material, a mandrel made by a country blacksmith, which scarcely did even _him_ credit; the value of the whole, with stand and beechen bed complete, was £2 sterling, and sufficiently dear at that price. Now, we do not recommend such a tool, and in the present day a much better may be had at that price, but, notwithstanding its evident defects, very tolerable work may be produced from it. We state this to deter the reader from a very common fault--namely, the purchase of an expensive tool and elaborate fittings when the purse is shallow, and the skill shallower still. In fact, any amount may be spent in lathes, and in fitting up a workshop, but to gain real pleasure and satisfaction from the pursuit of the mechanical arts, the outlay should not be more than the probable result in work fairly warrants. A hundred pounds is often expended in the purchase of a lathe, and a hundred shillings would more than purchase the work done by it. We speak from our own experience in this matter, and believe our advice proportionately valuable; and we well know the satisfaction that ensues when good work has been produced in spite of the defects in the appliances at command. If the means do not admit of the purchase of a good lathe necessity must decide the question, and an inferior one must take its place in the workshop. Nevertheless, we would rather counsel a certain amount of delay, and economy and hoarding, that a good foundation may be laid and a lathe purchased of such average excellence that future additions may convert it into a really serviceable tool. It would be invidious and perhaps rather unfair in this little work to send the reader to any particular lathe-maker. There are several good and two or three first-class ones in London, and if prices range high, the work is at any rate of undeniable excellence. There are also many cheaper firms than those alluded to, where the work is rather of rough-and-ready style; all depends on what _class_ of work the would-be purchaser proposes to engage in, whether he intends to confine himself to plain hand-turning in wood, to the construction of steam engine, and other models of machinery in metal, or to the more beautiful finished work in hard wood and ivory, which develop the full power of the machine itself, and the skill of the accomplished turner. In the former cases, a very plain and inexpensive lathe will suffice. In the latter, it is absolutely necessary to purchase one of the best construction, at a tolerably high figure. The best advice to those of slender means, and who, therefore, vastly predominate, is to sacrifice all else to the mandrel and collar. The latter may be bought at from twenty to thirty shillings, ready for mounting in detached wooden headstocks, and will be far superior to any that an ordinary smith can produce. In this case, the two poppets that carry the mandrel and centre screw should be connected together by a block of wood between them, which latter may be rounded off and shaped to something near the form of a cast-iron headstock. The only care necessary in mounting such a mandrel, will be to keep the axial line parallel to the lathe-bed, and directly over the centre of the latter. Whether the mandrel is thus a separate purchase, as may happen from necessity, or obtained as part of the lathe, and fitted in a cast-iron headstock, it should certainly be hardened, and also the collar, if of steel. Both will take a higher polish for this process, and will run easier in consequence. The cost of such a mandrel is rather greater, because many warp or split in the process, and have to be thrown aside; and the labour of grinding mandrel and collar to an exact fit, is considerably increased. The gain, however, is greater than the loss to the purchaser, and the extra outlay must not, therefore, be grudged. It is very annoying to find a conical mandrel worn down by the collar after a twelvemonths' work; for a collar is thus formed on the conical part, so that it cannot be tightened up by the back screw. The first tool to be noticed is the gouge, the form of which is a longitudinal section of a tube, and is shown in Fig. 41. Of this tool not less than three sizes should be selected, of the respective diameters of one inch, half-inch, and a quarter or three-eighths. When purchased, they require grinding, the bevel being too short. It is essential that this tool and the turning chisel have a long bevel, so that the cutting edge should be a very acute angle. (Fig. 41, not like 42.) It is impossible to do good work with the latter form of tool which is, nevertheless, of frequent occurrence in the workshops of amateurs. Both gouge and chisel must be sharpened on an oilstone (Arkansas or Turkey will be found the best) to a keen edge, _and no pains must be spared in preserving the tools in this condition_. Three sizes of chisel to match the gouges should be selected. The latter tool is not made like that intended for carpenter's use, with the edge at right angles to the sides, but is sloped like Fig. 43, so as to present an obtuse angle A, and an acute one B, and the cutting edge is central, the bevel being alike on both sides, so that the tool may be turned over, and used with either of the flat sides upwards. The handles of gouges and chisels should be much longer than those used by carpenters, and nicely rounded and shaped in the lathe. The most difficult thing to turn being a cylinder of soft wood; a description of the method of effecting this will be the best means of initiating the novice in the art of turning. In all the most perfect work by practised hands, there is a sharpness of edges and roundness of mouldings, that are exceedingly agreeable to the eye, and bespeak at once keenness in the tool with which the work has been done, and steadiness in the hand of the operator. The novice must aim at similar perfection, and to this end he must determine to avoid the use of sand-paper, and trust to his management of exceedingly keen tools to put a workmanlike finish to his work. To commence with the proposed cylinder. Let a piece of sound beech be selected for the first essay, as being less difficult to manage than deal, the grain of the latter tearing up in long shreds under the action of the tool. The first thing to be done, after sawing off the necessary quantity of sufficient diameter for the proposed work, is to round it off roughly by means of the hatchet and draw-knife, or spoke-shave. The next thing is to mount it in the lathe. For this purpose the prong chuck, or, better still, that represented as an improvement on the latter, and shown in Fig. 23B, must be screwed on the mandrel, and the work made secure by the aid of the back poppet centre. Care should be taken that the piece runs truly between the points of support, and that it revolves steadily without shake. There is no real necessity for using the compasses, or other contrivance for finding the exact centre at each end, as sometimes recommended, neither, indeed, is it always possible thus to find the axial line. It is easy to fix it at first lightly in its place, and ascertain by a turn or two of the mandrel, how nearly it runs as it ought to do. If it seems tolerably true, a turn of the back centre fixes it securely, if not, it can be shifted in any direction at pleasure. The tyro ought, however, to be warned that he is likely to be deceived in the size of the rough piece, and that he may very probably think it of sufficient diameter for the proposed work when in reality it is too small. Practice, or the use of the callipers, which are bow-legged compasses for measuring the diameters of work, will soon settle the question. The piece being properly fixed in the lathe, the latter is to be set in motion by means of the treadle, the rest having been first fixed as near as possible without touching the piece, and the T clamped parallel to it. If the tyro wishes to become a proficient, no pains must be spared to acquire the knack of working the treadle without moving the body to-and-fro. He must learn, therefore, to stand firmly on one leg, and after the wheel has been put in motion, he must let it and the treadle have its own way. He will thus soon _feel_ when the crank has passed the dead point at the highest point of revolution, and the proper moment to bear down with the foot. It is not necessary to describe the precise movement, as a few trials will teach the method much better than any written description. At first it is hard work, and constant change of leg from the right to the left, and back again, will have to be resorted to to diminish the fatigue. Practice will, however, remove all difficulties, and allow the whole undivided attention to be given to the management of the tool. [Illustration: FIG. 41.] [Illustration: FIG. 42.] [Illustration: FIG. 43.] The gouge must be held down firmly on the rest with the hollow side upwards, and the bevel of the edge forming a tangent to the work, Fig. 44. In this position it will cut freely and smoothly, and the edge will be preserved. If held horizontally, as in Fig. 45, it is evident that the fine edge of the tool will be immediately destroyed by the rapid blows it will receive as the rough wood revolves in contact with it. Its tendency in the latter position will be to scrape, instead of cutting, and the fibres of the wood will thus be torn out in threads, and the surface of the work be roughened. The gouge, then, being placed in the former tangential position, the right hand grasping the handle, the left the blade, as in Fig. 46, the tool is to be slowly slid along the rest, and a series of light shavings, more or less continuous, will be removed from end to end of the piece. Let the workman bear in mind that the tool is to take a firm bearing on the rest, and that it must not move to-and-fro with the inequalities of the piece to be turned. It is not necessary to remove large chips unless the turner has acquired from practice perfect command over the tools, and for the adept this chapter is not written. After the most prominent inequalities have been removed, the _side_ of the gouge will come into use instead of the extreme end, and with this the work may be rapidly reduced to its intended size, always allowing, however, for the final cut with the chisel. Before the latter is taken up, the piece of work is to be rendered as level and true as can be done by the aid of the gouge alone; indeed, if the latter is of tolerable size, and skilfully used, a finish can be put upon the work by it almost equal to that which the chisel can produce and if the work in hand were a moulded pattern, with hollows and raised work, great part would have to depend on the gouge alone. In the present case the chisel must be used, and the method is as follows: Take a hold with both hands, as directed for the management of the gouge, but instead of the flat part lying evenly on the rest, the tool must be partly raised from it, so that only the lower edge takes a firm bearing. By this means the upper angle of the cutting edge (_generally_ the most acute) is kept clear of the wood, and the latter is cut away only by means of the middle and lower part of the edge, as shown in Fig. 47. If placed as in Fig. 48, the acute angle, _a_, is sure to catch and stick into the work, spoiling in two seconds all that has been done. The chisel can be used with either of its flat sides upwards, and moved along the rest from right to left, or from left to right, or turned upside down, as Fig. 49, so that the acute angle is downwards. These positions are shown in the Figs. 47 to 51. The only care necessary is to keep the upper point clear, allow the chisel to rest as flatly on the wood as the above precaution will permit, and to take as _fine_ and _continuous_ shavings as possible. The chisel will be found to draw itself along in some degree as the cut proceeds, and when this action is felt, it is doing its work properly--still, it is a difficult thing to use a chisel well, and the tyro will fail many times and oft before he will succeed. [Illustration: FIG. 44.] [Illustration: FIG. 45.] [Illustration: FIG. 46.] [Illustration: FIG. 47.] [Illustration: FIG. 48.] [Illustration: FIG. 49.] [Illustration: FIG. 50.] [Illustration: FIG. 51.] The chances are that this initiatory lesson will result in anything but a correct cylinder--the surface will not be true like a ruler, but if tried by a straight edge it will be seen to be wavy. Tested by the callipers, Fig. 52, one part will be larger than another, even if the extreme portions be tolerably true to the proposed gauge. Now, the best turner on earth found just these difficulties, and nothing but perseverance and resolute determination will overcome them. Never mind spoiling the first piece of work, give up making it of a determined size, but do not give up making it a true cylinder. Keep the callipers at work, and gently level the prominent parts (you must work down to the size of the deepest hollow, for you cannot fill up such valleys like a railway engineer; you must throw down the adjacent hills instead), proceed gently, little by little; make the tool obey you, show it (as Ruskin speaks of pencil and brush) that you will not yield to its caprices and "henceforward it will be your most obedient servant." Having done the best you can with the surface of your cylinder, proceed to square up the ends, and mind the angle at this part is a right angle, _square_ and _sharp_, not rounded off. Now this again requires care and a knowledge of the proper method. You will work chiefly with the lower corner of the chisel, and we shall best describe the management of the tool by supposing the cylinder an inch too long, and that the extra piece is to be removed. Now there are three positions in which the chisel can be placed to bring its lower corner in contact with the cylinder. First, with the blade perpendicular to the work; secondly, with the blade inclined to the left, Fig. 53, as if to round off the end of the piece; thirdly, inclined to the right, Fig. 54. Held perpendicularly it will cut a fine line, but penetrate slightly; alternately in the other positions it will remove a V-shaped piece, and thus the cutting off is to be begun. One side of the cutting, however, has to be perpendicular, the other may be as sloping as convenient. Now, it is to be remembered in cutting the upright side, which is the end of the roller, the chisel is to incline _rather to the right_, for this reason,--if it incline to the left a momentary inattention will cause it to take the path _a, b_, Fig. 55, the tendency being to cut a spiral track towards the left. The experiment may be made by gently resting the edge thus inclined on any part of the roller, when it will describe a spiral at once. To the right, then, the chisel must _slightly_ incline, and it will cut off a thin curling shaving like Fig. 56, leaving the end of the piece quite smooth and shining. When the piece is nearly cut off, great care and lightness of hand must be used, as the central portion will have become weak and ready to break off before the work is finished. When it will no longer bear the chisel, take it out of the lathe, break it off, and neatly finish with the sharp chisel the central portion, and your first lesson is learnt. There is certainly very little of interest in turning an imperfect cylinder, for it is useless when done, but the alphabet of the art, though not amusing, must be first thoroughly mastered, and the rest will follow in due course. If, however, the work seem unreasonably dull and stupid, the cylinder may be converted into a tool handle, which will be at any rate a useful article, besides affording practice. No special directions are needed in addition to the above, except in respect to the ferrule. This is to be cut off a piece of brass tubing or an old gun barrel, or it may be had at the tool shops ready cut to any size. Begin by turning down the place for this ferrule, taking care not to cut it too small or the ferrule will drop off. Take the piece out of the lathe, and with a mallet hammer on the ferrule. Return it again, taking care to centre it in the old marks, and finish the handle. The brass or iron may be polished with a file for this first attempt. [Illustration: FIG. 52.] [Illustration: FIG. 53.] [Illustration: FIG. 54.] [Illustration: FIG. 55.] [Illustration: FIG. 56.] HOLLOWED WORK. It is now necessary to speak of hollowing out wood for the purpose of making boxes, cup chucks, &c., and the latter, which may be made in any quantity, and of all sizes, will afford excellent practice in this part of the turner's art. The majority of work of this kind is done rather by scraping or fretting out than by cutting; side tools of the forms of Figs. 51 and 56 being used for the purpose. These however, are specially adapted for ivory and hard woods, the grain of which, being very compact and close, is not torn out in shreds by the action of such tools, as would be the case with softer woods. Where the latter material is used in quantity, as in the manufacture of wooden bowls, hook tools, like Fig. 57, are made use of, which cut on their upper edges. These are exceedingly difficult to use, though the practised hands of those brought up to the art, make them cut with a surprising ease and rapidity--fairly surrounding the lathe with a ceaseless cloud of fine shavings removed in the progress of the work. The difficulty experienced in the use of these tools is not confined to the novice, for the majority of turners accustomed to hard wood often cut a sorry figure in the manipulation of softer material with the aid of the tools in question. The hard and soft wood turners form, in point of fact, two distinct branches of the trade. We have in part anticipated this section, by speaking of the making a wooden chuck when describing the use of the metal chuck with taper screw. We shall, therefore, proceed to describe the best method of turning a plain wooden box with cover, but not screwed; the latter being reserved for more extended notice hereafter. The best material to work upon is sound Turkey boxwood, and care must be taken that it is quite dry and well seasoned, or, after it is worked up with, it may be, great care and trouble, the box will split, or the cover become so loose as to fall off, either fatality being sufficiently vexatious. We may mention, in passing, that hard woods of all descriptions may be had in large or small quantities of Messrs. Fauntleroy[2] and Co., 110, Bunhill-row, Finsbury, or of Jacques and Sons, Covent-garden. Most of the lathe-makers also supply it, especially Holtzapffel and Co., of Charing-cross, but the first-named is a large dealer, wholesale and retail, and his charges are moderate. [2] Now Messrs. Mundy and Berrie. [Illustration: FIG. 51, 52, 53, 54, 55, 56, 57.] Supposing a selection made of size proportionate to that of the intended box, including cover and a tolerable margin for waste and accidents, proceed as before to rough it down between two centres and thus to reduce it to a cylindrical form--there is, however, no occasion to use the chisel at present, as we only need a rough cylinder. Remove this from the lathe, and if you have no brass cup chuck into which you can fit it, proceed to make one out of a piece of beech, ash or, if you have plenty, boxwood. Do not hurry the work, but cut the chuck out neatly, screw and fit it, as previously directed, on the nose of the mandrel. We shall suppose it as yet merely a short neat cylindrical block, quite solid. Place the rest with the tee across the end of the piece of wood, the top edge a little below the centre (by the thickness of the blade of the tool). For the latter select one of the three following--either will answer well--58, 59, 60. With one or the other drill a hole in the centre, keeping the tool quite horizontal across the rest. Enlarge this hole by a left side tool, working from the centre of the piece towards the outside, not taking the whole depth at once, but a quarter or half an inch at a time. You must hollow it out about one inch, and see how nicely you can fit the hollow to the size of the piece you are going to turn. You will, of course, have squared up one or both ends of the latter, which must now be driven tightly into the hollow chuck. If you squared the ends of the cylinder correctly and left also the bottom of your chuck level and true, you will be gratified by seeing the piece run evenly at once. [Illustration: FIG. 58, 59, 60.] Fig. 61 shows a section of the chuck with the piece to be turned fitted inside it. Now take the gouge and chisel and reduce the piece to a plain cylinder, and take special care to square up the outer end. This may be done by the aid of a carpenter's chisel held across the rest, like the side-tool. If the end is much out of truth you had better use first the round-ended tool, Fig. 60, but if you have worked carefully from the commencement this will be unnecessary. To ascertain the correctness of this part, apply a small steel square like Fig. 62, the blade of which slides through the brass part and is clamped by a small screw at the side. We show the method of applying this tool to gauge depth, test right angles, &c., in Figs. 63 and 64. It is a most convenient and necessary instrument, and should be at once provided. Having thus ascertained that the end of your cylinder is at right angles with the side, take the point tool, Fig. 58, or the acute corner of your chisel, and, setting the lathe in motion, mark off the intended depth of the _cover_, as D, C, Fig. 61. (Observe, it is the cover and not the box that first demands attention.) Now proceed to hollow out the cover as you hollowed out the chuck, but with greater care. You must allow in the thickness of the top rather more material than you will eventually require, the thickness of the sides, also, may be a trifle in excess, but take the utmost care to make the inside rectangular, that is, the line _f, g_, perpendicular to g, D. Upon the correctness of this the fit of the cover will depend. This being done and tested as to truth with the square, as before, you may cut off the cover with a parting tool, Fig. 65. This tool is thin, with a cutting edge at the end, and is held edgewise upon the rest. The blade is made rather thicker near the end, so that as the tool penetrates the work it may not bind, but allow the small chips made by it to escape freely. The rest must be removed from its former position and placed parallel to the side of the piece, and the tee at such a height that the latter may, when the tool is held horizontally, point to the axis of the work. The tool should be occasionally withdrawn, and the point, instead of being kept precisely in one position, may be slightly raised and lowered from time to time, describing a small arc. It will soon be ascertained in what position it cuts most easily. There are different sizes of parting tool, some very thin in the blade, for ivory and precious woods, some thicker, for box and less valuable stuff, some with a notched end, forming two points, for soft woods, the action of all being similar to a saw tooth, or, in the last, to two adjacent saw teeth set out to clear themselves in working. Care must be taken that the thin blades do not bend and twist while cutting, especially after the cut has become deep. To avoid this do not hurry the work, but take a little at a time, and be careful to keep the tool with its sides perpendicular to the rest. With these precautions the cover will soon be cut off neatly. If care is not taken to allow for the necessary thickness of the cover, the turner will be mortified by finding that instead of the latter, he has merely cut off a ring, and he will have to expiate his want of judgment by beginning a new cover and making a shallower box. We name this to put him on his guard. Supposing the above work satisfactorily accomplished--the top of the cover, however, being (as will probably be the case) either convex or concave, requiring a little touching up and finishing, it will be necessary to turn down on the solid bit of wood left in the chuck the part A, B (Fig. 66), on which the cover will eventually rest. On no account, however, must this be now turned small enough, it must be left so large as not quite to enter the cover, because if it is now nicely fitted, and the box subsequently hollowed out, the cover is sure to be too slack, the wood shrinking in the process of hollowing out. This shrinking may be accounted for by supposing the rings of woody fibre, the result of yearly growth, naturally elastic, with a tendency to contract, each one, like a series of india-rubber bands, embracing that within it. The central ones being removed by the tool, permit the outer ones to contract, their particles approaching nearer to each other and the structure becoming more dense. This tendency causes those radial cracks so often seen in the ends of pieces of wood sawn from the trunk or limbs of the tree. The outer parts becoming drier than the inner, and prevented by the latter from shrinking, necessarily split, hence, when it can be done, the centre of such pieces is bored out, while the wood is yet full of sap, and the rest is thereby preserved. Where this cannot be done the ends may be covered with glue or resin; or paper may be glued on, to prevent access of air, and thus the drying of the outer portion may be so retarded as only to keep pace with that nearer the centre. The concentric rings thus shrink equally, and no radial splitting takes place. [Illustration: FIG. 61, 62, 63, 64.] [Illustration: FIG. 65, 68, 66.] We will now return from this explanatory digression to the work in hand. Having cut down the flange for the cover to nearly the required size, proceed to hollow out the box. Work carefully, so that the sides shall be smooth and perpendicular to the bottom, and the latter plane and neat. Take care, as with the cover, to leave the necessary thickness of bottom, allowing for the cut of the parting tool, and, if possible, half an inch or more beyond it. Now finish that part on which the cover is to rest. Take great care, as before, to secure right angles, and cut away the wood little by little, trying on the cover from time to time, until at last it will just go smoothly and stiffly into its place. It must fit rather tightly, but take especial care not to force it on, or you will split and spoil it. We shall here introduce to the notice of the reader another form of callipers useful in such work as the above, and in many cases absolutely necessary. They are called in-and-out callipers, and are made as shown in Fig. 67. These are so arranged that whatever interval exists between _a_ and _b_, exists also between _c_ and _d_. If, therefore, the inside of a box cover (or similar article) is measured by the latter, the other end of the instrument will show the exact size to be given to the part A, B, Fig. 66. The convenience of such an arrangement for an infinity of cases will be apparent on an inspection of the figure. [Illustration: FIG. 67.] [Illustration: FIG. 69, 70.] The cover of the box must now be put on, the lathe set in motion, and the outside, and also the top of the cover, carefully turned and finished. If the box is to be cylindrical, care should be taken that it is truly so, and that the angle formed by the junction of the top and sides is sharp. If sand-paper is used to finish the work, the edges will be rounded and the workmanlike appearance spoiled. If, therefore, the article is made of box or other hard close-grained wood, this finishing-off may be done with a carpenter's chisel held so as to act as a scraper. The turning chisel will answer the same purpose, but it is a pity to spoil the edge, which should be always preserved keen and fit for use. If the box is made of soft wood, scraping will not answer; the turning chisel must then be made use of, held as previously, described. If the cylindrical form is not proposed, the sides of the box must be left thicker, and after the cover is fitted on the outside may be moulded by the gouge and chisel, and tools like 60 and 68 to 70, to any desired pattern. The only thing remaining to be done is to cut off the box with the parting tool, the same precautions being observed which we spoke of in separating the cover. If there should be any defect in the bottom after the work is detached, the box must be placed in a cup chuck turned to receive it, and the above defects removed. In hollowing out a piece of solid ivory or similar costly material, it would be exceedingly wasteful if the central part were removed as in a common box, by being reduced to small chips. It is possible to remove the whole interior in a solid block, and with exceedingly trifling loss of material. This is effected by means of side parting tools, 71, 72, 73. A common parting tool is first used and a groove cut therewith in the face of the block to be turned. Fig. 74 represents this face 75; the section after the groove is cut the depth of the box required. The shaded part in the centre represents the part to be removed. The smallest parting tool, Fig. 73, is now introduced, the back of the tool being laid across the rest, so that the crook takes a perpendicular position, A, B, Fig. 74. When at the bottom of the groove the hook is turned to the left, so that it may cut a groove underneath the block, until stopped by its shank. It is then withdrawn and Fig. 72, and subsequently Fig. 71 introduced, and used in a similar way. In Fig. 76 the black line shows the tool in position, with the under cutting done by it. The sizes are thus increased until the last tool removes the block entire.[3] [3] The side parting tools are sometimes inserted in the centre of the work, a hole being made for their introduction, they then cut from within outwards. In this case, however, instead of a solid piece a thick ring of the material is detached. [Illustration: FIG. 71, 72, 73.] [Illustration: FIG. 74, 75, 76, 77.] We now propose to describe the method of turning a round ball or globe, and, to make the work more interesting, it shall contain a small box. The first thing necessary is to decide upon the diameter. In the present case let it be an inch and a half. Turn a cylinder of boxwood a little exceeding this, and cut off from it rather more than an inch and a half in length. The excess is merely to allow for waste. You will thus have a cylinder whose diameter equals its length. Before removing it from the lathe, mark its centre by a groove with a point tool--subdivide the outer spaces with five lines, and from the latter remove the corners of the piece, thus reducing it to the form 77. Test the length and breadth by the callipers and take care that the ends of the cylinder are at right angles to the sides. Now place the piece in the chuck in the position shown in the figure, that is, at right angles to its original position in the lathe. It must be tested as to truth by holding a point tool on the central line E, F. If correctly placed this will only make a dot when the lathe is put in motion. If the piece does not lie evenly the point of the tool will make a small circle--it must then be corrected with a light tap or two, until it runs evenly. If the inside of the chuck is rubbed with chalk the work will be less liable to slip. The following operation, however, must be conducted very gently and with exceeding care, or a satisfactory result will not be produced. It will be observed that the central line having been marked or cut upon the side of the cylinder is necessarily a circle, and its revolution on its axis forms a sphere. We have therefore only to cut away the piece truly down to this line to finish what _ought_ to be a perfect globe. Bergeron, however, justly remarks that although the theory is correct it is next to impossible to manage the tools with sufficient skill to complete in this way a true sphere. One great cause of this difficulty, is that as the work revolves in its new position the central line is not visible as a line, but simply becomes the boundary of the sphere. This may be in part done away by making a _red_ line or black one (red is the best) instead of a mark with the tool. The work will then appear red as it revolves, and the gouge and chisel must be used to cut away this red part, great care being taken only just to remove what appears coloured. Thus you will in the end have cut the work away so as _barely_ to remove the line. Work from the central part outwards, and always with exceeding care, and you will eventually succeed to your satisfaction. It is, nevertheless, a very difficult bit of work to finish even fairly well--mainly on account of the great obscurity of your landmark, the red line. For the more perfect finishing of the above a template of steel may be made like Fig. 78, with which to test the work--its diameter is equal to that of the sphere, and it will serve as a gauge or scraper. It should be made of saw plate if intended for the latter purpose, otherwise sheet brass will answer as well. After the semi-globe has been turned in the first chuck, it will be necessary to turn another to receive the finished part, and for the more perfect formation of the same a semicircular template of the same gauge as the concave one first made may be provided, as the more nicely the ball fits the chuck, the less chance there will be of the work shifting during the turning of the latter half of the sphere. [Illustration: FIG. 78.] In order to obviate the difficulty of following the diametrical line with the cutting tool, the following contrivance has been suggested to the author by one who has followed lathe work as a profession for many years, and is an adept at the art. The lathe band is to be slightly slackened by partial untwisting (a turn or two will suffice), if of catgut, so that it will carry round the pulley, if desired, but will slip if the hand is placed on the latter. Thus, the tool may be applied, and a light cut taken, and the work instantly stopped for examination without stopping the lathe, as the flywheel continues to revolve all the time. This examination can be repeated, if necessary, every few seconds, by merely placing the hand on the pulley, and in this way the work being carried on little by little, a good result is attainable with comparatively little difficulty. The best position for the rest during the above operations will be across the face of the work, as in hollowing out boxes, working carefully, little by little, from centre to circumference. Towards the finish a scraper should be used, the common carpenter's chisel being as good a tool as any. Now to proceed with the box. Before removing the finished ball from the chuck, bore it through with tool Fig. 59, enlarge with Fig. 51, and make the hole conical, unscrew the chuck, with the ball remaining in it, and put on another with a piece of boxwood large enough to make a plug to fit this hole. This plug, when fitted, is to be hollowed out, and converted into a box, like Fig. 79. The latter, when put in place, must fit so neatly that only a light circle shows its position. To conceal it still more completely, a series of circles are to be set at each of the six sides of the ball, as shown at Fig. 80. To remove the box, the thumb is placed at the small end, and pressure made. This forms a neat pocket needle-case, and may be made of ivory as a present to your lady-love. [Illustration: FIG. 79.] [Illustration: FIG. 80.] There is no practical difficulty likely to be met with in the above after the round ball is itself made, unless it may arise in respect of the conical hole. Let this be turned out as directed, until at the furthest (smallest) end it will just allow a gauge, like the annexed figure, 80A, to pass through it. [Illustration: Fig. 80A.] Having also gauged the large end of the hole to the desired size, take care to finish the side evenly from one to the other. The gauge may be a disc of tin on a wire, or, still better, a short cylinder of box wood, on a similar handle, as there will be a little difficulty in feeling whether the disc is placed at right angles to the axis of the hole. Unless, however, you desire to work to a pre-arranged exact measurement, the above precautions will scarcely be necessary, inasmuch as the hole is first bored, and the conical plug afterwards fitted to it. The ball may, therefore, be taken from the chuck, each end of the bore measured, and the plug gauged at each end by the callipers, and turned to an exact fit. In the above account the unmathematical phrase of "_six sides_ of the _ball_" is used for want of a better; the _meaning_ of the author will, however, be evident. CUTTING SCREWS. The ambition of amateurs, especially, is very commonly centered in a desire to cut screws in the lathe, and there is good reason for this, because in the first place there is a difficulty presented which it is pleasant to overcome, and in the next place, a screw is of absolute necessity in the greater number of turned works. There is an apparatus of simple but ingenious construction called a screw box, which is commonly used by carpenters and others who have not attained the skill necessary for chasing screws in the lathe, and which is very convenient even for those who have obtained this power. A sketch of this is given in Fig. 81. A, shows the tool complete, B is a view after the top plate has been removed, showing the knife or cutting tool, the latter being delineated alone at D on a large scale, C is a section. To make this tool, which is within the power of any person of average skill, a block of hard wood is first selected, and drilled with a hole corresponding to the proposed size of the screw to be cut. If no tap is at hand of the desired diameter and pitch, this block must be mounted in the lathe, and the thread chased as we shall presently describe. It is absolutely necessary that the block be nicely squared up and level on the face. A small place must then be cut to receive the knife, the edge of which is so constructed as to form part of the thread cut away to make room for it. It is V shaped like Fig. D, and very keenly sharpened. The method used to clamp the knife in position, which is shown in Fig. D, permits the cutter to be advanced or withdrawn until its position is accurately determined as above. The top plate of wood is now fitted, and adjusted--the central hole, _which is not tapped_, but as large as the _outside_ of the screw-thread to be cut, forming a continuation of that which is tapped in the lower block. A slot _b_, Fig. A, forms a passage from the knife, to allow of the escape of the chips. The piece to be cut into a screw should be shaped like Fig. 82. The part _a_, will be left plain, _b_, is that on which the thread is to be cut, and must be truly cylindrical, and of such size as to just enter the hole in the top plate of the screw box. The part _c_ must pass through the threaded part of the screw box, not loosely, but just so as not to damage the threads in the least. The lower part of the central division is sloped off as seen in the sketch. To cut the thread the screw blank is fixed in the vice by its head, which, after being turned, should be planed off at each side. The screw box being then placed upon it the lowest and smallest part of the blank should just project, as in Fig. 83. This part is intended to insure the perpendicular position of the blank in respect of the screw box. The latter is then turned from left to right until the screw is cut, which ought to come from the tool clean and smooth. Box wood is especially suitable for this purpose. This method is, of course, wholly inapplicable to anything but wooden screw bolts, and for practice the tyro may set to work and make three or four of the following screw clamps, which are useful to hold pieces of wood that have been glued together. The tap for screwing nuts and the jaws of these clamps, is similar to that used for metal, but, the teeth, or cutting threads, are deeper and more pointed. The jaws of the clamps shown in Figs. 84, 85, are usually made of beech, which will take a very fair thread; or of birch, which is still better; and the screws may be made of the same material, box being too costly and scarce for such purposes. In making these clamps, there is to be no thread cut on that part at which the handle of the screws project, nor is there any thread on this part of the bolts, which pass through a smooth hole in one jaw and lay hold of the other only. Other forms will suggest themselves, but the two given will be found serviceable patterns. [Illustration: FIG. 81.] [Illustration: FIG. 83.] [Illustration: FIG. 82.] [Illustration: FIG. 84.] [Illustration: FIG. 85.] The above method of cutting screws is not of anything like universal application, nor specially the work of the turner; we shall now, therefore, speak of cutting them by the chasing tool in the lathe. To effect this with certainty requires much care and long practice, and at first the attempt should never be made on a box or ornamental piece of work, otherwise finished, but on a plain cylindrical bolt, such as those of the clamps just described. For the inside, or female screw, the making of chucks will afford endless practice, and a failure in either of these will be of little importance. The screw tool for male and female threads is represented in Figs. 86 and 87. It is of steel, and as each tooth inclines in the direction and with the pitch of the screw, it cannot be made with a file, but is cut by being held against a revolving tap (or screw hob, which is of similar form.) There is certainly a defect in the above common form of screw chaser, and a slight modification, to be presently described, will be found easier to use, and, in many respects, easier to make. To cut a thread with the chasing tool, the top of the rest must be quite level and smooth, so that the tool may readily slip along it. Suppose an outside thread to be required on a cylinder of box or other close grained wood. The rest being firmly fixed so that the upper edge is level with the axis of the piece, and about half an inch from it, as Fig. 88, the tool is advanced to touch the work, not in a line with the axis, but so as to bring the part, _a_, in contact with it first, and the moment the tool is felt to run along, which it will do as soon as this part of it indents the wood, the handle is raised a little so that the points of the teeth come into work. The tool in fact must describe the segment of a circle, as shown by the dotted line. If this is done cleverly the tool will not hitch, nor produce a drunken thread, but the latter will come out clean and sharp. It is, nevertheless, necessary to practise till the knack of thus chasing a thread is attained, and, considering that once acquired, the necessity of traversing mandrel or other expensive (and yet more or less defective) apparatus, no longer exists, it is evident that the young aspirant should spare neither time nor patience in becoming an adept in this useful art. [Illustration: FIG. 86.] [Illustration: FIG. 87.] [Illustration: FIG. 88.] One great difficulty in cutting the screw-threads to the top of a box, or the inside of its cover, arises from the necessity for stopping short, and removing the tool instantly as soon as it touches the shoulder, or the top of the cover. The latter should be made rather deeper than is necessary, so that there may be a turn or two of screw to spare. This will give more room for the play and removal of the inside chasing tool. The ordinary form of the latter is as shown in Fig. 87, the part under the plane upper surface (_a_) being either slightly hollowed or flat, generally the former, from having been cut by a revolving cylindrical hub. Now, although this form may be suitable for outside screw tools, which have to work on cylindrical pieces, it does not appear equally suitable for inside tools, which are to act on concave work. The writer of this article has experimented upon many patterns of chasing tool, and has found it perfectly easy to chase an inside thread with an ordinary grooved tap, which seldom makes a false cut, or crosses the threads. From this the idea naturally arose of a convex edged tool for inside chasing, and a concave one for outside work, as Fig. 89. [Illustration: FIG. 89.] [Illustration: FIG. 90.] Practically, however, the convex edge, Fig. 90, will answer satisfactorily for an outside cylinder. In order to obtain an efficient cutting edge from this form, the rounding must be very slight. The out or inside tool is used with a rolling movement on the rest as it advances. If for hard wood, a notch cut across in the line _e, f_, Fig. 90, with a saw-file, will, by making a partially cutting edge on the convex part, cause the tool to enter more readily at starting. Tools like the above must be necessarily the work of the amateur himself. The regular makers have a great objection to make any tool or machine out of the ordinary routine. Hence the same patterns are constantly reproduced year after year, until some one connected with the manufacture invents an improved form, or some one else of mechanical genius, and possessed of means, registers a new design. Amateurs are apt to cavil at this system, and in some cases it no doubt interferes with, and checks improvement in tools and machines, but the evil is almost a matter of necessity. Tools are made not singly, one of each pattern, but so many score or hundreds of one form are forged out, and handed over to the grinding and finishing department, and it would sadly interfere with the system and order of the manufacturer to make a single tool or two for individual purchasers of different pattern to those ordinarily used. If a design is sent in by a retail dealer who can order a hundred or so at his own risk, the above objection is obviated, and the new pattern of tool or machine is at once introduced. If, however, any new design by an amateur, being submitted to such men as Holtzapffel, Buck, Fenn, or Whitworth, appears to _them_ good and saleable, they will not only not object to introduce it, but may possibly give a premium to the inventor. We have thought it necessary to make these remarks to obviate the possible disappointment of amateurs in this respect. It is but natural to suppose that some ingenious device must have long since arisen to obviate the difficulty of thus cutting screws by hand. Every turner finds the difficulty, and few perhaps have failed to try some plan or other to counteract it. There are two methods whereby this can be done: one by causing the tool to traverse at a given rate according to the proposed pitch of the screw, the other by giving similar movement to the mandrel, while the tool remains still. For such work as screwing the lids of boxes, the traversing mandrel is commonly used, but for cutting long screws in metal, the tool is fixed in a slide rest, and the latter is made to traverse, if necessary, the whole length of the lathe bed, by means of a guide screw driven by suitable gearing put in motion by the mandrel itself, the speed being adjusted by a series of cog wheels which can be interchanged to cause various rates of motion. The latter method belongs to machine lathes, and will be treated of hereafter in this series. The author has great pleasure in here introducing a device, not exactly for _cutting_, but for starting the threads of a single, or double screw, or, indeed, a quadruple one. It is the invention of a gentleman whose _nom de plume_ is East Norfolk Amateur, and was by him kindly communicated to the _English Mechanic_, of June 21, 1867. The description is here given in his own words:-- "I think the plan to be described will produce to a certainty any required number of screws and turns to the inch. The screws are entirely cut with a common comb tool, but started by a revolving cutter set to the required angle, and applied firmly to the work, on the T-rest. I call it 'the universal screw guide tool,' contrived and made by myself, and I believe will prove as useful to others as it has to me: the drawing will almost explain the tool. The cutter, A, is 9/16ths of an inch in diameter, turned to a cutting edge, and finely tempered. The stem, B, in which it revolves, is round, and fits into the shoe, C, having a graduated collar, D, in front of C, to set the cutter to the required pitch or angle, the set screw, E, makes it fast; having turned a piece of rod, of brass, iron, or steel, a little above the size necessary, and supposing a quadruple screw is to be cut having ten turns to the inch, there would, of course, be forty threads when complete; if one of these four can be truly traced, the comb tool will easily follow by inserting the outside tooth, either right or left hand, as found convenient, in the line traced, when the other three will soon appear with perfect accuracy, provided the first one exactly corresponded to five points of the comb, which is easily accomplished after a few trials, and if not successful at first,[4] can be removed by a dead flat file several times, without reducing the rod too much. When found to exactly fit the five points, the cutter may be applied with more force to leave a good chase for the comb. The T-rest requires a smooth surface for the shoe, C, to slide freely on, and to be set parallel with the work, and the tool held at a right angle as it proceeds along the rest, or the lines formed would be of unequal distance. After a little experience it will be found to work with beautiful accuracy, and for those who have not screw-guide mandrels, and are not practised hands at flying common screws, it will be found a great assistance, as it sets to anything. I described only the quadruple, but the same rule applies to all quick screws; for a double the chase must correspond to three points, and so on for any number, that is, one more point of the comb than the number of screws to be cut, and for a common one the chase must fit the comb altogether." [4] This doubt seems to mar the invention. It is, however, on the whole a good design. [Illustration FIG. 90 and 91.] The above simple apparatus will, it is believed, be of great service to those who find difficulty in hand chasing of screws; it is, however, necessary to speak of other methods, and especially of that so universally used by the turners of "Tunbridge ware"--viz., the traversing mandrel. This is represented in Fig. 91. A is the poppet; B, the mandrel, no longer conical at the place where it traverses the collar, but cylindrical, and passing through _two_ cylindrical collars. It is prevented from advancing towards the left in its bearings by the shoulder, K, and in the other direction by a plain cylindrical collar, or ferrule, C, which slips over the end, and is secured by a nut, D. The whole is thus ready for use, as an ordinary mandrel. To cause it to traverse from left to right, as it revolves, the nut and collar, C, D, are removed, and a ferrule, or guide, F, which has a screw of the desired pitch cut on its edge, is slipped on the mandrel over a short feather against a shoulder, where it is retained by a nut or pin. There are several such guide-ferrules supplied with the mandrel of different pitches of screws. The nut G is then removed and the piece E, which is of brass or gun metal 3/8 or 1/2 inch in thickness, with similar screw threads in each of the hollows is attached. This guide is slipped on at H, and secured by replacing the nut. The pin, which carries the guide, is frequently made to slide up and down the face of the poppet, by the action of a screw, M, working through a brass piece attached to that which carries the pin. It is thus readily lowered out of gear or drawn up again to touch the screw ferule. This is better than a pin screwed to the head of the poppet, and is always adopted in the best lathes. In the frontispiece is a photograph of this arrangement. This guidepiece acts like a half nut, and as the mandrel revolves it gears into the ferule and causes the required traverse. A single point tool, therefore, held against the work will trace a screw of the same pitch as that of the guides, and of a length equal to that of the ferule. The above is not intended for cutting long screws, which would have to be done in successive short lengths, but for screws of box lids, chucks, and similar work it is a most excellent contrivance, and peculiarly adapted for the use of the amateur. The guide threads in the commoner patterns of these lathes are cut on the mandrel itself, which is made of greater length than usual, and these several guides are cut upon the part within the poppet heads, as Fig. 92, which represents such a lathe as is sometimes used by gasfitters and brass workers in general.[5] In the latter it will be noticed that there is added a sustaining screw at the back of the mandrel. This is a good addition, and indeed almost a necessary one if the lathe is to be used for ordinary rough work, especially drilling, as it takes off the pressure which must otherwise come against the shoulder, K, Fig. 91, and it must be remembered that these lathes are expensive, and, therefore, ought to be taken care of. The amateur may also be warned against bad work; none but the first-class makers can turn out a reliable lathe of this description. The collars and mandrel require _perfect_ fitting, and they must be quite hard, because there is no possibility of tightening them when worn. They must be kept well oiled, therefore, when in use, and the oil holes in the top of the poppet should be fitted with brass covers, to prevent any particles of metal, and especially emery dust, from working in between collars and mandrel. Be sure to have one guide screw of the same pitch as that on the nose of the mandrel, for the purpose of tapping chucks to fit thereon. In using the traversing mandrel, either the cord should be slackened so that the pressure of the hand on the pulley may stop the revolution of the work in a moment, or the flywheel should not be brought into use, the cord being instead grasped by the left hand, because it is generally necessary to cut to a shoulder or given point. It is, however, possible sometimes so to arrange the guides by insertion of a washer or other expedient as to cause the action to cease of itself at the required point. In a future chapter, the cutting of long metal screws will be treated in detail, but before concluding the present chapter, it may be useful to say a few words concerning the nature of the screw itself as a mechanical expedient. A screw may be defined as a continuous inclined plane--or an inclined plane wound round a cylinder--the pitch being the inclination of the plane, that is, the ratio of its height to the length of its base. From the mechanical principle of the inclined plane it follows that the greater number of threads in a given space the greater is the power of the screw when used as in a press, or to draw along its nut, as in the slide rest, in which endlong motion in the screw itself is prevented. It seems, at first sight, easy to devise a method for cutting screws of any desired pitch, but this is far from being the case, and when it becomes necessary to increase the number of threads to fifty, sixty, eighty, or even more to the inch, with such accuracy that one turn of the screw shall always produce an _equal_ longitudinal movement of the nut, the most delicate machinery scarcely suffices for the purpose. The microscope detects and shows errors even in the best work, and it is questionable whether a perfect screw of any length _can_ be cut by machinery, as every imperfection in the latter is communicated to the work done by it. If the amateur, therefore, requires a screw for a slide rest, eccentric chuck, microscope, or other delicate piece of machinery, or philosophical instrument, he had better get it cut by some practical mechanician, in the possession of the necessary apparatus. [5] There should be a collar or shoulder to this mandrel, the same as at K in the other figure. [Illustration: FIG. 91.] [Illustration: FIG. 92.] In the "Manual Bergeron" is an ingenious contrivance, by an amateur, which is worth notice, although unsuited for any work where extreme accuracy of pitch is required in the screw. The following, Fig. 93, is a description:--The mandrel is made to traverse in its bearings, as before detailed in this series, but instead of its motion being governed by guide hubs, it is dependent on the action of a pair of differential pulleys, B. A bent lever, C, is pivoted at E to the face of the poppet, having a bit of hardened steel fitted to work in a semicircular groove in the mandrel itself, and so arranged that on raising the tail or long arm of the lever the mandrel is thrust forward from left to right, while a reverse action of this lever causes a similar movement in the opposite direction. The movement of the lever is thus regulated:--At the extreme end of the long arm is a pulley and hook, as shown in the drawing; the double, or differential pulley, is fixed to the end of the mandrel, and from the smaller part depends a cord which passes thence through the pulley on the lever, and is wound round the larger one on the mandrel when its end is secured. On the hook is hung a weight. It will be evident, on an inspection of the drawing, that on putting the lathe in motion the cord on the differential pulley will coil itself round the largest part of the same, and will draw up the end of the lever with a speed proportionate to the difference of diameter between the larger and smaller parts of the double pulley. The short end of the lever will at the same time with similar proportionate motion move the mandrel and work, and cause the fixed tool to cut a spiral or screw thread on the latter--a good deal of ingenuity is displayed in the above, and it has the advantage of being easily fitted up, but it is evident that some alterations and additions would be required to adapt it to any other use but that specified. A contrivance similar to Fig. 94, may in some cases be a sufficient makeshift, when a more perfect one is not at hand. A screw is here cut on the outside of the chuck, and a kind of double tool is used, the tracer which is in contact with the guide thread being adjustable as to its length, and the cutting tool having a sidelong adjustment as well. The rest being placed between the connecting bar of the tool and the work, the former will be held with sufficient steadiness to enable the workman to traverse the whole easily by hand. The use of this tool is of course limited, but the plan is simple and fairly effective. The only really serviceable plan is the slide rest, to be hereafter described. But one other plan is here added, which is called "Healey's chuck." The description and sketch are from Holtzapffel's work, in which it was however copied from an older treatise. The author, it must be understood, has never seen the contrivance himself, and there is a fault in its principle of construction which must militate against its use except in a very limited degree. Since, however, Holtzapffel has considered it worthy of a place in his work, it is at any rate well to introduce it to the reader, especially as its defects will not be of great importance in tracing screws of half a dozen threads or so. The apparatus is represented in Fig. 95. in plan. C is the chuck which carries the work to be screwed, and T is the tool which lies upon R, R, the lathe rest, that is placed at right angles to the bearers and is always free to move in its socket S, as on a centre, because the binding screw is either loosened or removed. On the outside of the chuck C is cut a coarse guide screw which we will suppose to be right handed. The nut N, N, which fits the screw of the chuck is extended into a long arm, and the latter communicates with the lathe rest by the connecting rod C, C. As the lathe revolves backwards and forwards, the arm, N (which is retained horizontally by a guide pin, G), traverses to and fro, as regards the chuck and work, and causes the lathe rest R, R, to oscillate in its socket S. The distance S, T being half S, R, a right hand screw of half the coarseness of the guide will be cut, or the tool being nearer to and on the other side of the centre, S, as in the dotted position T, a finer and left hand screw will be cut. The rod C, C, may be attached indifferently to any part of N, N, but the smallest change of the relation of S, T to S, R would mar the correspondence of screws cut at different periods, and therefore T and R should be united by a swiveljoint capable of being fixed at any part of the lathe rest R, R, which is omitted in Mr. Healey's perspective drawing of the apparatus. [Illustration: FIG. 93.] [Illustration: FIG. 94.] [Illustration: FIG. 95.] This is one of the least perfect modes of originating screws, it should, therefore, be only applied to such as are very short, as, owing to the variation in the angular relation of the parts the motion given to the tool is not strictly constant nor equable. When in the midway position the several parts should lie exactly at right angles to each other in order as far as possible to avoid the error. The inequality of the threads is imperceptible in a short screw. A little modification of the screw-chuck of Healey would result in a more correct and serviceable arrangement. The disadvantage, for instance, of being obliged to set the T of the rest across the face of the work is apparent at once, and it is difficult to understand how such an arrangement could be made to answer when the work might be of a length to require the support of the back poppet. The following plan, Fig. 96, would obviate this and the other disadvantages, and make a more efficient apparatus. B is the chuck with screw chased on the outside, A the nut travelling upon the same. To this is attached a bar H, which passes through the bar K, to which it is clamped by the binding screw visible at H. Two short pillars, F, F, are screwed into the bed of the lathe, in which there might be more than one hole for each to permit the pillars to be fixed at different distances from the line of centre. Through slots in these passes the square bar of polished iron or steel E, supporting the traversing rest socket, D, of which two other views are given at Figs. 97 and 98. It will be evident on inspecting the drawing that as the nut A travels to and fro, it carries with it in a line parallel to the lathe bed the rest socket and T. To enable the workman to steady the tool, the latter should rest against two short pins fixed in the top surface of the rest in holes made for the purpose; with the aid of these the tool will be made to traverse the work with great ease and regularity. In chasing a right-handed screw, the tool would have to lie on the left side of the pins, and the latter would insure its traversing with the rest. A longer T (or half T) being turned in its socket to stand across the face of the work will enable an inside thread to be cut with the ordinary tool either of one or more points. Of course, in this modification of Healey's chuck, the screw cut will be of the same pitch as that of the chuck itself; but as the latter may be of boxwood, there would be no difficulty in having from three to six with the most generally useful pitches of screws, as the arm may be screwed into the near side of the nut, and, therefore, it, and all the other parts of the apparatus, would answer for the whole set of chucks. If the work to be screwed is merely a box cover, or some such work where great length of screw is not required, it is evident that to rig up this kind of contrivance, or Healey's, or indeed anything of similar elaboration, would appear like summoning a gang of navvies to remove a mole-hill. Hence, if a traversing mandrel cannot be obtained, by far the simplest plan is the chasing tool used by hand; it is therefore well worth while to get into the knack of using this tool. To give confidence (which is essential to success, the least nervousness generally proving fatal to such work) the part on which the screw is to be cut may be left larger than will finally be necessary. The screw is then commenced, and if a failure takes place it is again levelled, but if, as is more probable, the attempt is successful, the chisel and chase are alternately used, the cuts of the latter not being obliterated by the former but always left sufficiently deep to form a guide until the desired object is satisfactorily accomplished. [Illustration: FIG. 96.] [Illustration: FIG. 97.] [Illustration: FIG. 98.] Having treated of screw cutting so far as we are able without trespassing on that section of the present series which is to be devoted to machine work with slide rest and change wheels, we shall enter on the matter of spirals, or Elizabethan twists, the method of making which was long kept a secret by the trade. These twists are essentially screws of very extended pitch, and generally rounded threads. The latter sometimes embrace the central cylinder or core, and sometimes are detached so as to assume a more open form like a corkscrew, and in the latter case two, three, or more threads can be cut, so that the spirals appear to intertwine. These spirals, too, are frequently ornamented with the aid of the eccentric chuck, and thus the work becomes fit for the adornment of the drawing-rooms of the highest in the land. No turned work can in short exceed in beauty these delicate and elaborate specimens of the turner's art. To commence with a single twist of one thread. A cylinder of the requisite length must first be turned. The number of turns the thread or cord of the spiral is to make in a given space must next be determined. We will suppose the cylinder one foot long, exclusive of any mouldings or tenons at the ends, and that the spiral is to make three turns round it, that is, one turn in four inches of its length. Divide the cylinder into three equal parts by the lines B, C, Fig. 99. Next rule equidistant lines D, E, F, along the cylinder in the direction of its length; in the present case let there be _four_ such lines. The three divisions first made must be subdivided each into four (always the number of the longitudinal lines). The angles of the parallelograms thus formed must then be connected diagonally as shown in the figure, which diagonals being continued, will be found to describe a spiral line. A second similarly constructed spiral determines the thickness of the thread or cord of the twist. These spirals may now be cut with a tenon saw, and all the material outside the cord carefully removed with the gouge, so as to form a semicircular hollow between the threads. This cannot be done by putting the treadle and flywheel in motion, but the work itself must be grasped with the left hand, while the right holds the gouge upon the rest and guides its edge. After the work has thus been roughed out, it must be finished by rasps and files, or by a kind of plane with a semicircular cutting edge. While the latter is being used, the flywheel must be brought into action, so that the work may be made to revolve with sufficient rapidity to ensure a clean and smooth cut. A hollow plane may be used to round the cord of the twist, and the whole finished with glass paper and polished. [Illustration FIG. 99.] The "kind of plane" named was designed by a regular workman for his own use, and was made thus and grasped in the fist, or rather hollow of the hand. The iron was like _c_, sharp at one edge, the block of wood being slightly bevelled off in front of the cutting edge. The workman, who made scores of these twisted works for the trade, of all dimensions, would run this along the hollows, while the lathe was in motion, with great speed and accuracy. He marked the spirals as described, and then grasping the work in the left hand, and the gouge in the right, turning the work round with the former (the cord thrown off the wheel), he cut out the wood boldly in large pieces with little apparent care, and perfect ease. Then came the plane described above. Fig. 100 shows a simple spiral thus made. If the piece to be turned is dark it is not easy thus to mark out the divisions. In that case the following method will answer equally well. It is the plan used and contrived by the writer,[6] and specially handy when a number of similar twists are to be cut, as in ornamented pieces of furniture. A, Fig. 101, is a straight edge of hard wood, through which, at any given angle (regulated by the number of turns the cord is desired to make in a given length of cylinder), a knife edge is fixed. If this is held as in the figure, and the blade is pressed down upon the cylinder to be cut, the lathe being put in motion, a very correct spiral will be traced, which can be at once deepened by a tenon saw as before. The thickness of the cord being determined it only remains to place this tool again upon the work so that the second line shall be traced at the required distance from the first. A second, or any number of cords, may be thus traced in succession parallel to each other by this simple method. By a slight modification of this instrument, which allows the knife to be clamped at any desired angle with the straight edge, the inclination of the cords, and, consequently, the pitch of the spiral can be varied at pleasure, and a second blade can be added to trace the second line, determining the thickness of the cord with one movement of the tool along the cylinder. The edge of the knife may be across the rest, the piece of wood just overlapping the T on the side next the workman, if the blade is long enough to reach across the work when thus held. The tool will be steadier and perhaps more easy of management in this position. One hand should then lightly press the back of the knife, while the other retains the wood against the rest as a straight edge. East Norfolk Amateur's design of a screw guide is on the same principle, the only difference being the substitution of a revolving instead of a fixed knife edge. In using either it requires some care to allow the tool free traverse, as the least check would spoil the thread. [6] A similar plan is noticed in Holtzapffel's mechanical manipulation, which the writer had not seen. It is satisfactory to him to find the method thus authorised. [Illustration: FIG. 100.] [Illustration: FIG. 101.] The next class of spirals is that in which no central core exists, but the coils stand separate and distinct, two or more rising from the same base. The coils are sometimes flat, sometimes rounded, and still more frequently, in the best work, exquisitely, and (as a casual spectator would say) _impossibly_ carved. The process is as follows:--Turn a cylinder of ivory or hard wood, forming at the end any required mouldings as a base and capital. Determine the number of coils and the pitch, and by one of the previous methods mark out the same. The cylinder is now to be bored out from end to end, leaving sufficient for the thickness of the required cords. This bore may with advantage be slightly larger at one end than at the other, so that a mandrel of wood may be fitted into it, to be afterwards easily withdrawn. This will certainly be necessary if the ivory cords are to be of light substance, as they require support to enable them to bear the action of the tool. After the cylinder has been bored as above directed, let a mandrel of common wood be inserted, and the lines, marked as shown, be cut quite through. The intermediate parts between the intended threads must then be removed carefully (with a round rasp, if of ivory) with any convenient tool if of wood. The cords must then in a similar way be rounded or otherwise moulded, and afterwards the common and now damaged mandrel removed. In the case of ivory the piece of work will not only be strengthened by the insertion of a polished mandrel of ebony, but its appearance will be improved. Sometimes, however, it may be preferable to line it with red velvet or silk, or it may be left entirely open. The further ornamentation of the cords, depending on the eccentric chuck or eccentric cutters, will not be described in the present paper. These open spirals are worth a vast amount of patience and trouble, which their elegant appearance when finished will amply repay. The reader is not to suppose that this method of cutting spirals by rasp and file is the only or best method, especially when ivory is the substance operated upon. Further on will be described various modes of accomplishing the same ends by self-acting machinery, and by the spiral apparatus designed for use with the ordinary lathe, but all these need the slide rest, whereas it is quite possible in the foregoing manner to make spirals by hand tools alone, which for correctness and finish may vie with those which may have been worked with more elaborate and costly apparatus. Before quitting the subject of plain hand turning in wood, a few more words may be necessary in respect of certain details of lathe manipulation, foremost among which comes Chucking work. This is often carelessly done, especially by amateurs, who, in consequence, are frequently annoyed by the shifting of the material under the influence of the cutting tool. If this is hard and valuable--as are many of the best woods for ornamental turning--the fork or prong chuck will not enter sufficiently to sustain the piece, and at the same time the stuff is too valuable to allow of the waste incurred in screwing it direct to the mandrel, or inserting it sufficiently far into a brass cup chuck. In such cases the best plan is to screw a piece of common wood upon the mandrel, face it truly, and cut a few shallow concentric circles upon the end thus levelled, both for the purpose of a guide to centrality, and also to give a hold to the glue by which the more precious material is to be attached to it. For this purpose, both chuck and work are to be well warmed, and the glue--boiling hot--brushed upon the parts to be united. The latter are then to be rubbed together a few seconds, and when the piece to be turned runs truly, the back poppet with boring flange attached--if the right hand end of the piece is level, otherwise, the point allowed to remain--is to be brought up and screwed as a clamp against it till dry. This process requires time, but is well worth the trouble, as the material will be securely held, and can be safely operated on. None but those who have had to contend personally with a tyro's difficulties, and have, in consequence, seen the work shift in the chuck when nearly completed, can truly appreciate the advantages of efficient chucking. In the case detailed, there is absolutely no waste of material, no possibility of the work becoming loose or out of truth; and the ornamentation by eccentric cutters, drills, and so forth, can be proceeded with, and carried out with that confidence which never fails to promote good workmanship. Even with the above arrangement the back poppet should be used while the excrescences are turned down, and retained as long as the gouge has to be used in bringing the design into an approximation to its intended form. This should be removed, however, before taking the final cut, as the work will generally seem to drop a little when the support is taken away, in consequence of the mandrel, which has been forced against the back centre, returning to its place in the collar. Pieces of six or seven inches in length, and of one or two inches diameter, requiring to be hollowed out, may frequently be turned by reversing the usual method and boring out the interior, previous to shaping the outside. A case for pencils, for instance, or a bodkin case, may be thus worked:--Mount in the square hole chuck, an American screw auger, sets of which are now to be had beautifully finished and polished. The kind meant has a scooping kind of edge above the screw, Fig. 102, and cuts cleanly and rapidly. The piece of wood--soft wood alone is meant--is brought against the tool, being grasped by the left hand, while the back centre, with flange, is steadily advanced with the right hand against the opposite end. This auger will run straight through several inches without requiring to be withdrawn, as the borings pass freely along the polished threads of the instrument and escape. If necessary, however, it can be readily withdrawn by reversing the action of the lathe, and replaced without difficulty. The piece thus bored may then be mounted in the lathe and finished on the outside. To do this satisfactorily, an arrangement is requisite by which the centrality of bore is insured, else in the process of cutting the external surface, the material will, in all probability, be cut through in one part, while in another it will remain of considerable thickness. If the piece is bored quite through, so as to become a tube, Fig. 103 will be satisfactory, as the cones preserve centrality, whilst the use of the carrier will prevent the necessity of screwing the cones up so tightly as to endanger splitting the wood. This is the best way to chuck small cylinders and brass tubes. The more obtuse the angle of the cones the better. [Illustration: FIG. 102.] [Illustration: FIG. 103.] [Illustration: FIG. 104.] In this method the bottom of the case must be turned as a plug and glued into its place. If the bottom of the case is left solid, an arrangement like Fig. 104 will answer well. The plug chuck, A, must not be at all conical, and the part that enters the work must be at least an inch long. If this is attended to, and the face of the work and of the chuck is square, the tube will be truly centred, only requiring the back poppet to take off the strain upon A, when the tool is applied. If A is chalked, there will be no slipping, provided it has been accurately fitted. Observe, nevertheless, that as a general rule, hollow work should be placed _inside_ and not _upon_ a chuck, unless you have to work upon the _whole_ exterior surface. By this plan, there will be no likelihood of splitting the object, an undesirable consummation which not unfrequently takes place when the contrary method is pursued. Thin discs of wood or brass are most conveniently turned upon a face-plate, to which they can be attached by turners' cement, already described. If, however, one surface only has to be worked, and the plate is not of less thickness than 1/8th of an inch, it may be mounted on a flat chuck with small projecting points, the back poppet being used to keep it firmly against the face of the chuck. Even a plate of brass may be thus turned if placed first of all against the chuck and gently tapped so as to mark the position of the points, and then drilled to suit them. Bread-platters are thus easily chucked, first of all _face downwards_, and then reversed with the bottom against the points, so that in the latter position, the chisel or broad may be applied to the face and the marks removed. The larger designs on these platters are carved by hand after their removal from the lathe, and the small figures forming the ground, which often appear round the main design, are made by figured punches. _Chucking Egg Shells_:--The method of doing this so as to enable the turner to cut the shell evenly in two parts, is given by Holtzapffel, in his "Mechanical Manipulation," and has been copied elsewhere. It is ingenious and effective. The object is simply to obtain a pair of delicate vases, to be edged with ivory, and mounted on a pedestal, as a curiosity. The following account is from the pen of the inventor, Mr. G. D. Kittoe, as communicated to Mr. Holtzapffel:--"In the accompanying figure--Fig. 105--is represented the nose of a lathe, with an egg chucked ready for cutting." Fig. 106 is the chuck used first "to prepare the egg, to be mounted in the above way. The latter is generally termed a spring chuck, and is made by rolling stout paper with glue upon a metal or hardwood cylinder, the surface of which has been greased to prevent the paper sticking to it, and upon which it must remain until perfectly dry, when it may be removed and cut or turned in the lathe as occasion may require." [N.B. Nothing is said in the above account of the evident necessity of fixing the paper cylinder to a wooden block, in which a screw must be cut to mount it on the nose of the lathe.] "This sort of chuck is very light--easily made and well adapted for the brittle material it is intended to hold. Before fixing the egg in it, the inner surface should be rubbed with some adhesive substance (common diachylon answers exceedingly well); when this is done the egg should be carefully placed in the chuck, the lathe being slowly kept in motion by one hand whilst with the other the operator must adjust its position until he observes that it runs perfectly true, then, with a sharp pointed tool he must mark the centre and drill a hole sufficiently large for the wire in the chuck, Fig. 105, to pass freely through. When this is done the egg must be reversed, and the same operation repeated on the opposite end, its contents must then be removed by blowing carefully through it. It is now ready for cutting, for which purpose it must be fixed in the chuck, Fig. 105. A is a chuck of box or hard wood having a recess turned in it at _a, b_, into which is fitted a piece of cork as a soft substance for the egg to rest against. B is a small cup of wood with a piece of cork fitted into it serving the same purpose as that in A. A piece of brass, _d_, is to be firmly screwed into the chuck A, and into this a steel wire screwed on the outer end, on which a small brass nut _e_ is fitted to work freely in a recess in the piece B. When the egg is threaded on the wire through the holes previously made in it, this nut is to be gradually tightened up until it presses the cup B against the egg sufficiently to hold it steady and firm enough to resist the action of a finely-pointed graver used to cut it. The tool requires to be held very lightly, as a little undue violence would crush the shell. Neither should the latter be pinched unduly tight in the chuck, as otherwise when the point of the tool divides the shell the two parts might spring together, and be destroyed by the pressure. It requires some delicacy of hand to attach the rings to the edges of the shell to constitute the fitting. The foot and top ornaments are fixed by very fine ivory screws, the heads of which are inserted within the shell." [Illustration: FIG. 105.] [Illustration: FIG. 106.] Box wood is decidedly the best material for ordinary chucks, as it takes a screw almost as well as brass, is pleasant to work, holds the material firmly, and is of good appearance, which last is not unimportant to those who possess good lathes, and like to see everything in decent order about the workshop, and it is certain that a disorderly workman will commonly produce slovenly work. This wood, however, though tolerably plentiful, is sufficiently costly to be worth preserving, and by a little management chucks may be made to answer for a longer period than might be at first supposed. A chuck, for instance, too large to hold the work, may be plugged with a worn-out chuck of smaller bore, or with wood of inferior character, to save the necessity for hollowing out a new piece of box wood. The latter material, moreover, excellent as it is, may be replaced by other kinds of wood, provided the latter will bear a good screw. _Beech_, if dry, will answer very well for the purpose. _Pear_ is tough and screws well. _Apple_ is little inferior. _Ilex_ or _evergreen oak_ is sufficiently hard and tough and will be found quite satisfactory. Elder of large size is good, and screws well. _Sycamore_ screws well, but is not always equally tough. All hollow or cup chucks should be furnished with rings of iron or brass to prevent splitting. About six sizes of rings will suffice for a great number of chucks. Bergeron, speaking of the barrel stave chucks already alluded to, prefers the encircling rings plain and not screwed. He gives the following reason:--"If a piece of work entered in such a chuck does not run quite truly, a tap on the ring in the proper place will, by closing the sawgates more in that part, rectify the error, whereas with a screwed ring this is impossible." There is reason in this, but at the same time it would be easy to unscrew the ring a turn or so, give a light tap to the work, test its position by putting the lathe in motion, and when true fix it securely by screwing up the ring. There is, however, one precaution to be taken in making these useful chucks--namely, to cut the staves of equal width, else they will not yield equally to pressure, and the work will not be so readily centred truly. A grip chuck of inexpensive make (one additional pattern of which is introduced from a design by contributors to the _English Mechanic_) should always be provided. A rough block of ivory for instance may be seized in its jaws, and the exterior useless part cut off by a parting tool as a ring, leaving the nicely rounded material ready for chucking. Ivory nuts or _corosos_ which are peculiarly awkwardly shaped for mounting in the lathe, may also be thus seized, and one portion faced up and rounded so as to allow of being fixed on a face chuck by glue or cement, or fitted into a cup chuck. Rough pieces, too, thus mounted may be faced up, bored and tapped to fit the mandrel as chucks, and a thousand similar works may thus be handled. The simple grip chuck in question is important as having the very useful addition of a centre point which the writer would, if he did not abominate and eschew puns, direct attention to, as the chief "point" of interest--"I call it," says the inventor, a "Universal Self-Centering Grip Chuck." The drawings 1, 2, and 3, almost speak for themselves, to practical turners. [Illustration: FIG.(drawing) 2.] [Illustration: FIG.(drawing) 1.] [Illustration: FIG.(drawing) 3.] 1, is an elevation of one of the grips. 2, a section through centre of chuck. 3, a side section of ditto. The body of the chuck is made of cast iron, to screw on to the mandrel; and the grips, 1, are moved simultaneously by a right and left-handed screw acting in a circular groove. The jaws of the grip are serrated and tempered, the same as in ordinary vices. In the centre of the grips, when closed, a three-sixteenth hole is bored true to the centre of the lathe. Behind this there is a true centre point screwed into the body of the chuck, as marked at _a_. The above hole and this centre point are to be particularly attended to, as on their truism depends the correctness of your work. If I want to turn a solid cylinder I make the usual centre at each end; put one on the above centre point and the other on the back centre of lathe, and then screw up the grips tight; but if the work is short you need not apply the above centre point or the back centre, as the grips are alone sufficient. The hole in the jaws of the grips admit of any kind of drill or other tool being put into them without using any centres, and the grips will admit anything up to two inches. In fact, I do almost every sort of thing with this chuck, and I think amateurs, if not others, will find it a most valuable and handy contrivance. Fig. 108, A and B, represents a modified form--a chuck already spoken of and recommended for ordinary plain turning, in which the work is supported at both ends. The present form is to a great extent self-centering and will hold the work also without the saw-cuts otherwise needed, the sharp edges of the double fork entering the work with the pressure caused by the back centre. The chuck is useful not only for ordinary work, but for re-mounting pieces centrally, which it may have been necessary to remove when partly finished, and to return to the lathe for completion. A still further addition to this chuck of a steel point sliding through the centre, as in the section, Fig. 109, makes it a very complete and serviceable apparatus, as by this means it is easy to reverse the work without destroying its centrality. The point is intended, as in the chuck of Wilcox, to slide back stiffly (being if necessary kept up by a spiral spring as shown), as it is only intended as a guide to assist in mounting the piece. If the mandrel is not bored the chuck must be long enough to receive the pointed wire within its substance. This will be found in every way a most serviceable chuck. It may be of iron or brass, or even of wood, if a round plate of brass is mounted on its face, to which the holding pieces can be soldered or brazed. [Illustration: FIG. 108.] [Illustration: FIG. 109.] HOLLOWING OUT SOFT WOOD. This is done, as already described, by the regular soft wood turners in Tunbridge and elsewhere, by means of hook tools. A great number of workmen, however, use only the gouge, and for boring out chucks, hollowing boxes, small bowls, and similar work, the latter tool will be found effectual if rightly held and carefully managed. It must not, however, be applied to the inner surface of the work at the point usual with scraping tools, but beyond the centre, Fig. 109A. The rest, B, does not require to be turned across the face of the work, but remains parallel to the bed of the lathe. The blade of the gouge is to press against the near side of the hollow as the work proceeds, which considerably aids in securing the position of the tool. The back of the gouge is to face the bottom of the hollow (next the mandrel), but the tool is generally rolled on the rest a little, so that its hollow side is often more or less below, towards the lathe bed, and the point is also lightly raised as it approaches the finish of the cut. Begin with the tool almost horizontal, and at the centre of the piece, the back against the wood, and, depressing the handle as the shaving is removed, finish at the top _outer_ edge of the hollow, rolling over the tool, so that it shall leave the work with its back upwards and hollow downwards. Thus used it will not stick in its course, and, after a few trials, will be found to cut out the wood cleanly and rapidly. [Illustration: FIG. 109A.] Another grip chuck, or self-centering scroll chuck may here be introduced, from the source of information previously alluded to. The writer thus describes it-- AMERICAN SCROLL CHUCK. This chuck is made upon the same principle as the Warwick Drill Chuck--namely, a flat spiral so acting on three jaws sliding in radial grooves as to make them recede from the centre to admit any object between certain sizes, and then to be tightened upon it. Fig. 1 is a plan of a 4-inch chuck. Fig. 2 is a vertical section of the same. Fig. 3 is a view of the outside of the chuck, and Fig. 4 is a separate section of the principal part _a, a_, taken through the line _z, z_ (Fig. 1). In Fig. 2, _a, a_ is this piece, _b, b_, has the spiral cut on it which actuates the jaws 1, 2, 3 (Fig. 1), _c, c_ screws on the piece _a, a_ to keep _b, b_ in its place and _d, d_ is the plate which screws on the mandrel, and which is fixed to _c, c_, by three countersunk screws, one of which is shown in section. [Illustration: FIG. 1.] [Illustration: FIG. 2.] [Illustration: FIG. 3.] [Illustration: FIG. 4.] If the foregoing observations are carefully studied the further practice of plain hand-turning in wood will not be difficult, and we shall proceed to speak of metal turning, before passing to a description of the Slide Rest and other apparatus usually added to the lathe. We may, however, observe here, that, for ivory and hard wood--especially the former, the first roughing down cannot be done with the gouge. A point or small round-ended tool must in these cases take its place, to be succeeded by one or more of those tools which rather scrape than cut, as described in detailing the process of hollowing out boxes and similar work. METAL TURNING BY HAND TOOLS. The first requisite for the above work is a well made and sharp tool, for, strange as it may appear, a keen edge is as necessary for making good work in metal as in turning wood. The principle of this cutting edge must be well understood, and this has been well explained by Nasmyth and others. The remarks of the above eminent mechanic upon this subject, as also those of Professor Willis and Mr. Babbage have been embodied in a very excellent paper by Dodsworth Haydon, Esq., an amateur, and will be found in the Appendix to this work. The whole principle of the formation and application of cutting tools is explained in that paper, so that it only remains to treat briefly of a few special _forms_ of tools which are required for metal-turning in the lathe, whether by hand or by the aid of the slide-rest. In the first place, however, a word or two may be necessary as to the kind or quality of steel required for such tools. What is called Blister steel may be at once passed over as unfit for the formation of tools--it is, however, the raw material (so to speak) from which, by the process of reheating and welding, the next quality, called Shear steel, is made. When bars of this are similarly heated and again welded into a homogeneous mass under the tilt-hammer or between rollers, double shear-steel is made, which is of extensive use for cutting tools, and must, moreover, of necessity be used in almost every case where there is to be an iron shank, for economy's sake, the steel being then welded to the iron, and forming that part of the tool intended for the edge. The third and best kind of all is Cast-steel, formed of blister steel, melted at an intense heat and run into iron moulds. This, however, can be welded only with great difficulty, and hence the whole tool, whatever its length, must be of the same material. This can be purchased in bars of a convenient size of round, triangular, square, or other section, and needs only the careful use of the hammer, file, and grindstone to become a tool of any required pattern. It would be very advantageous to an amateur to master the art of forging in a small way to enable him to make his own tools, for he may sometimes require them of unusual form, and if he lives far from a manufacturing town he will find it very difficult to get them fashioned to his liking. Cast-steel will not allow of the welding heat applied to iron--it will burn, and cannot then be made to recover its proper consistency, and is for ever useless for the purpose in question. Double shear will take a moderate white heat, while cast-steel must not be brought to a higher temperature than that indicated by bright red--a point never to be forgotten when shaping a tool at the forge. There are in every workshop a number of files laid aside as worn out. These being made of the best cast-steel, are invaluable to the turner in metal, as they supply the best material for his tools at no cost whatever. To begin with the saw files (called, by a horrible perversion of mathematical definition, "three square"). Here you possess a tool at once for the mere trouble of grinding off the teeth and reducing the sides to a smooth surface. Each angle is equally useful--each 60°, which, as the paper above alluded to demonstrates, is the best angle for cutting iron. On brass, however, its use is by no means to be recommended, being, as Holtzapffel remarks, "too penetrative and disposed to dig into the work." It is to be used upon iron in the position shown in Fig. 110, where A is the rest, B the cross section of the tool, C the diametrical line. The side, of which D is a continuation, is to form very nearly a tangent to the circumference of the work, being, as explained in the Appendix, only 3° from that position. Worn out square files being of rectangular section, are exactly suited for brass turning, for which metal a cutting edge is required of 80° to 90°, the former for the first or roughing down cut, the latter for finishing. The position of such tool is shown in Fig. 111. [Illustration: FIG. 110.] [Illustration: FIG. 111.] The flat files are not altogether so useful for making turning tools as those alluded to; they are too thin in proportion to their breadth. Their sides, moreover, generally speaking, are not rectilineal, but curved, so that they are more fit for grinding off at the ends to form brass-turning tools with rectangular edges. They may, however, by careful forging, be made to assume a square section, and thence be formed as desired; but a rectangular bar of steel, ready-made, is then to be preferred. A round or rat's tail file is of far greater service than the last-named--not, indeed, in its own shape, for the reasons stated by Mr. Haydon, but as being capable, with very little labour at the forge, of being converted into a bar of square section. The first tool to be made from such a bar is the graver, _the_ tool of the watchmaker, and not less useful to the general mechanician. This is formed by grinding the end of a square bar diagonally, so as to produce a lozenge-shaped face. The angle to be preferred in this operation is 45°, which will give two cutting edges of 60°. The latter may be varied at pleasure by varying the angle at which this face is ground, as explained in the chapter which treats upon this question. The graver will do all kinds of outside work, light or heavy, as it may be made of any size. It is represented in Fig. 112. Fig. 113 is the heel-tool shown in position for work; 114 and 115, two forms of nail-head tool very commonly used, but both requiring great attention to the angles of the cutting edge to become effective. All the above are for outside work, and are to be so held that the side next to the work--the _sole_ of the tool in Fig. 113--forms very nearly a tangent to the work--a position, as Holtzapffel remarks, strangely similar to that required by the soft wood chisel and similar tools. The heel-tool, indeed, if more keenly sharpened, will cut soft wood (on the face) with great rapidity, and is in principle similar to the broads used for that purpose. It is, however, an unsafe tool, owing to its great tendency to dig into the work. It is a good plan to make extensive use of various shapes of hand-tool before passing to the slide-rest, because the hand feels exactly the _resistance_ which the tool meets with, and the best form and position is thus _practically tested_, and will be found to bear out to the utmost the theory advanced in this work, and founded on mathematical truths worked out and applied by Willis, Babbage, and others. [Illustration: FIG. 112.] [Illustration: FIG. 113.] [Illustration: FIG. 114.] [Illustration: FIG. 115.] Inside tools must of course be made upon the same principles as the last, the particular form alone being modified to enable the cutting edges to penetrate into the various nooks and corners that may occur in such work. The inside tool for iron (Fig. 116), with cutting angles of 60°, is of a general and useful pattern. It must be so curved and so placed that _both_ cutting edges come into action, one on the face and one on the side of the cut, a condition explained in the Appendix as _essential_ to all good work. It being quite impossible to cut metal like wood, and necessary to allow sufficient time for such work, a pointed tool is in most cases preferable to one of a semicircular or rectangular form of edge, and the greater part of the heavy work done in large factories is thus executed. Inasmuch, however, as such a tool, well formed on correct principles, may be made to take a tolerably deep cut, the shaving detached will be of sufficient _thickness_, and consequently sufficient width to reduce work a satisfactory quantity at each cut. The cut, too, must be continuous wherever possible, the tool being slowly and steadily advanced the whole of the acquired distance without being removed, and then re-entered for a second cut. The result should be a smooth, even surface, and that great exertion is not required when thus working with hand-tools is sufficiently evidenced by a remark of Mr. Haydon to the writer, "I have often detached, with a graver alone, a tolerably thick shaving of iron, two feet and more in length." From what has been said, it will be understood that in hollowing out a piece of metal such as a chuck, the tool should not be made with a _long_ cutting edge, such as would be used if it were intended to scrape the whole depth of the side. A _broad_ shaving is not to be thus aimed at, nor is the _inside only_ to be thus attacked, but the tool advanced gradually inwards from the face of the work till it reaches the bottom, thus (to repeat the important point again) cutting at the same time the front and side of the shaving. The half-round or cylinder-boring bit already described is, of course, an inside turning tool, but is used with the aid of the back centre. In principle it follows other inside tools, the end being bevelled or sloped off 3°, and the side being 90°. The latter is to be regarded as a blunt cutting tool, being the largest angle that can be used; but, nevertheless, this bit must be regarded as cutting in the two required directions--forward and sideways. If a regular Goniometer for measuring angles is not to be obtained, nor any apparatus for grinding a tool to the required bevel, an addition to Nasmyth's tool-gauge, described in the Appendix, may be made by constructing in tin a set of templates, with the angles marked upon them. The easiest way is to mount on the lathe a few round sheets of tin, and mark the degrees by the division-plate, the outer circle of which contains 360°. The tin may then have pieces cut out, as shown in Fig. 117, to be applied as gauges over the ends of the tool, or _solid_ pieces of the required sections (those which are removed in forming the above) may be retained. It will, perhaps, be as well to finish up both neatly, taking care to mark the angles on each. The degrees most required are, as explained, 90°, 60°, 80°, and 3°; but intermediate numbers may be prepared, and will often be found convenient. An inside tool for brass must retain the angles 80° to 90°, the latter acting as a scraping tool to put a finish to the interior of work roughed out by a tool of the lesser angle. There are not many forms in general vogue, for brass work, whether internal or external. The round, the flat, and the point tools (Figs. 118 to 121) are more or less capable of hollowing out work, as well as surfacing. With the first ground to an angle of 80°, brass chucks can be hollowed, and, with the second at 90°, finished; and if there chance to be any internal angles out of reach by the point-tool, it is only necessary to use a similar one bent round at the end towards the left. Much of the turner's success in brass work depends upon the quality of the metal, which is often very hard and unequal in texture and perhaps blown and honey-combed. It is always the best plan to send patterns of any work of importance to some well-known firm, instead of trusting to a country foundry, whose business, if worthy the name, is generally iron work, and who only run brass once in a way, and make a terrible mess of it, too. The same may be said respecting iron castings. It is worth while, as an experiment, to test with turning tools the quality of a country casting, pulley, or what not, by the side of a similar work really made of malleable iron, such as is now so extensively used by the sewing-machine makers. Tools that will stand the first and make good work deserve a place in the British Museum, with a portrait of the turner! [Illustration: FIG. 116.] [Illustration: FIG. 117.] [Illustration: FIG. 118, 119, 120, 121.] For light brass work, such as small model engines now so generally sold, a description of lathe may be used of which no mention has yet been made--namely, a bar lathe Fig. 122. Such a tool may be made for £3 or £4, and will be found sufficient for such work as specified. [Illustration: FIG. 122.] In place of the double bed a triangular bar of cast iron is used, on which the poppets slide, and are clamped. D shows one of two sockets with feet which hold the ends of the bar, and by which the lathe can be mounted on any stout plank or on the window sill. The pulley A is made for a strap, because this allows of a plain flywheel, which is much cheaper than those which are bevelled and turned. The rest is shown at E and F. The part E slides upon the bar like the poppet--at the top is a dovetailed groove to receive the slide F, which carries the socket for the tee, and is fixed by a turn of the screw seen on the top of it. There is much to be said in favour of triangle bar lathes, they are very stiff, and can be fixed anywhere. The flywheel can be supported on a separate frame, which is an excellent plan, for the jerk of the treadle and crank is not communicated to the poppets and mandrel. In Maudslay's triangle bar lathe, which was made for amateurs, a slide rest was attached, and the whole work was first class--of late they have gone out of fashion, but are nevertheless good tools. Fig. 123 represents another very simple form of lathe for turning small articles of brass. It may be said to be one remove from the watchmaker's bow lathe, as it has no true mandrel or treadle; the small flywheel being attached to an arm at the back and worked by hand. The left hand is used for the latter purpose while the tool is held in the right. Through a tapped hole in the left hand poppet passes a steel pin shown at E, on a larger scale; this screws into the poppet after passing through a brass pulley B; this bolt ends in a point, and an arm fixed into the pulley becomes a dog to act against a carrier screwed on to the work as in turning iron. Thus the mandrel and point are fixtures, and the pulley only turns when motion is communicated to it by a catgut from the flywheel behind it. The back poppet and rest, which last is shown separately, slide on the rectangular bar; the latter is about two inches wide, and three eighths thick, and is made with feet to screw to any convenient support. This lathe is especially adapted for work of small size which can be centred at both ends, and on which a carrier can be fixed to bear against the pin, E, of the pulley; nevertheless it is even possible to use chucks, if cast in metal with a pulley to each like G. A spindle must in this case be made like H, on which the chuck must be slipped, and fixed by the nut in the hollow of the chuck. Although however this form of lathe is sometimes met with, and may be used as a makeshift, a small triangle bar or 3in. lathe of the usual form is far preferable. [Illustration: FIG. 123.] In centering a bar of iron in the lathe too much care cannot be exercised in causing it to run evenly. The ends should be drilled, first with a small, and afterwards with a larger drill, so that a countersunk hole may be obtained in order _to keep the point of the lathe-centre from touching the bottom of the hole_. If this is not done the friction of the work upon its bearing will soon spoil the lathe-centre, and the work itself will speedily get out of truth, and it will not be possible to screw up the spindle of the back poppet so as to correct this. Of course in turning up very small work this drilling cannot be done. A simple hole must then be made, sufficient for the safe support of the work while being turned, but even in this case the angle of the drill point should be less than that of the conical centre of the lathe, the point of which will then run free. To mark the true centres of a round bar of metal a punch has been devised like Fig. 124. This is figured in Bergeron's work, and is very serviceable. To insure its working truly be careful that the bar of metal is filed flat on the ends, and that the surface of the latter is at right angles to the length of the bar. It is then only necessary to place the end of the piece in the conical part of the cup (which will be best effected by fixing the bar in a vice) and by raising the spring and letting it go sudden by a sufficient mark will be made to guide the point of the drill. [Illustration: FIG. 124] The proper place at which to commence turning an iron bar is at one end, the rest being placed so as to bring the tool just upon the line of centres; if applied lower the tool would take too deep a hold, and would either be broken or lift the bar out of the lathe, damaging the centre points. The ends of the bar should be squared up before the circumference is turned, and on no account must a file be used after the turning tool has done its work. It is only at the commencement before a cutting tool has been applied, that an old file may be made use of to take off the scale and roughness left from the forging or casting. Brass may be attacked upon or just below the line of centres, because the form of tool is such as cannot penetrate deeply. This metal is perhaps easier in some respects to turn, but the tool is apt to form undulations on its surface (is apt to chatter). This is due, partly to the impossibility of obtaining continuous shavings, and partly to the vibration of the tool, and when once this has taken place there is a tendency to deepen these channels, which makes it difficult to produce a plane and even surface. If a rectangular tool is used in the position already shown and described under the head of tools for metal turning, this chattering will be avoided. If it takes place, the undulations should be worked off by gentle usage of the angle of the tool, the rest being placed close to the work, and only a light cut taken. With regard to the method of mounting a piece of brass in the lathe, any convenient chuck may be used, but sometimes the piece is short or irregular and requires to be bored out. In this case use solder and firmly attach the piece to a face plate of brass. The easiest way is to smear the two faces to be joined with sal-ammoniac made into a paste with water, and laying a piece of tin-foil between the surfaces, which must be quite clean and bright, apply heat. The tin will melt and a perfect union will be effected. When the piece is finished it is re-heated and detached. This may be considered a wrinkle worth knowing. The flat flanges of brass spoken of under the head of chucks are just suited for this method of working, and they are not damaged by the process, as the solder can be wiped off quite clean when the chuck is made hot. This is a good way to mount small cylinders of brass for model engines, as they can be bored and turned on the outside at one operation with great ease and certainty. If a piece is to be drilled or bored in the lathe, the following is the arrangement to be adopted. Fig. 125, A is the face plate, B, the piece to be drilled, C the drill, which is advanced by screwing up the point, E, of the back centre; D is a hand vice or similar article to prevent the drill from revolving with the work. If it is more convenient to fix the drill itself in a chuck, the point of the back centre is to be removed, and a flange of brass or iron substituted, as A, Fig. 126. If the drill is to penetrate quite through the work a piece of wood must be interposed between the latter and the flange to receive the point of the drill and protect it from injury. The pressure should be so regulated as to be constant and equal without being excessive, or the drill will be bent or broken. Boring is simply drilling on a larger scale, and is of such general use as to require detailed notice. In the first place there are several tools used for the purpose, according to the size of the work. The first is the cylinder bit, Fig. 127. This is a most excellent tool, as it will work very truly, and can hardly get out of place if properly directed at starting. The cutting part A is half a cylinder, the centre being just left visible, the end is not quite at right angles with the length of the tool, but is sloped off a little and bevelled also slightly below.[7] This forms the cutting edge. The other end of the tool has a central hole, drilled to receive the point of the back centre by which it is kept to its work. To use this tool, let the piece to be drilled be placed in a chuck, and a recess turned in it of the same diameter as the cylinder bit, the latter is then placed in this recess B, and when screwed up it cannot possibly rise or shift its position; a hand-vice or spanner is then fixed as shown in Fig. 125, and the lathe put in slow motion, oil or soap and water being freely used to lubricate the tool. Either a solid piece of metal, or a hollow casting can be thus bored. [7] To an angle of 3°. See Appendix. [Illustration: FIG. 125.] [Illustration: FIG. 126.] [Illustration: FIG. 127.] These cylinder bits can be had of all sizes, from one-eighth of an inch upwards. Pipe stems are bored with the smallest of these tools. For this purpose they are made of round steel wire, which is sometimes merely flattened with a hammer at one end to spread and enlarge it, this part being afterwards rounded on the underside with a file, and with the same tool finished on the upper flat face. These slender drills require to be delicately used, and are conveniently held in a pin vice or pair of pin pliers, the handle of which being hollow, allows the greater part of the drill shank to lie within it, a small part only being drawn out at a time for use; thus the drill will be kept from bending, and will work quickly and well. Of recent inventions in the matter of drills, the most important is the Morse American twist drills sold, in sets, at 30s. on a neat stand with a self-centering chuck, complete. The form is that of a cylinder with spiral grooves cut round it of extended pitch. The cutting edge is as difficult to draw as it is to describe, and must be seen to be understood. It is chiefly formed by the meeting of the spiral grooves and the solid end, the latter forming a blunt angular point rendered cutting by the edge of the grooves. They should have a place in every workshop. The next tool to be described is also much used, especially in agricultural implement manufactories, for boring out the brasses, or bearings. It is called a rose bit, or grinder, and is shown in Fig. 128 A and B. In this case also a recess is cut in the work as a guide, and as the tool fills up the whole interior as it proceeds, no change of position can occur. The rose bit is used as shown in 125. A bit of this pattern is very useful for brass work of all kinds, such as the cylinders of small engines, bosses of wheels, bearings and collars, and one of these tools of the exact size for hollowing out the sockets of brass chucks, previously to their being tapped, will be found serviceable. The third kind of boring tool is made with movable cutters, which can be removed at pleasure, to be sharpened or replaced by more convenient ones. The simplest consists of a cutter bar, A, Fig. 129, with a slot in it to hold the tool, which is fixed by driving a wedge at the back of it. The tool here shown has two cutting edges, _b_ and _c_ which should be shaped according to the principles already enunciated respecting hand tools for iron and brass. The cutter bar is usually fixed between the lathe centres, and turned by a driver chuck and carrier, while the cylinder to be bored is clamped to the slide rest, and thereby advanced against the cutting edge. This form is chiefly used upon work that has been cast hollow, or drilled. [Illustration: FIG. 128.] [Illustration: FIG. 129.] Fig. 130 is another form of boring tool for large and heavy work. A boss, A, is fixed to the cutter bar, having a series of dovetailed grooves, or slots, on its surface, in which cutters are fixed by wedges. In this and every similar form, it is expedient always to complete the circle, or, at any rate, two-thirds or three-quarters of it, by driving in blocks of wood in the slots not occupied by the cutters. This preserves the concentricity of the tool. One edge of these movable cutters should be radial to the centre of the bar, or boss, the other rather less than a right angle, which will ensure a good cutting edge. The best lubricant is oil for the first cut, and soap and water, or pure water, for the finishing cut. The surface will thus be left bright. It is not well to finish with emery any collar in which an axle is to work (as the collar in which the mandrel of the lathe runs). This substance imbeds itself in the pores of the metal, and by forming a grinding surface, considerably increases the friction and wear and tear of the parts.[8] Although boring and drilling are capable of being done in the lathe, a far superior plan is to employ an upright boring apparatus, as is now generally used in making steam cylinders. The work is not then suspended between two points, or carried on the slide rest, but takes up a firm bearing on a fixed support, and the boring tool descends by a pressure screw, or self-adjusting contrivance, as the work proceeds. [8] Oilstone powder may be substituted, especially for the best brass work. [Illustration: FIG. 130.] We have spoken of the slow motion as necessary for turning metal work. This is represented in Fig. 131 A B C D. The first is a plan seen from above. The poppet is cast double like F, so as to afford a bearing for the mandrel, and a second for the back spindle seen at A. This back spindle, it will be observed, passes through its two collars or bearings, and can slide freely in them from side to side. This can, however, be prevented by dropping a pin through a hole in the top of the poppet, which falls into a semicircular groove in the spindle. The pulley is securely attached to a small cog wheel, and can be firmly united to a larger one, as seen at A2, and separately at C and D. This pulley and small cog wheel run loosely on the mandrel, and do not revolve with it until clamped to the wheel, C, which is itself keyed to the mandrel. Suppose them to be thus free to revolve, and the wheels in position shown in the plan, A. On putting the fly wheel in motion, the pulley will revolve on the mandrel, carrying with it the small cog wheel, which in turn will act on the large wheel on the back spindle. The small cog wheel on the latter will thus put in motion the large one geared with it, the which being keyed to the mandrel, will put the latter in motion. There are many ways of clamping the pulley to the large cog wheel, perhaps the following is as good as any. It must be so clamped for wood turning when the back spindle is to be slipped on one side out of gear. [Illustration: FIG. 131.] In the face of the pulley, which is concave, is a piece of brass flush with the rim, and which forms a dovetailed groove, into which the head of a clamping screw, E, fits. This screw projects through a slot in the wheel D. When it is required to fix the pulley, this screw is slid up towards the rim till the head rests in the dovetailed projection, and it is clamped in that position by a nut. When it is desired to put the back action into gear, this nut is loosened, the screw-bolt dropped towards the axle (thus freeing the head from the dovetail), and again fixed by the nut. The wheel and pulley are thus independent of each other, the back spindle is slipped sideways into gear, and held by the pin, and the slow motion will be obtained. There is one fault in the arrangement of the back geared lathe that with amateurs in a private house is especially disagreeable, and it is questionable whether in large machinery establishments it might not with great advantage be corrected. In the action of toothed wheels, nuts and screws, and similar gearing, there occurs what is called _back lash_. If, for instance, the tool holder of a slide rest is advanced, and then the action is to be reversed, the movement of the nut and tool holder does not commence simultaneously with the movement of the screw. This is due to the play, or necessary looseness of the working parts, the pressure coming on one side of the thread when the screw is turned in one direction, and on the contrary side when the motion is reversed. In toothed wheels a similar defect exists, and gives rise to that disagreeable and ceaseless noise which assails the ear on entering a building where machinery is in motion. This may be avoided by the use of frictional gearing, a simple but excellent mechanical contrivance which deserves far more extensive notice than it has yet received. It is the invention of a Mr. Robertson, and is patented. A lathe fitted with it would be almost noiseless, and would work with a delicious smoothness, very conducive to the comfort of the workman. This gearing, represented in Fig. 132, is merely the substitution of V shaped or semicircular grooves for cogs, the former running round the periphery of the wheel like the grooves in an ordinary lathe pulley. In this method of gearing, it would be necessary to move the back spindle to-and-fro, the usual horizontal movement not being possible. This is easily effected by a screw or a cam, either of which might be made to act on the frame which carries the back spindle, and which may then work on a centre, as Fig. 133, where A is the poppet, B, the support of the spindle, D, a cam; when the handle of the latter is raised, the standard, B, is allowed to fall back out of gear into the position shown by the dotted line, C. A screw movement would have the advantage of enabling the workman to regulate with greater precision the pressure of the friction pulleys against each other. The drawing shows the grooves of these pulleys larger and deeper than usually made. They are generally rather shallow and numerous, and it is astonishing with what firm hold they grip each other without that violent pressure which it might be imagined would be necessary to prevent slipping when in use. [Illustration: FIG. 132.] [Illustration: FIG. 133.] The ordinary slide rest for hand lathes is made as follows:--That for ornamental turning will have a separate notice. Fig. 134, shows the slide rest viewed from above, and it is evident if the tool is clamped to the holder F on the top plate, it can be advanced from end to end of the top slide B, and also (with the upper frame itself) along the lower frame A, A, these movements being at right angles the one to the other. For parallel work this is sufficient. In this compound rest a third motion is arranged for turning cones or taper plugs like those of stop cocks, taps for screw plates and such like articles. For this purpose the upper frame is cast like Fig. 135, with a flat surface, but with two ribs underneath, uniting the frame to a circular plate with two concentric slots in it. This plate revolves on the plate G G, turning on a central pin, and it can be clamped by the two screws which pass through the slots into the plate in any desired position; once clamped at the required angle a piece of metal can be bored with a conical hole and a plug turned to fit it without possibility of failure. The details of construction allow of considerable variety, and different makers keep to their respective patterns; the main desideratum is strength and solidity, combined with accurate adjustment of the moving parts. The =V='s, underneath the frames, and the edges of the latter, must fit, so as not to be tighter in one place than another, and the upper and lower frames must cross each other accurately at right angles. It is likewise essential that the tool traverse the work in a perfectly horizontal line. Every part must, therefore, be accurately made by means of the lathe and planing machine, and the whole carefully put together. Notwithstanding the above desiderata, a slide rest is not necessarily beyond the skill of the amateur. We have, indeed, seen one thus made quite equal to the work of a professed mechanic, though the file and scraper had to take the place of the planing machine. The rough castings can be bought for about half-a-crown, suitable for a five-inch centre lathe, and it would be much better to try and fit up a set of these castings than to attempt such a substitute as a wooden slide rest. The latter has nevertheless been made, and we remember seeing one of mahogany edged with brass, the work of a cabinet maker, which did good service in turning and ornamenting wood.[9] This, however, was upwards of twenty years ago, since which time the facilities for obtaining slide rests of metal, properly constructed, have materially increased. As the dovetailed edges of the slides wear away by use, it is necessary to provide means for tightening up the =V=-pieces. This is shown in Fig. 136. The holes in the =V=-pieces through which the top screws pass are not round, but oval, so as to admit of lateral movement. [9] In the Paris Exhibition of this year (1867) are some slide-rests made of hardwood and metal. [Illustration: FIG. 134.] [Illustration: FIG. 135.] [Illustration: FIG. 136] Two large headed screws, E E, are tapped into the place on which the =V=-pieces rest, and when these are screwed up, their heads (which are sunk for the purpose in two recesses in the lower plate) press against the =V=-pieces, driving them closer to the dovetailed slide. When thus adjusted the top screws are made use of to fix the strips _c_, _c_. By this method the slides can be adjusted to work with the utmost ease and accuracy, without shake or side play. The edge of the circular plate and the heads of the leading screws are very frequently marked in graduated divisions, so that the advance of the tool or the angle to be made with the work by the tool can be accurately measured and preserved. There should at any rate be a mark on the circular plate to show when the rest is set for parallel work. There are several patterns of tool holder, of which the forms shewn are convenient for light work. The one shown in 138 & 139 on the rest is somewhat different. The plate F, Fig. 134, is cast with a boss and socket, like that of an ordinary rest. In this socket the tool holder fits, and can be not only turned round so as to set the tool at any angle, but also slightly adjusted in height, which is a great advantage. The tool is clamped by a single screw as shown in the sketch. The drawback to this form, and that on the rest, is this single screw, which will indeed hold the tool when the work is easy, but will not always retain it with sufficient firmness when the work is rough, or of tolerable size. In large workshops one usually meets with the holder represented in Fig. 140. A plate, A, with central block B, and slide C, are in one casting. Through A pass eight screws. The tool lies on either side of the central square block and is clamped with three screws, it has thus a fair bearing on two sides, and the screws form a third above, so that accidental shifting of the tool during the progress of the work is hardly possible. The tool holder of Professor Willis, which is described in the Appendix, is perhaps the best of all at present in use. It holds the tool firmly at any desired angle. [Illustration: FIG. 140.] [Illustration: FIG. 138.] [Illustration: FIG. 139.] It is quite possible that the novice who has seen mere boys working with slide rests at manufactories will be disappointed at his own first attempts to use this piece of machinery. All the difficulty lies in the shape and set of the tool. When turning metal with hand-tools it is easy to feel one's way. If the cut is not satisfactory, the hand at once modifies the angle of the tool, and regulates its direction to a nicety, but the slide rest cannot thus adapt itself to its work. It must be set with its slides in position, and the tool once fixed must pursue its own course. Hence it requires a very accurate knowledge of the nature of cutting tools, such as we have given in the Appendix to this work. If the tool is well placed upon the axis of the work for iron, a little below it for brass--it will cut cleanly and easily, without rubbing or jarring, both of which are proofs of either a wrong angle of edge, or a wrong form of tool. The work should proceed with as much apparent ease as if the metal were an apple, and the shaving should curl off like its peel. Moreover, this case is not merely apparent, it is perfectly easy to cut iron, and the strain on the tool, whether held by the hand or by slide rest, is comparatively slight, if the tool is properly made and held. Fig. 141 is quite the best form of tool for surfacing cylinders with the slide rest. It is to be so placed that both edges are made to cut near the point; hence the crank should slightly curve away to the left. It is not possible to cut metal quickly, be content with fine clean shavings curling off freely. You will soon see whether you can take a deeper cut with safety. The tool here sketched is not at all likely to dig in and hitch in the work; if it is not properly placed it will spring and jump, or its side will rub against it, and no cut will be made. To describe the exact position is very difficult, but the principle once grasped, little difficulty should be experienced in making and setting to work any tool, whether for inside or outside work. The _rule of thumb_ was all well enough in olden days and in the infancy of the art of metal working, but it is time to discard it; to master and man it is equally advantageous to do so. Indeed, in some of our leading firms, the old system of follow-my-leader, when the leader was as ignorant of his work as the follower, is waning, and the "how" is now, as it ought to be, coupled with the "reason why." One of the best papers ever written on this subject is to be found in Weale's series, "Mechanism and Construction of Machines," by T. Baker, and "Tools and Machines," by J. Nasmyth, 2s. 6d. The latter part is that specially referred to, and is well worth the whole price of the work. The remarks, however, of that eminent mechanic are embodied in the paper in the Appendix, and therefore, after the reader has studied the latter, he should make trial for himself of the principles laid down. Expend a quarter or a half an hour experimenting thus, with keen and obtuse tools, held at divers angles, and you will see and understand what is meant by setting a slide rest, or hand tool to cut metal as it ought to do. [Illustration: Fig. 141 is too much cranked; half the length of the hanging part would amply suffice.] Supposing the tool fixed in the tool holder in the position indicated, and just overlapping the circumference at one end (the right). Take hold of the handles, one in each hand, and with that which advances the tool from end to end of the bar try very carefully whether the tool will cut cleanly by making a turn or two while the lathe is in slow motion. If the tool bites too deeply, turn the other handle and ease it. If you still find the tool sticking into or scraping the work, instead of bringing off a fine shaving, look well to its position, and observe whether the edge is well placed on the axis of the piece. If it has been hitching in the work it is probably too low, if rubbing it, too high, and touches at some point below its edge. It is presupposed, of course, that the tool is made correctly as to angle of cutting edge. Do not lower the point by packing the end of the shank; _pack the whole length_ or none. It is astonishing what a great difference is made to the cutting power of a tool by slight adjustments of this kind, and how smoothly a tool will work with proper attention to these details, which would otherwise be probably cast aside as unfit for the work. Hence the greater ease in managing a hand-tool. The hand _feels_ the error, and at once, if experienced, corrects it by an almost imperceptible movement--slightly raising or depressing the handle or gently varying the angle sideways on the rest. When once the tool is found to cut as it ought to do, nothing remains but to turn the handle in the right hand, and thus cause the tool to progress steadily along the work from end to end. Then free it by a half turn of the other handle, reverse the movement until the tool has arrived at its old place, and having slightly advanced it to take a fresh bite, repeat the process until the whole bar is reduced to the required size. If the piece is slender and bends away from the tool, add to the slide rest a support; let it be fixed opposite to the tool, and it will keep the work steadily up against the cutting edge. It can be fixed (if a hole is made for the purpose) anywhere about the slide which traverses in the direction of the length of the work. It is well to drill and tap a few holes about the slide rest, and some along the side of the bed of the lathe. These will be found very useful at various times for fixing apparatus. For, be it observed, (and we shall recur to this with some practical hints by and by) the lathe may and ought to do many kinds of work beyond ordinary turning. It may become a machine for planing, slotting, drilling, wheel cutting, &c., and is to be pressed into the service of the jack-of-all-trades, without compunction. When ordering a slide rest let steel screws and nuts be specified, and gun metal V-pieces, and let the parts be strongly made (too strong for the supposed work); for the latter may unexpectedly turn out to be sometimes rather heavy. We have found the top plate of a 3in. slide-rest so weak that when the tool was clamped on the top of it, by the screw of the tool holder, the slide itself became jammed; a defect quite beyond remedy, except by the substitution of a new and stiffer plate. The same advice may be given respecting the tools. Let these also be strong; neat and pretty tools are all very well, but you seldom see them in a workshop; you don't require pretty tools, but good and serviceable ones. Nevertheless, let the material be of the best quality possible; and that you may not be ever at a loss, you should learn to make tools yourself. Procure some small square and round steel bars; save up as directed your old files, and you need but heat them red hot (not on any account white hot), and with hammer and file shape them to your mind. Then temper to a deep straw colour, and after being accurately ground and finished on the stone, they will be fit to use upon any metal. The form of tool given as the best for slide rest work may be exchanged, when the bar is nearly turned, to the required size, for a fresh one, keen, sharp, and of an almost flat edge instead of point. A tool, of which the edge is a segment of a very large circle, will serve the best as a finishing tool, just to take off the lines left by the pointed tool. With regard to lubricating the work, we may observe that the chief object is to prevent the point or edge of the tool from heating and losing temper; oil, water, or soap and water will therefore answer, but it is a curious fact that oil will not produce so polished a surface as water will. We should advise in all cases soap and water. Soft soap is best, boiled in water, and allowed to cool. The drills with which the huge armour plates of ships six inches thick are drilled are thus lubricated, and instead of throwing out dust in a wet state as usual, these large drills fairly turn out curled shavings similar to those produced by the planing tool. It is by no means a bad plan to lay the shank of the tool which falls upon the top plate of the rest, upon a piece of leather, wood, or sheet lead. The surface of the iron, when planed and finished, is often too smooth, and the tool will sometimes slip from this cause, unless screwed unduly tight, to the detriment of the rest. By the above plan this annoyance will cease at once. We will now say a word about hollowed work. Finishing a chuck will serve our purpose, and here be it advised not to go to much expense about chucks--get those which must be of brass in the rough, and practice metal turning by finishing them yourself. If no slide rest is available do it by hand. However, we are supposing the slide rest to have been procured, and may therefore proceed to use it. First you must drill the back part of your chuck as directed in a previous chapter. The drill is to be the size of the diameter of the hollows in the mandrel screw, that is, smaller by the depth of a thread, than the full size of the nose. Having drilled it, proceed with the most tapering of your taps, which we suppose to be provided to form the internal thread (external if your mandrel has female screw, in which case, instead of a drilled hole, the chuck will have a projection to be turned truly cylindrical, and a screw cut outside with stock and dies or chasing tool). Follow up with the intermediate and finish with the plug tap. If you were careful to square up the shoulder, the drill having been likewise placed perpendicularly to the face of the chuck, the latter will fit truly up to the collar or shoulder on the mandrel. If not, you must go to work again, and square up the back of the chuck till a good fit is produced. Now, if you have a compound slide rest--that is, one in which the slides turn on a centre pin--you can loosen the screws and turn it a quarter of a circle. If not, you simply put the tool into the holder, at right angles to its former position, so that the movement of that slide which is parallel to the lathe bed will become that requisite to advance the tool into the hollow of the chuck. Whichever way you set to work put in a side tool, like Fig. 142, and, as it is a brass chuck, remember that the bevel underneath is to be very slight. Introduce the tool so as to take a light cut at first, until the roughness is taken off, after which you may cause it to bite more freely. Repeat this until the chuck is sufficiently hollowed out, when you may substitute a similar shaped tool, but with a flat or slightly rounded edge, to take off the marks left by the point tool. To finish the bottom of the inside you will require a tool which cuts on the end, but it should not have a perfectly flat end--at any rate, not until, by means of a pointed or small round-ended tool, you have cut away the roughness left from the process of casting. This has always in its interstices a number of grains of sand fused, and very hard and detrimental to cutting edges of all kinds. The point tools dig these out very effectually, and should always precede those of other forms. [Illustration: FIG. 142.] The outside must be turned in a similar manner, and a hole drilled to receive a pointed bar or wrench, for the purpose of unscrewing it when screwed up tightly. To turn up a face plate of iron or brass proceed in a similar way, but commence from the centre with a point tool. This tool is the best for taking off the rough outside of hard wood, instead of the gouge, as well as for removing the roughness of a fresh casting. It is absolutely necessary that the faces of these flat chucks, or surface chucks, be truly at right angles with the mandrel; hence it is very difficult to turn and finish them by hand. We may here also state the necessity of knowing when the slides of the rest are at right angles to each other, without which no work can be turned correctly. It is necessary to ascertain this by help of a small steel square. Once fixed truly, it is only necessary to make a mark on the quadrant (which should be marked in true degrees), by which the same position can be found again at any time. We have spoken here of the quadrant--we mean the arc, or arcs with slot--allowing the circular movement of the compound slide rest. The chief use of these is to enable the workman to turn true cones instead of cylinders, which latter will only be produced when one slide is parallel to the lathe bed. Such is the common use of the slide rest; and it will be evident from these few remarks that there is an infinity of work, not only produced with ease by its aid, but which cannot, even with expenditure of time and labour, be produced without it; hence we advise this to be the chief ambition of the tyro after he has mastered the difficulties of ordinary hand turning (and not before). The cost of a fair one for 5-in. lathe will be £5, or thereabout. At Munro's, £7 or £8; at Holtzapffel's, £10 or £12. Both the latter are of course perfect. We have directed to tap the chuck where it is to be screwed to the mandrel with a set of three taps, or to cut it with stock and dies if an outside thread is required. In both cases more true and satisfactory work may be produced by the chasing tool. We speak of the latter as used by hand; an account of cutting the threads by help of the slide rest we reserve for the present. Mount the work in any convenient way, either driving it into a wooden chuck, or by clamping it to the face plate if you have one. Now in this way you have advantages. In the first place you need not have a drill the exact size, though it is convenient to have such a one, and also a cylinder bit. You can drill and enlarge the hole by the slide rest tools, and you can also with the slide rest ensure the perpendicular position of the hole with respect to the end. Thus it is sure to fit up close and snug to the shoulder of the mandrel. When bored thus it will be in position for chasing. It is not difficult to chase a thread in brass, as it does not chip away like wood, but cuts clean and sharp. Follow the directions already given and you will succeed in a few turns in getting the tool to run. Then let it have its own way; hold it lightly, but steadily, and do not force it either to cut too deeply, or to advance too quickly; it will run along of itself after the faintest thread is cut or scratched, and the lathe can be worked by means of the treadle all the time as soon as you have attained the knack of dropping the chaser into its place at the commencement of its cut, and suddenly withdrawing it when it has reached the bottom of the hole. A chuck thus turned and screwed entirely in the lathe is sure to prove a good fit, and there can be no better practice than to cut screws in all your brass and boxwood chucks in this way. A very good chuck to hold flat plates of brass was invented by a Mr. Wilcox, of Bishop's Stortford, some years ago--an amateur of rare ingenuity and mechanical knowledge, and who made all his own apparatus for plain and eccentric turning. The chuck, Fig. 143, as described by him in some unpublished manuscript, is made of boxwood, or may be of metal. It is a plain disc or surface chuck with three slots A B C. and a steel centre. This last must penetrate rather deeply into the wood of the chuck, but is only kept up so as to project from the surface by a spiral spring below it. Hence, when pressure is made upon its point by the application of the object to be turned, the pin recedes into the body of the chuck, suffering the work to lie flat on its surface. In the three slots are three screws, with nuts at the back of the chuck the screws pass through two pieces of brass, forming a pair of jaws, one of which is shown separately. [Illustration: FIG: 143.] Fig. 143 shows the chuck complete. Suppose we have to face up a round disc in its central part, or to perform any surface work in which the jaws will not be in the way of the tool, the centre of the plate is marked at the back of it, and this mark laid on the central pin. The work can be clamped down by the three jaws, and the necessary work may be done. Now so far the chuck is but a simple affair, and the receding pin does not show itself to such great advantage; we will therefore suppose a plate is to be drilled at several spots; let these be marked at the back by a centre punch. It is now only necessary to bring these marks in turn upon the central point, and clamp the plate in position. Bring the point of the drill against the work and keep it up to cut by the back poppet screw. In the same way eccentric work or any operation may be done to such a plate, with the certainty that the point to be thus worked upon is precisely central with the axis of the pulley, or mandrel. Many similar applications of this chuck will present themselves to the reader upon due consideration. We present the chuck in this place because we have had occasion to speak of drilling as connected with the slide rest, and there are many pieces of work that could not otherwise be conveniently held in the desired position.[10] [10] The MS. book containing the above was kindly lent to the author of the present work by Mr. Hoblyn, of Bishop's Stortford, who is the inventor of a new form of slide rest, which will be introduced in a later page. The chuck in question is, however, commonly attached to the watchmakers' lathes of the present day, and therefore may not, as the writer supposed, be actually the invention of the late Mr. Wilcox. OVERHEAD APPARATUS. It now becomes necessary to speak of another addition to the lathe, by means of which the use of the slide rest is considerably extended. We mean the overhead motion. Of this there are several patterns, and we have sketched three of these. As to their respective merits we can hardly venture to speak. They all answer equally well the purpose for which they have been designed, and the turner must select according to his fancy, or, if he please, design a better for himself. A, Fig. 144, represents the lathe bed. From the left-hand standard rises a round iron rod, not less than one inch in diameter. This is not generally fixed, but is attached to the standard by two staples, _a, b_, which hold it securely in an upright position, but allow it to turn with its projecting bar F, F, after the manner of a crane. It may thus be turned back, out of the way, or brought into any desired position. The part F, F is made to slide up and down on the part B, and is fixed by a clamping screw D. Thus, if the cord should break and require to be shortened, the arm can be brought nearer to the bed of the lathe. Upon F, F slide two rings, or rather short pieces of tube, from which depend two India rubber springs (door springs), E, E, now procurable at any ironmonger's at one shilling each. From these hang double pulleys, or better still two single ones. These pulleys, with their attachments, are adjustable at any position on the arm F, F, which may be round or square. If considered desirable, a second standard can be added, so as to uphold both ends of this bar; but it is hardly necessary, as the latter is seldom required of greater length than half that of this lathe-bed. It is evident that the above addition to the lathe can be made complete for a few shillings. The following are more expensive, but more general, the writer having devised the above to suit his own fancy, and for his own use. In Fig. 145 A represents the standard as before, the top of which is forked, as shown at E, and sustains the ring, free to revolve in its arms, as seen in the sketch. Through this passes a bar, B, B, with a heavy ball C cast on its end to act as a counterbalance to the longer arm and its connections, and to keep the cord stretched. By sliding this bar either way through the ring which supports it, the tension of the cord can be increased or lessened.[11] When in position it must be very securely fixed by the screw T, which should not simply press against it, but enter one of a row of depressions made for the purpose. The pulleys C, D are double, as in the previous plan of overhead, and are likewise adjustable at any position on the bar B, B. The only drawback to this pattern is the danger of the heavy ball slipping out and falling. We prefer to hang a weight from the end of the lever, as shown by the dotted line. This may be within a few inches of the floor, and if it should fall no harm can ensue. The third pattern, Fig. 146, is the most expensive, but although it is of a more finished appearance, and wears an aspect more stiff and stable, it is not practically any better than the last. From a standard A, with overhanging bar F, F, is suspended a frame H, by means of two coiled springs in brass boxes B, B, which keeps up the necessary tension on the cord, or rather cords, for in this case two are needed--one from the flywheel to the small pulley, and a second from the roller to the slide rest. [11] Sometimes the bar is merely hung on pivots, and the weight is made to slide upon it. [Illustration: FIG. 144.] [Illustration: FIG. 145.] [Illustration: FIG. 146.] [Illustration: FIG. 145.] [Illustration: FIG. 143] This roller, which may be grooved or plain, may be replaced by a second small pulley, which is capable of being slid along the round bar which forms its axle and turns with it between the centre screws. In this case the bar is made with a groove or channel along its length, Fig. 147, and a pin projecting from the central hole in the pulley enters this groove. Thus the two will turn together, and at the same time the position of the pulley is adjustable at pleasure. The tension of the springs B, B, is increased or lessened by a turn or two of the nuts C, C, just in the same manner as the spring of the safety valve is adjusted on the boiler of a locomotive.[12] The application of the overhead motion is plainly shown in Figs. 143 and 144. The work is fixed in the lathe, and the mandrel kept stationary. The cord passes to the overhead directly from the fly wheel, and thence to a pulley on the screw of the slide rest, as in 143, to a drill, as in 144, or to any other apparatus at pleasure. To fit the work in the lathe in such a manner as to enable any point in the face or side to be operated upon, a division plate and index are required. The first is a round plate of brass or gun metal, 1-16th of an inch thick, drilled with holes in concentric circles. The index is a steel spring with a projecting point, which, entering any one of the holes, retains the plate, and with it the pulley, on the face of which it is fixed immovable. There are generally four circles of holes, the number in each selected with reference to its divisibility by the greatest possible number of divisions--thus 360, which is usually on the outside or largest circle, can be divided without a remainder by 2, 3, 4, 5, 6, 8, or 9--144 is a good number for the second circle, being divisible by 2, 3, 4, 6, 8, 9. The other two may be 112 and 96. The uses of the division plate are many. Eccentric cutting and drilling could not be done without its aid, and wheel cutting for clocks, or for making cycloidal and other chucks, is entirely dependent on this contrivance. [12] The frontispiece shows another superior form of overhead, with balance-weights hanging close to the ground behind the lathe. [Illustration: FIG. 147.] The division plate and index are shown in Figs. 147, A, B, C. The part B is a knob with a round hole through it, to take the tail of the spring C. This is shown again at C on a larger scale, to bring to view a slot which allows of some slight adjustment of the point, to suit the different-sized circles. The milled-headed screw clamps the point at any desired part of this slot. When not in use, the spring is drawn back so as to release it from the division plate, and turned down in the position shown by the dotted line. The overhead apparatus is applicable not only to revolving cutters in the slide rest, but to other contrivances available where the latter is not possessed. There are many cases in which the back poppet may be brought into use to hold revolving drills, or stationary tools, if the resistance to their action is not too great. The only damage that can well happen in this method is to the pin working in the slot on the outside of the spindle. If this is of steel and tolerably stout and strong (being very short it cannot be subject to any very injurious strain), no harm is likely to result. With this it is possible to drill very neatly, and also to do a little eccentric cutter work, under certain conditions to be described. Screwing, or rather chasing, may likewise be done very passably. We do not, of course, advise this course when the more perfect slide rest is at hand, but there are many who are obliged to put up with all sorts of homemade contrivances, and to press into service for divers operations apparatus and tools not precisely meant to be thus used, and it is as well to learn how to act under an emergency, even if the practice is not intended to be carried out generally. The drill stock is shown in Fig. 148, in which the screw A fits into the spindle of the back poppet. If the hole in the latter is conical instead of cut with a screw thread, the drill must be made accordingly. [Illustration: FIG. 148.] The pulley of brass has a hole drilled through it, and the screw is also drilled, the hole in the latter being rather larger than that in the pulley (which is tapped). The steel pin H, shown white in the sectional drawing, passes truly through the centre of the screw in which it revolves, and is screwed into the pulley. The socket of steel to hold the drill is then screwed or soldered into the opposite face of the pulley. The black part shows a flange on the screw which abuts against the cylinder of the poppet into which it is screwed. Thus the pulley, being attached to the cord from the overhead apparatus, is free to revolve upon the steel pin with great rapidity, and will carry round any drills or cutters placed in the socket B. The simple straight drill being thus worked and advanced by the leading screw of the poppet, will suffice for holes in any work held on the mandrel. On page 335, vol. ii., of the _English Mechanic_, this method is mentioned, and also a similar pattern of slide tool to be used for boring, being, in fact, the head and spindle of the back poppet, but instead of the standard and sole, a pin, like that of a =T=, to fit the socket of the rest. This has the advantage of the back poppet, but must be made on purpose, and if any special slide tool is added, a proper slide rest is by far the best. Our present purpose is to describe the use of the back poppet as a substitute for a better tool. With the following modification of the eccentric cutter, a fair amount of good ornamental work may be done. Fig. 149 represents the back poppet with the apparatus in position. The various parts are shown separately in A, B, C, D. A is a small frame, two or three inches long, and 3/4 to 1 inch wide, cast in iron, with a circular piece at the back, 1-1/2 or 2 inches diameter. This circular piece is to be accurately divided on the edge with any even number, which is divisible as above explained. This is turned and drilled through the centre. B is a flange-shaped piece to screw to the poppet as before, and this is also accurately drilled, and the two are attached by a central steel pin, so that the two flanges can turn face to face, the outer one with frame revolving against the other. The pin must be put in its place in B, and turned at the same time as the face of B, that it may be truly central. The divisions on the edge of the outer flange are to be drilled like the division plate of the lathe, or cut into cogs, and in either case can be held at any point by a spring detent or index attached. C shows the front of the frame, with a screw down its centre and traversing slide _f_. The head of this screw is divided, and a small brass index marks its position; one side of the frame may likewise be divided. The small brass pulley and drill socket are fixed to revolve in the traversing nut or slide _f_, as shown in a side view at D. Drills of all shapes, as E 1, 2, 3, 4, may be fixed in the socket at pleasure. [Illustration: E] [Illustration: FIG. 149.] [Illustration: Fig. 150.] [Illustration: Fig. 151.] [Illustration: Fig. 152.] [Illustration: Fig. 153.] It is evident that the cutter frame last described having a division plate of its own dispenses with the necessity of one on the pulley of the mandrel. Indeed it was the impossibility of supplying the latter on the face of the cogwheel of the author's back-geared lathe that necessitated the substitution of that alluded to. The latter may consequently be omitted if applied to a lathe already fitted with division plate and index. With crank-form drills the cutting edges of which may be as E 1, 2, 3, 4, or other form, such patterns can be cut, as shown in Figs. 149, 150, 151, 152, which are merely samples of the simplest combinations of circles intersecting in straight, spiral, or other lines. Although not now treating of eccentric work, we may state in passing that to produce the pattern round the edge of 150 the division plate of the instrument only is required. Select a crank-form drill which by its revolution will produce the required size of circle. Turn the divided screw head until you find upon trial that the circle will come at the required distance from the edge, and putting the lathe in motion cut the first circle. The work on the mandrel is understood to be stationary, the mandrel being fixed so as not to turn. The cutter frame is now turned on its axis, one, two, or more of its divisions, and fixed by its detent, and a second circle cut intersecting the first. This is repeated till the whole circle is completed. The straight line of circles in Fig. 151 is cut as follows:--The first circle is made as before, but the cutter-frame should be placed so as to stand either horizontally or vertically. Between each cut the divided screw-head is moved so many points according to the proposed fineness of the pattern, and no movement of the cutter frame on its axis is to be made. The spiral, 152, is simply the result of a combination of the two movements. Start from the centre by turning the screw head until the shank of the crank-form drill is coincident with the axis of the mandrel. Cut the central circle. Thence for each successive circle turn the screw head and the frame an equal number of points, and the pattern will be formed. If the divided screw head is made to take off and a handle substituted, stars formed of channelled lines, or radial flutes can be made as Fig 153, but in this case the crank form drill is replaced by a plain straight tool with a rounded end like 149 E 4. Set the tool as for pattern 150 straight across the face of the work, put the drill in rapid motion, let it be advanced by the leading screw of the poppet so as to penetrate slightly, and with the handle that has been attached to the screw of the cutter frame cause it to traverse the face of the work as it revolves. When one flute is thus cut, turn the frame on its axis as many points as required, and proceed with number two, and so on to the completion of the star. It is not necessary at present to describe other patterns. Fig. 153 is therefore merely given without special details of the method of producing it. We must now return from this digression to speak of other applications of the slide rest. It is evident that when connection is made between the overhead and a pulley on the screw of the slide rest, the latter becomes self-acting. The speed is, however, far too great, and in addition, the mandrel is stationary. The above connection, therefore, is not practically possible, and the overhead is only connected with the pulleys of revolving drills and cutters fixed in the tool-holders of the rest. It is, however, very important to be able to form some such connection between the lathe mandrel and the screw of the rest, for the purpose of cutting screws or spirals. A little consideration will show the principle of this arrangement, from which some practical plan is not difficult to design. If, for instance, the tool simply remains in contact with a cylinder while the latter revolves with the mandrel, a simple line will be cut round its circumference; but if, while the mandrel revolves once, motion is given to the screw of the rest by which the tool is made to traverse a distance of one-eighth of an inch, the commencement of a spiral having that pitch will be made. A perfectly smooth surface, as it leaves the lathe, in which a slide rest has been used with a point tool, is in reality cut with a very fine screw thread readily discernable under the microscope. We have, therefore, only to devise some method of giving regular motion to the screw of the rest while the work revolves as usual, in order to turn plain surfaces, screws, or spirals. For the purpose of plain turning a plan is sketched by Nasmyth in the last chapter of "Baker's Mechanics," in Weale's series. A spur wheel is represented fixed to the slide rest screw, the teeth of which are alternately caught at every turn of the work, by an arm fixed to the latter, after the manner of a lathe carrier. This plan is simple, and might be to some extent used, but for one defect, due to the fact that the slides of ordinary rests are the reverse of what is required to make this plan available. The screw which advances the tool towards the work is generally underneath that which moves the tool along the surface of the work. The result is that, when the tool-holder is advanced to take the deeper cut the spur wheel is brought nearer to the arm which acts upon it, and greater traverse is thus given to the screw. This is shown in Fig. 154. A is the spur wheel, B the cylinder to be turned, C the arm or carrier. The arrow shows the direction of the movement. Now, if the lathe is put in motion, the arm will remain in contact with one tooth of the wheel until both arrive at _b_, giving a certain amount of motion to the screw, and thence to the tool-holder. After one cut is thus taken, the lower screw of the rest is turned to advance the tool nearer to the work, the effect of which is to cause the arm to extend further over the wheel. Suppose its position represented by the dotted line, it will remain in contact with the tooth till both arrive at _c_, having thus traversed a larger arc, and given more movement to the tool. Now if the frames of the slide rest were made to cross in the contrary direction so that the screw to advance the tool towards the work was above that which gave the traverse in the direction of the bed, this objection would no longer hold, and the above gearing would answer very well, since the necessary advance of the tool would not affect the relative position of the spur-wheel and carrier. In Fig. 5 of the same book, in which the gearing is effected by two cogwheels, this alteration in the rest appears in the drawing. In this case the work and rest are connected for screw cutting, and the arrangement is satisfactory and simple, and for the amateur especially is the simplest and best that can be devised. The range of screw pitches is however limited, and the rest must have a left-handed screw, or the result will be a left-hand thread to that which is cut. Hence another device has been arranged, represented in Fig. 155, A, B, C. A shows the apparatus complete. B is an arm of iron or brass which is about 1/4 inch thick or rather more. This is first slipped over the mandrel screw in front of the poppet and fixed in any desired position by a screw passing through the slot _a_, into the face of the poppet. This slot allows the arm to be raised or lowered at pleasure and adjusted, as will be presently described. In the slot formed in the long arm B, pins D with nuts, fit, on the rounded part of which cogwheels, _b_, _c_, _d_, are made to revolve and to gear with each other, and with a similar wheel attached to the back of the chuck, C. The centre of the outside wheel, whether one, two, or three are used, is connected to the screw of the slide-rest. For the production of a right-handed screw, the intermediate wheel comes into play, simply to reverse the direction of the motion imparted to the screw of the slide rest. The number of teeth which it may contain is of no importance, the calculation of the change wheel teeth being only necessary with the first and last. The central one is called an idle wheel, though its work is equal to that of the rest. Thus, suppose the wheel on the chuck to contain 40 teeth, and the third wheel 20, while the former revolves once, the third will, if in immediate contact with it, revolve twice, introduce an idle wheel with 10 teeth between these two. The wheel, with 40 teeth, revolving once, the idle wheel will revolve 4 times--the third wheel twice, just as if the idle wheel was not in use. In any train of wheels, if we regard relative speed, any number between the first and last become similarly idle wheels, and the ultimate result is the same as if the first and last were in immediate contact. [Illustration: FIG. 154.] [Illustration: FIG. 155.] Take, for example, the following train of five wheels, even numbers being given for the sake of clearness, to represent the circumferences or number of cogs in each, Fig. 156. We have here, as the first and last, 6 in. and 120 in., and, if in contact, the first must revolve 20 times, while the latter revolves once. Interpose the three idle wheels of 10, 30, and 60 in. respectively. During one revolution of the largest wheel, the second will revolve twice, the third four times, the fourth twelve times, the fifth twenty times, the same precisely as if the first and last had been in immediate contact. The range of a slide rest-screw is quite long enough for many purposes of the amateur, and a connection thus made between the mandrel and such screw is what may be termed a miniature of the arrangement adopted in the large self-acting lathes. In the latter, however, a leading screw is added the full length of the bed along which the slide rest travels bodily. We may, therefore, consider the screw of the slide-rest a leading screw, and make use of the rules applied in the case of large lathes to decide the proportions of wheels required to cut a given screw. It is plain that when the pitch of the required screw is greater than that of the leading screw, the revolution of the latter must be at a quicker rate than the former. If, for instance, a spiral is to be cut, like the Elizabethan twist, containing but one perfect thread in two inches, while the leading screw contains twenty threads in the inch, or forty in the 2 in., the latter must be arranged to make forty revolutions while the former makes one, because it takes 40 revolutions to carry the tool along 2 in., which is the pitch of the required spiral. The two outside wheels must therefore bear that proportion to one another. Forty to one, however, would be a practically difficult ratio, to place as described, even a pinion of ten teeth on the leading screw requiring 400 teeth on the chuck. Hence a different arrangement would be necessary if such very great difference exist between the pitch of the leading or rest screw and that to be cut. The same obvious difficulty would occur where a very fine screw is required, and the pitch of the leading screw is coarse. This will have to be referred to again. One example, therefore, of the method of overcoming this difficulty will suffice. A train of wheels is shown in Fig. 157, of which A has 60 teeth, B 10 teeth, C, _on the same axle and united to_ C, 30 teeth, D 20 teeth. While A turns once, B will turn six times, C necessarily six times also, D nine times. In this case, if the first and last had geared together D would have made but three turns, while A made one. [Illustration: FIG. 156.] [Illustration: FIG. 157.] The following is an easy method of calculating a series of such change wheels:-- Write down the number of threads in the screw to be cut, and also the number of threads in the leading screw; multiply both by any convenient number likely to give such results as to tally with the cogs in the set of change wheels. Suppose it is desired to cut eight threads to the inch, and that the leading screw has two threads in that length. Then: 8 80 8 120 8 160 - × 10 -- or - × 15 --- or - × 20 = --- &c. 2 20 2 30 2 40 If you have either couple of these wheels, you can put one on the leading screw, and another on the mandrel, and fill up the intermediate space with dummies. If the above is inconvenient, or the wheels are not to hand exactly as required, proceed thus. If you have the wheel for the mandrel, and the one you wish to use for the leading screw has only half the proper amount of teeth, it is evident that the leading screw would revolve twice as fast as required, for they are proportioned as two to one--or if I have the proper wheel for the leading screw, and the wheel I wish to use for the mandrel has twice the proper number of teeth, it amounts to the same thing. You can get over the difficulty by using any two wheels which are in the proportion of two to one (say 20 and 40, 30 and 60, 40 and 80, &c.), and coupling the two firmly together, so that the larger wheel of the two works into the mandrel wheel (or dummy working into the mandrel wheel) and the smallest into the screw wheel (or its dummy); if the speed is wrong in the contrary way, so that the case is reversed, the coupled wheels are made to gear in a reversed direction; and whatever may be the amount of error, whether such as to cause either mandrel or screw to revolve 1/8, 1/4, or 3/4 too slow or too fast, the same arrangement may be pursued, the coupled wheels bearing that proportion to each other. The above method was communicated to the _English Mechanic_ by a working man, James Connor, and is perhaps as easy as any; but tables are published of change wheels for any pitch, with any thread of leading screw. Where it is not possible or inconvenient to apply the above arrangement, and where only a few pitches are likely to be needed, another method can be arranged by connecting the lathe pulley to the overhead motion and thence to the screw of the rest. Such an arrangement is shown in Fig. 158. A is the fly wheel, B mandrel pulley, C, D, pulleys on the overhead, E pulley and screw of the slide rest. To facilitate calculation, let diameter of C equal that of the part of the mandrel pulley that drives it, by which it will revolve in the same time. The calculation of the sizes of pulleys, D and E, will be the same as for the cogwheels of the screw-cutting lathe, circumference and number of cogs being, so far as calculation is concerned, the same thing. Let the leading screw have eight threads to the inch, and let it be required to cut a spiral of two threads to the inch. Proceed as before by dividing the required number of threads to be cut by the number on the leading screw 2-8 =·25. The pulley on the leading screw will be therefore one quarter the size of that on the overhead (which is virtually that on the mandrel as it revolves at an equal speed with the latter). The overhead pulley may be conveniently twelve inches diameter, and that on the screw three inches. While the mandrel makes one revolution the screw will make four, advancing the tool half an inch, and cutting one thread of a spiral in that distance. The next revolution will advance the cutter a second half inch, cutting a second complete thread of spiral. Two threads will, therefore, have been cut in the space of one inch as desired. By the above method short screws and spirals of divers pitches may be cut at pleasure. _The practical difficulty in this plan is due regulation of the various speeds._ [Illustration: FIG. 158.] We here introduce a modification of self-acting lathe for cutting Elizabethan twist described by Mr. Wilcox in his MS. before alluded to. The work is here done by a leading screw and toothed gearing, the principle being that of the ordinary machine lathe. A chuck, A, with cogwheel attached holds the work as usual, the back centre being also required. The cogwheel gears with one of less diameter attached to the end of the guide-screw B. On the latter works the rest C, in which is a nut of the same thread as that on the guide screw, and which holds the tool in a notch or hollow upon its upper part. The tool is then used by hand, but is guided in its course along the surface of the work to be turned. This guide screw, with the rest and cogwheel, is mounted on a board as a separate piece of apparatus, and is, when used, clamped on the lathe bed. As the rest is after all little else than a large nut, it must be prevented from turning round, and must be arranged to bear the pressure of the tool, relieving the long screw from the strain that would be thus caused. This is effected by a long flat bar--like the rest of a chair maker's lathe--extending the full length of the bed shown here at E, and supported by standards F, F. A projecting part of the rest bears upon this, and slides along it with the tool. The work is begun with the rest on the right hand, and some care is necessary as it nears the cogwheel on the left, when the work must be stopped and the whole run back by hand to its starting-place. This is one chief defect in this apparatus, for the rest very quickly traverses the length of the screw, and great delay is caused by having thus constantly to stop the lathe and reverse the motion. The closest attention is also necessary to prevent the rest from overrunning its mark and striking the cogwheel. It is evident that by using different pitches of cogwheels, many screws of varied threads can be cut in the above lathe. There is, however, another defect in the above tool not noticed by the writer of the MS. from which the description is taken, namely, the difficulty (common to all such contrivances for turning wood), of obtaining the requisite speed. If the work is put in rapid motion, without which wood will not be cut clean, the movement of the rest will be so rapid also, from the effect of the multiplying wheel, that the tool will be carried from end to end in a few seconds. We will therefore proceed to describe a modification of this and similar apparatus, which allows the tool a slow traverse lengthwise of the work, but gives it immense rapidity in the necessary direction. The following is applicable to the lathe described above, to the ordinary slide rest worked by hand, or to the large self-acting screw-cutting lathes used in manufactories, and is specially adapted for cutting spirals or other patterns in wood. In the Fig. 160, A represents a shank, which may be made of any shape to fit particular patterns of tool holder. This shank is turned up and becomes a cylinder at B, like that of the ordinary revolving cutter. This part is bored, and fitted with a steel spindle, which should be of strength proportionate to the size of stuff likely to be operated on. One end of the spindle is fitted with a brass pulley, from which a cord is to be attached to the overhead apparatus, the other end terminates in a round or hexagonal boss, D, round the margin of which are securely held, by means of bridles B1 or other simple contrivance, a pair or more of small sharp gouges. This apparatus is put in the tool holder of the slide rest, set to the angle that corresponds with that of the screw or twist, and put in rapid revolution by means of the overhead apparatus. The whole rest, or merely the upper part, is then put in motion by one of the before-named means, and the tool advanced to make a cut. However slow the movement of the rest may be, the cutters move with such velocity as to make clean and beautiful work.[13] This may be applied to the slide-rest of the twist lathe, just described, or any similar apparatus. In the overhead, a roller, supplying the place of the second pulley, as described in a previous page, will allow the second cord sufficient power of traverse to keep up a proper position in reference to the pulley C. Revolving cutters on the same principle as the above, have of late years come into extensive use in wood-cutting and carving machinery. The steam planes now used in the preparation of flooring boards, the spoke turning lathe, moulding and shaping machines for wood are all thus fitted. The gouges or other cutters used must not be placed radially, but as tangents to the circumference of the boss in which they are fixed. An improvement upon the simple bridle to hold the cutters would be the substitution of Babbage's tool holder, four radial arms being substituted for the metal boss above alluded to. This tool is described and figured in Holtzapffel's "Mechanical Manipulation," to which the reader is referred for an accurate description. It chiefly consists of a shank turned up at the end like Fig. 161, the outside, at B, being rounded to fit hollow gouges such as Fig. 161H; against this the hollow of the gouge is laid, and opposite to it, at C, a small piece like D. A band or hoop, E, is now placed over both the above, and between the two a wedge-shaped piece, F, which is intended to bring a strain upon the hoop and tighten it round the gouge. This last piece is attached to the shank or holder by a screw passing through it into the shank. The tighter this screw is worked the lower the central wedge is drawn down, and the tighter the hoop is made to embrace the tool. This holder is also modified to suit flat chisels. The tool cannot possibly slip, but can be released in a few seconds if desired. Such a termination of two, three, or four arms revolving on a spindle in place of the boss would form the best possible circular cutter for shaping lathes. The above lathe for producing Elizabethan twist introduces the reader to self-acting, screw-cutting, and machine lathes, such as are used in all large manufactories. Hand-turning, indeed, except in such light work as turning up the heads of small bolts, and finishing up work which, from peculiarities of form, cannot easily be done by self-acting tools, has become a thing of the past in factories of any pretensions; hand labour, in fact, not only no longer pays, but is quite insufficient to meet the requirements of the present age. Take, for example, a piston-rod requiring to be as "true as a hair," to use a common expression, from end to end. The traverse of an ordinary slide-rest would only enable us to turn a short length at a time, and the result, when accomplished, would not be satisfactory. With a self-acting lathe the tool traverses in a perfectly straight line from end to end, is returned to its starting-point by a quick traverse, and the movement repeated until the proper dimensions are attained. The process is not absolutely rapid, because time is requisite in cutting iron and steel, but the work is executed as speedily as the nature of the metal to be cut will allow, and the execution is perfect. Of late, however, even the above has been improved upon, for two cutters are used at once--one on each side of the bar, so that by one traverse of the rest a cut of double depth is taken, and the tendency of the work to spring away from one tool is counteracted by the operation of the other. But we require something more than speed in the present day. We must have work of absolute truth of measurement. What would our ancestors, or the immortal Watt himself, think of measuring work to the hundredth part of an inch, yet it can be and is done to the thousandth part. I believe I am correct in saying that Whitworth constantly gauges work to that or even a higher degree of nicety. It is not too much to assert that the best engines of the present day really work with the precision of clockwork, and even the bore of an Armstrong or Whitworth gun is executed with no less accuracy and precision. Look again at that ponderous affair, the steam hammer, so ponderous as to require a depth of solid masonry and timbers to sustain the force of its terrific blows. In a few minutes a solid mass of metal is reduced to a flat plate such as would have taken the united strength of a dozen men wielding the heaviest sledge-hammers for an hour at least. The ground beneath the feet of the spectator trembles at every blow of the machine. The work is done, and behold! with a touch the same ponderous concern becomes a nutcracker, not even injuring the kernel when it breaks the shell. Such is one of a hundred specimens of accurate workmanship carrying out in practice the clever designs of the mechanical engineer. Sweep away self-acting machinery, and such work would become a simple impossibility. Again, so long as turning, boring, planing, and such work was performed by hand alone (even after the introduction of the slide principle), an attendant was required at each machine. Now that the latter is contrived to regulate its own movements, one man at two or three lathes is sufficient. Thus the same article that was once imperfect and costly, owing to the demand on skilled labour, which was difficult to procure and at best inefficient when procured, has now become cheap, and to all intents and purposes perfect; and although the demand for such work increases year by year, self-acting machinery being constantly improved and simplified, enables the manufacturer to keep pace with the demand. [13] The spiral chuck for fine work in ivory and costly woods is described in a later page. [Illustration: FIG. 159.] [Illustration: FIG. 160.] [Illustration: FIG. 161.] The advantages of self-acting machinery are of course chiefly confined to the trade, and it is not often that the mere amateur requires such aid. Indeed, the expense necessarily attendant on the fabrication of these machines deters the great majority from making such a purchase. SELF-ACTING AND SCREW-CUTTING LATHES. The first requisite for fitting up a lathe for screw-cutting and plain turning is the fitting a guide-screw, and adding a saddle to the slide-rest. But it must be observed that the ordinary mandrel of small foot-lathes, which works in a collar and back centre, is not convertible, and must be replaced by one working through two collars, so that a part may project at the opposite end to that intended for the chucks. On this projection various cogwheels have to be fitted. Now there are divers patterns of mandrel suitable for the above purpose; some are perfectly cylindrical, some have one conical part, some are fitted with a second cone, independent of the mandrel, and which slides upon it, and can be adjusted by means of regulating nuts. This latter being a good pattern, when well constructed, we shall first describe in detail. In Fig. 162 is shown A, the mandrel complete, with fittings in section, but without any of the change wheels. The cone _a_ is forged on the mandrel, which then becomes cylindrical. The cone is figured too large in proportion to size of mandrel; the latter should be represented as much more substantial. At _b_ the second cone slides on, the latter shown again at B. It is bored truly, and a slot cut to fit a feather on the mandrel. Thus it will slide along it, but must necessarily turn with it. Beyond D on the left are two screwed parts, one slightly larger than the other, one being made with a left-handed, the other with a right-handed thread. On these screw the two nuts, _d, e_, which drive the movable cone towards the right, causing it to fit more tightly into its collar, and also by the same movement tightening the fixed cone in its bearings. The mandrel is thus readily adjustable in the collars, and can be made to run very truly and easily without shake or endlong movement. Any pressure, however, against the front, such as would be caused by drilling, would jam the front cone in its collar, and tend to loosen the other. This is counteracted by the part _f, g_, with its screw, _h_, against which the end of the mandrel bears. That this form requires good workmanship is evident, for there are three points, or bearing surfaces, to be brought into a correct line, and the slightest deviation will cause the mandrel to jam in some part of its revolution. The nuts screw up in opposite directions to counteract the tendency in either to screw up more tightly, or to become looser by the revolution of the mandrel. On the whole the above is a good form of mandrel; if it has a fault, it is a slight tendency to work heavily. The next form is that of the ordinary mandrel, with single cone, but a second collar is added, which is cylindrical, through which the mandrel passes, and it then abuts on the sustaining screw as before. This is shown in Fig. 163, with the addition of the wheel, which is to be connected by intermediate wheels and pinions with the leading screw. If the conical collar is replaced by a cylindrical one, so that two similar bearings are made use of, a shoulder becomes necessary to prevent the mandrel from slipping endwise. The collars must also be split as in Fig. 164, so that they can be tightened up as they become worn. Either of the above forms of mandrel can be used; each has its advocates, and not unfrequently all may be found in different machines in the same manufactory. The bed of a self-acting lathe requires to be accurately surfaced, and formed by the planing machine with two V's or edges bevelled underneath, as 165 _b, b_. The saddle of which we have spoken is a flat plate of cast iron fitted with V pieces to match the bevelled edges of the lathe bed, along which it slides truly, its under-edge being planed. To this plate the slide rest is attached securely, either turning when required on a central pin, and being clamped at any desired angle, as before stated when treating of the compound slide rest, or, when this movement is preferred to be given to the upper slide, fixed permanently by nuts and screws. The saddle is represented detached in Fig. 166. The principle of the self-acting lathe is very simple. Motion is given to the screw by means of cog wheels geared with the mandrel, a nut fitting the screw is attached to a hanging bracket of the saddle, and this with the rest is thereby carried along the bed. It is necessary, however, to add some contrivance for instantly throwing the screw out of gear, without the necessity of stopping the lathe itself. There are many ways of effecting this, the most common being the use of a split nut, which embraces the leading screw when the two halves are brought together upon it, but which is instantly freed by separating them through the action of levers and cams, or other simple mechanical contrivance. In Fig. 167, _a_ is the bottom of the saddle from which depend the brackets E, E. The nut B, B, which is divided across the middle, slides up and down between these brackets, D being the leading screw which they embrace when closed. The movement of the halves of the nut is effected by the lever _c_, in the form of the letter T moving on a centre pin at K, and having two links, D, D, attached to the halves of the nut at one end, and to the ends of the cross lever at the other. A connecting bar pivoted to the part, L, is attached to a lever and handle, by which motion is communicated to the lever. When this rod is moved in the direction of the arrow the links will cause the nut to close and _vice versa_. The next form, 168 and 169, represents the split nut attached to two arms, A, A, hinged together at E. B, B, are slots in which work the pins attached to the cross head of the levers C, C. A heavy knob of iron keeps the latter in the position to which it may be moved. In 168 the pins keep the arms and nuts apart. When the lever is thrown over, as in 169, the nut is securely closed and held in gear. This form requires to be fixed to the lower part of a bracket attached to the saddle of the slide rest, such as is shown at B, C, Fig. 170. In this figure, A is the bottom of the saddle E, E, the V piece, that on the left, having an adjusting screw to tighten it on the lathe bed when necessary. At F is a projecting piece of the saddle fitting accurately between the lathe bed, and kept down by a screw with bed plate underneath. This serves to steady the movement of the saddle and relieve the pressure and strain upon the V pieces. The bed-plate may be cut out to fit the lower part of the bed on which it slides, both being planed for the purpose, as shown at H. [Illustration: FIG. 162.] [Illustration: FIG. 163.] [Illustration: FIG. 164.] [Illustration: FIG. 165.] [Illustration: FIG. 166.] [Illustration: FIG. 167.] [Illustration: FIG. 168.] [Illustration: FIG. 169.] [Illustration: FIG. 170.] [Illustration: FIG. 171.] In Fig. 171 the half nuts slide up and down on the front of the saddle, and are moved by a circular plate on the outside. The action is very similar to that of Fig. 167, intervening links, attached to the plate and to the halves of the nuts, giving motion to the latter as required. Cams and eccentrics of varied forms are also made use of for the same purpose, every lathe maker devising new and improved movements from time to time. There is indeed little difficulty in arranging a satisfactory method, the best being that which is under easy control, of adequate strength, and not likely to be easily disarranged by the rough treatment it is liable to receive at the hands of the workman. The leading screw may either be placed on the outside, in front of the bed next to the workman, or inside between the bearers. The former is preferable as being more accessible, but it is rather more exposed to injury. When between the bearers the large saddle of the slide rest serves to protect it from the falling chips and shavings of metal which, mixing with the oil, are apt to clog the threads and add to the friction of the parts, besides increasing considerably the wear and tear, and no accidental blow is likely to reach the screw thus protected on both sides by the lathe bed. Nevertheless, all the various parts of a machine should be made as accessible as possible, and, with the exercise of ordinary care in its preservation, the position outside is on the whole the best. If the lathe bed is very long, it may be desirable to support the screw by allowing it to rest on friction wheels fixed to the saddle at both ends, or by allowing it to pass through a pair of brasses. Thus, as the saddle is often two feet in length, such bearings at each end, with the split nut between the two, form points of support which go far to prevent the screw from jagging or bending in the middle from its own weight. The general arrangement of self-acting tools is similar with all the makers. Fig. 172 is a drawing of such a tool from a sketch of Eades & Son, an old firm in Lichfield-street, Birmingham, the screw being here placed in front. Whitworth, the eminent mechanician of Manchester, makes many lathes with the screw between the beds. He also uses a double slide rest, with a tool working at each side of the piece to be turned, which cannot thus spring away from the cut. This is called a duplex slide rest. By this method double the cut is taken, and the strain upon the work lessened. In addition to the screw there is usually a rack attached to the lathe bed, on the furthest side, and a cog wheel working upon this, attached to the back of the slide rest saddle, is turned by a handle in front of the rest, Fig. 173. This enables the workman, after having, by means of the screw, completed the cut to the end of the work, to run the rest back again very quickly, having first released the split nut from the screw. The tool is thus brought into position for the next cut far more rapidly than could be managed by reversing the motion of the screw. This is called, therefore, the quick return motion, and is almost always attached to the larger class of machine-lathes. Before entering upon the details of other forms of gearing, and the arrangement of change-wheels for cutting screws or for plain turning, we shall introduce a few remarks upon the often-repeated question as to the advisability of self-acting lathes for the purposes of the amateur. It must be remembered that the chief object of such a lathe is the manufacture of large screws, long shafts, and such work as the piston rods of engines, requiring perfect accuracy from one end to the other. Boring cylinders and similar work is now generally done in an upright or vertical boring machine, which is for many reasons more convenient. This class of work, of course, the amateur has nothing to do with. The traverse of an ordinary slide rest is generally adequate for surfacing or boring to a length of six inches, which is sufficient for most purposes, and can readily be done by turning the leading screw of the rest by hand. Then, as regards screw cutting in the lathe, it is questionable whether it is not easier to turn up the blank and cut with stock and dies. The thread thus formed is a copy of that of the tool, and the latter, as made by Whitworth and other first-class makers, is as perfect as machinery directed by talented workmen can produce. If it is really desirable, however, to make use of the lathe for this purpose, the plan already suggested is generally applicable, namely, gearing the leading screw of the slide rest to the mandrel, either by means of change-wheels attached to an arm, or by connection with the overhead pulleys. There is, in addition, a plan of attaching a pair of dies to the tool holder of the rest, after detachment of the screw from its nut, which may be available in some cases. There are also screw plates made in two halves, the plates being divided lengthwise and clamped together at pleasure, admitting of application to any screw-blank while revolving in the lathe; and, lastly, pairs of dies, fitted like pliers, can be similarly used by hand without any slide rest. On the whole, then, it will hardly pay to give £50, or £60, for a screw-cutting lathe that is merely destined for small work; that can be done sufficiently well in a common lathe with hand motion to the rest. For cutting short screws, such as those of boxes, a convenient and practically useful contrivance is still a desideratum. The traversing mandrel is, no doubt, the best, but it is an expensive pattern, if well made, and it is necessary to sacrifice, in a measure, general utility to questionable and certainly partial advantage. Turning is, moreover, an art, and to attain skill in it, perseverance and practice are necessary--hence the zest experienced in its pursuit by the real lover of it. This perseverance pays, and to attain the skill required to trace a short screw with the chasing tool is within the reach of any one who desires to accomplish it. The art once acquired, the desire for a traversing mandrel ceases; for no good workman would accept a contrivance of the kind when he can more easily and quickly accomplish his end without it. Writing this for the special benefit of amateurs, we would strongly advise them not to throw away money to purchase the means of doing what after all they will probably never, and certainly only seldom, carry into practice. The pleasure afforded by all the mechanical arts is greatly enhanced by meeting with and triumphantly surmounting all sorts of difficulties. Let it be a standing rule of our readers to make use of the appliances at hand instead of seeking others which only save trouble and render skill unnecessary. What can be more aggravating than for an amateur, with his hundred guinea lathe and chests of tools, to be obliged to take his work to a mechanic, and to see him, whose whole stock might be bought with perhaps a tenth part of the money, take in hand and finish with ease what has baffled the skill of his more wealthy patron? The common fault of the amateur is undue hurry. To him time is seldom an object, yet the mechanic, to whom it is so precious, readily spends more upon his work. He never hurries, never compromises, but with lathe and file fits the several parts of his work with the most patient care and practised skill. The result is at once seen when his productions are placed side by side with those of the zealous but too hasty amateur. It remains, as previously described, to arrange certain cogwheels gearing with each other upon the spindle of the mandrel and upon the end of the screw, to enable the workman at pleasure to vary their ratio of speed, in order to give him the means of regulating the pitch of thread to be cut. For this purpose a set of change wheels is supplied with the screw-cutting lathe, the number of cogs in which usually commencing at fifteen, increase by five, until the number one hundred and twenty is reached, then increasing by ten up to the complete set. Duplicates of some numbers are also convenient. The method of finding the proper sized wheels is, of course, based upon the proportion borne by the required pitch to that of the leading screw and one form of calculation for the purpose has already been given. Thus, supposing the leading screw to have two threads to the inch, it must revolve twice to move the tool that distance, and if we wish to cut a screw of ten threads to the inch, the work on the mandrel must revolve ten times while the leading screw revolves twice, or, which is the same thing, the mandrel must revolve five times while the screw revolves once. The cogs in the wheels must therefore be in the proportion of five to one, say fifty on the screw and ten on the mandrel, with an idle wheel on the stud to cause the motion of the tool to be such as will cut a right-handed thread, or to cause the mandrel and screw to take the same direction. Now, it seldom happens that two wheels and an idle one will give the requisite speed to the tool, and the number of cogs required soon mounts to inconvenient numbers. In this case, therefore, according to a principle already laid down, a stud-wheel with a pinion attached to the same, is placed in the train of wheels, and the object readily attained. A modification of the rule of calculation may make the system of change wheels still clearer. Let the pitch of guide screw be as before, namely, two threads to the inch, and let five be required. Place the numbers thus, 2-5, and divide both into their factors, twice one, or 2 × 1, and twice two and a half, or 2-1/2 × 2. 2 1 -------- 2-1/2..2 Now, it is certain you can have no wheels containing half notches, nor of such small numbers of cogs, therefore multiply by any convenient numbers--ten, for instance, which give 20..10 ------. 25..20 This is all that is needed. Put a wheel of twenty cogs on the mandrel, and let it work into one of twenty-five on the stud, the latter carrying a pinion of ten cogs, driving one of twenty cogs on the screw. To prove this, as before, the screw must make two revolutions to carry the tool one inch, and during that time the mandrel (carrying screws to be cut) must make five revolutions. Let the screw wheel revolve twice, the pinion of ten teeth will revolve four times (twice 20 = 40 and four times 10 = 40); but as the stud wheel and pinion are as one, and revolve together, the stud wheel must also revolve four times (4 × 25 = 100). Thus the mandrel wheel will revolve five times as required (20 × 5 = 100). No other method is so easy to understand and work as the above. To give full details and provide working drawings of the various screw cutting lathes by different makers would be to extend the present series to an unnecessary limit, but we shall nevertheless describe another method by which these lathes with traversing rests are made self-acting when screw cutting is not required. Instead of a leading screw extending from one end of the lathe to the other, there extends a bar of steel about the diameter of the screw with a key groove or slot from end to end. This bar is supported in bearings at each end, and carries upon its surface a ferrule of steel with a screw cut upon its outside similar to Fig. 174, where A is the bar and B the ferrule. The pitch of screw is coarse, being similar in its object to the guide screw previously described. A pin fixed into this ferrule falling into the slot permits it to travel along the bar but causes both to revolve together when the bar is put in motion by means of a cog wheel or strap pulley at one end. Along the same side of the lathe bed, and level with the surface, is a rack, C, upon the face of which works a pinion, D, carrying on the same axis a cog or rather worm wheel, E, to gear with the screw ferrule. The bearings of this axis are secured to the saddle of the slide rest. Consequently, when the bar revolves, the screw is also put in motion, the wheel, A, Fig. 175, and pinion, B, partake of the movement, and the latter traverses the face of the rack, carrying the saddle with its rest and tool holder along the bed of the lathe. By this movement the screw ferrule traverses the bar as it revolves, thereby virtually becoming a long leading screw. In Fig. 176, which is a view from above, looking down upon the lathe bed, A is the rack, B, B, the saddle cut away to show the rack and pinion C; E is the worm wheel, D the long bar, the screw ferrule, being under the worm wheel, is not visible. As above arranged it is evident that the ferrule might escape from the worm wheel instead of proceeding on its proper course. This is prevented by its lying in the hollow of a bracket attached to the rest, as Fig. 177, A and B. This retains it in contact with the worm wheel, and also becomes a support to the long bar. Fig. 174 shows the side of the lathe that is furthest from the operator. The axle of the worm wheel and pinion carries a handle on the near side to give the workman power to use the rack by hand as a quick return movement. The above is frequently attached to those lathes provided with a long screw, the latter being on the near side and the bar on the other. Thus, the same lathe can be used for ordinary or screwed work. Whitworth, however, commonly uses the long screw placed between the beds or bearers of the lathe for screwing and surfacing, instead of adding the apparatus just described. A long screw being, however, an expensive affair, ought to be carefully cherished, and when the work is such as the bar will suffice to accomplish, it may be well made use of to preserve the screw. There is an arrangement for forward or cross-feed in the above apparatus, the principle of which is the connection of the cross screw of the rest by means of a pinion, either with the worm wheel or with a cogwheel on the same axle. When this is put into gear the rack and pinion are disconnected. It is also necessary to provide a method of reversing the motion of the long screw bar, especially when the cross feed is used in surfacing. There are several modes of accomplishing this, the best being the following, Fig. 178, which is a simple expedient applicable to lathes or other machines. A is the end of the screw rod, with bevel wheel attached, B, C, are similar wheels on the axle, D, the latter being movable endwise in its bearings by means of the lever handle; E, D, is the driving axle. By moving the lever to the right B is geared to A. A movement to the left brings C into connection. Between the two, both wheels are thrown out of gear, and though they may continue to revolve, the screw bar will remain still. By this contrivance the motion of the leading screw is reversed or stopped in a second, with the advantage of its being unnecessary at the same time to stop the working of the lathe altogether. It has probably struck the reader that as the size of the change wheels are various, there would be in some cases an impossibility of their touching so as to gear together. This is partly remedied by the interposition of dummies, or idle wheels, and partly by the following arrangement. The stud wheel, or dummies, as the case may be, are not upon axles fixed to the lathe-head or end standard, but upon such an arm as Fig. 179, which turns upon a pin at A, and carries in the slot the pins upon which the different wheels centre. These pins being made similar to B, C, can be placed at any position in this slot, and are fixed by a nut underneath. This arrangement gives considerable power of adjustment, and enables the workman to place together wheels of various sizes according to his need. It would not be by any means difficult to arrange the above lathe for screw-cutting, especially if the pitch of the required screw is not of great importance. An amateur's lathe might be thus fitted to serve a good many purposes, although a leading screw is to be preferred as the more complete and perfect arrangement. It cannot, however, be denied that there is great friction produced by the worm wheel and endless screw, which soon tells its own tale by the wear and tear produced, and the power is not so economically used as it is when the screw works in a nut. Expediency, however, in this, as in many similar cases, must decide for or against the arrangement in any particular case. It is, at any rate, a good addition to a lathe provided with an ordinary leading screw, more especially in the facility with which it can be arranged as a self-acting cross-feed to the rest when used for surfacing. [Illustration: FIG. 172.] [Illustration: FIG. 173.] [Illustration: FIG. 174.] [Illustration: FIG. 175.] [Illustration: FIG. 177.] [Illustration: FIG. 176.] [Illustration: FIG. 178.] [Illustration: FIG. 179.] WHEEL CUTTING IN THE LATHE. Among the various uses to which a lathe may be put, wheel-cutting is one of the most important, so many pieces of mechanism requiring cogged wheels of various pitches and forms of tooth. By the aid of the slide rest such an apparatus as figured may be readily arranged, and the work rapidly and accurately performed. The guide by which the cogs and spaces are determined is the division plate already alluded to, and which is not visible in the present drawing, but the index of which is shown at G. C is the cutter frame with a side pulley (one on each side) to conduct the catgut band from the revolving spindle to the overhead motion on to the flywheel. The spindle carries a pulley for the cord and a cutter wheel, I, to which an exceedingly rapid evolution is given. There are many patterns of these wheels, the edges of which, cut into teeth like a fine saw or file, are the exact form of the spaces required between the cogs; hence, some are rectangular, some have a triangular section. The thicker the wheel to be cut the larger should be the cutter, so that the bottom of the cut may be virtually level. In Fig. 181 another form of cutter is shown, which if put into sufficiently rapid motion answers as well, if not better, than the wheel-shaped cutters. It is a simple short bar of hard steel, with the edges bevelled in alternate directions, fitted into a slot in the spindle and held by a wedge or screw. The shape of the end is as before, a cross section of the space between two teeth. The cutter frame is here arranged to fit into the ordinary tool-holder of the slide rest, but the form may, of course, be varied at pleasure. It will be noticed that the slide rest, as delineated here, is different to that of which details have been given. It is made without the sole, and fits into the socket of an ordinary rest. Thus it can be turned on a centre, and becomes, to all intents and purposes, a compound slide rest. It is on this plan the small ornamental turning rest of lighter construction is made. The spindle fitting the socket projects from the centre of the lowest frame, and is cast in one piece with it. If the apparatus is compactly and strongly made, it becomes a very serviceable form, and is much used for the small lathes in sea-going steamers. The sides are made very short, so that the extent of traverse is small. We may here mention an addition to the rest socket, enabling the workman to raise this kind, or that used with drills and cutters, which is simple and convenient. Inside the iron socket a few turns of a screw are cut, and a second socket of brass with an outside thread is made to fit into it Figs. 182 A and B, the latter being a section. The edge of the inside socket is sometimes milled round, to facilitate holding it by the thumb and finger. In this way the height of the slide rest, or tee of the common rest, is adjustable to a great nicety. [Illustration: FIG. 180.] [Illustration: FIG. 181.] [Illustration: FIG. 182.] When a wheel is to be cut of large size, or of substance exceeding that of clock-wheel work, the above method is not suitable. The wheel is then generally laid flat, and the cogs are shaped by a slotting machine, the chisel of which has a vertical motion. The lathe is then no longer used; as a separate machine is more convenient and economical. A most serviceable addition to a lathe, especially an amateur's foot lathe, is the circular saw, with guides for cutting parallel, taper, or mitred work. Great rapidity of work is thus combined with perfect accuracy. A five-inch lathe will of course take a saw nearly ten inches diameter, but it is not advisable to attach one of quite this size, for the larger the saw the greater is the leverage against which the turner has to contend, and the friction caused by a deep cut in stuff of two inches diameter is quite sufficient to make the labour considerable. When such work is necessary, it must be very gently brought to bear upon the saw, and the flywheel of the lathe should be heavy. The cord should also pass from the latter to the slowest division of the pulley. If the workman, amateur or professional, desires a lesson in practical mechanics, he has nothing to do but turn a piece of ash six inches in diameter, with the lathe-cord extending from the flywheel to the smallest part of the pulley, the diameter of which is about half that of the object to be turned. This will teach him what hard work is. Then let him try the job with the cord, from the smallest part of the flywheel rim, to the largest diameter of pulley. The change to a slower motion and greater power will not be disagreeable. It must be remembered that a circular saw of six inches diameter will not penetrate three-inch stuff, owing to the boss or nut by which it is attached to its spindle. The above size will not make good work of stuff exceeding two inches in thickness, and even less thickness would be preferable. As to the size of saw, indeed, that is most suitable to a five or six-inch foot lathe, much depends upon the proposed work, and still more upon the weight and size of the flywheel. As a general rule it is better to err upon the size of smallness. The service to which this tool is commonly put is but light; sawing narrow strips of mahogany, such as used at the angles of bird-cages, cutting strips or segments of ivory (for which let the saw be kept wet) sawing out mitred or dovetailed joints, and similar work is within the compass of a five or six inch saw, and it is better not to exceed this. The teeth should be tolerably fine for hardwood and ivory, and coarser for deal and soft woods. Smaller saws of hard steel, and made of thick plate, are used for metal. The method of mounting saws of small size, such as are suited to be worked by the treadle of a foot-lathe, is shown in Fig. 183. E is a steel spindle, of which the diameter equals that of the central hole in the saw B. At F, about the middle of the spindle, is a fixed flange, at the base of which is a short feather or inlaid key, X 184, which fits the small slot seen in the centre of the saw and reaches also within a similar slot in the movable flange, G, but it must not be so long as to come through to the back of the latter. This flange and nut H having been removed, the saw is slid upon the spindle till it rests against the fixed flange; the movable one is now to be brought against it and clamped by the nut. The spindle is sometimes made with a square end to fit the square hole chuck, and centred at the other, or it is drilled at both ends, so as to be driven by the carrier or driver chuck, C, D. It must be so placed as to run towards the operator. The above arrangement must now be made complete by the addition of a platform, B, on which to lay the work that is to be sawn, and on which some contrivance can be adjusted to guide the passage of the saw through the same, so as to cut the work in parallel pieces, or at any desired angle, such as would be necessary for mitred joints. For the general uses of the amateur a mahogany or hardwood platform is as good as any, and such as is delineated in vol. ii. of Holtzapffel's valuable work is perhaps the best arrangement. The saw table rests on the opposite ends of a kind of open box, which is represented without the two sides, although they may be added if desired, and the whole when removed from the lathe would then form a case for the saws, or serve other similar purpose. The platform is hinged, so as to overlap, as seen in the Fig. 184A, and there is in the middle of it a slit cut by the saw itself, which, when it is mounted on its centres will be in the position shown. If sides are added a notch must be made in the upper edge of both for the passage of the spindle. The fillet B fits between the bearers of the lathe, securing the parallelism of the whole. When made with four sides the box must first be placed on the lathe bed and loosely held by the bolt beneath. The saw is then mounted, and the box adjusted to its place and fixed. The cover is then (if for the first time) brought carefully down upon the saw, and the lathe being put in motion the slit is made, and its position will be truly at right angles with the spindle and the lathe bed. Of course, in future operations the platform is lowered over the saw before the holding down bolt is permanently screwed up. The sides of the saw-kerf may be edged with brass if preferred, but on the whole the plan is not to be recommended, for if, as will occasionally happen, the saw should get slightly out of truth, or vibrate a little when in use, the teeth will come into contact with the metal and be blunted or broken. If the saw-kerf by constant wear should widen too much, the whole platform is renewable at little cost, or a new piece can be let in, and a fresh saw-kerf made. There are several guides for parallel work. The one shown in Fig. 185 is precisely such as is to be seen in the ordinary parallel ruler--A is the back bar screwed to the platform at the right-hand edge; B the guide or fence which, when the connecting links C, C are perpendicular to A, should touch the saw; D, D are arcs of circles of which E, E are the centres. They may be arcs of brass pivoted to the links and passing through a slot in the bar, A, A, or may themselves be cut as mortises in the platform, in which fit a pair of bolts with thumb-nuts passing through the links, by which to clamp the fence in any desired position. This form of parallel guide is not very substantial, and is not correct in practice unless the pins are very nicely fitted, and the links precisely of a length. The second figure shows the sectional form of the fence G, the links being represented at H, and the fixed bar at K. The following is a more solid and unyielding guide, and much to be preferred. Holtzapffel attributes it to Professor Willis. It is merely a modification of the T-square as used with the ordinary drawing board with an arrangement for fixing it in the required position. The present arrangement differs from that in Holtzapffel's work in the manner of fixing it and the addition of a second T-piece on the side next the workman. In Fig. 186 A is the upright part of the fence, B the bottom or sole, to which is attached at each end the T or cross pieces, E, E, which slide along the straight edges of the platform and secure the constant parallelism of the fence to the surface of the saw; C is the groove or slot, in which a screw, D, traverses, and the fence is thus fixed by a turn of the thumb-nut, D. This fence can by no possibility get out of truth; it is easily removed by taking out the single screw, and it is far more simple and more easily made than the one previously described. The nearest edge of the platform may be marked in inches and eighths, and the fence can then be instantaneously adjusted for sawing pieces of any desired width. It is not always, however, that straight, rectangular, or parallel strips are required, and an additional arrangement is needed to form a guide for sawing angular pieces. Now it is not sufficient to lay the guide fence at a given angle, for if the latter were arranged for that adjustment by taking off the tees and causing it to turn upon the screw which secures it in place, and a piece of board were placed against it to be sawn, the latter would press against the saw sideways as seen in Fig. 187. The guide fence for angles must itself therefore travel in a line parallel to the saw and carry with it the piece to be cut. The simplest and usual arrangement is that given in Holtzapffel's work. A dovetailed groove in the platform running in a direction parallel with the saw carries a sector attached to a bar which fits the groove, and this bar is free to move forward or backward without lateral movement. The piece to be sawn is thus rested against the fence forming the straight face of the sector, and the whole is moved forward together against the edge of the saw. Fig. 188 explains this. It will be seen that several grooves are made side by side, all of which fit the slide alike, and by moving the latter into either of these a lateral adjustment is effected to suit pieces of different widths. The sliding strip should be made of hard wood and nicely fitted, and may be lubricated with soap, or polished with black lead, either of which will cause it to slide with diminished friction. Fig. 189 shows a somewhat different arrangement, by which more lateral adjustment may be given. The sector is replaced by a T-square, the blade of which has a slot through which a screw passes into the sliding bar. A second jointed rod is added, passing through a staple in the slide, and by a screw in the latter the T is fixed as required. The staple must turn on a centre to accommodate itself to all positions of the T-square, and a second eye may be placed on the opposite arm to allow the guide rod to be removed to that side, which is sometimes more convenient. The sector also may be made adjustable as in Fig. 190, and clamped by a simple screw in the slot. Either of the above methods will allow sufficient range for small work, such as is likely to be the object of amateurs or those who add small saws to the foot lathe. The guide for angular pieces may indeed be in many cases dispensed with by making use of patterns of wood chiefly in the form of triangles; these sliding against the parallel guide, and carrying the work with them, will answer well in a number of cases where other provision for such work has not been made in arranging the saw table. It must be remembered, however, that in this case the length of the piece (supposing it to be the side of a picture frame to be mitred) is limited to the space between the fence and the saw, which in the more perfect arrangement is an evil plainly avoided. It may sometimes be necessary to cut pieces with various angles not in the same plane. By using the hinged platform, and adding a screw attached to the front of the box, and standing perpendicularly, the front of the table can be raised to a given angle, but those who are likely to enter extensively into the cutting mathematical figures are referred to vol. ii. of Holtzapffel's work, where the subject is fully explained and illustrated. The following remarks upon the proper speed of saws and sizes of teeth are copied from that work, and may therefore be relied on:-- "The harder the wood the smaller and more upright should be the teeth, and the less the velocity of the saw. "In cutting with the grain the teeth should be coarse and inclined, so as rather to remove shreds than sawdust. "In cutting across the grain the teeth should be finer and more upright, and the velocity greater, so that each fibre may be cut by the passage of some few of the consecutive teeth rather than be torn asunder by the passage of one tooth only. "For gummy or resinous woods and ivory, the saw teeth must be keen, and the speed comparatively slow, to avoid the dust becoming adhesive (by reason of the heat engendered by friction), and thus sticking to, and impeding the action of the saw." [Illustration: FIG. 183.] [Illustration: FIG. 184.] [Illustration: FIG. 184.] [Illustration: FIG. 185.] [Illustration: FIG. 184A.] [Illustration: FIG. 186.] [Illustration: FIG. 187.] [Illustration: FIG. 188.] [Illustration: FIG. 189.] [Illustration: FIG. 190.] By raising the platform so as only to expose a small portion of the saw, it is easy to cut rebates, grooves for tongueing, and other work of a similar kind. The above arrangement of hinged table facilitates this application of the saw. FRET SAWS TO MOUNT UPON THE LATHE BED. Convenient as the circular saw is when fitted as an adjunct to the lathe, its use is confined to pieces which are rectilineal. Curved lines cannot be cut by its means, and as it must frequently happen that portions of the proposed work are composed of arcs of various dimensions, it becomes necessary to provide the means of cutting them out. We may remark here, that although the circular saw, and that of which we are about to speak may be fitted to mount on the ordinary lathe bed; it is better for many reasons to have a separate stand, made like that of the lathe, but smaller, and fitted with crank, treadle, and flywheel, to serve for the various purposes of sawing, grinding, or polishing; the latter operations especially soiling and tending to damage the lathe. The above description of the methods of mounting circular saws will answer for a separate stand, as will the following details of saws for curvilinear work. In respect of the latter we have to provide for the perpendicular motion of the blade, which is necessarily thin and narrow, and also for stretching the blade so as effectually to prevent it from bending or buckling--guides are not required in general, as the work is moved about by hand in all directions according to the intricacies of pattern to be traced. For plain circular pieces, however, a very simple expedient is sometimes used, which will be described in its proper place, when treating of Bergeron's _scie mecanique_. The guides for parallel motion are various, and a selection may be made from the following Fig. 191. No. 1 is the arrangement used by Professor Willis, and detailed in Holtzapffel's work. A, A are wooden springs, one above, the other below the platform B. C is a guide pulley, D an eccentric. The catgut band which gives motion to the saw may be passed round this, or affixed to a metal ring as in the eccentric of a steam engine--or may be attached to a ring slipped over the pin of a crank disc, as shown at E. This pin being adjustable, permits the traverse of the saw to be regulated, which gives it perhaps an advantage over the first method. In the above the motion of the saw is not truly in a right line, but the deviation in so short a traverse is unimportant. The reader may, perhaps, imagine wooden springs a somewhat primitive expedient, but this is by no means the case, as they will retain their elasticity longer than metal ones when they are subjected to the rapid vibration which they are called upon to undergo. No. 2 is the parallel guide, used by Mr. Lund, and also described by Holtzapffel; the metal springs, however, shown by the latter being here replaced by india-rubber, which is now formed into springs of various sizes and powers suitable for our present and many similar purposes. A, A, and D, here form guide pulleys, the saw, E, being suspended from the first by the two catgut bands, on the ends of which are the india-rubber springs, F, F. The lower end of the saw is attached to another catgut band which passes over the pulley, D, and thence to the eccentric or crank disc as before. The platform is at B, B. Number 3 is an arrangement similar to the beam of Newcomen's engines. The arc at the end of the oscillating rod, and from the furthest point of which the saw is suspended, forms the guide for parallelism. Underneath the platform the pulley and eccentric may be used as before, and the saw is raised by the spring attached to the arc as shown. It will be evident on inspection that this arrangement is similar in principal to the last, as the arc forms part of a large wheel of which the centre is the point of oscillation. Watt's parallel motion, represented in the next diagram, is also suitable, the saw being attached to the centre of the short link--the springs being so contrived as to act upon the ends of the longer bars. With regard to the means of producing the necessary rapidity of movement, the above-described eccentric or crank disc can hardly be surpassed. In the saw patented lately by Mr. Cunningham, the disc is attached to the mandrel like a chuck, and the crank pin is connected to the oscillating rods that carry the saw by an intervening rod or link. [Illustration: FIG. 191. N^o 1.] [Illustration: No. 2.] [Illustration: No. 3.] [Illustration: No. 4.] [Illustration: FIG. 192.] The whole is represented in Fig. 192, which is copied from the inventor's circular. There is a satisfactory parallel motion, and an india-rubber ball with a small tube attached is pressed at every stroke to blow away the sawdust. The whole plan and details are as good probably as can be devised, and as an addition to the lathe this saw is invaluable. Another form of mechanical saw to work with the foot, but without any flywheel, is figured by Bergeron, and is thence copied into Holtzapffel's book, and would therefore have been omitted here were it not that the price of Holtzapffel's work places it beyond the reach of many whom it is specially qualified to instruct; and that the former is in French and has not been translated. Therefore, as the arrangement of saw is exceedingly good, the writer has determined to introduce it here. Its construction is simple enough to be within the reach of any amateur in carpentry, and the only metal work required consists of a few iron rods screwed at the ends, such as the village blacksmith can readily supply. The saws are precisely those sold as turn or web-saw blades. It must be understood that the use of this tool is not the same as that to which fret or buhl saws are applied, but merely the cutting of boards in strips or curved pieces, such as the felloes of small wheels, circular plates to be finished in the lathe, as bread platters, or such other curvilinear works as the chair or pattern maker is accustomed to cut out with the several sizes of frame saws. A, B, Fig. 193, is a stout bench with cross bar, C, underneath, cut away to allow of the movement of the treadle and its rod. On the top of the bench is a pillar, D, to support the spring bow E, by which after depression the saw is raised to its original position. F, F, and G, G, are guide rods (not continuous). The lower ones are fixed to the cross bar, _c_, and under side of the bench. The upper form the sides of a rectangular frame, H, H, of which the top and bottom bars of wood are dovetailed at the back to slide up and down the chamfered bar behind them, K. The frame thus allows of being raised or lowered, not only to suit work of various thicknesses, but also to act as a stop to prevent the saw from lifting the work as it ascends. The lower bar is extended on one side as in the figure, and is divided into inches, and on this graduated part is a slide with a point below, which can be fixed by a screw. This is, as the drawing plainly shows, intended for the guidance of the wood in cutting circular pieces. The saw is similar to the ordinary framed saw used by chair makers, but has two blades, and one central stretcher. The saw for curved work is narrow, that for straight cutting is broader. Near the latter a parallel guide is fixed, as described when treating of circular saws. This simple contrivance, although planned so many years ago, is of great value, and deserves to be far more generally known. To the joiner and cabinet-maker it would form a most useful addition to the usual tools of the workshop. [Illustration: FIG. 193.] Akin to the circular saw are the various revolving cutters used either for the purpose of ornamentation or for grinding, such as circular files for flat surfaces, in which the teeth are cut upon the face or tool-cutters of particular sections for cutting the teeth of wheels, in the manner already described, to which may perhaps be added milling and embossing tools, although the action of the latter is rather that of a revolving die by which the work is stamped or indented with the pattern formed upon the edge of the cutter. The small grindstones and emery laps belong also to this section, as their action results from the abrasion of the material by means of the combined cutting power of innumerable small points or miniature teeth formed by the particles of emery or other material attached to the surface of the laps. Most of the steel cutters may be made by the amateur, the metal being turned to the required shape and the teeth cut by small files or punches while the material is in a soft state. The little discs are then hardened and mounted, by a central hole previously made, on suitable spindles, the latter being either attached at one end to the mandrel as arbor chucks, or centred at both ends and driven like miniature circular saws. The ornamental cutters for embossing, Fig. 193B, A and B, are turned to the form of short cylinders, and the patterns cut by punches. These and the milling tools are mounted alike, Fig. 194. The rest is placed a short distance from the work, and the tool revolves against it. Some pressure is necessary to imprint the design, and this is easily obtained if the cutter wheel is placed so as to attack the work below the axis; the rest then becomes a fulcrum, and the shank and handle of the tool acting as the long arm of a lever supply the required force with little exertion on the part of the operator. In this way the milling is done on the edges of screw heads, and the embossed patterns on soft wood boxes. It is not easy to understand how the patterns in these cases are produced clearly without one part cutting into and effacing another, unless the size of the work is exactly a multiple of that of the tool. The error is plain if the work is stopped exactly at the end of the first turn, but in successive revolutions this error becomes gradually obliterated, and the pattern is eventually impressed clear and well defined. The same shank is arranged for different patterns of wheel-cutters, as the pin which forms the central axis is readily withdrawn and is made to suit the holes in several sets of discs. [Illustration: Fig. 193B.] [Illustration: Fig. 194.] [Illustration: Fig. 195.] By the aid of the above simple tool a neat finish is readily given to many small works in wood and metal. A modification of the beading tools is here shown very similar to the screwing guide already given, but made with figured instead of sharp-cutting edge. This was communicated to the _English Mechanic_, Nov. 2, 1866. E, 195, is the guide which is placed on the handle A, B, C, D, and fixed by screw F. The mark _i_, on the guide, is placed against the rim, A, B, which is graduated and numbered. Each figure, as it is brought up and placed opposite _i_, will cut a different pattern when the guide is fixed. The tool must be held very firmly on the rest (the bottom of the guide G, H, being flat, is carried on the rest), the tool is advanced to the wood. The tool must be worked very steadily; but with a little practice, any amateur will soon use it perfectly, and produce many very pretty patterns. It is evident that provision is here made for placing the cutter at different angles to the work, by which means the circles of patterns may be traced spirally and in other positions varying from the ordinary one at right angles to the axis of the work. The laps alluded to, which are to be mounted on spindles like the circular saw, are composed of wood and metal of determinate forms. First, there is the thin sheet-iron slitting wheel used by lapidaries, and which, when charged with emery, or sand and water, forms the nearest approach to the circular saw. It _is_, in fact, the circular saw of the stone worker, the ordinary saw used in their trade being a flat blade without teeth, stretched in a wooden frame and similarly fed with sharp sand and water in lieu of being made with teeth, the latter being replaced by the grittiness of the material. The circular plate of iron, brass, or lead alloyed with antimony, mounted on a spindle vertically, is used in a similar manner for grinding flat surfaces with the aid of emery, crocus, oilstone powder, and other substances, and the same is used edgewise for other work, as grinding and polishing tools, the section of the lap being such as will form the article required by reproduction of the revised plan of its own edge. Thus a lap running horizontally with a convex edge will produce the concave form required in beading tools, the latter, however, are more conveniently ground on brass cones mounted like the arbor chucks used for turning washers, rings, &c. The face of the tool or flat side is held towards the small end of the cone, and the latter is armed with flour emery. See Fig. 196. [Illustration: Fig. 196.] Before describing the eccentric and other compound chucks, a few examples will be given of the method of turning some of those forms in which the circle does not appear, where, in short, the boundaries of the figures are straight lines. It seems at first sight impossible to produce in the lathe by any simple means such solids as are formed from squares or triangles, of which the cube or die is the most common and most generally understood. This can, however, be accomplished, and a number of mathematical problems may be clearly demonstrated to the eye by such works skilfully made in the lathe. In this kind of work it is absolutely necessary to strive after perfection. In short, as Bergeron rightly says, the work imperfectly done is simply worth nothing at all; but when accomplished with exactness, nothing can be more worthy of a place in a cabinet of curiosities. The usual method of turning a cube is by shaping it out of a perfect sphere, but as the latter can hardly be made without a special slide rest made for the purpose, a method of turning the cube by hand alone will be given, the foundation of it being that which the lathe so readily produces, namely, a cylinder. By far the most proper material for the work in question is sound boxwood, and special care is to be taken to keep all angles as sharp as possible, and therefore to cut clean with sharp tools, and to avoid as far as possible the use of sand or glass paper. Fig. 197 shows a square described in a circle. The non-mathematical reader may be told to draw through the centre two diameters at right angles to each other, and to complete the square, as in the figure, by joining the extremities. The largest square that is possible to be drawn in the circle is thus described. This square will form one face of the cube, and the diameter of the piece of wood must be regulated according to the proposed size of the finished work. It is evident that this diameter is equal to the line drawn from corner to corner called the diagonal of the square. Now, in turning a ball or sphere, a cylinder would be turned of the exact length of A, C, because every measurement taken on a diameter of the sphere would be of that length. In the present case, however, the cylinder must be of the same length as the line A, B. Turn, therefore, with great care a cylinder of any desired size, gauging it carefully with the callipers and squaring off the ends truly. On one end, in which the centre point just remains visible, draw diameters and construct the figure 197. Turn out a chuck to fit it exactly, and let the bottom of this chuck be truly square. Take the precise length of the line A, B, with finely pointed compasses that can be fixed with a screw, and measure off the same, and mark it on the side of the cylinder. When the figure is placed on the chuck, a mark must be traced round it at this point, A, B, Fig. 198, _and this must remain to the end_. It may be made with a hard pencil or steel scriber, and, though distinct, must be very fine. It is at this line the wood will have to be cut off, but in this operation keep beyond it so as not to erase it. While the piece is in the chuck, rule lines, as E, G, from the points C, D, E, F, 198. Bisect also the length of the cylinder by the line, H, K, also finely drawn. Draw two more diameters, as shown by the dotted lines bisecting the sides of the cylinder, which is now divided round its circumference into eight equal parts. The lines, E, G, &c., can be ruled along the edge of the rest, or, if the latter is untrue, the cylinder may be laid on a plane surface, and a scribing block, or gauge, Fig. 199, may be drawn across it, or, lastly, a small steel square may be used; one part being carefully placed on the lines at the end of the piece in succession, the other part will lie evenly along the side, and will form a ruler by which to work. A division plate on the lathe pulley will facilitate the above measurements, but they can be readily made without it, and once carefully marked, all the guides required for cutting out the cube will be complete, and the work can be proceeded with, with confidence and decision. Proceed, therefore, to cut off the piece at A, B, with a parting tool, but with the precaution already named of not erasing the line by so doing. Now prepare a chuck which will take the piece lengthwise, Fig. 199-2, and insert it in that position to the depth of the diameter so as to hold it securely, and the central line will show whether it lies evenly (which is, in fact, the use of this line). If even, a point-tool held on this line will form a mere dot upon it; if uneven, it will make a circle as it revolves. Place the rest across the face of the work, and, beginning at the centre, cut carefully towards the outside until you have cut away the wood as far as the line, A, B. You will thus complete one face of the cube, and an inspection of the end of the piece, shown black in the sketch to show the quantity removed, will prove that you thus produce a right line, C, D. Take out the work, and reverse it, and operate similarly on the opposite face; but in every case do not quite obliterate the lines first marked as guides. You have now a piece shaped like Fig. 200, A and B, and must make a smaller chuck to hold it; you have then to cut away in a similar manner the remaining parts of the cylindrical portion, and the cube will be complete. To finish the sides more neatly, lay upon the table the finest sand paper, and tack it at the corners, and with gentle movements work down precisely to the guide lines. This requires extreme care, for if once the piece is but in the slightest degree tilted up, an angle will lose its sharpness, and the beauty of the work will be marred. Hence we recommend to cut with sharp tools, instead of trusting to the finishing process. To cut, however, _exactly_ to the line is very delicate work, and to the less practised hand the use of the sand paper on the faces in succession may be the _necessary_ expedient. The main secret of sharp edges in works of wood and metal is to finish with hard substances, as emery stick or glass paper glued to a piece of wood, or the same nailed on the bench, and to try always to work on the centre, leaving the edges or angles to take care of themselves. When the reader has made a cube, as above, that will bear delicate measurement, he will be more than usually gratified, and will be qualified for still more difficult work. A chuck figured by Bergeron, Fig. 201, is very convenient, as it holds the work truly central; the jaws work simultaneously by a right and left-handed screw as in the die chuck. It is, however, perfectly easy to do good work without it, but the chucks should be carefully made, turned very flat at the bottom, with side truly perpendicular. A little extra care bestowed upon chucks will save many disappointments, and conduce to good work. The formation of a four-sided solid, consisting of triangles solely, in the lathe is a work of difficulty, owing to the impossibility of fixing the work satisfactorily in an ordinary chuck. The natural way to form such a solid is to turn a cone A, B, Fig. 202, and on its base to mark a triangle of the required size. It is then necessary to place the cone in a chuck, so that the ends of one of the lines thus marked and the apex of the cone are precisely level with the surface of the chuck, as shown in Fig. 203. But it is evident that adequate support is not thus obtainable. The apex of the cone cannot, in point of fact, be inside the chuck at all, as it is necessary to cut clean to its extremity, and even the base of the cone is imperfectly held at two points. Hence it becomes necessary to make use of "turner's cement," and to imbed the work fairly in it, while both are warm, to such a depth as will hold it securely and still allow the guide lines to be seen. The latter should be carried from the three angles of the triangle marked on the base to the apex. On the whole, this is the easiest method of fixing such work in the lathe; and if the piece is itself warmed before being placed, there will be time to adjust it precisely before the cement is cold. To do this, place the rest parallel to the lathe bed, hold a pointed tool steadily upon it, and note whether, as the work slowly revolves, the three points in question, viz., the two angles of the triangle and the top of the cone, are in one plane. When they are so placed, the rest is turned to face the work, and the material is carefully cut away till the gauge lines are just reached.[14] A pyramidical solid with a square base may be similarly turned. The following is the method of preparing the above turner's cement:--Burgundy pitch, 2 lb.; yellow wax, 2 oz. Melt together in a pipkin, and stir in 2 lb. of Spanish white. When the whole is well mixed, pour it out on a marble slab and roll it into sticks. Fine brickdust, whiteing, or any similar substance finely pulverised, will answer equally well to add to the pitch and beeswax. This cement is very useful, as it will hold the work firm enough to turn carefully, and nevertheless a slight blow will loosen it. To clean it off, warm or dip the work in hot water and wipe quickly with a piece of cloth. The above is from the "Handbook of Turning," the author of which has copied from Bergeron both the recipes given in his work; the one here described is stated to be specially serviceable in cold weather. It is perhaps rather less brittle than the first of Bergeron's, and for this cause is the best for general use. Holtzapffel sells this at one shilling the stick, which is of convenient size and generally of excellent quality. Bergeron gives a method of turning pilasters or balustrades, which is of great ingenuity, and applicable to work of various sections. The rectangular and triangular sections illustrated are not, indeed, strictly rectilineal figures, as the sides of the balustrades thus formed are not flat but rounded surfaces; they are, however, sufficiently curious, and when well turned are interesting specimens of lathe work. Bergeron's description relates to the pole lathe, or to work mounted between two centres with a pulley cut on the work itself to receive the lathe cord. The ordinary method of mounting on a foot-lathe will, of course, be much better and the whole operation of more easy performance. Let it be required to turn a moulded pillar or balustrade of the section Fig. 204, viz., a triangle with slightly curved sides. A piece of wood of the requisite length is planed up accurately to a triangular form, or, as it generally happens that a set of such pilasters are required, a number of such pieces are prepared which must be accurately planed to the same size, for which purpose a gauge or template, Fig. 205, should be made use of. Six or eight of these, if not too large, may be operated upon at the same time; but as six pieces of two inches across each face require a cylinder of about eight inches diameter, the number must depend on height of centres. The larger the cylinder, however (which, in fact, forms a chuck), the more nearly will the sides of the finished work approach to plane surfaces, as they will form arcs of a larger circle. Let a cylinder, then, be turned of sound wood with a reduced part at one end so as to form a shoulder. Divide the circumference into twice as many equal parts as there are pieces to be turned, the divisions being equal to one of the sides of these pieces as measured in a cross section. These divisions are to mark the positions of the grooves or channels in which the triangular strips are destined to lie. Half the circumference will be so cut out, the alternate divisions being left. Thus, to turn four pieces, each two inches wide, a cylinder of sixteen inches will be required, affording four grooves two inches wide, and four intermediate pieces forming the partitions between the grooves. The latter must, by means of the saw and chisel or other tools, be made to receive the strips exactly, and the ends of the latter being carefully squared off, are to be made to rest against the plate C, Fig. 206, which is cut out and screwed against the shoulder, after the above-mentioned grooves have been cut. The whole are then secured by two rings, with screws. Probably the stoutest india-rubber rings now made would answer as well as the iron clamps in Bergeron's description. Lay the strips in their places, but as they are flat they will not form part of the cylindrical surface, but will lie lower, as Fig. 207, or higher, Fig. 208; the latter is the best, and the pieces may, for this cause, be cut out a trifle deeper than ultimately required and they may be planed down a little to remove the angles and assimilate them to the cylindrical surface. The whole may then be turned together so as to form a plain cylinder, the clamping rings, Fig. 209, being shifted when requisite. The whole is now to be formed into a balustrade, but as the proportions of the mouldings of such a large cylinder would not suit the small pieces, the hollows must be less deep, and the raised parts less prominent than they would ordinarily be made. The clamps are now to be loosened, and the pieces reinserted with another face upwards, the flange or plate against which their ends rest forming a gauge or stop to ensure their position, without which precaution the mouldings would not eventually meet at the angles. In cutting a fresh side the utmost care is requisite, for if the work on the original cylinder is cut by the tool, it will be impossible to restore it, and the work will be spoiled. In replacing the strips, let the finished part lie below, so as to come first in contact with the tool, by which the angle will be clean. Extra care is for this purpose required in cutting the last side. It appears to the writer that another precaution should be taken which Bergeron omits, namely, to arrange the mouldings so that certain parts are left of the original size of the wood, in order to retain a certain number of points of contact with the sides of the grooves, so that the strips shall not fall deeper into them than at first. The extremities of the strips should certainly not be left smaller than the central portion, or the pieces will rock on the latter while in process of being turned. The two ends, therefore, should be allowed to retain their original triangular form, forming base and capital of the pillar, or the pattern may be so planned that, after the extremities have been left as supports they may be cut off when the work is complete. Care must be taken, in working as above, to have the cylinders so large above the estimated size that the inner apices of the triangles do not nearly meet at the centre, else the whole chuck would be very weak and split into triangular strips. The lathe called a spoke-turning lathe would accomplish this kind of work in a far more easy and speedy manner. The balustrade would have to be made by hand as a pattern, and cast in metal, and any number could be produced precisely similar. The lathe in question is on the following principle:--The frame carrying the tool (a set of revolving gauges) is made to oscillate backwards and forwards to and from the piece to be operated on. This is accomplished by its having attached to it a roller or rubber working against the cast-iron pattern placed parallel to the work, and below or one side of it. The rubber and frame are kept against the pattern by a strong steel spring. The cutters also travel in a direction parallel to the axis of the piece. Hence any elevated part of the pattern causes the tool to recede from the work in a corresponding degree, and a hollow allows a nearer approach of the tool. Thus, as the tool is carried by a screw slowly from end to end of the work, it is made to advance and recede in exact correspondence with the form of the pattern. An immense deal of work is done in this way, such as balustrades, spokes of wheels, the long handles of the American felling axes, and similar irregular forms. [14] With the universal cutting frame this kind of work is much more readily accomplished. [Illustration: FIG. 198.] [Illustration: FIG. 197.] [Illustration: FIG. 199^2.] [Illustration: FIG. 199.] [Illustration: FIG. 200.] [Illustration: FIG. 201.] [Illustration: Fig. 203.] [Illustration: Fig. 202.] [Illustration: Fig. 205.] [Illustration: Fig. 206.] [Illustration: Fig. 209.] [Illustration: Fig. 208.] [Illustration: Fig. 207.] The _principle_, indeed, is not new, as the rose engine is a similar tool, and, so long back as Bergeron's time, pattern plates were used giving any desired motion, endlong or otherwise, to the tool, or, which in effect is the same, to the work to be operated on. TURNING SPHERES. We must now recur to the sphere of which we have already spoken. The method previously given for producing it is not sufficiently accurate, although a very close approximation can thus be made to the perfect figure. It is probably impossible without special apparatus, rendering the tool independent of the hand, to turn out an absolutely correct sphere--indeed, it is a sufficiently delicate operation, even with the following or similar apparatus. For ordinary purposes, indeed, where the object is simply to produce a croquet ball, a spherical box, or a globe to be afterwards covered with paper, or any such work, the plan already given will generally suffice, and, indeed, is very extensively used. Some practised workmen, too, will, without even the aid of ruled lines, turn out spheres of average excellence by the eye alone, aided by a template. When, however, it is proposed to hollow out a sphere so as to leave a mere shell of 1/8 in. or less, and perhaps include a number of such shells one within the other, and a star in the centre of all, it evidently becomes necessary to work with greater accuracy, and still more so with respect to billiard balls, in which even the slight variation caused by increased temperature will seriously affect the result of the most skilful play, and cause the very best players to fail. The principle of the spherical rest is displayed by the diagram, Fig. 210. [Illustration: FIG. 210.] [Illustration: FIG. 211.] A is the chuck carrying the ball to be turned, of which C is the centre. In a right line with the latter, and below it, is a pin fixed to a block between the bearers of the lathe, and on this the arm, D, turns. The latter carries a tool-holder in which a pointed tool, E, is fixed. The point of this tool will evidently move in a circle, when the arm is moved by means of the handle, D; and, as the centre of the circle is exactly under that of the proposed sphere, the latter will be correctly shaped when the lathe is put in motion. Fig. 211 gives another view of the tool-holder. It is essential that the point of the tool should be in a line with the centre of the lathe mandrel, so that it shall act on a diametrical plane as it is carried round the work. Such is the principle upon which a practically useful tool for turning spheres has to be arranged. The faults in the above simple machine are many. In the first place no provision is here made for the advance of the tool towards the work. In the second place the requisite firmness and stability cannot be obtained by merely causing the bar to revolve upon a centre-pin; and thirdly, as the tool post is fixed to the horizontal bar, the diameter of the ball must be limited. In point of fact, therefore, the above arrangement would not answer, and it is only described in order to illustrate the principle of all inventions for the production of spheres in the lathe. To give steadiness of action the pin forming the centre of motion is connected with a circular metal plate truly turned, upon which a second similar plate works, and to the latter is attached the tool-holding apparatus. It is difficult to make choice of a circular or spherical rest so as to give it precedence, since most of the patterns ordinarily made are good. To obtain the requisite movement is, indeed, by no means a matter of difficulty; and one or two adjustments in respect of the height and radius of the tool being provided, a very simple apparatus will answer the purpose. To commence with Bergeron's, which, though venerable, is by no means inefficient. This is represented in Figs. 212 and 213. A, B, is the base, the tenon, B, accurately fitted to slide between the bearers of the lathe, the whole being held down as usual by the bolt and nut, _c_. The top part of the base is surmounted by the accurately faced plate 214, on which a side sectional view is given in Fig. 215. This is fastened to the base plate (which, in Bergeron's description, is of wood) by four countersunk screws. It is turned with a recess, so that the outer part stands up in the form of a rim, and from its centre rises a conical pin, _b_, the upper part of which is first octagonal, and then rounded and tapped. It is this strong pin which forms the centre of motion, and it must stand with its axial line precisely in the centre of the lathe bed, so that if the plate were slipped close to the poppet head this line would bisect the nose of the mandrel. This is essential in all patterns of spherical slide rest. Upon the lower circular plate rests that represented in Fig. 216, A and B, the latter being the sectional representation. This plate is drilled in the lathe with a central hole, the lower part conical to fit the pin in the base plate, the upper part countersunk as in the figure, to receive the octagonal part of the pin and the nut. The projections _a_, and _b_, in B, represent the projecting rim, _a_, in the Fig. 216, A, and this is made to fit very nicely within the rim of the lower plate, while the adjacent part, _c_, rests upon the rim itself. The accuracy of these bearing surfaces is of the utmost importance, It is evident that this arrangement is calculated to give great stability during the revolution of the upper part of the rest, which is fixed securely to the plate last named. This plate has a hollowed edge cut with a set of fine teeth to be acted on by the tangent, screw D, Figs. 212, 213, and shown in Fig. 217 on a larger scale. The bearings of this screw are attached to the base plate, and the screw is prevented from moving endwise by collars as usual. [Illustration: FIG. 212.] [Illustration: FIG. 213.] [Illustration: FIG. 214.] [Illustration: FIG. 215.] [Illustration: FIG. 216.] [Illustration: FIG. 217.] [Illustration: FIG. 218.] [Illustration: FIG. 219.] [Illustration: FIG. 220.] On the upper surface of the top plate are fixed parallel bars chamfered beneath like those of a slide rest, and between these the tool holder slides, the advance of the latter being effected by a screw precisely as in the slide rest already described. In the plan of this instrument, as seen from above, Fig. 218, A, B, are the bars. The tool is seen in position at C, the tangent at D. A scale is attached to the sliding part of the tool holder for determining the size of the sphere. The tool is again seen in position in 219, and detached in 220. In Bergeron's description of the above spherical slide rest the method of using the apparatus is thus described:--"Commence by placing in a chuck a cylinder of some sound wood, and reduce it to a convenient diameter, which should be a little greater than that of the proposed ball. With the gouge work down this, and give it roughly the form of a ball attached to a cylindrical base." This base serves to sustain the ball during the operation, and the form of an inclined plane is to be given to it where it is attached to the ball, as seen in the drawing, to facilitate the passage of the tool. After this preliminary work, place the instrument on the lathe bed, and cause the tool holder to advance by means of a screw (the one attached to the lower slide, not the tangent screw) until, reckoning from 0in., the starting point, the index attached to the sliding part has travelled over the graduated divisions of the scale, so as to denote the size of the ball in its present rough state. Then slide the instrument along the lathe bed, until the tool, accurately adjusted as to height, just touches the ball at the quarter circle. This will be better understood by the diagram Fig. 221, in which A, B, are the lathe bearers; C, the tool in position; D, the ball; E, the chuck or the base of the cylinder. Having previously determined the size of the finished ball, the work may now be carefully begun by clamping the rest underneath the bed, and making use of the tangent screw. Little by little the work is to be reduced, taking care not to cut too near the base on which the ball is yet carried. This base is to be cut away little by little as the tool comes round, and at the last cut the ball will drop off finished, and it is not to be further touched with sand paper or other material. Hence, as it approaches the finish, the tool must be delicately and steadily made to traverse, so as to leave a finished surface as it advances. Bergeron adds certain precautions as follows:--"If the material is very rough from the gouge, so that at any point the tool is likely to meet with such resistance as would endanger the work, such part may be pared down again by using the machine as a common rest for gouge or chisel; for the apparatus once arranged should not be altered nor the fixed tool shifted until the work is done. The tool throughout is to be advanced very gently forward at each turn by means of the screw, which causes the parallel movement, and the tool is to be accurately adjusted so as to be exactly in a line with the centre of the mandrel; it is also to be very keenly sharpened, and even polished." The first impression given by an inspection of the above figures is that the ball would be liable to drop off before it could be fairly severed by the tool. The writer determined to test this objection personally. He selected a piece of sycamore, which is very fit for the purpose, and useful as a kind of medium between hard and soft woods. A ball was turned by hand from this material having a diameter of about two inches. The neck by which it was held was retained of the size of a cedar pencil during the final shaping of the rest of the ball. It was of course not thus reduced until the ball was nearly spherical. Gradually the neck was cut away until it was perhaps as small as the lead of a pencil, yet still the ball retained its position, and the final stroke cut it off truly and tolerably cleanly, E, 212 and 213. It is really astonishing how small a portion of sound wood will retain a ball so turned, but the lathe should not be allowed to stop, else the tendency to hang down or sag would overcome the sustaining power of the fibres. Bergeron states, indeed, plainly, that the process answers satisfactorily, and as a man of large experience his opinion is certainly reliable. Nevertheless, since sand papering or after process is to be eschewed, it does appear to the writer that the final cut would leave a minute portion untouched requiring to be afterwards removed. Not having one of the rests in question the writer's opinion is to be taken _quantum valeat_. The spherical rest more commonly used is that represented in the "Handbook of Turning," since it is necessary not only that the machine should be efficient for turning a sphere, but likewise applicable to the ornamentation of the same by the revolving cutter and other apparatus used in such processes. This and some other forms will presently be described, and also an ingenious adaptation of the ordinary slide rest by means of guide pieces or templets to work of this character. A very good form of chuck for holding spheres during the operation of hollowing them out or forming stars or cubes within them will, however, be first introduced here as described by Bergeron. It will be at once seen how simply and efficiently a ball can be thus held during such processes. [Illustration: FIG. 221.] Fig. 222 represents a chuck for holding balls, A being a sectional view, B an elevation. In the first, _b, b_, represents the body of the chuck, made as usual to screw on the mandrel. At _a_, the chuck is formed with a shoulder like an ordinary box. This part of the chuck is to be hollowed out to fit the ball on which it is intended to operate. On the side of the chuck at _b_, is to be cut a screw of medium pitch. Mounting another piece of wood in the lathe a kind of cover, _c, c_, is now to be made to fit over the body of the chuck like the cover of a box, but hollowed out to the curvature of the ball. A ring of brass or wood of section D being screwed on the inside to the pitch of the male screw on the outside of the chuck will hold the three separate parts of the apparatus firmly together. Let them be thus arranged and finished as one piece on the mandrel. Afterwards drill a hole in the centre of the part which forms the cover, and enlarge it so that its diameter shall slightly exceed that of the openings necessary to be made in the ball for the purpose of hollowing out and forming within it stars, or lesser spheres, box, cube, or other design, at pleasure. In this chuck the ball will be held not only centrally but securely. It is of course necessary to have a chuck specially made for each different sized ball, but when it is considered that such things as these are merely turned as curiosities and to prove the capabilities of the workman, it is not probable that more than two or three sizes of chuck will be needed, and the difficulty of making them is not great nor the necessary expenditure of time, either. They should be made entirely of sound boxwood, and so arranged as to the size of the respective parts that when the ball is inserted and the cover placed on, the latter shall not quite reach the shoulder on the base of the chuck. In the spherical rest of more modern times the principle of that already described is almost necessarily retained. It is figured in 223. The sole A is formed like that of an ordinary hand rest, so that it can be advanced across the lathe bed, and secured by the nut and screw underneath as usual. From this rises a central circular plate, which need not be more than a quarter of an inch thick, but turned truly flat, that it may be parallel with the surface of the lathe bed. From this rises the conical central pin upon which works the plate B, the edge of which is racked to be moved by the tangent screw C. Across this circular plate is securely fixed the chamfered frame D surmounted by the part E which carries the socket and tool receptacle, the details of which will be entered into when describing the rest for ornamental work.[15] [15] The drawing shows a band at X encompassing the screw. This is an error, as the whole upper part, including this screw, is made to revolve by means of the tangent screw. [Illustration: FIG. 222.] [Illustration: FIG. 223.] The method of turning from a pattern acting on the tool has been alluded to. In some cases a similar method is pursued, in which the hand supplies the place of automatic machinery, an instance of this is the application of pattern plates or templets to the small slide rest now to be described, by which not only parallel or spherical work may be done, but the elevations and hollows in moulded work may be followed without difficulty. The pattern plates can be made by the amateur or workman so that not only is no extra cost incurred, but any desired form can be given to the work and as many duplicates made as may be requisite. The simple slide rest itself is represented in Fig. 224. The lower iron or steel frame is rectangular, chamfered underneath, and is cast with a projecting part B underneath to the socket of the hand rest. There is, therefore, no sole or saddle required, and the height is adjustable at pleasure to suit 3, 4 or 5-inch centres. C is a plate of brass, cast with one V-piece similar to D, the second E being removable at pleasure, or both V-pieces or guide bars may be attached by screws. They are attached by two or three screws passing through oval holes in the plate and tapped into the bar, so that a little play to or fro is allowed, by which they can be adjusted to grasp with more or less friction the iron bevelled frame. They are kept up to their places by a pair of large headed screws tapped into the edge of the brass plate and marked _e, e_, in the drawing of the rest. On the top of the brass plate is fixed in a like manner another pair of chamfered bars similar to those of a slide rest for metal, but in the ornamental turning slide rests, where lightness and accuracy are more needed than strength, the parts are proportionally smaller. The frame, for example, may be six inches or six and a half inches in length by two in width, the brass plate two inches square, or perhaps two and a half by two, the longest measurement in the direction of the upper guide bars, between which the tool receptacle will slide. This will be quite large enough for a five-inch lathe, although the measurement may be more or less if desired. If taken as above, the iron frame may be half an inch deep and the face of each side of similar size, leaving one inch between, in which the screw will lie. 224 B shows the under side of the frame with a cross piece to which the part, B 224, is attached. The guide bars for the tool receptacle may be similarly small and light. If the plate is 1/4 in. thick and two in width the bars may be 3/8 in. stuff before being bevelled, the attaching screws can then be 1/3 in. or 3/16 in. in the shank, the heads being large and flat, and not countersunk. It is probable that many amateurs would like to attempt such a rest themselves, hence we have given the above details. We must however, warn them that as the above is for ornamental turning, where accuracy is of the utmost importance, great care must be exercised in the work, and the various parts must be fitted to the utmost perfection. The upper face of the lower frame must be quite level, and the sides quite parallel, and the upper or cross slide must be fitted precisely at right angles to it. Above all, the screw by which the upper part is advanced in either direction requires great precision. It should be made with a fine thread deeply cut, and must fit its nut under the brass plate, D, without shake. The nut itself should be long, and must be carefully bored and tapped; it should be also sawn through its length underneath, to give it a spring, so that it may grasp the screw tightly yet easily, and this will also compensate for wear. This will be understood when it is stated that the milled head by which the screw can be turned is graduated round its circumference, as is also the face of the bed or lower frame of the rest. Hence to give the head a turn, or half, or a quarter turn, must draw the sliding plate exactly the same distance to or fro, at whatever part of the frame it may be at the time. This necessitates all the threads being precisely alike. [We say precisely with a certain mental reservation, for, strictly speaking, perfection is hardly possible, and the skill and science brought to bear upon screw cutting when perfect work has been necessary, as for astronomical instruments, would hardly be credited, so extremely difficult is this part of the mechanical art.] It would be better for the amateur to get the screw and nut cut by Holtzapffel, Munro, or other first-class maker, who has the requisite means and can command the highest skill. Between the upper guide bars are fitted various tool receptacles. The only one which need as yet be spoken of is that which holds the little inch-long tools for ordinary work or for use with the eccentric chuck. This consists of a brass plate bevelled to fit the chamfered bars, on the end of which is a small piece of steel with a rectangular hole and set screw, as seen in the drawing marked X. This plate has a tailpiece of rather thicker metal, through which pass two set screws, which regulate the depth of the cut to be made, their points bearing against the end of the brass plate on which this tool receptacle works. No screw is attached to move this upper slide, but a wooden handle projects from it at right angles to be moved by hand, or a lever Y is made use of. This has two projecting pins, the front one taking one of the holes, 1, 2, 3 of the slide, the other one of a set of similar holes in the top of the chamfered bars. By this the slide can be advanced with ease and great steadiness. We now come to the pattern plates or templets F, alluded to. These are formed of sheet iron about 1-20 in. to 1-16 in. thick, and must be long enough to reach from one end to the other of the iron frame A, underneath which at each end are two holes _a, a_., Fig. 224 B, to receive screws by which the templets are attached by means of the slots, _b, b_. The outer edge, _a_, of templet is the pattern to be copied. The dotted lines in Fig. 224 show a plate in position. The tailpiece of the tool holder to be used has a projecting stud, or is made with a screw with or without the roller seen at H, and this is kept in contact with the templet by the hand or by a spring, so that when the slide traverses the lower frame the tool-holder necessarily follows all the curves of the pattern plate. An inspection of K will make it evident that the projecting screw must be so regulated as to length as to allow the tool-holder to go to the extremes of the projections and hollows. It must therefore in the pattern shown be at least as long as the line _a, b_, Fig. K, and a tool-holder of sufficient length must for similar reasons be selected, or the tailpiece might touch the fixed plate on which it works before the guide pin had penetrated the deepest hollow of the pattern. With these precautions nothing can exceed the ease with which this clever adaptation of the slide rest is made and used, the greatest advantage being that the workman can make his own templets to any curve or series of curves that may be desired. [Illustration: FIG. 224.] [Illustration: FIG. 224B.] At a later page is described a slide rest with the arrangements of the tool-holder somewhat improved, and calculated for the reception of larger tools and apparatus. The little rest here described is, however, very light and useful. HOBLYN'S COMPOUND SLIDE-REST. A compound spherical slide-rest, for ornamental turning lathes, which has been patented by Mr. Hoblyn, Rickling-green, Essex, is capable of turning and ornamenting accurately spheres and any segments of circles convex or concave, either on the surface or cylinder; also, it is stated that by the addition of templates any other curves, not segments of circles, can be turned out, in addition to the work performed by an ordinary compound slide-rest. In our illustrations, Fig. 1 is a side view, and Fig. 2, an elevation of the rest. A is the lower, and B the top plate, C the carriage, and the saddle as usual. The lower plate, of iron, is planed on bottom and sides, and has a longitudinal bevelled slot in the bottom to receive the fastening bolt, so that the plate can be tightened up at any point on the lathe bed. At one end of this bottom plate is a piece raised the whole of its breadth, accurately turned and faced, with a stout turned pin, _b_, for a pivot in the centre. A wheel, _c_, is placed around this raised piece, having any specified number of cogs, and on its top any specified number of small holes drilled to receive two pins as segment stops. The top plate is slightly narrower than the bottom one, and has on its underside a corresponding surface to that raised on the plate A, turned and faced with countersunk hole in the centre to fit on the pivot _b_, on which it is tightened by a screw and washer. The top of B is placed to receive two parallel bars of brass, bevelled on the inner edge, so as to form sliding bars for the carriage C, one bar being a fixture, the other capable of adjustment by tightening screws. The sides are also accurately planed, and on one a tangent screw, _e_, is so fixed as to be put in and out of gear with the brass wheel, _c_, for the purpose of driving the top plate round the pivot _b_. In the raised surface of B, is a countersunk slot forming a quarter circle, with screw passing through it into the bottom plate; by this means the top plate can be firmly fixed at any angle to the bottom plate for the purpose of slide-rest turning. A small pointer, _f_, works clear of the brass wheel in the capacity of segment stop--two small pins being placed in the specified number of holes in _c_. On the opposite side of the screw, _e_, on the top surface, a screw, _g_, works in two standards screwed into the plate through slots in the bar, which works through a traveller, _h_, firmly attached to the carriage, C, and therefore capable of driving the carriage in a rectilinear direction--for slide-rest purposes. This carriage, C, consists of an iron plate _i_, with standard _k_, top plate _l_, with parallel brass bars to receive tool receptacle _m_, the bottom plate and standard being in one piece with the plate, planed side and bottom, so as to slide truly between the parallel bar on B. The standard has its surface accurately turned with a pin in centre to form pivot. The top plate is planed true, bottom, sides, and top, and has a countersunk hole in the exact centre, so as to work on the pin, and tightens up with a large nut. In the plate is a countersunk slot forming a quarter-circle, with screw passing through into the standard, to set the tool receptacle either parallel with B for spherical turning, at right angles to B for slide turning, or at any angle for thick and thin cuts, and similar patterns when used either as a spherical or slide rest. The parallel bars are to be similar to those on B, to enable the tool receptacle to be advanced or retired by screw or lever. This part of the machine can be adjusted for height of centre thus:--The standard _k_ to be a hollow cylinder with fixing screw on one side; the plate _i_ to be made with turned pin on bottom, to fit into standard; elevating screw; saddle as usual, but with the addition of a small hole drilled in one of the sides, and a corresponding one in the side of the lower plate A, so placed that when a pin is fixed into these holes the pivot is exactly central to the lathe centre. [Illustration: FIG. 1.] [Illustration: FIG. 2.] The way of using the spherical rest is thus described by Mr. Hoblyn:--"When altogether, and the point of tool adjusted by means of a square exactly over centre of pivot, it is evident, if the top plate moves round, the point of the tool will still be in the same place; but if we retire the point one half-inch, on moving the plate right round it would describe an inch circle, so that if the centre of pivot be exactly under the centre of the lathe, and we move the rest the half-circle, it will cut a perfect ball (or any part of one, if the cut be less than half a circle) of such size as the distance doubled of point of tool from centre of pivot. Therefore, by adjustment of the lower plate on the lathe bed according to the size of material (this, of course, does not allude to the act of turning a ball, when the centre of pivot must be exactly under centre of lathe), adjustment of carriage from centre according to the size of circle required, and adjustment of tool for depth of cut, we are enabled to turn any convex curve. To turn the concaves, instead of retiring from centre of pivot, it is only requisite to advance the point beyond the centre to the distance required, when the same rules apply as to the convex curves. In turning the concaves, however, it is necessary to turn the plates half-round, so that A and B are in the same straight line, instead of over each other. This enables you to work on any sized piece of wood, the object of the longitudinal slot in the lower plate being to enable you to adjust your previously arranged curve to any sized wood or ivory that your lathe will take, less 2 in., the height of machine. The desired curve having been turned, take out the chisel, and place in the receptacle any ornamenting instrument, drill, eccentric, &c.; advance the point till it touches the work, then set your screw for depth of cut, and work according to fancy. Whatever it is it must be mathematically correct on the curve, as you have not altered it in any way. You then remove your rest to cut the next desired curve, and proceed as before. The best way to execute a piece of work is first to make a sectional pattern of your design, either by drawing or cutting it out with scissors from a double piece of paper, when, of course, both sides come the same, the line where the paper is doubled being the line of centre of lathe. You can then, with a pair of compasses, ascertain with accuracy the necessary size of circle, and the position of centre of pivot to procure the desired curves. You may also produce a very good effect by a combination of two different curves in this way:--Let your ornamental instrument be the universal cutter; working horizontally follow up your curve with it, but, instead of cutting right out on your curve, let the instrument finish of itself in wood previously turned so as to fit its curve, when you get the lesser and greater curves following in unbroken succession. With the eccentric chuck numberless effects of the most curious description may be produced, even work supposed to be only possible with a rose engine. We believe the tool is to be seen at the shop of Mr. Evans, 104, Wardour-street. To turn a sphere by means of a template attached to the slide rest as described, the following adjustment of the rest and mode of proceeding should be followed. A, B, Fig. 225, is the chuck containing the material, H, to be worked into a sphere. Upon this the length, or diameter (equal to that of the template, as will be explained), is to be marked at K, K, which being divided equally by the line L, L, will give the dimensions of the ball as if it were about to be turned by hand. The corners are to be turned off with the gouge, as far as shown, K being equal to _e_ L, and K _f_ equal to K _e_. The outline of the ball will with these measurements not be touched. The angles left may also carefully be removed, but (as shown by the figure) this operation must be conducted with great care. A template must now be made containing a full semicircle, _every part_ of which can be traversed by the stud or screw upon the under part of the slide, or the ball will not be severed by the final cut. It is evident that the traverse of the slide during the operation will be the full radius of the ball, and in this, and indeed all cases of deep recesses, and greatly projecting mouldings, the ordinary tool-holder with tailpiece had better be removed, and replaced with a slide like M, having a pin straight through it to rest in contact with the template. This will preclude the necessity for the long stud or screw spoken of before as necessary when the slide with the tailpiece is used, but the tool cannot be advanced independently of the template as when the other form is used. Fix the rest so that when the top slide is at its central position the tool may stand as in the sketch exactly upon the central line of the ball. Take care that thus placed the tangent-pin of the slide is on the central mark of the template. The long frame of the rest must likewise be parallel with the bed of the lathe, keeping the top slide pressed against the template with the left hand, while the top part traverses the frame under the action of the screw moved by the right hand, the ball will be correctly cut.[16] One or two cautions must, however, be given here, to ensure a satisfactory result. In the first place the cylinder from which the ball is to be made must be exactly of the diameter of the semicircle on the template. H, H is the cylinder to be turned to a sphere, G, G, B shews the position of the tool at starting, the dot on A, the templet, the tangent pin of the slide, Fig. 226. As the work proceeds the tool will take the several positions shown, the dotted lines, D, being equal and parallel. The tool will thus repeat the form of the template. Let the latter remain as before, but let a smaller cylinder be inserted in the lathe, or, which is the same thing, let the tool be now lengthened so as to start at C on the inner dotted line. When the pin, F, has reached K, which should be the axis of the ball, the tool will be at M, quite out of cut. Fig. 227 represents three forms of tool in contact with the ball at two points. The first two will evidently be out of cut at the axial line, as the side of these bevels will then touch the piece to be turned. C is a form that will remain in contact from the diameter to the axial line. The left side of the edge is slightly overhanging the side line of the tool, D. [16] See Appendix. [Illustration: FIG. 225.] [Illustration: FIG. 226.] [Illustration: FIG. 227.] When the part shown has been cut this tool must be removed and a similar tool bevelled in the reverse direction, adjusted by reference to the central line of the ball as before.[17] It is recommended to roughly shape the work with the gouge, and partially to cut it off with the parting tool so as to relieve the tool as much as possible, and when the last finishing cut is to be taken a freshly sharpened tool is to be made use of. It is evident that in the above and similar work the rest may be placed across the end of the cylinder if preferred to turn the _right_ hand hemisphere, but it would have to be moved for the second half, which should be avoided, if possible. The advantage which the circular rest has over the above is due to the fact that the tool and rest once in position, neither has to be readjusted until the work is complete. The slide rest and semicircular template forms, however, if judiciously used, a very serviceable substitute and makes very satisfactory work. Whether or no the reader has a complete rest for spherical work, he should decidedly provide templates to use as above. They are not only useful for turning or ornamenting spheres, but any forms whatever that may be desired, and they possess this special advantage, that when a dome or other pattern has been thus turned with a plain tool the same template used with revolving cutters will enable the work to be ornamented with perfect ease, doing away in a great measure with the need of a dome chuck. Suppose, again, that a number of pieces are desired precisely similar, as a set of pawns for a set of chessmen, a sectional drawing made and transferred to a piece of sheet-iron, and the latter cut to form a pattern plate, will enable the most unskilful to work satisfactorily. Nothing more need be said of the uses of templates, and for the present the subject will be dismissed, though it may possibly be referred to again in a future page. [17] Holtzapffel uses a tool, the plan of which is semicircular, like a small round tool, cutting on front and two side edges; the tool is very narrow and bevelled below. CHUCKS WITH SLIDES AND COMPOUND MOVEMENTS. The first of the chucks comprised under the above head is the oval or elliptical chuck, and it is introduced first in order because it is not essentially a machine for ornamental turning, as are the eccentric and others of this class. There are many plain works required of elliptical section, as bradawl and other tool handles, for which a very simple arrangement is required. The principle of the oval chuck is as follows:--There is an arrangement of slide, by which as the piece revolves it is drawn gradually further from the tool during half a revolution, and in a similar manner caused to approach it during the remaining half revolution, each point in the circumference alternately partaking of such movement; the whole of these points together, which, of course, form the circumference, will become an ellipse. Let D, Fig. 228, be the centre of the mandrel, A, B the direction of the slide moving up and down in a right line, and carrying the work upon a screw in the centre of it. C, E become centres, and may be taken as the extremes, for as the work revolves a succession of centres are formed and instantaneously changed. The figure produced will be the oval shown. To render this, however, clearer, Fig. 229 may be taken, which represents the chuck in its most simple form with separate details of the parts which compose it. A is the chuck with central slider and chamfered bars, as described in speaking of the slide and rest and previous apparatus; B is the slide detached; D, front view of the same. The short arms _a, b_, pass through slots in the back plate as seen at C, which shows this plate with slide removed. Through these short arms pass a pair of adjusting screws; or still better _a_ and _b_ are themselves cross arms or pallets extending the width of the plate as seen next drawing, and in the chuck of Muir which follows. They are merely flat plates of steel embracing the guide ring, so that some point in their inner surface may rest against it during every part of the revolution of the chuck. [Illustration: FIG. 228.] [Illustration: FIG. 229.] The guide ring here alluded to is shown at E, and also at G, fixed in its place upon the poppet. It is in the form of a raised ring with arms, B, C., which are turned at right angles near their ends, and through which pass adjusting screws with conical points. This plate is flat at the back and bears against the face of the poppet, the mandrel nose falling into the central opening E. It is kept in place by the points of the screws falling into conical holes at the sides of the poppet head. At F is a side sectional view of this plate, with its raised and accurately turned ring, H, and at G is seen the poppet with the plate attached, the left arm being dotted to show the position of the adjusting screw. It is this ring and plate which regulate the movement of the slider, and, with it, of the work, the latter being attached to the screw in the centre of the sliding plate, which screw is a counterpart of that upon the nose of the mandrel. Suppose the chuck A screwed to the mandrel, and the ring accurately concentric with the mandrel, in which position, the pallets must touch at two opposite points. In the best chucks there is an adjusting screw to each, by which the contact can be regulated. In this position any object of a circular form can be turned, for the slider remains in one position, and its screw, upon which the work is fixed, is a continuation of the mandrel. But if now the adjusting screws of the part E are turned, the one being loosened and the other tightened, the guide ring will no longer be concentric with the mandrel, and, as the screws of the slider bear upon it, the slider will during its revolution be moved to and fro to a distance regulated by the eccentricity of the guide ring. The combination of this circular motion of the chuck and rectilineal movement of the slider will produce an ellipse, and a stationary tool applied to the work will cut it, into that form. The above simple arrangement of oval chuck suffices only for plain work. The only figures that can be described by its means, upon the cover of a box, for instance, being a series of ellipses of which the longest diameters fall in the same right line, and of which the centres are coincident with the axis of the mandrel, as Fig. 229. [Illustration: FIG. 229.] Even these, however, cannot be done without some compensating arrangement, as the minor axis does not diminish in length at the same rate as the major--hence the ellipses get narrower and narrower until the central one becomes a mere right line. This is referred to again in the ornamental section of this work. [Illustration: FIG. 231.] [Illustration: FIG. 232.] [Illustration: FIG. 233.] [Illustration: FIG. 234.] [Illustration] Combinations like 231, in which the ellipses intersect, cannot be so obtained. Hence the oval chuck is provided with a wheel, either racked to work by a tangent screw or fitted with a spring catch, by which it becomes a dividing plate. This wheel revolves on a central pin[18] fixed to the middle of the sliding plate, and carries a screw of the same pitch as that upon the mandrel to which other chucks can be attached. By this means the axial lines of the ellipse can be varied in direction. This addition is shown in Fig. 232, which is a section, and 233, which is a front view. In the former, A is the wheel, which, as previously explained, should be so arranged as to contain a number of cogs divisible by as many figures as possible; 96 is such a number, being divisible by 2, 3, 4, 6, 8, 12; 72 is also a good number, as it will divide by 2, 3, 4, 6, 8, 9. If the edge is racked and moved by a tangent-screw with divided head a greater range can be taken and finer work done. In this case the face of the wheel can be marked with divisions, and a fine steel pointer, as shown at F, added to count by. The pin B, which is firmly attached to the centre of the slider plate, must be strong, and the lower part at least should be conical. It is drilled and tapped at the smallest end, and when the circular plate with its screw is slipped upon it, a screw, E, the head of which is countersunk into the face of the large screw, retains it in place. The slide, C, has a recess turned to fit the wheel plate, and the latter is cut as shown at X, which ensures a more accurate bearing than if it was left flat on the lower surface. In making this chuck certain precautions are necessary. In the first place, the guide ring fixed to the poppet must be exactly concentric with the mandrel when in its central position; and when it is drawn by the adjusting screws to the right or left the central line must remain parallel with the surface of the lathe bed. To ensure this centrality it is necessary to turn its outer surface when it is in position on the lathe head. So at least says Bergeron; and it is perhaps the best method whereby to ensure the accuracy that is required.[19] For this purpose Bergeron directs the use of a cutter similar to Fig. 234 attached to the mandrel as a chuck, the edge which is on the inside of the bent part at _a_ acting on the exterior of the ring as the mandrel revolves. The screws allow the tool to be advanced closer to the ring as the work proceeds, while they secure it at any desired point. Such a contrivance as this, used merely as a finishing tool to correct any slight error, is no doubt sufficiently satisfactory. The various parts of this and other compound chucks should be first turned separately to near the required size, and accurately finished when in their respective places upon the chuck. Any parts which present a difficulty from the impossibility of retaining them in place while operated upon, may be soldered with tinman's solder, and thus turned, after which the application of moderate heat will detach them, and the fluid solder can at the same time be wiped off with a pledget of tow or cotton waste. As many of our readers may wish to make such apparatus as the above, it may be desirable to add a few directions for the preparation of chamfered edges such as those of the slide and guide bars, the latter of which should be of iron or steel. Let the slide, for instance, be cast as a rectangular plate and the two flat surfaces be roughly levelled with a file. One of these must now be made perfectly true, either by mounting it with solder upon the face plate of the lathe, and levelling it with the aid of the slide rest, which is perhaps the safest plan, or by careful working with the file, using a straight-edge in all directions, and finishing by careful grinding upon a flat stone slab with water, or on a wooden grinder charged with emery and oil. After one side is finished, the opposite face may be similarly treated; but for this the plate may be secured to the finished surface of the lower plate of the chuck itself, and turned with a tool fixed in the slide rest. The edges must now be filed truly at right angles to the sides, care being taken to keep the long sides of the plate parallel. (The short sides or ends will be rounded by being turned true with the edge of the chuck.) The work must now be tested with the straight-edge and small steel square, and any error carefully corrected. Of course, if the reader is the happy possessor of a planing machine, all these operations will be facilitated and accuracy more likely to be ensured. It may here be mentioned that, to supply the want of such planing machine (a want often felt by amateurs who have not mastered the use of file and scraper), Monro, of Gibson-street, has cleverly added a planing apparatus to the ordinary foot lathe, rendering the latter tool complete for all purposes of amateur engineering. [18] This pin should have been shown of a conical not cylindrical form, and much stronger in proportion. [19] This part is always so turned by the best makers. This handy apparatus will be found on a later page fully described and illustrated by a photograph of the machine. The writer has seen it and used it, and can testify to its satisfactory working, as a lathe thus fitted does not run heavier or require greater exertion than when used for ordinary turning. The next step will be the chamfering of the edges of the plate. Let 235 represent the plate in its present condition, with rectangular edges. To produce a chamfer of 45°, draw a line, _a, b_, at a distance from the edge equal to the thickness of the piece. If a smaller angle is desired, the line must be drawn further back. An angle of 30° to 35°, is, in the writer's opinion, better than one of 45°, as the chamfered bars will then have a wider bearing on the upper surface of the plate, tending to hold it more securely down upon the lower part of the chuck. Nothing remains but to file carefully down from the line thus drawn to the lower edge, by no means a difficult operation if care is exercised not to obliterate the mark, or to trespass the least beyond the assigned limit. A template, cut like Fig. 236, of the desired angle, will be a gauge for the edges of the plate, as well as for those of the chamfered bars, and will serve to make assurance doubly sure. The arms which stand out at the back of the slider to embrace the guide ring are not fastened to the plate immovably, but with power of adjustment. A pair of short slots are made in the slider, into which a square projection from the arms fits, and the whole is clamped by a screw, as shown in 237, A, B, and C. [Illustration: FIG. 235.] [Illustration: FIG. 236.] [Illustration: FIG. 237.] A more accurate method is shown in the Ornamental Section for finer adjustment than can be secured in this way, but for a home made chuck the above will suffice and is the easiest plan to carry into effect. To use this chuck, the guide is first arranged, so that its ring is concentric with the mandrel. A mark is generally made upon it, and also upon the lathe-head, by which this position can be readily insured. The chuck is then screwed upon the mandrel, and the arms adjusted, as just described, so as to embrace accurately, but not too tightly, the guide ring. They are then, once for all, fixed in that position by the screws alluded to. A few drops of oil are necessary to lubricate their inner surface and the exterior of the guide, and the latter being withdrawn by its adjusting screws to the desired eccentricity, the work may be proceeded with. A rough piece of wood, however, should always be first turned to a cylindrical form, as an oval chuck being an expensive article is to be carefully preserved, and not exposed to the shocks inseparable from the process of roughing down the work. Moreover, there should always be one or two screws passing through the slider into the back plate, to take away the strain from the chamfered bars, which can be removed when the slider is to be brought into action. Two precautions are here laid down respecting oval turning, which, in all probability, a tyro would not suspect to be necessary until taught by failure. In the first place, at whatever point of the circumference the tool is held, at that point it must remain, or rather, it must remain in the same horizontal line, being neither raised nor depressed. Hence, for all work where accuracy is needed, oval turning should be done with the slide rest. In the second place, when it is desired to place a succession of ellipses one within the other on the face of the work, like Fig. 229, it will not be sufficient to place the tool nearer to the centre for each ring, but the eccentricity of the guide ring must be reduced at the same time; otherwise, when the middle is reached, a straight line will be the result, instead of the proposed ellipse, as already stated. The lathe should not be driven at a very high speed, and the moving parts should be lubricated from time to time. There are other ways of compensating the error produced by the oval chuck, or elliptic cutting frame, which however are so entirely connected with ornamental turning that they are reserved to be introduced into that section. A contrivance for turning ovals invented, and communicated to the _English Mechanic_ by a Suffolk amateur, deserves a place here. It is thus described by the inventor:-- TURNING OVALS, ETC., BY MEANS OF A TEMPLATE. Ovals are generally turned by causing the work to move in and under guidance of an "oval chuck". [Illustration: FIG. 238.] There seems no reason why the same result should not be arrived at by communicating a movement to the rest supporting the cutting tool in the following manner:--Let A, A, be lathe bearers, B, pulley, C, screw of mandrel, D, template fixed thereon, E, friction wheel on the end of bar F, G rest (a board of any convenient width) moving on pivots at H. The friction roller, E, is to be kept in contact with the template by the cord running over the pulley T, stretched by the weight L. The rest will thus oscillate under the guidance of the template, which may be either oval or rose engine pattern, and the cutting tool form the pattern of the template used. There might be other modes of causing the rest to oscillate on the same principle. The lathe would require a slow motion, the same as with an oscillating mandrel. ECCENTRIC CHUCK. [Illustration: FIG. 239] Next in order of the compound chucks stands the eccentric, the use of which is not entirely confined to mere ornamentation, as it is often very convenient to the turner to have the power of shifting the centre of his work. Thus, a _solitaire_ board may be drilled with the necessary cup-shaped holes, or any work of a similar character completed by the help of this chuck without the necessity for constant re-centering. The _general_ work of the chuck in question is nevertheless ornamentation, for which it is peculiarly adapted either alone or in combination with other compound chucks, or overhead apparatus. The sliding plate of this chuck works between chamfered steel bars, the same as in the oval chuck. There is, however, no guide ring on the lathe head to regulate the movement of the slide, and therefore also no necessity for the projecting arms at the back. The slide, in fact, is moved by a screw with a graduated head, similar to those already described. Fig. 239 represents the common form of this chuck, in which the wheel which forms a dividing plate is moved by a tangent screw. The sliding plate is shown slightly drawn out by its screw, the degree to which it is moved being that of its required eccentricity. When the plate is drawn back to correspond with the base plate, the centre will be in a line with that of the mandrel, and any work turned upon the chuck in this position of the slide will be cylindrical. The central screw of all these compound chucks being alike and of the pitch of that on the mandrel, any of the ordinary cup chucks can be used with them to hold the work; or the eccentric chuck can be screwed to the elliptic, cycloidal, or any other in the set, by which means an endless variety of curves can be described. The effect produced by the simple eccentric chuck now described is as follows, the slide rest being used with it as a matter of course. Let a piece of box or other wood be fixed by means of a cup or other chuck upon the screw of the eccentric chuck, and the slide rest with a single point tool be brought in front of it. By means of this the work must be carefully faced, and made uniformly level. A ring A, Fig. 240, may now be cut, which will be concentric with the mandrel. The slide of the chuck being now drawn down by a few turns of the leading screw (the tool and rest being kept in its original position), the centre of the work will thereby be shifted, and the tool being advanced to touch the same, the circle B will be formed of the same size as the first, but necessarily cutting it at two points. Another turn of the screw will enable C, and similarly D, or any number of circles to be successively formed. The centres of these circles will be in a line across the face of the work. The ratchet wheel is added to enable the turner to arrange his circles round a common centre, instead of being thus obliged to keep them in a right line, and it will presently be seen what a beautiful variety of interlaced circles can thus be accomplished. The dividing wheel is, as previously explained, divided on its edge into an equal number of teeth, or racked for a tangent screw and divided on the face and edge. We shall suppose the number of divisions to be 120. Face the work afresh, and, drawing back the slide until the centre is concentric with the mandrel, as at first, cut a boundary circle, A, Fig. 241. Move the slide of the chuck a few turns, as before, and cut an eccentric circle. Now move the dividing wheel thirty teeth, and cut a second, and, advancing by thirty each time, cut a third and fourth, and Fig. 241 will be the result; the centres of the eccentric circles falling upon four points of the inner dotted circle, which is itself concentric with that first made. [Illustration: FIG. 240.] [Illustration: FIG. 241.] [Illustration: FIG. 242.] [Illustration: FIG. 243.] If the same process is followed, but the number of the circles increased, a very neat snake-like ring will be formed, constituting a border, in the inside of which other combinations may be made. In Fig. 242, twelve interlacing circles are shown; in Fig. 243, twelve circles, described upon centres, which lie upon the circumference of a central circle of equal size. This last pattern, when more finely executed, by doubling or trebling the number of eccentric circles, forms the device generally cut upon watch cases, under the name of engine-turned. The best way to _try_ patterns, is to cover the face of a piece of boxwood with paper, using a pencil in the tool-holder of a slide rest instead of a cutting tool. If a softer disc is used instead of box, round pieces of paper or thin card can be fixed upon it with ordinary drawing pins; and if the first pattern is unsatisfactory, a second, and any successive number of pieces, can be mounted, and fresh patterns traced by the same means. It would be mere waste of time to multiply specimens of the patterns that may be executed by the aid of the chuck just described; and, indeed, this could only be done by cutting in the lathe itself the blocks from which such specimens must be printed. For the present, at any rate, the _principles_ only by which such devices may be executed will be given (as above,) and the designs will be left to exercise the ingenuity and taste of the reader. It happens, moreover, that few as are the works devoted to the general principles and practice of plain turning, more than one has been published on ornamentation by the eccentric and other compound chucks, in which a variety of executed patterns appear, of more or less beauty; and in the _English Mechanic_ has lately been printed a selection of exquisite designs by Mr. G. Plant, whose chuck, indeed (to be presently noticed), bids fair to supplant the most simple one now described. The chief recommendation, perhaps, in the latter, is its great simplicity, as it may be made by any amateur sufficiently practised in the use of tools; whereas the geometric chuck is too complicated to permit this. It will be observed, on inspecting the drawing, Fig. 239, that the divisions on the face of the wheel are continued on the side above the part that is racked; this permits them to be seen when the piece of work overlaps the circle of the wheel. The steel point shown at B, answers as an index, either to the surface marks, or to those on the side. The tangent screw is now generally fitted in a small frame, which is itself pinned at one end to the top plate, and kept up to the dividing wheel by an eccentric cam. This is not shown in the drawing; the plan is nevertheless good, as the screw is instantaneously released from gear at pleasure, when the wheel may be turned by hand to any desired position; after which a slight movement of the cam brings up the screw, and all is made ready for work. The eccentric chuck becomes available for such work as shown in Fig. 244, representing the bottom of a candlestick, ringstand, or similar article. In this case the centres of the eccentric work (now cut quite through) are on the circumference of a circle larger than, and outside, the work itself. Instead of cutting through the whole thickness of the stuff the outer circle may remain such, and the blackened part may represent an inner raised surface, when the contrast formed by the sharp edges round the pattern with the smooth circular part will be very agreeable to the eye. To improve still more this design, the outer part may be ebony nicely moulded and edged with ivory, and the raised part ivory; or the same may be alternations of ebony and holly, which will form a contrast almost equally agreeable. A small chisel-ended tool must be made for this work if the whole is in one block, as it will be necessary to leave a level surface upon the face of the lower part. There are an infinite number of designs of similar nature, which will occur to the reader when the principles of the chuck have been mastered, some of which would at first sight appear to have been worked by other means. Fig. 245, for instance, which is but a modification of the last, scarcely looks like lathe work, but can be cut more rapidly this way than any other--of course the fret saw will do similar work, but it would first have to be marked out, and afterwards the marks of the saw teeth removed, whereas the above is cut and polished at once. It may here be observed that the eccentric chuck itself is used to fix the _position_ of the various circles to be cut, whereas the _size_ of these circles is determined by the slide rest. Thus in Fig. 246, while the centre of the chuck is concentric with the mandrel, bring up the tool in the rest and cut the circle F, G, H, of which B is the centre; draw down the slide of the chuck until its centre is at C, leaving the slide rest as it is, and the circle F, E, D, will be formed of _equal size with the first_. Now move the screw of the slide rest so as to draw in the tool towards the centre of the lathe bed without altering the chuck, and the small circle will be the result, whose centre (being dependent on the chuck alone) is the same as that of the larger circle. Bearing in mind this principle, that the chuck determines the various centres only, and the slide rest the radii, little difficulty will be experienced in devising and executing designs. Such is the simple eccentric chuck, of which the use is tolerably extensive; but there are, nevertheless, certain positions in which the eccentric designs are required, which cannot readily be obtained by its means. Fig. 247 is one of these, in which a moment's inspection will show the necessity of two distinct movements of the slide at right angles to each other. Hence a second slide is attached to the first at right angles, much the same in effect as a second chuck screwed upon the first but standing across it. This is the compound eccentric chuck to be subsequently described in detail. There is one drawback to the use of these chucks, namely--their excessive weight, which causes a great deal of vibration in the lathe itself, especially when the eccentricity of the slide or slides is great. An accidental blow moreover from the chuck under the above condition would be very severe. Hence the various cutters eccentric and others, worked by the overhead apparatus already in part described are infinitely more pleasant to use and even more effective and more easily managed. The eccentric chuck can be used in combination with these, and the capabilities of the two will thus be vastly extended, but in this case the chuck is kept stationary while motion is given to the tool, and the defect just alluded to no longer exists. In cutting patterns upon hard wood and ivory a common defect is shallowness of work, the cuts should not be so light as to give merely an effect of a design _scratched_ upon the surface. The cut should be deep and clean, and the tool not only sharpened but polished so as to leave the device boldly executed, the small triangular and other shaped pieces left between the cuts standing up clear and solid. Some patterns, as the shell, which will be presently spoken of, require to be deep at one part and shallow at another. Some devices look best when cut with a point tool with double and others with single bevel to the edge, and the same design worked with different tools will appear almost like two distinct patterns. [Illustration: FIG. 244.] [Illustration: FIG. 245.] [Illustration: FIG. 246.] [Illustration: FIG. 247.] [Illustration: FIG. 248.] The double eccentric is represented in Fig. 248. The part A is the foundation plate, with a projection at the back, tapped to fit the mandrel. B, B, the lower guide bars; K, K, the lower sliding plate. All the above parts are precisely similar to those of the simple eccentric chuck. Upon the face of this lower slide are attached two chamfered guides, C, C, at right angles to the first. They are kept in place by screws passing through oval holes on their faces, and tightened when required by screws, tapped into four little square blocks, D, D. Between these guides slides the upper plate, which carries the screw for chucks, and the dividing wheel as before worked by a tangent screw, G; to either end of which a key is fitted. The leading screws, E and F, which move the two slides, have squared ends projecting both ways, so that the plates can be made to work eccentrically in either direction, which is sometimes an advantage. The chucks do not screw down upon the face of the division plate, on account of their projecting parts at the back; and very commonly a round plate, O, somewhat smaller than the wheel and about 1/4 in. thick is attached to the face of the latter to raise the work still higher, so that the dividing plate can be readily seen. The more compactly, however, the parts of this chuck are made, and the less the work projects from its face the better; as there will be the less strain upon the central pin, and upon the plates and their guide bars when the tools are applied to the work. To be able thus to place in the centre of rotation any given point in a piece of work, whatever may be the form of its boundary lines, is of immeasurable advantage, even though the capabilities of this chuck are confined to objects of plane superficies, it being impossible to reach by its means the side of a cylinder, or the surface of a sphere or spheroid. It is evident that any line upon the face of a box, for instance, whether the latter be square, round, octagonal, or of any other form, may be followed with two movements of the slides, combined with the rotatory movement of the dividing wheel. Thus, a border of interlacing circles may be carried round the edge of such a box, Fig. 248; or, a series of such circles forming constantly diminishing octagons, hexagons, squares, &c., may be thus readily executed. Nevertheless, what was said of the simple eccentric chuck, applies with even greater force to the compound eccentric. It is a heavy piece of apparatus, requiring a lathe with substantial poppets and bed; the whole well braced to the floor and wall, to withstand the excessive vibration caused by the revolution of the apparatus. It was, indeed, in view of this and similar appliances that we insisted in our initiatory paper upon the great importance to the workman, of adequate strength and solidity in the various parts of the lathe itself. In Fig. 249, we give a simple specimen of work to be executed by the compound eccentric chuck. [Illustration: FIG. 249.] [Illustration: FIG. 250.] The compound geometric chuck of Ibbetson, manufactured by Holtzapffel and Co., is a double eccentric considerably improved and of very extensive application. A full description of it is published in a book written by the inventor, in which an immense number of patterns executed by its means is given with detailed directions for their execution. As these patterns are almost essential to a description of the apparatus as exemplifying the working of its several parts, the reader is referred to the book in question, or to a translation of it into French in the supplement to Bergeron's work. To enable the turner to execute patterns on the side of cylindrical pieces a chuck is used called a dome chuck, similar to Fig. 250. A rectangular frame of brass, A, carries a sliding plate C, at right angles to it, the latter having a tailpiece which fits accurately between the frame, and is tapped to receive the finely cut leading screw with divided head, B. A nut at the back of the frame clamps the slide in any desired position. Upon the upper face of the latter is a wheel racked on the edge so as to be moved by the tangent screw, E. This wheel, like that of the oval and eccentric chucks, turns on a strong conical central pin, and has a screw attached of the same pitch as that on the mandrel. The chuck is screwed to the mandrel by the projecting flange, F. The work is thus mounted at right angles to its ordinary position. By this arrangement any point in the side of a cylinder can be brought in contact with a tool fixed in the slide rest, and by means of the graduated screw heads of the latter and of the chuck various devices can be accurately made. This chuck may be used alone or in combination with the eccentric, and the quick revolution of such cumbrous pieces that would be a great drawback to their use is less frequently required, now that the following apparatus has been added to the lathe, and eccentric revolving cutters, with drills and other tools, have taken the place of heavier and more inconvenient apparatus. It is indeed much more convenient in the majority of cases to keep the work itself fixed, and to operate upon it by tools put in rapid motion, because the latter, from their excessive velocity compared with that which can be conveniently given to the material, make better work, and at the same time from their lightness impart no tremor to the lathe while in motion. The cuts thus made are in consequence very clean and smooth, and free from those slight undulations apparent when any vibration takes place in the lathe itself. The different varieties of overhead apparatus have been already described and illustrated, and it only remains to describe more in detail the revolving cutter frame, drills, and other apparatus used therewith. The following pieces fit into the top of the slide rest in what is called the tool receptacle, and are advanced to the work by means of a lever as already described. Fig. 251 is the revolving cutter frame, the spindle of which is put in rapid motion by a cord from the flywheel passing to the small pulley through the medium of the overhead apparatus, as shown in a previous page. For the purpose of cutting _small_ intersecting circles, a forked drill, Fig. 252, or a crank formed drill, 253, will suffice, and if these are made to cut deeply the result will be a succession of hemispherical knobs or beads (these must not intersect). A drill like Fig. 254 will give a knob raised in steps, and it is plain that by cutting the end of the drill to a section of the required moulding the latter may be rapidly executed. The flat inch long cutters used with the geometrical chucks (when the work revolves instead of the tool) are, of course, made of a variety of forms upon the same principle. Cases of these drills and cutters beautifully finished are sold by all the leading dealers in turning lathes and apparatus. It is essential that these tools be kept very sharp, and that their cutting edges should be _polished_ if first-class work is to be done. The difference in the appearance of execution is very evident when the cutter is thus perfect, as every cut bears a high polish, which cannot otherwise be imparted. Nothing can be applied to finish eccentric work except friction with a hard brush, and even this is much better avoided, as rubbing of any kind tends to round edges which should be kept sharp and to obliterate the finer and more delicate lines. It is likewise the best plan to finish with any particular tool all the work to be done by it without removing it from the tool holder for the purpose of sharpening. If, however, this is necessary the following contrivance must be used to insure the precise form which the cutter had at the commencement of the work. This being likewise necessary with respect to the fixed tools for ornamentation, the apparatus requisite in either case will be introduced here, the drawings and description being extracted from Holtzapffel's valuable work already alluded to. [Illustration: FIG. 251.] [Illustration: FIG. 252.] [Illustration: FIG. 253.] [Illustration: FIG. 254.] Fig. 255 is arranged for flat tools of various angles, or drills with single joints. A, is the stand of brass, with two turned and hardened steel legs. To this is hinged at G, by a screw joint, the part K, the upper part of which forms a semicircular arc, C. A second arc, B is fixed at one end to the stand A, and passes stiffly through a mortise at the top of K. The latter can be raised, therefore or lowered at pleasure upon this second graduated arc, and clamped at any angle by the screw H. To the lower part of K is pivotted the tool holder, D, the upper part of which is pointed, and screws as an index upon the arc C, showing the angle at which it is placed. This tool holder is clamped by a nut at the back, which fits the end of a screw seen near the point. The figure below shows a tool holder which fits into the projecting parts of D, and serves to hold the small flat tools. Below is a similar holder, used for round-shanked drills. F is one of three flat slabs upon which the tools are to be ground, there being one of iron, one of brass, and one of hard wood with a flat strip of oilstone imbedded in it, flush with its upper surface. The tool and its fittings are generally arranged in a box with three drawers; these contain the slabs of oilstone and metal, with the powders necessary for grinding and polishing. To use this instrument, the point of D is adjusted to the required angle for one side of the point of the tool. (It is shown at 40 deg. in the sketch.) The latter is then placed in the holder, and made to project until, when the angle of the chamfer is adjusted on the arc B, the part A is level, and therefore parallel to the surface of the grinding plate. The whole thus forms a tripod, the third leg of which is formed by the tool itself. The latter is first rubbed on the oilstone with a little oil. It is then finished more perfectly on the brass slab, dressed with oilstone powder and oil. Previous to this the tool is moved one or two degrees more upright by the arc B. A narrow facet is thus ground, having a dull grey polish. The tool is now carefully wiped clean, and polished with crocus and oil upon the slab of iron. If the point of the tool is central, with a chamfer both ways, the point of the tool holder is first adjusted on one limb of the arc and the tool ground, and then the same adjustment made on the opposite limb, so that the other side of the point can be operated upon. Thus tools of any angle and any bevel may be sharpened to a nicety without fear of altering the original form of the point, and this may be done, if necessary, during the process of eccentric turning, although, as before stated, it is better to fix the tools well sharpened at the commencement of the work, and not remove them until at _least_ one complete set of circles or other patterns have been cut. [Illustration: FIG. 255.] [Illustration: FIG. 246.] [Illustration: FIG. 247.] The instrument just described is evidently unsuited for the drills and bead tools which present a concave edge like 246 A, B, C, enlarged sketches of tools copied from Holtzapffel's work. For these the latter directs to use large or small cones (247) of iron and brass, to be dressed, the first (which is the polisher) with crocus, the second with fine emery and oil, the flat side of the tool being held towards the point of the cone, the bevel towards the thick end. Part of the edge of C must be delicately sharpened by hand, as no guide can be used for the step-like portion of the edge. The cones for sharpening are either mounted in the usual manner, by one or both ends in the mandrel of the lathe, or fitted into the spindle of a small drilling lathe-head, the pulley of which is connected by a catgut band with that of the mandrel of the small lathe-head, being fitted with a tailpiece to fit the rest socket, or otherwise mounted on the lathe-bed. The smaller cones especially require to be driven at a high speed. When larger circles or mouldings are to be cut, these small crank-form drills are no longer available, and are replaced by a very simple, but most effective contrivance called the eccentric cutter, by which any work that is within the scope of the eccentric chuck and fixed tool may be executed with great precision and rapidity. This is represented in Fig. 248[20]--a small oblong frame of brass, about two or two-and-a-half inches in length, and half an inch or so in breadth is traversed by a fine screw, prevented from moving endwise by a collar, as in the slide rest (of which, indeed, this is a miniature). A slide, C, with a little tool holder at the top of it, is moved along the frame by the leading screw, the head of the latter being graduated, and also the upper surface of one or both sides of the frame. The projection A, fits into the end of the drill holder, and is secured by a screw. Circles of a diameter equal to B, B" may thus be cut, and their effect varied by placing tools of any form of edge in the tool holder. Such a tool as A, will thus no longer cut a minute circle forming a hemispherical raised knob, but will form a circular moulding, such as that shown in part at Fig. 249, except when the tool holder is on the middle of the frame and the tool concentric with the mandrel. The single point tools, however, with single or double bevel, are more commonly used, in this cutter, as mouldings can be turned as efficiently with hand beading tools, with or without the eccentric chuck, according to their required position. It may here be mentioned that eccentric work should always be cut on wood of one colour, or on ivory, as the veinings of the richer fancy woods, which are so beautiful in other cases, only serve to confuse the tracery made by the eccentric cutter. Of all woods for fancy work with the eccentric chuck or cutter, nothing equals African black wood. It is, however, costly, and only ranges to a diameter of five inches, as great part is unsound. The rind is hard, thick, and white, similar to boxwood. Next to this for such work stands, perhaps, cocus, or cocoa wood, which is not the tree bearing the cocoa nut, the latter being a palm, which is more like cane in texture. One of the most effective patterns to be formed by the eccentric cutter is the shell, Fig. 250, in which one side, or rather one portion of the circles composing it, is very deeply cut, while the opposite part is shallow. This can be simply effected by throwing the sole of the rest out of the level, by placing a thin piece of wood or metal across the lathe bed, so as to tilt up the rest and place it (with the cutter) in an inclined position. The tool will thus begin to cut at one part before it touches the surface elsewhere, and the desired effect will be readily produced. In using the eccentric cutter great rapidity of motion must be given to it, but the tool must be advanced very carefully, or it will be broken. The lever handle is the best to use for the purpose. Akin to the shell pattern are those in which part only of the circles are cut, leaving an effect shown by the border round Fig. 250. This is produced in the same way as the last, being, in fact, a ring of shells in their initiatory stages. This is a very effective snake-like pattern, when fairly and cleanly cut. When the eccentric cutter is used, it must be remembered that the principle of work is not quite the same as with the eccentric chuck. With the latter it was stated that the size of the circles depends on the slide rest and the position of their centres on the chuck. In the present case the eccentric cutter regulates the sizes, and the screw of the slide rest itself the positions of the centres of the circles, since the part A of the cutter will always be in the centres of the same, and this part is attached to the rest. It will be understood that this remark respecting position of centres only relates to circles lying on the diameter of the work, such as Fig. 251, the distance between _a_ and _b_ will be taken from the division plate on the pulley of the lathe. The way to cut the above, for example, will be as follows:--Place the slide rest so that when the cutter tool is in the centre of the frame it shall be concentric with the mandrel. In this position it will only make a dot in the centre of the work. Turn the screw of the cutter frame until you have a radius sufficient for the centre circle. Set the mandrel pulley with the index in No. 360, put in motion the overhead apparatus and cut the circle, move the screw of the slide rest a few turns (_thus fixing the centre of the second circle_), until you find that the cutter will form the circle cutting the first, and passing through its centre. (_Observe, this being the size of the first, the screw of the cutter frame is not turned._) Cut the circle in question, move the mandrel pulley a quarter round, so that the index is in No. 90, and cut another; repeat the process twice more, and 1, 2, 3, 4, will be cut. The _position of the centres_ of Nos. 5, 6, 7, 8, will now have to be determined as before, by working the main screw of the slide rest; but, as their size is less than the preceding set, the screw of the cutter frame must likewise be turned to diminish them to the required degree. When by these combined movements their position and size have been determined, they must be cut by the aid of the division plate, in the same manner as the last, and so on, till the whole have been cut. With respect to the ratio in which the circles diminish, and the precise sizes of them, no rule can be given, as this must depend on the taste of the operator. The sole object in this place is to show the _principles_ whereby these patterns are to be executed. A good deal of care is requisite in practice, and the memory has to be often rather severely tasked. The best plan is always to try a proposed pattern upon boxwood or paper, before risking it upon more valuable material; and, where it can be done, it is well to write down the numbers to be used on the various division plates. A single false cut, it must be remembered, will spoil the whole work, at a great waste of time, loss of material, and annoyance, only to be appreciated by those to whom such an untoward accident may have happened. The drilling apparatus, without the eccentric cutter, but fitted with a round-headed drill, is used for the production of fluted works, such as that shown in Fig. 252, A and B. The drill being inserted in the end of the spindle, and its point or end (of any desired form, either round, flat, or pointed) being brought opposite one end of the flute, the lathe is to be put in motion as in ordinary ornamental drilling, the mandrel being, of course, held fast by the index and division plate. At the same time that the drill in rapid motion is brought against the work by the lever handle, the screw of the slide rest is slowly turned, and thus the groove or flute is drilled out by the combination of longitudinal and vertical action. The number of flutes in any given size of cylinder is determined, first by a horizontal sectional plan on paper, and regulated accordingly by help of the division plate and index. In making such an article as Fig. 252, it will economise material, whether ivory or blackwood, or a combination of the two, to form it of at least three pieces, making the divisions at C, D. Care should be taken to leave below the bowl, which should be as thin as paper if of ivory, the part C on which the beads are to be drilled. The pedestal can then be screwed into this, and will not penetrate the bottom of the bowl. Ivory may be screwed in an ordinary set of stocks and dies if care is taken not to screw up the latter too quickly. Lard may be used as a lubricant in cutting this material, whether for sawing or drilling. The part with raised mouldings between A and D is ornamented with a vertical or universal cutter, and for greater ease and exactness a template may be used in the slide rest by means of which all the curves of the moulding may be accurately followed by drill or cutter. The minute beads round the edges of the small mouldings are made with two sizes of A, Fig. 246; a little knob is thus formed rising from a hollow. The small knobs used as feet may be rapidly formed by a hand beading tool of semicircular section, similar also to A, Fig. 246. A pin may be left on each, or they may be drilled and attached by small screws of brass wire made on purpose. The following cement will enable the turner to make an ivory bowl for the above ornament so thin as to be transparent; indeed it may be thus made so thin as to bend under the fingers, although such extreme tenuity is not required in the present case. [20] A newer pattern appears on a later page. [Illustration: FIG. 248.] [Illustration: FIG. 249.] [Illustration: FIG. 250.] [Illustration: FIG. 251.] [Illustration: FIG. 252.] Take the finest sifted lampblack and make it into a paste with glue, about as thick in consistency as paint. After turning the ivory tolerably thin, paint this on the inside; let it dry, and repeat the process till sufficient is laid on to form a kind of hollow core, of strength sufficient to support the ivory against the action of the tool. The material may now be thinned and ornamented from the outside. When finished, soak a few minutes in warm water, and then agitate in cold; it will become quite clean as before. By altering the direction of the motion of the revolving cutter, the several cuts made by it will assume a different character, and the work will present a series of hollows scooped out, so to speak. The cutter, 253, being fixed in the tool holder of the top slide, will work vertically only, and produce patterns similar to Fig. 254, of the nature of basket work. This is exceedingly effective, and, as it may be cut so deeply as to penetrate the material of hollowed works, the latter may be lined with red or other bright coloured silk or velvet, and a variety of designs thus worked out. It is very necessary in using the vertical cutters to move the tool holder forward very gently, giving it at the same time great rapidity of revolution. Without this it will at once stick fast in the work. The character of the designs may, of course, be infinitely varied by using cutters of different sections, as in the case of work done with fixed tools with the aid of the eccentric chuck. The same cutters will, in fact, serve both purposes. Fig. 255 represents a tool similar to the last, but arranged to cut horizontally. With this, fluted work can be done: but it is evident that the cord from the overhead apparatus cannot here be directly applied, owing to the horizontal position of the driving pulley. Additional guide pulleys, therefore, become necessary, and, when these have to be arranged, the apparatus is generally modified, and the universal cutter is used, of which one form is shown in Fig. 256, and though it is not so good a pattern as that which is described in a later page, it is nevertheless suited for use with the old pattern of slide rest already delineated. With this the direction of the cuts may be varied at pleasure--they may be perpendicular, horizontal, or radial, and, when the templates before mentioned are added to the slide rest, an infinite variety of devices may be cut upon spherical and curved surfaces, so that the cutter thus modified is fully entitled to its title of "universal." The design, Fig. 258, is entirely the work of revolving cutters and drills used with a template of the required section. It is intended for a lady's workbox, opening with a hinge on the line, _a, b_, and containing in separate compartments the various articles required. It may be made entirely of ivory, lined with red or blue satin, and the flutes round the body may be cut through to allow the lining to appear. In the latter case, however, if the box is of ivory, black velvet may be used to enhance the contrast, and, as the glossy pile would be outwards, a second lining of any desired colour should be added with the best side inwards. The rings for the handles, as for all similar purposes, can be quickly made with the tool, Fig. 259. A hollow piece of ivory being taken, and turned smooth inside and out, one side of the tool is applied, as in the figure, so as to cut half through the work. It is then removed, and the opposite edge applied to the inside until the ring falls off completely finished. It is then cut through with a thin saw or knife, and inserted in the tailed ring or other projection intended to receive it. Handsome works in ivory should always be kept under glass shades. The universal cutter shown in Fig. 256 consists of a plate with chamfered edges to fit the tool receptacle of the slide rest, having near each end small poppets which support the round rod connecting the pulley bearing piece, A, with the part, E, which carries the tool, F, the latter being attached by a small slot and set screw to a cylinder revolving in E, and having at its upper end the driving wheel, C. At G is a circular piece or wheel racked on the edge, and turned by the tangent screw, G. The hinder poppet is rectangular, and has divisions marked upon it on each side of the angle numbered from the apex. The racked wheel may with advantage be similarly graduated. When the part E is vertical the cutter will be in a position to work horizontally, and the pulley support will be vertical. By turning the tangent screw, both the parts move together; but if desired the pulleys can move independently by unscrewing D and L. The angular poppet may be made semicircular if preferred, the degrees being numbered either way from 0" in the centre. When the tool holder is horizontal, or approaching that position, the nut, D, must be loosened, and the pulleys placed so that the cord will not slip off. They may be dispensed with if the apparatus is to be used ONLY for vertical cuts (the _holder_, E, will be horizontal); but if a radial pattern is to be cut, in which the angle is to be constantly varied, the pulley piece must be used and the pulleys re-arranged at D, as required from time to time. There is a somewhat neat and serviceable little apparatus represented in Fig. 259A, to take the place of the slide rest and its revolving cutters, and although its powers are limited, much may be done with it. The spindle A, works through brasses in the poppets, B, B, and is put in motion by a cord from the overhead passing over the pulley in the centre. This spindle, which holds the crank-formed and other drills in a socket at one end, moves freely through the bearings endwise, and is kept back from the work by a spiral spring working against the end of the handle, C. This handle does not turn with the spindle, but is mounted like the handle of a carpenter's brace, or that of an Archimedean drill stock. The whole apparatus fits into the socket of the ordinary rest. A screw should have been shown in the drawing, passing through B towards the pulley, to regulate depth of cut. [Illustration: FIG. 253.] [Illustration: FIG. 254.] [Illustration: FIG. 255.] [Illustration: FIG. 256.] [Illustration: FIG. 258.] [Illustration: FIG. 259.] [Illustration: FIG. 259A.] [Illustration: FIG. 260.] Once fixed by the screw of the latter in its intended position the tool is advanced to the work in a straight line by pressing the handle C, and is released from the cut as soon as this pressure is withdrawn. With different sizes of cranked, forked, or round ended drills, a good deal of ornamentation may be done with this simple tool, which is also useful for ordinary light drilling. By putting in the socket a round ended drill, and using the radial movement (turning the whole round in its socket in the arc of a circle), short flutes can be drilled out deep in the middle, forming basket work similar to Fig. 260, which is exceedingly pretty when carefully executed. There is little difficulty in making drills and cutters, as steel of all sizes in round and square bars may be had at the chief tool shops, especially at Fenn's, in Newgate-street. In making the revolving cutters, however, it is necessary to observe the position of the axial line, which must pass through the cutting edge. After the drill is roughly finished, therefore, it should be mounted in the tool holder with which it is to be used, and carefully tested upon a piece of unimportant work. If in revolving against the latter it leaves a part of the material untouched, the edge is not truly in the centre of rotation. The flat side of the drills are to be diametrical, and hence, as Holtzapffel remarks, these drills can only be sharpened on the end. The latter authority also says most of the drills embrace (in contour of edge) only about one-fourth of the circle, as when the drills are sharpened with one bevel they can only cut on the one side of the centre, and if the drills were made to embrace the half circle the chamfer of the edge on the second side would be in the wrong direction for cutting, and consequently it could only rub against the work and impede the action of the drill. All ornamental cutters and drills should be kept in a box with small separate divisions to fit the shanks, which are all of one size. The points can then be seen and the selection made of any required pattern. CURIOSITIES. Many turners take special interest in the production of objects in the lathe, that at first sight appear impossible to be produced solely by its means. Inasmuch as such works manifest the skill and patience of the artificer, they will always meet with appreciation; and, although otherwise useless, they serve as elegant objects of vertu, and are well worthy a place among the rare ornaments of the drawing rooms. When first the Chinese balls, consisting of a set of hollow spheres one within the other, all exquisitely carved, were brought to England, it was believed they were made in hemispherical pieces, united round the equatorial line with some kind of cement, the joint being carefully concealed. I am not sure that they are made in a lathe in China; but, at all events, they are so made in England, and our home productions almost rival those of that strange yet clever nation. I say almost, because the carving in ivory done by the Chinese is in some respects unequalled, nor do I suppose that work requiring in many instances years of patient industry could be made to repay the cost of manufacture in England. No sooner were these curiosities in vogue here than all kinds of similar impossibilities were manufactured. Stars with from three to a dozen rays made their appearance, enclosed sometimes in similar sets of hollow spheres--the rays projecting beyond the limits of the outer shell--others were wondrously enclosed in cases with flat sides, cubes, pyramids, six, eight, twelve-sided hollow cases, all turned fairly in the lathe, were produced with similar contents, so that the apple in King George's dumpling became a very secondary wonder. The starry inmates were evidently too large for the houses; yet there they were--legs and arms, of course, sticking out through doors and windows, simply because there was no room for them inside. We will penetrate the mystery, commencing with a single hollow ball containing a star of six rays, the bases of the latter standing on a central cube. In the first place a perfect sphere is required, and consequently the slide rest and template, or spherical rest, must come into requisition unless the turner can produce a ball by hand tools alone. Let this sphere, or rather its boundary line, be drawn on paper of full size with the compasses, Fig. 262, A, B, C, D. Draw the diameters A, D, C, B, at right angles to each other. This will give you five points, which on the sphere itself (on which these lines will have to be drawn, including also another, answering to A, B, C, D) are centres of six openings, here represented by the circles, through which the tools have to be introduced to hollow out the sphere and form the star. The points of the latter will be in the centres of these openings. Draw in addition the plan of the central cube, and one ray of the proposed star; next draw an inner circle, here dotted to mark the thickness of the outer envelope. The object of this drawing is to enable you to make a set of curved tools, one of which is shown black at E, and a set are marked on a plate of steel, from which they must be cut out. A close inspection of the figure will show that if ball, Fig. 262, were turning on the point A, A D being its axis of revolution, tools of the given section introduced at D would cut away the material round the point or ray, leaving the latter standing;[21] and this operation repeated at the five remaining openings would entirely free the central cube with its rays according to the proposed design. The tools have to be introduced in order, beginning with the smallest; and although the above remarks will make clear the principle, there are several points to be attended to in practice, and some few accessories are required which will now be explained. It is evident that for every different sized sphere fresh sets of tools will be requisite, which will also vary in pattern according to the intended form of the central base on which the rays stand; a cube or flat-sided solid requiring one tool at least, with a rectilineal edge; spherical or other solids demanding others whose ends are of different section. Hence, in all cases, full-sized plans of the proposed work must be drawn, and special tools designed therefrom. [21] There is an error in the position of this tool, which, thus placed, would not leave the point of the star. Fig. 270 will explain the method better. [Illustration: FIG. 262.] [Illustration: FIG. 269A.] [Illustration: FIG. 269B.] Fig. 269A is introduced to show more clearly the result of the application of the first set of tools, or rather of the first application of the set, as the latter are used throughout. The blackened part will be entirely cut away in this operation, the shaded part meeting it will be removed when the tools are transferred to the adjacent opening, the cuts meeting those first made. Hence the tools need only reach from _a_ to _b_, and can be more easily introduced than if the curved part were longer. Gauges, Fig. 269B, A, must likewise be made of thin brass or tin, that the progress of the work may be examined, and each opening in the sphere should likewise be measured with a gauge, or with compasses fixed to one width by an adjusting screw. The proper chuck for this work is the capped ball chuck already described, by loosening the cap of which any one of the six openings may be brought under the action of the tool, these openings being, in fact, bored out simultaneously with the formation of the star. After the first point or ray of the star has been completed, the ball may be reversed and the opposite ray formed. These are now to be secured by plugs, which are to be turned conical, to fit the opening of the ball at one end, and of a length to rest upon the central cube at the other, being also bored out to fit over the rays, which they should embrace closely at top and bottom, even if not at the other points of its length. (Fig. 269C, A and B.) This is to be repeated as each ray is formed, so that the central star may be held in place until the work is finished, when the plugs are removed, and the star will be entirely detached. The above-named tools being straight on the right hand side of the shank will not form a finished _conical_ point or ray. Hence it is recommended to file away that side, so that when flat upon the rest, the back of the tool may be an exact counterpart of a ray, Fig. 270, A. There is, however, no absolute necessity for this, as the star point can be first made blunt, with perpendicular sides, which can then be neatly finished by a separate tool made for the purpose, and kept up to a very keen edge. The first and smallest of the set of tools here shown, is the one with which the flat sides of the cube are formed, and it must be bevelled from underneath, so as to present a cutting edge on the end. The curved tools should cut on the end and both sides of the crook. [Illustration: FIG. 269CC.] [Illustration: FIG. 270.] [Illustration: FIG. 270A.] [Illustration: FIG. 271.] It is quite possible to make the above in mahogany, but a closer grained wood is much to be preferred, as the tools used--which are held flat upon the rest--are rather scraping than cutting, and mahogany, and fibrous woods in general, cannot be thus worked neatly. Boxwood is, in every respect, the best material to begin upon, ivory and blackwood being reserved until the eye and hand have become accustomed to such work. The whole operation requires great care, and is rather tedious, but the result ought to be a sufficient reward. The external surface may, of course, be ornamented with the usual apparatus, but the star should be left clear and sharp. The edges of the openings should have a light beading, cut with a bead tool, Fig. 271, A and B. GROOVING AND MORTISING SMALL WORK. Amongst the various purposes to which it is possible to apply the lathe, may be noticed the drilling out grooves and mortises, a method used in some of our Government arsenals, for cutting the recesses for the reception of the Venetian lath work in cabin doors. The same method is, of course, applicable to numberless similar cases, although designed for the special object named. The apparatus is shown complete in the drawing, Fig. 272, and the component parts in the succeeding diagrams. A is a kind of compound slide rest, or vertical straight line chuck, having a movement in a direction parallel with the lathe bed at F; while the circular plate being pinned through its centre to a slide, H, can be moved up and down by means of the handle G. This circular plate can be set in any position, and has a projecting shelf or rest to carry the work, which is steadied by guide pins, as will presently be explained. The part F, has a bed similar to that of an ordinary slide rest, which is clamped to the lathe bed by a bolt and nut, as usual. This carries likewise chamfered bars, between which slides the horizontal plate to which the vertical part of the apparatus is attached. This is first a plate with chamfered edges, Fig. 273 A, and a second similar but rather wider plate, Fig. 274 B, with guide bars, likewise chamfered, to slide upon A. From the front of B rises a stout pin, on which the circular plate, C, turns, which can be clamped by a central nut, or otherwise, as in an ordinary compound slide rest. This nut should not project above the general level of the plate. On the face of the latter is, as previously stated, a rest, or narrow metal shelf, D, and pins, _e_, _f_. The plate may be variously arranged in this respect by substituting any kind of holdfast or guide, according to the work desired to be done by its aid. The upper slide is depressed by a hand lever acting on a pin fixed in the sliding plate, Fig. 275; or, if preferred, by a similar lever, with a quadrant and chain, or rack movement. The horizontal slide is worked by means of a stirrup for the foot, with cord attached, acting on a bell-cranked lever, seen in the first figure. To cut the grooves in a bar, for Venetian blinds--as described--the lath to be drilled is attached to a flat strip of thin iron, drilled with holes, Fig. 276 A, as wide apart as the required distance between the grooves. It is then laid against the shelf, and the guide pins are made to enter the holes in the iron. The clamping nut of the round plate is loosened, until the bar is set to such an angle that the grooves to be cut will form vertical lines, Fig. 276. It is then clamped securely. [Illustration: FIG. 272.] [Illustration: FIG. 274.] [Illustration: FIG. 275.] [Illustration: FIG. 273.] [Illustration: FIG. 276.] It is necessary to be able to adjust the piece to be cut, as regards its height, above the lathe bed. This is effected in part by the position of the movable shelf--fixed by pins--and partly by guide or set screws, which regulate the traverse of the slides. Suppose the bar adjusted as in Fig. 276, the groove to be cut being brought opposite to the drill. The set screws--two of which are seen at _x, x_, Fig. 275--acting on the handle, regulate the precise length of each groove. A similar stop, connected with the horizontal part of the machine, regulates the advance of the wood towards the drill, and thus the depth of the cut. Hence it is only necessary to set these carefully at starting--the pins on the guide plate insuring the proper width between the grooves--and the lathe being put in motion, any number of precisely similar grooves can be drilled with the utmost rapidity and neatness. An inspection of the drawings will show what numberless purposes may be served by this simple apparatus, which may be modified in its details, while its principle of action is maintained. The drill should have a chisel and be kept to a keen edge. The lathe should be put in rapid motion, and if the required cut is to be deep, it should be cut at twice. The lower slide should return to its place by means of a spring when the foot is raised, the vertical slide being movable in both directions by means of the slotted part of the handle. NOTE.--The above being taken from an apparatus for a steam lathe, the stirrup action maybe used, as the foot is at liberty. A foot lathe would require a slight modification. In Fig. 275, the depressing handle is shown as if the chamfered bars were fixed to the sole plate, and the plate A, were movable, as is sometimes the case. When made according to the above description, the handle would, of course, be pinned to the fixed vertical plate, A, to which also the stops would be attached, and the pin which passes through the slot of the handle, must project from one of the chamfered bars. Either plan may be followed, but the pattern described is calculated for a stronger apparatus; inasmuch as the vertical plate can be secured more firmly to the chamfered horizontal slide than the mere pair of guide bars--the two might, in fact, be made in one casting, if preferred. ORNAMENTAL TURNING. The slide rest previously described, although applicable to the purposes of ornamental turning, has one disadvantage. It is necessary that the various pieces of apparatus to be used with it should have a foundation plate with chamfered edges to fit accurately between the guide bars. This is often inconvenient, and adds to the difficulty of making, and consequently to the cost of such pieces. In addition to this drawback, it may happen that one of these fittings by being more frequently used becomes more worn than another, so that the guide bars require constant re-adjustment, and their accuracy and parallelism become impaired. To obviate these and similar inconveniences the slide rest is now commonly made like Fig. 277, and a tool receptacle, Fig. 278, is fitted to slide between M, M, and is so arranged as to hold securely the universal cutters and other apparatus required for ornamentation or for plain turning. These are all made with a rectangular bar fitting the longitudinal channel in the middle of the receptacle, and are secured by the following simple contrivance. It will be seen by the drawing that the central channel is widened at A, A, and that a groove or saw-cut B runs along the inside from end to end. This groove is continued in a similar manner on the side next to the reader. Fig. 280 represents an ordinary tool holder, with a rectangular shank A, and clamping screw B, by which the tool _c_ is secured. The part A is laid in the central channel, and a small piece of metal shaped like Fig. 279 is inserted in one of the open spaces, A, A of the receptacle and slid along with its lower flange in the saw-cut until clear of the enlarged part of the channel. It is thus retained, and the clamping screw which passes through its centre is brought to bear upon the piece to be fixed, which is thereby securely held in its required position. Two of these holdfasts are generally used at the same time. If the main bar of the tool holder is not quite thick enough to be clamped, then it is only necessary to lay a small plate below it. By the above simple means, the necessity for fitting each individual piece of apparatus to work upon the chamfered guides is done away. In order to ensure the position of the sole of the rest at right angles to the lathe bed a kind of saddle, A, Fig. 281, is used. This is of cast iron or brass, accurately planed on the upper surface, and has a projection fitting between the bearers of the lathe. The usual holding down-bolt passes through the hole in the centre, securing the saddle and the rest at the same time. The usual arrangement of a kind of double socket, the inner one rising at pleasure by being tapped into the outer, has already been described, and serves for accurate adjustment of the height of the rest. It is convenient, in addition, to have a stop or set screw under the bed of the rest, and a similar one on the top of the socket, so placed that when the frame is swung round it shall stop precisely at right angles to its former position. Thus, if the tool is first required to be used upon the side, and then upon the face of the object to be turned, these two positions are obtained at once, and can, if necessary, be alternated without any re-adjustment of the moving parts of the rest by the aid of the set square. The receptacle-holder is generally advanced by the hand lever, Fig. 279, one pin of which fits into the hole in the guide-bar as seen in the drawing, while the other falls into a short slot _e_, made in the upper surface of the receptacle, or of the piece of apparatus to be used in it. Of course, this arrangement may be reversed, one or both pins being fixed to the rest and its receptacle slide, and the holes made in the lever. Sometimes, however, a slower and more regular movement is required than it is possible to give in this way, and the lever is replaced by the leading screw C, D, Fig. 278, the head of which is removable, and can be replaced by a small winch handle. This screw is tapped into the lug cast upon the receptacle, and its point is of the form shown. The latter fits into a hole in the pillar A, 278, and is retained by a pin, which falls into the groove, D, Fig. 278, and prevents the screw from advancing or receding without carrying the sliding plate with it. The pin being removed, the screw will no longer act in this way, and the slide may be moved by the lever instead. The other screw, E, F, of fine pitch, serves to regulate the advance of the receptacle, and consequently the depth of cut of the tool--a round head with divisions on its edge is attached to one end, which abuts against the pillar B, Fig. 277, which latter has a mark on its top to act as an index. Thus the advance of the tool can be regulated to a great nicety, and successive predetermined and different depths may be reached and repeated at pleasure, as is sometimes necessary. C, C, Fig. 277, is one of a pair of stops which can be fixed by their screws at any two points of the bed of the slide rest. These serve to regulate the distance which the top slide and tool holder are intended to traverse, as in drilling a number of flutes of equal length, and many similar works. They are usually made of gun-metal, the screws of iron or steel, or of a metal called homogeneous, which may be described as between the two, and, being pleasant to work, is worthy of notice. It is absolutely necessary that the slide rest for ornamentation should be made with the greatest nicety. The slides must work equally smoothly from end to end of their traverse. The pitch of the screws must be not only fine, but even and regular, and the screw itself of precisely the same diameter from end to end, else it will work loosely through its nut in one place, and jamb in another. It is extremely pleasant to feel the exquisite smoothness and oiliness, for no other word will express it, of the movements of sliding parts in the workmanship of Munro or Holtzapffel, especially if compared with inferior work. _Good_ amateur's work indeed is often far superior to that which is sometimes advertised, and perhaps a few hints may not be out of place here, relative to the construction of this necessary addition to the lathe. [Illustration: FIG. 277.] [Illustration: FIG. 279.] [Illustration: FIG. 280.] [Illustration: FIG. 278.] [Illustration: FIG. 281.] [Illustration: FIG. 282.] First of all, the frame of the rest must be accurately at right angles to the spindle, which fits into the socket. These should, therefore, be turned together, supposing the amateur not to have a planing machine. The whole may be mounted as Fig. 282, where A represents the carrier plate or chuck; B, the driver, the tail of which should be as long or nearly so as the frame from _c_ to D; F is the side tool to be fixed in the slide rest for metal. The effect of this arrangement is to plane the face of the slide with transverse strokes instead of lengthwise. It may be afterwards finished and polished with oilstone powder on a flat slab of planed iron. When the face is finished, the whole must be reversed, the pin of the carrier plate will bear against the frame, which thus acts as a driver, and the spindle must be turned. In this way accuracy is ensured if the slide rest used is carefully set. The chamfered sides of the slides are difficult to work with the file, but may be so done with care, and with a template of the desired bevel as a guide. The great secret is to take plenty of time, not to press too much upon the file nor to move it too quickly over the surface; fine even strokes, especially towards the finish, must be given, and a final polish with oilstone powder and oil used on a piece of a stick. In turning the screw a back stay must be fixed opposite to the tool in the slide rest to insure the contact of the cutting edge without bending the work. Presuming that the screw will be cut with stock and dies, it may be stated as a caution that the latter must not be tightened except at the commencement of cutting the thread deeper. The return of the tool by a backward motion (or unscrewing), should not be used as a cutting action, and therefore, should be carried on with the dies in the same position which they had during their descent. At the beginning, therefore, of each downward movement the dies must be tightened and oiled, and they must not again be touched till the bottom of the screw has been reached, and the upward movement also has been completed, so that they have arrived again at the starting point. If tightened at any other time the screw will be either conical or of a wavy section, either of which forms would be fatal to its use. The castings for such a rest should be of malleable iron, if possible, as being much more easy to work; the guide bars may be of gun metal, as also the chamfered bars, which work on the main frame. This will give a more finished appearance, and will on the whole be more durable and satisfactory. THE ECCENTRIC CUTTER FRAME. One of the most useful tools for ornamentation, especially of plain surfaces, such as the top of a box cover, is the eccentric cutter, Fig. 283. The shank, A, lies in the receptacle holder of the slide rest, and is drilled throughout to receive a steel spindle, carrying at one end a double pulley, B, to receive the cord from the overhead motion, and at the other frame, E, with its leading screw, of which the movable milled and graduated head is seen at H. This frame has one surface, level with the centre of the main spindle, which is cut away as shown, and, consequently, as the point of the tool is on its flat side, which latter rests upon the frame (the bevel being below), this point can, by the tangent screw, be brought into a line with the centre of the main spindle, so that when the cord from the overhead is passed round B, the spindle revolves with great rapidity, and the point of the tool, K, in the position described, makes a simple dot. By turning round the milled screw head, H, either by the thumb and finger or by a small winch handle, fitted on the square part beyond the head of the screw, the tool holder, D (which is in one piece with the nut of the leading screw), is made to traverse the frame, and the tool will cut a circle small or large according to the eccentricity thus given to it. In Fig. 285 D, is the tool holder on the front of the frame; C, the end of the spindle; L, a bell-shaped washer, which is acted on by the small square-headed screw, drawing D towards the frame and clamping the tool. The whole is in the figure of full size. The tool holder is in one piece with the nut, through which passes the leading screw, and which is continued as a screw for the action of the bell-shaped washer and tightening nut; hence it is necessary to allow a degree of play between the nut and leading screw, to prevent bending the latter when clamping the tool. This is effected by filing off the threads in the nut at the top and bottom, to render the whole slightly oval. The remaining threads suffice for the action of the leading screw: a very slight degree of play in the required direction will be found sufficient. The powers of the eccentric cutter frame will be found sufficiently extensive to make it a most serviceable, perhaps necessary, piece of lathe apparatus. If it cannot be said absolutely to supply the place of the eccentric chuck, it has nevertheless the advantage of great lightness of construction, lowness of cost, and ease of manipulation. The weight of the eccentric chuck, whether single or double, as of all chucks in which sliding plates are used, is a sad drawback to their value--a drawback unfortunately beyond remedy, and specially felt when the slides are drawn out to a great degree of eccentricity. Combined together, these two form a _compound_ eccentric chuck, and in this way are capable of nearly everything in the way of eccentric ornamentation. Where the _chuck_ is not to be had, it is by all means advisable to procure the cutting frame, for which the writer confesses a great partiality. It appears, indeed, to him a far more rational proceeding, as it is also now of extensive application, to act upon fixed work by revolving or moving tools, instead of proceeding in the contrary way; and all these little tools used with the overhead apparatus are so lightly and elegantly constructed, and so well adapted for the parts they have to perform, that the originator of them (_native talent devised them_), deserves to be well and lastingly remembered; instead of which it is doubtful whether his name is even known. (_Sic transit_ is a quotation too stale for this work.) [Illustration: FIG. 283.] [Illustration: FIG. 285.] [Illustration: FIG. 285B] To cut circles deeper in one part than another--the shell pattern, for instance--with this tool, it is not necessary to alter the level of the sole of the rest, as it is when the eccentric chuck is used with a fixed tool, as it suffices to set the rest itself at an angle, by moving it round in the socket, so that the revolving tool should touch the face of the work sooner at one point than at an opposite one. In the same way the work may be considerably undercut on one side of the circles, by giving the angular set to the rest, and placing a tool in the holder, with a point of the form shown at 285 B. There is nothing prettier than this undercut work when well and sharply done, for which purpose the tool should not only be rendered keen on the hone, but burnished and polished on the brass and iron slabs already described. The following remarks on the work of this cutter frame on flat surfaces only, will be useful to the reader in designing and working out the various combinations of circles, intersecting or otherwise, which it is calculated to produce. On a surface represented by 286 A, the line of circles, _a, a_, is on a diameter, and, supposing them to be described by the eccentric cutter (or by a simple double-pointed drill), their centres are obtained by means of the leading screw of the slide rest, moved the requisite number of turns between each cut, while the work is retained in a fixed position on the mandrel. But if the line of circles is on such a line as _b b_, above or below the centre, and consequently not on a diameter, it is plain that no movement of the slide rest or cutter, or both, can avail to place them in position, except with great difficulty and tedious working with the division plate of the lathe and the screw of the slide rest. Hence the eccentric chuck must be brought into play, and being fixed with its slide in a vertical position, the screw is turned and the work is lowered thereby until the line _b, b_, is on a level with the point of the tool. The eccentric cutter or double drill will then suffice to work the row of circles. When the centres of the circles are themselves on parts of the circumferences of other circles, the division plate of the lathe or of the eccentric chuck will be called into requisition, according as these circles are concentric with the mandrel or otherwise. In Fig. 286B, the curved lines are parts of circles of equal size with that representing the surface of the work, and their centres lie on one and the same diameter, viz., at opposite extremities of the line, _a, b_. Being thus eccentric to the work, the division plate of the chuck is used to arrange the intersecting circles of the pattern--its slide having been first drawn down, until the centre of the arc to be worked with circles is brought opposite to the tool. The work will be in position when, on turning the mandrel slowly, the cutting point of the tool passes across its centre. The division of the original circle is in this instance into four parts, two of which are thirds, and two sixths of its circumference. The arcs of circles are also lines equal to thirds of the circumference of the work. It is well to remember this division of a circle by other equal circles described round it from points on its circumference, these circles passing through the centre. The original circle will in this way be divided, as shown at C, into six equal parts. To produce it with the aid of the eccentric cutter is easy. Set the tool of the cutter first to the centre of the work, so that on revolving it will make a simple dot. This should always be done, whatever pattern is subsequently to be cut. Fix the index of the division plate of the lathe at 360. Move the screw of the slide rest until the point of the cutter, on being advanced, rests on the circumference of the circle previously cut upon the work, or on the circumference of the work itself, if the divisions are to reach the edge. Screw back the _tool_ (not the rest) until its point reaches the centre of the work and cause it to revolve so as to cut one arc. Move the lathe pulley forward to 60° and cut a second arc, and so on, advancing 60° each time, and the figure will be cut. This division of the circle will form the groundwork of many handsome patterns. When the arcs thus formed are intended merely to be the lines of centres, and not themselves to form integral parts of the pattern, they should, nevertheless, be marked with a pencil in the tool holder, if possible, as there will be less liability to error in working the proposed pattern. In the present advanced stage of the art of turning, mere surface work done by the eccentric cutter is rather apt to be despised, owing to the extended powers of Ibbetson's or Plant's geometric chuck; but, valuable as the two latter are, they are necessarily so costly that few can obtain them, whereas the little cutter frame is comparatively cheap, and it is really capable of very exquisite work in skilful hands. [Illustration: FIG. 286A] [Illustration: FIG. 286B] [Illustration: FIG. 286C] SEGMENT ENGINE. Fig. 287. In very many cases of ornamentation it is required that the mandrel, instead of making an entire revolution, should stop at a given point in both directions, so that, for instance, the turner should be able to move it 60, 80, or 100 divisions to and fro, with the certainty of its not advancing beyond that distance. This is effected by the racked and divided brass wheel B, fixed on the mandrel against the small end of the pulley. This wheel is sufficiently thick to allow of racking part of its edge to be acted on when necessary by the tangent screw, and leaving the other part for divisions, which are generally seventy-two in number, and marked in figures at every sixth division. On the other side of the plate are a number of holes drilled through its whole thickness to receive stop pins, Fig. 289, P, which are sawn through as shown, that they may spring, and fit the holes tightly. There are seventy-two holes corresponding with the divisions. These pins are about 3/16ths of an inch diameter, generally with flattened heads, and a hole through them to receive a pin to aid in removing them. The holes are sometimes made in the edge, instead of the side of the segment plate, but the latter is the best position. At Fig. 288, T, is seen the interior part of the poppet, with a piece of brass let in, and fixed securely, in which are inserted two screws, against which the segment stops abut, and prevents further rotation of the pulley. Side by side with this latter piece is placed the frame which carries the tangent screw. It is shown at Fig. 289. This frame is not fixed to the base of the poppet, but pivotted at _e_, between two short standards screwed into the poppet for that purpose. When not in use, the whole frame, therefore, drops down towards the front, but it can be raised by the small cam, K, Fig. 289, so as to gear with the worm wheel. In many cases the latter is not used, but the pulley turned by hand. The screw, however, gives a steadier and more easily regulated movement, essential in delicate operations, and sometimes convenient, even when the stops do not require to be inserted. The use of the cam, acting on the frame which carries the tangent screw, is now generally followed in the eccentric and oval chucks, and also in the dome chuck. It enables the workman, by throwing out of gear this part, to turn the worm wheel with the fingers, to set it at the required number on the division plate, a slow process when effected by the screw. [Illustration: FIG. 287.] [Illustration: FIG. 289.] [Illustration: FIG. 288.] HOLTZAPFFEL'S ROSE CUTTER FRAME. Among the newer devices for ornamental turning, must be mentioned the rose cutter frame of Holtzapffel and Co., an ingenious adaptation of the principle of the rose engine, without the drawback of cumbersomeness and costliness. It works like the ordinary eccentric and other cutters by a cord from overhead motion. The apparatus is represented in Fig. 290, and its various parts in Fig. 291, &c. [Illustration: FIG. 290.] [Illustration: FIG. 294.] [Illustration: FIG. 291.] [Illustration: FIG. 293A.] [Illustration: FIG. 293B.] In the first of these figures, A is the shank, fitting the receptacle of the slide rest, and drilled to receive a hardened spindle, at one end of which is a worm wheel, turned by tangent screw B C, and shown again at A, B, C, Fig. 292. By this are turned the parts beyond K, namely, the frame D, carrying the tool, as in the eccentric cutter, adjacent parts S, representing chamfered bar, P, back plate, and O, which is a round piece in one casting, with the back plate, and having a hole through it for the coiled spring seen between O and N. All these are secured to the spindle, and turn together as one piece with it. Fig. 291 is a front view of these parts. H is the back plate of brass, with steel chamfered bars on its face, E, E, as in the eccentric chuck. Between these slides the plate, D, D, to the face of which is attached the long steel frame, carrying the tool holder. Close to the letter H, it will be noticed that a slot is cut in the back plate, through which projects a hard steel pin, screwed into the back of the sliding plate. This is seen at O, Fig. 290, and is attached to one end of a coiled spring, the opposite end of which is secured to a pin fixed in the back plate of this part. The pin O, is thus kept in contact with the edge of the rosette or pattern plate, K, and, as the whole turns with the spindle while the rosette is fixed, the pin, or rubber, is compelled to follow the undulations of the pattern, the motion being, of course, communicated to the tool. An inspection of Fig. 294 will show the arrangement of the parts on which the rosettes are fixed, and which is capable of turning, but does not, unless the tangent screw and wheel, H, are brought into requisition, as will be presently explained. The end of the main shank of the instrument is round, as seen at C, the worm wheel B being screwed fast, by four small screws, to the end of the square part of the shank. Upon this rounded end fits what may be called the sleeve E, to which is fixed the tangent screw, and on which also are placed the rosettes. The latter have a large central hole, Fig. 293, A and B, and fitting closely beyond the screw F, F, of the sleeve, and, being prohibited from turning upon it by a small key or feather, are secured by a screwed ring or ferrule seen at L, Fig. 296, the edge of which is milled. At F, Fig. 291, is seen a short stop, or set screw, the head of which is divided into ten degrees. By this, the rubber is prevented from penetrating to the bottom of the undulations on the edge of the rosette, and, if it is allowed only just to touch the summits of them, the tool will cut a circle. Thus, as the screw stop can be accurately set, one rosette will produce at pleasure graduated waved lines, the waves growing less and less undulated as the centre (or circumference) of the work is approached, giving a most delicate and chaste pattern, and _chased_ it certainly is. Another variation of the pattern producible from any rosette results from the frame of the tool holder being extended beyond the axis of the spindle in both directions. When the tool is on that side of the axis nearest to the rubber pin, the undulations of the rosettes will be so followed as to produce their exact counterpart on the work. When the tool-holder is on the other side of the axis, the undulations become reversed, the raised parts of the rosettes producing hollows and _vice versa_. It may here be mentioned that in the case of the rose cutter, eccentric, and universal cutter, and similar apparatus, the screw heads carry ten chief divisions and ten smaller divisions. The screws are cut with ten threads to the inch, so that one turn advances the slide, or the tool, or wheel as the case may be, one-tenth of an inch. One large division, therefore, produces a movement equal to one-hundredth, and one small division one two-hundredth of an inch. If the screw is small it is generally cut with a double thread equal to one-twentieth of an inch. It is evident that in addition to the movements of the various parts of the rose cutter, the turner also has in his power those of the slide rest, and of the division plate on the lathe pulley, by one or both of which further complications become possible. Six modifications of pattern produced from one rosette alone are shown in Holtzapffel and Co.'s catalogue, and these may be further multiplied according to the taste and skill of the operator. It is not possible to apply rapid movement to this rose cutter, else the rubber would probably miss touching the rosette in places; hence the tangent or worm wheel is used to give motion to the central spindle. An end view of this is given in Fig. 292. The object of the other tangent screw is, to move the sleeve and therewith the rosette at pleasure, so that the higher parts of the undulations in the second cut may, if desired, be arranged to meet the lower parts of the same in the first cut or to fall intermediately. The effect of the gradual shifting of the rosettes in this way is perfectly marvellous, and the writer much regrets that he is unable to supply specimen plates, as he is not in possession of the rose cutter. In the end of Holtzapffel's latest edition of his catalogue are several such specimens, but without any drawing or description of the instrument, the cost of which is moreover omitted. [Illustration: FIG. 292.] The centres of circles cut by this eccentric tool will be always regulated in regard to position by the slide rest, because these centres are, as explained, always in a line with the centre of the spindle. Hence, to place a circle in any desired position, it is only necessary to determine its centre, and, after drawing back the tool by means of the screw till its centre runs truly as a mere drill, turn the screw of the slide rest until the point touches the required spot. UNIVERSAL CUTTER FRAME. This is represented in Fig. 284, in its latest improved form. It consists of a shank, A, which fits the tool receptacle, and is bored throughout its length for the reception of a central steel spindle, to which is securely attached at one end the worm wheel, G, acting as a dividing plate, and at the other the crank-formed frame, B, C, with its small poppets, D, D. These are sawn lengthwise, and thus spring upon the centre screws, which pass through them and carry the revolving cutter spindle, K, L, M, in the centre of which is a slot to receive the tool, the latter being clamped by the tightening screw, L. There are certain points to be attended to in the construction of this instrument, which must on no account be neglected. In the first place, the screws which pass through the poppets must lie in the line which would bisect at right angles that of the main spindle in the same plane. A line, in fact (as dotted), passing from screw to screw will pass across the centre of the end of the spindle. In the next place, when the tool-holder, with its pulleys, is in place between D, D, this line must be even with the _top line_ of the central mortise, H, for the _point_ of the tool is level with its upper surface, it being bevelled below; and it is essential that this point be capable of being so placed as to form a continuation of the centre of the main spindle. At E, E, are shown two of four thin pulleys. The two front ones are removed to show the poppets. They should not be made thicker than necessary, in order to avoid their interfering with the action of the tool. Either pair will be used with either pulley, K, K, according as the right or left side of the instrument is the highest, for, as will be explained, the cutter frame is used at all angles between the horizontal and the vertical lines, the cuts being consequently inclined in either direction, left, or right, at pleasure. The centre screws and points of the tool spindle must be carefully hardened. Before commencing to use this cutter, it is necessary to test the centrality of the point of the tool. Place the latter in its holder. Let the part C of the instrument be turned till vertical; cause the tool to revolve and to cut a light line or scratch on the face of the work. By means of the tangent screw cause C to become vertical in the opposite direction, so as to bring the other pulley upwards, and with the small screws in the poppets set the revolving tool holder, till the tool falls exactly on the line first made. It is, of course, understood that the line in question passed through the _centre_ of the work. If in both positions of the tool the central point is passed through, the cutter tool is correctly placed. The poppet screws are for this purpose specially, though sometimes used to place the cutter purposely above or below the centre of the work. Compared with the old form previously given, this pattern of universal cutter is very superior. [Illustration: FIG. 284.] ROSE ENGINE. The rose engine, as hitherto constructed, has not been entirely supplanted by the neat little apparatus already described, but is still used almost universally by the watch case makers; and its construction differs little, if at all, from that described by Bergeron; although the slide rest used with it is somewhat modified and improved. There are two kinds of rose engine, in one of which the mandrel with its poppets and fittings oscillates between centres fixed beneath the lathe bed; while in the other, the frame carrying the slide rest is thus movable, the mandrel head remaining stationary as in an ordinary lathe. In both cases the mandrel is allowed a to-and-fro or pumping movement in its collars; as the rosettes used are cut upon the face as well as upon the edge; and the rounded parts of an article can be operated on as well as the plane surfaces. The second pattern, in which the poppet remains a fixture, will be first described, because it is capable of being applied to an ordinary lathe for surface work, and if the lathe has a traversing mandrel, it can be completely fitted for rose work. The drawings and description annexed are from Bergeron's work; but the slide rest there represented, and arrangement of screwed mandrel, are omitted as obsolete:-- A strong iron frame, A, A, Figs. 295 A, 295 B, and 296, is made with one of the ends carried up and branched, so as to embrace the mandrel and rosette; which latter is attached to the back part of the chuck which carries the work. The top of the frame is double, so as to form of itself a lathe bed of small dimensions, upon which an ordinary slide rest can be fitted. It must, however, be used with a short socket, or it will be too high; as the top of the frame alluded to stands slightly above the level of the bearers. B, is a point of hardened steel which fits into a conical hole in the bottom of the lathe poppet, or (if this is not long enough to reach a good way down between the bearers) into a piece of iron arranged for the purpose similar to that now to be described, and which is again shown in Figs. 297 and 298. This is a kind of poppet in a reversed position, the clamping nut and screw being above the bed, and the head with centre screw below. The frame lies, therefore, between the mandrel head and this reversed poppet, or between two of the latter, and oscillates upon their centres whenever the projections or depressions of the rosette compel it to assume such motion. [Illustration: FIG. 295A.] [Illustration: FIG. 295B.] [Illustration: FIG. 296.] Fig. 299 is a section of the chuck which carries the rosette, the latter being shown in position. A, is the body of the chuck; B, the inside screw to fit the mandrel. On the outside of this part are a few turns of a somewhat finer thread, beyond which a plain part is left next to the flange, C, and on this the rosette is placed, and is clamped by the nut, cut outside into beads, or milled, or left plain and drilled for the insertion of a lever pin; this nut is marked D in the figure. It will be seen to lie within a recess formed in the face of the rosette, E. The latter is shown in Fig. 300. A, is the recess just alluded to; B, C, the pattern on the face and edge; D, the large hole in its centre, allowing it to be slipped on the back of the chuck. It is prevented from turning on the latter by a pin, which fits into the small hole, F. From the front face of the chuck rises a conical pin, G, similar to that on the eccentric chuck, over which fits the circular division plate, I, with its projecting screw, H, to hold the ordinary chucks. This plate is recessed at the back, leaving a mere ring of metal, _e, e_, which fits a corresponding circular groove, and secures the steady movement of the plate, which is fixed by a conical washer and screw, as seen in the plate. This division plate is formed with cogs, into which a stop falls, as described, when treating of the eccentric, but the divisions are differently arranged, the cogs being divided into sets of eight or ten teeth. Let the whole circumference be first divided into six equal parts, and, beginning at the first division, cut six or eight teeth, as if the whole circle were to be divided into 60. Pass to the second portion, and cut eight teeth, as if the circle were to be divided into 72. Let the third carry eight teeth, with a pitch of 80 to the circle; the fourth a similar number, with a pitch of 84; the fifth 96; the sixth 100 to the circle. These must be cut with the same cutter, so that the spring click, or stop teeth, may fit any of the six sets. There will be several undivided spaces, which are to be left plain. The several sets are to be marked in numbers, so that the pitch may be discovered at a glance, and the teeth in each being so few will hardly require separate numbering. The part of the apparatus which carries the rubber--that is to say, the heads of the branched part of the swinging frame, are made flat on the top, which projects on three sides, forming small tables on which the actual holder or clamp can be fixed by a turn of the screw, X, in the first figure. The rubbers are merely flat pieces of steel, with edges sufficiently sharp to penetrate to the lowest depths of the undulations and recesses on the rosettes, but rounded off and polished, so as not to cut and damage the softer metal against which they act; other materials have been tried, as ivory, and the harder tusk of the hippopotamus, but hard steel is most generally preferred. It is, of course, necessary that the rubber press with some force against the rosette, which force should, moreover, admit of being regulated at pleasure. This is effected by a spring of steel under the lathe bed, to the end of which is affixed the arm, W, which has a ring handle nearest to the operator, and is perforated with a row of holes from end to end. This arm is flat, and falls into a fork at the end of the tail piece, Y, which is seen in the second figure attached to the centre of the lower bar of the frame. A pin passes through holes in this fork, and through one of those in the arm. By this arrangement it is easy to regulate the force which the spring shall exercise, as this will be increased by moving the pin nearer to the spring, and diminished by placing it in a hole nearer to the ring handle. In forming the rosettes great care should be exercised to make the corresponding parts agree. The depth of similar hollows must be precisely equal, and elevated portions intended to match, must do so with great accuracy. Supposing, for instance, a rosette to be made with ten elevations and ten recesses, all of equal curves. If these are accidentally unequal, and it is desired to arrange a set of these waved rings one within the other, so that the depressions of the one shall be opposite to the elevations of the other, or so that this effect shall take place gradually--if the curves of the pattern are unequally cut the several portions of the device will not tally, and an irregularity will be produced of disagreeable appearance; an inspection showing at once that such irregularity is not part of the device, but unintentional and erroneous. This leads to a consideration of the division plate of this rose engine, and an explanation of the object of its peculiar construction. The pattern of the rosette is, as it were, in sections; either similar elevations and recesses are alternately repeated, or there may be a variety of such, extending over a part of the circumference, and forming a certain complete device, which may then give place to a second pattern, extending a similar distance; and these two may alternate regularly round the circumference. Each of these sections must be of precisely similar length, and the repetition of the pattern must also be precisely similar, for the reason stated above. [Illustration: FIG. 299.] [Illustration: FIG. 300.] [Illustration: FIG. 297.] [Illustration: FIG. 298.] It is evident that all possible alternations of the device or set of devices may be obtained by means of six or eight notches of the division plate; for, by moving it forward to that extent, the whole pattern may be compassed. In treating of the second form of rose engine, and of the method of using it, this will again be adverted to, and illustrated by an example. Hitherto we have spoken only of the use of the pattern on the edge of the rosette, but, as already stated, it is frequently repeated on the face, and by this means it becomes easier to work upon the outside of a cylindrical piece, as well as on the two ends. Patterns thus cut on the face of a rosette tend, of course, to move the mandrel to and fro in its collars, which is only possible when the lathe is made on the plan of a screw-cutting or traversing mandrel lathe. The spring which keeps the rubber in contact with the face of the rosette is shown at P. The head on the top of the arm, which forms the clamp or holder of the rubber, must be turned round to face the rosette, or a separate rubber must be used, which passes through the clamp at right angles to that used in surface work, and the frame must be prevented from oscillating by a stop which fits between the bearers of the lathe, and embraces the upright side of the frame. The top of the slide rest must be turned round, or a side tool used. In this case, the rest and frame with its rubber become fixtures, as in ordinary turning, the mandrel and work being alone moved in correspondence with the pattern on the face of the rosette. It would indeed be much better to do away with the frame altogether, fixing the rubber to an upright pedestal mounted on the lathe bed, and using the slide rest in the usual way, were it not that in general the work is constantly being varied, the side and face being worked in turn--and the apparatus is rather cumbrous to remove and re-mount often. It is, nevertheless, easy to finish the ornamentation of plane surfaces first, and then to remove the frame altogether, and substitute a fixed rubber, as stated. The rose engine now described has certain evident advantages over the rose cutter frame, and is capable of the most exquisite devices. It may be, perhaps, a mere question of taste, whether rose engine work finely executed is not in point of beauty, superior to any that can be done by geometric chucks, however elaborate. That it is so, is decidedly the writer's opinion, more especially when this apparatus is used in combination with the oval chuck. Moreover, there is nothing in the form of rose engine described to make it a very expensive article, or beyond the skill of an amateur; and with a set of only three rosettes, the patterns may be varied continually, and multiplied--if not _ad infinitum_--yet quite sufficiently for the display of skill and taste of the operator. In using the rose engine, it is necessary to carry the cord to the pulley from a very small wheel on the axle. Sometimes the lowest speed pulley of the flywheel may answer, but if the recesses of the rosette are deep and sharp, or only slightly rounded, it may become necessary to mount a still smaller wheel on purpose; else the rubber will jump over and miss parts of the design, thereby spoiling the work. The watch-case turners, indeed, altogether dispense with the flywheel, and use instead a small pulley, fixed to the side of the lathe bed, and turned by hand. These artificers always use a more elaborate form of rose engine, which will be presently described, and which is the most perfect in detail of all similar contrivances, but it is necessarily costly, and cannot be said to be well adapted for plain turning also, except in a limited degree. The work, if not of soft material, like a watch-case, should be turned first of all upon an ordinary lathe, the mandrel screw of which is a counterpart to that of the rose engine, and the latter should merely be used for the final cut, to perfect the form of the material previous to its ornamentation. In the Appendix will be found a new method of obtaining the required oscillatory motion of the rose engine, which might apparently be applied to tool holder[22] frame here described, or to the poppet head. [22] _I.e._, the main frame carrying the slide rest. The rose engine proper is arranged with an oscillating poppet head carrying the mandrel and its rosettes, the tool being stationary. The following account of this machine, and the drawings, are copied almost exactly from Bergeron. The modern rose engine is not indeed made with the projecting lugs referred to as intended for the application of the guide ring in oval turning, as this guide is now altered to fit a poppet head of ordinary form, as already detailed. The pulley and division plate are also of obsolete form, but as the main arrangement of parts described are sufficiently similar to that now followed, Bergeron's drawing and description have been retained. Fig. 302 is a longitudinal view, and Fig. 303 a transverse view of the working parts of this lathe. A, A are the poppets, which are in one casting, with the connecting piece shown by the dotted lines, which latter has a tail piece firmly attached to its centre, to which a spring is affixed as in the lathe previously described. In the drawing the cylindrical collars carrying the mandrel are split, so that in case of wear they can be tightened in the usual manner by a screw at the top of the poppet marked B, 303. The lugs, _f, f_, with square holes _e, e_, are for the application of the guide for oval turning, the latter being originally a ring with slotted arms on either side. The points of oscillation are precisely similar to those of the rose engine first described, two short poppets C, Figs. 302 and 303, having centre screws, whose points fall into conical holes made in opposite faces of the poppet, a little below the level of the lathe bed. These are formed with a slit to receive the stop _h_, which is hinged at the point _o_, and which, when raised by a wedge, catches into a small projection _p_, thereby fixing the poppet in a perpendicular position and preventing its oscillation. The rose engine can then be used as an ordinary lathe, to finish the preparation of the work to be operated on, which should, if possible, be commenced and mainly formed on an ordinary lathe, the mandrel of which is a counterpart of that of the rose engine. The tail piece, E, does not require a separate description, being precisely similar to that already described. The to-and-fro movement of the mandrel caused by the action of the rubbers on the face of rosette, is also arranged in a manner similar to the last. F is the spring, turning in the middle of its length on a pin in a piece of iron fixed on the bed, so that if both ends wore free it could swing backwards and forwards between the cheeks of the lathe on this pin as a centre. The upper end of this spring is branched in a semicircular form to embrace the mandrel, this fork falling into a groove formed to receive it. It can thus be brought to bear against either of the shoulders visible at this part. The lower end of the spring fits into a notch, or rather a slot in the arm H of the second figure; the handle of this arm being L in both figs. This piece is pivotted at K, and at its other end falls into one of the notches in the retaining plate, G, of the first figure. By this plan the tension of the spring, can be brought against the mandrel in either direction at pleasure, for if the lever is placed in one of the left hand notches, the tendency of the spring will be to move the mandrel towards the right, and _vice versa_. The tension of the spring can also be regulated by the use of the groove B or X at pleasure. In the second figure of Bergeron's the piece which at first sight appears to be a continuation of the holding down bolt of the short poppet carrying the centre screw, is the tail piece or lower end of the long spring just described, and its reduced extremity is visible passing through a short slot in the lever H, near the handle of which appears the _edge_ of the notched piece G of the other figure. All the above parts are commonly of iron, the following are in brass or gun metal. [Illustration: FIG. 303.] [Illustration: FIG. 304.] [Illustration: FIG. 302.] On the bed and parallel to it, two pieces of brass, or standards, rise, similar to H in the first figure, the two being opposite to each other, one on each side of the mandrel, as shown in the second figure. Both these are firmly secured to the bed by long bolts and nuts, it being of the utmost importance that they should not move or vibrate in the least. They are in addition united to each other by two horizontal braces, one of which is seen at N in the second figure. At _l, l_ are seen two rectangular notches, which are the ends of grooves made in the upper part of the head piece, H, and which traverse its whole length. They receive the crooked part, _a_, of the rubber holder, Fig. 304, so that the latter can be slid along this bar, and brought opposite to any one of the rosettes, after which it can be secured in position by the screw, _b_, Fig. 304. The mandrel is thus arranged. It is cylindrical, with a shoulder against which the chucks can rest, as in an ordinary traversing mandrel, and a similar but reversed shoulder at _g_, Fig. 302. Against the latter abuts the end of an accurately turned sleeve of brass, which fits over the mandrel with slight friction, so as to have no shake or play upon it. Upon this sleeve the rosettes are placed. They fit accurately over it, and are prevented from turning round upon it by a feather extending the length of the sleeve, which fits into a corresponding notch cut on the inside of the rosettes. These are arranged in pairs back to back, and each couple is separated from the next by a short sleeve or ferrule, which Bergeron recommends to be of wood, as tending to hold the rosettes more securely than metal when pressed together by the nut at the end of the set. The fibres of the wood are to be placed parallel with the mandrel, because there is no shrinkage of this substance as regards its length. The pulley is fixed beyond the rosettes on a part of the mandrel filed into six faces for that purpose, and lastly comes the nut, which secures all the parts to their several positions, but which nevertheless does not so jam them together but that the mandrel can be turned within the sleeve when the positions of the rosettes are to be changed in the course of working a pattern. The division plate is not attached to the pulley, though lying close upon its surface. It slips on to the sleeve on which the rosettes fit, and its spring-catch only on the face of the pulley. Thus the latter is held to the sleeve and its fittings when the catch is down, so that all turn together, but, when the catch is raised, the division plate, carrying with it the rosettes, can be turned round upon the mandrel as may be required. It is not necessary to repeat what has been said respecting the manner of graduating the division plate, as that used with the lathe already described is in that respect a counterpart of what is used with the rose engine now treated of. [Illustration: FIG. 305, 306.] [Illustration: FIG. 307.] The following description of the method pursued in turning a pattern shown in Fig. 307 will suffice to show the working of the rose engine:--First, says Bergeron:--It is not enough to know the general construction of the rose engine, it is necessary to know thoroughly the particular one in use, _i. e._, as regards the details of its construction, the slight defects or imperfections it may chance to have, and the means whereby they may be lessened or corrected. It is necessary, in addition, to know well, and to have always at hand, the numbers of each rosette, or any rate to have a table of them which can be readily referred to. It is equally necessary to recognise at a glance the various sets of divisions on the division plate, for which purpose, and that no mistake may be made, such numbers ought to be engraved upon each. The same holds good with regard to the slide rest, and, in addition, practice should be frequent upon box or other inexpensive material by which the turner may have made himself perfect in the several combinations possible, and the various effects producible by the rosettes and different shaped tools over which he has control. It is thus, by actual experiment only, that the turner can become acquainted with the powers of his own lathe and apparatus, and thus only, after working out the patterns already executed, will he be in a position to design new ones, and to work with ease and certainty. The rose engines are usually fitted with tools of variously shaped edges, as shown in Figs. 305 and 306, by this means a pattern of some width and great variety is of course produced at once, and by one rosette. In the following, however, a tool with single point, Fig. 308, is to be used. This simplest design is supposed to be on the cover of a box or other plane surface, and it is evident that the movement or oscillation required of the mandrel is that at right angles to the bed of the lathe. To obtain this movement, when the rubber is fixed in its clamp, on the side of the workman, as it is necessary that the rubber should press against the rosette through the medium of the spring, the handle of the lever, Fig. 302, must be drawn forward towards the operator, and kept by a pin, as described, passing through it and the tail piece of the mandrel frame. The tension must not be too great, especially if the rosette to be used is deeply indented, and care must be taken to free the frame from the action of the stop, _p_, by removing its wedge before making any attempt to try the pressure by moving the mandrel. The design under consideration is produced from rosette numbered 2 in the drawing, and in fixing the rubber care must be taken that it does not bear against the adjacent rosette. Choose a rosette of forty-eight teeth or undulations, and as the second circle of ornamentation exactly intersects the first, the raised part of the one falling under the depression of the other, and as it were _halving_ it, the set of divisions on the click plate to be used will be twice 48, or 96. Place the rest parallel to the face of the work and so that the forward motion of the tool shall be perpendicular to it. By means of the leading screw of the rest, place the tool near the edge of the work and level with the centre, and gently moving it forward and putting the lathe in motion, commence the cut. After having made a light cut, without moving the tool, stop the lathe and judge of the depth of cut, and if sufficient, screw up the stop screw of the slide rest, to insure all the following cuts penetrating to the same depth. Observe the position of the tool as marked by the graduations of the slide rest, and then withdrawing it from the cut, move the click plate one notch, which will divide exactly in half the several undulations of the rosette. By the rest screw move the tool towards the centre of the work and mark the number of divisions passed over, so that the circles of undulations may be equidistant, and cut a second. Now for the third, _go back or advance_ on the click plate one division, for the position of the undulations in the third is precisely that of the first circle. It is indeed immaterial whether an advance or retreat of one notch is made in this case, but now is evident the reason for not dividing the plate equally all round, five or six teeth being ample for each division. If there are eight rosettes the plate should be first divided into eight parts, and each rosette having a different number of undulations, these eight parts should be divided into degrees proportionate to the numbers on the rosette, the one being a multiple of the other. In working the _side_ of a cylinder, that of a box, for example, the longitudinal movement of the mandrel is required, the poppet being retained immovable by the wedge and stop. The tool is to be placed at right angles to the side of the work, the rubber brought to bear on the face of the rosette. The method of working will be self-evident, after the description already given. It is impossible in a brief work like the present, to go into details of other patterns referred to and illustrated by Bergeron, one or two of which are nevertheless of great beauty, and are executed with the aid of the eccentric chuck mounted on the mandrel of the rose engine. There is, however, a different class of work, to which reference will be made in our next, and we shall also give a description of a simple addition to the slide rest, used by watch case turners, which does away with the necessity of counting the number of divisions upon this instrument when used as above. The slide rest used by the watch case turners is almost identical in form with one figured and described by Bergeron. It is necessary that the tool holder should have a circular motion, somewhat similar to that of a spherical rest, in order to reach the sides and curved surfaces of the articles to be engine turned; hence the tool receptacle and its bed work upon a central pin. The pin here called "the bed" is usually a flat brass plate of a quadrant form, the central pin being at the apex, and carrying on its face the guides for the tool receptacle. The pin on which it turns is a reversed truncated cone rising from a similar flat plate, which itself forms the sole of the rest, or traverses the lower frame as usual; when the tool is beyond the central pin, it will ornament conical surfaces, and _vice versa_. On the edge of the arc is a racked part, and a tangent screw works into it. The tool is moved to and fro by a lever, as usual, the depth of cut being regulated by a stop screw. These details being already entered into, in treating of slide rests and chucks, need not be more specially explained here; but a contrivance for regulating the traverse of the upper part upon the frame underneath, is ingenious and serviceable, and will therefore be described. The end of the leading screw is fitted with a ratchet wheel of the same construction as that of the ratchet brace for drilling, patented by Fenn, of Newgate Street, to which in the same way a handle and spring are attached, as shown in the drawing, Fig. 309, A, and Fig. 310. The handle rises between two semicircular plates drilled in the face, with holes for the reception of stop pins, B, C. These regulate the traverse of the handle, and thence of the screw. If the former, therefore, is thrown over till the left stop is touched, and then pulled forward to the other stop, between each cut of the tool, the latter will leave equidistant spaces upon the work, without need of counting divisions at each cut. As a traverse of one inch or more of the lever handle at the place of the stop pins only moves the screw a very minute quantity, the holes for the pins need not be very close together even for fine work. This is a very simple contrivance, and perfect in action, enabling the operator to work with ease and certainty, and with great speed. [Illustration: FIG. 309.] [Illustration: FIG. 310.] RECTILINEAL CHUCK. Fig. 311 represents a modification of the eccentric chuck, when the latter is used as a fixture, to present to revolving cutters and drills the different parts of the work which is to be operated on. The eccentric chuck is commonly made to slide in one direction only, and the traverse is limited. In the present case there is ample traverse in both directions, the slide being arranged to descend to the lathe bed, and upwards to an equal degree. A is a cross section of this chuck, the length of which is 7-1/2 inches. It is very strongly made in brass, and is altogether much more substantial than the eccentric chuck. B and C are the guide bars, between which works the sliding part. The nut of the leading screw is below this as usual. The tangent wheel has 120 teeth, and is thus divided: 0--12--24, &c. The tangent screw head is divided thus: 0--1--2--3--4--5, with half divisions, marked but not numbered. This rectilineal chuck is most commonly used in a vertical position, but may be otherwise placed. In using it for any work likely to bring a strain upon it, the ordinary spring index attached to the lathe for use with the face plate, should not be entirely relied on to keep it in position. It is safer to make use in addition of the segment engine stops or other available contrivance. The special function of the chuck is the production of straight lines on the face of work forming stars or radial flutes, which can be worked with a drill. Fluting is also readily done by its aid, with the addition of the vertical eccentric, or dome chuck, already described. Its use is, however, by no means confined to ornamental work--small tenons, mortises, and even dovetails are producible by it; and in fitting together the various parts of temples, shrines, and similar complicated specimens, its uses will be innumerable; and here may be noted the extension of the lathe and its apparatus to work apparently in no way suited to it. It has now become more of a universal shaping machine than it used to be, owing to the great accuracy of the work done by it, and the variety of fittings that can be added to it. In a later page will be found a drawing and description of a new device of the kind--a planing machine, devised by an ingenious and first-class maker, Munro, of Lambeth, and patented by him. Mention is made of it in this place, because the rectilineal chuck is in some degree capable of similar work. The slide moved up and down by a screw the handle of which is of extra length to allow the vertical traverse, is also capable of being moved by a cam-eccentric chain or rack and cogged wheel, so that by pulling down a handle the slide may be made to slide up and down more rapidly than by the screw motion; any piece of wood of rectangular or other figure may thus be planed on the face, by being fixed on the rectilineal chuck, and acted upon by a fixed tool in the slide rest, the latter affording the horizontal traverse of the tool across the face of the work, the former the perpendicular movement of the material. If a slide rest is thus arranged in combination with the chuck in question, and the lathe bed is imagined to be set up on end with the chuck downwards and horizontal, the whole will become, in fact, a precise counterpart of those planing machines, the bed of which traverses to and fro, with the work under a fixed tool. Munro's arrangement is, of course, of far more extended application, and more suited for metal work; but for lighter and more delicate operations of a similar kind the rectilinear chuck and slide rest will be found very serviceable. It is with such an adaptation of this chuck as has been alluded to, namely, a quick speed movement of the slide by a lever handle, that the rays are drawn so exquisitely fine and close upon the faces of many gold dial plates of watches, the handle being arrested by a stop at any given point, so that these rays shall not transgress their appointed limits. It will be hardly necessary to allude to those other applications of this apparatus, or other particulars in which it is identical with the eccentric chuck, as the description already given of the latter applies to both alike, the extra traverse of the present in both directions being its chief distinguishing feature. [Illustration: FIG. 311.] [Illustration: FIG. 312.] EPICYCLOIDAL CHUCK. This chuck has been in use for many years, and has in consequence been of late rather neglected. It is, nevertheless, the parent of those more elaborate contrivances included under the general title of Geometric Chucks, of which Ibbetson's stands first in order of date, and possibly of merit, though this last qualification may admit of question. The epicycloid, defined mathematically, is a curve described by the revolution of a point in the circumference of a circle, when the latter is made to roll upon the concave or convex side of another circle. A pin in the rim of a wheel revolving round and in contact with another wheel, therefore, describes this curve, which constitutes two or more loops, as will be seen by the annexed illustrations. The number of these loops is variable, and the chuck will produce almost any number by changing the pinions, and thus altering the relative velocities of the revolving parts. The following description will make the action of this chuck clear, and enable any good mechanic to construct one for himself. In the first place, the above remarks show a necessity for a fixed wheel, round which another may revolve. Fig. 313 represents this attached to a plate of brass, which can be fixed to the lathe head, the mandrel passing through its centre. This is the original pattern of plate, and need not, of course, be adhered to, as the form can be modified to suit the lathe to which it is to be applied. It is merely necessary to affix such a wheel to the face of the poppet, so as to be concentric with the mandrel [a plan done away with, however, or rather reversed, in Plant's geometric chuck]. The epicycloidal chuck, which screws to the mandrel as usual, consists of a foundation plate of brass, A, Fig. 314, behind which is mounted the cogwheel, B. The axis of this wheel passes through the plate, and is carried by another plate, _e_, which is curved and adjustable upon the former. The axis of this wheel carries a small pinion, D, so that the whole turn together. This pinion being one of a set of change wheels, necessitates the possibility of adjusting the plate which carries its axis, as all the several change wheels must gear with E, which always retains its position on the chuck. The sliding plate in question being put in place, is clamped by the screw F. A plate of iron, G, of the form shown, and of sufficient thickness for the secure attachment of the wheel and of the screw which carries the ordinary chucks, is fitted to turn on the axis of the wheel E. Its larger end traverses within the arc H, which is graduated. The arc is bevelled underneath, serving to hold down securely to the foundation plate the piece of iron which is chamfered to fit it. At the left side of the back plate is seen a stop, L, which is placed in such a position, that when the iron plate rests against it, the screw M is concentric with the mandrel, and work may be turned as upon an ordinary chuck. To throw the iron plate, and consequently the nose of the chuck, on one side, or in other words to place the work eccentrically, the screws which retain the arc are loosened and the adjustment made by hand. The eccentricity is marked by an index on the iron plate, which points to the graduations seen upon the face of the arc. The eccentricity being determined, the arc is again screwed down to retain the movable plate in its new position. [Although this is Bergeron's method, it appears vastly inferior to the plan of racking the edge of the iron plate, and moving it to any required degree of eccentricity by the aid of a tangent screw.] When made as above, the chuck will produce loops varying in number according to the relative dimensions of the pinion (or change wheels gearing with E) and the central wheel, M. If the latter has 120 teeth, and the change wheel 60, two loops will result. If the pinion has ten teeth, the number of loops will be 12, and so forth. The practical _limit_ to the number depends on the possibility of diminishing the pinion in size and number of cogs, and still keeping the latter of such size and pitch as to gear with E. If, therefore, a larger number of loops is required than can be obtained thus, it becomes necessary so to modify the form of chuck as to permit of intermediate change wheels, and when the modification is carried out, we have the geometric chuck, the most perfect, but the most complicated and expensive of all. To understand the nature of the work, the following is given in clear language by Bergeron, and will sufficiently explain and simplify matters. [Illustration: FIG. 313.] [Illustration: FIG. 314.] [Illustration: FIG. 315.] If one considers the movement of the piece (of work) when the wheel M is concentric with the mandrel, it will be perceived that although it makes two revolutions upon its axis, yet inasmuch as it has no eccentricity it will describe no particular curve or figure; but if an eccentricity of three divisions is given to it, two buckles or loops will result as in Fig. 315. Before cutting the material, however, approach the tool as near the work as possible, and putting the lathe in motion, observe whether the buckle[23] passes too near the centre or too far from it, and also how near it goes to the circumference. If another change wheel with forty teeth instead of sixty is substituted, the slide C, being adjusted accordingly, three loops will be described (forty being one-third of one hundred and twenty), but it is always necessary before actually cutting the material, to try whether the buckles will pass near to the centre without going beyond it. The result of the latter movement will be shown presently, as it entirely alters the appearance of the pattern. The divisions commence on the arc at the left hand, the index resting at 0° when the plate is against the stop L, and the screw of the chuck concentric with the mandrel. The preceding figure of three loops will become similar to Fig. 317, retaining the same wheels and some degree of eccentricity, but by means of the slide rest moving the tool towards the circumference, so that the buckles overlap the centre. The effect thus produced is, that of a set of three curvilineal triangles of which the apex of one falls upon the base of the next. The use of this chuck is stated to require upon the part of the operator more care than any other, as regards the derangement of work or tool in the least during the operation, as, if either is once moved in the least out of position, it will be found next to impossible to strike the line again, owing to the peculiar nature of the curve, for although the tool may be replaced upon any one part of the line already cut with the intention of deepening--it is by no means certain that it will trace the same curve again. This curve, says Bergeron does not produce an agreeable effect on the cover of a box, unless it is very finely cut, the tool, therefore, should be very sharp in the angle and very keen. Bergeron specially mentions this in reference to filling the cuts with thin strips of horn or shell, a method of inlaid ornamentation not much known or admired in the present day, but to which allusion may probably be made again in this series. To form the second set of loops, which are parallel with the first in these designs, it is only necessary to use the leading screw of the slide rest, to move the tool nearer to or further from the centre, while the eccentricity and the arrangement of change wheels remain as before. It is scarcely necessary to detail the formation of the larger series of four loops and upwards, as these are simply the result of different sized change wheels: the following principles, however, by which the buckling of the several loops is controlled or prevented, may perhaps be serviceable. "When, for example an eccentricity of sixteen divisions is used--if the tool is placed at a distance of two such divisions from the centre of the piece, a line only will be produced of as many _curves_ as the wheel or pinion D would produce _buckles_. If the tool is moved further from the centre by a quarter division, the angles (connecting the curves) will be more defined, but still no buckles will be made. A little further movement of the tool will produce very small buckles which will thus gradually increase as the tool is set further and farther from the centre--until at last when the curves pass beyond the centre, the result is arrived at already shown in Fig. 317. Another form of this chuck is shown in 318, in which, instead of the iron plate being pivotted for the purpose of eccentricity upon the axis of the wheel E, a parallel slide motion is given to the main wheel by guide bars, as in the eccentric and oval chucks. This form is figured in "Lardner's Cabinet Cyclopædia." The large front wheel carrying the screw for chucks is pivotted to the slide C, and protected by a plate D which nearly covers it. The wheel L, is arranged to follow this slide, so as to remain in gear with the large wheel without leaving the fixed wheel or ring on the face of the poppet. In both patterns of this chuck the front wheel is used as a division plate, being moved in either direction as many cogs as desired to produce interlacing of the looped designs. It is better, however, to add a racked division plate and tangent screw, as in the eccentric chuck to act as one piece with the chuck screw, and with the latter turning on a conical pin in the centre of the large wheel underneath. The above apparatus requires to be used with a slow motion owing to the complication of parts, and the whole ought to be so well constructed, that the various wheels revolve with perfect smoothness and without shake or noise. [23] The word _buckle_ is used to signify the small loops--not the large curves. [Illustration: FIG. 316.] [Illustration: FIG. 317.] [Illustration: FIG. 318.] THE SPIRAL CHUCK (FIG. 319). There is no class of work on the whole more interesting than that executed by the aid of the spiral chuck, especially with an addition to be described here. This apparatus has grown, almost as a matter of course, from the adaptation to the ordinary lathe of the system of change wheels for the production of screws of various pitches. A spiral is, in fact, a screw with very extended pitch, the threads either closely enwrapping a cylinder which forms the core or body of the screw, or being entirely separate and independent of such core, the latter being by far the most light and elegant. The chuck here described is used with the same arm or bracket as has been already spoken of, standing out from the poppet to carry change wheels, and is itself adjustable to suit different diameters of the same. In the sectional view of this chuck given here, A, H, is the body with internal screw as B, to fit the mandrel. The cog wheel of the chuck which gears into the first on the movable arm or standard, is cast with a large central hole to allow it to be stopped on at D, where it is retained by a nut C. This permits a change of such wheel for one of different size or for the apparatus to be presently described. Thus far the chuck is only applicable to the production of screws or spirals with a single thread. F, is a dividing plate with racked edge acted on by the tangent-screw E, and carrying the screw, G, a counterpart of that upon the mandrel. This plate carries 96 divisions or teeth. The latter may be used with a spring click if preferred; but the racked edge gives perhaps the more delicate power of adjustment. The spiral chuck constructed in this way is capable of producing any required number of screw threads or spirals, solid or detached, and of any ordinary pitch. It is, however, chiefly intended for the production of spirals or twists for articles of _virtu_. The method of proceeding has already been described in a previous page. It is one rather of care than skill, as the lathe apparatus ensures the correct movement of the tool where the shape of the latter determines the form of thread, angular, round, or moulded at pleasure. A few of the tools required are shown in the drawing. For finishing the rounded threads, Nos. 3 and 4 may be used, which are similar to those required for turning ivory rings, the one completing half the thread, the other applied in the opposite direction, meeting the cut of the first and finishing the operation. As it is necessary to get round to the back of the threads in this case, no inner mandrel can be used to support the work, and, therefore, great care and delicate handling are necessary to prevent breaking the twists. The stops should also be used upon the bed of the slide-rest, to limit the traverse of the tool and prevent it from striking the shoulder, and destroying any bead or other moulding formed there. This is more specially needed, when there are two or more such twists rising from the same base (that is when there are two or more threads to the screw). The additional apparatus now to be described, adds considerably to the powers of the spiral chuck. It is called the reciprocating apparatus, and its effect is, to cause a to and fro movement of the work, at the same time that the motion of the tool is continued in a horizontal direction. Fig. 320 shows the simplest of the effects thus produced. The screw is commenced and carried to any desired distance on the cylinder. The action and horizontal traverse of the tool is continued, but that of the cylinder reversed, and the cut is thus carried upwards. The tool may be a revolving cutter, the action of which, being continuous and in the same direction, would seem preferable, as the greater the speed with which the tool attacks the material the better is generally the result in work of this kind. A fixed tool, moreover, must have a central edge chamfered above and below, and there is also a tendency with any such fixed tool to unscrew the chuck, as the resistance occurs in that direction in the upward cut. [Illustration: FIG. 320, 321, 322, 323, 324, 325.] The details of the arrangement are as follows:--The several parts being drawn of full size, Fig. 321 A is an eccentric capable of slight adjustment by the use of either hole, one being further from the centre than the other. Fig. 322 gives another view of this eccentric, which is precisely similar to that used in model engines. It is turned as a circular plate of gun-metal, with one flange. The plate being five-tenths of an inch thick, a second plate, forming another flange, is attached by four small screws, after the ring of the eccentric is in place. This ring is of iron, or, still better, of steel, and is made in one piece, with the arm B, which is six inches long; the main part of it is flat, but it is rounded towards the end, and turned at E, after which it is again flattened to work against the arm D, or still better forked to embrace the latter. It will be seen that D is also a flat plate, with a turned ring similar to the first, but without the enclosed eccentric. In this is drilled a series of ten holes, into any of which a pin can be fitted, so as to unite the arms B and D, the pin becoming a hinge or centre of oscillation. The circular ring of the part D fits on the part D, D of the chuck, on which it can be secured by the ferrule C, the arm D being then in a vertical position. The holes in the eccentric can (either of them) be fitted over and secured to the end of the leading screw of the slide-rest. The handle being then placed on the other end of the screw and turned by the hand, the eccentric will cause the arm D to oscillate to and fro through the medium of the connecting rod B, thereby giving to the chuck, and to the work attached to it, a similar to and fro movement. The extent of this movement depends upon the length of the lever D brought into action. With the pin in the holes 1, 2, 3, the oscillation will be inconsiderable, but with the pin in either hole numbered 8, 9, 10, it will be much increased. In the first, therefore, a short wave, Fig. 320, will result; in the second case these will be more like Fig. 320 B. This apparatus will completely alter the character of a spiral, which, if cut through a hollow cylinder (as in the case of _detached_ twists) becomes a zigzag of curved sides curious enough to behold. The apparatus, it must be understood, is worked entirely by the handle of the slide-rest, the lathe-cord being thrown off unless the latter is carried to the overhead instead, to put in action revolving cutters. The reciprocal action is, in fact, a self-acting segment engine. It has been already stated that for the production of spiral work revolving cutters are preferable to fixed ones, unless, indeed, it is required to finish up a perfectly round thread, when Figs. 3 and 4 of the tools drawn are required. Revolving cutters must be placed in the frame of the universal cutter and set to the rake of the thread. Drills may be used for the reciprocating movement, as they make very clean work, and the rake need not with these be attended to. In face work drills are specially to be used to produce patterns like Fig. 325, and others derived from this simple one. An additional apparatus, represented in Fig. 323, is required for the latter process, to enable the rest to be turned in its socket so as to face the work, and notwithstanding the alteration of its position still to keep up the gearing of the wheels. A rest socket to be made and mounted as usual is fitted with a stem surmounted by an accurately drilled boss A, through which passes a spindle fitted with the wheel C, to gear with that on the arm carrying the change-wheels, and which may be changed for one of larger or smaller size. This is for cutting such work as Fig. 324, representing, of course, only a single spiral, very open and of itself of no beauty, but which by intersection of other spirals can be converted into a pattern of great elegance. When it is desired to produce the waved spiral the eccentric is fixed to the rod instead of the wheel C, and the work proceeds the same as when a cylindrical surface is to be worked. In the Fig. shown the division plate of this chuck is of course used. [Illustration: 1.] [Illustration: 2.] [Illustration: 3.] [Illustration: 4.] [Illustration: 5.] [Illustration: 6.] It is evident that the variations producible by working intersecting spirals and waved lines are very numerous, and these may be additionally varied by the combination of eccentric and spiral movements. The following six patterns are re-engraved from Valicourt's Hand Book, which is almost identical with that of Bergeron. They were not engraved in time to be inserted under the head of eccentric chuck work. The notation and description annexed is from a manuscript book kindly lent to the writer by an amateur. "_Bed-plate_," 4 deg., must be taken to mean that the work is shifted (on one of the beds of the chuck) four of the marked divisions for eccentricity, counting from the axial line of the mandrel. "_Slide rest_, 4 deg.," means that the cutting tool is moved four corresponding divisions in its bed for radius of the circle to be cut; and so throughout. "4 *," means four times repeated. The cutting tools, unless otherwise expressed, are double angled, and "25 cutting tool," means 25 deg. of cutting edge. Holtzapffel's scale of divisions is [Illustration] The scale used in Valicourt is which is that here quoted. [Illustration] If bed-plate and slide rest are both equally diminished at each cut, a shell results, with the close part internal. If bed-plate is increased and slide rest diminished, the close part of the shell is external. SPECIMEN I.--Tools 25, 32, 36; Click-plate 96 or 288. Bed-plate moved. Slide rest moved. Circles done. Tool. 3 2 12* (1 done 7 missed) 25 6 1 12* (1 done 7 missed) 10 3 48* (1 done 1 missed) 36 3 16 24* (1 done 3 missed) 23 4-1/2 4* (16 done 8 missed) 29-1/2 2 96* 25 33 1 96* or 33 5/8 288* SPECIMEN II.--Tools 28, 36; Click-plate 288. Bed-plate. Slide rest. Circles done. Tool. 1 1/2 12 28 4 1-1/2 12 7-1/2 2 4 (8 done 4 missed) 36 13 3-1/2 24 28 19-3/4 3-1/2 4 (16 done 8 missed) 36 19-3/4 1/2 4 (in spaces) 21-3/4 1 4 (above last) B 17-3/4 m 1 4 (below last) 36 30 1/2 12 (20 done 4 missed) 28 29-3/8 1/2 12 {( 1 " 18 " ) {( 1 " 4 " ) 28-3/4 1/2 12 Ditto. 28-1/8 1/2 12 27-1/2 1/2 12 {(15 done 4 missed) {( 1 " 4 " ) 26-7/8 1/2 12 {( 1 " 18 " ) {( 1 " 4 " ) 26-1/4 1/2 As before 25-5/8 1/2 Ditto. 25 1/2 12 (20 done 4 missed) From B to here, border, if with 96 click-plate, not good-looking; tool a boring-bit. 33-1/16 7/8 12 (7 done 1 missed) 31-9/16 13-16th 12 {(1 " 5 " ) {(1 " 1 " ) 29-1/16 3/4 12 {(1 " 1 " ) {(5 " 1 " ) 27-9/16 11-16th 12 {(1 " 1 " ) {(1 " 5 " ) 25-3/4 3/4 12 {(1 " 1 " ) {(7 " 1 " ) SPECIMEN III.--Click-plate 96. Bed-plate. Slide rest. Circles done. Tool. 1-1/4 1-1/8 8 36 4-1/4 2-1/8 24 5-1/8 11-3/4 24 21-1/2 4-3/4 96 27-3/4 1-1/2 96 28 SPECIMEN IV. The centre of this is a star of six curved rays, described by fixing the cutter at the centre and turning the mandrel by hand through so many divisions--for convenience so many 48ths of the circumference. These rays are marked by B. (The segment stop is constructed for this very kind of work, and is to be used in the present case):-- Bed-plate. Slide rest. Arcs done for star. 5 B 5 6 (12/48ths of the circle) 5 B 5 12 (11/48ths " ) 5 B 5 12 (10/48ths " ) 5 B 5 12 ( 8/48ths " ) 14-1/8 5 24 (2 done, 2 missed) 19-3/4 1/2 96 24-1/4 4 32 29-1/2 2-1/2 32 (intersecting) 30-1/2 2 32 SPECIMEN V.--Catherine wheel; tool 28. The ground grailed by concentric circles contiguous to each other. The arcs by fours, all of same radius. Bed-plate. Rest. Arcs done. 0 1/2 3/4 1-1/4 &c. (for grailing) B 30 30 12 (16/48) (Repeat at three next divisions.) SPECIMEN VI.--Tools 28, 36; Click-plate, 288. Bed-plate. Rest. Number. 1-1/4 1 8 done B 12 12 12-7/48 (to meet next circle) 4-3/8 17 24 30 1/2 12 29-1/2 1 12 (On same radius as the last, and surrounding it.) 29 1-1/2 12 28-1/2 2 12 28 2-1/2 12 27-1/2 3 12 27 3-1/2 12 26-1/2 4 12 23-1/2 1 12 (3 done, 21 missed between last, or if click-plate 96.) 25 1 12 (between last) Although in the matter of beauty the patterns here given are by no means comparable to many others, especially to some lately published from blocks cut by Mr. George Plant, for the _English Mechanic_; they are, by their comparative simplicity, well selected to give the learner a good idea of designing and working with the eccentric chuck. It is not, indeed, proposed by the writer to multiply patterns, as mere copying of such is of small interest to those who are really endued with taste and skill; and the variations producible by combinations of different numbers of divisions of the click-plate and slide rest are of such infinite number, that printed designs of a score or two would not serve to teach the nature of this work better than the half dozen now before the reader. When a new chuck, indeed, is brought out, it is well to give a few specimens of its work, to show the possible purchaser its value as a means of ornamentation and the extent of its capabilities; but when these are understood, the purchaser had much better design for himself, instead of becoming a lazy imitator and copying patterns laid down by others. Details of designs that are presented in a tabular form remind us sadly (for we are married) of the old "_knit one, drop two_," "_purl_" or some such mysterious and, to us, detestable jargon wherewith ladies were, or are, wont to worry the ears of mankind. * * * * * The chuck of Professor Ibbetson, and the elliptic cutting frame of Captain Ash, are not introduced here, partly because this work has reached its intended limit, and partly because the inventors themselves have published separate works entirely devoted to a description of the arrangements and capabilities of their respective chucks. A brief notice is appended of Plant's geometric chuck, contributed by the inventor to the pages of the _English Mechanic_.[24] [24] See Appendix. * * * * * The author now concludes his pleasant labours, the result of which is contained in the preceding pages. These labours have been lightened, and the work itself benefited, by several kindly-written remarks received from various readers of the _English Mechanic_, while the articles were in course of production in that paper. Criticisms and suggestions also came to hand in which no such kindly feelings appeared. These also have, nevertheless, had an equal share of attention, and where they appeared to be of value they have been turned to profit, and have resulted in various more or less important alterations and additions. "The Lathe and its Uses," thus re-arranged and modified, must now take its chance in the world with other productions of a similar character; and the writer hopes it may suffice to help those who need such assistance, and may be well received by others who though able to walk alone may yet cherish a kindly feeling for the friendly walking-stick. APPENDIX. PROFESSOR WILLIS'S TOOL HOLDER FOR THE SLIDE REST. [Illustration] This--described and drawn first in "Holtzapffel's Mechanical Manipulation," to which work the author, and, indeed, most authors of books of the nature of the present, are indebted for much of their information--is now become very general, and from its perfect action ought to be universally used in all factories in which the lathe bears a part. It permits the tool to be set at any required angle upon the bed of the slide rest, and holds it securely when placed in position. It is likewise so constructed as to be easily removed from the table of the rest, so that other forms of apparatus may be attached if desired. One nut only has to be turned to fix the tool, this nut turning on a strong central screw, A, in the figure, the lower part of which, as far as the shoulder, is screwed into the top plate of the rest. This shoulder is directed to be made with flattened sides, so as to be capable of being unscrewed by the application of a wrench. The actual clamp is a triangular piece of cast or wrought iron, B, in the centre of which is a hole to allow this piece to go easily over the screw. The hole is hollowed out into a cup-shaped cavity, into which fits a hemispherical washer, shown at C in the section. The clamping nut, D, acts upon this washer, which permits the triangle to take up a position not _necessarily_ quite parallel to the bed of the slide rest, and thus a tool whose upper and lower surfaces may not be strictly parallel will be securely grasped. The piece called triangular is not precisely of that form, but of the shape shown in the second figure, in which E, E, represent two hard steel pins, slightly projecting--one of these, E, appearing in the first figure. These pins rest upon the upper surface of the tool. At the third angle the clamping piece is drilled and tapped to receive a screw, which must work stiffly in this hole. Thus when a tool is placed in position, as shown, the clamping nut maintains a pressure upon the three points beneath the apices of the triangle. As thus arranged the tool would be stiffly and securely held; but Professor Willis has added a second triangular piece, nearly similar to the first, except that it is provided with a boss, in which a notch or groove is cut, K, in both figures, into which the point of the small screw falls. This lower triangle, which is free to revolve round the central screw, is also cut away at the line L, L, of the second figure, so as to form a guide or rest for the side of the tool, which is thus kept at the same distance from the central screw, and placed in a moment exactly under the studs or points of the upper plate. A careful inspection of the two drawings will make the precise arrangement clear. In _making_ it, which is not very difficult, care must be taken to make the triangle of such size and so to place it, that no angle can overhang the top plate of the rest, in whatever position it may be. The hole in the upper triangle or clamp must be tolerably large and slightly conical--the base of the cone upwards, to allow this piece to take up a bearing, as described. The hemispherical washer is always in a horizontal position, and the hole through it may be only of sufficient diameter to allow it to pass freely over the central screw. MUNRO'S PLANING MACHINE TO BE ATTACHED TO THE LATHE, AND WORKED WITH THE FOOT. In the _English Mechanic_ of Nov. 2, 1866, a brief notice was given of the above. The author of the present work having carefully inspected the machine and seen it in operation, considers it of such great value to the amateur mechanic, as well as to the professional turner of metal work, that he has had an engraving of the machine carefully made from a photograph, and has here appended it to illustrate the description given. It is a lathe for planing, cutting key-grooves in wheels, collars, &c., and cutting racks on the teeth of wheels. The lathe is of the usual construction, but outside the right hand standard is fixed a vertical spindle, which is made to rotate by a pair of bevel wheels, the pinion being fast to the end of the crank shaft, and in contact with a wheel of double the number of teeth on the vertical spindle. On the top of the latter is a crank-plate, which will give a stroke of ten inches or less at pleasure. The planing-machine is fixed by two bolts to the lathe-bed, and a connecting rod is attached to the sliding plate or bed of the planing machine, the other end of which is made fast to the pin of the crank-plate. The work is clamped by simple means to this sliding bed, and thus passes to and fro under the tool which, by self-acting gear, is made to traverse sideways after each stroke as in the large planing machines. The whole works almost noiselessly and with the greatest ease, each part being accurately fitted, and the whole well finished. For such purposes as planing the face of the slide valve and its bed in small engines, or shaping the guide bars of eccentric and other chucks, facing the frames of slide-rests, &c., it is exactly what is needed by the amateur, rendering the workshop complete for all purposes without the necessity for adding a large and separate planing machine, which takes up room that cannot always be conveniently spared. With such a lathe as that in the frontispiece, fitted with one of these planing machines, there is scarcely a model of machinery that could not be made. Any of our readers interested in mechanics would be wise to trip over to Lambeth and view the machine in operation; and the writer will guarantee, not only the most civil and obliging attention from the inventor, but the greatest pleasure and satisfaction from the working of the machine itself. There is a _simple arrangement_ for key-grooving and slotting, by attaching the upper slide of the ordinary rest to the crank plate of this machine, in which case most of the apparatus is removed. [Illustration: MUNRO'S MACHINE TURNING LATHE FOR PLANING, ETC.] HICKS' EXPANDING MANDREL. Mention of this has been made in the body of the work. It is used for turning rings and washers, and various sizes of these can be turned upon the same mandrel, so that a set of three will suffice for all the work likely to be met with even in the largest factories. Fig. 1 represents the mandrel complete. F, F is the central part, with a conical boss, A, cast upon it, and the whole turned with great accuracy. Four longitudinal dovetailed slots, seen plainly in Fig. 3, are then planed in the conical part, and into these are fitted steel wedges, Fig. 2, A and B, and B, Fig. 3. C, Fig. 1, is a hollow conical washer, which can be advanced over the central part when driven forward by the nut D. This washer, acting on the ends of the sliding wedges, causes them to move towards the large end of the cone A, and, from the form of these and of the cone, any washer or ring will be held tightly when placed outside these wedges, and will also be mounted concentrically. [Illustration: FIG. 1.] [Illustration: FIG. 2.] [Illustration: FIG. 3.] TURNING SPHERES BY MEANS OF TEMPLATES. It is but right to state that the above method has been objected to by a practical workman, whose business has led him to study the matter closely. He states that it is impossible in this way to effect the desired object. As the writer has not been able to test the working of the apparatus on his own lathe, he felt inclined, at first, to withdraw the whole chapter. The objections offered, however, were not, to his mind, entirely satisfactory; and the opinion of other equally scientific and practical men being favourable, the chapter has been retained. It is possible, nevertheless, that there may be a mathematical reason which the writer is not competent to work out, and the objector being a man of great mechanical knowledge and experience, his remarks are worthy of consideration. The practical (not insuperable) difficulty appears to be the production of a proper tool for this work. PLANT'S GEOMETRIC CHUCK. This chuck is put in motion by an entirely new method; none of its parts being attached to the lathe head, the whole can be put in motion or released in an instant, and without stopping the lathe. The whole of its work is executed by the continuous motion of the lathe, so that, when the chuck is adjusted, any figure (no matter how complex) may be begun and completed without once stopping the lathe. By the different arrangements and adjustments of the chuck and slide rest, an infinite variety of the most beautiful geometrical figures may be produced; and some of them of so strange and fortuitous a nature as to bid defiance to any imitation. _Description of the Drawings._ Fig. 1 is a front view, and Fig. 2 a view of the back of the chuck. [Illustration: Fig. 1.] [Illustration: Fig. 2] [Illustration: FRONT ELEVATION.] [Illustration] [Illustration] [Illustration] [Illustration] [Illustration] [Illustration] A A. The foundation plate screwing on the plate of the mandrel and carrying the whole of the other parts of the chuck. B, C. The two driving wheels giving an independent motion to the chuck. D. Angular wheel moving freely on the wheel C for the angular adjustment of the figures. E. Pinion of any number of teeth fitting on the shaft carrying D and C. H. Large wheel of 120 teeth, forming the foundation of the second part, and driven from the pinion E by the wheels F, G, and T. L. Large wheel of 96 teeth driven by the pinions and wheels U, I, J, K, and forming the foundation plate of the third part, M, which carries the nose of the chuck. N, N. Self-adjusting radius plates for carrying the various change wheels. O, P. The eccentric slides of the first and second parts. Fig. 2 shows the arrangement of the driving wheels and pinions on the back of the chuck. The working of the chuck is as follows:-- If the pinion E has 20 teeth, and is geared direct into the wheel H, by means of an intermediate wheel, it will give six loops inwards if the motions are similar, and outward loops if the motions are contrary. If the wheel H is driven from the pinion G it will give 12, 24, or 48 loops. Pinion of 24 teeth will give 5, 10, 20, or 40 loops. Pinion of 30 teeth will give 4, 8, 16, or 32 loops. Pinion of 40 teeth will give 3, 6, 18, or 36 loops. Pinion of 60 teeth will give two loops inwards, if the motions are similar, but, if the motions are contrary, it will produce an ellipse of any proportion from a straight line to a circle. Other combinations will give circulating or overlaying loops. By the different arrangements of wheels and pinions on the plates N, N any number of loops can be produced up to 2,592 in the circle. On the opposite page we illustrate some work executed with this chuck by Mr. Plant. Fig. 3 is a side elevation of the chuck full size. A, A, the foundation plate screwing on the nose of the mandrel, and carrying the whole of the other parts of the chuck. B, C, the two driving wheels giving an independent motion to the chuck. D, D, angular wheel moving freely on the wheel C, for the angular adjustment of the figures. E, E, pinion of any number of teeth fitting on the shaft carrying C and D. H, H, large wheel of 120 teeth, forming foundation of the second part, and driven from the pinion E by the wheels F, G, and T. L, large wheel of 96 teeth driven by the wheels and pinions I, J, K, and forming the foundation of the third part, M, which carries the nose of the chuck. N, N, self-adjusting radius plates for carrying the various change wheels, &c. O, P, the eccentric slides of the first and second parts. Q, R, the screws working the eccentric slides. A PAPER ON THE PRINCIPLES WHICH GOVERN THE FORMATION AND APPLICATION OF ACUTE EDGES, WITH SPECIAL REFERENCE TO FIXED TURNING-TOOLS, CONTRIBUTED BY MR. DODSWORTH HAYDON. "The formation of the tools used for turning and planing the metals is a subject of very great importance to the practical engineer, and it is indeed only when the mathematical principles upon which such tools act are closely followed by the workman that they produce their best effects."--Holtzapffel, vol. 2, p. 983. As the best lathe can do no more than place the work in the most favourable position for the operation of the tool, and the best tool can only do good work when _applied_ as well as _constructed_ on true principles, no argument is needed to prove the truth of the statement taken as the text of this paper. But while many of our most eminent practical authorities, such as Nasmyth, Holtzapffel, Babbage, Prof. Willis, and others, have contributed valuable papers on the subject, no single writer can be said to have embodied all that should be known upon it as a whole. Principle may be looked upon as the essence of practice, and in connection with this particular subject, the reduction of practice to principle is of comparatively modern growth. This will account for the fragmentary character and occasional difference of opinion, which marks the treatises of the above-named eminent authorities when compared with each other. As a step towards some more concise and perfect code of principle, I have endeavoured to collate and arrange in consecutive order, all those laws which govern the action of acute edged turning tools. The object of this paper is not to supply patterns of tools, as the best form will be no better than the worst unless properly applied; but to set forth those general principles, which may enable the workman to distinguish between forms which are accidental and those which are essential, and thus to make the shape of any tool his servant rather than his guide. Whatever the shape or purpose of any acute-edged tool may be, its action will always depend on the manner in which the extreme edge is applied to the surface acted upon; and as the same laws govern the action of every acute edge, whether formed on a razor or a tool for cast iron, it will assist a clear comprehension of this subject to consider first the action of edges generally, without reference to any particular tool. The same edge may be made to act in four different ways, viz.: to cut, dig, chatter or scrape. Digging and chattering are intermediate stages between cutting and scraping, and are fatal to good work. Thus _cutting_ and _scraping_ remain the two standard principles, on one of which every tool should be made to act; and while cutting depends on the penetration of the edge, scraping results from using an edge so that it cannot penetrate. Consequently, the conditions most favourable to cutting will give the key to both principles of action. Every cutting edge is simply a wedge, keen enough to guide its own path without depending on the grain or other accidental line of separation in the material on which it is employed; and when such a wedge is forced into any substance, it will show a constant tendency to penetrate in a line with that face which receives most opposition. The comparative amount of opposition which each face receives, will be determined either by one having more of its surface in contact with the material than the other as in Fig. 2, or by the material giving way on one side, as in Figs. 1 and 3. These last two figures illustrate the action of all _paring_ tools, to which class cutting lathe tools belong. The dotted lines are added in Fig. 2, to show that the action of the edge is the same, whether it be formed by one or two bevels. [Illustration: ILLUS. No. 1] [Illustration: ILLUS. No. 2] [Illustration: ILLUS. No. 3] Thus in all cases,--except when an edge is applied so that the pressure is equal on both faces,--one face will guide the course of the edge, and in paring tools this will always be the lower face, or that next the surface of the work. The first consideration in placing any paring tool must therefore always be that, _the lower face of the edge should lie as nearly as possible in a line with the direction the cut is intended to follow_, so as to place the whole edge in its natural wedge-like position: for when any edge is compelled to act in a manner contrary to this, it will assuredly assert its natural tendency by digging and chattering in the direction of its lower face. But when the action of the tool is continuous as in turning, planing, or boring, care must be taken that this face of the edge does not actually rub against that of the work; and, to avoid this, Nasmyth recommends that the face of the edge should be inclined from the surface of the work at an angle of 3°. Babbage calls this angle "the angle of relief," because it relieves the friction; and to show how little variation is admissible in this angle, Holtzapffel places its maximum at 6°. In cylindrical work the angle of relief is estimated from a tangent to the circumference. Thus, in Figs. 4 and 7, the lines C, D, may represent plane surfaces or tangents at pleasure, and in either case the lower face of each edge is supposed to make an angle of 3° with these lines respectively. An examination of the nature of the force required to separate any shaving will show the importance of close attention to the above rule. Babbage has pointed out that this process involves two forces, which, though simultaneous in their action, are distinct in the nature of their operation. The first is that necessary to divide the material atom from atom, and depends on the kind of edge employed. The second force is that required to wedge back the shaving, so as to make way for the further progress of the edge, and depends on the manner in which it is applied to the work. Now in fibrous and cohesive materials, the amount of force required to wedge back the shaving is usually greater than that required to effect the initial penetration, and must always depend on the angle which the _upper surface_ of the edge makes with the face of the work; while it is obvious that, whatever the acuteness of the particular edge employed may be, this angle will be reduced to the minimum obtainable with such an edge, by keeping its lower face as close as possible to the surface from which the shaving is being wedged off.[25] A comparison of Figs. 4 and 5 will illustrate this. Both edges are supposed to be of the same acuteness, viz., 60°, and in Fig. 4, where the angle of relief is only 3°, the edge of 60° will wedge off the shaving at the smallest available angle, viz., 63°, while the position of the same edge in Fig. 5 increases this angle to 90°. [25] In adopting Mr. Babbage's arguments I have varied their form. Mr. Babbage takes the square of 90° and divides it into three parts, viz.: Angle of relief 3° } ditto edge 60° } 90° ditto escape 27° } The angle of escape is thus estimated from the horizontal line perpendicular to a base line presented by the surface of the work or by a tangent to it. But as the value of this angle depends directly on its relation to the base line, and has only a complementary relation to the horizontal line, I have thought it better to confine the illustration to the same base as being more directly connected with the wedge-like action of the edge. Thus, as far as regards the force required to bend back the shaving, the edge of Fig. 5 might just as well be nearly square, or 87°, taking off 3° for the angle of relief. Indeed, this less acute edge would work better than one more acute but badly placed, as in Fig. 5; for the lower face here points too much _into_ the work, creating the tendency to dig explained above. The same arguments and illustrations apply with equal force to drills and boring tools, and Fig. 5 may be looked at as representing one edge of a common drill, in which the acuteness is obtained by bevelling the under sides only, leaving the upper face of each edge perpendicular to the surface acted upon. Nasmyth has pointed out that the less acute drills of this class are made the better and more smoothly they will cut; for, so long as the upper faces are left square to the surface of the work, increasing the bevel of the lower faces can only increase the tendency to dig and chatter. Thus, whenever acuteness is desired in any cutting edge, it should always be obtained from the upper face; and the dotted lines in Fig. 4, suggesting a tool for metal in one case, and a common wood-turning chisel in the other, are added to illustrate this, by showing that the line of the lower face is common to both. No tools afford a better illustration of this principle in boring tools than the American twist drills, which owe the ease and beauty of their action to the spiral flutes being placed so as to give the necessary acuteness from the upper face of each edge, thus allowing the lower faces to be kept as close as possible to the surface of the work. There is yet one more important practical advantage to be gained from adopting the smallest possible angle of relief. The arrow in Figs. 4 and 5 shows the direction in which the strain of the cut will fall on the edges respectively. It has been shown that the position of Fig. 5 increases the amount of strain on the edge, and yet it is apparent that it is less able to bear this increased strain; for while this falls on Fig. 4 in its strongest direction--viz., almost down the length of one face--it falls on Fig. 5 _across_ the end of the edge, thus rendering it far more liable to wear and fracture. It is therefore evident that, in treating plane surfaces, the cutting action of any acute edge is most favoured when its lower face is placed nearly parallel with the surface acted on; and in treating cylindrical surfaces, when the same face occupies the same position with regard to some tangent of the circumference; or, in other words, when the lower face is almost at right angles to some radius of the circle, as in Fig. 4: and it follows that the tendency to penetrate will be most effectually counteracted when a line at right angles to the surface, or a radius of the circle, as in Fig. 6, bisects the edge, making each face equidistant from the surface which moves across it. Thus, Fig. 6 represents the _scraping_ position; and it is obvious that all bow-drills or other tools, which are _said to cut both ways_, must really act on the scraping principle. Practical illustrations in support of the universal application of these principles might be multiplied indefinitely; but two very common operations will suffice to prove that the position of the edge determines the nature of its action. If a penknife be not held with its blade perpendicular to the paper, when used for scratching out, it will be sure to hang and chatter; and the flatter a razor is held to the skin in shaving the more free will the chin be from uncomfortable digs and chatters afterwards. The conditions which next demand notice in the case of turning-tools are those which must be observed to preserve the proper position of the edge under the strain put upon it. These relate to the form of the tool, and, in the case of cylindrical work with fixed tools, to the part of the surface at which the edge of the tool should be applied. Drills and boring tools require little notice in this respect, for, as the strain is round their axis, it is only necessary that their shafts should be strong enough not to twist or bend. It must, however, be remembered that when common drills are required to be very acute, the edges should be thrown up a little or hollowed out so as to give the acuteness on the upper face as explained above.[26] [26] The common form of drill is rendered far more efficient with wrought iron and materials that require _cutting_, by twisting the flat shaft when hot, so as to reverse the position of each edge after the manner of a screw-auger. The lower faces can then be kept as close as possible to the face of the work while the twist will give a moderate degree of acuteness on the upper face. Hand-turning is simply a matter of manual dexterity, and as any part of the same plane or the same circumference presents the same surface to the edge of the tool, the correct relation between the edge and the surface can be obtained in many places, and therefore the particular point at which the edge should be applied is simply a matter of personal convenience, and may vary with the height of the lathe or that of the workman, or the shape and nature of the tool employed. The use of the graver affords a good illustration of this; and it may be remarked, in connection with this tool, that none is more simple in construction, more perfect in principle, or more convenient in application. When its use is once thoroughly mastered it will do anything from smoothing a pin to roughing out a cylinder four or five inches in diameter. The graver is simply a square bar of steel ground off obliquely at the end; and by varying the obliquity of this slope the act of grinding one plane face will give two cutting edges of any desired acuteness, and three heels from which to use these edges at choice. In hand-turning only one edge of the graver is used at a time, and the lozenge-shaped face is made the lower face common to each edge. Now, when the graver is used for roughing, the point is generally buried in the clean metal _below_ the central line of the work, and the lower face is placed against, and takes the shaving from, the little shoulder which it forms on the cylinder. When the graver is used for smoothing, the lower face is placed nearly flat against the face of the work, and the edge is generally made to bite on, or a _little above_, the central line. But for very light finishing cuts the graver may be used from the heel at the bottom of its lozenge face, and in this position its point is over the top of the work, bringing the biting part of the edge _still more above_ the central line. Thus, the only three points to consider in placing the tool in hand-turning are--first, that the lower face of the edge should occupy the proper position with regard to the surface; secondly, that the handle of the tool should come up conveniently to the hands of the operator; and thirdly, that while these two conditions are observed, the heel of the tool should be able to take a firm bearing on the rest. The best rule for hand-turning is, therefore, to apply the tool to the work, with these ends in view before fixing the rest, and then to bring that up to the necessary position. When the heel of any hand tool has a firm bearing on the rest, and the edge is applied in the wedge-like position, the preservation of this during the progress of the work depends on delicacy of touch rather than muscular power. But when the edges are applied out of their natural line, it puzzles a strong wrist to keep them to their cut at all without digging into the work. This affords the best practical illustration of the necessity of careful attention to the position of slide-rest tools, which are deprived of all power of accommodation to the sense of touch, and which therefore require accurate adjustment in the first instance. For the motion of the tool is now confined to that of the rest, and as this moves in horizontal planes, the edge of the tool must be applied to the work on that parallel plane which passes through the lathe centres. The reason for this rule will be at once apparent, if the edge be not placed on this central line in facing up a plate--for then it will lose its cut before reaching the centre, leaving a core untouched. Now although it would require an exaggerated error in the position of the edge to lose cut altogether in turning a cylinder, yet this example proves that, unless the edge be applied exactly on the central line the relative position between it and the surface of the work, on which the cutting action depends, will imperceptibly change with the reduction of the work; and supposing this to vary much in diameter, the same tool may cut beautifully on one part and badly on another. Fig. 4, which illustrates the cutting action of the edge, has been purposely placed on a part of the circle where a slide-rest tool could only act for a very short time, in order to draw attention to the difference between those conditions which govern the cutting action, and those which depend on the motion of the rest from which the tool is used. It is obvious that if Fig. 4 were moved inwards on a horizontal line the edge would pass over the smaller circle without touching it. The illustration is of course exaggerated, but it proves that Fig. 7 is the only position in which the tool will cut over varying diameters without some change in the relative positions of its lower face and that of the work. Hence the usual instructions to apply the edge about the centre of the work. But Babbage has observed, that however good this direction may be as far it goes, it is insufficient and liable to mislead when given alone. It is impossible to do away with elasticity when the tool is supported at some lateral distance from the line of strain, as in the slide rest or planing machine; and unless this elasticity is counteracted by the position of the tool, it may upset the best position of the edge. To meet this, Babbage gives the following rule--First, consider whereabouts the tool itself will bend under strain on its edge, when fixed in the rest; and then take care that this part of the tool, which Babbage calls "the centre of flexure,"--is placed above a line joining the centre of the work and the edge of the tool. Fig. 7 will explain the reasons for this rule and the consequences of neglecting it when there is much strain put on the edge. Let E, I, F, be the line joining the centre of the work and the edge of the tool. Then if G above this line be the centre of flexure, when the tool bends its edge must follow some part of the arc, H, I, J, from G as a centre, and will be thrown out of the work. But if K below the line, E, I, F, be the centre of flexure, then, under the same circumstances, the edge will follow some part of the arc L, I, M, from K as a centre, and must dig into the work. It is important to recognise this principle, because while it shows that every tool in which the top of the edge stands _above_ the shaft must be liable to the evils resulting from elasticity, it shows also that even cranked tools may fail to obviate the danger, unless care is taken to place the weakest point in the shaft above the central line. Babbage remarks, that although it is not always possible to strengthen any part of a tool, it is always possible and sometimes desirable to make some particular point weaker than the rest, by cutting away a little where the weak point should be. Fig. 9 shows that the crank principle may be applied in another form, and although the crank is upwards in this case, the same object is attained by making P the weakest point, and placing it above the central line, N, O. This form, however, is only used for light finishing cuts; for any unnecessary length of crank evidently adds elasticity, and Holtzapffel observes that, "in adopting the crank form tools the principle must not be carried to excess, as it must be remembered we can never expunge elasticity from our materials, whether viewed in relation to the machine, the tool, or the work." The crank, therefore, should only be just sufficient to give the edge the right direction if the tool should spring; and Holtzapffel remarks, that as a tool will generally bend somewhere in the central line of its shaft, it is sufficient if the top of the edge is kept on or just below this line, as in Fig. 8. Referring again to Fig. 7, and looking at the line C, D, as a plane surface, and I, F, as a line perpendicular to that surface, the same arguments and illustrations apply to the form of a tool in the planing machine. The point at which the tool is now applied ceases to be of moment. Having considered the conditions necessary to insure the best cutting action of acute edges and the preservation of that action during the progress of the work, it remains to treat of the edges most suitable to particular materials, the method of giving them any desired angle, and the manner of applying slide-rest tools so as to obtain the best work with the least expenditure of force and time. Willis observes that different metals and qualities of the same metal require to be treated with edges differing in their degree of acuteness, and all the standard authorities concur in giving the following code as near enough for all practical purposes. The modification of these angles is ruled by the general principle that fibrous and cohesive materials require more acute edges than crystalline and granular substances, as will be apparent in the following code:-- Wrought iron and steel 60° Cast do. do. 70° Roughing brass 80° Finishing do. 90° Thus the edges available for the metals commonly treated in the lathe find their maximum at 90° and minimum at 60°. The maximum requires no explanation, as when any edge is larger it ceases to be an acute edge. With regard to the minimum of 60°, Babbage has pointed out that this is dependent not only on the strength necessary to resist the strain of the cut, but further and chiefly on the temper which must be preserved in the edge; and if this be less than 60° the mass of metal composing the extreme edge will be too small to carry off the heat generated by the cut, consequently the extreme edge would soon lose temper and become useless. But these different edges are formed in very different ways according to the purpose for which the tool is intended; and this will be best understood by comparing the action of a hand-turning chisel with that of a pointed slide-rest tool. In the first case the edge is applied at an oblique tangent to the surface, and removes the shaving by passing under its whole width, much after the manner in which an apple is pared, or a ribbon unwound from a stick, when the lower edge of one turn just overlaps the top edge of the turn below it, and so on. In this case the shaving can be cleanly detached by one straight edge. But the position and motion of the slide-rest tool being perpendicular to the axis of the work, its action becomes that of uncoiling rather than paring; and as a cord or wire wound round a stick touches the face of the stick in one direction, and the coil next to itself in another, so in this case the width and thickness of the shaving lie in opposite directions, as illustrated by the dark band in Fig. 10. Consequently, unless the shaving be cut simultaneously in these two directions--viz., from the face of the work on one side, and from the matter under removal on the other, it is obvious that it must be _torn_ from the work in one direction, thus increasing the labour and spoiling the appearance of the work if the tearing should be from its face. Now, in practice, at any rate in the rough cut, it is usual to take the width of the shaving from the superfluous matter; and if the tool be placed, as in Fig. 11, it can only cut on one edge; thus the edge of the shaving will be torn from the face of the work, while the point of the tool will trace a fine thread in its progress along it, leaving the face with a rough unfinished appearance. But if the edges be formed so that they can be placed as in Figs. 10 and 12, then both can cut simultaneously, and the screw-like trace of the point may be obliterated. This method of using the tool will leave the work with a good face from the first rough cut, leaving very little for the finishing cut to do; in addition to which the labour will be reduced to a minimum, thereby permitting a much heavier cut from the same amount of force. In turning any plane surface the corner of the edge should be sufficiently relieved from it to avoid the danger of catching; but, in turning cylindrical surfaces, if the tool be carefully made and placed, the slope of the upper surface will carry the corner out of cut. Experiment must decide the exact adjustment; but the great aim should be to keep the face of the tool next the work as nearly parallel with it as possible, because it is only that face which leaves any trace of the tool's action on the face of the work--the action of the other edge being lost with the shaving. [Illustration: ILLUS. No. 4] Thus tools may be broadly divided into two classes--viz., single-edged and double-edged--remembering always that this distinction refers to the manner in which they should act, and not to the number of edges which it may be convenient to form on the same tool. In single-edged tools, whether there be one or many edges, each edge acts independently in removing its own shaving, and may therefore be formed separately. In this case a longitudinal section, showing the angle of the point, will give a true idea of that of the cutting edge. But, in the case of double-edged tools, as the two edges should co-operate in the removal of the same shaving, they must also be formed so that, while each lower face can occupy its proper position with regard to that surface of the work opposed to it, both edges shall possess the same degree of acuteness. In this case the two edges are formed by three planes--viz., two side faces and one upper surface common to both; and the angle of the point is now not only not that of the cutting edges, but has not even any fixed relation to them, for the cutting edges may vary some 25° or more on the very same longitudinal section of the point. Prof. Willis has pointed out that in these tools the angles of the cutting edges depend on the _section_ and _plan_ angles of the point _conjointly_ (Fig. 8 is a _section_ view; Figs. 10, 11 and 12 are _plan_ views). From this it follows that cutting edges of exactly the same angle may be obtained by a great variety of combinations in the plan and section angles; and in note A, U, of Holtzapffel's work, vol. ii. p. 994, Prof. Willis has given a table, showing some of the different combinations by which cutting edges of certain angles may be produced with accuracy and simplicity. The following short table is arranged from this source and though much abbreviated will be found sufficient for all ordinary purposes. [Illustration: +-------------------------------------+ |PLAN ANGLE WITH SECTION ANGLES | | +-------+-------+-------+ | 140° | 79.5° | 69° | 58° | | 120° | 78.5 | 67 | 55 | | 100° | 77 | 63.5 | 49.5 | | 90° | 76 | 61 | 45 | | 70° | 72.5 | 53.5 | 29 | | +-------+-------+-------+ |WILL GIVE ------- CUTTING EDGES | | -------+-------+-------+ | 80° | 70° | 60° | +---------------------+-------+-------+ ] The graver will again serve to illustrate the use of this table; for although only one edge is employed at the same time in hand turning, it belongs properly to the double edged class. This will be very apparent if a graver is held point upwards side by side with a point tool, and the dotted lines are added in Fig. 8, to make the similarity of form more evident. Now Holtzapffel has said of the graver when employed for its original purpose of engraving, that "no instrument works more perfectly," pointing out that, while both the edges are engaged in cutting the same shaving, both the lower faces of the edges are respectively inclined at the smallest possible angle from the sides of the V-shaped groove. Fig. 10 has already been used to illustrate the best position of the slide-rest tool, and if the illustration be turned round until the letters Q, R, read horizontally, and this line be taken to represent a flat surface with the graver acting upon it, it will be seen that the shaving is removed in exactly the same manner in both cases; the only difference being that the section of the shaving is triangular in one case and rectangular in the other. But so far as the tool is concerned the action is identical in each case, thus proving that every point tool may be so made and placed as to merit Holtzapffel's eulogium on the graver, and that this simple tool is in fact the type of all double-edged tools. The graver being made from a square bar has of course a plan angle of 90°, and using it to illustrate the table, we will suppose that it is desired to give it two cutting edges of 60° each. Referring to 90° under the heading of "plan angle," 45° will be found on this line in the column over "cutting edge" 60°; denoting that the section angle of the point, _i.e._, the slope at which the graver is ground, must be 45° to give the desired edges. In the same way, if the section angle were 61° the cutting edges would be 70°. But taking the plan angle of 120°, the table shows that this would produce the same cutting edges of 60° with the larger section of 55°; and from this we have the important rule that, _in obtaining cutting edges of any given degree of acuteness the larger the plan angle is made, the larger also may be the section angle_. Thus pointed tools though constructed on the principle of the graver are an improvement on it in its simple form; for by making both plan and section angles as wide as possible, it is obvious that the strength and durability of the point will be much increased. It is, therefore, always better to give slide-rest tools a large plan angle, as in Fig. 12; and plan 120°, with section 55°, will be found a very useful and durable tool for surfacing purposes with wrought iron. When there are rectangular corners to cut in and out of, of course the plan angle cannot be more than 90°, and then it is well to sacrifice a little of the acuteness, as the section of 45° makes the point rather too weak. It is also worthy of remark as a mathematical fact, that unless the plan angle exceed 60°, it is impossible to obtain two cutting edges of that degree of acuteness; and in any case, such a plan angle would be radically bad, because it could not be used on the double-edged principle without _undercutting_ the shaving. It is somewhat remarkable, in connection with this point, that while Holtzapffel, vol. ii. p. 536, recommends prismatic cutters, he should add a footnote which indirectly but most conclusively corroborates Prof. Willis' condemnation of that particular form, by admitting that the proper degree of acuteness cannot be given to both edges. As the practical result of a circular edge is to cut in two opposite directions,--the edge passing gradually from one to the other,--so round-nosed tools belong properly to the double-edged class, and are open to great objections unless carefully formed on this principle. [Illustration: ILLUS. No. 5] This is illustrated in Fig. 13, representing an oblique section of a round bar; and supposing the section to be made at an angle of 45°, it is obvious that the highest part of the edge at S will be exactly of this angle, while the lower point at T will be 135°, and the side points at U and V will be 90° each. Thus, between the point S and the points U and V on each side respectively, the edge will gradually pass through a range of 45°, consequently no two adjacent points on the same side will be of the same angle, and the highest point S may be too acute to stand while the lowest, U or V, is too blunt to cut. Whenever, therefore, it is intended to round the nose of the tool, it should be first formed as a double-edged point tool, with a section angle agreeing as nearly as practicable with the intended degree of acuteness in the edge, so as to secure the highest points from being too weak, and the table given above will show what plan angle must be used, in combination with this section, to secure any part from being too blunt. Thus, supposing a circular edge of about 60° is desired, the section of 58° approaches this most nearly, and if the plan of 140°, which, with this section, gives two straight cutting edges of 60°, be adopted, there can only be a variation of 2° in different parts of the edge. But it will be observed that this combination admits of very little rounding; and although less acute edges, being obtainable with a smaller plan-angle, admit of rather more rounding, it may be taken as a general rule that when any tool is much rounded on the nose, so as to present a large segment of a circle, different parts of the edge must vary considerably in acuteness. Although Professor Willis objects to rounding the nose of a tool at all on account of the necessary variation in the character of the edge and some other reasons, I am disposed to think that when the tool is carefully formed on the principles given above, it is very advantageous to round off the point slightly for taking heavy cuts; and I have found this form a favourite one in such workshops as Woolwich Arsenal and Portsmouth Dockyard. But care must be taken to place the nose of the tool towards the width of the shaving (presuming that this is taken from the matter to be removed, as it usually is,) for unless the edge is straight, and almost parallel with the face of the work as it leaves it, the face would be marked with a series of concave grooves of greater or less width, according to the feed given to the tool; and even when this is very slow, if the curved part of the edge were placed towards the face of the work it would present the appearance of corrugated iron, when examined under a magnifying lens. Willis further advances against the round nose that, as the shaving removed by it must be of a curvilinear section, it will oppose more force in rolling itself off the edge, than a flat shaving. This would be quite true if a flat shaving could be rolled up on itself like a piece of tape or ribbon; but I think the professor has overlooked the fact that when two cutting edges have one common upper face the shaving must be bent laterally as well as in its length; and I am disposed to think, from practical experiment, that there is very little difference on the point of the force required, and that when a point of large plan angle is just rounded off it stands better and cuts sweeter than when the point is not so rounded. But this only applies to heavy cuts, and for ordinary surfacing work nothing can act more perfectly than a point tool of wide plan-angle placed as described above. If a double-edged tool, with edges of 60°, be thus used in turning wrought iron or steel, and be well lubricated with clean water during the progress of the work, its face may be left with a burnished brilliancy that a touch of the finest emery would spoil. But, as the scheme of this paper is confined to the principles which determine the action of edges, and the rules by which those edges may be formed with certainty, it will be well to conclude these remarks with a few hints as to the construction of ordinary slide-rest tools. Bearing in mind that all double-edged tools belong to the graver class, it is well to form the side faces carefully in the first instance, and then never to alter these, but to keep the tool in order by grinding in the upper surface only, just as the graver is treated. Nasmyth's cone gauge, illustrated in Holtzapffel, vol. ii., p. 534, and also in "Baker's Mechanism," p. 236, affords a ready means of forming the side faces with accuracy. But the range and convenience of this gauge is much increased by dispensing with every part of the arrangement, except the cone itself. This can be made of any piece of stout metal bar turned truly, with the slide-rest set at an angle of 3°, and the base should be broad enough to stand steady by itself when squared off truly in the lathe, as in Fig. 14. Two marks can then be made upon it: one as at W, showing the exact height of the lathe-centre when the cone stands on the bed of the lathe, and another as at X, showing the height of the centre when the cone is placed on any given part of the slide-rest. Thus, in whatever direction the tool is to be used, its adjustment can be accurately made in the first instance on the slide-rest itself, and again tested after the tool is clamped down. It is too common a practice in setting slide-rest tools to wedge up one end or the other, with regard only to the application of the edge on the central line. But this generally sacrifices the position of the lower faces, which is essential, to a consideration which has been shown to be only secondary. The best plan is to keep several strips, varying from 1/32 to 1/2 inch in thickness, but all about as long and wide as the shaft of the tool. These can be made of bar iron for the thicker strips, and sheet iron or tin for the thinner ones; and by using any two or three of these together, the tool can be packed up parallel to the bed of the slide-rest. The adjustment of the edge can thus be made with the greatest ease and certainty without altering the relative position of the lower faces. It may be well to remark that in using the cone gauge, it is the lower faces of each edge which are to be tried against it, and not the front line of the point, as the inclination of this rule will vary slightly with variations in the plan-angle of the tool, although the slope of the faces remains the same. But the section angle is always to be estimated from the front line, whatever its slope may be. [Illustration: No. 6] When the principles which this paper has endeavoured to embody are once thoroughly understood, no handy workmen need ever be at a loss to form and apply his edges with the best effect under any shape the circumstances may require. The first point to be observed is the manner in which the work should be attacked--that is to say, whether the removal of the shaving or scraping requires the use of a single or double-edged tool. The next point is the position of the lower face or faces of the edges, so that they may be applied in the required direction, and in the position explained above. This involves the nature of the treatment best suited to the material, both as regards the kind of edge employed and the principle on which it should be applied--viz., cutting or scraping. In double-edged tools the position of the two lower faces determines that of the point, which is simply an accident resulting from the meeting of the cutting edges; but which, when so determined, affords a guide for the slope of the upper face. This must be so ground that it gives each edge the same degree of acuteness. Thus, in Fig. 15, the point of the tool being at A, the slope must be made in the direction A, B; while, in Fig. 16, the point being at C, the slope of the upper face must be in the direction C, D. The writer is fully aware that those who expect to find "a rule of thumb" in this paper, will be miserably disappointed. But while he is conscious that the principles of which he has treated admit of a much fuller and yet more concise definition, he would remind the novice that there is "no royal road to learning," and that where practice of hand is wanting it can only be supplied by greater knowledge of principle. His object will therefore be fulfilled if this supplementary paper can supply any explanation or illustration of principle that may add to the practical utility of a work so exhaustive of its subject as "the Lathe and its Uses." DETACHED-CUTTER HOLDERS. Where amateurs experience inconvenience in making their tools from the want of a forge, the use of detached cutters in a tool holder will be found of the greatest advantage for outside work. Even in plain turning there must always be some special forms for cutting into odd corners and deep grooves; but with a good tool holder and a grindstone, which is an indispensable piece of furniture in every metal turner's shop, the cumbrous array of slide-rest tools may be reduced to a few special forms and a very small box of cutters. These also possess another great advantage; for the spirit of the old adage quoted by Holtzapffel-- "He that would a good edge win Must forge thick and grind thin," may be carried out far more conveniently than in the case of whole tools which are generally filed into shape before tempering, and when worn down must go to the fire again and have the process repeated. But the detached cutter admits of being tempered evenly throughout its whole length and ground up afterwards as long as it lasts, without going to the forge again to the deterioration of the steel. The patterns of tool-holders are innumerable, but very few are good for general service, because most of them are arranged so that the natural sides of the cutter are used for the face or faces of the edge. Thus either the plan angle of the point is limited to the angles presented by the transverse section of the cutter employed, or else the section angle is fixed by the position in which the cutter is clamped. Holtzapffel's arrangement is open to the first objection, Babbage's to the second. To obviate this inconvenience, Prof. Willis arranged a holder which clamps the cutter at an angle of 55° from the horizontal line. Thus no side can be used either for the lower or upper face of the edge, but any faces can be ground upon it; and the plan and section angle of the edge may be varied at pleasure within the whole range available for metal turning. Prof. Willis's holder for the cutter is almost a facsimile of his admirable tool-holder for the slide-rest, than which none is more convenient or can act more perfectly. But the arrangement is a little complicated for a cutter holder, and must be very carefully made with the knowledge of certain laws, if it is to insure a perfect grip of the cutter. It is also designed for the use of sound wire cutters which require filing flat on one side. [Illustration] Adopting Willis's inclination for the cutter I have found that all its advantages may be secured with a simpler form of holder and common square for steel for the cutter. The holder is simply the modification of an old pattern to suit the inclination of 55°, and the sketch needs little explanation beyond saying that the nick in the solid part should be rather less than a square angle, and made perfectly true all the way down, or, if anything, rather hollowed in the middle, so as to insure the greatest amount of pressure at the top and bottom, as otherwise the cutter might not sit quite true and firm. The angle at the end of the strap against which the cutter bears should be rather _more_ than square, both to allow for any want of exact truth in the squaring of the cutter and to avoid the wedging action which would be set up on tightening the screw if this angle were _less_ than square, as this could of course create a risk of splitting the strap. The end of the screw and the cup in which it fits should be round, as this allows of a little play and insures a truer grip in the strap than a pointed screw working into a conical hole. A perspective sketch of a detached cutter is added, with dotted lines to show how exactly the arrangement of the faces can be accommodated to the positions which have been shown to be the best in solid tools for the slide-rest. D. HAYDON. NEW FORM OF ROSE ENGINE BY E. TAYLOR. Seeing that the Editor of the above Articles has illustrated and described Holtzapffel and Co.'s Rose Cutter and two methods of executing rose cutting, the latter being the ordinary rose engine, I am induced to send you a description of a method that I have adopted whereby I can with considerable despatch execute this description of turning. I will first preface my description by saying some thirty years ago I purchased Ibbetson's Book on eccentric turning, and I was so much taken with it and the illustrations, that I determined to make myself in accordance with his description and engravings an eccentric chuck; and although I was a long time about it, being at the time much otherwise engaged, I succeeded beyond my expectations, and was enabled to do some very fine work with it; and I have never regretted the time I spent over the chuck, as I became familiar with metal turning and screw cutting _flying_ in the lathe, which latter I was surprised to find how easily I could execute. However, I was much disappointed in the usefulness of the chuck (Holtzapffel's eccentric cutter, which I purchased is far more useful), and also with the tediousness of using it (fancy stopping the lathe to alter the chuck 360 times or 180 times to cut a row of circles either distinct or overlaying each other), and there was also a certain vibration occasioned in using the chuck which I also disliked. I therefore determined to cut up some rosettes and convert my headstock into a rose engine, to effect which object I got Holtzapffel and Co. to return up with a new steel collar and make my mandrel traversing. I cut myself a rosette both ways with 16 waves, and I was much pleased with the variety of work I could perform with this one, but the rosette took me a long time to make, and disheartened me from cutting up a variety. It, however, occurred to me that if I added an extra mandrel by the side of and attached to my headstock, and on which extra mandrel, if I had an eccentric chuck connected with a rod to the wall of my room, I could get my headstock to oscillate, and by connecting and multiplying wheels cause as many waves on each revolution of my principal mandrel I pleased; this after much time and patience I succeeded in doing, and worked it with the hand motion often adopted for rose work. After between two and three years, I put the extra mandrel over my principal mandrel instead of by the side as before, to enable me to dispense with the hand motion and to work the upper mandrel with the slow motion on my lathe wheel, and which I found a very great improvement, and I now give the details of the plan I have adopted for the benefit of your numerous readers. The drawings are to a two-inch scale, or one sixth of their full size. Fig. 400 is a side view of my headstock (part in section) with the upper mandrel, A, added, showing the connection by an intermediate spindle, B, with the large cog wheel, C, on my lower mandrel, D, and other additions. The back centre, E, of my headstock is connected with the back screw, F, and drawn out or pushed in with it, and is fixed by the set screw, G. When drawn out the steel screw, H, at the end of the mandrel, D, removes to receive the screw guides which are then fastened by it, and the piece, I, with segments of a thread to match the guides, is slid up by a wedge to the guides and then fastened by the screw J, I, can also fix some roses cut on the side, and other apparatus with this screw H.[27] [27] It is not a good plan to make the point, E, movable. It would be better to slip the guides or rosettes over it: and generally to arrange this part as usual with a traversing mandrel, P, H. The large cog wheel, C, is screwed up with the screw, K, to the mandrel pulley, L. On the front of the pulley is the division plate as usual. The intermediate adjustable spindle, B, is carried in a frame shown separately by Fig. 405; it is allowed to rise or fall as may be required for the wheel, M, to gear with the great wheel, C; provision being also made for an intermediate wheel, N, (see Fig. 403) to connect the wheel, O, with the wheel, P, on the upper mandrel when required. The eccentric chuck is fixed on screw Q of the upper mandrel. Fig. 401 is a plan of the mould for the back cast-iron upright, fixed to the headstock with screws at the foot, showing the circular grooves 1, 2 and 3, necessary for the spindles for the connecting wheels; the centre hole, 4, is for the gun-metal collar, or the upper mandrel. Fig. 402, is a plan of the mould for the front cast-iron upright; the centre holes 1 and 2 are for the collars of the mandrels. No. 2 is made to just fit over the steel collar of the lower mandrel, and is fixed to the headstock by a brass rose and three screws; it is also fixed at the foot with two screws to the headstock. These two castings, 401 and 402, are bolted together with two bolts and nuts through the holes 5 and 6, as shown in Fig. 400. Fig. 403, is a back view of the additions, showing the cog wheels and their connections, also the brass bearings for the lower mandrel required when allowed to traverse. This was a solid piece of brass with a hole bored out and ground to fit the mandrel. It was then drilled the whole depth in two places, for two steel steady pins, _b_, _c_, made to fit quite tight, and at both ends for bolts and nuts, _a_, _d_, afterwards sawn in two with the circular saw, and when put together and two holes drilled through the thickness for fixing it was put in its place, adjusted, and re-ground on. The holes for fixing were very carefully continued through the cast iron upright, and the whole was finally fixed with two screw bolts and nuts. Fig. 404, is a front view, showing the eccentric chuck, R, on the upper mandrel, the slide of which when used is connected with the bracket in the wall, Fig. 406, causing the whole apparatus to oscillate in proportion to the eccentricity of the chuck on its centres one of which is marked at S. The chuck has a circular movement for laying the waves in any position with one another, but which also is effected by another plan to be presently described. The whole poppet with its fittings is hung on centres similar to the rose engine described in this work. The top part of the bed T removes, and the two screws, one shown at V, are taken out to allow the oscillation. The large cog wheel has 192 teeth. [Illustration: FIG. 400.] [Illustration: FIG. 401.] [Illustration: FIG. 402.] [Illustration: FIG. 403.] [Illustration: FIG. 404.] [Illustration: FIG. 405.] [Illustration: FIG. 406.] The whole of the additions to my headstock were all of my own fitting up. The brass cog wheels were bored out and ground to fit an arbor made on purpose, exactly corresponding in diameter with the ends of the spindles so that they might fit indiscriminately on either spindle. When turned up, the teeth were cut with a circular cutter, which I made just of the exact shape and thickness required for the space between the teeth. The cutter was turned of steel; then wrapped in leather and enclosed in sheet iron. It was then put in the fire, made red hot, and left for the fire to go out, the next day being soft, it was cut with sharp chisels into a circular file and hardened, and with it in the cutter frame the teeth of the wheels were cut. The central boss of each wheel has a notch cut across the face to receive a pin in the arbor and in the spindles, which prevents the wheels from turning round on the latter when screwed up. This rose engine works beautifully smooth and easy, and ornamentation can be done with it with greater rapidity than with the ordinary engine, by arranging the connecting wheels so that the upper mandrel makes so many waves and one-half, one-third, one-fourth, one-fifth, one-sixth, or any other part of a wave, on each revolution of the lower mandrel, because then it requires certain revolutions of the lower mandrel before the tool comes into the same cut again--say, for instance, it makes 4-5/6 waves on each revolution, then it takes 29 revolutions of the upper mandrel to complete the pattern, whereby certain patterns are completed without stopping the lathe, which is an advantage that the rose engine proper does not possess. Another great advantage is, that the waves can be either flat, sharp, or intermediate, as required for large or small work, by altering the eccentric chuck on the upper mandrel. I give a few specimens, not for the beauty of design, but to illustrate the working of the engine. The centre of Fig. 407 is performed by having a wheel of 80 teeth on the upper mandrel, connected with one of 25 teeth on the intermediate spindle, which has another of 50 teeth connected with the large wheel of 192 teeth on the lower mandrel; thus, 80/25 50/190 = 1-1/5 producing on each revolution of the lower mandrel one wave, and one-fifth of another wave, requiring six revolutions to complete the pattern. The remainder of the pattern is completed by wheels, 16, 50; 48, 192 making 12-1/2 waves on each revolution of the lower mandrel, requiring 25 waves to complete the pattern, and laying the waves over each other, and with the slide rest movement of the tool. Fig. 408 is produced by wheels 32, 48; 24, 192 making 12 waves. The centre is done by altering the eccentric chuck each time. It was purposely executed askew, by the tool not being placed in the centre, to show the importance of doing so for some patterns. The rim was executed with the same wheels, and with the slide rest movement of the tool, and, after two cuts, the chuck turned half round, to lay the waves over each other for the other two cuts. Fig. 409 is all executed with wheels 96, 30; 25, 192 making two waves and two-fifths of another wave, requiring 12 waves to complete the pattern. The two centre rims produced by placing the tool above the centre. The outside by four movements of the slide rest tool, illustrating how soon patterns are produced, and when well cut up look very pretty. Fig. 410 is executed with wheels 80, 50; 25, 192 making four waves and four-fifths of another wave, requiring 24 waves to complete the pattern. The centre is all done without stopping; the outside rim by altering the eccentric chuck four times, to make each successive wave flatter. Fig. 411 is an illustration of the upper mandrel, making 5-1/3 revolutions to one of the lathe, requiring 16 revolutions to complete the pattern and slide-rest movement. Fig. 412. The outer pattern of this figure is produced by the upper mandrel making 12-4/5 revolutions to one of the lathe, requiring 64 revolutions to complete the pattern. The centre is a rosette of 5 waves, slide-rest movement and placed across each other. [Illustration: FIG. 407.] [Illustration: FIG. 408.] [Illustration: FIG. 409.] [Illustration: FIG. 410.] [Illustration: FIG. 411.] [Illustration: FIG. 412.] Fig. 413. The whole of this pattern produced by the upper mandrel making 3-3/5 revolutions to one of the lathe, producing 18 waves across each other with slide-rest movement for the middle rim. Fig. 414 illustrates a rosette of nine waves with slide-rest movement, and 3 divisions of the circular movement of the eccentric chuck for each successive line, producing the waved appearance. Fig. 415 illustrates a rosette of 24 waves with the slide-rest movement. Fig. 416. Another illustration of a rosette of 24 waves, rather more sharp than in Fig. 415, with slide-rest movement and 9 divisions of the circular movement of the eccentric chuck, giving it a pleasing circular waved appearance. Fig. 417. Also another illustration as the last, but with the waves much sharper, the slide-rest movement and only two divisions of the circular movement of the eccentric chuck producing the star-like pattern. Fig. 418 illustrates also a rosette of 24 waves, with the eccentric chuck turned half-way round with each movement of the slide-rest, producing the pattern so often seen on the back of watches, only being on wood it is on a larger scale. [Illustration: FIG. 413.] [Illustration: FIG. 414.] [Illustration: FIG. 415.] [Illustration: FIG. 416.] [Illustration: FIG. 417.] [Illustration: FIG. 418.] The above illustrations are sufficient to give a distinct idea of the working of my engine, and the last four show how easily patterns are multiplied and varied. The whole of the preceding patterns were executed by the wood being chucked in the lathe in the usual ordinary way without any particular chuck whatever, but in combination with any of the ornamental chucks innumerable patterns can be produced. Fig. 419 is one illustration with an eccentric chuck on the lathe mandrel. [Illustration: FIG. 419.] That my description may be complete I will now give drawings of my eccentric chuck for the upper mandrel. It requires to be constructed differently to the ordinary eccentric chuck, as the circular movement requires to be always _central_, and only the slide carrying the pin to receive the rod must move eccentrically. [Illustration: FIG. 420, also 422.] [Illustration: FIG. 421, also 423.] Figs. 420 and 421, are full-size drawings of my eccentric chuck on my upper mandrel, used for producing the foregoing specimens. In this case I have preferred a wood foundation, as not being so likely to run off as metal, on reversing the motion which is sometimes necessary on account of idle wheels for the connections. I used a piece of well-seasoned Spanish mahogany, taking care that the grain of the wood was at right angles with the length of the screw of the mandrel. A piece of brass is screwed at the back to prevent the screw cutting into the wood. Fig. 420 is a section, and Fig. 421 a front view of the chuck, and I think all sufficiently clear. I will just say the long fine threaded screw I cut up with the stocks and dies in the lathe, using steel wire of the necessary size. This I manage easily, and keep the wire straight _by allowing it to expand in length_. I chuck the steel wire concentrically, and removing the centre from the back poppet, substitute a brass centre with a hole the size of the steel wire, which is allowed about a quarter of an inch entry. I then turn down a little below the depth of the intended screw thread for about half an inch in length next the back centre, to allow the dies to come back to be tightened up, and which must only be done at the commencement and not on the return motion of the dies. The collar on the screw is a piece of brass with a hole of a size to drive on the wire tight, and is then pinned on and turned up true, and finished with the division marks. OVAL TURNING AND ROSE CUTTING WITH TEMPLATES WITH MY APPARATUS. Figs. 422 and 423 are full size drawings of my chuck, with circular movement for templates for my upper mandrel, which has also a wood foundation. Fig. 422 is a section, and Fig. 423 is a front view. By removing the eccentric chuck from the upper mandrel, and substituting the chuck Figs. 422 and 423 with a circular movement, to receive templates of any pattern, OVALS with the oval template can be turned and also with any irregular templates, patterns cut and placed in any direction over each other, by causing the templates to work against a rubber or roller as most desirable, with an india-rubber spring to keep them together. The following illustrations will give some faint idea of productions from templates. Fig. 424, is the production of an oval template and slide-rest movement, both mandrels making equal revolutions. Fig. 425 the same as Fig. 424, with the patterns laid across each other by turning the circular movement of the chuck 12 divisions. Fig. 426, is from an oval template, which is caused to make two revolutions to one of the lathe mandrel producing 4 waves and undulations and with the slide-rest movement. It will be perceived in this case the form of the _oval_ is superseded by another pattern, and shows how great a change in the form of patterns from templates my rose engine with change wheels effects. Fig. 427, is also from an oval template, caused to make 5 revolutions to one of the lathe, and with the circular movement of the chuck and the slide-rest movement, and in this case the form of the oval is also superseded. Indeed, none but those who have made the matter their study would have the slightest idea that this pattern could be produced from an oval template. Fig. 428, is also from an oval template, it is finer than 427, but is done in the same way by the template making _nine_ revolutions to one of the lathe mandrel. [Illustration: FIG. 424.] [Illustration: FIG. 425.] [Illustration: FIG. 426.] [Illustration: FIG. 427.] [Illustration: FIG. 428.] The above are a few specimens of the oval, but sufficient to draw attention to the great variety of patterns that can be executed, and these illustrations have only been made to go even revolutions with the lathe mandrel; but of course can be made to go, as already described, uneven revolutions, laying the lines over each other for variety of patterns. Fig. 429, is a curiosity from a square template with equal revolutions, the outside rim and inside pattern by the circular movement of the template chuck. Fig. 430, is also from a square template made to go two revolutions to one of the lathe and with the slide-rest movement. The centre pattern with the circular movement of the chuck. Fig. 431, is the production of a heart-shape template, and with the slide-rest movement and the patterns laid across each other, the mandrels making equal revolutions. Fig. 432, is also from a heart-shape template made to go two revolutions to one of the lathe and the slide-rest movement. But in this case the slide-rest tool is used _on the opposite side of the lathe bed_ to the roller against the template, and therefore reversing the pattern, that is, the projections of the pattern are the hollows of the template, and _vice versa_. I have introduced it to show how easily patterns are multiplied in the most simple way. It will also be observed that the form of the template is superseded. Fig. 433, is another illustration of the heart-shape template, but made to go five revolutions to one of the lathe, with the circular movement of the template chuck, and the slide-rest movement, and in which case the form of the template is entirely superseded. Fig. 434, is also a similar illustration to 433, only finer; they can be of course as fine as desired. The above are, I think, sufficient to illustrate the productions from templates, some very pretty patterns can be executed. My object is more particularly to exhibit the use and extended application of my rose engine, and it will be perceived the last two are not the most easily working templates. The variety of patterns that can be executed with this engine are so innumerable that one may say they are infinite. Well may you in your article quote what Bergeron says of the rose engine, "that it is necessary to know thoroughly the particular one in use." I also make use of the cogwheel on my mandrel, by connecting it by a spindle and the change wheels with a large compound slide rest, for executing spiral turning, and also with my slide rest for ornamental turning, for small spiral work; and with a chuck with a circular movement I can cut several spirals to one stem. [Illustration: FIG. 429.] [Illustration: FIG. 430.] [Illustration: FIG. 431.] [Illustration: FIG. 432.] [Illustration: FIG. 433.] [Illustration: FIG. 434.] In concluding my description I will say the specimens given have all been cut on a plain surface, and this has been unavoidable on account of printing, but for the information of those unacquainted with the rose engine, the very great advantages of which over the eccentric and geometrical chucks are that the work can be executed on concave or convex surfaces. I make use of mine for ornamenting the roofs of temples and Chinese pagodas, either domed, curvilinear, or circular pointed, by representing them covered with shingles, &c. The geometric chuck will produce very beautiful intricate lacework, but not more so than my apparatus, as they both are on the same principle of change wheels, and can both produce equally fine work; but with my apparatus the work is always concentric with the mandrel, and therefore much more pleasing to execute. ELIAS TAYLOR. Hartford Villa, Patcham, near Brighton, Sussex. JUDD & GLASS, PHOENIX PRINTING WORKS, DOCTORS' COMMONS, E.C. ADVERTISEMENTS. ESTABLISHED A.D. 1822. [Illustration] JAMES LEWIS. 41, GREAT QUEEN STREET, LINCOLN'S INN FIELDS, (Late LEWIS & SON, of Wych Street, Strand), Engineer, Machinist, Lathe and Tool Maker, and Modeller of New Inventions, for English or Foreign Patents, from Drawings or Specifications, in Brass, Iron, or Wood. Also Manufacturer of Steam Engines and Boilers for driving Amateur Lathes, Pleasure Boats, &c., the Boilers fitted with Messrs. Field's Patent Circulating Tubes; whereby a great saving of Fuel and space is effected; or can be fitted for Gas. Model Steam Engines and Boilers kept in Stock, and the different parts may be had for making the same. _Estimates given for all kinds of Work. Country Orders punctually attended to._ JOSEPH LEWIS'S. PATENT COMBINED DRILL, CIRCULAR SAW, AND FRET MACHINE. [Illustration] _Patterns and designs for Picture Frames, Brackets, Reading Desks, etc., from 3d. each, or 2s. 6d. per dozen assorted._ To fix on Lathe £3 0 0 Ladies' Machine 4 0 0 Ditto ditto 5 0 0 Gentlemen's ditto 5 0 0 Ditto, with drill 6 10 0 Gentlemen's Machines with Circular Saw 8 0 0 Ditto, ditto, ditto, with the improved Saw-shifting Apparatus complete 9 10 0 Best Saws from 4-1/2d. per doz., 4s. per gross. Ornamental Drills from 1s. each. 51, HIGH STREET, BLOOMSBURY. [Illustration] JOSEPH LEWIS, ENGINEER, MACHINIST, LATHE AND TOOL MAKER, AND MODELLER OF NEW INVENTIONS. Manufacturer of every description of Plain and Ornamental Lathes, Chucks, Slide Rests, Tools, Drills, over-hand motions, Division Plates, &c. Lathes £8 0 0, £10 0 0, £12 0 0, £14 0 0, £16 0 0, £25 0 0. Amateurs supplied with Castings, Forgings of Lathe Engines, &c., and assisted in making the same. [Illustration] JOSEPH LEWIS'S Apparatus for cutting Screws of all nitches, self-acting, made and fitted to any Lathe. 51, High St., Bloomsbury, London. JAMES MUNRO, (_From Messrs. HOLTZAPFFEL & Co._) ENGINEER, MACHINIST, LATHE AND TOOL MAKER, MANUFACTURER OF ALL KINDS OF LATHE APPARATUS FOR PLAIN OR ORNAMENTAL TURNING, DIE STOCKS, TAPS, SCREW TOOLS, OVAL AND ECCENTRIC CHUCKS, CUTTING FRAMES, &c. 4, GIBSON STREET, WATERLOO ROAD, LONDON, S. [Illustration: MACHINE TURNING LATHE FOR PLANING, ETC., ETC. INVENTED BY J. MUNRO.] [Illustration: HAND PLANING MACHINE.] * * * * * JAMES MUNRO respectfully invites the attention of Amateurs and Manufacturers to the excellence of workmanship and construction of the various descriptions of Lathe Machines and apparatus produced in his manufactory, which has secured the approval of numerous patrons. * * * * * Specimens may be seen at the Museum of Patents, South Kensington. THE ENGLISH MECHANIC And Mirror of Science, IS AN ILLUSTRATED RECORD OF Engineering, Building, New Inventions, Photography, Chemistry, Electricity, &c., &c. * * * * * Weekly, price 2d.; post 3d. Monthly parts, 9d.; post 11d. Quarterly Subscription, post-free, 3s. 3d. Vol. VI. now ready, 7s.; post-free, 8s. * * * * * (From the _Weekly Times_.) "Technical education forms just now a topic of more than ordinary importance, and, as far as we can see, 'The English Mechanic' fills a large space in providing technical food for the workmen of Great Britain. There is scarcely a subject in the scientific or mechanical world that is not practically described in this excellent journal, and all the technicalities explained with a particularity quite remarkable. Here the workman in all departments of trade will find something to interest him, and many things explained by which he will be able to make the best use of his knowledge. The editor is always anxious to satisfy the cravings of his readers by giving every information possible to those who may require it. The trouble taken in this department is apparent on reference to the 'Letters to the Editor' and 'Replies to Queries,' both of which form original, very important, and useful features of the magazine. Under the head, also, of 'Our Subscribers' Exchange Club,' a means is opened for persons to exchange one article for another on mutually advantageous terms, and for this accommodation no charge is made. For instance, one correspondent says he has a silver watch which he would exchange for 'The Lives of Eminent Men;' another wants 'a cottage piano' for 'a three-horse power horizontal engine;' and a third has 'a hand sewing machine,' which he would give for 'a parallel sliding vice.' The illustrations of 'The English Mechanic' are worthy of all praise; they are drawn with an exactness which is so necessary, and so much appreciated by workmen, and are also well printed. Throughout the whole publication there is a visible, a practical, and technical knowledge of a high order--a kind of knowledge that is highly prized by all mechanics and men of science." * * * * * (From the Morning _Advertiser_) "'The English Mechanic.'--Illustrated with appropriate engravings, this valuable periodical is replete with information of the most valuable kind in every department of engineering, and in all applications of the principles of physical science. Its contents are exceedingly varied, and embrace, in a form adapted for immediate and convenient reference, a well-digested account of any noteworthy progress made in the mechanical or chemical arts, at home or abroad. For all purposes of the inventor, we do not know a periodical more likely to give him that assistance which he could expect to derive from recent means and appliances." * * * * * (From the _Observer_.) "'The English Mechanic and Mirror of Science' is a publication which contains much that is new and instructive in various branches of science." * * * * * Now ready, price 9d.; post free, 10d. THE ENGINEER'S SLIDE RULE, and its APPLICATIONS. A complete investigation of the principles upon which the Slide Rule is constructed, together with the method of its application to all purposes of the Practical Mechanic. * * * * * Published by the Proprietor, GEO. MADDICK, 2 & 3, Shoe Lane, Fleet Street, _And to be had of all Booksellers._ ESTABLISHED A.D. 1810. [Illustration] W. J. EVANS, =ENGINE, LATHE AND TOOL MAKER, AND GENERAL MACHINIST,= 104, WARDOUR STREET, SOHO, LONDON. TURNING, PLANING, SCREW AND WHEEL CUTTING TO DRAWINGS AND MODELS. Amateurs' turning Lathes of every description for Plain, Eccentric, Oval and Ornamental turning, also the various tools and apparatus the Mechanical Arts. _Instruction given to Amateurs in Plain and Ornamental Turning in all its Branches._ Contractor to Her Majesty's War Department. * * * * * LATHES, =AND EVERY DESCRIPTION OF TOOL FOR AMATEUR TURNERS.= Lathes complete, £7 5s., £9, £11, £16 16s. CHUCKS & ALL KINDS OF APPARATUS FITTED TO LATHES. =Engineers' Files and Tools of every description. AMERICAN TWIST DRILLS=, _And Self-centering Chucks for holding all sized Drills._ =AMERICAN SCROLL CHUCKS OF ALL SIZES= Can be readily fitted to any Lathe. * * * * * JOSEPH BUCK, =124, NEWGATE STREET, E.C., And 164, WATERLOO ROAD, S., LONDON.= W. BLACKETT, HOPE IRON WORKS, SOUTHWARK BRIDGE ROAD, LONDON, MANUFACTURER OF Engineers, Millwrights, Iron Ship Builders, and Boiler Makers' Tools. [Illustration: PLANING MACHINE.] [Illustration: SCREW CUTTING FOOT LATHE.] [Illustration: SLIDING AND SCREW CUTTING LATHE.] The Machines usually on hand consist of large and small Boring and Drilling Machines; Universal Shaping, Planing, Slotting, Bolt-screwing, Single and Double ended Punching and Shearing Machines; a variety of Self-acting, Sliding, and Screw-cutting Lathes, Hand Lathes, Foot Lathes, Compound Slide Rests, Planed Iron Lathe Beds, Ratchet Drill Braces, Screwing Tackle, Screw Jacks, and other Tools, such as are usually required in Engineering Establishments. Tools not in stock made to order. ADVERTISEMENTS. By Her Majesty's Royal Letters Patent. [Illustration] CUNNINGHAM AND CO., 480, NEW OXFORD STREET, LONDON, W.C., ORNAMENTAL WOOD AND METAL CUTTING MACHINES, AND DRILLING APPARATUS. ADAPTED FOR LADIES' USE. [Illustration] =Useful to the following Trades=--Organ Builders--Cabinet Makers--Pattern Makers--Chair Makers--Gun Case Makers--Marqueterie Makers--Toy Maker--Jewel Case Makers--Carvers--Cutlers--Leather Cutters--Engravers--Jewellers--Chandelier Makers--Electrotypers--Stereotypers--&c. Will cut Brass a Quarter inch thick with ease. The working of the Machine is very simple, and can be learnt by an amateur in five minutes. Patentees of the CAM ROLLER BUFFING, FOR Preventing Noise in Machinery. [Illustration] _See ENGINEER, Jan. 24th, 1868._ W. J. CUNNINGHAM AND CO. Beg to call the attention of the Public to their newly-invented Ornamental Wood and Metal Cutting Machine. Its extreme simplicity of construction precluding the possibility of speedily getting out of order, having no springs, and its peculiar adaptability to all kinds of fret-work render it at once an acquisition and an indispensability where accuracy, expedition, and high finish are required. The working is exceedingly easy, requiring no more exertion than an ordinary Sewing Machine for ladies' use, and making as little noise. Its great utility, combined with neatness of construction, fits it not only for the workshop, but the drawing-room of the amateur. The saw takes the place of a pencil in the hands of the operator, enabling him to produce the most elaborate artistic designs in wood-work. Box or other hard texture woods, 1 inch thick, are as readily sawn through as the finest veneer; metallic plates of 1/8 inch thick are also speedily pierced. Magnificent specimens executed by this machine, which have been universally admired for their extreme delicacy and perfection, and acknowledged to be unrivalled, may be seen at the inventor's address. The length of stroke of the saw can be varied to the work in hand. A simple mechanical contrivance is attached for blowing the sawdust from the saw whilst working, also a Circular Saw. An equally valuable invention is W. J. C. & Co.'s PATENTED DRILLING APPARATUS which is with the greatest advantage combined with the Sawing Machine, enhancing and enlarging its range of usefulness, or it may be adapted to a lathe, or as a distinct machine. Its great advantages over the ordinary lathe for drilling purposes must be apparent when by the addition of this apparatus to a 5 inch centre lathe the operator is enabled to drill in the centre of three or more feet, and the drill being vertical and worked by leverage, greater accuracy and facility is ensured. For ornamental purposes it surpasses all hitherto contrived methods, not being limited to one centre around which to describe curves, angles, circles, or any other mathematical figure, the operator is at perfect liberty to describe every conceivable device the fancy can dictate. Advantages and Capabilities of this Machine. _This Machine can be adapted to any Lathe, see page 131._ This Machine has a Circular Saw. This Machine has a Vertical Saw. This Machine has a true Parallel Motion. This Machine has no Springs whatever. This Machine has a Bead and Moulding Apparatus. This Machine has a Planing Apparatus. This Machine has a Drilling and Grooving Apparatus. This Machine has a Kinography that will engrave hundreds of different patterns on wood or metal. This Machine will cut Spirals and Ovals. This Machine has a Pentagraph, for reducing, enlarging, and cutting on the face of wood any drawing from paper or fret-work. _Circulars and all particulars on application._ Every kind of Materials, viz., Saws, Fret Patterns, Fancy Wood Drills, Cutters, &c., kept in stock. MANUFACTURERS OF TURNING LATHES. AND ALL KINDS OF MECHANICAL TOOLS. MOSELEY AND SIMPSON, LATE JOHN MOSELEY & SON, 17 & 18, KING ST. AND 27, BEDFORD ST., COVENT GARDEN, LONDON, W.C. ESTABLISHED 1730. [Illustration] [Illustration] LATHE AND TOOL MANUFACTURERS, &c., &c. PRICE LIST OF LATHES. Turning Lathe, Iron Frame and Bed planed true, Wood Tool Board, Iron Cone Mandrel, Cylinder poppet head, Rest and two Tees, Turned Grooved Wheel Crank, Treadle complete with 3 Chucks:-- No. 1. 3-1/2 inch centre, and 2 foot 6 inch Bed £10 10 0 " 2. 4-1/2 " " 3 " Bed 12 12 0 " 3. 5 " " 4 " " 15 15 0 " 4. 5 " " 4 " " } with Brass Pulley and Slide Rest } 21 0 0 " 5. 6 inch centre and 4 feet Bed with Slide Rest complete 25 0 0 " 6. 7 inch centre, 6 feet Bed, self-acting, and Screw Cutting leading Screw, and 22 Change Wheels 40 0 0 For Lathes of other descriptions, Estimates are furnished on Application. TURNING TOOLS. s. d. Chisels for Soft Wood, the set of 6 handled 8 0 Gouges " " 9 0 Tools for hardwood and metal, handled and ready for use, per dozen 15 0 Drills handled 0 7 Arm Rests Handled 2 6 Callipers from 1 0 Turner's Squares from 6 0 All Kinds of Chucks, Cutters, &c., made to order. Transcriber's Note: 1. Page 38, Bunhill-row, Covent-garden and Charing-cross seems to be an old-fashioned way of writing. 2. Italics are shown as _text_, bold is shown as =text=. 3. Carat characters are shown as ^X. 4. This table of contents has been created by the transcriber to aid the reader. 5. Footnote 20, Page 183: Footnote marker is missing. 6. Page 238: starting the 3rd table, there is a fraction 33-1/14. This has been changed this to 33-1/16, as it seems to be a mistake. 7. Spelling errors such as guidepiece, sawgates, swiveljoint, tongueing and whiteing have been retained as they are in the original. 8. Discrepancies with 3/4-inch and 1/4in. have been retained as in the original. 9. Inconsistencies with images: a. Page 22: Fig 31D is incorrect in the book as E. Changed to 31D and the fig. no. on the image has been removed. b. Pages 36 & 38: numbers 53-56 are repeated. c. Page 74: It seems the reference (Fig. 126) should be Fig.116. d. Page 89: There is no Fig. 137 or a reference to it. e. Page 99: The number 9 on the image is back to front. There does not seem to be a Fig. 148, although it is referred to (page 98). f. Page 98: Fig. 148 is incorrectly numbered on the image as 143. g. Page 100: There is a 2nd reference to Fig. 149, which it seems has to be an illustration of a pattern, but there is no 2nd Fig. 149. It seems the Fig. nos. mentioned in the reference should be 150 to 153. h. Page 104: The illustration is incorrectly numbered as 153 (should be 156). i. Page 107: The number 9 on the image is back to front. j. Page 111: The number 6 on the images is back to front. k. Page 112: Fig. 166 incorrectly numbered as 165. l. Page 141: There is no Fig. 204. (assumed to be the top image above Fig.205). m. Page 159/160: Number repeat for Fig. 229. n. Page 160: There is no Fig. 230. Possibly the 2nd no. 229. o. Page 178-184: Numbers 246-255 are number repeats. p. Page 185/6: There is no Fig. 257, but no reference to it either, so it is assumed this was an omission by the author. q. Page 189: There is no Fig. 261, although it is referred to on page 189. The reference has been changed to Fig. 262, which it pertains to. r. Page 201: Fig. 284 is out of sequence, it appears on page 209. s. Page 207: It seems the reference should be to Fig. 290, not 296 which has no L in the figure. t. Page 231: Fig, 319 is referred to, but there is no Fig. 319. Presumably the first figure on Page 233. u. Page 236: Illustration top un-numbered, presumably 4. v. Page 278: Figs, 422/3 is referred to, but there are no Figs. 422/3. Based on extensive research, comparing two different copies of a matching edition, and correlation of illustrations with the text, it appears that the inconsistencies in numbering within the book make it seem that something is missing. The images are in fact Figs. 420 and 421. 
55428	----	[Illustration: Pl. XIII. AMERICAN HIGH-PRESSURE ENGINE] THE STEAM ENGINE FAMILIARLY EXPLAINED AND ILLUSTRATED; WITH AN HISTORICAL SKETCH OF ITS INVENTION AND PROGRESSIVE IMPROVEMENT; ITS APPLICATIONS TO NAVIGATION AND RAILWAYS; WITH PLAIN MAXIMS FOR RAILWAY SPECULATORS. BY THE REV. DIONYSIUS LARDNER, LL. D., F. R. S., FELLOW OF THE ROYAL SOCIETY OF EDINBURGH; OF THE ROYAL IRISH ACADEMY; OF THE ROYAL ASTRONOMICAL SOCIETY; OF THE CAMBRIDGE PHILOSOPHICAL SOCIETY; OF THE STATISTICAL SOCIETY OF PARIS; OF THE LINNÆAN AND ZOOLOGICAL SOCIETIES; OF THE SOCIETY FOR PROMOTING USEFUL ARTS IN SCOTLAND, ETC. WITH ADDITIONS AND NOTES, BY JAMES RENWICK, LL. D., PROFESSOR OF NATURAL EXPERIMENTAL PHILOSOPHY AND CHEMISTRY IN COLUMBIA COLLEGE, NEW YORK. ILLUSTRATED BY ENGRAVINGS AND WOODCUTS. SECOND AMERICAN, FROM THE FIFTH LONDON, EDITION, CONSIDERABLY ENLARGED. PHILADELPHIA: E. L. CAREY & A. HART. 1836 Entered, according to the Act of Congress, in the year 1836, by E. L. CAREY & A. HART, in the Clerk's office of the District Court for the Eastern District of Pennsylvania. PREFACE OF THE AMERICAN EDITOR. Several of the additions, which were made by the Editor to the first American edition, have been superseded by the great extension, which the original has from time to time received from its author. This is more particularly the case, with the sections which had reference to the character of steam at temperatures other than that of boiling water, to the use of steam in navigation, and to its application to locomotion. These sections have of course been omitted. A few new sections, and several notes have been added, illustrative of such points as may be most interesting to the American reader. COLUMBIA COLLEGE, _New York, March, 1836_. PREFACE TO THE FIFTH EDITION. This volume should more properly be called a new work than a new edition of the former one. In fact the book has been almost rewritten. The change which has taken place, even in the short period which has elapsed since the publication of the first edition, in the relation of the steam engine to the useful arts, has been so considerable as to render this inevitable. The great extension of railroads, and the increasing number of projects which have been brought forward for new lines connecting various points of the kingdom, as well as the extension of steam navigation, not only through the seas and channels surrounding and intersecting these islands, and throughout other parts of Europe, but through the larger waters which are interposed between our dominions in the East and the countries of Egypt and Syria, have conferred so much interest on the application of steam to transport, that I have thought it adviseable to extend the limits of the present edition considerably beyond those of the last. The chapter on railroads has been enlarged and improved. Three chapters have been added. The twelfth chapter contains a view of steam navigation; the thirteenth contains several important points connected with the economy of steam power, which, when this work was first published, would not have offered sufficient interest to justify their admission into a popular treatise; and the fourteenth chapter contains a series of compendious maxims, for the instruction and guidance of persons desirous of making investments or speculating in railway property. _London, December, 1835._ PREFACE TO THE FIRST EDITION. There are two classes of persons whose attention may be attracted by a treatise on such a subject as the Steam Engine. One consists of those who, by trade or profession, are interested in mechanical science, and who therefore seek information on the subject of which it treats, as a matter of necessity, and a wish to acquire it in a manner and to an extent which may be practically available in their avocations. The other and more numerous class is that part of the public in general, who, impelled by choice rather than necessity, think the interest of the subject itself, and the pleasure derivable from the instances of ingenuity which it unfolds, motives sufficiently strong to induce them to undertake the study of it. Without leaving the former class altogether out of view, it is for the use of the latter principally that the following lectures are designed. To this class of readers the Steam Engine is a subject which, if properly treated of, must present strong and peculiar attractions. Whether we consider the history of its invention as to time and place, the effects which it has produced, or the means by which it has caused these effects, we find everything to gratify our national pride, stimulate our curiosity, excite our wonder, and command our admiration. The invention and progressive improvement of this extraordinary machine, is the work of our own time and our own country; it has been produced and brought to perfection almost within the last century, and is the exclusive offspring of British genius fostered and supported by British capital. To enumerate the effects of this invention, would be to count every comfort and luxury of life. It has increased the sum of human happiness, not only by calling new pleasures into existence, but by so cheapening former enjoyments as to render them attainable by those who before never could have hoped to share them. Nor are its effects confined to England alone: they extend over the whole civilized world; and the savage tribes of America, Asia, and Africa, must ere long feel the benefits, remote or immediate, of this all-powerful agent. If the effect which this machine has had on commerce and the wealth of nations raise our astonishment, the means by which this effect has been produced will not less excite our admiration. The history of the Steam Engine presents a series of contrivances, which, for exquisite and refined ingenuity, stand without a parallel in the annals of human invention. These admirable contrivances, unlike other results of scientific investigation, have also this peculiarity, that to understand and appreciate their excellence requires little previous or subsidiary knowledge. A simple and clear explanation, divested as far as possible of technicalities, and assisted by well selected diagrams, is all that is necessary to render the principles of the construction and operation of the Steam Engine intelligible to a person of plain understanding and moderate information. The purpose for which this volume is designed, as already explained, has rendered necessary the omission of many particulars which, however interesting and instructive to the practical mechanic or professional engineer, would have little attraction for the general reader. Our readers require to be informed of the general principles of the construction and operation of Steam Engines, rather than of their practical details. For the same reasons we have confined ourselves to the more striking and important circumstances in the history of the invention and progressive improvement of this machine, excluding many petty disputes which arose from time to time respecting the rights of invention, the interest of which is buried in the graves of their respective claimants. In the descriptive parts of the work we have been governed by the same considerations. The application of the force of steam to mechanical purposes has been proposed on various occasions, in various countries, and under a great variety of forms. The list of British patents alone would furnish an author of common industry and application with matter to swell his book to many times the bulk of this volume. By far the greater number of these projects have, however, proved abortive. Descriptions of such unsuccessful, though frequently ingenious machines, we have thought it adviseable to exclude from our pages, as not possessing sufficient interest for the readers to whose use this volume is dedicated. We have therefore strictly confined our descriptions either to those Steam Engines which have come into general use, or to those which form an important link in the chain of invention. _December 26, 1827._ CONTENTS. CHAPTER I. PRELIMINARY MATTER. Motion the Agent in Manufactures. -- Animal Power. -- Power depending on physical Phenomena. -- Purpose of a Machine. -- Prime Mover. -- Mechanical qualities of the Atmosphere. -- Its Weight. -- The Barometer. -- Fluid Pressure. -- Pressure of rarefied Air. -- Elasticity of Air. -- Bellows. -- Effects of Heat. -- Thermometer. -- Method of making one. -- Freezing and Boiling Points. -- Degrees. -- Dilatation of bodies. -- Liquefaction and Solidification. -- Vaporisation and Condensation. -- Latent Heat of Steam. -- Expansion of Water in Evaporating. -- Effects of Repulsion and Cohesion. -- Effect of Pressure upon Boiling Point. -- Formation of a Vacuum by Condensation. Page 17 CHAPTER II. FIRST STEPS IN THE INVENTION. Futility of early Claims. -- Watt the real Inventor. -- Hero of Alexandria. -- Blasco Garay. -- Solomon De Caus. -- Giovanni Branca. -- Marquis of Worcester. -- Sir Samuel Morland. -- Denis Papin. -- Thomas Savery. 38 CHAPTER III. ENGINES OF SAVERY AND NEWCOMEN. Savery's Engine. -- Boilers and their Appendages. -- Working Apparatus. -- Mode of Operation. -- Defects of the Engine. -- Newcomen and Cawley. -- Atmospheric Engine. -- Accidental discovery of Condensation by Jet. -- Potter's discovery of the Method of working the Valves. 51 CHAPTER IV. ENGINE OF JAMES WATT. Advantages of the Atmospheric Engine over that of Captain Savery. -- It contained no new Principle. -- Papin's Engine. -- James Watt. -- Particulars of his Life. -- His first conceptions of the Means of economising Heat. -- Principle of his projected Improvements. 69 CHAPTER V. WATT'S SINGLE-ACTING STEAM ENGINE. Expansive Principle applied. -- Failure of Roebuck, and partnership with Bolton. -- Patent extended to 1800. -- Counter. -- Difficulties in getting the Engines into Use. 80 CHAPTER VI. DOUBLE-ACTING STEAM ENGINE. The Single-acting Engine unfit to impel Machinery. -- Various Contrivances to adapt it to this Purpose. -- Double-Cylinder. -- Double-acting Cylinder. -- Various modes of connecting the Piston with the Beam. -- Rack and Sector. -- Double Chain. -- Parallel Motion. -- Crank. -- Sun and Planet Motion. -- Fly Wheel. -- Governor. 91 CHAPTER VII. DOUBLE-ACTING STEAM ENGINE, _continued_. On the Valves of the Double-acting Steam Engine. -- Original Valves. -- Spindle Valves. -- Sliding Valve. -- D Valve. -- Four-Way Cock. 108 CHAPTER VIII. BOILER AND ITS APPENDAGES. Level Gauges. -- Feeding apparatus. -- Steam Gauge. -- Barometer Gauge. -- Safety Valves. -- Self-regulating Damper. -- Edelcrantz's Valve. -- Furnace. -- Smoke-consuming Furnace. -- Brunton's Self-regulating Furnace. -- Oldham's Modification. 117 CHAPTER IX. DOUBLE-CYLINDER ENGINES. Hornblower's Engine. -- Woolf's Engine. -- Cartwright's Engine. 134 CHAPTER X. LOCOMOTIVE ENGINES ON RAILWAYS. High-pressure Engines. -- Leupold's Engine. -- Trevithick and Vivian. -- Effects of Improvement in Locomotion. -- Historical Account of the Locomotive Engine. -- Blenkinsop's Patent. -- Chapman's Improvement. -- Walking Engine. -- Stephenson's First Engines. -- His Improvements. -- Liverpool and Manchester Railway Company. -- Their Preliminary Proceedings. -- The Great Competition of 1829. -- The Rocket. -- The Sanspareil. -- The Novelty. -- Qualities of the Rocket. -- Successive Improvements. -- Experiments. -- Defects of the Present Engines. -- Inclined Planes. -- Methods of surmounting them. -- Circumstances of the Manchester Railway Company. -- Probable Improvements in Locomotives. -- Their capabilities with respect to speed. -- Probable Effects of the Projected Railroads. -- Steam Power compared with Horse Power. -- Railroads compared with Canals. 145 CHAPTER XI. LOCOMOTIVE ENGINES ON TURNPIKE ROADS. Railway and Turnpike Roads compared. -- Mr. Gurney's inventions. -- His Locomotive Steam Engine. -- Its performances. -- Prejudices and errors. -- Committee of the House of Commons. -- Convenience and safety of Steam Carriages. -- Hancock's Steam Carriage. -- Mr. N. Ogle. -- Trevithick's invention. -- Proceedings against Steam Carriages. -- Turnpike Bills. -- Steam Carriage between Gloucester and Cheltenham. -- Its discontinuance. -- Report of the Committee of the Commons. -- Present State and Prospects of Steam Carriages. 213 CHAPTER XII. STEAM NAVIGATION. Propulsion by paddle-wheels. -- Manner of driving them. -- Marine Engine. -- Its form and arrangement. -- Proportion of its cylinder. -- Injury to boilers by deposites and incrustation. -- Not effectually removed by blowing out. -- Mr. Samuel Hall's condenser. -- Its advantages. -- Originally suggested by Watt. -- Hall's _steam saver_. -- Howard's vapour engine. -- Morgan's paddle-wheels. -- Limits of steam navigation. -- Proportion of tonnage to power. -- Average speed. -- Consumption of fuel. -- Iron Steamers. -- American steam raft. -- Steam navigation to India. -- By Egypt and the Red Sea to Bombay. -- By same route to Calcutta. -- By Syria and the Euphrates to Bombay. -- Steam communication with the United States from the west coast of Ireland to St. Johns, Halifax, and New York. 241 CHAPTER XIII. GENERAL ECONOMY OF STEAM POWER. Mechanical efficacy of steam -- proportional to the quantity of water evaporated, and to the fuel consumed. -- Independent of the pressure. -- Its mechanical efficacy by condensation alone. -- By condensation and expansion combined -- by direct pressure and expansion -- by direct pressure and condensation -- by direct pressure, condensation, and expansion. -- The power of engines. -- The duty of engines. -- Meaning of horse power. -- To compute the power of an engine. -- Of the power of boilers. -- The structure of the grate-bars. -- Quantity of water and steam room. -- Fire surface and flue surface. -- Dimensions of steam pipes. -- Velocity of piston. -- Economy of fuel. -- Cornish duty reports. 277 CHAPTER XIV. Plain Rules for Railway Speculators. 307 THE STEAM ENGINE EXPLAINED AND ILLUSTRATED. CHAPTER I. PRELIMINARY MATTER. Motion the Agent in Manufactures. -- Animal Power. -- Power depending on Physical Phenomena. -- Purpose of a Machine. -- Prime Mover. -- Mechanical qualities of the Atmosphere. -- Its Weight. -- The Barometer. -- Fluid Pressure. -- Pressure of Rarefied Air. -- Elasticity of Air. -- Bellows. -- Effects of Heat. -- Thermometer. -- Method of making one. -- Freezing and Boiling Points. -- Degrees. -- Dilatation of Bodies. -- Liquefaction and Solidification. -- Vaporisation and Condensation. -- Latent heat of Steam. -- Expansion of Water in Evaporating. -- Effects of Repulsion and Cohesion. -- Effect of Pressure upon Boiling-Point. -- Formation of a Vacuum by Condensation. (1.) Of the various productions designed by nature to supply the wants of man, there are few which are suited to his necessities in the state in which the earth spontaneously offers them: if we except atmospheric air, we shall scarcely find another instance: even water, in most cases, requires to be transported from its streams or reservoirs; and food itself, in almost every form, requires culture and preparation. But if, from the mere necessities of physical existence in a primitive state, we rise to the demands of civil and social life,--to say nothing of luxuries and refinements,--we shall find that everything which contributes to our convenience, or ministers to our pleasure, requires a previous and extensive expenditure of labour. In most cases, the objects of our enjoyment derive all their excellences, not from any qualities originally inherent in the natural substances out of which they are formed, but from those qualities which have been bestowed upon them by the application of human labour and human skill. In all those changes to which the raw productions of the earth are submitted in order to adapt them to our wants, one of the principal agents is _motion_. Thus, for example, in the preparation of clothing for our bodies, the various processes necessary for the culture of the cotton require the application of moving power, first to the soil, and subsequently to the plant from which the raw material is obtained: the wool must afterwards be picked and cleansed, twisted into threads, and woven into cloth. In all these processes motion is the agent: to cleanse the wool and arrange the fibres of the cotton, the wool must be beaten, teased, carded, and submitted to other processes, by which all the foreign and coarser matter may be separated, and the fibres or threads arranged evenly, side by side. The threads must then receive a rotatory motion, by which they may be twisted into the required form; and finally peculiar motions must be given to them in order to produce among them that arrangement which characterises the cloth which it is our final purpose to produce. In a rude state of society, the motions required in the infant manufactures are communicated by the immediate application of the hand. Observation and reflection, however, soon suggest more easy and effectual means of attaining these ends: the strength of animals is first resorted to for the relief of human labour. Further reflection and inquiry suggest still better expedients. When we look around us in the natural world, we perceive inanimate matter undergoing various effects in which motion plays a conspicuous part: we see the falls of cataracts, the currents of rivers, the elevation and depression of the waters of the ocean, the currents of the atmosphere; and the question instantly arises, whether, without sharing our own means of subsistence with the animals whose force we use, we may not equally, or more effectually, derive the powers required from these various phenomena of nature? A difficulty, however, immediately presents itself: we require motion of a particular kind; but wind will not blow, nor water fall as we please, nor as suits our peculiar wants, but according to the fixed laws of nature. We want an _upward_ motion; water falls _downwards_: we want a _circular_ motion; wind blows in a _straight_ line. The motions, therefore, which are in actual existence must be modified to suit our purposes: the means whereby these modifications are produced, are called _machines_. A machine, therefore, is an instrument interposed between some natural force or motion, and the object to which force or motion is desired to be transmitted. The construction of the machine is such as to modify the natural motion which is impressed upon it, so that it may transmit to the object to be moved that peculiar species of motion which it is required to have. To give a very obvious example, let us suppose that a circular or rotatory motion is required to be produced, and that the only natural source of motion at our command is a perpendicular fall of water: a wheel is provided, placed upon the axle destined to receive the rotatory motion; this wheel is furnished with cavities in its rim; the water is conducted into the cavities near the top of the wheel on one side; and being caught by these, its weight bears down that side of the wheel, the cavities on the opposite side being empty and in an inverted position. As the wheel turns, the cavities on the descending side discharge their contents as they arrive near the lowest point, and ascend empty on the other side. Thus a load of water is continually pressing down one side of the wheel, from which the other side is free, and a continued motion of rotation is produced. In every machine, therefore, there are three objects demanding attention:--first, The power which imparts motion to it, this is called the _prime mover_; secondly, The nature of the _machine_ itself; and thirdly, The object to which the motion is to be conveyed. In the steam engine the first mover arises from certain phenomena which are exhibited when heat is applied to liquids; but in the details of the machine and in its application there are several physical effects brought into play, which it is necessary perfectly to understand before the nature of the machine or its mode of operation can be rendered intelligible. We propose therefore to devote the present chapter to the explanation and illustration of these phenomena. (2.) The physical effects most intimately connected with the operations of steam engines are some of the mechanical properties of atmospheric air. The atmosphere is the thin transparent fluid in which we live and move, and which, by respiration, supports animal life. This fluid is apparently so light and attenuated, that it might be at first doubted whether it be really a body at all. It may therefore excite some surprise when we assert, not only that it is a body, but also that it is one of considerable _weight_. We shall be able to prove that it presses on every _square inch_[1] of surface with a weight of about 15lb. avoirdupois. [Footnote 1: As we shall have frequent occasion to mention this magnitude, it would be well that the reader should be familiar with it. It is a _square_, each side of which is an inch. Such as A B C D, Fig. 1.] (3.) Take a glass tube A B (fig. 2.) more than 32 inches long, open at one end A, and closed at the other end B, and let it be filled with mercury (quicksilver.) Let a glass vessel or cistern C, containing a quantity of mercury, be also provided. Applying the finger at A so as to prevent the mercury in the tube from falling out, let the tube be inverted, and the end, stopped by the finger, plunged into the mercury in _C_. When the end of the tube is below the surface of the mercury in C (fig. 3.) let the finger be removed. It will be found that the mercury in the tube will not, as might be expected, fall to the level of the mercury in the cistern C, which it would do were the end B open so as to admit the air into the upper part of the tube. On the other hand, the level D of the mercury in the tube will be about 30 inches above the level C of the mercury in the cistern. (4.) The cause of this effect is, that the weight of the atmosphere rests on the surface C of the mercury in the cistern, and tends thereby to press it up, or rather to resist its fall in the tube; and as the fall is not assisted by the weight of the atmosphere on the surface D (since B is closed), it follows, that as much mercury remains suspended in the tube above the level C as the weight of the atmosphere is able to support. If we suppose the section of the tube to be equal to the magnitude of a square inch, the weight of the column of mercury in the tube above the level C will be exactly equal to the weight of the atmosphere on each square inch of the surface C. The height of the level D above C being about 30 inches, and a column of mercury two inches in height, and having a base of a square inch, weighing about one pound avoirdupois, it follows that the weight with which the atmosphere presses on each square inch of a level surface is about 15lb. avoirdupois. An apparatus thus constructed, and furnished with a scale to indicate the height of the level D above the level C, is the _common barometer_. The difference of these levels is subject to a small variation, which indicates a corresponding change in the atmospheric pressure. But we take 30 inches as a standard or average. (5.) It is an established property of fluids that they press equally in all directions; and air, like every other fluid, participates in this quality. Hence it follows, that since the downward pressure or weight of the atmosphere is about 15lb. on the square inch, the lateral, upward, and oblique pressures are of the same amount. But, independently of the general principle, it may be satisfactory to give experimental proof of this. Let four glass tubes A, B, C, D, (fig. 4.) be constructed of sufficient length, closed at one end A, B, C, D, and open at the other. Let the open ends of three of them be bent, as represented in the tubes B, C, D. Being previously filled with mercury, let them all be gently inverted so as to have their closed ends up as here represented. It will be found that the mercury will be sustained in all,[2] and that the difference of the levels in all will be the same. Thus the mercury is sustained in A by the upward pressure of the atmosphere, in B by its horizontal or lateral pressure, in C by its downward pressure, and in D by its oblique pressure; and as the difference of the levels is the same in all, these pressures are exactly equal. [Footnote 2: This experiment with the tube A requires to be very carefully executed, and the tube should be one of small bore.] (6.) In the experiment described in (3.) the space B D (fig. 3.) at the top of the tube from which the mercury has fallen is perfectly void and empty, containing neither air nor any other fluid: it is called therefore a _vacuum_. If, however, a small quantity of air be introduced into that space, it will immediately begin to exert a pressure on D, which will cause the surface D to descend, and it will continue to descend until the column of mercury C D is so far diminished that the weight of the atmosphere is sufficient to sustain it, as well as the pressure exerted upon it by the air in the space B D. The quantity of mercury which falls from the tube in this case is necessarily an equivalent for the pressure of the air introduced, so that the pressure of this air may be exactly ascertained by allowing about one pound per square inch for every two inches of mercury which has fallen from the tube. The pressure of the air or any other fluid above the mercury in the tube, may at once be ascertained by comparing the height of the mercury in the tube with the height of the barometer; the difference of the heights will always determine the pressure on the surface of the mercury in the tube. This principle will be found of some importance in considering the action of the modern steam engines. The air which we have supposed to be introduced into the upper part of the tube, presses on the surface of the mercury with a force much greater than its weight. For example, if the space B D (fig. 3.) were filled with atmospheric air in its ordinary state, it would exert a pressure on the surface D equal to the whole pressure of the atmosphere, although its weight might not amount to a single grain. The property in virtue of which the air exerts this pressure is its _elasticity_, and this force is diminished in precisely the proportion in which the space which the air occupies is increased. Thus it is known that atmospheric air in its ordinary state exerts a pressure on the surface of any vessel in which it is confined, amounting to about 15lb. on every square inch. If the capacity of the vessel which contains it be doubled, it immediately expands and fills the double space, but in doing so it loses half its elastic force, and presses only with the force of 7-1/2lb. on every square inch. If the capacity of the vessel had been enlarged five times, the air would still have expanded so as to fill it, but would exert only a fifth part of its first pressure, or 3lb. on every square inch. This property of losing its elastic force as its volume or bulk is increased, is not peculiar to air. It is common to all elastic fluids, and we accordingly find it in steam; and it is absolutely necessary to take account of it in estimating the effects of that agent. (7.) There are numerous instances of the effects of these properties of atmospheric air which continually fall under our observation. If the nozzle and valve-hole of a pair of bellows be stopped, it will require a very considerable force to separate the boards. This effect is produced by the diminished elastic force of the air remaining between the boards upon the least increase of the space within the bellows, while the atmosphere presses, with undiminished force, on the external surfaces of the boards. If the boards be separated so as to double the space within, the elastic force of the included air will be about 7-1/2lb. on every square inch, while the pressure on the external surfaces will be 15lb. on every square inch; consequently, it will require as great a force to sustain the boards in such a position, as it would to separate them if each board were forced against the other, with a pressure of 7-1/2lb. per square inch on their external surfaces. When boys apply a piece of moistened leather to a stone, so as to exclude the air from between them, the stone, though it be of considerable weight, may be lifted by a string attached to the leather: the cause of which is the atmospheric pressure, which keeps the leather and the stone in close contact. (8.) The next class of physical effects which it is necessary to explain, are those which are produced when heat is imparted or abstracted from bodies. In general, when heat is imparted to a body, an enlargement of bulk will be the immediate consequence, and at the same time the body will become warmer to the touch. These two effects of expansion and increase of warmth going on always together, the one has been taken as a measure of the other; and upon this principle the common thermometer is constructed. That instrument consists of a tube of glass, terminated in a bulb, the magnitude of which is considerable, compared with the bore of the tube. The bulb and part of the tube are filled with mercury, or some other liquid. When the bulb is exposed to any source of heat, the mercury contained in it, being warmed or increased in temperature, is at the same time increased in bulk, or expanded or dilated, as it is called. The bulb not having sufficient capacity to contain the increased bulk of mercury, the liquid is forced up in the tube, and the quantity of expansion is determined by observing the ascent of the column in the tube. An instrument of this kind, exposed to heat or cold, will fluctuate accordingly, the mercury rising as the heat to which it is exposed is increased, and falling by exposure to cold. In order, however, to render it an accurate measure of temperature, it is necessary to connect with it a scale by which the elevation or depression of the mercury in the tube may be measured. Such a scale is constructed for thermometers in this country in the following manner:--Let us suppose the instrument immersed in a vessel of melting ice: the column of mercury in the tube will be observed to fall to a certain point, and there maintain its position unaltered: let that point be marked upon the tube. Let the instrument be now transferred to a vessel of boiling water at a time when the barometer stands at the altitude of 30 inches: the mercury in the tube will be observed to rise until it attain a certain elevation, and will there maintain its position. It will be found, that though the water continue to be exposed to the action of the fire, and continue to boil, the mercury in the tube will not continue to rise, but will maintain a fixed position: let the point to which the mercury has risen, in this case, be likewise marked upon the tube. The two points, thus determined, are called the _freezing_ and the _boiling_ points. If the distance upon the tube between these two points be divided into 180 equal parts, each of these parts is called a _degree_; and if this division be continued, by taking equal divisions below the freezing point, until 32 divisions be taken, the last division is called the _zero_, or _nought_ of the thermometer. It is the point to which the mercury would fall, if the thermometer were immersed in a certain mixture of snow and salt. When thermometers were first invented, this point was taken as the zero point, from an erroneous supposition that the temperature of such a mixture was the lowest possible temperature. The degrees upon the instrument thus divided are counted upwards from the zero, and are expressed, like the degrees of a circle, by placing a small ° over the number. Thus it will be perceived that the freezing point is 32° of our thermometer, and the boiling-point will be found by adding 180° to 32°; it is therefore 212°. The temperature of a body is that elevation to which the thermometer would rise when the mercury enclosed in it would acquire the same temperature. Thus, if we should immerse the thermometer, and should find that the mercury would rise to the division marked 100°, we should then affirm that the temperature of the water was 100°. (9.) The dilatation which attends an increase of temperature is one of the most universal effects of heat. It varies, however, in different bodies: it is least in solid bodies; greater in liquids; and greatest of all in bodies in the aeriform state. Again, different solids are differently susceptible of this expansion. Metals are the most susceptible of it; but metals of different kinds are differently expansible. As an increase of temperature causes an increase of bulk, so a diminution of temperature causes a corresponding diminution of bulk, and the same body always has the same bulk at the same temperature. A flaccid bladder, containing a small quantity of air, will, when heated, become quite distended; but it will again resume its flaccid appearance when cold. A corked bottle of fermented liquor, placed before the fire, will burst by the effort of the air contained in it to expand when heated. Let the tube A B (fig. 5.) open at both ends, have one end inserted in the neck of a vessel C D, containing a coloured liquid, with common air above it; and let the tube be fixed so as to be air-tight in the neck: upon heating the vessel, the warm air inclosed in the vessel C D above the liquid will begin to expand, and will press upon the surface of the liquid, so as to force it up in the tube A B. In bridges and other structures, formed of iron, mechanical provisions are introduced to prevent the fracture or strain which would take place by the expansion and contraction which the metal must undergo by the changes of temperature at different seasons of the year, and even at different hours of the day. Thus all nature, animate and inanimate, organized and unorganized, may be considered to be incessantly breathing heat; at one moment drawing in that principle through all its dimensions, and at another moment dismissing it. (10.) Change of bulk, however, is not the only nor the most striking effect which attends the increase or diminution of the quantity of heat in a body. In some cases, a total change of form and of mechanical qualities is effected by it. If heat be imparted in sufficient quantity to a solid body, that body, after a certain time, will be converted into a liquid. And again, if heat be imparted in sufficient quantity to this liquid, it will cease to exist in the liquid state, and pass into the form of vapour. By the abstraction of heat, a series of changes will be produced in the opposite order. If from the vapour produced in this case, a sufficient quantity of heat be taken, it will return to the liquid state; and if again from this liquid heat be further abstracted, it will at length resume its original solid state. The transmission of a body from the solid to the liquid state, by the application of heat, is called _fusion_ or _liquefaction_, and the body is said to be fused, _liquefied_, or melted. The reciprocal transmission from the liquid to the solid state, is called _congelation_, or _solidification_; and the liquid is said to be _congealed_ or _solidified_. The transmission of a body from the liquid to the vaporous or aeriform state, is called _vaporization_, and the liquid is said to be _vaporized_ or _evaporated_. The reciprocal transmission of vapour to the liquid state is called _condensation_, and the vapour is said to be _condensed_. We shall now examine more minutely the circumstances which attend these remarkable and important changes in the state of body. (11.) Let us suppose that a thermometer is imbedded in any solid body; for example, in a mass of sulphur; and that it stands at the ordinary temperature of 60 degrees: let the sulphur be placed in a vessel, and exposed to the action of fire. The thermometer will now be observed gradually to rise, and it will continue to rise until it exhibit the temperature of 218°. Here, however, notwithstanding the continued action of the fire upon the sulphur, the thermometer will become stationary; proving, that notwithstanding the supply of heat received from the fire, the sulphur has ceased to become hotter. At the moment that the thermometer attains this stationary point, it will be observed that the sulphur has commenced the process of fusion; and this process will be continued, the thermometer being stationary, until the whole mass has been liquefied. The moment the liquefaction is complete, the thermometer will be observed again to rise, and it will continue to rise until it attain the elevation of 570°. Here, however, it will once more become stationary; and notwithstanding the heat supplied to the sulphur by the fire, the liquid will cease to become hotter: when this happens, the sulphur will boil; and if it continue to be exposed to the fire a sufficient length of time, it will be found that its quantity will gradually diminish, until at length it will all disappear from the vessel which contained it. The sulphur will, in fact, be converted into vapour. From this process we infer, that all the heat supplied during the processes of liquefaction and vaporization is consumed in effecting these changes in the state of the body; and that under such circumstances, it does not increase the temperature of the body on which the change is produced. These effects are general: all solid bodies would pass into the liquid state by a sufficient application of heat; and all liquid bodies would pass into the vaporous state by the same means. In all cases the thermometer would be stationary during these changes, and consequently the temperature of the body, in those periods, would be maintained unaltered. (12.) Solids differ from one another in the temperatures at which they become liquid. These temperatures are called their _melting points_. Thus the melting point of ice is 32°; that of lead 612°; that of gold 5237°.[3] The heat which is supplied to a body during the processes of fusion or vaporization, and which does not affect the thermometer, or increase the temperature of the body fused or vaporized, is said to become _latent_. It can be proved to exist in the body fused or vaporized, and may even be taken from that body. In parting with it the body does not fall in temperature, and consequently the loss of this heat is not indicated by the thermometer any more than its reception. The term latent heat is merely intended to express this fact, of the thermometer being insensible to the presence or absence of this portion of heat, and is not intended to express any theoretical notions concerning it. [Footnote 3: Temperatures above 650° cannot be measured by the mercurial thermometer. They can be inferred only with probability by pyrometers.] (13.) In explaining the construction and operation of the steam engine, although it is necessary occasionally to refer to the effects of heat upon bodies in general, yet the body, which is by far the most important to be attended to, so far as the effects of heat upon it are concerned, is water. This body is observed to exist in the three different states, the solid, the liquid, and the vaporous, according to the varying temperature to which it is exposed. All the circumstances which have been explained in reference to metals, and the substance sulphur in particular, will, _mutatis mutandis_, be applicable to water. But in order perfectly to comprehend the properties of the steam engine, it is necessary to render a more rigorous and exact account of these phenomena, so far as they apply to the changes produced upon water by the effects of heat. Let us suppose a mass of ice immersed in the mixture of snow and salt which determines the zero point of the thermometer: this mass, if allowed to continue a sufficient length of time submerged in the mixture, will necessarily acquire its temperature, and the thermometer immersed in it will stand at zero. Let the ice be now withdrawn from the mixture, still keeping the thermometer immersed in it, and let it be exposed to the atmosphere at the ordinary temperature, say 60°. At first the thermometer will be observed gradually and continuously to rise until it attain the elevation of 32°; it will then become stationary, and the ice will begin to melt: the thermometer will continue standing at 32° until the ice shall be completely liquefied. The liquid ice and the thermometer being contained in the same vessel, it will be found, when the liquefaction is completed, that the thermometer will again begin to rise, and will continue to rise until it attain the temperature of the atmosphere, viz. 60°. Hitherto the ice or water has received a supply of heat from the surrounding air; but now an equilibrium of temperature having been established, no further supply of heat can be received; and if we would investigate the further effects of increased heat, it will be necessary to expose the liquid to fire, or some other source of heat. But previous to this, let us observe the time which the thermometer remains stationary during the liquefaction of the ice: if noted by a chronometer, it would be found to be a hundred and forty times the time during which the water in the liquid state was elevated one degree; the inference from which is, that in order to convert the solid ice into liquid water, it was necessary to receive from the surrounding atmosphere one hundred and forty times as much heat as would elevate the liquid water one degree in temperature; or, in other words, that to liquefy a given weight of ice requires as much heat as would raise the same weight of water 140° in temperature: or from 32° to 172°. The latent heat of water acquired in liquefaction is therefore 140°. (14.) Let us now suppose that, a spirit lamp being applied to the water already raised to 60°, the effects of a further supply of heat be observed: the thermometer will continue to rise until it attain the elevation of 212°, the barometer being supposed to stand at 30 inches. The thermometer having attained this elevation will cease to rise; the water will therefore cease to become hotter, and at the same time bubbles of steam will be observed to be formed at the bottom of the vessel containing the water, near the flame of the spirit lamp. These bubbles will rise through the water, and escape at the surface, exhibiting the phenomena of ebullition, and the water will undergo the process of _boiling_. During this process, the thermometer will constantly be maintained at the same elevation of 212°; but if the time be noted, it will be found that the water will be altogether evaporated, if the same source of heat be continued to be applied to it six and a half times as long as was necessary to raise it from the freezing to the boiling-point. Thus, if the application of the lamp to water at 32°, be capable of raising that water to 212° in one hour, the same lamp will require to be applied to the boiling water for six hours and a half, in order to convert the whole of it into steam. Now if the steam into which it is thus converted were carefully preserved in a receiver, maintained at the temperature of 212°, this steam would be found to have that temperature, and not a greater one; but it would be found to fill a space about 1700 times greater than the space it occupied in the liquid state, and it would possess an elastic force equal to the pressure of the atmosphere under which it was boiled; that is to say, it would press the sides of the vessel which contained it with a pressure equivalent to that of a column of mercury of 30 inches in height; or what is the same thing, at the rate of about 15lb. on every square inch of surface. (15.) As the quantity of heat expended in raising the water from 32° to 212°, is 180°; and as the quantity of heat necessary to convert the same water into steam is six and a half times this quantity, it follows that the quantity of heat requisite for converting a given weight of water into steam, will be found by multiplying 180° by 5-1/2. The product of these numbers being 990°, it follows, that, to convert a given weight of water at 212° into steam of the same temperature, under the pressure of the atmosphere, when the barometer stands at 30 inches, requires as much heat as would be necessary to raise the same water 990° higher in temperature. The heat, not being sensible to the thermometer, is latent heat; and accordingly it may be stated, that the latent heat, necessary to convert water into steam under this pressure is, in round numbers, 1000°. (16.) All the effects of heat which we have just described may be satisfactorily accounted for, by supposing that the principle of heat imparts to the constituent atoms of bodies a force, by virtue of which they acquire a tendency to repel each other. But in conjunction with this, it is necessary to notice another force, which is known to exist in nature: there is observable among the corpuscles of bodies a force, in virtue of which they have a tendency to cohere, and collect themselves together in solid concrete masses: this force is called the attraction of cohesion. These two forces--the natural cohesion of the particles, and the repulsive energy introduced by heat--are directly opposed to one another, and the state of the body will be decided by the predominance of the one or the other, or their mutual equilibrium. If the natural cohesion of the constituent particles of the body considerably predominate over the repulsive energy introduced by the heat, then the cohesion will take effect; the particles of the body will coalesce, the mass will become rigid and solid, and the particles will hold together in one invariable mass, so that they cannot drop asunder by the mere effect of their weight. In such cases, a more or less considerable force must be applied, in order to break the body, or to tear its parts asunder. Such is the quality which characterises the state, which in mechanics is called the state of solidity. If the repulsive energy introduced by the application of heat be equal, or nearly equal, to the natural cohesion with which the particles of the body are endued, then the predominance of the cohesive force may be insufficient to resist the tendency which the particles may have to drop asunder by their weight. In such a case, the constituent particles of the body cannot cohere in a solid mass, but will separate by their weight, fall asunder, and drop into the various corners, and adapt themselves to the shape of any vessel in which the body may be contained. In fact, the body will take the liquid form. In this state, however, it does not follow that the cohesive principle will be altogether inoperative: it may, and does, in some cases, exist in a perceptible degree, though insufficient to resist the separate gravitation of the particles. The tendency which particles of liquids have, in some cases, to collect in globules, plainly indicates the predominance of the cohesive principle: drops of water collected upon the window pane; drops of rain condensed in the atmosphere; the tear which trickles on the cheek; drops of mercury, which glide over any flat surface, and which it is difficult to subdivide or scatter into smaller parts; are all obvious indications of the predominance of the cohesive principle in liquids. By the due application of heat, even this small degree of cohesion may be conquered, and a preponderance of the opposite principle of repulsion may be created. But another physical influence here interposes its aid, and conspires with cohesion in resisting the transmission of the body from the liquid to the vaporous state: this force is no other than the pressure of the atmosphere, already explained. This pressure has an obvious tendency to restrain the particles of the liquid, to press them together, and to resist their separation. The repulsive principle of the heat introduced must therefore not only neutralize the cohesion, but must also impart to the atoms of the liquid a sufficient elasticity or repulsive energy to enable them to fly asunder, and assume the vaporous form in spite of this atmospheric resistance. Now it is clear, that if this atmospheric resistance be subject to any variation in its intensity, from causes whether natural or artificial, the repulsive energy necessary to be introduced by the heat, will vary proportionally: if the atmospheric pressure be diminished, then less heat will be necessary to vaporize the liquid. If, on the other hand, this pressure be increased, a greater quantity of heat will be required to impart the necessary elasticity. (17.) From this reasoning we must expect that any cause, whether natural or artificial, which diminishes the atmospheric pressure upon the surface of a liquid, will cause that liquid to boil at a lower temperature: and on the other hand, any cause which may increase the atmospheric pressure upon the liquid, will render it necessary to raise it to a higher temperature before it can boil. These inferences we accordingly find supported by experience. Under a pressure of 15lb. on the square inch, _i. e._ when the barometer is at 30 inches, water boils at the temperature of 212° of the common thermometer. But if water at a lower temperature, suppose 180°, be placed under the receiver of an air-pump, and, by the process of exhaustion the atmospheric pressure be removed, or very much diminished, the water will boil, although its temperature still remain at 180°, as may be indicated by a thermometer placed in it. On the other hand, if a thermometer be inserted air-tight in the lid of a close digester containing water with common atmospheric air above it, when the vessel is heated the air acquires an increased elasticity; and being confined by the cover, presses, with increased force, on the surface of the water. By observing the thermometer while the vessel is exposed to the action of heat, it will be seen to rise considerably above 212°, suppose to 230°, and would continue so to rise until the strength of the vessel could no longer resist the pressure within it. The temperature at which water boils is commonly said to be 212°, which is called _the boiling-point_ of the thermometer; but, strictly speaking, this is only true when the barometer stands at 30 inches. If it be lower, water will boil at a lower temperature, because the atmospheric pressure is less; and if it be higher, as at 31, water will not boil until it receives a higher temperature, the pressure being greater. According as the cohesive forces of the particles of liquids are more or less active, they boil at greater or less temperatures. In general the lighter liquids, such as _alcohol_ and _ether_, boil at lower temperatures. These fluids, in fact, would boil by merely removing the atmospheric pressure, as may be proved by placing them under the receiver of an air-pump, and withdrawing the air. From this we may conclude that these and similar substances would never exist in the liquid state at all, but for the atmospheric pressure. (18.) The elasticity of vapour raised from a boiling liquid, is equal to the pressure under which it is produced. Thus, steam raised from water at 212°, and, therefore, under a pressure of 15lb. on the square inch, is endued with an elastic force which would exert a pressure on the sides of any vessel which confines it, also equal to 15lb. on the square inch. Since an increased pressure infers an increased temperature in boiling, it follows, that where steam of a higher pressure than the atmosphere is required, it is necessary that the water should be boiled at a higher temperature. (19.) We have already stated that there is a certain point at which the temperature of a liquid will cease to rise, and that all the heat communicated to it beyond this is consumed in the formation of vapour. It has been ascertained, that when water boils at 212°, under a pressure equal to 30 inches of mercury, a cubic inch of water forms a cubic foot[4] of steam, the elastic force of which is equal to the atmospheric pressure, and the temperature of which is 212°. Since there are 1728 cubic inches in a cubic foot, it follows, that when water at this temperature passes from the liquid to the vaporous state, it is dilated into 1728 times its bulk. [Footnote 4: The terms _cubic inch_ and _cubic foot_ are easily explained. A common die, used in games of chance, has the figure which is called a cube. It is a solid having twelve straight edges equal to one another. It has six sides, each of which is square, and which are also equal to one another. If its edges be each one inch in length, it is called a _cubic inch_, if one foot, a _cubic foot_, if one yard, a _cubic yard_, &c. This figure is represented in perspective, in fig. 6.] (20.) We have seen that about 1000 degrees of heat must be communicated to any given quantity of water at 212°, in order to convert it into steam of the same temperature, and possessing a pressure amounting to about 15 pounds on the square inch, and that such steam will occupy above 1700 times the bulk of the water from which it was raised. Now we might anticipate, that by abstracting the heat thus employed in converting the liquid into vapour, a series of changes would be produced exactly the reverse of those already described; and such is found to be actually the case. Let us suppose a vessel, the capacity of which is 1728 cubic inches, to be filled with steam, of the temperature of 212°, and exerting a pressure of 15 pounds on the square inch; let 5-1/2 cubic inches of water, at the temperature of 32°, be injected into this vessel, immediately the steam will impart the heat, which it has absorbed in the process of vaporisation to the water thus injected, and will itself resume the liquid form. It will shrink into its primitive dimensions of one cubic inch, and the heat which it will dismiss will be sufficient to raise the 5-1/2 cubic inches of injected water to the temperature of 212°. The contents of the vessel will thus be 6-1/2 cubic inches of water at the temperature of 212°. One of these cubic inches is in fact the steam which previously filled the vessel reconverted into water, the other 5-1/2 are the injected water which has been raised from the temperature of 32° to 212° by the heat which has been dismissed by the steam in resuming the liquid state. It will be observed that in this transmission no temperature is lost, since the cubic inch of water into which the steam is converted has the same temperature as the steam had before the cold water was injected. These consequences are in perfect accordance with the results already obtained from observing the time necessary to convert a given quantity of water into steam by the application of heat. From the present result it follows, that in the reduction of a given quantity of steam to water it parts with as much heat as is sufficient to raise 5-1/2 cubic inches from 32° to 212°, that is, 5-1/2 times 180° or 990°. (21.) There is an effect produced in this process to which it is material that we should attend. The steam which filled the space of 1728 cubic inches shrinks when reconverted into water into the dimensions of 1 cubic inch. It therefore leaves 1727 cubic inches of the vessel it contains unoccupied. By this property steam is rendered instrumental in the formation of a vacuum. By allowing steam to circulate through a vessel, the air may be expelled from it, and its place filled by steam. If the vessel be then closed and cooled the steam will be reduced to water, and, falling in drops on the bottom and sides of the vessel, the space which it filled will become a _vacuum_. This may be easily established by experiment. Let a long glass tube be provided with a hollow ball at one end, and having the other end open.[5] Let a small quantity of spirits be poured in at the open end, and placing the glass ball over the flame of a lamp, let the spirits be boiled. After some time the steam will be observed to issue copiously from the open end of the tube which is presented upwards. When this takes place, let the tube be inverted, and its open end plunged in a basin of cold water. The heat being thus removed, the cool air will reconvert the steam in the tube into liquid, and a vacuum will be produced, into which the pressure of the atmosphere on the surface of the water in the basin will force the water through the tube, and it will rush up with considerable force, and fill the glass ball. [Footnote 5: A common glass flask with a long neck will answer the purpose.] In this experiment it is better to use spirits than water, because they boil at a lower heat, and expose the glass to less liability to break, and also the tube may more easily be handled. CHAPTER II. FIRST STEPS IN THE INVENTION. Futility of early claims. -- Watt, the real Inventor. -- Hero of Alexandria. -- Blasco Garay. -- Solomon de Caus. -- Giovanni Branca. -- Marquis of Worcester. -- Sir Samuel Morland. -- Denis Papin. -- Thomas Savery. (22.) In the history of the progress of the useful arts and manufactures, there is perhaps no example of any invention the credit of which has been so keenly contested as that of the steam engine. Claims to it have been advanced by different nations, and by different individuals of the same nation. The partisans of the competitors for this honour have argued their pretensions, and pressed their claims, with a zeal which has occasionally outstripped the bounds of discretion; and the contest has not unfrequently been tinged with prejudices, both national and personal, and marked with a degree of asperity quite unworthy of so noble a cause, and altogether beneath the dignity of science. The efficacy of the steam engine considered as a mechanical agent depends, first, on the several physical properties from which it derives its operation, and, secondly, on the various pieces of mechanism and details of mechanical arrangement by which these properties are rendered practically available. If the merit of the invention must be ascribed to the discoverer and contriver of these, then the contest will be easily decided, because it will be obvious that the prize is not due to any one individual, but must be distributed in different proportions among several. If, however, he is best entitled to the credit of the invention, who has by the powers of his mechanical genius imparted to the machine that form and those qualities from which it has received its present extensive utility, and by which it has become an agent of transcendent power, which has spread its beneficial effects throughout every part of the civilized globe, then the universal consent of mankind will, as it were by acclamation, award the prize to one individual, whose pre-eminent genius places him far above all other competitors, and from the application of whose mental energies to this machine may be dated those grand effects which have rendered it a topic of interest to every individual for whom the progress of human civilization has any attractions. Before the era marked by the discoveries of JAMES WATT, the steam engine, which has since become an object of such universal interest, was a machine of extremely limited power, greatly inferior in importance to most other mechanical contrivances used as prime movers. But from that time it is scarcely necessary here to state that it became a subject not of British interest only, but one with which the progress of the human race became intimately mixed up. Since, however, the question of the progressive developement of those physical principles on which the steam engine depends, and of their mechanical application, has of late years received some importance, as well from the interest which the public manifest towards them as from the rank of the writers who have investigated them, we have thought it expedient to state briefly, but we trust with candour and fairness, the successive steps which appear to have led to this invention. The engine as it exists at present is not, strictly speaking, the exclusive invention of any one individual: it is the result of a series of discoveries and inventions which have for the last two centuries been accumulating. When we attempt to trace back its history, and to determine its first inventor, we experience the same difficulty as is felt in tracing the head of a great river: as we ascend its course, we are embarrassed by the variety of its tributary streams, and find it impossible to decide which of those channels into which it ramifies ought to be regarded as the principal stream; and it terminates at length in a number of threads of water, each in itself so insignificant as to be unworthy of being regarded as the source of the majestic object which has excited the inquiry. From a very early period the effects of heat upon liquids, and more especially the production of steam or vapour, was regarded as a probable source of mechanical power, and numerous speculators directed their attention to it, and exerted their inventive faculties to derive from it an effective mover. It was not, however, until the commencement of the eighteenth century that any invention was produced which was practically applied, even unsuccessfully. All the attempts previous to that time were either suggestions which were limited to paper or experiments confined to models; or, if they exceeded this, they never outlived a single trial on a larger scale. Nevertheless many of these suggestions and experiments being recorded and accessible to future inquirers doubtless offered useful hints and some practical aid to those more successful investigators who subsequently contrived engines in such forms as to be practically available on a large scale for mechanical purposes. It is right and just, therefore--mere suggestions and abortive experiments though they may have been--to record them, that each inventor and discoverer may receive the just credit due to his share in this splendid mechanical invention. We shall then in the present chapter briefly enumerate, in chronological order, the successive steps so far as they have come to our knowledge. HERO OF ALEXANDRIA, 120 B. C. [Illustration: Fig. 1.] (23.) In a work entitled _Spiritalia seu Pneumatica_, one of the numerous works of this philosopher which has remained to us, is contained a description of a machine moved by vapour of water. A hollow sphere, of which A B represents a section, is supported on two pivots at A and B, which are the extremities of tubes A C D and B E F, which pass into a boiler where steam is generated. This steam flows through small apertures at the extremities A and B, and fills the hollow sphere. One or more horizontal arms K G, I H, project from this sphere, and are likewise filled with steam, but are closed at their extremities. Conceive a small hole made near the extremity G, but at one side of one of the tubes; the steam confined in the tube and globe would immediately rush from the hole with a force proportionate to its pressure within the globe. On the common principle of mechanics a re-action would be produced, and the tube would recoil in the same manner as a gun when discharged. The tubular arm K G being thus pressed in a direction opposed to that in which the steam issues, the sphere would revolve accordingly, and would continue to revolve so long as the steam would continue to flow from the aperture. The force of recoil would be increased by making a similar aperture in two or more arms, care being taken that all the apertures should be placed so as to cause the sphere to revolve in the same direction. This motion being once produced might be transmitted by ordinary mechanical contrivance to any machinery which its power might be adequate to move. This method of using steam is not adopted in any part or any form of the modern steam engine. BLASCO DE GARAY, A. D. 1543. (24.) In the year 1826 there appeared in Zach's Correspondence a communication from Thomas Gonsalez, Director of the Royal Archives of Simancas, giving an account of an experiment reported to have been made in the year 1543 by order of Charles V. in the port of Barcelona. Blasco de Garay, a sea captain, had contrived a machine by which he proposed to propel vessels without oars or sails. Garay concealed altogether the nature of the machine which he used: all that was seen during the experiment was that it consisted of a great boiler for water, and that wheels were kept in revolution at each side of the vessel. The experiment was made upon a vessel called the Trinity, of 200 tons burden, and was witnessed by several official personages, whose presence on the occasion was commanded by the king. One of the witnesses reported that it was capable of moving the vessel at the rate of two leagues in three hours, that the machine was too complicated and expensive, and was exposed to the danger of explosion. The other witnesses, however, reported more favourably. The result of the experiment was thought to be favourable: the inventor was promoted, and received a pecuniary reward, besides having all his expenses defrayed. From the circumstance of the nature of the impelling power having been concealed by the inventor it is impossible to say in what this machine consisted, or even whether steam exerted any agency whatever in it, or, if it did, whether it might not have been, as was most probably the case, a reproduction of Hero's contrivance. It is rather unfavourable to the claims advanced by the advocates of the Spaniard, that although it is admitted that he was rewarded and promoted in consequence of the experiment, yet it does not appear that it was again tried, much less brought into practical use. SOLOMON DE CAUS, 1615. [Illustration: Fig. 2.] (25.) A work entitled "Les Raisons des Forces Mouvantes, avec diverses Machines tant utiles que plaisantes," published at Frankfort in 1615, by Solomon de Caus, a native of France, contains the following theorem:-- "_Water will mount by the help of fire higher than its level_," which is explained and proved in the following terms:-- "The third method of raising water is by the aid of fire. On this principle may be constructed various machines: I shall here describe one. Let a ball of copper marked A, well soldered in every part, to which is attached a tube and stopcock marked D, by which water may be introduced; and also another tube marked B C, which will be soldered into the top of the ball, and the lower end C of which shall descend nearly to the bottom of the ball without touching it. Let the said ball be filled with water through the tube D, then shutting the stopcock D, and opening the stopcock in the vertical tube B C, let the ball be placed upon a fire, the heat acting upon the said ball will cause the water to rise in the tube B C." Such is the description of the apparatus of De Caus as given by himself; and on this has been founded a claim to the invention of the steam engine. It will be observed, that neither in the original theorem nor in the description of the machine which accompanies it, is the word _steam_ anywhere used. Now it was well known, by all conversant in physics, long before the date of the publication containing this description, that atmospheric air when heated acquires an increased elastic force. As the experiment is described, the other part of the ball A is filled with atmospheric air; the heat of the fire acting upon the air through the external surface of the ball, and likewise transmitted through the water, would of course raise the temperature of the air contained in the vessel, would thereby increase its elasticity, and would cause the water to rise in the tube B C, upon a physical principle altogether independent of the qualities of steam. The effect produced, therefore, is just what might have been expected by any one acquainted with the common properties of air, though entirely ignorant of those of steam; and, in point of fact, the pressure of the air is as much concerned in this case in raising the water as the pressure of the steam. This objection, however, is combated by another theorem contained in the same work, in which De Caus speaks of "the strength of the vapour produced by the action of the fire, which causes water to mount; which vapour will issue from the stopcock with great violence after the water has been expelled." If De Caus be admitted to have understood the elastic property of the vapour of water, and to have attributed the ascent of the water in the tube C B to the pressure of that vapour upon the surface of the water confined in the copper ball, it must be admitted that he suggested one of the ways of using the power of steam as a mechanical agent. In the modern steam engine this pressure is not now used against a liquid surface, but against the solid surface of a piston. This, however, should not take from De Caus whatever credit be due to the suggestion of the physical property in question. GIOVANNI BRANCA, 1629. (26.) In a work published at Rome in 1629, entitled "Le Machine del G. Branca," is contained a description of a machine for propelling a wheel by a blast of steam. This contrivance consists of a wheel furnished with flat vanes upon its rim, like the boards of a paddle-wheel. The steam is produced in a close vessel, and made to issue with violence from the extremity of a pipe. Being directed against the vanes, it causes the wheel to revolve, and this motion may be imparted by the usual mechanical contrivances to any machinery which it was intended to move. This contrivance has no analogy whatever to any part of the modern steam engines in any of their various forms. EDWARD SOMERSET, MARQUIS OF WORCESTER, 1663. (27.) Of all the individuals to whom the invention of the steam engine has been ascribed the most celebrated was the Marquis of Worcester, the author of a work entitled "The Scantling of One Hundred Inventions," but which is more commonly known by the title "A Century of Inventions." It is to him that by far the greater number of writers and inquirers on this subject ascribe the merit of the discovery of the invention. This contrivance is described in the following terms in the sixty-eighth invention in the work above named:-- "I have invented an admirable and forcible way to drive up water by fire; not by drawing or sucking it upwards, for that must be, as the philosopher terms it, _infra spæram activitatis_, which is but at such a distance. But this way hath no bounder if the vessels be strong enough. For I have taken a piece of whole cannon whereof the end was burst, and filled it three quarters full of water, stopping and screwing up the broken end, as also the touch-hole and making a constant fire under it; within twenty-four hours, it burst and made a great crack. So that, having a way to make my vessels so that they are strengthened by the force within them, and the one to fill after the other, I have seen the water run like a constant fountain stream forty feet high. One vessel of water rarefied by fire driveth up forty of cold water, and a man that tends the work has but to turn two cocks; that one vessel of water being consumed, another begins to force and refill with cold water, and so successively; the fire being tended and kept constant, which the self-same person may likewise abundantly perform in the interim between the necessity of turning the said cocks." These experiments must have been made before the year 1663, in which the "Century of Inventions" was published. The description of the machine here given, like other descriptions in the same work, was only intended to express the effects produced, and the physical principle on which their production depends. It is, however, sufficiently explicit to enable any one conversant with the subsequent contrivance of Savery, to perceive that Lord Worcester must have contrived a machine containing all that part of Savery's engine in which the direct force of steam is employed. As in the above description, the separate boiler or generator of steam is distinctly mentioned; that the steam from this is conducted into another vessel containing the cold water to be raised; that this water is raised by the pressure of steam acting upon its surface; that when one vessel of water has thus been discharged, the steam acts upon the water contained in another vessel, while the first is being replenished; and that a continued upward current of water is maintained by causing the steam to act alternately upon two vessels, employing the interval to fill one while the water is discharged from the other. On comparing this with the contrivance previously suggested by De Caus, it will be observed, that even if De Caus knew the physical agent by which the water was driven upwards in the apparatus contrived by him, still it was only a means of causing a vessel of boiling water to empty itself; and before a repetition of the process could be obtained, the vessel should be refilled, and again boiled. In the contrivance of Lord Worcester, on the other hand, the agency of the steam was employed in the same manner as it is in the steam engines of the present day, being generated in one vessel, and used for mechanical purposes in another. Nor must this distinction be regarded as trifling and insignificant, because on it depends the whole practicability of using steam as a mechanical agent. Had its action been confined to the vessel in which it was produced, it never could have been employed for any useful purpose. SIR SAMUEL MORLAND, 1683. (28.) It appears, by a MS. in the Harleian Collection in the British Museum, that a mode of applying steam to raise water was proposed to Louis XIV. by Sir Samuel Morland. It contains, however, nothing more than might have been collected from Lord Worcester's description, and is only curious, because of the knowledge the writer appears to have had of the expansion which water undergoes in passing into steam. The following is extracted from the MS.: "The principles of the new force of fire invented by Chevalier Morland in 1682, and presented to his Most Christian Majesty in 1683:--'Water being converted into vapour by the force of fire, these vapours shortly require a greater space (about 2000 times) than the water before occupied, and sooner than be constantly confined would split a piece of cannon. But being duly regulated according to the rules of statics, and by science reduced to measure, weight, and balance, then they bear their load peaceably (like good horses,) and thus become of great use to mankind, particularly for raising water, according to the following table, which shows the number of pounds that may be raised 1800 times per hour to a height of six inches by cylinders half filled with water, as well as the different diameters and depths of the said cylinders.'" DENIS PAPIN, 1695. (29.) Denis Papin, a native of Blois in France, and professor of mathematics at Marbourg, had been engaged about this period in the contrivance of a machine in which the atmospheric pressure should be made available as a mechanical agent by creating a partial vacuum in a cylinder under a piston. His first attempts were directed to the production of this vacuum by mechanical means, having proposed to apply a water-wheel to work an air-pump, and so maintain the degree of rarefaction required. This, however, would eventually have amounted to nothing more than a mode of transmitting the power of the water-wheel to another engine, since the vacuum produced in this way could only give back the power exerted by the water-wheel diminished by the friction of the pumps; still this would attain the end first proposed by Papin, which was merely to transmit the force of the stream of a river, or a fall of water, to a distant point, by partially exhausted pipes or tubes. He next, however, attempted to produce a partial vacuum by the explosion of gunpowder; but this was found to be insufficient, since so much air remained in the cylinder under the piston, that at least half the power due to a vacuum would have been lost. "I have, therefore," proceeds Papin, "attempted to attain this end by another method. Since water being converted into steam by heat acquires the property of elasticity like air, and may afterwards be recondensed so perfectly by cold that there will no longer remain the appearance of elasticity in it, I have thought that it would not be difficult to construct machines in which, by means of a moderate heat, and at a small expense, water would produce that perfect vacuum which has been vainly sought by means of gunpowder." Papin accordingly constructed the model of a machine, consisting of a small pump, in which was placed a solid piston, and in the bottom of the cylinder under the piston was contained a small quantity of water. The piston being in immediate contact with this water, so as to exclude the atmospheric air, on applying fire to the bottom of the cylinder steam was produced, the elastic force of which raised the piston to the top of the cylinder: the fire being then removed, and the cylinder being cooled by the surrounding air, the steam was condensed and reconverted into water, leaving a vacuum in the cylinder into which the piston was pressed by the force of the atmosphere. The fire being applied and subsequently removed, another ascent and descent were accomplished; and in the same manner the alternate motion of the piston might be continued. Papin described no other form of machine by which this property could be rendered available in practice; but he states generally that the same end may be attained by various forms of machines easy to be imagined.[6] [Footnote 6: Recueil de diverses pièces touchant quelques nouvelles machines, p. 38.] THOMAS SAVERY, 1698. (30.) The discovery of the method of producing a vacuum by the condensation of steam was reproduced before 1688, by Captain Thomas Savery, to whom a patent was granted in that year for a steam engine to be applied to the raising of water, &c. Savery proposed to combine the machine described by the Marquis of Worcester, with an apparatus for raising water by suction into a vacuum produced by the condensation of steam. Savery appears to have been ignorant of the publication of Papin, in 1695, and states that his discovery of the condensing principle arises from the following circumstance:-- Having drunk a flask of Florence at a tavern and flung the empty flask on the fire, he called for a basin of water to wash his hands. A small quantity which remained in the flask began to boil and steam issued from its mouth. It occurred to him to try what effect would be produced by inverting the flask and plunging its mouth in the cold water. Putting on a thick glove to defend his hand from the heat, he seized the flask, and the moment he plunged its mouth in the water, the liquid immediately rushed up into the flask and filled it. (21.) Savery stated that this circumstance immediately suggested to him the possibility of giving effect to the atmospheric pressure by creating a vacuum in this manner. He thought that if, instead of exhausting the barrel of a pump by the usual laborious method of a piston and sucker, it was exhausted by first filling it with steam and then condensing the same steam, the atmospheric pressure would force the water from the well into the pump-barrel and into any vessel connected with it, provided that vessel were not more than about 34 feet above the elevation of the water in the well. He perceived, also, that, having lifted the water to this height, he might use the elastic force of steam in the manner described by the Marquis of Worcester to raise the same water to a still greater elevation, and that the same steam which accomplished this mechanical effect would serve by its subsequent condensation to repeat the vacuum and draw up more water. It was on this principle that Savery constructed the first engine in which steam was ever brought into practical operation. CHAPTER III. ENGINES OF SAVERY AND NEWCOMEN. Savery's Engine. -- Boilers and their appendages. -- Working apparatus. -- Mode of Operation. -- Defects of the Engine. -- Newcomen and Cawley. -- Atmospheric Engine. -- Accidental Discovery of Condensation by Jet. -- Potter's Discovery of the Method of Working the Valves. (31.) The steam engine contrived by Savery, like every other which has since been constructed, consists of two parts essentially distinct. The first is that which is employed to generate the steam, which is called the boiler, and the second, that in which the steam is applied as a moving power. The former apparatus in Savery's engine consists of two strong boilers, sections of which are represented at D and E in fig. 7.; D the greater boiler, and E the less. The tubes T and T´ communicate with the working apparatus which we shall presently describe. A thin plate of metal R is applied closely to the top of the greater boiler D turning on a centre C, so that by moving a lever applied to the axis C on the outside of the top, the sliding plate R can be brought from the mouth of the one tube to the mouth of the other alternately. This sliding valve is called the _regulator_, since it is by it that the communications between the boiler and two steam vessels (hereafter described,) are alternately opened and closed, the lever which effects this being constantly wrought by the hand of the attendant. Two _gauge-pipes_ are represented at G, G´, the use of which is to determine the depth of water in the boiler. One G has its lower aperture a little above the proper depth, and the other G´ a little below it. Cocks are attached to the upper ends G, G´, which can be opened or closed at pleasure. The steam collected in the top of the boiler pressing on the surface of the water forces it up in the tubes G, G´, if their lower ends be immersed. Upon opening the cocks G, G´, if water be forced from them, there is too much water in the boiler, since the mouth of G is _below_ its level. If steam issue from both there is too little water in the boiler, since the mouth of G´ is _above_ its level. But if steam issue from G and water from G´ the water in the boiler is at its proper level. This ingenious contrivance for determining the level of the water in the boiler is the invention of Savery, and is used in many instances at the present day. The mouth of G should be at a level of a little less than one-third of the whole depth, and the mouth of G´ at a level a little lower than one-third; for it is requisite that about two-thirds of the boiler should be kept filled with water. The tube I forms a communication between the greater boiler D and the lesser or feeding boiler E, descending nearly to the bottom of it. This communication can be opened and closed at pleasure by the cock K. A gauge pipe is inserted similar to G, G´, but extending nearly to the bottom. From this boiler a tube F extends which is continued to a cistern C (fig. 8.) and a cock is placed at M which, when opened, allows the water from the cistern to flow into the feeding boiler E, and which is closed when that boiler is filled. The manner in which this cistern is supplied will be described hereafter. Let us now suppose that the principal boiler is filled to the level between the gauge-pipes, and that the subsidiary boiler is nearly full of water, the cock K and the gauge cocks G, G´ being all closed. The fire being lighted beneath D and the water boiled, steam is produced and is transmitted through one or other of the tubes T T´, to the working apparatus. When evaporation has reduced the water in D below the level of G´ it will be necessary to replenish the boiler D. This is effected thus. A fire being lighted beneath the feeding boiler E, steam is produced in it above the surface of the water, which having no escape presses on the surface so as to force it up in the pipe I. The cock K being then opened, the boiling water is forced into the principal boiler D, into which it is allowed to flow until water issues from the gauge cock G´. When this takes place, the cock K is closed, and the fire removed from E until the great boiler again wants replenishing. When the feeding boiler E has been exhausted, it is replenished from the cistern C (fig. 8.) through the pipe F by opening the cock M. (32.) We shall now describe the working apparatus in which the steam is used as a moving power. Let V V´ (fig. 8.) be two steam vessels communicating by the tubes T T´ (marked by the same letters in fig. 7.) with the greater boiler D. Let S be a pipe, called the _suction pipe_, descending into the well or reservoir from which the water is to be raised, and communicating with each of the steam vessels through tubes D D´ by valves A A´ which open upwards. Let F be a pipe continued from the level of the engine of whatever higher level it is intended to elevate the water. The steam vessels V V´ communicate with the _force-pipe_ F by valves B B´ which open upward, through the tubes E E´. Over the steam vessels and on the force-pipe is placed a small cistern C already mentioned, which is kept filled with cold water from the force-pipe, and from the bottom of which proceeds a pipe terminated with a cock G. This is called the _condensing pipe_, and can be brought alternately over each steam vessel. From this cistern another pipe communicates with the feeding boiler (fig. 7.) by the cock M.[7] [Footnote 7: This pipe in fig. 9. is represented as proceeding from the force-pipe above the cistern C.] The communication of the pipes T T´ with the boiler can be opened and closed, alternately, by the regulator R, (fig. 7.) already described. Now suppose the steam vessels and tubes to be all filled with common atmospheric air, and that the regulator be placed so that the communication between the tube T and the boiler be opened, the communication between the other tube T´ and the boiler being closed, steam will flow into V through T. At first, while the vessel V is cold, the steam will be condensed and will fall in drops of water on the bottom and sides of the vessel. The continued supply of steam from the boiler will at length impart such a degree of heat to the vessel V that it will cease to condense it. Mixed with the heated air contained in the vessel V, it will have an elastic force greater than the atmospheric pressure, and will therefore force open the valve B, through which a mixture of air and steam will be driven until all the air in the vessel V will have passed out, and it will contain nothing but the pure vapour of water. When this has taken place, suppose the regulator be moved so as to close the communication between the tube T and the boiler, and to stop the further supply of steam to the vessel V; and at the same time let the condensing pipe G be brought over the vessel V and the cock opened so as to let a stream of cold water flow upon it. This will cool the vessel V, and the steam with which it is filled will be condensed and fall in a few drops of water, leaving the interior of the vessel a vacuum. The valve B will be kept closed by the atmospheric pressure. But the elastic force of the air between the valve A and the surface of the water in the well or reservoir, will open A, so that a part of this air will rush in (6.) and occupy the vessel V. The air in the suction pipe S, being thus allowed an increased space, will be proportionably diminished in its elastic force (6.), and its pressure will no longer balance that of the atmosphere acting on the external surface L[8] of the water in the reservoir. This pressure will, therefore, force water up in the tube S until its weight, together with the elastic force of the air above it, balances the atmospheric pressure on L (7.). When this has taken place, the water will cease to ascend. [Footnote 8: Not in the diagram.] Let us now suppose that, by shifting the regulator, the communication is opened between T and the boiler, so that steam flows again into V. The condensing cock G being removed, the vessel will be again heated as before, the air expelled, and its place filled by the steam. The condensing pipe being again allowed to play upon the vessel V, and the further supply of steam being stopped, a vacuum will be produced in V, and the atmospheric pressure on L will force the water through the valve A into the vessel V, which it will nearly fill, a small quantity of air, however, remaining above it. Thus far the mechanical agency employed in elevating the water is the atmospheric pressure; and the power of steam is no further employed than in the production of a vacuum. But, in order to continue the elevation of the water through the force-pipe F, above the level of the steam vessel, it will be necessary to use the elastic pressure of the steam. The vessel V is now nearly filled by the water which has been forced into it by the atmosphere. Let us suppose that, the regulator being shifted again, the communication between the tube T and the boiler is opened, the condensing cock removed, and that steam flows into V. At first coming in contact with the cold surface of the water and that of the vessel, it is condensed; but the vessel is soon heated, and the water formed by the condensed steam collects in a sheet or film on the surface of the water in V, so as to form a surface as hot as boiling water.[9] The steam then being no longer condensed, presses on the surface of the water with its elastic force; and when that pressure becomes greater than the atmospheric pressure, the valve B is forced open and the water, issuing through it, passes through E into the force-pipe F; and this is continued until the steam has forced all the water from V, and occupies its place. [Footnote 9: Hot water being lighter than cold, it floats on the surface.] The further admission of steam through T is once more stopped by moving the regulator; and the condensing pipe being again allowed to play on V, so as to condense the steam which fills it, produces a vacuum. Into this vacuum, as before, the atmospheric pressure on L will force the water, and fill the vessel V. The condensing pipe being then closed and steam admitted through T, the water in V will be forced by its pressure through the valve B and tube E into F, and so the process is continued. We have not yet noticed the other steam vessel V´, which as far as we have described, would have remained filled with common atmospheric air, the pressure of which, on the valve A´, would have prevented the water raised in the suction pipe S from passing through it. However, this is not the case; for, during the entire process which has been described in V, similar effects have been produced in V´, which we have only omitted to notice, to avoid the confusion which the two processes might produce. It will be remembered, that after the steam, in the first instance, having flowed from the boiler through T, has blown the air out of V through B, the communication between T and the boiler is closed. Now the same motion of the regulator which closes this opens the communication between T´ and the boiler; for the sliding plate R (fig. 7.) is moved from the one tube to the other, and at the same time, as we have already stated, the condensing pipe is brought to play on V. While, therefore, a vacuum is being formed in V by condensation, the steam, flowing through T´, blows out the air through B´, as already described in the other vessel V; and, while the air in S is rushing up through A into V followed by the water raised in S by the atmospheric pressure on L, the vessel V´ is being filled with steam, and the air is completely expelled from it. The communication between T and the boiler is now again opened, and the communication between T´ and the boiler closed by moving the regulator R (fig. 7.) from the tube T to T´; at the same time the condensing pipe is removed from over V and brought to play upon V´. While the steam once more expels the air from V through B, a vacuum is formed by condensation in V´, into which the water in S rushes through the valve A´. In the mean time V is again filled with steam. The communication between T and the boiler is now closed, and that between T´ and the boiler is opened, and the condensing pipe removed from V´ and brought to play on V. While the steam from the boiler forces the water in V´ through B´ into the force-pipe F, a vacuum is being produced in V into which water is raised by the atmospheric pressure at L. Thus each of the vessels V V´ is alternately filled from S and the water thence forced into F. The same steam which forces the water from the vessels into F, having done its duty, is condensed, and brings up the water from S by giving effect to the atmospheric pressure. During this process, two alternate motions or adjustments must be constantly made; the communication between T and the boiler must be opened, and that between T´ and the boiler closed, which is done by one motion of the regulator. The condensing pipe at the same time must be brought from V to play on V´ which is done by the lever placed upon it. Again the communication between T´ and the boiler is to be opened, and that between T and the boiler closed; this is done by moving back the regulator. The condensing pipe is brought from V´ to V by moving back the other lever, and so on alternately. For the clearness and convenience of description, some slight and otherwise unimportant changes have been made in the position of the parts.[10] A perspective view of this engine is presented in fig. 9. The different parts already described will easily be recognised, being marked with the same letters as in figs. 6, 7. [Footnote 10: In the diagrams used for explaining the principles and operations of machines, I have found it contribute much to the clearness of the description to adopt an arrangement of parts somewhat different from that of the real machine. When once the nature and principles on which the machine acts are well understood, the reader will find no difficulty in transferring every part to its proper place, which is represented in the perspective drawings.] (33.) In order duly to appreciate the value of improvements, it is necessary first to perceive the defects which these improvements are designed to remove. Savery's steam engine, considering how little was known of the value and properties of steam, and how low the general standard of mechanical knowledge was in his day, is certainly highly creditable to his genius. Nevertheless it had very considerable defects, and was finally found to be inefficient for the most important purposes to which he proposed applying it. At the time of this invention, the mines in England had greatly increased in depth, and the process of draining them had become both expensive and difficult; so much so, that it was found in many instances that their produce did not cover the cost of working them. The drainage of these mines was the most important purpose to which Savery proposed to apply his steam engine. It has been already stated, that the pressure of the atmosphere amounts to about 15 lbs. (3.) on every square inch. Now, a column of water, whose base is one square inch, and whose height is 34 feet, weighs about 15lbs. If we suppose that a perfect vacuum were produced in the steam-vessels V V´ (fig. 8.) by condensation, the atmospheric pressure on L would fail to force up the water, if the height of the top of these vessels exceeded 34 feet. It is plain, therefore, that the engine cannot be more than 34 feet above the water which it is intended to elevate. But in fact it cannot be so much; for the vacuum produced in the steam-vessels V V´ is never perfect. Water, when not submitted to the pressure of the atmosphere, will vaporise at a very low temperature (17.); and it was found that a vapour possessing a considerable elasticity would, notwithstanding the condensation, remain in the vessels V V´ and the pipe S, and would oppose the ascent of the water. In consequence of this, it was found that the engine could never be placed with practical advantage at a greater height than 26 feet above the level of the water to be raised. (34.) When the water is elevated to the engine, and the steam-vessels filled, if steam be introduced above the water in V, it must first balance the atmospheric pressure, before it can force the water through the valve B. Here, then, is a mechanical pressure of 15lbs. per square inch expended, without any water being raised by it. If steam of twice that elastic force be used, it will elevate a column in F of 34 feet in height; and if steam of triple the force be used, it will raise a column of 68 feet high, which, added to 26 feet raised by the atmosphere, gives a total lift of 94 feet. In effecting this, steam of a pressure equal to three times that of the atmosphere acts on the inner surface of the vessels V V´. One third of this bursting of the pressure is balanced by the pressure of the atmosphere on the external surface of the vessels; but an effective pressure of 30lbs. per square inch still remains, tending to burst the vessels. It was found, that the apparatus could not be constructed to bear more than this with safety; and, therefore, in practice the lift of such an engine was limited to about 90 perpendicular feet. In order to raise the water from the bottom of the mine by these engines, therefore, it was necessary to place one at every 90 feet of the depth; so that the water raised by one through the first 90 feet should be received in a reservoir, from which it was to be elevated the next 90 feet by another, and so on. Besides this, it was found that sufficient strength could not be given to those engines, if constructed upon a large scale. They were, therefore, necessarily very limited in their dimensions, and were incapable of raising the water with sufficient speed. Hence arose a necessity for several engines at each level, which greatly enhanced the expense. (35.) These, however, were not the only defects of Savery's engines. The consumption of fuel was enormous, the proportion of heat wasted being much more than what was used in either forcing up the water, or producing a _vacuum_. This will be very easily understood by attending to the process of working the engine already described. When the steam is first introduced from the boiler into the steam-vessels V V´, preparatory to the formation of a vacuum, it is necessary that it should heat these vessels up to the temperature of the steam itself; for until then the steam will be condensed the moment it enters the vessel by the cool surface. All this heat, therefore, spent in raising the temperature of the steam vessels is wasted. Again, when the water has ascended and filled the vessels V V´, and steam is introduced to force this water through B B´ into F, it is immediately condensed by the cold surface in V V´, and does not begin to act until a quantity of hot water, formed by condensed steam, is collected on the surface of the cold water which fills the vessel V V´. Hence another source of the waste of heat arises. When the steam begins to act upon the surface of the water in V V´, and to force it down, the cold surface of the vessel is gradually exposed to the steam, and must be heated while the steam continues its action; and when the water has been forced out of the vessel, the vessel itself has been heated to the temperature of the steam which fills it, all which heat is dissipated by the subsequent process of condensation. It must thus be evident that the steam used in forcing up the water in F, and in producing a vacuum, bears a very small proportion indeed to what is consumed in heating the apparatus after condensation. [Illustration: Pl. I.] (36.) There is also another circumstance which increases the consumption of fuel. The water must be forced through b, not only against the atmospheric pressure, but also against a column of 68 feet of water. Steam is therefore required of a pressure of 45lbs. on the square inch. Consequently the water in the boiler must be boiled under this pressure. That this should take place, it is necessary that the water should be raised to a temperature considerably above 212° (17.), even so high as 267°; and thus an increased heat must be given to the boiler. Independently of the other defects, this intense heat weakened and gradually destroyed the apparatus. Besides the drainage of mines, Savery proposed to apply his steam engine to a variety of other purposes; such as supplying cities with water, forming ornamental waterworks in pleasure grounds, turning mills, &c. Savery was the first who suggested the method of expressing the power of an engine with reference to that of horses. In this comparison, however, he supposed each horse to work but 8 hours a day, while the engine works for 24 hours. This method of expressing the power of steam engines will be explained hereafter. (37.) The failure of the engines proposed by Captain Savery in the great work of drainage, from the causes which have been just mentioned and the increasing necessity for effecting this object arising from the circumstance of the large property in mines, which became every year unproductive by it, stimulated the ingenuity of mechanics to contrive some means of rendering those powers of steam exhibited in Savery's engine practically available. Among others, Thomas Newcomen, a blacksmith of Dartmouth, and John Cawley, a plumber of the same place, turned their attention to this inquiry. Newcomen appears to have resumed the old method of raising the water from the mines by ordinary pumps, but conceived the idea of working these pumps by some moving power less expensive than that of horses. The means whereby he proposed effecting this was by connecting the end of a pump rod D (fig. 10.), by a chain, with the arch-head A of a working beam A B, playing on an axis C. The other arch-head B of this beam was connected by a chain with the rod E of a solid piston P, which moved air-tight in a cylinder F. If a vacuum be created beneath the piston P, the atmospheric pressure acting upon it will press it down with a force of 15 lbs. per square inch; and the end A of the beam being thus raised, the pump-rod D will be drawn up. If a pressure equivalent to the atmosphere be then introduced below the piston, so as to neutralize the downward pressure, the piston will be in a state of indifference as to rising or falling; and if in this case the rod D be made heavier than the piston and its rod, so as to overcome the friction, &c. it will descend, and elevate the piston again to the top of the cylinder. The vacuum being again produced, another descent of the piston, and consequent elevation of the pump-rod, will take place; and so the process may be continued. [Illustration: Pl. II. SAVERY'S STEAM ENGINE.] Such was Newcomen's first conception of the _atmospheric engine_; and the contrivance had much, even at the first view, to recommend it. The power of such a machine would depend entirely on the magnitude of the piston; and being independent of a highly elastic steam, would not expose the materials to the destructive heat which was necessary for working Savery's engine. Supposing a perfect vacuum to be produced under the piston in the cylinder, an effective downward pressure would be obtained, amounting to 15 times as many pounds as there are square inches in the section of the piston.[11] Thus, if the base of the piston were 100 square inches, a pressure equal to 1500lbs. would be obtained. [Footnote 11: As the calculation of the power of an engine depends on the number of square inches in the section of the piston, it may be useful to give a rule for computing the number of square inches in a circle. The following rule will always give the dimensions with sufficient accuracy:--_Multiply the number of inches in the diameter by itself; divide the product by 14, and multiply the quotient thus obtained by 11, and the result will be the number of square inches in the circle._ Thus if there be 12 inches in the diameter, this multiplied by itself gives 144, which divided by 14 gives 10-4/14, which multiplied by 11 gives 115, neglecting fractions. There are, therefore, 115 square inches in a circle whose diameter is 12 inches.] (38.) In order to accomplish this design, two things were necessary: 1. To make a speedy and effectual vacuum below the piston in the descent; and 2. To contrive a counterpoise for the atmosphere in the ascent. The condensation of steam immediately presented itself as the most effectual means of accomplishing the former; and the elastic force of the same steam previous to condensation an obvious method of effecting the latter. Nothing now remained to carry the design into execution, but the contrivance of means for the alternate introduction and condensation of the steam; and Newcomen and Cawley were accordingly granted a patent in 1707, in which Savery was united, in consequence of the principle of condensation for which he had previously received a patent being necessary to the projected machine. We shall now describe the _atmospheric engine_, as first constructed by Newcomen:-- The boiler K is placed over a furnace I, the flue of which winds round it, so as to communicate heat to every part of the bottom of it. In the top, which is hemispherical, two gauge-pipes G G´ are placed, as in Savery's engine, and a _puppet valve_ V, which opens upward, and is loaded at one pound per square inch; so that when the steam produced in the boiler exceeds the pressure of the atmosphere by more than one pound on the square inch, the valve V is lifted, and the steam escapes through it, and continues to escape until its pressure is sufficiently diminished, when the valve V again falls into its seat. The great steam-tube is represented at S, which conducts steam from the boiler to the cylinder; and a feeding pipe T furnished with a cock, which is opened and closed at pleasure, proceeds from a cistern L to the boiler. By this pipe the boiler may be replenished from the cistern, when the gauge cock G´ indicates that the level has fallen below it. The cistern L is supplied with hot water by means which we shall presently explain. (39.) To understand the mechanism necessary to work the piston, let us consider how the supply and condensation of steam must be regulated. When the piston has been forced to the bottom of the cylinder by the atmospheric pressure acting against a vacuum, in order to balance that pressure, and enable it to be drawn up by the weight of the pump-rod, it is necessary to introduce steam from the boiler. This is accomplished by opening the cock R in the steam-pipe S. The steam being thus introduced from the boiler, its pressure balances the action of the atmosphere upon the piston, which is immediately drawn to the top of the cylinder by the weight of the pump-rod D. It then becomes necessary to condense this steam, in order to produce a vacuum. To accomplish this the further supply of steam must be cut off, which is done by closing the cock R. The supply of steam from the boiler being thus suspended, the diffusion of cold water on the external surface of the cylinder becomes necessary to condense the steam within it. This was done by enclosing the cylinder within another, leaving a space between them.[12] Into this space cold water is allowed to flow from a cock M placed over it, which is supplied by a pipe from the cistern N. This cistern is supplied with water by a pump O, which is worked by the engine itself, from the beam above it. [Footnote 12: The external cylinder is not represented in the diagram.] The cold water supplied from M, having filled the space between the two cylinders, abstracts the heat from the inner one; and condensing the steam, produces a vacuum, into which the piston is immediately forced by the atmospheric pressure. Preparatory to the next descent, the water which thus fills the space between the cylinders, and which is warmed by the heat it has abstracted from the steam, must be discharged, in order to give room for a fresh supply of cold water from M. An aperture, furnished with a cock, is accordingly provided in the bottom of the cylinder, through which the water is discharged into the cistern L; and being warm, is adapted for the supply of the boiler through T, as already mentioned. The cock R being now again opened, steam is admitted below the piston, which, as before, ascends, and the descent is again accomplished by opening the cock M, admitting cold water between the cylinders, and thereby condensing the steam below the piston. The condensed steam, thus reduced to water, will collect in the bottom of the cylinder, and resist the descent of the piston. It is, therefore, necessary to provide an exit for it, which is done by a valve opening _outwards_ into a tube which leads to the feeding cistern L, into which the condensed steam is driven. That the piston should continue to be air-tight, it was necessary to keep a constant supply of water over it; this was done by a cock similar to M, which allowed water to flow from the pipe M on the piston. (40.) Soon after the first construction of these engines, an accidental circumstance suggested to Newcomen a much better method of condensation than the effusion of cold water on the external surface of the cylinder. An engine was observed to work several strokes with unusual rapidity, and without the regular supply of the condensing water. Upon examining the piston, a hole was found in it, through which the water, which was poured on to keep it air-tight, flowed, and instantly condensed the steam under it. On this suggestion Newcomen abandoned the external cylinder, and introduced a pipe H furnished with a cock Q into the bottom of the cylinder, so that on turning the cock the pressure of the water in the pipe H, from the level of the water in the cistern N, would force the water to rise as a jet into the cylinder, and would instantly condense the steam. This method of condensing by a jet formed a very important improvement in the engine, and is the method still used. (41.) Having taken a general view of the parts of the atmospheric engine, let us now consider more particularly its operation. When the engine is not working the weight of the pump-rod D draws down the beam A, and draws the piston to the top of the cylinder, where it rests. Let us suppose all the cocks and valves closed, and the boiler filled to the proper depth. The fire being lighted beneath it, the water is boiled until the steam acquires sufficient force to lift the valve V. When this takes place, the engine may be started. For this purpose the regulating valve R is opened. The steam rushes in and is first condensed by the cold cylinder. After a short time the cylinder acquires the temperature of the steam, which then ceases to be condensed, and mixes with the air which filled the cylinder. The steam and heated air, having a greater force than the atmospheric pressure, will open a valve placed at the end X of a small tube in the bottom of the cylinder, and which opens outwards. From this (which is called the _blowing valve_[13]) the steam and air rush in a constant stream until all the air has been expelled, and the cylinder is filled with the pure vapour of water. This process is called _blowing_ the engine preparatory to starting it. [Footnote 13: Also called the _snifting_ valve, from the peculiar noise made by the air and steam escaping from it.] When it is about to be started, the engine-man closes the regulator R, and thereby suspends the supply of steam from the boiler. At the same time he opens the _condensing valve_ H,[14] and thereby throws up a jet of cold water into the cylinder. This immediately condenses the steam contained in the cylinder, and produces the vacuum. (The atmosphere cannot enter the _blowing_ valve, because it opens _outwards_, so that no air can enter to vitiate the vacuum.) The atmospheric pressure above the piston now takes effect, and forces it down in the cylinder. The descent being completed, the engine-man closes the condensing valve H, and opens the regulator R. By this means he stops the play of the jet within the cylinder, and admits the steam from the boiler. The first effect of the steam is to expel the condensing water and condensed steam which are collected in the bottom of the cylinder through the tube Y, containing a valve which opens _outwards_, (called the _eduction valve_,) which leads to the hot cistern L, into which this water is therefore discharged. [Footnote 14: Also called the _injection valve_.] When the steam admitted through R ceases to be condensed, it balances the atmospheric pressure above the piston, and thus permits it to be drawn to the top of the cylinder by the weight of the rod D. This ascent of the piston is also assisted by the circumstance of the steam being somewhat stronger than the atmosphere. When the piston has reached the top, the regulating valve r is closed, and the condensing valve H opened, and another descent produced as before, and so the process is continued. The manipulation necessary in working this engine was, therefore, the alternate opening and closing of two valves; the regulating and condensing valves. When the piston reached the top of the cylinder, the former was to be closed, and the latter opened; and, on reaching the bottom, the former was to be opened, and the latter closed. (42.) From the imperfect attention which even an assiduous attendant could give to the management of these valves, the performance of the engines was very irregular, and the waste of fuel very great, until a boy named _Humphrey Potter_ contrived means of making the engine work its own valves. This contrivance, although made with no other design than the indulgence of an idle disposition, nevertheless constituted a most important step in the progressive improvement of the steam-engine; for by its means, not only the irregularity arising from the negligence of attendants was avoided, but the speed of the engine was doubled. Potter attached strings to the levers which worked the valves, and carrying these strings to the working beam, fastened them upon it in such a manner that as the beam ascended and descended, it pulled the strings so as to open and close the proper valves with the most perfect regularity and certainty. This contrivance was afterwards much improved by an engineer named _Beighton_, who attached to the working beam a straight beam called a _plug frame_, carrying pins which, in the ascent and descent of the beam, struck the levers attached to the valves, and opened and closed them exactly at the proper moment. The engine thus improved required no other attendance except to feed the boiler occasionally by the cock T, and to attend the furnace. CHAP. IV. ENGINE OF JAMES WATT. Advantages of the Atmospheric Engine over that of Captain Savery. -- It contained no new Principle. -- Papin's Engine. -- James Watt. -- Particulars of his Life. -- His first conceptions of the means of Economising Heat. -- Principle of his projected Improvements. (43.) Considered practically, the engine described in the last chapter possessed considerable advantages over that of Savery; and even at the present day this machine is not unfrequently used in districts where fuel is very abundant and cheap, the first cost being considerably less than that of a modern engine. The low pressure of the steam necessary to work it rendered the use of the atmospheric engine perfectly safe; there being only a bursting pressure of about 1lb. per inch, while in Savery's there was a bursting pressure amounting to 30lbs. The temperature of the steam not exceeding 216°, did not weaken or destroy the materials; while Savery's engines required steam raised from water at 267°, which in a short time rendered the engine unable to sustain the pressure. The power of Savery's engines was also very limited, both as to the quantity of water raised, and the height to which it was elevated (34.). On the other hand, the atmospheric engine had no other limit than the dimensions of the piston. In estimating the power of these engines, however, we cannot allow the full atmospheric pressure as an effective force. The condensing water being mixed with the condensed steam, forms a quantity of hot water in the bottom of the cylinder, which, not being submitted to the atmospheric pressure (17.), produces a vapour which resists the descent of the piston. In practice we find that an allowance of at least 3lbs. per square inch should be made for the resistance of this vapour, and 1lb. per square inch for friction, &c.; so that the effective force will be found by subtracting these 4lbs. per square inch from the atmospheric pressure; which, if estimated at 15lbs., leaves an effective working power of about 11lbs. per square inch. This, however, is rather above what is commonly obtained. Another advantage which this engine has over those of Savery, is the facility with which it might be applied to drive machinery by means of the working beam. The merit of this engine as an invention, must be ascribed principally to its mechanism and combinations. We find in it no new principle; the agency of atmospheric pressure acting against a vacuum, or a partial vacuum, was long known. The formation of a vacuum by the condensation of steam had been suggested by Papin and Savery, and carried into practical effect by the latter. The mechanical power derivable from the direct pressure of the elastic force of steam was distinctly pointed out by Lord Worcester, and even prior to his time; the boiler, gauge-pipes, and regulator of the atmospheric engine, were evidently borrowed from Savery's engine. The idea of working a piston in a cylinder by the atmospheric pressure against a vacuum below, was suggested by Otto Guericke, an ingenious German philosopher, the inventor of the air-pump, and subsequently by Papin; and the use of a working beam could not have been unknown. Nevertheless, considerable credit must be acknowledged to be due to Newcomen for the judicious combination of those scattered principles. "The mechanism contrived by him," says Tredgold, "produces all the difference between an efficient and inefficient engine, and should be more highly valued than the fortuitous discovery of a new principle." The rapid condensation of steam by the injection of water, the method of clearing the cylinder of air and water after the stroke, are two contrivances not before in use, and which are quite essential to the effective operation of the engine: these are wholly due to Newcomen and his associates. (44.) The patent of Newcomen was granted in 1705; and in 1707, Papin published a work, entitled "A New Method of raising Water by Fire," in which a steam engine is described, which would scarcely merit notice here but for the contests which have arisen upon the claims of different nations for a share in the invention of the steam engine. The publication of this work of Papin was nine years after Savery's patent, with which he acknowledges himself acquainted, and two years after Newcomen's. The following is a description of Papin's steam engine:-- An oval boiler, A (fig. 11.), is filled to about two thirds of its entire capacity with water, through a valve B in the top, which opens upwards, and is kept down by a lever carrying a sliding weight. The pressure on the valve is regulated by moving the weight to or from B, like the common steelyard. This boiler communicates with a cylinder, C, by a syphon tube furnished with a stopcock at D. The cylinder C has a valve F in the top, closed by a lever and weight similar to B, and a tube with a stopcock G opening into the atmosphere. In this cylinder is placed a hollow copper piston H, which moves freely in it, and floats upon the water. Another tube forms a communication between the bottom of this cylinder and the bottom of a close cylindrical vessel I, called the _air-vessel_. In this tube is a valve at K, opening _upwards_; also a pipe terminated in a funnel, and furnished with a valve L, which opens _downwards_. From the lower part of the air-vessel a tube proceeds, furnished also with a stopcock M, which is continued to whatever height the water is to be raised. Water being poured into the funnel, passes through the valve L, which opens downwards; and filling the tube, ascends into the cylinder C, carrying the floating piston H on its surface, and maintains the same level in C which it has in the funnel. In this manner the cylinder C may be filled to the level of the top of the funnel. In this process the cock G should be left open, to allow the air in the cylinder to escape as the water rises. Let us now suppose that, a fire being placed beneath the boiler, steam is being produced. On opening the cock D, and closing G, the steam, flowing through the syphon tube into the top of the cylinder, presses down the floating piston, and forces the water into the lower tube. The passage at L being stopped, since L opens _downwards_, the water forces open the valve K, and passes into the air-vessel I. When the piston H has been forced to the bottom of the cylinder, the cock D is closed, and G is opened, and the steam allowed to escape into the atmosphere. The cylinder is then replenished from the funnel as before; and the cock G being closed, and D opened, the process is repeated, and more water forced into the air-vessel I. By continuing this process, water is forced into the air-vessel, and the air which originally filled that vessel is compressed into the space above the water; and its elastic force increases exactly in the same proportion as its bulk is diminished. (6.) Now, suppose that half of the vessel I has been filled by the water which is forced in, the air above the water being reduced to half its bulk has acquired twice the elastic force, and therefore presses on the surface of the water with twice the pressure of the atmosphere. Again, if two thirds of the air-vessel be filled with water, the air is compressed into one third of its bulk, and presses on the surface of the water with three times the pressure of the atmosphere, and so on. [Illustration: Pl. III.] Now if the cock M be opened, the pressure of the condensed air will force the water up in the tube N, and it will continue to rise until the column balances the pressure of the condensed air. If, when the water is suspended in the tube, and the cock M open, the vessel I is half filled, the height of the column in N will be 34 feet, because 34 feet of water has a pressure equal to the atmosphere; and this, added to the atmospheric pressure on it, gives a total pressure equal to twice that of the atmosphere, which balances the pressure of the air in I reduced to half its bulk. If two thirds of I be filled with water, a column of 68 feet will be supported in N; for such a column, united with the atmospheric pressure on it, gives a total pressure equal to three times that of the atmosphere, which balances the air in I compressed into one third of its original bulk. By omitting the principle of condensation, this machine loses 26 feet in the perpendicular lift. But, indeed, in every point of view, it is inferior to the engines of Savery and Newcomen. (45.) From the construction of the atmospheric engine by Newcomen, in 1705, for about half a century, no very important step had been made in the improvement of the steam engine. During this time the celebrated Smeaton had given much attention to the details of the atmospheric engine, and brought that machine to as high a state of perfection as its principle seemed to admit, and as it has ever since reached. In the year 1763, JAMES WATT, a name illustrious in the history of mechanical science, commenced his experiments on steam. He was born at Greenock, in the year 1736; and at the age of 16 was apprenticed to a mathematical instrument-maker, with whom he spent four years. At the age of 20 he removed to London, where he still pursued the same trade under a mathematical instrument-maker in that city. After a short time, however, finding his health declining, he returned to Scotland, and commenced business on his own account at Glasgow. In 1757 he was appointed mathematical instrument-maker to the university of Glasgow, where he resided and carried on business. This circumstance produced an acquaintance between him and the celebrated Dr. Robison, then a student in Glasgow, who directed Watt's attention to the steam engine. In his first experiments he used steam of a high-pressure; but found it attended with so much danger of bursting the boiler, and difficulty of keeping the joints tight, and other objections, that he relinquished the inquiry at that time. (46.) In the winter of 1763, Watt was employed to repair the model of an atmospheric engine, belonging to the natural philosophy class in the university--a circumstance which again turned his attention to the subject of the steam engine. He found the consumption of steam in working this model so great, that he inferred that the quantity wasted, must have had a very large proportion to that used in working the piston. His first conclusion was, that the material of the cylinder (brass) was too good a conductor of heat, and that much was thereby lost. He made some experiments, accordingly, with wooden cylinders, soaked in linseed oil, which, however, he soon laid aside. Further consideration convinced him that a prodigious waste of steam was essential to the very principle of the atmospheric engine. This will be easily understood. When the steam has filled the cylinder so as to balance the atmospheric pressure on the piston, the cylinder must have the same temperature as the steam itself. Now, on introducing the condensing jet, the steam mixed with this water forms a mass of hot water in the bottom of the cylinder. This water, not being under the atmospheric pressure, boils at very low temperatures, and produces a vapour which resists the descent of the piston. The heat of the cylinder itself assists this process; so that in order to produce a tolerably perfect vacuum, it was found necessary to introduce a quantity of condensing water, sufficient to reduce the temperature of the water in the cylinder lower than 100°, and consequently to cool the cylinder itself to that temperature. Under these circumstances, the descent of the piston was found to suffer very little resistance from any vapour within the cylinder: but then on the subsequent ascent, an immense waste of steam ensued; for the steam, on being admitted under the piston, was immediately condensed by the cold cylinder and water of condensation, and this continued until the cylinder became again heated up to 212°, to which point the whole cylinder should be heated before the ascent could be completed. Here, then, was an obvious and an extensive cause of the waste of heat. At every descent of the piston, the cylinder should be cooled below 100°; and at every ascent it should be again heated to 212°. It, therefore, became a question whether the force gained by the increased perfection of the vacuum was adequate to the waste of fuel in producing the vacuum; and it was found, on the whole, more profitable not to cool the cylinder to so low a temperature, and consequently to work with a very imperfect vacuum, and a diminished power. Watt, therefore, found the engine involved in this dilemma: either much or little condensation-water must be used. If much were used, the vacuum would be perfect; but then the cylinder would be cooled, and would entail an extensive waste of fuel in heating it. If little were used, a vapour would remain, which would resist the descent of the piston, and rob the atmosphere of a part of its power. The great problem then pressed itself on his attention, _to condense the steam without cooling the cylinder_. From the small quantity of water in the form of steam which filled the cylinder, and the large quantity of injected water to which this communicated heat, Watt was led to inquire what proportion the bulk of water in the liquid state bore to its bulk in the vaporous state; and also what proportion subsisted between the heat which it contained in these two states. He found by experiment that a cubic inch of water formed about a cubic foot of steam; and that the cubic foot of steam contained as much heat as would raise a cubic inch of water to about 1000°. (15.) This gave him some surprise, as the thermometer indicated the same temperature, 212°, for both the steam and the water from which it was raised. What then became of all the additional heat which was contained in the steam, and not indicated by the thermometer? Watt concluded that this heat must be in some way engaged in maintaining the water in its new form. Struck with the singularity of this circumstance, he communicated it to Dr. Black, who then explained to Watt his doctrine of _latent heat_, which he had been teaching for a short time before that, but of which Watt had not previously heard; and thus, says Watt, "I stumbled upon one of the material facts on which that theory is founded." (47.) Watt now gave his whole mind to the discovery of a method of "condensing the steam without cooling the cylinder." The idea occurred to him of providing a vessel separate from the cylinder, in which a constant vacuum might be sustained. If a communication could be opened between the cylinder and this vessel, the steam, by its expansive property, would rush from the cylinder to this vessel, where, being exposed to cold, it would be immediately condensed, the cylinder meanwhile being sustained at the temperature of 212°. This happy conception formed the first step of that brilliant career which has immortalized the name of Watt, and which has spread his fame to the very skirts of civilization. He states, that the moment the notion of "separate condensation" struck him, all the other details of his improved engine followed in rapid and immediate succession, so that in the course of a day his invention was so complete that he proceeded to submit it to experiment. His first notion was, as we have stated, to provide a separate vessel, called a _condenser_, having a pipe or tube communicating with the cylinder. This condenser he proposed to keep cold by being immersed in a cistern of cold water, and by providing a jet of cold water to play within it. When the communication with the cylinder is opened, the steam, rushing into the condenser, is immediately condensed by the jet and the cold surface. But here a difficulty presented itself, viz. how to dispose of the condensing water, and condensed steam, which would collect in the bottom of the condenser. But besides this, a quantity of air or permanent uncondensible gas would collect from various sources. Water in its ordinary state always holds more or less air in combination with it: the air thus combined with the water in the boiler passes through the tubes and cylinder with the steam, and would collect in the condenser. Air also would enter in combination with the condensing water, which would be set free by the heat it would receive from admixture with the steam. The air proceeding from these sources would, as Watt foresaw, accumulate in the condenser, even though the water might be withdrawn from it, and would at length resist the descent of the piston. To remedy this he proposed _to form a communication between the bottom of the condenser and a pump which he called the_ AIR PUMP, _so that the water and air which might be collected in the condenser would be drawn off_; and it was easy to see how this pump could be worked by the machine itself. This constituted the second great step in the invention. To make it air-tight in the cylinder, it had been found necessary to keep a quantity of water supplied above the piston. In the present case, any of this water which might escape through the piston, or between it and the cylinder, would boil, the cylinder being kept at 212°; and would thus, by the steam it would produce, vitiate the vacuum. To avoid this inconvenience, Watt proposed to lubricate the piston, and keep it air-tight, by employing melted wax and tallow. Another inconvenience was still to be removed. On the descent of the piston, the air which must then enter the cylinder would lower its temperature; so that upon the next ascent, some of the steam which would enter it would be condensed, and hence would arise a source of waste. To remove this difficulty, Watt proposed to close the top of the cylinder altogether by an air-tight and steam-tight cover, allowing the piston-rod to play through a hole furnished with a stuffing-box, and _to press down the piston by steam instead of the atmosphere_. This was the third step in this great invention, and one which totally changed the character of the machine. It now became really a _steam engine_ in every sense; for the pressure above the piston was the elastic force of steam, and the vacuum below it was produced by the condensation of steam; so that steam was used both directly and indirectly as a moving power; whereas, in the atmospheric engine, the indirect force of steam only was used, being adopted merely as an easy method of producing a vacuum. The last difficulty respecting the economy of heat which remained to be removed, was the circumstance of the cylinder being liable to be cooled on the external surface by the atmosphere. To obviate this, he first proposed casing the cylinder in wood, that being a substance which conducted heat slowly. He subsequently, however, adopted a different method, and inclosed one cylinder within another, leaving a space between them, which he kept constantly supplied with steam. Thus the inner cylinder was kept continually at the temperature of the steam which surrounded it. The outer cylinder was called the _jacket_.[15] [Footnote 15: It is a remarkable circumstance, that Watt used the same means for keeping the cylinder hot as Newcomen used in his earlier engines to cool it. (38.)] (48.) Watt computed that in the atmospheric engine three times as much heat was wasted in heating the cylinder, &c. as was spent in useful effect. And, as by the improvements proposed by him nearly all this waste was removed, he contemplated, and afterwards actually effected, a saving of three fourths of the fuel. The honour due to Watt for his discoveries is enhanced by the difficulties under which he laboured from contracted circumstances at the time he made them. He relates, that when he was endeavouring to determine the heat consumed in the production of steam, his means did not permit him to use an efficient and proper apparatus, which would have been attended with expense; and it was by experiments made with apothecaries' phials, that he discovered the property already mentioned, which was one of the facts on which the doctrine of latent heat was founded. A large share of the merit of Watt's discoveries has, by some writers, been attributed to Dr. Black, to whose instructions on the subject of latent heat it is said that Watt owed the knowledge of those facts which led to his improvements. Such, however, was not the case; and the mistake arose chiefly from some passages respecting Watt in the works of Dr. Robison, in one of which he states that Watt had been a _pupil_ and intimate friend of Dr. Black; and that he attended two courses of his lectures at college in Glasgow. Such, however, was not the case; for "Unfortunately for me," says Watt in a letter to Dr. Brewster, "the necessary avocations of my business prevented me from attending his or any other lectures at college. In further noticing Dr. Black's opinion, that his fortunate observation of what happens in the formation and condensation of elastic vapour 'has contributed in no inconsiderable degree to the public good, by suggesting to my friend Mr. Watt of Birmingham, then of Glasgow, his improvements on the steam-engine,' it is very painful for me to controvert any opinion or assertion of my revered friend; yet, in the present case, I find it necessary to say, that he appears to me to have fallen into an error. These improvements proceeded upon the established fact, that steam was condensed by the contact of cold bodies, and the later known one, that water boiled at heats below 100°, and consequently that a vacuum could not be obtained unless the cylinder and its contents were cooled every stroke below the heat." CHAPTER V. WATT'S SINGLE-ACTING STEAM ENGINE. Expansive Principle applied. -- Failure of Roebuck, and Partnership with Bolton. -- Patent extended to 1800. -- Counter. -- Difficulties in getting the Engines into use. (49.) The first machine in which Watt realised the conceptions which we mentioned in the last chapter, is that which was afterwards called his _Single-acting Steam Engine_. We shall now describe the working apparatus in this machine. The cylinder is represented at C (fig. 12.)--in which the piston P moves steam-tight. It is closed at the top, and the piston-rod being very accurately turned, runs in a steam-tight collar B furnished with a stuffing-box, and constantly supplied with melted tallow or wax. Through a funnel in the top of the cylinder, melted grease flows upon the piston so as to maintain it steam-tight. Two boxes A A, containing the valves for admitting and withdrawing the steam, connected by a tube of communication T, are attached to the cylinder; the action of these valves will be presently described. Below the cylinder, placed in a cistern of cold water, is a close cylindrical vessel D, called the condenser, communicating with the cylinder by a tube T´, leading to the lower valve-box A. In the side of this condenser is inserted a tube, the inner end of which is pierced with holes like the rose of a watering-pot; and a cock E in the cold cistern is placed on the outside, through which, when open, the water passing, rises in a jet on the inside. The tube S, which conducts steam from the boiler, enters the top of the upper valve-box at F. Immediately under it is placed a valve G, which is opened and closed by a lever or rod G´. This valve, when open, admits steam to the top of the piston, and also to the tube T, which communicates between the two valve-boxes, and when closed suspends the admission of steam. There are two valves in the lower box, one H in the top worked by the lever H´, and one I in the bottom worked by the lever I´. The valve H, when open, admits steam to pass from the cylinder _above_ the piston, by the tube T, to the cylinder _below_ the piston, the valve I being supposed in this case to be closed. This valve I, when open, (the valve H being closed,) admits steam to pass from below the cylinder through T´ to the condenser. This steam, entering the condenser, meets the jet, admitted to play by the valve E, and is condensed. The valve G is called the _upper steam valve_; H, _lower steam valve_; I, the _exhausting-valve_; and E, the _condensing valve_. Let us now consider how these valves must be worked in order to produce the alternate ascent and descent of the piston. It is in the first place necessary that all the air which fills the cylinder, tubes, and condenser should be expelled. To accomplish this it is only necessary to open at once the valves G, H, and I. The steam then rushing from F through the valve G will pass into the upper part of the cylinder, and through the tube T and the valve H into the lower part, and also through the valve I into the condenser. After the steam ceases to be condensed by the cold of the apparatus, it will rush out mixed with air through the valve M, which opens outward; and this will continue until all the air has been expelled, and the apparatus filled with pure steam. Then suppose all the valves again closed. The cylinder both above and below the piston is filled with steam; and the steam which filled the condenser being cooled by the cold surface, a vacuum has been produced in that vessel. The apparatus being in this state, let the upper steam valve G, the exhausting-valve I, and the condensing valve E be opened. Steam will thus be admitted through G to press on the top of the piston; and this steam will be prevented from circulating to the lower part of the cylinder by the lower steam-valve H being closed. Also the steam which filled the cylinder below the piston rushes through the open exhausting-valve I to the condenser, where it meets the jet allowed to play by the open condensing valve E. It is thus instantly condensed, and a vacuum is left in the cylinder below the piston. Into this vacuum the piston is pressed without resistance by the steam which is admitted through G. When the piston has thus been forced to the bottom of the cylinder, let the three valves G, I, and E, which were before opened, be closed, and let the lower steam-valve H be opened. The effects of this change are easily perceived. By closing the upper steam-valve G, the further admission of steam to the apparatus is stopped. By closing the exhausting-valve I, all transmission of steam from the cylinder to the condenser is stopped. Thus the steam which is _in_ the cylinder, valve-boxes, and tubes is shut up in them, and no more admitted, nor any allowed to escape. By closing the condensing valve E, the play of the jet in the condenser is suspended. Previously to opening the valve H, the steam contained in the apparatus was confined to the part of the cylinder _above_ the piston and the tube T and the valve-box A. But on opening this valve, the steam is allowed to circulate above and below the piston; and in fact through every part included between the upper steam valve G, and the exhausting-valve I. The same steam circulating on both sides, the piston is thus equally pressed upward and downward. In this case there is no force tending to retain the piston at the bottom of the cylinder except its own weight. Its ascent is produced in the same manner as the ascent of the piston in the atmospheric engine. The piston-rod is connected by chains G to the arch-head of the beam, and the weight of the pump-rod R, or any other counterpoise acting on the chains suspended from the other arch-head, draws the piston to the top of the cylinder. When the piston has arrived at the top of the cylinder, suppose the three valves G, I, and E to be again opened, and H closed. Steam passes from the steam-pipe F through the upper steam-valve G to the top of the piston, and at the same time the steam which filled the cylinder below the piston is drawn off through the open exhausting-valve I into the condenser, where it is condensed by the jet allowed to play by the open condensing valve E. The pressure of the steam above the piston then forces it without resistance into the vacuum below it, and so the process is continued. It should be remembered, that of the four valves necessary to work the piston, three are to be opened the moment the piston reaches the top of the cylinder, and the fourth is to be closed; and on the piston arriving at the bottom of the cylinder, these three are to be closed and the fourth opened. The three valves which are thus opened and closed together are the upper steam-valve, the exhausting-valve, and the condensing valve. The lower steam-valve is to be opened at the same instant that these are closed, and _vice versâ_. The manner of working these valves we shall describe hereafter. The process which has just been described, if continued for any considerable number of reciprocations of the piston, would be attended with two very obvious effects which would obstruct and finally destroy the action of the machine. First, the condensing water and condensed steam would collect in the condenser D, and fill it; and secondly, the water in the cistern in which the condenser is placed would gradually become heated, until at last it would not be cold enough to condense the steam when introduced in the jet. Besides this, it will be recollected that water boils in a vacuum at a very low temperature (17); and, therefore, the hot water collected in the bottom of the condenser would produce steam which, rising into the cylinder through the exhausting-valve, would resist the descent of the piston, and counteract the effects of the steam above it. A further disadvantage arises from the air or other permanently elastic fluid which enters in combination with the water, both in the boiler and condensing jet, and which is disengaged by its own elasticity. To remove these difficulties, a pump is placed near the condenser communicating with it by a valve M, which opens from the condenser into the pump. In this pump is placed a piston which moves air-tight, and in which there is a valve N, which opens upwards. Now suppose the piston at the bottom of the pump. As it rises, since the valve in it opens _upwards_, no air can pass _down_ through it, and consequently it leaves a vacuum _below_ it. The water and any air which may be collected in the condenser open the valve M, and pass into the lower part of the pump from which they cannot return in consequence of the valve M opening _outwards_. On the descent of the pump-piston, the fluids which occupy the lower part of the pump, force open the piston-valve N; and passing through it, get _above_ the piston, from which their return is prevented by the valve N. In the next ascent, the piston lifts these fluids to the top of the pump, whence they are discharged through a conduit into a small cistern B by a valve K which opens outwards. The water which is thus collected in B is heated by the condensed steam, and is reserved in B, which is called the hot well for feeding the boiler, which is effected by means which we shall presently explain. The pump which draws off the hot water and air from the condenser is called the _air-pump_. (50.) We have not yet explained the manner in which the valves and the air-pump piston are worked. The rod Q of the latter is connected with the working beam, and the pump is therefore wrought by the engine itself. It is not very material to which arm of the beam it is attached. If it be on the same side of the centre of the beam with the cylinder, it rises and falls with the steam-piston; but if it be on the opposite side, the pump-piston rises when the steam-piston falls, and _vice versâ_. In the single-engine there are some advantages in the latter arrangement. As the steam-piston _descends_, the steam rushes into the condenser, and the jet is playing; and this, therefore, is the most favourable time for drawing out the water and condensed steam from the condenser by the ascent of the pump-piston, since by this means the descent of the steam-piston is assisted; an effect which would not be produced if the steam-piston and pump-piston descended together. With respect to the method of opening and closing the valves, it is evident that the three valves which are simultaneously opened and closed may be so connected as to be worked by the same lever. This lever may be struck by a pin fixed upon the rod Q of the air-pump, so that when the pistons have arrived at the top of the cylinders the pin strikes the lever and opens the three valves. A catch or detent is provided for keeping them open during the descent of the piston, from which they are disengaged in a similar manner on the arrival of the piston at the bottom of the cylinder, and they close by their own weight. In exactly the same way the lower steam-valve is opened on the arrival of the piston at the bottom of the cylinder, and closed on its arrival at the top by the action of a pin placed on the piston-rod of the air-pump. (51.) Soon after the invention of these engines, Watt found that in some instances inconvenience arose from the too rapid motion of the steam-piston at the end of its stroke, owing to its being moved with an _accelerated motion_. This was owing to the uniform action of the steam-pressure upon it: for upon first putting it in motion at the top of the cylinder, the motion was comparatively slow; but from the continuance of the same pressure the velocity with which the piston descended was continually increasing, until it reached the bottom of the cylinder, where it acquired its greatest velocity. To prevent this, and to render the descent as nearly as possible uniform, it was proposed to cut off the steam before the descent was completed, so that the remainder might be effected merely by the expansion of the steam which was admitted to the cylinder. To accomplish this, he contrived, by means of a pin on the rod of the air-pump, to close the upper steam-valve when the steam-piston had completed one-third of its entire descent, and to keep it closed during the remainder of the descent, and until the piston again reached the top of the cylinder. By this arrangement the steam pressed the piston with its full force through one-third of the descent, and thus put it into motion; during the other two thirds the steam thus admitted acted merely by its expansive force, which became less in exactly the same proportion as the space given to it by the descent of the piston increased. Thus, during the last two thirds of the descent the piston is urged by a gradually decreasing force, which in practice was found just sufficient to sustain in the piston a uniform velocity. (52.) We have already mentioned the difficulty arising from the water in the cistern, in which the condenser and air-pump are placed, becoming heated, and the condensation therefore being imperfect. To prevent this, a waste-pipe is placed in this cistern, from which the water is continually discharged, and a pump L (called the _cold-water-pump_) is worked by the engine itself, which raises a supply of cold water and sends it through a pipe in a constant stream into the cold cistern. The waste-pipe, through which the water flows from the cistern, is placed near the top of it, since the heated water, being lighter than the cold, remains on the top. Thus the heated water is continually flowing off, and a constant stream of cold water supplied. The piston-rod of the cold-water-pump is attached to the beam (by which it is worked), usually on the opposite side from the cylinder. Another pump O (called the _hot-water-pump_) enters the _hot well_ B; and raising the water from it, forces it through a tube to the boiler for the purpose of feeding it. The manner in which this is effected will be more particularly described hereafter. A part of the heat which would otherwise be lost, is thus restored to the boiler to assist in the production of fresh steam. We may consider a portion of the heat to be in this manner _circulating_ continually through the machine. It proceeds from the boiler in steam, works the piston, passes into the condenser, and is reconverted into hot water; thence it is passed to the hot well, from whence it is pumped back into the boiler, and is again converted into steam, and so proceeds in constant circulation. From what has been described, it appears that there are four pistons attached to the great beam and worked by the piston of the steam-cylinder. On the same side of the centre with the cylinder is the piston-rod of the air-pump, and on the opposite side are the piston-rods of the hot-water pump and the cold-water-pump; and lastly, at the extremity of the beam opposite to that at which the steam-piston works, is the piston of the pump to be wrought by the engine. (53.) The position of these piston-rods with respect to the centre of the beam depends on the play necessary to be given to the piston. If the play of the piston be short, its rod will be attached to the beam near the centre; and if longer, more remote from the centre. The cylinder of the air-pump is commonly half the length of the steam-cylinder, and its piston-rod is attached to the beam at the point exactly in the middle between the end of the beam and the centre. The hot-water pump not being required to raise a considerable quantity of water, its piston requires but little play, and is therefore placed near the centre of the beam, the piston-rod of the cold-water pump being farther from the centre. (54.) It appears to have been about the year 1763, that Watt made these improvements in the steam engine, and constructed a model which fully realized his expectations. Either from want of influence or the fear of prejudice and opposition, he did not make known his discovery or attempt to secure it by a patent at that time. Having adopted the profession of a land surveyor, his business brought him into communication with Dr. Roebuck, at that time extensively engaged in mining speculations, who possessed some command of capital, and was of a very enterprising disposition. By Roebuck's assistance and countenance, Watt erected an engine of the new construction at a coal mine on the estate of the Duke of Hamilton, at Kinneil near Burrowstoness. This engine being a kind of experimental one, was improved from time to time as circumstances suggested, until it reached considerable perfection. While it was being erected, Watt in conjunction with Roebuck applied for and obtained a patent to secure the property in the invention. This patent was enrolled in 1769, six years after Watt invented the improved engine. Watt was now preparing to manufacture the new engines on an extensive scale, when his partner Roebuck suffered a considerable loss by the failure of a mining speculation in which he had engaged, and became involved in embarrassments, so as to be unable to make the pecuniary advances necessary to carry Watt's designs into execution. Again disappointed, and harassed by the difficulties which he had to encounter, Watt was about to relinquish the further prosecution of his plans, when Mr. Matthew Bolton, a gentleman who had established a factory at Birmingham a short time before, made proposals to purchase Dr. Roebuck's share in the patent, in which he succeeded; and in 1773, Watt entered into partnership with Bolton. His situation was now completely changed. Bolton was not only a man of extensive capital, but also of considerable personal influence, and had a disposition which led him, from taste, to undertakings which were great and difficult, and which he prosecuted with the most unremitting ardency and spirit. "Mr. Watt," says Playfair, "was studious and reserved, keeping aloof from the world; while Mr. Bolton was a man of address, delighting in society, active, and mixing with people of all ranks with great freedom, and without ceremony. Had Mr. Watt searched all Europe, he probably would not have found another person so fitted to bring his invention before the public, in a manner worthy of its merit and importance; and although of most opposite habits, it fortunately so happened that no two men ever more cordially agreed in their intercourse with each other." The delay in the progress of the manufacture of engines occasioned by the failure of Dr. Roebuck was such, that Watt found that the duration of his patent would probably expire before he would even be reimbursed the necessary expenses attending the various arrangements for the manufacture of the engines. He therefore, with the advice and influence of Bolton, Roebuck, and other friends, in 1775, applied to parliament for an extension of the terms of his patent, which was granted for 25 years from the date of his application, so that his exclusive privilege should expire in 1800. An engine was now erected at Soho (the name of Bolton's factory) as a specimen for the examination of mining speculators, and the engines were beginning to come into demand. The manner in which Watt chose to receive remuneration from those who used his engines was as remarkable for its ingenuity as for its fairness and liberality. He required that one-third of the saving of coals effected by his engines, compared with the atmospheric engines hitherto used, should be paid to him, leaving the benefit of the other two-thirds to the public. Accurate experiments were made to ascertain the saving of coals; and as the amount of this saving in each engine depended on the length of time it was worked, or rather on the number of descents of the piston, Watt invented a very ingenious method of determining this. The vibrations of the great working beam were made to communicate with a train of wheelwork, in the same way as those of a pendulum communicate with the work of a clock. Each vibration of the beam moved one tooth of a small wheel, and the motion was communicated to a hand or index, which moved on a kind of graduated plate like the dial plate of a clock. The position of this hand marked the number of vibrations of the beam. This apparatus, which was called the _counter_, was locked up and secured by two different keys, one of which was kept by the proprietor, and the other by Bolton and Watt, whose agents went round periodically to examine the engines, when the counters were opened by both parties and examined, and the number of vibrations of the beam determined, and the value of the patent third found.[16] [Footnote 16: The extent of the saving in fuel may be judged from this: that for three engines erected at Chacewater mine in Cornwall, it was agreed by the proprietors that they would compound for the patent third at 2400_l._ per annum; so that the whole saving must have exceeded 7200_l._ per annum.] Notwithstanding the manifest superiority of these engines over the old atmospheric engines; yet such were the influence of prejudice and the dislike of what is new, that Watt found great difficulties in getting them into general use. The comparative first cost also probably operated against them; for it was necessary that all the parts should be executed with great accuracy, which entailed proportionally increased expense. In many instances they felt themselves obliged to induce the proprietors of the old atmospheric engines to replace them by the new ones, by allowing them in exchange an exorbitant price for the old engines; and in some cases they were induced to erect engines at their own expense, upon an agreement that they should only be paid if the engines were found to fulfil the expectations, and brought the advantages which they promised. It appeared since, that Bolton and Watt had actually expended a sum of nearly 50,000_l._ on these engines before they began to receive any return. When we contemplate the immense advantages which the commercial interests of the country have gained by the improvements in the steam engine, we cannot but look back with disgust at the influence of that fatal prejudice which opposes the progress of improvement under the pretence of resisting innovation. It would be a problem of curious calculation to determine what would have been lost to the resources of this country, if chance had not united the genius of such a man as Watt with the spirit, enterprise, and capital, of such a man as Bolton! The result would reflect little credit on those who think novelty alone a sufficient reason for opposition. CHAPTER VI. DOUBLE-ACTING STEAM ENGINE. The Single-Acting Engine unfit to impel Machinery. -- Various contrivances to adapt it to this purpose. -- Double-Cylinder. -- Double-Acting Cylinder. -- Various mode of connecting the Piston with the Beam. -- Rack and Sector. -- Double Chain. -- Parallel Motion. -- Crank. -- Sun and Planet Motion. -- Fly Wheel. -- Governor. In the atmospheric engine of Newcomen, and in the improved steam engine of Watt, described in the last chapter, the action of the moving power is an intermitting one. While the piston descends, the moving power is in action, but its action is suspended during the ascent. Thus the opposite or working end of the beam can only be applied in cases where a lifting power is required. This action is quite suitable to the purposes of pumping, which was the chief or only object to which the steam engine had hitherto been applied. In a more extended application of the machine, this intermission of the moving power and its action taking place only in one direction would be inadmissible. To drive the machinery generally employed in manufactures a constant and uniform force is required; and to render the steam engine available for this purpose, it would be necessary that the beam should be driven by the moving power as well in its ascent as in its descent. When Watt first conceived the notion of extending the application of the engine to manufactures generally, he proposed to accomplish this double action upon the beam by placing a steam cylinder under each end of it, so that while each piston would be ascending, and not impelled by the steam, the other would be descending, being urged downwards by the steam above it acting against the vacuum below. Thus, the power acting on each during the time when its action on the other would be suspended, a constant force would be exerted upon the beam, and the uniformity of the motion would be produced by making both cylinders communicate with the same boiler, so that both pistons would be driven by steam of the same pressure. One condenser might also be used for both cylinders, so that a similar vacuum would be produced under each. This arrangement, however, was soon laid aside for one much more simple and obvious. This consisted in the production of exactly the same effect by a single cylinder in which steam was introduced alternately above and below the piston, being at the same time withdrawn by the condenser at the opposite side. Thus the piston being at the top of the cylinder, steam is introduced from the boiler above it, while the steam in the cylinder below it is drawn off by the condenser. The piston, therefore, is pressed from above into the vacuum below, and descends to the bottom of the cylinder. Having arrived there, the top of the cylinder is cut off from all communication with the boiler; and, on the other hand, a communication is opened between it and the condenser. The steam which has pressed the piston down is therefore drawn off by the condenser, while a communication is opened between the boiler and the bottom of the cylinder, so that steam is admitted below the piston: the piston, thus pressed from below into the vacuum above, ascends, and in the same way the alternate motion is continued. Such is the principle of what is called the _Double-acting Steam Engine_, in contradistinction to that described in the last chapter, in which the steam acts only above the piston while a vacuum is produced below it. It is evident that, in the arrangement now described, the condenser must be in constant action: while the piston is descending the condenser must draw off the steam below it, and while it is ascending, it must draw off the steam above it. As steam, therefore, must be constantly drawn into the condenser, the jet of cold water which condenses the steam must be kept constantly playing. This jet, therefore, will not be worked by the valve alternately opening and closing, as in the single engine, but will be worked by a cock, the opening of which will be adjusted according to the quantity of cold water necessary to condense the steam. When the steam is used at a low pressure, and, therefore, in a less compressed state, less condensing water would be necessary than when it is used at a higher pressure and in a more compressed state. In the one case, therefore, the condensing cock would be less open than in the other. Again, the quantity of condensing water must vary with the speed of the engine, because the greater the speed of the engine, the more rapidly will the steam flow from the cylinder into the condenser; and, as the same quantity of steam requires the same quantity of condensing water, the supply of the condensing water must be proportional to the speed of the engine. In the double-acting engine, then, the jet cock is regulated by a lever or index which moves upon a graduated arch, and which is regulated by the engineer according to the manner in which the engine works. This change in the action of the steam upon the piston rendered it necessary to make a corresponding change in the mechanism by which the piston-rod was connected with the beam. In the single acting engine, the piston-rod pulled the end of the beam down during the descent, and was pulled up by it in the ascent. The connection by which this action was transmitted between the beam and piston was, as we have seen, a flexible chain passing from the end of the piston and playing upon the arch-head of the beam. Now, where the mechanical action to be transmitted is a _pull_, and not a _push_, a flexible chain, or cord, or strap, is always sufficient; but if a _push_ or _thrust_ is required to be transmitted, then the flexibility of the medium of mechanical communication afforded by a chain, renders it inapplicable. In the double-acting engine, during the descent, the piston-rod still pulls the beam down, and so far a chain connecting the piston-rod with the beam would be sufficient to transmit the action of the one to the other; but in the ascent the beam no longer pulls up the piston-rod, but is pushed up by it. A chain from the piston-rod to the arch-head, as described in the single acting engine, would fail to transmit this force. If such a chain were used with the double engine, where there is no counter weight on the opposite end of the beam, the consequence would be, that in the ascent of the piston the chain would slacken, and the beam would still remain depressed. It is therefore necessary that some other mechanical connection be contrived between the piston-rod and the beam, of such a nature that in the _descent_ the piston-rod may _pull_ the beam down, and may _push_ it up in the _ascent_. Watt first proposed to effect this by attaching to the end of the piston-rod a straight rack, faced with teeth, which should work in corresponding teeth raised on the arch-head of the beam as represented in fig. 13. If his improved steam engines required no further precision of operation and construction than the atmospheric engines, this might have been sufficient; but in these engines it was indispensably necessary that the piston-rod should be guided with a smooth and even motion through the stuffing-box in the top of the cylinder, otherwise any shake or irregularity would cause it to work loose in the stuffing-box, and either to admit the air, or to let the steam escape. In fact, it was necessary to turn these piston-rods very accurately in the lathe, so that they may work with sufficient precision in the cylinder. Under these circumstances, the motion of the rack and toothed arch-head were inadmissible, since it was impossible by such means to impart to the piston-rod that smooth and equable motion which was requisite. Another contrivance which occurred to Watt was, to attach to the top of the piston-rod a bar which should extend above the beam, and to use two chains or straps, one extending from the top of the bar to the lower end of the arch-head, and the other from the bottom of the bar to the upper end of the arch-head. By such means the latter strap would pull the beam down when the piston would descend, and the former would pull the beam up when the piston would ascend. These contrivances, however, were superseded by the celebrated mechanism, since called the _Parallel Motion_, one of the most ingenious mechanical combinations connected with the history of the steam engine. It will be observed that the object was to connect by some inflexible means the end of the piston-rod with the extremity of the beam, and so to contrive the mechanism, that while the end of the beam would move alternately up and down in a circle, the end of the piston-rod connected with the beam should move exactly up and down in a straight line. If the end of the piston-rod were fastened upon the end of the beam by a pivot without any other connexion, it is evident that, being moved up and down in the arch of a circle, it would be bent to the left and the right alternately, and would consequently either be broken, or would work loose in the stuffing box. Instead of connecting the end of the rod immediately with the end of the beam by a pivot, Watt proposed to connect them by certain moveable rods so arranged that, as the end of the beam would move up and down in the circular arch, the rods would so accommodate themselves to that motion, that the end connected with the piston-rod should not be disturbed from its rectilinear course. To accomplish this, he conceived the notion of connecting three rods in the following manner:--A B and C D (fig. 14.), are two rods or levers turning on fixed pivots or centres at A and C. A third rod, B D, is connected with them by pivots placed at their extremities, B and D, and the lengths of the rods are so adjusted that when A B and C D are horizontal, B D shall be perpendicular or vertical, and that A B and C D shall be of equal lengths. Now, let a pencil be imagined to be placed at P, exactly in the middle of the rod B D: if the rod A B be caused to move up and down like the beam of the steam engine in the arch represented in the figure, it is clear, from the mode of their connexion, that the rod C D will be moved up and down in the other arch. Now Watt conceived that, under such circumstances, the pencil P would be moved up and down in a perpendicular straight line. However difficult the first conception of this mechanism may have been, it is easy to perceive why the desired effect will be produced by it. When the rod A B rises to the upper extremity of the arch, the point B departs a little to the right; at the same time, the point D is moved a little to the left. Now the extremities of the rod B D being thus at the same time, carried slightly in opposite directions, the pencil in the middle of it will ascend directly upwards; the one extremity of the rod having a tendency to draw it as much to the right as the other has to draw it to the left. In the same manner, when the rod A B moves to the lower extremity of the arch, the rod C D will be likewise moved to the lower extremity of its arch. The point B is thus transferred a little to the right, and the point D to the left; and, for the same reason as before, the point P in the middle will move neither to the right nor to the left, but straight downwards.[17] [Footnote 17: In a strict mathematical sense, the path of the point P is a curve of a high order, but in the play which is given to it in the application used in the steam engine, it describes only a part of its entire locus; and this part extending equally on each side of a point of inflection, its radius of curvature is infinite, so that, in practice, the deviation from a straight line, when proper proportions are observed in the rods, and too great a play not given to them, is insignificant.] Now Watt conceived that his object would be attained if he could contrive to make the beam perform the part of A B in fig. 14., and to connect with it other two rods, C D and D B, attaching the end of the piston to the middle of the rod D B. The practical application of this principle required some modification, but is as elegant as the notion itself is ingenious. The apparatus adopted for carrying it into effect is represented on the arm which works the piston in fig. 15. The beam, moving on its axis C, every point in its arm moves in the arc of a circle of which C is the centre. Let B be the point which divides the arm A C into equal parts, A B and B C; and let D E be a straight rod equal in length to C B, and playing on the fixed centre or pivot D. The end E of this rod is connected by a straight bar, E B, with the point B, by pivots at B and E on which the rod B E plays freely. If the beam be supposed to move alternately on its axis C, the point B will move up and down in a circular arc, of which C is the centre, and at the same time the point E will move in an equal circular arc round the point D as a centre. According to what we have just explained, the middle point F of the rod B E will move up and down in a straight line. Also, let a rod, A G, equal in length to B E, be attached to the end A of the beam by a pivot on which it moves freely, and let its extremity G be connected with E by a rod, G E, equal in length to A B, and playing on pivots at G and E. By this arrangement the joint A G being always parallel to B E, the three points C, A, and G will be in circumstances precisely similar to the points C, B, and F, except that the system C A G will be on a scale of double the magnitude of C B F: C A being twice C B, and A G twice B F, it is clear, then, that whatever course the point F may follow, the point G must follow a similar line,[18] but will move twice as fast. But, since the point F has been already shown to move up and down in a straight line, the point G must also move up and down in a straight line, but of double the length.[19] [Footnote 18: It is, in fact, the principle of the pantograph. The points C, F, and G evidently lie in the same straight line, since C B : C A :: B F : A G, and the latter lines are parallel. Taking C as the common _pole_ of the _loci_ of the points F G, the _radius vector_ of the one will always be twice the corresponding _radius vector_ of the other; and therefore these curves are similar, similarly placed, and parallel. Hence, by the last note, the point G must move in a line differing imperceptibly from a right line.] [Footnote 19: It is not necessary that the rods, forming the parallel motion, should have the proportions which we have assigned to them. There are various proportions which answer the purpose, and which will be seen by reference to practical works on the steam engine.] By this arrangement the pistons of both the steam cylinder and air-pump are worked; the rod of the latter being attached to the point F, and that of the former to the point G. This beautiful contrivance, which is incontestably one of the happiest mechanical inventions of Watt, affords an example with what facility the mind of a mere mechanician can perceive, as it were instinctively, a result to obtain which by strict reasoning would require a very complicated mathematical analysis. Watt, when asked, by persons whose admiration was justly excited by this invention, to what process of reasoning he could trace back his discovery, replied that he was aware of none; that the conception flashed upon his mind without previous investigation, and so as to excite in himself surprise at the perfection of its action; and that on looking at it for the first time, he experienced all that pleasurable sense of novelty which arises from the first contemplation of the results of the invention of others. This and the other inventions of Watt seem to have been the pure creations of his natural genius, very little assisted by the results of practice, and not at all by the light of education. It does not even appear that he was a dexterous mechanic; for he never assisted in the construction of the first models of his own inventions. His dwelling-house was two miles from the factory, to which he never went more than once in a week, and then did not stay half an hour. (_a_) However beautiful and ingenious in principle the parallel motion may be, it has recently been shown in the United States that much simpler means are sufficient to subserve the same purpose. In the engines constructed recently, under the direction of Mr. R. L. Stevens, a substitute for the parallel motion has been introduced that performs the task equally well, and is much less complex. On the head of the piston-rod a bar is fixed, at right angles to it, and to the longitudinal section of the engine. The ends of this bar work in guides formed of two parallel and vertical bars of iron, by which the upper end of the piston-rod is constrained to move in a straight line. The cross-bar that moves in the guides is connected with the end of the working beam by an inflexible bar, having a motion on two circular gudgeons, one of which is in the working beam, the other in the cross-bar. This is therefore free to accommodate itself to the changes in the respective position of the piston-rod and working beam, and yet transmits the power exerted by the steam upon the former whether it be ascending or descending, to the latter and through it to the other parts of the machine.--A. E. (_b_) The most improved form of Watt's engine was reached by successive additions to the old atmospheric engine of Newcomen and Cawley. Hence, the working-beam, derived from the pump brake of that engine, always formed a part; and the parallel motion, or some equivalent contrivance was absolutely necessary. In many American engines, and particularly in those used in steam boats, the working beam is no longer used for the purpose of transmitting motion to the machinery. This is effected by applying a bar, called the cross-head, at right angles to the upper ends of the piston-rod. The ends of the cross-head work in iron guides, adapted to a gallows-frame of wood. On each side of the cylinder, connecting rods are applied, which take hold of the cranks of the shafts of the water-wheel. Two other connecting rods give motion to a short beam, which works the air and supply pumps. The working beam is also suppressed in engines which work horizontally. The connecting rod is in them merely a jointed prolongation of the piston-rod, extending to the crank, whose axis lies in the same horizontal plane with and at right angles to the axis of the cylinder.--A. E. (55.) A perfect motion being thus obtained of conveying the alternate motion of the piston to the working beam, the use of a counterpoise to lift the piston was discontinued, and the beam was made to balance itself exactly on its centre. The next end to be obtained was to adapt the reciprocating motion of the working end of the beam to machinery. The motion most generally useful for this purpose is one of _continued rotation_. The object, therefore, was by the _alternate_ motion of the end of the beam to transmit to a shaft or axis a _continued circular_ motion. In the first instance, Watt proposed effecting this by a _crank_, connected with the working end of the beam by a metal connector or rod. Let K be the centre or axis, or shaft by which motion is given to the machinery, and to which rotation is to be imparted by the beam C H. On the axle K, suppose a lever, K I, fixed, so that when K I is turned round the centre K, the wheel must be turned with it. Let a connector or rod, H I, be attached to the points H and I, playing freely on pivots or joints. As the end H is moved upwards and downwards, the lever K I is turned round the centre K, so as to give a continued rotatory motion to the shaft which revolves on that centre. The different positions which the connector and lever K I assume in the different parts of a revolution are represented in fig. 16. (56.) This was the first method which occurred to Watt for producing a continued rotatory motion by means of the vibrating motion of the beam, and is the method now universally used. A workman, however, from Mr. Watt's factory, who was aware of the construction of a model of this, communicated the method to Mr. Washborough of Bristol, who anticipated Watt in taking out a patent; and although it was in his power to have disputed the patent, yet rather than be involved in litigation, he gave up the point, and contrived another way of producing the same effect, which he called the _sun and planet_ wheel, and which he used until the expiration of Washborough's patent, when the crank was resumed. The toothed wheel B (fig. 17.) is fixed on the end of the connector, so that it does not turn on its axis. The teeth of this wheel work in those of another wheel, A, which is the wheel to which rotation is to be imparted, and which is turned by the wheel B revolving round it, urged by the rod H I, which receives its motion from the working-beam. The wheel A is called the sun-wheel, and B the planet-wheel, from the obvious resemblance to the motion of these bodies. This contrivance, although in the main inferior to the more simple one of the crank, is not without some advantages; among others, it gives to the sun-wheel double the velocity which would be communicated by the simple crank, for in the simple crank one revolution only on the axle is produced by one revolution of the crank, but in the sun and planet-wheel two revolutions of the sun-wheel are produced by one of the planet-wheel; thus a double velocity is obtained from the same motion of the beam. This will be evident from considering that when the planet-wheel is in its highest position, its lowest tooth is engaged with the highest tooth of the sun-wheel; as the planet-wheel passes from the highest position, its teeth drive those of the sun-wheel before them, and when it comes into the lowest position, the highest tooth of the planet-wheel is engaged with the lowest of the sun-wheel: but then half of the sun-wheel has _rolled off_ the planet-wheel, and, therefore, the tooth which was engaged with it in its higher position, must now be distant from it by half the circumference of the wheel, and must therefore be again in the highest position, so that while the planet-wheel has been carried from the top to the bottom, the sun-wheel has made a complete revolution. A little reflection, however, on the nature of the motion, will render this plainer than any description can. This advantage of giving an increased velocity, may be obtained also by the simple crank, by placing toothed wheels on its axle. Independently of the greater expense attending the construction of the sun and planet-wheel, its liability to go out of order, and the rapid wear of the teeth, and other objections, rendered it decidedly inferior to the crank, which has now entirely superseded it. (58.) Whether the simple crank or the sun and planet wheel be used, there still remains a difficulty of a peculiar nature attending the continuance of the rotatory motion. There are two positions in which the engine can give no motion whatever to the crank. These are when the end of the beam, the axle of the crank, and the pivot which joins the connector with the crank, are in the same straight line. This will be easily understood. Suppose the beam, connector, and crank to assume the position represented in fig. 15. If steam urge the piston downwards, the point H and the connector H I will be drawn directly upwards. But it must be very evident that in the present situation of the connector H I, and the lever I K, the force which draws the point I in the direction I K can have no effect whatever in turning I K round the centre K, but will merely exert a pressure on the axle or pivots of the wheel. Again, suppose the crank and connector to be in the position H I K (fig. 16.), the piston being consequently at the bottom of the cylinder. If steam now press the piston _upwards_, the pivot H and the connector H I will be pressed _downwards_, and this pressure will urge the crank I K in the direction I K. It is evident that such a force cannot turn the crank round the centre K, and can be attended with no other effect than a pressure on the axle or pivots of the wheel. Hence in these two positions, the engine can have no effect whatever in turning the crank. What, then, it may be asked, extricates the machine from this mechanical dilemma in which it is placed twice in every revolution, on arriving at those positions in which the crank escapes the influence of the power? There is a tendency in bodies, when once put in motion, to continue that motion until stopped by some opposing force, and this tendency carries the crank out of those two critical situations. The velocity which is given to it, while it is under the influence of the impelling force of the beam, is retained in a sufficient degree to carry it through that situation in which it is deserted by this impelling force. Although the rotatory motion intended to be produced by the crank is, therefore, not absolutely destroyed by this circumstance, yet it is rendered extremely irregular, since, in passing through the two positions already described, where the machine loses its power over the crank, the motion will be very slow, and, in the positions of the crank most remote from these, where the power of the beam upon it is greatest, the motion will be very quick. As the crank revolves from each of those positions where the power of the machine over it is greatest, to where that power is altogether lost, it is continually diminished, so that, in fact, the crank is driven by a varying power, and therefore produces a varying motion. This will be easily understood by considering the successive positions of the crank and connector represented in fig. 16. This variable motion becomes particularly objectionable when the engine is employed to drive machinery. To remove this defect, we have recourse to the property of bodies just mentioned, viz. their tendency to retain a motion which is communicated to them. A large metal wheel called a _fly-wheel_ is placed upon the axis of the crank (fig. 15.), and is turned by it. The effect of this wheel is to equalize the motion communicated by the action of the beam on the crank, that action being just sufficient to sustain in the fly-wheel a uniform velocity, and the tendency of this wheel to retain the velocity it receives, renders its rotation sufficiently uniform for all practical purposes. This uniformity of motion, however, will only be preserved on two conditions; _first_, that the supply of steam from the boiler shall be uniform; and secondly, that the machine have always the same resistance to overcome or be _loaded_ equally. If the supply of steam from the boiler to the cylinder be increased, the motion of the piston will be rendered more rapid, and, therefore, the revolution of the fly-wheel will also be more rapid, and, on the other hand, a diminished supply of steam will retard the fly-wheel. Again, if the resistance or load upon the engine be diminished, the supply of steam remaining the same, the velocity will be increased, since a less resistance is opposed to the energy of the moving power; and, on the other hand, if the resistance or load be increased, the speed will be diminished, since a greater resistance will be opposed to the same moving power. To insure a uniform velocity, in whatever manner the load or resistance may be changed, it is necessary to proportion the supply of steam to the resistance, so that, upon the least variation in the velocity, the supply of steam will be increased or diminished, so as to keep the engine going at the same rate. (59.) One of the most striking and elegant appendages of the steam engine is the apparatus contrived by Watt for effecting this purpose. An apparatus, called a _regulator_ or _governor_, had been long known to mill-wrights for rendering uniform the action of the stones in corn-mills, and was used generally in machinery. Mr. Watt contrived a beautiful application of this apparatus for the regulation of the steam engine. In the pipe which conducts steam from the boiler to the cylinder he placed a thin circular plate, so that when placed with its face presented towards the length of the pipe, it nearly stopped it, and allowed little or no steam to pass to the cylinder, but when its edge was placed in the direction of the pipe, it offered no resistance whatever to the passage of the steam. This circular plate, called the throttle valve, was made to turn on a diameter as an axis, passing consequently through the centre of the tube, and was worked by a lever outside the tube. According to the position given to it, it would permit more or less steam to pass. If the valve be placed with its edge nearly in the direction of the tube, the supply of steam is abundant; if it be placed with its face nearly in the direction of the tube, the supply of steam is more limited, and it appears that, by the position given to this valve, the steam may be measured in any quantity to the cylinder. At first it was proposed that the engine-man should adjust this valve with his hand; when the engine was observed to increase its speed too much, he would check the supply of steam by partially closing the valve; but if, on the other hand, the motion was too slow, he would open the valve and let in a more abundant supply of steam. Watt, however, was not content with this, and desired to make the engine itself discharge this task with more steadiness and regularity than any attendant could, and for this purpose he applied the governor already alluded to. This apparatus is represented in fig. 15.; L is a perpendicular shaft or axle to which a wheel, M, with a groove is attached. A strap or rope, which is rolled upon the axle of the fly-wheel, is passed round the groove in the wheel M, in the same manner as the strap acts in a turning lathe. By means of this strap the rotation of the fly-wheel will produce a rotation of the wheel M and the shaft L, and the speed of the one will always increase or diminish in the same proportion as the speed of the other. N, N are two heavy balls of metal placed at the ends of rods, which play on an axis fixed on the revolving shaft at O, and extend beyond the axis to Q Q. Connected with these by joints at Q Q are two other rods, Q R, which are attached to a broad ring of metal, moving freely up and down the revolving shaft. This ring is attached to a lever whose centre is S, and is connected by a series of levers with the throttle-valve T. When the speed of the fly-wheel is much increased, the spindle L is whirled round with considerable rapidity, and by their natural tendency[20] the balls N N fly from the centre. The levers which play on the axis O, by this motion, diverge from each other, and thereby depress the joints Q Q, and draw down the joints R, and with them the ring of metal which slides upon the spindle. By these means the end of the lever playing on S is depressed, and the end V raised, and the motion is transmitted to the throttle-valve, which is thereby partially closed, and the supply of steam to the cylinder checked. If, on the contrary, the velocity of the fly-wheel be diminished, the balls will fall towards the axis, and the opposite effects ensuing, the supply of steam will be increased, and the velocity restored. [Footnote 20: The _centrifugal force_.] [Illustration: Pl. IV. WATT'S SINGLE ACTING STEAM ENGINE.] The peculiar beauty of this apparatus is, that in whatever position the balls settle themselves, the velocity with which the governor revolves must be the same,[21] and in this, in fact, consists its whole efficacy as a regulator. Its regulating power is limited, and it is only small changes of velocity that it will correct. It is evident that such a velocity as, on the one hand, would cause the balls to fly to the extremity of their play, or, on the other, would cause them to fall down on their rests, would not be influenced by the governor. [Footnote 21: Strictly speaking, this is only true when the divergence of the rods from the spindle is not very great, and, in practice, this divergence is never sufficient to render the above assertion untrue. This property of the conical pendulum arises from the circumstance of the centrifugal force, in this instance, varying as the radius of the circle in which the balls are moved; and when this is the case, as is well known, the _periodic time_ is constant. The time of one revolution of the balls is equal to twice the time in which either ball, as a common pendulum, would vibrate on the centre, and as all its vibrations, though the arcs be unequal, are equal in time, provided those arcs be small, so also is the periodic time of the revolving ball invariable. These observations, however, only apply when the balls settle themselves steadily into a circular motion; for while they are ascending they describe a spiral curve with double curvature, and the period will vary. This takes place during the momentary changes in the velocity of the engine.] We have thus described the principal parts of the double-acting steam engine. The valves and the methods of working them have been reserved for the next chapter, as they admit of considerable variety, and will be better treated of separately. We have also reserved the consideration of the boiler, which is far from being the least interesting part of the modern steam engine, for a future chapter. CHAPTER VII. DOUBLE-ACTING STEAM ENGINE (_continued_.) On the Valves of the Double-Acting Steam Engine. -- Original Valves. -- Spindle Valves. -- Sliding Valve. -- D Valve. -- Four-Way Cock. (60.) The various improvements described in the last chapter were secured to Watt by patent in the year 1782. The engine now acquired an enlarged sphere of action; for its dominion over manufactures was decided by the _fly-wheel_, _crank_, and _governor_. By means of these appendages, its motions were regulated with the most delicate precision; so that while it retained a power whose magnitude was almost unlimited, that power was under as exact regulation as the motion of a time-piece. There is no species of manufacture, therefore, to which this machine is not applicable, from the power which spins the finest thread, or produces the most delicate web, to that which is necessary to elevate the most enormous weights, or overcome the most unlimited resistances. Although it be true, that in later times the steam engine has received many improvements, some of which are very creditable to the invention and talents of their projectors, yet it is undeniable that all its great and leading perfections, all those qualities by which it has produced such wonderful effects on the resources of these countries, by the extension of manufactures and commerce,--those qualities by which its influence is felt and acknowledged in every part of the civilized globe, in increasing the happiness, in multiplying the enjoyments, and cheapening the pleasures of life,--that these qualities are due to the predominating powers of one man, and that man one who possessed neither the influence of wealth, rank, nor education, to give that first impetus which is so often necessary to carry into circulation the earlier productions of genius. The method of working the valves of the double-acting steam engine, is a subject which has much exercised the ingenuity of engineers, and many elegant contrivances have been suggested, some of which we shall now proceed to describe. But even in this the invention of Watt has anticipated his successors; and the contrivances suggested by him are those which are now almost universally used. In order perfectly to comprehend the action of the several systems of valves which we are about to describe, it will be necessary distinctly to remember the manner in which the steam is to be communicated to the cylinder, and withdrawn from it. When the piston is at the top of the cylinder, the steam below it is to be drawn off to the condenser, and the steam from the boiler is to be admitted above it. Again, when it has arrived at the bottom of the cylinder, the steam above is to be drawn off to the condenser, and the steam from the boiler is to be admitted below it. In the earlier engines constructed by Watt, this was accomplished by four valves, which were opened and closed in pairs. Valve boxes were placed at the top and bottom of the cylinder, each of which communicated by tubes both with the steam-pipe from the boiler and the condenser. Each valve-box accordingly contained two valves, one to admit steam from the steam-pipe to the cylinder, and the other to allow that steam to pass into the condenser. Thus each valve-box contained a steam valve and an exhausting valve. The valves at the top of the cylinder are called the _upper steam valve_ and the _upper exhausting-valve_, and those at the bottom, the _lower steam valve_ and the _lower exhausting-valve_. In fig. 15. A´ is the upper steam valve, which, when open, admits steam above the piston; B´ is the upper exhausting-valve, which, when open, draws off the steam from the piston to the condenser. C´ is the lower steam valve, which admits steam below the piston; and D´, the lower exhausting-valve, which draws off the steam from below the piston to the condenser. Now, suppose the piston to be at the top of the cylinder, the cylinder below it being filled with steam, which has just pressed it up. Let the _upper steam valve_ A´, and the _lower exhausting-valve_ D´ be opened, and the other two valves closed. The steam which fills the cylinder below the piston will immediately pass through the valve D´ into the condenser, and a vacuum will be produced below the piston. At the same time, steam is admitted from the steam-pipe through the valve A´ above the piston, and its pressure will force the piston to the bottom of the cylinder. On the arrival of the piston at the bottom of the cylinder, the upper steam valve A´, and lower exhausting-valve D´, are closed; and the lower steam valve C´, and upper exhausting-valve B´ are opened. The steam which fills the cylinder above the piston now passes off through B´ into the condenser, and leaves a vacuum above the piston. At the same time, steam from the boiler is admitted through the lower steam valve C´, below the piston, so that it will press the piston to the top of the cylinder; and so the process is continued. It appears, therefore, that the upper steam valve, and the lower exhausting-valve, must be opened together, on the arrival of the piston at the top of the cylinder. To effect this, one lever, E´, is made to communicate by jointed rods with both these valves, and this lever is moved by a pin placed on the piston-rod of the air-pump; and such a position may be given to this pin as to produce the desired effect exactly at the proper moment of time. In like manner, another lever, F´, communicates by jointed rods with the upper exhausting valve and lower steam valve, so as to open them and close them together; and this lever, in like manner, is worked by a pin on the piston-rod of the air-pump. (61.) This method of connecting the valves, and working them, has been superseded by another, for which Mr. MURRAY of Leeds obtained a patent, which was, however, set aside by Messrs. Bolton and Watt, who showed that they had previously practised it. This method is represented in figs. 18, 19. The stems of the valves are perpendicular, and move in steam-tight sockets in the top of the valve-boxes. The stem of the upper steam valve A is a tube through which the stem of the upper exhausting-valve B passes, and in which it moves steam-tight; both these stems moving steam-tight through the top of the valve-box. The lower steam valve C, and exhausting-valve D, are similarly circumstanced; the stem of the former being a tube through which the stem of the latter passes. The stems of the upper steam valve and lower exhausting-valve are then connected by a rod, E; and those of the upper exhausting-valve and lower steam valve by another rod, F. These rods, therefore, are capable of moving the valves in pairs, when elevated and depressed. The motion which works the valves is, however, not communicated by the rod of the air-pump, but is received from the axis of the fly-wheel. This axis works an apparatus called an _eccentric_; the principle which regulates the motion of this may be thus explained:-- D E (figs. 20, 21.) is a circular metallic ring, the inner surface of which is perfectly smooth. This ring is connected with a shaft, F B, which communicates motion to the valves by levers which are attached to it at B. A circular metallic plate is fitted in the ring so as to be capable of turning within it, the surfaces of the ring and plate which are in contact being smooth and lubricated with oil or grease. This circular plate revolves, but not on its centre. It turns on an axis C, at some distance from its centre A; the effect of which, evidently, is that the ring within which it is turned is moved alternately in opposite directions, and through a space equal to twice the distance (C A) of the axis of the circular plate from the common centre of it and the ring. The eccentric in its two extreme positions is represented in figs. 20, 21. The plate and ring D E are placed on the axis of the fly-wheel, or on the axis of some other wheel which is worked by the fly-wheel. So that the motion of continued rotation in the fly-wheel is thus made to produce an alternate motion in a straight line in the shaft F B. This rod is made to communicate by levers with the rods E and F (figs. 18, 19.), which work the valves in such a manner, that, when the eccentric is in the position fig. 20., one pair of valves are opened, and the other pair closed; and when it is brought to the position fig. 21., the other pair are opened and the former closed and so on. It is by means of such an apparatus as this that the valves are worked almost universally at present. The piston being supposed to be at the top of the cylinder (fig. 18.), and the rod E raised, the valves A and D are opened, and B and C closed. The steam enters from the steam-pipe at an aperture immediately above the valve A, and, passing through the open valve, enters the cylinder above the piston. At the same time, the steam which is below the piston, and which has just pressed it up, flows through the open valve D, and through a tube immediately under it to the condenser. A vacuum being thus produced below the piston, and steam pressure acting above it, it descends; and when it arrives at the bottom of the cylinder (fig. 19.) the rod F is drawn down, and the valves A and D fall into their seats, and at the same time the rod F is raised, and the valves B and C are opened. Steam is now admitted through an aperture above the valve C, and passes below the piston, while the steam above it passes through the open valve B into a tube immediately under it, which leads to the condenser. A vacuum being thus produced above the piston, and steam pressure acting below it, the piston ascends, and thus the alternate ascent and descent is continued by the motion communicated to the rods E F from the fly-wheel. [Illustration: Pl. V. WATT'S DOUBLE-ACTING STEAM ENGINE.] [Illustration: Pl. VI.] (_c_) An improvement has been made in the United States in the mode of working the puppet valve. It consists in placing them by pairs in two different vertical planes instead of one. The rods then work through four separate stuffing boxes, and the necessity of making two of them hollow cylinders is avoided.--A. E. (62.) There are various other contrivances for regulating the circulation of steam through the cylinder. In figs. 22, 23. is represented a section of a slide valve suggested by Mr. Murray of Leeds. The steam-pipe from the boiler enters the valve-box D E at S. Curved passages, A A, B B, communicate between this valve-box and the top and bottom of the cylinder; and a fourth passage leads to the tube C, which passes to the condenser. A sliding piece within the valve-box opens a communication alternately between each end of the cylinder and the tube C, which leads to the condenser. In the position of the apparatus in fig. 22. steam is passing from the steam-pipes, through the curved passage A A above the piston, and at the same time the steam below the piston is passing through the passage B B into the tube C, and thence to the condenser. A vacuum is thus formed below the piston, and steam is introduced above it. The piston, therefore, descends; and when it arrives at the bottom of the cylinder, the slide is moved into the position represented in fig. 23. Steam now passes from S through B B below the piston, and the steam above it passes through A A and C to the condenser. A vacuum is thus produced above the piston, and steam pressure is introduced below it, and the piston ascends; and in this way the motion is continued. The slide is moved by a lever, which is worked by the eccentric from the fly-wheel. (63.) Watt suggested a method of regulating the circulation of steam, which is called the D valve, from the resemblance which the horizontal section of the valve has to the letter D. This method, which is very generally used, is represented in section in figs. 24, 25. Steam from the boiler enters through S. A rod of metal connects two solid plugs, A B, which move steam-tight in the passage D. In the position of the apparatus represented in fig. 24. the steam passes from S through the passage D, and enters the cylinder above the piston; while the steam below the piston passes through the open passage by the tube C to the condenser. A vacuum is thus formed below the piston, while the pressure of steam is introduced above it, and it accordingly descends. When it has arrived at the bottom of the cylinder, the plugs A B are moved into the position in fig. 25. Steam now passing from S through D, enters the cylinder below the piston; while the steam which is above the piston, and has just pressed it down, passes through the open passage into the condenser. A vacuum is thus produced above the piston, and the steam pressure below forces it up. When it has arrived at the top of the cylinder, the position of the plugs A B is again changed to that represented in fig. 24., and a similar effect to that already described is produced, and the piston is pressed down; and so the process is continued. The plugs A B, and the rod which connects them, are moved up and down by proper levers, which receive their motion from the eccentric. This contrivance is frequently modified, by conducting the steam from above the piston to the condenser, through a tube in the plugs A B, and their connecting rod. In figs. 26, 27. a tube passes through the plugs A B and the rod which joins them. In the position fig. 26. steam entering at S passes through the tube to the cylinder above the piston, while the steam below the piston passes through C into the condenser. A vacuum being thus made below the piston, and steam pressing above it, it descends; and when it has arrived at the bottom of the cylinder, the position of the plugs A B and the tube is changed to that represented at fig. 27. The steam now entering at S passes to the cylinder below the piston, while the steam above the piston passes through C into the condenser. A vacuum is thus produced above the piston, and steam pressure introduced below it, so that it ascends. When it has arrived at the top of the cylinder, the plugs are moved into the position represented in fig. 26., and similar effects being produced, the piston again descends; and so the motion is continued. The motion of the sliding tube may be produced as in the former contrivances, by the action of the eccentric. It is also sometimes done by a bracket fastened on the piston-rod of the air-pump. This bracket, in the descent of the piston, strikes a projection on the valve-rod, and drives it down; and in the ascent meets a similar projection, and raises it. (64.) Another method, worthy of notice for its elegance and simplicity, is the _four-way cock_. A section of this contrivance is given in figs. 28, 29.: C T S B are four passages or tubes; S leads from the boiler, and introduces steam; C, opposite to it, leads to the condenser; T is a tube which communicates with the top of the cylinder; and B one which communicates with the bottom of the cylinder. These four tubes communicate with a cock, which is furnished with two curved passages, as represented in the figures; and these passages are so formed, that, according to the position given to the cock, they may be made to open a communication between any two adjacent tubes of the four just mentioned. When the cock is placed as in fig. 28. communication is opened between the steam-pipe and the top of the cylinder by one of the curved passages, and between the condenser and the bottom of the cylinder by the other curved passage. In this case the steam passes from below the piston to the condenser, leaving a vacuum under it, and steam is introduced from the boiler above the piston. The piston therefore descends; and when it has arrived at the bottom of the cylinder, the position of the cock is changed to that represented in fig. 29. This change is made by turning the cock through one fourth of an entire revolution, which may be done by a lever moved by the eccentric, or by various other means. One of the curved passages in the cock now opens a communication between the steam-pipe and the bottom of the cylinder; while the other opens a communication between the condenser and the top of the cylinder. By these means, the steam from the boiler is introduced below the piston, while the steam above the piston is drawn off to the condenser. A vacuum being thus made above the piston, and steam introduced below it, it ascends; and when it has arrived at the top of the cylinder, the cock being moved back, it resumes the position in fig. 28., and the same consequences ensue, the piston descends; and so the process is continued. In figs. 30, 31. the four-way cock with the passages to the top and bottom of the cylinder is represented on a larger scale. This beautiful contrivance is not of late invention. It was used by Papin, and is also described by Leupold in his _Theatrum Machinarum_, a work published about the year 1720, in which an engine is described acting with steam of high pressure, on a principle which we shall describe in a subsequent chapter. The four-way cock is liable to some practical objections. The quantity of steam which fills the tubes between the cock and the cylinder, is wasted every stroke. This objection, however, also applies to the sliding valve (figs. 22, 23.), and to the sliding tube or D valves (figs. 24, 25, 26, 27.). In fact, it is applicable to every contrivance in which means of shutting off the steam are not placed at both top and bottom of the cylinder. Besides this, however, the various passages and tubes cannot be conveniently made large enough to supply steam in sufficient abundance; and consequently it becomes necessary to produce steam in the boiler of a more than ordinary strength to bear the attenuation which it suffers in its passage through so many narrow tubes. [Illustration: Pl. VII.] One of the greatest objections, however, to the use of the four-way cock, particularly in large engines, is its unequal wear. The parts of it near the passages having smaller surfaces, become more affected by the friction, and in a short time the steam leaks between the cock and its case, and becomes wasted, and tends to vitiate the vacuum. These cocks are seldom used in condensing engines, except they be small engines, but are frequently adopted in high-pressure steam-engines; for in these the leakage is not of so much consequence, as will appear hereafter. CHAPTER VIII. BOILER AND ITS APPENDAGES.--FURNACE. The Boiler and its Appendages. -- Level Gauges. -- Feeding Apparatus. -- Steam Gauge. -- Barometer Gauge. -- Safety Valves. -- Self-regulating Damper. -- Edelcrantz's Valve. -- Furnace. -- Self-consuming Furnace. -- Brunton's Self-regulating Furnace. -- Oldham's Modification. (65.) The regular action of a steam engine, as well as the economy of fuel, depends in a great degree on the construction of the boiler or apparatus for generating the steam. The boiler may be conceived as a great magazine of steam for the use of the engine; and care must be taken not only that a sufficient quantity be always ready for the supply of the machine, but also that it shall be of the proper quality; that is, that its pressure shall not exceed that which is required, nor fall short of it. Precautions should, therefore, be taken that the production of steam should be exactly proportioned to the work to be done, and that the steam so produced shall be admitted to the cylinder in the same proportion. To accomplish this, various contrivances, eminently remarkable for their ingenuity, have been resorted to, and which we shall now proceed to describe. (_d_) It may be premised that boilers have been made of various figures, each having its own peculiar advantages and defects. That which possesses the greatest degree of strength, is one of the shape of a cylinder. This form was originally introduced by Oliver Evans, in the United States. It will have its entire superiority when the fire is made beneath it in a furnace of masonry. But this method is not applicable to steam boats or locomotive engines. In these instances the weight of the separate furnace is an objection; when, therefore, this form is applied in them, the fire is usually made in a chamber of cylindric shape, within the boiler, and the smoke is conveyed to the chimney by flues, which pass through the water. These flues have, in some cases, been reduced to the size of small tubes, and of this method an example will be found in a subsequent part of this work.--A. E. (66.) Different methods have been, from time to time, suggested for indicating the level of the water in the boiler. We have already mentioned the two gauge-pipes used in the earlier steam engines (31.); and which are still generally continued. There are, however, some other methods which merit our attention. A weight, F (fig. 32.), half immersed in the water in the boiler, is supported by a wire, which, passing steam-tight through a small hole in the top, is connected by a flexible string or chain passing over a wheel, W, with a counterpoise, A, which is just sufficient to balance F, when half immersed. If F be raised above the water, A being lighter, will no longer balance it, and F will descend, pulling up A, and turning the wheel W. If, on the other hand, F be plunged deeper in the water, A, will more than balance it, and will pull it up. So that the only position in which F and A will balance each other is when F is half immersed. The wheel W is so adjusted, that when two pins, placed on its rim, are in the horizontal position, as in fig. 32., the water is at its proper level. Consequently it follows, that if the water rise above this level, the weight F is lifted, and A falls, so that the pins P P´ come into the position in fig. 33. If, on the other hand, the level of the water falls, F falls and A rises, so that the pins P P´ assume the position in fig. 34. Thus, in general, the position of the pins P P´ becomes an indication of the quantity of water in the boiler. Another method is to place a glass tube (fig. 35.) with one end, T, entering the boiler above the proper level, and the other end, T´, entering it below the proper level. It must be evident that the water in the tube will always stand at the same level as the water in the boiler; since the lower part has a free communication with that water, while the surface is submitted to the pressure of the same steam as the water in the boiler. This, and the last-mentioned gauge, have the advantage of addressing the eye of the engineer at once, without any adjustment; whereas the gauge cocks must be both opened, whenever the depth is to be ascertained. These gauges, however, require the frequent attention of the engine-man; and it becomes desirable either to find some more effectual means of awakening that attention, or to render the supply of the boiler independent of any attention. In order to enforce the attention of the engine-man to replenish the boiler when partially exhausted by evaporation, a tube was sometimes inserted at the lowest level to which it was intended that the water should be permitted to fall. This tube was conducted from the boiler into the engine-house, where it terminated in a mouth-piece or whistle, so that whenever the water fell below the level at which this tube was inserted in the boiler, the steam would rush through it, and, issuing with great velocity at the mouth-piece, would summon the engineer to his duty with a call that would rouse him even from sleep. (67.) In the most effectual of these methods, the task of replenishing the boiler should still be executed by the engineer; and the utmost that the boiler itself was made to do was to give due notice of the necessity for the supply of water. The consequence was, among other inconveniences, that the level of the water was subject to constant variation. To remedy this, a method has been invented by which the engine is made to feed its own boiler. The pipe G´ (fig. 15.), which leads from the hot water pump H´, terminates in a small cistern, C (fig. 36.), in which the water is received. In the bottom of this cistern a valve, V, is placed, which opens upwards, and communicates with a feed-pipe, which descends into the boiler below the level of the water in it. The stem of the valve V is connected with a lever turning on the centre D, and loaded with a weight, F, dipped in the water in the boiler in a manner similar to that described in fig. 32., and balanced by a counterpoise, A, in exactly the same way. When the level of the water in the boiler falls, the float F falls with it, and, pulling down the arm E of the lever, raises the valve V, and lets the water descend into the boiler from the cistern C. When the boiler has thus been replenished, and the level raised to its former place, F will again be raised, and the valve V closed by the weight A. In practice, however, the valve V adjusts itself by means of the effect of the water on the weight F, so as to permit the water from the feeding cistern C to flow in a continued stream, just sufficient in quantity to supply the consumption from evaporation, and to maintain the level of the water in the boiler constantly the same. By this singularly felicitous arrangement, the boiler is made to replenish itself, or, more properly speaking, it is made to receive such a supply as that it never wants replenishing, an effect which no effort of attention on the part of an engine-man could produce. But this is not the only good effect produced by this contrivance. A part of the steam which originally left the boiler, and having discharged its duty in moving the piston, was condensed and reconverted into water, and lodged by the air-pump in the hot-well (47.), is here again restored to the source from which it came, bringing back all the unconsumed portion of its heat preparatory to being once more put in circulation through the machine. The entire quantity of hot water pumped into the cistern C is not always required for the boiler. A waste-pipe may be provided for carrying off the surplus, which may be turned to any purpose for which it may be required; or it may be discharged into a cistern to cool, preparatory to being restored to the cold cistern (fig. 12.), in case water for the supply of that cistern be not sufficiently abundant. In cities and places in which it becomes an object to prevent the waste of water, the waste-pipes proceeding from the feed-cistern C (fig. 36.) and from the cold cistern containing the condenser and air-pump, may be conducted to a cistern A B (fig. 37.). Let C be the pipe from the feeding cistern, and D that from the cold cistern; by these pipes the waste water, from both these cisterns is deposited in A B. In the bottom of A B is a valve V, opening upwards, connected with a float F. When the quantity of water collected in the cistern A B is such that the level rises considerably, the float F is raised, and lifts the valve V, and the water flows into the main pipe, which supplies water for working the engine: G is the cold water-pump for the supply of the cold cistern. This arrangement for saving the water discharged from the feeding and condensing cisterns has been adopted in the printing office of the Bank of Ireland, and a very considerable waste of water is thereby prevented. (68.) It is necessary to have a ready method of ascertaining at all times the strength of the steam which is used in working the engine. For this purpose a bent tube containing mercury is inserted into some part of the apparatus which has free communication with the steam. It is usually inserted in the _jacket_ of the cylinder (44.). Let A B C (fig. 38.) be such a tube. The pressure of the steam forces the mercury down in the leg A B, and up in the leg B C. If the mercury in both legs be at exactly the same level, the pressure of the steam must be exactly equal to that of the atmosphere; because the steam pressure on the mercury in A B balances the atmospheric pressure on the mercury in B C. If, however, the level of the mercury in B C be above the level of the mercury in B A, the pressure of the steam will exceed that of the atmosphere. The excess of its pressure above that of the atmosphere may be found by observing the difference of the levels of the mercury in the tubes B C and B A; allowing a pressure of one pound on each square inch for every two inches in the difference of the levels. If, on the contrary, the level of the mercury in B C should fall below its level in A B, the atmospheric pressure will exceed that of the steam, and the degree or quantity of the excess may be ascertained exactly in the same way. If the tube be glass, the difference of levels of the mercury would be visible: but it is most commonly made of iron; and in order to ascertain the level, a thin wooden rod with a float is inserted in the open end of B C; so that the portion of the stick within the tube indicates the distance of the level of the mercury from its mouth. A bulb or cistern of mercury might be substituted for the leg A B, as in the common barometer. This instrument is called the STEAM-GAUGE. If the steam-gauge be used as a measure of the strength of the steam which presses on the piston, it ought to be on the same side of the throttle valve (which is regulated by the governor) as the cylinder; for if it were on the same side of the throttle valve with the boiler, it would not be affected by the changes which the steam may undergo in passing through the throttle valve, when partially closed by the agency of the governor. (69.) The force with which the piston is pressed depends on two things: 1º, the actual strength of the steam which presses on it; and 2º, on the actual strength of the vapour which resists it. For although the vacuum produced by the method of separate condensation be much more perfect than what had been produced in the atmospheric engines, yet still some vapour of a small degree of elasticity is found to be raised from the hot water in the bottom of the condenser before it can be extracted by the air-pump. One of these pressures is indicated by the steam-gauge already described; but still, before we can estimate the force with which the piston descends, it is necessary to ascertain the force of the vapour which remains uncondensed, and resists the motion of the piston. Another gauge, called the barometer-gauge, is provided for this purpose. A glass tube A B (fig. 39.), more than thirty inches long, and open at both ends, is placed in an upright or vertical position, having the lower end B immersed in a cistern of mercury C. To the upper end is attached a metal tube, which communicates with the condenser, in which a constant vacuum, or rather high degree of rarefaction, is sustained. The same vacuum must, therefore, exist in the tube A B, above the level of the mercury; and the atmospheric pressure on the surface of the mercury in the cistern C will force the mercury up in the tube A B, until the column which is suspended in it is equal to the difference between the atmospheric pressure and the pressure of the uncondensed steam. The difference between the column of mercury sustained in this instrument and in the common barometer will determine the strength of the uncondensed steam, allowing a force proportional to one pound per square inch for every two inches of mercury in the difference of the two columns. In a well-constructed engine, which is in good order, there is very little difference between the altitude in the barometer-gauge and the common barometer. To compute the force with which the piston descends, thus becomes a very simple arithmetical process. First ascertain the difference of the levels of the mercury in the steam-gauge. This gives the excess of the steam pressure above the atmospheric pressure. Then find the height of the mercury in the barometer-gauge. This gives the excess of the atmospheric pressure above the uncondensed steam. Hence, if these two heights be added together, we shall obtain the excess of the impelling force of the steam from the boiler on the one side of the piston, above the resistance of the uncondensed steam on the other side. This will give the effective impelling force. Now, if one pound be allowed for every two inches of mercury in the two columns just mentioned, we shall have the number of pounds of impelling pressure on every square inch of the piston. Then if the number of square inches in the section of the piston be found, and multiplied by the number of pounds on each square inch, the whole effective force with which it moves will be obtained. In the computation of the power of the engine, however, all this force, thus computed, is not to be allowed as the effective working power. For it requires some force, and by no means an inconsiderable portion, to move the engine itself, even when unloaded; all this, therefore, which is spent in overcoming friction, &c. is to be left out of account, and only the balance set down as the effective working power. From what we have stated, it appears that in order to estimate the effective force with which the piston is urged, it is necessary to refer to both the barometer and the steam-gauge. This double computation may be obviated by making one gauge serve both purposes. If the end C of the steam-gauge (fig. 38.) instead of communicating with the atmosphere, were continued to the condenser, we should have the pressure of the steam acting upon the mercury in the tube B A, and the pressure of the uncondensed vapour which resists the piston acting on the mercury in the tube B C. Hence the difference of the levels of the mercury in the tubes will at once indicate the difference between the force of the steam and that of the uncondensed vapour, which is the effective force with which the piston is urged. (70.) To secure the boiler from accidents arising from the steam becoming too strong, a safety valve is used, similar to those described in Papin's steam engine, loaded with a weight equal to the strength which the steam is intended to have above the atmospheric pressure; for it is found expedient, even in condensing engines, to use the steam of a pressure somewhat above that of the atmosphere. Besides this valve, another of the very opposite kind is sometimes used. Upon stopping the engine, and extinguishing the fire, it is found that the steam condensed within the boiler produces a vacuum; so that the atmosphere, pressing on the external surface of the boiler, has a tendency to crush it. To prevent this, a safety valve is provided, which opens inwards, and which being forced open by the atmospheric pressure when a vacuum is produced within, the air rushes in, and a balance is obtained between the pressures within and without. (71.) We have already explained the manner in which the governor regulates the supply of steam from the boiler to the cylinder, proportioning the quantity to the work to be done, and thereby sustaining a uniform motion. Since, then, the _consumption_ of steam in the engine is subject to variation, owing to the various quantities of work it may have to perform, it is evident that the PRODUCTION of steam in the boiler should be subject to a proportional variation. For, otherwise, one of two effects would ensue: the boiler would either fail to supply the engine with steam, or steam would accumulate in the boiler, from being produced in too great abundance, and would escape at the safety valve, and thus be wasted. In order to vary the production of steam in proportion to the demands of the engine, it is necessary to increase or mitigate the furnace, as production is to be augmented or diminished. To effect this by any attention on the part of the engine-man would be impossible; but a most ingenious method has been contrived, of making the boiler regulate itself in these respects. Let T (fig. 40.) be a tube inserted in the top of the boiler, and descending nearly to the bottom. The pressure of the steam on the surface of the water in the boiler forces water up in the tube T, until the difference of the levels is equal to the difference between the pressure of the steam in the boiler and that of the atmosphere. A weight F, half immersed in the water in the tube, is suspended by a chain which passes over the wheels P P´, and is balanced by a metal plate D, in the same manner as the float in fig. 32. is balanced by the weight A. The plate D passes through the mouth of the flue E, as it issues finally from the boiler; so that when the plate D falls, it stops the flue and thereby suspends the draught of air through the furnace, mitigates the fire, and diminishes the production of steam. If, on the contrary, the plate D be drawn up, the draught is increased, the fire rendered more effective, and the production of steam in the boiler stimulated. Now suppose that the boiler is producing steam faster than the engine consumes it, either because the load on the engine has been diminished, and therefore its consumption of steam proportionally diminished, or because the fire has become too intense. The consequence is, that the steam beginning to accumulate, will press upon the surface of the water in the boiler with increased force, and the water will rise in the tube T. The weight F will therefore be lifted, and the plate D will descend, stop the draught, mitigate the fire, and check the production of steam; and it will continue so to do, until the production of steam becomes exactly equal to the demands of the engine. If, on the other hand, the production of steam be not equal to the wants of the machine, either because of the increased load, or the insufficiency of the fire, the steam in the boiler losing its elasticity, the surface of the water rises, not sustaining a pressure sufficient to keep it at its wonted level. Therefore, the surface in the tube T falls, and the weight F falls, and the plate D rises. The draught is thus increased, by opening the flue, and the fire rendered more intense; and thus the production of steam is stimulated, until it is sufficiently rapid for the purposes of the engine. This apparatus is called the _self-acting damper_. (72.) It has been proposed to connect this damper with the safety-valve invented by the Chevalier Edelcrantz. A small brass cylinder is fixed to the boiler, and is fitted with a piston which moves in it, without much friction, and nearly steam-tight. The cylinder is closed at top, having a hole through which the piston-rod plays; so that the piston is thus prevented from being blown out of the cylinder by the steam. The side of the cylinder is pierced with small holes opening into the air, and placed at short distances above each other. Let the piston be loaded with a weight proportional to the pressure of the steam intended to be produced. When the steam has acquired a sufficient elasticity, the piston will be lifted, and steam will escape through the first hole. If the production of steam be not too rapid, and that its pressure be not increasing, the piston will remain suspended in this manner: but if it increase, the piston will be raised above the second hole, and it will continue to rise until the escape of the steam through the holes is sufficient to render the weight of the piston a counterpoise for the steam. This safety valve is particularly well adapted to cases where steam of an exactly uniform pressure is required; for the pressure must necessarily be always equal to the weight on the piston. Thus, suppose the section of the piston be equal to a square inch; if it be loaded with 10 lbs., including its own weight, the steam which will sustain it in any position in the cylinder, whether near the bottom or top, must always be exactly equal in pressure to 10 lbs. per inch. In this respect it resembles the quality already explained in the governor, and renders the pressure of the steam uniform, exactly in the same manner as the governor renders the velocity of the engine uniform. (73.) The economy of fuel depends, in a great degree, on the construction of the furnace, independently of the effects of the arrangements we have already described. The grate or fire-place of an ordinary furnace is placed under the boiler; and the atmospheric air passing through the ignited fuel, supplies sufficient oxygen to support a large volume of flame, which is carried by the draught into a flue, which circulates twice or oftener round the boiler, and in immediate contact with it, and finally issues into the chimney. Through this flue the flame circulates, so as to act on every part of the boiler near which the flue passes; and it is frequently not until it passes into the chimney, and sometimes not until it leaves the chimney, that it ceases to exist in the state of flame. The dense black smoke which is observed to issue from the chimneys of furnaces is formed of a quantity of unconsumed fuel, and may be therefore considered as so much fuel wasted. Besides this, in large manufacturing towns, where a great number of furnaces are employed, it is found that the quantity of smoke which thus becomes diffused through the atmosphere, renders it pernicious to the health, and destructive to the comforts of the inhabitants. These circumstances have directed the attention of engineers to the discovery of means whereby this smoke or wasted fuel may be consumed for the use of the engine itself, or for whatever use the furnace may be applied to. The most usual method of accomplishing this is by so arranging matters that fuel in a state of high combustion, and, therefore, producing no smoke, shall be always kept on that part of the grate which is nearest to the mouth of the flue (and which we shall call the back); by this means the smoke which arises from the imperfectly ignited fuel which is nearer to the front of the grate must pass over the surface of the red fuel, before it enters the flue, and is thereby ignited, and passes in a state of flame into the flue. A passage called the _feeding-mouth_ leads to the front of the grate, and both this passage and the grate are generally inclined at a small angle to the horizon, in order to facilitate the advance of the fuel according as its combustion proceeds. When fresh fuel for feeding the boiler is first introduced, it is merely laid in the feeding-mouth. Here it is exposed to the action of a part of the heat of the burning fuel on the grate, and undergoes, in some degree, the process of coking. The door of the feeding-mouth is furnished with small apertures for the admission of a stream of air, which carries the smoke evolved by the coking of the fresh fuel over the burning fuel on the grate, by which this smoke is ignited, and becomes flame, and in this state enters the flue, and circulates round the boiler. When the furnace is to be fed, the door of the feeding-mouth is opened, and the fuel which had been laid in it, and partially coked, is forced upon the front part of the grate. At first, its combustion being imperfect, but proceeding rapidly, a dense black smoke arises from it. The current of air from the open door through the feeding-mouth carries this over the vividly burning fuel in the back part of the grate, by which the smoke being ignited, passes in a state of flame into the flue. When the furnace again requires feeding, every part of this fuel will be in a state of active combustion, and it is forced to the back part of the grate next the flue, preparatory to the introduction of more fuel from the feeding-mouth. The apertures in the door of the feeding-mouth are furnished with covers, so that the quantity of air admitted through them can be regulated by the workmen. The efficiency of these furnaces in a great degree depends on the judicious admission of the air through the feeding-mouth: for if less than the quantity necessary to support the combustion of the fuel be admitted, a part of the smoke will remain unconsumed; and if more than the proper quantity be admitted, it will defeat the effects of the fuel by cooling the boiler. If the process which we have just described be considered, it will not be difficult to perceive the total impossibility in such a furnace of exactly regulating the draught of air, so that too much shall not pass at one time, and too little at another. When the door is open to introduce fresh fuel into the feeding-mouth, and advance that which occupied it upon the grate, the workman ceases to have any control whatever over the draught of air; and even at other times when the door is closed, his discretion and attention cannot be depended on. The consequence is, that with these defects the proprietors of steam engines found, that in the place of economising the fuel, the use of these furnaces entailed on them such an increased expense that they were generally obliged to lay them aside. (74.) Mr. Brunton of Birmingham having turned his attention to the subject, has produced a furnace which seems to be free from the objections against those we have just mentioned. The advantages of his contrivance, as stated by himself, are as follow:-- "First, I put the coal upon the grate by small quantities, and at very short intervals, say every two or three seconds. 2dly, I so dispose of the coals upon the grate, that the smoke evolved must pass over that part of the grate upon which the coal is in full combustion, and is thereby consumed. 3dly, As the introduction of coal is uniform in short spaces of time, the introduction of air is also uniform, and requires no attention from the fireman. [Illustration: Pl. VIII.] "As it respects economy: 1st, The coal is put upon the fire by an apparatus driven by the engine, and so contrived that the quantity of coal is proportioned to the quantity of work which the engine is performing, and the quantity of air admitted to consume the smoke is regulated in the same manner. 2dly, The fire-door is never opened, excepting to clean the fire; the boiler of course is not exposed to that continual irregularity of temperature which is unavoidable in the common furnace, and which is found exceedingly injurious to boilers. 3dly, The only attention required is to fill the coal receiver, every two or three hours, and clean the fire when necessary. 4thly, The coal is more completely consumed than by the common furnace, as all the effect of what is termed stirring up the fire (by which no inconsiderable quantity of coal is passed into the ash-pit) is attained without moving the coal upon the grate." The fire-place is a circular grate placed on a vertical shaft in a horizontal position. It is capable of revolving, and is made to do so by the vertical shaft, which is turned by wheelwork, which is worked by the engine itself; or this shaft or spindle may be turned by a water-wheel, on which a stream of water is allowed to flow from a reservoir into which it is pumped by the power of the engine; and by regulating the quantity of water in the stream, the grate may be made to revolve with a greater or less speed. In that part of the boiler which is over the grate, there is an aperture, in which is placed a hopper, through which fuel is let down upon the grate at the rate of any quantity per minute that may be required. The apparatus which admits the coals through this hopper is worked by the engine also, and by the same means as the grate is turned so that the grate revolves with a speed proportional to the rapidity with which the fuel is admitted through the hopper, and by this ingenious arrangement the fuel falls equally thick upon the grate. The supply of water which turns the wheel which works the grate and the machinery in the hopper, is regulated by a cock connected with the self-regulating damper; so that when the steam is being produced too fast, the supply of water will be diminished, and by that means the supply of fuel to the grate will be diminished, and the grate will revolve less rapidly: and when the steam is being produced too slowly for the demands of the engine, the contrary effects take place. In this way the fuel which is introduced into the furnace is exactly proportioned to the work which the engine has to perform. The hopper may be made large enough to hold coals for a day's work, so that the furnace requires no other attendance than to deposite coals in the hopper each morning. The coals are let down from the hopper on the grate at that part which is most remote from the flue; and as they descend in very small quantities at a time, they are almost immediately ignited. But until their ignition is complete, a smoke will arise, which, passing to the flue over the vividly burning fuel, will be ignited. Air is admitted through proper apertures, and its quantity regulated by the damper in the same manner as the supply of fuel. The superiority of this beautiful invention over the common smoke-consuming furnaces is very striking. Its principle of self-adjustment as to the supply of coals and atmospheric air, and the proportioning of these to the quantity of work to be performed by the engine, not only independent of human labour, but with a greater degree of accuracy than any human skill or attention could possibly effect, produces saving of expense, both in fuel and labour. (75.) Mr. Oldham, engineer to the Bank of Ireland, has proposed another modification of the self-regulating furnace, which seems to possess several advantages, and evinces considerable ingenuity. He uses a slightly inclined grate, at the back or lower end of which is the flue, and at the front or higher end, the hopper for admitting the coals. In the bottom or narrow end of the hopper is a moveable shelf, worked by the engine. Upon drawing back this shelf, a small quantity of fuel is allowed to descend upon a fixed shelf under it; and upon the return of the moveable shelf, this fuel is protruded forward upon the grate. Every alternate bar of the grate is fixed, but the intermediate ones are connected with levers, by which they are moved alternately up and down.[22] The effect is, that the coals upon the bars are continually stirred, and gradually advanced by their own weight from the front of the grate, where they fall from the hopper, to the back, where they are deposited in the ash-pit. By the shape and construction of the bars, the air is conducted upwards between them, and rushes through the burning fuel, so as to act in the manner of a blowpipe, and the entire surface of the fire presents a sheet of flame. [Footnote 22: Mr. Brunton used moveable bars in a furnace constructed by him before he adopted the horizontal revolving grate. That plan, however, does not appear to have been as successful as the latter, as he has abandoned it. Mr. Oldham states that his furnace has been in use for several years without any appearance of derangement in the mechanism, and with a considerable saving of fuel.] We cannot fail to be struck with the beauty of all these contrivances, by which the engine is made to regulate itself, and supply its own wants. It is in fact, all but alive. It was observed by Belidor, long before the steam engine reached the perfection which it has now acquired, that it resembled an animal, and that no mere work of man ever approached so near to actual _life_. Heat is the principle of its existence. The boiler acts the part of the heart, from which its vivifying fluid rushes copiously through all the tubes, where having discharged the various functions of life, and deposited its heat in the proper places, it returns again to the source it sprung from, to be duly prepared for another circulation. The healthfulness of its action is indicated by the regularity of its pulsations; it procures its own food by its own labour; it selects those parts which are fit for its support, both as to quantity and quality; and has its natural evacuations, by which all the useless and innutritious parts are discharged. It frequently cures its own diseases, and corrects the irregularity of its own actions, exerting something like moral faculties. Without designing to carry on the analogy, Mr. Farey, in speaking of the variations incident to the work performed by different steam engines, states some further particulars in which it maybe curiously extended. "We must observe," says he, "that the variation in the performance of different steam engines, which are constructed on the same principle, working under the same advantages, is the same as would be found in the produce of the labour of so many different horses or other animals when compared with their consumption of food; for the effects of different steam engines will vary as much from small differences in the proportion of their parts, as the strength of animals from the vigour of their constitutions; and again, there will be as great differences in the performance of the same engine when in good and bad order, from all the parts being tight and well oiled, so as to move with little friction, as there is in the labour of an animal from his being in good or bad health, or excessively fatigued: but in all these cases there will be a maximum which cannot be exceeded, and an average which we ought to expect to obtain." CHAPTER IX. DOUBLE-CYLINDER ENGINES. Hornblower's Engine. -- Woolf's Engine. -- Cartwright's Engine. (76.) The expansive property of steam, of which Watt availed himself in his single engine by cutting off the supply of steam before the descent of the piston was completed, was applied in a peculiar manner by an engineer named Hornblower, about the year 1781, and at a later period by Woolf. Hornblower was the first who conceived the idea of working an engine with two cylinders of different sizes, by allowing the steam to flow freely from the boiler until it fills the smaller cylinder, and then permitting it to expand into the greater one, employing it thus to press down two pistons in the manner which we shall presently describe. The condensing apparatus of Hornblower, as well as the other appendages of the engine, do not differ materially from those of Watt; so that it will be sufficient for our present purpose to explain the manner in which the steam is made to act in moving the piston. Let C, fig. 41., be the centre of the great working beam, carrying two arch heads, on which the chains of the piston rods play. The distances of these arch heads from the centre C must be in the same proportion as the length of the cylinders, in order that the same play of the beam may correspond to the plays of both pistons. Let F be the steam-pipe from the boiler, and G a valve to admit the steam above the lesser piston, H is a tube by which a communication may be opened by the valve I between the top and bottom of the lesser cylinder B. K is a tube communicating, by the valve L, between the bottom of the lesser cylinder B and the top of the greater cylinder A. M is a tube communicating, by the valve N, between the top and bottom of the greater cylinder A; and P a tube leading to the condenser by the exhausting valve O. At the commencement of the operation, suppose all the valves opened, and steam allowed to flow through the entire engine until the air be completely expelled, and then let all the valves be closed. To start the engine, let the exhausting valve O and the steam valves G and L be opened, as in fig. 41. The steam will flow freely from the boiler, and press upon the lesser piston, and at the same time the steam below the greater piston will flow into the condenser, leaving a vacuum in the greater cylinder. The valve L being opened, the steam which is under the piston in the lesser cylinder will flow through K, and press on the greater piston, which, having a vacuum beneath it, will consequently descend. At the commencement of the motion, the lesser piston is as much resisted by the steam below it as it is urged by the steam above it; but after a part of the descent has been effected, the steam below the lesser piston passing into the greater, expands into an increased space, and therefore loses its elastic force proportionally. The steam above the lesser piston retaining its full force by having a free communication with the boiler by the valve G, the lesser piston will be urged by a force equal to the excess of the pressure of this steam above the diminished pressure of the expanded steam below it. As the pistons descend, the steam which is between it continually increasing in its bulk, and therefore decreasing in its pressure, from whence it follows, that the force which resists the lesser piston is continually decreasing, while that which presses it down remains the same, and therefore the effective force which impels it must be continually increasing. On the other hand, the force which urges the greater piston is continually decreasing, since there is a vacuum below it, and the steam which presses it is continually expanding into an increased bulk. Impelled in this way, let us suppose the pistons to have arrived at the bottoms of the cylinders, as in fig. 42., and let the valves G, L, and O be closed, and the valves I and N opened. No steam is allowed to flow from the boiler, G being closed, nor any allowed to pass into the condenser, since O is closed, and all communications between the cylinders is stopped by closing L. By opening the valve I, a free communication is made between the top and bottom of the lesser piston through the tube H, so that the steam which presses above the lesser piston will exert the same pressure below it, and the piston is in a state of indifference. In the same manner the valve N being open, a free communication is made between the top and bottom of the greater piston, and the steam circulates above and below the piston, and leaves it free to rise. A counterpoise attached to the pump-rods in this case, draws up the piston, as in Watt's single engine; and when they arrive at the top, the valves I and N are closed, and G, L, and O opened, and the next descent of the pistons is produced in the manner already described, and so the process is continued. The valves are worked by the engine itself, by means similar to some of those already described. By computation, we find the power of this engine to be nearly the same as a similar engine on Watt's expansive principle. It does not however appear, that any adequate advantage was gained by this modification of the principle, since no engines of this construction are now made. (77.) The use of two cylinders was revived by _Arthur Woolf_, in 1804, who, in this and the succeeding year, obtained patents for the application of steam raised under a high pressure to double-cylinder engines. The specification of his patent states, that he has proved by experiment that steam raised under a safety-valve loaded with any given number of pounds upon the square inch, will, if allowed to expand into as many times its bulk as there are pounds of pressure on the square inch, have a pressure equal to that of the atmosphere. Thus, if the safety-valve be loaded with four pounds on the square inch, the steam, after expanding into four times its bulk, will have the atmospheric pressure. If it be loaded with 5, 6, or 10 lbs. on the square inch, it will have the atmospheric pressure when it has expanded into 5, 6, or 10 times its bulk, and so on. It was, however, understood in this case, that the vessel into which it was allowed to expand should have the same temperature as the steam before it expands. It is very unaccountable how a person of Mr. Woolf's experience in the practical application of steam could be led into errors so gross as those involved in the averments of this patent; and it is still more unaccountable how the experiments could have been conducted which led him to conclusions not only incompatible with all the established properties of elastic fluids--properties which at that time were perfectly understood--but even involving in themselves palpable contradiction and absurdity. If it were admitted that every additional pound avoirdupois which should be placed upon the safety-valve would enable steam, by its expansion into a proportionally enlarged space, to attain a pressure equal to the atmosphere, the obvious consequence would be, that a physical relation would subsist between the atmospheric pressure and the pound avoirdupois! It is wonderful that it did not occur to Mr. Woolf, that, granting his principle to be true at any given place, it would necessarily be false at another place where the barometer would stand at a different height. Thus if the principle were true at the foot of a mountain, it would be false at the top of it; and if it were true in fair weather, it would be false in foul weather, since these circumstances would be attended by a change in the atmospheric pressure, without making any change in the pound avoirdupois.[23] [Footnote 23: It is strange that this absurdity has been repeatedly given as unquestionable fact in various encyclopædias on the article "Steam Engine," as well as in by far the greater number of treatises expressly on the subject.] The method by which Mr. Woolf proposed to apply the principle which he imagined himself to have discovered was by an arrangement of cylinders similar to those of Hornblower, but having their magnitudes proportioned to the greater extent of expansion which he proposed to use. Two cylinders, like those of Hornblower, were placed under the working beam, having their piston-rods at distances from the axis proportioned to the lengths of their respective strokes. The relative magnitudes of the cylinders A and B must be adjusted according to the extent to which the principle of expansion is intended to be used. The valves C C´ were placed at each end of the lesser cylinder in tubes communicating with the boiler, so as to admit steam on each side of the lesser piston, and cut it off at pleasure. A tube, D´, formed a communication between the upper end of the lesser and lower end of the greater cylinder, which communication is opened and closed at pleasure by the valve E´. In like manner, the tube D forms a communication between the lower end of the lesser cylinder and the upper end of the greater, which may be opened and closed by the valve E. The top and bottom of the greater cylinder communicated with the condenser by valves F´ F. Let us suppose that the air is blown from the engine in the usual way, all the valves closed, and the engine ready to start, the pistons being at the top of the cylinders. Open the valves C, E, and F. The steam which occupies the greater cylinder below the piston will now pass into the condenser through F, leaving a vacuum below the piston. The steam which is in the lesser cylinder below the piston will pass through D and open the valve E, and will press down the greater piston. The steam from the boiler will flow in at C, and press on the lesser piston. At first the whole motion will proceed from the pressure upon the greater piston, since the steam, both above and below the lesser piston, has the same pressure. But, as the pistons descend, the steam below the less passing into the greater cylinder, expands into a greater space, and consequently exerts a diminished pressure, and, therefore, the steam on the other side exerting an undiminished pressure, acquires an impelling force exactly equal to the pressure lost in the expansion of the steam between the two pistons. Thus both pistons will be pressed to the bottoms of their respective cylinders. It will be observed that in the descent the greater piston is urged by a continually decreasing force, while the lesser is urged by continually increasing force. Upon the arrival of the pistons at the bottoms of the cylinders, let the valves, C, E, F be closed, and C´, E´, F´ be opened, as in fig. 44. The steam which is above the greater piston now flows through F´ into the condenser, leaving the space above the piston a vacuum. The steam which is above the lesser piston passes through E´ and D´ below the greater, while the steam from the boiler is admitted through C´ below the lesser piston. The pressure of the steam entering through E´ below the greater piston, pressing on it against the vacuum above it, commences the ascent. In the mean time the steam above the lesser piston passing into the enlarged space of the greater cylinder, loses gradually its elastic force, so that the steam entering from the boiler at C´ becomes in part effective, and the ascent is completed under exactly the same circumstances as the descent, and in this way the process is continued. It is evident that the valves may be easily worked by the mechanism of the engine itself. In this arrangement the pistons ascend and descend together, and their rods must consequently be attached to the beam at the same side of the centre. It is sometimes desirable that they should act on different sides of the centre of the beam, and consequently that one should ascend while the other descends. It is easy to arrange the valves so as to effect this. In fig. 45., the lesser piston is at the bottom of the cylinder, and the greater at the top. On opening the valves C´, E´, F´, a vacuum is produced below the greater piston, and steam flows from the lesser cylinder, through E´, _above_ the greater piston, and presses it down. At the same time steam being admitted from the boiler through C´ below the lesser piston, forces it up against the diminishing force of the steam above it, which expands into the greater cylinder. Thus as the greater piston descends the lesser ascends. When each has traversed its cylinder, the valves C´, E´, F´ being closed, and C, E, F opened, the lesser piston will descend, and the greater ascend, and so on. (78.) The law according to which the elastic force of steam diminishes as it expands, of which Mr. Woolf appears to have been entirely ignorant, is precisely similar to the same property in air and other elastic fluids. If steam expands into twice or thrice its volume, it will lose its elastic force in precisely the same proportion as it enlarges its bulk; and therefore will have only a half or a third of its former pressure, supposing that as it expands its temperature is kept up. Although Mr. Woolf's patent contained the erroneous principle which we have noticed, yet, so far as his invention suggested the idea of employing steam at a very high-pressure, and allowing it to expand in a much greater degree than was contemplated either by Watt or Hornblower, it became the means of effecting a considerable saving in fuel; for engines used for pumping on a large scale, the steam being produced under a pressure of forty or fifty pounds or more upon the square inch, might be worked first through a small space with intense force, and the communication with the boiler being then cut off, it might be allowed, with great advantage, to expand through a very large space. Some double-cylinder engines upon this principle have been worked in Cornwall, with considerable economy. But the form in which the expansive principle, combined with high pressure, is now applied in the engines used for raising water from the mines, is that in which it was originally proposed by Watt. A single cylinder of considerable length is employed; the piston is driven through a small proportion of this length by steam, admitted from the boiler at a very intense pressure: the steam being then cut off, the piston is urged by the expansive force of the steam which has been admitted, and is by that means brought to the bottom of the cylinder. It is evident, under such circumstances, that the pressure of the steam admitted from the boiler must be much greater than the resistance opposed to the piston, and that the motion of the piston must, in the first instance, be accelerated and not uniform. If the piston moved from the commencement with a uniform motion, the pressure of the steam urging it must necessarily be exactly equal to the resistance opposed to it, and then cutting off the supply of steam from the boiler, the piston could only continue its motion by inertia, the steam immediately becoming of less pressure than the resistance; and after advancing through a very small space, the piston would recoil upon the steam, and come to a state of rest. The steam, however, at the moment it is cut off being of much greater pressure than the amount of resistance upon the piston, will continue to drive the piston forward, until by its expansion its force is so far diminished as to become equal to the resistance of the piston. From that point the impelling power of the steam will cease, and the piston will move forward by its inertia only. The point at which the steam is cut off should therefore be so regulated that it shall acquire a pressure equal to the resistance on the piston by its expansion, just at such a distance from the end of the stroke as the piston may be able to move through by its inertia. It is evident the adjustment of this will require great care and nicety of management. (79.) In 1797 a patent was granted to the _Rev. Mr. Cartwright_, a gentleman well known for other mechanical inventions, for some improvements in the steam-engine. His contrivance is at once so elegant and simple, that, although it has not been carried into practice, we cannot here pass it over without notice. The steam-pipe from the boiler is represented cut off at B (fig. 46.); T is a spindle-valve for admitting steam above the piston, and R is a spindle-valve in the piston; D is a curved pipe forming a communication between the cylinder and the condenser, which is of very peculiar construction. Cartwright proposed effecting a condensation without a jet, by exposing the steam to contact with a very large quantity of cold surface. For this purpose, he formed his condenser by placing two cylinders nearly equal in size one within the other, allowing the water of the cold cistern in which they were placed to flow through the inner cylinder, and to surround the outer one. Thus the thin space between the two cylinders formed the condenser. [Illustration: Pl. IX.] [Illustration: Pl. X.] The air-pump is placed immediately under the cylinder, and the continuation of the piston-rod works its piston, which is solid and without a valve: F is the pipe from the condenser to the air-pump, through which the condensed steam is drawn off through the valve G on the ascent of the piston, and on the descent, this is forced through a tube into a hot well, H, for the purpose of feeding the boiler through the feed-pipe I. In the top of the hot well H is a valve which opens inwards, and is kept closed by a ball floating on the surface of the liquid. The pressure of the condensed air above the surface of the liquid in H forces it through I into the boiler. When the air accumulates in too great a degree in H, the surface of the liquid is pressed so low that the ball falls and opens the valve, and allows it to escape. The air in H is that which is pumped from the condenser with the liquid, and which was disengaged from it. Let us suppose the piston at the top of the cylinder; it strikes the tail of the valve T, and raises it, while the stem of the piston-valve R strikes the top of the cylinder, and is pressed into its seat. A free communication is at the same time open between the cylinder, below the piston and the condenser, through the tube D. The pressure of the steam thus admitted above the piston, acting against the vacuum below it, will cause its descent. On arriving at the bottom of the cylinder, the tail of the piston-valve R will strike the bottom, and it will be lifted from its seat, so that a communication will be opened through it with the condenser. At the same moment a projecting spring, K, attached to the piston-rod, strikes the stem of the steam-valve T, and presses it into its seat. Thus, while the further admission of steam is cut off, the steam above the piston flows into the condenser, and the piston being relieved from all pressure, is drawn up by the momentum of the fly-wheel, which continues the motion it received from the descending force. On the arrival of the piston again at the top of the cylinder, the valve T is opened and R closed, and the piston descends as before, and so the process is continued. The mechanism by which motion is communicated from the piston to the fly-wheel is peculiarly elegant. On the axis of the fly-wheel is a small wheel with teeth, which work in the teeth of another large wheel L. This wheel is turned by a crank, which is worked by a cross-piece attached to the end of the piston-rod. Another equal-toothed wheel, M, is turned by a crank, which is worked by the other end of the cross-arm attached to the piston-rod. One of the peculiarities of this engine is, that the liquid which is used for the production of steam in the boiler circulates through the machine without either diminution or admixture with any other fluid, so that the boiler never wants more feeding than what can be supplied from the hot-well H. This circumstance forms a most important feature in the machine, as it allows of ardent spirits being used in the boiler instead of water, which, since they boil at low heats, promised a saving of half the fuel. The inventor even proposed, that the engine should be used as a still, as well as a mechanical power, in which case the whole of the fuel would be saved. In this engine, the ordinary method of rendering the piston steam-tight, by oil or melted wax or tallow poured upon it, could not be applied, since the steam above the piston must always have a free passage through the piston-valve R. The ingenious inventor therefore contrived a method of making the piston steam-tight in the cylinder, without oil or stuffing, and his method has since been adopted with success in other engines. A ring of metal is ground into the cylinder, so as to fit it perfectly, and is then cut into four equal segments. The inner surface of this ring being slightly conical, another ring is ground into it, so as to fit it perfectly, and this is also cut into four segments, and one is placed within the other, but in such a manner that the joints or divisions do not coincide. The arrangement of the two rings is represented in fig. 47. Within the inner ring are placed four springs, which press the pieces outward against the sides of the cylinder, and are represented in the diagram. Four pairs of these rings are placed one over another, so that their joints do not coincide, and the whole is screwed together by plates placed at top and bottom. A vertical section of the piston is given in fig. 48. One of the advantages of this piston is, that the longer it is worked, the more accurately it fits the cylinder, so that, as the machine wears it improves. Metallic pistons have lately come into very general use, and such contrivances differ very little from the above. CHAPTER X. LOCOMOTIVE ENGINES ON RAILWAYS. High-pressure Engines. -- Leupold's Engine. -- Trevithick and Vivian. -- Effects of Improvement in Locomotion. -- Historical Account of the Locomotive Engine. -- Blenkinsop's Patent. -- Chapman's Improvement. -- Walking Engine. -- Stephenson's First Engines. -- His Improvements. -- Liverpool and Manchester Railway Company. -- Their Preliminary Proceedings. -- The Great Competition of 1829. -- The Rocket. -- The Sanspareil. -- The Novelty. -- Qualities of the Rocket. -- Successive Improvements. -- Experiments. -- Defects of the Present Engines. -- Inclined Planes. -- Methods of surmounting them. -- Circumstances of the Manchester Railway Company. -- Probable Improvements in Locomotives. -- Their capabilities with respect to speed. -- Probable Effects of the Projected Railroads. -- Steam Power compared with Horse Power. -- Railroads compared with Canals. (80.) In the various modifications of the steam engine which we have hitherto considered, the pressure introduced on one side of the piston derives its efficacy either wholly or partially from the vacuum produced by condensation on the other side. This always requires a condensing apparatus, and a constant and abundant supply of cold water. An engine of this kind must therefore necessarily have considerable dimensions and weight, and is inapplicable to uses in which a small and light machine only is admissible. If the condensing apparatus be dispensed with, the piston will always be resisted by a force equal to the atmospheric pressure, and the only part of the steam pressure which will be available as a moving power, is that part by which it exceeds the pressure of the atmosphere. Hence, in engines which do not work by condensation, steam of a much higher pressure than that of the atmosphere is indispensably necessary, and such engines are therefore called _high-pressure engines_. We are not, however, to understand that every engine, in which steam is used of a pressure exceeding that of the atmosphere, is what is meant by a _high-pressure engine_; for in the ordinary engines in common use, constructed on Watt's principle, the safety-valve is loaded with from 3 to 5 lbs. on the square inch; and in Woolf's engines, the steam is produced under a pressure of 40 lbs. on the square inch. These would therefore be more properly called _condensing engines_ than _high-pressure engines_; a term quite inapplicable to those of Woolf. In fact, by _high-pressure engines_ is meant engines in which no vacuum is produced, and, therefore, in which the piston works against a pressure equal to that of the atmosphere. In these engines, the whole of the condensing apparatus, _viz._ the cold-water cistern, condenser, air-pump, cold-water pump, &c. are dispensed with, and nothing is retained except the boiler, cylinder, piston, and valves. Consequently, such an engine is small, light, and cheap. It is portable also, and may be moved, if necessary, along with its load, and is therefore well adapted to locomotive purposes. (81.) High-pressure engines were one of the earliest modifications of the steam engine. The contrivance, which is obscurely described in the article already quoted (27.), from the Century of Inventions, is a high-pressure engine; for the power there alluded to is the elastic force of steam working against the atmospheric pressure. _Newcomen_, in 1705, applied the working-beam, cylinder, and piston to the atmospheric engine; and _Leupold_, about 1720, combined the working-beam and cylinder with the high-pressure principle, and produced the earliest high-pressure engine worked by a cylinder and piston. The following is a description of _Leupold's_ engine:-- A (fig. 49.) is the boiler, with the furnace beneath it; C C´ are two cylinders with two solid pistons, P P´, connected with the working-beams B B´, to which are attached the pump-rods, R R´, of two forcing-pumps, F F´, which communicate with a great force-pipe S; G is a _four-way cock_ (66.) already described. In the position in which it stands in the figure, the steam is issuing from below the piston P into the atmosphere, and the piston is descending by its own weight; steam from the boiler is at the same time pressing up the piston P´, with a force equal to the difference between the pressure of the steam and that of the atmosphere. Thus the piston R of the forcing-pump is being drawn up, and the piston P´ is forcing the piston R´ down, and thereby driving water into the force-pipe S. On the arrival of the piston P at the bottom of the cylinder C, and P´ at the top of the cylinder C´, the position of the cock is changed as represented in fig. 50. The steam, which has just pressed up the piston P´, is allowed to escape into the atmosphere, while the steam, passing from the boiler below the piston P, presses it up, and thus P ascends by the steam pressure, and P´ descends by its own weight. By these means the piston R is forced down, driving before it the water in the pump cylinder into the force-pipe S, and the piston R´ is drawn up to allow the other pump-cylinder to be re-filled; and so the process is continued. A valve is placed in the bottom of the force-pipes, to prevent the water which has been driven into it from returning. This valve opens upwards; and, consequently, the weight of the water pressing upon it only keeps it more effectually closed. On each descent of the piston, the pressure transmitted to the valve acting upwards being greater than the weight of the water resting upon it, forces it open, and an increased quantity of water is introduced. (82.) From the date of the improvement of Watt until the commencement of the present century, high-pressure engines were altogether neglected in these countries. In the year 1802, Messrs. _Trevithick_ and _Vivian_ constructed the first high-pressure engine which was ever brought into extensive practical use in this kingdom. A section of this machine, made by a vertical plane, is represented in fig. 51. The boiler A B is a cylinder with flat circular ends. The fire-place is constructed in the following manner:--A tube enters the cylindrical boiler at one end; and, proceeding onwards, near the other extremity, is turned and recurved, so as to be carried back parallel to the direction in which it entered. It is thus conducted out of the boiler, at another part of the same end at which it entered. One of the ends of this tube communicates with the chimney E, which is carried upwards, as represented in the figure. The other mouth is furnished with a door; and in it is placed the grate, which is formed of horizontal bars, dividing the tube into two parts; the upper part forming the fire-place, and the lower the ash-pit. The fuel is maintained in a state of combustion, on the bars, in that part of the tube represented at C D; and the flame is carried by the draft of the chimney round the curved flue, and issues at E into the chimney. The flame is thus conducted through the water, so as to expose the latter to as much heat as possible. A section of the cylinder is represented at F, immersed in the boiler, except a few inches of the upper end, where the four-way cock G is placed for regulating the admission of the steam. A tube is represented at H, which leads from this four-way cock into the chimney; so that the waste steam, after working the piston, is carried off through this tube, and passes into the chimney. The upper end of the piston-rod is furnished with a cross-bar, which is placed in a direction at right angles to the length of the boiler, and also to the piston-rod. This bar is guided in its motion by sliding on two iron perpendicular rods fixed to the sides of the boiler, and parallel to each other. To the ends of this cross-bar are joined two connecting rods, the lower ends of which work two cranks fixed on an axis extending across and beneath the boiler, and immediately under the centre of the cylinder. This axis is sustained in bearings formed in the legs which support the boiler, and upon its extremity is fixed the fly-wheel as represented at B. A large-toothed wheel is placed on this axis; which, being turned with the cranked axle, communicates motion to other wheels; and, through them, to any machinery which the engine may be applied to move. As the four-way cock is represented in the figure, the steam passes from the boiler through the curved passage G above the piston, while the steam below the piston is carried off through a tube which does not appear in the figure, by which it is conducted to the tube H, and thence to the chimney. The steam, therefore, which passes above the piston presses it downwards; while the pressure upwards does not exceed that of the atmosphere. The piston will therefore descend with a force depending on the excess of the pressure of the steam produced in the boiler above the atmospheric pressure. When the piston has arrived at the bottom of the cylinder, the cock is made to assume the position represented in the figure 52. This effect is produced by the motion of the piston-rod. The steam now passes from above the piston, through the tube H, into the chimney, while the steam from the boiler is conducted through another tube below the piston. The pressure above the piston, in this case, does not exceed that of the atmosphere; while the pressure below it will be that of the steam in the boiler. The piston will therefore ascend with the difference of these pressures. On the arrival of the piston at the top of the cylinder, the four-way cock is again turned to the position represented in fig. 51., and the piston again descends; and in the same manner the process is continued. A safety-valve is placed on the boiler at V, loaded with a weight W, proportionate to the strength of the steam with which it is proposed to work. [Illustration: Pl. XI.] In the engines now described, this valve was frequently loaded at the rate of from 60 to 80 lbs. on the square inch. As the boilers of high-pressure engines were considered more liable to accidents from bursting than those in which steam of a lower pressure was used, greater precautions were taken against such effects. A second safety-valve was provided, which was not left in the power of the engine-man. By this means he had a power to diminish the pressure of the steam, but could not increase it beyond the limit determined by the valve which was removed from his interference. The greatest cause of danger, however, arose from the water in the boiler being consumed by evaporation faster than it was supplied; and therefore falling below the level of the tube containing the furnace. To guard against accidents arising from this circumstance, a hole was bored in the boiler, at a certain depth, below which the water should not be allowed to fall; and in this hole a plug of metal was soldered with lead, or with some other metal, which would fuse at that temperature which would expose the boiler to danger. Thus, in the event of the water being exhausted, so that its level would fall below the plug, the heat of the furnace would immediately melt the solder, and the plug would fall out, affording a vent for the steam, without allowing the boiler to burst. The mercurial steam-gauge, already described, was also used as an additional security. When the force of the steam exceeded the length of the column of mercury which the tube would contain, the mercury would be blown out, and the tube would give vent to the steam. The water by which the boiler was replenished was forced into it by a pump worked by the engine. In order to economise the heat, this water was contained in a tube T, which surrounded the pipe H. As the waste steam, after working the piston, passed off through H, it imparted a portion of its heat to the water contained in the tube T, which was thus warmed to a certain temperature before it was forced into the boiler by the pump. Thus a part of the heat, which was originally carried from the boiler in the form of steam, was returned again to the boiler with the water with which it was fed. It is evident that engines constructed in this manner may be applied to all the purposes to which the condensing engines are applicable. (_e_) To the plates of the English edition has been added one, (plate A) representing a high-pressure engine as constructed by the West Point Foundry in the state of New York. The principal parts will be readily distinguished from their resemblance to the analogous parts of a condensing engine. The condenser and air-pump of that engine, it will be observed, are suppressed. At _v x_ and _y z_ are forcing-pumps by which a supply of water is injected into the boiler at each motion of the engine. For the four-way cock, used in the English high-pressure engines, a slide valve at _r s_, is substituted, and is found to work to much greater advantage. It is set in motion by an eccentric, in a manner that will be more obvious from an inspection of the plate than from any description.--A. E. (_f_) A very safe and convenient boiler for a high-pressure engine has been invented in the United States by Mr. Babcock. The boiler consists of small tubes, into which water is flashed by a small forcing-pump at every stroke of the engine. The tubes are kept so hot in a furnace, as to generate steam of the required temperature, but not hot enough to cause any risk of the decomposition of the water. The strength of the apparatus is such, and the quantity of water exposed to heat at one time so small, as to leave hardly any risk of danger.--A. E. (83.) Two years after the date of the patent of this engine, its inventor constructed a machine of the same kind for the purpose of moving carriages on railroads; and applied it successfully, in the year 1804, on the railroad at Merthyr Tydvil, in South Wales. It was in principle the same as that already described. The cylinder however was in a horizontal position, the piston-rod working in the direction of the line of road: the extremity of the piston-rod, by means of a connecting rod, worked cranks placed on the axletree, on which were fixed two cogged wheels: these worked in others, by which their motion was communicated finally to cogged wheels fixed on the axle of the hind wheels of the carriage, by which this axle was kept in a state of revolution. The hind wheels being fixed on the axletree, and turning with it, were caused likewise to revolve; and so long as the weight of the carriage did not exceed that which the friction of the road was capable of propelling, the carriage would thus be moved forwards. On this axle was placed a fly-wheel to continue the rotatory motion at the termination of each stroke. The fore wheels are described as being capable of turning like the fore wheels of a carriage, so as to guide the vehicle. The projectors appear to have contemplated, in the first instance, the use of this carriage on turnpike roads; but that notion seems to have been abandoned, and its use was only adopted on the railroad before mentioned. On the occasion of its first trial, it drew after it as many carriages as contained 10 tons of iron a distance of nine miles; which stage it performed without any fresh supply of water, and travelled at the rate of five miles an hour. (84.) Capital and skill have of late years been directed with extraordinary energy to the improvement of inland transport; and this important instrument of national wealth and civilisation has received a proportionate impulse. Effects are now witnessed, which, had they been narrated a few years since, could only have been admitted into the pages of fiction or volumes of romance. Who could have credited the possibility of a ponderous engine of iron, loaded with several hundred passengers, in a train of carriages of corresponding magnitude, and a large quantity of water and coal, taking flight from Manchester and arriving at Liverpool, a distance of about thirty miles, in little more than an hour? And yet this is a matter of daily and almost hourly occurrence. Neither is the road, on which this wondrous performance is effected, the most favourable which could be constructed for such machines. It is subject to undulations and acclivities, which reduce the rate of speed much more than similar inequalities affect the velocity on common roads. The rapidity of transport thus attained is not less wonderful than the weights transported. Its capabilities in this respect far transcend the exigencies even of the two greatest commercial marts in Great Britain. Loads, varying from 50 to 150 tons are transported at the average rate of 15 miles an hour; but the engines in this case are loaded below their power; and in one instance we have seen a load--we should rather say a _cargo_--of wagons, conveying merchandise to the amount of 230 tons gross, transported from Liverpool to Manchester at the average rate of 12 miles an hour. The astonishment with which such performances must be viewed, might be qualified, if the art of transport by steam on railways had been matured, and had attained that full state of perfection which such an art is always capable of receiving from long experience, aided by great scientific knowledge, and the unbounded application of capital. But such is not the present case. The art of constructing locomotive engines, so far from having attained a state of maturity, has not even emerged from its infancy. So complete was the ignorance of its powers which prevailed, even among engineers, previous to the opening of the Liverpool railway, that the transport of heavy goods was regarded as the chief object of the undertaking, and its principal source of revenue. The incredible speed of transport, effected even in the very first experiments in 1830, burst upon the public, and on the scientific world, with all the effect of a new and unlooked-for phenomenon. On the unfortunate occasion which deprived this country of Mr. Huskisson, the wounded body of that statesman was transported a distance of about fifteen miles in twenty-five minutes, being at the rate of thirty-six miles an hour. The revenue of the road arising from passengers since its opening, has, contrary to all that was foreseen, been nearly double that which has been derived from merchandise. So great was the want of experience in the construction of engines, that the company was at first ignorant whether they should adopt large steam-engines fixed at different stations on the line, to pull the carriages from station to station, or travelling engines to drag the loads the entire distance. Having decided on the latter, they have, even to the present moment, laboured under the disadvantage of the want of that knowledge which experience alone can give. The engines have been constantly varied in their weight and proportions, in their magnitude and form, as the experience of each successive month has indicated. As defects became manifest they were remedied; improvements suggested were adopted; and each quarter produced engines of such increased power and efficiency, that their predecessors were abandoned, not because they were worn out, but because they had been outstripped in the rapid march of improvement. Add to this, that only one species of travelling engine has been effectively tried; the capabilities of others remain still to be developed; and even that form of engine which has received the advantage of a course of experiments on so grand a scale to carry it towards perfection, is far short of this point, and still has defects, many of which, it is obvious, time and experience will remove. If then travelling steam engines, with all the imperfections of an incipient invention--with the want of experience, the great parent of practical improvements--with the want of the common advantage of the full application of the skill and capital of the country--subjected to but one great experiment, and that experiment limited to one form of engine; if, under such disadvantages, the effects to which we have referred have been produced, what may we not expect from this extraordinary power, when the enterprise of the country shall be unfettered, when greater fields of experience are opened, when time, ingenuity, and capital have removed the existing imperfections, and have brought to light new and more powerful principles? This is not mere speculation on possibilities, but refers to what is in a state of actual progression. Railways are in progress between the points of greatest intercourse in the United Kingdom, and travelling steam engines are in preparation for the common turnpike roads; the practicability and utility of that application of the steam engine having not only been established by experiment to the satisfaction of their projectors, but proved before the legislature in a committee of inquiry on the subject. The important commercial and political effects attending such increased facility and speed in the transport of persons and goods, are too obvious to require any very extended notice here. A part of the price (and in many cases a considerable part) of every article of necessity or luxury, consists of the cost of transporting it from the producer to the consumer; and consequently every abatement or saving in this cost must produce a corresponding reduction in the price of every article transported; that is to say, of everything which is necessary for the subsistence of the poor, or for the enjoyment of the rich, of every comfort, and of every luxury of life. The benefit of this will extend, not to the consumer only, but to the producer: by lowering the expense of transport of the produce, whether of the soil or of the loom, a less quantity of that produce will be spent in bringing the remainder to market, and consequently a greater surplus will reward the labour of the producer. The benefit of this will be felt even more by the agriculturist than by the manufacturer; because the proportional cost of transport of the produce of the soil is greater than that of manufactures. If 200 quarters of corn be necessary to raise 400, and 100 more be required to bring the 400 to market, then the net surplus will be 100. But if by the use of steam carriages the same quantity can be brought to market with an expenditure of 50 quarters, then the net surplus will be increased from 100 to 150 quarters; and either the profit of the farmer, or the rent of the landlord, must be increased by the same amount. But the agriculturist would not merely be benefited by an increased return from the soil already under cultivation. Any reduction in the cost of transporting the produce to market would call into cultivation tracts of inferior fertility, the returns from which would not at present repay the cost of cultivation and transport. Thus land would become productive which is now waste, and an effect would be produced equivalent to adding so much fertile soil to the present extent of the country. It is well known, that land of a given degree of fertility will yield increased produce by the increased application of capital and labour. By a reduction in the cost of transport, a saving will be made which may enable the agriculturist to apply to tracts already under cultivation the capital thus saved, and thereby increase their actual production. Not only, therefore, would such an effect be attended with an increased extent of cultivated land, but also with an increased degree of cultivation in that which is already productive. It has been said, that in Great Britain there are above a million of horses engaged in various ways in the transport of passengers and goods, and that to support each horse requires as much land as would, upon an average, support eight men. If this quantity of animal power were displaced by steam engines, and the means of transport drawn from the bowels of the earth, instead of being raised upon its surface, then, supposing the above calculation correct, as much land would become available for the support of human beings as would suffice for an additional population of eight millions; or, what amounts to the same, would increase the means of support of the present population by about one-third of the present available means. The land which now supports horses for transport would then support men, or produce corn for food. The objection that a quantity of land exists in the country capable of supporting horses alone, and that such land would be thrown out of cultivation, scarcely deserves notice here. The existence of any considerable quantity of such land is extremely doubtful. What is the soil which will feed a horse and not feed oxen or sheep, or produce food for man? But even if it be admitted that there exists in the country a small portion of such land, that portion cannot exceed, nor indeed equal, what would be sufficient for the number of horses which must after all continue to be employed for the purposes of pleasure, and in a variety of cases where steam must necessarily be inapplicable. It is to be remembered, also, that the displacing of horses in one extensive occupation, by diminishing their price must necessarily increase the demand for them in others. The reduction in the cost of transport of manufactured articles, by lowering their price in the market, will stimulate their consumption. This observation applies of course not only to home but to foreign markets. In the latter we already in many branches of manufacture command a monopoly. The reduced price which we shall attain by cheapness and facility of transport will still further extend and increase our advantages. The necessary consequence will be, an increased demand for manufacturing population; and this increased population again reacting on the agricultural interests, will form an increased market for that species of produce. So interwoven and complicated are the fibres which form the texture of the highly civilized and artificial community in which we live, that an effect produced on any one point is instantly transmitted to the most remote and apparently unconnected parts of the system. The two advantages of increased cheapness and speed, besides extending the amount of existing traffic, call into existence new objects of commercial intercourse. For the same reason that the reduced cost of transport, as we have shown, calls new soils into cultivation, it also calls into existence new markets for manufactured and agricultural produce. The great speed of transit which has been proved to be practicable, must open a commerce between distant points in various articles, the nature of which does not permit them to be preserved so as to be fit for use beyond a certain time. Such are, for example, many species of vegetable and animal food, which at present are confined to markets at a very limited distance from the grower or feeder. The truth of this observation is manifested by the effects which have followed the intercourse by steam on the Irish Channel. The western towns of England have become markets for a prodigious quantity of Irish produce, which it had been previously impossible to export. If animal food be transported alive from the grower to the consumer, the distance of the market is limited by the power of the animal to travel, and the cost of its support on the road. It is only particular species of cattle which bear to be carried to market on common roads and by horse carriages. But the peculiar nature of a railway, the magnitude and weight of the loads which may be transported on it, and the prodigious speed which may be attained, render the transport of cattle, of every species, to almost any distance, both easy and cheap. In process of time, when the railway system becomes extended, the metropolis and populous towns will therefore become markets, not as at present to districts within limited distances of them, but to the whole country. The moral and political consequences of so great a change in the powers of transition of persons and intelligence from place to place are not easily calculated. The concentration of mind and exertion which a great metropolis always exhibits, will be extended in a considerable degree to the whole realm. The same effect will be produced as if all distances were lessened in the proportion in which the speed and cheapness of transit are increased. Towns, at present removed some stages from the metropolis, will become its suburbs; others, now a day's journey, will be removed to its immediate vicinity; business will be carried on with as much ease between them and the metropolis, as it is now between distant points of the metropolis itself. Let those who discard speculations like these as wild and improbable, recur to the state of public opinion, at no very remote period, on the subject of steam navigation. Within the memory of persons who have not yet passed the meridian of life, the possibility of traversing by the steam engine the channels and seas that surround and intersect these islands, was regarded as the dream of enthusiasts. Nautical men and men of science rejected such speculations with equal incredulity, and with little less than scorn for the understanding of those who could for a moment entertain them. Yet we have witnessed steam engines traversing not these channels and seas alone, but sweeping the face of the waters round every coast in Europe. The seas which interpose between our Asiatic dominions and Egypt, and those which separate our own shores from our West Indian possessions, have offered an equally ineffectual barrier to its powers. Nor have the terrors of the Pacific prevented the "Enterprise" from doubling the Cape, and reaching the shores of India. If steam be not used as the only means of connecting the most distant points of our planet, it is not because it is inadequate to the accomplishment of that end, but because the supply of the material from which at the present moment it derives its powers, is restricted by local and accidental circumstances.[24] [Footnote 24: Some of the preceding observations on inland transport, as well as other parts of the present chapter, appeared in articles written by me in the Edinburgh Review for October, 1832, and October, 1834.] We propose in the present chapter to lay before our readers some account of the means whereby the effects above referred to have been produced; of the manner and degree in which the public have availed themselves of these means; and of the improvements of which they seem to us to be susceptible. (85.) It is a singular fact, that in the history of this invention considerable time and great ingenuity were vainly expended in attempting to overcome a difficulty, which in the end turned out to be purely imaginary. To comprehend distinctly the manner in which a wheel carriage is propelled by steam, suppose that a pin or handle is attached to the spoke of the wheel at some distance from its centre, and that a force is applied to this pin in such a manner as to make the wheel revolve. If the face of the wheel and the surface of the road were absolutely smooth and free from friction, so that the face of the wheel would slide without resistance upon the road, then the effect of the force thus applied would be merely to cause the wheel to turn round, the carriage being stationary, the surface of the wheel would slip or slide upon the road as the wheel is made to revolve. But if, on the other hand, the pressure of the face of the wheel upon the road is such as to produce between them such a degree of adhesion as will render it impossible for the wheel to slide or slip upon the road by the force which is applied to it, the consequence will be, that the wheel can only turn round in obedience to the force which moves it by causing the carriage to advance, so that the wheel will roll upon the road, and the carriage will be moved forward, through a distance equal to the circumference of the wheel, each time it performs a complete revolution. It is obvious that both of these effects may be partially produced; the adhesion of the wheel to the road may be insufficient to prevent slipping altogether, and yet it may be sufficient to prevent the wheel from slipping as fast as it revolves. Under such circumstances the carriage would advance and the wheel would slip. The progressive motion of the carriage during one complete revolution of the wheel would be equal to the difference between the complete circumference of the wheel and the portion through which in one revolution it has slipped. When the construction of travelling steam engines first engaged the attention of engineers, and for a considerable period afterwards, a notion was impressed upon their minds that the adhesion between the face of the wheel and the surface of the road must necessarily be of very small amount, and that in every practical case the wheels thus driven would either slip altogether, and produce no advance of the carriage, or that a considerable portion of the impelling power would be lost by the partial slipping or sliding of the wheels. It is singular that it should never have occurred to the many ingenious persons who for several years were engaged in such experiments and speculations, to ascertain by experiment the actual amount of adhesion in any particular case between the wheels and the road. Had they done so, we should probably now have found locomotive engines in a more advanced state than that to which they have attained. To remedy this imaginary difficulty, Messrs. _Trevithick_ and _Vivian_ proposed to make the external rims of the wheels rough and uneven, by surrounding them with projecting heads of nails or bolts, or by cutting transverse grooves on them. They proposed, in cases where considerable elevations were to be ascended, to cause claws or nails to project from the surface during the ascent, so as to take hold of the road. In seven years after the construction of the first locomotive engine by these engineers, another locomotive engine was constructed by Mr. _Blinkensop_, of Middleton Colliery, near Leeds. He obtained a patent, in 1811, for the application of a rack-rail. The railroad thus, instead of being composed of smooth bars of iron, presented a line of projecting teeth, like those of a cog-wheel, which stretched along the entire distance to be travelled. The wheels on which the engine rolled were furnished with corresponding teeth, which worked in the teeth of the railroad; and, in this way, produced a progressive motion in the carriage. The next contrivance for overcoming this fictitious difficulty, was that of Messrs. _Chapman_, who, in the year 1812, obtained a patent for working a locomotive engine by a chain extending along the middle of the line of railroad, from the one end to the other. This chain was passed once round a grooved wheel under the centre of the carriage; so that, when this grooved wheel was turned by the engine, the chain being incapable of slipping upon it, the carriage was consequently advanced on the road. In order to prevent the strain from acting on the whole length of the chain, its links were made to fall upon upright forks placed at certain intervals, which between those intervals sustained the tension of the chain produced by the engine. Friction-rollers were used to press the chain into the groove of the wheel, so as to prevent it from slipping. This contrivance was soon abandoned, for the very obvious reason that a prodigious loss of force was incurred by the friction of the chain. The following year, 1813, produced a contrivance, of singular ingenuity, for overcoming the supposed difficulty arising from the want of adhesion between the wheels and the road. This was no other than a pair of mechanical legs and feet, which were made to walk and propel in a manner somewhat resembling the feet of an animal. [Illustration: _Fig. 53._] A sketch of these propellers is given in fig. 53. A is the carriage moving on the railroad, L and L´ are the legs, F and F´ the feet. The foot F has a joint at O, which corresponds to the ankle; another joint is placed at K, which corresponds to the knee; and a third is placed at L, which corresponds to the hip. Similar joints are placed at the corresponding letters in the other leg. The knee-joint K is attached to the end of the piston of the cylinder. When the piston, which is horizontal, is pressed outwards, the leg L presses the foot F against the ground, and the resistance forces the carriage A onwards. As the carriage proceeds, the angle K at the knee becomes larger, so that the leg and thigh take a straighter position; and this continues until the piston has reached the end of its stroke. At the hip L there is a short lever, L M, the extremity of which is connected by a cord or chain with a point, S, placed near the shin of the leg. When the piston is pressed into the cylinder, the knee, K, is drawn towards the engine, and the cord, M S, is made to lift the foot, F, from the ground; to which it does not return until the piston has arrived at the extremity of the cylinder. On the piston being again driven out of the cylinder, the foot, F, being placed on the road, is pressed backwards by the force of the piston-rod at K; but the friction of the ground preventing its backward motion, the re-action causes the engine to advance: and in the same manner this process is continued. Attached to the thigh, at N, above the knee, by a joint, is a horizontal rod, N R, which works a rack, R. This rack has beneath it a cog-wheel. This cog-wheel acts in another rack below it. By these means, when the knee K is driven _from_ the engine, the rack R is moved _backwards_; but the cog-wheel, acting on the other rack beneath it, will move the latter _in the contrary direction_. The rack R being then moved _in the same direction with the knee_, K, it follows that the other rack will always be moved _in a contrary direction_. The lower rack is connected by another horizontal rod with the thigh of the leg, L´ F´, immediately above the knee, at N´. When the piston is forced _inwards_, the knee, K´, will thus be forced _backwards_; and when the piston is forced _outwards_, the knee, K´, will be drawn _forwards_. It therefore follows that the two knees, K and K´, are pressed alternately backwards and forwards. The foot, F´, when the knee, K´, is drawn forward, is lifted by the means already described for the foot, F. It will be apparent, from this description, that the piece of mechanism here exhibited is a contrivance derived from the motion of the legs of an animal, and resembling in all respects the fore legs of a horse. It is however to be regarded rather as a specimen of great ingenuity than as a contrivance of practical utility. (86.) It was about this period that the important fact was first ascertained that the adhesion or friction of the wheels with the rails on which they moved was amply sufficient to propel the engine, even when dragging after it a load of great weight; and that in such case, the progressive motion would be effected without any slipping of the wheels. The consequence of this fact rendered totally useless all the contrivances for giving wheels a purchase on the road, such as racks, chains, feet, &c. The experiment by which this was determined appears to have been first tried on the Wylam railroad; where it was proved, that, when the road was level, and the rails clean, the adhesion of the wheels was sufficient, in all kind of weather, to propel considerable loads. By manual labour it was first ascertained how much weight the wheels of a common carriage would overcome without slipping round on the rail; and having found the proportion which that bore to the weight, they then ascertained that the weight of the engine would produce sufficient adhesion to drag after it, on the railroad, the requisite number of wagons.[25] [Footnote 25: Wood on Railroads, 2d edit.] In 1814, an engine was constructed at Killingworth, by Mr. _Stephenson_, having two cylinders with a cylindrical boiler, and working two pair of wheels, by cranks placed at right angles; so that when the one was in full operation, the other was at its dead points. By these means the propelling power was always in action. The cranks were maintained in this position by an endless chain, which passed round two cogged wheels placed under the engine, and which were fixed on the same axles on which the wheels were placed. The wheels in this case were fixed on the axles, and turned with them. [Illustration: _Fig. 54._] This engine is represented in fig. 54., the sides being open, to render the interior mechanism visible. A B is the cylindrical boiler; C C are the working cylinders; D E are the cogged wheels fixed on the axle of the wheels of the engine, and surrounded by the endless chain. These wheels being equal in magnitude, perform their revolutions in the same time; so that, when the crank, F, descends to the lowest point, the crank, G, rises from the lowest point to the horizontal position, D; and, again, when the crank, F, rises from the lowest point to the horizontal position, E, the other crank rises to the highest point; and so on. A very beautiful contrivance was adopted in this engine, by which it was suspended on springs of steam. Small cylinders, represented at H, are screwed by flanges to one side of the boiler, and project within it a few inches; they have free communication at the top with the water or steam of the boiler. Solid pistons are represented at I, which move steam-tight in these cylinders; the cylinders are open at the bottom, and the piston-rods are screwed on the carriage of the engine, over the axle of each pair of wheels, the pistons being presented upwards. As the engine is represented in the figure, it is supported on four pistons, two at each side. The pistons are pressed upon by the water or steam which occupies the upper chamber of the cylinder; and the latter being elastic in a high degree, the engine has all the advantage of spring suspension. The defect of this method of supporting the engine is, that when the steam loses that amount of elasticity necessary for the support of the machine, the pistons are forced into the cylinders, and the bottoms of the cylinders bear upon them. All spring suspension is then lost. This mode of suspension has consequently since been laid aside. In an engine subsequently constructed by Mr. _Stephenson_, for the Killingworth railroad, the mode adopted of connecting the wheels by an endless chain and cog-wheels was abandoned; and the same effect was produced by connecting the two cranks by a straight rod. All such contrivances, however, have this great defect, that, if the fore and hind wheels be not constructed with dimensions accurately equal, there must necessarily be a slipping or dragging on the road. The nature of the machinery requires that each wheel should perform its revolution exactly in the same time; and consequently, in doing so, must pass over exactly equal lengths of the road. If, therefore, the circumference of the wheels be not accurately equal, that wheel which has the lesser circumference must be dragged along so much of the road as that by which it falls short of the circumference of the greater wheel; or, on the other hand, the greater must be dragged in the opposite direction, to compensate for the same difference. As no mechanism can accomplish a perfect equality in four, much less in six, wheels, it may be assumed that a great portion of that dragging effect is a necessary consequence of the principle of this machine; and even were the wheels, in the first instance, accurately constructed, it is not possible that their wear could be so exactly uniform as to continue equal. (87.) The next stimulus which the progress of this invention received, proceeded from the great national work undertaken at Liverpool, by which that town and the extensive commercial mart of Manchester were connected by a double line of railway. When this project was undertaken, it was not decided what moving power it might be most expedient to adopt as a means of transport on the proposed road: the choice lay between horse-power, fixed steam engines, and locomotive engines; but the first, for many obvious reasons, was at once rejected in favour of one or other of the last two. The steam engine may be applied, by two distinct methods, to move wagons either on a turnpike road or on a railway. By the one method the steam engine is fixed, and draws the carriage or train of carriages towards it by a chain extending the whole length of road on which the engine works. By this method the line of road over which the transport is conducted is divided into a number of short intervals, at the extremity of each of which an engine is placed. The wagons or carriages, when drawn by any engine to its own station, or detached, and connected with the extremity of the chain worked by the next stationary engine; and thus the journey is performed, from station to station, by separate engines. By the other method the same engine draws the load the whole journey, travelling with it. The Directors of the Liverpool and Manchester railroad, when that work was advanced towards its completion, employed, in the spring of the year 1829, Messrs. _Stephenson_ and _Lock_ and Messrs. _Walker_ and _Rastrick_, experienced engineers, to visit the different railways where practical information respecting the comparative effects of stationary and locomotive engines was likely to be obtained; and from these gentlemen they received reports on the relative merits, according to their judgment, of the two methods. The particulars of their calculations are given at large in the valuable work of Mr. _Nicholas Wood_ on railways; to which we refer the reader, not only on this, but on many other subjects connected with the locomotive steam engine into which it would be foreign to our subject to enter. The result of the comparison of the two systems was, that the capital necessary to be advanced to establish a line of stationary engines was considerably greater than that which was necessary to establish an equivalent power in locomotive engines; that the annual expense by the stationary engines was likewise greater; and that, consequently, the expense of transport by the latter was greater, in a like proportion. The subjoined table exhibits the results numerically:-- +------------------------+------------+-------------+------------------+ | | | Annual | Expense of | | | Capital. | Expense. | taking a Ton of | | | | | Goods One Mile. | +------------------------+------------+-------------+------------------+ | | £ s. d.| £ s. d.| | | Locomotive Engines | 58,000 0 0 | 25,517 8 2 | 0·164 of a penny.| | Stationary Engines |121,496 7 0 | 42,031 16 5 | 0·269 | | +------------+-------------+------------------+ | Locomotive System--less| 63,496 7 0 | 16,514 8 3 | 0·105 | +------------------------+------------+-------------+------------------+ On the score of economy, therefore, the system of locomotive engines was entitled to a preference; but there were other considerations which conspired with this to decide the choice of the Directors in its favour. An accident occurring in any part of a road worked by stationary engines must necessarily produce a total suspension of work along the entire line. The most vigilant and active attention on the part of every workman, however employed, in every part of the line, would therefore be necessary; but, independently of this, accidents arising from the fracture or derangement of any of the chains, or from the suspension of the working of any of the fixed engines, would be equally injurious, and would effectually stop the intercourse along the line. On the other hand, in locomotive engines an accident could only affect the particular train of carriages drawn by the engine to which the accident might occur; and even then the difficulty could be remedied by having a supply of spare engines at convenient stations along the line. It is true that the _probability_ of accident is, perhaps, less in the stationary than in the locomotive system; but the _injurious consequences_, when accident _does_ happen, are prodigiously greater in the former. "The one system," says Mr. _Walker_, "is like a chain extending from Liverpool to Manchester, the failure of a single link of which would destroy the whole; while the other is like a number of short and unconnected chains," the destruction of any one of which does not interfere with the effect of the others, and the loss of which may be supplied with facility. The decision of the Directors was, therefore, in favour of locomotive engines; and their next measure was to devise some means by which the inventive genius of the country might be stimulated to supply them with the best possible form of engines for this purpose. With this view, it was proposed and carried into effect to offer a prize for the best locomotive engine which might be produced under certain proposed conditions, and to appoint a time for a public trial of the claims of the candidates. A premium of 500_l._ was accordingly offered for the best locomotive engine to run on the Liverpool and Manchester Railway; under the condition that it should produce no smoke; that the pressure of the steam should be limited to 50 lbs. on the inch; and that it should draw at least three times its own weight, at the rate of not less than ten miles an hour; that the engine should be supported on springs, and should not exceed fifteen feet in height. Precautions were also proposed against the consequences of the boiler bursting; and other matters, not necessary to mention more particularly here. This proposal was announced in the spring of 1829, and the time of trial was appointed in the following October. The engines which underwent the trial were, the Rocket, constructed by Mr. _Stephenson_; the Sanspariel, by _Hackworth_; and the Novelty, by Messrs. _Braithwait_ and _Ericson_. Of these, the Rocket obtained the premium. A line of railway was selected for the trial, on a level piece of road about two miles in length, near a place called Rainhill, between Liverpool and Manchester; the distance between the two stations was a mile and a half, and the engine had to travel this distance backwards and forwards ten times, which made altogether a journey of 30 miles. The Rocket performed this journey twice: the first time in 2 hours 14 minutes and 8 seconds; and the second time, in 2 hours 6 minutes and 49 seconds. Its speed at different parts of the journey varied: its greatest rate of motion was rather above 29 miles an hour; and its least, about 11-1/2 miles an hour. The average rate of the one journey was 13-4/10 miles an hour; and of the other, 14-2/20 miles. This was the only engine which performed the complete journey proposed, the others having been stopped from accidents which occurred to them in the experiment. The Sanspariel performed the distance between the stations eight times, travelling 22-1/2 miles in 1 hour 37 minutes and 16 seconds. The greatest velocity to which this engine attained was something less than 23 miles per hour. The Novelty had only passed twice between the stations when the joints of the boiler gave way, and put an end to the experiment. (88.) The great object to be attained in the construction of these engines was, to combine with sufficient lightness the greatest possible heating power. The fire necessarily acts on the water in two ways: first, by its radiant heat; and, second, by the current of heated air which is carried by the draft through the fire, and finally passes into the chimney. To accomplish this object, therefore, it is necessary to expose to both these sources of heat the greatest possible quantity of surface in contact with the water. These ends were attained by the following admirable arrangement in the Rocket:-- [Illustration: _Fig. 55._] [Illustration: _Fig. 56._] This engine is represented in fig. 55. It is supported on four wheels; the principal part of the weight being thrown on one pair, which are worked by the engine. The boiler consists of a cylinder 6 feet in length, with flat ends; the chimney issues from one end, and to the other end is attached a square box, B, the bottom of which is furnished with the grate on which the fuel is placed. This box is composed of two casings of iron, one contained within the other, having between them a space about 3 inches in breadth; the magnitude of the box being 3 feet in length, 2 feet in width, and 3 feet in depth. The casing which surrounds the box communicates with the lower part of the boiler by a pipe marked C; and the same casing at the top of the box communicates with the upper part of the boiler by another pipe marked D. When water is admitted into the boiler, therefore, it flows freely through the pipe C, into the casing which surrounds the furnace or fire-box, and fills this casing to the same level as that which it has in the boiler. When the engine is at work, the boiler is kept about half filled with water; and, consequently, the casing surrounding the furnace is completely filled. The steam which is generated in the water contained in the casing finds its exit through the pipe D, and escapes into the upper part of the boiler. A section of the engine, taken at right angles to its length is represented at fig. 56. Through the lower part of the boiler pass a number of copper tubes of small size, which communicate at one end with the fire-box, and at the other with the chimney, and form a passage for the heated air from the furnace to the chimney. The ignited fuel spread on the grate at the bottom of the fire-box disperses its heat by radiation, and acts in this manner on the whole surface of the casing surrounding the fire-box; and thus raises the temperature of the thin shell of water contained in that casing. The chief part of the water in the casing, being lower in its position than the water in the boiler, acquires a tendency to ascend when heated, and passes into the boiler; so that a constant circulation of the heated water is maintained, and the water in the boiler must necessarily be kept at nearly the same temperature as the water in the casing. The air which passes through the burning fuel, and which fills the fire-box, is carried by the draft through the tubes which extend through the lower part of the boiler; and as these tubes are surrounded on every side with the water contained in the boiler, this air transmits its heat through these tubes to the water. It finally issues into the chimney, and rises by the draft. The power of this furnace must necessarily depend on the power of draft in the chimney; and to increase this, and at the same time to dispose of the waste steam after it has worked the piston, this steam is carried off by a pipe L, which passes from the cylinder to the chimney, and escapes there in a jet which is turned upwards. By the velocity with which it issues from this jet, and by its great comparative levity, it produces a strong current upwards in the chimney, and thus gives force to the draft of the furnace. In fig. 56. the grate-bars are represented at the bottom of the fire-box at F. There are two cylinders, one of which works each wheel; one only appearing in the drawing, fig. 55., the other being concealed by the engine. The spokes which these cylinders work are placed at right angles on the wheels; the wheels being fixed on a common axle, with which they turn. In this engine, the surface of water surrounding the fire-box, exposed to the action of radiant heat, amounted to 20 square feet, which received heat from the surface of 6 square feet of burning fuel on the bars. The surface exposed to the action of the heated air amounted to 118 square feet. The engine drew after it another carriage, containing fuel and water; the fuel used was coke, for the purpose of avoiding the production of smoke. (89.) The Sanspareil of Mr. _Hackworth_ is represented in fig. 57.; the horizontal section being exhibited in fig. 58. [Illustration: _Fig. 57._] [Illustration: _Fig. 58._] The draft of the furnace is produced in the same manner as in the Rocket, by ejecting the waste steam coming from the cylinder into the chimney; the boiler, however, differs considerably from that of the Rocket. A recurved tube passes through the boiler, somewhat similar to that already described in the early engine of Messrs. _Trevithick_ and _Vivian_. In the horizontal section (fig. 58.), D expresses the opening of the furnace at the end of the boiler, beside the chimney. The grate-bars appear at A, supporting the burning fuel; and a curved tube passing through the boiler, and terminating in the chimney, is expressed at B, the direction of the draft being indicated by the arrow; C is a section of the chimney. The cylinders are placed, as in the Rocket, on each side of the boiler; each working a separate wheel, but acting on spokes placed at right angles to each other. The tube in which the grate and flue are placed diminishes in diameter as it approaches the chimney. At the mouth where the grate was placed, its diameter was 2 feet; and it was gradually reduced, so that, at the chimney, its diameter was only 15 inches. The grate-bars extended 5 feet into the tube. The surface of water exposed to the radiant heat of the fire was 16 square feet; and that exposed to the action of the heated air and flame was about 75 square feet. The magnitude of the grate or sheet of burning fuel which radiated heat, was 10 square feet. (90.) The Novelty, of Messrs. _Braithwait_ and _Ericson_, is represented in fig. 59.; and a section of the generator and boiler is exhibited in fig. 60.: the corresponding parts in the two figures are marked by the same letters. [Illustration: _Fig. 59._] A is the generator or receiver, containing the steam which works the engine; this communicates with a lower generator, B, which extends in a horizontal direction the entire length of the carriage. Within the generator, A, is contained the furnace, F, which communicates in a tube, C; carried up through the generator, and terminated at the top by sliding shutters, which exclude the air, and which are only opened to supply fuel to the grate, F. Below the grate the furnace is not open, as usual, to the atmosphere, but communicates by a tube, E, with a bellows, D; which is worked by the engine, and which forces a constant stream of air, by the tube E, through the fuel on F, so as to keep that fuel in vivid combustion. The heated air, contained in the furnace, F, is driven on, by the same force, through a small curved tube marked _e_, which circulates like a worm (as represented in fig. 60.) through the horizontal generator or receiver; and, tapering gradually, until reduced to very small dimensions, it finally issues into the chimney, G. The air, in passing along this tube, imparts its heat to the water by which the tube is surrounded, and is brought to a considerably reduced temperature when discharged into the chimney. The cylinder, which is represented at K, works one pair of wheels, by means of a bell-crank; the other pair, when necessary, being connected with them. [Illustration: _Fig. 60._] In this engine, the magnitude of the surface of burning fuel on the grate-bars is less than 2 square feet; the surface exposed to radiant heat is 9-1/2 square feet; and the surface of water exposed to heated air is about 33 square feet. The superiority of the Rocket may be attributed chiefly to the greater quantity of surface of the water which is exposed to the action of the fire. With a less extent of grate-bars than the Sanspareil, in the proportion of 3 to 5, it exposes a greater surface of water to radiant heat, in the proportion of 4 to 3; and a greater surface of water to heated air, in the proportion of more than 3 to 2. It was found that the Rocket, compared with the Sanspareil, consumed fuel, in the evaporation of a given quantity of water, in the proportion of 11 to 28. The suggestion of using the tubes to conduct through the water the heated air to the chimney is due to Mr. _Booth_, treasurer of the Liverpool and Manchester Railway Company; and, certainly, nothing has been more conducive to the efficiency of the engines since used than this improvement. It is much to be regretted that the ingenious gentleman who suggested this has reaped none of the advantages to which a patentee would be legally entitled.[26] [Footnote 26: Mr. _Booth_ received a part of the premium of 500_l._, but has not participated in any degree in the profits of the manufacture of the engines.] (91.) The great object to be effected in the boilers of these engines is, to keep a small quantity of water at an excessive temperature, by means of a small quantity of fuel kept in the most active state of combustion. To accomplish this, it is necessary, first, so to shape the boiler, furnace, and flues, that the water shall be in contact with as extensive a surface as possible, every part of which is acted on either immediately, by the heat radiating from the fire, or mediately, by the air which has passed through the fire, and which finally rushes into the chimney: and, secondly, that such a forcible draught should be maintained in the furnace, that a quantity of heat shall be extricated from the fuel, by combustion, sufficient to maintain the water at the necessary temperature, and to produce the steam with sufficient rapidity. To accomplish these objects, therefore, the chamber containing the grate should be completely surrounded by water, and should be below the level of the water in the boiler. The magnitude of the surface exposed to radiation should be as great as is consistent with the whole magnitude of the machine. The comparative advantage which the Rocket possessed in these respects over the other engines will be evident on inspection. In the next place, it is necessary that the heat, which is absorbed by the air passing through the fuel, and keeping it in a state of combustion, should be transferred to the water before the air escapes into the chimney. Air being a bad conductor of heat, to accomplish this it is necessary that the air in the flues should be exposed to as great an extent of surface in contact with the water as possible. No contrivance can be less adapted for the attainment of this end than one or two large tubes traversing the boiler, as in the earliest locomotive engines: the body of air which passes through the centre of these tubes had no contact with their surface, and, consequently, passed into the chimney at nearly the same temperature as that which it had when it quitted the fire. The only portion of air which imparted its heat to the water was that portion which passed next to the surface of the tube. Several methods suggest themselves to increase the surface of water in contact with a given quantity of air passing through it. This would be accomplished by causing the air to pass between plates placed near each other, so as to divide the current into thin strata, having between them strata of water, or it might be made to pass between tubes differing slightly in diameter, the water passing through an inner tube, and being also in contact with the external surface of the outer tube. Such a method would be similar in principle to the steam-jacket used in _Watt's_ steam engines, or to the condenser of _Cartwright's_ engine already described. But, considering the facility of constructing small tubes, and of placing them in the boiler, that method, perhaps, is, on the whole, the best in practice; although the shape of a tube, geometrically considered, is most unfavourable for the exposure of a fluid contained in it to its surface. The air which passes from the fire-chamber, being subdivided as it passes through the boiler by a great number of very small tubes, may be made to impart all its excess of heat to the water before it issues into the chimney. This is all which the most refined contrivance can effect. The Rocket engine was traversed by 25 tubes, each 3 inches in diameter; and the principle has since been carried to a much greater extent. The abstraction of a great quantity of heat from the air before it reaches the chimney is attended with one consequence, which, at first view, would present a difficulty apparently insurmountable; the chimney would, in fact, lose its power of draught. This difficulty, however, was removed by using the waste steam, which had passed from the cylinder after working the engine, for the purpose of producing a draught. This steam was urged through a jet presented upwards in the chimney, and driven out with such force in that direction as to create a sufficient draught to work the furnace. It will be observed that the principle of draught in the Novelty is totally distinct from this: in that engine the draught is produced by a bellows worked by the engine. The question, as far as relates to these two methods, is, whether more power is lost in supplying the steam through the jet, as in the Rocket, or in working the bellows, as in the Novelty. The force requisite to impel the steam through the jet must be exerted by the returning stroke of the piston, and, consequently, must rob the working effect to an equivalent amount. On the other hand, the power requisite to work the bellows in the Novelty must be subducted from the available power of the engine. The former method is found to be the more effectual and economical. The importance of these details will be understood, when it is considered that the only limit to the attainment of speed by locomotive engines is the power to produce in a given time a certain quantity of steam. Each stroke of the piston causes one revolution of the wheels, and consumes two cylinders full of steam: consequently, a cylinder of steam corresponds to a certain number of feet of road travelled over: hence it is that the production of a rapid and abundant supply of heat, and the imparting of that heat quickly and effectually to the water, is the key to the solution of the problem to construct an engine capable of rapid motion. The method of subdividing the flue into tubes was carried much further by Mr. _Stephenson_ after the construction of the Rocket; and, indeed, the principle was so very obvious, that it is only surprising that, in the first instance, tubes of smaller diameter than 3 inches were not used. In engines since constructed, the number of tubes vary from 90 to 120, the diameter being reduced to 2 inches or less, and in some instances tubes have been introduced, even to the number of 150, of 1-1/2 inch diameter. In the Meteor, 20 square feet are exposed to radiation, and 139 to the contact of heated air; in the Arrow, 20 square feet to radiation, and 145 to the contact of heated air. The superior economy of fuel gained by this means will be apparent by inspecting the following table, which exhibits the consumption of fuel which was requisite to convey a ton weight a mile in each of four engines, expressing also the rate of the motion:-- +------------------+---------------+-----------------+ | |Average rate of|Consumption of | | Engines. | speed in miles|Coke in pounds | | | per hour. |per ton per mile.| +------------------+---------------+-----------------+ |No. 1. Rocket | 14 | 2·41 | | 2. Sanspareil | 15 | 2·47 | | 3. Phoenix | 12 | 1·42 | | 4. Arrow | 12 | 1·25 | +------------------+---------------+-----------------+ (92.) Since the period at which the railway was opened for the actual purposes of transport, the locomotive engines have been in a state of progressive improvement. Scarcely a month has passed without suggesting some change in the details, by which fuel might be economised, the production of steam rendered more rapid, the wear of the engine rendered slower, the proportionate strength of the different parts improved, or some other desirable end obtained. The consequence of this has been, that the particular engines to which we have alluded, and others of the same class, without having, as it were, lived their natural life, or without having been worn out by work, have been laid aside to give place to others of improved powers. By the exposure of the cylinders to the atmosphere in the Rocket, and engines of a similar form, a great waste of heat was incurred, and it was accordingly determined to remove them from the exterior of the boiler, and to place them within a casing immediately under the chimney: this chamber was necessarily kept warm by its proximity to the end of the boiler, but more by the current of heated air which constantly rushed into it from the tubes. This change, also, rendered necessary another, which improved the working of the engine. In the earlier engines the motion of the piston was communicated to the wheel by a connecting rod attached to one of the spokes on the exterior of the wheel, as represented in fig. 55. By the change to which we have just alluded, the cylinders being placed between the wheels under the chimney, this mode of working became inapplicable, and it was considered better to connect the piston-rods with two cranks placed at right angles on the axles of the great wheels. By this means, it was found that the working of the machine was more even, and productive of less strain than in the former arrangement. On the other hand, a serious disadvantage was incurred by the adoption of a cranked axle. The weakness necessarily arising from such a form of axle could only be counterbalanced by great thickness and weight of metal; and even this precaution does not prevent the occasional fracture of such axles at the angles of the cranks. The advantages, however, of this plan, on the whole, are considered to predominate. In the most improved engines in present use two safety-valves are provided, of which only one is in the power of the engine-man. The tubes being smaller and more numerous than in the earlier engines, the heat is more completely extracted from the air before it enters the chimney. A powerful draft is rendered still more necessary by the smallness of the tubes: this is effected by forcing the steam which has worked the pistons through a contracted orifice, presented upwards in the chimney, by the regulation of which any degree of draft may be obtained. One of the most improved engines at present in use is represented in fig. 61. A represents the cylindrical boiler, the lower half of which is traversed by tubes, as described in the Rocket. They are usually from 80 to 100 in number, and about 1-1/2 inch in diameter; the boiler is about 7 feet in length; the fire-chamber is attached to one end of it, at F, as in the Rocket, and similar in construction; the cylinders are inserted in a chamber at the other end, immediately under the chimney. The piston-rods are supported in the horizontal position by guides; and connecting rods extend from them, under the engine, to the two cranks placed on the axle of the large wheels. The effects of any inequality in the road are counteracted by springs, on which the engine rests; the springs being below the axle of the great wheels, and above that of the less. The steam is supplied to the cylinders, and withdrawn, by means of the common sliding valves, which are worked by an eccentric wheel placed on the axle of the large wheels of the carriage. The motion is communicated from this eccentric wheel to the valve by sliding rods. The stand is placed for the attendant at the end of the engine, next the fire-place, F; and two levers, L, project from the end, which communicate with the valves by means of rods, by which the engine is governed, so as to stop or reverse the motion. [Illustration: _Fig. 61._] The wheels of these engines have been commonly constructed of wood, with strong iron tires, furnished with flanges adapted to the rails. But Mr. _Stephenson_ has recently substituted, in some instances, wheels of iron with hollow spokes. The engine draws after it a tender carriage containing the fuel and water; and, when carrying a light load, is capable of performing the whole journey from Liverpool to Manchester without a fresh supply of water. When a heavy load of merchandise is drawn, it is usual to take in water at the middle of the trip. (93.) In reviewing all that has been stated, it will be perceived that the efficiency of the locomotive engines used on this railway is mainly owing to three circumstances: 1st, The unlimited power of draft in the furnace, by projecting the waste steam into the chimney; 2d, The unlimited abstraction of heat from the air passing from the furnace, by Mr. _Booth's_ ingenious arrangement of tubes traversing the boiler; and, 3d, Keeping the cylinders warm, by immersing them in the chamber under the chimney.[27] There are many minor details which might be noticed with approbation, but these constitute the main features of the improvements, and should never, for a moment, be lost sight of by projectors of locomotive engines. [Footnote 27: Mr. Robert Stephenson, whose experience and skill in the construction of locomotives attaches great importance to this condition. It has lately, however, been abandoned by some other engine-makers, for the purpose of getting rid of the cranked axle which must accompany it.] The successive introduction of improvements in the engines, some of which we have mentioned, has been accompanied by corresponding accessions to their practical power, and to the economy of fuel; and they have now arrived at a point which is as far beyond the former expectations of the most sanguine locomotive projectors, as it assuredly is short of the perfection of which these wonderful machines are still susceptible. In the spring of the year 1832, I made several experiments on the Manchester railway, with a view to determine, in the actual state of the locomotive engines at that time, their powers with respect to the amount of load and the economy of fuel. Since that time I am not aware that, in these respects, the engine has received any material improvement. The following are the particulars of three experiments thus made:-- I. On Saturday, the 5th of May, the engine called the "Victory" took 20 wagons of merchandise, weighing gross 92 tons 19 cwt. 1 qr., together with the tender containing fuel and water, of the weight of which I have no account, from Liverpool to Manchester (30 miles,) in 1 h. 34 min. 45 sec. The train stopped to take in water half-way, for 10 minutes, not included in the above mentioned time. On the inclined plane rising 1 in 96, and extending 1-1/2 mile, the engine was assisted by another engine called the "Samson," and the ascent was performed in 9 minutes. At starting, the fire-place was well filled with coke, and the coke supplied to the tender accurately weighed. On arriving at Manchester the fire-place was again filled, and the coke remaining in the tender weighed. The consumption was found to amount to 929 pounds net weight, being at the rate of one third of a pound per ton per mile. Speed on the level was 18 miles an hour; on a fall of 4 feet in a mile, 21-1/2 miles an hour; fall of 6 feet in a mile, 25-1/2 miles an hour; on the rise over Chatmoss, 8 feet in a mile 17-5/8 miles an hour; on level ground sheltered from the wind, 20 miles an hour. The wind was moderate, but direct ahead. The working wheels slipped three times on Chatmoss, and the train was retarded from 2 to 3 minutes. The engine, on this occasion, was not examined before or after the journey, but was presumed to be in good working order. II. On Tuesday, the 8th of May, the same engine performed the same journey, with 20 wagons, weighing gross 90 tons 7 cwt. 2 qrs., exclusive of the unascertained weight of the tender. The time of the journey was 1 h. 41 min. The consumption of coke 1040 lbs. net weight, estimated as before. Rate of speed:-- Level 17-5/8 miles per hour. Fall of 4 feet in a mile 22 ---- 6 22-1/2 Rise of 8 15 On this occasion there was a high wind ahead on the quarter, and the connecting rod worked hot, owing to having been keyed too tight. On arriving at Manchester, I caused the cylinders to be opened, and found that the pistons were so loose, that the steam blew through the cylinders with great violence. By this cause, therefore, the machine was robbed of a part of its power during the journey; and this circumstance may explain the slight decrease in speed, and increase in the consumption of fuel, with a lighter load in this journey compared with that performed on the 5th of May. The Victory weighs 8 tons 2 cwt., of which 5 tons 4 cwt. rest on the drawing wheels. The cylinders are 11 inches diameter, and 16 inches stroke; and the diameter of the drawing wheels is 5 feet. III. On the 29th of May, the engine called the "Samson," (weighing 10 tons 2 cwt., with 14-inch cylinders, and 16-inch stroke; wheels 4 feet 6 inches diameter, both pairs being worked by the engine; steam 50 lbs. pressure, 130 tubes) was attached to 50 wagons, laden with merchandise; net weight about 150 tons; gross weight, including wagons, tender, &c., 223 tons 6 cwt. The engine with this load travelled from Liverpool to Manchester (30 miles) in 2 h. and 40 min., exclusive of delays upon the road for watering, &c., being at the rate of nearly 12 miles an hour. The speed varied according to the inclinations of the road. Upon a level, it was 12 miles an hour; upon a descent of 6 feet in a mile, it was 16 miles an hour: upon a rise of 8 feet in a mile, it was about 9 miles an hour. The weather was calm, the rails very wet; but the wheels did not slip, even in the slowest speed, except at starting, the rails being at that place soiled and greasy with the slime and dirt to which they are always exposed at the stations. The coke consumed in this journey, exclusive of what was raised in getting up the steam, was 1762 lbs., being at the rate of a quarter of a pound per ton per mile. (94.) From the above experiments it appears that a locomotive engine, in good working order, with its full complement of load, is capable of transporting weights at an expense in fuel amounting to about 4 ounces of coke per ton per mile. The attendance required on the journey is that of an engine-man and a fire-boy; the former being paid 1_s._ 6_d._ for each trip of 30 miles, and the latter 1_s._ In practice, however, we are to consider, that it rarely happens that the full complement of load can be sent with the engines; and when lesser loads are transported, the _proportionate expense_ must for obvious reasons, be greater. The practical expenditure of fuel on the Liverpool and Manchester line may, perhaps, be fairly estimated at half a pound of coke per ton per mile. (95.) Having explained the power and efficiency of these locomotive engines, it is now right to notice some of the defects under which they labour. The great original cost, and the heavy expense of keeping the engines used on the railway in repair, have pressed severely on the resources of the undertaking. One of the best constructed of the later engines costs originally about 800_l._ It may be hoped that, by the excitement of competition, the facilities derived from practice, and from the manufacture of a greater number of engines of the same kind, some reduction of this cost may be effected. The original cost, however, is far from being the principal source of expense: the wear and tear of these machines, and the occasional fracture of those parts on which the greatest strain has been laid, have greatly exceeded what the directors had anticipated. Although this source of expense must be in part attributed to the engines not having yet attained that state of perfection, in the proportion and adjustment of their parts, of which they are susceptible, and to which experience alone can lead, yet there are some obvious defects which demand attention. The heads of the boilers are flat, and formed of iron, similar to the material of the boilers themselves. The tubes which traverse the boiler were, until recently, copper, and so inserted into the flat head or ends as to be water-tight. When the boiler is heated, the tubes are found to expand in a greater degree than the other parts of the boiler; which frequently causes them either to be loosened at the extremities, so as to cause leakage, or to bend from want of room for expansion. The necessity of removing and refastening the tubes causes, therefore, a constant expense. It will be recollected that the fire-place is situated at one end of the boiler, immediately below the mouths of the tubes: a powerful draught of air, passing through the fire, carries with it ashes and cinders, which are driven violently through the tubes, and especially the lower ones, situated near the fuel. These tubes are, by this means, subject to rapid wear, the cinders continually acting upon their interior surface. After a short time it becomes necessary to replace single tubes, according as they are found to be worn, by new ones; and it not unfrequently happens, when this is neglected, that tubes burst. After a certain length of time the engines require new tubing, which is done at the expense of about 70_l._, allowing for the value of the old tubes. This wear of the tubes might possibly be avoided by constructing the fire-place in a lower position, so as to be more removed from their mouths; or, still more effectually, by interposing a casing of metal, which might be filled with water, between the fire-place and those tubes which are the most exposed to the cinders and ashes. The unequal expansion of the tubes and boilers appears to be an incurable defect, if the present form of the engine be retained. If the fire-place and chimney could be placed at the same end of the boiler, so that the tubes might be recurved, the unequal expansion would then produce no injurious effect; but it would be difficult to clean the tubes if they were exposed, as they are at present, to the cinders. The next source of expense arises from the wear of the boiler-head, which is exposed to the action of the fire. These require constant patching and frequent renewal. A considerable improvement has lately been introduced into the method of tubing, by substituting brass for copper tubes. We are not aware that the cause of this improvement has been discovered; but it is certain, whatever be the cause, that brass tubes are subject to considerably slower wear than copper. It has been said by some whose opinions are adverse to the advantage of railways, but more especially to the particular species of locomotive engines now under consideration, that the repairs of one of these engines cost so great a sum as 1500_l._ per annum, and that the directors now think of abandoning them, or adopting either stationary engines or horse-power. As to the first of these statements I must observe, that the expense of repairs of such machines should never be computed in reference to _time_, but rather to the work done, or the distance travelled over. I have ascertained that engines frequently travel a distance of from 25,000 to 30,000 miles before they require new tubing. During that work, however, single tubes are, of course, occasionally renewed, and other repairs are made, the expense of which may safely be stated as under the original cost of the engine. The second statement, that the company contemplate substituting stationary engines, or horses, for locomotives, is altogether at variance with the truth. Whatever improvements may be contemplated in locomotives, the directors assuredly have not the slightest intention of going back in the progress of improvement, in the manner just mentioned. The expense of locomotive power having so far exceeded what was anticipated at the commencement of the undertaking, it was thought advisable, about the beginning of the year 1834, to institute an inquiry into the causes which produced the discrepancy between the estimated and actual expenses, with a view to the discovery of some practical means by which they could be reduced. The directors of the company, for this purpose, appointed a sub-committee of their own body, assisted by Mr. _Booth_, their treasurer, to inquire and report respecting the causes of the amount of this item of their expenditure, and to ascertain whether any and what measures could be devised for the attainment of greater economy. A very able and satisfactory report was made by this committee, or, to speak more correctly by Mr. _Booth_. It appears that, previous to the establishment of the railway, Messrs. _Walker_ and _Rastrick_, engineers, were employed by the company to visit various places where steam power was applied on railways, for the purpose of forming an estimate of the probable expense of working the railway by locomotive and by fixed power. These engineers recommended the adoption of locomotive power, and their estimate was, that the transport might be effected at the rate of .278 of a penny, or very little more than a farthing per ton per mile. In the year 1833, five years after this investigation took place, it was found that the actual cost was .625 of a penny, or something more than a halfpenny per ton per mile, being considerably above double the estimated rate. Mr. _Booth_ very properly directed his inquiries to ascertain the cause of this discrepancy, by comparing the various circumstances assumed by Messrs. _Walker_ and _Rastrick_, in making their estimate, with those under which the transport was actually effected. The first point of difference which he observed was the speed of transport: the estimate was founded on an assumed _speed_ of ten miles an hour, and it was stated that a fourfold speed would require an addition of 50 per cent. to the power, without taking into account wear and tear. Now the actual speed of transport being double the speed assumed in the statement, Mr. _Booth_ holds it to be necessary to add 25 per cent. on that score. The next point of difference is in the amount of the loads: the estimate is founded upon the assumption, that every engine shall start with its full complement of load, and that with this it shall go the whole distance. "The facts, however, are," says Mr. _Booth_, "that, instead of a _full load_ of profitable carriage _from_ Manchester, about half the wagons _come back empty_, and, instead of the tonnage being conveyed the whole way, many thousand tons are conveyed only half the way; also, instead of the daily work being uniform, it is extremely fluctuating." It is further remarked, that in order to accomplish the transport of goods from the branches and from intermediate places, engines are despatched several times a day, from both ends of the line, _to clear the road_; the object of this arrangement being rather to lay the foundation of a beneficial intercourse in future, than with a view to any immediate profit. Mr. _Booth_ makes a rough estimate of the disadvantages arising from these circumstances by stating them at 33 per cent. in addition to the original estimate. The next point of difference is the fuel. In the original estimate _coal_ is assumed as the fuel, and it is taken at the price of five shillings and tenpence per ton: now the act of parliament forbids the use of coal which would produce smoke; the company have, therefore, been obliged to use _coke_, at seventeen shillings and sixpence a ton. Taking coke, then, to be equivalent to coal, ton for ton, this would add .162 to the original estimate. These several discrepancies being allowed for, and a proportional amount being added to the original estimate, the amount would be raised to .601 of a penny per ton per mile, which is within one fortieth of a penny of the actual cost. This difference is considered to be sufficiently accounted for by the wear and tear produced by the very rapid motion, more especially when it is considered that many of the engines were constructed before the engineer was aware of the great speed that would be required. "What then," says Mr. _Booth_, in the Report already alluded to, "is the result of these opposite and mutually counteracting circumstances? and what is the present position of the company in respect of their moving power? Simply, that they are still in a course of experiment, to ascertain practically the best construction, and the most durable materials, for engines required to transport greater weights, and at greater velocities, than had, till very recently, been considered possible; and which, a few years ago, it had not entered into the imagination of the most daring and sanguine inventor to conceive: and, farther, that these experiments have necessarily been made, not with the calm deliberation and quiet pace which a salutary caution recommends,--making good each step in the progress of discovery before advancing another stage,--but amidst the bustle and responsibilities of a large and increasing traffic; the directors being altogether ignorant of the time each engine would last before it would be laid up as inefficient, but compelled to have engines, whether good or bad; being aware of various defects and imperfections, which it was impossible at the time to remedy, yet obliged to keep the machines in motion, under all the disadvantages of heavy repairs, constantly going on during the night, in order that the requisite number of engines might be ready for the morning's work. Neither is this great experiment yet complete; it is still going forward. But the most prominent difficulties have been in a great measure surmounted, and your committee conceive, that they are warranted in expecting, that the expenditure in this department will, ere long, be materially reduced, more especially when they consider the relative performances of the engines at the _present time_ compared with what it was two years ago." In the half year ending 31st December, 1831, the six best engines performed as follows:-- Miles. Planet 9,986 Mercury 11,040 Jupiter 11,618 Saturn 11,786 Venus 12,850 Etna 8,764 ------ Making in all 66,044 ------ In the half year ending 31st December, 1833, the six best engines performed as follows:-- Miles. Jupiter 16,572 Saturn 18,678 Sun 15,552 Etna 17,763 Ajax 11,678 Firefly 15,608 ------ Making in all 95,851 ------ (96.) The advantages derivable from railroads are greatly abridged by the difficulty arising from those changes of level to which all roads are necessarily liable; but in the case of railroads, from causes peculiar to themselves, these changes of level occasion great inconvenience. To explain the nature of these difficulties, it will be necessary to consider the relative proportion which must subsist between the power of traction on a level and on an inclined plane. On a level railroad the force of traction necessary to propel any load, placed on wheel carriages of the construction now commonly used, may perhaps be estimated at 7-1/2 pounds,[28] for every ton gross in the load; that is to say, if a load of one ton gross were placed upon wheel carriages upon a level railroad, the traces of horses drawing it would be stretched with a force equivalent to 7-1/2 pounds. If the load amounted to two or three tons, the tension of the traces would be increased to 15 or 22-1/2 pounds, and so on. The necessity of this force of traction, arising from the want of perfect smoothness in the road, and from the friction of the wheels and axles of the carriages, must be the same whether the road be level or inclined; and consequently, in ascending an inclined plane, the same force of traction will be necessary in addition to that which arises from the tendency of the load to fall down the plane. This latter tendency is always in the proportion of the elevation of the plane to its length; that is to say, a plane which rises 1 foot in 100 will give a weight of 100 tons a tendency to fall down the plane amounting to 1 ton, and would therefore add 1 ton to the force of traction necessary for such a load on a level. [Footnote 28: The estimate commonly adopted by engineers at present is 9 pounds per ton. I have no doubt, however, that this is too high. I am now (November, 1835,) engaged in an extensive course of experiments on different railways, with a view to determine with precision this and other points connected with the full developement of their theory; and I have reason to believe, from the observations I have already made, that even 7-1/2 pounds per ton is above the average force of traction upon the level.] Now since 7-1/2 pounds is very nearly the 300th part of a ton, it follows that if an inclination upon a railroad rises at the rate of 1 foot in 300, or, what is the same, 17-1/2 feet in a mile, such an acclivity will add 7-1/2 pounds per ton to the force of traction. This acclivity therefore would require a force of traction twice as great as a level. In like manner a rise of 35 feet in a mile would require three times the force of traction of a level, 52-1/2 feet in a mile four times that force, and so on. In fact, for every 7 feet in a mile which an acclivity rises, 3 pounds per ton will be added to the force of traction. If we would then ascertain the power necessary to pull a load up any given acclivity upon a railroad, we must first take 7-1/2 pounds as the force necessary to overcome the common resistance of the road, and then add 3 pounds for every 7 feet which the acclivity rises per mile. For example, suppose an acclivity to rise at the rate of 70 feet in a mile, the force of traction necessary to draw a ton up it would be thus calculated:-- Friction 7-1/2 lbs. 70 feet = 10 times 3 lbs. 30 ------ Total force 37-1/2 It will be apparent, therefore, that if a railroad undulates by inclined planes, even of the most moderate inclinations, the propelling power to be used upon it must be of such a nature as to be capable of increasing its intensity in a great degree, according to the elevation of the planes which it has to encounter. A plane which rises 52-1/2 feet per mile presents to the eye scarcely the appearance of an ascent, and yet requires the power of traction to be increased in a fourfold proportion. It is the property of animal power, that within certain limits its energy can be put forth at will, according to the exigency of the occasion; but the intensity of mechanical power, in the instance now considered, cannot so conveniently be varied, except indeed within narrow limits. In the application of locomotive engines upon railways the difficulty arising from inclined planes has been attempted to be surmounted by several methods, which we shall now explain. 1. Upon arriving at the foot of the plane the load is divided, and the engine carries it up in several successive trips, descending the plane unloaded after each trip. The objection to this method is the delay which it occasions,--a circumstance which is incompatible with a large transport of passengers. From what has been stated, it would be necessary, when the engine is fully loaded on a level, to divide its load into four parts, to be successively carried up when the incline rises 52 feet per mile. This method has been practised in the transport of merchandise occasionally, when heavy loads were carried on the Liverpool and Manchester line, upon the Rainhill incline. 2. A subsidiary or assistant locomotive engine may be kept in constant readiness at the foot of each incline, for the purpose of aiding the different trains, as they arrive, in ascending. The objection to this mode is the cost of keeping such an engine with its boiler continually prepared, and its steam up. It would be necessary to keep its fire continually lighted, whether employed or not; otherwise, when the train would arrive at the foot of the incline, it should wait until the subsidiary engine was prepared for work. In cases where trains would start and arrive at stated times, this objection, however, would have less force. This method is at present generally adopted on the Liverpool and Manchester line. This method, however, cannot be profitably applied to planes of any considerable length. 3. A fixed steam engine may be erected on the crest of the incline, so as to communicate by ropes with the train at the foot. Such an engine would be capable of drawing up one or two trains together, with their locomotives, according as they would arrive, and no delay need be occasioned. This method requires that the fixed engine should be kept constantly prepared for work, and the steam continually up in the boiler. This expedient is scarcely compatible with a large transit of passengers, except at the terminus of a line. 4. In working on the level, the communication between the boiler and the cylinder in the locomotives may be so restrained by partially closing the throttle valve, as to cause the pressure upon the piston to be less in a considerable degree than the pressure of steam in the boiler. If under such circumstances a sufficient pressure upon the piston can be obtained to draw the load on the level, the throttle valve may be opened on approaching the inclined plane, so as to throw on the piston a pressure increased in the same proportion as the previous pressure in the boiler was greater than that upon the piston. If the fire be sufficiently active to keep up the supply of steam in this manner during the ascent, and if the rise be not greater in proportion than the power thus obtained, the locomotive will draw the load up the incline without further assistance. It is, however, to be observed, that in this case the load upon the engine must be less than the amount which the adhesion of its working wheels with the railroad is capable of drawing; for this adhesion must be adequate to the traction of the same load up the incline, otherwise whatever increase of power might be obtained by opening the throttle valve, the drawing wheels would revolve without causing the load to advance. This method has been generally practised upon the Liverpool and Manchester line in the transport of passengers; and, indeed, it is the only method yet discovered, which is consistent with the expedition necessary for that species of traffic. The objections to this method are, the necessity of maintaining a much higher pressure in the boiler than is sufficient for the purposes of the load upon more level parts of the line. In the practice of this method considerable aid may be derived also by suspending the supply of feeding water during the ascent. It will be recollected that a reservoir of cold water is placed in the tender which follows the engine, and that the water is driven from this reservoir into the boiler by a forcing-pump, which is worked by the engine itself. This pump is so constructed that it will supply as much cold water as is equal to the evaporation, so as to maintain constantly the same quantity of water in the boiler. But it is evident, on the other hand, that the supply of this water has a tendency to check the rate of evaporation, since in being raised to the temperature of the water with which it mixes, it must absorb a considerable portion of the heat supplied by the fire. With a view to accelerate the production of steam, therefore, in ascending the inclines, the engine-man may suspend the action of the forcing-pump, and thereby stop the supply of cold water to the boiler; the evaporation will go on with increased rapidity, and the exhaustion of water produced by it will be repaid by the forcing-pump on the next level, or still more effectually on the next descending incline. Indeed the feeding pump may be made to act in descending an incline if necessary, when the action of the engine itself is suspended, and when the train descends by its own gravity, in which case it will perform the part of a brake upon the descending train. This method, on railroads intended for passengers, may be successfully applied on inclines which do not exceed 18 feet in a mile; and, with a sacrifice of the expense of locomotive power, inclines so steep as 36 feet in a mile may be worked in this manner. As, however, the sacrifice is considerable, it will, perhaps, be always better to work the more steep inclines by assistant engines. 5. The mechanical connexion between the piston of the cylinder and the points of contact of the working wheels with the road may be so altered, upon arriving at the incline, as to give the piston a greater power over the working wheels. This may be done in an infinite variety of ways, but hitherto no method has been suggested sufficiently simple to be applicable in practice; and even were any means suggested which would accomplish this, unless the intensity of the impelling power were at the same time increased, it would necessarily follow that the speed of the motion would be diminished in exactly the same proportion as the power of the piston over the working wheels would be increased. Thus, on the inclined plane, which rises 55 feet per mile, upon the Liverpool line, the speed would be diminished to nearly one fourth of its amount upon the level. Whatever be the method adopted to surmount inclined planes upon a railway, inconvenience attends the descent upon them. The motion down the incline by the force of gravity is accelerated; and if the train be not retarded, a descent of any considerable length, even at a small elevation, would produce a velocity which would be attended with great danger. The shoe used to retard the descent down hills on turnpike roads cannot be used upon railroads, and the application of brakes to the faces of the wheels is likewise attended with some uncertainty. The friction produced by the rapid motion of the wheel sometimes sets fire to wood, and iron would be inadmissible. The action of the steam on the piston may be reversed, so as to oppose the motion of the wheels; but even this is attended with peculiar difficulty. From all that has been stated, it will be apparent that, with our present knowledge, considerable inclines are fatal to the profitable performance on a railway, and even small inclinations are attended with great inconvenience.[29] [Footnote 29: A contrivance might be applied in changes of level in railroads somewhat similar to locks in a canal. The train might be rolled upon a platform which might be raised by machinery; and thus at the change of level there would be as it were _steps_ from one level to another, up which the loads would be lifted by any power applied to work the machinery. The advantage in this case would be, that the trains might be adapted to work always upon a level.] (97.) To obtain from the locomotive steam engines now used on the railway the most powerful effects, it is necessary that the load placed on each engine should be very considerable. It is not possible, with our present knowledge, to construct and work three locomotive engines of this kind, each drawing a load of 30 tons, at the same expense and with the same effect as one locomotive engine drawing 90 tons. Hence arises what must appear an inconvenience and difficulty in applying these engines to one of the most profitable species of transport--the transport of passengers. It is impracticable, even between places of the most considerable intercourse to obtain loads of passengers sufficiently great at each trip to maintain such an engine working on a railway.[30] The difficulty of collecting so considerable a number of persons, at any stated hour, to perform the journey, is obvious; and therefore, the only method of removing the inconvenience is _to cause the same engine which transports passengers also to transport goods_, so that the goods may make up the requisite supplement to the load of passengers. In this way, provided the traffic in goods be sufficient, such engines may start with their full complement of load, whatever be the number of passengers. [Footnote 30: On the occasion of races held at Newton, a place about 15 miles from Liverpool, two engines were sent, with trains of carriages, to take back to Liverpool the visitors to the races. Some accident prevented one of the engines from working on the occasion, and both trains were attached to the same engine: 800 persons were on this occasion drawn by the single engine to Liverpool in the space of about an hour.] (98.) In comparing the extent of capital, and the annual expenditure of the Liverpool and Manchester line, and adopting it as a modulus in estimating the expenses of similar undertakings projected elsewhere, there are several circumstances to which it is important to attend. I have already observed on the large waste of capital in the item of locomotive engines which ought to be regarded as little more than experimental machines, leading to a rapid succession of improvements. Most of these engines are still in good working order, but have been abandoned for the reasons already assigned. Other companies will, of course, profit by the experience which has been thus purchased at a high price by the Liverpool Company. This advantage in favour of future companies will go on increasing until such companies have their works completed. A large portion of the current expense of a line of railway is independent of its length; and is little less for the line connecting Liverpool and Manchester, than it would be for a line connecting Birmingham with Liverpool or London. The establishments of resident engineers, coach and wagon yards, &c. at the extremities of the line, would be little increased by a very great increase in the length of the railway; and the same observation will apply to other heads of expenditure. It has been the practice of the canal companies between Liverpool and Manchester to warehouse the goods transported between these towns, without any additional charge beyond the price of transport. The Railway Company, in competing with the canals, were, of course, obliged to offer like advantages: this compelled them to invest a considerable amount of capital in the building of extensive warehouses, and to incur the annual expense of porterage, salaries, &c. connected with the maintenance of such storage. In a longer line of railway such expenses (if necessary at all) would not be proportionally increased. (99.) The comparison of steam-transport with the transport by horses, even when working on a railway, exhibits the advantage of this new power in a most striking point of view. To comprehend these advantages fully, it will be necessary to consider the manner in which animal power is expended as a means of transport. The portion of the strength of a horse available for the purpose of a load depends on the speed of a horse's motion. To this speed there is a certain limit, at which the whole power of the horse will be necessary to move his own body, and at which, therefore, he is incapable of carrying any load; and, on the other hand, there is a certain load which the horse is barely able to support, but incapable of moving with any useful speed. Between these two limits there is a certain rate of motion at which the useful effect of the animal is greatest. In horses of the heavier class, this rate of motion may be taken on the average as that of 2 miles an hour; and in the lighter description of horses, 2-1/2 miles an hour. Beyond this speed, the load which they are capable of transporting diminishes in a very rapid ratio as the speed increases: thus, if 121 express the load which a horse is able to transport a given distance in a day, working at the rate of four miles an hour, the same horse will not be able to transport more than the load expressed by 64, _the same distance_, at 7 miles an hour; and, at 10 miles an hour, the load which he can transport will be reduced to 25. The most advantageous speed at which a horse can work being 2 miles an hour, it is found that, at this rate, working for 10 hours daily, he can transport 12 tons, on a level railway, a distance of 20 miles; so that the whole effect of a day's work may be expressed by 240 tons carried 1 mile. But this rate of transport is inapplicable to the purposes of travelling; and therefore it becomes necessary, when horses are the moving power, to have carriages for passengers distinct from those intended for the conveyance of goods; so that the goods may be conveyed at that rate of speed at which the whole effect of the horse will be the greatest possible; while the passengers are conveyed at that speed which, whatever the cost, is indispensably necessary. The weight of an ordinary mail-coach is about two tons; and, on a tolerably level turnpike road, it travels at the rate of 10 miles an hour. At this rate, the number of horses necessary to keep it constantly at work, including the spare horses indispensably necessary to be kept at the several stages, is computed at the rate of a horse per mile. Assuming the distance between London and Birmingham at 100 miles, a mail-coach running between these two places would require 100 horses; making the journey to and from Birmingham daily. The performance, therefore, of a horse working at this rate may be estimated at 2 tons carried 2 miles per day, or 4 tons carried 1 mile in a day. The force of traction on a good turnpike road is at least 20 times its amount on a level railroad. It therefore follows, that the performance of a horse on a railroad will be 20 times the amount of its performance on a common road under similar circumstances. We may, therefore, take the performance of a horse working at 10 miles an hour, on a level railroad, at 80 tons conveyed 1 mile daily. The best locomotive engines used on the Liverpool railway are capable of transporting 150 tons on a level railroad at the same rate; and, allowing the same time for stoppage, its work per day would be 150 tons conveyed 200 miles, or 30,000 tons conveyed 1 mile; from which it follows, that the performance of one locomotive engine of this kind is equivalent to that of 7500 horses working on a good turnpike road, or to 375 horses working on a railway. The consumption of fuel requisite for this performance, with the most improved engines used at present on the Manchester and Liverpool line, would be at the rate of eight[31] ounces of coke per ton per mile, including the waste of fuel incurred by the stoppages. Thus the daily consumption of fuel, under such circumstances, would amount to 15000 lbs. of coke; and 2 lbs. of coke daily would perform the work of one horse on a good turnpike road; and 40 lbs. of coke daily would perform the work of one horse on a railway. [Footnote 31: In an experimental trip with a heavy train at 12 miles an hour, I found the consumption of coke to be only _four_ ounces per ton per hour. I believe, however, the practical consumption in ordinary work to be very nearly eight ounces.] In this comparison, the engine is taken at its most advantageous speed, while horse-power is taken at its least advantageous speed, if regard be only had to the total quantity of weight transported to a given distance. But, in the case above alluded to, speed is an indispensable element; and steam, therefore, possesses this great advantage over horse power, that _its most advantageous speed is that which is at once adapted to all the purposes of transport, whether of passengers or of goods_. (100.) The effects of steam compared with horse-power, at lower rates of motion, will exhibit the advantages of the former, though in a less striking degree. An eight-horse wagon commonly weighs 8 tons, and travels at the rate of 2-1/2 miles an hour. Strong horses working in this way can travel 8 hours daily; thus each horse performs 20 miles a day. The performance, therefore, of each horse may be taken as equivalent to 20 tons transported 1 mile; and his performance on a railway being 20 times this amount, may be taken as equivalent to 400 tons transported 1 mile a day. The performance of a horse working in this manner is, therefore, 5 times the performance of a horse working at 10 miles an hour; the latter effecting only the performance of 4 tons transported 1 mile per day on a good turnpike road, or 80 tons on a railway. We shall hence obtain the proportion of the performance of horses working in wagons to that of a locomotive steam engine. Since 2 lbs. of coke are equivalent to the daily performance of a horse in a mail-coach, and 40 lbs. on a railway, at 10 miles an hour, it follows that 10 lbs. will be equivalent to the performance of a horse on a turnpike road, and 200 lbs. on a railway, at 2-1/2 miles an hour. Since a locomotive engine can perform the daily work of 7500 mail-coach horses, it follows that it performs the work of 1500 wagon horses. These results must be understood to be subject to modifications in particular cases, and to be only average calculations. Different steam-engines, as well as different horses, varying in their performance to a considerable extent; and the roads on which horses work being in different states of perfection, and subject to different declivities, the performance must vary accordingly. In the practical comparison, also, of the results of so powerful an agent as steam applied on railways, with so slight a power as that of horses on common roads, it must be considered that the great subdivision of load, and frequent times of starting, operate in favour of the performance of horses; inasmuch as it would oftener occur that engines capable of transporting enormous weights would start with loads inferior to their power, than would happen in the application of horse-power, where small loads may start at short intervals. This, in fact, constitutes a practical difficulty in the application of steam engines on railroads; and will, perhaps, for the present, limit their application to lines connecting places of great intercourse. The most striking effect of steam power, applied on a railroad, is the extreme speed of transport which is attained by it; and it is the more remarkable, as this advantage never was foreseen before experience proved it. When the Liverpool and Manchester line was projected, the transport of heavy goods was the object chiefly contemplated; and although an intercourse in passengers was expected, it was not foreseen that this would be the greatest source of revenue to the proprietors. The calculations of future projectors will, therefore, be materially altered, and a great intercourse in passengers will be regarded as a necessary condition for the prosperity of such an undertaking. If this advantage of speed be taken into account, horse-power can scarcely admit of any comparison whatever with steam-power on a railway. In the experiments which I have already detailed, it appears that a steam engine is capable of drawing 90 tons at the rate of about 20 miles an hour, and that it could transport that weight twice between Liverpool and Manchester in about 3 hours. Two hundred and seventy horses working in wagons would be necessary to transport the same load the same distance in a day. It may be objected, that this was an experiment performed under favourable circumstances, and that assistance was obtained at the difficult point of the inclined plane. In the ordinary performance, however, of the engines drawing merchandise, where great speed is not attempted, the rate of motion is not less than 15 miles an hour. In the trains which draw passengers, the chief difficulty of maintaining a great speed arises from the stoppages on the road to take up and let down passengers. There are two classes of carriages at present used: the first class stops but once, at a point half-way between Liverpool and Manchester, for the space of a few minutes. This class performs the thirty miles in an hour and a half, and sometimes in 1 hour and 10 minutes. On the level part of the road its common rate of motion is 27 miles an hour; and I have occasionally marked its rate, and found it above 30 miles an hour. But these, which are velocities obtained in the regular working of the engines for the transport of passengers and goods, are considerably inferior to the power of the present locomotives with respect to speed. I have made some experimental trips, in which more limited loads were placed upon the engines, by which I have ascertained that very considerably increased rates of motion are quite practicable. In one experiment I placed a carriage containing 36 persons upon an engine, with which I succeeded in obtaining the velocity of about 48 miles an hour, and I believe that an engine loaded only with its own tender has moved over 15 miles in 15 minutes. It will then perhaps be asked, if the engines possess these great capabilities of speed, why they have not been brought into practical operation on the railroad, where, on the other hand, the average speed when actually in motion, does not exceed 25 miles an hour? In answer to this it may be stated, that the distance of 30 miles between Liverpool and Manchester is performed in an hour and a half, and that 10 trains of passengers pass daily between these places: the mail, also, is transmitted three times a day between them. It is obvious that any greater speed than this, in so short a distance, would be quite needless. When, however, more extended lines of road shall be completed, the circumstances will be otherwise, and the despatch of mails especially will demand attention. Full trains of passengers, commonly transported upon the Manchester railroad, weigh about 50 tons gross: with a lighter load, a lighter and more expeditious engine might be used. The expense of transport with such an engine would of course be increased; but for this the increased expedition there would be ample compensation. When, therefore, London shall have been connected with Liverpool, by a line of railroad through Birmingham, the commercial interest of these places will naturally direct attention to the greatest possible expedition of intercommunication. For the transmission of mails, doubtless, peculiar engines will be built, adapted to lighter loads and greater speed. With such engines, the mails, with a limited number of passengers, will be despatched; and, apart from any possible improvement which the engines may hereafter receive, and looking only at their present capabilities, I cannot hesitate to express my conviction that such a load may be transported at the rate of above 60 miles an hour. If we may indulge in expectations of what the probable improvements of locomotive steam engines may effect, I do not think that even double that speed is beyond the limits of mechanical probability. On the completion of the line of road from the metropolis to Liverpool we may, therefore, expect to witness the transport of mails and passengers in the short space of three hours. There will probably be about three posts a day between these and intermediate places. The great extension which the application of steam to the purpose of inland transport is about to receive from the numerous railroads which are already in progress, and from a still greater number of others which are hourly projected, impart to these subjects of inquiry considerable interest. Neither the wisdom of the philosopher, nor the skill of the statistician, nor the foresight of the statesman is sufficient to determine the important consequences by which the realization of these schemes must affect the progress of the human race. How much the spread of civilization, the diffusion of knowledge, the cultivation of taste, and the refinement of habits and manners depend upon the easy and rapid inter-mixture of the constituent elements of society, it is needless to point out. Whilst population exists in detached and independent masses, incapable of transfusion amongst each other, their dormant affinities are never called into action, and the most precious qualities of each are never imparted to the other. Like solids in physics, they are slow to form combinations; but when the quality of fluidity has been imparted to them, when their constituent atoms are loosened by fusion, and the particles of each flow freely through and among those of the other, then the affinities are awakened, new combinations are formed, a mutual interchange of qualities takes place, and compounds of value far exceeding those of the original elements are produced. Extreme facility of intercourse is the fluidity and fusion of the social masses, from whence such an activity of the affinities results, and from whence such an inestimable interchange of precious qualities must follow. We have, accordingly, observed, that the advancement in civilization and the promotion of intercourse between distant masses of people have ever gone on with contemporaneous progress, each appearing occasionally to be the cause or the consequence of the other. Hence it is that the urban population is ever in advance of the rural in its intellectual character. But, without sacrificing the peculiar advantages of either, the benefits of intercourse may be extended to both, by the extraordinary facilities which must be the consequence of the locomotive projects now in progress. By the great line of railroad which is in progress from London to Birmingham, the time and expense of passing between these places will probably be halved, and the quantity of intercourse at least quadrupled, if we consider only the direct transit between the terminal points of the line; but if the innumerable tributary streams which will flow from every adjacent point be considered, we have no analogies on which to build a calculation of the enormous increase of intercommunication which must ensue. Perishable vegetable productions necessary for the wants of towns must at present be raised in their immediate suburbs; these, however, where they can be transported with a perfectly smooth motion at the rate of twenty miles an hour, will be supplied by the agricultural labourer of more distant points. The population engaged in towns, no longer limited to their narrow streets, and piled story over story in confined habitations, will be free to reside at distances which would now place them far beyond reach of their daily occupations. The salubrity of cities and towns will thus be increased by spreading the population over a larger extent of surface, without incurring the inconvenience of distance. Thus the advantages of the country will be conferred upon the town, and the refinement and civilization of the town will spread their benefits among the rural population.[32] [Footnote 32: Some of the preceding observations appeared in an article contributed by me to the British and Foreign Review.] (101.) The quantity of canal property in these countries gives considerable interest to every inquiry which has for its object the relative advantage of this mode of transport, compared with that of railways, whether worked by horses or by steam-power; and this interest has been greatly increased by the recent extension of railway projects. This is a subject which I shall have occasion, in another work, to examine in all its details; and, therefore, in this place I shall advert to it but very briefly. When a floating body is moved on a liquid, it will suffer a resistance, which will depend partly upon the transverse section of the part immersed, and partly on the speed with which it is moved. It is evident that the quantity of the liquid which it must drive before it will depend upon that transverse section, and the velocity with which it will impel the liquid will depend upon its own speed. Now, so long as the depth of its immersion remains the same, it is demonstrable that the resistance will increase in proportion to the square of the speed; that is, with a double velocity there will be a fourfold resistance, with a triple velocity a ninefold resistance, and so on. Again, if the part immersed should be increased or diminished by any cause, the resistance, on that account alone, will be increased or diminished in the same proportion. From these circumstances it will be apparent that a vessel floating on water, if moved with a certain speed, will require four times the impelling force to carry it forward with double the speed, unless the depth of its immersion be diminished as its speed is increased. Some experiments which have been made upon canals with boats of a peculiar construction, drawn by horses, have led to the unexpected conclusion, that, after a certain speed has been attained, the resistance, instead of being increased, has been diminished. This fact is not at variance with the law of resistance already explained. The cause of the phenomenon is found in the fact, that when the velocity has attained a certain point, the boat gradually rises out of the water; so that, in fact, the immersed part is diminished. The two conditions, therefore, which determine the resistance, thus modify each other: while the resistance is, on the one hand, increased in proportion to the square of the speed, it is, on the other hand, diminished in proportion to the diminution of the transverse section of the immersed part of the vessel. It would appear that, at a certain velocity, these two effects neutralise each other; and, probably, at higher velocities the immersed part may be so much diminished as to diminish the resistance in a greater degree than it is increased by the speed, and thus actually to diminish the power of traction. It is known that boats are worked on some of the Scottish canals, and also on the canal which connects Kendal with Preston, by which passengers are transported, at the rate of about ten miles an hour, exclusive of the stoppages at the locks, &c. The power of horses, exerted in this way, is, of course, exerted more economically than they could be worked at the same speed on common roads; and, probably, it is as economical as they would be worked by railroad. It is, probably, more economical than the transport of passengers by steam upon railroads; but the speed is considerably less, nor, from the nature of the impelling power, is it possible that it can be increased. There is reason to suppose that a like effect takes place with steam vessels. Upon increasing the power of the engines in some of the Post Office steam packets, it has been found, that, while the time of performing the same voyage is diminished, the consumption of fuel is also diminished. Now, since the consumption of fuel is in the direct ratio of the moving power, and the latter in the direct ratio of the resistance, it follows that the resistance must in this case be likewise diminished. (102.) When a very slow rate of travelling is considered, the useful effects of horse-power applied on canals is somewhat greater than the effect of the same power applied on railways; but at all speeds above three miles an hour, the effect on railways is greater; and when the speed is considerable, the canal becomes wholly inapplicable, while the railway loses none of its advantages. At three miles an hour, the performance of a horse on a canal and a railway is in the proportion of four to three to the advantage of the canal; but at four miles an hour his performance on a railway has the advantage in very nearly the same proportion. At six miles an hour, a horse will perform three times more work on a railway than on a canal. At eight miles an hour, he will perform nearly five times more work. But the circumstance which, so far as respects passengers, must give railways, as compared with canals, an advantage which cannot be considered as less than fatal to the latter, is the fact, that the great speed and cheapness of transit attainable upon a railway by the aid of steam-power will always secure to such lines not only a monopoly of the travelling, but will increase the actual amount of that source of profit in an enormous proportion, as has been already made manifest between Liverpool and Manchester. Before the opening of the railway there were about twenty-five coaches daily running between Liverpool and Manchester. If we assume these coaches on the average to take ten persons at each trip, it will follow that the number of persons passing daily between these towns was about 500. Let us, then, assume that 3000 persons passed weekly. This gives in six months 78,000. In the six months which terminated on the 31st of December 1831, the number of passengers between the same towns, exclusive of any taken up on the road, was 256,321; and if some allowance be made for those taken up on the road, the number may be fairly stated at 300,000. At present there is but one coach on the road between Liverpool and Manchester; and it follows, therefore, that, besides taking the monopoly of the transit in travellers, the actual number has been already increased in a fourfold proportion. The monopoly of the transit of passengers thus secured to the line of communication by railroad will always yield so large a profit as to enable merchandise to be carried at a comparatively low rate. In light goods, which require despatch, it is obvious that the railroad will always command the preference; and the question between that mode of communication and canals is circumscribed to the transit of those classes of heavy goods in which even a small saving in the cost of transport is a greater object than despatch. (103.) The first effect which the Liverpool railroad produced on the Liverpool and Manchester canals was a fall in the price of transport; and at this time, I believe, the cost of transport per ton on the railroads and on the canals is the same. It will, therefore, be naturally asked, this being the case, why the greater speed and certainty of the railroad does not in every instance give it the preference, and altogether deprive the canals of transport? This effect, however, is prevented by several local and accidental causes, as well as by direct influence and individual interest. A large portion of the commercial and manufacturing population of Liverpool and Manchester have property invested in the canals, and are deeply interested to sustain them in opposition to the railway. Such persons will give the preference to the canals in their own business, and will induce those over whom they have influence to do so in every case where speed of transport is not absolutely indispensable. Besides these circumstances, the canal communicates immediately with the shipping at Liverpool, and it ramifies in various directions through Manchester, washing the walls of many of the warehouses and factories for which the goods transported are destined. The merchandise is thus transferred from the shipping to the boat, and brought directly to the door of its owner, or _vice versâ_. If transported by the railway, on the other hand, it must be carried to the station at one extremity; and, when transported to the station at the other, it has still to be carried to its destination in different parts of the town. These circumstances will sufficiently explain why the canals still retain, and may probably continue to retain, a share of the traffic between these great marts. CHAPTER XI. LOCOMOTIVE ENGINES ON TURNPIKE ROADS. Railways and Turnpike Roads compared. -- Mr. Gurney's inventions. -- His Locomotive Steam Engine. -- Its performances. -- Prejudices and errors. -- Committee of the House of Commons. -- Convenience and safety of Steam Carriages. -- Hancock's Steam Carriage. -- Mr. N. Ogle. -- Trevithick's invention. -- Proceedings against Steam Carriages. -- Turnpike Bills. -- Steam Carriage between Gloucester and Cheltenham. -- Its discontinuance. -- Report of the Committee of the Commons. -- Present State and Prospects of Steam Carriages. (104.) We have hitherto confined our observations to steam-power as a means of transport applied on railways, but modern speculation has not stopped here. Several attempts have been made, and some of them attended with considerable success, to work steam-carriages on turnpike roads. The practicability of this project has been hitherto generally considered to be very questionable; but if we carry back our view to the various epochs in the history of the invention of the steam engine, we shall find the same doubt, and the same difficulty, started at almost every important step in its progress. In comparing the effect of a turnpike road with that of a railway, there are two circumstances which obviously give facility and advantage to the railway. One is, that the obstructions to the rolling motion of the wheels, produced by the inequalities of the surface, are very considerably less on a railway than on a road; less in the proportion of at least 1 to 20. This proportion, however, must depend much on the nature of the road with which the railway is compared. It is obvious that a well-constructed road will offer less resistance than one ill constructed; and it is ascertained that the resistance of a Macadamised road is considerably more than that of a road well paved with stones: the decision of this question, therefore, must involve the consideration of another, viz. whether roads may not be constructed by pavement or otherwise, smoother and better adapted to carriages moved in the manner of steam-carriages than the roads now used for horse-power? But besides the greater smoothness of railroads compared with turnpike roads, they have another advantage, which we suspect to have been considerably exaggerated by those who have opposed the project for steam-carriages on turnpike roads. One of the laws of adhesion, long since developed by experiment, and known to scientific men, is, that it is greater between the surfaces of bodies of the same nature than between those of a different nature. Thus between two metals of the same kind it is greater than between two metals of different kinds. Between two metals of any kind it is greater than between metal and stone, or between metal and wood. Hence, the wheels of steam-carriages running on a railroad have a greater adhesion with the road, and therefore offer a greater resistance to slip round without the advance of the carriage, than wheels would offer on a turnpike road; for on a railroad the iron tire of the wheel rests in contact with the iron rail, while on a common road the iron tire rests in contact with the surface of stone, or whatever material the road may be composed of. Besides this, the dust and loose matter which necessarily collect on a common road, when pressed between the wheels and the solid base of the road act somewhat in the manner of rollers, and give the wheels a greater facility to slip than if the road were swept clean, and the wheels rested in immediate contact with its hard surface. The truth of this observation is illustrated on the railroads themselves, where the adhesion is found to be diminished whenever the rails are covered with any extraneous matter, such as dust or moist clay. Although the adhesion of the wheels of a carriage with a common road, however, be less than those of the wheels of a steam-carriage with a railroad, yet still the actual adhesion on turnpike roads is greater in amount than has been generally supposed, and is quite sufficient to propel carriages dragging after them loads of large amount. The relative facility with which carriages are propelled on railroads and turnpike roads equally affects any moving power, whether that of horses or steam engines; and whether loads be propelled by the one power or the other, the railroad, as compared with the turnpike road, will always possess the same proportionate advantage; and a given amount of power, whether of the one kind or the other, will always perform a quantity of work less in the same proportion on a turnpike road than on a railroad. But, on the other hand, the expense of original construction, and of maintaining the repairs of a railroad, is to be placed against the certain facility which it offers to draught. In the attempts which have been made to adapt locomotive engines to turnpike roads, the projectors have aimed at the accomplishment of two objects: first, the construction of lighter and smaller engines; and, secondly, increased power. These ends, it is plain, can only be attained, with our present knowledge, by the production of steam of very high temperature and pressure, so that the smallest volume of steam shall produce the greatest possible mechanical effect. The methods of propelling the carriage have been in general similar to that used in the railroad engines, viz. either by cranks placed on the axles, the wheels being fixed upon the same axles, or by connecting the piston-rods with the spokes of the wheels, as in the engine represented in fig. 55. In some carriages, the boiler and moving power, and the body of the carriage which bears the passengers, are placed on the same wheels. In others, the engine is placed on a separate carriage, and draws after it the carriage which transports the passengers, as is always the case on railways. The chief difference between the steam engines used on railways, and those adapted to propel carriages on turnpike roads, is in the structure of the boiler. In the latter it is essential that, while the power remains undiminished, the boiler should be lighter and smaller. The accomplishment of this has been attempted by various contrivances for so distributing the water, as to expose a considerable quantity of surface in contact with it to the action of the fire; spreading it in thin layers on flat plates; inserting it between plates of iron placed at a small distance asunder, the fire being admitted between the intermediate plates; dividing it into small tubes, round which the fire has play; introducing it between the surfaces of cylinders placed one within another, the fire being admitted between the alternate cylinders,--have all been resorted to by different projectors. (105.) First and most prominent in the history of the application of steam to the propelling of carriages on turnpike roads, stands the name of Mr. GOLDSWORTHY GURNEY, a medical gentleman and scientific chemist, of Cornwall. In 1822, Mr. _Gurney_ succeeded Dr. Thompson as lecturer on chemistry at the Surrey Institution; and, in consequence of the results of some experiments on heat, his attention was directed to the project of working steam carriages on common roads; and since 1825 he has devoted his exertions in perfecting a steam engine capable of attaining the end he had in view. Numerous other projectors, as might have been expected, have followed in his wake. Whether they, or any of them, by better fortune, greater public support, or more powerful genius, may outstrip him in the career on which he has ventured, it would not, perhaps, at present, be easy to predict. But whatever be the event, to Mr. _Gurney_ is due, and will be paid, the honour of first proving the practicability of the project; and in the history of the adaptation of the locomotive engine to common roads, his name will stand before all others in point of time, and the success of his attempts will be recorded as the origin and cause of the success of others in the same race. The incredulity, opposition, and even ridicule, with which the project of Mr. _Gurney_ was met, are very remarkable. His views were from the first opposed by engineers, without one exception. The contracted habit of mind, sometimes produced by an education chiefly, if not exclusively, directed to a merely practical object, subsequently confirmed by exclusively practical pursuits, may, perhaps, in some degree, account for this. But, I confess, it has not been without surprise that I have observed, during the last ten years, the utter incredulity which has prevailed among men of general science on this subject,--an incredulity which the most unequivocal practical proof has scarcely yet dispelled. "Among scientific men," says Mr. _Gurney_, "my opinion had not a single supporter, with the exception of the late Dr. _Wollaston_." The mistake which so long prevailed in the application of locomotives on railroads, and which, as we have shown, materially retarded the progress of that invention, was shared by Mr. _Gurney_. Without reducing the question to the test of experiment, he took for granted, in his first attempts, that the adhesion of the wheels with the road was too slight to propel the carriage. He was assured, he says, by eminent engineers, that this was a point settled by actual experiment. It is strange, however, that a person of his quickness and sagacity did not inquire after the particulars of these "actual experiments." So, however, it was; and, taking for granted the inability of the wheels to propel, he wasted much labour and skill in the contrivance of levers and propellers, which acted on the ground in a manner somewhat resembling the feet of horses, to drive the carriage forward. After various fruitless attempts of this kind, the experience acquired in the trials to which they gave rise at last forced the truth upon his notice, and he found that the adhesion of the wheels was not only sufficient to propel the carriage heavily laden on level roads, but was capable of causing it to ascend all the hills which occur on ordinary turnpike roads. In this manner it ascended all the hills between London and Barnet, London and Stanmore, Stanmore Hill, Brockley Hill, and mounted Old Highgate Hill, the last at one point rising one foot in nine. It would be foreign to my present object to detail minutely all the steps by which Mr. _Gurney_ gradually improved his contrivance. This, like other inventions, has advanced by a series of partial failures; but it has at length attained that state, in which, by practice alone, on a more extensive scale, a further degree of perfection can be obtained. (106.) The boiler of this engine is so constructed that there is no part of it, not even excepting the grate-bars, in which metal exposed to the action of the fire is out of contact with water. If it be considered how rapidly the action of an intense furnace destroys metal when water is not present to prevent the heat from accumulating, the advantage of this circumstance will be appreciated. I have seen the bars of a new grate, never before used, melted in a single trip between Liverpool and Manchester; and the inventor of another form of locomotive engine has admitted to me that his grate-bars, though of a considerable thickness, would not last more than a week. In the boiler of Mr. _Gurney_, the grate-bars themselves are tubes filled with water, and form, in fact, a part of the boiler itself. This boiler consists of three strong metal cylinders placed in a horizontal position one above the other. A section, made by a perpendicular or vertical plane, is represented in fig. 62. The ends of the three cylinders, just mentioned, are represented at D, H, and I. In the side of the lowest cylinder D are inserted a row of tubes, a ground plan of which is represented in fig. 63. These tubes, proceeding from the side of the lowest cylinder D, are inclined slightly upwards, for a reason which I shall presently explain. From the nature of the section, only one of these tubes is visible in fig. 62. at C. The other extremities of these tubes at A are connected with the same number of upright tubes, one of which is expressed at E. The upper extremities G of these upright tubes are connected with another set of tubes K, equal in number, proceeding from G, inclining slightly upwards, and terminating in the second cylinder H. [Illustration: _Fig. 62._] [Illustration: _Fig. 63._] An end view of the boiler is exhibited in fig. 64., where the three cylinders are expressed by the same letters. Between the cylinders D and H there are two tubes of communication B, and two similar tubes between the cylinders H and I. From the nature of the section these appear only as a single tube in fig. 62. From the top of the cylinder I proceeds a tube N, by which steam is conducted to the engine. [Illustration: _Fig. 64._] It will be perceived that the space F is enclosed on every side by a grating of tubes, which have free communication with the cylinders D and H, which cylinders have also a free communication with each other by the tubes B. It follows, therefore, that if water be supplied to the cylinder I, it will descend through the tubes, and first filling the cylinder D and the tubes C, will gradually rise in the tubes B and E, will next fill the tubes K and the cylinder H. The grating of water pipes C E K forms the furnace, the pipes C being the fire-bars, and the pipes E and K being the back and roof of the stove. The fire-door, for the supply of fuel, appears at M, fig. 64. The flue issuing between the tubes F is conducted over the tubes K, and the flame and hot air are carried off through a chimney. That portion of the heat of the burning fuel, which in other furnaces destroys the bars of the grate, is here expended in heating the water contained in the tubes C. The radiant heat of the fire acts upon the tubes K, forming the roof of the furnace, on the tube E at the back of it, and partially on the cylinders D and H, and the tubes B. The draft of hot air and flame passing into the flue at A, acts upon the posterior surfaces of the tubes E, and the upper sides of the tubes K, and finally passes into the chimney. As the water in the tubes C E K is heated, it becomes specifically lighter than water of a less temperature, and consequently acquires a tendency to ascend. It passes, therefore, rapidly into H. Meanwhile the colder portions descend, and the inclined positions of the tubes C and K give play to this tendency of the heated water, so that a prodigiously rapid circulation is produced, when the fire begins to act upon the tubes. When the water acquires such a temperature that steam is rapidly produced, steam bubbles are constantly formed in the tubes surrounding the fire; and if these remained stationary in the tubes, the action of the fire would not only decompose the steam, but render the tubes red hot, the water not passing through them to carry off the heat. But the inclined position of the tubes, already noticed, effectually prevents this injurious consequence. A steam bubble which is formed either in the tubes C or K, having a tendency to ascend proportional to its lightness as compared with water, necessarily rushes upwards; if in C towards A, and if in K towards H. But this motion of the steam is also aided by the rapid circulation of the water which is continually maintained in the tubes, as already explained, otherwise it might be possible, notwithstanding the levity of steam compared with water, that a bubble might remain in a narrow tube without rising. I notice this more particularly, because the burning of the tubes is a defect which has been erroneously, in my opinion, attributed to this boiler. To bring the matter to the test of experiment, I have connected two cylinders, such as D and H, by a system of glass tubes, such as represented at C E K. The rapid and constant circulation of the water was then made evident: bubbles of steam were formed in the tubes, it is true; but they passed with great rapidity into the upper cylinder, and rose to the surface, so that the glass tubes never acquired a higher temperature than that of the water which passed through them. This I conceive to be the chief excellence of Mr. _Gurney's_ boiler. It is impossible that any part of the metal of which it is formed can receive a greater temperature than that of the water which it contains; and that temperature, as is obvious, can be regulated with the most perfect certainty and precision. I have seen the tubes of this boiler, while exposed to the action of the furnace, after that action has continued for a long period of time, and I have never observed the soot which covers them to redden, as it would do if the tube attained a certain temperature. Every part of the boiler being cylindrical, it has the form which, mechanically considered, is most favourable to strength, and which, within given dimensions, contains the greatest quantity of water. It is also free from the defects arising from unequal expansion, which are found to be most injurious in tubular boilers. The tubes C and K can freely expand in the direction of their length, without being loosened at their joints, and without straining any part of the apparatus; the tubes E, being short, are subject to a very slight degree of expansion; and it is obvious that the long tubes, with which they are connected, will yield to this without suffering a strain, and without causing any part of the apparatus to be loosened. When water is converted into steam, any foreign matter which may be combined with it is disengaged, and is deposited on the bottom of the vessel in which the water is evaporated. All boilers, therefore, require occasional cleansing, to prevent the crust thus formed from accumulating; and this operation, for obvious reasons, is attended with peculiar difficulty in tubular boilers. In the case before us, the crust of deposited matter would gather and thicken in the tubes C and K, and if not removed, would at length choke them. But besides this, it would be attended with a still worse effect; for, being a bad conductor, it would intercept the heat in its transit from the fire to the water and would cause the metal of the tube to become unduly heated. Mr. _Gurney_ of course foresaw this inconvenience, and contrived an ingenious chemical method of removing it by occasionally injecting through the tubes such an acid as would combine with the deposite, and carry it away. This method was perfectly effectual; and although its practical application was found to be attended with difficulty in the hands of common workmen, Mr. _Gurney_ was persuaded to adhere to it by the late Dr. _Wollaston_, until experience proved the impossibility of getting it effectually performed, under the circumstances in which boilers are commonly used. Mr. _Gurney_ then adopted the more simple, but not less effectual, method of removing the deposite by mechanical means. Opposite the mouths of the tubes, and on the other side of the cylinders D and H, are placed a number of holes, which, when the boiler is in use, are stopped by pieces of metal screwed into them. When the tubes require to be cleaned these stoppers are removed, and an iron scraper is introduced through the holes into the tubes, which being passed backwards and forwards, removes the deposite. The boiler may be thus cleaned by a common labourer in half a day, at an expense of about 1_s._ 6_d._ The frequency of the periods at which a boiler of this kind requires cleaning must depend, in a great degree, on the nature of the water which is used; one in daily use with the water of the river Thames would not require cleaning more than once in a month. Mr. _Gurney_ states that with water of the most unfavourable description, once a fortnight would be sufficient. (107.) In the more recent boilers constructed by Mr. _Gurney_, he has maintained the draught through the furnace, by the method of projecting the waste steam into the chimneys; a method so perfectly effectual, that it is unlikely to be superseded by any other. The objection which has been urged against it in locomotive engines, working on turnpike roads, is, that the noise which it produces has a tendency to frighten horses. In the engines on the Liverpool road, the steam is allowed to pass directly from the eduction pipe of the cylinder to the chimney, and it there escapes in puffs corresponding with the alternate motion of the pistons, and produces a noise, which, although attended with no inconvenience on the railroad, would certainly be objectionable on turnpike roads. In the engine used in Mr. _Gurney's_ steam-carriage, the steam which passes from the cylinders is conducted to a receptacle, which he calls a blowing box. This box serves the same purpose as the upper chamber of a smith's bellows. It receives the steam from the cylinders in alternate puffs, but lets it escape into the chimney in a continued stream by a number of small jets. Regular draught is by this means produced, and no noise is perceived. Another exit for the steam is also provided, by which the conductor is enabled to increase or diminish, or to suspend altogether, the draught in the chimney, so as to adapt the intensity of the fire to the exigencies of the road. This is a great convenience in practice; because, on some roads, a draught is scarcely required, while on others a powerful blast is indispensable. Connected with this blowing box, is another ingenious apparatus of considerable practical importance. The pipe through which the water which feeds the boiler is conducted to it from the tank is carried through this blowing box, within which it is coiled in a spiral form, so that an extensive thread of the feeding water is exposed to the heat of the waste steam which has escaped from the cylinders, and which is enclosed in this blowing box. In passing through this pipe the feeding water is raised from the ordinary temperature of about 60° to the temperature of 212°. The fuel necessary to accomplish this is, therefore, saved, and the amount of this is calculated at 1/6th of all that is necessary to evaporate the water. Thus, 1/6th of the expense of fuel is saved. But, what is much more important in a locomotive engine, a portion of the weight of the engine is saved without any sacrifice of its power. There is still another great advantage attending this process. The feeding water in the worm just mentioned, while it takes up the heat from the surrounding steam in the blowing box, condenses 1/6th of the waste steam, which is thence conducted to the tank, from which the feeding water is pumped, saving in this manner 1/6th in weight and room of the water necessary to be carried in the carriage for feeding the boiler.[33] [Footnote 33: In boilers constructed for stationary purposes, or for steam navigation, the steam-pipe, after it has passed through the blowing box, is continued and made to form a series of returned flues over the boiler, so as to take up the waste heat after it has passed the boiler, and before it reaches the chimney. But in locomotive engines for common roads, it has been found by experience, that the power gained by the waste heat is not sufficient to propel the weight of the material necessary for taking it up.] So far as the removal of all inconvenience arising from noise, this contrivance has been proved by experience to be perfectly effectual.[34] [Footnote 34: See Report of the Commons.] In all boilers, the process of violent ebullition causes a state of agitation in the water, and a number of counter currents, by which, as the steam is disengaged from the surface of the water, it takes with it a considerable quantity of water in mechanical mixture. If this be carried through the cylinders, since it possesses none of the qualities of steam, and adds nothing to the power of the vapour with which it is combined, it causes an extensive waste of heat and water, and produces other injurious effects. In every boiler therefore, some means should be provided for the separation of the water thus suspended in the steam, before the steam is conducted to the cylinder. In ordinary plate boilers, the large space which remains above the surface of the water serves this purpose. The steam being there subject to no agitation or disturbance, the water mechanically suspended in it descends by its own gravity, and leaves pure steam in the upper part. In the small tubular boilers, this has been a matter, however, of greater difficulty. The contracted spaces in which the ebullition takes place, causes the water to be mixed with the steam in a greater quantity than could happen in common plate boilers: and the want of the same steam-room renders the separation of the water from the steam a matter of some difficulty. These inconveniences have been overcome by a succession of contrivances of great ingenuity. I have already described the rapid and regular circulation effected by the arrangement of the tubes. By this a regularity in the currents is established, which alone has a tendency to diminish the mixture of water with the steam. But in addition to this, a most effectual method of separation is provided in the vessel I, which is a strong iron cylinder of some magnitude, placed out of the immediate influence of the fire. A partial separation of the steam from the water takes place in the cylinder H; and the steam with the water mechanically suspended in it, technically called moist steam, rises into the _separator_ I. Here, being free from all agitation and currents, and being, in fact, quiescent, the particles of water fall to the bottom, while the pure steam remains at the top. This separator, therefore, serves all the purposes of the steam-room above the surface of the water in the large plate boilers. The dry steam is thus collected and ready for the supply of the engine through the tube N, while the water, which is disengaged from it, is collected at the bottom of the separator, and is conducted through the tube T to the lowest vessel D, to be again circulated through the boiler. The pistons of the engine work on the axles of the hind wheels of the carriage which bears the engine, by cranks, as in the locomotives on the Manchester railway, so that the axle is kept in a constant state of rotation while the engine is at work. The wheels placed on this axle are not permanently fixed or keyed upon it, as in the Manchester locomotives; but they are capable of turning upon it in the same manner as ordinary carriage wheels. Immediately within these wheels there are fixed upon the axles two projecting spokes or levers, which revolve with the axle, and which take the position of two opposite spokes of the wheel. These may be occasionally attached to the wheel or detached from it; so that they are capable of compelling the wheels to turn with the axle, or leaving the axle free to turn independent of the wheel, or the wheel independent of the axle, at the pleasure of the conductor. It is by these levers that the engine is made to propel either or both of the wheels. If both pairs of spokes are thrown into connexion with the wheels, the crank shaft or axle will cause both wheels to turn with it, and in that case the operation of the carriage is precisely the same as those of the locomotives already described upon the Liverpool and Manchester line; but this is rarely found to be necessary, since the adhesion of one wheel with the road is generally sufficient to propel the carriage, and consequently only one pair of these fixed levers are generally used, and the carriage propelled by only one of the two hind wheels. The fore wheels of the carriage turn upon a pivot similar to those of a four-wheeled coach. The position of these wheels is changed at pleasure by a simple pinion and circular rack, which is moved by the conductor, and in this manner the carriage is guided with precision and facility. The force of traction necessary to propel a carriage upon common roads must vary with the variable quality of the road, and consequently the propelling power, or the pressure upon the pistons of the engine, must be susceptible of a corresponding variation; but a still greater variation becomes necessary from the undulations and hills which are upon all ordinary roads. This necessary change in the intensity of the impelling power is obtained by restraining the steam in the boiler by the throttle valve, as already described in the locomotive engines on the railroad. This principle, however, is carried much further in the present case. The steam in the boiler may be at a pressure of from 100 to 200 lbs. on the square inch; while the steam on the working piston may not exceed 30 or 40 lbs. on the inch. Thus an immense increase of power is always at the command of the conductor; so that when a hill is encountered, or a rough piece of road, he is enabled to lay on power sufficient to meet the exigency of the occasion. The two difficulties which have been always apprehended in the practical working of steam carriages upon common roads are, first, the command of sufficient power for hills and rough pieces of road; and, secondly, the apprehended insufficiency of the adhesion of the wheels with the road to propel the carriage. The former of these difficulties has been met by allowing steam of a very great pressure to be constantly maintained in the boiler with perfect safety. As to the second, all experiments tend to show that there is no ground for the supposition that the adhesion of the wheels is in any case insufficient for the purposes of propulsion. Mr. _Gurney_ states, that he has succeeded in driving carriages thus propelled up considerable hills on the turnpike roads about London. He made a journey to Barnet with only one wheel attached to the axle, which was found sufficient to propel the carriage up all the hills upon that road. The same carriage, with only one propelling wheel, also went to Bath, and surmounted all the hills between Cranford Bridge and Bath, going and returning. A double stroke of the piston produces one revolution of the propelling wheels, and causes the carriage to move through a space equal to the circumference of those wheels. It will therefore be obvious, that the greater the diameter of the wheels, the better adapted the carriage is for speed; and, on the other hand, wheels of smaller diameter are better adapted for power. In fact, the propelling power of an engine on the wheels will be in the inverse proportion to their diameter. In carriages designed to carry great weights at a moderate speed, smaller wheels will be used; while in those intended for the transport of passengers at considerable velocities, wheels of at least 5 feet in diameter are most advantageous. Among the numerous popular prejudices to which this new invention has given rise, one of the most mischievous in its effects, and most glaring in its falsehood, is the notion that carriages thus propelled are more injurious to roads than carriages drawn by horses. This error has been most clearly and successfully exposed in the evidence taken before the committee of the House of Commons upon steam carriages. It is there fully demonstrated, not only that carriages thus propelled did not wear a turnpike road more rapidly than those drawn by horses, but that, on the other hand, the wear by the feet of horses is far more rapid and destructive than any which could be produced by the wheels of carriages. Steam carriages admit of having the tires of the wheels broad, so as to act upon the road more in the manner of rollers, and thereby to give consistency and firmness to the material of which the road is composed. The driving wheels, being fully proved not to slip upon the road, do not produce any effects more injurious than the ordinary rolling wheels; consequently the wear occasioned by a steam carriage upon a road is not more than that produced by a carriage drawn by horses of an equivalent weight and the same or equal tires; but the wear produced by the pounding and digging of horses' feet in draught is many times greater than that produced by the wear of any carriage. Those who still have doubts upon this subject, if there be any such persons, will be fully satisfied by referring to the evidence which accompanies the report of the committee of the House of Commons, printed in October, 1831. In that report they will not only find demonstrative evidence that the introduction of steam carriages will materially contribute to the saving in the wear of turnpike roads, but also that the practicability of working such carriages with a great saving to the public--with great increase of speed and other conveniences to the traveller--is fully established. The weight of machinery necessary for steam carriages is sometimes urged as an objection to their practical utility. Mr. _Gurney_ states, that, by successive improvements in the details of the machinery, the weight of his carriages, without losing any of the propelling power, may be reduced to 35 cwt., exclusive of the load and fuel and water: but thinks that it is possible to reduce the weight still further. A steam carriage constructed by Mr. _Gurney_, weighing 35 cwt., working for 8 hours, is found, according to his statement, to do the work of about 30 horses. He calculates that the weight of his propelling carriage, which would be capable of drawing 18 persons, would be equal to the weight of 4 horses; and the carriage in which these persons would be drawn would have the same weight as a common stage coach capable of carrying the same number of persons. Thus the weight of the whole--the propelling carriage and the carriage for passengers taken together--would be the same with the weight of a common stage coach, with 4 horses inclusive. (108.) There are two methods of applying locomotives upon common roads to the transport of passengers or goods; the one is by causing the locomotive to carry, and the other to draw the load; and different projectors have adopted the one and the other method. Each is attended with its advantages and disadvantages. If the same carriage transport the engine and the load, the weight of the whole will be less in proportion to the load carried; also a greater pressure may be produced on the wheels by which the load is propelled. It is also thought that a greater facility in turning and guiding the vehicle, greater safety in descending the hills, and a saving in the original cost, will be obtained. On the other hand, when the passengers are placed in the same carriage with the engine, they are necessarily more exposed to the noise of the machinery and to the heat of the boiler and furnace. The danger of explosion is so slight, that, perhaps, it scarcely deserves to be mentioned; but still _the apprehension_ of danger on the part of the passengers, even though groundless, should not be disregarded. This apprehension will be obviously removed or diminished by transferring the passengers into a carriage separate from the engine; but the greatest advantage of keeping the engine separate from the passengers is the facility which it affords of changing one engine for another in case of accident or derangement on the road, in the same manner as horses are changed at the different stages: or, if such an accident occur in a place where a new engine cannot be procured, the load of passengers may be carried forward by horses, until it is brought to some station where a locomotive may be obtained. There is also an advantage arising from the circumstance that when the engines are under repair, or in process of cleaning, the carriages for passengers are not necessarily idle. Thus the same number of carriages for passengers will not be required when the engine is used to draw as when it is used to carry. In case of a very powerful engine being used to carry great loads, it would be quite impracticable to place the engine and loads on four wheels, the pressure being such as no turnpike road could bear. In this case it would be indispensably necessary to place a part of the load at least upon separate carriages to be drawn by the engine. In the comparison of carriages propelled by steam with carriages drawn by horses, there is no respect in which the advantage of the former is so apparent as the safety afforded to the passenger. Steam power is under the most perfect control, and a carriage thus propelled is capable of being guided with the most admirable precision. It is also capable of being stopped almost suddenly, whatever be its speed; it is capable of being turned within a space considerably less than that which would be necessary for four-horse coaches. In turning sharp corners, there is no danger, with the most ordinary care on the part of the conductor. On the other hand, horse-power, as is well known, is under very imperfect control, especially when horses are used, adapted to that speed which at present is generally considered necessary for the purpose of travelling. "The danger of being run away with and overturned," says Mr. _Farey_, in his evidence before the House of Commons, "is greatly diminished in a steam coach. It is very difficult to control four such horses as can draw a heavy stage coach ten miles an hour, in case they are frightened or choose to run away; and, for such quick travelling, they must be kept in that state of courage that they are always inclined to run away, particularly down hill, and at sharp turns in the road. Steam power has very little corresponding danger, being perfectly controllable, and capable of having its power reversed to retard in going down hill. It must be carelessness that would occasion the overturning of a steam carriage. The chance of breaking down has been hitherto considerable, but it will not be more than in stage coaches when the work is truly proportioned and properly executed. The risk from explosion of the boiler is the only new cause of danger, and that I consider not equivalent to the danger from horses." That the risk of accident from explosion is very slight indeed, if any such risk exists, may be proved from the fact that the boilers used on the Liverpool and Manchester railroad being much larger, and, in proportion, inferior in strength to those of Mr. _Gurney_, and other steam carriage projectors, have never yet been productive of any injurious consequences by explosion, although they have frequently burst. I have stood close to a locomotive on the railroad when the boiler burst. The effect was that the water passed through the tubes into the fire and extinguished it, but no other consequence ensued. In fig. 65. is represented the appearance of a locomotive of Mr. _Gurney's_ drawing after it a carriage for passengers. [Illustration: Fig. 65.] (109.) One of the greatest difficulties which locomotives upon a turnpike road have to encounter is the ascent of very steep hills, for it is agreed upon all hands that hills of very moderate inclinations present no difficulty which may not be easily overcome, even in the present state of our knowledge. The fact of Mr. _Gurney_ having propelled his carriage up Old Highgate Hill, when the apparatus was in a a much more imperfect state than that to which it has now attained, establishes the mere question of the possibility of overcoming the difficulty; but it remains still to be decided whether the inconvenience caused by providing means of meeting the exigency of very steep hills may not be greater than the advantage of being able to surmount them can compensate for: and Mr. _Farey_, whose authority upon subjects of this kind is entitled to the highest respect, thinks that it is upon the whole more advantageous to provide, at very steep hills, post horses to assist the steam carriage up them, than to incur the inconvenience of providing the necessary power and strength of machinery for occasions which at best but rarely occur. If the question merely referred to the command of motive power, it appears to me that Mr. _Gurney's_ boiler would be amply sufficient to supply all that could be required for any hills which occur upon turnpike roads; but it is not to be forgotten, that not merely an ample supply of motive power, but also a strength and weight in the machinery proportionate to the power to be exerted, is indispensably necessary. The strength and weight necessary to ascend a very steep hill will be considerably greater than that which is necessary for a level road, or for hills of moderate inclinations; and it follows that if we ascend those steep hills by the unaided power of the locomotive, we must load the engine with all the weight of machinery requisite for such emergencies, such additional weight being altogether unnecessary, and therefore a serious impediment upon all other parts of the road, inasmuch as it must exclude an equivalent weight of goods or passengers, which might otherwise be transported, and thereby in fact diminish proportionally the efficiency of the machine. It is right, however, to observe, that this is a point upon which a difference of opinion is entertained by persons equally competent to form a judgment, and that some consider that it is practicable to construct an engine without inconvenient weight which will ascend all the hills which occur upon turnpike roads. However this may be, the difficulty is one which the improved system of roads in England renders of a comparatively trifling nature. If horses were resorted to as the means of assistance up such hills as the engine would be incapable of surmounting, such aid would not be requisite more than twice or thrice upon the mail-coach road between London and Holyhead; and the same may be said of the roads connecting the greatest points of intercourse in the kingdom. Such hills as the ascent at Pentonville upon the New Road, the ascent in St. James's Street, the ascent from Waterloo Place to the County Fire Office, the ascent at Highgate Archway, present no difficulty whatever. It is only Old Highgate Hill, and hills of a similar kind, which would ever require a supply of horses in aid of the engine. I therefore incline to agree with Mr. _Farey_, that, at least for the present, it will be more expedient to construct carriages adapted to surmount moderate hills only, and to provide post horses in aid of the extreme emergencies to which I have just alluded. (110.) In the boiler to be used in the steam carriage projected by Mr. _Walter Hancock_, the subdivision of the water is accomplished by dividing a case or box by a number of thin plates of metal like a galvanic battery, the water being allowed to flow between every alternate pair of plates, at E, fig. 66., and the intermediate spaces H forming the flue through which the flame and hot air are propelled. [Illustration: Fig. 66.] In fact, a number of thin plates of water are exposed on both sides to the most intense action of flame and heated air; so that steam of a high-pressure is produced in great abundance and with considerable rapidity. The plates forming the boiler are bolted together by strong iron ties, extending across the boiler, at right angles to the plates, as represented in the figure. The distance between the plates is two inches. There are ten flat chambers of this kind for water, and intermediately between them ten flues. Under the flues is the fire-place, or grate; containing six square feet of fuel in vivid combustion. The chambers are all filled to about two thirds of their depth with water, and the other third is left for steam. The water-chambers, throughout the whole series, communicate with each other both at top and bottom, and are held together by two large bolts. By releasing these bolts, at any time, the chambers fall asunder; and by screwing them up they may be all made tight again. The water is supplied to the boiler by a forcing-pump, and the steam issues from the centre of one of the flues at the top. These boilers are constructed to bear a pressure of 400 or 500 lbs. on the square inch; but the average pressure of the steam on the safety valve is from 60 to 100. There are 100 square feet of surface in contact with the water exposed to the fire. The stages which such an engine performs are eight miles, at the end of which a fresh supply of fuel and water are taken in. It requires about two bushels of coke for each stage. The steam carriage of Mr. _Hancock_ differs from that of Mr. _Gurney_ in this,--that in the former the passengers and engine are all placed on the same carriage. The boiler is placed behind the carriage; and there is an engine-house between the boiler and the passengers, who are placed on the fore part of the vehicle; so that all the machinery is behind them. The carriages are adapted to carry 14 passengers, and weigh, exclusive of their load, about 3-1/2 tons, the tires of the wheels being about 3-1/2 inches in breadth. Mr. _Hancock_ states, that the construction of his boiler is of such a nature, that, even in the case of bursting, no danger is to be apprehended, nor any other inconvenience than the stoppage of the carriage. He states that, while travelling about 9 miles an hour, and working with a pressure of about 100 lbs. on the square inch, loaded with 13 passengers, the carriage was suddenly stopped. At first the cause of the accident was not apparent; but, on opening one of the cocks of the boiler, it was found that it contained neither steam nor water. Further examination proved that the boiler had burst. On unscrewing the bolts, it was found there were several large holes in the plates of the water-chamber, through which the water had flowed on the fire; but neither noise nor explosion, nor any dangerous consequences ensued. This boiler has some obvious defects. It is evident that thin flat plates are the form which, mechanically considered, is least favourable to strength; nor does it appear that any material advantage is gained to compensate for this by the magnitude of the surface exposed to the action of the fire. It is a great defect that a part of the surface of each of the plates is exposed to the action of the fire while it is out of contact with the water; in fact, in the upper part of the spaces marked E, fig. 66., steam only is contained. It has been observed by engineers, and usually shown by experiment, that if steam be heated on the surface of water it will be decomposed, and its elasticity destroyed; this is not the only evil connected with the arrangement, for on this part of the metal, nevertheless, the fire acts,--with less intensity, it is true, than on that part which contains the water,--but still with sufficient intensity to destroy the metal. Mr. _Hancock_ appears to have attempted to remedy this defect by occasionally inverting the position of the flat chambers, placing that which at one time was at the bottom at the top, and _vice versâ_. This may equalise the wear produced by the action of the fire upon the metal out of contact with water, but still the wear on the whole will not be less rapid. There appears to be no provision or space for separating the steam from the water with which it is charged; in fact, there are no means in this engine of discharging the function of Mr. _Gurney's_ separator. This will be found to produce considerable waste and loss of power in practice. The bars upon which the fire rests are of solid metal; and such is the intense heat to which they are subject, that, in an engine constantly at work, it is unlikely that they will last, without being renewed, more than about a week, if so much. The draft is maintained in this engine by means of a revolving fan worked by the engine. This, perhaps, is one of the greatest defects as compared with other locomotives. The quantity of power requisite to work this bellows, and of which the engine is robbed, is very great. This defect is so fatal, that I consider it is quite impossible that the ingenious inventor can persevere in the use of it. Mr. _Hancock_ has abandoned the use of the cranks upon his working axle, and has substituted an endless chain and rag-wheels. This also appears to me defective, and a source by which considerable power is lost. On the other hand, however, the weakness of the axle which is always produced by cranks is avoided. (111.) Mr. _Nathaniel Ogle_ of Southampton obtained a patent for a locomotive carriage, and worked it for some time experimentally; but as his operations do not appear to have been continued, I suppose he was unsuccessful in fulfilling those conditions, without which the machine could not be worked with economy and profit. In his evidence before a committee of the House of Commons, he has thus described his contrivance:-- "The base of the boiler and the summit are composed of cross pieces, cylindrical within and square without; there are holes bored through these cross pieces, and inserted through the whole is an air tube. The inner hole of the lower surface, and the under hole of the upper surface, are rather larger than the other ones. Round the air tube is placed a small cylinder, the collar of which fits round the larger aperture on the inner surface of the lower frame, and the under surface of the upper frame-work. These are both drawn together by screws from the top; these cross pieces are united by connecting pieces, the whole strongly bolted together; so that we obtain, in one tenth of the space, and with one tenth of the weight, the same heating surface and power as is now obtained in other and low-pressure boilers, with incalculably greater safety. Our present experimental boiler contains 250 superficial feet of heating surface in the space of 3 feet 8 inches high, 3 feet long, and 2 feet 4 inches broad, and weighs about 8 cwt. We supply the two cylinders with steam, communicating by their pistons with a crank axle, to the ends of which either one or both wheels are affixed, as may be required. One wheel is found to be sufficient, except under very difficult circumstances, and when the elevation is about one foot in six, to impel the vehicle forward. "The cylinders of which the boiler is composed are so small as to bear a greater pressure than could be produced by the quantity of fire beneath the boiler; and if any one of these cylinders should be injured by violence, or any other way, it would become merely a safety valve to the rest. We never, with the greatest pressure, burst, rent, or injured our boiler; and it has not once required cleaning, after having been in use twelve months." (112.) Dr. _Church_ of Birmingham has obtained a succession of patents for contrivances connected with a locomotive engine for stone roads; and a company, consisting of a considerable number of individuals, possessing sufficient capital, has been formed in Birmingham for carrying into effect his designs, and working carriages on his principle. The present boiler of Dr. _Church_ is formed of copper. The water is contained between two sheets of copper, united together by copper nails, in a manner resembling the way in which the cloth forming the top of a mattress or cushion is united with the cloth which forms the bottom of it, except that the nails or pins, which bind the sheets of copper, are much closer together. The water, in fact, seems to be "quilted" or "padded," in between two sheets of thin copper. This double sheet of copper is formed into an oblong rectangular box, the interior of which is the fire-place and ash-pit, and over the end of which is the steam-chest. The great extent of surface exposed to the immediate action of the fire causes steam to be produced with great rapidity. An obvious defect which such a boiler presents is the difficulty of removing from it any deposite or incrustation, which may collect between the sheets of copper so closely and intricately connected. Dr. Church proposes to effect this, when it is required, by the use of an acid, which will combine readily with the incrustation, and by which the boiler may therefore be washed. This method of cleansing boilers was recommended by Dr. Wollaston to Mr. Gurney, who informed me, however, that he found that it was not practicable in the way in which boilers must commonly be used. I apprehend, also, that the spaces between the sheets of copper, in Dr. Church's boiler just described, will hardly permit the steam bubbles which will be formed to escape with sufficient facility into the steam-chest; and being retained in that part of the boiler which is exposed to the action of the fire, the metal will be liable to receive an undue temperature. I have, however, seen this engine working, and its performance was very satisfactory. (113.) Various other projects for steam carriages on common roads are in various degrees of advancement, among which may be mentioned those of Messrs. Maudslay and Field, Col. Macerone, and Mr. Russell of Edinburgh; but our limits compel us to omit any detailed account of them. CHAPTER XII. STEAM NAVIGATION. Propulsion by paddle-wheels. -- Manner of driving them. -- Marine Engine. -- Its form and arrangement. -- Proportion of its cylinder. -- Injury to boilers by deposites and incrustation. -- Not effectually removed by _blowing out_. -- Mr. Samuel Hall's condenser. -- Its advantages. -- Originally suggested by Watt. -- Hall's _steam saver_. -- Howard's vapour engine. -- Morgan's paddle-wheels. -- Limits of steam navigation. -- Proportion of tonnage to power. -- Average speed. -- Consumption of fuel. -- Iron steamers. -- American steam raft. -- Steam navigation to India. -- By Egypt and the Red Sea to Bombay. -- By same route to Calcutta. -- By Syria and the Euphrates to Bombay. -- Steam communication with the United States from the west coast of Ireland to St. John's, Halifax, and New York. (114.) Among the various ways in which the steam engine has ministered to the social progress of our race, none is more important and interesting than the aid it has afforded to navigation. Before it lent its giant powers to that art, locomotion over the waters of the deep was attended with a degree of danger and uncertainty, which seemed so necessary and so inevitable, that, as a common proverb, it became the type and representative of everything else which was precarious and perilous. The application, however, of steam to navigation has rescued the mariner from much of the perils of the winds and waves; and even in its actual state, apart from the improvements which it is still likely to receive, it has rendered all voyages of moderate length as safe and as regular as journeys over land. We are even now upon the brink of such improvements as will probably so extend the powers of the steam engine, as to render it available as the means of connecting the most distant points of the earth. The manner in which the steam engine is commonly applied to propel vessels must be so familiar as to require but short explanation. A pair of wheels, like common under-shot water-wheels, bearing on their rims a number of flat boards called _paddle boards_, are placed one at each side of the vessel, in such a position that when the vessel is immersed to her ordinary depth the lowest paddle boards shall be submerged. These wheels are fixed upon a shaft, which is made to revolve by cranks placed upon it, in the same manner as the fly-wheel of a common steam engine is turned. It is now the invariable custom to place in steam vessels two engines, each of which works a crank: these two cranks are placed at right angles to each other, in the same manner as the cranks already described upon the working axles of locomotive engines. When either crank is at its dead point, the other is in full activity, so that the necessity for a fly wheel is superseded. The engines may be either condensing or high-pressure engines; but in Europe the low-pressure condensing engine has been invariably used for nautical purposes. In the United States, where steam navigation had its origin, and where it was, until a recent period, much more extensively practised than in Europe, less objection was felt to the use of high-pressure engines; and their limited bulk, their small original cost, and simplicity of structure, strongly recommended them, more especially for the purposes of river navigation. (_g._) The original type of nearly all the engines used in steam navigation was that constructed at Soho by Watt and Bolton for Mr. Fulton, and first used by him upon the Hudson river. This had the beam below the piston-rod as in the English boat-engines, but the cylinder above deck, as in the American. From this primitive form, the two nations have diverged in opposite directions. The Americans, navigating rivers, and having speed for their principal object, have not hesitated to keep the cylinder above deck, and have lengthened the stroke of the piston in order to make the power cut on a more advantageous point of the wheel. Compactness has been gained by the suppression of the working beam. On the other hand, the English, having the safe navigation of stormy seas as their more important object, have shortened the cylinder in order that the piston-rod may work wholly under the deck, and the arrangement of Fulton's working beam has been retained by them. In this way there can be no doubt, that they have lost the power of obtaining equal speed from a given expenditure of power, and those conversant in the practice and theory of stowing ships may well doubt whether security is not also sacrificed.--A. E. The arrangement of the parts of the maritime engine differs in some respects, from that of the land engine. Want of room renders greater compactness necessary; and in order to diminish the height of the machine, the working beam is transferred from above the cylinder to below it. In fact, there are two beams, one at each side of the engine, which are connected by a parallel motion with the piston, the rods of the parallel motion extending from the lower part of the engine to the top of the piston-rod. The working end of the beam is connected with the crank by a connecting rod, presented upwards instead of downwards, as in the land engine. The proportion of the length and diameters of the cylinders differ from those of land engines for a like reason: to save height, short cylinders with large diameters are used. Thus, in an engine of 200 horse-power, the length of the cylinder is sometimes 60 inches, and its diameter 53 inches: the valves and the gearing which work them, the air-pump, condenser, and other parts of the machine, do not differ materially from those already described in the land engines. (_h._) The action of machinery may be rendered more equable by using two engines, each of half the power, instead of a single one. If one of these be working with its maximum force when the other is changing the direction of its motion, the result of their joint action will be a force nearly constant. Such a combination was invented by Mr. Francis Ogden, and has been used in several steam boats constructed under his directions. It would however be far more valuable in other cases, particularly where great uniformity in the velocity is indispensable. This method has now become almost universal in the engines used in the English steam boats, each of which has usually two, both applied to the same shaft, and therefore capable of being used singly or together to turn the paddle wheels. In the American steam boats, although two engines have been often applied, each usually acts upon no more than one of the wheels. We can see no other good reason for this, than that our engineers do not wish to be thought to copy Mr. Ogden.--A. E. The nature of the work which the marine engine has to perform, is such, that great regularity of action is neither necessary nor possible. The agitation of the surface of the sea will cause the immersion of the paddle-wheels to vary very much, and the resistance to the engine will undergo a corresponding change: the governor, and other parts of the apparatus already described, contrived for imparting to the engine that extreme regularity which is indispensable in its application to manufactures, are therefore here omitted; and nothing is introduced except what is necessary to maintain the engine in its full working power. It is evident that it must be a matter of considerable importance to reduce the space occupied by the machinery on board a vessel to the least possible dimensions. The marine boilers, therefore, are constructed so as to yield the necessary quantity of steam with the smallest practical dimensions. With this view a much more extensive surface in proportion to the size of the boiler is exposed to the action of the fire. In fact, the flues which carry off the heated air to the chimney are conducted through the boiler, so as to act upon the water on every side in thin oblong shells, which traverse the boiler backward and forward repeatedly, until finally they terminate in the chimney. By this arrangement the original expense of the boilers is very considerably increased; but, on the other hand, their steam-producing power is also greatly augmented; and from experiments lately made by Mr. Watt at Birmingham, it appears that they work with an economy of fuel compared with common land boilers in the proportion of about two to three. Thus they have the additional advantage of saving the tonnage as well as the expense of one third of the fuel. One of the most formidable difficulties which has been encountered in applying the steam engine to the purposes of navigation has arisen from the necessity of supplying the boiler with sea water, instead of pure fresh water. This water (also used for the purpose of condensation) being injected into the condenser and mixed with the condensed steam, is conducted as feeding water into the boiler. The salt contained in the sea water, not being evaporated, remains in the boiler. In fact, it is separated from the water in the same manner as by the process of distillation. As the evaporation in the boiler is continued, the proportion of salt contained in the water is, therefore, constantly increased, until a greater proportion is accumulated than the water is capable of holding in solution; a deposition of salt then commences, and is lodged in the cavities at the bottom of the boiler. The continuance of this process, it is evident, would at length fill the boiler with salt. But besides this, under some circumstances, a deposition of lime[35] is made, and a hard incrustation is formed on the inner surface of the boiler. In some situations, also, sand and mud are received into the boiler, being suspended in the water pumped in for feeding it. All these substances, whether deposited in a loose form in the lower parts of the boiler or collected in a crust on its inner surface, form obstructions to the passage of heat from the fire to the water. The crust thus formed is not unfrequently an inch or more in thickness, and so hard that good chisels are broken in removing it. The heat more or less intercepted by these substances collects in the metal of the boiler, and raises it to a temperature far exceeding that of the water within. It may even, if the incrustation be great, be sufficient to render the boiler red-hot. These circumstances occasion the rapid wear of the boiler, and endanger its safety by softening it. [Footnote 35: Ten thousand grains of pure sea water contain muriate of soda 220 grs., sulphate of soda 33 grs., muriate of magnesia 42 grs., and muriate of lime 8 grs.] The remedy which has generally been adopted to remove or diminish these injurious effects consists in allowing a stream of hot water continually to flow from the boiler, and supplying from the feed-pipe a corresponding portion of cold water. While the hot water which flows from the boiler in this case contains, besides its just proportion of salt, that portion which has been liberated from the water converted into vapour, the cold water which is supplied through the feed-pipe contains less than its just proportion of salt, since it is composed of the natural sea water, mixed with the condensed steam, which latter contains no salt. In this manner, the proportion of the salt in the boiler may be prevented from accumulating; but this is attended with considerable inconvenience and loss. It is evident that the discharge of the hot water, and the introduction of so considerable a quantity of cold water, entails upon the machine a great waste of fuel, and, consequently, renders it necessary that the vessel should be supplied with a much larger quantity of coals than are merely necessary for propelling it. In long voyages, where this inconvenience is most felt, this is a circumstance of obvious importance. But besides the waste of fuel, the speed of the vessel is diminished by the rate of evaporation in the boiler being checked by the constant stream of cold water flowing into it. This process of discharging the water, which is called _blowing out_, is only practised occasionally. In the Admiralty steamers, the engineers are ordered to blow out every two hours. But it is more usual to do so only once a day. This method, however, of blowing out furnishes but a partial remedy for the evils we have alluded to: a loose deposite will perhaps be removed by such means, but an incrustation, more or less according to the circumstances and quality of the water, will be formed; besides which, the temptation to work the vessel with efficiency for the moment influences the engine men to neglect blowing out; and it is found that this class of persons can rarely be relied upon to resort to this remedy with that constancy and regularity which are essential for the due preservation of the boilers. The class of steam vessels which, at present, are exposed to the greatest injury from these causes are the sea-going steamers employed by the Admiralty; and we find, by a report made by Messrs. Lloyd and Kingston to the Admiralty, in August, 1834, that it is admitted that the method of blowing out is, even when daily attended to, ineffectual. "The water in the boiler," these gentlemen observe, "is kept from exceeding a certain degree of saltness, by periodically blowing a portion of it into the sea; but whatever care is taken, in long voyages especially, salt will accumulate, and sometimes in great quantities and of great hardness, so that it is with difficulty it can be removed. Boilers are thus often injured as much in a few months as they would otherwise be in as many years. The other evil necessarily resulting from this state of things is, besides the rapid destruction of the boilers, a great waste of fuel, occasioned by the difficulty with which the heat passes through the incrustation on the inside, by the leaks which are thereby caused, and by the practice of blowing out periodically, as before mentioned, a considerable portion of the boiling water." It would be impracticable to carry on board the vessel a sufficient quantity of pure fresh water to work the engine exclusively by its means. To accomplish this, it would be necessary to have a sufficient supply of cold water to keep the condensing cistern cold, to supply the jet in the condenser, and to have a reservoir in which the warm water coming from the waste pipe of the cold cistern might be allowed to cool. Engineers have therefore directed their attention to some method by which the steam may be condensed without a jet, and after condensation be preserved for the purpose of feeding the boiler. If this could be accomplished, it would not be necessary to provide a greater quantity of pure water than would be sufficient to make up the small portion of waste which might proceed from leakage and from other causes; and it is evident that this portion might always be readily obtained by the distillation of sea water, which might be effected by a small vessel exposed to the same fire which acts upon the boiler. (115.) Mr. _Samuel Hall_ of _Basford_, near Nottingham, has taken out patents for a new form of condenser, contrived for the attainment of these ends, besides some other improvements in the engine. The condenser of Mr. _Hall_ consists of a great number of narrow tubes immersed in a cistern of cold water: the steam as it passes from the cylinder, after having worked the piston, enters these tubes, and is immediately condensed by their cold surfaces. It flows in the form of water from their remote extremities, and is drawn off by the air-pump, and conducted in the usual way to a cistern from which the boiler is fed. In the marine engines constructed under Mr. _Hall_'s patents, the tubes of the condenser being in an upright or vertical position, the steam flows from the cylinder into the upper part of the condenser, which is a low flat chamber, in the bottom of which is inserted the upper extremities of the tubes, through which the steam passes downwards, and as it passes is condensed. It flows thence into a similar chamber below, from whence it is drawn off by the air-pump. It is evident that at sea an unlimited supply of cold water may be obtained to keep the condensing cistern cold, so that a perfect condensation may always be effected by these tubes, if they be made sufficiently small. The water formed by the condensed steam will be pure distilled water; and if the boiler be originally filled with water which does not hold in solution any earthy or other matter which might be deposited or encrusted, it may be worked for any length of time without injury. The small quantity of waste from leakage is supplied in Mr. Hall's engine by a simple apparatus in which a sufficient quantity of sea water may be distilled. The following are the advantages, as stated by Mr. Hall, to be gained by his condenser:-- 1. A saving of fuel, amounting in some cases to so much as a third of the ordinary consumption. 2. The preservation of the boilers from the destruction produced in common engines by the corrosive action of sea or other impure water, and by encrustations of earthy matter. 3. The saving of the time spent in cleaning the boilers. 4. A considerable increase of power, owing to the cleanness of the boilers; the absence of injected water to be pumped out of a vacuum; the greater perfection of the vacuum; the better preservation of the piston and valves of the air-pump; and (by another contrivance of his) the more perfect lubrication of the parts of the engine. 5. The water in the boiler being constantly maintained at the same height by self-acting arrangement. 6. The size of a boiler exerting a given power, being much smaller than the common kind, owing to its more perfect action. Messrs. _Lloyd_ and _Kingston_ were employed by government to examine and report the effects of Mr. Hall's boilers, and they stated in their report, already referred to, that the result is so successful as to leave nothing to be wished for. Among the advantages which they enumerate are the increased durability of the engines; the prevention of accidents through carelessness, or otherwise, arising from the condenser and air-pump becoming choked with injection water; and the additional security against the boilers being burnt in consequence of the water being suffered to get too low. But the greatest advantages, compared with which they consider all others to be of secondary importance, are the increased durability of the boilers and the saving of fuel. About 16 engines, built either wholly upon Mr. Hall's principle or having his condenser attached to them, have now (October, 1835) been working in different parts of England, and on board different vessels for various periods, from three years to three months; and it appears from the concurrent testimony of the proprietors and managers of them, that they are attended with all the advantages which the patentee engaged for. The part of the contrivance the performance of which would have appeared most doubtful would have been the maintenance of a sufficiently good vacuum in the condenser, in the absence of the usual method of condensation by the injection of cold water; nevertheless it appears that a better vacuum is sustained in these engines than in the ordinary engines which condense by jet. The barometer-gauge varies from 29 to 29-1/2 inches, and in some cases comes up to 30 inches, according to the state of the barometer: this is a vacuum very nearly perfect, and indeed may be said to be so for all practical purposes. The _Prince Llewellyn_ and the _Air_ steam packets, belonging to the St. George Steam Packet Company, have worked such a pair of these engines for about a year. The _City of London_ steam packet, the property of the General Steam Navigation Company, has been furnished with two fifty-horse engines, and has worked them during the same period. In all cases the boilers have been found perfectly free from scale or incrustation; and the deposite is either absolutely nothing or very trifling, requiring the boiler to be swept about once in half a year, and sometimes not so often. The trial which has been made of these engines in the navy has proved satisfactory, so far as it has been carried. The Lords of the Admiralty have lately ordered a pair of seventy-horse engines to be constructed on this principle for a vessel now (October, 1835) in process of construction;[36] and another vessel in all respects similar, except having copper boilers, is likewise ordered; so that a just comparison may be made. It would, however, have been more fair if both vessels had been provided with iron boilers, since copper does not receive incrustation as readily as iron. [Footnote 36: This order has, as Mr. Hall informs me, been given without requiring any guarantee as to the performance of the engines.] It would seem that the advantages of these boilers in the vessels of the St. George Steam Packet Company were regarded by the directors as sufficiently evident, since, after more than a year's experience, they are about to place a pair of ninety-horse engines of this kind in a new and powerful steamer called the _Hercules_. Engines furnished with Mr. Hall's apparatus have not yet, so far as I am informed, been tried with reference to the power exerted by the consumption of a given quantity of fuel. The mere fact of a good vacuum being sustained in the condenser cannot by itself be regarded as a conclusive proof of the efficiency of the engine, without the water or air introduced by a condensing jet. Mr. Hall, nevertheless, uses as large an air-pump as that of an ordinary condensing engine, and recommends even a larger one. For what purpose, it may be asked, is such an appendage introduced? If there be nothing to be removed but the condensed steam, a very small pump ought to be sufficient. It is not wonderful that a good vacuum is sustained in the condenser, if the power expended on the air-pump is employed in _pumping away uncondensed steam_. Such a contrivance would be merely a deception, giving an apparent but no real advantage to the engine. Having mentioned these advantages, which are said to arise from Mr. Hall's condenser, it is right to state that it is in fact a reproduction of an early invention of Mr. Watt. There is in possession of James Watt, esquire, a drawing of a condenser laid before parliament in 1776, in which the same method of condensing without a jet is proposed. Mr. Watt, however, finding that he could not procure by that means so sudden or so perfect a vacuum as by injection, abandoned it. I believe he also found that the tubes of the condenser became furred with a deposite which impeded the process of condensation. It would seem, however, that Mr. Hall has found means to obviate these effects. It is right to add, that Mr. Hall, in his specification, distinctly disclaims all claim to the method of condensing by tubes without jet. There is another part of Mr. Hall's contrivance which merits notice. In all engines, a considerable quantity of steam is allowed to escape from the safety valve. Whenever the vessel stops, the steam, which would otherwise be taken from the boiler by the cylinders, passes out through this valve into the atmosphere. Also, whenever the cylinders work at under-power, and do not consume the steam as fast as it is produced by the boiler, the surplus steam escapes through the valve. Now, according to the principle of Mr. Hall's method, it is necessary to save the water which thus escapes in vapour, since otherwise the pure water of the boiler would be more rapidly wasted. Mr. Hall accordingly places a safety valve of peculiar construction in communication with a tube which leads to the condenser, so that whenever, either by stopping the engine or diminishing its working power, steam accumulates in the boiler, its increased pressure opens the safety valve, and it passes through this pipe to the condenser, where it is reconverted into water, and pumped off by the air-pump into the cistern from which the boiler is fed. The attainment of an object so advantageous as to extend the powers of steam navigation, and to render the performance of voyages of any length practicable, so far as the efficiency of the machinery is concerned, has naturally stimulated the inventive genius of the country. The preservation of the boiler by the prevention of deposite and incrustation is an object of paramount importance; and its attainment necessarily involves, to a certain degree, another condition on which the extension of steam voyages must depend, viz. the economy of fuel. In proportion as the economy of fuel is increased, in the same proportion will the limit to which steam navigation may be carried be extended. (116.) A patent has been obtained by Mr. Thomas Howard of London for a form of engine possessing much novelty and ingenuity, and having pretensions to the attainment of a very extraordinary economy of fuel, in addition to those advantages which have been already explained as attending Mr. Hall's engines. In these engines, as in Mr. Hall's, the steam is constantly reproduced from the same water, so that pure or distilled water may be used; but Mr. Howard dispenses with the use of a boiler altogether. The steam also with which he works is in a state essentially different from the steam used in ordinary engines. In these, the vapour is raised directly from the water in a boiling state, and it contains as much water as it is capable of holding at its temperature. Thus, at the temperature of 212°, a cubic foot of steam used in common engines will contain about a cubic inch of water; but in the contrivance of Mr. Howard, a considerable quantity of heat is imparted to the steam before it passes into the cylinder in addition to what is necessary to maintain it in the vaporous form. A quantity of mercury is placed in a shallow wrought-iron vessel over a coke fire, by which it is maintained at the temperature of from 400° to 500°. The surface exposed to the fire is three fourths of a square foot for each horse-power. The upper surface of the mercury is covered by a very thin plate of iron, which rests in contact with it, and which is so contrived as to present about four times as much surface as that exposed beneath to the fire. Adjacent to this a vessel of water is placed, kept heated nearly to the boiling-point, which communicates by a nozzle and valve with the chamber or vessel immediately above the mercury. At intervals corresponding to the motion of the piston, a small quantity of water is injected from this vessel, and thrown upon the plate of iron which rests upon the hot mercury: from this it receives the heat necessary not only to convert it into steam, but to expand that steam, and raise it to a temperature above the temperature it would receive if raised in immediate contact with water. In fact, the steam thus produced will have a temperature not corresponding to its pressure, but considerably above that point, and it will therefore be in circumstances under which it will part with more or less of its heat, and allow its temperature to be lowered without being even partially condensed, whereas steam used in the ordinary steam engines must be more or less condensed by the slightest diminution of its temperature. The quantity of liquid injected into the steam chamber must be regulated by the power at which the engine is intended to work. The fire is supplied with air by a blowing machine, which is subject to exact regulation. The steam, produced in the manner already explained, passes into a chamber which surrounds the working cylinder; and this chamber itself is enclosed by another space, through which the air from the furnace must pass before it reaches the flue. In this way it imparts its redundant heat to the steam which is about to work the cylinder, and raises it to a temperature of about 400°; the pressure, however, not exceeding 25 lbs. per square inch. The arrangement of valves for the admission of the steam to the cylinder is such as to cause the steam to act expansively. The vacuum on the opposite side of the piston is maintained by condensation in the following manner:--The condenser is a copper vessel placed in a cistern constantly supplied with cold water, and the steam flows to it from the cylinder by an eduction pipe in the usual way: a jet is admitted to it from an adjacent vessel, which, before the engine commences work, is filled with distilled water; the condensing water and condensed steam are pumped from the condenser by air-pumps of the usual construction, but smaller, inasmuch as there is no air to be withdrawn, as in common engines. The warm water thus pumped out of the condenser is driven into a copper pipe or worm, which is carried with many coils through a cistern of cold water, so that when it arrives at the end of this pipe it is reduced to the common temperature of the atmosphere. The pipe is then conducted into the vessel of distilled water already mentioned, and the water flowing from it continually replaces the water which flows into the condenser through the condensing jet. The condensing water being purged of air, a very small air-pump is sufficient; since it has only to exhaust the condenser and tubes at starting, and to remove whatever air may enter by casual leakage. The patentee states that the condensation takes place as rapidly and as perfectly as in the best steam engine, and it is evident that this method of condensation is applicable even where the mercurial generator already described may not be employed. The vessel from which the water is injected into the mercurial generator is likewise fed by the air-pump connected with the condenser. There is another pipe besides the copper worm already described, which is carried from the hot well to this vessel, and the water is of course returned through it without being cooled. This vessel is likewise sufficiently exposed to the action of the fire to maintain it at a temperature somewhat below the boiling point. An apparatus of this construction was in the spring of the present year (1835) placed in the Admiralty steamer called the COMET, in connexion with a pair of 40-horse engines. The patentee states that these engines were ill adapted to the contrivance; nevertheless, the vessel was successfully worked in the Thames for 800 miles: she also performed a voyage from Falmouth to Lisbon, but was prevented from returning by an accident which occurred to the machinery near the latter port. In this experimental voyage, the consumption of fuel is stated never to have exceeded a third of her former consumption, when worked by Bolton and Watt's engines; the former consumption of coals being about 800 lbs. per hour, and the consumption with Mr. Howard's engine being under 250 lbs. of coke per hour. After this failure (which, however, was admitted to be one of accident and not of principle) the government did not consider itself justified in bestowing further time or incurring greater expense in trying this engine. Mr. Howard, however, has himself built a new vessel, in which he is about to place a pair of forty-horse engines. This vessel is now (December, 1835) nearly ready, and will bring the question to issue by a fair experiment. The advantages of the contrivance as enumerated by the patentee are:-- _First_, The small space and weight occupied by the machinery, arising from the absence of a boiler. _Secondly_, The diminished consumption of fuel. _Thirdly_, The reduced size of the flues. _Fourthly_, The removal of the injurious effects arising from deposite and incrustation. _Fifthly_, The absence of smoke. Some of these improvements, if realized, will be attended with important advantages in steam navigation. Steamers of a given tonnage and power will have more disposable space for lading and fuel, and in short voyages may carry greater freight, or an increased number of passengers; or by taking a larger quantity of fuel,[37] may make greater runs than are now attainable; or, finally, with the same tonnage and the same lading, they may be supplied with more powerful machinery. [Footnote 37: The fuel used in this form of engine is coke, and not coal. A ton of coke occupies the same space as two tons of coal; the saving of tonnage, therefore, by the increased economy of fuel will not be in so great a proportion as the saving of fuel. A quantity of fuel of equivalent power will occupy about half the present space, but the displacement or immersion which it produces will be only one fourth of its present effect.] (117.) To obtain from the moving power its full amount of mechanical effect in propelling the vessel, it would be necessary that its force should propel, by constantly acting against the water in a horizontal direction, and with a motion contrary to the course of the vessel. No system of mechanical propellers has, however, yet been contrived capable of perfectly attaining this end. Patents have been granted for many ingenious mechanical combinations to impart to the propelling surfaces such angles as appeared to the respective contrivers most advantageous. In most of these, however, the mechanical complexity has formed a fatal objection. No part of the machinery of a steam vessel is so liable to become deranged at sea as the paddle-wheels; and, therefore, such simplicity of construction as is compatible with those repairs which are possible on such emergencies is quite essential for safe practical use. [Illustration: Fig. 67.] The ordinary paddle-wheel, as I have already stated, is a wheel revolving upon a shaft driven by the engine, and carrying upon its circumference a number of flat boards, called paddle boards, which are secured by nuts or braces in a fixed position; and that position is such that the planes of the paddle boards diverge nearly from the centre of the shaft on which the wheel turns. The consequence of this arrangement is that each paddle board can only act in that direction which is most advantageous for the propulsion of the vessel when it arrives near the lowest point of the wheel. In figure 67. let o be the shaft on which the common paddle wheel revolves; the position of the paddle boards are represented at A, B, C, &c.; X, Y represents the water line, the course of the vessel being supposed to be from X to Y; the arrows represent the direction in which the paddle-wheel revolves. The wheel is immersed to the depth of the lowest paddle board, since a less degree of immersion would render a portion of the surface of each paddle board mechanically useless. In the position A the whole force of the paddle board is efficient for propelling the vessel; but, as the paddle enters the water in the position H, its action upon the water, not being horizontal, is only partially effective for propulsion: a part of the force which drives the paddle is expended in depressing the water, and the remainder in driving it contrary to the course of the vessel, and, therefore, by its reaction producing a certain propelling effect. The tendency, however, of the paddle entering the water at H, is to form a hollow or trough, which the water, by its ordinary property, has a continual tendency to fill up. After passing the lowest point A, as the paddle approaches the position B, where it emerges from the water, its action again becomes oblique, a part only having a propelling effect, and the remainder having a tendency to raise the water, and throw up a wave and spray behind the paddle-wheel. It is evident that the more deeply the paddle-wheel becomes immersed the greater will be the proportion of the propelling power thus wasted in elevating and depressing the water; and, if the wheel were immersed to its axis, the whole force of the paddle boards, on entering and leaving the water, would be lost, no part of it having a tendency to propel. If a still deeper immersion takes place, the paddle boards above the axis would have a tendency to retard the course of the vessel. When the vessel is, therefore, in proper trim, the immersion should not exceed nor fall short of the depth of the lowest paddle; but for various reasons it is impossible in practice to maintain this fixed immersion: the agitation of the surface of the sea, causing the vessel to roll, will necessarily produce a great variation in the immersion of the paddle-wheels, one becoming frequently immersed to its axle, while the other is raised altogether out of the water. Also the draught of water of the vessel is liable to change, by the variation in her cargo: this will necessarily happen in steamers which take long voyages. At starting they are heavily laden with fuel, which as they proceed is gradually consumed, whereby the vessel is lightened; and it does not appear that it is practicable to use sea water as ballast to restore the proper degree of immersion. (118.) Among the contrivances which have been proposed for remedying these defects of the common paddle wheel by introducing paddle boards capable of shifting their position as they revolve with the circumference of the wheel, the only one which has been adopted to any considerable extent in practice is that which is commonly known as Morgan's Paddle Wheel. The original patent for this contrivance was granted to Elijah Galloway, and sold by him to Mr. William Morgan. Subsequently to the purchase some improvements in its structure and arrangements were introduced, and it is now extensively adopted by Government in the Admiralty steamers. It was first tried on board His Majesty's steamer the CONFIANCE; and after several successful experiments was ordered by the Lords of the Admiralty to be introduced on board the FLAMER, the FIREBRAND, the COLUMBIA, the SPITFIRE, the LIGHTNING, a large war steamer called the MEDEA,[38] the TARTARUS, the BLAZER, &c. It has been tried by Government in several well-conducted experiments, where two vessels of precisely the same model, supplied with similar engines of equal power, and propelled, one by Morgan's paddle-wheels, and the other by the common paddle-wheels; when it was found that the advantage of the former, whether in smooth or in rough water, was quite apparent. One of the commanders in these experiments (Lieutenant Belson) states that the improvement in the speed of the CONFIANCE, after being supplied with these wheels, was proportionately greater in a sea way than in smooth water; that their action was not impeded by the waves, since the variation of the velocity of the engine did not exceed one or two revolutions per minute: the vessel's way was never stopped, and there was no sensible increase of vibration on the paddle boxes during the gale. Another commander reported that on a comparison of the CONFIANCE and a similar and equally powerful vessel, the CARRON, the CONFIANCE performed in fifty-four hours the voyage which occupied the CARRON eighty-four hours in running. Independently of the great saving of fuel effected (namely, ten bushels per hour[39]), or the time saved in running the same distance, other advantages have been secured by the modification in question. On a comparison of the respective logs of the two vessels, it appeared that the CONFIANCE had gained by the alteration in her wheels an increase of speed amounting to 2 knots on 7 in smooth water, and 2-1/2 knots on 4 to 4-1/2 knots in rough weather; that the action of the paddles did not bring up the engine or retard their velocity in a head sea; that in rolling their action assisted in righting the vessel; and that the wear and strain, as well on the vessel as on the engines, were materially reduced. With respect to the durability of these wheels, the commander of the FLAMER reported in January, 1834, that in six weeks of the most tempestuous weather they found them to act remarkably well, without even a single float being shifted.[40] [Footnote 38: This splendid ship is 860 tons burden, with engines of 220 horse power.] [Footnote 39: See Report quoted in Mechanic's Magazine, vol. xxii. p. 275. This saving cannot amount to less than 40 per cent. upon the whole consumption of fuel; it certainly is considerably beyond what I should have conceived to be possible; but I have no reason to doubt the accuracy of the Report. I estimate the former consumption at 10 pounds per horse power per hour, which on 220 horse-power would be 2200 pounds, of which 840 pounds = 10 bushels, would be about 4-10ths.] [Footnote 40: See a more detailed account of these reports in the Mechanic's Magazine, vol. xxii. p. 274., from which I have taken the drawing of this paddle-wheel; and also see Report of the Committee of the House of Commons on Steam Navigation to India, Evidence of William Morgan, p. 95.] This paddle-wheel is represented in figure 68. The contrivance may be shortly stated to consist in causing the wheel which bears the paddles to revolve on one centre, and the radial arms which move the paddles to revolve on another centre. Let A B C D E F G H I be the polygonal circumference of the paddle-wheel, formed of straight bars, securely connected together at the extremities of the spokes or radii of the wheel which turns on the shaft which is worked by the engine; the centre of this wheel being at O. So far this wheel is similar to the common paddle-wheel; but the paddle boards are not, as in the common wheel, fixed at A B C, &c., so as to be always directed to the centre O, but are so placed that they are capable of turning on axles which are always horizontal, so that they can take any angle with respect to the water which may be given to them. From the centres, or the line joining the pivots on which these paddle boards turn, there proceed short arms K, firmly fixed to the paddle boards at an angle of about 120°. On a motion given to this arm K, it will therefore give a corresponding angular motion to the paddle board, so as to make it turn on its pivots. At the extremities of the several arms marked K is a pin or pivot, to which the extremities of the radial arms L are severally attached, so that the angle between each radial arm L and the short paddle arm K is capable of being changed by any motion imparted to L; the radial arms L are connected at the other end with a centre P, round which they are capable of revolving. Now since the points A B C, &c., which are the pivots on which the paddle boards turn, are moved in the circumference of a circle, of which the centre is O, they are always at the same distance from that point; consequently they will continually vary their distance from the other centre P. Thus, when a paddle board arrives at that point of its revolution at which the centre P lies precisely between it and the centre O, its distance from P is less than in any other position. As it departs from that point, its distance from the centre P gradually increases until it arrives at the opposite point of its revolution, where the centre O is exactly between it and the centre P; then the distance of the paddle board from the centre P is greatest. This constant change of distance between each paddle board and the centre P is accommodated by the variation of the angle between the radial arm L and the short paddle board arm K; as the paddle board approaches the centre P this gradually diminishes; and as the distance of the paddle board from P increases, the angle is likewise augmented. This change in the magnitude of the angle, which thus accommodates the varying position of the paddle board with respect to the centre P, will be observed in the figure. The paddle board D is nearest to P; and it will be observed that the angle contained between L and K is there very acute; at E the angle between L and K increases, but is still acute; at F it increases to a right angle; at G it becomes obtuse; and at K, where it is most distant from the centre P, it becomes most obtuse. It again diminishes at I, and becomes a right angle between A and B. Now this continual shifting of the direction of the short arm K is necessarily accompanied by an equivalent change of position in the paddle board to which it is attached; and the position of the second centre P is, or may be, so adjusted that this paddle board, as it enters the water and emerges from it, shall be such as shall be most advantageous for propelling the vessel, and therefore attended with less of that vibration which arises chiefly from the alternate depression and elevation of the water, owing to the oblique action of the paddle boards.[41] [Footnote 41: A paddle-wheel resembling this has lately been constructed by Messrs. Seawards. It has been charged by Mr. Morgan as being a colourable invasion of his patent, and the dispute has been brought into the courts of law.] (_i_) The relative value of the two wheels, namely, the common paddle-wheel, and that of Morgan has been investigated by Professor Barlow of the Military School, at Woolwich, and the results published in a paper of much ability in the Philosophical Transactions for 1834. By this paper it appears, that, when the paddles are not wholly immersed, the wheel of Morgan has no important advantage over the other, and only acquires one when the wheel wallows. But the most important of his inferences is that the common paddle is least efficient when in a vertical position, contrary to the usual opinion. From this we have a right to infer that the search for a form of wheel which shall always keep the paddle vertical is one whose success need not be attended with any important consequence. The superior qualities of Morgan's wheel when the paddles are deeply immersed is ascribed by Barlow to the lessening of the shock sustained by the common paddle-wheel when it strikes the water. This being the case, the triple wheel of Stevens is probably superior to that of Morgan in its efficiency, while it has the advantage of being far simpler and less liable to be put out of order.--A. E. (119.) To form an approximate estimate of the limit of the present powers of steam navigation, it will be necessary to consider the mutual relation of the capacity or tonnage of the vessel; the magnitude, weight, and power of the machinery; the available stowage for fuel; and the average speed attainable in all weathers, as well as the general purposes to which the vessel is to be appropriated, whether for the transport of goods and merchandise, or merely of despatches and passengers. That portion of the capacity of the vessel which is appropriated to the moving power consists of the space occupied by the machinery and the space occupied by the fuel; the magnitude of the latter will necessarily depend upon the length of the voyage which the vessel must make without receiving a fresh supply of coals. If the voyage be short, this space may be proportionally limited, and a greater portion of room will be left for the machinery. If, on the contrary, the voyage be longer, a greater stock of coals will be necessary, and a less space will remain for the machinery. More powerful vessels, therefore, in proportion to their tonnage, may be used for short than for long voyages. [Illustration: Pl. XII.] Taking an average of fifty-one voyages made by the Admiralty steamers, from Falmouth to Corfu and back during four years ending June, 1834, it was found that the average rate of steaming, exclusive of stoppages, was 7-1/4 miles per hour, taken in a direct line between the places, and without allowing for the necessary deviations in the course of the vessel. The vessels which performed this voyage varied from 350 to 700 tons burthen by measurement, and were provided with engines varying from 100 horse to 200 horse-power, with stowage for coals varying from 80 to 240 tons. The proportion of the power to the tonnage varied from 1 horse to 3 tons to 1 horse to 4 tons; thus, the MESSENGER had a power of 200 horses, and measured 730 tons; the FLAMER had a power of 120 horses, and measured 500 tons; the COLUMBIA had 120 horses, and measured 360 tons. In general, it may be assumed that for the shortest class of trips, such as those of the Margate steamers, and the packets between Liverpool or Holyhead and Dublin, the proportion of the power to the tonnage should be that of 1 horse-power to every 2 tons by measure; while for the longest voyages the proportion would be reduced to 1 horse to 4 tons, voyages of intermediate lengths having every variety of intermediate proportion. Steamers thus proportioned in their power and tonnage may then, on an average of weathers, be expected to make 7-1/4 miles an hour while steaming, which is equivalent to 174 miles per day of twenty-four hours. But, in very long voyages, it rarely happens that a steamer can work constantly without interruption. Besides stress of weather, in which she must sometimes lie-to, she is liable to occasional derangements of her machinery, and more especially of her paddles. In almost every long voyage hitherto attempted, some time has been lost in occasional repairs of this nature while at sea. We shall perhaps, therefore, for long voyages, arrive at a more correct estimate of the daily run of a steamer by taking it at 160 miles.[42] [Footnote 42: The American reader will hardly be able to refrain from a smile at this estimate of Dr. Lardner of the speed of steamboats, founded upon the most improved practice of Europe at the close of the year 1835. The boats on the Hudson River have for years past averaged a speed of 15 miles per hour, and the Lexington, which was constructed for a navigation part of which is performed in the open ocean, could probably keep up a speed of the same amount, except in severe storms. With boats, constructed on the principles of those which navigate Long Island Sound and the Chesapeake, we should not fear to assume 12 miles per hour, or, upwards of 280 miles per day as their average rate of crossing the ocean.--A. E.] By a series of carefully conducted experiments on the consumption of coals, under marine boilers and common land boilers, which have been lately made at the works of Mr. Watt, near Birmingham, it has been proved that the consumption of fuel under marine boilers is less than under land boilers, in the proportion of 2 to 3 very nearly. On the other hand, I have ascertained from general observation throughout the manufacturing districts in the North of England, that the average consumption of coals under land boilers of all powers above the very smallest class is at the rate of 15 pounds of coals per horse-power per hour. From this result, the accuracy of which may be fully relied upon, combined with the result of the experiments just mentioned at Soho, we may conclude that the average consumption of marine boilers will be at the rate of 10 lbs. of coal per horse power per hour. Mr. Field, of the firm of Maudslay and Field, in his evidence before a Select Committee of the House of Commons on Steam Navigation to India, has stated from his observation, and from experiments made at different periods, that the consumption is only 8 lbs. per horse-power per hour. In the evidence of Mr. William Morgan, however, before the same committee, the actual consumption of fuel on board the Mediterranean packets is estimated at 16 cwt. per hour for engines of 200 horse power, and 8-1/4 cwt. for engines of 100 horse-power. From my own observation, which has been rather extensive both with respect to land and marine boilers, I feel assured that 10 lbs. per hour more nearly represents the practical consumption than the lower estimate of Mr. Field. We may then assume the daily consumption of coal by marine boilers, allowing them to work upon an average for 22 hours, the remainder of the time being left for casual stoppages, at 220 lbs. of coal per horse-power, or very nearly 1 ton for every ten horses' power. In short voyages, where there will be no stoppage, the daily consumption will a little exceed this; but the distance traversed will be proportionally greater. When the proportion of the power to the tonnage remains unaltered, the speed of the vessel does not materially change. We may therefore assume that 10 pounds of coal per horse power will carry a sea-going steamer adapted for long voyages 7-1/4 miles direct distance; and therefore to carry her 100 miles will require 138 pounds, or the 1/16th part of a ton nearly. Now, the Mediterranean steamers are capable of taking a quantity of fuel at the rate of 1-1/4 tons per horse power; but the proportion of their power to their tonnage is greater than that which would probably be adapted for longer runs. We shall, therefore, perhaps be warranted in assuming that it is practicable to construct a steamer capable of taking 1-1/2 tons of fuel per horse-power. At the rate of consumption just mentioned, this would be sufficient to carry her 2400 miles in average weather; but as an allowance of fuel must always be made for emergencies, we cannot suppose it possible for her to encounter this extreme run. Allowing, then, spare fuel to the extent of a quarter of a ton per horse-power, we should have as an extreme limit of a steamer's practicable voyage, without receiving a relay of coals, a run of about 2000 miles. (120.) This computation is founded upon results obtained from the use chiefly of the North of England coal. It has, however, been stated in evidence before the select committee above mentioned, that the _Llangennech_ coal of Wales is considerably more powerful. Captain Wilson, who commanded the HUGH LINDSAY steamer in India, has stated that this coal is more powerful than Newcastle, in the proportion of 9 to 6-1/2.[43] Some of the commanders of the Mediterranean packets have likewise stated that the strength of this coal is greater than that of Newcastle in the proportion of 16 to 11.[44] So far then as relates to this coal, the above estimate must be modified, by reducing the consumption nearly in the proportion of 3 to 2. [Footnote 43: Vide Report of Select Committee on Steam Navigation, p. 152.] [Footnote 44: Ibid. p. 7.] The class of vessels best fitted for undertaking long voyages, without relays of coal, would be one from about 800 to 1000 tons measurement furnished with engines from 200 to 250 horse-power.[45] Such vessels could take a supply of from 300 to 400 tons of coals, which being consumed at the rate of from 20 to 25 tons per day, would last about fifteen days. [Footnote 45: Engines in steam vessels generally work considerably above their nominal power. The power, however, to which we uniformly refer is the nominal power, or that power at which they would work with steam of the ordinary pressure.] Applying these results, however, to particular cases, it will be necessary to remember that they are average calculations, and must be subject to such modifications as the circumstances may suggest in the particular instances: thus, if a voyage is contemplated under circumstances in which an adverse wind generally prevails, less than the average speed must be allowed, or, what is the same, a greater consumption of fuel for a given distance. Against a strong head wind, in which a sailing vessel would double-reef her top-sails, even a powerful steamer cannot make more than from 2 to 3 miles an hour, especially if she has a head sea to encounter. (121.) In considering the general economy of fuel, it may be right to state, that the results of experience obtained in the steam navigation of our channels, and particularly in the case of the Post Office packets on the Liverpool station, have clearly established the fact, that by increasing the ratio of the power to the tonnage, an actual saving of fuel in a given distance is effected, while at the same time the speed of the vessel is increased. In the case of the Post Office steamers called the DOLPHIN and the THETIS (Liverpool station,) the power has been successively increased, and the speed proportionably augmented; but the consumption of fuel per voyage between Liverpool and Dublin has been diminished. This, at first view, appears inconsistent with the known theory of the resistance of solids moving through fluids; since this resistance increases in the same proportion as the square of the speed. But this physical principle is founded on the supposition that the immersed part of the floating body remains the same. Now I have myself proved by experiments on canals, that when the speed of the boat is increased beyond a certain limit, its draught of water is rapidly diminished; and in the case of a large steam raft constructed upon the river Hudson, it was found that when the speed was raised to 20 miles an hour, the draught of water was diminished by 7 inches. I have therefore no doubt that the increased speed of steamers is attended with a like effect; that, in fact, they rise out of the water; so that, although the resistance is increased by reason of their increased speed, it is diminished in a still greater proportion by reason of their diminished immersion. Meanwhile, whatever be the cause, it is quite certain that the resistance in moving through the water must be diminished, because the moving power is always in proportion to the quantity of coals consumed, and at the same time in the proportion to the resistance overcome. Since, then, the quantity of coals consumed in a given distance is diminished while the speed is increased, the resistance encountered throughout the same distance must be proportionally diminished. (122.) Increased facility in the extension and application of steam navigation is expected to arise from the substitution of iron for wood, in the construction of vessels. Hitherto iron steamers have been chiefly confined to river navigation; but there appears no sufficient reason why their use should be thus limited. For sea voyages they offer many advantages; they are not half the weight of vessels of equal tonnage constructed of wood; and, consequently, with the same tonnage they will have less draught of water, and therefore less resistance to the propelling power; or, with the same draught of water and the same resistance, they will carry a proportionally heavier cargo. The nature of their material renders them more stiff and unyielding than timber; and they do not suffer that effect which is called _hogging_, which arises from a slight alteration which takes place in the figure of a timber vessel in rolling, accompanied by an alternate opening and closing of the seams. Iron vessels have the further advantage of being more proof against fracture upon rocks. If a timber vessel strike, a plank is broken, and a chasm opened in her many times greater than the point of rock which produces the concussion. If an iron vessel strike she will either merely receive a dinge, or be pierced by a hole equal in size to the point of rock which she encounters. Some examples of the strength of iron vessels was given by Mr. Macgregor Laird, in his evidence before the Committee of the Commons on Steam Navigation, among which the following may be mentioned:--An iron vessel, called the ALBURKAH, in one of their experimental trials got aground, and lay upon her anchor: in a wooden vessel the anchor would probably have pierced her bottom; in this case, however, the bottom was only dinged. An iron vessel, built for the Irish Inland Navigation Company, was being towed across Lough Derg in a gale of wind, when the towing rope broke, and she was driven upon rocks, on which she bumped for a considerable time without any injury. A wooden vessel would in this case have gone to pieces. A further advantage of iron vessels (which in warm climates is deserving of consideration) is their greater coolness and perfect freedom from vermin. (123.) The greatest speed which has yet been attained upon water by the application of steam has been accomplished in the case of a river steamer of peculiar form, which has been constructed upon the river Hudson. This boat, or rather raft, consisted of two hollow vessels formed of thin sheet iron, somewhat in the shape of spindles or cigars (from whence it was called the _cigar boat_.) In the thickest part these floats were eight feet in diameter, tapering towards the ends, and about 300 feet long: these floats or buoys, being placed parallel to each other, having a distance of more than 16 feet between them, supported a deck or raft 300 feet long, and 32 feet wide. A paddle-wheel 30 feet in diameter and 16 feet broad revolved between the spindles, impelled by a steam engine placed upon the deck. This vessel drew about 30 inches of water, and attained a speed of from 20 to 25 miles an hour: she ran upon a bank in the river Hudson, and was lost. The projector is now employed in constructing another vessel of still larger dimensions. It is evident that such a structure is altogether unfitted for sea navigation. In the case of a wide navigable river, however, such as the Hudson, it will no doubt be attended with the advantage of greater expedition. (124.) Several projects for the extension of steam navigation to voyages of considerable length have lately been entertained both by the public and by the legislature, and have imparted to every attempt to improve steam navigation increased interest. A committee of the House of Commons collected evidence and made a report in the last session in favour of an experiment to establish a line of steam communication between Great Britain and India. Two routes have been suggested by the committee, each being a continuation of the line of Admiralty steam packets already established to Malta and the Ionian Isles. One of the routes proposed is through Egypt, the Red Sea, and across the Indian Ocean to Bombay, or some of the other Presidencies; the other across the north part of Syria to the banks of the Euphrates, by that river to the Persian Gulf, and from thence to Bombay. Each of these routes will be attended with peculiar difficulties, and in both a long sea voyage will be encountered. In the route by the Red Sea, it is proposed to establish steamers between Malta and Alexandria (860 miles). A steamer of 400 tons burthen and 100 horse-power would perform this voyage, upon an average of all weathers incident to the situation, in from 5 to 6 days, consuming 10 tons of coal per day. But it is probable that it might be found more advantageous to establish a higher ratio between the power and the tonnage. From Alexandria, the transit might be effected by land across the Isthmus to Suez--a journey of from 4 to 5 days--by caravan and camels; or the transit might be made either by land or water from Alexandria to Cairo, a distance of 173 miles; and from Cairo to Suez, 93 miles, across the desert, in about 5 days. At Suez would be a station for steamers, and the Red Sea would be traversed in 3 runs or more. If necessary, stations for coals might be established at Cosseir, Judda, Mocha, and finally at Socatra--an island immediately beyond the mouth of the Red Sea, in the Indian Ocean: the run from Suez to Cosseir would be 300 miles--somewhat more than twice the distance from Liverpool to Dublin. From Cosseir to Judda, 450 miles; from Judda to Mocha, 517 miles; and from Mocha to Socatra, 632 miles. It is evident that all this would, without difficulty, in the most unfavourable weather, fall within the present powers of steam navigation. If the terminus of the passage be Bombay, the run from Socatra to Bombay will be 1200 miles, which would be, upon an average of weather, about 8 days' steaming. The whole passage from Alexandria to Bombay, allowing 3 days for delay between Suez and Bombay, would be 26 days: the time from Bombay to Malta would therefore be about 33 days; and adding 14 days to this for the transit from Malta to England, we should have a total of 47 days from London to Bombay, or about 7 weeks. If the terminus proposed were Calcutta, the course from Socatra would be 1250 miles south-east to the Maldives, where a station for coals would be established. This distance would be equal to that from Socatra to Bombay. From the Maldives, a run of 400 miles would reach the southern point of Ceylon, called the Point de Galle, which is the best harbour (Bombay excepted) in British India: from the Point de Galle, a run of 600 miles will reach Madras; and from Madras to Calcutta would be a run of about 600 miles. The voyage from London to Calcutta would be performed in about 60 days. At a certain season of the year there exists a powerful physical opponent to the transit from India to Suez: from the middle of June until the end of September, the south-west monsoon blows with unabated force across the Indian Ocean, and more particularly between Socatra and Bombay. This wind is so violent as to leave it barely possible for the most powerful steam packet to make head against it, and the voyage could not be accomplished without serious wear and tear upon the vessels during these months--if indeed it would be practicable at all for any continuance in that season. The attention of parliament has therefore been directed to another line of communication, not liable to this difficulty: it is proposed to establish a line of steamers from Bombay through the Persian Gulf to the Euphrates. The run from Bombay to a place called Muscat, on the southern shore of the Gulf, would be 840 miles in a north-west direction, and therefore not opposed to the south-west monsoon. From Muscat to Bassidore, a point upon the northern coast of the strait at the mouth of the Persian Gulf, would be a run of 255 miles; from Bassidore to Bushire, another point on the eastern coast of the Persian Gulf, would be a run of 300 miles; and from Bushire to the mouth of the Euphrates, would be 120 miles. It is evident that the longest of these runs would offer no more difficulty than the passage from Malta to Alexandria. From Bussora near the mouth of the Euphrates, to Bir, a town upon its left bank near Aleppo, would be 1143 miles, throughout which there are no physical obstacles to the river navigation which may not be overcome. Some difficulties arise from the wild and savage character of the tribes who occupy its banks. It is, however, thought that by proper measures, and securing the co-operation of the Pacha of Egypt, any serious obstruction from this cause may be removed. From Bir, by Aleppo, to Scanderoon, a port upon the Mediterranean, opposite Cyprus, is a land journey, said to be attended with some difficulty but not of great length; and from Scandaroon to Malta is about the same distance as between the latter place and Alexandria. It is calculated that the time from London to Bombay by the Euphrates--supposing the passage to be successfully established--would be a few days shorter than by Egypt and the Red Sea. Whichever of these courses may be adopted, it is clear that the difficulties, so far as the powers of the steam engine are concerned, lie in the one case between Socatra and Bombay, or between Socatra and the Maldives, and in the other case between Bombay and Muscat. Even the run from Malta to Alexandria or Scandaroon is liable to objection, from the liability of the boiler to deposite and incrustation, unless some effectual method be taken to remove this source of injury. If, however, the contrivance of Mr. Hall, or of Mr. Howard, or any other expedient for a like object, be successful, the difficulty will then be limited to the necessary supply of coals for so long a voyage. This, however, has already been encountered and overcome on four several voyages by the HUGH LINDSAY steamer from Bombay to Suez: that vessel encountered a still longer run on these several trips, by going, not to Socatra but to Aden, a point on the coast of Arabia near the Straits of Babel Mandeb, being a run of 1641 miles, which she performed in 10 days and 19 hours. The entire distance from Bombay to Suez was in one case performed in 16 days and 16 hours; and under the most unfavourable circumstances, in 23 days. The average was 21 days for each trip. (125.) Another projected line of steam communication, which offers circumstances of equal interest to the people of these countries and the United States, is that which is proposed to be established between London and New York. On the completion of the London and Liverpool railroad, Dublin will be connected with London, by a continuous line of steam transport. It is proposed to continue this line by a railroad from Dublin to some point on the western coast of Ireland; among others, the harbour of VALENTIA has been mentioned. The nearest point of the western continent is St. John's, Newfoundland, the distance of which from Valentia is 1900 miles; the distance from St. John's to New York is about 1200 miles, Halifax (Nova Scotia) being a convenient intermediate station. The distance from Valentia to St. John's comes very near the point which we have already assigned as the probable present limit of steam navigation. The Atlantic Ocean also offers a formidable opponent in the westerly winds which almost constantly prevail in it. These winds are, in fact, the reaction of the trades, which blow near the equator in a contrary direction, and are produced by those portions of the equatorial atmosphere which, rushing down the northern latitudes, carry with them the velocity from west to east proper to the equator. Besides this difficulty, St. John's and Halifax are both inaccessible, by reason of the climate, during certain months of the year. Should these causes prevent this project from being realized, another course may be adopted. We may proceed from the southern point of Ireland or England to the Azores, a distance of about 1800 miles: from the Azores to New York would be a distance of about 2000 miles, or from the Azores to St. John's would be 1600 miles.[46] [Footnote 46: A treatise on the Steam Engine is not the place to enter into discussion on the causes of the several constant, periodic, and prevailing winds, otherwise we should feel it our duty to correct the opinion adopted by Dr. Lardner from the older authorities, in relation to the course of the westerly winds. These winds are, in the South Atlantic, and in both South and North Pacific, constant winds. In the North Atlantic between the latitudes, of 35° and 45°, and, therefore, in the track of the vessels which navigate between the United States and Great Britain, they are the most frequent prevailing winds, except in the months of April and October. They are certainly not the reaction of the trade winds, which is in a well known zone, to the south of the region in which these westerly winds prevail, under the name of the Horse latitudes of our navigations, and the Grassy sea of the Spaniards. Those who wish to study the true theory of these winds will find it in Daniell's learned and ingenious work, "On Atmospheric Phenomena," or in the analysis of that work in the American Quarterly Review.] (_k_) While the inhabitants of Great Britain are discussing the project of the communication with New York, by means of the stations described by Dr. Lardner, those of the United States appear to be seriously occupied in carrying into effect a direct communication from New York to Liverpool. At the speed which has been given to the American steam boats, this presents no greater difficulties than the voyage from the Azores to New York, would, to one having the speed of no more than 7-1/4 miles per hour. As this attempt is beyond the limit of individual enterprise, there is, at the present moment, an application before the Legislature of the State of New York for a charter to carry this project into effect. It will be difficult to estimate the results of this enterprise, which will bring the old and new world within 12 or 15 days voyage of each other.--A. E.[47] [Footnote 47: Dr. Lardner appears purposely to have omitted any detail of the history of Steam Navigation. It would be an invidious task on the part of a mere editor to attempt to supply what he has thought proper to avoid. We therefore merely refer to this subject for the purpose of expressing the hope, that this silence is an earnest that the writers of Europe are about to abandon the claims they have set up for their countrymen to the merit of introducing the successful practice of Steam navigation, and that the respective services of Fitch, Evans, Fulton, and the elder Stevens will soon be universally acknowledged.--A. E.] CHAPTER XII. GENERAL ECONOMY OF STEAM POWER. Mechanical efficacy of steam -- proportional to the quantity of water evaporated, and to the fuel consumed -- Independent of the pressure. -- Its mechanical efficacy by condensation alone. -- By condensation and expansion combined -- by direct pressure and expansion -- by direct pressure and condensation -- by direct pressure, condensation, and expansion. -- The power of engines. -- The duty of engines. -- Meaning of horse power. -- To compute the power of an engine. -- Of the power of boilers. -- The structure of the grate-bars. -- Quantity of water and steam room. -- Fire surface and flue surface. -- Dimensions of steam pipes. -- Velocity of piston. -- Economy of fuel. -- Cornish duty reports. (130.) Having explained in the preceding chapters the most important circumstances connected with the principal varieties of steam engines, it remains now to explain some matters of detail connected with the power, efficiency, and economy of these machines, which, though perhaps less striking and attractive than the subjects which have hitherto engaged us, are still not undeserving of attention. It has been shown in the first chapter, that water exposed to the ordinary atmospheric pressure (the amount of which may be expressed by a column of 30 inches of mercury) will pass from the liquid into the vaporous state when it arrives at the temperature of 212°; and the vapour thus produced from it will have an elastic force equal to that of the atmosphere. If the water, however, to which heat is applied, be submitted to a greater or less pressure than that of the atmosphere, it will boil at a greater or less temperature, and will always produce steam of an elastic force equal to the pressure under which it boils. Now it is a fact as remarkable as it is important, that to convert a given weight of water into vapour will require the same quantity of heat, under whatever pressure, and at whatever temperature the water may boil. Let us suppose a tube, the base of which is equal to a square foot, in which a piston fits air-tight and steam-tight. Immediately under the piston, let a cubic inch of water be placed, which will be spread in a thin layer over the bottom of the tube. Let the piston be counterbalanced by a weight (acting over a pulley) which will be equivalent to the weight of the piston, so that it shall be free to ascend by the application of any pressure below it. Now let the flame of a lamp be applied at the bottom of the tube: the water under the piston being affected by no pressure from above, except that of the atmosphere acting upon the piston, will boil at the temperature of 212°, and by the continued application of the lamp it will at length be converted into steam. The steam into which the cubic inch of water is converted will expand into the magnitude of a cubic foot, exerting an elastic force equal to the atmospheric pressure; consequently the piston will be raised one foot above its first position in the tube, and the cubic foot beneath it will be completely filled with steam. Let us suppose, that to produce this effect required the lamp to be applied to the tube for the space of fifteen minutes. The water being again supposed at its original temperature, and the piston in its first position, let a weight be placed upon the piston equal to the pressure of the atmosphere, so that the water beneath the piston will be pressed down by double the atmospheric pressure. If the lamp be once more applied, the water will, as before, be converted into vapour; but the piston will now be raised to the height of only six inches[48] from the bottom, the steam expanding into only half its former bulk. The temperature at which the water would commence to be converted into vapour, instead of being 212°, would be 250°; but the time elapsed between the moment of the first application of the lamp, and the complete conversion of the water into steam, will still be fifteen minutes. [Footnote 48: Strictly speaking, the height to which the piston would be raised would not diminish in so great a proportion as the pressure is increased, because the increase of pressure being necessarily accompanied by an increase of temperature, a corresponding expansion would be produced. Therefore there will be a slight increase in the total mechanical effect of the steam. The difference, however, is not very important in practice, and it is usual to consider the density of steam as proportional to the pressure.] Again, if the piston be loaded with a weight equal to double the atmospheric pressure, the water will be pressed down by the force of three atmospheres. If the lamp be applied as before, the water would be converted into steam in the same time; but the piston will now be raised only four inches above its first position, and the steam will consequently be three times as dense as when the piston was pressed down only by the atmosphere. From these and similar experiments we infer:-- _First_, That the elastic pressure of steam is equal to the mechanical pressure under which the water producing the steam has been boiled. _Secondly_, That the bulk which steam fills is diminished in the same proportion as the pressure of the steam is increased; or, in other words, that the density of steam is always in the same proportion as its pressure. _Thirdly_, That the same quantity of heat is sufficient to convert the same weight of water into steam, whatever be the pressure under which the water is boiled, or whatever be the density and pressure of the steam produced. _Fourthly_, That the same quantity of water being converted into steam, produces the same mechanical effect, whatever be the pressure or the density of the steam. Thus, in the first case, the weight of one atmosphere was raised a foot high; in the second case, the weight of two atmospheres was raised through half a foot; and, in the third case, the weight of three atmospheres was raised through the third of a foot; the weight raised being in every case increased in the same proportion as the height through which it is elevated is diminished. Every increase of the weight is, therefore, compensated by a proportionate diminution of the height through which it is raised, and the mechanical effect is consequently the same. _Fifthly_, That the same quantity of heat or fuel is necessary and sufficient to produce the same mechanical effect, whatever be the pressure of the steam which it produces. If steam be used to raise a piston against the atmospheric pressure only, although a definite physical force will be exerted by it, and a mechanical effect produced, yet under such circumstances it will exert no directly useful efficiency; but after the piston has been raised, and the tube beneath it filled with steam balancing the atmosphere above it, a useful effect to the same amount may be obtained by cooling the tube, and thereby reconverting the steam into water. The piston will thus be urged downwards by the unresisted force of the atmosphere, and any chain or rod attached to it will be drawn downwards with a corresponding force. If the area of the piston be, as already supposed, equal to the magnitude of one square foot, the atmospheric pressure upon it, being 15 pounds for each square inch, will amount to 144 times 15 pounds, or 2160 pounds. By drawing down a chain or rope acting over a pulley, the piston would in its descent (omitting the consideration of friction, &c.) raise a weight of 2160 pounds a foot high. Since 2160 pounds are nearly equal to one ton, it may, for the sake of round numbers be stated thus:-- "_A cubic inch of water, being converted into steam, will, by the condensation of that steam, raise a ton weight a foot high._" Such is the way in which the force of steam is rendered practically available in the atmospheric engine. (131.) The method by which steam is used in the single-acting steam engine of Watt is, in all respects, similar, except that the piston, instead of being urged downwards by the force of the atmosphere, is pressed by steam of a force equal to the atmospheric pressure. It is evident, however, that this does not alter the mechanical result. We have stated that a considerable increase of power, from a given quantity of steam, was produced by cutting off the steam after the piston had made a part of its descent, and allowing the remainder of the descent to be produced by the expansive force of the steam already admitted. We shall now more fully explain the principle on which this increase of power depends. Let A B (_fig. 69._,) as before, represent a tube, the bottom of which is equal to a square foot, and let P be a piston in it, resting upon a cubic inch of water spread over the bottom; and let w be an empty vessel, the weight of which exactly counterpoises the piston. By the application of the lamp, the water will be converted into steam of the atmospheric pressure, and the piston will be raised from P to P´, through the height of one foot, the space in the tube beneath it being filled with steam, and the vessel w will have descended through one foot. Let half a ton of water be now poured into the vessel W; its weight will draw the piston P´ upwards, so that the steam below it will expand into a larger space. When the piston P´ was only balanced by the empty vessel W, it was pressed downwards by the whole weight of the atmosphere above, which amounts to about one ton: now, however, half of this pressure is balanced by the half ton of water poured into the vessel W; consequently the effective downward pressure on the piston P´ will be only half a ton, or half its former amount. The piston will therefore rise, until the pressure of the steam below it is diminished to the same extent. By what has been already explained, this will take place when the steam is allowed to expand into double its former bulk; consequently, when the piston has risen to P´´, one foot higher, or two feet from the bottom of the tube, the steam will then exactly balance the downward pressure on the piston, and the latter will remain stationary; the vessel W, with the half ton of water it contains, will have descended one foot lower, or two feet below its first position. Let the steam now be cooled and reconverted into water, and at the same time let another half ton of water be supplied to the vessel W; the pressure below the piston being entirely removed, the atmospheric pressure will act above it with undiminished force; and this force, amounting to one ton, will draw up the vessel W, with its contents. When the piston descends, as it will do, to the bottom of the tube, the ton of water contained in the vessel W will be raised through two perpendicular feet.[49] [Footnote 49: Strictly speaking, the quantity of water supposed in these cases to be placed in the vessel W would just _balance_ the atmospheric pressure. A slight preponderance must therefore be given to the piston, to produce the motion.] Now, in this process it will be observed that the quantity of steam consumed is not more than in the former case, viz. the vapour produced by boiling one cubic inch of water. Let us consider, however, the mechanical effect which has resulted from it; half a ton of water has been allowed to descend through one foot, while a ton has been raised through two feet: deducting the force lost by the descent of half a ton through one foot from the force obtained by the ascent of one ton through the two feet, we obtain for the whole mechanical effect one ton and a half raised through one foot; for it is evident that half a ton has been raised from the lowest point to which the vessel W descended one foot above that point, and one ton has been raised through the other foot, which is equivalent to one ton and a half through one foot. Comparing this with the effect produced in the first case, where the steam was condensed without causing its expansion, it will be evident that there is an increase of 50 per cent. upon the whole mechanical effect produced. But this is not the limit of the increase of power by expansion. Instead of condensing the steam when the piston had arrived at P´´, let a further quantity of water amounting to one sixth of a ton be poured into the vessel W, in addition to the half ton which it previously contained; the effective pressure on the piston P´´, being only half a ton, will be overbalanced by the preponderating weight in the vessel w, and the piston will consequently ascend. It will become stationary when the steam by expansion loses a quantity of force equal to the additional weight which the vessel W has received: now, that vessel, having successively received a half and a sixth of a ton will contain two thirds of a ton; consequently the effective downward pressure on the piston will be only a third of a ton, and the steam to balance this must expand into three times the space it occupied when equal, to the atmospheric pressure. It must therefore ascend to P´´´, three feet above the bottom of the tube. If the steam in the tube be now condensed, and at the same time one third of a ton of water be supplied to the vessel W, so as to make its total contents amount to one ton, the piston will descend, being urged downwards by the unresisted atmospheric pressure, and the ton of water contained in the vessel W will be raised through three perpendicular feet. In this case, as in the former, the total quantity of steam consumed is that of one cubic inch of water; but the mechanical effect it produces is still further increased. To calculate its amount, we must consider that half a ton of water has fallen through two feet, which is equivalent to a ton falling through one foot, besides which the sixth part of a ton has fallen through one foot. The total loss, therefore, by the fall of water has been one ton and one sixth through one foot, while the force gained by the ascent of water has been one ton raised through three feet, which is equivalent to three tons through one foot. If, then, from three tons we deduct one and one sixth, the remainder will be one ton and five sixths raised through one foot; this effect being above 80 per cent. more than that which is produced in the first case, where the steam was not allowed to expand. To carry the inquiry one step further: Let us suppose that, upon the arrival of the piston at P´´´, a further addition of water to the amount of one twelfth of a ton be added to it: this, with the water it already contained, would make the total contents three fourths of a ton; consequently, the effective pressure upon the piston would now be reduced to one fourth of the atmospheric pressure. The atmospheric steam would balance this when expanded into four times its original volume: consequently, the piston would come to a state of rest at P´´´´, four feet above the bottom of the tube, and the vessel W would consequently have descended through four perpendicular feet. If the steam in the tube be now condensed as in the former cases, and at the same time a quarter of a ton of water be added to the vessel W, the piston will descend to the bottom of the tube, and the ton of water in the vessel W will be raised through four perpendicular feet. To estimate the mechanical effect thus produced, we have, as before, to deduct the total force lost by the fall of water from the force gained by its elevation: the water has fallen in three distinct portions: first, half a ton has fallen through three perpendicular feet, which is equivalent to one ton and a half through one foot; secondly, one sixth of a ton has fallen through two perpendicular feet, which is equivalent to one third of a ton through one foot; and thirdly, one twelfth of a ton has fallen through one foot: these added together will be equivalent to one ton and eleven twelfths through one foot. One ton has been raised through four feet, which is equivalent to four tons through one foot: deducting from this the force lost by the descent, the surplus gained will be two tons and one twelfth through one foot, being about 108 per cent. more than the force resulting from the condensation of steam without expansion. To the increase of mechanical effect to be produced in this way, there is no theoretical limit. According to the manner in which we have here explained it, to produce the greatest possible effect by a given extent of expansion, it would be necessary to supply the water or other counterpoise to the vessel W, not in separate masses, as we have here supposed, but continuously, so as to produce a regular motion of the piston upwards. Such is the principle on which the advantages of the expansive engine of Watt and Hornblower depend, explained so far as it can be without the aid of the language and reasoning of analysis.[50] [Footnote 50: A strict investigation of this important property, as well as of the other consequences of the quality of expansion, would require more abstruse mathematical processes than would be consistent with the nature of this work.] (132.) We have here, however, only considered the mechanical effect produced by the condensation of steam. Let us now examine its direct action. Let the piston P be supposed to be connected by a rod with a load or resistance which it is intended to raise, and let the load placed upon it be supposed to amount to one ton, the total pressure on the piston will then be two tons; one due to the atmospheric pressure, and the other to the amount of the load. Upon applying heat to the water, steam will be produced; and when the water has been completely evaporated, the piston will rise to the height of six inches from the bottom of the tube. The total mechanical effect thus produced will be one ton weight raised through six perpendicular inches, which is equivalent to half a ton raised through one foot. Again, let the load upon the piston be two tons; this will produce a total pressure upon the water below it amounting to three tons, including the atmospheric pressure. The water, when converted into vapour under this pressure, will raise the piston and its load through four perpendicular inches: the useful mechanical effect will then be two tons raised through the third of a foot, which is equivalent to two thirds of a ton raised one foot. In the same manner, if the piston were loaded with three tons, the mechanical effect would be equivalent to three fourths of a ton raised through one foot, and so on. It appears therefore from this reasoning, that when the direct force of steam of greater pressure than the atmosphere is used without condensation, the total mechanical effect is always less than that produced by the condensation of atmospheric steam without expansion; but that the greater the pressure under which the steam is produced, the less will be the difference between these effects. In general, the proportion of the mechanical effect of high-pressure steam to the effect produced by the condensation of atmospheric steam, will be as the number of atmospheres expressing the pressure of the steam to the same number increased by one. Thus, if steam be produced under the pressure of six atmospheres, the proportion of its effect to that of the condensation of atmospheric steam will be as six to seven. (133.) Another method of applying the power of steam mechanically is, to combine its direct action with condensation but without expansion. The piston being, as before, loaded with one ton, the evaporation of the water will raise it through six perpendicular inches, and the result so far will be equivalent to a ton raised half a foot; but if the piston-rod be supposed also to act by a chain or cord over a wheel, so as to pull a weight up, the steam which has just raised the ton weight through six inches, may be condensed, and the piston will descend with a force of one ton into the vacuum thus produced, and another ton may be thus raised through half a foot. The total mechanical power thus yielded by the steam, adding to its direct action its effect by condensation, will then be one ton raised through one foot, being an effect exactly equal to that obtained by the condensation of atmospheric steam. If the piston be loaded with two tons, its direct action will, as we have shown, raise these two tons through four inches, which is equivalent to two thirds of a ton raised a foot. By condensing this steam a ton weight may be raised in the same manner, by the descent of the piston through a third of a foot, which is equivalent to the third of a ton raised through one foot. By pursuing like reasoning, it will appear that, if the direct force of high-pressure steam be combined with the indirect force produced by its condensation, the total mechanical effect will be precisely equal to the mechanical effect by the mere condensation of atmospheric steam. (134.) In applying the principle of expansion to the direct action of high-pressure steam, advantages are gained analogous to those already explained with reference to the method of condensation. Let the piston be supposed to be loaded with three tons: the evaporation of the water beneath it will raise this weight, including the atmospheric pressure, through three perpendicular inches. Let one ton be now removed, and the remaining two tons will be raised, by the expansion of the steam, through another perpendicular inch. Let the second ton be now removed, and the piston loaded with the remaining ton will rise, by the expansion of the steam, to the height of six inches from the bottom. These consequences follow immediately from the principle that steam will expand in proportion as the pressure upon it is diminished, observing that in this case the atmospheric pressure, amounting to one ton, must always be added to the load. In this process three separate effects are produced: one ton is raised through three inches, which is equivalent to a quarter of a ton raised through one foot; another ton is raised through four inches, which is equivalent to a third of a ton through a foot, and the third ton is raised through six inches, which is equivalent to half a ton raised through a foot. The total of these effects amounts to one and one-twelfth of a ton raised through one foot, while the same load, raised by the high-pressure steam without expansion, would be equivalent to only half a ton raised through one foot. Again, let the load placed upon the piston be five tons: the evaporation of the water will raise this through the sixth part of a foot; if one ton be now removed, the other four tons will be raised to a height above the bottom of the tube equal to a fifth part of a foot; another ton being removed, the remaining three will be raised to a height from the bottom equal to a fourth of a foot; and so on, the last ton being raised through half a foot. To estimate the total mechanical effect thus produced, we are to consider that the several tons raised from their first position are raised through the sixth, fifth, fourth, third, and half of a perpendicular foot, giving a total effect equal to the sixth, fifth, fourth, third, and half of a ton severally raised through one foot; these, therefore, added together, will give a total of nineteen twentieths of a ton raised through one foot. In general, the expansive force applied to the direct action of high-pressure steam, therefore, will increase its effect according to the same law, and subject to the same principles as were shown with respect to the method of condensation accompanied with expansion. The expansive action of high-pressure steam may be accompanied with condensation, so as considerably to increase the mechanical effect produced; for, after the weights with which the piston is loaded have been successively raised to the extent permitted by the elastic force of the steam, and are removed from the piston, the steam will expand until it balances the atmospheric pressure. It may afterwards be made further to expand, by adding weights to the counterpoise W in the manner already explained; and, the steam being subsequently condensed, all the effects will be produced upon the descent of the piston which we have before noticed. It is evident that by this means the mechanical effect admits of very considerable increase. (135.) We have hitherto considered the piston to be resisted by the atmospheric pressure above it; but, as is shown in the preceding chapters, in the modern steam engines, the atmosphere is expelled from the interior of the machine by allowing the steam to pass freely through all its cavities in the first instance, and to escape at some convenient aperture, which, opening outwards, will effectually prevent the subsequent re-admission of air. The piston-rod and other parts which pass from the external atmosphere to the interior of the machine, are likewise so constructed and so supplied with oil or other lubricating matter that neither the escape of steam nor the entrance of air is permitted. We are therefore now to consider the effect of the action of steam against the piston P, when subjected to a resistance which may be less in amount, to any extent, than the atmospheric pressure. In such machines the steam always acts both directly by its power, and indirectly by its condensation. In calculating its effects, excluding friction, &c., we have therefore only to estimate its total force upon the piston, and to deduct the force of the uncondensed vapour which will resist the motion of the piston. Supposing, then, the total force exerted upon the piston, after deducting the resistance from the uncondensed vapour, to be one ton, and the length of the cylinder to be one foot, each motion of the piston from end to end of the cylinder will produce a mechanical force equivalent to a ton weight raised one foot high. If in this case the magnitude of the piston be equivalent to one square foot, the pressure of the steam will be equal to that of the atmosphere, and the quantity of water in the form of steam which the cylinder will contain will be a cubic inch, while the quantity of steam in it will be a cubic foot. In proportion as the area of the piston is enlarged the pressure of the steam will be diminished, if the moving force is required to remain the same; but with every diminution of pressure the density of the steam will be diminished in the same proportion, and the cylinder will still contain the same quantity of water in the form of vapour. In this way steam may be used, as a mechanical agent, with a pressure to almost any extent less than that of the atmosphere, and at temperatures considerably lower than 212°. To obtain the same mechanical force, it is only necessary to enlarge the piston in the same proportion as the pressure of the steam is diminished. By a due attention to this circumstance, the expansive power of steam, both in its direct action and by condensation, may be used with very much increased advantage; and such is the principle on which the benefits derived from Woolf's contrivances depend. If steam of a high-pressure, say of three or four atmospheres, be admitted to the piston, and allowed to impel it through a very small portion of the descent, it may then be cut off and its expansion may be allowed to act upon the piston until the pressure of the steam is diminished considerably below the atmospheric pressure; the steam may then be condensed and a vacuum produced, and the process repeated. In the double-acting engines, commonly used in manufactures and in navigation, and still more in the high-pressure engines used for locomotion, the advantageous application of the principle of expansion appears to have been hitherto attended with difficulties; for, notwithstanding the benefits which unquestionably attend it in the economy of fuel, it has not been generally resorted to. To derive from this principle full advantage, it would be necessary that the varying power of the expanding steam should encounter a corresponding, or a nearly corresponding, variation in the resistance: this requisite may be attained, in engines applied to the purpose of raising water, by many obvious expedients; but when they have, as in manufactures, to encounter a nearly uniform resistance, or, in navigation and locomotion, a very irregular resistance, the due application of expansion is difficult, if indeed it be practicable. We have seen that the mechanical effect produced by steam when the principle of expansion is not used, is always proportional to the quantity of water contained in the steam, and is likewise in the same proportion so long as a given degree of expansion is used. It is apparent, therefore, that the mechanical power which is or ought to be exerted by an engine is in the direct proportion of the quantity of water evaporated. It has also been shown that the quantity of water evaporated, whatever be the pressure of the steam, will be in the direct proportion of the quantity of heat received from the fuel, and therefore in the direct proportion of the quantity of fuel itself, so long as the same proportion of its heat is imparted to the water. (136.) The POWER of an engine is a term which has been used to express the rate at which it is able to raise a given load, or overcome a given resistance. The DUTY of an engine is another term, which has been adopted to express the load which may be raised a given perpendicular height, by the combustion of a given quantity of fuel. When steam engines were first introduced, they were commonly applied to work pumps or mills which had been previously wrought by horses. It was, therefore, convenient, and indeed necessary, in the first instance, to be able to express the performance of these machines by reference to the effects of animal power, to which manufacturers, miners, and others, had been long accustomed. When an engine, therefore, was capable of performing the same work in a given time, as any given number of horses of average strength usually performed, it was said to be an engine of so many _horses' power_. This term was long used with much vagueness and uncertainty: at length, as the use of steam engines became more extended, it was apparent that confusion and inconvenience would ensue, if some fixed and definite meaning were not assigned to it, so that the engineers and others should clearly understand each other in expressing the powers of these machines. The term _horse-power_ had so long been in use, that it was obviously convenient to retain it. It was only necessary to agree upon some standard by which it might be defined. The performance of a horse of average strength, working for eight hours a day, was, therefore, selected as a standard or unit of steam-engine power. Smeaton estimated the amount of mechanical effect which the animal could produce at 22,916 pounds, raised one foot per minute; Desaguiliers makes it 27,500 pounds, raised through the same height. Messrs. Bolton and Watt caused experiments to be made with the strong horses used in the breweries in London; and from the result of these they assigned 33,000 pounds raised one foot per minute, as the value of a horse's power: this is, accordingly, the estimate now generally adopted; and, when an engine is said to be of so many horses' power, it is meant that, when in good working order and properly managed, it is capable of overcoming a resistance equivalent to so many times 33,000 pounds raised one foot per minute. Thus, an engine of ten-horse-power would be capable of raising 330,000 pounds one foot per minute. As the same quantity of water converted into steam will always produce the same mechanical effect, whatever be the density of the steam produced from it, and at whatever rate the evaporation may proceed, it is evident that the _power_ of a steam engine will depend on two circumstances: first, the rate at which the boiler with its appendages is capable of evaporating water; and, secondly, the rate at which the engine is capable of consuming the steam by its work. We shall consider these two circumstances separately. The rate at which the boiler produces steam will depend upon the rate at which heat can be transmitted from the fire to the water which it contains. Now this heat is transmitted in two ways: either by the direct action of the fire radiating heat against the surface of the boiler; or by the flame, and heated air which escapes from the fire, passing through the flues, as already explained. The surface of the boiler exposed to the direct radiation of the fire is technically called _fire surface_; and that which takes heat from the flame and air, on its way to the chimney, is called _flue surface_. Of these the most efficient in the generation of steam is the former. In stationary boilers, used for condensing engines, where magnitude and weight are matters of little importance, it has been found that the greatest effect has been produced in general by allowing four and a half square feet of fire surface, and four and a half square feet of flue surface, for every horse-power. By means of this quantity of fire and flue surface, a cubic foot of water per hour may be evaporated. It has been already shown that the total power exerted by a cubic inch of water, converted into steam, will be equivalent to 2160 pounds raised one foot. A cubic foot of water consists of 1728 cubic inches, and the power produced by its evaporation will therefore be found by multiplying 2160 by 1728; the product, 3,732,480, expresses the number of pounds' weight which the evaporation of a cubic foot of water would raise one foot high, supposing that its entire mechanical force were rendered available: but to suppose this in practice, would be to suppose the machine, through the medium of which it is worked, moved without any power being expended upon its own parts. It would be, in fact, supposing all its moving parts to be free from friction and other causes of resistance. To form a practical estimate, then, of the real quantity of available mechanical power obtained from the evaporation of a given quantity of water, it will be necessary to inquire what quantity of this power is intercepted by the engine through which it is transmitted. In different forms of steam engine--indeed, we may say in every individual steam engine--the amount thus lost is different; nevertheless, an approximate estimate may be obtained, sufficiently exact to form the basis of a general conclusion. Let us consider, then, severally, the means by which mechanical power is intercepted by the engine. _First_, The steam must flow from the boiler into the cylinder to work the piston; it passes necessarily through pipes more or less contracted, and is, therefore, subject to friction as well as cooling in its passage. _Second_, Force is lost by the radiation of heat from the cylinder and its appendages. _Third_, The friction of the piston in the cylinder must be overcome. _Fourth_, Loss of steam takes place by leakage. _Fifth_, Force is expended in expelling the steam after having worked the piston. _Sixth_, Force is required to open and close the several valves, to pump up the water for condensation, and to overcome the friction of the various axes. _Seventh_, Force is expended upon working the air-pump. In engines which do not condense the steam, and which, therefore, work with steam of high-pressure, some of these sources of waste are absent, but others are of increased amount. If we suppose the total effective force of the water evaporated per hour in the boiler to be expressed by 1000, it is calculated that the waste in a high-pressure engine will be expressed by the number 392; or, in other words, taking the whole undiminished force obtained by evaporation as expressed by 10, very nearly 4 of these parts will be consumed in moving the engine, and the other 6 only will be available. In a single-acting engine which condenses the steam, taking, as before, 1000 to express the total mechanical power of the water evaporated in the boiler, 402 will express the part of this consumed in moving the engine, and 598, therefore, will express the portion of the power practically available; or, taking round numbers, we shall have the same result as in the non-condensing engine, viz. the whole force of the water evaporated being expressed by 10, 4 will express the waste, and 6 the available part. In a double-acting engine the available part of the power bears a somewhat greater proportion to the whole. Taking, as before, 1000 to express the whole force of the water evaporated, 368 will express the proportion of that force expended on the engine, and 632 the proportion which is available for work. In general, then, taking round numbers, we may consider that the mechanical force of four tenths of the water evaporated in the boiler is intercepted by the engine, and the other six tenths are available as a moving force. In this calculation, however, the resistance produced in the condensing engine by the uncondensed steam is not taken into account: the amount of this force will depend upon the temperature at which the water is maintained in the condenser. If this water be kept at the temperature of 120°, the vapour arising from it will have a pressure expressed by three inches seven tenths of mercury; if we suppose the pressure of steam in the boiler to be measured by 37 inches of mercury, then the resistance from the uncondensed steam will amount to one tenth of the whole power of the boiler; this, added to the four tenths already accounted for, would show a waste amounting to half the whole power of the boiler, and consequently only half the water evaporated would be available as a moving power. If the temperature of the condenser be kept down to 100°, then the pressure of uncondensed steam will be expressed by two inches of mercury, and the loss of power consequent upon it would amount to a proportionally less fraction of the whole power. The following example will illustrate the method of estimating the effective power of an engine. In a double-acting engine, in good working condition, the total power of steam in the boiler being expressed by 1000, the proportion intercepted by the engine, exclusive of the resistance of the uncondensed steam, will be 368, and the effective part 632. Now, suppose the pressure of steam in the boiler to be measured by a column of 35 inches of mercury; the thousandth part of this will be seven two hundredths of an inch of mercury, and 632 of these parts will express the effective portion of the power. By multiplying seven two hundredths by 632, we obtain 22 nearly. Now, suppose the temperature in the condenser is 1200, the pressure of steam corresponding to that temperature will be measured by 3-7/10 inches of mercury. Subtracting this from 22, there will remain 18-3/10 inches of mercury, as the effective moving force upon the piston; this will be equivalent to about 7 lbs. on each circular inch. If the diameter of the piston then be 24 inches, its surface will consist of a number of circular inches expressed by the square of 24, or 24 × 24 = 576; and, as upon each of these circular inches there is an effective pressure of 7 lbs., we shall find the total pressure in pounds by multiplying 576 by 7, which gives 4032 lbs. We shall find the space through which this force works per minute, by knowing the length of the cylinder and the number of strokes per minute. Suppose the length of the cylinder to be 5 feet, and the number of strokes per minute 21-1/2. In each stroke[51] the piston will, therefore, move through 10 feet, and in one minute it will move through 215 feet. The moving force, therefore, is 4032 lbs. moved through 215 feet per minute, which is equivalent to 215 times 4032 lbs., or 866,880 lbs., raised one foot per minute. [Footnote 51: By a stroke of the piston is meant its motion from one end of the cylinder and back again.] For every 33,000 lbs. contained in this, the engine has a horse-power. To find the horse-power, then, of the engine, we have only to divide 866,880 by 33,000; the quotient is 26 nearly, and, therefore, the engine is one of 26 horse power. Let it be required to determine the quantity of water which a boiler must evaporate per hour, for each horse-power of the engine which it works. It has been already explained that one horse-power expresses 33,000 lbs. raised one foot high per minute, or, 1,980,000 lbs. raised one foot high per hour. The quantity of water necessary to produce this mechanical effect by evaporation, will be found by considering that a cubic inch of water, being evaporated, will produce a mechanical force equivalent to 2160 lbs. raised a foot high. If we divide 1,980,000, therefore, by 2160, we shall find the number of cubic inches of water which must be evaporated per hour, in order to produce the mechanical effect expressed by one horse-power; the result of this division will be 916,6, which is therefore the number of cubic inches of water per hour, whose evaporation is equivalent to one horse-power. But it has been shown that, for every 6 cubic inches of water evaporated in the boiler which are available as a moving power, there will be 4 cubic inches intercepted by the engine. To find, then, the quantity of waste corresponding to 916 cubic inches of water, it will be necessary to divide that number by 6, and to multiply the result by 4: this process will give 610 as the number of cubic inches of water wasted. The total quantity of water, therefore, which must be evaporated per hour, to produce the effect of one horse-power, will be found by adding 610 to 916, which gives 1526. This result, however, being calculated upon a supposition of a degree of efficiency in the engines which is, perhaps, somewhat above their average state, it has been customary with engineers to allow a cubic foot of water per hour for each horse-power, a cubic foot being 1728 cubic inches, or above 11 per cent. more than the above estimate. (137.) It has been stated, that to evaporate a cubic foot of water per hour requires 9 square feet of surface exposed to the action of the fire and heated air. This, therefore, is the quantity of surface necessary for each horse-power, and we shall find the total quantity of fire and flue surface necessary for a boiler of a given power, by multiplying the number of horses in the power by 9; the product will express, in square feet, the quantity of boiler surface which must be exposed to the fire, one half of this being fire surface and the other half flue surface. Since the supply of heat to the boiler must be proportionate to the quantity of fuel maintained in combustion, and the quantity of that fuel must depend on the extent of grate surface, it is clear that a determinate proportion must exist between the power of the boiler, and the extent of grating in the fire place. The quantity of oxygen which combines with the fuel varies with the quality of that fuel; for different kinds of coal it varies from two to three pounds for each pound of coal. We shall take it an average of 2-1/2 pounds. Now 2-1/2 pounds of oxygen will measure 30 cubic feet; also 5 cubic feet of atmospheric air contain 1 cubic foot of oxygen; and consequently 150 cubic feet of atmospheric air will be necessary for the combustion of 1 pound of average coals. At least one third of the air, which passes through a fire, escapes uncombined into the chimney. We must, therefore, allow 220 cubic feet of atmospheric air to pass through the grate-bars for every pound of fuel which is consumed. Now since land boilers will consume 15 pounds, and marine boilers 10 pounds, per hour per horse-power, it follows that the spaces between the grate-bars, and the extent of grate surface, must be sufficient to allow 3000 cubic feet of air per hour in land boilers, and 2000 cubic feet in marine boilers, to pass through them for each horse-power, or, what is the same, for each foot of water converted into steam per hour. The quantity of grate surface necessary for this does not seem to be ascertained with precision; but, perhaps, we may take as an approximate estimate for land boilers one square foot of grate surface per horse-power, and for marine boilers two thirds of a square foot, the spaces between the grate-bars being equal to their breadth. It is evident that the capacity of a boiler for water and steam must have a determinate relation to the power of the engine it is intended to supply. For each horse-power of the engine, it has been shown that a cubic foot of water must pass from the boiler in the form of steam per hour. Now, it is evident that the steam could not be supplied of a uniform force, if the quantity of steam contained at any moment in the boiler were not considerably greater than the contents of the cylinder. For example, if the volume of steam in the boiler were precisely equal to the capacity of the cylinder, then one measure of the cylinder would for the moment cause the steam to expand into double its bulk and to lose half its force, supposing it to pass freely from the boiler to the cylinder. In the same manner, if the volume of steam contained in the boiler were twice the contents of the cylinder, the steam would for a moment lose a third of its force, and so on. It is clear, therefore, that the space allotted to steam in the boiler must be so many times greater than the magnitude of the cylinder, that the abstraction of a cylinder full of steam from it shall cause a very trifling diminution of its force. In the same manner, we may perceive the necessity of maintaining a large proportion between the total quantity of water in the boiler, and the quantity supplied in the form of steam to the cylinder. If, for example (taking as before an extreme case,) the quantity of water in the boiler were only equal to the quantity supplied in the form of steam to the cylinder in a minute, it would be necessary that the contents of the boiler should be replaced by cold water once in each minute: and, under such circumstances, it is evident that the action of the heat upon the water would be quite unmanageable. But, independent of this, the quantity of water must be sufficient to fill the boiler above the point at which the flue surface terminates, otherwise the heat of the fuel would act upon the part of the boiler containing steam and not water; and, steam receiving heat sluggishly, the metal of the boiler would be gradually destroyed by undue temperature. The total quantity of space for water and steam in boilers is subject to considerable variation in proportion to their power. Small boilers require a greater proportion of steam and water-room, or a greater capacity of boiler, in proportion, than large ones; and the same applies to their fire surface and flue surface. The general experience of engineers has led to the conclusion, that a low-pressure boiler of the common kind requires ten cubic feet of water-room, and ten cubic feet of steam-room in the boiler, for every cubic foot which the engine consumes per hour, or, what is the same, for each horse-power of the engine. Thus, an engine of ten-horse-power, according to this rule, would require a boiler having the capacity of 200 cubic feet which should be constantly kept half filled with water. There are, however, different estimates of this. Some engineers hold that a boiler should have twenty-five cubic feet of capacity for each horse-power of the engine, while others reduce the steam so low as eight cubic feet. In a table of the capacities of boilers of different powers, and the feed of water necessary to be maintained in them, Mr. Tredgold assigns to a boiler of five-horse-power fourteen cubic feet of water per horse-power; for one of ten-horse power, twelve and a half cubic feet; and, for one of forty-horse, eleven cubic feet. For engines of greater power it is generally found advantageous to have two or more boilers of small power, instead of one of large power. This method is almost invariably adopted on board steam boats, and has the advantage of securing the continuance of the working of the engine, in case of one of the boilers being deranged. It is also found convenient to keep an excess of power in the boilers, above the wants of the engine. Thus, an engine of sixty-horse-power may be advantageously supplied with two forty-horse boilers, and an engine of eighty-horse-power with two fifty-horse boilers, and so on. (138.) The pressure of steam in the cylinder of an engine is always less than the pressure of steam in the boiler, owing to the obstructions which it encounters in its passage through the steam pipes and valves. The difference between these pressures will depend upon the form and magnitude of the passages: the straighter and wider they are, the less the difference will be; if they are contracted and subject to bends, especially to angular inflexions, the steam will be considerably diminished in its pressure before it reaches the cylinder. The throttle valve placed in the steam pipe may also be so managed as to diminish the pressure of steam in the cylinder to any extent: this effect, which is well understood by practical engineers, is called _wire-drawing_ the steam. By such means it is evidently possible for the steam in the boiler to have any degree of high-pressure while the engine is worked at any degree of low pressure. Since, however, the pressure of the steam in the cylinder is a material element in the performance of the engine, the magnitude, position, and shape of the steam pipe and of the valves are a matter of considerable practical importance. But theory furnishes us with little more than very general principles to guide us. One practical rule which has been adopted is, to make the diameter of the steam pipe about one fifth of that of the cylinder: by this means the area of the transverse action of the pipe will be one twenty-fifth part of the superficial magnitude of the piston; and, since the same quantity of steam per minute must flow through this pipe as through the cylinder, it follows that the velocity of the steam, in passing through the steam pipe, will be twenty-five times the velocity of the piston. (139.) Another rule which has been adopted is, to allow a square inch of magnitude, in the section of the steam pipe, for each horse-power of the engine. The result of this and all similar rules is, that the steam should always pass through the steam pipe with the same velocity, whatever be the power of the engine. In engines of the same power, the piston will have very different velocities in the cylinder, according to the effective pressure of the steam, and the proportions and capacity of the cylinder. It is clear from what has been already explained, that, when the power is the same, the same actual quantity of water, in the form of steam, must pass through the cylinder per minute: but, if the steam be used with a considerable pressure, being in a condensed state, the same weight of it will occupy a less space; and consequently the cylinders of high-pressure engines are smaller than those of the same power in low-pressure engines: the magnitude of the cylinder and the piston therefore, as well as the velocity of the latter, will depend first upon the pressure of the steam. But with steam of a given pressure, the velocity of the piston will be different: with a given capacity of cylinder, and a given pressure of steam, the power of the engine will determine the number of strokes per minute. But the actual velocity of the piston will depend, in that case, on the proportion which the diameter of the cylinder bears to its length; the greater the diameter of the piston is with respect to its length, the less will be its velocity. In case of stationary engines used on land, that proportion of the diameter of the cylinder to its length is selected, which is thought to contribute to the most efficient performance of the machine. According to some engineers, the length of the cylinder should be twice its diameter;[52] others make the length equal to two diameters and a half; but there are circumstances in which considerations of practical convenience render it necessary to depart from these proportions. In marine engines, where great length of cylinder would be inadmissible, and where, on the other hand, considerable power is required, cylinders of short stroke and great diameter are used. In these engines the length of the stroke is often not greater than the diameter of the piston, and sometimes even less. [Footnote 52: This is the proportion under which the cylinder with a given capacity will present the least possible surface to the cooling effect of the atmosphere.] The actual velocity which has been found to have the best practical effect, for the piston in low-pressure engines, is about 200 feet per minute. This, however, is subject to some variation. (140.) A given weight or measure of fuel burnt under the boiler of an engine is capable of producing a mechanical effect through the means of that engine, which, when expressed in an equivalent number of pounds' weight lifted a foot high, is called the _duty_ of the engine. If all the heat developed in the combustion of the fuel could be imparted to the water in the boiler, and could be rendered instrumental in producing its evaporation; and if, besides, the steam thus produced could be all rendered mechanically available at the working point; then the duty of the engine would be the entire undiminished effect of the heat of combustion; but it is evident that this can never practically be the case. In the first place, the heat developed by the combustion can never be wholly imparted to the water in the boiler: some part of it will necessarily escape without reaching the boiler at all; another portion will be consumed in heating the metal of the boiler, and in supplying the loss by radiation from its surface; another portion will be abstracted by the various sources of the waste and leakage of steam; another portion will be abstracted by the reaction of the condensed steam; and another portion of the power will be consumed in overcoming the friction and resistance of the engine itself. It is apparent that all these sources of waste will vary according to the circumstances and conditions of the machine, and according to the form and construction of the furnace, flues, boilers, &c. The duty, therefore, of different engines will be different; and when such machines are compared, with a view to ascertain their economy of fuel, it has been found necessary carefully to register and to compare the fuel consumed with the weight or resistance overcome. In engines applied to manufactures generally or navigation, it is not easy to measure the amount of resistance which the engine encounters, but when the engine is applied to the pumping of water, its performance is more easily determined. In the year 1811, several of the proprietors of the mines in Cornwall, suspecting that some of their engines might not be doing a duty adequate to their consumption of fuel, came to a determination to establish a uniform method of testing the performance of their engines. For this purpose a counter was attached to each engine, to register the number of strokes of the piston. All the engines were put under the superintendence of Messrs. Thomas and John Lean, engineers; and the different proprietors of the mines, as well as their directing engineers, respectively pledged themselves to give every facility and assistance in their power for the attainment of so desirable an end. Messrs. Lean were directed to publish a monthly report of the performance of each engine, specifying the name of the mine, the size of the cylinder, the load upon the engine, the length of the stroke, the number of pump lifts, the depth of the lift, the diameter of the pumps, the time worked, the consumption of coals, the load on the pump, and, finally, the duty of the engine, or the number of pounds lifted one foot high by a bushel of coals. The publication of these monthly reports commenced in August, 1811, and have been regularly continued to the present time. The favourable effect which these reports have produced upon the vigilance of the several engineers, and the emulation they have excited, both among engine-makers and those to whom the working of the machines are intrusted, are rendered conspicuous in the improvement which has gradually taken place in the performance of the engines, up to the present time. In a report published in December, 1826, the highest duty was that of an engine at Wheal Hope mine in Cornwall. By the consumption of one bushel of coals, this engine raised 46,838,246 pounds a foot high, or, in round numbers, forty-seven millions of pounds. In a report published in the course of the present year (1835) it was announced that a steam engine, erected at a copper mine near St. Anstell, in Cornwall, had raised by its average work 95 millions of pounds 1 foot high, with a bushel of coals. This enormous mechanical effect having given rise to some doubts as to the correctness of the experiments on which the report was founded, it was agreed that another trial should be made in the presence of a number of competent and disinterested witnesses. This trial accordingly took place a short time since, and was witnessed by a number of the most experienced mining engineers and agents: the result was, that for every bushel of coal consumed under the boiler the engine raised 125-1/2 millions of pounds weight one foot high. (141.) It may not be uninteresting to illustrate the amount of mechanical virtue, which is thus proved to reside in coals, in a more familiar manner. Since a bushel of coal weighs 84 lbs. and can lift 56,027 tons a foot high, it follows that a pound of coal would raise 667 tons the same height; and that an ounce of coal would raise 42 tons one foot high, or it would raise 18 lbs. a mile high. Since a force of 18 lbs. is capable of drawing 2 tons upon a railway, it follows that an ounce of coal possesses mechanical virtue sufficient to draw 2 tons a mile, or 1 ton 2 miles, upon a level railway.[53] [Footnote 53: The actual consumption of coal upon railways is in practice about eight ounces per ton per mile. It is, therefore, worked with sixteen times less effect than in the engine above mentioned.] The circumference of the earth measures 25,000 miles. If it were begirt by an iron railway, a load of one ton would be drawn round it in six weeks by the amount of mechanical power which resides in the third part of a ton of coals. The great pyramid of Egypt stands upon a base measuring 700 feet each way, and is 500 feet high; its weight being 12,760,000,000 lbs. To construct it, cost the labour of 100,000 men for 20 years. Its materials would be raised from the ground to their present position by the combustion of 479 tons of coals. The weight of metal in the Menai bridge is 4,000,000 lbs., and its height above the level of the water is 120 feet: its mass might be lifted from the level of the water to its present position by the combustion of 4 bushels of coals.[54] [Footnote 54: Some of these examples were given by Sir John Herschel, in his Preliminary Discourse on Natural Philosophy; but since that work was written an increased power has been obtained from coals, in the proportion of 7 to 12-1/2.] The enormous consumption of coals in the arts and manufactures, and in steam navigation, has of late years excited the fears of some persons as to the possibility of the exhaustion of our mines. These apprehensions, however, may be allayed by the assurance received from the highest mining and geological authorities, that, estimating the present demand from our coal mines at 16 millions of tons annually, the coal fields of Northumberland and Durham alone are sufficient to supply it for 1700 years, and after the expiration of that time the great coal basin of South Wales will be sufficient to supply the same demand for 2000 years longer. But, in speculations like these, the probable, if not certain, progress of improvement and discovery ought not to be overlooked; and we may safely pronounce that, long before a minute fraction of such a period of time shall have rolled over, other and more powerful mechanical agents will altogether supersede the use of coal. Philosophy already directs her finger at sources of inexhaustible power in the phenomena of electricity and magnetism. The alternate decomposition and recomposition of water, by magnetism and electricity, has too close an analogy to the alternate processes of vaporisation and condensation, not to occur at once to every mind: the development of the gases from solid matter by the operation of the chemical affinities, and their subsequent condensation into the liquid form, has already been essayed as a source of power. In a word, the general state of physical science, at the present moment, the vigour, activity, and sagacity with which researches in it are prosecuted in every civilized country, the increasing consideration in which scientific men are held, and the personal honours and rewards which begin to be conferred upon them, all justify the expectation that we are on the eve of mechanical discoveries still greater than any which have yet appeared; and that the steam engine itself, with the gigantic powers conferred upon it by the immortal Watt, will dwindle into insignificance in comparison with the hidden powers of nature still to be revealed; and that the day will come when that machine, which is now extending the blessings of civilisation to the most remote skirts of the globe, will cease to have existence except in the page of history. CHAPTER XIX. PLAIN RULES FOR RAILWAY SPECULATORS. (142.) For some time after the completion of the Liverpool and Manchester railway, doubts were entertained of its ultimate success as a commercial speculation; and, even still, after several years' continuance, some persons are found, sceptical by temperament, who have not acquired full confidence in the permanency of its advantages. The possibility of sustaining a system of regular transport upon it, with the unheard of speed effected at the commencement of the undertaking, was, for a long period, questioned by a considerable portion even of the scientific world; and, after that possibility was established, by the regular performance of some years, the practicability of permanently profitable work, at that rate of speed, was still doubted by many, and altogether denied by some. The numerous difficulties to be encountered, and the enormous expense of locomotive power, have been fully admitted by the directors in their semi-annual reports. Persons interested in canals and other rival establishments, and others constitutionally doubtful of everything, attributed the dividends to the indirect proceedings of the managers, and asserted that when they appeared to be sharing their profit's, they, in reality, were sharing their capital. This delusion, however, could not long continue, and the payment of a steady semi-annual dividend of 4-1/2 per cent. since the opening of the railway, together with the commencement of a reserved fund of a considerable amount, with a premium of above 100 per cent. on the original shares, has brought conviction to understandings impenetrable to general reasoning; and the tide of opinion, which, for a time, had turned against railways, has now, by the usual reaction, set in so violently in their favour, that it becomes the duty of those who professionally devote themselves to such inquiries, to restrain and keep within moderate bounds the public ardour, rather than to stimulate it. The projects for the construction of great lines of internal communication which have been announced would require, if realized, a very large amount of capital. Considering that the estimated capital is invariably less than the amount actually required, we shall not, perhaps, overrate the extent of the projected investments if we estimate them at fifty millions. The magnitude of this amount has created alarm in the minds of some persons, lest a change of investment so extensive should produce a serious commercial shock. It should, however, be considered that, even if all the projected undertakings should be ultimately carried into execution, a long period must elapse, perhaps not less than fifteen or twenty years, before they can be all completed: the capital will be required, not suddenly, but by small instalments, at distant intervals of time. Even if it were true, therefore, that, to sustain their enterprises, an equivalent amount of capital must be withdrawn from other investments, the transfer would lake place by such slow degrees as to create no serious inconvenience. But, in fact, it is not probable that any transfer of capital whatever will be necessary. Trade and manufacturers are at the present moment in a highly flourishing condition; and the annual accumulation of capital in the country is so great, that the difficulty will probably be, not to find capital to meet investments, but to find suitable investments for the increasing capital. In Manchester alone, it is said that the annual increment on capital is no less than three millions. In fifteen years, therefore, this mart alone would be sufficient to supply all the funds necessary for the completion of all the proposed railroads, without withdrawing capital from any other investment. The facilities which these Joint Stock Companies offer for the investment of capital, even of the smallest amount, the temptations which the prospect of large profits hold out, and the low interest obtained on national stock of every description, have attracted a vast body of capitalists, small and great, who have subscribed to these undertakings with the real intention of investment. But, on the other hand, there is a very extensive body of speculators who engage in them upon a large scale, without the most distant intention, and, indeed, without the ability, of paying up the amount of their shares. The loss which the latter class of persons may sustain would, probably, excite little commiseration, were it not for the consequences which must result to the former, should a revolution take place, and the market be inundated with the shares of these gambling speculators, who buy only to sell again. Effects would be produced which must be ruinous to a large proportion of the _bonâ fide_ subscribers. It may, therefore, be attended with some advantage to persons who really intend to make permanent investments of this nature, to state, in succinct and intelligible terms, the principal circumstances on which the efficiency and economy of railroads depend, so as to enable them, in some measure, to form a probable conjecture of the prospective advantages which the various projects hold out. In doing this, we shall endeavour, as much as possible, to confine our statements to simple facts and results, which can neither be denied nor disputed, leaving, for the most part, the inferences to which they lead to be deduced from them by others. It may be premised, that persons proposing to engage in any railroad speculation should obtain _first_ a table of _gradients_; that is, an account of all the acclivities upon the line from terminus to terminus, stating how many feet in a mile each incline rises or falls, and its length. _Secondly_, it would also be advantageous to have a statement of the lengths of the radii of the different _curves_ as well as the lengths of the curves themselves. _Thirdly_, an account of the actual intercourse which has taken place, for a given time, upon the turnpike road connecting the proposed termini, stating the number of coaches licensed, and the average number of passengers they carry; also as near an account of the transport of merchandise as may be obtained. The latter, however, is of less moment. An approximate estimate may be made of the intercourse in passengers, by allowing for each coach, upon each trip, half its licensed complement of load. _Fourthly_, the water communication by canal or otherwise between the places; and the amount of tonnage transported by it. With the information thus obtained, the following succinct maxims will be found useful:-- I. No railroad can be profitably worked without a large intercourse of passengers. Goods, merchandise, agricultural produce, &c., ought to be regarded as of secondary importance. II. A probable estimate of the number of passengers to be expected upon a projected line of railroad may be made by increasing the average number of passengers for the last three years, by the common road, in a twofold proportion. The average number of passengers daily between Liverpool and Manchester, before the formation of the railway, was about 450; the present average number is above 1300. A short railroad of about five miles is constructed between Dublin and Kingstown: on which the average number of passengers daily between those places has increased in nearly the same proportion. III. Passengers can be profitably transported by canal, at a speed not exceeding nine miles an hour, exclusive of delays at locks, at the rate of one penny per head per mile. The average fares charged upon the Manchester railway are at the rate of 1-84/100_d._ per head per mile, the average speed being twenty miles an hour. To transport passengers at the rate of ten miles an hour on a railway, would cost very little less than the greater speed of twenty miles an hour, so that a railroad could not enter into competition on equal terms with a canal by equalising the speed. The canal between Kendal and Preston measures 57 miles: passengers are transported upon it between these places at the average speed of a mile in 6-1/2 minutes, or 9-1/4 miles an hour nearly, exclusive of delays at locks. The fare charged is at the average rate of a penny a mile. There are eight locks, rising 9 feet each, and a tunnel 400 yards long, through which the boat is tracked by hand; the tunnel requires 5 minutes, and the locks from 25 to 28 minutes, in descending, and 45 to 48 minutes in ascending. Similar boats are worked on the Forth and Clyde, and the Union canals in Scotland, and on the Paisley and Johnstone canal at nearly the same fares. IV. At the fare of 1-84/100_d._ per head per mile, the profit on the Manchester railroad is 100 per cent. on the disbursements for passengers. V. Goods can be profitably transported by canal at a lower tonnage than by railroads; the speed on the canal (for goods) being, however, but one-fifth of the speed on the railroad. VI. Goods are transported on the Liverpool and Manchester railroad at three-pence three farthings per ton per mile, with a profit of about 40 per cent. upon the disbursement, having the competition of a canal between its termini. VII. A long railroad can be worked with greater relative economy than a short one. VIII. Steam engines work with the greatest efficiency and economy, when the resistance they have to overcome is perfectly uniform and invariable. IX. The variation of resistance on railroads depends, first, on acclivities, secondly, on curves. By curves are meant the changes of direction of the road to the right or to the left. The direction of a railroad cannot be changed suddenly by an angle, but must be effected gradually by a curve. Supposing the curve to be (as it generally is) the arc of a circle, the radius of the curve is the distance of the centre of the circle from the curve. This radius is an important element in the estimate of the road. X. The more nearly a railroad approaches to an absolute level, and perfect straightness, the more profitably will it be worked. XI. The total amount of mechanical power necessary to transfer a given load from one extremity of a railroad to another is a matter of easy and exact calculation, when the gradients and curves are known; and the merits of different lines may be compared together in this respect: but it is not the only test of their efficiency which must be applied. XII. A railroad having gradients exceeding seventeen feet in a mile will require more mechanical power to work it than it would were it level; and the more of these excessive gradients there are upon it, and the more steep they are, the greater will be this disadvantage. XIII. Although a railroad having no gradients exceeding seventeen feet in a mile does not require more mechanical power than a level, yet the mechanical power which it requires will not be so advantageously expended, and, therefore, it will not be so economical. XIV. A railroad which has gradients above thirty feet in a mile will require such gradients to be worked by assistant locomotive engines, which will be attended with a waste of power, and an increase of expenditure, more or less, according to the number and length of such gradients. XV. A very long inclined plane cannot be worked by an assistant locomotive without a wasteful expense. Gradients exceeding seventeen feet per mile must, therefore, be short. XVI. Gradients exceeding fifty feet in a mile cannot be profitably worked except by stationary engines and ropes, an expedient attended with so many objections as to be scarcely compatible with a large intercourse of passengers. XVII. Steep gradients, provided they descend from the extremities of a line, are admissible provided they be short. It is evident that in this case the inclined planes will help at starting to put the trains in motion, at the time when, in general, there would be the greatest strain upon the moving power; and, in approaching the terminus, the momentum would be sufficient to carry the train to the top of the plane, if its length were not great, since it must, at all events, come to a stop at the extremity. XVIII. The effect of gradients in increasing the resistance during the ascent may be estimated by considering that a gradient of seventeen feet in a mile doubles the resistance of the level, thirty-four feet in a mile triples it, and eight and a half feet in a mile adds one half its amount, and so on. XIX. With the speed now attainable on railways, curves should be avoided with radii shorter than a mile. Expedients may diminish the resistance, but, through the negligence of engine drivers, they must always be attended with danger. Curves are not objectionable near the extremities of a line. XX. The worst position for a curve is the foot of an inclined plane, because of the velocity which the trains acquire in the descent, and the occasional impracticability of checking them. XXI. In proportion as the speed of locomotives is increased by the improvements they are likely to receive, the objections and dangers incident to curves will be increased. XXII. The difficulty which attends the use of long tunnels arises from the destruction of the vital air which is produced by the combustion in the furnaces of the engines. Tunnels on a level should, therefore, be from twenty-five to thirty feet high, and should be ventilated by shafts or other contrivances. XXIII. The transition from light to darkness, the sensation of humidity, and the change in summer from a warm atmosphere to a cold one, will always form an objection to long tunnels on lines of railroad intended for a large intercourse of passengers. XXIV. All the objections to a tunnel are aggravated when it happens to be upon an acclivity. The destruction of vital air in ascending it will be increased in exactly the same proportion as the moving power is increased. Thus, if it ascend 17 feet in a mile, the destruction of vital air will be twice as great as on a level; if it ascend 34 feet in a mile, it will be three times as great; 51 feet in a mile, four times as great, and so on. XXV. If by an overruling necessity a tunnel is constructed on an acclivity, its magnitude and means of ventilation should be greater than on a level, in the same proportion as the resistance produced by the acclivity is greater than the resistance upon a level. XXVI. Tunnels should be ventilated by shafts at intervals of not more than 200 yards. XXVII. While a train is passing through a tunnel, no beneficial ventilation can be obtained from shafts. The engine will leave behind it the impure air which it produces, and the passengers will be enveloped in it before it has time to ascend the shafts. Sufficient magnitude, however, may be given to the tunnel to prevent any injurious consequences from this cause. A disagreeable and inconvenient odour will be experienced. XXVIII. Tunnels on a level, the length of which do not exceed a third of a mile, will probably not be objectionable. Tunnels of equal length upon acclivities would be more objectionable. I may observe generally that we have as yet little or no experience of the effect of tunnels on lines of railroad worked by locomotive engines, where there is a large intercourse of passengers. On the Leicester and Swannington railroad, there is a tunnel of about a mile long, on a part of the road which is nearly level; it is ventilated by eight shafts, and I have frequently passed through it with a locomotive engine. Even when shut up in a close carriage the annoyance is very great, and such as would never be tolerated on a line of road having a large intercourse in passengers. This railroad is chiefly used to take coals from some collieries near Swannington, and there is no intercourse in passengers upon it, except of the labouring classes from the adjacent villages: the engines burn coal, and not coke; and they consequently produce smoke, which is more disagreeable than the gases which result from the combustion of coke. This tunnel also is of small calibre. On the Leeds and Selby railroad there is a tunnel, on a part which is nearly level, the length of which is 700 yards, width 22 feet, height 17. It is ventilated by three shafts of about 10 feet diameter and 60 feet high. There is an intercourse of passengers amounting to four hundred per day, upon this road, and, generally speaking, they do not object to go through the tunnel with a locomotive engine. The fuel is coke. (_l_) In order to show the present state of railroad transportation in the United States, and enable our readers to compare it with the opinions and facts adduced by Dr. Lardner, we take the latest accounts from the Charleston and Hamburgh Railroad. The engines drag a train of cars which carry a load of 130 tons, and perform the distance (240 miles) in three days, travelling only by day-light. With these loads they mount planes having inclinations of 37 feet per mile. The same engines are capable of carrying passengers at the rate of 40 miles per hour, and often perform 30, but their average speed is limited by regulation to 20 miles per hour. This railroad is remarkable for being the largest which has yet been constructed, and is besides an object of just pride, in as much as it was commenced at a time, when according to Dr. Lardner, the subject was but imperfectly understood even in Europe, and all its arrangements are due to native talent and skill, unassisted by previous discoveries in Europe.--A. E. INDEX. A. Atmospheric air, elastic force of, 23 Atmospheric pressure rendered available as a mechanic agent by Denis Papin, 48 Atmospheric engine, first conception of by Newcomen, 61. Description of, 63. Advantage of over that of Savery, 69 B. Barometer, the, 21 Barometer gauge, the, 123 Belidor, 133 Birmingham and London railroad, probable advantages to be derived from, 206 Black, Dr., his doctrine of latent heat, 76 Blasco de Garay, his contrivance to propel vessels, 42 Blinkensop, Mr., constructs a locomotive engine, 161 Boiler, methods for showing the level of water in the, 118. Its power and proportions, 297 Bolton, Matthew, his connexion with Watt, 88 ---- and Watt, Messrs., immense expenditure of, in bringing their engines into use, 91 Booth, Mr., his method of using tubes to conduct heated air through locomotive boilers, 176. His report to the directors of the Liverpool and Manchester railway on the apparent discrepancies of Messrs. Walker and Rastrick's estimate of locomotive power, 189 Braithwaite and Ericsson, Messrs., their "Novelty" described, 175 Branca, Giovanni, his machine for propelling a wheel by a blast of steam, 45 Brewster, Dr., 79 Brunton, Mr., his improved furnace described, 130 C. Canals, transport on, 208. Experiments with boats on, 209, Comparison of with railroads, 210 Cartwright, Rev. Mr., description of his improvements in the steam engine, 142 Cawley, John, 61 "Century of Inventions" by the Marquis of Worcester, 46 Chapman, Messrs., obtain a patent for working a locomotive by means of a chain, 162 Church, Dr., his steam carriage, 239 Cohesion, attraction of, 32 Condensation of solids, 28 Condensation by jet, accidental discovery of, 65 Cornwall, reports of duty of steam engines in, 303 Cotton, processes in the culture of, 18 Cylinder, its proportions, 300 D. D valve, description of the, 113 Damper, the, 126 Duty of a steam engine, 291 Duty, reports of, in Cornwall, 303 E. Eccentric; description of the, 111 Edelcrantz, the Chevalier, 127 F. Farey, Mr., his statement respecting the variations in the work of different steam engines, 133 Fluids, property of, 21 Fly-wheel, introduction of the, 104 Four-way cock, description of the, 115 Fuel, table of the consumption of, in different locomotives, 180 G. Governor, description of the, 105 Guericke, Otto, inventor of the air-pump, 70 Gurney, Mr., his steam carriage, 216 H. Hackworth, Mr., description of his engine, the "Sanspareil," 173 Hall, Mr. Samuel, his patent steam engine, 248. Its advantages for navigation, 249. Its successful application, 250 Hamilton, Duke of, 88 Hancock, Mr. Walter, his steam carriage, 235 Heat, phenomena of, 29 Hero of Alexandria, description of his machine, 41 Hopper, the, or apparatus for supplying the fire-place with coals, 131 Hornblower, Mr., his double-cylinder engine, 134 Horse power and steam power, comparison between, 202 Horse power of an engine, 291. Method of calculating it, 293 Howard, Mr. Thomas, his patent steam engine, 253. Its advantages in navigation, 256 Huskisson, Mr., 154 I. Inclined planes, their injurious effects on railroads, 194. Methods proposed to remedy these, 194 India, steam communication with, 271 K. Kendal and Preston canal, speed of boats on, 209 L. Leeds and Selby railroad, 317 Leicester and Swannington railroad, 317 Leupold, his "Theatrum Machinarum," 116. His engine described, 147 Liquids converted into vapour by the application of heat, 27. Difference of temperatures of, 35 Liverpool and Manchester railroad, effects of the introduction of steam transport on, 152. Want of experience in the construction of the engines, 154. Proceedings of the directors, 167. Premium offered by them for the best engine, 169. Experiments made on, 183. Passengers the chief source of profit to the proprietors, 204 Liverpool and London, supposed advantages from the connexion of these places by railroad, 206 Llangennech coal, its economy, 267 Locomotive engines, description of the "Rocket," 171. The "Sanspareil," 173. The "Novelty," 175. Mr. Booth's method of using tubes to conduct heated air through boilers, 177. Mr. Stephenson's method of subdividing the flue, 179. Amount of fuel consumed in, 180. Progressive improvement of, 180. Description of an improved form of engine, 181. Circumstances on which their efficiency depends, 183. Experiments with, on Liverpool and Manchester railroad, 184. Defects of, 186. Improvement in the method of tubing, 188. Proposed methods for working them on levels and inclined planes, 194. Extraordinary speed and power of, 204. Their introduction on turnpike roads, 213 Locomotive power, expense of, 188 Locomotive boilers, improved form of, 177 M. Machines, definition of, 19 Manufactures, motions required in, 19 Morgan, Mr., his patent paddle-wheel, 259 Morland, Sir Samuel, his application of steam to raise water, 47 Motion, a primary agent in the cultivation of cotton, 18. Variety of, 19 Murray, Mr., description of his suggested slide valve, 113 N. Newcomen, Thomas, and John Cawley, turn their attention to the practicability of applying steam engines to the drainage of mines, 61 Newcomen, Thomas, his construction of the atmospheric engine, 63 "Novelty," description of the, 175 O. Ogle, Mr., his steam carriage, 239 Oldham, Mr., his modification of the self-regulating furnace, 132 P. Paddle-wheel, the common one, 257. Mr. Morgan's patent one, 259 Papin, Denis, his contrivance, by which atmospheric pressure is rendered available as a mechanical agent, 48. Description of his steam engine, 71 Parallel motion, description of the, 95 Piston, its velocity, 302 Post-office steam packets, their speed, 268 Potter, Humphrey, his contrivance for working the valves, 67 Power of a steam engine, how estimated, 291 R. Railroads, first introduction of locomotives on, 151. Important effects to be expected from their adoption, 155. Imaginary difficulty respecting the progression of carriages on, 160. Various methods resorted to, to remedy this supposed difficulty, 161. One of these methods described, 162. Comparative estimate of the expenses of locomotive and stationary engines, 168. Difficulties arising from changes of level, 192. Their great extension, 206. Comparison of, with turnpike roads, 213. Inclined planes on, 194 Railway speculators, plain rules for, 307 Roads, their resistance to draft, 213. Compared with railroads, 213 Robinson, Dr., 73 Roebuck, Dr., assistance rendered by him to Watt, 87. His embarrassments, 88 "Rocket," description of the, 171 S. Savery, Thomas, obtains a patent for an engine to raise water, 49. His discovery of the principle of condensation, 49. Constructs the first engine brought into operation, 50. Description of, 51. Inefficiency of, 57. Great consumption of fuel necessary in his engines, 60. Different purposes to which he proposed to apply the steam engine, 61. Limited power of his engine, 69 "Sanspareil", description of the, 173 Smeaton turns his attention to the details of the atmospheric engines, 73 Solids converted into liquids by the application of heat, 27 Solomon De Caus, description of the apparatus of, 43 Somerset, Edward, Marquis of Worcester, invention of the steam engine ascribed to him, 45. Description of his contrivance, 45. Similar to Savery's, 46. His "Century of Inventions," 46 Steam carriages, Mr. Gurney's, 216. Mr. Hancock's, 235. Mr. Ogle's, 238. Dr. Church's, 239 Steam, its properties described, 30. Its mechanical power in proportion to the water evaporated, 277. Its volume, 279. Its quantity of heat, 279. Its power in respect of fuel, 280. Its expansive action, how advantageous, 280. Combination of expansion with condensation, 285. High-pressure, its expansive action, 288. Examples illustrative of its mechanical force, 305 Steam engine, first mover in, 19. Physical effects connected with, 20. Claims to the invention of, 38. Efficacy of, as a mechanical agent, 39. First brought into operation by Savery, 50. Its inefficiency, 58. First proposed to be applied to the drainage of mines, 61. Accidental discovery of condensation by jet, 65. Further improvements by Humphrey Potter and Beighton, 67, 68. Description of Papin's engine, 71. First experiments of Watt and subsequent improvements, 73. Dr. Black's theory of latent heat, 76. Watt's method of condensation, 76. Further improvements of Watt, 77. Description of Watt's single-acting engine, 80. The cold water pump, 86. The hot water pump, 86. Erection of a specimen engine at Soho, and gradual demand for them, 89. The single-acting engine inapplicable to manufactures, 91. The double-acting engine, 92. Invention of the parallel motion, 95. Introduction of the rotatory motion, 100. The fly-wheel, 104. The governor, 105. The throttle valve, 105. The eccentric, 111. The D valve, 113. The four-way cock, 115. Methods for ascertaining the level of water in the boiler, 118. The engine made to feed its own boiler, 120. Waste of water prevented, 121. The steam gauge, 122. Barometer gauge, 123. The damper, 125. Methods proposed for preventing the waste of fuel, 128. Mr. Brunton's furnace described, 130. Mr. Oldham's modification of the self-regulating furnace, 132. Improvements by Hornblower and Woolf, 134. Description of the improvements of Mr. Cartwright, 142. High-pressure engines, 145. Leupold's engine described, 147. Construction of the first high-pressure engine by Messrs. Trevithick and Vivian, 148. First application of the steam engine to propel carriages on railroads, 151. How applied to navigation, 242. Marine engine; its form and arrangement, 243. Mr. Howard's patent engine described, 253. Mr. Hall's engine described, 248 Steam gauge, the, 122 Steam navigation, incredulity which existed respecting, 159. The limit of its present powers, 264 Steam vessels, their average speed, 265. Their average consumption of fuel, 265. Proportion of their power to their tonnage, 266. Speed of post-office packets, 268. Iron steam vessels, 269. American vessel called the "Cigar Boat," its great speed, 270 Stephenson's, Mr., description of an engine constructed by him, 164. Premium awarded to this engine by the Liverpool and Manchester Railway Directors, 170. His method of dividing the flues, 179 Stephenson and Lock, Messrs., appointed by the Directors of the Liverpool and Manchester Railroad to make reports on the merits of various railroads, 167 Sun and planet wheels, 101 T. Thermometer, description of, 24 Throttle valve, use of, 104 Traction, force of, on a railroad, 192 Tredgold,70 Trevithick and Vivian, Messrs., construct the first high-pressure engine used in this country, 148 U. United States, steam communication with, 274 V. Vacuum, production of, by experiment, 37 Vapour, elastic, force of, 35 Valves, Watt's method of working the, 109 W. Walker and Rastrick, Messrs., apparent discrepancy of their estimated expense of locomotive power, 189 Washborough takes out a patent for Watt's invention of the rotatory motion, 100 Water, sea, injurious to marine boilers, 245. How remedied by blowing out, 246 Watt, James, important discoveries of, 39. His acquaintance with Dr. Robinson and first experiments on the steam engine, 73. His subsequent improvements, 75. His method of condensation, 76. His first introduction of the air-pump into the steam engine, 77. Further improvements, 78. His difficulties, 78. Description of his single-acting engine, 80. His introduction to Dr. Roebuck, 88. Erects his first engine on the estate of the Duke of Hamilton, 88. After further improvements, obtains a patent for this engine, in conjunction with Roebuck, 88. His difficulties owing to Dr. Roebuck's failure, and subsequent connexion with Bolton, 88. Obtains an extension of his patent, 89. Ingenious invention of, to determine the rate of remuneration he should receive, 89. His invention of the parallel motion, 95. His method for producing a rotatory motion anticipated by Washborough, who takes out a patent for it, 101. His contrivance of the governor, 104. His method of working the valves, 109. His suggestion of the D valve, 113 Wood, Mr. Nicholas, 168 Woolf, Mr., his improvements in the steam engine, 134. Obtains a patent for the double-cylinder engine, 137 * * * * * JUST PUBLISHED, IN ONE VOLUME, 8VO. MATHEMATICS FOR PRACTICAL MEN; BEING A COMMON-PLACE BOOK OF PRINCIPLES, THEOREMS, RULES AND TABLES, IN VARIOUS DEPARTMENTS OF PURE AND MIXED MATHEMATICS, With their applications; especially to the pursuits of Surveyors, Architects, Mechanics, and Civil Engineers. With numerous engravings. BY OLINTHUS GREGORY, LL. D., F. R. A. S. "Only let men awake, and fix their eyes, one while on the nature of things, another while on the application of them to the use and service of mankind."--_Lord Bacon._ SECOND EDITION, CORRECTED AND IMPROVED. _Extract of a Letter from_ WALTER R. JOHNSON, _Professor of Mechanics and Natural Philosophy in the Franklin Institute_. "This treatise is intended and admirably calculated to supply the deficiency in the means of mathematical instruction to those who have neither time nor inclination to peruse numerous abstract treatises in the same departments. It has, besides the claims of a good elementary manual, the merit of embracing several of the most interesting and important departments of Mechanics, applying to these the rules and principles embraced in the earlier sections of the work. "Questions in Statics, Dynamics, Hydrostatics, Hydrodynamics, &c., are treated with a clearness and precision which must increase the powers of the student over his own intellectual resources by the methodical habits which a perusal of such works cannot fail to impart. "With respect to Engineering, and the various incidents of that important profession, much valuable matter is contained, in this volume; and the results of many laborious series of experiments are presented with conciseness and accuracy." _Letter from_ ALBERT B. DOD, _Professor of Mathematics in the College of New Jersey_. "MESSRS. CAREY & HART, "Gentlemen,--I am glad to learn that you have published an American edition of Dr. Gregory's 'Mathematics for Practical Men.' I have for some time been acquainted with this work, and I esteem it highly. It contains the best digest, within my knowledge, of such scientific facts and principles, involved in the subjects of which it treats, as are susceptible of direct practical application. While it avoids such details of investigation and processes of mathematical reasoning as would render it unintelligible to the general reader, it equally avoids the sacrifice of precision in its statement of scientific results, which is too often made in popular treatises upon the Mathematics and Natural Philosophy. The author has succeeded to a remarkable degree in collecting such truths as will be found generally useful, and in presenting them, in an available form, to the practical mechanic. To such, the work cannot be too strongly recommended; and to the student, too, it will often be found highly useful as a book of reference. "With much respect, "Your obedient servant, "ALBERT B. DOD, "Professor of Mathematics in the College of New Jersey. "_Princeton, Nov. 11, 1834._" _Extract of a Letter from_ EDWARD H. COURTENAY, _Professor of Mathematics in the University of Pennsylvania_. "The design of the author--that of furnishing a valuable collection of rules and theorems for the use of such as are unable, from the want of time and previous preparation, to investigate mathematical principles--appears to have been very successfully attained in the present volume. The information which it affords in various branches of the pure and mixed Mathematics embraces a great variety of subjects, is arranged conveniently, and is in general conveyed in accurate and concise terms. To THE ENGINEER, THE ARCHITECT, THE MECHANIC--indeed to all for whom _results_ are chiefly necessary--the work will doubtless form a very valuable acquisition." _Letter from_ CHARLES DAVIES, _Professor of Mathematics in the Military Academy, West Point_. "MILITARY ACADEMY, West Point, May 14th, 1835. "_To Messrs. E. L. Carey & A. Hart_,-- "The 'Mathematics for Practical Men,' by Dr. Gregory, which you have recently published, is a work that cannot fail to be extensively useful. "It embraces, within a comparatively small compass, all the rules and formulas for mathematical computation, and all the practical results of mechanical philosophy. It is, indeed, a collection of the useful results of science and the interesting facts which have been developed by experience. It may safely be said, that no work, of the same extent, contains so much information, with the rules for applying it to practical purposes. "I have the honour to be, "With great respect, "Your obedient servant, "CHARLES DAVIES, "_Professor of Mathematics_." _Extract from a Letter from_ J. A. MILLER, _Professor of Mathematics in Mount St. Mary's College, Emmettsburg, Md._ "Since the London edition of Gregory's Mathematics for Practical Men appeared in this country, it has been much used in this institution. The accuracy of its definitions, its beautiful systematic arrangement, the many simplified and facilitated methods which it proposes, and its highly practical character, must recommend it strongly to public patronage, as one of the very best works which have lately issued from the press. I have examined your edition of this valuable work sufficiently to say with confidence that it is very accurately printed." * * * * * [Transcriber's note: Only obvious printer's errors have been corrected (e.g.: 3 s instead of 2, etc.). The author's spelling has been maintained and inconsistencies have not been standardised. The advertisement page has been move from the front to the end of the book. Other corrections made: --Page x: "the wealth of rations" has been replaced by "the wealth of nations". --Page 17: "Pressure of Rarified Air." has been replaced by "Pressure of Rarefied Air." --Page 98: "This beautiful contrivance, which is incontestibly" has been replaced by "This beautiful contrivance, which is incontestably". --Page 100: "the working beam no longer used" has been replaced by "the working beam is no longer used". --Page 223: "is attended with peliar difficulty" has been replaced by "is attended with peculiar difficulty". --Page 271: "The projecter is now employed in" has been replaced by "The projector is now employed in".] 
46634	----	Internet Archive (https://archive.org) Note: Project Gutenberg also has an HTML version of this file which includes the original illustrations. See 46634-h.htm or 46634-h.zip: (http://www.gutenberg.org/files/46634/46634-h/46634-h.htm) or (http://www.gutenberg.org/files/46634/46634-h.zip) Images of the original pages are available through Internet Archive. See https://archive.org/details/lifeofrichardtre02trevrich LIFE OF RICHARD TREVITHICK, With an Account of His Inventions. by FRANCIS TREVITHICK, C.E. Illustrated with Engravings on Wood by W. J. Welch. VOLUME II. London: E. & F. N. Spon, 48, Charing Cross. New York: 446, Broome Street. 1872. London: Printed by William Clowes and Sons, Duke Street, Stamford Street and Charing Cross. CONTENTS OF VOLUME II. CHAPTER XVII. VARIOUS INVENTIONS. Stone-crushing mill, 1804--Portable puffer, 1805--Staffordshire potteries--Engine for South America--Diversity of steam appliance--Numerous high-pressure engines--West India Dock locomotive--Engines at Newcastle--Blacklead lubricator--Engines in Wales--Mine engines on wheels, 1804--Engines in London--Engines to be sold in market towns--Blast-furnaces--Aërated steam-boiler--St. Ives Breakwater--Dolcoath blast copper furnace--Davies Gilbert's opinion of the aërated steam-boiler--Trevithick's advice to a brewer--Agricultural engines--West India engines--Thrashing engine--Horizontal engines--Expansive steam--Cold surface condenser--Air-pump--Expansive cam--Fire-bars--Comparison with Watt's engine--Stone-boring engine, 1813--Plymouth Breakwater, reduction in cost--Locomotive engine, 1813--Stone splitting--New method of stone boring, 1813--Screw bit, 1813--Falmouth Harbour--Exeter Bridge--Engine at Lima--Proposed train from Buenos Ayres to Lima--West India portable engine Page 1-35 CHAPTER XVIII. AGRICULTURAL ENGINES; LOSS OF PAPERS. Sir Christopher Hawkins's thrashing machine, 1812--Report of three wise men--Cost of horse and steam power--Wheal Liberty engine--Sir John Sinclair and the Board of Agriculture--Cost of engine--Power of engine--Welsh locomotive--Trevithick on steam agriculture--West Indies engine--Horse-power--Trevithick on patents--Engines in charge of labourers--Teapot--Detail of agricultural engine--Lord Dedunstanville's thrashing machine--Plymouth Breakwater locomotive--Wheal Prosper engine--Wheal Alfred engine--Steam-plough--Cultivation of commons--Combined steam-tormentor, narrower, and shoveller--Mr. Rendal's thrashing machine--Cost and work performed by thrashing engines--Their durability--Bridgenorth engine--Trevithick's drawings light the tires 36-68 CHAPTER XIX. POLE STEAM-ENGINE. Return to Cornwall, 1810--Wheal Prosper pole vacuum engine, 1811--Cylindrical boilers, 1811--Steam pressure, 100 lbs.--Duty of engine, 40 millions--Expansive working, 1811--Herland high-pressure pole puffer, 1815--Steam pressure, 150 lbs.--Boiler making--Comparison with Watt's engine--Blue-fire--Steam--Patent specification--Steam-ring stuffing box--Engines in Lima--A 33-inch pole-puffer more powerful than a 72-inch Watt engine--Description of pole engine and boilers--Trevithick's calculation--Trial of Herland engines--Steam-cushion--Power of the pole-engine--Defective workmanship--Sims examines the pole-engine--Opposition from shareholders--Defective boilers--Challenge to Woolf--Davies Giddy's opinion--First cost, and cost of working one-third of the Watt engine--Meeting of opposing shareholders--Duty of the high-pressure steam pole puffer-engine, 1816--Comparison with the Watt engine--Combined high-pressure pole and cylinder for expansion--Wheal Alfred Watt engine converted to high pressure--Wheal Chance combined engine--Mr. Michael Williams's opinion--Woolf and Trevithick Page 69-113 CHAPTER XX. THE WATT AND THE TREVITHICK ENGINES AT DOLCOATH. Early steam-engines--Semicircular boiler, 1775, net power 7 lbs. on the inch--Watt's statement in 1777--Engines in Dolcoath--Watt's engine, 1778--Watt's engine at Herland, 1798--Trevithick's tubular boiler, 1799--Reconstruction of the Carloose 45-inch, 1799--Gross and net power of engines--Comparison of Newcomen, Watt, and Trevithick engines--Boiler explosion, 1803--Strong rivalry with Watt--Locomotive at Coalbrookdale, 1803--Watt's proposed locomotive--Competition in Wales--Numerous high-pressure engines, 1803--Patent difficulty--Watt's opposition, 1804--Government inquiry--Competitive trials in Wales--Tramway locomotive, 1804--The bet--Opposition because of saving of labour--Worcester engine--West India Docks engine--High-pressure steam condensing engines--One or two cylinders for expansion--Sirhowey boilers--Mr. Homfray's opinion of the Watt opposition--Mr. Whitehead makes engines in Manchester--Cylindrical tubular boiler in Wales for large engines, 1805--Watt contests at Dolcoath, 1805--Steam-blast--Superiority of high-pressure whim-engines--Proposed boiler for the large pumping engine, 1806--Steam pressure--The Watt boiler--Comparison of size of fire-place and coal used--Dredger contract--Theory of steam--Trevithick's Dolcoath boiler when applied to the Watt engine, with expansive gear, to save 300l. monthly, 1806--Momentum of pumping engine--Continued tests of high and low pressure whim-engines at Dolcoath--Watt engine put aside, 1806--High-pressure engines ordered, 1806--High-pressure pumping engine for Wheal Abraham, 1806--Disputed patent right--Expansion reduces heat--Boiler for the Watt 63-inch engine, 1806--Cost of Trevithick's boiler--Advantage of small tubes in boilers--Trinity Board--Watt's steam-cylinder unsuitable for high steam, 1806--Sims' trial of engines--Little fight--Tubular boilers, 1806--High-pressure steam pumping engines, 1818--Reporter of engines--Application to Government, 1810--Dolcoath engines and boilers--High steam to the Watt engine--Duty of engines, 1812--Watt's boiler thrown out--Expansive valve--Dolcoath manager--Saving by boilers and expansive working, 1812--Lean's reports--Increased duty of the three old Dolcoath engines, 1814--76-inch engine, 1816--80,000l. a year saved--Durability of engine--Its removal--Cylindrical boilers--Hornblower and Watt engines--Davies Gilbert's report, 1798--Lean's report, 1816--Watt's views of expansive working--Watt's steam of 1 or 2 lbs. to the inch--Pole's statement--Engine at Marazion, 1804--Woolf in Cornwall--Rees' Cyclopædia--'Encyclopædia Britannica'--Application to Parliament--Wheal Towan--Newcomen and Watt engines--Pompe-à-feu 'La Belle Machine,' Dolcoath Page 114-194 CHAPTER XXI. ENGINES FOR SOUTH AMERICA. Engines for Lima, 1813--Uville's application to Watt--High-pressure model--Cerro de Pasco mines--Uville's return in search of Trevithick--Engines ordered--Pump-work--Modern pumping engines--Money difficulty--Weight of pieces--'Sanspareil' of 1813--Expansive working--Quartz crusher--Locomotive for South America, 1813--Sketch of winding engine--Their simplicity of form--Power and cost of engines--Trevarthen and Bull to accompany the engines--A third man recommended--Boilers put together at Cerro de Pasco--Uville's arrest--Trevithick a shareholder--Vivian's application--Departure of machinery, 1814--Uville's agreement--Invoice of engines sent Page 195-220 CHAPTER XXII. PERU. Agreement for working the Peruvian mines, 1812--Uville and Watt, 1811--Uville and Trevithick, 1813--Uville's opinion of Trevithick--Estimated value of the mines--Machinery reached Peru, 1815--Trevithick's departure from Penzance, 1816--Mr. Edmond's statement--Cerro de Pasco mines in 1850--Report from the Viceroy of Peru, 1816--Report from the Magisterial Deputation of Yauricocha, 1816--Despatch from the Governor of the Province of Tarma, 1816--Pumping engines at work--The Viceroy's reply--Report in the 'Lima Gazette,' 1816--Trevithick's reception at Lima--Trevithick's report, 1817--Differences between Trevithick and Uville--Trevithick's thoughtless acts--His visit to the nunnery--The Lord Warden proposed to erect a statue in silver to Trevithick--Bust of Trevithick in Cornwall--Quicksilver--Sunk ship--Chili--Copper and silver mine--Departure from Lima--Cerro de Pasco mines Page 221-259 CHAPTER XXIII. COSTA RICA. Gerard at Punta de Arenas, in the Pacific, in 1822--Nicolas Castro worked a gold mine, 1821--Alverado's ore-grinding machine, 1822--Climate of Costa Rica--Mines in the Cordillera--Canal from the river Machuca to Quebrada-honda--Castro's mine--Padre Arias, or the Priest's mine--Trevithick and Gerard's proposal for iron railroads, &c., for the mines of Costa Rica, 1827--New line of road from San Juan, on the Atlantic, to the Costa Rica mines--Serapique River navigable--Trevithick's diary--A mule track easily constructed--Comparative distance to the mines from the head of the Serapique on the Atlantic, and Punta de Arenas on the Pacific--Trevithick nearly drowned in the Serapique--Nearly starved before reaching San Juan--Performs a surgical operation--Designed the locomotive between breakfast and dinner--Robert Stephenson and Trevithick at Carthagena--Nearly drowned in the Magdalena--Saved by Mr. Bruce Napier Hall--Trevithick nursed Robert Stephenson Page 260-275 CHAPTER XXIV. RETURN TO ENGLAND. Bodmin School, 1827--Cube root--Trevithick's reception--Saving in Cornish mines--Model gun--Gerard's return, 1827--His meeting Robert Stephenson--His remarks on Costa Rica--Montelegre's search for a better line of road--Mr. M. Williams's proposal--Change of Ministry, and the gun-carriage--Model of iron packet-ship and engine--Robert Stephenson's remarks on mining--Trevithick's rejection of purchase-money Page 276-283 CHAPTER XXV. GUN-CARRIAGE--IRON SHIPS--HYDRAULIC CRANE--ICE MAKING--DRAINAGE OF HOLLAND--CHAIN-PUMP--OPEN-TOP CYLINDER--HAYLE HARBOUR--PATENT RIGHTS--PETITION TO PARLIAMENT. Trevithick's description of gun-carriage and iron ship--Select committee--Glasgow iron-ship builders--Trevithick's comparison of gunpowder and steam--Cranes worked by air or water--Artificial cold--Liberality--Holland--Drainage--Dredging--Zuyder Zee--Hydraulic crane--Dutch pumping engine--Chain-pump--Haarlem Lake--Rhine--Windmills--Hayle Harbour--Disputed pole-engine patent right--Petition to Parliament, 1828--Marine boilers--Steam pressure--Engine duty--Lords of the Treasury refuse the petition--Davies Gilbert's views--Marine compound engine of 1871 Page 284-314 CHAPTER XXVI. TUBULAR BOILER--SUPERHEATING STEAM--SURFACE CONDENSER. Binner Downs engine, 1828--Fires around cylinder and steam-pipes--Saving of coal--Surface condensation at sea--Superheating tubes--Used steam returned to the boiler, 1828--Holland pumping engine--Woolf at the Consolidated Mines--Laws of steam--Power of heat from 1 lb. of coal--Loss of heat--Experiments at Binner Downs--Surface condensation--Partial surface condensation for ships or railways--Effect of superheating--Watt's theory doubted--Wheal Towan and other engines--Loss of heat--Injection-water--Surface condensation and superheating--Partial condensation engine--Duty of chain pumping engine--Surface condensation by cold water or air--Results of the experiment--Hayle Harbour--Condenser of copper tubes, 1829--Suitability for steam-ships--Proposal to erect at his own expense a marine engine with surface condenser and screw-propeller for the instruction of the Admiralty, 1830.--Sketch of tubular boiler and surface-air condenser--Screw draught--Preservation of heat in condensing by air--Comptroller of the Navy--Patent of 1831--Boiler within the condenser--Surface condensation by air or water--Safety boiler of concentric tubes--Blowing vessel for air condensation and draught--Tubes for distilling water--Steam pressure--Expansive working--Robert Stephenson's statement--'Echo' steamboat, 1831--Bottle-neck boiler--Admiralty--Steam Users' Association--Mr. Alexander Crichton's boiler and surface condenser--Captain Dick and Captain Andrew--Captain King and the 'Echo' Page 315-362 CHAPTER XXVII. HEATING APPARATUS--MARINE STEAM-ENGINES--REFORM COLUMN. Ill health, 1830--Hot-house boiler--Heating rooms--Discharging coal-ships by steam--Hot-water stoves for France--Patent for heating apparatus, 1831--Marine portable engines--Boat propeller--Wheal Towan--Discharging coal by steam at Hayle--Proposal to the Common Council of London--Every vessel to carry a steam-engine--Mr. George Rennie--Proposal to the Admiralty--Surface condensation--Locomotives supplying their own feed-water--Petition in Trevithick's favour--Davies Gilbert's suggestion--His comparison of the Watt and Trevithick engines--Maudslay on Trevithick's proposals--Patent of 1832--Superheating steam--Cylinder placed in flue from boiler--Expansive steam--Tubular boiler--Water propulsion--Superheating and surface condensation for locomotives--Detail of engine--Proposal to send steamboats to Buenos Ayres--Waterwitch Company--Messrs. Hall and Sons--Hall's condenser--Rennie and the Admiralty--'Syria' steamboat--Compound engines--Watt on high-pressure steam--Trevithick on compound engines--Tubular boiler and variable blast-pipe--Refusal of Trevithick's petition to Government--Ill health--Davies Gilbert's statement to Spring Rice--Meeting on proposed Reform Column--Trevithick's description--Means of ascent and descent--Placed before the King--Death--Funeral--His last letter Page 363-396 ILLUSTRATIONS TO VOLUME II. PAGE AËRATED STEAM-BOILER 7 ROCK SPLITTING 25 STEAM THRASHING ENGINE 37 AGRICULTURAL MACHINE 58 WHEAL PROSPER HIGH-PRESSURE STEAM POLE-ENGINE 70 CYLINDRICAL HIGH-PRESSURE STEAM-BOILERS 71 EXPANSIVE STEAM POLE-ENGINE 81 CARN BREA CASTLE 147 TREVITHICK'S DOLCOATH ENGINE OF 1816 168 TREVITHICK'S DOLCOATH BOILERS OF 1811 169 STEAM DIAGRAM 185 'LA BELLE MACHINE' 190 CARRIAGE-WHEELS 207 WINDING ENGINES 208 PENZANCE IN OLDEN TIME 228 MARKET, JEW STREET, PENZANCE 243 MULE TRACK FROM LIMA TO CERRO DE PASCO 258 MAP OF COSTA RICA MINES 260 GUN-CARRIAGE 285 DUTCH PUMPING ENGINE 298 MOUNT'S BAY 318 PARTIAL CONDENSATION ENGINE 332 TUBULAR BOILER AND CONDENSER 339 BOTTLE-NECK BOILER 357 CAPTAIN DICK AND CAPTAIN ANDREW 361 HOT-WATER ROOM-WARMER 364 PATENT HEATING APPARATUS 366 DUCK'S-FOOT PADDLE 369 MARINE ENGINE AND BOILER 380 COMPOUND MARINE ENGINE 385 REFORM COLUMN IN DETAIL 391 GENERAL VIEW OF REFORM COLUMN 393 LIFE OF TREVITHICK. CHAPTER XVII. VARIOUS INVENTIONS. "About 1804 Captain Trevithick put up in Dolcoath Mine a stone-crushing mill, having large cast-iron rollers, for breaking into small pieces the large stones of ore; it was spoken of as the first ever used for such a purpose; the same form of crusher is still used in the mines. It caused a great saving compared with breaking by a hand hammer."[1] "I saw at the Weith Mine in 1805 a portable high-pressure engine, made by Captain Trevithick. "It was called a puffer; the cylinder was in the boiler; the steam about 30 lbs. on the inch above the atmosphere. A wooden shed sheltered the engine and man. "The facility of manufacture and cheapness of those engines caused them to be much used in the mines, and also elsewhere."[2] [Footnote 1: Recollections of the late Captain Charles Thomas, manager of Dolcoath.] [Footnote 2: Captain Samuel Grose's recollections.] Mrs. Trevithick, about the time we are speaking of, accompanied her husband through one of the Staffordshire china manufactories. Trevithick said to the manufacturer, "You would grind your clay much better by using my cast-iron rolls and high-pressure steam-engine." The manufacturer begged him to accept a set of china. Mrs. Trevithick was disappointed at hearing her husband say "No! I have only told you what was passing in my mind." Driving rolling-mills was among the early applications of the high-pressure steam-engines; but pulverizing hard rock by the use of iron rollers was a novelty: though his patent of 1802 shows the proposed rolls driven by steam for crushing sugar-canes, yet no one had dreamt, prior to 1804, of economy in crushing stone and clay by such a means. The plan, however, remains in use to this day in many mines, and is frequently spoken of under the name of quartz-crusher. "MR. GIDDY, COALBROOKDALE, _September 23rd, 1804_. "Sir,--Yours of the 13th this day came to hand. I left Wales about eight weeks since, and put an engine to work in Worcester, of 10-horse power, for driving a pair of grist-stones, and a leather-dressing machine, and another in Staffordshire for winding coals; each of them works exceedingly well. "From Coalbrookdale I went to Liverpool, where a founder had made two of them, which also worked exceedingly well; one other was nearly finished, and three others begun. Some Spanish merchants there saw one of them at work, and said that as soon as they returned to Spain they would send an order for twelve engines, of 12-horse power, for South America. In South America and the Spanish West Indies water is very scarce; in several places there is scarcely water for the inhabitants to drink, therefore there is no water for any engine. By making inquiry, I found that ten mules would roll as much cane in an hour as would produce 250 gallons of cane-juice, which they boil until the water is evaporated, and the sugar produced. "I told them that the engine-boiler might be fed with this juice, and by a cock in the bottom of the boiler constantly turning, and by taking a greater or smaller stream from it, they might make the juice as rich as they liked. In this process the juice would be so far on towards sugar, and the fire that worked the engine would cost nothing, because it would have taken the same quantity of fuel under the sugar-pans to evaporate the water, as it would in the engine-boiler. "The steam from the engine might be turned around the outside of the furnace for distilling rum, as the distilleries require but a slow heat. "I think the steam would answer a good purpose around the outside of the pan. "If this method answers, the cost of working the engine would be nothing, and the engine would be then working, as it were, without fire or water. "The Spaniards told me that if this plan answers, they would take a thousand engines for South America and the Spanish West Indies. I shall be very much obliged to you for your opinion on this business. These merchants make a trade of buying up sugar mills and pans, with every other thing they want from England, and exchange them with the Spaniards for sugar. "At Manchester I found two engines had been made and put to work; they worked very well: three more are in building. From there I went to Derbyshire. The great pressure-engine I expect will be at work before the middle of October. A foundry at Chesterfield is building a steam-engine as a sample; two foundries in Manchester are at full work on them, and one in Liverpool. There are six engines nearly finished at Coalbrookdale, and seven in a foundry at Bridgenorth. "I am making drawings for several other foundries. Any number of them would sell. A vast number are now being erected, and no other engine is erected where these are known. The engine for the West India Docks was neglected during my absence from the Dale, but I expect it will be ready to send off in ten days. "In about three weeks I shall be in London to set it up. It will please you very much, for it is a very neat and complete job, and I have no doubt will answer every purpose exceedingly well. At Newcastle I found four engines at work, and four more nearly ready; six of these were for winding coal, one for lifting water, and one for grinding corn. "That grinding corn was an 11-inch cylinder, driving two pair of 5-feet stones 120 rounds per minute; ground 150 winchesters of wheat in twelve hours with 12 cwt. of small coal. It worked exceedingly well, and was a very complete engine, only the stroke was much too short, not more than 2 feet 6 inches, which made very much against the duty. "The other engine that was lifting water had a 5-1/2-inch diameter cylinder, with a 3-feet stroke, drawing 100-gallon barrels, twenty-four every hour, 80 yards, burning 5 cwt. of coal in twenty-four hours. "This work it did with very great ease. I believe you will find this an exceeding good duty for a 5-1/2-inch cylinder engine. "Below I send a copy of Mr. Homfray's and Mr. Wood's letters to me:-- "Mr. Homfray's, of the 10th September.--'Our great engine goes on extremely well here, nothing can go better; the piston gives no trouble; it goes about three weeks, and we work it with blacklead and water; the cylinder is as bright as a looking-glass; it uses about 2 lbs. of blacklead in a week; about once in twelve or fifteen hours we put a small quantity of blacklead, mixed with a little water, through the hole in the cylinder screw, and we never use any grease. We rolled last week 140 tons of iron with it, and it will roll as fast with the both pair of rolls, as they can bring to it.' "Mr. Wood's letter, September 12th.--'We are going on, as it is likely we always shall, in the old dog-trot way, puddling and rolling from the beginning of the week till the end of it. Your engine is the favourite engine with every man about the place, and Mr. Homfray says it is the best in the kingdom.' "I have not the smallest doubt but that I can make a piston without any friction or any packing whatever, that needs not to have the cylinder screw taken up once in seven years. It is a very simple plan, and will be perfectly tight; it is by restoring an equilibrium on both sides of the piston. I expect to see you in London soon, and then will give you the plan for inspection before I put it in practice. "I am very much obliged to you for recommending these engines in Cornwall, but you have not stated in what manner they are to be applied; whether to work pumps, or barrels, or both. They may be made both winding and pumping engines at the same time, if so required. "A rotative engine will cost more than an up-and-down-stroke, on account of the expense of the fly-wheel and axle. An engine capable of lifting 180 gallons of water per minute 20 fathoms would cost, when complete and at work, patent right included, about 220_l._ If it is a rotative engine, with a winding barrel, it will cost 270_l._ I expect that a 7-inch cylinder would be sufficient for winding at Penberthy Crofts, which might have a Crank on the fly for lifting water in pumps, and a winding barrel on its back. This would cost about 170_l._; the erection of them, when on the spot, will cost nothing. You do not say when you intend to be in town. I hope you will be present when the dock-engine is set to work. "The engines first sent to Cornwall, must be from Coalbrookdale; then they will be well executed, but from Wales it would not be so. "You may depend on having a real good engine sent down, with sufficient openings given to the passages. "The engineer from the Dale has been lately in London, and has just returned; he gives a wonderful account of the engines working in London. There are twelve now at work there. They have well established their utility in different parts of the kingdom, and any number would sell. The founders intend to make a great number, of different sizes, and send them to different markets for sale, completely finished, as they stand. "You do not say anything about wheels to the engine for Penberthy Crofts. There are several engines here nearly finished; if they suit in size for Penberthy, one may be sent down in four or five weeks, otherwise it may be two months. "I am, Sir, "Your very humble servant, "RICHARD TREVITHICK. "Direct for me at the Talbot Inn, Coalbrookdale." Trevithick worked hard and successfully in making his steam-engines useful, and firmly believed that he could and would make them universal labourers. Even the Spanish merchants, unacquainted with steam, talked of giving an order for several engines for South America; and their glowing account of the wide field open to him may have been instrumental to his going to that country by making his engines known there. His proposal to make the sugar-cane convert itself into sugar by the use of his patent high-pressure steam-engine may be more theoretical than practical; but many more unlikely things have come to pass. At that time several of his engines were at work in Wales, Worcester, Staffordshire, Coalbrookdale, Manchester, Derbyshire, Liverpool, Cornwall, and Newcastle-upon-Tyne. Twelve were at work in London, and so familiar were people with them, that founders intended to construct them of different sizes, and send them for sale at the large market or county towns; their cost complete, ready for work, to be 200_l._, more or less, according to size, with a range of application unlimited. His one letter, casually written sixty-seven years ago, mentions them as grinding corn, dressing leather, winding coal, crushing sugar-cane, prepared to boil sugar, and distil rum; pumping water, rolling iron, railway locomotion, portable steam fire-engine, portable steam-crane, mine engines on wheels; so that it may almost be said he was not too sanguine in hoping to send in 1804 a thousand of his engines to South America, for in those cursory remarks he draws attention to no less than thirty-six high-pressure steam-puffers at work. The Penberthy Croft Mine portable engine could be placed on wheels or otherwise, according to the wish of the purchaser, as though steam locomotion was an every day occurrence in 1804. "CAMBORNE, _January 13th, 1811_. "MR. GIDDY, "Sir,--From calculating the quantity of blast given to a blast-furnace, I find a considerable quantity more of coal consumed by the same quantity of air in this way, than by the usual way in common engine chimneys. Of course the more cold air admitted to pass through the fire, the more heat carried to the top of the stack. Crenver 63-inch cylinder, double-power, 8-feet stroke, with but one boiler, works five strokes per minute. This gives about 1600 square feet of steam per minute, and burns about 8 tons of coals in twenty-four hours. The stack for this boiler is 3-1/2 feet square, and the draught rises 10 feet per second, and will set white paper in a flame at the top of it in about a minute. Therefore, this chimney delivers 7200 square feet of air per minute, which is four and a half times the quantity of heated air, at nearly four times the temperature of heat that there is of steam produced from the same fire, and delivered to the cylinder. "A blast-furnace that burns 100 tons of coal per week is blown by a 5-feet diameter air-cylinder, 4-feet stroke, ten strokes per minute, double-power, giving about 1600 square feet of air per minute, to consume 100 tons of coal, besides giving a melting heat to 350 tons of ore and limestone. "Crenver engine has 7200 square feet of air to burn 56 tons of coal per week, which is above eight times the quantity of air used by air fire-places to what is used in a blast-furnace, and of course must carry off a great proportion of the heat to the top of the stack, that might be saved if the engine-fire was a blast instead of an air fire. "But suppose the idea to be carried still further, by making an apparatus to condense and take the whole of the heat into the cylinder instead of its passing up the chimney. By having a very small boiler, and a blast-cylinder to blow the whole of the blast into the bottom of the boiler, under a cylinder full of small holes under the water, to make the heated air give all its heat to the water. [Illustration] "The furnace must be made in a tight cast-iron cylinder. Both the fire-door and the hole through which the blast enters must be quite tight, as the pressure will be as strong in the fire-place as in the boiler. The whole of the air driven into the fire-place, with all the steam raised by its passage up through the water in the boiler, must go into the cylinder. There will also be the advantage of the expansion of the air by the heat over and above what it was when taken cold into the blast-cylinder. "From the great quantity of coal burnt in blast-furnaces you will find that a very small blast-cylinder would work a 63-inch cylinder double. If there is as much heat in a square foot of air as in steam of the same temperature, the saving will be beyond all conception; but for my own part I cannot calculate from theory what the advantages will be, if any, and for that reason, before I drop or condemn the idea, I must request you will have the goodness, when you have an hour to spare, to turn your thoughts to this subject, and inform me of your sentiments on it. "Perhaps it is like many other wild fancies that fly through the brain, but I did not like to let it go unnoticed without first getting your opinion. I hope you will excuse me for so often troubling you. "St. Ives plans will be delivered to them on Tuesday, when I expect they will be forwarded to you. "I hear there is a good course of ore in the adit end at Wheat Providence Mine. "A Mr. Sheffield, of Cumberland, writes to Mr. Gould that he has turned idle his air-furnaces, and smelted his ores by a blast near a year since. "His furnace is but 10 feet high and 4 feet diameter, and it melts 28 tons of ore, of from 4 to 5 in the 100 per week, and makes a regel of from 65 to 70 in the 100, and answers beyond what we calculated for them. "Suppose a furnace 20 feet high and 4 feet diameter, it would smelt eight times the quantity of his, which would be near 900 tons per month, or nearly double the quantity raised by any one mine in the country. The expense of the ... would be very trifling. "To-morrow Dolcoath account will be held, when I expect to have orders to begin to erect a furnace on the spot. "This trial of Mr. Sheffield's has put it out of my power to get a patent, and now I do not know how to get paid. "I should be content with 5 per cent. on the profits gained by this plan, and would conduct the business for the mines without salary. Should you chance to fall on the subject with his Lordship, be pleased to mention something about the mode of my payment, as his Lordship is by far the properest person to begin with about my pay, for after his Lordship has agreed to the sum, and Dolcoath Mine the first to try the experiment, I think all the county will give way to what he might propose. But I wish something to be fixed on before all the agents in the mines know how to be smelters themselves, after which I expect no favour, unless first arranged. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK." How great was the practical insight his genius gave him, and how imperfectly his followers have acted on this advice given sixty years ago! The chimney that at its top would ignite paper, threw to waste four and a half times more heated air than was requisite to supply the quantity of heat which passed through the working cylinder in steam, and at a temperature nearly four times greater than the temperature of the steam. It needs only to observe the burnt appearance of a steamboat funnel of the present day to know how wasteful we still are, or how very ignorant of improved methods of economizing fuel. To prevent this waste of heat up the chimney be proposed to do away with the chimney altogether; the fire-place was to be a close one, having a blast under the fire-bars of a strength sufficient to force the air, heated by its passage through the fire, direct through a small valve into the water in the boiler, by which means all the heat given by ignition would pass into the steam, and his steam-puffer become an aërated steam-engine. From the following it appears that this plan of Trevithick's is now coming into use as something quite new:-- "In your last impression, under the head of 'Air and Steam combined, as a Motive Power,' you state 'the invention was described to be that of Mr. Warsop, but we have recently heard that a few years back (1865) the same invention had been protected in an earlier patent than Mr. Warsop's, by Mr. Bell Galloway.'"[3] Trevithick thought of patenting a plan for reducing copper ore by the use of a blast, in preference to the usual air-furnace and chimney, but something similar had been tried by Mr. Gould, and he therefore proposed to erect a blast-furnace in Dolcoath Mine, receiving a portion of the saving of fuel as his remuneration. Such a furnace worked there for many years, until copper smelting was removed from Cornwall to Wales. The plans for a breakwater at St. Ives were for an undertaking that has since been in many hands, but without success, except perhaps for the convenient making of members of Parliament. Some slight progress has been made by engineers and contractors, but vessels are not willingly taken to the port, and ratepayers grumble at unprofitable harbour taxes. "LONDON, _January 20th, 1811_. "DEAR TREVITHICK, "I have not lost any time in mentioning your wishes respecting a compensation for the plan of smelting copper to Lord Dedunstanville, who intends mentioning the affair in his next letter to Mr. Reynolds. Lord Dedunstanville wishes you extremely well, but it is impossible for him to settle anything apart from the adventurers. [Footnote 3: See the 'Mechanics' Magazine,' June 3rd, 1870.] "I am very sorry that anyone should have executed the plan of reducing copper ore by a blast-furnace before you had put into practice the idea suggested to me ten years ago. It ascertains, however, that the contrivance will succeed, although you are certainly reduced to ask moderate terms, and I know not what can be more moderate than those you have asked, except that I would recommend some limit as to time. "The plan you suggest for an engine on a new construction is, I fear, very doubtful. "According to the data furnished to me, the air in the blast would be to that in a common fire-place as 6-1/4 to 1 very nearly, provided their densities were the same; but you have measured one entering the furnace at the common temperature, and the other going to the stack so hot as to set on fire a piece of paper held at the top. Thus the increase of temperature that augments the elasticity of a fluid confined, would expand it in the same degree. It is therefore uncertain from these statements which furnace consumes the greater quantity of air. I apprehend the general principles of an engine worked by hot air, through the medium of a blast, would be as follows:-- "Let any quantity of air be driven into a furnace with the pressure of an atmosphere, and let it be there expanded ten times. It should then be taken off ten times as quick, but in that case no power whatever would be produced, so the external atmosphere would balance the internal. Now, let the blast be two atmospheres strong, and let them be expanded ten times, and be taken off ten times as fast, each stroke will be opposed by one, equal in all to ten; subtract two for the blast, there remain eight. "But air so hot would burn every vegetable or animal substance, and such a furnace I suppose could scarcely be kept air-*tight. If the heated air is made to act on water, then it becomes a mere question of how much absolute heat is given out by the fuel, and whether that excess is more than sufficient to compensate the burden of the blast; for the water will absorb an immense quantity of heat in changing itself into steam, and thus reduce the force of the air as to make it almost impossible for that addition to add so much power as the blast takes away. "I have, therefore, no hesitation in saying that this plan will certainly not do. Write to me by all means whenever anything strikes you, and you may always depend on having my best advice. "I am, dear Sir, "Ever most truly yours, "DAVIES GIDDY." Trevithick saw without apparent reasoning, while his friend's reasonings failed to make plain the full bearing of the questions, and so cramped the position as to make a change of front difficult--an operation in which Trevithick excelled. We learn, however, that in 1801 he suggested a blast in copper-ore furnaces, and in 1811 was on the verge of a discovery that has since revolutionized the iron-smelter's art by the use of hot blast. Wasted heat from a blast-furnace 10 feet high led him to the conclusion that by doubling the height of the furnace, enabling the cold mineral thrown in at the top to take up the heat wasted through the top of the low furnace, seven-eighths of the coal would be saved. His idea of sending blast through the furnace of his steam-boiler to economize heat could have been readily applied to the iron furnace, and we should have had the modern hot-blast iron furnaces. [Rough draft.] "CAMBORNE, _March 5th, 1812_. "GENTLEMEN, "Your favour of the 15th February, with a sketch of your brewery, I have received; and from which I find the head of water is 30 feet above the brewery, which makes it difficult to erect the chain and buckets so as to take advantage of the whole height of water; and as the stream is so very small, it will not admit of losing any part of the power. "To erect a machine so high, to engage the whole fall, would be, I fear, more expense than the power you would get would warrant; therefore I would recommend it to be made use of in a cylinder, in the same way as we use falls of water of 200 feet in our Cornish copper mines. We allow one-third loss for friction and leakage in those machines; but your machine being so very small, the loss will exceed that proportion; therefore I cannot promise you above one-half of the real weight and fall to be performed on your machinery, and that must be by a well-executed machine, for a small defect would destroy the value of so trifling a power. "As there is no expansion in water, it will be somewhat difficult to make the machine turn the centres with a fly-wheel, for if the valve shuts a little too early or too late for the turn of the crank over the centre, the fly-wheel's velocity must break something by confining the water between the piston and the bottom of the cylinder, which, after the valve is shut, cannot make its escape, and not having an elastic principle, the piston will strike as dead on the water as on a piece of iron, because, unless the valve is shut by the engine before the stroke is finished, it cannot shut at all. "I know persons who have attempted to put fly-wheels on pressure-engines of this kind, but never yet has one been made to work rotative. I do not see much difficulty in making an engine of this kind to work a crank and fly-wheel, by connecting an air-vessel with the cylinder to receive the pressure and contract and expand and shut the valves, the same as in steam-engines. "A machine on this plan ought to be placed as near the low level as possible. If I furnish you with drawings and directions for the executing of the work yourselves, I shall charge you fifteen guineas for them. If I send the machine finished, the charge will be 50_l._ "Your objections respecting steam-engines I do not doubt are correct, when executed by persons who do not understand the construction of them. In England some persons privately erected my engine to evade the patent premium, but have severely paid for their saving knowledge by accidents and defects in their engineering ability. I have erected above 100 steam-engines on this principle, but never met with one accident or complaint against them. To prevent mischief from bad castings, or from the fire injuring the surface of cast iron, I make the boilers of wrought iron, and always prove them with a pressure of water, forced in equal to four times the strength of steam intended to be worked with. "Some persons have worked those engines under a pressure above 100 lbs. on the square inch, but in general practice I do not exceed 20 lbs., finding under this pressure the piston will stand six or eight weeks, and the joints remain perfect, and no risk of bursting the boiler, it being made of wrought iron, and proved by pressure before sent off; but cast-iron boilers may, by defects not discernible, and are very apt to break by the water being left low in the boiler, and if heated red hot, exploding without the smallest notice; but wrought-iron boilers, when defective, give way only partially, without injury to anyone. With respect to the erecting and management of the engine, you need not have an engineer, for any common tradesman can do this from the drawings and directions sent with the engine; for, as I before informed you, farmers and their labourers set up and keep in order the thrashing-machine engines without my going on the spot or sending any person to assist them. I never saw a steam-engine rolling malt, therefore cannot judge the quantity the engine would roll, only by a comparison with horse labour, against the consumption of coal, which will be in some cases as about 42 lbs. to one horse; but where great speed is required in the machine, the coal will be less, as steam-engines make more revolutions in a minute than horse mills, therefore the work is done with less friction. "I have several times applied the steam, after it has worked the engine, to boil water and other purposes, with as good effect as if the engine had not been there, therefore the work of the engine will be a clear profit. "You say about a 1-horse engine. The boiler would be so small that it would not be worth applying that steam to any other purpose, as any large quantity of water would be but slowly heated. "I find that it does not answer either the purpose of the vendor or the user of an engine, to make less than a 2-horse power, as the expense on a very small engine is nearly as much as one of the power I use for thrashing, those being only 80_l._, and a 2-horse is 60_l._ Respecting the mashing with steam, I never before heard of it, but from the theory of the plan I think it cannot fail to answer a far better purpose than any other that can possibly be applied for extracting the essence of the malt. However, should it not answer your purpose, it is only the loss of the expense of a few yards of 1-inch lead pipe. "In an engine of the size used for thrashing, if the fire is kept brisk, it will boil, by the steam sent into a separate vessel, near 300 gallons of water per hour. "The room required to work in is about 7 feet diameter, and 12 feet high. It would be useless to put you to the expense of drawings, until you have made up your minds on what you intend to have done. "I remain, Gentlemen, "Your most obedient humble servant, "RICHARD TREVITHICK. "To ROBINSON AND BUCHANAN, Brewers, "_Londonderry, Ireland_." Engineers of the present day do not volunteer such general information without charge, or give such a variety of practical mechanism slightly but clearly described, and principles reduced to practice. An endless chain with buckets is a form of water-wheel not then in use. A water-pressure engine for so small a quantity of water, with a fall of about 30 feet, would cause a loss of 50 per cent. from friction and small defects. The non-elastic character of water made it unsuitable for a machine requiring a fly-wheel. Air-vessels should be used to lessen the rigidity of water. Cast-iron boilers dangerous. Wrought-iron boilers to be tested with a water pressure four times as great as the proposed working steam pressure. A steam pressure of 20 lbs. to the inch most suitable for engines in charge of inexperienced persons. The brewers' mash tub to be heated by the waste or surplus steam. [Rough draft.] "CAMBORNE, _December 5th_, 1812. "GENTLEMEN, "I have yours of the 20th November. The letter you directed for Truro never came to hand. I find by your letter that you have been trying to put into practice the hints I gave you about the chain and buckets, and that you expect it will answer if properly executed. You are not the first that has picked up my hints, and stuck fast in their execution. I make it a rule never to send a drawing until I have received my fee, and when you remit to me fifteen guineas I will furnish you with proper drawings and directions to enable you to make and erect the machine. "I remain, Gentlemen, "Your very humble servant, "RICHARD TREVITHICK. "ROBINSON AND BUCHANAN, Brewers, "_Londonderry_." What a pocket encyclopædia of inventions! from which, as by stealth, Robinson and Buchanan selected the least applicable, declining a suitable steam-engine at a very small cost, rather than pay an engineer for his opinion. [Rough draft.] "CAMBORNE, _April 26th_, 1812. "SIR CHARLES HAWKINS, Bart., "Sir,--I have received yours of the 7th, respecting the small breakwater at St. Ives. As far as I can judge from a rough calculation, I think it an undertaking likely to pay well; but as you wished me not to mention anything about your intentions, and not receiving your orders to make a minute inquiry and estimate, I cannot answer your letter so fully as I should wish, fearing that giving a random and imperfect statement might be apt to lead you into errors, and also make me look simple. If an engineer were employed to survey and estimate after me, every information in my power is at your service; therefore be pleased to state particularly what information you wish, and I will attend to the business and answer your questions as early as possible. "I have received a letter from Sir John Sinclair requesting correct drawings and statements of the thrashing engine to be forwarded to the President of the Board of Agriculture, which I shall attend to. He also says that he has sent my letter to the Navy Board, in hopes that the experiment of propelling vessels by steam may be tried under its sanction and expense. "Perhaps it might be proper to wait the answer of the Navy Board before writing to Mr. Praed about propelling the canal boats. I am very much obliged to you for writing to Captain Gundry, about the Wheal Friendship engine. I expect to have a portable steam-whim and stamps at work at my own expense in a few days, which will prove for itself its utility; that being the only way to introduce new things. I would be very much obliged to you to say if Mr. Halse is to pay me for my past attendance at St. Ives about the breakwater. Enclosed you have a letter to Sir John Sinclair, unsealed for your inspection, which, if you approve of, please to forward. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK." Trevithick's skill did not prevent his being reasonably modest, or cause him to be envious of others; neither did his dear-bought experience, that one's own pocket must pay for making public one's own inventions, prevent his again soliciting the assistance of persons of influence, though it does not seem that Mr. Praed helped forward the screw-propeller, or that Sir John Sinclair gave direct help, though he probably made known the high-pressure steam-engine to the marine experimenters on the Clyde. [Rough draft.] "MR. RASTRICK, "CAMBORNE, _December 7th, 1812_. "Sir,--I have been waiting your answer to my last, and especially that part respecting the West India engine, as I have not nor could not answer their letter to me without first hearing from you; therefore must beg you will be so good as to answer me by return of post on that subject. If they get impatient about the time, and refuse to take the engine, I have no doubt the Plymouth people will take it and several others; but I very much wish to send one to the West Indies, as there is a large field open there for engines of this kind. I have received an order for a thrashing engine for Lord de Dunstanville, of Tehidy; and as I wish those thrashing engines to be known through the country, I intend to take one of the engines ordered for Padstow and send it to Tehidy. One of the Padstow farmers can wait until you make another for him. Therefore I would thank you to send the first finished by ship from Bristol for Portreath or Hayle. Send a drum with everything complete, of which you are a better judge than I. Probably about 3 feet in diameter and 3-1/2 feet long will be sufficient. "There must be a fly-wheel with a notch to carry the rope, and also a small notch-wheel on the drum-axle. I think 6-1/2 feet diameter for the fly, and 9-1/2 inches diameter for the small wheel, will give speed enough to the drum. Mind to cast a lump, or screw on a balance, of about 1 cwt., on one side of the fly-wheel. There must be two stands on the boiler, and a crank-axle, or otherwise a crank-pin, in the fly-wheel, whichever you please; with a shaft 3 feet long with a carriage. "The engine is to stand in a room under the barn, about 7-1/2 feet high, 7 feet wide, and 14 feet long. The fly-wheel will stand across the narrow way of the room. The rope will go up through the floor, and the drum be shifted by a screw, horizontally, on the barn floor, so as to tighten the rope. I shall put down the top of the boiler level with the surface, with an arched way to the fire and ash-pit under ground, to prevent the chance of fire, which the farmers are very much afraid of. I send you a sketch showing how it is to stand. "I do not bind you to the size of the drum or wheels, only the room that the fly-wheel works in is but 7 feet wide. "Now to Mr. Richards' mill. "Query 1st.--The length of the piston, and the small variation that the beam will give it, is so trifling that it will not be felt. "The cylinders that have been working on their sides for seven years past, are now working as well as any engine with upright cylinders, which is a proof that the little rubbing is of no consequence. "Query 2nd.--The passage in the cock is equal to the passage we make in our large engines, which is only one-fortieth part of the piston; and as we shall work with high steam, we do not mind the pressing through the steam-passage; and as the steam will be very much expanded, it will not be felt in the passage to the condenser. I know where we have removed cylinders and put larger ones on the same nozzles and condensing work, and the engines did good duty. "Query 3rd.--I find by experience that if you give double the quantity of injection to an engine one stroke, and none the other, that the quicksilver in the gauge will stand nearly the same; the cold sides of the condenser are sufficient to work an engine a great many strokes without any injection. "Query 4th.--You may put a hanging to the air-pump bucket, and foot-valve; either that or a rising one will do very well, but I think the rising cover and wood face on the top, best. "Query 5th.--The air-pump bucket is large enough. At Wheal Alfred they have a 64-inch cylinder; the air-pump is 20 inches, and the stroke is half that of the engine. They were afraid that it was too small; they then put another of 14 inches by the side of the first, the same stroke. The quicksilver tube stands as high with the one 20-inch bucket as with the two buckets; the engine works best with the one bucket. I have found by experience that size to be sufficient, and (especially in an engine that works quickly) make the cistern high enough to cover the condensing work well with water. "Query 6th.--My reason for making the forcing pump with duck-valves is, because they do not bum like the others, and we find them seldom out of repair; but make it whichever way you think best, and work it in any way you like. "Query 7th.--I mean by 3/4 expansive, that the steam is to be shut off from the cylinder when the piston has moved up from the bottom one quarter of its stroke. Make the cam to your own mind. "Query 8th.--I do not think the engine will require a heavier fly-wheel, as the stones will act as a fly, and the power, though so very irregular, will be so sudden in its changes, that the speed of the machinery will not let it be felt. If you make a crank, you may make the fly-wheel 3 or 4 feet more in diameter. But if with a pin in the fly-wheel, the beam would come down on the top of it; therefore, I think it will be better to put a crank, and put the fly-wheel in the middle of the shaft. "Query 9th.--The steam will be raised to 25 lbs. to the inch above the atmosphere, or 40 lbs. to the inch on a vacuum; but I think you need not calculate for much more strength on that account. It is not the power that breaks the machinery, but bangs, and not the uniform weight that this will give. "Query 10th.--Twenty strokes per minute I propose, which I think a fair speed. "Query 11th.--The fire-bars must be of wrought iron; we find them answer much better than cast iron. Let them be 5/8ths of an inch from bar to bar, 1 inch thick at the top, 3/8ths of an inch at the bottom, 2 inches deep, 4 feet long, with bits on them at the ends, to prevent their getting too close together. I find the nearer the fire is to the door, the better and handier it is to work. All the large engines are in this way, and we do not find the door or front plate get hot, as they are lined with brick. Cast the door with a rib to hold a brick on its edge. Tube, 2 feet 9 inches by 1 foot 11 inches; manhole, 15 by 10 inches. "Query 12th.--A governor will be required; perhaps as good a place as any for it, out of the way, will be on the cast iron that carries the beam; you may turn the fly-wheel whichever way you please. If this engine is worked with steam of 25 lbs. to the inch above the atmosphere, and the steam shut off at one-twentieth part of the ascending stroke of the piston, the power will be as three is to two of Boulton and Watt's single engines. "Only two pairs of stones for the present, but calculate those stones to stand in such a way that another pair may be placed, on a future day, if wanted. I have not seen Mr. Richards lately. I wish you to write a form of an order, in your next, such as you wish, and I will get him to write to you accordingly. Put the engine and drum for Lord de Dunstanville out of hand neat and well, as it will be well paid for; and make the stands, &c., in your own way. "RD. TREVITHICK." Mr. Richards' flour-mill engine may claim to be the first practical smoke-burner: keeping the fire much thinner at the inner end of the grate-bars than at the fire-door end of the grate, allowed of the freer passage of air through the thinner layer of coal, near the fire-*bridge, causing the combustion of the passing gas. This idea has, since the date of Trevithick's letter, led to several smoke-burning patents. The boiler fire-tube was oval, 2 feet 9 inches by 1 foot 11 inches. The open-topped cylinder was supplied with a heavy and deep piston serving as a counterweight, and also as a guide in the cylinder for correcting the angle of the connecting rod. Experience had taught him that the cold sides of the condenser were sufficient to work an engine a great many strokes without a supply of injection; and he had already used high-pressure steam of 25 lbs. to the inch above the atmosphere, cut off from the cylinder when the piston had performed one quarter of its course: thus both these things were as first steps leading to the modern expansive steam-engine and surface condensation. The simplicity of the engine is remarkable--a high-pressure, expansive, condensing engine, worked by a single four-way cock, without cylinder-cover, or parallel motion. The low first cost, and non-liability to derangement, were always kept in view; and his confirmed experience in the satisfactory working of horizontal cylinders prior to 1812 illustrates their extended application; for at that time scarcely any other engineer had constructed other than upright cylinder engines. No detail escaped his observant gaze. The fire-bars were to be 2 inches deep, 1 inch thick at the top edge, tapered to 3/4ths of an inch at the bottom, giving the required strength, with free room for air, which in its passage cooled the bar, carrying the heat into the fire. Years before and after that period the fire-bar in common use by thoughtless people was a square iron bar that was always burning and bending. The letter is descriptive of the high-pressure steam-engine in the sixteenth year of its age; and its expansive steam, made practical by Trevithick's high-pressure boilers. This engine only took steam during the first quarter of its stroke, the remaining three-quarters were by the expansion. Had it taken steam only during one-twentieth of its stroke, it would have been more powerful than Boulton and Watt's low-pressure steam vacuum engine of the same size. [Rough draft.] "SIR, "CAMBORNE, _November 8th, 1812_. "I have your favour of the 3rd inst., informing me that Messrs. Fox and Williams have engaged to quarry the stone for e breakwater at Plymouth, but does not say whether you hold any share with them in the contract or not. Therefore I cannot understand from your letter whether you wish to see an engine fitted to the purpose of the breakwater, or for pumping the water from the foundations of the Exeter Bridge. Please to inform me which of the two purposes you wish to see the engine calculated for, and about what time you think you shall want it, and I will get one finished suitable to the purpose you intend it for. "Yours, &c., "R. T. "JAS. GREEN, ESQ., _St. David's Hill, Exeter_. "N.B.--To what extent have Messrs. Fox engaged, and what parts of the work do they perform? I think more good might be done by loading, carrying, and discharging, than by quarrying only." Trevithick was equally ready with the application of steam-power either for pumping of water or for boring and removing rock. The use of chisels and rock-breakers in the Thames in 1803[4] had prepared the way for the more perfect engine for boring, lifting, and carrying rock from the quarries to its destination at the Plymouth Breakwater in 1812.[5] [Footnote 4: See Stonebreaker of 1803, vol. i., p. 239.] [Footnote 5: See Steam-crane, vol. i., pp. 162, 274.] "SIR, "106, HOLBORN HILL, _November 26th, 1812_. "I am in receipt of yours of the 22nd inst. Mr. Giddy informs me that Mr. Fox and Mr. Williams are to have 2_s._ 6_d._ per ton for making the breakwater at Plymouth, and he considers that they can do it for 2_s._, which he thought would give them 50,000_l._ profit. If you meet those gentlemen, I have to caution you not to LEARN THEM anything until you make a bargain, as I know Mr. Williams will endeavour to learn all he can and then you may go whistle. "If 6_d._ per ton will give 50,000_l._ profit, a halfpenny per ton would give upwards of 4000_l._ Would they agree to give you that for your labour only? However, this will depend in a great measure on the time it will take in doing. If it takes eight years it would be 500_l._ a year for you (according to Mr. Giddy's calculation). "Your well-wisher, "HENRY HARVEY. "MR. RD. TREVITHICK, _Camborne_." Mr. Harvey knew Trevithick's weakness in money matters. Rennie had been employed to report on the proposed Plymouth Breakwater, and in 1811 was desired by Lord Melville, the head of the Admiralty, to proceed with the work. "The price paid in 1812 for taking and depositing rubble in the breakwater was 2_s._ 9_d._ per ton; it was afterwards reduced to 1_s._ per ton. A piece of ground was purchased from the Duke of Bedford at Oreston, up the Catwater, containing 25 acres of limestone, well adapted for the purposes of the work; and steps were taken to open out the quarry, to lay down railways to the wharves, to erect cranes."[6] The idea of the plan to be followed in conveying stone with greater economy and dispatch than was contemplated by Rennie, originated with Trevithick, while the former received the credit and the pay, as he before had done with the steam-dredger. [Footnote 6: 'Lives of the Engineers,' by Smiles, vol. ii., p. 260.] [Rough draft.] "MR. FOX Jun., "CAMBORNE, _January 29th, 1813_. "Sir,--Since I was at Roskrow I have been making trial on boring lumps of Plymouth limestone at Hayle Foundry, and find that I can bore holes five times as fast with a borer turned round than by a blow or jumping-down in the usual way, and the edge of the boring bit was scarcely worn or injured by grinding against the stone, as might have been expected. I think the engine that is preparing for this purpose will bore ten holes of 2-1/2 inches in diameter 4 feet deep per hour. Now suppose the engine to stand on the top of the cliff, or on any level surface, and a row of holes bored, 4 feet in from the edge of the cliff, 4 feet deep, and about 12 inches from hole to hole for the width of the piece to be brought down at one time, and wedges driven into the holes to split the rock in the same way as they cleave moorstone, only instead of holes 4 inches deep, which will cleave a moorstone rock 10 feet deep when the holes are 14 or 15 inches apart, the holes in limestone must go as deep as you intend to cleave out each stope, otherwise the rock will cleave in an oblique direction, because detached moorstone rocks have nothing to hold them at the bottom, and split down the whole depth of the rock. In carrying down a large piece of solid ground the bottom will always be fast, therefore unless it is wedged hard at the bottom of the hole the stope cannot be carried down square. In a hole 2-1/2 inches diameter and 4 feet deep put in two pieces of iron, one on each side of the hole, having a rounded back, then put a wedge between the two pieces, which might be made thus, if required to wedge tighter at the bottom of the hole than at the top. [Illustration] "If this plan answers, the whole of the stones would be fit for service, even for building, and would all be nearly of the same size and figure. Each piece would be easily removed from the spot by an engine on a carriage working a crane, which would place them into the ship's hold at once. It would all stand on a plain surface, and might be had in one, two, three, or four tons in a stone, as might best suit the purpose, which would make the work from beginning to end one uniform piece. Steam machinery would accomplish more than nine-tenths of all the work, besides saving the expense of all the powder. I find that limestone will split much easier than moorstone, and I think that a very great saving in expense and time may be made if the plan is adopted. "Please to think of these hints and write me when and where I may see you to consult on the best method of making the tools for this purpose before I set the workmen to make them. Any day will suit me, except Monday, the 8th of February. The sooner the better, as I cannot set to work to make the tools until we have arranged the plan. "I am, Sir, "Your humble servant, "RD. T." The successful completion of the Mont Cenis Tunnel in 1871 was mainly due to an ingenious application of combined mechanical force to boring tools, before limited to man's strength; but the applied principle existed sixty years ago, and though not so perfect in detail, yet more comprehensive. Trevithick's high-pressure steam boring engine enabled him to penetrate the rock five times as fast as the quarryman's power. Ten holes, 2-1/2 inches in diameter, 4 feet deep, could be bored in an hour, and he sagaciously suggested that in quarrying the limestone for the breakwater, a row of holes should be bored by his engine 4 feet in from the face of the rock, 2-1/2 inches in diameter, 4 feet deep, and 12 inches apart; and by dropping into each hole two half-round pieces of iron, to be driven asunder by a steel wedge, large blocks would be forced off without the use of gunpowder. The high-pressure steam-puffer having bored the stone, moved itself toward the broken mass, lifted it into waggons, and again changing its powers from steam-crane to steam-locomotive, conveyed it to the port, and lifted it into the ship's hold. The whole operation was thus aptly described by the inventor, who then counted on contracting for the breakwater work:--"Steam machinery will accomplish more than nine-tenths of all the work, besides saving the expense of all the gunpowder." [Rough draft.] "MR. ROBERT FOX, Jun., "CAMBORNE, _February 4th, 1813_. "Sir,--Since I was with you at Falmouth I have made a trial of boring limestone, and find that the men will bore a hole 1-1/2 inch in diameter 1 inch deep in every minute, with a weight of 500 lbs. on the bit. I had no lump more than 12 inches deep; but to that depth I found that having a flat stem to the bit of the same width as the diameter of the hole, twisted like a screw, completely discharged the powdered limestone from the bottom of the hole without the least inconvenience. "From the time the two men were employed boring a hole 12 inches deep, I am convinced to a certainty that the engine at Hayle will bore as many holes in one day as will be sufficient to split above 100 tons of limestone, and would draw that 100 tons of stone from the spot and put them into the ship's hold in one other day. The engine would burn in two days 15 bushels of coal, four men would be sufficient to attend on the engine, cleave the stone, and put it into the ship's hold. I think it would not amount to above 9_d._ per ton, every expense included, but say 1s., which I am certain it will not amount to. Perhaps it may not be amiss to withhold the method of executing this work until the partners have more fully arranged with me the agreement as to what I was to receive for carrying the plan into execution. I do not wish that anyone but your father should be made acquainted with the plan, and have no doubt he will have sufficient confidence in the scheme to adopt it. I shall be glad to hear from you soon, as I intend to go to Padstow in a few days and shall not return under a fortnight. "Your humble servant, "RD. TREVITHICK. "N.B.--I this day received a letter from Mr. Gould, requesting to know what the expense of an engine and apparatus would be for clearing Falmouth Harbour, which I have sent by the post."[7] [Footnote 7: See letter, 4th February, 1813, vol. i., p. 248.] It had been and still is the custom to bore rock either with a long and heavy jumper-chisel, lifted a foot or two, and falling by its own weight, pounding to powder a portion of the rock, or by the use of a much smaller chisel called a borer, struck by a hammer. Trevithick having made his steam-engine perform those jumper and borer movements, turned his attention to the improvement of the borer, and found that a revolving bit was more suitable for drilling limestone than the borer-chisel. The powdered stone was removed from the hole by giving a screw form to the stem of the bit. Many years afterwards precisely similar bits for boring wood were patented as new things, and are still used. Within five months of his first communication with the contractors for the Plymouth Breakwater he had designed and made an engine to bore, lift, and convey to the ship's hold 50 tons of stone daily at less than half the cost Rennie was then paying for it. [Rough draft.] "SIR, "CAMBORNE, _February 4th, 1813_. "I have your letter of the 31st January requesting to know the time in which the engine will be ready for the bridge at Exeter, and also about giving an additional power to it. "The engine shall be ready in six weeks from the end of January, and shall be capable of lifting the 10-inch bucket you have ordered instead of the 9-inch before proposed, which was to have delivered 500 gallons of water 12 feet high per minute; but now the engine shall be made to lift in the same proportion as a 9-inch is to a 10-inch bucket, which will be 617 gallons of water per minute instead of 500 gallons, as was before agreed on, and I shall charge you accordingly. I observe that you have ordered the pump, and from the description you give of it, I think it will answer very well. If you wish a perpendicular cylinder instead of a horizontal, I can construct it in that way, but it will not be so convenient for a portable engine. I have now engines with horizontal cylinders at work above ten years, and find them answer equally as well as a perpendicular cylinder. "I remain, Sir, "Your very humble servant, "RICHD. TREVITHICK. "JAS. GREEN, Esq., _Exeter_." Engineers nowaday are not in the habit of designing and constructing a steam-engine in six weeks, or willing to alter the agreed form from the horizontal to the vertical without charge. [Rough draft.] "Mr. Robert Fox, jun., informed me the other day that you had the sole direction of the work at Plymouth. Had I known it at the time you were at Scorier I should have communicated to you my ideas relating to the application of machinery there; but until a few days since I had an idea that the young Mr. Fox was about to take an active part in the management, which I now find was never his intention, only he very much wishes to have an experiment tried to see to what extent an engine was capable of performing as against men. An engine is now preparing for that purpose." "SIR, "CAMBORNE, _February 24th, 1813_. "On my return from Padstow this evening, where I have been for the last fortnight, I found your letter of the 11th inst. respecting the getting an apparatus ready for the Plymouth undertaking. Before I set about it I wish to see you and Mr. Fox, and will call any day you may appoint. Waiting your reply, "I remain, Sir, "Your very humble servant, "R. TREVITHICK. "MR. ROBERT FOX, Jun., _Falmouth_" After three months of experimental scheming, without a thought of keeping his inventions secret, Trevithick for a moment became worldly wise, and asked for a written agreement before sending his locomotive boring engine to the breakwater. [Rough draft.] "MR. FOX, "CAMBORNE, _14th March, 1814_. "Sir,--I expect to be called to London immediately after the end of this month. The engine with the boring apparatus for Plymouth remains at Redruth. I very much wish to see you on that business before I leave home, and would be much obliged by your dropping me a note by post, saying what day it would be convenient for me to wait on you. "R. T." The rock-boring machine was completed, and reached the breakwater two months after his interview with the Foxes, who were prominent in the quarrying work. "The engine for Plymouth will be put to break the ground as soon as I can find time to go up there."[8] It was impossible for any one man, single-handed, to make perfect such numerous practical inventions as were undertaken by Trevithick at that time. His letter of a few months before[9] reveals the facility with which he moulded the steam-engine to his requirements. "The ploughing engine that I sent you a drawing for, after being used for that purpose, was to have been sent to Exeter for pumping water. I have been obliged to take the small portable engine from Wheal Alfred Mine, and have a new apparatus fitted to it for Plymouth Breakwater. A small engine which I had at work at a mine I have been obliged to send to the farmers for thrashing." Messrs. Fox would probably require many engines for the Plymouth Breakwater, having engaged with Government to deliver three million tons of stone; and to prevent delay, the boring apparatus was applied to an engine made for another purpose, while drawings for a new and more suitable engine for boring stone were sent to Mr. Rastrick. [Footnote 8: Trevithick's letter, May 20, 1813, chap. xxi.] [Footnote 9: See letter to Mr. Rastrick, January 26, 1813, chap. xviii.] He engaged that an engine should bore holes to split 100 tons of limestone a day; and that on the following day it should, as a locomotive and steam-crane, load that quantity in waggons, convey it from the quarry to the port of shipment, and then by steam-crane place it in the hold of a vessel. The whole of the work to be done by 11 cwt. of coal and four men. The gross cost would be 1_s._ per ton for breaking and removing, though at that time Mr. Rennie was paying 2_s._ 9_d._ a ton, which in after years was reduced to 1_s._, just what Trevithick said was a fair price. While this ready application of the high-pressure steam-engine was going on in England, it had also extended to, and was coining money in the Mint at Lima, where Trevithick contemplated going to look after it, intending to land at Buenos Ayres, and make his way across the continent of South America and the mountains of the Cordilleras as best he could, leaving the home field he had made so fertile to be reaped by others, and the stone-boring locomotive to be forgotten for many years. [Rough draft.] "SIRS, "PENZANCE, _December 9th, 1815_. "Your very great neglect in not writing.... Herland engine will work, I expect, in about fifteen days. It is a plunger of 33 inches diameter, 10-feet stroke, with a double packing around the top of the plunger-pole, in the same way as the steam is turned into the stuffing box of a double engine to exclude the air, only there is a small tube from the bottom of the boiler to the middle of the stuffing box to prevent the escape of steam. "I am sorry to find by Mr. Uville's letter that the Mint engine does not go well. I wish you had put the fire under the boiler and through the tube, as I desired you to do, in the usual way of the long boilers; then you might have made your fire-place as large as you pleased, which would have answered the purpose and worked with wood just as well as with coal. I always told you that the fire-place in the boiler was large enough for coal, but not for wood; also if you found that the cock did not open and shut in proper time, to make the gear to it work the same as the Dolcoath puffer whim-engine instead of the circular gear. The boiler is strong enough and large enough to work this engine with 30 lbs. to the inch, thirty strokes per minute. I hope to leave Cornwall for Lima about the end of this month, and go by way of Buenos Ayres, and cross over the continent of South America, because I cannot get any other passage. None of the South Sea whalers will engage to take me to Lima, as they say they may touch at Lima or they may not. Unless I give them an immense sum they will not engage to drop me there. To be brought back to England after a two years' voyage without seeing Lima would be a very foolish trip. To make a certainty I shall take the first ship for Buenos Ayres, preparations for which I have already made." This unfinished rough draft was intended for one of the men who had gone to Lima, less fruitful in emergency than Trevithick, who, without a moment's hesitation, would have constructed a fire-place outside the boiler, when the internal tube fire-place was found to be too small for a wood fire. Trevithick's proposing sixty years ago to make his way over the almost unknown track from Buenos Ayres, on the Atlantic, to Lima, on the Pacific, was perhaps characteristic of his daring spirit, that turned all things to good account; but he dreamed not that his grandson and namesake would at this time be conducting the steam-horse on the same line of march on the Central Argentine Railway from Rosario to Cordoba, in the Argentine Republic. [Rough draft.] "GENTLEMEN, "CAMBORNE, _August 19th, 1813_. "I received yours at Bridgenorth of the 19th July, ordering a steam-engine for rolling sugar-cane. I immediately set the founders to work on one for you, which is to be ready by my return to Bridgenorth about the end of September. I intend to ship it for Bristol, and will call on you on my journey down to Cornwall, as I intend to set it to work at Bristol for your inspection before it is put on board ship. The price I cannot accurately say at present, as the engine now making is on a new principle; and as it will be more simple in construction, I hope to be able to render it within the price before stated to you. As it is on a new plan I cannot fix the price until I know the cost of making. All I can say at present is that it shall not exceed what I stated to you in my former letter. "I remain, Sirs, "Your humble servant, "RD. TREVITHICK. "MESSRS. PINNEYS AND AMES, _Bristol_." The engine for the sugar plantations in Jamaica, on an improved plan, was to be constructed in the short space of six weeks, and if a saving in cost was effected, the inventor would hand the whole of it to the purchaser. [Rough draft.] "SIR, "PENZANCE, CORNWALL, _March 8th, 1816_. "I received your favour of the 25th January, but did not answer it in due course, because I was then erecting a very large engine, which is the first on a new plan. This engine, which has been at work about a month, performs exceedingly well. The cost of erection and the consumption of coal are not above one-third of a Boulton and Watt's, to perform the same work. An engine of 4-horse power will not require a space of more than 5 feet high, 5 feet long, and 3 feet 6 inches wide. In some instances I employ a balanced wheel 5 feet in diameter. The water required will be a pint and a half per minute. The coal, one quarter of a bushel or 21 lbs. per hour. The price of a machine, finished and set to work, 100 guineas. It does not require either wood or mason work, but stands independent of every fixture, and may be set to work in half an hour after being brought on your premises. "Your obedient servant, "RICHD. TREVITHICK. "DR. MOORE, M.D., _Exeter_." A 4-horse-power portable high-pressure steam-puffer engine cost 105_l._, with internal fire-tube and machinery attached to the boiler, ready for work in half an hour after lighting the fire, consumed 21 lbs. of coal and 11 gallons of water for each hour's work, at a cost of threepence. The reader's attention has been very imperfectly drawn to the numerous subjects touched on in these remnants of Trevithick's correspondence between the years 1804 and 1816; among them may be traced the portable high-pressure steam-engine, the tubular cylindrical boiler of wrought iron, the economy of expansive working with steam of 100 lbs. on the inch, but limiting it to 20 lbs. when not in the charge of experienced workmen, and testing boilers by water pressure to four times the intended working pressure. The economy of heat in smelting furnaces and in the aërated steam-engine were bold means to large results. The cheap 100l. steam-engine of 1812, with open-top cylinder and rigid simplicity of gear, resembling Newcomen's first atmospheric engine, was really a high-pressure steam expansive engine, with the germ of surface condensation, as ready to convey itself from mine to mine or from farm to farm, and to join in performing labourer's work, even to boring and conveying rock by land or sea, as the most perfect of modern engines; and yet this unadorned engine, as seen in the agricultural engine of the following chapter, followed the excellent mechanism of the double-acting Kensington model of 1798, and the still more beautiful engine of the 1802 patent and London locomotive. CHAPTER XVIII. AGRICULTURAL ENGINES. The late Mrs. Trevithick said "that during the difficulties in London in 1808 and 1810, when Trevithick was overwhelming himself with new experiments and the cost of patents, and law expenses, lawyers and bailiffs took everything worth having from her house, including account-books, drawings, papers, and models, which she never saw again." His earlier account-books left in safety in his Cornish home, though very disconnected, give trustworthy traces of his work up to 1803. From that time only detached accounts or papers are found until 1812, when the unused pages in two old mine account-books of his father served as his letter (rough-draft) books; and judging from their number and style, his correspondence was most extensive and varied. [Rough draft.] "HAYLE FOUNDRY, _February 13th, 1812_. "TO SIR CHRISTOPHER HAWKINS, Baronet. "Sir,--I now send you, agreeable to your request, a plan and description of my patent steam-engine, which I lately erected on your farm for working a thrashing mill. The steam-engine is equal in power to four horses, having a cylinder of 9 inches in diameter. The cylinder, with a moderate heat in the boiler, makes thirty strokes in a minute, and as many revolutions of the fly-wheel, to every one of which the drum of the thrashing mill (which is 3 feet in diameter) is turned twelve times. The boiler evaporates 9 gallons of water in an hour, and works six hours without being replenished. The engine requires very little attention--a common labouring man easily regulates it. [Illustration: TREVITHICK'S HIGH-PRESSURE STEAM-PUFFER THRASHING ENGINE, 1812.] "The expense of your engine of 4-horse power, compared with the expense of four horses, is as follows:-- £ _s._ Original cost of the steam-engine 80 0 Building material and rope 10 0 ------ £90 0 ------ Interest on the above 90_l._ at 5 per cent. 4 10 Wear and tear at 5 per cent. 4 10 ------ 9 0 ------ Original cost of horse machinery for four horses £60 0 Interest on the above at 5 per cent. 3 0 ------ Wear and tear at 15 per cent. 9 0 ------ 12 0 "Two bushels or 164 lbs. of coal will do the work of four horses, costing 2_s._ 6_d._ "Four horses at 5_s._ each, gives 20_s._ Cost of coal, 2_s._ 6_d._ as compared with 20_s._ for horses. "I remain, Sir, "Your obedient servant, "RICHARD TREVITHICK." "CORNWALL, _February 20th, 1812_. "Having been requested to witness and report on the effect of steam applied to work a mill for thrashing corn at Trewithen, we hereby certify that a fire was lighted under the boiler of the engine five minutes after eight o'clock, and at twenty-five minutes after nine the thrashing mill began to work, in which time 1 bushel of coal was consumed. That from the time the mill began to work to two minutes after two o'clock, being four hours and three-quarters, 1500 sheaves of barley were thrashed clean, and 1 bushel of coal more was consumed. We think there was sufficient steam remaining in the boiler to have thrashed from 50 to 100 sheaves more barley, and the water in the boiler was by no means exhausted. We had the satisfaction to observe that a common labourer regulated the thrashing mill, and in a moment of time made it go faster, slower, or entirely to cease working. We approve of the steadiness and the velocity with which the machine worked; and in every respect we prefer the power of steam, as here applied, to that of horses. (Signed) "MATTHEW ROBERTS, Lamellyn. "THOMAS NANKIVILL, Golden. "MATTHEW DOBLE, Barthlever." This first high-pressure steam thrashing machine was working on the 13th February, 1812, at Trewithen, the property of Sir Christopher Hawkins, as proved by Trevithick's drawing of the machine, his account of the work performed, and the report of the three wise men that the power of steam was preferable to the power of horses. Its first cost was less than that of a horse machine; but to make the calculated amounts come right Trevithick charged 15 per cent. for wear and tear on the horse machinery, and but 5 per cent. on the steam-engine; overlooking the cost of the horses, which would have made the outlay for the horses and machinery greater than for the steam-engine. The whole design evidences simplicity and consequent cheapness; no complication of valves or valve-gear, no cylinder cover, parallel motion, guide-rods, or air-pump, with its condenser and injection-water. The 4-horse engine, with boiler complete, cost 90_l._ A common labourer worked it, and as it needed no supply of feed-water during six hours of work, the cost and attention of supplying feed were avoided. If a supply was required during the day it could be given by a pipe with two taps. This first use of steam in agriculture was immediately followed by Lord Dedunstanville of Tehidy, Mr. Kendal of Padstow, and Mr. Jasper of Bridgenorth. Sir Charles' request for a more official report signed by disinterested persons brought a reply that the thrashing engine continued to work well. "It far exceeds my expectation. I am now building a portable steam-whim, on the same plan, to go itself from shaft to shaft." "If you should fall in with any West India planter that stands in want of an engine, he may see this at work in a month, which will prove to him the advantage of a portable engine to travel from one plantation to another. The price complete is 105_l._"[10] [Footnote 10: See Trevithick's letter, 10th March, 1812, chap, xx.] "DEAR SIR, "ARGYLE STREET, _19th March, 1812_. "I am sorry it is not convenient for me to advance you the money for Wheal Liberty; adventurers having the dues very low, ought to furnish the needful. I am very glad you have succeeded with your portable steam-engine, and am persuaded they will be more and more adopted. I have shown your account of your thrashing by steam, and Sir John Sinclair and Mr. ---- very highly approve it. Sir John Sinclair wished the communication had been made to the Board of Agriculture. Sir John wished me to transmit you the enclosed on coals moved by steam ... whether you had a plan of this sort, as they would be very serviceable in passing the friths in Scotland. He seems to think you ought to advertise your steam-engines for thrashing; indeed, I think so too. "By the enclosed letter, Sir John Sinclair wishes you to send him an account of your improved steam-engines. You will be careful in drawing up your letter to Sir John, because it will probably be read to the Board of Agriculture, and perhaps inserted in their publication. You will begin by acknowledging his letter, of date ... respecting the American passage boat ... and your improved small steam-engine. You will give him an account of the saving you have effected at Dolcoath, and a certificate of the same by the mining captains; the engine for thrashing you built for me, and the work it did, and the coals it consumed; the expense of the steam-engines, and the uses they may be applied to. "I remain, dear Sir, "Yours most obediently, "C. HAWKINS." In 1812 Trevithick advertised the use and sale of steam-engines, weighing 15 cwt., costing 63_l._, for thrashing, grinding, sawing, or other home work; and also a more powerful engine for the steam-plough, or the harrow and spade machine for 105_l._, to travel from farm to farm. He wrote to Sir John Sinclair:[11]-- "I received from Sir Charles Hawkins a copy of Dr. Logan's letter to you, also a note from you to Sir Charles Hawkins, both respecting the driving boats by steam; respecting the engine for thrashing, chaff-cutting, sawing, &c. I am now making one of about two-thirds the size of Sir Charles Hawkins', which will be portable on wheels. By placing the engine in the farm-yard, and passing the rope from the fly-wheel through the barn-door, or window, and around the drum on the machine axle, it may be driven. [Footnote 11: See Trevithick's letter, 26th March, 1812, chap. xv.] "The steam may be raised, and the engine moved a distance of two miles, and the thrashing machine at work, within one hour. "The weight, including engine, carriage, and wheels, will not exceed 15 cwt.; about the weight of an empty one-horse cart. "The size is 3 feet diameter, and 6 feet high. If you wish to have one of this size sent to the Board of Agriculture as a specimen, the price delivered in London will be sixty guineas." This engine differed from that referred to in the drawing of Sir Charles Hawkins, mainly in the boiler having the fire-place in the fire-tube, requiring no brickwork, and having the advantage of portability. It was very like the earlier locomotive boiler, except that it was placed upright, as steam-cranes now use boilers, instead of being horizontal. [Rough draft.] "CAMBORNE, CORNWALL, _April 26th, 1812_. "TO SIR JOHN SINCLAIR. "I have your favour of the 4th instant, informing me that you had sent my letter respecting propelling ships by steam to the Navy Board; and also requesting a drawing and statement of the thrashing engine to be sent to the President of the Board of Agriculture, which shall be forwarded immediately. "I beg to trouble you with a few wild ideas of mine, which perhaps may some future day benefit the public, but at this time remain buried, for want of encouragement to carry it into execution. "The average consumption of coals in large steam-engines is about 84 lbs. (or one bushel), to lift 10,000 tons of water or earth 1 foot high. "The average cost of this coal in the kingdom is sixpence. The average of a horse's labour for one day is about 4000 tons lifted 1 foot high, costing about 5_s._ "A man's labour for one day is about 500 tons lifted 1 foot high, costing 3_s._ 6_d._ "I have had repeated trials of the water lifted by coals, horses, and men, proving that where a bushel of coal can be purchased for sixpence, that sixpence is equal to 20_s._ of horse labour, and to 3_l._ 10_s._ of men's labour. "If you calculate a man to lift 500 tons 1 foot high, it is equal to 100 tons lifted 5 feet high; a very hard task for a man to perform in a day's work. "This calculation proves the great advantage of elemental power over animal power, which latter I believe can in a great part be dispensed with if properly attended to, especially as we have an inexhaustible quantity of coals. "To prove to you that my ideas are not _mere_ ideas, in general my wild ideas lead to theory, and theory leads to practice, and then follows the result, which sometimes proves of essential service to the public. "About six years ago I turned my thoughts to this subject, and made a travelling steam-engine at my own expense to try the experiment. "I chained four waggons to the engine, each loaded with 2-1/2 tons of iron, besides seventy men riding on the waggons, making altogether about 25 tons, and drew it on the road from Merthyr to the Quaker's-yard (in South Wales), a distance of 9-3/4 miles, at the rate of four miles per hour, without the assistance of either man or beast, and then, without the load, drove the engine on the road sixteen miles per hour. "I thought this experiment would show to the public quite enough to recommend its general use; but though promising to be of so much consequence, has so far remained buried, which discourages me from again trying, at my own expense, for the public, especially when my family call for the whole of my receipts from my mining concerns for their maintenance. "It is my opinion that every part of agriculture might be performed by steam; carrying manure for the land, ploughing, harrowing, sowing, reaping, thrashing, and grinding; and all by the same machine, however large the estate. "Even extensive commons might be tilled and effectually managed by a very few labourers, without the use of cattle. "Two men would be sufficient to manage an engine, capable of performing the work of 100 horses every twenty-four hours; requiring no extensive buildings or preparations for labourers or cattle, and having such immense power in one machine as could perform every part in its proper season, without trusting to labourers. "I think a machine that would be equal to the power of 100 horses would cost about 500_l._ "My labour in invention I would readily give to the public, if by a subscription such a machine could be accomplished and be made useful. "It would double the population of this kingdom, for a great part of man's food now goes to horses, which would then be dispensed with, and so prevent importation of corn, and at a trifling expense make our markets the cheapest in the whole world; because there are scarcely any coals to be found except in England, where the extreme price, duty included, does not exceed 2_s._ per bushel. "I beg your pardon for having troubled you with such a wild idea, and so distant from being carried into execution; but having already made the experiment before stated, which was carried out in the presence of above 10,000 spectators, who will vouch for the facts, I venture to write to you on the subject, for the first and only self-moving machine that ever was made to travel on a road, with 25 tons, at four miles per hour, and completely manageable by only one man, I think ought not to be dropped without further experiments, as the main point is already obtained, which is the power and its management. "Your most obedient servant, "RICHARD TREVITHICK." The Board of Agriculture in 1812 had their attention drawn to the feasibility of using the steam-engine to save agricultural labour and lessen the cost of working land. Trevithick's intuitive knowledge told him his application would be in vain, though an engine was at work proving the saving of horse-power in the item of thrashing corn. "I beg to trouble you with a few wild ideas of mine, which _perhaps may some future day benefit the public_." A steam-engine could exert as much power by the consumption of 6_d._ worth of coal as could be given by 20_s._ of horse-power, or by 70_s._ worth of men's power. "Ideas lead to theory, theory leads to practice, then follows the result, which sometimes proves of essential service to the public." "It is my opinion that every part of agriculture might be performed by steam. Carrying manure for the land, ploughing, harrowing, sowing, reaping, thrashing, and grinding; and all by the same machine, however large the estate." "Two men would manage an engine capable of performing the work of 100 horses." Such a use of the steam-engine, judiciously managed, "would double the population of this kingdom, and make our markets the cheapest in the world; because England is the country best supplied with coal and iron for steam-engines, and the land now growing food for horses would be available for man." Its cost would be 500_l._, and its power sufficient to propel the largest subsoil ploughs and tormentors; and had the Board of Agriculture supplied such a sum of money as is now ordinarily given by a farmer for a steam-plough, we should have had in 1812 ploughing, harrowing, sowing, reaping, &c., by steam. Years before, the same kind of engine had been made to work pumps, wind coal from shafts, drive rolling mills, tilt hammers, and steamboats, and convey material from place to place; and why should not his promise to the farmer be also made good with his increased knowledge derived from eight years of active experience? Receiving small encouragement in England, he applied to sugar-cane planters to give his engines a trial in the West Indies. [Rough draft.] "SIR CHARLES HAWKINS, Bart., "CAMBORNE, _1st May, 1812_. "Sir,--I have your favour of the 27th April, respecting a steam-engine for your friend for the West Indies, of the power of ten mules employed at one time. This power we calculate equal to forty mules every twenty-four hours, as six hours' hard labour is sufficient for one mule for one day. "The expense of an engine of this power complete delivered in London would be 200_l._ The consumption of coals about 84 lbs., or one bushel, to equal the labour of three mules, or from 13 to 14 bushels of coal every twenty-four hours to perform the full work of forty mules (or in proportion for a lesser number), with a waste of about 15 gallons of water per hour, unless a reservoir was made to receive the steam, and then to work the same water over again. "Where water is scarce, nearly the whole may be saved. "You remarked that the rope might slip round the notch in the wheel; but to prevent any risk of that kind, I apply a small chain instead of the rope, which works the same as a chain on the barrel of a common thirty-hour clock. "The speed of the periphery of the fly-wheel is about eight miles per hour, which I think is nearly double the speed of the mules when at work in the mill. This would reduce the size of the part which carries the chain on the cattle mill to half the diameter of the present walk of the cattle, which might be done without altering or interfering with the present cattle mills, and might, if required, either work separately or in conjunction with the mules in the same mill at the same time. "To inform your friend of the power and effect of such an engine, I prefer his sending some person down to Cornwall, to see it tried on some of the cattle mills or whims in the mines. "Engines that have been sent to the West Indies hitherto have cost nearer 2000_l._; very large, heavy, and complicated machines, requiring 2500 gallons of water per hour for condensing, and could only be managed by a professed engineer, while any common labourer can keep in order and work these engines. If you prefer to send a person with it, the cost will be about 40_s._ per week. "I remain, Sir, "Your most obedient servant, "RICHARD TREVITHICK." This letter indirectly points out two long-standing radical errors in engineering phraseology. An early method of describing the value of an engine was by stating the number of pounds it would lift one foot high by the burning a bushel of coal, called the duty of an engine. Trevithick's bushel was 84 lbs., while other engineers, under the same term of bushel, meant various weights, up to 120 lbs. Another form of speaking was the horse-power of an engine; meaning that a horse could lift a certain number of pounds one foot high in a minute, and that a steam-engine lifting ten times as much was a 10-horse engine; but, as Trevithick points out, a horse only works at that rate for six hours out of twenty-four, while the steam-engine works continuously, performing the work of forty horses, yet is called a 10-horse engine. The high-pressure engine suitable for the West Indies was to be adapted to the existing horse or mule machinery, that either power might be used. Its first cost and expense in working to be much less than that of the Watt low-pressure steam vacuum engine. [Rough draft.] "SIR CHARLES HAWKINS, Bart., "CAMBORNE, _June 13th, 1812_. "Sir,--Yours of the 15th of last month I received, enclosing a drawing of a sugar-mill from Mr. Trecothick, which I should have answered per return, but was at that time in treaty for an engine for a sugar-mill with a Mr. Pickwood, who is in St. Kitts in the West Indies. "The engine is now being erected at Hayle Foundry, of the power of twelve mules at a time, or equal to forty-eight mules during twenty-four hours. "The cost is 210_l._ complete, with numerous duplicate parts. "I hope she will be finished and sent off in a short time. "I have now so fully proved the use of those engines, that I have engaged to take this one back if it does not answer their purpose, and to refund the whole sum if they return the engine to me in working order within four years. "This gentleman says, if this engine answers he shall have two more for his own use, and four of his friends are waiting to see the result before ordering their engines. "The mules that will be turned out of use by Mr. Pickwood's engine will sell for five times the sum the engine will cost him, exclusive of the wear of mules, with their keep and drivers, besides the greater dispatch and pleasantness of working a machine instead of forcing animals in so hot a climate. "If your friend wishes an engine of this power and on the same terms, I can get two made and sent to London nearly in the same time as one. Enclosed I send to you a rough sketch of the engine and mill. I am of your opinion, that Sir John Sinclair has taken a useless journey by calling on the Navy Board, for nothing experimental will ever be tried or carried into effect except by individuals. "If I could get an Act of Parliament for twenty-one years for only one-tenth part of the saving which I could gain over animal power and expense, I have no doubt but that I could get money to carry the plan fully into effect for propelling ships, for travelling with weights on roads, and doing almost every kind of agricultural labour. "But a patent is but for fourteen years, and open to constant infringement; for the inventor of general and useful machinery is a target for every mechanic to shoot at, and unless protected or encouraged by some better plan than a common patent, will have the whole kingdom to contend with in law, and most likely receive ruin for his reward, which has too often been the case. "A plan of such magnitude as this promises to be of, I think ought to be carried into effect by subscription, and as soon as accomplished, the subscribers to be repaid, and the invention thrown open for the use of the kingdom at large. I think about 1000_l._ or 1500_l._ would test the designs. "It is expected that Mr. Praed will spend some time in this neighbourhood; I hope I shall be able to prove to you and to him the great use of propelling barges by steam. I have a small engine now at foundry, and would put it on board one of their barges for your inspection. I am very much obliged for your continued favours, and beg pardon for so often troubling you. I have so fully proved the great advantages resulting from those portable engines, that I very much wish the public to have the full use of them. "I remain, Sir, "Your most humble servant, "RICHARD TREVITHICK." A 12-mule-power engine for St. Kitts was being erected at Harvey's foundry at Hayle; Trevithick making himself liable for the whole cost, in case it should not answer the purpose. The mules thrown out of work by the engine would sell for five times as much as the engine cost, to say nothing of the saving in wear and tear of drivers and mules, and the unpleasantness of driving a mule in hot weather as compared with a machine. If an Act of Parliament would give him one-tenth of the saving he could effect during twenty-one years, a company might be formed for carrying into full effect his plans for propelling ships, travelling with weights on roads, and performing almost every kind of agricultural labour, while a patent for fourteen years was open to constant infringement, and the inventor of useful machinery was a target for every mechanic to shoot at, had law suits with the kingdom at large, and ultimate ruin, as a reward for his labours. Inventions of such general application, when fairly established, should be thrown open to the public, Government paying the inventors their expenses, and reasonable reward for their time. [Rough draft.] "MR. PICKWOOD, "CORNWALL, CAMBORNE, _17th June, 1812_. "Sir,--Yours of the 17th April I received about twenty days since, and from that time to the present have been in treaty with Messrs. Plummer, Barham, and Co., for your engine. We have now closed for an engine complete, of the power of twelve mules at a time, with suitable duplicates, chains, &c., for 210_l._ I very much wish for your engine to be set to work by your own workmen, to show the planters the simplicity and easy management of the machine, and also save the expense of an engineer, which will tend to promote their use. The engine will be set to work before it is sent off, and every possible care taken to execute it in the most perfect order. From the experience I have had with common labourers keeping these engines in order, since I wrote to you, I have no doubt you will get on satisfactorily. "I hope to get the engine ready in five or six weeks, but I fear there will be loss of time in shipping it. You may rest assured that I will spare no time or attention to promote the performance of this engine. I am so far satisfied with the probability of its fully answering your purpose that I voluntarily offered Messrs. Plummer, Barham, and Co., that if you return it to me for working repairs within four years, I will refund the whole of the sum I am to receive for it. I will take particular care to mark every part and send you a full description. "Enclosed I send you a sketch of the engine attached to a sugar-mill. Please write to me by return of the packet; it may be in time, before the engine is shipped, to alter, or send you such things as I may not be acquainted with. I shall be glad to know the number of yards your mules travel in an hour when going at what you call a fair speed, in the mill, and also what number of rounds you wish the centre roll to make in an hour when worked by the engine. "I remain, Sir, "Your very humble servant, "RD. TREVITHICK. "R. W. PICKWOOD, Esq., "_St. Kitts, West Indies_." These are not the remarks of an uncertain schemer; every sentence having the impress of the ability and fixed intention of perfecting the work, and the belief that the simplicity of the engine would enable a common labourer to use it. [Rough draft.] "SIR CH. HAWKINS, Bart., "CAMBORNE, _5th July, 1812_. "Sir,--If your friend Mr. Trecothick intends to have a sugar-mill engine immediately finished and sent out with the one I am now making for Mr. Pickwood, he ought not to lose any time in giving his orders. I have made inquiry at Falmouth about sending out Mr. Pickwood's engine for St. Kitts on board a packet, which would save much time, but I fear it cannot be granted unless application is made by some person of note to the Post Office in London. Mr. Banfield of Falmouth told me that if application was made to send out a model as a trial, he had no doubt but it would be granted. "This experiment with the portable engine that will travel from one plantation to another and work without condensing water, is certainly of the greatest consequence to the planters, and as the whole weight will not exceed 1-3/4 ton, I should hope that the Commissioners at the Post Office will grant this request. I am sorry to trouble you so often about my business, but I beg the favour of your goodness to inform me through what channel I ought to make this application. "I remain, Sir, "Your most obedient humble servant, "RD. TREVITHICK." This experiment with the 1-3/4 ton portable engine to travel from one plantation to another, needing no condensing water, was certainly of the greatest consequence to the planters in the West Indies, and should have been of equal importance to the people in England. Judging from the weight and cost, as compared with agricultural engines of the present day, Trevithick was nearer the mark then than we are now; its working without condensing water the engineers of that day believed to be impracticable, a fundamental error which greatly retarded the use of the high-pressure steam-engine. The providing sufficient condensing water was often a most serious item of cost, and as water mains were not in use, a deep well was a necessary part of a steam vacuum engine. [Rough draft.] "GENTLEMEN, "CORNWALL, CAMBORNE, _October 16th, 1812_. "Yours of the 30th of September I found at my house on my return yesterday from a journey. I am sorry to inform you that Mr. Pickwood's engine is not ready. Near three months ago I set my smiths and boiler-makers to work to complete an engine for Mr. Pickwood, which parts were finished five or six weeks ago. The other parts of the engine, which were to have been made of cast iron, were ordered and commenced at a foundry in this county, belonging to Blewett, Harvey, and Vivian, and would have been finished and the engine shipped long since had not these partners in the iron foundry quarrelled with each other, and the Lord Chancellor has laid an injunction and set idle their foundry. I have since ordered the castings to be made at a foundry at Bridgenorth, in Shropshire, belonging to Hazeldine, Rastrick, and Co., who will complete the engine and send it to you in about two months, at which time I intend to be in town to set it to work before it is shipped for the West Indies. "I remain, Gentlemen, "Your very humble servant, "RICHD. TREVITHICK. "MESSRS. PLUMMER, BARHAM, AND CO., "_London_. "P.S.--Immediately on my receiving your order to prepare an engine for Mr. Pickwood I wrote to inform him that I had begun it, and enclosed a drawing of the engine with the method of connecting the engine to the cattle-mills, and requested he would remit to me his remarks on it, which I received by the last packet, from which it appears for the best that the engine is not in a forward state, because the parts would not have been so suitable to the purpose as they will now be." Fortune was against Trevithick. A difficulty between his brother-in-law Harvey, and his old partner Vivian, with Blewett, retarded the completion of the engine; and the castings so anxiously waited for were ordered from Hazeldine and Rastrick. The wrought-iron work was made by the old smiths in his neighbourhood, who had long been in the habit of hammering his schemes into shape. This patchwork way of constructing engines made success much more difficult. Trevithick often laughed heartily at the following incident which occurred during this quarrel at Harvey's works:--Blewett sent a handsome silver teapot to Miss Betsy Harvey, who kept her brother's house, called Foundry House. Trevithick was sitting with them when the box was brought in and opened. Mr. Henry Harvey was indignant at Mr. Blewett sending a bribe or make-peace to his sister, and threw the silver teapot under the fire-place. Trevithick, however, quietly picked it up, pointed out the dinge it had received, wrapped his pocket handkerchief around it, and saying, if it causes bad feeling here it will do for Jane, marched away home with the pot. The writer drank tea from it recently, and also laughed at the dinge. The following was written to Mr. Rastrick in December, 1812:[12]-- "I have been waiting your answer to my last, and especially that part respecting the West India engine, as there is a large field there for engines of this kind. I have received an order for a thrashing engine for Lord de Dunstanville of Tehidy, and as I wish those thrashing engines to be known through the country, I intend to take one of the engines ordered for Padstow and send it to Tehidy; one of the Padstow farmers can wait until you make another for him; therefore I would thank you to send the first finished by ship from Bristol for Portreath or Hayle. Send a drum with everything complete, of which you are a better judge than I; probably about 3 feet in diameter and 3-1/2 feet long will be sufficient. There must be a fly-wheel, with a notch to carry the rope, and also a small notch wheel on the drum-axle. I think 6-1/2 feet diameter for the fly and 9-1/2 inches diameter for the small wheel, will give speed enough to the drum. Mind to cast a lump or screw on a balance of about 1 cwt. on one side of the wheel. There must be two stands on the boiler, and a crank-axle or otherwise a crank-pin in the fly-wheel, whichever you please; with a shaft 3 feet long with a carriage. The engine to stand in a room under the turn-about, 7-1/2 feet high, 7 feet wide, and 17 feet long. The fly-wheel will stand across the narrow way of the room. The rope will go up through the floor and the drum be shifted by a screw, horizontally on the barn floor, so as to tighten the rope. I shall put down the top of the boiler level with the surface, with an arched way to the fire and ash-pit underground to prevent the chance of fire, which the farmers are very much afraid of. [Footnote 12: See rough draft, Trevithick's letter, 7th December, 1812, chap. xvii.] "I send you a sketch showing how it is to stand. I do not bind you to the size of the drum or wheels, only the room that the fly-wheel works in is but 7 feet wide. Put the engine and drum for Lord de Dunstanville out of hand neat and well, as it will be well paid for, and make the stands, &c., in your own way." This description of Lord Dedunstanville's thrashing machine illustrates the drawing of that supplied to Sir Charles Hawkins. [Rough draft.] "MR. RASTRICK, "CAMBORNE, _January 26th, 1813_. "Sir,--I have your favour of the 10th inst., in which you do not state the time when you expect I shall have either of the engines that you are executing. As so much time has elapsed since the orders were given, the persons that ordered them are quite impotent. The ploughing engine that I sent you a drawing for, after being tried for that purpose, was to have been sent to Exeter for pumping water out of the foundations of a new bridge; but as they intend to begin their work at the bridge before the end of March, the engine must be there before that time, or they will erect horse machines and not use the engine. I have therefore been obliged to send the small boiler that I had for that purpose to Hayle Foundry, and get the castings made there for this engine to get it in time to prevent losing the order. I have also been obliged to take the small portable engine from Wheal Alfred Mine and have new apparatus fitted to it, to apply this engine for Plymouth Breakwater. A small engine, from the same patterns as Sir Charles Hawkins' thrashing engine, which I had at work in a mine, I have been obliged to send to one of the farmers at Padstow for thrashing, instead of one of those engines that I ordered from you. I expect that the people who ordered the engine for the West Indies are also tired of waiting. I have two other applications for engines for the West Indies, and the Messrs. Fox will want a great many engines of that size for the Plymouth Breakwater. They are to provide machinery, with every other expense, and I am to have a certain proportion of what I can save over what it now costs them to do it by manual labour. I think I have made a very good bargain, for if the plan succeeds I shall get a great deal of money, and if it fails I shall lose nothing. They have engaged with the Government to deliver 3,000,000 tons, for which they have a very good price, even if it was to be done by men's labour. I hope I shall get the engine soon on the spot, and will then let you know the result. As the boiler that was intended for the ploughing engine is to be sent to Exeter, I wish you to finish that engine with boiler, wheels, and everything complete for ploughing and thrashing, as shown in the drawing, unless you can improve on it. There is no doubt about the wheels turning around as you suppose, for when that engine in Wales travelled on the tramroad, which was very smooth, yet all the power of the engine could not slip around the wheels when the engine was chained to a post for that particular experiment. "That new engine you saw near the seaside with me is now lifting forty millions 1 foot high with 1 bushel of coal, which is very nearly double the duty that is done by any other engine in the county. A few days since I altered a 64-inch cylinder engine at Wheal Alfred to the same plan, and I think she will do equally as much duty. I have a notice to attend a mine meeting to erect a new engine equal in power to a 63-inch cylinder single, which I hope to be able to send to you for. I have also an appointment to meet some gentlemen at Swansea, to erect two engines for them, one to lift water, the other coal, which you will hear more about, I expect, soon. If I can spare a few days when at Swansea, I will call to see you at Bridgenorth. I have not seen Mr. Richard since you left, but will call on him in a few days and do as you request. If you think the fly-wheel is not sufficiently heavy for his engine, add half a ton more to the ring. "If you cannot finish all these engines at the same time, I would rather the smaller ones should be finished first and Mr. Richards' stand a little, because if his engine was now ready he would not pull down his thrashing machine until he had nearly thrashed all his corn, and the machine now stands on the spot where the mill is to be erected. "If I call on you from Swansea I think I shall be able to show you a new idea, which I think will, if carried into practice, be of immense value. Please to write to me and say particularly how you are getting on, and when you are likely to finish the engines ordered. "R. T." Trevithick had sent a drawing of a _ploughing_ engine to Rastrick at Bridgenorth, that the castings might be made, while he himself was having the boiler and wrought-iron work constructed in Cornwall. The engine had been ordered as a portable pumping engine, for removing water from the foundation of a bridge at Exeter; but before sending it to its destination, he had arranged to plough with it, as a means of perfecting the plans and drawings for a more suitable ploughing engine then in construction, to be fitted "with boiler, wheels, and everything complete for ploughing and thrashing, as shown in the drawing." The _friction of the wheels on the ground would be greater than the power of the engine_; therefore they would not slip when the full power was applied to draw a plough any more than the Welsh engine, the wheels of which did not slip though resting on smooth iron. One of his small engines, which had been at work in a mine, was sent as a thrashing engine to Padstow. It is evident that, having given a portion of his attention for a year or two to the question of steam agriculture, he had so far progressed in 1813 as to construct thrashing machines, portable agricultural engines, and steam-ploughs to be moved by wheels as in locomotives; reaping, sowing, and other work, was also in future to be the work of the steam-engine. A drawing by Trevithick--having as usual neither name, date, nor scale, nor writing of any kind, but the watermark in the paper is 1813--illustrates his ideas expressed to Sir Charles Sinclair in 1812:--"It is my opinion that every part of agriculture might be performed by steam." The thrashing and grinding engines were at work, and the tormenting harrowing engine was probably designed for bringing under steam cultivation the extensive commons referred to. In those days, before the practice of underground drainage, the surface of cultivated land was thrown into furrows, or a series of small hills and vales, the latter acting as the surface drain for carrying off the water. Suppose the first step in cultivating a common to be the breaking of the soil, and throwing it into uniform lines of rise and fall that facilitated drainage without inconveniencing the tillage, what better machine could have been devised than Trevithick's? A combination of the modern tormentor and harrow loosened the ground to the required depth, which was then, by a revolving wheel with spades, thrown on one side, resulting in uniform lines of ridges and hollows. The steam-shoveller was removed, or the tormentor irons raised, when only the harrow was required. The absence of the ordinary shafts at the front end of the framing indicates that the spade-tormentor was not to be drawn by horses, but whether by a locomotive or by a fixed engine is not self-evident. [Illustration: TREVITHICK'S STEAM SPADE-TORMENTOR, 1813.] [Rough draft.] "MR. KENDAL, "CAMBORNE, _January 26th, 1813._ "Sir,--I have yours of the 17th inst. The thrashing machine engine is ready for you, and shall be sent up immediately. I wish you to get about 100 fire bricks, 200 common bricks, 20 loads of stone, and 20 bushels of lime. The house will get finished while I am fixing the engine. About 1500 or 1600 weight of iron for your engine has been sent to the Blue Hills Mine, St. Agness. I wish you could send down your cart to fetch it from there to Padstow. There is no part of these castings but may be easily conveyed in a common butt or cart. When you have the stone, brick, and lime ready, and a cart to send to St. Agness for the castings, please to write me, and I will come to Padstow at the same time with them, and finish the engine. The sooner you get ready the better, as I expect to have an engagement in about four weeks' time, that would prevent my coming to Padstow for some time; therefore I wish to get your engine finished before that time. Please to write me as early as possible, and let me know when you will be ready for me, and what day I shall meet your cart at St. Agness for the castings. "Your obedient servant, "RICHARD TREVITHICK." Real inventors hesitate not to erect their own engines, lend a hand in building the house, walk to the scene of action, or take a lift in a cart; and by such steps was the gift of genius moulded to the wants of daily life; while the modern engineer of eminence, living in large cities, knows little of the minutiæ of his work, or even of the working mechanics on whose skill the success of his ideas is dependent. "In 1815, Mr. Kendal, the proctor of Padstow, sent for me to repair his steam-engine. To prevent the old disputes in collecting his corn tithes, he had at work one of Captain Trevithick's steam thrashing machines. The small farmers sent their corn produce to him to be thrashed; the grain was measured, the tenth taken out, the remainder returned to the farmer. The three-way cock, which worked the engine, was joined in its shell; on freeing it the engine continued to work very well."[13] [Footnote 13: Captain Samuel Grote's recollections, 1858.] "In 1818 I put a new four-way cock to a thrashing engine that Captain Trevithick had made for Mr. Kendal, of Padstow, who was the receiver of tithe corn. The boiler was a tube of wrought iron, about 4 feet in diameter and 6 feet long, standing on its end. The cylinder was fixed in the top of the boiler; an upright from the top of the cylinder supported the fly-wheel shaft; a connecting rod from the crank-pin in the fly-wheel was fastened to a joint-pin in the piston. The cylinder had no cover. The four-way cock was worked by an excentric on the shaft, moving a lever, which was kept in contact with the excentric by a spring."[14] [Footnote 14: Recollections of Captain H. A. Artha, Penzance, 1868.] "About 1824 I worked in Binner Downs Mine one of Captain Trevithick's puffer whim-engines. The boiler was cylindrical, made of wrought iron. It stood on its end, with the fire under it, and brick flues around it. The cylinder was let down into the top of the boiler. A four-way cock near the top of the cylinder turned the steam on and off. The fly-wheel and its shaft were fixed just over the cylinder. A lever and rod worked the four-way cock and feed-pole. The waste steam puffed through a launder into the feed-cistern. The cylinder was about 12 inches in diameter, with a 3-feet stroke."[15] [Footnote 15: Recollections of Henry Vivian, Harvey and Co.'s Works, 1869.] Mr. Kendal's steam thrashing machine remained at work at least six years, during which time the only apparent repair was the four-way cock, worked by an excentric, which, if neglected, was apt to stick fast in its shell. One of the puffer-whims erected about this time was similar to the thrashing engine for Padstow, differing from the earlier one made for Sir C. Hawkins, in having a portable boiler so arranged that if necessary it could be easily placed on wheels. [Rough draft.] "SIR, "CAMBORNE, _March 15th, 1813_. "I have your favour of the 11th inst. respecting a steam-engine for thrashing. I have made several, all of which answer the purpose exceedingly well. They are made on a very simple construction so as to be free from repairs, and are kept in order and worked by the farm labourers, who never before saw a steam-engine. The first I made on this plan was for Sir Christopher Hawkins, who resides at this time in Argyll Street, Oxford Street, London. If you call on him, he, I doubt not, would give you every information you require respecting its performance. This was a fixed engine, because it was only required to work on one farm. It has been at work nearly eighteen months, and has not cost anything in repairs, nor any assistance but from the labourer who puts in the corn; he only gives three or four minutes every hour to put on a little coal. A few pails of water, put into the furnace in the morning, is sufficient for a day's work. They have at different times tried what duty the engine would perform with a given quantity of coal, and found that two Cornish bushels, weighing 168 lbs., would get up steam and thrash 1500 sheaves of wheat in about six hours. "Before this engine was erected, they usually thrashed 500 sheaves, with three heavy cart-horses for a day's work. I cannot say exactly the measurement of the corn that it thrashed, but it was considerably above 60 winchesters of wheat with 168 lbs. of coal; not a halfpenny in coal for each winchester of wheat. "The engines that I have since erected have performed the same duty. "The horse machinery is thrown out of use, but the same drum is turned by the engine. "A fixed engine of this power I would deliver to you in London for 100 guineas; it would cost you about 15_l._ more to fix the furnace in brickwork. "A portable engine costs 160 guineas, but it would cost nothing in erecting, as it will be sent with chimney and every thing complete on its own wheels (the drum, &c., excepted), which you may convey with one horse from farm to farm as easy as a common cart. "If you have not sufficient work for it you can lend it to your neighbours. The last engine I erected was about three weeks since, for a farmer that kept four horses and two drivers. The parts of the horse machine thrown out of use, together with the four horses, sold for more money than he gave me for the engine, exclusive of 4_l._ per week that it cost him in horse keep and drivers to thrash 3000 sheaves per week. "Now the engine performs more than double that work, and does not cost above 10_s._ per week; and the labourer in the barn does double the work he did before for the same money. If you wish the same engine to have sufficient power to turn one pair of mill-stones, the cost will be 220 guineas. "R. TREVITHICK. "MR. J. RAWLINGS, _Strood, Kent_." "CAMBORNE, _28th August, 1813._ "MESSRS. HAZELDINE, RASTRICK, AND CO., "Gentlemen,--Lord Dedunstanville's engine thrashed yesterday 1500 sheaves in 90 minutes with 40 lbs. of coal. "RD. TREVITHICK." The first steam thrashing engine was worked by a labouring man for eighteen months, without needing repair, or even attention beyond three or four minutes each hour to put on a little coal. Necessary stoppages for various purposes caused a day's work to be no more than the engine could perform in half a day. No additional feed-water was required during an ordinary day's work to thrash 1500 sheaves of wheat with 168 lbs. of coal, while on a special occasion that quantity was thrashed in an hour and a half, consuming only 40 lbs. of coal. Three horses during three days were required to do the same amount of work. A farmer sold his horses used in thrashing for more money than his engine cost, which did twice as much work at a reduced expenditure, and also saved the feed of the horses. Such an engine could be delivered in London for 100 guineas, while a portable engine on wheels with a differently constructed boiler, requiring no mason work, would cost 160 guineas. [Rough draft.] "GENTLEMEN, "CORNWALL, CAMBORNE, _19th August, 1813_. "I have your favour of the 9th August, respecting steam-engines for St. Kitts. I fear it will not be possible to get an engine ready by the 1st of November. "As you say the gentleman that is about to take them out is a clever man, and likely to promote the use of them, I will make immediate inquiry, and, if possible, will get one ready, of which I will inform you in a short time. "I very much wish that every person who intends to employ a steam-engine of mine would first examine the engine, and be satisfied with the construction before giving an order, for which reason I must request you to send your friend down to Messrs. Hazeldine and Rastrick's foundry, Bridgenorth, Shropshire, where he may see the portable steam-engine that was made for Mr. Pickwood, which the founders will set to work for his inspection in half an hour after his arrival. As this gentleman has a taste for machines, and wishes to make himself fully acquainted with the principle and use of the steam-engine, he will be much gratified with the sight of this curious machine and with the information he will receive from the founders, which will be essentially necessary to him before leaving England. "I am extremely disappointed that this engine was not forwarded to Mr. Pickwood, as I find from his letter that he has an exceedingly clever and active mind, and is a very fit person to take the management of introducing a machine into a new country. "This engine is engaged by a Spanish gentleman, who is going to take out nine of my engines with him to Lima, in South America, in about six weeks. "I remain, your obedient servant, "RICHD. TREVITHICK. "MESSRS. PLUMMER, BARHAM, AND CO., "_London_. "N.B.--If your friend goes to Bridgenorth, let him show this letter to the founders." The engine, intended for the West Indies, so pleased Mr. Uville, that he begged to have it made over to him for South America, where it worked the machinery for rolling gold and silver in the Mint at Lima. "About 1815, while erecting a high-pressure pole-engine at Legassack for Mr. Trevithick, and doing some repairs to Mr. Kendal's thrashing engine, a Creole, I think called Nash, brought a note from Captain Trevithick, stating that the bearer was anxious to be taught to erect and work the portable engines for Jamaica. "Sir Rose Price, who had property in the West Indies, had sent him to Mr. Trevithick for that purpose."[16] [Footnote 16: Recollections of Captain H. A. Artha, Penzance, 1869.] It is therefore probable that some of Trevithick's engines reached Jamaica. Sir Rose Price was well known to Lord Dedunstanville and Sir Charles Hawkins, and living near them, saw the engines at work and their fitness for his property in Jamaica. Lord Dedunstanville's engine of 1812 was sold as old iron to Messrs. Harvey and Co. not long before 1843. Having remained for some time on the old-scrap heap, it was in that year again worked to drive machinery. Instead of the original rope-driver on the fly-wheel, a chain was used, the links of which caught on projecting pins on the driving wheel. In that form it continued to work until 1853, before which it was frequently seen by the writer prior to its removal to make room for a more powerful engine. What greater proof could be given of the fitness of design of this early engine, than its long life of forty years under such rough treatment, and the facility with which it was applied to different uses. Mr. Bickle, who, from recollection, had made a sketch of this engine before the writer had found Trevithick's sketch, says that after the engine had ceased to work, the boiler was turned to account in heating tar in the ship-builder's yard. "In 1854 I saw working in a shed at Carnsew, in the ship-*building yard of Harvey and Co., of Hayle, an engine working a stamps for pounding up the slag and furnace bottoms from the brass-casting foundry. "I was then the foreman hammerman in Harvey and Co.'s smiths' shop and hammer-mill, and frequently noticed this old engine and inquired about it. It had been brought from Lord Dedunstanville's, at Tehidy Park, where it at one time worked a thrashing machine. The boiler was of wrought iron, built in brickwork, and looked like a big kitchen-boiler. A flattish cover was bolted on to the top of the boiler, and the cylinder was let down into this top. "The cylinder had no cover; it was about 8 or 10 inches in diameter and 2 or 3 feet stroke. The piston was a very deep one, with a joint for the connecting rod which went direct to the crank, which was supported on two upright stands from the cover on the boiler. The fly-wheel had a balance-weight for the down-stroke. A pitch-chain for driving passed over the wheel, which had pins in it, or projections, to catch into the square links of the driving chain; it was worked by a four-way cock."[17] [Footnote 17: Recollections of Banfield, foreman with Harvey and Co., Penzance, 1869.] "About 1843, when we were building iron boats for the Rhine, the old engine was put to work to drive the tools or machinery in the yard. She was very useful to us and worked very well. She worked about ten years, and was then thrown out to make room for a new and larger engine for our saw-mills. The chain-wheel for driving was made here, it did not belong to it originally."[18] [Footnote 18: Recollections of Mr. Warren, master ship-builder, Harvey and Co., 1869.] "My father (then the foreman boiler-maker) about twenty-four years ago took the old engine from the scrap heap, where it had been for many years, and set it to work in the tool shop. My father said it had come from Tehidy as old iron."[19] [Footnote 19: Recollections of Mr. Burral, jun., master boiler-maker, Harvey and Co., 1869.] The use of the high-pressure steam agricultural engine was not confined to Cornwall. Mr. H. Pape, still carrying on business in Hazeldine and Rastrick's old engine manufactory at Bridgenorth, says:-- "My father worked as a smith under Mr. Rastrick. Mr. Hazeldine had the foundry when Trevithick's engines were made, and have heard my father speak of them. I have seen three of them at work in Bridgenorth; one of them at Mr. Jasper's flour-mill, it drove four stones, and continued in work up to 1837; one at Sing's tan-yard worked up to 1840; and one was on Mr. Jasper's farm at Stapleford for doing farm work. Mr. Smith, now on the farm, worked it up to about 1858. "The engines that worked in Bridgenorth had cast-iron cylinders for the outer casing of the boiler, one cylinder for small engines, three or four cylinders bolted together for the larger ones. The fire-tube was wrought iron, the chimney stood up by the fire-door. The cylinder was let down into the boiler; it worked with a four-way cock. There was a piston-rod, cross-*head, two guide-rods on the top of the cylinder, and two side rods to the crank and pin in 'the fly-wheel.'"[20] [Footnote 20: Recollections of Mr. William H. Pape, Bridgenorth, 13th June, 1869.] "My first husband had to do with the foundry; his father, Mr. Hazeldine, was a partner with Mr. Davies and Co. in 1816. In 1817 the partnership was broken up, and the foundry carried on by Hazeldine. I used to have two or three drawers full of drawings and account-books that were brought from the works. I kept them for many years, but now the greater part of them have gone to light the fire; all the drawings are gone."[21] [Footnote 21: Recollections of Mrs. Marm, Bridgenorth, 12th June, 1869.] The engines described by Mr. Pape are of the type made by Trevithick, in Wales, about 1804, having a fire-place in the boiler, and similar in form to the Welsh locomotive. The drawings which served to light the fires certainly included Trevithick's plans for the steam-locomotive, ploughing engine, the screw-propeller, and many others of equal interest. "DEAR SIR, "STABLEFORD, _March 26th, 1870_. "My grandfather's name was John Jasper, Esq., of Stableford; he must have been one, if not the first, user of a steam-engine for thrashing, winnowing, and shaking the straw all at one operation; it may have been erected eighty years ago, for an old servant of the family just now dead, aged ninety, worked when a boy in the steam-mill at Bridgenorth erected by my grandfather about the same time. "The thrashing engine was a side-lever engine, worked with a three side-way cock and tappet, a cylinder about 8-1/4 inches in diameter, and a 3 feet 4 inch stroke, cast-iron crank-shaft, cross-head, and guides. The boiler was placed underneath the engine, the fire under it, with brick flues. The boiler was about 9 feet long and 4 feet diameter. "The old side rods made of wood are still here, and so was the engine until about twelve years ago. I sent the cylinder, &c., to Coalbrookdale. "I am, Sir, "Yours truly, "THOMAS SMITH." The Stableford agricultural engine was probably made in 1804. The cylinder, of 8-1/4 inches in diameter, is precisely the size of that in the Welsh locomotive, but the stroke was reduced from 4 feet 6 inches to 3 feet 4 inches, being very nearly the same as the Newcastle locomotive. The cross-head, side rods, and boiler were very similar to the Welsh stationary engines of that date. This engine remained in use more than fifty years. The engines specially referred to in this chapter fully prove, from their length of service, the practical character of Trevithick's inventions, and of his having persevered with his high-pressure portables until their usefulness as locomotives and as agricultural helps had been established; but the ploughing, though fully designed, and probably put into practice, was not followed up to the same approach to perfection, or the record of its progress has been lost. Since the foregoing was written, the following has been received:-- "DEAR SIR, "TREWITHEN, PROBUS, _May 17th, 1872_. "The engine you refer to is still occasionally used here; when first erected there was a large quantity of corn thrashed by it, but of late years it has not been much used except for chaffing, bruising, &c. "I remain, dear Sir, "Yours truly, "WM. TRETHNOY. "F. TREVITHICK, Esq." Trevithick's Trewithen engine, which sixty years ago was more manageable than horses going momentarily faster or slower at the will of a common labourer,[22] remains in use unchanged. [Footnote 22: See vol. ii., p. 38.] His preparations for South America, and application of high steam in the large Cornish pumping engines, interfered with the perfecting the smaller agricultural work. CHAPTER XIX. POLE STEAM-ENGINE. When in the autumn of 1810 Trevithick returned to Cornwall, the experience of ten busy years had established the practicability and usefulness of the high-pressure engine. The principles of the invention were now to be applied on engines of the largest size. In 1811, the late Captain S. Grose, a young pupil of Trevithick's, was employed to erect at Wheal Prosper Mine, in Gwythian, the first high-pressure steam pole condensing engine. It was placed immediately over the shaft and pump-rods, requiring no engine-beam. The air-pump, feed-pump, and plug-rod were worked from the balance-bob. The pole was 16 inches in diameter, with a stroke of 8 feet. The boilers were two wrought-iron tubes, 3 feet in diameter and 40 feet long. The fire was external. Shortly after Captain H. A. Artha erected several of those pole-engines for Trevithick. The drawing shows the simplicity of parts of this highly expansive steam-engine, beginning the up-stroke with steam of 100 lbs. to the inch above the atmospheric pressure, expanding it during the stroke down to a pressure of 10 lbs., and then condensing to form a vacuum for the down-stroke. It cost 750 guineas. The drawings of this expansive pole condensing engine are from the dimensions given by Captain Grose who erected it, and by Captain Artha who knew it well. [Illustration: WHEAL PROSPER HIGH-PRESSURE EXPANSIVE STEAM-CONDENSING POLE-ENGINE, 1811. _a_, cast-iron pole, 16 inches diameter, 8-feet stroke; _b_, pole-case, a small bit larger in internal diameter than the pole; _c_, cross-head, fixed on top of pole; _d_, guides for cross-head; _e_, side rods connecting the two cross-heads[**typo beads corrected]; _f_, bottom cross-head; _g_, pump-rod; _h_, balance-beam, with box for weights; _i_, connecting rods from balance-beam to bottom cross-head; _k_, guides for air-pump cross-head; _l_, cross-head and side rods for working air-pump; _m_, air-pump, condenser, and water-cistern; _n_, feed-pump worked from air-pump cross-head; _o_, plug-rod worked from balance-beam; _p_, exhaust-valve; _q_, steam-valve; _r_, exhaust-pipe; _s_, steam-pipe; _t_, bracket for carrying working gear; _u_, expansive steam-horn and tappets; _v_, handles for working valves.] [Illustration: TREVITHICK'S CYLINDRICAL BOILER FOR WHEAL PROSPER ENGINE, 1811. Detail of Boilers:--_a_, two wrought-iron boilers, 3 feet in diameter, 40 feet long, using steam of 100 lbs. on the square inch above the atmosphere; _b_, cast-iron manhole door and safety-valve; _c_, ash-pit; _d_, fire-place; _e_, flues, the fire going first the whole length under the bottom of the boiler, then back again over the top, and into the chimney; _f_, brickwork; _g_, ashes or other convenient non-*conductor of heat; the fire-place ends of the boilers were 15 inches lower than the opposite ends, increasing the safety, with less liability to prime, and greater surface for superheating.] "When a boy I was placed as an apprentice or learner with Captain Trevithick, before he left Cornwall for London. On his return to Cornwall, about 1810, he employed me to erect his first high-pressure expansive pole pumping engine at a mine in Gwythian. "The pole was 16 inches in diameter; the stroke was very long, but I do not exactly recollect the length. It had a condenser and air-pump. There were two boilers made of wrought iron, 8 feet in diameter and 40 feet long. The fire was placed under them at one end, and flues went round them. A feed-pump forced water into the boilers; each had a safety-valve with a lever and weight. The steam in the boiler was 100 lbs. to the square inch. The pole was raised by the admission of the strong steam under its bottom. The steam-valve was closed at an early part of the stroke, and the steam allowed to expand; at the end of the stroke it was reduced to 20 lbs. or less, when the exhaust-valve allowed the steam to pass to the condenser, and the pole made its down-stroke in vacuum. A balance-bob regulated the movement of the engine. "Trevithick's character in those days was, that he always began some new thing before he had finished the old."[23] [Footnote 23: Captain Samuel Grose's recollections. 1858. Gwinear.] Captain Artha, one of his assistants, said:-- "I erected several of Captain Trevithick's pole-engines. My brother Richard worked the one at Wheal Prosper when first erected. The pole made an 8-feet stroke. The case was fixed over the engine-shaft on two beams of timber from wall to wall. A cross-head was bolted to the top of the pole, and from it two side rods descended to a cross-piece under the pole-case, from which the pump-rod went into the shaft. A connecting rod worked a balance-beam, which worked the air-pump, feed-pump, and plug-rod for moving the valves. The steam, of a very high pressure, worked expansively."[24] [Footnote 24: Captain H. A. Artha's recollections. Penzance, 1869.] The first admission of the high-pressure steam under the pole was equal to a force of 8 or 9 tons, causing it and its attached pump-rods to take a rapid upward spring. Having travelled 1 or 2 feet of its stroke of 8 feet, the further supply of steam from the boiler was cut off, and its expansion, together with the momentum of the mass of pump-rods, completed the upward stroke. The pressure of the steam in the pole-case at the finish of the up-stroke would be reduced to say 10 or 20 lbs. to the inch, according to the amount of work on the engine. The steam then passed to the condenser and air-pump, and the engine made its down-stroke by the vacuum under the pole, and by the weight of the descending pole and pump-rods. Each boiler was a wrought-iron tube 3 feet in diameter and 40 feet long, the fire-place under one end, with brick flues carrying the heated air under the whole length of the bottom of the boiler, and back again over the top or steam portion for superheating. [Rough draft.] "CAMBORNE, _28th February, 1813_. "I will engage to erect a puffer steam-engine, everything complete at the surface, on the Cost-all-lost Mine, capable of lifting an 8-inch bucket, 4-1/2-feet stroke, twenty-four strokes per minute, 30 fathoms deep, or 280 gallons of water per minute from that same depth, being a duty equal thereto, for 550 guineas. But if a condensing engine, 600 guineas. If of the same size as Wheal Prosper, 750 guineas. "RICHARD TREVITHICK." The engines, erected in 1811 or 1812, combined the novelty of the steam pole-engine, with the use of high-pressure steam of 100 lbs. on the square inch, and the comparatively untried principle of steam expansion, carried to what in the present day is thought an extreme and unmanageable limit. The Wheal Prosper engine fixed near the sea-shore at Gwythian is referred to in Trevithick's note to Mr. Rastrick,[25] as "that new engine you saw near the sea-side, with me, is now lifting forty millions, 1 foot high, with 1 bushel of coal" (84 lbs.), "which is very nearly double the duty that is done by any other engine in the county." [Footnote 25: See Trevithick's letter, January 26th, 1813, chap, xviii.] This was probably the first application of high-pressure steam to give motion to pump-rods. The engine, as compared with the neighbouring Watt low-pressure steam vacuum pumping engines, was small, but the principles of high steam, expansive working, and vacuum, were combined successfully to an extent scarcely ventured on by modern engineers. Trevithick's high-pressure condensing whim-engines had been for some years at work in Cornwall, but mine adventurers had not dared to risk the application of high-pressure steam to the large pumping engines, fearing its great power would prove unmanageable, and its rapid movement cause breakage of the pump-rods and valves. Two distinct inventions or improvements, each of which was actually followed up in different mines, show themselves in this engine: one being the form of boiler to give with economy and safety high-pressure expansive steam for large engines; the other, the application of a pole in lieu of a piston, as a more simple engine for working with strong expansive steam, and more easily constructed by inexperienced mechanics, who had none of the slide lathes or planing machines so much used by engine builders of the present day. "About 1814 Captain Trevithick erected a large high-pressure steam-puffer pumping engine at the Herland Mine. The pole was about 30 inches in diameter, and 10 or 12 feet stroke. There was a cross-head on the top of the pole, and side rods to a cross-head under the pole-case. The side rods worked in guides. The pole-case was fixed to strong beams immediately over the pump-shaft. The steam was turned on and off by a four-way cock. The pressure was 150 lbs. to the inch above the atmosphere. The boilers were of wrought iron, cylindrical, about 5 feet 6 inches in diameter and 40 feet long, with an internal tube 3 ft. in diameter. The fire-place was in the tube. The return draught passed through external brick flues.[26] [Footnote 26: Recollections of the late Captain Charles Thomas, manager of Dolcoath Mine.] "When a young man, living on a farm at Gurlyn, I was sent to Gwinear to bring home six or seven bullocks. Herland Mine was not much out of my way, so I drove the bullocks across Herland Common toward the engine-house. Just as the bullocks came near the engine-house the engine was put to work. The steam roared like thunder through an underground pipe about 50 feet long, and then went off like a gun every stroke of the engine. The bullocks galloped off--some one way and some another. I went into the engine-house. The engine was a great pole about 3 feet in diameter and 12 feet long. A cast-iron cross-head was bolted to the top of the pole. It had side rods and guides. A piece of iron sticking out from the cross-head carried the plug-rod for working the gear-handles. The top of the pole worked in a stuffing box. A large balance-beam was attached to the pump-rods, near the bottom cross-head. "There were two or three of Captain Trevithick's boilers with a tube through them, the fire in the tube. They seemed to be placed in a pit in the ground. The brick flues and top of the bricks were covered with ashes just level with the ground. A great cloud of steam came from the covering of ashes. "I should think the pressure was more than 100 lbs. to the inch. People used to say that she forked the mine better than two of Boulton and Watt's 80-inch cylinder engines. We could hear the puffer blowing at Gurlyn, five or six miles from the Herland Mine. "In 1813 I carried rivets to make Captain Trevithick's boilers in the Mellinear Mine; they were 5 feet in diameter and 30 or 40 feet long, with an internal fire-tube. It took four or five months to build them. In the present day (1869) a fortnight would build them. The largest boiler-plates obtainable were 3 feet by 1 foot. We had to hammer them into the proper curve. The rivet-holes were not opposite one another. A light hammer was held against the rivet-head in riveting, in place of the present heavy one, so the rivet used to slip about, and the plates were never hammered home so as to make a tight joint."[27] [Footnote 27: Recollections of Mr. James Banfield, Penzance, 1871.] Lest the reader should doubt the comparative power of the Watt low-pressure vacuum and Trevithick's high-pressure steam-engines, a short but sufficiently close calculation shows that taking Stuart's[28] estimate of the effective power of the Watt engine at 8-1/2 lbs. on each square inch of the piston, and Trevithick's engine at anything approaching to 150 lbs. on each square inch, it becomes evident that the latter would be ten or twenty times more powerful than the former. A few figures will put the question in more practical form. [Footnote 28: See Stuart's 'History of the Steam-Engine.'] The Wheal Prosper 16-inch pole high-pressure expansive steam vacuum engine commenced its up-stroke with steam of 100 lbs. on the inch, acting on the 122 square inches of the pole, which steam at the finish of the stroke was reduced by expansion to 10 lbs., giving, say, an average steam pressure of 55 lbs. The down-stroke was caused by a vacuum under the pole of 14 lbs. on the inch, reduced by, say, one-third loss in working the air-pump to 9 lbs., giving from the compound stroke a force of 64 lbs. on each square inch, which, multiplied by the area of the pole, gives a net force of 7808 lbs. The Herland 33-inch pole high-pressure expansive steam puffer-engine commenced its up-stroke with steam of 150 lbs. on the inch, acting on the 855 square inches of the pole, which steam at the finish of the stroke--we will suppose--was reduced by expansion to 75 lbs., giving an average steam pressure of, say, 112. As this puffer-engine used no vacuum, the down-stroke gave no increase of power; its compound stroke was therefore a force of 112 lbs. on each square inch, which, multiplied by the area of the pole, gives a net force of 95,760 lbs. To compare the Trevithick high-pressure steam pumping engine, with the Watt low-pressure steam pumping engine, take one of the largest of the latter, made about that time, say, with an 80-inch cylinder, which commenced its down-stroke with steam of, say, 3 lbs. on the inch, acting on the 5000 square inches of the piston, which steam at the finish of the stroke--the writer is describing the usage at that time, for Watt himself advocated a less steam pressure--was reduced by expansion to, say, 1 lb., giving an average steam pressure of, say, 2 lbs. on the top of the piston, whose under side was in vacuum equal to 14 lbs. on the inch, reduced by, say, one-third loss in working the air-pump to 9 lbs., which power, from vacuum added to the 2 lbs. from steam, gives a net force of 11 lbs. on each square inch of the piston. As the Watt pumping engine moved in equilibrium during its up-stroke, it thereby gained no increase of power; its compound stroke was therefore a force of 11 lbs. on each square inch, which, multiplied by the area of the piston, gives a net force of 55,000 lbs. The practical comparison therefore stands,--Trevithick's 16-inch pole high-pressure steam, and vacuum, on each inch 64 lbs., net force 7808 lbs.; Trevithick's 33-inch pole high-pressure steam, without vacuum, on each inch 112 lbs., net force 95,760 lbs.; Watt's 80-inch piston, low-pressure steam, and vacuum, on each inch 11 lbs., net force 55,000 lbs. As the first cost was mainly dependent on the size, the Trevithick engine was commercially much more valuable than the Watt engine. "I saw Captain Trevithick's puffer working at the Herland Mine. The steam used to blow off like blue fire--it was so strong. The lever on the safety-valve was about 3 feet long, with a great weight on it, more than a hundredweight. The engine did not answer very well, for the packing in the pole stuffing box used to burn out, and a cloud of steam escaped. The greatest difficulty was in the leaking of the boilers. You could hardly go near them. Before that time we always put rope-yarn between the lap of the boiler-plates to make the seams tight. Captain Dick's high-pressure steam burnt it all out. He said, 'Now you shall never make another boiler for me with rope-yarn.' Everybody said it was impossible to make a tight boiler without it. We put barrowfuls of horse-dung and bran in Captain Dick's boilers to stop the leaks."[29] [Footnote 29: Henry Clark of Redruth, in 1869, aged eighty-three years.] This difficulty of making a tight and safe boiler, that puzzled Watt, was moonshine to Trevithick. When the strained boiler and flinching rivets allowed the boiler-house to become full of dense steam, Trevithick told them to cover it up with ashes, they would not see it quite so much then, and it would keep the heat in the boiler. Bran or horse-dung inside was a good thing as a stop-gap, though it added not to the strength of the boiler. Trevithick was himself in a cloud of steam in the engine-house; yet, with such surroundings, he turned on and off his gunpowder steam, from his cannon of a pole-case, of 40 tons force, sending his bolt-shot pole, 33 inches in diameter, its destined course of ten feet, and back again, as though it were a shuttlecock, several times in a minute. Having by one or two years of experience proved the value of his new pole-engine, he applied for a patent on the 13th June, 1815,[30] of which the following is the portion referring particularly to the pole-engine:-- [Footnote 30: See full copy of patent, chap. xvi.] "Instead of a piston working in the main cylinder of the steam-engine, I do use a plunger-pole similar to those employed in pumps for lifting water, and I do make the said plunger-pole nearly of the same diameter as the working cylinder, having only space enough between the pole and the cylinder to prevent friction, or, in case the steam is admitted near the stuffing box, I leave sufficient room for the steam to pass to the bottom of the cylinder, and I do make at the upper end of the cylinder for the plunger-pole to pass through a stuffing box of much greater depth than usual, into which stuffing box I do introduce enough of the usual packing to fill it one-third high. Upon this packing I place a ring of metal, occupying about another third part of the depth of the stuffing box, this ring having a circular groove at the inside, and a hole or holes through it communicating with the outside, and with a hole through the side of the stuffing box; or, instead of one ring containing a groove, I sometimes place two thinner rings, kept asunder by a number of pillars to about the distance of one-third of the depth of the stuffing box, and I pack the remaining space above the ring or rings, and secure the whole down in the usual manner. The intention of this arrangement is to produce the effect of two stuffing boxes, allowing a space between the two stuffings for water to pass freely in from the boiler or forcing pump through a pipe and through the hole in the side of the stuffing box, so as to surround the plunger-pole and form the ring of water for the purpose of preventing the escape of steam by keeping up an equilibrium between the water above the lower stuffing and the steam in the cylinder. By this part of my said invention I obviate the necessity of that tight packing which is requisite when steam of a high pressure is used, and consequently I avoid a greater proportion of the usual friction, because a very moderate degree of tightness in the packing is quite sufficient to prevent the passage of any injurious quantity of so dense a fluid as water. And I do further declare that I use the plunger-pole, working in a cylinder and through a double stuffing, either with or without a condenser, according to the nature of the work which the steam-engine is to perform." Though Trevithick has been spoken of as a visionary, intractable schemer, observation shows that he adhered with tenacity to original ideas, proved to be good. The plunger-pole pump, the water-pressure engine, the Camborne locomotive, the pole steam-engine, were all built on the same groundwork originally started with, of greatest simplicity of form, and absence of many pieces; and it may be observed that he never applied for a patent until the value of the idea had been proved by experiment. In practice the difficulty of keeping the pole-packing in order was one of the objections to the plan; for it either leaked, or, if packed tight, caused much friction and wearing away of the middle of the pole faster than the ends, from the greater speed at the middle of the stroke. The steam-ring was therefore of importance in the engine, in those days of inaccurate workmanship; like the water cup on the gland of the plunger-pump packing, it prevented external air from injuring the vacuum. "MR. GIDDY, "CAMBORNE, _July 8th, 1815_. "Sir,--About a fortnight since I received letters from Lima, and also letters to the friends of the men who sailed with the engines. They arrived on the 29th January, after a very good passage, and without one hour's sickness. Both their and my agreements were immediately ratified, and they are in high spirits. The ship finished discharging on the 11th February, which was the day those letters sailed from Lima with $12,000 for me, which has all arrived safe. "I shall make another fit-out for them immediately. I expect that all the engines will be at work before the end of October; half of them must be at work before this time. The next day, after their letters sailed for Europe, they intended to go back to the mines. Woolf's engine is stopped at Herland, and I have orders to proceed. A great part of the work is finished for them, and will be at work within two months from the time I began. I only engage that the engine shall be equal to a B. and Watt's 72-inch single, but it will be equal to a double 72-inch cylinder. It is a cast-iron plunger-pole, over the shaft, of 33 inches diameter, 10-feet stroke. The boiler is two tubes, 45 feet long each, 3 feet diameter, 1/2 an inch thick, of wrought iron, side by side, nearly horizontal, only 15 inches higher at the steam end of the tubes, to allow the free passage of steam to the steam-pipe. There are two 4-inch valves, one the steam-valve, the other the discharging valve. I have made the plunger-case and steam-vessel of wrought iron 3/4 of an inch thick. The steam-vessel is 48 inches in diameter. The plunger stands on beams over the shaft, with the top of it at the level of the surface, with a short T-piece above the plunger-pole, and a side rod on each side, that comes up between the two plunger-beams in the shaft; this does away with the use of an engine-beam, and the plungers do away with the use of a balance-beam. [Illustration: POLE-ENGINE.] "The fire is under the two tubes, and goes under them for 45 feet, and then returns again over them, and then up the chimney. Those tubes need no boiler-house, because they are arched over with brick, which keeps them from the weather, and scarcely any engine-house is needed, only just to cover the engineman. "Suppose a 72-inch cylinder (having 4000 inches), at 10 lbs. to the inch, an 8-feet stroke, working nine strokes per minute (which is more strokes of that length than she will make when loaded to 10 lbs. to the inch). Inches. 4000 in a 72-inch cylinder, single. 10 lbs. to the inch. ------- 40000 8 feet stroke. ------- 320000 9 strokes per minute. ------- 2880000 lbs. lifted one foot high per minute. ------- "Suppose a 33-inch plunger-pole, 10-feet stroke, ten strokes per minute (which is not so fast by three or four strokes per minute as this engine will go, because she will have no heavy beam to return, neither will she have to wait for condensing, like B. and Watt's, which, when loaded, hangs very long on the injection). 855 square inches in a 33-inch plunger-pole. 10 strokes per minute. ------- 8550 10 feet stroke. ------- 85500 34 lbs. to the inch, real duty. ------- 342000 256500 ------- 2907000 lbs. lifted one foot high per minute. ------- "I should judge that less than 50 lbs. to the inch above the atmosphere would be quite enough to do the work of a 72-inch cylinder single, which is but a trifle for those wrought-iron tubes to stand. This engine, everything new, house included, ready for work, will not exceed 700_l._ Two months are sufficient for erecting it. The engine of Woolf's, at Wheal Vor, which is but two-thirds the power of a 72-inch cylinder, single power, cost 8000_l._, and was two years erecting. I would be much obliged to you for your opinion on this business. "I remain, Sir, "Your very humble servant, "Richard Trevithick. "I am sorry to say that the mines in general are very poor." He shows that with steam of 34 lbs. to the inch, his Herland pole puffer steam-engine of 33 inches in diameter would be equal in power to the Watt low-pressure steam vacuum engine, with a 72-inch cylinder. Herland, like Dolcoath and Wheal Treasury, was the chosen battle-ground of rival engineers; fifty years after Newcomen had there erected his famously large 70-inch cylinder engine, Watt surpassed it in size by a cylinder 2 inches more in diameter, and, after personally superintending its erection in 1798, declared that "it could not be improved on." Mr. Davey, the mine manager, considered that it did twenty millions of duty, though Mr. Watt had made it twenty-seven millions with a bushel of coal.[31] This difference is probably explained by the then Cornish bushel weighing 84 lbs., while Watt generally calculated a bushel at 112 lbs. [Footnote 31: Lean's 'Historical Statement of the Steam-Engine,' p. 7.] Trevithick declining to believe Watt's prognostication, a public test of Watt's engines in the county was demanded; Mr. Davies Gilbert, with Mr. Jenkin, were requested to report on their duty, and gave it in 1798 as averaging seventeen millions.[32] During the same year the adventurers in Herland Mine engaged Trevithick and Bull, jun., to erect a 60-inch cylinder Bull engine to compete with Watt's 72-inch cylinder. The result of this fight is not traceable, nor what took place there during the succeeding fifteen years; when in 1814 Woolf erected in Cornwall his double-cylinder engine to compete with Watt's engine, and Trevithick attacked them both with his Herland high-pressure pole puffer in 1815, when he erected at his own risk and cost a 33-inch pole-engine, engaging that it should, both in power and economical duty, equal the Watt 72-inch engine. The boilers were similar in form to those used a year before in Wheal Prosper high-pressure steam vacuum pole-engine, being two wrought-iron tubes, each 45 feet long and 3 feet in diameter, made of plates half an inch thick. The fire was in external flues. The engine was fixed directly over the pump-rods in the shaft, using neither main beam nor air-pump. [Footnote 32: Lean's 'Historical Statement of the Steam-Engine,' p. 7.] Trevithick's rough hand-sketch shows the steam-ring in the stuffing box and the steam-vessel; the particular use of the latter he has not described: probably it was because Cornish pumping engines, not having the controlling crank to limit the movement of the piston, are obliged to trust to the very admirable, but little understood, steam-cushion, without which the ascending piston would inevitably strike and break the cylinder-cover, while in the pole puffer-engine this danger was during the descent of the pole, and therefore the discharge-steam valve was closed, while the steam in the pole-case was still of ten or more pounds to the inch, so that by the time the pole reached the finish of its down-stroke, it had compressed this steam-cushion, filling also the steam-vessel, with a pressure approaching to that in the boiler, and equal to the weight of the pole and pump-rods. A comparatively small supply of steam from the boiler into the steam-vessel brought it up to the boiler pressure, sending the pole and pump-rods upwards with a spring. The steam-valve then closed, allowing the momentum of the great weight of pump-rods, together with the expanding steam, to complete the up-stroke. The discharge-valve was then opened for a moment, allowing a blast of steam to escape, reducing the pressure say to one-half. The weight of the rods caused their downward movement, raising the load of water in the plunger-pole pumps, and at the same time compressing the steam from the pole-case into the steam-vessel, equal at the finish of the stroke to the support of the pole and pump-rods. This most simple steam-engine combined in the greatest degree the two elements of expansion and momentum. The up-stroke began with a much higher pressure of steam than was necessary to raise the load; having given momentum to the rods, the supply of steam was cut off, and the stroke was completed by expansion. The down-stroke began with a comparatively low pressure of steam under the pole. The unsupported pump-rods fell downwards, setting in upward motion the column of water in the plunger-pole pumps. The discharge-valve was closed long before the completion of the down-stroke, and the momentum of the moving mass of rods and water compressed the steam driven from the pole-case into the steam-vessel up to a pressure equal to the support of the pole and pump-rods. The pole was, therefore, continually floating or rising and falling in steam of ever-varying pressure. Trevithick' s figures show the working power of the 33-inch pole as much greater than Watt's 72-inch cylinder engine, even when the steam pressure in the former was much reduced, and that Woolf's double-cylinder engine, of less power, cost ten times as much as the pole-engine. This sum probably included the costly buildings required for the beam-engines, which Trevithick's plan dispensed with. The reader may judge of the perfection of mechanism in this plain-looking engine from the fact that a pole, with 150 lbs. of steam to the inch in the boiler, was equal to 50 or 60 tons weight, thrown up and down its 10-feet stroke ten or fourteen times a minute, with a limit of movement perfectly under control, while modern engineers are building ships' turrets because of the difficulty of raising and depressing a 30-ton gun from the hold to above the water level. [Rough draft.] "SIR, "CAMBORNE, _September 12th, 1815_. "I received a letter dated the 20th of August, from Mr. Davies, in which he did not mention the name of Herland castings. On the 24th of the same month I wrote to you, informing you of the same, and requesting to know what state of forwardness the castings were in. On the 30th of August I received another letter from Mr. Davies, not saying what state of forwardness the castings were in, nor when they would be finished, only that they would set their hands about them, and that I might expect a letter from you stating the particulars, which has not yet come to hand. I have waited so long that I am quite out of patience. You will know that it is now nearly double the time that the castings were to have been finished in, and you have not yet answered my letters as to the state of the castings nor when they will be finished. I must again request you to write to me on this subject, otherwise I must immediately remove the orders to some other founders that may be a little more attentive to their customers. I must be informed in the positive, whether the castings will be at Bristol by the next spring-tide, as a vessel is engaged for the purpose of taking them to Cornwall. "Yours, &c., "R. T. "MR. JOHN RASTRICK, "_Chepstow, South Wales_." Rastrick, whom he had known at the Thames Driftway, had become the managing engineer at the Bridgenorth Foundry. [Rough draft.] "MR. GEORGE COWIE, "CAMBORNE, _September 29th, 1815_. "I received your favour of the 20th, and on the 23rd called on Mr. Wm. Sims, your engineer, who went with me to Beeralstone Mine the same day. We arranged on the spot what was necessary for the engine. I hope it will be at work in good time, before the winter's floods set in. Nothing can prevent it, unless the castings are detained by contrary winds. The boilers are nearly finished in Cornwall. The castings at Bridgenorth are in a forward state. I intend leaving this evening for Bridgenorth, to ship the castings, both for Herland and Beeralstone. It was the wish of the agents on the mine that these castings might be sent to Swansea, and taken from thence to the mine with a freight of coal. I shall, if possible, get the Herland castings in the same ship. The workmen making your boilers want an advance of cash to enable them to finish. They provide both iron and labour, for which they are to receive 42_l._ per ton for the boiler when finished; the weight will be about 8 tons. You may send this money to Mr. Sims or to me, or otherwise you may direct it to Mr. N. Holman, boiler-maker, Pool, near Truro. 100_l._ will satisfy them for the present. I hope to be in London this day week, and will call at your office. "Yours, &c., "R. TREVITHICK." The pole-engine was not only used in several mines shortly after its first introduction, but Mr. Sims, the leading engineer of the eastern mines, not generally favourable to Trevithick, advocated its application in the traditional Watt district. Scarcely had he smoothed the way with one opponent than another sprung up in an unexpected quarter. His brother-in-law, Harvey, with his once friend, Andrew Vivian, then a partner with Harvey, opposed his plans at the Herland. They were annoyed at Trevithick's sending his orders for castings and machinery to Bridgenorth, and may have had doubts of the success of the new inventions. They had authority in the mine, probably as shareholders, a position generally acquired in Cornwall by those who supply necessary mine material, as well as by the smelters who buy the mineral from the mines. The Williamses and Foxes, controlling the eastern district of mines, were also shareholders and managers, supplying machinery and buying the mine produce. [Rough draft.] "SIR, "PENZANCE, _13th December, 1815_. "Yesterday I was at Herland, where I was informed that Captain Andrew Vivian had been the day before, on his return from Mr. Harvey's, and discharged all the men on the mine, without giving them a moment's notice. Before the arrival of the castings the pitmen, sumpmen, carpenters, and smiths were very busy getting the pit-work ready; at which time H. Harvey and A. Vivian were exulting in reporting that the iron ore was not yet raised that was to make the Herland castings. The day that they heard of their arrival they discharged all the labourers, and ordered the agents not to admit another sixpence-worth of materials on the adventurers' account, or employ any person whatever. "The agents sent a short time since to Perran Foundry[33] for the iron saddles and brasses belonging to the balance-bob, the property of the adventurers; but they refused to make them, with a great deal of ill-natured language about my engine. [Footnote 33: Belonging to Williams and Co.] "I am determined to fulfil my engagement with the adventurers, and yesterday ordered all the smiths, carpenters, pitmen, and sumpmen to prepare the adventurers' pit-work, and ordered the agents to get the balance-bob and every other thing that may be wanted at my expense, so as to fork the first lift, which I hope to have dry by Monday three weeks. The engine will be in the mine this week, and in one fortnight after I hope the engine will be at work, and in less than a week more the first twenty fathoms under the adit will be dry. "In consequence of the Perran people refusing to send the saddles and brasses for the balance-bob, we will make shift in the best way we can without them. The brasses I have ordered on my own account at Mr. Scantlebury's. The coals for the smiths I have also ordered, and the same for the engine to fork the first lift. This is very uncivil treatment in return for inventing and bringing to the public, at my own risk and expense, what I believe the country could not exist without. I am determined to erect the engine at all events and upset this coalition before I leave Europe, if it detains me one year to accomplish it. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK. "MR. PHILLIP, "_George Yard, Lombard Street_. "P.S.--I should be glad to hear from you what is going forward respecting an arrangement of the shares." [Rough draft.] "GENTLEMEN, "PENZANCE, _23rd December, 1815_. "I have received the Herland castings, and am very seriously sorry to say, after we had fixed together the castings on the mine and made the joints, on attempting to put the plunger-pole into the case it would not go down; neither would either of the rings go to their places into the cylinder and on to the pole; therefore the whole engine must be again taken to pieces and sent to a turning and boring mill to be newly turned and bored. How to get this done I cannot tell, for the founders here will not do it because they had not the casting them. Already great expenses have been incurred by delays, and now to send them back to Bridgenorth at an immense loss of time and money will be a very serious business indeed. I think that either the cylinder is bored crooked or the plunger-pole turned crooked, or both, as it will sink farther down into the cylinder on turning it round on one side than it will on the other. The whole job is most shamefully fitted up, and was never tried together before sent off. Write to me by return of post and say what I am to do in this dilemma. "Yours, &c., "RICHARD TREVITHICK. "HAZELDINE, RASTRICK, AND CO., "_Bridgenorth_." The new engine-work from Bridgenorth on arrival was found to be so inaccurately made that the pole would not go into the pole-case. Henry Phillips,[34] who saw the engine make its first start, says:-- [Footnote 34: Still working in Harvey's foundry at Hayle, 1869.] "I was a boy working in the mine, and several of us peeped in at the door to see what was doing. Captain Dick was in a great way, the engine would not start; after a bit Captain Dick threw himself down upon the floor of the engine-house, and there he lay upon his back; then up he jumped, and snatched a sledge-hammer out of the hands of a man who was driving in a wedge, and lashed it home in a minute. There never was a man could use a sledge like Captain Dick; he was as strong as a bull. Then, he picked up a spanner and unscrewed something, and off she went. Captain Vivian was near me, looking in at the doorway; Captain Dick saw him, and shaking his fist, said: 'If you come in here I'll throw you down the shaft.' I suppose Captain Vivian had something to do with making the boilers, and Captain Dick was angry because they leaked clouds of steam. You could hardly see, or hear anybody speak in the engine-house, it was so full of steam and noise; we could hear the steam-puffer roaring at St. Erth, more than three miles off." By the end of January, 1816, the engine was ready for work, and after ten days of experience, he thus described the result:-- "MR. DAVIES GIDDY, M.P., "PENZANCE, _11th February, 1816_. Sir,--I was unwilling to write you until I had made a little trial of the Herland engine. It has been at work about ten days, and works exceedingly well; everyone who has seen it is satisfied that it is the best engine ever erected. It goes more smoothly than any engine I ever saw, and is very easy and regular in its stroke. It's a 33-inch cylinder, 10-1/2-feet stroke. We have driven it eighteen strokes per minute. In the middle, or about two-thirds of the stroke, it moved about 8 feet per second, with a matter in motion of 24 tons; and that weight returned thirty-six times in a minute, with 2 bushels of coal per hour. This of itself, without the friction, or load of water, is far more duty than ever was done before by an engine. I found that it required about 80 lbs. to the inch to work the engine the first twelve hours, going one-third expansive, twelve strokes per minute, 10-1/2-feet stroke, with 24 bushels of coal. The load of water was about 30,000. This was occasioned by the extreme friction, the plunger-pole being turned, and the plunger-case bored, to fit so nicely from end to end, that it was with great difficulty we could at all force the plunger-pole down to the bottom of the plunger-case. This is now in a great degree removed, and since we went to work we have thrown into the balance-box 4 tons of balance, and it would carry 3 tons more at this time. We must have carried that load in friction against the engine, therefore, if you calculate this, you will find it did an immense duty, going twelve strokes per minute, 10-1/2-feet stroke, with 2 bushels of coal per hour. The engine is now working regularly twelve strokes per minute, with 60 lbs. of steam, 10-1/2-feet stroke, three-quarters of the stroke expansive, and ends with the steam rather under atmosphere strong, with considerably within 2 bushels of coal per hour. I would drive her faster, but as the lift is hanging in the capstan rope under water, they are not willing to risk it. I have raised the steam to 120 lbs. to the inch, the joints and everything perfectly tight. I took the packing out of the stuffing box and examined it, and found that the heat had not at all injured it; the packing is perfectly tight, not a particle of steam is lost. "I have offered to deposit 1000_l._ to 500_l._ as a bet against Woolf's best engine, and give him twenty millions, but that party refuses to accept the challenge. I have no doubt but that by the time she is in fork she will do 100 millions, which is the general opinion here. The boilers are certainly the best ever invented, as well as the other parts. The draught is the best you ever saw; I have only one-quarter part of the fire-bars uncovered, yet from one-quarter part of the fire-place that I first made, I find plenty of steam. The greatest part of the waste steam is condensed in heating the water to fill the boiler; what escapes is a mere nothing. The engine will be loaded, when in fork, about 52 lbs. to the inch. Now suppose I raise the steam so high at the first part of the stroke as to go so expansive as to leave the steam, at the finish, only atmosphere strong, shall I, in that case, use any more coal than at present? The materials and joints will stand far more than that pressure; 500 lbs. to the inch would not injure them. When the engine gets on two lifts, I will write to you again, and in the meantime please to give me your thoughts on the engine. Every engine that was erecting is stopped, and the whole county thinks of no other engine. "Your very obedient servant, "RD. TREVITHICK." The new pole puffer-engine worked so satisfactorily and its movements were so manageable that the length of the stroke was increased by the spare 6 inches, which had been allowed as a margin in case of its overrunning its intended stroke. It would bear being worked at eighteen strokes a minute, while the Watt 72-inch engine did not exceed nine strokes a minute; with steam in the boiler of 80 lbs. to the inch it performed its work when the steam supply was cut off at two-thirds of the stroke, completing it by expansion. It also worked well with steam of 120 lbs. to the inch; but the want of strength in the pump-rods and the requirements of the mine caused the regular working pressure of steam to be reduced to 60 lbs. on the inch, and to be cut off when the pole had moved through the first quarter of its stroke. The excellent draught causing the fire-bars to be reduced to one-quarter of their original surface, and the heating the feed-water by the waste steam in this powerful pumping engine, indicate the use of the blast-pipe as at that time worked in the Welsh puddling-mill engine. Watt's engine was for a moment forgotten, that he might challenge Woolf to a trial, giving him as a help twenty millions, or the understood duty of the Watt engine. This non-condensing pole-engine, with 20 tons of pump-rods, moved at a maximum speed of 8 feet a second, and was equal to its work with a steam pressure of 52 lbs. on the inch. Trevithick contemplated extending the expansive principle even further than he had done in the Wheal Prosper pole condensing engine, so that at the finish of the up-stroke the steam should only be about the pressure of the atmosphere, or say from 1 to 10 lbs. on the inch, having commenced it with steam of from 100 to 200 lbs. on the inch, and cutting off the supply from the boiler when the pole had gone but a very small part of its upward stroke, more or less as the mine requirements admitted of it. The principle of expansive working and momentum of moving parts was of necessity modified in its application to pump-work. "DEAR TREVITHICK, "EASTBOURNE, _February 15th, 1816_. "I have been called here by the decease of my wife's uncle, and consequently your letters of the 11th did not reach me till this day. "The account you give me of your new engine has been extremely gratifying. The duty performed by the engine in giving a velocity of 8 feet in a second, thirty-six different times in a minute, to 24 tons of matter, by the consumption of 2 bushels of coal in an hour, is indeed very great, amounting to about fifty-seven and three-quarter millions. So that when you obtain a proper burden, and the extraordinary friction arising from the too close fitting of the plunger-pole and case is reduced, there seems to be no doubt of your engine performing wonders. "I am of opinion that the stronger steam is used, the more advantageous it will be found. To what degree it should be applied expansively must be determined by experience in different cases. It will depend on the rate at which the engine requires to be worked, and on the quantity of matter put into motion, so that as large a portion as possible of the inertia given in the beginning of the stroke may be taken out of it at the end. "Some recent experiments made in France prove, as I am told, for I have not seen them, that very little heat is consumed in raising the temperature of steam. And if this is true, of course there must be a great saving of fuel by using steam of several atmospheres' strength, and working expansive through a large portion of the cylinder. I have really been impatient for a week past to receive some account of your machine, having learned nothing about it, except from a paragraph dated Hayle in the Truro paper of last Saturday week, and somehow or other the next paper has not reached me, "I hope to be in London about Tuesday next, but at all events direct to me there, as my letters are regularly forwarded. "Believe me, dear Sir, "Yours ever most faithfully, "DAVIES GIDDY." [Rough draft,] "MR. JOHN ADAMS, "BROMSGROVE, _8th March, 1816_. "Sir,--I received your favour of the 12th February, but did not answer it in due course, because I was then erecting an engine on the new plan, which is now at work, and performs exceedingly well. It is equal in power to a 72-inch diameter cylinder, double power of B. and Watt's. The expense of erection, and the consumption of coals in this engine, are not one-third of a B. and Watt's to perform the same work. I am the same Trevithick that invented the high-pressure engine. I have sent out nine steam-engines to the gold and silver mines of Peru. I intend to sail for that place in about a month or six weeks, but shall appoint agents in England to erect these engines. "No publication or description whatever has been in circulation, neither is it required, for I have a great many more orders than I can execute. "I have not seen anything of Mr. Losh's patent engine, or Mr. Collins'. "If you should go to London I advise you to call on Mr. Jas. Smith, Limekiln Lane, Greenwich, who is an agent for me, and will soon be able to show you an engine on this plan at work. "I remain, &c., "R. TREVITHICK." Unless the foregoing letters are based on error, the only conclusion to be drawn is that Watt, on the expiry of his patent right and of twenty-eight years of labour, having erected his masterpiece in Cornwall, was within a few years so beaten that Trevithick, in his challenge to Woolf, offered to throw in the Watt engine as a make-*weight, and with such odds to bet him two to one that his comparatively small and cheap high-pressure engine should beat the two big ones, both in power, in first cost, and in economical working. The Watt engine was one of his largest, with a 72-inch cylinder. Its power was equal to Trevithick's 33-inch pole-engine, when worked with steam of 34 lbs. to the inch; but the latter also worked with three times that pressure of steam, whereby its power was increased threefold. The first cost of these engines was probably in inverse proportion to their power. Trevithick's cost 700_l._, while three times that sum would not pay for the Watt engine. The reported duty of Watt's Herland engine was twenty-seven millions; and if the trial was with his ordinary bushel of 112 lbs. of coal, the duty would only be equal to twenty millions with 84 lbs. of coal, which constituted the Cornish bushel. Trevithick's pole high-pressure steam-engine did fifty-seven millions; in other words, performed the same work as the Watt engine with less than half of the daily coal. This large economy led to orders for many engines, on his promise that they should cost much less than those of Watt of equal power, and should perform the work with one-third of the coal. Some believed him, though others were stony-hearted, and as obstinate as donkeys. [Rough draft.] "MR. PHILLIP, "PENZANCE, _8th March, 1816_. "Sir,--I long since expected to have heard from you that my agreement with the Herland adventurers was executed. I have in every respect fulfilled my part of the engagement with the adventurers, and expect that they will do the same with me. The engine continues to work well. Every person that has seen it, except Joseph Price, A. Vivian, Woolf, and a few other such like beasts, agrees that it is by far the best engine ever erected. Its performance tells its effects, in spite of all false reports. "Joseph Price and A. Vivian reported that the engine was good for nothing, that it would not do four millions, and that at the next Tuesday meeting they would turn it idle. On the evening before the meeting they met at Camborne for that purpose. "Captain A. Vivian did not attend the meeting. I could not help at the meeting threatening to horsewhip J. Price for the falsehoods that he with the others had reported. "I hear that he is to go to London to meet the London committee on Monday. I hope the committee will consider J. Price's report as from a disappointed man. It is reported that he has bought very largely in Woolf's patent, which now is not worth a farthing, besides losing the making my castings, which galls him very sorely. "The water sinks regularly 20 fathoms per month, including every stoppage. On Monday next I expect they will be putting down the second lift. The water rises about 8 inches per hour when the engine is idle, and when at work will sink it again at the same rate, showing that the engine is equal to double the growing stream. When drawing from the pool the sinking is not much above 4 inches per hour, which shows that the water drains from a great distance from the country. The engine is going fourteen strokes per minute, 10-feet stroke, 14-1/2-inch box. When Herland worked last they drew a 14-inch box, 7-feet stroke, twelve strokes per minute in winter, and seven strokes per minute in summer. Therefore it appears that the winter water is about from seven to eight strokes per minute, and the summer water from four to five strokes per minute for this engine. "The engine has forked faster the last week than she did before. I think that the great quantity of water that was laying round the mine at the surface is nearly drawn down, and that as we get down to a closer ground the drainage will not be so much. If we have dry weather the water will, at the next shallow level, fall off two strokes per minute before the next lift is in fork. If it continues the same we can continue to sink 20 fathoms per month, exclusive of the time it will take to fix the lifts. As we get down the house of water will lessen considerably. The expense of the engine is about 100l. per month. The sumpmen and others attending on the forking the water, about 100_l._ per month more. They have all the materials on the mine for the pit-work, therefore a very trifling sum will bring the water down to the 60-fathom level, when the mine will pay her own expense. "I will thank you for an account of the meeting. "Your obedient servant, "R. TREVITHICK." Mr. Phillip was the financial managing shareholder--more particularly with the Londoners--at that resuscitation of Herland Mine; and though the new engine was comparatively cheap, both in its first cost and in its consumption of coal, and satisfactorily reduced the water in the mine, payment for it was withheld because the currents of self-interest were against Trevithick. Mr. Joseph Price was the manager of a steam-engine manufactory at Neath Abbey, in South Wales, and had been in the habit of supplying castings for Cornish mines. Arthur Woolf was then striving to bring into use his patent double-cylinder engine, and patent high-pressure steam-boiler, which Trevithick looked on as copies from Hornblower and himself. This, added to Woolf's sarcastic manner of speech, roused Trevithick's anger. Putting aside the words of the disputants, the fact is stated that the pole-engine, with a reduced steam pressure, worked a pump 14-1/2 inches in diameter, 10-feet stroke, fourteen strokes per minute; while the largest and best engine by Watt in Cornwall, placed on the same mine, with a 72-inch steam-cylinder, gave motion to a pump of 14 inches in diameter, 7-feet stroke, at twelve strokes a minute; being in round numbers just one-half the amount of the work performed by Trevithick's comparatively small engine, which had not a single feature of the Watt engine in it. [Rough draft.] "CAPTAIN JOE ODGERS, "PENZANCE, _March 7, 1816_. "Sir,--I have your favour of the 27th February, and requested Mr. Page to send to you a sketch of the agreement. On seeing him yesterday, I found that he had neglected to send it to you. He will leave the country for London in a few days, and intends to call on you at Dolley's as soon as he arrives. I do not know that the agreement matters much for a few days up or down. The terms are well understood between us, which is that the adventurers and I equally share the advantages that may arise from this new engine over Boulton and Watt's. When you have fully arranged with your adventurers about the engine, please to write me, and I will immediately proceed to order the engine; and in the interim the agreement will be drawn up by Mr. Page, and executed either here or in London, just as may suit. "I remain, &c., "R. TREVITHICK. "P.S.--Herland engine goes on better and better. Your adventurers will get a satisfactory account by applying in town to Mr. Wm. Phillip, No. 2, George Yard, Lombard Street. He is the principal of the London adventurers." Trevithick believed that mine adventurers would agree to pay him one-half the saving caused by his engines, as compared with the cost of fuel in the Watt engine. The duty performed by the latter was understood and agreed to generally; persons were chosen by the adventurers to experiment and report on the duty of Trevithick's pole-engine, that the amount of payment might be ascertained in proportion to the saving effected. "MR. GIDDY, "PENZANCE, _April 2, 1816_. "Sir,--I have long wished to write to you about the Herland engine, but first wished to see the engine loaded with a second lift, and a trial made of the duty. Yesterday was fixed on, before ordering another engine for the eastern shaft. "The persons attended. The arbitrators gave the duty as forty-eight millions, and said they had no doubt the engine would perform above sixty millions before getting to the bottom of the mine. "They were much within the duty, but I did not contend with them, as they said it was quite duty enough. "The engine worked 9-1/4 strokes per minute, with 2 bushels of coal per hour for the whole time, 10-feet stroke. There were two pump-lifts of 14-1/2-inch bucket, making 43 fathoms, and 26 fathoms of 6-inch for house-water. "The steam was from 100 to 120 lbs. to the inch. The valve open while the plunger-pole ascended 20 inches, then went the remainder of the 10-feet stroke expansive. "It went exceedingly smooth and regular. Some time since, by way of trying the power of the engine, we disengaged the balance-bob. The engine worked twenty strokes per minute, with 17 tons of rods, &c., and drew 14-1/2-inch bucket 23-1/2 fathoms, and a 6-inch bucket 26 fathoms, 10-feet stroke, twenty strokes per minute. "This was about 45,000 lbs. weight, with the speed of 200 feet per minute, which makes the duty performed more than the power of three 72-inch cylinders, single, of Boulton and Watt, say of 8-feet stroke, 10 lbs. to the inch, nine strokes per minute, which is more than these engines will perform. I have all the orders for every engine now required in the country, which is not to be wondered at, for one-tenth part of the expense in the erection will do, and the duty is not less than three times as much as other engines. This will be proved before we get to the bottom. "The engine now works at about two-fifths of the load which she will have when at the bottom. When the next lift is in fork I will write to you again. "I am, Sir, your humble servant, "RICHARD TREVITHICK." Independent examiners reported that the Herland pole-engine did forty-eight millions of duty, under various pressures of steam, up to 120 lbs. to the inch, working five-sixths of the stroke expansively, with a speed of twenty strokes a minute, or double the speed of the Watt engine; and the importance of those facts deserves the scrutiny and close study of youthful engineers. A small cheap engine, of 33-inch cylinder, similar in general construction to the Wheal Prosper pole-engine, but still more simple from the absence of air-pump and condenser, did as much work as three of Watt's largest engines with cylinders of 72 inches in diameter. This great stride in the useful value of the steam-engine was forced on the public by Trevithick's single-handed energy, when every man was against him, even Henry Harvey, his brother-in-law and friend, his former partner, Andrew Vivian, and his once carpenter and assistant, Arthur Woolf. As a closing attempt to finally crush him, he was made personally responsible for the payment of an engine erected for the benefit of others. This was the great trial test of the power and economy of the purely high-pressure expansive steam-engine as compared with the Watt low-pressure vacuum engine applied to large pumps. "SIR, "HAYLE FOUNDRY, _18th April, 1816_. "I was at Herland to-day. Captain Grose received a letter while I was there, signed by Captain William Davey and Joseph Vivian, requesting him to appoint others to attend the trial of the engine, as it would not be convenient for them to do it. "Captain Samuel Grose, jun., brought down the drawing for your engine. He said he had taken off the working gear only. If you would wish it, we will make the working-gear and all the wrought-iron work on the drawing for the two engines ordered, and will take on a man or two immediately for that purpose. You will let me know about this before you set off, and also if any alteration is to be made in the beam for Wheal Treasure engine, since you have altered the size of the pole. We had cast the case, but I suppose it will suit some place else. "Your obedient servant, "HENRY HARVEY. "MR. RICHARD TREVITHICK." "About 1815 or 1816 I was employed by Captain Trevithick to erect various pole-engines, one of them at Saltram Stream. It had worked at Tavistock; it was a horizontal high-pressure pole puffer. Captain Samuel Grose was then erecting for Captain Trevithick a 24-inch high-pressure pole-engine at Beeralstone, on the Tamar, to drain a lead mine. I assisted Captain Grose. The stroke was about 8 feet. It worked with cross-head and side rods. There were two wrought-iron boilers about 3 feet 6 inches in diameter and 40 feet long. The fire and flues were outside. The steam pressure, 60 lbs. to the inch. I also erected a similar engine with a 20-inch pole at Wheal Treasure, now called Fowey Consols Mine; and one at Logassack, near Padstow. Those two had brass poles. It was found that the poles cut and wore in their passage through the stuffing box, the middle wearing more than the ends, causing steam to escape. A similar pole of Captain Trevithick's erecting was then working at Wheal Regent, near St. Austell. "In 1818 I saw working at Wheal Chance Mine, near Scorrier, an old 60-inch cylinder Boulton and Watt engine. A pole of Trevithick's was fixed between the cylinder and the centre of the main beam. High-pressure steam was first worked under the pole and then expanded in the cylinder."[35] [Footnote 35: Recollections of Captain H. A. Artha, Penzance, 1870.] The late Mr. William Burral, for many years manager of the boiler-making department at Messrs. Harvey and Co., at Hayle, said:-- "About the year 1815 or 1816 I helped to erect at Treskerby Mine an engine for Captain Trevithick. Mr. Sims was the engineer of the mine. The engine had the usual cylinder, and close to it one of Captain Trevithick's poles was fixed. The boilers were Captain Trevithick's high-pressure. The steam was first turned on under the pole. When she had finished her up-stroke the steam passed from under the pole on to the top of the piston in the cylinder. There was a vacuum under the piston. The steam-cylinder was 58 inches in diameter, about 9 or 10 feet stroke. The pole was 36 inches in diameter, and a less stroke than the piston, because it was fixed inside the cylinder, nearer to the centre of the beam. There was a pole-engine then working at Wheal Lushington, also at Poldice, and at Wheal Damsel." "Captain Artha recollects at Wheal Alfred Mine in 1812 the 66-inch cylinder pumping engine used a pole air-pump; one or two whim-engines on the same mine also used them. Wheal Concord pumping engine, in 1827 had a similar air-pump. Old Wheal Damsel, near Treloweth, used one as late as 1865. The condensing water and air passed through a branch with a valve on it near the top of the pole-case, just under the stuffing box There was a foot-valve at the bottom of the pole-case."[36] [Footnote 36: Captain Artha became the resident engineer at the Real del Monte mines in Mexico; Captain Samuel Grose, one of the first Cornish mine engineers; and Mr. Burral, the engineer of a department at the engine-works of Messrs. Harvey and Co.] The writer has had the pleasure of personal acquaintance with each of those three gentlemen, who as young engineers commenced their labours in the erection of Trevithick's engines. No sooner had Trevithick perfected the pole condensing engine and then the pole puffer-engine, than he, in conjunction with Sims, who had just taken part in the erection of one of his high-pressure steam pole-engines for working the pumps at Beeralstone Mine, combined the pole with the ordinary Watt vacuum engines, supplying them with steam from his high-pressure boilers, in other words, converting them from their original form of low-pressure vacuum engines to high-pressure expansive compound steam-engines. The old 60-inch cylinder Boulton and Watt engine, at Wheal Chance (one of Watt's favourite engines), was in 1818 transformed into a high-pressure engine, with Trevithick's pole placed between the centre of the main beam and the steam-cylinder. The high-pressure steam from Trevithick's new boilers was turned under the pole for the up-stroke, after which it was expanded in the old and much larger cylinder on the top of the piston causing the down-stroke; it then, by its passage through the equilibrium valve, allowed the piston in the large cylinder to make its up-stroke, by equalizing the pressure of steam on its top and bottom, while a fresh supply of strong steam from the boiler admitted under the pole gave power to the up-stroke; and finally, the comparatively low-pressure steam under the large piston passed to the condenser and air-pump to form a vacuum for the down-stroke, as in the Watt engine. Sims, the engineer at Wheal Chance, one of the mines in the eastern or Watt district, was converted and became in 1815 or 1816 a partner with Trevithick, and erected, at Treskerby Mine, Trevithick's high-pressure pole of 36 inches in diameter, as an addition to the old Watt engine working with a cylinder 58 inches in diameter. Watt, then, within a year or two of his death, was too old to any longer take part in the contest; his engine in the hands of others was converted and became a high-pressure expansive engine. Trevithick, as a further proof that he could do without the Watt patent air-pump bucket, with its piston and valves, removed it from a Watt engine at Wheal Alfred Mine in 1812, replacing it by one of his poles, answering the same purpose, but different in construction. Many other mines used them; one remained at work in Old Wheal Damsel in 1860. They have also been used in steamboat air-pumps. Having traced during a period of five or six years the rise and progress of the high-pressure expansive pole condensing-engines, the high-pressure expansive pole puffer-engine, and the combined pole and cylinder high-pressure engine, their value in a commercial sense may be further tested by the public acts of the time. Lean, an authority on such matters, and certainly not given to unduly praise Trevithick, spoke as follows on the duty of those particular engines at various periods; and not the least noteworthy is the fact, that Herland, Poldice, and Treskerby, that were prominent in the early use of the Watt engine, threw off their allegiance but shortly before the last days of the great engineer, and converted his low-pressure steam vacuum engines into Trevithick high-pressures. "In 1798 Messrs. Boulton and Watt, who on a visit to Cornwall, came to see it--'the Herland engine'--and had many experiments tried to ascertain its duty; it was under the care of Mr. Murdoch, their agent in the county. Captain John Davey, the manager of the mine, used to state that it usually did twenty millions, and that Mr. Watt, at the time he inspected it, pronounced it perfect, and that further improvement could not be expected. "In 1811 the average duty of the three engines (Boulton and Watt's) on Wheal Alfred Mine was about twenty millions. These engines were at that time reckoned the best in the county. "In 1816 Sims erected an engine at Wheal Chance, to which he applied the pole adopted by Trevithick in his high-pressure engine. This engine attained to forty-five millions; and in 1817 it did 46·9 millions. "In 1814 Treskerby engine is reported as doing 17·48 millions.--Wm. Sims, engineer. "In 1820 Treskerby engine, to which Trevithick's high-pressure pole had been adapted, had reached 40·3 millions."[37] [Footnote 37: Lean's 'Historical Account of the Steam-Engine in Cornwall,' pp. 11, 32, 36.] The Herland engine of Watt in 1798 did twenty millions; in 1816 Trevithick's high-pressure pole puffer in the same mine did forty-eight millions. In 1820 his high-pressure pole-engine was combined with a Watt low-pressure engine, thereby more than doubling its economical duty. In 1813 Trevithick wrote:-- "That new engine you saw near the sea-side with me (Wheal Prosper high-pressure pole condensing engine) is now lifting forty millions one foot high, with a bushel of coal, which is nearly double the duty that is done by any other engine in the county. A few days since I altered a 60-inch cylinder engine at Wheal Alfred to the same plan, and I think she will do equally as much duty. I have a notice to attend a mine meeting, to erect a new engine equal in power to a 63-inch cylinder single."[38] [Footnote 38: See Trevithick's letter, January, 1813, vol. ii., p. 55.] In the four or five years from his return to Cornwall in 1810, to his leaving for South America in 1816, he doubled the duty and the power of the steam-engine. Watt once said he had received an oblique look from Trevithick, sen. The time was now come for Trevithick, jun., to return the compliment; his improved engines having made their way into the eastern mine district, which Watt once looked upon as his own. Trevithick was short of money and on the point of leaving England for South America, when Mr. Sims, in the employ of Messrs. Williams and Co., favourable to low pressure, was sent to negotiate for the purchase of a share in Trevithick's patent of 1815 for the high-pressure steam expansive pole-engine. "18th October, 1816.--Agreement between Trevithick and Mr. William Sims, prepared by myself and Mr. Day, solicitor for Mr. Sims, or for Mr. Michael Williams, under whom Sims acted, recites, that in consideration of 200_l._ paid by Sims, he was to have a moiety of the patent for Cornwall and Devon, and that I should have power to act and make contracts whilst Trevithick was out of England. "The day after contract signed, Trevithick sailed in the 'Asp,' Captain Kenny, for South America. I was on board when the ship sailed. "I see among my papers, in May, 1819, in reference to the patent, is the following note:--'Mr. Michael Williams said it was verbally agreed that Captain Trevithick should have one-quarter part of the savings above twenty-six millions.' This, I believe, was the average duty of the engines at that time. "I had several assurances relative to Trevithick's claims, and much correspondence, but no allowance was made from any mines but Treskerby and Wheal Chance; though Trevithick's patent and boilers were used throughout the county without acknowledgment; and the duty of the engines had soon increased from twenty-six millions to about seventy millions. "In 1819 I attended at the account-houses of Treskerby and Wheal Chance, of which the late Mr. John Williams, of Scorrier, was the manager, in consequence of some of the adventurers objecting to continue the allowances on the savings to Captain Trevithick, when Mr. Williams warmly observed, that whatever other mines might do, he would insist, as long as he was manager for Treskerby and Wheal Chance, the agreement made should be carried into effect. "I remain, my dear Thomas, "Your very affectionate father, "RD. EDMONDS."[39] [Footnote 39: Portion of a letter written at Penzance, 8th February, 1853.] The agreement with Mr. Sims, or rather with Mr. Michael Williams, late M.P. for Cornwall, who exercised large authority in Cornish mines, was that he should have for 200_l._ one-half of the patent for the high-pressure pole-engine, as applied to Cornwall and Devon. Trevithick had desisted from securing a patent for the large high-pressure steam-boilers and expansive working, on a verbal understanding that he should receive one quarter of the saving from the reduced consumption of coal by those two particular inventions, twenty-six millions of pounds of water raised one foot high by a bushel of coal of 84 lbs., being the duty of the best Watt engines, to be taken as a starting-point for the payment. Treskerby and Wheal Chance paid for the pole-engine, but the Trevithick boilers suitable for high steam, and the simple methods of working it expansively, had been made so generally public, that people professed to think they had a right to them, when but a few years before they had thrown the inventor off his guard by saying "everybody knows that the Cornish boiler is your plan, and as it cannot be denied, a patent will be of no service." Mr. John Williams[40] stated "that whatever other mines might do, he would insist, as long as he was manager for Treskerby and Wheal Chance, the agreement made should be carried into effect." The Williamses paid to Trevithick 300_l._ for the saving of coal by the pole patent engine, as an "acknowledgment of the benefits received by us in our mines;" but no payment was made for the greater invention of the high-pressure steam-boilers then in general use. [Footnote 40: Mr. John Williams had the remarkable dream, many hours before the event, enabling him to describe the particulars of the assassination of Perceval in 1812.] In 1814 the Watt Treskerby engine did seventeen and a half millions. Trevithick's boiler and pole were applied, and the duty was increased to more than forty millions. In 1816 the same changes were made in Wheal Chance, and the duty rose to more than forty-six millions. The consumption of coal was reduced to one-half, amounting in round numbers to a gain of 500_l._ a month in those two mines alone. /# "TREVINCE, near TRURO, "DEAR SIR, _5th January, 1853_. "I am favoured with your letter of the 31st ult., enclosing also one from Mr. F. Trevithick, of the 24th idem, and have much pleasure in complying with your joint request to the best of my ability. I was well acquainted with the late Mr. Rd. Trevithick, having had frequent occasion to meet him on business and to consult him professionally; and I am gratified in having the present opportunity of bearing testimony to his distinguished abilities, and to the high estimation in which the first Cornish engineers of the day then regarded him. I need scarcely say that time has not lessened the desire in this county especially to do him justice. As a man of inventive mechanical genius, few, if any, have surpassed him, and Cornwall may well be proud of so illustrious a son. "At this distance of time I can scarcely speak with sufficient exactness for your purpose of the numerous ingenious and valuable mechanical contrivances for which we are indebted to him, but in reference to his great improvements in the steam-engine I have a more particular recollection, and can confidently affirm that he was the first to introduce the high-pressure principle of working, thus establishing a way to the present high state of efficiency of the steam-engine, and forming a new era in the history of steam-power. To the use of high-pressure steam, in conjunction with the cylindrical boiler, also invented by Mr. Trevithick, I have no hesitation in saying that the greatly-increased duty of our Cornish pumping engines, since the time of Watt, is mainly owing; and when it is recollected that the working power now attained amounts to double or treble that of the old Boulton and Watt engine, it will be at once seen that it is impossible to over-estimate the benefit conferred, either directly or indirectly, by the late Mr. Trevithick, on the mines of this county. The cylindrical boiler above referred to effected a saving of at least one-third in the quantity of coal previously required; and in the year 1812 I remember our house at Scorrier paying Mr. Trevithick the sum of 300_l._ as an acknowledgment of the benefits received by us in our mines from this source alone. Mr. Trevithick's subsequent absence from the county, and perhaps a certain degree of laxity on his own part in the legal establishment and prosecution of his claims, deprived him of much of the pecuniary advantage to which his labours and inventions justly entitled him; and I have often expressed my opinion that he was at the same time the greatest and the worst-used man in the county. "Amongst the minor improvements introduced by him, it occurs to me to notice that he was the first to apply an outer casing to the cylinder, and by this means prevent, still further than Watt had succeeded in doing, the loss of heat by radiation. "As connected with one of the most interesting of my recollections of Mr. Trevithick, I must mention that I was present by invitation at the first trial of his locomotive engine, intended to run upon common roads, and of course equally applicable to train and railways. This was, I think, about the year 1803, and the locomotive then exhibited was the very first worked by steam-power ever constructed. "The great merit of establishing the practicability of so important an application of steam, and the superiority of the high-pressure engine for this purpose, will perhaps more than any other circumstance serve to do honour through all times to the name of Trevithick. The experiment which was made on the public road close by Camborne was perfectly successful; and although many improvements in the details of such description of engines have been since effected, the leading principles of construction and arrangements are continued, I believe, with little alteration, in the magnificent railroad-engines of the present day. Of his stamping engine for breaking down the black rock in the Thames, his river-clearing or dredging machine, and his extensive draining operations in Holland, I can only speak in general terms, that they were eminently successful, and displayed, it was considered, the highest constructive and engineering skill. As a man of enlarged views and great inventive genius, abounding in practical ideas of the greatest utility, and communicating them freely to others, he could not fail of imparting a valuable impulse to the age in which he lived; and it would be scarcely doing him justice to limit his claims as a public benefactor to the inventions now clearly traceable to him, important and numerous as these are. From my own impressions I may say that no one could be in his presence without being struck with the originality and richness of his mind, and without deriving benefit from his suggestive conversation. His exploits and adventures in South America, in connection with the Earl of Dundonald, then Lord Cochrane, will form an interesting episode in his career; and altogether, I am of opinion that the Biography which you have undertaken will prove highly interesting and valuable, and I wish you every success in carrying it out. "Believe me, my dear Sir, "Yours very faithfully, "MICHAEL WILLIAMS. "E. WATKIN, Esq., "_London and North-Western Railway_, "_Euston Station, London_." Arthur Woolf shortly after that time (1811) erected his double-cylinder engines in Cornwall. The late Captain Samuel Grose, when giving the writer his recollections of Trevithick, said:-- "When he returned from London to Cornwall, about 1810 or 1811, he employed me to look after the erection of the Wheal Prosper high-pressure engine. Oats, Captain Trevithick's head boiler-maker, was constructing the boilers; Woolf came into the yard, and examined them. 'What do'st thee want here?' asked Oats. 'D--n thee, I'll soon make boilers that shall turn thee out of a job!' was Woolf's reply. He was a roughish man. When his brother Henry mutinied at the Nore, Woolf, who was then working an engine in Meux's brewery, and had married the lady's maid, made interest with his employer to save Henry from being hanged at the yard-arm, and afterwards found employ for him in Cornwall. He was but a clumsy mechanic. Woolf used to blow him up by saying, 'D--n thee, I wish I'd left thee to be hanged.'" The writer, who knew Oats, has heard him tell similar stories of the rival engineers. In 1800, Woolf, who had been a mine carpenter, went to London with the first high-pressure steam-engine which Trevithick had sent beyond the limits of Cornwall[41]--probably to Meux's brewery,[42] for he was there in 1803, and in the receipt of 30_l._ a year from Trevithick as engine-fireman. From the date of Woolf's patent in 1804, his pay from Trevithick ceased, and with it their friendship. Trevithick used to say, "Woolf is a shabby fellow." [Footnote 41: See Trevithick's account-book, vol. i., p. 90.] [Footnote 42: Captain John Vivian's recollections, vol. i., p. 142.] Patents sprang up like mushrooms after Trevithick had so liberally cast forth the seeds of the high-pressure engine, making the security, or even the form of a patent, a doubtful matter. The perfecting of expansive high-pressure engines was like the boiler, the result of years of trial. When matured in 1816 it saved Cornwall and the world one-half of the coal that before had been consumed in low-pressure steam-engines. Every engineer became, more or less, an expansive worker, and Trevithick's saving of hundreds of thousands of pounds annually to the general public, gave to him little or no reward. At the period of those high-pressure pole-engine experiments, Trevithick had devoted twenty years of constant labour to the improvement and extended use of the steam-engine, causing it to assume every variety of form except that of the Watt patent engine, an approach to which was unusual, as evidenced in the high-pressure steam Kensington model of 1796, without beam, parallel motion, air-pump, or condenser, having no one portion either in principle or detail similar to the Watt engine, being portable and not requiring condensing water, with single and double cylinders, placed vertically or horizontally. Having during twelve busy years constructed over a hundred high-pressure steam-engines, scarcely any two of which were exactly alike, he departed if possible still further from the Watt type, and went back apparently, though not in reality, to the Newcomen engine, simplifying it by the omission of the great bob, and use of condensing water, as in the nautical labourer and steamboat engine of about 1810,[43] and the South American mine engines of 1816,[44] which had open-top cylinders, more like a Newcomen than a Watt, but if possible even more simple and primitive-looking than the former. Again, compare the thrashing engine of 1812[45] with the Newcomen of 1712:[46] the great and all-important difference being that one was a high-pressure steam-engine, the other a low-pressure atmospheric engine. Then came the varieties of high-pressure steam pole-engines, working very expansively either as puffers or condensers, retaining the same dissimilarity to the Watt engine: and lastly, the combination of the high-pressure pole with the Watt patent engine, thereby causing the old Watt engine to do more than double the work it had done when new from the hands of the maker, and also to perform this increase of work with a decrease in the consumption of coal. [Footnote 43: See vol. i., p. 336.] [Footnote 44: See chap. xxi.] [Footnote 45: Vol. ii., p. 37.] [Footnote 46: Vol. i., p. 5.] The following chapter will trace the adaptation of high-pressure expansive steam, from cylindrical boilers, to the form of pumping engine still in general use. CHAPTER XX. THE WATT AND THE TREVITHICK ENGINES AT DOLCOATH. Having up to 1816 traced the progress of the steam-engine in Cornwall through a century, during the latter half of which Trevithick, sen., and his son were among its most prominent improvers, the latter having devoted a quarter of a century to the work, the effect of which is shown in the skeleton outlines of a few classes of engines, one important feature still remains for examination before a correct judgment can be formed of the events of this period and their prime movers. The use of an increasing pressure of steam gave increased force and value to the improved steam-engine, but the power of constructing engines and boilers to render the increased pressure manageable was the result of a lifetime of labour. Savery, whose engine was scarcely more than a steam-boiler, failed to control its force, and is said to have blown the roof from over his head. The mechanism of Newcomen's engine was well arranged, but suitable only for the working of pumps, and its power was limited to the weight of the atmosphere, from which it was called the atmospheric engine. In 1756, an atmospheric engine with a cylinder of 70 inches in diameter worked at the Herland Mine, "the only objection to which was the cost of the coal, to lessen which several methods had been suggested for increasing the elasticity of the steam, and reducing the size of the boiler."[47] [Footnote 47: Borlase's 'Natural History of Cornwall.'] In 1775 Richard Trevithick, sen., removed the flat top of a Newcomen boiler, and substituted a semicircular top, enabling it to contain stronger steam, and at the same time he improved the mechanical part of the engine by finding a better resting-place for the steam-cylinder than the top of the large boiler. Pryce gives a drawing of this engine as the best at that time in Cornwall.[48] [Footnote 48: See drawing, vol. i., p. 25.] "It is known as a fact that every engine of magnitude consumes 3000_l._ worth of coal every year. "The fire-place has been diminished and enlarged again. The flame has been carried round from the bottom of the boiler in a spiral direction, and conveyed through the body of the water in a tube (one, two, or three) before its arrival at the chimney. "Some have used a double boiler, so that fire might act on every possible point of contact, and some have built a moorstone boiler, heated by three tubes of flame passing through it. "A judicious engineer does not attempt to load his engine with a column of water heavier than 7 lbs. on each square inch of the piston."[49] [Footnote 49: See Pryce's 'Mineralogia Cornubiensis,' published 1778. Appendix.] While Pryce's book was being printed, Watt in 1777 wrote of the Cornish steam-engines:-- "I have seen five of Bonze's engines, but was far from seeing the wonders promised. They were 60, 63, and 70 inch cylinders at Dolcoath and Wheal Chance. They are said to use each about 130 bushels of coals in the twenty-four hours, and to make about six or seven strokes per minute, the stroke being under 6 feet each. They are burdened to 6, 6-1/2, and 7 lbs. per inch."[50] [Footnote 50: Smiles' 'Lives of Boulton and Watt.'] The 63-inch was an open-top cylinder atmospheric engine at Dolcoath Mine under the management of Trevithick, sen.; and shortly after, in 1777 or 1778, Watt's first engine was erected in Cornwall.[51] [Footnote 51: See vol. i., p. 30.] In 1783 Trevithick, sen., gave Watt an order for a patent engine for Dolcoath, in size similar to the old Newcomen atmospheric, having a cylinder 63 inches in diameter, that a working trial might be made between the rival engines. The Watt engine having a cylinder-cover, with the patent air-pump and condenser, was known in the county as the Dolcoath great 63-inch double-acting engine. Three steam-engines were then at work in that mine: Trevithick senior's Carloose (then called Bullan Garden) atmospheric 45-inch cylinder, the atmospheric 63-inch cylinder, and Watt's 63-inch cylinder double-acting vacuum engine; all of which continued in operation side by side for five years until 1788, when for a time Dolcoath ceased to be an active mine. Trevithick, jun., was then a boy of seventeen years. After ten years of idleness and rust, as if mourning the death of Trevithick, sen., in 1798 Richard Trevithick, jun., as engineer, and Andrew Vivian as manager, induced shareholders to resuscitate the old mine. Fire was again given to the voracious jaws of the boilers, and the three engines recommenced their labours and their rivalries. A year or two before this Trevithick had made models of high-pressure steam-engines. Davies Gilbert, in 1796, met him among other engineers, giving evidence in the Watt lawsuits, when he mentioned his ideas of an engine to be worked solely by the force of steam. Watt had claimed such an engine in his patent twenty-seven years before, but had failed to carry it into practice. Hornblower had tried something like it in his double-cylinder expansion engine, but he did not use high-pressure steam, and consequently also failed. The _idea_, therefore, of expansive steam was not new, but the _useful mastery_ of it was. Savery had tried expansive steam before Watt patented it; the latter went to law with Hornblower for an infringement of the _idea_, when neither of them had in truth constructed an expansive steam-engine. The low pressure of the steam from the boilers used by Hornblower and Watt did not admit of profitable expansion in the cylinder; at its full boiler pressure it constituted but a comparatively small portion of the power of the engine: to reduce that power by expansion was as apt to be a loss as a gain. The steam-engine was still dependent for its power mainly on steam as an agent for causing the required vacuum, until 1796, when Trevithick disclosed his method of constructing small cylindrical boilers and engines suitable for giving power from the strong pressure of the steam, irrespective of vacuum. Lean, who favoured Watt rather than Trevithick, thus records the advent of Watt's expansive engine:-- "In 1779 to 1788 Mr. Watt introduced the improvement of working steam expansively, and he calculated that engines which would previously do nineteen to twenty millions would thus perform twenty-six millions; but I do not find any record of this duty being performed in practice. In 1785 Boulton and Watt had engines in Cornwall working expansively, as at Wheal Gons and Wheal Chance in Camborne; but in these the steam was not raised higher than before, and the piston made a considerable part of the stroke therefore before the steam-valve was closed. "In 1798, on account of a suit respecting their patent, which was carrying on by Boulton and Watt, an account of the duty of all the engines in Cornwall was taken by Davies Gilbert, Esq., and the late Captain Jenkin, of Treworgie, and they found the average to be about seventeen millions."[52] [Footnote 52: Lean's 'Historical Statement of Steam-Engines in Cornwall,' p. 7.] One of these so-called expansive Watt engines, erected at Wheal Chance, was converted into a real expansive engine by Trevithick, as described in the foregoing chapter, by his high-pressure steam-boilers and the addition of his pole-engine. The conversion of the other, a 63-inch low-pressure vacuum engine at Wheal Gons, will be traced in this chapter. Mr. Taylor, who for many years took an active interest in Cornish mining, says:-- "In 1798 an engine at Herland was found to be the best in the county, and was doing twenty-seven millions, but being so much above all others, some error was apprehended. This engine was probably the best then ever erected, and attracted therefore the particular attention of Messrs. Boulton and Watt, who, on a visit to Cornwall, came to see it, and had many experiments tried to ascertain its duty. It was under the care of Mr. Murdoch, their agent in the county. "Captain John Davey, the manager of the mine, used to state that it usually did twenty millions, and that Mr. Watt, at the time he inspected it, pronounced it perfect, and that further improvement could not be expected."[53] [Footnote 53: 'Records of Mining,' by John Taylor, F.R.S., &c., part i., p. 155; published 1829.] This best engine from the hands of Watt and Murdoch in the Herland Mine in 1798 may be taken as a Watt stand-point, when its usual duty was twenty millions; and Trevithick and Bull erected a competing engine, probably with an increased steam pressure, for Trevithick's portable high-pressure engines were at that time coming into notice;[54] but no trace remains of the result of this contest of the Watt and the Bull engine, though it was one of the causes of the lawsuits. [Footnote 54: See vol. i., p. 95.] "In 1799 Henry Clark worked as a rivet boy in Dolcoath, and carried rivets to construct Captain Trevithick's new boiler, said to be the first of the kind ever made. It looked like a great globe about 20 feet in diameter, the bottom hollowed up like the bottom of a bottle; under this the fire was placed: a copper tube attached to this bottom went around the inside of the boiler, and then passed out through the side of the boiler, the outside brick flues then carrying the heat around the outside of the boiler and into the chimney. "Captain Trevithick's first plunger-pole lifts in Dolcoath were put in at this time and worked by this engine. Glanville, the mine carpenter, was head man over the engines when Captain Trevithick was away."[55] [Footnote 55: Henry Clark's recollections in 1869.] "Charles Swaine worked as a rivet boy in making Captain Trevithick's cylindrical wrought-iron boilers for the Dolcoath engine. Several of Captain Trevithick's high-pressure boilers were working in the mines before that, but not made exactly like the Dolcoath engine boilers. When I was a boy about the year 1804, several years before I worked on the Dolcoath engine boilers, I carried father's dinner to the Dolcoath smiths' shop, where he worked, and used to stop and watch the wood beam going up and down of Captain Dick's first high-pressure steam-whim. She was not a puffer, but a puffer-whim worked near by, called the Valley puffer. At that time most of Captain Dick's high-pressure boilers were smallish, cast iron outside, and wrought-iron tube."[56] [Footnote 56: Working in the Valley smiths' shop, in Dolcoath Mine, in 1869.] In 1799, shortly after the reopening of Dolcoath Mine, Trevithick, jun., selected his father's second-hand atmospheric engine of 1775,[57] to further improve it by a new boiler of uniformly globular figure, with concave circular bottom, under which fire was placed; it was of wrought iron, 24 feet in diameter, surrounded by external brick flues; a large copper tube, starting from the boiler bottom, immediately over the fire, served as an internal flue, carrying the fire by a sweep around the interior in the water space, and then out through the side of the boiler into the external brick flue. It may be said that there was nothing new in a circular form of boiler, or in an internal tube; but it will be admitted that this repaired engine, in this its third stride in the march of advancement, made publicly known those principles which in a few years more than doubled the power, the economy, and the applicability of the steam-engine. His patent drawing of 1802 shows this form of boiler applied to a small portable engine, in which, for the sake of simplicity of structure and cheapness, cast iron was used instead of wrought iron, and the internal tube omitted.[58] [Footnote 57: See vol. i., p. 25.] [Footnote 58: See vol. i., p. 128.] The full detail estimate, from which the following items are extracted, of the cost of alteration was written by Trevithick, jun., in the book and on the page adjoining that containing the account of the former alteration and re-erection of the same engine by Trevithick, sen., in 1775. "A 45-inch cylinder engine, working 20 lbs. to the inch:-- £ _s._ _d._ Boilers, 8 tons at 42_l._ 336 0 0 Iron about ditto, 6 cwt. at 42_l._ 12 12 0 Castings about ditto, 15 cwt. at 42_s._ 18 0 0 Safety-valve and cocks 1 0 0 Wood about bob, 200 ft. at 6_s._ 60 0 0 Cast iron about ditto, 45 cwt. at 25_s._ 56 5 0 Brass about ditto, 60 lbs. at 2_s._ 6 0 0 Piston-rod, 4 in., 14 ft. long, 550 lbs. at 1_s._ 27 10 0 T-piece, 10 cwt. at 25_s._ 12 10 0 Cover, and bottom, and piston, 35 cwt. at 32_s._ 56 0 0 Nozzles, 6 cwt. at 32_s._ 9 12 0 Steam and perpendicular pipe, 10 cwt. at 25_s._ 12 10 0 Receiver, 2 ft. 4 in. long, and bottom, 15 cwt. at 25_s._ 18 15 0 Air-pump, bottom, and case, 10 cwt. at 25_s._ 12 10 0 Plunger, 22 in., 6 ft. long, 12 cwt. at 40_s._ 24 0 0 Force lift 5 0 0 Engineer 66 0 0" The term "single" refers to its open-top cylinder as originally erected by Newcomen, when it was called the Carloose engine, and so it remained after its re-erection in 1775, under the name Dolcoath new engine, alias Bullan Garden; but after the last re-erection in 1799 it had a cylinder-cover, and was called the Shammal 45-inch engine; "working 20 lbs. to the inch" meant the force on each inch of the piston, including vacuum on the one side of 14 lbs. and steam on the other side of 6 lbs. to the inch. Watt, on his first visit to Cornwall, in 1777, spoke disparagingly of the Newcomen atmospheric engines "burdened to 6 or 7 lbs. net to the inch." Fifty years later Stuart described Watt's engine as "using steam of a somewhat higher temperature than 212 degrees, so as to produce a pressure between 17 and 18 lbs. on each square inch of the piston; yet in practice, from imperfect vacuum and friction, it cannot raise more water per inch than would weigh about 8-1/2 lbs.,"[59] or an increase of net force--when compared with the Newcomen atmospheric--of only a pound or two on the inch in the lapse of years embracing the active lifetime of Watt. The cause of this slight increase of power is so simple that it has been passed by unnoticed by very many. The steam pressure in the Newcomen atmospheric was continued unaltered in the Watt vacuum engine. Trevithick constructed the first boiler and engine capable of safely and economically using the power of high-pressure steam. Nelson was obliged to come to close quarters, that his shot, propelled by weak cannon and low-pressure powder, might penetrate wooden ships. We now manufacture and control high-pressure powder, so that 12 inches of iron armour-plates cannot resist its force; but this knowledge has taken nearly as long in growing to perfection as did the mastery of high-pressure steam, and its use in the much more complicated steam-engine. [Footnote 59: Stuart's 'History of the Steam-Engine,' published 1824.] Watt's engine, as described a quarter of a century after the expiration of his patent and the advent of the high-pressure steam-engine, still derived its gross force from 14 lbs. of vacuum and 2 or 3 lbs. of steam, resulting in a net force of 8-1/2 lbs. Trevithick's engine of 1799, which heralded the last hours of the Watt patent authority, and may be taken as the first distinct evidence of comparatively high-pressure steam in large Cornish pumping engines, derived its power from 14 lbs. of vacuum and 6 lbs. of steam, being together but 2 or 3 lbs. on the inch more than the Watt engine, but its net force of 12 lbs. to the inch was half again as much as the net force of the Watt engine, the increase being wholly from the steam pressure, which was never practised by Watt, and which in its almost unlimited force gives the greatly increased power to modern steam-engines. Trevithick's estimate for a new engine of the same size as the old was 2000_l._, but as the old one could be improved for 1300_l._, the latter course was adopted, the wooden main beam with its segment head was retained, a cover was added to the cylinder, and a new piston-rod and piston; a pole air-pump was used in lieu of the more usual Watt air-pump bucket; a feed-pole forced water into the boiler,--an indirect proof of increased steam pressure. The new globular boiler with internal tube weighed 8 tons; the engineer's charge for carrying out the work was 66_l._ The use of strong steam as the prime mover of the steam-engine increased more rapidly beyond than within the limits of Cornwall, for in 1802 was erected at Coalbrookdale a high-pressure steam-puffer engine, to which Trevithick attached a pump which forced water through a column of upright pipes, that the power of the engine might be accurately measured. It worked with steam of from 50 to 145 lbs. on the inch, and wholly discarded the vacuum which had been Watt's mainstay. "The boiler is 4 feet diameter, the cylinder 7 inches diameter, 3-feet stroke. The water-piston is 10 inches in diameter, drawing and forcing 35 feet perpendicular, equal beam. I first set it off with about 50 lbs. on the inch pressure against the steam-valve, for the inspection of the engineers about this neighbourhood. The steam continued to rise the whole of the time it worked; it went from 50 to 145 lbs. to the inch. "The engineers at this place all said that it was impossible for so small a cylinder to lift water to the top of the pumps, and degraded the principle, though at the same time they spoke highly in favour of the simple and well-contrived engine. "After they had seen the water at the pump-head, they said that it was possible, but that the boiler would not maintain its steam at that pressure for five minutes; but after a short time they went off, with a solid countenance and a silent tongue."[60] [Footnote 60: See Trevithick's letter, August 22nd, 1802, vol. i., p. 153.] This high-pressure steam pumping engine in 1802 may be taken as the first pumping engine of the puffer class using such strong steam. In the spring of the following year[61] a somewhat similar engine was erected in London. "The cylinder is 11 inches in diameter, with a 3-1/2-feet stroke. It requires the steam at a pressure of 40 to 45 lbs. to the inch to do its work well, working about twenty-six or twenty-seven strokes per minute. It is much admired by everyone that has seen it, and saves a considerable quantity of coal when compared with a Boulton and Watt. Mr. Williams, Mr. Robert Fox, Mr. Gould, and Captain William Davey were here, and much liked the engine; they gave me an order for one for Cornwall as a specimen." This particular engine was for driving machinery in a cannon manufactory. A high-pressure pumping engine was at work at Greenwich, and some were at work in Cornwall. [Footnote 61: See Trevithick's letter, May 2nd, 1803, vol. i., p. 158.] "PENYDARRAN, near CARDIFF,[**Check order of these lines] "MR. GIDDY, "_October 1st, 1803_. "Sir,--In consequence of the engine bursting at Greenwich, I have been on the spot to inspect its effects. I found it had burst in every direction. The bottom stood whole on its seating; it parted at the level of the chimney. The boiler was cast iron, about 1 inch thick, but some parts were nearly 1-1/2 inch; it was a round boiler, 6 feet diameter; the cylinder was 8 inches diameter, working double; the bucket was 18 inches diameter, 21 feet column, working single, from which you can judge the pressure required to work this engine. The pressure, it appears, when the engine burst, must have been very great, for there was one piece of the boiler, about 1 inch thick and about 5 cwt., thrown upwards of 125 yards; and from the hole it cut in the ground on its fall, it must have been nearly perpendicular and from a very great height, for the hole it cut was from 12 to 18 inches deep. Some of the bricks were thrown 200 yards, and not two bricks were left fast to each other, either in the stack or round the boiler. It appears the boy that had care of the engine was gone to catch eels in the foundation of the building, and had left the care of it to one of the labourers; this man, seeing the engine working much faster than usual, stopped it, without taking off a spanner which fastened down the steam-lever, and a short time after being idle it burst, killed three on the spot and another died soon after of his injuries. The boy returned that instant, and was then going to take off the trig from the valve. He was hurt, but is now recovering; he had left the engine about an hour. I would be much obliged to you if you would calculate the pressure required to burst this boiler at 1 inch thick, supposing it to be a sound casting, and what pressure it would require to throw the materials the distance I have before stated, for Boulton and Watt have sent a letter to a gentleman of this place, who is about to erect some of those engines, saying that they knew the effects of strong steam long since, and should have erected them, but knew the risk was too great to be left to careless enginemen, and that it was an invention of Mr. Watt, and the patent was not worth anything. This letter has much encouraged the gentlemen of this neighbourhood respecting its utility; and as to the risk of bursting, they say it can be made quite secure. I believe that Messrs. Boulton and Watt are about to do me every injury in their power, for they have done their utmost to report the explosion, both in the newspapers and in private letters, very different to what it really was; they also state that driving a carriage was their invention; that their agent, Murdoch, had made one in Cornwall and shown it to Captain Andrew Vivian, from which I have been enabled to do what I have done. I would thank you for any information that you might have collected from Boulton and Watt, or from any of their agents, respecting their even working with strong steam, and if Mr. Watt has ever stated in any of his publications the effects of it, because if he condemns it in any of his writings, it will clearly show from that, that he did not know the use of it. Mr. Homfray, of this place, has taken me by the hand, and will carry both the engines and the patent to the test. There are several of Boulton and Watt's engines being taken down here, and the new engines being erected in their place. Above 700 horse-powers have been ordered at 12_l._ 12_s._ for each horse-power for the patent right, and the persons that ordered them make them themselves, without any expense to me whatever. If I can be left quiet a short time I shall do well, for the engines will far exceed those of Boulton and Watt. The engine at Greenwich did fourteen millions with a bushel of coals; it was only an 8-inch cylinder, and worked without an expansive cock, and under too light a load to do good duty; also on a bad construction, for the fly-wheel was loaded on one side, so as to divide the power of the double engine, and connected to the pump-rods on a very bad plan. I remember that Boulton and Watt's 20-inch cylinders when on trial did not exceed ten millions; I believe you have the figures in your keeping. Let us have the 60-horse power at work that is now building, and then I will show what is to be done. It will be loaded at 30 lbs. to the inch on each side the piston, it has an 8-feet stroke with an expansive cock, and the blowing cylinder directly over the steam-cylinder, as free from friction as possible. There was no engine stopped on account of this accident; but I shall never let the fire come in contact again with the cast iron. The boiler at Greenwich was heated red hot and burnt all the joints the Sunday before the explosion. "I have received a letter from a person in Staffordshire who has a cylinder-boiler at work with the fire in it, and he says the engine performs above all expectation; he requests me to give him leave to build a great many more. I shall put two steam-valves and a steam-gauge in future, so that the quicksilver shall blow out in case the valve should stick, and all the steam be discharged through the gauge. A small hole will discharge a great quantity of steam at that pressure. There will be a railroad-engine at work here in a fortnight; it will go on rails not exceeding an elevation of one-fiftieth part of a perpendicular and of considerable length. The cylinder is 8-1/2 inches in diameter, to go about two and a half miles an hour; it is to have the same velocity of the piston-rod. It will weigh, water and all complete, within 5 tons. "I have desired Captain A. Vivian to wait on you to give you every information respecting Murdoch carriage, whether the large one at Mr. Budge's foundry was to be a condensing engine or not. "Is it possible that this engine might be burst by gas? "I am, Sir, "Your very obedient servant, "RICHARD TREVITHICK." This high-pressure puffer pumping engine at Greenwich, in 1803, worked a pump of 18 inches in diameter. The engine boy having fixed the safety-valve while he fished for eels, caused an explosion of the boiler. This was the first mishap from the use of high-pressure steam. The boiler was globular, 6 feet in diameter, and from an inch to an inch and half in thickness, made of cast iron; the cylinder, of 8 inches in diameter, was partly let into and fixed on the boiler. Its general design is seen in the patent drawing of 1802, Fig. 1.[62] Trevithick determined in future to use two safety-valves, and also a safety steam-gauge. At that time one of his high-pressure puffer-engines, with a cylindrical boiler and internal tube, was working in Staffordshire. [Footnote 62: See vol. i., p. 128.] The Greenwich high-pressure puffer-engine did fourteen millions of duty with a bushel of coals, 84 lbs. A 60-horse-power engine was being built in Wales, with an 8-feet stroke, to work expansively with 30 lbs. of steam on the inch in the boiler. For a more thorough test with the low-pressure vacuum engines, in competition, the Government intended to use the new engines, and some of Watt's engines having been removed to make room for them, Boulton and Watt wrote to a gentleman who was about to order an engine from Trevithick, "We knew the effects of strong steam long since, and should have erected them, but knew the risk was too great." Moreover, "it was an invention of Mr. Watt's, and the patent (Trevithick's) was not worth anything." This admission clearly shows not only that Watt did not make high-pressure steam-engines, but that he did his best to prevent others from making them. "MR. GIDDY, "PENYDARRAN, CARDIFF, _January 5th, 1804_. "Sir,--I received yours a few days since, and should have answered it sooner, but I was at Swansea for the last four weeks, and wished to return here to give you as full an account of our proceedings as possible. "We have had an 8-inch cylinder at work here by way of trial; it worked exceedingly well a hammer of the same size as is now being worked here by an atmospheric engine 28 inches diameter, 5-feet stroke, which does not master its work with greater ease than the 8-inch cylinder. The 8-inch is now removed to Swansea, and is winding coals; the baskets hold 6 cwt. of coal; it lifts 80 yards in a minute and a quarter, and burns 6 cwt. of coal in twenty-four hours. There were twelve horses on this pit before, lifting 80 tons of coal in the course of the twenty-four hours. You may fairly state that the 8-inch cylinder does between thirty and forty horses' work in twenty-four hours, with 6 cwt. of coal. "One of Boulton and Watt's 18-inch double engine, about half a mile from it, lifting baskets of the same size, and with the same velocity, burns above three times the quantity of coal. "The 8-inch engine requires the steam to be about 46 or 48 lbs. to the inch to do its work well. The standers-by would not believe that such a small engine could lift a basket of coal, but are now much pleased with it, and have given orders for several more. There will be another at work here for the same purpose in about six weeks, a 15-inch cylinder, 6-feet stroke, which is a great power for a winding engine. "Mr. Watt says, in a letter to Mr. Homfray, that he could not make any of his experiments in strong steam answer the purpose. It is my belief that he never made any experiments of any consequence in strong steam. "A great number are building at different foundries. Mr. Sharratt, a founder at Manchester, who has four in building, said that he would not pay the patent right; on giving him notice of a trial he agreed to pay the patent right. "I have received a letter from London, saying that an engineer called Dixon has two engines on the same plan working; and says that he shall not pay anything to the patentee; that the words in Mr. Watt's specification are enough to indemnify him from my threats. We have had three counsels' opinions on the subject, and they all agree that the patent is good. Counsels Marratt and Gibbs principally treated on the construction of the engine, more than on the principle; but Erskine was principally on the principle of the engine, and said very little of its construction. They all say the words in Mr. Watt's specification will have no weight whatever against us. "I shall leave this place to-morrow for London to make inquiry into those engines, and to get the business into court if they will contend. I shall be at No. 2, Southampton Street, Strand, and expect to be in town about five or six days, and if you will be so good as to return here, from Oxford, with me, I will call on you in my journey down. It is but 50 miles from Bristol, and not so much as 100 miles from Oxford, and the coach passes very near this place. "There is a great deal of machinery and mining here, which would engage your attention for a few days, and very pleasant gentlemen about the neighbourhood. "If I had not been called to Swansea to put up the winding engine, the road-engine would have been at work long since, but in my absence very little was done to it. The work is all ready, and a part of it put together. If I could tarry four or five days longer I could set it to work before going to London. They promise me that it shall be completed before my return. I think there is no doubt of its being finished, as I have Frank Bennetts here from Cornwall about it, and a plenty of hands to assist him. "I have a thousand things to relate to you, too much for paper to contain, therefore must request you to be so good as to go down from Oxford with me, and I will promise, on warrant, that the road-engine shall be finished before my return. When it is set to work I shall return to Cornwall. "I remain, Sir, "Your humble servant, "RICHARD TREVITHICK." In 1804 an 8-inch cylinder high-pressure puffer-engine, with steam of 48 lbs. to the inch, worked a large hammer as well as a 28-inch cylinder atmospheric engine, and more economically than a Watt low-pressure steam vacuum engine with an 18-inch cylinder, which was five times as large as the little high-pressure. In consequence of this superiority those who came to witness the trial ordered several more of Trevithick's engines, one of which with a 15-inch cylinder and 6-feet stroke was to be at work in a few weeks. Watt wrote to Mr. Homfray "that he could not make any of his experiments in strong steam answer the purpose," and Trevithick declared Watt never could have tried any experiments with high steam. Dixon refused to pay patent right because the words of Mr. Watt's specification, "in cases where cold water cannot be had in plenty, the engines may be wrought by the force of steam only, by discharging the steam into the open air after it has done its office," "are enough to indemnify him." Eminent counsel were of opinion that "the words in Watt's specification will have no weight whatever." Marratt and Gibbs were inclined to rest on the difference in the construction of the two kinds of engines, while Erskine boldly said that the principle was different, and he cared little for the kind of construction. The admission by Watt that he could do nothing with high steam after an experience of thirty years from the date of his patent, shows how difficult the work was to those who had to find the way; yet Trevithick had several at work within a few months of his first mental sight of a steam-engine without condensing water, fitful glimpses of which passed and repassed while he sat unobserved in the crowded law court in 1796 hearing the remarks of engineers and counsel. "The public until now called me a scheming fellow, but their tone is much altered. An engine is ordered for the West India Docks, to travel itself from ship to ship, to unload and to take up the goods to the upper floors of the storehouses. "Boulton and Watt have strained every nerve to get a Bill in the House to stop these engines, saying the lives of the public are endangered by them, and I have no doubt they would have carried their point, if Mr. Homfray had not gone to London to prevent it; in consequence of which an engineer from Woolwich was ordered down, and one from the Admiralty Office, to inspect and make trial of the strength of the materials."[63] [Footnote 63: See Trevithick's letter, 22nd February, 1804, vol. i., p. 161.] After a week or two another letter states,[64]-- "We are preparing to get the materials ready for the experiments by the London engineers, who are to be here on Sunday next. We have fixed up 28 feet of 18-inch pumps for the engine to lift water. "These engineers particularly requested that they might have a given weight lifted, so as to be able to calculate the real duty done by a bushel of coal. "As they intend to make trial of the duty performed by the coal consumed, they will state it as against the duty performed by Boulton's great engines, which did upward of twenty-five millions, when their 20-inch cylinders, after being put in the best order possible, did not exceed ten millions. As you were consulted on all those trials of Boulton's engines, your presence would have great weight with those gents, otherwise I shall not have fair play. Let me meet them on fair grounds and I will soon convince them of the superiority of the '_Pressure-of-steam engine_.'" [Footnote 64: See Trevithick's letter, 4th March, 1804, vol. i., p. 166.] Watt left no stone unturned to prevent the use of high-pressure steam-engines, and fortune favoured him, for after four or five days Trevithick again wrote:-- "I am sorry to inform you that the experiments that were to be exhibited before the London gents are put off, on account of an accident which happened to Mr. Homfray. I find myself much disappointed on account of the accident, for I was desirous to make the engine go through its different work, that its effect might be published as early as possible."[65] [Footnote 65: See Trevithick's letter, 9th March, 1804, vol. i., p. 168.] While constructing those numerous high-pressure engines for rolling mills, winding engines, and pumping engines, the Welsh and Newcastle locomotives were being made and worked, yet he found time to teach the people of Stourbridge. "MR. GIDDY, "STOURBRIDGE, _July 5th, 1804_. "Sir,--I should have answered your letter some time since, but waited to set two other engines to work first. The great engine at Penydarran goes on exceedingly well. The engine will roll 150 tons of iron a week with 18 tons of coal. The two engines of Boulton's at Dowlais burn 40 tons to roll 160 tons; they are a 24-inch and a 27-inch double. The engine at Penydarran is 18-1/2 inches, 6-feet stroke, works about eighteen strokes per minute: it requires the steam about 45 lbs. to the inch above the atmosphere. I worked it expansive first, when working the hammer, which was a more regular load than rolling; then with steam high enough to work twelve strokes per minute with the cock open all the stroke; then I shut it off at half the stroke, which reduced the number of strokes to ten and a half per minute, the steam and load the same in both; but I did not continue to work it expansively, because the work in rolling is very uneven, and the careless workmen would stop the engine when working expansive. "When the cylinder was full of steam the rollers could not stop it; and as coal is not an object here, Mr. Homfray wished the engine might be worked to its full power. The saving of coal would be very great by working expansively. "The trials we have made for several weeks past against Boulton's engines have been by working with the cylinder full of steam. The cock springs out of its seat when water gets into the cylinder, and prevents any mischief from the velocity of the fly-wheel. "The tram-engine has carried two loads of 10 tons of iron to the shipping place since you left this. Mr. Hill says he will not pay the bet, because there were some of the tram-plates in the tunnel removed so as to get the road into the middle of the arch. "The first objection he started was that one man should go with the engine, without any assistance, which I performed myself without help; and now his objection is that the road is not in the same place as when the bet was made. "I expect Mr. Homfray will be forced to take steps that will force him to pay. As soon as I return from here there will be another trial, and some person will be called to testify its effects, and then I expect there will be a lawsuit immediately. The travelling engine is now working a hammer. "At Worcester last week we put a 10-horse engine to work in a glover's manufactory. The flue from the engine is carried through the drying room and dries his leather. The steam from the engine goes to take the essence out of the bark, and also to extract the colour out of the wood for dyeing the leather. Then it boils the dye, and the steam that is left is carried into his hot-house. It works exceedingly well. This week I put another to wind coals at this place, a 10-horse power, which works very well. All the tradesmen are set against it; they say that there is no carpenter or mason work about it, and very little smith-work, and that it will destroy their business. The engineer on the spot is also against it very much. I do not expect that it will be kept long at work after I leave it, unless the proprietor takes care to prevent those people from doing an injury to it. Mr. Homfray was here yesterday, but is now returned to Penydarran. I shall go from here to Coalbrookdale. "There is an engine there almost ready for the West India Docks. It will be ready to send off to London in about four weeks. It will be a very complete engine. The pumps for forcing the water will be fixed on the back of the boiler. It will force 500 gallons of water 100 feet high in a minute; above ten times the quantity that engines worked by men can do. Mr. Homfray and myself shall be in town as soon as the castings are sent off. I hope you will be there at the time. If you wish to see the engines already at work in London, call on Mr. David Watson, steam-engine maker, Blackfriars Road. He lives up about 500 or 600 yards above the bridge on the left-hand side; you will see his name over his door. If you have time to inspect those engines you will find by comparing them against Boulton's, doing the same work, that there is a great saving of coal above other engines.... I shall go to Liverpool and Manchester from here, and again to Coalbrookdale. "There are three engines at the Dale begun, to work with condensers, for places where coal is scarce. I think it is better to make them ourselves, for if we do not, some others will, for there must be a saving of coal by condensing. But with small engines, or where coal is plentiful, the engine would be best without it. They say at the Dale about putting two cylinders, but I think one cylinder partly filled with steam would do equally as well as two cylinders. "That engine at Worcester shuts off the steam at the first third of the stroke, and works very uniformly. I cannot tell what coal it burns yet, but I believe it is a very small quantity. I shall know in a short time what advantage will be gained by working expansive. I expect it will be very considerable. There are a great many engines making and ordered. Boulton and Watt and several others are doing everything to destroy their credit, but it is impossible to destroy it now that it is so well known. I have not taken any of the ground at Bristol to remove. I called on them and told them it was possible to break the ground without men, and they wish me to take a piece to clear out, but would not set but a small piece at a time; therefore it would be disclosing the business to no purpose. They were very desirous to know the plan, but I would not satisfy them, neither will I unless they pay me for it in some way or other. If you direct for me at the Dale it will find me. I am happy to find that you have a seat in the House. I wish every seat was filled with such. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK." Trevithick fully understood the value of the expansive principle in 1804: when working with steam of 45 lbs. to the inch, the engine went at a speed of twelve strokes a minute. On cutting off the steam at half-stroke, the speed and consequent work done fell to ten and a half strokes a minute; in other words, the work performed by the engine fell off only one-eighth part, while the quantity of steam and consequently of coal was reduced by one-half. The principle was established, but the application was practically incomplete from the want of heavier fly-wheels, to give out their momentum during the latter half of the stroke, when the expanding steam was lessening its force. "The saving of coal would be very great by working expansively, but as coal is not an object here," Mr. Homfray was careless about the expansion. Thirty-three years after this indirect check to steam-engine economy, the writer, then living in the Sirhowey Iron Works, and within stone's-throw of Mr. Homfray's Works, recommended the removal of the Boulton and Watt's waggon boilers, to make room for Trevithick's boilers, on the plea of saving one-half the fuel, and at the same time increasing the power of the engine, and thereby the pressure of the blast in the iron furnaces. The proprietor was careless about the saving of coal, and was doubtful that an increased blast would increase the quantity of iron smelted. The promise that the wages of one-half of the number of boiler firemen would be saved, was understood. Trevithick's high-pressure boilers replaced the Watt low-pressure, resulting in a largely-increased quantity of iron from the greater power and pressure of blast in the furnaces, and at one-half the expenditure of coal in the boilers: ten men had been employed as firemen of the Watt boilers during twenty-four hours; with Trevithick's boilers, five men did the work. The high-pressure puffer-engine, with an 18-inch cylinder, working with 45 lbs. of steam, rolled as much iron as the two larger low-pressure vacuum engines of Watt, of 24 and 27 inch cylinders, which together were more than three times the size of the high-pressure engine, and cost three times as much. At Stourbridge, as elsewhere, everyone was against the new plan. The engineer in charge did not like it, and the carpenters, smiths, and masons saw the end of their occupation as engine erectors, if there was no longer a necessity for foundations, well-work, &c., for condensing water, and many other things, necessary to complete a Watt engine; while the high-pressure puffer was no sooner unloaded than it was ready to work. A great charm in Trevithick's character was his freedom and largeness of view in questions of competition. He was then making three engines at Coalbrookdale, to be worked with high-pressure steam, combined with the Watt air-pump and condenser; and though smarting from the contest with his great rival, yet wrote, "I think it is better to make them ourselves, for if we do not, some others will, for there must be a saving of coal by condensing. But with small engines, or where coal is plentiful, the engine would be best without it." Those words accurately describe the practice of the present day, though written sixty-six years ago, and were followed by others equally true in principle, though varied in form to suit special requirement. "They say at the Dale about putting two cylinders, but I think one cylinder partly filled with steam would, do equally as well as two cylinders." These sagacious views required the untiring labour of the following twelve years to perfect and make practical, when applied to the largest engines of the time; which we shall now trace in the construction of a strong and economical boiler, supplying high-pressure steam to the cylinder during only a comparatively small portion of the stroke, completing it by expansion, so that at its finish the steam had become of low pressure when passed to the condenser. The moving parts and expansive gear were so simplified as to be applicable to the then existing low-pressure steam vacuum engines without the complication of the double cylinders of Hornblower and Woolf. "DEAR SIR, "PENYDARRAN PLACE, _December 26th, 1804_. "I have been favoured with your letter, and in answer, respecting Mr. Mitchell, I am at a loss to know from your letter what kind of iron he may likely want. If you will direct him to write to me, and explain himself, I will immediately reply to him and do what I can to assist and serve him. I believe there are vessels going over frequently from Cardiff to Cornwall with coals, that he might have part in cargo and the remainder in coals. I am happy to give you the most satisfactory account of our 'Trevithick's engine' going on well. It has now been at work many months, and is by far the best engine we have. We have for weeks weighed the coal, and knowing the work it does, can speak with confidence. Its 18 inches diameter steam-cylinder consumes as near as can be 3 tons of coal in twenty-four hours, or 18 tons per week; and in this time it rolls with ease 130 tons long weight of iron from the puddling furnaces, at the same heat, into bars of 3 inches by about half an inch thick. Now, one on Messrs. Boulton and Watt's plan, of '24 inches' steam-cylinder, at our neighbouring works at Dowlais, employed in doing exactly the same kind of work, consumes _full_ as much coal, and rolls only 90 tons in the week. These being facts, open for any person daily to see, must convince any dispassionate man of the superiority of 'Trevithick's engines,' and that the saving of fuel is nearly one-third, besides the other advantages of saving water and grease, which is no little. The packing of the piston now gives us little or no trouble, it goes from a fortnight to a month, opening the top now and then to screw it down, as it gets slack, which should be attended to. We use no grease or oil in packing the piston or working the engine, having found blacklead mixed with water, and poured 'a little now and then' through a hole on the top into the steam-cylinder, suits the packing of the piston much better, and is cheaper than anything else. About 1_s._ worth of blacklead will last our engine a week. We are now so thoroughly convinced of the superiority of these engines that I have just begun another of larger size. The boiler is to be 24 or 26 feet long, 7 feet diameter, fire-tube at wide end 4 feet 4 inches, and at narrow end, where it takes the chimney, 21 inches, steam-cylinder 23 inches diameter. This boiler, on account of the length of its tube withinside, will, I have no doubt, get steam in proportion, and work the engine with much less coals than our present one. Trevithick is at Coalbrookdale, Manchester, &c., &c., very busy, a great number of engines being in hand in that part of the world; and I think by perseverance the prejudice is wearing away very fast, and in spite of all Messrs. Boulton and Watt's opposition, they must and will take the lead of theirs. Any person now wanting engines, must be next kin to an idiot to erect one of Boulton's in preference to Trevithick's. I find there is a small one making near you by Mr. Vivian. I hope they have corresponded with Trevithick about the proportions of it; if they have not, I shall be particularly obliged to you to desire them to do so, for by his experience of what he has done they may be benefited, for it would be a shocking thing to have a bad engine put up for the first time in his native county. "Mrs. Homfray unites with me in best compliments, and wishing you many happy returns of the season. "I remain, dear Sir, "Your most obedient servant, "SAMUEL HOMFRAY. "_To Mr. Davies Giddy._" The evidence in this contest between the Watt low-pressure steam vacuum engine and the Trevithick high-pressure steam-puffer engine is in favour of the new principle; for the steam-engine with an 18-inch cylinder did fifty per cent. more work than the vacuum engine with a 24-inch cylinder with an equal quantity of coal, though the latter was seventy-five per cent. larger than the former; and a still greater economy was expected from the larger boiler to be built, 26 feet long, 7 feet in diameter, with internal fire-tube 4 feet 4 inches diameter at the fire end, tapering to 21 inches at the chimney end. Thus in 1804 the cylindrical boiler in Wales had nearly reached its present form, and Homfray thought that none but idiots would prefer the Watt engine; forgetting that Trevithick's near friends and neighbours were carrying on a similar contest at Dolcoath Mine. "PENYDARRAN PLACE, _January 2nd, 1805_. "MR. DAVIES GIDDY, "Dear Sir,--I have duly received your favour enclosing a letter for Mr. Trevithick, and which I, according to your desire, forwarded to him at Manchester, where he now is; and a letter directed to him, to the care of Mr. Whitehead, Soho Foundry, Manchester, will find him, as he will stay a little time there, being very busy. I had lately the pleasure of writing to you, and gave you the account of our engine working, and the satisfaction it gives; I have nothing more to add on the subject, but that it is now at work, going on as usual, and I should be happy for you to have a sight of it. "We are beginning another of a larger size, and I have no doubt but by making the cylindrical boiler larger, so as to take a longer tube withinside it, by which means the fire will spend itself before it leaves the tube to go up the chimney, that we shall work to much better advantage in point of fuel than we do at this present one, as this boiler is so short that a great deal of the flame of the fire goes up the chimney. We are now better acquainted with the different proportions than we at first were, for which reason I am anxious that one now making by Mr. Vivian should be made according to the directions of Mr. Trevithick. "I beg leave to offer you the compliments of the season, and many happy returns, and "Remain, respectfully, dear Sir, "Your most obedient servant, "SAMUEL HOMFRAY." Trevithick, always busy, was just now doing the work of a host, for everybody had to be taught how to make high-pressure steam-engines; and the Newcastle locomotive, the Thames steam-dredging, and other special applications of steam-power required his presence, especially the fight with Watt at Dolcoath Mine, where Andrew Vivian, as mine manager, was erecting a high-pressure steam-puffer whim-engine to compete with a Watt low-pressure steam vacuum whim-engine. "The adventurers grumbled because Captain Trevithick was so often away from the mine. Glanville, the mine carpenter, the head man over the engines, made a trial between Trevithick's high-pressure puffer whim and Watt's low-pressure condenser. When Captain Trevithick heard of it, he wrote down from London that he would bet Glanville 50_l._ that his high-pressure puffer should beat Watt's low-pressure condenser. Then he came down from London and found that the piston of his engine was half an inch smaller in diameter than the cylinder. When a new piston was put in, she beat Boulton and Watt all to nothing. Persons were chosen to make a three or four weeks' trial, and when it was over, 'a little pit was found with coal buried in it, that Glanville meant to use in the Watt engine.'"[66] [Footnote 66: Recollections of Henry Clark, living at Redruth in 1869.] Pooly, Smith, and others, say that Trevithick's Dolcoath puffer had the outer case of the boiler of cast iron, the fire-tube of wrought iron, the cylinder horizontal, and fixed in the boiler. Captain Joseph Vivian saw Trevithick's whim in Stray Park Mine about 1800 or 1801, and a similar one was erected in Dolcoath, and after a year or two a Boulton and Watt low-pressure whim was put up to beat it. The trial was in favour of the Watt engine, but everybody said the agents were told beforehand which way the report ought to go; so the engine that _puffed the steam up the chimney_ was beaten. Trevithick, who was busily engaged in Manchester at that time, the early part of 1805, when informed of what was going on in Cornwall, wrote:-- "I fear that engine at Dolcoath will be a bad one. I never knew anything about its being built until you wrote to me about Penberthy Crofts engine, when you mentioned it. I then requested Captain A. Vivian to inform me the particulars about it, and I find that it will not be a good job. I wish it never was begun."[67] [Footnote 67: See Trevithick's letter, January 10th, 1805, vol. i., p. 324.] "MR. GIDDY, "CAMBORNE, _February 18th, 1806_. "Sir,--On my return from town I altered the pressure of the steam-engine at the bottom of the hill, Dolcoath. Before I returned there was a trial between mine and one of Boulton's; both engines in the same mine and drawing ores from the same depth. The result was, Boulton's beat the pressure-engine as 120 to 55. Since it was altered there have been three other trials; the result was 147 to 35 in favour of the pressure of the steam-engine. They are now on trial for another month, and at the next account _they intend to order a new boiler for the great engine_, and work with high-pressure steam and condenser, provided this engine continues to do the same duty as was done in the former trials. This engine is now drawing from a perpendicular shaft, and Boulton and Watt's from an underlay shaft; but to convince Captain Jos. Vivian, we put it to draw out of the worst shaft in the mine, and then we beat more than three to one; we lifted in forty-seven hours, 233 tons of stuff 100 fathoms with 47 bushels of coal. The engine was on trial sixty-six hours, but nineteen hours were hindered by the shaft and ropes, &c., which made the consumption of coals about 3/4ths of a bushel per hour. The fire-tube is 2 feet 3 inches diameter, and the fire-bars were only 14 inches long. The fire-place was but 2 feet 3 inches wide by 14 inches long, and the fire about 4 or 5 inches thick; it raised steam in plenty; it was as bright as a star. The engine is now doing the work of two steam-whims; the other steam-whim in the Valley is turned idle, and both shafts will not more than half supply it. 233 tons are equal to nearly 2000 kibbals, which were drawn in forty-seven hours. "Mr. Harris has a 12-inch cylinder making at Hayle, for Crenver, and Mr. Daniel has a 14-inch for Perran-sand, and a great number are waiting for the trial of this month, _before altering their boilers to the great engines_. "The steam-whim that is now turned idle at the Valley was 13-1/2-inch cylinder, 4-feet stroke; it turned the whim one revolution to one stroke, and lifted the kibbal the same height at a stroke as my engine did, and I think took the same number of gallons of steam to lift a kibbal as mine did. Their steam was not above 4 lbs. to the inch; _mine was near 40 lbs. to the inch_; yet I raised my steam of near 40 lbs. with a third of the coals by which they got theirs of 4 lbs. to the inch. This is what I cannot account for, unless it is by getting the fire very small and extremely hot. Another advantage I have is, that there is no smoke that goes off from my fire to clog the fire sides of the boiler, while the common boilers get soot half an inch thick, and the mud falls on the bottom of the boiler, where the fire ought to act; but in these new boilers the mud falls to the bottom, where there is no fire, and both the inside and outside of the tube are clean and exposed both to fire and water. This fire-*place[**hyphenated below] of 14 inches was 5 feet long when I came down, and then the coal did not do above one-seventh of the duty that it now does. "I would be very much obliged to you for your opinion on what I have stated, and what _advantage you think the great engine is likely to get from working with steam about 25 lbs. to the inch, and shut off early in the stroke, so as to have the steam about 4 lbs. to the inch when the piston is at the bottom. I think this, with the advantage of the fire-place, will make a great saving._ "The present fire-place is 22 feet from fire-door to fire-door, 9 feet wide, and 7 feet thick in fire. There is not one-tenth of the coals that are in the fire-place on fire at the same time; it will hold 30 tons of coals at one time, and I think that a great deal of coal is destroyed by a partial heat before it takes fire. A boiler on the new plan will not cost more than two-thirds of the old way, and will last double the time, and can be cleaned in three hours. It requires twenty-four hours in the old way, and we need to clean the boilers only one-fourth the number of times. "Though these trials have shown so fairly that it is a great advantage, my old acquaintances are still striving with all their might to destroy the use of it; but facts will soon silence them. "I am about to enter into a contract with the Trinity Board for lifting up the ballast out of the bottom of the Thames for all the shipping. The first quantity stated was 300,000 tons per year, but now they state 500,000 tons per year. I am to do nothing but wind up the chain for 6_d._ per ton, which is now done by men. They never lift it above 25 feet high. A man will now get up 10 tons for 7_s._ My engine at Dolcoath has lifted above 100 tons that height with 1 bushel of coals. I have two engines already finished for this purpose, and shall be in town in about fifteen days to set them at work. They propose to engage with me for twenty-one years. The outlines of the contract they have sent me down, which I think is on very fair terms. I would thank you for your answer before I leave this county. "I am, Sir, "Your very humble servant, "RD. TREVITHICK." In the trial at Dolcoath during his absence the high-pressure steam-puffer whim was beaten by Watt's low-pressure steam vacuum whim-engine as 55 to 120; but having corrected some oversight in the puffer-engine, it then beat Watt as 147 to 35. The trial was to be continued for a month; and provided the superiority of his whim-engine could be maintained, the adventurers would allow him to apply his high-pressure boilers to their large Boulton and Watt pumping engine. The trial with the whim-engines was for the greatest number of kibbals of mineral raised to the surface by the least consumption of coal. A dispute arose on the difference of the shafts, the one causing more friction to the moving kibbal than the other, when Trevithick agreed to take the worst shaft in the mine. On a trial during sixty-six hours Watt's engine was beaten by more than four times; and as Trevithick's engine did the work that before required two engines, one of the low-pressure steam Watt engines was removed that the engine working with 40 lbs. on the inch might perform the whole work. "My fire-tube is 2 feet 3 inches in diameter, and the fire-bars only 14 inches long, and the fire only about 4 or 5 inches thick; it raised steam in plenty, and was as bright as a star." These words certainly imply the use of the blast-pipe, making the fire as bright as a star, and enabling the small boiler to give the required supply of steam. Several high-pressure puffer-engines had been ordered, and many persons were waiting the conclusion of the month's public trial to enable them to judge between the Watt and the Trevithick engine. "MR. GIDDY, "CAMBORNE, _March 4th, 1806_. "Sir,--The day after I wrote to you the first letter, I received yours, and this day I have yours of the 1st instant. "I am very much obliged to you for the figures you have sent me. I am convinced that the _pressure of steam will not hold good as theory points it out, because on expanding it will get colder, and of course lose a part of its expansive force after the steam-valve shuts_. I think there can be no risk in making this trial on Dolcoath great engine, as they intend to have a new boiler immediately, so as to prevent stopping to cleanse; and a boiler on this new plan can be made for one-third less expense than on the old plan, when you count the large boiler-house and ashes-pit, and brickwork round the boiler. It is not intended to alter any part of the engine or condenser, but only work with high steam from this new boiler; and if this boiler only performs as good duty as the old one, it will be a saving of near 300l. to them on the erection. _The vast matter this great engine has in motion will answer in part the use of a fly-wheel_: the whole of the matter in motion is near about 200 tons, at a velocity of about 160 feet a minute. This I know will not be sufficient; but it will be about equal to a fly-wheel of 20 feet diameter, 25 tons weight, twenty rounds per minute, if weight and velocity answer the same purpose. "Since Monday, the 18th February, being Dolcoath account-day, both engines have been on trial, and are to be continued until the next account, 17th instant. The engines are kept on in the usual way, as at other times. Neither of the engines have done so much duty as on the first trials, as they have not been so strictly attended to. The average of the trial at this time stands 26 cwt. for a bushel of coals to Boulton and Watt's engine; mine, 83 cwt. for a bushel of coals. "If I do not remain in Cornwall to attend next Dolcoath account, I shall be in town about the 15th instant, otherwise about the 20th instant. I shall call on you immediately on my arrival. In this time I should be glad to hear from you again. The Trinity business will answer exceedingly well; I have two engines ready for that purpose to put to work on my arrival in town. "I am, Sir, "Your very humble servant, "RD. TREVITHICK. "P.S.--I would try the evaporation of water by both boilers, but Boulton and Watt's engine is so pressed with work, and being on the best part of the mine, they will not stop it a moment. A boiler of 8 feet diameter and 30 feet long will have as much fire-sides in the tube as there is now in Dolcoath great boiler. The fire-tube in this boiler would be 5 feet diameter, and a fire-place 6 feet long in it would be 30 feet of fire-bars. In the whim-engines I find that a fire-place 14 inches long and the tube 2 feet 3 inches diameter would, being forced, burn 1 bushel per hour. At this rate the great tube would burn near 12 bushels per hour, which is above the quantity that the great engine boiler can consume, now at work. Small tubes would have an advantage over large ones. Two boilers would not cost much more than one large one, and be much stronger." The battle-ground of the fight between low and high pressure from 1806 to 1812 had also served for the personal encounter of Trevithick, sen., and Watt a quarter of a century before, when the Dolcoath great pumping engine was erected to compete with the two earlier atmospherics; all three were still at work, overlooked by Carn Brea hill and castle, once the resort of Druid priests, whose sacrificial rites are still traced, by the hollows and channels for the blood of victims on the granite rocks. [Illustration: CARN BREA CASTLE. [W. J. Welch.]] "MR. GIDDY, "CAMBORNE, _March 21st, 1806_. "Sir,--The trial between the two engines ended last Monday, which was Dolcoath day. Boulton and Watt's engine, per average of trial, 1 ton 20 cwt. 2 qrs., with 1 bushel of coals; the other, 5 tons 11 cwt. 3 qrs., with 1 ditto, the same depth of shaft. The adventurers ordered the new castings that were made for another of Boulton and Watt's engines to be thrown aside, and another new engine of mine to be built immediately. The great boiler for the old engine is not yet ordered. "I have received orders for nine engines within these four weeks, all for Cornwall. Two 12-inch cylinders, two 16-inch ditto, three 9-inch ditto, one 8-inch ditto, one 7-inch ditto. I expect one will be put to work next week at Wheal Abraham, for lifting water. "This day I shall leave Cornwall for London. Shall stop two days in the neighbourhood of Tavistock, and take orders for three engines. As soon as I arrive in town I will call at your lodgings. I expect that the patent will be brought into court about the end of May. A person in Wales owes us about 600_l._ patent premium, and he says that the patent is not good. More particulars you shall have on my arrival. "The railroad is going forward. I have the drawings in hand for the inclined plane. "I am, Sir, "Your very humble servant, "RD. TREVITHICK." The fact that expansion of steam caused reduction of heat was so evident to Trevithick that he ventured to doubt his friend's theory. The trials between the whim-engines having continued a fortnight, showed that the high-pressure steam-puffer had lifted 83 cwt., while the low-pressure steam vacuum only lifted 26 cwt. with the consumption of a bushel of coal. A suitable high-pressure boiler for the Watt low-pressure steam 63-inch pumping engine should be 30 feet long, 8 feet in diameter, with an internal fire-tube 5 feet in diameter; proportions approved of in the present day. The recommendation in 1806 to use small tubes may claim to be the first practical decision on the advantage of tubular boilers; and at the same time we read of the first hesitating step on the part of the public to use high-pressure steam in a Watt low-pressure engine, which was still deferred for further consideration, even with the limited pressure of 25 lbs. to an inch; so the large Watt pumping engines were doomed for another four or five years to struggle through their work with low-pressure steam, though at that time Cook's Kitchen high-pressure expansive condensing whim-engine had been for years at work close by. The shareholders professed to have fear of explosion; but party-feeling and ignorance were the real causes of opposition, for working men had no dread of the new engines, while influential men leaned toward Watt's old-fashioned plans. This fear of Trevithick's expansive plans and high steam is the more surprising, because at that time a new boiler was required for the Watt 63-inch cylinder pumping engine and Trevithick's cylindrical tubular boiler could be made for one-third less cost than the Watt waggon boiler, thus saving 300_l._, and in addition he promised to apply the higher pressure of steam to the Watt engine without any change in its parts or expenditure of money, and make it set in motion at the commencement of the stroke the 200 tons of pump-rods, the momentum of which would, with the expansion of the steam, when shutting it off soon after the first start in the movement of each stroke, carry it through to the end; and he practically compares this advantage from hoarded momentum in the pumping engine with his experience of the fly-wheel of the rolling-mill expansive engine in Wales. The whim-engine with a fire-tube 2 feet 3 inches in diameter used 84 lbs. of coal per hour; and at that rate one cylindrical boiler 30 feet long, 8 feet in diameter, with internal fire-tube 5 feet in diameter, would supply steam for Watt's 63-inch cylinder; but in place of it he preferred two smaller boilers, because small tubes have an advantage over large ones, and are much stronger. The whim trials--high-pressure puffer against low-pressure vacuum--went on for another fortnight, when high pressure, having done twice as much work as low pressure, with an equal consumption of coal, the adventurers threw aside the work that had been made for another Watt engine, ordering one in its stead from Trevithick; but they could not just then make up their minds to place the Watt 63-inch pumping engine in his hands. "DEAR SIR, "CAMBORNE, _May 30th, 1806_. "I am very happy to find you have so far continued your agreement with the Trinity gents, and think the bargain is a good one. Must still beg leave to remind you not to proceed to show what your engine will do till the agreement is fully drawn up and regularly signed. "Dolcoath agents, since they are informed of the accident at the iron-works in Wales, _of the engine blowing to pieces_, have requested me to have your opinion whether the old cylinder is strong enough for the boiler of the intended new engine, or whether you would recommend them to have a new one. Your answer to this as soon as possible, as Mr. Williams and some others are likely to make some objections. "Mr. Sims, the engineer, has published in the Truro paper, that one of Boulton and Watt's engines at Wheal Jewell has drawn more than a ton of ore over and above that drawn by the Dolcoath engine from the same depth by a bushel of coal. On inquiry I found they had only tried for twenty-two hours. They said they left off with as good a fire as they began with. This I argued was not a fair trial. They say they are now on a trial for a month. "The little engine at Wheal Abraham does its duty extremely well. The particulars as to consumption of coal cannot be fairly ascertained, as she has never been covered, is fed with cold water, and has not water to draw to keep her constantly at work. "I wish I could give a better account of the mines than is in my power to give, or of the standard price for ore, though the latter is rather looking up than otherwise. Our friend, North Binner Downs, is better than paying cost, but very little. At present the levels are all poor; the lode in the west shaft has underlayed faster than the shaft, and we have not seen it for several fathoms. The ground lately in the shaft has been cleaner killas, and if any alteration, better ground. It is now 9 fathoms under the 55-fathom level, and we are driving to cut the lode. The ground in the cross-cut is harder than when you were on the spot. The water is sinking in old Binner; it is about 7 fathoms under the adit in the western part, and deeper in the eastern part; we do not account for this. Wheal St. Aubyn combined poor. Wheal Abraham looks promising, and Creuver about paying cost. Dolcoath is better than when you left us, or when I was in London. The last sale was only about 800 tons. The next sale on Thursday is upwards of 1100 tons, and we expect a little better standard. "I wish you could discover who that old gent is that wanted a large slice in Dolcoath, that I might get at him through some unknown channel, for I want money sadly. "Cook's Kitchen continues poor, Tin Croft ditto; Wheal Fanny not rich. We had a pretty little fight last account there with T. Kevill and W. Reynolds, Esquires: black eyes and bloody noses the worst effects. T. Kevill's face was much disfigured, and he might have found a new road out of his coat. "At a meeting of Condurrow adventurers yesterday, twenty-four of them agreed to have one of our engines, cylinder 12 inches in diameter and 6-feet stroke, provided the Foxes do not object to it. When the order is given I shall write to Mr. Hazeldine, provided I do not hear from you that it is better to send the order to any other place. "If you have occasion to write Mr. Hazeldine, I wish you would press him to hasten the engines for Wheal Goshen, &c. "I am served with a Vice-warden's petition by Mr. Harris for not working the Weith mine in a more effectual manner, and he prays the Vice-warden to make the sett void. The trial will come on some time the beginning of July, and by that time I suppose we shall have two fire-engines working thereon. "Had Mr. Harvey done as he was desired we should have had one working there at this time, but he has but now begun to do anything to it. We have the cylinder and ends home from Polgooth, and my cousin Simon Vivian is making the tubes. We have the other cylinder from Wheal Treasury, and I have ordered Horton to cast a cock for it the same as that at Dolcoath. We have cut the south lode at the adit level about 50 or 60 fathoms east of the engine, and have driven about 20 fathoms on it. It turns out about half a ton per fathom at 20_l._ a ton. The ground at 40_s._ per fathom; this all in a hole, and is better going down. The back is sett to four men at 3_s._ 11_d._; their time is out this week, and I suppose they must have 5_s._ next. This may turn out a few thousands, and I think too promising a thing to give up to Mr. Harris. "I am happy to inform you that all our friends are in good health, and beg my most respectful compliments to Mrs. Rogers and adopted son; and am, "Dear Sir, "Yours very sincerely, "ANDW. VIVIAN. "The promised news respecting the engine business I am very anxious to have, as it will I hope make me _proud_, as proud I shall be when I am able to pay everyone their demands, and have sufficient to carry on a little business to maintain my family and self without the assistance of others. May you succeed in your undertaking and also be independent, is the sincere wish of your friend. John Finnis and others are anxious to know when they will be wanted. "A. V." The explosion at Greenwich in 1803 was made much of, though the fault was clearly not in the boiler. Three years afterwards, in 1806, a steam-cylinder burst in Wales, therefore Mr. Williams, a large shareholder in Dolcoath, objected to the use of high-pressure expansive steam in their large Watt pumping engine, and desired their engineer, Mr. Sims, to make a competitive trial after his own fashion. At Condurrow Mine one of Trevithick's engines was to be ordered if the Foxes and Williamses did not object; and so it was that Trevithick's high-pressure steam-boiler was not ordered, and the Watt vacuum engine was for a longer time to receive no increase of power. "Some of Captain Dick's early boilers had flattish or oval fire-tubes. In 1820 I repaired an old one in Wheal Clowance Mine in Gwinear. The flat top had come down a little; we put in a line of bolts, fastening the top of the tube to the outer casing. "About 1818 I saw in Carsize Mine in Gwinear a pumping engine that Captain Dick had put up. The boiler was a cylinder of cast iron, with a wrought-iron tube going through its length in which the fire was placed. The steam-cylinder was vertical, fixed in the boiler. She had an air-pump and worked with a four-way cock. The steam was about 100 lbs. to the inch."[68] [Footnote 68: Banfield's recollections in 1869.] "About 1820 I removed one of Captain Trevithick's early high-pressure whim-engines from Creuver and Wheal Abraham, and put it as a pumping engine in Wheal Kitty, where it continued at work for about fifteen years. The boiler was of cast iron, in two lengths bolted together, about 6 feet in diameter and 10 feet long. At one end a piece was bolted, into which the cylinder was fixed, so that it had the steam and water around it. There was an internal wrought-iron tube that turned back again to the fire-door end, where the wrought-iron chimney was fixed; the fire-grate end of the tube was about 2 feet 6 inches in diameter, and tapered down to about 1 foot 6 inches at the chimney end. It was a puffer, working 60 lbs. of steam to the inch; it worked very well. There were several others in the county at that time something like it. It was made at the Neath Abbey Works in Wales."[69] [Footnote 69: Recollections of Captain G. Eustace, engineer, residing at Hayle, 1868.] These boilers were of the kind first tried in Cornwall about 1800. The oval tube in the Kensington model of 1798 continued in use in Cornwall for many years. The cast-iron outer casing was soon abandoned, though one of them in Wales remained in work fifty years, using steam of 60 lbs. to 100 lbs. to the inch. "MY DEAR JANE, "HAYLE FOUNDRY, _August 26th, 1810_. "I saw Captain Andrew Vivian on Wednesday, who told me that he had been offered 150_l._ a year to inspect all the engines in the county, and report what duty they were doing, in order to stimulate the engineers. He declined accepting it, having too much to do already; and he thought it would be worth Trevithick's notice, as it would not take him more than a day or two in a month. "I remain, my dear Jane, "Yours sincerely, "H. HARVEY. "I wrote this letter on Sunday, with an intention of sending it then, but thought it best to wait until this day, in hopes of hearing the determination of Government in your favour; but your letter has arrived without the desired information. All that I can now say is, to desire that Trevithick will make up his mind to return to Cornwall immediately. "H. H." The application to the Government for remuneration for benefits conferred on the public was unsuccessful. The office of registrar of Cornish engines was unsuitable; fortunately for mining interests, illness obliged Trevithick to revisit his native county, for by the increased power and economy of his engines Dolcoath Mine, so frequently mentioned, and so important in olden time, now returns 70,000_l._ worth of tin yearly. Trevithick's first act on returning to Cornwall in 1810 was the erection of the high-pressure boilers and pole vacuum engine at Wheal Prosper; at the same time renewing his proposals to Dolcoath to use his improved boilers, which had been broken off in 1806, and to apply high-pressure steam to their low-pressure Watt engine, with the same safety and profit as in Wheal Prosper; the evidence was undeniable, so his plans were agreed to, and in the early part of 1811 the high-pressure boilers, called the Trevithick or Cornish boilers, were constructed in the Dolcoath Mine under his directions. Old John Bryant, who worked the Dolcoath large engines both before and after the introduction of higher pressure steam, including the Carloose or Bullan Garden 45-inch cylinder engine, Wheal Gons 63-inch cylinder single engine, and the Watt 63-inch cylinder double, with the bee-but boiler, such as Trevithick, sen., used in 1775,[70] followed by the Watt waggon boiler, and afterwards by the globular boiler of Trevithick, jun., in 1799,[71] and still later also with the cylindrical boiler of 1811, gave the following statement, when seventy-four years old, to the writer:-- [Footnote 70: See vol. i., p. 25.] [Footnote 71: See vol ii., p. 119.] "In the old bee-but and the waggon boiler the steam pressure in the boiler was not much; we did not trouble about it so long as the engines kept going: when the steam was too high it blew off through the feed-cistern. When Captain Trevithick tried his high steam in Dolcoath we hoisted up the feed-cistern as high as we could; when the steam got up, it blew the water out of the cistern. Captain Dick holloed out, 'Why don't you trig down the clack?' "The cylindrical boilers when they were first put in leaked very much; we could hardly keep up the fire sometimes. I reckon the steam was 30 or 40 lbs. to the inch. Captain Dick's boilers made him lots of enemies. I heard say in one mine where he was trying his boilers against Boulton and Watt's waggon, a lot of gunpowder was put into the heap of coal."[72] [Footnote 72: Old John Bryant's statement in 1858.] The waggon or hearse Watt boiler was attached to his 63-inch cylinder double, and the old man recollected having raised the water cistern, when Trevithick's globe boiler gave an increased pressure in 1799, ten or twelve years before the cylindrical boilers were made in Dolcoath. "Some time after Captain Dick's globe boiler and steam-whims had been at work in Dolcoath, a letter came down from London, saying that he would save the mine 100_l._ a month if they would put in one of his new plan boilers. "They were put in hand in the mine, and I worked about them; they were wrought-iron cylindrical boilers, about 20 feet long, and 5 or 6 feet in diameter; the fire-tube was about 3 feet in diameter; the fire returned around the outside in brick flues. Three boilers were put in side by side. "When Captain Dick first tried them, he said to the men, Now mind, the fire-bars must never have more than six inches of coal on them; give a shovel or two to one boiler, and then to another. When Captain Dick's back was turned, the men said they wasn't going to do anything of the sort, there would never be no rest for them. They used to say that the boilers saved more than 170l. the first month."[73] [Footnote 73: Clark's recollections in 1869, when he was eighty-three years old, and resided at Redruth.] Clark, when a boy, in 1799, helped to construct Trevithick's globular boiler in Dolcoath, and recollected the events of the few following years, during the contests with the whim-engines about 1806, and the introduction of the large cylindrical wrought-iron boilers for the pumping engines in 1811, and the struggle preceding the downfall of the Watt low-pressure steam vacuum engine, to make room for the high-pressure expansive steam-engine, with or without vacuum. "About 1812 Captain Trevithick threw out the Boulton and Watt waggon boilers at Dolcoath and put in his own, known as Trevithick's boiler. They were about 30 feet long, 6 feet in diameter, with a tube about 3 feet 6 inches in diameter going through its length. There was a space of about 6 inches between the bottom of the tube and the outer casing. Many persons opposed the new plans. The Boulton and Watt low-pressure engine did not work well with the high steam, and the water rose in the mine workings. Captain Trevithick, seeing that he was being swamped, received permission from the mine managers to dismiss the old engine hands and employ his own staff. Captain Jacob Thomas was the man chosen to put things right. He never left the mine until the engine worked better than ever before, and forked the water to the bottom of the mine. Before that time the average duty in the county by the Boulton and Watt engines was seventeen or eighteen millions, and in two or three years, with Trevithick's boilers and improvements in the engines, the duty rose to forty millions. About 1826 he (Captain Vivian) was manager of Wheal Towan; their engines were considered the best in the county, doing eighty-seven millions; they had Trevithick's boilers, working with high-pressure steam and expansive gear; few if any of Boulton and Watt's boilers could then be found in the county. Sir John Rennie and other scientific men, who doubted the reports of the duty, came and made their own trials with the engines, and were satisfied that the duty was correctly reported. "About that time a Mr. Neville requested him to report on the engines at his colliery at Llanelthy; one was an atmospheric of Newcomen's, doing six millions; and four or five of Boulton and Watt's patent engines averaged fourteen millions."[74] [Footnote 74: Captain Nicholas Vivian was a schoolfellow and intimate friend of Trevithick's; he resided at Camborne in 1858, when he gave his recollections.] When at last the cylindrical high-pressure boiler was admitted, and men had been taught to fire them, many persons still liked the old plans, and among them the easy-going low-pressure enginemen. The consequence was that the Watt engines under their management refused the early doses of Trevithick's high steam, not easily digesting it, and their obstinacy nearly swamped Trevithick and his plans. "When a little boy, about 1812, I frequently carried my father's dinner from Penponds to Dolcoath Mine. One day, not finding him in the engine-house, I sought him in the account-house, but not knowing him in a miner's working dress, refused to give him his dinner. William West then worked with him. I heard there was difficulty in making the new boilers and the old engine work well; engineers from other mines looked on from a distance, not liking the risk of explosion. People seemed to be against the new plans; some labourers worked with them." This narration--sixty years after the events--from Mr. Richard Trevithick, the eldest son of the engineer, shows that William West helped in applying high-pressure steam to the Watt low-pressure engine, and that but few sympathized with the innovators on old customs; but among them was Captain Jacob Thomas, who successfully fed the old engine with strong steam. At that time the Watt engines in Cornwall had been doing seventeen or eighteen millions; Trevithick's new boilers increased their duty to forty millions. "William Pooly[75] was working in Dolcoath before Captain Trevithick's new boilers were put in, and helped to put them in. [Footnote 75: William Pooly worked the Dolcoath 76-inch engine in 1869; his recollections were given in the old engine-house, on the spot once occupied by Watt and his 63-inch great double engine.] "The Shammal 45-inch engine was an open-top cylinder, with a chain to the segment-head wooden beam. So was the 63-inch cylinder Stray Park engine, then called Wheal Gons[76] in Dolcoath sett, and the Boulton and Watt 63-inch cylinder double-acting. [Footnote 76: Smiles speaks of this as Bonze's.] "There used to be great talking about different boilers; a boiler of Captain Trevithick's worked with higher steam than the others. Just before Captain Dick came back to the mine a Boulton and Watt hearse boiler had been repaired with a new bottom; it was never used. I and William Causan took a job to cut up the boiler at 1_s._ 6_d._ the hundredweight; it weighed 17 tons. Jeffrie and Gribble were the mine engineers; Glanville used to be considered Captain Dick's man in the mine. You could stand upright on the fire-bars in the middle hollow of the hearse boiler, and so you could in the outside brick flues; the middle hollow was like a horse-shoe. When Captain Dick put in his cylindrical boilers he altered the 63-inch single; there was hardly anything of her left but the main wall, with the wood bob and a chain to the piston-rod, and also to the pump-rods. There was an air-pump, and I think a second-hand cylinder was brought, but it was a 63-inch; the old Shammal engine had been altered, too. "The new boiler put in was about 8 feet in diameter and from 30 to 40 feet long, two round tubes went through it; the fire-place in one end of one tube and in the other end of the other tube; after going through the tubes the draught went into the brick flues under the bottom and sides. When the new engine was put in, Gribble said, �Why, these little things will never get steam enough;� everybody said so. "In the Boulton and Watt engines we didn't trouble about feed-pumps and gauge-cocks. "A wire came through a stuffing box in the top of the boiler; a biggish stone in the boiler was fastened to one end of the wire, the other end was fastened to a weighted lever near the water cistern, just above the boiler; when the water got low the stone opened the valve in the water cistern. That was when they were putting in Captain Dick's new cylindrical boilers to the old 63-inch engine. She did so much more work, with less coal, that in a year or so they agreed to throw out Boulton and Watt's engine, and to put in a stronger one that could stand Captain Dick's high steam. Jeffrie and Gribble were the mine engineers that put her up. The 76-inch cylinder came from Wales. The big beam was cast at Perran Foundry in 1815; you can see the name and date upon it now. The boiler and the gear-work were made in the mine. The exhaust-valve is exactly as when it was put in, worked by a rack-and-tooth segment. The equilibrium valve is unchanged, except that the rack is taken out and a link put in. "The steam-valve was taken out soon after she went to work, and the present double-beat valve was put in; it is the first of the kind I ever saw. Some were made before that time with a small valve on the top of the big one, that opened first, to ease the pressure. "John West[77] fitted up the valve-gear in the mine with the expansive tappets, the same as when she stopped a month or two ago, and the same as the present new one has. [Footnote 77: Three Wests, all skilful mechanical engineers, were employed at that time in Dolcoath, all of them known to the writer, who thinks the double-beat valve was the handiwork of John West, not related to Trevithick's partner.] "Captain Dick's cutting off his strong steam at an early part of the stroke, used to make the steam-valve strike very hard; so the new plan valve, with a double beat, was put in; that must have been about 1816 or 1817; and the valve and expansive horn for working were just exactly like what they have put into the present new engine in 1869. She was the engine that showed them how to fork the water, and burn only half the coal. "I worked in this mine the old atmospheric engines, and then Boulton and Watt; and then Trevithick's boilers in Boulton and Watt; and then Trevithick's boilers and engine; and now I come every day to the new engine, though I can't do much. They give me 35_s._ a month; and my name is William Pooly, Dolcoath, 1869." Three years ago (in 1869), when the writer entered the old engine-house in which Watt's 63-inch cylinder double had been erected in 1780, adjoining the old walls that then enclosed that early Newcomen 45-inch cylinder Carloose engine, re-erected by Trevithick, sen., in 1775 in Bullan Garden portion of Dolcoath, an old man sat near a small window in a recess in the thick wall of the engine-house, within reach of the gear-handles of the Jeffrie and Gribble 76-inch cylinder engine that Trevithick, jun., had erected in 1816 on the foundations of the removed Watt engine; he held in one hand a portion of slate from the roof, and in the other an old pocket-knife, one-half of the blade of which had been broken off, leaving a jagged fracture, with which he made the figures of some calculation on the rude slate; on his nose rested the brass frame of a pair of very ancient spectacles, with horn glasses. He answered the writer's question by, "Yes, I am William Pooly; I worked this engine, and the other engines before it--the great double and the little Shammal working out of the same shaft; and I am seventy-four years of age. The 63 single worked upon a shaft up there; she was called Wheal Gons." That old man, still living, had worked in Dolcoath Mine one of the first steam-engines of Newcomen; the 45-inch, modified by Trevithick, sen.; then the 63-inch double of Watt; and, finally, the high-pressure engines of Trevithick, jun.; he saw the open-top cylinders, atmospheric of Newcomen, in the Shammal 45-inch and Wheal Gons 63-inch, with their wooden beams with segment-headed ends, moving in rivalry with the Watt 63-inch double, with cylinder-cover and parallel motion; he saw the two former engines, as altered by Trevithick, jun., using the higher steam from the globular boiler on which Henry Clark worked in 1799, when "there used to be great talking about different boilers, and a boiler of Captain Trevithick's worked with higher steam than the others; and the waggon boiler of Watt, that had just been repaired, was discarded and cut up;" thus described by Trevithick, "the fire-place is 22 feet from fire-door to fire-door, 9 feet wide, and 7 feet thick in fire,"[78] which he proposed to replace in 1806 by a cylindrical boiler to give steam of 25 lbs. on the inch. [Footnote 78: See Trevithick's letter, February 18th, 1806, vol. ii., p. 143.] Pooly also saw the finishing stroke in 1811, when the boilers still known as the Trevithick or Cornish boilers, gave steam to the three engines; after a twelve years' fight between low and high pressure, commencing with Trevithick's globular boiler and internal tube, in Dolcoath, in the year 1799, from which time it gained step by step, though in comparatively small engines, up to 1811, when the cylindrical boilers took the place of the condemned hearse and globular boilers, and gave really strong and expansive steam to the three Dolcoath pumping engines that from time immemorial had been rivals, causing all three of them to lift an increased quantity of water, and at the same time to save one-half in the cost of coal; this continued for four or five years, when in 1816 the 63-inch double and the 45-inch, being the youngest and the oldest of the three, were removed, that a new 76-inch cylinder, better adapted to Trevithick's expansive steam might more cheaply perform their joint work. Prior to this change the three engines were known by the names Shammal 45-inch, formerly Bullan Garden,[79] but before that as Carloose, of the period and form of the Pool engine;[80] Stray Park 63 single, formerly Wheal Gons,[81] dated from 1770 to 1777; and the 63-inch double of Watt in 1780. [Footnote 79: See vol. i., p. 25.] [Footnote 80: See vol. i., p. 5.] [Footnote 81: Query Bonze, spoken of by Smiles.] "SIR, "DOLCOATH MINE, _March 29th, 1858_. "I have obtained the following information respecting the building of the first cylindrical boilers, as ordered by your late father for Dolcoath; and some information of the results as to the coals consumed, compared with the consumption by the boilers previously in use here. "George Row, now about seventy-two years old, and working at Camborne Vean Mine, says he assisted to build the two first cylindrical boilers with internal tubes used in Cornwall. They were built in Dolcoath Mine in the year 1811; they were 18 feet long, 5 feet diameter, having an oval tube 3 feet 4 inches in the largest diameter at the fire end; the other or chimney end of the tube was somewhat smaller. They were found too small for the work to be done, and another boiler was built immediately, 22 feet long, 6 feet 2 inches diameter, and he believed a 4-feet tube. "John Bryant, now seventy-four years old, works a steam-engine at West Wheal Francis. He worked at Dolcoath the 63-inch cylinder double-acting engine, upon Boulton and Watt's plan. When he first worked her she had the old bee-but boiler, 24 feet in diameter. They were taken out for the Boulton and Watt waggon boiler, 22 feet long and 8 feet wide, with two fire-doors opposite one another. "Then the Boulton and Watt waggon was taken out for Captain Trevithick's boilers, which he worked for several years. Two boilers were put in, each 18 feet long, 5 feet diameter, with an internal oval tube, he thinks, 3 feet by 2 feet 6 inches. Shortly after, another boiler of similar form was added, 22 feet long, 6 feet diameter, 4-feet tube. "He cannot say what the saving of coal was, but remembers that the duty performed by the engine with the waggon boiler was thirteen to fourteen millions. Mr. William West came to the mine as an engineer, and by paying great attention increased the duty of the Boulton and Watt engine and boiler to about fifteen millions. He does not recollect the duty the engine performed with the cylindrical boilers. "Mr. Thomas Lean, of Praze, the present reporter of mine engines in the western part of Cornwall, in answer to a note I sent to him, says he has no account of any report of Dolcoath engines for the _year 1812_, but during the month of April in that year the engines did 21-1/2 millions. During the whole of 1813 that engine was reported to average a duty of twenty-one millions. The whole of the above are at per bushel of 93 lbs., and the whole of the accounts furnished by Mr. Lean are for Trevithick's cylindrical boilers. "From the Dolcoath Mine books I find the following: Paid for coals for the whole mine during the year 1811, 1150_l._ 15_s._ 10_d._, or per month, 931_l._ 14_s._ 7_d._ During the first three months of 1812 the coal averaged 1000_l._ per month. In May of this year, 1812, Captain Trevithick is entered on the books as paid 40_l._ on account of boilers; and in August of the same year, for erecting three boilers, 105_l._ I think the three boilers were at work in April, 1812, the month Mr. Lean gives as the first reported. From April, 1812, to December, during nine months, the cost of coals was 5512_l._ 6_s._, averaging 612_l._ 9_s._ 6_d._ per month. During the next year, 1813, the cost for coal was 7019_l._ 17_s._ 5_d._, or an average per month of 590_l._ 16_s._ 5_d._ I cannot find the price paid per ton for the coal in these years, but the average price during 1808 and 1815 was much alike, making it probable that the price per ton during 1811, 1812, and 1813, was nearly the same; and that the saving of the above 300_l._ per month in Dolcoath was wholly on account of the saving effected by Trevithick's cylindrical boilers. "The testimony of John Bryant, that the duty with the waggon boiler was say fourteen millions, and that of Mr. Lean, giving twenty-one millions with the new Trevithick boiler, bear much the same proportion as the charges for coals in the respective periods above given. "In the year 1816 a new 76-inch single engine was erected in the place of the old Boulton and Watt 63-inch double engine with Trevithick's cylindrical boilers. The average duty performed during the year 1817 was 43-3/4 millions. This same engine is still at work, and her regular duty is from thirty-six to thirty-eight millions. "I am, Sir, "Your most obedient servant, "CHARLES THOMAS. "FRANCIS TREVITHICK, Esq." Captain Charles Thomas, who was one of the most experienced of Cornish miners, for many years the manager of Dolcoath, and in youth the acquaintance of Trevithick, states that the new high-pressure boilers were made in the mine in 1811, and gave their first supplies of strong steam to the three large pumping engines in April, 1812, with such good effect that the increasing water which had threatened to drown the mine was speedily removed, and that with a saving of nearly one-half of the coal before consumed. Prior to their use Dolcoath Mine paid 1000_l._ monthly for coal; but for the latter nine months of the year, in consequence of the new boilers, the cost was reduced to 612_l._ a month. This saving in the pumping cost of one mine crowned with success the high-pressure steam engineer, who had been steadily gaining ground during his fight of twelve or fourteen years on the battle-ground chosen by Watt thirty-three years before. The low price of tin and copper, which caused so many engines to cease working about the close of the last century, had changed for the better, and the present century opened with an increasing demand for steam power. Trevithick's high-pressure portable engines had worked satisfactorily for several years; and as a means of making public the relative duty performed by Cornish pumping engines, and of solving conflicting statements on the rival systems of low and high pressure steam, it was determined that an intelligent person should examine and give printed monthly reports of the amount of duty done by the different engines, and in 1810 Captain Andrew Vivian was requested to take this work of engine reporter in hand; on his refusal it was offered to Trevithick. In August, 1811, Mr. Lean commenced such monthly reports, showing that the duty of twelve pumping engines at the end of that year averaged seventeen millions, exactly the duty done by the Boulton and Watt engines thirteen years before, as reported by Davies Gilbert and Captain Jenkin in 1798, proving the small inherent vitality of the Watt engine. In 1814 the Dolcoath pumping engines, with Trevithick's cylindrical boiler and high steam expansion, are thus reported:--"The Boulton and Watt, Dolcoath great double engine, 63-inch cylinder, did a duty of 21-1/2 millions; the Shammal 45-inch cylinder, single engine, did 26-3/4 millions; and the 63-inch single, Stray Park engine, 32 millions." Shammal engine, nearly 100 years old, beat the Watt engine of more than half a century later; and so did Stray Park 63-inch, which Watt had laughed at when he first tried his hand as an engineer in Cornwall in 1777.[82] [Footnote 82: See vol. i., p. 30; vol. ii., p. 115.] The marked change in these three engines, while for two or three years under Trevithick's guidance, becoming more powerful and economical, raised the usual swarm of detractors, and in 1815 a special trial was made, which lasted for two days, to test the reported increased duty by the cylindrical boilers and expansive working. The unbelievers were then convinced, and agreed to throw out the Boulton and Watt great double engine 63-inch cylinder, together with its neighbour, the worn-out old 45-inch, and put in their stead one engine with a cylinder of 76 inches in diameter, with expansive valve and gear, and parts strong enough and suitable to the high-pressure steam, on Trevithick's promise that it should do more than the combined work of the other two with one-half the coal. In 1816 this new engine commenced work, and did forty millions of duty, increasing it during the next two or three years to forty-eight millions, being three times the duty performed by the Watt 63-inch double engine before it was supplied with steam from Trevithick's boilers, and twice as much as it performed when so supplied. Lean says, "This was the first instance of such duty having been performed by an engine of that simple construction." The other mines followed Trevithick's advice, but never paid him a penny. On this Lean again says, "The engines at work in the county in 1835 would have consumed 80,000_l._ worth of coal over and above their actual consumption yearly, but for the improvements that had been made since 1814." Trevithick's engines were very durable, as well as cheap in first cost and in working expense. This famous Dolcoath 76-inch engine remained in constant work night and day for fifty-four years; after which good service the steam-pipes, being thinned by rust, were held together by bands and bolts; the steam-case around the cylinder would no longer bear the pressure of steam; the interior of the cylinder from wear was one inch larger in diameter than when first put in, and had to be held together by strap-bolts. The original boilers were said to remain, only they had been repaired until not an original plate remained; but there they were in the old stoke-hole in 1869, when, from the fear of some part of the engine breaking and causing accident, it was removed. [Illustration: TREVITHICK'S DOLCOATH 76-INCH CYLINDER PUMPING ENGINE, ERECTED IN 1816, CEASED WORKING 1869. _a_, steam-cylinder, 76 inches in diameter, 9-feet stroke; _b_, steam-jacket; _c_, steam expansion-valve, 11 inches diameter, double beat; the upper beat 11 inches diameter, the under beat 9-1/2 inches, valve 8 inches long; _d_, expansive cam on plug-rod; _e_, plug-rod for moving the gear; _f_, expansive horn; _g_, equilibrium valve, 13 inches in diameter, single beat moved by a tooth-rack and segment; _h_, exhaust-valve, 14-1/2 inches in diameter, single beat moved by a lever and link; _i_, equilibrium-valve handle; _j_, exhaust-valve handle; _k_, Y-posts for carrying the gear arbors; _l_, main beam in two plates of cast iron; _m_, parallel motion; _n_, feed-pump rod; _o_, air-pump bucket-rod, the pump, 2 feet 9 inches diameter; _p_, the main pump rods.] [Illustration: CYLINDER, MAIN BEAM, AND PUMP-ROD OF DOLCOATH 76-INCH CYLINDER ENGINE.] In 1867 the writer was a member of the Dolcoath Managing Committee, when it was determined that the old engine of 1816 should be replaced by a new one. The cylinder sides were reduced in thickness by half an inch; the steam-pipes and nozzles were thinned by rust and decay; the valves and gear-work remained in good order. Captain Josiah Thomas, the present manager of the mine, offered to sell this old engine at scrap price, that it might be stored in the Patent Museum at Kensington as a memento of the early high-pressure expansive steam pumping engine. [Illustration: BOILERS ERECTED IN 1811 IN DOLCOATH, USED IN THE BOULTON AND WATT 63-INCH ENGINE, THEN IN THE NEW 76-INCH UNTIL 1869. _a a_, two wrought-iron cylindrical boilers, 5 feet in diameter, 18 feet long, with internal fire-tube, oval, 3 feet 4 inches by 3 feet; _b_, a boiler, 6 feet 2 inches diameter, 22 feet long, cylindrical tube, 4 feet diameter in the fire-place, the remainder 3 feet; _c_, brick bridge; _d_, fire-bars; _e_, brick external flues under boiler; _f_, brick side-flues; _g_, ashes, or other non-conductor; steam 30 to 50[**unclear] lbs. on the inch above the atmosphere.] The steam-cylinder of 1816 was cast in South Wales; the beam still working in the new engine of 1869 was cast in the foundry of the Williams' at Perran. John West replaced the original flat expansive steam-valve with a double-beat valve; the gear was principally made by him on the mine, and remained in good working to the last. This double-beat valve is the first the writer has met with; it is of the same form as the modern double-beat valve; an earlier plan was to have a small valve on the top of the main valve. The steam in ordinary working was shut off when the piston had moved from an eighth to a quarter of its stroke. The Gons, or Stray Park 63-inch cylinder, survived its companions, the 63 double, and 45 single, for some ten or fifteen years, having beaten both of them in duty. A memorandum in Trevithick's handwriting shows that he in 1798, when designing his large globular boiler with internal flue at the reworking of Dolcoath, tested the relative duty of the Watt 63-inch double and the 63-inch single engine, then called Wheal Gons, the latter in its original form of open-top cylinder atmospheric; shortly after which it probably received a cover about the same time as the 45-inch, for both those engines were thoroughly repaired by Trevithick at the reworking of the mine, twelve or fourteen years prior to the use of the cylindrical boilers. "At the time that Boulton and Watt made their trial of Seal-hole engine against Hornblower's engine at Tin Croft, the engines were put in the best order, and good coals brought in for the purpose, to work for twenty-four hours. The trial was attended by the principal mining agents; the result was about ten millions by each engine. "At Dolcoath Mine an old atmospheric engine continued to work for several years by the side of one of Boulton and Watt's engines of the same size; the water lifted and coals consumed were carefully taken and made known to the public, showing that Boulton and Watt's engine performed, when compared with the old engine, as 16 to 10."[83] [Footnote 83: Memorandum in Trevithick's writing.] Hornblower was an active engineer in Cornwall before Watt; the patent of the latter claiming the sole right of working an engine by steam in the cylinder,[84] drove the former to use two cylinders, in one of which the expansion was carried out, as a means not described in Watt's patent; a lawsuit was the consequence. The two engines when tried by Trevithick[85] performed an equal duty of ten millions. In 1798 he tested the Dolcoath atmospheric 63-inch single against Watt's great 63-inch double action. "The atmospheric performed ten millions," precisely the duty of the patent Watt and the patent Hornblower contests of six years before; but the Watt Dolcoath engine, then considered the best he had made, did sixteen millions. These trials in 1792 and 1798 enable us to compare the Newcomen, the Hornblower, and the Watt engines; shortly after which Trevithick tried higher steam in one or more of those same engines from his globular boiler.[86] [Footnote 84: See vol. i., p. 46.] [Footnote 85: See vol. i., p. 57.] [Footnote 86: See vol. ii, p. 119.] "SIR CH. HAWKINS, "CAMBORNE, _March 10th, 1812_. "Sir,--This day I shall attend the account at Wheal Prosper Mine, in Gwythian, to contract with the adventurers for erecting a steam-engine on my improved plan, for drawing the water 50 fathoms under the adit. I called on Wheal Liberty adventurers at St. Agnes last week, and found that several of them had given up their shares rather than put in a new engine, and the remainder of them very sick. "I told them that I would fork the water with the present engine, and draw instead of 40 gallons each stroke, 47 fathoms deep (which she did), 85 gallons per stroke, 65 fathoms deep, by altering the engine on the same principle as I have done with the Dolcoath great engine, and several more that are now altering. The expense of altering the engine, and forking the water to bottom, and proving the mine, will not exceed 1000_l._ "All the adventurers are very anxious to again resume their shares and make the trial, on condition that I will undertake the completion of the job at a certain sum, but not otherwise. "I am certain, from what Dolcoath engine is doing, that I can far exceed the power above stated, and perform the duty with one-half the coal the engine consumed before, and would not hesitate a moment to engage the job on the terms they propose, but I have not money sufficient to carry it into execution, as I must lay out a large sum in erecting the engine on the Gwythian Mine, and unless I can be assisted with 500_l._, shall not be able to undertake the job. "If you think it worth your notice to encourage this undertaking by lending me the above sum for six months, I will pay you interest for it, and before drawing any part of it from you would get materials in the mine that should amount to above that sum, and also give you an order on the adventurers to repay you the whole sum before receiving any part myself. "As I have been a bankrupt, perhaps you may scruple on that account, but that business is finally settled, and I have my certificate; and indeed I never was in debt to any person; not one shilling of debt was proved against me under the commission, nothing more than the private debts of my swindling partner. "At Wendron we are working an engine lately erected on a copper lode, which has a very promising appearance, and near this spot you have land at Besperson, where there is also a very kindly copper lode, which deserves trial; if you are inclined to grant a sett, I think I can find adventurers to join me to try the mine. "I have lately read a letter from your hind, that the engine continues to mend; it far exceeds my expectation. I am now building a portable steam-whim, on the same plan, _to go itself_ from shaft to shaft; the whole weight will be about 30 cwt., and the power equal to twenty-six horses in twenty-four hours. "The only difference in this engine and yours will be the fire in the boiler, and without mason-work, on account of making it portable. I shall pass the rope from the fly-wheel round the cage of the horse-whim. "If you should fall in with any West India planter that stands in want of an engine, he may see this one at work in a month, which will prove to him the advantage of a portable engine, to travel from one plantation to another. The price, completely finished and set to work, free of all expense, in London, 105_l._ "I am, Sir, "Your very humble servant, "RD. TREVITHICK. "N.B.--Captain John Stephens informed me, a few days since, that the lead mine at Newlyn was rich." In Wheal Prosper Mine the first high-pressure expansive steam-condensing pole-engine had been worked, just before the date of the foregoing letter, and that evidence of increased power and economy was immediately followed by the application of the same principles of high-pressure steam and very expansive working to the Watt low-pressure steam vacuum engines at Wheal Alfred, Dolcoath, and other mines, with such satisfactory results as to warrant his offering, on the battle-ground of his first attack on the Watt low-pressure steam vacuum principle at Seal-hole in St. Agnes, fourteen years before,[87] at his own pecuniary risk, to so apply those principles in the Wheal Liberty low-pressure steam-engine, which had failed to drain the mine, lifting only at the rate of 1880 gallons of water one fathom high at each stroke; that it should lift an increased quantity of water, and that, too, from an increased depth, making the load equal to 5525 gallons, and to perform such increase of work with one-half of the quantity of coal before used; in other words, he was willing to engage to make the old low-pressure steam-engine perform by its conversion into a high-pressure steam-engine threefold its original work, and also to increase its duty or economic value sixfold; resting his argument on the similar changes, then to be seen in operation at Wheal Alfred Mine, and especially in the Watt 63-inch double-acting engine at Dolcoath, whose history we have been tracing. Well might Sir Charles Hawkins hesitate to believe what the experience of sixty years has barely sufficed to make plain to us. [Footnote 87: See vol. i., p. 90.] "CAPTN. TREVITHICK, "PENZANCE, _March 27th, 1813_. "Sir,--In consequence of the conversation that has passed between you and West Wheal Tin Croft adventurers, the said adventurers have resolved to put an engine on that mine, agreeable to the proposals offered by you; that is, the engine shall be capable of lifting a 5-inch bucket, 50 fathoms, 4-feet stroke, 15 strokes per minute, or a duty equal thereto; for which they will pay you 50 guineas one month after the engine shall be at work, and 50 guineas more at four months after that, and 50 guineas more at four months from that time, making the full payment of 150 guineas in nine months from the time the engine shall set at work, the adventurers paying all expense, except the engine materials, which shall be delivered on the mine. But in case the engine not performing the above duty, the adventurers to be at liberty to return the same engine, and you to pay back all the money that you had received for the said engine. "Signed by GABL. BLEWETT, "in behalf of the Adventurers and Company." Trevithick was willing to spend more than his last penny in establishing the superiority of his high-pressure steam expansive engines, but the selfishness of adventurers retarded their progress. The atmospheric, mentioned by Watt as working in Dolcoath in 1777,[88] did five or six millions of duty, yet in Trevithick's hands, about 1798 to 1800, when he erected his globular boiler with internal tube, one of them was tested with the 63-inch Watt low-pressure vacuum engine, when the latter did sixteen millions to ten millions by the atmospheric engine, being nearly double the duty it performed in its original form; and we shall still trace this same engine as Bonze or Gons until it increased to six times its first duty under the name of Stray Park 63-inch. [Footnote 88: See vol. i., pp. 30, 57; vol. ii., p. 115.] Trevithick having erected a high-pressure steam condensing whim-engine at Cook's Kitchen,[89] and in Dolcoath[90] a high-pressure puffer whim-engine, pleaded hard in 1806[91] to be allowed to supply the large pumping engines of Newcomen and Watt with higher pressure steam from his cylindrical boiler, which after years of consideration Dolcoath, in 1811, agreed to. In 1813 he wrote:--"That new engine you saw near the sea-side with me is now lifting forty millions, one foot high, with one bushel of coal, which is very nearly double the duty that is done by any other engine in the county. A few days since I altered a 64-inch cylinder engine at Wheal Alfred to the same plan, and I think she will do equally as much duty. I have a notice to attend a mine meeting to erect a new engine, equal in power to a 63-inch cylinder single."[92] [Footnote 89: See vol. i., p. 91.] [Footnote 90: See vol. i., p. 91.] [Footnote 91: See vol. ii., p. 142.] [Footnote 92: See Trevithick's letter, January 26th, 1813, vol. ii., p. 55.] The beneficial results of those acts are too large to be here entered into in detail. In round numbers, the early pumping engines of Newcomen did five millions;[93] Trevithick caused them to do ten millions of duty with a bushel of coal. Watt, during thirty years of improvements, caused the duty to reach sixteen or twenty millions in 1800. Trevithick, on the expiry of the Watt patent, then came into play, and before he had reigned half the time of Watt, again doubled the duty of the steam-engine, as he states in 1813 "his new engine was doing forty millions, being nearly double the duty of any other engine in the county." These statements by Trevithick agree very nearly with the generally-received accounts of the progressive duty of the large pumping steam-engine. [Footnote 93: See vol. i., p. 41.] "In 1798 Davies Gilbert, Esq., and the late Captain Jenkin of Treworgie, found the average of the Boulton and Watt engines in Cornwall to be about seventeen millions. In August, 1811, the eight engines reported averaged 15·7 millions. During the year 1814 Dolcoath great engine, with a cylinder of 63 inches in diameter, did twenty-one and a half millions nearly. Dolcoath Shammal engine, with a cylinder of 45 inches in diameter, did twenty-six and three-quarter millions. Dolcoath Stray Park engine, with a cylinder of 63 inches in diameter, did thirty-two millions. "In 1815 a trial was made, to prove the correctness of the monthly reports. Stray Park engine at Dolcoath was chosen for the purpose, because its reported duty was such as led some persons to entertain doubts of its accuracy. The trial was continued for ten days, to the full satisfaction of all concerned. "In 1816, Jeffrie and Gribble erected a new engine, 76-inch cylinder, single, at Dolcoath, which did forty millions. This was the first instance of such duty having been performed by an engine of that simple construction. "In 1819, Dolcoath engine performed the best during this year, and at one time reached forty-eight millions. "In 1820, Treskerby engine, to which Trevithick's high-pressure pole had been adapted, reached 40·3 millions. "In 1816, Sims also erected an engine at Wheal Chance, to which he applied the pole adopted by Trevithick in his high-pressure engines. This engine attained to forty-five millions. "In 1828 public attention had now been attracted to the improvements which Captain Grose had introduced into his engine at Wheal Towan. The duty of this engine, in the month of April this year, equalled eighty-seven millions. "This again gave rise to suspicions of error in the returns. This engine was accordingly subjected to a trial (as Stray Park engine had been in 1815), which was superintended and conducted by many of the principal mine agents, engineers, and pitmen of other mines. "The quantity of coal consumed in 1835, compared with the quantity that would have been consumed by the same engines in the same time, had they remained unimproved from the year 1814, shows that the saving to the county amounts to 100,000 tons of coal, or 80,000_l._ sterling per annum."[94] [Footnote 94: Lean's 'Steam-Engine in Cornwall.'] Lean seems to have calculated on a bushel of coal as 94 lbs. In 1798, when Trevithick was about to give increased pressure of steam to the Cornish engines, his friend Davies Gilbert reported the average duty of the Watt engine in Cornwall to be seventeen millions. In August, 1811, the reported duty averaged 15·7 millions. This was the month and year in which Trevithick, after twelve years of working evidences of the reasonableness of his promises of increased power and economy from using high-pressure steam, was allowed to erect his cylindrical boilers for the large pumping engines in Dolcoath Mine. Has the reader realized that the 45-inch atmospheric Carloose engine, of nearly 100 years before,[95] had in 1775[96] become the Bullan Garden engine of Trevithick, sen., which was improved and re-erected by Trevithick, jun., in 1799,[97] when the name was again changed, this time to Shammal, because it was linked to another engine, no other than the Watt 63-inch double engine? This Shammal 45-inch took steam from the globular boiler, using a pole air-pump[98] and a Watt condenser, though retaining the beam with the arched head and chain connection; and again in 1811 took still more highly expansive steam from the cylindrical boilers with a new beam and parallel motion, enabling it in 1814 to beat its rival, the Watt Dolcoath great double engine.[99] The old 63-inch Gons, under the name of Dolcoath Stray Park engine, with Trevithick's improvements, did sixty-seven per cent. more work than the Watt 63-inch with an equal quantity of coal. [Footnote 95: See vol. i., p. 21.] [Footnote 96: See vol. i., p. 25.] [Footnote 97: See vol. ii., p. 120.] [Footnote 98: See vol. ii., p. 122.] [Footnote 99: See Lean's report, vol. ii., p. 175.] This startling fact was disbelieved by the advocates of low-pressure steam, and as the visible change in the Dolcoath engine from Newcomen to Watt, and from Watt to Trevithick, had been gradual and not very striking, and the public were careless of principles, the one most puffed was most thought of; but the money saved was tangible, and in 1815 a special trial was made, which lasted two days, to discover if it was really true that Trevithick's appliances could so increase the duty of the engine. The 63-inch cylinder, then called Stray Park engine, was selected; the result proved that the large saving reported from Trevithick's boilers and expansive working during the last three or four years, was an incontrovertible fact. The high-pressure steam was also given to the defeated Watt 63-inch double engine; yet this newest of the three engines was the first to be condemned, and her place was taken in 1816 by an engine of 76 inches in diameter, which Trevithick promised should, with his high steam and new expansive gear, do the work of the Watt 63-inch and the old 45-inch put together; which was more than fulfilled by its doing forty millions, and, as Lean says, "was the first instance of such duty having been performed by an engine of that simple construction." In 1819 the new 76-inch engine which had been erected by the mine engineers, Jeffrie[100] and Gribble, who had long been employed by Trevithick in Dolcoath, was the best in the county, doing forty-eight millions, nearly three times the duty as given by Mr. Gilbert for the Watt engine in 1798. In 1827 Trevithick's pupil, Captain Samuel Grose, erected his Wheal Towan engine, which performed a duty of eighty-seven millions, some of the working drawings of which were made by the writer. In 1835 the principle laid down by Trevithick had become so general in the county as to cause a saving to the Cornish mines, in coal alone, of 80,000_l._ yearly. In addition to this, the increased power of the engine lessened the first cost by at least one-half. [Footnote 100: See vol. i., p. 106.] The national importance of such weighty facts calls for further corroborative proof, for we can scarcely believe that two atmospheric low-pressure steam-engines, made before the time of Watt, could be altered so as to perform more work, and at a less cost than the Watt engine, by an ingenious supply of higher steam pressure from Trevithick's boilers, together with the Watt air-pump and condenser. The following words from Watt are descriptive of his practice, though contrary to his patent claim:-- "At a very early period, while experimenting at Kinneil, he had formed the idea of working steam expansively, and altered his model from time to time with that object. Boulton had taken up and continued the experiments at Soho, believing the principle to be sound, and that great economy would attend its adoption. "The early engines were accordingly made so that the steam might be cut off before the piston had made its full stroke, and expand within the cylinder, the heat outside it being maintained by the expedient of the steam-case. But it was shortly found that this method of working was beyond the capacity of the average enginemen of that day, and it was consequently given up for a time. "'We used to send out,' said Watt to Robert Hart, 'a cylinder of double the size wanted, and cut off the steam at half-stroke.' "This was a great saving of steam, so long as the valves remained as at first; but when our men left her to the charge of the person who was to keep her, he began to make, or try to make, improvements, often by giving more steam. The engine did more work while the steam lasted, but the boiler could not keep up the demand. Then complaints came of want of steam, and we had to send a man down to see what was wrong. "This was so expensive, that we resolved to give up the expansion of the steam until we could get men that could work it, as a few tons of coal per year was less expensive than having the work stopped. In some of the mines a few hours' stoppage was a serious matter, as it would cost the proprietor as much as 70l. per hour."[101] [Footnote 101: Smiles' 'Lives of Boulton and Watt,' p. 228.] Pole expresses the same view, intimating that Watt only used steam of 1 or 2 lbs. pressure to the inch. "In Watt's engine, as is well known, the pressure of steam in the boiler very little exceeded the pressure of the atmosphere. He recommended that when the engine was underloaded, this excess should be equal to about 1 inch of mercury; and when full loaded, ought not to exceed 2 inches; adding, 'It is never advisable to work with a strong steam when it can be avoided, as it increases the leakages of the boiler and joints of the steam-case, and answers no good end.'[102] [Footnote 102: Appendix A to Tredgold, 'Pole on Cornish Engines,' p. 49.] "Mr. Watt's engines with such boilers" (which will not retain steam of more than 3-1/6 lbs. per square inch above the atmosphere) "cannot be made to exert a competent power to drain deep mines, unless the supply of steam to the cylinder is continued until the piston has run through more than half its course.[103] [Footnote 103: 'Phil. Mag. and Annals,' N.S., vol. viii., p. 309, by W. J. Henwood.] "In 1801-2 Captain Trevithick erected a high-pressure engine of small size at Marazion, which was worked by steam of at least 30 lbs. on the square inch above atmospheric pressure. In 1804, as Mr. Farey admits,[104] the same gentleman introduced his celebrated and valuable wrought-iron cylindrical boilers,[105] now universally used in this county. [Footnote 104: Ibid., p. 313.] [Footnote 105: Ibid., vol. i., p. 127.] "To these, everyone at all acquainted with the Cornish improvements ascribes a great part of the saving we have obtained. This will farther appear from an extract from a valuable work edited by John Taylor, Esq., F.R.S.[106] [Footnote 106: 'Records of Mining,' p. 163.] "The monthly consumption of coal in Dolcoath Mine was, in 1811, 6912 bushels; in 1812, 4752 bushels.[107] The alteration in the boilers was the introduction of Captain Trevithick's cylindrical boilers in the place of the common waggon boilers, which had until then been there in use. [Footnote 107: Alteration in the boilers that year.] "Mr. Woolf, as Mr. Farey states, came to reside in Cornwall about the year 1813, and his 'first engines for pumping water from mines were set up by him in 1814.'"[108] [Footnote 108: 'Phil. Mag. and Annals,' vol. x., p. 97, "Notes on Some Recent Improvements of the Steam-Engine in Cornwall," by W. Jory Henwood, F.G.S.] The foregoing was read at the Philosophical Society in 1831, to refute erroneous statements on the Watt and Trevithick engines. My friend Mr. Henwood had at that time made official experiments in conjunction with Mr. John Rennie on the detail, working, and duty of high-pressure steam Cornish engines, the Watt low-pressure steam principle having been wholly given up. Rees's 'Cyclopædia'[109] also bears the following similar testimony to date of the increased duty:-- [Footnote 109: See Rees 'On the Steam-Engine,' published 1819.] "Trevithick's high-pressure engine was erected in Wales in 1804 to ascertain its powers to raise water. The duty was seventeen millions and a half pounds raised one foot high for each bushel of coals. "The high-pressure steam-engines require a greater quantity of coals, in proportion to the force exerted, than the engine of Mr. Watt, and consequently are not worked with advantage in a situation where coals are dear. "From the reports of the engines now working in the mines of Cornwall, which, with the exception of a few of Woolf's engines, are all on Mr. Watt's principle, and most of them constructed by Messrs. Boulton and Watt, taking the average of nine engines--bad, good, and indifferent together--they were found in August, 1811, to raise only thirteen millions and a half. But when it was known by the engine keepers that their engines were under examination, they took so much pains to improve the effects, that by gradual increase the engines in 1815 lifted twenty-one millions and a half, taking the average of thirty-three engines. In 1816, Stray Park, a 63-inch cylinder, 7 feet 9 inches stroke, single-acting, being one of the three engines on the vast Dolcoath Mine; its performance in four different months was thirty-one, thirty-one and a quarter, twenty-eight, and twenty-eight and a half millions." This statement reveals a source of error in estimating the relative values of the Watt and the Trevithick engine; that of the latter was the Welsh locomotive, compared in duty with the large Watt pumping engine, pointed out in Trevithick's letter[110] of that time, as an unfair comparison; the small high-pressure puffer, in 1804, is admitted to have done seventeen and a half millions of duty with a bushel of coal of 84 lbs., while in Rees' calculation of the engines, he gives Watt 94 lbs. of coal to a bushel; and having stated that the Watt pumping engines in Cornwall, in 1811, averaged but thirteen and a half millions of duty, draws the false conclusion that the high-pressure cannot compete with the low-pressure where coals are dear; yet he agrees with other writers that the great increase in the duty of the Cornish pumping engines commenced from 1811 (when Trevithick first gave them his high-pressure steam); and states that in 1816 the Stray Park 63-inch cylinder single-acting engine,[111] being one of three then working in Dolcoath, did thirty-one millions. [Footnote 110: See vol. i., p. 166.] [Footnote 111: See Watt's statement, vol. ii., p. 115.] The 'Encyclopædia Britannica' on the question of duty states:[112]-- [Footnote 112: See "Steam-Engine," published 1860.] "The duty of the best of Smeaton's engines was, in 1772, 9,450,000 foot pounds per cwt. of coal. On the expiration of Watt's patent, about the year 1800, the highest duty of his engines amounted to twenty millions, or more than double the former duty, which may represent the economical value of the improvement effected by Watt under his various patents. "The reported duty of Cornish pumping engines, by the consumption of 94 lbs. of coals, rose from an average of nineteen millions and a half, and a maximum of twenty-six millions in 1813, to an average of sixty millions and a maximum of ninety-six millions in 1843. It is necessary to bear in mind the distinction between the duty of a bushel of coal and 112 lbs." Here, also, are the same general facts as to the duty of the Watt engine, and the marked and rapid increase of duty dating from Trevithick's Dolcoath engines in 1811; but the confusion and even contradictions in the statements prove how little the subject was understood. "A rough draft, prepared by Mr. Edmonds on Trevithick's return from America, dated 1828, for an application to Parliament for remuneration to Trevithick, says, 'That this kingdom is indebted to your petitioner for some of the most important improvements that have been made in the steam-engine. "'That the duty performed by Messrs. Boulton and Watt's improved steam-engines in 1798, as appears by a statement made by Davies Gilbert, Esq., and other gentlemen associated for that purpose, averaged only fourteen millions and a half (pounds of water lifted 1 foot high by 1 bushel of coal), although a chosen engine of theirs under the most favourable circumstances lifted twenty-seven millions, which was the greatest duty ever performed till your petitioner's improvements were adopted, since which the greatest duty ever performed has been sixty-seven millions, being much more than double the former duty. That, prior to the invention of your petitioner's boiler, the most striking defect observable in every steam-engine was in the form of the boiler, which in shape resembled a tilted waggon, the fire being applied under it, and the whole being surrounded with mason work. That such shaped boilers were incapable of supporting steam of a high pressure or temperature, and did not admit so much of the water to the action of the fire as your petitioner's boiler does, and were also in other respects attended with many disadvantages. That your petitioner's invention consists principally in introducing the fire into the midst of the boiler, and in making the boiler of a cylindrical form, which is the form best adapted for sustaining the pressure of high steam. "'That the following very important advantages are derived from this your petitioner's invention. This boiler does not require half of the materials, nor does it occupy half the space required for any other boiler. No mason work is necessary to encircle the boiler.[**'"] "'That, had it not been for this your petitioner's invention, those late vast improvements which have been made in the use of steam could not have taken place, inasmuch as none of the old boilers could have withstood a pressure of above 6 lbs. to the inch beyond the atmosphere, much less a pressure of 60 lbs. to the inch, and is capable of standing a pressure of above 150 lbs. to the inch.'" Trevithick's retrospect views of 1828 are supported by the letter of the late Michael Williams, M.P., the most experienced of Cornish mine workers, but belonging to the eastern district that had been for many years the users of the Watt engines in Cornwall. "In reference to his great improvements in the steam-engine, I have a more particular recollection, and can confidently affirm that he was the first to introduce the high-pressure principle of working, thus establishing a way to the present high state of efficiency of the steam-engine, and forming a new era in the history of steam power. To the use of high-pressure steam, in conjunction with the cylindrical boilers, also invented by Mr. Trevithick, I have no hesitation in saying that the greatly-increased duty of our Cornish pumping engines, since the time of Watt, is mainly owing; and when it is recollected that the working power now attained amounts to double or treble that of the old Boulton and Watt engine, it will be at once seen that it is impossible to overestimate the benefit conferred, either directly or indirectly, by the late Mr. Trevithick on the mines of this county. I have often expressed my opinion that he was at the same time the greatest and the worst-used man in the county."[113] [Footnote 113: See letter of Michael Williams, chap. xix.] The late Sir John Rennie and other scientific persons were, about 1830, associated with Mr. Henwood[114] in examining the work performed by Cornish pumping engines: their reports are curtailed in the following comments on Wheal Towan engine, similar to Trevithick's Dolcoath engine of 1816, except perhaps that the last named was a little inferior in its detail movements, while much less care was taken to avoid unnecessary loss of heat. [Footnote 114: Henwood, 'Edinburgh Journal of Science,' 10.] [Illustration: STEAM DIAGRAM OF WHEAL TOWAN PUMPING ENGINE, ERECTED 1827.] Mr. Henwood also gave indicator diagrams of the expansion of the steam, on one of which the writer has marked ten horizontal lines, indicating the position of the piston at each foot of its stroke, and ten longitudinal lines dividing the diameter of the cylinder into tenths. The steam pressure in the boiler was 46·8 lbs. on the square inch above the atmosphere, or 4·68 lbs. for each of the ten longitudinal line divisions. _x_ to _c_ represents the top of the steam-cylinder 80 inches, diameter; _x_ to F the length of the cylinder for a 10-feet stroke of the piston. By the time the piston had moved through one-twentieth of its course, reaching _c_, the expansive working had commenced; and when one-tenth of the stroke had been run, half of a division was cut off, showing by the curved indicator line the decrease in pressure of steam to 44.46 lbs. The comparatively small passage through the steam-valve not giving room for sufficient steam to follow up the increasing speed of the piston, led to its continued expansion in the cylinder, and by the time the piston had moved 2 feet, reaching D, the steam pressure was reduced by two divisions or 9.36 lbs., or a pressure of 37.44 lbs. on the piston; at this point the steam-valve was closed, and the remaining four-fifths of the stroke was performed by expansion; at the fifth horizontal line, or middle of the stroke, only three divisions of steam are left, giving a pressure of 14.04 lbs. to the inch; at the finish of the stroke there is only half a division, from E to F, or 2.34 lbs. of steam to the inch above the pressure of the atmosphere. On the return up-stroke of the piston, when it had reached within a foot of the finish of its course at C, the equilibrium valve closed, causing the enclosed steam of 2.34 lbs. to the inch to be compressed at the finish of the up-stroke shown by the curve G A to 9.36 lbs. on the inch, equal to its pressure about the middle of the down-stroke at N. Trevithick's expansive engine therefore, commencing its work with steam of 46.8 lbs. on the inch above the atmosphere, only took a full supply from the boiler during one-tenth of its stroke, and none after one-fifth had been performed, while at the finish of the stroke it had about the same pressure as Watt began with. The _power_ of the Watt low-pressure steam vacuum pumping engine was increased by Trevithick from two to three fold, and its economical duty in about the same proportion; in other words, he increased the effective power of the steam-engine two or three fold without additional consumption of coal. In the Wheal Towan engine the steam-cylinder was 80 inches in diameter, with a 10-feet stroke. The shaft was 900 feet in depth; the main pumps 16 inches in diameter; the pump-rods were of wood, about 14 inches square, and weighed more than the column of water in the pipes. The boilers were Trevithick's cylindrical with internal tube, wholly of wrought iron. The cylinder and steam-pipes were surrounded with sawdust about 20 inches in thickness, as a non-conductor of heat. The upper surfaces of the boilers were covered with a layer of ashes for the same purpose. The duty performed was 86·58 millions of pounds of water, raised one foot high by the consumption of a bushel of coal weighing 84 lbs. The immense power and economy of this engine are best understood by its average labour costing only one farthing in coal for lifting 1000 tons one foot high. At or about that time an old intimate of Trevithick's, Captain Nicholas Vivian, managed the mine, and Mr. Neville, a shareholder, also a user of steam-engines in Wales, observing the economical working of Wheal Towan high-pressure steam expansive engine, doing eighty-seven millions, requested its manager to examine colliery engines, all of which were of the low-pressure kind; one of them was a Newcomen atmospheric, whose duty was six millions; four or five others were Watt low-pressure steam vacuum engines, doing fourteen millions; therefore the high-pressure steam-engine did six times as much work with a bucket of coal as the low-pressure steam vacuum, and fourteen times as much as the low-pressure steam atmospheric engine. Several competitive trials by the county engineers were published about that time, in one of which, after a personal examination of the engine, Mr. W. J. Henwood[115] and others reported a duty of 92·6 millions with a 91-lb. bushel of coal.[116] [Footnote 115: Address, Royal Institution of Cornwall, by W. J. Henwood, 1871.] [Footnote 116: Trevithick calculated 84 lbs. to a bushel; Watt generally 112 lbs.; Lean 94 lbs., but latterly 112 lbs.] Mr. Rennie had been a pupil, a fellow-worker with low-pressure Watt, and while his son, Sir John Rennie, was examining the high-pressure steam expansive engine erected by Trevithick's pupil, Captain Samuel Grose, under the management of Trevithick's friend, Captain Nicholas Vivian, the latter was engaged in reporting on certain low-pressure steam-engines in Wales, one of which was a Newcomen's atmospheric, probably the last of its race, whose principle of construction was a century old, working in company with the Watt low-pressure steam vacuum engine, then half a century old, the principles of both systems being on their last legs, and under the care of Trevithick's supporters. During this jumble of engines, old and new, without a clear comprehension of their differences in principle, Trevithick, who had just returned from America, and lived within a few miles of Wheal Towan, looked on unconsulted and unconcerned on questions which in his mind had been settled by him in Dolcoath fifteen or twenty years before. The writer, during the Wheal Towan controversy, was the daily companion of Trevithick, and made drawings of the engine at the works of Harvey and Co., of Hayle, where it was constructed about 1827. Captain Samuel Grose's Wheal Towan engine was in general character similar to his teacher's Dolcoath 76-inch engine of 1816, working with about the same steam pressure and degree of expansion. The valves, gear, and nozzles were perhaps improved in detail; but the groundwork was unchanged. The first high-pressure steam Cornish pumping engine made in France was designed and superintended by the writer at the works of Messrs. Perrier, Edwards, and Chaper, at Pompe-à-feu, in Chaillot, a suburb of Paris. The principle was the same as the Dolcoath engine, and the detail differed but little from it or the Wheal Towan, except that its exterior was a little more artistic than its prototypes in Cornwall, in keeping with French requirements. It was built in 1836, within a few yards of the low-pressure steam pumping engine erected by Perrier and others in 1779, which still continued pumping water from the Seine for the supply of Paris. Stuart says, "An engine by Boulton and Watt was sent to France, and erected by M. Perrier at Chaillot, near Paris. The French engineer, Proney, with a detestable illiberality, attributes all the merit of the improvements in the Chaillot engine to his friend Perrier, the person who merely put together the pieces he had brought from Soho."[117] [Footnote 117: Stuart 'On the Steam-Engine,' p. 141.] The Perrier of 1779 was related to the Perrier of the Pompe-à-feu engine-building works of 1836, and his nephew took the Trevithick engine from Paris to a coal mine not far from Brussels, but not fully understanding the use of the balance-bob--the woodwork for which had not been completed in Paris, though all other parts had been fully erected--did not find it easy to manage the engine. The writer viewed Perrier's move as an infringement of the agreement between him and Edwards, the partner of Perrier and Chaper, and therefore declined to take any further interest in the engine. Mr. Edwards had before that been a partner with Woolf, in a small engineering works in Lambeth; and the writer had also before that been a pupil of Woolf's, in the works of Messrs. Harvey and Co., of Hayle. The drawing of 'La Belle Machine' (Plate XIII.), of 1836, serves not only as a record of that time, but also in conjunction with the drawing of Dolcoath engine of 1816, enables an engineer to form a sufficiently correct idea of the Wheal Towan engine and boilers of 1827, which in effective duty is scarcely excelled by the best pumping engines of the present day. The events connected with those Paris engines bring together the engineering works of Watt, Proney, Perrier, Trevithick, and Woolf, in the person of his once partner, Edwards. The writer, when constructing 'La Belle Machine,' had not the slightest knowledge of those links, and heard the name and repute of his engine by the following chance:-- In 1838 a passenger leaving the train of the Great Western Railway at Drayton Station, asked the writer's permission to walk on the line and examine its construction. During a short conversation he mentioned the having purchased at a sale in France the drawings of an engine known as 'La Belle Machine,' representing the Cornish high-pressure expansive steam pumping engine:--_a_, steam-cylinder, 48 inches in diameter, 8-feet stroke; _b_, steam-pipe from boiler; _c_, regulating steam-valve, double beat; _d_, regulating rod and handle for steam-valve; _e_, expansive steam-valve, double beat; _f_, balanced lever and rod for opening expansive valve; _g_, expansive clamp on plug-rod, with regulating rod and thumb-screws; _h_, cataract-rod for relieving expansive valve-catch; _i_, quadrant relieving the catch; _j_, plug-rod; _k_, equilibrium valve, double beat; _l_, clamp in plug-rod to close equilibrium valve by its action on the handle; _m_, balanced lever and rod to open equilibrium valve; _n_, quadrant and catch relieving equilibrium valve by the action of cataract-rod; _o_, regulating slide on cataract-rod; _p_, equilibrium steam-pipe conveying steam from the top to the bottom of the piston; _q_, exhaust-valve, double beat; _r_, clamp on plug-rod, closing the exhaust-valve by its descent on the handle; _s_, balance lever and rod, opening exhaust-valve; _t_, quadrant and catch, relieving equilibrium valve by the action of cataract-rod; _u_, regulating slide on cataract-rod; _v_, exhaust-pipe to condenser; _w_, Y-posts for carrying the gear. The steam in the boiler was from 40 lbs. to 50 lbs. on the square inch above the atmosphere. [Illustration: PLATE 13. LA BELLE MACHINE. HIGH PRESSURE STEAM EXPANSION PUMPING ENGINE.--1836. London: E.& F N. Span. 48, Charing Cross. Kell. Bro^s. Lith. London.] Lean states that had the pumping engines at work in Cornwall in 1835 remained unimproved since 1814, at which time they had benefited by three years of continuous improvement, a yearly additional expenditure of 80,000_l._ for coal would have been the consequence, and that the first step was Trevithick's expansive steam from the cylindrical tubular boiler, engines using such steam performing a duty three or four fold what Boulton and Watt had ever attained, or perhaps thought possible of attainment.[118] The birth of the idea of using expansive steam may in truth be traced back nearly one hundred years to the time of Newcomen's atmospheric engine, and the hope expressed in 1746 of a smaller boiler and more elastic steam[119] was partially realized in the engine and boiler of Trevithick, sen., in Bullan Garden in 1775, followed in 1780 by the competing engine erected by Watt in Dolcoath Mine, under Trevithick's management. Little further change was made until 1799, when the globular boiler and internal tube of Trevithick, jun., gave a second start to the use in large engines of more expansive steam; and even this partial move was the result of years of thought and practical experiment; for in 1792, when twenty-one years of age, he was the elected judge on a competitive trial between the Watt engine at Seal-hole, patented in 1782, and Hornblower's double-cylinder engine at Tin Croft. Each engine performed a duty of ten millions, both of them were called expansive, while in fact neither of them were so, for the pressure of the steam in the boiler did not admit of it. As Lean says, "As the steam used was raised but little above the pressure of the atmosphere, it was found that the power gained did not compensate for the inconvenience of a more complicated and more expensive machine." Or, as Watt said to Robert Hart, "We resolved to give up the expansion of the steam until we could get men that could work it," as he found it more costly than profitable. Again in 1798, Trevithick's own writing records his experiment in Dolcoath between the Bullan Garden 45-inch atmospheric engine and the Watt 63-inch great double-acting engine, when the latter did sixteen millions to ten millions by the atmospheric. At that very time he was constructing his high-pressure steam portable engines, and in the following year, after seven years of most active experience, prompted by the Watt lawsuit against Cornish engineers, he in 1799 gave the beaten 45-inch engine steam of a higher pressure from the stronger globular boiler. People, following the ideas of Watt, were still afraid of Trevithick's plans, distinctly laid down in his letters of 1806, recommending a cylindrical boiler for the Dolcoath pumping engine, because similar boilers giving steam to his whim-engines have enabled them to beat the Watt whims. This continued until 1810, when the greatly-increased power and economy of the high-pressure expansive steam pumping engine at Wheal Prosper caused the neighbouring Dolcoath in 1811 to give Trevithick's plans free scope. The long smouldering rivalry between low and high pressure, on the eve of the final discomfiture of the former, burst forth in loud words and evil prognostications, causing the mining interest of Cornwall to appoint an examiner who should publish monthly the duty performed by the various pumping engines, the first of which appeared in the autumn of 1811, when Trevithick was building his boilers in Dolcoath, and preparing the engines, as far as was possible, to submit to strong steam. By expansive valves and suitable gear, balance of power between the engine and the pump-work necessitating balance-bobs, strengthening the pit-work to bear the more powerful and sudden movement, and fifty other things, which we know must have presented themselves in such work, occupied the greater part of Trevithick's time from 1811 to 1814. That first report enumerates twelve pumping-engines, probably all of them Watt engines, averaging a duty of seventeen millions. [Footnote 118: See Lean's Historical Statement, p. 154; published 1839.] [Footnote 119: See vol. i., p. 7.] We have before traced the rapid and immense increase in the power and in the duty of Cornish pumping engines from 1811, and it may be taken as comparatively true in the larger sense applying to the improvement of the steam-engine everywhere. Dolcoath Mine, one hundred years ago, under the management of Trevithick, sen., followed by his son as the strong-steam engineer, and by his grandson as one of the committee of management in these modern times, has served during that long period to illustrate the progress of the steam-engine, and still in active operation, was thus spoken of in 'The Times' of Dec. 18th, 1871:--"This old and extraordinary mine is now raising about 100 tons of tin every month, worth from 8000_l._ to 9000_l._" CHAPTER XXI. ENGINES FOR SOUTH AMERICA. [Rough draft.] "SIR, "CAMBORNE, _May 20th, 1813_. "Yours of the 7th inst. I should have answered by return, as requested; but an unexpected circumstance prevented my being at Swansea as early as proposed, which, as it happens, best suits your purpose as well as my own. I shall not be able to be there within twenty days from this time, of which I will give you timely notice. I hope before that time Mrs. Rastrick will be safe out of the straw. I have been detained in consequence of a strange gentleman calling on me, who arrived at Falmouth about ten days since, from Lima, in South America, for the sole purpose of taking out steam-engines, pumps, and sundry other mining materials to the gold and silver mines of Mexico and Peru. He was recommended to me to furnish him with mining utensils and mining information. He was six months on his passage, which did not agree with his health, and has kept his bed ever since he came on shore; but is now much recovered, and hopes to be able to go down in the Cornish mines with me in a few days. I have already an order from him for six engines, which is but a very small part of what he wants. I am making drawings for you, and intend to be with you as soon as they are finished. Money is very plentiful with him, and if you will engage to finish a certain quantity of work by a given time, you may have the money before you begin the job. The West India engine will suit his purpose. I shall have a great deal of business to do with you when we meet. In the meantime please to forward the thrashing engines to Cornwall as quickly as possible. The engine for Plymouth will be put to break the ground as soon as I can find time to go up there. Please to say when and by what ship I shall have the small engines. "I remain, Sir, "Your very obedient servant, "R. T. "To MR. JOHN U. RASTRICK, "_Bridgenorth, Shropshire._ "The copper mine mentioned in my last is improving very fast." The strange gentleman referred to was Don Francisco Uville, a person of great influence in Lima, who a year or two before had travelled from Peru to England and back, in search of steam-engines to pump water from the ancient gold and silver mines then flooded and idle. Boulton and Watt, at Soho, on being consulted, discouraged the attempt, because of the difficulty of conveying heavy machinery over mountain pathways, and also because their low-pressure vacuum engine, using steam but slightly above atmospheric pressure, would be much less effective in the comparatively light atmosphere on the high summits of the Cordillera Mountains than in England. Uville, who had heard of the wonderful ability of English engineers to construct steam pumping engines, was utterly downhearted at this decision of the great Soho engineers, and while dejectedly wandering through the streets of London, unconsciously gazed into the shop window of Mr. Roland in Fitzroy Square, near the spot on which Trevithick had run his railway locomotive three years before.[120] Rumour of passed events may have led him to visit the ground on which had worked a new kind of steam-engine. His searching glance discovered among numerous articles for sale, an unknown form that might be the talisman he had travelled thousands of miles in search of. The shopkeeper informed him that it was a model of Richard Trevithick's high-pressure steam-engine, which worked without condensing water, or vacuum. If what he heard was true, why should it not work equally well in the light atmosphere of the mines? The great engineer at Soho might be in error or ignorance. The experiment, as a last resource, was worth making. He would pay the 20_l._ for the model, carry it to the mines of Cerro de Pasco, in the high mountains above Lima, where, if it worked as well as it did in London, the rich mines of Peru would again reveal their long-hidden treasure. The model was conveyed by ship to Lima, and then on a mule up the narrow precipitous ascents to Cerro de Pasco, over mountains more than 20,000 feet high. Fire was placed in the small boiler as he had seen it done in London, and with the same result, to the great joy of Uville, who determined to revisit England in search of the inventor of this new and wonderful power. On his return voyage, when rounding Cape Horn, bets were made on the chances of his finding the man who had invented the high-pressure steam-puffer engine,[121] and of his being able to persuade such a person to make the required engines and accompany them to Peru. Such gloomy forebodings ended in an attack of brain fever. The vessel touched at Jamaica, where Uville was landed. On recovering health and strength he embarked for England in one of the packet-ships, and during the voyage still spoke of the object of his search. A fellow-traveller, called Captain Teague, rejoiced him by saying, "I know all about it; it is the easiest thing in the world. The inventor of your high-pressure steam-engine is a cousin of mine, living within a few miles of Falmouth, the port we are bound for." On landing, Uville, still weak and obliged to keep his bed, was told that Trevithick, the engineer, lived in London, and was constructing the Thames Tunnel; but further inquiry showed that he also had suffered from brain fever, and had just returned to Penponds, only a few miles from Falmouth. On the 10th of May, 1813, a letter reached Trevithick, requesting him to visit the sick Uville, and in a fortnight from that time the engineer had mastered the requirements of the Peruvian mines, and had designed and made arrangements for the supply of six pumping engines, together with the pumps and all things necessary for the underground workings; the whole to be delivered in four months. [Footnote 120: See vol. i., p. 194.] [Footnote 121: See London locomotive, vol. i., p. 198.] [Rough draft.] "SIR, "CAMBORNE, _May 22nd, 1813_. "I have engaged to get six engines, with pit-work, &c., to send abroad. A great part of the wrought-iron work and the boilers I have arranged for in Cornwall. These engines will be high-pressure engines, because the place they are for has a very deep adit driven into the mountain; and lifting condensing water to the surface would be a greater load than the whole of the work under the adit level. "I call a set of work, a 24-inch cylinder single engine, 6-feet stroke, piston, cylinder bottom, single nozzle, with two 5-inch valves and perpendicular pipe; no cylinder top; the piston-rod not to be turned; 3-inch safety-valve, fire-door, two small Y[**symbol] shafts and gear-handles, &c.; a good strong winch set in a broadish frame, such as is often used on quays or in quarries, 25 fathoms of 12-inch pumps, a 12-inch plunger, an 11-inch working barrel, clack-seat and wind-bore, with brass boshes and clacks, a force-pump for the boiler, and 10 fathoms of 3-inch pipes to carry the water to and from the engines. I have engaged to supply six full sets of the above-mentioned materials. "All these castings must be delivered in Cornwall in four months from the time the orders are given; therefore, if you take the job, or any part of it, you must enter into an engagement to fulfil it in the time. As there ought not to be a moment lost, I wish you to answer me immediately in what time you will deliver those materials in Cornwall; or otherways, what part of them you can execute in the time. "I am making the drawing, which will be ready before I can receive your answer. For whatever part of the job you may engage I will lodge the money to pay for the whole in Mr. Fox's hands, which will then be paid for before you begin the work, as soon as you execute the agreement. "R. T. "MR. PENGILLY, _Neath Abbey, South Wales_." It is an odd coincidence that while writing of the events of fifty-eight years ago, pumping engines are being sent to those same mines with the steam-cylinder in twenty-two pieces, no piece to weigh more than 300 lbs.--a facility in mechanical arrangements not enjoyed by Trevithick--having Trevithick's high-pressure boilers, giving steam of 50 lbs. on the inch.[122] [Footnote 122: Made by Harvey and Co., Hayle, 1870.] [Rough draft.] "SIR. "CAMBORNE, _June 2nd, 1813_. "I drop you this note just to inform you that I have begun your job. Yesterday I engaged a great many smiths and boiler-builders, who set to work this morning. I have also engaged all the boiler-plates in the county, which will be sent to-day to the different workmen. The master-smiths that I have engaged are the best in the kingdom. I have obligated them to put the best quality of iron, and to be delivered at Falmouth within four months. I have been obliged to give them a greater price than I expected, otherwise they would not turn aside their usual business employment for a short job of four months. "Mr. Teague is with me, and one other, assisting about the drawings. If you call at Camborne about Friday, shall be able to show you the designs. The drawings for the castings will be sent to the iron-founders by the end of this week; and by the end of next week shall have the whole of the different tradesmen in full employ. If you wish to have a greater quantity of machinery ready by the end of September, there ought to be as little time as possible lost in giving your orders. I can get you double the quantity, provided you give the orders in time. "As soon as it is convenient to you to arrange the payments I would thank you to inform me, because we find in practice that the best way to make a labouring machine turn quickly on its centres, is to keep them well oiled. "R. T. "F. UVILLE, Esq., MR. HOOPER'S, _Falmouth_. "N.B.--If you intend to be at Camborne, please to drop me a note by post, and I will be at home." In all Trevithick's moves there was a scramble for money, in which he invariably came worst off. He could give a good hint that working centres would not turn well without the essential oil; but he failed to apply the principle to himself. Liberal words and golden prospects carried him off at once; and before Uville was strong enough to visit the Cornish mines and to fully explain what he wanted, the machinery was being made, though at that same time the thrashing and ploughing engines, and the locomotive and rock-boring engine, and the great fight with Watt at Dolcoath, were in progress. [Rough draft.] "MR. RASTRICK, "CAMBORNE, _June 8th, 1813_. "Sir,--Enclosed I send to you a drawing for a set of pumps for one of the engines for South America, with a drawing for a part of the castings for one of the boilers, for you to make a beginning. The drawings for the engines I will send in a few days. The Spanish gentleman who is now gone to London to arrange his money concerns, will be down again in about ten or twelve days, and then we shall both call at Bridgenorth, and bring with us the engagement for you to sign, for the performance of such quantities of work as you can execute in four months. "I have made arrangements with the smiths and boiler-*builders here, to weigh and pay at the end of every week. The regulation of your payment is left to you to point out in any way you please. As time is of the greatest consequence, I hope you will set to work immediately. "The reason for making the pumps so short, is on account of the extreme badness of the roads over the mountains, where these engines are to be conveyed, it being almost impossible to carry above five hundredweight in one piece. The West India engine is sold to send to Lima, but not to be conveyed over the mountains. I shall also bring drawings with me for one or two winding engines for the same place. Please write to me by return of post. "R. T." [Rough draft.] "CAMBORNE, near TRURO, _June 11th, 1813_. "MR. FRANCIS UVILLE, "at MESSRS. CAMPBELL AND CO.'S, London. "Sir,--I have your favour of the 9th instant, respecting the weight of the largest parts of the engines. I will take care to reduce the weight if possible, so as to be carried on the backs of mules. "By the time I receive your letter I shall have arranged the whole of the engine business, and intend to go immediately to Wales and Shropshire, to get the engagements executed for the performance of the work by the time proposed. I shall write to you again before I leave home, and as soon as I arrive in Wales will also write to you. I shall not stay in Wales above two days, but go to Bridgenorth in Shropshire, where I hope to have the pleasure of meeting you, as it will only be about twelve hours' ride out of your road to Cornwall. "In the North I shall introduce you to the sight of a great deal of mining and machinery, and in about ten days from the time you arrive at Bridgenorth, shall be able to accomplish the business so as to return again to Cornwall. "I would thank you to inform me as early as you can, of the number of engines you intend to get executed by the proposed time, because when I am in the North I shall be able to arrange with the founders accordingly. The smiths are all at work for you. "R. T." [Rough draft.] "MR. UVILLE, "CORNWALL, CAMBORNE, _June 19th, 1813_. "Sir,--Your favour of the 9th instant, dated from Falmouth, I received, and in return wrote to you immediately--directed for you at Messrs. Campbell and Co.'s, London. As you said in your last letter, that immediately on your arrival in town you would write to me, I have expected every post since last Tuesday would have brought me a letter; but as I have not received it according to your promise, I am fearful that your letter may be unexpectedly detained, especially as you told me the last time I saw you at Falmouth, that you would enclose me a bank post bill. All the founders and other tradesmen are in full employ on your engines. "I intended to have left Cornwall for Wales and Shropshire by this time, with the founders' articles for execution; but being disappointed in not hearing from you, agreeable to our appointment, I shall delay it until I hear from you, which I must request you to have the goodness to do by return of post, because those delays make very much against the execution of your work; and as time is of so great a consequence to you, I hope you will not lose a moment in writing and giving me the necessary instructions, with a few drops of that essential oil that you proposed sending me on your arrival in town. "R. T." The sugar rolling-mill engine that had been made for the West Indies so pleased Uville that he purchased it at once, intending it for the Mint at Lima. He also ordered one or two winding engines, in addition to the pumping engines. Trevithick had arranged that no piece should exceed 560 lbs. in weight. Then came Uville's order, "if possible to be reduced so as to be carried on the backs of mules." Since that time the path on the mountains has been improved, yet the present limit of weight is 300 lbs. The absence of the promised bank post bill was another difficulty. [Rough draft.] "CAMBORNE, _June 23rd, 1813_. "MR. FRANCIS UVILLE, "at MESSRS. CAMPBELL AND CO.'S, Park Buildings, London. "Sir,--Your favour of the 19th instant came safe to hand. "I was in hopes that I should have found a remittance enclosed. All the tradesmen that I have employed on your work were to have been paid every Saturday, and I made my arrangement with you accordingly. Unless this mode of proceeding is followed up, you cannot get your work done in any reasonable time, especially as you are an entire stranger. For my own part I have placed the greatest confidence in your honour, with which I am fully satisfied. "But I have to get this work from a great number of different tradesmen, and must make regular payments agreeable with my engagements with them. As the articles are about to be executed by different tradesmen, regular weekly payments ought to be established, of which I informed you before the work began. "I am ready for my journey to Wales and Shropshire, but cannot proceed with further engagements until I hear again from you. I have placed the fullest confidence in your word, a proof of which you have in the great exertion I have made to get the work done; but unless you in return place some confidence in me, or any other engineer that you may employ, a work of this magnitude cannot be carried on with promptitude. "As the whole of the work in my part has been put into immediate operation, it would be a very serious loss both of money and time to discharge the hands. I hope you will fully consider this business, and must beg you will have the goodness to write to me by return of post. On receiving the needful from you I shall leave Cornwall for Wales and Shropshire. "R. T." Trevithick for once in his life was wise, and would not start on his journey to Bridgenorth until the money had reached him. This prudent resolve was soon forgotten in the love of making the steam-engine useful; and as such creations in his hands grew into shape and size before other men would have got through preliminary discussions, pecuniary difficulties sprang up, as mushrooms do in a night. [Rough draft.] "CAMBORNE, _September 4th, 1813_. "MESSRS. HAZELDINE, RASTRICK, AND CO., "Gentlemen,--Enclosed you have three of Mr. Uville's drafts, value one hundred and fifty pounds. "I should have sent it in one draft, but had not a suitable stamp. The castings, pipes, ale, &c., arrived safely. I hope that all the boilers and wrought-iron work will be finished by the end of this month, and shipped off for London. Immediately after Mr. Uville and I shall leave Cornwall for Bridgenorth on our journey to town. We are both very anxious to see the 'Sanspareil' engine at work, and hope you will have it ready by that time. I have received orders from different persons since I have been here, for steam-engines for the West Indies, and must, if possible, have three ready early in November, as the ships sail then that will take them. "I wish you would say in your next if this can be done in time, because these persons are very extensive agents for the planters, and are extremely anxious to generally adopt them in the West Indies. "We find from your letter that you are getting on pretty fairly with Uville's work. "I remain, "Your very humble servant, "RICHARD TREVITHICK." [Rough draft.] "GENTLEMEN, "CAMBORNE, _September 7th, 1813_. "After writing to you on Sunday last, Mr. Uville received letters from Cadiz, from the Spanish Government, informing him that there was a line-of-battle ship there that should take the engines to Lima. Now as this ship is detained for this purpose, all possible dispatch must be made to get the whole of the materials shipped as early as possible for Cadiz. I am pushing the smiths as hard as possible, and you must do the same at your works, that the greatest dispatch may be made. I am ordered by Mr. Uville to request you to get one water-engine, pumps, &c., complete, one winding engine, winding apparatus, &c., complete, and one crushing apparatus, complete, in addition to the former order. I wish you would also get on as fast as possible with the new engine, but do not let this engine prevent the getting forward the work for Lima. "I wish to have made apparatus to work expansively, and also a temporary water-pump, to load the engine, so as to prove its duty by the consumption of coal. "If the jobs are not completed by our arrival, you need not expect any rest until its completion. Your answer will oblige, "R. T." "MESSRS. HAZELDINE, RASTRICK, AND CO." The money difficulty was for a time surmounted, with a prospect of the completion and shipment of the work for London within four months of the giving of the order; and the Spanish Government proposed that a line-of-battle ship should take the engines to Lima from Cadiz. An order was given for another pumping engine and another winding engine, to be provided with gear for working expansively, and a temporary water-pump, that in case of need the amount of work the engines could do with a given amount of coal might be tested. A crushing machine, now called "quartz-crusher," also formed part of this additional order. The new engine, which he hoped they would get on with, was probably the steam locomotive plough then being constructed at Bridgenorth. [Rough draft.] "GENTLEMEN, "CAMBORNE, _September 22nd, 1813_. "I have your favour of the 14th instant, and hope to find you as forward on your job on our arrival at Bridgenorth as you state. I expect all the boiler and smith work will be shipped for London early in October; we shall then leave Cornwall for your works, at which time you will be very much annoyed with our company, unless we find your assertions grounded on facts. Enclosed I send you Mr. Uville's draft for 150_l._ Your receipt for the draft enclosed in my letter of the 16th instant has not yet arrived. "I hope you will also have all the apparatus ready to try the new engine; Mr. Uville is very anxious to take the first of these new engines with him. When you send a receipt for the enclosed, please to say what state of forwardness the whole of our work is in, and do not neglect a moment to get the whole executed with all possible dispatch. "Nothing short of a want of cast iron will confine our friend in England one day after the end of this month. "I am, Gentlemen, "Your very humble servant, "RICHARD TREVITHICK. "MESSRS. HAZELDINE, RASTRICK, AND CO." It seems probable that in 1813 a railway locomotive, with apparatus for rock boring, and steam-crane, was made for South America as the forerunner of the 'Sanspareil' of 1829. [Rough draft.] "GENTLEMEN, "CAMBORNE, _October 1st, 1813_. "I received your favour of the 27th last evening, and now enclose you another draft of Mr. Uville's for 150_l._ We shall wait impatiently for your next letter to know when you will finish. Mind, this is the 1st of October, and agreeable to promise the time is up. Mr. Uville wishes you to cast sixty carriage-wheels for him, 11 inches in diameter from out to out, and to weigh about 20 lbs.; cast them of strong iron, and of a strong pattern, to take a 1-1/2-inch axle by 2-1/2 inches deep in the hole; also cast four plunger-pistons 11 inches diameter to suit the 11-inch working barrels, provided it should be used for the purpose of a plunger. They must be in every respect the same as the 14-inch plunger-pistons, only 3 inches less in diameter. [Illustration] "Soon after the receipt of your next letter you may expect to see us, as a vessel has been engaged to take all the boilers and smith work on board to-morrow week for London. "I remain, Sir, "Your humble servant, "RICHARD TREVITHICK. "MESSRS. HAZELDINE, RASTRICK, AND CO." Probably those cast-iron wheels were ordered with a view to steam locomotion in the Cordilleras. An engine is described in the invoice as having chimney, axles, carriage-wheels, &c. [Rough draft]. "GENTLEMEN, "CAMBORNE, _October 11th, 1813_. "On making the drawings of the engine with the winding and crushing apparatus, when at work I find that if there is no crank, but the sweep rod is connected to a pin in the arm of the fly-wheel; in that case the fly-wheel will cut off the engineer from getting at the cock; but if the sweep is connected to a crank, then there will be sufficient room. The copy of materials taken from your books and given to Mr. Uville does not say in which way it was intended. I send you a sketch how it will stand worked by a pin in the fly-wheel, and also if worked by a crank over the cylinder, with the fly-wheel outside the wood partition of the house. If you have cast all the parts for the winding engine, you should try to alter it, having the fly-wheel outside the wall of the house, and a crank for the inside end of the shaft. The fly-wheel shaft will be nearly the same length both ways, only it must be long enough for the fly-wheel to pass between the wood partition and the 4-feet cog-wheel. The centre of the winding cylinder will be 17 inches from the outside of the wood end of the house, against which the fly-wheel ought to run. I have received your favour of the 5th instant, and have enclosed, agreeably to your request, a draft of Mr. Uville's for 800_l._, which will be the last from Cornwall. All I have to say is, you have taken longer time for the completion of your work than you first proposed, which has made Mr. Uville apprehensive that it will be the means of his losing the Spanish ship promised him to take the engines. He desires me to inform you that he has complied with this advance on purpose to enable you to push your work with the utmost exertion. [Illustration: WINDING ENGINE FOR SOUTH AMERICA.] "Please to inform us the precise time we must quit Cornwall for Bridgenorth; we now wait entirely on you without any other thing to engage us. I fear Mr. Rastrick being so much from home will impede our job. If we miss this ship it will certainly make much against us all, losing three or four months in getting a South Sea whaler, and having the engine in a vessel not able to defend herself against an enemy, and having to pay 15 or 20 per cent. insurance, and prevent our getting other orders for another set of engines, and if taken by the enemy perhaps altogether damn the undertaking. Therefore I would have you to well consider the great inconveniences attending delay. "I think I need not say much more to you on this head, as you ought to feel more for your own interest than I can scribble to you on paper. "Yours, &c., "R. TREVITHICK. "MESSRS. HAZELDINE, RASTRICK, AND CO." This rough hand-sketch and letter fully describing his requirements, is an illustration of the facility with which Trevithick designed his engines and made known his wishes to others. [Rough draft.] "GENTLEMEN, "CAMBORNE, _October 23rd, 1813_. "Mr. Uville wishes everything to be sent off as soon as finished, except the rolling engine, which is to remain until he arrives. We intend to leave Cornwall for Bridgenorth on Monday, November 1st. You may expect to see us three days after that date. The wheels ordered for the carriages are to run on the ground and not on railroads. Mr. Uville now wishes to have seventy-two instead of sixty as ordered before. "I remain, Gentlemen, "Yours, &c., "R. TREVITHICK. "MESSRS. HAZELDINE AND CO." The last-named engine was intended for the coinage operations in the Mint at Lima. The use of railway locomotion had been under discussion with the engine builders, and probably those particular carriage-wheels were ordered in the hope that the portable engine built for conveying itself from place to place in the sugar plantations of Jamaica, would in the Cordilleras be made to draw waggons on common roads. The hand sketch of the winding engine in the letter of the 11th October, was to correct an error in an order hastily given a month before; when, to save time, outline instructions for this complicated work were hurriedly sent to the manufacturer, that a commencement might be made while the more perfect detail drawings were being completed; the first-proposed position of the fly-wheel would prevent the engineman from conveniently reaching the four-way cock; Trevithick therefore suggested that the fly-wheel should be moved to the outside of the house, and a crank placed on the end of the driving shaft in lieu of the crank-pin in an arm of the fly-wheel. The sketch illustrating this change makes us fully acquainted with the kind of winding high-pressure steam-puffer engines of 8-horse power, with open-top cylinders of 12 inches in diameter and about 3 feet 6 inch stroke, sent to Peru in 1814. Steam, of 30 lbs. to the inch above the pressure of the atmosphere, was admitted under the bottom of the piston by a cock moved by an eccentric on the fly-wheel shaft; the gradual closing of the cock reduced the supply of steam when about one-third of the stroke had been made, wholly cutting it off some time before its completion, making it a high-pressure steam expansive engine. The movement of the cock then turned the steam from under the piston into the chimney blast-pipe, and the down-stroke was performed by the weight of the descending piston, made more than usually deep and heavy to prevent the tendency to twist in the cylinder from the angle of the jointed connecting rod, and also by the momentum of the fly-wheel and its balance-weight, moving at a speed of thirty strokes a minute. Its boiler was the Trevithick wrought-iron cylindrical, with internal tube and fire-place, but so arranged that if necessary the fire could be placed in brick flues under the boiler, returning through the tube. The cylinder for the winding engine was probably fixed in the boiler, costing, with whim-barrel and winding apparatus complete and ready for work, 210_l._ Does the reader ask, Did so cheap an engine ever work? Or perhaps his knowledge of engineering gives rise to the question, How did it work? for it looks like a Newcomen of just exactly a hundred years before, only it needs no injection water or great main beam; and certainly it is not a Watt, for it has neither air-pump nor condenser, nor vacuum, nor cylinder-cover, nor parallel motion, nor any other thing like Watt invented; but it has high-pressure steam, which he disapproved of, and it really worked thousands of miles away, where there were no mechanics to keep it in order, and on mountains so difficult of access, and in so light an atmosphere, that Watt, who had the first chance of supplying steam-engines to the New World, declared it to be impossible. The pumping engines are described in Trevithick's note of 22nd May. They also were high-pressure puffer-engines with open-top cylinder, 24 inches in diameter, 6-feet stroke, with a cross-head working in guides, and side rods connecting to the pump-rods. Two valves turned the steam on and off from under the piston, with the ordinary gear and handles. The boiler was similar to that for the winding engine, but larger, and had not the cylinder fixed in it; a balance-beam regulated the movements, as it had no great main beam, and differed from ordinary engines just as the winding engine did. The power was 33 horses, and with an 11-inch pump barrel, 150 feet of 11-inch pumps, a winch, and all apparatus necessary for draining the mine, the cost was but 1400_l._ [Rough draft.] "PLOUGH INN, BLACKWALL, _December 28th, 1813_. "MR. RASTRICK, "Sir,--I am requested by Mr. Uville to write to you, to push the boilers as fast as possible. A ship will sail for the South Sea fishery in about five weeks, and will engage to take the whole of the engines. We have not finally closed with her, because we cannot state the exact time until we hear from you. You must not lose a moment in sending the boiler to town. I should have gone to Cornwall before this, but have been detained, getting a ship; and I do not like leaving until my agreements are executed, which cannot be done until the beginning of next week. "I have been obliged to have all the transactions between the mines, and the Spanish Government, and Mr. Uville, translated into English, before the outlines of an agreement could be drawn up, which has been a most tedious job. "Most of the people have been out of town, and those that were not would do no business in the Christmas, which has occasioned a loss of near ten days. "As soon as the agreements are executed, I will immediately send to you money from this place. I have been kept so long here, that it will not be worth returning to Cornwall until after Mr. Uville sails. I shall be at Bridgenorth in about ten days, and will remain until the work is finished. Write how the work is getting on, and what state the winding engine is in. "Yours, &c., "RD. TREVITHICK." [Rough draft.] "DEAR SIR, "CAMBORNE, _March 4th, 1814_. "Your favour of the 23rd February was sent to me from Bridgenorth. I have also received your favour of the 1st instant, and will attend to the drawings you mention, and be prepared to meet you as early as you please, only give me as much notice as you can. "I hope by this time that Mr. Page has done something toward the needful, to be at your service. I have, agreeably with your letter this day, desired Capt. Thomas Trevarthen to hold himself in readiness for London about the end of this month. I have not yet seen Bull. I wish you to write me if I am to give him notice also to hold himself in readiness for town. I fear that those two persons will not be sufficient to conduct the work with speed, especially if Capt. Trevarthen should be unwell; he is a good miner and pitman, and could assist in fixing the engines. Bull can only act as an assistant to an engineer, therefore neither of them can take the sole direction of the work. "There will be those four large boilers to be put together on the spot, which neither of those persons know but little about. I think it would take a great charge and care from your mind to have a third person with you that could go through the whole of the undertaking, especially as the distance from England is so great. This undertaking of such immense magnitude and value ought not to depend solely on your own health, as neither of the other two could get on without your assistance in laying down and planning the outline of the whole of the work belonging to the machinery. If any one of the parts should be lost or broken, it would require some ability in that country to contrive a substitute. The expense of a third able man might prevent much loss of time and difficulty, and would not be an object in a business of such a scale as you have commenced with. "I recommend a third person, that you might count on a speedy and effectual start. Even in this kingdom, where machinery is so well understood, I have known several good undertakings fail, from not employing at first an experienced engineer to conduct the work; which I am doubtful would be the case at Pascoe, if you were not able to attend yourself to the erection, and do not take a person with you for that purpose. I beg your pardon for thus attempting to recommend to you a third person to go out; but I think a work of this magnitude, where expedition is important, ought not to rest on the health of one man, especially under a changeable climate. Please to consult your friends, and give me your opinion on it in your next. "My health is much improved; my wife desires her best respects, and thanks for your present. Please to write soon. "Yours, &c., "RD. TREVITHICK. "MR. UVILLE, _12, East Stien, London_." [Rough draft.] "MR. PAGE, "CAMBORNE, _March 8th, 1814_. "Sir,--Yesterday Mr. Joseph Edwards, of Truro, informed me that Teague had given notice of trial, and that the case would come on at the Assize on the 26th, and requested me to desire you to write to him immediately, and give him the whole of the transaction relative to Mr. Uville's arrest in London. "He also wishes that some attention had been paid to the threat that Mr. Uville received from Teague's so-called friend, so as to ascertain whether it came direct from him, which he thought would have some weight in court. I shall attend to give evidence at the Assize with Mr. Edwards. I shall anxiously await a reply to my last. How does Harvey's business get on? "My respects to Mr. Day, and shall be very glad to find him recovering his health as fast as I am. A crust of bread and clear air are far preferable to luxuries enveloped in clouds of smoke and heaps of filth. "Your obedient servant, "RD. TREVITHICK. "P.S.--I hear that Teague is still in London, and that his furniture is removed to his friend's house, to save it from the hands of surrounding evil spirits." Trevithick showed no undue amount of discontent on discovering that Uville had led him into pecuniary difficulties, and even his tendency to interfere in engineering matters was not hastily resented. In December, 1813, while in London, arranging for a vessel to convey the engines to Lima, and also to secure written agreements with Uville, who expected to leave England in a week or two, the going into the documents made known many weak points, one of them being shortness of money. The expected week or two had lengthened out to three months, and Uville was still in London, and Capt. Thomas Trevarthen and Bull were to be there, ready to start, about the middle of March, 1814. Four large boilers, in pieces, were to go for the pumping engines, to be put together in the mines; and Trevithick strongly recommended the sending a third man, to take general charge of the practical work, which Mr. Uville thought he himself could manage. Page and Day were lawyers, who drew up very long documents. Money to pay expenses was raised by the sale of shares in a company formed by Uville without sufficient authority, and Page was to go to the mines to look after his own and the English shareholders' interests; between them Uville was arrested, apparently for some trifle. [Rough draft.] "MR. UVILLE, "CAMBORNE, _March 15th, 1814_. "Sir,--I shall write to him again by this post, and push him to send down the transfer of my shares, already agreed on, for my execution, and hope I shall be able to meet Messrs. Hazeldine and Co.'s demand before it will be due. The young man Bull has been with me. I told him I expected that you intended to take him with you, and Capt. Trevarthen is making preparation for going. I am glad you intend to take a third person with you. I have not thought or said anything to anyone about this business. Mr. Vivian informed me that, from the conversation he had with you on the subject, he had expected to hear from you. I can answer for Mr. Vivian's honesty, ability, and pleasant behaviour, and he is a person very suitable for the engagement, only that one failing of making too free with an evening glass, which you were not unacquainted with while in Cornwall at Dolcoath Mine. I do not like to take an active part in this business, because if any accident should happen to him, my sister or his family might charge me with being accessory to his going; therefore I must beg to be exempt from taking any part in this engagement. "I remain, Sir, yours, "RD. TREVITHICK." [Rough draft.] "MR. PAGE, "CAMBORNE, _April 9th, 1814_. "Sir,--I have your favour of the 5th instant. I intend to be in town on Sunday week, but this need not prevent their writing to me here; and both you and they may still be doing your best towards disposing of shares. "Your obedient servant, "RD. TREVITHICK." [Rough draft.] "MR. UVILLE, "CAMBORNE, _April 9th, 1814_. "Sir,--I intend to be in London on Sunday, the 17th, and shall call immediately on this person for money, which shall be at your service. Wheal Alfred and Wheal Prosper agents wish you a prosperous voyage, and success in your mines. "I remain, Sir, "Your obedient servant, "RD. TREVITHICK." Trevithick was now embarked with a crew of speculators, and in payment for his services was made a partner, and sold a portion of his shares to pay for the engines which Uville had ordered. Henry Vivian, his brother-in-law, and the brother of his late partner Andrew Vivian, wished to be the third person engaged to go with the machinery to America. Trevithick spoke of his honesty and ability, but declined, on account of the family relationship, to take any part in the appointment. The two notes on the 9th April, 1814, close the correspondence. Page was busy selling shares to raise money, and Trevithick was to get some money, which was to be at the service of Uville. The delay between this period and the time of starting was mainly caused by financial and other arrangements managed by Uville. On the 1st September, 1814, Uville, Henry Vivian, Thomas Trevarthen, and William Bull sailed from Portsmouth for Lima in the 'Wildman,' taking with them four pumping engines, with pump-work and rods complete; four winding whim-engines, with all winding apparatus complete; one portable locomotive engine on wheels, to be used for a rolling mill or other purposes; one mill for grinding ore; and one rolling mill, probably for the Mint at Lima. These nine steam-engines, with their apparatus complete for work at the mines, cost 6838_l._; the grinding and rolling mill cost 700_l._ more; but various other expenses more than doubled the amount, which reached the large sum of over 16,000_l._ On reference to the conditions of agreement under which Uville acted, dated 17th July, 1812, Don Pedro Abadia, Don José Arismendi, and Don Francisco Uville, were partners engaging to drain a range of mines. Uville was to go to London to purchase two steam-engines, and was authorized to expend $30,000 (say 6000_l._). $2000 (say 400_l._) was to be paid to him as the value of Trevithick's model, which he had a few years before bought in London for 21_l._ He was to engage one or two English workmen. No new partner was to be allowed. They also contracted with the various workers of mines in Yauricocha, Yanacancha, Caya Chica, Santa Rosa, and in the mining ridge of Colquijilca, for a period of nine years, to commence within eighteen months of that time, to sink a general pit for the drainage of those mines, and to pump out the water by steam-engines. The payment for this drainage was to be one-twentieth part of the ore raised by the different mines. "An agreement made at London this 8th day of January, 1814, between Don Francisco Uville, of Lima, in the Viceroyalty of Peru, of the one part, and Richard Trevithick, of Camborne, in Cornwall, engineer, of the other part. Whereas, by an agreement of partnership made and signed at Lima, and whereas the said Francisco Uville did in pursuance of his contract with the said miners soon after the ratification thereof, embark for England, for the purpose of fulfilling the same on his part, and on his arrival there in the month of April last, made application to the said Richard Trevithick, who is an experienced engineer and miner, and requested him to assist him in promoting the object of his journey, which the said Richard Trevithick (being penetrated with a high sense of its utility) agreed to do, and hath accordingly applied himself wholly to that object, ever since the arrival of the said Francisco Uville in England: And whereas under the direction of the said Richard Trevithick, and by the orders of the said Francisco Uville, various machines and engines have been made for the purposes of the said concern, a part of which has been already paid for by the said Francisco Uville; but several of the bills brought by him to England not having been honoured, by reason of the absence from England of the parties upon whom they were drawn, the said Francisco Uville hath not at present sufficient funds to answer the engagements he has entered into in this country, and Don Juan ..,[**] to whom he was in that case directed by his partners to offer shares in the said concern, and from whom he could have received supplies, not being at this time in London, the said Francisco Uville has agreed to admit the said Richard Trevithick to be a partner in the concern, upon his advancing and paying a proportionable part of the expenses necessary for carrying on the same. Now these presents witness that in consideration of the said Richard Trevithick having paid and agreeing by these presents to pay certain bills for machinery ordered by the said Francisco Uville to the amount of 3000_l._ or thereabouts, the particulars of which have been ascertained and settled by and between the said Francisco Uville and Richard Trevithick, and also in consideration of the services which the said Richard Trevithick hath already rendered to the said undertaking, and of the future benefits which he is expected to perform for it, the said Francisco Uville for himself, and on the behalf and in the name of the said Pedro Abadia and José Arismendi (who will ratify these presents in the capital of Lima as soon as it shall be produced to them, to which the said Uville holds himself bound), Doth, by virtue of the power and authority given to him by his said partners, agree to admit the said Richard Trevithick to be a member of the said company, and doth hereby declare him to be a member thereof and a partner therein to the extent of 12,000 dollars, and as such, entitled to a share and interest in all the profits and advantages of the company in the proportion which the said sum of 12,000 dollars shall bear to the amount of capital employed by the company in the purposes of their establishment, which proportion will amount as nearly as can now be ascertained to one-fifth of the capital stock embarked in the said concern. "FRAN. UVILLE. "RICHARD TREVITHICK. "_8th January, 1814._" So Trevithick paid 3000_l._ and received nothing for his engineer's work, to be made a partner, contrary to Uville's limit of authority, in a speculation that proved to be not worth a farthing. The following is a summary of the detail invoice of engines and machinery which left London for Lima in September, 1814, in charge of Uville, just fifteen months after his landing at Falmouth in search of Trevithick:-- "Invoice of four steam-engines, four winding engines, one portable rolling engine and materials for ditto, two crushing mills, four extra-patent boilers, spare materials for engines, boring rods, miners', blacksmiths', and carpenters' tools, &c., shipped on board the 'Wildman,' John Leith, master, from London to Lima, by, on account and risque of Don Francisco Uville, Don Pedro Abadia, and Don José Arismendi, merchants at Lima. Dated 1814. To four steam-engines of 33-horse-power each £ _s._ _d._ (complete for lifting water with under-adit and house lift-pumps, and wrought-iron pit-work, rods, &c., at 1399_l._ 13_s._ each 5,598 12 0 To four winding engines of 8-horse-power each, with whims, barrels, shafts, &c., complete for lifting ore, at 210_l._ each 840 0 0 To one portable steam-engine of 8-horse power, for rolling, with its chimney, axles, carriage-wheels, &c. 400 0 0 ----------- 6,838 12 0 A mill for grinding ore £517 0 0 A rolling mill 204 0 0 Duplicates, sundries, freight, insurance, &c., &c. 8,592 9 1 ------------- 9,313 9 1 ------------- £16,152 1 1" The nine steam-engines, including a locomotive, with its chimney, axles, carriage-wheels, &c., a crushing mill and a rolling mill, cost but 7560_l._ Other expenses, for freight, insurance, &c., &c., increased the amount to 16,152_l._ William Williams,[123] on his return from the Cerro de Pasco Mines, states:-- [Footnote 123: Residing at Angarrack, near Hayle, 1872.] "On the 3rd March, 1872, I saw in Yauricocha Mine two of Mr. Trevithick's engines at work; one of them was a horizontal 12-inch open-top cylinder pumping engine, about a 4-feet stroke; there were two fly-wheels about 10 feet diameter and a cog-*wheel 7 feet diameter, giving motion to two wrought-iron beams working a 10-inch pump bucket. The other was a 12-inch cylinder winding engine with a large fly-wheel. Three Cornish boilers, about 5 feet 6 inches diameter, with 3 feet 9 inch tube, 30 feet long, made of 7/16ths of an inch plates, supplied steam of 40 lbs. on the inch." CHAPTER XXII. PERU. "Conditions under which Don Pedro Abadia, Don José Arismendi, and Don Francisco Uville, establish the project of draining the mines by means of steam-engines, to be brought from England. "1st. The company is composed of three contracting persons without admitting therein any other whatever. "2nd. There are intended as a fund for the undertaking 40,000 dollars, to be divided into four shares in the following manner:--Two shares to Don Pedro Abadia, one to Don José Arismendi, one to Don Francisco Uville. Four shares, dollars 40,000. "5th. These principles of good faith and friendship being established, the project is to be carried into effect with the greatest possible activity, for which purpose, by the first opportunity, the funds shall be forwarded by Don Pedro Abadia to the amount of 30,000 dollars, with the necessary instructions for the construction of the machinery to a person who may be appointed. "7th. As it has been estimated that 30,000 dollars will cover the cost of two engines in England, if the said Uville finds another on credit, he is authorized to purchase it on account of the company. "11th. Should the undertaking yield profits, Uville shall also be credited for 2000 dollars for the value of the model. "12th. In the instructions that may be given to Uville, it shall be stipulated on what terms he may engage one or two English workmen. "LIMA, _17th July, 1812_." "_Contract._ "1st. The present contract shall be considered binding for nine years, to be computed from the time the steam-engines may be erected in the different parts of these mines that may be judged suitable. "2nd. The miners herein contracting cede their mines in Yauricocha, Yanacancha, Caya Chica, Santa Rosa, and in the mining ridge of Colquijilca, and the company offer the means, steam-engines, and instruments for draining the same, and on these principles the obligations of both parties are as follow, to wit. "3rd. The company binds itself within the period of eighteen months, or sooner if possible, to bring over the steam-engines to drain successively the different parts of these mines, and immediately on their arrival to place them in Yauricocha, and afterwards in Yanacancha, Caya Chica, Santa Rosa, and in the mining ridge of Colquijilca, to sink a general pit for the collection of the waters at a depth of 40 varas from the adit or drainage level of Santa Rosa. "8th. Each miner whose mine situated in the parts above specified is not perfectly drained in consequence of the filtration or natural gravity of the water to the general pit, is to continue a tube to communicate with the said general pit on his own account, in order fully to enjoy the benefit of the draining, it being well understood that the company shall not refuse to admit the waters of any of the mines situated in this part whatever their quantity may be. And the company shall be further bound to supply funds to any miner who may not have sufficient to defray the expenses of such tube of communication at an interest of 6 per cent., to be refunded out of the first metals which may be obtained. "10th. The recompense to be made to the company for the general drain procured in the place or places agreed on, shall be, with regard to Yanacancha and Yauricocha, in consequence of the known richness of those places, and of the timber required by the softness of the ground to secure the mines, 15 per cent. on the ore that shall be extracted therefrom, and lodged either in the common depots or in the respective warehouses; and in the mines of Santa Rosa, Caya Chica, and Colquijilca, 20 per cent., which distribution is respectively to be made on the quantities obtained. "14th. That the miner who refuses to enter into this fair contract whose mines are benefited by the means of the engines, shall be compelled to pay the contributions and to perform what has been therein stipulated according to ordinance. "This contract being agreed to, the contracting parties signed respectively to be bound and compelled; and I, the Royal Judge and Sub-delegate hereof for His Majesty, signing it with all the contracting parties and witnesses before me on the said day, month, and year. "Pedro Abadia, José Arismendi, Francisco Uville, José Maria de Ulloa, Ignacio Beistequi, The Marquis de la Real Confianza, José Herressæ, Publo Anellfuertes, Ramon Garcia de Purga, José Antonio de Arrieta, José Camilo de Mier, José Lago y Lemus. "For myself and Don Remiqia, p. procuration Manuel Queypo, Rafael Doper, Juan Gonzalez, Augustin Zambrano, Francisco Rasines, Francisco Fuyre, Manuel Ysasi, Alberto de Abellaneda, Ysidro Crespo, Juan Antonio Arrasas, Pedro Gusman, Manuel Yglesias, Patricio Bermudez, Bartolome de Estrada. For the miners, Don Castano Villanueva, Juan Isidoro, Manuel de Santalla, Juan Palencia, Antonio Perez, Manuel Cavellero, Domingo Pallacios, Matias Canallero, Ambrosio Ortega, Francisco de Otayequi, Pedro de Arrieta, Juan de Erquiaga, José Zeferino Abaytad, Antonio Villaseca, Estanislas Maria de Arriola, José Maria del Veto, Ambrosio Guidones, Santiago Oreguela. For Don Pedro Mirales, p. procuration, Thomas Hidalgo, Nicholas Berrotarran, Barnabe Perez de Ybarrela, Augustin Bayroa, Francisco Xavier de Uribe, Manuel Varela. For my brother, Juan Francisco de Aspiroz, Juan Miguel de Aspiroz. "In the city of Los Reyes on the 26th September, 1812." These extracts from an agreement drawn up by the leading men in Peru in 1812 are proofs of remarkable energy. Rumours of the power of steam-engines used in mines in England had reached Lima, Don Francisco Uville was sent on a mission of inquiry, and in 1811 consulted Boulton and Watt at Soho, who gave an opinion that their engines were not suitable to so elevated a position where the atmosphere was so much lighter than in England, and the difficulties of transit so great. On his return to Lima he carried with him a small model of Trevithick's high-pressure steam-engine. The Spaniards on seeing it work had the good sense and courage to put aside the Watt report and adopt the principle of the small but active high-pressure steam-puffer engine. An influential company was formed, which sent Uville again to England to seek out the high-pressure engineer and purchase his engines. What stronger evidence could be given of the great difference between the rival engineers and their engines? The one with low-pressure steam and vacuum, the other with high-pressure steam and without vacuum. The three persons contracting to drain the Peruvian mines agreed that no other should be allowed to join them in the contract; two steam-engines were to be purchased, and if convenient a third engine might be ordered on credit. One or two English mechanics were to accompany the engines which the contractors engaged should be in Lima within eighteen months. Ten months had passed before Uville reached Trevithick, and when in May, 1813, he communicated to the Cornish engineer the same wants that he had made known to Watt two years before, how different was the answer received. "I engage to supply in four months six 24-inch cylinder high-pressure steam pumping engines, with pumps and all necessary apparatus complete."[124] This promise was nearly fulfilled,[125] but want of money, the ordering of additional machinery, and difficulty in finding a ship,--for Spain was then at war, or on the verge of it, with the South American republics,--delayed for a time the completion of the order; but within eight months even the additional work seems to have been ready, and the following agreement was entered into, though the ship with her freight of _nine_ steam-engines did not leave England until September, 1814, fifteen months after Uville's first meeting with Trevithick. [Footnote 124: See Trevithick's letter, 22nd May, 1813, vol. ii., p. 198.] [Footnote 125: See Trevithick's letters, 22nd Sept. and 23rd Oct., 1813, vol. ii., pp. 206, 209.] "_Agreement dated the 8th January, 1814._ "The said persons from whom he (Uville) would have received supplies, not being at that time in London, the said Francisco Uville has agreed to admit the said Richard Trevithick to be a partner in the concern, upon his advancing and paying a proportionable part of the expenses necessary for carrying on the same. Now these presents witness, that in consideration of the said Richard Trevithick having paid, and agreeing by those instruments to pay certain bills for machinery ordered by the said Francisco Uville to the amount of 3000_l._, and also in consideration of the services which the said Richard Trevithick hath already rendered, and of the future benefits which he is expected to perform, doth agree to admit the said Richard Trevithick a partner therein, as nearly as can be ascertained to one-fifth share of the whole. "He hath planned and directed the particular construction of three steam-engines, and hath for that purpose taken many journeys to manufacturing towns and other places. "He hath given to the said Francisco Uville a general knowledge of English mining, miners' tools, winding and crushing engines, &c., &c., and for that purpose hath taken him to various mines in England, to which the said Richard Trevithick, through his interest, had access. He hath instructed the said Francisco Uville in the art of making drawings of mines, and in engineering. "He hath furnished him with various drawings of English mines, and plans for the future working of Spanish mines, and hath given to him every other engineering and mining information. "He hath increased the power of the three engines above mentioned to the extent of one full third, without making any additional charge for so doing, and he hath agreed to supply the said company with a fourth engine, and to wait for the payment of it, until the return of the said Francisco Uville to Lima, in recompense for all which the said Francisco Uville doth for himself and his partners grant to the said Richard Trevithick one and quarter per cent. of the net produce or profits (all expenses first deducted) of the ore extracted from the said mines, and as a further recompense, doth appoint him sole engineer in Europe for all the machinery that shall be used or required." The nine steam-engines, with apparatus for minting, crushing ores, draining, winding, and even locomotion, with miners' tools complete down to mine ladders, borers, picks and gads, and hammers, were received by a large and influential body of Spaniards residing near Lima, under the special patronage of the Viceroy. The machinery had then to be taken up precipitous tracks that foot-passengers trembled to walk on, to the height of more than 15,000 feet. The calculated profit was 500,000_l._ a year, of which 100,000_l._ a year was to be Trevithick's share, a portion of which was sold to pay for the engines. A prospectus drawn up in England states that "the whole capital was in four hundred shares, of which Trevithick held eighty, valued at 40,000_l._, together with special advantages to be accorded to him." The machinery having left England in September, 1814, reached Peru in the early part of 1815, shortly after which one of the engines was at work in the Mint at Lima, within two years from the giving the order for it in England; for in the early part of the latter year Trevithick wrote to one of his men:-- "I am sorry to find by Mr. Uville's letter that the Mint engine does not go well. I wish you had put the fire under the boiler and through the tube, as I desired you to do, in the usual way of the old long boilers, then you might have made your fire-place as large as you pleased, which would have answered the purpose, and have worked with wood as well as with coal, and have answered every expectation. "I always told you that the fire-place _in the boiler_ was large enough for coal, but not for wood, and desired you to put it under it. The boiler is strong enough and large enough to work the engine thirty strokes per minute, with 30 lbs. of steam to the inch. I hope to leave Cornwall for Lima about the end of this month, and go by way of Buenos Ayres, and cross over the continent of South America, because I cannot get a passage; none of the South Sea whalers will engage to take me to Lima, they say that they may touch at Lima or they may not, in the whole course of their voyage; therefore, unless I give them an immense sum of money for my passage, they will not engage to put me on shore at Lima, and for me to risk a passage in that way, and to be brought back again to England after two years' voyage, without seeing Lima, would be a very foolish trip; therefore to make a certainty, I shall take the first ship for Buenos Ayres, preparations for which I have already made."[126] [Footnote 126: Unfinished rough draft of letter by Trevithick.] The whole of the machinery having been sent off, Trevithick was prepared to make his way across the then little-known continent of South America in its broadest part, from Buenos Ayres to Cerro de Pasco.[127] His departure was deferred from various causes until the 20th October, 1816, when he sailed from Penzance in the South Sea whaler 'Asp,' Capt. Kenny. [Footnote 127: See Trevithick's letter, December 9th, 1815, vol. ii., p. 31.] [Illustration: PENZANCE IN OLDEN TIME. [W. J. Welch.]] "DEAR SIR, "PENZANCE, _20th August, 1817_. "I am enabled to furnish you with a few particulars which led to the introduction of steam-engines into Spanish America, which you will embody into your interesting paper for our next Geological meeting, as you deem most proper. "Captain Trevithick was born in Illogan, Cornwall, 1771, but he has generally resided at Camborne, the adjoining parish. He has devoted the greatest part of his life to mechanics and to improvements in the high-pressure steam-engine, and many engines of Captain Trevithick's construction are now working in different parts of England. "Mr. Francisco Uville, a native of Switzerland, visited Lima and the rich Peruvian mines in the neighbourhood of Lima, at an early age, and being a gentleman of great intelligence, he thought it possible that the silver mines at Pasco, about 150 miles from Lima, which were fast falling into decay for want of machinery to drain the water, might be restored to their former celebrity by the introduction of steam-engines. "Mr. Uville, who is now about thirty-six years of age, came to England in 1811, where he continued a few months, and just as he was about to leave London he observed by accident a model of a steam-engine, made by Captain Trevithick, at the shop of a Mr. Roland, Fitzroy Square, and Mr. Uville so much liked the simplicity of its construction, that he immediately purchased it at twenty guineas. Mr. Uville returned to Lima with it, and tried it on the mountains of Pasco, in consequence of which, on the 17th of July, 1812, Mr. Uville, with Don Pedro Abadia and Don José Aresmendi, eminent merchants at Lima, were so confident of success, that they formed a company to drain the mines at Pasco and its vicinity; and on the 22nd of August then following a contract was entered into by these gentlemen and the proprietors of the mines in that district. Soon after which Mr. Uville was deputed by the company to return to England and to find out some able engineer to assist him in procuring proper steam-engines to be conveyed to the mines. "Uville having put into Jamaica, came to England in the 'Fox' packet, Capt. Tilly, and arrived at Falmouth early in the summer of 1813. During the passage Mr. Uville frequently talked of the object of his voyage, and that he was particularly anxious to find out the maker of the model of the engine he took to Lima, and recollecting that the name of 'Trevithick' was on the model, he mentioned it to a Mr. Teague, who happened to be on board the packet, when the latter informed him that Capt. Trevithick was his first cousin, and that he resided within a few miles from Falmouth. Immediately on Mr. Uville's arrival an interview took place between him and Capt. Trevithick, and soon after Mr. Uville removed to Capt. Trevithick's house in Camborne, where he resided several months, during which time Capt. Trevithick instructed him in mining, machinery, &c. "Capt. Trevithick and Mr. Uville, after seeing most of the mines in Cornwall, visited several other mining districts in England, to afford Mr. Uville a better opportunity of acquiring the best knowledge of engineering by examining the steam-engines erected. Afterwards they went to London, when Mr. Uville was introduced to a Mr. Campbell, of the East India Company's department. Mr. Campbell informed Mr. Uville that the best engineers in Europe were Messrs. Boulton and Watt, of Birmingham; and strongly recommending them to him, he observed that he was convinced if engines could be made capable of being transported to the mines of Pasco across the mountains they would be able to do it. Mr. Uville accordingly applied to these gentlemen, and fully explained to them the nature of the engines which would be wanted, and the state of the road by which they must be conveyed, and Messrs. Boulton and Watt returned an answer that it would be impossible to make engines small enough to be carried across the Cordillera to the mines. "Capt. Trevithick, however, was not startled at the difficulties, and having applied himself to the improvements of his high-pressure engines, entered into a contract with Mr. Uville to provide nine steam-engines for the company at Lima; and, by virtue of the powers with which Mr. Uville was invested, Capt. Trevithick was admitted a partner of one-fifth in the concern; besides which, for his great pains and services he had rendered, Mr. Uville guaranteed to him a handsome percentage on the profits of the company (_vide_ Articles of Agreement of 8th January, 1814). "These matters being settled, nine engines were provided at an expense of about 10,000_l._, and were shipped on board the 'Wildman,' South Sea whaler, Capt. Leith, who sailed from Portsmouth for Lima the 1st September, 1814, accompanied by Mr. Uville and the following Cornish engineers,--Thomas Trevarthen, of Crowan; Henry Vivian, of Camborne; and William Bull, of Chacewater, in Gwennap. "The engines arrived at Lima, and were received by a salute from the Government batteries, and the greatest joy was testified on the occasion. "On the 27th July, 1816, the first steam-engine was set to work at Santa Rosa, one of the mines of Pasco, under the direction of Mr. Bull (_vide_ despatch of that date, signed José G. de Prada). "On the 20th October, 1816, Capt. Trevithick sailed for Lima in the 'Asp,' South Sea whaler, Capt. Kenny, accompanied by Mr. Page, a gentleman of London, and James Saunders, of Camborne, an engine maker; and on the 6th February, 1817, they arrived at Lima, where Capt. Trevithick was immediately introduced to the Viceroy by Don P. Abadia, and he received the most marked attention from the inhabitants (_vide_ 'Lima Gazette' of 12th February). "Perhaps you will think it proper to notice the furnaces which Captain Trevithick took out in the 'Asp' to Lima for the purpose of purifying the silver by sulphur. A great expense will be saved by these means. Any further information which I can afford you I will readily give. "I am, dear Sir, "Your very obedient and humble servant, "RD. EDMONDS. "H. F. BOAZE, Esq." This statement, from a solicitor more than fifty years ago, inadvertently points out the difference between the steam-engine of Watt and that of Trevithick. The former said it was impossible to make engines having the required power small enough to be carried to the mountain mines, whereas a small high-pressure engine by the latter had sufficient power. Day and Page were lawyers advising Mr. Uville in London. Page sailed from Penzance with Trevithick and James Saunders, a boiler maker, in the 'Asp,' a South Sea whaler, on the 20th October, 1816, just two years after the departure of Uville with the machinery and engines. The difficulty of conveying heavy weights up the mountain foot-paths was almost insurmountable. Mr. Rowe, who went to these mines in 1850, says,-- "The Cerro de Pasco mines are about 170 miles from Lima; we crossed a ridge 25,000 feet high. The mines were about 13,400 feet high above the sea. There was but one road; no wheel vehicle could be used; everything was carried on mules. Sometimes the road was only 2-1/2 feet wide, cut in precipices three or four hundred feet perpendicular: some of the men were afraid to walk, and dared not ride. "I lived in the house that used to be Mr. Trevithick's office and store-room; it was in the suburbs of the town of Cerro de Pasco. The shafts are some of them in the middle of the town; several pieces of Captain Trevithick's engines lay about the shafts, and some on the way up, as though they had stuck fast, and some we saw at Lima. Mr. Jump, a director on the mine, pointed out a balance-beam that Mr. Trevithick had put up thirty years before. Only one Englishman then remained there who had worked for Mr. Trevithick; he was called Sycombe, and said Trevithick's men were an unmanageable lot. "The natives worked in the mines underground. The atmosphere was only about 10 lbs. on the inch. We found a coal mine not far off; the quality was not very good. The smiths had difficulty in welding with it. Our heaviest pieces of machinery did not exceed 280 lbs. The worst parts of the road have been a little improved since that time." Just one month before Trevithick sailed from Penzance for Lima, the first pumping engine taken out by Uville had been satisfactorily put to work in the mountain mine of Santa Rosa, with its steam-cylinder weighing double the limit fixed on by modern engineers. The following information respecting the progress of the steam-engine fixed on the Santa Rosa Mines, one of the mineral ridges of Pasco, in the Viceroyalty of Peru, is extracted from the Government-Gazettes of Lima, dated the 10th of August and 25th of September, 1816:-- "PROGRESS OF THE STEAM-ENGINE, &c. "_His Excellency the Viceroy of Peru to the Editor._ "In order to satisfy the eager expectations of the inhabitants of this Viceroyalty, those of the greater part of these Americas, and even of the Peninsula itself, I hereby order the printing, at full length, in the next Government Gazette, or at same time in a separate sheet, the enclosed despatch from the Intendant Governor of Tarma, giving the details of the admirable results of the steam-engine fixed in the mineral territory of Pasco, for the most important purpose of draining its mines, and for the extraction of its rich ores. This authentic communication must produce the most lively and grateful sensations in those true Spaniards, who with grief contemplated as irreparably lost the only spring from which flowed the prosperity of this continent, excite their just acknowledgments to the meritorious co-operators in such an expensive and difficult as well as eminently-advantageous enterprise, and encourage to similar undertakings in other parts those who, with personal aptitudes and patriotic sentiments, have been waiting the final success of the first. "JOAQUIN DE LA PEZUELA. "LIMA, _4th August, 1816_." "_Certificate of the Deputation._ "We, Don Domingo Gonzales de Castañeda and Don José Lago y Lemus, Commissaries and Territorial Magistrates in this Royal Mineral Territory, and deputed by the United Corporation of Miners in this district, do hereby certify judicially, and as the law directs, in manner following:-- "Though this deputation never doubted the extraordinary power of steam compressed, and consequently the certain operation of engines worked by its influence, it nevertheless entertained some fears respecting the perfect organization of all the mechanical powers of the machines. This uncertainty, rather than any doubt, has been completely dissipated by our personal attendance this day to witness the draining of the first pit, situated in Santa Rosa. The few instants employed in the same produce a full conviction that a general drainage of the mines will take place, and that their metals will be extracted with the greatest facility from their utmost profundity: as also that the skill of the company's partners and agents will easily overcome whatsoever difficulties nature may oppose, until they shall have completed all the perpendiculars and levels; and consequently that the meritorious undertakers who have risked their property in the enterprise will be rewarded with riches. "We and the whole Corporation of Miners would do but little were we to erect them a monument, which should transmit down to the remotest posterity the remembrance of an undertaking of such magnitude and heroism; but for the present we will congratulate ourselves that our labours, co-operation, and fidelity, keeping pace in perfect harmony with the exertions of the agents, the company may thus attain the full completion of their utmost wishes, extracting from the bowels of these prolific mountains, not the riches of Amilcar's inexhaustible wells, not the treasures of the boasted Potosi in its happiest days, but a torrent of silver, which will fill all surrounding nations with admiration, will give energy to commerce, prosperity to this Viceroyalty and to the Peninsula, and fill the royal treasury of our beloved sovereign. "Thus certifies this Magisterial Deputation of Yauricocha, the 27th of July, 1816. "DOMINGO GONZALES DE CASTAÑEDA. "JOSÉ LAGO Y LEMUS." "_Despatch from the Intendant Governor of the Province of Tarma to His Excellency the Viceroy._ "MOST EXCELLENT SIR, "PASCO, _27th July, 1816_. "Having finally conquered the great difficulties consequent on the enterprise, though with immense and incessant labour, and at an enormous expense, the object has been accomplished of purchasing, importing, and erecting the steam-engine in the celebrated rich and royal mineral territory, called 'The Mountains of Yauricocha,' in this province of Tarma, of which I have the honour to be Governor, the chief and valuable works of which have ceased to produce ore, in consequence of their bases being completely submerged in water. "The day is arrived when we witness with admiration the advantageous and useful effects of the before-named steam-engine; the completion of the promises made by the generous and undaunted individuals who united themselves to supply the funds sufficient for the realization of an enterprise so important, and the fulfilment of the wishes of these valuable subjects, to render to the State the highest possible service; a service, although at all times of extreme importance, at this crisis is infinite; because the State, being weakened by a series of disastrous events for six years past, requires salutary remedies; and none exist so effectual as the re-establishment of the mines, which the steam-engines are achieving. "After some experiments, which (although they left no doubt of ultimate success in draining the mine) discovered some slight defects, these were corrected on the 23rd instant; and this day the first of the four pumps which arrived for the use of the royal mines was erected in the particular mine called Santa Rosa; the result of its operation has been the exhaustion of the water from the well or hollow below the adit. In twenty minutes, by this engine, an aggregate of water is ejected amounting to 6 yards or 18 feet in diameter, 3 yards 24 inches in length, and 1 yard 30 inches in breadth. In the same manner a second engine, accessory to that which drains the water, is worked by the same steam, on the same point, and in the same perpendicular shaft, from the surface of the earth, which extracts the ore, and with advantages hitherto unknown here, on account of the considerable saving of expense and the economy of manual labour. "The steam-engine will continue evacuating the water from the pit until it is reduced to 6 yards below the old adit, whence they must eject the water raised by the engine by a continued elongation of the barrel of the pump gaining depth, until they have completed the number of yards required, or until the progress of the work indicates a proper situation for forming a new line of levels and channels of communication to those mines which are not yet drained. In proportion to the successive acquisition to these subterranean works which are daily advancing, will be the increased operations of the mines, and consequently the increased prosperity of the mining interest, which had most astonishingly fallen from the degree it had attained in former years. "In a short time, similar effects will be seen in the three remaining mineral ridges of Yauricocha, Caya, and Yanacancha, productive of ores of a better quality than that of Santa Rosa, which has nevertheless obtained the preference for the erection of the first engine upon it from its being more abundant in its peculiar produce, and on account of the greater number of persons interested in this property; as also its contributing immediately to relieve the necessitous, by employing the workmen in the vicinity of the mines. In my opinion, no event so beneficial has occurred as the erection of the steam-engine, since the discovery and addition of these dominions to the crown of Castile. From this time, by the help of these machines, immense and incalculable riches will accrue to the nation. "God preserve your Excellency many years, "JOSÉ GONZALES DE PRADA." "_The Viceroy's Answer._ "LIMA, _5th August, 1816_. "Your Lordship's official despatch, No. 898, the 27th of last month, communicated to me the satisfactory detail of the complete results which you witnessed on the 23rd and 27th, produced by the grand steam-engine placed over the mine of Santa Rosa, one of those situated in the mountains of Pasco, for the purpose of draining the mine and extracting the ores. "I desire particularly to distinguish and patronize the chief agent and assistant, Don Francisco Uville; the generous promoters of the undertaking, Don Pedro Abadia and Don José Arismendi; their agents and assistants, Don Luis de Landavere and Don Tomas Gallegos; and lastly, Mr. Bull, and all those associated in this great work, whom you recommend to my notice. Your Lordship, by having exerted yourself to facilitate, by all the means which your zeal and authority could procure, the happy consummation of so profitable an enterprise, has added a new claim to the many preceding which you possessed, to the high consideration of the king and the public. "JOAQUIN DE LA PEZUELA, "Viceroy of Lima." _Extract from the 'Lima Gazette' of the 25th of September, 1816._ "We have the satisfaction of communicating to the public the information that the company for draining the mines of Pasco have just received accounts from their agents in that mineral territory; and they promise for our next Gazette a description of the state of the works for fixing the remaining three engines.--EDITOR. "CERRO, _September 20th, 1816_. "'After having observed the progress of the machine at the Santa Rosa Mine last Saturday, the 14th instant, at 10 o'clock at night we began to act; at 11 o'clock the pitmen went down to clear the shaft, and have not since ceased working an instant. The clearing of the mud and rubbish which had remained at the bottom of the shaft, and clogged every moment the buckets and suckers of the engine, lasted till Wednesday; but this being accomplished, at 12 o'clock at noon they began to break through the level. At half a yard below the shaft we found a lively coppery ore, with its particles of silver. This bronze-coloured ore indicates that the veins of Yauricocha and San Diego incline to the west, or towards the Santa Rosa Mine. The mines in the vicinity of this pit are all dry. Some of them, at the distance of 300 yards, in the ridge of Santa Rita, have also felt its effects; and even as far as the territory of Caya, behind our steam-works, the waters have fallen in several mines. Don John Vivas has begun to work in San Diego Mine. They are also going next Monday to begin working in several points of the Santa Rosa Mine. The pit is already 8 yards in depth, and we are proceeding with the greatest activity. The workmen are relieved every two hours, and as they go out they give up their tools to those who succeed them, by which means not a minute is lost. Continuing thus, in the course of a month we shall be at more than 20 yards depth, and have many mines in full activity. The winding engine raises a basket (which is a load) in two minutes; the draining or steam-engine, with two vibrations per minute, keeps the surface always dry. Both work with the greatest ease, certainty, and regularity. "'By dint of searching after a vein of coal, we have at last found one near at hand, of excellent quality and of great richness. The pit we are now at work at is at the distance of a quarter of a league from Rancas, and at the same distance from Vista Alegre which the Cerro is from these works. We have likewise found a vein of plumbago, which was an object of search, on the supposition that it was coal. This substance, of which much is consumed, mixed with grease, to soften the friction of the piston, &c., we have now here; and thus the necessity of sending to Lima, or perhaps to Europe, for it is obviated.'" Within six months of the setting to work the pumping engine in Santa Rosa, another pumping engine was at work at Yanacancha Mine. The following extracts from the 'Lima Gazette' were published in the Cornish papers by Mr. Edmonds:-- "_From the Government Gazette of Lima, 12th Feb., 1817._ "We have had the pleasure of receiving a letter from Pasco, dated 6th instant, containing the following account:-- "The second engine established in the mine called Yanacancha, which is far superior in point of beauty, convenience, and size to that called Santa Rosa, was set to work on Friday last, and notwithstanding the great quantity of water which filtered into this mine the engine with only half its power drained the mine completely in nine minutes. This filtration did not happen in Santa Rosa, on account of the quantity of hard copper ore on which the engine is situated. "By this successful operation, the water in several mines has been lessened considerably, amongst which in particular is that belonging to Don Juan Vivas, situate in the hill called Chucarillo, which at present affords ore of 400 marcos per caxon (50 cwt.). Of this ore about 25 lbs. has been received in this city, with a proof of 2 lbs. made in Pasco, showing not only the richness of the ore, but its easy extraction and cleanness for the ready refinement of it. And another proof has also been received from another mine, situate in Chucarillo, belonging to the widow Mier, in company with Don Joachin Aitola, which yields 100 marcos per caxon of 25 cargas. "To this agreeable news we ought to add that at the arrival of the whaling ship 'Asp,' bound from London, having on board a large quantity of machinery for the Royal Mint, and for the constructing of eight engines more, equal to those in Pasco, with the advantage that they are of the last patent and more easy to be worked; but what is of greater importance is the arrival of Don Ricardo Trevithick, an eminent professor of mechanics, the same who directed in England the execution of the machinery now existing in Pasco. This professor can, with the assistance of the workmen who accompany him, construct as many engines as are necessary in Peru, without any need of sending to England for any part of these vast machines. The excellent character of Don R. Trevithick, and his ardent desire for promoting the interests of Peru, recommend him in the highest degree to public estimation, and make us hope that his arrival in this kingdom will form the epoch of its prosperity, with the enjoyment of the riches enclosed in it, which could not be enjoyed without this class of assistance, or if the British Government had not permitted the exportation from England, which appeared doubtful to all those who knew how jealous that nation is in the exclusive possession of all superior inventions in arts or industry." So far everything promised success. Two pumping engines had so reduced the water in two of the mines, that the miners were at work, and the people of Lima believed that many more such engines would be usefully employed, now that Don Ricardo Trevithick was with them. "DEAR SIR, "LIMA, _February 15th, 1817_. "We arrived here last Saturday in good health. The (our) Mint is at work, and coined five millions last year, and in their way of working does very well; but I trust to make it coin thirty millions per year. "Two engines are drawing water, and two drawing ore, at the mines, but in an imperfect state. If I had not arrived, it must have all fallen to the ground, both in their mining and in their engines. I expect we shall go to the mines in about ten days, from where I will write to you every particular. "There are still two engines to put up for lifting water, and two for winding ore, and those at work to be put to rights. They are raising ores from one mine which is immensely rich, and from what I can learn, a much greater quantity will be got up, when the whole are at work, than these people have any idea of. Several other mines will also be set to work by engines that we shall make here. We have been received with every mark of respect, and both Government and the public are in high spirits on account of our arrival, from which they expect much good to result. "Mr. Vivian died the 19th of May. I believe that too much drink was the cause of it. Uville, I think, wished him gone, and was in great hope that I should not arrive. His conduct has thrown down his power very much, which he never can again recover. "They all say that the whole concern shall be put entirely under my management, and every obstacle shall be removed out of my road. Unless this is done, I shall soon be with you in England. I am very sorry that I did not embark with the first cargo, which would have made a million difference to the company. The first engine was put to work about three months since, the other about two months; but they are as much at a loss in their mining as in their engineering. The Mint is the property of our company, and Government pays us for coining, which gives us an immense income; the particulars of which, and the shares in the mines, I have not yet gone into. I shall be short in this letter, because I know but little as yet, and that little I expect Mr. Page will inform you. A full account you shall have by the next ship, which I expect will sail in three weeks. This letter goes by a Spanish ship that will sail this afternoon for Cadiz. My respects, and good wishes to your family and to Mr. Day, and hope this will find you all as hearty as we are. "Mr. Page would not depart this life under the line, as he promised when at Penzance; but, on the contrary, has a nose as red as a cherry, and his face very little short of it. His health and spirits far exceed what they were in England. I am glad to have such a companion. With ... think he will have no reason to repent.... He will get a command at Pasco ... such as his ingenuity may find out, when on the spot; whether as a miner or an engineer I cannot say, but time will show. "If you have not insured my life I would thank you to do it now, if you can on reasonable terms. I do not wish them to take the risk of the seas in the policy, because the voyage here is over, and on my return I hope I shall not want it, therefore it must be for two years in the country. I will get a certificate of my health, if they wish it, from the most respectable inhabitants, and also from the Vice-king, if they wish it. The policy may be drawn accordingly. "Be so good as to write me often, with all the news you can collect. If you wish your dividends in this company to be applied to further advantage in any new mines I may engage in, in preference to having it sent to England, I will, as the dividends are made, do everything in my power to improve the talent. On this subject I must have your answer before I can make any new arrangement under this head. I will thank you to send a copy of Mr. Page's letter to my wife; I mean such parts of it as belong to the business; there may be some things that I have forgotten to mention. "I remain, Sir, "Your humble servant, "RICHD. TREVITHICK. "MR. JAMES SMITH, _Limekiln Lane, Greenwich_." In the early part of 1817 four engines were at work in the mines, two pumping water and two raising the ore; while a fifth engine was coining in the Mint at Lima. Trevithick believed that he could much improve the engines and the mining, and that it would be necessary and practicable to arrange for the construction of engines in Lima; for though death and dissension had caused difficulty, the authorities were still prepared to give him full power. A strange defect in his character is evidenced in this letter. He wished his life to be insured for the benefit of his wife and family, but never thought of paying the yearly insurance premium, leaving it for his wife to pay, whom he had left, as far as he knew, penniless in England. On his sailing from Penzance, he told his wife that he had paid the house-rent for a year in advance, mentioning the sum. At the end of that time a demand was made on Mrs. Trevithick for a year's rent, being a larger sum than her husband had mentioned as the proper rent. It turned out that Trevithick had taken and paid for the house at six-monthly periods, instead of yearly periods. It was in the same street, and but three or four houses from that occupied by the parents of the eminent Sir Humphry Davy. A person pressed him for payment of a bill. Trevithick said, "Give me your bill," and writing on the bottom of it "Received, Richard Trevithick," handed it back to the claimant with "Now, will that do for you?" The payment of the life insurance obliged Mrs. Trevithick to part with her personal property, on which she had counted for support during her husband's absence. This inability to see the necessity of methodical action, when working with others, and utter disregard for hoarded money, caused him to be a somewhat unmanageable partner, though his genius never allowed him to sink; and in November, 1817, he wrote a letter, of which the following is an extract:-- [Illustration: MARKET, JEW STREET, PENZANCE. [W. J. Welch.]] "There are also nunneries beyond number, and in those places no male is ever suffered to put his foot. Through one of the most noted runs a watercourse, which works the Mint; and Mr. Abadia has repeatedly made all the interest he could to be admitted, for the purpose of inspecting it, but could never get a grant. The Mint belongs to our engine concern, and now coins about five millions per year. We have a contract from Government for making all the coin, both gold and silver, which gives an immense profit; and as there must now be coined six times as much as before, I must build new water-*wheels to work the rolls which we took with us from England. It was on this account that I wished to examine the watercourse for this purpose, without the knowledge of Mr. Abadia or anyone but Mr. Page and the interpreter, who always attends me. I walked up and knocked, in my blunt way, at the nunnery court door, _without knowing there were any objections to admit men_; it was opened by a female slave, to whom the interpreter told my name and business. Very shortly three old abbesses made their appearance, who said I could not be admitted. I told them I came from England, for the purpose of making an addition to the Mint, and could not do it without measuring the watercourse; upon which a council was held amongst them; very soon we were ordered to walk in, and all further nunnery nonsense was done away. We were taken round the building and were shown their chapel and other places without reserve. "Uville knew nothing about the practical part of the engines, and Bull very little, therefore you may judge what a wretched state this great undertaking was in before my arrival; no one put any confidence in it, and believed it was all lost, together with five hundred thousand dollars that had been expended on it. The Lord Warden was sent from Pasco to offer me protection and to welcome me to the mines. They have a court over the mines and miners, the same as the Vice-Warden's Court in England, only much more respected and powerful. The Viceroy sent orders to the military at Pasco to attend to my call, and told me he would send whatever troops I wished with me. The Spanish Government and the Vice-king since my arrival are quite satisfied that the mines will now be fully carried into effect, and will do everything in their power to assist me. As soon as the news of our arrival had reached Pasco, the bells rang, and they were all alive down to the lowest labouring miner, and several of the most noted men of property have arrived here--150 miles. On this occasion the Lord Warden has proposed erecting my statue in silver. On my arrival Mr. Uville wrote me a letter from Pasco, expressing the great pleasure he had in hearing of my arrival, and at the same time he wrote to Mr. Abadia that he thought Heaven had sent me to them for the good of the mines. The water in the mines is from four to five strokes per minute. "Tell the members of the Geological Society that Mr. Abadia is making out a very good collection of specimens for them, which will be sent by the first opportunity; and soon after I arrive at Pasco I will write them very fully." After Trevithick's death, in 1833, casts were taken from the head, and busts presented to scientific societies were thankfully received, with the single exception of his near neighbours at Penzance, who, under the name of the Royal Geological Society of Cornwall, refused it. Mr. W. J. Henwood, who had frequently drawn the attention of Cornishmen to Trevithick's engines, being about 1870 President of the Royal Institution of Cornwall, presented to it a bust of Trevithick, which was admitted within its walls. In 1819 Mr. R. Edmonds forwarded to the 'Cornwall Gazette' news from Lima, from which the following is extracted:-- "We have much pleasure in stating that accounts have lately reached England from Lima, giving the satisfactory intelligence that our countryman and able engineer, Captain Trevithick, was in February last in good health, and super-*intending the rich and extensive mines of Pasco. "Don Francisco Uville, a Spanish gentleman, having, with Don Pedro Abadia and others, formed a company to drain the mines of Pasco, unfortunately for Captain Trevithick, F. Uville was anxious to impress his countrymen with an opinion that it was _solely_ owing to him that steam-engines were first introduced into the silver mines of South America; and notwithstanding the obligations he was under to Captain Trevithick, he sought every opportunity, soon after Captain Trevithick's arrival at Pasco, to oppose him, in claiming to have the direction of the mines. "Captain Trevithick, knowing but little of the country, and disgusted with the treatment he received from Uville and the party he had formed against him, amongst whom was a gent who had lately arrived from England, retired from the concern, and proceeded on other important discoveries on his own account. "Things remained in this state until August, 1818, when Uville met his death, in consequence of the cold penetrating air of the Cordilleras on coming out of the mines in a strong perspiration. Mr. Abadia and his friends were then under the necessity of soliciting the assistance of Captain Trevithick. On condition of his having the sole direction of the mines, he was prevailed upon to accept the situation which had been first most faithfully agreed he should have had; and when the accounts last left Lima in February, Captain Trevithick had been five months at the mines as the chief superintendent. The mines are represented as being in the most prosperous state, and likely to realize the sanguine expectations of the share-*holders. Mr. Bull, an engineer from Chacewater, who left England with Uville, died at Pasco about ten months since." When this was written, Trevithick had been two years in the country, and found the immense difficulties of the undertaking increased by jealousies and jobberies. Mr. Uville was no more, neither were Vivian or Bull; but one man remained alive out of the four who had sailed from England with the first cargo of machinery. In August, 1818, Mr. Abadia, who from the first was a leading authority, requested Trevithick to take upon himself the sole management of the mines, where he continued until April, 1819, as shown by the following extract from Captain Hodge's journal, supplied by my friend Mr. Charles Hodge:-- "The first time they met was at Lima, on the 26th April, 1819, at Dr. Thorne's; your father had just come down from the Cerro de Pasco mines. On the 8th May following, I find my father witnessed the hanging of three men for killing two of your father's men, named Judson and Watson." Mr. W. B. Stevenson says:[128]-- [Footnote 128: See 'Historical and Descriptive Narrative of Twenty Years' Residence in South America,' by W. B. Stevenson, published 1842.] "The Mint was established in Lima, in 1565. The machinery was formerly worked by mules, eighty being daily employed till the year 1817, when Don Pedro Abadia, being the contractor for the coinage, Mr. Trevithick directed the erection of a water-wheel, which caused a great saving of expense. In the year 1817 two Englishmen, sent from Pasco by Mr. Trevithick (who afterwards followed with the intention of working some of the silver mines in Conchucos), were murdered by the guides at a place called Puloseco. This horrid act was perpetrated by crushing their heads with two large stones, as they lay asleep on the ground. The murderers were men who had come with them from Pasco. "I have heard Mr. Trevithick say, that on shaking hands with the men who work in those quicksilver evaporating rooms, drops of quicksilver show themselves at the fingers' ends, and that the workmen wearing shoes take them off before leaving the work, to pour out any quicksilver that had oozed through the pores of the skin, which had been respired in the floating state of vapour. The men so employed fell a sacrifice in twelve or eighteen months." Trevithick's experience in applying the force of running streams was turned to good account in giving an economical helpmate to the steam-engine then at work in the Mint. Miers says:[129]-- [Footnote 129: See Miers' 'Travels in Chili and La Plata,' published 1826.] "Another instance occurs in the unfortunately ruinous result and lamentable ill-treatment of the persons engaged in the attempt to introduce European improvements and British machinery into the great silver-mining district of Pasco (Chili), in which was engaged one of our most celebrated engineers, a most able mechanic, to whom the grand improvements in our Cornish mines are chiefly indebted--I mean Mr. Richard Trevithick. Trevithick was induced to furnish the machinery at an expense of 3000_l._ sterling, upon condition of being admitted a partner in the amount of 12,000 dollars in the joint stock of the company, and entitled to a share corresponding to the capital employed. This share was calculated at a fifth. Trevithick, before he embarked for Peru, divided his interest in the concern into 320 shares, each representing 38 dollars, and these were sold in the market for 125_l._ sterling each; some few were sold for 100_l._ cash. The success of the engines gave to some of the persons interested much confidence, who conceived they could now do without the management of the ingenious Trevithick. Every possible obstacle was therefore thrown in his way by those who, from motives of jealousy, wished to get rid of him. The persons to whom Trevithick's and other shares had been sold in London, sent out to Lima an agent, whose duty it was to look after their interests in the concern; but as it was found a much larger sum would be necessary for carrying the enterprise into effect than had been calculated, a collision of interests took place; complaints were made on all sides as to the delays and expenses which those who did not comprehend the almost insurmountable difficulties of the undertaking attributed to mismanagement and carelessness. The greatest share of opprobrium fell unjustly upon Trevithick, who, being a man of great inventive genius and restless activity, was at length completely disgusted, and retired from the undertaking. He left Pasco, although Abadia offered him 8000 dollars per annum, together with all his expenses, if he would continue to superintend the works; on no conditions would he consent to contend with the jealousies and ill-treatment of the persons with whom he had to deal. He soon after entered into speculations with some of the miners at Conchucos, for whom he constructed grinding mills and furnaces, with the view to substitute the process of smelting for that of amalgamation in silver ores, in which vain pursuit he became a considerable loser." "MY DEAR SIR, "BODMIN, _November 3rd, 1869_. "Forty-seven years are now passed since I had the great pleasure of meeting your father in Peru, and I have a vivid remembrance of the gratification afforded to my messmates when he came to dine with us on board H.M.S. 'Aurora,' then lying in Callao. I was then a lieutenant of that beautiful frigate, and was introduced to your father by Mr. Hodge, of St. Erth, with whom I had become acquainted in Chili. I remember your father delighting us all on board the 'Aurora' by his striking description of the steam-engine, and his calculation of the 'horse-power' of the mighty wings of the condor in his perpendicular ascent to the summit of the Andes. Your father's strong Cornish dialect seemed to give an additional charm to his very interesting conversation, and my messmates were most anxious to see him on board again, but he left shortly after for the Sierra. "The Pasco-Peruvian mines were those which your father was engaged to superintend before he left England, and he had actually managed, by incredible labour, to transport one or two steam-engines from the coast to the mines, when the war of independence broke out, and the patriots threw most of the machinery down the shafts. This fearful war was a deathblow to your father's sanguine hopes of making a rapid fortune. About a year after this terrible disappointment (I think in 1822), the 'San Martin,' an old Russian fir frigate, purchased by the Chilian Government, sank at her anchors in Chorillos Bay, ten miles south of Callao, and your father entered into an engagement with the Government in Lima to recover a large number of brass cannon, provided that all the prize tin and copper on board which might be got up should belong to him. This was a very successful speculation, and in a few weeks your father realized about 2500_l._ I remember visiting the spot with your father whilst the operations were carried on, and being astonished at the rude diving bell by which so much property was recovered from the wreck, and at the indomitable energy displayed by him. It was Mr. Hodge, and not I, who then urged in the strongest manner that at least 2000_l._ should be immediately remitted to your mother. Instead of this, he embarked the money in some Utopian scheme for pearl fishing at Panama, and lost all! "I had the honour of dining with Lord Dundonald on board the crazy frigate 'Esmeralda,' which carried his flag in Callao Bay, but I never heard of the gallant conduct of your father in swimming off to his ship and advising him of an intended assassination. I fancy that this must have occurred before I came on the station, probably in 1820, or 1821. "Believe me, "My dear Sir, "Very sincerely yours, "JAMES LIDDELL." Trevithick's floating caissons for the sunken ship of Margate Bay in 1810[130] were similarly applied in 1821 in the Bay of Callao. In Lima he became acquainted with Lord Dundonald, whom he warned of a plot on his life, discovered in his friendly intimacy at the residence of President Bolivar. Those two remarkable Englishmen were alike in their daring inventiveness, and not unlike in face and person. [Footnote 130: In 1834 the writer was employed at a marine engine works in London, and made working drawings for a scheme of Lord Dundonald's, who expressed great pleasure in meeting the son of his old friend.] We have traced Trevithick's steps from his landing at Lima in 1817 to the destruction of the mine machinery by the civil wars, and his departure from there about 1822. But one link in the chain has been nearly lost. During some portion of those five years he visited Chili, and set to work mines which are still producing large and profitable quantities of copper. The late Mr. Waters, an eminent Cornish miner, who for many years managed some of these mines in the neighbourhood of Valparaiso, said that Trevithick's name was better known to the miners there than to the miners in Cornwall. This statement was made in the Dolcoath account-house at a public meeting, the speaker and the writer being both on the committee of management. Simon Whitbarn, of St. Day, informed the writer that at Copiapo and at Coquimbo he had seen large heaps of copper ore, apparently unclaimed, which the people said had been raised by Don Ricardo Trevithick. About 1830 a miner, returned from South America, made a claim for wages for watching mineral left behind by Mr. Trevithick. To further illustrate this history, we have a report written by himself:-- "_Memoranda regarding the Copper and Silver Mine of * * * *._ "In 1814 an arrangement was made between the miners of Peru and myself for furnishing them with nine steam-engines and a mint, to be executed in England and erected in the mines of Pasco; and in October, 1816, I sailed from England for that country, for the express purpose of taking the management of those mines and erecting the machinery, being myself a large proprietor of the same. The Government of Peru was at that time subject to old Spain, under the immediate superintendence of a Viceroy. The machinery having been erected, and its sufficiency for the intended purpose of draining the mines having been proved to the satisfaction of all parties, there was granted to me a special passport by the Viceroy, for the purpose of travelling through the country to inspect the general mining system, and to make the native miners acquainted with the English modes of working. In return for which Government conceded to me the privilege of taking possession for my own benefit and account of such mining spots as were not previously engaged. In this way I travelled through many of the mining districts, and although I met with several unoccupied spots which would have paid well for working, yet, being a considerable distance inland, and requiring more capital to do them justice than I could then advance, I abandoned for the time all ideas of undertaking them. "To this, indeed, there was but one exception, and that was a copper and silver mine, the ores of which are uniformly united, in the province of Caxatambo. "When the patriots arrived in Peru, the mine was deserted by all the labourers, in order to avoid being forced into the army. In this state it remained for a considerable time; but on the Spaniards retreating into the interior, I recommenced working; and to secure my right to this mine under the new Government I at the same time transmitted a memorial and petition to the established authorities, accompanied by a plan and description of the mine, the result of which was the formal grant, as exhibited in the Spanish document now in your possession. It was not my good fortune to be allowed to follow up my plans, which almost warranted a certainty of success. I had scarcely commenced a second time when the Spaniards returned, and everyone again was obliged to fly. The country, as is well known, continued for a long time in a most distracted state, and I was ultimately compelled to quit that part of Peru, robbed of all my money, leaving everything behind me, miners' tools and about 5000_l._ worth of ores on the spot ready to be carried to the shipping port. Numerous as my misfortunes had been in Peru, and heavy as my disappointments, I felt none so sensibly as this, because it was an enterprise entirely of my own creation, and so open to view that I was enabled to calculate at a certainty the immense value contained within the external circle where the copper vein made its appearance in the cap of the mountain, and to be obtained without risk or capital. However, revolution followed revolution, and the war appeared to me to be interminable. Even Bolivar's arrival at Lima made it still worse, for he forced me into the army, with my property, which is not paid to this day, to the amount of $20,000; and at his urgent solicitations, disgusted as I was with what I had seen and suffered in Peru, I determined on quitting it for a time at least, and on visiting Colombia. Being at Guayaquil I first heard the name of Costa Rica and its recently-discovered mines, and having no doubt of the authenticity of my information, I immediately proceeded thither instead of going to Bogota to carry Bolivar's orders into execution, not having been paid. This short digression you will excuse, as it points to the causes of my separation from a property of so much value, as I consider the mine of * * * * *. Thirty years ago the neighbourhood of * * * * was famous for its silver mines. At the foot of the copper hill, on a fine stream, are two sets of works on a most extensive scale, which were carried on on account of the Spanish Government. The silver was found in lead veins, which are very large and numerous all around. The soil is very rich, and the climate as good as any in the world, wheat and Indian corn both growing round the mountain. Provisions and wages are low, the latter 1_s._ per day, and there are about 20,000 inhabitants within three miles. Wood for smelting and other purposes is abundant on the spot. "* * * * is * * leagues from Lima; the port of * * * * where the ores are to be shipped, is 37 leagues north from Lima; and * * * * copper mine * * leagues back in the country east from this port, a good road for mules and plenty of them. The miners contracted with me to break the ores and deliver them at the surface for 4_l._ per ton, which was double what I ought to have paid them; the farmers likewise contracted to carry the ores to the port at the same rate, which comes to sixpence a league for each mule cargo. But even at present wheel-carriages might travel over a large proportion of the road, and a small outlay would make it a carriage-road the whole distance, and then the expense of carriage would be diminished more than one-half. Taking it, however, at what it cost me, the whole expense on the ores delivered on board would not amount to 9_l._ a ton, and as I conceive the freight to England would not exceed 4_l._ a ton, the total cost would be 13_l._, but say 15_l._ a ton. Its value in England would be above 80_l._ a ton. At the time I worked I intended to have sent 300 tons of ore to England, for in the then disturbed state of the country it would not have been prudent to risk myself on smelting works. I think it will ultimately be found preferable to smelt on the spot, but the course I should recommend in the meantime would be to send out two practical miners to direct and superintend the natives, who ought to be employed by contract to break and raise the ores and deliver them on board. In that case no erections whatever would be wanted; nothing but about 70_l._ worth of labourers' tools. "I remain, Sir, "Your very humble servant, (Signed) "RICHARD TREVITHICK." The foregoing undated report was written after his return to England from South America. The Viceroy granted him a special passport through the country, that he might give general instructions to the workers of mines, with the right to claim any mineral spot for his own working not under grant to others. He often spoke of his discovery and working of the great vein of copper ore in Caxatambo, estimated to contain copper worth twelve millions sterling, the working of which was prevented by the frequent revolutions and unsettled government of the country; and of residing for months with Bolivar, at that time the Republican Governor of Peru. Bolivar's cavalry were short of fire-arms. Trevithick invented and made a carbine with a short barrel of large bore, having a hollow frame-work stock. The whole was cast of brass, stock and barrel in one piece, with the necessary recess for the lock; the bullet was a flat piece of lead, cut into four quarters, held in their places in a cartridge until fired, when they spread, inflicting jagged wounds. He was obliged to serve in the army, and to prove the efficiency of his own gun. He was never a good shot, nor particularly fond of shooting; and, after a long time, Bolivar allowed him to return to his engineering and mining. Scarcely had he got to work again when the Royal Spanish troops, getting the best of it, overran the mines, and drove Trevithick away penniless, leaving 5000_l._ worth of ore behind him ready for sale. The 300 tons of ore, valued at 24,000_l._, never reached England; and the writer, who was to have returned to Peru in the ship that had been engaged to convey it, lost the chance of being a youthful traveller in foreign lands. Trevithick left Lima about 1821 or 1822, for Bogota, in Colombia, on a special mission for Bolivar. On his way, putting in at Guayaquil, he heard of rich mines in Costa Rica, and thinking they would pay better than Bolivar's promises, he threw up his engagement and made for the new venture. It was probably at Guayaquil that he met Mr. Gerard, a Scotchman of good family and education, then sailing on the Pacific coast as a speculator. Since Trevithick left the mines of Cerro de Pasco, more than one English adventurer has attempted to work them. At the present time they are in the hands of a large company, and are thus spoken of in the 'Cornish Telegraph' of May 10, 1871:-- "_Cerro de Pasco and its Silver Mines._ "This place, in the Republic of Peru, is situated on the top of the Andes, on the eastern side of the Western Cordillera. It stands about 15,000 feet above the sea level, and is said to be one of the highest, if not the highest, inhabited place of importance in the whole world. "From Callao to here is a distance of 160 miles, but, in consequence of the rapid ascent in such a comparatively short distance, it is considered a quick journey if mules make it in six days; it more frequently takes them a week, and at times, during the season of snow and rain, the pampas, which are the table-lands of these mountains, are impassable for several days together. "The town of Cerro de Pasco, which at present numbers 10,000 souls, is of no small importance, considering its great altitude and inconvenient distance from the coast, but it lacks order and design in every part. The streets are crooked and uneven; and the houses are stuck about anywhere and everywhere, with the greatest display of uneducated taste that I have ever before witnessed; moreover, it would be difficult to find another such place so equally dirty. "It rains and snows on these heights with not much cessation for about six months in the year, and in what is termed the dry season there are also frequent falls of snow. Furthermore, water boils at 180° Fahr. instead of at 212°, as with you; consequently it requires six minutes to cook an egg. "The majority of the inhabitants are a low type of Indians, who are small in stature and mind, but are large in cunning, and have exceedingly plain features--not possessing the slightest trace of the noble features and bold simplicity of the Indians of the North. "Any person acquainted with minerals and mining coming up to Cerro de Pasco would fancy that the whole town was built on the back of one huge lode; go wherever one may, through the streets, or on the outskirts of the town, and even up to the slopes of the hill surrounding it, he finds it to be all lodestuff everywhere; its composition is what we Cornish miners generally term an iron gossan. "The greater portion of this mineral spot is parcelled out into setts or grants, which consist of pieces of ground 60 yards in length by 30 in width, giving to the place no less than 664 mines. At present there are no more than seventy-eight of them at work, and only sixty-three of which are producing ore, and the united returns amount to 2,000,000 oz. of silver per annum. Owners or companies have roads leading down to their mines, formed of steps cut out in the rock, dipping at angles varying from 30° to 50°. When you have descended to the depth of the mines, the levels or holes leading to many of them are so small that one has to drag himself along snake fashion until he reaches the main excavation. The miners break down the silver ore with pointed bars of iron, and then shovel it into bags made of hide with the shoulder-bone of some animal; after which the stuff is carried to surface on men's and boys' backs. "When all the mineral has been extracted there remains an immense excavation, and in consequence of the roof not being properly supported with timber, one risks his life in entering it. Heavy falls of rock frequently occur, and by which means a vast number of persons are annually killed. One day in the last century, at the mines of 'Matagente' (which word means killed people), which are situated in the rising ground on the northern side of the town, while a great number of men and boys were at work, the roof of one of these immense chambers, consisting of many thousands of tons, fell in without giving the least warning, and 'in the twinkling of an eye' the souls of 300 Peruvian miners rushed into the presence of their Redeemer. Their bodies have never been exhumed, and their shattered bones, still remaining, will bear evidence of the catastrophe to future explorers. An adit has been driven through the district, beginning at the Lake of Quiulacocha on the south-west, and terminating at the mines of Ganacaucha on the north. The entire length of the adit, including its branches, is about 3 miles, and its average depth from surface 50 fathoms. Three perpendicular shafts, situated at about 600 yards apart, have also been sunk from surface to a short distance below the adit. "The whole of the machinery for the mines in question, which is being made and dispatched by Messrs. Harvey and Co., of Hayle, Cornwall, consists of four steam pumping engines, six boilers, four iron main beams, four balance ditto, and also a sufficient quantity of 24-inch pit-work for both shafts. No single piece of all this cumbrous machinery must weigh more than 300 lbs., in consequence of its having to be transported on the backs of mules from the coast to this mountainous region. Although the main distance is no more than 160 miles, these beasts with their burdens have to climb an altitude of 15,000 feet before they reach their destination. Moreover, the passes in ascending the Andes and Cordillera can only be correctly imagined by experienced travellers. Some of the defiles are not much wider than a sheep-path, and with a thousand feet below you a roaring cataract, and thousands of feet above you snow-capped overhanging mountains, looking so dreadful that the awe-struck stranger in the pass fears that the next peal of thunder will cause them to topple." [Illustration: MULE TRACK FROM LIMA TO CERRO DE PASCO. [W. J. Welch.]] "I observe in a paper which is now before me, entitled 'The Introduction of the Steam-Engine in the Peruvian Mines, by Richard Trevithick, in 1816,' that when Captain Trevithick arrived at Lima on board the ship 'Asp,' with sundry small engines for the draining of the mines of Cerro de Pasco, he was immediately presented to the Marquis de Concordia, then Viceroy of Peru, was most graciously received by the most flattering attention of the inhabitants, and subsequently the Viceroy ordered the Lord Warden of the mines to escort the great man with a guard of honour to the mining district. In contrasting the two epochs, that of Trevithick in 1816, with this of Wyman and Harrison in 1871, one is led to exclaim that there were _gentlemen_ in Peru in 1816, and they gave unto Cæsar that which belonged to Cæsar."[131] [Footnote 131: In 'Mining Journal,' W. R. Rutter.] The same newspaper, on the 9th November, 1870, stated:-- "The 'Bride' sailed from Hayle on Thursday with a portion of the machinery made by Messrs. Harvey and Co., of Hayle, destined for Cerro de Pasco, in Peru. The work comprises four 37-inch cylinder pumping engines; no part to weigh more than 300 lbs." To enable the parts to be reduced in weight, each steam-cylinder was made of thirty-seven different pieces. The mechanics of Trevithick's time could not make a steam-cylinder in parts; therefore his difficulties in designing and conveying the machinery were ten times greater than they would be in the present day, and necessitated the extreme simplicity of his engines. His residence with the Peruvians from 1816 to 1822 taught them the use of high-pressure steam-engines in their mines; and indirectly heralded the advent of the steam-horse, now as familiar to them as to the residents in many English towns. CHAPTER XXIII. COSTA RICA. "MY DEAR SIR, "In the month of June, 1822, I disembarked in the port of Punta de Arenas, in the Gulf of Nicoya, the only one corresponding to that province at present in use on the Pacific side. My object was to dispose of a cargo of cotton which I had brought from Realejo, and to purchase sugar in return. Circumstances, not necessary to mention, and the loss of the small vessel with which I was trading on the coast, caused me to remain in Costa Rica. Its name implies a very early conviction of its natural opulence; it is certain that gold and silver abounded among the Indians at the period of its conquest by the Spaniards. It was at one time a favoured and flourishing agricultural colony, but from various causes sank into neglect. Such was the apathy, both of the Government and of individuals, that the very existence of the precious metals in the country had been almost entirely forgotten. In the end of 1821, a poor man, Nicolas Castro by name, opened the first gold mine known in Costa Rica since the conquest, and his success soon induced others to try their fortunes; with fortunate results, in a few months a mining district sprang into being. "A gentleman of the name of Alverado constructed at a very considerable expense what is called an Ingenio, consisting of various edifices for depositing the ore, machinery driven by water for grinding it and afterwards blending it with quicksilver for amalgamation. [Illustration: PLATE 14. London: E. & F. N. Spon, 48, Charing Cross. Kell. Bro^s Lith. London. TREVITHICK'S ROUTE ACROSS THE ISTHMUS OF COSTA-RICA.] "When I landed in June, 1822, only five or six mines had been discovered, but in January 1823, when I left the country, I cannot pretend to enumerate those in a state of progress and of promise. It is not only in the mining part of the business that the want of skill is prejudicial to the result. It is imperfectly ground, for instance, and consequently cannot be brought into that intimate contact with the quicksilver which is necessary to perfect amalgamation. The machine for grinding is very simple: a large flat stone, like a mill-stone, is made to revolve upon its fellow by an ox or mule power. The poorest people reduce it to powder by manual labour, in the same way as they grind corn preparatory to baking it into cakes. Alverado's machine promised to be a great acquisition. The grinding was facilitated by a little water; when the ore is judged to be sufficiently well ground, a portion of quicksilver is thrown in by guess, and the motion of the machine continued until the union of the metals is supposed to be complete; the whole is then removed into large wide-mouthed conical-shaped wooden vessels. In these receptacles it undergoes repeated washings, by stirring occasionally round, and afterwards communicating to the vessel a swinging or half-rotary motion, by which a quantity of the water, having the earthy particles suspended, is driven over the edges; the amalgamated mass naturally sinks to the bottom, and at last remains tolerably clean. "The next step is the recovery of the quicksilver by distillation, after which the gold is melted in a crucible and run into ingots. The coasts are hot, and from the luxuriant vegetation that everywhere abounds, emit, as in all situations of the kind, febrile miasma in abundance when acted on by heat and moisture; but black vomit is unknown, and all the fever cases I have seen have been of the remitting and intermitting, free from character of malignancy. As the ground begins immediately to spring from the coast, and does so indeed very rapidly, a few miles takes us beyond the region of even these slight fevers, and as we continue ascending to the central table-land, a climate is encountered that may vie with any in the world for benignancy and beauty. We there meet with the fruits of the torrid zone, and near them the apple and the peach of Europe. The orange tree is in bearing the whole year. As in all situations within the tropics, it has a proper rainy season, but it is less inconvenient and disagreeable than might be expected, for it seldom rains two days in succession, and when it does, is invariably succeeded by an interval of fine weather; for the most part every day presents a few dry hours. The mines are situated on the ridges of the Cordillera, which without presenting snow-covered peaks, attain, nevertheless, considerable elevation. The clouds, constantly attracted by those high summits, render the rainy season more severe in the mining district than in the plains. The greatest inconvenience was from the snakes, which in those solitary jungles, now first invaded by man, are very numerous and many of them venomous. Provisions are cheap and excellent. In short, there is but one fault I find with the country, and it is a great one, I mean the frequency of earthquakes. "J. M. GERARD." MEM. IN MR. GERARD'S WRITING. "_Illustrations of the Map._ "Though the plans and sections explain themselves, a few observations will not be misplaced. The deep adit for the Coralillo would be 600 yards, that for Quebrada-honda 400 yards, and besides serving as drains would form admirable roads for conveying the ores into the vale where the stamps must be erected. "The veins would be worked upward from the adits, and thus no expense would be incurred for ages to come in lifting either water, ore, or rubbish to the surface. Padre Arias Mine is an exception, requiring a powerful water-wheel, or an hydraulic pressure-engine, for which there is a fine fall of water of 135 feet. The mines in Quebrada-honda are those in which an interest has been procured. Captain Trevithick has an interest in the mine of Coralillo; the great watercourse is also his. "It will be seen by the plan that there are 75 fathoms fall to the point where his present mill is situated, and other 75 fathoms to the junction of the rivers of Quebrada-honda and Machuca. The whole length does not amount to two miles, within which it is estimated that sufficient power may be commanded to stamp 500,000 of quintals annually. To bring it up to that pitch, the waters of Machuca must be brought to join those of Quebrada-honda at Trevithick's mill, and then 40 tons of water per minute could be delivered in the dry season." Extracts from a report by Trevithick and Gerard in 1827:-- "This map consists of several distinct parts. The middle part shows the mining district, the present dimensions of which are small, the length being hardly four miles, breadth from two to three, and the superficial extent from eight to ten miles. The upper part of the plan is a section of the north ridge, called Quebrada-honda, and shows the line of the proposed adits. The lower part in like manner exhibits the south ridge, called Coralillo. The map further shows the inclination or gradual fall of the ground along the valley, and of the streams by which the mills are driven. "The canal is likewise shown 5000 yards in length, by which the rivers of Machuca would be brought to join that of Quebrada-honda. "Castro's mine is situated on the southern ridge, and was the first mine worked to any extent. There the veins are very large; in fact, from the manner in which a number of horizontal veins are seen falling into the perpendicular or master vein, the great body of the mountain would appear to consist of lodes. This mass of ore is in general rich. It has been worked open to the surface, somewhat like a quarry, so that it is not difficult to calculate in cubic feet the quantity that has been excavated. The mine is supposed to have yielded in the course of the last six years gold to the value of 40,000_l._, and by measuring the excavations it would appear that this amounts to, on an average, one ounce of fine gold to every ten or twelve quintals of ore. In 1821 the existence of silver was only imagined. In 1823 it was fully ascertained. Ever since 1824 it has constituted a small but constant portion of the produce of Quebrada-honda, and in 1827 it was decidedly evinced in Coralillo. The discovery of gold in Coralillo led them to work in Quebrada-honda, where they found both gold and silver, and the discovery of silver in Quebrada-honda, by strengthening the expectation of it in Coralillo, led in its turn to the discovery of silver there. In Quebrada-honda they only work on the ground in the immediate vicinity of the stream, and that in the most imperfect manner; but great light has been thrown on the value of the ores on this spot and in the district generally by the progress made in working what is called Padre Arias Mine, which takes its name from an ecclesiastic who first worked it. This mine is situated in low ground near the verge of the stream, and was at first only worked for gold. There were soon, however, indications of silver, which increased progressively in sinking, till at the depth of only 10 yards the influx of water exceeded the means of draining, and the works under water-level were necessarily abandoned, at a time when ores were yielding upwards of 200 oz. of silver to the ton, a striking proof of the tendency of silver ore to improve in this district as the depth increases. "Mr. Richard Trevithick, that eminent Cornish miner and engineer, so well known for his inventions, and particularly for the high-pressure steam-engine and the drainage of the Pasco Mines in Peru, when unfortunately civil war burst out in Peru, and the Royalists, considering those engines as the main instrument for supplying money to the Independents, rendered them useless by destroying or carrying off some of the most important pieces. "Mr. Trevithick having heard favourable reports of the mining district we are now describing, soon after repaired thither, and was so fully impressed with its value and importance that he made an extensive contract for different properties, and resided in the country for four years. "He is now in England ready to give explicit answers to any inquiries that may be made as to the mineral wealth of Costa Rica, and the extraordinary facilities afforded by its position and natural advantages. An estimate has been made for establishing a complete mining concern in Costa Rica, with houses, iron railroads, stamping mills, &c., so as to raise, stamp, and bring into refined gold the produce contained in 250,000 tons of ore per year. "The result of six years' experience shows that the following list of machinery and tools with a few miles of railroad would be sufficient. The communication with the mines being satisfactorily established by the route of the port of San Juan de Nicaragua and the river Serapique, the materials would be sent by the Atlantic at very much less cost than by around Cape Horn. "It is situated within 14 leagues of the Pacific Ocean and 30 leagues of the Atlantic, in a mountainous district intersected by deep valleys or ravines. The mountains are covered with wood fit for fuel, mining, architecture, and machinery. There is a population of 50,000 inhabitants within one day's journey of the mines. The climate is perfectly salubrious, provisions of all kinds remarkably cheap, labourers' wages from four to five dollars per month. The mines secured are freehold property, and with one exception are unencumbered by tribute or native partners. The attention of Government and of individuals has recently been directed to the discovery of a road from the interior to the river Serapique, which, rising in the high lands of Costa Rica, pursues a northerly course and joins the San Juan about 10 leagues above the harbour of that name, being itself navigable for about 12 leagues above the junction. The opening of this road is a matter of much importance to Costa Rica in a general point of view; the port of Matina being always bad and impracticable during the prevalence of northerly winds; that of San Juan being, on the contrary, capacious, easy of access, and at all times perfectly secure. The distance is much the same as by the way of Matina. Several expeditions have been undertaken with a view of exploring an eligible road to the highest navigable point of Serapique, and although as yet none fit for mules has been discovered, the results of the experiments justify the expectation of success. Individual enterprise is active in the attempt, and Government has wisely offered a reward to successful speculators. "Captain Trevithick and Mr. Gerard, with a particular view to the enterprise now under consideration, and after considerable risk and labour, succeeded in laying down the navigable head of the Serapique and in throwing such light on the intervening tract as will be of great assistance to future adventurers. They ultimately constructed a canoe in which they sailed down to the port of San Juan." Plate XIV. shows Trevithick's route across Costa Rica. A memorandum in Trevithick's writing, apparently a diary, says:-- "From where we returned our mules to the place where we commenced to make our rafts and boat was eleven days' journey, a distance of 50 or 60 miles. The first and second days after parting with the mules we passed some soft ground, with three or four rivulets of water in narrow vales, about 10 miles on the side of the decline of the high ridge on our left. It could easily be made passable for mules, as the bad places where they could not travel did not exceed two or three miles; and had we kept a little more to the left above the soft ground, probably they could have passed. The next bad place was about a mile after the second pass across the San José River, being a very deep and abrupt vale. Had we never passed the San José River, but left it on our right hand, the road would have been much shorter, and we should have avoided this deep vale, and also the three other vales, and their three rivers of Montelegre, Juan Mora, and Ajerbi. They were, however, small, not more than half the leg in water, which is a proof that their source was not above 10 miles off and must have originated in the side of the high ridge on our left. None of the vales were impassable to mules, except that between the second passing of the river San José and the river Montelegre, which was about a mile, and might be made passable for mules by a diagonal road to be made in the side of the hill a little higher up. "Only five or six miles of road would require to be made for mules on the whole of the way we came, to where the river Serapique is navigable. We observed that we should have avoided those vales by passing a few miles more to the left, where we saw one continued high ridge running from the highest ridge of the continent, commencing at the volcano and terminating in a point near to where the Serapique River is navigable. "On a regular decline for perhaps 7000 or 8000 feet in height, down to near sea-level, which would in that distance have given a fall of about half an inch in a yard, four men in ten days would make, I have no doubt, this ridge passable for mules on a regular descent to where the Serapique River is navigable. I have no doubt if we could have spent one week more on our journey we might have passed mules the whole distance with us. To carry machinery from where the Serapique is navigable to the mines is about one-third farther than from the port of Arenas on the south, on which the carriage is two dollars per mule load; three dollars might therefore be charged per mule from the Atlantic side, a much less cost than by way of Matina, or by going around Cape Horn. It would give a speedy communication and a great accommodation to the province of Costa Rica, which I doubt not would gladly contribute to its making. "The mining district occupies the mountain of Aquacate, nearly equidistant from the port of Punta de Arenas, in the Gulf of Nicoya, and from San José, the capital of the state, about 14 leagues from the former and 12 from the latter. The high road passes through the centre of the district. "The chief outlay after paying for the mines would be for erecting stamping mills and making railroads." This broken information barely gives an idea of the importance of the Costa Rica mines, or of what Trevithick did between the time of his landing on the Pacific shore, about 1822, and his leaving the mines on his search for a new route over the Cordillera to the Atlantic shore, about 1826 or 1827. Judging from the rough map on which Trevithick has marked his line of travel across the isthmus, the mines of Machucha, Quebrada-honda, and Coralillo, were inland from the Gulf of Nicoya, on the Pacific, some forty or fifty miles, the latter mine having its water shed into the Rio Grande, while the two other mines, not far off, opened into the Quebrada-honda River. The central high ridge of the Cordillera was between the mines and the Atlantic; indeed the mines are on high ground at the foot of volcanic mountains. San Mateo seems to have been the place of importance near the mines, and probably a well-known mule-track was in use through the mountain ridge to San José, the capital, once numbering thirty thousand inhabitants; but this line failed to reach a good port on the Atlantic coast. The travellers, therefore, abandoned the known track, and turning to the left, made their way between the volcanic peaks of Potos and Barba, hoping that on the eastern slope of the Cordillera navigable rivers would be found either to the Atlantic or to the San Juan de Nicaragua, which joined the Atlantic at the port of San Juan. It was probably at this volcanic ridge that the precipitous road obliged the mules to be sent back. The track was then due north, towards Buona Vista, below which the river Serapique took its rise, running into the river San Juan. Where they crossed this river was fifty or sixty miles from where the mules had left them. Trevithick marked the river-crossing with a steamboat, indicating its navigability; but the writer infers that it had so much of the mountain torrent about it, that the travellers took a line still through unexplored country towards the port of San Juan, on the Atlantic, for the track and the description show that the river San José was crossed, and also another river running to the Atlantic. They probably were stopped by swamps on approaching the San Juan, and retracing their steps to the Serapique, constructed rafts or canoes, and after hairbreadth escapes sailed down it to the junction with the San Juan, and down the latter to its junction with the Atlantic at Port San Juan, or Greytown. Eleven days were passed from the parting with the mules near the crossing of the highest ground, from whence they saw a continuous ridge, commencing at the volcano and terminating near to where the Serapique is navigable on a regular decline for perhaps seven or eight thousand feet down to near sea-level, giving a fall for the whole distance of about half an inch in a yard, or in railway parlance 1 in 70; for this was what was in Trevithick's head, that his steam-horse should carry where the mule could not, and that miners and machinery should be so taken to his mines from the Atlantic, giving those who chose an opportunity of continuing their railway journey to the Pacific. The writer has heard Trevithick describe the excursion as lasting three weeks, through woods, swamps, and over rapids; their food, monkeys and wild fruit; their clothes, at the end of the journey, shreds and scraps, the larger portion having been torn off in the underwood. Mr. Thomas Edmonds also listened to Trevithick's narrations, some of which he gives in the following:-- "In 1830 I frequently saw Trevithick at the house of Mr. Gittins, at Highgate, a schoolmaster, with whom were two boys that had accompanied him from Costa Rica, called Montelegre. Before Captain Trevithick no European had adventured on or explored the passage along the river from the Lake Nicaragua to the sea. In the adventure he was accompanied by Mr. J. M. Gerard, a native of Scotland; two boys of Spanish origin going to England for their education; a half-caste, as servant to Mr. Gerard; and by six working men of the country, of whom three went back, after helping to remove obstructions in the forest through which the first part of the journey was undertaken. The risks to which the party were exposed on their passage were very great: they all had a narrow escape from starvation, one of the labourers was drowned, and Captain Trevithick was saved from drowning by Mr. Gerard. The intended passage was along the banks of the river. To avoid the labour of cutting through the forest, the party determined to construct a raft, on which they placed themselves, their provisions, and utensils; after a passage of no long duration they came to a rapid, which almost overturned their raft, and swept away the principal part of their provisions and utensils. The raft, being unmanageable, was then stopped by a tree lying in the river, with its roots attached to the bank; on this tree three of the passengers, including Captain Trevithick, landed, and reached the bank; this was no sooner done than the current drove the raft away from the tree, and carried it, with the remaining passengers, to the opposite bank, where they landed in safety, and abandoned the raft as too dangerous for further use. The next object was to unite the party again into one body. The three left on the other side of the river were called upon to swim over: one of the men swam over in safety, the next made the attempt and was drowned, the third and last remaining was Captain Trevithick, who was either unable to swim or could swim very little. In order to improve his chances of safety, he gathered several sticks, which he tied in a bundle and placed under his arms; with these he plunged into the stream; but the contrivance of the bundle of sticks afforded him very doubtful assistance, for the current appeared to seize the sticks and whirl him round and round. He, however, finally reached within two or three yards of the bank in a state of extreme exhaustion. Mr. Gerard going into the water himself and holding the branch of a tree, then threw to his assistance the stem of a water-plant, holding one of the extremities in his own hand. It was not until the fourth time of throwing that Captain Trevithick was able to seize the very extremity of the plant (which was leaf) in his fingers; on the strength of the leaf his life on the occasion was dependent. It was determined to give up any further idea of using a raft on the river, and to continue their journey along the banks of the river. For subsistence for the remainder of their journey they had to depend on the produce of one fowling-piece and a small quantity of gunpowder; after a few days the gunpowder got wet by accident, and in the attempt to dry it, it was lost by explosion. The party finally arrived in a state of great exhaustion at the village, now the considerable port of San Juan de Nicaragua, or Greytown; and shortly after their arrival a small vessel arrived, which conveyed the party to one of the West India islands. "Upon one occasion Captain Trevithick was called upon to act in a novel capacity, that of a surgeon. An accident happened to a native engaged in working an engine erected at a place distant about two hundred miles from Lima, by which accident both of his arms were crushed. There was no medical man within the distance of two hundred miles, and Captain Trevithick, believing that death would ensue if amputation was not immediately performed, offered his services, which were accepted by the patient. The operation, he informed me, was successful; the man rapidly recovered, and showed a pair of stumps which could have hardly been distinguished from the result of an operation by a regular surgeon. It is not improbable that in the warfare in which he had been engaged Captain Trevithick had been present and assisted at amputations of limbs of wounded soldiers. He thus probably acquired sufficient confidence to undertake and perform the operation himself. "From Costa Rica Captain Trevithick came to England, with a design, among others, of forming a company to work a mine which had been granted him (for a term of years) by the Costa Rica Government. Mr. Gerard came to England with a similar object in view. Both failed in their object. Mr. Gerard was extremely unfortunate with regard to his mine, for he spent a considerable fortune of his own in working his mine to a loss. "The eminence of Captain Trevithick as an engineer is well known. The public are indebted to him for the invention of the high-pressure steam-engine and the first railway steam-carriage. The latter being dependent on the former, Captain Trevithick informed me that the idea of the high-pressure engine occurred to him suddenly one day whilst at breakfast, and that before dinner-time he had the drawing complete, on which the first steam-carriage was constructed. Captain Trevithick informed me that in 1830 the original steam railway-engine constructed by him in 1808[132] at that time was still running in Wales." [Footnote 132: Probably referring to the Welsh locomotive of 1804.] "SIR, "STANWIK, CUMBERLAND, _27th November, 1864_. "I read in the public prints that in a speech made by you in Belle Vue Gardens you referred to the meeting of Robert Stephenson with Trevithick at Carthagena, which, if your speech be correctly reported, you attribute to accident. The meeting was not an accident, although an accident led to it, and that accident nearly cost Mr. Trevithick his life; and he was taken to Carthagena by the gentleman that saved him, that he might be restored. When Mr. Stephenson saw him he was so recovering, and if he looked, as you say, in a sombre and silent mood, it was not surprising, after being, as he said, 'half drowned and half hanged, and the rest devoured by alligators,' which was too near the fact to be pleasant. Mr. Trevithick had been upset at the mouth of the river Magdalena by a black man he had in some way offended, and who capsized the boat in revenge. An officer in the Venezuelan and the Peruvian services was fortunately nigh the banks of the river, shooting wild pigs. He heard Mr. Trevithick's cries for help, and seeing a large alligator approaching him, shot him in the eye, and then, as he had no boat, lassoed Mr. Trevithick, and by his lasso drew him ashore much exhausted and all but dead. After doing all he could to restore him, he took him on to Carthagena, and thus it was he fell in with Mr. Stephenson, who, like most Englishmen, was reserved, and took no notice of Mr. Trevithick, until the officer said to him, meeting Mr. Stephenson at the door, 'I suppose the old proverb of "two of a trade cannot agree" is true, by the way you keep aloof from your brother chip. It is not thus your father would have treated that worthy man, and it is not creditable to your father's son that he and you should be here day after day like two strange cats in a garret; it would not sound well at home.' 'Who is it?' said Mr. Stephenson. 'The inventor of the locomotive, your father's friend and fellow-worker; his name is Trevithick, you may have heard it,' the officer said; and then Mr. Stephenson went up to Trevithick. That Mr. Trevithick felt the previous neglect was clear. He had sat with Robert on his knee many a night while talking to his father, and it was through him Robert was made an engineer. My informant states that there was not that cordiality between them he would have wished to see at Carthagena. "The officer that rescued Mr. Trevithick is now living. I am sure he will confirm what I say, if needful. A letter will find him if addressed to No. 4, Earl Street, Carlisle, Cumberland. "There are more details, but I cannot state them in a letter, and you might not wish to hear them if I could. "I am, Sir, "Your very obedient servant, "JAMES FAIRBAIRN, "who writes as well as rheumatic gout will let him. "P.S.--I forgot to say the name of the officer is Hall. "To ---- WATKIN, Esq." "DEAR SIR, "4, EARL STREET, CARLISLE, _16th December, 1864_. "On my return from Liverpool this day I find your letter of the 9th. "In reply I have the honour to say that if you will be pleased to state upon what points you require information, I shall be but too happy to furnish it if I can. "I have barely time to add that Mr. Fairbairn has left for America, which is his home, and has been for many years. He must have been at Birkenhead or Liverpool at the date of your letter to me. I was not aware that he had written to you. He brought me a paper with your remarks about the meeting of Mr. Robert Stephenson and Mr. Trevithick, and asked me if it were true that they met at Carthagena as stated, as he (Mr. Fairbairn) thought it was at Angostura, and that Mr. Trevithick was in danger of being drowned at the Bocasses, _i. e._ the mouths of the Orinoco, the Apure, &c, &c. I explained that it was near the mouth of the Magdalena. "I will just say that it was quite possible Mr. R. Stephenson had forgotten Mr. Trevithick, but they must have seen each other many times. This was shown by Mr. Trevithick's exclamation, 'Is that Bobby?' and after a pause he added, 'I've nursed him many a time.' "I know not the cause, but they were not so cordial as I could have wished. It might have been their difference of opinion about the construction of the proposed engine, or it might have been from another cause, which I should not like to refer to at present; indeed, there is not time. "Pray address me as before. I hold no rank in the British service, and in England never assume any. "I have the honour to be, dear Sir, "Faithfully yours, "BRUCE NAPIER HALL. "EDWARD W. WATKIN, Esq., M.P., &c., "_Currente Calamo_." These notes from Mr. Hall and Mr. Fairbairn to Mr. (now Sir Edward) Watkin[133] arose from the latter repeating what Mr. Robert Stephenson had related, of his meeting with Trevithick and Gerard at the inn at Carthagena. Stephenson said, "on his way home from Colombo, and in the public room at the inn, he was much struck by the appearance and manner of two tall persons speaking English; the taller of them, wearing a large-brimmed straw or whitish hat, paced restlessly from end to end of the room." Gerard and Stephenson entered into conversation, and Trevithick joined them. Stephenson said that he had a hundred pounds in his pocket, of which he gave fifty to Trevithick to enable him to reach England. It seems that had it not been for Mr. Hall's quick eye and steady hand rescuing Trevithick from the jaws of the blind alligator, he never would have returned to his native country. [Footnote 133: Sir Edward Watkin contemplated writing a life of Trevithick.] Here was the inventor of the locomotive a beggar in a strange land, helped by the man whom he had nursed in baby-boyhood, then returning to England to become a great railway engineer in making known the use of the locomotive on the level road of the Liverpool and Manchester, while the real inventor, who looked upon railways and locomotives as things of a quarter of a century before, was about to recommend them as the means of passing across the isthmus of Costa Rica from the Atlantic to the Pacific, over the heights of the Cordillera, by the river San Juan from Greytown, and by its tributary the Serapique, then by railway towards the high ground of San José, the capital, and down the western slope, passing, somewhere not far from the mines, forward to the Gulf of Nicoya in the Pacific. The approximate distance would be fifty miles of river navigation, and eighty or a hundred of railway, with perhaps stiffish but still manageable inclines, and no avalanches. A loan by the Costa Rica Government of 1872 states,[134] "for the completion of the railway from the port of Limon, in the Atlantic Ocean, to San José de Costa Rica, and on to Heredia and Alajuela," near to Trevithick's mines, as if to carry out his design of forty-six years ago to connect the Atlantic and Pacific by railway. [Footnote 134: See 'The Times,' 7th May, 1872.] CHAPTER XXIV. RETURN TO ENGLAND. In the early part of October, 1827, the writer, then a boy at Bodmin school, was asked by the master if any particular news had come from home. Scarcely had the curiosity of the boys subsided, when a tall man with a broad-brimmed Leghorn hat on his head entered at the door, and after a quick glance at his whereabouts, marched towards the master's desk at the other end of the room. When about half-way, and opposite the writer's class, he stopped, took his hat off, and asked if his son Francis was there. Mr. Boar, who had watched his approach, rose at the removal of the hat, and replied in the affirmative. For a moment a breathless silence reigned in the school, while all eyes were turned on the gaunt sun-burnt visitor; and the blood, without a defined reason, caused the writer's heart to beat as though the unknown was his father, who eleven years before had carried him on his shoulder to the pier-head steps, and the boat going to the South Sea whaler. During the next six months father and son sat together daily, the one drawing new schemes and calculations, the other observing, and learning, and calculating the weight and size and speed of a poor swallow he had shot, that the proportions of wings necessary to carry a man's weight might be known. In these calculations cube roots of quantities were extracted, which did not accurately agree with Trevithick's figures, who, asking for explanations, received a rehearsal, word for word, of the school-book rule for such extractions, which threw no more light on his understanding than did his own self-made rule on the writer's comprehension, though both methods produced nearly the same result. Within a month of that time he heard of the arrival in England of Mr. Gerard, his companion in travel, from whom he had separated at Carthagena. "MY DEAR GOOD SIR, "HAYLE FOUNDRY, _15th November, 1827_. "I cannot express the extreme pleasure that the receipt of your favour of the 11th inst. from Liverpool gave me, as I had almost given up hopes of ever seeing you again, which you will see from the letters that I wrote Mr. Lowe; and after the severe rubs that we have undergone together, the parting us by shipwreck, as I supposed, at the close of our hardships, I doubly felt, and from your long absence, I supposed you must have encountered some severe gales; but thank God that we are safe landed to meet you and the dear boys again soon. We had a very good passage home, six days from Carthagena to Jamaica, and thirty-four days from thence for England; and on my return was so fortunate as to join all my family in good health, and also welcomed home by all the neighbourhood by ringing of bells, and entertained at the tables of the county and borough members, and all the first-class of gentlemen in the west of Cornwall, with a provision about to be made for me for the past services that this county has received from my inventions just before I left for Peru, which they acknowledge to be a saving in the mines since I left of above 500,000_l._, and that the present existence of the deep mines is owing to my inventions. I confess that this reception is gratifying, and have no doubt but that you will also feel a pleasure in it. I should be extremely happy to see you down here; it is but thirty-six hours' ride, and it will prepare you for meeting your London friends, as I would take you through our mines and introduce you to the first mining characters, which will give you new ideas and enable you to make out a prospectus that will show the great advantages in Costa Rica mines over every other in South America. I think it would not be amiss for you to bring with you a few specimens, and after you have seen the Cornish mines and miners I doubt not but we shall be able to state facts in so clear a light that the first blow well aimed will be more than half the battle, and prove a complete knock-down blow, which in my opinion ought to be completed previous to your opening your mining speculation in general in London. I have made a very complete model of the gun, and it is approved of by all who have seen it. Be so good as to remember me to the lads and the Manilla man, and write me by return of post. I have not as yet made any inquiry about the probability of getting adventurers for this new concern. I hope and trust that I shall see you in Cornwall previous to our being together in London, as it is my opinion that the nature of the concern requires it. "I remain, Sir, "Your humble servant, (Signed) "RICHARD TREVITHICK. "MR. JNO. GERARD, "_No. 42, St. Mary Axe, London_." Trevithick's hopeful character enabled him to enjoy life in the midst of neglect and poverty. During the eleven years of absence in America his wife and family received no assistance from him. Shortly after leaving his Quebrada-honda mountains of gold and silver, he was penniless at Carthagena. On reaching England he possessed nothing but the clothes he stood in, a gold watch, a drawing compass, a magnetic compass, and a pair of silver spurs. His passage-money being unpaid, a chance friend enabled him to leave the ship. In a month from that time he counted on getting a share of the 500,000_l._ saved in the Cornish mines by the improvements he had effected in their steam-engines. The ringing of bells and the talk of the neighbourhood made him forget that he was a poor man, and the Costa Rica mines were, he believed, soon to be in full working, though not a single adventurer had been found. The two lads Montelegre, coming to England to be educated, were sons of a gentleman of influence and authority in Costa Rica. On their perilous journey an attack of measles increased their discomforts. Probably one of those gentlemen has since filled the honourable position in this country of minister representing the Republic of Costa Rica. "MY DEAR SIR, "LONDON, _November 17th, 1827_. "I arrived here from Liverpool last night, and this morning had the pleasure of receiving your kind letter of the 15th. The brig 'Bunker's Hill,' in which we came from Carthagena to New York, was wrecked within a few hours' sail of the port. We were in rather a disagreeable situation for some time, but more afraid than hurt. The cargo was nearly all lost. The ship was got off, but a complete wreck. The cause, however, of my delay in arriving arose from the want of the needful. You recollect Mr. Stephenson and Mr. Empson, agents for the Colombian Mining Association, whom we met at Carthagena. They kindly offered to supply me, but having determined to visit the celebrated Falls of Niagara, they insisted on my accompanying them, which I did. "I am truly rejoiced to learn that your countrymen retain so lively a sense of the importance of your services. I think with you that before sounding the public or proceeding further, it might be well we should meet quietly to talk over everything and arrange our ideas, and that Cornwall, for the reasons you mention and others, would be the better place. "The boys are well, and desire their respects to you. "Your sincere friend, "J. M. GERARD. "CAPT. TREVITHICK." Trevithick was friendly with George Stephenson when, in 1805, he nursed little Bobby. Twenty years afterwards, when George had comprehended Trevithick's locomotive, and desired his son's return to England to assist him in making it useful, Robert Stephenson, grown to manhood, met his father's friend in the wilds of Central America, both of them having been engaged in mining operations, and both on their return to England. George Stephenson's son made for himself a fortune and a name, his friend earned poverty and neglect. These two men, though well known to the engineering world, had no mutual attraction, and in their native land remained strangers to each other. "MY DEAR SIR, "42, ST. MARY AXE, _January 13th, 1828_. "I had very unexpectedly a letter from Costa Rica this morning by the way of Jamaica, including two for you, which I have the pleasure of transmitting. Mine is from Montelegre, begun on the 25th of August, and finished on the 11th of September, when Don Antonio Pinto, with some people from the Alajuela, was to start by the road of Sarapique on his way to Jamaica. His intention was to find a better route as far as Buona Vista, after which he would probably nearly follow our course to the Embarcadero of Gamboa. "Whether he succeeded in finding a less rugged road to Buona Vista I do not know. That he reached his destination seems clear from our letters having come to hand; but from their old date it would appear that he had either met with difficulties on the road or with considerable detention at San Juan. Montelegre writes me that Don Yonge had effected a compromise on your account with the Castros. Gamboa got back to San José on the 18th August, twelve days after he parted from us, to the great joy of our mutual friends. Mr. Paynter had been unwell after our departure. Both he and Montelegre desire their kindest recollections to you "Yours most sincerely, "J. M. GERARD. "CAPT. TREVITHICK." The newly-discovered track taken by the homeward bound over the Cordilleras soon brought Don Antonio Pinto and others into the field in search of passable roads to the Atlantic. Twelve days required by Gamboa to effect his return to San José, a distance of perhaps sixty miles, indicate the difficulty. Mr. Gerard passed some weeks with Trevithick in Cornwall arranging the best means of getting together a company to work on a large scale the Costa Rica mines. "DEAR SIR, "HAYLE FOUNDRY, _January 24th, 1828_. "Yesterday I saw Mr. M. Williams, who informed me that he should leave Cornwall for London on next Thursday week, and requested that I would accompany him. If you think it absolutely necessary that I should be in town at the same time, I would attend to everything that would promote the mining interest. When I met the Messrs. Williams on the mining concerns some time since, they mentioned the same as you now mention of sending some one out with me to inspect the mines, and that they would pay me my expenses and also satisfy me for my trouble with any sum that I would mention, because such proceedings would be satisfactory to all who might be connected in this concern. I objected to this proposal on the ground that a great deal of time would be lost and that the circumstances of your contracts in San José would not admit of such a detention; for that reason alone was my objection grounded, and if that objection could have been removed I should have been very glad to have the mines inspected by any able person chosen for that purpose, because it would not only take off the responsibility from us, but also strengthen our reports, as the mining prospects there will bear it out, and that far beyond our report. Some time since I informed you that I had drawn on the company for 100_l._ to pay 70_l._ passage-money, and would have left 30_l._ to defray my expenses returning to London. The time for payment is up, but I have not as yet heard anything about it, therefore I expect there must be an omission by the bankers whose hands it was to have passed through for tendering it for payment. Perhaps in a day or two I shall hear something about it; I would thank you to inform me should you know anything about it. The unfavourable result of the gun I attribute in a great measure to the change in the Ministry and my not being present to explain the practicability of making the machinery about it simple. When Lord Cochrane has seen it, and a meeting takes place with him, my return to London may again revive its merits. This unfavourable report does not lessen its merits, neither will it deter me from again moving forward to convince the public of its practicability. I shall make immediately a portable model of the iron ship and engine, as they will be applicable to packets, which have been attempted at Falmouth, but found that the consumption of coals was so great that the whole of the ships' burthen would not contain sufficient coals to take them to Lisbon and return again, and on that account it was discontinued. That insurmountable object will now be totally removed, and I think that Lord Cochrane will make a very excellent tool to remove many weak objections made by persons not having sufficient ability to judge for themselves. His Lordship, being a complete master of science, is capable of appreciating their value from theory and from practice. I should not be surprised to see him down here to inspect it. It will be very agreeable if his Lordship comes here at the same time as yourself; he is a remarkably pleasant companion. My hearty thanks for your mother's good wishes towards me. "Your humble servant, "RD. TREVITHICK. "MR. JNO. GERARD, "_No. 42, St. Mary Axe, London_." Gerard and Trevithick believed in the great value of the Costa Rica mines, and in the feasibility of working them profitably could capital sufficient be obtained. After a year or two passed in fruitless attempts to form a mining company in England, Mr. Gerard visited Holland and France with no better success; and while on this mission died in poverty in Paris, though brought up in youth as the expectant inheritor of family estates in Scotland. One of his letters says:-- "Robert Stephenson has given us his experience that it was unwise to take many English miners or workers to such countries. The chief reliance must after all be placed on the native inhabitants, under the direction and training of a small but well-selected party of Englishmen. "Mining operations in that country are of such recent origin that a mining population can scarcely be said to exist. English workmen are not so manageable even in this country, and much less so in Spanish America, where they are apt to be spoiled by the simplicity and excessive indulgence even of the better classes, and where the high salaries they receive place them far above the country people of the same condition. All this tends to presumption and intolerance on their part, and ultimately to disputes and irreconcilable disgusts between them and the natives." Mr. Michael Williams, Mr. Gibson, Mr. Macqueen, and others, were anxious to take up the mining scheme. The former proposed to send a person to examine the mines. This was a safe course, but not convenient to those who had made engagements to return without loss of time with miners and material to Costa Rica. Mr. M. Williams informed the writer's brother that at a meeting of several gentlemen in London, a cheque for 8000_l._ was offered to Trevithick for his mining grant of the copper mountain in South America. Words waxed warm, and the proffered money was refused. The next day Mr. Williams said to him, "Why did you not pocket the cheque before you quarrelled with them?" Trevithick replied, "I would rather kick them down stairs!" In the end Trevithick got nothing for either his South American mines or those in Costa Rica. CHAPTER XXV. GUN-CARRIAGE--IRON SHIPS--HYDRAULIC CRANE--ICE MAKING--DRAINAGE OF HOLLAND--CHAIN-PUMP--OPEN-TOP CYLINDER--HAYLE HARBOUR--PATENT RIGHTS--PETITION TO PARLIAMENT. "Richard Trevithick, of the parish of Saint Erth, in the county of Cornwall, civil engineer, maketh oath and saith that he hath invented new methods for centering ordnance on pivots, facilitating the discharge of the same, and reducing manual labour in time of action. That he is the true inventor thereof, and that the same hath not been practised by any other person or persons whomsoever to his knowledge or belief. "Sworn, 10th November, 1827, before me, Rd. Edmonds." "This gun is worked by machinery balanced on pivots giving it universal motion, by one man, with the facility of a soldier's musket. On one side a man puts in a copper charge of powder; on the opposite side a man drops a ball in a bag down the gun, as it stands muzzle up. The gunner, who sits on the seat behind the gun, points it and pulls the trigger. The firing causes it to run up an inclined plane at an angle of 25° for the purpose of breaking the recoil; it runs down again with its muzzle at the port, requiring no wadding, swabbing, cartridge, or ramming, but runs in, out, primes, cocks, shuts the pan, and breaks the recoil of itself; and by three men can be fired three times in a minute with accuracy. The gun-carriage is a tube 3 feet long and 3 feet diameter, made of wrought-iron plate 1/4 of an inch thick, centered on a pivot to the deck, with the gunner's seat attached, from which he looks through the case. As the gun requires no tackle, and but a man on each side to work it, only a space of 5 feet 6 inches is required from centre to centre of ports, therefore a single-deck ship will carry a greater number of guns than are now carried on a double-deck ship, be worked with one-third of the hands, and be fired five times as fast as at present. A frigate would mount fifty 42-pound guns on one deck, with 150 men, and would discharge in the same time a greater weight of ball with greater precision than five 74-gun ships."[135] [Footnote 135: Description in Trevithick's handwriting.] [Illustration: TREVITHICK'S GUN-CARRIAGE AND FRICTION SLIDES, 1827.] "HAYLE, CORNWALL, _21st February, 1828_. "MY LORD COCHRANE,[136] "With great pleasure I read in the papers the announcement of your arrival again in England, and am much gratified to find a person of your superior natural and practical talents, so rare to be obtained, to whom I may communicate my views. "I have proposed to Government to build an iron ship, and a gun on a new principle, which are to undergo an investigation, and have lodged a drawing of the ship and a model of the gun with my friend Mr. Gerard, a gentleman who returned with me from America, and who will present to you this letter with the above-mentioned drawing and model. "I have had an iron boat made for the purpose of sending it to London, to show the method of constructing ships on this plan, roomy, strong, and cheap. Also a wrought-iron ship with a steam-engine on an improved principle, which in a few days will be laid on the stocks at the Hayle Foundry iron manufactory." [Footnote 136: Rough draft, by Trevithick, of unfinished letter.] Though Lord Cochrane was just the person to be interested in such schemes, it does not appear that he took any part in them. At that time he was at work on his own particular ideas for marine propulsion. "MY DEAR SIR, "LONDON, _February, 1828_. "Immediately after the receipt of your last, which I only received after twelve o'clock on the 7th, I went to the Ordnance Office, where, though Colonel Gossett was no longer an official personage, I had the good luck to meet him. He told me that the model of the gun was at Woolwich, and could not be got at in time to stop the progress of the other patent, and which he considered of but little moment, as he thought it very unlikely there could be any collision between the two inventions. He likewise said that from the official changes that had taken place in the office, much loss of time might be incurred by recalling the model, which was in train of being examined. To-day I have received a letter addressed to you from the Ordnance, by which it appears that your model has passed through an unsuccessful ordeal before the special committee. "'SIR, "'OFFICE OF ORDNANCE, _21st February, 1828_. "'I am directed by the Master General to acquaint you that the Select Committee of Artillery Officers, to whom your model of a 42-pounder carronade and carriage on a new principle were referred, have reported that on examination of the invention, they consider it to be wholly inapplicable to practical purposes. Your model is at the Ordnance Office, and will be delivered on your sending for it. "'I am, Sir, "'Your most obedient humble servant, "'LOWNDES. "'R. TREVITHICK, Esq.' "My poor mother, who I regret to say has been very delicate ever since your departure, and is now again confined to bed, desires me to say that she is very sorry she is not Master General of the Ordnance, to give it a fair _practical_ trial, as she thinks Captain Trevithick's opinions, though she cannot pronounce his name, may be fairly placed in opposition to that of the special committee of artillery officers. "Ever faithfully yours, "J. M. GERARD." The recoil gun-carriage was his first occupation after twelve years of travel in countries where mechanical appliances were less thought of than weapons of war. He commenced this, his second era of inventions, with what he called a new thing, though it was but an extension of his schemes of 1809, when he patented iron vessels, hollow sliding masts and yards, self-reefing sails, and sliding keels. The model gun was of brass, resting on a railway formed of two inclined bars of iron, up which the recoil propelled it into a convenient position for cleaning and loading. Its own gravity caused it to fall into the required place for being again fired. The slides also served as friction-bars to regulate the recoil. The gun and the slides carrying it were enclosed in a wrought-iron box, having openings in the front and rear for the passage of the muzzle and the breech. The muzzle front of the box was pivoted to the deck by a strong bolt as a centre of motion, whilst its rear was supported on two small wheels resting on the deck, allowing the gun to change its line of horizontal fire by sweeping from the centre pivot. The gunner's seat moved with the carriage, from which he could elevate or depress the muzzle by a lever. The gun was self-priming and self-cocking; the powder charge was enclosed in a copper case. Captain Moncrieff's patent gun-carriage of the present day is described in words somewhat like those used by Trevithick forty years before. "The recoil lifted a weight smoothly and without friction; the gun and the weight were held in the position arrived at by a catch until the gun was loaded and ready to fire again."[137] [Footnote 137: See 'The Times,' August 12th, 1870.] The iron boat mentioned in his note to Lord Cochrane as being made at Hayle, was "for the purpose of sending to London to show the method of constructing ships on this plan, roomy, strong, and cheap," and was thus spoken of in a newspaper of the 26th April, 1829. "The 'Scotsman' alludes to the intended construction of iron steamboats at Glasgow by Mr. Neilson:--"For fear of the public being misled on this subject, we beg to state that so far back as last Christmas twelvemonths we saw Trevithick, of Cornwall, superintending the construction of an iron man-of-war launch, with the avowed intention of applying a similar principle of construction to the building of fast-sailing iron steamboats." This intimation, in 1829, to the since famous Glasgow iron-ship builders, that they could not claim the invention because Trevithick had made such a boat in 1827, was probably in ignorance of Trevithick's patent and models of 1809,[138] explaining the advantages of ships of iron, either under sail or under steam, for commerce or for fighting-ships. The improved high-pressure steam-engine then in hand for iron ships was but the perfecting of his plans of twenty years before.[139] [Footnote 138: See vol. i., p. 302.] [Footnote 139: See vol. i., p. 329.] "LAUDERDALE HOUSE, HIGHGATE, _April 19th, 1830_. "MR. GILBERT, "Sir,--I find by looking into the 'Art of Gunnery' that a 42-lb. shot discharged at the rate of 2000 feet a second in vacuum would send it to the height of 63,360 feet, which multiplied by the weight of the shot would be 2,661,120 lbs., with 12 lbs. of powder; and as guns, after being heated to about the heat of boiling water, will recoil their usual distance with half their first charge of powder, it proves that one-half the powder at first is lost in heating the gun to about 212°, which is a great deal under the heat of fired powder, therefore only 6 lbs. of powder effective force is applied to the ball. Now suppose this 6 lbs. of powder to be one quarter part carbon, 1-1/2 lb. is all the heat that can possibly be applied to perform this duty; then 1 lb. of carbon would be equal to 1,774,080 lbs. of duty actually performed; but if you take into calculation the great loss of power by the powder not being instantly all set on fire, with the gun so much below the heat of fired powder, the windage by the sides of the shot, the ball flying from the powder, and the immense power remaining in the gun at the time of the ball leaving its muzzle; if this was applied expansively, as in a cylinder, it may fairly be said to have double this power, or 3,548,160 lbs. for 1 lb. of carbon consumed, which, multiplied by 84, being the pounds in 1 bushel of carbon, gives 300 millions of duty. If it was applied to the best advantage, say on a piston, calling powder one thousand atmospheres, it would far exceed that duty. A gun 9 feet long and 7-inch bore has 16 feet of cold sides, and condenses at first one-half of its force by its cold sides and loses 150 millions in a 200th part of a second, while the ball passes from the breech to the muzzle. This gives 221,760 lbs. condensed by each foot of surface sides in so short a time. Binner Downs cylinder was taken as condensing 2500 lbs. for each surface foot in six seconds; therefore, without taking into account the great difference in time, there is eighty-eight times as much power lost by each foot of cold sides of the gun as by the cylinder sides. This shows what a considerable power is lost by cold sides where the vapour is so rare. Boulton and Watt's engine, doing twenty millions, performs with 1 lb. of coal a duty of 240,000 lbs., or about 1/14th part of what is done by 1 lb. of carbon in powder. The water evaporated by the boiler is 7 lbs. thrown into steam by 1 lb. of coal, and a duty of 33,750 lbs. for each pound of water evaporated. "Suppose 1 lb. of powder to contain 12 oz. of nitre and 4 oz. of carbon, and 1/24th part of the nitre to be a fixed water, which would be half an ounce of water in every pound of powder, making the carbon eight times as much as the water; from this data 1 lb. of water in powder would perform a duty of 28,385,280 lbs. lbs. 1 lb. of carbon in powder 3,548,160 } 14 times the consumption 1 lb. of coal in Boulton and Watt's } engine 240,000 } by the engine. 1 foot of cold sides of the gun 221,760 { 88 times as much loss 1 " " of the cylinder 33,750 { by the cold sides of { the gun 1 lb. of coal for 7 lbs. of water in { 14 times as much coal steam { for water into steam 1 lb. of carbon for 8 oz. of water in powder { as for water in powder { powder. "By this it appears that heat is loaded with fourteen times as much water in steam-engines as in powder, and does only 1/14th part of the duty of the water in powder. It is possible to heat steam independent of water, because if we work with steam of ten atmospheres, it would have ten times the capacity for heat, being in proportion to its gravity. The boiler standing on its end, with the fire in the bottom, and the water 1 foot thick above it, with a great number of small tubes from bottom to top, having great surface sides to heat the steam above the water, by working with a low chimney and slow fire, the tubes in the steam part of the boiler would not exceed 600° or 700° of heat, which would not injure them; as less water would be generated into steam, a very small part of the boiler would be sufficient for it; and as the coal required would be less, the boiler required would be very small. I state the foregoing to remind you that but little is yet known of what heat may be capable of performing; as this data so far exceeds whatever has been calculated on the power of heat before, when compared with steam in an engine. "The power is sure, if we can find how to conduct it. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK. "If you can spare time please to write to me." The foregoing may be classed either under cannon or steam-engine; TREVITHICK combined them under the general laws of expansion by heat. Three years had passed since the committee of artillery officers sitting on his gun had given a verdict of no go; yet the subject was not forgotten, and his calculations enabled him to discover the explosive force, and the speed of the projectile in different parts of the gun, things which are now ascertained by mechanical tests and measures. If a 7-inch cannon 9 feet long loses by absorption of heat during the time of the passage of the shot to the muzzle one-half of the expansive force of the powder, it is time to wrap our guns as well as our steam-engines in non-conductors. The greater heat of exploded powder than of steam caused eighty-eight times the amount of loss from abstracted heat, and yet the force from a pound of carbon in powder, was fourteen times as much as the Watt engine gave from a pound of coal. "MR. GIDDY, "LONDON, NO. 42, ST. MARY AXE, _June 18th, 1828_. "Sir,--A few days since a Mr. Linthorn called on me and requested me to accompany him to Cable Street, near the Brunswick Theatre, to see a crane worked by the atmosphere, in a double-acting engine attached to it. He has a patent, and has entered into a contract with the St. Katharine's Dock Company to work their cranes, 140 in number, by a steam-engine of sufficient power to command the whole of them, by placing air-pipes around the docks, with a branch to each crane. To each crane is fixed a 10-inch cylinder, 20-inch stroke, double-acting. The atmosphere pressing on the piston like steam, the air is drawn from the pipes by a large air-pump and steam-engine. "On being requested to give my opinion on this plan, after seeing one crane worked, I informed them of the disappointment that the ironmaster, Mr. Wilkinson, in Shropshire, several years since experienced, on the resistance of air in passing through long pipes from his blast-engine to his furnaces. He said he was aware of that circumstance, and it had since been further proved in London by one of the gas companies attempting to force gas a considerable distance, and who also failed. "He thought that forcing an elastic fluid, and drawing it by a vacuum, were very different things, and that the error was removed by drawing in place of forcing. For my part I am not convinced on this head; but am still of opinion that the result on trial will be found nearly the same. However, let that be as it may, the expense and complication of the machine, having a double engine, with its gear attached to every separate crane, together with the immense quantity of air thrown into the air-pump from 140 double engines of 10 inches diameter, 20-inch stroke, eighty strokes per minute, and considering the numerous air leaks in such an extent of pipes and machines, must reduce the effect of the pressure of the atmosphere on each piston to a comparatively small power, unless the air-pump and steam-engine are beyond all reasonable bounds. "Those objections I made them acquainted with, and said that, before they went to such an expense, it would be a safer plan to first make further inquiry, so that their first experiment might be on a sure plan, for the other dock companies were looking for the results of this experiment. "At the time I was informed of this plan, a thought struck me that it might be accomplished by another mode preferable to this: by a steam-engine to force water in pipes round the dock, to say 30 or 40 lbs. to the inch, more or less, and to have a worm-shaft, working in a worm-wheel, the same as a common roasting-jack, and apply to the worm-shaft a spouting arm like Barker's mill; the worm-shaft standing perpendicular would work the worm-wheel fixed in the chain-barrel shaft of the crane. "This would make a very simple and cheap machine, and produce a circular motion at once, instead of a piston alternating motion to drive a rotary motion. My report had some weight with them; inquiry is to be made into the plan proposed by me, so as to remunerate me, provided my plan is considered good. Mr. Linthorn wishes an investigation before scientific and able judges, and requested me to name some one. I must again make free in asking the favour of your advice (which you have so ably given me for thirty years) on this plan. Mr. Linthorn intends to request Dr. Wollaston to accompany you, any day convenient to you. In the meantime, should you see him, it might not be amiss to mention it to him; and should you be able to attend for an hour or two to this business, I would thank you to drop me a note, saying when it may be convenient. There is a memorandum of an agreement between Mr. Linthorn and me; but the plan I suggest is only at present made public to him and yourself. "Your most obedient servant, "RICHARD TREVITHICK." The reduction of friction by the use of an air-vacuum engine for working cranes, as designed by Mr. Linthorn, in lieu of an air-pressure engine, was doubted by Trevithick. The Mont Cenis pneumatic-pressure machines which the writer saw at work lost much power by friction before experience had taught remedies. The pneumatic vacuum tubes which propelled the trains on the South Devon Railway, failed to give the power that was expected. Sir William Armstrong's hydraulic cranes, brought into use not many years after the date of Trevithick's letter, have been found effective. The writer, not knowing that Trevithick had before recommended hydraulic cranes for warehouses, accompanied Sir William over his works, then being erected near Newcastle-on-Tyne, and talked with him on the detail of his crane designs. Trevithick thought of giving circular motion to the crane chain-barrel by the attachment of a screw-propeller, acted on by the force of a current of water at a pressure of 30 or 40 lbs. to the inch. Sir William Armstrong's arrangement was quite different; the merit due to Trevithick was for having pointed out the suitability of water as a means of conveying power through warehouses where fire was inadmissible. "MR. GILBERT, "LONDON, 42, ST. MARY AXE, _June 29th, 1828_. "Sir,--Fancy and whim still prompt me to trouble you, and perhaps may continue to do until I exhaust your patience. A few days since I was in company where a person said that 100,000_l._ a year was paid for ice, the greatest part of which was brought by ships sent on purpose to the Greenland seas. A thought struck me at the moment that artificial cold might be made very cheap by the power of steam-engines; by compressing air in a condenser surrounded by water, and an injection to the same, so as to instantly cool down the highly-compressed air to the temperature of the surrounding air, and then admitting it to escape into liquid. This would reduce the temperature to any state of cold required. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK." Trevithick's ideas for making ice have since been patented and made useful, though the detail of the operation has been improved by experience. The Dutch, extending the use of steam on the Rhine and also in sea-going ships, wished Trevithick to see what was going on in Holland, where his nephew, Mr. Nicholas Harvey, was actively engaged in engineering. He had not money enough for the journey, and borrowed 2_l._ from a neighbour and relative, Mr. John Tyack. During his walk home a begging man said to him, "Please your honour, my pig is dead; help a poor man." Trevithick gave him 5_s._ out of the 40_s._ he had just begged for himself. How he managed to reach Holland his family never knew; but on his return he related the honour done him by the King at sundry interviews, and the kindness of men of influence in friendly communion and feasting. "MR. GILBERT, "LONDON, _July 31st, 1828_. "Sir,--The night before last I arrived from Holland, where I spent ten days. I found my relative there, Mr. Nicholas Harvey, the son of John and Nancy Harvey. He is the engineer to the Steam Navigation Company at Rotterdam. They have a ship 235 feet long, 1500 tons burthen, with three 50-inch cylinders double, also two other vessels 150 feet long, each with two 50-inch cylinders double, ready to take troops to Batavia. The large ship with three engines cost 80,000_l._ The Steam Navigation Company built them, and many others of different sizes. This company has been anxious to get me to Holland, having heard of the duty performed by the Cornish engines. They were anxious to know what might be done towards draining and relieving Holland from its ruinous state. "Immediately on arrival I joined the Dutch company, and entered into bonds with them. "I give you, as near as I can, the present state of the country. About 250 years since, a strong wind threw a bank of sand across the mouth of the river Rhine, which made it overflow its banks; 80,000 lives were lost, and about 40,000 acres of land, which remain to this time under 12 feet of water. "About 100 years since the head and surface of the river Rhine was 5 feet below what it now is. The under floors of houses in Holland are nearly useless, and in another century must be totally lost, unless something is done to prevent it. The river at present is nearly overflowing its banks. In consequence of the rise of water, the windmill engines cannot lift it out. To erect steam-engines, they never could believe would repay the expense. Nearly one-half of Holland is at present under water, either totally or partially, because the ground kept dry in winter is flooded in summer. "About six years since it was in contemplation to recover the 40,000 acres before mentioned, and a company was formed of the King and the principal men in Holland, to drain this by windmills, which they estimated would cost 250,000_l._, and making the banks and canals 450,000_l._ more, when made by men's labour, and seven years to accomplish it. "This seven years was a great objection, because of the unhealthy state of the country while draining. The water is about 18 inches every year, to be lifted on an average 10 feet high. I have been furnished with correct calculations and drawings from this company. "They expected to have drained 40,000 acres in seven years, at a cost of 700,000_l._, which, when drained, would have sold at 50_l._ per acre, about two millions. "I find, from the statement given me, of 18 inches of water to be lifted 10 feet high, it would require about one bushel of coal to lift the water from one acre of ground for one year, and that a 63-inch cylinder double would perform the work of 40,000 acres, when working with high steam and condensing, at an expense of less than 3000_l._ per year. Engines in boats would cut and make the embankments and canals, without the help of men. I proposed six cylinders of 60 inches diameter, double power, which would drain the water in one year; and also four others for cutting the canals and making embankments. The expense would not exceed 100,000_l._ and one year, instead of 700,000_l._ and seven years. Above 60,000 acres more are to be drained. "It was also proposed by Government to cut open the river Rhine to 1000 yards wide and 6 feet deep for 50 or 60 miles in length; they supposed it would cost them ten millions sterling. I proposed to make iron ships of 1000 tons burthen, with an engine in each, which would load them, propel, and also empty them for about 1_d._ per ton. Each ton will be about a square yard, and the cutting the river Rhine 1000 yards wide, 6 feet deep, 50 or 60 miles in length, will not cost one and a half million, and be accomplished in a short time. I further proposed that all this rubbish be carried into the sea of the Zuyder Zee, which would make dry, by embanking with the rubbish, nearly 1,000,000 acres of good land, capable of paying ten times the sum of cutting open the river Rhine. "All this would add 100 per cent. more to the surface of Holland, and at this time it is much wanted, because their settlements abroad are free almost of the mother-country, and they have too many inhabitants for the land at present. I made them plans for carrying the whole into effect, and have closed my agreement with them. "In a few days I shall go to Cornwall, and promised to return again to Holland within a month. I saw Mr. Hall and the engineer of the Dock Company to-day. They are satisfied that the plan for working the cranes is a good one. I am to see them again on Monday next; after which I shall return home, where I hope to see you, to consult you on the best plan for constructing the machines for lifting the water, cutting the canals, and making the dykes. "I remain, Sir, "Your very obedient servant, "RICHARD TREVITHICK." In this mere outline of a life it is impossible to go fully into the merit of Trevithick's plans for doubling the land surface of Holland. A drainage company was formed in London with a board of directors, some of whom thought that a new kind of engine should be invented and patented as a means of excluding others from carrying on similar but competing operations. Trevithick, always ready to invent new things, though never forgetting his experience with old things, instinctively returned to the Dolcoath engines, and recommended them as suitable for the pumping work; but finally a new design was determined on, and Harvey and Co., of Hayle, received orders for the construction, with the greatest possible dispatch, of a pumping engine for Holland. This happening shortly after the writer had been taken from the Bodmin school, he was desired to help in the erection of this engine, and after working-hours made a drawing of its original form. Plate XV. _a_, iron barge; _b_, wood frame supporting pump; _c_, open-top steam-cylinder 3 feet diameter, 8-feet stroke; _d_, piston guide-wheel; _e_, connecting rod; _f_, fly-wheel; _g_, cranked axle working air-pump bucket; _h_, connecting rod for air-pump bucket; _i_, air-pump; _j_, condenser; _k_, steam and exhaust nozzles; _l_, eccentrics working steam and exhaust valves; _m_, steam-pipe; _n_, cylindrical boiler, with internal fire-tube; _o_, external brick flues; _p_, chimney; _q_, feed-pump; _r_, feed-pipe; _s_, cup or rag-wheel; _t_, rag-chain, with iron balls; _u_, pump-barrel, 3 feet diameter; _v_, wheel guiding balls into bottom of pump-barrel; _w_, launder. [Illustration: PLATE 15 TREVITHICK'S CHAIN AND BALL PUMP. London: E. & F. N. Spon, 48, Charing Cross Kell Bro^s. Lith London ] After a few successful though noisy trials, an alteration was made in the endless chain and in the guide-roller near the pump bottom. An amount of slack in the chain caused the balls to knock on passing this roller before entering the pump bottom. A chain having long links or bars of iron of uniform length, from ball to ball, jointed together by cross-pins, was substituted for the short link chain, and passed over a revolving hollow square frame at the bottom of the pump, in place of the curved roller-guide in the drawing. Each of the four sides of this square hollow frame was of the same length as the jointed link, and the balls lay in the hollow of the frame without touching it, contact being only on the links. The balls were thus guided directly into the bottom of the pump on their upward course with a rigid chain, and the swing and knocking was avoided. This pump was in principle the traditional rag-and-chain pump of a hundred years before; yet no trace of its use is met with during Trevithick's life in Cornwall. The early pump had rag balls, in keeping with the mechanical ignorance of the time, and suitable to man's power. Trevithick's pump with iron balls raised "7200 gallons of water 10 feet high in a minute with 1-1/2 lb. of coal,"[140] retaining all the original simplicity of the earlier rag-pump, having uniform circular motion and constant stream, without the use of a single valve. The engine and pump are thus described by him:-- [Footnote 140: See letter, vol. ii., p. 332.] "The first engine that will be finished here for Holland will be a 36-inch cylinder and a 36-inch water-pump, to lift water about 8 feet high. On the crank-shaft there is a rag-head of 8 feet diameter, going 8 feet per second, with balls of 3 feet diameter passing through the water-pump, which will lift about 100 tons of water per minute. It is in an iron boat, 14 feet wide, 25 feet long, 6 feet high, so as to be portable and pass from one spot to another without loss of time. This will drain 18 inches deep of water (the annual produce on the surface of each acre of land) in about twenty minutes; to drain each acre with about a bushel of coal costing 6_d._ per year. The engine is high pressure and condensing."[141] [Footnote 141: See Trevithick's letter, vol. ii., p. 315.] It was something like the Newcomen open-topped cylinder of a hundred years before, but with a heavy piston, on the top of which a guide-wheel equal in diameter to the cylinder turned on a pin, to which the main connecting rod was jointed. The guide-wheel prevented any tendency to twist the piston from the angular positions of the connecting rod, and allowed the crank-shaft to be brought comparatively near to the cylinder top. The boiler was cylindrical, of wrought iron, with internal fire-tube and external brick flues; and gave steam of about 40 lbs. on the inch above the atmosphere, which, acting under the piston, caused the up-stroke, an expansive valve reducing the average pressure in the cylinder by one-half. The down-stroke was made by the atmospheric pressure of 14 lbs. on the inch, on the piston, its lower side being in vacuum, together with the weight of the thick piston and connecting rod, and the momentum of the revolving parts. My readers must not suppose that this was an attempt to revive the discarded Newcomen engine; the likeness was only apparent; its power was mainly from the use of strong expansive steam, giving motion in the up-stroke through a rigid connecting rod, with controlling and equalizing crank and fly-wheel. It was not, as the Newcomen,[142] dependent for its power on the atmospheric pressure; and having no cylinder cover, or parallel motion, or beam, was not a Watt engine, though it had the Watt air-pump and condenser. [Footnote 142: See vol. i., p. 5.] The Dolcoath engines continued to work with open-topped cylinders a quarter of a century after the Watt patent; and when they had passed away, many of Trevithick's high-pressure steam-engines retained the same form of outline, but had neither cylinder covers, parallel motion, air-pump, nor vacuum. The agricultural engines of 1813[143] and the South American engines of 1816[144] had neither cylinder cover nor any other part of the Watt engine, yet they successfully competed with it in power, economy, and usefulness. [Footnote 143: See vol. ii., p. 37.] [Footnote 144: See vol. ii., p. 208.] This design reveals a stumbling-block that superficial people fall over. The boiler in the boat was surrounded by brick flues, while a life-long claim of Trevithick's is that before his tubular boiler with internal fire, there could not be a successful steamboat, because brick flues were dangerous in sea-going vessels, but in an iron boat in smooth water it answered its purpose without in any respect falsifying Trevithick's former claims or plans. The chain pumping machine was in an iron barge, the 36-inch diameter pump fixed just outside the bow, its lower end a foot in the water; its height of 8 or 9 feet enabled the water from the pump-head to flow through launders over the banks of the lakes to be drained. Some of the directors came to Hayle to see it work, and were well pleased at the constant stream of water rushing from the foaming pump-head into the launders. The large size of the rag-wheel gave the rapidly revolving chain and balls a great speed. In passing through the pump each ball forced upwards the water above it, and drew up after it the following water; before any ball had passed out at the top of the pump the following ball had entered its bottom. The directors having desired the writer to take the engine to Holland and set it to work with the least possible delay, adjourned for refreshment before starting for London. In those few minutes differences arose, resulting in the engine remaining for months in the barge, and then going to the scrap heap. Years afterwards others acted on Trevithick's drainage ideas, and Harvey and Co. built Cornish pumping engines with steam-cylinders 112 inches in diameter, similar in principle to the Dolcoath engine[145] of 1816, which effectually drained the Haarlem lake. [Footnote 145: See vol. ii., p. 168.] The Rhine during 100 years, in its passage through the low flat lands, had by deposit raised the level of its waters 5 feet, threatening to overflow the embankments and drown the surrounding country, that to a large extent was at a lower level than the river. All drainage from such land had to be pumped over the river bank, in many places 10 feet above the cultivated surface. Windmills had been used as pumping power, and a company had contemplated laying out 700,000_l._ in windmills and canals for drainage. If the surface water averaged 18 inches in depth yearly, Trevithick could by steam-engines drain an acre of land by the consumption of a bushel of coal yearly. Four engines with cylinder of 63 inches in diameter would drain 160,000 acres, and four smaller engines in barges with suitable apparatus were to cut canals and construct embankments. The deposit of a hundred years was also to be removed, and the Rhine deepened 6 feet for a breadth of 1000 yards, and a length of 50 or 60 miles, by steam-dredgers, as used twenty years before in deepening the Thames,[146] to be fixed in iron ships of a thousand tons burthen. The cost of dredging from the bed of the river into a barge would be 1_d._ per ton; but this would be more than repaid by making with it an embankment, enclosing the Zuyder Zee, which would then in its turn be drained and made pasture land. [Footnote 146: See vol. i., p. 243.] Before leaving for America he had reported on the best means of improving St. Ives Bay.[147] Hayle Harbour was a branch of it, and he now suggested to Mr. Henry Harvey methods for deepening and improving it. A rival company of merchants and engineers, known then as Sandys, Carne, and Vivian, after many fights had recourse to law on the question of the course of a stream which had been changed by alterations during the making of wharfs and channels for ships. [Footnote 147: See vol. i., p. 343.] Trevithick made a model in wood, movable layers of which indicated changes of level caused by workmen at different periods, giving a different course to the river bed. Mr. Harvey's counsel, since known as Lord Abinger and Sir William Follett, complimented Trevithick on the facility of understanding the case by reference to the model. The writer having carried the surveying chain, was present at the trial at the Bodmin assizes in 1829. "MR. GILBERT, "HAYLE FOUNDRY, _September 14th, 1829._ "Sir,--I expected to have seen you before this, but am detained by Mr. Harvey's attorney to settle the Foundry Quay. As I made the drawing and model of the disputed ground, and was examined in evidence in court, it was thought proper that I should be present at the time that Mr. Peters came to determine the boundary line between the two companies. This cannot be concluded for ten days. "As I have been so long detained I wish to await your arrival in Cornwall for the purpose of trying the new engine while you are down, and will thank you to inform me when you intend to be with us. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK." Erskine, who had expressed the opinion favourable to Trevithick's engine more than twenty years before,[148] was in this trial the counsel for the opposing side. The verdict was in favour of Mr. Harvey, or Trevithick's side. [Footnote 148: See vol. ii., p. 129.] A former chapter[149] speaks of promises to pay certain savings by the use of Trevithick's inventions prior to his leaving for America. The United Mines refused to continue the payment, and on Mrs. Trevithick's application to Mr. Davies Gilbert for advice he kindly wrote to the Williamses, who managed those mines, and received the following reply:-- [Footnote 149: See vol. ii., p. 108.] "DEAR SIR, "SCORRIER HOUSE, _November 14th, 1820_. "... with regard to Mrs. Trevithick's claims for savings on engines at the United Mines, there is much to be said. "Before Mr. Trevithick went abroad he sold half the patent right to William Sims, our engineer, who very strongly recommended that two of the engines at the United Mines should be altered to what he considered his patent principle, but the alterations proved very inferior to his expectations, and to this circumstance I attribute much of the objections in question. Mr. Henry Harvey has perhaps told you who the partners are in the patent, and when you next come into this county I shall be much pleased to wait on you at Tredrea that you may hear the whole of the case; and though the United Mines adventurers are far from being a united body, I am very sure my sons, who are their managers, are desirous to recommend what appears to them right, and they will with myself be obliged for your opinion after you have heard the whole matter on both sides. "Dear Sir, "Yours very sincerely, "JNO. WILLIAMS. "DAVIES GILBERT, Esq., M.P." The opinion of Mr. Williams' elder son, Michael, has been given.[150] Some of the family were quakers. No further money payment for the saving of fuel followed this carefully civil note, until Trevithick, on his return from America, called at Scorrier House in a very threatening attitude on 31st October, 1827, when Mr. Williams, sen., said his reason for not continuing the payment was from his belief that the term of the patent had expired. Then came the following lawyer's letter:-- [Footnote 150: See letter from Mr. Michael Williams, vol. ii., p. 109.] "SIR, "PENZANCE, _7th November, 1827_. "I was at Captain Trevithick's yesterday, who observed to me he saw you at Scorrier a few days ago, and requested you would be good enough to settle the arrears on the savings on some of the engines in the mines for which you acted, none having been paid for a year or two, when you stated that the payment had been discontinued on account of the patent having expired. I find on a reference to the patent that it will not expire till May, 1830. "I am, Sir, "Your obedient servant, "RD. EDMONDS. "JOHN WILLIAMS, Esq., _Scorrier_." "SIR, "HAYLE, _January 24th, 1828_. "Yesterday I called on Mr. Williams, and after a long dispute brought the old man to agree to pay me 150_l._ on giving him an indemnification in full from all demands on Treskerby and Wheal Chance Mines in future. He requested that you should make out this indemnification. I could not possibly get them to pay more, and thought it most prudent to accept their offer rather than risk a lawsuit with them. "I remain, Sir, "Your obedient servant, "RICHARD TREVITHICK. "RD. EDMONDS, Esq. "Treskerby and Wheal Chance were, I believe, the only mines that paid for the use of the pole patent. Mr. John Williams, sen., of Scorrier, was purser of those mines. The agreement was that patentees should have one-fourth part of the savings of coal above twenty-six millions. The one-half of this fourth part from these two mines for some years was about 150_l._ per annum. This did not relate to the boilers; Trevithick unfortunately did not take out a patent for that improvement. The adventurers of two or three mines only had the honesty to pay 100_l._ for each mine; others made use of it without acknowledgment. "RD. EDMONDS. "PENZANCE, _12th January, 1853_." Such were the recollections of the family solicitor many years after the events had passed. The cylindrical high-pressure steam boiler and engine was really included in the patent of 1802; but frequent detail changes, consequent on size and position and local requirements, were made up to 1811, when a perfected form was arrived at, which is still in use. In principle it was unaltered and not materially different in form, but being used for larger engines, looked different. The inventor saw nothing in this difference, but the public did, and in the absence of the only man who could prove their error refused to pay on the plea of its not being patented. On his return from America he demanded 1000_l._ from each of the large Cornish mines, as a settlement in full for all benefits derived from the use of the Trevithick high-pressure steam-boiler. He had proved the weakness of the law years before, when three eminent counsel had given opinions on the 1802 patent, one of them believing the patent good, because the principle contained was new; two of them feared that similarity of details might invalidate it:[151] so he determined to apply to the Government for remuneration for benefits that might be called national. [Footnote 151: See vol. ii, p. 129.] "MR. RD. EDMONDS, "HAYLE, _December 20th, 1827_. "Sir,--I send the principal heads of what you will have to put in form to lay before the House. It is very defective; but you will be assisted by Captain Andrew Vivian, who can give dates and particulars, having been engaged with Mr. Gilbert and Captain Matthew Moyle in making out the duty performed at that time by Boulton and Watt and Hornblower's engines. He can also give you the results of the late improvements, with much more information than I can give. I saw him yesterday for this purpose; he will assist you with all his power, and will call on you at Penzance on Friday or Saturday. As I shall with pleasure pay him for his trouble, you need not fear calling on him for what assistance you need. "Mr. Gerard and I propose to leave this for London on Saturday. If you think it necessary to see me, let Captain Vivian know it, and all meet at my house. I have sent you one of the monthly reports, in which you will see John Lean's report of Dolcoath engines, from which I have given you in my statement the average results and savings. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK. "P.S.--I was at Dolcoath account on Monday, and made known to them my intention of applying to Government, and not to individuals, for remuneration. They are ready to put their signatures to the petition, and so will all the county. I fear that it is as much as we shall do to get it before the House in time." The following petition was drawn up and put into the hands of his old friend Davies Gilbert, then a Member of Parliament:-- "TO THE HONOURABLE THE COMMONS OF THE KINGDOM OF GREAT BRITAIN AND IRELAND IN PARLIAMENT ASSEMBLED. "The Humble Petition of Richard Trevithick, of the Parish of Saint Erth, in the County of Cornwall, Civil Engineer, 27th February, 1828, "SHEWETH: "That this kingdom is indebted to your petitioner for some of the most important improvements that have been made in the steam-engine, for which your petitioner has not hitherto been remunerated, and for which he has no prospect of being ever remunerated except through the assistance of your Honourable House. "That the duty performed by Messrs. Boulton and Watt's improved steam-engines in 1798, as appears by a statement made by Davies Gilbert, Esq., and other gentlemen associated for that purpose, averaged only fourteen millions and half (pounds of water lifted 1 foot high by 1 bushel of coals), although a chosen engine of theirs, under the most favourable circumstances, at Herland Mine lifted twenty-seven millions,[152] which was the greatest duty ever performed till your petitioner's improvements were adopted, since which the greatest duty has been sixty-seven millions, being more than double the former duty. That prior to the invention of your petitioner's boiler the most striking defect observable in every steam-engine was in the form of the boiler, which in shape resembled a tilted waggon, the fire applied under it, and the whole surrounded with mason-work. That such shaped boilers were incapable of supporting steam of a high pressure, and did not admit so much of the water to the action of the fire as your petitioner's boiler does, and were also in other respects attended with many disadvantages. [Footnote 152: See Mr. Taylor's report on Herland engine, vol. ii. p. 118.] "That your petitioner, who had been for many years employed in making steam-engines on the principle of Boulton and Watt, and had made considerable improvements in their machinery, directed his attention principally to the invention of a boiler which should be free from these disadvantages; and after having devoted much of his time and spent nearly all his property in the attainment of this object, he at length succeeded in inventing and perfecting that which has since been generally adopted throughout the kingdom. "That your petitioner's invention consists principally in introducing the fire into the midst of the boiler, and in making the boiler of a cylindrical form, which is the form best adapted for sustaining the pressure of high steam. "That the following very important advantages are derived from this, your petitioner's, invention. This boiler does not require half of the materials, nor does it occupy half the space required for any other boiler. No mason-work is necessary to encircle the boiler. Accidents by fire can never occur, as the fire is entirely surrounded by water, and greater duty can be performed by an engine with this boiler, with less than half the fuel, than has ever been accomplished by any engine without it. These great advantages render this small and portable boiler not only superior to all others used in mining and manufacturing, but likewise is the only one which can be used with success in steam-vessels or steam-engine carriages. The boilers in use prior to your petitioner's invention could never with any degree of safety or convenience be used for steam navigation, because they required a protection of brick and mason work around them, to confine the fire by which they were encircled, and it would have been impossible, independent of the great additional bulk and weight, that boilers thus constructed could withstand the rolling of vessels in heavy seas; and notwithstanding every precaution the danger of the fire bursting through the brick and mason work could never be effectually guarded against. "That had it not been for this, your petitioner's, invention, those vast improvements which have been made in the use of steam could not have taken place, inasmuch as none of the old boilers could have withstood a pressure of above 6 lbs. to the inch, much less a pressure of 60 lbs. to the inch, or even of above 150 lbs. to the inch when necessary. "That as soon as your petitioner had brought his invention into general use in Cornwall, and had proved to the public its immense utility, he was obliged in 1816 to leave England for South America to superintend extensive silver mines in Peru, from whence he did not return until October last. That at the time of your petitioner's departure the old boilers were falling rapidly into disuse, and when he returned he found they had been generally replaced by those of his invention, and that the saving of coals occasioned thereby during that period amounted in Cornwall alone to above 500,000_l._[153] [Footnote 153: See Lean's report, vol. ii., p. 175.] "That the engines in Cornwall, in which county the steam-engines used are more powerful than those used in any other part of the kingdom, have now your petitioner's improved boilers, and it appears from the monthly reports that these engines, which in 1798 averaged only fourteen and half millions now average three times that duty with the same quantity of coals, making a saving to Cornwall alone of 2,781,264 bushels of coals, or about 100,000_l._ per annum. And the engines at the Consolidated Mines in November, 1827, performed sixty-seven millions, being forty millions more than had been performed by Boulton and Watt's chosen engine at Herland, as before stated. "That had it not been for your petitioner's invention, the greater number of the Cornish mines, which produce nearly 2,000,000_l._ per annum, must have been abandoned in consequence of the enormous expense attendant on the engines previously in use. "That your petitioner has also invented the iron stowage water-tanks and iron buoys now in general use in His Majesty's navy, and with merchant's ships. "That twenty years ago your petitioner likewise invented the steam-carriage, and carried it into general use on iron railroads. "That your petitioner is the inventor of high-pressure steam-engines, and also of water-pressure engines now in general use. "That his high-pressure steam-engines work without condensing water, an improvement essentially necessary to portable steam-engines, and where condensing water cannot be procured. "That all the inventions above alluded to have proved of immense national utility, but your petitioner has not been reimbursed the money he has expended in perfecting his inventions. That your petitioner has a wife and large family who are not provided for. "That Parliament granted to Messrs. Boulton and Watt, after the expiration of their patent for fourteen years, an extension of their privileges as patentees for an additional period, whereby they gained, as your petitioner has been informed, above 200,000_l._ "That your petitioner therefore trusts that these his own important inventions and improvements will not be suffered to go unrewarded by the English nation, particularly as he has hitherto received no compensation for the loss himself and his family have sustained by his having thus consumed his property for the public benefit. "Your petitioner therefore most humbly prays that your Honourable House will be pleased to take his case into consideration, and to grant him such remuneration or relief as to your Honourable House shall seem meet. "And your petitioner, as in duty bound, will ever pray, &c. "RD. EDMONDS, "_Solicitor, Penzance_." From the Patent Office to the House of Commons was, for a petitioner, as bad as out of the frying-pan into the fire. Trevithick solicited the support of Members of Parliament until tired of running after friends, and the petition became a dead letter, though the mining interests of Cornwall had in twelve years saved 500,000_l._ by his unrewarded inventions. "LAUDERDALE HOUSE, HIGHGATE, _December 24th, 1831_. "MR. GILBERT, "Sir,--I find that Mr. Spring Rice cannot get the Lords of the Treasury to agree to remunerate or assist me in any way. He appeared to be much disappointed, and said that he would write to the Admiralty Board on Thursday last, recommending them to adopt this engine. As yet I have heard nothing respecting it, nor do I expect to during the holy days; but in the interim I wish to look out for some moneyed man to join in it, otherwise I fear I shall lose the whole. Can you assist in recommending anyone you know? I wish Mr. Thompson would come into it, he would be a good man. Can you furnish me with a copy of your report to Mr. Spring Rice, or something relating thereto? It would be a great assistance in getting some one to join. "The sum required is small, and the risk is less; but the prospect is great, beyond anything I ever knew offered on such easy terms. Waiting your reply, "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK." "DEAR TREVITHICK, "EASTBOURNE, _December 26th, 1831_. "I am sorry to find that you have not any prospect of assistance from Government. I have not any copy or memorandum of my letter to Mr. Spring Rice; but it was to the effect of first bearing testimony to the large share that you have had in almost all the improvements on Mr. Watt's engine, which have altogether about trebled its power; to your having made a travelling engine twenty-eight years ago; of your having invented the iron-tanks for carrying water on board ships, &c. "I then went on to state that the great defect in all steam-engines seemed to be the loss, by condensation, of all the heat rendered latent in the conversion of water into steam; that high-pressure engines owed their advantages mainly to a reduction of the relative temperatures of this latent heat; that I had long wished to see the plan of a differential engine tried, in which the temperatures and consequently elasticities of the fluid might be varied on the opposite sides of the piston, without condensation; that the engine you have now constructed promised to effect that object; and that, in the event of its succeeding at all, although it might not be applicable to the drawing water out of mines, yet that for steam-vessels and for steam-carriages its obvious advantages would be of the greatest importance; and I ended by saying that although it was clearly impossible for me to ensure the success of any plan till it had been actually proved by experiment, yet judging theoretically, and also from the imperfect trial exhibited on the Thames, I thought it well worthy of being pursued. Your plan unquestionably must be to associate some one with you (as Mr. Watt did Mr. Boulton), and I certainly think it a very fair speculation for any such person as Mr. Boulton to undertake. "It is impossible for me to point out any individual, as never having had the slightest connection with trade or with manufacture in any part of my life, I am entirely unacquainted with mercantile concerns. I cannot, however, but conjecture that you should make a fair and full estimate of what would be the expense of making a decisive experiment on a scale sufficiently large to remove all doubt; and that your proposal should be, that anyone willing to incur that expense should, in the event of success, be entitled to a certain share of your patent. On such conditions some man of property may perhaps be found who would undertake the risk; and if the experiment proves successful, he will be sure to use every exertion afterwards for his own sake. With every wish for your success, "Believe me, "Yours very sincerely and faithfully, "DAVIES GILBERT." The petition to Parliament for a national payment for national gains, so hopefully taken up on his return from America, when experience had proved the value of his inventions, after four weary years of deferred expectation, was consigned to the tomb of forgetfulness. Compare the petition of 1828 with a modern report. "Prior to the invention of your petitioner's boiler, the most striking defect observable in every steam-engine was in the form of the boiler which in shape resembled a tilted wagon; your petitioner's invention consists principally in introducing the fire into the midst of the boiler, and in making the boiler of a cylindrical form, which is the form best adapted for sustaining the pressure of high steam, and does not require half of the materials, nor does it occupy half the space required for any other boiler, and greater duty can be performed by an engine with this boiler with less than half the fuel, than by any engine without it, and is the only one that can be used with success in steam-vessels, as none of the old boilers could have withstood a pressure of above 6 lbs. on the inch, much less a pressure of 60 lbs. or even of 150 lbs. when necessary." A report of the Royal Mail Steam Packet Company in 1871 states, "by placing compound engines in the 'Tasmania,' they had reduced the consumption of coal to one-half the former quantity, doubled her capacity for freight, and increased her speed."[154] Presuming that the compound engines of the 'Tasmania' are like other engines known by that name, having high-pressure steam in a comparatively small cylinder from which it expands in a larger one, tubular boilers, surface condensers, and screw-propeller, the saving admitted in the 'Tasmania' is just what Trevithick's petition pointed out forty-three years ago--to lessen by one-half the weight, space, and fuel in marine steam-engines--his opinion being founded on the experience of a lifetime, for as early as 1804 he wrote on the question of compound engines, "I think one cylinder partly filled with steam would do equally as well as two cylinders;"[155] and again in 1816, describing expansion, "The engine is now working with 60 lbs. of steam, three-quarters of the stroke expansive, and ends with the steam rather under atmosphere strong;"[156] and in the same year worked the expansive compound engine at Treskerby.[157] [Footnote 154: See 'The Times,' October 26th, 1871, Half-yearly Report of the Chairman.] [Footnote 155: See vol. ii., p. 134.] [Footnote 156: See vol. ii., p. 91.] [Footnote 157: See vol. ii., p. 104.] CHAPTER XXVI. TUBULAR BOILER, SUPERHEATING STEAM, AND SURFACE CONDENSER. "MR. GILBERT, "HAYLE FOUNDRY, _December 14th, 1828_. "Sir,--On my return from London five weeks since I was disappointed at not finding you in Cornwall. I have made inquiry into the duty performed by the best engines, and the circumstances they are under, from which it appears to me there is something which as yet has not been accounted for, particularly in Binner Downs engines. A statement was given to me by Captain Gregor, the chief agent and engineer of the mine, which appears so plain that I cannot doubt the facts, though they differ very widely from all former opinions. There are two engines, one of 42 inches diameter, the other of 70 inches diameter, 10-feet stroke. "Formerly those engines worked without cylinder cases, when the 70-inch cylinder burnt 1-1/2 wey of coal, and performed a regular duty of forty-one millions; since that time brickwork has been placed round the cylinder and steam-pipes, leaving a narrow flue, which is heated by separate fires. These flues consume about 5 bushels of coal in twenty-four hours; the heat is not so great as to injure the packing, which stands good for thirteen weeks; the saving for several months past has increased the duty to sixty-three millions. "Before the use of this flue 108 bushels of coal were consumed under the boiler, now only 67 bushels are needed, which with the 5 bushels in the flue gives 72 bushels. The coal burnt under the boiler gives a duty of sixty-six millions, or an expansion of 60 per cent. by the heat of 5 bushels of coal in the flues, and a duty of 1781 millions gained in twenty-four hours by 5 bushels of coal, which amounts to 350 millions gained by each of these 5 bushels. The 42-inch cylinder is as near as possible under the same circumstances, no other alterations have been made; and to prove this they left out the fires in the flues, and the engines fell back to their former duty, and the condensing water increased in the same proportion. "The surface sides heated by this 5 bushels of coal is about 300 surface feet, the saving effected is 1781 millions, which is six millions saving for each foot of surface on the castings in the flues. In Wheal Towan engine that did eighty-seven millions, the surface sides of the boiler was 1000 feet of fire-sides for every bushel of coal burnt in an hour, and the duty performed per minute from each foot of boiler fire-sides was 1500 lbs. 1 foot high. Now it appears that the heating of Binner Downs 300 surface feet gave a saving of 6000 lbs. per minute per surface foot; whereas the boiler sides only gave 1500 lbs. of duty per minute for each foot of boiler fire-sides. Therefore the saving by heating the sides of the cylinder is equal to four times the duty done by each square foot of boiler sides; and further, it appears that the 300 feet, when not heated, though clothed round with brickwork, condensed or prevented from expanding the steam of 41 bushels of coals, which was eight times as much steam condensed as the 5 bushels of coal would raise. Now if this be a report of facts, which I have no reason to doubt (but still I will be an eye-witness to it next week), there must be an unknown propensity in steam above atmosphere strong to a very sudden condensation, and _vice versâ_, to also a sudden expansion, by a small heat applied to the steam-sides; and if by heating steam, independent of water, such a rapid expansion takes place, certainly a rapid condensation must take place in the same ratio, which might be done at sea by cold sides to a great advantage, always working with fresh water. "I shall have a small portable engine finished here next week, and will try to heat steam, independent of water, in small tubes of iron, on its passage from the boiler to the cylinder, and also try cold sides for condensing. "If the above statement prove to be correct, almost anything might be done by steam, because then additional water would not be wanted for portable engines, but partially condensed and again returned into the boiler, without any fresh supply or the incumbrance of a great quantity; and boilers might be made with extensive fire-sides, both to heat water and steam, and yet be very light. "It appears that this engine, when working without the heated flues round the cylinder and pipes, evaporated 20,000 gallons of water into steam, in twenty-four hours, more than when the flues were heated, and the increase of condensing water was in the same proportion. It is so unaccountable to me that I shall not be satisfied until I prove the fact, the result of which I will inform you, and shall be very glad to receive your remarks on the foregoing statement. "The first engine that will be finished here for Holland will be a 36-inch cylinder, and a 36-inch water-pump, to lift water about 8 feet high; on the crank-shaft there is a rag-head of 8 feet diameter, going 8 feet per second, with balls of 3 feet diameter passing through the water-pump, which will lift about 100 tons of water per minute. It is in a boat of iron, 14 feet wide, 25 feet long, 6 feet high, so as to be portable, and pass from one spot to another, without loss of time. It will drain 18 inches deep of water (the annual produce on the surface of each acre of land) in about twenty minutes for the drainage of each acre, with one bushel or sixpennyworth of coal per year. The engine is high pressure and condensing. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK. "P.S.-Woolf is making an apparatus to throw back from the bottom of the cylinder on to the top of the piston a fluid metal every stroke. He says he proved by an indicator that he raised 18,000 inches of steam from 1 inch of water, of 11 lbs. to the inch pressure on a vacuum, and that the reason why this engine did not do 300 millions, was because the steam passed by the sides of the piston. That an engine at the Consolidated Mines working 10 feet 2 inch stroke, going 7/8ths expansive, beginning with steam of 20 lbs. to the inch above the atmosphere, and ending with 11 lbs. on a vacuum. I doubt this statement; however, there is some hidden theory as yet, because some engines perform double as much as others, under the same known circumstances, and I believe that nothing but practice will discover where this defect is, for, in my opinion, no statement of theory yet given is satisfactory why high-pressure engines so far exceed low-pressure engines. It is facts that prove it to be so, therefore all theory yet laid down must be defective." [Illustration: MOUNT'S BAY. [W. J. Welch.]] At the date of this letter Trevithick had been rather more than a year in England, residing generally at Hayle, within half-a-dozen miles of Mount's Bay, from which he had sailed for America; and after eleven years of wandering in countries where steam-engines were unknown, except those that he himself had constructed, was again on his return giving his whole thoughts to the idol of his life. During that period scientific men in Europe thought and wrote much on the question of relative temperature, pressure, economy, and manageability of steam. Newcomen's great discovery a century before was the avoidance of the loss of heat by the cooling at each stroke of the exterior of the steam-vessel of Savery's engine by injecting cold water into the steam in the cylinder. After fifty years came the Watt improvement, still reducing the loss of heat by removing the cold injection-water from the steam-cylinder to a separate condenser. The high-pressure steam-engine was perfect without injection-water, though when convenient its use was equally applicable as in the low-pressure engine. Trevithick, on his return to civilized life, read the views of Watt on steam, as given in 'Farey on the Steam-Engine.' On informing Davies Gilbert of his doubts of the accuracy of those views, and of his intention of testing them by comparison with the work performed by Cornish pumping engines, his friend, who had just published his 'Observations on the Steam-Engine,'[158] forwarded a copy, from which the following is an extract:-- [Footnote 158: 'Observations on the Steam-Engine,' by Davies Gilbert, V.P.R.S., January 25th, 1827. See 'Philosophical Transactions.'] "One bushel of coal, weighing 84 lbs., has been found to perform a duty of thirty, forty, and even fifty millions, augmenting with improvements, chiefly in the fire-place, which produce a more rapid combustion with consequently increased temperature, and a more complete absorption of the generated heat; in addition to expansive working, and to the use of steam raised considerably above atmospheric pressure." Those words gave the result of Trevithick's experience made known to his friend during twenty years of labour,[159] and yet by a seeming fatality his name is not found in his friend's book. [Footnote 159: See letter, vol. ii., p. 143.] Sir John Rennie, who in youth had been employed under Boulton and Watt at Soho, and had risen to be a member of the Royal Society, came about that time into Cornwall, at the request of the Admiralty, to make examination into the work performed by Cornish pumping engines, and selected Wheal Towan engine on which to make special experiments.[160] The subject of Trevithick's note was therefore at that period, and still is, a matter of importance; and his practical treatment of the question is more instructive to young engineers than complex rules. Arthur Woolf was at the same time experimenting on steam at the Consolidated Mines, and finding the want of agreement between the rules of low-pressure and the practice of high-pressure engines, imputed the error to the escape of steam by the sides of the piston. Trevithick disbelieved this, "because some engines perform double as much as others, under the same known circumstances," and advocated the observance of general practice to prove why high-pressure engines were more economical than those of low-pressure. Captain Gregor had placed fire-flues around the steam cylinder and pipes, hoping thereby to exceed the duty of the Wheal Towan engine, whose boiler, cylinder, and steam-pipes were carefully clothed with a thick coating of sawdust or other non-conductor of heat, and lifted eighty-seven millions of pounds of water 1 foot high by the heat from a bushel of coal weighing 84 lbs. This was the greatest duty that had ever been recorded from a steam-engine. The Trevithick or Cornish boilers, similar to those in Dolcoath,[161] measured at the rate of 1000 superficial feet of heating surface for each bushel of coal burnt in an hour, and in round numbers gave a duty of 1500 lbs. lifted a foot high to each foot of boiler surface. In words not technical, the heat from 1 lb. of coal gave steam that raised 460 tons weight of water 1 foot high. [Footnote 160: See vol. ii., p. 185.] [Footnote 161: See drawing, vol. ii., p. 169.] The cylinder of this engine used the Watt steam-jacket. The Binner Downs engine was doing not one-half this duty, namely, forty-one millions; when brick flues were built around the cylinder, cylinder cover, and steam-pipes, and one or two fire-places, fixed near the bottom of the cylinder, of a size to conveniently burn 5 bushels of coal in twenty-four hours, the heat from which circulated through those flues on its way to the chimney, and increased the duty of the engine by one-half, raising it to sixty-three millions; in other words, during twenty-four hours of working, 67 bushels of coal in the boiler, and 5 bushels in the cylinder flues, did the same work as 108 bushels in the boiler without the cylinder flues, causing a saving of fifty per cent. by their use. Another startling fact was the greater effect for each foot of heating surface in the steam-cylinder flues than in the boiler flues; the latter gave a power of 1500 lbs. raised 1 foot high by a bushel of coal, while the former gave 6000 lbs. of power from the same amount of coal and heating surface. Here was a mystery that Trevithick would not believe until he had seen it with his own eyes: he searched for it for a year or two, and overlooking the fact that the more simply arranged engine of his once pupil, Captain Samuel Grose, was doing more duty than the superheating steam-engine at Binner Downs, he worked at what seemed to be new facts, and converted them into a new engine. We have traced how succeeding engineers tried to prevent loss of heat. Trevithick took the first bold step, and aiming at the same object, made the boiler the steam-jacket for the cylinder, and in his patent of 1802 went still further and protected the boiler from external cold, and thus describes it:--"The steam which escapes in this engine is made to circulate in the case round the boiler, where it prevents the external atmosphere from affecting the temperature of the included water, and affords by its partial condensation a supply for the boiler itself."[162] So that a quarter of a century before the date of those Binner Downs experiments he had patented an engine having neither cylinder nor boiler exposed to the cooling atmosphere. The flues around the Binner Downs cylinder were difficult of control. Trevithick says the piston packing had not been injured, showing that observers thought it would be, and even the cylinder was endangered, for the writer, who stoked those heating flues, recollects the fires burning very brightly in them. The ready transmission of heat through thin metal, used by Trevithick in 1802 for heating feed-water, and in the cellular bottom of the iron ship of 1808, serving as a surface condenser,[163] and his experience in 1812, that "the cold sides of the condenser are sufficient to work an engine a great many strokes without any injection,"[164] still followed up in 1828 by condensing steam without the use of injection-water, led to what is since known as Hall's surface condenser. [Footnote 162: See patent specification, vol. i., p. 132.] [Footnote 163: See vol. i., p. 335.] [Footnote 164: See Trevithick's letter, 7th December, 1812, vol. ii., p. 18.] The following letter is in the handwriting of the present writer; it is the only one of Trevithick's numerous letters not written by himself:-- "MR. GILBERT, "HAYLE, _December 30th, 1828_. "Sir,--On the 28th inst. I received your printed report on steam, and have examined Farey's publication on sundry experiments made by Mr. Watt, which are very far from agreeing with the actual performance of the engines at Binner Downs. Mr. Watt says that steam at one atmosphere pressure expands 1700 times its own bulk as water at 212°, and that large engines ought to perform eighteen millions when loaded with 10 lbs. to the inch of actual work, the amount of condensing water being one-fortieth part of the content of the steam in the cylinder at one atmosphere strength, the cold condensing water at 50°, and when heated 100°. This would give for the Binner Downs engine, with a 70-inch cylinder, 10-inch stroke, 11 lbs. effective work on the inch (this load being one-tenth more than in Watt's table, by Farey, for an engine of this size and stroke), 57 gallons of injection-water for each stroke, and when working eight strokes per minute, to do eighteen millions would consume 11-1/4 bushels of coal per hour. "Now the actual fact at Binner Downs, at the rate of working and power above mentioned, is that 3 bushels of coal per hour were burnt, using 13 gallons of injection-water at each stroke at 70° of heat, which was raised by its use to 104°, or an increase of 34°, which, multiplied by 13 gallons, gives 442. Mr. Watt's table for this engine and work gives 57 gallons of condensing water at 50°, heated by use to 100°. This 50° raised, multiplied by the 57 gallons of water, amounts to 2850, or six and a half times the quantity really used in the Binner Downs engine, and nearly four times the coal actually used at present. Mr. Watt further says that steam of 15 lbs. to the inch, or one atmosphere, from 1 inch of water at 212° occupies 1170 inches, and that steam of four atmospheres, or 60 lbs. to the inch, gives only 471 inches at a heat of 293°. Now deducting 50° from 212° leaves 162° of heat raised by the fire. Multiply 15 lbs. to the inch by 1700 inches of steam, and divide it by 162°, gives 138°, whereas if you deduct 50° from 293°, it leaves the increase of heat by the fire 243°. Steam of 60 lbs. to the inch multiplied by 471, being the inches of steam made by 1 inch of water divided by 243°, the degrees of heat raised by the coal, gives a product of 116; therefore, by Mr. Watt's view it appears that low steam would do one-fifth more duty than high steam, and yet Binner Downs engine in actual work performs about four times the duty given by Mr. Watt's theory and practice, with only one-sixth part of the amount of heat carried off by the condensing water, proving that high steam has much less heat, in proportion to its effective force; and this is further proved by the small quantity of condensing water required to extract its heat. "Yesterday I proved this 70-inch cylinder while working with the fire-flues round it, which flues only consumed 5 bushels of coal in twenty-four hours. The engine worked eight strokes a minute, 10-feet stroke, 11 lbs. to the inch effective force on the piston; steam in the boiler 45 lbs. above the atmosphere, consuming 12 bushels of coal in four hours, using 13 gallons of condensing water at each stroke, which was heated from 70° to 104°; but when the fires round the cylinder were not kept up, though still having the casing of hot brickwork around it, and performing the same work, burnt 17 bushels of coal in the same time of four hours, and required 15-1/2 gallons of condensing water, which was heated from 70° to 112°. You will find that the increased consumption of coal, by removing the fire from around the cylinder, was nearly in the same proportion as the increase and temperature of the condensing water, showing the experiment to be nearly correct. "From the general reports of the working of the engines it appears that when the surface sides of the castings are heated, either by hot air or high steam, the duty increases nearly fifty per cent. from this circumstance alone. "A further proof of the more easy condensation of high steam was in the Binner Downs 42-inch cylinder engine, 9-feet stroke, six strokes per minute, 11 lbs. effective power on each inch, burning 1-1/3 bushel of coal an hour. In this engine the proportion of saving by the heating flues was the same as in the large engine. I tried to condense the steam by the cold sides of the condenser, without using injection-water. The water in the condenser cistern was at 50°. After working for twenty-five minutes the small quantity of hot water discharged at the top of the air-pump reached 130° of heat, but then would rise no higher, the cold sides of the condenser being equal to the condensation of all the steam. The eduction-pipe and air-pump, with its bottom and top, gave 60 feet of surface sides of thick cast iron, and about 20 feet more of surface sides of a thin copper condenser; altogether, 80 feet of surface cold sides, surrounded by cold water. About half a pound on the inch was lost in the vacuum, the discharged water being 130° of heat instead of 100°. The vacuum was made imperfect by about 1-1/2 lb. to the inch. "It is my opinion that high steam will expand and contract with a much less degree of heat or cold in proportion to its effect, than what steam of atmosphere strong will do. I intend to try steam of five or six atmospheres strong, and partially condense it down to nearly one atmosphere strong, and then by an air-pump of more content than is usual to return the steam, air, and water, from the top of the air-pump, all back into the boiler again, above the water-level in the boiler, and by a great number of small tubes, with greatly heated surface sides, to reheat the returned steam; though by this plan I shall lose the power of the vacuum, and also the power required on the air-bucket to force the steam and water back again into the boiler, yet by returning so much heat I shall over-balance the loss of power, besides having a continued supply of water, which in portable engines, either on the road or on the sea, will be of great value. "I shall esteem it a very great favour if you will be so good as to turn over in your mind the probable theory of those statements, and give me your opinion. If Mr. Watt's reports of his experiments are correct, how is it possible that the high-pressure engine that I built at the Herland thirteen years ago, which discharged the steam in open air, did more than twenty-eight millions? If you wish, I will send a copy of the certificate of the duty done by this engine, which states very minutely every circumstance. Now that cylinder, with every part of the engine, was exposed to the cold; had it been heated around those surfaces, as on the present plan, it would have done above forty millions. "Suppose the Binner Downs 70-inch cylinder engine, 10-feet stroke, working with full steam to the bottom of the stroke, when, by the experiment, the heated flues were again laid on would have worked one-third expansive, by the heat of 5 bushels of coal around the cylinder. Now one-third of the power would make a 3 feet 4 inch stroke, 11 lbs. to the inch effective power, eight strokes a minute, during twenty-four hours, by the consumption of 5 bushels of coal applied on the surface sides of the cylinder, performing a duty of 324 millions with a bushel of coal. Now suppose the cylinder without the heating flues had the steam cut off at two-thirds of the stroke, and that it is possible in a moment to heat the cylinder by the flues; in that case the steam would, by its expansion from the hot sides, fill the last third of the cylinder to the bottom of the stroke; then if that steam could be suddenly cooled, so as to contract it one-third, the piston would ascend one-third its stroke in the cylinder; and it appears in theory by this plan, that a cylinder once filled two-thirds full of steam, by receiving the heat on its surface sides from 5 bushels of coal, and again suddenly cooling down, would continue to work for ever, without removing the steam from the cylinder, and would perform a duty of 324 millions. This never can be accomplished in practice in this way, but the effect may be obtained by partially condensing in a suitable condenser, and again heating by hot sides. "This mystery ought to be laid open by experiment, for what I have stated are plain facts from actual proofs, and I have no doubt that time will show that the theory of Mr. Watt is incorrect. Though there were 300 feet of cold sides, yet 200 feet were not condensing steam, because on the return of the piston, what was condensed below, and while the engine was resting, did not make against it more than what was condensed above the piston on its descent; therefore you may count on 150 feet of cold external sides constantly condensing, that made this third-part difference against the expansion of the steam. "I remain, Sir, "Your very humble servant, "RICHD. TREVITHICK." The writer's note-book used during those experiments is in his possession, as well as Trevithick's note-book giving particulars of experiments at several mines, from which the following extracts are taken:-- "CORNWALL, _August, 1828_.--Wheal Towan 80-inch cylinder, 10-feet stroke, 6·9 strokes per minute, loaded to 9·5 lbs. on the inch of the piston, with three of Trevithick's boilers, each 37 feet long, 6 feet 2 inches diameter, with fire-tube 3 feet 9 inches diameter, fire-place 6 feet long, evaporated 13 square feet of water with 1 bushel of coal,[165] duty 87 millions. The heat in the stack was just the same as the heat of the steam in the boiler. Another engine of the same size on the same mine, with similar boilers, but working only 4·06 strokes per minute, loaded to 4·55 lbs. on each inch of the piston, did 50·8 millions. [Footnote 165: 84 lbs.] "Wheal Vor 53-inch cylinder, 9-feet stroke, 6·59 strokes per minute, loaded to 19·58 lbs. on each square inch of the piston, did 36·6 millions. "Wheal Damsel 41-inch cylinder, 7 feet 6 inch stroke, 5·52 strokes per minute, loaded to 21·5 lbs. on the inch of the piston, did 33 millions. "It would appear, therefore, that about 10 lbs. to the inch on the piston allows of the best duty, and that a 10-feet stroke exceeds in duty a 7 feet 6 inch stroke. "The Wheal Towan engine, doing 87 millions, had 1248 feet of tube fire-surface, and a similar amount of external boiler surface in the flues. 2-1/2 bushels of coal were consumed each hour, giving about 1000 feet of fire-sides for each bushel of coal consumed per hour, and 50 feet of fire-bars. Those boilers were intended to supply steam for working the engine at ten strokes a minute; a bushel of coal an hour would in that case have had 600 feet of boiler fire-surface. "Binner Downs 70-inch cylinder, 10-feet stroke, did 41 millions. A fire was then put around the cylinder and steam-pipes, which burnt 5 bushels of coal in twenty-four hours, by which the duty was increased to 63 millions. The surface sides of the cylinder, cylinder-top, and steam-pipes heated by flues was 300 feet, and caused a saving of 41 bushels of coal in twenty-four hours. Another engine in the same mine was tried, having a 42-inch cylinder; when the fire was around the cylinder, she worked 100 strokes without injection-water; the expansion-valve was closed at half-stroke, the steam in the boiler 56 lbs. on the inch above the atmosphere." It is not easy to deal with the important reasonings flowing from those facts, and influencing the form and economy of the steam-engine, nor to show if Trevithick was right in discrediting the laws laid down by Watt. Newcomen's engine had the interior, as well as the exterior of the steam-cylinder exposed to the cooling atmosphere. Watt, by putting a cover on the cylinder, reduced the loss of the heat from the interior, and by his steam-case hoped to reduce the loss from the exterior, though by it he increased the amount of surface exposed to the cold. In Trevithick's early engines the boiler alone exposed heat-losing surface, and this was further reduced by its own comparatively small size, the engine and boiler complete not exposing one-quarter of the surface of a Watt low-pressure engine of equal power. One object of the Binner Downs experiment was to further curtail this loss of power by increasing the heat of the steam while in operation in the cylinder, since called superheating steam. This principle of giving increased heat to steam, after it had left its state as water, was made practical by Trevithick's boiler at Wheal Prosper in 1810, where the flues having first been carried around the water portion of the boiler, then passed over the steam portion;[166] and again in the upright boiler of 1815, having the upper end of the fire-tube surrounded by steam above the water line.[167] Those early beginnings of superheating steam and surface condensation culminated in the Binner Downs experiments of 1828, one immediate practical result of which was the tubular surface condenser, enabling steamboat boilers to avoid, in a great measure, the use of salt water, facilitating in a marked degree the application of marine boilers and engines with steam of an increased pressure. [Footnote 166: See vol. ii., p. 71.] [Footnote 167: See vol. i., p 354.] The Binner Downs engine, with a cylinder of 70 inches in diameter, and a stroke of 10 feet when working with steam in the boilers of 45 lbs. to the square inch above the atmosphere, and using the heating flues around the cylinder, required 13 gallons of injection-water at each stroke, and consumed at the rate of 3 bushels of coal an hour, to produce a duty equal to eighteen millions; by removing the cylinder superheating flues, the quantity of injection-water for the same amount of work increased to 15-1/2 gallons, and the coal to 4-1/4 bushels. Watt's rule for his low-pressure steam vacuum engine doing a duty of eighteen millions, gave 57 gallons of injection-water, and 11-1/4 bushels of coal. On the question of coal, this statement agrees very nearly with Trevithick's letters of sixteen years before, when he used the high-pressure boilers in the Dolcoath pumping engine,[168] promising that his high-pressure expansive engine would do the work with one-third of the coal required in the low-pressure vacuum engine. [Footnote 168: See vol. ii., p. 171.] The high-pressure steam required a less amount of injection-water to condense it than the low-pressure steam, in proportion to the work done, showing the Watt rule and the Watt experience to be inapplicable to high-pressure engines; for instead of 57 gallons of injection-water the Binner Downs engine with steam of 45 lbs. to the inch required but 15-1/2 gallons of injection-water, and this amount was further reduced to 13 gallons by superheating the steam; this roughly agrees with the coal consumed, or in other words, with the amount of heat to be carried off by injection-water: the Watt rule giving 11-1/4 bushels as the fair allowance for low-pressure steam vacuum engines, while the high-pressure steam vacuum engine burnt but 4-1/4 bushels. This was further reduced to 3 bushels by superheating. Those facts led to the idea that if the steam pressure was sufficiently increased, condensation might be carried out without any injection-water, by the transmission of the heat in the steam through the metal sides of the condenser. An experiment was at once made by removing the Watt condenser and injection-water, as he had done seventeen years before,[169] using in their stead a thin copper surface-condenser immersed in cold water, producing, within 1/2 lb. on the inch, as good a vacuum as when injection-water was used, leading to the conclusion,-- [Footnote 169: See Query 3rd, vol. ii., p. 19.] "It is my opinion that high steam will expand and contract with a much less degree of heat or cold, in proportion to its effect, than what steam of atmosphere strong will do. I intend to try steam of five or six atmospheres strong, and partially condense it down to nearly one atmosphere strong, and then by an air-pump of more content than is usual to return the steam, air, and water back into the boiler again, and by a great number of small tubes, with greatly heated surface sides, to reheat the returned steam." This, in practical words, is the surface condenser by which the used steam is returned to the boiler in the form of water. The more general use of high-pressure steam of 70 or 90 lbs. to the inch, increasing its expansive force on one side of the piston by superheating it on its passage through numbers of small tubes, and decreasing its expansive force on the other side of the piston by cooling it in passage through similar tubes exposed to cold, is partly effected in steamboats, but has not yet been attempted in engines on the road. After a month's further consideration he wrote:-- "Wheal Towan engine is working with three boilers, all of the same size, and the strong steam from the boilers going to the cylinder-case; the boilers are so low as to admit the condensed water to run back from the case again into the boiler: they find that this water is sufficient to feed one of these boilers without any other feed-water, therefore one-third of the steam generated must be condensed by the cold sides of the cylinder-case, and this agrees with the experiments I sent to you from Binner Downs. Wheal Towan engine has an 80-inch cylinder, and requires 72 bushels of coal in twenty-four hours, therefore, the cylinder-case must, in condensing high-pressure steam, use 24 bushels of coal in twenty-four hours. Boulton and Watt's case for a 63-inch cylinder working with low-pressure steam, condensed only 4-1/2 bushels of coal in equal time, the proportions of surface being as 190 to 240 in Wheal Towan. Nearly five times the quantity was condensed of high steam than of low steam, proving that there is a theory yet unaccounted for."[170] [Footnote 170: See Trevithick's letter, January 24th, 1829, vol. ii., p. 368.] These apparent facts are, in the case of steamboats, more culpably overlooked now than when he wrote forty-two years ago; engines have been examined and reported on by eminent scientific men, but it was left for Trevithick to point out that cold on the surface of the steam-case of a Watt low-pressure steam vacuum engine condensed about one-fifteenth of the steam given from the boilers, and that the loss from exposure to cold was nearly five times more from high-pressure steam than from low-pressure. Within a few more months he determined on constructing an engine for the purpose of more accurately testing those views. "MR. GILBERT, "HAYLE FOUNDRY, _July 27th, 1829_. "Sir,--Below you have a sketch of the engine that I am making here for the express purpose of experimenting on the working the same steam and water over and over again, heating the returned steam by passing it in small streams up through the hot water from the bottom of the boiler. The boiler is 3 feet in diameter, standing perpendicular; the interior fire-tube is 2 feet in diameter; there is a steam-case round the outside of the boiler with a 1-1/2-inch space. This keeps the boiler hot and partially condenses the steam before it is again forced into the boiler. [Illustration] "The boiler is 15 feet high; the cylinder 14 inches diameter, with a 6-feet stroke, single power. The pump for forcing the steam and water back again is 10 inches in diameter, with a 2 feet 9 inch stroke, about one-quarter part of the content of the steam-cylinder. The bottom of the boiler will have a great number of small holes, about 1/16th of an inch in diameter, through which the steam delivered into the boiler will pass up through the hot water, by which I should think it will heat those small streams of steam again to their usual temperature. "The pump for lifting water to prove the duty of the engine is 30 inches in diameter, with a 6-feet stroke, but this may be lengthened to a 12-feet lift, as the trial or load in the experiments may require, giving from 12 to 24 lbs. to the inch in the piston. This machine will be ready before your return to Cornwall, and I intend to prove it effectually before I go to Holland. "The Holland engine lifted on the trial, when they came down to see it, 7200 gallons of water a minute 10 feet high with 1 bushel of coal an hour; exceedingly good duty for a small engine of 24-inch cylinder, being 34,560,000 of duty. "On the 17th August the trial comes on between the two companies about the quays. They are as desperate as possible on both sides, and castings and every other article are thrown down to 30 per cent. below cost price; iron pumps for 6_s._ 6_d._ per cwt., and coal sold to the mines for 37_s._ 3_d._ per wey, when 48_s._ per wey on board ship was paid for it. Several thousands lost per year by each party. This never can last long. If you can think of any improvement I shall be very glad to hear in time, before it may be too late to adopt it. At all events, if it is not too much trouble to write, I shall be very glad to hear from you. What effect do you think the water will have in heating the steam on its passage to the top of the water from the false bottom of the boiler? "I have a cistern of cold water, with a proper condenser in it, connected between the bottom of the boiler-case and the force-pump to the bottom of the boiler, therefore I can partially condense by cold water sides, or by cold air sides just as I please, by rising or sinking the water in the cistern. "The boiler is made very strong to try different temperatures, and an additional length to the water-pump makes all very suitable for a great number of experiments, and if there is any good in the thing I will bring it out. "I shall have indicators at different places to prove what advantages can be gained. I hope to have the pleasure of your company during those experiments, which I think will throw more light on this subject than ever has yet been done. Some trials since I last wrote to you make me very confident that much good will arise from these experiments, but to what extent is uncertain. "I remain, Sir, "Your most obedient servant, "RICHARD TREVITHICK." Trevithick did not use letters to illustrate his sketch, knowing that Davies Gilbert would comprehend it; but the reader of to-day may not find it so easy, therefore the writer has added them with a slight detail description, he having been Trevithick's daily companion when those drawings and experiments were made. _a_, top of boiler; _b_, water line; _c_, centre of wheel; _d_, cast-iron wheel and chain; _e_, chimney, 13 in. in diameter; _f_, fire-tube, 2 ft. diameter; _g_, outer boiler-*case, 3 ft. diameter, 15 ft. long; _h_, water space of 6 in.; _i_, boiler steam-case, 3 ft. 4 in. diameter; _j_, small holes through which steam and water are forced into the boiler; _k_, force-pump, 10 in. diameter, 2 ft. 9 in. stroke; _l_, steam-cylinder, 14 in. diameter, 6-ft. stroke; _m_, piston-rod; _n_, fire-door; _o_, fire-bars; _p_, pump for testing the power of the engine. There is a natural tendency in men of genius to unwittingly return, under new forms, to old ideas. The ideas are similar, though in combination with new forms and new acquirements; even the outline of this 1828 boiler, with the exception of its outer steam-casing, is very like that in a letter to Davies Gilbert fourteen years before,[171] of which Trevithick had kept no copy. When in the foregoing letter he wrote, "There is a steam-case round the outside with a 1-1/2-inch space; this keeps the boiler hot and partially condenses the steam before it is again forced into the boiler," he had forgotten that twenty-seven years before, when constructing his first high-pressure steam-engines, he thus specified his invention:--"The steam which escapes in this engine is made to circulate in the case round the boiler, where it prevents the external atmosphere from affecting the temperature of the included water, and affords by its partial condensation a supply for the boiler itself."[172] [Footnote 171: See Trevithick's letter, 7th May, 1815, vol. i., p. 364.] [Footnote 172: See patent specification of 1802, vol. i., p. 128.] Not one of his numerous patent specifications has been found among his papers, neither do his letters refer to them; probably he never read them after the first necessary examinations. "MR. GILBERT, "HAYLE FOUNDRY, _November 5th, 1829_. "Sir,--The engine has been worked. The result is ten strokes per minute, 6-feet stroke, with half a bushel of coal per hour, lifting six thousand pounds weight. This was done with water in the cistern round the condenser, which water came up to 180 degrees of heat, and remained so. The water sides of the condenser covered with this hot water was 50 surface feet. I tried it to work with the cold air sides, but I found that the cold air sides of 120 feet would only work it four strokes per minute. I should have worked the steam much higher than 50 lbs. to the inch, but being an old boiler I thought it a risk. I am now placing an old boiler of 350 feet of cold sides more to the condenser, to give a fair trial to condensing with cold sides alone. The steam below the piston was about 6 or 7 lbs. to the inch above the atmosphere. The force-pump to the boiler was about one-fifth part of the content of the cylinder, and the valve close to the boiler lifted when the force-piston was down about two-thirds of its stroke, at which time the returned steam entered the boiler again. I have no doubt of doing near ten times the duty that is now done on board ships, without using salt water in the boiler, as at present. Our boiler has been working three days and the water has not sunk 1 inch per day. I am quite satisfied the trial will be a great success. "Mr. Praed and Sir John St. Aubyn are anxious to get a high bank carried out from Chapel Angel to 15 feet below low-water mark on the bar, to make Hayle a floating harbour. "I have proposed to make a sand-lifting engine. When I built that engine for deepening Woolwich Harbour, we lifted 300 tons per hour through 36 feet of water, and 20 feet above water, 56 feet above the bottom. This was done with two bushels of coal per hour, therefore it will not cost above one penny per square fathom to lift the sand over this embankment. It is intended to get down Mr. Telford to give his opinion on it. Your remarks on it would be of service. "I remain, Sir, "Your humble servant, "RICHARD TREVITHICK." The writer having worked at these experiments, knows that their object was to employ high-pressure steam in the boiler, using it very expansively in the cylinder, and by cold surface sides reducing its bulk either to low-pressure steam or boiling water, and then force it again into the boiler. "MR. GILBERT, "HAYLE FOUNDRY, _November 14th, 1829_. "Sir,--I have both of your letters and sketches, which shall be put in hand. I understand it perfectly well. Since I wrote to you last I have made several satisfactory trials of the engine, and think it unnecessary to make any further experiments. The statement below may be depended on for a future data. The load of the engine was 6280 lbs., being 20 lbs. to the inch for a 20-inch cylinder with a 6-feet stroke, 12 strokes per minute, with three-quarters of a bushel of coals per hour, giving a duty of 361,728,000 for 1 bushel of coal, a duty far beyond anything done in the county by so small an engine. The cold water sides round the condenser was 60 feet, and the water at 112 degrees temperature, not having a sufficient stream of cold water to supply the cistern. Each foot of cold water sides did 7536 lbs. per minute, about three times the work done in the county per foot of hot boiler sides; therefore the condenser need not be more than one-third of the boiler sides. By making the condenser of 4-inch copper tubes and of an inch thick, it would stand in one-twentieth part of the space of the boiler. "I put a boiler naked to try cold air sides; it was very rusty, and did not condense as fast as I expected. The engine worked exceedingly well, but slow. The duty performed for each foot of cold air sides was 565 lbs. per minute, about one-thirteenth part of the condensing of cold water sides. We never wanted to get the steam above 60 lbs. to the inch. I have no doubt but that copper pipes of 1/32nd of an inch thick, clean and small, would do considerably more, because the hot water that came out of the boiler from the condensed steam was but 170 decrees, and the external sides the same heat when the steam was 15 lbs. above the atmosphere in the condensing boiler. This boiler was 4 feet 6 inches diameter, and I think that towards the external sides of the boiler there was a colder atmosphere, if I may call it so, than what it was in the middle of this large condensing boiler, because I found by trying a small tin tube, that it would condense 1500 lbs. for each foot of cold air sides. "However, as it is, it will do exceedingly well for portable purposes. "The duty, I doubt not, will be, both for water and air sides condensing, at least 50 per cent. above our Cornish engines, which will be above four times what is now done with ships' engines, especially when you take into consideration their getting steam from salt water, and letting out so much water from the boiler to prevent the salt from accumulating in the boiler, which will make 30 per cent. more in its favour. "If strong boilers to stand 200 lbs. to the inch are made with small tubes, I have no doubt but that the duty would be considerably more, and my engines will not be one-quarter part of the weight, price, or space of others; and when every advantage is taken it will be 1000 per cent. superior in saving of coal to those now at work on board. This engine works well, and returns the steam very regularly every stroke into the boiler. "I am extremely sorry you were not present to see these experiments. Please make your remarks on these statements, with any further information you may judge useful. "I shall now make drawings agreeable to my experiments for actual performance on board ships. In hope of hearing from you soon, "I remain, Sir, "Your very humble servant, "RICHD. TREVITHICK." The large old boilers used as surface condensers, in which the steam was partially condensed by the transmission of heat to the external atmosphere, together with its further condensation in a smaller condenser with cold water around it, so reduced its expansiveness, that a large feed-pump drew the hot water and steam from the small condenser, and forced it back into the boiler without any reduction of quantity; those temporary contrivances, almost immediately resolved themselves into a condenser made of copper tubes surrounded by cold water. Having proved by six months' experiment on a working scale the practicability of the plan which in reality he had invented twenty years before in the iron steamship,[173] he wrote in June, 1830:-- [Footnote 173: Drawing of iron steamship, vol. i., p. 336.] "TO THE RIGHT HONOURABLE THE LORDS COMMISSIONERS OF THE ADMIRALTY, &c., &c., &c. "MY LORDS, "About one year since I had the honour of attending your honourable Board with proposed plans for the improvement of steam navigation, and as you expressed a wish to see it accomplished, I immediately made an engine of considerable power for the express purpose of proving by practice what I then advanced in theory. I humbly request your lordships will grant me the loan of a vessel of about 200 or 300 tons burthen, in which I will fix at my own expense and risk an engine of suitable power to propel the same at the speed required: no alterations whatever in the vessel will be necessary. When under sail the propelling apparatus can be removed, and when propelled by steam alone, the apparatus outside the ship will scarcely receive any shock from a heavy sea. This new invention entirely removes the great objection of feeding the boiler with salt water." This petition was backed by Mr. Gilbert and Mr. George Rennie. His old friend Mr. Mills took an interest in it, and wrote, "I am going to meet Captain Symonds at Woolwich again to-morrow, and hope to be able to persuade him to use his influence with Sir T. Hardy," "LAUDERDALE HOUSE, HIGHGATE, "MR. GILBERT, "_August 19th, 1830_. "Sir,--The boiler with the fire-place, cold air tubes outside the boiler but within the steam-case, fire-tubes in the boiler from the top of the fire-place to the top of the boiler, the ash-pit close, except a small door to clear out the ashes. [Illustration: FIG. 1.--PLAN SECTION.] [Illustration: FIG. 2.--ELEVATION SECTION.[174]] [Footnote 174: _a_, steam-case; _b_, boiler-case; _c_, space for condensation of steam; _d_, water and steam space; _e_, fire-tubes; _f_, fire-box; _g_, fire-door; _h_, fire-bars; _i_, ash-box; _j_, ash-box door; _k_, air-tubes in condenser; _l_, chimney; _m_, water level; a smoke-jack fan draught.] "The design is for the cold air to pass down from the top of the boiler through the air-tubes within the steam-case surrounding the boilers, becoming heated in its passage by condensing the steam in the case, and then to pass up through the fire-bars in, the hot state, nearly as hot as the steam in the case; because this air, heated to nearly 212 degrees by condensing the steam in its passage without any of its oxygen being burnt, it will not carry off so much heat from the fire as cold air would, and still have the same oxygen as cold air to consume the coal. "The cold air will be passing down the steam-case in the air-tubes, and up through the fire and fire-tubes in the boiler. I find by experiments I have made here, by placing a tin tube 2-1/2 inches in diameter, 4 feet long, inside a 4-inch tube of the same length, having boiling water and steam between the tubes, kept hot by a fire round the outer tube, with a smith's bellows blowing in at the bottom of the inside tube, having 2-2/3rds surface feet of condensing sides, measuring the inside, where the air is passing up from the bellows, heats from 60 to 134 degrees 15 square feet of cold air per minute. When you compare the effective heat of 74 degrees given to 15 cubic feet of air every minute from 2-2/3rds surface feet of tin plate, and the heat contained in 15 cubic feet of air charged with 74 degrees of effective heat, compared with steam of atmosphere strong, you will find that the condensing power of surface sides is very great, and for locomotive purposes might be carried still further, by forcing the air more quickly through the tubes. If the statements on air given in some books that I have read are correct, that there is about three times as much heat in 1 gallon of steam of atmosphere strong as there is in 1 gallon of air of 212 degrees of heat, in that case 1 surface foot of tin-plate sides of this pipe, by sending off the hot air before described, would take out the heat of 1-1/2 cubic foot of steam per minute of atmosphere strong, which in the common condensing engine would be equal to a duty of 2700 lbs. lifted 1 foot high per minute; but in the high-pressure expansive engine, the heat of 1-1/2 cubic foot of steam would give a duty of 10,800 lbs., or four times the duty of the Boulton and Watt engine. "If you calculate on the air being heated to nearly 212 degrees before it enters the fire, together with the heat given to the sides of the boiler, the fuel saved will be above one-half on what has been done by the high-pressure engines in Cornwall, because at present the coal must pay for heating the cold air, therefore a less proportion goes through the sides of the boiler, and is lost through the chimney; whereas if the heat of the steam, by passing into the cold air, on its way through the condenser tubes, is carried into the fire-place, one-half of the coal must be saved; and you will find by calculation that the quantity of air required to burn the coal, and also to condense the steam, goes exactly in proper proportion for each other, and for locomotive engines with a blast will go hand-in-hand almost to any extent, and the size of an engine, for its power, is a mere nothing. "A smoke-jack fan in the ash-pit under the fire-bars, worked by the engine, would draw air down the condensing tubes, and force it up through the fire and fire-tubes always with the speed required, as the steam and the condensation would increase in the same ratio. "As it is possible to blow so much cold air into a fire as to put it out, by first heating the air it would burn all the stronger, and whatever heat is taken out of the condenser into the fire-place from the steam that has been made use of, half this extra heat will go into the boiler again, or in other words, but half the quantity of cold will be put into the fire, being the same in effect as saving fuel. Taking heat from the condenser through the boiler sides is an additional new principle in this engine. I find by blowing through tubes that the condensation of a surface foot of air-tube against a surface foot of boiler fire-tube is greater than the fire that passes through the boiler sides, where the common chimney draught is used, by nearly double; but I expect when both air and fire tubes are forced by a strong current of air it will be nearly equal, and the increase of steam and of condensation can be increased by an increased current of air, so as to cause a surface foot of fire and of air sides to do perhaps five times as much; and of course the machine will be lighter in proportion. I think air sides condensation preferable to water sides, as so small a space does the work, and is always convenient, and its power uniformly increasing with its speed, by the increased quantity of air, without the weight of water vessels. This kind of engine can be made to suit every place and purpose, and I think such an engine of the weight of a Boulton and Watt engine will perform twenty times the duty. "Air sides condensation will be advantageous on board ship, because there are holes for the passage of water through the bottom and sides of the ship. "I am anxious to have your opinion on this plan of returning the hot air from the condenser to the fire-place, and what you think the effect will be. "The Comptroller of the Navy has not yet returned from Plymouth, therefore no answer has been given to me. "You will see by the sketch how very small and compact an engine is now brought without complication or difficulty; each surface foot of boiler and condenser is equal to one-third of a horse-power, weighing 20 lbs., or 60 lbs. weight for each horse-power. The consumption of fuel is so small when working a differential engine, that I expect it will not exceed 1 lb. of coal per hour for each horse-power. "The cost of erection and required room are so small from its simplicity that it will be generally used. As I am very anxious that every possible improvement should be considered prior to making a specification for a patent, I must beg that you will have the goodness to consider and calculate on the data I have given you. I am sorry to trouble you, but I am satisfied this will be to you rather a pleasing amusement than a trouble. The warming machines will take a very extensive run, and I believe will pay exceedingly well. "I am almost in the mind to take a ride down to see you in a few days, but am now detained here about the American mining concerns. "I remain, Sir, "Your very humble servant, "RD. TREVITHICK." The letters and foot-note are the only changes made by the writer in Trevithick's original sketch so descriptive of a wonderful application of varied and improved principles of long-known difficulty and importance; the beautifully compact tubular boiler for giving high-pressure superheated steam, surface condensation, absence of feed and condensing water, and return of the heat, in other engines wasted in condensation, to the fire-place; though there is little or no mention of the mechanical or moving parts of the steam-engine, yet its vital principles are grasped with the hand of a master. The sketch in the letter hastily made forty years ago is more ingenious than any portable engine since constructed, though there may be no sufficient proof of its practical success. The propeller to be worked by this novel engine was of course his long-idle screw. _Steam Engines, 21st February, 1831._ "NOW KNOW YE, that in compliance with the said proviso, I, the said Richard Trevithick, do declare that the essential points in my improved steam-engine, for which I claim to be the first and true inventor, are:-- "Firstly, the placing of the boiler within the condenser, in order to obtain the additional security of the strength of the condenser to prevent mischief in case the boiler should burst, and also by the same arrangement to conveniently make the condenser, with a very extensive surface, enabling me to condense the steam without injecting water into it. "Secondly, the enclosing of the condenser in an air or water vessel, by which the intention of safety from explosion is further provided for, and my engine really rendered what I denominate it, a high-pressure safety engine. "Thirdly, the condensing of the steam in the condenser by means of a current of cold air or cold water forced against the outsides of the condenser. "Fourthly, the returning of the condensed steam from the condenser back again into the boiler, to the end that sediment and concretion in the boiler may be prevented; and, "Fifthly, the blowing of the fire with the air after it has been heated by condensing the steam. "In forming my improved steam-engine I employ several or all of these points according to convenience, in combination with the other necessary parts of steam-engines in common use. "These, my essential points, will admit of various modifications as to form and proportions such as must be and are quite familiar to every competent steam-engine manufacturer, and therefore it will be sufficient for the perfect description of my improved steam-engine that I explain some of the modes of forming and combining the essential points of my invention with the other parts of steam-engines in common use. In my most favourite form of engine in which I condense by a current of cold air, the fire-place and flue, the boiler, the condenser, and the air-vessel, are made of six concentric tubes, standing in an upright position. The inner or first tube forms the fire-place and flue, and at the same time the inner side of the boiler. This tube is conical, having its small end upwards. The next or second tube is cylindrical, about 6 inches larger in diameter than the lower end of the first tube, and forms the outside of the boiler, leaving a space all round of about 3 inches at the bottom, and so much more at the top, as the flue is taper for holding water and steam between the two tubes. The third tube is about 2 inches larger in diameter than the second, in order to allow a space of about an inch for powdered charcoal or some other slow conductor of heat. This tube also constitutes the inner side of the air-vessel. The fourth tube is about 2 inches larger than the third, and forms the inner side of the condenser. The fifth tube, about 2 inches larger than the fourth, forms the outside of the condenser; and the sixth tube, about 2 inches larger than the fifth, forms the outside of the air-vessel, and at the same time the outside of the whole of the generating and condensing apparatus, consisting of fire-place, flue, boiler, condenser, and air-vessel. These tubes are made of wrought-iron plates riveted together, and are all cylindrical, except the first, which is conical, the bottom or fire end being the largest. The first or inner tube is closed at bottom, but has an opening on one side near the bottom, through which the fire-bars are introduced, and the ashes and clinkers taken away. To this opening a neck-piece about 3 inches long is riveted, having a flange to fit against the inside of the second tube, when the two tubes are concentric, through, the side of which second tube is an opening corresponding with that in the first tube, and the flanch is screwed to the second tube so as to make one opening through the sides of the two tubes. The second tube extends downwards about 5 inches below the first tube, and has a flanch turning inwards, to which a second round plate of iron is screwed, forming the bottom of the boiler. The first tube has an external flanch at the top, and the second tube an internal flanch, both of the same height, and screwed to a cast-iron circular plate or cap-piece, which extends wide enough around the boiler to form also the cover for the air-vessel. This plate has a hole in the middle as large as the flue. The sides of the condenser and air-vessel are formed of four concentric tubes, each about 2 inches larger than the one within it. The inner and outer of these tubes constitute the sides of the air-vessel, and are each furnished with an external flanch at the top by which they are screwed to the cap-piece. The two intermediate tubes constituting the sides of the condenser are riveted together at the top, leaving a space of about an inch between their upper ends and the cap-piece, so as to allow of a free communication over them between the outer and inner parts of the air-vessel. The inner tube of the air-vessel extends downwards about an inch below the boiler, and is closed by a flat plate screwed on to a flanch projecting inwards from the tube; the two tubes of the condenser descend about 3 inches lower than the boiler. The inner tube has an internal flanch, to which a flat circular plate is screwed to close up the tube. The outer tube of the condenser is of the same length with the inner, and is provided with an external flanch about 3 inches broad. The outer tube of the air-vessel has an external flanch 2 inches broad, and is just long enough to come down upon the broad flanch of the condenser last described, and these two flanches are together bolted upon a bottom piece of cast iron, which is a dish of 4 inches deep, and equal in diameter with the diameter of the outer tube, and having a flanch the same breadth as the flanch of the outer tube, and the bottom piece is secured to the air-vessel and outer tube of the condenser by bolts going through all the three flanches. An opening is made through the sides of all the four tubes of the condenser and air-vessel opposite to and as wide as the fire-place opening through the sides of the boiler. The upper part of both openings to be of the same height, but the outer opening is made as low as the bottom of the boiler, in order to allow room for a pipe to enter that part of the boiler for forcing the water into it, and also another pipe and cock for drawing off the water or sediment, in case foul water be used by accident or carelessness. These two openings through the condenser and air-vessel, and through the boiler, constitute one fire doorway through all the six tubes for access to the fire-place; a ring is placed between the two tubes of the condenser around the fire doorway, so as to cut off all communication of the steam in the condenser with the air in the doorway; another similar ring is placed between the condenser and the outer tube to prevent the escape of air into the fire doorway, and a half ring is placed in the lower part of the fire doorway between the condenser and the inner tube of the air-vessel, to prevent ashes from falling into the air-vessel, and yet allow a free passage for the air from the inner part of the air-vessel into the upper part of the fire doorway. These two rings and the half ring are secured in their places by rivets passing through all of them and through the tubes, and uniting all firmly together, the interstices being filled with iron cement. A ring is also placed between the boiler and the air-vessel around the fire doorway, against the outside of which ring the charcoal powder is tightly rammed, and will hold the ring in its place without the necessity of either rivets or screws. That part of the fire doorway which is above the fire-bars is supplied with an inner door, to shut the fire-place even with the outside of the boiler, and exclude all access of air to the fire, except through the grating. The whole of the fire doorway is enclosed by an outer door even with the outside of the air-vessel, to exclude all air, except that which comes through the air-vessel; a pipe is fixed in the bottom or dish-piece leading to a forcing pump to draw the water out of the condenser and force it into the bottom of the boiler through the pipe before described. A blowing cylinder of about ten times the content of the main cylinder is screwed against the outside of the air-vessel, and opposite to the two outlet valves of the blowing cylinder two apertures are made in the air-vessel, through which the air is forced in. The main cylinder of the engine, of the usual dimensions according to power wanted, is also screwed against the outside of the air-vessel high enough above the blowing cylinder to allow room for the main-crank shaft to work between them. The forcing pump before mentioned is also screwed to the outside of the air-vessel, and thus my improved steam-engine becomes more compact and convenient than any preceding steam-engine. For the purpose of supplying the boiler with distilled water, in case there should be a deficiency in it, a small vessel made of two upright tubes, one within the other, is placed on the cap-piece. The inner tube is of the same diameter as the flue, and forms a continuation of it. The outer tube is about 6 inches larger than the inner, and the space at the top and bottom between the two tubes is closed by two ring-shaped pieces. This vessel may be about 18 inches high; a cock is fixed in the top of this vessel, to which a bent pipe is fastened, leading to and united with a pipe which arises from the top of the condenser and passes through a hole in the cap-piece, and thus a communication between the supplying vessel and the condenser may be opened or shut at pleasure; another pipe, also furnished with a stop-cock, arises from the vessel, and communicates with a water-cistern to receive its supply of water when required; a third pipe, having a cock in it, opens into the vessel near the bottom to let out the sediment; a small cock to let the air out is also fixed in the top of the vessel, which cock may also be used for letting air out of the condenser. In order to supply the boiler with water by means of this vessel, the stop-cock leading to the condenser is shut, and that leading to the cistern is opened, and at the same time the air-cock is opened to allow the air to escape that the water may fill the vessel. When the vessel is nearly full of water, the air-cock and the cock from the cistern are shut, and that in the pipe leading to the condenser is opened. The water being then heated by the flue is converted into steam, which, passing into the condenser, is there reduced to water again, leaving the sediment or salt in the supplying vessel, which sediment or salt may be occasionally blown out through the bottom pipe by filling the vessel with, water, shutting the water, steam, and air cocks, and opening the cock of the outlet pipe at a time when the steam in the vessel is strong. But the supply of water from the condenser being always equal to that converted into steam and used in the engine, there is no tendency to a variation in the height of the water in the boiler, except there be leakage or waste of steam in some part of the engine. An upright glass tube, having an iron tube of communication with the lower part of the boiler and another iron tube of communication to the upper part of the boiler, is conveniently placed against the outside of the air-vessel to indicate at all times the height of the water in the boiler; as is usual in steam-boilers, a valve is placed on the top of the air-vessel to allow of the escape of a portion of the air in case that the quality of the fuel should not require so much air for perfect combustion as the steam requires for good condensation. The degree of the condensation of the steam may be increased at pleasure, by increasing the velocity of the air passing into and through the air-vessel. The other parts of my improved steam-engine, such as the steam-pipes, the throttle-valve, the safety-valve, the vacuum-valve, the working valves, crank, connecting rods, cross-heads, pistons, piston-rods, and various other minor parts common to engines in general use may be made in the usual forms, and placed in the most convenient situations; they cannot, therefore, need any description. When it is intended to use water for condensing instead of air, my improved steam-engine must be made as before directed, except that the communication between the air-vessel and the fire-place must be closed, which may be done by a perfect ring of iron surrounding the opening leading to the fire-place, instead of the half ring before described, and a forcing pump must be employed to draw water from a reservoir, and force it into the vessel which I have hereinbefore denominated the air-vessel, but which in this mode of working would more properly bear the name of water-vessel. In this case a blowing cylinder, the dimensions of which must be calculated according to the quality of the fuel to be used, may be worked to blow the fire through a pipe leading into the ash-pit. This, however, will not be necessary where there is a chimney high enough to create a strong draught. In respect to proportions, my improved steam-engine admits of considerable latitude, and it will be sufficient direction to any practical engineer to say that for engines working with steam of 120 lbs. to the inch, used expansively till it be nearly reduced to atmospheric strength and then condensed, a 10-horse engine may have a fire-place of 20 inches diameter, the flue at the top 10 inches diameter, and a boiler of 20 feet high; a 60-horse engine, a fire-place of 36 inches diameter, a flue of 16 inches diameter, and a boiler of 20 feet high. In boat-engines, and in other cases where height cannot be allowed, the diameter must be increased. The thickness of the two tubes constituting the boiler sides of a 10-horse engine may be 1/8th of an inch, that of a 60-horse a quarter of an inch, and so in proportion for engines of other power. The tubes constituting the condenser and inner tube of the air-vessel may in all cases be 1/8th of an inch thick. The outer tube may be 3/8ths of an inch thick, to afford stability to the working cylinder, the blowing cylinder, and the forcing pump fastened to this tube, and as an ultimate perfect barrier against explosion. The respective distances of the other tubes constituting the outside of the boiler, the condenser, and air-vessel, will be the same as hereinbefore given, and therefore their diameters will depend upon the diameter of the fire-place. The cap-piece in small engines may be half an inch thick, and in large engines an inch. The bottom of the ash-pit and bottom of the boiler must have about half an inch of thickness for every foot diameter, or they may be cast with ribs to afford equivalent strength. The fuel is supplied through a door in the flue, at the top of the boiler, consisting of coke or coals the least liable to swell with heat. The flue may be filled to about one-third of the height of the boiler, and the water fill about three-fourths of the boiler, leaving one-fourth for steam. "Having clearly explained my improved steam-engine so that any person competent to make a steam-engine can from this description understand my invention and carry the same into effect in as beneficial a manner as myself, I proceed to observe that the extreme safety of my improved steam-engine will be seen, from considering that in case the boiler should explode inwards into the flue, the power of the steam would be first reduced by filling the flue and fire-place, and could not escape through the chimney and fire doorway faster than it would diffuse itself and be condensed by mixing with the surrounding air, and thus lose all its force. But should the outside of the boiler burst, part of the force of the steam would be spent in filling up the interstices between the particles of the charcoal, and would then probably be too weak to effect a breach through the inner tube of the air-vessel; and should such a second breach be effected, the space within the air-vessel would allow the steam to expand and partly condense, and a portion to escape into and through the fire doorway, where it would divide itself, and proceed harmlessly up the flue, and out at the doorway; so that the outer case being a reserve of strength, would to a certainty withstand the force remaining in the steam after the before-mentioned successive reductions of power." The patent of February, 1831, perfects the sketch in his letter of July 27th, 1829, which in its turn made more perfect the plans put into practice in 1815, just before leaving England for America.[175] The prejudice against the use of his high-pressure steam-engine he tried to meet by calling it "a high-pressure safety engine." The boiler was of six wrought-iron upright tubes, one within the other. The inner one was the fire-tube, surrounded by a tube of larger diameter, forming the water and steam space. This was again surrounded by another tube, 2 inches larger in diameter, the space being filled with charcoal or other non-conductor of heat; another tube, 2 inches more in diameter, formed the inner circle of the condenser, having an inch space for the passage of cold air from the blowing cylinder, carrying the heat from the condensing steam back to the fire-place. Still another tube, 2 inches more in diameter, giving a space into which the used steam from the cylinder passed to be condensed. Then came the outside tube, 2 inches more in diameter, forming a second space for the passage of air, taking heat from the condenser into the fire. The steam-boiler had its heat retained by a coating of charcoal; next to it came a current of cold air an inch thick, carrying back to the fire any heat that had passed through the charcoal coat, and also the heat from the inner surface of the condenser. Then came the inch-thick circle of steam, on its exit from the cylinder, to be condensed; and finally an outside circle of cold air, performing the same functions as the inner circle in condensing the steam and carrying its heat back again to the fire. [Footnote 175: See Trevithick's letters, July 8th, 1815, vol. ii., p. 80, and 7th, vol. i., p. 364; and 16th May, vol. i., p. 370; and patent of 1815, vol. i., p. 375.] The object or principle of this engine was to avoid the loss of heat, and the necessity for either condensing water or feed-water, as described in the letter and drawing of August 19th, 1830, but the detail was changed, mainly to facilitate construction. As in practice it might be impossible to fully attain those objects, preparation was made to get rid of the salt from such water as might be required as feed-water to make good the loss from leakage or other defects in the working of marine steam-engines. The specification states: "For the purpose of supplying the boiler with distilled water, in case there should be a deficiency in it, a small vessel made of two upright tubes, one within the other, is placed on the cap-piece. The inner tube is of the same diameter as the flue, and forms a continuation of it. The water being heated by the flue is converted into steam, which, passing into the condenser, is there reduced to water again, leaving the sediment or salt in the supplying vessel." Where water condensation was preferred the surface-air condenser could be converted into a surface-water condenser by a current of cold water in place of the air; in which case the air from the blowing cylinder was taken direct in to the fire-place or other means used for giving the necessary draught. Steam of about 135 lbs. to the inch was to be so expansively worked as at the finish of the stroke, on its escape to the condenser, to be no more than atmospheric pressure, or 15 lbs. to the inch--just the strength with which Watt preferred to commence his work in the cylinder. The most prominent feature in Trevithick's numerous modifications of the steam-engine was the boiler. In the 'Life of Watt,' though his commentators have been numerous and eminent, little or nothing is said about the boiler or the steam pressure. He left that all-important part of the steam-engine just as he found it, resisting the increase of steam pressure, which was the mainspring of Trevithick's engine. The boiler of the high-pressure engines of 1796[176] sheltered the steam-cylinder from cold; and the used steam from the cylinder circulated around the exterior of the boiler, on its way to the blast-pipe, while the condensed portion was returned as feed-water in the patent engine of 1802.[177] In 1811 he proposed to force air into the fire-place, hoping thereby to reduce the amount of heat lost by the chimney.[178] His various forms of tubular boilers, as at the Herland Mine,[179] and at Dolcoath,[180] and the upright multitubular boilers patented in 1815.[181] followed up in 1828. "I shall have a small portable engine finished here next week, and will try to heat steam independent of water, in small tubes of iron, on its passage from the boiler to the cylinder, and also try cold sides for condensing." In 1829 a simple boiler and condenser composed of three tubes was made, the inner or fire-tube being 2 feet in diameter and 15 feet long, "for the express purpose of experimenting on the working the same steam and water over and over again;"[182] and on the same subject, "By making the condenser of 4-inch copper tubes 1/32nd of an inch thick, it would stand in one-twentieth part of the space of the boiler:"[183] and finally the sketch of the tubular boiler and tubular condenser of 1830, in its boiler portion similar to the best portable boilers of the present day, and the patent specification of 1831. Surely therefore to him belongs the credit of having invented and perfected the tubular boiler and surface condenser. [Footnote 176: See vol. i., p. 104.] [Footnote 177: See patent specification, vol. i., p. 128.] [Footnote 178: See Trevithick's letter, 13th Jan., 1811, vol. ii., p. 6.] [Footnote 179: See vol. ii., p. 71.] [Footnote 180: See chap. xx.] [Footnote 181: See Trevithick's letters, 8th July, 1815, vol. ii., p. 80; and 7th and 16th May, vol. i., pp. 364, 370.] [Footnote 182: See vol. ii., p. 332.] [Footnote 183: See vol. ii., p. 336.] Smiles has written:[184]-- [Footnote 184: See 'Life of George Stephenson,' by Smiles, p. 279; published 1857.] "For many years previous to this period (1829), ingenious mechanics had been engaged in attempting to solve the problem of the best and most economical boiler for the production of high-pressure steam. Various improvements had been suggested and made in the Trevithick boiler, as it was called, from the supposition that Mr. Trevithick was its inventor. But Mr. Oliver Evans, of Pennsylvania, many years before employed the same kind of boiler, and as he did not claim the invention, the probability is that it was in use before his time. The boiler in question was provided with an internal flue, through which the heated air and flames passed, after traversing the length of the under side of the boiler, before entering the chimney. "This was the form of boiler adopted by Mr. Stephenson in his Killingworth engine, to which he added the steam-blast with such effect. We cannot do better than here quote the words of Mr. Robert Stephenson on the construction of the 'Rocket' engine:--'After the opening of the Stockton and Darlington, and before that of the Liverpool and Manchester Railway, my father directed his attention to various methods of increasing the evaporative power of the boiler of the locomotive engine. Amongst other attempts, he introduced tubes (as had before been done in other engines)--small tubes containing water, by which the heating surface was materially increased. Two engines with such tubes were constructed for the St. Etienne Railway, in France, which was in progress of construction in the year 1828; but the expedient was not successful; the tubes became furred with deposit, and burned out. "'Other engines, with boilers of a variety of construction, were made, all having in view the increase of the heating surface, as it then became obvious to my father that the speed of the engine could not be increased without increasing the evaporative power of the boiler. Increase of surface was in some cases obtained by inserting two tubes, each containing a separate fire, into the boiler; in other cases the same result was obtained by returning the same tube through the boiler; but it was not until he was engaged in making some experiments, during the progress of the Liverpool and Manchester Railway, in conjunction with Mr. Henry Booth, the well-known secretary of the company, that any decided movement in this direction was effected, and that the present multitubular boiler assumed a practicable shape. It was in conjunction with Mr. Booth that my father constructed the 'Rocket' engine. "'In this instance, as in every other important step in science or art, various claimants have arisen for the merit of having suggested the multitubular boiler as a means of obtaining the necessary heating surface. Whatever may be the value of their respective claims, the public, useful, and extensive application of the invention must certainly date from the experiments made at Rainhill. M. Seguin, for whom engines had been made by my father some few years previously, states that he patented a similar multitubular boiler in France several years before. A still prior claim is made by Mr. Stevens, of New York, who was all but a rival to Mr. Fulton in the introduction of steamboats on the American rivers. It is stated that as early as 1807 he used the multitubular boiler. "'These claimants may all be entitled to great and independent merit; but certain it is, that the perfect establishment of the success of the multitubular boiler is more immediately due to the suggestion of Mr. Henry Booth, and to my father's practical knowledge in carrying it out.' "We may here briefly state that the boiler of the 'Rocket' was cylindrical, with flat ends, 6 feet in length, and 3 feet 4 inches in diameter. The upper half of the boiler was used as a reservoir for the steam, the lower half being filled with water. Through the lower part twenty-five copper tubes of 3 inches diameter extended, which were open to the fire-box at one end and to the chimney at the other. The fire-box, or furnace, 2 feet wide and 3 feet high, was attached immediately behind the boiler, and was also surrounded with water." Stephenson knew of Trevithick's patent of 1802,[185] in which a three-tubed boiler is shown; and it was after that time that Oliver Evans and Fulton tried their experiments, and also the numerous engines with single or return double tube, at work in the principal towns of England prior to 1804,[186] and near his residence in childhood and in manhood.[187] [Footnote 185: See vol. i., p. 128.] [Footnote 186: See Trevithick's letter, Sept. 23rd, 1804, vol. ii., p. 2.] [Footnote 187: Mr. Armstrong's note, vol. i., p. 184.] George Stephenson's Killingworth boiler, "to which he added the steam-blast with such effect," was a copy of Trevithick's boiler and blast, working since 1804 in Newcastle-on-Tyne, and was precisely the boiler described by Stephenson; "in other cases the same result was obtained by returning the same tube through the boiler." This is an admission from Stephenson that Trevithick's patent boiler was the best in use up to about 1828. A further proof of the indirect public gain from the use of Trevithick's return-tube boiler over a period of thirty years is their having supplied high-pressure expansive steam in the first experiments made with such steam by the Admiralty, at whose request Mr. Rennie and others examined the duty of the Cornish high-pressure expansive engine, and Captain King, R.N., in charge of the Admiralty Department at Falmouth in 1830, gave an order to Harvey and Co. to construct high-pressure steam-boilers for the Government vessel 'Echo'; in 1831 the machinery was put on board the 'Echo' in the Government Dockyard at Plymouth, and included three of Trevithick's return-tube boilers, made of wrought iron, each 5 feet 6 inches in diameter and 24 feet long, with internal return fire-tube 2 feet 2 inches in diameter. The fire-place end of the boiler was 6 feet 9 inches deep by 5 feet 6 inches wide, to give room for the fire-place and ash-pit. The steam pressure was 20 lbs. on the inch above the atmosphere, worked by double-beat valves, 6 inches in diameter, with expansive gear. This new machinery was fixed under the superintendence of the writer, after which the Government engineers took charge of the vessel, and the writer who had, as the mechanic in charge, worked like a slave, though receiving but 1_s._ 6_d._ a day and expenses, was not invited to take any part in the experimental trials, nor ever heard of the result except in the ordinary rumours of Admiralty bungling on board the 'Echo.' Those boilers were similar to the Trevithick boiler that had served the locomotive in Newcastle and elsewhere from 1801 to 1828, the first steamboat experiments in England, in Scotland, and in America, and the numerous high-pressure engines then at work. [Illustration: BOTTLE-NECK BOILER.] The enlarging the fire-place end of boilers or fire-tubes has led to many forms. Trevithick's model of 1796[188] had an oval tube giving a greater spread of fire-*bars; the same is seen in the 1808 steamboat;[189] the Dolcoath boilers of 1811[190] show the oval and also the bottle-neck fire-tube; the Welsh locomotive of 1804[191] had the fire-tube contracted at its bend or return portion; the Tredegar puddling-mill fire-tube of 1801[192] tapered gradually from the fire-bridge to the chimney end; in the London locomotive of 1808[193] the fire-tube took the bottle-neck shape close to the fire-bridge. The accompanying sketch shows the bottle-neck contraction, only on the top and sides of the fire-tube was to give breadth to the fire-bars _d_, and thickness to the fire at bridge _c_, after which the flue portion of the fire-tube was contracted: this boiler was for many years a favourite in Cornwall. The bottle-neck contraction of the 'Echo' boiler was similar to the above, except that the enlargement of the fire-place was downwards instead of upwards, and the fire-tube, instead of going through the end of the boiler, returned to near the enlarged fire-place, when it passed out through the side of the boiler to the chimney, just as in the Tredegar puddling-mill boiler; all those variations were with the object of increasing the fire-grate, and at the same time keeping down the gross size and weight of boiler and its water. [Footnote 188: See vol. i., p. 104.] [Footnote 189: See vol. i., p. 335.] [Footnote 190: See vol. ii., p. 169.] [Footnote 191: See vol. i., p. 181.] [Footnote 192: See vol. i., p. 223.] [Footnote 193: See vol. i., p. 207.] In 1805, Lord Melville failed to keep his appointment with Trevithick, on his proposal to construct a high-pressure steamboat.[194] Rennie, a pupil and friend of Watt, and familiar with Trevithick's high-pressure steam-dredgers on the Thames, was employed by Lord Melville and the Admiralty on the Plymouth Breakwater, where in 1813 Trevithick proposed the use of his high-pressure steam locomotive and boring engine.[195] In 1820 Rennie wrote to Watt, that the Admiralty had at last decided upon having a steamer; at that time fifteen years had passed since Trevithick's offer to propel the Admiralty by steam-puffers, and ten years more were to pass before they could make up their minds to venture on high-pressure steam from his boilers. The Steam Users' Association are equally hesitating, judging from words just spoken by an engineer, the son of an engineer:-- [Footnote 194: See Trevithick's letter, 10th Jan., 1805, vol. i., p. 324.] [Footnote 195: Ibid., vol. ii., p. 24.] "Sir William Fairbairn said he had come to the conclusion, after many years' experience, that it was in their power to economize the present expenditure of fuel by a system which might not be altogether in accordance with the views of the members of the association or the public at large, and that was to increase the pressure of steam. He would have great pleasure in stating a few facts which might some day tend to bring about a change, if not a new era, in the use of steam. From the result of a series of experimental researches in which he had been engaged for several years on the density, force, and temperature of steam, he had become convinced that in case we were ever to attain a large economy of fuel in the use of steam, it must be at greatly-increased pressure, and at a rate of expansion greatly enlarged from what it was at present. Already steam users had effected a saving of one-half the coal consumed by raising the pressure from 7 lbs. and 10 lbs.--the pressure at which engines were worked forty years ago--to 50 lbs., or in some cases as high as 70 lbs. on the square inch."[196] [Footnote 196: 'The Engineer,' March 15th, 1872: remarks by the Chairman at a meeting of the Manchester Steam Users' Association.] Dear me! would have been Trevithick's exclamation had he read this; did I devote my whole life to the making known the advantages of high-pressure steam, and did I, seventy years ago,[197] really work expansive steam of 145 lbs. on the inch in the presence of many of the leading engineers of the day! Of course this short extract of a speech made by a member of a practical society, may not be taken as conveying fully the speaker's views, but it illustrates the immense difficulty Trevithick encountered in making his numerous plans acceptable to the public. [Footnote 197: See Trevithick's letter, August 20th, 1802, vol. i., p. 154.] Another modern statement bearing on inventions originating with Trevithick, but wearing new garbs with new names, shows the same tendency to ignore old friends, or, to say the least of it, to pass them by:-- "The trial of No. 36 steam-pinnace was made at Portsmouth yesterday. Her peculiarity consists in the arrangement of her propelling machinery, in the adaptation of the outside surface condenser, and a vertical boiler, both patented by Mr. Alexander Crichton. The condenser is simply a copper pipe passing out from the boat on one quarter at the garboard strake, and along the side of the keel, returning along the keel on the opposite side, and re-entering the boat on that quarter. The boiler is designed for boats fitted with condensing engines, and which, therefore, are without the acceleration of draught given by the exhausted steam being discharged into the funnel. It is of the vertical kind, and stands on a shallow square tank, which forms the hot well. The tubes are horizontal over the fire, the water circulating through them. The condensed steam is pumped into the well at a temperature of 100°, and being there subjected to the heat radiating from the furnace, is pumped back into the boilers at nearly boiling point. It is estimated that, under these conditions, the pinnace would run for nearly 48 hours without having to 'blow off' or carry a supply of fresh water, the waste water being made good by sea water."[198] [Footnote 198: 'The Times,' November 24th, 1871.] The peculiarity of this steam-pinnace of 1871, on which a patent was granted, is stated to be a metal surface condenser exposed to the cold water at the bottom of the boat, returning the condensed steam at about boiling temperature to the boiler, and a vertical boiler with horizontal tubes through which the water circulates, both of which in principle, if not in detail, are seen in the surface condenser of Trevithick's iron-bottom ship of 1809, and his vertical boiler of 1816,[199] and further illustrated in the inventions spoken of in this and the following chapter; and yet on so all-important a subject, dealt with in various ways by Trevithick from 1804 to 1832, his plans are reproduced as discoveries in 1871. [Footnote 199: See vol. i., pp. 336, 364, 370.] About 1828, Mr. Rennie, Mr. Henwood, and others, reported on the advantages of high-pressure expansive steam in Wheal Towan engine,[200] on the north cliffs of Cornwall, near Wheal Seal-hole Mine on St. Agnes Head, where in 1797 Trevithick had worked his first high-pressure steam-puffer engine in competition with the Watt low-pressure steam-vacuum engine. Captain Andrew Vivian was then his companion, and the Cow and Calf, two rocks of unequal size, a mile from the land, were from that time called Captain Dick and Captain Andrew, or the Man and his Man, and there they still remain in the Atlantic waves, fit emblems of their namesakes and their still living inventions. The stir made by those expansive trials led to the experiment in the 'Echo,' of which Mr. Henwood[201] thus speaks:-- [Footnote 200: See Mr. Henwood's report, vol. ii., p. 185.] [Footnote 201: Residing at Penzance, 1871.] "Captain William King, R.N., Superintendent of the Packet Station at Falmouth, attempted to impress on Viscount Melville, then First Lord of the Admiralty, the advantage of using high-pressure steam expansively in the Royal Navy, to whom Lord Melville replied that he had been taught by his friend, the late Mr. Rennie, that the danger attending such a course was very great, and that it would be difficult, if not impossible, to persuade him to the contrary." [Illustration: CAPTAIN DICK AND CAPTAIN ANDREW, OR THE MAN AND HIS MAN. [W. J. Welch.]] Twenty-five years of precept and example caused the Admiralty to follow suit, and to request Mr. Ward, a Cornish engineer, to construct boilers and expansive valves for the Government steamboat 'Echo.' The writer was entrusted with fixing the machinery in the vessel at the Plymouth Dockyard, and before starting with it from Harvey and Co.'s foundry, waited on Captain King, R.N., at Falmouth, for his instructions, in happy ignorance of the fear of the Lords of the Admiralty to tread on Cornish high-pressure. After eying the applicant as captains in Her Majesty's service are apt to do when dealing with boys in the civil service, he vouchsafed to say, "Mind, young man, what you are about, for if there is a blow up, by ---- you'll swing at the yard-arm." CHAPTER XXVII. HEATING APPARATUS--MARINE STEAM-ENGINES--REFORM COLUMN. "LAUDERDALE HOUSE, HIGHGATE, "MR. GILBERT, "_March 1st, 1830_. "Sir,--I have to apologize for my neglect in not calling on you, but ill-health prevented it. I left home on the 11th February, arrived in town on the 14th, and remained there until the 24th, when I was compelled to leave for this place, having a free good air. I am now taking, twice a day, the flowers of zinc, from which I hope to be soon right again. I am much better, but afraid to enter the city. I hope to be able to call on you before the end of this week, being very anxious to see you, having a great deal to communicate respecting the experiments I have been making, which will bear out to the full our expectations. "Your hot-house apparatus has been finished nearly three months, all but two or three days' work to fit the parts together; I expect that before this they are in Penzance, waiting a ship for London. While making a sketch of your work for the founder, a thought struck me that rooms might be better heated by hot water than by either steam or fire, and I send to you my thoughts on it, with a sketch for your consideration. I find that steam-pipes applied to heat cotton factories, with 1 surface foot of steam-pipe, heat 200 cubic feet of space to 60 degrees. I also found in Germany, where all the rooms are heated by cast-iron pipes about the heat of steam, that 1 foot of external flue heated 160 cubic feet of space to 70 degrees. "I find also that about 200 surface feet of steam-engine cylinder-case will condense about as much steam as will produce 15 gallons of water per hour, and will consume about 4 bushels in twenty-four hours to keep the temperature of 212 degrees. One bushel of coal will raise the temperature of 3600 lbs. of water from 40 to 212 degrees. "A boiler, as the drawing, will contain 1200 lbs. of water, and consume one-third of a bushel of coal to raise the water from 40 to 212 degrees. It has 40 surface feet of hot sides giving out its heat. The 12-inch fire-tube in the boiler would raise the temperature to 212 degrees in about forty minutes. By these proofs it appears that 50 feet of surface steam sides will require 1 bushel of coal every twenty-four hours to keep up the boiling heat; therefore this boiler, having 40 surface feet, would give out the heat from one-third of a bushel of coal in twelve hours. "Now suppose this charge of heat required to be thrown off in either more or less than twelve hours, the circular curtain would adjust the heat and time for extracting it. [Illustration: HOT-WATER ROOM-WARMER.] "By the foregoing this coal and surface sides would heat to 60 degrees for twelve hours a space of 6800 cubic feet, equal to a room of 25 feet square and 11 feet high. If this boiler was placed in a room with a chimney, its water could be heated by having a small shifting wrought-iron chimney-tube of 4 inches diameter and 2 or 3 feet long attached to the end of the boiler while it was getting up steam, after which it might be removed, and the doors at both ends of the boiler closed; and as the boiler contains and retains its heat for twelve hours, more or less, it might be run on its wheels to any fire-place or chimney to get charged with heat, and then run into any room, where there was no chimney, or into bed-rooms, offices, or public buildings; it would be free from risk, not having either steam or loose fire. The circular curtain, being fast to a wood table, would by being drawn up or down adjust the required heat and hide the boiler, and would be warm and comfortable to sit at. I think this plan would save three-quarters of the coal at present consumed; the expense of the boiler will not exceed 5l. When you have taken it into consideration, please to write me your opinion. "I remain, Sir, "Your very humble servant, "RD. TREVITHICK. "P.S.--Boiler, 3 feet diameter, 3 feet long; fire-tube, 12 inches diameter, placed in the boiler, the same as my old boilers, made of iron plates 1/8th of an inch thick, weighing about 2 cwt. "I had a summons to attend at Guildhall last Saturday on the coal trade, and was requested to attend a committee at Westminster for the same purpose, in consequence of my applying small engines to discharge ships. "I attended, but with difficulty, from my ill-health." Trevithick was not above scheming for his friend's hot-house, warming it by a boiler on wheels, in form like his high-pressure steam-boiler. Rooms had before been heated by steam or hot air in pipes; but he thought a more simple and economical plan was to heat a certain quantity of water to boiling heat at any convenient place having a chimney, or in the open air, and then wheel the apparatus into the room to be warmed. If the room had a chimney, the fire could be kept up, or the temporary iron connecting chimney be removed and the apparatus wheeled into the middle of the room and used as a table. The scheme promised to be successful, for in a letter nine months after the former he wrote that he had taken a patent for France, where it had made a great bustle among the scientific class, for coal in Paris was 3_s._ a hundredweight; some hot-water room-heaters were the following day to be forwarded from London to Paris; while the numerous orders were more than he could execute. One in use at the 'George and Vulture' Tavern, of a Gothic shape, handsomely ornamented with brass, about two-thirds the size of the one in Mr. Gilbert's hot-house, burns 7 lbs. of coal a day, keeping the room at 65 degrees of heat during fifteen hours. The rage amongst the ladies was to have them handsomely ornamented. Believing that they would be remunerative, he applied for the following English patent in February, 1831. [Illustration: PLATE 16. HEATING APPARATUS. London: E & F.N. Spon, 48. Charing Gross. Kell Bros. Lith. London.] _Apparatus for Heating Apartments. 21st February, 1831._ "NOW KNOW YE, that in compliance with the said proviso, I, the said Richard Trevithick, do hereby declare that the nature of my said invention of a method or apparatus for heating apartments, and the manner in which the same is to be carried into effect, is shown by the following drawings and description, where Fig. 1, Plate XVI., represents a longitudinal vertical section through the middle of a metallic vessel capable of containing a considerable quantity of water, with a fire-place in the inside, surrounded with water in all parts except at the doorway and at an opening where the smoke may pass off into a common chimney. Fig. 2, a vertical section near the fire-door, at right angles to the section shown at Fig. 1; with the sections are also shown wheels and handles, which lie out of the planes of the sections. The letters of reference indicate the same parts in both figures, _a_, the vessel; _b_, the space for containing the water; _c_, the fire-place; _d_, the fire-bars, or grating; _e_, the ash-pit; _f_, an inner door, to prevent the air from entering over the fire, yet allow it to pass into the ash-pit, and thence up to the fire through the grating; _g_, an outer door, to be shut when the fire is to be extinguished; _h_, a chimney or flue, to convey the smoke into a common chimney: this flue may be removed when the water boils, and then the opening of the flue may be shut, to keep in the heat, either by a door or by a plug fitting the opening; _k_, the cover of the vessel, having a rim all round, within which iron cement is to be driven to make the vessel steam-tight; _l_, a hole in the middle of the cover, into which a plug is dropped having a fluted stem and a flat head ground steam-tight upon the cover; this plug or valve is for the purpose of allowing the escape of steam if it should be raised above boiling point, and the valve is taken out when it may be necessary to pour water into the vessel; _m_, four wheels, on which the vessel may be easily removed from one room to another; _n_, two handles, to facilitate the removal. To use this apparatus for the warming of an apartment, the vessel is nearly filled with water, and placed so near to a chimney in another room, if more convenient, that the flue-piece _h_ may convey away the smoke; a fire is then lighted upon the grating _d_, and continued till the water boils, when the flue-piece is taken away, and the flue opening stopped with the plug or door, and also the outer fire-door closed. In this state the apparatus is drawn into the apartment to be warmed, where it will continue for many hours to give off a most agreeable heat without any of that offensive odour usually experienced from stoves heated by an enclosed fire. Figs. 3, 4, 5, and 6 represent another form of my apparatus for heating churches or other large buildings. Fig. 3, a vertical section, from A to B, of Figs. 5 and 6, with a representation of the flue and its flanch, which lie beyond that section and the fire doorway and its flanch, which lie nearer, and also the four wheels, two of which are on each side of the section. Fig. 5, a horizontal section, from E to F, of Figs. 3 and 4. Fig. 6, a horizontal section, from G to H, of Figs. 3 and 4, with a view of the four handles situated at a higher level than the section, and of the fire-bars at a lower level; the same letters of reference signify the same parts in all the four figures, _a_, the outer case of the water-vessel; _b_, the cover; _c_, the space for water; _d_, the fire-place and flue; _e_, the fire-bars, made in two pieces, to be introduced through the fire doorway; _f_, the ash-pit; _g_, the fire-door; _h_, pipes open at top and bottom, cemented into holes in the bottom, and in the cover of the water-vessel; these pipes are to admit a current of air up through them, in order the more speedily to carry the heat into the building; _k_, the aperture in the cover, to supply the vessel with water, and the plug to keep in the steam; _l_, four wheels, on which the whole is moved, each wheel revolving in a recess cast in the bottom of the outer case, as represented by dotted lines in Figs. 3 and 4; _m_, four handles; _n_, the flanches of the fire doorway and of the flue, represented in Fig. 4 by dotted lines. A pipe to communicate with a chimney while the water is being heated must be made to suit locality, and therefore cannot require any description. This apparatus can be heated in a vestry room, and the fire-door and flue closed and then wheeled into the church, where it will soon diffuse a most comfortable warmth; or the heat may be kept up while standing in its place by having a constant communication with a chimney, and thus diffuse a much more salubrious heat than can be obtained by metallic or earthen stoves heated immediately by the fire." It is doubtful if the profits he received from the heating apparatus covered the cost of the patent. The first stove was not unlike his first locomotive boiler. The more highly-finished stove resembled the marine tubular boiler, also of former years, in the further application of which we now follow him. "MR. GILBERT, "HAYLE, _January 24th, 1829_. "Sir,--Since I have been down I have made a small portable engine, and set it to work on board a coal-ship for discharging the cargo; it is very manageable, and discharges 100 tons with 1 bushel of coal, without any person to attend it, there being a string that the man in the hold draws when the coal-basket is hooked, which is again drawn by the man who lands the basket on the deck; the string turns and re-turns the engine. It is near a ton weight, but as I find it double the power required, I am now making a smaller one, 3-1/2 feet high and 3-1/2 feet diameter, about 12 cwt. "I intend this engine to warp the ship, pump it, cook the victuals, take in and out the cargo, and do all the hard work. The captains are very anxious to get them on board every ship. I think that an engine of 39 cwt. would propel their ships four miles an hour over and above the other work of the ship, and would neither be so heavy or take so much room as their present cooking house and furnace. I think that two iron paddles, one on each side of the rudder, under the stern, would do this very well; they would be in dead water, and out of the swell of the sea, and by being deep in the water would have a good resistance. Two paddles, each about 4 feet deep and 3 feet wide, would do this, without their rising out of the water; therefore their stroke would be nearly horizontal. The return stroke would be in the water. Thus, let the paddle stand perpendicular in the water, two-fifths of its width on one side, and three-fifths on the other side, the centre, which would turn its edge to the water on its back stroke, and its flat to the water on the forward stroke; it would be light, and out of the way of anything. I have a patent now going through the office for all this, which will also cover the new principle of returning the heat back again, as already described to you. The engine for drawing in Holland will be ready about the end of February, and by that time I shall have a complete portable engine ready for London for discharging, when I shall be in town. [Illustration: BOAT AND PROPELLER.] "I remain, Sir, "Your very humble servant, "RD. TREVITHICK. "P.S.--Wheal Towan engine is working with three boilers, all of the same size, and the strong steam from the boilers to the cylinder-case; the boilers are so low as to admit the condensed water to run back from the case again into the boiler. They find that this water is sufficient to feed one of these boilers without any other feed-water; therefore one-third of the steam generated must be condensed by the cold sides of the cylinder-case, and this agrees with the experiments I sent to you from Binner Downs. Wheal Towan engine has an 80-inch cylinder, and requires 72 bushels of coal in twenty-four hours; therefore the cylinder-case must in condensing high-pressure steam use 24 bushels of coal in twenty-four hours. Boulton and Watt's case for a 63-inch cylinder, working with low-pressure steam, condensed only 4-1/2 bushels of coal in equal time, the proportions of surface being as 190 to 240 in Wheal Towan. Nearly five times the quantity was condensed of high steam than of low steam, proving that there is a theory yet unaccounted for." Trevithick's portable high-pressure steam-puffer engine, when it discharged the first cargo of coal from a vessel at Hayle, was worked by the writer; it stood on the wharf near the ship, and on a signal from the hold, steam was turned on, raising rapidly the basket of coal the required height. In trying how quickly the work could be done the hook missed the basket-rope, and caught the man under the chin, swinging him high in the air, much to the engineman's discomfiture. Fortunately the suspended man had the good sense to lay hold of the rope above his head, and so supporting his weight, no great harm was done. The object and the means were the revival of the nautical labourer of twenty years before.[202] The boiler was a wrought-iron barrel on its end, on small wheels, with internal fire-tube, in shape like the boiler of the recoil engine of 1815;[203] but less high in proportion to its diameter. The cylinder was let down into the top of the boiler, and like Newcomen's atmospheric engine had no cylinder cover. The piston-rod was a rack giving motion to a small pinion fixed on a shaft on the top of the boiler, and to a large grooved wheel, around which was wound the whip-rope from the vessel's hold; a brake-lever enabled the engineman either to stop or to reduce the speed. Four months prior to the date of this letter he had sent a written offer to the Common Council of the city of London, offering to provide engines to discharge all coal-ships for the saving he would effect in six months, or he would supply an engine and boxes complete for 100 guineas. He at the same time suggested that in place of the baskets holding 1 bushel, iron boxes on wheels, holding 4 bushels, with a spring steelyard attached, should be used with his steam-engine, giving the exact weight without delay. He seems to have forgotten his nautical labourer patented twenty years before;[204] but yet reproduced something very similar. [Footnote 202: See chapters xiv. and xv.] [Footnote 203: See Trevithick's letter, 7th May, 1815, vol. i., p. 364.] [Footnote 204: See vol. i., p. 325, and patent, 1809, vol. i., p. 302.] Every trading vessel was recommended to carry at least a 12-cwt. high-pressure steam-puffer engine, suitable for warping, pumping, and discharging cargo; but a 30-cwt. engine, not occupying more room than a caboose, would in addition cook for the crew, and propel the vessel at three or four miles an hour. Two iron paddles, like the duck's feet described to his Binner Downs friends many years before,[205] were to be fixed on an iron shaft across the stern of the vessel, receiving from the engine a motion like a pendulum. Each duck's foot was an iron plate 4 feet deep and 3 feet wide, turning partly round on its iron leg, to which it was attached as a vane, about 1 foot of its width on one side of its leg, and 2 feet on the other side; when the leg and foot were drawn toward the vessel, the foot, turning on its leg as a centre, exposed its edge only to the water; on the reverse movement, the longer side like a vane turned round until its flat was opposed to the water, in which position it was kept by a catch until the return movement, so that when it propelled, its whole surface pressed against the water, and when moving in a contrary sense, only its edge offered resistance to the water. [Footnote 205: See Mr. Newton's letter, vol. i., p. 342.] The writer has no record of the practical application of the duck's foot as a steamboat propeller; but the portable puffer-engine now pulls on board the fisherman's heavy nets, and the magnificent steamer 'Adriatic' hoists her sails on iron yards and masts by six of those steam helps.[206] [Footnote 206: See 'Illustrated News,' 27th April, 1872.] Twenty years before he had solicited the Navy Board to try his iron ships propelled by high-pressure steam-engines, and had shown their applicability as steam-dredgers; and again, shortly after his return from America, he pressed on their attention the same subject under new forms, followed by communications with their engineer, Mr. Rennie, and a proposal to place an engine in a boat at his own cost. The writer has attempted in this and the preceding chapter to classify Trevithick's schemes, crowded together in those last years of his life, but the subjects so run into one another that the acts of twenty years before must be borne in mind to enable the more modern plans to be understood. The letter introducing the surface condenser, in 1828, at the commencement of the former chapter, was in a month followed by that recommending a particular kind of paddle to be used as auxiliary steam-power, and after six months of experiments, by the patent of 1831, and the following correspondence:-- "MR. GILBERT, "LAUDERDALE HOUSE, HIGHGATE, _June 10th, 1830_. "Sir,--Yesterday I saw Mr. George Rennie, and he requested me to write to the Admiralty, a copy of which I send both to you and to him, for your inspection. Mr. Rennie said there was a great deal contained in what I had stated to him, and that he would with pleasure forward my views, as far as he could with consistency. "I remain, Sir, "Your very humble servant, "RICHARD TREVITHICK." "TO THE RIGHT HONOURABLE THE LORDS COMMISSIONERS OF THE ADMIRALTY, &c., &c., &c. "MY LORDS, "About one year since I had the honour of attending your honourable Board, with proposed plans for the improvement of steam navigation; and as you expressed a wish to see it accomplished, I immediately made an engine of considerable power, for the express purpose of proving by practice what I then advanced in theory. The result has fully answered my expectations; therefore I now make the following propositions to your honourable Board, that this entirely new principle and new mode may be fully demonstrated, on a sufficient scale for the use of the public. "I humbly request that your Lordships will grant me the loan of a vessel of about two or three hundred tons burthen, in which I will fix, at my own expense and risk, an engine of suitable power to propel the same at the speed required. No alteration in the vessel will be necessary, and the whole apparatus required to receive its propelling force from the water can be removed and again replaced with the same facility as the sails, thus leaving the ship without any apparatus beyond its sides when propelled by wind alone, and when propelled by steam alone the apparatus outside the ship will receive scarcely any shock from the sea. "This new invention entirely removes the great objection of feeding the boiler with salt and foul water, and not one-sixth part of the room for fuel, or of weight of machinery now used, will be required; it is also much more simple and safe, not only for navigation, but for all other purposes where locomotive power is required, and will supersede all animal power, as the objections of weight, room, and difficulty of getting and of carrying water in locomotive engines is entirely removed. It will therefore prove an investigation of greater utility to the public than anything yet introduced. "I have to beg the great favour of your Lordships appointing not only scientific but practical engineers to inspect my plans, that you may be perfectly satisfied of their utility, not only in theory, but also as to the practicability of carrying the same into full effect." The petition in June, 1830, for the loan of a Government hulk, hung fire up to January 1832, when an attempt was made to move the Lords Commissioners of the Admiralty by the force of numbers. "We, whose names are hereunto subscribed, have known Mr. Richard Trevithick, of Hale, in the county of Cornwall, for a period of years, and during which time his conduct has merited our unqualified approbation. As an engineer of experience and eminence few, if any, can surpass him, and his present improvement of the steam-engine seems to outvie all others. We therefore, in justice to his talent, strongly recommend to the Lords Commissioners of the Admiralty that he may be permitted, at his own costs and charges, to fit and make trial of his engine in one of His Majesty's vessels. "Dated in London this 27th day of January, 1832." This was sent to Mr. Davies Gilbert, who on the same date suggested the following:-- "RECOMMENDATION OF MR. RD. TREVITHICK, January 27, 1832. "We have not any doubt or hesitation in recommending Mr. Richard Trevithick as a man of extraordinary powers of mind, and of fertility of invention. "Cornwall owes to him much of the improvements that have been made on Mr. Watt's engine--improvements that have reduced the consumption of coal to a third; nor have his exertions been confined to steam-engines alone. He now proposes to make the same water act over and over again by alternate expansion and contraction, which plan, if it succeeds, will be found of immense importance to vessels and locomotive engines. "Understanding that Mr. Trevithick is desirous of making the experiment at his own expense, we clearly recommend that facilities may be afforded him."[207] [Footnote 207: In the handwriting of Mr. Davies Gilbert.] This paltry question with the Admiralty indirectly produced more trustworthy evidence of the great importance of Trevithick's inventions than all that has been written of him under the professional terms Engineers, and Engineering. The names are not given of those who believed that he had, as an established fact, reduced the consumption of coal in the Watt engine to one-third; they were not Cornishmen, or they would not have misspelt the word Hayle, but they understood the great value of using the same fresh water over and over again in marine steam-engines. Mr. Mills, who had taken an active part in the screw-propeller experiments in 1815, was again interested in the proposed trial in a Government ship, and wrote, "I have just left Captain Johnstone; he has communicated with Faucett and Co., Barnes and Miller, and with the firm of Maudslay. He has had his mind disturbed again by Maudslay about the greater quantity of water required to condense steam at higher temperatures; I repeated the same as yourself, about the cylinder full of steam, atmosphere strong; however, he appears quite different to what he was on Friday." Such a clique of professional friends would sink a stronger man than Trevithick. A year or two from that time the writer designed a high-pressure steam-engine suitable for a steamboat, and on presenting it to the eminent marine-engine builders whom he served, was told that the lightness of the engine would cause less profit to the makers. Their bills were based on the pounds weight delivered, and new designs necessitated new patterns and new troubles. It was unreasonable to expect those makers of marine steam-engines to report that Trevithick knew better than they did. They knew of his screw-propeller experiments fifteen years before, but they in no way benefited him, and the Admiralty Captain was either a tool in their hands, or powerless without them. The primary object, when the loan of the ship was asked, was the using for marine purposes a high-pressure steam tubular boiler, combined with tubular condenser, supplying or returning its water as feed, thereby avoiding the use of salt water in the boiler; and this steam-engine, as shown in his patent of 1831, was to be applied either to his screw, or his duck's foot, or other propeller; but during the year or two of suspense, other schemes for propelling ships had occupied his thoughts, resulting in the patent of 1832. _Steam-Engines, 1832._ "NOW KNOW YE, that in compliance with the said proviso, I, the said Richard Trevithick, do hereby declare the nature of my said invention, as regards the improvement or improvements on the steam-engine, to consist in interposing between the boiler and the working cylinder, in a situation to be strongly heated, a long pipe formed of a compact series of curved or bent pipes, which I denominate the dry pipes, or steam-expanding apparatus, through which dry pipes I cause the steam, after it has been generated in the boiler in contact and consequently saturated with water, to pass with very great velocity, in order that it may imbibe a copious supply of additional heat without any addition of water, and by this additional heat to be expanded into a greater bulk of steam, of about the same expansive force that it had acquired in the boiler, by which means I obtain a greater volume of steam for use in the working cylinder than the boiler alone would supply; and in order still further to augment this volume of steam, I place the working cylinder within a case constituting a part of the flue or chimney, that the cylinder may be kept considerably hotter than the steam employed in it by absorbing a great portion of the heat remaining in the flue after having heated the boiler and the dry pipes, which heat would otherwise pass away out of the top of the chimney and be wasted, but by this arrangement is converted into a useful power by further expanding the steam in the cylinder. "And I do further declare, that in carrying this part of my said improvement into effect, I do not find it necessary to confine myself to any particular form of boiler, or arrangement of pipes, in which the steam is to be heated; but by preference, as being very compact in form, and economical of fuel in using, I make my boiler of a number of upright pipes, standing upon and communicating with a tubular ring placed around and a little below the fire-grate; these pipes all surround the fire-place, except two or three, the lower ends of which are elevated above the fire-door, but connected at the bottom by a branch pipe united to one of the adjoining upright pipes, thereby leaving an opening or place of access to the fire. These pipes all extend upwards to the height of several feet, according to the quantity of steam required to be raised, combined with local convenience, for it is obvious that the power of this boiler to raise steam may be increased either by increase of the length of the pipes, of their diameters, or of their numbers. And I do lay upon the upper ends of the pipes hereinbefore described and connect with them a tubular ring similar to that upon which the pipes stand, the two rings and the upright pipes forming together a vessel in which water has free communication by means of the bottom ring to stand at the same level in all the pipes, and the steam has free communication to pass from all the pipes into the upper ring; and I do, for the sake of obtaining great heat, place my system of dry pipes over the fire, and within the circular row of upright pipes of the boiler hereinbefore described; and I form my dry pipes in pairs, each pair constituting the figure that is well understood by the term inverted syphon; and I unite several of these syphons together by short bent pipes at the top, so as to constitute one long zigzag pipe, through which the steam must successively pass down and up the alternate legs of each syphon with great velocity, necessary for the rapid absorption of heat in its passage from the boiler to the working cylinder of the engine, the working cock, valves, or slide of which being united by a pipe of communication with that leg which is last in the succession of syphons; and I unite the first in succession of these inverted syphons with the upper tubular ring of the boiler by means of a bent pipe, in which a throttle-valve or cock is placed in order to limit the supply of steam, that it may have space in the dry pipes and working cylinder to expand in proportion as it receives additional heat; and I fix a safety-valve in communication with the boiler, and another in communication with the dry pipes; and I place around outside the boiler, at a small distance from the upright pipes, two cylindrical casings, one within the other, and fill up the space between the two casings with sand, ashes, or other material which conducts heat but slowly; and I close up the upper end of the casings over the boiler and the dry pipes with a covering in the form of a dome, and out of this enclosure I make the flue to pass to and around the working cylinder of the engine, whence the flue carries the smoke and little remaining heat away in any convenient manner; and I make my boiler-pipes, rings, and casings by preference of iron or copper, and my dry pipes of copper or other strong metal not liable to rapid oxidation by heat when in contact with steam; and I supply my boiler with water by means of a forcing pump, so adjusted as to keep the water of the proper height. "And I do hereby further declare, that the nature of my said invention, as regards the improvements in the application of steam-power to navigation, consists in the drawing of water into a receptacle placed near within the stern of the navigable vessel, which water is drawn in through an orifice in the stern with a moderate degree of velocity in the direction of the course of the vessel, and ejected with great force and speed in a direction opposite to the course of the vessel through the same orifice, reduced to about a quarter of the area by means of a valve opening as the water enters, and partially shutting as the water is ejected; and thus I propel the vessel with great force, derived from the recoil of the water set into rapid motion in a direction opposite to the course of the vessel, the rapidity of the jet of water to be at least equal to double the required speed of the vessel to be navigated. "And I further declare, that by preference I effect the purpose of receiving and of ejecting the water, and of deriving a motive force from its recoil, by means of a large vertical cylinder of cast iron or other metal, closed at both ends, in which a piston is forced up and down by a piston-rod sliding through a stuffing box in the lid, which piston-rod receives its motive force from a steam-engine; and I fix a tube into the after side of this cylinder, near the bottom, in communication with the space below the piston, which tube leads through the stern of the vessel, as low down as practicable, and opens on one side of the rudder; and I fix another tube into the after side of this cylinder, near the top, in communication with the space above the piston, which tube also leads through the stern of the vessel, as low down as practicable, but opens out on the other side of the rudder; and I place in the mouth of each of these tubes a valve opening inwards, to allow the water free entrance, equal to the bore of the tube, and partially shutting when the water is ejected, so as to reduce the opening through the stern to about one-fourth of the area of the tube. "And I do hereby further declare, that the nature of my said invention, as regards the improvement in the application of steam-power to locomotion, consists in the application of such a boiler, together with the expanding apparatus as aforesaid, to locomotive engines, whereby a diminished weight of boiler and quantity of water and fuel is obtained; and in farther compliance with the said proviso, I, the said Richard Trevithick, do hereby describe the manner in which my said invention is to be performed, by the following description of its various parts in detail, reference being had to the drawing annexed, and to the figures and letters marked thereon, that is to say:-- "_Description of the Drawing._ [Plate XVII.] [Illustration: PLATE 17. TREVITHICK'S PATENT BOILER AND ENGINE, 1832. London: E. & F.N. Spon. 48, Charing Cross. Kell Lith. London.] "Figure 1 represents a series of vertical sections through the various essential parts of the boiler, the dry pipes, the steam-pipe, the working cylinder, the propelling cylinder, and the flue, together with sections and views of other minor parts, serving to show the connections of the essential ones. The places at which these sections are taken are shown in Figure 2 by the dotted line from A to B, from B to C, from C to D, and from E to F. Figure 2 represents a plan of Figure 1, with the top coverings of the boiler and working cylinder removed. Figure 3 shows the manner of uniting the shorter upright pipes over the fire doorway with one of the adjoining ones, so as to give free circulation of the water in all the pipes. Figure 4 represents three pairs of syphons, which in their places stand in a circular form, but in this Figure are shown as spread out into a plane, in order the better to explain their structure and joinings. Similar small letters and numbers of reference are used to denote similar parts in all the Figures; _a_, the upright boiler-pipes, the upright and lower ends of which are contracted to leave room for bolt-heads and nuts, without throwing the pipes too far asunder; _b_, the tubular ring having a flanch projecting inwards and outwards at the upper side, perforated with apertures upon which the upright pipes are bolted, and another flanch at the bottom, projecting inwards, to bolt the ring down to the foundation plate; _c_, the foundation plate; _d_, the fire-grate; _e_, the fire doorway; _f_, the upper tubular ring, having a flanch at the bottom projecting inwards and outwards, and perforated with apertures corresponding with the tops of the upright pipes upon which the tubular ring lies, and to all which it is bolted; _g_, the level of the water in the boiler-pipes; _h_, the dry pipes formed like inverted syphons, so as to require no joining at the lower part near the fire; one leg of each of the two syphons shown in Figure 1 is in section, and broken near the bottom; an outside view of the other leg appears partly behind the section; _k_, the short bent pipes, each bolted to two syphons, to unite them into one continuous pipe; _l_, the bent pipe uniting the upper tubular ring with the first in succession of the syphons; the proper situation for this pipe is that shown in Figure 2, but for the sake of clearness and simplicity in the drawing, it is shown in Figure 1 as if on the left-hand pipe and syphon; _m_, the throttle-cock on the bent pipe _l_; _n_, the safety-valve lever, and weight on the same; _p_, the pipe of communication from the last in the succession of syphons to the working cylinder of the engine; _r_, the throttle-cock in the pipe _p_; _s_, a four-way cock, worked by the hand-gear, to direct the steam alternately under and over the piston; _t_, the safety-valve in communication with the dry pipes; _u_, the two cylindrical casings surrounding the boiler-pipes, the space between the two being filled up with a slow conducting medium; _v_, the domical covering over the cylindrical enclosure; _w_, the flue leading out of the enclosure into the casing of the working cylinder; _x_, the casing of the working cylinder forming a continuation of the flue; _y_, the further continuation of the flue to the chimney; _z_, the waste-steam pipe leading into the chimney; 1, the steam-pipes leading from the working cock into the top and bottom of the working cylinder; 2, the working cylinder; 3, the piston with metallic packing; 4, the piston-rod passing down through a stuffing box at the bottom of the working cylinder, and also continuing downwards, to form the rod of the propelling piston; 5, the propelling cylinder; 6, the water or propelling piston; 7, the upper aperture leading to one of the tubes opening through the stern of the navigable vessel; 8, the lower aperture leading to the other tube, opening also through the stern of the navigable vessel; these apertures are made as wide as the cylinder will allow, in order that they may have but little depth, and not occasion an inconvenient length of the propelling cylinder; 9, a frame supporting the steam-cylinder upon the propelling cylinder; 10, the feed-pump for supplying the boiler with water; 11, an arm fastened on the piston-rod to work the feed-pump and hand-gear; 12, the hand-gear. "Now, whereas I claim as my invention, firstly, the interposing between the boiler and the working cylinder of the steam-engine a long many-curved heated pipe, through which the steam is forced to pass with great rapidity without being permitted to come in direct contact with water, by which arrangement the steam is made to absorb additional heat, and at the same time allowed to expand itself into a greater volume. "Secondly, placing the working cylinder of the engine within such part of the flue or chimney as shall ensure the cylinder to be kept hotter than the steam used in it, by which means the expanding of the steam is still further promoted. "Thirdly, propelling a navigable vessel by the force of the recoil produced from water received with a moderate degree of velocity, into a receptacle near within the stern, in the direction of the course of the vessel, and ejected with great velocity in a direction opposite to that course, the velocity of the jet being at least double the required speed of the vessel to be propelled, provided always that the same be effected in manner hereinbefore described. "Fourthly, applying a boiler combined with a steam expanding apparatus, as before described, instead of a boiler alone, to a locomotive engine, whereby the power of the steam is applied after the steam has undergone the expanding process, and whereby a diminution is effected in the weight of the boiler, and in the weight and consumption of water and of fuel." The two great objects in this 1832 patent were superheating steam in tubular boilers, and propelling ships by forcing a stream of water from the stern at a speed of at least double that of the vessel. Similar ideas may be traced in his patent of 1815, where a tubular boiler gave superheated steam, and in 1809 his patent for propelling steamboats "consists of a tube of considerable length disposed horizontally in the water, and the stroke of rowing is made by means of a piston with valves." An engine of 100-horse power was ordered in Shropshire to be placed on board the Government ship to test the value of those patents of 1831 and 1832. One consequence was that a gentleman who had helped this scheme with his money wrote:-- "My case with Trevithick is strictly this; he was represented to me as a man of property; and as to his talents for mechanics, no man could be in his company long without being struck with them. I was induced to trust him to the amount of nearly 500_l._, and I then learned for the first time that it was only on the possible contingency of a grant from Government that he relied for the payment of my claim." A company called the New Improved Patent Steam-Navigation Company was formed, of which Trevithick was a member, though apparently not a subscriber, for a note in November, 1831, informed him that "if in seven days he did not pay up his calls, his shares would be entirely forfeited." This company, among other proposals, opened negotiations for sending steamboats to Buenos Ayres to help in the commerce of the port and inland river. In 1832 the Waterwitch Company made experiments with those plans, propelling by forcing water through pipes, since which a Government ship of war called the 'Waterwitch' has been so propelled. Twenty years ago the writer saw steamboats so propelled in daily use on the Meuse; they needed no rudder, for by turning the mouth of the exit-water pipes on either side of the ship it was made to turn in its length, or even to move sideways. Messrs. John Hall and Sons, of Dartford, also experimented on these two patents, and from this the tubular condenser was called Hall's Condenser. I think the boat it was first tried in was called the 'Dartford.' Trevithick's difficulties in urging so many and great changes in marine propulsion may be estimated by the acts of other engineers. "Mr. Rennie was engaged for many years in urging the introduction of steam-power in the Royal Navy. In 1817, we find him writing to Lord Melville, Sir J. Yorke, Sir D. Milne, and others on the subject. In July, 1818, he laments that he cannot convince Sir G. Hope or Mr. Secretary Yorke of their utility, but that he is persuaded their adoption _must_ come at last. On the 30th May, 1820, he writes James Watt, of Birmingham, informing him that the Admiralty had at last decided upon having a steamboat, notwithstanding the strong resistance of the Navy Board."[208] [Footnote 208: 'Lives of the Engineers,' by Smiles, vol. ii., p. 267.] So that Mr. Bennie, as professional adviser of the Navy Board, had to persuade for three years, with a knowledge of Trevithick's prior experiments, before active steps were agreed to; for twelve years had then passed since Trevithick's nautical labourer and iron steamboat had been tried on the Thames, and five since his experiments with the screw-propeller. An article in 'The Times' gives in strong contrast the relative value of screw and paddle-wheels as propellers. The 'Syria' was originally a paddle-wheel steamer, having oscillating cylinders worked with steam of 25 lbs. on the inch, and Hall's tubular condenser; after a time the paddle-wheels were removed for a screw-propeller, driven by two steam-cylinders side by side, of different diameters, the high-pressure steam exerting its full force in the small cylinder, and then expanding in the larger cylinder. All the leading features in this improved steamboat of the present day, such as high-pressure expansive steam in one or two cylinders, with tubular condenser and screw-propeller, had been publicly proved by Trevithick fifty years before. [Illustration: PLATE 18. COMPOUND MARINE ENGINE, 1871. London: E.& F. N. Spon, 48, Charing Cross. Kell Bro^{s}. Lith. London.] "_Screw against Paddle._--An interesting and important trial trip has recently been made, which serves to exhibit the advantages of the screw over the paddle as a means of propulsion for ocean-going steamships. In 1863, the steamship 'Syria,' of 1998 tons, was built for the Peninsular and Oriental Company by Messrs. Day, Summers, and Co., and fitted with paddle-wheel engines of 450-horse power. The 'Syria' then attained a speed of 13·038 knots per hour, and the consumption of coal was at the rate of 45 tons per diem. The builders have lately converted her into a screw-steamer (for carrying the mails between Southampton and the Cape of Good Hope), who, without in any way disturbing the configuration of the hull, have fitted the 'Syria' with compound inverted engines of 300 nominal horse-*power. These engines have two cylinders, respectively of 36 in. and 72 in. diameter, with a stroke of 4 ft. 2 in. On Monday last the 'Syria' attained an average speed of 12·637 knots, with a consumption of coal equivalent to 18 tons per diem; thus showing a difference of only 0·401 knot per hour, with a lessened power of 150 horses, and a saving in consumption of coal of 27 tons per diem; while the carrying capacity of the ship, arising from the economy of space in the engine-room, has been enormously increased, as she can now stow 1200 tons of cargo against 500 tons previously."[209] [Footnote 209: See 'The Times,' May 20th, 1871.] Mr. Husband, of the firm of Harvey and Co., of Hayle, has obliged me with the annexed sketch (Plate XVIII.) of a modern high-pressure steam expansive compound marine engine, with surface condensers, on which the grandsons of Trevithick are now working, to be placed in the 'Batara Bayon Syree,' an iron yacht for an Indian Rajah, embracing the modern improvements of direct-action compound engines, and illustrating the principles which governed the constructors of the 'Syria.' The first glance shows a seeming resemblance in outline to Trevithick's patent drawing of 1832, having one cylinder above the other; but a closer examination proves the application of the principles of his patents of 1815 and 1831, embracing screw-propeller, direct-acting engines, tubular boilers, high-pressure steam used expansively, and condensation by cold surface preventing the necessity of using salt water in the boilers. This engine, in outline, has a strong likeness to Trevithick's engines, going back even to his first patent of 1802,[210] followed by the direct-action high-pressure steam yacht of 1806,[211] and again in 1808[212] by the iron steamer with direct-action long-stroke cylinders, with highly expansive steam and surface condensers, to which, in 1815,[213] was added the patent compound expansive steam pole and piston engine and screw-propeller, embodying during the first fifteen years of the present century, both in principle and in detail, the most approved form of marine steam-engine with fewness and simplicity of form of moving parts; but compare it with the Watt patent engine, and its difference is obvious; no beam or parallel motion, no injection-water necessitating the air-pump, no low-pressure steam. The late Mr. William Wilson, of Perran Foundry, son of Boulton and Watt's financial agent in Cornwall, informed Mr. Henwood that he was with Mr. Watt when some one stated that Mr. Trevithick was working his engine with steam of 40 lbs. on the inch; when Mr. Watt replied, "I could work my engine with steam of 100 lbs. to the inch, but I [would not] be the engineman."[214] [Footnote 210: See vol. i., p. 59.] [Footnote 211: See vol. i., p. 327.] [Footnote 212: See vol. i., p. 386.] [Footnote 213: See vol. ii., p. 103.] [Footnote 214: Henwood, Address to the Royal Institution of Cornwall, 1871.] Progressive experience, with increasing demand for economy and speed, have caused the principles and the details of Trevithick's steam-engines to be matters of national importance seventy years after their discovery, for as far back as that he used highly-expansive steam,[215] and on the question of a separate cylinder for expansion as used in the modern steamboat combined engines, he wrote, "I think one cylinder partly filled with steam would do equally as well as two cylinders; that one at Worcester shuts off the steam at the first third of the stroke, and works very uniformly with a considerable saving of coal."[216] Those modern marine engines use about the same steam pressure and expand about in the same proportion. With the direct action from the piston-rod to the crank-shaft, the multitubular boiler and screw-propeller, and the surface condenser perfected in 1831 and 1832, at which time his construction of a marine steam-engine would have been just what it now is forty years later. Those latter patents also embrace the principle of superheating steam, practically shown many years before,[217] and still used by marine engineers of modern times. [Footnote 215: See Trevithick's letter, 22nd August, 1802, vol. i., p. 153.] [Footnote 216: See Trevithick's letter, 5th July, 1804, vol. ii., p. 132.] [Footnote 217: See Trevithick's letter, 16th May, 1815, vol. i., p. 370.] In tracing the wisdom of his designs just before the close of an eventful life, reference may be made to the trial of a common road locomotive in 1871:--"Experimental trip of the Indian Government steam train engine, 'Ranee,' from Ipswich to Edinburgh.--The results of the trial with the 'Chenah,' though satisfactory so far as the engines proper were concerned, were vitiated by the failure of the boiler; on the completion of the second engine, the 'Ranee,' the field boiler and variable blast-pipe were used; the boiler is about 4 feet diameter at the bottom and 8 feet high."[218] [Footnote 218: 'The Engineer,' 27th October, 1871.] The form and dimensions of the exterior of the Ranee tubular boiler are very similar to Trevithick's patent drawing and specification of 1832; even the variable blast-pipe was used by him in 1802.[219] [Footnote 219: Trevithick's letter, 22nd August, 1802, vol. i., p. 153.] The last years of Trevithick's eventful life were chequered with hopes and disappointments when, in the early part of 1830, he wrote to his friend Gerard:-- "This morning I called here for the purpose of forwarding my information to the committee of the House. I called on Mr. Thompson to inform him what Mr. Gilbert said respecting it. His answer was, that the direct method would be by forwarding a petition in the way proposed when at the lobby. In consequence, I have forwarded the petition to Sir Matthew Ridley. Yesterday I took the coach to Highgate, by way of Camden Town, and of course had to walk up Highgate Hill. I found I was able to walk up that hill with as much ease and speed as any of my coach companions. However strange this maggot may appear in my chest and brain, it is no more than true. I wish among all you long-life-preserving doctors you could find out the cause of this defect, so as to remedy this troublesome companion of mine." His health was breaking down, and his petition for a gift from the public purse, so hopefully commenced two years before, was doomed, after another year's bandying from pillar to post, to be forgotten and unanswered. "DEAR TREVITHICK, "EASTBOURNE, _December 26th, 1831_. "I am sorry to find that you have not any prospect of assistance from Government. I have not any copy or memorandum of my letter to Mr. Spring Rice, but it was to the effect of first bearing testimony to the large share that you have had in almost all the improvements on Mr. Watt's engine, which have altogether about trebled its power; your having made a travelling engine twenty-eight years ago; of your having invented the iron tanks for carrying water on board ship. I then went on to state that the great defect in all steam-engines seemed to be the loss by condensation of all the heat rendered latent in the conversion of water into steam. That high-pressure engines owed their advantages mainly to a reduction of the relative importance of this latent heat. That I had long wished to see the plan of a differential engine tried, in which the temperatures, and consequently elasticities, of the fluid might be varied on the opposite sides of the piston without condensation; that the engine you had now constructed promised to effect that object, and that in the event of its succeeding at all, although it might not be applicable to the driving water out of mines, yet that for steam-vessels and for steam-carriages its obvious advantages would be of the greatest importance; and I ended by saying that although it was clearly impossible for me to ensure the success of any plan till it had been actually proved by experiment, yet judging theoretically, and also from the imperfect trial exhibited on the Thames, I thought it well worthy of being favoured. "Your plan unquestionably must be to appoint some one with you, as Mr. Watt did Mr. Boulton, and I certainly think it a very fair speculation for any such person as Mr. Boulton to undertake. "It is impossible for me to point out any individual, as never having had the slightest motive with such or with manufacturers in any part of my life, I am entirely unacquainted with mercantile concerns. I cannot, however, but conjecture that you should make a fair and full estimate of what would be the expense of making a decisive experiment on a scale sufficiently large to remove all doubt; and that your proposal should be, that anyone wishing to incur that expense should, in the event of success, be entitled to a certain share of your patent; on such conditions some one of property may perhaps be found who would undertake the risk, and if the experiment proved successful, he would be sure to use every exertion afterwards for his own sake. With every wish for your success, "Believe me, yours very faithfully, "DAVIES GILBERT." The statement of the President of the Royal Society, that the power of the Watt engine had been trebled by Trevithick, brought him no gain. He never troubled himself with politics, but the passing of the Reform Bill caused him to suggest that it should be commemorated by a pillar higher than had ever before been erected. The following memorandum is in his own writing:-- "'Morning Herald,' July 11th, 1832. "_National Monument in honour of Reform._--The great measure of Reform having become the law of the land, it is proposed to commemorate the event by the erection of a stupendous column, exceeding in dimensions Cleopatra's Needle, or Pompey's Pillar, and symbolical of the beauty, strength, and unaffected grandeur of the British Constitution. "In furtherance of this great object, a public meeting is proposed to be held, of which due notice will be given, to set on foot a subscription throughout the United Kingdoms, limiting individual contributions to two guineas, but receiving the smallest sums in aid of the design. "The following noblemen and gentlemen have signified their approbation of the measure:--His Grace the Duke of Norfolk, of Somerset, of Bedford; the Right Honourable Earl of Morley, of Shrewsbury, of Darlington; Lord Stafford; Sir Francis Burdett, M.P.; Joseph Hume, M.P.; R. H. Howard, M.P.; Win. Brougham, M.P.; J. E. Denison, M.P.; A. W. Robarts, M.P.; J. Easthope, M.P.; General Palmer, M.P." "Design and specification for erecting a gilded conical cast-*iron monument. Scale, 40 feet to the inch of 1000 feet in height, 100 feet diameter at the base, and 12 feet diameter at the top; 2 inches thick, in 1500 pieces of 10 feet square, with an opening in the centre of each piece 6 feet diameter, also in each corner of 18 inches diameter, for the purpose of lessening the resistance of the wind, and lightening the structure; with flanges on every edge on their inside to screw them together; seated on a circular stone foundation of 6 feet wide, with an ornamental base column of 60 feet high; and a capital with 50 feet diameter platform, and figure on the top of 40 feet high; with a cylinder of 10 feet diameter in the centre of the cone, the whole height, for the accommodation of persons ascending to the top. Each cast-iron square would weigh about 3 tons, to be all screwed together, with sheet lead between every joint. The whole weight would be about 6000 tons. The proportions of this cone to its height would be about the same as the general shape of spires in England. [Illustration: PLAN AND SECTIONAL ELEVATION OF PROPOSED REFORM COLUMN.] "A steam-engine of 20-horse power is sufficient for lifting one square of iron to the top in ten minutes, and as any number of men might work at the same time, screwing them together, one square could easily be fixed every hour; 1500 squares requiring less than six months for the completion of the cone. A proposal has been made by iron founders to deliver these castings on the spot at 7_l._ a ton; at this rate the whole expense of completing this national monument would not exceed 80,000_l._ "By a cylinder of 10 feet diameter, through which the public would ascend to the top, bored and screwed together, in which a hollow floating sheet-iron piston, with a seat round it, accommodating 25 persons; a steam-engine forces air into the cylinder-column from a blast-cylinder of the same diameter and working 3 feet a second, would raise the floating piston to the top at the same speed, or five or six minutes ascending the whole height; the descent would require the same time. A door at the bottom of the ascending cylinder opens inwards, which, when shut, could not be opened again, having a pressure of 1500 lbs. of air tending to keep it shut until the piston descends to the bottom. By closing the valve in the piston it would ascend to the top with the passengers floating on air, the same as a regulating blast-piston, or the upper plank of a smith's bellows. The air apparatus from the engine should be of a proper size to admit the floating piston with the passengers to rise and fall gradually, by the partially opening or shutting of the valves in the top of the piston. Supposing no springs or soft substance for the piston to strike on at the bottom of the column-cylinder, descending 3 feet a second would give no greater shock than falling from 9 inches high, that being the rate of falling bodies, or the same as a person being suddenly stopped when walking at the rate of two miles an hour. The pressure of the air under the piston would be about 1/2 lb. on the square inch; the aperture cannot let the piston move above 3 feet a second, but this speed may be reduced to any rate required by opening or shutting the valves on the floating piston." [Illustration: GENERAL VIEW OF REFORM COLUMN.] To Trevithick's soaring genius nothing appeared very small, or very large, or very costly; not even the cast-iron column 1000 feet high covered with gold. The stone monument of London, 210 feet high, is admired by many; others climb into the cross on St. Paul's Cathedral, 420 feet high; some make a long journey to the great Pyramids, 500 feet high. How much more pleasant would be Trevithick's proposed floating 1000 feet upward on an air-cushion, controlled by his high-pressure steam-engine, and having, from the loftiest pedestal of human art, surveyed imperial London, to be again lowered to the every-day level at a safe speed, regulated by valves closed by such simple acts as rising from the seat; but should this be neglected, the passage of compressed air escaping from under the piston-carriage would only allow of its descent at a speed of 3 feet in a second, giving but the same shock on bumping the bottom as jumping off a 9-inch door-step. Perhaps the King in 1833 could not take an active part in advocating a memento of the golden days of reform; but this is no reason why the suggestion should have been so slightly noticed in 1862, to erect it in memory of the good and wise Prince Albert. Various meetings were held, and after nine months the plan had so far advanced as to be placed before the King. "Sir Herbert Taylor begs to acknowledge the receipt of Mr. R. Trevithick's letter, with the accompanying design for a national monument, which he has had the honour of submitting to the King. "ST. JAMES'S PALACE, _1st March, 1833_."[220] [Footnote 220: The column was suggested in 1862 as a suitable monument to the memory of the late Prince Albert.] Within two months from the date of the design for a gilded column Trevithick had passed away. His family in Cornwall received a note, dated 22nd April, 1833, from Mr. Rowley Potter, of Dartford, stating that Trevithick had died on the morning of that day, after a week's confinement to his bed. He was penniless, and without a relative by him in his last illness, and for the last offices of kindness was indebted to some who were losers by his schemes. The mechanics from the works of Messrs. Hall were the bearers, and mourners at the funeral, and at their expense night watchers remained by the grave to prevent body-snatching, then frequent in that neighbourhood. A few years after the funeral, the writer was refused permission to go through the works to inquire into the character of the experiments that had been tried, but the working mechanics were glad to see the son of Trevithick, and their wives and children joined in the welcome as he passed through the small town. Trevithick's grave was among those of the poor buried by the charitable; no stone or mark distinguished it from its neighbours. He is known by his works. His high-pressure steam-engine was the pioneer of locomotion and its wide-spreading civilization. England's mineral and mechanical wealth on land or sea are indebted to its expansive power, its applicability, and durable economy. His comprehensive and ingenious designs, given to the world seventy years ago,[221] are still instructive guides; and many of his works, dating from the dawn of the present century, remained as active evidences of his skill almost to the present day, with their three-score years,[222] while some few reaching three-score years and ten still remain good servants[223] in the solitude of the Peruvian mountains, where no mechanical hand repairs the errors of human skill or the wear and tear of time.[224] [Footnote 221: See 1802 patent, vol. i., p. 128.] [Footnote 222: See vol. i., pp. 222, 100, 82, 184.] [Footnote 223: Agricultural engine, vol. ii., p. 68.] [Footnote 224: See vol. ii., p. 220.] If these material proofs fail to convince, the reader has but to ponder on the bitterly natural reflections written by himself a few months before his last illness to his friend Davies Gilbert:-- "I have been branded with folly and madness for attempting what the world calls impossibilities, and even from the great engineer, the late Mr. James Watt, who said to an eminent scientific character still living,[225] that I deserved hanging for bringing into use the high-pressure engine. This so far has been my reward from the public; but should this be all, I shall be satisfied by the great secret pleasure and laudable pride that I feel in my own breast from having been the instrument of bringing forward and maturing new principles and new arrangements of boundless value to my country. However much I may be straitened in pecuniary circumstances, the great honour of being a useful subject can never be taken from me, which to me far exceeds riches." [Footnote 225: Mr. John Isaac Hawkins.] INDEX TO VOLUME II. A. ABADIA, Don PEDRO, 217, 219, 221, 229, 231, 236, 243, 245, 247. ABINGER, Lord, 303. ADAMS, Mr., 94. ADMIRALTY, 311, 338, 356, 358, 361, 372, 384. ADRIATIC STEAMER, 372. AËRATED STEAM, 7, 11. AGRICULTURAL ENGINE, 17, 18, 19, 36, 40, 41, 42, 47, 50, 53, 58. AGRICULTURAL MACHINE, 58. AIR-ENGINE, 292. AIR-PUMP, 19, 103, 122. AJERBI RIVER, 266. ALVERADO, 260, 261. AMALGAMATION, 261. AMPUTATION, 271. APPLICATION TO PARLIAMENT, 183, 317. AQUACATE, 267. ARISMENDI, Don JOSÉ, 217, 219, 221, 229. ARMSTRONG, Sir WILLIAM, 294. ARTHA, Captain, 60, 64, 69, 102. 'ASP,' SHIP, 228, 239. B. BAILIFFS, 36. BANFIELD, Mr., 50. BANFIELD, Mr. J., 65, 74, 153. BARNES and MILLER, 375. BEDFORD, Duke of, 390. BEERALSTONE, 87, 102. BENNETTS, FRANK, 129. BICKLE, Mr., 65. BINNER DOWNS, 315, 323, 327, 369. BLACKLEAD, 4, 138. BLAST BY CYLINDER, 343, 352. BLAST BY SCREW, 341. BLAST-FURNACE, 6. BLAST-PIPE, 94, 141, 144, 210. BLEWETT, Captain, 174. BLEWETT, Mr., 51. BOILER, 7, 14, 19, 32, 41, 60, 66, 69, 74, 81, 84, 92, 102, 115, 119, 124, 126, 138, 142, 145, 153, 156, 159, 169, 180, 183, 213, 227, 290, 300, 308, 321, 327, 339, 343, 356, 357, 359, 369, 377. BOLIVAR, President, 252, 254. BOOTH, Mr., 354. BORER OF ROCK, 24, 27. BOTTLE-NECK BOILER, 357. BREAKWATER, 22. BRIDGENORTH, 3, 87. BROUGHAM, Mr., 390. BRYANT, JOHN, 155, 163, 164. BUDGE, Mr., 126. BUENOS AYRES, 31, 227, 383. BULL, Mr., 84, 118, 213, 230, 237, 244, 246. BULLAN GARDEN, 116, 121, 155, 177. BURDETT, Sir FRANCIS, 390. BURRAL, Jun., Mr., 66. BURRAL, Sen., Mr., 102. BUSHEL, 46, 83, 96, 182. BUST, 245. C. CAMBORNE, 110. CAMPBELL and Co., 201, 230. CANAL BOAT, 17. CARLOOSE ENGINE, 116, 120, 155, 177. CARRIAGE-WHEELS, 207. CARTHAGENA, 272, 277, 279. CASTRO, NICOLAS, 260, 263, 280. CAUSON, WILLIAM, 159. CAXATAMBO, 252. CENTRAL ARGENTINE RAILWAY, 33. CERRO DE PASCO, 197, 201, 227, 229, 232, 255, 258. CHAIN-AND-BUCKET, 12. CHAIN-PUMP, 298, 317. CHAPER, Mr., 188. CHILI, 247, 249. CIRCULAR MOTION, 294. CLARK, HENRY, 78, 119, 141, 156. CLAY MILL, 1. COALBROOKDALE, 2, 3, 5, 138. COAL-LIFTING ENGINE, 365, 368, 370. COCHRANE, Lord, 282, 284. COLLINS, Mr., 95. COLOMBIA, 252. COMMON-ROAD LOCOMOTIVE, 110, 123, 126, 158, 300, 377. COMPETITION, 21, 33, 88, 92, 122, 132, 141, 150, 156, 374, 395. COMPOUND ENGINE, 103, 314, 386. COMPTROLLER OF THE NAVY, 342. CONDENSER, 134. COOKING BY STEAM, 368. COOK'S KITCHEN, 149. COPIAPO, 251. COPPER-ORE FURNACE, 10. CORALILLO, 262. CORDILLERA, 262. COST-ALL-LOST-ALL, 73. COST OF ENGINE, 5, 15, 34, 37, 43, 45, 46, 49, 61, 73, 83, 122, 145, 149. COSTA RICA, 252, 260, 264, 278. COWIE, Mr., 87. CRICHTON, Mr. ALEXANDER, 359. CYLINDER, 19, 28, 39, 60, 67, 148, 210. CYLINDER-CASE, 370, 377. CYLINDRICAL BOILER, 60, 67, 69, 71, 74, 92, 102, 109, 119, 123, 138, 140, 145, 148, 156, 163, 169, 186, 210, 227, 300, 308, 344. D. DANIEL, Mr., 142. DARLINGTON, Earl of, 390. DARTFORD, 393. DAVEY, Captain JOHN, 118. DAVEY, Captain WILLIAM, 83, 101, 124. DAVIES, Mr., 86. DAY, Mr., 215. DEDUNSTANVILLE, Lord, 9, 18, 21, 39, 53. DENISON, Mr., 390. DERBYSHIRE, 3. DIXON, Mr., 128. DOBLE, Mr., 38. DOLCOATH, 1, 8, 10, 32, 40, 115, 116, 119, 141, 143, 145, 147, 150, 153, 155, 157, 162, 168, 171, 175, 180, 194, 250, 307, 316, 321. DOMINGO GONZALES DE CASTAÑEDA, 234. DREDGER, 110, 143, 150, 297, 335. DRIVING WHEELS, 56. DUNDONALD, Lord, 111, 249, 282, 286. DUTY OF ENGINES, 73, 83, 96, 99, 105, 108, 109, 117, 124, 128, 142, 157, 163, 166, 170, 175, 178, 181, 183, 187, 191, 205, 277, 290, 305, 308, 310, 327, 333, 374. E. EASTHOPE, Mr., 390. ECCENTRIC, 208. 'ECHO,' STEAMER, 356, 360. EDMONDS, Mr. RICHARD, 107, 183, 238, 245, 305. EDMONDS, Mr. THOMAS, 269. EDWARDS, Mr., 188. EMPSON, Mr., 279. 'ENCYCLOPÆDIA BRITANNICA,' 182. ERSKINE, Mr., 130, 303. ESSENTIAL OIL, 202. EXETER BRIDGE, 23, 28, 54. EXPANSION, 19, 69, 85, 91, 100, 117, 128, 132, 143, 145, 148, 179, 185, 205, 210, 325, 330, 352, 361, 376, 382. EXPLOSION, 153. F. FAIRBAIRN, Mr. JAMES, 273. FAIRBAIRN, Sir WILLIAM, 358. FALMOUTH, 27. FAREY, Mr., 180, 323. FAUCETT and Co., 375. FEED-POLE, 159. FEED-WATER, 39, 369, 373, 376. FIRE-ARMS, 254. FIRE-BARS, 20. FIRE-ENGINE, 134. FOLLETT, Sir WILLIAM, 358. FOUR-WAY COCK, 19, 29, 60, 67, 153. FOXES, Messrs., 22, 27, 30, 55, 88, 124, 151, 153. FRANCE, 365. G. GALLOWAY, Mr., 10. GAMBOA, 280. GEAR-WORK, 160. GEOLOGICAL SOCIETY, 245. 'GEORGE AND VULTURE,' 366. GERARD, Mr., 255, 262, 265, 269, 271, 279, 280, 282, 286, 287. GIBBS, Mr., 129. GILBERT, DAVIES, 10, 23, 83, 93, 116, 118, 166, 183, 304, 307, 308, 313, 319, 338, 363, 374, 388. GITTINS, Mr., 269. GLANVILLE, Captain, 119, 140, 159. GLOBULAR BOILER, 119, 124. GOSSETT, Colonel, 286. GOULD, Mr., 8, 27. GOVERNMENT, 154, 183, 311, 338, 388. GOVERNOR, 21. GREEN, Mr., 23, 29. GREENWICH, 124. GREGOR, Captain, 315. GREYTOWN, 271. GRIBBLE, 159, 176. GRINDING ENGINE, 2. GRIP, 56. GRIST MILL, 19. GROSE, Captain SAMUEL, 1, 60, 69, 101, 102, 111, 176, 178, 188, 321. GUAYAQUIL, 252. GUILDHALL, 365. GUN-CARRIAGE, 278, 282, 284, 286. GUNDRY, Mr., 17. GUNNERY, 289. H. HAARLEM LAKE, 302. HALL and SONS, 283, 393. HALL, Mr., 297. HALL, Mr. B. N., 273. HALL'S CONDENSER, 19, 322, 383. HALSE, Mr., 17. HARDY, Sir T. H., 339. HARRIS, Mr., 142, 152. HARROW BY STEAM, 40, 43, 58. HARVEY, Mr. HENRY, 23, 48, 52, 64, 88, 101, 152, 154, 188, 189, 257, 298, 301, 302, 303, 356, 361, 385. HARVEY, Mr. NICHOLAS, 295. HAWKINS, Mr., 395. HAWKINS, Sir C., 16, 36, 39, 40, 45, 47, 54, 61, 171. HAYLE HARBOUR, 335. HAZELDINE, Mr., 52, 66, 151, 204, 215. HEARSE-BOILER, 155, 157, 163, 180, 308. HEAT LOST, 7. HEATING APPARATUS, 363. HENWOOD, Mr., 180, 185, 245, 360, 386. HERLAND, 31, 74, 83, 87, 91, 96, 99, 101, 105, 114, 118, 308, 310. HIGH PRESSURE, 19, 109, 119, 148, 150, 198, 271, 310, 376. HILL, Mr., 133. HODGE, Captain, 246, 249. HOLLAND, 110, 296, 299, 317, 333, 369. HOLMAN, Mr., 87. HOMFRAY, Mr., 4, 125, 128, 132, 134, 139, 140. HORIZONTAL CYLINDER, 19, 28. HORNBLOWER, 117, 170. HORSE-POWER, 36, 42. HOT BLAST, 11. HOT-HOUSE, 133. HOT-HOUSE STORE, 363. HOWARD, Mr., 390. HUME, JOSEPH, 390. HUSBAND, Mr., 385. HYDRAULIC CRANE, 385. I. ICE MAKING, 294. ILLNESS, 363, 388. ILLOGAN, 228. INCLINE, 267, 269. INJECTION, 19, 324. INVOICE, 220. IRON FURNACE, 8. IRON SHIPS, 286, 297, 299, 317. J. JAMAICA, 277. JASPER, Mr., 39, 66. JEFFRY, RICHARD, 159, 176. JENKIN, Mr., 83, 118, 166. JOAQUIN DE LA PEZULA, 233, 237. JOHNSTONE, Captain, 375. JOSÉ GONZALES DE PRADA, 236. JOSÉ LAGO Y LEMUS, 234. JUAN MORA RIVER, 266. JUDSON, Mr., 247. K. KENDAL, Mr., 39, 59. KENNY, Captain, 107, 228, 231. KING, Captain, 356, 361. L. 'LA BELLE MACHINE,' 189. LAW PROCEEDINGS, 148, 150. LEAN, Mr., 117, 160, 164. LEAN, Mr. JOHN, 317. LEGASSACK, 102. LEITH, Captain, 230. LETTERS,--Edmonds, Mr. Richard, 106; 228, Aug. 20, 1817; 305, Nov. 7, 1827; 305, Jan. 24, 1828; 306, Jan. 12, 1853; Fairbairn, Mr. James, 272, Nov. 27, 1864; Gerard, Mr., 273, Nov. 17, 1827; 280, Jan. 13, 1826; 286, Feb. 21, 1828; Gilbert, Davies, 10, Jan. 20, 1811; 93, Feb. 15, 1816; 312, Dec. 25, 1831; 388, Dec. 26, 1831; Hall, Mr. B. N., 273, Dec. 16, 1864; Harvey, Mr., 23, Nov. 26, 1812; 101, April 18, 1816; 154, Aug. 26, 1810; Hawkins, Sir C., 39, March 19, 1812; Homfray, Mr., 137, Dec. 26, 1804; 139, Jan. 2, 1805; Liddell, Captain, 250, Nov. 3, 1869; Smith, Mr. T., 67, March 26, 1870; Thomas, Captain C., 162, March 29, 1858; Trethuoy, Mr. W., 68, May 17, 1872; Trevithick, Richard, 2, Sept. 23, 1804; 6, Jan. 13, 1811; 12, March 5, 1812; 16, Dec. 5, 1812; 16, April 28, 1812; 18, Dec. 7, 1812; 22, Nov. 8, 1812; 24, Jan. 29, 1813; 27, Feb. 4, 1813; 28, Feb. 4, 1813; 30, March 14, 1814; 31, Dec. 9, 1815; 33, Aug. 19, 1813; 33, March 8, 1816; 36, Feb. 13, 1812; 41, April 26, 1812; 45, May 1, 1812; 47, June 13, 1812; 49, June 17, 1812; 50, July 5, 1812; 51, Oct. 16, 1812; 54, Jan. 26, 1813; 59, Jan. 26, 1813; 61, March 15, 1813; 61, Aug. 19, 1813; 80, July 8, 1815; 86, Sept. 12, 1815; 87, Sept. 29, 1815; 88, Dec. 13, 1815; 89, Dec. 23, 1815; 91, Feb. 11, 1816; 94, March 8, 1816; 96, March 8, 1816; 98, March 7, 1816; 99, April 2, 1816; 124, Oct. 1, 1803; 128, Jan. 5, 1804; 132, July 5, 1804; 141, Feb. 18, 1806; 145, March 4, 1806; 146, March 21, 1806; 171, March 10, 1812; 173, March 27, 1813; 193, May 20, 1813; 198, May 22, 1813; 199, June 2, 1813; 200, June 8, 1813; 201, June 11, 1813; 202, June 19, 1813; 203, June 23, 1813; 204, Sept. 4, 1813; 205, Sept. 7, 1813; 206, Sept. 22, 1813; 206, Oct. 1, 1813; 207, Oct. 11, 1813; 209, Oct. 23, 1813; 212, Dec. 28, 1813; 212, March 4, 1814; 240, Feb. 15, 1817; 243, Nov. 1817; 251, 277, Nov. 15, 1827; 281, Jan. 24, 1828; 286, Feb. 21, 1828; 289, April 19, 1830; 292, June 18, 1828; 294, June 29, 1828; 295, July 31, 1828; 303, Sept. 14, 1829; 305, Jan. 24, 1828; 306, Dec. 20, 1827; 311, Dec. 24, 1831; 315, Dec. 14, 1828; 323, Dec. 30, 1828; 332, July 27, 1829; 335, Nov. 5, 1829; 336, Nov. 14, 1829; 339, Aug. 19, 1830; 363, March 1, 1830; 368, Jan. 24, 1829; 372, June 10, 1830; Vivian, Captain A., 150, May 30, 1806; Williams, Mr. M., 111, Jan. 5, 1853; Williams, Messrs., 304, Nov. 14, 1820. LIBERALITY, 49. LIBERTY, WHEAL, 39. LIDDELL, Captain, 250. LIMA, 31, 32, 64, 80, 195, 206, 217, 218, 224, 226, 240, 247, 249, 271. LINTHORN, Mr., 292. LOCOMOTIVE, 23, 26, 27, 39, 41, 43, 48, 50, 126, 133, 206, 217, 271, 374, 379, 387, 388. LOGAN, Dr., 40. LONDON ENGINE, 5. LOSH, Mr., 95. LOW PRESSURE, 76, 140, 148, 157, 179, 180, 192, 395. LOWE, Mr., 277. LOWNDES, Lord, 287. M. MACHUCA, 262. MAGDALENA, 272. MAN AND HIS MAN, 361. MANCHESTER, 3, 138, 139. MAN'S POWER, 42. MARAZION, 180. MARRATT, Mr., 129. MATINA, 265, 267. MAUDSLAY, Mr., 375. MELLINEAR MINE, 75. MELVILLE, Lord, 24, 361. MEUX'S BREWERY, 111. MIERS, Mr., 247. MILLS, Mr., 339, 375. MINT ENGINE, 32, 201, 209, 217, 227, 239, 240, 243, 247. MITCHELL, Mr., 137. MODEL, 197. MOMENTUM, 20, 85, 91, 145, 149. MONT CENIS, 26, 293. MONTELEGRE, Mr., 269. MONTELEGRE RIVER, 266, 279, 280. MOORE, Dr., 34. MORLEY, Earl of, 390. MOYLE, Captain M., 307. MULE-POWER, 45, 47, 201. MURDOCH, 105, 118, 125, 126. N. NANKIVILL, Mr., 38. NAVY BOARD, 17, 41, 47, 372. NEATH ABBEY, 154, 199. NELSON, Lord, 121. NEVILLE, Mr., 157, 187. NEW STEAM NAVIGATION COMPANY, 383. NEWCASTLE-UPON-TYNE, 3. NEWCOMEN, 83, 114, 121, 157, 175, 211, 300, 319, 328. NICARAGUA LAKE, 269. NORFOLK, Duke of, 390. NUMBER OF ENGINES, 14, 148. O. OATS, JAMES, 111. ODGERS, Captain, 98. OPEN-TOP CYLINDERS, 19, 60, 208, 210, 211, 300, 363. OVAL TUBE, 21, 153. P. PADDLE-WHEEL, 384. PADRE ARIAS MINE, 262. PADSTOW ENGINE, 18, 27, 29. PAGE, Mr., 98, 99, 212, 214, 231, 241. PALMER, General, 390. PAPE, Mrs., 66. PARALLEL MOTION, 39. PATENT LAWS, 48, 128, 304. PATENTS, 343 of 1831; 366 of 1831; 376 of 1832. PAYNTER, Mr., 280. PENPONDS, 158. PENYDARRAN, 132. PERCEVAL, Mr., 108. PERRIER, Mr., 188. PERU, 210, 221, 252. PETITION TO PARLIAMENT, 306, 374, 388. PHILLIP, Mr., 89, 96, 99. PHILLIPS, HENRY, 90. PICKWOOD, Mr., 47. PINNEYS and AMES, 33, 49, 50, 51, 63. PINTO, DON ANTONIO, 280. PLOUGHING BY STEAM, 40, 54, 67. PLUMMER, BARHAM, and Co., 49. PLUNGER-POLE PUMP, 119, 198. PLYMOUTH BREAKWATER, 22, 23, 25, 27, 29, 30, 54, 195. PLYMOUTH DOCKYARD, 361. PNEUMATIC ELEVATOR, 392. POLDICE, 103. POLE-ENGINE, 31, 69, 80, 83, 90, 92, 99, 102, 176. POLE, Professor, 179. POOLY, WILLIAM, 158. POPULATION, 44, 265. PORTABLE ENGINE, 1, 5, 17, 22, 39, 50, 54, 170, 220, 309, 368, 370, 374. POWER OF ENGINE, 14, 27, 42, 72, 76, 80, 86, 100, 115, 121, 143, 148, 210, 211, 333. PRAED, Mr., 17, 48, 335. PRICE, Mr. JOSEPH, 96. PRICE, Sir ROSE, 64. PRONEY, Mr., 189. PUFFER-ENGINE, 1, 26, 32, 60, 74, 91, 102, 136, 140, 150, 154, 210. PUMPING ENGINE, 131, 148, 150, 171, 182, 189, 198, 207, 211, 217, 220, 240, 257. PUMPS, 119, 124, 198, 207, 211, 333. PUNTA DE ARENAS, 260, 267. Q. QUARRYING, 22, 26. QUEBRADA-HONDA, 262. R. RAILWAY, 148. 'RANEE' LOCOMOTIVE, 387. RASTRICK, Mr., 18, 54, 63, 66, 73, 87, 195, 200, 204, 212. RAWLINGS, Mr., 62. REES'S CYCLOPÆDIA, 181. REFORM COLUMN, 390. RENNIE, Mr., 24, 28, 31, 157, 181, 184, 187, 320, 339, 356, 358, 372, 381. REYNOLDS, Mr., 10, 151. RHINE RIVER, 295, 297, 302. RICE, SPRING, 311, 388. RICHARDS, Mr., 19, 56. RIDLEY, Sir MATTHEW, 388. ROBARTS, Mr., 390. ROBERTS, Mr., 38. ROBINSON and BUCHANAN, 15, 16. ROCK BORING, 110, 206. 'ROCKET,' 354. ROLAND, Mr., 196, 229. ROLLING MILL, 4, 132, 137, 209, 220. ROTTERDAM, 295. ROWE, GEORGE, 163. ROWE, Mr., 231. S. SAFETY-PLUG, 126. ST. AGNES HEAD, 59, 171. ST. AUBYN, Sir JOHN, 335. ST. IVES, 8, 16, 302. SALTRAM STREAM, 102. SAN JOSÉ, 267. SAN JOSÉ RIVER, 266. SAN JUAN DE NICARAGUA, 265, 269, 271. SAN MARTIN, 249. SANDYS, CARNE, and VIVIAN, 303. 'SANSPAREIL,' 204. SANTA ROSA, 237. SAUNDERS, JAMES, 231. SAVERY, 114, 117, 319. SAWING BY STEAM, 41. SCREW-BIT, 27. SCREW-POWER, 293. SCREW-PROPELLER, 67, 384. SERAPIQUE, 265, 266, 280. SHAMMAL ENGINE, 121, 158, 166, 177. SHARRATT, Mr., 128. SHEFFIELD, Mr., 9. SHIPS OF IRON, 286. SILVER STATUE, 244. SIMS, Mr., 87, 102, 106, 150, 153, 176, 304. SINCLAIR, Sir JOHN, 17, 40, 41, 47. SING, Mr., 66. SMELTING FURNACE, 8. SMILES, Mr., 353. SMITH, Mr., 95, 241. SMITH, Mr. THOMAS, 66, 67. SMOKE BURNER, 20. SOHO, 179. SOMERSET, Duke of, 390. SOUTH AMERICA, 188, 195, 225, 227, 260, 309. SPADE BY STEAM, 40, 58. SPANISH GOVERNMENT, 205, 254. SPANISH MERCHANTS, 2. SPRING STEELYARD, 371. STEAM AGRICULTURE, 41, 43, 58. " BOAT, 17, 41, 329, 337, 356, 359, 375, 378. STEAM CRANE, 23, 27. " CUSHION, 84. " MASH-TUB, 14. " NAVIGATION COMPANY, 295. " PADDLE, 369. " PLOUGH, 43, 58. STEAM PRESSURE, 1, 14, 20, 32, 34, 69, 74, 86, 91, 100, 102, 109, 121, 123, 126, 142, 149, 153, 155, 179, 184, 192, 210, 309, 330, 337, 358, 386. STEAM STONE-BORING, 25, 27, 29, 30. " USERS' ASSOCIATION, 358. STEPHENSON, 272, 273, 279, 283, 353. STEVENSON, Mr. W. B., 247. STONE-BORER, 22, 24, 27. STONE-CRUSHER, 1. STONE-SPLITTER, 25. STOURBRIDGE, 132. STRAY PARK, 159, 166, 169, 175, 177, 183. STRENGTH, 90. STROKES, 20, 32, 36, 82, 91, 98, 100, 210. STUFFING BOX, 31, 79, 84. SUGAR-BOILING, 3. SUGAR MILL, 2, 50. SUPERHEATING STEAM, 290, 315, 324, 330, 376. SURFACE-AIR CONDENSER, 333, 335, 339, 341, 343, 374. SURFACE-WATER CONDENSER, 19, 316, 322, 324, 329, 332, 335, 338, 341, 343, 374. SWAINE, CHARLES, 119. SYCOMBE, Mr., 232. SYMONDS, Captain, 339. 'SYRIA,' STEAMBOAT, 384. T. TANKS, 388. 'TASMANIA,' STEAMBOAT, 314. TAYLOR, Mr., 118, 180. TEAGUE, Captain, 197, 199, 229. TELFORD, Mr., 336. THOMAS, Captain CHARLES, 1, 74, 162. THOMAS, Captain JACOB, 157. THOMAS, Captain JOSIAH, 167. THOMPSON, Mr., 388. THORNE, Dr., 246. THRASHING ENGINE, 17, 21, 36, 38, 40, 42, 54, 61, 64, 68. TILLY, Captain, 229. TIN CROFT, 170, 173. TORMENTOR, 58. TREASURY, WHEAL, 152. TRECOTHICK, Mr., 47, 50. TRESKERBY, 102, 105, 107, 176, 305. TRETHUOY, Mr. WILLIAM, 68. TREVARTHEN, Captain, 213, 230. TREVITHICK, R., Jun., 158. TREVITHICK, Sen., 115. TREVITHICK, Mrs., 1. TREWITHEN, 38, 68. TRINITY BOARD, 143, 150. TUBULAR BOILER, 32, 115, 119, 153, 291, 308, 325, 339, 344, 359, 376, 387. TYACK, Mr. JOHN, 295. U. UNITED MINES, 304. UPRIGHT BOILER, 41, 60, 290, 332, 339. UVILLE, Mr., 32, 63, 196, 200, 204, 208, 212, 214, 217, 221, 224, 227, 229, 236, 240, 244, 245. V. VACUUM, 69, 157, 325. VALLEY PUFFER, 119, 142. VALVES, 160. VICEROY, 226, 251, 259. VIVIAN, Captain ANDREW, 52, 88, 96, 116, 125, 138, 140, 141, 152, 154, 165, 306. VIVIAN, Captain HENRY, 90, 215, 230, 240. VIVIAN, Captain JOSEPH, 101, 142. " Captain NICHOLAS, 157, 187. " HENRY, 60. " Mr. SIMON, 152. W. WARD, Mr., 361. WARREN, Mr., 66. WARSOP, Mr., 10. WATER-PRESSURE ENGINE, 13, 293, 310. WATER-PROPELLER, 378. WATERS, Mr., 250. WATERWITCH COMPANY, 383. WATKIN, Sir EDWARD, 273. WATSON, Mr., 247. WATT, 21, 33, 47, 75, 80, 83, 86, 92, 95, 98, 103, 105, 112, 115, 118, 124, 125, 126, 128, 150, 156, 159, 163, 170, 175, 178, 180, 183, 189, 191, 196, 211, 224, 230, 290, 300, 308, 312, 319, 323, 328, 331, 352, 370, 374, 386, 388, 395. WELSH LOCOMOTIVE, 42, 68. WEST INDIA DOCKS, 3, 133. WEST INDIA ENGINE, 39, 45, 53, 63, 195, 201. WEST, JOHN, 160. " WILLIAM, 158, 163. WHEAL, ABRAHAM, 148, 151, 153. " ALFRED, 19, 54, 103, 105, 106. WHEAL CLOWANCE, 153. " CONCORD, 103. " DAMSEL, 103, 327. " GENS, 117, 118, 155, 159, 169, 177. WHEAL JEWEL, 150. " KITTY, 153. " LIBERTY, 171. " LUSHINGTON, 103. " PROSPER, 69, 84, 106, 171. " REGENT, 102. " SEAL-HOLE, 170, 360. " TOWAN, 157, 178, 185, 316, 327, 331, 360, 369. WHEAL TREASURE, 102. " VOR, 83, 327. WHIMS, 17, 32, 39, 60, 119, 128, 141, 150, 153, 172. WHITEHEAD, Mr., 139. 'WILDMAN,' SHIP, 217. WILLIAMS, Messrs., 22, 88, 106, 109, 124, 150, 153, 184, 281, 283, 304. WILLIAMS, WILLIAM, 220. WILSON, Mr., 386. WINDING ENGINE, 2, 201, 208, 217, 220, 240. WINDMILL, 296. WOLLASTON, Dr., 293. WOOD, Mr., 4. WOOLF, ARTHUR, 80, 83, 86, 92, 96, 111, 180, 189, 316. WOOLWICH, 286, 335. WORCESTER, 133. Y. YANACANCHA, 238. YONGE, DON, 280. Z. ZUYDER ZEE, 302. LONDON: PRINTED BY W. CLOWES AND SONS, STAMFORD STREET AND CHARING CROSS * * * * * * Transcriber's note: Inconsistencies in spelling and punctuation are as in the original. 
56332	----	KEELY AND HIS DISCOVERIES AERIAL NAVIGATION BY Mrs. BLOOMFIELD MOORE The universe is ONE. There is no supernatural: all is related, cause and sequence. Nothing exists but substance and its modes of motion. Spinoza. LONDON KEGAN PAUL, TRENCH, TRÜBNER & CO., Ltd. PATERNOSTER HOUSE, CHARING CROSS ROAD 1893 John Stuart Mill, in order to protect science, carried empiricism to its extreme sceptical consequences, and thereby cut the ground from under the feet of all science.--Professor Otto Pfleiderer, D.D. The word of our God shall stand for ever.--Isa. xl. 8. Imagination is wholly taken captive by the stupendous revelation of the God-force which modern conceptions of the Cosmos furnish. Through the whole universe beats the one life-force, that is God, controlling every molecule in the petal of a daisy, in the meteoric ring of Saturn, in the remotest nebula that outskirts space, as though that molecule were the universe. In each molecule and atom God lives and moves and has His being, thereby sustaining theirs.... Prophet after prophet cries, and psalmist after psalmist sings, that so indeed he has found it; that therein is the divine sonship of man, therein the assurance of eternal life.--Rev. R. A. Armstrong. The living man with his interior consciousness of self and individuality is on two planes of nature at once, as a ship is in two media at once, half in the water and half in the air. To manage your ship successfully you must take cognizance of the laws governing each of those media. To deal successfully with your human being you must understand his physiology no doubt, but you must equally understand his psychology, and something of the collateral phenomena of nature in those regions or planes to which the phenomena of the psychic man belong.--A. P. Sinnett. The splendid generalizations of our physicists and our naturalists, have had for me an enthralling and entrancing interest. I find as I look out on the world, in the light of all this new knowledge, a pressure of God upon consciousness everywhere; and if this physical force which is God, moves through, sustains, communes, with each smallest physical atom of the whole, much more must that conscious energy which is God, move through, sustain, commune with, these conscious atoms, these several monads, which are you and I, and our friend, and our brother far away. The even flow of the divine force through every material atom, which is the supreme revelation of physical science in our time, itself leads irresistibly on to the suggestion of the constant flow of spiritual energy in actual communion with every spiritual monad that there is. It becomes but a question of opening the eyes of the soul, unstopping the ears of the inward spirit, to see and hear the God who in us also surely lives and moves and has His being, thereby sustaining ours. As the physical atom is physically touched and held and thrilled by God, it is what we should expect that the conscious monad, no less should be consciously touched and held and thrilled by Him.--Rev. R. A. Armstrong. "Euroclydon driveth us--where? On quicksands and shoals of the sea, On rocks that wait hungry to tear And devour with tigerish glee. "But lo! where we land tempest-tost Is the work that has waited our hand;-- Not one step of that life shall be lost Whose way an All-seeing hath planned." We never know through what divine mysteries of compensation the Great Father of the Universe may be carrying out His sublime plans.--Miss Murdoch. Enthusiasm is the genius of sincerity, and Truth accomplishes no victory without it.--Bulwer Lytton. Science is bound by the everlasting law of honour to face every problem fearlessly.--Lord Kelvin. For my part, I too much value the pursuit of truth and the discovery of any new fact in nature, to avoid inquiry because it appears to clash with prevailing opinions.--Wm. Crookes, F.R.S. The secret of success is constancy to purpose.--Lord Beaconsfield. The simple peasant who observes a fact And from a fact deduces principles, Adds social treasure to the public wealth. Facts are the basis of Philosophy. Philosophy is the harmony of facts Seen in their right relations.--Lyrics of a Golden Age. DEDICATED TO JAMES DEWAR, M.A., LL.D., F.R.S., M.R.I. FULLERIAN PROFESSOR OF CHEMISTRY, R.I. JACKSON PROFESSOR, UNIVERSITY OF CAMBRIDGE, IN ADMIRATION OF HIS DISTINGUISHED SERVICES FOR SCIENCE, AND IN GRATEFUL ACKNOWLEDGMENT OF HIS PROLONGED AND STEADFAST INTEREST IN KEELY'S WORK OF EVOLUTION. 12, Great Stanhope Street, Mayfair, 16th May, 1893. CONTENTS.   PAGE Preface.--By the Rev. John Andrew xi Introduction xv CHAPTER I. 1872-1882. Introductory 1 CHAPTER II. 1882-1886. Ether the True Protoplasm, An Epitome of Macvicar's Sketch of a Philosophy 11 CHAPTER III. 1885-1887. The Nature of Keely's Problems 30 CHAPTER IV. 1887. Sympathetic Vibratory Force 41 CHAPTER V. Etheric Vibration.--The Key Force 54 CHAPTER VI. The Fountain Head of Force 65 CHAPTER VII. The Key to the Problems.--Keely's Secrets 72 CHAPTER VIII. 1888. Helpers on the Road, and Hinderers 101 CHAPTER IX. 1889-1890. Keely supported by Eminent Men of Science.--Aerial Navigation 113 CHAPTER X. 1881-1891. The Keely Motor Bubble.--Macvicar's Logical Analysis 129 CHAPTER XI. 1890. Vibratory Sympathetic and Polar Flows.--Keely's Contributions to Science 145 CHAPTER XII. Vibratory Physics.--True Science 167 CHAPTER XIII. "More Science" 186 CHAPTER XIV. Vibratory Physics.--The Connecting Link between Mind and Matter 206 CHAPTER XV. The Philosophy of History.--Keely the Founder of a System 229 CHAPTER XVI. 1891. An Appeal in Behalf of the Continuance of Keely's Researches 238 CHAPTER XVII. 1891. More of Keely's Theories.--His Traducers exposed 265 CHAPTER XVIII. A Pioneer in an Unknown Realm 285 CHAPTER XIX. Latent Force in Interstitial Spaces.--Electro-Magnetic Radiation.--Molecular Dissociation. By John Ernst Worrell Keely 298 CHAPTER XX. 1892. Progressive Science.--Keely's Present Position.--A Review of the Situation 319 CHAPTER XXI. Faith by Science: The Dawn of a New Order of Things 332 CONCLUSION. Keely's Physical Philosophy.--By Professor D. G. Brinton, M.D., of the University of Pennsylvania 358 Appendix I. 365 Appendix II. 368 Appendix III. 370 Verses 373 PREFACE. By the Rev. John Andrew, of Belfast. "Wait on the Lord." When the Almighty is taking men into His deeper confidence as to His Creation ways, and how His ways may be taken advantage of for man's service and benefit, the gifted one through whom such revealing is being made should not be hurried by the common bustle of the world, but should be protected in the privacy where the Creator and he are closeted together in the giving and receiving which is thus transpiring. Scientific patience is, in all such cases, imperative. When the gifted one is bustled by the world, as Mr. Keely has been, his inspiration is disturbed and his advance hindered. If the first inkling of some great revealing thus in progress should promise some mighty find for the material advantage of mankind, there is naturally a quickened desire to gain possession; but if in such an event impatience should impel the seer, ere his far-visioned sight has reached the end, deplorable delay may be the result. This is the thing which has happened in the case which this little volume comes forth to relate and explain. It is not intended to unfold the systematic methods of the gifted genius concerning whom it speaks; that will come, in his own words, in due time. The aim of this volume is to show the course of events in relation to his researches; and to open the mystery of how it came about that he should have been so much misunderstood and hindered. It tells how he, in the dim dawn of initial inspiration, first glimpsed and touched The Power which is about to be given to the possession of mankind for the supply of wants, and the relief of toil. How he struggled and wrestled like the patriarch of old who said, "I will not let Thee go, except Thou bless me." How men of the world, seeing the struggle and estimating the power, said, "Make haste and harness this power to our machinery, and we shall pay you." How, in his need of means, he was tempted and fell; making an attempt to harness to machinery a power whose very form and kind he had not yet been given to discern. And then, when this too hasty attempt had failed, how the disappointed world laughed and mocked, and fumed, and called him an impostor. This volume seeks to explain this Keely Mystery; and to show that although a mistake was made, it was only a passing mistake. The mistake has been rectified; and the seer, now in possession of peace and privacy, has fully sighted the power, and is making progress in bringing it into subjugation. He has been interviewed by competent men, men of enlarged scientific vision; and in the protection of their esteem, and by the liberal pecuniary aid of one who has made scientific interests an object of sacred solicitude, Mr. Keely is likely to succeed in opening to the world another of the stores which the Almighty Creator and Preserver, ever provident of His children's needs, has prepared in reserve against the time of their necessity. We may theorize, but God alone knows the means by which the regeneration of mankind, and the establishment of the kingdom of righteousness and peace shall come about. The All-merciful has a purpose and plan of His own. The power which Mr. Keely is dealing with belongs to the ways and means of the evolution of civilization and material providence; and it will depend on how men make use of it how far it may clear or block the way of this planet's highest weal. The power, however, which Mr. Keely is dealing with lies so close to the spiritual realm of things, and brings us so near to the point at which the Almighty is in immediate touch of His Creation in His unceasing upholding of it, that all Christian men might be expected to take a deep interest in researches which promise so much. It may reasonably be hoped that this volume may promote this interest, and turn the attention to coming events which are casting more than shadows before. With this hope we commend it to the reading of the wise. Those who delight in yellow-covered literature may pass it by; it contains no plot for the excitement of such. INTRODUCTION. Ex Vivo Omnia. We stand before the dawning of a new day in science and humanity,--a new discovery, surpassing any that has been hitherto made; which promises to afford us a key to some of the most recondite secrets of nature, and to open up to our view a new world.--Dr. Hufeland. The error of our century in questions of research seems to have been in the persistent investigation of the phenomena of matter (or material organization) as the sole province of physics, regarding psychical research as lying outside. The term physics is derived from a Greek word signifying "nature." Nature does not limit herself to matter and mechanism. The phenomena of spirit are as much a part of Nature as are those of matter. The psychological theories of our physicists display a decided leaning towards materialism, disregarding the manifestations of the vital principle,--the vis motrix,--and refusing to investigate beyond the limits which they have imposed upon themselves, and which, if accepted by all, would take us back to the belief of the pagans, as echoed by Voltaire: Est-ce-là ce rayon de l'Essence Suprême Que l'on nous peint si lumineux? Est-ce-là cet Esprit survivant à nous-même? Il nait avec nos sens, croît, s'affaiblit comme eux: Hélas! il périra de même. Sympathetic philosophy teaches that the various phenomena of the human constitution cannot be properly comprehended and explained without observing the distinction between the physical and material, and the moral and spiritual nature of man. It demonstrates incontrovertibly the separate existence and independent activity of the soul of man, and that the spirit governs the body instead of being governed by the body. As Spenser has said,-- For of the soul the body form doth take; For soul is form, and doth the body make. Huxley tells us that science prospers exactly in proportion as it is religious, and that religion flourishes in exact proportion to the scientific depth and firmness of its basis. "Civilization, society, and morals," says Figuier, "are like a string of beads, whose fastening is the belief in the immortality of the soul. Break the fastening and the beads are scattered." Now, as Nature nowhere exhibits to our visual perceptions a soul acting without a body, and as we do not know in what manner the spiritual faculties are united to the organization, psychology is compelled to investigate the operations of the intellect as if they were performed altogether independently of the body; whereas they are only manifested, in the ordinary state of existence, through the intermediate agency of the corporeal organs. The accumulation of psychological facts and speculations which characterize this age appears to have made little or no permanent impression upon the minds of our scientists and our philosophers. Bishop Berkeley asks, "Have not Fatalism and Sadducism gained ground during the general passion for the corpuscularian and mechanical philosophy which hath prevailed?" Buffon, in writing of the sympathy, or relation, which exists throughout the whole animal economy, said, "Let us, with the ancients, call this singular correspondence of the different parts of the body a sympathy, or, with the moderns consider it as an unknown relation in the action of the nervous system, we cannot too carefully observe its effects, if we wish to perfect the theory of medicine." Colquhoun, commenting upon Buffon's statement, says that far too little attention has been paid to the spiritual nature of man,--to the effects of those immaterial and invisible influences which, analogous to the chemical and electrical agents, are the true springs of our organization, continually producing changes internally which are externally perceived as the marked effects of unseen causes, and which cannot be explained upon the principles of any law of mechanism. These unseen causes are now made clear to us by the truths which Vibratory Physics and Sympathetic Philosophy demonstrate and sustain. The prophecy of Dr. Hufeland (made in connection with an account of certain phenomena arising from the unchangeable laws of sympathetic association) is soon to be fulfilled, and the door thrown open to "a new world" of research. Professor Rücker in his papers on "Molecular Forces," William Crookes in his lecture on "The Genesis of Elements," Norman Lockyer in his book on "The Chemistry of the Sun,"--all these scientists have approached so near to this hitherto bolted, double-barred and locked portal that the wonder is not so much that they have approached as that, drawing so near, they have not passed within. Professor Rücker, in his papers (read before the Royal Institution of Great Britain) explaining the attractive and repulsive action of molecules, found himself obliged to apologize to scientists for suggesting the possibility of an intelligence by which alone he could explain certain phenomena unaccounted for by science; but do we not find proof in ourselves that the action of molecules is an intelligent action? For we must admit the individuality of the molecules in our organisms, in order to understand how it is that nourishment maintains life. Try as we may to account for the action of aliment upon the system, all is resolved into the fact that there must be some intelligent force at work. Do we ourselves disunite and intermingle, by myriad channels, in order to rejoin and replace a molecule which awaits this aid? We must either affirm that it is so, that we place them where we think they are needed, or that it is the molecules that find a place of themselves. We know that we are occupied in other ways which demand all our thoughts. It must, therefore, be that these molecules find their own place. Admit this, and we accord life and intelligence to them. If we reason that it is our nerves which appropriate substances that they need for the maintenance of their energy and their harmonious action, we then concede to the nerves what we deny to the molecules. Or, if we think it more natural to attribute this power to the viscera,--the stomach, for example,--we only change the thesis. It will be said that it is pantheism to assert that matter, under all the forms which it presents, is only groups of aggregates of sympathetic molecules, of a substance unalterable in its individualities; a thinking, acting substance. Let us not deny what we are unable to explain. God is all that is, without everything that is being individually God. Etheric force has been compared to the trunk of a tree, the roots of which rest in Infinity. The branches of the tree correspond to the various modifications of this one force,--heat, light, electricity, and its close companion force, magnetism. It is held in suspension in our atmosphere. It exists throughout the universe. Actual science not admitting a void, then all things must touch one another. To touch is to be but one by contiguity, or there would be between one thing and another something which might be termed space, or nothing. Now, as nothing cannot exist, there must be something between "the atomic triplets" which are, according to the Keely theory, found in each molecule. This something in the molecule he affirms to be "the universal fluid," or molecular ether. One thing touching another, all must therefore be all in all, and through all, by the sensitive combination of all the molecules in the universe, as is demonstrated by electricity, galvanism, the loadstone, etc. If we account for the intelligent action of molecules by attributing it to what has been variously called "the universal fluid," "the electric fluid," "the galvanic fluid," "the nervous fluid," "the magnetic fluid," it will only be substituting one name for another; it is still some part or other of the organization which discerns and joins to itself a portion of one of the fluids referred to, or one of these fluids which discerns and mingles with the material molecules; it is still the life of the part, the life of the molecule, life individualized in all and through all. Admitting, then, that there is a universal fluid, it must exist in and through all things. If void does not exist, everything is full; if all is full, everything is in contact; if everything is in contact, the whole influences and is influenced because all is life; and life is movement, because movement is a continual disunion and union of all the molecules which compose the whole. The ancient philosophers admitted all this. Under the different names of "macrocosm," "microcosm," "corpuscles," "emanations," "attraction," "repulsion," "sympathy," and "antipathy,"--all names which are only one,--their various propositions were merely the product of inductions influenced by their modes of observing, as the deductions of scientists are influenced in our day. Balzac tells us that everything here below is the product of an ethereal substance, the common basis of various phenomena, known under the inappropriate names of electricity, heat, light, galvanic and magnetic fluid, etc., and that the universality of its transmutations constitutes what is vulgarly called matter. We cannot take up a book on physics (written with true scientific knowledge) in which we do not find evidence that its author acknowledges that there is, correctly speaking, but one force in nature. Radcliffe tells us that what is called electricity is only a one-sided aspect of a law which, when fully revealed, will be found to rule over organic as well as inorganic nature--a law to which the discoveries of science and the teachings of philosophy alike bear testimony,--a law which does not entomb life in matter, but which transfigures matter with a life which, when traced to its source, will prove only to be the effluence of the Divine life. Macvicar teaches that the nearer we ascend to the fountain-head of being and of action, the more magical must everything inevitably become; for that fountain-head is pure volition. And pure volition, as a cause is precisely what is meant by magic; for by magic is meant a mode of producing a phenomenon without mechanical appliances,--that is, without that seeming continuity of resisting parts and that leverage which satisfy our muscular sense and our imagination and bring the phenomenon into the category of what we call "the natural;" that is, the sphere of the elastic, the gravitating,--the sphere into which the vis inertiæ is alone admitted. There is in Professor Crookes's "Genesis of the Elements" an hypothesis of great interest,--a projectment of philosophical truth which brings him nearer than any known living scientist to the ground held by Keely. Davy defines hypothesis as the scaffolding of science, useful to build up true knowledge, but capable of being put up or taken down at pleasure, without injuring the edifice of philosophy. When we find men in different parts of the world constructing the same kind of scaffolding, we may feel fairly sure that they have an edifice to build. The scaffolding may prove to be insecure, but it can be flung away and another constructed. It is the edifice that is all-important,--the philosophy not the hypotheses. The science of learning, says Professor Lesley, and the science of knowledge are not quite identical; and learning has too often, in the case of individuals, overwhelmed and smothered to death knowledge. It is a familiar fact that great discoveries come at long intervals, brought by specially-commissioned and highly-endowed messengers; while a perpetual procession of humble servants of nature arrive with gifts of lesser moment, but equally genuine, curious, and interesting novelties. From what unknown land does all this wealth of information come? Who are these bearers of it? And who intrusted each with his particular burden, which he carries aloft as if it deserved exclusive admiration? Why do those who bring the best things walk so seriously and modestly along as if they were in the performance of a sacred duty, for which they scarcely esteem themselves worthy? The Bishop of Carlisle, in his paper on "The Uniformity of Nature," suggests the answer to all who are prepared to approach the abyss which has hitherto divided physical science from spiritual science,--an abyss which is soon to be illumined by the sunlight of demonstration and spanned by the bridge of knowledge. To quote from the paper of the Bishop of Carlisle, "There are matters of the highest moment which manifestly do lie outside the domain of physical science. The possibility of the continuance of human existence in a spiritual form after the termination of physical life is, beyond contradiction, one of the grandest and most momentous of possibilities, but in the nature of things it lies outside physics. Yet there is nothing absolutely absurd, nothing which contradicts any human instinct, in the supposition of such possibility; consequently, the student of physical science, even if he cannot find time or inclination to look into such matters himself, may well have patience with those who can. And he may easily afford to be generous: the field of physical science is grand enough for any ambition, and there is room enough in the wide world both for physical and for psychical research." But does psychical research lie outside the domain of physical science? What is the supernatural but the higher workings of laws which we call natural, as far as we have been able to investigate them? Is not the supernatural, then, just as legitimate a subject of consideration, for the truly scientific mind, as is the natural? If it explains, satisfactorily, phenomena which cannot be otherwise explained, there is no good reason why its aid should not be invoked by men of science. The truth is, that the ordinary course of nature is one continued miracle, one continued manifestation of the Divine mind. "Everything which is, is thought," says Amiel, "but not conscious and individual thought. Everything is a symbol of a symbol; and a symbol of what?--of mind. We are hemmed round with mystery, and the greatest mysteries are contained in what we see, and do, every day." Keely affirms, with other philosophers, that there is only one unique substance, and that this substance is the Divine spirit, the spirit of life, and that this spirit of life is God, who fills everything with His thoughts; disjoining and grouping together these multitudes of thoughts in different bodies called atmospheres, fluids, matters, animal, vegetable, and mineral forms. Herbert Spencer says that amid the mysteries that become the more mysterious the more they are thought about, there will remain the one absolute certainty, that we are ever in the presence of an infinite and an eternal energy, from which all things proceed. Macvicar foreshadowed the teachings of this new philosophy when he wrote, "All motion in the universe is rhythmical. This is seen in the forward and backward movement of the pendulum, the ebb and the flow of the tides, the succession of day and night, the systolic and diastolic action of the heart, and in the inspiration and expiration of the lungs. Our breathing is a double motion of universal æther, an active and a reactive movement. This androgyne principle, with its dual motion, is the breath of God in man." The writings of the ancients teem with these ideas, which have been handed down to us from generation to generation, and are now flashing their light, like torches in the darkness, upon mysteries too long regarded as "lying outside the domains of physical science." Twenty years ago Macvicar wrote his "Sketch of a Philosophy," in which he advanced the above views, with other views now maintained and demonstrated by Keely, who during these twenty years, without knowing Macvicar's views, or of his existence even, has been engaged in that "dead-work which cannot be delegated," the result of which is not learning, but knowledge; for learning, says Lessing, is only our knowledge of the experience of others; knowledge is our own. This burden of dead-work, writes Lesley, every great discoverer has had to carry for years and years, unknown to the world at large, before the world was electrified by his appearance as its genius. Without it, there can be no discovery of what is rightly called a scientific truth. Every advancement in science comes from this "dead-work," and creates, of its own nature, an improvement in the condition of the race; putting, as it does, the multitudes of human society on a fairer and friendlier footing with one another. And during these twenty years of "dead-work" the discoverer of etheric force has pursued the even tenor of his way, under circumstances which show him to be a giant in intellectual greatness, insensible to paltry, hostile criticism, patient under opposition, dead to all temptations of self-interest, calmly superior to the misjudgments of the short-sighted and ignoble; noble means as indispensable to him as noble ends; fame and riches less important than his honour; his joys arising from the accomplishment of his work and the love and the sympathy of the few who have comprehended him! "Only the noble-hearted can understand the noble-hearted." Keely's chief ambition has been to utilize the force he discovered; not for his own aggrandizement, but to bless the lives of his fellow-men. He has scaled the rocks which barricade earth from heaven, and he knows that the fire which he has brought down with him is divine. This so-called secret is an open secret, which, after it is known, may be read everywhere,--in the revolution of the planets as well as in the crystallization of minerals and in the growth of a flower. "But why does not Keely share his knowledge with others?" "Why does he not proclaim his secret to the world?" are questions that are often asked. Keely has no secret to proclaim to the world. Not until the aerial ship is in operation will the world be able to comprehend the nature of Keely's discoveries. When the distinguished physicist, Professor Dewar, of the Royal Institution of Great Britain, goes to America this summer, he will be instructed by Mr. Keely in his dissociation processes. Every man who has passed the mere threshold of science ought to be aware that it is quite possible to be in possession of a series of facts long before he is capable of giving a rational and satisfactory explanation of them--in short, before he is enabled to discover their causes even. This "dead-work" has occupied many years of Keely's life; and only within the last five years has he reached that degree of perfection which warranted the erection of a scaffolding for the construction of the true edifice of philosophy. We have only to recall the wonderful discoveries which have been made in modern times, relative to the properties of heat, of electricity, of galvanism, etc., in order to acknowledge that had any man ventured to anticipate the powers and uses of the steam-engine, the voltaic pile, the electrical battery, or of any other of those mighty instruments by means of which the mind of man has acquired so vast a dominion over the world of matter, he would probably have been considered a visionary; and had he been able to exhibit the effects of any of these instruments, before the principles which regulate their action had become generally known to philosophers, they would in all likelihood have been attributed to fraud or to juggling. Herein lies the secret of Keely's delay. His work is not yet completed to that point where he can cease experimenting and publish the results of his "dead-work" to the world. "When will he be ready?" is a question often asked; but it is one that God only can answer, as to the year and day. It now seems as if the time were near at hand,--within this very year; but not even Keely himself can fix the date, until he has finished his present course of experiments, his "graduation" of his twenty-seventh and last group of depolar disks, for effecting change and interchange with polar force. "But what are his hypotheses? And what the tenets of his new philosophy?" His hypotheses are as antithetic to existing hypotheses in chemistry as the Newtonian system, at its first publication, was antithetic to the vortices of Descartes. The philosophy is not of his creation; nor is it a new philosophy. It is as old as the universe. Its tenets are unpopular, heterodox tenets, but their grandeur, when compared with prevailing theories, will cause the latter to appear like the soap-bubbles that Sir William Drummond said the grown-up children of science amuse themselves with; whilst the honest vulgar stand gazing in stupid admiration, dignifying these learned vagaries with the name of science. It is the sole edifice of true philosophy, the corner-stone of which was laid at Creation, when God said, "Let there be light; and there was light." The scaffolding which our modern Prometheus has built is not the airy fabric of delusion, nor the baser fabric of a fraud, as has been so often asserted. It has been built plank by plank, upon firm ground, and every plank is of pure gold, as will be seen in due time. It has been justly said that we have no ground for assuming that we have approached a limit in the field of discovery, or for claiming finality in our interpretations of Nature. We have, as yet, only lifted one corner of the curtain, enabling us to peep at some of the machinery by which her operations are effected, while much more remains concealed; and we know little of the marvels which in course of time may be made clear to us. Earnest minds in all ages and in all countries have arrived at the same inferences which Keely has reached in his researches,--viz., that the one intelligent force in nature is not a mere mathematical dynamism in space and time, but a true Power existing in its type and fulness,--deity. You may say that such an inference belongs to religion, not to science, but you cannot divorce the two. No systematic distinction between philosophical, religious, and scientific ideas can be maintained. All the three run into one another with the most perfect legitimacy. Their dissociation can be effected only by art, their divorce only by violence. Great as is the revolution in mechanics which is to take place through this discovery, it has an equally important bearing on all questions connected with psychical research. Once demonstrated, we shall hear no more of the brain secreting thought, as the liver secretes bile. The laws of "rhythmical harmony," of "assimilation," of "sympathetic association," will be found governing all things, in the glorious heavens above us, down to the least atom upon our earth. Leibnitz's assertion, that "perceptivity and its correlative perceptibility are coextensive with the whole sphere of individualized being," will be accounted for without depriving us of a Creator. "The music of the spheres" will be proved a reality, instead of a figure of speech. St. Paul's words, "In Him we live, and move, and have our being," will be better understood. The power of mind over matter will be incontrovertibly demonstrated. "The requirement of every demonstration is that it shall give sufficient proof of the truth it asserts." This Keely is prepared to give,--mechanical demonstration; and should he really have discovered the fundamental creative law, which he long since divined must exist, proving that the universal ether which permeates all molecules is the tangible link between God and man, connecting the infinite with the finite,--that it is the true protoplasm, or mother element of everything,--we may look for a philosophy which will explain all unexplained phenomena and reconcile the conflicting opinions of scientists. The great law of sympathetic association, once understood, will become known as it is,--viz., as the governing medium of the universe. Herein lies the secret, the revelation of which will usher in the spiritual age foretold by the Prophets of the Old Testament and the Apostles of the New Testament. Inspiration is not confined to prophets and apostles and poets: the man of science, the writer, all who reach out after the Infinite, receive their measure of inspiration according to their capacity. We need a new revelation to turn back "the tidal wave of materialism" which has rolled in upon the scientific world, as much as Moses needed one when he sought to penetrate the mysteries of the Creation; and our revelation is near at hand,--a revelation which will change the statical "I am" into the dynamical "I will,"--a revelation which, while teaching us to look from Nature up to Nature's God, will reveal to us our own powers as "children of God," as "heirs of immortality." "Knowledge," said Lord Beaconsfield, "is like the mystic ladder in the Patriarch's dream. Its base rests on the primeval earth--its crest is lost in the shadowy splendour of the empyrean; while the great authors who, for traditionary ages, have held the chain of science and philosophy, of poesy and erudition, are the angels ascending and descending the sacred scale, maintaining, as it were, the communication between man and heaven." This beautiful imagery holds within it that seed of truth, which is said to exist in the wildest fable; for, although all great discoveries, pertaining to the material world, have been made gradually, with much starting on the wrong track, much false deduction and much worthless result, spiritual truths can be revealed to man in no other way than by that spiritual influence which maintains communication between the terrestrial and the celestial, or the material and the spiritual. "Truth is attained through immediate intuition," say the Aryan teachers; but only by those who have educated their sixth sense; as will be seen in Mr. Sinclair's new work, "Vera Vita; or, the Philosophy of Sympathy." While the imaginative scientist is puzzling himself about new natural forces and the apparent suspension of old and hitherto invariable laws, Sinclair, in his writings, shows us that it is because we do not recognize the elements of nature that their influences remain mysterious to us. Mr. Sinclair is as firm in his belief as is Mr. Keely that this element is the great connecting link between the Creator and the created, and that it is capable of rendering more marvellous services to man than all the discovered uses of electricity. The coincidences in the theories of these two philosophers are the more remarkable, inasmuch as Mr. Sinclair's have their origin, as set forth in his book "A New Creed," in metaphysics; while "Keely's wide and far-reaching philosophy" (to quote the words of a distinguished physicist) "has a physical genesis, and has been developed by long years of patient and persistent research." But it is an undisputed fact that, in countries far distant from each other, different men have fallen into the same lines of research; and have made correspondent discoveries, at the same time, without having had any communication with each other; and never has there been a time when so many were testing all things that appear to give proof of the super-sensual element in man. There is a very general impression all over the world, says Marie Correlli, that the time is ripe for a clearer revelation of God and "the hidden things of God" than we have ever had before. All persons who are interested in Keely's discoveries and the nature of the unknown element discovered by Keely and Sinclair, will find in the writings of the latter a more lucid explanation of sympathetic association than Keely himself has ever been able to give in writing. The title of this remarkable book would have been more wisely chosen had its author called it "A New Element and a New Order of Things." The Rev. Philip Schaff, D.D., says of creeds:--"The Bible is the word of God to man: the Creed is the answer of man to God. The Bible is the book to be explained and applied; the Creed is the Church's understanding and summary of the Bible." It is in this light that Mr. Sinclair's new creed, human and humane, should be read. There is no conductivity in the ether lines, writes Sinclair, for selfish desires and motives; for they are not of the soul, but are only sounds of the lips (or wishes of the material part of us), so that the established connecting-rod between the living soul and the source of life is insulated from desires that are not begotten in sympathy, and they at once run to earth. Where there is no connection there can be no communion. Without the natural sympathetic etheric connection between the source of life and the soul, there can be no communication. "A New Creed," like the sympathetic etheric philosophy of Keely, reveals the connecting link between the finite and the Infinite, and teaches us that the primal law of evolution and of progress is slowly but surely preparing our race for the time when Christianity will be something more than a mere profession, and "the brotherhood of humanity" will no longer be the meaningless phrase that it now is. We are led to see, by this pure philosophy, that "our solar system is a type of a healthy social system; that in it each one affects, binds, controls, sustains, helps, makes free each other; that no star lives for itself alone;" that man was not made to mourn, and that our sufferings arise from our ignorance of the laws governing the innate motive power within us. The times are not degenerate! Men's faith Mounts higher than of old. No crumbling creed Can take from the immortal soul its need Of something greater than itself. The wraith Of dead belief we cherished in our youth, Fades but to let us welcome new born truth. Man may not worship at the ancient shrine, Prone on his face, in self-accusing scorn. That night is passed; he hails a fairer morn, And knows himself a something half divine! No humble worm whose heritage is sin, But part of God--he feels the Christ within! No fierce Jehovah with a frowning mien He worships. Nay, through love, and not through fear, He seeks the truth, and finds its source is near! He feels and owns the power of things unseen, Where once he scoffed. God's great primeval plan Is fast unfolding in the soul of man.--Ella W. Wilcox. KEELY AND HIS DISCOVERIES. CHAPTER I. 1872 TO 1882. INTRODUCTORY. Within the half-century the hypothetical ether has amply vindicated its novel claim to take its place as a mysterious entity side by side with matter and energy among the ultimate components of the objective universe.... Modern science sets before our eyes the comprehensive and glorious idea of a cosmos which is one and the same throughout, in sun and star and world and atom, in light and heat and life and mechanism, in herb and tree and man and animal, in body, soul, and spirit, mind and matter.--Grant Allen on Evolution. The man who can demonstrate the existence of an unsuspected and unknown force has a right, in the absence of demonstrative proof to the contrary, to form his own theory of its origin, and to make it the basis of his own system. Keely is looking at physical phenomena and their explanations from a point of view so different from that of the inductive school, that we hardly know how to combine the two, or show their bearings upon each other. For myself, I think now, as I thought and said in my address, that the absolutely exclusive position, taken up by Huxley, Tyndall, and the so-called Material School, is ludicrously indefensible; and that we should be as perfectly open to evidence in any direction, as we were 2000 years ago.--The Rev. H. W. Watson, D.Sc., F.R.S. So many men of learning are now holding Dr. Watson's views that the time seems to have arrived, in which the theories of Keely will receive, from those who are competent to judge of their value, the attention that they deserve. Before entering upon their merits, or setting them down for others to judge of their worth, the way must be prepared by showing the claims which they possess from their correspondence with some of the most advanced ideas of the present day, as well as with the teachings of the wisest men in past centuries. The mode which is the least laborious to accomplish this end, is by collecting what has been written and printed, which bears upon, and elucidates this subject. It is now very generally known that Mr. Keely, while pursuing a line of experiment in vibrations, "accidentally" as Edison would say, made his discovery of an energy, the origin of which was unknown to himself; and six years passed, in experiment, before he was able to repeat its production at will. In the meantime he had exhausted his resources and willingly accepted the proposal of men, who, after witnessing the operation of the energy that he was able to show with this unknown force, offered to organize a company to furnish him with the means to construct an engine to use this force as the motive power, anticipating immediate success. But discovery is one thing, invention quite another thing, and the years rolled on without Mr. Keely's being able to fulfil his promises. In 1882, which was about ten years after the company was formed, an action at law was brought against him for non-fulfilment of his contract. The Evening Bulletin of March 30th of that year thus explains, truthfully, the position. THE KEELY MOTOR. A STATEMENT FROM ONE OF THE INVENTOR'S STOCKHOLDERS. "To the Editor of the Evening Bulletin: In your issue of last Tuesday appears an article which deserves attention, and also calls for some explanation upon that very much misunderstood question of the Keely motor. From some cause not easy to learn, there seems to be a tendency to keep only one side of that subject before the public. "Being one of the unfortunates of the Keely motor speculation, interest has led me to investigate not only the invention and the man who has everything to do with it, but also the management of the company, which is equally important to those who put their money into the enterprise as an investment. Permit me, therefore, to state a few of the facts which, if known, would very much change some of the popular views now held. "There are perhaps a thousand stockholders in the Keely Motor Company. The mass of these, like myself, are not the prosecutors in this case against Mr. Keely. We do not believe that Mr. Keely can be forced to divulge any valuable secrets if he possesses them. We do not believe that a case in court is calculated to prolong the inventor's life, or render it more safe from the accidents to which he is exposed. We do not believe that these proceedings are likely to increase his good will towards the company. Some of us know that by purchasing Keely motor stock, we have not thereby put our money into the invention, nor has Mr. Keely had the benefit of it. We also know that some, if not all, of the parties to this prosecution, especially those who are most vehement in its favour under the pretence of protecting the common stockholders, are selfish to the last degree, while for themselves they have the least cause to complain. Their official records show an utter disregard of the interests of stockholders or the rights of the inventor: while the success of the invention is to them a secondary consideration. It is they, and not the inventor, who have drummed up the customers, and recommended and sold the stock. They, and not he, are answerable to the purchasers. If Mr. Keely is guilty of deception, they are to say the least equally so. Look at a few statements: "When the Keely Motor Company was started, in 1874, its organizers received their stock without paying for it. About three-fourths of the whole amount were thus given away by Mr. Keely. He retained about one-seventh, and was cheated out of a good portion of that before he had gone far. Only 400 shares out of 20,000 were retained in the treasury, and that but a short time; for these recipients of the "dead-head stock" made hasty havoc of the market by a rapid unloading of their shares and pocketing the proceeds. So the poor little 400 shares of treasury stock brought only the minimum price to afford temporary relief to a distressed company. "The bankrupt condition of this incipient corporation threatened it with a cessation of existence, unless somebody came to the rescue, for the 'originals,' who had received a harvest by the sale of their 'free stock,' would not now give a dollar to save the concern. They were all fixed, but what of the innocent stockholders who had purchased this stock? They should not be allowed to suffer, as they must if the company went out. So Mr. Keely came to the rescue, and consented to the following scheme, which was prepared by schemers, as the sequel proved. He had two inventions besides the motor, and they could be handled to advantage in this emergency. These Mr. Keely assigned to the company, and the stock was increased from 20,000 to 100,000 shares. The 80,000 new shares were to be divided equally: 40,000 to pay for the inventions, and 40,000 went to the company without one dollar of pay. So, Mr. Keely received no money in this transaction; and of the 40,000 shares which he should have received, not 5000 ever reached him; fraudulent claims having captured the rest while in the hands of the 'trustee.' Of the 5000 shares also, much had been obligated in advance by the inventor to carry forward the work which otherwise must have been delayed, so that he had less than 1000 shares left when all claims were settled. This grand act is called the 'consolidation,' which took place in 1879, and since which all moneys raised by the company have come from the sale of shares out of this 40,000, which Mr. Keely then gave to the company. By some mysterious operations in the 'management' this 'Treasury Stock' has shrunk away very rapidly, bringing at times only a fraction of the price which other stocks of the same kind were selling for in the market, while the little cash which it has brought has only in part been used by Mr. Keely, and that has been served out to him in a sparing way, which would be shameful even if he had not furnished it all to begin with. The company now owe to Mr. Keely fifty thousand dollars loaned outright in its early history. To this indebtedness considerable has since been added. The public statements that Mr. Keely has been supplied with large amounts of money from the company are untrue, while it is true that of those who are regarded as his dupes a half dozen or more have made on an average at least $50,000 each from the 'enterprise.' The money with which Mr. Keely capitalized the company, in the first place, was obtained from the sale of territorial rights to men who have formed other companies for the purpose. "If Mr. Keely deserves prosecution by any parties, it is those who bought these rights, and not the ring who now control the company with stock which has cost them nothing. "If anybody deserves to be sued by the stockholders it is these very persons who recommended and sold them the stock, and have taken the benefit of it, and who at the same time are responsible for the miserable management which has caused detention of the work, distress in the company, depreciation in the stock and dissatisfaction among stockholders. "One." The further history of "The Keely Motor Bubble" will be given later on, but it is the position in earlier years, that we must first deal with, to get a clear comprehension of the causes of the delays which again and again shattered the hopes of the sanguine investors just when they were the most buoyant, from an apparent increased control of the mysterious force Keely was handling. Further quotations from the press will best show the light in which Keely's work was regarded by those who considered themselves competent to pass judgment upon him and his efforts. The Daily News in Philadelphia, on May 25th, 1886, contained a most sensible editorial, with the heading What has Keely Discovered? "For a number of years Mr. John W. Keely, of this city, and various associates have occupied the attention of the public to a greater or less extent, from time to time. The claim on behalf of Mr. Keely is that he has discovered a new motive power, so far transcending all previous achievements in this direction, as to overturn most of the universally recognized conclusions regarding dynamics. Of course such a claim was sure to be met with derision, and the derision was sure of continuance until silenced by the most thorough practical demonstration. "Discussion of the matter has not seemed profitable in the absence of such a demonstration; but now it seems proper to note an apparently new status of Mr. Keely's affairs, as shown by some experiments conducted last Saturday in the presence of a number of visitors. Some, at least, of these visitors were qualified for critical observation, and the noteworthy fact is that Mr. Keely was able to produce, under their close inspection, a dynamic result which none of them pretended to account for by any known law of physics, outside of that which Mr. Keely claims as the base of his operation. He evolved, almost instantaneously, according to the united report of those who were present, a substance having an elastic energy varying from 10,000 to 20,000 pounds per square inch, and instantly discharged or liberated it into the atmosphere, without the evolution of heat in its production, or of cold on its sudden liberation. These phenomena alone would seem to establish that the substance he is dealing with is one not hitherto known to science. "It seems rather frivolous to dismiss this matter with the supposition that trained specialists are to be hoodwinked by concealed springs, buried pipes for the introduction of compressed air and the like. Surely such gentlemen ought very easily to determine at once whether the surroundings and conditions of the experiments were such as to favour any kind of legerdemain; and if they found them so, it is strange that they should spend some hours in investigating that which has been asserted to be 'a transparent humbug.' "The appearances are that Mr. Keely has at least removed his enterprise from the domain of ridicule to that of respectful investigation, and this, after all, is great progress." On Wednesday, July 28th, 1886, the Public Ledger had a leader headed, Let us have some actual useful Work. "With regard to the occasional revivals of the Keely motor, whether annual, semi-annual, or biennial, as they have come along in the last ten or a dozen years, the Ledger has paid but little attention to them for a long time; and possibly this last display last week might have been allowed to take the same unnoticed course, but that the "whizz" of the big sphere seems to have been so rapid, and the racket so stunning, as to more greatly puzzle those present at the exhibition than on any former occasion. The matter for a long time has presented itself to us in but two aspects mainly. First, there was large public interest in the asserted development of physical force by new and very strange means--very interesting if there really was a probability of a new device or new means of developing power that could be harnessed and made to do useful work; and second, so far as the matter took the form of exploiting a private enterprise or stimulating a boom for a private speculation, there was but very limited interest for the public. In this latter aspect it was almost exclusively an affair between Mr. Keely and the stockholders of his company, who felt willing to back their faith in the substantiality of his invention or discovery, by investing their money in the company's stock. This was no affair for a public journal to meddle in, unless some imposture was designed that might affect the general public. "That is the way the Ledger has regarded the matter for several years; and, as during that period it seemed to be almost exclusively a private matter of little public interest, we have had little or no concern with it. Of course the Ledger stood ready all the time, as it stands now ready, to welcome anything that promises to be useful or of advantage in any way as an addition to the mechanical or other working facilities of our day. That Mr. Keely might have a clue to such an addition we did not dispute on the mere ground that it was new or strange, or because experts pronounced it impossible; for many stranger things have happened. Mankind, even those who are illumined by the highest human knowledge and intelligence, do not yet know all that is to be known, as we are reminded almost every day by the strides of scientific and mechanical progress. We would rather have found Mr. Keely less inclined to be mysterious; we could have wished him to have been less disposed to talk in terms that sound very like meaningless jargon to most well-informed persons; but still we did not think it proper, or fair, or wise, to reject his claims on these grounds, but have simply let them rest in abeyance, so far as the Ledger is concerned, because behind all this, and behind many more such essays, is the possibility that the success of some one of them may solve the problem of what is to be done when the world's supply of fuel, whether in form of wood, or coal, or peat, or gas, is either practically exhausted or to be got at only at a cost that would largely preclude its use. Mr. Keely, we say, may have a clue to that, as also may some one of those who are experimenting with the several manifestations of electric or magnetic force. "What we would have had Mr. Keely do, and, until he does it, his operations have but little practical value in the sight of the Ledger, would have been to harness his motor to do some useful work, to gear it by cogwheel or by belt and pulley, or by some other mechanical device, to a main shaft that has driving lathes, or planers, or other machines--something that was doing actual useful work, day in and day out, as other machines do. Of machines that will manifest great pressure on a gauge, of contrivances that have enormous lifting power, of explosives that demonstrate stupendous force, the appliances of science and the mechanic arts have large numbers, and they are handier and more manageable than any Mr. Keely has shown. These are not to the point--except, perhaps, to persons endowed with large faith. The machine that will do actual, useful, large work, by a manipulation of new energy, or by a display of energy by new and manageable means, this or these are the things the public and the Ledger will be glad to hail." At this time Mr. Keely had not reached that stage in his researches when he could carry out the suggestions made by the able writer of the Ledger leader; and if our discoverer of an unknown force had not been known to some persons "endowed with large faith" in his discovery, it would have been lost to the world. An anonymous writer has said the idea that living nature is not a collection of dead-heads, never seems to have struck the non-progressivists. The thing that is has been, and the thing that is will continue to be; this is the sum and substance of the doctrine they profess. They commit the mistake of supposing they live in a finished planet when in reality they exist on an orb that has relatively just begun to live. The time allowed us for observation and study of nature and of ourselves, is limited in a marked degree. Just when we are beginning to know how to read the book, we are forced to close its pages because the intellectual eyesight finds itself within the trammels of age. All we can do is to make a hit here, and a hit there, and to hand on our little bit of intelligence to those who come after us, in the hope that they also will keep their eyes and ears open, and, in like manner, hand on a cumulative store of knowledge to their heirs and successors. During the brief span of a man's existence, then, it is difficult for him to prove much progress either in himself or in his surroundings. The eternal hills seem the same to him when the light of life dies out, as when first his eyes beheld their outlines. Stern, uncompromising, apparently immutable, the hills remain to him the type of all that is fixed, all that is unchangeable around. Yet this is not the story of science. Tennyson, who is always true to nature, says:-- "The hills are shadows, and they flow From form to form, and nothing stands; They melt like mists, the solid lands; Like clouds they shape themselves and go." In Memoriam, cxxiii., 2nd Stanza. This is good poetry; better still, it is good science. The Himalayas, big and grand as they are, must represent mountains whose rise was a thing of a very "recent" date, geologically speaking. This is proved, because we see rocks belonging to a relatively recent age, appearing as part and parcel of their lofty peaks. Very different is the case with the hills and mountains of, say, north-western Scotland. There you come upon peaks of an age well-nigh coëval with the world's earliest settling down to a steady, solid, and respectable existence. The Scottish hills are the old, the very old, aristocrats of the cosmical circle; the Himalayas, Alps, and the rest, are the new race whose origin goes not further back than a generation, as it were. Yet, about the oldest of the mountains there is nothing which is absolutely enduring. Equally with the newer hills, geological progress and action are written on the face of their history. The hills are only phases of cosmical arrangement; they are here in the to-day of the world; they may be gone in the world's to-morrow. Before Science had learned to lisp this, the prophetic word of men moved by the Holy Ghost had said: "Of old Thou hast laid the foundations of the earth, and the heavens are the work of Thy hands. They shall perish, but Thou remainest; yea, all of them shall wax old like a garment, and as a vesture shalt Thou change them and they shall be changed." The world is neither perfect nor finished in a geological sense, any more than it is perfect in an ethical sense. It is full of progressive action everywhere, and, to quote from another author, "our planet and our solar system are but as the small dust of the balance in the colossal scale of the worlds that are." Had there been no one to read the future in the light of the past, among those who witnessed the production of the force discovered by Keely in 1872, he could not have continued his researches, as he has done during these intervening years, from lack of the funds necessary to carry them on. But there were men who knew the worth of the discovery, and who, sanguine as to almost immediate results, did something more than stand idly "ready to welcome" them when produced. They furnished the money with which Keely laboured year after year, and encouraged him to persevere, when without such aid he might have been forced to abandon his researches for want of the necessaries of life. During this period, Keely's discovery was only thought of in reference to its commercial value, and for a decade he made no progress: but, after his researches led up to the conviction that he was on the road to another and infinitely more important discovery, namely, the source of life and the connecting link between intelligent will and matter, his progress has been almost uninterrupted. His ambition is not only to give a costless motive power to the world, but to make clear to men of science the path he is exploring. CHAPTER II. 1882 TO 1886. ETHER THE TRUE PROTOPLASM, AN EPITOME OF MACVICAR'S SKETCH OF A PHILOSOPHY. All that has been predicted of atoms, their attractions and repulsions, according to the primary laws of their being, only becomes intelligible when we assume the presence of mind.--Sir John F. W. Herschell (1865). It is in no small degree reassuring to find that we are not chained to inert matter, but to the living energies of its forms.... This leads us to the inference, long suspected, that all matter, as well as the ethereal medium itself consists ultimately of one and the same primordial element.--Col. A. T. Fraser, Darkness and Light in the Land of Egypt. For ten years Keely's demonstrations were confined to the liberation, at will, of the energy he had "stumbled over" while experimenting on vibrations in 1872; and his efforts were put forth for the construction of "the perfect engine," which he had promised to The Keely Motor Company. He made the mistake of pursuing his researches on the line of invention instead of discovery. All his thoughts were concentrated in this direction up to the year 1882. Engine after engine was abandoned and sold as old metal, in his repeated failures to construct one that would keep up the rotary motion of the ether that was necessary to hold it in any structure. Explosion after explosion occurred, sometimes harmless to him, at other times laying him up for weeks at a time. Two more years were lost in efforts to devise an automatic arrangement, which should enable the machine, invented by Keely for liberating the energy, to be handled by any operator, and it was not until 1884 that steady progress was seen, from year to year, as the result of his enlarged researches. When Keely was asked, at this time, how long he thought it would be before he would have the engine he was then at work upon ready to patent, he illustrated his situation by an anecdote: "A man fell down, one dark night, into a mine; catching a rope in his descent, he clung to it until morning. With the first glimpse of daylight, he saw that had he let go his hold of the rope he would have had but a few inches to fall. I am precisely in the situation of that man. I do not know how near success may be, nor yet how far off it is." August 5th, 1885, the New York Home Journal announced that Keely had imprisoned the ether; and, as was then wrongly supposed, that the unknown force was the ether itself; not the medium of the force, as it is now known to be. The late George Perry, who was then editor of that journal, heralded the announcement with these comments:--"No object seems to be too high or remote for human endeavour. It is not strange that some of these attempts should stagger the faith of all but the boldest imaginations. A notable example of this class is the famous etheric motor invented by Keely, of Philadelphia, and the subject of a communication which we print below from a well-known American lady in Italy. The inventor claims to have found a new force, one that entirely transcends those that have been hitherto appropriated for human use. Heat, steam, electricity, magnetism are but crude antetypes of this new discovery. It is essentially the creator of these forces. It is scarcely less than the 'primum mobile.' Indeed in reading the exposition of its potentialities one can hardly help doubting whether the concrete matter of our earth is not too weak and volatile to contain, restrain, and direct this vast cosmic energy except in infinitesimal proportions. How shall iron and steel stand before the power which builds up and clasps the very atoms of their mass? Where shall the inventor look for 'safety discs' to stay his new-found force, when every substance within his reach is but a residuum of the activity of this identical principle? How shall strength of materials avail against the power that gives, and indeed is, strength of materials? This, however, is but a metaphysical doubt, and as the invention has already demonstrated its practical efficiency on a small scale, there is a presumption that it may be extended to the higher degrees. At all events, whether the force can or cannot be harnessed to do the daily work of the world, the discovery is one that will mark an epoch in the progress of science and give the inventor and his patrons a meed of immortality. Granted they are but poets building a lofty cosmical rhyme, their work shall have not the less an enduring honour." The New Force--Etheric Vapour. The discoverer of a hitherto unknown force in nature which, when certain inventions are perfected, will create a revolution in science, as well as in mechanics, has for many years concentrated his mind upon gaining supreme control over one of nature's greatest and grandest forces. Or, more correctly speaking, in efforts to control and apply to mechanics one of the various manifestations of the one force in nature. "The force which binds the atoms, which controls secreting glands, Is the same that guides the planets, acting by divine commands." The hypothetical ether conceived of by scientists, to account for the transmission of light, is not hypothetical to this discoverer. He knows its nature and its power. By the operation of an instrument of his own invention, he can release it at will from the suspension in which it is always held in our atmosphere. It is so liberated, by an almost instantaneous process of intense vibratory action, and passed through a tube the opening of which is no larger than a pin's head, furnishing sufficient power to run a one hundred horse-power engine. The importance of this discovery cannot be conceived; its limit seems boundless; its value cannot be put in figures. Step by step, with a patient perseverance which one day the world will honour, this man of genius has made his researches, fighting with and overcoming difficulties which seemed insurmountable, during years in which no disinterested hands were extended to aid him, no encouraging words of appreciation bestowed upon him by the scientists whom he vainly tried to interest in his experiments; assailed by calumnies, which, emanating from those who should have been the first to extend aid, have over and over pierced his noble heart like poisoned arrows. History will not forget that, in the nineteenth century, the story of Prometheus found a counterpart, and that the greatest man of the age, seeking to scale the heavens to bring down blessings for mankind, met with Prometheus's reward from the vultures of calumny who, up to the present moment, have not spared their talons upon him. The dangerous conditions attending the introductory features of the development of etheric vapour are not yet entirely overcome; but this throws no shadow of a doubt as to the inventor's eventual success in the minds of those who know the magnitude of the difficulties he has already mastered. O. W. Babcock, in an American journal says of this discovery, "Human comprehension is inadequate to grasp its possibilities or power, for prosperity and for peace. It includes all that relates mechanically to travel, manufacture, mining, engineering and warfare. The discoverer has entered a new world, and although an unexplored wilderness of untold wealth lies beyond, he is treading firmly its border, which daily widens as with ever-increasing interest he pursues his explorations. He has passed the dreary realm where scientists are groping. His researches are made in the open field of elemental force, where gravity, inertia, cohesion, momentum are disturbed in their haunts and diverted to use; where, from the unity of origin, emanates infinite energy in its diversified forms," and to this I would add--where he, the discoverer, is able to look from nature up to nature's God, understanding and explaining, as no mortal ever before understood and explained, how simple is the way in which God "works His wonders to perform." A compilation of Macvicar's "Sketch of a Philosophy," entitled "Ether the true Protoplasm," was sent to Mr. Keely; and shortly after, Mrs. Hughes' book on the evolution of tones and colours. Mr. Keely will himself, in his theoretical exposé make known the manner in which he was led, by the writings of Dr. Macvicar and Mrs. Hughes, into the knowledge which raised the veil that had before hidden from him the operations of Nature with this "the most powerful and most general of all her forces;" operations which will explain all that is now mysterious to us in the workings of gravity. The question has been asked whether science, having destroyed faith, has supplied us with anything better. But has science destroyed faith? Certainly not. There would be no such thing as counterfeit coin were it not for the existence of sterling gold. True science has its counterfeit, and it is due to spurious science that the bulwarks of religious faith have been besieged; but they are not destroyed. Drummond says that it will be the splendid task of the future theology to disclose to scepticism the naturalness of the supernatural. The pure Philosophy which true science seems about to reveal discloses not a universe of dead matter, but a universe alive from its core to its outermost extremity, and animated by mind and means, to which matter, perfectly organized, is absolutely subservient. It illuminates mysteries of nature which have only been partially revealed to us, and lifts the veil which has hitherto shrouded in darkness still greater mysteries involved in this universal power, which keeps and sustains all systems of worlds in their relation towards each and all. More and more clearly shall we be led by true science to see that the universe "is founded upon a distinct idea," and that the harmony of this distinct idea is manifested in all of God's works. Sir Isaac Newton, in his "Fundamental Principles of Natural Philosophy," calls the great magnetic agent "the soul of the world," and says, "all senses are excited by this spirit, and through it the animals move their limbs; but these things cannot be explained in few words, and we have not yet sufficient experience to determine fully the laws by which this universal spirit operates." Centuries may pass before these laws will be "fully understood"; but Etheric Philosophy casts a plummet into depths that have never been sounded, and reveals this "unparticled substance," "the cosmic matter," "the primal stuff," "the celestial ocean of universal ether," as the true protoplasm, and the medium by which mind shapes matter and gives it all its properties. It teaches us that, through it, we are connected in sympathy with all other souls and with all the objects of nature, even, to the stars and all the heavenly bodies. But even though we do not understand the laws which control its operations, we find therein a legitimate field of research. It is surely more legitimate for science to ascribe failures in such researches to our still existing ignorance of that which we may possibly know in time than to set such laws down as unknowable. "Thought in its spontaneity has the run of the universe, and there should be no bar to discovery." Our only hope, says Macvicar, lies in the universality of the cosmical laws and the ultimate homogeneity of created substances, or reality. In stating some of the various hypotheses which have been put forward by Macvicar, more as a sketch than as a new system of philosophy, it is not necessary to make any comments. If the scaffolding be good the edifice will appear in time. If worthless, no edifice can be constructed. Therefore, it must be remembered that it is only with the scaffolding that we have to do at present. If it has been left for our age to demonstrate the truth or the falsity of certain deductions made in past ages--if we arrive at a partial knowledge, even, of truths which ancient wisdom saw with dim vision, we must never forget that our century has had the benefit of the light reflected down the stream of time. Macvicar's "Sketch of a Philosophy" was published in 1868. He said that his ideas would not be acceptable, or even intelligible, to an age when the popular demand is for very light reading; when science is marvellously content with the attainments which it has already made; and when, "as to the method of science we are told, with more and more confidence every day, that all we can do for the discovery of realities is to go out of doors, leaving 'the inner man' all alone, and to compare the odour of the present with the smell of the past, and then, turning our noses towards the future, to follow them wherever they may lead us." He continues, Sensation, we are taught, is the alone architect of all trustworthy knowledge; the author both as to form and substance of all that is belief-worthy. No such thing as intuition, we are told; reason merely a habit, rising from the long-continued use of the organism. This looking only to mechanism is as much the plague and sorrow of our times as it was when Macvicar complained of it as divorcing science from philosophy. Philosophic wisdom, says Willcox, is a structure built up of all knowledges--grand and sublime: permanent, not of the present nor the past. Science holds, in its relation to philosophy, the same position that theology sustains to religion. "En dehors de toutes les sciences spéciales et au-dessus d'elles, il y a lieu à une science plus haute et plus générale, et, c'est ce qu' on appelle philosophie."--(Paul Janet, Revue des Deux Mondes.) Of what nature are the ideas which Macvicar was so sure would be unpopular? In compiling from his writings, such are selected as seem to be the best, toward elucidating the mysteries which lie in the operation of the laws governing the universal ether, so far as his hypotheses carried him. If matter without form preceded the creation of vitality, "it is only when the principle of life had been given," says Charpignon, "that the intrinsic properties of atoms were compelled, by the law of affinities, to form individualities; which, from that moment, becoming a centre of action, were enabled to act as modifying causes of the principle of life, and assimilate themselves to it, according to the ends of their creation." Here is a conjecture, to start with, that it will be well to remember; for, as in the hypotheses of Macvicar and the demonstrations of Keely, the law of assimilation is made the pivot upon which all turns, "providing at once for the free and the forced, at once for mind and for matter, and placing them in a scientific relationship to one another." This law Macvicar calls the "cosmical law," because to it alone, ever operating under the eye and fulfilling the design of the great Creator who is always and in all places immanent to His creation, an appeal is ever made. By this law a far greater number of the phenomena of nature and the laboratory can be explained than have been otherwise explained by scores of laws which are frankly admitted to be empirical. Surely this is no slight claim for this law to be studied, with a view to its acceptance or rejection. To repeat, this law is to the effect that every individualized object tends to assimilate itself to itself, in successive moments of its existence, and all objects to assimilate one another. The ground of it is, that the simple and pure substance of creation, has for its special function to manifest the Creator; and consequently to assimilate itself to His will and attributes, in so far as the finite can assimilate itself to the Infinite. Hence it is, in its own nature, wholly plastic or devoid of fixed innate properties, and wholly assimilative, both with respect to its own portions or parts and to surrounding objects, as well as to its position in space, and, in so far as it is capable, to the mind of the Creator. Thus, there immediately awake, in the material elements, individuality and the properties of sphericity, elasticity, and inertia, along with a tendency to be assimilated as to place, or, as it is commonly called, reciprocal attraction. Hence, in the first place, the construction in the ether, or realm of light, of groups of ethereal elements, generating material elements. Hence, secondly, a tendency in the material elements, when previously distributed in space, to form into groups, in which their ethereal atmospheres may become completely confluent; while their material nuclei, being possessed of a more powerful individuality than ethereal elements, come into juxtaposition merely, thus constituting molecules. By legitimate deductions from cosmical law, the forms and structures of these molecules must always be as symmetrical as the reaction of their own constituent particles, and that of their surroundings, will allow. The law of assimilation gives the same results as mathematics in determining the forms of systems of equal, and similar, elastic and reciprocally attractive spherical forces, or centres of force, when they have settled in a state of equilibrium; proving these forms to be symmetrical in the highest degree. Here, however, Macvicar and Keely differ, in hypothesis, as to the structure of the ultimate material element; but this difference does not affect "the scaffolding" of pure philosophy, in which everything that is cognizable has its own place, is on a solid basis, is harmonious with its surroundings, and is explained and justified by them:--raising chemistry to the level and bringing it within the sphere of mechanics; investing its objects, at the same time, with all the distinctness of the objects of other branches of natural science. Because the chemist in his laboratory cannot succeed in decomposing certain substances, it has been inferred that they are essentially undecomposable, simple and untransformable; and on this hypothesis the whole science of mineralogy proceeds. But when it is considered that all of these chemical atoms, before they have come into the chemist's hands, have been securely consolidated and mineralized, so as to be able to withstand the ordeal of the volcano and the central heat, compared with which the most powerful analytic agencies of the laboratory are but a mimicry, is it for a moment to be supposed, although their internal structure were still molecular, that they would break down in the chemist's hands? Surely, all his containing vessels, which are but things of human art, must go to pieces before them. The present prevailing theory of development contradicts one half by the other half. It extends the doctrine of development and transmutation to species which happen to be visible to such eyes as we have; it denies it to such as happen to be invisible to us. If all animals and plants have been obtained by the secular synthesis of transformed monera, and the differentiation of the organs composing them--thus giving in the last analysis one form and kind of protoplasm as the root of all; the pursuit of the same line of thought--the same theory, applied to the atoms of the chemist, with their various properties and atomic weights, gives, as the common ground of all, a single material element; each chemical atom being a structure composed of this material element, but so stable as to be indecomposable in the laboratory. Let this be granted, as asserted by Macvicar in 1868, and by Keely now, and the theory of evolution, whatever may be the case as to its cogency, at least possesses a scientific form. It is no longer a conception which breaks down midway between its first and its last terms. But letting science, in this respect, stand for the present as it is, and supposing the seventy recognized elements of the laboratory (which do not include the twenty or more new elements recently said to have been discovered by Krüss and Nilson in certain rare Scandinavian minerals) or rather, perhaps, some very high multiple of their number to constitute that cosmic gas from which the solar system has been evolved, the theory of development shows itself to be as imperfect on the great scale, and in point of extent, as it is in point of homogeneity in its intimate material. Macvicar continues--Beyond that cosmic gas there certainly is the ether, a medium which no longer can be ignored in any physical theory of nature. What, then, is the relation of the cosmic gas to the ether? Evolutionists do not answer this question, but Macvicar seeks to render the whole system of thought homogeneous, and to show that, just as all organisms are the synthetic developments of one kind of moneron, and all chemical atoms and molecules the synthetic development of one kind of material element, so is the material element a synthetic development of ethereal elements. These also are Mr. Keely's views; but neither Macvicar nor Keely rest in the conception of a congeries of particles which are wholly blind and devoid of feeling and thought, diffused throughout all space, believing such particles to be the first of things. "Reason, if it is to enjoy intellectual repose, can have it only in finding, beyond and above all things else, a unity, a power, intelligence, personality--in one word, God. This is the only legitimate haven of a theory of development: sending back the tide of materialism and pantheism which has swept its mire over our age into the ebb again; as, after having reached the full, it has so often done already, before the constitutional instincts or inspirations of humanity, with which speculative minds may, indeed, dally for a generation but which are ultimately inexorable." Macvicar maintains with Keely that from God, as the Author of all, nature may be reached with those very features which it is seen to possess; that it is essential to every philosophy, which is or shall be in harmony with intelligence, that it shall be based upon a unity; that no philosophy possesses all the claims to intellectual regard which it may possibly have, unless that unity be an intelligent Being; that to suppose thought and feeling to wake up for the first time in that which was previously blind and dead from all eternity, is nothing short of absurd to those who are led by the evidence of design, to look from nature up to nature's God, in whom all nature lives and moves and has its being. While the protoplasm of the biologist is a substance which is more or less opaque or visible, the protoplasm now conceived of as the material of the whole creation in its first state, when development is to begin, must, on the contrary, be altogether homogeneous and invisible. But none the less is it entitled to the name of protoplasm; nay, it alone must be justly entitled to that name, for it is the first of created things, and, being the product of an Almighty Being, it must be altogether plastic in His hands. It can have no constitution of its own derived from itself; but must, so far as the finite can, with respect to the infinite, reflect, represent, embody, show forth His attributes and being. Still, there is limitation to this. Certain properties and demands with regard to that which exists, with limited extension, in space, are inexorable. Macvicar reasons that with such limitations the primal substance of creation must be fully obedient or assimilated to the Creator--not in a transient manner, but permanently; and that in its nature the primal substance, the true protoplasm, must be an assimilative substance. Granting that this protoplasm be partitioned into individualities, he makes the deduction that each and all of these individualized beings and things would, up to the full measure of their capacity, not only tend to assimilate themselves to the ever-present Being to whom they owe their own being, but they would tend also to assimilate themselves each to itself, with respect both to space and time; as also that they would all tend to assimilate one another. Taking this as the cosmical mode of action, or law, and on the strength of this law alone, without invoking the aid of any other law, he attempts to explain all those phenomena to which the physicist, the chemist, and the biologist usually address themselves. Illustrating the manner in which this law applies itself to phenomena, he gives as the first products of this law the perpetuation of an original mode of existence, and the establishment of permanence of properties under certain restrictions; the ground of the remarkable persistency and permanence of well-constituted species; a general harmony and homology throughout all creation: proceeding to illustrate its action on the mental or spiritual world; accounting for perception, remembrance, reasoning, imagining, judging, and upon all our other modes of mental activity, as operations of the cosmical law of assimilation. In the world of physics he gives, as illustrations of this same law of assimilation, attraction, inertia, elasticity, heredity, reversion, symmetry culminating in sphericity or symmetrical cellularity, chemical and electrical action; especially in voltaic action the influence and the persistence of this law is most remarkably displayed. By the way of familiar illustration, he takes the original voltaic cell, and without attempting to explain how one solid, copper or platinum, comes to be less assimilable to a liquid than another, such as zinc, he shows that just what we are to expect, from this law of assimilation, takes place--viz., that at the zinc there tends to form a stratum of oxygen, and that, at the platinum, there tends to form a stratum of hydrogen. Pursuing the old view as to the cause of the state of tension induced in the dilute sulphuric acid, the continuous decomposition of the water, the solidifying action of the zinc surface, he confines his attention to the current of force instituted by the oxygen; advancing the idea that this is not merely force in general, of which all that is to be considered is its quantity and direction; but force, of which the form of its elements or their formative power is also to be considered;--that formative power being representative or productive of oxygen. To the objection that such a conception is occult and mysterious, he asks if it is more occult and mysterious than what is implied and confessed to be hid under the term electricity, or in the phenomena of heredity, or than anything else which is adduced as a cause of a particular phenomenon. The cosmical law of assimilation explains all these phenomena, and, without any special hypothesis, is precisely what is wanted, in order to render natural knowledge as a whole accessible to the student: something which puts him in possession, from the first, of a master-thought, which, if he carry it along with him, will present all nature as a harmony; explaining all that stands in need of explanation. Macvicar continues:-- If it be asked how possibly out of one law, and such a one, there could arise anything like that endless variety which nature displays, the answer is, that the law operates between two limits, poles, or points of assimilation, which are entirely dissimilar, and by two processes simultaneously, analysis and synthesis, which are the opposites of each other. Hence it comes to pass that actual nature is a web, in which unity and multiplicity, identity and difference, are everywhere interwoven, and in such harmony that nature is everywhere beautiful. It is not necessary here to repeat the illustrations by which Macvicar seeks to demonstrate that existence is force--self-manifesting, or spontaneously radiant, so to speak, into that which is idea, if there be a recipient of ideas, or a percipient of ideas; or, more generally, a percipient within the sphere of its action. He does not prescribe any limits, in space, as to the extent of this self-manifesting power. Thus, it is one of the most certain facts in physics that every atom of this planet, nay, every atom of the planet Neptune, whose distance from the sun is thirty times as great as our distance, manifests itself to every atom of this planet--not, indeed, as a percept, but as the subject and the object of attraction or motion. Nay, by the aid of the ether, which is the grand medium whereby the self-manifesting power of being is enabled to take effect at a distance when no other being is interposed, the fixed stars manifest themselves at our planet, though their distances be inconceivably great. Distant objects acting like all objects assimilatively, assimilate the intervening ether and the optic apparatus to themselves, and thus render themselves perceptible. This they do, indeed, only under great limitation, imposed by the laws of inertia or motion in space, to which the ether is subject--limitation which, in man, it requires self-teaching and experience to remove, so that he may perceive the object in its true forms and dimensions. But this is only man's peculiarity, in consequence of his organic defects at birth. The chick, the day it leaves the egg, can run up with equal precision to a crumb of bread, or to an ant's egg at a distance. And so with all species whose myo-neuro-cerebral system functions perfectly from their birth. At his best, the embodied mind in man sees objects only in perspective. But the nature of this self-manifesting power need not be dwelt upon, since it is only the existence of this power that is insisted upon. How far beyond the visible and tangible parts of the body, the spirit, as a power exerting some kind of action or other, extends, Macvicar thinks cannot be determined. No doubt, every force has a centre of action; but as to the full extent in space of a unit of natural force, as an agent of one kind or another, no limits can be assigned. Who shall tell us the boundary in the outward of that power which says "I will," "I feel," "I see"? Its modes of acting mechanically are, no doubt, limited to the extent of the investing organism. Nay, in order to their extending even so far, it is necessary that the unity of the organism be maintained by the healthy integrity of the nervous system. In that case consciousness claims all the organism as its domain; and not only when the organism is entire does it refer any pain that arises to the region that is hurt, but after a limb has been amputated, and when it exists only as a phantom, consciousness still feels towards it as if it were still the old reality. Such is the effect of habit, or present assimilation to previous practice. Our cosmical law, the law of assimilation, must determine, if not the nature, at least the mode of action of this force--this self-manifesting power--for plainly this action must be assimilative. And that it is so, when giving rise to perception, is clearly and distinctly seen; for what is the perceiving of an object, but the mind, as a percipient, assimilating itself to that object? and what is the percept or remembrance of the object, which remains in the mind but the idea--that is, the assimilated symbol of the object, which, however, in consequence of the intrusion in the perception of the mind's own activity, and of other previously acquired ideas, as also the perceptive image is often very defective as a representation of the reality perceived? We may say that this self-manifesting power, which is thus the characteristic of all that exists, is the agency provided whereby the cosmical law of assimilation shall be realized, though the intimate nature of that agency remains, as now, wholly inscrutable. Nor can it be said to be physical until it is embodied in the ether. In that case, it is rhythmical, or undulatory, and formally representative of the object whence it emanates. But it is enough to know that the most intimate and ultimate property--the characteristic, in short, of that which exists--is self-manifesting power. Now, the existence of a self-manifesting power in an object implies that the object is itself a power or force, or an aggregate of such. This is enough for the purposes of philosophy and science, and we only deceive ourselves when we suppose that we can think of anything that exists and which is not at the same time a force or power.... Of most things that exist, if not of all, let us say that they are capable of existing in either of two states--the dynamical or the statical--and that, when viewed as dynamical, they are forces or powers; when viewed as statical, they are substances. When we exhaust or think away the properties of existence, the last which vanishes is self-manifesting power in the object which exists, this property being such that when it vanishes so does the object to which existence was awarded. In the science of the day it is maintained by our most popular authors and lecturers that the "physical forces"--taken in the singular number, physical force--is the last word, the ultimate principle. The physical forces are represented as all that there is for God, whereas they are but as the fingers of God. The idea of antecedent design, either in reference to nature as a whole, or in reference to any object in particular, is dropped as unscientific, or repudiated as unsound; in short, a reference to the physical forces, is the last word permitted in any treatise, if that treatise is to be admitted as possessing a scientific character. Or, if there be one word more, it is only the "correlation" of those same physical forces, and their "conservation," or persistence eternally in the same amount of energy in the universe. In their own place and within their own sphere, these are physical truths, which are of the greatest value. The former is a wholesome relapse into the old philosophy of nature. The latter is also a return to a view which is more sound than that which was popular before the doctrine of conservation was resuscitated. Descartes' opinion, that there was a conservation of motion in the universe, was demonstrated by Newton to be a mistake. Leibnitz adjusted the truth between these great men, showing that it was not motion, but the possibility or means of motion--in one word, energy--that was conserved in the universe. The doctrine of the conservation of energy amounts to nothing more than this, that inasmuch as every ultimate atom of matter is perfectly elastic, so is the whole universe of atoms perfectly elastic. Hence it is a doctrine which cannot be legitimately extended beyond the merely material sphere; except on the assumption that matter is the only reality, and that there is no such thing as a spiritual world at all--an assumption which, however often it has been made, serves only to awaken a prevailing voice to the contrary, and the firm vote of a large majority to the effect that mind exists as well as matter. Taking the law of assimilation as the cosmical law, together with self-manifesting power as the characteristic of being, we reach a primary classification of created objects, which corresponds with that which is known as mind and matter--or rather let us say mind and that which is not mind; for there is ground for the apprehension that mind and matter do not include all that exists; and that, along with matter, ether ought to be considered as something intimately related to matter indeed, but yet not just matter. When the elements of the ethereal medium are regarded as truly and simply material, however small and light they may be, the elasticity and pressure which must be assigned to that medium in order to admit of the velocity of light, are altogether out of the harmony of things, and wholly incredible, especially when confronted with the phenomena and the theory of astronomy. Thus, to justify the velocity of light on the same principles as those of sound, in various material media, the ethereal pressure must be 122,400,000,000 times greater than that of the atmosphere--which is incredible, says Macvicar. But what as to mind? To find what shall be called mind, let us suppose an individualized object which is not an isolated object, or a universe to itself, but a member in a system; then, in obedience to what has been stated, that object must be at once self-manifesting and impressed by the other objects around it, and, in being so impressed, assimilated to them more or less.... Admitting the self-manifesting power to be sensitive, percipient, or conscious, then quantity or intensity of substance or power in a monad is the condition requisite for feeling and thought. And thus, by an immediate co-ordination of our fundamental ideas of self-manifesting power and assimilative action, more or less, we reach a distinct conception of mind viewed in relation with that which is not mind. By this deduction, the primeval created substance, the true protoplasm is still supposed to be homogeneous, animated by its assimilation to the everlasting, the Infinite. This protoplasm is partitioned in varying degrees so that there are in creation some individualized or separate objects or forces consisting of so small an amount or such weakness of substance that they are wholly fixed and merely perceptible, while there are others consisting of so much more that they are free in their inner life, and have power to perceive themselves also--not, indeed, in the centres of their being, and as unimpressed and without ideas, but as members in a system, impressed or assimilated by other objects, and so having ideas, with power to look in this direction or that, and to act accordingly. Such, then, according to Macvicar, is the nature of mind or spirit. It is a being so constituted as to be at once in possession of ideas, and so far fixed; and also in possession of undetermined life or activity, and so far free. These are, as it were, the opposite poles of its being, and the conditions of its activity. If either is wanting, the other vanishes. Without something fixed in the mind, some object of thought or feeling, there can be no thinking or feeling. Without something unfixed there can be nothing to think or to feel with, much less can there be any thinking or feeling of self--that is, self-consciousness. But, grant this condition in the individual, and add the law of assimilation, operating first from God above, thus giving reason and conscience, on the higher aspect of our being; and, secondly, from nature around, thus giving observation and instincts harmonious with our situation in the system of the universe, and then human nature emerges. But human nature plainly belongs to the last day of the work of creation rather than the first, where we are now. In man, to all appearance, the organism is the mother and nurse of the spirit. And though the assimilative action of the mind upon the body becomes normally, at least, stronger and stronger as life advances, so long as the organ retains all its perfection, yet at first the assimilative action of the body upon the mind is almost everything. The infant, the child, is little else but the victim of sensation--that is, of assimilations in its mind, effected by the force of external nature, including the organism itself. But as the mind, through the sustained action towards the focus of the myo-neuro-cerebral system, which is in the brain, gains quantity or intensity--in one word, energy--it becomes more independent and free, and more able to react out of itself upon the organism in any direction of which it makes choice.... Hitherto, Macvicar has proceeded analytically, or from the one to the many; now, synthetically, from multiplicity to unity:--he continues:--As to the matter in hand, we may say, shortly, that a world of substances becoming multiple and diffuse, and at last merging into ethereal elements, being now given as the product of the law of assimilation in reference to the immensity of the Creator, the same law, when viewed in reference to the unity of the Creator, leads us to infer a process of quite a contrary character. It leads us to expect to find the ethereal elements tending to construct unities of greater energy than themselves. Then, if all cosmical action is cyclical, matter, when existing free in the ether, must ultimately tend to dissolve into pure ether again; for, if the law of creation is as a cycle, in which, after development and as its fruit, the last term gives the first, then has he grounds for his conjecture that complication in structure is necessary to the segregation of nervous matter, and the construction of a "myo-neuro-cerebral system"; and that ether and matter, after developing a molecular economy, as the mother and nurse of a soul or monad of a higher order than the merely material element, through or by this organism, complete the cycle of the economy of the material nature, and eventually touch upon the spiritual world again and contribute to it. Whether this inference is correct or not, it presents a noble hypothesis for consideration, and one which should command attention at a time when the writings of John Worrell Keely, the discoverer of polar energy, and the inventor of vibratory machinery for the utilization of this force in mechanics, are about to be given to the world, supporting as they do, some of "the unwelcome views" advanced by Macvicar a quarter of a century ago. Although Macvicar and Keely differ in their theories of molecular morphology, they agree entirely in calling the cosmical law of sympathetic association or assimilation the watchword and the law of creation. This true protoplasm, the ether, which Macvicar postulated, Keely claims to have proved "a reality": making use of the ether, which he liberates by vibratory machinery, as the medium of a motive power, which he calls "sympathetic negative attraction." CHAPTER III. THE NATURE OF KEELY'S PROBLEMS. 1885 TO 1887. Too few the helpers on the road, Too heavy burdens in the load. When a movement is willed a current is sent forth from the brain. Sir James Crichton Browne. In November 1884, Mr. Keely obtained a standard for progressive research in the success of an experiment, which he had tried many times before, without arriving at the result that his theories had led him to expect. One of those present, at the time that this test was made, afterwards wrote to Mr. Keely, to obtain an explanation of the dynamic force which had been witnessed, causing a small globe to rotate when two persons had taken hold of the rod together, with a firm grasp; one of whom was standing on a circular sheet of metal, from which piano wires stretched toward the globe, near enough to touch one of the plates of glass which insulated the ball. Mr. Keely replied, "I cannot describe it other than the receptive concussion of the two forces, positive and negative, coming together, seeking their coincidents and thus producing rotation by harmonious waves, not streams. You ask if sound waves had anything to do with the motion of the globe? Nothing; the introductory settings are entirely different. The ball ceased to rotate when I took your left hand in my right hand, while with our other hands holding the iron rod resting on the metal plate, because the receptive flows became independent of the circular chord of resonation as set up mechanically. The power of rotation comes on the positive; and the power of negation breaks it up."... Encouraged by this confirmation of his theories, Keely pursued his researches with renewed vigour. At this time he wrote, "I am straining every nerve to accomplish certain matters in a given time, working from twelve to fourteen hours daily. Although in my illness I have had some peaceful hours in thinking over the fascinating points associated with the researches to which I am devoting my life, I have also had some very stormy ones in reviewing the many unjust insinuations and denouncements that have been heaped upon me by the ignorant and the base-hearted. My one desire has been the acquisition of knowledge; and, no matter how great the impediment thrown in my path, I will work without ceasing to attain my end. After struggling for over seventeen years, allowing scientists to examine my machinery in the most thorough manner, and to make the most sensitive tests, denunciations have multiplied against me. One charge is that I use sodium in my mercury, in the vacuum test. I have thought that I would never again make any effort to prove that I am honest; but I am working in a new lead, and for the satisfaction of the few friends that I have I propose to show my introductory evolutions, in proof of the negatization of an etheric substance to produce vacuum. The mercury may be delivered to me by an expert: I will operate from an open mercury bath: using the most perfect mercury gauge obtainable, attached to the same sphere that the column is operated from. Professor Rogers, the highest authority we have, saw the operation of inducing these etheric vacuums and pronounced the result wonderful. He said that the scientific world would go down on its knees, if I produced only one pound of vacuum under the conditions named. I showed from one to fourteen lbs. during the evolutions.... As soon as I have been able to combine all the positive and negative forces of etheric vibration in the triple vibratory sphere-engine that I am now at work upon, in short, as soon as I have completed a perfect, patentable machine, then my labours will cease on the Motor line; and after my patents are taken out, I will devote the remainder of my life to Aerial Navigation, for I have the only true system to make it an entire success in the vibratory lift and the vibratory push-process." It will be seen that, at this stage, Keely had no idea of giving up the engine; and was still as confident of ultimate success as in the beginning. There is no doubt that, had not the time arrived when the directing power of Providence led him away in quite another direction from the line that he was then working upon, his system for Aerial Navigation would have been lost to this century. "The heart of man deviseth his way, but the Lord directs his steps." About this time Keely met with an accident. Under date March 22nd, he wrote, "It has been impossible for me to write, my right hand and arm were so severely strained, but I have not been idle. I have had time for reflection, and I have been setting up a key to explain vibratory rotation. I have also a plan for a device to be attached to the Liberator as an indicator to show when the neutral centre is free from its intensification while operating. In this way the dangerous influences will be avoided which present themselves on the extension of the vibratory waves that operate the gun. All the introductory details of the present engine are as perfect as is possible for the first lead. It is in the form of a sphere, about thirty inches in diameter and weighs 800 lbs. Yesterday saw the pure, positive action of my new Liberator. Mr. Collier and his brother George were present, and witnessed thirty expulsions, made by myself; after which I had them produce the vapour, by imitating my manipulations; which they were unable to do with the old generator. They were very much delighted. To say that the last three weeks have been trying ones, is using very mild language to express what I have suffered from accidents, disappointments, etc., etc. I have been frozen in at my workshop; and all things seemed to go wrong; but my present successes are as an anchor, which I thank God for, who, in His bountiful goodness, has carried me into a port of safety over tempestuous seas." Again, under various dates, Keely wrote:--"Unbounded success has crowned my new departure. I am now preparing new features that are necessary as adjuncts to denote the true condition, as regards safety in my different vibratory operations." "Without the aid sent me from on high there would have been nothing left of the discovery mechanically; nor would there now be a single foot-hold on which hope could rest for a completion of the Keely Motor enterprise."... "I had an accident to one of my registers this morning. It burst with a tremendous report, shaking things up in a lively way, but no other damage was done beyond that to the register." "The draughts are nearly completed for the compound vibratory engine, and next week the work will be commenced and pushed forward with all possible speed. This is the machine for continuous operation. The Liberator is as perfect as is possible; and, if the outside adjuncts are in proper sympathy, my struggles will soon be at an end."... "All things are verging into a condition of perfection through the aid that I have received, but for which the science of vibratory etheric force would, as far as my researches are concerned, have been lost to the world. I feel that the world is waiting for this force; that this advance in science is necessary to keep the proper equilibrium in our age of progress."... "There are moments in which I feel that I can measure the very stars, which shine like Edens in planetary space; fit abodes for beings who have made it the study of their lives on earth to create peace and happiness for all around them. Is nature a mystery? No, God is in nature. I do not believe in the line, 'God moves in a mysterious way His wonders to perform.' In my estimation, He moves in a very plain and simple way, if we will open our hearts to the understanding of His way. To the man who cannot appreciate the workings of nature, chemically and otherwise, God's ways may appear mysterious; but when he comes to know nature's works he will find simplicity itself in its highest order of expression. "Could I have one wish, as to science, gratified, I would ask to live long enough to be able to appreciate even but one etheric variation in planetary evolution. It might take fifty thousand years to attain this knowledge, but what is that period of time when compared with the cycles that have passed away since this earth existed? Yes, in one sense, 'God does move in a mysterious way His wonders to perform.'"... "The whirlpool of science has indeed engulphed me in its fascinating vortex."... "May 20th.--Yesterday was a day of trials and disappointments. It seemed as if nothing would work right. After labouring six hours to set my safety process, the first operation of the Liberator tore the caps all to pieces. I replaced them by a set of duplicates, and set the Liberator down to the low octaves, when everything worked to a charm. Night was approaching, and I left the workshop to get something to eat, returning about eight o'clock to re-conduct experiments, in order to discover if possible the cause of the sudden and most unexpected intensification. I followed up with great care the progressive lines until I reached the tenth octave, and then liberated a score of times, yet no variation on liberator. Next, I made an attachment to my safety arrangement, and also to my strongest resonator, to experiment on vibratory rotation with my shell; when, within two minutes, it attained a frightful velocity: then I suddenly retracted to the negative, bringing the velocity down from about 1500 per minute to 150. The operation was magnificent, lasting sixty-four minutes, when a second intensification took place, demolishing two safety-shells and one vibratory indicator. I was perfectly dumbfounded, and unable to account for such a phenomenon. It was then near midnight, but I had made up my mind not to discontinue until I had solved the mystery. After an hour's reflection, I set up a new position on the resonating wave plates in the forty resonating circuit on the base of liberator; and got a result which for purity of uniformity surpassed all experiments that I have ever made. I believe I have now struck the root of this difficulty, and that I shall be able to master it; and obtain continuity of action with perfect rotation." "June 1st, 1885.--I am in a perfect sea of mental and physical strain, intensified in anticipation of the near approach of final and complete success, and bombarded from all points of the compass by demands and inquiries; yet, in my researches, months pass as minutes. The immense mental and physical strain of the past few weeks, the struggles and disappointments have almost broken me up. Until the reaction took place, which followed my success, I could never have conceived the possibility of my becoming so reduced in strength as I am now. My labours in the future will be of a much milder character; but, before I again commence them, I must have a few days more of recuperation. I was so absorbed in my researches that I forgot my duty to myself, as regards the requirements of health, and I am now paying the penalty. It has been misery to me to have absorbed so much more time and capital than I anticipated; and without the heaven-sent aid which I have received the world would have lost sight of me for ever."... "In view of the unjust comments in certain journals, I intend to withdraw entirely from all contact with newspaper men, to give no more exhibitions after the one which closes the series, and to devote all my time and energies to bringing my models into a patentable condition. It is said that the New York reporters intended to denounce me before witnessing my last experiments. Certainly utter ignorance of my philosophy was displayed in their articles, but they were like the viper biting on the file, and only hurt themselves: for men who possess but a moderate degree of scientific knowledge have denounced them, in turn, as the most ignorant men they had ever come in contact with. They stated that I started with a power estimated at over one million pounds pressure to the square inch on the head of my liberator, a sheer absurdity. The rock I am standing on can no more be moved by a whirlwind of such attacks than the atmospheric disturbance of equilibrium emanating from a butterfly's wing in motion could blow down the rock of Gibraltar. I enclose a newspaper cutting: it was written by an engineer who has interested himself sufficiently in my work to be able to thoroughly understand my position."... "July 15th.--My researches teach me that electricity is but a certain condensed form of atomic vibration, a form showing only the introductory features which precede the etheric vibratory condition. It is a modulated force so conditioned, in its more modest flows, as to be susceptible of benefit to all organisms. Though destructive to a great degree in its explosive positions, it is the medium by which the whole system of organic nature is permeated beneficially; transfusing certain forms of inert matter with life-giving principles. It is to a certain degree an effluence of divinity; but only as the branch is to the tree. We have to go far beyond this condition to reach the pure etheric one, or the body of the tree. The Vibratory Etheric tree has many branches, and electricity is but one of them. Though it is a medium by which the operations of vital forces are performed, it cannot in my opinion be considered the soul of matter."... "My safety arrangements (governors and indicators) for liberating are not working well; but I am labouring to attain perfection on these devices, and I hope soon to have them all right."... "I have extraordinary powers, it is true, and I must use them to the best advantage; for I know they are the gift of the Almighty, who will, I feel sure, carry me to the end of the work which He has given me to accomplish."... "I am positive that this year will terminate my struggles. My work is all progressing satisfactorily, and I am pushing everything forward as rapidly as possible."... August 5th.--Mr. Keely wrote to one of his friends,--"I have met with an accident to the Liberator. I was experimenting on the third order of intensification, when the rotation on the circuit was thrown down in the compound resonating chamber, which, by the instantaneous multiplication of the volume induced thereby, caused an explosion bursting the metal casing which enclosed the forty resonators, completely dismantling the Liberator. The shock took my senses from me for a few moments, but I was not even scratched this time. A part of the wall was torn away, and resonators and vibrators were thrown all over the room. The neighbourhood was quite lively for a time, but I quieted all fears by telling the frightened ones that I was only experimenting. I allowed everything to remain until Dr. Woods and Mr. Collier had seen the effect of the explosion." The orders of intensification for accelerating dissociation would not be understood by any explanations that could be made, if unaccompanied by the demonstrations witnessed by the late Professor Leidy, Dr. Brinton, and others. When the ether flows from a tube, its negative centre represents molecular sub-division, carrying interstitially (or between its molecules) the lowest order of liberated ozone. This is the first order of ozone and is wonderfully refreshing and vitalizing to those who breathe it. The second order, or atomic separation, releases a much higher grade of ozone; in fact, too pure for inhalation, as it produces insensibility. The third order, or etheric, is the one that has been (though attended with much danger to the operator) utilized by Keely in his carbon register to produce the circuit of high vibration that breaks up the molecular magnetism which is recognized as cohesion. The acceleration of these orders is governed by the introductory impulse on a certain combination of vibratory chords, arranged for this purpose in the instrument, with which Keely dissociates the elements of water; and which he calls a liberator. In molecular dissociation one fork of 620 is used, setting the chords on the first octave. In atomic separation, two forks: one of 620 and one of 630 per second; setting the chords on the second octave. In the etheric three forks: one of 620, one of 630, and one of 12,000, setting the chords on the third octave. Keely's Three Systems. My first system is the one which requires introductory mediums of differential gravities, air and water, to induce disturbance of equilibrium on the liberation of vapour, which only reached the inter-atomic position and was held there by the submersion of the molecular and atomic leads in the 'generator' I then used. It was impossible with these mediums to go beyond the atomic with this instrument; and I could not dispense with the water until my liberator was invented, nor reach the maximum of the full line of vibration. My first system embraces liberator engine and gun. "My second system of dissociation I consider complete, as far as the liberation of the ether is concerned, but not sufficiently complete, as yet, in its devices for indicating and governing the vibratory etheric circuit, to make it a safe medium. "My third system embraces aerial and sub-marine navigation. The experimental sphere intended to test the combination of the positive and negative rotation is nearly completed. ... "I have done everything that I could do to demonstrate the integrity of my inventions, and I will never again allow my devices to be submitted to examinations; not that I am afraid they will be stolen, but I do not wish to have the construction of my improved mechanical devices known until my patents are taken out. Nor will I ever again make a statement, specifying the time when certain work will be finished. If I thought to-morrow would end all my struggles on this system, I would not say so. I have been a great sufferer from my inability to keep my promises, fully believing in my power to keep them, and now I must and will prove that all is right before I promise. ... "The work on the vibratory engine is progressing rapidly. I spend an hour or two every day at the shop where my work is being done, examining every part of it critically as it is being put together. The safety arrangements which I am having attached to my liberator will greatly improve it. Its operation will now be conducted with a gum bulb instead of a violin bow, the pressure of which gives the introductory chord of impulse that vitalizes the whole machine. The chords will all be set in progressive sympathy from the first octave to the fortieth.... "I have been writing out some of my theories as to sound and odour. These two subjects have intensified me considerably of late, on account of the peculiar position they occupy in their lines of sub-division; as also the peculiar laws that govern them in their dissemination. I see the time approaching when I will be able to write up my system of the true philosophy of nature's grandest force, and have at my control the proper apparatus to analyze and demonstrate all the progressive links of transmittive sympathy from the crude molecular to the high etheric."... "December 17th, 1885.--The setting up of the circles for computing the different lines of etheric chords, in setting the vibratory conditions for continuity, requires close study. I feel convinced that a perfect solution of my difficulties will follow when this part of the work has been completed; and that, before many weeks have passed, a revelation will be unfolded that will startle the world; a revelation, so simple in its character, that the physicists will stand aghast, and perhaps feel humiliated by the nature of their efforts in the past to solve certain problems.... I find my chief trouble in chording up the masses of the different parts composing the negative centres. The negative centre is included in the one-third volume of shell or sphere, starting from the neutral axis or point of suspension. This point of suspension only becomes perfect when the rotation is established on the sphere. One hundred revolutions per minute is all the velocity required to neutralize the gravity of the central third with the velocity of the vibratory circuit at one hundred thousand per second. Taking all matters into consideration associated with the mechanical part of the enterprise, the month of January ought to find all completed, ready for sympathetic graduation. But I fear to be too sanguine when I remember the loss of time and the interferences from exhibitions to which I have been subjected in the past. I feel more and more the great importance of devoting all my energies to the great task that Divine Power has ordained me to perform."... At the close of the year 1885, everything seemed to promise full and complete success during the coming year. Mr. Charles Collier, the patent lawyer, shared Keely's confidence in the near completion of his "struggles." The stock-holders were enthusiastic, and the stockbrokers were on the qui vive, anticipating a great rise in the shares of The Keely Motor Company. Mr. Collier had written in August to Major Ricarde-Seaver [1]: "The Bank of England is not more solid than is our enterprise. My belief is that the present year will see us through, patents and all." The journals had ceased to ridicule, and some of them were giving serious attention to the possibilities lying hidden in the discovery of an unknown force. In 1886, Mr. William Walsh, editor of "Lippincott's Magazine," accepted a paper on the subject, publishing it in the September number. It was entitled Keely's Etheric Force. This was the first article accepted by any Philadelphia editor, setting forth Keely's claims on the public for the patience and protection which the discoverer of a force in nature needs, while researching the unknown laws that govern its operation. Up to this time Keely had been held responsible for the errors made in the premature organization of a Keely Motor Company, and the selling of stock before there was anything to give in return for the money paid in by investors. CHAPTER IV. SYMPATHETIC VIBRATORY FORCE, 1887. The teleological view was opposed to the mechanical, which regarded the universe as a collocation of mere facts without any further significance. The mechanical view looked backward to the antecedents of a phenomenon, and explained things by reducing them to their lowest terms; the teleological or philosophical view looked forward to the end or purpose which was being realized, which was the reason of the whole development, and in the deepest sense its cause. Mechanical explanation was an infinite progress, which could ultimately explain nothing; in the last resort, causæ efficientes pendent a finalibus. In defining the nature of the end which it thus asserted, philosophy had to wage unsparing battle against the naturalistic tendencies of our time.--(From a Review of Professor Seth's address delivered in Glasgow in 1891.) In 1887, a series of articles appeared in The British Mercantile Gazette, then edited by Mr. Arthur Goddard. The June number devoted more than eight columns to the progress and present position of the discoverer of Etheric Force. To the Editor of the British Mercantile Gazette. Sir,--Dr. Ziermann, a German writer, has said that a great deal of sound sense and moral courage are required to introduce ideas which will only be recognised as truth after the lapse of time. He adds, "Nay, even to recognize their truth will require more understanding than falls to the share of most men." The day will come, I think, when your action in giving the pages of your journal to quotations from Mr. Keely's papers on Etheric Physics and Etheric Philosophy, will make known your claim to this 'understanding.' In the meantime, you have, by your appreciation of his labours and your sympathy in his trials, extended that assistance to the discoverer of this newly-known force in Nature which is more powerful than any other agent in inspiring to renewed efforts; after ridicule and calumny, long continued, have done their worst towards depressing the vital centres of nerve-force. When Mr. Keely has made known the law of sympathetic association to the world, the full meaning of the words "sympathy," "help," "consolation," will be better understood than they are now. The most important discoveries, the most difficult problems of research, the most arduous scientific labours have been achieved by men who have battled with persecution and contempt at every step of their progress; enduring all, as he has done, with patience; in the full assurance that the glorious truths entrusted to him to reveal will, in the end, be proclaimed for the advancement of the race. "The nobler the soul," writes Ouida, "the more sensitive it is to the blows of injustice." Cicero tells us that praise stimulates great souls into greater exertions; and Plutarch said that souls are sensitive to sympathy, to praise, and to blame, in exact proportions to the fineness of their fibre. Mr. Keely proves this truth by actual tests, as will be seen in time, to the satisfaction of all investigators. Every branch of science, every doctrine of extensive application, has had its alphabet, its rudiments, its grammar; indeed, at each fresh step in the path of discovery, the researcher has to work out by experiments the unknown laws which govern his discovery. Ignorant himself, he builds up his knowledge upon a foundation which, uncertain as it must be at first, becomes as secure as that of Gibraltar rocks when, one by one, he has removed the misshapen stones of error, and replaced them with the hewn granite blocks of truth. To attempt to introduce scientists, without any previous preparation, to any new system, no matter how solid its foundation, would be like giving a book published in Greek to a man to read who had never before seen its characters. We do not expect a complicated problem in the higher mathematical analysis to be solved by one who is ignorant of the elementary rules of arithmetic. Just as futile would it be to expect scientists to comprehend the laws of etheric physics and etheric philosophy at one glance. 'There are some secrets which, who knows not now, Must, ere he reach them, climb the heapy Alps Of science, and devote long years to toil.' Norman Lockyer, in his 'Chemistry of the Sun,' writes of molecules that 'one feels as if dealing with something that is more like a mental than a physical attribute--a sort of expression of free will on the part of the molecules.' Herein lies one of the secrets of Mr. Keely's so-called 'compound secret.' Again, Mr. Lockyer writes: 'The law which connects radiation with absorption, and at once enables us to read the riddle set by the sun and stars, is, then, simply the law of sympathetic vibration.' This is the very corner-stone of Mr. Keely's philosophy--yes, even of his discovery. It has been said that all great men who have lived, or who now live, have been indebted for their knowledge to teachers or to books; but all progress depends upon the use made of such knowledge when acquired. In order to bear fruit, knowledge must be increased by reflection, and by placing the mind in that attitude which brings into play the powers of intuition; or, rather, placing it in the receptive state which admits of the in-flowing of what is called inspiration. Molecular vibration is Keely's legitimate field of research. In this field his discovery was made, many years since; but it is only now, within this year, that he has reached any approach to a solution of the stupendous problems which have arisen barring and baffling all progress, at times, towards the complete subjugation and control of the force that he had discovered. Again and again has he invited the attention of scientists to his discovery, from the commencement of his researches; but the few scientists who condescended to accept his invitations were so ignorant of the mysteries which they sought to investigate--of 'the alphabet and rudiments' of etheric physics--that they found it easier to accuse him of jugglery and of fraud than to account for the phenomena that they witnessed. They addressed their report to a public even more ignorant than themselves, if such a thing could be possible, with the result of preventing other scientists, who would have better understood the experiments, from examining into Keely's claims, as the discoverer of an unknown force. A system of doctrine can be legitimately refuted only upon its own principles, viz., by disproving its facts, and invalidating the principles deduced from them. It is, then, the facts, and not the opinions of the ignorant or the prejudiced, which are of chief importance here, as in all other questions of moment. All those men who have witnessed the production of etheric force and its application experimentally, during the exhibitions given at various times, have, if capable of understanding such a marvellous discovery as Keely has made, agreed to a man in bearing testimony, at the time, that no known force could have produced such results under the same conditions. It is now three years since Keely invited certain English men of science (experimenting in the same field where his explorations commenced) to examine his Liberator; which was dismantled for the purpose, and all its parts assembled for examination before being put together for the production of etheric force, when these men refused to visit his workshop, and it has been said that a Professor of the University of Pennsylvania prevented the investigation by his assertion that compressed air is the force used by Keely with which to dupe his audiences. A schoolboy's knowledge of the change of temperature always accompanying the compression of air would prevent such an assertion from being made by anyone who had witnessed the operation of the Liberator in the production and storage of etheric force, during which there is not the slightest change of temperature. Had these English scientists, with their knowledge of acoustics, been present on the occasion referred to, no such groundless assertion would have possessed any influence with either; and the world of science would have sooner known and acknowledged the nature and the worth of this great discovery. Roget says that if we are to reason at all, we can reason only upon the principle that for every effect there must exist a corresponding cause; or, in other words, that there is an established and invariable order of sequence among the changes which take place in the universe. The bar to all further reasoning lies in the fact that there are men who, admitting all the phenomena we behold are the effects of certain causes, still say that these causes are utterly unknown to us, and that their discovery is wholly beyond the reach of our faculties. Those who urge this do not seem to be aware that its general application in every sense would shake the foundation of every kind of knowledge--even that which we regard as built upon the most solid basis. Of causation it is agreed that we know nothing; all that we do know is that one event succeeds another with undeviating constancy; and what do we know of magnetism, electricity, galvanism, but such facts as have been elicited by the labours of experimental enquirers, and the laws which have been deduced from their generalization? Would it be considered a sufficient reason for the absolute rejection of any of these facts--or a whole class of facts--that we are still ignorant of the principle upon which they depend, and that such knowledge is beyond our reach? Facts are every day believed, upon observation, or upon testimony, which we should be exceedingly puzzled to account for, if called upon to do so. Every man who has passed the mere threshold of science ought to be aware that it is quite possible to be in possession of a series of facts, long before he is capable of giving a rational and satisfactory explanation of them; in short, before he is enabled to discover their causes. Also that he must classify his facts and construct hypotheses before he can impart his experimental position to others. Many things which were, for a long time, treated as fabulous and incredible have been proved, in our age, to be authentic facts, as soon as the evidence in support of them was duly subjected to the crucible of scientific investigation. Take, for example, Professor Dewar's researches in the cause, or origin, of meteoric stones. Fortunately for his branches of research and experiment, he is possessed of that philosophical spirit and energy which enables him to divest himself of all prejudice, and, in constructing his theories, to welcome the evidence of truth from whatever quarter it approaches. More than two thousand years elapsed between the first record of the phenomenon, by Anaxagoras, and Mr. Howard's observations in 1802, during which time the fact was disputed most strenuously by many, while, in our time, Professor Dewar's explanations of the same, upon intelligible and satisfactory principles, have confirmed the statements made centuries ago. How few the years, in comparison, since Keely's grand discovery first broke upon his own mind, which he has devoted to experiment, to invention, to the classification of facts, and the building up of hypotheses, before reaching the goal of his desires. Men will marvel at the shortness of the period when all that he has accomplished is made known. The delays which have occurred in bringing before the world the actual discovery of this primal force, from which all the forces of nature spring, have been in part occasioned by the want of that sympathy and appreciation which Keely would have received from his fellow-men, had scientists believed him to be honest in his claims. He would not then have been left in the merciless hands of "a ring," which gave or withheld financial aid according as he could be "thumbscrewed," into giving exhibitions for speculative ends on the part of "the ring." These costly days of delay are now a thing of the past. Keely's programme of work for the remainder of the year embraces such exhibitions of his progress as can be given without interfering with this programme. Coleridge says in "Table Talk,"--"I have seen what I am certain I would not have believed on your telling; and in all reason, therefore, I can neither expect nor wish that you should believe on mine." It is of all tasks the most difficult to procure any favourable reception for doctrines which are objectionable only because they are deemed to be incompatible with preconceived notions. It does not answer to disturb the calmness of views now held by our most eminent physicists, who seem to expect that nature will always accommodate her operations to their preconceived notions of possibility, and adapt her phenomena to their arbitrary systems of philosophy. We are all familiar with the anecdote of the wise Indian potentate who imagined that his informant was imposing upon his credulity when giving him an accurate description of the steam-engine. Now what would be thought of that philosopher who, in attempting to communicate an adequate idea of the operation of the steam-engine, should content himself with a mere description of its mechanism--of its wheels and levers, and cylinders and pistons--keeping entirely out of view the moving power--the steam; and ridiculing all investigation into the nature, application, and phenomena of this power. Yet this is exactly what microscopic observers of the animal economy call "absurd and useless inquiry." The true springs of our organization are not these muscles, these arteries, these nerves, which are described and experimented upon with so much care and exactness. They are hidden springs, the action of which are as miracles to those who have vainly tried to account for the motion of the muscles at the command of the will; for the power of vision, which places the human eye in intimate and immediate connection with the soul--dependent as they are upon unknown laws, assigned them by the great, omniscient and omnipotent Being by whom they were originally created, and Who is the one source of all power. Although in our present ordinary state of existence we are permitted to see only "as through a glass darkly," ignorant of many of the powers and processes of nature, as well as of the causes to which they are to be ascribed, we are not, therefore, entitled to set limits to her operations, and to say to her, "Hitherto shalt thou go, and no further! "We must not presume, says Glanvill, to assign bounds to the exercise of the power of the Almighty, nor are these operations and that power to be controlled by the arbitrary theories and capricious fancies of man. We are surrounded by the incredible--the seemingly miraculous. Who would not ask for demonstration when told that a gnat's wing, in its ordinary flight, beats many hundred times in a second? But what is this, when compared to the astonishing truths which modern optical inquiries reveal--such as teach us that the sensation of violet light affects our eyes 707 millions of millions of times per second in order to effect that sensation? How strangely must they estimate nature, how highly must they value their own conceits, who deny the possibility of any cause of any effect, merely because it is incomprehensible. In fact, what do men comprehend? What do they know of causes? When Newton said that gravitation held the world together, he assigned no reason why the heavenly bodies do not fly off from each other into infinite space. The discoverer of etheric force is able to give the reasons for, and the explanations of, the laws involved in all that he asserts; or, rather, all that he propounds; for, with the true humility of wisdom, he asserts nothing. Newton at first thought that he had discovered in electricity the ether which he asserted pervades all nature, until, by repeated experiments, he became convinced of the insufficiency of that principle to explain the phenomena. Other philosophers have speculated upon magnetism in the same way, and upon the similarity between magnetism and electricity. Mr. Keely's experiments show that the two are, in part, antagonistic, and that both are but modifications of the one force in nature. There have been some physiologists who have maintained that the nerves are merely the conductors of some fluid from the brain and spinal cord to the different parts of the body, and that this circulating fluid is capable of an external expansion, which takes place with such energy as to form an atmosphere, or sphere of activity, similar to that of electrical bodies. Dr. Roget observes that the velocity with which the nerves subservient to sensation transmit the impressions they receive at one extremity, along their whole course, exceeds all measurement, and can be compared only to that of electricity passing along a conducting wire. A comparison with gravity would have been nearer the truth, though no computation ever has been made, or ever can be made, between the flight of gravity and of electricity, so infinitely swifter is the former. Béclard almost completely demonstrated the truth of Roget's hypothesis concerning the action of "the nervous fluid" by cutting a nerve of considerable size, adjoining a muscle, which induced paralysis in this part. Perceiving the contractile action reappear, when he approached the two ends of the nerve to the distance of three lines, he became convinced that an imponderable substance, a fluid of some kind, traversed the interval of separation, in order to restore the muscular action. By another experiment he demonstrated its striking analogy to galvanic electricity. The late Professor Keil, of Jena, also made some very interesting experiments of the same character, one of which tends to demonstrate the susceptibility of the nervous system to the magnetic influence, and the efficacy of the magnet in the cure of certain infirmities. It was communicated by him to a meeting of the Royal Society of London more than fifty years since. If we are justified, then, in assuming the existence of this nervous fluid, writes Colquhoun, in 1836, whether secreted by, or merely conducted by the nerves, and of its analogy to the other known, active, and imponderable fluids, and of its capability of external expansion, as in the case of electricity, it does not appear to be a very violent or unwarrantable proceeding to extend the hypothesis a little further, and to infer that it is also capable of being transmitted or directed outwards, either involuntarily or by the volition of one individual, with such energy as to produce certain real and perceptible effects upon the organism of another, in a manner analogous to what is known to occur in the case of the torpedo the gymnotus-electricus, etc. Should it be that Mr. Keely's compound secret includes any explanation of this operation of will-force, showing that it may be cultivated, in common with the other powers which God has given us, we shall then recover some of the knowledge lost out of the world, or retained only in gipsy tribes and among Indian adepts. The effects of the law of sympathetic association, which Mr. Keely demonstrates as the governing medium of the universe, find illustrations in inanimate nature. What else is the influence which one string of a lute has upon a string of another lute when a stroke upon it causes a proportionable motion and sound in the sympathizing consort, which is distant from it, and not perceptibly touched? It has been found that, in a watchmaker's shop, the timepieces, or clocks, connected with the same wall or shelf, have such a sympathetic effect in keeping time, that they stop those which beat in irregular time; and, if any are at rest, set those going which beat accurately. Norman Lockyer deals with the law of sympathetic association as follows:--"While in the giving out of light we are dealing with molecular vibration taking place so energetically as to give rise to luminous radiation, absorption phenomena afford no evidence of this motion of the molecules when their vibrations are far less violent."... "The molecules are so apt to vibrate each in its own period that they will take up vibrations from light which is passing among them, provided always that the light thus passing among them contains the proper vibrations."... "Let us try to get a mental image of what goes on. There is an experiment in the world of sound which will help us."... "Take two large tuning-forks, mounted on sounding-boxes, and tuned to exact unison. One of the forks is set in active vibration by means of a fiddle-bow, and then brought near to the other one, the open mouths presented to each other. After a few moments, if the fork originally sounded is damped to stop its sound, it will be found that the other fork has taken up the vibration, and is sounding distinctly. If the two forks are not in unison, no amount of bowing of the one will have the slightest effect in producing sound from the other." Although physicists know that this extraordinary influence exists between inanimate objects as a class, they look upon the human organism as little more than a machine, taking small interest in researches which evince the dominion of mind over matter. Keely's experimental research in this province has shown him that it is neither the electric nor the magnetic flow, but the etheric, which sends its current along our nerves; that the electric or the magnetic bears an infinitely small ratio to that of an etheric flow, both as to velocity and tenuity; that true coincidents can exist between any mediums--cartilage to steel, steel to wood, wood to stone, and stone to cartilage; that the same influence (sympathetic association) which governs all the solids holds the same governing influence over all liquids; and again, from liquid to solid, embracing the three kingdoms, animal, vegetable and mineral; that the action of mind over matter thoroughly substantiates these incontrovertible laws of sympathetic etheric influence; that the only true medium which exists in nature is the sympathetic flow emanating from the normal human brain, governing correctly the graduating and setting-up of the true sympathetic vibratory positions in machinery necessary to success; that these flows come in on the order of the fifth and seventh positions of atomic subdivision, compound ether a resultant of this subdivision; that, if metallic mediums are brought under the influence of this sympathetic flow they become organisms which carry the same influence with them that the human brain does over living physical positions--that the composition of the metallic and of the physical are one and the same thing, although the molecular arrangement of the physical may be entirely opposite to the metallic on their aggregations; that the harmonious chords induced by sympathetic positive vibration permeate the molecules in each, notwithstanding, and bring about the perfect equation of any differentiation that may exist--in one, the same as in the other--and thus they become one and the same medium [2] for sympathetic transmission; that the etheric flow is of a tenuity coincident to the condition governing the seventh subdivision of matter--a condition of subtlety that readily and instantaneously permeates all forms of aggregated matter, from air to solid hammered steel--the velocity of the permeation being the same with the one as with the other; that the tenuity of the etheric flow is so infinitely fine that any magnifying glass, the power of which would enlarge the smallest grain of sand to the size of the sun, brought to bear upon it, would not make it visible to us; that light, traversing at the speed of 200,000 miles per second a distance requiring a thousand centuries to reach, would be traversed by the etheric flow in an indefinite fragment of a second. These are some of the problems which Mr. Keely has had to solve before he could adapt his vibratory machinery to the etheric flow. The true conditions for transmitting it sympathetically through a differential wire of platinum and silver have now been attained, after eight years of intense study and elaborate experiment. The introductory indications began to show themselves about two years ago, but the intermissions on transmission were so frequent and so great as to discourage Mr. Keely from further research on this line. Then came one of those "inspirations" which men call "accident," revealing to him "the true conditions" necessary to produce a sympathetic flow, free of differentiation, proving conclusively the truth of his theory of the law governing the atomic triplets in their association. Differentiation, by compound negative vibration of their neutral centres, causes antagonism, and thus the great attractive power that aggregates them becomes one of dispersion or expansion, accompanied by immense velocity of rotation, which carries its influence through the whole volume of air, 230 cubic inches contained in sphere, within its 33 1/3 chord of its circle of coincidence. By this wire of platinum and silver the current of force is now passed to run the vibratory disk, thus altogether upsetting the "compressed air" theory of Professor Barker, Dr. Hall, and others of less note. "In setting the conditions of molecular sympathetic transmission by wire," writes Keely, "the same law calls for the harmonious adjustment of the thirds, to produce a non-intermittent flow of sympathy. Intermission means failure here. That differential molecular volume is required, in two different mediums of molecular density, to destroy differentiation of sympathetic flow, seems at first sight to controvert the very law established by the great Creator, which constitutes harmony--a paradoxical position which has heretofore misled physicists who have propounded and set forth most erroneous doctrines, because they have accepted the introductory conditions, discarding their sympathetic surroundings. The volume of the neutral centre of the earth is of no more magnitude than the one of a molecule: the sympathetic condition of one can be reached in the same time as the other by its coincident chord." Thus it will be seen what difficulties Keely has encountered in his persevering efforts to use the etheric flow in vibratory machinery. One by one he has conquered each, attaining the transmission of the etheric current in the same manner as the electric current, with this one notable difference--that, in order to show insulation to the sceptical, he passes the etheric current through blocks of glass in running his vibratory devices. When Keely's system is finished, then, and not until then, all that is involved in his discovery will be made known to the world. NOTE. Five years after this paper on Etheric force was written, Dr. Henry Wood, of Boston, wrote an article, which appeared in The Arena of October, 1891, having the title Healing through Mind. Dr. Wood says: "Truth may be considered as a rounded unit. Truths have various and unequal values, but each has its peculiar place, and if it be missing or distorted, the loss is not only local but general. Unity is made up of variety, and therein is completeness. Any honest search after truth is profitable, for thereby is made manifest the kingdom of the real.... "We forget that immaterial forces rule not only the invisible but the visible universe. Matter, whether in the vegetable, animal, or human organism, is moulded, shaped, and its quality determined by unseen forces back of and higher than itself. We rely upon the drug, because we can feel, taste, see, and smell it. We are colour-blind to invisible potency of a higher order, and practically conclude that it is non-existent."--Healing through Mind. CHAPTER V. ETHERIC VIBRATION. THE KEY FORCE. Discovery is not invention.--Edison. Science has been compared to a stately and wide-spreading tree, stretching outward and upward its ever-growing boughs. As yet mankind has reached only to its lowermost branches, too often satisfied with the dead calyxes which have fallen from it to the ground, after serving their uses for the protection of the vital germs of truth. The seed of the next advance in science can only germinate as the dry husk decays, within which its potentiality was secretly developed. For upwards of ten centuries false portions of the philosophy of Aristotle enslaved the minds of civilized Europe, only, at last, to perish and pass away like withered leaves. The most perfect system of philosophy must always be that which can reconcile and bring together the greatest number of facts that can come within the sphere of the subject. In this consists the sole glory of Newton, whose discovery rests upon no higher order of proof. In the words of Dr. Chalmers, "Authority scowled upon this discovery, taste was disgusted by it, and fashion was ashamed of it. All the beauteous speculation of former days was cruelly broken up by this new announcement of the better philosophy, and scattered like the fragments of an aerial vision, over which the past generations of the world had been slumbering in profound and pleasing reverie." Thus we see that time is no sure test of a doctrine, nor ages of ignorance any standard by which to measure a system. Facts can have a value only when properly represented and demonstrated by proof. Velpeau said nothing can lie like a fact. Sir Humphry Davy asserted that no one thing had so much checked the progress of philosophy as the confidence of teachers in delivering dogmas as facts, which it would be presumptuous to question. This reveals the spirit which made the crude physics of Aristotle the natural philosophy of Europe. The philosophy of vibratory rotation, which is yet to be propounded to the world, reveals the identity of facts which seem dissimilar, binding together into a system the most unconnected and unlike results of experience, apparently. John Worrell Keely, the discoverer of an unknown force and the propounder of a pure philosophy, learned at an early stage of his researches not to accept dogmas as truths, finding it safer to trust to that "inner light" which has guided him than to wander after the ignis fatuus of a false system. He has been like a traveller exploring an unknown zone in the shade of night, losing his way at times, but ever keeping before him the gleam of breaking day which dawned upon him at the start. Scientists have kept aloof from him, or, after superficial examinations, have branded him as "a modern Cagliostro," "a wizard," "a magician," and "a fraud." Calumnies he never stoops to answer, for he knows that when his last problem is solved to his own satisfaction his discovery and his inventions will defend him in trumpet tones around our globe. Buchanan says, "Who would expect a society of learned men, the special cultivators and guardians of science, as they claim to be, to know as much of the wonderful philosophy now developing as those who have no artificial reputation to risk in expressing an opinion, no false and inflated conceptions of dignity and stability to hold them back, and who stand ready to march on from truth to truth as fast and far as experimental demonstration can lead them?" Johnson tells us that the first care of the builder of a new system is to demolish the fabrics that are standing. But the cobwebs of age cannot be disturbed without rousing the bats, to whom daylight is death. When has Nature ever whispered her secrets but for the advancement of our race on that royal road which leads to the subjugation of the power she reveals? But not until the inspiration of thought has done its work in applying the power to mechanics, can the tyrant thus encountered be transformed into the slave. So was it with steam, so has it been with electricity, and so will it be with vibratory force. All experience shows that the steady progress of the patient study of what are termed Nature's laws does not attract public attention until there are some practical results. Professor Tyndall has said that the men who go close to the mouth of Nature and listen to her communications leave the discoveries they make for the benefit of posterity to be developed by practical men. The invention of vibratory machinery for the liberation and the operation in mechanics of sympathetic force is an instance where practical application of the discovery may be made by the discoverer. After years of experiments with this force, what does the public know of its nature? Nothing; for as yet no practical results have been obtained. Here is a power sustaining the same relations to electricity that the trunk of a tree does to its branches,--the discovery of which heralds to the scientific world possibilities affecting motive industries, such as should command the attention of all men; and yet it is known only as a theme for jest and ridicule and reproach! And why is this? Partly from the mismanagement of a prematurely-organized Keely Motor Company, and partly because men competent to judge for themselves have preferred to take the opinion of others not competent, instead of investigating each for himself. Attempts to interest scientists in the marvellous mechanism by which etheric force is evolved from the atmosphere have failed, even as Galileo failed at Padua to persuade the principal professor of philosophy there to look at the moon and planets through his glasses. The professor pertinaciously refused, as wrote Galileo to his friend Kepler. Mankind hate truth, said Lady Mary Montague: she should have said, mankind hate new truths. The most simple and rational advances in medical science have been received with scorn and derision, or with stupid censure. Harvey was nicknamed "the circulator" [3] after his discovery of the circulation of the blood,--which discovery was ridiculed by his colleagues and compeers. The same reception awaited Jenner's introduction of vaccination. The revelation of new truths is compared to the upheaval of rocks which reveal deeply-hidden strata. Stolid conservatism dislikes and avoids such facts, because they involve new thinking and disturb old theories. The leaden weight of scepticism drags down the minds of many, paralyzing their power of reasoning upon facts which reveal truth, from another standpoint than their own, with new simplicity and grandeur in the divine laws of the universe. Others there are, embracing the majority of mankind, according to Hazlitt, who stick to an opinion that they have long supported, and that supports them. But whenever a discovery or invention has made its way so well by itself as to achieve reputation, most people assert that they always believed in it from the first; and so will it be with Keely's inventions, in time. In our day so rapidly are anticipations realized and sanguine hopes converted into existing facts, one wonderful discovery followed by another, that it is strange to find men possessing any breadth of intellect rejecting truths from hearsay, instead of examining all things and holding fast to the truth. The laws of sympathetic association need only to be demonstrated and understood to carry conviction of their truth with them. They control our world and everything in it, from matter to spirit. They control all the systems of worlds in the universe; for they are the laws which Kepler predicted would in this century he revealed to man. The divine element is shown by these laws to be like the sun behind the clouds,--the source of all light, though itself unseen. Already the existence of this unknown force is as well established as was the expansive power of steam in the days when the world looked on and laughed at Rumsey and Fitch and Fulton while they were constructing their steamboats. Even when they were used for inland navigation, men of science declared ocean navigation by steam impracticable, up to the very hour of its consummation. In like manner with electricity, scientists declared an ocean telegraph impossible, asserting that the current strong enough to bear messages would melt the wires. Nothing could be more unpopular than railways were at their start. In England, Stephenson's were called "nuisances," and false prophets arose then (as now with Keely's inventions) to foretell their failure. It was predicted that they would soon be abandoned, and, if not given up, that they would starve the poor, destroy canal interests, crush thousands in fearful accidents, and cover the land with horror. When I say that the existence of this force is established, I do not mean that it is established by a favourable verdict from public opinion,--which, as Douglas Jerrold said, is but the average stupidity of mankind, and which is always steadily and persistently opposed to great and revolutionary discoveries. Establishment consists in convincing men competent to judge that the effects produced by etheric force could not be caused by any known force. And it is now years since such a verdict was first given, substantiated repeatedly since, by the testimony of men as incapable of fraud or collusion as is the discoverer himself. Newton, in discovering the existence of a force which we call gravity, did not pursue his investigations sufficiently far to proclaim a power which neutralizes or overcomes gravity, the existence of which Keely demonstrates in his vibratory-lift experiments. But it is one thing to discover a force in nature, and quite another thing to control it. It is one thing to lasso a wild horse, and quite another thing to subdue the animal, harness it, bridle it, and get the curb-bit in the mouth. Keely has lassoed his wild horse; he has harnessed it and bridled it; and when he has the bit in its place, this force will take its stand with steam and electricity, asking nothing, and giving more than science ever before conferred on the human race. The Home Journal of October 20th, 1886, contained a paper which possesses some interest as having been written at the time Mr. Keely was using what he called a "Liberator," which enabled him to dispense with the use of water; but he was obliged to return to his former method soon after. Etheric Vibration. The late editor of the New York Home Journal, noticing the preceding paper, which appeared in Lippincott's Magazine, asks:--"But is not this new force too mighty to be managed by mere earthly instruments, such as iron, copper, or lead? It is the key force, the one that presided over the creation of these very metals, and can it reasonably be expected to be caged and fettered by them? Can the bubble withstand the onset of the wave, of which it is a mere drift?" When lightning was first drawn from the clouds by Franklin, did it occur to any man living to predict that electricity (which Keely defines as a certain form of atomic vibration) could be stored, to use at will as a motive power? If atomic vibration can be made to serve the purposes of mechanics, why not etheric vibration? But let Keely answer for himself. Some years since he wrote as follows:--"In analyzing theoretically the mechanical standard necessary for a solution of the philosophy of 'Etheric Vibration,' and the systematic mechanism to produce a rotating circle of etheric force, I must admit that the phenomenon, as presented to myself, by seeming accident, after almost a lifetime of study, still partially holds itself to my understanding as paradoxical. After constructing many mechanical devices in my vain attempts to come more closely to what I term a radiaphonic vibratory position, with microphonic adjustments, I have only been able to reach a few true and standard positions, which I can satisfactorily analyze. There is but one principle underlying all, and this principle is the key to the problem." Keely continues with an explanation of the mechanism of his generator, which he invented and constructed for the multiplication of vibrations, under the disturbance of equilibrium by mediums of different specific gravities--air as one, water as the other. He has since abandoned the generator for a vibratory machine which he calls a "liberator," in which no water is used to develop the force: the disturbance of the equilibrium being effected by a medium thoroughly vibratory in its character. The vapour which Keely produces from this liberator is perfectly free from all humidity, thus giving it a tenuity which he had never been able to reach before, and of a character most desirable for the perfect and high lines of action. In the various improvements which Keely has made in his mechanism, feeling his way in the dark as it were, he sometimes speaks of having "stupidly stumbled over them," of "seeming accident," or "seeming chance," where another would call it "inspiration." "Providence sends chance, and man moulds it to his own design." The improvement upon the generator was conceived by Keely during his desperate struggles to effect a simultaneous action between the molecular and atomic leads--an action that was absolutely essential for the full line of continuation. This shorter and simpler way of reaching his desired end was suggested, in part, to him by a quotation from some one of our scientific writings, made in a letter that he received. I am not sure about this quotation, but I think it was: "Nature works with dual force, but at rest she is a unit." "In the image of God made He man," and in the image of man Keely has constructed his liberator. Not literally, but, as his vibrophone (for collecting the waves of sound and making each wave distinct from the other in tone when the "wave-plate" is struck after the sound has died away) is constructed after the human ear, so his liberator corresponds in its parts to the human head. But to return to the question asked in the Home Journal. "Can this subtle force reasonably be expected to be caged and fettered by mere earthly instruments? "This is the answer, as given by Keely himself: "You ask my opinion regarding my ultimate success in the practical use of etheric force. My faith is unbounded by doubts. The successful result is as positive as the revolutions of our globe, and comes under the great law which governs all nature's highest and grandest and most sensitive operations." Since Keely wrote the above lines he has had time to get discouraged, if he could know discouragement; but he has conquered too many of the stupendous problems, which barricaded his way in the past, not to feel equally sanguine now of eventual success in his last problem, viz. the attaining of continuity of action, which at the present time seems all but within his grasp. Some of his views may prove of interest at a time when his achievements are beginning to be a little better understood. Gravity he defines as transmittive inter-etheric force under immense etheric vibration. He continues:--The action of the mind itself is a vibratory etheric evolution, controlling the physical, its negative power being depreciatory in its effects, and its positive influence elevating. The idea of getting a power as tenuous as this under such control as to make it useful in mechanics is scouted by all physicists. And no wonder that it is so. But when the character of the velocity of etheric force, even in a molecule, is understood, the mind that comprehends it must succumb to its philosophy. To move suddenly a square inch of air, at the velocity of this vibratory circuit, on full line of graduation, and at a vibration only of 2,750,000 per second, would require a force at least of twenty-five times that of gunpowder. Taking the expansive force of gunpowder at 21,000 lbs. per square inch, it would be 525,000 lbs. per square inch. This is incomprehensible. The explosion of nitroglycerine, which has two and a half times less vibrations per second, when placed on the surface of a solid rock, will tear up the rock before disturbing the equilibrium of the air above it. The disturbance takes place after the explosion. To induce an action on a weight of only twenty grains, the weight of a small bird-shot, with a range of motion of but one inch, giving it an action of one million per second, would require the actual force of two and a half tons per second; or, in other words, ten-horse power per minute. Etheric vibration would move tons at the same velocity when submitted to the vibratory circuit. Thus, the finer the substance the greater the power and the velocity under such vibration. The vapour from the liberator, registered at 20,000 pounds per square inch, has a range of atomic motion of 1333 1/3 the diameter of the atmospheric molecule, with constant rotary vibratory action. At 10,000 pounds, 666 2/3; at 5000, 333 1/3; at 2500, 166 2/3; at 1250, 83 1/3; at 625, 41 2/3. The higher the range of atomic motion the greater is its tenuity, and the range is according to the registered pressure. This rule cannot be applied to any other vapour or gas at present known to scientists. The very evolution on the negative shows a vacuum of a much higher order than was ever produced before, thus confounding, to perfect blindness, all theories that have been brought to bear upon the situation, in its analysis. The highest vacuum known is 17 999999-1000000 pounds, or not quite 30 inches; but by this process etheric vacuums have been repeatedly produced of 50 to 57 inches; ranging down to 30 inches, or 15 pounds. All operations of nature have for their sensitizing centres of introductory action, triple vacuum evolutions. These evolutions are centred in what I call atomic triple revolutions, highly radiaphonic in their character, and thoroughly independent of all outside forces in their spheres of action. In fact, no conceivable power, however great, can break up their independent centres. So infinitely minute are they in their position that, within a circle that would enclose the smallest grain of sand, hundreds of billions of them perform, with infinite mathematical precision, their continuous vibratory revolution of inconceivable velocity. These triple centres are the very foundation of the universe, and the great Creator has, in His majestic designs, fixed them indissolubly in their position. Mathematically considered, the respective and relative motion of these atomic triplets, gravitating to and revolving around each other, is about one and one-third of their circumference. The problem of this action, when reduced to a mathematical analysis (presupposing taking it as the quadrature of the circle) would baffle the highest order of mathematical science known to bring it to a numerical equation. The requirement of every demonstration is that it shall give sufficient proof of the truth it asserts. Any demonstration which does less than this cannot be relied upon, and no demonstration ever made has done more than this. We ought to know that the possibilities of success are in proportion as the means applied are adequate or inadequate for the purpose; and, as different principles exist in various forms of matter, it is quite impossible to demonstrate every truth by the same means or the same principles. I look upon it as the prejudice of ignorance which exacts that every demonstration shall be given by a prescribed rule of science, as if the science of the present were thoroughly conversant with every principle that exists in nature. The majority of physicists exact this, though some of them know that these means are entirely inadequate. Every revolving body is impressed by nature with certain laws making it susceptible of the operation of force which, being applied, impels motion. These laws may all be expressed under the general term, "Forces," which, though various in their nature, possess an equalizing power; controlling each other (as in the case of the atomic triplets) in such a way that neither can predominate beyond a certain limit. Consequently, these bodies can never approach nearer each other than a fixed point: nor recede from each other beyond another certain point. Hence, these forces are, at some mean point, made perfectly equal, and therefore may be considered as but one force; therefore as but one element. It matters not that other and disturbing forces exist outside or inside the space these bodies revolve in, because if this force must be considered as acting uniformly--applying itself to each of these bodies in a way to produce a perfect equation on all, it is as if this outside force were non-existing. The true study of the Deity by man being in the observation of His marvellous works, the discovery of a fundamental, creative law of as wide and comprehensive grasp as would make this etheric vapour a tangible link between God and man would enable us to realize, in a measure, the actual existing working qualities of God Himself (speaking most reverentially) as he would those of a fellow-man. Such a link would constitute a base or superstructure of recognition, praise, worship and imitation, such as seems to underlie the whole Biblical structure as a foundation.--Keely. Dr. Macvicar, in his theories of the bearing of the cosmical law of assimilation on molecular action, says: "During this retreat of matter into ether in single material elements or units of weight, the molecules and masses from which such vaporization into the common vapour of matter is going on, may be expected to be phosphorescent." This surmise Keely has, over and over, demonstrated, as a fact; also showing how gravitation operates as a lever: etheric wave motion: concentration under vibratory concussion: and negative vacuous tenuity. Mrs. F. J. Hughes, writing upon "Tones and Colours," advances theories of her own, which correspond with those demonstrated by Keely. She writes, in a private letter: "I firmly believe that exactly the same laws as those which develop sound keep the heavenly bodies in their order. You can even trace the poles in sound. My great desire is for some philosophical mind to take up my views, as entirely gained from the Scriptures; and I am certain that they will be found to be the laws developing every natural science throughout the universe." Thus men and women in various parts of the world who still hold to their belief in and worship of God, are "standing on ground which is truly scientific, having nothing to fear from the progress of thought, in so far as it is entitled to the name of scientific--nay, are in a position to lead the way in all that can be justly so called." CHAPTER VI. THE FOUNTAIN HEAD OF FORCE. Those who occupy themselves with the mysteries of molecular vibration bear the victorious wreaths of successful discovery, and show that every atom teems with wonders not less incomprehensible than those of the vast and bright far-off suns.--Reynolds. The famous Keely motor, which has been hovering on the horizon of success for a decade, is but an attempt to repeat in an engine of metal the play of forces which goes on at the inmost focus of life, the human will, or in the cosmic spaces occupied only by the ultimate atoms. The engineer with his mallet shooting the cannon-ball by means of a few light taps on a receiver of depolarized atoms of water is only re-enacting the rôle of the will when with subtle blows it sets the nerve aura in vibration, and this goes on multiplying in force and sweep of muscle until the ball is thrown from the hand with a power proportionate to the one-man machinery. The inventor Keely seeks a more effective machinery; a combination of thousands of will-forces in a single arm, as it were. But he keeps the same vibrating principle, and the power in both cases is psychical. That is, in its last analysis.--George Perry. One eternal and immutable law embraces all things and all times.--Cicero. When the truth is made known, it will unwarp the complications of man's manufacture; and show everything in nature to be very simple.--David Sinclair, author of A New Creed.--Digby, Long & Co. A gradual change seems to be taking place in the minds of the well-informed in reference to the discoverer of, and experimenter with, etheric force--John Worrell Keely--which will in time remove the burden of accusations from him to those who are responsible for the load which he has had to carry. Those who know the most of Mr. Keely's philosophy, and of his inventions to apply this new force to mechanics, are the most sanguine as to his ultimate success. They say he is great enough in soul, wise enough in mind, and sublime enough in courage to overcome all difficulties, and to stand at last before the world as the greatest discoverer and inventor in the world:--that the hour demanded his coming--that he was not born for his great work before his appointed time. They predict that he will, with the hammer of science, demolish the idols of science; that the demonstration of the truth of his system will humble the pride of those scientists who are materialists, by revealing some of the mysteries which lie behind the world of matter; proving that physical disintegration affects only the mode, and not the existence, of individual consciousness. The discovery of vibratory etheric force, even though never utilized in mechanics, brings us upon the bridge which divides physical science from spiritual science, and opens up domains the grandeur and glory of which eye hath not seen, ear hath not heard, nor hath it entered into the mind of man to conceive. The few who understand the nature and the extent of Keely's vast researches say that he is about to give a new philosophy to the world, which will upset all other systems; they say that he knows what force is; and that he seeks to know what impels and fixes the neutral centre, which attracts to itself countless correlations of matter, until it becomes a world; that he is approaching the origin of life, of memory, and of death; and more, that he knows how ignorant he still is: possessing the humility of a little child who knows nothing of science. Such a philosopher deserves the appreciation and the encouragement of all who hold Truth as the one thing most worth living for--and dying for, if need be. What is etheric force? the inquirer asks. It is the soul of nature. It is the primal force from which all the forces of nature spring. Fichte writes: "The will is the living principle of the world of spirit, as motion is of the world of sense. I stand between two opposite worlds; the one visible, in which the act alone avails; the other invisible and incomprehensible, acted on only by the will. I am an effective force in both these worlds." Newton said that this subtle ether penetrates through all, even the hardest bodies, and is concealed in their substance. Through the strength and activity of this spirit, bodies attract each other, and adhere together when brought into contact. In it, and by it, distance is annihilated, and all objects touch each other. Through this "life spirit" light also flows, and is refracted and reflected, and warms bodies. Through it we are connected in sympathy with all other souls, and all the objects of nature, even to all the heavenly bodies. The word ether is from "aithô," to light up or kindle. According to Pythagoras and all the oldest philosophers, it was viewed as a divine luminous principle or substance, which permeates all things, and, at the same time, contains all things. They called it the astral light. The Germans call it the "Weltgeist," the breath of the Father, the Holy Ghost, the life-principle. The sheet-anchor of Keely's philosophy is, in the words of Hooker, one power, ever present, ever ruling, neglecting not the least, not quailing before the greatest: the lowest not excluded from its care, nor the highest exempted from its dominion. A power that presents itself to us as a force: the one force in nature, thrilling to its deepest heart, and flowing forth responsive to every call. A power which does all things, and assumes all forms; which has been called electricity in the storm, heat in the fire, magnetism in the iron bar, light in the taper, but ever one grand reality, one all-embracing law. Cosmical law at the fountain-head, suggesting that, as the Creator Himself is only one in substance, so also, primarily, will the creation be, to which He awards existence. The extreme simplicity of this deduction, made as it is in the face of all the variety and multiplicity of individualized objects that there are in the universe, seems to involve many difficulties. But, as Macvicar writes, different beings, whether classes or individuals, are known to us, not by any difference in their substance, but only by differences in their attributes. And since being or substance, and power or potentiality, differ from each other only in conception, only as the statical differs from the dynamical, it is reasonable, nay, in the circumstances it is alone legitimate, to suppose that it is not in virtue of some absolute difference in substance (for none appears), but only from differences in the quantity or intensity of substance or power in the individual, and from the variety of their build, that different individuals display such different potentialities or endowments as they do display; and come to be justly classified as they are into various orders of beings. Inasmuch as the Author of all is Himself a Spiritual Being, cosmical law leads us to expect that the type of created being shall be spirit also. Nor can Being in any object be so attenuated or so far removed from Him who filleth all in all, but it must surely retain an aura of the spiritual nature. This, then, is the corner-stone of Keely's philosophy--one power; one law; order and method reigning throughout creation; spirit controlling matter; as the divine order and law of creation, that the spiritual should govern the material,--that the whole realm of matter should be under the dominion of the world of spirit. When Keely's discovery has been made known to scientists, a new field of research will be opened up in the realm of Philosophy, where all eternal, physical, and metaphysical truths are correlated; for Philosophy has been well defined by Willcox as the science of that human thought which contains all human knowledges. He who possesses the structure of philosophic wisdom built up of all knowledges--grand and sublime--has a mental abode wherein to dwell which other men have not. Dr. Macvicar says:--"The nearer we ascend to the fountain-head of being and of action, the more magical must everything inevitably become, for that fountain-head is pure volition. And pure volition, as a cause, is precisely what is meant by magic; for by magic is merely meant a mode of producing a phenomenon without mechanical appliances--that is, without that seeming continuity of resisting parts and that leverage which satisfy our muscular sense and our imagination, and bring the phenomenon into the category of what we call 'the natural'--that is, the sphere of the elastic, the gravitating, the sphere into which the vis inertiæ is alone admitted." In Keely's philosophy, as in Dr. Macvicar's "Sketch of a Philosophy," the economy of creation is not regarded as a theory of development all in one direction, which is the popular supposition, but as a cycle in which, after development and as its fruit, the last term gives again the first. Herein is found the link by which the law of continuity is maintained throughout, and the cycle of things is made to be complete:--the link which is missing in the popular science of the day, with this very serious consequence, that, to keep the break out of sight, the entire doctrine of spirit and the spiritual world is ignored or denied altogether. Joseph Cook affirms that, "as science progresses, it draws nearer in all its forms to the proof of the spiritual origin of force--that is, of the divine immanence in natural law. God was not transiently present in nature--that is, in a mere creative moment; nor has He now left the world in a state of orphanage, bereft of a deific influence and care, but He is immanent in nature, as the Apostle Paul affirmed: In Him we live, and are moved, and have our being; as certainly as the unborn infant's life is that of the mother, so it is divinely true that somehow God's life includes ours." The philosophy of Keely sets forth the universal ether (denied by scientists in the last century to suit their views of the celestial spaces, which they declared to be a vacuum) as the medium by which our lives are included in God's life; demonstrating how it is that we live because He lives, and shall live as long as He exists: how our being is comprised in His, so that if we could suppose the divine life to come to an end, ours would terminate with it as surely--to compare great things with small--as a stream would cease to flow when its fountain is dried up; teaching that our existence may be distinct, but never separate from His, and that in the hidden depth of the soul there is somewhere a point where our individual being comes in contact with God, and is identified with the infinite life. "If extreme vicissitudes of belief on the part of men of science are evidence of uncertainty, it may be affirmed that, of all kinds of knowledge, none is more uncertain than science." The existence of the universal ether is now affirmed again, and must be affirmed, as one of the most elementary facts in physical science. Sir J. F. Herschel asserts that, supposing the ether to be analogous to other elastic media, an amount of it equal in quantity of matter to that which is contained in a cubic inch of air (which weighs about one-third of a grain), if enclosed in a cube of one inch in the side, would exert a bursting power of upwards of seventeen billions of pounds on each side of the cube, while common air exerts only fifteen pounds. It should not, therefore, be surprising to those who have witnessed the manifestations of etheric force, as exhibited by Keely in producing a pressure ranging from 8000 to 30,000 pounds to the square inch, when modern scientists support Herschel's views, as they do, unhesitatingly; rather should they be surprised at the marvellous perseverance which has kept Keely, in the face of every discouragement, true to his inspired mission; conquering every difficulty, surmounting every obstacle, and turning his mistakes into stepping-stones which have helped him to attain the goal he has, from the start, aimed at reaching--viz. the utilizing in mechanics of the power he discovered many years ago. Before the grandeur and glory of such an attainment, all things had to give way. Like a General who sees the fortress looming up in the distance which he must take to complete his victory, his horse's hoofs trampling the dead and dying in his path, so has this discoverer and inventor been unmindful of all that lay between him and his goal. Taking for the key-note of his experiments, in applying inter-molecular vapour to the running of an engine, that all the movements of elastic elements are rhythmical, he has had problems to solve which needed the full measure of inspiration he has received before he could attain that degree of success which he has now reached. Mr. Keely realizes the full extent of the difficulties which he yet has to contend with in obtaining continuity of action, though, with his sanguine temperament, anticipating near and complete success. To quote from his writings:--"The mathematics of vibratory etheric science, both pure and applied, require long and arduous research. It seems to me that no man's life is sufficient, with the most intense application, to cover more than the introductory branch. The theory of elliptic functions, the calculus of probabilities, are but as pigmies in comparison to a science which requires the utmost tension of the human mind to grasp. But let us wait patiently for the light that will come--that is even now dawning." All we can dream of loveliness within, All ever hoped for by a will intense, This shall one day be palpable to sense, And earth at last become to heaven akin. These four lines, from Robert Browning's sonnet on Keely's discoveries, read like an inspired insight into that "Age of Harmony," which interpreters of scripture prophecies anticipate the twentieth century will usher into our world; recalling Shakespeare's seeming knowledge, before Harvey's discovery even, of the circulation of the blood. "All truth is inspired." CHAPTER VII. THE KEY TO THE PROBLEMS. KEELY'S SECRETS. Causa latet, vis est notissima.--Proverb. (The cause is hidden, the power is most apparent.) Electricity is in principle as material as water; so it appears, and Mr. Carl Hering has expressed the fact with much of clearness and force. He says, "It is a well-known fact that the quantity of electricity measured in coulombs never is generated, never is consumed, and never does grow less, excepting leakage. The current flowing out of a lamp is exactly the same in quantity as that going into it; the same is true of motors and of generators, showing that electricity of itself is neither consumed while doing work nor is it generated. After doing work in a lamp or motor, it comes out in precisely the same quantity as it entered. A battery is not able to generate quantity or coulombs of electricity; all it is able to do is to take the quantity which pours in at one pole, and sends out at the other pole with an increased pressure. Electricity, therefore, is not merely force (or a form of energy), but matter. It is precisely analogous to water in a water circuit....--The Court Journal. The theory of Aristotle concerning heat, viz. that it is a condition of matter, together with the dicta of Locke, Davy, Rumford, and Tyndall, have been consigned of late by many to the tomb of exploded theories, and are replaced by those of Lavoisier and Black, which make caloric an actual substance. The Rev. J. J. Smith, M.A., D.D., tells us that the only way the great problem of the universe can ever be scientifically solved is by studying, and arriving at just conclusions with regard to, the true nature and character of force. He maintains, in his paper upon "The Unity and Origin of Force," that, as it is the great organizer of matter, it must not only be superior to it, but also must have been prior, as it existed before organization commenced, and immanent always. Newton, who scoffed at Epicurus's idea that "gravitation is essential and inherent in matter," asserted that gravity must be caused by an agent acting, constantly, according to certain laws. Heat, gravity, light, electricity, magnetism, chemical affinities, are all different phases of the primal force discovered by Keely, and all these forces, it is said, can be obtained from a single ray of sunlight. "The evidence of unity or oneness even between the physical, vital, mental, and spiritual is seen in the light of this law of correlation," says Smith. "A great portion of our muscles contract and relax in obedience to our wills, thereby proving that the mental force can be, and is, in every such instance actually converted into the muscular or the physical." Keely demonstrates the truth of this assertion, claiming that "all forces are indestructible, immaterial, and homogeneous entities, having their origin and unity in one great intelligent personal will force." The Duke of Argyll says:--"We know nothing of the ultimate seat of force. Science, in the modern doctrine of conservation of energy, and the convertibility of forces, is already getting something like a firm hold of the idea that all kinds of forces are but forms or manifestations of some one central force, issuing from some one fountain-head of power." It is Keely's province to prove to materialists--to the world--that this one fountain-head is none other than the Omnipotent and all-pervading Will-Force of the Almighty, "which upholds, guides, and governs, not only our world, but the entire universe. This important truth is destined to shiver the tottering fabric of materialism into fragments at no distant day." Professor George Bush writes:--"The progress of scientific research, at the present day, has distinguished itself not less by the wideness of the field over which its triumphs have spread, than by the soundness and certainty of the inductions by which it is sustained. It is equally indisputable that we are approximating the true philosophy which underlies the enlarged and enlarging spiritual experiences and phenomena of the current age. That this philosophy, when reached, will conduct us into the realm of the spiritual as the true region of causes, and disclose new and unthought-of relations between the world of matter and of mind, is doubtless a very reasonable anticipation, and one that even now is widely, though vaguely, entertained." The Egyptians worshipped Ra, their name for the sun, and Ammon, the emblem of a mysterious power concealed from human perception. The Supreme Being is the grand central spiritual sun, the source and centre of all life, "whose revelation is traced in imperishable figures of universal harmony on the face of Cosmos." "The outward visible world is but the clothing of the invisible," wrote Coleridge. "The whole world process, in its content," says von Hartmann, "is only a logical process; but in its existence a continued act of will." Lilly continues, "That is what physical law means. Reason and Will are inseparably united in the universe, as they are in idea. If we will anything, it is for some reason. In contemplating the structure of the universe, we cannot resist the conclusion that the whole is founded upon a distinct idea." Keely demonstrates the harmony of this "distinct idea" throughout creation, and shows us that "the sun is the visible effluence and agent, earthward, of the Being without whose prior design and decree there would be no order and no systematic rule on earth," as well as that in "the universal ether" we find the link between mind and matter. "There is more of heaven than of earth, in all terrestrial things; more of spirit than of matter in what are termed material laws." Lange, with prophetic tongue, says that this age of materialism may prove to be but the stillness before the storm which bursts from unknown gulfs to give a new shape to the world. Inch by inch, step by step, physical science has marched towards its desired goal--the verge of physical nature, says Alcott. When it was thought that the verge was reached, that the mysteries which lay beyond were for ever barred to mortals by the iron gate of death, then the discoveries of Faraday, Edison, and Crookes pushed further away the chasm which separates the confessedly knowable from the fancied unknowable, and whole domains previously undreamt of were suddenly exposed to view. Not long since, Canon Wilberforce asked Keely what would become of his discovery and his inventions in case of his death before they became of commercial value to the public. Keely replied that he had written thousands of pages, which he hoped would, in such an event, be mastered by some mind capable of pursuing his researches to practical ends; but in the opinion of the writer, there is no man living who is fitted for this work. Diogenes of Apollonia identified the reason that regulated the world with the original substance, air. Keely teaches that "the original substance" is ether, not air; and that the world is regulated through this ether by its Creator. There are many molecules which contain no air--not one molecule that does not contain the one true "original substance," ether. Up to 1888 Keely was still pursuing the wrong line of research, still trying to construct an engine which could hold the ether in "a rotating circle of etheric force;" still ignorant of the impossibility of ever reaching commercial success on that line. It was the end of the year before he could be brought to entirely abandon his "perfect engine;" and to confine himself to researches, which he had been pursuing in connection with his repeated failures on the commercial line, to gain more knowledge of the laws which govern the operation of the force that, like a "Will-o'-the-wisp," seemed to delight in leading him astray. Up to this time his researching devices had been principally of his own construction; but from the time that he devoted himself to the line of research, marked out for him to follow, he was supplied with the best instruments that opticians could make for him after the models or designs which he furnished. If, from 1882 to 1888, he walked with giant strides along the borders of the domain that he had entered, from 1888 to the present time he has made the same progress beyond its borders. From the hour in which he grasped "the key to the problem," the "principle underlying all," the dawn of "a new order of things," broke upon his vision, and he was no longer left at the mercy of the genii whom he had aroused. In July, 1888, the T.P.S. published the succeeding paper, which had a wide circulation. KEELY'S SECRETS. 1888. Part I. Science is to know things.--Herodotus. Knowledge is developed by experience from innate ideas.--Plato. Truth is not attained through reflection, but through immediate intuition. "We neither originate thought nor its form.--Aryan Teachings. It may be said that if all things come from only one cause or internal source, acting within itself, then motion and matter must be fundamentally and essentially one and the same, and we may look upon matter as being latent force and upon force as being free matter.--Franz Hartmann, M.D. John Worrell Keely--the discoverer of compound inter-etheric force, as the result of more than twenty years of persistent effort to apply this force to the operation of machinery has, at last, been enabled to produce partial continuity of motion in his engine; but, up to this time, he has not so mastered this subtle force as to control reversions. The development of his various discoveries has been one uninterrupted work of evolution, reaching, within the last year, he thinks, the sphere of perfect vibratory sympathy, both theoretically and practically. The proof of this is found in the fact that he now transmits vibrations along a wire, connected at one end with the vibratory machine which is the source of power, and at its other end with the engine or cannon, as the case may be, which is operated by such vibratory power. Until recently, comparatively speaking, Keely stored force, as he generated it, in a receiver; and experiments were made by him in the presence of thousands, at various times, for the purpose of testing the operations of this force, liberated in the presence of his audience and stored up in this small receiver. The editor of the Scientific Arena thus describes what took place at one of these exhibitions, when he was present:--"The confined vapour was passed through one of the small flexible tubes to a steel cylinder on another table, in which a vertical piston was fitted so that its upper end bore against the underside of a powerful, weighted lever. The superficial area of this piston was equal to one-half of a square inch, and it acted as a movable fulcrum placed close to the hinged end of the short arm of this lever, whose weight alone required a pressure of 1500 pounds to the square inch against the piston to lift it. "After testing the pressure by several small weights, added to that of the lever itself, in order, to determine how much power had already been accumulated in the receiver, the maximum test was made by placing an iron weight of 580 pounds, by means of a differential pulley, on the extreme end of the long arm of the lever. To lift this weight, without that of the lever supporting it, would require a pressure against the piston of 18,900 pounds to the square inch, counting the difference in the length of the two arms and the area of the piston, which we, as well as several others present, accurately calculated. When all was ready, and the crowded gathering had formed as well as possible to see the test, Keely turned the valve-wheel leading from the receiver to the flexible tube, and through it into the steel cylinder beneath the piston, and simultaneously with the motion of his hand the weighted lever shot up against its stop, a distance of several inches, as if the great mass of iron had been only cork. Then, in order to assure ourselves of the full 25,000 pounds to the square inch claimed, we added most of our weight to the arm of the lever without forcing the piston back again. "After repeating this experiment till all expressed themselves satisfied, Keely diverted his etheric gas to the exciting work of firing a cannon, into which he placed a leaden bullet about an inch in diameter. He conveyed the force from the receiver by the same kind of flexible copper tube, attaching one end of it to the breech of the gun. When all was again in readiness he gave a quick turn to the inlet valve, and a report like that of a small cannon followed, the ball passing through an inch board and flattening itself out to about three inches in diameter, showing the marvellous power and instantaneous action of this strange vapour." The difficulty encountered by Keely in his old generator of etheric force grew out of the fact, in part, that the vaporic power produced was so humid that he could not, when he attempted to utilize it, obtain its theoretical value in work. This difficulty has been entirely overcome by dispensing with the water which he used in liberating etheric force, by his old generator; and, by this departure, he has attained a success beyond that which was anticipated by himself, when he abandoned his original line of experiment. [4] Ignorant, indeed, of the nature of Keely's work must those men be who accuse him of "abandoning his base" or "principle," each time that he discovers his mistakes:--using them as stepping-stones to approach nearer and still nearer to his goal. Reproaching him, even, for keeping his own counsel, until certainty of success rendered it prudent for him to make known that he had changed his field of experiment from positive attraction to negative attraction. Equally ignorant are those, who would wrench by force his secrets from him before the time is ripe for their disclosure. Let us suppose that Faraday, when he discovered radiant matter in 1816, had formed a "Faraday Phospho-Genetic Radiant Company," to enable him to experiment: fully cognizant of all that Crookes has since discovered, and had taken for his base in experimenting the principle involved in Crookes's discovery. Not succeeding at first, we will suppose that the Company became clamorous for returns, and demanded that his secret principle should be made public. Had he been driven into making it known, who would have credited what Crookes is now able to prove? The effect would have been upon the Faraday Company the same as if a balloon were punctured just as it was soaring heavenward. The same with the Keely Motor Company, had Keely obeyed the order of the Court in 1882, and made his marvellous secret public. It would have collapsed. Therefore, he has maintained his secret in the interests of the stockholders of the Keely Motor Company with a firmness worthy of a Christian martyr. The one person to whom alone Keely then disclosed it thought him under a delusion, until he had demonstrated its soundness. Charles B. Collier, Keely's patent lawyer, writes as follows, concerning the difficulties attendant upon "the supposed duty" of his client's imparting his "secrets," as ordered by the Court to do, some time since:-- "If to-day, for the first time in your lives, you saw a harp, attuned and being played upon, and the science of music was unknown to you, you would hardly expect, without considerable time and study, to be able to reproduce the harp, attune its strings in proper relation to each other, and to play upon it so as to produce the harmonies which you had listened to. Mr. Keely's work is analogous to the illustration which I have presented, inasmuch as he is dealing with the subject of sound, or acoustics, but in a much more involved form than as applied simply for the production of harmonies for the delight of the ear. Mr. Keely's engine is analogous to the mechanism of the human ear, in the respect that it is a structure operated upon, and its motion induced by vibration; and to the end of securing and attaining, in and by it, uniformity or regularity of motion, there must be perfect unison, or synchronism, as between it and his structure which is the prime source of vibration. To attain this perfect unison or synchronism, has involved unparalleled research and experiment upon his part--experiments that have varied from day to day. No one, in my opinion, who had not stood by his side, as his shadow, watching every experiment, could have kept fully abreast of him. To pursue my simile, I may say that his harp (engine) is not yet perfectly attuned ("graduated"); when it is so, it will produce nothing but harmony (regularity of motion), and his work will be finished. "At such time, I doubt not that he will be able to give to Mr. Boekel, myself or another, the scale with which to reconstruct and attune another apparatus so as to produce like results with it; but to go over the ground that he has gone over, to explore the wilderness in which he has been the pioneer, in other words, the study, to a full understanding of them, of his experiments and researches, as recorded in his writings and illustrated in the beautiful charts which he has produced, will be a work rather for scientists than for mechanicians or engineers." Keely's "Theoretical Exposé" is in preparation for the press; and, when these volumes are issued, we may look for a change of attitude towards him in all men who hold themselves "ready to abandon, preconceived notions, however cherished, if they be found to contradict truths;" which, Herbert Spencer says, is the first condition of success in scientific research. The Rev. J. J. Smith, M.A., D.D., tells us that the only way the great problem of the universe can ever be scientifically solved is by studying, and arriving at just conclusions with regard to the true nature and character of force. This has been Mr. Keely's life study; and he is able to demonstrate all that he asserts. Laurence Oliphant writes: "Recent scientific research has proved conclusively that all force is atomic--that electricity consists of files of particles, and that the interstellar spaces contain substances, whether it be called ether or astral fluid (or by any other name), which is composed of atoms, because it is not possible to dissever force from its transmitting medium. The whole universe, therefore, and all that it contains, consists of matter in motion, and is animated by a vital principle which we call God. "Science has further discovered that these atoms are severally encompassed by an ethereal substance which prevents their touching each other, and to this circumambient, inter-atomic element they have given the name of dynasphere; but, inasmuch as has further been found, that in these dynaspheres there resides a tremendous potency, it is evident that they also must contain atoms, and that these atoms must in their turn be surrounded by dynaspheres, which again contain atoms, and so on ad infinitum. Matter thus becomes infinite and indestructible, and the force which pervades it persistent and everlasting. "This dynaspheric force, which is also called etheric, is conditioned as to its nature on the quality of the atoms which form its transmitting media; and which are infinite both in variety and in their combinations. They may, however, be broadly divided into two categories; viz. the sentient and the non-sentient atoms. Dynaspheric force, composed of non-sentient atoms, is the force that has been already mechanically applied by Mr. Keely to his motor; and which will probably ere long supersede the agencies now used for locomotive, projectile, and other purposes. When the laws which govern it come to be understood, it will produce materially a great commercial and industrial revolution.... "The most remarkable illustration of the stupendous energy of atomic vibratory force is to be found in that singular apparatus in Philadelphia--which for the last fifteen years has excited in turn the amazement, the scepticism, the admiration, and the ridicule of those who have examined it--called 'Keely's Motor'" ... "In the practical land of its origin, it has popularly been esteemed a fraud. I have not examined it personally, but I believe it to be based upon a sound principle of dynamics, and to be probably the first of a series of discoveries destined to revolutionize all existing mechanical theories, and many of the principles upon which they are founded." ... "Those who are sufficiently unprejudiced to connect the bearings of this discovery, of what must be dynaspheric force, with phenomena which have hitherto been regarded as supernatural by the ignorant, will perceive how rapidly we are bridging over the chasm which has divided the seen from the unseen."... In 1882 a lady, conversing with Mr. Keely, said, "You have opened the door into the spirit-world." He answered, "Do you think so? I have sometimes thought I might be able to discover the origin of life." At this time Mr. Keely had given no attention whatever to the occult bearing of his discovery; and it was only after he had pursued his researches, under the advantages which his small Liberator afforded him for such experiments, that he realized the truth of this woman's assertion. It was then, in 1887, that a "bridge of mist" formed itself before him, connecting the laws which govern physical science with the laws which govern spiritual science, and year by year this bridge of mist has solidified, until now he is in a position to stand upon it, and proclaim that its abutments have a solid foundation--one resting in the material and visible world, and the other in the spiritual and unseen world; or, rather, that no bridge is needed to connect the two worlds, one law governing both in its needed modifications. "The physical thing," writes a modern scientist, "which energizes and does work in and upon ordinary matter, is a separate form of matter, infinitely refined, and infinitely rapid in its vibrations, and is thus able to penetrate through all ordinary matter, and to make everywhere a fountain of motion, no less real because unseen. It is among the atoms of the crystal and the molecules of living matter; and, whether producing locked effects or free, it is the same cosmic thing, matter in motion, which we conceive as material energy, and with difficulty think of as only a peculiar form of matter in motion." The President of the British Association, Sir Henry Roscoe, in his address before that body, said: "In nature there is no such thing as great or small; the structure of the smallest particle, invisible even to our most searching vision, may be as complicated as that of any of the heavenly bodies which circle round our sun." As to the indivisibility of the atom, he asks this question: "Notwithstanding the properties of these elements have been studied, and are now known with a degree of precision formerly undreamt of, have the atoms of our present elements been made to yield?" He continues: "A negative answer must undoubtedly be given, for even the highest of terrestrial temperatures, that of the electric spark, has failed to shake any one of these atoms in two." This is an error, for it is well known by those who are fully acquainted with the principle involved in Keely's inventions that the intense vibratory action which is induced in his "Liberator" has accomplished what the retort of the chemist has failed to do, what the electric spark has left intact, and what the inconceivably fierce temperature of the sun and of volcanic fires has turned over to us unscathed. The mighty Genii imprisoned within the molecule, thus released from the chains and fetters which Nature forged, has been for years the tyrant of the one who rashly intruded, without first paving the way with the gold which he has since been accused of using in experiments with reckless and wanton waste! For more than a score of years has Keely been fighting a hand-to-hand fight with this Genii; often beaten back by it, paralyzed at times, even, by its monstrous blows; and only now so approaching its subjugation as to make it safe to harness it for the work that is calling for a power mightier than steam, safer and more uniform in operation than electricity; a power which, by its might and beneficence, will ameliorate the condition of the masses, and reconcile and solve all that now menaces our race: as it was never menaced before, as has been said. The structure of the air molecule, as believed in by Keely, is as follows:--Broken up, by vibratory action, he finds it to contain what he calls an atomic triplet. The position of a molecule, on the point of a fine cambric needle sustains the same relation to the point of the needle that a grain of sand sustains to a field of ten acres. Although, as Sir H. Roscoe has said, "In nature there is no such thing as great or small," the human mind cannot conceive such infinitesimal minuteness. We will, then, imagine a molecule magnified to the size of a billiard ball, and the atomic triplet magnified to the size of three marbles, in the triangular position, within that molecule, at its centre; unless acted upon by electricity, when the molecule, the billiard ball, becomes oblate, and the three atoms are ranged in a line within, unless broken up by the mighty force of vibratory action. Nature never gives us a vacuum; consequently, the space within the molecule not occupied by the atomic triplet must e filled with something. This is where the Genii--"the all-pervading ether"--has made its secret abode through untold æons, during which our world has been in course of preparation for its release, to fulfil its appointed task in advancing the progress of the human race. Step by step, with a patient perseverance which some day the world will honour, this man of genius has made his researches, overcoming the colossal difficulties which have raised up in his path what seemed to be insurmountable barriers to further progress: but never before has the world's index finger so pointed to an hour when all is making ready for the advent of the new form of force that mankind is waiting for. Nature, always reluctant to yield her secrets, is listening to the demands made upon her by her master, necessity. The coal mines of the world cannot long afford the increasing drain made upon them. Steam has reached its utmost limits of power, and does not fulfil the requirements of the age. Electricity holds back, with bated breath, dependent upon the approach of her sister colleague. Air ships are riding at anchor, as it were, waiting for the force which is to make aerial navigation something more than a dream. As easily as men communicate with their offices from their homes by means of the telephone, so will the inhabitants of separate continents talk across the ocean. Imagination is palsied when seeking to foresee the grand results of this marvellous discovery when once it is applied to art and mechanics. In taking the throne which it will force steam to abdicate, dynaspheric force will rule the world with a power so mighty in the interests of civilization, that no finite mind can conjecture the results. In 1746, when Franklin's attention was drawn to the phenomena of electricity, little more was known on the subject than Thales had announced two thousand years before. Von Kleist in Leyden, Collinson in London, and others in as widely-separated cities in Europe, were experimenting in the same field of research. What our last century has done toward subduing this tyrant which Franklin succeeded in bringing down to earth, from the clouds, the next century will see surpassed beyond man's wildest conjectures, should Keely's utilization of this unknown force of nature bestow upon humanity the costless motive power, which he anticipates it will. Reynolds predicted that those who "studied the mysteries of molecular vibration would win the victorious wreaths of successful discovery." After such discoveries as Mr. Keely has made in this field of research, it matters not to him whether he succeeds commercially or not. His work of discovery commenced when, as a boy of twelve, he held the sea-shells to his ear as he walked the shore and noted that no two gave forth the same tone. From the construction of his first crude instrument, his work of evolution progressed slowly for years; but within the last five years he has made giant strides towards the "Dark Tower" which is his last fortress to take. When he is ready, "Dauntless the slug-horn to his lips" he will set; and the world will hear the blast, and awaken from its slumber into new life. Molecular vibration is thus seen to be Keely's legitimate field of research; but more than once has he had to tear down portions of the vibratory scaffolding which aided him in the building up of his edifice of philosophy; therefore, he is ever ready to admit that some of the present scaffolding may have to be removed. The charge of "abandoning his base," recently brought against him by one of the editors of The New York Times, could only have been made by one who is utterly ignorant of the subject upon which he writes. Under the heading "A Cool Confession," this editor asserts that Keely has "given up the Keely Motor as a bad job," and that he admits that he is a "bogus inventor" and a "fraud." This is not true. What Keely does admit is that, baffled in applying vibratory force to mechanics, upon his first and second lines of experimental research, he was obliged either to confess a commercial failure, or to try a third departure from his base or principle; seeking success through another channel of experiment. While experimenting upon this third line, until his efforts were crowned with success, he kept his secret from all men; with the approbation of the one who furnished the money for these experiments. There is a time when silence is golden; and the charge made by the same editor that Keely had been "receiving money from the Keely Motor Company on false pretences from the time that he abandoned his original plans," could only have been made by one who knows nothing of the facts of the case: for years have passed away since the Keely Motor Company broke its contract with him, and since it has furnished him with any money for his experiments. But let Keely speak for himself in reference to his work:-- "In considering the operation of my engine, the visitor, in order to have even an approximate conception of its modus operandi, must discard all thought of engines that are operated upon the principle of pressure and exhaustion, by the expansion of steam or other analogous gas which impinges upon an abutment, such as the piston of a steam-engine. My engine has neither piston nor eccentrics, nor is there one grain of pressure exerted in the engine, whatever may be the size or capacity of it. "My system, in every part and detail, both in the developing of this power and in every branch of its utilization, is based and founded on sympathetic vibration. In no other way would it be possible to awaken or develop this force, and equally impossible would it be to operate my engine upon any other principle. "All that remains to be done is to secure a uniform speed under different velocities and control reversions. That I shall accomplish this is absolutely certain. Some few years ago, I contemplated using a wire as a connective link between two sympathetic mediums, to evolve this power as also to operate my machinery--instead of tubular connections as heretofore employed--I have only recently succeeded in accomplishing successfully such change. This, however, is the true system; and henceforth all my operations will be conducted in this manner--that is to say, the power will be generated, my engines run, my cannon operated, through a wire. "It has been only after years of incessant labour, and the making of almost innumerable experiments, involving not only the construction of a great many most peculiar mechanical structures, and the closest investigation and study of the phenomenal properties of the substance "ether," per se, produced, that I have been able to dispense with complicated mechanism, and to obtain, as I claim, mastery over the subtle and strange force with which I am dealing. "When my present process of adjustment is completed, the force, the mechanism, and all that pertains to it, will be fully explained in a theoretical exposition of the subject, with appropriate diagrams, which I shall publish to the world; through which medium, and my patents, when taken out, a knowledge of all that is required for its commercial employment will be more easily acquired than is the necessary skill required to enable one to safely operate a steam-engine. "The power will be adapted to engines of all sizes and capacities, as well to an engine capable of propelling the largest ship as to one that will operate a sewing machine. Equally well and certain is it that it will be adapted as a projectile force for guns and cannons of all sizes, from the ordinary shoulder-piece to the heaviest artillery.".... When Keely obtained continuity of motion (for a time) in his engine he thought that his last difficulty had been overcome: but, up to the present time, he has not succeeded in governing its speed nor in controlling reversions. He has, however, again reduced in size the instrument with which he produces the force. From 1882 to 1884 the "Generator" was a structure six feet long and correspondingly wide and high; but, failing in his attempt to make an automatic arrangement upon which its usefulness in mechanics depended, Keely found a new standard for research in an experiment often made by himself, but never before successful, which resulted in the production of a machine in 1885 which he named a "Liberator"--not so large as a lady's small round work-table. Continuing his labour of evolution Keely within one year made such astonishing progress, from experiments with this beautiful piece of vibratory mechanism, as to combine the production of the power, and the operation of his cannon, his engine and his disintegrator in a machine no larger than a dinner plate, and only three or four inches in thickness. This instrument was completed in 1886, up to which time his experiments had been conducted upon a principle of sympathetic vibration, for the purpose of liberating a vapoury or etheric product. His later experiments have been confined to another modification of vibratory sympathy; and the size of the instrument used now, '88, for the same purposes is no larger than an old-fashioned silver watch, such as we see in Museum collections. The raising of a lever with an apparent uplifting expansive force of between 20,000 and 30,000 pounds to the square inch, the running of the engine, the firing of the cannon, are conducted without one ounce of pressure in any part of the apparatus, and without the production or presence of what has been known as Keely's ether. The force is now transmitted along a wire (of platinum and silver), and when the lever is lowered there is no exhaustion, into the atmosphere of the room, of any up-lifting vapour, as was always the case when the ether was used in this experiment; nor is there any vapour impinging upon the piston under the lever to raise it. Keely has named this new modification of the one force in nature "Negative Attraction," which to the uninitiated does not suggest as much as it would had he called it "Negative Humbug." The two forms of force which he has been experimenting with, and the phenomena attending them, are the very antithesis of each other. Keely does not feel the shadow of a doubt as to his eventual success in producing engines of varying capacities; small enough, on the one hand, to operate sewing machines with, and large enough, on the other hand, to propel the largest ships that plough the seas. Every fact and feature surrounding the case warrants the belief, notwithstanding the incredulity of all who have not witnessed the progress of Mr. Keely, step by step, that his success will be complete, and his work stand as the most colossal example of the survival of the fittest, in the process of inventive evolution. Cox says: "Not one of the great facts which science now accepts as incontrovertible truths but was vehemently denied by the scientists of its time:--declared to be a priori impossible, its discoverers and supporters denounced as fools or charlatans, and even investigation of it refused as being a waste of time and thought." "History repeats itself," and Amiel's definition of science gives the key to the incredulity of scientists in reference to Mr. Keely's discovery; for if, as Amiel has said, "science is a lucid madness occupied with tabulating its own hallucinations," it is not strange that men of science should refuse to investigate what they consider the hallucinations of others. It is an undisputed fact that "too much has been conceded to science, too little to those sublime laws which make science possible." But the one law which regulates creation, and to which all other laws are made subservient, keeping in harmony the systems upon systems of worlds throughout space, developing sound and colour, animal and vegetable growth, the crystallization of minerals, is the hidden law, which develops every natural science throughout the universe; and which both Kepler and Newton anticipated would be revealed in our age. "You can even trace the poles in sound," writes Mrs. F. J. Hughes, in her work upon the "Evolution of Tones and Colours." The experiments made by Mrs. Watts Hughes, at the annual Reception of the Royal Society, and the [5]Pendulograph writings by Andrew of Belfast, have a bearing upon Keely's discovery; illustrating the workings of this hidden law of nature. Of the law of periodicity, Hartmann writes: "Its actions have long ago been known to exist in the vibrations producing light and sound, and it has been recognized in chemistry by experiments tending to prove that all so-called simple elements are only various states of vibration of one primordial element, manifesting itself in seven principal modes of action, each of which may be subdivided into seven again. The difference which exists between so-called single substances appears, therefore, to be no difference of substance or matter, but only a difference of the function of matter in the ratio of its atomic vibration." It is by changing the vibrations of cosmic ether that Mr. Keely releases this energy, and Dr. Kellner in Austria produces electricity in the same way; while it is said that a chemist in Prague produces magnetism; also Dr. Dupuy, of New York, who has been for years experimenting in this field without meeting with Keely's progressive successes. Horace Wemyss Smith, in commenting upon the fact that, at the time of Franklin's discovery, men in France, in Belgium, in Holland, and in Germany were pursuing the same line of experiment, says that there is something worthy of observation in the progress of science and human genius, inasmuch as in countries far distant from each other men have fallen into the same tracks, and have made similar and corresponding discoveries, at the same period of time, without the least communication with each other. Laurence Oliphant's recent works give us the clue to an explanation of this fact; and Lowe, in his "Fragments of Physiology," condenses the answer in these words: "Man is not the governor and commander of the created world; and were it not for superhuman influence constantly flowing into created forms, the world would perish in a moment." There are men in various parts of the world, unknown even by name to each other, who tell us by "the signs of the times" that the season of harvesting is approaching; the season for gathering the fruit, which has been deferred, century after century, because mankind is not yet ready, in the opinion of many, to share the fruit with one another. It has been said that when Keely's vibratory force shall have taken the place of steam-engines, the millions of working men who gain with difficulty their daily bread by the work of their hands, will find themselves without occupation. The same prediction was made in regard to steam, but instead we find the city of Boston giving work to thirty thousand men in one manufactory of boots and shoes by steam, in place of the three thousand shoemakers who were all that were occupied in this branch of labour in that city when the work was done by hand. Dr. Kellner's colleague, Franz Hartmann, M.D., writing in reference to Keely's discovery, says: "I have taken great interest in him ever since I first heard of him in 1882. As gaslight has driven away, in part, the smoky petroleum lamp, and is about to be displaced by electricity, which in the course of time may be supplanted by magnetism, and as the power of steam has caused muscular labour to disappear to a certain extent, and will itself give way before the new vibratory force of Keely, likewise the orthodox medical quackery that now prevails will be dethroned by the employment of the finer forces of nature, such as light, electricity, magnetism, etc." When the time is ripe, these are of the true scientists who will come to the front "to lead as progress leads," men who know how to wait upon God, viz., to work while waiting; and to such the end is, sooner or later, victory! "God never hurries." He counts the centuries as we count the seconds, and the nearer we approach to the least comprehension of His "underlying purpose" the more we become like Tolstoi's labourer, who knew that the fruit was ripening for him and his fellow-men, trusting implicitly in the superior wisdom of his master. No man, whose spiritual eyes have been opened to "discern the signs of the times," can doubt that we are on the eve of revelations which are to usher in the dawn of a brighter day than our race has yet known; and no prophecy of this brighter day, foretold by prophets, apostles, and inspired poets, was ever made in truer strains than in these glorious lines of Elizabeth Barrett Browning:-- Verily many thinkers of this age, Aye, many Christian teachers, half in heaven, Are wrong in just my sense who understood Our natural world too insularly, as if No spiritual counterpart completed it, Consummating its meaning, rounding all To justice and perfection, line by line, Form by form, nothing single nor alone; The Great Below clenched by the Great Above. Part II. One Phase of Keely's Discovery in its Relations to the Cure or Disease. I know medicine is called a science. It is nothing like a science. It is a great humbug! Doctors are mere empirics when they are not charlatans. We are as ignorant as men can be. Who knows anything in the world about medicine? Gentlemen, you have done me the honour to come here to attend my lectures, and I must tell you now, frankly, in the beginning, that I know nothing about medicine, nor do I know anyone who does know anything about it. Nature does a great deal, imagination does a great deal, doctors do devilish little when they do not do harm. Sick people always feel they are neglected, unless they are well drugged, les imbéciles! Professor Magendie (before the students of his class in "The Allopathic College of Paris"). In the year 1871, the writer was sent from Paris to Schwalbach, by Dr. Beylard, and recommended to the care of Dr. Adolph Genth. She said to the physician, "I wish for your opinion and your advice, if you can give it to me without giving me any medicine." He replied, "With all my heart, madam; and I wish to God there were more women like you, but we should soon lose most of our patients if we did not dose them." This is a terrible excuse for the use of those agencies which Dr. John Good says have sent more human beings to their graves than war, pestilence and famine combined. Keely holds the opinion that Nature works under the one law of Compensation and Equilibrium--the law of Harmony; and that when disease indicates the disturbance of this law Nature at once seeks to banish the disease by restoring equilibrium, He seeks to render assistance on the same plan; replacing grossly material agencies by the finer forces of nature; as has been so successfully done by Dr. Pancoast and Dr. Babbitt in America. "Nature," says Dr. Pancoast, author of The True Science of Light, "works by antagonism in all her operations: when one of her forces overdoes its work, disease, or at least a local disorder, is the immediate consequence; now, if we attack this force, and overcome it, the opposite force has a clear field and may re-assert its rights--thus equilibrium is restored, and Equilibrium is health. The Sympathetic System, instead of attacking the stronger force, sends recruits to the weaker one, and enables it to recover its powers; or, if the disorder be the result of excessive tension of Nerves or Ganglia, a negative remedy may be employed to reduce the tension. Thus, too, equilibrium is restored." Dr. Hartmann writes:-- Mr. Keely is perfectly right in saying that 'all disease is a disturbance of the equilibrium between positive and negative forces.' In my opinion, no doctor ever cured any disease. All he can possibly do is to establish conditions under which the patient (or nature) may cure himself. If you enter the field of therapeutics and medicine, we find a decided fermentation of new ideas; not among the fossil specimens of antediluvian quackery, but among those who are called "irregulars," because they have the courage to depart from the tracks trodden out by their predecessors. The more intelligent classes of physicians have long ago realized the fact that drugs and medicines are perfectly useless, excepting in cases where diseases can be traced to some mechanical obstruction, in some organ that may be reached by mechanical action. In all other cases our best physicians have become agnostics, leaving nature to have her own way, and observing the expectative method, which, in fact, is no method of cure at all, but merely consists in doing no harm to the patient. Recently, however, light, electricity, and magnetism have been employed; so that even in the medical guild the finer forces of nature are taking the place of grossly material, and therefore injurious substances. The time is probably near when these finer forces will be employed universally. Everybody knows that a note struck upon an instrument will produce sound in a correspondingly attuned instrument in its vicinity. If connected with a tuning fork, it will produce a corresponding sound in the latter; and if connected with a thousand such tuning forks, it will make all the thousand sound, and produce a noise far greater than the original sound, without the latter becoming any weaker for it. Here, then, is an augmentation or multiplication of power. If we had any means to transform sound again into mechanical motion, we would have a thousand-fold multiplication of mechanical motion. It would be presumptuous to say that it will not be as easy for the scientists of the future to transform sound into mechanical motion, as it is for the scientist of the present to transform heat into electricity. Perhaps Mr. Keely has already solved the problem. There is a fair prospect that in the very near future, we shall have, in his ethereal force, a power far surpassing that of steam or electricity. Nor does the idea seem to be Utopian if we remember that modern science heretofore only knew the law of the conservation of energy; while to the scientist of the future the law of the augmentation of energy will be unveiled.... As the age which has passed away has been the age of steam, the coming era will be the age of induction. There will be a universal rising up of lower vibrations into higher ones, in the realm of motion. Mr. Keely will, perhaps, transform sound into mechanical motion by applying the law of augmentation and multiplication of force."... Keely, writing on brain disturbance, says, In considering the mental forces as associated with the physical, I find, by my past researches, that the convolutions which exist in the cerebral field are entirely governed by the sympathetic conditions that surround them. The question arises, what are these aggregations and what do they represent, as being linked with physical impulses? They are simply vibrometric resonators, thoroughly subservient to sympathetic acoustic impulses given to them by their atomic sympathetic surrounding media, all the sympathetic impulses that so entirely govern the physical in their many and perfect impulses (we are now discussing purity of conditions) are not emanations properly inherent in their own composition. They are only media--the acoustic media--for transferring from their vibratory surroundings the conditions necessary to the pure connective link for vitalizing and bringing into action the varied impulses of the physical. All abnormal discordant aggregations in these resonating convolutions produce differentiation to concordant transmission; and, according as these differentiations exist in volume, so the transmissions are discordantly transferred, producing antagonism to pure physical action. Thus, in Motor Ataxy a differentiation of the minor thirds of the posterior parietal lobule produces the same condition between the retractors and extensors of the leg and foot; and thus the control of the proper movements is lost through this differentiation. The same truth can be universally applied to any of the cerebral convolutions that are in a state of differential harmony to the mass of immediate cerebral surroundings. Taking the cerebral condition of the whole mass as one, it is subservient to one general head centre, although as many neutrals are represented as there are convolutions. The introductory minors are controlled by the molecular; the next progressive third by the atomic; and the high third by the Etheric. All these progressive links have their positive, negative, and neutral position. When we take into consideration the structural condition of the human brain, we ought not to be bewildered by the infinite variety of its sympathetic impulses; inasmuch as it unerringly proves the true philosophy that the mass chords of such structures are governed by vibratory etheric flows--the very material which composes them. There is no structure whatever, animal, vegetable, mineral, that is not built up from the universal cosmic ether. Certain orders of attractive vibration produce certain orders of structure; thus, the infinite variety of effects--more especially in the cerebral organs. The bar of iron or the mass of steel, have, in each, all the qualifications necessary, under certain vibratory impulses, to evolve all the conditions that govern that animal organism--the brain: and it is as possible to differentiate the molecular conditions of a mass of metal of any shape so as to produce what you may express as a crazy piece of iron or a crazy piece of steel; or, vice versâ, an intelligent condition in the same. I find in my researches, as to the condition of molecules under vibration, that discordance cannot exist in the molecule proper; and that it is the highest and most perfect structural condition that exists; providing that all the progressive orders are the same. Discordance in any mass is the result of differentiated groups, induced by antagonistic chords, and the flight or motions of such, when intensified by sound, are very tortuous and zig-zag; but when free of this differentiation are in straight lines. Tortuous lines denote discord, or pain; straight lines denote harmony, or pleasure. Any differentiated mass can be brought to a condition of harmony, or equation, by proper chord media, and an equated sympathy produced. There is good reason for believing that insanity is simply a condition of differentiation in the mass chords of the cerebral convolutions, which creates an antagonistic molecular bombardment towards the neutral or attractive centres of such convolutions; which, in turn, produce a morbid irritation in the cortical sensory centres in the substance of ideation; accompanied, as a general thing, by sensory hallucinations, ushered in by subjective sensations; such as flashes of light and colour, or confused sounds and disagreeable odours, etc., etc. There is no condition of the human brain that ought not to be sympathetically coincident to that order of atomic flow to which its position, in the cerebral field, is fitted. Any differentiation in that special organ, or, more plainly, any discordant grouping tends to produce a discordant bombardment--an antagonistic conflict; which means the same disturbance transferred to the physical, producing inharmonious disaster to that portion of the physical field which is controlled by that especial convolution. This unstable aggregation may be compared to a knot on a violin string. As long as this knot remains it is impossible to elicit, from its sympathetic surroundings, the condition which transfers pure concordance to its resonating body. Discordant conditions, i.e., differentiation of mass, produce negatization to coincident action. The question now arises, What condition is it necessary to bring about in order to bring back normality, or to produce stable equilibrium in the sympathetic centres? The normal brain is like a harp of many strings strung to perfect harmony. The transmitting conditions being perfect, are ready, at any impulse, to induce pure sympathetic assimilation. The different strings represent the different ventricles and convolutions. The differentiations of any one from its true setting is fatal, to a certain degree, to the harmony of the whole combination. If the sympathetic condition of any physical organism carries a positive flow of 80 per cent. on its whole combination, and a negative one of 20 per cent., it is the medium of perfect assimilation to one of the same ratio, if it is distributed under the same conditions to the mass of the other. If two masses of metal, of any shape whatever, are brought under perfect assimilation, to one another, their unition, when brought into contact, will be instant. If we live in a sympathetic field we become sympathetic, and a tendency from the abnormal to the normal presents itself by an evolution of a purely sympathetic flow towards its attractive centres. It is only under these conditions that differentiation can be broken up, and a pure equation established. The only condition under which equation can never be established is when a differential disaster has taken place, of 66 2/3 against the 100 pure, taking the full volume as one. If this 66 2/3 or even 100 exists in one organ alone, and the surrounding ones are normal, then a condition can be easily brought about to establish the concordant harmony or equation to that organ. It is as rare to find a negative condition of 66 2/3 against the volume of the whole cerebral mass, as it is to find a coincident between differentiation; or, more plainly, between two individuals under a state of negative influence. Under this new system, it is as possible to induce negations alike as it is to induce positives alike. Pure sympathetic concordants are as antagonistic to negative discordants as the negative is to the positive; but the vast volume the sympathetic holds over the non-sympathetic, in ethereal space, makes it at once the ruling medium and re-adjuster of all opposing conditions if properly brought to bear upon them. Until Keely's "Theoretical Exposé" is given to science, there are few who will fathom the full meaning of these views. His discoveries embrace the manner or way of obtaining the keynote, or "chord of mass," of mineral, vegetable, and animal substances; therefore, the construction of instruments, or machines, by which this law can be utilized in mechanics, in arts, and in restoration of equilibrium in disease, is only a question of the full understanding of the operation of this law. Keely estimates that, after the introductory impulse is given on the harmonic thirds, molecular vibration is increased from 20,000 per second to 100,000,000. On the enharmonic sixths, that the vibration of the inter-molecule is increased to 300,000,000. On the diatonic ninths, that atomic vibration reaches 900,000,000; on the dominant etheric sixths, 8,100,000,000; and on the inter-etheric ninths, 24,300,000,000; all of which can be demonstrated by sound colours. In such fields of research, Mr. Keely finds little leisure. Those who accuse him of "dilly-dallying," of idleness, of "always going to do and never doing," of "visionary plans," etc., etc., know nothing of the infinite patience, the persistent energy, which for a quarter of a century has upheld him in his struggle to attain this end. Still less, if possible, is he understood by those who think he is seeking self-aggrandizement, fame, fortune, or glory. The time is approaching when all who have sought to defame this discoverer and inventor, all who have stabbed him with unmerited accusations, all who have denounced him as "a bogus inventor," "a fraud," "an impostor," "a charlatan," "a modern Cagliostro," will be forced to acknowledge that he has done a giant's work for true science, even though he should not live to attain commercial success. But history will not forget that, in the nineteenth century, the story of Prometheus has been repeated, and that the greatest mind of the age, seeking to scale the heavens to bring down the light of truth for mankind, met with Prometheus's reward. Note.--Dr. Hartmann, in a report, or condensed statement, in reference to Keely's discovery, writes as follows: "He will never invent a machine by which the equilibrium of the living forces in a disordered brain can be restored." As such a statement would lead the reader of the report to fancy that Keely expected to invent such an instrument, it is better to correct the error that Dr. Hartmann has fallen into. Keely has never dreamed of inventing such an instrument. He hopes, however, to perfect one that he is now at work upon, which will enable the operator to localize the seat of disturbance in the brain in mental disorders. If he succeeds, this will greatly simplify the work of "re-adjusting opposing conditions"; and will also enable the physician to decide whether the "differential disaster" has taken place which prevents the possibility of establishing the equation that is necessary to a cure. According to Keely's theories it is that form of energy known as magnetism--not electricity--which is to be the curative agent of the future, thus reviving a mode of treatment handed down from the time of the earliest records, and made known to the Royal Society of London more than fifty years since by Professor Keil, of Jena, who demonstrated the susceptibility of the nervous system to the influence of the natural magnet, and its efficacy in the cure of certain infirmities. As Cheston Morris, M.D., has well said in his paper on "Vital Molecular Vibrations," "We are entering upon a new field in biology, pathology, and of course, therapeutics, whose limits are at present far beyond our ken." "The adaptability of drugs," says Dr. Henry Wood, "to heal disease is becoming a matter of doubt, even among many who have not yet studied deeper causation. Materia Medica lacks the exact elements of a science. The just preponderance, for good or ill, of any drug upon the human system is an unsolved problem, and will so remain.... After centuries of professional research, in order to perfect "the art of healing," diseases have steadily grown more subtle and more numerous.... Only when internal, divine forces come to be relied upon, rather than outside reinforcement, will deterioration cease. Said Plato, 'You ought not to attempt to cure the body without the soul.'" CHAPTER VIII. 1888. HELPERS ON THE ROAD, AND HINDERERS. Blindfolded and alone we stand, With unknown thresholds on each hand: The darkness deepens as we grope, Afraid to fear, afraid to hope. Yet this one thing we learn to know Each day more surely as we go: That doors are opened, ways are made, Burdens are lifted, or are laid By some great law unseen and still Unfathomed purpose to fulfil. "Not as I will." The next "helper on the road" was an Austrian nobleman, the Chevalier Griez de Ronse, who printed a series of papers on Keely's discoveries in a journal in Vienna, then owned by him--The Vienna Weekly News. One of these articles mentions that the attention of Englishmen of science had been drawn to Keely's claims, in regard to having imprisoned the ether, by Professor Henri Hertz's experiments in ether vibrations at the Bonn University. "Keely, like the late Dr. Schuster," says The Vienna Weekly News, "claims on behalf of science the right to prosecute its investigations until a mechanical explanation of all things is attained. The public are still but the children of those who murdered Socrates, tolerated the persecution of Galileo, and deserted Columbus. This remark is now illustrated by the imprisonment with felons last month of Inventor Keely in Moyamensing Prison, Philadelphia, where Judge Finletter committed him for contempt of court, without the shadow of an excuse in the opinions of men who had followed the proceedings against him. Under the heading, "Keely's Sunday in Jail," says a Philadelphia journal, Inventor Keely spent a quiet Sunday in Moyamensing Prison. The outside iron doors of his cell were thrown open, when the religious services of the morning began. The imprisoned inventor listened with deep interest. The soft peals of the organ and the melody of the choir, singing "Nearer, my God, to Thee," floated into the narrow cell. Keely sat near the grated door while the minister read selections from the Scriptures and preached his sermon. While the inventor was resting in his cell, during the afternoon, a number of persons made inquiries at the "Untried Department." They were all told that no one could be admitted on Sunday, but a young man with a pallid face lingered. He told the gate-keeper that he was an inventor himself, and had been waiting for eight years for a patent from Washington; adding that, when he read of Keely's commitment, he was reminded of Galileo who was thrown in a dungeon because he said, "The world moves." The following day Keely was released by order of the Judges of the Supreme Court. His imprisonment exalted him, instead of degrading him as "the unjust judge" hoped to do; drawing the sympathies to him of all men who know what it is to be "persecuted for righteousness' sake;" of all men, in all parts of the world, who are truth-loving, justice-loving men. The Keely Motor Company should learn a lesson in this experience. Tyndall said, long since, that the community that severs itself from great discoveries, that merely runs after the practical application without reference to the sources of a discovery, would by-and-by find itself at the end of its tether. This has been verified in the fate of the Keely Motor Company, which was organized for the purpose of reaping financial benefit from Keely's grand discovery of an unknown force before his "work of evolution," in obtaining mechanical results, had fairly commenced. This company has thrown upon the discoverer's shoulders the burden of its stock-jobbing operations, until Keely is looked upon by men of science, as well as by men ignorant of the A B C of science, as a man working for personal ends; instead of, as he should be regarded, a Prometheus seeking to give to his fellow-men a costless motive force; and who, whether he succeeds financially or not, is entitled to the admiration of all who believe, with Browning, that "effort, not success, makes man great." If the Keely Motor Company managers would profit by this lesson, they will in future seek to find, among scientific men of world-wide renown, some one man, broad enough in mind to care nothing for the ridicule of the ignorant, who will investigate the nature of Keely's discoveries, as demonstrated by his experiments, instead of inviting reporters to witness the demonstrations, in their efforts "to boom the stock" of their company, by a reporter's accounts of the marvels he has witnessed. For years Keely had nothing to show, beyond the generation of the force, the production of a 30 lb. vacuum and the discharge of a gun. When once his giant mind had grasped the knowledge, which again by seeming chance was imparted to him, he made colossal strides across that unknown tract, the boundaries of which others are now but beginning to explore. Colonel Le Mat was no false prophet, Le Figaro was no untrustworthy herald, when the announcement was made by this French inventor to Monsieur Chevreul, and by this French journal to the public on the 1st day of September, 1888, that the chain which holds the aerial ship to the earth would be broken asunder by Keely's discovery. The nineteenth century holds in its strong arms the pledge, that sooner or later the aerial navy, so long waited for, will traverse the trackless high roads of space from Continent to Continent. It has been supposed by many, Dr. Franz Hartmann among the number, that it requires Keely himself, or another person constituted like him, to set his machinery in motion. Therefore, it has been reasoned that the commercial success of an engine is only possible in case Keely is himself the engineer; or if another man possessing the same seemingly abnormal power could be the engineer. For this reason, says Dr. Hartmann, it is impossible for Keely to instruct any one in his method, so as to enable that one to do what he does. There has been ground in the past for such a statement, it is true, but not now. Keely asserts that when his system is completed, the knowledge of all that is needed for its commercial employment will be more easily acquired than is the necessary skill demanded to enable one to safely operate a steam-engine. When Dr. Hartmann's opinion was made known to Keely, he replied, "Dr. Hartmann's whole conception, in regard to other men being unable to control the operations of my inventions on the sympathetic attractive system, is as incorrect as would be the same conception in reference to operating an electric battery by anyone but its inventor." Let anyone imagine the years on years of research that would have been necessary before Gilbert (who, after Thales, discovered electricity) could have perfected a system which would have enabled men to accomplish all that is accomplished in our age, with electricity as a motive power. Keely's labours would be better understood by those who accuse him of "always promising, and never performing," under such a conception. The inventor must be sanguine of success; he must day by day think that he is on the eve of perfecting his invention, in order to keep up his courage to persevere to the end; otherwise, how could he work, year after year, in the face of obstacle after obstacle that seems, each one, to be insurmountable? After Keely's imprisonment when, among the men who knew that he was incapable of fraud, there was one so incensed by Keely's repeated failures to perfect his engine that he had said he "hoped to live to see Keely rotting in a gutter," Mr. R. Harte wrote: "And now that it has been proved in a hundred ways and before thousands of persons competent to judge of the merits of Keely's claims, that he has really discovered previously unknown forces in nature, studied them, mastered some of their laws, invented and is perfecting researching apparatus that will make his discoveries of practical application in numerous ways--now that he has actually done this, how does the world treat him? Does Congress come forward with a grant to enable him to complete his marvellous work? Do men of science hail him as a great discoverer, or hold out the hand of fellowship? Do people do honour to the man whose sole entreaty to them will be to receive from his hands a gift a thousand times more precious to them than steam engine or dynamo? It is a literal fact that if Keely fell exhausted to-day, in the terrible struggle he has so long maintained, his failure to establish his claims would be received with a shout of malignant delight from nearly every lecture-hall, pulpit, counting-house and newspaper office in the so-called civilized world. The world has hardly ever recognized its benefactors until it has become time to raise a statue to their memory, 'in order to beautify the town.' Jealousy, stupidity, the malignity which is born of conscious inferiority, are at this moment putting in Keely's road every impediment which law and injustice can manufacture. Two hundred years ago he would have been burned, a century since he would have probably been mobbed to death; but thank God we are too civilized, too humane now to burn or mob to death those who make great discoveries, who wish to benefit their fellow-men, or whose ideas are in advance of their age--we only break their hearts with slander, ridicule, and neglect, and when that fails to drive them to suicide, we bring to bear upon them the ponderous pressure of the law, and heap upon them the 'peine forte et dure' of injunctions, and orders, and suits, to crush them out of a world they have had the impertinence to try to improve, and the folly to imagine they could save from suffering, without paying in their own persons the inevitable penalty. Had it not been for the obligations incurred by Keely, in accepting the aid of the Keely Motor Company--in other words, had scientists, instead of speculators, furnished him with the means necessary to carry on his work of evolution, the secrets which he has so carefully guarded would now have been public property, so little does he care personally for financial results. As it is, those who have witnessed his beautiful experiments in acoustics and sympathetic vibration were often too ignorant to comprehend their meaning, and, consequently, even after expressing gratification to him, went away from his workshop to denounce him as a Cagliostro; while others, competent to judge, have refused to witness the production of the ether, as Sir William Thomson and Lord Raleigh refused, when they were in America a few years since. The company here mentioned has been a thorn in the inventor's side ever since it was organized. It has been 'bulled and beared' by greedy speculators, in whose varying interests the American newspapers for years have been worked, the results of which the inventor has had to bear. For many years the Company has contributed nothing towards Keely's expenses or support, and in the opinion of many lawyers it is virtually dead. How far it is entitled to his gratitude may be gathered from the fact, as stated, that 'when Mr. Keely abandoned his old generator of etheric force, baffled in his attempts to wrest from nature one of her most carefully guarded secrets, harassed by his connection with the Keely Motor Company, some of the officers and stockholders of which had instituted law proceedings against him, which threatened him with the indignity of imprisonment, he destroyed many of his marvellous models, and determined that, if taken to prison, it should be his dead body and not himself. "Those who argue, if Keely had really obtained knowledge which contributes towards making man master of the material world, that science would hail the glad tidings with great joy, know but little of modern science and its votaries. An Anglican bishop never ignored a dissenting preacher with more dignified grace than the professor of orthodox science ignores the heterodox genius who has the audacity to wander beyond the limitations which 'received opinion' has placed upon the possibilities of nature. The fact is that men of science have persistently ignored, and know absolutely nothing about, the great department of nature into which Keely penetrated years ago, and in which he has now made himself at home. Not long ago a Fellow of the Royal Society of Edinburgh, Major Ricarde-Seaver, went to Philadelphia to convince himself as to the nature of Keely's discovery. He returned, saying that Keely was working with, and had the apparent command over forces, the nature, or even the very existence, of which was absolutely unknown to him, and, so far as he is aware, to modern science. "Beyond disintegration lies dispersion, and Keely can just as easily disperse the atoms of matter as disintegrate its molecules. Disperse them into what? Well,--into ether, apparently; into the hypothetical substratum which modern scientists have postulated, and about whose nature they know absolutely nothing but what they invent themselves, but which to Keely is not hypothesis, but a fact as real as his own shoes; and which ether, indeed, seems to be 'the protoplasm of all things.' As to the 'law of gravity,' it appears in the light of Keely's experiments, but one manifestation of a law of very much wider application--a law which provides for the reversion of the process of attraction in the shape of a process of repulsion. "While Major Ricarde-Seaver, F.R.S., [6] was in Philadelphia, Keely, by means of a belt and certain appliances which he wore upon his person, moved single-handed, a 500 horse-power vibratory engine from one part of his shop to another. There was not a scratch on the floor, and astounded engineers declared that they could not have moved it without a derrick, the operation of which would have required the removal of the roof of the shop. Of course it is but a step in advance of this to construct a machine which, when polarized with a 'negative attraction,' will rise from the earth and move under the influence of an etheric current at the rate of 500 miles an hour, in any given direction. This is, in fact, Keely's 'air ship.' "When the history of his discoveries and inventions come to be written there will be no more pathetic story in the annals of genius than that of John Worrell Keely. The world hereafter will find it hard to believe that in the last quarter of the 19th century a man with an insight into the secret workings of nature, and a knowledge of her subtler forces, which, whenever it is utilized, will relieve mankind from much of the grinding toil that now makes bitter the existence of the vast majority, that such a man should have been left unaided, because in all the ranks of science there was not found one man capable of understanding his colossal work--because in all the ranks of religion there was not found one man able to realize the enlarged conception of Deity immanent in Keely's great thoughts--because in all the ranks of commerce, of speculation, of literature, of art, there was not found one man large enough, generous enough, unselfish enough, to furnish money for a purpose that did not promise an immediate dividend." Again in 1888, more than ever was Keely held up to ridicule by all those men who possess the instinct of the brute to hound down its prey, and his supporters came in for their share of abuse. Among this class, or of it, were men so ignorant of Keely's claims, and of the object of his researches, that they represented him as "a seeker of the impossible," a "perpetual motion crank," throwing upon his character other odium which the speculating managers of "The Keely Motor Company" were justly responsible for. One of these communications alone is enough to show the quality of the weapons used against him. It appeared in The New York Daily Tribune. THE KEELY MOTOR CRAZE. A Donkey-Cabbage Race. HOW MUCH LONGER WILL THE CLEVER JUGGLER BE ABLE TO DELUDE HIS VICTIMS? To the Editor of "The Tribune." Sir,--The success with which Keely has deluded his victims by appealing to their credulity with a mystery, and to their cupidity with a promise of "all the kingdoms of the earth," which would not be of greater value than the monopoly of infinite power without cost, which he dangles before their astonished vision, makes him and his antics subjects of unusual interest. His last performance appears to be an issue of 5,000,000 dols. of new stock representing a new discovery veiled in mystery, which is to far outstrip his former one, on which 5,000,000 dols. of stock was issued and is now held by his dupes. Two of these new millions are to go to the old holders as a compensation to them for their disappointment in not realizing perpetual motion under the old discovery; two more to go to Keely to be sold to the public; and the remaining one million is in the treasury to be sold for the benefit of Keely and the others, half and half. For fifteen years the donkey has been ridden by Keely with the cabbage on a pole held just in front of his hungry mouth, and now the donkey is told that the cabbage after all is only sham, but that the new cabbage is real, and if he will only consent to run fast enough and far enough he certainly will reach it and grow fat. It would seem that the donkey ought to pause and consider before he begins another fifteen-year race after perpetual motion, and it is here proposed to assist him in his reflections by a few facts. More than fifteen years ago Keely made himself known to the public by exhibiting an apparatus in which a great pressure was manifested, which, he said, resulted from the discovery by him of a new force the nature of which was his secret. Several people, as usual, were astonished at the show, and bought and paid for shares in the patent which was promised. To give colour to the pretence, Keely applied for a patent before 1876, but did not assign to the purchasers their shares; whereupon some of them protested against the issue of the patent unless their shares were recognized in the grant. The Patent Office replied to these protests that it could not recognize the rights claimed unless there was a written assignment filed in the office, which the claimants did not have. The Commissioner, however, called upon Keely to furnish a "working model" of his invention, which, of course, he could not do, and his application was rejected. The specification and drawings of this apparatus show a very silly form of the common perpetual motion machine, of which there are thousands. It was open to the public for some years, when, under a new rule of the office, it, along with all other rejected applications, was withdrawn from inspection; but it is in the office, together with the protests of those who had paid Keely for a share in it. I examined it years ago, and informed Mr. Lamson, and others of Keely's stockholders, of it. Mr. Lamson told me that he had charged Keely with deception, because he had always said that he never had applied for a patent, and that Keely explained it by saying that he had purposely concealed his invention from the Patent Office in that application to which he had made oath. Keely, however, finding the perpetual motion trick profitable, extended his operations and became well known to many influential people by his exhibitions. In the winter of 1875-76 he produced two metallic spheres, one about thirty inches in diameter, hung like an ordinary terrestrial globe, which, he said, would revolve with a force equal to two horse-power, and would continue to run when once started as long as the Centennial Exhibition should be open, and until the thing was worn out by friction. In starting it Keely used to have a blackboard in the room, on which he would write a few figures in chalk in the presence of his dupes, and would say that at a certain time the globe would start--and it did, and would revolve as long as the lookers-on remained to see it. Keely pretended to explain this phenomenon by a string of unintelligible jargon; but the point of it all was that he said the thing ran in consequence of its internal mechanical arrangement--or, in other words, that by combining pieces of metal in a certain way power was generated without any other expense than that required to construct the apparatus. Naturally he refused to show the interior construction which did the miracle; but if his statements were true, it existed inside of that globe, and could be produced indefinitely with the result of producing an indefinite amount of horse-power without current expense. The stock about this time rose to a great price--about 600 per cent.--as it well might if this ball was an "honest ghost." Some of the stockholders had sense enough to see that if Keely's story were true, nothing more could be desired, for it must at once supersede coal and all other means of producing power, and its novelty could not be doubted. It was in effect, "all the kingdoms of the earth," which Satan once offered. But, on the other hand, if Keely's story were not true, then he was simply an impostor who had been defrauding the stockholders out of their money; and they demanded of Keely that he should proceed at once to patent this miraculous machine, which could create power by a peculiar-shaped hole in a sphere of iron. Of course Keely refused to comply with this reasonable request, and many of his stockholders sold out and left him; since which time the stock has gradually declined down to the present time, when its value is admitted to be nothing. In view of these facts the curious question is why the donkey goes on any further. The revolving ball is a fact known to hundreds of the stockholders. It is either a real cabbage capable of feeding the donkey with a perpetual feast, like the widow's cruse of oil, or it is only a sham such as any good mechanic could construct and operate as Keely did. Why doesn't the donkey balk and insist on biting into the cabbage? If it is real the Keely stock is worth untold millions. It would put an end to steam engines and electric batteries for ever. One of those balls in the corner of a room would make all the heat and light which could be used, and have power to sell; and all that would be needed would be to learn Keely's cabalistic signs on the blackboard in order to make it start, and to stop it when it had done enough. But if the ball is only a trick, then, of course, Keely could be sent to prison, and his victims could close their accounts and be sure that they would lose no more by him. Without going any further into the history of this remarkable delusion, which is full of similar tricks too numerous to mention now, it seems clear that these facts ought to be used to bring to an end in one way or the other the Keely craze. Edward N. Dickerson. New York, Nov. 30, 1888. It is difficult to understand how anyone could concoct and put together such a tissue of fabrications as this, when the sole foundation for such a tissue lay in the fact that it was at this juncture that Keely made the announcement that he had proved the uselessness of building engines to employ the ether as a motive power; which could only be used as the medium for the power which he had discovered, namely, a condition of sympathetic vibration, associated both positively and negatively with the polar stream. The statement made of the issue of new stock is absolutely untrue. The revolving globe was never created to be "the source of power," and the representation of the manner in which the globe was made to revolve, and that Keely affirmed he could produce with it "an indefinite amount of horse power without current expense," is denied. The suggestion that Keely could be sent to prison was welcomed by those who eventually acted upon it, with the result that Judge Finletter committed Keely to Moyamensing Prison, for contempt of court, but not for fraud. Mr. Keely, at that time, wrote of those who called him a perpetual motion seeker:--"I console myself by thinking that if they were not ignorant of the grand truths which I am devoting my life to develop into a system, they could never bring forward such an absurd charge. Perpetual motion is against nature, and it is only by following nature's laws that I can ever hope to reach the goal I am aiming to reach." The Supreme Court reversed and set aside the order of the court committing Keely for contempt, and released him from custody, upon the writ of habeas corpus taken out on his behalf, within three days of his commitment. The Chief Justice, in delivering his opinion, made some remarks which fully vindicated Mr. Keely's character. After alluding to the proper procedure which ought to have been taken in the court below, the Judge continued:-- "Instead of so proceeding, a commission of experts was appointed to examine the defendant's machine, and the order of April 7th was made, by which the defendant, in advance of any issue, was not only required to exhibit his machine, but also to operate it and explain the mode of its construction and operation, although it clearly appeared that it would require considerable expense to clean the machine, put it together and operate it. The defendant appears to have been willing to exhibit it, and in point of fact did so. That he might have been compelled to do so at a proper stage of the case is conceded. But to make an order not only to exhibit it, but to operate it, the practical effect of which was to wring from him his defence in advance of any issue joined, was an improvident and excessive exercise of Chancery powers. We are of opinion that the order was improvidently made. It follows that the learned court had no power to enforce it by attachment. The relator is discharged." It was in this year, 1888, that a woman, interested in all branches of science, who had proved to her own satisfaction the value to humanity, as well as to science, of Keely's discoveries, was deprived of legal and maternal rights on account of the delusions that she was very generally believed to be under. A journalist, wishing to obtain information concerning Keely's work, called upon this woman, by appointment, and at the close of the interview said,-- "May I venture to ask you if it is true that you have furnished Mr. Keely with large sums of money as rumour declares; and that you have invested largely in the stock?" "Were I not glad of the opportunity to answer this question in justice to Mr. Keely, I might have said that this is a subject which is of no interest to the public; but I have heard the amount estimated as nearly 100,000l. too often not to be willing to have the truth made known. What I have given to Mr. Keely has been saved by economies in my expenses; and, if not given to him, would have been given to others; as I believe in those who have the most doing all that lies in their power for those who have less. In regard to investments in Keely Motor stock, I have bought no stock excepting to give away." "There is one other question I should like to ask you," said our representative, "Is Mr. Keely a spiritualist? I use the word in its ordinary sense. Does he claim that he has bridged the gulf between the finite and the infinite?" "When Mr. Keely first commenced his wonderful investigations he would have scouted the idea of being in any way whatever associated with so-called spiritualism, but of recent years, and especially during the last few months, he has made such startling progress that he now admits--as I told him a long time ago he would come to admit--that if not in actual experiment, at least in theory he has passed into the world of spirit." The interview being ended, our representative took his departure, after expressing his thanks for the information so willingly given. How far this lady's anticipations of the inventor's success will be realized, or how far her confidence in his integrity is justified, we must leave our readers to judge for themselves. The whole subject is enveloped in much mystery, but it is full of interest, and if half that is narrated of Mr. Keely be true, he is indeed a wonderful man!--The Tatler. CHAPTER IX. 1889-1890. KEELY SUPPORTED BY DISTINGUISHED MEN OF SCIENCE. AERIAL NAVIGATION. Is not ether infinitely more rare and more subtle than air, and exceedingly more elastic and more active? Does it not easily penetrate all bodies? And is it not by its elastic force diffused through the universe?--Sir Isaac Newton. In 1889 a series of short articles were written, which, for the first time, made known to the public that Keely had theories which he was able to sustain by mechanical demonstration: and once more an attempt was made to have men of science acquaint themselves with the theories, and witness the demonstrations. Capitalists also were appealed to, to convince themselves of the existence of an unknown force, and of Mr. Keely's honesty in his efforts to control it for commercial purposes; money being required to enable him to complete his researches for science, and to protect him from those who were harassing him in such a way as to impede his progress at every step. The appeal to capitalists might as well have been made to stone walls; but among the men of scientific and philosophical attainments who were invited, the late Professor Joseph Leidy, M.D., of the Pennsylvania University, and James M. Willcox, Ph.D., author of "Rational Philosophy," and other works, accepted the invitation and attended a series of Keely's researching experiments. For years Mr. Keely's experiments were confined to the production of the force; the raising of a lever; the firing of a cannon; and the showing of a vacuum greater than had ever been produced. Since 1888 he has pursued his researches on a line which enabled him to show uninterrupted progress year after year: so that now he never repeats his experiments; but, discarding or improving his researching instruments, after he has gained the results which his theories lead him to expect, he continues his investigations, thereafter, from the solid basis which he has attained by those researches. The result of the attention given by Professor Leidy and Dr. Willcox is best set down in their own words:-- "April 8th, 1890. "After having had the opportunity of witnessing a series of experiments made by Mr. John Keely, illustrative of a reputed new motor power, it has appeared to me that he has fairly demonstrated the discovery of a force previously unknown to science. I have no theory to account for the phenomena observed, but I believe Mr. Keely to be honest in his attempt to explain them. His demonstrations appear to indicate great mechanical power, which, when applied to appropriate machinery, must supersede all ordinary appliances. "Joseph Leidy." "Philadelphia, April 8th, 1890. "After having witnessed, on several occasions and under favourable circumstances, Mr. Keely's experiments in what he terms sympathetic vibration, I am satisfied that he has made new and important demonstrations in physical science. He has made manifest the existence of natural forces that cannot be explained by any known physical laws, and has shown that he possesses over them a very considerable control. "James M. Willcox." Shortly after these announcements were made public, with the consent of the writers, Anglo-Austria contained two papers on the subject, from which, principally, the article on Etheric Philosophy is taken. S. Zolver Preston, in his "Physics of the Ether," says: "A quantity of matter representing a total mass of only one grain, and possessing the normal velocity of the ether particles, that of a wave of light, encloses a state of energy represented by upward of one thousand millions of foot tons. Or the mass of one single grain contains an energy not less than that possessed by a mass of 70,000 tons, moving at the speed of a cannon ball (1200 feet per second); or, otherwise, a quantity of matter, representing a mass of one grain, endued with the velocity of the ether particles, encloses an amount of energy which, if entirely utilized, would be competent to project a weight of 100 tons to a height of one mile and nine-tenths of a mile." Etheric philosophy has a scientific basis in fact; and in the light of Keely's progressive demonstrations, his views are no longer abnormal to the scientific mind which is willing to admit the possibility of a discovery in which it has had no part. To discover an unknown power is one thing; to subjugate it is quite another thing. The one may be stumbled over; the other can only be attained after laborious investigation. No one who has followed Keely in his "dead work," during the last ten years, can doubt that he has been, and still is, dealing with the same force which, as Professor Hertz has disclosed to us, is already imprisoned, without our knowledge, in electro-magnetic engines. If thus, unknowingly, it has been made the servant of man, in machinery not especially constructed for its use, may it not also have been imprisoned by one who is adapting his inventions to its special requirements? Keely demonstrates, with what he calls vibratory machinery, that all corpuscules of matter may be subdivided by a certain order of vibration, thus showing up new elements; and having demonstrated what he asserts, by releasing the various orders of ether from the suspension in which it is always held in our atmosphere, he has answered the sceptical demand "Give us some bread." It has been said that as men penetrate deeper and deeper into a knowledge of the wonderful laws which govern the universe they may find mysterious forces which remain still undiscovered. Keely's discoveries promise to burst upon the world of science as the one mighty and complete revelation of the universe. There are more things in heaven and earth than are dreamt of in the materialistic science of our age, or in our philosophy. "All we have cognizance of around us are results, the causes of which are supersensuous. Of the nature which we behold around us, the cause is supernatural." The Reverend Albert H. Plumb, of Roxbury, Mass., who has followed Mr. Keely's efforts, to obtain control of the unknown force which he discovered more than twenty years ago, up to his present successful demonstration before scientists, says: "Neither theological science nor any department of physical science, as it lies in the divine mind, is exactly expressed in any human system; yet no knowledge is to be decried nor despised, least of all in the highest realms of thought. The agnostic makes the mistake of confounding exhaustive knowledge with positive knowledge in declaring both unattainable. We can know positively that a thing is, if not how or why it is. As Gladstone says, 'Our hands can lay hold of truths which our arms cannot embrace. We can apprehend what we cannot comprehend.' If Keely should die, I fear no one could understand his writings. Every day we read of distinguished men dying. The other day a man carried with him into the grave his secret for the cheap production of aluminium. No one man entrusted by Providence with high interests has a right to allow a possibility of their sinking back, perhaps for ages, into the void of the unknown. Why not confine attention strictly to making the discovery practically intelligible to others, and thus securing to mankind the first steps by which the new force is evoked and controlled, and leave to later leisure the subtler relations of this power to the divine mind and to life?" For years Mr. Keely did "confine attention" to efforts to prove his discovery by practical methods, without making any advance; and it was not until he was led into the spiritual or philosophical bearings of his discovery that he himself gained "practically intelligible" ideas of its nature. To Dr. Macvicar's "Sketch of a Philosophy," from which Mrs. Moore compiled "Ether the True Protoplasm," and to Mrs. Hughes' book on the evolution of tones and colours, Mr. Keely is indebted for the pregnant germs which, falling from their writings upon his mind, took him from the line of experiment which he was pursuing, into the only line of research which can lead to scientific and commercial success. The hour in which he reaches one he reaches both; nor can one be gained without the other being gained. This should teach us that, though "the heart of man deviseth his way, the Lord directeth his steps." God never hurries, and He chooses His own instruments, employing them after a manner that is inscrutable to us, in our weak impatience for results. Admitting the truth of all that Dr. Plumb has said, but understanding fully the impossibility of directing Mr. Keely's steps, until he himself gains more control of the force that he has discovered, we must "wait upon the Lord," who is revealing to him "the deep mysteries of Creation." In the meantime, those in whom narrowness of mind has not caused stubbornness will hold themselves in readiness to prove all things and hold fast to the truth. We do not easily believe what is beyond our own knowledge, but faith in the claims of Keely as a discoverer, if not as an inventor, is steadily increasing. The following from a foreign publication about the Keely Motor will be of interest to all who have watched the progress of that enterprise. The correspondent writes:--"In the following brief article I purpose placing the latest aspect of Mr. Keely, perhaps the best abused man in America, and his investigations before the readers of Anglo-Austria;" continuing,-- "Under the heading of 'The Keely Motor Again,' Invention, of London, on October 19th, printed a communication, mentioning the leading scientist of America, Dr. Leidy, of the University of Pennsylvania, as supporting Mr. Keely's claims as a discoverer of an unknown force, as follows:--Dr. Leidy having expressed the wish that Professor Barker should again visit Mr. Keely and witness the experiments which had convinced himself that Keely had discovered a new force, has received the following letter:-- "909, Walnut Street, Philadelphia, October 4, 1889. "Dr. Leidy. Sir,--Referring to our conversation of a few days since, and the suggestion of another visit to the workshop of Mr. Keely, by Professor Barker, I would say that I have presented the matter to Mr. Keely and he acquiesces in what I stated to you. That is to say, if Dr. Barker desires to visit Mr. Keely's workshops again, and will make this known to him in writing or through yourself, for the purpose of further observation and of having confirmed or removed from his mind, as the case may be, the conclusions or impressions arrived at by him, and published in the columns of the Ledger, of this city, in 1878; and on condition that he will, if his further observations satisfy him that he did injustice to Mr. Keely, forthwith publish that fact through the same channel, the Ledger: he being, of course, at full liberty to confirm by further publication his previous condemnation, if satisfied with the correctness of that conclusion; then Dr. Barker will be cordially received by Mr. Keely, and a series of experiments will be conducted for him at an early day, say, Saturday, 12 inst. And in the event of the engagement being made, I shall request the pleasure of your presence, and that of Dr. McCook. I leave the matter in your hands for such action as you in your wise discretion may think proper to take. Very truly yours, "Charles B. Collier." Nothing could be fairer than Mr. Keely's proposal, and the result of Professor Barker's visit will be watched for with the keenest interest by all scientists on both sides of the Atlantic. [7] "Professor Barker, after due consideration, concluded not to accept the invitation, and declined it on October 11th, suggesting Professor Goodspeed, his associate in physics, as one who would probably be disposed to witness the series of experiments about to be given; showing the neutralizing or overcoming of gravity and the separation of metallic plates by vibration. After the date upon which these latter experiments were to have been made, and which I may mention, en passant, had been repeatedly made in the laboratory of Mr. Keely, this cablegram was sent from London to Philadelphia:-- 'Ask Dr. Leidy's permission to announce here his conviction that Keely has discovered a new force.'" The answer was returned as follows:-- "Having had the opportunity of seeing Mr. John Keely's experiments, it has appeared to me that he has command of some unknown force of most wonderful mechanical power. "Joseph Leidy." Invention, in commenting upon the communication, says: "We wish to make it quite clear that we do not identify ourselves with any of the opinions which are expressed in this communication. It is certainly desirable that the motor should be thoroughly tested, and particularly that all the secrecy, which has hitherto been practised in connection with it, should be abandoned. There can be no reason why this invention, if invention it be, should not be published to the world as long as it is fully protected by patents. We agree, however, so far, that Professor Barker's report, if his visit be paid, will be of considerable interest." These remarks of our English contemporary are based upon quite wrong premises. The motor cannot be tested nor patented until it is completed. Mr. Keely's work is one of experimental research. His machine for the production and liberation of the power is in daily operation. He has made many failures in constructing his commercial engine, but each failure has brought him nearer to perfection. When he has succeeded in building an engine in which he can regulate the speed, control reversions and govern its operations, as completely as the steam engine is now governed, then he will be ready to test its action publicly, take out patents for the same, and make known to the world the nature of his discovery. Up to the present time Mr. Keely's inventions have been principally devices, enabling him to experiment with the force which he has discovered and to obtain control over it. For years he was impeded by the frequency of the explosions which took place, breaking his ribs, paralyzing his left side for six weeks at one time, and frequently bursting iron tubes as if they were pipe stems. Little by little he learned the laws which governed the unknown force, and now he never has an explosion. Mr. Keely has not preserved any secrecy with regard to his experiments, but on the contrary he has lost much time in exhibiting the production of this force to those who desire to see it. For instance, some years ago he stopped his work on the graduating of his engine to take his liberator to pieces, in order to show its interior construction to Sir William Thompson and Lord Raleigh: these gentlemen, misled by Professor Barker's assertion, that Keely was deceiving his dupes with compressed air, refused to witness his experiments. This was in 1884. There is no "secrecy to be abandoned," therefore. The question to be settled was not one of secrecy, but whether Mr. Keely should continue his experimental research, unimpeded by exhibitions, until he should succeed in perfecting a commercial engine; or whether he should first convince scientists that he is not a modern Cagliostro as he has been called, and that he is a discoverer of an unknown force. The ground taken by those who urged the latter course was that the interests of the Keely Motor Company would thus be better served; reasoning that, when scientists have been convinced that Mr. Keely's researches are in a field comparatively unknown to them, the cries of execration would be drowned in the applause which would resound throughout the world as the result of his stupendous labours became better known. For this end several scientists were invited to witness the present stage of experiment, which Mr. Keely had reached in his efforts to provide his provisional engine with a governor, and Dr. Leidy was one of the number who, after witnessing the experiments on May 28th, 1889, confessed himself convinced that Keely was dealing with some unknown force. When we call to mind Watt's persevering efforts during thirty years, before he succeeded in his attempt to invent a governor for the steam engine, we can afford to be more patient with Mr. Keely than we have been. Taking into consideration the marvellous advance which Mr. Keely has made in the past five years in perfecting his liberator, we should not be surprised to hear at any moment that he has also perfected his commercial engine, the so-called "Keely Motor," thus overcoming his sole remaining obstacle to financial success. Those who talk of "testing" the motor, or of patenting it in its present condition, are not aware of the exertions which have been made by Mr. Keely to bring the motor to its present stage of development; nor that, although the motor now seems to be approaching perfection, the work of evolution will not be completed until it is in a patentable form. In 1759 James Watt made his first model of a steam carriage. In 1784 he took out a patent. In 1803 the first engine was built, but it was not until 1824 that the experiment of running a locomotive from Liverpool to Stockport was made. Until Mr. Keely's commercial engine is perfected and patented, now that scientists are beginning to support him as the discoverer of an unknown force, ridicule should give way to sympathy; for we know that nature never reveals one of her tyrant forces without at the same time showing how this force is to be transformed into the slave of man, and that complete success is only a question of time.--Anglo-Austria, March, 1890. SOME RECENT EXPERIMENTS. [8] Copy of a Letter addressed to Professor Dewar of the Royal Institution of Great Britain. Dear Professor Dewar,--As I have already informed you, I carried out your wishes in reference to Professor Rowland of the John Hopkins University, as far as extending to him an invitation to witness some of Mr. Keely's experiments in sympathetic vibration was concerned. Professor Rowland was not able to witness any demonstration whatever, on account of an accident which happened to the disintegrator, and he could not fail to have formed an unfavourable opinion of Mr. Keely from all that transpired on that occasion. I next renewed the invitation to Professor Barker, which had already been extended to him by Professor Leidy, both of these gentlemen being Professors in the Pennsylvania University. Professor Barker was not able to be present. The series of experiments which have been given for scientists, mechanical engineers, and others since my return, closed on the 12th. The steady progress from week to week, since the accident to the disintegrator was repaired, has given beautiful evidence of the wisdom of the plan adopted by Mr. Keely in the winter of 1888-89, which led him to turn his attention to a class of experiments of quite a different nature from those which, up to that time, had been made for commercial ends; experiments which have not failed to convince all who attended the entire series that Mr. Keely is dealing with an unknown force, the laws governing which he is still in partial ignorance concerning. He admits now that he cannot construct a patentable engine to use this force till he has mastered the principle; and a fund, with the approval of scientists, has been appropriated for this end, upon the condition that he will waste no more time upon what is known as the Keely Motor Engine until he has demonstrated his ability to control reversions and in all points to govern the revolutions. His last engine was built to exhibit the practical nature of his discovery to capitalists, the managers of "The Keely Motor Company"--which company died a natural death years since--hoping thereby to raise the price of its stock, and in this way to furnish Mr. Keely with the funds that he needed. But the exhibition of this engine was premature and did not succeed. There will be no further need for such exhibitions in future, for it is, as it always has been, in the interest of stock-holders that the stock should not rise until the system is completed, when it will rise to remain raised. From this time the interests of stock-holders will not be sacrificed to the interest of stock-jobbers. The experiments conducted on Saturday last surpassed preceding ones in the purity of the demonstrations, the instruments being in better condition. In demonstrating what seems to be the overcoming of gravity for aerial navigation, Mr. Keely used a model of an air-ship, weighing about eight pounds, which, when the differentiated wire of silver and platinum was attached to it, communicating with the sympathetic transmitter, rose, descended, or remained stationary midway, the motion as gentle as that of thistledown floating in the air. The experiment illustrating "chord of mass" sympathy was repeated, using a glass chamber, forty inches in height, filled with water, standing on a slab of glass. Three metal spheres, weighing about six ounces each, rested on the glass floor of the chamber. The chord of mass of these spheres was B flat first octave, E flat second octave, and B flat third octave. Upon sounding the note B flat on the sympathetic transmitter, the sphere having that chord of mass rose slowly to the top of the chamber; the positive end of the wire having been attached, which connected the covered jar with the transmitter. The same result followed the sound of the note in sympathy with the chord of mass of the other spheres, all of which descended as gently as they rose, upon changing the positive to the negative. J. M. Willcox, Ph.D., who was present, remarked,--"This experiment proves the truth of a fundamental law in scholastic philosophy, viz., that when one body attracts or seeks another body, it is not that the effect is the sum of effects produced by parts of one body upon parts of another, one aggregate of effects, but the result of the operation of one whole upon another whole." The experiments on the 12th closed with the disintegration of water, twelve drops of which we saw dropped, drop by drop, into the small sphere attached to the disintegrator after exhausting the air by suction. A pressure of over 20,000 pounds to the square inch was shown to the satisfaction of all present, and when Mr. Willcox accepted Mr. Keely's invitation to take a seat on the arm of the lever, adding his 260 pounds to the weight, applause broke forth. Mr. Keely showed control of the ether, inter-atomic subdivision, by graduating the escape of the residue, as he allowed it to discharge itself with a noise like the rushing of steam to an expulsion as gentle as the breathings of an infant. The three subdivisions acted simultaneously, showing instantaneous association and disassociation. The sympathetic globe was operated upon, 120 revolutions a second, ceasing the instant that the wire was detached. I regret to say that Professor Ira Remsen was prevented, I fear by Professor Rowland, from witnessing any one of this series of experiments as he intended doing; nor have I been able to get the opinion of any physicist in whom I felt any confidence; but Mr. Keely is satisfied to have the support of such men as J. M. Willcox, Ph.D., and Professor Leidy, LL.D. Dr. Leidy was awarded the Lyell Medal in 1884, when in London, and the Cuvier Prize in 1888, from the Academy of Sciences in France. He is known in America not only as possessing the broadest of minds and the gentlest of natures, but as holding in his heart that love for, and reverence of, truth and justice which alone can confer the power of forming a correct and a just judgment. I would like to have you make known in England that Mr. Keely is indebted to Macvicar's Sketch of a Philosophy for turning his attention, in 1884, to researches on the structure of ether, and to Mrs. F. J. Hughes (not Mrs. Watts Hughes), for the suggestions in her work on Harmonies of Tones and Colours Developed by Evolution, which led him into the line of experiment that will enable him to show on a disc the various colours of sound, each note having its colour, and to demonstrate in various ways Mrs. Hughes' own words "that the same laws which develop musical harmonies develop the universe," etc., etc. On the 10th of June, 1890, the Rev. John Andrew, of Belfast, whose pendulographs illustrate the ratios which rule in the domain of atmospheric vibrations, in which audible music has been located by the great numberer, wrote: "I think that now, at last, Keely's labours are about to be honourably recognized by the world of science. May he live to rejoice in his triumphs." Mr. Andrew, who was the friend of the late Dr. Macvicar, was instrumental in bringing "A Sketch of a Philosophy" to Mrs. Moore's notice, and has maintained great interest in Keely's researches since he first heard of them. Miss Mary Green, a governess in the family of Lord Wimborne, was another instrument used to make known to Keely the important nature of the energy he had liberated from the suspension in which it is always held in our atmosphere. About this time Professor James Dewar, who had been following Keely's claims as a discoverer since 1884, wrote: "If Mr. Keely succeeds in making his discovery practically useful, as it is said that he is demonstrating to scientists his ability to do--if this information be true, it is strange to contrast the past history of science with the present. Fancy the discoverer of electricity having succeeded in inventing the modern dynamo machine! Such a fact would mean the concentration of hundreds of years of scientific discovery and invention into the single life of one man. Such a result would be simply marvellous." At this time a number of the leading journals in various parts of the United States announced that, although Keely's methods and his failures had combined to engender distrust and arouse ridicule, it could no longer be denied that he had discovered what no other man has discovered. Still "penny-a-liners" continued to employ those "weapons of small souls and narrow minds," sneers and ridicule and calumny, which Lavater's allegorical vignette so well depicts: A hand holding a lighted torch is stung by a wasp, and the gnats that swarm around it are consumed in its flame. Underneath are these lines:-- And although it singes the wings of the gnats, Destroys their heads and all their little brains, Light is still light; And although I am stung by the angriest wasp, I will not yield. Every defender of the truth, at whom shafts of ridicule are levelled, should recall these words. Never, for one moment, has Keely turned aside from his work to answer his assailants. It is not to be wondered at that the magical nature of his demonstrations, more inexplicable than any feats of legerdemain, should have brought upon him the suspicion of fraudulent representation, concerning the production of the force and its manipulation; but his persistency alone in seeking to unravel the mysteries of nature, ought to have brought around him sooner men who, like the revered and great Leidy, were able to appreciate his researches in sympathetic vibration, the laws of which govern everything in creation, from the movements of the planets, down to the movements of atoms. From the time in which it was made known to Keely that the same principle underlies harmonies and the motion of heavenly bodies, as announced by Pythagoras, his grasping intellect conceived the idea that planetary bodies have a nerve-system, subject to conditions which govern it and keep it under control, just as our human mechanism is controlled by the law which governs its operation. In Keely's theories all is mechanical in nature. A molecule of steel, a molecule of gas, a molecule of brain matter are all of the one primeval substance--the Ether. AERIAL NAVIGATION. The instrument devised by Mr. Keely for bringing the air-ship under control in its ascent and descent, consists of a row of bars, like the keys of a piano, representing the enharmonic and the diatonic conditions. These bars range from 0 to 100. At 50 Mr. Keely thinks the progress of the vessel ought to be about 500 miles an hour. At 100 gravity resumes its control. If pushed to that speed it would descend like a rifle-ball to the earth. There is no force known so safe to use as the polar flow if, as Mr. Keely thinks, that, when the conditions are once set up, they remain for ever, with perpetual molecular action as the result, until the machinery wears out. In the event of meeting a cyclone, the course of the vessel, he teaches, can be guided so as to ascend above the cyclone by simply dampening a certain proportion of these vibratory bars. The instrument for guiding the ship has nothing to do with the propelling of it, which is a distinct feature of itself, acting by molecular bombardment; moving the molecules in the same order as in the suspension process, but transversely. After the molecular mass of the vessel is sensitized, or made concordant with the celestial and terrestrial streams, the control of it in all particulars is easy and simple. In ascending the positive force is used, or the celestial, as Keely has named it, and in descending the negative or terrestrial. Passing through a cyclone the air-ship would not be affected by it. The breaking up of cyclones will open a field for future research, if any way can be discovered for obtaining the chord of mass of the cyclone. To differentiate the chord of its thirds would destroy it; but to those who know nothing of the underlying principle, on which Keely has based his system, all such assertions are the merest "rubbish." For a few months following the announcement of Professor Leidy's and Dr. Willcox's opinions, Mr. Keely continued his researches under favourable circumstances; but, in the autumn of 1890, he was again threatened with suits-at-law and harassed by demands to give exhibitions in order to raise the price of stock. A subscription was started to raise funds for the prosecution. These threats made it necessary to make public the history of Keely's connection with an organization which was supposed by many to have been formed for speculative purposes, before the stock of the company possessed any value other than prospective; but to which company, notwithstanding, the world is indebted for supplying Mr. Keely with the means to continue his work, at a time when it was impossible for him to gain the recognition of science or the aid of capitalists. The discovery would in all probability have been lost, but for the help which this organization gave, at a time when Keely needed help; he had made a discovery, and these shrewd business men, totally ignorant of physics, knew enough to comprehend its financial importance. Never doubting that Keely would be able to master the difficulties at once, in the way of its subjugation, and not realizing the width of the gulf that lies between discovery and invention, they expected him to leap it with one bound; and when he failed to do so they threw upon him all the odium which befell the enterprise. Keely, who had twice destroyed his researching instruments, when harassed and threatened by the managers of the company, first in 1882, and again in 1887, was now placed by their threatened proceedings in a position where he had to choose between continuing his researches with the end in view of completing his system; or diverting his course and resuming his efforts to perfect an engine, to continue exhibitions for the purpose of raising the stock of the company. At this juncture an attempt was made to have circulated among the stock-holders a narrative setting forth facts to show that their interests would be better served by a continuance of the researches that had led to the results attained within the last two years; and which were of so important a character as to justify Keely in saying that he had learned more of the law, governing the operation of the force he was dealing with, in that time, than in the many preceding years during which he had been scarcely doing more than liberating the ether. The effort to have the narrative circulated failed; and, as a last resort, the history of the company was made public in a pamphlet, entitled The Keely Motor Bubble; which contained the Minority Report of Mr. John Lorimer, made, in 1881, when he was a member of the Board of Directors of "the now defunct Keely Motor Company;" giving a masterly analysis of the situation at that time. Mr. Lorimer's faith in, and loyalty to, Mr. Keely, has never been questioned. He is probably the best and most disinterested adviser that Mr. Keely has ever had; among those who are interested solely in the commercial aspect of the discovery. CHAPTER X. 1881-1891. THE KEELY MOTOR BUBBLE. MACVICAR'S LOGICAL ANALYSIS. For it is well known that bodies act upon one another by the attraction of gravity, magnetism, and electricity; and these instances show the tenour and course of Nature and make it not improbable that there may be more attractive powers than these. For Nature is very consonant and comfortable to herself.--Sir Isaac Newton. The Scotch author, Macvicar, from whose "Sketch of a Philosophy" has been compiled "Ether the True Protoplasm," published this year in the New York Home Journal, says in his "Enquiry into Human Nature," written in 1852, "Modern science is certainly on the way to the discovery that, so far as is cognizable by us, throughout the whole universe the same laws are at work and regulate all things. The mécanique céleste of mind is still waiting its Newton to disclose them to us." Looking upon the discoverer of etheric force as the Newton, whose coming was forecast by Macvicar, it is satisfactory to see that Keely, in his field of research, eventually adopted the methods which his forerunner advocated nearly forty years ago; but not until after many years of blind grappling with the mechanical difficulties which he encountered, in his efforts to control the unknown Genii, which he himself declares that he stumbled upon in quite another field of research. Keely was experimenting in 1875 on what he called a hydro-pneumatic-pulsating-vacuo engine, when, "accidentally," the first evolution of disintegration was made. The focalization of this quadruple force, acting on one general centre of concentration, produced partial molecular subdivision, resulting in a pressure of some three thousand pounds per square inch. Mr. Keely was himself amazed at this evidence of the energy which he had evoked, and at once turned his attention to researching its nature, with the result that he came to the conclusion that he had partially resolved the gaseous element of water by crude molecular dissociation. This was his first step, and the necessary introductory one, towards the elimination of ether; but at that time, to use his own words, he had not the remotest idea of the etheric element proper. Since then he has constructed innumerable machines to subdivide or dissociate the molecular; but it was not until he had instituted certain acoustic vibratory conditions that he began to realize the magnitude of the element that he is now controlling with his vibratory disintegrator. Yet, even this instrument was only the stepping-stone towards polar-sympathetic-negative-attraction. In 1878 Mr. Keely conceived and constructed an instrument which he called a "vibratory lift," and, while experimenting on the improvised multiplication by this medium, he had occasion to put a piece of marble, weighing twenty-six pounds, on a steel bar to hold it in place, when then and there his first discovery of the disintegration of mineral substance took place. From that time progressive research of the most arduous nature has brought him to his present standard in vibratory physics. In the winter of 1881-82, when threatened with imprisonment by the managers of the Keely Motor Company for not disclosing his secret to them, which then would have been like pricking a bubble, he destroyed his vibratory lift and other instruments that he had been years in perfecting. At this time so hopeless was Keely, that his plans were made to destroy himself, after destroying his devices. At this critical juncture he received unexpected aid. Again, in 1888, before he was taken to a felon's cell in Moyamensing Prison by decree of Judge Finletter for alleged contempt of court, he broke up his vibratory microscope, his sympathetic transmitter, and some devices, which have taken much of his time since to reconstruct. It would seem to be incomprehensible that a man who believes he has been specially endowed by Providence to convey great truths to the world, should have destroyed instruments which were the result of the labour of many years of research; but Schopenhauer tells us that genius possesses an abnormally developed nervous and cerebral system that brings with it hyper-sensibility, which in union with intensity of will-energy, that is also characteristic of genius, occasions quick changes of mood and extravagant outbursts. Schopenhauer also explains why it is that men of genius are ignored by the age in which they appear:--"The genius comes into his age like a comet into the paths of the planets, to whose well-regulated and comprehensible order its entirely eccentric course is foreign. Accordingly he cannot go hand in hand with the existing regular progress to the culture of the age, but flings his works far out on the way in front (as the dying Emperor flung his spear among the enemy), which time has first to overtake. The achievement of the man of genius transcends not only the power of achievement of others, but also their power of apprehension; therefore they do not become directly conscious of him. The man of talent is like the marksman who hits a mark the others cannot hit; the man of genius is like the marksman who hits a mark that the sight of others cannot even reach." In one sense this truth applies to all men, for, says Cicero, no man is understood excepting by his equals or his superiors. Admitting all that has been said of the difficulties attendant upon the comprehension of a genius by the age in which he lives, it does not require genius to understand the blunders which, perpetrated by the managers of the prematurely organized Keely Motor Company, have placed Mr. Keely, as well as themselves, in false positions with the public; leaving him since the winter of 1880-81 to bear the whole burden of the infamy brought about by their having offered stock for investment which could possess no tangible existence in the shape of property until the laws governing the unknown force that he was handling had been studied out and applied to mechanics in a patentable machine. To those informed that this company ceased to hold annual meetings as far back as 1881 it will be a matter of surprise to hear that, sitting up in its coffin, seven or eight years after its burial, it called another annual meeting, and that now its managers are again applying the thumb-screw, as in past years; pressing their claims and threatening a suit for obtaining money under false pretences, unless Mr. Keely renounces his plan of progressive research, and gives his time to the construction of engines for the Keely Motor Company. This requirement, as was said in 1881, of a similar effort, is as sensible, under existing conditions, as it would be to require Keely to devote his time to growing figs on thorn trees. It is from the "Minority Report to the Stockholders of the Keely Motor Company from the Board of Directors" (made by a member of that board in 1881, John H. Lorimer), that the material is gleaned for disclosing facts which it is due to Mr. Keely should now, since this last attempt to intimidate him, be given to the public. The stock of that company is not lessened in value by the mismanagement of its officers and directors; for Mr. Keely's moral obligations to its stockholders are as sacred to him as if the company had not long since forfeited its charter. When Mr. Keely became financially independent of the company last March, speculation in the stock of that company received its death blow, and the "Keely Motor Bubble" burst, leaving to the stockholders all that ever had any tangible existence in the shape of property in a more valuable position than it had ever been before. Mr. Lorimer is a gentleman of Scotch birth, who was elected a director of the Keely Motor Company in 1881, and who resigned in 1882, because he was "unable to carry the enterprise," and unwilling to fall in with the policy of the old directors. Before resigning, he set himself to studying the position of affairs with a view to forming for the Board a definite plan of action which ordinary business principles would justify. This course resulted in a thoroughly business-like letter to Mr. Keely in which, under nine heads, Mr. Lorimer set down the conclusions he had reached as to the cause of the difficulties that had culminated in a threatened law suit, and Mr. Keely was ordered to ask that a special meeting of the Board should be called at once, to consider any proposition he should see fit to make towards settling the question whether he should proceed with the company's work or be permitted to defer it, as he so much desired, until he had fully developed the adaptations of his power already known to him or hereafter possible of discovery by him. Mr. Lorimer added:--"And now, in conclusion, I may say to you that the above deductions from the history of your motor are the result of patient and laborious inquiry on my part, and I am truly at a loss to understand how, or in what manner, other than that herein suggested, you can honourably vindicate your position; and as no one I have met connected with the enterprise, or personally acquainted with you, hesitates for an instant in crediting you with the most unswerving integrity, I have no hesitation in offering the above suggestions for your consideration; and I trust you will so far adopt them as to enable the active portion of your friends to bring the organization rapidly into harmonious accord with you in the development of what all seem to think is the greatest wonder of our civilization, the early completion of which will lift you to the highest pinnacle of fame as a scientist, and make them co-dispensers with you of the God-given wealth of which you hold the key." The date is 10th of February, 1881. This letter was followed by another dated February 11th, in which Mr. Lorimer submitted certain conclusions, arrived at after meeting in New York with several members of the Board of Directors, one of which reads:--"It seems to be generally understood that without your hearty co-operation and good will, the company cannot realize value upon any existing contracts, or any they may hereafter make with you." At this time Mr. Lorimer states that he had the opportunity presented of studying, semi-officially, the very peculiar man whose genius held his friends so spell-bound that they lost their power (if such they possessed) to adapt business methods to the enterprise. "To meet him socially in his shop," Mr. Lorimer writes, "after his day's work, was, I think, invariably to be impressed with his earnestness, honesty of purpose, and above all, with confidence in his knowledge of the plane of science he was working in (acoustics), and, at the same time to be impressed with the folly of basing calculations for the government of the business details of the organization upon the statements made by him while contemplating the possible result of his researches." With the hopeful spirit of an inventor, Mr. Keely always anticipated almost immediate mechanical success, up to the hour in which he abandoned the automatic arrangement that was necessary to make his generator patentable. From that time his line of perspective extended, and he began to realize that he had been too sanguine in the past. He had been like a man grappling in the dark with a foe, the form of which had not even presented itself to his imagination; but when, in 1884, Macvicar's work on the structure of ether came like a torch to reveal the face of his antagonist, what wonder that he, with the enthusiasm of Paracelsus, felt his ... "fluttering pulse give evidence that God Means good to me, will make my cause His own;" and, as in 1881, again rashly bound himself anew, by fresh promises, made to those who had the power to give or to withhold the sinews needed in the warfare he was waging? To return to the report. During the negotiations which followed, facts in the history of the company were developed which convinced Mr. Lorimer that Mr. Keely was totally unable to measure time, or define his plans, because of the ever-changing results attained by him, in researching the laws governing the force he was trying to harness. At this time the treasurer of the company was proposing to bring over from New York to Philadelphia a number of capitalists to witness an exhibition of the production of the force, in order to dispose of 500 shares at 25.00 dollars a share. To this plan Mr. Lorimer objected, writing to the treasurer, "I fear that you would be putting yourself in a false position with the friends you might induce to take stock at the figures named," and Mr. Keely himself at first refused to give the exhibition, but upon the application of the thumb-screw, kept in readiness, it took place. At this time Mr. Lorimer wrote to the president of the company, "If Keely gives us the benefit of his discoveries, it will require all our energies to guide our enterprise; and, on the other hand, if he dies or is forestalled, it will need all our care and attention to take care of our reputations.... The fact that the Board has some delicate and important work to perform, brings us to the question, Are we properly organized to perform our part? If we are, let us show it by our acts, and, if not, let us act like men, worthy the important trust before us. If I am overestimating the character and importance of this work, you can show it to me; and per contra, if I am correct, you can and will accept the responsibilities of the position you hold, no matter how unpleasant, no matter how irksome, if understood by you and honourably supported by us." Mr. Lorimer then prepared this summary, or analysis of the situation. SUMMARY. 26th July, 1881. "First.--The existence of a discovery or invention which from evidences of its adaptability (when complete) to the industrial arts and sciences, may be esteemed the most valuable discovery of civilization in modern or in ancient times, inasmuch as it revolutionizes all known methods of generating power. "Second.--The retention by the discoverer and inventor of all the secrets whereby these discoveries can be utilized by the public, thus making their future existence, so far as the Keely Motor Company is concerned, depend entirely upon his life and goodwill. "Third.--The existence of a corporated company, organized for the purpose of furnishing funds for the development and completion of the discovery, and for the final control of certain specified inventions, in certain specified localities. "Fourth.--The contracts under which the above-mentioned control of certain inventions is vested in the Keely Motor Company, being mere evidences of intention, have no real value until the inventor has received his patents and verified the contracts by transfer of the same to the company. "Fifth.--If any conflict should arise between the company and the inventor, in which the latter felt justified in withholding the transfer, the existing contracts might be a good foundation to build litigation upon but not good for investment in. "Sixth.--The uncertainty of the future of the enterprise, as thus indicated, must of necessity invite speculative management; and while speculation under some circumstances is legitimate and laudable, under other conditions it may become illegitimate and reprehensible. "Seventh.-- The existence of a speculative management in Keely Motor affairs has, of necessity, developed two interests--one which holds that the completion of the discovery in all its possible grandeur should ever be the sole object of its management, and the other, believing that on account of the human uncertainty of the completion of the invention, they are in duty bound to make quick recoveries on their investments, so that they may be safe financially, in the event of a failure by Keely to perfect his inventions." It is not necessary to pursue this summary farther, as the manner in which Mr. Lorimer has set down the facts already given, makes clear the nature of the conflicting interests that brought about the antagonism which he attempted to subdue, bringing such a spirit of fairness and justice into his efforts as must have crowned them with success, supported as he was by Mr. Keely, had it not been that those who advocated following a policy which, at best, aimed no farther than at the recouping of losses to themselves, were in the majority. It was at this time that Mr. Keely manifested his willingness to assume, on the one hand, all the responsibility of the proper development of his discovery; or, on the other hand, all the disgrace accompanying failure by his offer to purchase a controlling interest in the stock, fifty-one thousand shares of which, in order to prevent speculation, he agreed to lock up for five years, and to give the company a bond restraining him from negotiating or parting with a single share of it in that time, the stock to be paid for as soon as certain deferred payments had been made to him. This proposition of Mr. Keely to the Board of Directors, October 25th, 1881 (and laid upon the table by a large majority as unworthy of consideration), was made from his earnest desire to control the presentation of his life's work to the world in a just and honourable way; having recognized, with Mr. Lorimer, the utter impossibility of reconciling the numerous interests created by mistakes of himself and the mismanagement of the Board, unless he could thus obtain the power to deliver an unencumbered enterprise to the world. In the opinion of Mr. Lorimer, during the negotiations which he conducted between the management and Mr. Keely, the latter was the only one who had manifested any consistency or strength of purpose, so far as the facts gave evidence, which were brought before him, of the history of the company. When the validity of the contracts made with Mr. Keely while he was president, or director of the company, were disputed, he was called upon to resign, which he did; and yet no steps were taken to ascertain the value of the existing contracts, which had all been made with him while he was both president and director, and which were therefore illegal. Proceedings in equity were commenced against Mr. Keely, by the Committee of the Board of Directors having the matter in charge, late in the year 1881, while Mr. Lorimer's report was still in the hands of the printer. "The spectacle of a Board of thirteen Directors, composed of business men," writes Mr. Lorimer, "claiming that they have been foiled in their business calculations by a man whose mind has been so thoroughly absorbed in researching the problems presented by his wonderful discoveries that he could not possibly compare with any of them in business tact, is truly a phenomenon which is not easy of explanation on any hypothesis, but the one that their visions of prospective wealth have been so overpowering as to undo their prudence; and then having in due process of time discovered their error, it certainly is an edifying spectacle to see them now trying to throw all the blame on one poor mortal wholly absorbed in his inventions, and by these efforts disturbing that mental equilibrium of both the inventor and themselves, which is absolutely necessary to ultimate success. When boys, in early summer, pick unripe fruit and eat it, because of their unwillingness to await the ripening thereof, they sometimes suffer acutely for their haste. Yet no one ever thinks of punishing the tree because of their sufferings; nor is it deemed necessary to justice to preserve the fruit of the tree, when ripe, for the sole use of the impatient ones as a recompense for their early sufferings! So it has been with the Keely Motor Company; undue haste to gather the golden fruit that was to come from it, has led to a great deal of suffering financially among a few impatient believers. Still it does not seem to me to be wise to curse the inventor, or his inventions because he has not given us the fruit when we expected it would be ripe."... The effort to force Keely to divulge his secrets failed, for at that time he had nothing of a practical nature to divulge, and though possessing no business qualifications, he was too shrewd to cut off any of his resources for supplies, necessary to enable him to persevere in his efforts to attain some practical result, as he surely would have done, had he said, "I know very little more than you know of the laws governing the force I have discovered. I can only control their operation by experimental research, and the more time that is wasted in building engines, until I have made myself acquainted with these laws, the longer will you have to wait for your golden fruit." Mr. Keely was no more able at that time to give the faintest idea of the present stage of his researches than Professor Leidy or Dr. Wilcox could now, after witnessing the experiments in sympathetic attraction, write out a clear formulation of its governing law, and an inductive substantiation of it. Even were it possible, no reader could understand it because the discovery made by Mr. Keely is not in accordance with any of the facts known to science. Mr. Keely's experiments in disintegrating water prove that incalculable amounts of latent force exist in the molecular spaces; but in the opinion of scientists, molecular aggregation is attended with dissipation of energy, not with absorption of energy. If the men of science are right, then there must be an absolute creation of energy, for only by admitting its absorption in aggregation, could molecular dissociation supply the force witnessed. Keely, of course, denies any creation of energy, claiming only that he can produce an indefinite supply by the expenditure of an infinitesimally small amount of energy. Every new discovery necessitates a new nomenclature. The vocabulary coined by Mr. Keely, to meet his requirements in formulating his hypotheses into theories as he progresses, conveys as little meaning to those who read his writings, as the word "electricity" conveyed 200 years ago. Professor Crookes remarked that reading Mr. Keely's writings was like reading Persian without a dictionary. Another learned professor said that they seemed to him to be composed in an unknown tongue, so profoundly unintelligible had he found the extracts sent to him. One must be familiar with Mr. Keely's instruments and their operation, in order to comprehend even the nature of his researches. An author of philosophical works, who was present at some experiments illustrative of varying chords of mass, and whose theories had not been in unison with those of Mr. Keely on that subject, sat for some time after the demonstration with his eyes fixed upon the floor, wearing as serious an expression of countenance as if he were looking on the grave of his most cherished views. The first remark that he made was, "What would Jules Verne say if he were here?" The rotation of the needle of a compass, the compass placed on a glass slab and connected with the transmitter by a wire, 120 revolutions in a second, had the same effect upon the scientists present, one of awe; so completely were they transfixed and unable to form a conjecture as to the mysterious influence from any known law of science. There was only one professor present, a very young man, who ventured the whispered suggestion of concealed mechanism under the pedestal; and as Mr. Keely soon after had occasion to wheel the pedestal across the room, showing that it was not stationary, and could have no concealed connection within or without, the young professor took up another line of conjecture. As Macvicar says, it has grown to be the fashion, to a marvellous extent, to give predominance in education to physical and mathematical studies over moral and mental. Hence a very general and growing prepossession in favour of material nature. Astronomy, natural philosophy, chemistry, natural history, geology, these and the like are in our day held to be everything. He continues:-- Now, all these branches of study, however various in detail, agree in this, that they exclude the conception of a true self-directive power from the field of thought. They offer for consideration nothing but figures, movements, and laws. And thus they tend to form the popular mind to the habit of looking for figures, movements, and laws everywhere, and for rejecting all other conceptions as intruders. But of all such other conceptions, there is nothing so difficult and so intractable, under physical modes of investigation, as self-directive power. It therefore runs a great risk of being rejected, and thus the mind, from its first training, having been in physics, carrying out here, as it usually does everywhere, its first love into all its after thoughts, shuts up the student surreptitiously with materialism as his philosophy. Thus it is easy to see how materialism should come to be a current opinion, when the popular education runs all in favour of physical pursuits. But if philosophy must yield to the demands of the logical faculty for an extreme simplicity, unity, identity, at the fountain-head of nature, it were more logical to regard those phenomena and laws named physical, such as the laws of motion, elasticity, gravitation, etc., as manifestations, when existing under certain limiting conditions, of substances or beings which have also in them, when not so limited, and when existing under certain conditions, ability to manifest self-directive power. That every body is compounded, constituted, or made up of molecules, is universally agreed. Every body is therefore a fit subject for analysis. But when any body is submitted to analysis in reference to its mere corporeity or bodily nature, that is, its extension and impenetrability, what do we ultimately arrive at? Do we not, in reference to the attribute of extension, arrive at particles, of which the physical limit is that they have at least ceased to be extended, and are but mere points in space? And as to the attribute of impenetrability, what do we in the last analysis arrive at, but the idea of a substance that can resist the intrusion into its place of other similar substances, and, therefore, ultimately, a centre of force. And thus, under a logical analysis, which must be admitted to be legitimate, it may be maintained that a body or chemical element resolves itself into a system of centres of force balancing each other at certain distances, and thus rendering the whole molecule or mass extended, as body is known to be. The elements of body, therefore, are things of which these attributes are to be affirmed in the first instance, that they possess unextended substance and extensive power. But, if so, do they not touch upon the confines of the spiritual world to say the least? asks Macvicar; and the Newton whom he anticipated would give a mécanique céleste to mankind, solves the problem, answers the question by his discovery of the cerebellic stream or will-flow. Body and spirit, one at the fountain-head, when rising into existence, form, as it were, the first breath of creation; for, as Sir Wm. Thompson says: "Life proceeds from life and from nothing else." They are the opposite poles of being and constitute the two principles by the harmonious interweaving of which the beautiful system of creation is constituted, and its economy worked out. Such a view, far from being contrary to the canons of science, is even the necessary complement of science. That unity, which is the last word of science, must always include two objects, existing in contrast after all. The law of couples, of opposites, of reciprocal action between two contrasted yet homogeneous and harmonizing elements, each of which opens a field for the other, and brings it into action, is of universal extent. In the organic world, also, no less than in the purely physical and chemical, all is framed according to the same law of couples. In the sphere of sensibility, in like manner, everything turns on the antagonism of pleasure and pain, and in the moral sphere of good and evil. Nor is the world of pure intellect exempt from this law, but on the contrary displays its influence everywhere. Hence faith and sight, identity and difference, finite and infinite, objective and subjective, space and time, cause and effect, the world of realities and the world of ideas. In a word, every system of thought and of things, when complete, present as its basis two co-ordinate elements, the reciprocals of each other; or one parted into two reciprocally, and by the harmonious antagonism of both the beautiful web of nature is woven. If we are to be consistent, mind and matter ought always to be viewed as distinct, and the opposite poles of being; inertia, or unvarying submissiveness to the laws of motion being the characteristic of the one; self-directive power the characteristic of the other. The universal analogy of science sanctioned Macvicar in the characteristic he thus arrived at as that of animated nature, for if inertia, or the obedience to pressures and impulses from without, be the characteristic of matter, then that which is needed as the other term to complete the couple is just what has been insisted on, viz., self-directive power, the power to cause pressures and impulses. Here is shown the symmetrical relation in which this power, when viewed as the characteristic of the whole animal kingdom (which plainly points to man, and culminates in human nature), places the animal in relation with the vegetable and the mineral kingdoms. Of minerals or crystals, the characteristic is simply self-imposing or self-concreting power. They are, so to speak, merely insoluble seeds without an embryo. To this, self-developing power is added in plants, and forms their acknowledged characteristic. While of animals the characteristic, according to the view here advanced (the same seed-producing, self-developing, powers continuing) is self-directive power superadded. This relationship between these three kingdoms of nature is as homogeneous and symmetrical as is necessary to appear to be legitimate, and is a true expression of the order of nature. Granting these two principles, the inert and the self-directive, the necessary and the free, we obtain the materials for a universe, without disputing the fact of human liberty and bringing into suspicion even the possibility either of morality or immorality. If man be really free as well as under law, in this union of body and spirit, then in human nature heaven and earth truly embrace each other; and no reason appears why, as the ages roll on, our own free thought may not have the run of the universe.... What study then can be more replete with interest, what researches can possess more of fascination, than those which Mr. Keely's discoveries are preparing the way for? The discoveries of Mr. Keely (demonstrated--as he is now prepared to demonstrate them) cannot be disputed, though his system may be called in question. With the humility of genius, he calls his theories hypotheses, and his hypotheses conjectures. The solidity of the principles, as laid down by himself, cannot be decided upon by others until he has brought to light the whole system that grows out of them. But it is time the public should know that the odium thrown upon him by the Keely Motor Company, he does not deserve. It is time that the Press should cease its sneers, its cry of "Crucify him, crucify him!" morally speaking, and extend to him that discriminating appreciation of his work and encouragement which the New York Home Journal, Truth, Detroit Tribune, Chicago Herald, Toledo Blade, Atlanta Constitution, The Statesman, and Vienna News have been the first to do. Let the Press contrast the past history of science with the present position of Keely, as Professor Dewar has done. Only such a man who knows from experience the labour, the difficulties, the uncertainties, attendant upon researching unknown laws of nature is able to appreciate all that is now being concentrated in the single life of one man. It is time that capitalists should step from their ranks to protect Keely from the selfish policy of the managers of a speculative company, which has long since forfeited all claims upon him, to continue mechanical work for it, even admitting that it ever possessed that right; and, more than all else, it is time that science should send her delegates to confer with the broad-minded men who have had the courage to give testimony, without which Keely could not have stood where, this year, he stands for the first time, fearless of threats, pursuing his researches on his own line, to acquire that knowledge of the laws governing his discoveries by which alone he can gain sufficient control of machinery to insure financial success. Meanwhile, are there no men who are able to feel an interest (without reference to commercial results) in a discovery which sweeps away the débris of materialism as chaff is swept before a whirlwind?--giving indisputable proof that, as St. Paul teaches, "we are the offspring of God; "or, as Aratus wrote, from whom he quoted:-- "From God we must originate, Not any time we break the spell That binds us to the ineffable. Indeed, we all are evermore Having to do with God: for we His very kind and offspring be: And to His offspring the benign Fails not to give benignant sign." From New York Truth, 3rd July, 1890. "I think it is safe, for even the most conservative and pig-headed of scientists, to admit that Keely, the contemned, the scoffed at, the derided, the man whom every picayune peddler called charlatan because he could not harness the hitherto undiscovered forces of ether in less time than one might hitch up a mule, is the most original and the most straightforward of inventors, and that in his own good time he will give to the world a power that will throw steam and electricity into disuse, open the realms of air as a public highway for man, and send great ships careering over ocean with a power developed by sound. His theory of etheric vibration is now conclusively established, and it is only a question of time and material that delays its use as a servant to man. The fact is patent, so that he who runs may read, but the ox must have the yoke, the horse the collar, the engine the cylinder, and the dynamo the coil, ere they can work their wonders. While Keely was hampered by mere tradesmen, who only looked to the immediate recoupment of their outlay, men more anxious for dividends than discoveries, he could do little save turn showman, and exhibit his partial control of the harmonies of nature as springs catch woodcocks, and was forced to open his crude contrivances to divert the eternal will of the cosmos to work-a-day uses, that he might coax from the greed and credulity of mere mammon-worshippers the sorely grudged means to continue his exploration of the infinite. His genius was prisoned in a test tube, and only let out to play monkey tricks before muddle-headed merchants, who could see the effect, but not the means, and so the greatest discovery of the age was turned into a raree show, and the eternal music of the spheres was set, figuratively speaking, to play tunes to attract custom like a barrel organ before a dime museum." CHAPTER XI. VIBRATORY SYMPATHETIC POLAR FLOWS.--KEELY'S CONTRIBUTIONS TO SCIENCE. "Evermore brave feet in all the ages Climb the heights that hide the coming day,-- Evermore they cry, these seers and sages, From their cloud, 'Our doctrines make no way.' All too high they stand above the nations, Shouting forth their trumpet-calls sublime, Shouting downwards their interpretations Of the wondrous secrets born of Time." ... Who can say what secrets the now unread 'fairy tales of science' may have to tell to those who live in this later age?--The Globe. The question has often been asked, "How much energy does Keely expend in the production of the force he is handling?" or again, "Can Keely show that a foot-pound of vibratory sympathy can be more easily developed from the resources of nature, than a foot-pound of good honest work?" In the economy of nature profit and loss must balance in mechanical conditions; but Keely is not dealing with mechanical physics. There is an immense difference between vibratory physics, in which field Keely is researching, and mechanical physics. The consumption of coal to expand water for the production of steam power, in the operation of engines, cannot be compared to a force which is yielded in sympathetic vibration or by sympathetic flows. In mechanical physics, no matter what the nature of the force may be, its production must necessarily be accompanied by a corresponding expenditure of force in some form or other. The amount of force covered by a human volition cannot be measured, yet it produces the wonderful effects that are exhibited on the human frame in its overt actions. Something like this is the difference between sympathetical and mechanical force. The force of will cannot be multiplied by mechanical means, making it give pound for pound. This would annihilate both the mental and the physical, were it possible. In his researches, Mr. Keely, who is dealing entirely with VIBRATORY SYMPATHETIC and POLAR flows, is hopeless in regard to convincing the scientific world of the value of his discoveries until he has compelled its attention by commercial success. To the question, "What does the supply cost in dollars and cents, per horse-power developed?" he answers, "It costs nothing more after the machinery is made, than the vibratory concordant impulse which associates it with the polar stream." The twanging of a taut string, the agitation of a tuning-fork, as associated with the resonating condition of the sympathetic transmitter, is all that is necessary to induce the connective link, and to produce this "costless motive power." As long as the transmitter is in sympathy with the sympathetic current of the triune polar stream, the action of the sympathetic instrument or engine continues. Again, mechanical conservation of energy is one thing; sympathetic conservation is another, and we cannot expect Keely will reveal what he has discovered concerning the forces that he is dealing with until he has himself acquired that full knowledge of their action which will protect the rights of those who are interested in the "dollars and cents" part of "the enterprise." Macvicar said that "if extreme vicissitudes of belief on the part of men of science are evidences of uncertainty, it may be affirmed that of all kinds of knowledge none is more uncertain than science;" but slow as mankind is in the progress of discoveries bearing upon unknown laws of nature, men of science are still slower in recognizing truths after they have been discovered and demonstrated. Two centuries elapsed between the discoveries of Pythagoras and their revival by Copernicus. Tycho Brahe opposed the Pythagorean system until his death; Galileo, adopting it and demonstrating it in all its purity, suffered for his support of it at the hands of bigots. And so history now repeats itself. Were it possible to convince scientists en masse of the grandeur of Keely's work, they would protect him from the interruptions and law-suits which have so retarded his progress that now it looks very much as though he would never be permitted to complete his system. The world is full of inventors, but there is but one man able to unfold, to this age and generation, the wonderful mysteries attendant upon vibratory physics, while there are thousands who, when a mastery of the principle has been gained, can invent machinery to apply it to commercial uses. Macvicar asks, "Who that goes so far as to make a question of all, or almost all, the data of common sense can legitimately refrain from making it a question whether the laws of phenomena which men of science discover may not be laws of thinking, merely imposed upon nature as her laws? Nay, who can refrain from admitting with Kant that they can be nothing more?" As a suggestion to those interested in psychological researches I will mention that Keely has copied nature in all his instruments from the Vibrophone, which is fashioned after the human ear, up to the Disintegrator, in which the neutral centre represents the human heart. With the system which Keely is unfolding to us we may well say, with Buckle, "A vast and splendid career lies before us, which it will take many ages to complete. As we surpass our fathers, so will our children surpass us. Waging against the forces of nature what has too often been a precarious, unsteady, and unskilled warfare, we have never yet put forth the whole of our strength, and have never united all our faculties against our common foe. We have, therefore, been often worsted, and have sustained many and grievous reverses. But, even so, such is the elasticity of the human mind, such is the energy of that immortal and godlike principle which lives within us, that we are baffled without being discouraged, our very defeats quickening our resources, and we may hope that our descendants, benefiting by our failures, will profit by our example, and that for them is reserved that last and decisive stage of the great conflict between man and nature, in which advancing from success to success, fresh trophies will be constantly won; every struggle issuing in a conquest, and every battle ending in a victory." The force discovered by Keely--no, the force revealed to him--will rule the earth with an influence mighty in the interests of humanity. The completion of his system for science and commerce will usher in the dawning of a new era. While our leading men of science are everywhere occupying themselves with the mysteries of electro-magnetic radiation, with the action of the ether, with the structure of the molecule, the instruments with which they are researching are, in comparison with those which Keely has invented, for his researches, like the rudest implements of the savage, compared to those developed by modern civilization. A discussion has recently been carried on in one of our Reviews, as to whether the energy which feeds the magnet comes from the atmosphere, from gravity, from solar rays, or from earth currents. Nothing is more simple than Keely's explanation, as proved by his demonstrations. The energy of the magnet comes from the polar stream; and, though the introductory impulse is so slight that it cannot be weighed any more than can the flow of the mind, yet, if kept up for years, it could not be computed by billions of tons in its effect. The magnet that lifts pounds to-day, if the load of the armature is gradually increased day by day, will lift double the amount in time. Whence comes this energy? Keely teaches that it comes from sympathetic association with one of the triune currents of the polar stream, and that its energy will increase as long as sympathetic flows last, which is through eternity. The physicist tells you that "you cannot make something out of nothing;" that "in the economy of nature profit and loss must balance;" that "no matter what the nature of the force may be, its production must necessarily be accompanied by a corresponding expenditure of force in some form or other," etc., etc. But, in the prodigality of nature, this energy flows, without measure and without price, from the great storehouse of the Infinite Will. From the sympathetic portion of the etheric field, all visible aggregations of matter emanate, and on the same order that molecular masses of all living organisms are vitalized by the sympathetic flow from the brain. "Our most learned men," said Buckle, "know not what magnetism is, nor electricity, nor gravity, nor cohesion, nor force." Keely shows us, by mechanical means, what magnetism is. By neutralizing or overcoming gravity, he proves to us that he understands its nature; electricity he declares to be a certain form of atomic vibration; and, in the disintegration of quartz, he demonstrates that cohesive force, like gravity, is an ever-existing force, holding together all molecular masses by the infinite velocity of its vibrations; which, were these vibrations to cease for one instant, would fall apart, molecules and atoms, and return to the ether in which they originated. KEELY'S CONTRIBUTIONS TO SCIENCE. [9] An infinitely subtle substance, out of which all other substances are constituted, in varying forms, passes back again into simplicity. The same principle underlies the harmonies of music and the motion of heavenly bodies.--Pythagoras. One of the most arduous problems is that of energies acting at distances. Are they real? Of all those that appear incontrollable, one only remains, gravitation. Will it escape us also? The laws of its action incline us to think so. The nature of electricity is another problem which recalls us to the condition of electric and magnetic forces through space. Behind this question arises the most important problem of all, that of the nature and properties of the substance which fills space,--the ether,--its structure, its motion, its limits, if it possesses any. We find this subject of research, day by day, predominating over all others. It seems as though a knowledge of ether should not only reveal to us the nature of that imponderable substance, but will unveil to us the essence of matter itself and of its inherent properties, weight and inertia. Soon the question set by modern physics will be, "Are not all things due to conditions of ether?" That is the ultimate end of our science; these are the most exalted summits to which we can hope to attain. Shall we ever reach them? Will it be soon? We cannot answer.--Prof. Henri Hertz, in La Revue Scientifique, October 26, 1888. In the long delay attendant upon the application to mechanics of the unknown force which John Ernest Worrell Keely has discovered in the field of vibration, the question is often heard, "What has Keely done?" with the remark, "He has never done anything; he is always promising to do something, but he never keeps his promises." Let us see what Keely, in his researches, has done for science; although, as yet, he has done nothing for commerce. We are quick to forget the experiences of history, which show what a length of time has invariably elapsed between the discovery of a new force and its use in mechanics. Watt commenced his experiments on the elastic force of steam in 1764, obtaining about forty pounds total pressure per square inch. (It has been stated that it was thirty years before he succeeded in perfecting his safety-valve, or governor, which made it possible to use steam without running great risks.) Fifty years later, in 1814, the first steam locomotive was built; but it was not until 1825 that the locomotive was used for traffic--travelling at a speed of from six to eight miles in an hour. Keely commenced his experiments with ether in the winter of 1872-73, showing a pressure of two thousand pounds per square inch. It does not look now as though half a century would elapse before Keely's discovery will supersede steam in travel and traffic. In experimenting with ether, he has shown, from time to time, since 1873, a pressure of from twenty thousand to thirty-two thousand pounds per square inch; but he was occupied many years in his researches before he obtained sufficient control over the ether to prevent the explosions which made wrecks of his machines, bursting iron and steel pipes, twelve inches in circumference, as if they were straws. He has now arrived at a stage in his experimental research in which he can, without danger of explosions, exhibit to scientists such manifestations of an unknown force as to place him before the world where he would have stood many years ago, had it not been for the calumnious attacks of those men of science who found it easier to denounce him than to account for the phenomena which they witnessed in his workshop. Professor Ira Remsen, in his "Theoretical Chemistry," writes, "As regards the cause of the phenomena of the motion of the heavenly bodies, we have no conception at the present day. It is true we say that these phenomena are caused by the attraction of gravitation; but, after all, we do not know what pulls these bodies together." Let us see what Keely knows on this subject? 1st. After a lifetime of research into the laws governing vibrations, which develop this force, Keely is able to demonstrate partial control of the power that he has discovered,--a power which he believes to be the governing medium of the universe, throughout animate and inanimate nature, controlling the advance and recession of the solar and planetary masses, and reigning in the mineral, the vegetable, and the animal kingdom, according to the laws that rule its action in each, as undeviatingly as it governs the motions of the earth itself, and of all the heavenly bodies in space. Keely calls this power, which he is endeavouring to apply in mechanics for the benefit of mankind, "sympathetic negative attraction,"--it being necessary to use the word "attraction," as no other word has yet been coined to take its place. 2nd. He has determined and written out a system of the vibratory conditions governing the aggregation of all molecular masses, as to their relation sympathetically one to the other, stating the conditions to be brought about in order to induce antagonism or repellent action, disintegration, etc.; but he has not yet been able to control the operation of his Disintegrator so as to use it with safety to the operator, for mining purposes, etc. 3rd. He has proved by demonstration that the subdivision of matter under different orders of progressive vibration evolves by such subdivision entirely new and distinct elements, too multiple to enumerate. He has systematized the proper vibratory chords, progressively, from the introductory molecular to the inter-etheric, embracing seven distinct orders of triple subdivision. He has elaborated a system of inducing sympathetic negative attraction on metallic masses, with great range of motion, and instant depolarization of the same, by vibratory change of their neutral centres. Keely controls the transmission of these sympathetic streams by a medium of high molecular density, viz., drawn wires of differentiated metals, gold, silver, platinum, German silver, etc. In some recent experiments he took apart, for inspection of its interior construction, the instrument which he has invented for the production of the force, cutting the wires with which he had operated in sympathetic attraction and propulsion, and distributing the fragments to those who were present, among whom was Professor Leidy, to whom the Geological Society of London has awarded the Lyell Medal, and the Academy of Sciences of France the Cuvier Prize. 4th. Keely has discovered that all sympathetic streams, cerebellic, gravital, magnetic, and electric, are composed of triple flows; this fact governing all the terrestrial and celestial orders of positive and negative radiation. In gravity it would be more correct to speak of triple connective links, as there is no flow of gravity. 5th. Keely has discovered and was the first to demonstrate that electricity has never been handled; that it is in principle as material as is water; that it is not merely a force or a form of energy,--that it is matter; and that what we call electricity, and have diverted for commercial use in electric lighting, is but one of the triune currents, harmonic, enharmonic, and diatonic, which are united in pure electricity; that the enharmonic current seems to be sympathetically and mysteriously associated with the dominant current; and that the dominant current can no more be brought under control than can the lightning itself. The diversion of the dominant current would mean destruction to any mechanical medium used for that purpose, and death to the operator. The intense heat evolved by the electric stream Keely attributes to the velocity of the triple subdivision at the point of dispersion, as each triple seeks its medium of affinity. Sudden unition induces the same effect; but demonstration shows that the concentration of this triple force is as free of percussion as is the breath of an infant against the atmosphere; for the three currents flow together as in one stream, in the mildest sympathetic way, while their discharge after concentration is, in comparison to their accumulation, as the tornado's force to the waft of the butterfly's wing. The enharmonic current of this triple stream, Keely thinks, carries with it the power of propulsion that induces disturbance of negative equilibrium; which disturbance is essential to the co-ordination of its flow, in completing the, triune stream of electricity. When this fluid is discharged from the clouds, each triplet or third seeks its terrestrial concordant, there to remain until that supreme law which governs disturbance of equilibrium again induces sympathetic concordant concentration, continuing to pass through its evolutions, positively and negatively, until the solar forces are expended. "My researches have proved to me," writes Keely, "the subtle and pure conditions of the power of negative attraction and positive propulsion." 6th. These same researches have enabled Keely to pronounce definitely as to the nature of what is recognized as gravity, an ever-existing, eternal force, coexistent with the compound etheric, or high luminous, entering into all forms of aggregated matter at their birth. Keely thinks that gravity is the source from which all visible matter springs, and that the sympathetic or neutral centre of such aggregation becomes at birth a connective concordant link to all neutral centres that have preceded it and to all that may succeed it, and that disturbance of equilibrium, like gravity, is an ever-existing force. His researches in the vibratory subdivision of matter have revealed to him some of the mysteries of the hidden sympathetic world, teaching that "the visible world," as Coleridge wrote, "is but the clothing of the invisible world;" that "true philosophy," as Professor George Bush said, "when reached will conduct us into the realm of the spiritual as the true region of causes, disclosing new and unthought-of relations between the world of matter and of mind." Professor Thurston writes, in the January number of the North American Review, "We are continually expecting to see a limit reached by the discoverer, and by the inventor, and are as constantly finding that we are simply on a frontier which is being steadily pushed further and further out into the infinite unknown. The border-land is still ahead of us, constantly enlarging as we move on. The more we gain, the more is seen to be achievable." All planetary masses Keely calls terrestrial, showing in his writings that the beauty of the celestial concordant chords of sympathy forming the harmonious connective link, in what may be denominated "the music of the spheres," is seen in the alternate oscillating range of motion between the planetary systems; for at a certain range of the greater distance, harmony is established, and the attractive forces are brought into action, under the command, "Thus far shalt thou go, and no further." Then in the return towards the neutral centres, when at the nearest point to each other, the opposite or propulsive force is brought into play; and "thus near shalt thou come, and no nearer;" advancing and receding under the celestial law of etheric compensation and restoration, as originally established by the Great Creator. 7th. Keely has constructed instruments by which he is endeavouring to determine the nature of the triune action of the polar terrestrial stream, or envelope, as regards its vibratory philosophy. He is seeking to demonstrate its sympathetic association with the celestial stream, or luminiferous track,--the compound etheric field, from which all planetary masses spring. He considers the electric stream to be one of the triune sympathetic streams which help to build up, in their order of triple concentration, the high vitality of the polar stream, or, more correctly, the magnetic-electric terrestrial envelope, without which all living organisms would cease to exist. He classes the cohesive force of molecular masses as the dominant order of the electric stream, the molecule owing its negative attractive quality to the magnetic element. In Keely's beautiful experiments in antagonizing the polar stream, recently given before men of science, he has copied in his instruments the conditions which Nature has established in all her terrestrial ranges,--conditions necessary in order to equate a state of sympathetic disturbance for the revitalization of what is continually being displaced by negative dispersion. These mechanical conditions are principally differential vibratory settings on molecular aggregations of the metallic masses of gold, silver, and platinum. 8th. He has discovered that the range of molecular motion in all quiescent masses is equal to one-third of their diameters, and that all extended range is induced by sound-force, set at chords of the thirds which are antagonistic to the combined chords of the mass of the neutral centres that they represent, no two masses being alike, and that at a certain increased range of molecular motion, induced by the proper acoustic force, the molecules become repellent, and that when the sympathetic centres are influenced by a vibration concordant to the one that exists in themselves, the molecules become attractive; that the repellent condition seems to take place at a distance of about ten of the diameters of the molecules, this distance representing the neutral line of their attractive force, or the dividing line between the attractive and the repellent. Beyond this line, perfect triple separation takes place; inside of it, perfect attractive association is the result. The force which Mr. Keely uses in running machinery is the sympathetic attractive,--the force which, according to his theories, draws the planets together; while in his system of aërial navigation, should he live to perfect it, he will use a negation of this force,--the same that regulates the motion of the planets in their recession from each other. It is the sympathetic attractive force which keeps the planets subservient to a certain range of motion, between their oscillations. If this condition were broken up, the rotation of planets would cease; if destroyed at a given point of recession, all planets would become wanderers, like the comets; if destroyed at another given point, assimilation would take place, as two bullets fired through the air, meeting, would fuse into one mass. Nature has established her sympathetic concordants from the birth of the neutral centres of the planets, in a manner known only to the Infinite One. This is gravity. "The music of the spheres" is a reality. "The finer the power the greater the force." Thus, the inaudible atomic, etheric, and inter-etheric sounds, which control and direct the harmony of the movements of the celestial universe, are the most powerful of all sounds. If our faculty of hearing were a hundred billions of times intensified, we might be able to hear the streams of light as plainly as we now hear the sighings of the wind. Again, to answer the often-asked question, "What has Keely done?" 9th. He has broken joints of his fingers and thumbs, he has broken his ribs, he has had his left side paralyzed for weeks, he has lost the sight of one eye for months, in his hand-to-hand fight with the genii that he has encountered, and cannot completely subdue until he has effected the condition of polarization and depolarization which is necessary for the control of rotation and reversions in his commercial engine. An illness of nine weeks followed his abandonment of water in disintegrating; and he was obliged to return to its use, to avoid the percussion that was induced by the rapid vibration of the atmospheric air. To illustrate: if a bullet is fired at a man through a vessel of water a foot thick, the bullet is flattened out without injuring the man; while if nothing intervenes the man is killed. The question naturally arises, "Are not the forces with which Keely is dealing of too subtle a nature to be harnessed to do the daily work of the world?" Even were it so, the fascination attendant upon his researches would prevent him from abandoning them; but his faith in his ability to accomplish all that he has undertaken to do for the Keely Motor Company and for others is equalled only by the persistent energy which, in the face of gigantic obstacles, of cruel obloquy, of baffled endeavours, leads him to persevere to the end. He believes that the successful result is as positive as are the continued revolutions of our globe, under the great law which governs all Nature's highest, grandest, and most sensitive operations. And when has Nature ever revealed a force save to permit man to subjugate it for the progress of our race? Another question often heard is, "Why does not Keely make known his discoveries?" 10th. He has written three treatises to explain his system, the titles of which are as follows:-- I. Theoretical Exposé or Philosophical Analysis of Vibro-Molecular, Vibro-Atomic, and Sympathetic Vibro-Etheric Forces, as applied to induce Mechanical Rotation by Negative Sympathetic Attraction. II. Explanatory Analysis of Vibro-Acoustic Mechanism in all its Different Groupings or Combinations to induce Propulsion and Attraction (sympathetically) by the Power of Sound-Force; as also the Different Conditions of Intensity, both Positive and Negative, on the Progressive Octaves to Ozonic Liberation and Luminosity. III. The Determining Principle of Matter, or the Connective Link between the Finite and the Infinite, progressively considered from the Crude Molecular to the Compound Inter-Etheric; showing the Control of Spirit over Matter in all the Variations of Mass-Chords and Molecular Groupings, both Physical and Mechanical. If these treatises were read from the first page to the last, by men of science, they would not at present be any better understood than were Gilbert's writings in his age, author of "De Magnete." Newton was indebted to Gilbert for his discovery of the so-called law of gravitation. Keely defines gravity as transmittive inter-etheric force under immense etheric vibration, and electricity as a certain form of atomic vibration. When Gilbert, court-physician to Queen Elizabeth, announced his discovery of electricity, he was asked by his compeers of what use it was. No one dreamed then of it as a motive power. He replied, "Of what use is a baby? It may develop into a man or a woman, and, although we cannot make any use of electricity now, the world may in time find out uses for it." Just as little understood would Keely's writings be now on sympathetic negative attraction as were Gilbert's writings then on electricity and magnetism. Men found no sense in the words "electric" and "electricity," although derived from the Greek root for amber. The same fault is found with Keely for coining new words which no one understands. "Every branch of science, every doctrine of extensive application, has had its alphabet, its rudiments, its grammar: at each fresh step in the path of discovery the researcher has had to work out by experiment the unknown laws which govern his discovery." To attempt to introduce "the world"--even scientists--to any new system without previous preparation would be like giving a Persian book to a man to read who knew nothing of the language. As has been said, we do not expect a complicated problem in the higher mathematical analysis to be solved by one who is ignorant of the elementary rules of arithmetic. Just as useless would it be to expect every scientist to comprehend the laws of etheric physics and etheric philosophy after having witnessed Keely's experiments. The requirement of every demonstration is that it shall give sufficient proof of the truth that it asserts. A demonstration which does less than this cannot be relied upon, and no demonstration ever made has done more. The success of a demonstration is in proportion as the means applied are adequate or inadequate. As different principles exist in various forms of matter, it is quite impossible to demonstrate every truth by the same means or the same principles. It is only the prejudice of ignorance which exacts that every demonstration shall be given by a prescribed canon of science; as if the science of the present were thoroughly conversant with every principle that exists in nature. Yet physicists exact this, though they must know its inadequacy. Mr. Keely does not expect more from scientists than that they should withhold their defamatory opinions of him until they have witnessed his demonstrations and acquainted themselves with his theories. Yet, notwithstanding Professor Crooke's psychical researches and Professor Rücker's experiments in molecular vibration, demonstrating that molecules seem to have a "mental attribute, a sort of expression of free will," physicists still look upon the human organism as little more than a machine, taking small interest in experiments which evince the dominion of spirit over matter. Keely's researches in this province have shown him that it is neither the electric nor the magnetic flow, but the etheric, which sends its current along our nerves; that the electric and magnetic flows bear but an infinitely small ratio to the etheric flow, both as to velocity and tenuity; that true coincidents can exist between any mediums,--cartilage to steel, steel to wood, wood to stone, and stone to cartilage; that the same influence, sympathetic association, which governs all the solids holds the same control over all liquids, and again from liquid to solid, embracing the three kingdoms, animal, vegetable, and mineral; that the action of mind over matter thoroughly substantiates the incontrovertible laws of sympathetic etheric influence; that the only true medium which exists in nature is the sympathetic flow emanating from the normal human brain, governing correctly the graduating and setting-up of the true sympathetic vibratory positions in machinery, necessary to commercial success; that these flows come in on the order of the fifth and seventh positions of atomic subdivision, compound inter-etheric sympathy a resultant of this subdivision; that if metallic mediums are brought under the influence of this sympathetic flow they become organisms which carry the same influence with them that the human brain does over living physical positions, and that the composition of metallic and that of physical organisms are one and the same thing, although the molecular arrangement of the physical may be entirely opposite to the metallic on their aggregations; that the harmonious chords induced by sympathetic positive vibration permeate the molecules in each, notwithstanding, and bring about the perfect equation of any differentiation that may exist--in one the same as in the other--and thus they become one and the same medium for sympathetic transmission; that the etheric, or will-flow, is of a tenuity coincident to the condition governing the seventh subdivision of matter, a condition of subtlety that readily and instantaneously permeates all forms of aggregated matter, from air to solid hammered steel, the velocity of the permeation being the same with the one as with the other; that the tenuity of the etheric flow is so infinitely fine that a magnifying glass, the power of which would enlarge the smallest grain of sand to the size of the sun, brought to bear upon it would not make its structure visible to us; and that, light traversing space at the speed of two hundred thousand miles per second, a distance requiring light a thousand centuries to reach would be traversed by the etheric flow in an indefinite fragment of a second. 11th. Keely has given such proof of genius as should bring all scientists who approach him into that attitude of mind which would lead them to receive without prejudice the evidence of the truth of the claims he offers. Genius has been defined as an extraordinary power of synthetic creation. Another definition of the man of genius is, the man who unceasingly cultivates and perfects such great natural aptitudes and facilities as he has been endowed with at his birth. No man has ever lived on this earth who, according to these qualifications, so deserved to be known and acknowledged as a man of genius as John Worrell Keely. History will determine whether he is a man of genius or "a charlatan," as some scientists still persist in calling him. It is easier, as has been said, to accuse a man of fraud than to account for unknown phenomena. A system of doctrine can be legitimately refuted only upon its own principles, viz., by disproving its facts and invalidating the principles deduced from them. Abercrombie said that the necessary caution which preserves us from credulity should not be allowed to engender scepticism,--that both of these extremes are equally unworthy of a mind which devotes itself with candour to the discovery of truth. "We must not decide that a thing is impossible," says Lebrun, "because of the common belief that it cannot exist; for the opinion of man cannot set limits to the operations of Nature, nor to the power of the Almighty. He who attempts to hold up to contempt a scientific subject of which he is profoundly ignorant has but small pretensions to the character of a philosopher." Galileo said, after pronouncing his abjuration, "E pur si muove" ("But it does move"). What signified to him the opinion of men, when Nature confirmed his discovery? Of what value were their prejudices or their wisdom in opposition to her immutable laws? Kedzie, speculating upon the nature of force, writes, "Molecules and masses act precisely as they are acted on; they are governed by the iron instead of the golden rule. They do unto others as others have done unto them. Whence comes this energy? Not from atoms, but from the Creator, in the beginning." The Duke of Argyll says, "We know nothing of the ultimate seat of force. Science, in the modern doctrine of the conservation of energy and the convertibility of forces, is already getting something like a firm hold of the idea that all kinds of forces are but forms or manifestations of some one central force, arising from one fountain-head of power." 12th. Keely's researches have taught him that this one fountain-head is none other than the omnipotent and all-pervading Will-Force of the Almighty, which creates, upholds, guides, and governs the universe. "The whole world-process," says Von Hartmann, "in its context is only a logical process; but in its existence it is a continued act of will." Lilly says, "This is what physical law means. Reason and will are inseparably united in the universe as they are in idea. If we will anything, it is for some reason. In contemplating the structure of the universe, we cannot resist the conclusion that the whole is founded upon a distinct idea." Keely holds to the harmony of this "distinct idea" throughout creation, and he demonstrates by vibratory machinery that all forces are indestructible, immaterial, homogeneous entities, having their origin and unity in one great intelligent personal will-force. Were it not for this will-force eternally flowing into all created forms, the entire universe would disappear. As the workman employs his instrument to accomplish his designs, so Omnipotence may be said, in all reverence, to regulate His systems of worlds through and by the vibratory ether which He has created to serve His purpose. Well did Hertz reason when he wrote, "Soon the question set by modern physics will be, 'Are not all things due to conditions of ether?'" He had never heard of the toiler on this side of the Atlantic, when, after his own discovery, in 1888, that ether was imprisoned and used in every electro-magnetic engine, without this fact having been even so much as suspected by a single scientist, he wrote, in the Revue Scientifique, "We have gained a greater height than ever, and we possess a solid basis which will facilitate the ascent, in the research of new truths. The road which is open to us is not too steep, and the next resting-point does not appear inaccessible. Moreover, the crowds of researchers are full of ardour. We must therefore welcome with confidence all the efforts that are being made in this direction." Keely has found no "resting-point" in his researches of a lifetime; and, instead of being "welcomed with confidence" by his fellow-researchers in science, he has suffered at their hands more than will ever be known by his detractors. Keely's discoveries would have died with him, through the calumnies of these same scientists, as far as demonstration was concerned, had not a company been formed, in the early days of his inventions, which for many years furnished him with the necessary funds, expecting almost immediate financial success. The sneers of men of science crying "Charlatan," the ridicule of the public press, and the denunciations of the ignorant have been mighty factors in debasing the value of the shares of the company. The courage, faith, and contributing capacity of nearly all the stockholders have given out; and it is fortunate that now Mr. Keely's work of evolution has at last reached the point where he is able to convince those scientists of his integrity whose minds are broad enough to conform to what Herbert Spencer has said is the first condition of success in scientific research,--viz. "an honest receptivity, and willingness to abandon all preconceived notions, however cherished, if they be found to contradict the truth." Keely may be said to have spent years of his valuable time in giving exhibitions whereby to raise the funds needed for his scientific researches. Again and again has he taken apart his various machines, to show their interior construction to the sceptical; and what this means, in the attendant delay, will be better understood when he has made known how slight a thing, by the laws of sympathetic association, may retard his progress for days, even for weeks. Take, for example, his last experience with his preliminary commercial engine, to which, before he had completed his graduation, he was induced, in November 1889, to apply a brake, to show what resistance the vibratory current could bear under powerful friction. A force sufficient to stop a train of cars, it was estimated, did not interfere with its running; but under additional strain a "thud" was heard, and the shaft of the engine was twisted. The engine should not have been submitted to such a test until after the differentiation had been equated, and perfect control in reversions established. And yet, so often has Keely made what seemed to be disasters an advantage in the end, it is possible that the interruption and delay may enable him to produce a perfect engine sooner than he would have done on this model. The world will never know how many mechanical difficulties Keely has conquered before attaining his present degree of success, in which he thinks he has mastered all that pertains to the principle of the force that he is dealing with, so far as necessary for commercial purposes, the difficulties that he still has to contend with being merely the minor ones of mechanical detail. The fact that so much of Mr. Keely's success, in conducting his experiments when giving exhibitions, depends upon the complete perfection of his instruments, is one of the strongest arguments that could be advanced in proof of the genuineness of his claims. Has any one ever heard of a performer in legerdemain who, after assembling an audience to witness his tricks, announced that something was wrong with his conjuring apparatus and that he was unable to exhibit his dexterity? Feats of legerdemain can be performed, night after night, year in and year out, without any hitch on the part of the operator; but all who are conversant with the failures attendant upon a certain order of experiments, as for instance in the liquefying of oxygen gas, will be able to appreciate the uncertainty which characterizes the action of Mr. Keely's instruments at times. It is only by progressive experimental research that knowledge of the laws governing Nature's operations can be gained, and a system evolved to perpetuate such knowledge. The hypothesis of to-day must be discarded to-morrow, if further research proves its fallacy. Is it not, then, another strong argument in favour of Keely's integrity that, confessing ignorance of the laws that govern the force he has discovered, he has plodded on through all these years, experimenting upon its nature, with instruments of his own invention, which from their delicate and imperfect construction are uncertain in their operations, until he has so improved the defective machine as to make it a stepping-stone, by which he ascends to perfection? Take the imperfect comparison of a ladder: no workman can attain the summit in one effort; he must mount step by step. To quote from Keely's writings, "The mathematics of vibratory etheric science, both pure and applied, require long and arduous research. It seems to me that no man's life is long enough to cover more than the introductory branch. The theory of elliptic functions, the calculus of probabilities, are but pygmies in comparison to a science which requires the utmost tension of the human mind to grasp. But let us wait patiently for the light that will come, that is even now dawning." [10] On the 28th of May, 1889, Mr. Keely's workshop was visited by several men interested to see and judge for themselves of the nature of his researches. Among them were Professor Leidy, of the University of Pennsylvania, and James M. Willcox, author of "Elemental Philosophy." After seeing the experiments in acoustics, and the production, storage, and discharge of the ether, Mr. Willcox remarked that no one who had witnessed all that they had seen in the line of associative vibration, under the same advantages, could assert any fraud on the part of Keely without convicting himself of the rankest folly. These gentlemen met Mr. Keely with their minds open to conviction, though with strong prejudices against the discovery of any unknown force. They treated him as if he were all that he is, keeping out of sight whatever doubts they may have had of the genuineness of his claims as a discoverer; and, in the end, all who were present expressed their appreciation of his courtesy in answering the questions asked, and their admiration of what he has accomplished on his unknown path. In doing this, they were simply doing justice to him and to themselves,--to that self-respect which leads men to respect the rights of others, and to do unto others as they would be done by. Had they questioned Keely's integrity, or betrayed doubts of his honesty of purpose, he would at once have assumed the defensive, and would have informed them that he has no wish to conduct experiments for scientists who are ready to give their opinions of his theories before having heard them propounded, or of his experiments before witnessing them. When Keely's system of "sympathetic vibration" is made known ("sympathetic seeking" Mr. Willcox would call it), it will be seen how sensitive Mr. Keely's instruments are to the vibrations caused by street-noises, to vibrations of air from talking in the operating room, to touch even, as well as why it is that, although he is willing to take apart and explain the construction of his instruments in the presence of investigators, he objects to having them handled by others than himself, after they have been "harmonized," or "sensitized," or "graduated." Mr. Keely is his own worst enemy. When suspected of fraud he acts as if he were a fraud; and in breaking up his vibratory microscope and other instruments which he had been years in perfecting, at the time he was committed to prison in 1888, he laid himself open to the suspicion that his instruments are but devices with which he cunningly deceives his patrons. Yet these same instruments he has, since their reconstruction, dissected and explained to those who approached him in the proper spirit. It is only when he has been subjected to insulting suspicions by arrogant scientists that he refuses to explain his theories, and to demonstrate their truth, as far as it is in his power to do so. "Keely may be on the right track, after all," remarked an English scientist, after Prof. Hertz had made known his researches on the structure of ether; "for if we have imprisoned the ether without knowing it, why may not Keely know what he has got a hold of?" Norman Lockyer, in his "Chemistry of the Sun," confirms Keely's theories when he writes, "The law which connects radiation with absorption and at once enables us to read the riddle set by the sun and stars is, then, simply the law of 'sympathetic vibration.'" "It is remarkable," says Horace W. Smith, "that in countries far distant from each other, different men have fallen into the same tracks of science, and have made similar and correspondent discoveries, at the same period of time, without the least communication with each other." So has it been in all periods of progress and in all branches of science, from the discoveries of Euclid and Archimedes down to those of Galileo and Descartes and Bacon, and, in later days, of Gilbert and Newton and Leibnitz, then Franklin and Collison and Von Kliest and Muschenbröck; and now Keely and Hertz and Depuy and Rücker and Lockyer are examples. Never has a discovery leading to a new system been begun and perfected by the same individual so far as Keely is doing; but, as Morley has said, "the representative of a larger age must excel in genius all predecessors." The application of his discovery to the service of humanity is the aim and end of Keely's efforts; his success means "vastly more than the most sanguine to-day venture to predict," promising "a true millennial introduction into the unseen universe, and the glorious life that every man, Christian or sceptic, optimist or pessimist, would gladly hope for and believe possible." (Thurston.) Not the least among the ultimate blessings to our race which Keely's discovery foreshadows is the deeper insight that it will bestow into the healing power of the finer forces of nature, embracing cures of brain and nerve disorders that are now classed with incurable diseases. Only a partial answer has been given to the question, "What has Keely done for science?" But enough has been said to convey some idea of the subtle nature of the force he is dealing with, and of the cause of the delays which have again and again disappointed the inventor, as well as the too sanguine hopes of immediate commercial success which have animated the officers and stockholders of "The Keely Motor Company." Keely has no secret to wrest from him. Instead of "Keely's Secret," it should be called "Nature's Secret;" for the problem has still to be worked out, the solution of which will make it "Keely's Secret;" and until this problem is fully solved to the inventor's satisfaction for commercial application, Keely has no secret that he is not willing to disclose, as far as it is in his power to do so. CHAPTER XII. 1891. VIBRATORY PHYSICS.--TRUE SCIENCE. We seem to be approaching a theory as to the construction of ether. Hertz has produced vibrations, vibrating more than one hundred million times per second. He made use of the principle of resonance. You all understand how, by a succession of well-timed small impulses, a large vibration may be set up.--Prof. Fitzgerald. Dr. Schimmel, in his lecture on "The Unity of Nature's Forces," says:--"The Greek philosophers, Leucippus, Anaxagoras, Democritus, and Aristotle, base their philosophies on the existence of an ether and atoms." According to Spiller's system, "both ether and atoms are material. The atoms are indivisible. Chemistry, being based on the correctness of this statement, forces us to accept it." But we are not forced to accept it if it is proved to be false. Keely has now reached a stage in his researches at which he is able to demonstrate the truth of the hypotheses which he is formulating into a system; and consequently the stage where he can demonstrate whether theories, that have prevailed concerning the cause of physical phenomena, are sound or without basis in fact. Until this stage was reached it would have been as useless to make Mr. Keely's theories known, as it would be to publish a treatise to prove that two and two make five. Scientific men reject all theories in physics in which there is not an equal proportion of science and mathematics, excluding all questions of pure metaphysics. They are right; for, until the world had undergone a state of preparation for another revelation of truth, the man who demonstrated all that Keely is now prepared to demonstrate would have been burned alive as a wizard. To use the words of Babcock, one of Keely's staunchest adherents, in 1880:--"This discoverer has entered a new world, and although an unexplored region of untold wealth lies beyond, he is treading firmly its border, which daily widens as with ever-increasing interest he pursues his explorations. He has passed the dreary realm where scientists are groping. His researches are made in the open field of elemental force, where gravity, inertia, cohesion, momentum, are disturbed in their haunts and diverted to use; where, from unity of origin, emanates infinite energy in diversified forms," and, to this statement I would add--where he is able to look from nature up to nature's God, understanding and explaining, as no man before ever understood and explained, how simple is "the mysterious way in which God works His wonders to perform." Mr. Babcock continues:--"Human comprehension is inadequate to grasp the possibilities of this discovery for power, for increased prosperity, and for peace. It includes all that relates mechanically to travel, manufacture, mining, engineering, and warfare." Up to within two years, Keely, this discoverer of unknown laws of nature, has been left partially to the mercy of men who were interested only in mechanical "possibilities." In the autumn of 1888, he was led into a line of research which made the mechanical question one of secondary interest; and yet the present results are such as to prove that on this line alone can he ever hope to attain commercial success. The course then adopted has also been the means of placing his discoveries before the world, endorsed in such a manner as to command attention to his views and theories. It has been said that if extreme vicissitudes of belief on the part of men of science are evidences of uncertainty, it may be affirmed that of all kinds of knowledge none is more uncertain than science. The only hope for science is more science, says Drummond. Keely now bestows the only hope for science--"more science." He accounts for the non-recognition by scientists of his claims, in these words: "The system of arranging introductory etheric impulses by compound chords set by differential harmonies, is one that the world of science has never recognized, simply because the struggles of physicists, combating with the solution of the conditions governing the fourth order of matter, have been in a direction thoroughly antagonistic, and opposite to a right one. It is true that luminosity has been induced by chemical antagonism, and, in my mind, this ought to have been a stepping-stone towards a more perfect condition than was accepted by them; but independent of what might be necessary to its analysis, the bare truth remains that the conditions were isolated--robbed of their most vital essentials--by not having the medium of etheric vibration associated with them." In order to subdivide the atoms in the atomic triplet, the molecular ether, liberated from the molecule, is absolutely necessary to effect the rupture of the atoms; and so on, progressively, in each order of ether, molecular, inter-molecular, atomic, inter-atomic, etheric, inter-etheric, the ether liberated in each successive division is essential to the next subdivision. The keynote of Mr. Keely's researches is that the movements of elastic elements are rhythmical, and before he had reached his present stage in producing vibrations, on the principle of resonance, he has had problems to solve which needed the full measure of inspiration or apperception that he has received. Hertz has produced vibrations about one metre long, vibrating more than one hundred million times a second. Keely has produced, using an atmospheric medium alone, 519,655,633 vibrations per second; but, interposing pure hydrogen gas between soap films and using it as a medium of acceleration, he asserts that on the enharmonic third a rate of vibration may be induced which could not be set down in figures, and could only be represented in sound colours. He has invented instruments which demonstrate in many variations the colours of sound, registering the number of necessary vibrations to produce each variation. The transmissive sympathetic chord of B flat, third octave, when passing into inaudibility, would induce billions of billions of vibrations, represented by sound colour on a screen illuminated from a solar ray. But this experiment is one of infinite difficulty, from the almost utter impossibility of holding the hydrogen between the two films long enough to conduct the experiment. Keely made over 1200 trials before succeeding once in inducing the intense blue field necessary, covering a space of six weeks, four hours at a time daily; and should he ever succeed in his present efforts to produce a film that will stand, he anticipates being able to register the range of motion in all metallic mediums. On this subject Keely writes:--The highest range of vibration I ever induced was in the one experiment that I made in liberating ozone by molecular percussion, which induced luminosity, and registered a percussive molecular force of 110,000 lbs. per square inch, as registered on a lever constructed for the purpose. The vibrations induced by this experiment reached over 700,000,000 per second, unshipping the apparatus, thus making it insecure for a repetition of the experiments. The decarbonized steel compressors of said apparatus moved as if composed of putty. Volume of sphere, 15 cubic inches; weight of surrounding metal, 316 lbs. Recently some questions, propounded to Mr. Keely by a scientist, elicited answers which the man of science admitted were clear and definite, but no physicist could accept Keely's assertion that incalculable amounts of latent force exist in the molecular spaces, for the simple reason that science asserts that molecular aggregation is attended with dissipation of energy instead of its absorption. The questions asked were:-- I. "In disintegrating water, how many foot-pounds of energy have you to expend in order to produce or induce the vibratory energy in your acoustical apparatus?" Answer.--"No foot-pounds at all. The force necessary to excite disintegration when the instrument is sensitized, both in sensitization and developments, would not be sufficient to wind up a watch." II. "What is the amount of energy that you get out of that initial amount of water, say twelve drops, when decomposed into ether?" Answer.--"From twelve drops of water a force can be developed that will fill a chamber of seven pint volume no less than six times with a pressure of ten tons to the square inch." III. "In other words, if you put so many pounds of energy into vibratory motion, how many foot-pounds do you get out of this?" Answer.--"All molecular masses of metal represent in their interstitial molecular spaces incalculable amounts of latent force, which, if awakened and brought into intense vibratory action by the medium of sympathetic liberation, would result in thousands of billions more power in foot-pounds than that necessary to awaken it. The resultant development of any and all forces is only accomplished by conditions that awaken the latent energy they have carried with them during molecular aggregation. If the latent force that exists in a pound of water could be sympathetically evolved or liberated up to the seventh subdivision or compound inter-etheric, and could be stored free of rotation, it would be in my estimation sufficient to run the power of the world for a century." This statement gives another of Keely's discoveries to the world, viz., that molecular dissociation does not create energy, as men have asserted Keely has claimed, but supplies it in unlimited quantities, as the product of the latent energy accumulated in molecular aggregation. This is to the physicist as if Keely had asserted that two and two make a billion, but as a man of science, who is held to be "the scientific equal of any man in the world," has come forward to make known that, in his opinion, "Keely has fairly demonstrated the discovery of a force previously unknown to science," the discoverer at lasts feels at liberty to make public the nature of his discoveries. Until Dr. Joseph Leidy had taken this stand, Mr. Keely could not, without jeopardizing his interests, and the interests of the Keely Motor Company, have made known in what particulars his system conflicts with the systems upheld by the age in which we live. After the warning given in the history of Huxley's "Bathybius," we may feel quite sure that if Keely had failed to demonstrate the genuineness of his claims by actual experiment, no scientist would have risked the world-wide reputation of a lifetime by endorsement of the discovery of an unknown force, as Professor Leidy has done, while Keely himself was under such a cloud that, to advocate his integrity and uphold the importance of his discovery, has hitherto been enough to awaken doubts as to the sanity of his upholders. Among many others who have written of it from the standpoint of Keely's accountability for the mistakes of the managers of the Keely Motor Company--men who made no pretence of caring for anything but dividends--was one who asserted, in the New York Tribune, that it was a "remarkable delusion, full of tricks too numerous to mention, the exposure of which ought to be made to bring the Keely craze to an end." In the same journal an editorial states that "Mr. Keely appears to have no mechanical ingenuity, his strong point being his ability as a collector. He has one of the largest and best arranged collections of other people's money to be found in the United States. Having, a number of years ago, during a fit of temporary insanity, constructed a machine which, if any power on earth could start it, would explode and pierce the startled dome of heaven with flying fragments of cog-wheels and cranks, he now sits down calmly, and allows this same mechanical nightmare to make his living for him. This is genius; this is John W. Keely; he toils not, neither does he spin, but he has got an hysterical collection of crooked pipes and lob-sided wheels tied up in his back room that extract the reluctant dollar from the pocket of avarice without fail." This is a specimen of the nature of the ridicule which was encountered by Keely's "upholders," as well as by himself. Until Professor Leidy and Dr. Willcox came to the front, in March, 1890, Mr. Keely had no influential supporters, and not one scientist could be found who was ready to encounter the wasps. Such is the position of all defenders of the truth in all ages; but the torch being held aloft, in such hands as have now seized it, the opportunity is given to see what Keely proclaims as truth. We know that science denies the divisibility of atoms, but Keely affirms and demonstrates that all corpuscules of matter may be divided and subdivided by a certain order of vibration. During all these years in which he has given exhibitions of the operation of his generators, liberators, and disintegrators, in turn, each being an improvement, successively, on the preceding one, no one has attempted to give to the public any theory, or even so much as a sensible conjecture, of the origin of the force. When Mr. Keely was asked, by a woman in 1884, if it were not possible that he had dissociated hydrogen gas, and that his unknown force came from that dissociation, he replied that he thought it might be; but he made no assertion that he had. This conjecture was repeated to an English scientist, who replied that he was willing to make a bet of 10,000l. that hydrogen is a simple element. The same scientist says now that he should answer such a question with more caution, and say that he had never known hydrogen to be dissociated. Theory and Formula of Aqueous Disintegration. The peculiar conditions as associated with the gaseous elements of which water is composed, as regards the differential volume and gravity of its gases, make it a ready and fit subject of vibratory research. In submitting water to the influence of vibratory transmission, even on simple thirds, the high action induced on the hydrogen as contrasted with the one on the oxygen (under the same vibratory stream), causes the antagonism between these elements that induces dissociation. The differential antagonistic range of motion, so favouring the antagonistic thirds as to become thoroughly repellent. The gaseous element thus induced and registered, shows thousands of times much greater force as regards tenuity and volume than that induced by the chemical disintegration of heat, on the same medium. In all molecular dissociation or disintegration of both simple or compound elements, whether gaseous or solid, a stream of vibratory antagonistic thirds, sixths, or ninths, on their chord mass will compel progressive subdivisions. In the disintegration of water the instrument is set on thirds, sixths, and ninths, to get the best effects. These triple conditions are focalized on the neutral centre of said instrument so as to induce perfect harmony or concordance to the chord-note of the mass-chord of the instrument's full combination; after which the diatonic and the enharmonic scale located at the top of the instrument, or ring, is thoroughly harmonized with the scale of ninths which is placed at the base of the vibratory transmitter with the telephone head. The next step is to disturb the harmony on the concentrative thirds, between the transmitter and disintegrator. This is done by rotating the syren so as to induce a sympathetic communication along the nodal transmitter, or wire, that associates the two instruments. When the note of the syren becomes concordant to the neutral centre of the disintegrator, the highest order of sympathetic communication is established. It is now necessary to operate the transferable vibratory negatizer, or negative accelerator, which is seated in the centre of the diatonic and enharmonic ring, at the top of disintegrator, and complete disintegration will follow (from the antagonisms induced on the concordants by said adjunct), in triple progression, thus:--First, thirds: Molecular dissociation resolving the water into a gaseous compound of hydrogen and oxygen. Second, sixths: resolving the hydrogen and oxygen into a new element by second order of dissociation, producing what I call, low atomic ether. Third, ninths: The low atomic ether resolved into a new element, which I denominate high or second atomic harmonic. All these transmissions being simultaneous on the disturbance of sympathetic equilibrium by said negative accelerator. Example:--Taking the chord mass of the disintegrator B flat, or any chord mass that may be represented by the combined association of all the mechanical parts of its structure (no two structures being alike in their chord masses), taking B flat, the resonators of said structure are set at B flat first octave, B flat third octave, and B flat ninth octave, by drawing out the caps of resonators until the harmony of thirds, sixths, and ninths are reached; which a simple movement of the fingers on the diatonic scale, at the head, will determine by the tremulous action which is highly sensible to the touch, on said caps. The caps are then rigidly fixed in their different positions by set screws. The focalization to the neutral centre is then established by dampening the steel rods, on the scale at the back, representing the thirds, sixths, and ninths, drawing a piece of small gum tube over them, which establishes harmony to the chord mass of the instrument. Concordance is thus effected between the disintegrator and the ninths of the scale at base of transmitters with telephonic head. This scale has a permanent sympathetic one, set on the ninth of any mass chord that may be represented, on any and all the multiple variations of mechanical combinations. In fact, permanently set for universal accommodation. The next step is to establish pure harmony between the transmitter and the disintegrator, which is done by spinning the syren disk, then waiting until the sympathetic note is reached, as the syren chord, decreasing in velocity, descends the scale. At this juncture, the negative accelerator must be immediately and rapidly rotated, inducing high disturbance of equilibrium between the transmitter and the disintegrator by triple negative evolution, with the result that a force of from five to ten, fifteen, twenty, and thirty thousand pounds to the square inch is evolved by the focalization of this triple negative stream on the disintegrating cell, or chamber, whether there be one, two, three, five, or ten drops of water enclosed within it. Graduation of Machines. Mr. Keely gives a few introductory words concerning the necessary graduating of his instruments, for effecting conditions necessary to ensure perfect sympathetic transmission, which will serve to show how great are the difficulties that have been attendant upon getting his machines into a condition to control and equate the differentiation in molecular masses, requiring greater skill than in researching the force of a sunbeam. He writes:--The differentiation in molecular metallic masses, or grouping, is brought about in their manipulations in manufacturing them for commercial uses; in the forging of a piece of metal, in the drawing of a length of wire, and in the casting of a molten mass to any requisite form. The nearest approach to molecular uniformity in metallic masses is in the wire drawn for commercial uses, gold and platina being the nearest to freedom from differentiation. But even these wires, when tested by a certain condition of the first order of intensified molecular vibration for a transferring medium between centres of neutrality, I find to be entirely inadequate for the transfer of concordant unition, as between one and the other, on account of nodal interferences. We can appreciate the difficulty of converting such a medium to a uniform molecular link, by knowing that it can be accomplished only after removing all nodal interference, by inducing between the nodal waves a condition in which they become subservient to the inter-sympathetic vibratory molecular link of such structure or wire. Therefore, it is necessary to submit the wire to a system of graduation in order to find what the combined chords of these nodal interferences represent when focalized to one general centre. Then the differentiation between these nodal waves and the inter-molecular link must be equated, by what I call a process of vibratory induction, so as to induce pure concordance between one and the other. To elaborate on this system of graduation, for effecting conditions necessary to ensure perfect and unadulterated transmission, would make up a book that would take days to read and months to study. The graduating of a perfectly constructed instrument, to a condition to transmit sympathetically, is no standard whatever for any other one that may be built, nor ever will be, because no concordant conditions of compound molecular aggregation can ever exist in visible groupings. If it were even possible to make their parts perfectly accurate one to the other, in regard to atmospheric displacement and weight, their resonating qualities would still have a high rate of sympathetic variation in their molecular groupings alone. If one thousand million of coins, each one representing a certain standard value, and all struck from the same die, were sympathetically graduated under a vibratory subdivision of 150,000, the most amazing variation would present itself, as between each individual coin throughout the number, in regard to their molecular grouping and resonance.... It will be realized in the future what immense difficulties have been encountered by Mr. Keely in perfecting his system of graduation, and in constructing devices for the guidance of artificers and mechanicians, whereby those who are not as abnormally endowed as he is for his work, can bring a proper vibratory action into play to induce positive sympathetic transmission; as will also be realized the stupidity of the men who still seek to confine his researches to perfecting the so-called Keely motor, before his system is sufficiently developed to enable others to follow it up, should his physical strength give out. His system of graduating research, when completed, will enable men to take up the work, not from the standard of an already completed structure that is true in its operation, though a perfect duplicate as to size and gravity be made, for each successively constructed machine requires a knowledge of its own conditions of sensitivity, as regards its mass chords. Keely writes:-- "That tuning forks can be so constructed as to show coincident or concordant association with each other, is but a very weak illustration of the fact which governs pure acoustic assimilation. The best only approach a condition of about a fortieth, as regards pure attractive and propulsive receptiveness. By differentiating them to concordant thirds, they induce a condition of molecular bombardment between themselves, by alternate changes of long and short waves of sympathy. Bells rung in vacuo liberate the same number of corpuscules, at the same velocity as those surrounded by a normal atmosphere; and hence the same acoustic force attending them, but they are inaudible from the fact that, in vacuo, the molecular volume is reduced. Every gaseous molecule is a resonator of itself, and is sensitive to any and all sounds induced, whether accordant or discordant. Answers to Questions. The positive vibrations are the radiating or propulsive; the negative vibrations are the ones that are attracted towards the neutral centre. The action of the magnetic flow is dual in its evolutions, both attractive and propulsive. The sound vibrations of themselves have no power whatever to induce dissociation, even in its lowest form. Certain differential, dual, triple and quadruple, chords give introductory impulses which excite an action on molecular masses, liquid and gaseous, that increase their range of molecular motion and put them in that receptive state for sympathetic vibratory interchange which favours molecular disintegration; then, as I have shown, the diatonic enharmonic is brought into play, which further increases the molecular range of motion beyond fifty per cent. of their diameters, when molecular separation takes place, giving the tenuous substance that is necessary to induce progressive subdivision. This molecular gaseous substance, during its evolution, assumes a condition of high rotation in the sphere or tube in which it has been generated, and becomes itself the medium, with the proper exciters, for further progressive dissociation. The exciters include an illuminated revolving prism, condenser, and coloured lenses, with a capped glass tube strong enough to carry a pressure of at least one thousand pounds per square inch. To one of these caps a sectional wire of platinum and silver is attached; the other cap is attached to the tube, so screwed to the chamber as to allow it to lead to the neutral centre of said chamber. Mineral Disintegration. I have been repeatedly urged to repeat my disintegrations of quartz rock; but it has been utterly out of my power to do so. The mechanical device with which I conducted those experiments was destroyed at the time of the proceedings against me. Its graduation occupied over four years, after which it was operated successfully. It had been originally constructed as an instrument for overcoming gravity; a perfect, graduated scale of that device was accurately registered, a copy of which I kept; I have since built three successive disintegrators set up from that scale, but they did not operate. This peculiar feature remained a paradox to me until I had solved the conditions governing the chords of multiple masses; when this problem ceased to be paradoxical in its character. As I have said, there are no two compound aggregated forms of visible matter that are, or ever can be, so duplicated as to show pure sympathetic concordance one to the other. Hence the necessity of my system of graduation, and of a compound device that will enable anyone to correct the variations that exist in compound molecular structures; or in other words to graduate such, so as to bring them to a successful operation.... Keely. Disturbance of Magnetic Needle. If Keely's theories are correct, science will in time classify all the important modifications of the one force in nature as sympathetic streams, each stream composed of triple flows. Mr. Keely maintains that the static condition which the magnetic needle assumes, when undisturbed by any extraneous force outside of its own sympathetic one, proves conclusively that the power of the dominant third, of the triple combination of the magnetic terrestrial envelope, is the controlling one of this sympathetic triplet, and the one towards which all the others co-ordinate. All the dominant conditions of nature represent the focal centres towards which like surrounding ones become sympathetically subservient. The rapid rotation of the magnetic needle of a compass which Mr. Keely shows in his experiments, rests entirely on the alternating of the dominant alone, which is effected by a triple condition of vibration that is antagonistic to its harmonious flow as associated with its other attendants. A rapid change of polarity is induced, and rapid rotation necessarily follows. Quoting from Keely's writings,--"The human ear cannot detect the triple chord of any vibration, or sounding note, but every sound that is induced of any range, high or low, is governed by the same laws, as regards triple action of such, that govern every sympathetic flow in Nature. Were it not for these triple vibratory conditions, change of polarity could never be effected, and consequently there could be no rotation. Thus the compounding of the triple triple, to produce the effect, would give a vibration in multiplication reaching the ninth, in order to induce subservience, the enumeration of which it would be folly to undertake, as the result would be a string of figures nearly a mile in length to denote it. When the proper impulse is given to induce the rotation with pure alternating corpuscular action, the conditions of action become perpetual in their character, lasting long enough from that one impulse to wear out any machine denoting such action, and on the sympathetic stream eternally perpetual. The action of the neutral or focalizing centres represents molecular focalization and redistribution, not having any magnetism associated with them; but when the radiating arms of their centres are submitted to the triple compound vibratory force, representing their mass thirds, they become magnetic and consequently cease their rotation. Their rotation is induced by submitting them to three different orders of vibration, simultaneously giving the majority to the harmonic third. Theory of the Induction of Sympathetic Chords to excite rotation, by vibrophonic trajection to and from centres of neutrality, as induced and shown to Professor Leidy, Dr. Willcox, and others, on revolving globe. All hollow spheres, of certain diameters, represent, as per diameters and their volume of molecular mass, pure, unadulterated, sympathetic resonation towards the enharmonic and diatonic thirds of any, and in fact all, concordant sounds. In tubes it is adversely different, requiring a definite number of them so graduated as to represent a confliction by thirds, sixths, and ninths, as towards the harmonic scale. When the conditions are established, the acoustic result of this combination, when focalized, represents concordant harmony, as between the chord mass of the instrument to be operated and chord mass of the tubes of resonation. Therefore the shortest way towards establishing pure concordance, between any number of resonating mediums, is by the position that Nature herself assumes in her multitudinous arrangements of the varied forms and volumes of matter--the spherical. The great difficulty to overcome, in order to get a revolution of the said sphere, exists in equating the interior adjuncts of same. In other words, the differentiation induced must be so equated as to harmonize and make their conditions purely concordant to the molecular mass of the sphere. Example: Suppose the chord of the sphere mass represents B flat, or any other chord, and the internal adjuncts by displacement of atmospheric volume differentiates the volume one-twentieth; this displacement in the shell's atmospheric volume would represent an antagonistic twentieth against the shell's mass concordance, to equate which it would be necessary to so graduate the shell's internal adjuncts as to get at the same chord;--an octave or any number of octaves that comes nearest to the concordance of the shell's atmospheric volume. No intermediates between the octaves would ever reach sympathetic union. We will now take up the mechanical routine as associated with adjuncts of interference, and follow the system for chording the mechanical aggregation in its different parts, in order to induce the transmissive sympathy necessary to perfect evolution, and to produce revolution of the sphere or shell. Example.--Suppose that we had just received from the machine shop a spun shell of twelve inches internal diameter, 1·32 of an inch thick, which represents an atmospheric volume of 904·77 cubic inches. On determination by research we find the shell to be on its resonating volume B flat, and the molecular volume of the metal that the sphere is composed of, B natural. This or any other antagonistic chord, as between the chord mass of the shell and its atmospheric volume, would not interfere but would come under subservience. We now pass a steel shaft through its centre, 1/2 inch in diameter, which represents its axial rest. This shaft subjects the atmospheric volume of the shell to a certain displacement or reduction, to correct which we first register the chord note of its mass, and find it to be antagonistic to the chord mass of the shell, a certain portion of an octave. This must be corrected. The molecular volume of the shaft must be reduced in volume, either by filing or turning, so as to represent the first B flat chord that is reached by such reduction. When this is done the first line of interference is neutralized, and the condition of sympathy is as pure between the parts as it was when the globe was minus its axis. There is now introduced on its axis a ring which has seven tubes or graduating resonators, the ring being two-thirds the diameter of the globe, the resonators three inches long and 3/4 inch diameter, each one to be set on the chord of B flat, which is done by sliding the small diaphragm in the tube to a point that will indicate B flat. This setting then controls the metallic displacement of the metallic combination, as also of the arms necessary to hold the ring and resonators on shaft or axis. Thus the second equation is established, both on resonation and displacement. We are now ready to introduce the diatonic scale ring of three octaves which is set at two-thirds of the scale antagonistic to the chord mass of the globe itself. This is done by graduating every third pin of its scale to B flat, thirds, which represent antagonistic thirds to the shell's molecular mass. This antagonism must be thoroughly sensitive to the chord mass of one of the hemispheres of which the globe is composed. The axis of the scale ring must rotate loosely on the globe's shaft without revolving with the globe itself; which it is prevented from doing by being weighted on one side of the ring by a small hollow brass ball, holding about two ounces of lead. The remaining work on the device is finished by painting the interior of the globe, one hemisphere black and one white, and attaching a rubber bulb such as is used to spray perfume, to the hollow end of the shaft. This bulb equates vibratory undulations, thus preventing an equation of molecular bombardment on its dark side when sympathetically influenced. It is now in condition to denote the sympathetic concordance between living physical organisms, or the receptive transmittive concordance necessary to induce rotation. Philosophy of Transmission and Rotation of Musical Sphere. The only two vibratory conditions that can be so associated as to excite high sympathetic affinity, as between two physical organisms, are:--Etheric chord of B flat, 3rd octave, and on etheric sympathetic chords transmission E flat on the scale 3rd, 6ths, and 9ths; octaves harmonic; having the 3rd dominant, the 6th enharmonic, and the 9th diatonic. The chord mass representing the musical sphere, being the sympathetic etheric chord of B flat third octave, indicated by the focalization of its interior mechanical combination, as against the neutral sevenths of its atmospheric volume, makes the shell highly sensitive to the reception of pure sympathetic concordance, whether it be physical, mechanical, or a combination of both. Taking the chord mass of the different mechanical parts of the sphere and its adjuncts, as previously explained, when associated and focalized to represent pure concordance, as between its atmospheric volume and sphere mass, which means the pure unit of concordance, we have the highest position that can be established in relation to its sympathetic susceptiveness to negative antagonism. The beauty of the perfection of the laws that govern the action of Nature's sympathetic flows is here demonstrated in all the purity of its workings, actually requiring antagonistic chords to move and accelerate. The dark side of the shell, which represents fifty per cent. of its full area of pure concordant harmony, is the receptive area for the influence of the negative transmissive chords of the thirds, sixths and ninths to bombard upon; which bombardment disturbs the equilibrium of said sphere, and induces rotation. The rotation can be accelerated or retarded, according as the antagonistic chords of the acoustic forces are transmitted in greater or lesser volume. The action induced by the mouth organ, transmitted at a distance from the sphere without any connection of wire, demonstrates the purity of the principle of sympathetic transmission, as negatized or disturbed by discordants; which, focalizing on the resonating sevenths of resonators, or tubes attached to ring, the sympathetic flow is by this means transmitted to the focalizing centre, or centre of neutrality, to be re-distributed at each revolution of sphere, keeping intact the sympathetic volume during sensitization, thus preventing the equation or stoppage of its rotation. Again, the sphere resting on its journals in the ring, as graduated to the condition of its interior combinations, represents a pure sympathetic concordant under perfect equation ready to receive the sympathetic, or to reject the non-sympathetic. If a pure sympathetic chord is transmitted coincident to its full combination, the sphere will remain quiescent; but if a transmission of discordance is brought to bear upon it, its sympathetic conditions become repellent to this discordance.... Keely. Hertz in his conjectures that a knowledge of the structure of ether should unveil the essence of matter itself, and of its inherent properties, weight and inertia, is treading the path that leads to this knowledge. Professor Fitzgerald says:--"Ether must be the means by which electric and magnetic forces exist, it should explain chemical actions, and if possible gravity." The law of sympathetic vibration explains chemical affinities as a sympathetic attractive, but inherent, force; in short, as gravity. This opens up too wide a territory even but to peer into in the dawning light of Keely's system of vibratory physics. The boundary line is crossed, and the crowds of researchers in electro-magnetism are full of ardour. Hertz constructed a circuit, whose period of vibration for electric currents was such that he was able to see sparks, due to the increased vibration, leaping across a small air-space in this resonant circuit; his experiments have proved and demonstrated the ethereal theory of electro-magnetism:--that electro-magnetic actions are due to a medium pervading all known space; while Keely's experiments have proved that all things are due to conditions of ether. Professor Fitzgerald closes one of his lectures on ether in these words:--"There are metaphysical grounds for reducing matter to motion, and potential to kinetic energy. Let us for a moment contemplate what is betokened by this theory that in electro-magnetic engines we are using as our mechanism the ether, the medium that fills all known space. It was a great step in human progress when man learnt to make material machines, when he used the elasticity of his bow, and the rigidity of his arrow to provide food and defeat his enemies. It was a great advance when he learnt to use the chemical action of fire; when he learnt to use water to float his boats, and air to drive them; when, by artificial selection, he provided himself with food and domestic animals. For two hundred years he has made heat his slave to drive his machinery. Fire, water, earth, and air have long been his slaves, but it is only within the last few years that man has won the battle lost by the giants of old, has snatched the thunderbolt from Jove himself, and enslaved the all-pervading ether." Of the experiments of Hertz, in inducing vibrations "in ether waves," Professor Fitzgerald says: "If we consider the possible radiating power of an atom, we find that it may be millions of millions of times as great as Professor Wiedermann has found to be the radiating power of a sodium atom in a Bunsen burner; so if there is reason to think that any greater oscillation might disintegrate the atom, we are still a long way from it." Here we have an admission that the atom may be divisible; but the professor's conjecture is made upon an incorrect hypothesis. The "possible theory of ether and matter" which Professor Fitzgerald puts forward, in his lecture on Electro-Magnetic Radiation, is in harmony with Keely's theories. This hypothesis explains the differences in nature as differences in motion, ending: "Can we resist the conclusion that all motion is thought? Not that contradiction in terms, 'unconscious thought,' but living thought; that all nature is the language of One in whom we live, and move, and have our being?" This great truth the Buddhists have taught for ages. There is no such thing as blind or dead matter, as there is no blind nor unconscious thought. CHAPTER XIII. 1891. "MORE SCIENCE." The only hope for science is more science.--Drummond. "Philosophy must finally endeavour to be itself constructive." Here Professor Seth laid stress on the necessity of a teleological view of the universe, not in the paltry, mechanical sense sometimes associated with the word teleology, but as vindicating the existence of an end or organic unity in the process of the world, constituting it an evolution and not a series of aimless changes.... As Goethe taught, in one of his finest poems, we do well to recognize in the highest attributes of human-kind our nearest glimpse into the nature of the divine. The part was not greater than the whole, and we might rest assured that whatever of wisdom and goodness there was in us had not been born out of nothing, but had its fount, somewhere and somehow, in a more perfect Goodness and Truth.--Review of Professor Seth's address. Believe nothing which is unreasonable, and reject nothing as unreasonable without proper examination.--Gautama Buddha. I do not believe that matter is inert, acted upon by an outside force. To me it seems that every atom is possessed by a certain amount of primitive intelligence.--Edison. History tells us that Pythagoras would not allow himself to be called a sage, as his predecessors had done, but designated himself as a lover of wisdom; ardent in the pursuit of wisdom, he could not arrogate to himself the possession of wisdom. Yet, in our time, so unwilling are the searchers after wisdom to admit that there can be anything "new under the sun," anything that they do not already know, that we find the number of men of science to be marvellously small who possess the first condition of success in scientific research, as set down by Herbert Spencer, very few who do not arrogate to themselves too much learning to permit them to admit the possibility of any new revelation of truth. In every age of our world, to meet the requirements of the age, in its step-by-step progress from barbarism to civilization and enlightenment, there have appeared extraordinary men, having knowledge far in advance of the era in which they lived. Of such, among many, were Moses, Zoroaster, Confucius, Plato, and above these, Gautama the Buddha. But Moses, with all his knowledge of bacilli and bacteria, could not have met the requirements of any later age. The "eye for an eye" and "tooth for a tooth" period passed, and King David, who was so superior to other Kings of marauding tribes, that he was called "a man after God's own heart," satisfied his desire for punishment, to be meted out to his personal enemies, by prayer to God to "put out their eyes," and to "let them fall from one wickedness to another." This was a step in advance, for it gave those who had offended him a chance to escape all such summary proceedings as Moses had authorized. Still, the time was a long way off before a greater than Moses appeared to teach the world that such prayers are unavailing, that we can hate sin without hating the sinner, and that the Alpha and Omega of religion is to live in love and in the performance of duty. The Jewish prophets foretold the coming of Jesus of Nazareth; and the interpreters of Scripture are not alone now in having predicted that we are approaching a new dispensation, an age of harmony, which the twentieth century is to usher in, according to Biblical prophets. Renan has said that he envies those who shall live to see the wonders which the light of the new dawn that is breaking upon the world of science will unfold; that those who live in this coming age will know things of which we have no conception. Morley, in the spirit of prophecy, has said that in the near future a great intellectual giant will arise to bless our globe, who will surpass all other men of genius, reasoning that the representative of a larger age must be greater in genius than any predecessor. When the system is made known by which Keely dissociates the molecule and atoms by successive orders of vibration, proving two laws in physics as fallacious, we shall not hesitate to say that "the light of the new dawn" has now broken upon the world of science, and that the discoverer of the divisibility of the atom and of the absorption of energy in all molecular aggregation is the genius foretold by Morley. One quality of true genius is humility. "What a brain you must have!" said a man of science to Keely, not long since, "to have thought this all out." This man of genius replied, "I was but the instrument of a Higher Power." We are all instruments of a Higher Power, but the instruments chosen and set apart for any special work are always choice instruments which have been fitted or adapted to that work--the furnace perhaps seven times heated before the annealing was perfected. It has been said that man enters upon life as a born idiot; and there are many who think that, in comparison with the possibilities which the future promises in the way of the physical evolution of the race, we are but as idiots still. Having reached our present stage of physical and mental development, the history of the civilization of our race cannot but lead reflecting men and women into the opinion that the work of evolution will become more purely psychical in future. After which, as a consequence, there can be no doubt that physical development will again take its turn; for, as Tennyson has said,-- "When reign the world's great bridals, chaste and calm, Then springs the coming race that rules mankind." Not the least among the many applications of Keely's discoveries will be that which will prove, by demonstration, whether the chord of mass in a man and woman is near enough in the octaves to be beneficial, or so far apart as to be deteriorating. "There is no truer truth obtainable By man than comes of music." The earlier processes of civilization belonged to an age of spontaneity, of unreflective productivity; an age that expressed itself in myths, created religious and organized social forms and habits of life in harmony with these spontaneous creations. "O, ye delicious fables! where the wave And woods were peopled and the air with things So lovely! Why, ah why, has Science grave Scattered afar your sweet imaginings?" asks Barry Cornwall. But now that we have entered upon a more advanced age in thought, as in all things pertaining to discovery and practical application, or invention, a critical defining intellectual age, we must henceforth depend upon true science for our progress toward a higher enlightenment. Science, as will be seen, embraces religion, and must become, as Keely asserts, the religion of the world, when it is made known in all its glory and grandeur, sweeping away all foot-holds for scepticism, and spreading the knowledge of God, as a God of love, until this knowledge covers the earth as the waters cover the sea. As has been said, the word science, in its largest signification, includes intellectual achievement in every direction open to the mind, and the co-ordination of the results in a progressive philosophy of life. Philosophy has been defined as the science of causes or of first principles, and should be limited, almost exclusively, to the mental sciences. This is the field which Keely is exploring; the knowledge of the "hidden things" which he is bringing to the light is pure philosophical knowledge, in the widest acceptation of the term: the knowledge of effects as dependent on their causes. "Behold an infinite of floating worlds Dividing crystal waves of ether pure In endless voyage without port." Is it not a marvel of inspiration to have been able to cast line and plummet in such a sea of knowledge, to be able to demonstrate the power of that "sympathetic outreach" which, acting from our satellite upon the waters of our oceans and seas, through the vast space that separates it from our earth, lifts these waters, once in every twenty-four hours, from their beds; and, as gently as a mother would lay her infant on its couch, places them again where they rest? God hath chosen, as Paul said, the foolish things of the world to confound the wise; and God hath chosen the weak things of the world to confound the things which are mighty, and base things of the world and things which are despised hath God chosen, yea, and things which are not to bring to naught things which are; that no flesh should glory in His presence. Christ said, "I thank Thee, O Father, Lord of heaven and earth, because Thou hast hid these things from the wise and prudent, and hast revealed them unto babes." Truth never changes; but as new truths are revealed to us, to meet the necessities of progress (in our development from ignorance into the wisdom of angels), our point of view is ever changing, like the landscape which we look out upon from the swiftly gliding railway-carriage that bears us to our destination. As yet, "Earth has shown us only the title-page of a book" that we may, if we will, read its first pages here, and continue reading throughout eternity. When Bulwer wrote of "a power that can replenish or invigorate life, heal and preserve, cure disease: enabling the physical organism to re-establish the due equilibrium of its natural powers, thereby curing itself," he foreshadowed one of Keely's discoveries. "Once admit the possibility that the secrets of nature conceal forces yet undeveloped," says the author of "Masollam," "which may contain a cure for the evils by which it is now afflicted, and it is culpable timidity to shrink from risking all to discover that cure." This author teaches that humanity at large has a claim higher than the claims of the blood-tie; that a love based upon no higher sentiment, makes us blind to the claims of duty; and this is why, when men or women are chosen to do a great work, for the human family, the ligaments which have bound them too exclusively to their own families, are cut and torn apart. No greater work has ever been committed to a man to do than that which Keely's discoveries are preparing the way for. Science was rocking the world into the sleep of death--for materialism is death--its votaries declaring atoms to be eternally active, and the intellect which had discovered the existence of these atoms to end with the life of the molecular body. On this subject Simmons has written:-- "Shall impalpable light speed so swiftly and safely through infinite space--and the mind that measures its speed, and makes it tell its secrets in the spectroscope, be buried with the body? Shall mere breath send its pulsations through the wire and, after fifty miles of silence, sound again in speech or music in a far-off city, or stamp itself in the phonograph to sound again in far-off centuries--and the soul that has wrought these wonders pass to eternal silence? Shall physical force persist for ever--and this love, which is the strongest force in nature, perish? It would seem wiser to trust that the infinite law, which is everywhere else so true, will take care of this human longing which it has made, and fulfil it in eternal safety. We make no argument, but we cannot ignore all the intimations of immortality. Cyrus Field tells us of the night when, after his weary search for that long-lost cable two miles deep in mid-ocean, the grapnel caught it and, trembling with suspense, they drew it to the deck, hardly trusting their eyes, but creeping to feel it and make sure it was there. And when, as they watched, a spark soon came from a finger in England, showing that the line was sound, strong men wept and rockets rent the midnight darkness. We and our world float like a ship on the mysterious sea of being, in whose abysses the grapnel of science touches no solid line of logic connecting us to another land. But now and then there come from convictions, stronger than cables, flashes of light bidding us trust that our dead share in divine immortality, and are safe in the arms of Infinite Law and Eternal Love." Keely's demonstrations suggest "the missing link" between matter and mind, the solid line of logic which may yet be laid in "the widening dominion of the human mind over the forces of nature." In "Keely's Secrets," No. 9, Vol. I. of the T.P.S., some of the elements of the possibilities resulting to the world from Keely's discoveries were set down. War will become an impossibility; and, as Browning's poem of "Childe Roland" forecasts, "The Dark Tower" of unbelief will crumble at the bugle-blast which levels its walls to their foundation, revealing such a boundless region of research as the mind of man could never conceive were he not the offspring of the Creator. Not long since, Mr. Keely was congratulated upon having secured the attention of men of science, connected with the University of Pennsylvania, to his work of research. "Now, you will be known as a great discoverer, not as Keely the motor-man," said one of them present; whom he answered, "I have discovered so little, in comparison with what remains to be discovered, that I cannot call myself a discoverer." One of the professors present took Keely by the hand and said, "You are a great discoverer." All thoughtful men who have witnessed the latest developments of the force displayed by Keely, in his researching experiments for aerial navigation, are made to realize that more through his discoveries, than by the progressive development of the altruistic element in humanity (dreamed of by speculative optimists), our race will be brought into that dispensation of peace and harmony, anticipated by "seers" and foretold by prophets as the millennial age. It requires no great measure of foresight to discern, as a natural consequence of the control and application of this force in art and commerce, that ameliorated condition of the masses which will end the mighty conflict now so blindly being waged between capital and labour. [11] And to the eye of faith, it is not difficult to look beyond the intervening æons of centuries, to the literal fulfilment of the promise of that millennial period when men shall live in brotherly love together; making heaven of earth as even now it is in our power to do if we live up to Christ's command: "Whatsoever ye would that others should do unto you, that do ye also unto them." Had some of the dogmatic scientists of this age followed this command, Keely's discovery might have been sooner known in all its importance, protecting him, as their acknowledgment would have done, from the persecutions that have operated so detrimentally against the completion of researches which should have been finished before any attempt was made to apply the discovery to commercial ends. No scientist who witnessed the production of the force, displayed by Keely, in a proper spirit, but would have been welcomed by him to further experiments in its operations, as were Professor Leidy and Dr. Wilcox in 1889. So, in truth, those who printed their edicts against Keely about ten years since are, in part, responsible for the loss to the world which this long delay has occasioned. Still, in view of the acknowledged fact that not one of the great laws which science now accepts as incontrovertible truths, but was vehemently denied by the scientists of its time, declared to be a priori impossible; its discoverers and supporters denounced as fools or charlatans, and even investigation refused as being a waste of time and thought; it would be too much to expect from the thinkers of this age any greater degree of readiness to investigate claims, that threatened to demolish their cherished notions, than characterized their predecessors. But the time was not ripe for the disclosure: "God never hurries." He counts the centuries as we count the seconds, and the nearer that we approach to the least comprehension of His "underlying purpose," the better fitted are we to do the work He assigns us, while waiting patiently for our path of duty to be made clear to us; like the labourer, in Tolstoi's Confession, who completed the work that had been laid out for him, without understanding what the result would be, and unable to judge whether his master had planned well. If the prophecies of Scripture are fulfilled, the twentieth century will usher in the commencement of that age in which men and women will become aware of the great powers which they inherit, and of which Oliphant has said that we are so ignorant that we wholly fail to see them, though they sweep like mighty seas throughout all human nature. What is the character of these powers which Oliphant has written so eloquently concerning? Can we not form an inference from St. Paul's most precious and deeply scientific context, in which he introduced the quotation from the Greek poet Aratus, who was well known in Athens, having studied there? If we are the offspring of God, how rich must be our inheritance! If we are the children of God, why do we not trust our Father? But this is not science! A philosopher has said that if ever a human being needed divine pity, it is the man of science who believes in nothing but what he can prove by scientific methods. Scientists will have to admit, in the light of Keely's discoveries, that the sensibility and intelligence, which confer upon us our self-directive power, do not have their origin in our molecular structures. That they take their first beginning in matter is one of the most inadequate conceptions that was ever proposed for scientific belief. If it were so, we could not claim to be the offspring of God, who is the Fountain of all life, the ever living, from whom, as "His very kind," we inherit this self-directive power; not the molecular bodies which are our clothing. God is our Father. The material structure is the mother and nurse. The hypothesis that there are no beings in the universe but those which possess molecular bodies, is the conjecture of a mind that has no conception of the illimitable power of the Almighty. The link, which connects mind with matter, gives us a higher conception of the Deity. Keely places it in the mind flow, the result of the sixth subdivision. When we are done with "the things of Time," and not before, we are ready to rise out of our molecular bondage into the freedom we inherit as heirs of God and co-heirs with Christ of sonship with the Father. The problem of the origin of life would become a matter of easy analysis, writes Keely, if the properties governing the different orders of matter could be understood in their different evolutions. Disturbance of equilibrium is the prime mover, aggregator and disperser of all forces that exist in nature. The force of the mind on matter is a grand illustration of the power of the finer over the crude, of the etheric over the molecular. If the differential forces of the brain could become equated, eternal perpetuity would be the result. Under such a condition the physical would remain free of disintegration or decomposition. But the law, laid out by the Great Master, which governs the disturbance of equilibrium, making the crude forms of matter subservient to the finer or higher forms, forbidding anything molecular or terrestrial to assimilate with the high etheric, the law that has fixed the planets in their places, is an unknown law to the finite mind, comprehended only by the Infinite One.... Some of our men of science once settled the problem of the origin of life to their own satisfaction, only to learn that "speculation is not science;" for a substance which, when dissolved, crystallizes as gypsum, cannot produce vital force; and it is like groping among the bones of a graveyard to look for spontaneous generation in a shining heap of jelly on the floor of the sea. When our learned men are forced to admit that "all motion is thought," that "all nature is the language of One in whom we live, and are moved, and have our being," the attempts to evolve life out of chemical elements will cease; the Mosaic records will no longer be denied, which tell us that the Creator's law for living organisms is that each plant seeds, and each animal bears, after its kind; not that each seeds and bears after another kind. The doctrine of evolution, as made known to us in Geology, is a fundamental truth; proving that "there has been a plan, glorious in its scheme, perfect in system, progressing through unmeasured ages, and looking ever toward man and a spiritual end." The Rev. John Andrew, in his "Thoughts on the Evolution Theory of Creation," mentions that Haeckel gives the pedigree of man from primeval moneron in twenty-two stages. Stage twenty is the man-like ape; stage twenty-one is the ape-like man; stage twenty-two is the man; but he confesses that the twenty-first stage--the ape-like man--is entirely wanting in all the records. There is no missing link in the evolution theory, as laid down in Keely's pure philosophy. Inasmuch as the Father of all is Himself a Spiritual Being, cosmical law leads us to expect that the type of created being, His offspring, shall be spirit also. Nor can Being in any object be so attenuated, or so far removed from Him who filleth all in all, but it must surely retain an aura of His spiritual nature. The corner-stone of this philosophy is one power, one law; order and method reigning throughout creation; spirit controlling matter, as the Divine order and law of creation that the spiritual should govern the material--that the whole realm of matter should be under the dominion of the world of spirit. Nor is this a new truth. According to Diogenes Laërtius, Thales taught that souls are the motive forces of the universe. Empedocles affirms that spiritual forces move the visible world. Virgil asserted that mind animates and moves the world; that the spiritual realm is the soul of the universe. The universe is not a mass of dead matter, says Gilbert (in his work, "De Magnate"), but is pervaded with this soul, this living principle, this unseen cause of all visible phenomena, underlying all movements in the earth beneath and in the heavens above. Joseph Cook affirms that as science progresses it draws nearer in all its forms to the proof of the spiritual origin of force--that is of the Divine immanence in natural law: and that God was not transiently present in nature--that is in a mere creative moment; nor has He left the world in a state of orphanage, bereft of a deific influence and care, but He is immanent in nature, as the Apostle Paul and Aratus and Spinoza declared. As certainly as the unborn infant's life is that of the mother, so is it divinely true that somehow God's life includes ours; and we shall understand the nature of that relationship when, in due time, we have been "born again" into the life of the spirit. "The economy of creation is not regarded in this philosophy as a theory of development all in one direction; but as a cycle in which, after development, and as its fruit, the last term gives again the first. Herein is found the link by which the law of continuity is maintained throughout--the link which is missing in the popular science of the day; with this very serious consequence that, to keep the break out of sight, the entire doctrine of spirit and the spiritual world is ignored or altogether denied." Science admits that nature works with dual force, though at rest she is a unit. "Nature is one eternal circle." Keely's discoveries prove that the doctrine of the Trinity should be set down as an established canon of science--the Trinity of force. All nature's sympathetic streams--cerebellic, gravital, electric and magnetic--are made up of triple currents. The ancients understood this dogma in a far deeper sense than modern theology has construed it. The great and universal Trinity of cause, motion and matter--or of will, thought and manifestation--was known to the Rosicrucians as prima materia. Paracelsus states that each of these three is also the other two; for, as nothing can possibly exist without cause, matter and energy--that is, spirit, matter and soul (the ultimate cause of existence being that it exists), we may therefore look upon all forms of activity as being the action of the universal or Divine will operating upon and through the ether, as the skilled artificer uses his tools to accomplish his designs; making the comparison in all reverence. "The existence of an intelligent Creator, a personal God, can to my mind, almost be proved from chemistry," writes Edison; and George Parsons Lathrop, in commenting upon Edison's belief, says:--"Surely it is a circumstance calculated to excite reflection, and to cause a good deal of satisfaction, that this keen and penetrating mind, so vigorously representing the practical side of American intelligence--the mind of a remarkable exponent of applied science, and of a brilliant and prolific inventor who has spent his life in dealing with the material part of the world--should so confidently arrive at belief in God through a study of those media that often obscure the perception of spiritual things." Edison, it seems, like Keely, has never been discouraged by the obstacles which he meets with, in his researches, nor even inclined to be hopeless of ultimate success. Unlike Keely, Edison through all his years of experimental research has never once made a discovery. All the work of this great and successful inventor has been deductive, and the results achieved by him have been simply those of pure invention. Like Keely he constructs a theory, and works on its lines until he finds it untenable; then, he at once discards it and forms another theory. In connection with the electric light, he evolved or constructed three thousand successive theories; each one reasonable and apparently likely to be true; yet, only in two cases was he able to prove by experiment that his theories were correct. Of such a nature is the "dead-work" which all researchers on scientific principles must toil through to attain success. They must keep their minds open to every suggestion or idea, no matter how fanciful it may seem to others, and they must never let go their hold of it until it has been tested in all its possibilities. The same words which Lathrop uses, in describing Edison's characteristics, are equally applicable to Keely, who, in addition to his native endowment of a genius for science and mechanics, brings to bear vast patience in logical deduction, careful calculation, unlimited experiment, a ceaseless industry, and a persistence which refuses to be discouraged. Edison has said that he does not philosophize. Like General Grant, he is a man of action. When asked what theory he held upon a subject under discussion, General Grant replied, "I never theorize: when there is anything to be done, I do it." [12] Edison is always doing something which the public can see and appreciate, but, unlike Keely, he has no system to work out and transmute into the pure philosophy which is now revealing to the world "the further link in the chain of causation," "the cause of the cause," which hitherto has rather been assumed than demonstrated. "If we believe," says Professor Sir G. G. Stokes, "that what are called the natural sciences spring from the same supreme source as those which are concerned with morals and Natural Theology in general, we may expect to find broad lines of analogy between the two; and thus it may conceivably happen that the investigations, which belong to natural science, may here and there afford us hints with respect even to the moral sciences, with which at first sight they might appear to have no connection. And if such are to be found, perhaps they are more likely to be indicated by one whose studies have lain mainly in the direction of those natural sciences than by one whose primary attention has been devoted to moral subjects." Mr. Keely's first discovery of an unknown force and the releasing of an unknown energy seemed to be by accident; and most certainly no one could then have foreseen that his researches in physical science would lead him on step by step, and very slow steps they have been, to such important findings. In the pursuit of physical science he encountered paradoxes and anomalies, the study of which led him on to fresh discoveries whereby he has been able to extend the boundary of ascertained truth and separate the wheat of science from the chaff. The late Dr. Macvicar said when he considered how difficult he had found it to believe that such insight into nature as his views imply is possible to be attained, he was not so unreasonable as to expect that others would, in his time, regard them even as probable, much less as proved. He expressed himself as content with the private enjoyment which these views imparted to himself, "especially as that enjoyment is not merely the gratification of a chemical curiosity, but attaches to a much larger field of thought." One of the points to which he refers, as possessing great value to his own mind, is the place which his investigation assigns to material nature in the universe of being. He says that it is much the fashion in the present day to regard matter and force, more shortly matter, as all in all. But, according to the view of things which has presented itself to both of these men, "matter comes out rather as a precipitate in the universal ether, determined by a mathematical necessity; a grand and beautiful cloud-work in the realm of light, bounded on both sides by a world of spirits; on the upper and anterior side, by the great Creator Himself, and the hierarchy of spirits to which He awarded immediate existence; and on the lower and posterior side, by that world of spirits of which the material body is the mother and nurse." Macvicar says the hypothesis that there are no beings in the universe but those which possess a molecular structure, and that sensibility and intelligence take their first beginnings in such structures, is one of the most inadequate conceptions that was ever proposed for scientific belief. Science is not only very blind, but glories in her blindness. She gropes among the dead seeking the origin of life, instead of going to the Fountain of all life, the Ever Living, as Dr. Macvicar and Keely have done. In theorizing on the philosophy of planetary suspension Mr. Keely writes: "As regards planetary volume, we would ask in a scientific point of view--How can the immense difference of volume in the planets exist without disorganizing the harmonious action that has always characterized them? I can only answer this question properly by entering into a progressive synthesis, starting on the rotating etheric centres that were fixed by the Creator with their attractive or accumulative power. If you ask what power it is that gives to each etheric atom its inconceivable velocity of rotation, or introductory impulse, I must answer that no finite mind will ever be able to conceive what it is. The philosophy of accumulation," assimilation, Macvicar calls it, "is the only proof that such a power has been given. The area, if we can so speak of such an atom, presents to the attractive or magnetic, the elective or propulsive, all the receptive force and all the antagonistic force that characterizes a planet of the largest magnitude; consequently, as the accumulation goes on, the perfect equation remains the same. When this minute centre has once been fixed, the power to rend it from its position would necessarily have to be as great as to displace the most immense planet that exists. When this atomic neutral centre is displaced, the planet must go with it. The neutral centre carries the full load of any accumulation from the start, and remains the same, for ever balanced in the eternal space." Mr. Keely illustrates his idea of "a neutral centre" in this way:--We will imagine that, after an accumulation of a planet of any diameter--say, 20,000 miles more or less, for the size has nothing to do with the problem--there should be a displacement of all the material, with the exception of a crust 5000 miles thick, leaving an intervening void between this crust and a centre of the size of an ordinary billiard ball, it would then require a force as great to move this small central mass as it would to move the shell of 5000 miles thickness. Moreover, this small central mass would carry the load of this crust for ever, keeping it equi-distant; and there could be no opposing power, however great, that could bring them together. The imagination staggers in contemplating the immense load which bears upon this point of centre, where weight ceases. This is what we understand by a neutral centre. Again, Mr. Keely, in explanation of the working of his engine, writes:--In the conception of any machine heretofore constructed, the medium for inducing a neutral centre has never been found. If it had, the difficulties of perpetual-motion seekers would have ended, and this problem would have become an established and operating fact. It would only require an introductory impulse of a few pounds, on such a device, to cause it to run for centuries. In the conception of my vibratory engine, I did not seek to attain perpetual motion; but a circuit is formed that actually has a neutral centre, which is in a condition to be vivified by my vibratory ether, and while under operation, by said substance, is really a machine that is virtually independent of the mass (or globe), and it is the wonderful velocity of the vibratory circuit which makes it so. Still, with all its perfection, it requires to be fed with the vibratory ether to make it an independent motor.... Alluding to his illustration of a neutral centre, Mr. Keely says:--The man who can, even in a simple way, appreciate this vast problem has been endowed by the Creator with one of the greatest gifts which He can bestow upon a mortal. It is well known that all structures require a foundation in strength according to the weight of the mass they have to carry, but the foundations of the universe rest on a vacuous point far more minute than a molecule; in fact, to express this truth properly, on an inter-etheric point, which requires an infinite mind to understand. To look down into the depths of an etheric centre is precisely the same as it would be to search into the broad space of heaven's ether to find the end; with this difference, that one is the positive field, while the other is the negative field.... Again, Mr. Keely gives some suggestive thoughts as follows:--In seeking to solve the great problems which have baffled me, from time to time, in my progressive researches, I have often been struck by the fact that I have, to all seeming, accidentally tripped over their solution. The mind of man is not infinite, and it requires an infinite brain to evolve infinite positions. My highest power of concentration failed to attain the results which, at last, seeming accident revealed. God moves in a mysterious way His wonders to perform; and if He has chosen me as the tool to carve out certain positions, what credit have I? None; and, though it is an exalting thought that He has singled me out for a specific work, I know that the finest tool is of no value without a manipulator. It is the artist who handles it that makes it what it is. Indifference to the marvels which surround us is a deep reproach. If we have neither leisure nor inclination to strive to unravel some of the mysteries of nature, which task to the utmost the highest order of human intelligence, we can at least exercise and improve our intellectual faculties by making ourselves acquainted with the operation of agencies already revealed to man; learning, by the experience of the past, to be tolerant of all truth; remembering that one of Nature's agencies, known once as of use only in awakening men's minds to an awful sense of the Creator's power, has now become a patient slave of man's will, rushing upon his errands with the speed of light around the inhabited globe.... In comparing the tenuity of the atmosphere with that of the etheric flows, obtained by Mr. Keely from his invention for dissociating the molecules of air by vibration, he says, It is as platina to hydrogen gas. Molecular separation of air brings us to the first subdivision only; inter-molecular, to the second; atomic, to the third; inter-atomic, to the fourth; etheric, to the fifth; and inter-etheric, to the sixth subdivision, or positive association with luminiferous ether. In my introductory argument I have contended that this is the vibratory envelope of all atoms. In my definition of atom I do not confine myself to the sixth subdivision, where this luminiferous ether is developed in its crude form, as far as my researches prove. I think this idea will be pronounced, by the physicists of the present day, a wild freak of the imagination. Possibly, in time, a light may fall upon this theory that will bring its simplicity forward for scientific research. At present I can only compare it to some planet in a dark space, where the light of the sun of science has not yet reached it.... I assume that sound, like odour, is a real substance of unknown and wonderful tenuity, emanating from a body where it has been induced by percussion, and throwing out absolute corpuscles of matter--inter-atomic particles--with a velocity of 1120 feet per second, in vacuo 20,000. The substance which is thus disseminated is a part and parcel of the mass agitated, and if kept under this agitation continuously would, in the course of a certain cycle of time, become thoroughly absorbed by the atmosphere; or, more truly, would pass through the atmosphere to an elevated point of tenuity corresponding to the condition of subdivision that governs its liberation from its parent body. The sounds from vibratory forks, set so as to produce etheric chords, while disseminating their compound tones permeate most thoroughly all substances that come under the range of their atomic bombardment. The clapping of a bell in vacuo liberates these atoms with the same velocity and volume as one in the open air; and were the agitation of the bell kept up continuously for a few millions of centuries, it would thoroughly return to its primitive element. If the chamber were hermetically sealed, and strong enough, the vacuous volume surrounding the bell would be brought to a pressure of many thousands of pounds to the square inch, by the tenuous substance evolved. In my estimation, sound truly defined is the disturbance of atomic equilibrium, rupturing actual atomic corpuscles; and the substance thus liberated must certainly be a certain order of etheric flow. Under these conditions is it unreasonable to suppose that, if this flow were kept up, and the body thus robbed of its element, it would in time disappear entirely? All bodies are formed primitively from this high tenuous ether, animal, vegetable and mineral, and they only return to their high gaseous condition when brought under a state of differential equilibrium. As regards odour, continues Mr. Keely, we can only get some definite idea of its extreme and wondrous tenuity by taking into consideration that a large area of atmosphere can be impregnated for a long series of years from a single grain of musk; which, if weighed after that long interval, will be found to be not appreciably diminished. The great paradox attending the flow of odorous particles is that they can be held under confinement in a glass vessel! Here is a substance of much higher tenuity than the glass that holds it, and yet it cannot escape. It is as a sieve with its meshes large enough to pass marbles, and yet holding fine sand which cannot pass through; in fact, a molecular vessel holding an atomic substance. This is a problem that would confound those who stop to recognize it. But infinitely tenuous as odour is, it holds a very crude relation to the substance of subdivision that governs a magnetic flow (a flow of sympathy, if you please to call it so). This subdivision comes next to sound, but is above sound. The action of the flow of a magnet coincides somewhat to the receiving and distributing portion of the human brain, giving off at all times a depreciating ratio of the amount received. It is a grand illustration of the control of mind over matter, which gradually depreciates the physical till dissolution takes place. The magnet on the same ratio gradually loses its power and becomes inert. If the relations that exist between mind and matter could be equated, and so held, we would live on in our physical state eternally, as there would be no physical depreciation. But this physical depreciation leads, at its terminus, to the source of a much higher development--viz., the liberation of the pure ether from the crude molecular; which in my estimation is to be much desired. Thus God moves in a simple way His wonders to perform...." When my theoretical exposé is finished and brought out, I shall be ready for the attacks that will be made upon it, and able to demonstrate what I assert. One would think that modern physicists, knowing the lesson taught by the disastrous overthrow of the primitive system of astronomy, would be somewhat cautious in reference to jeering at any announcement of scientific research, however preposterous, without first carefully weighing its claims. It is my belief that there are many to-day who occupy positions as professors in our colleges and in universities abroad, who for bigotry and ignorance can discount the opinion of the religionists of the dark ages; but those to whom has been given mental force to boldly investigate new truths in science may congratulate themselves upon the fact that there are investigators of truth who are not afraid to acknowledge its claims, in whatever garb it may appear, welcoming whatever new message it may have to deliver.... Professor Rücker, in closing his address read at the meeting of the British Association in 1891, said:-- "In studies such as these we are passing from the investigation of the properties of ordinary matter to those of the ether, which may perhaps be the material of which matter is composed. We may some day be able to control and use it, as we now control and use steam." For nearly fifteen years, Keely constructed engines of various models, with this end in view, before he discovered that it is impossible to use the ether in any other way than as a medium for the energy that he is now experimenting with; and which he defines, in its present operation, as a condition of sympathetic vibration associated with the polar stream positively and negatively. Should Keely succeed in controlling and directing this subtle energy, we shall then be able to "hook our machinery on to the machinery of nature." A writer in the Nineteenth Century says,--"Whether the molecules or particles of what we know as matter are independent matter, or whether they are ether-whirlpools; we know that they keep up an incessant hammering one on another, and thus on everything in space. Professor Crookes has shown that the forces contained in this bombardment are immensely greater than any forces we have yet handled.... It has also been found that the vibrations keep time in some unknown way with the vibrations of solid matter." Thus it is seen that Keely is not the only man of science who is trying to effect a passage over the untrodden wild lying between acoustics and music: "that Siberian bog where whole armies of scientific musicians and musical men of science have sunk, without filling it up." Helmholtz, it is said, has, by a series of daring strides, made a passage for himself; while Keely stands alone in seeking to build a solid causeway; over which all the nations of the earth may pass in safety, to the "new order of things," that lies in this "land of promise." CHAPTER XIV. VIBRATORY PHYSICS.--THE CONNECTING LINK BETWEEN MIND AND MATTER. The elements of Nature are made of the will of God.--Hermes Trismegistus. Newton and Faraday have indicated how force instead of leaping over nothing, acting at a distance, is transmitted consecutively through the ethereal substance. We must become as little children, not presuming to think of causes efficient, or causes final; for these are things we cannot grasp; but reverently and patiently waiting until, like a revelation, the hidden link between the familiar and the unfamiliar flashes into our mind, and thus an additional step is gained in the endless series of successive generalizations.--The Rev. H. W. Watson, F.R.S., President of the Birmingham Philosophical Society. All truth comes by inspiration.--Scripture. There is but one Deity, the Supreme Spirit: he is of the same nature as the soul of man.-- Vedic Theology. As for truth it endureth and is always strong, it liveth and conquereth for evermore.--Esdras. Everything happens according to the will of God and has its appointed time, which can neither be hastened nor avoided.--Mohammed. In the paper of the Rev. H. W. Watson, on "The Progress of Science, its Conditions and Limitations," he tells us that every thinking man recognizes the subjective Self and the objective non-Self, and that this non-Self, so far as it manifests its existence through the senses, is the object of investigation of natural philosophers; but he admits that their investigations have not bestowed upon modern science any results to justify the language of causation. Universal gravitation is declared to be a vast generalization, telling us that there is no more, but yet just as much, of mystery in the whole sequence of astronomical phenomena, as in the most humdrum processes of every-day experiences. The unfamiliar has been explained by the familiar, and both remain in their original mystery. The mystery, attendant upon gravitation, Kepler prophesied would be revealed to man in this age: and the cautious and inductive investigations which Keely has been pursuing, since 1888, have enabled him to demonstrate that the unknown force, which for fifteen years had baffled all his skill, is the same condition of sympathetic vibration which controls nature's highest and most general operations:--the identical force which Faraday divined when he wrote, in 1836: "Thus, either present elements are the true elements, or else there is the probability before us of obtaining some more high and general power of nature even than electricity, and which at the same time might reveal to us an entirely new grade of the elements of matter, now hidden from our view and almost from our suspicion." It was good advice given by the late Professor Clifford,--"Before teaching any doctrine wait until the nature of the evidence can be understood." But without attempting to teach Keely's system of vibratory physics, we may look into some of his views, notwithstanding the fact that, whatever truths there may be in them, they are approached from such a different standpoint, than that of the platform of mechanical physics, that it is utterly impossible to bring them into any definite relations with each other. [13] Dr. Gérard, of Paris, in his work on "Nervous Force," writes of this founder of a new system of philosophy: "The force discovered by Keely appears to me to be so entirely the counterpart of what passes primarily in the brain cells that we see in him but a plagiarist of cerebral dynamics--that is, he has had but to copy the delicate human mechanism to make a wonderful discovery; probably, the greatest the world has ever known. The word plagiarist has no deprecatory meaning as applied to the great American inventor, for he must possess an extraordinary power of assimilation to read so fluently the open book of nature, and to be able wisely to interpret her admirable laws: it is, therefore, with profound admiration that I here render homage to this man of science." Dr. Gérard's work treats of the production of electricity in the nerve centres, and its accumulation in storage. He says that fifty years ago it would have been difficult to explain this fact intelligently; but thanks to the scientific progress of the period, everyone now knows how electricity is produced, and how applied, to use in lighting our houses. He continues: "Let us say, then, in few words, how matters stand, for it will serve to illustrate how it is with our brain, the mechanism of which is precisely the same--only that our apparatus is much more perfect and much less costly. "A dynamo-electric machine is placed at any given spot; its object, being put in action, is to withdraw from the earth its neutral electricity, to decompose it into its two conditions and to collect, upon accumulators, the electricity thus separated. As soon as the accumulators are charged, the electricity is disposable; that is, our lamps can be lighted. But what is marvellous in all this is that the forces of nature can be transformed at will. Should we not wish for light, we turn a knob and we have sound, heat, motion, chemical action, magnetism. Little seems wanting to create intelligence, so entirely do these accumulated forces lend themselves to all the transformations which their engineer may imagine and desire. But let us consider how greatly superior is our cerebral mechanism to all invented mechanism. In order to light a theatre we require a wide space, a dynamo-electric machine of many horse-power, accumulators filling many receptacles, a considerable expense in fuel, and clever mechanicians. In the human organism these engines are in miniature, one décimêtre cube is all the space occupied by our brain; no wheels, no pistons, nothing to drive the apparatus, we suffice ourselves. In this sense, each of us can say, like the philosopher Biaz:--Omnia mecum porto. Our cerebral organ not only originates motion, heat, sound, light, chemical actions, magnetism; but it produces psychic forces, such as will, reasoning, judgment, hatred, love, and the whole series of intellectual faculties. They are all derived from the same source, and are always identical to each other, so long as the cerebral apparatus remains intact. The variations of our health alone are capable of causing a variation in the intensity and quality of our productions. "With a maximum of physical and moral health, we produce a maximum of physical and moral results. Our manual labour and our intellectual productions are always exactly proportionate to the integrity of our mechanism." Dr. Gérard has, it will be seen, grasped the same truth that Buckle enunciated in his lecture, The Influence of Women on the Progress of Knowledge, when he affirmed that not one single discovery that had ever been made has been connected with the laws of the mind that made it: declaring that until this connection is ascertained our knowledge has no sure basis, as "the laws of nature have their sole seat, origin, and function in the human mind." This is the foundation stone of vibratory physics, that all force is mind force. All the forces of nature, writes Keely, proceed from the one governing force; the source of all life, of all energy. These sympathetic flows, or streams of force, each consists of three currents, harmonic, enharmonic, and dominant; this classification governing all orders of positive and negative radiation. The sympathetic flow called "Animal Magnetism" is the transmissive link of sympathy in the fourth, or inter-atomic, subdivision of matter. It is the most intricate of problems to treat philosophically; isolated as it is from all approach by any of the prescribed rules in "the orthodox scheme of physics." It turns upon the interchangeable subdivision of inter-atomic acting agency, or the force of the mind. The action of this etheric flow, in substances of all kinds, is according to the character of the molecular interferences which exist in the volume of their atomic groupings. These interferences proceed from some description of atomic chemical nature, which tend to vary the uniformity of structure in the atomic triplets of each molecule. If these groupings were absolutely uniform there would be but one substance in nature, and all beings inhabiting this globe would be simultaneously impressed with the same feelings and actuated by the same desires; but nature has produced unlimited variety. Science, as yet, has not made so much as an introductory attempt to solve this problem of "the mind flow," but has left it with the hosts of impostors, who always beset any field that trenches on the land of marvel. Professor Olive Lodge, in his address before the British Association, at Cardiff, said: "Let me try to state what this field is, the exploration of which is regarded as so dangerous. I might call it the borderland of physics and psychology. I might call it the connection between life and energy; or the connection between mind and matter. It is an intermediate region, bounded on the north by psychology, on the south by physics, on the east by physiology, and on the west by pathology and medicine. An occasional psychologist has groped down into it and become a metaphysician. An occasional physicist has wandered up into it and lost his base, to the horror of his quondam brethren. Biologists mostly look at it askance, or deny its existence. A few medical practitioners, after long maintenance of a similar attitude, have begun to annex a portion of its western frontier.... Why not leave it to the metaphysicians? I say it has been left to them long enough. They have explored it with insufficient equipment. Their methods are not our methods; they are unsatisfactory to us, as physicists. We prefer to creep slowly from our base of physical knowledge; to engineer carefully as we go, establishing forts, constructing roads, and thoroughly exploring the country, making a progress very slow but very lasting. The psychologists from their side may meet us. I hope they will; but one or the other of us ought to begin...." In America, we have Buchanan and many others investigating in this field; and Dr. Bowne, the orthodox Dean of the Boston University, in his answer to Herbert Spencer, answering the question, "What is Force?" tells us: "Not gravitation, nor electricity, nor magnetism, nor chemical affinity, but will, is the typical idea of force. Self-determination, volition is the essence of the only causation we know. Will is the sum-total of the dynamic idea: it either stands for that or nothing. Now science professes itself unable to interpret nature without this metaphysical idea of power. The experiments made by Professor Barker and others, which are said to establish the identity of heat and mental force, really prove only a correlation between heat and the nervous action which attends thinking. Nervous action and heat correlate, but the real point is to prove that nervous action and mental force correlate. This has never been done." "The concept of will," says Arthur Schopenhauer, "has hitherto commonly been subordinated to that of force; but I reverse the matter entirely, and desire that every force in nature be thought of as will. It must not be supposed that this is mere verbal quibbling and of no consequence: rather it is of the greatest significance and importance." Thus it will be seen that the field which Professor Lodge, with rare courage, invited his fellow-physicists to enter and bring with them their appropriate methods of investigation (unless these philosophers are astray) may prove to be "the immense and untrodden field" which Buckle said must be conquered before Science can arrogate to herself any knowledge of nature's laws that is not purely empirical. A little reflection will enable the average mind to see in the signs of the times a tendency to movements on a grander scale, such as are involved in the higher view which Keely is himself now taking since his researches have extended beyond the order he was pursuing when he was thinking only of mechanical success. Man's progress has been so enormous that nothing too extravagant can be imagined for the future, when once psychical investigation is conducted as proposed by Professor Lodge; who is trying to unravel the mystery as to what force is, and by what means exerted. There is something here not definitely provided for in the orthodox scheme of physics; but Keely's themes explain this mystery. "Luminiferous ether," he writes, "or celestial mind force, a compound inter-etheric element, is the substance of which everything visible is composed. It is the great sympathetic protoplastic element; life itself. Consequently, our physical organisms are composed of this element. This focalizing, or controlling media, of the physical, has its seat in the cerebral convolutions; from which sympathetic radiation emanates. This sympathetic outreach is mind flow proper, or will force; sympathetic polarization to produce action; sympathetic depolarization to neutralize it. Polar and depolar differentiation, resulting in motion. The true protoplastic element sympathetically permeates all forms and conditions of matter; having, for its attendants, gravity, electricity, and magnetism; the triple conditions born in itself. In fact, it is the soul of matter; the element from which all forms of motion receive their introductory impulse." Not long since, Mr. Keely was congratulated upon having secured the attention of men of science, connected with the University of Pennsylvania, to his work of research. Now, you will be known as a great discoverer, not as Keely the motor-man, said one of the professors present. Keely answered, I have discovered so little, in comparison with what remains to be discovered, that I cannot call myself a discoverer. Another of the professors present took Keely by the hand and said, You are a great discoverer. Had the discoverer of this unknown force not been dependent upon a company, "a ring," for funds to pursue his investigations, scientists would have better understood the nature of this work at an earlier stage of his experimental research; but following close upon Keely's production of the latent force carried in all forms of aggregated matter, he became entangled in the meshes of an organization that cared nothing for science, and a great deal for the wealth which, it was seen by practical business men, must sooner or later accrue as the result of a costless motive power. In other words, those who interested themselves in Keely's discoveries were interested solely in their marketable value; or if there chanced to be one who was not so interested, that one was not of sufficient influence in the scientific world to be able to induce capitalists to come forward and contribute towards saving the discovery to this age, by protecting the discoverer from the persecution that he was subjected to from those who had the management of the commercial affairs of the company. Aratus, the poet of Cilicia, the author of "Phenomena," wrote, "We are the offspring of God;" and St. Paul, quoting Aratus, continued, "In Him we live and move and have our being." From that hour, down the blood-stained path of the age to the present, there have been men, spiritually endowed, who have taught that He who created, commands and governs, the universe, sustains it by the power of His will; and that were it not for the celestial streams of radiation, this superhuman influence, constantly flowing into all created forms, the universe would pass out of existence, would perish in a moment. So well did Macvicar, the great Scotch divine, understand this conception of Deity, that he wrote, "The nearer we ascend to the fountain-head of being and of action the more magical must everything inevitably become; for that fountain-head is pure volition. And pure volition as a cause is precisely what is meant by magic; for by magic is merely meant a mode of producing a phenomenon without mechanical appliances--that is, without that seeming continuity of resisting parts and that leverage which satisfy our muscular sense and our imagination, and bring the phenomenon into the category of what we call 'the natural;' that is, the sphere of the elastic, the gravitating; the sphere into which the 'vis inertiæ' is alone admitted." We call this the sphere of the natural; but, when we come to higher workings of natural laws, with which we are not familiar, we designate them as "supernatural;" and scientists witnessing some of Keely's experiments, like those of overcoming gravity, of rotation of the needle of a compass, [14] of the disintegration of water, etc., and not believing in any workings of laws unknown to them, followed in the footsteps, still unobliterated, of the narrow-minded, bigoted persecutors of Galileo; and have denounced Keely as "a modern Cagliostro." When men of more extended research have been on the eve of investigating for themselves they have, until 1889, been deterred from doing so by the representations made to them that Keely was "using compressed air to humbug his audiences." Until Professor Leidy and Dr. Willcox gave their attention to Mr. Keely's claims as the discoverer of a new form of energy, the way was not open for Mr. Keely to disclose his conjectures, his hypotheses and his theories. Regrettable as this fact has seemed to be, it is now seen that any previous revelation of his discovery, other than to scientists, might have been premature; so little did Keely himself know, until within two years, of the developments he has at last reached in his work of evolution. The time was not ripe for the disclosure. It is a canon of science that molecular aggregation generally involves dissipation of energy. On the contrary, for more than fifteen years Keely has demonstrated that all molecular aggregation is attended with an absorption of energy; relieving by vibratory power the latent force held in a few drops of water and showing thereby a pressure of from ten to fifteen tons per square inch; claiming that resultant development of any force and of all forces is only accomplished by conditions that awaken the latent energy carried during molecular aggregation. It is conceded by those most conversant with the nature of Keely's discoveries that he must either create force, or liberate latent energy. As Omnipotence alone creates, it follows that science must be wrong in two of her most fundamental laws; one relating to the indivisibility of the atom; the other to the dissipation of energy in molecular aggregation. This, Keely establishes in the one experiment of disintegration of water, releasing from three drops the latent energy carried, during and from the time of molecular aggregation, and showing a pressure of fifteen tons to the square inch. Therefore, it is not "a waste of time and thought" to give attention to Keely's theories, and to investigate from the standpoint of vibratory physics, instead of setting limits to the operations of Nature and the power of the Almighty from the narrow platform of mechanical physics. Keely's Theories. The action of Nature's sympathetic flows, writes Keely, regulates the differential oscillatory range of motion of the planetary masses as regards their approach toward and recession from each other. These flows may also be compared to the flow of the magnet which permeates the field, existing between the molecules themselves, sensitizing the combined neutral centres of the molecules without disturbing, in the least, the visible molecular mass itself. In the planetary masses--balanced as it were in the scales of universal space, like soap-bubbles floating in a field of atmospheric air--the concentration of these sympathetic streams evolves the universal power which moves them in their oscillating range of motion to and from each other. This sympathetic triple stream focalizes and defocalizes on the neutrals of all such masses; polarizing and depolarizing, positive and negative action, planetary rotation, etc., etc. It is thus that all the conditions governing light, heat, life, vegetation, motion, are all derived from the velocity of the positive and negative interchange of celestial sympathy with the terrestrial. Every harmonious condition of Nature's evolutions is governed by one incontrovertible law; that of concordant assimilative harmony. This concordant key is the ruling one over all the antagonistic, negative, discordant ones; the one that diverts the disturbance of sympathetic equilibrium to one general concentrative centre for redistribution. Harmony concentrates, harmony distributes. The focalizing point of concordant sympathetic concentration is the percussive electric field, where the velocity of its sympathetic streams rebounds with a power that throws them far out into universal space; and so far beyond their equative centre of equilibrium as to bring them in sympathy with the universal attraction of the combined neutral centres of all planetary masses. Sympathetic Streams which Control the Action and Reaction of all Visible Forms of Matter. What is light and heat, and how are they evolved? and why are they so intensely perceptible as emanating from the solar world? Light and heat, considered theoretically, belong to the highest orders of the phenomenal. They can only be accounted for by the velocity of sympathetic streams, as interchangeable to and from centres of negative and attractive focalization. In considering the velocity of vibration, as associated with the projection of a ray of light, to be at least one hundred thousand billions per second, it is easy to account for the origin and demonstration of these two elements by the action of celestial sympathetic streams. 1st. Light and heat are not evolved until the force of the vibratory sympathetic stream, from the neutral centre of the sun, comes into atomic percussive action against the molecular atmosphere or envelope of our planet. The visibility of the planets can only be accounted for in this way, some in a great degree, some in less. Innumerable thousands, it may be, remain invisible to us by not having the conditions surrounding them, and associated with them, which favour the atomic and molecular antagonistic friction necessary to make them visible. The velocity of a steel ball passing through the atmospheric envelope, at a speed of thousands of billions times less than an etheric sympathetic stream, would be dissipated into vapour in an indefinite period of a second of time. Light and heat, in a certain sense, are one and the same; light giving heat, and heat giving light. The whole mystery, as associated with their evolution, is explained by the bombardment of the sympathetic etheric stream on the dense portion of the molecular, in seeking the sympathetic, concordant, neutral centre of the planetary mass that surrounds the point of focalization. The positive and negative interchange of this true sympathetic stream keeps intact the magnetic force of the polar envelope of the earth; making it, as it were, a great magnet of itself. The fact of this magnetic force being universally present, on and in our planet, proves the immeasurable speed and power of etheric sympathetic interchange. Thus it is that, from the velocity of these sympathetic rays, the earth's standard of heat and light is evolved and kept in balance. This interchange of sympathetic radiation, between the solar world and its system of planets, equates the sympathetic volume by the reception of the full amount expended on sympathetic distribution; thus showing the never-ending restoration of equilibrium by the same medium that disturbs it during intermittent sympathetic action. There are very many facts in vibratory physics which prove that the volume of heat, supposed by many to emanate from the sun, if concentrated upon a centre of the volume represented by the sun, would give enough focal force, if projected upon the system of planets that is under its control, to vaporize them in one month's time. A ray of heat one billion times greater than the whole volume of the sun represents could not pass through the dark vacuous boundaries which lie between us and the sun without being neutralized and absorbed. What is Electricity? Electricity is the result of three differentiated sympathetic flows, combining the celestial and terrestrial flows by an order of assimilation negatively attractive in its character. It is one of Nature's efforts to restore attractive differentiation. In analyzing this triple union in its vibratory philosophy, I find the highest order of perfection in this assimilative action of Nature. The whole condition is atomic, and is the introductory one which has an affinity for terrestrial centres, uniting magnetically with the Polar stream; in other words, uniting with the Polar stream by neutral affinity. The magnetic or electric forces of the earth are thus kept in stable equilibrium by this triune force, and the chords of this force may be expressed as 1st, the dominant, 2nd, the harmonic, and 3rd, the enharmonic. The value of each is, one to the other, in the rates of figures, true thirds. E flat--transmissive chord or dominant; A flat--harmonic; A double flat--enharmonic. The unition of the two prime thirds is so rapid, when the negative and the positive conditions reach a certain range of vibratory motion, as to be compared to an explosion. During this action the positive electric stream is liberated and immediately seeks its neutral terrestrial centre, or centre of highest attraction. The power of attractive vibration of the solar forces is the great coincident towards which the terrestrial-magnetic-sympathetic flow is diverted. This force is the celestial current that makes up the prime third of the triple association. It also induces aqueous disintegration and thermal concentration, the two prime conductors towards this coincident chord of sympathy with itself. Without this aqueous disintegration there would be no connective link between the celestial and terrestrial. There would exist nothing but a condition of luminous radiation on the order of the aurora--a reaching out for the concordant without any sympathetic diversion to create unstable equilibrium of terrestrial magnetism. In fact, under such a condition, the absence of the sun on one side, or the absence of water on the other, the magnetic or electric force would remain in a stable state of equilibrium, or the highest order of the chaotic. Disturbance of equilibrium and sympathetic equation constitute the dual power that governs all the varied forms of life and motion which exist terrestrially, of which the electric or magnetic is the prime mover and regulator. All electrical action, no matter of what character, has its sympathetic birth by the intervention of that current of the triune flow, which I call the dominant, with the Polar harmonic current; all sympathetic flows being composed of three currents. They become associative one with the other only near the junction of terrestrial interference. The great vacuous field which exists between the planetary ranges holds this portion of the etheric flow free of all antagonism, molecularly or otherwise, till the associative point is reached; so wonderfully planned by the Great Creator, for instant electric evolution and assimilation with terrestrial centres of attraction. I call this intervention, atomic-inter-molecular and molecular density. The combination of the action of the triune sympathetic-celestial stream with the same intervening medium induces heat and light, as the resultant of these corpuscular conflictions with sympathetic celestial and terrestrial focalized centres of neutral radiation. I do not recognize electricity, nor light, nor heat as coming from the sun. These conditions, according to my theories, emanate from atomic and inter-atomic interference on induced molecular vibration, by sympathetic etheric vibration, the celestial-attractive being the prime mover. In my estimation this is not at all phenomenal; it is only phenomenal as far as the knowledge of its action in mechanical physics is concerned. Physicists have been working in the wrong direction to lead them to associate themselves with Nature's sympathetic evolutions. [15] The expression "Electricity attracts at a distance" is as bad as, if not worse than, the "microbe of the magnet." Clerk Maxwell seems, when theorizing on sound transmission by an atmospheric medium, not to have taken into consideration the philosophy attending the phenomena of the origination of electric streams in celestial space. Light is one of the prominent evolved mediums in electric action, and is evolved by corpuscular bombardment induced by sympathetic streams acting between the neutral centres of planetary masses, all of which are under a condition of unstable equilibrium. These unstable conditions were born in them, and were thus designed by the Architect of Creation in order to perpetuate the connective link between the dispersing positive and the attractive negative. The action that induces this link I call sympathetic planetary oscillation. Attraction, Propulsion, &c. The action of the magnetic flow is dual in its evolution, both attractive and propulsive. The inclination of the plane on which the subtle stream moves, either to the right or to the left, has nothing to do with positive or negative conditions. The difference in conditions of what is called, by electricians, positive and negative electricity, is the difference between receptive and propulsive vibrations. They can be right or left receptive, or right or left propulsive. The positive vibrations are the radiating; the negative vibrations are the ones that are attracted toward the neutral centre. The negative-sympathetic polar stream is the magnetic flow proper, and it is in sympathetic coincidence with the second atomic flow; the electric current is the first and second order of atomic vibration, a dual force, the flow of which is too tenuous to displace the molecules. It can no more do so than the flow from a magnet can displace the molecules of a glass plate when it is passed under it. The flow from a magnet is too fine to disturb the plate molecules, but passes as freely between them as a current of air would through a coarse sieve. Like poles do not repel each other, simply because there is a perfect sympathetic equation between them; the same in unlike poles. If a differentiation of 33 1/3 against 100 is established between them, whether like or unlike, they become attractive to each other. They become repellent after differentiating them, 66 2/3 of the one against 100 of the other, by sympathetic vibration. Taking into consideration even the introductory conditions of the etheric stage, etheric vibration has proved to me that the higher the velocity of its rotating stream the greater is its tendency towards the neutral centre or centre of sympathetic coincidence. Were it otherwise, how could there ever be any planetary formations or the building up of visible structures? If a billiard ball were rotated to a certain velocity, it would separate in pieces, and the pieces would fly off in a tangent; but if it were a ball of ether, the higher the velocity of rotation the stronger would be the tendency of its corpuscules to seek its centre of neutrality, and to hold together. It is not a magnetic force that is borne on the etheric atom which gives it its power to draw to it streams of coincidence. The magnet is only susceptive to certain aggregated forms of matter; iron, for instance, and its preparations. All moving bodies of visible matter produce heat as according to their velocity. The flow of gases only induces thermal reduction from molecular friction. By this term it must not be understood that the molecules actually come in contact, and rub against each other. There is no pressure, however great, that can cause molecular contact. The area of the volume of the molecule can be reduced by enormous pressure, and the tension thus brought to bear on their rotating envelopes induces heat. The heat thus induced is a positive proof of the wonderful velocity of the etheric envelope. If the molecules were dead--which is an infinite impossibility--to sympathetic vibration, and without a rotatory envelope if all the pressure possible to conceive were brought to bear upon them, it would not induce the slightest thermal change. Energy. Energy is a sympathetic condition inherent in all forms of aggregated matter, visible and invisible. It is ever present, in its latent condition, and is aroused by the sympathetic disturbers of its equilibrium. By this conservation it becomes transferable. The sympathetic correlation of will-force in the cerebral convolutionary centres transfers its energy to the physical organism. Bring a steel rod in contact with a magnet, and the latent energy in the rod is brought into action without its becoming impregnated by its magnetic exciter. Energy is an infinite latent force. If it did not exist it could not be generated. Consequently, there would be no energy to lose nor to conserve. The volume of latent energy in the etheric domain never increases nor ever grows less. It will remain the same, as yesterday to-day and for ever. Inaudible Vibrations. Nature has established her sympathetic concordants from the birth of the neutral centres of the planets. This is gravity; therefore gravity is fixed, inherent. There is no flight of gravity. The difference in the condition of the sympathetic nerve centres, and the variations in the chord aggregation of the masses, as established in the man or woman at birth, constitutes the molecular condition of the individual. The molecular state of animals, vegetables, and minerals, depends upon the aggregation of their chord centres. It is impossible to make two coins from one die the same in its molecular aggregation. The mere picking up of a coin and replacing it causes billions of molecules to be lost. This produces a change in the chord of mass of the coin. As this fact has only been developed by persistent progressive research, it is quite easy to comprehend the nature of the difficulties that lie in the way of perfecting devices for the guidance of artificers and mechanics, whereby they can bring a proper vibratory action into play to induce positive sympathetic transmission. In order to transmit my knowledge by demonstration it will be necessary to have much more perfect instruments than those crude devices which I first constructed for my researches. One of my perfected instruments shows to the eye, in the molecular effects produced by a certain order of vibration, when the chord of harmony is established between two neutral centres. Another, when connected with the sympathizer, denotes accurately, by the colour of a certain sound or combination of sounds the number of vibrations that are necessary to induce certain effects of mechanical combinations. Inaudible vibrations are tested by the magnetic needle and sound colours. Every gaseous molecule is a resonator of itself and is sensitive to any and all sounds induced, whether accordant or discordant. At the normal density of the atmosphere we hear a volume of sound, focalized by the combined association of every molecule brought under sound influence. When we reduce the atmospheric volume of a chamber to 50/100, then the ear is sensitive to the reduction of the acoustic force evolved on the same ratio, and so on, until sound becomes inaudible. This inaudibility to our organ of hearing is no proof whatever of any reduction of the acoustic force evolved on the introductory impulse given to the bell. It is only a proof that the number of the molecules left for the acoustic force to act upon has been so reduced by increasing the vacuum, that the concentration of sound from the diminished number cannot be heard. The ear is not susceptible to the acoustic force emanating from one molecule, nor even from the concentration of one hundred millions of billions of molecules. The highest vacuum that can be induced, taking but a cubic inch in volume to act upon, will leave a residual number of molecules one hundred billion times as great as the above given number, and yet be perfectly inaudible when all their acoustic forces are focalized. The audible has been conquered in my instruments to that extent which brings me into sympathetic contact with the inaudible, the vitalized conditions of which as regards sympathetic union with the terrestrial are the pure and only essentials necessary towards establishing the sensitive link, between the instrument and terrestrial chord-masses, in order to run sympathetic machinery. But there is still before me a vast region to be explored before the keystone of this sympathetic arch is set in position to carry the high order of sympathetic transfer that I aim at. I have every reason to hope that when I have mastered these mechanical difficulties I shall be able to control this most subtle of Nature's forces. When this is done, the commercial engine will soon follow. There is no truer nor quicker way to reach that end than the one I am now pursuing. My obligations on this line once fulfilled, I shall be at liberty to turn my attention to the consideration of the mental forces associated with the physical, and in fact the solution of the mechanical problem is one and the same in principle, as is the physical and mental. When one is solved all is solved. The convolutions which exist in the cerebral field are entirely governed by the sympathetic conditions that surround them. "The force which binds the atoms, which controls secreting glands, Is the same that guides the planets, acting by divine commands." All abnormal discordant aggregations in these resonating convolutions produce differentiation to concordant transmission; and according as these differentiations exist in volume, so the transmissions are discordantly transferred, producing antagonism to pure physical action. Thus, in motor ataxy, a differentiation of the minor thirds of the posterior parietal lobule produces the same condition between the retractors and exteriors of the leg and foot, and thus the control of the proper movements is lost through this differentiation. The same truth can be universally applied to any of the cerebral convolutions that are in a state of differential harmony to the mass of immediate cerebral surroundings. Taking the cerebral condition of the whole mass as one, it is subservient to one general head centre; although as many neutrals are represented as there are convolutions. The introductory minors are controlled by the molecular; the next progressive third by the atomic; and the high third by the etheric. All these progressive links have their positive, negative, and neutral position. When we take into consideration the structural condition of the human brain, we ought not to be bewildered by the infinite variety of its sympathetic impulses, inasmuch as it unerringly proves the true philosophy that the mass-chords of such structures are governed by vibratory etheric flows. There is no structure whatever--animal, vegetable, or mineral--that is not built up from the cosmic ether. Certain orders of attractive vibration produce certain orders of structure; thus the infinite variety of effects; more especially in the cerebral organs. Discordance cannot exist in the molecule proper. Discordance in any mass is the result of differentiated groups induced by antagonistic chords, and any differentiated mass can be brought to a condition of harmony or equation by proper chord media, and an equated sympathy produced whether the mass be metal or brain. There is good reason for believing that insanity is simply a condition of differentiation in the mass-chords of the convolutions, which creates an antagonistic molecular bombardment towards the neutral or attractive centres of such convolutions. This may be compared to a knot on a violin string. As long as this knot remains, it is impossible to elicit, from its sympathetic surroundings, the condition which transfers pure concordance to its resonating body. Discordant conditions (i.e., differentiation of mass) produce negatization to coincident action. Pure sympathetic concordants are as antagonistic to negative discordants as the negative is to the positive; but the vast volume the sympathetic holds over the non-sympathetic, in ethereal space, makes it at once the ruling medium and re-adjuster of all opposing conditions, when properly brought to bear upon them.... Josiah Royce is right as regards correspondent sympathetic association between two conditions. If concordance can be established, even of unlike states, no matter whether it be of the high tenuous forces of nature, gases with liquids, liquids with solids, solids with gases, the structural conditions can be perfectly adverse. Their neutral centres are the focalized seat of sympathetic concordance for controlling any differentiation that may exist outside, or in the mass that surrounds them. Certain orders of vibration can reach these centres and establish a concordant flow of sympathy, independent of any and all mass antagonism; in other words, certain orders of sympathetic vibratory transmission can correct and equate all differentiation that may exist between physical organisms and their cerebellic flows. Discord is disease. Harmony is health.--Keely. The Standard calls attention to the fact that Lord Rosebery has pointed out how fast mental disease of one form or another is growing among the population of London--so fast that a new asylum, containing 5000 patients, must be built every five years. "This," said his lordship, "is a penalty of civilization." When we take into consideration the effect upon the nerves, in sensitive organizations, of living in the vicinity of railways, more especially of the elevated railways in cities, the incessant jarring vibrations which are communicated to houses, even from underground railways, to say nothing of the piercing shrieks of the steam whistle, is it to be wondered at that mental disorders and nervous diseases are on the increase? With this increase of the most terrible form of affliction, the remedy will follow; for our necessities are known to One who "with a Father's care and affectionate attention supplies the wants, as they arise, of the worlds which lie like children in His bosom." Sympathetic Vibratory Physics will, in due time, make known the curableness of many disorders now considered incurable. On this subject Mr. Keely writes:--Every disease that the physical organism is subject to has its connective link in the cerebral domain; where it unerringly telegraphs, as it were, its molecular differentiations, through the spinal dura mater or physical sympathetic transmitter, and vice versâ back again. The sympathetic communication, as between the physical and mental forces, shows up truthfully the pure conditions that govern the celestial and terrestrial link of sympathy, as between the finite and the Infinite in planetary suspension. The whole system governing the suspension of the innumerable planetary masses,--the infinite certainty and harmony of their eccentric and concentric evolutions and revolutions, in their orbital and oscillating ranges of motion,--the triune sympathetic streams of Infinity that permeate their molecular masses--focalizing and defocalizing on their neutral centres of attraction--are all subservient to that Great Ruling Power: Mind-Flow. There is not a grain of sand, nor an invisible corpuscule of floating matter, that does not come under the same rule that governs the most mighty of planets.... "All's love, yet all's law." As the offspring of God, only by living in love and harmony can we fulfil the law and maintain health and happiness, either individually in family life, or collectively in our intercourse with the world. As Goethe taught:-- Let the God within thee speak, Love all things that lovely be, And God will show His best to thee. CHAPTER XV. THE PHILOSOPHY OF HISTORY.--KEELY THE FOUNDER OF A SYSTEM. "Were half the power that fills the world with terror, Were half the wealth bestowed on camps and courts, Given to redeem the human mind from error, There were no need of arsenals and forts." As long as men remain "demons of selfishness and ignorance," so long will they fight for their turn to tyrannize over their brother men. Instruction and education can alone prepare the way for a peaceful solution of the greatest problem that mankind has ever had to deal with; for, before we can hope to enter into a 'brotherhood of humanity,' the earth must be 'filled with the knowledge of the Lord.'--H. O. Ward, in the Nationalization News. As for myself I hold the firm conviction that unflagging research will be rewarded by an insight into natural mysteries such as now can rarely be conceived.--Prof. Wm. Crookes. Though "it is the spirit that quickeneth, and the flesh profiteth nothing," the grand reign of the Spirit will not commence until the material world shall be completely under man's control.--Renan, Future of Science. If truth is to obtain a complete victory, if Christianity is ever really to triumph on the earth, then must the State become Christian and science become Christian. Such then is the two-fold problem which our age is called upon to solve.--Frederich von Schlegel. I come soon and will renew all things.--Scripture. Frederich von Schlegel, in his Lecture "On the General Spirit of the Age," (1846) says, There are in the history of the eighteenth century, many phenomena which occurred so suddenly, so instantaneously, that although on deeper consideration we may discover their efficient causes in the past, in the natural state of things, and in the general situation of the world, yet are there many circumstances which prove that there was a deliberate, though secret, preparation of events, as, indeed, in many instances has been actually demonstrated. In tracing the origin of this "secret and mysterious branch of illuminism," and its influence in regard to the true restoration of society founded on the basis of Christian justice, Schlegel gives it as his opinion that the order of Templars was the channel by which this esoteric influence was introduced into the West, handing down the Solomonian traditions connected with the very foundation of this order, and the religious masonic symbols which admit of a Christian interpretation: but, as he says, the idea of an esoteric society for the propagation of any secret doctrine is not compatible with the very principle of Christianity itself; for Christianity is a divine mystery which lies open to all. Continuing from Schlegel's writings, the Christian faith has the living God and His revelation for its object, and is itself that revelation; hence every doctrine taken from this source is something real and positive, while, in science, the absolute is the idol of vain and empty systems, of dead and abstract reason. In the absolute spirit of our age, and in the absolute character of its factions, there is a deep-rooted intellectual pride, which is not so much personal or individual as social, for it refers to the historical destiny of mankind and of this age in particular. Actuated by this pride, a spirit exalted by moral energy, or invested with external power, fancies it can give a real existence to that which can only be the work of God; as from Him alone proceed all those mighty and real regenerations of the world, among which Christianity--a revolution in the high and divine sense of the word--occupies the first place. For the last three hundred years this human pride has been at work; a pride that wishes to originate events, instead of humbly awaiting them and of resting contented with the place assigned to it among those events.... It was indeed but a very small portion of this illuminism of the eighteenth century that was really derived from the truths of Christianity and the pure light of Revelation. The rest was the mere work of man, consequently vain and empty; or at least defective, corrupt in parts, and on the whole destitute of a solid foundation;--therefore devoid of all permanent strength and duration. But when once, after the complete victory of truth, the divine Reformation shall appear, that human Reformation which till now has existed will sink to the ground and disappear from the world. Then, by the universal triumph of Christianity, and the thorough religious regeneration of the age, of the world, and of governments themselves, will dawn the era of a true Christian Illuminism. This period is not perhaps so remote from our own as the natural indolence of the human mind would be disposed to believe, says Schlegel. Never was there a period that pointed so strongly, so clearly, so generally towards the future, as our own. In order to comprehend in all its magnitude the problem of our age, the birth of Christianity must be the great point of survey to which we must recur; in order to examine clearly what has remained incomplete, what has not yet been attained. For, unquestionably, all that has been neglected, in the earlier periods and stages of Christian civilization, must be made good in this true, consummate regeneration of society. If truth is to obtain a complete victory--if Christianity is really to triumph on the earth, then must the state become Christian and science become Christian. Such then is the two-fold problem which our age is called upon to solve. Whatever man may contribute towards the religious regeneration of government and science, Schlegel reasons that we must look for the consummation, in silent awe, to a higher Providence, to the creative fiat of a last period of dispensation, to "the dawn of an approaching era of love and harmony," which will emancipate the human race from the bondage in which it has been held by false teachings; leading men and nations to consider and estimate time, and all things temporal, not by the law and feeling of eternity:--but for temporal interests, or from temporal motives; forgetting the thoughts and faith of eternity. All progress in the great work of the religious regeneration of science Schlegel hails as the noblest triumph of genius; for it is, he says, precisely in the department of physics that the problem is the most difficult; and all that rich and boundless treasure of new discoveries in nature, which are ever better understood when viewed in connection with the high truths of religion, must be looked upon as the property of Christian science. Our various systems of philosophic Rationalism, he foretells, will fall to the ground: and vulgar Rationalism, which is but an emanation of the higher, will finally disappear. Then science will become thoroughly Christian. In the progress of mankind now, as in the past, a divine hand and conducting Providence are clearly discernible. Earthly and visible power has not alone co-operated in this progress;--that the struggle has been, in part, carried on under divine, and against invisible might, has been substantiated by Schlegel on firm and solid grounds, if not proved to mathematical evidence; which evidence, as he remarks, is neither appropriate nor applicable to the subject. Schlegel concludes his work on The Philosophy of History, by a retrospective view of society, considered in reference to that invisible world and higher region, from which a pure philosophy teaches us the operations of this visible world proceed; in which its great destinies have their root, and which is the ultimate and highest term of all its movements. Both Schlegel and Keely teach that we shall prize with deeper, more earnest and more solid affection the great and divine era of man's redemption and emancipation, by Christianity, the more accurately we discriminate between what is essentially divine and unchangeably eternal in this revelation of love, and those elements of destruction which false teachings have opposed thereto or intermingled therewith; tracing in the special dispensations of Providence, for the advancement of Christianity and the progress of civilization and regeneration, the wonderful concurrence of events towards the single object of divine love, or the unexpected exercise of divine justice long delayed. (See Vera Vita, by David Sinclair.) Sir G. G. Stokes Bart., M.P., reasoning on the difficulties as to good arising out of evil, says, "In our study of nature we are most forcibly impressed with the uniformity of her laws. Those uniform laws are, so far as we can judge, the method by which the ordinary course of nature is carried on. That is to say, if we recognize the ordinary course of nature as designed by a Supreme Being, that it is according to His will that the course of Nature should, as a rule, be carried on in this regular methodical manner, we should expect, therefore, to find the operation of regular laws in the moral, no less than in the physical world, although their existence is less obvious on account of the freedom of the will.... There is a conflict of opinion and a restlessness of men's minds at the present day; but we may confidently hope that if men will in a straightforward manner seek after what is true, and that in a humble spirit, without arrogating to themselves the monopoly of truth and contemning others whose opinions may be different, the present conflict of opinion will in time settle down.... It is in this frame of mind that searchers after truth are now examining the claims of Keely as a discoverer, and as the founder of a new and pure philosophy. If the most important subject and the first problem of philosophy is, as Schlegel declares, the restoration in man of the lost image of God, so far as this relates to science, all revolution, as well as all revelation, must tend toward the full understanding of this restoration in the internal consciousness, and not until it is really brought about will the object of pure philosophy be fully attained. The philosophy of history shows clearly how, in the first ages of the world, the original word of Divine revelation formed the firm central point of faith for the future reunion of the dispersed race of man; how later, amidst the various powers intellectual as well as political which (in the middle period of the world) all ruling nations exerted on their times, according to the measure allotted to them, it was alone the power of eternal love in the Christian religion which truly emancipated and redeemed mankind; and how the pure light of this Divine truth, universally diffused through the world and through all science, will crown in conclusion the progress of this restoration in the future. The fulfilment of the term of all Christian hope and Divine promise is reserved for the last period of consummation--for the new dispensation which the closing century is ushering in. The esoteric meaning of the second coming of our Lord is thus intimated to those who are watching for the triumph of justice and truth. "Behold I come quickly; and my reward is with me, to give every man according to his work." Theosophy interprets the often-quoted Scripture passage of "the seven Spirits which are before His throne" as the cosmical, creative, sustaining, and world-governing potencies, the principles of which God avails Himself as His instruments, organs, and media. This is what the Kabbala implies with its seven "Sephiroth," what Schelling means by the "potencies," or principles in the inner life of God; and it is by their emergence, separation, and tension that they become cosmical potencies. If we stop short at these general considerations, this is precisely the idea of Theosophy. When it is asked what special activities are to be ascribed to each of the seven Spirits, striving to apprehend more closely the uncreated potencies through which the Deity works in its manifestation, and to which Scripture itself makes unmistakable allusion, revelation is silent, intimating only by veiled suggestions. It is here that Theosophy leads the way to the open book of Nature: the title-page of which we have only begun to turn. Theosophy, says Bishop Martensen, signifies wisdom in God: "Church Theology is not wise in assuming a hostile attitude towards Theosophy, because it hereby deprives itself of a most valuable leavening influence, a source of renewal and rejuvenescence, which Theology so greatly needs, exposed as it is to the danger of stagnating in barren and dreary scholasticism and cold and trivial criticism. In such a course no real progress can be made in the Christian apprehension of truth." Jacob Böhme, who was the greatest and most famous of all Theosophists in the world, [16] said of philosophers and other disputants who attack not only Theosophy but also theology, and even Christianity itself, in the name of modern science:--"Every spirit sees no further than its mother, out of which it has its original, and wherein it stands; for it is impossible for any spirit, in its own natural power to look into another principle, and behold it, except it be regenerated therein." This is what Christ taught: "Ye must be born again." Only those who are regenerated, by the principle of which Christ spoke to Nicodemus, can understand the quickening of the Spirit which comes alone from Him who gives this new birth to all who seek it, and in whom all the treasures of wisdom and knowledge are hidden:--"hidden, not in order that they may remain secret, but in order that they may ever increasingly be made manifest and appropriated by us." Jacob Böhme, who was born in 1575, "brought to the birth" an idea which, three centuries later, is developing into a system of pure philosophy, that promises to "cover the earth with wisdom and understanding in the deep mysteries of God." Böhme gave birth to an idea. Keely is giving birth to a system. Both are exceedingly imperfect in the expression of their views; yet in points of detail each possesses a firm dialectical grip. In their writings both seem overwhelmed by the vast extent of the realm they are exploring. Both find in harmony the object and the ending of the world's development. Conflicting with modern science at very many points, visionary as both appear to be, powerful expression is given to an idea of life both in the macrocosm and the microcosm, the validity of which can be questioned only by materialism. The idea of the one and the system of the other teach that when Nature is affirmed in God it is in a figurative and symbolical sense:--that it is, in comparison with what we call nature, something infinitely more subtle and super-material than matter; that it is the source of matter; a plenitude of living forces and energies. This system teaches, as "Waterdale" has expressed it, "the existence of a Great Almighty, as being in virtue of the perfect organization of the universe, even as the existence of man is incidental to the organic structure of his body;" and that the attribute of omniscience is represented by "the perfect conveyance of signs of atomic movement in vibratory action through the length and breadth of our universe." We are led by it to look from nature up to nature's God and to comprehend the attributes of deity as never before in any other system. It lays hold, with a giant's grasp, of the heart of the problems which science is wrestling with. It answers the question asked by Professor Oliver Lodge in his paper, read at Cardiff, last August, "By what means is force exerted, and what definitely is force?" It was a bold speculation of Professor Lodge, who is known as "a very careful and sober physicist," when, after admitting that there is herein something not provided for in the orthodox scheme of physics, he suggested that good physicists should carry their appropriate methods of investigation into the field of psychology, admitting that a line of possible advance lies in this direction. Without speculation science could never advance in any direction; discussion precedes reform, there can be no progress without it. It required rare courage for a physicist to step from the serried ranks that have always been ready to point their javelins at psychologists, and to show, with the torch of science, the hand on the signpost at the cross roads pointing in the right direction. It is the great high road of knowledge; but those who would explore it must do so with cautious tread, until the system of sympathetic association is completed which Keely is bringing to birth, for the road is bordered with pitfalls and quicksands and the mists of ignorance envelop it. Ernest Renan, in "The Future of Science," illustrates the thesis that, henceforth, the advancement of civilization is to be the work of science; the word science being used in its largest signification as covering intellectual achievement in every direction open to the mind, and the co-ordination of the results in a progressive philosophy of life. The fundamental distinction which is expressed or implied, on every page, is that the earlier processes of civilization belong to an age of spontaneity, of unreflective productivity; an age that expressed itself in myths, created religions, organized social forms and habits, in harmony with the spontaneous creations; and that we have now entered upon the critical, defining, intellectual age; in short, as Mr. Nisbet has said, that the evolution of the human race has passed from the physiological into the psychical field; and that it is in the latter alone, henceforward, that progress may be looked for toward a higher civilization. [17] Philosophy, that is to say, rational research, is alone capable of solving the question of the future of humanity, says Renan. "The really efficacious revolution, that which will give its shape to the future, will not be a political, it will be a religious and moral revolution. Politics has exhausted its resources for solving this problem. The politician is the offscouring of humanity, not its inspired teacher. The great revolution can only come from men of thought and sentiment. It does not do to expect too much from governments. It is not for them to reveal to humanity the law for which it is in search. What humanity needs is a moral law and creed; and it is from the depths of human nature that they will emerge, and not from the well-trodden and sterile pathways of the official world." In order to know whence will come a better understanding of the religion which Christ taught, "the religion of the future, we must always look in the direction of liberty, equality, and fraternity." Not the French Commune liberty to cut one another's throats (an equality of misery, and a fraternity of crime), but that liberty to know and to love the truth of things which constitutes true religion, and which when it is bestowed without money and without price, as it will be, "humanity will accomplish the remainder, without asking anyone for permission." No one can say from what part of the sky will appear the star of this new redemption. The one thing certain is that the shepherds and the Magi will be once more the first to perceive it, that the germ of it is already formed, and that if we were able to see the present with the eyes of the future, we should be able to distinguish, in the complication of the hour, the imperceptible fibre which will bear life for the future. It is amid putrefaction that the germ of future life is developed, and no one has the right to say, "This is a rejected stone," for that stone may be the corner-stone of the future edifice. Human nature is without reproach, continues Renan (L'Avenir de la Science), and proceeds toward the perfect by means of forms successively and diversely imperfect. All the ideas which primitive science had formed of the world appear narrow, trivial, and ridiculous to us after that which progressive research has proven to be true. The fact is that science has only destroyed her dreams of the past, to put in their stead a reality a thousand times superior; but were science to remain what it is, we should have to submit to it while cursing it, for it has destroyed and not builded up again; it has awakened man from a sweet sleep without smoothing the reality to him. What science gives us is not enough, we are still hungry. True science is that which belongs neither to the school nor the drawing-room, but which corresponds exactly to the wants of man. Hence true science is a religion which will solve for men the eternal problems, the solution of which his nature imperatively demands. Herein lies the hope of humanity; for, like a wild beast, the uneducated masses stand at bay; ready to turn and rend those who are willing to keep them in their present condition, in order to be able to make them answer their own purposes.... I am firmly convinced, continues Renan, for my own part, that unless we make haste and elevate the people, we are upon the eve of a terrible outbreak of barbarism. For if the people triumph in their present state, it will be worse than it was with the Franks and Vandals. They will destroy of their own accord the instrument which might have served to elevate them; we shall then have to wait until civilization once more emerges spontaneously from the profound depths of nature. Morality, like politics, is summed up, then, in this grand saying: To elevate the people. If I were to see humanity collapse on its own foundations, mankind again slaughter one another in some fateful hour, I should still go on proclaiming that perfection is human nature's final aim, and that the day must come when reason and perfection shall reign supreme. Sailing, sailing in the same staunch ship-- We are sailing on together; We see the rocks and we mark the shoals, And we watch for cyclone weather. The perils we run for one alone Are perils for all together,-- The harbour we make for one alone, Makes haven for all, through the weather. Stand by your ship: be brave, brothers mine! Be brave, for we'll stand together! We'll yet reach the port for which we sail In this black and stormy weather. Sailing, sailing the same stormy sea, We are sailing all together! There are rocks ahead and shoals beneath, And 'round us hurricane weather. I see in the West a star arise, That will guide us all together:-- Stand firm by your helm and trust in God Who pilots us through this weather. The dawn of morning breaks in the skies Which will bring mankind together;-- To havens of peace, to havens of bliss, We'll ride through this cyclone weather. Clara Jessup Moore. CHAPTER XVI. 1891. AN APPEAL IN BEHALF OF THE CONTINUANCE OF KEELY'S RESEARCHES. There is a distinct advantage in having one section of scientific men beginning their work untrammelled by preconceived notions.--Engineering. A knowledge of scientific theories seems to kill all knowledge of scientific facts.--Professor Schuster. Tizeau found that the speed of light is increased in water which moves in the same direction as the light. This result must be due either to the motion of matter through the medium, or to the fact that moving matter carries the ether with it. The whole question of matter and motion as a medium is a vital one, and we shall hardly make any serious advance before experiment has found a new opening.--Professor Schuster. How Mr. Keely, in 1891, was Able To Secure the Attention Of Men of Science To His Researching Experiments. During the summer of 1890, Mr. Keely was harassed by threats, said to proceed from disappointed stockholders in the Keely Motor Company, of suits at law for "obtaining money under false pretences." After making many unsuccessful attempts with the editors of leading magazines in London, Boston, and New York, to bring before the public the claims of Mr. Keely for sympathy in his colossal work, the proposals of an editor, on the staff of the London Times (who had the year before introduced himself to Mrs. Bloomfield Moore to obtain information of Keely) to make known the researches of the persecuted discoverer and his need of assistance, at that time, were accepted. The programme, as laid out by this editor, was to use his extended influence with the leading journals throughout Great Britain, and to have brief notices of Keely inserted; to be followed up with a magazine article, for which the material was furnished. Later this arrangement was modified by the editor, who then proposed to write an essay for some influential journal, handling the various molecular and atomic theories; pointing out wherein Keely's views were original, and showing their revolutionizing tendencies. This work, which was to have been commenced in November, was delayed until all need was over. When the editor wrote to Philadelphia in January, 1891, that he had been unable to commence his work for want of sufficient material (enclosing questions to be answered by Mr. Keely before he could set about it), the answer returned was that the threatened troubles were over, that Mr. Keely had gained the protection of men of science, and the order for the essay was countermanded. At this very time a subscription was in circulation to raise money from disaffected stockholders for the purpose of bringing the threatened action at law, in case Mr. Keely did not resume work on his engine, instead of pursuing researches in order to gain more knowledge of the operation of this unknown polar force in nature. It was at this juncture that the late Professor Joseph Leidy, that eminent man of science who had been the first to recognize the importance of Keely's discovery to the scientific world, arranged with the Provost of the University of Pennsylvania that an appeal should be made to the trustees, the faculty and the professors of that institution, to permit Keely to continue his researches for science under their protection. Accordingly, on the 14th of January, 1891, a paper entitled "Keely's Discoveries" was read at the house of Provost Pepper. The answer sent by one of the professors, in reply to Dr. Pepper's invitation, probably expressed the views held by all the distinguished men who assembled to listen to the appeal, which was to the effect that the professor would be present to hear the paper read, if the Provost wished it; but, if he came, he should make it very unpleasant for the reader, as he had no faith in Keely nor in his discoveries. All those who were present listened with attention, and among the few who became interested in the claims of Keely as a discoverer, was the professor who had made this remark. The preamble to the appeal was read by the Provost, Dr. Pepper. Preamble. Before commencing to read my paper I wish to lay before you the object of this effort to interest men of science in the researches of a man who, in the cause of justice alone, is entitled to have his life's work fairly represented to you. Some of our men of science have, unwittingly, been the medium by which great injustice has been done to Mr. Keely; and to others also, by placing me before the world as a woman whom the Keely Motor Company management has robbed of large sums of money; whereas, in truth, I have never been in any way involved by the Keely Motor Company. In the winter of 1881-82, Mr. Keely, who was dependent upon "The Keely Motor Company" for the means to continue his researches, as to the nature of the unknown force he had discovered, was virtually abandoned by the Company. Himself as ignorant as were its managers of the source of the mysterious energy he had stumbled over, he was driven to despair by their action; and, when I was led to his assistance, I found his wife's roof mortgaged over her head, and that, his honour assailed, he had resolved to take his life rather than submit to the indignities threatening him. At this time I had taken from my private estate ten thousand dollars, to found a small public library to my father's memory, in the town of Westfield, Hampden Co., Massachusetts. After convincing myself that Mr. Keely had made a great discovery, I felt that if this money could save his discovery, jeopardized as it was, it was my duty to so appropriate it. At that time, Mr. Keely thought half of the amount so appropriated would be all that he should require; but, unfortunately, his efforts were for years confined to the construction of an engine for the Company that had abandoned him. Later, he commenced researches which resulted in the discovery that he had unknowingly imprisoned the ether; greatly increasing my interest in his work. The plan to which I shall allude in my paper, as framed by Professor Leidy for Mr. Keely to follow, and approved by Professor Hertz, of Bonn, and Professor Fitzgerald, of Trinity College, Dublin, may be summed up as one that permits Mr. Keely to pursue his researches on his own line, without further investigation, up to the completion of his system in a form which will enable him to give to commerce with one hand his model for aerial navigation, and to science, with the other, the knowledge that is necessary for extending its researches in the field of radiant energy--which Mr. Keely has been exploring for so many years. I ask the prestige of your sympathy, as well as for your interest in Mr. Keely's work, on this basis; and if in one year you are not convinced that satisfactory results have been attained for science, I will promise to leave Mr. Keely in the hands of the "usurers and Shylocks of commerce," who have already forced him into renouncing seven-eighths of his interest in what the Keely Motor Company claims as its property. At present I do not desire from anyone endorsement of Keely's discoveries. Until his system is completed he wishes to avoid all discussion and all public mention of the anticipated value of his inventions. Mr. Keely's programme of experimental research, as laid down by himself last March, when I first proposed to furnish him with all the funds needed to carry it out, comprises its continuance until he has gained sufficient knowledge of the energy he is controlling--which is derived from the disintegration of water--to enable him to impart to others a system that will permit men of science to produce and to handle the energy, and enable him to instruct artisans in the work which lies in their province; viz., the construction of machines to apply this costless motive power in mechanics. The prestige of your interest in Mr. Keely's labours can alone secure to him freedom to pursue researches on his own road; a course pronounced by Professor Leidy, Professor Hertz, and Professor Fitzgerald, to be "the only proper line for him to pursue." The building of an engine is not in Mr. Keely's province. His researches completed to that point which is necessary, for perfect control of the force, practical application will follow. The result of his experimental work for nine months on this line has been such as to revive the interest of the speculative management of the Keely Motor Company, to that extent that Mr. Keely is now offered the support of its stockholders if he will resume construction of an engine; and this after more than seven years of failure on the part of the company to furnish him with one dollar to carry on "the enterprise." The official Report put forth in January by the Keely Motor Company managers annulled my contract with Mr. Keely; but he is willing to abide by it, if I am able to continue to furnish him with the necessary funds. This position of affairs has forced me to the front, to ask whether you will place it in my power to renew the contract with Mr. Keely; or leave him under the control of men who seem to be oblivious of the interests of the stockholders of the company in their "clamour" for an engine. When this system is completed, in its application to mechanics, the present mode of running engines with shafts and beltings will disappear, creating a revolution in all branches of industry. Looking at my request from another point of view, do you not think it due to extend to Mr. Keely an opportunity to prove all that one of your number is ready to announce as his conviction in regard to the claims of Mr. Keely? You all know to whom I refer--Professor Joseph Leidy. "Oh, Leidy is a biologist," said an English physicist not long since; "get the opinion of a physicist for us." If I did not wish for the opinion of physicists, I should not have appealed to you for help at this most critical juncture. But I also ask that no opinion be given by any physicist until Mr. Keely's theories are understood and demonstrated, by experiment. Yes, Dr. Leidy is a biologist, and what better preparation could a man have than a study of the science of life to enable him to discern between laws of nature as invented by physicists, and nature's operations as demonstrated by Keely? The science of life has not been the only branch to which Dr. Leidy has given profound attention; it is his extensive and accurate knowledge of its methods, limits, and tendencies, which prepared the way for that quick comprehension of possibilities, lying hidden from the sight of those men of science whose minds have rested (rusted?) in the dead grooves of mechanical physics. In Dr. Leidy we find entire scientific and intellectual liberty of thought, with that love of justice and truth which keeps its possessor from arrogance and intolerance, leading him with humility to "prove all things and hold fast to truth." To such men the world owes all that we have of advance since the days when science taught that the earth is flat, arguing that were it round the seas and oceans would fall off into space. In Dr. Leidy's name and in justice to him, I ask your sanction to and approval of my efforts to preserve Keely's discoveries for science;--discoveries which explain, not only the causes of the planetary motions but the source of the one eternal and universal force. An Appeal in Behalf of Science. A paper read by Mrs. Bloomfield Moore at the house of Provost Pepper on the evening of January 14th, 1891, before members of the board of trustees and professors of the University of Pennsylvania. Each day he wrought, and better than he planned, Shape breeding shape beneath his restless hand; The soul without still helps the soul within, And its deft magic ends what we begin. George Eliot. I hope that I do not seem to be too presumptuous in my effort to awaken an interest, on your part, in the discoveries of Keely which have aroused a marked degree of attention among some of the most learned men in Europe. I should hardly have ventured to ask the prestige of your support to be given to Mr. Keely, in his further scientific researches, were it not that one of your number fully realizes, I think, the important nature of these researches. You all know to whom I refer--Professor Joseph Leidy. In his book, "Fresh Water Rhizopods of North America," he says, in his concluding remarks: "I may perhaps continue in the same field of research and give to the reader further results, but I cannot promise to do so, for though the subject has proved to me an unceasing source of pleasure I see before me so many wonderful things in other fields, that a strong impulse disposes me to leap the hedges to examine them." I have reason to know that, had Dr. Leidy not followed this impulse, our age might have been robbed of its birthright. It was not until I appealed to Professor Leidy and Dr. Willcox, to convince themselves whether I was right or wrong in extending aid to Mr. Keely, that their decision enabled me to continue to assist him until he has once more made such advances, in experimental research, as to cause the managers of the Keely Motor Company to believe that his engine is near completion, and that they can dispense with outside assistance hereafter. But I know as it has been in the past so will it be again, and that, as the months glide away, if no engine is completed, the company will once more desert the discoverer; while, if he is allowed to pursue his researches, up to the completion of his system under your protection, his discoveries will be guarded for science, and the interests of the stockholders will not be sacrificed to the greed of speculators, as has so often been done in the past. As I have had occasion to say, elsewhere, after the warning given in the history of Huxley's Bathybius, Professor Leidy would not have risked his world-wide reputation by the endorsement of Keely's claims, as the discoverer of hidden energy in inter-molecular and atomic spaces, had he not tested the demonstrations until fully convinced of the discovery of a force previously unknown to science, and of the honesty of Mr. Keely in his explanations. Therefore, following the advice of Professor G. Fr. Fitzgerald, of Dublin, I do not ask for further investigations. Until Professor Leidy and Dr. Willcox came to the front, in May, 1891, Mr. Keely had no influential supporters, and was under such a cloud, from his connection with speculators, that to advocate his integrity of purpose and to uphold the importance of his work, was enough to awaken doubts as to the sanity of his upholders. We are told by Herodotus that science is to know things truly; yet past experience shows us that what has been called knowledge at one period of time is proved to be but folly in another age. Science is to know things truly, and the laws of nature are the same yesterday, to-day, and forever. Throughout the universe the same laws are at work and regulate all things. Men interpret these laws to suit their own ideas. The system which Keely is unfolding shows us that there is not one grain of sand, nor one invisible corpuscule of floating matter, that does not come under the same law that governs the most mighty planet, and that all forms of matter are aggregated under one law. "The designs of the Creator as expounded by our latest teachers," writes Gilman, "have required millions of ages to carry out. They are so vast and complex that they can only be realized in the sweep of ages. One design is subordinated by another without ever being lost sight of, until the time has arrived for its complete fulfilment. These designs involve an infinitude of effort, ending often in what, to our view, looks like failure, to be crowned after a series of ages with complete success at last." In this long chain of physical causes, says Dr. Willcox, seemingly endless, but really commencing with that one link that touches the hand of Him who made all matter, and all potencies that dwell within matter, this cosmical activity has been ceaseless, these cosmical effects numerous past conception, by which universal nature has slowly unfolded and become the universe of to-day. In this way both Christianity and science unfold their truths progressively. Truth, like the laws of nature, never changes; yet truth as an absolute thing, existing in and by itself, is relatively capable of change; for as the atoms hold in their tenacious grasp undreamed-of potencies, so truths hold germs potential of all growth. Each new truth disclosed to the world, when its hour of need comes, unfolds and reveals undreamed-of means of growth. As the Rev. George Boardman has said of Christianity, so may it be said of science: Being a perennial vine, it is ever yielding new wine. A philosopher has said that if ever a human being needed divine pity it is the pseudo-scientist who believes in nothing but what he can prove by his own methods. In the light of Keely's discoveries, science will have to admit that when she concentrates her attention upon matter, to the exclusion of mind, she is as the hunter who has no string in reserve for his bow. When she recognizes that a full and adequate science of matter is impossible to man, and that the science of mind is destined ultimately to attain to a much higher degree of perfection than the science of matter--that it will give the typical ideas and laws to which all the laws of physics must be referred--then science will be better supplied with strings than she now is, to bring her quarry down. It is Professor Leidy's and Dr. Willcox's second strings, to their bows, which will enable you to secure to science the richest quarry that has ever been within its reach. I know that the experience of Professor Rowland, as related by him, must have had the effect to prejudice you against Mr. Keely. Professor Fitzgerald writes to me on this subject: "I am sorry that Mr. Keely did not cut the wire, wherever Professor Rowland asked to have it cut, because it will undoubtedly be said that he had some sinister reason for not doing so, whatever his real reasons were; but, of course, when one cuts a bit off a valuable string one prefers naturally to cut the bit off the end, as Keely did, rather than out of the middle." This very wire which Mr. Keely did cut at one end, twice, for Professor Rowland, one of the pieces falling into my hand, is now in Professor Fitzgerald's possession. It was the offensive manner of Professor Rowland when he seized the shears, telling Keely it was his guilty conscience which made him refuse to cut the wire, and that it must be cut in the middle, which put Keely on the defensive, causing him to refuse to allow Professor Rowland to cut it. It would seem that the professor in the Johns Hopkins University, from his remarks on that occasion, thought, instead of an experiment in negative attraction, that Keely was imposing upon the ignorant by giving a simple experiment in pneumatics, familiar to all schoolboys. Professor Rowland did not realize how low he was rating the powers of discernment of a professor in the University of Pennsylvania who had witnessed Keely's experiments again and again, when his instruments or devices were in perfect working order. Mr. Keely, who was ambitious to show Professor Rowland that his disintegrator had no connection with any concealed apparatus, had suspended it from the ceiling by a staple. The hook had given way, and the jar to the instrument in falling to the floor disarranged its interior construction on that day. To those who have not witnessed any of Keely's experiments, under favourable conditions, his theories naturally seem vague speculations; but not one theory has Keely put forward, as a theory, which he has not demonstrated as having a solid foundation in fact. Some of our men of science once settled the problem of the origin of life to their own satisfaction, only to learn in the end that speculation is not science; but this very problem is one the solution of which Keely now seems to be approaching. It would become a matter of easy analysis, writes Keely, if the properties governing the different orders of matter could be understood in their different evolutions. The force of the mind on matter is an illustration of the power of the finer over the crude, but the law making the crude forms of matter subservient to the finer or higher forms, is an unknown law to finite minds. Buckle has asserted that the highest of our so called laws of nature are as yet purely empirical; and that, until some law is discovered which is connected with the laws of the mind that made it, our knowledge has no sure basis. So saturated has Mr. Keely's mind been with his discovery of this law that he has contented himself to remain ignorant in physics, as taught by the schools; and also with simpler matters it would seem; while testing and building up his hypotheses into a system which no one but himself can complete, and which without completion must be lost to the world. I should form a very poor opinion of the mind that would accept an hypothesis as anything more than the signpost at cross roads, which points to the direction that may be taken. In physics the very first fact to which the learner is introduced is already sophisticated by hypotheses. Every experiment in chemistry is but a member of a series, all based upon some one or other of many hypotheses; which are as necessary to the construction of a system as is the scaffolding which is used in building an edifice. If the scaffolding proves unsound it does not affect the edifice, as it can be at once replaced with material more solid. So an hypothesis, which is merely a conjecture or a suggestion, cannot affect the solidity of a philosophy or a system. It must be tested and found to support all the facts which bear upon it, and capable of accounting for them, before it can be accepted as a theory. It is my wish to have the professors of the University of Pennsylvania meet at my house the founder of a system which, in my opinion, embraces a pure philosophy: to listen to his theories, and to elicit from him such information as to the nature of his researches, in what is called electro-magnetic radiation, as I trust will convince them that I have not been pursuing a will-o'-the-wisp during the years that my mind has been concentrated on the work in which Mr. Keely is engaged. The bearings of this work are so various that I shall not have time to touch upon more than the one which interests me beyond any or all of the others; namely, its connection with the medical art. Appreciating as I do the life of self-denial which physicians who are devoted to their profession must lead, and having in their ranks relatives and many warm friends on both sides of the ocean (one of them, my nephew, Dr. Jessup, is here to-night) I trust that what I say of the medical art will not be misconstrued. The great sorrows of my life have come upon me through the ignorance of medical men, who, I know, followed their best judgment in the course of treatment that they pursued in the illnesses of those dear to me. When my children were in their infancy I had reason to embrace the opinions of Professor Magendie, as set forth in one of his lectures before the students of his class in the Allopathic College of Paris. These are his words: "I know medicine is called a science. It is nothing like a science. It is a great humbug. Doctors are mere empirics when they are not charlatans. We are as ignorant as men can be. Who knows anything about medicine? I do not, nor do I know anyone who does know anything about it. Nature does a great deal; imagination does a great deal, doctors do d----h little when they do no harm." Later in life, in 1871, I was sent, while suffering with neurasthenia, from Paris to Schwalbach Baths by Dr. Beylard, who recommended me to the care of Dr. Adolph Genth; to whom, in my first interview, I said: "I wish for your opinion, and for your advice, if you can give it to me without prescribing any medicine." He replied: "With all my heart, Madam, and I wish to God there were more women like you; but we should soon lose our patients, if we did not dose them." A terrible excuse for the use of those agencies which Dr. John Good has said have sent more human beings to their graves than war, pestilence and famine combined. One of Mr. Keely's discoveries shapes his theory that all nervous and brain disorders may be cured by equating the differentiation that exists in the disordered structure. When his system is completed, medical men will have a new domain opened to them for experiment. Gross material agencies, such as drugs, will be replaced by the finer forces of nature: light, as taught by the late Dr. Pancoast of our city, and magnetism, as experimented with by the late Professor Keil of Jena, showing the efficacy of the ordinary magnet in the cure of certain infirmities,--these experiments were communicated by him more than fifty years since to the Royal Society of London. Paracelsus taught that man is nourished and sustained by magnetic power, which he called the universal motor of nature. In Switzerland, in Italy and in France, the light-treatment is now being tested; red light used in cases of melancholia; blue light in cases of great nervous excitement, operating like magic in some instances. Dr. Oscar Jennings, the electrician at St. Anne's Hospital for the Insane in Paris, tells me that students, versed in Biblical lore, declare that the esoteric teachings of the Book of Job enunciate a system of light-cure. Ostensibly because of my faith in the importance of Keely's discoveries, as opening up new fields of research to medical men, an invalid daughter (suffering from puerperal mania after the birth of her third child) was taken from me, in conformance with orders of the Swedish guardian of her monied interests in Sweden, and I was summoned before the Police Direction, in Vienna, and required to bind myself not to experiment upon my child. It is well known to the London experts in mental disorders, the most distinguished of whom I have consulted, that my daughter's treatment, while she was under my care, had been confined to giving no medicine, forcing no food, and such changes from time to time in her surroundings as she needed, with a few electric baths. The orthodox practice of medicine is nothing more and nothing less than "a system of blind experiment," as it has been called. At the opening of a clinical society in London, Sir Thomas Watson said: "We try this and not succeeding we try that, and baffled again we try something else." Other eminent medical men have given utterance to these aphorisms: "The science of medicine is founded on conjecture and improved by murder;" "Mercury has made more cripples than war;" "Ninety-nine medical facts are medical lies;" "Every dose of medicine is a blind experiment;" "The older physicians grow the more sceptical they become of the virtues of their own medicines." Dr. Ridge said: "Everything in nature is acknowledged to be governed by law. It is singular, however, that while science endeavours to reduce this to actual fact in all other studies, those of health and disease have not hitherto been arranged under any law whatever." Keely's system, should he live to complete it, will show that nature works under one law in everything; that discord is disease, that harmony is health. He believes that nervous and brain disorders are curable; but he will never have the leisure to enter this field of research himself, and it will be left for physicians to pursue their experiments to that point where they shall be able to decide whether he is right or wrong. This is why I seek to interest medical men in Keely's belief; his theories of latent energy he is able to handle without help, and to demonstrate a solid foundation for them on facts. "Nothing can lie like a fact," said Velpeau. But nature's laws are infallible facts, and the facts referred to by Velpeau are of the order of the fallible ones enunciated by science, such as "The atom is indivisible." "The atom is infinitely divisible," says Keely, repeating Schopenhauer's words, whose writings I dare say he has never read. Professor George Fr. Fitzgerald, of Trinity College, Dublin, in closing a lecture delivered before the British Association last March, on "Electro-magnetic Radiation," enunciates a possible theory of ether and matter. This hypothesis, he says, explains the differences in nature as differences of motion. If it be true, ether and matter--gold, air, wood, brains--are but different motions. You will be able to judge of the marvellous mechanism invented by Keely, for his researches, when I tell you that by his demonstrations with these instruments, he is able to place this hypothesis in the rank of theories, boldly announcing that all motion is thought, and that all force is mind force. With a clearness that characterizes his great brain he has plunged through the deep and broad questions surrounding the mechanism of the universe, and he claims, on behalf of science, as did the late Provost Jellett of the British Association, "the right to prosecute its investigations until it attains to a mechanical explanation of all things." In this lecture Professor Fitzgerald, commenting upon Professor Hertz's experiments in the vibration of ether waves, says: "If there is reason to think that any greater oscillation might disintegrate the atom, we are still a long way from it." Does not this statement border on an admission that the atom may be divisible? Those who are pursuing their researches in this field are farther off than they know from the great central truth which Faraday did not live long enough to reach, although conjectured by him. We have not only Faraday's discoveries, but those of Scheele, the Swedish chemist, as an example of exact observations leading to erroneous conclusions. The investigations of Scheele led up to the rich harvest which has since been reaped from a knowledge of the nature of the compounds of organic chemistry. Scheele was one of the founders of quantitative analysis, but the phlogistic theory advanced by him was overthrown--the fate of all theories which are not based on solid foundations. Faraday admitted that his own ideas on gravitating force, and of the ether, were but vague impressions of his mind thrown out as matter for speculation. He left no theory on these lines, for he had nothing to offer as the result of demonstration, nor even of sufficient consideration to broach a theory: merely impressions, which are allowable for a time as guides to thought and farther research. Yet more than once did these speculations of his giant intellect touch upon one of nature's hidden laws, the greatest one yet made known to man. Had Faraday lived long enough to pursue his researches, from his starting point of conjecture, he would have been, without doubt, instead of Keely, the discoverer of the latent or hidden potencies existing in all forms of matter, visible and invisible. But the physicists of his time looked upon his speculations as contrary to the received dogmas of science, and preferred their own errors to his speculations. They saw the signpost, but took the road directly opposite to the one Faraday had pointed out. It is admitted that even a false theory, when rightly constructed, has its uses, and that, instead of hindering, it hastens the advance of knowledge. Every one, possessing the slightest acquaintance with the history of astronomy, knows that the doctrines of cycles, epicycles and ellipses, were begotten naturally and necessarily out of each other; and that if Kepler had not propounded speculative errors Newton would not have hit upon speculative truth. It has been said that when men of science disclaim hypotheses, or speculation, they are either unfit for their vocation or, like Newton, they are better than their creed. Hypotheses are at once the effect and the cause of progress. One might as well attempt to preserve and employ an army without organization as to preserve and employ phenomena without a theory to weld them into one. But the theory must be provisionally, if not positively, true; it must be intelligible and consistent; it must explain a greater number of facts and reconcile a greater variety of apparent contradictions than any which has preceded it; and it must have become developed not by the addition merely, but by the addition and solution, of subsidiary explanations. I ask of you an examination of Keely's theories before giving an opinion of them. Time only can decide whether Keely's hypotheses and theories will outlive these tests. If not, his system must be overthrown, as past systems have been, to make room for a better one. All that I ask is that he may have the opportunity to develop it under your encouragement. There are scientists in Europe ready to assist him with pecuniary assistance. They know enough--those who are interested in his discoveries--to know that they can help him in no other way. Professor Hertz of Bonn, said to me: "Keely must work out his system himself to that point where he can instruct physicists to repeat his experiments." Picking up a photograph of Keely's instruments of research, grouped together, he added: "No man is likely to be a fraud who is working on these lines." Science is alert, on tiptoe as it were, waiting for the one mighty explanation of the force, "behind the framework of nature," which has hitherto "eluded its skill;" and which the system of Keely makes clear to the understanding, demonstrating that one power, one law, reigns throughout creation; the immaterial controlling the material, after the divine order and law of creation that the immaterial should govern the material--that the whole realm of matter is under the dominion of the immaterial. But "the known always excludes the unknown" when in opposition to it. As in past generations, so now in ours, physicists have said: "We will not waste our time in looking at facts and phenomena which cannot be accepted in opposition to established principles of science and to known laws of nature; and which, even if we beheld we should not believe." The recognition and practical application of new truths are, as has been said, notoriously slow processes. Harvey's beneficent discovery excited vehement opposition from his contemporaries. Professor Riolan combated this discovery with as much obstinacy as violence; even denying the existence and the functions of lymphatic vessels. Harvey himself united with Riolan in opposing the discoveries of Aselli and Pacquet respecting the lymphatic system. Jenner's discovery met with the same opposition, and more than forty years elapsed before the suggestion of Sir Humphrey Davy became of practical use. Mr. Wills was so affected by the ridicule which he encountered in his experiments with nitrous oxide in destroying physical pain, that he abandoned them. Nearly half a century later Dr. Morton was assailed by several of our journals in America for the use of ether in producing anæsthesia; as also was Sir James Simpson for his use of ether and chloroform. The scientists excommunicated Dr. Wigan, who had proved by anatomical examination that each brain-hemisphere is a perfect brain; that we have, in fact, two brains, as we have two eyes and two ears. His experiences as a physician were declared to be impostures or delusions; his deductions fallacious. They could not be true, because they were inconsistent with the established principles of physiology and mental science. And with such experiences in the past, we should keep in mind that the powers of nature are so mysterious and inscrutable that men must be cautious in limiting them to the ordinary laws of experience. Proclus wrote of the power of mind or will to set up certain vibrations--not in the grosser atmospheric particles whose undulations beget light, sound, heat, electricity--but in the latent immaterial principle of force, of which modern science knows scarcely anything. What is beyond their own power, men cannot comprehend to be in the power of others. Said Sextus: "If by magic you mean a perpetual research among all that is most latent and obscure in nature, I profess that magic, and he who does so comes nearer to the fountain of all knowledge." Sir Isaac Newton said: "It is well known that bodies act upon one another by the attractions of gravity, magnetism and electricity; and these instances show the tenour and course of nature, and make it not improbable that there may be more powers of attraction than these. For nature is very consonant and conformable to herself." With such intimations of the hidden force that is ever in operation, "behind the framework of nature," shall we, because it is hidden from science, refuse to listen to the explanations which Mr. Keely is now prepared to give? All nature is a compound of conflicting, and therefore of counter-balancing and equilibrating, forces. Without this there could be no such thing as stability. In nature nothing is great and nothing is little, writes Figuier. Sir Henry Roscoe says: "The structure of the smallest particle, invisible even to our most searching vision, may be as complicated as that of any of the heavenly bodies which circle around our sun." If you admit this, as stated by one of your own orthodox scientists, why refuse to admit the possibility of the subdivision of all corpuscles of matter, which Keely declares can be done by certain orders of vibration, thus showing up new elements? I do not ask endorsement of Keely's theories; but if physicists did not think it possible to rupture the atom, would they be calculating the chances of doing so, as Professor Fitzgerald has done? Why not admit that certain tenets of science may prove to be nothing more than hypotheses, too hastily adopted as theories, and that Keely has succeeded, as he claims, to have discovered the order of vibration, which by increasing the oscillation of the atom, causes it to rupture itself? This introductory impulse is given at forty-two thousand eight hundred vibrations, instead of one hundred millions; which, having been reached by Professor Hertz, failed to tear apart the atom, and convinced Professor Fitzgerald of the "long way off" that they still are from rupturing it. But even this conclusion was arrived at under an erroneous hypothesis; for the atomic charge does not oscillate across the diameter of the atom, and its possible radiating power was calculated on this hypothesis. Again, as to the canons of science, which are proved by Mr. Keely's researches to be erroneous: take the one which teaches that molecular aggregation is ever attended with dissipation of energy. From whence, then, comes the immense force which is liberated from the constituents of gunpowder by its exciter, fire?--which is a certain order of vibration. Concussion, another order of vibration, releases the hidden energy stored in the molecules of dynamite, which tears the rocks asunder as if they were egg-shells. Still another order of vibration, which Keely has discovered, dissociates the supposed elements of water, releasing from its corpuscular embrace almost immeasurable volumes of force. The discoverer of this law of nature has long been harassed and made to feel like a galley-slave chained to a rock, while with Prometheus aspirations he is seeking to bring down fire and light from heaven for his fellow-men. When Professor Leidy followed his impulse to leap the hedge which divided his special field of research from the domain that Keely was exploring, his was the first effort made by a man of science to save to the world "the hidden knowledge" bestowed upon one who, in my opinion, is alone capable of completing his system in a form to transmit this knowledge to others. I doubt not that this will seem to you as the language of fanaticism; but my convictions do not come from things hoped for. They are the result of the evidence of things seen, year after year, for nearly a decade of years. As a school-girl, fifty years ago, I had the privilege of attending courses of lectures at Yale College, where experiments were given in natural philosophy and in chemistry; which kept up the interest that was awakened in earlier years; when, with my mineral hammer and basket, my father took me in his walks, laying the foundation of that love of true science which has made the discoveries of Keely of such intense interest to me. Superficial as was and still is my knowledge of science, in its various branches, my interest has never abated; and thus, by my course of reading, I have kept myself abreast of the most advanced writers of modern thought, preparing the way for the help that I have been able to give Mr. Keely by putting books into his hands which, after more than twelve years of blind struggles to grapple with the force he had stumbled over, helped him to comprehend its nature, sooner than he would have done had he been left to work out his conjectures unaided, he tells me. Marvellous as is the extent of Keely's knowledge of vibratory physics, I doubt very much whether he knows enough of mechanical physics to perform the trickery which Professor Rowland accused him of attempting. "Of course every one is looking for a trick where Keely is concerned," writes a Baltimore man; and, so long as speculations in the stock of the Keely Motor Company are authorized by the managers of that company, or efforts made to dispose of it before any practical result is attained, so long will Keely be unjustly suspected of being in league with them to obtain money under false pretences. It was after six or seven years of failure on the part of the stockholders of the company to furnish Keely with one dollar, even, that I made a contract with him in April, 1890, to supply all that he needed for the completion of his system; having first received the assurance of Mr. Keely's lawyer that he would carry out the united wishes of Mr. Keely and myself. At that time this announcement was made in the public journals:-- "There has been placed in the hands of Professor Leidy a fund for the use of inventor John W. Keely. The stipulation attached is that no use shall be made of the financial assistance for speculative purposes. This provision, which is made in the interests of the Keely Motor Company as well as for science, will end with the first attempt to speculate on the stock by exhibitions given of the operations of unpatentable engines. Professor Leidy holds the fund at his disposition, and will pay all bills for instruments constructed for researching purposes." The report issued last month by the directors of the Keely Motor Company annulled this contract; and it now remains for your board to decide whether I shall, in behalf of science, continue to supply Mr. Keely with the means of continuing his researches, under the protecting auspices of the University of Pennsylvania, or leave him in the hands of those who are so blind to their own interests, as holders of stock in the Keely Motor Company, they cannot be made to see that their only hope of commercial success lies in the completion of the system that Keely is developing; and that the course proposed by Professor Leidy, and commended by Professor Hertz and Professor Fitzgerald, for Keely to follow, is the only one that will ever enable him to complete it. This system is as much a work of evolution as is any one of the slow operations of nature. "Truth can afford to wait:" she knows that the Creator of all things never hurries. In these twenty years of toil Keely's patient perseverance has been godlike. It is the sharpest rebuke that could be uttered to those whose impatient "hue and cry" has been, "Give us a commercial engine and we will immortalize you;"--grinding from him, meantime, seven-eighths of his interests in his inventions. But in his labours Keely finds a recompense that, as yet, "the world knows not of;" for day by day he sees the once, to him, obscure domain lit up with ever-increasing glory; a domain the boundaries of which are the boundaries of the universe: the entrance into which promises the fulfilment of the hopes of those who look forward to "a time when we shall no longer go to the blind to lead the blind in our search to make life worth living; but, instead, be able to promote, in accordance with scientific method and in harmony with law, the physical, intellectual and moral evolution of our race." As of Newton, with the change of one word only, so one day will it be said of Keely:-- All intellectual eye--our solar round First gazing through, he by the blended power Of laws etheric, universal, saw The whole in silent harmony revolve. What were his raptures then! How pure! How strong! And what the triumphs of old Greece and Rome With his compared? When Nature and her laws Stood all disclosed to him, and open laid Their every hidden glory to his view. On the 23rd of March, following the reading of this address, Professor Koenig, who had become deeply interested in Mr. Keely's researches, wrote:-- "With regard to the experiments, which I saw at Mr. Keely's, I venture upon the following suggestion, as a test of the nature of the force Mr. Keely is dealing with. The revolution of the compass as a result of negative polar attraction. It is stated in Mr. Keely's paper that he finds gold, silver, platinum, to be excellent media for the transmission of these triple currents. Now it is well known that these same metals are most diamagnetic, that is, unaffected by magnetic influences. If, therefore, a needle be made of one of these metals and suspended in place of the steel needle, in the compass, and put under the influence of Mr. Keely's force, it ought to revolve the same as the steel needle will under magnetic and polar and anti-polar influence. If Mr. Keely could make such a needle revolve, it would convince me that he is dealing with a force unknown to physicists." To this requirement Mr. Keely replied: "To run a needle, composed of non-magnetic material, by polar and depolar action is a matter of as infinite impossibility as would be the raising of a heavy weight from the bottom of a well by sucking a vacuum in it, or the inhalation of water into the lungs instead of air, to sustain life." However, at Dr. Brinton's suggestion, Mr. Keely took up a line of research that was new to him, and succeeded in making a needle of the three metals, gold, silver and platinum, rotate by differential molecular action; induced by negative attractive outreach, which is as free of magnetic force as a cork. Professor Brinton had so mastered Keely's working hypotheses as to say, early in April, that he was sure he could make them understood by any intelligent person--writing of them: "All that is needed now is to show that Keely's experiments sustain the principles that underlie these hypotheses. As soon as Professor Koenig is prepared to report on the purely technical and physical character of the experiments, I shall be ready to go into full details as to their significance in reference to both matter and mind. It will be enough for me if Dr. Koenig is enabled simply to say that the force handled by Keely is not any one of the already well-known forces. Let him say that, and I will undertake to say what it is." On the evening of the 13th of April, the Provost of the University of Pennsylvania, with others who were invited, met at Mrs. Moore's house to hear the report of the "observation" of Mr. Keely's researching experiments. The result was not made public; as it was desired, by all concerned, that nothing should be made known which could in any way influence the price of the stock of the company, to which Mr. Keely is under obligations; and which, as far as marketable value is concerned, is quite worthless until his system is completed to that point where some one device or machine can be patented. But, after Professor Koenig had made his report to those assembled, and Professor Brinton had read his abstract, all that had been asked for Mr. Keely, in behalf of the interests of science, was conceded to him. Mr. Keely has been able to continue his researches, up to the present time, without the delays which actions-at-law would have occasioned. Professor Brinton, before making public his "Abstract of Keely's Philosophy," wishes to add two parts, one on the difficulties in the way of physicists in understanding Keely's theories; the other on the relations of the conditions of the inter-etheric order to the laws of mind. The address of Mrs. Moore, type-copied, was sent to various editors and men of science in Philadelphia, as well as to leading capitalists; and, in this crisis of Keely's connection with the stockholders of The Keely Motor Company, some of these editors rendered substantial aid in making known his critical position; most notably the Inquirer, owned by Mr. Elverson, and the Evening Telegraph, owned by Mr. Warburton, with the result that a decided change in public opinion took place, after these journals announced, in April, that Professor Koenig had tested the energy, employed by Keely, with the most sensitive galvanometer of the university, in the presence of Professor Leidy, Professor Brinton, Doctor Tuttle (a Baltimore physicist) and others, finding no trace of electricity; and by other tests no magnetism. The two professors who thoroughly investigated Keely's theories, and observed his demonstrations, were chosen because they possessed the qualities of mind which Herbert Spencer said constitute the first condition of success in scientific research, viz. "an honest receptivity and a willingness to abandon all preconceived notions, however cherished, if they be found to contradict the truth." Professor Leidy and Dr. Willcox, during their observations of Keely's progressive experimental researches, had expressed no opinion of Keely's theories, other than that they did not correspond with their own ideas; but Professor Koenig boldly said, "I not only think Mr. Keely's theories possible, but I consider them quite probable." Professor Brinton, who made a study of Keely's theories, so mastered them as to be able to suggest to Keely a new line of research, required by Dr. Koenig in the tests proposed; and the synopsis of Keely's philosophy, prepared by Doctor Brinton, has made Keely's hitherto unintelligible language intelligible to men of science. Notwithstanding this favourable result, a New York journalist, under a fictitious name, pretended to have discovered that Keely is a fraud, using well-known forces; which statements were published (with woodcuts of instruments discarded by Keely two years before) in the New York Herald and The Press, in Philadelphia. It is amusing to see how "history repeats itself;" for, in the year 1724, in a letter to the Royal Society, Hatzfeldt attacked Sir Isaac Newton in much the same spirit. One would suppose in reading what Hatzfeldt has written of an invention of his time, that it had been written, word for word, of this ignorant investigator of Keely's experiments in researching. After commenting upon the corruption of human nature as shown, in his day, by want of veracity, and the tendency to vicious misrepresentation, he says: "If the said machine was contrived according to the weak sense and understanding of those who pretend it to be moved in other ways than that declared, it would have been discerned before this. "And those who pretend it to be moved by water, or air, or magnetism, one of which (meaning water) even our most famous author did in the beginning affirm it to be moved by, is so very weak that I don't at all think it deserving to be considered. "And what is still worse, to pretend it to be a cheat is a manner of proceeding which is neither consistent with equity nor common sense. As long as arts and sciences have the misfortune of depending on the direction of such like persons, no progress toward truth can be made, but I shall make it sufficiently appear that there is yet more truth behind the hill than ever has been brought to light. There be persons who, when disappointed of gain, turn their shafts against those who have circumvented them. "All those who know anything of philosophy know that gravity is generally (and chiefly by Sir Isaac Newton and his followers) denied to be essential to matter, which I shall not only prove the contrary of, but I shall likewise show the properties in matter, on which the principle depends, to be the most glorious means to prove the existence of God, and to establish natural religion." Is it not rather remarkable that, after a sleep of nearly two centuries, it is again claimed that gravity is inherent in all matter? It has been very generally supposed that Keely is working at haphazard, as it were; in other words, that he has no theory to go upon. Professor Brinton writes of Keely's theories: "Mr. Keely has a coherent and intelligent theory of things, or philosophy, on which he lays out his work and proceeds in his experiments." March 6th, the same professor writes: "Keely's paper on Latent Force in intermolecular spaces is clear enough and instructive, but the average reader will find the perusal up-hill work, from lack of preliminary teaching. Naturally, Mr. Keely, whose mind has been busy with this topic for years, and who is more familiar with it than with any other, does not appreciate how blankly ignorant of it is the average reader. Also naturally he writes above the heads of his audience." A correspondent in Invention, London, writes December 12, 1891: We have at various times in these columns alluded to the investigations of the Philadelphia scientist, J. W. Keely, and this researcher--who is now stated to be engaged in finding a method whereby the power [18] which he professes to have discovered can be employed as a motor in the place of steam--is just now the object of considerable attention in the press of the United States. To summarize the present state of the criticism to which this man is subjected, we may mention that for some time past The New York Herald, among other papers, has been printing a series of articles that have been recently prepared by an American inventor named Browne, professing to show how Keely has, for nearly twenty years, been deceiving expert engineers, shrewd men of the world, some few university professors and others, by the use of compressed air, obtaining testimonials of his discovery of an unknown force in nature. In reading his articles any one who has seen the photographs--as the writer has done--of the researching instruments discarded by Keely, in past years, and those that he is now employing in their place, cannot fail to detect the misstatements and misrepresentations made. Mr. Browne (?) even overrides the testimony of the late Professor Leidy, Dr. Willcox, Dr. Koenig, Dr. Brinton--the Baltimore physicist--Dr. Tuttle, and the engineers Linville and Le Van, all of whom have tested the force used by Keely, and admitted that no electricity, no magnetism, no compressed air is used. Without endorsing in the slightest anything that Keely has discovered, or claims to have discovered, we think that, with the English love of fair play, both sides should always fairly be heard before either is condemned, and as Mr. Keely has consented to instruct a well-known English physicist in his method of producing the force handled, there is every chance of the truth being known, and the correct state of the matter divulged to the scientific world at large, when, mayhap, this rival inventor may have to retract his assertions or stand a suit for libel. We do not say it will be so--we only assert it may be. Professor Brinton, who has made a study of Keely's methods, writes this month to a friend in London:--"The exposé of Keely's alleged methods continues each week. Some of the proposed explanations are plausible, others are plainly absurd. They only serve to attract renewed attention to Keely. I have written to the editor to ask him to arrange a meeting for me with the writer, but I have not yet been able to discover the Mr. Browne, [19] of Brooklyn, who is the supposititious author." Mr. Keely has chosen the successor [20] of Professor Tyndall, at the Royal Institution of Great Britain, as the physicist to whom he will communicate his method. This will be welcome news indeed to scientists on both sides of the Atlantic, and the result will be awaited with anxiety alike by both the friends and foes of Keely. We shall watch for the result, as will our American confrères.--Wm. Norman Brown. CHAPTER XVII. 1891. MORE OF KEELY'S THEORIES.--HIS TRADUCERS EXPOSED. It was in India that man first recognized the fact that force is indestructible and eternal. This implies ideas more or less distinct of that which we now term its correlation and conservation. The changes which we witness are in its distribution.--Professor Draper. "For all things that be not true, be lies." There is a principle in music which has yet to be discovered.--Sir John Herschel. From the Chicago Tribune. That was a happy inspiration which led the Quintet Club, of Philadelphia, to pay a visit to the workshop of Keely a few weeks ago. Its members had been told that the illustrious inventor had employed the power of music to develop the wonderful forces of nature, and evolve by a law of sympathetic vibrations a mighty energy through the disintegration of a few drops of water. Naturally they were anxious to go. They were familiar with the claim made by Paganini that he could throw down a building if he knew the chord of the mass of masonry, and wanted to know if it were possible that the dream of the great violinist is realized at last. So nearly as can be made out from the mysterious language of the man of many promises, there is a harmony of the universe that is controllable by the strains of music. Each of the molecules composing a mass of matter is in a state of incessant oscillation, and these movements can be so much changed by means of musical vibration that the matter will be disintegrated, its constituent molecules fly apart, and a propulsive force be generated similar to that which is evolved by the touching of a match to a single grain of powder stored in a magazine. He holds that matter is nothing but forces held in equilibrium, and that if the equilibrium be once destroyed the most tremendous consequences will ensue. According to the report, he proved to the satisfaction of more than one member of the club that he has already discovered the means of calling out this force, and is able to partially control it. In their presence he caused a heavy sphere to rotate rapidly or slowly, according to the notes given by the instrument on which he played. The sphere was so isolated as to prove that it could not be acted on by electricity or in any other way than by the sound waves. He disintegrated water into what he calls "etheric vapour" by means of a tuning fork and a zither. The disintegration of only four drops of water produced a pressure of 27,000 pounds to the square inch, and three drops of the harmless liquid fired off a cannon "with a tremendous roar." All this is wonderful--if true. And it is strangely parallel to the most advanced lines of modern thought in a scientific direction, if not coincident with them. There is the point. Is there a "thin partition" dividing the wisdom of the schools from the insanity of Keely, or will he yet prove his right to take rank among the greatest of earth's inventors? If he can do what is at present claimed for him, doing it honestly and without any hocus-pocus to beguile the fools, he has already earned a title higher than that worn by any man of the age. If he is simply cheating those to whom he exhibits his mechanism, he is one of the biggest charlatans that ever drew breath, and ought to be scouted accordingly. And here is the difficulty. The visit alluded to is claimed to have been made on May 9th, or fully six weeks ago. Surely if such results were achieved then, as reported by the Philadelphia Inquirer, many others would ere this have been asked and permitted to witness a repetition of the experiments, and the scientific world would now be in a blaze of excited admiration of the man and his methods. But nothing further is said about it. Keely is still plodding away in his workshop, and the world is still rolling round in happy ignorance of what he has done towards revolutionizing existing lines of thought and modes of action. Surely something is radically wrong. The scientists owe it to themselves as well as to the inventor to see to it that this condition is not allowed to continue. They should appoint a commission to investigate, and find out whether Keely is a genius worthy of the highest honours and rewards that can be bestowed, an arrant impostor, whose fittest place would be the penitentiary, or a crank that ought to be put in a lunatic asylum. It is hard to resist the conclusion that he is one or the other of these, and in either case he is not getting his deserts. Let Keely be scientifically investigated. He has been permitted to remain in obscurity too long already. He should be reported on, no matter whether the result be to raise a mortal to the skies or send an alleged angel down to the depths of infamy as a life-long deceiver of his species." [The Tribune is informed that the report was correct in every particular, and that Professor D. G. Brinton, of the University of Pennsylvania, has prepared a paper on the subject, and will publish it when Mr. Keely is ready to have his system made known.--Ed. Inquirer.] The writer of this article in the Chicago Tribune has expressed the prevailing sentiment of our time, in regard to Keely, as far as those are concerned who are in ignorance of the fact that Keely has discovered an unknown energy, and is working out a system which he must himself first learn, by researches into the laws of nature governing it, before he can apply it to mechanics, or make it even so much as understood by others. The unprincipled journalist before alluded to, after failing in an attempt to obtain admission to Mr. Keely's workshop, wrote a series of articles for the press, recounting Keely's researching experiments in 1889 and 1890, as then shown to Professor Joseph Leidy, Dr. James Willcox, and others. This journalist, who professed to give woodcuts of Keely's researching instruments, was entirely ignorant of the fact that the experiments which he described had never once been repeated, during the last eighteen months; Keely having taken up researches on another line, as soon as he had gained sufficient control of the force he was handling to cause the solid bronze weight weighing six and three quarters lbs., to rise in the jar, rest midway, or remain stationary at will. The "Generator," described by this journalist in the Philadelphia Press of November 1st, 1891, never had any existence beyond the journalist's brain and the woodcut. It was represented as a square structure, "big and thick walled enough to hold a donkey engine," whereas the true disintegrator (or improved generator) is round, and about the size of the wheel of a baby's perambulator. This form of generator Mr. Keely has been using for about three years; suspending it from a staple in the ceiling, or against the wall, when using it in the dissociation of the so-called elements of water. Consequently, it was impossible for the force to be "conducted from a reservoir eight or ten squares distance," as suggested by this inventing journalist, who says that he "spent sleepless nights" in devising the way in which the generator was operated by Keely: asserting that "this extraordinary force was loaded like electricity through a wire and discharged like steam through a pipe." In a romance called "The Prince and the Pauper" these lines occur: "For, look you, an it were not true, it would be a lie. It surely would be. Think on't. For all things that be not true, be lies,--thou canst make nought else out of it." Never were truer words written, and equally true is it that, as another author has written, "If the boy who cannot speak the truth, lives to be a man, and becomes a journalist, he will invent lie after lie as long as he can get a Journal to print them and to pay him for them." There are very few men, who take up journalism in the spirit of a St. Beuve. Quite as few are there who are competent to write, in any way, of Keely's discoveries and all that they involve. Even among men of science, only one man has been found who is able to comprehend Keely's theories, and to handle them in a way to make them intelligible to others. S. Laing, in "Modern Thought," says, "Science traces everything back to primeval atoms and germs, and there it leaves us. How came these atoms and energies there, from which this wonderful universe of worlds has been evolved by inevitable laws? What are they in their essence, and what do they mean? The only answer is, "It is unknowable. It is behind the veil. Spirit may be matter, matter may be spirit." Keely's researches have been of a nature which, grappling with these mysteries, has brought them to the light. He tells us that spirit is the soul of matter, and that no matter exists without a soul. More of Keely's Theories. The sympathetic conditions that we call mind are no more immaterial in their character than light or electricity. The substance of the brain is molecular, while the substance of the mind that permeates the brain is inter-etheric, and is the element by which the brain is impregnated; exciting it into action and controlling all the conditions of physical motion, as long as the sympathetic equatative is in harmony, as between the first, second, and third orders of transmission; molecular, atomic and etheric. By this soul-substance is the physical controlled. In order to trace the successive triple impulses, taking the introductory one of sympathetic negative outreach, towards the cerebral neutrals, which awakens the latent element to action, we find that mind may be considered a specific order of inter-atomic motion sympathetically influenced by the celestial flow, and that it becomes when thus excited by this medium a part and parcel of the celestial itself. Only under these conditions of sympathetic assimilation can it assert its power over the physical organisms; the finite associated with the infinite. The brain is not a laboratory. It is as static as the head of the positive negative attractor, [21] until influenced by certain orders of vibration, when it reveals the true character of the outreach so induced. The brain is the high resonating receptacle where the sympathetic celestial acts, and where molecular and atomic motion exhibits itself, as according to the intensification brought to bear upon it by the celestial mind flow. The cerebral forces, in their control of the physical organism, reveal to us the infinite power of the finer or spiritual fluid, though not immaterial, over the crude molecular. The luminous, etheric, protoplastic element, which is the highest tenuous condition of the ether, fills the regions of infinite space, and in its radiating outreach gives birth to the prime neutral centres that carry the planetary worlds through their ranges of motion. If the minds of all the most learned sages, of all time, were concentrated, into one mind, that one would be too feeble, in its mental outreach, to comprehend the conditions associated with the fourth order of sympathetic condensation. The controversies of the past in regard to the condensation of invisible matter prove this. The chemistry of the infinite and the chemistry of the finite are as wide apart, in their sympathetic ranges, as is the velocity of light from the movement of the hour-hand of a clock. Even the analysis of the visible conditions taxes our highest powers of concentration. The question naturally arises, Why is this condition of ether always under a state of luminosity of an especial order? Its characteristics are such, from its infinite tenuity and the sympathetic activity with which it is impregnated, that it possesses an order of vibratory, oscillatory velocity, which causes it to evolve its own luminosity. This celestial, latent power, that induces luminosity in this medium, is the same that registers in all aggregated forms of matter, visible and invisible. It is held in corpuscular embrace until liberated by a compound vibratory negative medium. What does this activity represent, by which luminosity is induced in the high etheric realm? Does not the force following permeation by the Divine Will show that even this order of ether, this luminiferous region, is bounded by a greater region still beyond?--that it is but the shore which borders the realm, from which the radiating forces of the Infinite emanate: the luminiferous being the intermediate which transfers the will force of the Almighty towards the neutral centres of all created things, animate and inanimate, visible and invisible; even down into the very depths of all molecular masses. The activity of the corpuscles, in all aggregations, represents the outflow of this celestial force, from the luminiferous track, towards all these molecular centres of neutrality, and reveals to us the connecting link between mind and matter. How plainly are we thus taught that God is everywhere, and at the same time in every place. It gives us a new sense of the omniscience and omnipresence of the Creator. In these researches I am brought so near to the celestial conditions that my pen is ready to fall from my hand while writing on this subject; so more and more sensibly do I feel my abject ignorance of its depths.... These conditions of luminosity have no thermal forces associated with them; although, paradoxically, all thermal conditions emanate from that source. The tenuity of this element accounts for it. It is only when these sympathetic streams come in conflict with the cruder elementary conditions, either the molecular or atomic, that heat is evolved from its latent state, and a different order of light from the etheric luminous is originated, which has all the high conditions of thermal force associated with it: the sun being the intermediate transmitter. Thus is shown the wonderful velocity of these sympathetic streams emanating from celestial space. The sympathetic forces transmitted by our solar planet, to which our earth is so susceptible, are continuously received from the luminiferous realm; the sympathetic volume of which, as expended, is constantly equated by the exhaustless will-force of the Creator. Had the solar energy been subservient to what physicists ascribe it, the sun would have been a dead planet thousands of centuries ago, as also all planets depending upon it as an intermediate. In fact, all planetary masses are sympathetic-transferring-mediums, or intermediates, of this prime, luminous, dominant element. In the vibratory subdivision of matter, as progressive evolution has been analyzed, it is evident that these transfers of sympathetic force extend beyond the limits of our orbital range, from system to system, throughout the realms of space: these progressive systems becoming themselves, after a certain range of sympathetic motion, sympathetic intermediates, as included in the whole of one system, exemplified so beautifully in the cerebral convolutions, with their connective sympathy for each other; transferring as a whole on the focalizing centre, from which it radiates to all parts of the physical organism, controlling in all its intricate variety the sympathetic action, of our movements. "What is there that we really know?" asks Buckle. "We talk of the law of gravitation, and yet we know not what gravitation is; we talk of the conservation of force and distribution of forces, and we know not what forces are." "The vibratory principles now discovered in physics," says Hemstreet, "are so fine and attenuated that they become an analogy to mental or cerebral vibrations." Let us see what Keely's system of vibratory physics says of gravity, cohesion, etc. What is Gravity?--Gravity is an eternal existing condition in etheric space, from which all visible forms are condensed. Consequently, it is inherent in all forms of matter, visible and invisible. It is not subject to time nor space. It is an established connective link between all forms of matter from their birth, or aggregation. Time is annihilated by it, as it has already traversed space when the neutral centres of the molecules were established. Gravity, then, is nothing more than an attractive, sympathetic stream, flowing towards the neutral centre of the earth, emanating from molecular centres of neutrality; concordant with the earth's centre of neutrality, and seeking its medium of affinity with a power corresponding to the character of the molecular mass. What is Cohesion?--Cohesion is sympathetic negative attraction. It is the negative, vibratory assimilation, or aggregation, of the molecules, acting according to the density or compactness of the molecular groupings on their structures. The differing character of molecular densities, or molecular range of motion, represents differing powers of attraction. The lower the range of motions on the molecular vibrations of these structures, the greater is the attractive force that holds them together; and vice versâ. What is Heat? Heat may be classed as a vibro-atomic element, not exceeding 14,000 vibrations per second at its greatest intensity, latent in all conditions of matter both visible and invisible. The velocity of the sympathetic flows which emanate from our solar world, the sun, coming into contact with our atmospheric medium, liberates this element in all the different degrees of intensity that give warmth to our earth. Light is another resultant; the different intensities of which are produced according to the different angles of this sympathetic projectment. The light that emanates from a glow-worm is the resultant of the action of the sympathetic medium of the insect itself on a centre of phosphorescent matter, which is included in its structure. The resultant of the two conditions are quite different, but they are governed by the same laws of sympathetic percussion. Radiation is the term used to express the reaching out of the thermal element, after its liberation from its corpuscular imprisonment, to be re-absorbed or returned again to its sympathetic environment; teaching us a lesson in the equation of disturbance of sympathetic equilibrium. Force. "By what means is force exerted, and what definitely is force? Given that force can be exerted by an act of will, do we understand the mechanism by which this is done? And if there is a gap in our knowledge between the conscious idea of a motion and the liberation of muscular energy needed to accomplish it, how do we know that a body may not be moved without ordinary material contact by an act of will?" These questions were asked by Professor Lodge in his paper on "Time;" and as Keely contends that all metallic substances after having been subjected to a certain order of vibration may be so moved, let us see how he would answer these questions. When Faraday endeavoured to elaborate some of his "unscientific notions in regard to force and matter," men of science then said that Faraday's writings were not translatable into scientific language. The same has been said of Keely's writings. Pierson says, "The very fact that there is about the product of another's genius what you and I cannot understand is a proof of genius, i.e., of a superior order of faculties." Keely, who claims to have discovered the existence of hidden energy in all aggregations of matter, imprisoned there by the infinite velocity of molecular rotation, asserts that "physicists in their mental rambles in the realm of analytical chemistry, analytical as understood by them, have failed to discover the key-note which is associated with the flow of the mental element;" that "they have antagonized or subverted all the conditions," in this unexplored territory of negative research, which he has demonstrated as existing in reference to latent energy locked in corpuscular space. These antagonisms might have been sooner removed had those physicists who witnessed some of Keely's experiments, while he was still working blindfold as it were, in past years, not belonged to that class of scientists "who only see what they want to see, and who array facts and figures adroitly on the side of preconceived opinion." Since the last meeting of the British Association, Keely, in writing of some of the addresses delivered, says: "It delights me to find that physicists are verging rapidly toward a region which, when they reach, will enable them to declare to the scientific world what they now deny; viz., that immense volumes of energy exist in all conditions of corpuscular spaces. My demonstrations of this truth have been ignored by them and now they must find it out for themselves. I do not doubt that they will reach it in their own way. I accept Professor Stoney's idea that an apsidal motion might be caused by an interaction between high and low tenuous matter; but such conditions, even of the highest accelerated motion, are too far down below the etheric realm to influence it sympathetically, even in the most remote way. I mean by this that no corpuscular action, nor interaction can disturb or change the character of etheric vibrations. The conception of the molecule disturbing the ether, by electrical discharges from its parts, is not correct; as the highest conditions associated with electricity come under the fourth descending order of sympathetic condensation, and consequently its corpuscular realm is too remote to take any part towards etheric disturbance. Hypothesis is one thing and actual experimental demonstration is another; one being as remote from the other as the electrical discharges from the recesses of the molecule are from the tenuous condition of the universal ether. The conjecture as regards the motion being a series of harmonic elliptic ones, accompanied by a slow apsidal one, I believe to be correct.... The combination of these motions would necessarily produce two circular motions of different amplitudes whose differing periods might correspond to two lines of the spectrum, as conjectured, and lead the experimenter, perhaps, into a position corresponding to an ocular illusion. Every line of the spectrum, I think, consists not of two close lines, but of compound triple lines: though not until an instrument has been constructed, which is as perfect in its parts as is the sympathetic field that environs matter, can any truthful conclusion be arrived at from demonstration." It must be remembered that Keely claims to have demonstrated the subdivision of matter in seven distinct orders: molecular, intermolecular, atomic, inter-atomic, etheric, inter-etheric, reaching the compound inter-etheric in the seventh order. In commenting further upon the experimental researches of men of science to show whether ether in contact with moving matter is affected by the motion of such matter, Keely writes: "The motion of any matter of less tenuity than the ether cannot affect it any more than atmospheric air could be held under pressure in a perforated chamber. The tenuous flow of a magnet cannot be waived aside by a plate of heavy glass, and yet the magnetic flow is only of an inter-atomic character and far more crude than the introductory etheric. The etheric element would remain perfectly static under the travel of the most furious cyclone; it would pass through the molecular interstices of any moving projectile with the same facility that atmospheric air would pass though a coarse sieve. Ether could not be affected by the motion of less tenuous matter, but if the matter were of the same tenuous condition it would sympathetically associate itself with it; consequently there would be no motion any more than motion accompanies gravity. In the same way that the mind flow induces motion on the physical organism, sympathetic flows on molecular masses induce motion on the molecular. The motion of the molecules in all vegetable and mineral forms in nature are the results of the sympathetic force of the celestial mind flow, or the etheric luminous, over terrestrial matter. This celestial flow is the controlling medium of the universe, and one of its closest associates is gravity.... The molecule is a world in itself, carrying with it all the ruling sympathetic conditions which govern the greatest of the planetary masses. It oscillates within its etheric rotating envelope with an inconceivable velocity, without percussing its nearest attendant, and is always held within its sphere of action by the fixed gravital power of its neutral centre, in the same sympathetic order that exists between the planetary worlds. The dissociation of aggregated molecules by intermolecular vibration does not disturb even to an atomic degree these fixed neutral points. Each molecule contributes its quota to the latent electrical force, which shows up by explosion after its gathering in the storm clouds, and then it returns to the molecular embrace it originally occupied. You may call this return, absorption; but it gets there first during corpuscular aggregation, and comes from there, or shows itself, during sympathetic disturbance of equilibrium. There are three kinds of electricity, the harmonic and enharmonic, which, with their leader, the dominant, form the first triple. Their sympathetic associations evolve the energy of matter. The dominant is electricity luminous, or propulsive positive. The harmonic, or the magnetic, which is the attractive, with its wonderful sympathetic outreach, is the negative current of the triune stream. The enharmonic, or high neutral, acts as the assimilative towards the reinstatement of sympathetic disturbance. In electric lighting, the velocity of the dynamos accumulates only the harmonic current--by atomic and inter-atomic conflict--transferring one two hundred thousandth of the light that the dominant current would give, if it were possible to construct a device whereby it could be concentrated and dispersed. But this supreme portion can never be handled by any finite mode. Each of these currents has its triple flow, representing the true lines of the sympathetic forces that are constantly assimilating with the polar terrestrial envelope. The rotation of the earth is one of the exciters that disturbs the equilibrium of these sensitive streams. The alternate light and darkness induced by this motion helps to keep up the activity of these streams, and the consequent assimilation and dissimilation. The light zone being ever followed by the dark zone, holds the sympathetic polar wave constant in its fluctuations. This fact may be looked upon as the foundation of the fable that the world rests upon a tortoise. The rotation of the earth is controlled and continued by the action of the positive and negative sympathetic celestial streams. Its pure and steady motion, so free from intermitting impulses, is governed to the most minute mathematical nicety by the mobility of the aqueous portion of its structure, i.e., its oceans and ocean's anastomosis. There is said to be a grain of truth in the wildest fable, and herein we have the elephant that the tortoise stands on. The fixed gravital centres of neutrality, the sympathetic concordants to the celestial outreach, that exist in the inter-atomic position, are the connective sympathetic links whereby the terrestrial is held in independent suspension. We cannot say that this corresponds to what the elephant stands upon, but we can say, "This is the power whereby the elephant is sympathetically suspended." The Atom. Question asked in Clerk Maxwell's memoirs: "Under what form, right, or light, can an atom be imagined?" Keely replies, It eludes the grasp of the imagination, for it is the introductory step to a conception of the eternity of the duration of matter. The magnitude of the molecule, as compared to the inter-atom, is about on the same ratio as a billiard ball to a grain of sand; the billiard ball being the domain wherein the triple inter-molecules rotate, the inter-molecules again being the field wherein the atomic triplets sympathetically act, and again progressively, in the inter-atomic field, the first order of the etheric triplets begins to show its sympathetic inreach for the centres of neutral focalization. It is impossible for the imagination to grasp such a position. Inter-atomic subdivision comes under the order of the fifth dimensional space in etheric condensation. Atoms and corpuscules can be represented by degrees of progressive tenuity, as according to progressive subdivision, but to imagine the ultimate position of the atomic alone would be like trying to take a measurement of immeasurable space. We often speak of the borders of the infinite. No matter what the outreach may be, nor how minute the corpuscular subdivision, we still remain on the borders, looking over the far beyond, as one on the shore of a boundless ocean who seeks to cross it with his gaze. Therefore, philosophically speaking, as the atom belongs to the infinite and the imagination to the finite, it can never be comprehended in any form or light, nor by any right; for in the range of the imagination it is as a bridge of mist which can never be crossed by any condition that is associated with a visible molecular mass, that is, by mind as associated with crude matter. Sympathetic Outreach is not induction. They are quite foreign to each other in principle. Sympathetic outreach is the seeking for concordance to establish an equation on the sympathetic disturbance of equilibrium. When a magnet is brought into contact with a keeper, there is no induction of magnetism from the magnet into the keeper. The static force of the magnet remains unchanged, and the action between the two may be compared to a sympathetic outreach of a very limited range of motion. The sympathetic outreach of the moon towards the earth, has a power strong enough to extend nearly a quarter of a million of miles to lift the oceans out of their beds. This is not the power of induction.... The sympathetic envelope of our earth owes its volume and its activity entirely to celestial radiating forces. Reception and dispersion are kept up by atomic and inter-atomic conflict, as between the dominant and enharmonic. Silver represents the 3rd, gold the 6th, and platina the 9th, in their links of association, one to the other, in the molecular range of their motions, when submitted to vibratory impulses. If an introductory impulse, representing the sympathetic chord of transmission, say B flat, or any other chord, be given to a sectional transmitting wire, the molecular triple, that is carried sympathetically along the path of such transmitter by the differentiation induced, excites high sympathy with the polar terrestrial stream. The polar terrestrial, being triune in its character, requires a triune sympathizer to meet its differential requirements: silver the harmonic, gold the enharmonic, and platina the dominant. When this triple metallic condition is properly sensitized, by any chord on the dominant, combined molecular, differentiated action is induced; showing a condition approaching magnetism in its development of related sympathy, without having the conditions that are truly magnetic, as this term (magnetic) is understood by all physicists. Magnetism is not polar negative attraction, any more than polar negative attraction is magnetism; for polar negative attraction shows positive sympathetic outreach, of a high order; which is a condition entirely foreign to magnetism. Sympathetic negative attraction is not the resultant of electrical sympathization, but it includes the full triune flow; the dominant being the leader and associate of the celestial. The sympathetic outreach, of negative attraction, is the power that holds the planetary masses in their orbital ranges of oscillatory action. Magnetism has no outreach, but it pervades all terrestrial masses--all planetary masses. It is highly electrical in its character, in fact magnetism is born of electricity; whereas negative attraction is not, but it has a sympathetic outreach for magnetism. Magnetism is static. Sympathetic negative attraction reaches from planet to planet; but electricity does not, nor does magnetism. Sympathetic negative attraction is born of the celestial, and impregnates every mass that floats in space: seeking out all magnetic or electric conditions; and all these masses are subservient to celestial outreach. All the magnets in the world could not induce rotation, no matter how differentiated, but polar negative attraction induces rotation. Hydrogen. The horizon of matter, which has been thought to rest over attenuated hydrogen, may extend to infinite reaches beyond, including stuffs or substances which have never been revealed to the senses. Beings fashioned of this attenuated substance might walk by our side unseen, nor cast a shadow in the noon-day sun.--Hudson Tuttle. This supposition of itself admits that hydrogen is a compound. If it were indivisible it would assimilate with the high luminous, from which all substances are formed or aggregated. If hydrogen were a simple it could not be confined. No molecular structure known to man can hold the inter-luminous; not even the low order of it that is chemically liberated. The word "attenuated" admits that hydrogen is a compound. I contend that hydrogen is composed of three elements, with a metallic base, and comes under the order of the second atomic, both in vibration and sympathetic outreach. Hydrogen exists only where planetary conditions exist: there it is always present, but never in uninterfered space. There is much celestial material that has never been revealed to the senses. My researches lead me to think that hydrogen carries heat in a latent condition, but I do not believe it will ever be possible to originate a device that will vibrate hydrogen with a velocity to induce heat. The word imponderable as applied to a molecule is incorrect. All gases as well as atmospheric air are molecular in their structures. If atmospheric air is subdivided, by atomic vibration, it merely dissociates the hydrogen from the oxygen; neither of which, though disunited, passes from the inter-molecular state; and not until hydrogen is sympathetically subdivided in its inter-molecular structure by inter-atomic vibrations can it assimilate with the introductory etheric element. There is a wonderful variation of gravital sympathy between the gaseous elements of compounds, all of which comes under the head of molecular.... Under date of October 1st, 1891, Mr. Keely writes: I see no possibility of failure, as I have demonstrated that my theories are correct in every particular, as far as I have gone; and if I am not handicapped in any way during the next eight months, and my depolarizer is perfect, I will then be prepared to demonstrate the truth of all that I assert in reference to disintegration, cerebral diagnosis, aerial suspension and dissociation, and to prove the celestial gravital link of sympathy as existing between the polar terrestrial and equation of mental disturbance of equilibrium. It is a broad assertion for one man, and 'an ignorant man' at that, to make; but the proof will then be so overwhelming in its truthful simplicity that the most simple-minded can understand it. Then I will be prepared to give to science and to commerce a system that will elevate both to a position far above that which they now occupy. Again, November 4th, Mr. Keely says: The proper system for the treatment of cerebral differentiation is not yet known to the physician of to-day. The dissimilarities of opinion existing, with regard to any case, are confounding. When the true system is recognized, the vast number of physical experimentalists, now torturing humanity, will die a natural death. Until this climax is reached, physical suffering must go on multiplying at the same ratio that experimentalists increase. Molecular differentiation is the fiend that wrecks the physical world, using the seat of the cerebral forces as its intermediate transmitter. It is the devastating dragon of the universe, and will continue to devastate until a St. George arises to destroy it. The system of equating molecular differentiation is the St. George that will conquer. When my system is completed for commerce, it will be ready for science and art. I have become an extensive night worker, giving not less than eighteen hours a day, in times of intensification. I have timed my race for life and I am bound to make it.... New York Truth, 15th May, 1890, in commenting upon Keely's claims to have "annihilated gravity and turned the mysterious polar current to a mill-race," continues: "I sincerely hope that Mr. Keely may prove, AS FROM LATE DEVELOPMENTS HE IS LIKE TO DO, that the hidden spirit of the Cosmos, which men call Deity, First Cause, Nature, and other sonorous but indefinite names, has manifested itself to him; that the music of the spheres is a truth, not an imagination, and that vibration, which is sight, hearing, taste and smell, is in serious verity, all else. The fable of Orpheus and Arion may have a foundation in actual physics, the harmonies that move our souls to grief or joy as music, may be the same as those that govern and impel the stars in their courses, cause molecules to crystallize into symmetry, and from symmetry into life. Who shall say? If the accounts of Keely's late achievements be true, and they are honestly vouched for by men of worth and note, then the secret is laid bare, the core of being is opened out. In this age of dawning reason the candle cannot always be hidden under a bushel; some enterprising hand will lift the obstruction and let the light shine before men." Two years have nearly passed away since this was written, during which time Mr. Keely has been engaged in perfecting his system for aerial navigation. He has, one by one, overcome all obstacles, and so far gained control, of the mysterious polar current, that he has been able to exhibit on the thirds, or molecular graduation of the propeller of his air-ship, 120 revolutions in a minute; and on the sixths, or atomic graduation, 360 revolutions in a minute. He still has the etheric field to conquer; but those who know how many years he has been making his mistakes stepping-stones in his upward progress, surmounting obstacle after obstacle which would have dismayed a less courageous soul, feel little doubt that he will "make the race," which he has timed for life, and reach the goal a conqueror, notwithstanding he is still so often "handicapped." All those who had the privilege of witnessing Keely's researching experiments, in the spring of 1890, when he first succeeded in raising the metal weight, and who were sufficiently acquainted with the laws of physics to understand the conditions under which the weight was raised, pronounced the force by which it was affected to be an unknown force. Had the weight been but a nail or a feather, lifted under such conditions, physicists know that, after he has gained as perfect control of it as we now have of steam, air-ships weighing thousands of tons can be raised to any height in our atmosphere, and the seemingly untraversable highways of the air opened to commerce. This force is not, like steam or electricity, fraught with danger in certain states to those who use it; for, after the molecular mass of the vessel has been fitted to the conditions required, its control becomes of such a nature that seemingly a star might as soon go astray, and be lost to the universe, as for the aerial ship to meet with an accident, unless its speed was pushed to that point where gravity resumes its control. In fact, Keely asserts that there is no known force so safe to use as the polar terrestrial force, for when the celestial and terrestrial conditions are once set up, they remain for ever; perpetual molecular action the result. In using the word celestial, Keely refers to the air, in the same sense that terrestrial refers to the earth. Wide through the waste of ether, sun and star All linked by harmony, which is the chain That binds to earth the orbs that wheel afar Through the blue fields of Nature's wide domain. Percival. From the New York Home Journal. THE SONG OF THE CARBONS. [22] A weird, sweet melody, faint and far, A humming murmur, a rhythmic ring, Floats down from the tower where the lenses are:-- Can you hear the song which the carbons sing? Millions of æons have rolled away In the grand chorale which the stars rehearse, Since the note, so sweet in our song to-day, Was struck in the chord of the universe. The vast vibration went floating on Through the diapason of space and time, Till the impulse swelled to a deeper tone, And mellowed and thrilled with a finer rhyme. Backward and forward the atoms go In the surging tide of that soundless sea, Whose billows from nowhere to nowhere flow, As they break on the sands of eternity. Yet, through all the coasts of the endless All, In the ages to come, as in ages gone, We feel but the throb of that mystic thrall Which binds responsive the whole in one. We feel but the pulse of that viewless hand Which ever has been and still shall be, In the stellar orb and the grain of sand, Through nature's endless paternity. The smile which plays in the maiden's glance, Or stirs in the beat of an insect's wing, Is of kin with the north light's spectral dance, Or the dazzling zone of the planet's ring. From our lonely tower aloft in air, With the breezes around us, tranquil and free, When the storm rack pales in the lightning's glare, Or the starlight sleeps in the sleeping sea, We send our greeting through breathless space, To our distant cousins, the nebulæ, And catch in the comet's misty trace, But a drifting leaf from the tribal tree. The song we hum is but one faint sound In the hymn which echoes from pole to pole, Which fills the domes of creation's round, And catches its key from the over-soul. And when it ceases all life shall fail, Time's metronome shall arrested stand; All voice be voiceless, the stars turn pale, And the great conductor shall drop his wand. CHAPTER XVIII. A PIONEER IN AN UNKNOWN REALM. Thus, either present elements are the true elements, or there is a probability of eventually obtaining some more high and general power of Nature, even than electricity; and which, at the same time, might reveal to us an entirely new grade of the elements of matter, now hidden from our view and almost from our suspicion.--The Nature of the Chemical Elements. Faraday, 1836. A mysterious force exists in the vibrations of the ether, called sound, which science and invention have so far failed to utilize; but which, no doubt in the near future, will come under man's control, for driving the wheels of industry.--Thought as Force. E. S. Huntington. Force and forces-- No end of forces! Have they mind like men? Browning. The Spectator, commenting on the jubilee of the Chemical Society, last year, said it was notable for two remarkable speeches; one by Lord Salisbury, and the other by Sir Lyon Playfair. Lord Salisbury reminded his hearers that about one hundred years ago, a very celebrated tribunal had informed Lavoisier that the French Republic had no need of chemists; "but," said his Lordship, "Lavoisier, though a man of very advanced opinions, was behind this age." Lord Salisbury proceeded to exalt chemistry as an instrument of the higher educational discipline. Astronomy, he said, was hardly more than a science of things that probably are; for, at such distance in space, it was impossible to verify your inferences. Geology he regarded as a science of things as they probably were; verification being impossible after such a lapse of time. But chemistry he treated as a science of things as they actually are at the present time. The Spectator remarks:--Surely that is questionable. All hypothesis is more or less a matter of probability. No one has ever verified the existence of atoms. Sir Lyon Playfair, following Lord Salisbury, said, Boyle has been called the father of chemistry and the brother of the Earl of Cork; ironically hinting, perhaps, that Lord Salisbury was reflecting as much immediate glory on chemistry, by his interest in it, as did the relationship of the first considerable chemist to the Irish earl. Sir Lyon, acknowledging the revolutionizing progress of chemistry, remarked that within the last fifty years it had seen great changes; then, oxygen was regarded as the universal lover of other elements; and nitrogen was looked upon as a quiet, confirmed bachelor; but oxygen had turned out to be a comparatively respectable bigamist, that only marries two wives at a time; and nitrogen had turned out to be a polygamist; generally requiring three conjugates, and sometimes five, at a time. The false teachings of physicists in the past were admitted, including Sir Lyon's own errors; his old conceptions concerning carbonic acid and carbonic oxide all having broken down, under the crushing feet of progress. After all, says the Spectator, it seems that the French revolutionists should have welcomed chemistry, instead of snubbing it, for it has been the most revolutionary of sciences. At the present time, notwithstanding the experiences of the past, Science stands as calmly on the pedestal, to which she has exalted herself, as if not even an earthquake could rock its foundations. In her own opinion, she holds the key to nature's domains. Some few there are who are ready to admit that it is possible Nature still holds the key herself; and who are not unwilling to encounter another revolution, if they can extend their knowledge of Nature's laws; even though it may leave only ruins, where now all is supposed to be so solid as to defy earthquakes and other revolutionizing forces. In reviewing the history of the onward march of chemistry in the past, we find that Robert Boyle, who lived from 1627 to 1691, was the first chemist who grasped the idea of the distinctions between an elementary and a compound body. He has been called the first scientific chemist, and he certainly did much to advance chemical science, particularly in the borderland of chemistry and physics, but he did this more by his overthrow of false theories, than in any other way. It was left for Scheele (born 1742), an obscure Swedish chemist whose discoveries extended over the whole range of chemical science, and his French contemporary, Lavoisier (born 1743), to bring about a complete revolution in chemistry. Thus, step by step, and period by period, experimental science has prepared the way to reach that elevation which humanity is destined eventually to attain, when all errors have been discarded and truth reigns triumphant. The question has been asked, in view of the past history of discovery, what may not the science of the future accomplish in the unseen pathways of the air? That still unconquered field lies before us, and we know that it is only a question of time when man will hold dominion there with as firm sway as he now holds it on land and sea. Physics and chemistry walk hand in hand. Scientists cannot cut the tie that joins them together in experimental science. Physics treats of the changes of matter without regard to its internal constitution. The laws of gravitation and cohesion belong to physical science. They concern matter without reference to its composition. Chemistry makes us acquainted with the constituents of the different forms of matter, their proportions and the changes which they are capable of bringing about in each other. But notwithstanding the lessons of the past, both chemistry and physics are blind to what the future has in store for them. Scientists have erected barriers to progress, building them so as to appear of solid masonry on the ground of false hypotheses; but, when the hour is ripe, these will be swept away as if by a cyclone, leaving not one stone on another. It was Boyle who overthrew the so-called Aristotelian doctrine, and Paracelsus's teachings of the three constitutents of matter, disputed first by Van Helmont. Boyle taught that chemical combination consists of an approximation of the smallest particles of matter, and that a decomposition takes place when a third body is present, capable of exerting on the particles of the one element a greater attraction than is exercised by the particles of the element with which it is combined. In this conjecture there is just a hint of the grand potentialities in the unknown realm which is now being explored by Keely, the discoverer of the order of vibration that releases the latent force held in the interstitial spaces of the constituents of water; one order of vibration, being more in sympathy with one of the elements of water than with the other, possesses a greater attraction for that element and thereby raptures its atoms, showing up new elements. Not all men of science are willing to admit the atomic theory; although it explains satisfactorily all the known laws of chemical combination. Dalton, accepting the teachings of the ancients as to the atomic constitution of matter, was the first to propound a truly chemical atomic theory; a quantitative theory, declaring that the atoms of the different elements are not of the same weight, and that the relative atomic weights of the elements are the proportions, by weight, in which the elements combine. All previous theories, or suggestions, had been simply qualitative. Berzelius, the renowned Swedish chemist, advancing Dalton's atomic theory, laid the foundation stones of chemical science, as it now exists. Since his day, by the new methods of spectrum analysis, elements unknown before have been discovered; and researchers in this field are now boldly questioning whether all the supposed elements are really undecomposable substances, and are conjecturing that they are not. On this subject Sir Henry Roscoe says:-- "So far as our chemical knowledge enables us to judge, we may assume, with a considerable degree of probability, that by the application of more powerful means than are known at present, chemists will succeed in obtaining still more simple bodies from the so-called elements. Indeed, if we examine the history of our science, we find frequent examples occurring of bodies, that only a short time ago were considered to be elementary, which have been shown to be compounds, upon more careful examination." What the chemist's retort has failed to accomplish has been effected by the discoverer of latent force existing in all forms of matter, where it is held locked in the interstitial spaces, until released by a certain order of vibration. As yet, the order of vibration which releases this force, has not been discovered in any forms of matter, excepting in the constituents of gunpowder, dynamite, and water. The Chinese are supposed to have invented, centuries before the birth of Christ, the explosive compound gunpowder, which requires that order of vibration known as heat to bring about a rupture of the molecules of the nitre, sulphur, and charcoal, of which it is composed. Dynamite requires another order of vibration--concussion--to release the latent force held in the molecular embrace of its constituents. The order of vibration discovered by Keely, which causes the rupture of the molecular and atomic capsules of the constituents of water, must remain--though in one point only--a secret with the discoverer, until he has completed his system for science, and some one patentable invention. Let physicists be incredulous or cautious, it matters not to him. He has proved to his own satisfaction the actual existence of atoms and their divisibility--and, to the satisfaction of thousands capable of forming an opinion, the existence of an unknown force. Men of science have not been in any haste to aid him, either with money or with sympathy, in his researches; and he will take his own time to bestow upon them the fruit of those researches. Those who have not clear ideas as to the nature of elementary bodies--molecules and atoms--may like to know that elements are defined as simple substances, out of which no other two or more essentially differing substances have been obtained. Compounds are bodies out of which two or more essentially differing substances have been obtained. A molecule is the smallest part of a compound or element that is capable of existence in a free state. Atoms are set down, by those who believe in the atomic theory, as the indivisible constituents of molecules. Thus, an element is a substance made up of atoms of the same kind; a compound is a substance made up of atoms of unlike kind. Over seventy elements are now known, out of which, or compounds of these with each other, our globe is composed, and also the meteoric stones which have fallen on our earth. The science of chemistry aims at the experimental examination of the elements and their compounds, and the investigation of the laws which regulate their combination one with another. For example, in the year 1805, Gay-Lussac and Von Humboldt found that one volume of oxygen combines with exactly two volumes of hydrogen to form water, and that these exact proportions hold good at whatever temperature the gases are brought into contact. Oxygen and hydrogen are now classified as elementary bodies. The existence of atoms, if proved, as claimed by the pioneer of whom we write, confirms Priestly's idea that all discoveries are made by chance; for it certainly was by a mere chance, as we view things with our limited knowledge, that Keely stumbled over the dissociation of the supposed simple elements of water by vibratory force; [23] thus making good Roscoe's assumption that, by the application of more powerful means than were known to him, still more simple bodies would be shown up. Had Keely subdivided these corpuscles of matter, after a method known to physicists, he would have been hailed as a discoverer, when it was announced by Arthur Goddard, in the British Mercantile Gazette, in 1887, that Keely declared electricity to be a certain form of atomic vibration of what is called the luminiferous ether. Had Keely been better understood, science might have been marching with giant strides across this unknown realm during the many years in which men of learning have refused to witness the operation of the dissociation of water, because one of their number decided, in 1876, that Keely was using compressed air. Fixing bounds to human knowledge, she still refuses to listen to the suggestion that what she has declared as truth may be as grossly erroneous as were her teachings in the days when the rotation of the earth was denied; this denial being based upon the assertions of all the great authorities of more than one thousand years, that the earth could not move because it was flat and stationary. Herodotus ridiculed those who did not believe this. For two thousand years after the daily rotation of the earth was first suggested, the idea was disputed and derided. The history of the past, says General Drayson, who claims to have discovered a third movement of the earth, teaches us that erroneous theories were accepted as grand truths by all the scientific authorities of the whole world during more than five thousand years. [24] Although the daily rotation of the earth and its annual revolution around the sun had been received as facts by the few advanced minds, some five hundred years before Christ, yet the obstructions caused by ignorance and prejudice prevented these truths from being generally accepted until about three hundred years ago, when Copernicus first, and afterwards Galileo, revived the theory of the earth's two principal movements. Human nature is the same as in the days when Seneca said that men would rather cling to an error than admit they were in the wrong; so it is not strange that General Drayson, as the discoverer of a third movement, has not received the attention that he deserves, although his mathematical demonstrations seem to be beyond dispute. With Keely's claim, that latent force exists in all forms of matter, it is different; for it is susceptible of proof by experiment. In the days when the sphericity of the earth was denied, for the asserted reason that the waters of the oceans and seas on its surface would be thrown off in its revolutions were it so, because water could not stay on a round ball, the statement could not be disputed; the theory of the laws of gravitation being then unknown. Copernicus and Galileo had nothing but theories to offer; consequently it took long years to overcome the bigotry and the baneful influence of the great authorities of the time. It is otherwise with Keely, who, for fifteen years and more, has been demonstrating this discovery to thousands of men; some of whom, but not all, were competent to form an opinion as to whether he was "humbugging with compressed air," or with a concealed dynamo, or, still more absurd, with tricks in suction, as I asserted by a learned professor. Now that some of our men of science have consented to form their opinions from observation, without interfering with the lines of progressive experimental research which the discoverer is pursuing, there seems to be no doubt as to the result; nor of the protection of the discovery by science. Truth is mighty, and must in the end prevail over mere authority. It has been said that we need nothing more than the history of astronomy to teach us how obstinately the strongholds of error are clung to by incompetent reasoners; but when a stronghold is demolished, there is nothing left to cling to. Sir John Lubbock says:--The great lesson which science teaches is how little we yet know, and how much we have still to learn. To which it might be added, and how much we have to unlearn! All mysteries are said to be either truths concealing deeper truths, or errors concealing deeper errors; and thus, as the mysteries unfold, truth or error will show itself in a gradually clearer light, enabling us to distinguish between the two. It is now left for men of science to decide as to the nature of the mysteries which Keely is slowly unfolding, and whether his demonstrations substantiate his theories. They have been invited to follow him in his experimental research, step by step; to bestow upon him sympathy and encouragement, so long withheld, until he reaches that stage where he will no longer need their protection. Then, if science is satisfied that he has gained a treasure for her, in his years of dead-work, she must step aside and wait patiently until he has fulfilled his obligations to those who organized themselves into a company to aid him, long before she came forward to interest herself in his behalf. Those men of science who have refused to countenance this great work, even by witnessing experiments made to prove the discovery of an unknown force, are men who attempt no explanation of the miracles of nature by which we are surrounded, assuming that no explanation can be given; but, as Bacon has said, he is a bad mariner, who concludes, when all is sea around him, that there is no land beyond. If the multitude of so-called laws of nature could be resolved into one grand universal law, would it not be considered a great step in the progress of scientific knowledge? This is what our pioneer claims for his discoveries, one law working throughout nature, in all things; for, as Macvicar says, the productive and conservative agency in creation, as it exists and acts, does not consist of two things, "idea" and "power"; but of a unity embracing both, for which there is no special name. The relation between the Creator and the Creation, the First Cause and what he has effected, is altogether inscrutable; but intelligence acting analytically, as it cannot be kept from doing, insists on these two elements in the problem, viz. idea and power. "The law of the universe is a distinct dualism while the creative energies are at work; and of a compound union when at rest." The hypothesis that motion can only be effected mechanically, by pressure or traction or contact of some kind, is an utterly helpless one to explain even familiar movements. Gravitation itself, the grandest and most prevailing phenomenon of the material universe, has set all genius at defiance when attempting to conceive a mechanism which might account for it. The law of sympathetic association, or sympathetic assimilation, between two or more atoms, or masses of atoms, explains this grand phenomenon; but Roscoe, in theorizing on the atomic theory, says that from purely chemical considerations it appears unlikely the existence of atoms will ever be proved. It never could have been proved by mechanical physics nor by chemistry. The law which locks the atoms together would have remained an unknown law, had not Keely opened the door leading into one of nature's domains which was never entered before, unless by the fabled Orpheus, who, mythology tells us, was killed because he revealed to man what the gods wished to conceal. Certainly, whether Orpheus ever existed or not, the principle which Pythagoras promulgated as the teaching of Orpheus is disclosed in one of Keely's discoveries. In the great fresco of the school of Athens, by Raphael, Pythagoras is represented as explaining to his pupils his theory that the same principle underlies the harmonies of music and the motion of heavenly bodies. One of these pupils holds in his hand a tablet, shaped like a zither, on which are inscribed the Greek words, Diapason, Diapente, Diatessaron. Of the diapason, or concord of all, Spenser writes, in The Faerie Queen:-- Nine was the circle set in heaven's place, All which compacted made a goodly diapase. Here we have a clue to the Thirds, Sixths and Ninths of Keely's theories, in the operation of his polar negative attractor. The conception of the Pythagoreans of music, as the principle of the creation's order, and the mainstay and supporter of the material world, is strictly in accordance with the marvellous truths which are now being unfolded to science. Rightly divined Browning when he wrote of ... music's mystery, which mind fails To fathom; its solution no mere clue; and Cardinal Newman also, when he discoursed of musical sounds, "under which great wonders unknown to us seem to have been typified," as "the living law of divine government." Since the days of Leucippus, poets and philosophers have often touched upon the mysteries hidden in sound, which are now being revealed in the experimental researches of Keely. These truths make no impression on those who are not gifted with any comprehension of nature's harmonious workings, and are regarded as flights of fancy and of rhetoric. Among the utterances of inspiration--and all truth is inspired--one of the most remarkable, when taken in connection with these discoveries, is found in these eloquent words of the Dean of Boston University in his "Review of Herbert Spencer," printed in 1876:-- "Think of the universal warring of tremendous forces which is for ever going on, and remember that out of this strife is born, not chaos void and formless, but a creation of law and harmony. Bear in mind, too, that this creation is filled with the most marvellous mechanisms, with the most exquisite contrivances, and with forms of the rarest beauty. Remember, also, that the existence of these forms for even a minute depends upon the nicest balance of destructive forces. Abysses of chaos yawn on every side, and yet creation holds on its way. Nature's keys need but to be jarred to turn the tune into unutterable discord, and yet the harmony is preserved. Bring hither your glasses--and see that, from atomic recess to the farthest depth, there is naught but 'toil co-operant to an end.' All these atoms move to music; all march in tune. Listen until you catch the strain, and then say whether it is credible that a blind force should originate and maintain all this." Sir John Herschel said:--There is some principle in the science of music that has yet to be discovered. It is this principle which has been discovered by Keely. Let his theories be disputed as they have been, and as they still may be, the time has come in which his supporters claim that he is able to demonstrate what he teaches; is able to show how superficial are the foundations of the strongholds to which physicists are clinging; and able to prove purity of conditions in physical science which not even the philosophers and poets of the past have so much as dreamed of in their hours of inspiration. ... ways are made, Burdens are lifted, or are laid, By some great law unseen and still, Unfathomed purpose to fulfil. Our materialistic physicists, our Comtist and agnostic philosophers, have done their best to destroy our faith. Of him who will not believe in Soul because his scalpel cannot detect it, Browning wrote: To know of, think about-- Is all man's sum of faculty effects, When exercised on earth's least atom. What was, what is, what may such atoms be?-- Unthinkable, unknowable to man. Yet, since to think and know fire through and through Exceeds man, is the warmth of fire unknown? Its uses--are they so unthinkable? Pass from such obvious power to powers unseen, Undreamed of save in their sure consequence: Take that we spoke of late, which draws to ground The staff my hand lets fall; it draws at least-- Thus much man thinks and knows, if nothing more. These lines were written in reference to Keely's discovery of the infinite subdivision of the atom; for not until a much later period was Browning influenced by a New York journalist to look upon Keely as "a modern Cagliostro." Keely's discovery was the key-note of "Ferishtah's Fancies," written by Browning before he met this journalist. Professor Koenig writes:--I have long given up the idea of understanding the Universe; with a little insight into its microcosm, I would feel quite satisfied; as every day it becomes more puzzling. But there are no boundaries set to knowledge in the life of the Soul, and these discoveries reach out so far towards the Infinite, that we are led by them to realize how much there is left for science to explore in the supposed unfathomable depths of the etheric domain, whence proceeds the influence that connects us with that infinite and eternal energy from which all things proceed. The attitude of willingness to receive truths, of whatever nature, now manifested by men of science in regard to Keely's experimental research, is shared by all who are not "wise in their own conceit." They stand ready to welcome, while waiting for proof, the discovery of Darwin's grand-niece, Mrs. F. J. Hughes, as now demonstrated by Keely, viz., that the laws which develop and control harmonies, develop and control the universe; and they will rejoice to be convinced (as Keely teaches) that all corpuscular aggregation absorbs energy, holding it latent in its embrace until liberated by a certain order of vibration; that nature does not aggregate one form of matter under one law, and another form of matter under another law. When this has been demonstrated, to their entire satisfaction, they will acknowledge that Faraday's speculations on the nature of force and matter pointed the way to Keely's discoveries. Some broad-minded men have been pursuing lines of research which give evidence of their desire to solve the problem for themselves as to the mode of rupturing the atom, which science declares to be indivisible. Before any great scientific principle receives distinct enunciation, says Tyndall, it has dwelt more or less clearly in many minds. The intellectual plateau is already high, and our discoverers are those who, like peaks above the plateau, rise over the general level of thought at the time. If, as Browning has said, 'Tis not what man does which exalts him, but what man would do, surely this discoverer merits the sympathy and the admiration of all men, whether he succeeds commercially or not, for his persistent efforts to make his discoveries of use to the world. Keely has always said that scientists would never be able to understand his discoveries until he had reached some practical or commercial result. Only now he sees an interest awakened among men of science, which is as gratifying to him as it is unexpected. For the first time in his life, he is working with the appreciation of men competent to comprehend what he has done in the past, and what remains to be done in the future, without one aspiration on their part for monetary results. Foremost among these men was the late Joseph Leidy, Professor of Biology in the University of Pennsylvania; but physicists were not satisfied to take the opinion of this great man, because he was a biologist. What better preparation than the study of the science of life could a man have to qualify him for discriminating between laws of nature as conjectured by physicists, and Nature's operations as demonstrated by Keely? To such men, possessing entire scientific and intellectual liberty of thought, with that love of justice and truth which keeps its possessor from self-conceit, arrogance and intolerance, the world owes all that we now possess of scientific advance, since the days when men believed the thunder and lightning to be the artillery of the gods. Lucifer, September, 1892. CHAPTER XIX. LATENT FORCE IN INTERSTITIAL SPACES--ELECTRO-MAGNETIC RADIATION--MOLECULAR DISSOCIATION. (By John Ernst Worrell Keely.) The atom is infinitely divisible.--Arthur Schopenhauer. For thou well knowest that the imbecility of our understanding, in not comprehending the more abstruse and retired causes of things, is not to be ascribed to any defect in their nature, but in our own hoodwinkt intellect.--P. 6, A Ternary of Paradoxes.--Van Helmont. The advance of science, which for a time overshadowed philosophy, has brought men face to face once more with ultimate questions, and has revealed the impotence of science to deal with its own conditions and pre-suppositions. The needs of science itself call for a critical doctrine of knowledge as the basis of an ultimate theory of things. Philosophy must criticize not only the categories of science but also the metaphysical systems of the past.--Prof. Seth. Latent Force. Science, even in its highest progressive conditions, cannot assert anything definite. The many mistakes that men of science have made in the past prove the fallacy of asserting. By doing so they bastardize true philosophy and, as it were, place the wisdom of God at variance; as in the assertion that latent power does not exist in corpuscular aggregations of matter, in all its different forms, visible or invisible. Take, for example, gunpowder, which is composed of three different mediums of aggregated matter, saltpetre, charcoal, and sulphur, each representing different orders of molecular density which, when associated under proper conditions, gives what is called an explosive compound. In fact it is a mass which is made susceptible at any moment by its exciter fire, which is an order of vibration, to evolve a most wonderful energy in volume many thousands of times greater than the volume it represents in its molecular mass. If it be not latent force that is thus liberated by its exciter, a mere spark, what is it? Are not the gases that are evolved in such great volume and power held latent in the molecular embrace of its aggregated matter, before being excited into action? If this force is not compressed there, nor placed there by absorption, how did it get there? And by what power was it held in its quiescent state? I contend that it was placed there at the birth of the molecule by the law of sympathetic etheric focalization towards the negative centres of neutrality with a velocity as inconceivable in its character as would be the subdivision of matter to an ultimate end. Again, what is the energy that is held in the molecular embrace of that small portion of dynamite which by slight concussion, another order of vibration, evolves volumes of terrific force, riving the solid rock and hurling massive projectiles for miles? If it is not latent power that is excited into action, what is it? Finally, what is held in the interstitial corpuscular embrace of water, which by its proper exciter another form of vibration, is liberated showing almost immeasurable volume and power? Is not this energy latent, quiet, until brought forth by its sympathetic negative exciter? Could the force thus evolved from these different substances be confined again, or pressed back and absorbed into the interstitial spaces occupied before liberation, where the sympathetic negative power of the Infinite One originally placed it? [25] If latent force is not accumulated and held in corpuscular aggregations how is it that progressive orders of disintegration of water induce progressive conditions of increased volume and of higher power? I hold that in the evolved gases of all explosive compounds, dynamite or any other, there exists deeper down in the corpuscular embrace of the gaseous element, induced by the first explosion, a still greater degree of latent energy that could be awakened by the proper condition of vibration; and still further on ad infinitum. [26] Is it possible to imagine that mere molecular dissociation could show up such immense volumes of energy, unassociated with the medium of latent force? The question arises, How is this sympathetic power held in the interstitial corpuscular condition? Answer.--By the incalculable velocity of the molecular and atomic etheric capsules, [27] which velocity represents billions of revolutions per second in their rotations. We shall imagine a sphere of twelve inches in diameter, representing a magnified molecule surrounded by an atmospheric envelope of one sixteenth of an inch in depth; the envelope rotating at a velocity of the same increased ratio of the molecule's magnification. At the very lowest estimate it would give a velocity of six hundred thousand miles per second, or twenty-four thousand times the circumference of the earth in that time. Is it possible to compute what the velocity would be, on the same ratio, up to the earth's diameter?[#2] It is only under such illustrations that we can be brought even to faintly imagine the wonderful sympathetic activity that exists in the molecular realm. An atmospheric film, rotating on a twelve inch sphere at the same ratio as the molecular one, would be impenetrable to a steel-pointed projectile at its greatest velocity; and would hermetically enclose a resisting pressure of many thousands of pounds per square inch. The latent force evolved in the disintegration of water proves this fact; for under etheric evolution, in progressive orders of vibration, these pressures are evolved, and show their energy on a lever especially constructed for the purpose, strong enough for measuring a force over three times that of gunpowder. We shall continue this subject a little farther, and this little farther will reach out into infinity. The speculations of the physicists of the present age, in regard to latent energy, would neutralize the sympathetic conditions that are associated with the governing force of the cerebral and the muscular organism. The evolution of a volition, the infinite exciter, arouses the latent energy of the physical organism to do its work; differential orders of brain-force acting against each other under dual conditions. If there were no latent energy to arouse sympathetically, there would be no action in the physical frame; as all force is will-force. All the evolutions of latent power in its varied multiplicity of action induced by its proper exciters, prove the connecting link between the celestial and the terrestrial, the finite and the infinite. (See Appendix I.) There would be no life, and therefore no action in aggregated matter, had the latent negative force been left out of it. If a bar of steel or iron is brought into contact with a magnet, the latent force that the steel or iron is impregnated with is aroused, and shows its interstitial latent action by still holding another bar. But this experiment does not give the most remote idea of the immensity of the force that would show itself on more progressive exciters. Enough alternate active energy could be evolved, by the proper sympathetic exciter, in one cubic inch of steel to do the work of a horse, by its sympathetic association with the polar force in alternate polarization and depolarization. This is the power that I am now getting under control (using the proper exciters as associated with the mechanical media) to do commercial work. In other words, I am making a sympathetic harness for the polar terrestrial force: first, by exciting the sympathetic concordant force that exists in the corpuscular interstitial domain, which is concordant to it; and secondly, after the concordance is established, by negatizing the thirds, sixths, and ninths of this concordance, thereby inducing high velocities with great power by intermittent negation, as associated with the dominant thirds. Again: Take away the sympathetic latent force that all matter is impregnated with, the connective link between the finite and the infinite would be dissociated, and gravity would be neutralized; bringing all visible and invisible aggregations back into the great etheric realm. Here let me ask, What does the term cohesion mean? What is the power that holds molecules together, but electro-magnetic negative attraction? What is the state that is brought about by certain conditions of sympathetic vibration, causing molecules to repel each other, but electro-magnetic radiation? It must not be understood that the character of the action of the latent force liberated from liquids and gases is the same, in its evolution, as that of the latent force existing in metals. The former shows up an elastic energy, which emanates from the breaking up of their rotating envelopes; increasing, at the same time, the range of their corpuscular action: thus giving, under confinement, elastic forces of an almost infinite character. By liberation from the tube it is confined in, it seeks its medium of concordant tenuity with a velocity greater than that of light. In metals, the latent force, as excited by the same sympathizer, extends its range of neutral sympathetic attraction without corpuscular rupture, and reaches out as it were to link itself with its harmonic sympathizer, as long as its exciter is kept in action. When its exciter is dissociated, its outreach nestles back again into the corpuscular embrace of the molecular mass that has been acted upon. [28] This is the polar sympathetic harness, as between metallic mediums and the polar dominant current,--the leader of the triune stream of the terrestrial flow. (See Appendix II.) The velocity of the sympathetic bombarding streams, towards the centres of neutrality, in the corpuscular atoms, during sympathetic aggregation of visible molecular masses (in registering the latent force in their interstitial spaces), is thousands of times greater than that of the most sensitive explosives. An atmospheric stream of that velocity would atomize the plate of an ironclad, if brought to bear on it. If the evolution of the power of a volition be set down as one, what number would that represent in the power evolved by such volition on the physical organism? To answer this we must first be able, mentally, to get down to the neutral central depths of the corpuscular atoms, where gravity ceases, to get its unit; and in the second place we must be able to weigh it as against the force physically evolved. How true, "the finer the force the greater the power!" and the greater is the velocity, also; and the more mathematically infinite the computation. Yet all these conditions of evolution and concentration are accomplished by the celestial mind force, as associated with terrestrial brain matter. The first seal is being broken, in the book of vibratory philosophy: the first stepping-stone is placed toward reaching the solution of that infinite problem,--the source of life. Theory of Vibratory Lift for Air-Ships. All molecular masses of terrestrial matter are composed of the ultimate ether,--from which all things originally emanated. They are sympathetically drawn towards the earth's centre, as according to the density of their molecular aggregation, minus their force or sympathetic outreach towards celestial association. In other words, the celestial flow as controlling terrestrial physical organisms. The sympathetic outflow from the celestial streams reaches the infinite depths of all the diversified forms of matter. Thus it is seen that the celestial flow which permeates, to its atomic depths, the terrestrial convolutions of all matter, forms the exact sympathetic parallel to the human brain-flow and the physical organism,--a perfect connective link of controlling sympathy, or sympathetic control. Under certain orders of sympathetic vibration, polar and anti-polar, the attractive sympathies of either stream can be intensified, so as to give the predominance to the celestial or to the terrestrial. If the predominance be given to the celestial, to a certain degree, on a mass of metal, it will ascend from the earth's surface, towards the etheric field, with a velocity as according to the dominant concentration that is brought to bear on the negative thirds of its mass chords, by inducing high radiation from their neutral centres, in combination with the power of the celestial attractive. The power of the terrestrial propulsive and celestial attractive to lift; and these conditions reversed, or the celestial propulsive and the terrestrial attractive, to descend. Associating these conditions with the one of corpuscular bombardment, it is evident to me with what perfection an air-ship of any number of tons weight can, when my system is completed, be controlled in all the varied movements necessary for complete commercial use at any desired elevation, and at any desired speed. It can float off into atmospheric space as gentle in motion as thistle-down, or with a velocity out-rivalling a cyclone. [29] Electro-Magnetic Radiation. If the persistency of our vision could be reversed, so as to have the power to follow the track of the molecule's oscillations under a high condition of vibratory acceleration, associated with the assisting power of the finest instruments known at present in scientific research, it would not help us to determine the period of time wherein the sympathetic actions in nature are propagated. Therefore, we cannot, with any degree of certainty, establish a foundation whereon observation, so associated, is reliable. (Theoretically explained in 'Soul of Matter.') As far as my researches have gone, I find that there is but one condition approaching reliability; and that is in computing the intermittent periodic disturbances along a nodal vibratory transmitter--the nodes of gold, silver and platina--a fixed number placed at such different distances, along its line, as to take up and equalize (by a certain order of vibratory transmissions) the chord masses of the nodal interferences between the triple metals of which the nodes are composed, and also the acoustic introductory impulse of whatever chord is set. This will determine the rate of their accelerated molecular oscillation, so induced beyond their normal standard, and give us some definite figures in the computing of vibrations, thousands of billions of times more than those of light. Light is induced by electro-magnetic percussion emanating from the ether, and in its action represents the plane of magnetism. In fact it is the plane of magnetism when under polarization. [30] Some scientific theories of the past have taught us that electricity and magnetism are one and the same thing. Sympathetic vibratory philosophy teaches that they are two distinct forces of one of the triune sympathetic family. I will try to make comprehensible the computation of the number (even to infinity) of the corpuscular oscillations, induced on the introductory ninths, over their normal standard. The molecules of all visible masses, when not influenced by surrounding acoustic vibratory impulses, move at a rate of 20,000 oscillations per second, one third of their diameters. We have before us one of these masses; either a silver dollar, a pound weight, a horse-shoe, or any other metallic medium, which I associate to one of my nodal transmitters, the other end of which is attached to the clustered thirds (or third octave) of my focalizing neutral concentrator. Another transmitter, of gold, silver and platina sections, is attached to the sixth cluster of same disk, the other end of which is connected to resonating sphere on my compound instrument: all of which must be brought to a state of complete rest. Then, a slight tap, with a vulcanite rubber hammer on the chladna resonating disk, will accelerate the 20,000 molecular oscillations to 180,000 per second,--an increase of nine times the normal number. The nine nodes each touching the extreme end, next the mass operated upon, in this arrangement; silver, gold, platina, make up the nine. When I associate the seventh, I start with gold and end with platina; always on the triplets. Silver represents the lowest introductory third, gold the next, and platina the highest. If we start with a gold node, the multiplication on oscillation will be nine times nine, or 81 times the 20,000; which is 1,620,000 per second. Each node represents one wave length of a certain number of vibrations when shifted along the transmitter, over the section representing its opposite metal. The shifting of the gold one over the silver extreme section will hold the corpuscular range of the mass velocity at 1,620,000 per second: the introductory chord being set at B, third octave. It requires an accelerated oscillation on the molecules of a soft steel mass, at that chord, of a transmissive multiplication of the full nine, in order to induce a rotary action on the neutral centre indicator of focalizing disk; which by computation, means, per second, 156,057,552,198,220,000 corpuscular intermittent oscillations to move the disk 110 revolutions per second. This only represents the multiplication on the first nodal dissociator of the ninth. The second transition, on same, would mean this number multiplied by itself, and the residue of each multiplication by itself 81 times progressively. This throws us infinitely far beyond computation, leaving us only on the second of the full ninth, towards reaching the sympathetic corpuscular velocity attending the high luminiferous. I have induced rotation up to 123 revolutions per second on a neutral indicator that required billions of vibrations per second to accomplish; but even this vibration represents only a minute fraction of the conditions governing the sympathetic vitality which exists in the far luminous centres. The interposition of hydrogen gas between soap-film, of the differential diameters of thirds, illuminated by a solar ray in whose focus a quiescent prism is set posteriorly--the prism to be adjusted at the proper distance and angle, to throw the seven colours through the film enclosing the hydrogen in a way that will give the bow an arch of three feet--will register deep down, inaudible tones or sounds, and indicate their different conditions by the dissolving and re-dissolving of certain of the colours of such arch. To conduct such experiments properly necessitates, first, a location as nearly isolated from all extraneous audible sounds as is possible to get; and second, a pedestal of the lowest vibrating material, the base of it set deep in the earth, to arrange the instruments upon; and third, a room of the highest resonating qualities to enclose them. Under such conditions the inaudible sounds emanating from the operator, would have to be neutralized by a negative device to get at the proper conditions while under his manipulation. Thus the hidden inaudible world of sounds could be shown up, as the microscope shows up to the eye the hidden invisible forms of nature. The condition of the mechanical requirements necessary to conduct successfully the line of research that I am now pursuing, will never be properly appreciated until the beauty of this system is shown up under perfect control for commercial use. I have spoken elsewhere of the almost infinite difficulties of getting into position, to hold hydrogen gas in suspension between soap-film a proper period of time, to conduct these experiments. The setting of the other parts of the apparatus is quite easy in comparison. All wave propagations, electro-magnetic or otherwise, by being thus reflected can be measured in regard to the time of their propagation; all of which are introductorily subservient to the luminiferous ether. The theory put forward by "men of science," in regard to electro-magnetic forces shows that they are misled by the imperfection of their instruments. They are trying to measure the infinite by the finite; necessitating terms of avoidance, to the instantaneous propagation of nature's sympathetic evolutions, of the same nature as the one advanced in the assertion that force does not exist in the interstitial embrace of all matter. Maxwell's theory is correct that the plane of polarized light is the plane of the magnetic force. The sympathetic vibrations associated with polarized light constitute the pure coincident of the plane of magnetism. Therefore, they both tend to the same path, for both are inter-atomic, assimilating sympathetically, in a given time, to continue the race together; although one precedes the other at the time of experimental evolution. The time is approaching when electro-magnetic waves with an outreach of two feet will be produced, having an energy equal to that now shown up on the magnet when it is about to kiss its keeper; and showing a radiating force too stupendous for actual measurement. I have already shown, to a certain point, the power of this radiation, by breaking a rope that had a resisting strain of over two tons, which was attached to the periphery of a steel disk, twelve inches in diameter, moving at the slow rate of one revolution in two minutes; its molecular structure vitalized with 42,800 vibrations per second. There was no retardation while breaking the rope, and no acceleration when it was broken. This experiment has been repeated scores of times, before scores of visitors who came to my laboratory for the purpose of seeing it. A computation of the conditions, already shown up in part, proves conclusively that the power of an electro-magnetic wave at an outreach of ten inches would be, if properly developed, equal to a lifting force of 36,000 pounds on a disk but three inches in diameter. Ten of such on the periphery of a vibratory disk, 36 inches in diameter, would represent 360,000 pounds actual lift at one revolution per minute. Perfect depolarization at one hundred times per minute would represent 360,000,000 pounds, lifted twelve times per minute, or 1000 horse power in the same time. An excess of 100 extra revolutions, under the same conditions, would mean 2000 horse power per minute. By this new system, to perfect which I am now devoting all my time and my energies, dynamos will become a thing of the past, eventually; and electric lighting will be conducted by a polar negative disk, independent of extraneous power to run it, other than that of sympathetic polar attraction, as simple in its construction, almost, as an ordinary type-writing machine. Answers made in Letters from Mr. Keely, to Questions asked of Him. Light incident to any body that absorbs or reflects it does not press upon it. The radiometer of Professor Crookes's invention is not operated by the pressure of light, but by corpuscular bombardment on the reflecting side of its vanes. You have called my attention to the receding movement in the metal silver, which it assumes when the flow of an alternating current from an electro-magnet, in front, is thrown upon it. This does not prove that light presses upon it to induce that movement. It moves by inter-atomic bombardment of some 800 millions of corpuscular percussions a second; or, more truly, by inter-sympathetic vibrations. If a homogeneous disk of gold, silver and platina, in proper proportions, were made the medium of interference, the resultant action would be startling in showing up the movement of molecular antagonistic thirds. The movement would be very erratic and gyroscopic. If the same disk were used or an intermediate transmitter to a negative focalizer, or in other words a polar radiator only one of which is in existence, by a nodal wire of gold, silver and platina, the effect on the disk at the negative terminus would be to set into action the latent force held in its molecular embrace, and would cause it to sympathetically adhere to the focalizer, with a power that would make it practically inseparable. Professor Fitzgerald's lecture on electro-magnetic radiation shows that scientific men are beginning to realize, and that fairly, the truths appertaining to the new philosophy. The professor admits that electricity and magnetism are of differential character, and he is right. The progressive subdivision, induced on molecules by different orders of sympathetic vibration, and the resultant conditions evolved on the inter-molecule and inter-atom, by introductory etheric dispersion, prove that the magnetic flow of itself is a triple one, as is also the electric. Again, the professor says that electricity and magnetism would be essentially interchangeable if such a thing existed as magnetic conduction, adding: 'It is in this difference that we must look for the difference between electricity and magnetism.' Thus you see how plain it is that progressive scientists are approaching true science. The rotation of the magnetic needle, as produced in my researching experiments, proves conclusively that the interchange spoken of, in Professor Fitzgerald's lecture, is a differentiated vibratory one, in which the dominant and enharmonic forces exchange compliments with each other, in a differential way; thus inducing rotation, in other words polarization and depolarization. The transmission of sympathetic atomic vibration, through a triple nodal transmitter, induces an inter-atomic percussion, that results in triple atomic subdivision, not oscillating across the diameter of the atom, but accelerating to an infinite degree the atomic film that surrounds it and at the same time extending the vibratory range of the atom far enough to set free the gaseous atomic element. Molecular Dissociation. If our sight could reach into the remote depths of the interstitial spaces which exist between the molecular ranges, and observe their wonderful action, in their oscillating motion, to and from each other, as guided by the Infinite in their sphere of vibrating action--could we comprehend the astonishing velocity of their gaseous capsules, combined as it is with the accompanying acoustic force, we would be, as it were, paralyzed with amazement. But we would then only be bordering on the still more remote depths of the interstitial atomic realm, stretching far down towards the neutral depths of the inter-atomic; and again, still farther to the borders of its etheric neutral radiating centre. If our earth were to be submitted to the force governing the rotative action of the molecule, in its gaseous envelope, and its oscillatory range of motion were in the same ratio to the differential magnitude of each, the force of the vibration induced by its atmospheric surrounding would, in a short time, disintegrate its full volume, precipitating it into a ring of impalpable inter-molecular dust, many thousands of miles in diameter. If brought face to face with such conditions we could better understand the mighty and sympathetic force which exists in the far remote domain of the molecular and atomic embrace. The question arises, how and by what means are we able to measure the velocity of these capsules and the differential range of their vibratory action? Also, how can we prove beyond dispute the facts relating to their sympathetic government? By progressive disintegration; this is the only way; and it is accomplished by the proper exciters of vibratory focalization; the introductory acoustic impulses which negatize their molecular, inter-molecular, atomic and inter-atomic media of neutral attractions, towards their focalized centres of sympathetic aggregation. I hold that the sympathetic neutral flow which exists in this remote region is the latent power that, under the disintegration of water, is liberated; showing immense volume and infinite pressure. The same condition of latent power exists in metallic masses and, paradoxical as it may seem, exerts its force, under the proper exciter, only in a negative attractive way, while in water in a positive one. In minerals under liberation this latent power seeks its medium of tenuous equilibrium, leaving behind an impalpable dust, that represents molecular dissociation. In order to get at the conditions which govern and give introductory impulses to that peculiar force which acts on the sympathetic medium that associates matter with matter, inducing magnetic antagonisms, it will be necessary to explain the triune conditions that govern sympathetic streams; as also the triune conditions of corpuscular association. All forces in nature are mind forces: magnetic, electric, galvanic, acoustic, solar, are all governed by the triune streams of celestial infinity; as also the molecular, inter-molecular, atomic, and inter-atomic. The remote depths of all their acoustic centres become subservient to the third, sixth, and ninth position of the diatonic, harmonic and enharmonic chords; which, when resonantly induced, concentrate concordant harmony, by reducing their range of corpuscular motion, drawing them as if towards each other's neutral centre of attractive infinity. The sympathetic acoustic exciters, or impulses, are: 1st. the third diatonic; 2nd. the harmonic sixths neutralizing affinity; 3rd. the enharmonic ninths--positive acceleration, which induces infinite trajective velocity from neutral centres; in other words, neutral radiation. Every molecule in nature represents, without variation, the same chord. Variations that show up in the mass chord of different visible aggregations, are accounted for by the non-uniformity of their molecular groupings. If all were molecularly homogeneous, the chord masses of all structures would be perfectly alike in their resonant impulses. When the triple introductory impulse is transmitted towards the mass to be sensitized, it subserves the molecular concordant thirds and antagonizes the discordant sixths extending the range of their oscillating paths; and thus induces the highest order of repellent antagonism towards the centre of neutral equilibrium. We will now follow out, in their progressive orders, the conditions necessary to give to these acoustic introductory impulses the power, as transmitted through the proper media, to induce molecular dissociation. First: If I wish to disturb and bring into action the latent force held in the embrace of any molecular mass, I first find out what the harmonic chord or note of its mass represents; and as no two masses are alike, it would seem to necessitate an infinite number of variations to operate on different masses; but such is not the case. All masses can be subserved to one general condition by the compound mechanical devices which I use for that purpose. We will suppose that the mass to be experimented upon, when chorded, represents B flat. Then, first, the negative radiating focalizing bar on the disk is liberated from its dampening rod, and associated with the magnetic defocalizing one. There are seven ranges of bars in all. (See symbol representing sympathetic transmissive chord of B flat, third octave on third diatonic.) The seven assemblings are in this order: Electro Harmonic Dominant Magnetic Diatonic Enharmonic. Negative 3rd. 6ths. 7ths. I. II. III. IIII. IIIII. IIIIII. IIIIIII. Twenty-eight in number. The second step is to liberate, according to symbolic meaning, second harmonic bar on sixths, or neutralizing one, and third, enharmonic ninths, which is the one counting from negative sevenths. Now all is in readiness for the transmissive nodal wire, one end of which must be attached to the magnetic dispersing ring, over the negative-sevenths cluster, and the other end to the high polar negative attractor. Then, one end of a transmitting wire, of very fine proportions of gold, silver and platina, is connected to the resonating sphere, and the other end to the mass to be experimented upon. I then give to the syren a rotatory impulse of a velocity to indicate the concordant of the mass attached. If the introductory settings are all right, the neutral centre indicator will rotate with high velocity: and a single tap on the chladna wave-plate is all that is necessary to induce pure evolution. Either attraction or dispersion can be induced on any mass by setting the instrument to the proper triple introductory positions, towards the mass chords it represents, either positive or negative. This system of evolution might be expressed as disintegration induced by the intensified oscillations of inter-atomic-electro-magnetic waves. How plainly this principle of harmonic sympathetic evolution indicates the structural condition of the atom as one of wonderfully complex form; as also is the progressive step toward it in the molecular and inter-molecular field. During the effect induced by disintegration of molecular mineral masses, there is no molecular collision when forced asunder from their radiating centres of neutrality. Their atomic and inter-atomic centres seek their media of tenuous affinity in the far borders of the etheric field, leaving all metallic masses, that are associated with them, behind in their virgin form. Keynote of electric-magnetic sympathy, transmissive combinations, 3rds, on the subdivision of first octave B flat, diatonic. 6ths, on same subdivision of 3rds, octave harmonic; and 9ths, on the same subdivision of 6ths, octave enharmonic. I find that there is no medium in the range of vibratory philosophic research, that is as unerringly exact, towards the centre of sympathetic attraction, as the negative attractive influence of a certain triple association of the metallic masses of gold, silver and platina. In fact they are as accurate indicators of the earth's terrestrial sympathetic envelope, and its triple focalized action towards the earth's neutral centre, as the magnet is an indicator of the diversion of the attractive flow of the dominant current of the electric stream. Although much has been written on the subject, the conditions attending the continuous flow of the magnet remains a problem that has never been solved by any other theory. Yet the solution is very simple when harmonic vibratory influence is brought to bear upon it. The harmonic attractive chord, thirds, induces a nodal interference on that third of the triune combination of the terrestrial envelope, that is immediately associated with this medium of interference, and moves towards the negative pole of the magnet, then flows through it to re-associate with the full triune combination, through the positive, thus:-- Dominant Harmonic Enharmonic The triune stream; one current of which is diverted from the Dominant, flowing in at the Negative end of the magnet; and out to join the triune terrestrial stream at the Positive end. The continuous flow of the magnet is merely a diversion of that portion of the terrestrial envelope that electricians have never controlled. This third current, of this triune stream, has never been subdivided and only slightly diverted towards the negative pole of the magnet, flowing unbrokenly back to associate sympathetically with the full triune combination of the earth's negative neutral force. [31] Thus the problem is solved of the continuous and never-ending force of the magnet, in carrying its load without any diminution of its energy. There is no influence, as yet known, that can break up its line of sympathetic flow as associated with the triune combination. Polarization and de-polarization, in its action, is nodal negative interference, intermittently excited, inducing differential disturbance of polar sympathetic equilibrium. The attractive power, evolved by a magnet in sustaining its load, is no evidence that it is molecularly attractive: for, under the influence of the dominant current of the electric stream, the range of its molecular mass is not extended; but by the action induced in atomic vibration, the latent, or undisturbed power, that is locked up in its atomic embrace, is put into sympathetic action, and evolves the force that is recognized as magnetic. When its exciter is removed, it returns to atomic recesses to remain perfectly latent, until again brought into action by its proper exciter. When a steel unmagnetized bar is associated with a magnetized one, the latent force in the unmagnetized one is sympathetically brought into action, associating itself to the magnetic one, without depreciating the power of it one iota. Dissociation and association between the two bars can go on indefinitely with the same result. The suspension and propelling of an atmospheric navigator of any number of tons weight, can be successfully accomplished by thus exciting the molecular mass of the metal it is constructed of; and the vibratory neutral negative attraction evolved, will bring it into perfect control, commercially, by keeping it in sympathy with the earth's triune polar stream. There is enough of this latent power locked up in the embrace of the iron ore, that is contained in our planet, which, if liberated and applied to proper vibratory machinery, would furnish force enough to run the commercial power of the world: leaving millions of times more to draw upon, as the needs increase. The velocity of the vibration governing the flow of the magnetic stream, comes under the head of the first inter-atomic, and ranges from 300,000 to 780,000 vibrations per second; the first order above odour permeating the molecules, of the glass plate of the compass (with the same facility that atmospheric air would go through an ordinary sieve through which it passes), to arouse sympathetically in the needle the concordant condition that harmonizes with its own. The course of this sympathetic flow is governed by the full harmonic chord; and, consequently, moves in straight lines; thus transmitting its sympathy free of molecular interferences. The order of vibration associated with the transmission of odour acts by sympathetic negative interference; and, consequently, moves in circles, with a velocity of 220,000 per second, at least. If in any way the circle of its rotatory diameter could be reduced to that of its corpuscular structure, then a bottle containing an odorous substance, though sealed as hermetically as an Edison-light bulb, could no more confine its corpuscles than an open chimney the smoke ascending from the fire burning at its base. The sympathetic influence of the terrestrial envelope gets its introductory impulse from the infinite depths of the earth's neutral centre. This impulse radiates in undulating lines far enough into etheric space to become sympathetically associated with the etheric (or Infinite) under the same conditions that associate the mental with the physical organism of man. We can define man's molecular condition in its physical organism as the earth, and its connective link with the convolutionary cerebral centres as the Infinite etheric domain. Thus, we have, represented in the planetary masses moving in etheric space, the same conditions of governing rule as exists between the mental and physical forces. With this medium it is plain to see how simply God works, as well as mysteriously, His wonders to perform; the mental forces kept vitalized from the great store-house of the etheric realm; and, in controlling the physical, the deficit caused thereby renewed and kept balanced by the power of its sympathetic concordant receptiveness. Any visible molecular mass of metal can be so impregnated by triple orders of sympathetic vibration as to give it the same sympathetic transmissive qualities that exist in the mental forces, which make such mass subservient to either the attractive or repulsive conditions of terrestrial sympathy. Gravity is nothing more than a concordant attractive sympathetic stream flowing towards the neutral centre of the earth. This force is inherent in all visible and invisible aggregated forms of matter, from the very birth of a planet, around whose centre the molecules cluster by the sympathetic affinity which is thus induced. If these conditions had always maintained a neutral position in etheric space, no planet would ever have been evolved. These conditions have been fixed by the Infinite. These rotating neutral centres, set in celestial space, have been endowed with the power of rotation to become their own accumulators. It is through the action of these sympathetic forces of the Infinite etheric realm that planets are born, and their volume of matter augmented. If we pick up an object, we feel a resisting power in it which physicists call gravity; but they do not explain what gravity is. It is simply a sympathetic flow, proceeding from the molecular centres of neutrality; which flow is concordant with the earth's neutral centre of same, seeking this medium of its affinity with a power corresponding to the character of its molecular mass. There is no actual weight in the molecules of the mass of which the earth is composed. If the sympathetic negative polar stream that flows towards the neutral centre of the earth were cut off from it, the earth's molecular mass would become independent, and would float away into space as would a soap-bubble filled with warm air. The gravital flow comes, in this system, under the order of the sympathetic concordant of the 9ths, and belongs to that third of the triune combination called polar propulsive. Magnetism is polar attraction. Gravity is polar propulsion. Both magnetism and gravity can be accelerated by the proper medium of sympathetic vibratory influences. A Conjecture. If we take into proper consideration the sympathetic affinity that exists between the centres of the cerebral convolutionary organism, and the polar terrestrial forces, as linked to the celestial, or Infinite, the harmonizing effects they have on the normal brain, and the antagonistic negative bombardment of these streams on the abnormal one, is it not possible, by the diversion of pure, sympathetic streams, to antagonize abnormal conditions, by concordant or magnetic polar sympathetic mechanical exciters, and thus to induce pure normal equilibrium of its corpuscular mass?--which means perfect mental restoration. CHAPTER XX. 1892. PROGRESSIVE SCIENCE--KEELY's PRESENT POSITION. (A Review of the Situation.) This amount of repetition to some will probably appear to be tedious, but only by varied iteration can alien conceptions be forced on reluctant minds.--Herbert Spencer. The researches of Lodge in England and of Hertz in Germany give us an almost infinite range of ethereal vibrations.... Here is unfolded to us a new and astonishing world,--one which it is hard to conceive should contain no possibilities of transmitting and receiving intelligence.... Here also is revealed to us the bewildering possibility of telegraphy without wires, posts, cables, or any of our present costly appliances.... As for myself, I hold the firm conviction that unflagging research will be rewarded by an insight into natural mysteries, such as now can rarely be conceived.--Professor Wm. Crookes, M.R.A., F.R.S., &c. Vibratory Philosophy teaches that "in the great workshop of Nature there are no lines of demarcation to be drawn between the most exalted speculation and common-place practice, and that all knowledge must lead up to one great result; that of an intelligent recognition of the Creator through His works." "Facts are the body of science; speculation is its soul." It has been said that there is nothing more sublime in the history of mind than the lonely struggles which generate and precede success. After the admission made by Professor Rücker, M.A., at the last meeting of the British Association, that the ether may be "the material of which all matter is composed," and that "we may, perhaps, be able to use and control the ether as we now use and control steam," there would seem to be grounds for hoping that Keely's "lonely and prolonged struggles" to utilize in mechanics the ether product which he obtains from his method of dissociating the elements of water, will be more universally recognized and appreciated than they have yet been. Discovery may be unsought and instantaneous, but the inventions for utilizing discoveries may be, and generally are, the work of years. Keely first imprisoned the ether in 1872, when its existence was denied; or, if admitted by a few, it was called "the hypothetical ether." In 1888, Professor Henri Hertz discovered and announced, in the Revue des Deux Mondes, that the ether is held in a state of bondage in all electro-magnetic engines. Not until this fact had been made known, were there any scientific men, with one notable exception, who were willing to admit it was possible that Keely might also have "stumbled over" the manner of effecting its imprisonment. The nature of Keely's researches, and the length of time in which he has been absorbed by the necessary dead-work, attendant upon research before a discovery can be utilized, may be gathered from a letter recently written by Mr. C. G. Till, of Brooklyn, New York:-- "In Keely's early struggles, somewhere about twenty years ago, I became acquainted with him, and helped him then to the best of my ability. Indeed I may say that I was god-father to his discovery; for I was with him when the idea first entered his head that he could combine steam and water to run an engine. At that time he made a crude machine, which he actually ran for some time; and this was the original model of the Pneumatic-Pulsating-Vacuo-Engine, in the operation of which he discovered his present force. From that day to this he has been in pursuit of some method as a medium to use what he calls his etheric force with. That he has actually discovered a new force there is not a shadow of doubt. In those days I have known him to sell and pawn everything of value in his house to obtain means to continue his investigations with the money thus acquired; and I am sure that he will eventually give to the world the greatest boon that has been received by it since the advent of Christianity," etc., etc. It has been very generally thought that Keely is pursuing the ignis fatuus of perpetual motion. No greater mistake could have been made. The genuineness of his claims as a discoverer rests upon a correct answer to the question, "Is hydrogen gas an element or a compound?" Science, as Herodotus said, is to know things truly: but science tells us that hydrogen is a simple, that the atom is not divisible, and that latent energy is not locked in the interstitial spaces of all forms of matter from their birth or aggregation. Keely's system of Vibratory Physics refutes these canons of science. How absurd must seem the idea to many that the schools can be wrong, and that Keely, who has been branded by some of these schools as an impostor, should be right: but time will show whether Keely's discoveries have "come to stay." The history of the past shows us that science has never been infallible; that like Christianity she unfolds her truths progressively. Keely teaches that an unknown potency is held in the atom's tenacious grasp, until released by an introductory impulse given by a certain order of vibration, depending upon the mass-chord of the aggregation; which impulse so increases the oscillation of the atoms as to rupture their etheric capsules. All great truths hold germs potential of ever-increasing growth. It took half a century for the "Principia" of Newton to overcome the contempt that was showered upon it; and now progressive science is overshadowing Newton's vast attainments. In his giant mind was born the hypothesis that the ether is the cause of light and gravity. Keely has been teaching for years, that ether is the medium of all force. For every effect science requires an efficient cause. Hence, when Faraday found no definite knowledge in exact sciences to satisfy him on certain points he was led into speculative science, or the preliminary reaching after truths which we feel must exist by reason of certain effects that come under our observation, analogous to already known laws:--"reduced facts lie behind us; speculative ones lie before us;" and without these latter science could make no progress. Faraday was only speculating when he said: "Thus either present elements are the true elements; or else there is the probability before us of obtaining some more high and general power of nature even than electricity; and which, at the same time, might reveal to us an entirely new grade of elements of matter, now hidden from our view and almost from our suspicion." Faraday's keen perception and acute practical judgment, were never better exemplified than in Keely's discovery of Negative Attraction; the laws governing which he is still researching; theorizing that it is the energy which controls the planetary masses in their advance toward each other, and in their recession from each other,--the energy which lifts the seas and the oceans out of their beds, and replaces them once in twenty-four hours; in other words, explaining the mystery of the action of gravity. Had Faraday lived longer he might have anticipated Keely in one of his discoveries; for he certainly was on the road to it, in the views of force and matter which he held that were not in accordance with the accepted views of his time; and which were then set aside as "wild speculations," by the physicists who complained of his "want of mathematical accuracy," of his "entertaining notions altogether distinct from the views generally held by men of science," who continued their experimental researches on their own lines. In 1885, before Keely's scientific explorations had taught him that no engine can ever be constructed by which the ether can be used and controlled, as we now use and control steam, he wrote, in a letter to a friend, "I shall not forestall an unproved conclusion, but fight step by step the dark paths I am exploring, knowing that, should I succeed in proving one single fact in science heretofore unknown, I shall in so doing be rewarded in the highest degree. In whatever direction the human mind travels it comes quickly to a boundary line which it cannot pass. There is a knowable field of research, bordered by an unknown tract. My experience teaches me how narrow is the strip of territory which belongs to the knowable, how very small the portion that has been traversed and taken possession of. The further we traverse this unknown territory, the stronger will become our faith in the immovable order of the world; for, at each advancing step, we find fresh fruits of the immutable laws that reign over all things,--from the falling apple, up to the thoughts, the words, the deeds, the will of man: and we find these laws irreversible and eternal, order and method reigning throughout the universe. Some details of this universal method have been worked up, and we know them by the names of 'gravitation,' 'chemical affinity,' 'nerve-power,' &c. These material certainties are as sacred as moral certainties.... The nearest approach to a certainty is made through harmony with nature's laws. The surest media are those which nature has laid out in her wonderful workings. The man who deviates from these paths will suffer the penalty of a defeat, as is seen in the record of 'perpetual motion' seekers. I have been classed with such dreamers; but I find consolation in the thought that it is only by those men who are utterly ignorant of the great and marvellous truths which I have devoted my life to demonstrate and to bring within reach of all. I believe the time is near at hand when the principles of etheric evolution will be established, and when the world will be eager to recognize and accept a system that will certainly create a revolution for the highest benefits of mankind, inaugurating an era undreamed of by those who are now ignorant of the existence of this etheric force." These views which have guided Keely in all his researches cannot be made known to any just, discerning mind without an accompanying perception of the gross way in which he has been misrepresented by his defamers; as well as some appreciation of the scientifically cautious manner in which he has pursued his investigations, since he abandoned his efforts to construct an engine that would hold the ether in rotation. At the present time Keely is concentrating his efforts on the perfecting of his mechanical conditions to that point where, according to his theories, he will be able to establish, on the ninths, a sympathetic affinity with pure, polar, negative attraction, minus magnetism. In his own opinion he has so nearly gained the summit, or completion of his "graduation," as to feel that he holds the key to the control of the infinitely tenuous conditions which lie before him to be conquered, before he gains mastery of the group of depolar disks that he is now working upon. Twenty-six groups are completed, and when the twenty-seventh and last group is under equal control, Keely expects to establish a circuit of vibratory force, for running machinery: both for aerial navigation and for terrestrial use. If this result be obtained, Keely will then be in a position to give his system to science; and to demonstrate the ever-operative immanence of the Infinite builder of all things of whom our Lord said, "My Father worketh hitherto, and I work." In commercial use Keely expects that when the motion has been once set up, in any of his machines, it will continue until the material is worn out. It is this claim which has caused Keely to be classed with perpetual-motion seekers. For years Keely has been trying to utilize his discoveries for the material and moral advantage of humanity: and yet he feels, as Buckle has said of the present acquirements of science, that the ground only is broken, that the crust only is touched. The loftiest pinnacle which has been reached by the men who are foremost in their constructions of the method by which the one source of all energy works in the material world, is too insignificant a position to obtain even an outlook towards the vast realm that Keely figuratively describes as the infinite brain; or the source from which all "sympathetic-leads" emanate, that connect mind with matter. Realizing that all conditions of matter are but as vain illusions, he never falters in his determination to reach after the hidden things of God, if haply he may find them. Even the goal which he seeks to attain lies, in his own estimation, on the outermost border of this crust; and well he knows that it never can be reached in any other way than by principles of exact science and by pursuing a path that is at all times lighted by reason. Believing that "the horizon of the world of matter, which has been thought to rest over hydrogen, extends to infinite reaches, including substances which have never been revealed to the senses," he knows how unfathomable is the ocean that lies beyond, and like Newton compares himself to one who is gathering pebbles on its shore. Science, which has ever been interested both in the infinitely small and infinitely great, has in our age dropped the only clue that can guide through the obscure labyrinth which leads into depths of nature lying beyond the knowledge of our unaided senses. The evolution of the human race, says Nesbit, has passed from the physiological into the psychological field; and it is in the latter alone that progress may be looked for. This is the realm into which Keely's efforts, to give to the world a costless motive power, have slowly conducted him through the black darkness of the region in which he has been fighting his way, for a score of years, in behalf of true science and humanity. Lord Derby has said that modern science, on its popular side, is really a great factory of popular fallacies; that its expounders in one decade are kept busy refuting the errors to which the preceding decade has given currency. There is hardly a branch of science, he says, susceptible of general and wide-reaching conclusions, which might not be revolutionized by some discovery to-morrow. If Keely is able to establish his theories, physical science will have to abandon the positions to which she clings, and forced to admit that there exists a purity of conditions in Vibratory Physics unknown in mechanical physics, undreamed of even in philosophy; for he will then be in a position to demonstrate the outflow of the Infinite mind as sympathetically associated with matter visible and invisible. Of this philosophy Professor Daniel G. Brinton has said, "It is so simple, beautiful and comprehensive in its vibratory theory that I hope it will be found experimentally to be true. To me all commercial and practical results, motors, air-ships, engines, are of no importance by the side of the theoretical truth of the demonstrations of this cosmic force. As soon as Dr. Koenig is prepared to report on the purely technical and physical character of the experiments, I shall be, in fact I am, ready to go into full details as to their significance in reference to both matter and mind. It will be enough for me if Dr. Koenig is able to say that the force handled by Keely is not gravity, electricity, magnetism, compressed air, nor other of the well-known forces. Let him say that, and I will undertake to say what the force is." Tests were made last year by Dr. Koenig and Dr. Tuttle, a Baltimore physicist, in the presence of other men of science with the most sensitive galvanometer belonging to the University of Pennsylvania, all of whom were satisfied that no known force had been detected. The abstract of Keely's philosophy, written by Dr. Brinton, has made Keely's theories intelligible for the first time. Each new discovery necessitates a new vocabulary; and Keely's writings are obscure because of his new nomenclature. When Faraday's ideas differed from those held by the authorities of his time, they were pronounced to be "untranslatable into scientific language;" and as was then said of Faraday, so can it now be said of Keely, with equal truth, that, working at the very boundaries of our knowledge, his mind habitually dwells "in the boundless contiguity of shade" by which that knowledge is surrounded. The brain of an Aristotle was needed to discern and grasp Keely's meaning, to interpret and define it. Dr. Brinton never touches a subject without throwing light upon it, and his penetrating mind perceived the ideas to be defined in all their relations. His keen logical acumen separated and classified them in their order, in a true, sound, and scientific manner. In the words of Sir James Crichton Browne, who heard Professor Brinton read this abstract in London, "Professor Brinton's synopsis is an able, lucid and logical paper." Now that such distinguished men are interesting themselves in Keely's discoveries, there is no longer any danger of their being lost to science; nor to commerce, if his life is spared. The action of Dr. Pepper (Provost of the University of Pennsylvania) in January, 1891, gave Keely all the protection that he then needed in order to continue his researches up to the completion of his system. Professor Dewar of the Royal Institution of Great Britain, whose Cambridge duties prevented him from keeping the engagement made for him to visit Mr. Keely's workshop in December, 1891, is now compelled to wait, until notified that Keely is in a position to demonstrate his theories, as it is desirable that he should not be interrupted in the critical work that is at present engrossing him, at times eighteen hours out of the twenty-four. But although Keely has not instructed anyone in his method of disintegrating water, to obtain the ether, which he uses as the medium of the polar force, he does not withhold the principle by which he obtains it. Sir John Herschell said, "There is a principle in the science of music that has yet to be discovered." Pythagoras taught that the principle which underlies the harmonies of music, underlies the motion of the heavenly bodies. It is this principle which Keely has discovered; but until he has utilized it in mechanics, he has nothing more to sell than Sir Isaac Newton had when he discovered gravity, as Professor Fitzgerald has said. Discovery and invention are walking side by side in our age, the glorious scientific age of the world. Never before have they so linked themselves together, working for humanity; and it is but natural that those savants who have seen no demonstrations of the force Keely is handling should regard with apathy claims, which, if established, would sweep away like chaff before a whirlwind, some of the canons of their schools. In fact, this apathy is a great improvement upon the active persecution of the learned men who hurried Copernicus and Galileo to prison, and established the Inquisition to deal with heretics in science as well as heretics in religion. Commerce rushed Keely into a dungeon; science looking on in approval; notwithstanding that conjectures of the most celebrated modern member of its school supported Keely's teachings. Galileo was brought before the Inquisition; the tribunal pronounced him a deluded teacher and a lying heretic. They intended to subject him to the severest torture and death. Galileo was old, and felt that he could not endure such a terrible death. He knelt on the crucifix, with one hand on the Bible, and renounced all. When he arose, however, it is reported that he whispered to one of the attendants, "The earth does move for all that." Sir Isaac Newton has written of the possibility of discovering unknown forms of energy, in Nature, in these strong words: "For it is well known that bodies act upon one another by the attractions of gravity, magnetism and electricity, and these instances show the tenor and course of nature and make it not improbable that there may be more powers of attraction than these. For Nature is very consonant and conformable to herself." All progress of whatever kind would be put back, if it were in the power of bigots to arrest its triumphal march, as they have done in the past, but the evolution of the human race remains in the hands of the Infinite One, who never fails to open up new paths when the farther development of humanity requires it. All systems may be said to have descended from previous ones. "The ideas of one generation are the mysterious progenitors of those in the next. Each age is the dawn of its successor; and in the eternal advance of truth, 'There always is a rising sun, The day is ever but begun.'" Religious and scientific reformation have always gone hand in hand, says Dr. Lowber. In fact, religious science is superior to any other science. As Christianity is the pure religion which contains the truth of all the rest, so it is the highest of the sciences, for it represents the development of the highest faculty of the human nature. Religion develops manhood as nothing else will, and Christianity represents the highest culture to which it is possible for man to attain.... The system, now being evolved and worked out to demonstration by Keely, restores, by religious science, the faith of which materialistic science has been robbing the world, thus confirming Dr. Lowber's assertions that materialists will never be able to reduce all natural and spiritual forces to mere vibratory action of matter; and that the reformatory movement in philosophy, which characterizes our age, will continue until all the sciences point to God and immortality. A writer in Galignani's Messenger, March 2, 1892, says: "When the nineteenth century closes, the most marvellous period ever known to man will be stored away in Time's granary. Can the twentieth century by any possibility be more productive, more fertile, more prolific of wonders than its predecessor? The face of the world has been changed; space has been annihilated; science puts 'a girdle round about the earth in forty minutes.' We may be almost excused if we are tempted to believe that the serpent's promise is fulfilled in our persons, and we are as gods. Alas for human complacency! Perhaps our descendants a thousand years hence will look upon us as pigmies. Be that as it may, the past and the present are ours, with their achievement, and we believe we shall hand down to posterity a goodly heritage." The New York Home Journal, of the week before Christmas, 1892, points out, in its leader, the road on which this advance in the cause of humanity may be made. The writer, Mr. Howard Hinton, says: "The spirit of the salutation, 'A Merry Christmas,' lies in the desire that peace and goodwill shall reign among men, nor, if we may trust the intimations of the latest science, will this universality of good wishing be without avail in effecting its own accomplishment. For, as we are told by the wise men of science, every thought, every mental impulse of ours, sets in motion, in that realm of ether which it is said interfuses all coarser forms of matter, certain vibrations, corresponding in force to their cause, which have power to communicate themselves to other minds favourably conditioned to receive them, and so excite in them like thoughts and impulses. "And are not common observation and individual experience in accord with this suggestion of science? Do we not say at times that a certain thought is in the air, revealing itself contemporaneously to many widely separated minds without any recognizable means of communication? And do we not sometimes find a noble, or it may be an ignoble, impulse breaking out in a community with a suddenness and universality that would seem to transcend all the ordinary forms of the contact of mind with mind? Perhaps, too, this theory of vibratory communication through an ethereal medium may explain, in part at least, that 'Welt-Geist,' that 'Spirit of the Age,' of which the philosophers discourse so bravely. "Again, there are times--if the experiences and observations of sensitive minds have any worth--when a general spirit of expectancy seems to be awakened, as if the world were on the eve of some new and epoch-making revelation of science, or some new enthusiasm of regenerative impulse. Are we not now, at this hour, in this mood of silent expectancy, thrilled with an indefinable awe of what the brooding life of the world is maturing for the sons of men?--sensitive, perhaps, to ethereal vibrations that have not yet accumulated force for expression in conscious thought or for the definite determination of our hearts' desires? "This may be fanciful. It may be simply that we are beginning to perceive that physical science has reached a stage of development when some new and more central truth, some profounder generalization, is needed to give further impulse to its essential progress. It may be that we are becoming aware that the conditions of society are such that some new unifying motive, some new enthusiasm of humanity is needed for its salvation; and that therefore we wait in expectancy for what--knowing that there can be no let nor hindrance in the onward movement of life--we feel in our hearts must come. "And yet does not this sense of expectancy seem to communicate itself from mind to mind by some other means than that of oral or written expression, and to touch with more or less force even minds that are free from these intellectual anticipations? Are there not certain intellects at the fore-front of the world's progress, and certain hearts filled above the ordinary measure with the love of mankind, who are thus centres of power, from whom spread ever widening circles of vibratory emanations that gradually involve all minds in a common thought and all hearts in a common purpose? 'Many men of many minds.' Yes, truly; but there is the one mind of humanity that thinks and thinks, and alone has the power to externalize its thought as part of the world's history, while all purely individual thought is blown finally into the abyss of the Absolute Nothing. "But it is not only the great souls that thus move and shape the world. We are all, in various degrees, centres and distributors of the ethereal force, so far as we are in touch with its waves of vibration. We can all make our thoughts, if they are one with the thought of humanity, and our desires, if they are one with the heart of humanity, felt by our fellows in extending circles of effluence till finally the very clods of human kind know the stirrings of a new life and wake to the higher reality as from a dream. "And if individually we can thus set in movement this ethereal medium, how must not this movement be quickened and extended when collectively we give utterance to some great thought and heart's desire, announcing it in song and prayer and merry-making. Hence the use and potency of the great festivals, the best and sweetest of which is the Christmas festival that we are now about to celebrate--the Evening Star of the year that is passing, the Morning Star of the new." CHAPTER XXI. FAITH BY SCIENCE: THE DAWN OF A NEW ORDER OF THINGS. "All for each and each for all." God will take account of the selfishness of wealth, and His quarrel has yet to be fought out.--Rev. F. Robertson. All the great things of time have been done by single men, from Judas Maccabeus down to Cromwell. We hear the age spoken of as degenerative because of the vast accumulations of wealth. But wealth may be a power for beneficence, as great brains may be, and we have no more reason for regretting large fortunes than large heads. No doubt to secure a perfect equality of all people we need small heads, and small heads or empty heads go with empty purses. By no other means can you level us. So also by wealth the world has been moved, and will continue to be moved. Can we consecrate money power to humanity, as we do mind power? We do not see why not. And in our judgment anyone who does not feel the change that is going on must be blind. It is not legislation that will produce a moral revolution, but a new enthusiasm. The future holds for us a grand enthusiasm of this sort--a moralization of property and possession.--Social Science in Science Siftings. A wave of unrest seems to be passing over the world. Uneasiness prevails on every side. We walk gingerly as though on the edge of a precipice. Discontent is spreading everywhere. The struggle between capital and labour threatens to reach unheard-of proportions.... What is the meaning of the general restlessness? What are its causes? Is the world growing old and effete? Is the human race worn out? Is this generation incapable of the great achievements of the past? Does its materialism clog its powers and prevent its progress? Is the world going wrong for want of an ideal? A people which does not believe in its lofty mission will never accomplish it. Science has made gigantic strides in our days; but have its discoveries added much to the sum of human happiness? It has contributed to our material comfort in various ways, but it has not done much for the federation of the world. The great growth of luxury is not a good, but an evil, if it rob us of our belief in our great destiny and if it weaken our endeavour. If "the time is out of joint," is it not possible that worship of wealth is responsible for it? "He who makes haste to be rich shall not be innocent." Ours is emphatically the age in which men "make haste to be rich," without much regard to the means. Capital has profited unduly at the expense of labour; employers have attained to fortune too quickly for the welfare of the employed. Commerce has forsaken the path of safety to indulge in rash and reckless speculation. Businesses have been converted into companies more for the benefit of vendors and financial houses than for the public. Company promotion has been carried to reckless lengths, and schemes for getting rich rapidly--schemes of the South Sea bubble order--have multiplied in every part of the civilized world. The Nemesis has come in the shape of restlessness, discontent, paralysis of trade, strikes, disorganization of finance, demoralization of Bourses, and general insecurity. It is a fact proved countless times in history that whenever a national need is felt, a man is raised up to supply the want.--Galignani's Messenger. The first seal is being broken in the book of vibratory philosophy; the first stepping-stone is placed toward reaching the solution of that infinite problem, the origin of life.--John Ernst Worrell Keely, 1890. The seals are opened, as it were, under the sign Leo--as believing that such an age is coming on in which prophecy may be fulfilled that the earth be filled with the knowledge of the Lord, which shall cover it with wisdom and understanding in the deep mysteries of God.--Jane Lead, 1699. Evils bear in themselves the causes of their own extirpation. Providence is bringing the old order of things to a close in order to provide place for something better and higher.--Julian Hawthorne. Professor Rowland, in his paper on the "Spectra of Metals," which he read at Leeds, says that the object of his research is primarily to find out what sort of things molecules are, and in what way they vibrate. The primary object of Mr. Keely's researches has been to find out all that he could about the laws that control vibrations, and on this line of research he made his discoveries, as to "what sort of things molecules and atoms are, and in what way they vibrate." One of the editors of the Times, in London, in January, 1891, wrote out this question for Keely to answer:--"What impulse led you primarily into the research of acoustic physics?" Keely replied, "An impulse associated sympathetically with my mental organism from birth, seemingly, as I was acutely sensible of it in my childhood. Before I had reached my tenth year, researching in the realm of acoustic physics had a perfect fascination for me; my whole organism seemed attuned as if it were a harp of a thousand strings; set for the reception of all the conditions associated with sound force as a controlling medium, positive and negative; and with an intensity of enjoyment not to be described. From that time to the present, I have been absorbed in this research, and it has opened up to me the laws that govern the higher workings of nature's sympathetic, hidden forces; leading me gradually on to the solution of the problem relating to the conditions that exist between the celestial and terrestrial outreaches, viz., polar negative attraction." Another question asked by the same editor: "What is the main difficulty to be overcome before completing the system for commercial benefit?" Answer: "The principal difficulty rests in equating the thirds of the thirds of the transmitters (i.e., the gold, silver, and platina sections, of which the transmitting wires are composed) to free them of molecular differentiation. The full control of this force can never be accomplished, until pure molecular equation is established between the nodal interferences (that result in their manufacture) and the chord mass of their sectional parts. When this has been done, the chasm between the alternation of the polar forces, which now exists, preventing the inducing of polar and depolar conditions, will be bridged over and commercial benefits at once established as the result. The devices for inducing these conditions, primarily, are perfect: but the pure, connective link on transmission has to be equated, before continued mechanical rotation and reversion can be attained." As has already been said, Keely's researches have all been on the line of vibrations; and it was while pursuing them that he "stumbled over," to use his own words, the inter-atomic subdivision of the molecule, which released the Geni that for years thereafter was his master. Keely's attention not having been turned to molecules and atoms, he was not able, in the earliest years of his discovery of the existence of a "force of nature more powerful and more general even than electricity," to form any opinion as to the origin of the force. He was as one who, in the thick darkness of an underground labyrinth, found himself face to face with a giant, whose form even he could not see to lay hold of in a death grapple; but when a germ of the knowledge that he needed fell on his mind, he was quick to seize it, and the acorn grew into an oak. Here again, to use his own words: "I was as a boulder resting on the summit of a mountain, until an introductory impulse was given to start it on its course; then rushing onwards and carrying all before it, when the goal is reached its concussion will produce the crash that will awaken a sleeping world." Priestley proclaimed it as his belief that all discoveries are made by chance; but Providence sends chance, and the man of genius is he who is able to improve all opportunities and mould them to his own ends. In a discovery, says Edison, there must be an element of the accidental, and an important one too; discovery is an inspiration, while an invention is purely deductive. The story of the apple dropping from the tree, and Newton starting with a species of "Eureka," he rejects absolutely. Maintaining that an abstract idea or a natural law may, in one sense, be invented, he gives it as his opinion that Newton did not discover the theory of gravitation, but invented it; and that he might have been at work on the problem for years, inventing theory after theory, to which he found it impossible to fit his facts. That Keely claims to have discovered an unknown source of energy has not seemed to disturb the equilibriums of some of the men of science who have witnessed the demonstrations of the force, as much as that he should have invented theories in regard to the operation of the laws that control it. For a man who had lived more than half a century without troubling himself as to the existence of molecules and atoms to suddenly awaken to the knowledge of their existence, and to invent theories as to "what sort of things they are and how they vibrate," was sufficient proof, in their eyes, that he invented his discovery; but men who are, in thought, reaching out into unknown realms, are the very men who are most likely to lay hold of a discovery;--as did Bell, who, speculating upon the nature of sound, filed an invention for his telephone before he discovered that articulate speech could be conveyed along a wire. It was in the same way that Keely, speculating upon the nature of vibration, was led into the field of invention; and while experimenting with one of his inventions, he suddenly stepped into that great unknown territory which lies beyond the horizon of ordinary matter. It took him nearly a score of years to find out where he was. Years of experiment followed before he was able to summon the Geni at will; for when his lever first registered a pressure of 2000 lbs., while subjecting water to the action of multiplied vibrations, he had no idea how to proceed, as far as the number of vibrations were concerned, to repeat the operation. Commencing at a certain point, he increased the vibrations day by day until, six years later, he was able to effect the dissociation at will. But at that time Mr. Keely had too much mechanical work to do to give any of his time to theorizing. He was in the clutches of a speculating Keely Motor Company, whose cry was, "Give us an engine!" and day and night this toiler fought his way in the underground labyrinth, thinking only of a commercial engine. It was not until Macvicar's "Sketch of a Philosophy" fell into Mr. Keely's hands that he realized he had imprisoned the ether. This was in 1884, and, four years later, in 1888, Professor Hertz of Bonn announced that we were using the ether, without knowing it, in all electro-magnetic engines. By this time Keely's researches in vibratory physics had led him well on his way in the construction of hypotheses as to "what sort of things molecules are, and in what way they vibrate." An hypothesis treats a supposed thing as an existing thing, for the purpose of proving, by experimental demonstration, whether the supposition is correct or not. At a critical juncture, Mrs. J. F. Hughes (a grand-niece of Charles Darwin), hearing of Keely's researches, became interested in his work; and her book on "The Evolution of Tones and Colours" was sent to Mr. Keely. An expression used by Mrs. Hughes in that work, brought a suggestion to Mr. Keely. The veil of darkness was rent asunder which had enveloped him in what he called "Egyptian blackness," and from that time he worked no longer in the dark. Pythagoras taught that the same law which underlies harmonies underlies the motion of the heavenly bodies, or, as Mrs. Hughes has expressed it, "The law which develops and controls harmony, develops and controls the universe." Mr. Keely, nothing daunted by the vast extent, the stupendous "outreach" of the domain, the boundary line of which he had thus crossed, concentrated all his energies upon "the situation;" thinking thereafter, not alone of the interests of commerce as before, but of the developing of a system, which he could give to science in the same hour that he should hand over, to those whose thoughts were only on financial gain, the inventions that our age is demanding, in the interests of humanity, with the stern voice of the master necessity; a voice that never fails to make itself heard in "the voice of the people." Experiment after experiment justified his hypotheses, and converted them into theories. To keep pace with the wants of humanity, invention must now walk side by side with philosophy. It took half a century for the "Principia" of Newton to tread down the contempt and opposition that its publication met with; and now progressive knowledge is overshadowing Newton's vast attainments. Faraday, after discovering electro-magnetic conditions, as related to latent or hidden energy, did not pursue his researches far enough to establish a theory as to the mode of transference of magnetic force, though, in some of his speculations on the line of force, he hit upon truths now advanced in Keely's theories. The physicists of Faraday's time could not reach up to him. They complained of his "obscurity of language," of his "want of mathematical precision," of his "entertaining notions regarding matter and force altogether distinct from the views generally held by men of science." It is not then to be wondered at that modern physicists took up lines of research more in accordance with their own views. The experiences of one age are repeated in another age; and the same charges that were brought against Faraday are now brought against Keely; coupled with shameful attempts to prove him to be "a fraud;" a man "living upon the credulity of his victims;" "a modern Cagliostro;" "an artful pretender." The question is often asked, "Is he not an ignorant man?" Yes, so ignorant, that he knows how ignorant he is; so ignorant, that he asserts with Anaxagoras, that intelligent will is the disposer and cause of everything; and not satisfied with asserting this great truth, he has devoted the remnant of his days to finding out and demonstrating how this cause operates throughout nature. But ignorant as Keely has always confessed himself to be, he knows more of the mysterious laws of nature which hold the planets in their courses and exert their dynamic effect upon the tides, more of the "shock effect" which, brought to bear upon molecules, causes their disruption and supplies the fine fluid thus liberated, that extends the "shock effect," as Frederick Major has conjectured, to the atoms that compose them. Ignorant as Keely is, he knows that "out of the strife of tremendous forces which is ever going on in nature, is born a creation of law and harmony;" that from atomic recesses to the farthest depth there is naught but "toil co-operant to an end," that "all these atoms march in time, and that it is no blind cause which originates and maintains all." Admitting his ignorance, Keely claims with Dr. Watson that "the many who are compelled to walk should not scoff at those who try to fly." All who agree in believing that "the advance of the modern school of natural philosophy affords no justification for the intolerant and exclusive position taken by certain physicists," will be ready to examine Keely's theories, in the light of his demonstrations, even although they have been stigmatized as fallacies. Science owes large obligations to many fallacious theories. Canon Moseley has said that the perfecting of the theory of epicycles is due to the astrologers of the middle ages; and that but for them the system of Copernicus would have remained a bare speculation, as did that of Pythagoras for more than two thousand years. In the same way that astrology nurtured astronomy, chemistry was cradled by alchemy. Keely welcomes criticism of his theories, and is able to answer all who come to him with criticisms in a proper spirit. To quote one of his own expressions, "as far as a physical truth is concerned I never throw up the sponge for any one." Of Professor Crookes, Keely wrote quite recently: "Your friend is wrong in saying that I dabble in chemical heresies. There must be some misunderstanding on his part, for I have never asserted that nitrogen is a necessary constituent of water. I only said that, after a thousand experiments had been conducted, there was a residual deposit, in one of my tubes, of a resinous substance that showed nitrogenous elements, which I could not account for. I consider Professor Crookes one of the greatest of discoverers, and, when he understands my system, he will be one of the first to endorse it." A philosophical journalist says of the force discovered by Keely, that "it is harder to believe in than either steam or electricity, because it has no visible manifestation in nature. It does not rise in white clouds from every boiling kettle, or flash with vivid light in every thunderstorm. It does not show itself in the fall of every loosened body to the earth, like gravitation, nor can it be discovered, like oxygen, by chemical investigation. If it exists at all, it is in a form entirely passive, giving no hint of its presence until it is brought out by the patient investigator, as the sculptor's chisel brings out the beautiful statue from the shapeless mass of marble. "Working thus entirely in the dark, with an intangible, imponderable, invisible something whose nature and attributes are all unknown, and whose characteristics differ essentially from those of any other known force, what wonder if the inventor's progress is slow and his disappointments many? Mr. Keely may be deceived, or he may have discovered an actual force which he is unable to harness; but the fact that he is very slow in perfecting whatever discovery he may have made is no proof that he has not made a very great one. "Far be it from us to say in this age of scientific marvels, that any proposition whatever is impossible of accomplishment; but while we wait for Mr. Keely to make his alleged discovery public, before we become enthusiastic over it, we would not set it down as a fraud and the reputed discovery as a humbug. It is the nature of inventors to be enthusiastic and to think that they are on the eve of success when, in fact, a great deal remains to be done. "Especially is this the case in the development of a hitherto unknown force. James Watt had a comparatively straight road to travel from his mother's tea-kettle to his first steam-engine, but it took him many years to traverse it. More than a lifetime elapsed after Franklin drew electricity from a cloud before Morse sent it over a telegraph wire, and Morse himself worked for years to make it available for business purposes; while men are still constantly finding new adaptations of the mysterious force of which that was the first practical application." But, as Frederick Major has said, "Science at present is too full of its own erroneous theories to accept or even notice theories outside of science, until practically proved, and probably not even then unless they can foist them upon the public as partially their own." These words are not applicable to all men of science. There are some, among those most eminent, who, in the spirit of true science, are quite prepared for other roads to knowledge than those of our three hundred years old induction school. The late Professor W. K. Clifford, F.R.S., was one of those men who, in their earnest desire for "truth at any cost," was ready to advance in every direction open to him. No "fear of a false step" held him back. He did not belong to the category of philosophical sceptics whom Dr. Stoney has so well classified as damping all advance, unless it can be carried on, from the beginning, under such conditions of perfection as are impossible in the early stages of every discovery and of almost every inquiry. Professor Stoney has well described Keely's method of work in these remarks: "In the scientific method of investigating the validity of our beliefs, we take our existing beliefs as our starting point, or a careful selection of those which are fitted to enable us to advance. After the legitimate consequences of these have been worked out, the inquirer finds himself in a better position to return and test the validity of the bases on which he proceeded. After these revisions, and such corrections as he finds possible, he makes a step of a like kind farther forward: after which another revision and another advance. Thus real progress is accomplished. Probabilities acquire strength and accumulate; and in the end a state of mind is attained replete with knowledge of the realities within and around us. The sea of knowledge on which man makes his brief voyage is for the most part unfathomable. He cannot hope, except near shore, to measure the whole depth, and thus attain philosophical certainty. But the scientific student may diligently use such a sounding line as he possesses--that of probability--and with it explore wide expanses under which there are no rocks nor shoals within the utmost depth that he can plumb, and over which he may securely sail. Compare this with the situation of the philosophical sceptic, groping among rocks along the shore, and not venturing beyond the shallow margin which he can probe with his little pole." Professor Clifford struck out boldly in this unfathomable ocean of knowledge, when he admitted the infinite divisibility of the atom, which is one of the bases of Keely's theories. And how exquisitely did his penetrating vision pierce the mists of materialism when he wrote:--"Every time that analysis strips from nature the gilding that we prized, she is forging thereat a new picture more glorious than before, to be suddenly revealed by the advent of a new sense whereby we see it--a new creation, at sight of which the sons of God shall have cause to shout for joy. What now shall I say of this new-grown perception of Law, which finds the infinite in a speck of dust, and the act of eternity in every second of time? Shall I say that it kills our sense of the beautiful, and takes all the romance out of nature? And, moreover, that it is nothing more than a combining and reorganizing of our old experiences; that it never can give us anything really new; that we must progress in the same monotonous way for ever. But wait a moment. What if this combining and organizing is to become first habitual, then organic and unconscious, so that the sense of law becomes a direct perception? Shall we not then be really seeing something new? Shall there not be a new revelation of a great and more perfect cosmos, a universe fresh-born, a new heaven and a new earth? Mors janua vitæ, by death to this world we enter upon a new life in the next. Doubtless there shall by-and-by be laws as far transcending those we now know as they do the simplest observation. The new incarnation may need a second passion; but, evermore, beyond it is the Easter glory." In these words there is the true ring of divinely inspired prophecy to those who know of the pure philosophy which Keely's system unfolds; teaching the "wondrous ways of Him who is perfect in knowledge." Professor Clifford was one of those whom Ernest Renan has classified as scouts in the great army, who divine beforehand that which becomes ere long patent to all. In their rapid and venturesome advance they catch sight before the others of the smiling plains and lofty peaks. The student of nature has been compared to a hound, wildly running after, and here and there chancing on game, universal exploration, a beating up of the game on all sides, that and that only is the sole possible method. And this is the spirit of those who pursue their researches in a scientific frame of mind: while those who enter the field in a sceptical mood, are indisposed to step out of the beaten track where they feel sure of their footing. They have no ambitions to meet the fate of the trilobites in Professor Clifford's amusing apologue. "Once upon a time--much longer than six thousand years ago--the Trilobites were the only people that had eyes; and they were only just beginning to have them. Some of the Trilobites, even, had as yet no signs of coming sight. So that the utmost they could know was that they were living in darkness, and that perhaps there was such a thing as light. But at last one of them got so far advanced that when he happened to come to the top of the water in the daytime he saw the sun. So he went down and told the others that in general the world was light, but there was one great light which caused it all. Then they killed him for disturbing the commonwealth; but they considered it impious to doubt that in general the world was light, and that there was one great light which caused it all. And they had great disputes about the manner in which they had come to know this. Afterwards, another of them got so far advanced that when he happened to come to the top of the water, in the night-time, he saw the stars. So he went down and told the others that in general the world was dark, but that, nevertheless, there were a great number of little lights in it. Then they killed him for maintaining false doctrines; but from that time there was a division amongst them, and all the Trilobites were split in two parties, some maintaining one thing and some the other, until such time as so many of them had learned to see that there could be no doubt about the matter that both of the savant Trilobites were right." Bacon has compared the mind of man to a prisoner in a cave with his back to the light, who sees only shadows of the events passing outside. Dr. Stoney, in his paper on "Natural Science and Ontology," frames a working hypothesis, which leads up to Keely's theory, that "the laws of the universe are the laws of thought." "This is a very different thing," says Dr. Stoney, "from saying that they are the laws of human thought. The laws of human thought bear to them the same small proportion which the laws of the action of the wheels of a watch upon one another bear to the entire science of dynamics.... Natural science is thus, as it were, the study of an ever-changing shadow cast in a special and very indirect way by the mighty march of actual events." "The history of philosophy," writes Ernest Renan, "should be the history of the thoughts of mankind. Hence we must look upon philology, or the study of ancient literatures, as a science having a distinct object, viz., the knowledge of the human intellect." The philologist and the chemist, because of the results of the researches of the one, and of the nature of the researches of the other, are the students who are best able to comprehend the discoveries of Keely. "It is the characteristic and the pride of modern science to attain its most lofty results only through the most scrupulous methods of experiment, and to arrive at the knowledge of the highest laws of nature, its hands resting on its apparatus. If the highest truths can, as it were, emanate from the alembic and the crucible, why should they not equally be the result of the study of the remains of the past, covered with the dust of ages? Shall the philologist who toils on words and syllables be less honoured than the student of chemistry labouring in his laboratory? It is impossible to guess beforehand what may result from philological researches, any more than one can know, in digging a mine, the wealth it may contain. We may be on our way to the discovery of a new world. Science always presents itself to man as an unknown country. The most important discoveries have been brought about in a roundabout way. Very few problems have been deliberately grappled with at the outset, 'taken at the core.' There is nothing more difficult to foretell than the importance with which posterity will invest this or that order of facts; the researches that will be abandoned, the researches that will be continued. In looking for one thing one may stumble upon another; in the pursuit of a mere vision, one may hit upon a magnificent reality." When a result has been attained, it is difficult to realize the trouble its attainment has cost, says Ernest Renan in "The Future of Science." Of this nature have been the researches of the present distinguished Professor of Chemistry in the Royal Institution; leading him into a discovery, the great importance of which the future alone can unfold. Professor Dewar's brilliant success in producing liquid oxygen will be remembered by all who had the privilege of witnessing it last year, on the occasion of the celebration of Faraday's Centenary. Its production is attended with the greatest difficulties; so great that Professor Dewar even felt doubts as to his being successful in his attempt at that time, which made his complete success all the more gratifying to him. When produced, it is difficult to hold and difficult to manipulate; but nothing daunted by these difficulties, Professor Dewar continued his researches, subjecting it to tests which no mind less penetrating than his own would ever have thought of, with the result that, most unexpectedly to himself, he has "hit upon a magnificent reality." The ordeal to which, with consummate skill, he subjected this unstable fluid, disclosed its marvellous affinity for the magnet; and iron is now no longer able to claim the distinction which it has hitherto enjoyed, of monopolizing the affections of the magnet. Sir Robert Ball, LL.D., F.R.S., in commenting upon this important and most interesting addition to our knowledge of the properties of oxygen, says:--"Seeing that water, which is so largely composed of oxygen, is not attracted by a magnet, it might certainly have seemed unlikely that a liquid which was nothing but pure oxygen should be affected to any noteworthy degree. I suspect, however, that Professor Dewar must have had some sagacious reason for anticipating that the magnet would treat liquid oxygen with much more attention than it bestowed on water. At all events, whether he expected it or not, the result as described was of the most extraordinary character. The liquid oxygen was vehemently attracted by the great magnet; it seems to have leaped from the vessel, to have clung round the poles, and continued to adhere to them until it had all evaporated and resumed the form of gas. The appreciation of this discovery will be shared not alone by chemists, but by all who are interested in the great truths of nature." When Mr. Keely fell upon his discovery of an unknown force, he had not the faintest conception of the infinite extent, nor of the nature, of the territory he had invaded. Step by step he has been led on through years of patient and persistent research, yet even now feeling that he has but lifted one corner of the veil of the goddess of nature, and that a lifetime is too short to do more than this. The physicists whom Keely, in the earlier years of his discovery, invited to confer with him as to the origin of the force which was generated by the disintegration of water, preferred rather to pronounce him an impostor, after witnessing his demonstrations, than to admit that such results should have escaped the penetration of their all-powerful methods. "It indicates," says Dr. Watson, "a mistaken apprehension of the basis of our own so highly valued system of inquiry, that we should arrogate to it absolute exclusiveness, and deride, as though they were searchers after proved impossibilities, all those who choose to make the trial whether truth may be sought by any method besides our own." History repeats itself, but on new planes. It is not those who are mighty in their own eyes whom Providence chooses as instruments to reveal new truths to the world when the needs of humanity require "a new order of things." The evolution of the human race is slow but sure. If in one century some backward steps are taken, in the next with giant strides all is regained that seemed to have been lost. Each age answers the need of its own time. "The condition of mankind, during the last quarter of the fifteenth century, bore some curious analogies to its state at present," writes Julian Hawthorne, under the heading, "The New Columbus." "A certain stage or epoch of human life seemed to have run its course and come to a stop. The impulses which had started it were exhausted. Once more, it seems, we have reached the limits of a dispensation, and are halted by a blank wall. There is no visible way over it, nor around it. We cannot stand still; still less can we turn back. What is to happen? What happens when an irresistible force encounters an impenetrable barrier? That was the question asked in Columbus' day, and he found an answer to it. Are we to expect the appearance of a new Columbus to answer it again? What Columbus can help us out of our dangers now? The time has come when the spirit of Columbus shall avouch itself, vindicating the patient purpose of Him who brings the flower from the seed. Great discoveries come when they are needed; never too early nor too late. When nothing else will serve the turn, then, and not till then, the rock opens and the spring gushes forth. Who that has considered the philosophy of the infinitely great and of the infinitely minute can doubt the inexhaustibleness of nature? And what is nature but the characteristic echo of the spirit of man? A prophet has arisen, during these latter days, in Philadelphia, who is commonly regarded as a charlatan; but men, cognizant of the latest advances of science, admit themselves unable to explain upon any known principles the effects he produces." "What we are to expect is an awakening of the soul; the rediscovery and rehabilitation of the genuine and indestructible religious instinct. Such a religious revival will be something very different from what we have known under that name. It will be a spontaneous and joyful realization by the soul of its vital relations with its Creator. Nature will be recognized as a language whereby God converses with man. The interpretation of this language, based as it is upon an eternal and living symbolism, containing infinite depths beyond depths of meaning, will be a sufficient study and employment for mankind for ever. Science will become, in truth, the handmaid of religion, in that it will be devoted to reporting the physical analogies of spiritual truths, and following them out in their subtler details. Hitherto the progress of science has been slow, and subject to constant error and revision. But as soon as physical research begins to go hand in hand with moral or psychical research it will advance with a rapidity hitherto unimagined, each assisting and classifying the other. "The attitude of men towards one another will undergo a corresponding change. It is already become evident that selfishness is a colossal failure.... Recent social theorists propose a universal co-operation, to save the waste of personal competition. But competition is a wholesome and vital law; it is only the direction of it that requires alteration. When the cessation of working for one's livelihood takes place, human energy and love of production will not cease with it, but will persist and must find their channels. But competition to outdo each in the service of all is free from collisions, and its range is limitless. Not to support life, but to make life more lovely, will be the effort; and not to make it more lovely for one's self alone but for one's neighbour. Nor is this all. "The love of the neighbour will be a true act of divine worship, since it will then be acknowledged that mankind, though multiplied to human sense, is in essence one; and that in this universal one, which can have no self-consciousness, God is incarnate. "The divine humanity is the only real and possible object of mortal adoration, and no genuine sentiment of human brotherhood is conceivable apart from its recognition. But, with it, the stature of our common manhood will grow toward the celestial. Obviously, with thoughts and pursuits of this calibre to engage our attention, we shall be very far from regretting those which harass and enslave us to-day. Leaving out of account the extension of psychical faculties, which will enable the antipodes to commune together at will, and even give us the means of communicating with the inhabitants of other planets, and which will so simplify and deepen language that audible speech, other than the musical sounds indicative of emotion, will be regarded as a comic and clumsy archaism,--apart from all this, the fathomless riches of wisdom to be gathered from the commonest daily objects and outwardly most trivial occurrences, will put an end to all craving for merely physical change of place and excitement. Gradually the human race will become stationary, each family occupying its own place, and living in patriarchal simplicity, though endowed with power and wisdom that we should now consider god-like.... We have only attempted to indicate what regions await the genius of the new Columbus; nor does the conjecture seem too bold that perhaps they are not so distant from us in time as they appear to be in quality." If we turn, from this seemingly Utopian forecast, to the matter-of-fact utterances of Ernest Renan, we will find that he anticipates nothing less as the destiny of humanity, than the perfecting of it as a unity. Asserting that the nineteenth century is preparing the way for the enfranchisement of the mind, he proceeds logically to show how this evolution is to be brought about, strong in the faith that Providence will not fail in its design to secure the ultimate happiness of the human race. To quote, at length, from Renan:--"It is the law of science, as of every human undertaking, to draw its plans on a large scale, and with a great deal that is superfluous around them. Mankind finally assimilates only a small number of the elements of food. But the portions that have been eliminated played their part in the act of nutrition. So the countless generations that have appeared and disappeared like a dream, have served to build the great Babel of humanity which uprises toward the sky, each layer of which means a people. In God's vast bosom all that lived will live again, and then it will be true to the very letter that not a glass of water, not a word that has furthered the divine work of progress will be lost. That is the law of humanity; an enormous and lavish expenditure of the individual; for God only sets Himself the large, general plan; and each created being finds subsequently in himself the instincts which make his lot as mild as possible. All help to accelerate the day when the knowledge of the world shall equal the world, when the subject and the object having become identified, God will be complete. Philosophy up till now has scarcely been anything but fancy, a priori, and science has only been an insignificant display of learning. As for us, we have shifted the field of the science of man. We want to know what his life is, and life means both the body and the soul; not placed facing one another like clocks that tick in time, not soldered together like two different metals, but united into one two-fronted phenomenon which cannot be divided, without destroying it. It is time to proclaim the fact that one sole Cause has wrought everything in the domain of intellect, operating according to identical laws, but among different surroundings. "The lofty serenity of science becomes possible only when it handles its imperturbable instrument with the inflexibility of the geometrician, without anger and without pity. True science, the complete and felt science, will be for the future, if civilization is not once again arrested in its march by blind superstition and the invasion of barbarism, in one form or another. But it is contended that the inferiority of the philosophy of science consists in its being accessible to the small minority. This is, on the contrary, its chief title to glory, showing us that we should labour to hasten the advent of the blessed day in which all men will have their place in the sunshine of intelligence, and will live in the true light of the children of God. It is the property of hope to hope against hope, and there is nothing which the past does not justify us in hoping from the future of humanity. Perfect happiness, as I understand it, is that all men should be perfect. I cannot understand how the opulent man can fully enjoy his happiness while he is obliged to veil his face in presence of the misery of a portion of his fellow-creatures. There can only be perfect happiness when all are equal, but there will only be equality when all are perfect. Thus we see that it is not a question of being happy; it is a question of being perfect; a question of true religion, the only thing which is serious and sacred. Inequality is legitimate whenever inequality is necessary for the good of humanity. Rights create themselves like other things. The French Revolution is not legitimate because it has taken place, but it took place because it was legitimate; the freeing of the negroes was neither achieved nor deserved by the negroes, but by the progress in civilization of their masters. Right is the progress of humanity; there is no right in opposition to this progress, and, vice versâ, progress legitimizes everything. Never, since the origin of things, has human intelligence set itself so terrible a problem as the one which now menaces our age. Upon the one hand, it is necessary to preserve the conquests already secured for civilization; while upon the other, all must have their share in the blessings of this civilization. It took centuries to conceive the possibility of a society without slavery. The traveller who looks only at the horizon of the plain, risks not seeing the precipice or the quagmire at his feet. In the same way, humanity when looking only to the distant object is tempted to make a jump for it, without regard to the intermediate objects against which it may not improbably dash itself to pieces. Socialism is, therefore, right to the extent of discerning the problem, but solves it badly; or rather socialism is not yet possible of solution. Reforms never triumph directly; they triumph by compelling their adversaries to partially adopt them in order to overcome them. It might be said of reforms as of the crusades: 'Not one succeeded: all succeeded.' As one sees the tide bringing the ever-collapsing waves upon the shore, the feeling aroused is one of powerlessness. The wave arrived so proudly, and yet it is dashed to pieces against the sand, and it expires in a feeble career against the shore which it seemed about to devour. But, upon reflection, one finds that this process is not as idle as it seems; for each wave, as it dies away, has its effect; and all the waves combined make the rising tide against which heaven and hell would be powerless. Humanity, when it is fatigued, is willing to pause; but to pause is not to rest. The calm is but an armistice and a breathing space. It is impossible for society to find calm in a state when it is suffering from an open wound such as that of to-day. The age is oppressed by this inevitable and seemingly insoluble problem. We barricade ourselves in one party, in order not to see the reasons of the other side. The conservatives are wrong, for the state of things which they uphold, and which they do right to uphold, is intolerable. The revolutionists are wrong; for it is absurd to destroy when you have nothing to put in place of what you destroy. At these epochs, doubt and indecision are the truth; the man who is not in doubt is either a simpleton or a charlatan. Revolutions must be made for well-ascertained principles, and not for tendencies which have not yet been formulated in a practical manner. They are the upheavals of the everlasting Enceladus turning over when Etna weighs too heavily upon him. It is horrible that one man should be sacrificed to the enjoyment of another. If it were merely a question of self-indulgence, it would be better that all should have Spartan fare, than that some should have luxuries and others go hungry; but, as long as material ease is to a certain extent the indispensable condition of intellectual perfection, the sacrifice is not effected for the enjoyment of another individual, of the luxuries of life, but it is made upon behalf of society as a whole. A society is entitled to what is necessary for its existence, however great may be the apparent injustice resulting for the individual. It is the idea of the ancient sacrifice--the man for the nation. If the object of life were but self-indulgence, it would not be unreasonable that each one should claim his share, and from this point of view any enjoyment which one might procure at the expense of others would be in reality an injustice and a robbery: but the object of life, the aim of society, should be the greatest possible perfecting of all. The State is neither an institution of police, as Smith would have it, nor a charity bureau and a hospital as the Socialists would have it. It is a machine for making progress. In the state of things which I should like to see, manual labour would be the recreation of mental labour. The immense majority of humanity is still at school: to let them out too soon would be to encourage them in idleness. Necessity, says Herder, is the weight of the clock which causes all the wheels to turn. Without the idea of progress, all the ideas of humanity are incomprehensible. We must keep our machines in order, if we would bring down paradise upon earth; and paradise will be here below when all have their share in light, perfection, beauty, and therefore in happiness. "It matters little whether the law grants or refuses liberty to new ideas, for they make their way all the same; they come into existence without the law, and they are all the better for this than if they had grown in full legality. When a river which has overflown its banks pours onward, you may erect dykes to arrest its progress, but the flood continues to rise; you may work with eager energy and employ skilful labourers to make good all the fissures, but the flood will continue to rise until the torrent has surmounted the obstacle, or until, by making a circuit of the dyke, it comes back by some other way to inundate the land which you have attempted to protect from it." These are the advanced views of Ernest Renan, who still sees nothing before us but a fresh cataclysm, a general upheaval and chaos, terrible disturbances when human intelligence will be checkmated, thrown off the rails so to speak, by events as yet unparalleled. We have not yet suffered sufficiently, he says, to see the kingdom of heaven. When a few millions of men have died of hunger, when thousands have devoured one another, when the brains of the others, carried off their balance by these darksome scenes, have plunged into extravagancies of one kind and another, then life will begin anew. Suffering has been for man the mistress and the revealer of great things. Order is an end, not a beginning; but out of respect for the rights of bears and lions are we to open the bars of a menagerie? Are these beasts to be let loose upon men? No, for humanity and civilization must be saved at any cost. But these problems, which make up the capital question of the nineteenth century, are, in a speculative sense, insoluble; they will be solved by brute force, says Renan. The crowd behind is ever pressing forward; those in the foremost ranks are toppled over into the yawning gulf, and when their bodies have filled up the abyss, the last comers pass over on the level. But let us suppose that what pseudo-science has wrested from us, true science is ready to restore; ready to offer all that Renan himself tells us is necessary to open the way for the elevation of the people, by giving all men a share in the delights of education; thus widening the basis of the brotherhood of humanity, and making room for all at the banqueting-table of knowledge, enabling men to be "perfect in their measure," for "absolute equality is as impossible in humanity as it would be in the animal reign. Each part is perfect in the hierarchy of the parts when it is all that it can be, and does well all that it ought to do." Let us suppose that true science offers confirmation of all that revelation has taught of the attributes of the Creator of all things, reiterating the promise of a time when this knowledge shall be spread over the face of the whole earth and made known to all men. Let us imagine that, in addition to the opening of these floodgates of knowledge, the time is drawing near when machinery, unknown now, will be employed to help the workman in his task, and abridge his hours of labour, leaving leisure for the cultivation of his mind. Aristotle has told us what would be the result, "if every instrument could work of its own accord, if the spindles worked of themselves, if the bow played the violin without being held, the contractors could do without workmen and the masters without slaves." Man would so master nature that material requirements would no longer be the supreme motive, and human activity would be directed towards the things of the mind. In such a state of existence men of intelligence would "conquer the infinite." We are living in a period of wondrous revelations of the power of God, and the crowning discovery of this epoch promises the fulfilment of Scripture prophecy in a dispensation of harmony and peace, that will restore to mankind that measure of faith in God and immortality, which can alone give strength "to endure the evil days without feeling the weight of them" that lie between the present time and the realization of our hopes for the perfection of humanity. With the knowledge that lies in this new revelation of the power of the All-Mighty, no hopes seem chimerical or Utopian. We shall all be as gods, when the fulness of the love of God and the power of God is made known to, and understood by, all men. Tossing as we are in a seething whirlpool of scepticism, threatened as are the nations with dangers on all sides, if we were bereft of our God, as the leading lights of science would have us believe, there would be no hope for humanity. But though the anchor of ancient faiths has been swept away by materialism, the sheet-anchor of faith by science has been let down from heaven, as it were in our hour of peril, for the saving of the peoples: teaching as often before that the world lies in the bosom of God, like a child in its mother's arms, who with watchful solicitude ministers to its wants as they arise. Religion as revealed to us by our Holy Master, Jesus Christ, is to know and to love the truth of things. When this religion is understood and practised, then, and not before, will the earth be full of the knowledge that it is God who is, and that all the rest only appears to be. If anarchy and disorder would but wait for this time to arrive, no devastating cataclysms, no destroying whirlwinds, will come as forerunners to prepare the way, as in the past, for progress. The light now dawning will usher in "the new order of things," and we may expect that an era of material prosperity will soon set in, such as the world has never dreamed of; arresting the outbreak of barbarism which seems near at hand. There are some who contend that this revelation of an unknown force will, in the hands of anarchists, put back the progress of civilization and enlightenment for centuries; there are others who proclaim that it will take the bread from the mouths of the hungry and swell the sums amassed by capitalists. But history shows that discovery heralds progress, and walks with it hand in hand. With the costless and unlimited power which will be made available, in every direction where power is required, all works of improvement will be carried out on a far grander scale than has ever been anticipated. The great polar stream, with its exhaustless supply of energy, places at our disposal a force as harmless as the current that draws its keeper to the magnet. We have but to "hook our machinery on to the machinery of nature," and we have a safe and harmless propelling and controlling force, the conditions of which when once set up remain for ever, perpetual molecular action the result. Another step made toward the conquering of the material world which must precede the advent of the reign of the spirit. Schlegel foresaw that the only hope for a brotherhood of humanity lay in the thorough religious regeneration of the State and of science, and that through these combined powers the underlying purpose of Eternal Mind is to be made known, covering the earth with the knowledge of God as the waters cover the beds of the seas, obtaining a complete triumph for Christianity. It would fill with despair the hearts of those who are working to bring about this end (so slow, so retrograde at times does the evolution seem to be) did they not know that they have an Invincible Power working with them. History has again repeated itself, and truth has once more had its birth in a stable. A star has arisen in the West which heralds to all races what the Star of Bethlehem heralded in Judea, viz. the coming of the time when the earth shall be filled with the knowledge of the Lord. There are both Magi and shepherds now, as of old, who have watched for the rising of this star, and who were the first to behold the gold and crimson light of the approaching dawn; in which Faith, which modern science has crucified and laid away in its sepulchre, will have its resurrection and dwell on earth for evermore--the tabernacle of God with men. THE DAWN. Dante called his lifetime, "The time of my debt." I. Have I not paid my debt, O God, What have I left to give? Yet blest my life in rendering all To help the nations live In harmony, in peace, in love, As nations all will be, When knowledge true shall cover earth As waters cover sea. II. Nailed to the cross are all my hopes-- Thou hast not spared me aught: But raised thereby above the world Its treasures count as naught: Empty its titles and its show, Its honours and its fame; Better the love of God to know Than riches, rank, or name. III. Two avenues there are, 'tis said, From paltry passions vile, From all calamities of earth, From artifice and wile. Science and Art their votaries lead From quicksands and from shoal; Their guiding torches held aloft Will light us to our goal. IV. When ended this--my "time of debt"-- 'Tis only Thou canst know; But when the longed-for quittance comes I stay not here below. Till then give me the torch of Art To light my pathway drear, Let Science lift my thoughts to Thee, My lonely hours to cheer. V. And when my life-long debt is paid-- My soul from body free-- No bondage can enslave me more, For I shall go to Thee. Hasten the hour when summons comes, To take me to my home; Here have I lived an exile's life, An exile forced to roam. VI. The face of love was turned from me When most I felt its need, And in the wilds my feet were set To plough and sow the seed. Ashes and tears to me were given; I sat not by the way, With folded hands to make lament, But laboured day by day. VII. Thou hast not dealt one useless blow, What time I worked in field: Each tear of blood, each hour of toil, Increased the harvest yield; And now the furrows all are ploughed, If I have paid my debt, By waters still, in paths of peace, Thou wilt my footsteps set. VIII. Æons may pass before my hopes For earth are all fulfilled; But let "the dawn" approach, I pray, Before my lips are stilled! And let true knowledge cover earth As waters cover sea-- Knowledge of truth, knowledge of love, Knowledge, dear God, of Thee! IX. I wait the music of the spheres, The rhythmic pulse of earth, Which, when Death's angelus doth ring, Announce immortal birth: In that blest home beyond the veil No discord rends the air The law of harmony prevails And love reigns everywhere. CONCLUSION. KEELY'S PHYSICAL PHILOSOPHY. Mr. Keely begins with sounds whose vibrations can be known and registered. I presume that the laws of ratio, position, duality, and continuity, all the laws which go to mould the plastic air by elastic bodies into the sweetness of music, will also be found ruling and determining all in the high silence of interior vibrations, which hold together or shake asunder the combinations that we call atoms and ultimate elements.--The Science of Music. D. C. Ramsay. Edited by the Rev. John Andrew. Marcus Ward & Co. What Keely has discovered in physics, I am in some measure credited with discovering in metaphysics: this is nothing strange, according to this philosophy, which shows that many people may divine the same original truth at the same time by means of the etheric element which connects the Deity, the source of all truth, with all His creatures.--Preface to Vera Vita; or, the Philosophy of Sympathy. David Sinclair. Author of A New Creed. Digby, Long & Co., London. Abstract of Keely's Physical Philosophy in its main features up to the point of practical application; by Professor Daniel G. Brinton, of the Pennsylvania University; subject to modifications and additions when Keely has made public his system. The fundamental conception of the Universe is force manifesting itself in rhythmical relations. This definition is exhaustive, including both thought and extension, matter and mind. The law for the one is the law for the other. The distinction between them is simply relative, i.e. quantitative, not qualitative. The rhythmic relations in which force acts are everywhere, under all conditions, and at all times, the same. They are found experimentally to be universally expressible by the mathematical relations of thirds. These threefold relations may be expressed with regard to their results as,-- I. Assimilative. II. Individualizing. III. Dominant or Resultant. From these three actions are derived the three fundamental LAWS OF BEING. I. Law of Assimilation: every individualized object assimilates itself to all other objects. II. Law of Individualization: every such object tends to assimilate all other objects to itself. III. Law of the Dominant: every such object is such by virtue of the higher or dominant force which controls these two tendencies. Applying these fundamental laws to an explanation of the universe, as it is brought to human cognition, all manifestations of force may be treated as modes of vibrations. The essential differences give rise to three modes of vibration:-- I. The Radiating: called also the "Dispersing," the "Propulsive," the "Positive," and the "Enharmonic." II. The Focalizing: called also the "Negative," the "Negative Attractive," the "Polarizing," and the "Harmonic." III. The Dominant: called also the "Etheric," or the "Celestial." These, it will be noted, correspond to the three laws of being. It is not to be understood that any one of these three modes of vibration can exist independently. Each by itself is called a "current," and all three must be present in every "stream" or "flow" of force. The relations of the currents in every flow are expressible in thirds, and it is experimentally demonstrable that the relation of the three are in the order named: as 33 1/3 : 66 2/3 : 100. The evolution of what is called "matter" from the different modes of vibration is through the action of the second law, that of focalization, or "negative attraction," or "negative affinity." Where the vibrations under this mode meet, and are maintained in a state of mutual affinity or equilibrium, there is established what is called a "neutral centre," or, as otherwise expressed, "a centre of sympathetic coincidence." The terms "neutral attraction," "neutral affinity," "negative attraction," or "polar negative attraction," are employed to express the property of a mode of vibration to direct its components towards such centre. As no current or flow of force can be composed of one mode of vibration only, but must always be composed of three modes uniting in varying thirds, we have 1 × 2 × 3 = 6 as the total possible forms of sympathetic coincidence, or, to speak in ordinary terms, there can be six; and six only, possible forms of individualized being. These are what Keely calls the six orders of atomic subdivision, or orders of vibratory motion, and he names them as follows: I. Molecular. II. Inter-molecular. III. Atomic. IV. Inter-atomic. V. Etheric. VI. Inter-etheric. In this list the forms of matter are arranged in the mathematical sequence of the rapidity of the oscillations of their constituent members; the proportion being proved by experiment to be as follows: for the molecular orders: 1 : 3 : 9 : 27 : 81 : 243. This arithmetical progression changes in the atomic orders to a geometrical progression as follows: 3 : 9 : 81 : 6561 : 43046721, etc. This same method of progression is believed to hold in all the orders of vibrations above the molecular, and soon passes into mathematical infinity. Actually, however, all matter of which we are capable of cognition through the medium of our senses is in one of three forms of aggregation: I. Molecular. II. Atomic. III. Etheric. in each of which the controlling mode of vibration is respectively, I. The Enharmonic. II. The Harmonic. III. The Dominant. But it must be understood that each of these modes is a positive and real constituent of every atom and molecule. It will be seen that as every form of material aggregation is to be considered as a "neutral centre of attraction," where the vibratory force of all three orders are held in "sympathetic coincidence," that is, in balanced activity or harmonized motion, and not by any means cancelled or mutually destroyed, there is no diminution of force, but only temporary suspension of its radiating or propulsive activity or expression. This is the foundation of Keely's doctrine of "latent force," and of the indefinite power which can be obtained by breaking up the harmonious balance or equation of forces of every mode, which exists in every "neutral centre," that is to say in every mass of matter. Insomuch as every mass of matter consists thus, in fact, of vibrations in harmonic equilibrium, related by simple proportions of thirds, it follows that every mass of every description stands in harmonic relation to every other mass. This is, in part, what is meant by the sympathy of all forms of matter and of motion; and it is through the study of the methods of increasing or diminishing this sympathy that we reach practical results in this field of research. At present this is best accomplished by resonance; that is, through the harmonic vibrations created by musical instruments, bringing out the acoustic world as the microscope reveals the hidden visual world. Every visible or tangible mass of matter must be regarded as an aggregation of molecules; the molecules being the true centres of the equated forces of "neutralized attraction." These molecules have been experimentally proved by Keely to be formed of all three modes of vibration; the proof being that they respond to all three modes when subjected to the tests of compound concordant impulses. When in that state of neutral aggregation which we know as matter, each molecule is in perpetual oscillation, the range of the oscillation being one-third of the molecule, and its rapidity 20,000 oscillations in a second. It is through the disturbance of this oscillatory equilibrium, by means of resonant impulses, that Keely alters the relations of the vibratory impulses which constitute matter. This he does by striking the same chord in three octaves, representing the third, sixth, and ninth of the scale. Of these, the sixth reduces the range of molecular vibrations or oscillations; and, by thus bringing nearer to each other the neutral centres, increases solidification. The ninth extends the range of molecular oscillation, and thus tends to give greater tenuity to the mass. It induces "trajectile velocity" from neutral centres, or "neutral radiation." Experiment shows that molecular dissociation does not take place until the molecule attains an oscillation approaching, if not fully reaching two-thirds of its diameter. This can be effected by means of the action of the "enharmonic" or "radiating" current applied to the mass, after its molecules have once been disturbed by an "introductory impulse;" that is, by the musical note above mentioned. The third represents the "dominant," and when brought under control of a harmonic resonant impulse induces a complete rearrangement of the modes of vibration and oscillation; in other words, will transform the mass either into its component initial forces, or into some other form of matter. It is the study of the dominant to which Keely has devoted his recent researches. He aims to control the power he evolves by altering the dominant or etheric mode of vibration in the triplicate flows of force. As all molecules and masses are mere centres of harmonized vibrations, temporarily held in suspension by simple laws identical with those of resonance, it follows that these centres can be broken up or divided by certain orders of vibration impinging upon and disturbing them. It is a familiar fact that a cord in vibration tends to produce a similar vibration in a cord placed near it. This property belongs to all vibrations, whether resonant or not, and they exert it in proportion to the "order" to which they belong. The distance in space to which this power extends, or can be extended, is what is called "the sympathetic outreach" of the current or flow. In this manner we have "sympathetic negative attraction," and "sympathetic positive propulsion," with reference to the "outreach" of the third or dominant current of the stream, which is allied to the order of etheric vibrations. Each molecule of a given mass of matter represents the same harmonic chord or note in its oscillatory motion. The "chord of the mass" is, therefore, the chord of every molecule of the mass. But as the condition of absolutely stable equilibrium is theoretical only, and does not exist in nature, the chord of the mass is constantly changing. Yet we must learn to control this "chord of the mass" by resonant induction, if we would gain command of the molecular forces. Keely believes he has solved this problem, by the invention of a mechanical device which brings the chords of all masses within the conditions of a few simple acoustic tests. The range of molecular oscillation is affected differently in different substances when submitted to the same vibratory impulse, and these ranges can be measured. In the three metals, silver, gold, and platina, we obtain the proportions----3 : 6 : 9 :--As this is the primary relation of the modes of vibration, a wire made of these three metals is peculiarly adapted to transmit concordant impulses; and nodes made of these substances placed upon a wire, transmitting resonant vibrations, indicate, by the different orders of vibration induced in them, the rate of oscillations of the atomic constituents. The phenomenon of rotation arises from the harmonic interaction of the dominant and enharmonic elements of the flow: in other words, the first and third, the third and ninth, etc.; those whose vibrations bear the proportions to each other 33 1/3 : 100. A practical example of rotation is a wheel in revolution on its axis. This is force in its commercial or economic aspect. To accomplish this result by molecular vibratory action, we must gain control of the "negative attractive" or "enharmonic" current of the triple flow, and the problem is then solved up to any limit of power. APPENDIX I. More than four centuries B.C., Leucippus and his disciple Democritus--who expounded the atomic theory of his master--introduced the doctrine of indivisible atoms, possessing within themselves a principle of energy. Democritus, it is said, travelling in search of wisdom, visited the Gymnosophists of India (who, by leading ascetic lives, thought they could effect a reunion of the spiritual nature of man, with the divine essence of Deity), and in so doing incurred the risk of being deprived of the rites of sepulture by his "waste of patrimony," there being a law in Abdera to that effect. Anaxagoras, Heraclitus, Empedocles and other philosophers, had taught that matter was indefinitely divisible, but Leucippus and Democritus were the first to assert that these particles or atoms were originally destitute of all qualities except form and energy; and they are, therefore, called the originators of the atomic philosophy; which is the basis of Keely's system of sympathetic physics. Sympathetic physics teaches that light is an etheric evolution, propagated by sympathetic conflict between celestial and terrestrial outflows: solar tensions as against terrestrial condensation. True luminosity cannot be induced in any other way. The high order of triple vibration, that induces (progressively) molecular and intermolecular separation, shows luminous results which, when thus mechanically produced, are virtually on a small scale, a facsimile of nature's operations. "All such experiments that I have made," writes Keely, "resulted in vortex motion invariably, both sympathetically and otherwise. Vortex motion follows nature in all corpuscular action. "The undulatory theory, regarding light, I have not been able to reconcile myself to, as anything but hypothetical. The conditions which govern electro-magnetic radiation, disprove the theory in many particulars. The vortex action induced in space, by the differential conflict between the low and high tenuous, shows up results that harmonize with the conditions accompanying the dissociation of hydrogen and oxygen, in disintegrating water: viz., vortex action of the highest order, but peripheral only. If it were not so, the ether could not be held in suspension, neither in the molecular nor atomic envelopes. Undulatory effects are produced by certain conditions of sound; and by other conditions quite opposite effects. In organ pipes, of a certain calibre, very sensitive waves occur at intervals; as according to the character of the sound evolved; but on a combination of resonators composed of brass tubes of more than nine in number, a wave of sound, induced by certain chords passing over them, produces high vortex action of the air enclosed in them. The vibration of tuning forks induces alternate conditions of the air that surrounds them, if in open atmosphere; but quite a different action presents itself when the forks are exercised in resonating tubes, set to thirds of the mass chord they represent. Then high vortex action is the instant result. Vibrators cannot be set promiscuously in tubes, and get such results, any more than a musician can render a musical composition on the violin before tuning it. The conditions under which light is evolved negatize whatever is associated with undulation, as this word is understood by physicists. Aqueous undulations there are, but not etheric undulations. "The mighty forces latent in corpuscular matter, by which we are surrounded, are all held in oscillating vortex action by the Infinite Designer of workings hidden from us, until the time is ripe for their disclosure. This latent, registered power interchanges sympathetically with the celestial radiating streams, whereby light, heat, electricity, magnetism and galvanic action are propagated in their different orders, vitalizing all nature with their life-giving principles. When this great scientific and religious truth has been made known, and established by demonstration, all controversy as to the source of energy will be for ever silenced. If I am the chosen instrument to develop this knowledge, and to make known the conditions which surround this pure truth, it is only that I may hand the key to those who will use it to enter the doorway that opens into the inaudible, and thus gain an insight into the now invisible region of the operation of Nature's most powerful governing forces, in the control, over terrestrial mind by celestial matter." APPENDIX II. The flow of electricity, as set down in Keely's system, is governed by triple conditions: 1st. the dominant or high vibratory; 2nd. the sub-dominant or low vibratory; 3rd. the harmonic or undulatory; in combination one flow. Keely writes:--"When electrical experts can construct a mechanical device whereby the low vibratory conditions of the sub-dominant can be assimilated to the harmonic undulatory, by thirds, they will be able to run their dynamos without any extraneous appliances. An introductory impulse, on a certain order of vibration, being all that would be required to give the sub-dominant a concordant relation to the dominant; which would more effectually operate the dynamo than any number of steam-engines; allowing the harmonic stream to be the governor. This concordance, as towards the dominant, would only excite its sympathetic action in a way that would divert the ruling conditions of the two, without being submitted to the destructive effects of the dominant current. I think many lives will be lost before such a position is attained. Tesla has reached out almost to the crest of the harmonic wave, leaving all electrical explorers far behind him. It is only when such a condition is reached that the true value of electrical lighting will be understood, and extraneous power dispensed with; but, in my opinion, the present conditions for transferring power will remain unaltered, in the use of electricity, for generations. "There is but one position to arrive at, that will redeem the many failures of the past decade, in attempts to find an economizing medium for commercial benefit in regard to power; and that position will be attained when the polar sympathetic harness is completed, which will give to the world the control of the polar forces." In reply to the question, "What do you include in the polar forces?" Keely answers, "Magnetism, electricity, and gravital sympathy; each stream composed of three currents, or triune streams, which make up the governing conditions of the controlling medium of the universe: the infinite ninths that I am now endeavouring to graduate to a sympathetic mechanical combination, will, if I succeed, close my researches in sympathetic physics, and complete my system. These sympathetic streams from celestial space, percussing on the dense atmospheric environment of our earth, by their infinite velocities, wrest from their atomic confinement the latent energies which we call heat and light." Question.--And where do these sympathetic conditions or streams of force have their origin? Answer.--'So God created man in His own image, in the image of God created He him: male and female created He them,' Genesis i. 27. All sympathetic conditions, or streams of force, are derived (if we dare to make use of such a term in speaking of Deity) from the cerebral convolutions of the Infinite: from the centre of the vast realm of the compound luminous. From the celestial intermediate, the brain of Deity, proceed the sympathetic flows that vitalize the polar terrestrial forces."--Keely. APPENDIX III. Some faint idea of the infinite patience which the nature of Keely's work requires may be gained by a knowledge of his process of converting straight tubes into resonating rings. The tubes, in sections long enough to form a semicircle, are passed between triple rollers, which are set to give them a slight bend. They are then fastened to a bed-plate, and a steel ball, the exact diameter of the interior of the tube, is passed into it and forced through it. It is then passed between the rollers again; which are set so as to slightly increase the curvature, and again the interior of the tube is corrected by the steel ball. This process is intermittently continued until the semicircle is reached. Each process of bending and correcting requires over two hours. Eighty bends are sometimes necessary for the completion of the full circle. When the two semicircles, which form the circle, are finished, they are placed in a steel mould and kept under hydraulic pressure for two or three days, to correct any lateral deflection which has taken place in bending them. They are then taken out of the moulds and screwed rigidly to a face-plate, and joined together by a solder of refined brass and silver. Next they are placed in a hot sand bath of sufficient volume to require seventy-two hours to cool down. This corrects the differentiation in their molecular groupings. They are then submitted to a vibratory flow from the sympathetic negative transmitter, until their intonation, by percussion, represents a pure unmixed chord. The indicator, attached to the rings, denotes when this condition is attained. They are then centred on a steel shaft and rotated at the rate of 2000 revolutions per minute, surrounded by the triple circuit ring. If the indicator, on the circuit ring, should vary five degrees on a subdivision of 8000, the process for correcting has to be repeated until the variations are reduced to three; which is near enough to be considered perfect, inasmuch as the circular resonator will then hold the neutral focalization intact during the graduation of the full ninths, or triple triplets, for sympathetic association to polar negative attraction. Professor Dewar's recent brilliant achievements, in his line of experimental research, not only have an important bearing upon one of the greatest problems of modern science, but upon the science of the future, as forecast by Keely. Thermal radiation (and its negative, cold), the field of Professor Dewar's researches, in Keely's system comes below the first atomic; while celestial sympathetic radiation comes as the fountain head; the compound inter-etheric, from which all aggregated matter springs, the governing force of all aggregations. If there were no sympathetic radiation from the great celestial centre, space would be void of suspended, or floating, earthy and gaseous matter; consequently, planetary worlds would never have had their birth and growth. The suggestion of Professor Dewar, that an increase in low temperatures might lead to the liquefying of hydrogen, is an admission that hydrogen may be a compound; for no simple can ever be condensed into a visible form. Keely's experimental researches have proved, to his own satisfaction, that all known gases are compounds, inasmuch as, when the intensity which accompanies sympathetic vibration, in his process, is brought to bear upon any gas, it submits to dissociation. The low temperatures with which Professor Dewar is dealing cause molecular motion to cease; but the matter thus experimented upon is not "dead matter" after this cessation of motion. Nothing can rob matter of the latent energy which it contains; water is not robbed of it by being frozen. The oxygen and hydrogen still occupy their relative positions and conditions, without depreciation of their vitality. Were water dead matter when frozen, its molecular activity could not be restored by elevating its temperature. Matter can never be robbed of its soul by any conditions of intensity of heat nor of cold that could be brought to bear upon it. When Professor Dewar uses the term "dead," in regard to matter, it is purely in reference to the present orthodox theory of heat energy. Take the analogy of a tuning fork or a bell; both are dead, so far as sound is concerned, if they are not in vibration;--they can be examined at rest or in motion, but science has not yet been able to do the same thing with those general motions of a molecular nature called heat. This is what Professor Dewar means by the term "dead," knowing well that the molecular activity can return alike to the fork or the molecule; only the energy must be supplied from some other source. Such are the conditions with which orthodox science is dealing, without acknowledging Deity as the fountain head of all force. Not until Professor Dewar has witnessed the dissociation of hydrogen will he be able to judge of the truth of the claim, that for nearly twenty years Keely has been researching the nature of the product of this dissociation: leading him to define and classify force and energy very much as Grant Allen has done in his heretical work, on this subject, published by Longmans & Co., in 1887. James B. Alexander, in his book on "The Dynamic Theory," [32] makes this distinction between Force and Energy: "Energy is simply the motion of material bodies, large or small. Force is the measure of energy, its degree or quantity.... The ether is the universal agent of Energy, and the medium in all motion and phenomena. It may with propriety be called the Soul of Things." TO JOHN ERNST WORRELL KEELY. "Palmam qui meruit ferat." Prized secret of aerial space Is thine! Not firmly caught Without long years of patient toil-- Of more than giant thought. Unfaltering thy steadfast faith, In all its wise control, 'Mid insults, taunts and sneers, enough To crush the bravest soul. Such the ordeal on the paths Of Stephenson, Daguerre, Of Fulton, Goodyear, Morse, to which They gave no heed nor care. Like them still fearless thou hast toiled With heart and will intense, Until discovery now brings Its grandest recompense. Displaced all powers known, before This force of latest birth; So great no mind can comprehend-- No being born of earth. We hail thee, revolutionist From every point of view; For from the marvels thou hast wrought Science must start anew. Longed-for-attainment now is grasped, Thy cherished hopes to bless; And near at hand stands thy reward In laurel crowned success! Anonymous, in Cincinnati Illustrated News. NOTES [1] This electrician took the first box of stored electricity from Paris to Sir William Thomson (now Lord Kelvin) in Edinburgh; and as early as in 1884 he had convinced himself that Keely had grounds for his claims as a discoverer of an unknown force in nature. [2] The stretching of a catgut chord over a resonator set to the chord of B flat is precisely the same in its resultant issue as the steel wire set over the same resonator. [3] In Latin "circulator" means "quack." [4] Keely was obliged to return to his former method soon after, for in overcoming one difficulty he found a more obstinate one to contend with. [5] A system of Pendulums tuned to swing the various ratios of the musical scale, form a "Silent Harp" of extraordinary interest. This "Silent Harp," D. C. Ramsay, of Glasgow, has shown to his students of harmony for many a year. A pen, placed by means of a universal-jointed arrangement between any two pendulums of this "Silent Harp," so as to be moved by a blend of their various motions, writes, with all the precision of gravitation, a portrait of the chord which two corresponding strings of a sounding harp would utter to the ear. This spiral writing is a Pendulograph; exquisite forms such as no human hand could trace. [6] By his advocacy of Keely's claims, as a discoverer, Major Ricarde-Seaver had reason to fear that he would lose his election to membership of the Athenæum Club in London; as he was notified by Sir William Thomson (who had proposed him for membership in or about the year 1873) that such would probably be the case. The members however, rallied in force and, led by one of the Major's oldest friends Prince Lucien Buonaparte, he was elected by an overwhelming majority. [7] The Philadelphia Inquirer of March 30, 1890, copied this article from Anglo-Austria, headed "The Keely Motor: some observations on the invention from a foreign publication." [8] From the Evening Telegraph, Philadelphia, April 13th, 1890: headed "Professor Leidy's Adherence to the New Force." [9] From Lippincott's Magazine, July, 1890. Edited by J. M. Stoddart. [10] Quotation from one of Keely's letters in 1885. [11] The steam engines of the world now represent the work of 1,000,000,000 men, or more than double the working population of the earth, whose total population is about 1,500,000,000 inhabitants. Steam has accordingly trebled man's working power, enabling him to economize his physical strength while attending to his intellectual development. Our race, which seems to have reached its limit of physical development, is ready to enter upon the foretold stage of psychical evolution. [12] Carried out in the taking of the forts one after another during our civil war, which other generals had been unable to do. [13] The paper which Mr. J. F. Nisbet was commissioned to write, in behalf of this discoverer's claims on the world for patience, while pursuing his researches (and paid in advance for writing), illustrates the truth of this assertion. Mr. Nisbet's essay, entitled "The Present Aspect of the Molecular Theory, or Mr. Keely's Relations to Modern Science," closes with these lines:--"If science looks askance at Mr. Keely's professions, therefore, it has its reasons for doing so. These reasons, as I have shown, are not mere prejudices. In more than one line of inquiry they have, what seems to be, a substantial basis of fact, which must be explained away before Mr. Keely's theory of 'etheric force' can commend itself to the mind of the impartial observer." Fortunately, for the interests of science and of humanity, the threatened prosecution of Mr. Keely (for obtaining money under false pretences) was checkmated by Provost Pepper's action, early in January, before Mr. Nisbet wrote to America that he could not commence his paper until he had received more information; sending a series of questions to be answered by Mr. Keely. The superficial character of the essay will be seen, when printed, as well as that Mr. Nisbet promised more than he was able to perform when he accepted the cheque in order to enable him to devote time to the writing of a paper, for an influential quarter, which it was hoped would enlist public sympathy in Keely's behalf. But that power which is mightier than the sword, in putting down error and injustice, has hitherto turned its weapons against Keely (with some rare exceptions) as Mr. Nisbet did in his essay.--C.J.M. [14] This is effected by polarization and depolarization, and the rotation of a non-magnetic needle by molecular differentiation: both needles revolving about 120 times in a second. [15] Electricians are now admitting that, in electric currents the energy does not flow through, or along the wire, itself; but is actually transmitted by the ether vibrations outside of the wire, just as in Keely's experiments, running his musical sphere with a fine "thread" of silk, the energy is not transmitted through the sewing-silk, which acts only as the medium that makes the transfer of energy in this way possible; though not itself transferring it. [16] See "Jacob Böhme, his Life and Teaching; or, Studies in Theosophy," by Dr. Hans Lassen Martensen. [17] The apparent comprehension of Keely's discovery by Mr. Nisbet, was what led the compiler of this work to apply to him for help, in making known the nature of the researches which Keely is pursuing, at the time that Keely was threatened with imprisonment, in 1890, for obtaining money under false pretences. [18] Mr. Keely explains the energy he is handling to be a condition of sympathetic vibration, associated with the Polar stream of our planet, positively and negatively. [19] Mr. B. (not Browne) was afterwards discovered to be an inventing journalist, who had been "disappointed of gain," and whose statements concerning Dr. Leidy had to be corrected. [20] Professor Dewar's visit to Keely's workshop has been delayed until he goes to America as Royal Commissioner this year. [21] One of Keely's researching instruments. [22] The universal physical law of molecular vibration is finely illustrated in the carbon pencils of the electric arc light used in some of the largest lighthouses. The molecular stir set up in the armatures of the dynamo machines by rapid magnetization and demagnetization is transmitted to the carbon points of the lantern, and reappears as a distinct musical tone. [23] It will be a matter of interest to those who have given attention to the laws of heredity to know that John Ernst Worrell Keely is a grandson of a German composer, Ernst, who led the Baden-Baden orchestra in his day; and that Keely's experiments in vibration had their origin in his knowledge of music, and were commenced in his childhood. [24] See "Untrodden Ground in Astronomy and Geology." [25] There are some paradoxical conditions shown up in the disintegration of water which require further research to get at the solution. In disintegrating, say five drops of water in a steel bulb of two cubic inches volume of atmospheric air, the force generated by the triple order of vibration, when weighed on a lever, shows ten tons pressure per square inch. In using the same number of drops in the same bulb, and associating it with a tube of two hundred cubic inches, the result is the same in the force developed per square inch as is shown on the volume of the one of two cubic inches. The solution of this problem seems to rest in the fact that the gaseous element thereby induced even in minute quantities, must possess the property of exciting atmospheric air to that extent as to force it to give up, to quite an extended degree, the latent energy that is held in its corpuscular depths. This introductory medium seems to act on the air in the same manner that a spark of fire acts on a magazine of gunpowder. [26] The ether is the capsule to the molecules and atoms all the way up to the perfect stream of structural ether. [27] A volume of pure ether equivalent to the atmospheric displacement caused by our Earth, could be compressed and absorbed in a volume of one cubic inch, by the velocity and sympathetic power of the etheric triple flows, focalizing toward the neutral centre, at the birth of the molecule. [28] This is what Keely terms "sympathetic outreach." [29] A facetious journalist commenting on this paper reprints its last paragraphs as "the only part that is perfectly lucid to the lay mind," continuing:--"We trust Keely will continue to bombard his corpuscles until he accomplishes it. And when he does, all other scientific men of this or any other age will sink by comparison into insignificance. Let no man say he cannot do it. Mr. Keely, the world is still waiting for you." [30] Platina wires the thickness of a fine hair associated with each of the nine nodal beads, and concentrated towards a general centre of localization, attaching the other end of the wires to the focal centre, will determine, by the magnetic conduction, the number of corpuscular oscillations per second induced by a thought, either positive or negative, in the central centres. These are the only conditions--those of magnetic conduction--whereby the evolution of a thought can be computed in regard to its force under propagation, as against the amount of latent energy set free to act as induced by such thought on the physical organism. [31] It is always interesting to trace the germ of a scientific idea, hypothesis, or established truth. A writer in La Lumière Electrique, vol. xlv., has drawn attention to the fact that Descartes gave a theory of magnetism, in 1656, which resembles the modern conception of lines of stress in the ether. He considers that all magnets are traversed by a subtle fluid which flows out at the North Pole, and curving round, in the ether, re-enters at the South Pole, thus completing the circuit. Some of the greatest doctrines of science have recurred again and again, like the motif of a piece of music, until they finally assume a definite shape and become a working part of human progress; as will be seen when Keely's system is recognized. [32] "The Dynamic Theory of Life and Mind." The Housekeeper Press, Minneapolis, Minn. 
39225	----	+------------------------------------------------------------------+ | TRANSCRIBER'S NOTES | | | | Transcriptions used in this e-text: | | italics text in the original work is presented here between | | underscores, as in _text_; | | bold-face text in the original work is presented here between | | equal-signs, as in =text=; | | small-capitals in the original work are presented here as ALL | | CAPITALS; | | fractions are transcribed as, for example, 2-1/2 for 2½; where | | the author uses the form 1-64, this form has been retained, | | except in tables; | | superscript texts are transcribed as in ^{text}; | | subscript texts are transcribed as in _{text}; | | single Greek letters are transcribed as [alpha], [beta], etc.; | | the (single) oe-ligature used in the book has been transcribed | | as oe (Phoenixville); | | multi-line in-line formulas and calculations from the original | | work have been transcribed as single-line in-line formulas and | | calculations, where necessary with the addition of brackets. | | The following transcriptions are used for special characters and | | symbols, where x can be any character: | | [=x] x-macron; | | [)x] x-breve; | | [x.] x-dot-below; | | [<--] left-pointing hand. | | The author uses letters from a different font to describe shapes.| | These are transcribed between square brackets: [V] or [V]-shaped,| | [T] or [T]-shaped, etc. Where the original work uses regular | | letters for the same purpose, this transcription has not been | | used. Special cases are __|¯¯ for a stretched S-shape, [/\] for | | an upside-down V, and [_|_] for an upside-down T. | | | | More extensive Transcriber's Notes will be found at the end of | | this text. | +------------------------------------------------------------------+ [Illustration: _VOL. I. MODERN MACHINE-SHOP PRACTICE FRONTISPIECE_ _Copyright, 1887 by Charles Scribner's Sons._ =MODERN AMERICAN FREIGHT LOCOMOTIVE.=] MODERN MACHINE-SHOP PRACTICE BY JOSHUA ROSE, M.E. ILLUSTRATED WITH MORE THAN 3000 ENGRAVINGS VOLUME I. NEW YORK CHARLES SCRIBNER'S SONS 1887 COPYRIGHT, 1887, BY CHARLES SCRIBNER'S SONS Press of J. J. Little & Co. Astor Place, New York. PREFACE. MODERN MACHINE-SHOP PRACTICE is presented to American mechanics as a complete guide to the operations of the best equipped and best managed workshops, and to the care and management of engines and boilers. The materials have been gathered in part from the author's experience of thirty-one years as a practical mechanic; and in part from the many skilled workmen and eminent mechanics and engineers who have generously aided in its preparation. Grateful acknowledgment is here made to all who have contributed information about improved machines and details of new methods. The object of the work is practical instruction, and it has been written throughout from the point of view, not of theory, but of approved practice. The language is that of the workshop. The mathematical problems and tables are in simple arithmetical terms, and involve no algebra or higher mathematics. The method of treatment is strictly progressive, following the successive steps necessary to becoming an intelligent and skilled mechanic. The work is designed to form a complete manual of reference for all who handle tools or operate machinery of any kind, and treats exhaustively of the following general topics: I. The construction and use of machinery for making machines and tools; II. The construction and use of work-holding appliances and tools used in machines for working metal or wood; III. The construction and use of hand tools for working metal or wood; IV. The construction and management of steam engines and boilers. The reader is referred to the TABLE OF CONTENTS for a view of the multitude of special topics considered. The work will also be found to give numerous details of practice never before in print, and known hitherto only to their originators, and aims to be useful as well to master-workmen as to apprentices, and to owners and managers of manufacturing establishments equally with their employees, whether machinists, draughtsmen, wood-workers, engineers, or operators of special machines. The illustrations, over three thousand in number, are taken from modern practice; they represent the machines, tools, appliances and methods now used in the leading manufactories of the world, and the typical steam engines and boilers of American manufacture. The new PRONOUNCING AND DEFINING DICTIONARY at the end of the work, aims to include all the technical words and phrases of the machine shop, both those of recent origin and many old terms that have never before appeared in a vocabulary of this kind. The wide range of subjects treated, their convenient arrangement and thorough illustration, with the exhaustive TABLE OF CONTENTS of each volume and the full ANALYTICAL INDEX to both, will, the author hopes, make the work serve as a fairly complete ready reference library and manual of self-instruction for all practical mechanics, and will lighten, while making more profitable, the labor of his fellow-workmen. CONTENTS. VOLUME I. CHAPTER I. =THE TEETH OF GEAR-WHEELS.= PAGE =Gear-Wheels.= Spur-wheels, bevel-wheels, mitre-wheels, crown-wheels, annular or internal wheels 1 Trundle-wheels, rack and pinion-wheel and tangent screw, or worm and worm-wheel 1 The diameter of the pitch circle of 1 =Gear-Wheel Teeth.= The face, the flank, the depth or height 1 The space, the pitch line, the point, the arc pitch, the chord pitch, the line of centres 2 Rules for finding the chord pitch from the arc pitch; table of natural sines; diametral pitch; finding the arc from the diametral pitch; table of arc and diametral pitches 3 =Gear-Wheels.= The driver and follower, a train of gears 3 Intermediate gears 3 The velocity of compounded wheels 4 Finding the diameters of the pitch circles of 4 Considered as revolving levers 5 Calculating the revolutions of, and power transmitted by 5 The angular velocity of 6 =Gear-Wheels.= Hunting tooth in, stop motion of 7 =Gear-Wheel Teeth.= The requirements and nature of the teeth curves 7 Cycloidal curves for the faces of; epicycloidal and involute curves; the hypocycloidal curve; method of forming or generating the epicycloidal and hypocycloidal curves for the faces and flanks of gear teeth 8 Applications of the epicycloidal and hypocycloidal curves in the formation of gear teeth 9 The diameter of the circle for generating the epicycloidal and hypocycloidal curves; graphical demonstration that the flank curves are correctly formed to work with the face curves of the other wheel 10 Graphical demonstration that the curves are correct independent of either the respective sizes of the wheels, or of the curve generating circles 11 =Gear-Wheels.= Hand applications of the rolling or generating circle to mark the tooth curves for a pair of wheels 12 =Gear-Wheel Teeth.= The variation of curve due to different diameters of wheels or of rolling circles 12 Tracing the path of contact of tooth upon tooth in a pair of gear-wheels; definition of the "arc of approach;" definition of the "arc of recess;" demonstration that the flanks of the teeth on the driver or driving-wheel have contact with the faces of the driven wheel during the arc of approach, and with the flanks of the driven wheel during the arc of recess 13 Confining the action of the teeth to one side only of the line of centres, when motion rather than power is to be conveyed 13 Demonstration that the appearance or symmetry of a tooth has no significance with regard to its action 14 Finding how many teeth will be in constant action, the diameter of the wheels, the pitch of the teeth, and the diameter of the rolling circle being given 15 Example of the variation of tooth form due to variation of wheel diameter 15 =Gear Teeth.= Variation of shape from using different diameters of rolling circles 16 Thrust on the wheel shafts caused by different shapes of teeth 16 =Gear-Wheels.= Willis' system of one size of rolling circle for trains of interchangeable gearing 16 Conditions necessary to obtain a uniform velocity of 16 =Gear Teeth.= The amount of rolling and of sliding motion of 16 The path of the point of contact of 16 The arcs of approaching and of receding contact 16 Lengths of the arcs of approach and of recess 16 The influence of the sizes of the wheels upon the arcs of contact 17 Influence of the size of the rolling circle upon the amount of flank contact 18 Demonstration that incorrectly formed teeth cannot correct themselves by wear 18 The smaller the diameter of the rolling circle, the less the sliding motion 18 Influence of the size of the rolling upon the number of teeth in contact in a given pair of wheels 19 Demonstration that the degrees of angle the teeth move through exceed those of the path of contact, unless the tooth faces meet in a point 19 Influence of the height of the teeth upon the number of teeth in contact 20 Increasing the arc of recess without increasing the arc of approach 20 Wheels for transmitting motion rather than power 21 Clock wheels 21 Forms of teeth having generating or rolling circles, as large or nearly as large as the diameters of the wheels 21 =Gear-Wheels.= Bevel 21 The principles governing the formation of the teeth of bevel- wheels 22 Demonstration that the faces of the wheels must be in line with the point of intersection of the axis of the two shafts 22 =Gear Teeth.= Method of finding the curves of, for bevel gear 22 =Gear-Wheels.= Internal or annular 23 to 27 Demonstration that the teeth of annular wheels correspond to the spaces of spur-wheels 23 =Gear-Wheels Internal.= Increase in the length of the path of contact on spur-wheels of the same diameter, and having the same diameter of generating or rolling circle 23 Demonstration that the teeth of internal wheels may interfere when spur-wheels would not do so 23 Methods of avoiding the above interference 23 Comparison of, with spur-wheels 23 The teeth of: demonstration that it is practicable to so form the teeth faces that they will have contact together as well as with the flanks of the other wheel 24 Intermediate rolling circle for accomplishing the above result 24 The application of two rolling circles for accomplishing the above result 24 Demonstration that the result reached by the employment of two rolling circles of proper diameter is theoretically and practically perfect 24 Limits of the diameters of the two rolling circles 25 Increase in the arc of contact obtained by using two rolling circles 25 Demonstration that the above increase is on the arc of recess or receding contact, and therefore gives a smooth action 25 Demonstration that by using two rolling circles each tooth has for a certain period two points of contact 25 The laws governing the diameters of the two rolling circles 25 Practical application of two rolling circles 26 Demonstration that by using two rolling circles the pinion may contain but one tooth less than the wheel 26 The sliding and rolling motion of the teeth of 27 CHAPTER II. =THE TEETH OF GEAR-WHEELS (Continued).= =Worm and Worm-Wheel=, or wheel and tangent screw 28 to 31 General description of 28 Qualifications of 28 The wear of 28 =Worm-Wheel Teeth=, the sliding motion of 28 When straight have contact on the centres only of the tooth sides 28 That envelop a part of the worm circumference 28 The location of the pitch line of the worm 28 The proper number of teeth in the worm-wheel 29 Locating the pitch line of the worm so as to insure durability 29 Rule for finding the best location for the pitch line of the worm 29 Increasing the face of the worm to obtain a smoother action 29 =Worms=, to work with a square thread 29 =Worm-Wheels=, applications of 30 =Gear-Wheels= with involute teeth 31 to 34 =Gear Teeth.= Generating the involute curve 31 Templates for marking the involute curve 32 =Involute Teeth=, the advantages of 34 =Gear Teeth=, Pratt and Whitney's machine for cutting templates for 35 CHAPTER III. =THE TEETH OF GEAR-WHEELS (Continued).= =Gear Teeth=, revolving cutters for 37 Pantagraph engine for dressing the cutters for 38 Numbers of cutters used for a train of wheels 39 =Gear-Wheel Teeth.= Table of equidistant value of cutters 41 Depth of, in the Brown and Sharpe system 42 Cutting the teeth of worm-wheels 42 Finding the angle of the cutter for cutting worm-wheels 43 The construction of templates for rolling the tooth curves 43 Rolling the curves for gear teeth 43 Forms of templates for gear teeth 44 Pivoted arms for tooth templates 44 Marking the curves by hand 45 Former or Template of the Corliss bevel gear-wheel engine or cutting machine 45 The use of extra circles in marking the curves with compasses 46 Finding the face curves by geometrical constructions 47 The Willis odontograph for finding the radius for striking the curves by hand 47 The method of using the Willis odontograph 48 Professor Robinson's odontograph 49 Method of using Professor Robinson's odontograph 49 Application of Professor Robinson's odontograph for trains of gearing 51 Tabular values and setting numbers for Professor Robinson's odontograph 51 Walker's patent wheel scale for marking the curves of cast teeth 51 The amount of side clearance in cast teeth 53 Filleting the roots of epicycloidal teeth with radial flanks 53 Scale of tooth proportions given by Professor Willis 54 The construction of a pattern for a spur-wheel that is to be cast with the teeth on 54 Template for planing the tooth to shape 54 Method of marking the curves on teeth that are to be glued on 55 Method of getting out the teeth of 56 Spacing the teeth on the wheel rim 56 Methods of accurately spacing the pattern when it has an even number of teeth 58 Method of spacing the wheel rim when it has an odd number of teeth 58 =Gear-Wheels, Bevel Pinion=, drawings for 59 Getting out the body for a bevel-wheel 59 Template for marking the division lines on the face of the wheel 59 Marking the lines of the division on the wheel 60 =Gear-Wheels, Pinion=, with dovetail teeth 60 Testing the angle of bevel-wheels while in the lathe 60 =Gear-Wheels, Skew Bevel.= Finding the line of contact 61 Marking the inclination of the teeth 61 =Gear-Wheels, Bevel=, drawing for built up 61 =Gear-Wheels, Worm=, or endless screw 62 Constructing a pattern from which the worm is to be cast 62 Tools for cutting the worm in a lathe 62 Cutting the teeth by hand 62 =Gear-Wheels, Mortise= or cogged 63 Methods of fastening cogs 63 Methods of getting out cogs for 63 =Gear-Wheel Teeth=, calculating the strength of epicycloidal 64 Factors of safety for 64 Tredgold's rule for calculating the strength of 65 Cut, calculating the strength of 65 =Gear-Wheel Teeth.= The strength of cogs 66 The thickness of cogs 66 The durability of cogs 66 Table for calculating the strength of different kinds of 67 The contact of cast teeth 67 Table for determining the relation between pitch diameter, pitch, and number of teeth in gear-wheels 68 Examples of the use of the above table 68 With stepped teeth 69 Angular or helical teeth 69 End thrust of angular teeth 69 Herring-bone angular teeth 69 For transmitting motion at a right angle by means of angular or helical teeth 69 Cutting helical teeth in the lathe 69 For wheels whose shaft axes are neither parallel nor meeting 70 Elliptical 70 Elliptical, marking the pitch lines of 70 Elliptical, drawing the teeth curves of 73 For variable motion 74 Form of worm to give a period of rest 74 Various applications of 74 =Gear-Wheels=, arrangement of, for periodically reversing the direction of motion 75 Watt's sun and planet motion 75 Arrangements for the rapid multiplication of motion 75 Arrangement of, for the steering gear of steam fire-engines 75 Various forms of mangle gearing 79 =Gear-Wheel and Rack=, for reciprocating motion 77 =Friction Wheels.= 77 The material for 77 Paper 78 For the feed motion of machines 78 The unequal wear upon grooved 79 Form of, for relieving the journals of strain 79 =Cams=, for irregular motion 80 Finding the pitch line of 80 Finding the working face of 80 The effect the diameter roller has upon the motion produced by a cam 80 Demonstration of the different motion produced by different diameters of rollers upon the same cam 80 Diagram of motion produced from the same cam with different diameters of rollers 81 Return or backing 82 Methods of finding the shape of return or backing 82 =Cam Motion=, for an engine slide valve without steam lap 83 For a slide valve with steam lap 83 =Groove Cams=, proper construction of 84 The wear of 84 Brady's improved groove cam with rolling motion and adjustment for wear 84 CHAPTER IV. =SCREW-THREADS.= =Screw Threads=, the various forms of 85 The pitch of 85 Self-locking 85 The Whitworth 86 The United States standard 86 The Common V 86 The requirements of 86 Tools for cutting 87 Variation of pitch from hardening 87 The wear of thread-cutting tools 88 Methods of producing 88 Alteration of shape of, from the wear of the tools they are cut by 89 =Screw Thread Cutting Tools.= The wear of the tap and the die 89 Improved form of chaser to equalize the wear 90 Form of, to eliminate the effects of the wear in altering the fit 90 Originating standard angles for 91 Standard micrometer gauge for the United States standard screw thread 91 Standard plug and collar gauges for 91 Producing gauges for 92 Table of United States standard for bolts and nuts 93 Table of standard for the V-thread 93 United States standard for gas and steam pipes 93 Taper for standard pipe threads 95 Tables of the pitches and diameters at root of thread, of the Whitworth thread 95 Table of Whitworth's screw threads for gas, water, and hydraulic piping 96 Whitworth's standard gauges for watch and instrument makers 96 Screw-cutting hand tools 96 =Thread-Cutting Tools.= American and English forms of stocks and dies 97 Adjustable or jamb dies 98 The friction of jamb dies 98 The sizes of hobs that should be used on jamb dies 99 Cutting right or left-hand thread with either single, double, or treble threads with the same dies 99 Hobs for hobbing or threading dies 100 Various forms of stocks with dies adjustable to take up the wear 101 Dies for gas and steam pipes 101 =Thread-Cutting Tool Taps.= The general forms of taps 102 Reducing the friction of 102 Giving clearance to 102 The friction of taper 103 Improved forms of 103 Professor J. E. Sweet's form of tap 104 Adjustable standard 104 The various shapes of flutes employed on taps 105 The number of flutes a tap should have 105 Demonstration that a tap should have four cutting edges rather than three 106 The position of the square or driving end, with relation to the cutting edges 106 Taper taps for blacksmiths 106 Collapsing taps for use in tapping machines 107 Collapsing tap for use in a screw machine 107 The alteration of pitch that occurs in hardening 108 Gauging the pitch after the hardening 108 Correcting the errors of pitch caused by the hardening 109 For lead 109 Elliptical in cross section 109 For very straight holes 109 Tap wrenches solid and adjustable 110 =Thread-Cutting.= Tapping 110 Appliances for tapping standard work 111 CHAPTER V. =FASTENING DEVICES.= =Bolts=, classification of, from the shapes of their heads 112 Classification of, from the shapes of their bodies 112 Countersunk 112 Holes for, classification of 112 For foundations, various forms of 113 Hook bolts 113 The United States standard for finished bolts and nuts 113 The United States standard for rough bolts and nuts, or black bolts 114 The Whitworth standard for bolts and nuts 114 =Screws= 114 =Studs= 115 =Set Screws= 115 =Bolts= for quick removal 116 That do not pass through the work 117 That self-lock in grooves and are readily removable 117 Heads and their bedding 117 =Nuts=, the forms of, when they are to be steam tight 118 Various forms of 118 Jamb nuts and lock nuts 119 =Differential Threads= for locking purposes 119 For fine adjustments 119 =Nuts=, taking up the wear of 120 Securing devices 120 Securing by taper pins 121 Securing by cotters 121 Securing by notched plates 121 =Pins.= Securing for exact adjustments 121 And double eyes fitting 121 Fixed 122 Working 122 =Bolts=, removing corroded 122 =Nuts=, removing corroded 122 =Washers=, standard sizes of 122 =Wrench=, the proper angles of 123 Box 124 Monkey 125 Adjustable, various forms of 125 Sockets 125 Novel for carriage bolts 125 Pin 126 Improved form of 126 =Keys=, the various kinds of 126 The bearing surfaces of 126 =Set Screws=, application of, to hubs or bosses 127 =Keys=, with set-screws 127 The draught of 127 =Feathers=, and their applications 127 =Keys=, for parallel rods 128 =Taper Pins=, proper position of, for locking purposes 128 Improved method of fitting 128 CHAPTER VI. =THE LATHE.= =Lathe=, the importance and advantages of 129 Classification of lathes 129 Foot 130 Methods of designating the sizes of 130 Bench 130 Power 130 Hand 130 Slide Rest for 131 American form of, their advantages and disadvantages 132 English forms of 132 For spherical work 132 Methods of taking up lost motion of 133 =Engine Lathe=, general construction of 133 The construction of the shears of 134 Construction of the headstock 134 Construction of the bearings 134 Construction of the back gear 135 Means of giving motion to the feed spindle 135 Construction of the tailstock 135 Method of rapidly securing and releasing the tailstock 136 =Lathe Tailstock=, setting over for turning tapers 136 =Engine Lathe=, construction of carriage 137 Feed motion for carriage or saddle 137 =Lathe Apron=, Construction of the feed traverse 138 Construction of the cross-feed motion 138 =Engine Lathe=, lead screw and change wheels of 139 Feed spindle and lead screw bearings 139 Swing frame for lead screw 139 Lead screw nuts 140 With compound slide rest 140 Construction of compound slide rest 141 Advantages of compound slide rest 141 For taper turning 142 Taper-turning attachments 142 With compound duplex slide rest 143 Detachable slide rest 143 Three-tool slide rest for turning shafting 143 With flat saddle for chucking work on 143 =The Sellers Lathe= 143 Construction of the headstock and treble gear 144 Construction of the tailstock and method of keeping it in line 145 Construction of the carriage and slide rest 145 Methods of engaging and disengaging the feed motions 146 =Car Axle Lathe=, with central driving motion and two slide rests 147 The feed motions of 148 =Self-Acting Lathe=, English form of 148 =Pattern Maker's Lathe= 148 Brake for cone pulley 149 With wooden bed 149 Slide rest for 149 =Chucking Lathe=, English 149 Feed motions of 150 =Pulley Lathe= 150 =Gap or Break Lathe= 151 =Extension Lathe= 151 =Wheel Lathe= 151 =Chucking Lathe= for boring purposes 152 =Lathe= for turning crank axles 152 Construction of the headstock 153 Construction of the feed motions 154 For turning crank, Arrangements of the slide rests 154 Application of the slide rest to a crank 155 CHAPTER VII. =DETAILS IN LATHE CONSTRUCTION.= =Live Spindle= of a lathe, the fit of 157 With coned journals 157 Methods of taking up the end motion of 158 Arranging the swing frame for the change gears 158 Taking up the wear of the back bearing 158 The wear of the front bearing of 158 =The Taper= for the live centre 159 =Methods= of removing the lathe centres 159 =Tapers= for the live centres 159 =Methods= of removing the dead centre 159 =Driving Cone=, arranging the steps of 159 Requirements of proportioning the steps of 159 Rules for proportioning the diameters of the steps of, when the two pulleys are exactly alike and are connected by an open belt 159 to 161 When the two pulleys are unlike 161 to 164 =Back Gear=, methods of throwing in and out 165 =Conveying= motion to the lead screw 165 =Attaching= the swing frame 166 =Feed Gear.= Arrangement for cutting worm threads or tangent screws 167 =Feed Motion= for reversing the direction of tool traverse in screw cutting 168 For lathe aprons 168 =Slide Rest=, weighted elevated 168 Double tool holder for 169 Gibbed elevating 169 =Examples= of feed motions 170 =Feed Regulators= for screw cutting 171 The star feed 172 =Ratchet Feeds= 173 =Tool Holding= devices, the various kinds of 173 =Tool Rest= swiveling 174 =Tool Holder= for compound slide rests 174 For octagon boring tools 175 =Lathe Lead and Feed Screws= 175 Lead screws, supporting, long 176 Position of the feed nut 177 Form of threads of lead screws 177 The effect the form of thread has in causing the nut to lock properly or improperly 177 Example of a lead screw with a pitch of three threads per inch 177 Example of a lead screw with five threads per inch 178 Example with a lead screw of five threads per inch 179 Device for correcting the errors of pitch of 179 =Table= for finding the change wheels for screw cutting when the teeth in the change wheels advance by four 180 For finding the change wheels when the teeth in the wheels advance by six 180 Constructing a table to cut fractional threads on any lathe 181 Finding the change wheels necessary to enable the lathe to cut threads of any given pitches 181 Finding the change wheels necessary to cut fractional pitches 181 =Determining= the pitches of the teeth for change wheels 182 =Lathe Shears= or beds 182 Advantages and disadvantages of, with raised V-guide-ways 182 Examples of various forms of 183 =Lathe Shears= with one V and one flat side 183 Methods of ribbing 184 The arrangement of the legs of 184 =Lathe Tailblock= 185 With rapid spindle motion 185 With rapid fastenings and releasing devices 185 The wear of the spindles of 185 Spindles, the various methods of locking 186 Testing, various methods of 187 CHAPTER VIII. =SPECIAL FORMS OF THE LATHE.= =Watchmaker's Lathes= 188 Construction of the headstock 188 Construction of chucks for 188 Expanding chucks for 188 Contracting chucks for 188 Construction of the tailblock 189 Open spindle tailstocks for 189 Filing fixture for 189 Fixture for wheel and pinion cutting 189 Jewelers' rest for 189 =Watch Manufacturers' Lathe= 190 Special chucks for 190 Pump centre rest 190 =Lathe=, hand 191 Screw slotting 192 With variable speed for facing purposes 192 Cutting-off machine 193 Grinding Lathes 193 With elevating rest 194 Universal 195 Special chucks for 196 The Morton Poole calender roll grinding lathe 196 The construction of the bed and carriages 197 Principles of action of the carriages 197, 198 Construction of the emery-wheel arbors and the driving motion 198, 199 The advantages of 199 The method of driving the roll 200 Construction of the headstock 200 The transverse motion 200 =The Brown and Sharpe Screw Machine=, or screw-making lathe 200 Threading tools for 203 Examples of the use of 203 =The Secor Screw Machine=, construction of the headstock 204 The chuck 205 The feed gear 205 The turret 205 The cross slide 205 The stop motions 206 =Pratt and Whitney's Screw Machine= 206 Parkhurst's wire feed, construction of the headstock, chuck and feed motion 207 Box tools for 208 Applications of box tools 208 Threading tool for 208 Cutting-off tool for 208 =Special Lathe= for wood working 208 The construction of the carriage and reducing knife 209 Construction of the various feed motions 209 Construction of the tailstock 209 =Lathes for irregular forms= 210 Axe-handle 210 Back knife gauge 210 Special, for pulley turning 211 =Boring and Turning= mill or lathe 211 Construction of the feed motions 213 Construction of the framing and means of grinding the lathe 214 Construction of the vertical feed motions 215 =The Morton Poole= roll turning lathe 215 Construction of the slide rest 216 The tools for 216 =Special Lathes= for brass work 216, 217 =Boring Lathe= with traversing spindle 218 For engine cylinders 219 Cylinder, with facing slide rests 219 With double heads and facing rests 220 =Lathe for turning Wheel= hubs 221 CHAPTER IX. =DRIVING WORK IN THE LATHE.= =Drivers=, carriers, dogs, or clamps, and their defects 222 Lathe clamps 222 Equalizing drivers 223 The Clements driver 223 Driver and face plate for screw cutting 223 Forms of, for bolt heads 224 Adjustable, for bolt heads 224 For threaded work 225 For steady rest work 225 For cored work 225 For wood 225 =Centres= for hollow work 226 For taper work 226 =Lathe Mandrels=, or arbors 227 Drivers for 227 For tubular work 227 Expanding mandrels 227 With expanding cones 228 With expanding pieces 228 Expanding, for large work 228 For threaded work 228 For nuts, various forms of 229 For eccentric work 229 =Centring devices= for crank axles 230 =The Steady Rest= or back rest 231 Steady rest, improved form of 232 Cone chuck 232 Steady rest for square and taper work 233 The cat head 233 Clamps for 233 Follower rests 234 =Chucks and Chucking= 234 Simple forms of chucks 234 Adjustable chucks for true work 235 Two-jawed chucks 236 Box body chucks 237 Reversible jawed chucks 237 Three and four-jawed chucks 237 Combination chucks 237 The wear of scroll chuck threads 237 Universal chucks 238 The wear of chucks 240 Special forms of chucks 241 Expanding chucks for ring-work 241 Cement chuck 241 Chucks for wood-working lathes 242 =Lathe Face Plates= 243 Face plates, errors in, and their effects 243 Work-holding straps 244 Face plate, clamping work on 245 Forms of clamps for 245 Examples of chucking work on 246, 247 For wood work 247 =Special Lathe Chuck= for cranks 248 =Face Plate Work=, examples of 249 Errors in chucking 250 Movable dogs for 250 The angle plate 251 Applications of 251 Angle plate chucking, examples of 251 Cross-head chucking 251-253 CHAPTER X. =CUTTING TOOLS FOR LATHES.= =Principles= governing the shapes of lathe tools 254 =Diamond-pointed=, or front tool 254 =Principles= governing use of tools 254 Front rake and clearance of front tools 254 Influence of the height of a tool upon its clearance and keenness 255 Tools with side rake in various directions 256 The effect of side rake 256 The angle of clearance in lathe tools 257 Variation of clearance from different rates of feed and diameters of work 257 =Round-nosed= tools 258 =Utmost Duty= of cutting tools 258 Judging the quantity of the tool from the shape of its cutting 259 =Square-nosed= tools 260 The height of lathe tools 260 Side tools for lathe work 261 Cutting-off or grooving tools 262 Facing tools or knife tools 262 Spring tools 263 =Brass Work=, front tools for 264 Side tools for 264 =Threading= tools 264 Internal threading tools 264 The length of threading tools 265 The level of threading tools 265 Gauges for threading tools 266 Setting threading tools 266 Circular threading tools 267 Threading tool holders 267 =Chasers= 268 Chaser holders 268 Setting chasers 268 =Square Threads=, clearance of tools for 269 Diameter at the roots of threads 269 Cutting coarse pitch square threads 269 Dies for finishing square threads 269 =Tool Holders= for outside work 270 For circular cutters 272 Swiveled 273 Combined tool holders and cutting-off tools 273 =Power Required= to drive cutting tools 273 CHAPTER XI. =DRILLING AND BORING IN THE LATHE.= =The Twist Drill= 274 Twist drill holders 274 The diametral clearance of twist drills 274 The front rake of twist drills 275 The variable clearance on twist drills as usually ground 275 Demonstration of the common error in grinding twist drills 276 The effects of improper grinding upon twist drills 276 Table of speeds and feeds for twist drills 277 Grinding twist drills by hand 279 Twist drills for wood work 279 =Tailstock Chucks= for drilled work 279 =Flat Drills= for lathe work 280 Holders for lathe work 281 =Half-round= bit or pod auger 281 With front rake for wrought iron or steel 281 With adjustable cutter 281 For very true work 281 =Chucking Reamer= 281 The number of teeth for reamers 282 Spacing the teeth of reamers 282 Spiral teeth for reamers 282 Grinding the teeth of reamers 282 Various positions of emery-wheel in grinding reamers 282 Chucking reamers for true work 283 Shell reamers 283 Arbor for shell reamers 283 Rose-bit or rose reamers 283 Shell rose reamers 284 Adjustable reamers 284 Stepped reamers for taper work 285 Half-round reamers 285 Reamers for rifle barrels 285 =Boring Tools= for lathe work 285 Countersinks 285 Shapes of lathe boring tools 285 Boring tools for brass work 286 The spring of boring tools 286 Boring tools for small work 287 Boring tool holders 287 =Boring Devices for Lathes= 288 =Boring Heads= 288 =Boring Bars= 289 Boring bar cutters 289 Three _versus_ four cutters for boring bars 290 Boring bars with fixed heads 290 With sliding heads 290 Bar cutters, the shapes of 291 Boring head with nut feed 291 Boring bars for taper work, various forms of 292 Boring double-coned work 293 Boring bar, centres for 293 =Cutting Speeds= and feeds for wrought iron 294 Examples of speeds taken from practice 295 CHAPTER XII. =EXAMPLES IN LATHE WORK.= =Technical Terms= used in the work 296 =Lathe Centres= 296 Devices for truing 297 Tools for testing the truth of, for fine work 298 Shapes of, for light and heavy work 299 =Centre Drilling=, attachment for lathes 300 The error induced by straightening work after 300 Machine 300 Combined centre-drill and countersink 300 Countersink with adjustable drill 300 Centring square 300 Centre-punch 300 Centre-punch guide 301 Centring work with the scribing block 301 Finding the centre of very rough work 301 Centre-drill chuck 302 The proper form of countersink for lathe work 302 Countersinks for lathe work 302 Various forms of square centres 303 The advantage of the square centre for countersinking 303 Novel form of countersink for hardened work 303 Chucks for centre-drilling and countersinking 303 Recentring turned work 304 =Straightening Work.= Straightening machine for bar iron 304 Hand device for straightening lathe work 305 Chuck for straightening wire 305 =Cutting Rods= into small pieces of exact length, tools for 305 =Roughing cuts=, the change of shape of work that occurs from removing the surface by 306 Feeds for 306 Rates of feed for 307 =Finishing Work=, the position of the tool for 307 Finishing cast-iron with water 307 Specks in finished cast-iron work 307 Scrapers for finishing cast-iron work 307 Method of polishing lathe work 308 Filing lathe work 308 The use of emery paper on lathe work 308 The direction of tool feed in finishing long work 309 Forms of laps for finishing gauges or other cylindrical lathe work 310 Forms of laps for finishing internal work 311 Grinding and polishing clamps for lathe work 311 Burnishing lathe work 311 =Taper Work=, turning 312 The wear of the centres of 312 Setting over the tailstock to turn 312 Gauge for setting over 313 Fitting 313 Grinding 313 The order of procedure in turning 313 The influence of the height of the tool in producing true 314 =Special Forms.= Curved work 314, 315 Standard gauges for taper work 316 Methods of turning an eccentric 317 Turning a cylinder cover 318 Turning pulleys 318 Chucking device for pulleys 318 =Cutting Screws= in the lathe 319 The arrangement of the change gears 319 The intermediate wheels 319 The compounded gears 320 Finding the change wheels to cut a given thread 320 Finding the change wheels for a lathe whose gears are compounded 321 Finding the change gears for cutting fractional pitches 321 To find what pitch of thread the wheels already on the lathe will cut 322 Cutting left-hand threads 322 Cutting double threads 322 Cutting screws whose pitches are given in the terms of the metric system 322 Cutting threads on taper work 323 Errors in cutting threads on taper work 324 CHAPTER XIII. =EXAMPLES IN LATHE WORK (Continued).= =Ball Turning= with tubular saw 325 With a single tooth on the end of a revolving tube 325 With a removable tool on an arbor 325 Tool holder with worm feed 325 By hand 325 =Cams=, cutting in the lathe 326 Improved method of originating cams in the lathe 326 Motions for turning cams in the lathe 326, 327 Application of cam motions to special work 327 Cam chuck for irregular work 328 =Milling= or knurling tool 328 Improved forms of 328 =Winding Spiral Springs= in the lathe 329 =Hand Turning= 330 The heel tool 330 The graver and its applications 330, 331 Hand side tools 331 Hand round-nosed tools for iron 331 Hand finishing tool 331 =Hand Tools=, for roughing out brass work 332 Various forms and applications of scrapers 332, 333 Clockmakers' hand tool for special or standard work 334 Screw cutting with hand tools 334 Outside and inside chasers 334 Hobs and their uses 335 The application of chasers, and errors that may arise from the position in which they are presented to the work 336 Errors commonly made in cutting up inside chasers 337 V-tool for starting outside threads 337 Starting outside threads 338 Cutting taper threads 338 Wood turning hand tools 338 The gauge and how to use it 338 The chisel and its use 339 The skew chisel and how to use it 339 Wood turners' boring tools for lathe work 340 CHAPTER XIV. =MEASURING MACHINES, TOOLS AND DEVICES.= =Standards of Measurements=, in various countries 341 Use of, by sight and by the sense of feeling 341 Variations in standard gauges 341 The necessity for accurate standards 341 The Rogers Bond standard measuring machine 342 Details of construction of 343, 344 The principle of construction of 344 The methods of using 345 The Whitworth measuring machine 345 The Betts Machine Company's measuring machine 346 Professor Sweet's measuring machine 347 Measuring machine for sheet metal 348 =Circle=, division of the 348 Troughton's method of dividing the circle 348, 349 Ramsden's dividing engine 349 The construction of 350, 351 Pratt and Whitney's dividing device 352 Practical application of 353 Index wheel, method of originating, by R. Hoe & Co. 353 Application of the index wheel (Hoe & Co.'s system) 353 =Classification= of the measuring tools used by workmen 354 =Micrometer Caliper= and its principle of construction 354, 355 =Gauges.= Standard plug and collar gauges 356 Methods of comparing standard plug and collar gauges 356 The effects of variations of temperature upon standard gauges 356 Plug and collar gauges for taper work 357 The Baldwin standards for taper bolts 359 Workmen's gauges for lathe work 359 =Calipers=, outside, the various forms of 360 Inside calipers 360 Calipers with locking devices 360 Spring calipers 360 The methods of holding and using 361, 362 Keyway calipers 363 The advantages of calipers 363 =Fitting.= The four kinds of fit in machine work 363 The influence of the diameter of the work in limiting the application of standard gauges 363 The wear of tools and its influence upon the application of the standard gauge system 364 The influence of the smoothness of the surface upon the allowance to be made for drilling or hydraulic fits 365 Examples of allowance for hydraulic fits 365 Parallel holes and taper plugs for hydraulic fits 365 =Fitting.= Practicable methods of testing the fit of axle brasses forced in by hydraulic pressure 366 Shrinkage or contraction fits 366 Allowances for 366 Gauge for 367 The shrinkage system at the Royal Gun Factory at Woolwich 367 Experiments by Thomas Wrightson upon the shrinkage of iron under repeated heatings and coolings 368 to 374 Shrinking work, to refit it 374, 375 CHAPTER XV. =MEASURING TOOLS.= =End Measurements= of large lathe work 376 Template gauges for 376 Trammels or Trains 377 Adjustable gauges for 377 =Compasses=--Dividers 377 Compass calipers 378 =Key Seating= rule 378 =Surface Gauge= 378 Pattern makers' pipe gauge 379 =Squares.= The try square 379 The T square 379 Various methods of testing squares 379, 380 Bevel squares 380 =Bevel Protractors= 380 =Hexagon Gauge= 381 =Straight Edge= and its applications 381, 382 Winding strips and their application 382 =Surface Plate= or planimeter 383 =Templates= for curves 384 =Wire Gauges=, notch 384 Standard gauges for wire, &c. 384, 386 Gauge for music wire 386 Brown and Sharpe wire gauge 387 Birmingham wire gauge for rolled shell silver and gold 387 Sheet iron gauge, Russian 387 Galvanized iron 387 Belgian sheet zinc 387 American sheet zinc 387 =Rifle Bore= gauge 387 =Strength of Wire=, Kirkaldy's experiments 387, 388 CHAPTER XVI. =SHAPING AND PLANING MACHINES.= =General description= of a shaping machine 389 =Construction= of swivel head 389 Slide 390 Vice chuck 390 Feed motion 390 =Hand= shaping machine 392 =Quick Return Motion=, Whitworth's 392 =Vice Chucks=, the principles of construction of plain, for planing machine 392 The proper methods of chucking work in 393 Holding taper work in 394 Various forms of 394 Swiveling 395 Rapid motion 396 For vice work 396 =Centres= for shaping machines 397 =Traveling Head= in shaping machine 397 =Planer Shapers= or shaping machines, having a tappet motion for reversing the direction of motion 398, 399 =Quick Return Motion= shaping machines, link 399 The Whitworth 400 Comparisons of the link motion and Whitworth 401 =Simple Crank=, investigating the motion of 401 =Planing Machines=, or planer 402 The various motions of 402, 403 The table driving gear 404 Planing machine with double heads 404 Rotary planing machine 405 CHAPTER XVII. =PLANING MACHINERY.= =The Sellers= planing machine 406 The belt shifting mechanism 406, 407 The automatic feed motions 408 =Sliding Head= 408 =Cross Bar= 409 =Slides of Planers=, the various forms of construction of 410 =Wear of the Slides= of planer heads, various methods of taking up the 410 =Swivel Heads= 411 =Tool Aprons= 411 =Swivel Tool-holding devices= for planers 411 =Planer Heads=, graduations of 412 Safety devices for 413 Feed motions for 414 V-guideways for 414 Flat guideways for 415 Oiling devices for 415 =Planing Machine Tables= 415 Slots and holes in planing machine tables 416 Forms of bolts for planer tables 417 Supplementary tables for planer tables 417 Angle plates for planer tables 418 Chucking devices for planer tables 418 =Planer Centres= 418 =Planer Chucks= 419 For spiral grooved work 419 For curved work 420 Chucking machine beds on planer tables 420 For large planing machines 422 Chucking the halves of large pulleys on a planer 423 =Gauges= for planing V-guideways in machine beds 421 Planing guideways in machine beds 422 Gauge for planer tools 424 =Planer Tools=, the shapes of 424 For coarse finishing feeds 424 The clearance of 424 For slotted work 424 =Planer Tool Holder=, with tool post 425 Various applications of 425 Simple and advantageous form of 426 Examples of application of 426 CHAPTER XVIII. =DRILLING MACHINES.= =Drilling Machines.= General description of a power drilling machine 428 Lever feed 428 With automatic and quick return feed motions 428 Improved, with simple belt and uniform motion, two series of rates of automatic feed, and guide for boring bar 429, 430 Radial 430, 431 For boiler shells 436 Cotter or keyway 438 Drilling Machine, three-spindle 434 Four-spindle 434 =Drilling and Boring= machine 431 Feed motion of 432 =Combined Drilling Machine= and lathe 433 =Boring Machine=, horizontal 433 For car wheels 438 For pulleys 438 =Quartering Machine= 434 =Drilling and Turning Machine= for boiler makers 435 Feed motions of 436 CHAPTER XIX. =DRILLS AND CUTTERS FOR DRILLING MACHINES.= =Jigs or Fixtures= for drilling machines 439 Limits of error in 439 Examples of, for simple work, as for links, &c. 440 Considerations in designing 440 For drilling engine cylinders 440 to 441 For cutting out steam ports 441 =Drills and Cutters= for drilling machines 442 Table of sizes of twist drills, and their shanks 442 Flat drills for drilling machines 442 Errors in grinding flat drills 443 The tit-drill 443 The lip drill 443 Cotter or keyway drills 446 =Drilling holes= true to location with flat drills 444 Drilling hard metal 444 Table of sizes of tapping holes 445 =Drill Shanks= and sockets 445 Improved form of drill shank 446 Square shanked drills and their disadvantages 446 =Drill Chucks= 446 =Stocks and Cutters= for drilling machines 447 Tube plate cutters 448 =Stocks and Cutters.= Adjustable stock and cutter 448 Facing tool with reamer pin 449 Counterbores for drilling machines 449 Drill and counterbore for wood work 449 Facing and countersink cutters 449 Device for drilling square holes 450 Device for drilling taper holes in a drilling machine 451 CHAPTER XX. =HAND-DRILLING AND BORING TOOLS, AND DEVICES.= =The Brad-awl= 452 =Bits.= The gimlet bit 452 The German bit 452 The nail bit 452 The spoon bit 452 The nose bit 453 The auger bit 453 Cook's auger bit 453 Principles governing the shapes of the cutting edges of auger bits 453 Auger bit for boring end grain wood 453 The centre bit 454 The expanding bit 454 =Drills.= Drill for stone 454 The fiddle drill 455 The fiddle drill with feeding device 455 Drill with cord and spring motion 455 Drill stock with spiral grooves 455 Drill brace 455 Drill brace with ratchet motion 456 Universal joint for drill brace 456 Drill brace with multiplying gear and ratchet motion 456 Breast drill with double gear 456 Drilling levers for blacksmiths 457 Drill cranks 457 Ratchet brace 457 Flexible shaft for driving drills 458 Drilling device for lock work 459 Hand drilling machine 459 =Slotting Machine= 459 Sectional view of 460 Tool holders 460, 461 Tools 461, 462 CHAPTER XXI. =THREAD-CUTTING MACHINERY AND BROACHING PRESS.= =Pipe Threading=, die stock for, by hand 463 Die stock for, by power 463 Pipe threading machines, general construction of 463 =Bolt Threading= hand machine 464 With revolving head 465 Power threading machine 465 With automatic stop motion 466 Construction of the head 466 Construction of the chasers 466 Bolt threading machine with back gear 467 Single rapid bolt threading machine 467 Double rapid bolt threading machine 467 Construction of the heads of the rapid machines 468 Bolt threading machinery, the Acme 468 Construction of the head of 468 to 470 Capacity of 470 =Cutting Edges= for taps, the number of 471 Examples when three and when four cutting edges are used, and the results upon bolts that are not round 471, 472 Demonstration that four cutting edges are correct for bar iron 472 =Positions of Dies=, or chasers in the heads of bolt cutting machine 473 =Dies=, methods of hobbing, to avoid undue friction 473 The construction of, for bolt threading machines 473 Method of avoiding friction in thread cutting 474 Hob for threading 474 Cutting speeds for threading 474 =Nut Tapping= machine 475 Automatic socket for 475 Rotary 475 Three-spindle 475 =Pipe Threading Machine= 475 to 477 =Tapping Machine= for steam pipe fittings 478 =Broaching Press= 478 Principles of broaching 478 Examples in the construction of broaches 479 FULL-PAGE PLATES. Volume I. _Facing_ _Frontispiece._ MODERN LOCOMOTIVE ENGINE. TITLE PAGE PLATE I. TEMPLATE-CUTTING MACHINES FOR GEAR TEETH. 34 " II. FORMS OF SCREW THREADS. 85 " III. MEASURING AND GAUGING SCREW THREADS. 93 " IV. END-ADJUSTMENT AND LOCKING DEVICES. 120 " V. EXAMPLES IN LATHE CONSTRUCTION. 148 " VI. CHUCKING LATHES. 150 " VII. TOOL-HOLDING AND ADJUSTING APPLIANCES. 174 " VIII. WATCHMAKER'S LATHE. 188 " IX. DETAILS OF WATCHMAKER'S LATHE. 188 " X. EXAMPLES OF SCREW MACHINES. 200 " XI. ROLL-TURNING LATHE. 215 " XII. EXAMPLES IN ANGLE-PLATE CHUCKING. 252 " XIII. METHODS OF BALL-TURNING. 325 " XIV. STANDARD MEASURING MACHINES. 341 " XV. DIVIDING ENGINE AND MICROMETER. 354 " XVI. SHAPING MACHINES AND TABLE-SWIVELING DEVICES. 398 " XVII. EXAMPLES OF PLANING MACHINES. 404 " XVIII. EXAMPLES IN PLANING WORK. 422 " XIX. LIGHT DRILLING MACHINES. 428 " XX. HEAVY DRILLING MACHINES. 430 " XXI. EXAMPLES IN BORING MACHINERY. 434 " XXII. BOILER-DRILLING MACHINERY. 436 " XXIII. NUT-TAPPING MACHINERY. 475 MODERN MACHINE SHOP PRACTICE. CHAPTER I.--THE TEETH OF GEAR-WHEELS. A wheel that is provided with teeth to mesh, engage, or gear with similar teeth upon another wheel, so that the motion of one may be imparted to the other, is called, in general terms, a gear-wheel. [Illustration: Fig. 1.] When the teeth are arranged to be parallel to the wheel-axis, as in Fig. 1, the wheel is termed a spur-wheel. In the figure, A represents the axial line or axis of the wheel or of its shaft, to which the teeth are parallel while spaced equidistant around the rim, or face, as it is termed, of the wheel. [Illustration: Fig. 2.] [Illustration: Fig. 3.] When the wheel has its teeth arranged at an angle to the shaft, as in Fig. 2, it is termed a bevel-wheel, or bevel gear; but when this angle is one of 45°, as in Fig. 3, as it must be if the pair of wheels are of the same diameter, so as to make the revolutions of their shafts equal, then the wheel is called a mitre-wheel. When the teeth are arranged upon the radial or side face of the wheel, as in Fig. 4, it is termed a crown-wheel. The smallest wheel of a pair, or of a train or set of gear-wheels, is termed the pinion; and when the teeth are composed of rungs, as in Fig. 5, it is termed a lantern, trundle, or wallower; and each cylindrical piece serving as a tooth is termed a _stave_, _spindle_, or _round_, and by some a _leaf_. [Illustration: Fig. 4.] An annular or internal gear-wheel is one in which the faces of the teeth are within and the flanks without, or outside the pitch-circle, as in Fig. 6; hence the pinion P operates within the wheel. [Illustration: Fig. 5.] [Illustration: Fig. 6.] When the teeth of a wheel are inserted in mortises or slots provided in the wheel-rim, it is termed a mortised-wheel, or a cogged-wheel, and the teeth are termed cogs. When the teeth are arranged along a plane surface or straight line, as in Fig. 7, the toothed plane is termed a _rack_, and the wheel is termed a pinion. A wheel that is driven by a revolving screw, or worm as it is termed, is called a worm-wheel, the arrangement of a worm and worm-wheel being shown in Fig. 8. The screw or worm is sometimes also called an endless screw, because its action upon the wheel does not come to an end as it does when it is revolved in one continuous direction and actuates a nut. So also, since the worm is tangent to the wheel, the arrangement is sometimes called a wheel and tangent screw. The diameter of a gear-wheel is always taken at the pitch circle, unless otherwise specially stated as "diameter over all," "diameter of addendum," or "diameter at root of teeth," &c., &c. [Illustration: Fig. 7.] When the teeth of wheels engage to the proper distance, which is when the pitch circles meet, they are said to be in gear, or geared together. It is obvious that if two wheels are to be geared together their teeth must be the same distance apart, or the same _pitch_, as it is called. The designations of the various parts or surfaces of a tooth of a gear-wheel are represented in Fig. 9, in which the surface A is the face of the tooth, while the dimension F is the width of face of the wheel, when its size is referred to. B is the flank or distance from the pitch line to the root of the tooth, and C the point. H is the _space_, or the distance from the side of one tooth to the nearest side of the next tooth, the width of space being measured on the pitch circle P P. E is the depth of the tooth, and G its thickness, the latter also being measured on the pitch circle P P. When spoken of with reference to a tooth, P P is called the pitch line, but when the whole wheel is referred to it becomes the pitch circle. [Illustration: Fig. 8.] The points C and the surface H are true to the wheel axis. The teeth are designated for measurement by the pitch; the height or depth above and below pitch line; and the thickness. The pitch, however, may be measured in two ways, to wit, around the pitch circle A, in Fig. 10, which is called the arc or circular pitch, and across B, which is termed the chord pitch. [Illustration: Fig. 9.] In proportion as the diameter of a wheel (having a given pitch) is increased, or as the pitch of the teeth is made finer (on a wheel of a given diameter) the arc and chord pitches more nearly coincide in length. In the practical operations of marking out the teeth, however, the arc pitch is not necessarily referred to, for if the diameter of the pitch circle be made correct for the required number of teeth having the necessary arc pitch, and the wheel be accurately divided off into the requisite number of divisions with compasses set to the chord pitch, or by means of an index plate, then the arc pitch must necessarily be correct, although not referred to, save in determining the diameter of the wheel at the pitch circle. The difference between the width of a space and the thickness of the tooth (both being measured on the pitch circle or pitch line) is termed the clearance or side clearance, which is necessary to prevent the teeth of one wheel from becoming locked in the spaces of the other. The amount of clearance is, when the teeth are cut to shape in a machine, made just sufficient to prevent contact on one side of the teeth when they are in proper gear (the pitch circles meeting in the line of centres). But when the teeth are cast upon the wheel the clearance is increased to allow for the slight inequalities of tooth shape that is incidental to casting them. The amount of clearance given is varied to suit the method employed to mould the wheels, as will be explained hereafter. The line of centres is an imaginary line from the centre or axis of one wheel to the axis of the other when the two are in gear; hence each tooth is most deeply engaged, in the space of the other wheel, when it is on the line of centres. There are three methods of designating the sizes of gear-wheels. First, by their diameters at the pitch circle or pitch diameter and the number of teeth they contain; second, by the number of teeth in the wheel and the pitch of the teeth; and third, by a system known as diametral pitch. [Illustration: Fig. 10.] The first is objectionable because it involves a calculation to find the pitch of the teeth; furthermore, if this calculation be made by dividing the circumference of the pitch circle by the number of teeth in the wheel, the result gives the arc pitch, which cannot be measured correctly by a lineal measuring rule, especially if the wheel be a small one having but few teeth, or of coarse pitch, as, in that case, the arc pitch very sensibly differs from the chord pitch, and a second calculation may become necessary to find the chord pitch from the arc pitch. The second method (the number and pitch of the teeth) possesses the disadvantage that it is necessary to state whether the pitch is the arc or the chord pitch. If the arc pitch is given it is difficult to measure as before, while if the chord pitch is given it possesses the disadvantage that the diameters of the wheels will not be exactly proportional to the numbers of teeth in the respective wheels. For instance, a wheel with 20 teeth of 2 inch chord pitch is not exactly half the diameter of one of 40 teeth and 2 inch chord pitch. To find the chord pitch of a wheel take 180 (= half the degrees in a circle) and divide it by the number of teeth in the wheel. In a table of natural sines find the sine for the number so found, which multiply by 2, and then by the radius of the wheel in inches. Example.--What is the chord pitch of a wheel having 12 teeth and a diameter (at pitch circle) of 8 inches? Here 180 ÷ 12 = 15; (sine of 15 is .25881). Then .25881 × 2 = .51762 × 4 (= radius of wheel) = 2.07048 inches = chord pitch. TABLE OF NATURAL SINES. +--------+--------++--------+--------++--------+--------+ |Degrees.| Sine. ||Degrees.| Sine. ||Degrees.| Sine. | +--------+--------++--------+--------++--------+--------+ | 1 | .01745 || 16 | .27563 || 31 | .51503 | | 2 | .03489 || 17 | .29237 || 32 | .52991 | | 3 | .05233 || 18 | .30901 || 33 | .54463 | | 4 | .06975 || 19 | .32556 || 34 | .55919 | | 5 | .08715 || 20 | .34202 || 35 | .57357 | | 6 | .10452 || 21 | .35836 || 36 | .58778 | | 7 | .12186 || 22 | .37460 || 37 | .60181 | | 8 | .13917 || 23 | .39073 || 38 | .61566 | | 9 | .15643 || 24 | .40673 || 39 | .62932 | | 10 | .17364 || 25 | .42261 || 40 | .64278 | | 11 | .19080 || 26 | .43837 || 41 | .65605 | | 12 | .20791 || 27 | .45399 || 42 | .66913 | | 13 | .22495 || 28 | .46947 || 43 | .68199 | | 14 | .24192 || 29 | .48480 || 44 | .69465 | | 15 | .25881 || 30 | .50000 || 45 | .70710 | +--------+--------++--------+--------++--------+--------+ The principle upon which diametral pitch is based is as follows:-- The diameter of the wheel at the pitch circle is supposed to be divided into as many equal parts or divisions as there are teeth in the wheel, and the length of one of these parts is the diametral pitch. The relationship which the diametral bears to the arc pitch is the same as the diameter to the circumference, hence a diametral pitch which measures 1 inch will accord with an arc pitch of 3.1416; and it becomes evident that, for all arc pitches of less than 3.1416 inches, the corresponding diametral pitch must be expressed in fractions of an inch, as 1/2, 1/3, 1/4, and so on, increasing the denominator until the fraction becomes so small that an arc with which it accords is too fine to be of practical service. The numerators of these fractions being 1, in each case, they are in practice discarded, the denominators only being used, so that, instead of saying diametral pitches of 1/2, 1/3, or 1/4, we say diametral pitches of 2, 3, or 4, meaning that there are 2, 3, or 4 teeth on the wheel for every inch in the diameter of the pitch circle. Suppose now we are given a diametral pitch of 2. To obtain the corresponding arc pitch we divide 3.1416 (the relation of the circumference to the diameter) by 2 (the diametral pitch), and 3.1416 ÷ 2 = 1.57 = the arc pitch in inches and decimal parts of an inch. The reason of this is plain, because, an arc pitch of 3.1416 inches being represented by a diametral pitch of 1, a diametral pitch of 1/2 (or 2 as it is called) will be one half of 3.1416. The advantage of discarding the numerator is, then, that we avoid the use of fractions and are readily enabled to find any arc pitch from a given diametral pitch. Examples.--Given a 5 diametral pitch; what is the arc pitch? First (using the full fraction 1/5) we have 1/5 × 3.1416 = .628 = the arc pitch. Second (discarding the numerator), we have 3.1416 ÷ 5 = .628 = arc pitch. If we are given an arc pitch to find a corresponding diametral pitch we again simply divide 3.1416 by the given arc pitch. Example.--What is the diametral pitch of a wheel whose arc pitch is 1-1/2 inches? Here 3.1416 ÷ 1.5 = 2.09 = diametral pitch. The reason of this is also plain, for since the arc pitch is to the diametral pitch as the circumference is to the diameter we have: as 3.1416 is to 1, so is 1.5 to the required diametral pitch; then 3.1416 × 1 ÷ 1.5 = 2.09 = the required diametral pitch. To find the number of teeth contained in a wheel when the diameter and diametral pitch is given, multiply the diameter in inches by the diametral pitch. The product is the answer. Thus, how many teeth in a wheel 36 inches diameter and of 3 diametral pitch? Here 36 × 3 = 108 = the number of teeth sought. Or, per contra, a wheel of 36 inches diameter has 108 teeth. What is the diametral pitch? 108 ÷ 36 = 3 = the diametral pitch. Thus it will be seen that, for determining the relative sizes of wheels, this system is excellent from its simplicity. It also possesses the advantage that, by adding two parts of the diametral pitch to the pitch diameter, the outside diameter of the wheel or the diameter of the addendum is obtained. For instance, a wheel containing 30 teeth of 10 pitch would be 3 inches diameter on the pitch circle and 3-2/10 outside or total diameter. Again, a wheel having 40 teeth of 8 diametral pitch would have a pitch circle diameter of 5 inches, because 40 ÷ 8 = 5, and its full diameter would be 5-1/4 inches, because the diametral pitch is 1/8, and this multiplied by 2 gives 1/4, which added to the pitch circle diameter of 5 inches makes 5-1/4 inches, which is therefore the diameter of the addendum, or, in other words, the full diameter of the wheel. Suppose now that a pair of wheels require to have pitch circles of 5 and 8 inches diameter respectively, and that the arc pitch requires to be, say, as near as may be 4/10 inch; to find a suitable pitch and the number of teeth by the diametral pitch system we proceed as follows: In the following table are given various arc pitches, and the corresponding diametral pitch. +----------------+----------+----------+----------------+ |Diametral Pitch.|Arc Pitch.|Arc Pitch.|Diametral Pitch.| +----------------+----------+----------+----------------+ | | | Inch. | | | 2 | 1.57 | 1.75 | 1.79 | | 2.25 | 1.39 | 1.5 | 2.09 | | 2.5 | 1.25 | 1.4375 | 2.18 | | 2.75 | 1.14 | 1.375 | 2.28 | | 3 | 1.04 | 1.3125 | 2.39 | | 3.5 | .890 | 1.25 | 2.51 | | 4 | .785 | 1.1875 | 2.65 | | 5 | .628 | 1.125 | 2.79 | | 6 | .523 | 1.0625 | 2.96 | | 7 | .448 | 1.0000 | 3.14 | | 8 | .392 | 0.9375 | 3.35 | | 9 | .350 | 0.875 | 3.59 | | 10 | .314 | 0.8125 | 3.86 | | 11 | .280 | 0.75 | 4.19 | | 12 | .261 | 0.6875 | 4.57 | | 14 | .224 | 0.625 | 5.03 | | 16 | .196 | 0.5625 | 5.58 | | 18 | .174 | 0.5 | 6.28 | | 20 | .157 | 0.4375 | 7.18 | | 22 | .143 | 0.375 | 8.38 | | 24 | .130 | 0.3125 | 10.00 | | 26 | .120 | 0.25 | 12.56 | +----------------+----------+----------+----------------+ From this table we find that the nearest diametral pitch that will correspond to an arc pitch of 4/10 inch is a diametral pitch of 8, which equals an arc pitch of .392, hence we multiply the pitch circles (5 and 8,) by 8, and obtain 40 and 64 as the number of teeth, the arc pitch being .392 of an inch. To find the number of teeth and pitch by the arc pitch and circumference of the pitch circle, we should require to find the circumference of the pitch circle, and divide this by the nearest arc pitch that would divide the circumference without leaving a remainder, which would entail more calculating than by the diametral pitch system. The designation of pitch by the diametral pitch system is, however, not applied in practice to coarse pitches, nor to gears in which the teeth are cast upon the wheels, pattern makers generally preferring to make the pitch to some measurement that accords with the divisions of the ordinary measuring rule. Of two gear-wheels that which impels the other is termed the driver, and that which receives motion from the other is termed the driven wheel or follower; hence in a single pair of wheels in gear together, one is the driver and the other the driven wheel or follower. But if there are three wheels in gear together, the middle one will be the follower when spoken of with reference to the first or prime mover, and the driver, when mentioned with reference to the third wheel, which will be a follower. A series of more than two wheels in gear together is termed a train of wheels or of gearing. When the wheels in a train are in gear continuously, so that each wheel, save the first and last, both receives and imparts motion, it is a simple train, the first wheel being the driver, and the last the follower, the others being termed intermediate wheels. Each of these intermediates is a follower with reference to the wheel that drives it, and a driver to the one that it drives. But the velocity of all the wheels in the train is the same in fact per second (or in a given space of time), although the revolutions in that space of time may vary; hence a simple train of wheels transmits motion without influencing its velocity. To alter the velocity (which is always taken at a point on the pitch circle) the gearing must be compounded, as in Fig. 11, in which A, B, C, E are four wheels in gear, B and C being compounded, that is, so held together on the shaft D that both make an equal number of revolutions in a given time. Hence the velocity of C will be less than that of B in proportion as the diameter, circumference, radius, or number of teeth in C, varies from the diameter, radius, circumference, or number of teeth (all the wheels being supposed to have teeth of the same pitch) in B, although the rotations of B and C are equal. It is most convenient, and therefore usual, to take the number of teeth, but if the teeth on C (and therefore those on E also) were of different pitch from those on B, the radius or diameters of the wheels must be taken instead of the pitch, when the velocities of the various wheels are to be computed. It is obvious that the compounded pair of wheels will diminish the velocity when the driver of the compounded pair (as C in the figure) is of less radius than the follower B, and conversely that the velocity will be increased when the driver is of greater radius than the follower of the compound pair. [Illustration: Fig. 11.] The diameter of the addendum or outer circle of a wheel has no influence upon the velocity of the wheel. Suppose, for example, that we have a pair of wheels of 3 inch arc or circular pitch, and containing 20 teeth, the driver of the two making one revolution per minute. Suppose the driven wheel to have fast upon its shaft a pulley whose diameter is one foot, and that a weight is suspended from a line or cord wound around this pulley, then (not taking the thickness of the line into account) each rotation of the driven wheel would raise the weight 3.1416 feet (that being the circumference of the pulley). Now suppose that the addendum circle of either of the wheels were cut off down to the pitch circle, and that they were again set in motion, then each rotation of the driven wheel would still raise the weight 3.1416 feet as before. It is obvious, however, that the addendum circle must be sufficiently larger than the pitch circle to enable at least one pair of teeth to be in continuous contact; that is to say, it is obvious that contact between any two teeth must not cease before contact between the next two has taken place, for otherwise the motion would not be conveyed continuously. The diameter of the pitch circle cannot be obtained from that of the addendum circle unless the pitch of the teeth and the proportion of the pitch allowed for the addendum be known. But if these be known the diameter of the pitch circle may be obtained by subtracting from that of the addendum circle twice the amount allowed for the addendum of the tooth. Example.--A wheel has 19 teeth of 3 inch arc pitch; the addendum of the tooth or teeth equals 3/10 of the pitch, and its addendum circle measures 19.943 inches; what is the diameter of the pitch circle? Here the addendum on each side of the wheel equals (3/10 of 3 inches) = .9 inches, hence the .9 must be multiplied by 2 for the two sides of the wheel, thus, .9 × 2 = 1.8. Then, diameter of addendum circle 19.943 inches less 1.8 inches = 18.143 inches, which is the diameter of the pitch circle. Proof.--Number of teeth = 19, arc pitch 3, hence 19 × 3 = 57 inches, which, divided by 3.1416 (the proportion of the circumference to the diameter) = 18.143 inches. If the distance between the centres of a pair of wheels that are in gear be divided into two parts whose lengths are in the same proportion one to the other as are the numbers of teeth in the wheels, then these two parts will represent the radius of the pitch circles of the respective wheels. Thus, suppose one wheel to contain 100 and the other 50 teeth, and that the distance between their centres is 18 inches, then the pitch radius or pitch diameter of one will be twice that of the other, because one contains twice as many teeth as the other. In this case the radius of pitch circle for the large wheel will be 12 inches, and that for the small one 6 inches, because 12 added to 6 makes 18, which is the distance between the wheel centres, and 12 is in the same proportion to 6 that 100 is to 50. A simple rule whereby to find the radius of the pitch circles of a pair of wheels is as follows:-- Rule.--Divide number of teeth in the large wheel by the number in the small one, and to the sum so obtained add 1. Take this amount and divide it into the distance between the centres of the wheels, and the result will be the radius of the smallest wheel. To obtain the radius of the largest wheel subtract the radius of the smallest wheel from the distance between the wheel centres. Example.--Of a pair of wheels, one has 100 and the other 50 teeth, the distance between their centres is 18 inches; what is the pitch radius of each wheel? Here 100 ÷ 50 = 2, and 2 + 1 = 3. Then 18 ÷ 3 = 6, hence the pitch radius of the small wheel is 6 inches. Then 18 - 6 = 12 = pitch radius of large wheel. Example 2.--Of a pair of wheels one has 40 and the other 90 teeth. The distance between the wheel centres is 32-1/2 inches; what are the radii of the respective pitch circles? 90 ÷ 40 = 2.25 and 2.25 + 1 = 3.25. Then 32.5 ÷ 3.25 = 10 = pitch radius of small wheel, and 32.5 - 10 = 22.5, which is the pitch radius of the large wheel. To prove this we may show that the pitch radii of the two wheels are in the same proportion as their numbers of teeth, thus:-- Proof.--Radius of small wheel = 10 × 4 = 40 ---- ---- radius of large wheel = 22.5 × 4 = 90.0 Suppose now that a pair of wheels are constructed, having respectively 50 and 100 teeth, and that the radii of their true pitch circles are 12 and 6 respectively, but that from wear in their journals or journal bearings this 18 inches (12 + 6 = 18) between centres (or line of centres, as it is termed) has become 18-3/8 inches. Then the acting effective or operative radii of the pitch circles will bear the same proportion to the 18-3/8 as the numbers of teeth in the respective wheels, and will be 12.25 for the large, and 6.125 for the small wheel, instead of 12 and 6, as would be the case were the wheels 18 inches apart. Working this out under the rule given we have 100 ÷ 50 = 2, and 2 + 1 = 3. Then 18.375 ÷ 3 = 6.125 = pitch radius of small wheel, and 18.375 - 6.125 = 12.25 = pitch radius of the large wheel. The true pitch line of a tooth is the line or point where the face curve joins the flank curve, and it is essential to the transmission of uniform motion that the pitch circles of epicycloidal wheels exactly coincide on the line of centres, but if they do not coincide (as by not meeting or by overlapping each other), then a false pitch circle becomes operative instead of the true one, and the motion of the driven wheel will be unequal at different instants of time, although the revolutions of the wheels will of course be in proportion to the respective numbers of their teeth. If the pitch circle is not marked on a single wheel and its arc pitch is not known, it is practically a difficult matter to obtain either the arc pitch or diameter of the pitch circle. If the wheel is a new one, and its teeth are of the proper curves, the pitch circle will be shown by the junction of the curves forming the faces with those forming the flanks of the teeth, because that is the location of the pitch circle; but in worn wheels, where from play or looseness between the journals and their bearings, this point of junction becomes rounded, it cannot be defined with certainty. In wheels of large diameter the arc pitch so nearly coincides with the chord pitch, that if the pitch circle is not marked on the wheel and the arc pitch is not known, the chord pitch is in practice often assumed to represent the arc pitch, and the diameter of the wheel is obtained by multiplying the number of teeth by the chord pitch. This induces no error in wheels of coarse pitches, because those pitches advance by 1/4 or 1/2 inch at a step, and a pitch measuring about, say, 1-1/4 inch chord pitch, would be known to be 1-1/4 arc pitch, because the difference between the arc and chord pitch would be too minute to cause sensible error. Thus the next coarsest pitch to 1 inch would be 1-1/8, or more often 1-1/4 inch, and the difference between the arc and chord pitch of the smallest wheel would not amount to anything near 1/8 inch, hence there would be no liability to mistake a pitch of 1-1/8 for 1 inch or _vice versâ_. The diameter of wheel that will be large enough to transmit continuous motion is diminished in proportion as the pitch is decreased; in proportion, also, as the wheel diameter is reduced, the difference between the arc and chord pitch increases, and further the steps by which fine pitches advance are more minute (as 1/4, 9/32, 5/16, &c.). From these facts there is much more liability to err in estimating the arc from the measured chord pitch in fine pitches, hence the employment of diametral pitch for small wheels of fine pitches is on this account also very advantageous. In marking out a wheel the chord pitch will be correct if the pitch circle be of correct diameter and be divided off into as many points of equal division (with compasses) as there are to be teeth in the wheel. We may then mark from these points others giving the thickness of the teeth, which will make the spaces also correct. But when the wheel teeth are to be cut in a machine out of solid metal, the mechanism of the machine enables the marking out to be dispensed with, and all that is necessary is to turn the wheel to the required addendum diameter, and mark the pitch circle. The following are rules for the purposes they indicate. The circumference of a circle is obtained by multiplying its diameter by 3.1416, and the diameter may be obtained by dividing the circumference by 3.1416. The circumference of the pitch circle divided by the arc pitch gives the number of teeth in the wheel. The arc pitch multiplied by the number of teeth in the wheel gives the circumference of the pitch circle. Gear-wheels are simply rotating levers transmitting the power they receive, less the amount of friction necessary to rotate them under the given conditions. All that is accomplished by a simple train of gearing is, as has been said, to vary the number of revolutions, the speed or velocity measured in feet moved through per minute remaining the same for every wheel in the train. But in a compound train of gears the speed in feet per minute, as well as the revolutions, may be varied by means of the compounded pairs of wheels. In either a simple or a compound train of gearing the power remains the same in amount for every wheel in the train, because what is in a compound train lost in velocity is gained in force, or what is gained in velocity is lost in force, the word force being used to convey the idea of strain, pressure, or pull. In Fig. 12, let A, B, and C represent the pitch circles of three gears of which A and B are in gear, while C is compounded with B; let E be the shaft of A, and G that for B and C. Let A be 60 inches, B = 30 inches, and C = 40 inches in diameter. Now suppose that shaft E suspends from its perimeter a weight of 50 lbs., the shaft being 4 inches in diameter. Then this weight will be at a leverage of 2 inches from the centre of E and the 50 must be multiplied by 2, making 100 lbs. at the centre of E. Then at the perimeter of A this 100 will become one-thirtieth of one hundred, because from the centre to the perimeter of A is 30. One-thirtieth of 100 is 3-33/100 lbs., which will be the force exerted by A on the perimeter of B. Now from the perimeter of B to its centre (or in other words its radius) is 15 inches, hence the 3-33/100 lbs. at its perimeter will become fifteen times as much at the centre G of B, and 3-33/100 × 15 = 49-95/100 lbs. From the centre G to the perimeter of C being 20 inches, the 49-95/100 lbs. at the centre will be only one-twentieth of that amount at the perimeter of C, hence 49-95/100 ÷ 20 = 2-49/100 lbs., which is the amount of force at the perimeter of C. Here we have treated the wheels as simple levers, dividing the weight by the length of the levers in all cases where it is transmitted from the shaft to the perimeter, and multiplying it by the length of the lever when it is transmitted from the perimeter of the wheel to the centre of the shaft. The precise same result will be reached if we take the diameter of the wheels or the number of the teeth, providing the pitch of the teeth on all the wheels is alike. Suppose, for example, that A has 60 teeth, B has 30 teeth, and C has 40 teeth, all being of the same pitch. Suppose the 50 lb. weight be suspended as before, and that the circumference of the shaft be equal to that of a pinion having 4 teeth of the same pitch as the wheels. Then the 50 multiplied by the 4 becomes 200, which divided by 60 (the number of teeth on A) becomes 3-33/100, which multiplied by 30 (the number of teeth on B) becomes 99-90/100, which divided by 40 (the number of teeth on C) becomes 2-49/100 lbs. as before. [Illustration: Fig. 12.] It may now be explained why the shaft was taken as equal to a pinion having 4 teeth. Its diameter was taken as 4 inches and the wheel diameter was taken as being 60 inches, and it was supposed to contain 60 teeth, hence there was 1 tooth to each inch of diameter, and the 4 inches diameter of shaft was therefore equal to a pinion having 4 teeth. From this we may perceive the philosophy of the rule that to obtain the revolutions of wheels we multiply the given revolutions by the teeth in the driving wheels and divide by the teeth in the driven wheels. Suppose that A (Fig. 13) makes 1 revolution per minute, how many will C make, A having 60 teeth, B 30 teeth, and C 40 teeth? In this case we have but one driving wheel A, and one driven wheel B, the driver having 60 teeth, the driven 30, hence 60 ÷ 30 = 2, equals revolutions of B and also of C, the two latter being on the same shaft. It will be observed then that the revolutions are in the same proportion as the numbers of the teeth or the radii of the wheels, or what is the same thing, in the same proportion as their diameters. The number of teeth, however, is usually taken as being easier obtained than the diameter of the pitch circles, and easier to calculate, because the teeth will be represented by a whole number, whereas the diameter, radius, or circumference, will generally contain fractions. Suppose that the 4 wheels in Fig. 14 have the respective numbers of teeth marked beside them, and that the upper one having 40 teeth makes 60 revolutions per minute, then we may obtain the revolutions of the others as follows:-- Revolu- Teeth Teeth Teeth Teeth tions. in first in first in second in second driver. driven. driver. driven. 60 × 40 ÷ 60 × 20 ÷ 120 = 6-66/100 and a remainder of the reciprocating decimals. We may now prove this by reversing the question, thus. Suppose the 120 wheel to make 6-66/100 revolutions per minute, how many will the 40 wheel make? Revolu- Teeth Teeth Teeth Teeth tions. in first in first in second in second driver. driven. driver. driven. 6.66 × 120 ÷ 20 × 60 ÷ 40 = 59-99/100 = revolutions of the 40 wheel, the discrepancy of 1/100 being due to the 6.66 leaving a remainder and not therefore being absolutely correct. That the amount of power transmitted by gearing, whether compounded or not, is equal throughout every wheel in the train, may be shown as follows:-- [Illustration: Fig. 13.] Referring again to Fig. 10, it has been shown that with a 50 lb. weight suspended from a 4 inch shaft E, there would be 30-33/100 lbs. at the perimeter of A. Now suppose a rotation be made, then the 50 lb. weight would fall a distance equal to the circumference of the shaft, which is (3.1416 × 4 = 12-56/100) 12-56/100 inches. Now the circumference of the wheel is (60 dia. × 3.1416 = 188-49/100 cir.) 188-49/100 inches, which is the distance through which the 3-33/100 lbs. would move during one rotation of A. Now 3.33 lbs. moving through 188.49 inches represents the same amount of power as does 50 lbs. moving through a distance of 12.56 inches, as may be found by converting the two into inch lbs. (that is to say, into the number of inches moved by 1 lb.), bearing in mind that there will be a slight discrepancy due to the fact that the fractions .33 in the one case, and .56 in the other are not quite correct. Thus: 188.49 inches × 3.33 lbs. = 627.67 inch lbs., and 12.56 " × 50 " = 628 " " Taking the next wheels in Fig. 12, it has been shown that the 3.33 lbs. delivered from A to the perimeter of B, becomes 2.49 lbs. at the perimeter of C, and it has also been shown that C makes two revolutions to one of A, and its diameter being 40 inches, the distance this 2.49 lbs. will move through in one revolution of A will therefore be equal to twice its circumference, which is (40 dia. × 3.1416 = 125.666 cir., and 125.666 × 2 = 251.332) 251.332 inches. Now 2.49 lbs. moving through 251.332 gives when brought to inch lbs. 627.67 inch lbs., thus 251.332 × 2.49 = 627.67. Hence the amount of power remains constant, but is altered in form, merely being converted from a heavy weight moving a short distance, into a lighter one moving a distance exactly as much greater as the weight or force is lessened or lighter. [Illustration: Fig. 14.] Gear-wheels therefore form a convenient method of either simply transmitting motion or power, as when the wheels are all of equal diameter, or of transmitting it and simultaneously varying its velocity of motion, as when the wheels are compounded either to reduce or increase the speed or velocity in feet per second of the prime mover or first driver of the train or pair, as the case may be. [Illustration: Fig. 15.] In considering the action of gear-teeth, however, it sometimes is more convenient to denote their motion by the number of degrees of angle they move through during a certain portion of a revolution, and to refer to their relative velocities in terms of the ratio or proportion existing between their velocities. The first of these is termed the angular velocity, or the number of degrees of angle the wheel moves through during a given period, while the second is termed the velocity ratio of the pair of wheels. Let it be supposed that two wheels of equal diameter have contact at their perimeters so that one drives the other by friction without any slip, then the velocity of a point on the perimeter of one will equal that of a point on the other. Thus in Fig. 15 let A and B represent the pitch circles of two wheels, and C an imaginary line joining the axes of the two wheels and termed the line of centres. Now the point of contact of the two wheels will be on the line of centres as at D, and if a point or dot be marked at D and motion be imparted from A to B, then when each wheel has made a quarter revolution the dot on A will have arrived at E while that on B will have arrived at F. As each wheel has moved through one quarter revolution, it has moved through 90° of angle, because in the whole circle there is 360°, one quarter of which is 90°, hence instead of saying that the wheels have each moved through one quarter of a revolution we may say they have moved through an angle of 90°, or, in other words, their angular velocity has, during this period, been 90°. And as both wheels have moved through an equal number of degrees of angle their velocity ratio or proportion of velocity has been equal. Obviously then the angular velocity of a wheel represents a portion of a revolution irrespective of the diameter of the wheel, while the velocity ratio represents the diameter of one in proportion to that of the other irrespective of the actual diameter of either of them. [Illustration: Fig. 16.] Now suppose that in Fig. 16 A is a wheel of twice the diameter of B; that the two are free to revolve about their fixed centres, but that there is frictional contact between their perimeters at the line of centres sufficient to cause the motion of one to be imparted to the other without slip or lost motion, and that a point be marked on both wheels at the point of contact D. Now let motion be communicated to A until the mark that was made at D has moved one-eighth of a revolution and it will have moved through an eighth of a circle, or 45°. But during this motion the mark on B will have moved a quarter of a revolution, or through an angle of 90° (which is one quarter of the 360° that there are in the whole circle). The angular velocities of the two are, therefore, in the same ratio as their diameters, or two to one, and the velocity ratio is also two to one. The angular velocity of each is therefore the number of degrees of angle that it moves through in a certain portion of a revolution, or during the period that the other wheel of the pair makes a certain portion of a revolution, while the velocity ratio is the proportion existing between the velocity of one wheel and that of the other; hence if the diameter of one only of the wheels be changed, its angular velocity will be changed and the velocity ratio of the pair will be changed. The velocity ratio may be obtained by dividing either the radius, pitch, diameter, or number of teeth of one wheel into that of the other. Conversely, if a given velocity ratio is to be obtained, the radius, diameter, or number of teeth of the driver must bear the same relation to the radius, diameter, or number of teeth of the follower, as the velocity of the follower is desired to bear to that of the driver. If a pair of wheels have an equal number of teeth, the same pairs of teeth will come into action at every revolution; but if of two wheels one is twice as large as the other, each tooth on the small wheel will come into action twice during each revolution of the large one, and will work during each successive revolution with the same two teeth on the large wheel; and an application of the principle of the hunting tooth is sometimes employed in clocks to prevent the overwinding of their springs, the device being shown in Fig. 17, which is from "Willis' Principles of Mechanism." For this purpose the winding arbor C has a pinion A of 19 teeth fixed to it close to the front plate. A pinion B of 18 teeth is mounted on a stud so as to be in gear with the former. A radial plate C D is fixed to the face of the upper wheel A, and a similar plate F E to the lower wheel B. These plates terminate outward in semicircular noses D, E, so proportioned as to cause their extremities to abut against each other, as shown in the figure, when the motion given to the upper arbor by the winding has brought them into the position of contact. The clock being now wound up, the winding arbor and wheel A will begin to turn in the opposite direction. When its first complete rotation is effected the wheel B will have gained one tooth distance from the line of centres, so as to place the stop D in advance of E and thus avoid a contact with E, which would stop the motion. As each turn of the upper wheel increases the distance of the stops, it follows from the principle of the hunting cog, that after eighteen revolutions of A and nineteen of B the stops will come together again and the clock be prevented from running down too far. The winding key being applied, the upper wheel A will be rotated in the opposite direction, and the winding repeated as above. [Illustration: Fig. 17.] Thus the teeth on one wheel will wear to imbed one upon the other. On the other hand the teeth of the two wheels may be of such numbers that those on one wheel will not fall into gear with the same teeth on the other except at intervals, and thus an inequality on any one tooth is subjected to correction by all the teeth in the other wheel. When a tooth is added to the number of teeth on a wheel to effect this purpose it is termed a hunting cog, or hunting tooth, because if one wheel have a tooth less, then any two teeth which meet in the first revolution are distant, one tooth in the second, two teeth in the third, three in the fourth, and so on. The odd tooth is on this account termed a hunting tooth. It is obvious then that the shape or form to be given to the teeth must, to obtain correct results, be such that the motion of the driver will be communicated to the follower with the velocity due to the relative diameters of the wheels at the pitch circles, and since the teeth move in the arc of a circle it is also obvious that the sides of the teeth, which are the only parts that come into contact, must be of same curve. The nature of this curve must be such that the teeth shall possess the strength necessary to transmit the required amount of power, shall possess ample wearing surface, shall be as easily produced as possible for all the varying conditions, shall give as many teeth in constant contact as possible, and shall, as far as possible, exert a pressure in a direction to rotate the wheels without inducing undue wear upon the journals of the shafts upon which the wheels rotate. In cases, however, in which some of these requirements must be partly sacrificed to increase the value of the others, or of some of the others, to suit the special circumstances under which the wheels are to operate, the selection is left to the judgment of the designer, and the considerations which should influence his determinations will appear hereafter. [Illustration: Fig. 18.] Modern practice has accepted the curve known in general terms as the cycloid, as that best filling all the requirements of wheel teeth, and this curve is employed to produce two distinct forms of teeth, epicycloidal and involute. In epicycloidal teeth the curve forming the face of the tooth is designated an epicycloid, and that forming the flank an hypocycloid. An epicycloid may be traced or generated, as it is termed, by a point in the circumference of a circle that rolls without slip upon the circumference of another circle. Thus, in Fig. 18, A and B represent two wooden wheels, A having a pencil at P, to serve as a tracing or marking point. Now, if the wheels are laid upon a sheet of paper and while holding B in a fixed position, roll A in contact with B and let the tracing point touch the paper, the point P will trace the curve C C. Suppose now the diameter of the base circle B to be infinitely large, a portion of its circumference may be represented by a straight line, and the curve traced by a point on the circumference of the generating circle as it rolls along the base line B is termed a cycloid. Thus, in Fig. 19, B is the base line, A the rolling wheel or generating circle, and C C the cycloidal curve traced or marked by the point D when A is rolled along B. If now we suppose the base line B to represent the pitch line of a rack, it will be obvious that part of the cycloid at one end is suitable for the face on one side of the tooth, and a part at the other end is suitable for the face of the other side of the tooth. [Illustration: Fig. 19.] A hypocycloid is a curve traced or generated by a point on the circumference of a circle rolling within and in contact (without slip) with another circle. Thus, in Fig. 20, A represents a wheel in contact with the internal circumference of B, and a point on its circumference will trace the two curves, C C, both curves starting from the same point, the upper having been traced by rolling the generating circle or wheel A in one direction and the lower curve by rolling it in the opposite direction. [Illustration: Fig. 20.] To demonstrate that by the epicycloidal and hypocycloidal curves, forming the faces and flanks of what are known as epicycloidal teeth, motion may be communicated from one wheel to another with as much uniformity as by frictional contact of their circumferential surfaces, let A, B, in Fig. 21, represent two plain wheel disks at liberty to revolve about their fixed centres, and let C C represent a margin of stiff white paper attached to the face of B so as to revolve with it. Now suppose that A and B are in close contact at their perimeters at the point G, and that there is no slip, and that rotary motion commenced when the point E (where as tracing point a pencil is attached), in conjunction with the point F, formed the point of contact of the two wheels, and continued until the points E and F had arrived at their respective positions as shown in the figure; the pencil at E will have traced upon the margin of white paper the portion of an epicycloid denoted by the curve E F; and as the movement of the two wheels A, B, took place by reason of the contact of their circumferences, it is evident that the length of the arc E G must be equal to that of the arc G F, and that the motion of A (supposing it to be the driver) would be communicated uniformly to B. [Illustration: Fig. 21.] Now suppose that the wheels had been rotated in the opposite direction and the same form of curve would be produced, but it would run in the opposite direction, and these two curves may be utilized to form teeth, as in Fig. 22, the points on the wheel A working against the curved sides of the teeth on B. To render such a pair of wheels useful in practice, all that is necessary is to diminish the teeth on B without altering the nature of the curves, and increase the diameter of the points on A, making them into rungs or pins, thus forming the wheels into what is termed a wheel and lantern, which are illustrated in Fig. 23. [Illustration: Fig. 22.] A represents the pinion (or lantern), and B the wheel, and C, C, the primitive teeth reduced in thickness to receive the pins on A. This reduction we may make by setting a pair of compasses to the radius of the rung and describing half-circles at the bottom of the spaces in B. We may then set a pair of compasses to the curve of C, and mark off the faces of the teeth of B to meet the half-circles at the pitch line, and reduce the teeth heights so as to leave the points of the proper thickness; having in this operation maintained the same epicycloidal curves, but brought them closer together and made them shorter. It is obvious, however, that such a method of communicating rotary motion is unsuited to the transmission of much power; because of the weakness of, and small amount of wearing surface on, the points or rungs in A. [Illustration: Fig. 23.] [Illustration: Fig. 24.] In place of points or rungs we may have radial lines, these lines, representing the surfaces of ribs, set equidistant on the radial face of the pinion, as in Fig. 24. To determine the epicycloidal curves for the faces of teeth to work with these radial lines, we may take a generating circle C, of half the diameter of A, and cause it to roll in contact with the internal circumference of A, and a tracing point fixed in the circumference of C will draw the radial lines shown upon A. The circumstances will not be altered if we suppose the three circles, A, B, C, to be movable about their fixed centres, and let their centres be in a straight line; and if, under these circumstances, we suppose rotation to be imparted to the three circles, through frictional contact of their perimeters, a tracing point on the circumference of C would trace the epicycloids shown upon B and the radial lines shown upon A, evidencing the capability of one to impart uniform rotary motion to the other. [Illustration: Fig. 25.] To render the radial lines capable of use we must let them be the surfaces of lugs or projections on the face of the wheel, as shown in Fig. 25 at D, E, &c., or the faces of notches cut in the wheel as at F, G, H, &c., the metal between F and G forming a tooth J, having flanks only. The wheel B has the curves of each tooth brought closer together to give room for the reception of the teeth upon A. We have here a pair of gears that possess sufficient strength and are capable of working correctly in either direction. [Illustration: Fig. 26.] But the form of tooth on one wheel is conformed simply to suit those on the other, hence, neither two of the wheels A, nor would two of B, work correctly together. They may be qualified to do so, however, by simply adding to the tops of the teeth on A, teeth of the form of those on B, and adding to those on B, and within the pitch circle, teeth corresponding to those on A, as in Fig. 26, where at K´ and J´ teeth are provided on B corresponding to J and K on A, while on A there are added teeth O´, N´, corresponding to O, N, on B, with the result that two wheels such as A or two such as B would work correctly together, either being the driver or either the follower, and rotation may occur in either direction. In this operation we have simply added faces to the teeth on A, and flanks to those on B, the curves being generated or obtained by rolling the generating, or curve marking, circle C upon the pitch circles P and P´. Thus, for the flanks of the teeth of A, C is rolled upon, and within the pitch circle P of A; while for the face curves of the same teeth C is rolled upon, but without or outside of P. Similarly for the teeth of wheel B the generating circle C is rolled within P´ for the flanks and without for the faces. With the curves rolled or produced with the same diameter of generating circle the wheels will work correctly together, no matter what their relative diameter may be, as will be shown hereafter. [Illustration: Fig. 27.] In this demonstration, however, the curves for the faces of the teeth being produced by an operation distinct from that employed to produce the flank curves, it is not clearly seen that the curves for the flanks of one wheel are the proper curves to insure a uniform velocity to the other. This, however, may be made clear as follows:-- In Fig. 27 let _a_ _a_ and _b_ _b_ represent the pitch circles of two wheels of equal diameters, and therefore having the same number of teeth. On the left, the wheels are shown with the teeth in, while on the right-hand side of the line of centres A B, the wheels are shown blank; _a_ _a_ is the pitch line of one wheel, and _b_ _b_ that for the other. Now suppose that both wheels are capable of being rotated on their shafts, whose centres will of course be on the line A B, and suppose a third disk, Q, be also capable of rotation upon its centre, C, which is also on the line A B. Let these three wheels have sufficient contact at their perimeters at the point _n_, that if one be rotated it will rotate both the others (by friction) without any slip or lost motion, and of course all three will rotate at an equal velocity. Suppose that there is fixed to wheel Q a pencil whose point is at _n_. If then rotation be given to _a_ _a_ in the direction of the arrow _s_, all three wheels will rotate in that direction as denoted by their respective arrows _s_. Assume, then, that rotation of the three has occurred until the pencil point at _n_ has arrived at the point _m_, and during this period of rotation the point _n_ will recede from the line of centres A B, and will also recede from the arcs or lines of the two pitch circles _a_ _a_, _b_ _b_. The pencil point being capable of marking its path, it will be found on reaching _m_ to have marked inside the pitch circle _b_ _b_ the curve denoted by the full line _m_ _x_, and simultaneously with this curve it has marked another curve outside of _a_ _a_, as denoted by the dotted line _y_ _m_. These two curves being marked by the pencil point at the same time and extending from _y_ to _m_, and _x_ also to _m_. They are prolonged respectively to _p_ and to K for clearness of illustration only. The rotation of the three wheels being continued, when the pencil point has arrived at O it will have continued the same curves as shown at O _f_, and O _g_, curve O _f_ being the same as _m_ _x_ placed in a new position, and O _g_ being the same as _m_ _y_, but placed in a new position. Now since both these curves (O _f_ and O _g_) were marked by the one pencil point, and at the same time, it follows that at every point in its course that point must have touched both curves at once. Now the pencil point having moved around the arc of the circle Q from _n_ to _m_, it is obvious that the two curves must always be in contact, or coincide with each other, at some point in the path of the pencil or describing point, or, in other words, the curves will always touch each other at some point on the curve of Q, and between _n_ and O. Thus when the pencil has arrived at _m_, curve _m_ _y_ touches curve K _x_ at the point _m_, while when the pencil had arrived at point O, the curves O _f_ and O _g_ will touch at O. Now the pitch circles _a_ _a_ and _b_ _b_, and the describing circle Q, having had constant and uniform velocity while the traced curves had constant contact at some point in their lengths, it is evident that if instead of being mere lines, _m_ _y_ was the face of a tooth on _a_ _a_, and _m_ _x_ was the flank of a tooth on _b_ _b_, the same uniform motion may be transmitted from _a_ _a_, to _b_ _b_, by pressing the tooth face _m_ _y_ against the tooth flank _m_ _x_. Let it now be noted that the curve _y_ _m_ corresponds to the face of a tooth, as say the face E of a tooth on _a_ _a_, and that curve _x_ _m_ corresponds to the flank of a tooth on _b_ _b_, as say to the flank F, short portions only of the curves being used for those flanks. If the direction of rotation of the three wheels was reversed, the same shape of curves would be produced, but they would lie in an opposite direction, and would, therefore, be suitable for the other sides of the teeth. In this case, the contact of tooth upon tooth will be on the other side of the line of centres, as at some point between _n_ and Q. [Illustration: Fig. 28.] In this illustration the diameter of the rolling or describing circle Q, being less than the radius of the wheels _a_ _a_ or _b_ _b_, the flanks of the teeth are curves, and the two wheels being of the same diameter, the teeth on the two are of the same shape. But the principles governing the proper formation of the curve remain the same whatever be the conditions. Thus in Fig. 28 are segments of a pair of wheels of equal diameter, but the describing, rolling, or curve-generating circle is equal in diameter to the radius of the wheels. Motion is supposed to have occurred in the direction of the arrows, and the tracing point to have moved from _n_ to _m_. During this motion it will have marked a curve _y_ _m_, a portion of the _y_ end serving for the face of a tooth on one wheel, and also the line _k_ _x_, a continuation of which serves for the flank of a tooth on the other wheel. In Fig. 29 the pitch circles only of the wheels are marked, _a_ _a_ being twice the diameter of _b_ _b_, and the curve-generating circle being equal in diameter to the radius of wheel _b_ _b_. Motion is assumed to have occurred until the pencil point, starting from _n_, had arrived at _o_, marking curves suitable for the face of the teeth on one wheel and for the flanks of the other as before, and the contact of tooth upon tooth still, at every point in the path of the teeth, occurring at some point of the arc _n_ _o_. Thus when the point had proceeded as far as point _m_ it will have marked the curve _y_ and the radial line _x_, and when the point had arrived at _o_, it will have prolonged _m_ _y_ into _o_ _g_ and _x_ into _o_ _f_, while in either position the point is marking both lines. The velocities of the wheels remain the same notwithstanding their different diameters, for the arc _n_ _g_ must obviously (if the wheels rotate without slip by friction of their surfaces while the curves are traced) be equal in length to the arc _n_ _f_ or the arc _n_ _o_. [Illustration: Fig. 29.] [Illustration: Fig. 30.] In Fig. 30 _a_ _a_ and _b_ _b_ are the pitch circles of two wheels as before, and _c_ _c_ the pitch circle of an annular or internal gear, and D is the rolling or describing circle. When the describing point arrived at _m_, it will have marked the curve _y_ for the face of a tooth on _a_ _a_, the curve _x_ for the flank of a tooth on _b_ _b_, and the curve _e_ for the face of a tooth on the internal wheel _c_ _c_. Motion being continued _m_ _y_ will be prolonged to _o_ _g_, while simultaneously _x_ will be extended into _o_ _f_ and _e_ into _h_ _v_, the velocity of all the wheels being uniform and equal. Thus the arcs _n_ _v_, _n_ _f_, and _n_ _g_, are of equal length. [Illustration: Fig. 31.] In Fig. 31 is shown the case of a rack and pinion; _a_ _a_ is the pitch line of the rack, _b_ _b_ that of the pinion, A B at a right angle to _a_ _a_, the line of centres, and D the generating circle. The wheel and rack are shown with teeth _n_ on one side simply for clearness of illustration. The pencil point _n_ will, on arriving at _m_, have traced the flank curve _x_ and the curve _y_ for the face of the rack teeth. [Illustration: Fig. 32.] It has been supposed that the three circles rotated together by the frictional contact of their perimeters on the line of centres, but the circumstances will remain the same if the wheels remain at rest while the generating or describing circle is rolled around them. Thus in Fig. 32 are two segments of wheels as before, _c_ representing the centre of a tooth on _a_ _a_, and _d_ representing the centre of a tooth on _b_ _b_. Now suppose that a generating or rolling circle be placed with its pencil point at _e_, and that it then be rolled around _a_ _a_ until it had reached the position marked 1, then it will have marked the curve from _e_ to _n_, a part of this curve serving for the face of tooth _c_. Now let the rolling circle be placed within the pitch circle _a_ _a_ and its pencil point _n_ be set to _e_, then, on being rolled to position 2, it will have marked the flank of tooth _c_. For the other wheel suppose the rolling wheel or circle to have started from _f_ and rolled to the line of centres as in the cut, it will have traced the curve forming the face of the tooth _d_. For the flank of _d_ the rolling circle or wheel is placed within _b_ _b_, its tracing point set at _f_ on the pitch circle, and on being rolled to position 3 it will have marked the flank curve. The curves thus produced will be precisely the same as those produced by rotating all three wheels about their axes, as in our previous demonstrations. The curves both for the faces and for the flanks thus obtained will vary in their curvature with every variation in either the diameter of the generating circle or of the base or pitch circle of the wheel. Thus it will be observable to the eye that the face curve of tooth _c_ is more curved than that of _d_, and also that the flank curve of _d_ is more spread at the root than is that for _c_, which has in this case resulted from the difference between the diameter of the wheels _a_ _a_ and _b_ _b_. But the curves obtained by a given diameter of rolling circle on a given diameter of pitch circle will be correct for any pitch of teeth that can be used upon wheels having that diameter of pitch circle. Thus, suppose we have a curve obtained by rolling a wheel of 20 inches circumference on a pitch circle of 40 inches circumference--now a wheel of 40 inches in circumference may contain 20 teeth of 2 inch arc pitch, or 10 teeth of 4 inch arc pitch, or 8 teeth of 5 inch arc pitch, and the curve may be used for either of those pitches. If we trace the path of contact of each tooth, from the moment it takes until it leaves contact with a tooth upon the other wheel, we shall find that contact begins at the point where the flank of the tooth on the wheel that drives or imparts motion to the other wheel, meets the face of the tooth on the driven wheel, which will always be where the point of the driven tooth cuts or meets the generating or rolling circle of the driving tooth. Thus in Fig. 33 are represented segments of two spur-wheels marked respectively the driver and the driven, their generating circles being marked at G and G´, and X X representing the line of centres. Tooth A is shown in the position in which it commences its contact with tooth B at B. Secondly, we shall find that as these two teeth approach the line of centres X, the point of contact between them moves or takes place along the thickened arc or curve C X, or along the path of the generating circle G. Thus we may suppose tooth D to be another position of tooth A, the contact being at F, and as motion was continued the contact would pass along the thickened curve until it arrived at the line of centres X. Now since the teeth have during this path of contact approached the line of centres, this part of the whole arc of action or of the path of contact is termed the arc of approach. After the two teeth have passed the line of centres X, the path of contact of the teeth will be along the dotted arc from X to L, and as the teeth are during this period of motion receding from X this part of the contact path is termed the arc of recess. That contact of the teeth would not occur earlier than at C nor later than at L, is shown by the dotted teeth sides; thus A and B would not touch when in the position denoted by the dotted teeth, nor would teeth I and K if in the position denoted by their dotted lines. [Illustration: Fig. 33.] If we examine further into this path of contact we find that throughout its whole path the face of the tooth of one wheel has contact with the flank only of the tooth of the other wheel, and also that the flank only of the driving-wheel tooth has contact before the tooth reaches the line of centres, while the face of only the driving tooth has contact after the tooth has passed the line of centres. Thus the flanks of tooth A and of tooth D are in driving contact with the faces of teeth B and E, while the face of tooth H is in contact with the flank of tooth I. These conditions will always exist, whatever be the diameters of the wheels, their number of teeth or the diameter of the generating circle. That is to say, in fully developed epicycloidal teeth, no matter which of two wheels is the driver or which the driven wheel, contact on the teeth of the driver will always be on the tooth flank during the arc of approach and on the tooth face during the arc of recess; while on the driven wheel contact during the arc of approach will be on the tooth face only, and during the arc of recess on the tooth flank only, it being borne in mind that the arcs of approach and recess are reversed in location if the direction of revolution be reversed. Thus if the direction of wheel motion was opposite to that denoted by the arrows in Fig. 33 then the arc of approach would be from M to X, and the arc of recess from X to N. It is laid down by Professor Willis that the motion of a pair of gear-wheels is smoother in cases where the path of contact begins at the line of centres, or, in other words, when there is no arc of approach; and this action may be secured by giving to the driven wheel flanks only, as in Fig. 34, in which the driver has fully developed teeth, while the teeth on the driven have no faces. In this case, supposing the wheels to revolve in the direction of arrow P, the contact will begin at the line of centres X, move or pass along the thickened arc and end at B, and there will be contact during the arc of recess only. Similarly, if the direction of motion be reversed as denoted by arrow Q, the driver will begin contact at X, and cease contact at H, having, as before, contact during the arc of recess only. But if the wheel W were the driver and V the driven, then these conditions would be exactly reversed. Thus, suppose this to be the case and the direction of motion be as denoted by arrow P, the contact would occur during the arc of approach, from H to X, ceasing at X. Or if W were the driver, and the direction of motion was as denoted by Q, then, again, the path of contact would be during the arc of approach only, beginning at B and ceasing at X, as denoted by the thickened arc B X. The action of the teeth will in either case serve to give a theoretically perfect motion so far as uniformity of velocity is concerned, or, in other words, the motion of the driver will be transmitted with perfect uniformity to the driven wheel. It will be observed, however, that by the removal of the faces of the teeth, there are a less number of teeth in contact at each instant of time; thus, in Fig. 33 there is driving contact at three points, C, F, and J, while in Fig. 34 there is driving contact at two points only. From the fact that the faces of the teeth work with the flanks only, and that one side only of the teeth comes into action, it becomes apparent that each tooth may have curves formed by four different diameters of rolling or generating circles and yet work correctly, no matter which wheel be the driver, or which the driven wheel or follower, or in which direction motion occurs. Thus in Fig. 35, suppose wheel V to be the driver, having motion in the direction of arrow P, then faces a on the teeth of V will work with flanks B of the teeth on W, and so long as the curves for these faces and flanks are obtained with the same diameter of rolling circle, the action of the teeth will be correct, no matter what the shapes of the other parts of the teeth. Now suppose that V still being the driver, motion occurs in the other direction as denoted by Q, then the faces C of the teeth on V will drive the flanks C of the teeth on W, and the motion will again be correct, providing that the same diameter (whatever it may be) of rolling circle be used for these faces and flanks, irrespective, of course, of what diameter of rolling circle is used for any other of the teeth curves. Now suppose that W is the driver, motion occurring in the direction of P, then faces E will drive flanks F, and the motion will be correct as before if the curves E and F are produced with the same diameter of rolling circle. Finally, let W be the driving wheel and motion occur in the direction of Q, and faces G will drive flanks H, and yet another diameter of rolling circle may be used for these faces and flanks. Here then it is shown that four different diameters of rolling circles may be used upon a pair of wheels, giving teeth-forms that will fill all the requirements so far as correctly transmitting motion is concerned. In the case of a pair of wheels having an equal number of teeth, so that each tooth on one wheel will always fall into gear with the same tooth on the other wheel, every tooth may have its individual curves differing from all the others, providing that the corresponding teeth on the other wheel are formed to match them by using the same size of rolling circle for each flank and face that work together. [Illustration: Fig. 34.] [Illustration: Fig. 35.] It is obvious, however, that such teeth would involve a great deal of labor in their formation and would possess no advantage, hence they are not employed. It is not unusual, however, in a pair of wheels that are to gear together and that are not intended to interchange with other wheels, to use such sizes as will give to for the face of the teeth on the largest wheel of the pair and for the flanks of the teeth of the smallest wheel, a generating circle equal in diameter to the radius of the smallest wheel, and for the faces of the teeth of the small wheel and the flanks of the teeth of the large one, a generating circle whose diameter equals the radius of the large wheel. [Illustration: Fig. 36.] It will now be evident that if we have planned a pair or a train of wheels we may find how many teeth will be in contact for any given pitch, as follows. In Fig. 36 let A, B, and C, represent three blanks for gear-wheels whose addendum circles are M, N and O; P representing the pitch circles, and Q representing the circles for the roots of the teeth. Let X and Y represent the lines of centres, and A, H, I and K the generating or rolling circle, whose centres are on the respective lines of centres--the diameter of the generating circle being equal to the radius of the pinion, as in the Willis system, then, the pinion M being the driver, and the wheels revolving in the direction denoted by the respective arrows, the arc or path of contact for the first pair will be from point D, where the generating circle G crosses circle N to E, where generating circle H crosses the circle M, this path being composed of two arcs of a circle. All that is necessary, therefore, is to set the compasses to the pitch the teeth are to have and step them along these arcs, and the number of steps will be the number of teeth that will be in contact. Similarly, for the second pair contact will begin at R and end at S, and the compasses applied as before (from R to S) along the arc of generating circle I to the line of centres, and thence along the arc of generating circle K to S, will give in the number of steps, the number of teeth that will be in contact. If for any given purpose the number of teeth thus found to be in contact is insufficient; the pitch may be made finer. [Illustration: Fig. 37.] When a wheel is intended to be formed to work correctly with any other wheel having the same pitch, or when there are more than two wheels in the train, it is necessary that the same size of generating circle be used for all the faces and all the flanks in the set, and if this be done the wheels will work correctly together, no matter what the number of the teeth in each wheel may be, nor in what way they are interchanged. Thus in Fig. 37, let A represent the pitch line of a rack, and B and C the pitch circles of two wheels, then the generating circle would be rolled within B, as at 1, for the flank curves, and without it, as at 2, for the face curves of B. It would be rolled without the pitch line, as at 3, for the rack faces, and within it, as at 4, for the rack flanks, and without C, as at 5, for the faces, and within it, as at 6, for flanks of the teeth on C, and all the teeth will work correctly together however they be placed; thus C might receive motion from the rack, and B receive motion from C. Or if any number of different diameters of wheels are used they will all work correctly together and interchange perfectly, with the single condition that the same size of generating circle be used throughout. But the curves of the teeth so formed will not be alike. Thus in Fig. 38 are shown three teeth, all struck with the same size of generating circle, D being for a wheel of 12 teeth, E for a wheel of 50 teeth, and F a tooth of a rack; teeth E, F, being made wider so as to let the curves show clearly on each side, it being obvious that since the curves are due to the relative sizes of the pitch and generating circles they are equally applicable to any pitch or thickness of teeth on wheels having the same diameters of pitch circle. [Illustration: Fig. 38.] In determining the diameter of a generating circle for a set or train of wheels, we have the consideration that the smaller the diameter of the generating circle in proportion to that of the pitch circle the more the teeth are spread at the roots, and this creates a pressure tending to thrust the wheels apart, thus causing the axle journals to wear. In Fig. 39, for example, A A is the line of centres, and the contact of the curves at B C would cause a thrust in the direction of the arrows D, E. This thrust would exist throughout the whole path of contact save at the point F, on the line of centres. This thrust is reduced in proportion as the diameter of the generating circle is increased; thus in Fig. 40, is represented a pair of pinions of 12 teeth and 3 inch pitch, and C being the driver, there is contact at E, and at G, and E being a radial line, there is obviously a minimum of thrust. [Illustration: Fig. 39.] [Illustration: Fig. 40.] What is known as the Willis system for interchangeable gearing, consists of using for every pitch of the teeth a generating circle whose diameter is equal to the radius of a pinion having 12 teeth, hence the pinion will in each pitch have radial flanks, and the roots of the teeth will be more spread as the number of teeth in the wheel is increased. Twelve teeth is the least number that it is considered practicable to use; hence it is obvious that under this system all wheels of the same pitch will work correctly together. [Illustration: Fig. 41.] Unless the faces of the teeth and the flanks with which they work are curves produced from the same size of generating circle, the velocity of the teeth will not be uniform. Obviously the revolutions of the wheels will be proportionate to their numbers of teeth; hence in a pair of wheels having an equal number of teeth, the revolutions will per force be equal, but the driver will not impart uniform motion to the driven wheel, but each tooth will during the path of contact move irregularly. The velocity of a pair of wheels will be uniform at each instant of time, if a line normal to the surfaces of the curves at their point of contact passes through the point of contact of the pitch circles on the line of centres of the wheels. Thus in Fig. 41, the line A A is tangent to the teeth curves where they touch, and D at a right angle to A A, and meets it at the point of the tooth curves, hence it is normal to the point of contact, and as it meets the pitch circles on the line of centres the velocity of the wheels will be uniform. The amount of rolling motion of the teeth one upon the other while passing through the path of contact, will be a minimum when the tooth curves are correctly formed according to the rules given. But furthermore the sliding motion will be increased in proportion as the diameter of the generating circle is increased, and the number of teeth in contact will be increased because the arc, or path, of contact is longer as the generating circle is made larger. [Illustration: Fig. 42.] Thus in Fig. 42 is a pair of wheels whose tooth curves are from a generating circle equal to the radius of the wheels, hence the flanks are radial. The teeth are made of unusual depth to keep the lines in the engraving clear. Suppose V to be the driver, W the driven wheel or follower, and the direction of motion as at P, contact upon tooth A will begin at C, and while A is passing to the line of centres the path of contact will pass along the thickened line to X. During this time the whole length of face from C to R will have had contact with the length of flank from C to N, and it follows that the length of face on A that rolled on C N can only equal the length of C N, and that the amount of sliding motion must be represented by the length of R N on A, and the amount of rolling motion by the length N C. Again, during the arc of recess (marked by dots) the length of flank that will have had contact is the depth from S to Ls, and over this depth the full length of tooth face on wheel V will have swept, and as L S equals C N, the amount of rolling and of sliding motion during the arc of recess is equal to that during the arc of approach, and the action is in both cases partly a rolling and partly a sliding one. The two wheels are here shown of the same diameter, and therefore contain an equal number of teeth, hence the arcs of approach and of recess are equal in length, which will not be the case when one wheel contains more teeth than the other. Thus in Fig. 43, let A represent a segment of a pinion, and B a segment of a spur-wheel, both segments being blank with their pitch circles, the tooth height and depth being marked by arcs of circles. Let C and D represent the generating circles shown in the two respective positions on the line of centres. Let pinion A be the driver moving in the direction of P, and the arc of approach will be from E to X along the thickened arc, while the arc of recess will be as denoted by the dotted arc from X to F. The distance E X being greater than distance X F, therefore the arc of approach is longer than that of recess. But suppose B to be the driver and the reverse will be the case, the arc of approach will begin at G and end at X, while the arc of recess will begin at X and end at H, the latter being farther from the line of centres than G is. It will be found also that, one wheel being larger than the other, the amount of sliding and rolling contact is different for the two wheels, and that the flanks of the teeth on the larger wheel B, have contact along a greater portion of their depths than do the flanks of those on the smaller, as is shown by the dotted arc I being farther from the pitch circle than the dotted arc J is, these two dotted arcs representing the paths of the lowest points of flank contact, points F and G, marking the initial lowest contact for the two directions of revolution. [Illustration: Fig. 43.] Thus it appears that there is more sliding action upon the teeth of the smaller than upon those of the larger wheel, and this is a condition that will always exist. In Fig. 44 is represented portion of a pair of wheels corresponding to those shown in Fig. 42, except that in this case the diameter of the generating circle is reduced to one quarter that of the pitch diameter of the wheels. V is the driver in the direction the teeth of V that will have contact is C N, which, the wheels, being of equal diameter, will remain the same whichever wheel be the driver, and in whatever direction motion occurs. The amount of rolling motion is, therefore, C N, and that of sliding is the difference between the distance C N and the length of the tooth face. [Illustration: Fig. 44.] If now we examine the distance C N in Fig. 42, we find that reducing the diameter of generating circle in Fig. 44 has increased the depth of flank that has contact, and therefore increased the rolling motion of the tooth face along the flank, and correspondingly diminished the sliding action of the tooth contact. But at the same time we have diminished the number of teeth in contact. Thus in Fig. 42 there are three teeth in driving contact, while in Fig. 44 there are but two, viz., D and E. [Illustration: Fig. 45.] In an article by Professor Robinson, attention is called to the fact that if the teeth of wheels are not formed to have correct curves when new, they cannot be improved by wear; and this will be clearly perceived from the preceding remarks upon the amount of rolling and sliding contact. It will also readily appear that the nearer the diameter of the generating to that of the base circle the more the teeth wear out of correct shape; hence, in a train of gearing in which the generating circle equals the radius of the pinion, the pinion will wear out of shape the quickest, and the largest wheel the least; because not only does each tooth on the pinion more frequently come into action on account of its increased revolutions, but furthermore the length of flank that has contact is less, while the amount of sliding action is greater. In Fig. 45, for example, are a wheel and pinion, the latter having radial flanks and the pinion being the driver, the arc of approach is the thickened arc from C to the line of centres, while the arc of recess is denoted by the dotted arc. As contact on the pinion flank begins at point C and ends at the line of centres, the total depth of flank that suffers wear from the contact is that from C to N; and as the whole length of the wheel tooth face sweeps over this depth C N, the pinion flanks must wear faster than the wheel faces, and the pinion flanks will wear underneath, as denoted by the dotted curve on the flanks of tooth W. In the case of the wheel, contact on its tooth flanks begins at the line of centres and ends at L, hence that flank can only wear between point L and the pitch line L; and as the whole length of pinion face sweeps on this short length L S, the pinion flank will wear most, the wear being in the direction of the dotted arc on the left-hand side V of the tooth. Now the pinion flank depth C N, being less than the wheel flank depth S L, and the same length of tooth face sweeping (during the path of contact) over both, obviously the pinion tooth will wear the most, while both will, as the wear proceeds, lose their proper flank curve. In Fig. 46 the generating arcs, G and G´, and the wheel are the same, but the pinion is larger. As a result the acting length C N, of pinion flank is increased, as is also the acting length S L, of wheel flank; hence, the flanks of both wheels would wear better, and also better preserve their correct and original shapes. It has been shown, when referring to Figs. 42 and 44, when treating of the amount of sliding and of rolling motion, that the smaller the diameter of rolling circle in proportion to that of pitch circle, the longer the acting length of flank and the more the amount of rolling motion; and it follows that the teeth would also preserve their original and true shape better. But the wear of the teeth, and the alteration of tooth form by reason of that wear, will, in any event, be greater upon the pinion than upon the wheel, and can only be equal when the two wheels are of equal diameter, in which case the tooth curves will be alike on both wheels, and the acting depths of flank will be equal, as shown in Fig. 47, the flanks being radial, and the acting depths of flank being shown at J K. In Fig. 48 is shown a pair of wheels with a generating circle, G and G´, of one quarter the diameter of the base circle or pitch diameter, and the acting length of flank is shown at L M. The wear of the teeth would, therefore, in this latter case, cause it in time to assume the form shown in Fig. 49. But it is to be noted that while the acting depth of flank has been increased the arcs of contact have been diminished, and that in Fig. 47 there are two teeth in contact, while in Fig. 48 there is but one, hence the pressure upon each tooth is less in proportion as the diameter of the generating circle is increased. If a train of wheels are to be constructed, or if the wheels are to be capable of interchanging with other combinations of wheels of the same pitch, the diameter of the generating circle must be equal to the smallest wheel or pinion, which is, under the Willis system, a pinion of 12 teeth; under the Pratt and Whitney, and Brown and Sharpe systems, a pinion of 15 teeth. [Illustration: Fig. 46.] [Illustration: Fig. 47.] But if a pair or a particular train of gears are to be constructed, then a diameter of generating circle may be selected that is considered most suitable to the particular conditions; as, for example, it may be equal to the radius of the smallest wheel giving it radial flanks, or less than that radius giving parallel or spread flanks. But in any event, in order to transmit continuous motion, the diameter of generating circle must be such as to give arcs of action that are equal to the pitch, so that each pair of teeth will come into action before the preceding pair have gone out of action. [Illustration: Fig. 48.] It may now be pointed out that the degrees of angle that the teeth move through always exceeds the number of degrees of angle contained in the paths of contact, or, in other words, exceeds the degrees contained in the arcs of approach and recess combined. [Illustration: Fig. 49.] In Fig. 50, for example, are a wheel A and pinion B, the teeth on the wheel being extended to a point. Suppose that the wheel A is the driver, and contact will begin between the two teeth D and F on the dotted arc. Now suppose tooth D to have moved to position C, and F will have been moved to position H. The degrees of angle the pinion has been moved through are therefore denoted by I, whereas the degrees of angle the arcs of contact contain are therefore denoted by J. The degrees of angle that the wheel A has moved through are obviously denoted by E, because the point of tooth D has during the arcs of contact moved from position D to position C. The degrees of angle contained in its path of contact are denoted by K, and are less than E, hence, in the case of teeth terminating in a point as tooth D, the excess of angle of action over path of contact is as many degrees as are contained in one-half the thickness of the tooth, while when the points of the teeth are cut off, the excess is the number of degrees contained in the distance between the corner and the side of the tooth as marked on a tooth at P. [Illustration: Fig. 50.] With a given diameter of pitch circle and pitch diameter of wheel, the length of the arc of contact will be influenced by the height of the addendum from the pitch circle, because, as has been shown, the arcs of approach and of recess, respectively, begin and end on the addendum circle. If the height of the addendum on the follower be reduced, the arc of approach will be reduced, while the arc of recess will not be altered; and if the follower have no addendum, contact between the teeth will occur on the arc of recess only, which gives a smoother motion, because the action of the driver is that of dragging rather than that of pushing the follower. In this case, however, the arc of recess must, to produce continuous motion, be at least equal to the pitch. It is obvious, however, that the follower having no addendum would, if acting as a driver to a third wheel, as in a train of wheels, act on its follower, or the fourth wheel of the train, on the arc of approach only; hence it follows that the addendum might be reduced to diminish, or dispensed with to eliminate action, on the arc of approach in the follower of a pair of wheels only, and not in the case of a train of wheels. To make this clear to the reader it may be necessary to refer again to Fig. 33 or 34, from which it will be seen that the action of the teeth of the driver on the follower during the arc of approach is produced by the flanks of the driver on the faces of the follower. But if there are no such faces there can be no such contact. On the arc of recess, however, the faces of the driver act on the flanks of the follower, hence the absence of faces on the follower is of no import. From these considerations it also appears that by giving to the driver an increase of addendum the arc of recess may be increased without affecting the arc of approach. But the height of addendum in machinists' practice is made a constant proportion of the pitch, so that the wheel may be used indiscriminately, as circumstances may require, as either a driver or a follower, the arcs of approach and of recess being equal. The height of addendum, however, is an element in determining the number of teeth in contact, and upon small pinions this is of importance. [Illustration: Fig. 51.] In Fig. 51, for example, is shown a section of two pinions of equal diameters, and it will be observed that if the full line A determined the height of the addendum there would be contact either at C or B only (according to the direction in which the motion took place). With the addendum extended to the dotted circle, contact would be just avoided, while with the addendum extended to D there would be contact either at E or at F, according to which direction the wheel had motion. This, by dividing the strain over two teeth instead of placing it all upon one tooth, not only doubles the strength for driving capacity, but decreases the wear by giving more area of bearing surface at each instant of time, although not increasing that area in proportion to the number of teeth contained in the wheel. In wheels of larger diameter, short teeth are more permissible, because there are more teeth in contact, the number increasing with the diameters of the wheels. It is to be observed, however, that from having radial flanks, the smallest wheel is always the weakest, and that from making the most revolutions in a given time, it suffers the most from wear, and hence requires the greatest attainable number of teeth in constant contact at each period of time, as well as the largest possible area of bearing or wearing surface on the teeth. It is true that increasing the "depth of tooth to pitch line" increases the whole length of tooth, and, therefore, weakens it; but this is far more than compensated for by distributing the strain over a greater number of teeth. This is in practice accomplished, _when circumstances will permit_, by making the pitch finer, giving to a wheel, of a given diameter, a greater number of teeth. [Illustration: Fig. 52.] When the wheels are required to transmit motion rather than power (as in the case of clock wheels), to move as frictionless as possible, and to place a minimum of thrust on the journals of the shafts of the wheels, the generating circle may be made nearly as large as the diameter of the pitch circle, producing teeth of the form shown in Fig. 52. But the minimum of friction is attained when the two flanks for the tooth are drawn into one common hypocycloid, as in Fig. 53. The difference between the form of tooth shown in Fig. 52 and that shown in Fig. 53, is merely due to an increase in the diameter of the generating circle for the latter. It will be observed that in these forms the acting length of flank diminishes in proportion as the diameter of the generating circle is increased, the ultimate diameter of generating circle being as large as the pitch circles. [Illustration: Fig. 53.] [1]This form is undesirable in that there is contact on one side only (on the arc of approach) of the line of centres, but the flanks of the teeth may be so modified as to give contact on the arc of recess also, by forming the flanks as shown in Fig. 54, the flanks, or rather the parts within the pitch circles, being nearly half circles, and the parts without with peculiarly formed faces, as shown in the figure. The pitch circles must still be regarded as the rolling circles rolling upon each other. Suppose _b_ a tracing point on B, then as B rolls on A it will describe the epicycloid _a_ _b_. A parallel line _c_ _d_ will work at a constant distance as at _c_ _d_ from _a_ _b_, and this distance may be the radius of that part of D that is within the pitch line, the same process being applied to the teeth on both wheels. Each tooth is thus composed of a spur based upon a half cylinder. [1] From an article by Professor Robinson. [Illustration: Fig. 54.] Comparing Figs. 53 and 54, we see that the bases in 53 are flattest, and that the contact of faces upon them must range nearer the pitch line than in 54. Hence, 53 presents a more favorable obliquity of the line of direction of the pressures of tooth upon tooth. In seeking a still more favorable direction by going outside for the point of contact, we see by simply recalling the method of generating the tooth curves, that tooth contacts outside the pitch lines have no possible existence; and hence, Fig. 53 may be regarded as representing that form of toothed gear which will operate with less friction than any other known form. [Illustration: Fig. 55.] This statement is intended to cover fixed teeth only, and not that complicated form of the trundle wheel in which the cylinder teeth are friction rollers. No doubt such would run still easier, even with their necessary one-sided contacts. Also, the statement is supposed to be confined to such forms of teeth as have good practical contacts at and near the line of centres. Bevel-gear wheels are employed to transmit motion from one shaft to another when the axis of one is at an angle to that of the other. Thus in Fig. 55 is shown a pair of bevel-wheels to transmit motion from shafts at a right angle. In bevel-wheels all the lines of the teeth, both at the tops or points of the teeth, at the bottoms of the spaces, and on the sides of the teeth, radiate from the centre E, where the axes of the two shafts would meet if produced. Hence the depth, thickness, and height of the tooth decreases as the point E is approached from the diameter of the wheel, which is always measured on the pitch circle at the largest end of the cone, or in other words, at the largest pitch diameter. The principles governing the practical construction of the curves for the teeth of the bevel-wheels may be explained as follows:-- In Fig. 56 let F and G represent two shafts, rotating about their respective axes; and having cones whose greatest diameters are at A and B, and whose points are at E. The diameter A being equal to that of B their circumferences will be equal, and the angular and velocity ratios will therefore be equal. [Illustration: Fig. 56.] Let C and D represent two circles about the respective cones, being equidistant from E, and therefore of equal diameters and circumferences, and it is obvious that at every point in the length of each cone the velocity will be equal to a point upon the other so long as both points are equidistant from the points of intersection of the axes of the two shafts; hence if one cone drive the other by frictional contact of surfaces, both shafts will be rotated at an equal speed of rotation, or if one cone be fixed and the other moved around it, the contact of the surfaces will be a rolling contact throughout. The line of contact between the two cones will be a straight line, radiating at all times from the point E. If such, however, is not the case, then the contact will no longer be a rolling one. Thus, in Fig. 57 the diameters or circumferences at A and B being equal, the surfaces would roll upon each other, but on account of the line of contact not radiating from E (which is the common centre of motion for the two shafts) the circumference C is less than that of D, rendering a rolling contact impossible. [Illustration: Fig. 57.] We have supposed that the diameters of the cones be equal, but the conditions will remain the same when their diameters are unequal; thus, in Fig. 58 the circumference of A is twice that of B, hence the latter will make two rotations to one of the former, and the contact will still be a rolling one. Similarly the circumference of D is one half that of C, hence D will also make two rotations to one of C, and the contact will also be a rolling one; a condition which will always exist independent of the diameters of the wheels so long as the angles of the faces, or wheels, or (what is the same thing, the line of contact between the two,) radiates from the point E, which is located where the axes of the shafts would meet. [Illustration: Fig. 58.] [Illustration: Fig. 59.] The principles governing the forms of the cones on which the teeth are to be located thus being explained, we may now consider the curves of the teeth. Suppose that in Fig. 59 the cone A is fixed, and that the cone whose axis is F be rotated upon it in the direction of the arrow. Then let a point be fixed in any part of the circumference of B (say at _d_), and it is evident that the path of this point will be as B rolls around the axis F, and at the same time around A from the centre of motion, E. The curve so generated or described by the point _d_ will be a spherical epicycloid. In this case the exterior of one cone has rolled upon the coned surface of the other; but suppose it rolls upon the interior, as around the walls of a conical recess in a solid body; then a point in its circumference would describe a curve known as the spherical hypocycloid; both curves agreeing (except in their spherical property) to the epicycloid and hypocycloid of the spur-wheel. But this spherical property renders it very difficult indeed to practically delineate or mark the curves by rolling contact, and on account of this difficulty Tredgold devised a method of construction whereby the curves may be produced sufficiently accurate for all practical purposes, as follows:-- [Illustration: Fig. 60.] In Fig. 60 let A A represent the axis of one shaft, and B the axis of the other, the axes of the two meeting at W. Mark E, representing the diameter of one wheel, and F that of the other (both lines representing the pitch circles of the respective wheels). Draw the line G G passing through the point W, and the point T, where the pitch circles E, F meet, and G G will be the line of contact between the cones. From W as a centre, draw on each side of G G dotted lines as _p_, representing the height of the teeth above and below the pitch line G G. At a right angle to G G mark the line J K, and from the junction of this line with axis B (as at Q) as a centre, mark the arc _a_, which will represent the pitch circle for the large diameter of pinion D; mark also the arc _b_ for the addendum and _c_ for the roots of the teeth, so that from _b_ to _c_ will represent the height of the tooth at that end. [Illustration: Fig. 61.] Similarly from P, as a centre, mark (for the large diameter of wheel C,) the pitch circle _g_, root circle _h_, and addendum _i_. On these arcs mark the curves in the same manner as for spur-wheels. To obtain these arcs for the small diameters of the wheels, draw M M parallel to J K. Set the compasses to the radius R L, and from P, as a centre, draw the pitch circle _k_. To obtain the depth for the tooth, draw the dotted line _p_, meeting the circle _h_, and the point W. A similar line from circle _i_ to W will show the height of the addendum, or extreme diameter; and mark the tooth curves on _k_, _l_, _m_, in the same manner as for a spur-wheel. Similarly for the pitch circle of the small end of the pinion teeth, set the compasses to the radius S L, and from Q as a centre, mark the pitch circle _d_, outside of _d_ mark _e_ for the height of the addendum and inside of _d_ mark _f_ for the roots of the teeth at that end. The distance between the dotted lines (as _p_) represents the full height of the teeth, hence _h_ meets line _p_, being the root of tooth for the large wheel, and to give clearance, the point of the pinion teeth is marked below, thus arc _b_ does not meet _h_ or _p_. Having obtained these arcs the curves are rolled as for a spur-wheel. A tooth thus marked out is shown at _x_, and from its curves between _b_ _c_, a template for the large diameter of the pinion tooth may be made, while from the tooth curves between the arcs _e_ _f_, a template for the smallest tooth diameter of the pinion can be made. Similarly for the wheel C the outer end curves are marked on the lines _g_, _h_, _i_, and those for the inner end on the lines _k_, _l_, _m_. [Illustration: Fig. 62.] Internal or annular gear-wheels have their tooth curves formed by rolling the generating circle upon the pitch circle or base circle, upon the same general principle as external or spur-wheels. But the tooth of the annular wheel corresponds with the space in the spur-wheel, as is shown in Fig. 61, in which curve A forms the flank of a tooth on a spur-wheel P, and the face of a tooth on the annular wheel W. It is obvious then that the generating circle is rolled within the pitch circle for the face of the wheel and without for its flank, or the reverse of the process for spur-wheels. But in the case of internal or annular wheels the path of contact of tooth upon tooth with a pinion having a given number of teeth increases in proportion as the number of teeth in the wheel is diminished, which is also the reverse of what occurs in spur-wheels; as will readily be perceived when it is considered that if in an internal wheel the pinion have as many teeth as the wheel the contact would exist around the whole pitch circles of the wheel and pinion and the two would rotate together without any motion of tooth upon tooth. Obviously then we have, in the case of internal wheels, a consideration as to what is the greatest number (as well as what is the least number) of teeth a pinion may contain to work with a given wheel, whereas in spur-wheels the reverse is again the case, the consideration being how few teeth the wheel may contain to work with a given pinion. Now it is found that although the curves of the teeth in internal wheels and pinions may be rolled according to the principles already laid down for spur-wheels, yet cases may arise in which internal gears will not work under conditions in which spur-wheels would work, because the internal wheels will not engage together. Thus, in Fig. 62, is a pinion of 12 teeth and a wheel of 22 teeth, a generating circle having a diameter equal to the radius of the pinion having been used for all the tooth curves of both wheel and pinion. It will be observed that teeth A, B, and C clearly overlap teeth D, E, and F, and would therefore prevent the wheels from engaging to the requisite depth. This may of course be remedied by taking the faces off the pinion, as in Fig. 63, and thus confining the arc of contact to an arc of recess if the pinion drives, or an arc of approach if the wheel drives; or the number of teeth in the pinion may be reduced, or that in the wheel increased; either of which may be carried out to a degree sufficient to enable the teeth to engage and not interfere one with the other. In Fig. 64 the number of teeth in the pinion P is reduced from 12 to 6, the wheel W having 22 as before, and it will be observed that the teeth engage and properly clear each other. [Illustration: Fig. 63.] By the introduction into the figure of a segment of a spur-wheel also having 22 teeth and placed on the other side of the pinion, it is shown that the path of contact is greater, and therefore the angle of action is greater, in internal than in spur gearing. Thus suppose the pinion to drive in the direction of the arrows and the thickened arcs A B will be the arcs of approach, A measuring longer than B. The dotted arcs C D represent the arcs of receding contact and C is found longer than D, the angles of action being 66° for the spur-wheels and 72° for the annular wheel. On referring again to Fig. 62 it will be observed that it is the faces of the teeth on the two wheels that interfere and will prevent them from engaging, hence it will readily occur to the mind that it is possible to form the curves of the pinion faces correct to work with the faces of the wheel teeth as well as with the flanks; or it is possible to form the wheel faces with curves that will work correctly with the faces, as well as with the flanks of the pinion teeth, which will therefore increase the angle of action, and Professor McCord has shown in an article in the London _Engineering_ how to accomplish this in a simple and yet exceedingly ingenious manner which may be described as follows:-- [Illustration: Fig. 64.] It is required to find a describing circle that will roll the curves for the flanks of the pinion and the faces of the wheels, and also a describing circle for the flanks of the wheel and the faces of the pinion; the curve for the wheel faces to work correctly with the faces as well as with the flanks of the pinion, and the curve for the pinion faces to work correctly with both the flanks and faces of the internal wheel. [Illustration: Fig. 65.] [Illustration: Fig. 66.] In Fig. 65 let P represent the pitch circle of an annular or internal wheel whose centre is at A, and Q the pitch circle of a pinion whose centre is at B, and let R be a describing circle whose centre is at C, and which is to be used to roll all the curves for the teeth. For the flanks of the annular wheel we may roll R within P, while for the faces of the wheel we may roll R outside of P, but in the case of the pinion we cannot roll R within Q, because R is larger than Q, hence we must find some other rolling circle of less diameter than R, and that can be used in its stead (the radius of R always being greater than the radius of the axis of the wheel and pinion for reasons that will appear presently). Suppose then that in Fig. 66 we have a ring whose bore R corresponds in diameter to the intermediate describing circle R, Fig. 65 and that Q represents the pinion. Then we may roll R around and in contact with the pinion Q, and a tracing point in R will trace the curve M N O, giving a curve a portion of which may be used for the faces of the pinion. But suppose that instead of rolling the intermediate describing circle R around P, we roll the circle T around P, and it will trace precisely the same curve M N O; hence for the faces of the pinion we have found a rolling circle T which is a perfect substitute for the intermediate circle Q, and which it will always be, no matter what the diameters of the pinion and of the intermediate describing circle may be, providing that the diameter of T is equal to the difference between the diameters of the pinion and that of the intermediate describing circle as in the figure. If now we use this describing circle to roll the flanks of the annular wheel as well as the faces of the pinion, these faces and flanks will obviously work correctly together. Since this describing circle is rolled on the outside of the pinion and on the outside of the annular wheel we may distinguish it as the exterior describing circle. [Illustration: Fig. 67.] Now instead of rolling the intermediate describing circle R within the annular wheel P for the face curves of the teeth upon P, we may find some other circle that will give the same curve and be small enough to be rolled within the pinion Q for its teeth flanks. Thus in Fig. 67 P represents the pitch circle of the annular wheel and R the intermediate circle, and if R be rolled within P, a point on the circumference of R will trace the curve V W. But if we take the circle S, having a diameter equal to the difference between the diameter of R and that of P, and roll it within P, a point in its circumference will trace the same curve V W; hence S is a perfect substitute for R, and a portion of the curve V W may be used for the faces of the teeth on the annular wheel. The circle S being used for the pinion flanks, the wheel faces and pinion flanks will work correctly together, and as the circle S is rolled within the pinion for its flanks and within the wheel for its faces, it may be distinguished as the interior describing circle. To prove the correctness of the construction it may be noted that with the particular diameter of intermediate describing circle used in Fig. 65, the interior and exterior describing circles are of equal diameters; hence, as the same diameter of describing circle is used for all the faces and flanks of the pair of wheels they will obviously work correctly together, in accordance with the rules laid down for spur gearing. The radius of S in Fig. 69 is equal to the radius of the annular wheel, less the radius of the intermediate circle, or the radius from A to C. The radius of the exterior describing circle T is the radius of the intermediate circle less the radius of the pinion, or radius C B in the figure. [Illustration: Fig. 68.] [Illustration: Fig. 69.] Now the diameter of the intermediate circle may be determined at will, but cannot exceed that of the annular wheel or be less than the pinion. But having been selected between these two limits the interior and exterior describing circles derived from it give teeth that not only engage properly and avoid the interference shown in Fig. 62, but that will also have an additional arc of action during the recess, as is shown in Fig. 68, which represents the wheel and pinion shown in Fig. 62, but produced by means of the interior and exterior describing circles. Supposing the pinion to be the driver the arc of approach will be along the thickened arc of the interior describing circle, while during the arc of recess there will be an arc of contact along the dotted portion of the exterior describing circle as in ordinary gearing. But in addition there will be an arc of recess along the dotted portion of the intermediate circle R, which arc is due to the faces of the pinion acting upon the faces as well as upon the flanks of the wheel teeth. It is obvious from this that as soon as a tooth passes the line of centres it will, during a certain period, have two points of contact, one on the arc of the exterior describing circle, and another along the arc of R, this period continuing until the addendum circle of the pinion crosses the dotted arc of the exterior describing circle at Z. The diameters of the interior and exterior describing circles obviously depend upon the diameter of the intermediate circle, and as this may, as already stated, be selected, within certain limits, at will, it is evident that the relative diameters of the interior and exterior describing circles will vary in proportion, the interior becoming smaller and the exterior larger, while from the very mode of construction the radius of the two will equal that of the axes of the wheel and pinion. Thus in Fig. 69 the radii of S, T, equal A B, or the line of centres, and their diameters, therefore, equal the radius of the annular wheel, as is shown by dotting them in at the upper half of the figure. But after their diameters have been determined by this construction either of them may be decreased in diameter and the teeth of the wheels will clear (and not interfere as in Fig. 62), but the action will be the same as in ordinary gear, or in other words there will be no arc of action on the circle R. But S cannot be increased without correspondingly decreasing T, nor can T be increased without correspondingly decreasing S. [Illustration: Fig. 70.] Fig. 70 shows the same pair of gears as in Fig. 68 (the wheel having 22 and the pinion 12 teeth), the diameter of the intermediate circle having been enlarged to decrease the diameter of S and increase that of T, and as these are left of the diameter derived from the construction there is receding action along R from the line of centres to T. [Illustration: Fig. 71.] In Fig. 71 are represented a wheel and pinion, the pinion having but four teeth less than the wheel, and a tooth, J, being shown in position in which it has contact at two places. Thus at _k_ it is in contact with the flank of a tooth on the annular wheel, while at L it is in contact with the face of the same tooth. As the faces of the teeth on the wheel do not have contact higher than point _t_, it is obvious that instead of having them 3/10 of the pitch as at the bottom of the figure, we may cut off the portion X without diminishing the arc of contact, leaving them formed as at the top of the figure. These faces being thus reduced in height we may correspondingly reduce the depth of flank on the pinion by filling in the portion G, leaving the teeth formed as at the top of the pinion. The teeth faces of the wheel being thus reduced we may, by using a sufficiently large intermediate circle, obtain interior and exterior describing circles that will form teeth that will permit of the pinion having but one tooth less than the wheel, or that will form a wheel having but one tooth more than the pinion. The limits to the diameter of the intermediate describing circle are as follows: in Fig. 72 it is made equal in diameter to the pitch diameter of the pinion, hence B will represent the centre of the intermediate circle as well as of the pinion, and the pitch circle of the pinion will also represent the intermediate circle R. To obtain the radius for the interior describing circle we subtract the radius of the intermediate circle from the radius of the annular wheel, which gives A P, hence the pitch circle of the pinion also represents the interior circle R. But when we come to obtain the radius for the exterior describing circle (T), by subtracting the radius of the pinion from that of the intermediate circle, we find that the two being equal give O for the radius of (T), hence there could be no flanks on the pinion. [Illustration: Fig. 72.] Now suppose that the intermediate circle be made equal in diameter to the pitch circle of the annular wheel, and we may obtain the radius for the exterior describing circle T; by subtracting the radius of the pinion from that of the intermediate circle, we shall obtain the radius A B; hence the radius of (T) will equal that of the pinion. But when we come to obtain the radius for the interior describing circle by subtracting the radius of the intermediate circle from that of the annular wheel, we find these two to be equal, hence there would be no interior describing circle, and, therefore, no faces to the pinion. [Illustration: Fig. 73.] The action of the teeth in internal wheels is less a sliding and more a rolling one than that in any other form of toothed gearing. This may be shown as follows: In Fig. 73 let A A represent the pitch circle of an external pinion, and B B that of an internal one, and P P the pitch circle of an external wheel for A A or an internal one for B B, the point of contact at the line of centres being at C, and the direction of rotation P P being as denoted by the arrow; the two pinions being driven, we suppose a point at C, on the pitch circle P P, to be coincident with a point on each of the two pinions at the line of centres. If P P be rotated so as to bring this point to the position denoted by D, the point on the external pinion having moved to E, while that on the internal pinion has moved to F, both having moved through an arc equal to C D, then the distance from E to D being greater than from D to F, more sliding motion must have accompanied the contact of the teeth at the point E than at the point F; and the difference in the length of the arc E D and that of F D, may be taken to represent the excess of sliding action for the teeth on E; for whatever, under any given condition, the amount of sliding contact may be, it will be in the proportion of the length of E D to that of F D. Presuming, then, that the amount of power transmitted be equal for the two pinions, and the friction of all other things being equal--being in proportion to the space passed (or in this case slid) over--it is obvious that the internal pinion has the least friction. CHAPTER II.--THE TEETH OF GEAR-WHEELS.--CAMS. WHEEL AND TANGENT SCREW OR WORM AND WORM GEAR. In Fig. 74 are shown a worm and worm gear partly in section on the line of centres. The worm or tangent screw W is simply one long tooth wound around a cylinder, and its form may be determined by the rules laid down for a rack and pinion, the tangent screw or worm being considered as a rack and the wheel as an ordinary spur-wheel. [Illustration: Fig. 74.] Worm gearing is employed for transmitting motion at a right angle, while greatly reducing the motion. Thus one rotation of the screw will rotate the wheel to the amount of the pitch of its teeth only. Worm gearing possesses the qualification that, unless of very coarse pitch, the worm locks the wheel in any position in which the two may come to a state of rest, while at the same time the excess of movement of the worm over that of the wheel enables the movement of the latter, through a very minute portion of a revolution. And it is evident that, when the plane of rotation of the worm is at a right angle to that of the wheel, the contact of the teeth is wholly a sliding one. The wear of the worm is greater than that of the wheel, because its teeth are in continuous contact, whereas the wheel teeth are in contact only when passing through the angle of action. It may be noted, however, that each tooth upon the worm is longer than the teeth on the wheel in proportion as the circumference of the worm is to the length of wheel tooth. [Illustration: Fig. 75.] If the teeth of the wheel are straight and are set at an angle equal to the angle of the worm thread to its axis, as in Fig. 75, P P representing the pitch line of the worm, C D the line of centres, and _d_ the worm axis, the contact of tooth upon tooth will be at the centre only of the sides of the wheel teeth. It is generally preferred, however, to have the wheel teeth curved to envelop a part of the circumference of the worm, and thus increase the line of contact of tooth upon tooth, and thereby provide more ample wearing surface. [Illustration: Fig. 76.] In this case the form of the teeth upon the worm wheel varies at every point in its length as the line of centres is departed from. Thus in Fig. 76 is shown an end view of a worm and a worm gear in section, _c_ _d_ being the line of centres, and it will be readily perceived that the shape of the teeth if taken on the line _e_ _f_, will differ from that on the line of centres _c_ _d_; hence the form of the wheel teeth must, if contact is to occur along the full length of the tooth, be conformed to fit to the worm, which may be done by taking a series of section of the worm thread at varying distances from, and parallel to, the line of centres and joining the wheel teeth to the shape so obtained. But if the teeth of the wheel are to be cut to shape, then obviously a worm may be provided with teeth (by serrating it along its length) and mounted in position upon the wheel so as to cut the teeth of the wheel to shape as the worm rotates. The pitch line of the wheel teeth, whether they be straight and are disposed at an angle as in Fig. 75, or curved as in Fig. 76, is at a right angle to the line of centres _c_ _d_, or in other words in the plane of _g_ _h_, in Fig. 76. This is evident because the pitch line must be parallel to the wheel axis, being at an equal radius from that axis, and therefore having an equal velocity of rotation at every point in the length of the pitch line of the wheel tooth. If we multiply the number of teeth by their pitch to obtain the circumference of the pitch circle we shall obtain the circumference due to the radius of _g_ _h_, from the wheel axis, and so long as _g_ _h_ is parallel to the wheel axis we shall by this means obtain the same diameter of pitch circle, so long as we measure it on a line parallel to the line of centres _c_ _d_. The pitch of the worm is the same at whatever point in the tooth depth it may be measured, because the teeth curves are parallel one to the other, thus in Fig. 77 the pitch measures are equal at _m_, _n_, or _o_. But the action of the worm and wheel will nevertheless not be correct unless the pitch line from which the curves were rolled coincides with the pitch line of the wheel on the line of centres, for although, if the pitch lines do not so coincide, the worm will at each revolution move the pitch line of the wheel through a distance equal to the pitch of the worm, yet the motion of the wheel will not be uniform because, supposing the two pitch lines not to meet, the faces of the pinion teeth will act against those of the wheel, as shown in Fig. 78, instead of against their flanks, and as the faces are not formed to work correctly together the motion will be irregular. [Illustration: Fig. 77.] The diameter of the worm is usually made equal to four times the pitch of the teeth, and if the teeth are curved as in figure 76 they are made to envelop not more than 30° of the worm. The number of teeth in the wheel should not be less than thirty, a double worm being employed when a quicker ratio of wheel to worm motion is required. [Illustration: Fig. 78.] [Illustration: Fig. 79.] When the teeth of the wheel are curved to partly envelop the worm circumference it has been found, from experiments made by Robert Briggs, that the worm and the wheel will be more durable, and will work with greatly diminished friction, if the pitch line of the worm be located to increase the length of face and diminish that of the flank, which will decrease the length of face and increase the length of flank on the wheel, as is shown in Fig. 79; the location for the pitch line of the worm being determined as follows:-- [Illustration: Fig. 80.] The full radius of the worm is made equal to twice the pitch of its teeth, and the total depth of its teeth is made equal to .65 of its pitch. The pitch line is then drawn at a radius of 1.606 of the pitch from the worm axis. The pitch line is thus determined in Fig. 76, with the result that the area of tooth face and of worm surface is equalized on the two sides of the pitch line in the figure. In addition to this, however, it may be observed that by thus locating the pitch line the arcs both of approach and of recess are altered. Thus in Fig. 80 is represented the same worm and wheel as in Fig. 79, but the pitch lines are here laid down as in ordinary gearing. In the two figures the arcs of approach are marked by the thickened part of the generating circle, while the arcs of recess are denoted by the dotted arc on the generating circle, and it is shown that increasing the worm face, as in Fig. 79, increases the arc of recess, while diminishing the worm flank diminishes the arc of approach, and the action of the worm is smoother because the worm exerts more pulling than pushing action, it being noted that the action of the worm on the wheel is a pushing one before reaching, and a pulling one after passing, the line of centres. [Illustration: Fig. 81.] It may here be shown that a worm-wheel may be made to work correctly with a square thread. Suppose, for example, that the diameter of the generating circle be supposed to be infinite, and the sides of the thread may be accepted as rolled by the circle. On the wheel we roll a straight line, which gives a cycloidal curve suitable to work with the square thread. But the action will be confined to the points of the teeth, as is shown in Fig. 81, and also to the arc of approach. This is the same thing as taking the faces off the worm and filling in the flanks of the wheel. Obviously, then, we may reverse the process and give the worm faces only, and the wheel, flanks only, using such size of generating circle as will make the spaces of the wheel parallel in their depths and rolling the same generating circle upon the pitch line of the worm to obtain its face curve. This would enable the teeth on the wheel to be cut by a square-threaded tap, and would confine the contact of tooth upon tooth to the recess. The diameter of generating circle used to roll the curves for a worm and worm-wheel should in all cases be larger than the radius of the worm-wheel, so that the flanks of the wheel teeth may be at least as thick at the root as they are at the pitch circle. To find the diameter of a wheel, driven by a tangent-screw, which is required to make one revolution for a given number of turns of the screw, it is obvious, in the first place, that when the screw is single-threaded, the number of teeth in the wheel must be equal to the number of turns of the screw. Consequently, the pitch being also given, the radius of the wheel will be found by multiplying the pitch by the number of turns of the screw during one turn of the wheel, and dividing the product by 6.28. [Illustration: Fig. 82.] When a wheel pattern is to be made, the first consideration is the determination of the diameter to suit the required speed; the next is the pitch which the teeth ought to have, so that the wheel may be in accordance with the power which it is intended to transmit; the next, the number of the teeth in relation to the pitch and diameter; and, lastly, the proportions of the teeth, the clearance, length, and breadth. [Illustration: Fig. 83.] When the amount of power to be transmitted is sufficient to cause excessive wear, or when the velocity is so great as to cause rapid wear, the worm instead of being made parallel in diameter from end to end, is sometimes given a curvature equal to that of the worm-wheel, as is shown in Fig. 82. [Illustration: Fig. 84.] [Illustration: Fig. 85.] The object of this design is to increase the bearing area, and thus, by causing the power transmitted to be spread over a larger area of contact, to diminish the wear. A mechanical means of cutting a worm to the required form for this arrangement is shown in Fig. 83, which is extracted from "Willis' Principles of Mechanism." "A is a wheel driven by an endless screw or worm-wheel, B, C is a toothed wheel fixed to the axis of the endless screw B and in gear with another and equal toothed gear D, upon whose axis is mounted the smooth surfaced solid E, which it is desired to cut into Hindley's[2] endless screw. For this purpose a cutting tooth F is clamped to the face of the wheel A. When the handle attached to the axis of B C is turned round, the wheel A and solid wheel E will revolve with the same relative velocity as A and B, and the tool F will trace upon the surface of the solid E a thread which will correspond to the conditions. For from the very mode of its formation the section of every thread through the axis will point to the centre of the wheel A. The axis of E lies considerably higher than that of B to enable the solid E to clear the wheel A. [2] The inventor of this form of endless screw. "The edges of the section of the solid E along its horizontal centre line exactly fit the segment of the toothed wheel, but if a section be made by a plane parallel to this the teeth will no longer be equally divided as they are in the common screw, and therefore this kind of screw can only be in contact with each tooth along a line corresponding to its middle section. So that the advantage of this form over the common one is not so great as appears at first sight. "If the inclination of the thread of a screw be very great, one or more intermediate threads may be added, as in Fig. 84, in which case the screw is said to be double or triple according to the number of separate spiral threads that are so placed upon its surface. As every one of these will pass its own wheel-tooth across the line of centres in each revolution of the screw, it follows that as many teeth of the wheel will pass that line during one revolution of the screw as there are threads to the screw. If we suppose the number of these threads to be considerable, for example, equal to those of the wheel teeth, then the screw and wheel may be made exactly alike, as in Fig. 85; which may serve as an example of the disguised forms which some common arrangements may assume." [Illustration: Fig. 86.] In Fig. 86 is shown Hawkins's worm gearing. The object of this ingenious mechanical device is to transmit motion by means of screw or worm gearing, either by a screw in which the threads are of equal diameter throughout its length, or by a spiral worm, in which the threads are not of equal diameter throughout, but increase in diameter each way from the centre of its length, or about the centre of its length outwardly. Parallel screws are most applicable to this device when rectilinear motions are produced from circular motions of the driver, and spiral worms are applied when a circular motion is given by the driver, and imparted to the driven wheel. The threads of a spiral worm instead of gearing into teeth like those of an ordinary worm-wheel, actuate a series of rollers turning upon studs, which studs are attached to a wheel whose axis is not parallel to that of the worm, but placed at a suitable inclination thereto. When motion is given to the worm then rotation is produced in the roller wheel at a rate proportionable to the pitch of worm and diameter of wheel respectively. In the arrangement for transmitting rectilinear motion from a screw, rollers may be employed whose axes are inclined to the axis of the driving screw, or else at right angles to or parallel to the same. When separate rollers are employed with inclined axes, or axes at right angles with that of the main driving screw, each thread in gear touches a roller at one part only; but when the rollers are employed with axes parallel to that of the driving screw a succession of grooves are turned in these rollers, into which the threads of the driving screw will be in gear throughout the entire length of the roller. These grooves may be separate and apart from each other, or else form a screw whose pitch is equal to that of the driving screw or some multiple thereof. In Fig. 86 the spiral worm is made of such a length that the edge of one roller does not cease contact until the edge of the next comes into contact; a wheel carries four rollers which turn on studs, the latter being secured by cottars; the axis of the worm is at right angles with that of the wheel. The edges of the rollers come near together, leaving sufficient space for the thread of the worm to fit between any two contiguous rollers. The pitch line of the screw thread forms an arc of a circle, whose centre coincides with that of the wheel, therefore the thread will always bear fairly against the rollers and maintain rolling contact therewith during the whole of the time each roller is in gear, and by turning the screw in either direction the wheel will rotate. [Illustration: Fig. 87.] To prevent end thrust on a worm shaft it may have a right-hand worm A, and a left-hand one C (Fig. 87), driving two wheels B and D which are in gear, and either of which may transmit the power. The thrust of the two worms A and C, being in opposite directions, one neutralizes the other, and it is obvious that as each revolution of the worm shaft moves both wheels to an amount equal to the pitch of the worms, the two wheels B D may, if desirable, be of different diameters. [Illustration: Fig. 88.] [Illustration: Fig. 89.] Involute teeth.--These are teeth having their whole operative surfaces formed of one continuous involute curve. The diameter of the generating circle being supposed as infinite, then a portion of its circumference may be represented by a straight line, such as A in Fig. 88, and if this straight line be made to roll upon the circumference of a circle, as shown, then the curve traced will be involute P. In practice, a piece of flat spring steel, such as a piece of clock spring, is used for tracing involutes. It may be of any length, but at one end it should be filed so as to leave a scribing point that will come close to the base circle or line, and have a short handle, as shown in Fig. 89, in which S represents the piece of spring, having the point P´, and the handle H. The operation is, to make a template for the base circle, rest this template on drawing paper and mark a circle round its edge to represent on the paper the pitch circle, and to then bend the spring around the circle B, holding the point P´ in contact with the drawing paper, securing the other end of the piece of steel, so that it cannot slip upon B, and allowing the steel to unwind from the cylinder or circle B. The point P´ will mark the involute curve P. Another way to mark an involute is to use a piece of twine in place of the spring and a pencil instead of the tracing point; but this is not so accurate, unless, indeed, a piece of wood be laid on the drawing-board and the pencil held firmly against it, so as to steady the pencil point and prevent the variation in the curve that would arise from variation in the vertical position of the pencil. The flanks being composed of the same curve as the faces of the teeth, it is obvious that the circle from which the tracing point starts, or around which the straight line rolls, must be of less diameter than the pitch circle, or the teeth would have no flanks. A circle of less diameter than the pitch circle of the wheel is, therefore, introduced, wherefrom to produce the involute curves forming the full side of the tooth. [Illustration: Fig. 90.] The depth below pitch line or the length of flank is, therefore, the distance between the pitch circle and the base circle. Now even supposing a straight line to be a portion of the circumference of a circle of infinite diameter or radius, the conditions would here appear to be imperfect, because the generating circle is not rolled upon the pitch circle but upon a circle of lesser diameter. But it can be shown that the requirements of a proper velocity ratio will be met, notwithstanding the employment of the base instead of the pitch circle. Thus, in Fig. 90, let A and B represent the respective centres of the two pitch circles, marked in dotted lines. Draw the base circle for B as E Q, which may be of any radius less than that of the pitch circle of B. Draw the straight line Q D R touching this base circle at its perimeter and passing through the point of contact on the pitch circles as at D. Draw the circle whose radius is A R forming the base circle for wheel A. Thus the line R P Q will meet the perimeters of the two circles while passing through the point of contact D at the line of centres (a condition which the relative diameters of the base circles must always be so proportioned as to attain). If now we take any point on R Q, as P in the figure, as a tracing point, and suppose the radius or distance P Q to represent the steel spring shown in Fig. 89, and move the tracing point back to the base circle of B, it will trace the involute E P. Again we may take the tracing point P (supposing the line P R to represent the steel spring), and trace the involute P F, and these two involutes represent each one side of the teeth on the respective wheels. [Illustration: Fig. 91.] The line R P Q is at a right angle to the curves P E and P F, at their point of contact, and, therefore, fills the conditions referred to in Fig. 41. Now the line R P Q denotes the path of contact of tooth upon tooth as the wheels revolve; or, in other words, the point of contact between the side of a tooth on one wheel, and the side of a tooth on the other wheel, will always move along the line Q R, or upon a similar line passing through D, but meeting the base circles upon the opposite sides of the line of centres, and since line Q R always cuts the line of centres at the point of contact of the pitch circles, the conditions necessary to obtain a correct angular velocity are completely fulfilled. The velocity ratio is, therefore, as the length of B Q is to that of A R, or, what is the same thing, as the radius of the base circle of one wheel is to that of the other. It is to be observed that the line Q R will vary in its angle to the line of centres A B, according to the diameter of the base circle from which it is struck, and it becomes a consideration as to what is its most desirable angle to produce the least possible amount of thrust tending to separate the wheels, because this thrust (described in Fig. 39) tends to wear the journals and bearings carrying the wheel shafts, and thus to permit the pitch circles to separate. To avoid, as far as possible, this thrust the proportions between the diameters of the base circles D and E, Fig. 91, must be such that the line D E passes through the point of contact on the line of centres, as at C, while the angles of the straight line D E should be as nearly 90° to a radial line, meeting it from the centres of the wheels (as shown in the figure, by the lines B E and D E), as is consistent with the length of D E, which in order to impart continuous motion must at least equal the pitch of the teeth. It is obvious, also, that, to give continuous motion, the length of D E must be more than the pitch in proportion, as the points of the teeth come short of passing through the base circles at D and E, as denoted by the dotted arcs, which should therefore represent the addendum circles. The least possible obliquity, or angle of D E, will be when the construction under any given conditions be made such by trial, that the base circles D and E coincide with the addendum circles on the line of centres, and thus, with a given depth of both beyond, the pitch circle, or addenda as it is termed, will cause the tooth contacts to extend over the greatest attainable length of line between the limits of the addendum circles, thus giving a maximum number of teeth in contact at any instant of time. These conditions are fulfilled in Fig. 92,[3] the addendum on the small wheel being longer than the depth below pitch line, while the faces of the teeth are the narrowest. [3] From an article by Prof. Robinson. [Illustration: Fig. 92.] In seeking the minimum obliquity or angle of D E in the figure, it is to be observed that the less it is, the nearer the base circle approaches the pitch circle; hence, the shorter the operative length of tooth flank and the greater its wear. In comparing the merits of involute with those of epicycloidal teeth, the direction of the line of pressure at each point of contact must always be the common perpendicular to the surfaces at the point of contact, and these perpendiculars or normals must pass through the pitch circles on the line of centres, as was shown in Fig. 41, and it follows that a line drawn from C (Fig. 91) to any point of contact, is in the direction of the pressure on the surfaces at that point of contact. In involute teeth, the contact will always be on the line D E (Fig. 92), but in epicycloidal, on the line of the generating circle, when that circle is tangent at the line of centres; hence, the direction of pressure will be a chord of the circle drawn from the pitch circle at the line of centres to the position of contact considered. Comparing involute with radial flanked epicycloidal teeth, let C D A (Fig. 91) represent the rolling circle for the latter, and D C will be the direction of pressure for the contact at D; but for point of contact nearer C, the direction will be much nearer 90°, reaching that angle as the point of contact approaches C. Now, D is the most remote legitimate contact for involute teeth (and considering it so far as epicycloidal struck with a generating circle of infinite diameter), we find that the aggregate directions of the pressures of the teeth upon each other is much nearer perpendicular in epicycloidal, than in involute gearing; hence, the latter exert a greater pressure, tending to force the wheels apart. Hence, the former are, in this respect, preferable. It is to be observed, however, that in some experiments made by Mr. Hawkins, he states that he found "no tendency to press the wheels apart, which tendency would exist if the angle of the line D E (Fig. 92) deviated more than 20° from the line of centres A B of the two wheels." A method commonly employed in practice to strike the curves of involute teeth, is as follows:-- In Fig. 93 let C represent the centre of a wheel, D D the full diameter, P P the pitch circle, and E the circle of the roots of the teeth, while R is a radial line. Divide on R, the distance between the pitch circle and the wheel centre, into four equal parts, by 1, 2, 3, &c. From point or division 2, as a centre, describe the semicircle S, cutting the wheel centre and the pitch circle at its junction with R (as at A). From A, with compasses set to the length of one of the parts, as A 3, describe the arc B, cutting S at F, and F will be the centre from which one side of the tooth may be struck; hence from F as a centre, with the compasses set to the radius A B, mark the curve G. From the centre C strike, through F, a circle T T, and the centres wherefrom to strike all the teeth curves will fall on T T. Thus, to strike the other curve of the tooth, mark off from A the thickness of the tooth on the pitch circle P P, producing the point H. From H as a centre (with the same radius as before,) mark on T T the point I, and from I, as a centre, mark the curve J, forming the other side of the tooth. [Illustration: Fig. 93.] [Illustration: Fig. 94.] In Fig. 94 the process is shown carried out for several teeth. On the pitch circle P P, divisions 1, 2, 3, 4, &c., for the thickness of teeth and the width of the spaces are marked. The compasses are set to the radius by the construction shown in Fig. 93, then from _a_, the point _b_ on T is marked, and from _b_ the curve _c_ is struck. In like manner, from _d_, _g_, _j_, the centres _e_, _h_, _k_, wherefrom to strike the respective curves, _f_, _i_, _l_, are obtained. Then from _m_ the point _n_, on T T, is marked, giving the centre wherefrom to strike the curve at _h_ _m_, and from _o_ is obtained the point _p_, on T T, serving as a centre for the curve _e_ _o_. A more simple method of finding point F is to make a sheet metal template, C, as in Fig. 95, its edges being at an angle one to the other of 75° and 30'. One of its edges is marked off in quarters of an inch, as 1, 2, 3, 4, &c. Place one of its edges coincident with the line R, its point touching the pitch circle at the side of a tooth, as at A, and the centre for marking the curve on that side of the tooth will be found on the graduated edge at a distance from A equal to one-fourth the length of R. [Illustration: Fig. 95.] The result obtained in this process is precisely the same as that by the construction in Fig. 93, as will be plainly seen, because there are marked on Fig. 93 all the circles by which point F was arrived at in Fig. 95; and line 3, which in Fig. 95 gives the centre wherefrom to strike curve _o_, is coincident with point F, as is shown in Fig. 95. By marking the graduated edge of C in quarter-inch divisions, as 1, 2, 3, &c., then every division will represent the distance from A for the centre for every inch of wheel radius. Suppose, for example, that a wheel has 3 inches radius, then with the scale C set to the radial line R, the centre therefrom to strike the curve _o_ will be at 3; were the radius of the wheel 4 inches, then the scale being set the same as before (one edge coincident with R), the centre for the curve _o_ would be at 4, and arc T would require to meet the edge of C at 4. Having found the radius from the centre of the wheel of point F for one tooth, we may mark circle T, cutting point F, and mark off all the teeth by setting one point of the compasses (set to radius A F) on one side of the tooth and marking on circle T the centre wherefrom to mark the curve (as _o_), continuing the process all around the wheel and on both sides of the tooth. This operation of finding the location for the centre wherefrom to strike the tooth curves, must be performed separately for each wheel, because the distance or radius of the tooth curves varies with the radius of each wheel. In Fig. 96 this template is shown with all the lines necessary to set it, those shown in Fig. 95 to show the identity of its results with those given in Fig. 93 being omitted. The principles involved in the construction of a rack to work correctly with a wheel or pinion, having involute teeth, are as in Fig. 97, in which the pitch circle is shown by a dotted circle and the base circle by a full line circle. Now the diameter of the base circle has been shown to be arbitrary, but being assumed the radius B Q will be determined (since it extends from the centre B to the point of contact of D Q, with the base circle); B D is a straight line from the centre B of the pinion to the pitch line of the rack, and (whatever the angle of Q D to B D) the sides of the rack teeth must be straight lines inclined to the pitch line of the rack at an angle equal to that of B D Q. Involute teeth possess four great advantages--1st, they are thickest at the roots, where they should be to have a maximum of strength, which is of great importance in pinions transmitting much power; 2nd, the action of the teeth will remain practically perfect, even though the wheels are spread apart so that the pitch circles do not meet on the line of centres; 3rd, they are much easier to mark, and truth in the marking is easier attained; and 4th, they are much easier to cut, because the full depth of the teeth can, on spur-wheels, in all cases be cut with one revolving cutter, and at one passage of the cutter, if there is sufficient power to drive it, which is not the case with epicycloidal teeth whenever the flank space is wider below than it is at the pitch circle. On account of the first-named advantage, they are largely employed upon small gears, having their teeth cut true in a gear-cutting machine; while on account of the second advantage, interchangeable wheels, which are merely required to transmit motion, may be put in gear without a fine adjustment of the pitch circle, in which case the wear of the teeth will not prove destructive to the curves of the teeth. Another advantage is, that a greater number of teeth of equal strength may be given to a wheel than in the epicycloidal form, for with the latter the space must at least equal the thickness of the tooth, while in involute the space may be considerably less in width than the tooth, both measured, of course, at the pitch circle. There are also more teeth in contact at the same time; hence, the strain is distributed over more teeth. [Illustration: Fig. 96.] These advantages assume increased value from the following considerations. In a train of epicycloidal gearing in which the pinion or smallest wheel has radial flanks, the flanks of the teeth will become spread as the diameters of the wheels in the train increase. Coincident with spread at the roots is the thrust shown with reference to Fig. 39, hence under the most favorable conditions the wear on the journals of the wheel axles and the bearings containing them will take place, and the pitch circles will separate. Now so soon as this separation takes place, the motion of the wheels will not be as uniformly equal as when the pitch circles were in contact on the line of centres, because the conditions under which the tooth curves, necessary to produce a uniform velocity of motion, were formed, will have become altered, and the value of those curves to produce constant regularity of motion will have become impaired in proportion as the pitch circles have separated. [Illustration: Fig. 97.] In a single pair of epicycloidal wheels in which the flanks of the teeth are radial, the conditions are more favorable, but in this case the pinion teeth will be weaker than if of involute form, while the wear of the journals and bearings (which will take place to some extent) will have the injurious effect already stated, whereas in involute teeth, as has been noted, the separation of the pitch circles does not affect the uniformity of the motion or the correct working of the teeth. If the teeth of wheels are to be cut to shape in a gear-cutting machine, either the cutters employed determine from their shapes the shapes or curves of the teeth, or else the cutting tool is so guided to the work that the curves are determined by the operations of the machine. In either case nothing is left to the machine operator but to select the proper tools and set them, and the work in proper position in the machine. But when the teeth are to be cast upon the wheel the pattern wherefrom the wheel is to be moulded must have the teeth proportioned and shaped to proper curve and form. Wheels that require to run without noise or jar, and to have uniformity of motion, must be finished in gear-cutting machines, because it is impracticable to cast true wheels. When the teeth are to be cast upon the wheels the pattern-maker makes templates of the tooth curves (by some one of the methods to be hereafter described), and carefully cuts the teeth to shape. But the production of these templates is a tedious and costly operation, and one which is very liable to error unless much experience has been had. The Pratt and Whitney Company have, however, produced a machine that will produce templates of far greater accuracy than can be made by hand work. These templates are in metal, and for epicycloidal teeth from 15 to a rack, and having a diametral pitch ranging from 1-1/2 to 32. The principles of action of the machine are that a segment of a ring (representing a portion of the pitch circle of the wheel for whose teeth a template is to be produced) is fixed to the frame of the machine. Upon this ring rolls a disk representing the rolling, generating, or describing circle, this disk being carried by a frame mounted upon an arm representing the radius of the wheel, and therefore pivoted at a point central to the ring. The describing disk is rolled upon the ring describing the epicycloidal curve, and by suitable mechanical devices this curve is cut upon a piece of steel, thus producing a template by actually rolling the generating upon the base circle, and the rolling motion being produced by positive mechanical motion, there cannot possibly be any slip, hence the curves so produced are true epicycloids. The general construction of the machine is shown in the side view, Fig. 98 (Plate I.), and top view, Fig. 99 (Plate I.), details of construction being shown in Figs. 100, 101 (Plate I.), 102, 103, 104, 105, and 106. A A is the segment of a ring whose outer edge represents a part of the pitch circle. B is a disk representing the rolling or generating circle carried by the frame C, which is attached to a rod pivoted at D. The axis of pivot D represents the axis of the base circle or pitch circle of the wheel, and D is adjustable along the rod to suit the radius of A A, or what is the same thing, to equal the radius of the wheel for whose teeth a template is to be produced. When the frame C is moved its centre or axis of motion is therefore at D and its path of motion is around the circumference of A A, upon the edge of which it rolls. To prevent B from slipping instead of rolling upon A A, a flexible steel ribbon is fastened at one end upon A A, passes around the edge of A A and thence around the circumference of B, where its other end is fastened; due allowance for the thickness of this ribbon being made in adjusting the radii of A A and of B. E´ is a tubular pivot or stud fixed on the centre line of pivots E and D, and distant from the edge of A A to the same amount that E is. These two studs E and E´ carry two worm-wheels F and F´ in Fig. 102, which stand above A and B, so that the axis of the worm G is vertically over the common tangent of the pitch and describing circles. [Illustration: _VOL. I._ =TEMPLATE-CUTTING MACHINES FOR GEAR TEETH.= _PLATE I._ Fig. 98. Fig. 99. Fig. 100. Fig. 101.] The relative positions of these and other parts will be most clearly seen by a study of the vertical section, Fig. 102.[4] The worm G is supported in bearings secured to the carrier C and is driven by another small worm turned by the pulley I, as seen in Fig. 101 (Plate I.); the driving cord, passing through suitable guiding pulleys, is kept at uniform tension by a weight, however C moves; this is shown in Figs. 98 and 99 (Plate I.). [4] From "The Teeth of Spur Wheels," by Professor McCord. [Illustration: Fig. 102.] Upon the same studs, in a plane still higher than the worm-wheels turn the two disks H, H´, Figs. 103, 104, 105. The diameters of these are equal, and precisely the same as those of the describing circles which they represent, with due allowance, again, for the thickness of a steel ribbon, by which these also are connected. It will be understood that each of these disks is secured to the worm-wheel below it, and the outer one of these, to the disk B, so that as the worm G turns, H and H´ are rotated in opposite directions, the motion of H being identical with that of B; this last is a rolling one upon the edge of A, the carrier C with all its attached mechanism moving around D at the same time. Ultimately, then, the motions of H, H´, are those of two equal describing circles rolling in external and internal contact with a fixed pitch circle. [Illustration: Fig. 103.] [Illustration: Fig. 104.] In the edge of each disk a semicircular recess is formed, into which is accurately fitted a cylinder J, provided with flanges, between which the disks fit so as to prevent end play. This cylinder is perforated for the passage of the steel ribbon, the sides of the opening, as shown in Fig. 103, having the same curvature as the rims of the disks. Thus when these recesses are opposite each other, as in Fig. 104, the cylinder J fills them both, and the tendency of the steel ribbon is to carry it along with H when C moves to one side of this position, as in Fig. 105, and along with H´ when C moves to the other side, as in Fig. 103. This action is made positively certain by means of the hooks K, K´, which catch into recesses formed in the upper flange of J, as seen in Fig. 104. The spindles, with which these hooks turn, extend through the hollow studs, and the coiled springs attached to their lower ends, as seen in Fig. 102, urge the hooks in the directions of their points; their motions being limited by stops _o_, _o´_, fixed, not in the disks H, H´, but in projecting collars on the upper ends of the tubular studs. The action will be readily traced by comparing Fig. 104 with Fig. 105; as C goes to the left, the hook K´ is left behind, but the other one, K, cannot escape from its engagement with the flange of J; which, accordingly, is carried along with H by the combined action of the hook and the steel ribbon. On the top of the upper flange of J, is secured a bracket, carrying the bearing of a vertical spindle L, whose centre line is a prolongation of that of J itself. This spindle is driven by the spur-wheel N, keyed on its upper end, through a flexible train of gearing seen in Fig. 99; at its lower end it carries a small milling cutter M, which shapes the edge of the template T, Fig. 105, firmly clamped to the framing. [Illustration: Fig. 105.] When the machine is in operation, a heavy weight, seen in Fig. 98 (Plate I.), acts to move C about the pivot D, being attached to the carrier by a cord guided by suitably arranged pulleys; this keeps the cutter M up to its work, while the spindle L is independently driven, and the duty left for the worm G to perform is merely that of controlling the motions of the cutter by the means above described, and regulating their speed. The centre line of the cutter is thus automatically compelled to travel in the path R S, Fig. 105, composed of an epicycloid and a hypocycloid if A A be the segment of a circle as here shown; or of two cycloids, if A A be a straight bar. The radius of the cutter being constant, the edge of the template T is cut to an outline also composed of two curves; since the radius M is small, this outline closely resembles R S, but particular attention is called to the fact that it is _not identical with it, nor yet composed of truly epicycloidal curves of any generation whatever:_ the result of which will be subsequently explained. NUMBER AND SIZES OF TEMPLATES. With a given pitch every additional tooth increases the diameter of the wheel, and changes the form of the epicycloid; so that it would appear necessary to have as many different cutters, as there are wheels to be made, of any one pitch. But the proportional increment, and the actual change of form, due to the addition of one tooth, becomes less as the wheel becomes larger; and the alteration in the outline soon becomes imperceptible. Going still farther, we can presently add more teeth without producing a sensible variation in the contour. That is to say, several wheels can be cut with the same cutter, without introducing a perceptible error. It is obvious that this variation in the form is least near the pitch circle, which is the only part of the epicycloid made use of; and Prof. Willis many years ago deduced theoretically, what has since been abundantly proved by practice, that instead of an infinite number of cutters, 24 are sufficient of one pitch, for making all wheels, from one with 12 teeth up to a rack. [Illustration: Fig. 106.] Accordingly, in using the epicycloidal milling engine, for forming the template, segments of pitch circles are provided of the following diameters (in inches): 12, 16, 20, 27, 43, 100, 13, 17, 21, 30, 50, 150, 14, 18, 23, 34, 60, 300. 15, 19, 25, 38, 75, In Fig. 106, the edge T T is shaped by the cutter T T, whose centre travels in the path R S, therefore these two lines are at a constant normal distance from each other. Let a roller P, of any reasonable diameter, be run along T T, its centre will trace the line U V, which is at a constant normal distance from T T, and therefore from R S. Let the normal distance between U V and R S be the radius of another milling cutter N, having the same axis as the roller P, and carried by it, but in a different plane as shown in the side view; then whatever N cuts will have R S for its contour, if it lie upon the same side of the cutter as the template. The diameter of the disks which act as describing circles is 7-1/2 inches, and that of the milling cutter which shapes the edge of the template is 1/8 of an inch. Now if we make a set of 1-pitch wheels with the diameters above given, the smallest will have twelve teeth, and the one with fifteen teeth will have radial flanks. The curves will be the same whatever the pitch; but as shown in Fig. 106, the blank should be adjusted in the epicycloidal engine, so that its lower edge shall be 1/16th of an inch (the radius of the cutter M) above the bottom of the space; also its relation to the side of the proposed tooth should be as here shown. As previously explained, the depth of the space depends upon the pitch. In the system adopted by the Pratt & Whitney Company, the whole height of the tooth is 2-1/8 times the diametral pitch, the projection outside the pitch circle being just equal to the pitch, so that diameter of blank = diameter of pitch circle + 2 × diametral pitch. We have now to show how, from a single set of what may be called 1-pitch templates, complete sets of cutters of the true epicycloidal contour may be made of the same or any less pitch. Now if T T be a 1-pitch template as above mentioned, it is clear that N will correctly shape a cutting edge of a gear cutter for a 1-pitch wheel. The same figure, reduced to half size, would correctly represent the formation of a cutter for a 2-pitch wheel of the same number of teeth; if to quarter size, that of a cutter for a 4-pitch wheel, and so on. But since the actual size and curvature of the contour thus determined depend upon the dimensions and motion of the cutter N, it will be seen that the same result will practically be accomplished, if these only be reduced; the size of the template, the diameter and the path of the roller remaining unchanged. The nature of the mechanism by which this is effected in the Pratt & Whitney system of producing epicycloidal cutters will be hereafter explained in connection with cutters. CHAPTER III.--THE TEETH OF GEAR-WHEELS (continued). The revolving cutters employed in gear-cutting machines, gear-cutters, or cutting engines (as the machines for cutting the teeth of gear-wheels to shape are promiscuously termed), are of the form shown in Fig. 107, which represents what is known as a Brown and Sharpe patent cutter, whose peculiarities will be explained presently. This class of cutters is made as follows:-- [Illustration: Fig. 107.] A cast steel disk is turned in the lathe to the required form and outline. After turning, its circumference is serrated as shown, so as to provide protuberances, or teeth, on the face of which the cutting edges may be formed. To produce a cutting edge it is necessary that the metal behind that edge should slope or slant away leaving the cutting edge to project. Two methods of accomplishing this are employed: in the first, which is that embodied in the Brown and Sharpe system, each tooth has the curved outline, forming what may be termed its circumferential outline, of the same curvature and shape from end to end, and from front to back, as it may more properly be termed, the clearance being given by the back of the tooth approaching the centre of the cutter, so that if a line be traced along the circumference of a tooth, from the cutting edge to the back, it will approach the centre of the cutter as the back is approached, but the form of the tooth will be the same at every point in the line. It follows then that the radial faces of the teeth may be ground away to sharpen the teeth without affecting the shape of the tooth, which being made correct will remain correct. This not only saves a great deal of labor in sharpening the teeth, but also saves the softening and rehardening process, otherwise necessary at each resharpening. The ordinary method of producing the cutting edges after turning the cutter and serrating it, is to cut away the metal with a file or rotary cutter of some kind forming the cutting edge to correct shape, but paying no regard to the shape of the back of the tooth more than to give it the necessary amount of clearance. In this case the cutter must be softened and reset to sharpen it. To bring the cutting edge up to a sharp edge all around its profile, while still preserving the shape to which it was turned, the pantagraphic engine, shown in Fig. 108, has been made by the Pratt and Whitney Company. Figs. 109 and 110 show some details of its construction.[5] "The milling cutter N is driven by a flexible train acting upon the wheel O, whose spindle is carried by the bracket B, which can slide from right to left upon the piece B, and this again is free to slide in the frame F. These two motions are in horizontal planes, and perpendicular to each other. [5] From "The Teeth of Spur Wheels," by Professor McCord. [Illustration: Fig. 108.] "The upper end of the long lever P C is formed into a ball, working in a socket which is fixed to P C. Over the cylindrical upper part of this lever slides an accurately fitted sleeve D, partly spherical externally, and working in a socket which can be clamped at any height on the frame F. The lower end P of this lever being accurately turned, corresponds to the roller P in Fig. 109, and is moved along the edge of the template T, which is fastened in the frame in an invariable position. "By clamping D at various heights, the ratio of the lever arms P D, P D, may be varied at will, and the axis of N made to travel in a path similar to that of the axis of P, but as many times smaller as we choose; and the diameter of N must be made less than that of P in the same proportion. "The template being on the left of the roller, the cutter to be shaped is placed on the right of N, as shown in the plan view at Z, because the lever reverses the movement. "This arrangement is not mathematically perfect, by reason of the angular vibration of the lever. This is, however, very small, owing to the length of the lever; it might have been compensated for by the introduction of another universal joint, which would practically have introduced an error greater than the one to be obviated, and it has, with good judgment, been omitted. "The gear-cutter is turned nearly to the required form, the notches are cut in it, and the duty of the pantagraphic engine is merely to give the finishing touch to each cutting edge, and give it the correct outline. It is obvious that this machine is in no way connected with, or dependent upon, the epicycloidal engine; but by the use of proper templates it will make cutters for any desired form of tooth; and by its aid exact duplicates may be made in any numbers with the greatest facility. [Illustration: Fig. 109.] "It forms no part of our plan to represent as perfect that which is not so, and there are one or two facts, which at first thought might seem serious objections to the adoption of the epicycloidal system. These are: "1. It is physically impossible to mill out a _concave_ cycloid, by any means whatever, because at the pitch line its radius of curvature is zero, and a milling cutter must have a sensible diameter. "2. It is impossible to mill out even a _convex_ cycloid or epicycloid, by the means and in the manner above described. [Illustration: Fig. 110.] "This is on account of a hitherto unnoticed peculiarity of the curve at a constant normal distance from the cycloid. In order to show this clearly, we have, in Fig. 110, enormously exaggerated the radius C D, of the milling cutter (M of Figs. 105 and 106). The outer curve H L, evidently, could be milled out by the cutter, whose centre travels in the cycloid C A; it resembles the cycloid somewhat in form, and presents no remarkable features. But the inner one is quite different; it starts at D, and at first goes down, _inside the circle whose radius is_ C D, forms a cusp at E, then begins to rise, crossing this circle at G, and the base line at F. It will be seen, then, that if the centre of the cutter travel in the cycloid A C, its edge will cut away the part G E D, leaving the template of the form O G I. Now if a roller of the same radius C D, be rolled along this edge, its centre will travel in the cycloid from A, to the point P, where a normal from G, cuts it; then the roller will turn upon G as a fulcrum, and its centre will travel from P to C, in a circular arc whose radius G P = C D. "That is to say even a roller of the same size as the original milling cutter, will not retrace completely the cycloidal path in which the cutter travelled. "Now in making a rack template, the cutter, after reaching C, travels in the reversed cycloid C R, its left-hand edge, therefore, milling out a curve D K, similar to H L. This curve lies wholly _outside_ the circle D I, and therefore cuts O G at a point between F and G, but very near to G. This point of intersection is marked S in Fig. 110, where the actual form of the template O S K is shown. The roller which is run along this template is _larger_, as has been explained, than the milling cutter. When the point of contact reaches S (which so nearly corresponds to G that they practically coincide), this roller cannot now swing about S through an angle so great as P G C of Fig. 110; because at the root D, the radius of curvature of D K is only equal to that of the cutter, and G and S are so near the root that the curvature of S K, near the latter point, is greater than that of the roller. Consequently there must be some point U in the path of the centre of the roller, such, that when the centre reaches it, the circumference will pass through S, and be also tangent to S K. Let T be the point of tangency; draw S U and T U, cutting the cycloidal path A R in X and Y. Then, U Y being the radius of the new milling cutter (corresponding to N of Fig. 109), it is clear that in the outline of the gear cutter shaped by it, the circular arc X Y will be substituted for the true cycloid. [Illustration: Fig. 111.] THE SYSTEM PRACTICALLY PERFECT. "The above defects undeniably exist; now, what do they amount to? The diagram is drawn purposely with these sources of error greatly exaggerated, in order to make their nature apparent and their existence sensible. The diameters used in practice, as previously stated, are: describing circle, 7-1/2 inches; cutter for shaping template, 1/8 of an inch; roller used against edge of template, 1-1/8 inches; cutter for shaping a 1-pitch gear cutter, 1 inch. "With these data the writer has found that the _total length_ of the arc X Y of Fig. 110, which appears instead of the cycloid in the outline of a cutter for a 1-pitch rack, is less than 0.0175 inch; the real _deviation_ from the true form, obviously, must be much less than that. It need hardly be stated that the effect upon the velocity ratio of an error so minute, and in that part of the contour, is so extremely small as to defy detection. And the best proof of the practical perfection of this system of making epicycloidal teeth is found in the smoothness and precision with which the wheels run; a set of them is shown in gear in Fig. 111, the rack gearing as accurately with the largest as with the smallest. To which is to be added, finally, that objection taken, on whatever grounds, to the epicycloidal form of tooth, has no bearing upon the method above described of producing duplicate cutters for teeth of any form, which the pantagraphic engine will make with the same facility and exactness, if furnished with the proper templates. "The front faces of the teeth of rotary cutters for gear-cutting are usually radial lines, and are ground square across so as to stand parallel with the axis of the cutter driving spindle, so that to whatever depth the cutter may have entered the wheel, the whole of the cutting edge within the wheel will meet the cut simultaneously. If this is not the case the pressure of the cut will spring the cutter, and also the arbor driving it, to one side. Suppose, for example, that the tooth faces not being square across, one side of the teeth meets the work first, then there will be as each tooth meets its cut an endeavour to crowd away from the cut until such time as the other side of the tooth also takes its cut." It is obvious that rotating cutters of this class cannot be used to cut teeth having the width of the space wider below than it is at the pitch line. Hence, if such cutters are required to be used upon epicycloidal teeth, the curves to be theoretically correct must be such as are due to a generating circle that will give at least parallel flanks. From this it becomes apparent that involute teeth being always thicker at the root than at the pitch line, and the spaces being, therefore, narrower at the root, may be cut with these cutters, no matter what the diameter of the base circle of the involute. To produce with revolving cutters teeth of absolutely correct theoretical curvature of face and flank, it is essential that the cutter teeth be made of the exact curvature due to the diameter of pitch circle and generating circle of the wheel to be cut; while to produce a tooth thickness and space width, also theoretically correct, the thickness of the cutter must also be made to exactly answer the requirements of the particular wheel to be cut; hence, for every different number of teeth in wheels of an equal pitch a separate cutter is necessary if theoretical correctness is to be attained. This requirement of curvature is necessary because it has been shown that the curvatures of the epicycloid and hypocycloid, as also of the involute, vary with every different diameter of base circle, even though, in the case of epicycloidal teeth, the diameter of the generating circle remain the same. The requirement of thickness is necessary because the difference between the arc and the chord pitch is greater in proportion as the diameter of the base or pitch circle is decreased. But the difference in the curvature on the short portions of the curves used for the teeth of fine pitches (and therefore of but little height) due to a slight variation in the diameter of the base circle is so minute, that it is found in practice that no sensible error is produced if a cutter be used within certain limits upon wheels having a different number of teeth than that for which the cutter is theoretically correct. The range of these limits, however, must (to avoid sensible error) be more confined as the diameter of the base circle (or what is the same thing, the number of the teeth in the wheel) is decreased, because the error of curvature referred to increases as the diameters of either the base or the generating circles decrease. Thus the difference in the curve struck on a base circle of 20 inches diameter, and one of 40 inches diameter, using the same diameter of generating circle, would be very much less than that between the curves produced by the same diameter of generating circle on base circles respectively 10 and 5 inches diameter. For these reasons the cutters are limited to fewer wheels according as the number of teeth decreases, or, per contra, are allowed to be used over a greater range of wheels as the number of teeth in the wheels is increased. Thus in the Brown and Sharpe system for involute teeth there are 8 cutters numbered numerically (for convenience in ordering) from 1 to 8, and in the following table the range of the respective cutters is shown, and the number of teeth for which the cutter is theoretically correct is also given. BROWN AND SHARPE SYSTEM. No. of cutter. Involute teeth. Teeth. 1 Used upon all wheels having from 135 teeth to a rack correct for 200 2 " " " " " 55 " to 134 teeth, 68 3 " " " " " 35 " to 54 " 40 4 " " " " " 26 " to 34 " 29 5 " " " " " 21 " to 25 " 22 6 " " " " " 17 " to 20 " 18 7 " " " " " 14 " to 16 " 16 8 " " " " " 12 " to 14 " 13 Suppose that it was required that of a pair of wheels one make twice the revolutions of the other; then, knowing the particular number of teeth for which the cutters are made correct, we may obtain the nearest theoretically true results as follows: If we select cutters Nos. 8 and 4 and cut wheels having respectively 13 and 26 teeth, the 13 wheel will be theoretically correct, and the 26 will contain the minute error due to the fact that the cutter is used upon a wheel having three less teeth than the number it is theoretically correct for. But we may select the cutters that are correct for 16 and 29 teeth respectively, the 16th tooth being theoretically correct, and the 29th cutter (or cutter No. 4 in the table) being used to cut 32 teeth, this wheel will contain the error due to cutting 3 more teeth than the cutter was made correct for. This will be nearer correct, because the error is in a larger wheel, and, therefore, less in actual amount. The pitch of teeth may be selected so that with the given number of teeth the diameters of the wheels will be that required. We may now examine the effect of the variation of curvature in combination with that of the thickness, upon a wheel having less and upon one having more teeth than the number in the wheel for which the cutter is correct. First, then, suppose a cutter to be used upon a wheel having less teeth and it will cut the spaces too wide, because of the variation of thickness, and the curves too straight or insufficiently curved because of the error of curvature. Upon a wheel having more teeth it will cut the spaces too narrow, and the curvature of the teeth too great; but, as before stated, the number of wheels assigned to each cutter may be so apportioned that the error will be confined to practically unappreciable limits. If, however, the teeth are epicycloidal, it is apparent that the spaces of one wheel must be wide enough to admit the teeth of the other to a depth sufficient to permit the pitch lines to coincide on the line of centres; hence it is necessary in small diameters, in which there is a sensible difference between the arc and the chord pitches, to confine the use of a cutter to the special wheel for which it is designed, that is, having the same number of teeth as the cutter is designed for. Thus the Pratt and Whitney arrangement of cutters for epicycloidal teeth is as follows:-- PRATT AND WHITNEY SYSTEM. EPICYCLOIDAL TEETH. [All wheels having from 12 to 21 teeth have a special cutter for each number of teeth.][6] Cutter correct for No. of teeth. 23 Used on wheels having from 22 to 24 teeth. 25 " " " " 25 to 26 " 27 " " " " 26 to 29 " 30 " " " " 29 to 32 " 34 " " " " 32 to 36 " 38 " " " " 36 to 40 " 43 " " " " 40 to 46 " 50 " " " " 46 to 55 " 60 " " " " 55 to 67 " 76 " " " " 67 to 87 " 100 " " " " 87 to 123 " 150 " " " " 123 to 200 " 300 " " " " 200 to 600 " Rack " " " " 600 to rack. [6] For wheels having less than 12 teeth the Pratt and Whitney Co. use involute cutters. Here it will be observed that by a judicious selection of pitch and cutters, almost theoretically perfect results may be obtained for almost any conditions, while at the same time the cutters are so numerous that there is no necessity for making any selection with a view to taking into consideration for what particular number of teeth the cutter is made correct. For epicycloidal cutters made on the Brown and Sharpe system so as to enable the grinding of the face of the tooth to sharpen it, the Brown and Sharpe company make a separate cutter for wheels from 12 to 20 teeth, as is shown in the accompanying table, in which the cutters are for convenience of designation denoted by an alphabetical letter. 24 CUTTERS IN EACH SET. Letter A cuts 12 teeth. B " 13 " C " 14 " D " 15 " E " 16 " F " 17 " G " 18 " H " 19 " I " 20 " J " 21 to 22 " K " 23 " 24 " L " 25 " 26 " M " 27 " 29 " N " 30 " 33 " O " 34 " 37 " P " 38 " 42 " Q " 43 " 49 " R " 50 " 59 " S " 60 " 74 " T " 75 " 99 " U " 100 " 149 " V " 150 " 249 " W " 250 " Rack. X " Rack. In these cutters a shoulder having no clearance is placed on each side of the cutter, so that when the cutter has entered the wheel until the shoulder meets the circumference of the wheel, the tooth is of the correct depth to make the pitch circles coincide. In both the Brown and Sharpe and Pratt and Whitney systems, no side clearance is given other than that quite sufficient to prevent the teeth of one wheel from jambing into the spaces of the other. Pratt and Whitney allow 1/8 of the pitch for top and bottom clearance, while Brown and Sharpe allow 1/10 of the thickness of the tooth for top and bottom clearance. It may be explained now, why the thickness of the cutter if employed upon a wheel having more teeth than the cutter is correct for, interferes with theoretical exactitude. [Illustration: Fig. 112.] [Illustration: Fig. 113.] First, then, with regard to the thickness of tooth and width of space. Suppose, then, Fig. 112 to represent a section of a wheel having 12 teeth, then the pitch circle of the cutter will be represented by line A, and there will be the same difference between the arc and chord pitch on the cutter as there is on the wheel; but suppose that this same cutter be used on a wheel having 24 teeth, as in Fig. 113, then the pitch circle on the cutter will be more curved than that on the wheel as denoted at C, and there will be more difference between the arc and chord pitches on the cutter than there is on the wheel, and as a result the cutter will cut a groove too narrow. The amount of error thus induced diminishes as the diameter of the pitch circle of the cutter is increased. But to illustrate the amount. Suppose that a cutter is made to be theoretically correct in thickness at the pitch line for a wheel to contain 12 teeth, and having a pitch circle diameter of 8 inches, then we have 3.1416 = ratio of circumference to diameter. 8 = diameter. ------- Number of teeth = 12 ) 25.1328 = circumference. ------- 2.0944 = arc pitch of wheel. If now we subtract the chord pitch from the arc pitch, we shall obtain the difference between the arc and the chord pitches of the wheel; here 2.0944 = arc pitch. 2.0706 = chord pitch. ------ .0238 = difference between the arc and the chord pitch. Now suppose this cutter to be used upon a wheel having the same pitch, but containing 18 teeth; then we have 2.0944 = arc pitch. 2.0836 = chord pitch. ------ .0108 = difference between the arc and the chord pitch. Then .0238 = difference on wheel with 12 teeth. .0108 = " " " 18 " ----- .0130 = variation between the differences. And the thickness of the tooth equalling the width of the space, it becomes obvious that the thickness of the cutter at the pitch line being correct for the 12 teeth, is one half of .013 of an inch too thin for the 18 teeth, making the spaces too narrow and the teeth too thick by that amount. Now let us suppose that a cutter is made correct for a wheel having 96 teeth of 2.0944 arc pitch, and that it be used upon a wheel having 144 teeth. The proportion of the wheels one to the other remains as before (for 96 bears the proportion to 144 as 12 does to 18). Then we have for the 96 teeth 2.0944 = arc pitch. 2.0934 = chord pitch. ------ .0010 = difference. For the 144 teeth we have 2.0944 = arc pitch. 2.0937 = chord pitch. ------ .0007 = difference. We find, then, that the variation decreases as the size of the wheels increases, and is so small as to be of no practical consequence. If our examples were to be put into practice, and it were actually required to make one cutter serve for wheels having, say, from 12 to 18 teeth, a greater degree of correctness would be obtained if the cutter were made to some other wheel than the smallest. But it should be made for a wheel having less than the mean diameter (within the range of 12 and 18), that is, having less than 15 teeth; because the difference between the arc and chord pitch increases as the diameter of the pitch circle increases, as already shown. A rule for calculating the number of wheels to be cut by each cutter when the number of cutters in the set and the number of teeth in the smallest and largest wheel in the train are given is as follows:-- Rule.--Multiply the number of teeth in the smallest wheel of the train by the number of cutters it is proposed to have in the set, and divide the amount so obtained by a sum obtained as follows:-- From the number of cutters in the set subtract the number of the cutter, and to the remainder add the sum obtained by multiplying the number of the teeth in the smallest wheel of the set or train by the number of the cutter and dividing the product by the number of teeth in the largest wheel of the set or train. Example.--I require to find how many wheels each cutter should cut, there being 8 cutters and the smallest wheel having 12 teeth, while the largest has 300. Number of teeth in Number of cutters smallest wheel. in the set. 12 × 8 = 96 Then Number of cutters Number of in set. cutter. 8 - 7 = 1 Then Number of teeth in The number of the The number of the teeth smallest wheel. cutter. in largest wheel. 12 × 8 ÷ 300 12 8 --- 300 ) 960 ( 0.32 900 --- 600 600 Now add the 1 to the .32 and we have 1.32, which we must divide into the 96 first obtained. Thus 1.32 ) 96.00 ( 72 924 ---- 360 264 --- 96 Hence No. 8 cutter may be used for all wheels that have between 72 teeth and 300 teeth. To find the range of wheels to be cut by the next cutter, which we will call No. 7, proceed again as before, but using 7 instead of 8 as the number of the cutter. Thus Number of teeth in Number of cutters in smallest wheel. the set. 12 × 8 = 96 Then Number of cutters Number of in the set. cutters. 8 - 6 = 2 And Number of teeth in The number of the The number of teeth smallest wheel. cutter. in the largest wheel. 12 × 8 ÷ 300 Here 12 8 --- 300 ) 960 ( 0.32 900 --- 600 600 Add the 2 to the .32 and we have 2.32 to divide into the 96. Thus 2.32 ) 96.00 ( 41 928 --- 320 232 --- 88 Hence this cutter will cut all wheels having not less than the 41 teeth, and up to the 72 teeth where the other cutter begins. For the range of the next cutter proceed the same, using 6 as the number of the cutter, and so on. By this rule we obtain the lowest number of teeth in a wheel for which the cutter should be used, and it follows that its range will continue upwards to the smallest wheel cut by the cutter above it. Having by this means found the range of wheels for each cutter, it remains to find for what particular number of teeth within that range the cutter teeth should be made correct, in order to have whatever error there may be equal in amount on the largest and smallest wheel of its range. This is done by using precisely the same rule, but supposing there to be twice as many cutters as there actually are, and then taking the intermediate numbers as those to be used. Applying this plan to the first of the two previous examples we have-- Number of teeth in the Number of cutters in smallest wheel. the set. 12 × 16 = 192 Then Number of cutters Number of the in the set. cutter. 16 - 15 = 1 And Number of teeth in The number of the The number of the teeth in smallest wheel. cutter. the largest wheel. 12 × 15 ÷ 300 12 15 --- 60 12 ----- 300 ) 180.0 ( 0.6 1800 Then add the 1 to the .6 = 1.6, and this divided into 192 = 120. By continuing this process for each of the 16 cutters we obtain the following table:-- Number of Number of Cutter. Teeth. 1 12 *2 13 3 14 *4 15 5 17 *6 18 7 20.61 *8 23 9 26 *10 30 11 35 *12 42 13 54 *14 75 15 120 *16 300 Suppose now we take for our 8 cutters those marked by an asterisk, and use cutter 2 for all wheels having either 12, 13, or 14 teeth, then the next cutter would be that numbered 4, cutting 14, 15, or 16 toothed wheels, and so on. A similar table in which 8 cutters are required, but 16 are used in the calculation, the largest wheel having 200 teeth in the set, is given below. Number of Number of Cutter. Teeth. 1 12.7 2 13.5 3 14.5 4 15.6 5 16.9 6 18 7 21 8 23.5 9 26.5 10 29 11 35 12 40.6 13 52.9 14 67.6 15 101 16 200 To assist in the selections as to what wheels in a given set the determined number of cutters should be made correct for, so as to obtain the least limit of error, Professor Willis has calculated the following table, by means of which cutters may be selected that will give the same difference of form between any two consecutive numbers, and this table he terms the table of equidistant value of cutters. TABLE OF EQUIDISTANT VALUE OF CUTTERS. Number of Teeth. Rack--300, 150, 100, 76, 60, 50, 43, 38, 34, 30, 27, 25, 23, 21, 20, 19, 17, 16, 15, 14, 13, 12. The method of using the table is as follows:--Suppose it is required to make a set of wheels, the smallest of which is to contain 50 teeth and the largest 150, and it is determined to use but one cutter, then that cutter should be made correct for a wheel containing 76; because in the table 76 is midway between 50 and 150. But suppose it were determined to employ two cutters, then one of them should be made correct for a wheel having 60 teeth, and used on all the wheels having between 50 and 76 teeth, while the other should be made correct for a wheel containing 100 teeth, and used on all wheels containing between 76 and 150 teeth. In the following table, also arranged by Professor Willis, the most desirable selection of cutters for different circumstances is given, it being supposed that the set of wheels contains from 12 teeth to a rack. +-----------+------------------------------------------------------+ |Number of | | |cutters in | Number of Teeth in Wheel for which the Cutter is to | |the set. | be made correct. | +-----------+----+----+--------------------------------------------+ | 2 | 50 | 16 | | | --+----+----+----+ | | 3 | 75 | 25 | 15 | | | --+----+----+----+----+ | | 4 | 100| 34 | 20 | 14 | | | --+----+----+----+----+----+----+ | | 6 | 150| 50 | 30 | 21 | 16 | 13 | | | --+----+----+----+----+----+----+----+----+ | | 8 | 200| 67 | 40 | 29 | 22 | 18 | 15 | 13 | | | --+----+----+----+----+----+----+----+----+----+----+ | | 10 | 200| 77 | 50 | 35 | 27 | 22 | 19 | 16 | 14 | 13 | | | --+----+----+----+----+----+----+----+----+----+----+----+ | | 300| 100| 60 | 43 | 34 |27 | 23 | 20 | 17 | 15 | 14 | | 12 +----+----+----+----+----+----+----+----+----+----+----+ | | 13 | | | --+----+----+----+----+----+----+----+----+----+----+----+ | | 300| 150| 100| 70 | 50 | 40 | 30 | 26 | 24 | 22 | 20 | | 18 +----+----+----+----+----+----+----+----+----+----+----+ | | 18 | 16 | 15 | 14 | 13 | 12 | | | --+----+----+----+----+----+----+----+----+----+----+----+ | |Rack| 300| 150| 100| 76 | 60 | 50 | 43 | 38 | 34 | 30 | | +----+----+----+----+----+----+----+----+----+----+----+ | 24 | 27 | 25 | 23 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | | +----+----+----+----+----+----+----+----+----+----+----+ | | 13 | 12 | | +-----------+----+----+--------------------------------------------+ Suppose now we take the cutters, of a given pitch, necessary to cut all the wheels from 12 teeth to a rack, then the thickness of the teeth at the pitch line will for the purposes of designation be the thickness of the teeth of all the wheels, which thickness may be a certain proportion of the pitch. But in involute teeth while the depth of tooth on the cutter may be taken as the standard for all the wheels in the range, and the actual depth for the wheel for which the cutter is correct, yet the depth of the teeth in the other wheels in the range may be varied sufficiently on each wheel to make the thickness of the teeth equal the width of the spaces (notwithstanding the variation between the arc and chord pitches), so that by a variation in the tooth depth the error induced by that variation may be corrected. The following table gives the proportions in the Brown and Sharpe system. +------------+-----------------+-----------------+ | Arc Pitch. | Depth of Tooth. | Depth in terms | | | |of the arc pitch.| +------------+-----------------+-----------------+ | inches. | inches. | inches. | | 1.570 | 1.078 | .686 | | 1.394 | .958 | .687 | | 1.256 | .863 | .686 | | 1.140 | .784 | .697 | | 1.046 | .719 | .687 | | .896 | .616 | .686 | | .786 | .539 | .685 | | .628 | .431 | .686 | | .524 | .359 | .685 | | .448 | .307 | .685 | | .392 | .270 | .686 | | .350 | .240 | .686 | | .314 | .216 | .687 | +------------+-----------------+-----------------+ To avoid the trouble of measuring, and to assist in obtaining accuracy of depth, a gauge is employed to mark on the wheel face a line denoting the depth to which the cutter should be entered. Suppose now that it be required to make a set of cutters for a certain range of wheels, and it be determined that the cutters be so constructed that the greatest permissible amount of error in any wheel of the set be 1/100 inch. Then the curves for the smallest wheel, and those for the largest in the set, and the amount of difference between them ascertained, and assuming this difference to amount to 1/16 inch, which is about 6/100, then it is evident that 6 cutters must be employed for the set. It has been shown that on bevel-wheels the tooth curves vary at every point in the tooth breadth; hence it is obvious that the cutter being of a fixed curve will make the tooth to that curve. Again, the thickness of the teeth and breadth of the spaces vary at every point in the breadth, while with a cutter of fixed thickness the space cut will be parallel from end to end. To overcome these difficulties it is usual to give to the cutter a curve corresponding to the curve required at the middle of the wheel face and a thickness equal to the required width of space at its smallest end, which is at the smallest face diameter. The cutter thus formed produces, when passed through the wheel once, and to the required depth, a tooth of one curve from end to end, having its thickness and width of space correct at the smaller face diameter only, the teeth being too thick and the spaces too narrow as the outer diameter of the wheel is approached. But the position and line of traverse of the cutter may be altered so as to take a second cut, widening the space and reducing the tooth thickness at the outer diameter. By moving the cutter's position two or three times the points of contact between the teeth may be made to occur at two or three points across the breadth of the teeth and their points of contact; the wear will soon spread out so that the teeth bear all the way across. Another plan is to employ two or three cutters, one having the correct curve for the inner diameter, and of the correct thickness for that diameter, another having the correct curve for the pitch circle, and another having the correct curve at the largest diameter of the teeth. The thickness of the first and second cutters must not exceed the required width of space at the small end, while that for the third may be the same as the others, or equal to the thickness of the smallest space breadth that it will encounter in its traverse along the teeth. The second cutter must be so set that it will leave the inner end of the teeth intact, but cut the space to the required width in the middle of the wheel face. The third cutter must be so set as to leave the middle of the tooth breadth intact, and cut the teeth to the required thickness at the outer or largest diameter. CUTTING WORM-WHEELS. The most correct method of cutting the teeth of a worm-wheel is by means of a worm-cutter, which is a worm of the pitch and form of tooth that the working worm is intended to be, but of hardened steel, and having grooves cut lengthways of the worm so as to provide cutting edges similar to those on the cutter shown in Fig. 107. The wheel is mounted on an arbor or mandril free to rotate on its axis and at a right angle to the cutter worm, which is rotated and brought to bear upon the perimeter of the worm-wheel in the same manner as the working worm-wheel when in action. The worm-cutter will thus cut out the spaces in the wheel, and must therefore be of a thickness equal to those spaces. The cutter worm acting as a screw causes the worm-wheel to rotate upon its axis, and therefore to feed to the cutter. In wheels of fine pitch and small diameter this mode of procedure is a simple matter, especially if the form of tooth be such that it is thicker, as the root of the tooth is approached from the pitch line, because in that case the cutter worm may be entered a part of the depth in the worm-wheel and a cut be taken around the wheel. The cutter may then be moved farther into the wheel and a second cut taken around the wheel, so that by continuing the process until the pitch line of the cutter worm coincides with that of the worm-cutter, the worm-wheel may be cut with a number of light cuts, instead of at one heavy cut. But in the case of large wheels the strain due to such a long line of cutting edge as is possessed by the cutter worm-teeth springs or bends the worm-wheel, and on account of the circular form of the breadth of the teeth this bending or spring causes that part of the tooth arc above the centre of the wheel thickness to lock against the cutter. To prevent this, several means may be employed. Thus the grooves forming the cutting edges of the worm-cutter may wind spirally along instead of being parallel to the axis of the cutter. The distance apart of these grooves may be greater than the breadth of tooth a width of worm-wheel face, in which case the cutting edge of one tooth only will meet the work at one time. In addition to this two stationary supports may be placed beneath the worm-wheel (one on each side of the cutter). But on coarse pitches with their corresponding depth of tooth, the difficulty presents itself, that the arbor driving the worm-cutter will spring, causing the cutter to lift and lock as before; hence it is necessary to operate on part of the space at a time, and shape it out to so nearly the correct form that the finishing cut may be a very light one indeed, in which case the worm-cutter will answer for the final cut. The removal of the surplus metal preparatory to the introduction of the worm-cutter to finish, may be made with a cutter-worm that will cut out a narrow groove being of the thickness equal to the bottom of the tooth space and cutting on its circumference only. This cutter may be fed into the wheel to the permissible depth of cut, and after the cut is taken all around the wheel, it may be entered deeper and a second cut taken, and so on until it has entered the wheel to the necessary depth of tooth. A second cutter-worm may then be used, it being so shaped as to cut the face curve only of the teeth. A third may cut the flank curve only, and finally a worm-cutter of correct form may take a finishing cut over both the faces and the flanks. In this manner teeth of any pitch and depth may be cut. Another method is to use a revolving cutter such as shown in Fig. 107, and to set it at the required angle to the wheel, and then take a succession of cuts around the wheel, the first cut forming a certain part of the tooth depth, the second increasing this depth, and so on until the final cut forms the tooth to the requisite depth. In this case the cutter operates on each space separately, or on one space only at a time, and the angle at which to set the cutter may be obtained as follows in Fig. 114. Let the length of the line A A equal the diameter of the worm at the pitch circle, and B B (a line at a right angle to A A) represent the axial line of the worm. Let the distance C equal the pitch of the teeth, and the angle of the line D with A A or B B according to circumstances, will be that to which the cutter must be set with reference to the tooth. [Illustration: Fig. 114.] If then a piece of sheet metal be cut to the lines A, D, and the cutter so set that with the edge D of the piece held against the side face of the cutter (which must be flat or straight across), the edge A will stand truly vertical, and the cutter will be at the correct angle supposing the wheel to be horizontal. [Illustration: Fig. 115.] [Illustration: Fig. 116.] In making patterns wherefrom gear-wheels may be cast in a mould, the true curves are frequently represented by arcs of circles struck from the requisite centres and of the most desirable radius with compasses, and this will be treated after explaining the pattern maker's method of obtaining true curves by rolling segments by hand. If, then, the wheels are of small diameter, as say, less than 12 inches in diameter, and precision is required, it is best to turn in the lathe wooden disks representing in their diameters the base and generating circles. But otherwise, wooden segments to answer the same purpose may be made as from a piece of soft wood, such as pine or cedar, about three-eighths inch thick, make two pieces A and B, in Fig. 115, and trim the edges C and D to the circle of the pitch line of the required wheel. If the diameter of the pitch circle is marked on a drawing, the pieces may be laid on the drawing and sighted for curvature by the eye. In the absence of a drawing, strike a portion of the pitch circle with a pair of sharp-pointed compasses on a piece of zinc, which will show a very fine line quite clear. After the pieces are filed to the circle, try them together by laying them flat on a piece of board, bringing the curves in contact and sweeping A against B, and the places of contact will plainly show, and may be filed until continuous contact along the curves is obtained. Take another similar piece of wood and form it as shown in Fig. 116, the edge E representing a portion of the rolling circle. In preparing these segments it is an excellent plan to file the convex edges, as shown in Fig. 117, in which P is a piece of iron or wood having its surface S trued; F is a file held firmly to S, while its surface stands vertical, and T is the template laid flat on S, while swept against the file. This insures that the edge shall be square across or at least at the same angle all around, which is all that is absolutely necessary. It is better, however, that the edges be square. So likewise in fitting A and B (Fig. 115) together, they should be laid flat on a piece of board. This will insure that they will have contact clear across the edge, which will give more grip and make slip less likely when using the segments. Now take a piece of stiff drawing paper or of sheet zinc, lay segment A upon it, and mark a line coincident with the curved edge. Place the segment representing the generating circle flat on the paper or zinc, hold its edge against segment A, and roll it around a sufficient distance to give as much of the curve as may be required; the operation being illustrated in Fig. 118, in which A is the segment representing the pitch or base circle, E is the segment representing the generating circle, P is the paper, C the curve struck by the tracing point or pencil O. [Illustration: Fig. 117.] [Illustration: Fig. 118.] This tracing point should be, if paper be used to trace on, a piece of the _hardest_ pencil obtainable, and should be filed so that its edge, if flat, shall stand as near as may be in the line of motion when rolled, thus marking a fine line. If sheet zinc be used instead of paper a needle makes an excellent tracing point. Several of the curves, C, should be struck, moving the position of the generating segment a little each time. [Illustration: Fig. 119.] On removing the segments from the paper, there will appear the lines shown in Fig. 119; A representing the pitch circle, and O O O the curves struck by the tracing point. Cut out a piece of sheet zinc so that its edge will coincide with the curve A and the epicycloid O, trying it with all four of the epicycloids to see that no slip has occurred when marking them; shape a template as shown in Fig. 120. Cutting the notches at _a_ _b_, acts to let the file clear well when filing the template, and to allow the scriber to go clear into the corner. Now take the segment A in Fig. 118, and use it as a guide to carry the pitch circle across the template as at P, in Fig. 120. A zinc template for the flank curve is made after the same manner, using the rolling segment in conjunction with the segment B in Fig. 115. [Illustration: Fig. 120.] But the form of template for the flank should be such as shown in Fig. 121, the curve P representing, and being of the same radius as the pitch circle, and the curve F being that of the hypocycloid. Both these templates are set to the pitch circles and to coincide with the marks made on the wheel teeth to denote the thickness, and with a hardened steel point a line is traced on the tooth showing the correct curve for the same. [Illustration: Fig. 121.] An experienced hand will find no difficulty in producing true templates by this method, but to avoid all possibility of the segments slipping on coarse pitches, and with large segments, the segments may be connected, as shown in Fig. 122, in which O represents a strip of steel fastened at one end into one segment and at the other end to the other segment. Sometimes, indeed, where great accuracy is requisite, two pieces of steel are thus employed, the second one being shown at P P, in the figure. The surfaces of these pieces should exactly coincide with the edge of the segments. [Illustration: Fig. 122.] [Illustration: Fig. 123.] [Illustration: Fig. 124.] [Illustration: Fig. 125.] [Illustration: Fig. 126.] The curve templates thus produced being shaped to apply to the pitch circle may be correctly applied to that circle independently of its concentricity to the wheel axis or of the points of the teeth, but if the points of the teeth are turned in the lathe so as to be true (that is, concentric to the wheel axis) the form of the template may be such as shown in Fig. 123, the radius of the arc A A equalling that of the addendum circle or circumference at the points of the teeth, and the width at B (the pitch circle) equaling the width of a space instead of the thickness of a tooth. The curves on each side of the template may in this case be filed for the full side of a tooth on each side of the template so that it will completely fill the finished space, or the sides of two contiguous teeth may be marked at one operation. This template may be set to the marks made on the teeth at the pitch circle to denote their requisite thickness, or for greater accuracy, a similar template made double so as to fill two finished tooth spaces may be employed, the advantage being that in this case the template also serves to mark or test the thickness of the teeth. Since, however, a double template is difficult to make, a more simple method is to provide for the thickness of a tooth, the template shown in Fig. 124, the width from A to B being either the thickness of tooth required or twice the thickness of a tooth plus the width of a space, so that it may be applied to the outsides of two contiguous teeth. The arc C may be made both in its radius and distance from the pitch circle D D to equal that of the addendum circle, so as to serve as a gauge for the tooth points, if the latter are not turned true in the lathe, or to rest on the addendum circle (if the teeth points are turned true), and adjust the pitch circle D D to the pitch circle on the wheel. The curves for the template must be very carefully filed to the lines produced by the rolling segments, because any error in the template is copied on every tooth marked from it. Furthermore, instead of drawing the pitch circle only, the addendum circle and circle for the roots of the teeth or spaces should also be drawn, so that the template may be first filed to them, and then adjusted to them while filing the edges to the curves. Another form of template much used is shown in Fig. 125. The curves A and B are filed to the curve produced by rolling segments as before, and the holes C, D, E, are for fastening the template to an arm, such as shown in Fig. 126, which represents a section of a wheel W, with a plug P, fitting tightly into the hub H of the wheel. This plug carries at its centre a cylindrical pin on which pivots the arm A. The template T is fastened to the arm by screws, and set so that its pitch circle coincides with the pitch circle P on the wheel, when the curves for one side of all the teeth may be marked. The template must then be turned over to mark the other side of the teeth. The objection to this form of template is that the length of arc representing the pitch circle is too short, for it is absolutely essential that the pitch line on the template (or line representing the arc of the addendum if that be used) be greater than the width of a single tooth, because an error of the thickness of a line (in the thickness of a tooth), in the coincidence of the pitch line of the template with that of the tooth, would throw the tooth curves out to an extent altogether inadmissible where true work is essential. [Illustration: Fig. 127.] To overcome this objection the template may be made to equal half the thickness of a tooth and its edge filed to represent a radial line on the wheel. But there are other objections, as, for example, that the template can only be applied to the wheel when adjusted on the arm shown in Fig. 126, unless, indeed, a radial line be struck on every tooth of the wheel. Again, to produce the template a radial line representing the radius of the wheel must be produced, which is difficult where segments only are used to produce the curves. It is better, therefore, to form the template as shown in Fig. 127, the projections at A B having their edges filed to coincide with the pitch circle P, so that they may be applied to a length of one arc of pitch circle at least equal to the pitch of the teeth. The templates for the tooth curves being obtained, the wheel must be divided off on the pitch circle for the thickness of the teeth and the width of the spaces, and the templates applied to the marks or points of division to serve as guides to mark the tooth curves. Since, however, as already stated, the tooth curves are as often struck by arcs of circles as by templates, the application of such arcs and their suitability may be discussed. MARKING THE CURVES BY HAND. In the employment of arcs of circles several methods of finding the necessary radius are found in practice. [Illustration: Fig. 128.] In the best practice the true curve is marked by the rolling segments already described, and the compass points are set by trial to that radius which gives an arc nearest approaching to the true face and flank curves respectively. The degree of curve error thus induced is sufficient that the form of tooth produced cannot with propriety be termed epicycloidal teeth, except in the case of fine pitches in which the arc of a circle may be employed to so nearly approach the true curve as to be permissible as a substitute. But in coarse pitches the error is of much importance. Thus in Fig. 128 is shown the curve of the _former_ or _template_ attachment used on the celebrated Corliss Bevel Gear Cutting Machine, to cut the teeth on the bevel-wheels employed upon the line shafting at the Centennial Exhibition. These gears, it may be remarked, were marvels of smooth and noiseless running, and attracted wide attention both at home and abroad. The engraving is made from a drawing marked direct from the _former_ itself, and kindly furnished me by Mr. George H. Corliss. A A is the face and B B the flank of the tooth, C C is the arc of a circle nearest approaching to the face curve, and D D the arc of a circle nearest approaching the flank curve. In the face curve, there are but two points where the circle coincides with the true curve, while in the flank there are three such points; a circle of smaller radius than C C would increase the error at _b_, but decrease it at _a_; one of a greater radius would decrease it at _b_, and increase it at _a_. Again, a circle larger in radius than D D would decrease the error at _e_ and increase it at _f_; while one smaller would increase it at _e_ and decrease it at _f_. Only the working part of the tooth is given in the illustration, and it will be noted that the error is greatest in the flank, although the circle has three points of coincidence. [Illustration: Fig. 129.] In this case the depth of the _former_ tooth is about three and three-quarter times greater than the depth of tooth cut on the bevel-wheels; hence, in the figure the actual error is magnified three and three-quarter times. It demonstrates, however, the impropriety of calling coarsely pitched teeth that are found by arcs of circles "epicycloidal" teeth. When, however, the pitches of the teeth are fine as, say an inch or less, the coincidence of an arc of a circle with the true curve is sufficiently near for nearly all practical purposes, and in the case of cast gear the amount of variation in a pitch of 2 inches would be practically inappreciable. To obtain the necessary set of the compasses to mark the curves, the following methods may be employed. First by rolling the true curves with segments as already described, and the setting the compass points (by trial) to that radius which gives an arc nearest approaching the true curves. In this operation it is not found that the location for the centre from which the curve must be struck always falls on the pitch circle, and since that location will for every tooth curve lie at the same radius from the wheel centre it is obvious that after the proper location for one of the curves, as for the first tooth face or tooth flank as the case may be, is found, a circle may be struck denoting the radius of the location for all the teeth. In Fig. 129, for example, P P represents the pitch circle, A B the radius that will produce an arc nearest approaching the true curve produced by rolling segments, and A the location of the centre from which the face arc B should be struck. The point A being found by trial with the compasses applied to the curve B, the circle A C may be struck, and the location for the centres from which the face arcs of each tooth must be struck will also fall on this circle, and all that is necessary is to rest one point of the compasses on the side of the tooth as, say at E, and mark on the second circle A C the point C, which is the location wherefrom to mark the face arc D. If the teeth flanks are not radial, the locations of the centre wherefrom to strike the flank curves are found in like manner by trial of the compasses with the true curves, and a third circle, as I in Fig. 130, is struck to intersect the first point found, as at G in the figure. Thus there will be upon the wheel face three circles, P P the pitch circle, J J wherefrom to mark the face curves, and I wherefrom to mark the flank curves. When this method is pursued a little time may be saved, when dividing off the wheel, by dividing it into as many divisions as there are teeth in the wheel, and then find the locations for the curves as in Fig. 131, in which 1, 2, 3 are points of divisions on the pitch circle P P, while A, B, struck from point 2, are centres wherefrom to strike the arcs E, F; C, D, struck also from point 2 are centres wherefrom to strike the flank curves G, H. [Illustration: Fig. 130.] It will be noted that all the points serving as centres for the face curves, in Fig. 130, fall within a space; hence if the teeth were rudely cast in the wheel, and were to be subsequently cut or trimmed to the lines, some provision would have to be made to receive the compass points. To obviate the necessity of finding the necessary radius from rolling segments various forms of construction are sometimes employed. [Illustration: Fig. 131.] Thus Rankine gives that shown in Fig. 132, which is obtained as follows. Draw the generating circle D, and A D the line of centres. From the point of contact at C, mark on circle D, a point distance from C one-half the amount of the pitch, as at P, and draw the line P C of indefinite length beyond C. Draw a line from P, passing through the line of centres at E, which is equidistant between C and A. Then multiply the length from P to C by the distance from A to D, and divide by the distance between D and E. Take the length and radius so found, and mark it upon P C, as at F, and the latter will be the location of centre for compasses to strike the face curve. [Illustration: Fig. 132.] Another method of finding the face curve, with compasses, is as follows: In Fig. 133, let P P represent the pitch circle of the wheel to be marked, and B C the path of the centre of the generating or describing circle as it rolls outside of P P. Let the point B represent the centre of the generating circle when that circle is in contact with the pitch circle at A. Then from B, mark off on B C any number of equidistant points, as D, E, F, G, H, and from A, mark on the pitch circle, points of division, as 1, 2, 3, 4, 5, at the intersection of radial lines from D, E, F, G, and H. With the radius of the generating circle, that is, A B, from B, as a centre, mark the arc I, from D the arc J, from E the arc K, &c., to M, marking as many arcs as there are points of division on B C. With the compasses set to the radius of divisions 1, 2, step off on arc M the five divisions, N, O, S, T, V, and V will be a point in the epicycloidal curves. From point of division 4, step off on L four points of division, as _a_, _b_, _c_, _d_, and _d_ will be another point in the epicycloidal curve. From point 3 set off three divisions on K, from point 2 two dimensions on L, and so on, and through the points so obtained, draw by hand or with a scroll the curve represented in the cut by curve A V. [Illustration: Fig. 133.] Hypocycloids for the flanks of the teeth may be traced in a similar manner. Thus in Fig. 134 P P is the pitch circle, and B C the line of motion of the centre of the generating circle to be rolled within P P, and R a radial line. From 1 to 6 are points of equal division on the pitch circle, and D to I are arc locations for the centre of the generating circle. Starting from A, which represents the supposed location for the centre of the generating circle, the point of contact between the generating and base circles will be at B. Then from 1 to 6 are points of equal division on the pitch circle, and from D to I are the corresponding locations for the centres of the generating circle. From these centres the arcs J, K, L, M, N, O, are struck. From 6 mark the six points of division from _a_ to _f_, and _f_ is a point in the curve. Five divisions on N, four on M, and so on, give respectively points in the curve which is marked in the figure from A to _f_. There is this, however, to be noted concerning the constructions of the last two figures. Since the circle described by the centre of the generating circle is of different arc or curve to that of the pitch circle, the chord of an arc having an equal length on each will be different. The amount is so small as to be practically correct. The direction of the error is to give to the curves a less curvature, as though they had been produced by a generating circle of larger diameter. Suppose, for example, that the difference between the arc N 5 (Fig. 133) and its chord is .1, and that the difference between the arc 4 5, and its chord is .01, then the error in one step is .09, and, as the point V is formed in 5 steps, it will contain this error multiplied five times. Point _d_ would contain it multiplied four times, because it has 4 steps, and so on. The error will increase in proportion as the diameter of the generating is less than that of the pitch circle, and though in large wheels, working with large wheels (so that the difference between the radius of the generating circle and that of the smallest wheel is not excessive), it is so small as to be practically inappreciable, yet in small wheels, working with large ones, it may form a sensible error. [Illustration: Fig. 134.] An instrument much employed in the best practice to find the radius which will strike an arc of a circle approximating the true epicycloidal curve, _and for finding at the same time_ the location of the centre wherefrom that curve should be struck, is found in the Willis' odontograph. This is, in reality, a scale of centres or radii for different and various diameters of wheels and generating circles. It consists of a scale, shown in Fig. 135, and is formed of a piece of sheet metal, one edge of which is marked or graduated in divisions of one-twentieth of an inch. The edge meeting the graduated edge at O is at angle of 75° to the graduated edge. On one side of the odontograph is a table (as shown in the cut), for the flanks of the teeth, while on the other is the following table for the faces of the teeth: TABLE SHOWING THE PLACE OF THE CENTRES UPON THE SCALE. CENTRES FOR THE FACES OF THE TEETH. Pitch in Inches and Parts. +------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ |No. of|1/4|3/8|1/2|5/8|3/4| 1|1- |1- |1- | 2|2- |2- | 3|3- | |Teeth | | | | | | |1/4|1/2|3/4| |1/4|1/2| |1/2| |------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | 12 | 1| 2| 2| 3| 4| 5| 6| 7| 9| 10| 11| 12| 15| 17| | 15 | ..| ..| 3| ..| ..| ..| 7| 8| 10| 11| 12| 14| 17| 19| | 20 | 2| ..| ..| 4| 5| 6| 8| 9| 11| 12| 14| 15| 18| 21| | 30 | ..| 3| 4| ..| ..| 7| 9| 10| 12| 14| 16| 18| 21| 25| | 40 | ..| ..| ..| ..| 6| 8| ..| 11| 13| 15| 17| 19| 23| 26| | | | | | | | | | | | | | | | | | 60 | ..| ..| ..| 5| ..| ..| 10| 12| 14| 16| 18| 20| 25| 29| | 80 | ..| ..| ..| ..| ..| 9| 11| 13| 15| 17| 19| 21| 26| 30| | 100 | ..| ..| ..| ..| 7| ..| ..| ..| ..| 18| 20| 22| ..| 31| | 150 | ..| ..| 5| 6| ..| ..| ..| 14| 16| 19| 21| 23| 27| 32| |Rack. | ..| 4| ..| ..| ..| 10| 12| 15| 17| 20| 22| 25| 30| 34| +------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ The method of using the instrument is as follows: In Fig. 136, let C represent the centre, and P the pitch circle of a wheel to contain 30 teeth of 3 inch arc pitch. Draw the radial line L, meeting the pitch circle at A. From A mark on the pitch circle, as at B, a radius equal to the pitch of the teeth, and the thickness of the tooth as A _k_. Draw from B to C the radial line E. Then for the flanks place the slant edge of the odontograph coincident and parallel with E, and let its corners coincide with the pitch circle as shown. In the table headed _centres for the flanks of the teeth_, look down the column of 3 inch pitch, and opposite to the 30 in the column of numbers of teeth, will be found the number 49, which indicates that the centre from which to draw an arc for the flank is at 49 on the graduated edge of the odontograph, as denoted in the cut by _r_. Thus from _r_ to the side _k_ of the tooth is the radius for the compasses, and at _r_, or 49, is the location for the centre to strike the flank curve _f_. For the face curve set the slant edge of the odontograph coincident with the radial line L, and in the table of centres for the faces of teeth, look down the column of 3-inch pitch, and opposite to 30 in the number of teeth column will be found the number 21, indicating that at 21 on the graduated edge of the odontograph, is the location of the centre wherefrom to strike the curve _d_ for the face of the tooth, this location being denoted in the cut at R. [Illustration: Fig. 135. TABLE SHOWING THE PLACE OF THE CENTRES UPON THE SCALE. +--------------------------------------------------------------+ | CENTRES FOR THE FLANKS OF THE TEETH. | +--------------------------------------------------------------+ | PITCH IN INCHES AND PARTS. | +------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ |Number| | | | | | | | | | | | | | | | of | | | | | | 1 | 1-| 1-| 1-| 2 | 2-| 2-| 3 | 3-| |teeth.|1/4|3/8|1/2|5/8|3/4| |1/4|1/2|3/4| |1/4|1/2| |1/2| +------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ | 13| 32| 48| 64| 80| 96|129|160|193|225|257|289|321|386|450| | 14| 17| 26| 35| 43| 52| 69| 87|104|121|139|156|173|208|242| | 15| 12| 18| 25| 31| 37| 49| 62| 74| 86| 99|111|123|148|173| | 16| 10| 15| 20| 25| 30| 40| 50| 59| 69| 79| 89| 99|119|138| | 17| 8| 13| 17| 21| 25| 34| 43| 50| 59| 67| 75| 84|101|117| | 18| 7| 11| 15| 19| 22| 30| 37| 45| 52| 59| 67| 74| 89|104| | 19|...| 10| 13| 17| 20| 27| 35| 40| 47| 54| 60| 67| 80| 94| | 20| 6| 9| 12| 16| 19| 25| 31| 37| 43| 49| 56| 62| 74| 86| | 22| 5| 8| 11| 14| 16| 22| 27| 33| 39| 43| 49| 54| 65| 76| | 24|...| 7| 10| 12| 15| 20| 25| 30| 35| 40| 45| 49| 59| 69| | 26|...|...| 9| 11| 14| 18| 23| 27| 32| 37| 41| 46| 55| 64| | 28| 4| 6|...|...| 13|...| 22| 26| 30| 35| 40| 43| 52| 60| | 30|...|...| 8| 10| 12| 17| 21| 25| 29| 33| 37| 41| 49| 58| | 35|...|...|...| 9| 11| 16| 19| 23| 26| 30| 34| 38| 45| 53| | 40|...| 5| 7|...|...| 15| 18| 21| 25| 28| 32| 35| 42| 49| | 60| 3|...| 6| 8| 9| 13| 15| 19| 22| 25| 28| 31| 37| 43| | 80|...| 4|...| 7|...| 12|...| 17| 20| 23| 26| 29| 35| 41| | 100|...|...|...|...| 8| 11| 14|...|...| 22| 25| 28| 34| 39| | 150|...|...| 5|...|...|...| 13| 16| 19| 21| 24| 27| 32| 38| | Rack.| 2|...|...| 6| 7| 10| 12| 15| 17| 20| 22| 25| 30| 34| +------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+] The requisite number on the graduated edge for pitches beyond 3-1/2 (the greatest given in the tables), may be obtained by direct proportion from those given in the tables. Thus for 4 inch pitch, by doubling the numbers given for a 2 inch pitch, containing the same number of teeth, for 4-1/2 inch pitch by doubling the numbers given for a 2-1/4 inch pitch. If the pitch be a fraction that cannot be so obtained, no serious error will be induced if the nearest number marked be taken. [Illustration: Fig. 136.] An improved form of template odontograph, designed by Professor Robinson of the Illinois School of Industry, is shown in Fig. 137. In this instrument the curved edge, having graduated lines, approaches more nearly to the curves produced by rolling circles than can be obtained from any system in which an arc of a circle is taken to represent the curve; hence, that edge is applied direct to the teeth and used as a template wherefrom to mark the curve. The curve is a logarithmic spiral, and the use of the instrument involves no other labor than that of setting it in position. The applicability of this curve, for the purpose, arises from two of its properties: first, that the involute of the logarithmic spiral is another like spiral with poles in common; and, second, that the obliquity or angle between a normal and radius sector is constant, the latter property being possessed by this curve only. By the first property it is known that a line, lying tangent to the curve C E H, will be normal or perpendicular to the curve C D B; so that when the line D E F is tangent to the pitch line, the curve A D B will coincide very closely with the true epicycloidal curve, or, rather, with that portion of it which is applied to the tooth curve of the wheel. By the second quality, all sectors of the spiral, with given angle at the poles, are similar figures which admit of the same degree of coincidence for all similar epicycloids, whether great or small, and nearly the same for epicycloids in general; thus enabling the application of the instrument to epicycloids in general. To set the instrument in position for drawing a tooth face a table which accompanies the instrument is used. From this table a numerical value is taken, which value depends upon the diameters of the wheels, and the number of teeth in the wheel for which the curve is sought. This tabular value, when multiplied by the pitch of the teeth, is to be found on the graduated edge on the instrument A D B in Fig. 137. This done, draw the line D E F tangent to the pitch line at the middle of the tooth, and mark off the half thickness of the tooth, as E, D, either on the tangent line or the pitch line. Then place the graduated edge of the odontograph at D, and in such a position that the number and division found as already stated shall come precisely on the tangent line at D, and at the same time so set the curved edge H F C so that it shall be tangent to the tangent line, that is to say, the curved edge C H must just meet the tangent line at some one point, as at F in the figure. A line drawn coincident with the graduated edge will then mark the face curve required, and the odontograph may be turned over, and the face on the other side of the tooth marked from a similar setting and process. For the flanks of the teeth setting numbers are obtained from a separate table, and the instrument is turned upside down, and the tangent line D F, Fig. 137, is drawn from the side of the tooth (instead of from the centre), as shown in Fig. 138. It is obvious that this odontograph may be set upon a radial arm and used as a template, as shown in Fig. 126, in which case the instrument would require but four settings for the whole wheel, while rolling segments and the making of templates are entirely dispensed with, and the degree of accuracy is greater than is obtainable by means of the employment of arcs of circles. The tables wherefrom to find the number or mark on the graduated edge, which is to be placed coincident with the tangent line in each case, are as follows:-- TABLE OF TABULAR VALUES WHICH, MULTIPLIED BY THE ARC PITCH OF THE TEETH, GIVES THE SETTING NUMBER ON THE GRADUATED EDGE OF THE INSTRUMENT. +--------------------+-----------------------------------------------------+ | | Number of Teeth in Wheel Sought; or, Wheel for | | | Which Teeth are Sought. | | +-----+-----+-----+-----+-----+-----+-----+-----+-----+ | | 8 | 12 | 16 | 20 | 30 | 40 | 50 | 60 | 70 | | +-----+-----+-----+-----+-----+-----+-----+-----+-----+ | | _For Faces: Flanks Radial or Curved._ | | RATIOS.[7] | Draw Setting Tangent at Middle of Tooth.-- | | | Epicycloidal Spur or Bevel Gearing. | +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | 1/12 = .083 | .32 | .39 | .46 | .51 | | | | | | | 1/4 = .250 | .31 | .37 | .44 | .49 | .61 | .70 | .78 | .85 | .92 | | 1/2 = .500 | .28 | .34 | .41 | .46 | .57 | .66 | .73 | .80 | .87 | | 2/3 = .667 | .27 | .32 | .38 | .43 | .54 | .62 | .70 | .77 | .83 | | 1 | .23 | .28 | .34 | .39 | .49 | .58 | .65 | .72 | .78 | | 3/2 = 1.50 | .19 | .25 | .29 | .34 | .44 | .51 | .58 | .64 | .69 | | 2 | .17 | .22 | .26 | .30 | .38 | .46 | .53 | .59 | .63 | | 3 | | .16 | .19 | .23 | .31 | .38 | .44 | .49 | .53 | | 4 | | .14 | .17 | .20 | .26 | .33 | .38 | .42 | .46 | | 6 | | | | | .22 | .26 | .30 | .34 | .37 | | 12 | | | | | | .20 | .23 | .25 | .28 | | 24 | | | | | | | | | | +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | | Number of Teeth in Wheel Sought; or, Wheel for| | | Which Teeth are Sought. | | +-----+-----+-----+-----+-----+-----+-----+-----+ | | 80 | 90 | 100 | 120 | 150 | 200 | 300 | 500 | | +-----+-----+-----+-----+-----+-----+-----+-----+ | | _For Faces: Flanks Radial or Curved._ | | RATIOS.[7] | Draw Setting Tangent at Middle of Tooth.-- | | | Epicycloidal Spur or Bevel Gearing. | +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+ | 1/12 = .083 | | | | | | | | | | 1/4 = .250 | .99 | 1.05| 1.11| 1.22| 1.36| 1.55| 1.94| 2.54| | 1/2 = .500 | .93 | 1.00| 1.06| 1.15| 1.29| 1.50| 1.86| 2.41| | 2/3 = .667 | .89 | .95| 1.01| 1.11| 1.24| 1.45| 1.79| 2.32| | 1 | .83 | .89| .94| 1.03| 1.15| 1.36| 1.65| 2.10| | 3/2 = 1.50 | .74 | .79| .84| .93| 1.05| 1.25| 1.53| 1.94| | 2 | .68 | .72| .76| .84| .95| 1.13| 1.40| 1.81| | 3 | .57 | .60| .63| .71| .82| .97| 1.23| 1.60| | 4 | .49 | .53| .56| .63| .73| .87| 1.08| 1.42| | 6 | .41 | .44| .47| .53| .61| .71| .90| 1.20| | 12 | .30 | .32| .34| .37| .42| .49| .60| .82| | 24 | | .19| .21| .23| .26| .31| .40| .57| +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+ +--------------------+-----------------------------------------------------+ | | Number of Teeth in Wheel Sought; or, Wheel for | | | Which Teeth are Sought. | | +-----+-----+-----+-----+-----+-----+-----+-----+-----+ | | 8 | 12 | 16 | 20 | 30 | 40 | 50 | 60 | 70 | | +-----+-----+-----+-----+-----+-----+-----+-----+-----+ | | _For Flanks, when Curved._ | | | Draw Setting Tangent at Side of Tooth.-- | | | Epicycloidal Spur and Bevel Gearing. | |D C | Faces of Internal, and Flanks of Pinion Teeth. | |e u +-----+-----+-----+-----+-----+-----+-----+-----+-----+ |g F r { 1.5 slight.| .77 | .98 | 1.18| 1.36| 1.75| 2.05| 2.31| 2.56| 2.75| |r l v { 2 good. | .44 | .54 | .63| .72 | .92| 1.09| 1.24| 1.38| 1.49| |e a a { 3 more. | .20 | .28 | .35| .40 | .54| .65| .76| .86| .95| |e n t { 4 much. | | .20 | .23| .25 | .34| .42| .51| .59| .66| | k u { 6 | | | .16| .17 | .26| .32| .38| .43| .48| |o r {12 | | | | | .19| .24| .28| .31| .34| |f e {24 | | | | | | | | | | +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | | Number of Teeth in Wheel Sought; or, Wheel for| | | Which Teeth are Sought. | | +-----+-----+-----+-----+-----+-----+-----+-----+ | | 80 | 90 | 100 | 120 | 150 | 200 | 300 | 500 | | +-----+-----+-----+-----+-----+-----+-----+-----+ | | _For Flanks, when Curved._ | | | Draw Setting Tangent at Side of Tooth.-- | | | Epicycloidal Spur and Bevel Gearing. | |D C | Faces of Internal, and Flanks of Pinion Teeth.| |e u +-----+-----+-----+-----+-----+-----+-----+-----+ |g F r { 1.5 slight.| 2.92| 3.08| 3.24| 3.52| 3.87| 4.51| 5.50| 7.20| |r l v { 2 good. | 1.59| 1.79| 1.79| 1.98| 2.23| 2.67| 3.22| 4.50| |e a a { 3 more. | 1.02| 1.10| 1.18| 1.31| 1.46| 1.67| 2.08| 2.76| |e n t { 4 much. | .71| .77| .82| .92| 1.06| 1.25| 1.64| 2.15| | k u { 6 | .52| .56| .60| .66| .76| .93| 1.20| 1.54| |o r {12 | .36| .38| .40| .45| .52| .63| .80| .98| |f e {24 | | | .22| .25| .28| .33| .47| .60| +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+ +--------------------+-----------------------------------------------------+ | | Number of Teeth in Wheel Sought; or, Wheel for | | | Which Teeth are Sought. | | +-----+-----+-----+-----+-----+-----+-----+-----+-----+ | | 8 | 12 | 16 | 20 | 30 | 40 | 50 | 60 | 70 | | +-----+-----+-----+-----+-----+-----+-----+-----+-----+ | _For Faces of Racks; and of Pinions for Racks and Internal Gears; for | | Flanks of Internal and Sides of Involute Teeth._ | | Draw Setting Tangent at Middle of Tooth, regarding Space as Tooth in | | Internal Teeth. For Rack use Number of Teeth in Pinion. | +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | Pinion. | .31 | .39 | .48 | .57 | .73 | .88 | 1.00| 1.10| 1.20| | Rack. | .32 | .38 | .44 | .50 | .62 | .72 | .80| .87| .93| +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | | Number of Teeth in Wheel Sought; or, Wheel for| | | Which Teeth are Sought. | | +-----+-----+-----+-----+-----+-----+-----+-----+ | | 80 | 90 | 100 | 120 | 150 | 200 | 300 | 500 | | +-----+-----+-----+-----+-----+-----+-----+-----+ | _For Faces of Racks; and of Pinions for Racks and Internal Gears; | | for Flanks of Internal and Sides of Involute Teeth._ | |Draw Setting Tangent at Middle of Tooth, regarding Space as Tooth in| | Internal Teeth. For Rack use Number of Teeth in Pinion. | +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+ | Pinion. | 1.30| 1.40| 1.48| 1.65| 1.85| 2.15| 2.65| 3.50| | Rack. | .99| 1.03| 1.08| 1.16| 1.27| 1.49| 1.86| 2.44| +--------------------+-----+-----+-----+-----+-----+-----+-----+-----+ [7] These ratios are obtained by dividing the radius of the wheel sought by the diameter of the generating circle. From these tables may be found a tabular value which, multiplied by the pitch of the wheel to be marked (as stated at the head of the table), will give the setting number on the graduated edge of the instrument, the procedure being as follows:-- For the teeth of a pair of wheels intended to gear together only (and not with other wheels having a different number of teeth). For the face of such teeth where the flanks are to be radial lines. Rule.--Divide the pitch circle radius of the wheel to have its teeth marked by the pitch circle radius of the wheel with which it is to gear: or, what is the same thing, divide the number of teeth in the wheel to have its teeth marked by the number of teeth in the wheel with which it is to gear, and the quotient is the "ratio." In the ratio column find this number, and look along that line, and in the column at the head of which is the number of teeth contained in the wheel to be marked, is a number termed the tabular value, which, multiplied by the arc pitch of the teeth, will give the number on the graduated edge by which to set the instrument to the tangent line. Example.--What is the setting number for the face curves of a wheel to contain 12 teeth, of 3-inch arc pitch, and to gear with a wheel having 24 teeth? Here number of teeth in wheel to be marked = 12, divided by the number of teeth (24) with which it gears; 12 ÷ 24 = .5. Now in column of ratios may be found 1/2 = .500 (which is the same thing as .5), and along the same horizontal line in the table, and in the column headed 12 (the number of teeth in the wheel) is found .34. This is the tabular value, which, multiplied by 3 (the arc pitch of the teeth), gives 1.02, which is the setting number on the graduated edge. It will be noted, however, that the graduated edge is marked 1, 2, 3, &c., and that between each consecutive division are ten subdivisions; hence, for the decimal .02 an allowance may be made by setting the line 1 a proportionate amount below the tangent line marked on the wheel to set the instrument by. [Illustration: Fig. 137. NEW ODONTOGRAPH Full Size] Required now the setting number for the wheel to have the 24 teeth. Here number of teeth on the wheel = 24, divided by the number of teeth (12) on the wheel with which it gears; 24 ÷ 12 = 2. Now, there is no column in the "number of teeth sought" for 24 teeth; but we may find the necessary tabular value from the columns given for 20 teeth and 30 teeth, thus:--opposite ratio 2, and under 20 teeth is given .30, and under 30 teeth is given .38--the difference between the two being .08. Now the difference between 20 teeth and 24 teeth is 4/10; hence, we take 4/10 of the .08 and add it to the tabular value given for 20 teeth, thus: .08 × 4 ÷ 10 = .032, and this added to .30 (the tabular value given for 20 teeth = .33, which is the tabular value for 24 teeth). The .33 multiplied by arc pitch (3) gives .99. This, therefore, is the setting number for the instrument, being sufficiently near to the 1 on the graduated edge to allow that 1 to be used instead of .99. [Illustration: Fig. 138.] It is to be noted here that the pinion, having radial lines, the other wheel must have curved flanks; the rule for which is as follows:-- CURVED FLANKS FOR A PAIR OF WHEELS. Note.--When the flanks are desired to be curved instead of radial, it is necessary to the use of the instrument to select and assume a value for the degree of curve, as is done in the table in the column marked "Degree for flank curving;" in which 1.5 slight--a slight curvature of flank. 2 good--an increased curvature of flank. 3 more--a degree of pronounced spread at root. 4 much--spread at root is a distinguishing feature of tooth form. 6--still increased spread in cases where the strength at root of pinion is of much importance to give strength. 12--as above, under aggravated conditions. 24--undesirable (unless requirement of strength compels this degree), because of excessive strain on pinion. Rule.--For faces of teeth to have curved flanks. Divide the number of teeth in the wheel to be marked by the number of teeth in the wheel with which it gears, and multiply by the degree of flank curve selected for the wheel with which that to be marked is to gear, and this will give the ratio. Find this number in ratio column, and the tabular number under the column of number of teeth of wheel to be marked; multiply tabular number so found by arc pitch of wheel to be marked, and the product will be the setting number for the instrument. Example.--What is the setting number on the graduated edge of the odontograph for the faces of a wheel (of a pair) to contain 12 teeth of 2-inch arc pitch, and to gear with a wheel having 24 teeth and a flank curvature represented by 3 in "Degree of flank curving" column? Here teeth in wheel to be marked (12) divided by number of teeth in the wheel it is to gear with (24), 12 ÷ 24 = .5, which multiplied by 3 (degree of curvature selected for flanks of 24-teeth wheel), .5 × 3 = 1.5. In column of ratio numbers find 1.5, and in 12-teeth column is .25, which multiplied by pitch (2) gives .5 as the setting number for the instrument; this being the fifth line on the instrument, and half way between the end and mark 1. FOR CURVED FLANKS. Rule.--Assume the degree of curve desired for the flanks to be marked, select the corresponding value in the column of "Degrees of flank curving," and find the tabular value under the number of teeth column. Multiply tabular value so found by the arc pitch of the teeth, and the product is the setting number on the instrument. Example.--What is the setting number on the odontograph for the flanks of a wheel to contain 12 teeth and gear with one having 24 teeth, the degree of curvature for the flanks being represented by 4 in the column of "Degree of flank curvature?" Here in column of degrees of flank curvature on the 3 line and under 12 teeth is .20, which multiplied by pitch of teeth (2) is .20 × 2 = 40, or 4/10; hence, the fourth line of division on the curved corner is the setting line, it representing 4/10 of 1. FOR INTERCHANGEABLE GEARING (THAT IS, A TRAIN OF GEARS ANY ONE OF WHICH WILL WORK CORRECTLY WITH ANY OTHER OF THE SAME SET). Rule--both for the faces and for the flanks. For each respective wheel divide the number of teeth in that wheel by some one number not greater than the number of teeth in the smallest wheel in the set, which gives the ratio number for the wheel to be marked. On that line of ratio numbers, and in the column of numbers of teeth, find the tabular value number; multiply this by the arc pitch of the wheel to be marked, and the product is the setting number of the instrument. Example.--A set of wheels is to contain 10 wheels; the smallest is to contain 12 teeth; the arc pitch of the wheels is four inches. What is the setting number for the smallest wheel? Here number of teeth in smallest wheel of set is 10; divide this by any number smaller than itself (as say 5), 10 ÷ 5 = 2 = the ratio number on ratio line for 2; and under column for 12 is .17, which is the tabular value, which multiplied by pitch (4) is .17 × 4 = 68, or 6/10 and 8/100; hence, the instrument must be set with its seventh line of division just above the tangent line marked on the wheel. It will be noted that, if the seventh line were used as the setting, the adjustment would be only the 2/100 of a division out, an amount scarcely practically appreciable. Both for the faces and flanks, the second number is obtained in _precisely_ the same manner for every wheel in the set, except that instead of 10 the number of teeth in each wheel must be substituted. RACK AND PINION.--_For radial flanks_ use for faces the two lower lines of table. _For curved flanks_ find tabular value for pinion faces in lowest line. For flanks of pinion choose degree of curving, and find tabular value under "flanks," as for other wheels. For faces of rack divide number of teeth in pinion by degree of curving, which take for number of teeth in looking opposite "rack." Flanks of rack are still parallel, but may be arbitrarily curved beyond half way below pitch line. INTERNAL GEARS.--For tooth curves within the pitch lines, divide radius of each wheel by any number not greater than radius of pinion, and look in the table under "flanks." For curves outside pitch line use lower line of table; or, divide radii by any number and look under "faces." In applying instrument draw tangents at middle and side of _space_, for internal teeth. INVOLUTE TEETH.--For tabular values look opposite "Pinion," under proper number of teeth, for each wheel. Draw setting tangent from "base circle" of involute, at middle of tooth. For this the instrument gives the whole side of tooth at once. In all cases multiply the tabular value by the pitch in inches. BEVEL-WHEELS.--Apply above rules, using the developed normal cone bases as pitch lines. For right-angled axes this is done by using in place of the actual ratio of radii, or of teeth numbers, the square of that ratio; and for number of teeth, the actual number multiplied by the square root of one plus square of ratio or radii; the numerator of ratio, and number of teeth, belonging to wheel sought. When the first column ratio and teeth numbers fall between those given in the table, the tabular values are found by interpolating as seen in the following examples: EXAMPLES OF TABULAR VALUES AND SETTING NUMBERS. _Take a pair of 16 and 56 teeth; radii 5.09 and 17.82 inches respectively; and 2 inches pitch._ +----------------+------+----------------+------+---------------+-------+ | |Number} | | First Column | Tab. | |Kind of Gearing.| of } Kind of Flank. |Ratio | Ratio. | Val. | | |Teeth.} |Radii.+--------+------+---+---+ | | | | | Flank. |Face. |[A]|[B]| +----------------+------+----------------+------+--------+------+---+---+ |Epicycloidal, }|Small |Radial | .29 |Radial | .29 |.. |.44| |Radial Flanks }|Large |Radial | 3.5 |Radial | 3.5 |.. |.44| |Epicycloidal, } |Small |Curved 2 deg. | .29 | 2 | .87 |.63|.36| |Curved Flanks.} |Large |Curved 3 deg. } | 3.5 | 3 | 7. |.82|.30| |Epicycloidal, }|Small |"Sets," Divide} | 2. | 2 | 2. |.63|.26| |Interchange'bl.}|Large |Radii by 2.55 } | 7. | 7 | 7. |.40|.30| |Epicycloidal, } |Pinion|Curved 2 deg. | | 2 |Pinion|.63|.44| |Internal. } |Wheel |Int. face 7 deg.| 3.5 |Pinion | 7[8] |.84|.39| |Epicycloidal, }|Pinion|Curved 2 deg. | | 2 |Pinion|.63|.44| |Rack & Pinion. }|Rack |Parallel | |Parallel|Rack |.. |.31| |Involute } |Small |Face and Flank | | Pinion. | .44 | |Gearing. } |Large |One Curve | | Pinion. | .84 | +----------------+------+----------------+------+--------+------+-------+ Legend: A = Flank. B = Face. [8] The face being here internal, the tabular value is to be found under "flanks." If bevels, use ratio radii .082 and 12.25; and teeth numbers 16.6 and 203.8 respectively. WALKER'S PATENT WHEEL SCALE.--This scale is used in many manufactories in the United States to mark off the teeth for patterns, wherefrom to mould cast gears, and consists of a diagram from which the compasses may be set to the required radius to strike the curves of the teeth. [Illustration: Fig. 139.] The general form of this diagram is shown in Fig. 139. From the portion A the length of the teeth, according to the pitch, is obtained. From the portion B half the thickness of the tooth at the pitch line is obtained. From the part C half the thickness at the root is obtained, and from the part D half the thickness at the point is obtained. [Illustration: Fig. 140.] Each of these parts is marked with the number of teeth the wheel is to contain, and with the pitch of the teeth as shown in Fig. 140, which represents part C full size. Now suppose it is required to find the thickness at the root, for a tooth of a wheel having 60 teeth of one inch pitch, the circles from the point A, pitch line B and root C being drawn, and a radial line representing the middle of the tooth being marked, as is shown in Fig. 142, the compass points are set to the distance F B, Fig. 140--F being at the junction of line 1 with line 60; the compasses are then rested at G, and the points H I are marked. Then, from the portion B, Fig. 139 of the diagram, which is shown full-size in Fig. 141, the compasses may be set to half the thickness at the pitch circle, as in this case (for ordinary teeth) from E to E, and the points J K, Fig. 142, are marked. By a reference to the portion D of the diagram, half the thickness of the tooth at the point is obtained, and marked as at L M in Fig. 142. It now remains to set compasses to the radius for the face and that for the flank curves, both of which may be obtained from the part A of the diagram. The locations of the centres, wherefrom to strike these curves, are obtained as in Fig. 142. The compasses set for the face curve are rested at H, and the arc N is struck; they are then rested at J and the arc O struck; and from the intersection of N O, as a centre, the face curve H J is marked. By a similar process, reference to the portion D of the diagram, half the thickness of the tooth at the point is obtained, and marked as at L M in Fig. 142. It now remains to set the compasses to the radius to strike the respective face and flank curves, and for this purpose the operator turns to the portion A, Fig. 139, of the diagram or scale, and sets the compasses from the marks on that portion to the required radii. [Illustration: Fig. 141.] It now remains to find the proper location from which to strike the curves. [Illustration: Fig. 142.] The face curve on the other side of the tooth is struck. The compasses set to the flank radius is then rested at M, and the arc P is marked and rested at K to mark the arc Q; and from the intersection of P Q, as a centre, the flank curve K M is marked: that on the other side of the tooth being marked in a similar manner. Additional scales or diagrams, not shown in Fig. 139, give similar distances to set the compasses for the teeth of internal wheels and racks. It now remains to explain the method whereby the author of the scale has obtained the various radii, which is as follows: A wheel of 200 teeth was given the form of tooth curve that would be obtained by rolling it upon another wheel, containing 200 teeth of the same pitch. It was next given the form of tooth that would be obtained by rolling upon it a wheel having 10 teeth of the same pitch, and a line intermediate between the two curves was taken as representing the proper curve for the large wheel. The wheel having 10 teeth was then given the form of tooth that would be obtained by rolling upon it another wheel of the same diameter of pitch circle and pitch of teeth. It was next given the form of tooth that would be given by rolling upon it a wheel having 200 teeth, and a curve intermediate between the two curves thus obtained was taken as representing the proper curve for the pinion of 10 teeth. By this means the inventor does not claim to produce wheels having an exactly equal velocity ratio, but he claims that he obtains a curve that is the nearest approximation to the proper epicycloidal curve. The radii for the curves for all other numbers of teeth (between 10 and 200) are obtained in precisely the same manner, the pinion for each pitch being supposed to contain 10 teeth. Thus the scale is intended for interchangeable cast gears. The nature of the scale renders it necessary to assume a constant height of tooth for all wheels of the same pitch, and this Mr. Walker has assumed as .40 of the pitch, from the pitch line to the base, and .35 from the pitch line to the point. The curves for the faces obtained by this method have rather more curvature than would be due to the true epicycloid, which causes the points to begin and leave contact more easily than would otherwise be the case. For a pair of wheels Mr. Walker strikes the face curve by a point on the pitch rolling circle, and the flanks by a point on the addendum circle, fastening a piece of wood to the pitch circle to carry the tracing point. The flank of each wheel is struck with a tracing point, thus attached to the pitch circle of the other wheel. The proportions of teeth and of the spaces between them are usually given in turns of the pitch, so that all teeth of a given pitch shall have an equal thickness, height, and breadth, with an equal addendum and flank, and the same amount of clearance. The term "clearance" as applied to gear-wheel teeth means the amount of space left between the teeth of one wheel, and the spaces in the other, or, in other words, the difference between the width of the teeth and that of the spaces between the teeth. This clearance exists at the sides of the teeth, as in Fig. 143, at A, and between the tops of the teeth and the bottoms or roots of the spaces as at B. When, however, the simple term clearance is employed it implies the side clearance as at A, the clearance at B being usually designated as _top and bottom clearance_. Clearance is necessary for two purposes; first, in teeth cut in a machine to accurate form and dimensions, to prevent the teeth of one wheel from binding in the spaces of the other, and second, in cast teeth, to allow for the imperfections in the teeth which are incidental to casting in a founder's mould. In machine-cut teeth the amount of clearance is a minimum. In wheels which are cast with their teeth complete and on the pattern, the amount of clearance must be a maximum, because, in the first place, the teeth on the pattern must be made taper to enable the extraction of the pattern from the mould without damage to the teeth in the mould, and the amount of this taper must be greater than in machine-moulded teeth, because the pattern cannot be lifted so truly vertical by hand as to avoid, in all cases, damage to the mould; in which case the moulder repairs the mould either with his moulding tools and by the aid of the eye, or else with a tooth and a space made on a piece of wood for the purpose. But even in this case the concentricity of the teeth is scarcely likely to be preserved. It is obvious that by reason of this taper each wheel is larger in diameter on one side than on the other, hence to preserve the true curves to the teeth the pitch circle is made correspondingly smaller. But if in keying the wheels to their shafts the two large diameters of a pair of wheels be placed to work together, the teeth of the pair would have contact on that side of the wheel only, and to avoid this and give the teeth contact across their full breadth the wheels are so placed on their shafts that the large diameter of one shall work with the small one of the other, the amount of taper being the same in each wheel irrespective of their relative diameters. This also serves to keep the clearance equal in amount both top, and bottom, and sideways. A second imperfection is that in order to loosen the pattern in the sand or mould, and enable its extraction by hand from the mould, the pattern requires to be _rapped_ in the mould, the blows forcing back the sand of the mould and thus loosening the pattern. In ordinary practice the amount of this rapping is left entirely to the judgment of the moulder, who has nothing to guide him in securing an equal amount of pattern movement in each direction in the mould; hence, the finished mould may be of increased radius at the circumference in the direction in which the wheel moved most during the rapping. Again, the wood pattern is apt in time to shrink and become _out of round_, while even iron patterns are not entirely free from warping. Again, the cast metal is liable to contract in cooling more in one direction than in another. The amount of clearance usually allowed for pattern-moulded cast gearing is given by Professor Willis as follows:--Whole depth of tooth 7/10, of the pitch working depth 6/10; hence 1/10 of the pitch is allowed for top and bottom clearance, and this is the amount shown at B in Fig. 143. The amount of side clearance given by Willis as that ordinarily found in practice is as follows:--"Thickness of tooth 5/11 of the pitch; breadth of space 6/11; hence, the side clearance equals 1/11 of the pitch, which in a 3-inch pitch equals .27 of an inch in each wheel." Calling this in round figures, which is near enough for our purpose, 1/4 inch, we have thickness of tooth 1-1/4, width of space 1-3/4, or 1/2 inch of clearance in a 3-inch pitch, an amount which on wheels of coarse pitch is evidently more than that necessary in view of the accuracy of modern moulding, however suitable it may have been for the less perfect practice of Professor Willis's time. It is to be observed that the rapping of the pattern in the founder's mould reduces the thickness of the teeth and increases the width of the spaces somewhat, and to that extent augments the amount of side clearance allowed on the pattern, and the amount of clearance thus obtained would be nearly sufficient for a small wheel, as say of 2 inches diameter. It is further to be observed that the amount of rapping is not proportionate to the diameter of the wheel; thus, in a wheel of 2 inches diameter, the rapping would increase the size of the mould about 1/32 inch. But in the proportion of 1/32 inch to every 2 inches of diameter, the rapping on a 6-foot wheel would amount to 1-1/16 inches, whereas, in actual practice, a 6-foot wheel would not enlarge the mould more than at most 1/8 inch from the rapping. [Illustration: Fig. 143.] It is obvious, then, that it would be more in accordance with the requirements to proportion the amount of clearance to the diameter of the wheel, so as to keep the clearance as small as possible. This will possess the advantage that the teeth will be stronger, it being obvious that the teeth are weakened both from the loss of thickness and the increase of height due to the clearance. It is usual in epicycloidal teeth to fill in the corner at the root of the tooth with a fillet, as at C, D, in Fig. 143, to strengthen it. This is not requisite when the diameter of the generating circle is so small in proportion to the base circle as to produce teeth that are spread at the roots; but it is especially advantageous when the teeth have radial flanks, in which case the fillets may extend farther up the flanks than when they are spread; because, as shown in Fig. 47, the length of operative flank is a minimum in teeth having radial flanks, and as the smallest pinion in the set is that with radial flanks, and further as it has the least number of teeth in contact, it is the weakest, and requires all the strengthening that the fillets in the corners will give, and sometimes the addition of the flanges on the sides of the pinion, such gears being termed "shrouded." The proportion of the teeth to the pitch as found in ordinary practice is given by Professor Willis as follows:-- Depth to pitch line 3/10 of the pitch. Working depth 6/10 " " Whole depth 7/10 " " Thickness of tooth 5/11 " " Breadth of space 6/11 " " The depth to pitch line is, of course, the same thing as the height of the addendum, and is measured through the centre of the tooth from the point to the pitch line in the direction of a radial line and not following the curve of tooth face. Referring to the working depth, it was shown in Figs. 42 and 44 that the height of the addendum remaining constant, it varies with the diameter of the generating circle. [Illustration: Fig. 144. Scale of Proportions given by Willis] From these proportions or such others as may be selected, in which the proportions bear a fixed relation to the pitch, a scale may be made and used as a gauge, to set the compasses by, and in marking off the teeth for any pitch within the capacity of the scale. A vertical line A B in Fig. 144, is drawn and marked off in inches and parts of an inch, to represent the pitches of the teeth; at a right angle to A B, the line B C is drawn, its length equalling the whole depth of tooth, which since the coarsest pitch in the scale is 4 inches will be 7/10 of 4 inches. From the end of line C we draw a diagonal line to A, and this gives us the whole depth of tooth for any pitch up to 4 inches: thus the whole depth for a 4-inch pitch is the full length of the horizontal line B C; the whole depth for a 3-inch pitch will be the length of the horizontal line running from the 3 on line A B, to line A C on the right hand of the figure; similarly for the full depth of tooth for a 2-inch pitch is the length of the horizontal line running from 2 to A C. The working depth of tooth being 6/10 of the pitch a diagonal is drawn from A meeting line C at a distance from B of 6/10 of 4 inches and we get the working depth for any other pitch by measuring (along the horizontal line corresponding to that pitch), from the line of pitches to the diagonal line for working depth of tooth. The thickness of tooth is 5/11 of the pitch and its diagonal is distant 5/11 of 4 (from B) on line B C, the thickness for other pitches being obtained on the horizontal line corresponding to those pitches as before. [Illustration: Fig. 145.] The construction of a pattern wherefrom to make a foundry mould, in which to cast a spur gear-wheel, is as shown in section, and in plan of Fig. 145. The method of constructing these patterns depends somewhat on their size. Large patterns are constructed with the teeth separate, and the body of the wheel is built of separate pieces, forming the arms, the hub, the rim, and the teeth respectively. Pinion patterns, of six inches and less in diameter, are usually made out of a solid piece, in which case the grain of the wood must lie in the direction of the teeth height. The chuck or face plate of the lathe, for turning the piece, must be of smaller diameter than the pinion, so that it will permit access to a tool applied on both sides, so as to strike the pitch circle on both sides. A second circle is also struck for the roots or depths of the teeth, and also, if required, an extra circle for striking the curves of the teeth with compasses, as was described in Fig. 130. All these circles are to be struck on both sides of the pattern, and as the pattern is to be left slightly taper, to permit of its leaving the mould easily, they must be made of smaller diameter on one side than on the other of the pattern; the reduction in diameter all being made on the same side of the pattern. The pinion body must then be divided off on the pitch line into as many equal divisions as there are to be teeth in it; the curves of the teeth are then marked by some one of the methods described in the remarks on curves of gear-teeth. The top of the face curves are then marked along the points of the teeth by means of a square and scribe, and from these lines the curves are marked in on the other side of the pinion, and the spaces cut out, leaving the teeth projecting. For a larger pinion, without arms, the hub or body is built up of courses of quadrants, the joints of the second course _breaking joint_ with those of the first. [Illustration: Fig. 146.] The quadrants are glued together, and when the whole is formed and the glue dry, it is turned in the lathe to the diameter of the wheel at the roots of the teeth. Blocks of wood, to form the teeth, are then planed up, one face being a hollow curve to fit the circle of the wheel. The circumference of the wheel is divided, or pitched off, as it is termed, into as many points of equal division as there are to be teeth, and at these points lines are drawn, using a square, having its back held firmly against the radial face of the pinion, while the blade is brought coincidal with the point of division, so as to act as a guide in converting that point into a line running exactly true with the pinion. All the points of division being thus carried into lines, the blocks for the teeth are glued to the body of the pinion, as denoted by A, in Fig. 145. Another method is to dovetail the teeth into the pinion, as in Fig. 145 at B. After the teeth blocks are set, the process is, as already described, for a solid pinion. [Illustration: Fig. 147.] The construction of a wheel, such as shown in Fig. 145, is as follows: The rim R must be built up in segments, but when the courses of segments are high enough to reach the flat sides of the arms they should be turned in the lathe to the diameter on the inside, and the arms should be let in, as shown in the figure at O. The rest of the courses of segments should then be added. The arms are then put in, and the inside of the segments last added may then be turned up, and the outside of the rim turned. The hub should then be added, one-half on each side of the arms, as in the figure. The ribs C of the arms are then added, and the body is completed (ready to receive the teeth), by filleting in the corners. An excellent method of getting out the teeth is as follows: Shape A piece of hard wood, as in Fig. 146, making it some five or six inches longer than the teeth, and about three inches deeper, the thickness being not less than the thickness of the required teeth at the pitch line. Parallel to the edge B C, mark the line A D, distant from B C to an amount equal to the required depth of tooth. Mark off, about midway of the piece, the lines A B and C D, distant from each other to an amount equal to the breadth of the wheel rim, and make two saw cuts to those lines. Take a piece of board an inch or two longer than the radius of the gear-wheel and insert a piece of wood (which is termed a box) tightly into the board, as shown in Fig. 147, E representing the box. Let the point F on the board represent the centre of the wheel, and draw a radial line R from F through the centre of the box. From the centre F, with a trammel, mark the addendum line G G, pitch line H I, and line J K for the depth of the teeth (and also a line wherefrom to strike the teeth curves, as shown in Fig. 129 if necessary). From the radial line R, as a centre, mark off on the pitch circle, points of division for several teeth, so as to be able to test the accuracy of the spacing across the several points, as well as from one point to the next, and mark the curves for the teeth on the end of the box, as shown. Turn the box end for end in the board, and mark out a tooth by the same method on the other end of the box. The box being removed from the board must now have its sides planed to the lines, when it will be ready to shape the teeth in. The teeth are got out for length, breadth, and thickness at the pitch line as follows: The lumber from which they are cut should be very straight grained, and should be first cut into strips of a width and thickness slightly greater than that of the teeth at the pitch line. These strips (which should be about two feet long) should then be planed down on the sides to very nearly the thickness of the tooth at the pitch line, and hollow on one edge to fit the curvature of the wheel rim. From these strips, pieces a trifle longer than the breadth of the wheel rim are cut, these forming the teeth. The pieces are then planed on the ends to the exact width of the wheel rim. To facilitate this planing a number of the pieces or blank teeth may be set in a frame, as in Figs. 148 and 149, in which A is a piece having the blocks B B affixed to it. C is a clamp secured by the screws at S S, and 1, 2, 3, 4, 5, 6 are the ends of the blank teeth. The clamp need not be as wide as the teeth, as in Fig. 148, but it is well to let the pieces A and B B equal the breadth of the wheel rim, so that they will act as a template to plane the blank teeth ends to. The ends of B B may be blackleaded, so as to show plainly if the plane blade happens to shave them, and hence to prevent planing B B with the teeth. The blank teeth may now be separately placed in the box (Fig. 146) and secured by a screw, as shown in that figure, in which S is the screw, and T the blank tooth. The sides of the tooth must be carefully planed down equal and level with the surface of the box. The rim of the wheel, having been divided off into as many divisions as there are to be teeth in the wheel, as shown in Fig. 150, at _a_, _a_, _a_, &c., the finished teeth are glued so that the same respective side of each tooth exactly meets one of the lines _a_. Only a few spots of glue should be applied, and these at the middle of the root thickness, so that the glue shall not exude and hide the line _a_, which would make it difficult to set the teeth true to the line. When the teeth are all dry they must be additionally secured to the rim by nails. Wheels sufficiently large to incur difficulty of transportation are composed of a number of sections, each usually consisting of an arm, with an equal length of the rim arc on each side of it, so that the joint where the rim segments are bolted together will be midway between the two arms. [Illustration: Fig. 148.] This, however, is not absolutely necessary so long as the joints are so arranged as to occur in the middle of tooth spaces, and not in the thickness of the tooth. This sometimes necessitates that the rim sections have an unequal length of arc, in which event the pattern is made for the longest segment, and when these are cast the teeth superfluous for the shorter segments are stopped off by the foundry moulder. This saves cutting or altering the pattern, which, therefore, remains good for other wheels when required. [Illustration: Fig. 149.] When the teeth of wheels are to be cut in a gear-cutting machine the accurate spacing of the teeth is determined by the index plate and gearing of the machine itself; but when the teeth are to be cast upon the wheel and a pattern is to be made, wherefrom to cast the wheel the points of division denoting the thickness of the teeth and the width of the spaces are usually marked by hand. This is often rendered necessary from the wheels being of too large a diameter to go into dividing machines of the sizes usually constructed. To accurately divide off the pitch circle of a gear-wheel by hand, requires both patience and skilful manipulation, but it is time and trouble that well repays its cost, for in the accuracy of spaces lies the first requisite of a good gear-wheel. It is a very difficult matter to set the compasses so that by commencing at any one point and stepping the compasses around the circle continuously in one direction, the compass point shall fall into the precise point from which it started, for if the compass point be set the 1-200th inch out, the last space will come an inch out in a circle having 200 points of divisions. It is, therefore, almost impossible and quite impracticable to accurately mark or divide off a circle having many points of division in this manner, not only on account of the fineness of the adjustment of the compass points, but because the frequent trials will leave so many marks upon the circle that the true ones will not be distinguishable from the false. Furthermore, the compass points are apt to spring and fall into the false marks when those marks come close to the true ones. [Illustration: Fig. 150.] In Fig. 151 is shown a construction by means of which the compass points may be set more nearly than by dividing the circumference of the circle by the number of divisions it is required to be marked into and setting the compasses to the quotient, because such a calculation gives the length of the division measured around the arc of the circle, instead of the distance measured straight from point of division to point of division. [Illustration: Fig. 151.] The construction of Fig. 151 is as follows: P P is a portion of the circle to be divided, and A B is a line at a tangent to the point C of the circle P P. The point D is set off distant from C, to an amount obtained by dividing the circumference of P P by the number of divisions it is to have. Take one-quarter of this distance C D, and mark it from C, giving the point E, set one point of the compass at E and the other at D, and draw the arc D F, and the distance from F to C, as denoted by G, is the distance to which to set the compasses to divide the circle properly. The compasses being set to this distance G, we may rest one compass point at C, and mark the arc F H, and the distance between arc H and arc D, measured on the line A B, is the difference between the points C, F when measured around the circle P P, and straight across, as at G. [Illustration: Fig. 152.] A pair of compasses set even by this construction will not, however, be entirely accurate, because there will be some degree of error, even though it be in placing the compass points on the lines and on the points marked, hence it is necessary to step the compasses around the circle, and the best method of doing this is as follows: Commencing at A, Fig. 152, we mark off continuously one from the other, and taking care to be very exact to place the compass point exactly coincident with the line of the circle, the points B, C, D, &c., continuing until we have marked half as many divisions as the circle is to contain, and arriving at E, starting again at A, we mark off similar divisions (one half of the total number), F, G, H, arriving at I, and the centre K, between the two lines E, I, will be the true position of the point diametrally opposite to point A, whence we started. These points are all marked inside the circle to keep them distinct from those subsequently marked. [Illustration: Fig. 153.] It will be, perhaps, observed by the reader that it would be more expeditious, and perhaps cause less variation, were we to set the compasses to the radius of the circle and mark off the point K, as shown in Fig. 153, commencing at the point A, and marking off on the one side the lines B, C, and D, and on the other side E, F, and G, the junction or centre, between G and D, at the circle being the true position of the point K. For circles struck upon flat surfaces, this plan may be advantageous; and in cases where there are not at hand compasses large enough, a pair of trammels may be used for the purpose; but our instructions are intended to apply also to marking off equidistant points on such circumferences as the faces of pulleys or on the outsides of small rings or cylinders, in which cases the use of compasses is impracticable. The experienced hand may, it is true, adjust the compasses as instructed, and mark off three or four of the marks B, C, &c., in Fig. 152, and then open out the compasses to the distance between the two extreme marks, and proceed as before to find the centre K, but as a rule, the time saved will scarcely repay the trouble; and all that can be done to save time in such cases is, if the holes come reasonably close together, to mark off, after the compasses are adjusted, three or four spaces, as shown in Fig. 154. Commencing at the point A, and marking off the points B, C, and D, we then set another pair of compasses to the distance between A and D, and then mark, from D on one side and from A on the other, the marks from F to L and from M to T, thus obtaining the point K. This method, however expeditious and correct for certain work, is not applicable to circumferential work of small diameter and in which the distance between two of the adjacent points is, at the most, 1/20 of the circumference of the circle; because the angle of the surface of the metal to the compass point causes the latter to spring wider open in consequence of the pressure necessary to cause the compass point to mark the metal. This will be readily perceived on reference to Fig. 155 in which A represents the stationary, and B the scribing or marking point of the compasses. [Illustration: Fig. 154.] The error in the set of the compasses as shown by the distance apart of the two marks E and I on the circle in Fig. 152 is too fine to render it practicable to remedy it by moving the compass legs, hence we effect the adjustment by oilstoning the points on the outside, throwing them closer together as the figure shows is necessary. [Illustration: Fig. 155.] Having found the point K, we mark (on the outside of the circle, so as to keep the marks distinct from those first marked) the division B, C, D, Fig. 156, &c., up to G, the number of divisions between B and G being one quarter of those in the whole circle. Then, beginning at K, we mark off also one quarter of the number of divisions arriving at M in the figure and producing the point 3. By a similar operation on the other side of the circle, we get the true position of point No. 4. If, in obtaining points 3 and 4, the compasses are not found to be set dead true, the necessary adjustment must be made; and it will be seen that, so far, we have obtained four true positions, and the process of obtaining each of them has served as a justification of the distance of the compass points. From these four points we may proceed in like manner to mark off the holes or points between them; and the whole will be as true as it is practicable to mark them off upon that size of circle. In cases, however, where mathematical precision is required upon flat and not circumferential surfaces, the marking off may be performed upon a circle of larger diameter, as shown in Fig. 157. If it is required to mark off the circle A, Fig. 157, into any even number of equidistant points, and if, in consequence of the closeness together of the points, it becomes difficult to mark them (as described) with the compasses, we mark a circle B B of larger diameter, and perform our marking upon it, carrying the marks across the smaller circle with a straightedge placed to intersect the centres of the circles and the points marked on each side of the diameter. Thus, in Fig. 157, the lines 1 and 2 on the smaller circle would be obtained from a line struck through 1 and 4 on the outer circle; and supposing the larger circle to be three times the size of the smaller, the deviation from truth in the latter will be only 1/3 of whatever it is in the former. [Illustration: Fig. 156.] [Illustration: Fig. 157.] In this example we have supposed the number of divisions to be an even one, hence the point K, Fig. 152, falls diametrically opposite to A, whereas in an odd number of points of division this would not be the case, and we must proceed by either of the two following methods:-- [Illustration: Fig. 158.] In Fig. 158 is shown a circle requiring to be divided by 17 equidistant points. Starting from point 1 we mark on the outside of the circumference points 2, 3, 4, &c., up to point 9. Starting again from point 1 we mark points 10, 11, &c., up to 17. If, then, we try the compasses to 17 and 9 we shall find they come too close together, hence we take another pair of compasses (so as not to disturb the set of our first pair) and find the centre between 9 and 17 as shown by the point A. We then correct the set of our first pair of compasses, as near as the judgment dictates, and from point A, we mark with the second compasses (set to one half the new space of the first compasses) the points B, C. With the first pair of compasses, starting from B, we mark D, E, &c., to G; and from I, we mark divisions H, I, &c., to K, and if the compasses were set true, K and G would meet at the circle. We may, however, mark a point midway between K and G, as at 5. Starting again from points C and I, we mark the other side of the circle in a similar manner, producing the lines P and Q, midway between which (the compasses not being set quite correct as yet) is the true point for another division. After again correcting the compasses, we start from B and 5 respectively, and mark point 7, again correcting the compasses. Then from C and the point between P and Q, we may mark an intermediate point, and so on until all the points of division are made. This method is correct enough for most practical purposes, but the method shown in Fig. 159 is more correct for an odd number of points of division. Suppose that we have commenced at the point marked I, we mark off half the required number of holes on one side and arrive at the point 2; and then, commencing at the point I again, we mark off the other half of the required number of holes, arriving at the point 3. We then apply our compasses to the distance between the points 2 and 3; and if that distance is not exactly the same to which the compasses are set, we make the necessary adjustment, and try again and again until correct adjustment is secured. [Illustration: Fig. 159.] It is highly necessary, in this case, to make the lines drawn at each trial all on the same side of the circle and of equal length, but of a different length to those marked on previous trials. For example, left the lines A, B, C, D, in Fig. 159 represent those made on the first trial, and E, F, G, H, those made on the second trial; and when the adjustment is complete, let the last trial be made upon the outside or other side of the circle, as shown by the lines I, J, K, L. Having obtained the three true points, marked 1, 2, 3, we proceed to mark the intermediate divisions, as described for an even number of divisions, save that there will be a space, 2 and 3, opposite point 1, instead of a point, as in case of a circle having an even number of divisions. [Illustration: Fig. 160.] The equal points of division thus obtained may be taken for the centres of the tooth at the pitch circle or for one side of the teeth, as the method to be pursued to mark the tooth curves may render most desirable. If, for example, a template be used to mark off the tooth curves, the marks may be used to best advantage as representing the side of a tooth, and from them the thickness of the tooth may be marked or not as the kind of template used may require. Thus, if the template shown in Fig. 21 be used, no other marks will be used, because the sides of a tooth on each side of a space may be marked at one setting of the template to the lines or marks of division. If, however, a template, such as shown in Fig. 81 be used, a second set of lines marked distant from the first to a radius equal to the thickness of a tooth becomes necessary so that the template may be set to each line marked. If the Willis odontograph or the Robinson template odontograph be used the second set of lines will also be necessary. In using the Walker scale a radial line, as G in Fig. 142, will require to be marked through the points of equal division, and the thickness of the tooth at the points on the pitch circle and at the root must be marked as was shown in Fig. 142. But if the arcs for the tooth curves are to be marked by compasses, the location for the centres wherefrom to strike these arcs may be marked from the points of division as was shown in Fig. 130. To construct a pattern wherefrom to cast a bevel gear-wheel.--When a pair of bevel-wheels are in gear and upon their respective shafts all the teeth on each wheel incline, as has been shown, to a single point, hence the pattern maker draws upon a piece of board a sketch representing the conditions under which the wheels are to operate. A sketch of this kind is shown in Fig. 160, in which A, B, C, D, represent in section the body of a bevel pinion. F G is the point of a tooth on one side, and E the point of a tooth on the other side of the pinion, while H I are pitch lines for the two teeth. Thus, the cone surface, the points, the pitch lines and the bottom of the spaces, projected as denoted by the dotted lines, would all meet at X, which represents the point where the axes of the shafts would meet. [Illustration: Fig. 161.] In making wooden patterns wherefrom to cast the wheels, it is usual, therefore, to mark these lines on a drawing-board, so that they may be referred to by the workman in obtaining the degree of cone necessary for the body A B C D, to which the teeth are to be affixed. Suppose, then, that the diameter of the pinion is sufficiently small to permit the body A B C D to be formed of one piece instead of being put together in segments, the operation is as follows: The face D C is turned off on the lathe, and the piece is reversed on the lathe chuck, and the face A B is turned, leaving a slight recess at the centre to receive and hold the cone point true with the wheel. A bevel gauge is then set to the angle A B C, and the cone of the body is turned to coincide in angle with the gauge and to the required diameter, its surface being made true and straight so that the teeth may bed well. While turning the face D C in the lathe a fine line circle should be struck around the circumference of the cone and near D C, on which line the spacing for the teeth may be stepped off with the compasses. After this circle or line is divided off into as many equidistant points as there are to be teeth on the wheel, the points of division require to be drawn into lines, running across the cone surface of the wheel, and as the ordinary square is inapplicable for the purpose, a suitable square is improvised as follows: In Fig. 161 let the outline in full lines denote the body of a pinion ready to receive the teeth, and A B the circle referred to as necessary for the spacing or dividing with the compasses. On A B take any point, as C, as a centre, and with a pair of compasses mark equidistant on each side of it two lines, as D, D. From D, D as respective centres mark two lines, crossing each other as at F, and draw a line, joining the intersection of the lines at F with C, and the last line, so produced, will be in the place in which the teeth are to lie; hence the wheel will require as many of these lines as it is to contain teeth, and the sides of the teeth, being set to these lines all around the pinion, will be in their proper positions, with the pitch lines pointing to X, in Fig. 160. [Illustration: Fig. 162.] To avoid, however, the labor involved in producing these lines for each tooth, two other plans may be adopted. The first is to make a square, such as shown in Fig. 162, the face _f_ _f_ being fitted to the surface C, in Fig. 161, while the edges of its blade coincide with the line referred to; hence the edge of the blade may be placed coincident successively with each point of division, as D D, and the lines for the place of the length of each tooth be drawn. The second plan is to divide off the line A B before removing the body of the pinion from the lathe, and produce, as described, a line for one tooth. A piece of wood may then be placed so that when it lies on the surface of the hand-rest its upper surface will coincide with the line as shown in Fig. 163, in which W is the piece of wood, and A, B, C, &c., the lines referred to. If the teeth are to be glued and bradded to the body, they are first cut out in blocks, left a little larger every way than they are to be when finished, and the surfaces which are to bed on the cone are hollowed to fit it. Then blocks are glued to the body, one and the same relative side of each tooth being set fair to the lines. When the glue is dry, the pinion is again turned on the lathe, the gauge for the cone of the teeth being set in this case to the lines E, F, G in Fig. 160. The pitch circles must then be struck at the ends of the teeth. The turned wheel is then ready to have the curves of the teeth marked. The wheel must now again be divided off on the pitch circle at the large end of the cone into as many equidistant points as there are to be teeth on the wheel, and from these points, and on the same relative side of them, mark off a second series of points, distant from the points of division to an amount equal to the thickness the teeth are required to be. From these points draw in the outline of the teeth (upon the ends of the blocks to form the teeth) at the large end of the cone. Then, by use of the square, shown in Fig. 162, transfer the points of the teeth to the small end of the cone, and trace the outline of the teeth at the small end, taking centres and distances proportionate to the reduced diameter of the pitch circle at the small end, as shown in Fig. 160, where at J are three teeth so marked for the large end, and at K three for the small end, P P representing the pitch circle, and R R a circle for the compass points. The teeth for bevel pinions are sometimes put on by dovetails, as shown in Fig. 164, a plan which possesses points of advantage and disadvantage. Wood shrinks more across the grain than lengthwise with it, hence when the grain of the teeth crosses that of the body with every expansion or contraction of the wood (which always accompanies changes in the humidity of the atmosphere) there will be a movement between the two, because of the unequal expansion and contraction, causing the teeth to loosen or to move. In the employment of dovetails, however, a freedom of movement lengthways of the tooth is provided to accommodate the movement, while the teeth are detained in their proper positions. Again, if in making the founders' mould, one of the mould teeth should break or fall down when the pattern is withdrawn, a tooth may be removed from the pattern and used by the moulder to build up the damaged part of the mould again. And if the teeth of a bevel pinion are too much undercut on the flank curves to permit the whole pattern from being extracted from the mould without damaging it, dovetailed teeth may be drawn, leaving the body of the pattern to be extracted from the mould last. On the other hand, the dovetail is a costly construction if applied to large wheels. If the teeth are to be affixed by dovetails, the construction varies as follows: Cut out a wooden template of the dovetail, leaving it a little narrower than the thickness of the tooth at the root, and set the template on the cone at a distance from one of the lines A, B, C, Fig. 163, equal to the margin allowed between the edge of the dovetail and the side of the root of the tooth, and set it true by the employment of the square, shown in Fig. 162, and draw along the cone surface of the body lines representing the location of the dovetail grooves. The lines so drawn will give a taper toward X (Fig. 160), providing that, the template sides being parallel, each side is set to the square. While the body is in the lathe, a circle on each end may be struck for the depth of the dovetails, which should be cut out to gauge and to template, so that the teeth will interchange to any dovetail. The bottom of the dovetails need not be circular, but flat, which is easier to make. Dovetail pieces or strips are fitted to the grooves, being left to project slightly above the face of the cone or body. They are drawn in tight enough to enable them to keep their position while being turned in the lathe when the projecting points are turned down level with the cone of the body. The teeth may then be got out as described for glued teeth, and the dovetails added, each being marked to its place, and finally the teeth are cut to shape. [Illustration: Fig. 163.] [Illustration: Fig. 164.] [Illustration: Fig. 165.] In wheels too large to have their cones tested by a bevel gauge, a wooden gauge may be made by nailing two pieces of wood to stand at the required angle as shown in Fig. 165, which is extracted from _The American Machinist_, or the dead centre C and a straightedge may be used as follows. In the figure the other wheel of the pair is shown dotted in at B, and the dead centre is set at the point where the axes of A and B would meet; hence if the largest diameter of the cone of A is turned to correct size, the cone will be correct when a straightedge applied as shown lies flat on the cone and meets the point of the dead centre E. The pinion B, however, is merely introduced to explain the principle, and obviously could not be so applied practically, the distance to set _e_, however, is the radius _a_. Skew Bevel.[9]--When the axles of the shaft are inclined to each other instead of being in a straight line, and it is proposed to connect and communicate motion to the shafts by means of a single pair of bevel-gears, the teeth must be inclined to the base of the frustra to allow them to come into contact. [9] From the "Engineer and Machinists' Assistant." [Illustration: Fig. 166.] To find the line of contact upon a given frustrum of the tangent-cone; let the Fig. 166 be the plane of the frustrum; _a_ the centre. Set off _a_ _e_ equal to the shortest distance between the axes (called the _eccentricity_), and divide it in _c_, so that _a_ _c_ is to _e_ _c_ as the mean radius of the frustrum to the mean radius of that with which it is to work; draw _c_ _p_ perpendicular to _a_ _e_, and meeting the circumference of the conical surface at _m_; perform a similar operation on the base of the frustrum by drawing a line parallel to _c_ _m_ and at the same distance _a_ _c_ from the centre, meeting the circumference in _p_. The line _p_ _c_ is then plainly the line of direction of the teeth. We are also at liberty to employ the equally inclined line _c_ _q_ in the opposite direction, observing only that, in laying out the two wheels, the pair of directions be taken, of which the inclinations correspond. [Illustration: Fig. 167.] Fig. 167 renders this mode of laying off the outlines of the wheels at once obvious. In this figure the line _a_ _e_ corresponds to the line marked by the same letters in Fig. 166; and the division of it at _c_ is determined in the manner directed. The line _c_ _m_ being thus found in direction, it is drawn indefinitely to _d_. Parallel to this line and from the point _c_ draw _e_ to _e_, and in this line take the centre of the second wheel. The line _c_ _m_ _d_ gives the direction of the teeth; and if from the centre _a_ with radius at _c_ a circle be described, the direction of any tooth of the wheel will be a tangent to it, as at _c_, and similarly if a centre _e_ be taken in the line _e_ _d_, and with radius _e_ _d_, _c_ _e_ a circle be drawn, the direction of the teeth of the second wheel will be tangents to this last, as at _d_. Having thus found the direction of the teeth, these outlines may be formed as in the case of ordinary bevel-wheels and with equal exactness and facility, all that is necessary being to find the curves for the teeth as described for bevel-wheels, and follow precisely the same construction, except that the square, Fig. 162, marking the lines across the cones, requires to be set to the angle for the tooth instead of at a right angle, and this angle may be found by the construction shown in Fig. 167, it being there represented by line _d_ _c_. It is obvious, however, that the bottoms of the blocks to form the teeth must be curved to bed on the cone along the line _d_ _c_, Fig. 167, and this may best be done by bedding two teeth, testing them by trial of the actual surfaces. [Illustration: Fig. 168.] Then two teeth may be set in as No. 1 and No. 6 in the box shown in Fig. 148, the intermediate ones being dressed down to them. Where a bevel-wheel pattern is too large to be constructed in one piece and requires to be built up in pieces, the construction is as in Fig. 168, in which on the left is shown the courses of segments 1, 2, 3, 4, 5, &c., of which the rim is built up (as described for spur wheels), and on the right is shown the finished rim with a tooth, _c_, in position. The tooth proper is of the length of face of the wheel as denoted by _b b´_; now all the lines bounding the teeth must converge to the point X. Suppose, then, that the teeth are to be shaped for curve of face and flank in a box as described for spur-wheel teeth in Fig. 146, then in Fig. 168 let _a_, _a_ represent the bottom and _b b´_ the top of the box, and _c_ a tooth in the box, its ends filling the opening in the box at _b b´_ then the curve on the sides of the box at _b´_ must be of the form shown at F, and the curve on the sides of the box (at the point _b_ of its length) must be as shown at G, the teeth shown in profile at G and U representing the forms of the teeth at their ends, on the outside of the wheel rim at _b´_, and on the inside at _b_; having thus made a box of the correct form on its sides, the teeth may be placed in it and planed down to it, thus giving all the teeth the same curve. The spacing for the teeth and their fixing may be done as described for the bevel pinion. [Illustration: Fig. 169.] To construct a pattern wherefrom to cast an endless screw, worm, or tangent screw, which is to have the worm or thread cut in a lathe.--Take two pieces, each to form one longitudinal half of the pattern; peg and screw them together at the ends, an excess of stuff being allowed at each end for the accommodation of two screws to hold the two halves together while turning them in the lathe, or dogs, if the latter are more convenient, as they might be in a large pattern. Turn the piece down to the size over the top of the thread, after which the core prints are turned. The body thus formed will be ready to have the worm or thread cut, and for this purpose the tools shown in Figs. 169 and 140 are necessary. That shown in Fig. 169 should be flat on the face similar to a parting tool for cast iron, but should have a great deal more bottom rake, as strength is not so much an object, and the tool is more easily sharpened. It has also in addition two little projections A B like the point of a penknife, formed by filing away the steel in the centre; these points are to cut the fibres of the wood, the severed portion being scraped away by the flat part of the tool. [Illustration: Fig. 170.] The degree of side rake given to the tool must be sufficient to let the tool sides well clear the thread or worm, and will therefore vary with the pitch of the worm. The width of the tool must be a shade narrower than the narrowest part of the space in the worm. Having suitably adjusted the change wheels of the lathe to cut the pitch required the parting tool is fed in until the extreme points reach the bottom of the spaces, and a square nosed parting tool without any points or spurs will finish the worm to the required depth. This will have left a square thread, and this we have now to cut to the required curves on the thread or worm sides, and as the cutting will be performed on the end grain of the wood, the top face of the tool must be made keen by piercing through the tool a slot A, Fig. 170, and filing up the bevel faces B, C and D, and then carefully oilstoning them. This tool should be made slightly narrower than the width of the worm space, so that it may not cut on both sides at once, as it would have too great a length of cutting edge. [Illustration: Fig. 171.] Furthermore, if the pattern is very large, it will be necessary to have two tools for finishing, one to cut from the pitch line inwards and the other to complete the form from the pitch line outwards. It is advisable to use hard wood for the pattern. If it is decided to cut the thread by hand instead of with these lathe tools, then, the pattern being turned as before, separate the two halves by taking out the screws at the ends; select the half that has not the pegs, as being a little more convenient for tracing lines across. Set out the sections of the thread, A, B, C, and D, Fig. 171, similar to a rack; through the centres of A, B, C, and D, square lines across the piece; these lines, where they intersect the pitch line, will give the centres of teeth on that side: or if we draw lines, as E, F, through the centres of the spaces, they will pass through the centres of the teeth (so to speak) on the other side; in this position complete the outline on that side. It will be found, in drawing these outlines, that the centres of some of the arcs will lie outside the pattern. To obtain support for the compasses, we must fit over the pattern a piece of board such as shown by dotted lines at G H. [Illustration: Fig. 172.] It now remains to draw in the top of the thread upon the curved surface of the half pattern; for this purpose take a piece of stiff card or other flexible material, wrap it around the pattern and fix it temporarily by tacks, we then trim off the edges true to the pattern, and mark upon the edges of the card the position of the tops of the thread upon each side; we remove the card and spread it out on a flat surface, join the points marked on the edges by lines as in Fig. 172, replace the card exactly as before upon the pattern, and with a fine scriber we prick through the lines. The cutting out is commenced by sawing, keeping, of course, well within the lines; and it is facilitated by attaching a stop to the saw so as to insure cutting at all parts nearly to the exact depth. This stop is a simple strip of wood and may be clamped to the saw, though it is much more convenient to have a couple of holes in the saw blade for the passage of screws. For finishing, a pair of templates, P and Q, Fig. 173, right and left, will be found useful; and finally the work should be verified and slight imperfections corrected by the use of a form or template taking in three spaces, as shown at R in Fig. 173. In drawing the lines on the card, we must consider whether it is a right or left-handed worm that we desire. In the engraving the lines are those suitable for a right-handed thread. Having completed one half of the pattern, place the two halves together, and trace off the half that is uncut, using again the card template for drawing the lines on the curved surface. The cutting out will be the same as before. [Illustration: Fig. 173.] As the teeth of cast wheels are, from their deviation from accuracy in the tooth curves and the concentricity of the teeth to the wheel centre, apt to create noise in running, it is not unusual to cast one or both wheels with mortises in the rim to receive wooden teeth. In this case the wheel is termed a mortise wheel, and the teeth are termed _cogs_. If only one of a pair of wheels is to be cogged, the largest of the pair is usually selected, because there are in that case more teeth to withstand the wear, it being obvious that the wear is greatest upon the wheel having the fewest teeth, and that the iron wheel or pinion can better withstand the wear than the mortise wheel. The woods most used for cogs are hickory, maple, hornbeam and locust. The blocks wherefrom the teeth are to be formed are usually cut out to nearly the required dimensions, and kept in stock, so as to be thoroughly well-seasoned when required for use, and, therefore less liable to come loose from shrinkage after being fitted to the mortise in the wheel. The length of the shanks is made sufficient to project through the wheel rim and receive a pin, as shown in Fig. 174, in which B is a blank tooth, and C a finished tooth inserted in the wheel, the pin referred to being at P. But, if a mortise should fall in an arm of the wheel, this pin-hole must pass through the rim, as shown in the mortise A. The wheel, however, should be designed so that the mortises will not terminate in the arms of the wheel. [Illustration: Fig. 174.] [Illustration: Fig. 175.] Another method of securing the teeth in the mortises is to dovetail them at the small end and drive wedges between them, as shown in Fig. 175, in which C C are two contiguous teeth, R the wheel rim and W W two of the wedges. On account of the dovetailing the wedges exert A pressure pressing the teeth into the mortises. This plan is preferable to that shown in the Fig. 174 inasmuch as from the small bearing area of the pins they become loose quicker, and furthermore there is more elasticity to take up the wear in the case of the wedges. [Illustration: Fig. 176.] The mortises are first dressed out to a uniform size and taper, using two templates to test them with, one of which is for the breadth and the other for the width of the mortise. The height above the wheel requires to be considerably more than that due to the depth of the teeth, so that the surface bruised by driving the cogs or when fitting them into the mortises may be cut off. To avoid this damage as much as possible, a broad-face hammer should be employed--a copper, lead, lignum vitæ, or a raw hide hammer being preferable, and the last the best. The teeth are got out in a box and two guides, such as shown in Figs. 176, 177, and 178, similar letters of reference denoting the same parts in all three illustrations. In Fig. 176, X is a frame or box containing and holding the operative part of the tooth, and resting on two guides C D. The height of D from the saw table is sufficiently greater than that of C to give the shank G the correct taper, E F representing the circular saw. T is a plain piece of the full size of the box or frame, and serving simply to close up on that side the mortise in the frame. The grain of T should run at a right angle to the other piece of the frame so as to strengthen it. S is a binding screw to hold the cog on the frame, and H is a guide for the edge of the frame to slide against. It is obvious, now, that if the piece D be adjusted at a proper distance from the circular saw E F, and the edge of the frame be moved in contact with the guide H, one side of the tooth shank will be sawn. Then, by reversing the frame end for end, the other side of the shank may be sawn. Turning the frame to a right angle the edges of the cog shank can be sawn from the same box or frame, and pieces C, D, as shown in Fig. 177. [Illustration: Fig. 177.] The frame is now stood on edge, as in Fig. 178, and the underneath surfaces sawed off to the depth the saw entered when the shank taper was sawn. This operation requires to be performed on all four sides of the tooth. After this operation is performed on one cog, it should be tried in the wheel mortises, to test its correctness before cutting out the shanks on all the teeth. [Illustration: Fig. 178.] The shanks, being correctly sawn, may then be fitted to the mortises, and let in within 1/8 of butting down on the face of the wheel, this amount being left for the final driving. The cogs should be numbered to their places, and two of the mortises must be numbered to show the direction in which the numbers proceed. To mark the shoulders (which are now square) to the curvature of the rim, a fork scriber should be used, and the shanks of the cogs should have marked on them a line coincident with the inner edge of the wheel rim. This line serves as a guide in marking the pin-holes and for cutting the shanks to length; but it is to be remembered that the shanks will pass farther through to the amount of the distance marked by the fork scriber. The holes for the pins which pass through the shanks should be made slightly less in their distances (measured from the nearest edge of the pin-hole) from the shoulders of the cogs than is the thickness of the rim of the wheel, so that when the cogs are driven fully home the pin-holes will appear not quite full circles on the inside of the wheel rim; hence, the pins will bind tightly against the inside of the wheel rim, and act somewhat as keys, locking and drawing the shanks to their seats in the mortises. In cases where quietness of running is of more consequence than the durability of the teeth, or where the wear is not great, both wheels may be cogged, but as a rule the larger wheel is cogged, the smaller being of metal. This is done because the teeth of the smaller wheel are the most subject to wear. The teeth of the cogged wheel are usually made the thickest, so as to somewhat equalise the strength of the teeth on the two wheels. Since the power transmitted by a wheel in a given time is composed of the pressure or weight upon the wheel, and the space a point on the pitch circle moves through in the given time, it is obvious that in a train of wheels single geared, the velocities of all the wheels in the train being equal at the pitch circle, the teeth require to be of equal pitch and thickness throughout the train. But when the gearing is compounded the variation of velocity at the pitch circle, which is due to the compounding, has an important bearing upon the necessary strength of the teeth. Suppose, for example, that a wheel receives a tooth pressure of 100 lbs. at the pitch circle, which travels at the velocity of 100 feet per minute, and is keyed to the same shaft with another wheel whose velocity is 50 feet per minute. Now, in the power transmitted by the two wheels the element of time is 50 for one wheel and 100 for the other, hence the latter (supposing both wheels to have an equal number of teeth in contact with their driver or follower as the case may be) will be twice as strong in proportion to the duty, and it appears that in compounded gearing the strength in proportion to the duty may be varied in proportion as the velocity is modified by compounding of the wheels. Thus, when the velocity at the pitch circle is increased its strength is increased, and per contra when its velocity is decreased its strength is decreased, when considered in proportion to the duty. When, however, the wheels are upon long shafts, or when they overhang the bearing of the shaft, the corner contact will from tension of the shaft, continue much longer than when the shaft is maintained rigid. It is obvious that if a wheel transmits a certain amount of power, the pressure of tooth upon tooth will depend upon the number of teeth in contact, but since, in the case of very small wheels, that is to say, pinions of the smallest diameter of the given pitch that will transmit continuous motion, it occurs that only one tooth is in continuous contact, it is obvious that each single tooth must have sufficient strength to withstand the whole of the pressure when worn to the limits to which the teeth are supposed to wear. But when the pinion is so small that it has but one tooth in continuous contact, that contact takes place nearer the line of centres and to the root of the tooth, and therefore at a less leverage to the line of fracture, hence the ultimate strength of the tooth is proportionately increased. On the other hand, however, the whole stress of the wheel being concentrated on the arc of contact of one tooth only (instead of upon two or more teeth as in larger wheels), the wear is proportionately greater; hence, in a short time the teeth of the pinion are found to be thinner than those on the other wheel or wheels. The multiplicity of conditions under which small wheels may work with relation to the number of teeth in contact, the average leverage of the point of contact from the root of the tooth, the shape of the tooth, &c., renders it desirable in a general rule to suppose that the whole strain falls upon one tooth, so that the calculation shall give results to meet the requirements when a single tooth only is in continuous contact. It follows, then, that the thickness of tooth arrived at by calculation should be that which will give to a tooth, when worn to the extreme thinness allowed, sufficient strength (with a proper margin of safety) to transmit the whole of the power transmitted by the wheel. The margin (or factor) of safety, or in other words, the number of times the strength of the tooth should exceed the amount of power transmitted, varies (according to the conditions under which the wheels work) between 5 and 10. The lesser factor may be used for slow speeds when the power is continuously and uniformly transmitted. The greater factor is necessary when the wheels are subjected to violent shocks and the direction of revolution requires to be reversed. [Illustration: Fig. 179.] In pattern-cast teeth, contact between the teeth of one wheel and those of the other frequently occurs at one corner only, as shown in Fig. 179, and the line of fracture is in the direction denoted by the diagonal dotted lines. The causes of this corner contact have been already explained, but it may be added that as the wheels wear, the contact extends across the full breadths of the teeth, and the strength in proportion to the duty, therefore, steadily increases from the time the new wheels have action until the wear has caused contact fully across the breadth. Tredgold's rule for finding the proper thickness of tooth for a given stress upon cast-iron teeth loaded at the corner as in Fig. 179 and supposed to have a velocity of three feet per second of time, is as follows:-- Rule.--Divide the stress in pounds at the pitch circle by 1500, and the square root of the quotient is the required thickness of tooth in inches or parts of an inch. In the results obtained by the employment of this rule, an allowance of one-third the thickness for wear, and the margin for safety is included, so that the thickness of tooth arrived at is that to be given to the actual tooth. Further, the rule supposes the breadth of the tooth to be not less than twice the height of the same, any extra breadth not affecting the result (as already explained), when the pressure falls on a corner of the tooth. In practical application, however, the diameter of the wheel at the pitch circle is generally, or at least often a fixed quantity, as well as the amount of stress, and it will happen as a rule that taking the stress as a fixed element and arriving at the thickness of the tooth by calculation, the required diameter of wheel, or what is the same thing, its circumference, will not be such as to contain the exact number of teeth of the thickness found by the calculation, and still give the desired amount of side clearance. It is desirable, therefore, to deal with the stress upon the tooth at the pitch circle, and the diameter, radius, or circumference of the pitch circle, and its velocity, and deduce therefrom the required thickness for the teeth, and conform the pitch to the requirements as to clearance from the tooth thickness thus obtained. To deduce the thickness of the teeth from these elements we have Robertson Buchanan's rule, which is as follows:-- Find the amount of horse-power employed to move the wheel, and divide such horse-power by the velocity in feet per second of the pitch line of the wheel. Extract the square root of the quotient, and three-fourths of this root will be the least thickness of the tooth. To the result thus obtained, there must be added the allowance for wear of the teeth and the width of the space including the clearance which will determine the number of teeth in the wheel. In conforming strictly to this rule the difficulty is met with that it would give fractional pitches not usually employed and difficult to measure on an existing wheel. Cast wheels kept on hand or in stock by machinists have usually the following standard:-- Beginning with an inch pitch, the pitches increase by 1/8 inch up to 3-inch pitch, from 3 to 4-inch pitches the increase is by 1/4 inch, and from 4-inch pitch and upwards the increase is by 1/2 inch. Now, under the rule the pitches would, with the clearance made to bear a certain proportion to the pitch, be in odd fractions of an inch. It appears then, that, if in a calculation to obtain the necessary thickness of tooth, the diameter of the pitch circle is not an element, the rule cannot be strictly adhered to unless the diameter of the pitch circle be varied to suit the calculated thickness of tooth; or unless either the clearance, factor of safety, or amount of tooth thickness allowed for wear be varied to admit of the thickness of tooth arrived at by the calculation. But if the diameter of the pitch circle is one of the elements considered in arriving at the thickness of tooth requisite under given conditions, the pitch must, as a rule, either be in odd fractions, or else the allowance for wear, factor of safety, or amount of side clearance cannot bear a definite proportion to the pitch. But the allowance for clearance is in practice always a constant proportion of the pitch, and under these circumstances, all that can be done when the circumstances require a definite circumference of pitch circle, is to select such a pitch as will nearest meet the requirements of tooth thickness as found by calculation, while following the rule of making the clearance a constant proportion of the pitch. When following this plan gives a thinner tooth than the calculation calls for, the factor of safety and the allowance for wear are reduced. But this is of little consequence whenever more than one tooth on each wheel is in contact, because the rules provide for all the stress falling on one tooth. When, however, the number of teeth in the pinion is so small that one tooth only is in contact, it is better to select a pitch that will give a thicker rather than a thinner tooth than called for by the calculation, providing, of course, that the pitch be less than the arc of contact, so that the motion shall be continuous. But when the pinions are shrouded, that is, have flanges at each end, the teeth are strengthened; and since the wear will continue greater than in wheels having more teeth in contact, the shrouding may be regarded as a provision against breakage in consequence of the reduction of tooth thickness resulting from wear. In the following table is given the thickness of the tooth for a given stress at the pitch circle, calculated from Tredgold's rule for teeth supposed to have contact when new at one corner only. +-------------------+--------------------+---------------------+ | Stress in lbs. at | Thickness of tooth | Actual pitches to | | pitch circle. | in inches. | which wheels may be | | | | made. | +-------------------+--------------------+---------------------+ | 400 | .52 | 1-1/8 to 1-1/4 | | 800 | .75 | 1-1/2 " 1-5/8 | | 1,200 | .90 | 1-7/8 " 2 | | 1,600 | 1.03 | 2 " 2-1/8 | | 2,000 | 1.15 | 2-1/4 " 2-3/8 | | 2,400 | 1.26 | 2-1/2 " 2-5/8 | | 2,800 | 1.36 | 2-5/8 " 2-3/4 | | 3,200 | 1.43 | 2-7/8 " 3 | | 3,600 | 1.56 | 3-1/8 " 3-1/4 | | 4,000 | 1.63 | 3-1/4 " 3-3/8 | | 4,400 | 1.70 | 3-3/8 " 3-1/2 | | 4,800 | 1.78 | 3-1/2 " 3-5/8 | | 5,200 | 1.86 | 3-5/8 " 3-3/4 | | 5,600 | 1.93 | 3-3/4 " 4 | | 6,000 | 2.00 | 4 " 4-1/4 | +-------------------+--------------------+---------------------+ In wheels that have their teeth cut to form in a gear-cutting machine the thickness of tooth at any point in the depth is equal at any point across the breadth; hence, supposing the wheels to be properly keyed to their shafts so that the pitch line across the breadth of the wheel stands parallel to the axis of the shaft, the contact of tooth upon tooth occurs across the full breadth of the tooth. As the practical result of these conditions we have three important advantages: first, that the stress being exerted along the full breadth of the tooth instead of on one corner only, the tooth is stronger (with a given breadth and thickness) in proportion to the duty; second, that with a given pitch, the thickness and therefore the margin for safety and allowance for wear are increased, because the tooth may be increased in thickness at the expense of the clearance, which need be merely sufficient to prevent contact on both sides of the spaces so as to prevent the teeth from locking in the spaces; and thirdly, because the teeth will not be subject to sudden impacts or shocks of tooth upon tooth by reason of back lash. [Illustration: Fig. 180.] In determining the strength of cut gear-teeth we may suppose the weight to be disposed along the face at the extreme height of the tooth, in which case the theoretical shape of the tooth to possess equal strength at every point from the addendum circle to the root would be a parabola, as shown by the dotted lines in Fig. 180, which represents a tooth having radial flanks. In this case it is evident that the ultimate strength of the tooth is that due to the thickness at the root, because it is less than that at the pitch circle, and the strength, as a whole, is not greater than that at the weakest part. But since teeth with radial flanks are produced, as has been shown, with a generating circle equal in diameter to the radius of the pinion, and since with a generating circle bearing that ratio of diameter to diameter of pitch circle the acting part of the flank is limited, it is usual to fill in the corners with fillets or rounded corners, as shown in Fig. 129; hence, the weakest part of the tooth will be where the radial line of the flank joins the fillet and, therefore, nearer the pitch circle than is the root. But as only the smallest wheel of the set has radial flanks and the flanks thicken as the diameter of the wheels increase, it is usual to take the thickness of the tooth at the pitch circle as representing the weakest part of the tooth, and, therefore, that from which the strength of the tooth is to be computed. This, however, is not actually the case even in teeth which have considerable spread at the roots, as is shown in Fig. 181, in which the shape of the tooth to possess equal strength throughout its depth is denoted by the parabolic dotted lines. [Illustration: Fig. 181.] Considering a tooth as simply a beam supporting the strain as a weight we may calculate its strength as follows:-- Multiply the breadth of the tooth by the square of its thickness, and the product by the strength of the material, per square inch of section, of which the teeth are composed, and divide this last product by the distance of the pitch line from the root, and the quotient will give a tooth thickness having a strength equal to the weight of the load, but having no margin for safety, and no allowance for wear; hence, the result thus obtained must be multiplied by the factor of safety (which for this class of tooth may be taken as 6), and must have an additional thickness added to allow for wear, so that the factor of safety will be constant notwithstanding the wear. Another, and in some respects more convenient method, for obtaining the strength of a tooth, is to take the strength of a tooth having 1-inch pitch, and 1 inch of breadth, and multiply this quantity of strength by the pitch and the face of the tooth it is required to find the strength of, both teeth being of the same material. Example.--The safe working pressure for a cast-iron tooth of an inch pitch, and an inch broad will transmit, being taken as 400 lbs., what pressure will a tooth of 3/4-inch pitch and 3 inches broad transmit with safety? Here 400 lbs. × 3/4 pitch × 3 breadth = 900 = safe working pressure of tooth 3/4-inch pitch and 3 inches broad. Again, the safe working pressure of a cast-iron tooth, 1 inch in breadth and of 1-inch pitch, being considered as 400 lbs., what is the safe working pressure of a tooth of 1-inch pitch and 4-inch breadth? Here 400 × 1 × 4 = 1600. The philosophy of this is apparent when we consider that four wheels of 1-inch pitch and an inch face, placed together side by side, would constitute, if welded together, one wheel of an inch pitch and 4 inches face. (The term _face_ is applied to the wheel, and the term breadth to the tooth, because such is the custom of the workshop, both terms, however, mean, in the case of spur-wheels, the dimension of the tooth in a direction parallel to the axis of the wheel shaft or wheel bore.) The following table gives the safe working pressures for wheels having an inch pitch and an inch face when working at the given velocities, S.W.P. standing for "safe working pressure:"-- +------------+------------+------------+------------+--------------+ | Velocity of| | | | | |pitch circle| S.W.P. for | S.W.P. for |S.W.P. for | S.W.P. | | in feet | cast-iron |spur mortise| cast-iron | for bevel | |per second. |spur gears. | gears. |bevel gears.|mortise gears.| +------------+------------+------------+------------+--------------+ | 2 | 368 | 178 | 258 | 178 | | 3 | 322 | 178 | 225 | 157 | | 6 | 255 | 178 | 178 | 125 | | 12 | 203 | 142 | 142 | 99 | | 18 | 177 | 124 | 124 | 87 | | 24 | 161 | 113 | 113 | 79 | | 30 | 150 | 105 | 105 | 74 | | 36 | 140 | 98 | 98 | 69 | | 42 | 133 | 93 | 93 | 65 | | 48 | 127 | 88 | 88 | 62 | +------------+------------+------------+------------+--------------+ For velocities less than 2 feet per second, use the same value as for 2 feet per second. The proportions, in terms of the pitch, upon which this table is based, are as follows:-- Thickness of iron teeth .395 of the pitch. " wooden " .595 " Height of addendum .28 " Depth below pitch line .32 " The table is based upon 400 lbs. per inch of face for an inch pitch, as the safe working pressure of mortise wheel teeth or cogs; it may be noted that there is considerable difference of opinion. They are claimed by some to be in many cases practically stronger than teeth of cast iron. This may be, and probably is, the case when the conditions are such that the teeth being rigid and rigidly held (as in the case of cast-iron teeth), there is but one tooth on each wheel in contact. But when there is so nearly contact between two teeth on each wheel that but little elasticity in the teeth would cause a second pair of teeth to have contact, then the elasticity of the wood would cause this second contact. Added to this, however, we have the fact that under conditions where violent shock occurs the cog would have sufficient elasticity to give, or spring, and thus break the shock which cast iron would resist to the point of rupture. It is under these conditions, which mainly occur in high velocities with one of the wheels having cast teeth, that mortise wheels, or cogging, is employed, possessing the advantage that a broken or worn-out tooth, or teeth, may be readily replaced. It is usual, however, to assign to wooden teeth a value of strength more nearly equal to that of its strength in proportion to that of cast iron; hence, Thomas Box allows a wood tooth a value of about 3/10ths the strength of cast iron; a value as high as 7/10ths is, however, assigned by other authorities. But the strength of the tooth cannot exceed that at the top of the shank, where it fits into the mortise of the wheel, and on account of the leverage of the pressure the width of the mortise should exceed the thickness of the tooth. In some practice, the mortise teeth, or cogs, are made thicker in proportion to the pitch than the teeth on the iron wheel; thus Professor Unwin, in his "Elements of Machine Design," gives the following as "good proportions":-- Thickness of iron teeth 0.395 of the pitch. " wood cogs 0.595 " " which makes the cogs 2/10ths inch thicker than the teeth. The mortises in the wheel rim are made taper in both the breadth and the width, which enables the tooth shank to be more accurately fitted, and also of being driven more tightly home, than if parallel. The amount of this taper is a matter of judgment, but it may be observed that the greater the taper the more labor there is involved in fitting, and the more strain there is thrown upon the pins when locking the teeth with a given amount of strain. While the less the taper, the more care required to obtain an accurate fit. Taking these two elements into consideration, 1/8th inch of taper in a length of 4 inches may be given as a desirable proportion. [Illustration: Fig. 182.] As an evidence of the durability of wooden teeth, there appeared in _Engineering_ of January 7th, 1879, the illustration shown in Fig. 182, which represents a cog from a wheel of 14 ft. 1/2 in. diameter, and having a 10-inch face, its pinion being 4 ft. in diameter. This cog had been running for 26-1/2 years, day and night; not a cog in the wheel having been touched during that time. Its average revolutions were 38 per minute, the power developed by the engine being from 90 to 100 indicated horse-power. The teeth were composed of beech, and had been greased twice a week, with tallow and plumbago ore. Since the width of the face of a wheel influences its wear (by providing a larger area of contact over which the pressure may be distributed, as well as increasing the strength), two methods of proportioning the breadth may be adopted. First, it may be made a certain proportion of the pitch; and secondly, it may be proportioned to the pressure transmitted and the number of revolutions. The desirability of the second is manifest when we consider that each tooth will pass through the arcs of contact (and thus be subjected to wear) once during each revolution; hence, by making the number of revolutions an element in the calculation to find the breadth, the latter is more in proportion to the wear than it would be if proportioned to the pitch. It is obvious that the breadth should be sufficient to afford the required degree of strength with a suitable factor of safety, and allowance for wear of the smallest wheel in the pair or set, as the case may be. According to Reuleaux, the face of a wheel should never be less than that obtained by multiplying the gross pressure, transmitted in lbs., by the revolutions per minute, and dividing the product by 28,000. In the case of bevel-wheels the pitch increases, as the perimeter of the wheel is approached, and the maximum pitch is usually taken as the designated pitch of the wheel. But the mean pitch is that which should be taken for the purposes of calculating the strength, it being in the middle of the tooth breadth. The mean pitch is also the diameter of the pitch circle, used for ascertaining the velocity of the wheel as an element in calculating the safe pressure, or the amount of power the wheel is capable of transmitting, and it is upon this basis that the values for bevel-wheels in the above table are computed. In many cases it is required to find the amount of horse-power a wheel will transmit, or the proportions requisite for a wheel to transmit a given horse-power; and as an aid to the necessary calculations, the following table is given of the amount of horse-power that may be transmitted with safety, by the various wheels at the given velocities, with a wheel of an inch pitch and an inch face, from which that for other pitches and faces may be obtained by proportion. TABLE SHOWING THE HORSE-POWER WHICH DIFFERENT KINDS OF GEAR-WHEELS OF ONE INCH PITCH AND ONE INCH FACE WILL SAFELY TRANSMIT AT VARIOUS VELOCITIES OF PITCH CIRCLE. +------------+------------+------------+-------------+-------------+ |Velocity of | | | | | |Pitch Circle|Spur-Wheels.|Spur Mortise|Bevel-Wheels.|Bevel Mortise| |in Feet per | H.P. | Wheels. | H.P. | Wheels. | |Second. | | H.P. | | H.P. | +------------+------------+------------+-------------+-------------+ | 2 | 1.338 | .647 | .938 | .647 | | 3 | 1.756 | .971 | 1.227 | .856 | | 6 | 2.782 | 1.76 | 1.76 | 1.363 | | 12 | 4.43 | 3.1 | 3.1 | 2.16 | | 18 | 5.793 | 4.058 | 4.058 | 2.847 | | 24 | 7.025 | 4.931 | 4.931 | 3.447 | | 30 | 8.182 | 5.727 | 5.727 | 4.036 | | 36 | 9.163 | 6.414 | 6.414 | 4.516 | | 42 | 10.156 | 7.102 | 7.102 | 4.963 | | 48 | 11.083 | 7.680 | 7.680 | 5.411 | +------------+------------+------------+-------------+-------------+ In this table, as in the preceding one, the safe working pressure for 1-inch pitch and 1-inch breadth of face is supposed to be 400 lbs. In cast gearing, the mould for which is made by a gear moulding machine, the element of draft to permit the extraction of the pattern is reduced: hence, the pressure of tooth upon tooth may be supposed to be along the full breadth of the tooth instead of at one corner only, as in the case of pattern-moulded teeth. But from the inaccuracies which may occur from unequal contraction in the cooling of the casting, and from possible warping of the casting while cooling, which is sure to occur to some extent, however small the amount may be, it is not to be presumed that the contact of the teeth of one wheel will be in all the teeth as perfect across the full breadth as in the case of machine-cut teeth. Furthermore, the clearance allowed for machine-moulded teeth, while considerably less than that allowed for pattern-moulded teeth, is greater than that allowed for machine-cut teeth; hence, the strength of machine-moulded teeth in proportion to the pitch lies somewhere between that of pattern-moulded and machine-cut teeth--but exactly where, it would be difficult to determine in the absence of experiments made for the purpose of ascertaining. It is not improbable, however, that the contact of tooth upon tooth extends in cast gears across at least two-thirds of the breadth of the tooth, in which case the rules for ascertaining the strength of cut teeth of equal thickness may be employed, substituting 2/3rds of the actual tooth breadth as the breadth for the purposes of the calculation. If instead of supposing all the strain to fall upon one tooth and calculating the necessary strength of the teeth upon that basis (as is necessary in interchangeable gearing, because these conditions may exist in the case of the smallest pinion that can be used in pitch), the actual working condition of each separate application of gears be considered, it will appear that with a given diameter of pitch circle, all other things being equal, the arc of contact will remain constant whatever the pitch of the teeth, or in other words is independent of the pitch, and it follows that when the thickness of iron necessary to withstand (with the allowances for wear and factor of safety) the given stress under the given velocity has been determined, it may be disposed in a coarse pitch that will give one tooth always in contact, or a finer pitch that will give two or more teeth always in contact, the strength in proportion to the duty remaining the same in both cases. In this case the expense of producing the wheel patterns or in trimming the teeth is to be considered, because if there are a train of wheels the finer pitch would obviously involve the construction and dressing to shape of a much greater number of teeth on each wheel in the train, thus increasing the labor. When, however, it is required to reduce the pinion to a minimum diameter, it is obvious that this may be accomplished by selecting the finer pitch, because the finer the pitch, the less the diameter of the wheel may be. Thus with a given diameter of pitch circle it is possible to select a pitch so fine that motion from one wheel may be communicated to another, whatever the diameter of the pitch circle may be, the limit being bounded by the practicability of casting or producing teeth of the necessary fineness of pitch. The durability of a wheel having a fine pitch is greater for two reasons: first, because the metal nearest the cast surface of cast iron is stronger than the internal metal, and the finer pitch would have more of this surface to withstand the wear; and second, because in a wheel of a given width there would be two points, or twice the area of metal, to withstand the abrasion, it being remembered that the point of contact is a line which partly rolls and partly slides along the depth of the tooth as the wheel rotates, and that with two teeth in contact on each wheel there are two of such lines. There is also less sliding or rubbing action of the teeth, but this is offset by the fact that there are more teeth in contact, and that there are therefore a greater number of teeth simultaneously rubbing or sliding one upon the other. But when we deal with the number of teeth the circumstances are altered; thus with teeth of epicycloidal form it is manifestly impossible to communicate constant motion with a driving wheel having but one tooth, or to receive motion on a follower having but one tooth. The number of teeth must always be such that there is at all times a tooth of each wheel within the arc of action, or in contact, so that one pair of teeth may come into contact before the contact of the preceding teeth has ceased. In the construction of wheels designed to transmit power as well as simple motion, as is the case with the wheels employed in machine work, however, it is not considered desirable to employ wheels containing a less number of teeth than 12. The diameter of the wheel bearing such a relation to the pitch that both wheels containing the same number of teeth (12), the motion will be communicated from one to the other continuously. It is obvious that as the number of teeth in one of the wheels (of a pair in gear) is increased the number of teeth in the other may be (within certain limits) diminished, and still be capable of transmitting continuous motion. Thus a pinion containing, say 8 teeth, may be capable of receiving continuous motion from a rack in continuous motion, while it would not be capable of receiving continuous motion from a pinion having 4 teeth; and as the requirements of machine construction often call for the transmission of motion from one pinion to another of equal diameters, and as small as possible, 12 teeth are the smallest number it is considered desirable for a pinion to contain, except it be in the case of an internal wheel, in which the arc of contact is greater in proportion to the diameters than in spur-wheels, and continuous motion can therefore be transmitted either with coarser pitches or smaller diameters of pinion. For convenience in calculating the pitch diameter at pitch circle, or pitch diameter as it is termed, and the number of teeth of wheels, the following rules and table extracted from the _Cincinnati Artisan_ and arranged from a table by D. A. Clarke, are given. The first column gives the pitch, the following nine columns give the pitch diameters of wheels for each pitch from 1 tooth to 9. By multiplying these numbers by 10 we have the pitch diameters from 10 to 90 teeth, increasing by _tens_; by multiplying by 100 we likewise have the pitch diameters from 100 to 900, increasing by _hundreds_. TABLE FOR DETERMINING THE RELATION BETWEEN PITCH DIAMETER, PITCH, AND NUMBER OF TEETH IN GEAR-WHEELS. +-----+------------------------------------------------------------------+ | | NUMBER OF TEETH. | |Pitch.------+------+------+------+------+-------+-------+-------+-------+ | | 1. | 2. | 3. | 4. | 5. | 6. | 7. | 8. | 9. | +-----+------+------+------+------+------+-------+-------+-------+-------+ |1 | .3183| .6366| .9549|1.2732|1.5915| 1.9099| 2.2282| 2.5465| 2.8648| |1-1/8| .3581| .7162|1.0743|1.4324|1.7905| 2.1486| 2.5067| 2.8648| 3.2229| |1-1/4| .3979| .7958|1.1937|1.5915|1.9894| 2.3873| 2.7852| 3.1831| 3.5810| |1-3/8| .4377| .8753|1.3130|1.7507|2.1884| 2.6260| 3.0637| 3.5014| 3.9391| | | | | | | | | | | | |1-1/2| .4775| .9549|1.4324|1.9099|2.3873| 2.8648| 3.3422| 3.8197| 4.2971| |1-5/8| .5173|1.0345|1.5517|2.0690|2.5862| 3.1035| 3.6207| 4.1380| 4.6552| |1-3/4| .5570|1.1141|1.6711|2.2282|2.7852| 3.3422| 3.8993| 4.4563| 5.0134| |1-7/8| .5968|1.1937|1.7905|2.3873|2.9841| 3.5810| 4.1778| 4.7746| 5.3714| | | | | | | | | | | | |2 | .6366|1.2732|1.9099|2.5465|3.1831| 3.8197| 4.4563| 5.0929| 5.7296| |2-1/8| .6764|1.3528|2.0292|2.7056|3.3820| 4.0584| 4.7348| 5.4112| 6.0877| |2-1/4| .7162|1.4324|2.1486|2.8648|3.5810| 4.2972| 5.0134| 5.7296| 6.4457| |2-3/8| .7560|1.5120|2.2679|3.0239|3.7799| 4.5359| 5.2919| 6.0479| 6.8038| | | | | | | | | | | | |2-1/2| .7958|1.5915|2.3873|3.1831|3.9789| 4.7746| 5.5704| 6.3662| 7.1619| |2-5/8| .8355|1.6711|2.5067|3.3422|4.1778| 5.0133| 5.8499| 6.6845| 7.5200| |2-3/4| .8753|1.7507|2.6260|3.5014|4.3767| 5.2521| 6.1274| 7.0028| 7.8781| |2-7/8| .9151|1.8303|2.7454|3.6605|4.5757| 5.4908| 6.4059| 7.3211| 8.2362| | | | | | | | | | | | |3 | .9549|1.9099|2.8648|3.8197|4.7746| 5.7296| 6.6845| 7.6394| 8.5943| |3-1/4|1.0345|2.0690|3.1035|4.1380|5.1725| 6.2070| 7.2415| 8.2760| 9.3105| |3-1/2|1.1141|2.2282|3.3422|4.4563|5.5704| 6.6845| 7.7986| 8.9126|10.0268| |3-3/4|1.1937|2.3873|3.5810|4.7746|5.9683| 7.1619| 8.3556| 9.5493|10.7429| | | | | | | | | | | | |4 |1.2732|2.5465|3.8197|5.0929|6.3662| 7.6394| 8.9127|10.1839|11.4591| |4-1/2|1.4324|2.8648|4.2972|5.7296|7.1619| 8.5943|10.0267|11.4591|12.8915| |5 |1.5915|3.1831|4.7746|6.3662|7.9577| 9.5493|11.1408|12.7324|14.3240| |5-1/2|1.7507|3.5014|5.2521|7.0028|8.7535|10.5042|12.2549|14.0056|15.7563| |6 |1.9099|3.8196|5.7295|7.6394|9.5493|11.4591|13.3690|15.2788|17.1887| +-----+------+------+------+------+------+-------+-------+-------+-------+ The following rules and examples show how the table is used: Rule 1.--Given ---- number of teeth and pitch; to find ---- pitch diameter. Select from table in columns opposite the given pitch-- First, the value corresponding to the number of units in the number of teeth. Second, the value corresponding to the number of tens, and multiply this by 10. Third, the value corresponding to the number of hundreds, and multiply this by 100. Add these together, and their sum is the pitch diameter required. Example.--What is the pitch diameter of a wheel with 128 teeth, 1-1/2 inches pitch? We find in line corresponding to 1-1/2 inch pitch-- Pitch diameter for 8 teeth 3.8197 " " 20 " 9.549 " " 100 " 47.75 --- ------- " " 128 " 61.1187 Or about 61-1/8". Answer. Rule 2.--Given ---- pitch diameter and number of teeth; to find ---- pitch. First, ascertain by Rule 1 the pitch diameter for a wheel of 1-_inch pitch_, and the given _number of teeth_. Second, divide _given pitch diameter_ by the _pitch diameter_ for 1-_inch pitch_. The quotient is the pitch desired. Example.--What is the pitch of a wheel with 148 teeth, the pitch diameter being 72"? First, pitch diameter for 148 teeth, 1-inch pitch, is-- 8 teeth 2.5465 40 " 12.732 100 " 31.83 --- ------- 148 " 47.1085 Second, 72/47.1 = 1.53 inch equal to the pitch. This is nearly 1-1/2-inch pitch, and if possible the diameter would be reduced or the number of teeth increased so as to make the wheel exactly 1-1/2-inch pitch. Rule 3.--Given ---- pitch and pitch diameter; to find ---- number of teeth. First, ascertain from table the _pitch diameter_ for 1 _tooth_ of the given _pitch_. Second, divide the _given pitch diameter_ by the _value_ found in table. The quotient is the number required. Example.--What is the number of teeth in a wheel whose pitch diameter is 42 inches, and pitch is 2-1/2 inches? First, the pitch diameter, 1 tooth, 2-1/2-inch pitch, is 0.7958 inches. 42 Second. ------ = 52.8. Answer. 0.7958 This gives a fractional number of teeth, which is impossible; so the pitch diameter will have to be increased to correspond to 53 teeth, or the pitch changed so as to have the number of teeth come an even number. Whenever two parallel shafts are connected together by gearing, the distance between centres being a fixed quantity, and the speeds of the shafts being of a fixed ratio, then the pitch is generally the best proportion to be changed, and necessarily may not be of standard size. Suppose there are two shafts situated in this manner, so that the distance between their centres is 84 inches, and the speed of one is 2-1/2 times that of the other, what size wheels shall be used? In this case the pitch diameter and number of teeth of the wheel on the slow-running shaft have to be 2-1/2 times those of the wheel on the fast-running shaft; so that 84 inches must be divided into two parts, one of which is 2-1/2 times the other, and these quantities will be the pitch radii of the wheels; that is, 84 inches are to be divided into 3-1/2 equal parts, 1 of which is the radius of one wheel, and 2-1/2 of which the radius of the other, thus 84"/3-1/2 = 24 inches. So that 24 inches is the pitch radius of pinion, pitch diameter = 48 inches; and 2-1/2 × 24 inches = 60 inches is the pitch radius of the wheel, pitch diameter = 120 inches. The pitch used depends upon the power to be transmitted; suppose that 2-5/8 inches had been decided as about the pitch to be used, it is found by Rule 3 that the number of teeth are respectively 143.6, and 57.4 for wheel and pinion. As this is impossible, some whole number of teeth, nearest these in value, have to be taken, one of which is 2-1/2 times the other; thus 145 and 58 are the nearest, and the pitch for these values is found by Rule 2 to be 2.6 inches, being the best that can be done under the circumstances. [Illustration: Fig. 183.] [Illustration: Fig. 184.] The forms of spur-gearing having their teeth at an angle to the axis, or formed in advancing steps shown in Figs. 183 and 184, were designed by Dr. Hooke, and "were intended," says the inventor, "first to make a piece of wheel work so that both the wheel and pinion, though of never so small a size, shall have as great a number of teeth as shall be desired, and yet neither weaken the wheels nor make the teeth so small as not to be practicable by any ordinary workman. Next that the motion shall be so equally communicated from the wheel to the pinion that the work being well made there can be no inequality of force or motion communicated. "Thirdly, that the point of touching and bearing shall be always in the line that joins the two centres together. "Fourthly, that it shall have _no manner of rubbing_, nor be more difficult to make than common wheel work." The objections to this form of wheel lies in the difficulty of making the pattern and of moulding it in the foundry, and as a result it is rarely employed at the present day. For racks, however, two or more separate racks are cast and bolted together to form the full width of rack as shown in Fig. 185. This arrangement permits of the adjustment of the width of step so as to take up the lost motion due to the wear of the tooth curves. Another objection to the sloping of the teeth, as in Fig. 183, is that it induces an end pressure tending to force the wheels apart _laterally_, and this causes _end_ wear on the journals and bearings. [Illustration: Fig. 185.] [Illustration: Fig. 186.] To obviate this difficulty the form of gear shown in Fig. 186 is employed, the angles of the teeth from each side of the wheel to its centre being made equal so as to equalize the lateral pressure. It is obvious that the stepped gear, Fig. 184, is simply equivalent to a number of thin wheels bolted together to form a thick one, but possessing the advantage that with a sufficient number of steps, as in the figure, there is always contact on the line of centres, and that the condition of constant contact at the line of centres will be approached in proportion to the number of steps in the wheel, providing that the steps progress in one continuous direction across the wheel as in Fig. 184. The action of the wheels will, in this event, be smoother, because there will be less pressure tending to force the wheels apart. But in the form of gearing shown in Fig. 183, the contact of the teeth will bear every instant at a single point, which, as the wheels revolve, will pass from one end to the other of the tooth, a fresh contact always beginning on the first side immediately before the preceding contact has ceased on the opposite side. The contact, moreover, being always in the plane of the centres of the pair, the action is reduced to that of rolling, and as there is no sliding motion there is consequently no rubbing friction between the teeth. [Illustration: Fig. 187.] [Illustration: Fig. 188.] A further modification of Dr. Hooke's gearing has been somewhat extensively adopted, especially in cotton-spinning machines. This consists, when the direction of the motion is simply to be changed to an angle of 90°, in forming the teeth upon the periphery of the pair at an angle of 45° to the respective axes of the wheels, as in Figs. 187 and 188; it will then be perceived that if the sloped teeth be presented to each other in such a way as to have exactly the same horizontal angle, the wheels will gear together, and motion being communicated to one axis the same will be transmitted to the other at a right angle to it, as in a common bevel pair. Thus if the wheel A upon a horizontal shaft have the teeth formed upon its circumference at an angle of 45° to the plane of its axis it can gear with a similar wheel B upon a vertical axis. Let it be upon the driving shaft and the motion will be changed in direction as if A and B were a pair of bevel-wheels of the ordinary kind, and, as with bevels generally, the direction of motion will be changed through an equal angle to the sum of the angles which the teeth of the wheels of the pair form with their respective axes. The objection in respect of lateral or end pressure, however, applies to this form equally with that shown in Fig. 183, but in the case of a vertical shaft the end pressure may be (by sloping the teeth in the necessary direction) made to tend to lift the shaft and not force it down into the step bearing. This would act to keep the wheels in close contact by reason of the weight of the vertical shaft and at the same time reduce the friction between the end of that shaft and its step bearing. This renders this form of gearing preferable to skew bevels when employed upon vertical shafts. It is obvious that gears, such as shown in Figs. 187 and 188 may be turned up in the lathe, because the teeth are simply portions of spirals wound about the circumference of the wheel. For a pair of wheels of equal diameter a cylindrical piece equal in length to the required breadth of the two wheels is turned up in the lathe, and the teeth may be cut in the same manner as cutting a thread in the lathe, that is to say, by traversing the tool the requisite distance per lathe revolution. In pitches above about 1/4 inch, it will be necessary to shape one side of the tooth at a time on account of the broadness of the cutting edges. After the spiral (for the teeth are really spirals) is finished the piece may be cut in two in the lathe and each half will form a wheel. To find the full diameter to which to turn a cylinder for a pair of these wheels we proceed as in the following example: Required to cut a spiral wheel 5 inches in diameter and to have 30 teeth. First find the diametral pitch, thus 30 (number of teeth) ÷ 5 (diameter of wheel at pitch circle) = 6; thus there are 6 teeth or 6 parts to every inch of the wheel's diameter at the pitch circle; adding 2 of these parts to the diameter of the wheel, at the pitch circle we have 5 and 2/6 of another inch, or 5-2/6 inches, which is the full diameter of the wheel, or the diameter of the addendum, as it is termed. [Illustration: Fig. 189.] [Illustration: Fig. 190.] It is now necessary to find what change wheels to put on the lathe to cut the teeth out the proper angle. Suppose then the axes of the shafts are at a right angle one to the other, and that the teeth therefore require to be at an angle of 45° to the axes of the respective wheels, then we have the following considerations. In Fig. 189 let the line A represent the circumference of the wheel, and B a line of equal length but at a right angle to it, then the line C, joining A, B, is at an angle of 45°. It is obvious then that if the traverse of the lathe tool be equal at each lathe revolution to the circumference of the wheel at the pitch circle, the angle of the teeth will be 45° to the axis of the wheel. Hence, the change wheels on the lathe must be such as will traverse the tool a distance equal to the circumference at pitch circle of the wheel, and the wheels may be found as for ordinary screw cutting. If, however, the axes of the shafts are at any other angle we may find the distance the lathe tool must travel per lathe revolution to give teeth of the required angle (or in other words the pitch of the spiral) by direct proportion, thus: Let it be required to find the angle or pitch for wheels to connect shafts at an angle of 25°, the wheels to have 20 teeth, and to be of 10 diametral pitch. Here, 20 ÷ 10 = 2 = diameter of wheel at the pitch circle. The circumference of 2 inches being 6.28 inches we have, as the degrees of angle of the axes of the shafts are to 45°, so is 6.28 inches (the circumference of the wheels, to the pitch sought). Here, 6.28 inches × 45° ÷ 25° = 11.3 inches, which is the required pitch for the spiral. When the axes of the shafts are neither parallel nor meeting, motion from one shaft to another may be transmitted by means of a double gear. Thus (taking rolling cones of the diameters of the respective pitch circles as representing the wheels) in Fig. 190, let A be the shaft of gear _h_, and B _b_ that of wheel _e_. Then a double gear-wheel having teeth on _f_, _g_ may be placed as shown, and the face _f_ will gear with _e_, while face _g_ will gear with _h_, the cone surfaces meeting in a point as at C and D respectively, hence the velocity will be equal. When the axial line of the shafts for two gear-wheels are nearly in line one with the other, motion may be transmitted by gearing the wheels as in Fig. 191. This is a very strong method of gearing, because there are a large number of teeth in contact, hence the strain is distributed by a larger number of teeth and the wear is diminished. [Illustration: Fig. 191.] [Illustration: Fig. 192.] Fig. 192 (from Willis's "Principles of Mechanism") is another method of constructing the same combination, which admits of a steady support for the shafts at their point of intersection, A being a spherical bearing, and B, C being cupped to fit to A. Rotary motion variable at different parts of a rotation may be obtained by means of gear-wheels varied in form from the true circle. [Illustration: Fig. 193.] The commonest form of gearing for this purpose is elliptical gearing, the principles governing the construction of which are thus given by Professor McCord. "It is as well to begin at the foundation by defining the ellipse as a closed plane-curve, generated by the motion of a point subject to the condition that the sum of its distances from two fixed points within shall be constant: Thus, in Fig. 193, A and B are the two fixed points, called the _foci_; L, E, F, G, P are points in the curve; and A F + F B = A E + E B. Also, A L + L B = A P + P B = A G + G B. From this it follows that A G = L O, O being the centre of the curve, and G the extremity of the minor axis, whence the foci may be found if the axes be assumed, or, if the foci and one axis be given, the other axis may be determined. It is also apparent that if about either focus, as B, we describe an arc with a radius greater than B P and less than B L, for instance B E, and about A another arc with radius A E = L P-B E, the intersection, E, of these arcs will be on the ellipse; and in this manner any desired number of points may be found, and the curve drawn by the aid of sweeps. "Having completed this ellipse, prolong its major axis, and draw a similar and equal one, with its foci, C, D, upon that prolongation, and tangent to the first one at P; then B D = L P. About B describe an arc with any radius, cutting the first ellipse at Y and the line L at Z; about D describe an arc with radius D Z, cutting the second ellipse in X; draw A Y, B Y, C X, and D X. Then A Y = D X, and B Y = C X, and because the ellipses are alike, the arcs P Y and P X are equal. If then B and D are taken as fixed centres, and the ellipses turn about them as shown by the arrows, X and Y will come together at Z on the line of centres; and the same is true of any points equally distant from P on the two curves. But this is the condition of rolling contact. We see, then, that in order that two ellipses may roll together, and serve as the pitch-lines of wheels, they must be equal and similar, the fixed centres must be at corresponding foci, and the distance between these centres must be equal to the major axis. Were they to be toothless wheels, if would evidently be essential that the outlines should be truly elliptical; but the changes of curvature in the ellipse are gradual, and circular arcs may be drawn so nearly coinciding with it, that when teeth are employed, the errors resulting from the substitution are quite inappreciable. Nevertheless, the rapidity of these changes varies so much in ellipses of different proportions, that we believe it to be practically better to draw the curve accurately first, and to find the radii of the approximating arcs by trial and error, than to trust to any definite rule for determining them; and for this reason we give a second and more convenient method of finding points, in connection with the ellipse whose centre is R, Fig. 193. About the centre describe two circles, as shown, whose diameters are the major and minor axes; draw any radius, as R T, cutting the first circle in T, and the second in S; through T draw a parallel to one axis, through S a parallel to the other, and the intersection, V, will lie on the curve. In the left hand ellipse, the line bisecting the angle A F B is normal to the curve at F, and the perpendicular to it is tangent at the same point, and bisects the angles adjacent to A F B, formed by prolonging A F, B F. [Illustration: Fig. 194.] "To mark the pitch line we proceed as follows:-- "In Fig. 194, A A and B B are centre lines passing through the major and minor axes of the ellipse, of which _a_ is the axis or centre, _b_ _c_ is the major and _a_ _e_ half of the minor axis. Draw the rectangle _b_ _f_ _g_ _c_, and then the diagonal line _b_ _e_; at a right angle to _b_ _e_ draw line _f_ _h_ cutting B B at _i_. With radius _a_ _e_ and from _a_ as a centre draw the dotted arc _e_ _j_, giving the point _j_ on the line B B. From centre _k_, which is on line B B, and central between _b_ and _j_, draw the semicircle _b_ _m_ _j_, cutting A A at _l_. Draw the radius of the semicircle _b_ _m_ _j_ cutting _f_ _g_ at _n_. With radius _m_ _n_ mark on A A, at and from _a_ as a centre, the point _o_. With radius _h_ _o_ and from centre _h_ draw the arc _p_ _o_ _q_. With radius _a_ _l_ and from _b_ and _c_ as centres draw arcs cutting _p_ _o_ _q_ at the points _p_ _q_. Draw the lines _h_ _p_ _r_ and _h_ _q_ _s_, and also the lines _p_ _i_ _t_ and _q_ _v_ _w_. From _h_ as centre draw that part of the ellipse lying between _r_ and _s_. With radius _p_ _r_ and from _p_ as a centre draw that part of the ellipse lying between _r_ and _t_. With radius _q_ _s_ and from _q_ draw the ellipse from _s_ to _w_. With radius _i_ _t_ and from _i_ as a centre draw the ellipse from _t_ to _b_. With radius _v_ _w_ and from _v_ as a centre draw the ellipse from _w_ to _c_, and one half the ellipse will be drawn. It will be seen that the whole construction has been performed to find the centres _h_ _p_ _q_ _i_ and _v_, and that while _v_ and _i_ may be used to carry the curve around the other side or half of the ellipse, new centres must be provided for _h_ _p_ and _q_; these new centres correspond in position to _h_ _p_ _q_. "If it were possible to subdivide the ellipse into equal parts it would be unnecessary to resort to these processes of approximately representing the two curves by arcs of circles; but unless this be done, the spacing of the teeth can only be effected by the laborious process of stepping off the perimeter into such small subdivisions that the chords may be regarded as equal to the arcs, which after all is but an approximation; unless, indeed, we adopt the mechanical expedient of cutting out the ellipse in metal or other substance, measuring and subdividing it with a strip of paper or a steel tape, and wrapping back the divided measure in order to find the points of division on the curve. "But these circular arcs may be rectified and subdivided with great facility and accuracy by a very simple process, which we take from Prof. Rankine's "Machinery and Mill Work," and is illustrated in Fig. 195. Let O B be tangent at O to the arc O D, of which C is the centre. Draw the chord D O, bisect it in E, and produce it to A, making O A = O E; with centre A and radius A D describe an arc cutting the tangent in B; then O B will be very nearly equal in length to the arc O D, which, however, should not exceed about 60°; if it be 60°, the error is theoretically about 1/900 of the length of the arc, O B being so much too short; but this error varies with the fourth power of the angle subtended by the arc, so that for 30° it is reduced to 1/16 of that amount, that is, to 1/14400. Conversely, let O B be a tangent of given length; make O F = 1/4 O B; then with centre F and radius F B describe an arc cutting the circle O D G (tangent to O B at O) in the point D; then O D will be approximately equal to O B, the error being the same as in the other construction and following the same law. [Illustration: Fig. 195.] "The extreme simplicity of these two constructions and the facility with which they may be made with ordinary drawing instruments make them exceedingly convenient, and they should be more widely known than they are. Their application to the present problem is shown in Fig. 196, which represents a quadrant of an ellipse, the approximate arcs C D, D E, E F, F A having been determined by trial and error. In order to space this off, for the positions of the teeth, a tangent is drawn at D, upon which is constructed the rectification of D C, which is D G, and also that of D E in the opposite direction, that is, D H, by the process just explained. Then, drawing the tangent at F, we set off in the same manner F I = F E, and F K = F A, and then measuring H L = I K, we have finally G L, equal to the whole quadrant of the ellipse. [Illustration: Fig. 196.] "Let it now be required to lay out 24 teeth upon this ellipse; that is, 6 in each quadrant; and for symmetry's sake we will suppose that the centre of one tooth is to be at A, and that of another at C, Fig. 196. We therefore divide L G into six equal parts at the points 1, 2, 3, &c., which will be the centres of the teeth upon the rectified ellipse. It is practically necessary to make the spaces a little greater than the teeth; but if the greatest attainable exactness in the operation of the wheel is aimed at, it is important to observe that backlash, in elliptical gearing, has an effect quite different from that resulting in the case of circular wheels. When the pitch-curves are circles, they are always in contact; and we may, if we choose, make the tooth only half the breadth of the space, so long as its outline is correct. When the motion of the driver is reversed, the follower will stand still until the backlash is taken up, when the motion will go on with a perfectly constant velocity ratio as before. But in the ease of two elliptical wheels, if the follower stand still while the driver moves, which must happen when the motion is reversed if backlash exists, the pitch-curves are thrown out of contact, and, although the continuity of the motion will not be interrupted, the velocity ratio will be affected. If the motion is never to be reversed, the perfect law of the velocity ratio due to the elliptical pitch-curve may be preserved by reducing the thickness of the tooth, not equally on each side, as is done in circular wheels, but wholly on the side not in action. But if the machine must be capable of acting indifferently in both directions, the reduction must be made on both sides of the tooth: evidently the action will be slightly impaired, for which reason the backlash should be reduced to a minimum. Precisely what _is_ the minimum is not so easy to say, as it evidently depends much upon the excellence of the tools and the skill of the workmen. In many treatises on constructive mechanism it is variously stated that the backlash should be from one-fifteenth to one-eleventh of the pitch, which would seem to be an ample allowance in reasonably good castings not intended to be finished, and quite excessive if the teeth are to be cut; nor is it very obvious that its amount should depend upon the pitch any more than upon the precession of the equinoxes. On paper, at any rate, we may reduce it to zero, and make the teeth and spaces equal in breadth, as shown in the figure, the teeth being indicated by the double lines. Those upon the portion L H are then laid off upon K I, after which these divisions are transferred to curves. And since under that condition the motion of this third line, relatively to each of the others, is the same as though it rolled along each of them separately while they remained fixed, the process of constructing the generated curves becomes comparatively simple. For the describing line, we naturally select a circle, which, in order to fulfil the condition, must be small enough to roll within the pitch ellipse; its diameter is determined by the consideration, that if it be equal to A P, the radius of the arc A F, the flanks of the teeth in that region will be radial. We have, therefore, chosen a circle whose diameter, A B, is three-fourths of A P, as shown, so that the teeth, even at the ends of the wheels, will be broader at the base than on the pitch line. This circle ought strictly to roll upon the true elliptical curve, and assuming as usual the tracing-point upon the circumference, the generated curves would vary slightly from true epicycloids, and no two of those used in the same quadrant of the ellipse would be exactly alike. Were it possible to divide the ellipse accurately, there would be no difficulty in laying out these curves; but having substituted the circular arcs, we must now roll the generating circle upon these as bases, thus forming true epicycloidal teeth, of which those lying upon the same approximating arc will be exactly alike. Should the junction of two of these arcs fall within the breadth of a tooth, as at D, evidently both the face and the flank on one side of that tooth will be different from those on the other side; should the junction coincide with the edge of a tooth, which is very nearly the case at F, then the face on that side will be the epicycloid belonging to one of the arcs, its flank a hypocycloid belonging to the other; and it is possible that either the face or the flank on one side should be generated by the rolling of the describing circle partly on one arc, partly on the one adjacent, which, upon a large scale and where the best results are aimed at, may make a sensible change in the form of the curve. [Illustration: Fig. 197.] "The convenience of the constructions given in Fig. 194 is nowhere more apparent than in the drawing of the epicycloids, when, as in the case in hand, the base and generating circles may be of incommensurable diameters; for which reason we have, in Fig. 197, shown its application in connection with the most rapid and accurate mode yet known of describing those curves. Let C be the centre of the base circle; B that of the rolling one; A the point of contact. Divide the semi-circumference of B into six equal parts at 1, 2, 3, &c.; draw the common tangent at A, upon which rectify the arc A2 by process No. 1, then by process No. 2 set out an equal arc A2 on the base circle, and stepping it off three times to the right and left, bisect these spaces, thus making subdivisions on the base circle equal in length to those on the rolling one. Take in succession as radii the chords A1, A2, A3, &c., of the describing circle, and with centres 1, 2, 3, &c., on the base circle, strike arcs either externally or internally, as shown respectively on the right and left; the curve tangent to the external arcs is the epicycloid, that tangent to the internal ones the hypocycloid, forming the face and flank of a tooth for the base circle. "In the diagram, Fig. 196, we have shown a part of an ellipse whose length is 10 inches and breadth 6, the figure being half size. In order to give an idea of the actual appearance of the combination when complete, we show in Fig. 198 the pair in gear, on a scale of 3 inches to the foot. The excessive eccentricity was selected merely for the purpose of illustration. Fig. 198 will serve also to call attention to another serious circumstance, which is that although the ellipses are alike, the wheels are not; nor can they be made so if there be an even number of teeth, for the obvious reason that a tooth upon one wheel must fit into a space on the other; and since in the first wheel, Fig. 196, we chose to place a tooth at the extremity of each axis, we must in the second one place there a space instead; because at one time the major axes must coincide, at another the minor axis, as in Fig. 191. If then we use even numbers, the distribution and even the forms of the teeth are not the same in the two wheels of the pair. But this complication may be avoided by using an odd number of teeth, since, placing a tooth at one extremity of the major axis, a space will come at the other. "It is not, however, always necessary to cut teeth all round these wheels, as will be seen by an examination of Fig. 199, C and D being the fixed centres of the two ellipses in contact at P. Now P must be on the line C D, whence, considering the free foci, we see P B is equal to P C, and P A to P D; and the common tangent at P makes equal angles with C P and P A, as is also with P B and P D; therefore, C D being a straight line, A B is also a straight line and equal to C D. If then the wheels be overhung, that is, fixed on the ends of the shafts outside the bearings, leaving the outer faces free, the moving foci may be connected by a rigid link A B, as shown. [Illustration: Fig. 198.] "This link will then communicate the same motion that would result from the use of the complete elliptical wheels, and we may therefore dispense with most of the teeth, retaining only those near the extremities of the major axes which are necessary in order to assist and control the motion of the link at and near the dead-points. The arc of the pitch-curves through which the teeth must extend will vary with their eccentricity: but in many cases it would not be greater than that which in the approximation may be struck about one centre, so that, in fact, it would not be necessary to go through the process of rectifying and subdividing the quarter of the ellipse at all, as in this case it can make no possible difference whether the spacing adopted for the teeth to be cut would "come out even" or not if carried around the curve. By this expedient, then, we may save not only the trouble of drawing, but a great deal of labor in making, the teeth round the whole ellipse. We might even omit the intermediate portions of the pitch ellipses themselves; but as they move in rolling contact their retention can do no harm, and in one part of the movement will be beneficial, as they will do part of the work; for if, when turning, as shown by the arrows, we consider the wheel whose axis is D as the driver, it will be noted that its radius of contact, C P, is on the increase; and so long as this is the case the other wheel will be compelled to move by contact of the pitch lines, although the link be omitted. And even if teeth be cut all round the wheels, this link is a comparatively inexpensive and a useful addition to the combination, especially if the eccentricity be considerable. Of course the wheels shown in Fig. 198 might also have been made alike, by placing a tooth at one end of the major axis and a space at the other, as above suggested. In regard to the variation in the velocity ratio, it will be seen, by reference to Fig. 199, that if D be the axis of the driver, the follower will in the position there shown move faster, the ratio of the angular velocities being PD/PB; if the driver turn uniformly the velocity of the follower will diminish, until at the end of half a revolution, the velocity ratio will be PB/PD; in the other half of the revolution these changes will occur in a reverse order. But P D = L B; if then the centres B D are given in position, we know L P, the major axis; and in order to produce any assumed maximum or minimum velocity ratio, we have only to divide L P into segments whose ratio is equal to that assumed value, which will give the foci of the ellipse, whence the minor axis may be found and the curve described. For instance, in Fig. 198 the velocity ratio being nine to one at the maximum, the major axis is divided into two parts, of which one is nine times as long as the other; in Fig. 199 the ratio is as one to three, so that, the major axis being divided into four parts, the distance A C between the foci is equal to two of them, and the distance of either focus from the nearer extremity of the major axis equal to one, and from the more remote extremity equal to three of these parts." [Illustration: Fig. 199.] Another example of obtaining a variable motion is given in Fig. 200. The only condition necessary to the construction of wheels of this class is that the sum of the radii of the pitch circles on the line of centres shall equal the distance between the axes of the two wheels. The pitch curves are to be considered the same as pitch circles, "so that," says Willis, "if any given circle or curve be assumed as a describing (or generating) curve, and if it be made to roll on the inside of one of these pitch curves and on the outside of the corresponding portion of the other pitch curve, then the motion communicated by the pressure and sliding contact of one of the curved teeth so traced upon the other will be exactly the same as that effected by the rolling contact (by friction) of the original pitch curves." [Illustration: Fig. 200.] It is obvious that on B the corner sections are formed of simple segments of a circle of which the centre is the axis of the shaft, and that the sections between them are simply racks. The corners of A are segments of a circle of which the axis of A is the centre, and the sections between the corners curves meeting the pitch circles of the rack at every point as it passes the line of centres. Intermittent motion may also be obtained by means of a worm-wheel constructed as in Fig. 201, the worm having its teeth at a right angle to its axis for a distance around the circumference proportioned to the required duration of the period of rest; or the motion may be made variable by giving the worm teeth different degrees of inclination (to the axis), on different portions of the circumference. In addition to the simple operation of two or more wheels transmitting motion by rotating about their fixed centres and in fixed positions, the following examples of wheel motion may be given. [Illustration: Fig. 201.] [Illustration: Fig. 202.] In Fig. 202 are two gear-wheels, A, which is fast upon its stationary shaft, and B, which is free to rotate upon its shaft, the link C affording journal bearing to the two shafts. Suppose that A has 40 teeth, while B has 20 teeth, and that the link C is rotated once around the axis of A, how many revolutions will B make? By reason of there being twice as many teeth in A as in B the latter will make two rotations, and in addition to this it will, by reason of its connection to the arm C, also make a revolution, these being two distinct motions, one a rotation of B about the axis of A, and the other two rotations of B upon its own axis. A simple arrangement of gearing for reversing the direction of rotation of a shaft is shown in Fig. 203. I and F are fast and loose pulleys for the shaft D, A and C are gears free to rotate upon D, N is a clutch driven by D; hence if N be moved so as to engage with C the latter will act as a driver to rotate the shaft B, the wheel upon B rotating A in an opposite direction to the rotation of D. But if N be moved to engage with A the latter becomes the driving wheel, and B will be caused to rotate in the opposite direction. Since, however, the engagement of the clutch N with the clutch on the nut of the gear-wheels is accompanied with a violent shock and with noise, a preferable arrangement is shown in Fig. 204, in which the gears are all fast to their shafts, and the driving shaft for C passes through the core or bore of that for A, which is a sleeve, so that when the driving belt acts upon pulley F the shaft B rotates in one direction, while when the belt acts upon E, B rotates in the opposite direction, I being a loose pulley. [Illustration: Fig. 203.] If the speed of rotation of B require to be greater in one direction than in the other, then the bevel-wheel on B is made a double one, that is to say, it has two annular toothed surfaces on its radial face, one of larger diameter than the other; A gearing with one of these toothed surfaces, and C with the other. It is obvious that the pinions A C, being of equal diameters, that gearing with the surface or gear of largest diameter will give to B the slowest speed of rotation. [Illustration: Fig. 204.] Fig. 205 represents Watt's sun-and-planet motion for converting reciprocating into rotary motion; B D is the working beam of the engine, whose centre of motion is at D. The gear A is so connected to the connecting rod that it cannot rotate, and is kept in gear with the wheel C on the fly-wheel shaft by means of the link shown. The wheel A being prevented from rotation on its axis causes rotary motion to the wheel C, which makes two revolutions for one orbit of A. [Illustration: Fig. 205.] An arrangement for the rapid increase of motion by means of gears is shown in Fig. 206, in which A is a stationary gear, B is free to rotate upon its shaft, and being pivoted upon the shaft of A, at D, is capable of rotation around A while remaining in gear with C. Suppose now that the wheel A were absent, then if B were rotated around C with D as a centre of motion, C and its shaft E would make a revolution even though B would have no rotation upon its axis. But A will cause B to rotate upon its axis and thus communicate a second degree of motion to C, with the result that one revolution of B causes two rotations of C. The relation of motion between B and C is in this case constant (2 to 1), but this relation may be made variable by a construction such as shown in Fig. 207, in which the wheel B is carried in a gear-wheel H, which rides upon the shaft D. Suppose now that H remains stationary while A revolves, then motion will be transmitted through B to C, and this motion will be constant and in proportion to the relative diameters of A and C. But suppose by means of an independent pinion the wheel H be rotated upon its axis, then increased motion will be imparted to C, and the amount of the increase will be determined by the speed of rotation of H, which may be made variable by means of cone pulleys or other suitable mechanical devices. [Illustration: Fig. 206.] Fig. 208 represents an arrangement of gearing used upon steam fire-engines and traction engines to enable them to turn easily in a short radius, as in turning corners in narrow streets. The object is to enable the driving wheel on either side of the engine to increase or diminish its rotation to suit the conditions caused by the leading or front pair of steering wheels. [Illustration: Fig. 207.] In the figures A is a plate wheel having the lugs L, by means of which it may be rotated by a chain. A is a working fit on the shaft S, and carries three pinions E pivoted upon their axes P. F is a bevel-gear, a working fit on S, while C is a similar gear fast to S. The pinions B, D are to drive gears on the wheels of the engine, the wheels being a working fit on the axle. Let it now be noted that if S be rotated, C and F will rotate in opposite directions and A will remain stationary. But if A be rotated, then all the gears will rotate with it, but E will not rotate upon P unless there be an unequal resistance to the motion of pinions D and B. So soon, however, as there exists an inequality of resistance between D and B then pinions E operate. For example, let B have more resistance than D, and B will rotate more slowly, causing pinion E to rotate and move C faster than is due to the motion of the chain wheel A, thus causing the wheel on one side of the engine to retard and the other to increase its motion, and thus enable the engine to turn easily. From its action this arrangement is termed the equalizing gear. [Illustration: Fig. 208.] In Figs. 209 to 214 are shown what are known as mangle-wheels from their having been first used in clothes mangling machines. [Illustration: Fig. 209.] [Illustration: Fig. 210.] The mangle-wheel[10] in its simplest form is a revolving disc of metal with a centre of motion C (Fig. 209). Upon the face of the disc is fixed a projecting annulus _a_ _m_, the outer and inner edges of which are cut into teeth. This annulus is interrupted at _f_, and the teeth are continued round the edges of the interrupted portion so as to form a continued series passing from the outer to the inner edge and back again. [10] From Willis's "Principles of Mechanism." A pinion B, whose teeth are of the same pitch as those of the wheel, is fixed to the end of an axis, and this axis is mounted so as to allow of a short travelling motion in the direction B C. This may be effected by supporting this end of it either in a swing-frame moving upon a centre as at D, or in a sliding piece, according to the nature of the train with which it is connected. A short pivot projects from the centre of the pinion, and this rests in and is guided by a groove B S _f_ _t_ _b_ _h_ K, which is cut in the surface of the disc, and made concentric to the pitch circles of the inner and outer rays of teeth, and at a normal distance from them equal to the pitch radius of the pinion. Now when the pinion revolves it will, if it be on the outside, as in Fig. 209, act upon the spur teeth and turn the wheel in the opposite direction to its own, but when the interrupted portion _f_ of the teeth is thus brought to the pinion the groove will guide the pinion while it passes from the outside to the inside, and thus bring its teeth into action with the annular or internal teeth. The wheel will then receive motion in the same direction as that of the pinion, and this will continue until the gap _f_ is again brought to the pinion, when the latter will be carried outwards and the motion again be reversed. The _velocity ratio_ in either direction will remain constant, but the ratio when the pinion is inside will differ slightly from the ratio when it is outside, because the pitch radius of the annular or internal teeth is necessarily somewhat less than that of the spur teeth. However, the change of direction is not instantaneous, for the form of the groove S _f_ _t_, which connects the inner and outer grooves, is a semicircle, and when the axis of the pinion reaches S the velocity of the mangle-wheel begins to diminish gradually until it is brought to rest at _f_, and is again gradually set in motion from _f_ to _t_, when the constant ratio begins; and this retardation will be increased by increasing the difference between the radius of the inner and outer pitch circles. The teeth of a mangle-wheel are, however, most commonly formed by pins projecting from the face of the disc as in Fig. 210. In this manner the pitch circles for the inner and outer wheels coincide, and therefore the velocity ratio is the same within and without, also the space through which the pinion moves in shifting is reduced. [Illustration: Fig. 211.] [Illustration: Fig. 212.] This space may be still further reduced by arranging the teeth as in Fig. 211, that is, by placing the spur-wheel within the annular or internal one; but at the same time the difference of the two velocity ratios is increased. If it be required that the velocity ratio vary, then the pitch lines of the mangle-wheel must no longer be concentric. Thus in Fig. 212 the groove _k_ _l_ is directed to the centre of the mangle-wheel, and therefore the pinion will proceed during this portion of its path without giving any motion to the wheel, and in the other lines of teeth the pitch radius varies, hence the angular velocity ratio will vary. In Figs. 209, 210, and 211 the curves of the teeth are readily obtained by employing the same describing circle for the whole of them. But when the form Fig. 212 is adopted, the shape of the teeth requires some consideration. Every tooth of such a mangle-wheel may be considered as formed of two ordinary teeth set back to back, the pitch line passing through the middle. The outer half, therefore, appropriated to the action of the pinion on the outside of the wheel, resembles that portion of an ordinary spur-wheel tooth that lies beyond its pitch line, and the inner half which receives the inside action of the pinion resembles the half of an annular wheel that lies within the pitch circle. But the consequence of this arrangement is, that in both positions the action of the driving teeth must be confined to the approach of its teeth to the line of centres, and consequently these teeth must be wholly within their pitch line. To obtain the forms of the teeth, therefore, take any convenient describing circle, and employ it to describe the teeth of the pinion by rolling within its pitch circle, and to describe the teeth of the wheel by rolling within and without its pitch circle, and the pinion will then work truly with the teeth of the wheel in both positions. The tooth at each extremity of the series must be a circular one, whose centre lies on the pitch line and whose diameter is equal to half the pitch. [Illustration: Fig. 213.] If the reciprocating piece move in a straight line, as it very often does, then the mangle-_wheel_ is transformed into a _mangle-rack_ (Fig. 213) and its teeth may be simply made cylindrical pins, which those of the mangle-wheel do not admit of on correct principle. B _b_ is the sliding piece, and A the driving pinion, whose axis must have the power of shifting from A to _a_ through a space equal to its own diameter, to allow of the change from one side of the rack to the other at each extremity of the motion. The teeth of the mangle-rack may receive any of the forms which are given to common rack-teeth, if the arrangement be derived from either Fig. 210 or Fig. 211. But the mangle-rack admits of an arrangement by which the shifting motion of the driving pinion, which is often inconvenient, may be dispensed with. [Illustration: Fig. 214.] B _b_ Fig. 214, is the piece which receives the reciprocating motion, and which may be either guided between rollers, as shown, or in any other usual way; A the driving pinion, whose axis of motion is fixed; the mangle rack C _c_ is formed upon a separate plate, and in this example has the teeth upon the inside of the projecting ridge which borders it, and the guide-groove formed within the ring of teeth, similar to Fig. 211. This rack is connected with the piece B _b_ in such a manner as to allow of a short transverse motion with respect to that piece, by which the pinion, when it arrives at either end of the course, is enabled by shifting the rack to follow the course of the guide-groove, and thus to reverse the motion by acting upon the opposite row of teeth. The best mode of connecting the rack and its sliding piece is that represented in the figure, and is the same which is adopted in the well-known cylinder printing-engines of Mr. Cowper. Two guide-rods K C, _k_ _c_ are jointed at one end K _k_ to the reciprocating piece B _b_, and at the other end C _c_ to the shifting-rack; these rods are moreover connected by a rod M _m_ which is jointed to each midway between their extremities, so that the angular motion of these guide-rods round their centres K _k_ will be the same; and as the angular motion is small and the rods nearly parallel to the path of the slide, their extremities C _c_ may be supposed to move at a right angle to that path, and consequently the rack which is jointed to those extremities will also move upon B _b_ in a direction at a right angle to its path, which is the thing required, and admits of no other motion with respect to B _b_. [Illustration: Fig. 215.] To multiply plane motion the construction shown in Fig. 215 is frequently employed. A and B are two racks, and C is a wheel between them pivoted upon the rod R. A crank shaft or lever D is pivoted at E and also (at P) to R. If D be operated C traverses along A and also rotates upon its axis, thus giving to B a velocity equal to twice that of the lateral motion of C. The diameter of the wheel is immaterial, for the motion of B will always be twice that of C. Friction gearing-wheels which communicate motion one to the other by simple contact of their surfaces are termed friction-wheels, or friction-gearing. Thus in Fig. 216 let A and B be two wheels that touch each other at C, each being suspended upon a central shaft; then if either be made to revolve, it will cause the other to revolve also, by the friction of the surfaces meeting at C. The degree of force which will be thus conveyed from one to the other will depend upon the character of the surface and the length of the line of contact at C. [Illustration: Fig. 216.] These surfaces should be made as concentric to the axis of the wheel and as flat and smooth as possible in order to obtain a maximum power of transmission. Mr. E. S. Wicklin states that under these conditions and proper forms of construction as much as 300 horse-power may be (and is in some of the Western States) transmitted. In practice, small wheels of this class are often covered with some softer material, as leather; sometimes one wheel only is so covered, and it is preferred that the covered wheel drive the iron one, because, if a slip takes place and the iron wheel was the driver, it would be apt to wear a concave spot in the wood covered one, and the friction between the two would be so greatly diminished that there would be difficulty in starting them when the damaged spot was on the line of centre. If, however, the iron wheel ceased motion, the wooden one continuing to revolve, the damage would be spread over that part of the circumference of the wooden one which continued while the iron one was at rest, and if this occurred throughout a whole revolution of the wooden wheel its roundness would not be apt to be impaired, except in so far as differences in the hardness of the wood and similar causes might effect. "To select the best material for driving pulleys in friction-gearing has required considerable experience; nor is it certain that this object has yet been attained. Few, if any, well-arranged and careful experiments have been made with a view of determining the comparative value of different materials as a frictional medium for driving iron pulleys. The various theories and notions of builders have, however, caused the application to this use of several varieties of wood, and also of leather, india-rubber, and paper; and thus an opportunity has been given to judge of their different degrees of efficiency. The materials most easily obtained, and most used, are the different varieties of wood, and of these several have given good results. "For driving light machinery, running at high speed, as in sash, door, and blind factories, basswood, the linden of the Southern and Middle States (_Tilia Americana_) has been found to possess good qualities, having considerable durability and being unsurpassed in the smoothness and softness of its movement. Cotton wood (_Populus monilifera_) has been tried for small machinery with results somewhat similar to those of basswood, but is found to be more affected by atmospheric changes. And even white pine makes a driving surface which is, considering the softness of the wood, of astonishing efficiency and durability. But for all heavy work, where from twenty to sixty horse-power is transmitted by a single contact, soft maple (_Acer rubrum_) has, at present, no rival. Driving pulleys of this wood, if correctly proportioned and well built, will run for years with no perceptible wear. "For very small pulleys, leather is an excellent driver and is very durable; and rubber also possesses great adhesion as a driver; but a surface of soft rubber undoubtedly requires more power than one of a less elastic substance. "Recently paper has been introduced as a driver for small machinery, and has been applied in some situations where the test was most severe; and the remarkable manner in which it has thus far withstood the severity of these tests appears to point to it as the most efficient material yet tried. "The proportioning, however, of friction-pulleys to the work required and their substantial and accurate construction are matters of perhaps more importance than the selection of material. "Friction-wheels must be most accurately and substantially made and kept in perfect line so that the contact between the surfaces may not be diminished. The bodies are usually of iron lagged or covered with wooden segments. "All large drivers, say from four to ten feet diameter and from twelve to thirty inch face, should have rims of soft maple six or seven inches deep. These should be made up of plank, one and a half or two inches thick, cut into 'cants,' one-sixth, eighth, or tenth of the circle, so as to place the grain of the wood as nearly as practicable in the direction of the circumference. The cants should be closely fitted, and put together with white lead or glue, strongly nailed and bolted. The wooden rim, thus made up to within about three inches of the width required for the finished pulley, is mounted upon one or two heavy iron 'spiders,' with six or eight radial arms. If the pulley is above six feet in diameter, there should be eight arms, and two spiders when the width of face is more than eighteen inches. "Upon the ends of the arms are flat 'pads,' which should be of just sufficient width to extend across the inner face of the wooden rim, as described; that is, three inches less than the width of the finished pulley. These pads are gained into the inner side of the rim; the gains being cut large enough to admit keys under and beside the pads. When the keys are well driven, strong 'lag' screws are put through the ends of the arm into the rim. This done, an additional 'round' is put upon each side of the rim to cover bolt heads and secure the keys from ever working out. The pulley is now put to its place on the shaft and keyed, the edges trued up, and the face turned off with the utmost exactness. "For small drivers, the best construction is to make an iron pulley of about eight inches less diameter and three inches less face than the pulley required. Have four lugs, about an inch square, cast across the face of this pulley. Make a wooden rim, four inches deep, with face equal to that of the iron pulley, and the inside diameter equal to the outer diameter of the iron. Drive this rim snugly on over the rim of the iron pulley having cut gains to receive the lugs, together with a hard wood key beside each. Now add a round of cants upon each side, with their inner diameter less than the first, so as to cover the iron rim. If the pulley is designed for heavy work, the wood should be maple, and should be well fastened by lag screws put through the iron rim; but for light work, it may be of basswood or pine, and the lag screws omitted. But in all cases, the wood should be thoroughly seasoned. "In the early use of friction-gearing, when it was used only as backing gear in saw-mills, and for hoisting in grist-mills, the pulleys were made so as to present the head of the wood to the surface; and we occasionally yet meet with an instance where they are so made. But such pulleys never run so smoothly nor drive so well as those made with the fibre more nearly in a line with the work."[11] [11] By E. S. Wicklin. [Illustration: Fig. 217.] [Illustration: Fig. 218.] The driving friction may be obtained from contact of the radial surfaces in two ways: thus, Fig. 217 represents three discs, A, B, and C; the edge of A being gripped by and between B and C, which must be held together by a spiral spring S or other equivalent device. These wheels may be made to give a variable speed of rotation by curving the surfaces of the pair B C as in the figure. By means of suitable lever-motion A may be made to advance towards or recede from the centre of B and C, giving to their shaft an increased or diminished speed of revolution. [Illustration: Fig. 219.] A similar result may be obtained by the construction shown in Fig. 218, in which D and E are two discs fast upon their respective shafts, and C are discs of leather clamped in E. It is obvious that if D be the driver the speed of revolution of E will be diminished in proportion as it is moved nearer to the centre of D, and also that the direction of revolution of D remaining constant, that of E will be in one direction if on the side B of the centre of D, and in the other direction if it is on the side A of the centre of D, thus affording means of reversing the motion as well as of varying its speed. A similar arrangement is sometimes employed to enable the direction of rotation of the driver shaft to be reversed, or its motion to cease. Thus, in Fig. 219, R is a driving rope driving the discs A, B, and _c_, _d_, _e_, _f_, _g_ are discs of yellow pine clamped between the flanges _h_ _i_; when these five discs are forced (by lifting shaft H), against the face of a motion occurs in one direction, while if forced against B the direction of motion of H is reversed. For many purposes, such as hoisting, for example, where considerable power requires to be transmitted, the form of friction wheels shown in Fig. 220 is employed, the object being to increase the line of contact between wheels of a given width of face. In this case the strain due to the length of the line of contact partly counteracts itself, thus relieving to that extent the journals from friction. Thus in Fig. 221 is shown a single wedge and groove of a pair of wheels. The surface pressure on each side will be at a right angle to the face, or in the direction described by the arrows A and B. The surface contact acts to thrust the bearings of the two shafts apart. The effective length of surface acting to thrust the bearings apart being denoted by the dotted line C. The relative efficiency of this class of wheel, however, is not to be measured by the length of the line C, as compared to that of the two contacting sides of the groove, because it is increased from the wedge shape of the groove, and furthermore, no matter how solid the wheels may be, there will be some elasticity which will operate to increase the driving power due to the contact. It is to preserve the wedge principle that the wedges are made flat at the top, so that they shall not bottom in the grooves even after considerable wear has taken place. The object of employing this class of gear is to avoid noise and jar and to insure a uniform motion. The motion at the line of contact of such wheels is not a rolling, but, in part, a sliding one, which may readily be perceived from a consideration of the following. The circumference of the top of each wedge is greater than that of the bottom, and, in the case of the groove, the circumference of the top is greater than that of the bottom; and since the top or largest circumference of one contacts with the smallest circumference of the other, it follows that the difference between the two represents the amount of sliding motion that occurs in each revolution. Suppose, for example, we take two of such wheels 10 inches in diameter, having wedges and grooves 1/4 inch high and deep respectively; then the top of the groove will travel 31.416 inches in a revolution, and it will contact with the bottom of the wedge which travels (on account of its lesser diameter) 29.845 inches per revolution. [Illustration: Fig. 220.] [Illustration: Fig. 221.] Fig. 222 shows the construction for a pair of bevel wheels on the same principle. [Illustration: Fig. 222.] [Illustration: Fig. 223.] [Illustration: Fig. 224.] A form of friction-gearing in which the journals are relieved of the strain due to the pressure of contact, and in which slip is impossible, is shown in Fig. 223. It consists of projections on one wheel and corresponding depressions or cavities on the other. These projections and cavities are at opposite angles on each half of each wheel, so as to avoid the end pressure on the journals which would otherwise ensue. Their shapes may be formed at will, providing that the tops of the projections are narrower than their bases, which is necessary to enable the projections to enter and leave the cavities. In this class of positive gear great truth or exactness is possible, because both the projections and cavities may be turned in a lathe. Fig. 224 represents a similar kind of gear with the projections running lengthways of the cylinder approaching more nearly in its action to toothed gearing, and in this case the curves for the teeth and groves should be formed by the rules already laid down for toothed gearing. The action of this latter class may be made very smooth, because a continuous contact on the line of centres may be maintained by reason of the longitudinal curve of the teeth. [Illustration: Fig. 225.] Cams may be employed to impart either a uniform, an irregular, or an intermittent motion, the principles involved in their construction being as follows:--Let it be required to construct a cam that being revolved at a uniform velocity shall impart a uniform reciprocating motion. First draw an inner circle O, Fig. 225, whose radius must equal the radius of the shaft that is to drive it, plus the depth of the cam at its shallowest part, plus the radius of the roller the cam is to actuate. Then from the same centre draw an outer circle S, the radius between these two circles being equal to the amount the cam is to move the roller. Draw a line O P, and divide it into any convenient numbers of divisions (five being shown in the figure), and through these points draw circles. Divide the outer circle S into twice as many equal divisions as the line O P is divided into (as from 1 to 10 in the figure), and where these lines pass through the circles will be points through which the pitch line of the cam may be drawn. [Illustration: Fig. 226.] Thus where circle 1 meets line 1, or at point A, is one point in the pitch line of the cam; where circle 2 meets line 2, or at B, is another point in the pitch line of the cam, and so on until we reach the point E, where circle 5 meets line 5. From this point we simply repeat the process, the point E where line 6 cuts circle 4, being a point on the pitch line, and so on throughout the whole 10 divisions, and through the points so obtained we draw the pitch line. [Illustration: Fig. 227.] [Illustration: Fig. 228.] If we were to cut out a cam to the outline thus obtained, and revolve it at a uniform velocity, it would move a point held against its perimeter at a uniform velocity throughout the whole of the cam revolution. But such a point would rapidly become worn away and dulled, which would, as the point broadened, vary the motion imparted to it, as will be seen presently. To avoid this wear a roller is used in place of a point, and the diameter of the roller affects the action of the cam, causing it to accelerate the cam action at one and retard it at another part of the cam revolution, hence the pitch line obtained by the process in Fig. 225 represents the path of the centre of the roller, and from this pitch line we may mark out the actual cam by the construction shown in Fig. 226. A pair of compasses are set to the radius of the roller R, and from points (such as at A, B, E, F), as the pitch line, arcs of circles are struck, and a line drawn to just meet the crowns of these arcs will give the outline of the actual cam. The motion of the roller, however, in approaching and receding from the cam centre C, must be in a straight line G G that passes through the centre C of the cam. Suppose, for example, that instead of the roller lifting and falling in the line G G its arm is horizontal, as in Fig. 227, and that this arm being pivoted the roller moves in an arc of a circle as D D, and the motion imparted to the arm will no longer be uniform. Furthermore, different diameters of roller require different forms of cam to accomplish the same motion, or, in other words, with a given cam the action will vary with different diameters of roller. Suppose, for example, that in Fig. 228 we have a cam that is to operate a roller along the line A A, and that B represents a large and C a small roller, and with the cam in the position shown in the figure, C will have contact with the cam edge at point D, while B will have contact at the point E, and it follows that on account of the enlarged diameter of roller B over roller C, its action is at this point quicker under a given amount of cam motion, which has occurred because the point of contact has advanced upon the roller surface--rolling along it, as it were. In Fig. 229 we find that as the cam moves forward this action continues on both the large and the small roller, its effect being greater upon the large than upon the small one, and as this rolling motion of the point of contact evidently occurs easily, a quick roller motion is obtained without shock or vibration. Continuing the cam motion, we find in Fig. 230 that the point of contact is receding toward the line of motion on the large roller and advancing upon the small one, while in Fig. 231 the two have contact at about the same point, the forward motion being about completed. [Illustration: Fig. 229.] [Illustration: Fig. 230.] [Illustration: Fig. 231.] [Illustration: Fig. 232.] To compare the motions of the respective rollers along the line of motion A A we proceed as in Fig. 232, in which the two dots M and N are the same distance apart as are the centres of the two rollers B and C when in the positions they occupy in Fig. 228; hence a pair of compasses set to the radius from the axis of the cam to that of roller B will, if rested at N, strike the arc marked 1 above the line of motion A A, while a pair of compasses set to the radius from the axis of the cam to that of roller C in Fig. 228 will, if rested at M in Fig. 232, mark the arc 1 below the line of motion A A. Continuing this process, we set the compasses to the radius from the axis of the cam to that of roller B in Fig. 229, and mark this radius at arc 2 above the line A A in Fig. 232; hence the distance apart of these two arcs is the amount the roller travelled along the line A A while the cam moved from its position in Fig. 228 to its position in Fig. 229. Next we set the compasses from the axis of the cam to that of the large roller in Fig. 230, and then mark arc 3 above the line in Fig. 232, and repeat the process for Fig. 233, thus using the centre N for all the positions of the large roller and marking its motion above the line A A. To get the motion of the small roller C, we set the compasses to the radius from the axis of the cam to the small roller in Fig. 228, and then resting one point of these compasses on centre M in Fig. 232, we mark arc 1 below the line A A. Turning to Fig. 229 we set the compasses from the cam axis to the centre of roller C, and from centre N in Fig. 232 mark arc 2 below line A. From Figs. 230 and 231 proceed in the same way to get lines 3 and 4 below line A in Fig. 232, and we may at once compare the two motions. Thus we find that while the cam moved from the position in Fig. 228 to that in Fig. 229, the large roller moved twice as far as the small one, while at 230 the motions were rapidly equalizing again, the equalization being completed at 231. [Illustration: Fig. 233.] [Illustration: Fig. 234.] [Illustration: Fig. 235.] We may now consider the return motion, and in Fig. 233 we find that the order of things is reversed, for the small roller has contact at O, while the large one has contact at P; hence the small one leads and gives the most rapid motion, which it continues to do, as is shown in Figs. 234, 235, and 236, and we may plot out the two motions as in Fig. 237--that for the large roller being above and that for the small one below the line A A. First we set a pair of compasses to the radius from the axis of the large and small roller when in the position shown in Fig. 231 (which corresponds to the same radius in Fig. 228), and mark two centres, M and N, as we did in Fig. 232. Of these N is the centre for plotting the motion of the large roller and M the centre for plotting the motion of the small one. We set a pair of compasses to the radius from the axis of the cam and that of the large roller in Fig. 231, and then resting the compasses at N we mark arc 5 above the line A A, Fig. 237. The compasses are then set from the cam to the roller axis in Fig. 233, and arc 6 is marked above line A A. From Figs. 234, 235, and 236 we get the radii to mark arcs 7, 8, 9 above A A, and the motion of the large roller is plotted. We proceed in the same way for the small one, but use the centre M, Fig. 237, to mark the arcs 5, 6, 7, 8, and 9 below the line A A, and find that the small roller has moved quickest throughout. It appears, then, that the larger the roller the quicker the forward motion and the slower the return one, which is advantageous, because the object is to move the roller out quickly and close it slowly, so that under a quick speed the cam shall not run away from the roller as it is apt to do in the absence of a return or backing cam, which consists of a separate cam for moving the roller on its return stroke, thus dispensing with the use of springs or weights to keep the roller upon the cam and making the motion positive. [Illustration: Fig. 236.] [Illustration: Fig. 237.] [Illustration: Fig. 238.] The return or backing cam obviously depends for its shape upon the forward cam, and the latter having been determined, the requisite form for the return cam may be found as follows. In Fig. 238 let A represent the forward cam fastened in any suitable or convenient way to a disc of paper, or, what is better, sheet zinc, B. The cam is pivoted by a pin passing through it and the zinc, and driven into the drawing-board. A frame F is made to carry two rollers R and R´, whose width apart exactly equals the extreme length of the forward cam. The faces D D of the frame F are in a line with a line passing through the centres of the rolls R R´, and the cam is also pivoted on this line, so that when the four pins P are driven into the drawing-board, the frame F will be guided by them to move in a line that crosses the centre of the cam A. Suppose then that, the pieces occupying the position shown in the engraving, we slide F so that roller R touches the edge of cam A, and we may then take a needle and mark an arc or line around the edge of R´. We then revolve cam A a trifle, and, being fast to B, the two will move together, and with R against A we mark a second arc, coincident with the edge of roller R´. By continuing this process we mark the numerous short arcs shown upon B, and the crowns of these arcs give us the outline of the return cam. It is obvious that, while the edge of the cam A will not let roller R (and therefore frame F) move to the right, roller R´ being against the edge of the backing or return cam as marked upon B, prevents the frame F from moving to the left; hence neither roll can leave its cam. [Illustration: Fig. 239.] We have in this example supposed that the frame carrying the rollers is guided to move in a straight line, and it remains to give an example in which the rollers are carried on a pivoted shaft or rocking arm. In Fig. 239 we have the same cam A with a sheet of paper B fastened to it, the rollers R R´ being carried in a rock shaft pivoted at X. It is essential in this case that the rollers R and R´ and the centre upon which the cam revolves shall all three be in the arc of a circle whose centre is the axis of X, as is denoted by the arc D. The cam A is fastened to the piece of stiff paper or of sheet zinc B, and the two are pivoted by a pin passing through the axis E of the cam and into the drawing-board, while the lever is pivoted at X by a pin passing into the drawing-board. The backing or return cam is obviously marked out the same way as was described with reference to Fig. 238. [Illustration: Fig. 240.] In Fig. 240 we have as an example the construction of a cam to operate the slide valve of an engine which is to have the steam supply to the cylinder cut off at one-half the piston stroke, and that will admit the live steam as quickly as a valve having steam lap equal to, say, three-fourths the width of the port. In Fig. 240 let the line A represent a piston stroke of 24 inches, the outer circle B the path of the outer edge of the cam, and the inner circle C the inner edge of the cam, the radius between these circles representing the full width of the steam port. Now, in a valve having lap equal to three-fourths the width of the steam port, and travel enough to open both ports fully, the piston of a 24-inch-stroke engine will have moved about 2 inches before the steam port is fully opened, and to construct a cam that will effect the same movement we mark a dot D, distant from the end E of piston stroke 2/26 of the length of the line A, and by erecting the line F we get at point G, the point at which the cam must attain its greatest throw. It is obvious, therefore, that as the roller is at R the valve will be in mid-position, as shown at the bottom of the figure, and that when point G of the cam arrives at E the edge P of the valve will be moved fair with edge S of the steam port T, which will therefore be full open. To cut off at half stroke the valve must again be closed by the time point N of the cam meets the roller R; hence we may mark point N. We may then mark in the cam curve from N to M, making it as short as it will work properly without causing the roller to fail to follow the curve or strike a blow when reaching the circle C. To accomplish this end in a single cam, it is essential to make the curve as gradual as possible from point M to O, so as to start the roller motion easily. But once having fairly started, its motion may be rapidly accelerated, the descent from O to Q being rapid. To prevent the roller from meeting circle C with a blow, the curve from Q to N is again made gradual, so as to ease and retard the roller motion. The same remarks apply to the curve from R to G, the object being to cause the roller to begin and end its passage along the cam curve as slowly as the length of cam edge occupied by the curve will permit. There is one objection to starting the curve slowly at G, which is that the port S will be opened correspondingly slowly for the live steam. This, however, may be overcome by giving the valve an increased travel, as shown in Fig. 241, which will simply cause the valve edge to travel to a corresponding amount over the inside edge of the port. The increased travel is shown by the circles Y and Z, and it is seen that the cam curve from W to R is more gradual than in Fig. 240, while the roller R will be moved much more quickly in the position shown in Fig. 241 than it will in that shown in Fig. 240, both positions being that when the piston is at the end of the stroke and the port about to open. While that part of the cam curve from G to M in Fig. 241 is moving past the roller R, the valve will be moving over the bridge, the steam port remaining wide open, and therefore not affecting the steam distribution. After point M, Fig. 241, has passed the roller, we have from M to T to start the roller gradually, so that when it has arrived at T and the port begins to close for the cut-off it may move rapidly, and continue to do so until the point N reaches the roller and the cut-off has occurred, after which it does not matter how slowly the valve moves; hence we may make the curve from N to the circle Y as gradual as we like. [Illustration: Fig. 241.] [Illustration: Fig. 242.] Fig. 242 represents a cam for a valve having the amount of lap represented by the distance between circles C and Y, the cam occupying the position it would do with the piston at one end of the stroke, as at E. Obviously, a full port is obtained when point G reaches the roller, and as point N is distant from E three-quarters of the diameter of the outer circle, the cut-off occurs at three-quarter stroke, and we have from N to Y to make the curve as gradual as we like, and from W to R in moving the valve to open the port. We cannot, however, give more gradual curves at G and at M without retarding the roller motion, and therefore opening and closing the port slower, and it would simply be a matter of increase of speed to cause the roller to fail to follow the cam surface at these two points unless a return cam be employed. We have in these engine cams considered the steam supply and point of cut-off only, and it is obvious that a second and separate cam would be required to operate the exhaust valves. [Illustration: Fig. 243.] Fig. 243 represents a groove-cam, and it is to be observed that the roller cannot be maintained in a close fit in the groove, because the friction on its two sides endeavours to drive it in opposite directions at the same time, causing an abrasion that soon widens the groove and reduces the roller diameter; furthermore, when the grooves are made of equal width all the way down (and these cams are often made in this way) the roller cannot have a rolling action only, but must have some sliding motion. Thus, referring to Fig. 243, the amount of sliding motion will be equal to the differences in the circumferences of the outer circle A and the inner one B. To obviate this the groove and roller must be made of such a taper that the axis of the cam and of the roller will meet on the line of the cam axes and in the middle of the width, as is shown in Fig. 244; but even in this case the cam will grind away the roller to some extent, on account of rubbing its sides in opposite directions. To obviate this, Mr. James Brady, of Brooklyn, N. Y., has patented the use of two rollers, as in Fig. 245, one acting against one side and the other against the other side of the groove, by which means lost motion and rapid wear are successfully avoided. [Illustration: Fig. 244.] [Illustration: Fig. 245.] In making a cam of this form, the body of the cam is covered by a sleeve. The groove is cut through the sleeve and into the body, and is made wider than the diameter of the roller. When the rollers are in place on the spindle or journal, the sleeve is pushed forward, or rather endways, and fastened by a set-screw. This gives the desired bearing on both sides of the groove, while each roller touches one side only of the groove. The edges of the sleeve are then faced off even with the cam body, the whole appearing as in the figure. [Illustration: _VOL. I._ =FORMS OF SCREW THREADS.= _PLATE II._ THE [V]-THREAD. Fig. 246. THE UNITED STATES STANDARD THREAD. Fig. 247. THE WHITWORTH, OR ENGLISH STANDARD THREAD. Fig. 248. THE SQUARE THREAD. Fig. 249. THE PITCH OF A THREAD. Fig. 250. A DOUBLE THREAD. Fig. 251. A RATCHET THREAD. Fig. 252. A "DRUNKEN" THREAD. Fig. 253. RIGHT AND LEFT HAND THREAD. Fig. 254.] CHAPTER IV.--SCREW THREAD. Screw threads are employed for two principal purposes--for holding or securing, and for transmitting motion. There are in use, in ordinary machine shop practice, four forms of screw thread. There is, first, the sharp [V]-thread shown in Fig. 246; second, the United States standard thread, the Sellers thread, or the Franklin Institute thread, as it is sometimes called--all three designations signifying the same form of thread. This thread was originally proposed by William Sellers, and was afterward recommended by the Franklin Institute. It was finally adopted as a standard by the United States Navy Department. This form of thread is shown in Fig. 247. The third form is the Whitworth or English standard thread, shown in Fig. 248. It is sometimes termed the round top and bottom thread. The fourth form is the square thread shown in Fig. 249, which is used for coarse pitches, and usually for the transmission of motion. The sharp [V]-thread, Fig. 246, has its sides at an angle of 60° one to the other, as shown; or, in other words, each side of the thread is at an angle of 60° to the axial line of the bolt. The United States Standard, Fig. 247, is formed by dividing the depth of the sharp [V]-thread into 8 equal divisions and taking off one of the divisions at the top and filling in another at the bottom, so as to leave a flat place at the top and bottom. The Whitworth thread, Fig. 248, has its sides at an angle of 55° to each other, or to the axial line of the bolt. In this the depth of the thread is divided into 6 equal parts, and the sides of the thread are joined by arcs of circles that cut off one of these parts at the top and another at the bottom of the thread. The centres from which these arcs are struck are located on the second lines of division, as denoted in the figure by the dots. Screw threads are designated by their pitch or the distance between the threads. In Fig. 250 the pitch is 1/4 inch, but it is usual to take the number of threads in an inch of length; hence the pitch in Fig. 250 would generally be termed a pitch of 4, or 4 to the inch. The number of threads per inch of length does not, however, govern the true pitch of the thread, unless it be a "single" thread. A single thread is composed of one spiral projection, whose advance upon the bolt is equal in each revolution to the apparent pitch. In Fig. 251 is shown a double thread, which consists of two threads. In the figure, A denotes one spiral or thread, and B the other, the latter being carried as far as C only for the sake of illustration. The true pitch is in this case twice that of the apparent pitch, being, as is always the case, the number of revolutions the thread makes around the bolt (which gives the pitch per inch), or the distance along the bolt length that the nut or thread advances during one rotation. Threads may be made double, treble, quadruple and so on, the object being to increase the motion without the use of a coarser pitch single thread, whose increased depth would weaken the body of the bolt. The "ratchet" thread shown in Fig. 252 is sometimes used upon bolts for ironwork, the object being to have the sides A A of the thread at a right angle to the axis of the bolt, and therefore in the direct line of the strain. Modifications of this form of thread are used in coarse pitches for screws that are to thread direct into woodwork. A waved or drunken thread is one in which the path around the bolt is waved, as in Fig. 253, and not a continuous straight spiral, as it should be. All threads may be either left hand or right, according to their direction of inclination upon the bolt; thus, Fig. 254 is a cylinder having a right-hand thread at A and a left-hand one at B. When both ends of a piece have either right or left-hand threads, if the piece be rotated and the nuts be prevented from rotating, they will move in the same direction, and, if the pitches of the threads are alike, at the same rate of motion; but if one thread be a right and the other a left one, then, under the above conditions, the nuts will advance toward or recede from each other according to the direction of rotation of the male thread. [Illustration: Fig. 255.] In Fig. 255 is represented a form of thread designed to enable the nut to fit the bolt, and the thread sides to have a bearing one upon the other, notwithstanding that the diameter of the nut and bolt may differ. The thread in the nut is what may be termed a reversed ratchet thread, and that in the bolt an undercut ratchet thread, the amount of undercut being about 2°. Where this form of thread is used, the diameter of the bolt may vary as much as 1-32d of an inch in a bolt 3/4 inch in diameter, and yet the nut will screw home and be a tight fit. The difference in the thread fit that ordinarily arises from differences in the standards of measurement from wear of the threading tools, does not in this form affect the fit of the nut to the bolt. In screwing the nut on, the threads conform one to the other, giving a bearing area extending over the full sides of the thread. The undercutting on the leading face of the bolt thread gives room for the metal to conform itself to the nut thread, which it does very completely. The result is that the nut may be passed up and down the bolt several times and still remain too tight a fit to be worked by hand. Experiment has demonstrated that it may be run up and down the bolt dozens of times without becoming as loose as an ordinary bolt and nut. On account of this capacity of the peculiar form of thread employed, to adapt itself, the threads may be made a tight fit when the threading tools are new. The extra tightness that arises from the wear of these tools is accommodated in the undercutting, which gives room for the thread to adjust itself to the opposite part or nut. In a second form of self-locking thread, the thread on the bolt is made of the usual [V]-shape United States standard. The thread in the nut, however, is formed as illustrated in Fig. 256, which is a section of a 3/4-inch bolt, greatly enlarged for the sake of clearness of illustration. The leading threads are of the same angle as the thread on the bolt, but their diameters are 3/4 and 1-16th inch, which allows the nut to pass easily upon the bolt. The angle of the next thread following is 56°, the succeeding one 52°, and so on, each thread having 4° less angle than the one preceding, while the pitch remains the same throughout. As a result, the rear threads are deeper than the leading ones. As the nut is screwed home, the bolt thread is forced out or up, and fills the rear threads to a degree depending upon the diameter of the bolt thread. For example, if the bolt is 3/4 inch, its leading or end thread will simply change its angle from that of 60° to that of 44°, or if the bolt thread is 3/4 and 1-64th inch in diameter, its leading thread will change from an angle of 60° to one of 44°. It will almost completely fill the loose thread in the nut. The areas of spaces between the nut threads are very nearly equal, although slightly greater at the back end of the nut, so that if the front end will enter at all, the nut will screw home, while the thread fit will be tight, even under a considerable variation in the bolt itself. From this description, it is evident that the employment of nuts threaded in this manner is only necessary in order to give to ordinary bolts all the advantages of tightness due to this form of thread. The term "diameter" of a thread is understood to mean its diameter at the top of the thread and measured at a right angle to the axis of the bolt. When the diameter of the bottom or root of the thread is referred to it is usually specified as diameter at the bottom or at the root of the thread. The depth of a thread is the vertical height of the thread upon the bolt, measured at a right angle to the bolt axis and not along the side of the thread. A true thread is one that winds around the bolt in a continuous and even spiral and is not waved or drunken as is the thread in Fig. 253. An outside or male thread is one upon an external surface as upon a bolt; an internal or female thread is one produced in a bore or hole as in a nut. [Illustration: Fig. 256.] The Whitworth or English standard thread, shown in Fig. 248, is that employed in Great Britain and her colonies, and to a small extent in the United States. The [V]-thread fig. 246 is that in most common use in the United States, but it is being displaced by the United States standard thread. The reasons for the adoption of the latter by the Franklin Institute are set forth in the report of a committee appointed by that Institute to consider the matter. From that report the following extracts are made. "That in the course of their investigations they have become more deeply impressed with the necessity of some acknowledged standard, the varieties of threads in use being much greater than they had supposed possible; in fact, the difficulty of obtaining the exact pitch of a thread not a multiple or sub-multiple of the inch measure is sometimes a matter of extreme embarrassment. "Such a state of things must evidently be prejudicial to the best interests of the whole country; a great and unnecessary waste is its certain consequence, for not only must the various parts of new machinery be adjusted to each other, in place of being interchangeable, but no adequate provision can be made for repairs, and a costly variety of screwing apparatus becomes a necessity. It may reasonably be hoped that should a uniformity of practice result from the efforts and investigations now undertaken, the advantages flowing from it will be so manifest, as to induce reform in other particulars of scarcely less importance. "Your committee have held numerous meetings for the purpose of considering the various conditions required in any system which they could recommend for adoption. Strength, durability, with reference to wear from constant use, and ease of construction, would seem to be the principal requisites in any general system; for although in many cases, as, for instance, when a square thread is used, the strength of the thread and bolt are both sacrificed for the sake of securing some other advantage, yet all such have been considered as special cases, not affecting the general inquiry. With this in view, your committee decided that threads having their sides at an angle to each other must necessarily more nearly fulfil the first condition than any other form; but what this angle should be must be governed by a variety of considerations, for it is clear that if the two sides start from the same point at the top, the greater the angle contained between them, the greater will be the strength of the bolt; on the other hand, the greater this angle, supposing the apex of the thread to be over the centre of its base, the greater will be the tendency to burst the nut, and the greater the friction between the nut and the bolt, so that if carried to excess the bolt would be broken by torsional strain rather than by a strain in the direction of its length. If, however, we should make one side of the thread perpendicular to the axis of the bolt, and the other at an angle to the first, we should obtain the greatest amount of strength, together with the least frictional resistance; but we should have a thread only suitable for supporting strains in one direction, and constant care would be requisite to cut the thread in the nut in the proper direction to correspond with the bolt; we have consequently classed this form as exceptional, and decided that the two sides should be at an angle to each other and form equal angles with the base. "The general form of the thread having been determined upon the above considerations, the angle which the sides should bear to each other has been fixed at 60°, not only because this seems to fulfil the conditions of least frictional resistance combined with the greatest strength, but because it is an angle more readily obtained than any other, and it is also in more general use. As this form is in common use almost to the exclusion of any other, your committee have carefully weighed its advantages and disadvantages before deciding to recommend any modification of it. It cannot be doubted that the sharp thread offers us the simplest form, and that its general adoption would require no special tools for its construction, but its liability to accident, always great, becomes a serious matter upon large bolts, whilst the small amount of strength at the sharp top is a strong inducement to sacrifice some of it for the sake of better protection to the remainder; when this conclusion is reached, it is at once evident a corresponding space may be filled up in the bottom of the thread, and thus give an increased strength to the bolt, which may compensate for the reduction in strength and wearing surface upon the thread. It is also clear that such a modification, by avoiding the fine points and angles in the tools of construction, will increase their durability; all of which being admitted, the question comes up, what form shall be given to the top and bottom of the thread? for it is evident one should be the converse of the other. It being admitted that the sharp thread can be made interchangeable more readily than any other, it is clear that this advantage would not be impaired if we should stop cutting out the space before we had made the thread full or sharp; but to give the same shape at the bottom of the threads would require that a similar quantity should be taken off the point of the cutting tool, thus necessitating the use of some instrument capable of measuring the required amount, but when this is done the thread having a flat top and bottom can be quite as readily formed as if it was sharp. A very slight examination sufficed to satisfy us that in point of construction the rounded top and bottom presents much greater difficulties--in fact, all taps and screws that are chased or cut in a lathe require to be finished or rounded by a second process. As the radius of the curve to form this must vary for every thread, it will be impossible to make one gauge to answer for all sizes, and very difficult, in fact impossible, without special tools, to shape it correctly for one. "Your committee are of opinion that the introduction of a uniform system would be greatly facilitated by the adoption of such a form of thread as would enable any intelligent mechanic to construct it without any special tools, or if any are necessary, that they shall be as few and as simple as possible, so that although the round top and bottom presents some advantages when it is perfectly made, as increased strength to the thread and the best form to the cutting tools, yet we have considered that these are more than compensated by ease of construction, the certainty of fit, and increased wearing surface offered by the flat top and bottom, and therefore recommend its adoption. The amount of flat to be taken off should be as small as possible, and only sufficient to protect the thread; for this purpose one-eighth of the pitch would seem to be ample, and this will leave three-fourths of the pitch for bearing surface. The considerations governing the pitch are so various that their discussion has consumed much time. "As in every instance the threads now in use are stronger than their bolts, it became a question whether a finer scale would not be an advantage. It is possible that if the use of the screw thread was confined to wrought iron or brass, such a conclusion might have been reached, but as cast iron enters so largely into all engineering work, it was believed finer threads than those in general use might not be found an improvement; particularly when it was considered that so far as the vertical height of thread and strength of bolt are concerned, the adoption of a flat top and bottom thread was equivalent to decreasing the pitch of a sharp thread 25 per cent., or what is the same thing, increasing the number of threads per inch 33 per cent. If finer threads were adopted they would require also greater exactitude than at present exists in the machinery of construction, to avoid the liability of overriding, and the wearing surface would be diminished; moreover, we are of opinion that the average practice of the mechanical world would probably be found better adapted to the general want than any proportions founded upon theory alone." * * * * * [Illustration: Fig. 257.] [Illustration: Fig. 258.] The principal requirements for a screw thread are as follows: 1. That it shall possess a strength that, in the length or depth of a nut, shall be equal to the strength of the weakest part of the bolt, which is at the bottom of the bolt thread. 2. That the tools required to produce it shall be easily made, and shall not alter their form by reason of wear. 3. That these tools shall (in the case of lathe work) be easily sharpened, and set to correct position in the lathe. 4. That a minimum of measuring and gauging shall be required to test the diameter and form of the thread. 5. That the angles of the sides shall be as acute as is consistent with the required strength. 6. That it shall not be unduly liable to become loose in cases where the nut may require to be fastened and loosened occasionally. Referring to the first, by the term "the strength of a screw thread," is not meant the strength of one thread, but of so many threads as are contained in the nut. This obviously depends upon the depth or thickness of the nut-piece. The standard thickness of nut, both in the United States and Whitworth systems, as well as in general practice, or where the common [V]-thread is used, is made equal to the diameter of the top of the thread. Therefore, by the term "strength of thread" is meant the combined strength of as many threads as are contained in a nut of the above named depth. It is obvious, then, when it is advantageous to increase the strength of a thread, that it may be done by increasing the depth of the nut, or in other words, by increasing the number of threads used in computing its strength. This is undesirable by reason of increasing the cost and labor of producing the nuts, especially as the threading tools used for nuts are the weakest, and are especially liable to breakage, even with the present depth of nuts. It has been found from experiments that have been made that our present threads are stronger than their bolts, which is desirable, inasmuch as it gives a margin for wear on the sides of the threads. But for threads whose nuts are to remain permanently fastened and are not subject to wear, it is questionable whether it were not better for the bolts to be stronger than the threads. Suppose, for instance, that a thread strips, and the bolt will remain in place because the nut will not come off the bolt readily. Hence the pieces held by the bolt become loosened, but not disconnected. If, on the other hand, the bolt breaks, it is very liable to fall out, leaving the piece or pieces, as the case may be, to fall apart, or at least become disconnected, so far as the bolt is concerned. But since threads are used under conditions where the threads are liable to wear, and since it is undesirable to have more than one standard thread, it is better to have the threads, when new, stronger than the bolts. [Illustration: Fig. 259.] Referring to the second requirement, screw threads or the tools that produce them are originated in the lathe, and the difficulty with making a round top and bottom thread lies in shaping the corner to cut the top of the thread. This is shown in Fig. 257, where a Whitworth thread and a single-toothed thread-cutting tool are represented. The rounded point A of the tool will not be difficult to produce, but the hollow at B would require special tools to cut it. This is, in fact, the plan pursued under the Whitworth system, in which a hob or chaser-cutting tool is used to produce all the thread-cutting tools. A chaser is simply a toothed tool such as is shown in Fig. 258. Now, it would manifestly be impracticable to produce a chaser having all the curves, A and B, at the top and at the bottom of the teeth alike, by the grinding operations usually employed in the workshop, and hence the employment of the hob. Fig. 259 represents a hob, which is a threaded piece of steel with a number of grooves such as shown at A, A, A, which divide the thread into teeth, the edges of which will cut a chaser, of a form corresponding to that of the thread upon the hob. The chaser is employed to produce taps and secondary hobs to be used for cutting the threads in dies, &c., so that the original hob is the source from which all the thread-cutting tools are derived. [Illustration: Fig. 260.] For the United States standard or the common [V]-thread, however, no standard hob is necessary, because a single-pointed tool can be ground with the ordinary grinding appliances of the workshop. Thus, for the United States standard, a flat-pointed tool, Fig. 260, and for the common [V]-thread, a sharp-pointed tool, Fig. 260, may be used. So far as the correctness of angle of pitch and of thread depth are concerned, the United States standard and the common [V]-thread can both be produced, under skilful operation, more correctly than is possible with the Whitworth thread, for the following reasons:-- To enable a hob to cut, it must be hardened, and in the hardening process the pitch of the thread alters, becoming, as a general rule (although not always) finer. This alteration of pitch is not only irregular in different threads, but also in different parts of the same thread. Now, whatever error the hob thread receives from hardening it transfers to the chaser it cuts. But the chaser also alters its form in hardening, the pitch, as a general rule, becoming coarser. It may happen that the error induced in the hob hardening is corrected by that induced by hardening the chaser, but such is not necessarily the case. [Illustration: Fig. 261.] The single-pointed tool for the United States standard or for the common [V]-thread is accurately ground to form after the hardening, and hence need contain no error. On the other hand, however, the rounded top and bottom thread preserves its form and diameter upon the thread-cutting tools better than is the case with threads having sharp corners, for the reason that a rounded point will not wear away so quickly as a sharp point. To fully perceive the importance of this, it is necessary to consider the action of a tool in cutting a thread. In Fig. 261 there is shown a chaser, A, applied to a partly-formed thread, and it will be observed that the projecting ends or points of the teeth are in continuous action, cutting a groove deeper and deeper until a full thread is developed, at which time the bottoms of the chaser teeth will meet the perimeter of the work, but will perform no cutting duty upon it. As a result, the chaser points wear off, which they will do more quickly if they are pointed, and less quickly if they are rounded. This causes the thread cut to be of increased and improper diameter at the root. [Illustration: Fig. 262.] The same defect occurs on the tools for cutting internal threads, or threads in holes or bores. In Fig. 262, for example, is shown a tool cutting an internal thread, which tool may be taken to represent one tooth of a tap. Here again the projecting point of the tool is in continuous cutting action, while this, being a single-toothed tool, has no bottom corners to suffer from wear. As a result of the wear upon the tools for cutting internal threads, the thread grooves, when cut to their full widths, will be too shallow in depth, or, more correctly speaking, the full diameter of the thread will be too small to an amount corresponding to twice the amount of wear that the tool point has suffered. In single-pointed tools, such as are used upon lathe work, this has but little significance, because it is the work of but a minute or two to grind up the tool to a full point again, but in taps and solid dies, or in chasers in heads (as in some bolt-cutting machines) it is highly important, because it impairs the fit of the threads, and it is difficult to bring the tools to shape after they are once worn. [Illustration: Fig. 263.] The internal threads for the nuts of bolts are produced by a tap formed as at T in Fig. 263. It consists of a piece of steel having an external thread and longitudinal flutes or grooves which cut the thread into teeth. The end of the thread is tapered off as shown, to enable the end of the tap to enter the hole, and as it is rotated and the nut N held stationary, the teeth cut grooves as the tap winds through, thus forming the thread. [Illustration: Fig. 264.] The threads upon bolts are usually produced either by a head containing chasers or by a solid die such as shown at A in Fig. 264, B representing a bolt being threaded. The bore of A is threaded and fluted to provide cutting teeth, and the threads are chamfered off at the mouth to assist the cutting by spreading it over several teeth, which enables the bolt to enter the die more easily. We may now consider the effect of continued use and its consequent wear upon the threads or teeth of a tap and die or chaser. The wear of the corners at the tops of the thread (as at A B in Fig. 265) of a tap is greater than the wear at the bottom corners at E F, because the tops perform more cutting duty. [Illustration: Fig. 265.] First, the top has a larger circle of rotation than has the bottom, and, therefore, its cutting speed is greater, to an amount equal to the difference between the circumferences of the thread at the top and at the bottom. Secondly, the tops of the teeth of tap perform nearly all the cutting duty, because the thread in the nut is formed by the tops and sides of the tap, which on entering cut a groove which they gradually deepen, until a full thread is formed, while the bottoms of the teeth (supposing the tapping hole to be of proper diameter and not too small) simply meet the bore of the tapping hole as the thread is finished. If, as in the case of hot punched nuts, the nut bore contains scale, this scale is about removed by the time the bottoms of the top teeth come into action, hence the teeth bottoms are less affected by the hardness of the scale. In the case of the teeth on dies and chasers, the wear at the corners C D, in Fig. 266, is the greatest. Now, the tops of the teeth on the tap (A B, in Fig. 265) cut the bottom or full diameter of the thread in the nut, while the tops of the teeth (C D, in Fig. 266) in the die cut the bottom of the thread on the bolt; hence the rounded corners cut on the work by the tops of the teeth in the one case, meet the more square corners left by the tops of the teeth in the other, and providing that under these circumstances the thread in the nut were of equal diameter to that on the bolt the latter would not enter the former. If the bolt were made of a diameter to enable the nut to wind a close fit upon the bolt, the corners only of the threads would fit, as shown in Fig. 267, which represents at N a thread in a portion of a nut and at S a portion of a thread upon a tap or bolt, the two threads being magnified and shown slightly apart for clearness of illustration. The corners A, B of the nut are then cut by the corners A B of the tap in Fig. 265, and the corners C, C, D correspond to those cut by the corners C, D of the die teeth in Fig. 266; corners E, F, Fig. 267, are cut by corners C, D, in Fig. 266, and corners G, H are cut by corners G, H in Fig. 266, and it is obvious that the roundness of the corners A, B, C, and D in Fig. 267 will not permit the tops of the thread on the bolt to meet the bottoms of the thread in the nut, but that the threads will bear at the corners only. [Illustration: Fig. 266.] [Illustration: Fig. 267.] So far, however, we have only considered the wear tending to round off the sharp corners of the teeth, which wear is greater in proportion as the corners are sharp, and less as they are rounded or flattened, and we have to consider the wear as affecting the diameters of the male and female thread at their tops and bottoms respectively. Now, since the tops of the tap teeth wear the most, the diameter of the thread decreases in depth, while, since the tops of the die teeth wear most, the depth of the thread in the die also decreases. The tops of the tap teeth cut the bottom of the thread in the nut and the tops of the die teeth cut the bottoms of the thread upon the bolt. Let it be supposed then that the points of the teeth of a tap have worn off to a depth of the 1-2000th part of an inch, which they will by the time they become sufficiently dulled to require resharpening, and that the teeth of a die have become reduced by wear by the same amount, and the result will be the production of threads such as shown in Fig. 268, in which the diameter of the bolt is supposed to be an inch, and the proper thread depth 1-10th inch. Now, the diameter at the root of the thread on the bolt will be .802 inch in consequence of the wear, but the smallest diameter of the nut thread is .800 inch, and hence too small to admit the male or bolt thread. Again, the full diameter of the bolt thread is 1 inch, whereas the full diameter of the nut thread is but .998 inch, or, again, too small to admit the bolt thread. As a result, it is found in practice that any standard form of thread that makes no allowance for wear, cannot be rigidly adhered to, or if it is adhered to, the tap must be made when new above the standard diameter, causing the thread to be an easy fit, which fit will become closer as the thread-cutting tools wear, until finally it becomes too tight altogether. The fit, however, becomes too tight at the top and bottom, where it is not required, instead of at the sides, where it should occur. When this is the case, the nuts will soon wear loose because of their small amount of bearing area. [Illustration: Fig. 268.] [Illustration: Fig. 269.] It may be pointed out, however, that from the form in which the chasers or solid dies for bolt machines, and also that in which taps are made, the finishing points of the teeth are greatly relieved of cutting duty, as is shown in Figs. 269 and 270. In the die the first two or three threads are chamfered off, while in the tap the thread is tapered off for a length usually equal to about two or three times the diameter for taps to be used by hand, and six or seven times the diameter for taps to be used in a machine. The wear of the die is, therefore, more than that of the tap, because the amount of cutting duty to produce a given length of thread is obviously the same, whether the thread be an internal or an external one, and the die has less cutting edges to perform this duty than the tap has. The main part of the cutting is, it is true, in both cases borne by the beveled surfaces at the top of the chamfered teeth of the cutting tools, but the fact remains that the depth of the thread is finished by the extreme tops of the teeth, and these, therefore, must in time suffer from the consequent wear, while the bottoms of the teeth perform no cutting duty, providing that the hole in the one case and the bolt in the other are of just sufficient diameter to permit of a full thread being formed, as should be the case. In threads cut by chasers the same thing occurs; thus in Fig. 271 is shown at A a chaser having full teeth, as it must have when a full thread is to pass up to a shoulder, as up to the head of a bolt. Here the first tooth takes the whole depth of the cut, but if from wear this point becomes rounded, the next tooth may remedy the defect. When, however, a chaser is to be used upon a thread that terminates in a stem of smaller diameter, as C in Fig. 271, then the chaser may have its teeth bevelled off, as is shown on B. [Illustration: Fig. 270.] The evils thus pointed out as attending the wear of screw-cutting tools for bolts and nuts, may be overcome by a slight variation in the form of the thread. Thus in Fig. 272, at A is shown a form of thread for the tools to cut internal threads, and at B a form of thread for dies to cut external threads. The sides of the thread are in both cases at the same angle, as say, 60°. The depth of the thread, supposing the angle of the sides to meet in a point, is divided off into 11, or any number of equal divisions. For a tap one of these divisions is taken off, forming a flat top, while at the bottom two of these divisions are taken off, or if desirable, 1-1/2 divisions may be taken off, since the exact amount is not of primary importance. On the external thread cutting tool B, as say a solid die, two divisions are taken off at the largest diameter, and one at the smallest diameter, or, if any other proportion be selected for the tap, the same proportion may be selected for the die, so long as the least is taken off the largest diameter of the tap thread, and of the smallest diameter of the die thread. [Illustration: Fig. 271.] The diameter of the tap may still be standard to ring or collar gauge, as in the Franklin Institute thread, the angle at the sides being simply carried in a less distance. In the die the largest diameter of the thread has a flat equal to that on the bottom of the tap, while the smallest diameter has a flat equal to that on the tops of the tap teeth, the width or thickness of the threads remaining the same as in the Franklin Institute thread at each corresponding diameter in its depth. [Illustration: Fig. 272.] The effect is to give to the threads on the work a certain amount of clearance at the top and bottom of the thread, leaving the angles just the same as before, and insuring that the contact shall be at the sides, as shown in Fig. 273. This form of thread retains the valuable features of the Franklin Institute that it can be originated by any one, and that it can be formed with a single-toothed or single-pointed tool. Furthermore, the wear of the threading tools will not impair the diametral fit of the work, while the permissible limit of error in diameter will be increased. By this means great accuracy in the diameters of the threads is rendered unnecessary, and the wear of the screw-cutting tools at their corners is rendered harmless, nor can any confusion occur, because the tools for external threads cannot be employed upon internal ones. The sides only of the thread will fit, and the whole contact and pressure of the fit will be on those sides only. [Illustration: Fig. 273.] This is an important advantage, because if the tops of the thread are from the wear of the dies and taps of too large or small diameter, respectively, the threads cannot fit on the sides. Thus, suppose a bolt thread to be loose at the sides, but to be 1-1000 of an inch larger in diameter than the nut thread, then it cannot be screwed home until that amount has been worn or forced off the thread diameter, or has been bruised down by contact with the nut thread, and it would apparently be a tight fit at the sides. Suppose a thread to have been cut in the lathe to the correct diameter at the bottom of the thread, the sides of the thread being at the correct angle, but let the diameter at the top of the thread (a Franklin Institute thread is here referred to), be 1-1000 too large, then the nut cannot be forced on until that 1-1000 is removed by some means or other, unless the nut thread be deepened to correspond. Now take this last bolt and turn the 1-1000 inch off, and it will fit, turn off another 1-1000 or 1-64 inch, and it will still fit, and the fit will remain so nearly the same with the 1-64 inch off that the difference can scarcely be found. Furthermore, with a nut of a fit requiring a given amount of force to screw it upon the bolt, the area of contact will be much greater when that contact is on the sides than when it is upon the tops and bottoms of the thread, while the contact will be in a direction better to serve as an abutment to the thrust or strain. In very fine pitches of thread such as are used in the manufacture of watches, this plan of easing or keeping free the extremities of the thread is found to be essential, and there appears every probability that its adoption would obviate the necessity of using check nuts. It has been observed that the threads upon tools alter in pitch from the hardening operation, and this is an objection to the employment of chasers cut from hobs. Suppose, for instance, that a nut is produced having a thread of true and uniform pitch, then after hardening, the pitch may be no longer correct. The chasers cut from the hob will contain the error of pitch existing in the hob, and upon being hardened may have added to it errors of its own. If this chaser be used to produce a new hob, the latter will contain the errors in the chaser added to whatever error it may itself obtain in the hardening. The errors may not, it is true, all exist in one direction, and those of one hardening may affect or correct those caused by another hardening, but this is not necessarily the case, and it is therefore preferable to employ a form of thread that can be cut by a tool ground to correct shape after having been hardened, as is the case with the [V]-thread and the United States standard. [Illustration: Fig. 274.] It is obvious that in originating either the sharp [V] or the United States standard thread, the first requisite is to obtain a correct angle of 60°, which has been done in a very ingenious manner by Mr. J. H. Heyer for the Pratt and Whitney Company, the method being as follows. Fig. 274 is a face and an end view of an equilateral triangle employed as a guide in making standard triangles, and constructed as follows:--Three bars, A, A, A, of steel were made parallel and of exactly equal dimensions. Holes X were then pierced central in the width of each bar and the same distance apart in each bar; the method of insuring accuracy in this respect being shown in Figs. 275 and 276, in which S represents the live spindle of a lathe with its face-plate on and a plug, C, fitted into the live centre hole. The end of this plug is turned cylindrically true, and upon it is closely fitted a bush, the plug obviously holding the bush true by its hole. A rectangular piece _e_ is provided with a slot closely fitting to the bush. The rectangular piece _e_ is then bolted to the lathe face-plate and pierced with a hole, which from this method of chucking will be exactly central to its slot, and at a right angle to its base. The bush is now dispensed with and the piece _e_ is chucked with its base against the face-plate and the hole pierced as above, closely fitting to the pin on the end of the plug _c_, which, therefore, holds _e_ true. [Illustration: Fig. 275.] The bars A are then chucked one at a time in the piece _e_ (the outer end resting upon a parallel piece _f_), and a hole is pierced near one end, this hole being from this method of chucking exactly central to the width of the bar A, and at a right angle to its face. [Illustration: Fig. 276.] The parallel piece _f_ is then provided with a pin closely fitting the hole thus pierced in the bar. The bars were turned end for end with the hole enveloping the pin in _f_ (the latter being firmly fixed to the face-plate), and the other end laid in the slot in _e_, while the second hole was pierced. The holes (X, Fig. 274) must be, from this method of chucking, exactly an equal distance apart on each bar. The bars were then let together at their ends, each being cut half-way through and closely fitting pins inserted in the holes X, thus producing an equilateral triangle entirely by machine work, and therefore as correct as it can possibly be made, and this triangle is kept as a standard gauge whereby others for shop use may be made by the following process:-- Into the interior walls of this triangle there is fitted a cylindrical bush B, it being obvious that this bush is held axially true or central to the triangle, and it is secured in place by screws _y_, _y_, _y_, passing through its flange and into bars A. At one end of the bush B, is a cylindrical part D, whose diameter is 2 inches or equal to the length of one side of an equilateral triangle circumscribed about a circle whose diameter is 1.1547 inches, as shown in Fig. 278 and through this bush B passes a pin P, having a nut N. A small triangle is then roughed out, and its bore fitting to the stem of pin P, and by means of nut N, the small triangle is gripped between the under face of D and the head of P. The large triangle is then held to an angle-plate upon a machine while resting upon the machine-table, and the uppermost edge of the small triangle is dressed down level with the cylindrical stem D, which thus serves as a gauge to determine how much to take off each edge of the small triangle to bring it to correct dimensions. The truth of the angles of the small triangle depends, of course, also upon the large one; thus with face H resting upon the machine-table, face G is cut down level with stem D; with face F upon the table, face E is cut down level with D; and with face L upon the table, face K is dressed down level with D. And we have a true equilateral triangle produced by a very ingenious system of chuckings, each of which may be known to be true. The next operation is to cut upon the small triangle the flat representing the top and bottom of the United States standard thread, which is done by cutting off one-eighth part of its vertical height, and it then becomes a test piece or standard gauge of the form of thread. The next step is to provide a micrometer by means of which tools for various pitches may be tested both for angle and for width of flat, and this is accomplished as follows:-- [Illustration: _VOL. I_ =MEASURING AND GAUGING SCREW THREADS.= _PLATE III._ Fig. 279. Fig. 280. Fig. 281. Fig. 282. Fig. 285. Fig. 286. Fig. 283. Fig. 284. Fig. 287.] In Fig. 278 F is a jaw fixed by a set screw to the bar of the micrometer, and E is a sliding jaw; these two jaws being fitted to the edges of the triangle or test piece T in the figure which has been made as already described. To the sliding jaw E is attached the micrometer screw C, which has a pitch of 40 threads per inch; the drum A upon the screw has its circumference divided into 250 equidistant divisions, hence if the drum be moved through a space equal to one of these divisions the sliding jaw E will be moved the 1-250th part of 1-40th of an inch, or in other words the 1-10,000th of an inch. To properly adjust the position of the zero piece or pointer, the test piece T is placed in the position shown in Fig. 278, and when the jaws were so adjusted that light was excluded from the three edges of the test piece, the pointer R, Fig. 277, was set opposite to the zero mark on the drum and fastened. [Illustration: Fig. 277.] To set the instrument for any required pitch of thread of the United States standard form the micrometer is used to move the sliding jaw E away from the fixed jaw F to an amount equal to the width of flat upon the top and bottom, of the required thread, while for the sharp [V]-thread the jaws are simply closed. The gauge being set the tool is ground to the gauge. [Illustration: Fig. 278.] Referring to the third requirement, that the tools shall in the case of lathe work be easily sharpened and set to correct position in the lathe, it will be treated in connection with cutting screws in the lathe. Referring to the fourth requirement, that a minimum of measuring and gauging shall be required to test the diameter and form of thread, it is to be observed that in a Whitworth thread the angle and depth of the thread is determined by the chaser, which may be constantly ground to resharpen without altering the angles or depth of the thread, hence in cutting the tooth the full diameter of the thread is all that needs to be gauged or measured. In cutting a sharp [V]-thread, however, the thread top is apt to project (from the action of the single-pointed tool) slightly above the natural diameter of the work, producing a feather edge which it becomes necessary to file off to gauge the full diameter of the thread. In originating a sharp [V]-thread it is necessary first to grind the tool to correct angle; second, to set it at the correct height in the latter, and with the tool angles at the proper angle with the work (as is explained with reference to thread cutting in the lathe) and to gauge the thread to the proper diameter. In the absence of a standard cylindrical gauge or piece to measure from, a sheet metal gauge, such as in Fig. 279, may be applied to the thread; such gauges are, however, difficult to correctly produce. So far as the diameter of a thread is concerned it may be measured by calipers applied between the threads as in Figs. 280 and 281, a plan that is commonly practised in the workshop when there is at hand a standard thread or gauge known to be of proper diameter; and this method of measuring may be used upon any form of thread, but if it is required to test the form of the thread, as may occur when its form depends upon the workman's accuracy in producing the single-pointed threading tools, then, in the case of the United States standard thread, the top, the bottom, and the angle must be tested. The top of the thread may (for all threads) be readily measured, but the bottom is quite difficult to measure unless there is some standard to refer it to, to obtain its proper diameter, because the gauge or calipers applied to the bottom of the thread do not stand at a right angle to the axis of the bolt on which the thread is cut, but at an angle equal to the pitch of the thread, as shown in Fig. 282. Now, the same pitch of thread is necessarily used in mechanical manipulation upon work of widely varying diameters, and as the angle of the calipers upon the same pitch of thread would vary (decreasing as the diameter of the thread increases), the diameter measured at the bottom of the thread would bear a constantly varying proportion to the diameter measured across the tops of the thread at a right angle to the axial line of the work. Thus in Fig. 282, A A is the axial line of two threaded pieces, B, C. D, D represents a gauge applied to B, its width covering the tops of two threads and measuring the diameter at a right angle to A A, as denoted by the dotted line E. The dotted line F represents the measurement at the bottom of the thread standing at an angle to E equal to half the pitch. The dotted line G is the measurement of C at the bottom of the thread. Now suppose the diameter of B to be 1-1/2 inches at the top of the thread, and 1-1/8 inches at the bottom, while C is 1-1/8 inches on the top and 3/4 at the bottom of the thread, the pitches of the two threads being 1/4 inch; then the angle of F to E will be 1/8 inch (half the pitch) in its length of 1-1/8 inches. The angle of G to E will be 1/8 inch (half the pitch) in 3/4 (the diameter at the bottom or root of the thread). It is obvious, then, that it is impracticable to gauge threads from their diameters at the bottom, or root. On account of the minute exactitude necessary to produce with lathe tools threads of the sharp [V] and United States standard forms, the Pratt and Whitney Company manufacture thread-cutting tools which are made under a special system insuring accuracy, and provide standard gauges whereby the finished threads may be tested, and since these tools are more directly connected with the subject of lathe tools than with that of screw thread, they are illustrated in connection with such tools. It is upon the sides of threads that the contact should exist to make a fit, and the best method of testing the fit of a male and female thread is to try them together, winding them back and forth until the bright marks of contact show. Giving the male thread a faint tint of paint made of Venetian red mixed with lubricating oil, will cause the bearing of the threads to show very plainly. Figs. 283 and 284 represent standard reference gauges for the United States standard thread. Fig. 283 is the plug or male gauge. The top of the thread has, it will be observed, the standard flat, while the bottom of the thread is sharp. In the collar, or female gauge, or the template, as it may be termed, a side and a top view of which are shown in Fig. 284, and a sectional end view in Fig. 285, the flat is made on the smallest diameter of the thread, while the largest diameter is left sharp; hence, if we put the two together they will appear as in Fig. 286, there being clearance at both the tops and bottoms of the threads. This enables the diameters of the threads to be in both cases tested by standard cylindrical gauges, while it facilitates the making of the screw gauges. The male or plug gauge is made with a plain part, A, whose diameter is the standard size for the bottoms of the threads measured at a right angle to the axis of the gauge and taking the flats into account. The female gauge or template is constructed as follows:--A rectangular piece of steel is pierced with a plain hole at B, and a standard thread hole at A, and is split through at C. At D is a pin to prevent the two jaws from springing, this being an important element of the construction. E is a screw threaded through one jaw and abutting against the face of the other, while at F is another screw passing through one jaw and threaded into the other, and it is evident that while by operating these two screws the size of the gauge bore A may be adjusted, yet the screws will not move and destroy the adjustment, because the pressure of one acts as a lock to the other. It is obvious that in adjusting the female gauge to size, the thread of the male gauge may be used as a standard to set it by. To produce sheet metal templates such as was shown in Fig. 279, the following method may be employed, it being assumed that we have a threading tool correctly formed. [Illustration: Fig. 288.] [Illustration: Fig. 289.] Suppose it is required to make a gauge for a pitch of 6 per inch, then a piece of iron of any diameter may be put in the lathe and turned up to the required diameter for the top of the thread. The end of this piece should be turned up to the proper diameter for the bottom of the thread, as at G, in Fig. 287. Now, it will be seen that the angle of the thread to the axis A of the iron is that of line C to line A, and if we require to find the angle the thread passes through in once winding around the bolt, we proceed as in Fig. 288, in which D represents the circumference of the thread measured at a right angle to the bolt axis, as denoted by the line B in Fig. 287. F, Fig. 288 (at a right angle to D), is the pitch of the thread, and line C therefore represents the angle of the thread to the bolt axis, and corresponds to line C in Fig. 287. We now take a piece of iron whose length when turned true will equal its finished and threaded circumference, and after truing it up and leaving it a little above its required finished diameter, we put a pointed tool in the slide-rest and mark a line A A in Fig. 289, which will represent its axis. At one end of this line we mark off below A A the pitch of the thread, and then draw the line H J, its end H falling below A to an amount equal to the pitch of the thread to be cut. The piece is then put in a milling machine and a groove is cut along H J, this groove being to receive a tightly-fitting piece of sheet metal of which a thread gauge is to be made. This piece of sheet metal must be firmly secured in the groove by set-screws. The piece of iron is then again put in the lathe and its diameter finished to that of the required diameter of thread. Its two ends are then turned down to the required diameter for the bottom of the thread, leaving in the middle a section on which a full thread can be cut, as in Fig. 290, in which F F represents the sheet metal for the gauge. After the thread is cut, as in Fig. 290, we take out the gauge and it will appear as in Fig. 291, and all that is necessary is to file off the two outside teeth if only one tooth is wanted. [Illustration: Fig. 290.] The philosophy of this process is that we have set the gauge at an angle of 90°, or a right angle to the thread, as is shown in Fig. 289, the line C representing the angle of the thread to the axis A A, and therefore corresponding to the line C in Fig. 287. A gauge made in this way will serve as a test of its own correctness for the following reasons: Taking the middle tooth in Fig. 291, it is clear that one of its sides was cut by one angle and the other by the other angle of the tool that cut it, and as a correctly formed thread is of exactly the same shape as the space between two threads, it follows that if the gauge be applied to any part of the thread that was cut in forming it, and if it fits properly when tried, and then turned end for end and tried again, it is proof that the gauge and the thread are both correct. Suppose, for example, that the tool was correct in its shape, but was not set with its two angles equal to the line of lathe centres, and in that case the two sides of the thread will not be alike and the gauge will not reverse end for end and in both cases fit to the thread. Or suppose the flat on the tool point was too narrow, and the flat at the bottom of the thread will not be like that at the top, and the gauge will show it. [Illustration: Fig. 291.] Referring to the fifth requirement, that the angles of the sides of the threads shall be as acute as is consistent with the required strength, it is obvious that the more acute the angles of the sides of the thread one to the other the finer the pitch and the weaker the thread, but on the other hand, the more acute the angle the better the sides of the thread will conform one to the other. The importance of this arises from the fact that on account of the alteration of pitch, already explained, as accompanying the hardening of screw-cutting tools, the sides of threads cut even by unworn tools rarely have full contact, and a nut that is a tight fit on its first passage down its bolt may generally be caused to become quite easy by running it up and down the bolt a few times. Nuts that require a severe wrench force to wind them on the bolt, may, even though they be as large as a two-inch bolt, often be made to pass easily by hand, if while upon the bolt they are hammered on their sides with a hand hammer. The action is in both cases to cause the sides of the thread to conform one to the other, which they will the more readily do in proportion as their sides are more acute. Furthermore, the more acute the angles the less the importance of gauging the threads to precise diameter, especially if the tops and bottoms of the male and female thread are clear of one another, as in Fig. 273. Referring to the sixth requirement, that the nut shall not be unduly liable to become loose of itself in cases where it may require to be fastened and loosened occasionally, it may be observed, that in such cases the threads are apt from the wear to become a loose fit, and the nuts, if under jar or vibration, are apt to turn back of themselves upon the bolt. This is best obviated by insuring a full bearing upon the whole area of the sides of the thread, and by the employment of as fine pitches as is consistent with sufficient strength, since the finer the pitch the nearer the thread stands at right angle to the bolt axis, and the less the tendency to unscrew from the pressure on the nut face. The pitches, diameters, and widths of flat of the United States standard thread are as per the following table:-- UNITED STATES STANDARD SCREW THREADS. +-------------+-----------+-----------------+----------+ | Diameter of | Threads | Diameter at | Width of | | Screw. | per inch. | root of Thread. | Flat. | +-------------+-----------+-----------------+----------+ | 1/4 | 20 | .1850 | .0063 | | 5/16 | 18 | .2403 | .0069 | | 3/8 | 16 | .2938 | .0078 | | 7/16 | 14 | .3447 | .0089 | | 1/2 | 13 | .4001 | .0096 | | 9/16 | 12 | .4542 | .0104 | | 5/8 | 11 | .5069 | .0114 | | 3/4 | 10 | .6201 | .0125 | | 7/8 | 9 | .7307 | .0139 | | | | | | | 1 | 8 | .8376 | .0156 | | 1-1/8 | 7 | .9394 | .0179 | | 1-1/4 | 7 | 1.0644 | .0179 | | 1-3/8 | 6 | 1.1585 | .0208 | | 1-1/2 | 6 | 1.2835 | .0208 | | 1-5/8 | 5-1/2 | 1.3888 | .0227 | | 1-3/4 | 5 | 1.4902 | .0250 | | 1-7/8 | 5 | 1.6152 | .0250 | | 2 | 4-1/2 | 1.7113 | .0278 | +-------------+-----------+-----------------+----------+ The standard pitches for the sharp [V]-thread are as follows:-- SIZE OF BOLT. ---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--- 1/4| 5/|3/8| 7/|1/2|5/8|3/4|7/8| 1 | 1-| 1-| 1-| 1-| 1-| 1-| 1-| 2 | 16| | 16| | | | | |1/8|1/4|3/8|1/2|5/8|3/4|7/8| ---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--- NUMBER OF THREADS TO INCH. ---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--- 20| 18| 16| 14| 12| 11| 10| 9 | 8 | 7 | 7 | 6 | 6 | 5 | 5 | 4-| 4- | | | | | | | | | | | | | | |1/2|1/2 ---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--- The following table gives the threads per inch, pitches and diameters at root of thread of the Whitworth thread. The table being arranged from the diameter of the screw as a basis. +----------+---------+--------+----------------+ | Diameter | Threads | | Diameter at | | of | per | Pitch. | Root or Bottom | | Screw. | Inch. | | of Thread. | +----------+---------+--------+----------------+ | | | Inch. | Inch. | | 1/8 | 40 | .025 | .0929 | | 3/16 | 24 | .041 | .1341 | | 1/4 | 20 | .050 | .1859 | | 5/16 | 18 | .056 | .2413 | | 3/8 | 16 | .063 | .2949 | | 7/16 | 14 | .071 | .346 | | 1/2 | 12 | .083 | .3932 | | 9/16 | 12 | .083 | .4557 | | 5/8 | 11 | .091 | .5085 | | 11/16 | 11 | .095 | .571 | | 3/4 | 10 | .100 | .6219 | | 13/16 | 10 | .100 | .6844 | | 7/8 | 9 | .111 | .7327 | | 15/16 | 9 | .111 | .7952 | | 1 | 8 | .125 | .8399 | | 1-1/8 | 7 | .143 | .942 | | 1-1/4 | 7 | .143 | 1.067 | | 1-3/8 | 6 | .167 | 1.1615 | | 1-1/2 | 6 | .167 | 1.2865 | | 1-5/8 | 5 | .200 | 1.3688 | | 1-3/4 | 5 | .200 | 1.4938 | | 1-7/8 | 4-1/2 | .222 | 1.5904 | | 2 | 4-1/2 | .222 | 1.7154 | | 2-1/8 | 4-1/2 | .222 | 1.8404 | | 2-1/4 | 4 | .250 | 1.9298 | | 2-3/8 | 4 | .250 | 2.0548 | | 2-1/2 | 4 | .250 | 2.1798 | | 2-5/8 | 4 | .250 | 2.3048 | | 2-3/4 | 3-1/2 | .286 | 2.384 | | 2-7/8 | 3-1/2 | .286 | 2.509 | | 3 | 3-1/2 | .286 | 2.634 | | 3-1/4 | 3-1/4 | .308 | 2.884 | | 3-1/2 | 3-1/4 | .308 | 3.106 | | 3-3/4 | 3 | .333 | 3.356 | | 4 | 3 | .333 | 3.574 | | 4-1/4 | 2-7/8 | .348 | 3.824 | | 4-1/2 | 2-7/8 | .348 | 4.055 | | 4-3/4 | 2-3/4 | .364 | 4.305 | | 5 | 2-3/4 | .364 | 4.534 | | 5-1/4 | 2-5/8 | .381 | 4.764 | | 5-1/2 | 2-5/8 | .381 | 5.014 | | 5-3/4 | 2-1/2 | .400 | 5.238 | | 6 | 2-1/2 | .400 | 5.488 | +----------+---------+--------+----------------+ The standard degree of taper, both for the taps and the dies, is 1/16 inch per inch, or 3/4 inch per foot, for all sizes up to 10-inch bore. The sockets or couplings, however, are ordinarily tapped parallel and stretched to fit the pipe taper when forced on the pipe. For bores of pipe over 10 inches diameter the taper is reduced to 3/8 inch per foot. The pipes or casings for oil wells are given a taper of 3/8 inch per foot, and their couplings are tapped taper from both ends. There is, however, just enough difference made between the taper of the socket and that of the pipe to give the pipe threads a bearing at the pipe end first when tried with red marking, the threads increasing their bearing as the pieces are screwed together. The United States standard thread for steam, gas and water pipe is given below, which is taken from the Report of the Committee on Standard Pipe and Pipe Threads of The American Society of Mechanical Engineers, submitted at the 8th Annual Meeting held in New York, November-December, 1886. "A longitudinal section of the tapering tube end, with the screw-thread as actually formed, is shown full size in Fig. 291_a_ for a nominal 2-1/2 inch tube, that is, a tube of about 2-1/2 inches internal diameter, and 2-7/8 inches actual external diameter. [Illustration: Fig. 291_a_.] "The thread employed has an angle of 60°; it is slightly rounded off both at the top and at the bottom, so that the height or depth of the thread, instead of being exactly equal to the pitch, is only four fifths of the pitch, or equal to 0.8 × 1/_n_ if _n_ be the number of threads per inch. For the length of tube end throughout which the screw thread continues perfect, the empirical formula used is (0.8_D_ + 4.8) × 1/_n_, where _D_ is the actual external diameter of the tube throughout its parallel length, and is expressed in inches. Further back, beyond the perfect threads, come two having the same taper at the bottom, but imperfect at the top. The remaining imperfect portion of the screw thread, furthest back from the extremity of the tube, is not essential in any way to this system of joint; and its imperfection is simply incidental to the process of cutting the thread at a single operation. The standard thicknesses of the pipes and pitches of thread are as follows:-- STANDARD DIMENSIONS OF WROUGHT IRON WELDED TUBES. +-----------------------------+-----------+--------------------+ | DIAMETER OF TUBE. | | SCREWED ENDS. | +---------+---------+---------+ THICKNESS +----------+---------+ | Nominal | Actual | Actual | OF | Number |Length of| | Inside. | Inside. | Outside.| METAL. |of Threads| Perfect | | | | | |per Inch. | Screw. | +---------+---------+---------+-----------+----------+---------+ | Inches. | Inches. | Inches. | Inch. | No. | Inch. | | 1/8 | 0.270 | 0.405 | 0.068 | 27 | 0.19 | | 1/4 | 0.364 | 0.540 | 0.088 | 18 | 0.29 | | 3/8 | 0.494 | 0.675 | 0.091 | 18 | 0.30 | | 1/2 | 0.623 | 0.840 | 0.109 | 14 | 0.39 | | 3/4 | 0.824 | 1.050 | 0.113 | 14 | 0.40 | | 1 | 1.048 | 1.315 | 0.134 | 11-1/2 | 0.51 | | 1-1/4 | 1.380 | 1.660 | 0.140 | 11-1/2 | 0.54 | | 1-1/2 | 1.610 | 1.900 | 0.145 | 11-1/2 | 0.55 | | 2 | 2.067 | 2.375 | 0.154 | 11-1/2 | 0.58 | | 2-1/2 | 2.468 | 2.875 | 0.204 | 8 | 0.89 | | 3 | 3.067 | 3.500 | 0.217 | 8 | 0.95 | | 3-1/2 | 3.548 | 4.000 | 0.226 | 8 | 1.00 | | 4 | 4.026 | 4.500 | 0.237 | 8 | 1.05 | | 4-1/2 | 4.508 | 5.000 | 0.246 | 8 | 1.10 | | 5 | 5.045 | 5.563 | 0.259 | 8 | 1.16 | | 6 | 6.065 | 6.625 | 0.280 | 8 | 1.26 | | 7 | 7.023 | 7.625 | 0.301 | 8 | 1.36 | | 8 | 8.982 | 8.625 | 0.322 | 8 | 1.46 | | 9 | 9.000 | 9.688 | 0.344 | 8 | 1.57 | | 10 | 10.019 | 10.750 | 0.366 | 8 | 1.68 | +---------+---------+---------+-----------+----------+---------+ The taper of the threads is 1/16 inch in diameter for each inch of length or 3/4 inch per foot. WHITWORTH'S SCREW THREADS FOR GAS, WATER, AND HYDRAULIC IRON PIPING. NOTE.--The Internal and External diameters of Pipes, as given below, are those adopted by the firm of Messrs. JAMES RUSSELL & SONS, in Pipes of their manufacture. +---------------------------------------+ | GAS AND WATER PIPING. | +-------------+-------------+-----------+ | Internal | External | No. of | | Diameter of | Diameter of | Threads | | Pipe. | Pipe. | per Inch. | +-------------+-------------+-----------+ | 1/8 | .385 | 28 | | 1/4 | .520 | 19 | | 3/8 | .665 | 19 | | 1/2 | .822 | 14 | | 3/4 | 1.034 | 14 | | 1 | 1.302 } | | | 1-1/8 | 1.492 } | | | 1-1/4 | 1.650 } | | | 1-3/8 | 1.745 } | | | 1-1/2 | 1.882 } | | | 1-5/8 | 2.021 } | | | 1-3/4 | 2.047 } | | | 1-7/8 | 2.245 } | | | 2 | 2.347 } | | | 2-1/8 | 2.467 } | | | 2-1/4 | 2.587 } | 11 | | 2-3/8 | 2.794 } | | | 2-1/2 | 3.001 } | | | 2-5/8 | 3.124 } | | | 2-3/4 | 3.247 } | | | 2-7/8 | 3.367 } | | | 3 | 3.485 } | | | 3-1/4 | 3.698 } | | | 3-1/2 | 3.912 } | | | 3-3/4 | 4.125 } | | | 4 | 4.339 } | | +-------------+-------------+-----------+ +----------------------------------------------------+ | HYDRAULIC PIPING. | +----------+----------+------------------+-----------+ | Internal | External | Pressure in lbs. | No. of | | Diameter | Diameter | per Square | Threads | | of Pipe. | of Pipe. | Inch. | per Inch. | +----------+----------+------------------+-----------+ | | { 5/8 | 4,000} | | | 1/4 | { 3/4 | 6,000} | 14 | | | { 7/8 | 8,000} | | | | {1 | 10,000} | | | | | | | | | { 3/4 | 4,000} | | | 3/8 | { 7/8 | 6,000} | 14 | | | {1 | 8,000} | | | | {1-1/8 | 10,000} | | | | | | | | | {1 | 4,000} | 14 | | 1/2 | {1-1/8 | 6,000} | | | | {1-1/4 | 8,000 } | 11 | | | {1-3/8 | 10,000 } | | | | | | | | | {1-1/8 | 4,000 | 14 | | 5/8 | {1-1/4 | 6,000} | | | | {1-3/8 | 8,000} | 11 | | | {1-1/2 | 10,000} | | | | | | | | | {1-1/4 | 4,000} | | | 3/4 | {1-3/8 | 6,000} | 11 | | | {1-1/2 | 8,000} | | | | {1-5/8 | 10,000} | | | | | | | | | {1-3/8 | 4,000} | | | 7/8 | {1-1/2 | 6,000} | 11 | | | {1-5/8 | 8,000} | | | | {1-3/4 | 10,000} | | | | | | | | | {1-1/2 | 4,000} | | | 1 | {1-5/8 | 6,000} | 11 | | | {1-3/4 | 8,000} | | | | {1-7/8 | 10,000} | | | | | | | | | {1-5/8 | 4,000} | | | 1-1/8 | {1-3/4 | 6,000} | 11 | | | {1-7/8 | 8,000} | | | | {2 | 10,000} | | | | | | | | | {1-3/4 | 4,000} | | | 1-1/4 | {1-7/8 | 6,000} | 11 | | | {2 | 8,000} | | | | {2-1/8 | 10,000} | | | | | | | | | {1-7/8 | 4,000} | | | 1-3/8 | {2 | 6,000} | 11 | | | {2-1/8 | 8,000} | | | | {2-1/4 | 10,000} | | | | | | | | | {2 | 4,000} | | | | {2-1/8 | 6,000} | | | 1-1/2 | {2-1/4 | 8,000} | 11 | | | {2-3/8 | 10,000} | | | | {2-1/2 | 10,000} | | | | | | | | | {2-1/8 | 4,000} | | | 1-5/8 | {2-1/4 | 6,000} | 11 | | | {2-3/8 | 8,000} | | | | {2-1/2 | 10,000} | | | | | | | | | {2-1/4 | 3,000} | | | | {2-3/8 | 4,000} | | | 1-3/4 | {2-1/2 | 6,000} | 11 | | | {2-5/8 | 8,000} | | | | {2-3/4 | 10,000} | | | | | | | | | {2-3/8 | 3,000} | | | | {2-1/2 | 4,000} | | | 1-7/8 | {2-5/8 | 6,000} | 11 | | | {2-3/4 | 8,000} | | | | {2-7/8 | 10,000} | | | | | | | | | {2-1/2 | 3,000} | | | | {2-5/8 | 4,000} | | | 2 | {2-3/4 | 6,000} | 11 | | | {2-7/8 | 8,000} | | | | {3 | 10,000} | | +----------+----------+------------------+-----------+ The English pipe thread is a sharp [V]-thread having its sides at an angle of 60°, and therefore corresponds to the American pipe thread except that the pitches are different. The standard screw thread of The Royal Microscopical Society of London, England, is employed for microscope objectives, and the nose pieces of the microscope into which these objectives screw. The thread is a Whitworth one, the original standard threading tools now in the cabinet of the society having been made especially for the society by Sir Joseph Whitworth. The pitch of the thread is 36 per inch. The cylinder, or male gauge, is .7626 inch in diameter. The following table gives the Whitworth standard of thread pitches and diameters for watch and mathematical instrument makers. WHITWORTH'S STANDARD GAUGES FOR WATCH AND INSTRUMENT MAKERS, WITH SCREW THREADS FOR THE VARIOUS SIZES, 1881. +---------------------+-------------+-------------+ | No. of each | Size in | Number of | | size in thousandths | decimals of | Threads per | | of an inch. | an inch. | inch. | +---------------------+-------------+-------------+ | 10 | .010 | 400 | | 11 | .011 | " | | 12 | .012 | 350 | | 13 | .013 | " | | 14 | .014 | 300 | | 15 | .015 | " | | 16 | .016 | " | | 17 | .017 | 250 | | 18 | .018 | " | | 19 | .019 | " | | 20 | .020 | 210 | | 22 | .022 | " | | 24 | .024 | " | | 26 | .026 | 180 | | 28 | .028 | " | | 30 | .030 | " | | 32 | .032 | 150 | | 34 | .034 | " | | 36 | .036 | " | | 38 | .038 | 120 | | 40 | .040 | " | | 45 | .045 | " | | 50 | .050 | 100 | | 55 | .055 | " | | 60 | .060 | " | | 65 | .065 | 80 | | 70 | .070 | " | | 75 | .075 | " | | 80 | .080 | 60 | | 85 | .085 | " | | 90 | .090 | " | | 95 | .095 | " | | 100 | .100 | 50 | +---------------------+-------------+-------------+ For the pitches of the threads of lag screws there is no standard, but the following pitches are largely used. +-----------+-----------+ |Diameter of| Threads | | Screw. | per Inch. | +-----------+-----------+ | Inch. | | | 1/4 | 10 | | 5/16 | 9 | | 3/8 | 8 | | 7/16 | 7 | | 1/2 | 6 | | 9/16 | 6 | | 5/8 | 5 | | 11/16 | 5 | | 3/4 | 5 | | 7/8 | 4 | | 1 | 4 | +-----------+-----------+ SCREW-CUTTING HAND TOOLS. For cutting external or male threads by hand three classes of tools are employed. The first is the screw plate shown in Fig. 292. It consists of a hardened steel plate containing holes of varying diameters and threaded with screw threads of different pitches. These holes are provided with two diametrically opposite notches or slots so as to form cutting edges. [Illustration: Fig. 292.] This tool is placed upon the end of the work and slowly rotated while under a hand pressure tending to force it upon the work, the teeth cutting grooves to form the thread and advancing along the bolt at a rate determined by the pitch of the thread. The screw plate is suitable for the softer metals and upon diameters of 1/8 inch and less, in which the cutting duty is light; hence the holes do not so rapidly wear larger. The second class consists of a stock and dies such as shown in Fig. 293. For each stock there are provided a set of dies having different diameters and pitches of thread. In this class of tool the dies are opened out and placed upon the bolt. The set screw is tightened up, forcing the dies to their cut, and the stock is slowly rotated and a traverse taken down the work. [Illustration: Fig. 293.] In some cases the dies are then again forced to the work by the set screw, and a cut taken by winding the stocks up the bolt, the operation being continued until the thread is fully developed and cut to the required diameter. In other cases the cut is carried down the bolt, only the dies being wound back to the top of the bolt after each cut is carried down. The difference between these two operations will be shown presently. [Illustration: Fig. 294.] The thread in dies which take successive cuts to form a thread may be left full clear through the die, and will thus cut a full thread close up to the head collar or shoulder of the work. It is usual, however, to chamfer off the half threads at the ends of the dies, because if left of their full _height_ they are apt to break off when in use. It is sometimes the practice, however, to chamfer off the first two threads on one side of the dies, leaving the teeth on the other side full, and to use the chamfered as the leading side in all cases in which the thread on the work does not require to be cut up to a shoulder, but turning the dies over with the full threaded teeth as the leading ones when the thread _does_ require to be carried up to a head or shoulder on the work. To facilitate the insertion and extraction of the dies in and from their places in the stock, the Morse Twist Drill Co. employ the following construction. In Figs. 294 and 295 the pieces A, A´ which hold the dies are pivoted in the stock at B, so as to swing outward as in Fig. 295, and receive the dies which are slotted to fit them. These pieces are then swung into position in the stock. The lower die is provided with a hole to fit the pin C, hence when that die is placed home C acts as a detaining piece locking the pieces A, A´ through the medium of the bottom die. [Illustration: Fig. 295.] [Illustration: Fig. 296.] In other dies of this class the two side pieces or levers which hold the dies are pivoted at the corner of the angle, as in Fig. 296. In the bottom of the stock is a sliding piece beveled at its top and meeting the bottom face of the levers; hence, by pressing this piece inwards the side pieces recede into a slot provided in the stock, and leave the opening free for the dies to pass into their places, when the pin is released and a spring brings the side pieces back. Now, since the bottom die rests upon the bottom angle of the side pieces the pressure of the set screw closes the side pieces to the dies holding them firmly. [Illustration: Fig. 297.] In Fig. 297 is shown Whitworth's stocks and dies, the cap that holds the guide die _a_ and the two chasers _b_, _c_ in their seats or recesses in the stock being removed to expose the interior parts. The ends of the chasers _b_, _c_ are beveled and abut against correspondingly beveled recesses in the key _d_, so that by operating the nut _e_ on the end of the key the dies are caused to move longitudinally. The principles of action are more clearly shown in Fig. 298. The two cutting chasers B and C move in lines that would meet at D, and therefore at a point behind the centre or axis of the bolt being threaded; this has the effect of preserving their clearance. It is obvious, for example, that when these chasers cut a thread on the work it will move over toward guide A on account of the thread on the work sinking into the threads on A, and this motion would prevent the chasers B, C from cutting if they moved in a line pointing to the centre of the work. This is more clearly shown in Fig. 299, in which the guide die A and one of the cutting dies or chasers B is shown removed from the stock, while the bolt to be threaded is shown in two positions--one when the first cut is taken, and the other when the thread is finished. For the first cut the centre of the work is at E, for the last one it is at G, and this movement would, were the line of motion as denoted by the dotted lines, prevent the chaser from cutting, because, while the line of chaser motion would remain at J, pointing to the centre of work for the first cut, it would require a line at K to point to that centre for the last one; hence, when considered with relation to the work, the line of chaser motion has been moved forward, presenting the cutting edges at an angle that would prevent their cutting. By having their motion as shown in Fig. 299, however, the clearance of the chasers is preserved. [Illustration: Fig. 298.] [Illustration: Fig. 299.] [Illustration: Fig. 300.] Referring now to the die A, it acts as a guide rather than as a cutting chaser, because it has virtually no clearance and cannot cut so freely as B and C; hence it offers a resistance to the moving of the bolt, or of the dies upon the bolt, in a lateral direction when the chaser teeth meet either a projection or a depression upon the work. The guide principle is, however, much more fully carried out in a design by Bodmer, which is shown in Fig. 300. Here there is but one cutting chaser C, the bush G being a guide let into a recess in the stock and secured thereon by a pin _p_. The chaser is set in a stock, D also let into a recess in the stock, and this recess, being circular, permits of stock D swinging. At S are two set-screws, which are employed to limit the amount of motion permitted to D. the handle E screws through D, and acts upon the edge of chaser C to put on the cut. The action of the tool is shown in Fig. 301, where it is shown upon a piece of work. Pulling the handle E causes D to swing in the stock, thus giving the chaser clearance, as shown. When the cut is carried down, a new cut may be put on by means of E, and on winding the stock in the opposite direction, D will swing in its seat, and cant or tilt the chaser in the opposite direction, giving it the necessary clearance to enable it to cut on the upward or back traverse. Another point of advantage is that the cutting edges are not rubbed by the work during the back stroke, and their sharpness is, therefore, greatly preserved. A die of this kind will produce work almost as true as the lathe, and, in the case of long, slender work, more true than the lathe; but it is obvious that, on account of the friction caused by the pressure of the work to the guide G, the tool will require more power to operate than the ordinary stock and die or the solid die. [Illustration: Fig. 301.] In adjustable dies which require to take more than one cut along the bolt to produce a fully developed thread, there is always a certain amount of friction between the sides of the thread in the die and the grooves being cut, because the angle of the thread at the top of a thread is less than the angle at the bottom. Thus in Fig. 302 the pitch at the top of thread (at A, B) is the same as at the bottom (C, D). Now suppose that in Fig. 303 _a_ _b_ represents the axial line of a bolt, and _c_ _d_ a line at a right angle to _a_ _b_. The radius _e_ _f_ being equal to the circumference of the top of the thread, the pitch being represented by _b_; then _k_ represents the angle of the top of the thread to the axial line _a_ _b_. Now suppose that the radius _e_ _g_ represents the circumference at the bottom of the thread and to the pitch; then _l_ is the angle of the bottom of the thread to the axial line of the work, and the difference in angle between _k_ and _l_ is the difference in angle between the top and bottom of the thread in the dies and the thread to be cut on the work. [Illustration: Fig. 302.] Now the tops of the teeth on the die stand at the greatest angle _l_, in Fig. 303, when taking the first cut on the bolt, but the grooves they cut will be on the full diameter of the bolt, and will, therefore, stand at the angle _k_, hence the lengths of the teeth do not lie in the same planes as the grooves which they cut. [Illustration: Fig. 303.] In cutting [V]-threads, however, the angle of the die threads gradually right themselves with the plane of the grooves attaining their nearest coincidence when closed to finish the thread. Since, however, the full width of groove is in a square thread cut at the first cut taken by the dies, it is obvious that a square thread cannot be cut by this class of die, because the sides of the grooves would be cut away each time the dies were closed to take another cut. [Illustration: Fig. 304.] [Illustration: Fig. 305.] Dies of this class require to have the threaded hole made of a larger diameter than is the diameter of the bolt they are intended to thread, the reason being as follows:-- Suppose the threaded hole in the dies to be cut by a hob or master tap of the same diameter as the thread to be cut by the dies; when the dies are opened out and placed upon the work as in Fig. 304, the edges A, B will meet the work, and there will be nothing to steady the dies, which will, therefore, wobble and start a drunken thread, that is to say, a thread such as was shown in Fig. 253. [Illustration: Fig. 306.] Instances have been known in the use of dies made in this manner, wherein the workman using a right-hand single-threaded pair of dies has cut a right or left-hand double or treble thread; the teeth of the dies acting as chasers well canted over, as shown in Fig. 305. It is necessary to this operation, however, that the diameter of the work be larger than the size of hob the dies were threaded with. In Fig. 306 is shown a single right-hand and a treble left-hand thread cut by the author with the same pair of dies. All that is necessary to perform this operation is to rotate the dies from left to right to produce a right-hand thread, and from right to left for a left-hand thread, exerting a pressure to cause the dies to advance more rapidly along the bolt than is due to the pitch of the thread. A double thread is produced when the dies traverse along the work twice as fast as is due to the pitch of the thread in the dies, and so on. [Illustration: Fig. 307.] It is obvious, also, that a piece of a cylindrical thread may be used to cut a left-hand external thread. Thus in Fig. 307 is shown a square piece of metal having a notch cut in on one side of it and a piece of an external thread (as a tap inserted) in the notch. By forcing a piece of cylindrical work through the hole while rotating it, the piece of tap would cut upon the work a thread of the pitch of the tap, but a left-handed thread, which occurs because, as shown by the dotted lines of the figure, the thread on one side of a bolt slopes in opposite directions to its direction on the other, and in the above operation the thread on one side is taken to cut the thread on the other. These methods of cutting left-hand threads with right-handed ones are mentioned simply as curiosities of thread cutting, and not as being of any practical value. To proceed, then: to avoid these difficulties it is usual to thread the dies with a hob or master tap of a diameter equal to twice the depth of the thread, larger than the size of bolt the dies are to thread. In this case the dies fit to the bolt at the first cut, as shown in Fig. 308, C, D being the cutting edges. The relation of the circle of the thread in the dies to that of the work during the final cut is shown in Fig. 309. [Illustration: Fig. 308.] [Illustration: Fig. 309.] There is yet another objection to tapping the dies with a hob of the diameter of the bolt to be threaded, in that the teeth fit perfectly to the thread of the bolt when the latter is threaded to the proper diameter, producing a great deal of friction, and being difficult to make cut, especially when the cutting edges have become slightly dulled from use. Referring now to taking a cut up the bolt or work as well as down, it will be noted that supposing the dies to have a right-hand thread, and to be rotating from left to right, they will be passing down the bolt and the edges C, D (Fig. 308) will be the cutting ones. But when the dies are rotated from right to left to bring them to the end of the bolt again, C, D will be rubbed by the thread, which tends to abrade them and thus destroy their sharpness. [Illustration: Fig. 310.] In some cases two or more pairs of dies are fitted to the same stock, as shown in Fig. 310, but this is objectionable, because it is always desirable to have the hole in the dies central to the length of the stock, so that when placed to the work the stock shall be balanced, which will render it easier to start the thread true with the axial line of the bolt. [Illustration: Fig. 311.] From what has been said with reference to Fig. 303, it is obvious that a square thread cannot be cut by a die that opens and closes to take successive cuts along the work, but such threads may be cut upon work that is of sufficient strength to withstand the twisting pressure of the dies, by making a solid die, and tapering off the threads for some distance at the mouth of the die, so as to enable the die to take its bite or grip upon the work, and start itself. It is necessary, however, to give to the die as many flutes (and therefore cutting edges), as possible, or else to make flutes wide and the teeth as short as will leave them sufficiently strong, both these means serving to avoid friction. [Illustration: Fig. 312.] The teeth for adjustable dies, such as shown in Fig. 293, are cut as follows:--There is inserted between the two dies a piece of metal, separating them when set together to a distance equal to twice the depth of the thread, added to the distance the faces of the dies are to be apart when the dies are set to cut to this designated or proper diameter. The tapping hole is then drilled (with the pieces in place) to the diameter of the bolt the die is for. The form of hob used by the Morse Twist Drill & Machine Company, to cut the thread, is shown in Fig. 311. The unthreaded part at the entering end is made to a diameter equal to that of the work the dies are to be used in; the thread at the entering end is made sunk in one half the height of the full thread, and is flattened off one half the height of a full thread, so that the top of the thread is even with the diameter of the unthreaded part at the entering end. The thread then runs a straight taper up the hob until a distance equal to the diameter of the nut is reached, and the length of hob equal to its diameter is made a full and parallel thread for finishing the die teeth with. The thread on the taper part has more taper at the root of the thread than it has at the top of the same, and the diameter of the full and parallel part at the shank end of the thread is made of a diameter equal to twice the height or depth of a full thread, larger than the diameter at the entering end of the hob. The hob thus becomes a taper and relieved tap cutting a full thread at one passage through the dies. If the hob is made parallel and a full thread from end to end, as in Fig. 312, the dies must traverse up and down the hob, or the hob through the dies to form a full thread. The third class of stock and die is intended to cut a full thread at one passage along the work, while at the same time provision is made, whereby, to take up the wear due to the abrasion of the cutting edges, which wear would cause the diameter of thread cut to be above the standard. In Fig. 313 is shown the Grant adjustable die made by the Pratt & Whitney Company. It consists of four chasers or toothed cutting tools, inserted in radial recesses or slots in an iron disc or collet encircled by an iron ring. Each chaser is beveled at its end to fit a corresponding bevel in the ring, and is grooved on one of its side faces to receive the hardened point of a screw that is inserted in the collet to hold the chaser in its adjusted position. Four screws extend up through the central flange or body of the collet, two of which serve to draw down the ring, and by reason of the taper on the ring move the chasers equally towards the centre and reduce the cutting diameter of the die, while the other two hold the ring in the desired position, or force it upward to enlarge the cutting diameter of the die. The range of adjustment permitted by this arrangement is 1-32 inch. The dies may be taken out and ground up to sharpen. [Illustration: Fig. 313.] The object of cutting grooves in the sides of the chasers is that the fine burrs formed by the ends of the set screws do not prevent the chasers from moving easily in the collet during the process of adjustment; the groove also acts as a shoulder for the screw end to press the chaser down to its seat. These chasers are marked to their respective places in the collet, and are so made that if one chaser should break, a new one can be supplied to fit to its place, the teeth of the new one falling exactly in line with the teeth on the other three, whereas under ordinary conditions if one chaser breaks, a full set of four new ones must be obtained. In this die, as in all others which cut a full thread at one passage along the work, the front teeth of the chasers are beveled off as shown in the cut; this is necessary to enable the dies to take hold of or "bite" the work, the chamfer giving a relief to the cutting edge, while at the same time forming to a certain extent a wedge facilitating the entrance of the work into the die. Fig. 314 represents J. J. Grant's patent die, termed by its makers (Wiley and Russel) the "lightening die." In this, as in other similar stocks, several collets with dies of various pitches and diameters of thread, fit to one stock. The nut of the stock is split on one side, and is provided with lugs on that side to receive a screw, which operates to open and enlarge the bore to release a collet, or close thereon and grip it, as may be required when inserting or extracting the same. The dies are formed as shown in Fig. 315, in which A, A are the dies, and B the collet. To open the dies within the collet, the screws E are loosened and the screws D are tightened, while to close the dies D, D are loosened and E are tightened; thus the adjustment to size is effected by these four screws, while the screws D also serve to hold the dies to the collet B. The collets are provided with a collar having a bore F, through which the work passes, so that the dies may be guided true when starting upon the work; but if it is required to cut a thread close up to a head or shoulder, the stock is turned upside down, not only to have the collet out of the way of the head or shoulder, but also because the thread of the dies on the collet side are chamfered off (as is necessary in all solid dies, or dies which cut a full thread at one traverse down the work) so as to enable them to grip or bite the work, and start the thread upon it as before stated. [Illustration: Fig. 314.] [Illustration: Fig. 315.] In Fig. 316 is shown Stetson's die, which cuts a full thread at one passage, is adjustable to take up its wear, and has a guide to steady it upon the work and assist it in cutting a true thread. The guide piece consists of a hub (through which the work passes) having a flange fitting into the dies and being secured thereto by the two screws shown. The holes in the flanges are slotted to permit of the dies being closed (to take up wear) by means of the small screws shown at the end of the die, which screws pass through one die in a plain hole and screw into the other. [Illustration: Fig. 316.] In Fig. 317 is shown Everett's stocks and dies. In this tool the dies are set up by a cam lever, the dies being set to standard size when the lever arm stands parallel with the arm of the stock. By turning the straight side of the cam lever opposite to the dies, the latter may be instantly removed and another size of die inserted. The dies may be used to cut on their passage up and down the bolt or by operating the cam. When the dies are at the end of a cut the dies may be opened, lifted to the top of the work and another cut taken, thus saving the time necessary to wind the stock back. When the final cut is taken the dies may be opened and lifted off the work. [Illustration: Fig. 317.] The hardening process usually increases the thickness of these dies, making the pitch of the thread coarser. The amount of expansion due to hardening is variable, but increases with the thickness of the die. The hob as a rule shortens during the tempering, but the amount being variable, no rule for its quantity can be given.[12] [12] See also page 108. Stocks and dies for pipe work are made in the form shown in Fig. 318, in which B is the stock having the detachable handles (for ease of conveyance) A, H, the latter being shown detached. The solid screw-cutting dies C are placed in the square recess at B, and are secured in B by the cap D, which swings over (upon its pivoted end as a centre) and is locked by the thumbscrew E. To guide the stocks and cause them to cut a true thread, the bushes F are provided. These fit into the lower end of B and are locked in position by four set screws G. The bores of the bushes F are made an easy fit to the outside of the pipe to be threaded, there being a separate bush for each size of pipe. [Illustration: Fig. 318.] The dies employed in stocks for threading steam and gas pipes by hand are sometimes solid, as in Fig. 318 at C, and at others adjustable. In Fig. 319 is shown Stetson's adjustable pipe die containing four chasers or toothed thread-cutting tools. These are set to cut the required diameter by means of a small screw in each corner of the die, while they are locked in their adjusted position by four screws on the face. The tap is a tool employed to cut screw threads in internal surfaces, as holes or bores. A set of taps for hand use usually consist of three: the taper tap, Fig. 320; plug tap, Fig. 321; and bottoming tap, Fig. 322. (In England these taps are termed respectively the taper, second, and plug tap.) The taper tap is the first to be inserted, and (when the hole to be threaded passes entirely through the work) rotated until it passes through the work, thus cutting a thread parallel in diameter through the full length of the hole. If, however, the hole does not pass through the work, the taper tap leaves a taper-threaded hole containing more or less of a fully developed thread according to the distance the tap has entered. [Illustration: Fig. 319.] [Illustration: Fig. 320.] [Illustration: Fig. 321.] [Illustration: Fig. 322.] To further complete the thread the plug tap is inserted, it being parallel from four or five threads from the entering end of the tap to the other end. If the work will admit it, this tap is also passed through, which not only saves time in many cases, by avoiding the necessity to wind the tap back, but preserves the cutting edge which suffers abrasion from being wound back. To cut a full thread as near as possible to the bottom of a hole the bottoming tap is used, but when the circumstances will admit, it is best to drill the hole rather deeper than is actually necessary, to avoid the trouble incident to tapping a hole clear to the bottom. On wrought iron and steel, which are fibrous and tough, the tap, when used by hand, will not (if the hole be deeper than the diameter of the tap) readily operate by a continuous rotary motion, but requires to be rotated about half a revolution back occasionally, which gives opportunity for the oil to penetrate to the cutting edges of the tap, frees the tap and considerably facilitates the tapping operation, especially if the hole be a deep one. [Illustration: Fig. 323.] When the tap is intended to pass entirely through the work with a continuous rotary motion, as is the case, for example, in tapping nuts in a tapping machine, it is made of similar form to the taper hand tap, but longer, as shown in Fig. 323, the thread being full and parallel at the shank end for a distance at least equal to the full diameter of the tap measured across the tops of the thread. If the thread of a tap be in diametral section a full circle, the sides of the thread rub against the grooves cut by the teeth, producing a friction which augments as the sharp edge of the teeth become dulled from use, but the tap cuts a thread of great diametral accuracy. To reduce this friction to a minimum as much as is consistent with maintaining the standard size of the tapped hole, taps are sometimes given clearance in the thread, that is to say, the back of each tooth recedes from a true circle, as shown in Fig. 324, in which A A represents a washer, and B A tap in the same, the back of the teeth receding at C, D, E, from the true circle of the bore of A A, the tap cutting when revolved in the direction of the arrow. The objection to this is that when the tap is revolved backwards, as it must be to extract it unless the hole passes clear through the work, the cuttings lodge between the teeth and the thread in the work, rendering the extraction of the tap difficult, unless, indeed, the clearance be small enough in amount to clear the sides of the thread in the work sufficiently to avoid friction without leaving room for the cuttings to enter. If an excess of clearance be allowed upon taps that require to be used by hand, the tap will thread the hole taper, the diameter being largest at the top of the hole. This occurs because the tap is not so well steadied by its thread, which fails to act as a guide, and it is impossible to revolve the tap steadily by hand. Taps that are revolved by machine tools may be given clearance because both the taps and the work are detained in line, hence the tap cannot wobble. [Illustration: Fig. 324.] [Illustration: Fig. 325.] In some cases clearance is given by filing or cutting off the tops of the threads along the middle of the teeth, as shown in Fig. 325 at A, B, C, which considerably reduces the friction. If clearance were given to a tap after this manner but extended to the sides and to the bottom of the thread, it would produce the best of results (for all taps that do not pass entirely through the hole), reducing the friction and leaving no room for the cuttings to jam in the threads when the tap is being backed out. The threads of Sir Joseph Whitworth's taper hand taps are made parallel, measured at the bottom of the thread, and parallel at the tops of the thread for a distance equal to the diameter of the tap at the shank end; thence, to the entering end of the tap, the tops of the thread are turned off a straight taper, the amount of taper being slightly more than twice the depth of the thread: hence, the thread is just turned out at the entering end of the tap, and that end is the exact proper size for the tapping hole. This enables the tap to enter the tapping hole for a distance enveloping one or perhaps two of the tap threads, leaving the extreme end of the tap with the thread just turned out. In the practice of some tap makers the diameter of the thread at the top is made the same as in the Whitworth system, but there is more depth at the root of the thread and near the entering end of the tap, hence the bottoms of the thread at that end perform no cutting duty. This is done to enable the tap to take hold of, and start a thread in, the work more readily, which it does for the following reasons. In Fig. 326 is a piece of work with a tap A, having a tapered thread, and a tap B, in which the taper is given by turning off the thread. In the case of A the teeth points cut a groove that is gradually widened and deepened as the tap enters, until a full thread is finally produced. In the case of B the teeth cut at first a wide groove, leaving a small projection, that is a part of the actual finished thread, and the groove gets narrower as the tap enters; so that in the one case no part of the thread is finished until the tap has entered to its full diameter, while in the other the thread is finished as it is produced. On entering, therefore, more cutting duty is performed by B than by A, because a greater length of cutting edge is in operation and more metal is being removed, and as a result B requires more power to start it, so that in practice it is necessary to exert a pressure upon it, tending to force it into the hole while rotating it. The cutting duty on B decreases as the tap enters, because it gets less width and area of groove to cut, while the cutting duty on A increases as the tap enters, because it gets a greater width and area of groove to cut. In the latter case the maximum of pressure falls on the tap when it has entered the hole deepest, and hence can be operated steadiest, which, independent of its entering easiest, is an advantage. When, however, the bottom of a thread is taper (as must be the case to enable it to cut as at A), the cutting edge of each tooth does not cut a groove sufficiently large in diameter to permit the tooth itself to pass through. In Fig. 327, for example, is shown a tap which is taper and has a full thread from end to end (as is necessary for pipe tapping). Its diameter increases as the thread proceeds from the end towards the line A B. Now take the tooth O P, which stands lengthwise, in the plane C D. Its cutting edge is at P, but the diameter of the tap at P is less than it is at O, while O has to pass through the groove that P cuts. To obviate this difficulty the tap is given clearance, as shown in Fig. 324, the amount being slightly more than the difference in the diameter of the tap at O and at P in that figure. It follows, therefore, that a tap having taper from end to end and a full thread also, as shown in the lower tap in Fig. 328, is wrong in principle, and from the unsteady manner in which it operates is undesirable, even though its thread be given clearance. [Illustration: Fig. 326.] [Illustration: Fig. 327.] In some cases the thread is made parallel at the tops and turned taper for a distance of 1/3 or 1/2 the length of the tap, the root of the thread at the taper part being deepened and the tops being given a slight clearance. This answers very well for shallow holes, because the taper tap cuts more thread on entering a given depth so that the second tap can follow more easily, but the tap will not operate so steadily as when the taper part is longer. [Illustration: Fig. 328.] It is on account of the tops of the teeth performing the main part of the cutting that a tap taper may be sharpened by simply grinding the teeth tops. In the Pratt and Whitney taps, the hand taper tap is made parallel at the shank end for a distance equal in length to the diameter of the tap. The entering end of the taper tap is made straight or parallel for a distance equal in length to one half the diameter of the tap, the diameter at this end being the exact proper size of tapping hole. The parallel part serves as a guide, causing the tap to enter and keep axially true with the hole to be tapped. The plug and bottoming taps are made parallel in the thread, the former being tapered slightly at and for two or three threads from the entering, as shown in Fig. 328. The threads are made parallel at the roots. The Pratt and Whitney taper taps for use in machines are of the following form:-- The entering end of the tap is equal in diameter to the diameter of the tapping hole into which the tap will enter for a distance of two or three threads. The thread at the shank end is parallel both at the top and at the root for a distance equal, in length, to twice the diameter of the tap. The top of the thread has a straight taper running from the parallel part at the shank to the point or entering end, while the roots of the thread are made along this taper twice the taper that there is at the top of the thread, which is done to make the tap enter and take hold of the nut more easily. [Illustration: Fig. 329.] A form of tap that cuts very freely on account of the absence of friction on the sides of the thread is shown in Fig. 329. The thread is cut in parallel steps, increasing in size towards the shank, the last step (from D to E in the figure) being the full size. The end of the tap at A being the proper size for the tapping hole, and the flutes not being carried through A, insures that the tap shall not be used in holes too small for the size of the tap, and thus is prevented a great deal of tap breakage. The bottom of the thread of the first parallel step (from A to B) is below the diameter of A, so as to relieve the sides of the thread of friction and cause the tap to enter easily. The first tooth of each step does all the cutting, thus acting as a turning tool, while the step within the work holds the tooth to its cut, as shown in Fig. 330, in which N represents a nut and T the tap, both in section. The step C holds the tap to its work, and it is obvious that, as the tooth B enters, it will cut the thread to its own diameter, the rest of the teeth on that step merely following frictionless until the front tooth on the next step takes hold. Thus, to sharpen the tap equal to new, all that is required is to grind away the front tooth on each step, and it becomes practicable to sharpen the tap a dozen times without softening it at all. As a sample of duty, it may be mentioned that, at the Harris-Corliss Works, a tap of this class, 2-7/8 inches diameter, with a 4 pitch, and 10 inches long, will tap a hole 5 inches deep, passing the tap continuously through without any backing motion, two men performing the duty with a wrench 4 feet long over all, the work being of cast iron. [Illustration: Fig. 330.] [Illustration: Fig. 331.] [Illustration: Fig. 332.] Another form of free cutting tap especially applicable to taps of large diameter has been designed by Professor Sweet. Its principles may be explained as follows:-- In the ordinary tap, with the taper four or five diameters in length, there are far more cutting-edges than are necessary to do the work; and if the taper is made shorter, the difficulty of too little room for chips presents itself. The evil results arising from the extra cutting edges are that, if all cut, then it is cutting the metal uselessly fine--consuming power for nothing; or if some of the cutting edges fail to cut, they burnish down the metal, not only wasting power, but making it all the harder for the following cutters. One plan to avoid this is to file away a portion of the cutting edges; but the method adopted in the Cornell University tap is still better. Assume that it is desired to make three following cutters, to remove the stock down to the dotted line in Fig. 331. Instead of each cutter taking off a layer one-third the thickness and the full width, the first cutter is cut away on each side to about one-third its full width, so that it cuts out the centre to its full depth, as shown in Fig. 331, the next cutter cutting out the metal at A, and so on. This is accomplished by filing, or in any other way cutting away the sides of one row of the teeth all the way up; next cutting away the upper sides of the next row and the lower sides of the third, leaving the fourth row (if it be a four-fluted tap) as it is left by the lathe, to insure a uniform pitch and a smooth thread. [Illustration: Fig. 333.] Figs. 333, 334 and 335 represent an adjustable tap designed by C. R. French, of Providence, R. I., to thread holes accurate in diameter. The plug tap, Fig. 333, has at its end a taper screw, and the tap is split up as far as the flutes extend, a second screw binds the two sides of the tap together, hence by means of the two screws the size of the tap may be regulated at will. In the third or bottoming tap, Fig. 334, the split extends farther up the shank, and four adjusting screws are used as shown, hence the parallelism of the tap is maintained. In the machine tap, Fig. 335, there are six adjusting screws, two of those acting to close the tap being at the extreme ends so as to strengthen it as much as possible. [Illustration: Fig. 334.] [Illustration: Fig. 335.] In determining the number, the width, the depth, and the form of flutes for a tap, we have the following considerations. In a tap to be used in a machine and to pass entirely through the work, as in the case of tapping nuts, the flute need not be deep, because the taper part of the tap being long the cutting teeth extend farther along the tap; hence, each tooth takes a less amount of cut, producing less cuttings, and therefore less flute is required to hold them. In taps of this class, the thread being given clearance, the length of the teeth may be a maximum, because they are relieved of friction; on the other hand, however, the shallower and narrower the flute the stronger the tap, so long as there is room for the cuttings so that they shall not become wedged in the flutes. Taps for general use by hand are frequently used to tap holes that do not pass entirely through the work; hence, the taper tap must have a short length of taper so that the second tap may be enabled to carry a full thread as near as possible to the bottom of the hole without carrying so heavy a cut as to render it liable to breakage, and the second or plug tap must in turn have so short a length of its end tapered that it will not throw too much duty upon the bottoming tap. Now, according as the length of the taper on the taper tap is reduced, the duty of the teeth is increased, and more room is necessary in the flute to receive the cuttings, and supposing the tap to be rotated continuously to its duty the flute must possess space enough to contain all the cuttings produced by the teeth, but on account of the cuttings filling the flutes and preventing the oil fed to the tap from flowing down the flute to the teeth it is found necessary in hand taps (when they cannot pass through the work, or when the depth of the hole is equal to more than about the tap diameter), to withdraw the tap and remove the cuttings. On account of the tap not being accurately guided in hand-tapping it produces a hole that is largest at its mouth, and it is found undesirable on this account to give any clearance to hand taps, because such clearance gives more liberty to the tap to wobble in the hole and to enlarge its diameter at the mouth. It is obvious also, that the less of the tap circumference removed to form the flutes the longer the tap-teeth and the more steadily the tap may be operated. On the other hand, however, the longer the teeth the greater the amount of friction between them and the thread in the hole and the more work there is involved in the tapping, because the tap must occasionally be rotated back a little to ease its cut, which it is found to do. [Illustration: Fig. 336.] [Illustration: Fig. 337.] Fig. 336 represents a form of flute recommended by Brown and Sharp. The teeth are short, thus avoiding friction, and the flutes are shallow, which leaves the tap strong. The inclination of the cutting edges, as A B (the cutting direction of rotation being denoted by the arrow), is shown by the dotted lines, being in a direction to curve the chip or cutting somewhat upward and not throw them down upon the bottom of the flute. A more common form, and one that perhaps represents average American practice, is shown in Fig. 337, the cutting edges forming a radial line as denoted by the dotted line. The flute is deeper, giving more room for the chips, which is an advantage when the tap is required to cut a thread continuously without being moved back at all, but the tap is weaker on account of the increased flute depth, the teeth are longer and produce more friction, and the flutes are deeper than necessary for a tap having a long taper or that requires to be removed to clear out the cuttings. Fig. 338 shows the form of flute in the Pratt and Whitney Company's hand taps, the cutting edges forming radial lines and the bottoms of the flutes being more rounded than is usual. It may here be remarked that if the flutes have comparatively sharp corners, as at C in Fig. 339, the tap will be liable to crack in the hardening process. The form of flute employed in the Whitworth tap is shown in Fig. 340; here there being but three flutes the teeth are comparatively long, and on this account there is increased friction. But, on the other hand, such a tap produces, when used by hand, more accurate work, the threaded hole being more parallel and of a diameter more nearly equal to that of the tap, it being observed that even though a hand tap have no clearance it will usually tap a hole somewhat larger than itself so that it will unwind easily. If a hand tap is given clearance not only will it cut a hole widest at the mouth, but it will cut a thread larger than itself in an increased degree, and, furthermore, when the tap requires to be wound back to extract it the fine cuttings will become locked in the threads and the points of the tap teeth are liable to become broken off. To ease the friction of long teeth, therefore, it is preferable to do so either as in Fig. 325 at A, B, C, or as in Fig. 341. In Fig. 325 the tops of the teeth are shown filed away, leaving each end full, so that the cuttings cannot get in, no matter in which direction the tap is rotated; but the clearance is not so complete as in Fig. 341, in which the teeth are supposed to be eased away within the area enclosed by dotted lines, which gives clearance to the bottom as well as to the tops and sides of the thread and leaves the ends of each tooth a full thread. [Illustration: Fig. 338.] [Illustration: Fig. 339.] [Illustration: Fig. 340.] [Illustration: Fig. 341.] Concerning the number of flutes in taps, it is to be observed that the duty the tap is to be put to, has much influence in this respect. In hand tapping the object is to tap as parallel and straight as possible with the least expenditure of power. Now, the greater the number of flutes the less the tap is guided, because more of the circumferential guiding surface is cut away. But on the other hand, the less the number of flutes, and therefore the less the number of cutting edges, the more power it takes to operate the tap on account of the greater amount of friction between the tap and the walls of the hole. In hand tapping on what may be termed frame work (as distinguished from such loose work as nuts, &c.), the object is to tap the holes as parallel as possible with the least expenditure of power while avoiding having to remove the tap from the hole to clear it of the cuttings. Obviously the more flutes and cutting edges there are the more room there is for the cuttings and the less frequent the tap requires to be cleaned. If the tapping hole is round and straight the tapping may be made true and parallel if due care is taken, whatever the number of flutes, but less care will be required in proportion as there are less flutes, while, as before noted, more power and more frequent tap removals will be necessary. But if the hole is not round, other considerations intervene. [Illustration: Fig. 342.] Thus in Fig. 342 we have a three-flute tap in a hole out of round at A, and it is obvious that when a cutting edge meets the recess at A, all three teeth will cease to cut; hence there will be no inducement for the tap to move over toward A. But in the case of the four-flute tap in Fig. 343, when the teeth come to A there will be a strain tending to force the teeth over toward the depression A. How much a given tap would actually move over would, of course, depend upon the amount of clearance; but whether the tap has clearance or not, the three-flute tap will not move over, while with four flutes the tap would certainly do so. Again, with an equal width of flute there is more of the circumference tending to guide and steady the three-flute than the four-flute tap. If the hole has a projection instead of a depression, as at B, Figs. 344 and 345, then the advantage still remains with the three-flute tap, because in the case of the three flutes, any lateral movement of the tap will be resisted at the two points _c_ and D, neither of which are directly opposite to the location of the projection B; hence, if the projection caused the tap to move laterally, say, 1-100th inch, the effect at _c_ and D would be very small, whereas in the four-flute, Fig. 345, the effect at E would be equal to the full amount of lateral motion of the tap. [Illustration: Fig. 343.] [Illustration: Fig. 344.] [Illustration: Fig. 345.] In hand taps the position of the square at the head of the tap with relation to the cutting-edges is of consequence; thus, in Fig. 346, there being a cutting-edge A opposite to the handle, any undue pressure on that end of the handle would cause A to cut too freely and the tap to enlarge the hole; whereas in Fig. 347 this tendency would be greatly removed, because the cutting-edges are not in line with the handle. In a three-flute tap it makes but little difference what are the relative positions of the square to the flutes, as will be seen in Fig. 348, where one handle of the wrench comes in the most favorable and the other in the most unfavorable position. Taps for use by hand and not intended to pass through the work are sometimes made with the shank and the square end which receive the wrench of enlarged diameter. This is done to avoid the twisting of the shank which sometimes occurs when the tap is employed in deep holes, giving it much strain, and also to avoid as much as possible the wearing and twisting of the square which occurs, because in the course of time the square holes in solid wrenches enlarge from wear, and the larger the square the less the wear under a given amount of strain. [Illustration: Fig. 346.] Brass finishers frequently form the heads of their taps as in Fig. 349, using a wrench with a slot in it that is longer than the flat of the tap head. [Illustration: Fig. 347.] The thickness of the flat head at A is made equal for all the taps intended to be used with the same wrench. By this means one wrench may be used for many different diameters of taps. [Illustration: Fig. 348.] For gas, steam pipe, and other connections made by means of screw threads, and which require to be without leak when under pressure, the tap shown in Fig. 350 is employed. It is made taper and full threaded from end to end, so that the fittings may be entered easily into their places and screwed home sufficiently to form a tight joint. [Illustration: Fig. 349.] [Illustration: Fig. 350.] The standard degree of taper for steam-pipe taps is 3/4 inch per foot of length, the taper being the same in the dies as on the taps. The threading tools for the pipes or casings for petroleum oil wells are given a taper of 3/8 inch per foot, because it was not found practicable to tap such large fittings with a quick taper, because of the excessive strain upon the threading tools. Ordinary pipe couplings are, however, tapped straight and stretch to fit when screwed home on the pipe. Oil-well pipe couplings are tapped taper from both ends, and there is just enough difference in the taper on the pipe and that in the socket to show a bearing mark at the end only when the pipe and socket are tested with red marking. PITCHES OF TAP THREADS IN USE IN THE UNITED STATES. +-----------+---------+----------------+ | | | No. of Threads | | Diameter. | Length. | to Inch. | +-----------+---------+----------------+ | 1/4 | 2-3/4 | 16, 18 & 20 | | 5/16 | 2-7/8 | 16 & 18 | | 3/8 | 3-1/2 | 14 & 16 | | 7/16 | 3-13/16 | 14 & 16 | | 1/2 | 4-5/16 | 12, 13 & 14 | | 9/16 | 4-3/4 | 12 & 14 | | 5/8 | 5-1/8 | 10, 11 & 12 | | 11/16 | 5-3/8 | 11 & 12 | | 3/4 | 5-13/16 | 10, 11 & 12 | | 13/16 | 6 | 10 | | 7/8 | 6-1/8 | 9 & 10 | | 15/16 | 6-3/8 | 9 | | 1 | 6-13/16 | 8 | | 1-1/8 | 7-1/4 | 7 & 8 | | 1-1/4 | 8 | 7 & 8 | +-----------+---------+----------------+ Fig. 351 represents the form of tap employed by blacksmiths for rough work, and for the axles of wagon wheels. These taps are given a taper of 1/2 inch per foot of length, and are made with right and left-hand threads, so that the direction of rotation on both sides of a wagon wheel shall be in a direction to screw up the nuts and not to unscrew the nut, as would be the case if both ends of the axle were provided with right-hand threads. [Illustration: Fig. 351.] Taps that are used in a machine are sometimes so constructed that upon having tapped the holes to the required depth, the pieces containing the tap teeth recede from the walls of the hole, so that the tap may be instantly withdrawn from the hole instead of requiring to be rotated backwards. This is an advantage, not only on account of the time saved, but also because the cutting edges of the teeth are saved from the abrasion and its consequent wear which occur in rotating a tap backwards. [Illustration: Fig. 352.] Figs. 352 and 353 represent a collapsing tap that is much used in manufactories of pipe fittings. [Illustration: Fig. 353.] A is driven by the spindle of the machine, and drives B through the medium of the pin H. In B are three chasers C, fitting into the dovetail and taper grooves D. These chasers are provided with lugs fitting into an annular groove E sunk in A, so that if the piece H rises, the chasers will not rise with it, but will simply close together by reason of the lifting or rising of the core B, with its taper dovetail grooves; or, on the other hand, if the core B descends, the taper grooves in B force the chasers outward, increasing their cutting diameter. When the tap is cutting, it is driven as denoted by the arrow, and the pin H is driven by the ends of the grooves, of which there are two, one diametrically opposite the other, inclined in the same direction. But when the tap has cut a thread to the required depth on the work, the handles H may be pulled or pushed the working way, passing along the grooves I, and causing B to lift within A, and allowing the chasers to close away from the thread just cut, and the tap may be instantly withdrawn, and handles H pushed back to expand the chasers, ready for the next piece of work. [Illustration: Fig. 354.] Fig. 354 represents a collapsing tap used in Boston, Massachusetts, at the Hancock Inspirator Works, in a monitor or turret lathe. It consists of an outer shell A carrying three chasers B, pivoted to A at C, having a small lug E at one end, and being coned at the inner end D. The inner shell F is reduced along part of its length to receive the lug E of the chaser, and permit the chasers to open out full at their cutting end. F has a cone at the end G, fitting to the internal cone on the chasers at D. At the other end of F is a washer H, against which abuts the spiral spring shown, the other end of this spring abutting against a shoulder provided in A. The washer H is bevelled on its outer or end face to correspond with the bevel on a notch provided in lever I, as is shown. Within the inner tube F is the stem J, into the end of which is fitted the piece K, and on which is fixed the cone L. Piece K, and therefore L, is prevented from rotating by a spline in K, into which spline the pin M projects. The operation is as follows. In the position in which the parts are shown in the engraving, F is pushed forward so that its coned end G has opened out the chaser to its fullest extent, which opening is governed by contact of the lug E with the reduced diameter of F. Suppose that the tap is operating in the work, then, when the foot N of K meets with a resistance (as the end of the hole being tapped), J, and therefore L, will be gradually pushed to the right, until, finally, the cone on L will raise the end of lever I until the notch on I is clear of H, when the spiral spring, acting against H, will force F to the right, and the shoulder on F, at X, will lift the end E of the chaser, causing the cutting end to collapse within A, the pivot C being its centre of motion. The whole device may then be withdrawn from the work. To open the chasers out again the rod J is forced, by hand, to the left, the cone-piece L meeting the face of H and pushing it to the left until cone G meets cone D, when the chasers open until the end E meets the body of F, as in the cut. The rod J is then pulled to the right until L again meets the curved end of lever I and all the parts assume the positions shown in the cut. To regulate the depth of thread the tap shall cut, the body A is provided with a thread to receive the nut O, by means of which the collar P may be moved along A. This collar carries the pivots Q for levers I, so that, by shifting O, the position of I is varied, hence the point at which L will act upon the end of I and lift it to release H is adjustable. When used upon steel, wrought iron, cast iron, copper, or brass, a tap should be freely supplied with oil, which preserves its cutting edge as well as causes it to cut more freely, but for cutting the soft metals such as tin, lead, &c., oil is unnecessary. The diameters of tapping holes should be equal to the diameter of the thread at the root, but in the case of cast iron there is much difference of opinion and practice. On the one hand, it is claimed that the size of the tapping hole should be such as to permit of a full thread when it is tapped; on the other hand, it is claimed that two-thirds or even one-half of a full thread is all that is necessary in holes in cast iron, because such a thread is, it is claimed, equally as strong as a full one, and much easier to tap. In cases where it is not necessary for the thread to be steamtight, and where the depth of the thread is greater by at least 1/8 inch than the diameter of the bolt or stud, three-quarters of a full thread is all that is necessary, and can be tapped with much less labor than would be the case if the hole were small enough to admit of a full thread, partly because of the diminished duty performed by the tap, and partly because the oil (which should always be freely supplied to a tap) obtains so much more free access to the cutting edges of the tap. If a long tap is employed to cut a three-quarter full thread, it may be wound continuously down the hole, without requiring to be turned backwards at every revolution or so of the tap, to free it from the tap cuttings or shavings, as would be necessary in case a full thread were being cut. The saving of time in consequence of this advantage is equal to at least 50 per cent. in favor of the three-quarter full thread. As round bar iron is usually rolled about 1/32 inch larger than its designated diameter, a practice has arisen to cut the threads upon the rough iron just sufficiently to produce a full thread, leaving the latter 1/32 inch above the proper diameter, hence taps 1/32 inch above size are required to thread nuts to fit the bolts. This practice should be discountenanced as destroying in a great measure the interchangeability of bolts and nuts, because 1/32 inch is too small a measurement to be detected by the eye, and a measurement or trial of the bolt and nut becomes necessary. A defect in taps which it has been found so far impracticable to eliminate is the alteration of pitch which takes place during the hardening process. The direction as well as the amount of this variation is variable even with the most uniform grades of steel, and under the most careful manipulation. Mr. John J. Grant, in reply to a communication upon this subject, informs me that, using Jones and Colver's (Sheffield) steel, which is very uniform in grade, he finds that of one hundred taps, about 5 per cent. will increase in length, the pitch of the thread becoming coarser; 15 per cent. will suffer no appreciable alteration of pitch, and 80 per cent. will shrink in length, the pitch becoming finer, and these last not alike. But it must be borne in mind that with different steel the results will be different, and the greater the variation in the grade of the steel the greater the difference in the alteration of pitch due to hardening. It is further to be observed that the expansion or contraction of the steel is not constant throughout the same tap; thus the pitches of three or four consecutive teeth may measure correct to pitch, while the next three or four may be of too coarse or too fine a pitch. There is no general rule, even using the same grade of steel, for the direction in which the size of a tap may alter in hardening, as is attested by the following answers made by Mr. J. J. Grant to the respective questions:-- "Do the taps that shorten most in length increase the most in diameter?" Answer.--"Not always; sometimes a tap that shortens by hardening becomes also smaller in diameter, while sometimes a tap will increase in length, and also in diameter from hardening." "Do taps that remain of true pitch after hardening remain true, or increase or diminish in diameter?" Answer.--"They will generally be of larger diameter." "Do small taps alter more in diameter from hardening than large ones?" Answer.--"No; the proportion is about the same, and is about .002 per inch of diameter." "What increase in diameter do you allow for shrinkage in hardening of hob taps for tapping solid dies?" Answer.--"As follows:-- Diameter of Shrinkage Hob Tap about 1/4 inch .003 1/2 " .003 3/4 " .005 1 " .008" "Suppose a tap that had been hardened and tempered to a straw color contained an error 1/1000 inch both in diameter and in pitch, was softened again, would it when soft retain the errors, or in what way would softening affect the tap?" Answer.--"We have repeatedly tried annealing or softening taps that were of long or short pitch caused by tempering, and invariably found them about the same as before the annealing. The second tempering will generally shorten them more than the first. Sometimes, however, a second tempering will bring a long pitch nearer correct." "Do you soften your taps after roughing them out in the lathe?" Answer.--"Never, if we can possibly avoid it. Sometimes it is necessary because of improper annealing at first. The more times steel is annealed the worse the results obtained in making the tool, and the less durable the tool." The following are answers to similar questions addressed to the Morse Twist Drill and Machine Co.:-- "The expansion of taps during hardening varies with the diameter. A 1-inch tap would expand in diameter from 1/1000 to 3/1000 inch." "Taps above 1/2 inch diameter expand in diameter to stop the gauge every time." "The great majority of taps contract in pitch during the hardening, they seldom expand in length." "The shortening of the pitch and the expansion in diameter have not much connection necessarily, though steel that did not alter in one direction would be more likely to remain correct in the other." "There does not seem to be any change in the diameter or pitch of taps if measured after hardening (and before tempering) and again after tempering them." "Taps once out in length seem to get worse at every heating, whether to anneal or to harden." [Illustration: Fig. 355.] It will now be obvious to the reader that the diameter of a tap, to give a standard sized bolt a required tightness of fit, will, as a general rule, require to vary according to the depth of hole to be tapped, because the greater that depth the greater the error in the pitch. Suppose a tap, for example, to get of finer pitch to the amount of .002 per inch of length, then a hole an inch deep and tapped with that tap would err .002 in its depth, while a hole two inches deep would err twice as much in its depth. [Illustration: Fig. 356.] Therefore a bolt that would be a hand fit (that is, screw in under hand pressure) in the hole an inch deep would require more force, and probably the use of a wrench, to wind it through the hole 2 inches deep; hence in cases where a definite degree of fit is essential, the reduction in diameter of the male screw or thread necessary to compensate for the error in the tap pitch must vary according to the depth of the hole, and the degree of error in the tap. [Illustration: Fig. 357.] It is obvious that the longer a tap is the greater the error induced by hardening, and it often becomes a consideration how to tap a long hole, and obtain a thread true to pitch. This may be accomplished as follows. Several taps are made of slightly different diameters, the largest being of the required finished size. Each tap is made taper for a distance of two or three threads only, and is hardened at this tapered end, but left soft for the remainder of its length. The smallest tap is used first, and when it has tapped a certain distance, a larger one is inserted, and by continuing this interchange of taps and slightly varying the length of the taper, the work may be satisfactorily done. To test the accuracy, or rather the uniformity, of a thread that has been hardened, a sheet metal gauge, such as at G or at G´ (Fig. 355), may be used, there being at _a_ and _b_ teeth to fit the threads. If the edge of the gauge meets the tops of the threads, then their depth is correct. If it is desired to test only the pitch, then the gauge may be made as at G´, where, as is shown in the figure, the edge of the gauge clears the tops of the threads, and in this way may be tried at various points along the thread length. [Illustration: Fig. 358.] A method of truing hardened threads proposed by the author of this work in 1877, and since employed by the Pratt and Whitney Company to true their hardened steel plug-thread gauges, is as follows:--A soft steel wheel about 3-1/2 inches in diameter, whose circumference is turned off to the shape of the thread, is mounted upon the slide rest of a lathe, and driven by a separate belt after the manner of driving emery wheels; this wheel is charged with diamond dust, which is pressed into its surface by a roller, hence it grinds the thread true. The amount allowed for grinding is 3/1000 inch measured in the angles of the thread, as was shown in Figs. 280 and 281. In charging the wheel with diamond dust it is necessary to use a roller shaped as in Fig. 356, so that the axis of the roller R and wheel W shall be at a right angle, as denoted by the dotted lines. If the roller is not made to the correct cone its action will be partly a rolling and partly a sliding one, and it will strip the diamond dust from the wheel rather than force it in, the reasons for this being shown in Figs. 57 and 58 upon the subject of bevel-wheels. [Illustration: Fig. 359.] Taps for lead and similar soft metal are sometimes made with three flat sides instead of grooves. The tapping holes may in this case be made of larger diameter than the diameter of the end of the tap thread, because the metal in the hole will compress into the tap thread, and so form a full thread. Taps for other metal have also been made of half-round section. Fig. 357 represents a tap of oval cross section, having two flutes, as shown, but it may be observed that neither half-round nor oval taps possess any points of advantage over the ordinary forms of three or four fluted taps, while the former are more troublesome and costly to manufacture. [Illustration: Fig. 360.] When it is required to tap a hole very straight and true, it is sometimes the practice to provide a parallel stem to the tap, as shown in figure at C. This stem is made a neat working fit to the tapping hole, so that the latter serves as a guide to the tap, causing it to enter and to operate truly. TAP WRENCH.--Wrenches for rotating a tap are divided into two principal classes, single and double wrenches. The former has the hole which receives the squared end of the tap in the middle of its length, as shown in Fig. 358 at E, there being a handle on each side to turn it by. [Illustration: Fig. 361.] The single wrench has its hole at one end, as shown in Fig. 359 at D, and is employed for tapping holes in locations where the double wrench could not be got in. [Illustration: Fig. 362.] [Illustration: Fig. 363.] In some cases double tap wrenches are made with two or three sizes of square holes to serve as many different sizes of taps, but this is objectionable, because unless the handles of the wrench extend equally on each side of the tap, the overhanging weight on one side of the tap exerts an influence to pull the tap over to one side and tap the hole out of straight. For taps that have square heads the wrench should be a close but an easy fit to the tap head, otherwise the square corners of the tap become rounded. For the smaller sizes of taps, adjustable wrenches, such as shown in Fig. 360, are sometimes employed. These contain two dies; the upper one, which meets the threaded end of C, being a sliding fit, and the joint faces being formed as shown at A, B. By rotating the handle C its end leaves the upper die, which may be opened out, leaving the square hole between the dies large enough to admit the squared tap end. After the wrench is placed on the tap, C is rotated so as to close the dies upon the tap. [Illustration: Fig. 364.] [Illustration: Fig. 365.] When the location of the tapping hole leaves room for the wrench to rotate a full circle, C is screwed up so that the dies firmly grip the tap head, which preserves the tap head; but when the wrench can only be rotated a part of a revolution, C is adjusted to leave the dies an easy fit to the tap head, so as to enable the wrench to be removed from the tap head with facility and again placed upon the tap head. C is operated by a round lever or pin introduced in a hole in the collar, or the collar may be squared to receive a wrench. To insure that a tap shall tap a hole straight, the machinist, in the case of hand tapping, applies a square to the work and the tap, as shown in Fig. 361, in which W represents a piece of work, T a tap, and S S two squares. If the tap is a taper one the square is sighted with the shank of the tap, as shown in position 1, but if the thread of the tap is parallel, the square may be applied to the thread of the tap, as in position 2. If the tap leans over to one side, as in Fig. 362, it is brought upright by exerting a pressure on the tap wrench handle B (on the high side) in the direction of the arrow A, while the wrench is rotated; but if the tap leans much to one side it is necessary to rotate the tap back and forth, exerting the pressure on the forward stroke only. [Illustration: Fig. 366.] [Illustration: Fig. 367.] It is necessary to correct the errors before the tap has entered the hole deeply, because the deeper the tap has entered the greater the difficulty in making the correction. If the pressure on the tap wrench be made excessive, it is very liable to cause the tap to break, especially in the case of small taps, that is to say, those of 5/8 inch or less in diameter. The square should be applied as soon as the tap has entered the hole sufficiently to operate steadily, and should be applied several times during the tapping operation. When the tap does not pass through the hole it may be employed with a guide which will keep it true, as shown in Fig. 363, in which W is a piece of work, T the tap, and S a guide, the latter being bolted or clamped to the work at B. In this case the shank of the tap is made fully as large in diameter as the thread. In cases where a number of equidistant holes require tapping, as in the case of cylinder ends, this device saves a great deal of time and insures that the tapping be performed true, the hole to receive the bolt B and that to receive the tap being distant apart to the same amount as are the holes in the work. In shops where small work is made to standard gauge, and on the interchangeable system, devices are employed, by means of which a piece that has been threaded will screw firmly home to its place, and come to some definite position, as in the following examples. In Fig. 364 let it be required that the stud A shall screw in the slide S; the arm A to stand vertical when collar B is firmly home, and a device such as in Fig. 365 may be employed. P is a plate on which is fixed a chuck C to receive the slide S. In plate P is a groove G to hold the head H at a right angle to the slideway in C, there being a projection beneath H and beneath C to fit into G. The tap T is threaded through H, but not fluted at the part that winds through H when the tapping is being done, so as not to cause the thread in H to wear. H acts as a guide to the tap and causes it to start the thread at the same point in the bore of each piece S, and the stem will be so threaded that the screw starts at the same point in the circumference of each piece. [Illustration: Fig. 368.] A second example of uniform tapping is shown in Figs. 366, 367, and 368. The piece, Fig. 366, is to have its bore A tapped in line with the slot C, and the thread is to start at a certain point in its bore. In Fig. 367 this piece is shown chucked on a plate D. F is a chuck having a lug E fitting into the slot (C, Fig. 366) of the work. This adjusts the work in one direction. The face D of the plate adjusts the vertical height of the work, and the alignment of the hole to the axis of the tap is secured in the construction of the chuck, as is shown in Fig. 369. A lug K is at a right angle to the face B of the chuck and stands in a line with lug E, as denoted by the dotted line _g_ _g_, and as lug K fits into the slot G, Fig. 367, the work will adjust itself true when bolted to the plate. [Illustration: Fig. 369.] Fig. 368 shows a method of tapping or hobbing four chasers (as for a bolt cutter), so that if the chasers are marked 1, 2, 3 and 4, as shown, any chaser of No. 1 will work with the others, although not tapped at the same operation. C is a chuck with four dies (A, B, C, D) placed between the chasers. By tightening the set-screws S, the dies and chasers are locked ready for the tapping. N is a hub to receive a guide-pin P, which is passed through to hold the chasers true while being set in the chuck, and it is withdrawn before the tapping commences; _d_ _e_ _f_ are simply to take hold of when inserting and removing the dies. It is obvious that a chuck such as this used upon a plate, as in Fig. 365, with the hob guided in the head H there shown, would tap each successive set of chasers alike as a set, and individually alike, provided, of course, that the hob guide or head H is at each setting placed the same distance from the face of the chuck, a condition that applies to all this class of work. In the case of work like chasers, where the tap or hob does not have much bearing to guide it in the work, a three-flute hob should be used for four chasers, or a four-flute hob for three chasers, which is necessary so that the hob may work steadily and tap all to the same diameter. CHAPTER V.--FASTENING DEVICES. Bolts are usually designated for size by their diameters measured at the cylindrical stem or body, and by their lengths measured from the inner side of the head to the end of the thread, so that if a nut be used, the length of the bolt, less the thickness of the nut and washer (if the latter be used), is the thickness of work the bolt will hold. If the work is tapped, and no nut is used, the full length of the bolt stem is taken as the length of the bolt. A _black_ bolt is one left as forged. A finished bolt has its body, and usually its head also, machine finished, but a finished bolt sometimes has a black head, the body only being turned. A square-headed bolt usually has a square nut, but if the nut is in a situation difficult of access for the wrench, or where the head of the bolt is entirely out of sight (as secluded beneath a flange) the nut is often made hexagon. A machine-finished bolt usually has a machine-finished and hexagon nut. Square nuts are usually left black. [Illustration: Fig. 370.] The heads of bolts are designated by their shapes, irrespective of whether they are left black or finished. Fig. 370 represents the various forms: _a_, square head; _b_, hexagon head; _c_, capstan head; _d_, cheese head; _e_, snap head; _f_, oval head, or button head; _g_, conical head; _h_, pan head; _i_, countersink head. The square heads _a_ are usually left black, though in exceptional cases they are finished. Hexagon heads are left black or finished as circumstances may require; when a bolt head is to receive a wrench and is to be finished, it is usually made hexagon. Heads _c_ and _d_ are almost invariably finished when used on operative parts of machines, as are also _e_ and F. Heads _g_ are usually left black, while _h_ and _i_ are finished if used on machine work, and left black when used as rivets or on rough unfinished work. The heads from _e_ to _i_ assume various degrees of curve or angle to suit the requirements, but when the other end of the bolt is threaded to receive a nut, some means is necessary to prevent them from rotating in their holes when the nut is screwed up, thus preventing the nut from screwing up sufficiently tight. This is accomplished in woodwork by forging either a square under the head, as in Fig. 371, or by forging under the head a tit or stop, such as shown in Figs. 372 and 373 at P. Since, however, forging such stops on the bolt would prevent the heads from being turned up in the lathe, they are for lathe-turned bolts put in after the bolts have been finished in the lathe, a hole being subsequently drilled beneath the head to receive the pin or stop, P, Fig. 372, which may be tightly driven in. A small slot is cut in the edge of the hole to receive the stop. [Illustration: Fig. 371.] [Illustration: Fig. 372.] [Illustration: Fig. 373.] Bolts are designated for kinds, as in Fig. 374, in which _k_ is a machine bolt; _l_ a collar bolt, from having a collar on it; _m_ a cotter bolt, from having a cotter or key passing through it to serve in place of a nut; _n_ a carriage bolt, from having a square part under the head to sink in the wood and prevent the bolt from turning with the nut; and _o_ a countersink bolt for cases where the head of the bolt comes flush. [Illustration: Fig. 374.] The simple designation "machine bolt" is understood to mean a black or unfinished bolt having a square head and nut, and threaded, when the length of the bolt will admit it, and still leave an unthreaded part under the bolt head, for a length equal to about four times the diameter of the bolt head. If the bolt is to have other than a square head it is still called a machine bolt, but the shape of the head or nut is specially designated as "hexagon head machine bolt," this naturally implying that a hexagon nut also is required. In addition to these general names for bolts, there are others applied to special cases. Thus Fig. 375 represents a patch bolt or a bolt for fastening patches (as plate C to plate D), its peculiarity being that it has a square stem A for the wrench to screw it in by. When the piece the patch bolt screws into is thin, as in the case of patches on steam boilers, the pitch of the thread may, to avoid leakage, be finer than the usual standard. In countersink head bolts, such as the patch bolt in Fig. 375, the head is very liable to come off unless the countersink in the work (as in C) is quite fair with the tapped hole (as in D) because the thread of the bolt is made a tight fit to the hole, and all the bending that may take place is in the neck beneath the head, where fracture usually occurs. These bolts are provided with a square head A to screw them in by, and are turned in as at B to a diameter less than that at the bottom of the thread, so that if screwed up until they twist off, they will break in the neck at B. [Illustration: Fig. 375.] [Illustration: Fig. 376.] Instead of the hole being countersunk, however, it may be cupped or counterbored, as in Fig. 376, in which the names of the various forms of the enlargement of holes are given. The difference between a faced and a counterbored hole is that in a counterbored hole the head or collar of the pin passes within the counterbore, the use of the counterbore being in this case to cause the pin to stand firmly and straight. The difference between a dished and a cupped is merely that cupped is deeper than dished, and that between grooved and recessed is that a recess is a wide groove. Eye bolts are those having an eye in place of a head, as in Fig. 377, being secured by a pin passing through the eye, or by a second bolt, as in the figure. When the bolt requires to pivot, that part that is within the eye may be made of larger diameter than the thread, so as to form a shoulder against which the bolt may be screwed firmly home to secure it without gripping the eye bolt. [Illustration: Fig. 377.] [Illustration: Fig. 378.] Fig. 378 represents a foundation bolt for holding frames to the stone block of a foundation. The bolt head is coned and jagged with chisel cuts. It is let into a conical hole (widest at the bottom) in the stone block, and melted lead is poured around it to fill the hole and secure the bolt head. [Illustration: Fig. 379.] [Illustration: Fig. 380.] Another method of securing a foundation bolt head within a stone block is shown in Fig. 379; a similar coned hole is cut in the block, and besides the bolt head B a block W is inserted, the faces of the block and bolt being taper to fit to a taper key K, so that driving K locks both the bolt and the block in the stone. When the bolt can pass entirely through the foundation (as when the latter is brickwork) it is formed as in Fig. 380, in which B is a bolt threaded to receive a nut at the top. At the bottom it has a keyway for a key K, which abuts against the plate P. To prevent the key from slackening and coming out, it has a recess as shown in the figure at the sectional view of the bolt on the right of the illustration, the recess fitting down into the end of the keyway as shown. [Illustration: Fig. 381.] Another method is to give the bolt head the form at B in Fig. 381, and to cast a plate with a rectangular slot through, and with two lugs A C. The plate is bricked in and a hole large enough to pass the bolt head through is left in the brickwork. The bolt head is passed down through the brickwork in the position shown at the top, and when it has passed through the slot in the plate it is given a quarter turn, and then occupies the position shown in the lower view, the lugs A C preventing it from turning when the nut is screwed home. The objection to this is that the hole through the brickwork must be large enough to admit the bolt head. Obviously the bolt may have a solid square head, and a square shoulder fitting into a square hole in the plate, the whole being bricked in. [Illustration: Fig. 382.] [Illustration: Fig. 383.] Figs. 382 and 383 represent two forms of hook bolt for use in cases where it is not desired to have bolt holes through both pieces of the work. In Fig. 382 the head projects under the work and for some distance beneath and beyond the washer, as is denoted by the dotted line, hence it would suspend piece A from B or piece B from A. But in Fig. 383 the nut pressure is not beneath the part where the hook D grips the work, hence the nut would exert a pressure to pull piece B in the direction of the arrow; hence if B were a fixed piece the bolt would suspend A from it, but it could not suspend B from A. In woodwork the pressure of the nut is apt to compress the wood, causing the bolt head and nut to sink into the wood, and to obviate this, anchor plates are used to increase the area receiving the pressure; thus in Fig. 384 a plate is tapped to serve instead of a nut, and a similar plate may of course be placed under the bolt head. [Illustration: Fig. 384.] The Franklin Institute or United States Standard for the dimensions of bolt heads and nuts is as follows. In Fig. 385, D represents the diameter of the bolt, J represents the short diameter or width across flats of the bolt head or of the nut, being equal to one and a half times the diameter of the bolt, plus 1/16 inch for finished heads or nuts, and plus 1/8 inch for rough or unfinished heads or nuts. K represents the depth or thickness of the head or nut, which in finished heads or nuts equals the diameter of the bolt minus 1/16 inch, and in rough heads equals one half the distance between the parallel sides of the head, or in other words one half the width across the flats of the head. H represents the thickness or depth of the nut, which for finished nuts is made equal to the diameter of the bolt less 1/16 inch, and therefore the same thickness as the finished bolt head, while for rough or unfinished nuts it is made equal to the diameter of the bolt or the same as the rough bolt head. I represents the long diameter or diameter across corners, which, however, is a dimension not used to work to, and is inserted in the following tables merely for reference:-- [Illustration: Fig. 385.] TABLE OF THE FRANKLIN INSTITUTE STANDARD DIMENSIONS FOR THE HEADS OF BOLTS AND FOR THEIR NUTS, WHEN BOTH HEADS AND NUTS ARE OF HEXAGON FORM, AND ARE POLISHED OR FINISHED. +------------+-------------+-----------+---------------+-----------+ | Diameter | Diameter at | Number of | Diameter | Thickness | | at top | bottom of | Threads | across Flats, | or | | of Thread. | Thread. | per inch. | or short | Depth. | | | | | diameter. | | +------------+-------------+-----------+---------------+-----------+ | 1/4 | .185 | 20 | 7/16 | 3/16 | | 5/16 | .240 | 18 | 17/32 | 1/4 | | 3/8 | .294 | 16 | 5/8 | 5/16 | | 7/16 | .345 | 14 | 23/32 | 3/8 | | 1/2 | .400 | 13 | 13/16 | 7/16 | | 9/16 | .454 | 12 | 29/32 | 1/2 | | 5/8 | .507 | 11 | 1 | 9/16 | | 3/4 | .620 | 10 | 1-3/16 | 11/16 | | 7/8 | .731 | 9 | 1-3/8 | 13/16 | | 1 | .837 | 8 | 1-9/16 | 15/16 | | 1-1/8 | .940 | 7 | 1-3/4 | 1-1/16 | | 1-1/4 | 1.065 | 7 | 1-15/16 | 1-3/16 | | 1-3/8 | 1.160 | 6 | 2-1/8 | 1-5/16 | | 1-1/2 | 1.284 | 6 | 2-5/16 | 1-7/16 | | 1-5/8 | 1.389 | 5-1/2 | 2-1/2 | 1-9/16 | | 1-3/4 | 1.491 | 5 | 2-11/16 | 1-11/16 | | 1-7/8 | 1.616 | 5 | 2-7/8 | 1-13/16 | | 2 | 1.712 | 4-1/2 | 3-1/16 | 1-15/16 | | 2-1/4 | 1.962 | 4-1/2 | 3-7/16 | 2-3/16 | | 2-1/2 | 2.176 | 4 | 3-13/16 | 2-7/16 | | 2-3/4 | 2.426 | 4 | 4-3/16 | 2-11/16 | | 3 | 2.629 | 3-1/2 | 4-9/16 | 2-15/16 | | 3-1/4 | 2.879 | 3-1/2 | 4-15/16 | 3-3/16 | | 3-1/2 | 3.100 | 3-1/4 | 5-5/16 | 3-7/16 | | 3-3/4 | 3.377 | 3 | 5-11/16 | 3-13/16 | | 4 | 3.567 | 3 | 6-1/16 | 3-15/16 | | 4-1/4 | 3.798 | 2-7/8 | 6-7/16 | 4-3/16 | | 4-1/2 | 4.028 | 2-7/8 | 6-13/16 | 4-7/16 | | 4-3/4 | 4.256 | 2-5/8 | 7-3/16 | 4-11/16 | | 5 | 4.480 | 2-1/2 | 7-9/16 | 4-15/16 | | 5-1/4 | 4.730 | 2-1/2 | 7-15/16 | 5-3/16 | | 5-1/2 | 4.953 | 2-3/8 | 8-5/16 | 5-7/16 | | 5-3/4 | 5.203 | 2-3/8 | 8-11/16 | 5-11/16 | | 6 | 5.423 | 2-1/4 | 9-1/16 | 5-15/16 | +------------+-------------+-----------+---------------+-----------+ Note that square heads are supposed to be always unfinished, hence there is no standard for their sizes if finished. The Franklin Institute standard dimensions for hexagon and square bolt heads and nuts when the same are left unfinished or rough, as forged, are as follows:-- +----------+-------------+-------------+---------------+-----------+ | | Diameter | Diameter | Short | Thickness | | Bolt | across | across | diameter, | or | | Diameter | corners, or | corners or | or diameter | depth for | | in | long | long | across flats | square or | | Inches. | diameter of | diameter of | for square or | hexagon | | | hexagon | square | hexagon heads | heads. | | | heads. | heads. | and nuts. | | +----------+-------------+-------------+---------------+-----------+ | | Inch. | Inch. | Inch. | Inch. | | 1/4 | 37/64 | 7/10 | 1/2 | 1/4 | | 5/16 | 11/16 | 10/12 | 19/32 | 19/64 | | 3/8 | 51/64 | 63/64 | 11/16 | 11/32 | | 7/16 | 9/10 | 1-7/64 | 25/32 | 25/64 | | 1/2 | 1 | 1-15/64 | 7/8 | 7/16 | | 9/16 | 1-1/8 | 1-23/64 | 31/32 | 31/64 | | 5/8 | 1-7/32 | 1-1/2 | 1-1/16 | 17/32 | | 3/4 | 1-7/16 | 1-49/64 | 1-1/4 | 5/8 | | 7/8 | 1-21/32 | 2-1/32 | 1-7/16 | 23/32 | | 1 | 1-7/8 | 2-19/64 | 1-5/8 | 13/16 | | 1-1/8 | 2-2/32 | 2-9/16 | 1-13/16 | 29/32 | | 1-1/4 | 2-5/16 | 2-53/64 | 2 | 1 | | 1-3/8 | 2-17/32 | 3-3/32 | 2-3/16 | 1-3/32 | | 1-1/2 | 2-3/4 | 3-23/64 | 2-3/8 | 1-3/16 | | 1-5/8 | 2-31/32 | 3-5/8 | 2-9/16 | 1-9/32 | | 1-3/4 | 3-3/16 | 3-57/64 | 2-3/4 | 1-3/8 | | 1-7/8 | 3-13/32 | 4-5/32 | 2-15/16 | 1-15/32 | | 2 | 3-5/8 | 4-27/64 | 3-1/8 | 1-9/16 | | 2-1/4 | 4-1/16 | 4-61/64 | 3-1/2 | 1-3/4 | | 2-1/2 | 4-1/2 | 5-31/64 | 3-7/8 | 1-15/16 | | 2-3/4 | 4-29/32 | 6 | 4-1/4 | 2-1/8 | | 3 | 5-3/8 | 6-17/32 | 4-5/8 | 2-5/16 | | 3-1/4 | 5-13/16 | 7-1/16 | 5 | 2-1/2 | | 3-1/2 | 6-7/64 | 7-39/64 | 5-3/8 | 2-11/16 | | 3-3/4 | 6-21/32 | 8-1/8 | 5-3/4 | 2-7/8 | | 4 | 7-3/32 | 8-41/64 | 6-1/8 | 3-1/16 | | 4-1/4 | 7-9/16 | 9-3/16 | 6-1/2 | 3-1/4 | | 4-1/2 | 7-31/32 | 9-3/4 | 6-7/8 | 3-7/16 | | 4-3/4 | 8-13/32 | 10-1/4 | 7-1/4 | 3-5/8 | | 5 | 8-27/32 | 10-49/64 | 7-5/8 | 3-13/16 | | 5-1/4 | 9-9/32 | 11-23/64 | 8 | 4 | | 5-1/2 | 9-23/32 | 11-7/8 | 8-3/8 | 4-3/16 | | 5-3/4 | 10-5/32 | 12-3/8 | 8-3/4 | 4-3/8 | | 6 | 10-19/32 | 12-15/16 | 9-1/8 | 4-9/16 | +----------+-------------+-------------+---------------+-----------+ The depth or thickness of both the hexagon and square nuts when left rough or unfinished is, according to the above standard, equal to the diameter of the bolt. The following are the sizes of finished bolts and nuts according to the present Whitworth Standard. The exact sizes are given in decimals, and the nearest approximate sizes in sixty-fourths of an inch:-- +-------------+------------------------+----------------------+ | Diameter of | Width of nuts across | Height of bolt | | bolts. | flats. | heads. | +-------------+----------+-------------+--------+-------------+ | 1/8 | .338 | 21/64 _f_ | .1093 | 7/64 | | 3/16 | .448 | 29/64 _b_ | .1640 | 5/32 | | 1/4 | .525 | 33/64 _f_ | .2187 | 7/32 | | 5/16 | .6014 | 19/32 _f_ | .2734 | 17/64 | | 3/8 | .7094 | 45/64 _f_ | .3281 | 21/64 | | 7/16 | .8204 | 53/64 _b_ | .3828 | 3/8 _f_ | | 1/2 | .9191 | 29/32 _b_ | .4375 | 7/16 | | 9/16 | 1.011 | 1-1/64 _b_ | .4921 | 31/64 _f_ | | 5/8 | 1.101 | 1-3/32 _f_ | .5468 | 35/64 | | 11/16 | 1.2011 | 1-13/64 _b_ | .6015 | 19/32 _f_ | | 3/4 | 1.3012 | 1-19/64 _f_ | .6562 | 21/32 | | 13/16 | 1.39 | 1-25/64 _b_ | .7109 | 45/64 _f_ | | 7/8 | 1.4788 | 1-31/64 _b_ | .7656 | 49/64 | | 15/16 | 1.5745 | 1-37/64 _b_ | .8203 | 13/16 _f_ | | 1 | 1.6701 | 1-43/64 _b_ | .875 | 7/8 | | 1-1/8 | 1.8605 | 1-55/64 _f_ | .9843 | 63/64 | | 1-1/4 | 2.0483 | 2-3/64 _f_ | 1.0937 | 1-3/32 | | 1-3/8 | 2.2146 | 2-7/32 _b_ | 1.2031 | 1-13/64 | | 1-1/2 | 2.4134 | 2-13/32 _f_ | 1.3125 | 1-5/16 | | 1-5/8 | 2.5763 | 2-37/64 _b_ | 1.4128 | 1-27/64 | | 1-3/4 | 2.7578 | 2-3/4 _f_ | 1.5312 | 1-17/32 | | 1-7/8 | 3.0183 | 3-1/16 _f_ | 1.6406 | 1-41/64 | | 2 | 3.1491 | 3-5/32 _b_ | 1.75 | 1-3/4 | | 2-1/8 | 3.337 | 3-11/32 _b_ | 1.8523 | 1-55/64 | | 2-1/4 | 3.546 | 3-35/64 _b_ | 1.9687 | 1-31/32 | | 2-3/8 | 3.75 | 3-3/4 | 2.0781 | 2-5/64 | | 2-1/2 | 3.894 | 3-57/64 _f_ | 2.1875 | 2-3/16 | | 2-5/8 | 4.049 | 4-3/64 _f_ | 2.2968 | 2-19/64 | | 2-3/4 | 4.181 | 4-3/16 _b_ | 2.4062 | 2-13/32 | | 2-7/8 | 4.3456 | 4-11/32 _f_ | 2.5156 | 2-33/64 | | 3 | 4.531 | 4-17/32 _b_ | 2.625 | 2-5/8 | +-------------+----------+-------------+--------+-------------+ The thickness of the nuts is in every case the same as the diameter of the bolts: _f_ = full, _b_ = bare. When bolts screw directly into the work instead of passing through it and receiving a nut, they come under the head of either tap bolts, set screws, cap screws, or machine screws. A tap bolt is one in which the full length of the stem or body is threaded, and differs from a set screw, which is similarly threaded, in the respect that in a set screw the head is square and its diameter is the same as the square bar of steel or iron (as the case may be) from which the screw was made, while in the tap bolt the head is larger in diameter than the bar it was made from. Furthermore a tap bolt may have a hexagon head, which is usually left unfinished unless ordered to be finished, as is also the case with set screws. Cap screws are made with heads either hexagon, square, or round, and also with a square head and round collar, as in Fig. 386, the square heads being of larger diameter than the iron from which they were made. When the heads of cap screws are finished they are designated as "milled heads." [Illustration: Fig. 386.] [Illustration: Fig. 387.] A machine screw is a small screw, such as in Fig. 387, the diameter of the body being made to the Birmingham wire gauge, the heads being formed by upsetting the wire of which they are made. They have saw slots S for a screw driver, the threads having special pitches, which are given hereafter. The forms of the heads are as in Fig. 387, A being termed a Fillister, B a countersink, and C a round head. The difference between a Fillister head of a machine screw and the same form of head in a cap screw is that the former is upset cold, and the latter is either forged or cut out of the solid metal. When the end of a screw abuts against the work to secure it, it is termed a set screw. The ordinary form of set screw is shown in Fig. 389, the head being square and either black or polished as may be required. The ends of the set screws of commerce, that is to say, that are kept on sale, are usually either pointed as at A, Fig. 388, slightly bevelled as at B, or cupped as at D. If left flat or only slightly bevelled as at B, they are liable, if of steel and not hardened, or if of iron and case-hardened only, to bulge out as at C. This prevents them from slacking back easily or prevents removal if necessary, and even though of hardened steel they do not grip very firmly. On this account their points are sometimes made conical, as at A. This form, however, possesses a disadvantage when applied to a piece of work that requires accurate adjustment for position, inasmuch as it makes a conical indentation in the work, and unless the point be moved sufficiently to clear this indentation the point will fall back into it; hence the conical point is not desirable when the piece may require temporary fixture to find the adjustment before being finally screwed home. For these reasons the best form of set screw end is shown at D, the outside of the end being chamfered off and the inside being cupped, as denoted by the dotted lines. This form cuts a ring in the work, but will hold sufficiently for purposes of adjustment without being screwed home firmly. In some cases the end of the set screw is tapped through the enveloping piece (as a hub) and its end projects into a plain hole in the internal piece of the work, and in this case the end of the thread is turned off for a distance of two or three threads, as at A in Fig. 390. Similarly, when the head of the screw is to act or bear upon the work, the thread may be turned off as at B in the figure. When a bolt has no head, but is intended to screw into the work at one end, and receive a nut at the other, it is termed a stud or standing bolt. The simplest form of standing bolt is that in which it is parallel from end to end with a thread at each end, and an unthreaded part in the middle, but since standing bolts or studs require to remain fixed in the work, it is necessary to screw them tightly into their places, and therefore firmly home. This induces the difficulty that some studs may screw a trifle farther into the work than others, so that some of the stud ends may project farther through the nuts than others, giving an appearance that the studs have been made of different lengths. The causes of this may be slight variations in the tapping of the holes and the threading of the studs. If those that appear longest are taken out and reduced to the lengths of the others, it will be found sometimes that the stud on the second insertion will pass farther into the work than at the first, and the stud will project less through the nut than the others. To avoid this those protruding most may be worked backward and forward with the wrench and thus induced to screw home to the required distance, but it is better to provide to the stud a shoulder against which it may screw firmly home; thus in Fig. 391 is a stud, whose end A is to screw into the work, part B is to enter the hole in the work (the thread in the hole being cut away at the mouth to receive B). In this case the shoulder between B and C screwing firmly against the face of the work, all the studs being made of equal length from this shoulder to end E, then the thickness of the flange or work secured by the nut being equal, the nuts will pass an equal distance on end D, and E will project equally through all the nuts. The length of the plain part C is always made slightly less than the thickness of the flange or foot of the work to be bolted up, so that the nut shall not meet C before gripping the flange surface. There are, however, other considerations in determining the shape and size of the parts A and C of studs. Thus, suppose a stud to have been in place some time, the nut on end E being screwed firmly home on the work, and perhaps somewhat corroded on E. Then the wrench pressure applied to the nut will be in a direction to unscrew the stud out of the work, and if there be less friction between A and the thread in the work than there is between D and the thread in the nut, the stud and not the nut will unscrew. It is for this purpose that the end A requires firmly screwing into the work. But in the case of much corrosion this is not always sufficient, and the thread A is therefore sometimes made of a larger diameter than the thread at D. In this case the question at once arises, What shall be the diameter of the plain part C? [Illustration: Fig. 388.] [Illustration: Fig. 389.] [Illustration: Fig. 390.] [Illustration: Fig. 391.] If it be left slightly larger than D, but the depth of the thread less than A, then it may be held sufficiently firmly by the fit of the threads (without the aid of screwing against a shoulder) to prevent unscrewing when releasing the nut, and may be screwed within the work until its end projects the required distance; thus all the studs may project an equal distance, but there will be the disadvantage that when the studs require removing and are corroded the plain part is apt to twist off, leaving the end A plugging the hole. The plain part C may be left of same diameter as A, both being larger than D; but in this case the difficulty of having all the studs project equally when screwed home, as previously mentioned, is induced; hence C may be larger than A, and a shoulder left at B, as in the figure; this would afford excellent facility for unscrewing the stud to remove it, as well as insuring equal projection of E. The best method of all is, so far as quality goes, to make the plain part C square, as in Fig. 392, which is an English practice, the square affording a shoulder to screw up against and secure an equal projection while serving to receive a wrench to put in or remove the stud. In this case the holes in the flange or piece bolted up being squared, the stud cannot in any case unscrew with the nut. The objection to this squared stud is that the studs cannot be made from round bar iron, and are therefore not so easily made, and that the squaring of the holes in the flange or part of the work supported by the stud is again extra work, and for these reasons studs with square instead of cylindrical mid-sections have not found favor in the United States. [Illustration: Fig. 392.] [Illustration: Fig. 393.] An excellent method of preventing the stud from unscrewing with the nut is to make the end A longer than the nut end, as in Fig. 393, so that its threads will have more friction; and this has the further advantage that in cast iron it serves also to make the strength of the thread equal to that of the stud. As the faces of the nuts are apt when screwed home to score or mark the face of the work, it adds to the neatness of the appearance to use a washer W beneath the nut, which distributes the pressure over a greater area of work surface. In some practice the ends A of studs are threaded taper, which insures that they shall fit tight and enables their more easy extraction. [Illustration: Fig. 394.] An excellent tool for inserting studs of this kind to the proper distance is shown in Fig. 394. It consists of a square body _a_ threaded to receive the stud whose end is shown at _c_. The upper end is threaded to receive an adjusting screw _b_, which is screwed in so that its end _d_ meets the end _c_ of the stud. It is obvious that _b_ may be so adjusted that when _a_ is operated by a wrench applied to its body until its end face meets the work and the stud is inserted to the proper depth, all subsequent studs may be put into the same depth. [Illustration: Fig. 395.] When the work pivots upon a stem, as in Fig. 395, the bolt is termed a standing pin, and as in such cases the stem requires to stand firm and true it is usual to provide the pin with a collar, as shown in the figure, and to secure the pivoted piece in place with a washer and a taper pin because nuts are liable to loosen back of themselves. Furthermore, a pin and washer admit of more speedy disconnection than a nut does, and also give a more delicate adjustment for end fit. In drilling the tapping holes for standing bolts, it is the practice with some to drill the holes in cast iron of such a size that the tap will cut three-quarters only of a full thread, the claim being that it is as strong as a full thread. The difference in strength between a three-quarter and a full thread in cast iron is no doubt practically very small indeed, while the process of tapping is very much easier for the three-quarter full thread, because the tap may, in that case, be wound continuously forward without backing it at every quarter or half revolution, as would otherwise be necessary, in order to give the oil access to the cutting edges of the tap--and oil should always be used in the process of tapping (even though on cast iron it causes the cuttings to clog in the flutes of the tap, necessitating in many cases that the tap be once or twice during the operation taken out, and the cuttings removed) because the oil preserves the cutting edges of the tap teeth from undue abrasion, and, therefore, from unnecessarily rapid dulling. With a tap having ordinarily wide and deep flutes, and used upon a hole but little deeper than the diameter of the tap, the cuttings due to making a three-quarter full thread will not more than fill the flutes of the tap by the time its duty is performed. We have also to consider that with a three-quarter full thread it is much easier to extract the standing bolt when it is necessary to do so, so that all things considered it is permissible to have such a thread, providing the tapping hole does not pass through into a cylinder or chamber requiring to be kept steam-tight, for in that case the bolt would be almost sure to leak. As a preventive against such leakage, the threads are sometimes cut upon the standing bolts without having a terminal groove, and are then screwed in as far as they will go; the termination of the thread upon the standing bolt at the standing or short end being relied upon to jam into and close up the thread in the hole. A great objection to this, however, is the fact that the bolts are liable to screw into the holes to unequal depths, so that the outer ends will not project an equal distance through the nuts, and this has a bad appearance upon fine work. It is better, then, in such a case, to tap the holes a full thread, the extra trouble involved in the tapping being to some extent compensated for in the fact that a smaller hole, which can be more quickly drilled, is required for the full than for the three-quarter thread. The depth of the tapping hole should be made if possible equal to one and a half times the diameter of the tap, so that in case the hole bottoms and the tap cannot pass through, the taper, and what is called in England the second, and in the United States the plug tap, will finish the thread deep enough without employing a third tap, for the labor employed in drilling the hole deeper is less than that necessary to the employment of a third tap. If the hole passes through the work, its depth need not, except for cast-iron holes, be greater than 1/8 inch more than the diameter of the bolt thread, which amount of excess is desirable so that in case the nut corrodes, the nut being as thick as the diameter of the tap, and therefore an inch less than the depth of the hole at the standing end, will be more likely to leave the stud standing than to carry it with it when being unscrewed. [Illustration: Fig. 396.] When it is desirable to provide that bolts may be quickly removed, the flanges may be furnished with slots, as in Fig. 396, so that the bolts may be passed in from the outside, and in this case it is simply necessary to slacken back the nut only. It is preferable, however, in this case to have the bolt square under the head, as in Fig. 397, so as to prevent the bolt from turning when screwing up or unscrewing the nut. The bolt is squared at A, which fits easily into the flange. The flanges, however, should in this case be of ample depth or thickness to prevent their breakage, twice the depth of the nut being a common proportion. [Illustration: Fig. 397.] [Illustration: Fig. 398.] In cases where it is inconvenient for the bolt head to pass through the work a [T] groove is employed, as in Fig. 398. In this case the bolt head may fit easily at A B to the sides A B of the groove, so that while the bolt head will slide freely along the groove, the head, being square, cannot turn in the slot when the nut is screwed home. This, however, is more efficiently attained when there is a square part beneath the bolt head, as in Fig. 399, the square A of the bolt fitting easily to the slot B of the groove. [Illustration: Fig. 399.] [Illustration: Fig. 400.] When it is undesirable that the slots run out to the edge of the work they may terminate in a recess, as at A in Fig. 400, which affords ingress of the bolt head to the slot; or the bolt head may be formed as in Fig. 401, the width A B of the bolt head passing easily through the top A B of the slot, and the bolt head after its insertion being turned in the direction of the arrow, which it is enabled to do by reason of the rounded corners C D. In this case, also, there may be a square under the head to prevent the bolt head from locking in the slot, but the corners of the square must also be rounded as in Fig. 402. [Illustration: Fig. 401.] [Illustration: Fig. 402.] The underneath or gripping surface of a bolt head should be hollow, as at A in Fig. 403, rather than rounding as at B, because, if rounding, the bolt will rotate with the nut when the latter grips the work surface. It should also be true with the axial line of the bolt so as to bear fairly upon the work without bending. The same remarks apply to the bedding surface of the nut, because to whatever amount the face is out of true it will bend the threaded end of the bolt, and this may be sufficient to cause the bolt to break. [Illustration: Fig. 403.] In Fig. 404, for example, is shown a bolt and nut, neither of which bed fair, being open at A and B respectively, and it is obvious that the strain will tend to bend or break the bolt across the respective dotted lines C, D. In the case of the nut there is sufficient elasticity in the thread to allow of the nut forcing itself to a bed on the work, the bolt bending; but in the case of the bolt head the bending is very apt to break off the bolt short in the neck under the head. In a tap bolt where the wrench is applied to the bolt head, the rotation, under severe strain, of the head will usually cause it to break off in all cases where the bolt is rigidly held, so that it cannot cant over and allow the head to bed fair. [Illustration: Fig. 404.] A plain tap bolt should be turned up along its body, because if out of true the hole it passes through must be made large enough to suit the eccentricity of the bolt, or else a portion of the wrench pressure will be expended in rotating the bolt in the hole instead of being expended solely in screwing the bolt farther into the work. It is obvious therefore, that if a tap bolt be left black the hole it passes through must be sufficiently large to make full allowance for the want of truth in the bolt. For the same reasons the holes for tapped bolts require to be tapped very true. Black studs possess an advantage (over tap bolts) in this respect, inasmuch as that if the holes are not tapped quite straight the error may be to some extent remedied by screwing them fully home and then bending them by hammer blows. Nuts are varied in form to suit the nature of the work. For ordinary work, as upon bolts, their shape is usually made to conform to the shape of the bolt head, but when the nut is exposed to view and the bolt head hidden, the bolt end and the nut are (for finished work) finished while the bolt heads are left black. [Illustration: Fig. 405.] [Illustration: Fig. 406.] The most common form of hexagon nut is shown in Fig. 405, the upper edge being chamfered off at an angle of about 40°. In some cases the lower edge is cut away at the corners, as in Fig. 405 at A, the object being to prevent the corners of the nut from leaving a circle of bearing marks upon the work, but this gives an appearance at the corners that the nut does not bed fair. Another shape used by some for the end faces of deep nuts, that is to say, those whose depth exceeds the diameter of the bolt, is shown in Fig. 406. Nuts of extra depth are used when, from the nut being often tightened and released, the thread wear is increased, and the extra thread length is to diminish the wear. To avoid the difficulty of having some of the bolt ends project farther through some nuts than others on a given piece of work, as is liable to occur where the flanges to be bolted together are not turned on all four radial faces, the form of nut shown in Fig. 407 is sometimes employed, the thread in the nut extending beyond the bolt end. [Illustration: Fig. 407.] [Illustration: Fig. 408.] As an example of the application of this nut, suppose a cylinder cover to be held by bolts, then the cylinder flange not being turned on its back face is usually of unequal thickness; hence to have the bolt ends project equally through the nuts, each bolt would require to be made of a length to suit a particular hole, and this would demand that each hole and bolt be marked so that they may be replaced when taken out, without trying them in their places. Another application of this nut is to make a joint where the threads may be apt to leak. In this case the mouth of the hole is recessed and coned at the edge; the nut is chamfered off with a similar cone, and a washer W, Fig. 408, is placed beneath the nut to compress and conform to the coned recess; thus with the aid of a cement of some kind, as red or white lead (usually red lead), a tight joint may be made independent of the fit of the threads. When the hole through which the bolt passes is considerably larger in diameter than the bolt, the flange nut shown in Fig. 409 is employed, the flange covering the hole. A detached washer may be used for the same purpose, providing that its hole fit the bolt and it be of a sufficient thickness to withstand the pressure and not bend or sink into the hole. [Illustration: Fig. 409.] [Illustration: Fig. 410.] Circular nuts are employed where, on account of their rotating at high speed, it is necessary that they be balanced as nearly as possible so as not to generate unbalanced centrifugal force. Fig. 410 represents a nut of this kind: two diametrically opposite flat sides, as A, affording a hold for the wrench. Other forms of circular nuts are shown in Figs. 411 and 412. These are employed where the nuts are not subject to great strain, and where lightness is an object. [Illustration: Fig. 411.] [Illustration: Fig. 412.] That in Fig. 411 is pierced around its circumference with cylindrical holes, as A, B, C, to receive a round lever or rod or a wrench, such as shown in Fig. 459. That shown in Fig. 412 has slots instead of holes in its circumference, and the form of its wrench is shown in Fig. 461. When nuts are employed upon bolts in which the strain of the duty is longitudinal to the bolt, and especially if the direction of motion is periodically reversed, and also when a bolt is subject to shocks or vibrations, a single nut is liable to become loose upon the bolt, and a second nut, termed a check nut, jamb nut, or safety nut, becomes necessary, because it is found that if two nuts be employed, as in Fig. 413, and the second nut be screwed firmly home against the first, they are much less liable to come loose on the bolt. Considerable difference of practice exists in relation to the thickness of the two nuts when a check nut is employed. The first or ordinary nut is screwed home, and the second or check nut is then screwed home. If the second nut is screwed home as firmly as the first, it is obvious that the strain will fall mainly on the second. If it be screwed home more firmly than the first, the latter may be theoretically considered to be relieved entirely of the strain, while if it be screwed less firmly home, the first will be relieved to a proportionate degree of the strain. It is usual to screw the second home with the same force as applied to the first, and it would, therefore, appear that the first nut, being relieved of strain, need not be so thick as the first, but it is to be considered that, practically, the first nut will always have some contact with the bolt threads, because from the imperfections in the threads of ordinary bolts the area and the force of contact is not usually the same nor in the same direction in both nuts, unless both nuts were tapped with the same tap and at about the same time. When, for example, a tap is put into the tapping machine, it is at its normal temperature, and of a diameter due to that temperature, but as its work proceeds its temperature increases, notwithstanding that it may be freely supplied with oil, because the oil cannot, over the limited area of the tap, carry off all the heat generated by the cutting of a tap rotated at the speeds usually employed in practice. As a result of this increase of temperature, we have a corresponding increase in the diameter of the tap, and a variation in the diameter of the threads in the nuts. The variation in the nuts, however, is less than that in the tap diameter, because as the heated tap passes through the nut it imparts some of its heat to the nut, causing it also to expand, and hence to contract in cooling after it has been tapped, and, therefore, when cold, to be of a diameter nearer to that of the tap. Furthermore, as the tap becomes heated it expands in length, and its pitch increases, hence here is another influence tending to cause the pitches of the nut threads to vary, because although the temperature of the tap when in constant use reaches a limit beyond which, so long as its speed of rotation is constant, it never proceeds; yet, when the tap is taken from the machine to remove the tapped nuts which have collected on its shank, and it is cooled in the oil to prevent it from becoming heated any more than necessary, the pitch as well as the diameter of the tap is reduced nearer to its normal standard. [Illustration: Fig. 413.] [Illustration: Fig. 414.] So far, then, as theoretical correctness, either of pitch or diameter in nut threads, is concerned, it could only be attained (supposing that the errors induced by hardening the tap could be eliminated) by employing the taps at a speed of rotation sufficiently slow to give the oil time to carry off all the heat generated by the cutting process. But this would require a speed so comparatively slow as not to be commercially practicable, unless followed by all manufacturers. Practically, however, it may be considered that if two nuts be tapped by a tap that has become warmed by use, they will be of the same diameter and pitch, and should, therefore, have an equal area and nature of contact with the bolt thread, supposing that the bolt thread itself is of equal and uniform pitch. But the dies which cut the thread upon the bolt also become heated and expanded in pitch. But if the temperature of the dies be the same as that of the tap, the pitches on both the bolt and in the nut will correspond, though neither may be theoretically true to the designated standard. In some machines for nut tapping the tap is submerged in oil, and thus the error due to variations of temperature is practically eliminated, though even in this case the temperature of the oil will gradually increase, but not sufficiently to be of practical moment. Let it now be noted that from the hardening process the taps shrink in length and become of finer pitch, while the dies expand and become of coarser pitch, and that this alone precludes the possibility of having the nut threads fit perfectly to those on the bolt. It becomes apparent, then, that only by cutting the threads in the lathe, and with a single-toothed lathe tool that can be ground to correct angle after hardening, can a bolt and nut be theoretically or accurately threaded. Under skilful operation, however, both in the manufacture of the screw-cutting tools and in their operation, a degree of accuracy can be obtained in tapped nuts and die-threaded bolts that is sufficient with a single nut for ordinary uses, but in situations in which the direction of pressure on the nut is periodically reversed, or in which it is subject to shocks or vibrations, the check nut becomes necessary, as before stated. An excellent method of preventing a nut from slackening back of itself is shown in the safety nut in Fig. 414; it consists of a second nut having a finer thread than the first one, so that the motion of the first would in unscrewing exceed that of the second, hence the locking is effectually secured. [Illustration: Fig. 415.] Work may be very securely fastened together by the employment of what are called differential screws, the principle of whose action may be explained with reference to Fig. 415, which is extracted from "Mechanics." It represents a piston head and piston rod secured together by means of a differential screw nut. The nut contains an internal thread to screw on the rod, and an external one to screw into the piston head, but the internal thread and that on the rod differ from the external one, and that in the head by a certain amount, as say one tenth of the pitch. The nut itself is furnished with a hexagonal head, and when screwed into place draws the two parts together with the same power as a screw having a pitch equal to the difference between the two pitches. [Illustration: Fig. 416.] When putting the parts together the nut is first screwed upon the rod B. The outside threads are then entered into the thread in the piston C, and by means of a suitable wrench the nut is screwed into the proper depth. As shown in the engraving, the nut goes on to the rod a couple of threads before it is entered in the piston. The tightening then takes place precisely as though the nut had a solid bearing on the piston and a fine thread on the rod, the pitch of which is equal to the difference between the pitches of the two threads. Fig. 416 shows its application to the securing of a pump plunger upon the end of a piston-rod. In this case, as the rod does not pass through the nut, the latter is provided with a cap, which covers the end of the rod entirely. [Illustration: Fig. 417.] The principle of the differential screw may be employed to effect very fine adjustments in place of using a very fine thread, which would soon wear out or wear loose. Thus in Fig. 417 is shown the differential foot screws employed to level astronomical instruments. C D is a foot of the instrument to be levelled. It is threaded to receive screw A, which is in turn threaded to receive the screw B, whose foot rests in the recess or cup in E F. Suppose the pitch of screw A is 30 per inch, and that of B is 40, and we have as follows. If A and B are turned together the foot C D is moved the amount due to the pitch of A. If B is turned within a the foot is moved the amount due to the pitch of B. If A is turned the friction of the foot of B will hold B stationary, and the motion of C D will equal the difference between the pitches of the threads of A and B. Thus one revolution of A forward causes it to descend through C D 1/30 inch (its pitch), tending to raise C D 1/30 inch. But while doing this it has screwed down upon the thread of B 1/40 inch (the pitch of B) and this tends to lower C D, hence C D is moved 1/120 inch, because 1/30-1/40 = 1/120. To cause a single nut to lock itself and dispense with the second or jamb nut, various expedients have been employed. Thus in Fig. 418 is shown a nut split on one side; after being threaded the split is closed by hammer blows, appearing as shown in the detached nut. Upon screwing the nut upon the bolt the latter forces the split nut open again by thread pressure, and this pressure locks the nut. Now there will be considerable elasticity in the nut, so that if the thread compresses on its bearing area, this elasticity will take up the wear or compression and still cause the threads to bind. Sometimes a set screw is added to the split, as in Fig. 419, in which case the split need not be closed with the hammer. Another method is to split the nut across the end as shown in Fig. 420, tapping the nut with the split open, then closing the split by hammer blows. Here as before the nut would pass easily upon the bolt until the bolt reached the split, when the subsequent threads would bind. In yet another design, shown in Fig. 421, four splits are made across the end, while the face of the nut is hollowed, so that a flat place near each corner meets the work surface. The pressure induced on these corners by screwing the nut home is relied on in this case to spring the nut, causing the thread at the split end to close upon and grip the bolt thread. Check nuts are sometimes employed to lock in position a screw that is screwed into the work, thus screws that require to be operated to effect an adjustment of length (as in the case of eccentric rods and eccentric straps) are supplied with a check nut, the object being to firmly lock the screw in its adjusted position. The following are forms of nuts employed to effect end adjustments of length, or to prevent end motion in spindles or shafts that rotate in bearings. Fig. 422 shows two cylindrical check nuts, the inner one forming a flange for the bearing. The objection to this is that in screwing up the check nut the adjustment of the first nut is liable to become altered in screwing up the second one, notwithstanding that the first be held by a lever or wrench while the second is screwed home. Another method is to insert a threaded feather in the adjustment nut and having at its back a set screw to hold the nut in its adjusted position, as in Fig. 423. In this case the protruding head of the set screw is objectionable. In place of the feather the thread of the spindle may be turned off and a simple set screw employed, as in Fig. 424; here again, however, the projecting set screw head is objectionable. The grip of an adjustment nut may be increased by splitting it and using a pinching or binding screw, as in Fig. 425, in which case the bore of the thread is closed by the screw, and the nut may be countersunk to obviate the objection of a projecting head. For adjusting the length of rods or spindles a split nut with binding screws, such as shown in Fig. 426, is an excellent and substantial device. The bore is threaded with a right-hand thread at one end and a left-hand one at the other, so that by rotating the nut the rod is lengthened or shortened according to the direction of rod rotation. Obviously a clamp nut of this class, but intended to take up lost motion or effect end adjustment, may be formed as in Fig. 427, but the projecting ears or screw are objectionable. [Illustration: Fig. 429.] Where there is sufficient length to admit it an adjustment nut, such as in Fig. 428, is a substantial arrangement. The nut A is threaded on the spindle and has a taper threaded split nut to receive the nut B. Nut A effects the end adjustment by screwing upon the spindle, and is additionally locked thereon by screwing B up the taper split nut, causing it to close upon and grip the spindle. [Illustration: Fig. 430.] Lost motion in square threads and nuts may be taken up by forming the nut in two halves, A and B, in Fig. 429 (A being shown in section) and securing them together by the screws C C. The lost motion is taken up by letting the two halves together by filing away the joint face D of either half, causing the thread in the nut to bear against one side only of the thread of the screw. The same end may be accomplished in nuts for [V]-shaped threads by forming the nut either in two halves, as shown in Fig. 430, in which A is a cap secured by screws B, the joint face C being filed away to take up the lost motion. Or the nut may be in one piece with the joint C left open, the screws B crossing the nut upon the screw by pressure. In this case the nut closes upon the circumference of the thread, taking up the wear by closing upon both sides of the thread instead of on one side only as in the case of the square thread. [Illustration: Fig. 431.] [Illustration: Fig. 432.] [Illustration: Fig. 433.] In cases where nuts are placed under rapid vibration or motion they are sometimes detained in their places by pins or cotters. The simplest form of pin used for this purpose is the split pin, shown in Fig. 431. It is made from half round wire and is parallel, and does not, therefore, possess the capability of being tightened when the nut has become loosened from wear. As the wire from which these pins are made is not usually a full half circle the pins should, if the best results are to be obtained, be filed to fit the hole, and in doing this, care should be taken to have the pin bear fully in the direction of the split which is longitudinal to the bolt, as shown in Fig. 432, where the pin is shown with its ends opened out as is required to prevent the pin from coming out. If the pin bears in a direction across the bolt as at A D, in Fig. 433, it will soon become loose. [Illustration: _VOL. I._ =END-ADJUSTMENT AND LOCKING DEVICES.= _PLATE IV_. Fig. 418. Fig. 419. Fig. 420. Fig. 421. Fig. 422. Fig. 423. Fig. 424. Fig. 425. Fig. 426. Fig. 427. Fig. 428.] Pins of this class are sometimes passed through the nut itself as well as through the bolt; but when this is the case, there is the objection that the nut cannot be screwed up to take up any wear, because in that case the hole in the nut would not come fair with that in the bolt, and the pin could not be inserted. When, therefore, such a pin passes through the nut, lost motion must be taken up by placing an additional or a thicker washer behind the nut. The efficiency of this pin as a locking device is much increased by passing it through the nut, because its bearing, and, therefore, wearing area, is increased, and the pin is prevented from bending after the manner shown in Fig. 434, as it is apt to do under excessive wear, with the result that the end pressure of the nut almost shears or severs the pin close to the perimeter of the bolt. [Illustration: Fig. 434.] [Illustration: Fig. 435.] To enable the pin to take up the wear, it is a good plan to file on it a flat place, which must be parallel to the sides of the pin-head and placed against the nut-face. The hole in the bolt is in this case made to fall slightly under the nut, as in Fig. 435, so that the flat place is necessary to enable the pin to enter. By filing the flat place taper, the lost motion that may ensue from wear may be taken up by simply driving the pin in farther. [Illustration: Fig. 436.] [Illustration: Fig. 437.] In place of this class of split pin, solid taper pins are sometimes used, but these, if employed in situations where they are subject to jar and vibration, are apt sometimes to come loose, especially if they be given much taper, because in that case they do not wedge so tightly in the hole. But if a taper pin be made too nearly parallel, it will drive through too easily, and has less capability to take up the play due to wear. An ordinary degree of taper is about 5/8 inch per foot of length, but in long pins having ample bearing area, 1/2 inch per foot of length is ample. To prevent taper pins from coming loose from vibration, they are sometimes forged split at the small end, as in Fig. 436, and opened out at that end after the manner shown in Fig. 432. This forms a very secure locking device, and one easily applied. The split ends are closed by hammer blows to remove the pin, and it is found that such pins may be opened and closed many times without breaking, even though made of cast steel. The heads and ends are rounded so as to prevent them from swelling from the hammer blows necessary to drive them in and out. When a taper pin is passed through a nut and bolt, it simply serves as a locking device to secure the nut in position, and the lost motion due to wear must be taken up by the application of a washer beneath the nut, as already described. If, however, the taper pin be applied outside the nut, it may be made to take up the wear, by filing on it a flat place, and locating the hole in the bolt so that it will fall partly beneath the nut, as shown in Fig. 435. In this case, the nut may be screwed up to take up the wear, and the pin by being driven farther in will still bear against the nut and prevent its slacking back. Another and excellent locking device for bolts or nuts, is the cotter shown in Fig. 437, which is sometimes forged solid and sometimes split, as in the figure. By being made taper from A to B, it will take up the wear if driven farther in. Its width gives it strength in the direction in which it acts to lock, the overhanging head is to drive it out by, and the bevelled corner C is to enable its easy insertion, because if left sharp it would be liable to catch against the edge of the cotter-way and burr up. If made split, its ends are opened out after it is inserted, as shown at D. When closing the ends of either split cotters or split pins to extract them it is better to close one side first and bend it over a trifle too much, so that, when closing the other side, by the time the pin is straightened the two ends will be closed together, and extraction becomes easy. [Illustration: Fig. 438.] A very safe method in the case of a single nut or bolt head is to provide a separate plate, as in Fig. 438. The plate P is provided with three sides, corresponding to the sides of the hexagon, as shown, and in the middle of these sides are cut the notches A B C, so that by giving the nut N one-twelfth of a turn its corners D E would be held by the notches B C, S being a small screw to hold P. It is obvious that a simple set screw passed through the walls of the nut would grip the bolt thread and serve to hold the nut, but this would damage the bolt thread, and, furthermore, that thread would under jar or vibration compress and let the set screw come loose. A better plan than this is to provide a thick washer beneath the nut and let a set screw pass through the washer and grip the bolt, fastening or setting up the set screw after the nut is screwed home. This, however, makes the washer a gripping piece and in no wise serves to lock the nut. In addition to the washer a pin may project through the radial face of the washer and into the work surface, which will prevent, in connection with the set screw, both the bolt and the washer from turning. When a bolt has no thread but is secured by a taper pin, set screw, cotter, or device other than a nut, it is termed a pin. So, likewise, a cylindrical piece serving as a pivot, or to hold two pieces together and having no head, is termed a pin. The usual method of securing a pin is by a set screw or by a taper pin and a washer; and since the term pin applying to both may lead to misunderstanding, the term bolt will here be applied to the large and the term pin to the small or securing pin only. The object of pins and washers is to secure an exact degree of fit and permit of rapid connection or disconnection. An application of a taper pin and washer to a double eye is shown in Fig. 439. It is obvious, in this case, the pin E will drive home until it fills the hole through the bolt, and hence always to the same spot, so that the parts may be taken apart and put together again rapidly, while the fit is self-adjusting, providing that the pin fills the hole, bears upon the groove in the washer, and is driven home, so that by first letting the pin bind the washer W slightly too tight, and then filing the radial faces of the joint to a proper fit (which will ease the bearing of the pin on the washer), an exact degree of fit and great accuracy may be obtained, whereas when a nut is used it is difficult to bring the nut to the exact same position when screwing it home. When the joints are to be thus fitted, it is a good plan to drill the pin-hole (through the bolt) so that its centre falls coincident with the face of the washer; to then file out the grooves in the washer not quite deep enough. The pin may then be filed to fit the hole through the bolt, but left slightly too large, so that it shall not pass quite far enough through the bolt. The joint faces may then be filed true, and when finished, the parts may be put together, and the groove through the washer and hole through the bolt may be simultaneously finished by reaming with a taper reamer. This will leave the job a good fit, with a full bearing, without much trouble, the final reaming letting the taper pin pass to its proper distance through the bolt. [Illustration: Fig. 439.] [Illustration: Fig. 440.] Taper pins are sometimes employed to secure in position a bolt that rotates, or one that requires locking in position, in situations in which there is no room for the bolt end to project and receive a nut or washer. Examples of these kinds are shown in section in Figs. 440 and 441. In 441, B is a stud pin, to rotate in the bore of A. C is a semi circular groove in B, and P a taper pin entering one-half in the groove C and one-half in B, thus preventing B from moving endwise in A, while at the same time permitting its free rotation. In this case it is best to fit B to its place, a fit tight enough to hold it firmly while the pin-hole is drilled and reamed through A and B simultaneously, then B can be put in the lathe, and the groove cut in to coincide with the half-hole or groove caused in the pin by the drilling, and after the groove is turned the stud pin may be eased to the required degree of working fit. The process for Fig. 440 is precisely the same, except that no groove turning or easing of the pin will be necessary, because the pin being locked in position may be left a tight fit. If, however, it is considered desirable to give the taper pin in Fig. 440 a little draft, so that any looseness (that may occur to the pin or stud) from wear may be taken up, then after the taper pin-hole has been drilled and reamed, the pin or stud (D in the figure) may be taken out, and its taper pin-hole _in the arm E_ may be filed out all the way through on one side, as denoted by the dotted half-circle. This will give draft to the pin and allow it to drive farther through and grip the pin as it wears smaller. If a bolt and nut fit too tightly in their threads the nut may be wound back and forth upon the bolt under free lubrication, which will ease the fit by wearing away or compressing that part of the thread surface that is in contact. If this should not suffice we may generally ease a nut that fits so tight that it cannot be screwed upon the bolt with an ordinary wrench, by screwing the nut on a thread or two, then rest it on an iron block, and lightly hammer its sides; it will loosen its fit, and if continued, the nut may be made to pass down the bolt comparatively easily. Now, in this operation, it is not that the nut has been stretched, but that the points of contact on the threads have become compressed and imbedded; we have, in other words, caused the shape of each thread to conform nearer to that of the other than it is practicable to make them, because of reasons explained in the remarks on screw threads, and on taps. [Illustration: Fig. 441.] To remove nuts or bolts that have become corroded in their places, we may adopt the following methods:-- If the nuts are so corroded that they will not unscrew with an ordinary wrench, we may, if the standing bolts and the wrench are strong enough to stand it, place a piece of gas or other pipe on the end of the wrench, so as to get a longer leverage; and, while applying the power to the wrench, we may strike the end face of the nut a few sharp blows with the hammer, interposing a set chisel, if the nut is a small one, so as to be sure to strike the nut in the proper place, and not rivet the screw end. If the joint is made with tap bolts we may strike the bolt heads with the hammer direct, using as before a light hammer and sharp blows, which will, in a majority of cases, start the thread, after which the wrench alone will usually suffice to unscrew it. If, however, this is not effective, we should take a thick washer, large enough in its bore to pass over the nut, and heat it to a yellow heat and place it over the nut, and the nut heating more rapidly than the stud or standing bolt, will be proportionately expanded and loosened; and, furthermore, the iron becomes stronger by being heated, providing the temperature does not exceed about 400°. If standing bolts or studs are employed on the joint, the heating is still advantageous, for the increase of strength more than compensates for the expansion. In this case the heating, however, may be performed more slowly, so that the hole may also become heated, and the bolt, therefore, not made a tighter fit by its excessive expansion. So also, in taking out the standing bolts or studs, heating them will often enable one to extract them without breaking them off in the hole, which would necessitate drilling out the broken piece or part. If, however, this should become necessary, we may drill a hole a little smaller than the diameter of the bottom of the bolt thread, and then drive into the hole a taper square reamer, as shown in Fig. 442, in which W represents the work, R the square reamer, and S the drilled screw end, and then, with a wrench applied to the reamer, unscrew the bolt thread. If this plan fails there is no alternative, after drilling the hole, but to take a round-nosed cape or cross-cut chisel and cut out the screw as nearly as possible, then pick out the thread at the entrance of the hole, and insert a plug tap to cut out the remaining bolt thread. To take out a standing bolt, take two nuts and screw them on the bolt end; then hold the outer one still with a wrench and unscrew the inner one tightly against it. We may then remove the wrench from the outer or top nut, and unscrew the bolt by a wrench applied to the bottom or inner one. If the thread of a standing bolt has become damaged or burred, we can easily correct the evil by screwing a solid die or die nut down it, applying a little oil to preserve the cutting edge of the nut. If it is found impossible to take off a corroded nut without twisting off the standing bolt, it is the better plan to sacrifice the nut in order to save the bolt; and we may first hold a hammer beneath the nut, and take a cold chisel, and holding it so that the cutting edge stands parallel with the chamfered edge of the nut, and slanting it at an angle obtuse to the direction in which the nut in unscrewing would travel, strike it a few sharp blows, using a light hand-hammer; and this will often start it, especially if the nut is heated as before directed. The hammer held beneath the nut should be a heavy one, and should be pressed firmly against the square or hexagon side of the nut, the object being to support it, and thus prevent the standing bolt from bending or breaking, as it would otherwise be very apt to do. If this plan succeeds, the nut may, for rough work, be used over again, the burr raised by the chisel head being hammered down to close it as much as possible before filing it off. By holding the chisel precisely as directed, the seating of the nut acts to support it, and thus aids the heavy hammer in its duty. If this procedure fails we may cut the nut off, and thus preserve the bolt. [Illustration: Fig. 442.] To do this, we must use a cross-cut or cape chisel, and cut a groove from the end face to the seating of the nut--a narrow groove will do, and two may be cut if necessary; light cuts should be taken, and the chisel should be ground at a keen angle, so that it will keep to its cut when held at an angle, as nearly parallel to the centre line of the length of the bolt as possible, in which case the force of the blows delivered upon the chisel head will be in a direction not so liable to bend the bolt. The groove or grooves should be cut down nearly to the tops of the bolt threads, and then a wrench will unscrew the nut or else cause it to open if one, and break in halves, if two grooves were cut. After the nuts are all taken off, we may take a hammer and two or three wedges, or chisels (according to the size of the joint), and drive them an equal distance into the joint, striking one chisel first, and the diametrically opposite one next, and going over all the wedges to keep an equal strain upon each. If the joint resists this method, we may take a hammer and strike blows between the standing bolts on the outside face, interposing a block of hard wood to prevent damage to the face, and holding the wood so that the hammer strikes it endwise of the grain; and this will, in most cases, loosen the material of which the joint is made, and break the joint. If, however, the joint, after repeated trials, still resists, we may employ the hammer without the interposition of the wood, using a copper or lead hammer, if one is at hand, so as not to cause damage to the face of the work. To facilitate the entrance of the wedges, grooves should be cut in the joint of one face, their widths being about an inch, and their depth 1/16 inch. WASHERS.--Washers are placed upon bolts for the following purposes. First, to provide a smooth seating for the nut in the case of rough castings. Second, to prevent the nut corners from marking and marring the surface of finished work. Thirdly, to give a neat finish, and in some cases to increase the bearing area of the nut and provide an elastic cushion to prevent the nut from loosening. Washers are usually of wrought iron, except in the case of brass nuts, when the washers also are of brass. The standard sizes adopted by the manufacturers in the United States for wrought iron washers is given in the following table:-- MANUFACTURERS' STANDARD LIST. Adopted by "The Association of Bolt and Nut Manufacturers of the United States," at their meeting in New York, December 11th, 1872. +-----------+---------+-------------+---------+ | Diameter. | Size of | Thickness | Size of | | | Hole. | Wire Gauge. | Bolt. | +-----------+---------+-------------+---------+ | 1/2 | 1/4 | No. 18 | 3/16 | | 5/8 | 5/16 | " 16 | 1/4 | | 3/4 | 5/16 | " 16 | 1/4 | | 7/8 | 3/8 | " 16 | 5/16 | | 1 | 7/16 | " 14 | 3/8 | +-----------+---------+-------------+---------+ | 1-1/4 | 1/2 | " 14 | 7/16 | | 1-3/8 | 9/16 | " 12 | 1/2 | | 1-1/2 | 5/8 | " 12 | 9/16 | +-----------+---------+-------------+---------+ | 1-3/4 | 11/16 | " 10 | 5/8 | | 2 | 13/16 | " 10 | 3/4 | +-----------+---------+-------------+---------+ | 2-1/4 | 15/16 | " 9 | 7/8 | | 2-1/2 | 1-1/16 | " 9 | 1 | | 2-3/4 | 1-1/4 | " 9 | 1-1/8 | | 3 | 1-3/8 | " 9 | 1-1/4 | | 3-1/2 | 1-1/2 | " 9 | 1-3/8 | +-----------+---------+-------------+---------+ [Illustration: Fig. 443.] [Illustration: Fig. 444.] The various forms of wrenches employed to screw nuts home or to remove them are represented in the following figures. Fig. 443 represents what is known as a solid wrench, the width between the jaws a being an easy fit to the nuts across the flats. The opening between the jaws being at an angle to the body enables the wrench to be employed in a corner which would be too confined to receive a wrench in which the handle stood in a line with the jaws, because in that common form of wrench the position of the jaws relative to the handle would be the same whether the wrench be turned over or not, whereas with the jaws at an angle as in the figure, the wrench may be applied to the nut, rotating it a certain distance until its handle meet an abutting piece, flange, or other obstruction, and then turned over and the jaw embracing the same two sides of the nut the handle will be out of the way and may again operate the nut. [Illustration: Fig. 445.] In some cases each end of the wrench is provided with jaws, those at one end standing at the same angle but being on the opposite side of the wrench. The proper angle of the jaws to the centre line of the jaws may be determined as follows:--The most desirable angle is that which will enable the wrench to operate the nut with the least amount of wrench-motion, an object that is of great importance in cases where an opening has to be provided to admit the wrench to the nut, it being desirable to leave this opening as small as possible so as to impair the solidity of the work as little as practicable. For a hexagon nut this angle may be shown to be one of 15°, as in Fig. 444. [Illustration: Fig. 446.] [Illustration: Fig. 447.] In Fig. 445, for example, the wrench is shown in the position in which it will just engage the nut, and at the first movement it will move the nut to the position shown in Fig. 446. The wrench is then turned upside down and placed upon the nut as in Fig. 447, and moved to the position shown in Fig. 448, thus moving the nut the sixth part of a revolution, and bringing it to a position corresponding to that in Fig. 445, except that it has moved the nut around to a distance equal to one of its sides. Since the wrench has been moved twice to move the nut this distance, and since there are six sides, it will take twelve movements to give the nut a full revolution, and, there being 360° in the circle, each movement will move the nut 30°, or one-twelfth of 360°, and one-half of this must be the angle of the gripping faces of the jaws to the body of the wrench. The width of the opening in the work to admit the wrench in such a case as in Fig. 445 must be not less than 30°, plus the width of the wrench handle, at the radius of the outer corner of the opening. [Illustration: Fig. 448.] In the case of wrenches for square nuts it is similarly obvious that when the nut makes one-eighth of a revolution its sides will stand in the same position to receive the wrench that the nut started from, and in one-eighth of a revolution there are 45°. As the wrench is applied twice to the same side of the nut, its jaws must stand at one half this angle (or 22-1/2°) to the handle. [Illustration: Fig. 449.] When a nut is in such a position that it can only be operated upon from the direction of and in a line with the axis of the bolt, a box wrench such as shown in Fig. 449, is employed, the cavity at B fitting over the bolt head; but if there is no room to admit the cross handle, a hub or boss is employed instead, and this hub is pierced with four radial holes into which the point of a round lever may be inserted to turn the wrench. Adjustable wrenches that may be opened and closed to suit the varying sizes of nuts are represented in Figs. 450, 451, and 452. In Fig. 450, A is the fixed jaw solid upon the square or rectangular bar E, and passing through the wooden handle D. B is a sliding jaw embracing E, and operated thereon by the screw C, whose head is serrated to afford a good finger grip. Various modifications of this form of wrench are made; thus, for example, in Fig. 451 A is the jaw, B a slotted shank, C the handle, all made in one piece. D is the movable jaw having a sleeve extension D´, and recesses which permit the jaw to slide on the shank longitudinally, but which prevent it from turning. The movable jaw is run to and from the nut or bolt head to be turned, by means of the screw G. [Illustration: Fig. 450.] [Illustration: Fig. 451.] In another class of adjustable wrench the jaws slide one within the other; thus in Fig. 452, the fixed jaw of the wrench forms a part of the handle, and is hollowed out and slotted to receive the stem of the loose jaw, which plays therein, being guided by ribs in the slot, which take into grooves in the stem of the loose jaw. A screw with a milled head and a grooved neck serves to propel the loose jaw, being stopped from moving longitudinally by a partly open fixed collar on the fixed jaw, which admits the screw and engages the grooved neck of the same. The threaded extremity of the screw engages a female screw in the loose jaw, and while the same are engaged the screw cannot be released from the embrace of the fixed collar, as it requires considerable lateral movement to accomplish this. [Illustration: Fig. 452.] [Illustration: Fig. 453.] Adjustable wrenches are not suited for heavy work because the jaws are liable to spring open under heavy pressure and thus cause damage to the edges of finished nuts, and indeed these wrenches are not suitable for ordinary use on finely finished work unless the duty be light. Furthermore, the jaws being of larger size than the jaws of solid wrenches, will not pass so readily into corners, as may be seen from the [S] wrench shown in Fig. 453. In the adjustable [S] wrench in Fig. 454, each half is provided with a groove at one end and a tongue in the other, so that when put together the tongues are detained in the grooves. To open or close the wrench a right and left-hand screw is tapped into the wrench as shown, the head being knurled or milled to afford increased finger-grip. [Illustration: Fig. 454.] [Illustration: Fig. 455.] In all wrenches the location of contact and of pressure on the nut is mainly at the corners of the nut, and unless the wrench be a very close fit, the nut corners become damaged. A common method of avoiding this is to interpose between the wrench jaw and the nut a piece of soft metal, as copper, sheet zinc, or even a piece of leather. The jaws of the wrench are also formed to receive babbitt metal linings which may be renewed as often as required. To save the trouble of adjusting an accurately fitting wrench to the nut, Professor Sweet forms the jaws as in Fig. 455, so that when moved in one direction the jaws will pass around the nut without gripping it, but when moved in the opposite direction the jaws will grip the nut but not damage the corners, while to change the direction of a nut rotation it is simply necessary to turn the wrench over. [Illustration: Fig. 456.] Fig. 456 represents a key wrench which is suitable for nuts of very large size. The sliding jaw J is held by the key or wedge S, which is operated by hammer blows. The projection at R is necessary to give sufficient bearing to the sliding jaw. [Illustration: Fig. 457.] For use in confined places where but little handle-motion is obtainable, the ratchet wrench is employed, consisting of a lever affording journal bearing to a socket that fits the head of the bolt. The socket is provided with a ratchet or toothed wheel in which a catch or pawl engages. Fig. 457 represents the Lowell Wrench Company's ratchet wrench in which a lag screw socket is shown affixed. The socket is removable so that various sizes and shapes may be used with the same wrench. Each socket takes two sizes of square and one of hexagon heads or nuts. So long as the screw runs easily, it can be turned by the wooden handle more conveniently and faster than by the fingers, and independently of the ratchet motion. When this can no longer be done with ease, the twelve-inch handle is brought into use to turn the screw home. For carriage bolts used in woodwork that turn with the nut notwithstanding the square under the head (as they are apt to do from decay of the wood or from the bolt gradually working loose) the form of wrench shown in Fig. 458 is exceedingly useful, it is driven into the wood by hammer blows at A. The bevelled edges cause the jaws to close upon the head in addition to the handle-pressure. [Illustration: Fig. 458.] For circular nuts such as was shown in Fig. 411, the pin wrench or spanner wrench shown in Fig. 459 is employed, the pin P fitting into the holes in the nut circumference. The pin P should be parallel and slope very slightly in the direction of A, so that it may not meet and bruise the mouths of the pin-holes, A, B, C. The pin must, of course, pass easily into the pin-holes, and would, if vertical, therefore meet the edge of the hole at the top, bruising it and causing the wrench to spring or slip out, as would be the case if the pin stood in the direction of B. [Illustration: Fig. 459.] [Illustration: Fig. 460.] It is obvious that to reverse the motion of the nut it is necessary to reverse the position of the wrench, because the handle end must, to enable the wrench to grip the work, travel in advance of the pin end. To avoid this necessity Professor Sweet forms the wrench as in Fig. 460, in which case it can operate on the nut in either direction without being reversed. When a circular nut has its circumference provided with notches as was shown in Fig. 412 the wrench is provided with a rectangular piece as shown in Fig. 461. This piece should slope in the direction of a for the reasons already explained with reference to the cylindrical pin in Fig. 459. It is obvious, however, that this wrench also may be made upon Professor Sweet's plan, in which case the pin should be straight. [Illustration: Fig. 461.] KEYS AND KEYWAYS.--Keys and keyways are employed for two purposes--for locking permanently in a fixed position, and for locking and adjusting at the same time. Keys that simply permanently lock are usually simply embedded in the work, while those that adjust the parts and secure them in their adjusted position usually pass entirely through the work. The first are termed sunk keys and keyways, the latter adjusting keys and through keyways. [Illustration: Fig. 462.] The usual forms of sunk keyways are as follows:--Fig. 462 represents the common sunk key, the head _h_ forming a gib for use in extracting the key, which is done by driving a wedge between the head and the hub of the work. [Illustration: Fig. 463.] The flat key, sunk key, and feather shown in Fig. 463, are alike of rectangular form, their differences being in their respective thicknesses, which is varied to meet the form of key way which receives them. The flat key beds upon a flat place upon the shaft, the sunk key beds in a recess provided in the shaft, and the feather is fastened permanently in position in the shaft. The hollow key is employed in places where the wheel or pulley may require moving occasionally on the shaft, and it is undesirable that the latter have any flat place upon it or recess cut in it. The flat key is used where it is necessary to secure the wheel more firmly without weakening the shaft by cutting a keyway in it. The sunk key is that most commonly used; it is employed in all cases where the strain upon the parts is great. The feather is used in cases where the keyway extends along the shaft beyond the pulley or wheel, the feather being fast in the wheel, and its protruding part a working fit in the shaft keyway. This permits the wheel to be moved along the shaft while being driven through the medium of the feather along the keyway or spline. The heads of the taper keys are sometimes provided with a set screw as in Fig. 464, which may be screwed in to assist in extracting the key. [Illustration: Fig. 464.] [Illustration: Fig. 465.] Fig. 465 represents an application of keys to a square shaft that has not been planed true. The wheel is hung upon the shaft and four temporary gib-headed keys are inserted in the spaces _a_, _a_, _a_, _a_, in Fig. 465. (It may be mentioned here that similar heads are generally forged upon keys to facilitate their withdrawal while fitting them to their seats, the heads being cut off after the key is finally driven home.) These sustain the wheel while the permanent keys, eight in number, as shown in the figure at _b_, _b_, _b_, _b_, _b_, _b_, _b_, _b_, are fitted, the wheel being rotated and tested for truth from a fixed point, the fitting of the keys being made subservient to making the wheel run true. The proportions of sunk keys are thus given by the Manchester (England) rule. The key is square in cross section and its width or depth is obtained by subtracting 1/2 from the diameter of the shaft and dividing the sum thus obtained by 8, and then adding to the subtrahend 1/4. Example.--A shaft is 6 inches in diameter, what should be the cross section dimensions of its key diameter of shaft? 6 - 1/2 = 5-1/2, 5-1/2 ÷ 8 = .687, and .687 + .25 = 937/1000 inch. In general practice, however, the width of a key is made slightly greater than its depth, and one-half its depth should be sunk in the shaft. [Illustration: Fig. 466.] [Illustration: Fig. 467.] Taper keys are tapered on their surfaces A and B in Fig. 466, and are usually given 1/8-inch taper per foot of length. There is a tendency either in a key or a set screw to force the hub out of true in the direction of the arrow. It therefore causes the hub bore to grip the shaft, and this gives a driving duty more efficient than the friction of the key itself. But the sides also of the key being a sliding fit they perform driving duty in the same manner as a feather which fits on the sides A, D in Fig. 467, but are clear either top or bottom. In the figure the feather is supposed to be fast in the hub and therefore free at C, but were it fast in the shaft it would be free on the top face. [Illustration: Fig. 468.] [Illustration: Fig. 469.] Fig. 468 represents a shaft held by a single set screw, the strain being in the direction of the arrow, hence the driving duty is performed by the end of the set screw and the opposite half circumference of the bore and shaft. On account, however, of the small area of surface of the set screw point the metal of the shaft is apt, under heavy duty and when the direction of shaft rotation is periodically reversed, to compress (as will also the set screw point unless it is of steel and hardened), permitting the grip to become partly released no matter how tightly the set screw be screwed home. On this account a taper key will under a given amount of strain upon the hub perform more driving duty, because the increased area of contact prevents compression. Furthermore, the taper key will not become loose even though it suffer an equal amount of compression. Suppose, for example, that a key be driven lightly to a fair seating, then all the rest of the distance to which the key is driven home causes the hub to stretch as it were, and even though the metal of the key were to compress, the elasticity thus induced would take up the compression, preventing the key from coming loose. It is obvious, then, that set screws are suitable for light duty only, and keys for either heavy or light duty. It is advanced by some authorities that keys are more apt to cause a wheel or pulley to run out of true than a set screw, but such is not the case, because, as shown in Figs. 466 and 468, both of them tend to throw the wheel out of true in one direction; but a key may be made with proper fitting to cause a wheel to run true that would not run true if held by a set screw, as is explained in the directions for fitting keys given in examples in vice work. If two set screws be used they should both be in the same line (parallel to the shaft axis) or else at a right angle one to the other as in Fig. 469, so that the shaft and bore may drive by frictional contact on the side opposite to the screws. Theoretically the contact of their surface will be at a point only, but on account of the elasticity of the metal the contact will spread around the bore in the arc of a circle, the length of the arc depending upon the closeness of fit between the pulley bore and the shaft. If the bore is a close fit to the shaft it is by reason of the elasticity of the metal relieved of contact pressure on the side on which the set screw or key is to an amount depending upon the closeness of the bore fit, but this will not in a bore or driving fit to the shaft be sufficient to set the wheel out of true. If two set screws are placed diametrally opposite they will drive by the contact of their ends only, and not by reason of their inducing frictional contact between the bore and the shaft. A very true method of securing a hub to a shaft is to bore it larger than the shaft and to a taper of one inch to the foot. A bushing is then bored to fit the shaft and turned to the same taper as the hub is turned, but left, say, 1/100 inch larger in diameter and 1/4 or 3/8 longer. The bush is then cut into three pieces and these pieces are driven in the same as keys, but care must be taken to drive them equally to keep the hub true. [Illustration: Fig. 470.] [Illustration: Fig. 471.] Feathers are used under the following conditions:--When the wheel driven by a shaft requires to slide along the shaft during its rotation, in which case the feather is fast in the wheel and the shaft is provided with a keyway or spline (as it is termed when the sliding action takes place), of the necessary length, the sides of the feather being a close but sliding fit in the spline while fixed fast in the wheel. It is obvious that the feather might extend along the shaft to the requisite distance and the spline or keyway be made in the wheel: but in this case the work is greater, because the shaft would still require grooving to receive the feather, and the feather instead of being the simple width of the wheel would require to be the width of the wheel longer than the traverse of the wheel on the shaft. Nor would this method be any more durable, because the keyway's bearing length would be equal to the width of the wheel only. When a feather is used to enable the easy movement of a wheel from one position to another a set screw may be used to fix the wheel in position through the medium of the feather as is shown in Fig. 470. Through keys and keyways are employed to lock two pieces, and sometimes to enable the taking up of the wear of the parts. Fig. 471 represents an example in which the key is used to lock a taper shaft end into a socket by means of a key passing through both of them. When the keyway is completely filled by the key as in the figure it is termed a solid key and keyway, indicating that there is no draft to the keyway. Fig. 472 represents a key and keyway having draft. One edge, A C, of the key binds against the socket edges only, and the other edge E binds against the edge B of the enveloped piece or plug, so that by driving in the key with A hammer the two parts are forced together. The space or distance between the edge D and the key, and between edges E and F, is termed the draft. The amount of this draft is made equal to the taper of the key, hence, when the key is driven in so that its head comes level with the socket or work surface, the draft will be all taken up and the key will fill the keyway. [Illustration: Fig. 472.] Draft is given to ensure all the strain of the key forcing the parts together, to enable the key to be driven in to take up any wear and to adjust movable parts, as straps, journal boxes or brasses, &c. When the bore of the socket and the end of the rod are parallel, the end of the rod F, Fig. 473, should key firmly against the end E of the socket, while the end D of the socket should be clear of the shoulder on the rod; otherwise instead of the key merely compressing the metal at F it will exert a force tending to burst the end F from G of the rod, furthermore, the area of contact at the shoulder D being small the metal would be apt to compress and the key would soon come loose. In some cases two keys are employed passing through a sleeve, the arrangement being termed a coupling, or a butt coupling. [Illustration: Fig. 473.] The usual proportions for this class of key, when the rod ends and socket boxes are parallel, is width of key equals diameter of socket bore, thickness of key equals one-fourth its width, with a taper edgeways of about 1/4 inch in 10 inches of length. [Illustration: Fig. 474.] [Illustration: Fig. 475.] As the keys in through keyways often require to be driven in very tight, and as the parts keyed together often remain a long time without being taken apart and in some situations become rusted together, it is often a difficult matter to get them apart. First, it is difficult to drive it out because the blows swell the end of the key so that it cannot pass through the keyway, and secondly, driving the socket off the plug of the two parts keyed together often damages the socket and may bend the rod to which it is keyed. Furthermore, as the diameter of the socket is usually not more than half as much again as the diameter of the plug, misdirected blows are apt to fall upon the rod instead of upon the socket end and damage it. Hence, a piece of copper, of lead, or a block of wood should always be placed against the socket end to receive the hammer blows. To force a plug out of a socket, we may use reverse keys. These are pieces formed as shown in Fig. 474. A, A and B, B are edge and face views respectively of two pieces of metal, formed as shown, which are inserted in the keyway as shown in Fig. 475, in which A is the plug or taper end of a rod and B the socket, C is one and D the other of the reverse keys, while E is a taper key inserted between them, B driving E through the keyway, A and B are forced apart. The action of the reverse keys is simply to reverse the direction of the draft in the keyway so that the pressure due to driving E through the keyway is brought to bear upon the rod end in the part that was previously the draft side of the keyway, and in like manner upon the keyway in the socket on the side that previously served as draft. Reverse keys are especially serviceable to take off cross heads, piston heads, keyed crank-pins, and parts that are keyed very firmly together. [Illustration: Fig. 476.] [Illustration: Fig. 477.] Hubs are sometimes fastened to their shafts by pins passing through both the hub and the shaft. These pieces may be made parallel or taper, but the latter obviously secures the most firmly. If the pin is located as in Fig. 476, its resisting strength is that due to its cross sectional area at A and B. But if the pin be located as in Fig. 477 it secures the hub more firmly, because it draws the bore (on the side opposite to the pin) against the shaft, causing a certain amount of friction, and, furthermore, the area resisting the pressure of the hub is increased, and that pressure is to a certain degree in a crushing as well as a shearing direction. [Illustration: Fig. 478.] If unturned pins are used and the holes are rough or drilled but not reamed, it is better that two sides of the pin should be eased off with a file or on the emery wheel, so that all the locking pressure of the pin shall fall where it is the most important that it should--that is, where it performs locking duty. This is shown in Fig. 478, the hole being round and the pin being very slightly oval (not, of course, so much as shown in the drawing), so that it will bind at A B, and just escape touching at C, D, so that all the pressure of contact is in the direction to bind the hub to the shaft. CHAPTER VI.--THE LATHE. The lathe may be justly termed the most important of all metal-cutting machine tools. Not only on account of the rapidity of its execution which is due to its cutting continuously while many others cut intermittently, but also because of the great variety of the duty it will perform to advantage. In the general operations of the lathe, drilling, boring, reaming, and other processes corresponding to those performed by the drilling machine, are executed, while many operations usually performed by the planing machine, or planer as it is sometimes termed, may be so efficiently performed by the lathe that it sometimes becomes a matter of consideration whether the lathe or the planer is the best machine to use for the purpose. The forms of cutting tools employed in the planer, drilling machine, shaping machine, and boring machine, are all to be found among lathe tools, while the work-holding devices employed on lathe work include, substantially, very nearly all those employed on all other machines and, in addition, a great many that are peculiar to itself. In former times, and in England even at the present day, an efficient turner (as a lathe operator is termed), or lathe hand, is deemed capable of skilfully operating a planer, boring machine, screw-cutting machine, drilling machine, or any of the ordinary machine tools, whereas those who have learned to operate any or all of those machine tools would prove altogether inefficient if put to operate a lathe. [Illustration: Fig. 479.] In almost all the mechanic arts the lathe in some form or other is to be found, varying in weight from the jewellers' lathe of a few pounds to the pulley or fly-wheel lathe of the engine builder, weighing many tons. The lathe is the oldest of machine tools and exists in a greater variety of forms than any other machine tool. Fig. 479 represents a lathe of primitive construction actually in use at the present day, and concerning which the "Engineering" of London (England), says, "At the Vienna Exhibition there were exhibited wood, glasses, bottles, vases, &c., made by the Hucules, the remnant of an old Asiatic nation which had settled at the time of the general migration of nations in the remotest parts of Galicia, in the dense forests of the Carpathian Mountains. The lathe they are using has been employed by them from time immemorial. They make the cones _b_, _b_ (of maple) serve as centres, one being fixed and the other movable (longitudinally). They rough out the work with a hatchet, making one end _a_ cylindrical, to receive the rope for giving rotary motion. The cross-bar _d_ is fastened to the trees so as to form a rest for the cutting tool, which consists of a chisel." C, of course, is the treadle, the lathe or pole being a sapling. In other forms of ancient lathes a wooden frame was made to receive the work-centres, and one of these centres was carried in a block capable of adjustment along the frame to suit different lengths of work. In place of a sapling a pole or lath was employed, and from this lath is probably derived the term lathe. It is obvious, however, that with such a lathe no cutting operation can be performed while the work is rotating backwards, and further, that during the period of rest of the cutting tool it is liable to move and not meet the cut properly when the direction of work rotation is reversed and cutting recommences, hence the operation is crude in the extreme, being merely mentioned as a curiosity. The various forms in which the lathe appears in ordinary machine shop manipulation may be classified as follows:-- The _foot lathe_, signifying that the lathe is driven by foot. The _hand lathe_, denoting that the cutting tools must be held in the hands, there being no tool-carrying or feeding device on the lathe. The _single-geared lathe_, signifying that it has no gear-wheels to reduce the speed of rotation of the live spindle from that of the cone. The _back-geared lathe_, in which gear-wheels at the back of the headstock are employed to reduce the speed of the lathe. The _self-acting lathe_, or _engine lathe_, implying that there is a slide rest actuated automatically to traverse the tool to its cut or feed. The _screw-cutting lathe_, which is provided with a _lead_ screw, by means of which other screws may be cut. The _screw-cutting lathe with independent feed_, which denotes that the lathe has two feed motions, one for cutting threads and another for ordinary tool feeding; and The _chucking lathe_, which implies that the lathe has a face plate of larger diameter than usual, and that the bed is somewhat short, so as to adapt it mainly to work held by being chucked, that is to say, held by other means than between the lathe centres. There are other special applications of the lathe, as the boring lathe, the grinding lathe, the lathe for irregular forms, &c., &c. This classification, however, merely indicates the nature of the lathe with reference to the individual feature indicated in the title; thus, although a foot lathe is one run by foot, yet it may be a single or double gear (back-geared) lathe, or a hand or self-acting lathe, with lead screw and independent feed motion. Again, a hand lathe may have a hand slide rest, and in that case it may also be a back-geared lathe, and a back-geared lathe may have a hand slide rest or a self-acting feed motion or motions. Fig. 480 represents a simple form of foot lathe. The office of the shears or bed is to support the headstock and tailstock or tailblock, and to hold them so that the axes of their respective spindles shall be in line in whatever position the tailstock may be placed along the bed. The duty of the headstock is to carry the live spindle, which is driven by the cone, the latter being connected by the belt to the wheel upon the crank shaft driven by the crank hook and the treadle, which are pivoted by eyes W to the rod X, the operation of the treadle motion being obvious. The work is shown to be carried between the live centre, which is fitted to the live spindle, and the dead centre fitting into the tail spindle, and as it has an arm at the end, it is shown to be driven by a pin fixed in the face plate, this being the simplest method of holding and driving work. The lathe is shown provided with a hand tool rest, and in this case the cutting tools are supported upon the top of the tool rest N, whose height may be adjusted to bring the tool edge to the required height on the work by operating the set screw S, which secures the stem of N in the bore of the rest. To maintain the axes of the live and dead spindles in line, they are fitted to a slide or guideway on the shears, the headstock being fixed in position, while the tailstock is adjustable along the shears to suit the length of the work. To lock the tailstock in its adjusted position along the shears, it has a bolt projecting down through the plate C, which bolt receives the hand nut D. To secure the hand rest in position at any point along the shears, it sets upon a plate A and receives a bolt whose head fits into a [T]-shaped groove, and which, after passing through the plate P receives the nut N, by which the rest is secured to the shears. To adjust the end fit of the live spindle a bracket K receives an adjusting screw L, whose coned end has a seat in the end J of the live spindle, M being a check nut to secure L in its adjusted position. [Illustration: Fig. 480.] The sizes of lathes are designated in three ways, as follows:--First by the _swing_ of the lathe and the total length of the bed, the term _swing_ meaning the largest diameter of work that the lathe is capable of revolving or swinging. The second is by the _height of the centres_ (from the nearest corner of the bed) and the length of the shears. The height of the centres is obviously equal to half the swing of the lathe, hence, for example, a lathe of 28-inch swing is the same size as one of 14-inch centres. The third method is by the swing or height of centres and by the greatest length of work that can be held between the lathe centres, which is equal to the length of the bed less the lengths of the head and tailstock together. The effective size of a lathe, however, may be measured in yet another way, because since the hand rest or slide rest, as the case may be, rests upon the shears or bed, therefore the full diameter of work that the lathe will swing on the face plate cannot be held between the centres on account of the height of the body of the hand rest or slide rest above the shears. Fig. 481 shows a hand lathe by F. E. Reed, of Worcester, Massachusetts, the mechanism of the head and tail stock being shown by dotted lines. The live spindle is hollow, so that if the work is to be made from a piece of rod and held in any of the forms of chucks to be hereafter described, it may be passed through the spindle, which saves cutting the rod into short lengths. The front bearing of the headstock has two brasses or boxes, A and B, set together by a cap C. The rear bearing has also a bearing box, the lower half D being threaded to receive an adjustment screw F and check nut G to adjust the end fit of the spindle in its bearings. In place of grooved steps for the belt the cone has flat ones to receive a flat belt. The tail spindle is shown, in Fig. 482, to be operated by a screw H, having journal bearing at I, and threaded into a nut fast in the tail spindle at J. To hold the tail spindle firmly the end of the tail stock is split, and the hand screw K may be screwed up to close the split and cause the bore at L to clasp the tail spindle at that end. To lock the tail stock to the shears the bolt M receives the lever N at one end and at the other passes through the plate or clamp O, and receives the nut P, so that the tail stock is gripped to or released from the shears by operating N in the necessary direction. The hand rest, Fig. 483, has a wheel W in place of a nut, which dispenses with the use of a wrench. What are termed bench lathes are those having very short legs, so that they may for convenience be mounted on a bench or fastened to a second frame, as shown in Fig. 484. It is obvious that when work is turned by hand tools, the parallelism of the work depends upon the amount of metal cut off at every part of its length, which to obtain work of straight outline, whether parallel or taper, involves a great deal of testing and considerable skill, and to obviate these disadvantages various methods of carrying and accurately guiding tools are employed. The simplest of these methods is by means of a slide rest, such as shown in Fig. 485. The tool T is carried in the tool post P, being secured therein by the set screw shown, which at the same time locks the tool post to the upper slider. This upper slider fits closely to the cross slide, and has a nut projecting down into the slot shown in the same, and enveloping the cross feed screw, whose handle is shown at C, so that operating C traverses the upper slider on the cross slide and regulates the depth to which the tool enters the work, or in other words, the depth of cut. [Illustration: Fig. 481.] The cross slide is formed on the top of the lower slider, which has beneath a nut for the feed screw, whose handle is shown at A, hence rotating A will cause the lower slider to traverse along the lower slide and carry the tool along the work to its cut. To maintain the fit of the sliders to the slides a slip of metal is inserted, as at _e_ and at _c_, and these are set up by screws as at _f_, _f_ and _b_, _b_. [Illustration: Fig. 482.] The lower or feed traverse slide is pivoted to its base B, so that it may be swung horizontally upon the same, and is provided with means to secure it in its adjusted position, which is necessary to enable it to turn taper as well as parallel work. To set this lower slide to a given degree of angle it may be marked with a line and the edge of base B may be divided into degrees as shown at D. [Illustration: Fig. 483.] When a piece of work is rotated between the lathe centres its axis of rotation may be represented by an imaginary straight line and the lower slides must, to obtain parallel work, be set parallel to this straight line, while for taper work the slide rest must be set at an angle to it. Now, in the form of slide rest shown in figure the cross slide is carried by the lower or feed traverse slide, hence setting the lower slide out of parallel with the work axis sets the cross slide out of a right angle to the work axis, with the result that when a taper piece of work is turned that has a collar or flange on it, the face of that collar or flange will be turned not at a right angle to the work axis as it should be, but at a right angle to the surface of the cone. Thus in Fig. 486 A represents the axis of a piece of work, and the slide nut having been set parallel to the work axis, the face C will be at a right angle to the surface B or axis A, but with the slide nut set at an angle to turn the cone D, the cross slide will be at an angle to A, hence the face E will be undercut as shown, and at a right angle to the surface D instead of to A A. This may be obviated by letting the cross slide be the lower one as in the English form of slide rest shown in Fig. 487, in which the upper slide is pivoted at its centre to the cross slide and may be swung at an angle thereto and secured in its adjusted position by the bolt at F. The projection at the bottom of the lower slider fits between the shears of the lathe and holds the lower slider parallel with the line of lathe centres, which causes the slide rest to cut all faces at a sight angle to the work axis whether the feed traverse slide be set to turn parallel or taper. In either case, however, there is nothing to serve as a guide to set the feed traverse slide parallel to the work axis, and this must, therefore, be done as near as may be by the eye and by taking a cut and testing its parallelism. [Illustration: Fig. 484.] [Illustration: Fig. 485.] [Illustration: Fig. 486.] The rest may be set approximately true by bringing the operator's eye into such a position that the edge _a_ _a_, Fig. 488, of the slide rest come into line with the edge _b_ _b_ of the lathe shears, because that edge is parallel to the line of lathe centres, and therefore to the work axis. Slide rests which have a slide for traversing the tool along the work to its cut are but little used in the United States, being confined to very small lathes, and then (except in the case of watchmakers' lathes whose forms of slide rest will be shown hereafter), mainly as an expedient to save expense in the cost of the lathe, it being preferred to feed the tool for the feed traverse (as the motion of the cutting tool along the work is termed) by mechanism operated from the live spindle and to be hereafter described. In England, however, slide rests are much used, a specimen construction being shown in Fig. 489. The end face A of the rest comes flush so that the tool shall be carried firmly when taking facing cuts in which solidity in the rest is of most importance. The tool is held by two clamps instead of by single tool posts, because the slide rest is employed to take heavy cuts, and when this is the case with boring tools whose cutting edges stand far out from the slide rest, a single tool post will not hold the tool sufficiently firm. [Illustration: Fig. 487.] [Illustration: Fig. 488.] The gib _e_, Fig. 485, is sometimes placed on the front side of the slider, as in the figure, and at others on the back; when it is placed in the front the strain of the cut causes it to be compressed against the slide, and there is a strain placed upon the screws _f_ which lifts them up, whereas if placed on the other side the screws are relieved of strain, save such as is caused by the setting of the gib up. [Illustration: Fig. 489.] On the other hand, the screws are easier to get at for adjustment if placed in front. When the screws _b_ of the upper gib _c_, Fig. 485, are on the right-hand side, as in that figure, there is considerable strain on the screws when a boring tool is used to stand far out, as for boring deep holes. On the other hand, however, the screws can be readily got at in this position, and may therefore be screwed up tightly to lock the upper slider firmly to the cross slide, which will be a great advantage in boring and also in facing operations. But the screws must not in this case have simple saw slot heads, such as shown on a larger scale in Fig. 490, but should have square heads to receive a wrench, and if these four screws are used, the two end ones may be set to adjust the slicing fit of the slider, while the two middle ones may be used to set the slider form on its slide when either facing or boring. The corners of the gibs as well as those of the slider and slide may with advantage be rounded so that they may not become bruised or burred, and, furthermore, the slider is strengthened, and hence less liable to spring under the pressure of a heavy cut. [Illustration: Fig. 490.] A slide rest for turning spherical work is shown in Fig. 491. A is the lower slide way on which is traversed the slide B, upon which is fitted the piece C, pivoted by the bolt D; there is provided upon C a half-circle rack, shown at E, and into this rack gears a worm-wheel having journal bearing on B, and operated by the handle F. As F is rotated C would rotate on D as a centre of motion, hence the tool point would move in an arc of a circle whose radius would depend upon the distance of the tool point from D as denoted by J, which should be coincident with the line of centres of the lathe. [Illustration: Fig. 491.] The slide G is constructed in the ordinary manner, but the way on which it slides should be short, so as not to come into contact with the work. If the base slide way A be capable of being traversed along the lathe shears S S by a separate motion, then the upper slide way and slide may be omitted, G and C being in one piece. It is to be noted in a rest of this kind, however, that the tool must be for the roughing cut set too far from D to an amount equal to about the depth of cut allowed to finish with, and for the finishing cut to the radius of the finished sphere in order to obtain a true sphere, because if B be operated so that D does not stand directly coincident with the line of lathe centres, the centre of motion, or of the circle described by the tool point, will not be coincident with the centre on which the work rotates, hence the work though running true would not be a true sphere but an oval. This oval would be longest in the direction parallel with the line of centres whenever the pivot D was past the line of centres, and an oval of largest diameter at the middle or largest diameter turned by the tool whenever the pivot D was on the handle H side of the line of centres. To steady C it may be provided with a circular dovetail, as shown at the end I, provision being made (by set screw or otherwise) for locking C in a fixed position when using the rest for other than spherical work. To construct such a rest for turning curves or hollows whose outline required to be an arc of a circle, the pivot D would require to be directly beneath the tool post, which must in this case occupy a fixed position. The radius of the arc would here again be determined by the distance of the tool point from the centre of rotation of the pivot, or, what would be the same thing, from that of the tool post. Next to the hand slide rest lathe comes the self-acting or engine lathe. These are usually provided with a feed motion for traversing the slide rest in the direction of the length of the bed, and sometimes with a self-acting cross feed, that is to say, a feed motion that will traverse the tool to or from the line of centres and at a right angle to the same. In an engine lathe the parallelism or truth of the work depends upon the parallelism of the line of centres with the shears of the lathe, and therefore upon the truth of the shears or bed, and its alignment with the cone spindle and tail spindle, while the truth of the radial faces on the turned work depends upon the tool rest moving on the cross slide at a true right angle to the line of centres. [Illustration: Fig. 492.] Fig. 492 represents an 18-inch engine (or self-acting) lathe designed by and containing the patented improvements of S. W. Putnam, of the Putnam Tool Company, of Fitchburg, Massachusetts. The lathe has an elevating slide rest self-acting feed traverse and self-acting cross feed, both feeds being operative in either direction. It has also a feed rod for the ordinary tool feeding and a lead screw for screw-cutting purposes. Fig. 493 represents a cross-sectional view of the shears beneath the headstock; A A are the shears or bed having the raised [V]s marked V´ and V on which the headstock and tailstock rest, and V´´ and V´´´ on which the carriage slides. A and A´ are the shears connected at intervals by cross girts or webs B to stiffen them. C C are the bolts to secure the headstock to the shears. D is a bracket bolted to A´ and affording at E journal bearing for the spindle that operates the independent feed spindle. E is split at _f_ and a piece of soft wood or similar compressible material is inserted in the split. The bolt F is operated to close the split, and, therefore, to adjust the bore E to properly fit the journal of the feed spindle, and as similar means are provided in various parts of the lathe to adjust the fits of journals and bearings the advantages of the system may here be pointed out. First, then, the fit of the bearing may be adjusted by simply operating the screw, and, therefore, without either disconnecting the parts or performing any fitting operation, as by filing. Secondly, the presence of the wood prevents the ingress of dust, &c., which would cause the bearings and journals to abrade; and, thirdly, the compression of the wood causes a resistance and pressure on the adjusting screw thread, which pressure serves to lock it and prevent it from loosening back of itself, as such screws are otherwise apt to do. [Illustration: Fig. 493.] As the pressure of the tool cut falls mainly on the front side of the carriage, and as the weight of the carriage itself is greatest on that side, the wear is greatest; this is counteracted by forming the front [V], marked V´´´ in figure, at a less acute angle, which gives it more wearing area and causes the rest to lower less under a given amount of wear. The rib A´´ which is introduced to strengthen the shears against torsional strains, extends the full length of the shears. [Illustration: Fig. 494.] Fig. 494 is a sectional side elevation of the headstock; A A´ represents the headstock carrying the bearing boxes B and B´, which are capable of bore closure so as to be made to accurately fit the spindle S by the construction of the front bearing B, being more clearly shown in Fig. 495; B is of composition brass, its external diameter being coned to fit the taper hole in the head; it is split through longitudinally, and is threaded at each end to receive the ring nuts C and C´. If C be loosened from contact with the radial face of A, then C´ may be screwed up, drawing B through the coned hole in A, and, therefore, causing its bore to close upon S. At the other end of S, Fig. 496, C´´ is a ring nut for drawing the journal box B´ through _a´_ to adjust the bore of B´ to fit the journal of S, space to admit the passage of B´ being provided at _e_. D is a box nut serving to withdraw B´ or to secure it firmly in its adjusted position, and also to carry the end adjusting step E. F is a check nut to lock E in its adjusted position. The method of preventing end motion to S is more clearly shown in Fig. 496, in which _h_ is a steel washer enveloping S, having contact with the radial face of B´ and secured in its adjusted position by the check nuts _g_, hence it prevents S from moving forward to the right. _f_ is a disk of raw hide let into E; the latter is threaded in D and is squared at the end within F to admit of the application of a wrench, hence E may be screwed in until it causes contact between the face of _f_ and the end of S, thus preventing its motion to the left. By this construction the whole adjustment laterally of S is made with the short length from _h_ to _f_, hence any difference of expansion (under varying temperature) between the spindle and the head A A´, or between the boxes and the spindle S, has no effect towards impairing the end fit of S in its bearings. The method of adjusting the bearings to the spindle is as follows:--C´´ and C´ are slackened back by means of a "spanner wrench" inserted in the holes provided for that purpose. C and D are then screwed up, withdrawing B and B´ respectively, and leaving the journal fit too easy. C´ is then screwed up until B is closed upon the spindle sufficiently that the belt being loose on the cone pulley, the latter moved by the hand placed upon the smallest step of the cone can just detect that there is contact between the bore of B and the spindle, then, while still moving the cone, turn C´ back very slowly and a very little, the object being to relieve the bore of B from pressure against S. C may then be screwed up, firmly locking B in its adjusted position. C´´ may then be operated to adjust B´ in a similar manner, and D screwed up to lock it in its adjusted position. Before, however, screwing up D it is better to remove F and release E from pressure against _f_, adjusting the end pressure of E after D has been screwed home against A´. To prevent B and B´ from rotating in the head when the ring nuts are operated, each is provided with a pin, _q_, grooves _c_ and _c´_ permitting of the lateral movement of B and B´ for adjustment. The boxes B, B´ admit of being rotated in their sockets in A and A´ so as to assume different positions, the pins _q_ and _q´_ being removable from one to another of a series of holes in the boxes B, B´ when it is desired to partly rotate those boxes. The tops of the boxes are provided with oil holes, and the oil ways shown at _r_, _s_ being the oil groove through the head and _a_ simply a stopper to prevent the ingress of dust, &c. [Illustration: Fig. 495.] The thread on S at Z, Fig. 494, is to receive and drive the face plates, chucks, &c., which are bored and threaded to fit over Z. To cause the radial faces of such face plates or chucks to run true, there is provided the plain cylindrical part _l_, to which the bore in the hub of the face plate or chuck is an accurate fit when the radial face of that hub meets the radial face _m_. Referring again to Fig. 494, G´ is the pinion to drive the back gear while G receives motion from the back-gear pinion. The object of the back gear is to reduce the speed of rotation of S and to enable it to drive a heavier cut, which is accomplished as follows:--G´ is secured within the end K of the cone and is free to rotate with the cone upon S; at the other end the cone is secured to M, which is free to rotate upon S so far as its bore is concerned. G is fixed upon S and hence rotates at all times with it; but G may be locked to or released from M as follows:-- [Illustration: Fig. 496.] In G is a radial slot through which passes a bolt I provided with a cap nut H, in M is an annular groove J. When I is lifted its head passes into a recess in M, then H is screwed up and G is locked to M. This is the position of I when the back gear is not in use, the motion of the cone being communicated to S through I. But if H be loosened and I be moved inwards towards S, the head of I passes into the annular groove J, and the cone is free to rotate upon S while the latter and G remain stationary unless the back gear is put into operation. In this latter case the pinion G´ rotating with the cone drives the large gear of the back gear and the small pinion of the latter drives G, whose speed of rotation is reduced by reason of the relative proportions of the gear wheels. In this case it is obvious that since the pulley rotates upon the spindle it requires lubrication, which is accomplished through the oil hole tubes L. The means of giving motion to the feed spindle and lead screw are as follows:--N, Fig. 494, is a pinion fast upon S and operating the gear O, which is fast upon the spindle P, having journal bearing in a stem in A´ and also at G´´. P drives the three-stepped cone R, which is connected by belt to a similar cone fast upon the independent feed spindle. The seat for the driving gear of the change wheels for the lead screw is on P at V. To provide ample bearing surface for P in A´ the bush or sleeve shown is employed, but this sleeve also serves to pivot the swing frame W which carries the studs for the change wheels that go between the wheel on V and that on the lead screw; _x_ _y_ are simply oil holes to lubricate P in its bearings. To provide a wider range of tool feed than that obtainable by the steps on the feed cones, as R, they are provided at their ends with seats for change wheels, the swing frame W carrying the intermediate wheels for transmitting motion from V to a similar seat on the cone on the feed spindle. Fig. 497 represents the tailstock (or tailblock as it is sometimes termed), shown in section. A represents the base which slides upon the raised [V]s on the bed and carries the upper part B, in which slides the tail spindle C, which is operated longitudinally by the tail screw D, having journal bearing in E, and threaded through the nut F which is fast in C. The hand wheel G is for rotating D, whose thread operating in the nut F, causes C to slide within B in a direction determined by the direction of rotation of G. To lock C in its adjusted position the handled nut H is employed in connection with the bolt I, which is shown in dotted lines; C is split as shown by the dotted lines at _f_; J is the dead centre fitting accurately into a conical hole in C. When it is required to remove J from C the wheel G is operated to withdraw C entirely within B, and the end _d_ of D meets the end _e_ of J and forces J from the coned hole in C. The method of securing the tailstock to the shears or releasing it from the same is as follows. A vertical prolongation of B affords at B´´ a bearing surface for the nut-handle L and washer M. K is a bolt threaded into L passing through M, B´´ and N, the latter of which it carries. N spans the shears beneath the two [V]s on which the tailstock slides. Moving or rather partly rotating the handle L in the necessary direction lifts K and causes N to rise, and grip the shears beneath, while the pressure of M on B´´ causes B to grip A and the latter to grip the raised [V]s on the shears. If L be rotated in the opposite direction it will cause N to fall, leaving A free to slide along the shears. To prevent N from partly rotating when free, its ends are shaped to fit loosely between the shears as shown at _n_. To give to N sufficient rise and fall to enable it to grip or fall entirely free from the shears with the small amount of rotary motion which the handle-lever L is enabled from its position to have, the following device is provided. M is a washer interposed between L and B´´. This washer has upon it steps of different thickness as shown at M and _m_, the two thicknesses being formed by an incline as shown. The face of L has, as shown, similar steps; now as shown in the cut the step _l_ on lever L meets the steps _m_ of the washer, the handle having receded to the limit of its motion. The bolt K then has fallen to the amount due to unscrewing the threaded or nut end of L, and also to the amount of the difference of thickness at M and at _m_ of the washer, the plate N being clear of the lathe-shears. But suppose the handle L be pulled towards the operator, then the surface _l_ passing from a thin section on to a thick one as M of the washer, will lift the bolt K, causing N to meet the under surface of the shears, and then the motion of L continuing the pressure of the thread will bind or lock N to the bed. [Illustration: Fig. 497.] The surface A´ in Fig. 497 affords a shelf or table whereon tools, &c., may be placed instead of lying on the lathe bed, where they may cause or receive damage. Fig. 498 represents an end view of the tailstock viewed from the dead centre end, the same letters of reference applying to like parts that are shown in Fig. 497. The split at _f_ is here shown to be filled with a piece of soft wood which prevents the ingress of dust, &c. At _d_ is a cup or receptacle for oil, _e_ being a stopper, having attached to it a wire pin flattened and of barb shape at the end, the object being to cause the wire to withdraw from the cup a drop of oil to lubricate the dead centre and centre in the work. The proximity of _e_ to the dead centre makes this a great convenience, while the device uses much less oil than would be used by an oil can. [Illustration: Fig. 498.] The method of setting over the upper part B to enable the turning of the diameter of work conical or taper instead of parallel is shown in Fig. 498: P and P´ are square-headed screws threaded into the walls of A and meeting at their ends the surface of B´. In A there is at _a_ a wide groove or way, and on B there is at _b_ a projection fitting into the way _a_ so as to guide B when it slides across A, as it will when P is unscrewed in A and P´ is screwed into A. This operation is termed setting over the tailstock, and its effect is as follows:--Suppose it be required to turn a piece of work of smaller diameter at the end which runs on the dead centre, then, by operating the screw P towards the front of the lathe (or to the left as shown in the cut) and screwing P´ farther into A, the end of P´ will meet the surface of B´, causing B´ to move over, and the centre of the dead centre J (which is the axis of rotation of the work at that end) will be nearer to the point of the cutting tool. Or suppose the work requires to be turned a taper having its largest diameter at the end running on the dead centre, then P´ would be unscrewed and P screwed farther into A, carrying B farther towards the back of the lathe. The [V] grooves Q and Q´ fit upon the inner raised [V]s shown at V, V´ in Fig. 499. [Illustration: Fig. 499.] Fig. 499 is a side view of the slide rest for holding and traversing the cutting tool. A represents the carriage resting upon the raised [V]s marked V´´ and V´´´ and prevented from lifting by its own weight, and in front also by the gib _a_ secured to A by the bolt _b_ and having contact at _c_ with the shears. A carries at _d_ a pivot for the cross slide B and at _e_ a ball pivot for the cross slide elevating screw C. This screw is threaded through the end of B so that by operating it that end of B may be raised or lowered to adjust the height of the cutting tool point to suit the work. To steady B there is provided (in addition to the pivots at _d_) on A two lugs _f_, between the vertical surfaces of which B is a close working fit. The upper surface of B is provided with a [V]-slide-way _g_, to which is fitted the tool rest D (the construction being more clearly shown in Fig. 500). [Illustration: Fig. 500.] The means for traversing D along the slide _g_ on B is as follows:-- A nut _i_ is secured to D by the screw bolt _j_, and threaded through the nut _i_ is the cross-feed screw E, which has journal bearing in the piece _k_, which is screwed into the end face of B; there is a collar on E which meets the inner end of _k_, and the handle F being secured by nut to that end of E its radial face forms a shoulder at _m_ which with the collar prevents any end motion of E, so that when F is rotated E rotates and winds through the nut _i_ which moves D along B. An end view of A, B, and D is shown in Fig. 500, in which the letters of reference correspond to those in Fig. 499. B´ and B´´ are the projections that pass into A and receive the pivoting screws _d_ and _d_. To adjust the fit and take up any wear that may ensue on the slide _g_, on B and on the corresponding surface on D, the piece _n_ is provided, being set up by the adjusting screws O. To adjust the fit and take up the wear at the pivots _d_ they are made slightly taper, fitting into correspondingly taper holes in B. The dotted circle T´, represents a pinion fast upon the cross-feed screw (E, Fig. 499); the similar circles T and S´´ also represent pinions, the three composing a part of the method of providing an automatic or self-acting cross feed or cross traverse to D by rotating it through a gear-wheel motion derived from the rotation of the independent feed spindle, as is described with reference to Fig. 501. _m_ in Fig. 500 represents a cavity or pocket to receive wool, cotton or other elastic or fibrous material to be saturated with oil and thus lubricate the raised [V]s while keeping dirt from passing between the rest and the [V]s. The shape of these pockets is such as to enable them to hold the cotton with a slight degree of pressure against the slides, thus insuring contact between them. The mechanical devices for giving to the carriage a self-acting traverse in either direction along the bed, so as to feed the tool automatically to its cut, and for giving to the tool rest (D, Fig. 499) traverse motion so as to feed the tool to or from the line of centres along the cross slide, are shown in Fig. 501, which presents two views of the feed table or apron. The lower view supposes the feed table to be detached from the carriage and turned around so as to present a side elevation of the mechanism. The upper view is a plan of the same with two pinions (N and N´), omitted. A represents the part of the lathe carriage shown at A in Fig. 500. It has two bolts _p_ and _p´_, which secure the apron G, Fig. 501, to A. At H is the independent feed spindle or feed rod operated by belt from the cone pulley R, Fig. 494, or by a gear on stud P at V. H is carried in bearings fixed to each end of the lathe shears or bed, both of these bearings being seen in Fig. 492. H is also provided with a bearing fixed on the feed apron as seen in Fig. 501, and is splined as shown at _h_. At I is a bracket fast upon the apron G and affording journal bearing to J, which is a bevel pinion having a hub which has journal bearing in the bracket I. The fit of the bearing to the journal is here again adjusted by a split in the bearing with a screw passing through the split and threaded in the lower half (similar to the construction of D in Fig. 493); J is bored to receive H, and is driven by means of a feather projecting into the spline _h_. When therefore, the carriage A is moved it carries with it the apron G, and this carries the bracket I holding the bevel pinion J, which is in gear with the bevel-wheel K, and therefore operates it when H has rotary motion. At the back of K, and in one piece with it, is a pinion K´, both being carried upon the stud L; pivoted upon this same stud is a plate lever M, carrying two pinions N and N´ in gear together, but N only is in gear with K´, hence K´ drives N and N drives N´. Now in the position shown neither N or N´ is in gear with the gear-wheel O, but either of them may be placed in gear with it by means of the following construction:-- At the upper end of M there is provided a handle stud M´ passing through the slot M´´ in G. Screwing up this stud locks M fast by binding it against the surface of G. Suppose, then, M´ to be unscrewed, then if it be moved to the right in the slot M´´, N will be brought into gear with O and the motion will be transmitted in the direction of the arrows, and screwing up N would retain the gear in that position. But suppose that instead of moving M´ to the right it be moved to the left, then N´ will be brought into gear with O and the direction of rotation of O will be reversed. [Illustration: Fig. 501.] Thus, then, O may be made to remain stationary or to rotate in either direction according to the position of M´ in the slot M´´, and this position may be regulated at will. The gear O contains in its radial face a conical recess, and upon the same stud or pin (P) upon which O is pivoted, there is fixed the disk P´, which is in one piece with the pinion P´´; the edge of P´ is coned to fit the recess in the wheel O, so that if the stud P is operated to force the disk P´ into the coned recess in O the motion of wheel O will be communicated to disk P´, by reason of the friction between their two coned surfaces. Or if P be operated to force the coned edge of the disk out of contact with the coned bore or recess in gear O, then O will rotate while P´ and P´´ will remain stationary. Suppose the coned surfaces to be brought (by operating _x_) into contact and P´ to rotate with O, then P´´ being in gear with wheel Q will cause it to rotate. Now Q is fast to the pinion Q´, hence it will also rotate, and being in contact with the rack which is fixed along the shears of the lathe and a section of which is shown in the cut, the whole feed table or apron will be made to traverse along the lathe shears. The direction in which this traverse will take place depends upon the adjusted position of M´ in M´´, or in other words upon whether N or N´ be the pinion placed in gear with O. As shown in the cut neither of them is in gear, and motion from H would be communicated to N and N´ and would there cease; but if M´ be raised in the slot M´´, N would drive O, and supposing P´ to be held to O, the motion of all the gears would be as denoted by the arrows, and the lathe carriage A would traverse along the lathe bed in the direction of arrow Q´´. But if N´ be made to drive O all the motions would be in the opposite directions. The self-acting feed motion thus described is obviously employed to feed the cutting tool, being too slow in its operation for use to simply move the carriage from one part of the lathe bed to another; means for this purpose or for feeding the carriage and cutting tool by hand are provided as follows:--R is a pinion in gear with Q and fast upon the stud R´, which is operated by the handle R´´. The motion of R´´ passes from R to Q and Q´ which is in gear with the rack. But Q´ being in gear with P´´ the latter also rotates, motion ceasing at this point because the cone on P´ is not in contact with the coned recess in O. When, however, P´ and O are in contact and in motion, that motion is transmitted to R´´, which cannot then be operated by hand. It is often necessary when operating the cross feed to lock the carriage upon the lathe bed so that it shall not move and alter the depth of the tool-cut on the radial face of the work. One method of doing this is to throw off the belt that operates the feed spindle H, place N in gear with O and P´ in contact with O, so that the transverse feed motion will be in action, and then pull by hand the cone pulley driving H, thus feeding the tool to its necessary depth of cut. The objection to this method, however, is that when the operator is at the end of the lathe, operating the feed cone by hand he cannot see the tool and can but guess how deep a cut he has put on. To overcome this difficulty a brake is provided to the pinion R as follows:-- The brake whose handle is shown at V has a hub V´ enveloping the hub R´´´ which affords journal bearing to the stud R´. In the bore of this hub V´ is an eccentric groove, and in R´´´ is a pin projecting into the eccentric groove and meeting at its other end the surface of the stud R´. When, therefore, V is swung in the required direction (to the left as presented in the cut), the cam groove in V´ forces _r_ inwards, gripping it and preventing it from moving, and hence the movement of R which also locks Q and Q´. It remains now to describe the method of giving rotary motion to the cross-feed screw E (Fig. 499) so as to enable it to self-act in either direction. S is a lever pivoted upon the hub of O and carrying at one end the pinion S´´, while at the other end is a stud S´ passing through a slot in G. The pinion S´´ is in gear with O and would therefore receive rotary motion from it and communicate such motion to pinion T, which in turn imparts rotary motion to T´. Now T´ is fast upon the cross-feed screw as shown in Fig. 499 and the cross-feed screw E in that figure would by reason of the nut _i_ in figure cause the tool rest D to traverse along the cross-slide in a direction depending upon the direction of motion of T´, which may be governed as follows:-- If S´ be moved to the left S´´ will be out of gear with T and the cross-feed screw may be operated by the handle (F, Fig. 499). If S´ be in the position shown in cut and M´´ also in the position there shown (Fig. 501), operating the feed screw by its handle would cause its pinion T´ to operate T, S´´, and O; hence S´ should always be placed to disconnect S´´ from T when the cross-feed screw is to be operated by hand, and S´ operated to connect them only when the self-acting cross feed is to operate. In this way when the cross feed is operated by hand T´ and T will be the only gears having motion. It has been shown that the direction of motion of O is governed by the position of M´, or in other words, is governed by which of the two pinions N or N´ operates, and as O drives S´´ its motion, and therefore that of T´, is reversible by operating M´. The construction of S´ is as follows:--Within the apron as shown in the side elevation it consists of what may be described as a crank, its pin being at _t_; in the feed table is a slot through which the shaft of the crank passes; _s_ is a handle for operating the crank. By rotating _s_ the end S´ of S is caused to swing, the crank journal moving in the slot to accommodate the motion and permit S to swing on its centre. The device for forcing the cone disk P´ into contact with or releasing it from O is as follows:--The stud P is fast at the other end in P´ and has a collar at _b_; the face of this collar forms one radial face, and the nut W affords the other radial face, preventing end motion to _x_ without moving P endwise. If _x_ be rotated its thread at _x´_ causes it to move laterally, carrying P with it, and P being fast to P´ also moves it laterally. P´ is maintained from end motion by a groove at O´ in which the end of a screw _a_ projects, _a_ screwing through W and into the groove O´. [Illustration: Fig. 502.] The lead screw of a lathe is a screw for operating the lathe carriage when it is desired to cut threads upon the work. It is carried parallel to the lathe shears after the same manner as the independent feed spindle, and is operated by the change wheels shown in Fig. 492 at the end of the lathe. These wheels are termed change wheels on account of their requiring to be changed for every varying pitch of thread to be cut, so that their relative diameters, or, what is the same thing, their relative number of teeth, shall be such as to give to the lead screw the speed of rotation per lathe revolution necessary to cut upon the work a thread or screw of the required pitch. The construction of the bearings which carry the lead screw in the S. W. Putnam's improved lathe is shown in Fig. 502, in which A represents the bearing box for the headstock end of the lathe, having the foot A´ as a base to bolt it to the lathe shears. L represents the lead screw, having on one side of A the collar L´ and on the other the nut and washer N and N´. The seat for the change wheel that operates the lead screw is at L´´, the stop pin _l_ fitting into a recess in the change wheel so as to form a driving pin to the lead screw. The washer N´ is provided with a feather fitting into a recess into L so that it shall rotate with L and shall prevent the nut N from loosening back as it would be otherwise apt to do. End motion to L is therefore prevented by the radial faces of L´ and N´. [Illustration: Fig. 503.] At the other end of the lathe there are no collars on the lead screw, hence when it expands or contracts, which it will do throughout its whole length under variations of atmospheric temperature, it is free to pass through the bearing and will not be deflected, bent, or under any tension, as would be the case if there were collars at the ends of both bearings. The amount of this variation under given temperatures depends upon the difference in the coefficients of expansion for the metal of which the lead screw and the lathe shears are composed, the shears being of cast iron while lead screws are sometimes of wrought iron and sometimes of steel. The bearings at both ends are split, with soft wood placed in the split and a screw to close the split and adjust the bearing bore to fit the journal, in the manner already described with reference to other parts of this lathe. The construction of the swing frame for carrying the change wheels that go between the driving stud V, Fig. 494, and that on the seat L´´, Fig. 502, are as follows:-- Fig. 503 represents the change wheel swing frame, an edge view of which is partly shown at W in Fig. 494. S is a slot narrower at _a_ than at _b_. Into this slot fit the studs for carrying the change wheels. By enabling a feed traverse in either direction the lathe carriage may be traversed back (for screw-cutting operations) without the aid of an extra overhead pulley to reverse the direction of rotation of the lathe, but in long screws it is an advantage to have such extra overhead pulley and to so proportion it as to make the lathe rotate quicker backwards than forward, so as to save time in running the carriage back. The mechanical devices for transmitting motion from the lead screw to the carriage are shown in Fig. 504, representing a view from the end and one from the back of the lathe. B is a frame or casting bolted by the bolt _b_ to the carriage A of the lathe. C is a disk having a handle C´ and having rotary motion from its centre. Instead of being pivoted at its centre, however, it is guided in its rotary motion by fitting at _d_ _d_ into a cylindrical recess provided in B to receive it. C contains two slots D and D´ running entirely through it. These slots are not concentric but eccentric to the centre of motion of C. Through these slots there pass two stud bolts E and E´ shown by dotted lines in Fig. 504, and these bolts perform two services: first by reason of the nuts F and F´ they hold C to its place in B, and next they screw into and operate the two halves G and G´ of a nut. [Illustration: Fig. 504.] Suppose, now, that the handle C´ be operated or moved towards arrow _e_, then the dot at _f_ being the centre of its motion and the slots D and D´ gradually receding from _f_ as their ends _g_ are approached they will cause E to move vertically upward and E´ to move vertically downward, a slot in B (which slot is denoted by the dotted lines _h_) guiding them and permitting this vertical movement. Since E and E´ carry the two halves of the nut which envelops the lead screw L it is obvious that operating C´ will either close or release the half nuts from L according to which direction it (C´) is moved in. The screws H and H´ screw tightly into B, and the radial faces of their heads are made to have a fair and full bearing against the underside of the shears, so that they serve as back gibs to hold the carriage to the shears and may be operated to adjust the fit or to lock the carriage to the bed if occasion may require. This lathe is made with a simple tool rest as shown in the engravings or with a compound slide rest. In some sizes the rest is held to the carriage by a weight upon a principle to be hereafter described. The bed is made (as is usual) of any length to suit the purposes for which the lathe is to be used. The next addition to the lathe as it appears in the United States is that of a compound slide rest. [Illustration: Fig. 505.] Fig. 505 represents a 28-inch swing lathe by the Ames Manufacturing Company, of Chicopee, Massachusetts. It is provided with the usual self-acting feed motion and also with a compound slide rest. The swing frame for the studs carrying the change wheels for screw cutting here swings upon the end of the lead screw, the same spindle that carries the driving cone for the independent feed rod which is in front of the lathe, also carries the driving gear for the change wheels used for screw cutting. The construction of the compound rest is shown in Figs. 506 and 507. N is the nut for the cross-feed screw (not shown in the cut) and is carried in the slide A. A and the piece L above it are virtually in one, since the latter is made separate for convenience of construction and then secured to it firmly by screws. B is made separate from C also for convenience of construction and fixed to it by screws; L is provided with a conical circular recess into which the foot B of C fits. E is a segment of a circle operated by the set screw F to either grip or release B. The bolt D simply serves as a pivot for piece B C; at its foot C is circular and is divided off into the degrees of a circle to facilitate setting it to any designated angle. If, then, F be unscrewed, C may be rotated and set to the required angle, in which position screwing up F will lock it through the medium of E. G is the feed nut for the upper slider H, which operates along a slide way provided on C, the upper feed screw having journal bearing at C´. I is the tool post, having a stepped washer J, by means of which the height of the tool K may be regulated to suit the work. [Illustration: Fig. 506.] [Illustration: Fig. 507.] Suppose, now, that it be required to turn a shaft having a parallel and a taper part; then the carriage may be traversed to turn the parallel part, and the compound slide C may be set to turn the taper part, while the lower feed screw operating in N may be used to turn radial faces. [Illustration: Fig. 508.] The object of making A and L in two pieces is to enable the boring and insertion of B, which is done as follows:--The front end of L as L´ is planed out, leaving in it a groove equal in diameter and depth to the diameter and depth of B, so that B may be inserted laterally along this groove to its place in L. The segment E is then inserted and a piece is then fitted in at L´ and held fast to A by screws. It is into this piece that the set screw F is threaded. Various forms of construction are designed for compound rests, but the object in all is to provide an upper sliding piece carrying the tool holder, such sliding piece being capable of being so set and firmly fixed that it will feed the tool at an angle to the line of the lathe centres. Another and valuable feature of the compound rest is that it affords an excellent method of putting on a very fine cut or of accurately setting the depth of cut to turn to an exact diameter; this is accomplished by setting the upper slide at a slight angle to the line of centres and feeding the tool to the depth of cut by means of the screw operating the upper slide. In this way the amount of feed screw handle motion is increased in proportion to the amount to which the tool point moves towards the line of lathe centres, hence a delicate adjustment of depth of cut may be more easily made. Suppose, for example, that a cut be started and that it is not quite sufficiently deep, then, while the carriage traverse is still proceeding, the compound rest may be operated to increase the cut depth, or if it be started to have too deep a cut the compound rest may be operated to withdraw the tool and lessen its depth of cut. Or it may be used to feed the tool in sharp corners when the feed traverse is thrown out, or to turn the tops of collars or flanges when the tailstock is set over to turn a taper. It is obvious, however, that comparatively short tapers only can be conveniently turned by a compound slide rest; but most tapers, however, are short. To turn long tapers the tailstock of the lathe is set over as described with reference to the Putnam lathe, but for boring deep holes the slide rest must either be a compound one or a taper turning former or attachment must be employed. [Illustration: Fig. 509.] When, however, the tailstock is set over, the centres in the work are apt to wear out of true and move their location (the causes of which will be hereafter explained). In addition to this, however, the employment of a taper turning attachment enables the boring of taper holes without the use of a compound slide rest, thus increasing the capacity of the lathe not having a simple or single rest. In Fig. 508 is shown a back view of a Pratt and Whitney weighted lathe having a Slate's taper turning attachment, the construction of which is as follows:--Upon the back of the lathe shears are three brackets having their upper surfaces parallel with and in the same plane as the surface of the lathe shears. Pivoted to the middle bracket is a bar which has at each end a projection or lug fitting into grooves provided in the end brackets, these grooves being arcs of a circle whose centre is the axis of the pivot in the middle bracket. The end brackets are provided with handled nuts upon bolts, by which means the bar may be fixed at any adjusted angle to the lathe shears. Upon the upper surface of the bar is a groove or way in which slides a sliding block or die, so that this die in traversing the groove will move in a straight line but at an angle to the lathe bed corresponding to the angle at which the bar may be adjusted. The slide rest upon being connected by a bar or rod to the die or sliding block is therefore made to travel at the same angle to the lathe bed or line of centres as that to which the bar is set. The method of accomplishing this in the lathe, shown in Fig. 508, is as follows:-- In Fig. 509 A is the bar pivoted at C upon the centre bracket B; E is the sliding block pivoted to the nut bar F. This nut bar carries the cross-feed nut, which in turn carries the feed screw and hence the tool rest. When the nut bar is attached to the sliding block to turn a taper it is free to move endways upon the lower part of the carriage in which it slides, but when the taper attachment is not in use the bar is fastened to the lower part of the carriage by a set screw. The screw at D is provided to enable an accurate adjustment for the angle of the bar A. G and H are screws simply serving to adjust the diameter to which the tool will turn after the manner shown in Fig. 588, G being for external and H for internal work. When the lathe has a bed of sufficient length to require it, a slide is provided to receive the brackets, which may be adjusted to any required position along the slide, as shown in Fig. 510. This is a gibbed instead of a weighted lathe, and the method of attaching the sliding block to the lathe rest is as follows:-- A separate rod is pivoted to the sliding block. This rod carries at its other end a small cross head which affords general bearing to the end of the cross-feed screw, which has a collar on one side of the cross head and a fixed washer on the other, to prevent any end motion of the said screw. [Illustration: Fig. 510.] The cross-feed nut is attached to the traversing cross slide. The other or handle end of the cross-feed screw has simple journal bearing in the slide rest, but no radial faces to prevent end motion, so that one may from the rod attached to the sliding-block traverse the cross-feed slide, which will carry with it the feed screw. As a result, the line of motion of the tool rest is governed by the sliding die, but the diameter to which the tool will turn is determined by the feed screw in the usual manner. When it is not required to use the taper attachment, the rod or spindle is detached from the sliding die and is locked by a clamp, when the rest may be operated in the usual manner. Fig. 511 represents a compound duplex lathe of a design constructed by Sir Joseph Whitworth, of Manchester, England. The two rests are here operated on the same cross slide by means of a right and left-hand cross-feed screw. The tool for the back rest is here obviously turned upside down. The lead screw is engaged at two places by the feed nut, which is in two pieces attached to levers; while at a third point in its circumference it is supported by a bracket, bolted to the lathe bed. [Illustration: Fig. 511.] Fig. 512 represents the New Haven Manufacturing Company's three tool slide rest, for turning shafting. It is provided with a follower rest, in front of which are two cutting tools for the roughing cuts, and behind which is a third tool for the finishing cut. The follower rest receives bushes, bored to the requisite diameter, to leave a finishing cut. The first tool takes the preliminary roughing cut; the second tool turns the shaft down to fit the bush or collar in the follower rest; and, as stated, the last tool finishes the work. Fig. 513 represents a 44-inch swing lathe, showing an extra and detachable slide rest, bolted on one side of the carriage and intended for turning work of too large a diameter to swing over the slide rest. By means of this extra rest the cutting tool can be held close in the rest, instead of requiring to stand out from the tool-post to a distance equal to the width of the work. The ordinary tool post is placed in this extra rest. [Illustration: Fig. 512.] When it is desired to bolt work on the lathe carriage and rotate the cutting tools, as in the case of using boring bars, the cross slide is sunk into instead of standing above the top surface of the carriage so as to leave a flat surface to bolt the work to, and [T]-shaped slots are provided in the carriage, to receive bolts for fastening the work to the carriage, an example of this kind being shown in Fig. 514. [Illustration: Fig. 513.] Fig. 515 represents a self-acting slide or engine lathe by William Sellers and Co., of Philadelphia. These lathes are made in various sizes from 12 inches up to 48 inches swing on the same general design, possessing the following features:--The beds or shears are made with flat tops, the carriage being gibbed to the edges of the shears, these edges being at a right angle to the top face of the bed. The dead centre spindle is locked at each end of its bearing in the tailstock, thus securing it firmly in line with the live spindle. The ordinary tool feed is operated by a feed rod in front of the lathe, and this rod is operated by a disc feed, which may be altered without stopping the lathe so as to vary the rate of tool feed; and an index is provided whereby the operator may at once set the discs to give the required rate of feed. The lead screw for screw cutting is placed in a trough running inside the lathe bed, so that it is nearer to the cutting tool than if placed outside that bed, while it is entirely protected from the lathe cuttings and from dirt or dust; and the feed-driving mechanism is so arranged that both may be in gear with the live spindle, and either the rod feed or screw-cutting feed may be put into action instantly, while putting one into action throws the other out, and thus avoid the breakage that occurs when both may be put into action at the same time. The direction of the turning feed is determined by the motion of a lever conveniently placed on the lathe carriage, and the feed may be stopped or started in either direction instantly. The mechanism for putting the cross feed in action is so constructed (in those lathes having a self-acting cross feed) that the cross feed cannot be in action at the same time as the turning feed or carriage traverse by rod feed. Lathes of 12 and 16 inches swing are back-geared, affording six changes of speed, and the lathe tool has a vertical adjustment on a single slide rest. Lathes of 20 inches swing are back-geared with eight changes of speed. Lathes of 25 inches and up to 48 inches swing inclusive are triple-geared, affording fifteen changes of speed, having a uniformly progressive variation at each change. The construction of the live head or headstock for a 36-inch lathe is shown in the sectional side view in Fig. 516, and in the top view in Fig. 517, and it will be seen that there are five changes of speed on the cone, five with the ordinary back-gear, and five additional ones obtained by means of an extra pinion on the end of the back-gear spindle, and gearing with the teeth on the circumference of the face plate, the ordinary pinion of the back-gear moving on the back-gear spindle so as to be out of the way and clear the large gear on the cone spindle when the wheel of the extra back-gear pinion is in use, as shown in Fig. 517. [Illustration: Fig. 514.] The front bearing of the live spindle is made of large diameter to give rigidity, and the usual collar for the face plate to screw against is thus dispensed with. End motion to the live spindle is prevented by a collar of hardened steel, this collar being fast on the live spindle and abutting on one side against the end face of the back bearing and on the other against a hardened steel thrust collar. [Illustration: Fig. 515.] All these parts are enclosed in a tight cast-iron tail-block, which serves as an oil well to insure constant and perfect lubrication. The surfaces which confine the revolving collar back and front are so adjusted as to allow perfect freedom of rotary motion to the spindle and collar, but no perceptible end motion. The securing of the live spindle endwise is thus confined to the thickness of the steel collar only, and this is so enclosed in a large mass of cast iron as to insure uniformity of temperature in all its parts, hence there is no liability for the live spindle to stick or jam in its bearings, while the expansion of the live spindle endways from this collar (if it expands more than the lathe head) is allowed for in freedom of end motion through the front journal, which is a little longer than the bearing it runs in. In turning work held between the lathe centres the end thrust is taken against the hardened steel collar on the live spindle, and the hardened steel collar at the back of it, while in turning work chucked to the face plate the spindle is held in place endways by the confinement of the steel collar on the spindle between the steel collar behind it and the back end of the back bearing. With this arrangement of the spindle the change from turning between the lathe centres and turning chucked work requires no thought or attention to be given to any adjustment of the live spindle to accommodate it for the changed condition of end pressure between turning between the centres and turning chucked work, as is the case in ordinary lathes. The double-geared lathes, as those of 12, 16 and 20 inches swing, are provided with face plates that unscrew from the live spindle to afford convenience for changing from one size of face plate to another, and all such lathes have their front live spindle journal made of sufficiently enlarged diameter above that of the screw, to afford a shoulder for the face plate to abut against. The nose of the live spindle is not threaded along its entire length, but a portion next to the shoulder is made truly cylindrical but without any thread upon it, and to this unthreaded part the face plate accurately fits so that it is held true thereby, and the screw may fit somewhat loosely so that all the friction acts to hold the face plate true and hard up against the trued face of the spindle journal. Face plates fitted in this way may be taken off and replaced as often as need be, with the assurance that they will be true when in place unless the surfaces have been abused in their fitting parts. [Illustration: Fig. 516.] The construction of the tailstock or poppet-head, as it is sometimes termed, is shown in Figs. 518, 519, and 520. To hold it in line with the live spindle it is fitted between the inner edges of the bed, and it will be seen that one of the bed flanges (that on the left of the figure) is provided on its under side with a [V], and the clamp is provided with a corresponding [V], so that in tightening up the bolt that secures the tailstock to the bed the tailstock is drawn up to the edge of the shears, and therefore truly in line with the live spindle, while when this bolt is released the tailstock is quite free to be moved to its required position in the length of the bed. As a result of this form of design there is no wear between the clamp and the underneath [V], and the tailstock need not fit tightly between the edges of the bed, hence wear between these surfaces is also avoided, while the tailstock is firmly clamped against one edge of the bed as soon as the clamp is tightened up by the bolt on that side. [Illustration: Fig. 517.] Fig. 520 shows the method of locking the tailstock spindle and of preventing its lateral motion in the bearing in the tailstock. At the front or dead centre end of this bearing there is between the spindle a sleeve enveloping the spindle, and coned at its outer end, fitting into a corresponding cone in the bore of the tailstock. Its bore is a fit to the dead spindle, and it is split through on the lower side. Its inner end is threaded to a sleeve that is within the headstock, and whose end is coned to fit a corresponding cone at the inner end of the bore of the tailstock. [Illustration: Fig. 518.] To this second sleeve the line shown standing vertically on the left of the hand wheel is attached, so that operating this handle revolves the second sleeve and the two sleeves screw together, their coned ends abutting in their correspondingly coned seats in the tailstock bore, and thus causing the first-mentioned and split sleeve to close upon the dead centre spindle and yet be locked to the tailstock. [Illustration: Fig. 519.] As the bore of the tailstock is exactly in line with the live spindle, it follows that the dead spindle will be locked also in line with it. Figs. 521 and 522 represent sectional views of the carriage and slide rest of these lathes of a size over 16 inches swing. On the feed rod there are two bevel pinions P, one on each side of the bevel-wheel A, and by a clutch movement either of these wheels may be placed in gear with bevel-wheel A. The clutch motion is operated by a lever which, when swung over to the right, causes the bevel pinion on the right to engage with the bevel-wheel A, and the carriage feeds to the right, while with the lever swung over to the left the carriage feeds to the left. On the inclined shaft is a worm, or, as the makers term it, a spiral pinion of several teeth which gears into a straight toothed spur gear-wheel, giving a smooth and rolling tooth contact, and therefore producing an even and uniform feed motion. This spur gear is fast on a shaft C, which is capable of end motion and is provided on each of its side faces with an annular toothed clutch. On each side of this spur-wheel is a clutch, one of which connects with the train of gears for the turning feed, and the other with the cross-feed gear B. [Illustration: Fig. 520.] When the shaft (whose end is shown at C, and to which the spur gear referred to is fast) is pulled endways outwards from the lathe bed, its front annular clutch engages with the clutch that sets the cross-feed gear B in motion, and B engages with a pinion which forms the nut of the cross-feed screw. When shaft C is moved endways inwards its other annular clutch engages the clutch on that side of it, and the turning feed is put into operation. The method of operating shaft C endways is as follows:-- In a horizontal bearing D is a shaft at whose end is a weighted lever L, and on the end of this shaft is a crank pin shown engaging a sleeve E which affords journal bearing to the outer end of shaft C, so that operating the weighted lever L operates E, and therefore shaft C with the spur gear receiving motion from the worm. A simple catch confines lever L to either of its required limits of motion, and allows the free motion of the operating lever to start or stop either the longitudinal or the cross feed, either of which is started or stopped by this lever, but no mistake can occur as to which feed is operated, because the catch above mentioned requires to be shifted to permit the feed to be operated. The lower end of the bell crank F engages with the sleeve E, so that when the shaft C is operated outwards the horizontal arm of bell crank F is depressed and the spur pinion of the cross-feed nut is free to revolve, being driven by the cross-feed motion. When the lever F is moved towards the lathe bed (which occurs when the stop or catch is set to allow the longitudinal feed to be used) the nut of the cross feed is locked fast by the horizontal arm of the bell crank F. This device makes the whole action from one direction of feed to another automatic, and the attention of the workman is not needed for any complicated adjustment of parts preparatory to a change from one feed to the other. At H is a hand wheel for hand feeding, the pinion R meshing into the rack that extends along the front of the lathe bed; back of the hand wheel and at H´ a clamp is provided whereby the saddle or carriage may be locked to the lathe bed when the cross feed is being used, thus obviating the use of a separate clamp on the bed. The top slide of the compound rest is long and its guideway is short, the nut being in the stationary piece G, and it will be observed that by this arrangement at no time does the bearing surfaces of the slides become exposed to the action of chips or dirt. [Illustration: Fig. 521.] Fig. 523 is a sectional view of the carriage and slide rest as arranged for 12 and 16-inch lathes when not provided with a self-acting cross feed. In this case end motion to shaft C is given by lever H, which is held in its adjusted position by the tongue T. In this lathe the screw-cutting and the turning feed cannot be put into gear at the same time. [Illustration: Fig. 522.] The tool nut is arranged to enable the tool to be adjusted for height after it is fastened in the tool post by pivoting it to the cross slide, a spring S forcing it upwards at its outer end, thus holding the tool point down and in the direction in which the pressure of the cut forces it, thus preventing the wear of the pivot from letting the tool move when it first meets the cut. The nut N is operated to adjust the tool height, and at the same time enables the depth of cut to be adjusted very minutely. A trough catches the water, cuttings, &c., and thus protects the slides and slideways from undue wear. In all these lathes the feeding mechanism is so arranged that there are no overhanging or suspended shaft pins or spindles, each of such parts having a bearing at each end and not depending on the face surface of a collar or pin, as is common in many lathes. Furthermore, in these lathes the handle for the hand carriage feed moves to the right when the carriage moves to the right; the cross-feed screw (and the upper screw also in compound slide rests) has a left-hand thread, so that the nut being fixed the slides move in the same direction as though the nut moved as in ordinary lathes. The tailstock or poppet-head screw is a right hand because the nut moves in this case. The object of employing right-hand screws in some cases, and left-hand ones in others, is that it comes most natural in operating a screw to move it from right to left to unscrew, and from left to right to screw up a piece, this being the action of a right-hand screw, left-hand screws being comparatively rarely used in mechanism, save when to attain the object above referred to. [Illustration: Fig. 523.] Fig. 524 represents the Niles Tool Works car axle lathe, forming an example in which the work is driven from the middle of its length, leaving both ends free to be operated upon simultaneously by separate slide rests. [Illustration: Fig. 524.] The work being driven from its centre enables it to rotate upon two dead centres, possessing the advantage that both being locked fast there is no liberty for the work to move, as is the case when an ordinary lathe having one live or running spindle is used, because in that case the live spindle must be held less firmly and rigidly than a dead centre, so as to avoid undue wear in the live spindle bearings; furthermore, the liability of the workman to neglect to properly adjust the bearings to take up the wear is avoided in the case of two dead centres, and no error can occur because of either of the centres running out of true, as may be the case with a rotating centre. The cone pulley and back gear are here placed at the head of the lathe driving a shaft which runs between the lathe shears and drives a pinion which gears with the gear on the work driving head shown to stand on the middle of the shears. This head is hollow so that the axle passes through it. On the face of this gear is a Clement's equalizing driver constructed upon the principle of that shown hereafter in Fig. 756. The means for giving motion to the feed screw and for enabling a quick change from the coarse roughing feed to a finer finishing feed to the cutting tool without requiring to change the gears or alter their positions, is shown in Fig. 525. _a_ and _b_ are two separate pinions bored a working fit to the end of the driving shaft S, but pierced in the bore with a recess and having four notches or featherways _h_. The end of the driving shaft S is pierced or bored to receive the handled pin _i_, and contains four slots to receive the four feathers _j_ which are fast in _i_. In the position shown in the figure these feathers engage with neither _a_ nor _b_, hence the driving shaft would remain motionless, but it is obvious that if pin _i_ be pushed in the feathers would engage _b_ and therefore drive it; or if _i_ were pulled outwards the feathers would engage _a_ and drive it, because _a_ and _b_ are separate pinions with a space or annular recess between them sufficient in dimensions to receive the feathers. The difference in the rate of feed is obviously obtained through the difference in diameters of the pair of wheels _a_, _c_ and the pair _d_, _b_, the lathe giving to the lead screw the slowest motion and, therefore, the finest feed. The means for throwing the carriage in and out of feed gear with the feed screw and of providing a hand feed for operating the tool in corners or for quickly traversing the carriage, is shown in Fig. 526, in which S represents the feed screw and B a bracket or casting bolted to the carriage and carrying the hand wheel and feed mechanism shown in the general cut figure. [Illustration: Fig. 525.] B provides a slide way denoted by the dotted lines at _b_, for the two halves N and N´ of the feed nut. It also carries a pivot pin shown at _p_ in the front elevation, which screws into B as denoted by _p´_ in the end view; upon this pivot operates the piece D, having the handle _d_. In D are two cam grooves _a_ _a_; two pins _n_, which are fast in the two half-nuts N N´, pass through slots _c_ _c_ in B, and into the cam grooves _a_ _a_ respectively. [Illustration: Fig. 526.] As shown in the cut the handle _d_ of D is at its lowest point, and the half-nuts N´ and N are in gear upon the feed screw; but suppose _d_ be raised, then the grooves _a_ _a_ would force their respective pins _n_ up the slots _c_, and these pins _n_ being each fast to a half of the nut, the two half-nuts would be opened clear of the feed screw, and the carriage would cease to be fed. The hand-feed or guide-carriage traverse motion is accomplished as follows:--B provides at _e_ journal bearing to a stud on which is the hand wheel shown in the general cut; attached to this hand wheel is a pinion operating a large gear (also seen in general cut) whose pitch line is seen at _g_, in figure. The stud carrying _g_ has journal bearing at _f_, and carries a pinion whose pitch circle is at _h_ and which gears with the rack. Fig. 527, which is taken from _The American Machinist_, represents an English self-acting lathe capable of swinging work of 12 inches diameter over the top of the lathe shears, which are provided with a removable piece beneath the live centre, which when removed leaves a gap, increasing the capacity of the lathe swing. The gears for reversing the direction of feed screw motion are here placed at the end of the live head or headstock, the screw being used for feeding as well as for screw cutting. Fig. 528 represents a pattern-maker's lathe, by the Putnam Tool Co., of Fitchburg, Massachusetts. This lathe is provided with convenient means of feeding the tool to its cut by mechanism instead of by hand, as is usually done by pattern-makers, and this improvement saves considerable time, because the necessity of frequently testing the straightness of the work is avoided. It is provided with an iron extension shears, the upper shears sliding in [V]-ways provided in the lower one. The hand-wheel is connected with a shaft and pinion, which works in a rack, and is used for the purpose of changing the position of the upper bed, which is secured in its adjusted position by means of the tie bolts and nuts, as shown on the front of the lower shears. This enables the gap in the lower shears to be left open to receive work of large diameter, and has the advantage that the gap need be opened no more than is necessary to receive the required length of work. The slide-rest is operated by a worm set at an angle, so as to operate with a rolling rather than a sliding motion of the teeth, and the handle for operating the worm-shaft is balanced. The carriage is gibbed to the bed. The largest and smallest steps of the cone pulley are of iron, the intermediate steps being of wood, and a brake is provided to enable the lathe to be stopped quickly. This is an excellent improvement, because much time is often lost in stopping the lathe while running at a high velocity, or when work of large diameter is being turned. The lathe will swing work of 50 inches within the gap, and the upper shears will move sufficiently to take in 4 additional feet between the centres. In the general view of the lathe, Fig. 528, the slide-rest is shown provided with a [T]-rest for hand tools, but as this sets in a clip or split bore, it may readily be removed and replaced by a screw tool, poppet for holding a gauge, or other necessary tool. To enable the facing of work when the gap is used, the extra attachment shown in Figs. 529 and 530 is employed. It consists of an arm or bar A, bolted to the upper shears S by a bolt B, and clamp C, in the usual manner, and is provided with the usual slideway and feed-screw _f_ for operating the lower slide T, which carries a hollow stem D; over D fits a hub K, upon the upper slide E, which hub is split and has a bolt at F, by means of which the upper slide may be clamped to its adjusted angle or position. The upper slider H receives the tool-post, which is parallel and fits in a split hub, so that when relieved it may be rapidly raised or lowered to adjust the height of the tool. The construction of the brake for the cone pulley is shown in Figs. 531 and 532, in which P represents the pulley rim, L the brake lever, S a wooden shoe, and W a counter-weight. The lever is pivoted at G to a lug R, provided on the live headstock, and the brake obviously operates on the lowest part of the cone flange; hence the lever handle is depressed to put the brake in action. [Illustration: _VOL. I._ =EXAMPLES IN LATHE CONSTRUCTION.= _PLATE V._ Fig. 527. Fig. 528. Fig. 529.] The construction of the front and back bearings for the live spindle is the same as that shown in Figs. 495 and 496. [Illustration: Fig. 530.] Wood turners sometimes have their lathes so made that the headstock can be turned end for end on the lathe shears, so that the face plate may project beyond the bed, enabling it to turn work of large diameter. A better method than this is to provide the projecting end of the lathe with a screw to receive the face plate as shown in Fig. 533, which represents a lathe constructed by Walker Brothers of Philadelphia. At the end of the lathe is shown a hand rest upon a frame that can be moved about the floor to accommodate the location, requiring to be turned upon the work. [Illustration: Fig. 531.] For very large work, wood-workers sometimes improvise a facing lathe, as shown in Fig. 534, in which A is a headstock bolted to the upright B; C is the cone pulley, and E a face plate built up of wood, and fastened to an iron face plate by bolts. The legs A, of the tripod hand rest, Fig. 535, are weighted by means of the weights B. [Illustration: Fig. 532.] In Fig. 536 is shown a chucking lathe, especially adapted for boring and facing discs, wheels, &c. The live spindle is driven by a worm-wheel, provided around the circumference of the face plate. The driving worm (which runs in a cup of oil) is on a driving shaft, running across the lathe and standing parallel with the face of the face plate. This shaft is driven by a pulley as shown, changes of speed being effected by having a cone pulley on the counter-shaft and one on the line of shafting. [Illustration: Fig. 533.] This lathe is provided with two compound slide rests. One of which may be used for boring, while the other is employed for facing purposes. These rests are adjustable for location across the bed of the lathe by means of bolts in slots, running entirely across the lathe bed. These slide rests are given a self-acting motion by the following arrangement of parts: at the back of the live spindle is an eccentric rod, operating a connecting rod, which is attached at its lower end to the arm of a shaft running beneath the bed, and parallel to the lathe spindle. This shaft passes beyond the bed where it carries a bevel gear-wheel, which meshes with a bevel gear-wheel upon a cross shaft. This cross shaft carries three arms, one at each end and inside its journal bearings in the bed, and one beneath and at a right angle to the other two. These receive oscillating motion by reason of the eccentric connecting rod, &c. For each compound rest there are provided two handles as usual, and in addition an [L] lever, one arm of the latter being provided with a series of holes, while the other carries a weight. [Illustration: Fig. 534.] The [L] lever carries a pawl which operates a ratchet wheel, placed on the handle end of the slide rest cross feed screw. If then a chain be attached to one of the holes of the [L] lever, and to the oscillating arm, the motion in one direction of the latter will be imparted to the [L] lever (when the chain is pulled). On the return motion of the oscillating arm, the chain hangs loose, and the weight on the [L] lever causes that lever arm to fall, taking up the slack of the chain, the feed taking place (when the pawl is made to engage with the ratchet wheel) during the motion of the oscillating arm from right to left, or while pulling the chain. The rate of feed is varied by attaching the chain to different holes in the [L] lever. To operate the rests in a line parallel to the lathe spindle, a similar [L] lever is attached by chain to the third oscillating arm, which is placed on the cross shaft, mid-way of the bed, or between the two slide rests. It is obvious then that with an [L] lever attachment on each feed screw, both slides of each rest may be simultaneously operated, while either one may be stopped either by detaching the chain or removing the [L] lever. For operating the rests by hand, the usual feed-screw handles are used. Fig. 537 represents a 90-inch swing lathe by the Ames Manufacturing Company of Chicopee, Massachusetts. [Illustration: Fig. 535.] The distinguishing feature of this lathe is that the tailstock spindle is made square, to better enable it to bear the strain due to carrying cutting tools in place of the dead centre; and by means of a pulley instead of a simple hand wheel for operating the tail spindle, that spindle may be operated from an overhead countershaft, and a tool may be put in to cut key-ways in pulleys, wheels, &c., chucked on the face plate (which of course remains stationary during the operation), thus dispensing with the necessity of cutting out such key-ways by hammer, chisel, and file, in wheel bores too large and heavy to be operated upon in a slotting machine. [Illustration: Fig. 538.] On account of the weight of the tailstock it is fitted with rollers, which may be operated to lift it from the bed when it is to be moved along the lathe bed. [Illustration: _VOL. I._ =CHUCKING LATHES.= _PLATE VI._ Fig. 536. Fig. 537.] Fig. 538 represents a 50-inch swing lathe by the New Haven Manufacturing Company of New Haven, Connecticut. The compound rest is here provided with automatic feed so that it may be set at an angle to bore tapers with a uniform feed. The tailstock is provided with a bracket, carrying a pinion in gear with the hand-feed rack, so as to move the tailstock along the bed by means of the pinion. The feed screw is splined to give an independent feed, and the swing frame is operated by a worm as shown. [Illustration: Fig. 539.] GAP LATHE OR BREAK LATHE. The gap lathe is one in which the bed is provided with a gap beneath the face plate, so as to enable that plate or the chucks to swing work of larger diameter, an example being given in Fig. 539. [Illustration: Fig. 540.] It is obvious, however, that the existence of the gap deprives the slide rest of support on one side, when it is used close to the face plate. This is obviated in some forms of gap lathes by fitting into the gap a short piece of bed that may be taken out when the use of the gap is required. The gap lathe has not found favor in the United States, the same result being more frequently obtained by means of the extension lathe, which possesses the advantages of the gap lathe, while at the same time enabling the width of the gap to be varied to suit the length of the work. Fig. 540 represents an extension lathe by Edwin Harrington and Son, of Philadelphia. There are two beds A and B, the former sliding upon the latter when operated by the hand-wheel E, which is upon the end of a screw that passes between the two beds, has journal bearing in the upper bed, and engages a nut in the lower one, so that as the screw is operated the wheel moves longitudinally with the upper bed. C is the feed rod which communicates motion to the feeding screw D, which has journal bearing on the upper bed and therefore travels with it when it is moved or adjusted longitudinally. The cross slide has sufficient length to enable the slide rest to face work of the full diameter that will swing in the gap, and to support the slide rest when moved outwards to the full limit, it is provided with a piece F, which slides at its base upon the guideway or slide G. Fig. 541 represents a double face plate lathe such as is used for turning the wheels for locomotives. The circumference of both the face plates are provided with spur teeth, so that both are driven by pinions, which by being capable of moving endways into or out of gear, enable either face plate to be used singly, if required, as for boring purposes. The slide rests are operated by ratchet arms for the self feed, these arms being operated by an overhead shaft, with arms and chains. [Illustration: Fig. 541.] Fig. 542 represents a chucking lathe adapted more especially for boring purposes. Thus the cone pulley is of small diameter and the parts are light, so that the lathe is more handy than would be the case with a heavier built lathe, while at the same time it is sufficiently rigid for large work that is comparatively light. [Illustration: Fig. 542.] The compound rest is upon a pedestal that can be bolted in any required position on the lower cross slide, and is made self-acting for the feed traverse by the change wheels and feed screw, while the self-acting cross feed is operated by a ratchet handle, actuated by a chain from an overhead reciprocating lever; the latter being actuated from the crank pin at A, which is adjustable in a slot in the crank disk B. A lathe of this kind is very suitable for brass work of unusually large diameter, because in such work the cuts and feeds are light, and the cutting speed is quick, hence a heavy construction is not essential. Figs. 543 and 544 represent a large lathe built by Thomas Shanks and Co., of Johnstone, near Glasgow, Scotland; all the figures of this lathe being from _The American Machinist_. Fig. 543 shows the headstock and two of the slide rests, while Fig. 544 represents the remainder of the bed, the tailstock, and two of the slide rests. It will be seen from the figures that there are a compound rest and a column or pillar rest both at the front and at the back of the lathe, and that there is an additional rest on the front end of the tailstock which may be used for facing the ends of the work. Fig. 545 represents a section through, and a partial plan of the headstock, and it will be seen that the live spindle is free from the cone pulley and from the gearing, the chuck plate being driven from a pinion engaging an internal gear at the back of the chuck plate. By this construction the balancing of such work as crank shafts is facilitated, because the chuck plate is not affected by the friction of the driving gears, and may therefore be easily revolved to test the balance of the work. Fig. 546 represents a cross section through the bed, and through one of the compound rests, and one of the pillar rests, the latter rests being made thin so that they may pass between the cheeks of crank shafts, to turn their faces and the crank journals. Fig. 547 represents a view from the back end of the headstock, and Fig. 548 a view of the lathe from the tailstock end. Figs. 549 and 550 represent a plan and a side view of the headstock and the two slide rests nearest to it. The lathe being shown at work on the crank shaft of the steamship service, which is shown in dotted lines, and it will be seen that for turning the stem of the shaft all the rests can be used at once, those at the back of the lathe having their cutting tools turned upside down (as will be more clearly seen in the cross-sectional view of the rests in Fig. 546). [Illustration: Fig. 543.] Figs. 551 and 552 represent a plan and a side view of the other half of the lathe in operation upon the same crank shaft, which is again shown in dotted lines. [Illustration: Fig. 544.] Referring now to the general construction of the lathe, the headstock or live spindle has a front journal bearing 18 inches diameter and 24 inches long, and a back bearing 12 inches diameter and 15 inches long, the bearings being parallel. The driving cone has five changes of speed for a 6-inch belt, and is carried on an independent spindle. The cone is turned inside as well as outside, so as to be in balance at high speeds. [Illustration: Fig. 545.] The face plate is 12 feet diameter, cast with internal gear at the back. It is provided with [T]-slots and square holes for fixing work. It is bolted to a large flange in one piece with the spindle, and fitted with four steel expanding gripping jaws worked with screws and toothed blocks. These are for doing chuck work, or for gripping work to be driven, as the collars of propeller or crank shafts, or work of a similar character. By the system of gearing adopted, when desired, the face plate can be revolved almost free, which facilitates balancing for turning crank shafts, as well as other operations. The thrust against the live spindle is taken by an adjustable steel tail piece. [Illustration: Fig. 546.] [Illustration: Fig. 547.] [Illustration: Fig. 548.] [Illustration: Fig. 549.] The beds are double, 10 feet in width over all, the sections being joined together by massive ground plates and bolts. They are made with square lips to resist the upward strain of cutting. The front bed is fitted with two saddles, each carrying a compound slide rest having the following movements: First, screw-cutting, by means of a leading screw, situated inside the bed, with a sliding disengaging nut and reversing motion for right or left-hand threads, or for instantaneously stopping the longitudinal movement of the saddle. This is accomplished by a set of clutch mitres placed inside the bed at headstock end, and actuated by a lever in front: Second, a self-acting surfacing motion to slide rest by means of a longitudinal shaft at the front of the bed, and clutch mitres for reversing the saddle screw. [Illustration: Fig. 550.] Third, power motion for moving the saddles quickly to position along the bed. This is done through the fast and loose pulleys at the headstock end of lathe. Fourth, hand rack motion to saddle. The back bed is fitted with two saddles, each carrying a pillar rest, fitted for all movements in plain turning like the front rests, and also with swiveling motion for corner turning. [Illustration: Fig. 551.] The tailstock has a spindle 9 inches diameter. It is fitted in [V]s on the bed, and held down by three [T]-head bolts on each side. The top section is adjustable for turning tapers. It is moved along the ways by engaging a nut with the main screw. An end-cutting rest is fitted to the tailstock, which is adapted for operating on flanged couplings and similar work. There is a separate set of change wheels for each saddle, so arranged as to cut standard pitches up to 3-inch pitch, and for self-acting feeds down to 50 per inch. By this means, when both tools are in operation on a piece of work, one tool may be used with coarse feed for roughing out, while the other may be taking a fine or finishing cut either on the same or a different part of the piece; or one tool may be cutting towards and the other from the face plate, always maintaining the balance of a front and back cut. [Illustration: Fig. 552.] Complete counter driving motion, consisting of wall brackets, shaft, cone, and sets of fast and loose pulleys for quick reversing motion in screw cutting, also belt bar shipping motion, and full set of case-hardened wrenches are provided. CHAPTER VII.--DETAILS IN LATHE CONSTRUCTION. Although in each class of lathe the requirements may be practically the same, yet there is a variety of different details of construction by means of which these requirements may be met or filled, and it may be profitable to enter somewhat into these requirements and the different constructions generally employed to meet them. [Illustration: Fig. 553.] The cone spindle or live spindle of a lathe should be a close working fit to its boxes or bearings, so that it will not lift under a heavy cut, or lift and fall under a cut of varying pressure. This lifting and falling may occur even though the work be true, and the cut therefore of even depth all around the work, because of hard seams or spots in the metal. It is obvious that the bearings should form a guide, compelling the live spindle to revolve in a true circle and in a fixed plane, the axis of revolution being in line with the centre line of the tail spindle and that means should be provided to maintain this alignment while preserving the fit, or in other words taking up the wear. The spindle journals must, to produce truly cylindrical work, be cylindrically true, or otherwise the axis of its revolution will change as it revolves, and this change will be communicated through the live centre to the work, or through the chuck plate to the work, as the case may be. The construction of the bearings should be such, that end motion to the spindle is prevented in as short a length of the spindle as possible, the thrust in either direction being resisted by the mechanism contained in one bearing. In Fig. 553 is a form of construction for the front bearing (as that nearest to the live centre is called), in which end motion to the spindle is prevented at the same time as the diametral fit is adjusted. The spindle is provided with a cone at C and is threaded at T to receive two nuts N which draw the spindle cone within the bearing. In this case the journal at the back end may be made parallel, so that if the spindle either expands or contracts more under variations of temperature than the frame or head carrying the bearings or bearing boxes, it will not bind endwise, nor will the fit be impaired save inasmuch as there may be an inequality of expansion in the length of the front journal and its box. In this case, however, the end pressure caused by holding the work between the lathe centres acts to force the spindle into its bearing and increase the tightness of its fit, hence it is not unusual to provide at the back bearing additional means to resist the thrust of the dead centre. [Illustration: Fig. 554.] Fig. 554, which is taken from "Mechanics," represents Wohlemberg's patent lathe spindle, in which both journals are coned, fitting into bushes which can be replaced by new ones when worn; the end thrust is here taken by a steel screw, while the end fit is adjusted by means of a ring nut which binds the face of the large cone gear against the inside face of the front bearing and by the face of the gear that drives the change gears. It may be pointed out, however, that in this construction the spindle must be drawn within to adjust the fit of the front bearing, which can only be done by adjusting the pinion that drives the change gears, or by screwing up the nut that is inside the cone, and therefore cannot be got at. The back bearing can be adjusted by means of the ring nuts provided at each of its ends. [Illustration: Fig. 555.] Fig. 555 represents another design of cone bearing, in which the spindle is threaded to receive the nuts A which draw it within the front bearing and thus adjust the fit, and at the same time prevent end motion. The back bearing is provided with a bush parallel outside, and furnished with a nut at B to adjust the fit of the end bearing. To prevent the end pressure of the dead centre from forcing the spindle cones too tightly within their bearings a cross piece P is employed (being supported by two studs provided in the head), and through P passes an adjusting screw D, having nuts N and C, one on each side of P. Between the end of D and of the lathe spindle a washer of leather or of raw hide is placed to prevent the end faces from abrading. A similar device for taking up the end thrust is often provided to lathes in which the journals are both parallel, fitting in ordinary boxes, a top view of the device being illustrated in Fig. 556, in which B is the back bearing box, S S two studs supporting cross-piece P, and N and C are adjusting nuts. G is the gear for driving the change wheels for screw cutting or for ordinary feeding as the case may be. In this design the gear wheel G remains fixed and the combinations of gears necessary to cut various pitches of thread must be made on the lead screw and on the swing frame, which must be long enough to permit the change gear stud to pass up to permit the smallest change wheel to gear with wheel G, and which is provided with two grooves E and F, Fig. 557, for two studs to carry two compounded pairs of change wheels. This compounding in two places on the swing frame enables gear G to be comparatively large, and thus saves the teeth from rapid wear, while it facilitates the cutting of left-hand threads, because it affords more convenience for putting in a gear to change the direction of feed screw revolution. [Illustration: Fig. 556.] In many lathes of American design the journals are made parallel, and the end play is taken up at the back bearing, an example being given in Fig. 558, in which the back bearing boxes are made in two halves A and B, the latter having a set screw (with check nut) threaded through it and bearing against a washer that meets the end of the spindle. [Illustration: Fig. 557.] A simple method of preventing end motion is shown in Fig. 559, a bracket B affording a support for a threaded adjusting screw, which is sometimes made pointed and at others flat. When pointed it acts to support the spindle, but on the other hand it also acts to prevent the journal from bedding fairly in the boxes. In some cases of small lathes the back bearing is dispensed with, and a similar pointed adjusting screw takes its place, which answers very well for very small work. Since the strain of the cut carried by the cutting tool falls mainly upon the live centre end of the cone spindle, it is obvious that the bearing at that end has a greater tendency to wear. [Illustration: Fig. 558.] In addition to this the weight of the cone itself is greatest at that end, and furthermore the weight of the face plate or chuck, and of the work, is carried mainly at that end. If, however, one journal and bearing wears more than the other, the spindle is thrown out of line with the lathe shears, and with the tail block spindle. The usual method of obviating this as far as possible is to give that end a larger journal-bearing area. [Illustration: Fig. 559.] The direction in which this wear will take place depends in a great measure upon the kind of work done in the lathe; thus in a lathe running slowly and doing heavy work carried by chucks, or on the face plate, the wear would be downwards and towards the operator, the weight of the chuck, &c., causing the downward, and the resistance or work-lifting tendency of the cut causing the lateral wear. As a general rule the wear will be least in a lateral direction towards the back of the lathe, but the direction of wear is so variable that provision for its special prevention or adjustment is not usually made. In the S. W. Putnam lathe, provision is made that the bearing boxes may be rotated in the head, so that when the lathe is used on a class of work that caused the live spindle to wear the bearing boxes on one side more than on another, the boxes may be periodically partly rotated in the head so that further wear will correct the evil. The coned hole to receive the live centre should run quite true, so that the live centre will run true without requiring, when inserted, to be placed in exactly the same position it occupied when being turned up at its conical point. But when this hole does not run true a centre punch dot is made on the end of the spindle, and another on the centre, so that by placing the two dots to coincide at all times, the centre will run true. The taper given to lathe centres varies from 9/16 per foot to 1 inch per foot. In the practice of Pratt and Whitney a taper of 9/16 per foot is given to all lathes, the lengths of the tapers for different sizes of lathes being as follows: Length of Taper Socket Swing of Lathe. for Live Centre. 13 inches 5 inches. 16 " 3-3/4 " 18 and 19 inches 7-11/16 " " " with hollow spindle 5 inches long and 1-1/16 diameter at the small end. The less the amount of taper the more firmly the centre is held, but the more difficult it becomes to remove the centre when necessary. [Illustration: Fig. 560.] The principal methods of removing live centres are shown in Fig. 560, in which is shown at B a square part to receive a wrench, it being found that if not less than about 1/2-inch taper per foot of length be given to the live spindle socket, then revolving the centre with a wrench will cause it to release itself, enabling it to be removed by hand. Another method employed on small lathes is to drill a hole through the live spindle to receive a taper pin P, the live centre end being shown at C. Another and excellent plan for large lathes, is to thread the centre and provide it with a nut M, which on being screwed against the end face of the live spindle will release the centre. The objection to the use of the pin P is that it is apt to become mislaid, and it is not advisable to use a hammer about the parts of the lathe, especially in such an awkward place as between the journal bearing and the cone, which is where the pin hole requires to be located. The square section is, therefore, the best method for small lathes, and the nut for large ones. In cases where the live spindle is made hollow a bar may be passed through from the rear end to remove the centre; this also enables rods of iron to be passed through the spindle, leaving the end projecting through the chuck for any length necessary for the work to be turned out of its exposed end. The dead centre may be extracted from the tail spindle by a pin and hole as in Fig. 560, or, what is better, by contact with the end of the tail screw as described when referring to the tail stock of the S. W. Putnam lathe. The cone pulley should be perfectly balanced, otherwise at high speeds the lathe will shake or tremble from the unbalanced centrifugal motion, and the tremors will be produced to some extent on the work. The steps of the cone should be amply wide, so that it may have sufficient power, without overstraining the belt, to drive the heaviest cut the lathe is supposed to take without the aid of the back gear. In some cases, as in spinning lathes, the order of the steps is reversed, the smallest step of the cone being nearest to the live centre, the object being to have the largest step on the left, and therefore more out of the way. The steps of the cone should be so proportioned that the belt will shift from one to the other, and have the same degree of tension, while at the same time they should give a uniform graduation or variation of speed throughout, whether the lathe runs in single gear or with the back gear in. This is not usually quite the case although the graduation is sufficiently accurate for practical purposes. The variation in the diameter of the steps of a lathe cone varies from an inch for lathes of about 12-inch swing, up to 2 inches for lathes of about 30-inch swing, and 3 inches for lathes of 5 or more feet of swing. To enable the graduation of speed of the cone to be uniform throughout, while the tension of the belt is maintained the same on whatever step the cone may be, the graduation of the steps may be varied, and this graduation may be so proportioned as to answer all practical purposes if the overhead or countershaft cone and that on the lathe are alike. The following on this subject is from the pen of Professor D. E. Klein, of Yale College. "The numbers given in the following tables are the differences between the diameters of the adjacent steps on either cone pulley, and are accurate within half a hundredth of an inch, which is a degree of accuracy sufficient for practical purposes. By simply omitting a step at each end of the cone, the two tables given will be found equally well adapted for determining the diameters of cones having four and three steps respectively. The following are examples in the use of the tables. Suppose the centres of a pair of pulley shafts to be 60 inches apart, and that the difference of diameter between the adjacent steps is to be as near to 2-1/2 inches as can be, to obtain a uniformity of speed graduation and belt tension, also that each cone is to have six steps, the smallest of which is to be of five inches diameter. To find the diameters for the remaining steps, we look in Table I. (corresponding to cone pulleys with six steps), under 60 in. and opposite 2-1/2 in. and obtain the differences, 2.37 2.43 2.50 2.57 2.63 Each of these differences is _subtracted_ from the _larger_ diameter of the two adjacent steps to which it corresponds, thus: 17.50 = 1st step. Difference of 1st and 2nd = 2.37 ----- 15.13 = 2nd " " 2nd " 3rd = 2.43 ----- 12.70 = 3rd " " 3rd " 4th = 2.50 ----- 10.20 = 4th " " 4th " 5th = 2.57 ----- 7.63 = 5th " " 5th " 6th = 2.63 ----- 5.00 = 6th " EXAMPLE 2. If we suppose the same conditions as in Example 1, with the exception that each cone is to have four steps instead of six, the largest diameter will, in this case, equal 12-1/2 in. and we may obtain the remaining diameters by omitting the end differences of the above example, and then subtracting the remaining differences as follows: 12.50 = 2nd step. Difference of 2nd and 3rd = 2.43 ----- 10.07 = 3rd " " 3rd " 4th = 2.50 ----- 7.57 = 4th " " 4th " 5th = 2.57 ----- 5.00 = 5th " The 2nd, 3rd, 4th, and 5th steps of the table correspond respectively to the 1st, 2nd, 3rd, and 4th steps of the cone, having but four steps. If the smallest diameter had not been assumed equal to 5 in. we might have dropped a step at each end of the six-step cone of the preceding example, and employed the remaining four diameters, 15.13 in. 12.70 in. 10.20 in. and 7.63 in. for one four-step cone. The present and the previous examples show that we can assume the size of the smallest step anything that we please, and, other things being equal, can make the required cones large or small. I.--TABLE FOR FINDING CONE PULLEY DIAMETERS WHEN THE TWO PULLEYS ARE CONNECTED BY AN OPEN BELT, AND ARE EXACTLY ALIKE. The numbers given in table are the differences between the diameters of the adjacent steps on either cone pulley, and can be employed when there are either six or four steps on a cone. When there are six steps, the largest is the first, and the smallest the sixth step of the table. When there are four steps, the largest is the second, and the smallest the fifth step of the table. +-------------+-----------+------------------------------ | Average | Adjacent | DISTANCE BETWEEN THE CENTRES | difference | steps, | OF CONE PULLEYS. | between | whose +----+----+----+----+----+----+ | the | diffe- | | | | | | | | adjacent | rence is | 10 | 20 | 30 | 40 | 50 | 60 | | steps. | given in | i n c h e s. | | | table. | | | | | | | +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|0.87|0.94|0.96|0.97|0.98|0.98| | |2nd " 3rd|0.94|0.97|0.98|0.98|0.99|0.99| | 1 inch |3rd " 4th|1.00|1.00|1.00|1.00|1.00|1.00| | |4th " 5th|1.06|1.03|1.02|1.02|1.01|1.01| | |5th " 6th|1.13|1.06|1.04|1.03|1.02|1.02| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.21|1.36|1.40|1.43|1.44|1.45| | |2nd " 3rd|1.36|1.43|1.45|1.46|1.47|1.48| | 1-1/2 inch |3rd " 4th|1.50|1.50|1.50|1.50|1.50|1.50| | |4th " 5th|1.64|1.57|1.55|1.54|1.53|1.52| | |5th " 6th|1.79|1.64|1.60|1.57|1.56|1.55| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.47|1.74|1.83|1.87|1.90|1.92| | |2nd " 3rd|1.74|1.87|1.92|1.93|1.95|1.96| | 2 inches |3rd " 4th|2.00|2.00|2.00|2.00|2.00|2.00| | |4th " 5th|2.26|2.13|2.08|2.07|2.05|2.04| | |5th " 6th|2.53|2.26|2.17|2.13|2.10|2.08| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.66|2.10|2.23|2.30|2.34|2.37| | |2nd " 3rd|2.10|2.30|2.37|2.40|2.42|2.43| |2-1/2 inches |3rd " 4th|2.50|2.50|2.50|2.50|2.50|2.50| | |4th " 5th|2.90|2.70|2.63|2.60|2.58|2.57| | |5th " 6th|3.34|2.90|2.77|2.70|2.66|2.63| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.76|2.42|2.62|2.71|2.77|2.81| | |2nd " 3rd|2.42|2.71|2.81|2.86|2.88|2.90| | 3 inches |3rd " 4th|3.00|3.00|3.00|3.00|3.00|3.00| | |4th " 5th|3.58|3.29|3.19|3.14|3.12|3.10| | |5th " 6th|4.24|3.58|3.38|3.29|3.23|3.19| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd| |3.95|3.31|3.49|3.59|3.66| | |2nd " 3rd|2.94|3.49|3.66|3.75|3.80|3.83| | 4 inches |3rd " 4th|4.00|4.00|4.00|4.00|4.00|4.00| | |4th " 5th|5.06|4.51|4.34|4.25|4.20|4.17| | |5th " 6th| |5.05|4.69|4.51|4.41|4.34| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd| |3.33|3.92|4.20|4.36|4.47| | |2nd " 3rd|3.31|4.19|4.47|4.60|4.68|4.74| | 5 inches |3rd " 4th|5.00|5.00|5.00|5.00|5.00|5.00| | |4th " 5th|6.69|5.81|5.53|5.40|5.32|5.26| | |5th " 6th| |6.67|6.09|5.80|5.64|5.53| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd| |3.52|4.42|4.83|5.08|5.23| | |2nd " 3rd| |4.83|5.23|5.42|5.54|5.62| | 6 inches |3rd " 4th| |6.00|6.00|6.00|6.00|6.00| | |4th " 5th| |7.17|6.77|6.58|6.46|6.38| | |5th " 6th| |8.48|7.58|7.17|6.92|6.77| +-------------+-----------+----+----+----+----+----+----+ +-------------+-----------+-----------------------------+ | Average | Adjacent | DISTANCE BETWEEN THE CENTRES| | difference | steps, | OF CONE PULLEYS. | | between | whose +----+----+----+----+----+----+ | the | diffe- | | | | | | | | adjacent | rence is | 70 | 80 | 90 | 100| 120| 240| | steps. | given in | i n c h e s. | | | table. | | | | | | | +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|0.98|0.98|0.99|0.99|0.99|1.00| | |2nd " 3rd|0.99|0.99|0.99|0.99|1.00|1.00| | 1 inch |3rd " 4th|1.00|1.00|1.00|1.00|1.00|1.00| | |4th " 5th|1.01|1.01|1.01|1.01|1.00|1.00| | |5th " 6th|1.02|1.02|1.01|1.01|1.01|1.00| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.46|1.46|1.47|1.47|1.48|1.49| | |2nd " 3rd|1.48|1.48|1.49|1.49|1.49|1.49| | 1-1/2 inch |3rd " 4th|1.50|1.50|1.50|1.50|1.50|1.50| | |4th " 5th|1.52|1.52|1.51|1.51|1.51|1.51| | |5th " 6th|1.54|1.54|1.53|1.53|1.52|1.51| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.93|1.93|1.94|1.95|1.96|1.98| | |2nd " 3rd|1.96|1.97|1.97|1.97|1.98|1.99| | 2 inches |3rd " 4th|2.00|2.00|2.00|2.00|2.00|2.00| | |4th " 5th|2.04|2.03|2.03|2.03|2.02|2.01| | |5th " 6th|2.07|2.07|2.06|2.05|2.04|2.02| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|2.39|2.40|2.41|2.42|2.43|2.47| | |2nd " 3rd|2.44|2.45|2.46|2.46|2.47|2.49| | 2-1/2 inches|3rd " 4th|2.50|2.50|2.50|2.50|2.50|2.50| | |4th " 5th|2.56|2.55|2.54|2.54|2.53|2.51| | |5th " 6th|2.61|2.60|2.59|2.58|2.57|2.53| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|2.84|2.86|2.87|2.88|2.90|2.95| | |2nd " 3rd|2.92|2.93|2.94|2.94|2.95|2.98| | 3 inches |3rd " 4th|3.00|3.00|3.00|3.00|3.00|3.00| | |4th " 5th|3.08|3.07|3.06|2.06|3.05|3.02| | |5th " 6th|3.16|3.14|3.13|3.12|3.10|3.05| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|3.71|3.75|3.78|3.80|3.83|3.91| | |2nd " 3rd|3.85|3.87|3.88|3.89|3.91|3.96| | 4 inches |3rd " 4th|4.00|4.00|4.00|4.00|4.00|4.00| | |4th " 5th|4.15|4.13|4.12|4.11|4.09|4.04| | |5th " 6th|4.29|4.25|4.22|4.20|4.17|4.09| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|4.55|4.60|4.64|4.68|4.74|4.87| | |2nd " 3rd|4.77|4.80|4.82|4.84|4.86|4.93| | 5 inches |3rd " 4th|5.00|5.00|5.00|5.00|5.00|5.00| | |4th " 5th|5.23|5.20|5.18|5.16|5.14|5.07| | |5th " 6th|5.45|5.40|5.36|5.32|5.26|5.13| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|5.34|5.42|5.49|5.55|5.62|5.80| | |2nd " 3rd|5.67|5.71|5.75|5.77|5.81|5.90| | 6 inches |3rd " 4th|6.00|6.00|6.00|6.00|6.00|6.00| | |4th " 5th|6.33|6.29|6.25|6.23|6.19|6.10| | |5th " 6th|6.66|6.58|6.51|6.45|6.38|6.20| +-------------+-----------+----+----+----+----+----+----+ EXAMPLE 3. Let distance apart of the centres = 30 in. the average difference between adjacent steps = 2 in. the diameter of the smallest step = 4 in., and the number of steps on each of the cones = 5. The largest step will then equal 12 in., and from Table II., under 30 in. and opposite 2 in., we obtain the differences 1.87 1.96 2.04 2.13 and then subtracting as before we get the required diameters 12 in. 10.30 in. 8.17 in. 6.13 in. 4 in. EXAMPLE 4. Let the conditions be as in the preceding example, the cone pulley having, however, three steps instead of five, the largest diameter will then equal 8 in.; and by dropping the end differences and subtracting 8.00 = 2nd step. Difference of 2nd and 3rd = 1.96 ----- 6.04 = 3rd " " 3rd " 4th = 2.04 ----- 4.00 = 4th " we get the diameters 8 in., 6.04, and 4 in., which correspond respectively to 2nd, 3rd, and 4th steps of the table, and to the 1st, 2nd, and 3rd steps of the three-step cone. EXAMPLE 5. Let the distance apart of the centres be 60 in., the average difference between the adjacent steps be 2-1/8 in., the smallest step 7 in. and the number of steps = 5. The largest step will then be 7 in. + (4 × 2-1/8) = 15-1/2 inches. Now an inspection of Table II. will show that it contains no horizontal lines corresponding to the average difference 2-1/8 inches, we cannot, therefore, as heretofore, obtain the required differences directly, but must interpolate as follows: since 2-1/8 inches is quarter way between 2 inches and 2-1/2 inches, the numbers corresponding to 2-1/8 inches (for any given distance apart of the centres), will be quarter way between the numbers of the table corresponding to 2 inches and 2-1/2 inches. Thus, in Table II., we have under 60 inches, and opposite 2-1/2 in.: 2.40 2.47 2.53 2.60 " 2 1.93 1.98 2.02 2.07 ---- ---- ---- ---- .47 .49 .51 .53 Dividing these differences by 4, we get: .12 .12 .13 .13 to which we add, 1.93 1.98 2.02 2.07 and get for the differences corresponding to 2-1/8 inches 2.05 2.10 2.15 2.20 and subtracting as before, 15.5 1st step. difference of 1st and 2nd = 2.05 ----- 13.45 = 2nd " " 2nd " 3rd = 2.10 ----- 11.35 = 3rd " " 3rd " 4th = 2.15 ----- 9.20 = 4th " " 4th " 5th = 2.20 ----- 7.00 = 5th " Thus far, however, we have considered only the case where the two cone pulleys were exactly alike. Now although this case occurs much more frequently than the case in which the cone pulleys are unlike, it is nevertheless true that unlike cone pulleys occur with sufficient frequency to make it desirable that convenient means be established for obtaining the diameters of their steps rapidly and accurately, and Table III. was calculated by the writer for this purpose; its accuracy is more than sufficient for the requirements of practice, the numbers in the table being correct to within a unit of the fourth decimal place (_i.e._ within .0001). It should be noticed that the tabular quantities are not the diameters of the steps, but these diameters divided by the distance between the centres of the cone pulleys; in other words, the tabular quantities are the effective diameters of the steps only when the centres of the pulleys are a unit's distance apart. By thus expressing the tabular quantities in terms of the distance apart of the axis, the table becomes applicable to all cone pulleys whatever their distance from each other, the effective diameters of the steps being obtained by multiplying the proper tabular quantities by the distance between the centres of the pulleys. II.--TABLE FOR FINDING CONE PULLEY DIAMETERS WHEN THE TWO PULLEYS ARE CONNECTED BY AN OPEN BELT, AND ARE EXACTLY ALIKE. The numbers given in table are the differences between the diameters of the adjacent steps on either cone pulley, and can be employed when there are either five or three steps on a cone. +-------------+-----------+-----------------------------+ | Average | Adjacent | DISTANCE BETWEEN THE CENTRES| | difference | steps, | OF CONE PULLEYS. | | between | whose +----+----+----+----+----+----+ | the | diffe- | | | | | | | | adjacent | rence is | 10 | 20 | 30 | 40 | 50 | 60 | | steps. | given in | i n c h e s. | | | table. | | | | | | | +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|0.90|0.95|0.97|0.98|0.98|0.98| | |2nd " 3rd|0.97|0.98|0.99|0.99|0.99|0.99| | 1 inch |3rd " 4th|1.03|1.02|1.01|1.01|1.01|1.01| | |4th " 5th|1.10|1.05|1.03|1.02|1.02|1.02| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.28|1.39|1.43|1.45|1.46|1.46| | |2nd " 3rd|1.43|1.46|1.48|1.48|1.48|1.49| | 1-1/2 inch |3rd " 4th|1.57|1.54|1.52|1.52|1.52|1.51| | |4th " 5th|1.72|1.61|1.57|1.55|1.54|1.54| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.61|1.81|1.87|1.90|1.92|1.93| | |2nd " 3rd|1.87|1.94|1.96|1.97|1.97|1.98| | 2 inches |3rd " 4th|2.13|2.06|2.04|2.03|2.03|2.02| | |4th " 5th|2.39|2.19|2.13|2.10|2.08|2.07| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.89|2.20|2.30|2.35|1.38|2.40| | |2nd " 3rd|2.30|2.40|2.43|2.45|2.46|2.47| | 2-1/2 inches|3rd " 4th|2.70|2.60|2.57|2.55|2.54|2.53| | |4th " 5th|3.11|2.80|2.70|2.65|2.62|2.60| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|2.10|2.57|2.71|2.78|2.83|2.86| | |2nd " 3rd|2.71|2.86|2.90|2.93|2.94|2.95| | 3 inches |3rd " 4th|3.29|3.14|3.10|3.07|3.06|3.05| | |4th " 5th|3.90|3.43|3.29|3.22|3.17|3.14| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd| |3.22|3.49|3.62|3.69|3.75| | |2nd " 3rd|3.48|3.74|3.83|3.87|3.90|3.91| | 4 inches |3rd " 4th|4.52|4.26|4.17|4.13|4.10|4.09| | |4th " 5th| |4.78|4.51|4.38|4.31|4.25| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd| |3.77|4.20|4.40|4.52|4.60| | |2nd " 3rd|4.19|4.60|4.73|4.80|4.84|4.87| | 5 inches |3rd " 4th|5.81|5.40|5.27|5.20|5.16|5.13| | |4th " 5th| |6.23|5.80|5.60|5.48|5.40| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd| |4.21|4.83|5.13|5.31|5.42| | |2nd " 3rd|4.82|5.42|5.62|5.71|5.77|5.81| | 6 inches |3rd " 4th|7.18|6.58|6.38|6.29|6.23|6.19| | |4th " 5th| |7.79|7.17|6.87|6.69|6.58| +-------------+-----------+----+----+----+----+----+----+ +-------------+-----------+-----------------------------+ | Average | Adjacent | DISTANCE BETWEEN THE CENTRES| | difference | steps, | OF CONE PULLEYS. | | between | whose +----+----+----+----+----+----+ | the | diffe- | | | | | | | | adjacent | rence is | 70 | 80 | 90 | 100| 120| 240| | steps. | given in | i n c h e s. | | | table. | | | | | | | +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|0.99|0.99|0.99|0.99|0.99|1.00| | |2nd " 3rd|0.99|1.00|1.00|1.00|1.00|1.00| | 1 inch |3rd " 4th|1.01|1.00|1.00|1.00|1.00|1.00| | |4th " 5th|1.01|1.01|1.01|1.01|1.01|1.00| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.47|1.47|1.48|1.48|1.48|1.49| | |2nd " 3rd|1.49|1.49|1.49|1.49|1.49|1.49| | 1-1/2 inch |3rd " 4th|1.51|1.51|1.51|1.51|1.51|1.51| | |4th " 5th|1.53|1.53|1.52|1.52|1.52|1.51| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|1.94|1.95|1.96|1.96|1.97|1.98| | |2nd " 3rd|1.98|1.98|1.99|1.99|1.99|1.99| | 2 inches |3rd " 4th|2.02|2.02|2.01|2.01|2.01|2.01| | |4th " 5th|2.06|2.05|2.04|2.04|2.03|2.02| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|2.41|2.42|2.43|2.44|2.45|2.47| | |2nd " 3rd|2.47|2.47|2.48|2.48|2.48|2.49| | 2-1/2 inches|3rd " 4th|2.53|2.53|2.52|2.52|2.52|2.51| | |4th " 5th|2.59|2.58|2.57|2.56|2.55|2.53| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|2.87|2.89|2.90|2.91|2.93|2.96| | |2nd " 3rd|2.96|2.96|2.97|2.97|2.98|2.99| | 3 inches |3rd " 4th|3.04|3.04|3.03|3.03|3.02|3.01| | |4th " 5th|3.13|3.11|3.10|3.09|3.07|3.04| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|3.78|3.81|3.83|3.84|3.87|3.94| | |2nd " 3rd|3.92|3.94|3.94|3.95|3.96|3.98| | 4 inches |3rd " 4th|4.08|4.06|4.06|4.05|4.04|4.02| | |4th " 5th|4.22|4.19|4.17|4.16|4.13|4.06| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|4.66|4.71|4.73|4.76|4.80|4.90| | |2nd " 3rd|4.89|4.90|4.91|4.92|4.93|4.96| | 5 inches |3rd " 4th|5.11|5.10|5.09|5.08|5.07|5.04| | |4th " 5th|5.34|5.29|5.27|5.24|5.20|5.10| +-------------+-----------+----+----+----+----+----+----+ | |1st and 2nd|5.51|5.57|5.62|5.66|5.71|5.86| | |2nd " 3rd|5.83|5.86|5.87|5.88|5.90|5.95| | 6 inches |3rd " 4th|6.17|6.14|6.13|6.12|6.10|6.05| | |4th " 5th|6.49|6.43|6.38|6.34|6.29|6.14| +-------------+-----------+----+----+----+----+----+----+ Before describing and applying the table, we will call attention to the term "effective" diameter. The effective radius--as is well known--extends from the centre of the pulley to the centre of the belt; the effective diameter, being twice this effective radius, must also equal the actual diameter plus thickness of belt. The table is so arranged that the diameter (divided by distance between centres) of one step of a belted pair will always be found in the extreme right-hand column; while its companion step will be found on the same horizontal line, and in that vertical column of the table corresponding to the length of belt employed. For example, if column 14 of the table corresponded to the length of belt employed, some of the possible pairs of diameters would be as follows: .7118 .5813 .42 .2164 .0474 .06 .24 .42 .60 .72 The upper row of this series of pairs being taken from column 14, and the lower row from the extreme right-hand column, the numbers in each pair being on the same horizontal line. If the distance between the centers of the pulleys were 60 ins. the effective diameters of the steps corresponding to the above pairs would be: 42.71 34.88 25.2 12.98 2.84 ins. 3.6 14.4 25.2 36.0 43.20 being obtained by multiplying the first series of pairs by 60; the length of belt which would be equally tight on each of these pairs would be 3.3195 × 60 ins. = 199.17 ins. III.--TABLE FOR FINDING THE EFFECTIVE DIAMETERS OF THE STEPS OF CONE PULLEYS, WHEN THE PULLEYS ARE CONNECTED BY AN OPEN BELT AND ARE UNLIKE. Each vertical cone of the table corresponds to a given length of belt, and the numbers in these columns are the required effective diameters of the steps when the centres of the pulleys are a Unit's distance apart. +--------------------------------------------------------------+------+ | LENGTH OF BELT WHEN THE CENTRES OF THE CONE PULLEYS ARE A | | | UNIT'S DISTANCE APART. | | +------+------+------+------+------+------+------+------+------+ | |2.0942|2.1885|2.2827|2.3770|2.4712|2.5655|2.6597|2.7540|2.8482| | +------+------+------+------+------+------+------+------+------+ [A] | | =1= | =2= | =3= | =4= | =5= | =6= | =7= | =8= | =9= | | +------+------+------+------+------+------+------+------+------+------+ | .0594| .1177| .1750| .2313| .2867| .3413| .3950| .4479| .5000| 0.00 | | .03 | .0894| .1477| .2050| .2613| .3167| .3713| .4250| .4779| 0.03 | | | .06 | .1194| .1777| .2350| .2913| .3467| .4013| .4550| 0.06 | | | .0294| .09 | .1494| .2077| .2650| .3213| .3767| .4313| 0.09 | | | | .0594| .12 | .1794| .2377| .2950| .3513| .4067| 0.12 | | | | .0275| .0894| .15 | .2094| .2677| .3250| .3813| 0.15 | | | | | .0575| .1194| .18 | .2394| .2977| .3550| 0.18 | | | | | .0244| .0875| .1494| .21 | .2694| .3277| 0.21 | | | | | | .0544| .1175| .1794| .24 | .2994| 0.24 | | | | | | .0200| .0844| .1475| .2094| .27 | 0.27 | | | | | | | .0500| .1144| .1775| .2394| 0.30 | | | | | | | .0140| .0800| .1444| .2075| 0.33 | | | | | | | | .0440| .1100| .1744| 0.36 | | | | | | | | .0064| .0740| .1400| 0.39 | | | | | | | | | .0364| .1040| 0.42 | | | | | | | | | | .0664| 0.45 | | | | | | | | | | .0271| 0.48 | +------+------+------+------+------+------+------+------+------+------+ +--------------------------------------------------------------+------+ | LENGTH OF BELT WHEN THE CENTRES OF THE CONE PULLEYS ARE A | | | UNIT'S DISTANCE APART. | | +------+------+------+------+------+------+------+------+------+ | |2.9425|3.0367|3.1310|3.2252|3.3195|3.4137|3.5080|3.6022|3.6965| | |------+------+------+------+------+------+------+------+------+ [A] | | =10= | =11= | =12= | =13= | =14= | =15= | =16= | =17= | =18= | | +------+------+------+------+------+------+------+------+------+------+ | .5514| .6020| .6518| .7010| .7495| .7974| .8447| .8913| .9373| 0.00 | | .5300| .5814| .6320| .6818| .7310| .7795| .8274| .8747| .9213| 0.03 | | .5079| .5600| .6114| .6620| .7118| .7610| .8095| .8574| .9047| 0.06 | | .4850| .5379| .5900| .6414| .6920| .7418| .7910| .8395| .8874| 0.09 | | .4613| .5150| .5679| .6200| .6714| .7220| .7718| .8210| .8695| 0.12 | | .4367| .4913| .5450| .5979| .6500| .7014| .7520| .8018| .8510| 0.15 | | .4113| .4667| .5213| .5750| .6279| .6800| .7314| .7820| .8318| 0.18 | | .3850| .4413| .4967| .5513| .6050| .6579| .7100| .7614| .8120| 0.21 | | .3577| .4150| .4713| .5267| .5813| .6350| .6879| .7400| .7914| 0.24 | | .3294| .3877| .4450| .5013| .5567| .6113| .6650| .7179| .7700| 0.27 | | .30 | .3594| .4177| .4750| .5313| .5867| .6413| .6950| .7479| 0.30 | | .2694| .33 | .3894| .4477| .5050| .5613| .6167| .6713| .7250| 0.33 | | .2375| .2994| .36 | .4194| .4777| .5350| .5913| .6467| .7013| 0.36 | | .2044| .2675| .3294| .39 | .4494| .5077| .5650| .6213| .6767| 0.39 | | .1700| .2344| .2975| .3594| .42 | .4794| .5377| .5950| .6513| 0.42 | | .1340| .2000| .2644| .3275| .3894| .45 | .5094| .5677| .6250| 0.45 | | .0964| .1640| .2300| .2944| .3575| .4194| .48 | .5394| .5977| 0.48 | | .0571| .1264| .1940| .2600| .3244| .3875| .4494| .51 | .5694| 0.51 | | .0160| .0871| .1564| .2240| .2900| .3544| .4175| .4794| .54 | 0.54 | | | .0460| .1171| .1864| .2540| .3200| .3844| .4475| .5094| 0.57 | | | .0029| .0760| .1471| .2164| .2840| .3500| .4144| .4775| 0.60 | | | | .0329| .1060| .1771| .2464| .3140| .3800| .4444| 0.63 | | | | | .0629| .1360| .2071| .2764| .3440| .4100| 0.66 | | | | | .0174| .0929| .1660| .2371| .3064| .3740| 0.69 | | | | | | .0474| .1229| .1960| .2671| .3364| 0.72 | | | | | | | .0774| .1529| .2260| .2971| 0.75 | | | | | | | .0292| .1074| .1829| .2560| 0.78 | | | | | | | | .0592| .1374| .2129| 0.81 | | | | | | | | .0081| .0892| .1674| 0.84 | | | | | | | | | .0381| .1192| 0.87 | | | | | | | | | | .0681| 0.90 | | | | | | | | | | .0138| 0.93 | +------+------+------+------+------+------+------+------+------+------+ +--------------------------------------------------------------+------+ | LENGTH OF BELT WHEN THE CENTRES OF THE CONE PULLEYS ARE A | | | UNIT'S DISTANCE APART. | | +------+------+------+------+------+------+------+------+------+ | |3.7907|3.8850|3.9792|4.0735|4.1677|4.2620|4.3562|4.4504|4.5447| | |------+------+------+------+------+------+------+------+------+ [A] | | =19= | =20= | =21= | =22= | =23= | =24= | =25= | =26= | =27= | | +------+------+------+------+------+------+------+------+------+------+ | .9828|1.0277|1.0721|1.1159|1.1593|1.2021|1.2444|1.2861|1.3274| 0.00 | | .9673|1.0128|1.0577|1.1021|1.1459|1.1893|1.2321|1.2744|1.3161| 0.03 | | .9513| .9973|1.0428|1.0877|1.1321|1.1759|1.2193|1.2621|1.3044| 0.06 | | .9347| .9813|1.0273|1.0728|1.1177|1.1621|1.2059|1.2493|1.2921| 0.09 | | .9174| .9647|1.0113|1.0573|1.1028|1.1477|1.1921|1.2359|1.2793| 0.12 | | .8995| .9474| .9947|1.0413|1.0873|1.1328|1.1777|1.2221|1.2659| 0.15 | | .8810| .9295| .9774|1.0247|1.0713|1.1173|1.1628|1.2077|1.2521| 0.18 | | .8618| .9110| .9595|1.0074|1.0547|1.1013|1.1473|1.1928|1.2377| 0.21 | | .8420| .8918| .9410| .9895|1.0374|1.0847|1.1313|1.1773|1.2228| 0.24 | | .8214| .8720| .9218| .9710|1.0195|1.0674|1.1147|1.1613|1.2073| 0.27 | | .8000| .8514| .9020| .9518|1.0010|1.0495|1.0974|1.1447|1.1913| 0.30 | | .7779| .8300| .8814| .9320| .9818|1.0310|1.0795|1.1274|1.1747| 0.33 | | .7550| .8079| .8600| .9114| .9620|1.0118|1.0610|1.1095|1.1574| 0.36 | | .7313| .7850| .8379| .8900| .9414| .9920|1.0418|1.0910|1.1395| 0.39 | | .7067| .7613| .8150| .8679| .9200| .9714|1.0220|1.0718|1.1210| 0.42 | | .6813| .7367| .7913| .8450| .8979| .9500|1.0014|1.0520|1.1018| 0.45 | | .6550| .7113| .7667| .8213| .8750| .9279| .9800|1.0314|1.0820| 0.48 | | .6277| .6850| .7413| .7967| .8513| .9050| .9579|1.0100|1.0614| 0.51 | | .5994| .6577| .7150| .7713| .8267| .8813| .9350| .9879|1.0400| 0.54 | | .57 | .6294| .6877| .7450| .8013| .8567| .9113| .9650|1.0179| 0.57 | | .5394| .60 | .6594| .7177| .7750| .8313| .8867| .9413| .9950| 0.60 | | .5075| .5694| .63 | .6894| .7477| .8050| .8613| .9167| .9713| 0.63 | | .4744| .5375| .5994| .66 | .7194| .7777| .8350| .8913| .9467| 0.66 | | .4400| .5044| .5675| .6294| .69 | .7494| .8077| .8650| .9213| 0.69 | | .4040| .4700| .5344| .5975| .6594| .72 | .7794| .8377| .8950| 0.72 | | .3664| .4340| .5000| .5644| .6275| .6894| .75 | .8094| .8677| 0.75 | | .3271| .3964| .4640| .5300| .5944| .6575| .7194| .78 | .8394| 0.78 | | .2860| .3571| .4264| .4940| .5600| .6244| .6875| .7494| .81 | 0.81 | | .2429| .3160| .3871| .4564| .5240| .5900| .6544| .7175| .7794| 0.84 | | .1974| .2729| .3460| .4171| .4864| .5540| .6200| .6844| .7475| 0.87 | | .1492| .2274| .3029| .3760| .4471| .5164| .5840| .6500| .7144| 0.90 | | .0981| .1792| .2574| .3329| .4060| .4771| .5464| .6140| .6800| 0.93 | | .0438| .1281| .2092| .2874| .3629| .4360| .5071| .5764| .6440| 0.96 | | | .0738| .1581| .2392| .3174| .3929| .4660| .5371| .6064| 0.99 | | | .0157| .1038| .1881| .2692| .3474| .4229| .4960| .5671| 1.02 | | | | .0457| .1338| .2181| .2992| .3774| .4529| .5260| 1.05 | | | | | .0757| .1638| .2481| .3292| .4074| .4829| 1.08 | | | | | .0131| .1057| .1938| .2781| .3592| .4374| 1.11 | | | | | | .0431| .1357| .2238| .3081| .3892| 1.14 | | | | | | | .0731| .1657| .2538| .3381| 1.17 | | | | | | | .0050| .1031| .1957| .2838| 1.20 | | | | | | | | .0350| .1331| .2257| 1.23 | | | | | | | | | .0650| .1631| 1.26 | | | | | | | | | | .0950| 1.29 | | | | | | | | | | .0200| 1.32 | +------+------+------+------+------+------+------+------+------+------+ +-----------------------------------------+------+ | LENGTH OF BELT WHEN THE CENTRES OF THE | | |CONE PULLEYS ARE A UNIT'S DISTANCE APART.| | +------+------+------+------+------+------+ | |4.6389|4.7332|4.8274|4.9217|5.0159|5.1102| | |------+------+------+------+------+------+ [A] | | =28= | =29= | =30= | =31= | =32= | =33= | | +------+------+------+------+------+------+------+ |1.3682|1.4085|1.4484|1.4877|1.5266|1.5650| 0.00 | |1.3574|1.3982|1.4385|1.4784|1.5177|1.5566| 0.03 | |1.3461|1.3874|1.4282|1.4685|1.5084|1.5477| 0.06 | |1.3344|1.3761|1.4174|1.4582|1.4985|1.5384| 0.09 | |1.3221|1.3644|1.4061|1.4474|1.4882|1.5285| 0.12 | |1.3093|1.3521|1.3944|1.4361|1.4774|1.5182| 0.15 | |1.2959|1.3393|1.3821|1.4244|1.4661|1.5074| 0.18 | |1.2821|1.3259|1.3693|1.4121|1.4544|1.4961| 0.21 | |1.2677|1.3121|1.3559|1.3993|1.4421|1.4844| 0.24 | |1.2528|1.2977|1.3421|1.3859|1.4293|1.4721| 0.27 | |1.2373|1.2828|1.3277|1.3721|1.4159|1.4593| 0.30 | |1.2213|1.2673|1.3128|1.3577|1.4021|1.4459| 0.33 | |1.2047|1.2513|1.2973|1.3428|1.3877|1.4321| 0.36 | |1.1874|1.2347|1.2813|1.3273|1.3728|1.4177| 0.39 | |1.1695|1.2174|1.2647|1.3113|1.3573|1.4028| 0.42 | |1.1510|1.1995|1.2474|1.2947|1.3413|1.3873| 0.45 | |1.1318|1.1810|1.2295|1.2774|1.3247|1.3713| 0.48 | |1.1120|1.1618|1.2110|1.2595|1.3074|1.3547| 0.51 | |1.0914|1.1420|1.1918|1.2410|1.2895|1.3374| 0.54 | |1.0700|1.1214|1.1720|1.2218|1.2710|1.3195| 0.57 | |1.0479|1.1000|1.1514|1.2020|1.2518|1.3010| 0.60 | |1.0250|1.0779|1.1300|1.1814|1.2320|1.2818| 0.63 | |1.0013|1.0550|1.1079|1.1600|1.2114|1.2620| 0.66 | | .9767|1.0313|1.0850|1.1379|1.1900|1.2414| 0.69 | | .9513|1.0067|1.0613|1.1150|1.1679|1.2200| 0.72 | | .9250| .9813|1.0367|1.0913|1.1450|1.1979| 0.75 | | .8977| .9550|1.0113|1.0667|1.1213|1.1750| 0.78 | | .8694| .9277| .9850|1.0413|1.0967|1.1513| 0.81 | | .84 | .8994| .9577|1.0150|1.0713|1.1267| 0.84 | | .8094| .87 | .9294| .9877|1.0450|1.1013| 0.87 | | .7775| .8394| .90 | .9594|1.0177|1.0750| 0.90 | | .7444| .8075| .8694| .93 | .9894|1.0477| 0.93 | | .7100| .7744| .8375| .8994| .96 |1.0194| 0.96 | | .6740| .7400| .8044| .8675| .9294| .99 | 0.99 | | .6364| .7040| .7700| .8344| .8975| .9594| 1.02 | | .5971| .6664| .7340| .8000| .8644| .9275| 1.05 | | .5560| .6271| .6964| .7640| .8300| .8944| 1.08 | | .5129| .5860| .6571| .7264| .7940| .8600| 1.11 | | .4674| .5429| .6160| .6871| .7564| .8240| 1.14 | | .4192| .4974| .5729| .6460| .7171| .7864| 1.17 | | .3681| .4492| .5274| .6029| .6760| .7471| 1.20 | | .3138| .3981| .4792| .5574| .6329| .7060| 1.23 | | .2557| .3438| .4281| .5092| .5874| .6629| 1.26 | | .1931| .2857| .3738| .4581| .5392| .6174| 1.29 | | .1250| .2231| .3157| .4038| .4881| .5692| 1.32 | | .0500| .1550| .2531| .3457| .4338| .5181| 1.35 | | | .0800| .1850| .2831| .3757| .4638| 1.38 | | | | .1100| .2150| .3131| .4057| 1.41 | | | | .0255| .1400| .2450| .3431| 1.44 | | | | | .0555| .1700| .2750| 1.47 | | | | | | .0855| .2000| 1.50 | +------+------+------+------+------+------+------+ Legend: [A] = Assumed diameter of steps, divided by distance between the centres of Cone Pulleys. To get the actual diameters of these steps when thickness of belt = 7/32 = 0.22 in., we have simply to subtract 0.22 in. from the effective diameters just given, thus: 42.49 34.66 24.98 12.76 2.62 in. 3.38 14.18 24.98 35.78 42.98 would be the series of pairs of actual diameters. In solving problems relating to the diameters of cone pulleys by means of the accompanying table, we must have, besides the distance between centres, sufficient data to determine the column representing the length of belt. The length of belt is seldom known because it is of small practical importance to know its exact length; but it may be estimated approximately, and then the determination of suitable diameters of the steps becomes an extremely simple matter, as may be seen from what has already preceded. When the length of the belt is not known, and has not been assumed, we indirectly prescribe the length of belt by assuming the effective diameters of the two steps of a belted pair; thus, in the following Figure (561), the length of belt is prescribed when the distance A B, and any one of the pairs of steps D_{1}_d__{1}, D_{2}_d__{2}, D_{3}_d__{3} and D_{4}_d__{4} are given. We will show in the following examples how the length of belt and its corresponding column of diameter may be found when a pair of steps (like D_{1}_d__{1}), are given. [Illustration: Fig. 561.] EXAMPLE 1. Given the effective diameters 4.5 in. 9 in. 15 in. 21 in. on cone A, -- -- 15 in. -- " B, and the distance between centres equal to 50 inches. Required the remaining diameters on cone B. Since in this example the steps of the given pair are equal, we look for 15/50 = 0.30, in the extreme right-hand column of table; we will find it in the 11th line from the top; now looking along this line for the diameter of the other step, = 15/50 = 0.30, we will find it in column 10; consequently the numbers of this column may be taken as the diameters of the steps which are the companions or partners of those in the extreme right-hand column. We can now easily determine the remaining members of the pairs to which 4.5 in., 9 in., and 21 in. steps respectively belong. To find the partner of the 4.5 step, we find 4.5/50 = 0.09 in the right-hand column, and look along the horizontal line on which 0.09 is placed till we come to column 10, in which we will find the number 0.4850; 0.4850 × 50 in. = 24.25 in. will be the effective diameter of the companion to the 4.5 in. step. To find the partner to the 9 in. step, we proceed as before, looking for 9/50 = 0.18 in the right-hand column, and then along the horizontal line of 0.18 to column 10, then will 0.4113 × 50 in. = 20.57 in. be the required companion to the 9 in. step of cone A. In like manner for the partner of the 21 in. step we get 0.1700 × 50 in. = 8.5 in. The effective diameter therefore will be, 4.5 in. 9 in. 15 in. 21 in. on cone A, 24.25 20.57 15 in. 8.5 " B. If the thickness of belt employed were 0.25 in. the _actual_ diameters of steps would be, 4.25 8.75 14.75 20.75 on cone A, 24.00 20.32 14.75 8.25 " B, and the length of belt would be 2.9425 × 50 = 147.125 in. EXAMPLE 2. Given the effective diameters 6 in. 12 in. 18 in. 24 in. on cone A, 30 in. -- -- -- " B, and the distance between centres = 40 in. Required the unknown diameters on cone B. We must, as before, first find the vertical column corresponding to the length of belt which joins the pair of steps 6 in/30 in. We find the number 6/40 = .15 in the right-hand column, and then look along its horizontal line for its partner 30/40 = 0.75. Since we do not find any number exactly equal to .7500, we must interpolate. For the benefit of those not familiar with the method of interpolation we will give in detail the method of finding intermediate columns of the table. On the aforesaid horizontal line we find in column 16 a number 0.7520, larger than the required 0.7500, and in column 15 a number 0.7014, smaller than 0.7500; evidently the intermediate column, containing the required 0.7500, must lie between columns 16 and 15. To find how far the required column is from column 16, we subtract as follows: 0.7520 0.7520 0.7500 0.7014 ------ ------ .0020 0.0506 then the fraction .0020/.00506 = 0.04 nearly will represent the position of the required intermediate column; namely, that its distance from column 16 is about 4/100 of the distance between the adjacent columns, 15 and 16. To find other numbers in this intermediate column we have only to multiply the difference between the adjacent numbers of columns 16 and 15 by 0.04, and subtract the product from the number in column 16. But it is not necessary to find as many numbers of the intermediate columns as are contained in either of the adjacent columns; it is only necessary to find as many numbers as there are steps in each of the cone pulleys. We will now illustrate what has preceded, by finding the partner to the 12 in. step of cone A. Find, as before, the horizontal line corresponding to 12/40 = 0.30, then take the difference between the numbers 0.6413 and 0.5867 of columns 16 and 15, and multiply this difference, 0.0546, by 0.04; this product = 0.0022 subtracted from 0.6413, will give 0.6391, a number of the intermediate columns corresponding to the length of belt of the present problem. Multiplying by the distance between the axes = 40 in. we get 0.6391 × 40 = 25.56, for the diameter of the step of cone B which is partner to the 12 in. step of cone A. To find the companion to the 18 in. step, we proceed in the same manner, looking for the horizontal line 18/40 = 0.45, and interpolating as follows: 0.5094 - (0.5094 - 0.4500) × 0.04 = 0.5070. Consequently, 0.5070 × 40 in. = 20.28 in. will be the required partner of the 18 in. step. In like manner, for the 24 in. step, we have 0.3500 - (0.3500 - 0.2840) × 0.04 = 0.3474, and 0.3474 × 40 = 13.90. The effective diameters are therefore 6 in. 12 in. 18 in. 24 in. on cone A. 30 25.56 20.28 13.9 " B. The actual diameters, when thickness of belt = 0.20 in., are: 5.8 11.8 17.8 23.8 on cone A. 29.8 25.36 20.08 13.7 " B. And the length of belt will be: [3.5080 - (3.5080 - 3.4137) × 0.04] × 40 in. = 140.17 in. EXAMPLE 3. Given the effective diameters: 12 in. 18 in. 24 in. 30 in. on cone A, 33 in. -- -- -- " B, and the distance between the centres = 60 in. Required the remaining diameters on cone B. The horizontal corresponding to 12/60 = 0.20 lies 2/3rd way between the horizontal line, corresponding to 0.18 and 0.21; the number 33/60 = 0.5500, corresponding to the companion of the 12 in. step, will therefore lie 2/3rd way between the horizontal lines 0.18 and 0.21. We have now to find two numbers on this 2/3rd line, of which one will be less and the other greater than 0.5500. An inspection of the table will show that these greater and less numbers must lie in columns 13 and 12. The numbers on the 2/3rd line itself may now be found as follows: In column 13, 0.5750 - 2/3(0.5750 - 0.5513) = 0.5592. In column 12, 0.5213 - 2/3(0.5213 - 0.4967) = 0.5049. 0.5592 will be the number on the 2/3rd line, which is greater than 0.5500, and 0.5049 will be the one which is less than 0.5500. The position of the intermediate column, corresponding to the length of belt of the present example, may now be found, as before, briefly. It is: 0.5592 - 0.5500 = 0.0092 = 0.17. 0.5592 - 0.5049 = 0.0543 Consequently the required column lies nearest column 13, 17/100th way between columns 13 and 12. To find any other number in the required column, we have only to multiply the difference between two adjacent numbers of columns 13 and 12 by 17/100, and subtract the product from the number in column 13. For example, to find the diameter of the partner to the 18 in. step of cone A, we find the numbers 0.4750 and 0.4177 of columns 13 and 12, which lie on the horizontal line corresponding to 18/60 = 0.30; the difference, 0.0573, between the two numbers is multiplied by 0.17, and the product, 0.0573 × 0.17 = 0.0097, subtracted from 0.4750. This last difference will equal 0.4653, and will be the number sought. If we now multiply by 60, we will get 27.92 in. as the effective diameter of that step on cone B which is the partner to the 18 in. step of cone A. To find the companion of the 24 in. step, we proceed after the same fashion; the horizontal line 24/60 = 0.40 lies 1/3rd way between 0.39 and 0.42; hence, In column 13, 0.3900 - 1/3(0.3900 - 0.3594) = 0.3798; In column 12, 0.3294 - 1/3(0.3294 - 0.2975) = 0.3188; And 0.3798 - (0.3798 - 0.3188) × 0.17 = 0.3694. The required effective diameter of the step, which is partner to the 24 in. step, will therefore be 0.3694 × 60 = 22.16 in. In like manner we obtain partner for the 30 in. step, thus: In column 13, 0.2944 - 2/3(0.2944 - 0.2600) = 0.2715. In column 12, 0.2300 - 2/3(0.2300 - 0.1940) = 0.2060. Also 0.2715 - (0.2715 - 0.2060) × 0.17 = 0.2604, and 0.2604 × 60 in. = 15.62 in. = diam. of step belonging to the same belted pair as the 30 in. step of cone A. The effective diameters will be: 12 in. 18 in. 24 in. 30 in. on cone A, 33 27.92 22.16 15.62 " B, and the actual diameters when belt is 0.22" thick: 11.78 17.78 23.78 29.78 in. 32.78 27.70 21.94 15.40 and the length of belt is found to be: [3.2252 - (3.2252 - 3.1310) × 0.17] × 60 in. = 192.55 in. In all the preceding problems it should be noticed that we arbitrarily assumed _all_ the steps on one cone, and _one_ of the steps on the other cone. It will be found that all of the practical problems relating to cone-pulley diameters can finally be reduced to this form, and can consequently be solved according to the methods just given. For those who find difficulty in interpolating, the following procedure will be found convenient: Estimate approximately the necessary length of belt, then divide this length by the distance between the centres of the cone pulleys; now find which one of the 33 lengths of belt (per unit's distance apart of the centres) given in the table is most nearly equal to the quotient just obtained, and then take the vertical column, at the head of which it stands, for the companion to the right-hand column. Those numbers of these companion columns which are on the same horizontal line will be the companion steps of a belted pair. The table is so large, that in the great majority of cases not only exact, but otherwise satisfactory values can be obtained by this method, without any interpolation whatever." [Illustration: Fig. 562.] The teeth of the back gear should be accurately cut so that there is no lost motion between the teeth of one wheel, and the spaces of the other, because on account of the work being of large diameter or of hard metal (so as to require the slow speed), the strain of the cut is nearly always heavy when the back gear is in use, and the strain on the teeth is correspondingly great, causing a certain amount of spring or deflection in the live spindle and back gear spindle. Suppose then, that at certain parts of the work there is no cut, then when the tool again meets the cut the work will meet the tool and stand still until the lost motion in the gear teeth and the spring of the spindles is taken up, when the cut will proceed with a jump that will leave a mark on the work and very often break the tool. When the cut again leaves the tool a second jump also leaving a mark on the work will be made. If the teeth of the gears are cut at an angle to the axial line of the spindle, as is sometimes the case, this jumping from the play between the teeth will be magnified on account of a given amount of play, affording more back lash in such gears. The teeth of the wheels should always be of involute and not of epicycloidal form, for the following reasons. The transmission of motion by epicycloidal teeth is exactly uniform only when their pitch circles exactly coincide, and this may not be the case in time because of wear in the parts as in the live spindle journals and the bearings, and the back gear spindle and its bearings, and _every variation of speed_ in the cut, however slight it may be, produces a corresponding mark upon the work. In involute teeth the motion transmitted will be smooth and equal whether the pitch lines of the wheels coincide or not, hence the wear of the journals and bearings does not impair their action. The object of cutting the teeth at an angle is to have the point of contact move or roll as it were from one end to the other of the teeth, and thus preserve a more conterminous contact on the line of centres of the two wheels, the supposition being that this would remove the marks on the work produced by the tremor of the back gear. But such tremor is due to errors in the form of the teeth, and also in the case of epicycloidal teeth from the pitch lines of the teeth not exactly coinciding when in gear. The pitch of the teeth should be as fine as the requisite strength, with the usual allowance of margin for wear and safety will allow, so as to have as many teeth in continuous contact as possible. Various methods of moving the back gear into and out of gear with the cone spindle gears are employed. The object is to place the back gears into gear to the exact proper depth to hold them securely in position, and to enable the operator to operate the gears without passing to the back of the lathe. Sometimes a sliding bearing box, such as shown in Fig. 562, is employed; _a_ is the back gear spindle, _b_ its bearing box, and _d_ a pin which when on the side shown holds _b_ in position, when the back gear is in action. To throw it out of action _d_ is removed, _b_ pushed back, and _d_ inserted in a hole on the right hand of _b_; the objection is that there is no means of taking up the wear of _b_, and it is necessary to pass to the back of the lathe to operate the device. [Illustration: Fig. 563.] Another plan is to let the back gear move endwise and bush its bearing holes with hardened steel bushes. This possesses the advantage that the gear is sure, if made right, to keep so, but it has some decided disadvantages: first, the pinion A, Fig. 563, must be enough larger than the smallest cone-step B to give room between B and C for the belt, and this necessitates that D also be larger than otherwise; secondly, the gear-spindle F projects through the bearing at _f_, and this often comes in the way of the bolt-heads used for chucking work to the face plate. The method of securing the spindle from end motion is as follows: On the back of the head is pivoted at _i_, a catch G, and on the gear shaft F are two grooves. As shown in the sketch, G is in one of these grooves while H is the other, but when the back gear is in, G would be in H. [Illustration: Fig. 564.] Sometimes a simple eccentric bush and pin is used as in Fig. 564, in which _a_ is the spindle journal, _b_ a bush having bearing in the lathe head, and _d_ a taper pin to secure _b_ in its adjusted position. [Illustration: Fig. 565.] In large heavy lathes having many changes of speed, there are various other constructions, as will be seen upon the lathes themselves in the various illustrations concerning the methods of throwing the back gear in and out. The eccentric motion shown in Fig. 573 of the Putnam lathe, is far preferable to any means in which the back-gear spindle moves endways, because, as before stated, the end of the back-gear spindle often comes in the way of the bolts used to fasten work to the large face plate. This occurs mainly in chucked work of the largest diameter within the capacity of the lathe. [Illustration: Fig. 566.] In many American lathes the construction of the gearing that conveys motion from the live spindle is such that facility is afforded to throw the change gears out of action when the lathe is running fast, as for polishing purposes, so as to save the teeth from wear. Means are also provided to reverse the direction of lead screw or feed screw revolution. An example of a common construction of this kind is shown in Fig. 565, in which the driving wheel A is on the inner side of the back bearing as shown. It drives (when in gear) a pair of gears, one only of which is seen in the figure at B, which drives C, and through R, D, I, and S, the lead screw. A side view of the wheel A and the mechanism in connection therewith is shown in Fig. 566, in which S represents the live spindle and R is a spindle or shaft corresponding to R in Fig. 565. L is a lever pivoted upon R and carrying two pinions B and E; pinion B is of larger diameter than E, so that B gears with both C and E (C corresponding to wheel C in Fig. 565), while E gears with B only. [Illustration: Fig. 567.] With the lever L in the position shown, neither B nor E engages with A, hence they are at rest; but if lever L be raised as in Fig. 567, B will gear with wheels A and C, and motion will be conveyed from A to C, wheel E running as an idle wheel, thus C will revolve in the same direction as the lathe spindle. But if lever L be lowered as in fig. 568, then wheel E will gear with and receive motion from A, which it will convey to B, and C will revolve in the opposite direction to that in which the lathe spindle runs. To secure lever L in position, a pin F passes through it and into holes as I, J, provided in the lathe head. Lever L is sometimes placed inside the head, and sometimes outside as in Fig. 569, and it will be obvious that it may be used to cut left-hand threads without the use of an extra intermediate change gear, which is necessary in the construction shown in Fig. 570, in order to reverse the direction of lead screw revolution. Sometimes the pin F is operated by a small spring lever attached to L, so that the hand grasps the end of L and the spring lever simultaneously, removing F from the hole in H, and therefore freeing L, so as to permit its operation. By relaxing the pressure on the small spring lever pin F finds its own way into the necessary hole in H, when opposite to it, without requiring any hand manipulation. In larger lathes the lever L is generally attached to its stud outside the end bearing of the head H. [Illustration: Fig. 568.] It is preferable, however, that the device for changing the direction of feed traverse be operative from the lathe carriage as in the Sellers lathe, so that the operator need not leave it when it is necessary to reverse the direction of traverse. [Illustration: Fig. 569.] The swing frame, when the driving gear D is outside of the back bearing (as it is in Fig. 570), is swung from the axis of the lead screw as a centre of motion, and has two slots for receiving studs for change wheels. But when the driving gear is inside the back bearing as in Fig. 571, the swing frame may be suspended from the spindle (R, Fig. 565) that passes through the lathe head, which may also carry the cone for the independent feed as shown in Fig. 571, no matter on which side of the lathe the lead screw and feed rod are. This affords the convenience that when both lead screw and feed rod are in front of the lathe, the feed may be changed from the screw cutting to the rod feed, or _vice versâ_, by suitable mechanism in the apron, without requiring any change to be made in the driving gears. [Illustration: Fig. 570.] In the lathe shown in Fig. 572, which is from the design of S. W. Putnam, of the Putnam Tool Company of Fitchburg, Massachusetts, the cone pinion for the back gear, and that for driving the feed motion, are of the same diameter and pitch, so that the gear-wheel L in Fig. 573 may (by means of a lever shown dotted in) be caused to engage with either of them. When the latter is used in single gear it would obviously make no difference which wheel drives L, but when the back gear is put in and L is engaged with the cone pinion, its speed corresponds to that of the cone, which being nine times faster than the live spindle, enables the cutting of threads nine times as coarse as if the back gear was not in use. This affords very great advantages for cutting worms and threads of coarse pitches. An excellent method of changing the direction of feed motion, and of starting or stopping the same, is shown in Fig. 574, which represents the design of the Ames Manufacturing Company's lathe. [Illustration: Fig. 571.] In the figure, A is the small step of the lathe cone, B the pinion to drive the back gear, C a pinion to drive the feed gear, giving motion to D, which drives E, the latter being fast to G and rotating freely upon the shaft F, G drives H, which in turn drives I. The clutch J has a featherway into which fits the feather _c_, on the shaft F, so that when the clutch rotates it rotates J through the medium of _c_; K is a circular fork in a groove in J, and operated by a lever operated by a rod running along the front of the lathe bed. This rod is splined so that a lever carried by the apron or feed-table, having a hub and enveloping the rod, may by means of a feather filling into the spline operate the rod by partly rotating it, and hence operate K. Suppose now that this lever stands horizontal, then the clutch J would stand in the position shown in the cut, and D, E, G, H, and I, would rotate, while F would remain stationary. By lifting the lever, however, J would be moved laterally on F (by means of K) and the lug _a_ on J would engage with lug _b_ on G, and G would drive J, which through _c_ would drive F, on which is placed a change gear at L, thus traversing the carriage forward. To traverse it backward the lever would be lowered or depressed below the horizontal level moving K, and therefore J, to the right, so that lug _a_ would engage with lug _b_ on I, hence F would be driven by I, whose motion is in an opposite direction to G, as is denoted by the respective arrows. [Illustration: Fig. 572.] To throw all the feed motion out of gear, to run the lathe at its quickest for polishing, &c., the operation is as follows. [Illustration: Fig. 573.] M is tubular and fast in N and affords journal bearing to wheel D. Through M passes stud O, having a knob handle at P. At the end of the hub of D is a cap fast in D, the latter being held endways between the shoulder shown on O and the washer and nut T. If then P be pulled outwards O will slide through M, and through the medium of T will cause D to slide over M, in the direction of the arrow, and pass out of gear from C, motion therefore ceasing at C. Q is the swing frame for the studs to carry the change wheels, and R a bolt for securing Q in its adjusted position. S is a journal and bearing for H. If it be considered sufficient the feed motion on small lathes (instead of feeding in both directions on the lateral and cross feeds as in the Putnam Lathe), may feed in the direction from the dead to the live centre, and in one direction only on the cross slide. [Illustration: Fig. 574.] An example of a feed motion of this kind is shown in Figs. 575 and 576; _f_ _f_ is the feed spindle splined and through the medium of a feather driving the bevel pinion A having journal bearing in B. Pinion A drives the bevel gear C, which is in one piece with pinion D. The latter drives gear F, which drives pinion K, which is carried on a lever L, pivoted on the stud which carries F, so that by operating L, pinion K is brought into gear with pinion P, which is fast upon the cross-feed screw, and therefore rotates it to effect the automatic cross feed. [Illustration: Fig. 575.] [Illustration: Fig. 576.] As shown in the cut, the lever L is in such a position as to throw K out of gear with P, and the cross feed screw is free to be operated by the handle by hand. At M is a slot in L in which operates a cam or eccentric, one end of which projects into L, while at the other end is the round handle R, Fig. 575, which is rotated to raise or lower that end of L so as to operate K. To operate the saddle or carriage the motion is continued as follows:--at the centre of F is a pinion gear G which operates a gear H, which is in one piece with the pinion I, and the latter is in gear with the rack running along the lathe bed. If the motion from A to I was continuous, the carriage feed or traverse would be continuous, but means are provided whereby motion from F to I may be discontinued, as follows:--A hand traverse or feed is provided. J, Figs. 575 and 576, is carried by a stud having journal bearing in a hub on X and receiving the handle Q; hence by operating Q, J is rotated, operating the gear H, upon which is the pinion I, which is in gear with the rack running along the lathe bed. To lock the carriage in a fixed position, as is necessary when operating the cross feed on large radial surfaces, the following device is provided:--N is a stud fixed in a hub on X, and having a head which overlaps the rim of H, as shown in figure. On the other side of that rim is a washer Z on the same stud having a radial face also overlapping the rim of H, but its back face is bevelled to a corresponding bevel on the radial face on the hub of lever O (the hub of O being pivoted on the same stud). When therefore O is depressed the two-bevel face of the hub of O forces the washer Z against the face of the wheel H, whose radial faces at the rim are therefore gripped between the face of the collar N and that of the washer Z, hence H is locked fast. By raising the end of lever O, Z is released and H is free to rotate. Both the carriage feed and cross feed can only be traversed in one direction so far as these gears and levers are concerned, but means are provided on the lathe headstock for reversing the direction of motion of the feed spindle _f_ so as to reverse the direction of the feeds. It will be observed that so long as _f_ rotates, A, C, D, and F rotate, the remaining motions only operating when S is screwed up. In order to obtain a delicate tool motion from the handle Q it is necessary to reduce the motion between J and I as much as possible, a point in which a great many lathes as at present constructed are deficient, because Q, although used to simply traverse the carriage along the bed, in which case rapid motion of the latter is desirable, is also used to feed the tool into corners when the lathe has no compound rest to put on light cuts on radial faces, hence it should be capable of giving a delicate tool motion. [Illustration: Fig. 577.] On account of the deficiency referred to it is often necessary to put on a fine radial cut by putting the feed traverse in gear, and, throwing the feed screw gear out of contact with the other change wheels, pull it around by hand to put on the cut. In compound slide rests these remarks do not apply, because the upper part of the rest may be used instead of the handle Q. Many small lathes are provided with a tool rest known as the _elevating rest_, or weighted lathe. An excellent example of an elevating rest for a weighted lathe is shown in Figs. 577 and 578, which represent the construction in the Pratt and Whitney lathe. A is the lathe shears upon which slides the carriage provided with [V] slideways R for the sliding piece B, and provided at the other end with the guides H. The cross slide S is pivoted upon B at D, and fits at the other end between the guides H. At E is the elevating screw which when operated raises or lowers that end of the elevating rest to adjust the tool height. This also affords an excellent means of making a minute adjustment for depth of tool cut. The tool rest F is bolted to S. [Illustration: Fig. 578.] The weight W is suspended from S and, therefore, holds one end of S to B, the lathe to C, and C to A; at the other end the weight holds S to C (through the medium of the elevating screw E) and C to A. The cross feed nut N is fast to S, the cross feed screw being operated by hand wheel G. B is provided with the [V] slideways R, which slide upon corresponding [V] slides R´ upon C; P is a lug cast upon C, and K is a screw threaded in B. When the end of screw K abuts against P the motion of S, and, therefore, of the cutting tool T, towards the work is arrested, hence when the tool is adjusted to the proper depth of cut, K is operated to abut firmly against P, and successive pieces may be turned to the same diameter without requiring each piece to be measured for diameter. N is the handle for opening and closing the nut for the feed screw Q, and Z is the wheel for the hand feed traverse. The length of cross feed motion is determined by the length of the cross [V] slides R´. This class of rest possesses the advantage that no lost motion in the slides occurs by reason of the wear, because the weight keeps the parts in constant contact notwithstanding such wear; on the other hand, however, the slide [V]s sustain the extra wear due to the weight W in addition to the weight of the carriage. Lathes of this class are intended for light work, and are less suited for boring than for plain turning; they are, however, very convenient, and are preferred by many to any other kind of lathe for short and light work. [Illustration: Fig. 579.] The tool rest being removable may be supplanted by other special forms of rest. Thus Figs. 579 and 580 represent a special rest for carrying two tools to cut pieces of work to the exact same length. Bolts D and E are to secure the rest A to the elevating rest, and C C are the clamps for the two tools B. [Illustration: Fig. 580.] Fig. 581 represents a cross sectional view of the Putnam Tool Company's gibbed elevating rest, there being a gib on the underneath side of the front shear. The elevating screw is pivoted by a ball joint. By employing a gib instead of a weight, the bed may be provided with cross girts or ribs joining the two sides of the shear, thus giving much greater stiffness to it. Figs. 582, 583, and 584 represent a lathe feed motion by William Munzer, of New York. The object in this motion is to insure that no two feeds can be put into operation simultaneously, because putting the feed in motion in one direction throws it out of gear for either of the others. Another object is to have the transmitting motion as direct as possible so as to avoid the rotation of any wheels not actually necessary for the transmission of the motion; and a third object is to enable the throwing out of gear of all wheels (when no feed motion at all is required) without leaving the apron. The means employed to effect these objects are as follows:-- In Fig. 582 _f_ represents the independent feed spindle and S the lead-screw: _f_ is splined to drive A, A´ and A´´, which is a sleeve in one piece, and consists of a circular rack at A, a bevel pinion at A´, and a second bevel pinion at A´´. This sleeve may be operated in either direction along _f_ by rotating the pinion B. As shown in the cut A´ and A´´ are both out of gear with the bevel-wheel C, but if B be rotated to the right then A´ will be in gear with C, or if it be operated to the left then A´´ will be in gear with C. Now the direction of rotation of C will be governed by which pinion, A´ or A´´, drives it, and these are the means by which the direction of the feed traverse and also of the cross feed is determined. If none of the feeds are required to operate, the sleeve occupies the position shown in the cut, and the circular rack at A simply rotates while B and all other parts remain at rest. On the same central pin as C is the pinion D driving a spur gear E´´. On the same centre pin as E is the gear F driving G, which is on the same central pin as C and D. The gear H is fixed to and rotates with G and drives I; all these gears serving to reduce the speed of motion when operating to feed the carriage traverse in either direction. A gear J is carried on the end of a lever K, being pivoted at L. In the position shown J is out of gear with all gears, but it may be swung to the right so as to engage with wheel I and wheel M, and convey the motion of I to M. Upon the same spindle as M is the pinion N, engaging with the rack O, which is fast on the lathe bed. This completes the automatic feed traverse. For a hand feed traverse, pinion P is employed to drive M, which is fast to N. The cross feed is self-acted by moving lever K to the left, causing it to engage with pinion Q as well as with T, Q being fast on the cross feed screw. To lock J in either of its three positions there is provided on lever K a spring locking pin R, shown clearly in Fig. 584, which represents an irregular section of the gearing viewed from the headstock of the lathe. The pin R is pressed inward by the spiral spring shown, and has a conical end fitting into holes provided in the apron to receive it. There are three of these holes, shown in dotted lines at _a_ _b_ _c_ in Fig. 582. When the pin is in _a_ the lever K, and therefore wheel J, Fig. 582, is locked out of gear; when it is in hole _b_ wheel J is locked in gear with I and M, and when it is in _c_ the wheel J is in gear with T and Q, and the cross feed is actuated. [Illustration: Fig. 581.] [Illustration: Fig. 582.] A similar locking device is provided for the pinion B for actuating A; thus in Fig. 582 B is the lever, the spring pin being at R´´; or referring to Fig. 584, X is the lever fast at _x_ on the pin driving B, and R´´ is the spring pin. The nut for the lead screw is secured either in or out of gear with the screw in the same manner, _x´_, Fig. 583, being the lever and R´ the spring pin. In screw cutting the cutting tool requires to be withdrawn from the thread while the carriage traverses back, and it is somewhat difficult to know just how far to move the tool in again in order to put on a proper depth of cut. To facilitate this the device shown in Fig. 585 (which is taken from the "American Machinist,") is sometimes employed. It consists of a ring C inserted between the cross slide D and the handle hub B having journal bearing on and rotating with the latter. When the first cut is put on, the mark on C is coincident with that on D, and the ring is then, while the first cut is traversing, moved (supposing the cross feed screw to have a right-hand thread) to the left, as shown in the figure, to the amount the handle will be required to move to the right to put on the next cut, and when the next cut is put on the handle will be moved the distance it was moved to withdraw the tool for the back traverse, and in addition enough to make the marks coincide, then while the second cut is being taken the ring is again moved to the left, as in the cut, to give the depth of cut for the next traverse, and so on. [Illustration: Fig. 583.] If the cross feed screw has a left-hand thread, the mark on the ring would require to be moved to the right instead of to the left of the mark on D. It is obvious that this answers the same purpose, but is more exact than the chalk mark before referred to, and, indeed, that chalk mark could be used in the same way, leaving the chalk mark D and rubbing out that on C while the cut is proceeding and making a new one for the next cut. [Illustration: Fig. 584.] Another device for use on lathes specially designed for screw-cutting is shown in Fig. 586, in which A represents the cross feed screw. It is fast to the notched wheel B, and is operated by it in the usual way. C is a short screw which provides journal bearing for the screw A by a plain hole. It is screwed on the outside, and the plate in which it fits acts as its nut. It is fast to the handle D, and is in fact operated by it. The handle or lever is provided with a catch E, pivoted in the enclosed box F, which also contains a means of detaining the catch in the notches of the wheel, or of holding it free from the same when it is placed clear. If, then, the lever D be moved back and forth the feed screw A, and hence the slide rest, will be operated; while, if the catch be placed in one of the notches on the wheel B, both the screws, A and C, will act to operate the rests. When, therefore, the tool is set to touch the diameter of the work, the catch E is lifted and the feed wheel B rotated, putting on the cut until the catch E will fall into the next notch in B, the lever D resting in the meantime on the stud G. When the cut is carried along the work to the required distance the tool is withdrawn by moving D over until it rests upon stud or stop H. While the slide rest is traversing back E is lifted and B rotated so that E will fall into the next notch, and when the tool starts forward again D is moved over from H to G, as shown in the figure, and the tool cut is put on. [Illustration: Fig. 585.] When the device is not required to be used E is thrown out, D rests on E, and the feed is operated in the ordinary manner. [Illustration: Fig. 586.] A simple attachment for regulating on a slide rest the depth of tool cut in screw cutting or for adjusting the cut to a requisite diameter when a number of pieces are to be turned to diameter by a finishing cut, is shown in Fig. 587, in which B represents the slide rest carriage, and E the cross slide on which the slide rest A is traversed by means of the cross feed screw _f_. A screw is screwed into the rest, as shown, carrying the two circular milled edge nuts R P; the screw passes an easy fit through the piece C, which is capable of being fixed in any position along the slide E by means of the set screw S; the nut R is set in such a position on the screw that it will abut against C when the tool is clear of the work surface (for the back traverse) while P may be used in two ways:--First it may be set so that when it comes against C the thread is cut to the required depth, and thus act as stop to give the thread depth without trying the gauge: or it may be used to answer the same purpose and in the same way as the ring C in Fig. 585. [Illustration: Fig. 587.] The use of this device as a stop to gauge the thread depth is confined to such lengths of work as enable the tool to cut several pieces without requiring regrinding, because when the tool is removed to grind it, it is impracticable to set it exactly the same distance out from the tool post, hence the adjustment of P becomes destroyed. It is better, therefore, in most cases where a number of threads of equal pitch and diameter are to be cut, to rough them all out, cutting the threads a little above the gauge diameter so as to leave a finishing cut to be taken. In roughing out, however, the nut P may still be used to regulate the depth. For the finishing cut the tool may be ground and P adjusted to give the requisite depth of cut, taking a single traverse over each thread to finish it. This, of course, preserves the tool and enables it to finish a larger number of threads without regrinding, and the consequent readjustment of P. It is obvious that the nut P may be employed in the same manner to turn a number of plain pieces to an equal diameter. [Illustration: Fig. 588.] It is preferable in a device of this kind, however, to employ the two adjusting nuts P and Q in Fig. 588, Q being a clamp nut that can be closed by a screw so as to firmly grip the threaded stud. Q is adjusted so that when P abuts against it the tool will cut to the correct diameter when it is moved in as far as nuts P Q will permit. The use of the second nut P is as follows:--Suppose a first cut has been taken and P may be screwed up to just meet the face of clamp C. Then while the carriage is traversing, P may be screwed back towards Q sufficiently to put on the next cut, and so on, so that P is used to adjust the depths of the roughing, and Q that of the finishing cut. Sometimes a feed motion to a slide rest is improvised by what is known as the _star feed_, the principle of action of which is as follows: Upon the outer end of the feed screw of the boring bar or slide rest, as the case may be, is fastened a piece of iron plate, which, from having the form in which stars are usually represented, is called the star. If the feed is for a slide rest a pin is fastened to the lathe face plate or other revolving part, in such a position that during the portion of the revolution in which it passes the star it will strike one of the star wings, and move it around sufficiently to bring the next wing into position to be struck by the pin during its succeeding revolution. When the feed is applied to a revolving boring bar the construction is the same, but in this case the pin is stationary and the star revolves with the feed screw of the bar. In Fig. 589 is shown a star feed applied to a slide rest. A is the slide rest, upon the end of the feed screw of which the star, B, is fitted. C is a pin attached to the face plate of the lathe, which, as it revolves, strikes one of the star wings, causing it to partly rotate, and thus move the feed screw. The amount of rotation of the feed screw will depend upon the size of the star and how far the circle described by the pin C intersects the circle described by the extreme points of the star wings. Thus the circles denoted by D E show the path of the pin C; the circle F H the path of the star points, and the distance from F to G the amount which one intersects the other. It follows that at each revolution of C an arm or wing of the star will be carried from the point G to point F, which, in this case, is a sixth of a revolution. If more feed is required, we may move the pin C, so that it may describe a smaller circle than D E, and cause it to intersect F H to a greater extent, in which case it will move the star through a greater portion of its revolution, striking every other wing and doubling the amount of feed. It will be observed that the points F and G are both below the horizontal level of the slide rest's feed screw, and therefore that the sliding motion of the pin C upon the face of the star wings will be from the centre towards the points. This is better, because the motion is easier and involves less friction than would be the case if the pin contact first approached and then receded from the centre, a remark which applies equally to all forms of gearing, for a star feed is only a form of gearing in which the star represents a tooth wheel, and the pin a tooth in a wheel or a rack, according to whether its line of motion is a circle or a straight line. [Illustration: Fig. 589.] It is obvious that in designing a star feed, the pitch of the feed screw is of primary importance. Suppose, for example, that the pitch of a slide rest feed screw is 4 to an inch, and we require to feed the tool an inch to every 24 lathe revolutions; then the star must have 6 wings, because each revolution of the screw will move the rest 1/6 in., while each revolution of the pin C will move the star 1/6 of a revolution, and 4 × 6 = 24. To obtain a very coarse feed the star attachment would require to have two multiplying cogs placed between it and the feed screw, the smaller of the cogs being placed upon the feed screw. In many lathes of European design, the feeds or some of them, are actuated by ratchet handles, operated by an overhead shaft, having arms which rock back and forth. Thus in Fig. 590 is a lathe on which there is provided at A crank disc, carrying in a dovetail slot a pin P, for rocking the overhead shaft from whose arms a chain is attached which may be connected to the ratchet handle shown on the cross-feed screw, the weight being for the purpose of carrying that handle down while the chain pulls it up. To regulate the amount of feed the pin P is adjusted in the slot in A, or the chain may be attached in different positions along the length of the ratchet arm, the weight being provided with a set screw so that it may be set in any required position along the ratchet arm. [Illustration: Fig. 590.] TOOL-HOLDING DEVICES.--Perhaps no part of a lathe is found in American practice with so many different forms of construction as the device for holding the cutting tool. The requirements for a lathe to be used on light work and where frequent changes in the position of the tool are necessary, are quite different from those for a lathe intended to take as heavy a cut as the lathe will properly drive, and wherein tools having the cutting edge at times standing a long way out from the tool post (as sometimes occurs in the use of boring tools). In the former case a single holding screw will suffice, possessing the advantage that the tool may be quickly inserted, adjusted for height and set to one side or the other, with a range of motion which often permits of a tool that has taken a parallel cut being moved in position to capacitate it to take a facing one, which would not be the case were its capacity for side adjustment limited. In the case of the common American lathe having a self-acting feed and no compound rest, the tool post is usually employed, the rest being provided with a [T] slot such as shown in Fig. 577. This enables the tool post to be moved from side to side of the tool rest, and swing around in any required position. In connection with such tool posts various contrivances are employed to enable the height of the cutting edge of the tool to be readily adjusted. Thus in the Fig. 591, the tool post is surrounded by a cupped washer W, and through the slot in the tool post passes a gib G, which may be moved endways in the slot and thus elevates or depresses the tool point. The objection to this is that the tool is not lifted parallel, or in other words is caused to stand out of its proper horizontal position which alters the clearance of the tool, and by presenting the angles forming the tool edge in an improper position, with relation to the work, impair its cutting qualification, as will be shown hereafter when treating of lathe cutting tools. An improvement on this form has been pointed out by Professor John E. Sweet, whose device is shown in Fig. 592. Here the washer or ring is rounded and the bottom surface of the gib is hollowed, so that chips or dirt will to a great extent fall off, and every time the tool post is swung the gib acts to push off whatever dirt may lodge on the washer. In the design shown in Fig. 593, the tool rests upon two washers W that are tapered, and its height is adjusted by revolving one of these washers, it being obvious that the limit of action to depress the tool point is obtained when the two thin sides of the washers are placed together, and on the same side of the tool post as the cutting edge of the tool, while the limit of action to raise the tool point is obtained when the washers have their thick sides together and nearest to the tool point. Here again the tool is thrown out of level, and to obviate this difficulty the stepped washer shown in Fig. 594 may be used, the steps on opposite sides of the washer being of an equal height. This enables the tool to be raised or lowered without being set out of the horizontal position; but it has the defect that the adjustment cannot be made any finer than the height of the steps, and if the height is made to vary but slightly, in order to refine, as it were, the adjustment, the range of tool elevation or depression is correspondingly limited. Another form of stepped washer is shown in Fig. 595, in which no two steps are of the same height. This affords a wider range of adjustment, because the same two steps will alter the height of the tool by simply turning the washer one-half revolution. It has two defects, however; first, the least amount of adjustment is that due to the difference in height of the steps; and, second, when the tool is elevated it grips the washer at A, so that the tool is not supported across the full width of face of the washer, as it should be. A defect common to all devices in which the tool is thrown out of level, is that the binding screw does not bed fair upon the tool, and as a result it is apt, if screwed home very firmly, as is necessary to hold boring tools that stand far out from the tool post, to spread the screw end as in Fig. 596, or to bend it. A very convenient tool-adjusting device is shown in Fig. 597. It consists of a threaded ring N receiving the threaded bush M, the tool height being adjusted by screwing or unscrewing one within the other. The objection to this is, that it occupies so much vertical height that there is not always room to admit it, which occurs, for example, in compound slide rests on small lathes. On these rests, therefore, a single washer is more frequently used, which answers very well when the tool post is in a slot, so that it can be moved from side to side of the rest as occasion may require. When, however, the position of the tool post is fixed it has the disadvantage that the point P, Fig. 598, where the tool takes its leverage, is too far removed, and the tool is therefore liable to bend or spring from the pressure of the cut. In Fig. 599 is an elevating device sometimes used on the compound rests of large lathes. The top of the rest is provided with a hub H, threaded externally to receive a ring nut R, around whose edge there are numerous holes to receive a pin for operating the nut. The tool-post is situated central in the hub. When the tool is loose the ring nut can be operated by hand or the tool may be gripped lightly and the ring nut operated by a pin. The level of the tool is here maintained; it is supported to about the edge of the rest on account of the large diameter of the ring nut, and a very delicate adjustment for height can be made, but such a device is only suitable for large lathes on account of the depth of the ring nut and hub. [Illustration: Fig. 607.] On small slide-rests the device shown in Fig. 600 is often found. It consists of a holder H, in which is cut a seat for the tool, this seat being inclined to give the piece of steel used as a tool a certain constant degree of angle, and at the same time to permit of the tool being moved endwise in the holder to set it for height; but, as the tool requires to be pushed farther and farther through the holder to raise it, it is not so well supported as is desirable when slight tools are used, unless the holder is made long, so as to pass through the tool post with the tool. Again, it does not support the tool sideways unless the tool steel is dressed up and closely fits the groove in the holder. In Fig. 601 W W are two inverted wedges which afford an accurate adjustment, but the range is limited, because if the wedges have much taper they are apt to move endways when the tool is fastened. A convenient device for the compound rests of small lathes is shown in Fig. 602. It consists of a holder pivoted upon a central post and carrying two tool-binding screws, hence it can be revolved to set the tool in any required position. A similar device is shown in Fig. 603, in which the central post is slotted at A to receive the tool, and also carries a plate C, held by the nut N, and provided with tool-holding screws B and B´, which abut against the top of the rest, a top view of the device being shown in Fig. 604. Plate C may thus be swung around to set the tool in any required position on either side of the rest. In Maudslay's slide rest, the tool clamp shown in Fig. 605 is employed. Screws A are employed to grip the tool moderately firm, and a turn of screws B (whose ends abut against the top of the slide rest) very firmly secures the tool, since it moves the clamp C as a lever, whose fulcrum is the screw A. Figs. 606 and 607 represent the Whitworth tool clamp, the clamping plates of which change about upon the four studs, and are supported at their inner ends by a block equal in height to the height of the tool steel. Figs. 608, 609, 610, and 611 represent the "Lipe" tool post, so called from the name of its inventor. The top of the cross slide is cylindrical, and is bored to receive the tool post which has a cylindrical stem. The cylindrical part of the tool post is split vertically, and has two lips, the bolt D passing through one lip and threading into the other, so that by operating bolt D the tool post may be gripped very firmly or released, so that it may be revolved to bring the tool into any required position after it is fastened in the tool post, which is a great advantage because the tool is brought to a solid seating in the post before its height is adjusted, and will not therefore be altered in height by setting up the set screws as often occurs in ordinary tool posts. From the shape of the tool post, the tool may be gripped by one set screw only, when required for light duty, or by two set screws for heavy duty or for boring, while in either case it is supported clear to the edge of the rest. [Illustration: Fig. 608.] [Illustration: _VOL. I._ =TOOL-HOLDING AND ADJUSTING APPLIANCES.= _PLATE VII._ Fig. 591. Fig. 592. Fig. 593. Fig. 594. Fig. 595. Fig. 596. Fig. 597. Fig. 598. Fig. 599. Fig. 600. Fig. 601. Fig. 602. Fig. 603. Fig. 604. Fig. 605. Fig. 606.] Fig. 608 shows the tool in position, held by a single screw, for work requiring the tool to be close up to the work driver. In Fig. 609 a tool is shown held as is required by work between centres, but both set-screws are used. Fig. 610 shows a tool in position for boring, two set-screws being used. Fig. 611 shows a tool being held for the same purpose, but by a single screw, and it will be observed that the advantage of the second set-screw is obtained without in any way sacrificing the handiness of the post, when used with a single screw. Whether one or two set-screws are used, the boring tool may be forged from a single bar of octagon steel, which can be seated in a piece like that shown at E in Fig. 610, which is grooved so as to receive and hold the tool. As is well known, boring tools are the most troublesome both to forge and to adjust in the lathe, and, as the result, a light tool is often used because no other is at hand and it is costly to make a new one. When, however, the tool can be forged from a plain piece of steel, these objections are overcome, and a sufficient number of tools may be had so that one can always be found suitable for any ordinary sized hole, the object being to use as rigid a tool as can be got into the hole bored. The feature of maintaining the tool level is of great importance in boring work, because when the tool requires to be set out of level to adjust its height, it will generally strike against the mouth of the hole if the latter is of much depth. This annoyance is also frequently met with in boring tools which are forged out of rectangular steel, because the rounded stem is generally left taper. The largest end of the taper is generally nearest the tool post. Hence the capacity to use octagon steel and keep it level while adjusting its height, added to the fact that the tool is supported clear to the edge of the tool rest, and the tool post is so blocked as to virtually become a part of the rest, constitute a very important advantage. [Illustration: Fig. 609.] [Illustration: Fig. 610.] A common device on large lathes is shown in Fig. 612, the two clamps being shown in position for outside turning, and being changed (so as to stand at a right angle to the position they occupy in the figure) for holding boring tools. The bolts are enveloped by spiral springs which support the clamps. Figs. 613 and 614 represent the tool holders employed in the Brown and Sharpe small screw machines. In the front rest, Fig. 613, the piece R receives two adjusting and tool-gripping screws S, upon which sits the gib G, and upon this the tool is placed. The surface E at the top of the tool post slot is curved so that it will bear upon the top of the tool at a point only. The tool is here supported along the full length of the gib, and there is no set-screw at the top of the tool post, which enables a much more unobstructed view of the tool. Fig. 614 is the tool post used at the back of the rest, the piece B passing through the tool post slot. The tool rests upon the top of screw E and upon the top of B at F, and is secured by set-screw S; its height is therefore adjusted by means of screw E, which is threaded in B. The set-screw S is not in this case objectionable, because it is at the back of the rest, and therefore does not obstruct the view of the work, while it is at the same time convenient to get at. When the screw for traversing a lathe carriage is used for plain feeding, it is termed the feed screw, but when it is used to cut threads it is termed the lead screw. A lead screw should be used for screw cutting only, so that it may be preserved as much as possible from wear. As the greater portion of threads cut in a lathe of a given size are short in comparison with the length of the lathe, it follows that the part of the lead screw that is in operation when the carriage or saddle is traversing over short work is most worn, while the other end is least worn, hence it is not unusual to so construct the screw and its bearings that it may be changed end for end in the lathe, to equalize the wear. By turning a lead screw end for end, therefore, to equalize the wear, the middle of the length of the screw will become the least worn, and, therefore, the most true. Hence it is better to use one end of the lead screw for general work, and to reverse it and use the other end only for screws requiring to be of very correct pitch. [Illustration: Fig. 611.] [Illustration: Fig. 612.] [Illustration: Fig. 613.] [Illustration: Fig. 614.] To obviate the wear as much as possible the feed nut should embrace as great a length of the screw as convenient, and should be of a material that will suffer more from wear than the lead screw, or in other words shall relieve the feed screw from wear as much as possible. The wear on the nut being equal from end to end, the wearing away of one side of its thread does not vary its pitch; hence the only consideration as to its wearing qualification are the expense of its renewal and the length of time that may occur between its being engaged with the lead screw and giving motion to the lathe carriage, this time increasing in proportion as the nut thread is worn. Under quick speeds or when the lathe is in single gear, the rotation of the feed screw is so quick that not much time is lost before the carriage feeds, but when the back gear is in operation at the slowest speeds, the loss of time due to a nut much worn is an item of importance. In some lathes the feed screw is employed for screw cutting and for operating an independent feed also. This is accomplished by cutting a feather way or spline along it, so that a worm having journal bearing in the apron of the rest carriage may envelop the lead screw and be driven by it, through the medium of a feather fast into the worm gear. The motion obtained from the worm gear is transferred through suitable gearing to the rack pinion. The spline is cut deeper than the thread, so as to prevent the latter as far as possible from wear, by reason of the friction of the spline. The lead screw if long should be supported, to prevent its sagging of its own weight. In some cases the lead screw is supported in a trough along its whole length, as is done in the Sellers lathe. In other cases, bearings hanging from the [V]-slides, and movable along the bed, are employed. It is desirable that the feed screw and nut be as near the middle of the carriage as possible, so that it shall pull the carriage at as short a leverage as possible, thus avoiding the liability to tilt or twist the carriage; but it is not practicable to place it midway between the lathe shears, because in that case the cuttings, &c., from the work would fall upon it, and cause excessive and rapid wear of the screw and nut. In general the lead screw is located either in front, or at the back of the lathe, and in considering the more desirable of the two locations, we have as follows: The feed nut should obviously remain axially true with the lead screw, as by reason of the extra weight of the front of the carriage, both it and the lathe shears wear most at the front, and the carriage, therefore, falls to the amount of its own wear and the wear of the shears. If the lead screw is used to feed with (as it should not be), the nut wears coincidently with the carriage and the shears, and the screw alignment is not impaired; but with an independent feed, only a small portion of the carriage traversing is done with the lead screw, hence the carriage lowers from the wear due to the independent feeding, and when the lead screw comes to be used its nut is not in true alignment with it. It is obviously preferable, then, to place the lead screw at the back, where the carriage and shears wear the least. Furthermore, this relieves the carriage front from the weight of the nut, &c., tending to equalize the back and front wear, while removing the nut-operating device from the front to the back of the shears, and thus reducing the number of handles in front, and thus avoid complication in small lathes. LATHE LEAD SCREWS.--Lead screws have their pitches in terms of the inch throughout all parts of the world; or, in other words, the lead screws of all lathes contain so many full threads per inch of length. Lead screws are usually provided with square threads of the usual form, or with threads whose sides have about fifteen degrees of angle, so that the two halves of the feed nut may be let together to take up the wear. It is obvious that in a [V]-thread or in a thread whose sides are at an angle, the feeding strain tends to force the two halves of the feed nut apart, and therefore places a strain on the feed-nut operating mechanism that does not exist in the case of a square thread. Furthermore it can be shown that with a [V]-thread the opportunities to lock the carriage on a wrong place, after traversing it back by hand in screw cutting, are increased, thus augmenting the liability to cut intermediate and improper threads. [Illustration: Fig. 615.] In Fig. 615, for example, we have a pitch of lead screw of three threads per inch, and the gears arranged to cut six threads per inch on the work. As the bottom wheel has twice as many teeth as the top one, it is clear that, while the top one makes one, the bottom one will make half revolution, and the lead screw will make half a turn for every turn the work makes. Now, suppose the tool point to stand opposite to space A, and the nut (supposing it to have but one thread only, which is all that is required for our purpose), stand opposite to space D. Suppose, further, that the lathe makes one revolution, and space B on the work will have moved to occupy the position occupied by space A, or, rather, there will still be a place at A fully in front of the tool, as should be the case, but the lead screw will have made half revolution, the top _e_ of the thread coming opposite to the feed nut, as in the position of tool and nut shown in the figure at T and N; hence the nut would not engage, without moving the lathe carriage sideways, and thus throwing the tool to one side of the thread in the work. When, however, the work had made another revolution, both the feed screw and the work would again come into position for the tool and nut to engage properly, and it follows that in this case the tool will always fall into proper position for the nut to be locked. It is obvious, however, that had the lead screw thread been a square one, and the nut thread to accurately fit to the lead screw thread, so as to completely fill it, then the nut could not engage with the lead screw until the lathe had made a complete revolution, at which time the work will have made two full or complete revolutions, and the tool would, therefore, fall into proper position to follow in the groove or part of a thread cut at the first tool traverse. [Illustration: Fig. 616.] In Fig. 616, we have the same lead screw geared to cut five or an odd number of threads per inch. The tool and the nut are shown in position to properly engage, but suppose, the nut being disengaged, that the work makes one revolution, and during this period the lead screw will have made 3/5ths of a revolution, hence the nut will not be in position to engage properly, because, although space B will have travelled forward so as to occupy the position of space A in the figure (that is, there will be a space fairly in front of the tool point), yet the nut will not engage properly, because the nut point will not be opposite to the bottom of the lead screw thread. When the work has made its second revolution, and space C moves to the position occupied by A, the lead screw will have made 6/5 or 1-1/5 revolutions, and the nut cannot engage properly; when the lathe has made its third revolution, the lead screw will have made 1-4/5 revolutions and the nut will still fall to one side of the thread space, and will not lock properly. The work having made its fourth turn, the lead screw will have made 2-2/5 turns, and the nut will not be in position to lock fairly. The work having made its fifth turn, however, the lead screw will have made three turns, and the threads will fall into the same position that they occupy in the figure, and both tool and feed nut will fall into their proper positions in their respective threads. It does not follow, however, that, the lead screw having a [V]-shaped thread, the nut cannot be forced to engage but once in every five turns of the lead screw, because, were this the case, it would be impossible to lock the nut in an improper position. [Illustration: Fig. 617.] Suppose, for example, that we have in Fig. 617, the same piece of work and lead screw as in Fig. 616, and that a first groove, A, has been cut with the tool in the position shown, and the nut engaged in the position marked 1. Now, suppose the nut be disengaged and the work allowed to make one revolution, then the lead screw will, during this revolution, revolve 3/5 of a revolution, and the position of the nut point with relation to the lead screw will be as at position 2. If, then, the nut was forced into the lead screw thread, it would, acting on the wedge principle, move the carriage to the right sufficiently to permit the nut to engage fully in thread G, and the tool would then cut a second groove on thread B. If the nut then be withdrawn from thread G, and the work allowed to make another revolution, the nut will stand in a precisely similar position with relation to the lead screw thread as it did in position 2, and by forcing it down into thread H the carriage would be again forced to the right, causing a third thread, C, to be cut. By repeating the operation of withdrawing the nut, letting the work make another revolution and then engaging the nut again, it will seat in thread K, and a fourth thread D will be cut. On again repeating the operation, however, the nut will come into position 5, and, on being drawn home into thread, or, rather, into space L, the tool will fall into groove A again. Thus there will be four threads, each having a pitch equal to that of the lead screw. The second (B) of these four will fall to the left of thread A to an amount or distance equal to 2/5 of the pitch of the lead screw, because, in forcing the nut from position 2 down into the lead screw, the slide rest, and therefore the tool, will be moved to the right 2/5 of the pitch of the lead screw. The third thread C will fall to the left of thread B also to an amount equal to 2/5 of the pitch of the lead screw, because, in forcing the thread to seat itself into thread H from position 3, the slide rest was again moved (to that amount) to the right. The fourth thread D will fall to the left of thread C to the same amount and for the same reason. But in this case, as before, if the lead screw had a square thread and the nut threads completely filled the spaces between the lead screw threads, then the nut could not engage at the 2nd, 3rd, or 4th work revolution, hence the false threads B, C, and D, could not have been cut, even though the feed nut was disengaged and the lathe carriage was traversed back by hand. Now, suppose that two threads on the work measure less than the amount the lead screw advances during the time that the work makes a revolution, and if the lead screw has a [V]-shaped thread, the case is altered. We have, for example, in Fig. 618, a pitch of lead screw of 3 to cut 12 and 13 threads respectively. In the case of the 13 threads it will be seen that, supposing there to have been a first cut taken on the work, and the feed nut to be disengaged while the work makes a revolution, then the lead screw will revolve 3/13 revolution and the point A on the lead screw will have moved up to point B, and the nut point remaining at N, seating it in the thread, would cause it to engage with the same thread that it did before, and no second thread would be cut. If the nut be then released, the work allowed to make another revolution and the nut again closed, the operation would be the same as before, and no error would be induced, and so on. Suppose, further, that after the nut was disengaged the lathe was permitted to make two revolutions, and the lead screw would make 6/13, or less than half a turn, and closing it would still cause it to pass back into the same thread on the lead screw and produce correct work. But if after the nut was released the work made three turns, the lead screw would make 9/13 of a turn, and the nut would fall on the right-hand side of the lead screw thread, and in closing would move the lathe carriage to the right, causing the tool to cut a second thread. Now, the same operation that occurred with the first thread would during the next three trials occur with the second thread, and at the next or seventh trial a third thread would be cut, which would be again operated upon during the next succeeding three trials. At the eleventh trial a fourth thread would be cut, but on the next three trials the tool would again fall into the groove first cut and the work proceed correctly. In the case of the 12 threads, the thread cut at the first and second trials would be correct. At the third trial the nut would seat itself in the groove C of the lead screw, causing the carriage to move to the right to a distance equal to twice the pitch of thread being cut, but the tool would still fall into the same groove in the work, as it also would on the fourth. At the fifth trial the process would be repeated, and so on, so that no second thread would be cut. [Illustration: Fig. 618.] It may now be noted that if we draw the lead screw and the thread to be cut as in the figure, and draw the dotted lines shown, then those that meet the bottom of the thread on the lead screw, and also meet the groove cut on the work, at the first trial, represent the cases in which the nut will fall naturally into its proper position for the tool to fall into the correct groove, while whenever the nut is being forced home it seats in a groove in the lead screw, the bottom of which groove meets a line drawn from the first thread cut; the results obtained will be made correct by reason of the movement given to the slide nut when artificially seating the nut. This is shown to be the case in Fig. 619, which represents a lead screw having an even number of threads per inch, and from which it appears that in cutting 12 threads (an even number also) the nut cannot be engaged wrong, whereas in the case of 13 threads it can be engaged right three times in 13 trials, and 10 times wrong, the latter causing the tool to cut three wrong threads. [Illustration: Fig. 619.] To prevent end motion of a lead screw it should have collars on both sides of one bearing, and not one at each bearing. By this means the screw will be permitted to expand and contract under variations of atmospheric temperature, without binding against the bearing faces. When a lead screw is long it requires to be supported, otherwise, either its weight will be supported or lifted by the feed nut in gear, or if that nut does not lift the screw, the thread cut will be finer than that due to the pitch of the lead screw, by reason of its deflection or sag. A lead screw should preferably be as near as possible to the middle of the lathe shears, and as close to the surface as possible, so as to bring it as nearly in line with the strain on the tool as possible, but on account of the cuttings, which falling upon the screw would cause it to wear rapidly, it is usual to locate it on one side, so as to protect it from the cuttings. It is better to locate it on the front side of the lathe rather than on the back, because the strain of the cut falls mainly on the front side (especially in work of large diameter when this strain is usually greatest) and it is desirable to pull the carriage as near in a line with the resistance of the cut as possible, because the farther off the feed nut from the cutting tool point, the greater the tendency to twist the carriage on the shears. To preserve the nut from wear, it should be made as long as convenient, as, say, five or six times the diameter of the lead screw; it is usually made, however, three or four diameters. It is obvious that the pitch of the thread should be as accurate as possible, but it has not as yet been found practicable to produce a screw so accurate that it would not show an error, if sufficient of its length be tested, as, say, several feet. If the error in a screw be equal, and in the same direction at all parts of its length, various devices may be employed to correct it. Thus Fig. 620 represents a device employed by the Pratt and Whitney Co. It was first ascertained by testing the lathe that its lead screw was too short by 7/100ths of a revolution in a length of 2 feet, the pitch of its thread being 6 to an inch. Now in 2 feet of the screw there would be 144 threads, and since 7/100ths (the part of a revolution the thread was too short) × 1/6 (the pitch of the thread) = 7/600ths (which was called 1/85th), the error amounted to 1/85th inch in 144 turns of the screw. The construction of the device employed to correct this error is as follows: In Fig. 620, A represents the bearing of the feed screw of the lathe, and B _b_ a sleeve, a sliding fit upon A, prevented from revolving by the pin _h_, while still having liberty to move endways. C represents a casing affording journal bearing to B _b_, having a fixed gear-wheel at its end C´, and an external thread upon a hub at that end. D is the flange of C to fasten the device to the shears of the latter, being held by screws. E represents an arm fast upon the collar of the feed screw, and carrying the pinion F, the latter being in gear with the pinion C´, and also with G, which is a pinion containing two internal threads, one fitting to B at _b_, and the other fitting to C at _c_, the former having a pitch of 27 threads to an inch, the latter a pitch of 25 to an inch. [Illustration: Fig. 620.] The operation is as follows:--The ordinary change wheels are connected to the feed screw, or lead screw, as it is sometimes termed, at J in the usual manner. The arm E being fast to the feed screw will revolve with it, and cause the pinion F to revolve around the stationary gear-wheel C´. F also gears with G. Now, F is of 12 diametrical pitch and contains 26 teeth, C´ is of 12 diametrical pitch and contains 37 teeth, and G is of 12 diametrical pitch and contains 36 teeth. It follows that the pinion F, while moving around the fixed gear C´, will revolve the pinion G (which acts as a nut), to an amount depending upon the difference in the number of its teeth and those of fixed gear C´ (in this case as 36 is to 37), and upon the difference in the pitches of the two threads, so that at each revolution G will move the feed screw ahead of the speed imparted by the change gears, the end of the sleeve B abutting against the collar of the feed screw to move it forward. In this case there are 36 turns of the feed screw A for one turn of the nut pinion G, the thread on sleeve B being 27, and that on the hub of C being 25 to the inch; hence, 36 turns of the feed screw gives an end motion to the sleeve B of 1/25 minus 1/27 = 2/675, and 1/36 of that = 1/12150 of an inch = the amount of sliding motion of the sleeve _b_, for each revolution of the lathe feed screw. By varying the proportions between the number of teeth in C´ and G and the pitches of the two threads in a proper and suitable ratio, the device enables the cutting of a true thread from any untrue one in which the variation is regular. It is usual to fasten to the side of the lathe head stock a brass plate, giving a table of threads, and the wheels that will cut them, and obviously such tables vary according to the pitch of the lead screw, but a universal table may be constructed, such as the following table (prepared by the author) that will serve for any lathe. At the top of the table is the number of teeth in wheels, advancing by four from 12 to 80 teeth, but it may be carried as much beyond 80 as desired. On the left hand of the table is a column of the same wheels. At the bottom of the scale are pitches of lead screw from 3 up to 20 threads per inch. Over each lead screw pitch are thread pitches, thus on lead screw pitch 4 we have 20, 19, 18, and so on. The use of the table is as follows:-- Find the pitch of the lead screw, and at the head of that column is the number of teeth for the lathe stud or mandril. Then find in that column the number of threads to be cut, and on the same line, but at the left hand, will be found the number of teeth for the lead screw. NUMBERS OF TEETH FOR WHEEL TO GO ON LATHE SPINDLE, LATHE STUD, OR MANDRIL. ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- Lead |12|16|20|24|28|32|36| 40| 44| 48| 52| 56| 60| 64| 68| 72| 76| 80 Screw.| | *| | | | | | | | | | | | | | | | ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 12 | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 16 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 20 | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 24 | 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 28 | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 32 | 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 36 | 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 40 |10|10|10|10|10|10|10| 10| 10| 10| 10| 10| 10| 10| 10| 10| 10| 10 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 44 |11|11|11|11|11|11|11| 11| 11| 11| 11| 11| 11| 11| 11| 11| 11| 11 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 48 |12|12|12|12|12|12|12| 12| 12| 12| 12| 12| 12| 12| 12| 12| 12| 12 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- *52 |13|13|13|13|13|13|13| 13| 13| 13| 13| 13| 13| 13| 13| 13| 13| 13 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 56 |14|14|14|14|14|14|14| 14| 14| 14| 14| 14| 14| 14| 14| 14| 14| 14 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 60 |15|15|15|15|15|15|15| 15| 15| 15| 15| 15| 15| 15| 15| 15| 15| 15 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 64 |16|16|16|16|16|16|16| 16| 16| 16| 16| 16| 16| 16| 16| 16| 16| 16 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 68 |17|17|17|17|17|17|17| 17| 17| 17| 17| 17| 17| 17| 17| 17| 17| 17 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 72 |18|18|18|18|18|18|18| 18| 18| 18| 18| 18| 18| 18| 18| 18| 18| 18 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 76 |19|19|19|19|19|19|19| 19| 19| 19| 19| 19| 19| 19| 19| 19| 19| 19 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- 80 |20|20|20|20|20|20|20| 20| 20| 20| 20| 20| 20| 20| 20| 20| 20| 20 ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- Lead | | | | | | | | | | | | | | | | | | Screw |3.|4.|5.|6.|7.|8.|9.|10.|11.|12.|13.|14.|15.|16.|17.|18.|19.|20. Pitch | | | | | | | | | | | | | | | | | | ------+--+--+--+--+--+--+--+---+---+---+---+---+---+---+---+---+---+--- EXAMPLE.--The lead screw has a pitch of 4, and I require to cut 13 threads per inch. At the head of the column is 16, and on a line with the 13 of the column, but on the left is 52, each number being marked by a * hence the 16 and 52 are the wheels; if we have not those wheels, multiply both by 2 and 32, and 104 will answer. If the pitch of the lead screw is 2 threads per inch, the wheels must advance by 6 teeth, as indicated below:-- NUMBERS OF TEETH FOR WHEEL TO GO ON LATHE STUD, LATHE SPINDLE OR MANDRIL. +-----+--------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | |Lead |12|18|24|30|36|42|48|54|60|66|72|78|84|90|96| | |Screw. | | | | | | | | | | | | | | | | |NUM- +--------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |BER | 12 | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| |OF | 18 | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| |TEETH| 24 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| |FOR | 30 | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| |WHEEL| 36 | 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| |TO | 42 | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| |GO | 48 | 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| |ON | 54 | 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| |LEAD | 60 |10|10|10|10|10|10|10|10|10|10|10|10|10|10|10| |SCREW+--------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | |Pitch of| | | | | | | | | | | | | | | | | |Lead | 2| 3| 4| 5| 6| 7| 8| 9|10|11|12|13|14|15|16| | |Screw. | | | | | | | | | | | | | | | | +-----+--------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ This table may be used for compound lathes by simply dividing the pitch of the lead screw by the ratio of the compounded pair of wheels. For example, for the wheels to cut 8 threads per inch, the pitch of lead screw being 4 and the compounded gears 2 to 1, as the ratio of the compounded pair is 2 to 1, we divide the pitch of lead screw by 2, which gives us 2, and we thus find the wheels in the column of pitch of lead screw 2, getting 12 and 48 as the required wheels, the 12 going on top of the lathe because it is at the top of the table, and the 48 on the lead screw because it is at the left-hand end of the table, and the lead screw gear is at the left-hand end of the lathe. The table may be made for half threads as well as whole ones by simply advancing the left-hand column by two teeth, instead of by four, thus:-- +------+--------------------------------------------------------------+ |Teeth | Teeth for Wheel on Stud. | | for |------+------+------+------+------+------+------+------+------+ |Wheel | | | | | | | | | | | on | 12 | 16 | 20 | 24 | 28 | 32 | 36 | 40 | 44 | | Lead | | | | | | | | | | |Screw.| | | | | | | | | | +------+------+------+------+------+------+------+------+------+------+ | 12 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | +------+------+------+------+------+------+------+------+------+------+ | 14 | 3-1/2| 3-1/2| 3-1/2| 3-1/2| 3-1/2| 3-1/2| 3-1/2| 3-1/2| 3-1/2| +------+------+------+------+------+------+------+------+------+------+ | 16 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | +------+------+------+------+------+------+------+------+------+------+ | 18 | 4-1/2| 4-1/2| 4-1/2| 4-1/2| 4-1/2| 4-1/2| 4-1/2| 4-1/2| 4-1/2| +------+------+------+------+------+------+------+------+------+------+ | 20 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | +------+------+------+------+------+------+------+------+------+------+ | 22 | 5-1/2| 5-1/2| 5-1/2| 5-1/2| 5-1/2| 5-1/2| 5-1/2| 5-1/2| 5-1/2| +------+------+------+------+------+------+------+------+------+------+ | 24 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | +------+------+------+------+------+------+------+------+------+------+ | 26 | 6-1/2| 6-1/2| 6-1/2| 6-1/2| 6-1/2| 6-1/2| 6-1/2| 6-1/2| 6-1/2| +------+------+------+------+------+------+------+------+------+------+ | 28 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | +------+------+------+------+------+------+------+------+------+------+ | 30 | 7-1/2| 7-1/2| 7-1/2| 7-1/2| 7-1/2| 7-1/2| 7-1/2| 7-1/2| 7-1/2| +------+------+------+------+------+------+------+------+------+------+ | 32 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | +------+------+------+------+------+------+------+------+------+------+ | 34 | 8-1/2| 8-1/2| 8-1/2| 8-1/2| 8-1/2| 8-1/2| 8-1/2| 8-1/2| 8-1/2| +------+------+------+------+------+------+------+------+------+------+ | 36 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | +------+------+------+------+------+------+------+------+------+------+ | 38 | 9-1/2| 9-1/2| 9-1/2| 9-1/2| 9-1/2| 9-1/2| 9-1/2| 9-1/2| 9-1/2| +------+------+------+------+------+------+------+------+------+------+ | 40 |10 |10 |10 |10 |10 |10 |10 |10 |10 | +------+------+------+------+------+------+------+------+------+------+ | 42 |10-1/2|10-1/2|10-1/2|10-1/2|10-1/2|10-1/2|10-1/2|10-1/2|10-1/2| +------+------+------+------+------+------+------+------+------+------+ |Pitch | | | | | | | | | | | of | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 |11 | | Lead | | | | | | | | | | |Screw.| | | | | | | | | | +------+------+------+------+------+------+------+------+------+------+ For quarter threads we advance the left-hand column by one tooth, or for thirds of threads by three teeth, and so on. If we require to find what wheels to provide for a lathe, we take the pitch of the lead screw for the numerator, and the pitch required for the denominator, and multiply them first by 2, then by 3, then by 4, and so on, continuing until the numerator or denominator is as large as it can be to give the required proportion of teeth, and not exceed the greatest number that the largest wheel can contain. For example: A lathe has single gear, and its lead screw pitch is 8 per inch, what wheels will cut 18, 17, 16, 15, 14, or 13 threads per inch? Wheels. Pitch of lead screw 8 16 24 32 -- × 2 = -- -- -- Pitch required 18 36 54 72 Pitch of lead screw 8 16 24 32 -- " -- -- -- Pitch required 17 34 51 68 Pitch of lead screw 8 16 24 32 -- " -- -- -- Pitch required 16 32 48 64 Pitch of lead screw 8 16 24 32 -- " -- -- -- Pitch required 15 30 45 60 Pitch of lead screw 8 16 24 32 -- " -- -- -- Pitch required 14 28 42 56 Pitch of lead screw 8 16 24 32 40 -- " -- -- -- -- Pitch required 13 26 39 52 65 If we suppose that the greatest number of teeth permissible in one wheel is not to exceed 100, then in this table we have all the combinations of wheels that can be used to cut the given pitches; and having made out such a table, comprising all the pitches to be cut, we may select therefrom the least number of wheels that will cut those pitches. The whole table being made out it will be found, of course, that the numerators of the fractions are the same in each case; that is, in this case, 16, 18, 24, 32, and so on as far as we choose to carry the multiplication of the numerator. We shall also find that the denominators diminish in a regular order: thus taking the fractions whose numerators are in each case 16, we find their denominators are, as we pass down the column, 36, 34, 32, 30, 28, and 26, respectively, thus decreasing by 2, which is the number we multiplied the left-hand column by to obtain them. Similarly in the fractions whose numerators are 24, the denominators diminish by 3, being respectively 54, 51, 48, 45, 42, and 39; hence the construction of such a table is a very simple matter so far as whole numbered threads are concerned, as no multiplication is necessary save for the first line representing the finest pitch to be cut. For fractional threads, however, instead of using the pitch of the lead screw for the numerator, we must reduce it to terms of the fraction it is required to cut. For example, for 5-1/2 threads we proceed as follows. The pitch of the lead screw is 8, and in 8 there are 16 halves, hence we use 16 instead of 8, and as in the 5-1/2 there are 11 halves we use the fraction 16/11 and multiply it first by 2, then by 3, and then by 4, and so on, obtaining as follows: 16/11, 32/22, 48/33, 64/44, obtaining as before three sets of wheels either of which will cut the required pitch. In selecting from such a table the wheels to cut any required number of pitches, the set must, in order to cut a thread of the same pitch as the lead screw, contain two wheels having the same number of teeth. Now, suppose that the pitch of the lead screw was 6 instead of 8 threads per inch, and the table will be as follows:-- 6 12 18 24 -- -- -- -- 18 36 54 72 6 12 18 24 -- -- -- -- 17 34 51 68 6 12 18 24 -- -- -- -- 16 32 48 64 6 12 18 24 -- -- -- -- 15 30 45 60 6 12 18 24 -- -- -- -- 14 28 42 56 6 12 18 24 -- -- -- -- 13 26 39 52 Here, again, we find that in the first vertical column the denominators decrease by two for each thread less per inch, in the second column they decrease by three, and in the third by four; this decrease equalling the number the first fraction was multiplied by. But suppose the lead screw pitch is an odd one, as, say, 3 threads per inch, and we construct the table as before, thus-- Pitch of lead screw 3 6 9 12 15 -- -- -- -- -- Pitch to be cut 18 32 54 72 90 Now it is useless to multiply by 2 or by 3, because they give a less number of teeth than the smallest wheel should have, hence the first multiplier should be 4, giving the following table:-- 3 12 15 18 -- -- -- --- 18 72 90 108 3 12 15 18 -- -- -- --- 17 68 85 102 3 12 15 18 -- -- -- -- 16 64 80 96 3 12 15 18 -- -- -- -- 15 60 75 90 By continuing the table for other pitches we shall find that in the first vertical column the denominators diminish by 4, the second column by 5, and the third by 6; and it is seen that by diminishing the pitch of the lead screw, we have rendered necessary one of two things, which is, that either larger wheels containing more teeth must be used, or the change gears must be compounded. Assuming that the pitch of the lead screw was 5 per inch, the table would be as follows:-- 5 15 20 25 -- × 3 = -- -- -- 18 54 72 90 5 15 20 25 -- " -- -- -- 17 51 68 85 5 15 20 25 -- " -- -- -- 16 48 64 80 The wheels in the first column here decrease by 3, the second by 4, and the third by 5. In nearly all lathes the advance or decrease is by 4 or by 6. In determining this rate of advance or decrease, there are several elements, among which are the following. Suppose the lathe to be geared without compounding, then the distance between the lathe spindle and the lead screw will determine what shall be the diameters of the largest and of the smallest wheel in the set, it being understood that the smallest wheel must not contain less than 12 teeth. Assume that in a given case the distance is 10 inches, and it is obvious that the pitch of the teeth at once commands consideration, because the finer the pitch the smaller the wheel that will contain 12 teeth, and the larger the wheel on the lead screw may be made. Of course the pitch must be coarse enough to give the required tooth strength. Let it be supposed that the arc pitch is 3/4-inch, then the pitch circumference of a 12-toothed wheel would be 9 inches and its radius 1.432 in.; this subtracted from the 10 leaves 8.568 in. as the radius, or 17.136 in. as the largest diameter of wheel that can be used on the lead screw, supposing there to be no intermediate gears. Now a wheel of this diameter would be capable of containing more than 75 teeth, but less than 76. But from the foregoing tables it will be seen that it should contain a number of teeth divisible either by 4 or by 6 without leaving a remainder, and what that number should be is easily determined by means of a table constructed as before explained. Thus from the tables it would be found that 72 teeth would be best for a lead screw having a pitch of either 8, 6, 5, or 3 threads per inch, and the screw-cutting capacity of the lathe would (unless compounded) be confined to such pitches as may be cut with wheels containing between 12 and 72 teeth both inclusive. But assume that an arc pitch of 3/8-inch be used for the wheel teeth, and we have as follows: A wheel of this pitch and containing 12 teeth will have a radius of 7-16/1000 inches, leaving 9.284 in. as the radius of the largest wheel, assuming it to gear direct with the 12-tooth pinion. With this radius it would contain 155 teeth and a fraction of a tooth; we must, therefore, take some less number, and from what has been said, it will be obvious that this lesser number should be one divisible by either 4 or 6. If made divisible by 6, the number will be 150, because that is the highest number less than 155 that is divisible by 6 without leaving a remainder. But if made divisible by 4, it may contain 152 teeth, because that number is divisible by 4 without leaving a remainder. With 150 teeth the latter could cut a thread 12-1/2 times as fine as the lead screw, because the largest wheel contains 12-1/2 times as many teeth as the smallest one; or it would cut a thread 12-1/2 times as coarse as the lead screw, if the largest wheel be placed on the mandril and the smallest on the lead screw. With 152 teeth the lathe would be able to cut a thread 12-84/100 times as fine or as coarse as the lead screw. Unless, however, the lathe be required to cut fractional pitches, it is unnecessary that the largest wheel have more teeth than divisible, without leaving a remainder, by the number of teeth in the smallest wheel, which being 12 we have 144 as the number of teeth for the largest wheel. In the United States standard pitches of thread, however, there are several pitches in fractions of an inch, hence it is desirable to have wheels that will cut these pitches. LATHE SHEARS OR BEDS.--The forms of the shears and beds may be classified as follows. The term shear is generally applied when the lathe is provided with legs, while the term bed is used when there are no legs; it may be noted, however, that by some workmen the two terms of _shear_ and _bed_ are used indiscriminately. The forms of shears in use on common lathes are, in the United States, the raised [V], the flat shear and the shear, with the edge at an angle of 90° or with parallel edges. In England and on the continent of Europe, the flat shear is almost exclusively employed. Referring to the raised [V] it possesses an important advantage in that, first, the slide rest does not get loosely guided from the wear; and second, the wear is in the direction that least affects the diameter of the work. [Illustration: Fig. 621.] In Fig. 621, for example, is a section of a lathe shear, with a slide rest shown in place, and it will be observed that the wear of the [V] upon the lathe bed, and of the [V]-groove in the slide rest, will cause the rest to fall in the direction of arrow A, and that a given amount of motion in that direction will have less effect in altering the diameter than it would in any other direction. This is shown on the right hand of the figure as follows: Suppose the cutting point of the tool is at _a_, and the work will be of the diameter shown by the full circle in the figure. If we suppose the tool point to drop down to _f_, the work would be turned to the diameter denoted by dotted arc _g_, while if the tool were moved outwards from _a_ to _c_ the work would be turned to the diameter _e_. Now since _f_ and _c_ are equidistant from the point _a_, therefore the difference in the diameters of _e_ and _g_ represents the difference of effect between the wear letting the rest merely fall, or moving it outwards, and it follows that, as already stated, the diameter of the work is less affected by a given amount of wear, when this wear is in the direction of A, than when it is in the direction of B. When the carriage is held down by a weight as is shown in Figs. 577 and 578, there is therefore no lost motion or play in the carriage, which therefore moves steadily upon the shears, unless the pressure of the cut is sufficient in amount, and also in a direction to lift the carriage (as it is in the case of boring with boring tools); but to enable the carriage to remain firm upon the shears under all conditions, it is necessary to provide means to hold it down upon the [V]s, which is done by means of gibs G, G, which are secured to the carriage, and fit against the bottom of the bed flange as shown. Now since lathes are generally used much more frequently on short than on long work, therefore the carriage traverses one part of the shears more than another, and the [V]s wear more at the part most traversed, and it follows that if gibs G are set to slide properly at some parts they will not be properly set at another or other parts of the length of the shears; hence the carriage will in some parts have liberty to move from the bed, there being nothing but the weight of the carriage, &c., to hold it down to the [V]s. Now, the wear in the direction of A acts directly to cause this inequality of gib fit, whereas that in the direction of B does so to a less extent, as will appear hereafter. Meantime it may be noted that when the carriage is held down by a suspended weight the shears cannot be provided with cross girts, and are therefore less rigid and more subject to torsion under the strain of the cut; furthermore the amount of the weight must be sufficient to hold the carriage down under the maximum of cut, and this weight acts continuously to wear the [V]s, whether the carriage is under cutting duty or not, but the advantage of keeping the carriage firmly down upon the [V]s is sufficiently great to cause many to prefer the weighted carriage for light work driven between the lathe centres. [Illustration: Fig. 622.] Fig. 622 represents the flat shear, the edges being at an angle and the fit of the carriage to the shears being adjusted by the gibs at _a_ _a_, which are set up by bolts _c_ _c_ and _d_ _d_. In this case there is a large amount of wearing surface at _b_ _b_, to prevent the fall of the carriage _c_, but the amount of end motion (in the direction of B, Fig. 621), permitted to the carriage by reason of the wear of the gibs and shear edges, is greater than the amount of the wear because of the edges being at an angle. It is true that the amount of fall of the carriage on the raised [V] is also (on account of the angle of the [V]) greater than the actual amount of the wear, but the effect upon the work diameter is in this case much greater, as will be readily understood from what has already been said. The wearing surface of the raised [V] may obviously be increased by providing broader [V]s, or two [V]s instead of having four. This would tend to keep the lathe in line, because the wear due to moving the tailblock would act upon those parts of the shear length that are less acted upon by the carriage, and since the front journal and bearing of the live spindle wear the most, the alignment of the lathe centres would be more nearly preserved. [Illustration: Fig. 623.] Fig. 623 represents another form of parallel edged shears in which the fit of the carriage to the shears is effected at the front end only, the other or back edge being clear of contact with the carriage, but provided with a gib to prevent the carriage from lifting. This allows for any difference in expansion and contraction between the carriage and the shears, while maintaining the fit of the carriage to the bed. [Illustration: Fig. 624.] A modification of this form (both these forms being taken from "Mechanics") is shown in Fig. 624, in which the underneath side of the front edge is beveled so that but one row of screws is required to effect the adjustment. [Illustration: Fig. 625.] Fig. 625 represents a form of bed in which the fit adjustment is also made at the front end only of the bed, and there is a flange or slip at _a_, which receives the thrust outwards of the carriage; and a similar design, but with a bevelled edge, is shown in Fig. 626. [Illustration: Fig. 626.] [Illustration: Fig. 627.] In Fig. 627 is shown a lathe shear with parallel edges, the fit being adjusted by a single gib D, set up by set-screws S. In this case the carriage will fall or move endwise, to an amount equal to whatever the amount of the wear may be, and no more, but it may be observed that in all the forms that admit of wear endways (that is to say in the direction of B in Fig. 621), the straightness of the shears is impaired in proportion as its edges are more worn at one part than at another. [Illustration: Fig. 628.] A compromise between the flat and the raised [V]-shear is shown in Fig. 628, there being a [V]-guide on one side only, as at J. When the carriage is moved by mechanism on the front side of the lathe, and close to the [V], this plan may be used, but if the feed screw or other mechanism for traversing the carriage is within the two shears, the carriage should be guided at each end, or if the operating mechanism is at the back of the lathe, the carriage should be guided at the back end, if not at both ends. In flat shear lathes the tailstock is fitted between the inside edges of the two shears, and the alignment of the tailstock depends upon maintaining a proper fit notwithstanding the wear that will naturally take place in time. The inside edges of the shears are sometimes tapered; this taper makes it much easier to obtain a correct fit of the tailstock to the shears, but at the same time more hard to move the tailstock along the bed. To remedy this difficulty, rollers are sometimes mounted upon eccentrics having journal bearing in the tailstock, so that by operating these eccentrics one half a turn, the rollers will be brought down upon the upper face of the shears, lifting the tailstock and enabling it to be easily moved along the bed to its required position. In many of the watchmakers' lathes the outer edges are beveled off as in Fig. 629, the bearing surfaces being on the faces _b_ as well as on the edges _a_. As a result, edges _a_ are relieved of weight, and therefore to some extent of wear also, and whatever wear faces _b_ have helps the fit at _a_ _a_. In the Barnes lathe, as in several other forms in which the lathe is made (as, for example, in screw-making lathes) the form of bed in Fig. 630 is employed. The tailblock may rest on the surfaces A, A´, B, C, D, and E, or as in the Barnes lathe the tailstock may fit to angles A B, but not to E D, while the carriage fits to B E, and C D, but not to A, the intention being to equalize the wear as much as possible. [Illustration: Fig. 629.] The shears of lathes require to be as rigid as possible, because the pressure of the cut, as well as the weight of the carriage, slide rest, and tailstock, and of the work, tends to bend and twist them. [Illustration: Fig. 630.] The pressure of the dead centre against the end of the work considered individually, is in a direction to bend the lathe shears upward, but the weight of the work itself acts in an opposite direction. The strain due to the cut falls in a direction variable with the shape of the cutting tool, but mainly in a direction towards the operator, and, therefore, tending to twist the shears. To resist these strains, lathe shears are usually given the [I] form shown in the cuts. [Illustration: Fig. 631.] [Illustration: Fig. 632.] Figs. 631 and 632 represent the ribbing in the Putnam Tool Company's lathe; a middle rib running the entire length, which greatly stiffens it. The legs supporting lathe shears are, in lathes of ordinary length, placed at each end of the bed, so that the weight of the two heads, that of the work, and that of the carriage and slide rest, as well as the downward pressure of the cut, act combined to cause it to deflect or bend. It is necessary, therefore, in long beds to provide intermediate resting or supporting points to prevent this deflection. [Illustration: Fig. 633.] Professor Sweet has pointed out that a lathe shears will be more truly supported on three than on four resting points, if the foundation on which the legs rest do not remain permanently level, and in lathes designed by him has given the right-hand end of the shears a single supporting point, as shown at _a_ in Fig. 633. [Illustration: Fig. 634.] J. Richards in an article in "Engineering," has pointed out also that, when the lathe legs rest upon a floor that is liable from moving loads upon it to move its level, it is preferable that the legs be shaped as in Fig. 634, being narrowest at the foot, whereas when upon a permanent foundation, in which the foundation is intended to impart rigidity to the legs, they should be broader at the base, as in Fig. 635. [Illustration: Fig. 635.] The rack on a lathe bed should be a cut one, and not simply a cast one, because when a cutting tool is running up to a corner as against a radial face, the self-acting motion must be stopped and the tool fed into the corner by hand. As a very delicate tool movement is required to cut the corner out just square, it should be capable of easy and steady movement, but in the case of cast racks, the rest will, from defects in the rack teeth, move in little jumps, especially if the pitch of the teeth be coarse. On the other hand it is difficult to cast fine pitches of teeth perfectly, hence the racks as well as the gear teeth should be cut gear and of fine pitch. The tailblock of a lathe should be capable of easy motion for adjustment along the shears, or bed of the lathe, and readily fixable in its adjusted position. The design should be such as to hold the axial line of its spindle true with the axial line of the live spindle. If the lathe bed has raised [V]s there are usually provided two special [V]s for the tailblock to slide on, the slide rest carriage sliding on two separate ones. In this case the truth of the axial line of the tail spindle depends upon the truth of the [V]s. If the lathe bed is provided with ways having a flat surface, as was shown in Fig. 622, the surfaces of the edges and of the projection are apt in time to wear, permitting an amount of play which gives room for the tailblock to move out of line. To obviate this, various methods are resorted to, an example being given in the Sellers lathe, Fig. 518. In wood turners' lathes, where tools are often used in place of the dead centre, and in which a good deal of boring is done by such use of the tail spindle, it is not unusual to provide a device for the rapid motion of that spindle. Such a device is shown in Fig. 636; it consists of an arm A to receive the end C of the lever B, C being pivoted to A. The spindle is provided with an eye at E, the wheel W is removed and a pin passed through D and E, so that by operating the handle the spindle can be traversed in and out without any rotary motion of the screw. When the tailblock of a lathe fits between the edges of the shears, instead of upon raised [V]s, it is sometimes the practice to give them a slight taper fitting accurately a corresponding taper on the edges of the shears. This enables the obtenance of a very good fit between the surfaces, giving an increased area of contact, because the surfaces can be filed on their bearing marks to fit them together; but this taper is apt to cause the tailstock to fit so tightly between the shears as to render it difficult to move it along them, and in any event the friction is apt to cause the fit to be destroyed from the wear. An excellent method of obviating these difficulties is by the employment of rollers, such as shown at R in Figs. 637 and 638, which represent the tailstock of the Putnam Tool Company's lathe. In some cases such rollers are carried on eccentric shafts so that they may be operated to lift the tailstock from the bed when moving it. [Illustration: Fig. 636.] [Illustration: Fig. 637.] [Illustration: Fig. 638.] [Illustration: Fig. 639.] A very ready method of securing or releasing a small tailstock to a lathe shears is shown applied to a wood turner's hand rest in Fig. 639, in which A A represents the lathe shears, B the hand rest, C the fastening bolt, D a piece hinged at each end and having through its centre a hole to receive the fastening bolt, and a counter-sink or recess to receive the nut and prevent it unscrewing. E represents a hinged plate, and F a lever, having a cam at its pivoted end. A slot for the fastening bolt to pass through is provided in the plate E. In this arrangement a very moderate amount of force applied to bring up the cam lever will cause the plate D to be pressed down, carrying with it the nut, and binding the tailstock or the tool rest, as the case may be, with sufficient force for a small lathe. When a piece of work is driven between the lathe centres, the weight of the work tends to deflect or bend down the tail spindle. The pressure of the cut has also to be resisted by the tail spindle, but this pressure is variable in direction, according to the shape of the tool and the direction of the feed; usually it is laterally towards the operator and upwards. In any event, however, the spindle requires locking in its adjusted position, so as to keep it steady. The pressure on the conical point of the dead centre is in a direction to cause the tail screw to unwind, unless it be a left-hand thread, as is sometimes the case. If the spindle and the bore in which it operates have worn, the resulting looseness affords facility for the spindle to move in the bore as the pressure of the cut varies, especially when the spindle is far out from the tailstock. Now, in locking the tail spindle to obviate these difficulties, it is desirable that the locking device shall hold that spindle axially true with the live spindle of the lathe, notwithstanding any wear that may have taken place. The spindle is released from the pressure of the locking device whenever it is adjusted to the work, whether the cut be proceeding or not. Hence, the wear takes place on the bottom of the spindle and of the hole, wear only ensuing on the top of the spindle and bore when the spindle is operated under a slight locking pressure, while the cut is proceeding in order to take up the looseness that may have arisen from wear in the work centres. In all cases the feed of the cut should be stopped while the centre is adjusted, so as to relieve the spindle and bore from undue wear; but most workmen pay little heed to this; hence the wear ensues, being, as already stated, mainly at the bottom. It is obvious, then, that, if the spindle is to be locked to the side of the bore on which it slides, it will be held most truly in line if it be locked to that side which has suffered least from wear, and this has been shown to be at the top. [Illustration: Fig. 640.] [Illustration: Fig. 641.] The methods usually employed to effect this locking are as follows:--In Fig. 640, S is the tail spindle, B part of the tailblock in section, R a ring-bolt, and H a handled nut. Screwing up the nut H causes R to clamp S to the upper part of the bore of B; while releasing H leaves S free to slide. There are three objections to this plan. The ring R tends to spring or bend S. The weight of R tends to produce wear upon the top of the spindle, and the spindle is not gripped so near to its dead centre end as it might be. If S is a close fit in B the pressure of R could not spring or bend S; but, so soon as wear has taken place, S becomes simply suspended at R, having the pressure of R, and the weight of the work tending to bend it. Another locking device is shown in Fig. 641. It consists of a shoe placed beneath S, and a wedge-bolt beneath it, operated by the handled nut C. Here the pressure is again in a direction to lift S, as denoted by the arrow; but when the wedge W is released the shoe falls away from S, hence the locking device produces no wear upon S. This device may be placed nearer to the end of B, since the wedge may pass through the front leg of the tailstock instead of to the right of it, as in Fig. 640. But S is still suspended from the point of contact of the shoe, and the weight of the work still bends it as much as its play in B will permit. [Illustration: Fig. 642.] Another clamping device is shown in Fig. 642. In this the cylindrical part B of the tailblock is split on one side, and is provided with two lugs. A handled screw passes through the upper lug, and is threaded into the lower one, so that by operating the handle C, the bore may be closed, so as to grip S, or opened to relieve it. This possesses the advantages: First, that it will cause S to be gripped most firmly at the end of B, and give a longer length of bearing of B upon S; and, secondly, that it will grip S top and bottom, and, therefore, prevent its springing from the weight of the work. But, on the other hand, B will close mainly on the side of the split, as denoted by the dotted half-circle, and therefore tend to throw S somewhat in the direction of the arrow, which it will do to an amount answerable to the amount of looseness of S in B. In the Pratt and Whitney lathes this device is somewhat modified, as is shown in Fig. 643. A stud E screws into the lower lug D, having a collar at E let into the upper lug, with a square extending above the upper lug so that the stud may be screwed into D, exerting sufficient pressure to close the bore of B to a neat working fit to the spindle. The handled nut, when screwed up, causes B to grip the spindle firmly; but when released, leaves the spindle a neat working fit and not loose to the amount of the play; hence, the locking device may be released, and the centre adjusted to take up the wear in the work centres while the cut is proceeding, without any movement of the spindle in B, because there is no play between the spindle and B. [Illustration: Fig. 643.] [Illustration: Fig. 644.] In the design shown in Fig. 644, the end B of the tailblock is threaded and is provided with a handled cap nut A A. In the end of the tailblock where the spindle emerges, is provided a cone, and into this cone fits a wedge-shaped ring, as shown. This ring is split quite through on one side, while there are two other slots nearly but not quite splitting the wedge-ring. When the handle C is pulled towards the operator it screws A up on the end B, and forces the wedge-ring up in the conical bore in B. From the split the ring closes upon the spindle S, and grips it. Now, as the ring is weakened by slots in two places besides the split, it closes more nearly cylindrically true than if it had only a split, there being three points where the ring can spring when closing upon S; and from the cone being axially true with the live spindle of the lathe, S is held axially true, notwithstanding any wear of the spindle, because the locking device, being at the extreme end of B, is as near to the dead centre as it is possible to get it; and, furthermore, when C is operated for the release, the wedge-ring opens clear of S, so that S does not touch it when moved laterally. The wear of the bore of B has, therefore, no effect to throw S out of line, nor has the gripping device any tendency to bend or spring S, while the latter is held as close to the work as possible; hence the weight of the work has less influence in bending it. The pitch of the thread and the degree of cone are so proportioned that less than one-quarter rotation of A will suffice to grip or release S, the handle C being so placed on A as to be about vertical when the split ring binds S; hence C is always in a convenient position for the hand to grasp. [Illustration: Fig. 645.] In this case, however, the spindle being locked at the extreme end of the hole, there is more liability of the other end moving from the pressure of the cut, or from the weight of the work; hence it would seem desirable that a tail spindle should be locked in _two_ places; one at the dead centre end of the hole, and the other as near the actuating wheel, or handle, as possible, and also that each device should either hold it central to the original bore, notwithstanding the wear, an end that is attained in the Sellers lathes already described. Slide rests for self-acting or engine lathes are divided into seven kinds, termed respectively as follows: simple, or single, elevating, weighted, gibbed, compound, duplex, and duplex compound. A simple, or single, slide rest contains a carriage and one cross slide, as in Fig. 621. An elevating slide rest is one capable of elevation at one end to adjust the cutting tool height, as in Fig. 499. A weighted slide rest is one held to the shears by a weight, as in Fig. 577. A gibbed slide rest is held to the shears by gibs, as in Fig. 621. A compound slide rest has above the cross slide, a second slide carrying the tool holder, this second slide pivoting to stand at any required angle, as in Fig. 505. A duplex slide rest has two rests on the same cross slide, and in a compound duplex both these two rests are compound, as in Fig. 511. The rest shown on the Putnam lathe in Figs. 492 and 499, is thus an elevating gibbed single rest. TESTING A LATHE.--To test a lathe to find if its live and dead spindles are axially in line one with the other and with the guides on the lathe bed, the following methods may be employed in addition to those referred to under the heading of Erecting. To test if the live spindle is true with the bed or shear guides, a piece such as in Fig. 645 may be turned up between the lathe centres, the end A fitting into the live spindle in place of the live centre, and the collars B C being turned to an equal diameter, and the end face D squared off true. The end A must then be placed in the lathe in place of the live centre, the dead centre being removed from contact with the work; with the lathe at rest a tool point may be set to just touch collar C, and if when the carriage is moved to feed the tool past collar B, the tool draws a line along it of equal depth to that it drew along C, the live head is true; the dead centre may then be moved up to engage the work end D, and the lathe must be revolved so that (the tool not having been moved at all by the cross-feed screw) the tool may be traversed back to draw another line along C, and if all three lines are of equal depth the lathe is true. The tool should be fine pointed and set so as to mark as fine a line as possible. [Illustration: Any View. Fig. 646.] [Illustration: Side View. Fig. 647.] [Illustration: Side View. Fig. 648.] [Illustration: Top View. Fig. 649.] Another method is to turn up two discs, such as in Fig. 646, their stems A and B fitting in place of the live and dead centres. One of these discs is put in the place of the live, and the other in that of the dead centre, and if then the lathe tailstock be set up so that the face of B meets that of A, their coincidence will denote the truth of the live and dead spindles. The faces of the discs may be recessed to save work and to meet at their edges only, but their diameters must be equal. If the discs come one higher than the other, as in Fig. 647, the centres are of unequal height. If the faces meet at the top and are open at the bottom, as in Fig. 648, it shows that the back bearing of the live spindle is too high, or that the tail spindle is too low at the dead centre end. If the discs, when viewed from above, come as in Fig. 649, it is proof that either the live spindle or the tail spindle does not stand true with the lathe shears. If the disc faces come so nearly fair that it is difficult to see if they are in contact all around, four pieces of thin paper may be placed equidistant between them, and the grip upon them tested by pulling. If the tailstock has been set over to turn taper and it is required to set it back to turn parallel again, place a long rod (that has been accurately centred and centre-drilled) between the lathe centres, and turn up one end for a distance of an inch or two. Then turn it end for end in the lathe and let it run a few moments so that the work centre, running on the dead centre of the lathe, may wear to a proper bed or fit to the lathe centre, and then turn up a similar length at the dead centre end, taking two cuts, the last a fine finishing cut taken with a sharp tool, and feeding the finishing cut from left to right, so that it will be clear of the work end when the cut is finished. Without moving the cross-feed screw of the lathe after the finishing cut is set, take the bar out of the lathe and wind the slide rest carriage, so that the turning tool will stand close to the live centre. Place the bar of iron again in the lathe, with the turned end next to the live centre, and move the lathe carriage, so that the tool is on the turned end of the bar. Rotate the bar by hand, and if the tool just touches the work without taking a cut the line of centres is parallel with the ways. If there is space between the tool point and the turned end of the bar, the tailstock requires setting over towards the back of the lathe, while if the tool takes a cut the tailstock requires to be set over towards the operator. If a bar is at hand that is known to be true, a pointed tool may be adjusted to just make a mark on the end of the bar when the slide rest is traversed. On the bar being reversed, the tool should leave, when traversed along the bar, a similar mark on the bar. To test the workmanship of the back head or tailstock, place the forefinger on the spindle close to the hub whence it emerges, and observe how much the hand wheel can be moved without moving the spindle; this will show how much, if any, lost motion there is between the screw and the nut in the spindle. Next wind the back spindle about three quarters of its length out of the tailstock, take hold of the dead centre and pull it back and forth laterally, when an imperfect fit between the spindle and the hole in which it slides will be shown by the lateral motion of the dead centre. Wind the dead centre in again, and tighten and loosen the spindle clamp, and see if doing so moves the spindle in the socket. To examine the slide rest, move the screw handles back and forth to find how much they may be moved without giving motion to the slides; this will determine the amount of lost motion between the collars of the screws and between the screws themselves and the nuts in which they operate. To try the fit of the slide rest slides, in the stationary sliding ways or [V]s, remove the feed screws and move the slide so that only about one-half inch is in contact with the [V]s, then move the slide back and forth laterally to see if there is any play. Move the slide to the other end of the [V]s, and make a similar test, adjusting the slide to take up any play at either end. Then clean the bearing surfaces and move the slide back and forth on the [V]s, and the marks will show the fit, while the power required to move the slide will show the parallelism of the [V]s. If the lathe carriage have a rack feed, operate it slowly by hand, to ascertain if it can be fed slowly and regularly by hand, which is of great importance. Then put the automatic feed in gear, and operate the feed gear back and forth, to determine how much it can be moved without moving the slide rest. To test the fit of the feed screw to the feed nut, put the latter in gear and operate the rack motion back and forth. To determine whether the cross slide is at a right angle with the ways or shears, take a fine cut over a radial face, such, for example, as the largest face plate, and test the finished plate with a straight edge. If the face plate runs true and shows true with a straight edge, so that it is unnecessary to take a cut over it, grind a piece of steel a little rounding on its end, and fasten it in the tool post or clamp, with the rounded end next to the face plate. Let the rounded end be about 1/4 in. away from the face plate, and then put the feed motion into gear, and, with the steel near the periphery of the face plate, let the carriage feed up until the rounded steel end will just grip a piece of thin paper against the face plate tight enough to cause a slight strain in pulling the paper out, then wind the tool in towards the lathe centre and try the friction of the paper there; if equal, the cross slide is true. To find the amount of lost motion in the screw feed gear, adjust it ready to feed the saddle, and pull the lathe belt so as to revolve the cone spindle backward, until the slide rest saddle begins to move, then mark a fine line on the lathe bed making the line coincident with the end of the lathe saddle or carriage. Then revolve the cone spindle forward, and note how much the cone spindle rotates before the saddle begins to traverse. If the lathe has an independent feed motion it may be tested in the same manner as above. In large lathes this is of great consideration, because the work revolves very slowly, and if there is much lost motion in the feed gear, it may take considerable time after the feed is put in gear before the carriage begins to travel. Suppose, for example, a 14-foot pulley is being turned, and that the tool cuts at 15 feet per minute, it will take nearly three minutes for the work to make a revolution. CHAPTER VIII.--SPECIAL FORMS OF THE LATHE. The lathe is made in many special or limited forms, to suit particular purposes, the object being to increase its efficiency for those purposes, which necessarily diminishes its capacity for general work. In addition to this, however, there are machine tools whose construction varies considerably from the ordinary form of lathe, which nevertheless belong to the same family, and must, therefore, be classified with it, because they operate upon what is essentially lathe work. Thus boring and turning mills are essentially what may be termed horizontal lathes. Figs. 650 to 655 inclusive, represent the American Watch Tool Company's special lathes for watch-makers, which occupy a prominent position in Europe, as well as in the United States. In lathes of this class, refinement of fit, alignment, truth, and durability of parts are of the first importance, because of the smallness of the work they perform, and the accuracy to which that work must be made. Furthermore, such lathes must be constructed to hold and release the work as rapidly as possible, because in such small work the time occupied by the tools in cutting is less, while that occupied in the insertion and removal of it is greater in comparison than in larger jobs; it often takes longer to insert and remove the work than to perform it. These facts apply with equal force to all such parts as require the removal to or from the lathe-bed, or frequent adjustment upon the same. Thus the devices for holding and releasing the tool post or hand rest and tailblock are each so constructed that they may be set without the use of detached wrenches. Fig. 650 represents a general view of the lathe, while Fig. 651 represents a sectional view of the headstock. The live spindle consists of two parts, an outer sleeve A A, having journal bearing in the head, and an inner hollow spindle B B, threaded at its front end _e_, to receive the chucks. The main spindle at the front end works in a journal box _c_, that is cylindrical to fit the headstock, but double coned within to afford journal bearing to the spindle A. The inner step of this double cone is relied upon mainly to adjust the diametral fit of the bearing, while the outer step is relied upon mainly to adjust the end fit of the spindle; but it is obvious in both cases there is an action securing simultaneously the diametral and the end fit. In the back bearing there are two cones. The outer one _r_ is cylindrical outside where it fits into the head, and coned in its bore to receive the second cone _s_, which rotates with spindle A. The nut F is threaded upon A, so that by operating F, A is drawn within _c_, and S is simultaneously moved within _r_, so that both bearings are simultaneously adjusted. D D are _dust_ rings, being ring-caps which cover the ends of the bearings and the oil holes so as to prevent the ingress of dust. The inner spindle B has a bearing in A at the back end to steady it, and a bearing at end _e_, and is provided with the hand wheel H, by which it may be rotated to attach the chucks which screw into its mouth at _e_. To rotate or drive the chucks there is in A a feather at _g_, the chucks having a groove to receive this feather and screwing into B at E, when B is rotated. The mouth of A is coned, as shown at _h_, and the chucks are provided with a corresponding male cone, as shown at _h_ in Figs. 652 and 653, so that the chucks are supported and guided by the cone, and are therefore as close to the work as possible while having a bearing at _g_. But the cone on the chucks being split, (as is shown in Fig. 652), rotating B while holding A stationary (which may be done by means of the band pulley P), causes the chucks to move endwise in A, and if the motion is in the direction to draw the chuck within A, the cone _h_ causes the chuck to close upon and grip the work. Thus in Fig. 652 is shown a step chuck. The thread at J enters the end _e_ of B, in Fig. 651, which screws upon it. Cone _h_ fits mouth _h_ in Fig. 651, and _l_ represents the splits in the chuck, which enable it to close when the cone _h_ is drawn within the mouth _h_ of spindle A. The chuck is employed to hold cylindrical plates or discs, such as wheels and barrels, and the various steps are to suit the varying diameters of these parts in different sizes of watches. Fig. 653 represents a wire chuck, having the cone at _h_, and the three splits at _l_, as before, the cone-mouth _h_ closing the chuck as the latter is drawn within the spindle A. In both the chucks thus far described, the construction has been arranged to close the splits and thus grip the circumferences of cylindrical bodies, but in Fig. 654 is shown the arrangement for enabling the chuck to expand and grip the bores of hollow work, such as rings, &c. The outer spindle A corresponds to the outer spindle A in Fig. 651, and the inner one to spindle B in that figure. The chuck is here made in two separate parts, a sleeve V fitting in and driven by A, and a plug X fitting into a cone in the mouth of V, and screwing into the end of drawing spindle B. But while V is driven by and prevented from rotating within A by means of the feather at _g_, so likewise X is prevented from rotating within V by means of a feather _h_ fast in X and fitting into a groove or featherway in V. It follows then that when B is rotated X may be traversed endways in V, to open or close the steps Y according to the direction of rotation of B. It will now be apparent that in the case of chucks requiring to grip external diameters, the gripping jaws of the chucks will, when out of the lathe, be at their largest diameter, the splits _l_ being open to their fullest, and that when by the action of the cones, they are closed to grip the work, such closure must be effected against a slight spring or resistance of the jaws, and this it is that enables and causes the chuck to open out of itself, when the enveloping cone permits it to do so. But in the case of the opening or expanding chuck, the reverse is the case, and the chuck is at its smallest diameter (the splits _l_ being at their closest) when the chuck is removed from the lathe, as is obviously necessary. In reality the action is the same in both cases, for the chuck moves to grip the work under a slight resistance, and this it is that enables it to readily release the work when moved in the necessary endwise direction. The band pulley P is fast upon A, and is provided with an index of 60 holes on its face G, and which are adjusted for any especial work by a pin Q, so that a piece of work may have marked on it either 60, 30, 20, 15, 12, 10, 6, 5, 4, 3, or 2 equidistant lines of division, each of those numbers being divisors of 60. In marking such lines of division upon the work a sharp point may be used, supported by the face of the hand rest as a guide; or a sharp-pointed tool may be placed in the slide rest to cut a deeper line upon the work. The index plates used for cutting wheels and pinions may be placed on the rear end of A, the pawl being secured to the work-bench. The wheel H is for rotating spindle B to screw the chucks on or off the same. [Illustration: _VOL. I._ =WATCHMAKER'S LATHE.= _PLATE VIII._ Fig. 650. Fig. 651. Fig. 652. Fig. 653. Fig. 654.] [Illustration: _VOL. I._ =DETAILS OF WATCHMAKER'S LATHE.= _PLATE IX._ Fig. 655. Fig. 656. Fig. 657. Fig. 658. Fig. 659. Fig. 660. Fig. 661. Fig. 662.] Fig. 655 represents an end view from the tailstock end of the lathe; A´ is the bed having the angles _a_ _a_ to align the heads and rests. The means of holding or releasing the tailstock, on the lathe-bed, is the same as that for holding the headstock, the construction being as follows: _b_ is the shoulder of a bolt through which passes the shaft _c_, with a lever _d_ to operate it. This shaft is eccentric where it passes through the bolt, so that by using the lever aforesaid the bolt secures or releases the head according to the direction in which it is moved. A very small amount of motion is needed for this. The standard for the hand rest is split, and a screw is used to tighten it in an obvious manner, the screw being operated by the handle _e´_. An end view of the rest, showing the device for securing the foot _h_ to the bed, is shown in Fig. 656, _f_ is a shoe spanning the bed and fitting to the bed angles _a_. Through _f_ passes the bolt _g_, its head passing into the [T]-shaped groove _h_; N´ is a hand wheel for operating bolt _g_. At S is a spiral spring, which by exerting an end pressure on washer _w_ and nut N´, pulls _g_ and the head _h_ down upon _f_, and therefore _f_ down upon the bed, whether the rest be locked to the bed or not; hence when N´ is released to remove or adjust the rest, neither dust nor fine cuttings can pass either between the rest and shoe or the shoe and the lathe-bed, and the abrasion that would otherwise occur is thus avoided. Two qualities of these lathes are made: in the better quality all the working parts are hardened and afterwards ground true. In the other the parts are also ground true, but the parts (which in either case are of steel) are left soft for the sake of reducing the cost. In all, the parts are made to gauge and template, so that a new head, tailstock, or any other part in whole or in detail may be obtained from the factory, either to make additions to the lathe or to replace worn parts. Two styles of slide rest are made with these lathes: in the first, shown in Fig. 657, the swivel for setting the top slide at an angle for taper turning is at the base of the top slide, hence the lower slide turns all radial faces at a right angle to the line of lathe centres. In the second, Fig. 658, there is a third slide added at the top, so that the bottom slide turns radial faces to a right angle with the line of lathe centres, the next slide turns the taper and the top slide may be used to turn a radial face at a right angle to the surface of the taper, and not at a right angle to the axis of the work. Both these rests are provided with tool post clamps, to hold tools made of round wire, such clamps being shown in position in figure 657. Fig. 659 represents an additional tailstock for this lathe, the tail spindle lying in open bearings so that it can be laid in, which enables the rapid employment of several spindles holding tools for performing different duties, as drilling, counter-boring, chamfering, &c. Fig. 660 represents a filing fixture to be attached to the bed in the same manner as the slide rest. It consists of a base supporting a link, carrying two hardened steel rolls, upon which the file may rest, the rolls rotating by friction during the file strokes, and serving to keep the file flat and fair upon the work. Fig. 661 represents a fixture for wheel and pinion cutting; it is attached to the slide rest. When the cutter spindle is vertical the belt runs directly to it from the overhead counter shaft, but when it is horizontal the belt passes over idler pulleys, held above the lathe. The cutter spindle is carried on a frame, pivoted to the sliding piece on the vertical slide, so that it may be swivelled to set in either the vertical or horizontal position. Fig. 662 represents a jewelers' rest for this lathe. It fits on the bed in the place of the tailstock, and is used for cutting out the seats for jewels, in plates, or settings. It is especially constructed so as to receive the jewel at the top and bore the seating to the proper diameter, without requiring any measurements or fitting by trial, and the manner in which this is accomplished is as follows:-- [Illustration: Fig. 663.] [Illustration: Fig. 664.] [Illustration: Fig. 665.] Fig. 663 is a side elevation, Fig. 664 an end elevation, and Fig. 665 a plan view of this rest, and similar letters of reference indicate like parts in each of the three figures. A is the base, held to the lathe bed by the bolt B, whose operation is the same as that already described for the head and tailstocks. In one piece with A is the arm C, carrying at its head three gauge tongues or pieces D E F, which are adjustable by means of the screws _d_ _e_ _f_, which move the gauge tongues horizontally. Through a suitable guide I is a standard or head; pivoted to A at J J, and carrying at its top three gauge tongues K L M. Midway between pivots J J and the ends of the gauge tongues, is the centre or tool carrying spindle O. If a piece of work, as a jewel, be placed between the tongues F and M, Fig. 664 [swinging M, and with it I (which is pivoted at J), laterally], then the point of the centre N will be thrown out of line with the lathe live spindle half the diameter of the jewel, because from J to the centre N, of O, is exactly one half of the vertical distance from J to the jewel. If then a tool be placed in the dead centre and its cutting edge is in line with the axis of spindle O, it will bore a hole that will just fit the jewel. Hence placing the jewel between the two tongues sets the diameter to which the tool will bore and determines that it shall equal the diameter of the jewel. The object of having three pair of gauge tongues is to enable the obtaining of three degrees of fit; thus with a piece placed between D K the hole may be bored to fit the piece easily, with it placed between E L the fit may be made barely movable, while with it placed between F M the fit may be too tight to be a movable one save by pressure or driving, each degree of fit being adjusted by means of the screws _e_ _f_ _g_. The tool is fed by moving spindle O by hand, the screw P being adjusted so that its end abuts against stop Q, when the hole is bored to the requisite depth; R is simply a guide for the piece S, which being attached to O, prevents it from rotating. In watch manufactories special chucks and appliances are necessary to meet their particular requirements. There is found to exist, for example, in different rods of wire of the same nominal diameter, a slight variation in the actual diameter, and it is obvious that with the smaller diameters of wire the split chucks will pass farther within the mouth _h_ of A, Fig. 651, because the splits of the chucks will close to a greater extent, and the cones on the chucks therefore become reduced in diameter. If then it be required to turn a number of pieces of work to an exact end measurement, or a number of flanges or wheels to equal thicknesses, without adjusting the depth of cut for each it becomes necessary to insure that the successive pieces of work shall enter the chucks to an equal distance, notwithstanding any slight variation in the work diameter at the place or part where it is gripped by the chuck. To accomplish this end what is termed a sliding-spindle head is employed. In this the _outer spindle_ has the end motion necessary to open and close the chuck, the chuck having no end motion. [Illustration: Fig. 666.] The construction of this sliding-spindle head is shown in Fig. 666, in which a wire chuck is shown in position in the spindles; L is the live spindle passing through parallel bearings, so that it may have end motion when the nut M is operated. The inner spindle N to which the chucks are screwed is prevented from having end motion by means of the collar _p_ and nut _q_ at the rear bearing. When nut M is rotated and N is held stationary by means of the pulley P, L slides endways, and the chuck opens or closes according to the direction in which the nut moves the spindle L. To regulate the exact distance to which the work shall be placed within the chuck, a piece of wire rod may be placed within the hollow spindle N being detained in its adjusted position by the set screw S. The construction whereby the nut is permitted to revolve with spindle L, and be operated by hand to move spindle L when the lathe is at rest, is as follows. The cylindrical rim _t_ of the nut is provided with a series of notches arranged around its circumference. R is a lever whose hub envelops nut M, but has journal bearing on V. R receives the pin S, which rests upon a spiral spring T. When, therefore, S is pushed down it depresses the spring T and its end W enters some one of the notches in the rim _t_, and operates the nut after the manner of a ratchet. But so soon as the end pressure on R is released, the spiral spring lifts it and M is free to revolve with L as before. The inner spindle is driven by means of the feather G. Pulley P has two steps Y for the belt, and a friction step _z_, around which passes a friction band operated by the operator's foot to stop the lathe quickly. This performs two functions, as follows. The thread of M is a left-hand one so that the inertia of the nut will not, when the lathe is started, operate to screw the nut back, and release the chuck jaws from the work, by moving spindle L endwise. Per contra, however, in stopping the lathe suddenly by means of the brake, there is a tendency of nut M to stop less quickly than spindle L, and this operates to unscrew nut N and release the work. To assist this R is sometimes in lathes for watch manufactories provided with a hand wheel whose weight is made sufficient for the purpose. [Illustration: Fig. 667.] [Illustration: Fig. 668.] Figs. 667 and 668 represent a pump centre head for watch manufactories, being a device for so chucking a piece of work that a hole may be chucked true and enlarged or otherwise operated upon, with the assurance that the work will be chucked true with the hole. Suppose two discs be secured together at their edges, their centres being a certain distance apart, as, for example, a top and bottom plate of a watch movement, and that the holes of one plate require to be transferred to the other, then by means of this head they may be transferred with the assurance that they shall be axially in line one with the other, and at a right angle to the faces of the plates, as is necessary in setting jewels in a watch movement. In holes of such small diameters as are used in watch work, it is manifestly very difficult to set them true by the ordinary methods of chucking and it is tedious to test if they are true, and it is to obviate these difficulties that the pump centre head is designed. Its operation is as follows. There are in this case three spindles A, B, and C, in Fig. 667; A corresponds to spindle A in Fig. 651, driving the chuck D which screws on A as shown; B simply holds the work against the face _d_ of D, and C holds the work true by means of the centre _e_, which enters the hole or centre in the work and is withdrawn when the work is secured by spindle B. The chuck D is open on two sides as shown at E E in Fig. 668, which is an end face view of the chuck, and through these openings the work is admitted to the chuck. The rod or spindle C is then pushed, by hand, endwise, its centre _e_ entering the hole or centre in the work (so as to hold the same axially true) and forcing the work against the inside faces _d_, spindle B is then operated, the face _p_ forcing the work against face _d_, and between these two faces _d_ _p_ the work is held and driven by friction. The spindle C and its centre _e_ is then withdrawn by hand, leaving the hole in the work free to be operated upon. The journal bearings for spindle A are constructed as described for A in Fig. 666; spindle B is operated endways within A as follows. A is threaded at G to receive the hub H of wheel I, at the end of B is a collar which is held to and prevented from end motion within the hub H: hence when wheel I is rotated and A is held stationary (by means of the band pulley), H traverses on G and carries B with it. Operating I in one direction, therefore moves _p_ against the work, while operating it in the other direction releases face _p_ from contact with the work. It is obviously of the first importance that the spindle C be held and maintained axially true, notwithstanding any wear, and that it be a close fit within B so as to remain in any position when the lathe is running, and thus obviate requiring to remove it. To maintain this closeness of fit the following construction is designed. Between spindle A and spindle B, at the chuck end of the two, is a steel bush which can be replaced by a new one when any appreciable wear has taken place. Between B and C are two inverted conical steel bushes, which can also be replaced by new ones, to take up any wear that may have taken place. [Illustration: Fig. 669.] Fig. 669 represents an improved hand lathe by the Brown and Sharpe Manufacturing Company, of Providence, R. I. It is specially designed for the rapid production of such cylindrical work as may be held in a chuck, or cut from a rod of metal passing through the live spindle, which is hollow, so that the rod may pass through it. Short pieces may be driven by the chuck or between the centres of a face plate (shown on the floor at _e_) screwing on in the ordinary manner. When, however, this face plate is removed a nut _d_ screws on in its stead, to protect the thread on the live spindle. The chuck for driving work in the absence of face plate _e_ (as when the rod from which the work is to be made is passed through the live spindle) may be actuated to grip or release the work without stopping the lathe. The pieces _j_ _j_ are to support the hand tool shown in Figs. 1313 and 1314, in connection with hand turning, the tool stock or handle being shown at _k_ on the floor. The lever for securing the tailstock to or releasing it from the shears is shown at _t_. The tail spindle is operated by a lever pivoted at _g_ so that it may be operated quickly and easily, while the force with which the tail spindle is fed may be more sensitively felt than would be the case with the ordinary wheel and screw, this being a great advantage in small work. The tail spindle is also provided with a collar _r_, that may be set at any desired location on the spindle to act as a stop, determining how far the tail spindle can be fed forward, thus enabling it to drill holes, &c., of a uniform depth, in successive pieces of work. The live spindle is of steel and will receive rods up to 1/2 inch in diameter. Its journals are hardened and ground cylindrically true after the hardening. It runs in bearings which are split and are coned externally, fitting into correspondingly coned holes in the headstock. These bearings are provided with a nut by means of which they may be drawn through the headstock to take up such wear in the journal and bearing fit, as may from time to time occur. [Illustration: Fig. 670.] It is obvious that the lathe may be removed from the lower legs and frame and bolted to a bench, forming in that case a bench lathe. Fig. 670 represents a special lathe or screw slotting machine, as it is termed, for cutting the slots in the heads of machine or other screws. The live spindle drives a cutter or saw _e_, beneath which is the device for holding the screws to be slotted, this device also being shown detached and upon the floor. The screw-holding end of the lever _a_ acts similarly to a pair of pliers, one jaw of which is provided on handle _a_, while the other is upon the piece to which _a_ is pivoted. The screw to be slotted is placed between the jaws of _a_ beneath _e_; handle _a_ is then moved to the left, gripping the screw stem; by depressing _a_, the screw head is brought up to the cutter _e_ and the slot is cut to a depth depending upon the amount to which _a_ is depressed, which is regulated by a screw at _b_; hence after _b_ is properly adjusted, all screw heads will be slotted to the same depth. The frame carrying the piece to which _a_ is pivoted may be raised or lowered to suit screws having different thicknesses of head by means of a screw, whose hand nut is shown at _d_. The frame for the head of the machine is hollow, and is divided into compartments as shown, in which are placed the bushings used in connection with the screw-gripping device, to capacitate it for different diameters of screws, and also for the wrenches, cutters, &c. [Illustration: Fig. 671.] [Illustration: Fig. 672.] [Illustration: Fig. 673.] Figs. 671, 672, and 673, represent a lathe having a special feed motion designed and patented by Mr. Horace Lord, of Hartford, Connecticut. Its object is to give to a cutting tool a uniform rate of cutting speed (when used upon either flat or spherical surfaces), by causing the rotations of the work to be retarded as the cutting tool traverses from the centre to the perimeter of the work, or to increase as the tool traverses from a larger to a smaller diameter. If work of small diameter be turned at too slow a rate of cutting speed, it is difficult to obtain a true and smooth surface; hence, as the tool approaches the centre, it is necessary to increase the speed of rotation. As lathes are at present constructed, it is necessary to pass the belt from one step to another of the driving cone, to increase the speed. In this two disadvantages are met with. First, that the increase of speed occurs suddenly and does not meet the requirements with uniformity. Second, that the strain upon the cutting tool varies with the alteration of cutting speed. As a result, the spring of the parts of the lathe, as well as of the cutting tool, varies, so that the cut shows plainly where the sudden increase or decrease (as the case may be) of cutting speed has occurred. The greatest attainable degree of trueness is secured when the cutting speed and the strain due to the cut are maintained constant, notwithstanding variations of the diameter. This, Mr. Lord accomplishes by the following mechanism: Instead of driving the lathe from an ordinary countershaft, he introduces a pair of cones which will vary the speed of the lathe as shown in Fig. 672 as applied to ball turning. L is a belt cone upon the counter-shaft driven from the line shaft. L drives H, which may be termed the lathe countershaft, and from the stepped cone K the belt is connected to the lathe in the usual manner. P is a shipper bar to move the belt N upon and along the belt cones, and thus vary the speed. R is a vertical shaft extending up at the end of the lathe and carrying a segment. This segment is connected to the belt shipper bar P by two cords, one passing from _r_^{1} around half the segment to _r_^{2}, and the other passing from _r_^{3} to _r_^{4}, so that if the segment be rotated, say to the right, it and the bar will move as denoted by the dotted lines, or if moved in an opposite direction, the bar motion will correspond and move the belt N along the cones respectively left or right. At the back of the lathe is a horizontal shaft S, similar to an ordinary feed spindle, and connected to the segment shaft by a pair of bevel gears S^{2}. Between the two ears _e_ _e_, at the rear of the lathe carriage, is a pinion _t_, which drives the splined shaft S, which works in a rack T´. The tool rest is pivoted directly beneath the ball, to be turned after the usual manner of spherical slide rests, and carries a gear _a_^{2}, which, as the rest turns, rotates a gear _a_^{3}. Upon the face of the latter is a pin _a_^{4} working in a slot _a_^{5} at the end of the rack T´; hence as the tool rest feeds, motion is transmitted from _a_^{2} through _a_^{3}, _a_^{4}, _a_, T´, T, and _s_ _s_^{2} to R, which operates the belt shipper P. As it is the rate of tool feed that governs the speed of these motions, the effect is not influenced by irregularity in feeding; hence the speed of the work will be equalized with the tool feed under all conditions. The direction of motion of all the parts will correspond to that of the tool feed from which their motion is directed, and therefore the work speed will augment or diminish automatically to meet the requirements. [Illustration: Fig. 674.] Fig. 673 illustrates the action of the mechanism when used for surfaces, like a lathe face plate. In this case the two gears and the rack T´ simply traverse with the cross-feed slider, and the mechanism is actuated as before. In Fig. 674 a different method of actuating the belt shipper is illustrated. A pulley is attached to the intermediate stud of the change gears, being connected by belt to the shipper, which is threaded as shown at _d_, the belt guiding forks, as _p_^{2}, being carried on a nut actuated by the screw _d_. CUTTING-OFF MACHINE.--The cutting-off machine is employed to cut up into the requisite lengths pieces of iron from the bar. As the cutting is done by a tool, the end of the work is left true and square and a great saving of time is effected over the process of heating and cutting off the pieces in the blacksmith's forge, in which case the pieces must be cut off too long and the ends left rough. [Illustration: Fig. 675.] Fig. 675 represents Hyde's cutting-off machine, which consists of a hollow live spindle through which the bar of iron is passed and gripped by the chucks C C. At G is a gauge rod whose distance from the tool rest R determines the length of the work. F is a feed cone driven by a corresponding cone on the live spindle and driving the worm W, which actuates the self-acting tool feed, which is provided with an automatic motion, which throws the feed out of action when the work is cut off from the bar. The stand S is movable and is employed to support the ends of long or heavy bars. To finish work smooth and more true than can be done with steel cutting tools in a lathe, what are known as grinding lathes are employed. These lathes are not intended to remove a mass of metal, but simply to reduce the surfaces to cylindrical truth, to true outline and to standard diameter, hence the work is usually first turned up in the common lathe to the required form and very nearly to the required diameter, and then passed to the grinding lathe to be finished. The grinding lathe affords the best means we have of producing true and smooth cylindrical parallel work, and in the case of hardened work the only means. In place of steel cutting tools an emery wheel, revolved at high speed from an independent drum or wide pulley, is employed, the direction of rotation of the emery wheel being opposite to that of the work. [Illustration: Fig. 676.] Fig. 676 represents Pratt and Whitney's weighted grinding lathe. The headstock and tailstock are attached to the bed in the usual manner, the frame carrying the emery wheel is bolted to the slide rest as shown, the rest traversing by a feed spindle motion. The carriage traverse is self-acting and has three changes of feed, by means of the feed cones shown. To enable the lathe to grind taper work (whether internal or external) the lathe is fitted with the Slate taper attachment shown in Figs. 508 and 509. It is obvious that in a lathe of this kind, there must be an extra overhead shaft, driving a drum of a length equal to the full traverse of the lathe carriage, or of the plate carrying the head and tailstocks, and the arrangement of this drum with its belt connection to the pulley on the emery wheel arbor, is sufficiently shown in figure. To protect the ways of the bed from the abrasion that would be caused by the emery and water falling upon them, guards are attached to the carriage extending for some distance over the raised [V]s. [Illustration: Fig. 677.] It is essential that the work revolve in a direction opposite to that of the emery wheel, for the following reasons. In Fig. 677 let A represent a reamer and B a segment of an emery wheel. Now suppose A and B to revolve in the direction that would exist if one drove the other from frictional contact of the circumferential surfaces, then the pressure of the cut would cause the reamer A to spring vertically and a wedging action between the reamer and wheel would take place, the reamer vibrating back and forth under varying degrees of this wedging; as a result the surface of A would show waves and would be neither round nor smooth. [Illustration: Fig. 678.] In the absence of a proper grinding lathe, an ordinary lathe is sometimes improvised for grinding purposes, by attaching to the slide rest a simple frame and emery wheel arbor with pulley attached as in Fig. 678, in which A is the emery wheel, C the pulley for driving the arbor, and B the frame, D being a lug for a bolt hole to hold the frame to the lathe rest. In some cases the work may remain stationary and the emery wheel only rotate. Thus, suppose it was required to grind the necessary clearance to relieve the cutting edge C of the reamer, then A could be rotated until C stood in the required position with relation to B, and the revolving emery wheel may either be traversed along, or the work may traverse past the wheel, according to the design of the grinding lathe, but in either case A remains stationary during each cut traverse; after each successive traverse A may be rotated sufficiently to give a cut for the next traverse. Fig. 679 represents Brown and Sharpe's universal grinding lathe. [Illustration: Fig. 679.] This lathe is constructed to accomplish the following ends. First, to have the lathe centres axially true with the work when grinding tapers, so that the lathe centres shall not wear and gradually throw the work out of true from the causes explained in the remarks on turning tapers in a lathe of ordinary construction. Second, to have the headstock B capable of lateral swing, so as to enable the grinding of taper holes. The manner in which these results are accomplished is as follows: The headstock B and the tailstock are attached to the bed or table A, which is pivoted at its centre to a table beneath it, this latter table being denoted by C. This permits table A to swing laterally upon C and stand at any required angle. To enable a delicate adjustment of this angle, a screw _a_ having journal bearing in a lug on C is threaded through a piece carried in projection on the end of A. The table C traverses back and forth past the emery wheel, after the manner of an ordinary iron planing machine, the mechanical parts effecting this motion being placed within the bed upon which C slides. The carriage supporting the emery frame and table D remains stationary in its adjusted position, while C (carrying A with it) traverses back and forth. Now, if A be adjusted so that the line of centres is parallel with the line of motion of C, then the work will be ground parallel, but if _a_ be operated to move A upon its pivoted centre and draw the tailstock end of A towards the operator, then the work will be ground of larger diameter at the tailblock end. Conversely, by operating screw _a_ in the opposite direction, it will be of smaller diameter at that end. But whatever the degree of angle of A to C, the line of centres of the head and tailstocks will be axially true with the axial line of the work, hence the work centres are not liable to wear off true, as is the case when the tailstock only sets over (as will be fully explained in the remarks on taper turning). To grind conical holes the headstock B is pivoted at its centre upon a piece held by bolts to the table A, so that it is capable of being swung laterally to the degree requisite for the required amount of taper in the work bore, and of being locked in that adjusted position, the work being held in a chuck screwed upon the spindle in the usual manner. The pulley _d_ being removed to enable the grinding of cones, chamfers, or tapers of too great an angle to permit of A setting over to the required degree. The line of cross-feed motion of the emery wheel may be set to the required angle as follows. The frame carrying the emery wheel arbor is fixed to a table D, which is capable of being operated (in a direction across the table A) upon a carriage beneath A. This carriage, or saddle (as it may perhaps be more properly termed), is pivoted so as to allow of its movement and adjustment in a horizontal plane, and since D operates in the slide of the carriage, its line of motion in approaching or receding from the line of centres will be that to which the saddle is set. This enables the grinding of such short cones as the circumferences of bevelled cutters, chamfers, &c., at whatever angle the saddle may be set, however, D may be operated from the feed screw disc and handle _f_. The lever handle at the left hand is for operating or rather traversing C by hand; _b_ is a pan to catch the grit and water, the water being led to the back of machine into a pail; _c_ is a back rest to steady the work when it is slight and liable to deflection. The slot and stops shown upon the edge of C are to regulate the points of termination of the traverse (in the respective directions) of C. A guard is placed over the emery wheel to arrest and collect the water cuttings, &c., which would otherwise fly about. A large amount of work which has usually been filed in a lathe, can be much more expeditiously and accurately finished by grinding in this machine. Work to be ground may obviously be held in the same chucks or work-holding appliances as would be required to hold it to turn it with cutting tools, or where a quantity of similar work is to be done special chucks may be made. [Illustration: Fig. 680.] Fig. 680 (from _The American Machinist_) shows a special chuck for grinding the faces of thin discs, such as very thin milling cutters, which could not be held true by their bores alone. The object of the device is to hold the cutter by its bore and then draw it back against the face of the chuck, which, therefore, sets it true on the faces. The construction of the chuck is as follows. The hub screws upon the lathe like an ordinary face plate, and has a slot running diametrically through it. Upon its circumference is a knurled or milled nut C, which is threaded internally to receive the threaded wings of the bush B. A collar behind C holds it in place upon the hub. To admit piece B the front of the chuck is bored out, and after B is inserted and its threaded wings are engaged in the ring nut C a collar is fitted over it and into the counter-bore to prevent B from having end motion unless C is revolved. D is a split bushing that fits into B, its stem fitting the bore of the disc, or cutter to be ground: the enlarged end of D is countersunk to receive the head of the screw E, whose stem passes through D and threads at its end into B, so that when E is screwed up its head expands D and causes it to grip the bore of the disc or cutter to be ground. After E is screwed up the ring nut C is revolved, drawing B within the chuck and therefore bringing the inside face of the disc or cutter against the face of the chuck or face plate, and truing it upon the bushing D. All that is necessary therefore in using the chuck is to employ a bushing of the necessary diameter for the bore of the cutter, insert it in B, then screw up the screw E and then revolve the ring nut C until the work is brought to bear evenly and fair against the face of the chuck, and to insure this it is best not to screw E very tightly up until after the ring nut C has been operated and brought the work up fair against the chuck face. [Illustration: Fig. 681.] Fig. 681 represents the J. Morton Poole calender roll grinding lathe, which has attained pre-eminence both in Europe and the United States from the great accuracy and fine finish of the work it produces. In all other machine tools, surfaces are made true either by guiding the tool to the work or the work to the tool, and, in either case, guide-ways and slides are employed to determine the line of motion of the tool or the work, as the case may be. These guideways and slides are usually carried by a framing really independent of the work, so that the cutting depends entirely upon the truth or straightness of the guideways, and is not determined by the truth, straightness, or parallelism of the work itself. As a result, the surface produced depends for its truth upon the truth of the tool-guiding ways. In the Poole lathe, however, while guideways are necessarily employed to guide the emery wheels in as straight a line as is possible, by means of such guides, the roll itself is employed as a corrective agent to eliminate whatever errors may exist in the guide. The rolls come to this machine turned (in the lathe Fig. 730), and with their journals ground true (on dead centres). Fig. 681 represents a perspective view of the machine, as a whole. It consists of a driving head, answering to the headstock of an ordinary lathe. B B are bearings in which the rolls are revolved to be ground. C is a carriage answering to the carriage of an ordinary lathe, but seated in sunken [V]-guideways, corresponding to those on an ordinary iron planing machine. Referring to Fig. 682, F is a swing-frame suspended by four links at G, H, I, J, which are upon shafts having at their ends knife edges resting in small [V]-grooves on the surface of standards S, which are fixed to carriage C. The frame F being thus suspended and being in no way fixed to C, it may be swung back and forth crosswise of the latter, the links at G, H, I, J, swinging as pendulums. At the top of F are two slide rests A A, one on each end, carrying emery or corundum wheels W, and the roll R, which rests in the bearings B, rotates between these emery wheels. The carriage C is fed along the bed as an ordinary lathe carriage, and the emery wheels are revolved from an overhead countershaft. Now, it will be found that from this form of construction the surface of the roll, when ground true, serves as a guide to determine the line of motion of the emery wheels, and that the emery wheels may be compared to a pair of grinding calipers that will operate on such part of the roll length as may be of larger diameter than the distance apart of the perimeters of the emery wheels, and escape such parts in the roll length as may be of less diameter than the width apart of those perimeters; hence parallelism in the roll is inevitable, because it is governed solely by the width apart of the wheel perimeters, which remain the same, while the wheels traverse the roll, except in so far as it may be affected by wear of emery-wheel diameters in one traverse along the roll. [Illustration: Fig. 682.] Supposing now that we have a roll R (Fig. 683), placed in position and slowly revolved, and that the carriage C is fed along by feed screw E, then the line of motion of the emery wheels will be parallel to the axis of the roll, provided, of course, that the bearings B (Figs. 681 and 687) are set parallel to the [V]-guideways in the bed, and that these guideways are straight and parallel. But the line of travel of the emery wheels is not guided by the [V]s except in so far as concerns their height from those [V]s, because the swing-frame is quite free to swing either to the right or to the left, as the case may be. Its natural tendency is, from its weight, to swing into its lowest position, and this it will obviously do unless some pressure is put on it in a direction tending to swing it. Suppose, then, that instead of the roll running true, it runs eccentrically, or out of true, as it is termed, as shown in Fig. 683, when the high side meets the left-hand wheel it will push against it, causing the carriage C to swing to the left and to slightly raise. The pressure thus induced between the emery wheel and the roll causes the roll surface to be ground, and the grinding will continue until the roll has permitted the swing-frame to swing back to its lowest and normal position. When the high side of the roll meets the right-hand emery wheel it will bear against it, causing the swing-frame to move to the right, and the pressure between the wheel and the roll will again cause the high side of the latter to be reduced by grinding. This action will continue so long as the roll runs out of true, but when it runs true both emery wheels will operate, grinding it to a diameter equal to the distance between the emery-wheel perimeters, which are, of course, adjusted by the slide rests A A. If the roll is out of true in the same direction and to the same amount throughout its length, the emery wheel will act on an equal area (for equal lengths of roll) throughout the roll length; but the roll may be out in one direction at one part and in another at some other part of the length; still the emery wheel will only act on the high side, no matter where that high side may be or how often it may change in location as the carriage and wheels traverse along the roll. Now, the roll does not run true until its circumference is equidistant at every point of its surface from the axis on which the roll revolves, and obviously when it does run true its circumference is parallel to the axis of revolution of the roll, because this axis is the line which determines whether the roll runs true or not, and therefore the swing-frame is actually guided by the axis of revolution of the roll, and will therefore move parallel to it. [Illustration: Fig. 683.] It is obvious that if by any means the swinging of frame F is slightly resisted, as by a plate between it and C, with a spring to set up the plate against F, then the emery wheels will be capacitated to take a deeper cut than if the frame swing freely, this plan being adopted until such time as the roll is ground true, when both wheels will act continuously and simultaneously, and F may swing freely. A screw may be used to set up the spring and plate when they are required to act. Suppose now that the roll was not set exactly level with the [V]-guideways of the bed, there being a slight error in the adjustment of the roll journals in the bearings on B, and the emery-wheels would vary in height with relation to the height of the roll axis, and theoretically they would grind the roll of larger diameter at one end than at the other. [Illustration: Fig. 684.] This, however, is a theoretical, rather than a practical point, as may be perceived from Fig. 684, in which R is a part of a section of a roll, and W a part of a section of a wheel. Now, assuming that the [V]-ways were as much as even a sixteenth out of true, so far as height is concerned, all the influence of the variation in height is shown by the second line of emery-wheel perimeter, shown in the figure, the two arcs being drawn from centres, one of which is 1/16th inch higher than the other. It is plain, then, that with the ordinary errors found in such [V]-guideways, which will not be found to exceed 1/30th of an inch, no practical effect will be produced upon the roll. Again, if one [V] is not in line with the other, no practical effect is produced, because if the carriage C were inclined at an angle, though the plane of rotation of the emery-wheel would be varied, its face would yet be parallel to the roll axis. If the [V]s were to vary in their widths apart (the angles of the [V]s being 45° apart), all the effect it would have would be to raise or lower the carriage C to one-half the amount the [V]s were in error. It will be thus perceived that correctness of the roll both for parallelism and cylindricity is obtained independent of absolute truth in the [V]-guides. Referring now to some of the details of construction of the lathe, the slide rest A, Fig. 683, is bored to receive sockets D D, Fig. 685, and is provided with caps, so that the sockets may be firmly gripped and held axially true one with the other. The socket-bores are taper, to receive the taper ends of the arbor _x_, and are provided with oil pockets at each end. There is a driving pulley on each side of the emery-wheel, and equal belt-speed is obtained as follows: Two belt driving drums M N are employed, and each belt passes over both, as in Figs. 683 and 685, and down around the pulleys P. The diameter of the drum N is less than the diameter of the drum M by twice the thickness of the belt, thus equalizing inside and outside belt diameters, since they both pass over the pulley of the emery-arbor. The piece T is a guard to catch the water from the emery-wheels, and is hinged at the back so that the top is a lid that may be swung back out of the way when necessary. [Illustration: Fig. 685.] [Illustration: Fig. 686.] The method of securing the emery-wheels is shown in Fig. 686. Two flanges Z (made in halves) are let into the wheel, and clamp the wheel by means of the screws shown. The bore of these flanges Z is larger than the diameter of pulleys P, so that the emery-wheels may be changed on the arbor without removing the pulley. Fig. 687 represents an end view of the bearings B for the roll to revolve in, being provided with three pieces, the two side ones of which are adjustable by the set-screws, so as to facilitate setting the roll parallel with the bed of the lathe. The height is adjusted by means of screws K, K, which may also be used in grinding a roll of large diameter at the middle of its length, by occasionally raising the roll as the carriage C proceeds along the roll (the principle of this action is hereafter explained with reference to turning tapers on ordinary lathe work). When the wheels have traversed half the length of the roll, the screws K are operated to lower it again, it being found that the effect of a slight operating of the screws K is so small that the workman's judgment may be relied upon to use them to give to a roll with practical accuracy any required degree of enlarged diameter at the middle of its length with sufficient accuracy for all practical purposes. [Illustration: Fig. 687.] There are, however, other advantages of this system, which may be noted as follows. When a single emery-wheel is used there is evidently twice the amount of wear to take a given amount of metal off (per traverse) that there is when two wheels are used, and furthermore the reduction of every wheel diameter per traverse is evidently twice as great with one wheel as it is with two. From some experiments made by Messrs. Morton Poole, it was found that using a pair of 10-inch emery-wheels it would take 40,000 wheel traverses along an average sized calender roll, to reduce its diameter an inch, hence the amount of error due to the reduction of the emery-wheel diameters, per traverse, may be stated as 1/40000 of an inch per traverse, for the two wheels. [Illustration: Fig. 688.] Now referring to Fig. 688, let R represent a roll and W W the two emery-wheels. Suppose the wheels being at the end of a traverse, the roll is 1/40000 inch larger at that end on account of the wear of the emery-wheels, then each wheel will have worn 1/40000 inch diameter or 1/80000 inch radius, hence the increase of roll diameter is equal to the wear of wheel diameter. [Illustration: Fig. 689.] Now, suppose that one wheel be used as in Fig. 689, and its reduction of _diameter_ will be equal to that of the two wheels added together, or 1/20000 inch, this would be 1/40000 in the radius of the wheel, producing a difference of 1/20000 difference in the diameter of the wheel. There is another advantage, however, in that a finer cut can be easier put on in the Poole system, because if a feed be put on of 1/100th inch, the roll is only reduced 1/100th inch in diameter, but if the same amount of feed be put on with a single wheel, it will reduce the roll 1/50th inch, hence for a given amount of feed or movement of emery-wheel towards the roll axis, the amount of cut taken is only half as much as it would be if a single wheel is used. This enables a minimum of feed to be put on the wheel, wear being obviously reduced in proportion as the feed is lighter and the duty therefore diminished. The method of driving the roll is as follows: Shaft _t_, Fig. 681, runs in bearings in the head, and spindle _r r´_ passes through, and is driven by shaft _t_. A driving pulley is fitted on the spindle at end _r´_, at the other end is a driving chuck _p_ for driving the roll through the medium of a _wabbler_, whose construction will be shown presently. Spindle _r_ may be adjusted endwise in _t_, so that it may be adjusted to suit different lengths of rolls without moving the bearing blocks B. The wabbler is driven by _p_ and receives the end of the roll to be ground, as shown in Fig. 690, the end of the roll being a taper square and fitting very loosely in a square taper hole in the end of the wabbler; similarly _p_ may have a taper square hole loosely fitting the squared end of the wabbler. The looseness of fit enables the wabbler to drive the roll without putting any strain on it tending to lift or twist it in its bearings in block B, and obviates the necessity for the axis of the rolls to be dead in line with the axis of _r r´_. Various lengths of wabblers may be used to suit the lengths of roll and avoid moving blocks B, and it is obvious also that if the ends of the roll are round instead of square, two set-screws may be used to hold the roll end being set diametrically opposite, and if set screws are used in _p_ to drive the wabbler they should be two in number, set diametrically opposite, and at a right angle to the two in the wabbler, so that it may act as a universal joint. [Illustration: Fig. 690.] The method of automatically traversing the carriage C is as follows: Referring to Fig. 681, two gears _a_, _b_ are fast upon shaft _t_, gear _a_ drives _c_ which is on the same shaft as _e_, gear _b_ drives _d_ which drives a gear not seen in the cut, but which we will term _x_, it being on the same shaft as _c_ and _e_. Now if _e_ is driven through the medium of _a_ _c_, it runs in one direction, while if it is driven through the medium of _b_ _d_ _x_, it revolves _e_ in the opposite direction, and since _e_ drives _g_ and _g_ is on the end of the feed screw (E, Fig. 682) the direction of motion of carriage C is determined by which of the wheels _a_ or _b_ drives _e_. At _h_ is a stand affording journal bearing to a shaft _n_, whose end engages a clutch upon the shaft of wheels _c_, _x_ and _e_. On the outer end of shaft _n_ is ball lever _l´´_, whose lower end is attached to a rod _k_, upon which are stops _l l´_ adjustable along rod _k_ by means of set-screws. At _m_ is a bracket embracing rod _k_. Now suppose carriage C to traverse to the left, and _m_ will meet _l_ moving rod _k_ to the left, the ball _i_ will move up to a vertical position and then fall over to the right, causing the clutch to disengage from gear _c_ and engage with the unseen gear _x_, reversing the motion of _e_ and of _g_, and therefore of carriage C, which moves to the right until _m_ meets _l´_ and pushes it to the right, causing _i_ to move back to the position it occupies in the engraving, the clutch engaging _c_, which is then the driving wheel for _e_. SCREW MACHINE.--The screw machine is a special form of lathe in which the work is cut direct from the bar, without the intervention of forging operations, and it follows therefore that the bar must be large enough in diameter to suit the largest diameter of the work, the steps or sections of smaller diameter being turned down from the full size of the bar. The advantages of the screw machine are, that the work requires no centring since it is held in a chuck, that forging operations are dispensed with, that any number of pieces may be made of uniform dimensions without any measuring operations save those necessary when adjusting the tool for the first piece, and that it does not require skilled labor to operate the machine after the tools are once set. The capacity of the screw machine is, therefore, many times greater than that of a lathe, while the diameters and lengths of the various parts of the work will be more uniform than can be done by caliper measurements, being in this case varied by the wear of the cutting edges of the tools only, which eliminates the errors liable to independent caliper measurement. Hollow work, as nuts and washers, may be equally operated on being driven by a mandril held in the chuck. Fig. 691 represents Brown and Sharpe's Number 1 screw machine, which is designed for the rapid production of small work. Three separate tool-holding devices may be employed: first, cutting tools may be placed in the holes shown to pierce (horizontally) the circular head F; second, tools may be fixed in the tool posts shown in the double slide rest, which has two slides (one in the front and one at the back of the line of centres); and third, tools may be placed in what may be termed the screw-cutting slide-rest J. F is a head pierced horizontally with seven holes, and is capable of rotation upon L; when certain mechanism is operated L slides on D and the mechanism of these three parts is arranged to operate as follows. The lever arms K traverse L in D. When K is operated from right to left, L advances towards the live spindle until arrested at some particular point by a suitable stop motion, this stop motion being capable of adjustment so as to allow F to approach the live spindle a distance suitable for the work in hand. When, however, K is operated from left to right L moves back, and when it has traversed a certain distance, the head F rotates 1/7 of a rotation, and becomes again locked so far as rotation is concerned. Now the relation between the seven holes in F is such that when F has rotated its 1/7 rotation, one of the seven holes is in line with the live spindle. Suppose then seven cutting tools to be secured in the holes in F, then K may be operated from right to left, traversing L and F forward, and one of the cutting tools will operate upon the work until L meets the stop; K may then be moved from left to right, L and F will traverse back, then F will rotate 1/7 rotation and L and F may be traversed by K, and a second tool will operate upon the work, and so on. The diameter of the work is determined by the distance of the cutting edge of the tool from the line of centres, when such tool is in line with the work, or, in other words, is in position to operate upon the work. The end measurements of the work are secured by placing the cutting edges of the tools the requisite distance out from F, when L is moved forward as far as the stop motion will permit. But it is evident that the length of cut taken along the work, would under these simple conditions vary with the distance of the end of the work from the face of the chuck driving it, but this is obviated as follows:-- The live spindle is made hollow so that the rod of metal, of which the work is to be made, may pass through that spindle. A chuck on the spindle holds the work or releases it in the usual manner. Suppose then the chuck to be open and the bar free to be moved, then there is placed in the hole in F, that is in line with the work, a stop instead of a cutting tool. The end of the work may then, for the first piece turned, be squared up by a tool placed in the slide rest and then released from the chuck and pushed through the live spindle until it abuts against the stop so adjusted and affixed in the hole in F; K may then be operated to act on the work. The first tool may reduce the work to its largest required diameter, the second turn down a plain shoulder, the third may be a die cutting a thread a certain distance up the work, the fourth may be a tool turning a plain part at the beginning of the thread, the fifth may round off the end of the work, and the sixth may be a drill to pierce a hole a certain distance up the end of the work. [Illustration: _VOL. I._ =EXAMPLES OF SCREW MACHINES.= _PLATE X._ Fig. 691. Fig. 692.] Now suppose the work to require its edge at the other end to be chamfered, then there may be placed in the slide rest tool posts a tool to sever the work from the bar out of which it has been made, while the other may be used to chamfer the required edge, or to round it if needs be to any required form. Work held in the chuck but not formed from a rod may be, of course, operated upon in a similar manner. In the case, however, of work of large diameter requiring to be threaded, the threading tool may be held and operated differently and more rigidly as follows. I is a lever carrying under its bend and over the projecting end of the live spindle, a segment of a nut whose thread must equal in pitch the pitch of thread to be given to the work. A collar or ring, oftentimes called the leader, having a thread of the same pitch, is then secured upon the live spindle, so as to rotate with it, and have no end motion; when therefore I is depressed, the nut will come into work with the collar or ring, and I will be traversed at a speed proportioned to the pitch of the threads on the collar and nut. Now I is attached to a shaft having journal bearing (and capable of end motion) at the back of the lathe head, and on this bar is attached the slide rest J, in which the turning or threading tool may be placed. The shaft above referred to having end motion, may be operated (when the nut in the lever I is lifted clear of the collar) laterally by means of the lever I; hence to traverse J to the right, or for the back traverse, I is raised and pulled to the right, I is then lowered, the nut engages with the collar, and the tool is traversed to the cut. The cut is adjusted for diameter by the slide rest, which is provided with an adjustable stop to determine the depth to which the tool shall enter the work. It is obvious that this part of the machine, may be employed for ordinary turning operations, if the collar be of suitable pitch for the feed. [Illustration: Fig. 693.] Figs. 692 and 693 represent A screw machine for general work. A is a chuck with hardened steel [V]-shaped jaws. It is fast on the hollow arbor of the machine. B is a steadying chuck on the rear end of the arbor. The arbor has a two and one-sixteenth hole through it and its journals are very large and stiff. It is of steel, and runs in gun-metal boxes. The cone pulley and back gear is of the full proportion and power of an eighteen-inch lathe. C is an ordinary lathe carriage fitted to slide on the bed, and be operated by hand-wheel D and a rack pinion as usual. Across this carriage slides a tool rest E operated by screw as usual, and having two tool posts, one to the front and one to the rear of the work. This tool rest, instead of sliding directly in the carriage as is the case with lathes, slides on an intermediate slide which fits and slides in the carriage. This intermediate slide is moved in and out, a short distance only, by means of cam lever G. An apron on the front end of this slide carries the lead screw nut H. When the cam lever is raised it brings the slide outward about half an inch, and the tool rest E comes out with it and at the same time the nut leaves the lead screw. The inward movement of the slide is always to the same point, thus engaging the lead screw and resetting the tool. In cutting threads with a tool in the front tool post the tool is set by moving the tool rest as usual, and at the end of the cut the cam lever serves to quickly withdraw the tool and lead screw nut so that the carriage can be run back. The tool rest is then advanced slightly and the new cut taken. By this means threads are cut without any false motions, and the threads may be cut close up to a shoulder. I is the lead screw. This screw does not extend, as is usual, to the head of the machine. It is short and is socketed into a shaft which runs to the head of the machine and is driven by gearing as usual. The lead screw is thus a plain shaft with a short, removable, threaded end. The gearing is never changed. Different lead screws are used for different threads, thus permitting threads to be cut without running back. The lead screws are changed in an instant by removing knob J. The lead screw nut H is a sectional nut, double ended, so that each nut will do for two pitches, by turning end for end in the apron. L is an adjustable stop which determines the position of the carriage in cutting off, facing, &c. K is an arm pivoted to the rear of the carriage and carrying three open dies like a bolt cutter head. At M is a block sliding or capable of being fed along the bed. N is a gauge screw attached to this block and provided with two nuts. The stop lever shown in the cut turns up to straddle this screw, and the position of the nuts determines how far each way the block may slide. O is the turret fitted to turn on the block. It has six holes in its rim to receive sundry tools. It can be turned to bring any of these tools into action, and is secured by the lock lever P. [Illustration: Fig. 694.] The turret slide is moved quickly by hand, by means of the capstan levers U, which, by an in-and-out motion, also serve to lock the turret at any point. The turret slide is fed, in heavy work, by the crank-wheel R on its tail screw. This tail screw carries, inside the crank-wheel, two gears S, which are driven at different speeds by a back shaft behind the machine. These two gears are loose on the tail screw, and a clutch operated by lever T locks either one to the screw. Both the carriage and turret are provided with oil pots not shown in the cuts. [Illustration: Fig. 695.] A top view of the turret is shown in Fig. 694, a set of tools being shown in place. The end gauge which is shown removed from the chuck in Fig. 695, is composed of a hollow shank A fitting the hole in the turret, and a gauge rod B fitting the bore of the shank. The shank A may be set farther in or out of the turret, and the rod B may be set farther in or out of the shank, the two combined being so set that when the turret is clear back against its stop the end of the rod B will gauge the proper distance that the bar iron requires to project outwards from the chuck of the machine. The centre shown in Fig. 696 corresponds to an ordinary lathe centre, and is only used when chasing long work in steel. [Illustration: Fig. 696.] The turner shown removed from the chuck in Fig. 697, consists of a hollow shank A, fitting the turret and having at its front end a hardened bushing B secured to A by a set screw. It has also a heavy mortised bolt C in the front lug of the shank; an end-cutting tool D shaped like a carpenter's mortising chisel, and clamped by the mortised bolt; a collar screw E to hold the tool endwise; and a pair of set-screws F to swivel the tool and its bolt. Bushing B is to suit the work in hand. The tool D is a piece of square steel hardened throughout. It is held by its bolt with just the proper clearance on its face. It cuts with its end without any springing, and will on this account stand a very keen angle of cutting edge. There is hardly any limit to its cutting power. It will cut an inch bar away at one trip with a coarse feed. It does not do smooth work, and is, therefore, used only to remove the bulk of the metal, leaving the sizer to follow. [Illustration: Fig. 697.] [Illustration: Fig. 698.] The sizer Fig. 698, consists of a hollow shank A fitting the turret and carrying in its front end a hardened bushing B and a flat cutting tool C. The sizer follows the turner and takes a light finishing cut with oil or water, giving size and finish with a coarse feed, and having only a light and clean duty it maintains its size. [Illustration: Fig. 699.] The die holder shown in Figs. 699 and 700, is arranged to automatically stop cutting when the thread is cut far enough along the work. It will cut a full thread cleanly up against a solid shoulder. It consists of a hollow shank A fitting the turret; a sleeve B fitted to revolve and slide on the front end of the shank C; a groove E bored inside the sleeve; a pin D on the shank fitting freely in the groove E; a keyway F at one point in the groove and leading out each way from it; and a thread die G held in the front end of the sleeve. When the turret is run forward, the thread die takes hold of the bolt to be cut, but it revolves idly instead of standing still to cut, until the pin D comes opposite the keyway F when, the turret still being moved forward, the pin enters the back of the keyway. The sleeve now stands still, the die cuts the thread and pulls the turret along by the friction of the pin in the keyway. Finally the turret comes against its front stop and can move forward no farther. Consequently the sleeve is drawn forward on its shank C, and the instant the pin D reaches the groove E the die and sleeve commence to revolve with the work and cease cutting. The machine is then run backward, and the turret moved back a trifle. This causes the pin to catch in the front end of the keyway and the sleeve is again locked. The die then unscrews, and, in doing so, pushes the turret back. A tap holder may be inserted in place of the die, and plug taps may be run to an exact depth without danger. [Illustration: Fig. 700.] [Illustration: Fig. 701.] Drills and other boring tools are held in suitable sockets, which fit into the turret. [Illustration: Fig. 702.] The following are the operations necessary to produce in this machine an hexagon-headed bolt. First operation: The bar is inserted through the open chuck. Second operation: Turret being clear back against its stop and revolved to bring present the end gauge, the bar is set against the end gauge, and the chuck is tightened. This chucks the bar and leaves the proper length projecting from the chuck. Third operation: Front tool in the carriage, a bevelled side tool cones the end of the bar so turret tools will start nicely. Fourth operation: Turret being revolved to present the turner, the bar is reduced, at one heavy cut, to near the proper size, the turret stop determining the length of the reduced portion. Fifth operation: Turret being revolved to present the sizer, the body of the bolt is brought to exact size by a light, quick, sliding cut. Sixth operation: Open die arm being brought down, the bolt is threaded; the left carriage stop indicating the length of the threaded part. Seventh operation: Turret being revolved to present the die holder, the solid die is run over the bolt, bringing it to exact size with a light cut, and cutting _full thread to the exact point desired_. Eighth operation: Front tool in the carriage chamfers off the end thread. Ninth operation: Back tool of carriage, a parting tool, cuts off the bolt; the left carriage stop determining the proper length of head. Tenth operation: Bolt being reversed in chuck, the top of the head is water cut finished by a front tool in the carriage. This operation is deferred till all the bolts of the lot are ready for it. Fig. 703 represents a general view of a screw machine designed by Jerome B. Secor, of Bridgeport, Connecticut. The details of the machine are shown in Figs. 704, 705, 706, 707, 708, 709, 710, and 711.[13] The live spindle is of steel and is hollow, and its journals are ground. The boxes are lined with babbitt, so that no other metal touches the spindle, and may, by a special device, be re-babbitted and bored exactly parallel with the planing of the bed. [13] From _Mechanics_. A steel collar J, Fig. 704, between the front end of the forward box and the spindles, receives the thrust due to the cut, and a nut on the spindle acts against the cone to adjust it forward on a feather K in the spindle to take up end wear. The wire or rod from which the work is to be made is passed through the spindle and collar on the stand, and is held by a thumb-screw in the collar, which is influenced by the weight and cords, so that when the wire is released in the chuck the weight pulls the collar and wire forward, forcing the wire out through the front end of the chuck until it comes against the stop in the turret, which gauges the length needed to make the piece required. From time to time, as the rod is used up, the thumb-screw in the sliding collar is loosened, and the collar is shoved back on the rod as far as it will go, and the set-screw is again tightened. [Illustration: Fig. 703.] [Illustration: Fig. 704.] Fig. 704 shows in section the front bearing and the automatic chuck. M is a hollow spindle within which is the hollow spindle H, through which the rod or wire to make the work passes. It is prevented from end motion by the cone hub on one side and the collar J on the other side of the bearing, while H may be operated endwise within M by means of the hand-lever shown on the left-hand of the headstock in the general view. The core A of the chuck screws upon M, and is threaded to receive the adjustment nut B, which receives and holds the adjustment wedges C at their ends by the talon shown. The shell D is secured to H by the screws I, which pass through slots in A, and therefore move endwise when H is operated by its hand-lever. Now the mouth of D, against which the adjustment wedges C rest, is coned 2-1/2°, as marked; hence the end motion of D to the left causes C, and therefore F, to approach the axis of the chuck and grip the rod or wire, while its motion to the right causes C, and therefore F, to recede from the chuck axis and to release the wire. Since B is screwed upon A, and C is guided at the end by B, and since also F is detained endwise in A, the motions of C and of F are at a right angle to the chuck axis. Hence in gripping the rod or wire there is no tendency to move it endways, as there is where the gripping jaws have, as in many machines, a certain amount of end motion while closing. When this end motion exists, tightening the jaws upon the work draws it away from the stop in the turret and impairs the adjustment for length of work. The gripping jaws are closely guided in slots in D and in A, and three sets of these jaws are necessary to cover a range of work from the full diameter of the bore of H down to zero. The capacity of each of these sets of jaws, however, may be varied as follows: The adjustment ring B is threaded upon A, and may be operated along A to move C endwise by means of the tangent screw E, whose threads engage with teeth parallel to the axis of B, and running across its width all around its circumference, hence rotating E, rotates B, causing it to move along A, and carry C beneath F. By this method of adjustment F need be given only enough motion to and from the chuck axis to grip and release the work, and the reduction of motion between the hand-lever operating H and the motion of F is so great, that with a very moderate force at the lever the wire may be held so that its projecting end may be twisted off without slipping the wire within the jaws or impairing the jaw grip. [Illustration: Fig. 705.] Fig. 705 is a sectional and end view of the core A of the chuck, and Fig. 706 a sectional and end view of the shell D. [Illustration: Fig. 706.] Fig. 707 represents a sectional side view and an end view of the cross slide, or cutting-off slide, which carries two tool posts, and therefore two cutting tools, one of which is at the back of the rest. In place of a feed screw and nut, or of a hand lever and link, it is provided with a segment of a gear-wheel P operating in a rack R, which avoids the tendency to twist the cross slides in its guides which exists when a hand lever and link is used. [Illustration: Fig. 707.] The cross slide is adjusted to fit in its guideway by a jaw S^{1}, Fig. 707, which is firmly screwed to and recessed into R. To take up the wear, the face of S^{1} is simply reduced. This possesses a valuable advantage, because it is rigid and solid, does not admit of improper adjustment, nor can the adjustment become impaired at the hands of the operator. To adjust the position of the cross slide upon the shears a screw passes between the shears and is threaded into the stud Q. This screw is operated by a hand wheel shown in the general view, Fig. 703, beneath the rear bearing of the headstock. A special and excellent feature of the machine is the stop device for the motion of the cross slide which is shown in Fig. 707. The screw S has one collar C, solid on it, and the screwed end is tapped into the sliding sleeve T, which is held from turning by the stud A. Between the solid collar C and the loose collar B there is a short, stiff spiral spring, as shown; by means of the fast and loose collars, the spring and the screwed thimble D, a strong friction is had on the collar B, which is ample to keep the screw from turning while in use as a stop, although it permits the screw to turn easily enough when a wrench is applied to the square end. Precisely the same device is used at the other end of the slide to stop it in the opposite direction. [Illustration: Fig. 708.] Details of the mechanism of the turret and turret slide are shown in Figs. 708, 709, and 710. Fig. 708 is an end sectional view of the turret slide, which is traversed on its base by a segment D of a gear operating in a rack R (in the same manner as the cutting-off slide), the segment being connected by stud N to handle M. O represents the body of the slide, which is grooved at the sides to receive the gibs X, which secure it to the base P on which it slides. P is clamped to its adjusted position on the shears or bed by means of the gib, shown in dotted lines, which is pulled laterally forward by the screw S, which is tapped into the stem of the gib. The method of rotating the slide and of locking it in position is shown in Fig. 709, which is a top view of the turret head, and Fig. 710, which shows O removed from P and turned upside down. Pivoted to segment D is a rod E having at K a pin that as motion proceeds falls into S and rotates T, which is fast to the bottom of the turret. Upon the handle M being moved backward the segment begins its motion forward, as indicated by the arrow in Fig. 710, thereby moving the slide backward upon the gibs by the working of its cogs into the rack R, Fig. 708, which is attached to the base P. When the segment D has accomplished about one-half its motion the pin H, which is on the upper side of the segment D, comes in contact with the projection or lug on the side of the cam F, as shown by the arrow head in Fig. 710, bringing the opposite side of the cam against the pin G, Fig. 709, thereby moving it backward, compressing the spring U, and drawing the bolt L from its seat in the disc V. This operation is completed before the motion of the segment brings the pin K in contact with the ratchet-wheel T. The segment D in continuing its motion after the pin K is brought into the notch S, begins the revolution of the turret on its axis. As will be seen by the inspection of Fig. 710, the pin H works upon a much longer radius than the projection upon the cam with which it comes in contact, and therefore, after a given part of its motion is complete, gets beyond the reach of the cam, thereby releasing its hold and allowing the bolt L, Fig. 709, to be forced against the disc V by the expansion of the spring U, which occurs soon after the turret has commenced its revolution by the contact of pin K with the wheel T. The completion of the movement of the handle M (and the segment D) completes the revolution of the turret one-sixth of its circumference, thereby allowing the bolt L, by the further expansion of the spring U, to be forced into its next opening or seat in the disc V. The forward motion of the handle M brings the turret forward to its position at the work and restores the parts to their former positions, as shown in the illustrations. [Illustration: Fig. 709.] [Illustration: Fig. 710.] The stop motion for the forward motion of M, and that therefore determines the length of turret traverse forward, and hence the distance each tool shall carry its cut along the work, is shown in Fig. 711. The end of the screw A abuts against the stop B in the usual manner; it is, however, threaded through the eye of a bolt C, as well as through the end of the turret slide, so that it may be locked by simply operating the nut D. Thus the use of a wrench is obviated, and the adjustment is more readily effected. [Illustration: Fig. 711.] Figs. 712 and 713 represent a screw machine by the Pratt and Whitney Company, of Hartford, Connecticut, and having Parkhurst's patent wire or rod feed for moving the work through the hollow spindle and into position to be operated upon by the tools. The reference letters correspond in both figures. At A is the front and at B the back bearing, affording journal bearing to a hollow spindle C, which carries the shell D of the work-gripping chuck, the clutch ring H and a collar I, in which is pivoted, at J, the clutch levers G. This collar is threaded upon C and is locked in position by a ring lock nut J´. The clutch arm K slides upon a rod X, and has a feather projecting into a spline in X. The core E of the work-gripping chuck is fast upon the inner spindle F, which revolves with the outer one C. The left-hand end of F abuts against the short arms of the clutch levers G, and it is obvious that when K is operated back and forth upon X, it moves the clutch H endways upon C, and the cone upon H operates the levers G, causing them to move the inner spindle F endways and the inner cone E of the chuck to open or close. Suppose, for example, that K (and hence H) is moved to the right, and the long ends of G will be released and may close moving their short ends away from the end of F, and therefore releasing E from its grip upon the work. In moving K to the right the sleeve L is also moved to the right, and its serrations at L´ being engaged with the tongue P, the sleeve M is pulled forward. Now the bar or rod of which the work is made is held at one end by the chuck, it is supported by the bushing Z in the end of spindle C, and in the bushing S in the arm of sleeve M, while it has fast upon it a collar T. When therefore M is pulled forward or to the right, its arm meets T and pulls the rod or bar for the work through the chuck E. [Illustration: Fig. 712.] [Illustration: Fig. 713.] On the other hand when K and therefore H, L, and M, are moved to the left, levers G are opened at their long ends by the cone of H. The short ends of G push the inner spindle F to the right, E passes through D, and being split, closes upon the work and grips it, the parts occupying the positions shown in the figure. The same motion of K passes L through the sleeve M (the teeth at N raise the catch P, allowing L´ to pass through M) so that at the next movement of K to the right, M will be pulled a second step forward, again passing the work through the chuck. Q is merely a pin wherewith to lift P and enable M to be moved back, when putting in a new rod for the work; K is operated by a link from U to V, the handle for moving this link being shown at W in the general view. To prevent the sleeve M from moving back with L it is provided with a shoe O, pressed by the spring R against X, thus producing a friction between M and X that holds M while L slides through it. R´ is to regulate the tension of the spring at R. _y_ is merely a sleeve to protect the clutch mechanism from dust, &c. Box tools for screw machines are used for a great variety of special work. They are simply boxes or heads carrying tools and a work-steadying rest. Fig. 714 represents a box tool for a screw machine. The cylindrical stem fits into the turret holes and contains a steadying piece or rest G to support the work and keep it to its cut. In the box tool shown in the figure, there are four cutting tools set in to the depth of cut by the screws A, B, C, and D respectively, and a fifth for rounding off the end of the work is shown at E. [Illustration: Fig. 714.] Fig. 715 represents a top view, Fig. 715_a_ a front view, and Fig. 715_b_ an end view, of a box tool for shaping the handles for the wheels of the feeding mechanism of machines. The work is first turned true and to its required diameter, and the rest is set to just bear against the work to steady it and hold it against the pressure of the cut. The cutter is cylindrical with a gap cut in it at G, so as to give a cutting edge. By grinding the face of this gap the tool is sharpened without altering its shape, as is explained with reference to circular or disc tools for lathe work. The cutter is provided with a stem by which it is held in the slide, through the medium of the clamp. The slide is operated by an eccentric on the spindle or rod R, which is operated by the handle H. The stop obviously arrests the motion of the slide when it meets the box B, and this determines the diameter of the work, which is represented by W in the end view figure. [Illustration: Fig. 715.] [Illustration: Fig. 715_a_.] [Illustration: Fig. 715_b_.] Fig. 716 represents the die holder and die for the Pratt and Whitney Co.'s screw machine. The die is cut through on four sides, and is enveloped by a split ring having a screw through its two lugs, so that by operating the screw the die may be closed to take up the wear and adjust it for diameter. It is secured in a collar by the set-screw shown, and this collar is clutch shaped on its back face, engaging a similar clutch face on the shoulder of the arbor, the object of this arrangement being as follows. Suppose it is required to cut a thread a certain distance, as say, 3/4 inch, along a stud, and that the depth of the clutch is 1/4 inch. Suppose that when the turret is fed forward sufficiently the thread is cut half an inch along the work at the moment that the turret meets its stop and comes to rest, then the die will continue to feed forward one-quarter of an inch, moving along the body or stem of the holder until its clutch face disengages, when the die will revolve with the work. [Illustration: Fig. 716.] [Illustration: Fig. 717.] Fig. 717 represents a cutting-off tool and holder for a screw machine. The tool fits into a dovetail groove in the split end of the holder, and is ground taper in thickness to give the necessary clearance on the sides. It is held by the screw shown, which closes the split and grips the dovetail; obviously the top face only is ground to resharpen it. [Illustration: Fig. 718.] Fig. 718 represents a special lathe for wood work designed and constructed by Charles W. Wilder, of Fitchburg, Massachusetts. It is intended to produce small articles in large quantities, cutting them to duplicate form and size without any further measurements than those necessary to set the tools in their proper respective positions. It is employed mainly for such work as druggists' boxes, tool handles, straight spokes for toy vehicles, piano pins, balls, rings, and similar work. Its movements are such that the tools are guided by stops determining the length and the diameter of the work so as to make it exactly uniform, while the form of the cutting tools determines the form of the work, which must therefore be uniform. The lathe may be described as one having a carriage rest spanning the bed of the lathe, which rest holds the work axially true with the lathe centres without the aid of the dead centre, while it at the same time trues the end of the work and leaves it free to be operated upon by other tools, which, after once being set and adjusted, shape any number of pieces of work to exact and uniform diameter and shape. [Illustration: Fig. 719.] The manner in which this is accomplished is as follows: Fig. 718 is a general external view of the lathe; Fig. 719 is an end elevation view of the rest from the cone spindle end, and Fig. 720 is an end view of the rest viewed from the tailstock end of the lathe. A is a ring fastened in the rest R by the set-screw B. The mouth C of the ring which first meets the work is coned, or beveled, as shown, and an opening on one side of the ring admits a cutting tool T. Now the work is placed one end in the cone driving chuck on the lathe spindle, and the other end in the cone or mouth C, Fig. 719, being kept up to the driving chuck by the end pressure of C. As the work rotates, the tool T cuts it to the diameter D of the ring bore, the carriage or rest R traversing along the lathe bed as fast as tool cuts; hence the bore D serves as a guide to hold the work and make it run true, this bore being axially true with the lathe centres. The cone surface of C thus operates the same as the sole of an ordinary carpenter's plane, the tool T cutting more or less rapidly according as its cutting edge is set to project more or less in advance of the surface of the cone or recess C. This admits of the tool cutting at a rate of feed that may best suit the diameter of the work and the nature of the wood. The tool T, is operated laterally to increase or diminish the rate of feed by the screw E, which also serves as a pivot, so that by operating the thumb-screw F, the tool point may be adjusted for distance from the centre of the bore D, or in other words the diameter to which the tool T will turn the work is adjusted by the thumb-screw F. G is the head of the pivot screw that the swing tool holder H works upon, and this swing motion carries the forming tool or cutter X, which shapes the work to the required form. I is a shaft upon which a lever, carrying the tool holder J, works, the latter carrying the severing tool K, which severs the finished work from the stick of wood from which the work is made. The tool holders H and J are connected by means of the arms L and M to the stud O, fast in wheel P, operated by a knee lever Q, which is pivoted at S to _u_, which is fast to one of the gibs that hold the carriage to the lathe [V]s. The knee lever Q is connected to the wheel P by a raw-hide strap, or belt V, so that the operator, by pressing his knee upon the end of the lever Q, causes the wheel P, to partly rotate, carrying O with it (O being fast in P), and gives a forward radial motion to tool holder H and cutter X, causing the latter to enter the work until such time as the stud O and the screw stud W are in line, horizontally with the centre of the wheel P, after which tool holder H will move back, while the severing tool K (which has a continuous upward or vertical movement) is cutting off the finished work, which has been formed to shape, and reduced to the required diameter by the forward movement of the tool or cutter X. The object of the backward or retiring motion of H is to relieve the shaping tool X from contact with the work, while K cuts it off, or otherwise the work might meet X when cut off, and receive damage from contact with it. The stud W, connecting tool holder H with the wheel P, is threaded with a right and left-hand screw, by operating which the tool X may be operated to reduce the work to any required diameter. The rest or carriage R traverses along the lathe shears or bed Z, carrying with it all the levers and tools, so far described. [Illustration: Fig. 720.] The tailstock, or back head, carries a tool holder in the rear of the spindle, in which fits also a drill bit or other cutting tool. The method of traversing and operating the carriage R and the back head is as follows: At the back of the bed or shears is a table, shown at T, in Fig. 718. Upon this table is a stand to which is pivoted the end of a lever, as is shown at 1 in figure. This lever has a joint at 2, and is connected to the tailstock spindle at a joint marked 3. It is obvious that by operating the lever laterally, joint 2 will double, and the tail spindle will be moved along the bed. If the tail spindle is not locked it will simply feed through the tailstock and the tool in the spindle will operate, but if it is locked (by the ordinary screw shown), then the handle will slide the whole tailstock and the tool in the holder at the back of the tail spindle may operate. [Illustration: Fig. 721.] At 4 is an adjusting screw, which, by coming into contact with the carriage R causes it also to traverse, which it will do until it meets against a screw on the other side, marked 5, in Fig. 718, which, standing farther out than the chuck prevents the cutting tool from meeting the chuck. The movement of the carriage continues until the stop-gauge 6 meets the end of the work, hence the length of the work is from the cutting-off tool to the face of stop 6. The adjustment for the length of the work is made by means of screw 4, which will slide the carriage R, as soon as it meets it, independent of what distance the stop 6 may be from the work end. The tailstock carries two tool holders, similar to those on an ordinary lathe. When the cutting tools are used to cut completely over the end of the work, as in ball turning or a round ended handle, the stop 6 is not used, the tool which rounds the end acting as a stop of itself. When bits are used they are held in the tail spindle and are made of a proper length to give the required depth of hole, or sometimes the face of the bit-holder may be used as a stop. When the tools, cutters, and belts are all properly adjusted in position to cut to the required respective diameters or lengths the operator has simply to place a stick of wood in the lathe and operate the respective handles or levers in their proper consecutive order, and the work will be finished and cut off, the operation being repeated until the stick is used up, when a new one may be inserted, and so on. LATHES FOR IRREGULAR FORMS.--In lathes for irregular forms (which are chiefly applied to wood and very rarely to metal turning), the work is performed by rotary cutting tools carried in a rapidly rotating head. The work itself is rotated slowly, and the carriage or frame carrying the cutting tools is caused to follow the outline of the pattern or _former_ at every point in its circumference as well as in its length. The principle of action by means of which these ends are attained is represented in Fig. 721, in which S represents a slide which carries the sliding head, affording journal bearing to the rotating head H, driven by the belt E, and carrying the cutters, and also the wheel W. F represents the pattern or former, and B a piece of wood requiring to be turned to the same form as that of F. Suppose then that F be slowly rotated by A and C, receiving rotary motion from A (through the medium of D), then the rotations of C will equal those of F, because the diameter of A is equal to that of C. The diameter of the circle described by the cutters at H is also equal to the diameter of W, hence the motion of the extremities of the cutters is precisely the same as that of the circumference of W, and as W receives its motion from F it is obvious that the cutters will reduce G to the same form and size as F, and if the head be traversed in the same direction as the axis of F, then the diameter and form of B will be made to correspond to that of F at every corresponding point throughout its length. Contact between W and F is maintained by means of a weight or spring, the rotation of F being sufficiently slow to insure its being continuous, while the necessary rapidity of cutting speed for the tools is attained by rotating H at the required speed of rotation. This class of lathe is termed the "Blanchard" lathe from the name of the inventor, or "Lathe for irregular forms," from the chief characteristic of the work, but is sometimes designated from the special article it is intended to turn, as "The Shoe-last lathe," "Axe-handle lathe," "Spoke lathe," &c., &c. [Illustration: Fig. 722.] Let Fig. 722 represent a lathe of this kind provided with a frame A affording journal bearing to the shaft of the drum B, which is driven by the pulleys C. Let E represent a pulley receiving motion from B by the belt D. The cutting tools are carried by the head F which is rotated by pulley E. Let the carriage or frame carrying the shaft of E carry a dull pointed tracer, with continuous contact with the _former_ H by means of a weight or spring, the carriage being so connected to the way N on which it traverses that it is capable of rocking motion, and if H be rotated the carriage will, by reason of the tracing point, have a motion (at a right angle to the axis of H) that will be governed by the shape of H; hence since G rotates equally with H, the form of the blank work G will be similar to that of H, but modified by reason of the tracing point being at a greater distance than F from the centre of rocking motion. All that is necessary to render this motion positive throughout the lengths of G and H is to connect them together by gears of equal diameter, and traverse the carriage along N for the full length of the pieces. But the effect will be precisely the same if the frame carrying G and H be pivoted below, capable of a rocking motion, and H be kept against the tracing point by means of a spring or weight, in which case the carriage may travel in a straight line upon N and without any rocking motion. This would permit of the carriage operating in a slide way on N enabling it to traverse more steadily. To maintain continuous contact between the tracing point and the _former_ H, the rotations of H are slow, the necessary rapidity of tool cutting action being obtained by means of the rapid rotation of the head and cutters F. Since motion from the line shaft to the machine is communicated at C it is obvious that the gears or devices for giving motion to H and G may be conveniently derived from the shaft carrying C and B, for which purpose it extends beyond the frame at one end as shown. Lathes of this kind are made in various forms, but the principles of action in all are based upon the principles above described. [Illustration: Fig. 723.] BACK KNIFE GAUGE LATHE.--This lathe, Fig. 723, has a carriage similar to that described with reference to Fig. 718, and carries similar tools upon the tailstock. It is further provided, however, with a self-acting feed traverse to the carriage, and by means of a rope and a weight, with a rapid carriage feed back or from left to right on the bed, and also with a knife at the back. This knife stands, as seen in the engraving, at an angle, and is carried (by means of an arm at each end) on a pivoted shaft that can be revolved by the vertical handle shown. The purpose of this knife is first to shape the work and then to steady and polish the wood or work. Obviously when the knife is brought over upon the work its cutting edge meets it at an angle and cuts it to size and to shape; the surface behind the cutting edge having no clearance rubs against the work, thus steadying it while polishing it at the same time. These lathes are used for turning the parts of chairs, balusters, and other parts of household furniture, the beads or other curves or members being produced on the work by suitably shaped knives, which obviously cut the work to equal shape and length as well as diameter, and it is from this qualification that the term "gauge" is applied to it. Fig. 724 represents the Niles Tool Works special pulley turning lathe, in which motion from the cone spindle to the live spindle is conveyed by means of a worm on the cone spindle and a worm-wheel on the live spindle. Two compound slide rests are provided, the tool on the rear one being turned upside down as shown. These rests may be operated singly or simultaneously, and by hand or by a self-acting motion provided as follows:--A screw running parallel to the cone spindle is driven by suitable gearing from the cone spindle. At each end of this screw it gears into a worm-wheel having journal bearing on the end of the slide rest feed screw as shown. By a small hand wheel on the end of the slide rest feed screw the worm-wheel may be caused to impart motion to the feed screw by friction causing the slide rest to feed. But releasing this hand wheel or circular nut releases its grip upon the feed screw, and permits of its being operated by the handle provided at the other end. The rail carrying the slide rest is adjustable in and out to suit varying diameters of pulleys, being secured in its adjusted position by the bolts shown. The cut is put on by means of the upper part of the compound rest. To turn a crowning pulley the rails carrying the slide rests are set at an angle, the graduations shown on the edge of the ways to which they are bolted being to determine the degree of angle. When the pulley surface of the pulley is to be "straight" both tools may commence to operate on one edge of the pulley surface, the advance tool taking a roughing and the follower tool a finishing cut; but for crowning pulleys the tools may start from opposite edges of the pulley, the cuts meeting at the middle of the face; hence the angles at which the respective rails are set will be in opposite directions. The pulleys to be turned are placed upon mandrels and driven by two arms engaging opposite arms of the pulley. To drive both arms with an equal pressure, as is necessary to produce work cylindrically true, an equalizing driver on Clements' principle (which is explained in Fig. 756, and its accompanying remarks) is employed. For driving the pulleys to polish them after they are turned the cone spindle is hollow at the rear end and receives a mandrel. The high speed at which the cone spindle runs renders this possible, which would not be the case if wheels and pinions, instead of worm-gear, were employed to communicate motion from the cone to the live spindle. A wheel shown in position for polishing is exhibited in the cut, the pivoted arm in front affording a rest for the polishing stick or lever. BORING AND TURNING MILLS.--The boring and turning mill patented in England by Bodmer in 1839, has developed into its present improved form in the United States, being but little known in other countries. It possesses great advantages over the lathe for some kinds of turning and boring, as wheels, pulleys, &c. The principal advantages of its form of construction are:-- [Illustration: Fig. 724.] [Illustration: Fig. 725.] 1st. That its work table is supported by the bed at its perimeter as well as at its centre, whereas in a lathe the weight of the chuck plate as well as that of the work overhangs a journal of comparatively small diameter, and is therefore more subject to spring or deflection and vibration. 2nd. It will carry two slide rests more readily adjustable to an angle, and more readily operated simultaneously, than a lathe slide rest. 3rd. It is much more easy to chuck work on a boring mill table than on a lathe, because on the former the work is more readily placed upon the table, and rests upon the table, so that in wedging up or setting any part of the circumference of the work to the work table, there is no liability to move the work beneath the other holding plates; whereas in a lathe the work standing vertical is apt when moving or setting one part to become unset at other points, and furthermore requires to be held and steadied while first being gripped by the chucking dogs, plates, or other holding devices. Figs. 725, 726, 727, 728, and 729 represent the design of the Niles Tool Works (of Hamilton, Ohio), boring and turning mill. In this design provision is made to raise the table so that it takes its bearing at the centre spindle only when used upon small work where a quick speed of rotation is necessary, or it may be lowered so as to take its circumferential bearing for large heavy work where slower speeds and greater pressure are to be sustained. The bearing surfaces are, in either case, protected from dust, &c., and provided with ample means of lubrication. Each tool bar is so balanced that the strain due to the balancing weights is in a line parallel to the bar axis in whatever position and at whatever angle to the work table the bar may be set. This prevents the friction that is induced between the bar and its bearings when the balancing strain is at an angle to the bar axis, and consequently pulls the bar to one side of or in a line to twist the bar. The bar is therefore more easily operated, and the feed gear is therefore correspondingly relieved of strain and wear. The general construction of the machine is shown in Fig. 725. It consists of a base or bed, affording journal bearing and support to a horizontal work table, rotated by devices carried upon the bed. To each side of the bed are attached uprights or standards, forming a rigid support to a cross slide or rail for the two sliding heads carrying the tool bars. The various motions of the machine are as follows: There are 16 speeds of work table, 8 with the single, and the same with the back gear. The cross slide is capable of being raised or lowered, to suit the height of the work, by an automatic motion. Both tool rests are capable of hand or automatic feed motion at various rates of speed, in a line parallel to the surface of the work table. Both are also capable of automatic or hand feed motion, either vertically or at any required angle to the work table, and have a quick return motion for raising them, while each may be firmly locked while taking radial or surfacing cuts, thus preventing spring or vibration to the tool bar. In addition to this, however, there is provided, when required, a tailstock, carrying a dead centre after the manner of a lathe, so that the work may be steadied from above as well as by the work table. In Figs. 726 and 727 are shown the devices for raising the work table and those for actuating the feed screws and the feed rod; thus operating the sliding heads horizontally and the tool bars vertically. A is the base or bed supporting the work carrying table B´, and affording its spindle journal bearing at D´. A step within and at the foot of D´ rests upon the wedge F´ so that when the wedge is caused to pass within D´ it lifts the step, which in turn lifts the table spindle, and hence the table, sufficiently to relieve its contact with the outer diameter of the bed. F´ is operated as follows: The lever G´ is pivoted at E´ and carries at its upper end a nut H´, operated by a screw on the end of the bolt I´; hence rotating I´, operates wedge F´. For operating the automatic feed motions, _f_ is a disc upon a shaft that is rotated by suitable gears beneath the work table; _g_ is a disc composed of two plates, having a leather disc between them, the perimeter of the disc having sufficient frictional contact with _f_ to cause _g_ to rotate when _f_ does so: _g_ drives the vertical spindle _i_, which has a worm at J´ driving a worm-wheel which rotates the gears upon the feed spindles V, F, W, in the figures; _f_ rotates in a continuous direction, but the spindle _i_ is caused to rotate in either direction, according to whether it has contact with the top or bottom of the face of _f_, it being obvious that the motion of _f_ above its centre is in the opposite direction to that below its centre of rotation. The means of raising and lowering _g_ to effect this reversal of rotative direction is as follows: It is carried on a sleeve _g´_ which is provided with a rack operated by a pinion that is rotated by means of hand wheel _h_; hence, operating _h_ raises or lowers _g´_, and therefore _g_; _h´_ is a hand wheel for locking the pinion, and hence detaining the rack (and therefore _g_) in its adjusted position. This design is an excellent example of advanced American practice for obtaining a variable rate of feed motion in either direction, it being obvious that _g_, being driven by the radial face of _f_, its speed of rotation will be greater according as it is nearer to the perimeter of _f_ and less as it approaches the centre of _f_, at which point the rotary motion of _g_ would cease. Here, then, we have a simple device, by means of which the direction and rate of feed may be governed at will with the mechanism under continuous motion, and conveniently situated for the operator, without his requiring to move from the position he naturally occupies when working the machine. [Illustration: Fig. 726.] The means of raising or lowering the height of the rail R on the side standards Z are as follows: K is a pulley driven by belt from the countershaft and operating pinion _l_, which operates pinion _n_, driving _m_. O is a gear on the shaft driving the pinions _p_, _p_, which operate the gears _q_, _q_, on the vertical screws which engage with nuts attached to R; _m_ and _n_ are carried on a bell-crank _r_ pivoted on the shaft of pulley K. Pinion _n_ is always in gear with pinion _l_, and pinion _m_ is always in gear with pinion _n_ (and not with pinion _l_). With the bell-crank in one position, motion passes from _l_ to _n_ and to O; but with it in the other position, motion passes from _l_ to _n_, thence to _m_, and from it to O. The motion of _m_, therefore, is always in a direction opposite to that of _n_; hence O, and gears _p_ and _q_, may be operated in either direction by regulating which of the two gears _n_, _m_ shall drive O, and this is accomplished as follows: The bell-crank _r_ is connected by an arm to rod _s_, and the latter is connected by a strap to an eccentric _t_, operated by the handle shown. When this handle stands horizontally, both _m_ and _n_ are disengaged from pinion O; but if the handle be raised, rod _s_ is raised, and _m_ is brought into gear with O. If, however, it be lowered from the horizontal position, _n_ is brought into gear with O, and _m_ becomes an idle wheel. [Illustration: Fig. 727.] There are two feed screws--one for operating each boring bar-head, and a spindle for operating the vertical feeds of the bars in the sliding heads. Fig. 728 shows the arrangement for engaging and disengaging the feed nuts of these heads. A is the slide that traverses the rail. It carries a nut made in two halves, N and N´, which are carried in a guide or slide-way, and which open from or close upon the screw F when the handle O is operated in the necessary direction. Each half of the nut is provided with a pin projecting into eccentric slots _x_ in the face of a pivoted plate (shown dotted in), to which the handle O is attached. W, W represent bearings for the vertical feed spindle W in Fig. 726. _a_ is the annular groove for the bolts _b_ in Fig. 729. [Illustration: _VOL. I._ =ROLL-TURNING LATHE.= _PLATE XI._ Fig. 730. Fig. 731.] For a quick hand traverse for the head the ratchet, P is provided, operating a pinion _s_, which engages with a rack T, running along the underneath side of the cross-rail R. To adjust the fit of A to the rail the gibs _y_ and _y´_ and the wedge _x_ are employed. [Illustration: Fig. 728.] Fig. 729 represents the automatic feed motion within the head for operating the tool bars vertically. R is the cross rail on which slides A carrying B, and permitting it to swivel at any angle by means of bolts _b_, whose heads pass within an annular groove, _a_ in A. In B is carried the boring bar G, having the rack shown. P is a pinion to operate the rack. W is the feed-rod driving the worm H, which drives the worm-wheel I. This worm-wheel is provided with a coned recess, into which the friction plate C fits, so that when the two are forced together rotary motion from I is communicated to C, and thence to C´ (which is a sleeve upon C), where it drives pinion P by means of pin P´. _i_ rotates upon and is supported by the stud J, which is threaded into C^{2} (the latter being also a continuation of C); hence when hand-wheel K is operated in one direction, C^{2} acting as a nut causes J to clamp I to C, and the tool bar to therefore feed. Conversely, when K is operated in the opposite direction, I is released from C, and may, therefore, rotate while C remains at rest. For feeding the tool bar G by hand, or for moving it rapidly, the hand-wheel M is provided, being fast to the sleeve at its section C^{2}, and, therefore, capable of rotating pinion P. D affords journal bearing to C at its section C´. The chain from the weights which counterbalance the bars G pass over sheaves which are fixed to the piece B in which the bar slides, so that they occupy the same position with relation to the axis of the bar at whatever angle the latter may be set, and thus the counterbalancing weight is delivered upon the bar in a line parallel to its axis. As an example of the efficiency of the machine, it may be mentioned that at the Buckeye Engine Co.'s Works, at Salem, Ohio, a pulley 12 feet in diameter, weighing 8860 pounds, and having a 27-inch face, was bored and turned on one of these machines in 17 hours, taking three cuts across the face, turning the edge of the rim facing off the hub and recessing the bore in the middle of its length for a distance of several inches, the bore being in all 18 inches deep. The machine is made in different sizes, and with some slight variations in each, but the main features of the design, as clearly shown in our engravings, are common to all sizes. Fig. 730 represents a lathe for turning chilled rolls such as are used for paper calendering machines, and is constructed by the J. Morton Poole Company of Wilmington, Delaware. In the figure a roll is shown in position in the lathe. The journals of the rolls are first turned in a separate lathe, and form the guide by which the body of the roll is turned in the lathe shown in the figure. The lathe consists of a bed plate P, at one end of which is mounted the driving head. Upon this bed plate are also mounted three standards or vertical frames, to the two end ones of which are pivoted the binder arms shown. These frames hold the bushes at L and N, in which the journals of the roll revolve. They also carry the bar G, secured to the arm W of the frame by clamps _a_, _a_, _a_. Upon the bar G are two slide rests, consisting of a tool rest E, a tool clamp A, and a feed yoke B, which is screwed up by a wrench applied to the nuts as shown on the right-hand tool rest in the figure. The binder arm is adjusted to hold the bushings L N (which are varied to suit the size of the roll journal) a fair working fit upon the roll journals, the bolts S holding the binder arms firmly against the enormous pressure due to the cut. It is obvious that the frames W may be adjusted anywhere along the bed plate P to suit the length of roll to be turned, and that the slide rests may be moved to any required position along the bar G. Further details of the construction are as follows. Fig. 731 is an end, and Fig. 732 is a top view of the tool rest; A is the tool clamp securing the tool to the rest E, R representing a section of the roll, B is the feed yoke, which to put on a cut is screwed inwards by operating the nuts D. The pins C are fast in B, and their ends abut against the tool, which is fed in under the full pressure of the clamp A. The tool is shown at F in figure, and also at F in Fig. 733, which is a view of the rest with the clamp A removed. The form of tool employed is shown in Fig. 734, its length varying from five to six inches. As the tool feeds in and does not traverse along the roll it is obvious that it cuts along its entire length, the cuttings coming off like a bundle of fine ragged needles. [Illustration: Fig. 729.] When the tool has been fed in cutting the roll to the required diameter the rest is moved along the bar G, a distance equal to the length of the tool, and the operation is repeated until the full length of the roll has been turned. It is obvious that to feed the tool in parallel, both nuts D of the tool rest are operated. The tool is held as close in to the rest as the depth of cut to be taken will permit, and is used at a cutting speed varying from about 2-1/3 feet to 5 feet per minute according to the hardness of the roll. The tool has four cutting edges, and each cutting edge will carry in at least one cut, and may sometimes be used for a second one. The tools are used dry and the amount of clearance is just sufficient to clear the roll and no more. The rolls are driven by a socket bolted to the lathe face plate, and containing a square hole, in which fits loosely the square end of the roll. The object of this arrangement is to permit the roll to be guided entirely by the bearings in which it rotates, uninfluenced by the guiding effect that accompanies the use of centres in the ordinary method of turning. [Illustration: Fig. 732.] Fig. 735 represents a lathe designed and constructed by the American Tool and Machine Company, of Boston, Mass. This class of lathe is strictly of American origin, and has become the most important tool in the brass finishing shop. [Illustration: Fig. 733.] In its design the following advantages are obtained:-- 1st. The front of the lathe is entirely unobstructed by the ordinary lathe carriage and slide rest, hence the work may be more easily chucked and examined, while in the case of work requiring to be ground together, while one part is in the chuck, the trouble of moving the slide rest out of the way is entirely obviated. 2nd. In place of the single cutting tool carried in a slide rest and of the tailstock of the ordinary lathe, there is provided, what is known as a turret, or turret rest, carrying 6 tools, each of which can be successively brought into action upon the work by the simple motion of a lever or handle. [Illustration: Fig. 734.] 3rd. The rest for traversing single pointed screw cutting tools or chasers (for internal threads) is at the back of the lathe where it is out of the way. 4th. In place of the usual change wheels required to operate the lead screw, the chasing bar is operated by a single threaded collar or hob, which is more easy of application and removal. 5th. The slide rest carrying the screw cutting tool is capable of such adjustment, that the tool will thread successive pieces of duplicate work to an exactly equal diameter, so as to obviate the necessity of either measuring or trying the work after the tool has been accurately set for the first piece. 6th. When the threading tool has traversed to the end of its cut it may be lifted from the same and pulled back by hand, ready to take a second cut, thus avoiding the loss of time involved in traversing it back by a lead screw or its equivalent. 7th. Each of the tools in the turret may be set so as to operate to an equal depth and diameter upon successive pieces of work. [Illustration: Fig. 735.] In the particular lathe shown in our example, there is another and special advantage as follows:-- In lathes operating upon small work and upon the softer metals, as composition, brass, &c., the time occupied in traversing the cutting tool is comparatively short, and from the comparative softness of the metal the speed of lathe rotation is quick, and the tool motions must be correspondingly quick. In addition to this the work being so much more quickly performed, changes and readjustments of the parts are necessarily more frequent, hence the rests traverse the bed more rapidly as well as more frequently and the wear of the [V]s on the lathe, and the corresponding [V]-grooves in the tool rest, slide rest, or turret, is increased; as a result, tools carried in the tailstock or the turret, as the case may be, which tools should for a great many purposes stand axially true with the live spindle, stand below it, and hence instead of boring a hole equal to their own diameter, bore one of larger diameter. In the case of tools, however, which, as in the case of drills, endeavour to find their own centre in the work, this action takes place to some extent as the tool enters the work, and as a result the hole is made a taper, whose largest diameter is at the mouth. This induces another evil in that it dulls the advance edge of the drill flute, and wears away the clearance which is of such vital importance to the free action of the drill. The manner in which these advantages are obtained is as follows:-- In place of the ordinary tailstock a back head is provided which has a cross slide operating after the manner of the ordinary slide rest; this carries an upper slide, thus forming a compound slide rest. On the top of this rest is carried a rotating head or turret head, serving the same purpose as the head shown in Fig. 694, and carrying a series of tool holders. These tool holders may be operated by the feed screw of the compound rest, or may be operated by the hand lever shown standing horizontally. In addition to the ordinary back gear for reducing the live spindle speed there is provided on the live spindle a second small pinion, driving at the back of the lathe head a shaft, on the left-hand end of which is a seat for collars or hobs, operating a bar running along the back of the lathe, and forming what is termed the screw apparatus, whose operation is as follows:-- This bar carries the slide rest shown, a handle or lever for partly rotating the slide rest, spanning the bed of the lathe. When this handle is lifted, the bar at the back of the lathe rotates in its journals. On this bar is an arm which carries a segment of a circle, containing a thread corresponding in pitch to the thread on the collar or hob. When the lever is raised the segment moves away from the hob, and the bar may be moved laterally by hand, but when the lever is lowered the arm falls, and the segment comes into contact with the hob thread, which therefore feeds the bar; all that is necessary for thread cutting is, therefore, to place on the lathe a hob having the required pitch for the thread to be cut, and place in the slide rest a chaser or single-pointed threading tool, and set the tool to the work by means of the slide rest, depressing the lever to cause the tool to feed forward, and elevating it to move the bar back by a lateral hand pressure. To put on successive cuts the slide rest is operated, the lever always being lowered till it meets the surface of the lathe bed. To cause the slide rest to cut successive threads to the same diameter, a suitable stop motion is provided to the slide rest, and when the rest has been operated as far as the stop will permit it, the thread is cut to the required depth and diameter. A stop motion is also provided to the lateral motion of the turret, so that the tools being set to enter the work to their respectively required distances, all pieces will be turned to equal depths or lengths. To enable the centres of the tool holders to maintain true alignment with the live spindle, notwithstanding the wear of the lathe bed and back head, the bed is made in two parts. One of them carries the headstock, and on the vertical face of this part is a slide in which the end of the second part fits, so that by means of adjusting screws the second part may be elevated to effect the true alignment when necessary. Fig. 736 represents a square arbor brass-finisher's lathe. The object of the square arbor or tail spindle is to enable it to carry cutting tools in place of the dead centre. A cross slide is provided to the tailstock, and upon this slide the head of the tailstock is pivoted so as to bore taper holes; the tailstock thus virtually becomes a compound slide rest. This lathe is provided at the back of the bed with a bar carrying a slide rest, operated in the same way and for the same purpose as that described with reference to Fig. 735. Both these lathes are furnished with separate compound slide rests, and with a hand rest. [Illustration: Fig. 736.] When work of considerable weight requires to be bored with holes of moderate diameter, it is more convenient that it remain fixed upon a table, and that the boring tools rotate, and a machine constructed by the Ames Manufacturing Company for this purpose is shown in Fig. 737; a standard occupies the position of the ordinary tailstock. It carries an horizontal table, or angle plate, on which the work may be chucked. This table is capable of a vertical and a cross shear movement, so that when the work is chucked upon it, holes whose axes are parallel, but situated in different locations upon the same surface, may be drilled or bored by so moving the table as to bring each successive hole into line with the live spindle. The feed motions are as follows:-- [Illustration: Fig. 737.] At the back of the smallest step on the cone and fast on the cone spindle is a gear-wheel gearing into a pinion, which drives the lower shaft shown behind the back bearing, and on this shaft are two pinions. One drives the upper feed cone, shown at the back of the back bearing, which cone connects by belt to the feed cone below, which operates a traverse feed for the work table; the other drives the tool holding spindle which passes through the cone spindle. This tool holding or driving spindle is threaded at its back end, passing through a nut which causes it to self-feed from left to right, or in other words, towards the work table. To throw this feed out of operation the pinion on the end of the lower or feed driving spindle is moved laterally out of gear with the pinion driving it. To provide a quick hand-feed traverse the shaft or spindle, shown with a hand-wheel, is provided, being connected to the tool driving spindle by gearing. When employed to operate a boring bar, a bearing to support the bar at the tail or footstock end may be bolted to the table, such bearing carrying a bushing which may be changed to suit the diameter of the boring bar. [Illustration: Fig. 738.] Fig. 738 represents a cylinder boring lathe. D is the driving cone, on whose shaft is the worm W, driving the worm-wheel G, which is fast upon the boring bar _g_, having journal bearing in the standards H and H´, the latter of which must be moved out of the way to get the work over the bar. _h_ is a head provided with slots to carry the cutting tools; _h_ is a close sliding fit to the bar _g_, and is traversed along _g_ as follows:--_g_ is hollow and there passes through it a feed screw, which operates a nut on _h_, which nut passes through a longitudinal opening in the bar _g_. At the end of this feed screw is the gear-wheel D. Now fast upon the end of _g_, and therefore rotating with it, is the gear A, driving gear B, which is fast on the same sleeve as C, which it therefore drives; C drives D. The diameter of A is less than that of B, while that of C is less than that of D; hence the rotation of D is slower than that of A, and the difference in the relative velocities of D and A causes the feed screw to rotate upon its axis and feed the head _h_ along the bar. If C be placed out of gear with D, the feed screw (and hence the head H) may be operated by the handle E. [Illustration: Fig. 739.] There are several objections to this form of machine, as will be seen when comparison is made with Fig. 739, which represents a special cylinder boring lathe, designed and constructed by William Sellers and Co., of Philadelphia, Pennsylvania. The boring bar is here supported in two heads, and is hollow, the feed screw for traversing the head carrying the boring cutters being within the bar. The feed is effected through the medium of the train of gearing shown at the end. The two face plates shown which drive the boring bar, also carry two slide rests which are used to face off the ends of cylinders while the boring bar is in operation, these slide rests being operated by a star feed, acting on the principle described with reference to Fig. 589. The boring bar in this case being driven from each side of the work the torsion due to the strain of the cut is divided between the two halves of the bar; or in other words, when a boring bar is driven from one end the strain due to the cut falls upon that part of the bar that lies between the boring-head and the point at which the bar is driven; but when the bar is driven from each end then the strain is divided between the two ends, causing a bar of a given strength to operate more steadily and take a heavier cut for roughing, and a smoother one for finishing. A greater advantage, however, is that it gives to the bar a rigidity, enabling it to carry a cutter having a long cutting edge without chattering, thus allowing a very coarse finishing feed, which will finish a bore with less wear to the tool edge (and therefore more parallel) because for a given amount of work the cutting-edge is under duty for a less period of time, the cutting speed remaining the same, or even slower than would be desirable for a fine feed. The driving-cone, which is shown to be below the boring-bar, is so situated to accomplish two objects, which are to operate the two face plates by a shaft having two pinions (within the bed) gearing with the circumferential teeth on the face plates, and to operate at the same time the table (shown on the bed between the face-plates) to which the cylinder is bolted. In a boring machine it is of the utmost consequence that the bar shall be as free from vibration as possible, while lost motion, or looseness from wear, is especially to be avoided. By carrying the bar in two bearings, as it were, the wear is greatly reduced. The duty of facing the cylinder ends is sometimes done by facing cutters carried in the head. Such cutters, however, must have a cutting edge equal to the breadth of the surface faced by them, because the cutter cannot be fed radially to its cut. Furthermore, the cut is carried by the bar at a considerable leverage, and as a result it is very difficult indeed to make the radial faces true or even nearly true, the cutter dipping into the softer parts of the iron or into spongy places if there are any. In any event springing away from its cut, resisting it until forced to cut, and then cutting deeper than should be, so that on a finished surface it is often apparent to the eye where the cutter began and left off. When, however, the radial faces are operated upon by a slide rest, as in the Sellers machine, the tool is more firmly held, and may be fed radially to the cut, producing true faces, and saving a great deal of time in making the cylinder cover joints, as well as in the boring and facing operations. Fig. 740 represents a double boring and facing lathe by G. A. Gray, Junior, of Cincinnati, Ohio. Two driving heads are provided, each having a main spindle, but holding the boring bar after the manner of an ordinary lathe, and within each spindle is another capable of longitudinal traverse. The main spindle is provided with a head corresponding to a slide rest and carrying a cutting tool for facing purposes, the feed being obtained by means of a _star-feed_. The work is bolted to the carriage and fed to the cut for boring purposes. It is provided with an automatic feed and also with hand feed. When facing is to be done the carriage may be firmly locked to the lathe shears. In boring and facing a steam pump centre, or other similar piece, the casting is fastened to the carriage in a special fixture. The carriage is then moved so that the work will come nearly in contact with tool in the fast head, the loose head is moved up to the work, and both the carriage and loose head are clamped. [Illustration: Fig. 740.] Both ends of the casting may be operated upon at the same time or separately, as occasion requires, the object being, however, to work upon as many places at one time as the nature of the work will permit; this being the main point in the economical performance of work. It is evident also that if the machine is true, and the piece is finished at one setting, the work will be true. [Illustration: Fig. 741.] In the detail engravings, Fig. 741 represents boring, tapping, and facing steam pump centres, in which operations the carriage is locked. [Illustration: Fig. 742.] [Illustration: Fig. 743.] Fig. 742 illustrates the manner of boring and facing cylinders and similar pieces, the loose head stock being used as a tailstock and the fast headstock as the driver. The facing is done either before or after the boring, all the work obviously being done at one chucking. Fig. 743 shows a longitudinal cross section of the headstocks showing the main and the internal spindles. Fig. 744 represents a lathe constructed by the Defiance Machine Works for turning the hubs for carriage and wagon wheels. [Illustration: Fig. 744.] The blank from which the hub is turned is driven by a mandrel having a square stem fitting in the live or driving-spindle, this mandrel being supported at the other end by the ordinary dead centre operated by the upper hand-wheel. The bed is provided (between the driving-spindle and tailstock) with the usual raised [V]s on which rests a carriage carrying a cross slide. This cross slide carries, at the back of the lathe, a head or stock containing the roughing-knives, and at the front a table carrying the finishing-knives, hence, by operating the large hand-wheel (which gives transverse motion to the cross slide) in one direction the roughing-knives are brought into operation, while by operating it in the opposite direction the finishing-knives are brought into operation (the roughing-knives receding). By suitable stops, the motion of the roughing and finishing-knives respectively are arrested when those knives have cut the blanks to the desired diameter, the finishing-knives shaping the work correctly by reason of their form of outline. Upon the same cross slide are the equalizing-knives, one on each side of the front table. These knives operate simultaneously with the finishing-knives, cutting the hubs to uniform length. Thus the hubs are cut to exact uniformity of diameter, shape and length, by simply operating the large hand-wheel first in one direction and then in the other. If it be required to cup the hubs, as in the case of standard wagon hubs, suitable cutters carried in a bar (having sliding motion in a guide way on the tailstock) are caused to do such cupping, the cupper-bar being operated by the left-hand lever. The live, or driving, spindle is started and stopped by a tight and loose pulley, the belt being passed from one to the other by means of the lever on the right, which simultaneously operates a brake attached to the belt stopper, operating upon the tight pulley. By this means the lathe can be started and stopped more quickly than would be the case with a cone pulley, whose extra weight and inertia would take time to overcome. CHAPTER IX.--DRIVING WORK IN THE LATHE. The devices employed to drive work that is suspended between the lathe centres are shown in the following illustrations. They are termed lathe dogs, drivers, or carriers. It is to be observed, however, that since the term dog is also applied to a device for holding work to the lathe face plate, as well as to the jaws of chucks, either the term driver or the English term carrier is preferable to the term dog. [Illustration: Fig. 745.] [Illustration: Fig. 746.] Fig. 745 represents a lathe dog, driver, or carrier D, in position to drive a piece of work in the lathe. It is obvious that the work is secured within the carrier or driver by means of the set-screw shown. The tail of the driver here shown is bent around to pass within the slot provided in the face plate, a plan which is convenient, but is objectionable, because in this manner of driving the work two improper strains are induced, both of which act to spring or bend the work. The first of these strains is caused by the carrier being driven at a leverage to the work, as shown at A in the figure, which causes the live centre to act as a fulcrum, from which the work may be bent by the strain caused by the cut. [Illustration: Fig. 747.] The second strain is caused by driving the carrier from one side or end only, and is shown in Fig. 746, where the dog receives the face-plate pressure at the point A, and the cut or resistance being on the opposite side of the work, the leverage of the driving point causes a tendency to lift the work in the direction of the arrow C. The direction of this latter strain, however, varies as the work revolves. For example, in Fig. 747 the dog is shown in position at another point in its revolution, and the point A, where the power is applied to the carrier, is here on the same side as the tool cut; hence there is less tendency to spring the work. It becomes obvious then, that work driven in this manner will be liable to be oval, or out of round, as it is commonly termed. [Illustration: Fig. 748.] The methods of overcoming these two sources of error are as follows: Instead of the end of the dog being bent around to pass within the slot in the face plate, as in Fig. 745, the leverage A in that figure may be avoided by the means shown in Fig. 748, in which a driver having straight ends is used, and a pin P is fastened to the face plate to drive the carrier. But this does not remove the tendency (shown in Fig. 746) acting to spring the work from the pressure of the cut; hence, to obviate this latter tendency, two driving-pins P P, in Fig. 749, are sometimes used with the idea of driving the work from both sides, and thus equalizing the strain. But this is effective only when each pin is in working contact with the dog. This condition is difficult to secure for several reasons. First, suppose the two ends of the carrier to be of equal thickness, and the driving-pins to be of equal diameter, while the work receiving hole of the carrier is quite central to these two ends, then the work also must be true, in order to cause the pins to act equally on the ends of the carrier. Hence, this method is only applicable, even if all the above conditions be fulfilled, to the finishing cuts, and these would have to be taken on work that had been sprung in the roughing cuts, so that it would be difficult to obtain accurate results. A nearer approach to correctness is therefore sought by various means. Thus, Fig. 750 represents a face plate provided with an annular [T]-groove, having a cut at H to admit two nuts into which the pins P are screwed. These pins may be tightened lightly, so that they will slip under the pressure of the roughing cut, and thus come to an equal bearing upon the carrier or work, as in case of the arms of a pulley where a carrier is not used. When the pins have adjusted themselves to have as near as may be an equal driving bearing, they may be tightened up. By this means the pins are compelled to act at an equal leverage upon the carrier or work, but there is no assurance of an equal degree of pressure of the pins P. Another method is shown in Fig. 751, in which a clamp in two parts is employed, the driving-pins P fitting into two holes equidistant from the lathe centre, while loosening one bolt, J or K, and tightening the other is resorted to, to equalize the driving contact on the two arms, but in this case again there is no certainty that the two pins will drive equally, and there is danger of drawing the work somewhat out of true. Another form is shown in Fig. 752, the idea being to equalize the pressure of the driving pins, by means of the four screws, but here again, there is no means of knowing whether the driving pressure is equalized. [Illustration: Fig. 749.] The best form of driver is shown in Fig. 753, which represents a Clement's driver. The driving-plate F has four slots; two of them, A and B, pass entirely through this plate to admit bolts C D, which have a shoulder, so that they may be secured firmly to the lathe face plate, but which are an easy fit in the plate F, so as to permit it to move upon the lathe face plate. The other two are [T]-shaped slots to receive nuts, into which the pins P P are to be screwed. The bolts C D drive F, and the pins P drive the work, the freedom of the plate E to move upon the lathe face plate permitting this strain-equalizing action of the driving-plate and driving-pins. [Illustration: Fig. 750.] [Illustration: Fig. 751.] [Illustration: Fig. 752.] Sometimes, as in cutting screws, the work requires to be revolved backwards, without having any lost motion between the arm and carrier, or in other words, the carrier must revolve backwards as soon as the face plate does. To accomplish this, a common plan is to tie the driver or carrier to the driving-pin, but a better plan is to employ a bent tailed dog and secure its end in the face-plate slot. A convenient form of face plate for this purpose is shown in Fig. 754, A, B, C, and D, being slots, and E a set-screw for binding the dog as shown in Fig. 755. [Illustration: Fig. 753.] For special lathes in which the work is of uniform diameter, the driving pins P, Fig. 753, may be replaced by solid jaws, thus in Fig. 756 is a Clement driver, such as is used on axle lathes, C C being driving lugs in place of the pins P in figure. To prevent the ends of the set-screw or screws of the driver from damaging the surface of finished work, the form of driver shown in Fig. 757 has been patented in England. It consists of a disc arched to receive a lever C, which is pivoted in the disc at D. A set-screw provided in the disc binds one end of the lever to the work, and as the pressure to drive the work is applied at the other end of the same lever, it serves to assist (to some extent) the set-screw in binding the lever to the work. The work is held between a [V] in the disc and one on the lever, the object being to provide a large area of contact, and thus prevent the damage to finished work which screw ends are apt to cause. [Illustration: Fig. 754.] The same end may be obtained for ordinary drivers by using a copper or brass ring, such as shown in Fig. 758, which may be opened or closed, within certain limits, to suit the diameter of the work, being placed on the end of the work, and within the dog, to receive the pressure of the set-screws. [Illustration: Fig. 755.] One such ring will serve for several diameters of work, springing open when forced, under hand pressure, upon the work, or closing upon the work as the pressure of the dog set-screw is received. It is obvious that the split of the ring should be placed diametrally opposite to the dog set-screw. [Illustration: Fig. 756.] In very small lathes the driver is sometimes driven by the device shown in Fig. 759, which consists of a small chuck, screwed on the live spindle, and containing the live centre and a driving arm B, which passes through the chuck, and is set to any required distance out, by the set-screw C. The objection to this is, first, that either the live centre must be very short, or the arm B must be very long; and, second, if the chuck wears out of true, it carries the live centre also out of true; hence this class of driver is but little used, even in foot lathes. [Illustration: Fig. 757.] [Illustration: Fig. 758.] In small drivers of this kind it is sometimes the practice to cut away rather more than one quarter of the thread on each side of the live spindle as shown in Fig. 760 at A, and to then cut away one quarter of the thread on each side of the bore of the driver as at B in the figure. This enables the driver to be passed upon the spindle and screwed home with one quarter of a turn, thus saving time in putting on and taking off the driver. Fig. 761 illustrates a work driver very convenient for turning bolts. It consists of a piece of iron or plate P bolted to the lathe face plate F, and having jaws so as to fit to the sides of the bolt B and drive it. This not only saves the time that would otherwise be required to put on a driver or carrier but leaves the underneath face of the bolt clear to be faced up by the turning tool, an example of its use being shown in connection with the knife tool or facing tool. [Illustration: Fig. 759.] [Illustration: Fig. 760.] Fig. 762 represents a driver of this kind having a sliding jaw so that it may be set for different sizes of bolt heads. When the driving end of the work is threaded an ordinary dog or driver cannot be used because its screw would damage the thread on the work. A common method of overcoming this difficulty is to place over the ring a split ring of copper, or to place on it two nuts, putting a common dog on the end nut. It is better, however, to use a driver, threaded part of the way through, as in figure 762 (from _The American Machinist_) and to screw it upon the work. [Illustration: Fig. 761.] Fig. 763 represents a very useful form of work driver designed by Mr. William A. Lorenz. It consists of two jaws A, A held together by two screws, and threaded to receive two driving screws D, E in the figure, which enable it to be used to hold work to the live centre as is necessary when using the steady rest, as is shown in the figure, in which B represents the work and C the jaws of the steady rest. It is obvious that the dog may be thus employed to chuck work independently of the steady rest, because the live centre may be removed, and the face of the work held against the face of the chuck, the short screws H being used instead of the long ones D, E. [Illustration: Fig. 762.] If the carrier is used to simply drive the work without clamping it to the live centre or face plate, one or both of the screw pins J, K may be used in place of bolts D, E, the carrier being balanced when both are used. [Illustration: Fig. 763.] [Illustration: Fig. 764.] Fig. 764 represents a driver, carrier, or dog threaded in its bore to drive threaded work, which the screw of the ordinary dog would obviously damage. [Illustration: Fig. 765.] [Illustration: Fig. 766.] [Illustration: Fig. 767.] Fig. 765 represents an excellent driver for cored work such as the piece W. Its hub A is screwed on the live spindle in place of the face plate, and carries the rods B, B´, both of which are adjustable in the distance they stand out from A, so that B may be set to suit the work, and B´ set out sufficiently to balance B and D. The driving arm D is adjustable along B, and by being bent to the form shown is more out of the way, and obviates the necessity of using a dog on many kinds of work. The other end of the work is shown supported by a cone centre C, whose construction is shown in Figs. 766 and 767. Its object is to avoid the wear that occurs at the mouth of the hole in cored work, when it is run on the dead centre, and to avoid the necessity of plugging the hole to provide a temporary centre. In the figures, A represents a stem (fitting into the tailstock spindle S, in place of the ordinary dead centre), having a collar B and carrying the cone C. The work is supported upon C, which revolves upon the stem of A. At E is a raw-hide washer, intended to prevent the abrasion which would occur on the faces of B and C. The pin F prevents C from coming off D, one half of its cross section being in C, and the other half in a semicircular groove running around D. An oil groove is provided through the collar B, and passes along the stem D. This is an exceedingly handy device for cored work, and may also be used to sustain work against the lathe face plate, while chucking the work true by its bore. [Illustration: Fig. 768.] The work drivers employed by wood turners, for work held between the lathe centres, are as follows:-- Fig. 768 represents two views of a fork centre to be placed in the cone spindle of the lathe, and serve as a live centre, while also driving the work; C is a sharp conical point, which should run true, because it serves to centre the work; D, E are two wings which enter the wood to drive it. This device answers well for work that can be finished without taking it in and out of the lathe, it being difficult to place the work in the lathe so as to run true after removal therefrom; in case, however, that this should become necessary, the work should be replaced so that each wing falls into its original impression. For heavy work this device is unsuitable, hence the two plates shown in Fig. 769 are employed, being termed centre plates. They are composed of iron and are held to the work by screws passing through the respective holes shown at the corners of the plates. The plate having the round centre hole is for the dead centre end of the work, while that having the rectangular slot is for the live centre end of the work. The rectangular slot is made a close fit to the wings of the fork centre shown in figure. Figs. 770 and 771 represent a spur centre designed to hold pieces of soft wood, that may be liable to split from the pressure of the centres. The spurs are made parallel on their outer surfaces, while the inner ones are at an angle, so as to close the wood around the central point, and not spread the wood outwards. The plate for the dead centre is formed on the same principle as is shown in figure 769. [Illustration: Fig. 769.] [Illustration: Fig. 770.] Another form of chuck centre or driving centre for wood work is shown in Fig. 772, being especially useful when the work cannot be supported by the lathe dead centre. The body A screws on to the thread on the live spindle of the lathe, while the work screws on the pointed screw B, which will hold disc-shaped pieces of moderate diameter, as about 4 or 5 inches, leaving its face to be operated on as may be desired. To prevent B from splitting the work, or when hard wood is to be turned, a small hole may be bored up the work to permit B to enter sufficiently easily. [Illustration: Fig. 771.] [Illustration: Fig. 772.] When a piece of work to be turned between the lathe centres is of such a form that there is no place to receive centres, provision must be made to supply the deficiency. [Illustration: Fig. 773.] In Fig. 773, for example, a temporary centre B is fitted into the socket to receive the centre. In small work that has been drilled or bored, a short mandrel is used instead of the piece B. [Illustration: Fig. 774.] If a half-round piece is to be turned it should be forged with a small projecting piece to receive the lathe centre, as in Fig. 774. [Illustration: Fig. 775.] When the end of the work is flat and not in line with the axial line of the main body of the work, a piece of metal to contain the centre may be held to the work by a driving clamp, as in Fig. 775, in which A represents the end of the work and B a temporary piece containing the centre C. In this case it is best to make the centre C after the piece B is clamped to the work. [Illustration: Fig. 776.] To provide a temporary centre for a piece having a taper hole, a taper plug is used, as shown in Fig. 776, W representing the work and P the plug, which must be an accurate fit to the taper of the hole, and must not reach to the bottom of the hole. MANDRELS OR ARBORS.--Work (of about 6 inches and less in diameter) that is bored is driven by the aid of the mandrel or arbor, which is held between the lathe centres, as in Fig. 777, in which W represents a washer and M the mandrel, driven into the washer bore so as to drive it by friction. At A is a flat place to receive the set-screw of the driver or lathe dog, and at B a flat place upon which the diameter of the mandrel is marked. The mandrel diameter is made slightly larger at D than at C, so as to accommodate any slight variation in the diameter of holes bored by standard reamers, which gradually reduce in diameter by wear; thus if a reamer be made 1-1/1000 inch diameter, with a limit of wear of 1/1000 inch, then the mandrel may be made 1 inch at C and 1-1/1000 inch at D. It is well to taper the end of the mandrel from C to E about 1/2000 inch, so that it may enter the work easily before being driven in. Instead, however, of driving mandrels into work, it is better to force them in under a press. If driving be resorted to a lead hammer, or for very light mandrels a raw-hide mallet, may be used. [Illustration: Fig. 777.] [Illustration: Fig. 778.] In the absence of a lead hammer, a driver, such as in Fig. 778, is a good substitute, consisting of a socket containing babbitt or some other soft metal at B (the mandrel being represented by M). If copper be used instead of babbitt a hole may be drilled through it, as denoted by the dotted lines. [Illustration: Fig. 779.] [Illustration: Fig. 780.] The centres of mandrels should either have an extra countersink, as at A in Fig. 779, or else the cut should be recessed as at B, Fig. 780. Mandrels are best made of steel hardened and ground up after hardening. If the bore of the work is coned, and of too great a cone to permit the mandrel to be driven, and drive the work by friction, the cone mandrel shown in Fig. 781 may be used. M is the mandrel in one piece with the collar C. The work W is held between two cones A, A, which slide a close fit upon the mandrel, and grip the work by screwing up the nut N, there being a thread upon the mandrel, as at S, to receive the nut. It is obvious, however, that work having a parallel bore may also be held by the cone mandrel, as shown in Fig. 782. [Illustration: Fig. 781.] [Illustration: Fig. 782.] To obviate the necessity of having the large number of mandrels that would be necessary so as to have on hand a mandrel of any size that might happen to be required, mandrels with provision for expanding or contracting the diameter of the parts used to hold the work are made. [Illustration: Fig. 783.] Thus in Fig. 783 is shown Le Count's expanding mandrel, in which G H is the body of the mandrel, turned parallel along a certain distance, to fit the bore of the sleeve A, which is a close-sliding fit on this parallel part of E. From the end H of the mandrel there extends towards the end G four dovetail grooves, which receive four keys B. The heads of these four keys are enclosed and fit into an annular groove provided in the head C of the sleeve A, so that moving the sleeve A along the mandrel causes the four keys to slide simultaneously in their respective grooves. Now these grooves, while concentric at any one point in their transverse section to the axis of the mandrel, are taper to that axis, so that sliding the sleeve A along the parallel part of the mandrel increases or decreases (according to the direction in which A is moved) the diameter of the keys. If the sleeve be moved towards the end G, the keys while sliding in their taper grooves recede from the axis of the mandrel, while if moved towards H they approach the axis of the mandrel, or what is the same thing, if the sleeve be held stationary and the body of the mandrel be moved, the keys open or close in diameter in the same manner; hence all that is necessary is to insert the mandrel in the bore of the work, and drive the end G, when the keys will expand radially and grip the work bore. The keys, it will be observed, are stepped on their diametral or work-gripping surfaces, which is done to increase the capacity of the tool, since each step will expand to the amount equal to the whole movement of the keys in their grooves or slots. Mandrels or arbors are sometimes made adjustable for diameter by forcing a split cone upon a coned plug, examples being given in the following figures, which are extracted from _Mechanics_. In Fig. 784, A is a cone having the driving head extending on both sides of the centre so as to balance it. Over its coned body fits the shell B, which is split, as shown in Fig. 785, the splits C, D being at a right angle to splits E, F. It is obvious that the range of adjustment for such a shell is small, but several diameters of shell may be fitted to one cone, the thickness being increased to augment the diameter. The diameter of the shell should be made to enter the work without driving, the tightening being effected by screwing the nut up to force the shell up the cone. [Illustration: Fig. 784.] [Illustration: Fig. 785.] [Illustration: Fig. 786.] [Illustration: Fig. 787.] [Illustration: Fig. 788.] [Illustration: Fig. 789.] [Illustration: Fig. 790.] Figs. 786, 787, 788, and 789 represent an expanding mandrel designed by Mr. Hugh Thomas, of New York City. The body B of the mandrel is provided with a taper section _g_, and either three or four gripping pieces _a_, _a_, _a_, _a_, let through mortises or slots in a sleeve C, which fits the body of the mandrel at each end. This sleeve when forced up the mandrel by the nut D, carries the gripping pieces along the cone at _g_, and causes them to expand outwards and grip the bore of the work, which is shown in the end view in Fig. 788 to be a ring or washer W. The advantage of this form is that the cone at _g_ can be easily turned or ground to keep it true, and the gripping pieces _a_ may be fastened in their mortises by means of the screws shown at _h_ in the end view, and thus kept true. It is obvious that for long work there may be gripping pieces at each end of the mandrel, as in Fig. 789, and the work will be held true whether its bore be parallel, stepped, or taper, a valuable feature not usually found in expanding mandrels. [Illustration: Fig. 791.] When a mandrel is used upon work having its bore threaded the mandrel also must be threaded, and must abut against a radial face, as at _a_, in Fig. 790, because otherwise the pressure of the cut would hold the work still while the mandrel revolved, thus causing the work to traverse along the mandrel. If the thread of the mandrel be made so tight a fit that it will drive the work by friction it will require considerable force to remove the work from the mandrel, so much so, in fact, that finished pieces would be much damaged in the operation. It is better therefore to have the work such a fit that it can be just screwed home against the radial face of the mandrel under heavy hand pressure (if the work be not too heavy for this, in which case a clamp may be employed). Small work, as nuts, &c., are turned on a mandrel of this kind, which has a stem, and fits into the cone or live spindle in the same manner as the live centre, which will drive work up to about 1 inch in diameter without fear of slipping. Threaded mandrels that are in frequent use soon become a loose fit to the work by reason of the thread wear, with the result that if the face of the work is not true with the thread, it meets the mandrel shoulder, as in Fig. 791, and as the nut cants over, one side as T in the figure, is turned too thick. When the nut is reversed on the mandrel, the turned face will screw up fair against the mandrel shoulder, and the faces of the nut, though true one with the other, are not square with the axis of the thread, and will not therefore bed fair when placed in position upon the work. [Illustration: Fig. 792.] To obviate this difficulty we have Boardman's device, which is shown in Fig. 792. It consists of a threaded mandrel provided with a ring, with two rounded projections A, A and B, B, on each radial face, those on one side being at a right angle to those on the other. This ring adapts itself to the irregular surface of the nut and by equally distributing the pressure on each side of the nut destroys the tendency to cant over, hence the nut may be turned true, notwithstanding any irregularity of its radial faces, and independently of its fitting the arbor or mandrel thread tightly. [Illustration: Fig. 793.] Another form of mandrel for the same purpose is shown in Fig. 793, the mandrel being turned spherical, instead of having a square shoulder, and the washer W being cupped to fit, so that the washer will cant over and conform to the nut surface. [Illustration: Fig. 794.] The mandrel thread may be caused to fill the nut thread better if it be provided with three or more splits A, B, C, Fig. 794, a hole D being drilled up the centre of the mandrel, the thread may then be turned somewhat large, the splits permitting the thread to close from the nut thread pressure. [Illustration: Fig. 795.] When a mandrel is fitted to the sockets for the lathe centre, it should have a thread and nut, as shown in Fig. 795, so as to enable its extraction from the socket without striking it, as has been described with reference to lathe centres. [Illustration: Fig. 796.] [Illustration: Fig. 797.] Mandrels may be employed to turn work, requiring its outside diameter to be eccentric to the bore, by the following means:--In Fig. 796, let the centre C represent the centre of the mandrel, and D a centre provided in each end of the mandrel, distant from C to one half the amount the work is required to be eccentric. The mandrel must be placed with the centres D receiving the lathe centres. In this operation great care must be taken that a radial line drawn on each end of the mandrel, and passing through the centre of the centres D, shall exactly meet and coincide with the line L drawn parallel to the axis of the mandrel. If this be not the case the work will be less eccentric at one end than at the other. As it is a somewhat difficult matter to test this and ascertain if the mandrel has become out of true from use, it is an excellent plan to turn such a mandrel down at each end, as shown in Fig. 797, and draw on it the lines L, L, which correspond to the line L L in Fig. 796. If then a steel point be put in the lathe rest and fed in to the work, so that revolving the latter just causes the tool point to touch the lines L at each end, or if the tool point makes long lines as at _a_, _a_, the two lines L, L, should intersect the lines _a_, _a_ at the centre of their respective lengths. The lines L L should be marked as fine as possible, but deep enough to remain permanently, so that the truth of the eccentricity of the mandrel may be tested at any time. An equivalent device is employed in turning the journals of crank shafts, as is shown in Figs. 798 and 799, in which D, D are two pieces fitted on the ends of the crank shaft, being equal in thickness to the crank throw, as shown at A, B in the figure, so that when D, D lie in the same plane as the crank cheeks (as when all will lie level on a plate, as in the figure) the centres C will be in line with the journal in the crank throw. Pieces D are broadened at one end to counterbalance the weight of the crank, which will produce more true work than counterbalancing by means of weights bolted to the face plate of the lathe, as is sometimes done, causing the crank throw to be turned oval instead of round. In the case of a double crank, however, the centre pieces cannot be widened to counterbalance, because what would counterbalance when the centres A in Fig. 799 were used, would throw the crank more out of balance when centres B were used for the throw B. In this case, therefore, the centre pieces are provided with seats for the bars E, E, which may be bolted on to carry the counterbalancing weights, the bars being changed on the centre pieces when the centres are changed. The bars, for example, are shown in their position when the centres A are being used to turn up the journal A, the necessary amount of weight for counterbalancing being bolted on them with a set-screw through the weight. [Illustration: Fig. 798.] [Illustration: Fig. 799.] The centres are steel plugs screwed tightly into the pieces D, and are hardened after being properly centre-drilled and countersunk. [Illustration: Fig. 800.] To enable the pieces D to be easily put on and taken off, it is a good plan to make the bore a tight fit to the shaft and then cut it away as at E, as shown in Fig. 801, using set-screws to hold it. [Illustration: Fig. 801.] Great care is necessary in putting in the work centres, since they must, if the crank throws are to be at a right angle one to the other, as for steam engines, be true to the dotted lines in figure, these dotted lines passing through the centre of the axle and being at a right angle one to the other. If the thickness of the centre pieces are greater than the crank throws they may be adjusted as in Fig. 800, in which B, B´ represent the centre pieces, and C the crank, while S is a straight-edge; the edge surfaces of B, B being made true planes parallel to each other on each arm, and parallel to the axial line of the bore fitting the end of the crank axle. The straight-edge is pressed at one end, as at F, firmly to an edge face of B, the other end being aslant so as not to cover the edge of the piece B´ at the opposite end of the crank (as shown at G, Fig. 801). While being so pressed the other end must be swung over the end arm of B´ at the opposite end of the crank, when the edge of the straight-edge should just meet and have slight contact with the surface of the edge of B´. This test should be applied to all four edges of B, and in two positions on each, as at G, H--I, J, and for great exactitude may be applied from each end of the crank. It is to be observed, however, that the tests made on the edges standing vertical, as at I, J, will be the most correct, because the straightness of the straight-edge is when applied in those positions not affected by deflection of the straight-edge from its own weight. In shops where such a job as this is a constantly recurring one attachments are added to a press of some kind, so that the axle and the pieces B may be guided automatically and forced to their proper places, without requiring to be tested afterwards. [Illustration: Fig. 802.] When the work is sufficiently long or slender to cause it to sag and bend from its own weight, or bend from the pressure of the cut, it is supported by means of special guides or rests. Fig. 802 represents a steady rest of the ordinary pattern; its construction being as follows:--F is a base fitting to the [V]s of the lathe shears at F, and capable of being fastened thereto by the bolt C, nut N, and clamp A. F´ is the top half of the frame, being pivoted at P to F, the bolt P´ forming the pivot for both halves (F and F´), of the frame, which may be secured together by the nut of P´. On the other side of the frame the bolt is pivoted at _b_ to F. This bolt passes through an open slot in F´, so that its nut being loose, it may swing out of the way as denoted by the arrow _e_, and the top half frame _f´_ may be swung over in the direction of arrow _g_, the centre of motion or pivot being on the bolt P´. With F´ out of the way the work may be placed within the frame, the nut of B and also that of P´ may be tightened up so as to lock the two halves of the frame firmly together. On this frame and forming a part of it are the three ways, G G´ G´´, which contain cavities or slide ways to which are fitted and in which may slide the respective jaws J, and to operate these jaws are the respective square-headed screws S, which are threaded through the tops of the respective ways G, G´, and G´´. The screws are operated until the ends of the jaws J have contact with the work W, and hold it axially true with the line of centres of the lathe, or otherwise, as the nature of the work may require. When adjusted the jaws are locked to the frame by means of the bolts D, which are squared to fit in the rectangular openings, shown at _h_ in the respective jaws, so as to prevent the bolts from rotating when their locking nuts _d_ are screwed home. As an example of the use of this device as a steadying rest, suppose a long shaft to require turning from end to end and to be so slight as to require steadying, then a short piece of the shaft situated somewhat nearer the live centre than the middle of the length of the work is turned upon the work, so that this place shall be round and true to receive the jaws, or plates _p_, and revolve smoothly in them. The jaws are then adjusted to fit the turned part a close sliding fit, but not a tight fit, as that would cause the jaws to score the work. To prevent this even under a light pressure of contact, oil should be occasionally supplied. This steadies the work at its middle, preventing it from springing or trembling when under the pressure of the cut. By placing the steady rest to one side of the middle of the work length, at least one half of that length may be turned before reversing the work in the lathe centres. After reversing the work end for end in the lathe centres, the jaws, or plates _p_, are adjusted to the turned part, and the turning may be completed. In adjusting the plates _p_ to the work, great care is necessary or they will spring the work out of its normal line of straightness, and cause it to be out of parallel, or to run out of true in the middle of its length, as explained in the remarks referring to the cat head shown in Fig. 809. The plates _p_ should be gripped to the frame by the nuts with sufficient force to permit them to be moved by the set-screw S under a slight pressure, which will help their proper adjustment. They should also be adjusted to just touch the work, without springing it, the two lower ones being set up to the work first, so that their contact shall serve to relieve the work of its spring or deflection, due to its own weight. This is especially necessary in long slender spindles, in which the deflection may occur to a sensible degree. If the work does not require turning on its full length, the steady rest may be applied but a short distance from the length of the part to be turned, so as to hold the work more steadily against the pressure of the cuts. Steady rests are often used to support the end of work without the aid of the dead centre, but it is not altogether suitable for this class of work, because it has no provision to prevent the work from moving endways and becoming loose on the dead centre. A provision of this kind is sometimes made by tying the work driver to the face plate or to the pins driving the work driver or dog, or bolts and plates holding the work driver towards the lathe face plate; but these are all objectionable in that unless the pressure thus exerted be equal, it tends to spring or bend the work. Another method of preventing this is to drive the work by means of a universal chuck; but this again is objectionable, because the jaws of these chucks do not keep dead true under the wear, and indeed if made to run concentrically true (in cases where the chuck has provision for that purpose) the gripping surfaces of the chuck jaws have more wear at the outer than at the inner ends, hence those surfaces become in time tapering. Again the jaws wear in time so easy a fit in their radial slots that they spring under pressure, and the wear not being equal, the amount of spring is not equal, so that it is impracticable to do dead true work chucked in this way. The reasons that the chuck jaws do not wear equal in the radial slots may be various, as the more frequent presence of grit in one than in the other, less perfect lubrication, inequalities in the fit, less perfect cleaning, and so on, so that it is not often that the wear is precisely equal. In addition to these considerations there are others rendering the use of the steady rest in some cases objectionable; suppose, for example, a piece of cylindrical work, say 6 feet long, to have in one end a hole of 2 inches diameter, which requires to be very true (as, for example, the cone spindle for a lathe). Now let the face plate end be driven as it may, it will be a difficult matter to set the steady rest so as to hold the other end of the work in perfect line, so that its axial line shall be dead true with the line of lathe centres, because the work will run true though its axial line does not stand true in the lathe. Here it may be added that it will not materially aid the holding of the work true at the live centre end, by placing it on the live centre and then tightening the universal chuck jaws on it, because the pressure of those jaws will spring it away to some extent from the live centres. This will occur even though the work be placed between the two lathe centres, and held firmly by screwing up the dead centre tight upon the work, before tightening the chuck jaws upon the work, because so soon as the pressure of the dead centre is removed, the work will to some extent relieve its contact with the live one. If the jaws of the chuck are not hardened, they may be trued up to suit a job of this kind as follows:--A ring (of such a size that when gripped in the outer steps of the chuck jaws, the inner steps will be open to an amount about equal to the diameter of the work at the live centre end) may be fastened in the chuck, and the inner ends of the jaws may be turned up with a turning tool, in which case the jaws will be made true while under pressure, and while in the locations upon the chuck in which they will stand when gripping the work, under which conditions they ought to hold the work fairly upon the live centre. But even in this case the weight of the work will aid to spring it, and relieve it from contact with the live centre. [Illustration: Fig. 803.] Now let us suppose that the piece of work is taper on its external diameter at each end, even truing of the chuck jaws will be of no avail, nor will the steady rest be of avail, if the taper be largest at the dead centre end. Another form of steady rest designed to overcome these objectionable features is shown in Fig. 803. In this case the stand that is bolted to the lathe bed is bored to receive a ring. This ring is made with its middle section of enlarged diameter, as denoted by the dotted circle C. Into the wide part of the stand fits a ring F, its external diameter fitting into C. The ring carries the jaws, hence the ring is passed over the work, and is then inserted into the stand, while the work is placed between the lathe centres. The ring revolves with the work and has journal bearing in the stand, the enlarged diameter C preventing end motion. There is nothing here to take up the lost motion that would in time ensue from the wear of the radial faces of the ring, hence it is better to use the cone-plate shown in Fig. 805. [Illustration: Fig. 804.] When, however, the work will admit of being sufficiently reduced in diameter, it may be turned down, leaving a face F in Fig. 804, that may bear against the radial faces of the jaws of the steady rest; or a collar may be set upon the work as in Fig. 804 at C. But these are merely makeshifts involving extra labor and not producing the best of results, because the radial face is difficult to keep properly lubricated, and the work is apt to become loose on the live centre. [Illustration: Fig. 805.] For these reasons the cone plate shown in Fig. 805 is employed; A is a standard fitting the shears or bed of the lathe and carrying the circular plate C by means of the stud B, which is fitted so as to just clamp the plate C firmly to the frame A when the nut of B is screwed firmly home with a wrench. The plate C contains a number of conical holes, 1, 2, 3, &c., (as shown in section at D) of various diameters to suit varying diameters of work. The frame is fitted to the lathe bed so that the centre stud B stands sufficiently out of the line of lathe centres to bring the centres of the conical holes true with the line of lathe centres. The centres of the conical holes are all concentric to B. Around the outer diameter of the cone plate are arranged taper holes G, so situated with reference to the coned holes that when the pin, shown at G in the sectional view, will pass through the plate and into the frame A as shown, one of the coned holes will stand axially true with the line of lathe centres. Hence it is simply necessary to place one end of the work in the live centre, with a work driver attached in the usual manner; to select a coned hole of suitable size; to move the frame A along the lathe bed until it supports the overhanging end of the work in a suitably sized coned hole without allowing the work any end motion, and to then fasten the frame A to the lathe bed, and the work will be ready to operate on. The advantages of this device are that the pin shown at G in the sectional view holds the conical hole true, and thus saves all need of adjustment and liability to error, nor will the work be sprung out of true, furthermore the tool feed may traverse back and forth, without pulling the work off the live centre. With this device a coarse pitch left-hand internal thread may be cut as easily as if it were an external thread and the work was held between the lathe centres, heavy cuts being taken which would scarcely be practicable in the ordinary form of steady rest. The pins B and G and the coned holes should be of cast steel hardened, so as to avoid wear as much as possible. The plate may be made of cast iron with hardened steel bushes to fit the coned holes. It is obvious that the radial face of the work at the cone plate end, as well as the circumference, must be trued up, so that the work end may have equal contact around the bore of the coned rings. [Illustration: Fig. 806.] [Illustration: Fig. 807.] Figs. 806 and 807 represent a class of work that it would be very difficult to chuck and operate on without the aid of a cone plate. The former requires to have a left-hand thread cut in its bore A, and the latter a similar thread in end A. A universal chuck cannot be used to drive the work, because in the former case it would damage its thin edge, and in the latter the jaws would force the work out of the chuck; a steady rest cannot be used on the former on account of its being taper, while if used on the latter there would be nothing to prevent the work from moving endwise, unless a collar be improvised on the stem, which on account of the reduced diameter of the stem would require to be made in two halves. It can, however, be driven on the live centre by a driver or dog, and supported at the other end by the cone plate without any trouble, and with an assurance of true work. [Illustration: Fig. 808.] Fig. 808 represents a form of steady rest designed by Wm. MacFaul, of the Freeland Tool Works, for taper work. The frame affords journal bearing to a ring A, having four projections B, to which are a close but easy sliding fit, the steadying jaws C. These are held to the work or cue blank W by the spiral springs shown in the projections or sockets B, which act against the ends of C. It will be observed that the work being square could not move in any direction without moving sideways the two of the steadying jaws C which stand at a right angle to that direction. But the jaws C fit the bore of the sockets, and cannot, therefore, move sideways; hence it is evident that the work is firmly supported, although the steadying jaws are capable of expanding or contracting to follow the taper of the blank cue or other piece of work. This enables the steady rest to lead the cutting tool instead of following it, so that the work is steadied on both sides of the tool. Obviously, the stand may be fastened to the leading side of the lathe carriage or fitted upon the cross-slide, as may be most convenient. [Illustration: Fig. 809.] To steady work that is unturned and of so great a length that it springs too much to permit of its being turned true, the sleeve or cat head shown in Fig. 809 is employed; it may contain three or four screws C, to true it upon the work. The body B is turned true. The set-screws are so adjusted upon the work, that the outside runs quite true from end to end. The jaws of the steady rest are then set to just touch the circumference of the sleeve, care being taken that their pressure does not spring the axial line of the work out of its normal straight line. If the shaft is to be turned from end to end, the cat head should be placed sufficiently to one side of the centre of the length of the work and nearer the live centre, that the lathe tool may turn up the work for a distance of at least half its length, or slightly more than half. One half of the work being turned, the shaft is reversed end for end in the lathe, when the cat head may be moved to envelop the turned part, and again set true, or the jaws of the steady rest may be set direct upon the work; in this latter case, however, the friction between the jaws and the work will be apt to leave rings or marks upon the latter. If the cat head is not set to run quite true upon the work, the latter will not run true when the steady rest is removed, and if the jaws of the steady rest spring the axial line of the work out of its normal straightness, the work will be turned either larger or smaller in diameter in the middle of its length, according to the direction in which the work is sprung. Suppose, for example, that the work is sprung laterally towards the tool point, then the work will be turned smaller in the middle, or if the work were sprung laterally in the opposite direction, it would be turned larger in the middle than at the ends. If the work is sprung vertically so as to approach or recede from the lathe bed, the amount of the error will be less than if it were sprung laterally, and the nature of the error will depend upon the height of the cutting tool with relation to the work. If, for example, the point is above the centre of the work, and the latter is sprung towards the lathe bed, the work will turn of largest diameter in the middle of its length; or with the tool point placed at the centre of the work, the same result will follow, whether the work be sprung up or down; but if the work be sprung up or away from the lathe bed, and the tool point be placed above the centre, the diameter of the work will be turned smaller than that at the ends. [Illustration: Fig. 810.] When the work is to be turned from end to end or for a considerable distance, a follower rest such as shown in Fig. 810 should be employed, being similar to the steady rest shown in Fig. 802, except that it is open in front, and being fastened to the slide rest carriage, of course travels with the tool; hence the plates P may be either directly in front of the tool or following it, but if the work W has been turned true and parallel, the plates P may be in front of the tool, or rather may lead it. [Illustration: Fig. 811.] [Illustration: Fig. 812.] The follower rest should always be set to the work when as near as practicable to the dead centre, in which case it will be easier to set it without springing the work. For work of small diameter for which the plates P would be too large, and therefore in the way, the plate P, Fig. 811, may be used, being bolted to the follower rest. For work of larger diameter the device shown in Fig. 812 is sometimes used. It consists of a plate P with a cap C, and bolts for holding the bearings B, B. These bearings are bored slightly larger in diameter than the finished diameter of the work. The advantage of the use of this device is that bearings of the requisite bore having been selected they may be inserted and adjusted a proper fit to the work before P is fastened to the follower rest, thus avoiding the liability of being either too tight or too loose as may happen when the plates cannot be moved or rotated to test the fit. Another and great advantage is that if after the adjustment of the bearings B, B to the work, the plate P is carefully bolted to the follower rest, the liability of springing the work is eliminated, hence truer work will be produced. [Illustration: Fig. 813.] A representative of another class of follower rest is shown in Fig. 813, the hub H is accurately bored to receive collars or rings of various diameters of bore to suit the work. The bore of H may be made to stand axially true with the lathe centres, and thus avoid the trouble of setting, by employing the steady pin S, which, being a close fit in the follower rest and in the lathe carriage will bring the rest to its proper distance from the lathe centres, where it may be secured by the bolt B, which may screw into the metal of the carriage or operate to lift a wedge or guide slip so as to grip the [V]-slide of the carriage and take up any lost motion between the slide in the rest and that in the lathe carriage. [Illustration: Fig. 814.] Fig. 814 shows a follower rest in position on the cross slide of a lathe. CHUCKS AND CHUCKING. There is a large class of small work that could be held between the lathe centres, but that can be more conveniently held in chucks. Chucks are devices for holding work to the live spindle, and may be divided into classes as follows: 1st. Those in which the work is secured by a simple set-screw. 2nd. Drill chucks, which are applied mainly to drive drills, but which may also be used to drive very small work to be operated upon by cutting tools, the mechanism causing the jaws to move simultaneously to grip or release the work. 3rd. Independent chucks, in which the jaws are operated separately. 4th. Universal chucks, which are larger than drill chucks, and in which the jaws operate simultaneously. 5th. Combination chucks, in which the jaws may be operated either separately or simultaneously as may be required. [Illustration: Fig. 815.] Referring to the first, Fig. 815 represents a simple form of set-screw chuck, the stem S fitting into the live centre hole, and the outer end being pierced to receive a drill shank, and the iron from which a piece of work may require to be turned, which is secured in the chuck by the set-screw B. In the case of drill or other cutting tools, however, it is better that they be provided with a flat place A, to receive the set-screw pressure, and enable it to hold them more securely. The objections to this class of chuck are threefold: First, each chuck is suitable for one diameter of work only; secondly the screw head B is in the way; and thirdly, the set-screw pressure is in a direction to set the work out of true, which it will do unless the work is a tight fit to the bore of the chuck. In this case, however, it is troublesome to insert and remove the drill, unless the bore of the socket is relieved on the half circumference nearest to the set-screw, as shown at C in the end view, in which case the efficiency of the chuck is greatly enhanced. [Illustration: Fig. 816.] Referring to the second class they are made to contain either two or three jaws. [Illustration: Fig. 817.] When two jaws are employed they are made to slide in one slideway, and are operated therein by a right and left-handed screw, causing them to simultaneously advance or recede from the chuck axis. Fig. 816 represents a chuck of this class, the jaws fitting one into the other to maintain each other in line, and prevent their tilting over from the pressure. In scroll chucks the mechanism for operating the jaws is constructed upon two general principles. The first may be understood from Fig. 817, in which the body of the chuck is provided upon its end face with a scroll C, with which the ends of the jaws A engage. These jaws fit into radial slots in the shell E, which is capable of rotation upon B and is held thereto by the cap D; hence rotating E carries around the jaws A, and the thread C causes them to approach or recede from the chuck axis, according to their direction of rotation. [Illustration: Fig. 818.] The second general principle upon which small drill chucks are constructed may be understood from Fig. 818, in which C may be taken to represent the end of a lathe spindle or a stem fitting into the live centre hole in the same. At the other end it is to receive the shell D which screws upon it. D is coned at the outer end of its bore, and the jaws E are made to fit the cone, and it is obvious that if D be rotated to screw farther upon C, the coned bore of D will act to force the jaws E nearer to the chuck axis and cause them to close upon and grip the work. To operate D it is knurled or milled at G, or it may have pin spanner holes as at H. In this class of chuck it is essential that the direction of rotation of D to close the jaws must be opposite to that in which the drill rotates, otherwise the resistance of the work against the jaws would cause D to rotate upon C, and the work to become released from the jaw grip. Furthermore, as the larger the work the more severe the duty in driving it, it is usually provided by the construction of such chucks that the jaws shall be opened to their maximum when at their nearest approach to the body (as C) of the chuck, and shall close as they move outward or away from the same. This principle of moving the jaws radially by means of a cone sliding upon a cone is applied in numerous ways, thus sometimes the jaws are provided with wings that slide upon a cone or in slide ways that are at an angle to the chuck axis. [Illustration: Fig. 819.] [Illustration: Fig. 820.] [Illustration: Fig. 821.] Figs. 819, 820, and 821 represent Gage's patent chuck, in which the gripping surfaces of the jaws are serrated to increase the grip, and to further secure the same object the jaws move at an angle instead of in a radial line, so that the body of the jaws is more directly in the line of strain, and therefore resists it better. The serrations are left-handed, so that the tendency is to force the drill forward and toward the cut, supposing them to act as a nut and screw upon the drill shank. The jaws are supported by the central cylindrical piece that contains them out to the extreme end, and have in addition a lug which slides in radial grooves. Fig. 819 is a side elevation, with a piece of the shell removed to show the jaw and its slide way, and an end view showing the arrangement of the jaws. Fig. 820 is a sectional side elevation, and Fig. 821, two views of the jaws removed from the chuck; A represents the jaws with the lug E to slide in the radial slots provided in B. The wings A´ of the jaws slide in the ways in B, the ways passing through the opening F in Fig. 821; C is the cone for causing the jaws to open and close radially. The driving piece H has A left-hand thread operating in B. It also has a collar abutting over one side against the end of B, and secured on the other by the cap I, which threads into the shell G. A pin in C secures it to the cap I, so that if rotated both move together. On the other hand, if H be rotated and G is held stationary, the thread on H operates on B as a nut, causing it to slide, carrying the jaws with it, and the jaws are simultaneously opened or closed according to the direction of rotation of H. Fig. 819 shows the jaws screwed partly out, and therefore partially closed, while in Fig. 820 the jaws are shown within the chuck, and therefore opened to their fullest extent. [Illustration: Fig. 822.] Figs. 822 and 823 represent a chuck employed by the Hancock Inspirator Co., of Boston, for very true work. This chuck will not get out of true by wear, and holds brass work against a good lathe-cut without indenting it. Fig. 822 shows the chuck complete. Fig. 823 is a mid-section of chuck complete. Fig. 824 is a side and an end of the work-gripping piece. The chuck is composed of three pieces, A, B and C. Piece A screws upon the lathe spindle and is bored to receive C; piece B screws upon A and receives the outer end of C, which is provided with a double cone D E, and is split nearly its full length at three places, one of which is shown at F, so that when B is screwed upon A the two cones upon A, B compress C, and cause the diameter of its bore to decrease and grip the work. The splits F are made long, so that C shall not close at its outer end only, but on both sides of the cones, and thus grip the work parallel. There are several advantages in this form of construction; thus the parallel bore of A, in which C fits, is not subject to strain or wear, and therefore remains true and holds C true. Furthermore, B has no tendency to wear out of true, because it fits upon A at the part G, as well as at its threaded end, while the cone E of C also acts to keep it true. As B is screwed up with a wrench fitting its hexagon exterior, the work can be held against any amount of cut that the lathe will drive. [Illustration: Fig. 823.] It is obvious that the capacity of the chuck, so far as taking in range of different diameters, is quite limited, but the excellence of its execution far more than compensates for this when work is to be turned out true and correct to standard gauge. To increase the range of capacity of the chuck, the split piece only needs to be changed. Before hardening the split piece the jaws should be sprung well apart, so that they will spring open when released by unscrewing the outside shell to release the work and insert another piece. [Illustration: Fig. 824.] In proportion as the diameter of the work is increased it requires to be more firmly held, and the chucks are made with jaws moved by screws operated by wrench power. These chucks are made with two, three, or four jaws, and the bite of the jaw is shaped to suit the nature of the work, the gripping area being reduced for very small work, and serrated parallel to the chuck axis so as to form gripping teeth for firmly gripping rough work, as shown in some of the following examples:-- [Illustration: Fig. 825.] [Illustration: Fig. 826.] Figs. 825 and 826 represent the Horton two-jawed chucks with false or slip jaws, which are removable so that jaws of various shapes in the bore may be fitted to the same chuck, thus enabling the jaws to be varied to suit the shape of the work to be held. The jaws are secured in place by the pins shown. [Illustration: Fig. 827.] Fig. 827 shows a two-jawed solid jaw chuck, the bite of the jaws being made hollow, so as not to mark the surface of the work, while they will hold it very firmly. In Fig. 828 is shown what is termed a box-body two-jawed chuck, which is mainly used by brass turners. The object of this form of body is to permit the flanges, &c., of castings escaping the face of the chuck. Fig. 829 also represents a two-jawed chuck, the body being cylindrical, and having a [V]-groove at A to receive the work. The screws C, D may act independently of each other, or a continuous screw may be used, having, as in the figure, a left-hand thread at C, and a right-hand one at D, so that the jaws move simultaneously when the screw is operated. The difference between these two methods being as follows:-- When one screw is used the jaws will hold the work so that the centre of rotation will be midway between the points of contact of the jaws of the chuck and the work, hence work cannot be set eccentrically, unless pieces of iron are inserted between it and one of the jaws. When two screws are used the jaws may be operated separately, and one jaw may be set to such distance from the centre of rotation as the necessities of the work may require; but in this case more adjustment is required to set either square or cylindrical work to rotate on its axis than when the jaws operate simultaneously as with a right and left-hand screw. It is obvious that the axial line of the screw or screws must stand parallel with the plane of the face F. It will be observed that the back of each jaw is cut away at B: this serves two purposes, first it permits of a piece of work having a small flange, head or projection being held in the [V]s of the jaws; and secondly, it equalizes the wear on the jaws of the chuck, because in jaw chucks generally there is more wear at the outer than at the inner end of the jaws, because work shorter than the length of the jaws, or requiring to be held as far out from the jaws as possible, does not have contact at the back end of the work holding jaw faces, hence the jaws are apt to wear, in course of time, taper. By cutting away the jaws at the back, the tendency to unequal wear is greatly reduced, hence this plan is adopted to a more or less degree in the dogs or jaws of all chucks, being in many cases merely a small recess from 1/16 to 1/8 inch deep only. [Illustration: Fig. 828.] When the jaws have a [V]-groove as in the cut, the face F of the chuck does not form a guide in setting the work, the truth of the [V]-grooves being solely relied upon for that purpose. [Illustration: Fig. 829.] [Illustration: Fig. 830.] The form of two-jawed chuck shown in Fig. 830 is intended for square or rectangular work, and is mainly used by wood workers. It may be operated by a right and left-hand screw, but is generally preferred with independent screws. The face F of the chuck may be employed to serve as a guide in setting the work as shown in the cut, in which W represents a piece of work held between the jaws A, A, and resting against the face F, which therefore serves as a guide against which to set the work to insure that its axial line shall stand parallel with the face F, or in other words at a right angle to the line of centres of the lathe. [Illustration: Fig. 831.] In Fig. 831 is an example of a machinist's two-jawed chuck. The jaws are operated simultaneously by a right and left-hand screw. The jaws are provided with slides to receive the two separate pieces shown in figure, which may be made to suit the form of special work. The two screws shown on each side of the chuck face are to support a piece of work that is too large to be otherwise held firmly by the chuck. These screws may be operated by screw-driver wrench, to enable the face of the work to rest on them, and therefore be supported parallel or true with the chuck face. The jaws may be turned end for end in their slide ways as shown in Fig. 833, to enable them to grip work of small diameter, the separate pieces shown in Fig. 832, being placed on the jaws for such small pieces as drills, &c. [Illustration: Fig. 832.] In the larger sizes, lathe chucks are provided with either three or four jaws, which are caused to operate either independently or simultaneously, and in some cases the construction is such that the same chuck may be used as an independent or as a universal one at will, in which case they are termed combination chucks. Concerning the number of jaws it may be observed that a three-jawed chuck will hold the work with an equal pressure on all three jaws, whether it be cylindrical or not, but in a four-jawed chuck the jaws will not have an equal grip upon the work, unless the same be either cylindrically true or square, hence it is obvious that a three-jawed chuck is less liable to wear out of true, and is also preferable for holding unturned cylindrical work, while it is equal to a four-jawed one for true, but unsuitable for square work. [Illustration: Fig. 833.] [Illustration: Fig. 834.] Fig. 834 represents the construction of the Horton chuck. Upon the screws that operate the jaws are placed pinions that gear into a circular rack, so that by operating one jaw with a wrench the rack is revolved and the remaining jaws are operated simultaneously. The chuck being constructed in two halves, the rack may be removed and the jaws operated separately, or independently as it is termed. [Illustration: Fig. 835.] Fig. 835 represents one of the jaws with its operating screw and pinion removed from the chuck. The gripping surfaces of the steps in the jaws are serrated to increase their grip upon the work, and the nuts A, A, against which the works rests, are ground true with the face of the chuck. The corner between the faces A and the bite or gripping surfaces of the jaws are recessed so that the work cannot bind in them, but will bed fairly against the faces A, A, which serve to set the work against and hold it true instead of the face of the chuck. [Illustration: Fig. 836.] Fig. 836 represents a Horton chuck for work up to four inches diameter. [Illustration: Fig. 837.] Fig. 837 represents a similar chuck for all sizes between 4 and 15 inches, the designated sizes of the chuck being 6, 9, and 12 inches, these diameters being the largest the chucks will take in. [Illustration: Fig. 838.] Fig. 838 represents a Horton chuck with outside bites for opening out to grip the bores of rings or other hollow work. The term scroll chuck is applied to universal chucks in which the jaws are operated throughout their full range by means of a scroll thread such as was shown in Fig. 817. The objection to this form is that the threads on the jaws cannot be made to have a full bearing in the scroll thread. [Illustration: Fig. 839.] In Fig. 839, for example, let A A and B B represent grooves between the scroll threads, and if the thread on the jaws be made to the curve and width of A A, it would not pass in that of B B, and _vice-versâ_, and it would take but five revolutions of the thread to pass a nut thread from A to B. To overcome this difficulty the jaw threads are not made correct to either curvature but so formed as to fit at points C, D, E, when in the groove A and at points F, G, H, when in groove B. This obviously reduces their bearing area and therefore their durability. To avoid this defect the jaws of many universal chucks are operated by screws in the same way as independent jaw chucks, but provision is made whereby the operation of any one of the jaw screws will simultaneously operate all the others, so that all the jaws are moved by the operation of one screw. Thus in the following figures is shown the Sweetland chuck. [Illustration: Fig. 840.] Fig. 840 represents the chuck partly cut away to show the mechanism, which consists of a pinion on each jaw screw, and a circular rack beneath. The rack is shown in gear with a pinion at O, and out of gear with a pinion at C, which is effected as follows:-- The rack is stepped, being thicker at its outer diameter, and the thin part forms a recess and the shoulder between the thick and thin part forms a bevel or cone. Between this circular rack and the face of the plate at the back of the chuck is placed, beneath each jaw, a cam block bevelled to correspond with the bevelled edge of the recess in the ring. The cam block stem passes through radial slots in the face of the chuck, so that it can be moved to and from the centre of the chuck. When it is moved in, its cam head passes into the recess in the ring rack, which then falls out of gear with the jaw screw pinion; but when it is moved outward the cam head slides (on account of the bevelled edges) under the ring rack and puts it in gear with the jaw screw pinion. Thus, to change the chuck from an independent one to a universal one all that is necessary is to push out the bolt heads on the cam block stems, the said heads being outside the chuck. The washers beneath these heads are dished to give them elasticity and enable them to steady the cams without undue friction. [Illustration: Fig. 841.] To enable the setting of the jaws true for using the chuck as a universal one, after it has been used as an independent one, a ring is marked on the face, and to this ring the edges of all the jaws must be set before operating the cams radially to put the rack ring in gear. In Fig. 841 a three-jawed chuck on this principle is shown acting as an independent one to hold an eccentric. On account of the spring of the parts, which occurs when the strain is transmitted from one part to another, it is desirable when using the chuck as a universal one to first operate one screw to grip the work and then pass to the others and operate them so that they may receive the pressure direct from the screw head and not entirely through the medium of the rack, and there will be found enough movement of the screws when thus operated to effect the object of relieving the rack to some extent from strain. [Illustration: Fig. 842.] [Illustration: Fig. 843.] [Illustration: Fig. 844.] Figs. 842, 843, 844, and 845 represent Cushman's patent combination chuck, in which each jaw may be operated independently by means of its screw thread, or a circular rack may be made to engage with the respective pinions, as shown in Fig. 844, in which case operating any one of the screws operates simultaneously all the jaws. The method of engaging and disengaging is shown in Fig. 845. C represents the circular rack and D a circular ring beneath it. This ring is threaded on its circumference, screwing into the body of the chuck, so that revolving it in one direction moves the circular rack forward and into mesh with the pinions, while revolving it backward causes the rack to recede from the pinions. To operate this ring the lug shown near the top of the chuck in figure is simply pushed in the required direction, while to lock the ring when out of gear with the pinions the spring catch shown on the left of that figure is moved radially. When the rack is in gear, the chuck is a universal one, all the jaws moving simultaneously and equally, whether they be set in such position in their slots as may be necessary to grip an oval or round piece of work; when the rack is out of gear the jaws may be moved by their respective screws so as to run true as for round work, or to hold the work to any degree of eccentricity required. [Illustration: Fig. 845.] The jaws may be reversed in their slots and operated simultaneously as a universal chuck, or independently as a simple jaw chuck. It is obvious that the truth of the jaws for concentricity may be adjusted within the degree of accuracy due to the number of teeth in one pinion divided into the pitch of the jaw operating screw, because each screw may be revolved separately to bring each successive tooth into mesh until the greatest obtainable jaw truth is secured. [Illustration: Fig. 846.] Fig. 846 represents a front, and Fig. 847 a sectional view, of the Westcott combination chuck. F is the main body of the chuck screwing on to the lathe spindle. F carries the annular ring D, which has a thread on its face, as shown. D is kept in place by the ring E, which screws in an annular recess provided in the back of the chuck. C is a box fitting in the radial slots of the chuck. The back of the box C meshes into the radial thread on D, hence, when D is revolved, the boxes C move radially in the slots. Now the boxes C afford journal bearing to, and carry the worm or screws B as well as the chuck jaws A, hence revolving D operates the jaws simultaneously and concentrically as in a scroll or universal chuck. By means of the screws B, the jaws may be operated individually (the boxes C and ring D remaining stationary) as in an independent jaw chuck. [Illustration: Fig. 847.] Suppose, now, the jaws to have been used independently, and that they require to be set to work simultaneously and concentric to the centre of the chuck, then the screws B may be operated until the jaws at their outer edge are even with the circumference of the chuck (or, if the jaws are nearer the centre of the chuck, they may be set true with a pointer), and the ring D may be operated. In like manner, if a number of pieces of work are eccentric, the screws B may be used to chuck the work to the required eccentricity, and when the next piece is to be chucked the ring D may be operated, and the chuck will be used as a universal one, although the shape of the work be irregular, all that is necessary being to place the same part of the work to the same jaw on each occasion. [Illustration: Fig. 848.] The faces of the jaws of jaw chucks when they are true with the face of the chuck (or what is the same thing, run true, and are at a right angle to the axial line of the lathe centres), form guides wherefrom to set the work true, but this will only be the case when they remain true, notwithstanding the pressure of the jaws upon the work. Their truth, however, is often impaired by their wear in the chuck slots which gives them play and permits them to cant over. Thus in Fig. 848 is shown a chuck gripping a piece of work W, and it is obvious that to whatever extent the jaws may spring, or have lost motion in the ways or slots in the chucks, the jaws will move in the direction of the dotted lines A A, the face of the jaw then standing in the direction of dotted lines B B, instead of being parallel to the chuck face. If the spring or wear of the mechanism were equal for each jaw, the work would be held true, notwithstanding that the jaws be out of line, but such is not found to be the case, and as a result the work cannot be set quite true. [Illustration: Fig. 849.] When the jaws are applied within the work, as in Fig. 849 (representing the jaws of the chuck within the bore of a ring or piece of work W), the jaws spring in the opposite direction as denoted by dotted lines C, C, and when the jaws are locked to the work the latter moves in the direction of D and away from the chuck face. It will be observed that there is no true surface to put the face of the work against in either case. [Illustration: Fig. 850.] This is remedied in independent dog chucks by the construction shown in Fig. 850, in which each jaw has a square A, fitting in the grooves of the chuck, and a nut and washer at B secure the jaw to the face of the chuck so that the lost motion due to wear of the parts may be taken up. [Illustration: Fig. 851.] [Illustration: Fig. 852.] The Judson patent chuck is designed to overcome this difficulty, and is constructed as shown in Figs. 851 and 852, the former being a face view and the latter a sectional edge view of the chuck. The jaws A of the chuck are hollow, and the nut instead of being solid in the jaw is a separate piece, having two wings, the outer of which bears upon a pin in the jaw, while the inner bears upon an inclined surface as plainly shown in the cut, so that the pressure of the screw is distributed equally upon the pin and the inclined surface. The nut B being below the centre of the pin and inclined surface causes the pressure to throw the jaw fair against the face of the chuck, hence the faces of the jaws will serve (equally as well as the surface of the chuck) as a guide to set the work against. From the short length of gripping surface on the jaws of jaw chucks, they are incapable of holding work of any greater length than, say, about 6 inches, without the aid of the dead centre at the other end of the work; but if the dead centre be used in this way the work will be out of true, unless the jaws of the chuck be quite true, which is not always the case, especially after the chuck has been much in use. Furthermore, it is at times a difficult if not even an impracticable job to set work quite true in this way. For special work made in quantities the form of the chuck may be varied to conform to the special requirements of the work. The variety of chucks that may thus be formed is obviously as infinite as the variations in form of the work. Thus threaded work may be screwed into threaded chucks, or cylindrical work may be driven into bored blocks forming chucks, or a ring may be chucked and then used as a mandrel to drive the work by friction. [Illustration: Fig. 853.] An excellent example of special chuck is shown in Fig. 853, representing a chuck for holding piston rings. It resembles a face plate screwing on the live spindle at B, and having 8 radial dogs or jaws A, let into the face D, and secured thereto, when adjusted by the bolts and nuts E. A mandrel is fast in the centre of the chuck carrying the cone C, upon which rest the cone surfaces on the ends of the dogs A, so that screwing up C, by means of the nut shown, throws the dogs A outwards, causing them to grip the inside of the piston ring as shown in the face view of the chuck. [Illustration: Fig. 854.] In Fig. 854 is shown Swazey's expanding chuck. B is the body of the chuck driven on an arbor A. The hub of B is turned taper to receive a disc C, which is split partly through in three places, and wholly through at Z. By means of the nut and washer D E, the disc is forced up the taper hub and caused to expand in diameter and grip the bore of the work, or ring R, the face of B serving to set the face of the ring against to hold it true sideways. The chucks employed by wood workers for driving work without, the aid of the back or dead centre of the lathe are as follows:--On account of the fast speed at which the wood-workers' lathe revolves, it would be undesirable to have their chucks of iron, because of the time it would take the lathe to start them to full speed, and also to stop them after shifting the belt from the driving to the loose pulley of the countershaft, and further because of the damage the tool edges would receive if they accidentally came into contact with the face of the chuck. For these reasons wood workers' chucks are usually built up upon small iron face plates. [Illustration: Fig. 855.] Fig. 855 represents a cement chuck, consisting of a disc of hard wood A, screwed firmly to the face plate B; at C is a round steel point located at the axis of the chuck. This chuck is employed to drive very thin work by the adhesion between the surface of the work and that of the chuck. The surface of the chuck is coated with a mixture of 8 parts of resin to one part of beeswax run into sticks. The chuck is waxed or cemented by rotating it at high velocity while holding the sticks against it. The whole surface of the chuck being thus coated, the centre of the work is forced on the steel point C, and the lathe is kept running until the surface of the work nearly touches that of the chuck, when the belt is passed to the loose pulley overhead and the work forced against the chuck surface until it stops or else revolves the work against the hand pressure, the friction between the surfaces having melted the wax or cement, and cemented the work to the chuck. This leaves the face and the circumference of the work free to be operated upon. The work is removed from the chuck by the gradual insertion between the two of a long thin-bladed knife. For work of large diameter, however, a mere disc of wood will not answer, it being too weak across the grain: and here it may be remarked that the work often supports the chuck, and therefore we should always, in fixing, make the grain of the work cross that of the chuck, because the centrifugal force due to the high velocity is so great that both the chuck and the work have before now been rent asunder by reason of the non-observance of this apparently small matter. When it is considered that the chuck has not sufficient strength across the grain, battens should be screwed on at the back; but a chuck so strengthened will require truing frequently on account of the strains to which its fibres will be subjected from the unequal expansion or contraction of its component parts. Fig. 856 shows the back of a chuck strengthened by the battens A, A, A. [Illustration: Fig. 856.] [Illustration: Fig. 857.] Another and superior method of making a chuck suitable for work of about the same diameter is shown in Fig. 857. Its construction enables it to better resist outward strains in every direction, while the strains to which it must necessarily be subject, from variations of temperature and humidity, are less than in the former. It will also be found that it can be trued with greater facility, especially on the diameter, as the turning tool will not be exposed to the end grain of the wood. The crossed bars at the back of the chuck are half checked, as shown at A, so that both pieces may extend clear across the chuck and not terminate at the centre. They are fastened together at the centre by glue, and also with screws. Upon these bars as a frame, the four pieces composing the body or face of the chuck are fastened by both glue and screws. These pieces need not extend clear to the centre, but may leave an open square as shown, because the centre of a large chuck rarely requires to be used. [Illustration: Fig. 858.] For very large chucks a cross of this kind would not afford sufficient strength, hence, the form shown in Fig. 858 is employed. The arms are bolted to an iron face plate, as shown, their number increasing with the diameter of the chuck. To keep the chuck true, the arms should have a level and fair bed upon the face plate, the segments composing the rim being fairly bedded to the arms and well jointed at the ends. They should be both glued and screwed, care being taken that the points of the screws do not meet the face of the chuck, in which case they would damage the turning tools used to true the chuck. As wooden chucks are liable to warp and become out of true it is requisite to test them on each occasion before use, and true them if necessary. The work is fastened to these chucks by means of screws whose heads are sunk beneath the work surface a sufficient depth so that there is no danger of their coming into contact with the turning tools. In other cases the work is glued to the chuck, a piece of paper being interposed between the work and the chuck, which, by being damped, will enable the more ready removal of the work from the chuck. [Illustration: Fig. 859.] Another form of chuck used by wood workers is shown in Fig. 859. It consists of a disc of wood A; screwed to the face plate and carrying the two pieces B, B. The pieces C, C are wedges which slide endways to grip the work. This chuck is especially handy for small work of rectangular form. From the shape of some work, it cannot be chucked in jaw chucks of any description, and this is especially the case with work of large diameter, hence, large lathes, as, say those that will swing more than three feet, are not usually provided with universal chucks, although sometimes provided with independent jaw-chucks. So likewise in small lathes there are many forms of work that cannot be chucked in jaw chucks, and yet other forms that can be more conveniently held or chucked on face or chuck plates, &c. If, for example, the surface of the chuck requires to be used in setting the work, the jaws will often be in the way of the tools or instruments employed to set the work. Again, there may be projections on the work which will require the body of the work to be held too far from the face of the chuck to enable its jaws to grip the work. To meet the requirements of these classes of work chucking devices, which may be classified as follows, are employed:-- 1st. Chucking by bolting work to the face plate or chuck plate with bolts and plates. 2nd. Chucking between dogs movable about the face chuck plate, and holding the work from that plate. 3rd. Chucking with the aid of the angle plate, or with the angle plate employed in conjunction with the chuck plate. [Illustration: Fig. 860.] The chuck plate is simply a face as large in diameter as the lathe will swing, and is sometimes termed the large face plate. Chuck plates for smaller lathes, as 30 inches swing, or less, are sometimes provided with numerous round or square holes to receive the bolts which hold the work, but usually with slots and holes as in Fig. 860. The larger sizes of chuck plates are similarly formed, but are sometimes provided with short slots that meet the circumference of the plate as in Fig. 861, which represents a chuck plate of the Whitworth pattern. The face of the chuck plate must be maintained true in order that true work may be produced, and it is necessary when putting it upon the lathe to carefully clean its threads and those of the live spindle, as, on account of its large diameter, a very little dirt between it and the live spindle will throw it considerably out of truth at the circumference. [Illustration: Fig. 861.] It is better if there be any error in a chuck plate or face plate that it be hollow rather than rounding when tested with a straightedge, because in that case a given amount of error in the plate will produce less error in the work. [Illustration: Fig. 862.] [Illustration: Fig. 863.] [Illustration: Fig. 864.] In Fig. 862, for example, A represents a chuck plate hollow across the face, and B a link requiring to be bored through its double eye C, the centre line of the lathe being line E E, and the centre line of the hole in the hub D of the link being denoted by F, and as E and F are not parallel one to the other it is obvious that the holes will not be parallel. Suppose, now, that the chuck face was rounding, and the centre line of D would stand at G G, and the holes in C and D would be out of true in the opposite direction. In this case the error would be equal, but suppose we have a ring or disc such as B in Fig. 863 to chuck by bolts and plates C, D and it will be chucked true, notwithstanding that the face of the plate is hollow. But were the face of the plate rounding the disc may be chucked as in Fig. 864, the face F of the work not being held at a right angle to the line of centres E as it is in Fig. 863. The truth of the chucking in Fig. 864 depends upon whether the clamps C were screwed up with equal force upon the work. A hollow chuck plate will lose this advantage in proportion as the work covers more of one side of the chuck plate than it does of the other, but in any event it will chuck more true than a rounding one. Suppose we have, for example, a ring chucked eccentrically as in Figs. 865 and 866, the chuck being as much hollow in the one case as it is rounding in the other, and that shown in Fig. 866 will stand out of true to an amount greater than the chuck is in an equal amount of its radius. While that shown in Fig. 865 would be nearer true than the chuck is in an equal length of its radius, both amounts being in proportion to the length of the line A to that of line B. [Illustration: Fig. 865.] [Illustration: Fig. 866.] If the chuck plate is known to be either rounding or hollow, pieces of paper of sufficient thickness to remedy the error may be placed at C and D respectively. It is better, however, to true up the faces of plates so that the surface of the work bolted against it will be true and stand at a right angle to the line of lathe centres. In truing up a face plate, the bearings of the live spindle should be adjusted so that there is no play on them, and the screw or other device used to prevent end motion to the live spindle should be properly adjusted. A bar or rod of iron should also be placed between the lathe centres to further steady the live spindle, and the square holes or radial slots should have the edges rounded or bevelled off, as shown in Fig. 867, so that when the tool point strikes the sides A of the holes or slots it will leave its cut gradually and not with a sudden jerk or jump, while, when it again takes its cut on the side B, it will also meet it gradually and will not meet the sand or hard skin on the face of the casting, which would rapidly dull the tool. [Illustration: Fig. 867.] In facing or truing up a chuck plate, the feed nut should be put in gear with the feed screw or feed spindle, and the cut should be put on by revolving the feed spindle or feed screw. This will take up any lost motion in the feeding mechanism, after which the carriage may, if there are devices for the purpose, be locked to the lathe bed so as to prevent its moving. It is better that the thread of the chuck be not too tight a fit upon that on the lathe spindle, the radial face of the chuck hub and of the cone spindle collar being relied upon to set the chuck true, because it is somewhat difficult to produce threads so true as to hold the faces true. To preserve the threads both upon the chuck bore and the lathe spindle from undue wear, the chuck when taken off the lathe should be stood on edge so that falling dust may not accumulate in the thread. Before putting the chuck upon the lathe spindle the threads of both and the radial faces of the chuck hub and cone spindle collar should be carefully cleaned, because the presence of any dirt or dust on those faces will throw the face of the chuck plate out of true to an amount that may be of importance at and near the chuck's circumference. [Illustration: Fig. 868.] [Illustration: Fig. 869.] As an example of simple chucking on a face plate, or chuck plate, let it be required to bore, cut a thread in the bore, and recess the piece of work shown in Fig. 868, the radial faces being already true planes not requiring to be turned. [Illustration: Fig. 870.] This could be held as shown in Fig. 869, in which C is the chuck plate, W the work, S a strap plate, and B, B are bolts and nuts, a face view of the work already chucked being shown in Fig. 870. The surface of the work being bolted direct against the face of the chuck plate will be held true to that face, and all that is necessary is to set it true concentrically. While performing this setting, the work should not be bolted too firmly, but just firm enough to permit of its being moved on the chuck plate by light blows, the final tightening of the clamps being effected after the work is set true. The bolts should be tightened upon the work equally, otherwise one end of the plate will grip the work firmly, while the other being comparatively slack, the work will be apt to move under the pressure of a heavy cut. A form of strap not unusually employed for work chucked in this manner is shown in Fig. 871, its advantage being that it is capable of more adjustment about the chuck plate, because the slots afford a greater range for the bolts to come even with the holes in the chuck plate. If the work be light, it may be held to the face plate while the holding or clamping plates are applied as shown in Fig. 872, in which F is the face plate or chuck plate, W the work, P a plate of iron, D a rod, and C the back lathe centre. The latter is forced out by the hand wheel of the tailstock with sufficient force to hold the work by friction while the bolts and plates are applied. It is obvious, however, that if the work has no hole in its centre, the plate P may be dispensed with, and that if a strap plate, such as shown in Fig. 871, be employed, it must first be hung on the tail spindle so that it may be passed over the rod D to the work. Strap plates are suitable for work not exceeding about 6 inches in diameter. For larger work, bolts and plates are used, as shown, for example, in Fig. 873, which represents a piece of work W held to the chuck plate by plates P and bolts B, there being at E E packing pieces or pieces of iron to support those ends of the clamps or clamping plates P. It is necessary that these packing pieces E be of such a height as to cause the plates P to stand parallel to the face of the chuck for the following reasons:-- [Illustration: Fig. 871.] [Illustration: Fig. 872.] [Illustration: Fig. 873.] Suppose that in Fig. 874, W is a piece of work clamped to the chuck plate, and that packing piece E is too high, and packing piece E´ is too low, as shown, both pieces throwing the plates P out of level, then in setting the hole in the work to run true it will be found difficult to move it in the direction of the arrow, because moving it in that direction acts to force it farther under plate P´, and therefore, to tighten its nut. In the case of plate P, the packing piece E will be gripped by the plate more firmly than the work is, which will be held too loosely, receiving so little of the plate pressure as to be liable to move under the pressure of the tool cut. It is better, however, that the packing piece be slightly above, rather than below the level of the work surface. The position of the plates with relation to the work should be such as to drive rather than to pull it, which is accomplished in narrow work by placing them as in Fig. 873. [Illustration: Fig. 874.] The position of the bolts should be as close as possible or convenient to the work, because in that case a larger proportion of its pressure falls upon the work than upon the packing piece. For the same reason, the packing piece should be placed at the end of the plates. This explains one reason why it is preferable that the packing piece be slightly above rather than below the level of the work surface, because, the bolt being nearer to the work than to the packing piece, will offset in its increased pressure on the work the tendency of the packing piece to take the most bolt pressure on account of standing the highest. If a packing piece of the necessary height be not at hand, two or more pieces may be used, one being placed upon the other. Another plan is to bend the end of the clamping plate around, as in Fig. 875, in which case a less number of packing pieces will be required, or, in case the part bent around is of the right length or height, packing pieces may be dispensed with altogether. This is desirable because it is somewhat difficult to hold simultaneously the plate in its proper position and the packing pieces in place while the nut is screwed up, there being too many operations for the operator's two hands. To facilitate this handling, the nuts upon the bolts should not be a tight fit, because, in that case, the bolt will turn around in the bolt holes or slot of the chuck, requiring a wrench to hold the head of the bolt while the nut is screwed up, which, with holding the plate, would be more than one operator could perform. If the holes in the chuck plate are square, as they should be, the bolt may be made square under the head, as in Fig. 876 at A, which will prevent it from turning in the hole. This, however, necessitates that the head of the bolt be placed at the back of the chuck, the nut end of the bolt being on the work side, which is permissible providing that the bolt is not too long, for in that case the end of the bolt projecting beyond the nut would prevent the slide rest from traversing close up to the work, which would necessitate that the cutting tools stand farther out from the slide rest, which is always undesirable. Bolts that are not square under the head should, therefore, be placed with the head in the work side of the chuck plate, because it is of little consequence if the bolt ends project beyond the nuts at the back of the chuck plate. [Illustration: Fig. 875.] [Illustration: Fig. 876.] The heads of the bolts should be of larger diameter than the nuts, because the increased area under the head will tend to prevent the bolt from turning when the nut is screwed up. [Illustration: Fig. 877.] It sometimes happens that a projection on the work prevents the surface that should go against the surface of the chuck plate from meeting the latter. In this case, what are known as parallel pieces are employed. These are pieces of metal, such as shown in Fig. 877, the thickness A varying from the width B so as to be suitable for work requiring to stand at different distances from the chuck plate surface, it being always desirable to have the work held as near as possible to the chuck plate so that it may not overhang the live spindle bearings any more than necessary. [Illustration: Fig. 878.] An example of chucking with bolts and plates and with parallel pieces is given in Fig. 878, in which the work has projections _a_, _a_ and _b_, _b_, which prevent it going against the face of the chuck; E, E are the parallel pieces which, being of equal thickness, hold the inside face of the work parallel to the chuck face. [Illustration: Fig. 879.] Another example of the employment of parallel pieces is shown in Fig. 879, which represents a connecting rod strap with its brasses in place, and chucked to be bored. B is a small block of iron inserted so that the key may bind the brasses in the strap and P P is one parallel piece, the other being hidden beneath the key and gib. The object in this case is to chuck the brasses true with the face A of the strap, the plates S being placed directly above or over the parallel pieces. This is a point requiring the strictest attention, for otherwise the pressure of the clamping plates will bend both the work and the chuck plate. [Illustration: Fig. 880.] In Fig. 880, for example, the parallel pieces being placed at _p_, _p_, and the clamping plates at P, P, the pressure of the latter will bend the work as denoted by the dotted lines, and the chuck plate in the opposite direction, and in this case the work being weaker than the chuck plate will bend the most. As a result the face of the work will not be true when released from the pressure of the bolts and nuts holding it. Parallel pieces should therefore always be placed directly beneath the clamping plates, especially in the case of light work, because if they be but an inch away the work will be bent, or spring as it is termed, from the holding plate pressure. In very large work the want of truth thus induced would be practically discernible, even though the work be quite thick, as, say, three inches, if the parallel pieces were as much as, say, 6 inches from the holding plates. [Illustration: Fig. 881.] Fig. 881 shows an example of chucking by means of parallel strips in conjunction with parallel pieces. B, B are a pair of brasses clamped by the strips S, S, which are bolted together by the bolts A, A; P, P are the parallel pieces. The strips being thus held parallel to the surface of the chuck plate, all that is necessary is to set the flanges of the work fair against the surface of the strips and true with the dotted circle, and the brass bore will be bored at a true right angle to the inside face of the flange. If the inside face of the brasses was true, the parallel pieces might be omitted, but this is rarely the case. An excellent example of bolt and plate chucking is given in a heavy ring of, say, three feet diameter, and 5 or 6 inches cross section, requiring to be turned quite true, and of equal thickness all over. This job may be chucked in three different ways; for example, in Fig. 882, A, B, C, D are four-chucking dogs, so holding the work that its two radial faces and outside diameter may be turned. This being done, four more dogs may be placed to grip the diameter of the work, and the inside ones may then be removed and the bore turned out. In this way the work would not be unchucked until finished. There is danger, however, that the dogs applied outside may spring the work out of true, in which case it would require setting by a pointer in the slide rest. Another plan would be to hold the work by dogs applied on the outside, and turn the bore and both of the faces. To these fasten four plates on the chuck plate, and turn their ends to the size of the bore and place the work on them, as in Fig. 883, in which A, B, C, D are the four plates, and are clamping plates. This plan is often employed, but it is not a desirable one in heavy work, because the weight of the work is quite apt to move the plates during its setting. A better plan than either of these is to first turn off one face and then turn the work around in the lathe and hold it as in Fig. 884. The bore may then be turned, and all that part of the face not covered by the plates. Four holding plates must then be applied with the bolts within the bore, and when screwed firmly down the outside plates may be removed, leaving the work free to have the remainder of its face and its circumference turned up. In this way the work may be turned more true than by either of the two previously described methods, because it has no opportunity to move or become out of true. [Illustration: Fig. 882.] Cylindrical work to be chucked with its axis parallel to the face plate is chucked by wood workers as shown in Fig. 885, in which B, B are two blocks screwed to the chuck C, and having [V]s in to receive the work as shown; the work is held to the blocks B, by means of the straps S, S, which are held to B, B by screws. An example of a different class of chucking by bolts and clamps may be given in the engine crank. A common method of chucking such a crank is to level the surface of the crank in a planing machine, and to hold that surface to the chuck-plate by bolts and plates, while boring both the holes, merely reversing the crank end for end for the second chucking. This method has several inherent defects, especially in the case of large cranks. First, it is a difficult matter to maintain large chuck plates quite true, and as a result by this method of chucking any want of truth in the surface of the chuck will be doubled in the want of parallelism in the bores of the crank. [Illustration: Fig. 883.] Suppose, for example, that the chuck surface is either slightly hollow or rounding as tested with a straight-edge placed across its face, then the axial line of the hole bored in the crank will not be at a true right angle with the planed surface of the crank. When the crank is turned end for end on the chuck-plate and again bolted with its plain surface against the surface of the chuck, the second hole bored will again not stand at a true right angle to the planed surface, and furthermore the error in one hole will be in a directly opposite direction to that of the other hole, so that the error in the crank will be double the amount that it is on the chuck surface. To this it may be answered that if such an error is known to exist it may be corrected by placing a piece of paper of the requisite thickness at the necessary end of the crank for both chuckings. But this necessitates testing the chuck on each occasion of using it, and the selection of a sheet of paper of the exact proper thickness, which is labor thrown away so long as an equally easy and more true way of chucking can be found. Furthermore there is a second and more important element than want of truth in the chuck to be found, which is that of the alteration of form which occurs in the crank (as each part of its surface is cut away) as explained in the remarks with which the subject of chucking is prefaced. [Illustration: Fig. 884.] First, the planed surface of the crank will alter in truth so soon as the crank is released from the pressure of the holding devices on the planer or planing machine; second, that surface will again alter in form and truth from the removal of the metal around the surface of the hole first bored; and third, the planed surface will be _to some extent_ sprung from the pressure of the plates holding the crank to the chuck plate, hence the following method is far preferable. [Illustration: Fig. 885.] If it is intended to plane the back surface of the crank let that be done first as before, and let it be held to the face-plate by bolts and plates as before, while the hole and its radial face at the large end of the crank are turned and finished. In doing this, however, first rough out the radial face, and then rough out the hole, so that if the work alters in form a fine finishing cut on both the radial face and the bore will correct the evil. Then release the crank from the pressure of the holding plates; and it is obvious that however the planed surface may have altered in truth from removing the surface metal, the radial face just turned will be true with the bore turned at the same chucking. Now to chuck the crank to bore the second hole, turn it end for end as in Fig. 886, and bolt the face already turned to the chuck plate (as at A in the figure) with one or more bolts and strap plates. To steady the other end of the crank, and prevent it from moving under the pressure of the cut, take two bolts and plates B, and place a washer between them and the chuck surface as shown at C, then bolt the plates to the chuck plate, so adjusting them that their ends just have contact with the crank when it is set true. In setting it true it may be moved by striking the outer ends of the plates. [Illustration: Fig. 886.] In this method of chucking, we have the following advantages:-- 1st. If the chuck plate is not true we may place a piece of paper beneath the crank surface A, to correct the error as in the former method, or if this is neglected, the second hole bored will be out of true to an amount answerable to the want of truth in the chuck, and not to twice as much as in the former method. 2nd. Any alteration of form that may take place during the first chucking does not affect the truth of the second chucking as in the other case. 3rd. The crank being suspended during the second chucking, any alteration of form that may accompany the boring of the second hole will be corrected by the finishing cut, hence the crank will be bored with its two holes as axially true as they can be produced in the lathe. It now remains to explain the uses of the pieces W in Fig. 886, simply weights termed counterbalances bolted to the chuck plate to balance it against the overhanging weight of the crank on one side of the chuck plate. If these weights are omitted the holes in the work will be bored oval, because the centrifugal force generated by the revolution of the work will take up any lost motion there may be between the cone spindle journal and its bearings, or if there be no such lost motion the centrifugal force will in many cases be sufficient to spring the cone spindle. In selecting these weights it is well to have them as nearly as possible heavy enough to counterbalance the work when placed at the same distance from the lathe centre as the outer end of the work. The proper adjustment of the weight is ascertained by revolving the lathe and letting it slowly come to rest, when, if the outer end, or overhanging end as it termed, of the work comes to rest at the bottom of the circle of revolution on two or three successive trials the weight of the counterbalance must be increased by the addition of another weight, or the weight may be moved farther from the lathe centre. To enable a piece of work, such as a crank for example, to have two or more holes bored at one chucking, a class of chuck such as shown in Fig. 887 is sometimes employed. S is a slide in one piece with the hub that screws on the live spindle and standing at a true right angle with the axial line of the cone spindle and made as long as will swing over the lathe bed. It contains a dovetail groove (as shown in the edge view) into which a bar _t_, running across the back of the face plate P, passes. To cause the bar _t_ to accurately fit the dovetail, notwithstanding any wear of the surfaces, a slip G is introduced, being set up to _t_ by set-screws passing through that side of the dovetailed piece. The work, as the crank C, is bolted to the face plate, and the set-screws on G are eased so that the plate can be moved to set the work true; when true, the set-screws are tightened, and the first hole may be bored. To bore the second hole all that is necessary is to slacken the set-screws on G, move the plate, which will slide in the dovetail groove, and set the work; when the set-screws are again set up tight, the boring may again be proceeded with. In this way both holes may be bored without unclamping the work. The whole truth of the job, _before being unclamped from the chuck plate_, depends in this case upon the dovetail groove being at a true right angle to the axial line of the lathe cone spindle, it being of no consequence whether the face plate stands true or not. But suppose the removal of the metal to have released strains in the casting or forging, then the clamping plates will have prevented the crank from quite assuming its normal shape after the release of those strains, and the crank, when finished, though true while clamped, will change its form the instant the clamping plates are removed, and the holes bored will in all probability not have their axial lines true one with the other. Another objection is that throwing the chuck plate out of balance on the lathe spindle as well as the crank induces the evils due to the centrifugal motion. This may be offset by increased counterbalancing, of course, but the counterbalancing becomes cumbersome, and is not so easy a matter. For these reasons, chucks of this class are not desirable unless it may be for comparatively small and light work. It is obvious that the dovetail groove may be provided with a screw, and the back of the plate with a nut, so as to move the plate along the groove by revolving the screw. This will assist in adjusting or setting the work, but it will increase the amount of weight requiring to be counterbalanced. [Illustration: Fig. 887.] When a number of pieces are to be bored with their holes of equal diameters and of the same distance apart, the chucking should be performed as in Figs. 888 and 889; one and the same end of each link should be bored and faced, the links being held by the stem, placed on parallel pieces with plates. A pin such as shown in Fig. 889 should then be provided, its diameter across A being a close sliding fit into the bores of the links; while the length of A should be slightly less than the length of the hole in the link, the part D should be made to accurately fit the hole bored by any suitably sized reamer; a washer B should be provided, and each end should be threaded to receive nuts. There should then be provided in the chuck plate a hole whose distance from the centre of the chuck must exactly equal the distance apart the holes in the links are required to be, and into whose bore the end D of the pin shown in Fig. 889 must drive easily. The pin should be locked in this hole by a nut as shown in Fig. 889. The bored ends of the links may then be placed on the pin and fastened by a nut as in Fig. 888, which will regulate the distance apart of the holes. [Illustration: Fig. 888.] [Illustration: Fig. 889.] It is obvious that the pin may be passed through one of the radial slots in the chuck, and set the required distance from the centre, but in this case the pin would be liable to become moved in its position in the slot. Side plates to prevent the link from moving should of course be applied as at D, D in the figure. The whole process of the second chucking will thus consist of fastening the links on the pin, and setting the free end to the circle made to mark its location. This is done as shown in Fig. 890, which represents the free end of a link, D is the circle marked to set the link by, and P a pointed tool held firmly in the slide rest tool post. The link is obviously set true when the dotted circle on its end face runs true, the pointer merely serving to test the dotted circle. [Illustration: Fig. 890.] When, however, one or two links only require to be turned it will not pay to make the pins shown in Fig. 888, especially if the holes of the different links vary in diameter, hence the work must be set by lines. In the promiscuous practice of the general workshop, where it may and often does happen that two pieces of work are rarely of the same shape and size, lines whereby to set the work are an absolute necessity, not only to set the work by in chucking it, but also to denote the quantity of metal requiring to be taken off one face in order to bring its distance correct with relation to other faces. An example of this kind is given in Fig. 891, which represents a lever to be bored and faced at the two ends, the radial faces standing at different distances from the centre of the lever stem as denoted by the lines (defined by centre punch dots) E, F, G, H, I, J, K, L. It will be noted that at H, I, F, and E there is but little metal to be taken off, while there is ample at L. Suppose then that the face L were the first one turned, and it was only just trued up, then when F or H were turned there would be no metal to turn, for they may be too near the plane of L already. [Illustration: Fig. 891.] The necessity for these lines now being shown, we may proceed to show how they should be located and their services in setting the work. The line A is called the centre line, it passing through the centre of the thickness of the link body on both edges of the link. From it all the other lines, as J, F, L, G, E, K, and H, I, are marked. The first question that arises in the chucking is, which of the holes B, C, or D, shall be bored first. Now the faces K and L are those that project farthest from the centre line A, hence if the hole at that end be bored and the faces K, L, be turned first, we may bolt those faces against the chuck plate, and thus insure that all three holes shall stand axially true one with the other. If the holes B or C were bored first, L projecting beyond J and F (which are the faces of holes B, C) would prevent the radial face first turned from serving as a guide in the subsequent chuckings, unless a parallel piece were placed between the face and the chuck. In this case, however, there is not only the extra trouble of using the parallel piece, but there would obviously be more liability of error, as from the parallel piece not being dead true and the amount of the error multiplying in the length of the lever, and so on. The hole D is the one, therefore, to be bored first, the chucking proceeding as follows:--Two parallel pieces of sufficient thickness to keep L clear of the chuck plate should be placed one on each side of the hub E, and bolts and plates placed directly over them. The work must be set so that the line A on each side of the link stands exactly parallel with the face of the chuck, the parallelism being tried at each end of the line, because any error that may be made in setting the work by the full length of the line will have a less effect upon the work than the same amount of error in a shorter length of line. For this reason the centre line should always be marked as long as possible and used to set by, unless there is a longer line running parallel to it and marked on both sides of the link, as would be the case if the dotted line at J and that at L were equidistant from A, in which event they may preferably be used. The work is set true to the lines by a scribing block, or surface gauge, but as that instrument is more used in setting work with chuck dogs its application will be shown in connection with chucking by dogs; hence to proceed: To set the work true to the line A it may be necessary to place a thickness of paper, a piece of sheet tin, or the equivalent, beneath one of the parallel pieces to bring A parallel with the chuck plate surface. This being done, however, and the circle D being set to run true, the hole may be bored and the radial face L turned off so as to just split the dotted line at L, and this radial face may be used instead of the line A for all subsequent chuckings, so as to avoid the errors that might occur in referring to the line, and from the alterations that might occur in the form of the work from removing the surface metal. [Illustration: Fig. 892.] Fig. 892 represents a view of the end L as held for the second chucking. C is a section of the chuck plate, and O O represents the line of centres of the lathe, and it is obvious that the radial face of the lever end (which is here represented by L) being used for all but the first chucking, the holes will all stand axially true one with the other, no matter how many chuckings and holes there may be, hence it becomes obvious that the face that will meet the chuck plate is the one that should be turned at the first chucking. It is of no consequence in the case of a single lever whether the pin fits the hole in the end of L, Fig. 892, or not, because the dotted circles at B, C, D in Fig. 891 form the guides whereby to set the holes for distance apart, and any bolt may be used to clamp the work. It is usual in an example of this kind to turn the stem of the lever to its proper thickness for a short distance from the hubs, so as to have the stem true with the bores, and form a guide whereby to set the lever in the planer or shaper when cutting down the lever stem to size. The rules of chucking and the balance weighting described with reference to chucking a crank, of course also apply to this example. It will now be observed that in all cases in which work is chucked by bolts and plates, the whole of the faces cannot be turned at one chucking unless the shape of the work is such that it will permit the plates and the bolts to pass or be below the level of the work surface. It will further be noticed that if one face of the work is held against the chuck surface it cannot be turned at the same chucking that the other face is turned at. Now it may be very desirable that a part or the whole of the back face as well as the front one be turned at the same chucking as that at which the hole is bored, so as to have the hole and those two faces true without incurring the errors that might arise from a second chucking. Again, the diameter of the work may be equal to that of the chuck so as to preclude the possibility of using bolts and plates outside of the circumference, and though there be cavities or slots running through the work through which the bolts might be passed, yet the presence of the plates would prevent the face from being turned. [Illustration: Fig. 893.] To meet these and many other requirements that might be named, chucking by the aid of chucking dogs is resorted to, one of these dogs being shown in Fig. 893. B represents a section of the chuck plate with a piece broken out to show the stem A of the dog, which is squared to prevent its revolving when the nut D, which holds the dog to the chuck plate, is tightened, the holes of the chuck, of course, being square also; E is the set-screw which holds the work, its end at E being turned down below the thread, and the head squared to receive a wrench. [Illustration: Fig. 894.] Fig. 894 represents an example of chucking by dogs, it being required to face the work off to the dotted line F F. Three of the four dogs used are shown at D, D, D. To set the work the scribing block shown in the figure is employed, the point of the needle being set to the line at any one spot, and the scribing block or surface gauge carried around the work rested with its base against the chuck plate and the needle point tried for coincidence with the line at various points in the work's circumference. The work is not at first held too firmly by the dogs, so that light blows will suffice to so move the work that the surface gauge needle point applied as shown and at any point around the work will coincide with the line. It will here be observed that using the dogs obviates the necessity for parallel pieces, when the work has projections at the back face as shown in the cut. [Illustration: Fig. 895.] Fig. 895 represents another example in chucking by dogs. It is required to surface the whole of the surfaces shown, to bore the hole C and to face a face similar to A, but on the other side or chuck side of the work. Then the work is placed so that its outer face will project beyond the extreme surface of the dogs, and the whole of the operations can be performed at one chucking. It will be observed that in this case the surface of the chuck plate does not automatically serve to guide the work in the chucking, because there is no contact between the two, but the chuck surface can be used as a guide whereby to chuck the work as has just been shown. Or suppose the work to require to be set as true as can be to its exposed face, then the work end of the surface gauge is applied as shown in Fig. 896 at E. [Illustration: Fig. 896.] [Illustration: Fig. 897.] [Illustration: Fig. 898.] The surface gauge may indeed be dispensed with if the work is sufficiently light that the lathe can be swung around by pulling the chuck plate with the hand, and the work merely requires to be set to run true on its exposed radial face. A pointer held in the slide rest, and applied as in Fig. 890, will denote the setting of the work, which must be tapped until the pointer touches it equally on four equidistant points of the surface; but if it is essential to take as little as possible off the face while truing it up, the tool point should be held stationary, while the work should be so set that the four most distant points (in that circle on the work which is equivalent in radius to the radius to which the tool point stands from the chuck centre) are equidistant as measured by a rule from the tool point. The philosophy of this will be understood from a reference to Fig. 894 and the remarks thereon, this being a parallel case, but applied to a radial face instead of to a circumference. Now suppose we have the piece of work shown in Fig. 897, which requires to have its surfaces A and B parallel and at a right angle to C and D, the end faces E and F parallel to each other, and at a right angle to both A, B, C, and D, the hole at G is to be axially true with the surfaces A, B, C, and D, as well as with the pin at I, and the hole at H at a dead right angle to that at G. We may put a plug in G and turn up the surfaces E and F, and turn the pin I; this, however, would leave the hole G unbored, whereas it should be bored when the surface E is turned; again, after these surfaces are turned they are of no advantage as guides in the subsequent chuckings. We may grip the surfaces E and F in a jaw chuck to turn the surfaces A, B, C and D, but depending upon the face jaws of the dogs to set the work surface true by; but this would not be apt to produce true work on account of the spring of the jaws, as explained in the remarks upon jaw chucks; furthermore, the work, supposing it to be a foot long, could not be held in a dog chuck sufficiently firmly to enable the turning of the end face E or the pin I, and this brings us to that most excellent adjunct to a general chucking lathe, the angle plate shown in Fig. 898. It is simply a plate of the form shown in the figure, having two flat and true surfaces, one at a right angle to the other; one of these surfaces bolts to the chuck plate, while the other is to fasten the work on. The slots shown are to pass the bolts through to fasten the angle plate to the chuck plate, and the work surface of the plate contains similar slots and holes to receive the bolts used to fasten the work. [Illustration: Fig. 899.] Suppose, then, we fasten the piece of work to the angle plate as shown in Fig. 899, and face off the surface C, and bore the hole H, the work being set true with its surface, or to a line, by the aid of a surface gauge, as may be required. We then turn surface C down to meet the surface of the angle plate, fasten it to the same with bolts and plates and setting it as before, and on turning its surface A we shall have the two surfaces A and C at a right angle to one another. We then turn the surface A down upon the angle plate and bolt it again as before. But we have now to set it so that the surface C shall be quite parallel with the surface of the chuck plate. This we may do by placing one or more parallel strips behind it, as at S S, in the plan view, Fig. 900, setting the work so that it binds the parallel strips tight against the chuck plate along their full lengths; or we may measure the distance of C from the chuck plate surface with a pair of inside calipers; or we may turn the bent end of a surface-gauge needle outwards and gauge the work as shown in the plan view, trying the work all along. On turning the surface D, Fig. 897, we shall have three of the surfaces done at right angles and with C and D parallel. [Illustration: Fig. 900.] It is obvious that the surface D may be turned down on the angle plate and bolted as before, the surface A being set parallel to the chuck plate surface as before, and all four of these surfaces will be finished true as required. Next come the two end surfaces and the pin I. For F and the pin I we chuck the work on the angle plate, as shown in the plan view, Fig. 901, P, P representing the clamping-plates. The angle plate will here again serve to hold the work true one way, and all we have to do to set it true the other way is to fasten a pointer in the tool post and bring it up to just touch the corners of the work at the outer end, as at K. Now run the carriage up so as to bring the pointer to position L, and when the work is so set that all four corners just touch the pointer, tried in their two positions, _without touching the cross-feed screw_, the work is true, and the end surface E and hole G may be turned; E will then be at a true right angle to the four faces, A, B, C, D, while G will be axially true with them. [Illustration: Fig. 901.] We may, instead of using the pointer at K and L, or in addition to so using it, apply a square against the chuck plate and bring the blade against the work, as shown at R. We have now to turn the pin I and end face, and to do this we simply reverse the work, end for end, and bolt it as before. But we may now employ the trued surface E as an aid in setting by causing it to abut against the chuck plate surface, and, as an aid to finding that it abuts fair, we may put two strips of the same piece of paper behind it, one on each side of the square, and, after the work is bolted, see that both are held firm; but it is necessary to test with the pointer as before, as well as with the square. It is obvious that the angle plate requires counterbalancing, which is done by means of the weight W. (Fig. 900). An excellent example of angle plate chucking is furnished in a pipe bend requiring both flanges to be turned up. The method of chucking is shown in Figs. 902 and 903, the flanges being simply bolted to the angle plate. The work may be set true to the body of the bend close to the neck of the flange or by the circumference of the flange. The face of the flange will be held true one way by the face on the angle plate, but must be set true the other way. The truest flange should be the one first bolted to the angle plate. [Illustration: Fig. 902.] [Illustration: Fig. 903.] [Illustration: Fig. 904.] A common but good example of angle plate chucking is shown in Fig. 904, which represents a cross head requiring to have its two holes bored one at a right angle to the other, the jaws faced inside and outside, and the hub or boss turned. [Illustration: Fig. 905.] It would be proper to mark the cross-head out by lines, giving dotted circles to set the work by, and dotted lines to give the thickness of the jaws. In thus marking out two centre lines A A and B B in Fig. 905 would be used to locate the centres of the holes; and the thickness of the jaws would be marked from the line B B. In marking these lines the cross head should be rested upon a table or plate as in Fig. 905, and the line A A should be made with the jaws of the cross head lying flat on the table, that is without the interposition of any packing or paper between them and the plate, so that the edges of the jaws on that side will be true with the line A A, and will therefore serve to apply a square against when chucking to bore the hole through the jaws. If the jaw edges are not sufficiently true to permit of their lying on the table, they should be made so by filing a flat place on them, so that when a square is applied to them as in Fig. 906, the edges C, C will be parallel with the axis A A of the holes in the chucks or jaws. The first chucking should be as in Fig. 907, the cross head being bolted to an angle plate set true by the circle on the end face of its hub D, and a square being applied to the centre line A, as in Fig. 908, and to the dotted lines on the jaws as shown in Fig. 909. A balance weight W, Fig. 907, is necessary to counterbalance the weight of the angle plate. [Illustration: Fig. 906.] The second chucking to bore the cheeks and face them inside and out to the required thickness would be as in Fig. 910, a single plate and two bolts being used to hold the cross head to the angle plate. To set the cross head true in one direction, the outer circle shown marked upon the face of the cheek is used. It remains to so set the face of the cheeks that the hole through them shall be central with that already bored through the hub D and all that is necessary to accomplish this is to set the edge true as shown in the top view in Fig. 911, in which S is a square rested against the face of the chuck and applied to the edges of the cheeks, these edges being those that were rested on the plate when marking the line A A in Fig. 905, or that were filed square if it was found necessary as already mentioned. [Illustration: Fig. 912.] The inside faces of the cheeks are turned to the dotted lines shown in Fig. 909, and the outside faces being turned each to the proper thickness measured from the outside ones, the job will be complete and true in every direction. [Illustration: _VOL. I._ =EXAMPLES IN ANGLE-PLATE CHUCKING.= _PLATE XII._ Fig. 907. Fig. 908. Fig. 909. Fig. 910. Fig. 911.] An excellent example of angle plate chucking is shown in Fig. 912--the actual dimension of the piece, measuring, say, 24 inches in length. It is required to have the cylindrical stems A, B turned parallel to each other, of equal diameters, equidistant from the central hole C, and true with the hub D. A large piece of work of this kind would be marked off with lines defined by centre-punch dots, as shown. The ends of A, B, D would require dotted circles to set them by. Now, in all work of this kind it is advisable to turn that surface first that will afford the greatest length of finished surface, to serve as a guide for the subsequent chucking, which in this case is the hub D, and the face on that side as denoted by the dotted line which has to be cut to that line. The method of chucking would, for this purpose, be as in Fig. 913. [Illustration: Fig. 913.] [Illustration: Fig. 914.] [Illustration: Fig. 915.] The second chucking would be as in Fig. 914 to bore the hole at C, while, at the same time, the surface from F to G may be turned. Either inside calipers or a surface gauge may be employed to set E E parallel to the chuck plate surface. It is supposed that the location C is defined by a dotted circle, by which the work may be set for concentricity, as should be the case. At the next chucking it will simply be necessary to move the work on the angle plate to the position shown in Fig. 915, setting the circle on the end of A to run true, and the surface E parallel to the chuck surface as before. The third chucking is made by simply moving the work on the angle plate again, and setting as in the last instance. CHAPTER X.--CUTTING TOOLS FOR LATHES. The cutting tools for lathes are composed of a fine grain of cast steel termed "tool-steel," and are made hard, to enable them to cut, by heating them to a red heat and dipping them in water, and subsequently reheating them to temper them or lower their degree of hardness, which is necessary for weak tools. These cutting tools may be divided into two principal classes, viz., slide rest tools, or those held in the slide rest, and hand tools, which are held by hand. The latter, however, have lost most of their former importance in the practice of the machine shop, by reason of the employment of self-acting lathes. The proper shape for lathe slide rest tools depends upon-- 1st. The kind of metal to be cut. 2nd. Upon the amount of metal to be cut off. 3rd. Upon the purpose of the cut, as whether to rough out or to finish the surface. 4th. Upon the degree of hardness of the metal to be cut. 5th. Upon the distance the tool edge is required to stand out from the tool clamp, or part that supports it. Lathe tools are designated either from the nature of their duty, or from some characteristic peculiar to the tool itself. The term "diamond point" is given because the face of the tool is diamond shaped; but in England and in some practice in the United States the same tool is termed a front tool, because it is employed on the front of external work. A side tool is one intended for use on the side faces of the work, as the side of a collar or the face of a face plate. An outside tool is one for use on external surfaces, and an inside one for internal, as the walls or bores of holes, &c. A spring tool is formed to spring or yield to excessive pressure rather than dig or jump into the work. A boring tool is one used for boring purposes. [Illustration: Fig. 916.] [Illustration: Fig. 917.] The principal forms of cutting tools for lathes are the diamond points or front tools, the side tools (right and left), and the cutting off or parting tool. The cutting edges of lathe tools are formed by grinding the upper surface, as _a_ in Fig. 916, and the bottom or side faces as _b_, so that the cutting edges _c_ and _d_ shall be brought to a clean and sharp edge, the figure representing a common form of front tool. The manner in which this tool is used to cut is shown in Fig. 917, in which the work is supposed to be revolved between the lathe centres in the manner already described with reference to driving work in the lathe. The tool is firmly held in the tool post or tool clamp, as the case may be, and is fed into the work by the cross-feed screw taking a cut to reduce the work diameter and make it cylindrically true; the depth to which the tool enters the work is the depth of the cut. The tool is traversed, or fed, or moved parallel to the work axis, and the motion in that is termed the feed, or feed traverse. [Illustration: Fig. 918.] The cutting action of the tool depends upon the angles one to the other of faces B, D (Fig. 918), and the position in which they are presented to the work, and in discussing these elements the face D will be termed the top face, and its inclination or angle above an horizontal line, or in the direction of the arrow in Fig. 918, will be termed the rake, this angle being considered with relation to the top A A, or what is the same thing, the bottom E E of the tool steel. The angle of the bottom face B to the line C is the bottom rake, or more properly, the clearance. [Illustration: Fig. 919.] In the form of diamond point or front tool, shown in Fig. 916, there is an unnecessary amount of surface to grind at _b_, hence the form shown in Fig. 919 is also employed on light work, while it is in its main features also employed on large work, hence it will be here employed in preference to that shown in Fig. 916, the cutting action of the two being precisely alike so long as the angles of the faces are equal in the two tools. The strength of the cutting edge is determined by the angles of the rake and clearance, but in this combination the clearance has the greater strength value. On the other hand the keenness of the tool though dependent in some degree upon the amount of clearance, is much more dependent upon the angle of the top face. It follows therefore that for copper, tin, lead, and other metals that may be comparatively easily severed, a tool may be given a maximum of top rake, and it is found in practice that top rake can be employed to advantage upon steel, wrought iron, and cast iron, but the amount must be decreased in proportion as the nature of either of those metals is hard. For the combinations of copper and tin which are generally termed brass or composition, either no top rake or negative top rake is employed according to the conditions. [Illustration: Fig. 920.] It may be pointed out, however, that in a given tool the cutting qualification is governed to a great extent by the position in which the tool is presented to the work, thus in Fig. 920, let C represent a piece of work and B, B, B, B, four tools having their top and bottom faces ground at the same angle to each other. In position 1, the top face of the tool is at an acute angle below the radial line A, hence the tool possesses top rake, the amount being about suitable for hard steel or hard cast iron. In position 2 the top face is at an acute angle above the radial line A, hence the tool has negative top rake, the amount being about suitable for brass work under some conditions. In position 3 the top face has no rake of any kind, and the tool is suitable (in this respect) for ordinary brass work. In position 4 the tool possesses an amount of top rake about suitable for ordinary wrought-iron work. If the tool was presented to brass work in positions 1 or 4 it would rip or tear the metal instead of cutting it, while if the tool was presented to iron or steel (of an ordinary degree of hardness) in positions 2 or 3, it would force rather than cut the metal. Furthermore it will be readily perceived that though each tool may have its faces, whose junction forms the cutting edge, at the same angles, yet the strength of the cutting edge is varied by the position in which the tool is presented to the work, thus the edge in position 2, will be weaker than that in position 4. We have now to consider another point bearing upon the proper presentment of top rake and the presentment of the tool to the work. It is obvious that the strain of the cut falls upon the top face of the tool, and therefore the direction in which this strain is exerted is the direction in which the tool will endeavour to move if the strain is sufficient to bend the tool and cause motion. [Illustration: Fig. 921.] In Fig. 921 let W represent the work having a cut C being taken off by the tool T; let E represent the slide rest, and F the extreme point at which the tool is supported; then the pressure placed by C on the top face of the tool will be at a right angle to the plane of that top face, or in the direction of the arrow B; to whatever amount therefore the tool sprung under the cut pressure (its motion being in an arc of a circle, of which F is the centre) it would enter the work deeper, and as a result, the rough work not being cylindrically true, the tool will dip farthest beyond its proper line of work where the cut is deepest, and therefore will not cut the work cylindrically true; as this, however, naturally leads to a variation in the direction of the top rake, and as the cutting action of the point of such a tool differs from that of the side edge, which also leads to a variation in the direction of the top rake, it becomes necessary to consider just what the cutting action is both at the point and on the side of the tool. Suppose, then, that the tool carries so fine a cut that it cuts at the point only, and the pressure will be as denoted by the arrow B in Fig. 921. [Illustration: Fig. 922.] If the tool be given no traverse, but be merely moved in towards the centre of the work, the cut will move outward and in a line with the body of the tool, the cutting coming off as shown in Fig. 922. So soon, however, as the tool is fed to its feed traverse the form of the cutting alters to the special form shown in Fig. 917, and moves to one side of the tool, as well as outwards from the work. [Illustration: Fig. 923.] Fig. 923 is a top view of a tool and piece of work, and the arrow A denotes the direction of the resistance of the work to the cut, being at a right angle to plane of the cutting edge. Now the duty of the side edge is simply to remove metal, while that of the point is to finish the surface, and it is obvious that for finishing purposes the most important part of the tool edge is the point, and this it is that requires to be kept sharp, hence the angle or rake should be in the direction of the point. But when the object is to remove metal and prepare the work for the finishing cut the duty falls heavily on the side edge of the tool, and the angle of the top face and the direction of its rake may be varied with a view to increase the efficiency of the side edge, and at the same time to diminish the amount of power necessary to pull the tool along to its feed traverse. This may be accomplished by altering the top rake from front to side rake, which is done in varying degrees according to the nature of the work. [Illustration: Fig. 924.] In Fig. 924 the angle of the top face in the direction of A is the front, and that in the direction of B is the side rake. In small work where the cuts are not great, and where but one roughing cut is taken, it is an object to have the roughing cut leave the work with as smooth a surface as possible, and the amount of side rake may be small as in Fig. 924. For heavy deep cuts, however, a maximum of side rake may be used. [Illustration: Fig. 925.] Thus in Fig. 925 is an engraving of a tool used for roughing in the Morgan Iron Works, its top rake being all side rake. When a tool has side rake, its cutting capacity is obviously increased on one side only, hence it should be fed to cut on that side only. It is for this reason that no side rake is given to tools for very small and short work, because it is then more convenient to traverse the tool to cut in either direction at will. In long and large work, however, where the motion of the slide rest is slow, tools having right and left-hand side rake are used. The tools in Figs. 924 and 925 are right-hand tools, their direction of feed travel being to the left. [Illustration: Fig. 926.] In Fig. 926 is a left-hand tool, its direction of feed traverse being from left to right; hence edge G is the cutting one, edge F being dulled by the side angle B. [Illustration: Fig. 927.] It is obvious that various combinations of side rake and front rake may be given to produce the same degree of keenness to the tool. For example, a tool may have its keenness from side rake alone, or it may have the same degree of keenness by using less side rake and some front rake. The principles governing the selections of these combinations are as follows:-- Suppose that in addition to say 20 degrees of side rake a tool is given a certain amount of front rake as denoted in Fig. 927 by E E, and suppose that the tool is moved in to its cut by the cross feed screw. During this motion and until the tool point meets the work surface the contact between the cross feed screw and feed nut will be on the sides of the threads facing the line of lathe centres, and all the play between those threads will be on their other sides, but so soon as the tool meets the cut it will jump forward and into the work to the amount that the play between the threads will allow it, and this is very apt to cause the tool to break. Furthermore the point of the tool is apt from its extreme keenness to become dulled quickly. [Illustration: Fig. 928.] The amount of side rake may, however, be considerably increased if the heel D, Fig. 928, be made higher than the point A in that figure, the plane of the middle being denoted by the arrow at A; a view of the other side of this tool is shown in Fig. 929, the plane of the cutting edge being denoted by the dotted line. [Illustration: Fig. 929.] A tool thus formed will require a slight cross feed screw pressure to force it to its cut, thus causing the cross feed nut to have contact with the sides of the thread in contact when winding the tool into its cut, hence the tendency to jump into the depth of cut is eliminated, and regulating the depth of the cut is much more easily accomplished. In proportion as a tool is given side rake, it is more easily traversed to its cut, as will be perceived from the following:-- [Illustration: Fig. 930.] [Illustration: Fig. 931.] Fig. 930 represents a section of a tool T, whose feed traverse is in the direction of A. Now all the force that is expended in bending the cutting C out of the straight line, or in other words the pressure on the top face of the tool, acts to a great extent to force the tool to the left, and therefore traverse it to its feed. The more side rake a tool has the nearer the thickness of its cutting will accord to the thickness of the feed traverse. For example, if a tool having a side rake of say 35 degrees of angle feeds forward 1/32 inch per work revolution, the thickness of the cutting will but slightly exceed 1/32 inch, but if no top rake at all be given, as shown in Fig. 931, then the cutting will come off nearly straight, will be considerably thicker than 1/32 inch, and will be ragged and broken up, and it follows that the thickening and the bending of the cutting has required an expenditure of the driving power of the lathe, diminishing the depth of cut the lathe will be capable of driving. With such a tool the pressure of the cut will fall downwards as denoted by the arrow B. [Illustration: Fig. 932.] In the practice of many tool makers in the Eastern States the tool is ground to a point A, Fig. 932, that is, ground sharp and merely rounded off with an oil-stone. This may serve when the lathe has an exceedingly fine feed, and the strain being in that case very slight the tool point may be made to stand well above the level of the body of the steel, as in the figure, and thus save forging; but this is a slow method of procedure, and produces no better work than a tool which is rounded at the point, and therefore capable of producing smoother work with a much coarser feed. The diameter of the curls of the cutting, shaving, or chip produced by a turning and also the direction in which it moves after leaving the tool, depends upon the amount of the top rake and the direction in which it is provided. The greater the amount of rake, whether it be front or side rake, the larger the coils of the cutting, and, therefore, the less the amount of power expended in bending it. Furthermore, it may be remarked that the thickness of the cutting is always greater than is due to the amount of feed traverse, and it requires power to produce this thickening of the cutting. The larger the coils of the cutting the nearer the thickness accords with the rate of feed. [Illustration: Fig. 933.] In these considerations we have referred to the angle of the top face only, but if we consider the angle of the two faces one to the other we shall see that they form a wedge, and that all cutting tools are simply wedges which enter the material the more easily in proportion as the angles are more acute, providing always that they are presented to the work in the most desirable position, as was explained with reference to Fig. 920. [Illustration: Fig. 934.] We may now consider the degree of a bottom rake or clearance desirable for a tool, and this it can be shown depends entirely upon the conditions of work, diameter, and rate of tool traverse, and cannot, therefore, be made a constant degree of angle. This is shown in Fig. 934, in which a tool T is represented in three positions, marked respectively 1, 2, and 3. Line A A is at a right angle to the axis of the work W, and the side of the tool is given in each case 5° of angle from this line A A. In position 1 the tool has 3° of clearance from the side of the cut; in position 2 it has 2° clearance, but in position 3 it would require to have 2° more clearance given to it to enable the cutting-edge to meet the side of the cut, without even then having the clearance necessary to enable it to cut. This occurs because the side of the cut is not at a right angle to the work axis, but at an angle the degree of which depends upon the rate of feed. [Illustration: Fig. 935.] Thus in Fig. 935 the three tools have the same amount of clearance, and if they are supposed to be facing off the work they will maintain that clearance under all conditions of work, diameter, and rate of feed, but if they were traversed along instead of across the work the angle of the tool (both on the top and bottom face) to the cut will become changed, and will continue to change with every change of work diameter, so that the same tool stands at a different angle at each successive cut taken off the work, even though the lathe were used at or possessed but one rate of feed. But lathe tools are used at widely varying rates of feed, and we may therefore take an example in which a tool is at work taking a cut of the same diameter and depth at different rates of feed. [Illustration: Fig. 936.] This is shown in Fig. 936, tool 1 taking the coarsest, and 2 the finest feed, and it is seen that the finer the rate of feed the more clearance the tool has with a given degree of side clearance (for all the three tools have 7° of side angle). The only way to obtain an equal degree of clearance from the cut, therefore, clearly lies in giving to a tool a different angle for every variation, either in work diameter or in rate of feed traverse, and to show how much this will affect the shape of the tool, we have Fig. 937, in which the same rate of feed is used for all three cuts, and the tool is given in each position 5° of clearance from the cut. In position 1 the tool side stands at 8-1/2° of angle from line A, which is at a right angle to the work axis. In position 2 it stands at 10-1/2°, and in position 3 at 15° of angle from line A, a variation of 6-1/2°. Referring now to the top face of the tool, the variations occur to the same extent and from the same causes. It is in a fine degree of perception of these points that constitutes the skill of expert workmen in grinding their lathe tools, varying the angle of the tool at every grinding to suit the varying requirements. [Illustration: Fig. 937.] It has been shown that for freedom of cutting and ease of driving a given cut, the direction of top rake as well as its degree needs to be a maximum that the nature of the material and its degree of hardness will admit; but this is not the only consideration, because in a finishing cut the surface requires to be left as smooth and clean cut as possible, and it remains to consider how this may best be accomplished. Now let it again be considered that it is that part of the cutting edge that lies at a right angle to the axial line of the work that removes the metal, while it is that part that lies parallel to the work axis (or in other words parallel to the finished work surface) that performs the finishing cutting duty. [Illustration: Fig. 938.] Now, in proportion as the length of the cutting edge is disposed parallel to the work axis, the tool has a tendency to spring (under an increase of cut) into the work, and also to dip into soft places or seams in the work, and the amount of its front rake must be decreased, because such rake causes a pressure pulling the tool deeper into its cut, as was explained with reference to Fig. 921. Round-nosed front tools, therefore, such as in Fig. 938, cannot be given so much front rake as ordinary ones, such as in the preceding figures. [Illustration: Fig. 939.] Round-nosed tools are used to cut out round corners, and the roughing tools are given a less curvature than that to be formed on the work, thus in Fig. 939 is an ordinary form of small round nose shown operating in what is termed a hollow corner, the directions of tool feed being marked by arrows. The tool may be fed by the feed traverse, and the tool gradually withdrawn, thus forming the work to the required curve. The amount of cut a lathe will drive, the degree of hardness which the tool may be given, the length of time the tool will last without grinding, the speed at which the work may run, and the cleanness and truth of the cut, depend almost entirely upon the perfect adaptability of the tool to the conditions under which it is to be used. Upon the same kind of work, and using the same kind of tools, some workmen will give a tool from 20° to 30° more angle than others. [Illustration: Fig. 940.] It is a difficult matter to determine at just what point the utmost duty is being obtained from cutting tools, because the conditions of use are so variable; but one good general guide is the speed at which the tool cuts, and another is the appearance of the cuttings or chips. [Illustration: Fig. 941.] Both these guides, however, can only be applied to metal not unusually hard, and to tools rigidly held, and having their cutting edges sufficiently close to the tool point or clamp that the tool itself will not bend and spring from the pressure of the cut. The cutting speed for chilled cast-iron rolls, such, for example, as calender rolls, is but about 7 feet per minute, and the angles one to the other of the tool faces is about 75 degrees, the top face being horizontally level, and standing level with the axis of the roll. When a tool has front rake only, the form of its cutting will depend upon the depth of its cut. With a very fine cut the cutting will come off after the manner shown in Fig. 940, while as the depth of the cut is increased, the cutting becomes a coil such as shown in Fig. 941. These coils lie closer together in proportion as the top face of the tool is given less rake, as is necessary for steel and other hard metal. Thus Fig. 940 represents a cutting from steel, the tool having front rake only, while Fig. 941 represents a cutting from a steel crank pin, the tool having side rake. The following observations apply generally to the cuttings. [Illustration: Fig. 942.] The cleaner the surface of a cutting, and the less ragged its edges are, the keener the tool has cut; thus, in Fig. 941, the raggedness shows that the tool was slightly dulled, although not sufficiently so to warrant the regrinding of the tool. Such a cutting, however, taken off wrought iron would show a tool too much dulled, or else possessing too little top rake to cut to the best advantage. In wrought iron, the tool having a keener top face, the cuttings will coil larger, and the direction in which they coil and move as they leave the tool will depend upon the shape of the tool and its height to the work. [Illustration: Fig. 943.] [Illustration: Fig. 944.] In Fig. 942, for example, is a tool having front and side angle in about an equal degree, and its cutting is shown in Fig. 943, the side angle causing it to move to the right, and the front angle causing it to move towards the tool post. The tool in Fig. 944 has side rake mainly, and the point is slightly depressed, hence its cutting would leave the work moving horizontally and towards the right hand. [Illustration: Fig. 945.] [Illustration: Fig. 946.] In Fig. 945 the point of the tool is made considerably lower than the point B, and as a result the cutting would rise somewhat vertically as in Fig. 946. Indeed the heel B may be raised so as to cause the cutting to move but little to the right, but rise up almost vertically, being thrown over towards the work, and in extreme cases the cutting will rub against the surface of the work and the friction will prevent the cutting from moving to the right, hence it will roll up forming a ball, the direction of the rotation occasionally changing. Whatever irregularities may appear in the coil of the cuttings will, if the tool is not dulled from use, arise from irregularities in the work and not from any cause attributable to the tool. The strength of a cutting forms to a great extent a guide as to the quality of the tool, since the stronger the cutting the less it has become disintegrated, and therefore less power has been expended in removing it from the work. The cutting speed for wrought iron should be sufficiently great that water being allowed to fall upon the work in a quick succession of drops as, say, three per second, the cuttings will leave the work so hot as to be almost unbearable in the hands, if the cut is a heavy one, as, say, reducing the work diameter 1/2 inch at a cut. If wrought-iron cuttings break off in short pieces it may occur from black seams in the work, but if they break off short and show no tendency to coil, the tool has too little rake. If the tool gets dull too quickly and the cutting speed is not excessive, then the tool has too much clearance. If the tool edge breaks there is too much rake (providing of course that the tool has not been burnt in the forging or hardening), a fine feed will generally produce longer and closer coiled cuttings (that is of smaller diameter) than a coarse feed, especially if the work be turned dry or without the application of water. [Illustration: Fig. 947.] Aside from these general considerations which apply to all tools, there are peculiar characteristics of particular metals; thus, for example, cast iron will admit of the tool having a greater width of cutting edge in a line with the finished surface of the metal than either steel, wrought iron, copper or brass, which renders it possible to use a finishing tool of the form shown in Fig. 947, whose breadth of cutting edge A, lying parallel with the line of feed traverse, may always exceed that for other metals, and may in the case of cast iron be increased according to the rigidity of the work, especially when held close in to the tool post. [Illustration: Fig. 948.] The corners B C may for roughing the work be rounded so as to be more durable, but for finishing cuts they should be bevelled as shown, because by this means face A can more easily be left straight than would be the case with a rounded corner. In the absence of the bevels there would be a sharp corner that would soon become dull. For finishing purposes the corners need not be so much bevelled as in figure, but may be very slightly relieved at the corners A and B, in Fig. 948, the width of the flat nose being slightly greater than the amount of feed per lathe revolution. Such tools produce the quickest and best work without chattering when the conditions are such that the work and the tool are held sufficiently rigid, and in that case may be used for the harder and tougher metals, as wrought iron and steel. We have now to consider the height of the tool with relation to the work, which is a very important point. [Illustration: Fig. 949.] In Fig. 949, for example, let E be the washer or ring under the tool, and F therefore the fulcrum from which the tool will bend. Let the horizontal dotted line a represent the centre of the work, and it is plain that to whatever amount the tool may spring under the pressure of the cut, its motion from this spring will be in the direction of the dotted arc H, causing the tool to dip deeper into the work in proportion as the tool point is set above the work centre line A. Now the amount of tool spring will even under the most rigid conditions vary in a heavy cut with every variation in the depth of cut or in the hardness of the metal. Furthermore, as the cutting edge of the tool becomes dulled from use, its spring will increase, because the pressure required to force it to its cut becomes greater, and as a result when the conditions are such that a perceptible amount of tool spring or deflection occurs, the work will not be turned cylindrically true. Obviously the work under these conditions will be most true when the tool point is set level with the line A, passing through the work axis. [Illustration: Fig. 950.] There are two advantages, however, in setting the tool above the work centre: first it severs the metal easier; and second, it enables the employment of more bottom rake without increasing the bottom clearance. [Illustration: Fig. 951.] Thus in Figs. 950 and 951 the diameters of the work W and the top rake of the respective tools are equal, but the tool that is set above the centre, Fig. 950, has more bottom rake but no more clearance, which occurs from the manner in which the cutting edge is presented to the work; the dotted lines represent the line of severance for each, and it is obvious that in Fig. 950, being of the shortest length for the depth of the cut will require least power to drive, because it is, as presented to the work, the sharpest wedge, as will be perceived by referring to Fig. 952, in which the tool shown in Fig. 950 is simply placed below the work centre, all other conditions as angle, &c., being equal. From these considerations it appears that while for roughing cuts it is advantageous to set the tool above the centre, it is better where great cylindrical truth is required to set it at the centre for finishing cut. [Illustration: Fig. 952.] It may also be observed that if the lathe bed be worn it will usually be most worn at the live centre end, where it is most used, and a tool set above the centre will gradually fall as the cut proceeds towards the live centre, entering the work farther, and therefore reducing its diameter. This can be offset by setting the tailstock over, but in this case the wear of the work centres is increased, and the work will be more liable to gradually run out of true, as explained with reference to turning taper work. Sir Joseph Whitworth recommends that the tool edge be placed at the "centre" of the work, while at the same time on a line with the middle of the body of the steel. To accomplish this result it is necessary that the form of the tool be such as shown in Fig. 953, in which W represents a piece of work, R the slide rest, A the fulcrum of the tool support, the dotted line the centre of the work, and the arrow the direction in which the tool point would move from its deflection or spring. Now take the conditions shown in Fig. 954, and it will be perceived at once that the least tool deflection will have an appreciable effect in causing the tool point to advance into the work in the direction denoted by the arrow. This would impair the cylindrical truth of the work, because metals are not homogeneous but contain in forged metals seams and harder and softer places, and in cast metals different degrees of density, that part laying at the bottom of the mould being densest (and therefore hardest) by reason of having supported the weight of the metal above it when cooling in the mould. [Illustration: Fig. 953.] This brings us to another consideration, inasmuch as supposing the tool edge to be set level with the work centre (as in Figs. 951 and 953), the arc of deflection of the tool point will vary in its direction with relation to the work according to the vertical distance of the top of the tool rest (R in Figs. 953 and 954) from the horizontal centre of the work. Thus the vertical distance between the point A in Fig. 953 and the work centre is less than that between A and the horizontal work centre in Fig. 954, as may be measured by prolonging the dotted lines in both figures until they pass over A, and then measuring the respective vertical distances between A and those dotted lines. It is to be noted that this distance is governed by the vertical distance of the top of the tool rest R from the work centre, but where this distance is required or desired to be reduced a strip of metal may be placed beneath the tool and between it and the slide rest. [Illustration: Fig. 954.] It will now be obvious that to produce work as nearly cylindrical as possible, the tool edge should stand as near to the slide rest as the circumstances will permit, which will hold the tool more firmly and prevent, as far as possible, its deflection or spring from the cut pressure. Both in roughing out and in finishing, this is of great importance, influencing in many cases the depth of cut the tool will carry as well as the cylindrical truth of the work. We may now present some others of the ordinary forms of tools used in the slide rests on external or outside work, bearing in mind, however, that these are merely the principal forms, and that the conditions of practice require frequent changes in their forms, to suit the conditions of access to the work, &c. Fig. 955 represents a diamond point tool much used by eastern tool makers. The sides are ground flat and the point is merely oil-stoned to take off the sharp corner. This tool is used with very fine feeds as, say, 180 work revolutions to an inch of tool traverse, taking very fine cuts, and in sharpening it the top face only is ground; hence as the height of the tool varies greatly before it is worn out, the tool elevating device must have a great range of action. [Illustration: Fig. 955.] In Fig. 956 is shown a side tool for use on wrought iron; it is bent around so that its cutting edge A may be in advance of the side of the steel, and thus permit the cutting edge to pass up into a corner. When it is bent to the left as in the figure, it is termed a right-hand side tool, and per contra when bent to the right it is a left-hand tool. The edge A must form an acute angle to edge B, so that when in a corner the point only will cut, or when the edge A meets a radial face, as in Fig. 957, the cutting edge B will be clear of the work as shown. [Illustration: Fig. 956.] If the angle of A to B is such that both those edges cut at once, the pressure due to such a broad cutting surface would cause the tool to spring or dip into the work, breaking off the tool point and perhaps forcing the work from between the lathe centres. This tool may be fed from right to left on parallel work, or inwards and outwards on radial faces, but it produces the truest work when fed inwards on radial faces, and to the left on parallel work, while it cuts the smoothest in both cases when fed in the opposite direction. [Illustration: Fig. 957.] It is a very desirable tool on small work, since it may be used on both the stem of the work, and on the radial face, which saves the trouble of having to put in a front tool to turn the stem, and a separate tool for the radial face. In cutting down a radial face with this tool, it is best (especially if much metal is to be cut off), if the face of the metal is hard, to carry the cut from the circumference to the centre, as shown in the plan view in Fig. 958, in which _a_ is the cutting edge of the tool, B a collar on a piece of work, _c_ the depth of the cut, and D a hard skin surface. Thus the point of the tool cuts beneath the hard surface, which breaks away without requiring to be actually cut. [Illustration: Fig. 958.] [Illustration: Fig. 959.] Fig. 959 represents a cutting off or parting tool for wrought iron, its feed being directly into the metal, as denoted by the arrow. This tool should be set exactly level with the work centre when it is desired to completely sever the work. When, however, it is used to merely cut a groove, it may be set slightly above the centre. [Illustration: Fig. 960.] [Illustration: Fig. 961.] When the tool is very narrow at _c_, Fig. 960, or long as in Fig. 961, it may be strengthened by being deepened, the bottom B projecting below the level of the tool steel, which will prevent undue spring and the chattering to which this tool is liable. [Illustration: Fig. 962.] [Illustration: Fig. 963.] To enable the sides of the tool to clear the groove it cuts, the width at _c_ should slightly exceed that at D, and the thickness along the top _a_ should slightly exceed that at the bottom B. When the tool is used to cut a wide groove as, say, 3/8-inch wide, in a small lathe, it is necessary to carry down two cuts, making the tool about 1/4 inch wide at _c_, which is a convenient size, affording sufficient strength for ordinary uses. [Illustration: Fig. 964.] [Illustration: Fig. 965.] When used on wrought iron the top face may, with advantage, be given top rake as in Fig. 962, which on account of causing the tool to cut easier, will reduce the spring of the work W in the direction of arrow A. For brass work, however, the top should be ground in an opposite direction, as in Figs. 963 and 964, which will enable it to cut smoother and with less liability to rip into the metal, especially if the tool requires to be held far out from the tool post. To capacitate the tool to cut a groove close up to a shoulder, it should be forged to the shape shown in Fig. 965. As it is very subject to spring, it should not, unless the conditions are such as to give rigidity to both the work and the tool, be set above the work centres. [Illustration: Fig. 966.] When a grooving or parting tool is to be used close up to the lathe dog, its cutting end may be bent at an angle, as in Fig. 966, so that it may be adjusted on the lathe rest, so that the work driver will not strike against the slide rest. [Illustration: Fig. 967.] In Figs. 967, 968, and 969, are represented the facing tool, side tool, or knife tool, as it is promiscuously termed, which is sometimes made thicker at the bottom as in Fig. 969. It is mainly used for squaring up side faces, as upon the ends of work or the sides of heads or collars. A is the cutting edge which may be ground so as to cut at and near the end, for large work in which it is necessary to feed the tool in with the cross slide, or to cut along its full length for small work in which the longitudinal feed is used. To facilitate the grinding, the bottom may be cut away, as at B in Fig. 968. [Illustration: Fig. 968.] [Illustration: Fig. 969.] In some practice the bottom B, Fig. 969, of the tool, is made thicker than the top A, which is, however, unnecessary, unless for heavy cuts, for which the tool would be otherwise unsuitable on account of weakness. For all ordinary facing purposes, it should be made of equal thickness, which will reduce the area to be ground in sharpening the tool. [Illustration: Fig. 970.] [Illustration: Fig. 971.] On small work the edge A A should be ground straight, and set at a right angle to the work, so that it may face off the whole surface at once, but for work of large diameter it should be ground and set as in Figs. 970 and 971, so that it will cut deepest at the end E, enabling it to carry a finishing cut from the circumference to the centre, by feeding it with the cross-feed screw. [Illustration: Fig. 972.] The cutting edge should be level with the centre of the work, the angle of the top face D being about 35 degrees in the direction of the arrow C for wrought iron, and level if used for brass. When this tool is to be used for a face close to the work driver it should be bent at an angle as in Fig. 972, so as to enable the driver to clear the slide rest, and when used for countersunk head bolts, it may be bent at an angle as in Fig. 973, so that when it is once set to give the head the correct degree of taper, it will turn successive heads to the correct taper without requiring each head to be fitted to its place. [Illustration: Fig. 973.] In Fig. 974 is shown the spring tool which is employed to finish smoothly round corners or sweeps, which it will do to better advantage than any other slide rest tool, because it is capable of carrying a larger amount of cutting edge in simultaneous operation. This property is due to the shape of the tool, the bend or curve serving as a spring to enable the tool to bend rather than dig into the work. [Illustration: Fig. 974.] This form of tool is sometimes objected to on the ground that it does not turn true, but this is not the case if the tool is properly formed and placed at the correct height with relation to the work. In the first place the top face should, even on wrought iron, have but very little top rake, and indeed none at all if held far out from the tool post, while for brass, negative top rake may be employed to advantage. The height of the cutting edge B should be level with the top of the tool steel as denoted by the dotted line in the figure, and in no case should it stand above that level. The cutting edge should be placed about level with the horizontal centre of the work, but in no case above it. It is from this error that the tool is frequently condemned, because if placed above, the broad cutting edge causes the tool to spring slightly and dig into the metal, whereas when placed at the middle of the height of the work the spring will not have that effect, as already explained when referring to front tools. Furthermore, the spring of the tool (from inequalities in the texture or from seams in the metal) will be in a line so nearly coincident with the work surface that the latter will be practically true, and from the smoothness and the evenness of the curve this tool will produce a much better work than any other tool, unless indeed the curve be of a very small radius, as, say, about 1/4 inch only, in which case a hand tool such as shown in Fig. 1292 may be employed; spring tools are intended to finish only, and not to rough out the work. [Illustration: Fig. 975.] The curves, as B in Fig. 974 for a round corner and C for a bead, should be carefully and smoothly finished to the required curve and the top face only ground to sharpen the tool, so as to maintain the curve as nearly as possible; but if the curve is a very large one, the tool will require to be a part of the curve only, and must be operated by the slide rest around the curve. For finishing the curves or round corners in cast-iron work the spring tool is especially advantageous, as it will produce a polished clean surface of exquisite finish if used with water, and the cutting speed is exceedingly slow, as about 7 feet per minute. LATHE SLIDE REST TOOLS FOR BRASS WORK. Nearly all the tools used in the slide rest upon iron work may be employed upon brass work, but the top faces should not have rake, that is to say, they should have their top faces lying in the same plane as the bottom plane of the tool steel which rests on the slide rest. For if the top face is too keen it rips rather than cuts the brass, giving it a patchy, mottled appearance. [Illustration: Fig. 976.] Fig. 975 represents a front tool for brass, which is used for carrying cuts along outside work or for facing purposes, corresponding, so far as its use is concerned, to the diamond point or front tool for iron. The top face of this tool must in no case be given rake of any kind, as that would cause it to tear rather than to cut the metal, and also to chatter. The point A should be slightly rounded and the width at B and depth at C must be regulated to suit the depth of cut taken, the rule being that slightness in either of these directions causes the tool to chatter. When held far out from the tool post or under other conditions in which the tool cannot be rigidly held, the top face should be ground away towards the end, thus depressing the point A, after the manner shown with reference to the cutting-off tool for brass in Fig. 963. The manner in which the cuttings come off brass work when a front tool is used, depends upon the hardness of the brass and the speed at which the tool cuts. [Illustration: Fig. 977.] [Illustration: Fig. 978.] In the harder kinds of brass, such as that termed gun metal, composition, or bell metal, the cuttings will fly off the tool in short angular grains, such as indicated in Fig. 976, travelling a yard or two after leaving the tool if a fairly quick cutting speed is used. But if the cutting speed is too slow the cuttings will come off slowly and fly but a few inches. In the softer kinds of brass, such as yellow brass, the cuttings are longer and inclined to form short curls, which will, if cut at a high speed, fly a few inches only after leaving the tool. In Fig. 977 is shown a right-hand side tool for brass work. It is used to carry cuts along short work, and to carry facing cuts at the same time, thus avoiding the necessity to move the position of the tool to enable it to carry a facing cut, as would be necessary if a front tool for brass were used. It is peculiarly adapted, therefore, for brass bolts, or other short work having a head or collar to be faced especially; hence, it may be traversed to its cut in either direction without requiring to be moved in the tool post. It may also be used to advantage for boring purposes. It will be found that this tool will cut smoother and will be less liable to chatter if its top face is ground slightly down towards the point and if it be not forged too slight either in depth or across B. Its clearance on the side is given by forging it to the diamond shape shown in the sectional view. To make the tool a left-handed one it must be bent to the right, the clearance being in any case on the inside of the curve. [Illustration: Fig. 979.] The forms of single-pointed slide rest tools employed to cut [V]-threads in the lathe are shown in Fig. 978, which represents a tool for external, and Fig. 979, which represents one for an internal [V]-thread, the latter being a tool ground to accurate shape and secured in a holder by the set screw S. It is obvious that a Whitworth thread might be cut with a single-pointed tool such as shown in Fig. 980, the corner at B being rounded to cut the rounded tops of the thread. It is more usual, however, to employ a chaser set in the tool point in the same manner as a single-pointed tool, or in a holder fixed in the tool post. When a single-pointed tool is employed to cut a thread, the angles of its sides are not the same as the angle of the thread it produces, which occurs because the tool must have clearance to enable it to cut. In Fig. 981, for example, is a single-pointed tool without any clearance, and, as a result, it cannot enter the work to cut it. In Fig. 982 the tool is shown with clearance, and, as a result, the angle of the cutting edge is not the same angle as the sides of the tool are, because the top face is not at a right angle to the sides of the tool. It is obvious that the angle of the sides of the tool must be taken along the dotted line in Fig. 982. [Illustration: Fig. 980.] It follows then that a tool whose sides are at a given angle will cut a different angle of thread for every variation in the amount of clearance. But whatever the amount of clearance may be, the tool will produce correct results providing that the gauge to which the tool is ground is held level, as in Fig. 983 at A, and not at an angle as at B. The tool, however, must be set at the correct height with relation to the work, and its top surface must point to the work axis to produce correct results. [Illustration: Fig. 981.] [Illustration: Fig. 982.] Suppose, for example, that in Fig. 984 A is a piece of work, its horizontal centre being represented by the dotted line C, and its centre of revolution being at C. Now suppose D is a screw-cutting tool cutting a depth of thread denoted by E. G is another lathe tool having teeth of the same form and angle as D, but lifted above the horizontal centre of the work. The depth of thread cut by G is denoted by F, which is shallower, though it will be seen that the point of G has entered the work to the same depth or distance (of the tool point) as D has. It is obvious, however, that for any fixed height, a tool suitable to cut any required depth or angle can be made, but it would be difficult to gauge when the tool stood at its proper height. [Illustration: Fig. 983.] To facilitate setting the height of the tool, a gauge such as shown in Fig. 985 may be used, the height of the line A from the base equalling the height or distance between the top surface of the cross slides and the axial line of the lathe centres. If the lathe, however, have an elevating slide rest, the rest must be set level before applying the gauge. Or in place of using the gauge, the tool stool or tool holder, as the case may be, may be made of such height that when level in the tool post its top face points to the axis of the lathe centre, the tool being sharpened on the angles and not ground on the top face. [Illustration: Fig. 984.] [Illustration: Fig. 985.] But in the case of a tool holder, or of a chaser holder, the tool may be ground on the top face, and adjusted for height by any suitable means, the top of the holder serving as a guide to set the tool by. [Illustration: Fig. 986.] The line of the cutting edge of the tool must, to obtain correct results, be presented to the work in the same manner as it was presented to the gauge to which its angles were ground, so that if the tool were in position in the tool post, and the gauge were applied, it would point to the axis of the lathe centre, for if this is not the case the thread cut will not be of correct angle or depth. Thus, in Figs. 986 and 987 the tool T would cut threads too shallow, although placed at the correct height, because the cutting edges are at an angle to the radial lines C C. [Illustration: Fig. 987.] It becomes obvious, then, that it is improper to set the height of a screw-cutting tool by means of any tool elevating or setting-device that throws it out of the horizontal position. To enable the correct setting of threading tools, and to avoid having to grind the angles correct to gauge every time the tool requires sharpening, various kinds of tool holders have been designed by means of which the tool may be ground on the top face, and set at correct height and in the proper plane. [Illustration: Fig. 988.] [Illustration: Fig. 989.] To facilitate grinding the tools to a correct angle, the gauge shown in Fig. 988 is employed, the various notches being for the pitches of thread for which they are respectively marked, but, the edge of the gauge being circular, does not afford much guide to the eye in grinding the angles equal from the sides of the body of the tool; hence the form of gauge shown in Fig. 989 is preferable, because the tool can be so ground that the edge of the gauge stands parallel with the side of the tool steel, so that the tool will, when in correct position, point straight to the work axis. To insure correctness in setting the tool, it may then be set with a square S in Fig. 990, held firmly with its back against the side of the tool, which may be adjusted in the tool post until the blade B comes fair with the work. [Illustration: Fig. 990.] Another method of setting the tool is with a gauge as in Fig. 991, which sets it true with the angle independent of whether the angle is true with the side of the tool or not. In Fig. 992 is a form of gauge that will serve to grind the tool by to correct angle, and also to set it in the lathe by the angles, independent of the side of the tool. The same gauge may be used for setting internal threading tools by first facing the work quite true and then applying the gauge as in Fig. 993. [Illustration: Fig. 991.] [Illustration: Fig. 992.] [Illustration: Fig. 993.] By reason of the comparatively sharp points of thread-cutting tools, they are more readily dulled than the rounder pointed ordinary lathe tool, and by reason of their cutting edges extending along a greater length of the work, and therefore causing it to spring or bend more from the strain of the cut, they cannot be employed to take such heavy cuts as ordinary tools. Hence, in all thread cutting, it is necessary to turn the work down to the finished diameter before using the threading tool, so that the thread will be finished when it is cut to the proper depth. To test that depth on a piece of work having a United States standard, or a sharp [V]-thread, a gauge such as shown in Fig. 994 may be used, consisting of a piece of sheet steel about 1/50 inch thick, having a single tooth formed correct for the space of the thread, so that the edge of the gauge will meet the tops of the thread when the space is cut to admit the tooth on the gauge; the most accurate method of producing such a gauge having been described in the remarks upon screw threads. [Illustration: Fig. 994.] If the tool is known to be ground to the correct angle and is set properly, the gauge for depth may be dispensed with by turning the body of the work to correct diameter, and also turning a small part, as a in Fig. 995, down to the correct diameter for the bottom of the thread, so that when the tool point meets A the thread will be cut to correct depth. [Illustration: Fig. 995.] Figs. 996 and 997 represent a method of cutting a round top and bottom, or any other form of thread, by means of a single-pointed circular cutting tool, which is mounted on a holder. On the circumference of the cutter is cut a single thread, and a piece is cut out at E to form a cutting edge. To cut a right-hand thread on the work, a left-hand one must be cut on the cutter, so as to make its thread slant in the proper direction. The tool is sharpened by grinding the top face, and moved on the holding pin to set it to the proper height or in position to enable it to cut. A top view of the tool and holder is shown in figure 997. [Illustration: Fig. 996.] It is obvious that two gaps may be cut in the wheel or cutter so as to provide two cutting edges, one of which may be used for roughing, and the other for finishing cuts. [Illustration: Fig. 997.] In roughing out coarse threads, a single-pointed tool, formed as in Fig. 998, and set considerably above the centre as shown, may be used to great advantage. It will carry a heavy cut and throw off a cutting but very little curved; hence but little power is absorbed in bending the cutting. To preserve the cutting edge, the point of the tool should be slightly rounded. Such a tool, however, requires to be rigidly held, and requires experience to use it to the best advantage. [Illustration: Fig. 998.] An English tool holder for a single-pointed tool for cutting coarse pitch threads, such as square threads, is shown in Fig. 999. The stem of the holder is cylindrical, and is held between two clamping pieces, while the short piece of steel used as a tool (which is thinnest at the bottom, so as to provide for the clearance without grinding it) is clamped in a swiveled post, so that it may be set at the angle sideways required for the particular pitch of thread to be cut, as is shown in the end view. [Illustration: Fig. 999.] [Illustration: Fig. 1000.] [Illustration: Fig. 1001.] The difficulty of adjusting the height of threading tools that are ground on their top faces to sharpen them is obviated in a very satisfactory manner by the tool holder patented by the Pratt and Whitney Company, and represented in Figs. 1000 and 1001. A is the body of the holder, C is the tool clamp, and B the set screw for C; D is a pin fast in A and projecting into C to adjust it square upon A. The threading tool G has a groove H, into which the projection E fits, so that the tool is held accurately in position. F is the screw which adjusts the height of the tool, being threaded into A and partly into G, as is shown at I. The holder once being set in correct position, the threading tool may be removed for grinding, and reset with accuracy. The face K of the holder is made at 30° to the front or leading face of the holder, so that the stem or body of the holder will be at an angle and out of the way of the work driver. [Illustration: Fig. 1002.] If a chaser instead of a single-pointed tool be used to cut a thread, the thread requires to be gauged for its full diameter only, because both the angles of the thread sides and the thread depth are determined by the chaser itself. Chasers are also preferable to a single-pointed tool when the work does not require to be cut to an exact diameter, nor to have a fully developed thread clear up to a shoulder; but when such is the case a single-pointed tool is preferable, because if the leading tooth should happen to run against the shoulder the whole of the teeth dig into the work, and more damage is done to it than with a single-pointed tool. When the thread does not run up to a shoulder, or in cases where the thread may be permitted to run gradually out, and, again, where the thread is upon a part of enlarged diameter, a chaser may have its efficiency increased in two ways, the first of which is shown in Fig. 1002. When the chaser is set and formed as at A in the figure, the leading tooth takes all the cut, and the following tooth will only cut as it is permitted to do so from the wear of the leading bolt. This causes the tooth to wear, but the teeth may be caused to each take a proportion of the cut by chamfering them as at B in the figure, which will relieve the front tooth of a great part of its duty and let the following teeth perform duty, and thus preserve the sharpness of the cutting edges. We are limited in the degree of chamfer that may be given to the teeth, first, because as the cutting edge is broader and the strain of the cut is greater it causes the tool to spring or bend more under the cut pressure; and secondly, because if the tool be given many teeth in order to lengthen the chamfer, then the pitch is altered to a greater extent by reason of the expansion which accompanies the hardening of the chaser. [Illustration: Fig. 1003.] [Illustration: Fig. 1004.] A chaser thus chamfered may be set square in the tool post by placing a scale against the work as at S in Fig. 1003, and setting the bottoms of the chaser teeth fair with the outer edge of the scale as in the figure. The second method of increasing the efficiency of a chaser is to grind the top face at an angle as from A to B in Fig. 1004, and set it so that the last tooth B is at or a little above the work axis D. This causes the last tooth B to stand sufficiently nearer the work axis than the other teeth to enable it to take a light scraping cut, producing a smooth cut, because the duty on the last tooth being light it preserves its cutting edge, and therefore its form. Chasers are often in shops, doing general work, formed in one piece in the same way as an ordinary tool, but it is preferable to use short chasers and secure them in holders. [Illustration: Fig. 1005.] Figs. 1005 and 1006 show a convenient form of holder, the chaser A being accurately fitted into a recess in the holder D, so that it may be set square in the holder without requiring to be adjusted to come fair with the thread grooves after having been ground to resharpen it. The short chasers are held by the clamp B, which has at C a projection fitting into a recess in the holder to cause the clamp to adjust itself fairly. In setting a chaser to correct position in a tool post the points of the teeth may be set to the surface of the work as in Fig. 1007, or if the thread is partly produced and the lathe has a compound slide rest, the tool may be set to the tops of the thread as in Fig. 1008, and then brought into position to meet the thread grooves by operating the slide rest. [Illustration: Fig. 1006.] [Illustration: Fig. 1007.] [Illustration: Fig. 1008.] It is obvious that the height and position of a chaser require to be as accurately set as a single-pointed tool, but it is more difficult to set it because it can only be sharpened by grinding the top face, and this alters the height at each grinding. Thus, suppose that when new its teeth are of correct height, when the bottom face I, Fig. 1009, lies upon the rest R, the face H being in line with the centre B B of the work, then as face H is ground the tool must be lifted to adjust its height. On account, however, of the curve of the teeth it is very difficult to find when the chaser is in the exact proper position, which in an ordinary chaser will be when it has just sufficient clearance to enable it to cut, as is explained with reference to cutting up chasers and using them by hand. [Illustration: Fig. 1009.] To obviate these difficulties, an excellent form of chaser holder is shown in Figs. 1010 and 1011. Its top face C being made of such a height that when the holder rests on the surface of the slide rest and is in the tool box, C will stand horizontally level with the horizontal centre of the work, as denoted by the horizontal line D E; then the tool proper may have long teeth as denoted by A, and the surface of the teeth may always be brought up level with the top surface of the tool holder as tested with a straight-edge. This is a ready and accurate mode of adjustment. A top view of the tool holder is shown in Fig. 1011, in which A is the tool holder, B the threading tool, with a clamp to hold B, and a screw to tighten the clamp. [Illustration: Fig. 1010.] It may now be pointed out that a common sharp [V]-chaser may be used to cut a United States standard thread by simply grinding off the necessary flats at the points of the teeth, because when the chaser has entered the work to the proper depth it will leave the necessary flat places at the top of the thread, as is shown in Fig. 1012. In cutting internal, inside, or female threads (these terms being synonymous) the diameter of the bore or hole requires to be made of the diameter of the male thread _at the root_. [Illustration: Fig. 1011.] Since, however, it is impracticable to measure male threads at the root, it becomes a problem as to the proper size of hole to bore for any given diameter and pitch of thread. This, however, may be done by the following rules:-- To find the diameter at the roots or bottom of the thread of United States standard threads: Rule.--Diameter - (1.299 ÷ pitch) = diameter at root. Example.--What is the diameter at the root of a United States standard thread measuring an inch in diameter at the top of the thread and having an 8 pitch? Here 1.299 ÷ 8 = .162375. / 1.000000 \ Then 1 - .162375 | .162375 | = .8376. | -------- | \ .837635 / For the sharp [V]-thread the following rule is employed: Rule.--Diameter - (1.73205 ÷ pitch) = diameter at root. Example.--What is the diameter at the root of a sharp [V]-thread of 8 pitch, and measuring 1 inch diameter at the top of the thread? Here 1.73205 ÷ 8 = .21650. / 1.0000 \ Then 1 - .2165 | .2165 | = .7835. | ------ | \ .7835 / For cutting square threads the class of tool shown in Fig. 1013 is employed, being made wider at the cutting point C than at B or at D, so that the cutting may be done by the edge C, and the sides _a_ may clear, which is necessary to reduce the length of cutting edge and prevent an undue pressure of cut from springing the work. [Illustration: Fig. 1012.] The sides of the tool from _a_ to B must be inclined to the body of the tool steel, as shown in Fig. 1014, the degree of the inclination depending upon the pitch of thread to be cut. It may be determined, however, by the means shown in Fig. 1015. [Illustration: Fig. 1013.] [Illustration: Fig. 1014.] [Illustration: Fig. 1015.] Draw the line A, and at a right angle to it line B, whose length must equal the circumference of the thread to be cut and measured at its root. On the line A set off from B the pitch of thread to be cut as at C, then draw the diagonal D, which will represent the angle of the bottom of the thread to the work axis, and the angle of the tool sides must be sufficiently greater to give the necessary clearance. The width of the point C of the tool should be made sufficiently less than the width of the thread groove to permit of the sides of the thread being pinched (after the thread is cut to depth) with a tool such as was shown in Fig. 968. [Illustration: Fig. 1016.] For coarser pitches the thread is cut as shown in Fig. 1016. The tool is made one-half the width of the thread groove, and a groove, _a_, _a_, _a_, is cut on the work. The tool is then moved laterally and a second cut as at B B is taken, this second cut being shown in the engraving to have progressed as far as C only for clearness of illustration. When the thread has in this manner been cut to its proper depth, the side tools are introduced to finish the sides of the thread. If the thread is a shallow one each side may be finished at one cut by a side tool ground and set very true; but in the case of a deep one the tool may be made to cut at and wear its end only, and after taking a cut, the tool fed in and another cut taken, and so on until, having begun at the top of the thread, the tool operated or fed, after each traverse, by the cross feed, finally reaches the bottom of the thread. If a very fine or small amount of cut is taken, both sides of the thread may in this way be finished together, the tool being made to the exact proper width. [Illustration: Fig. 1017.] [Illustration: Fig. 1018.] When used on wrought iron the tool is sometimes given top rake, which greatly facilitates the operation, as the tool will then take a heavier as well as a cleaner cut. [Illustration: Fig. 1019.] After the first thread cut is taken along the work, it is usual to remove it from the lathe and drill, at the point where it is desired that the thread shall terminate, a hole equal in diameter to the width of the thread groove, and in depth to the depth of the thread. This affords relief to the cutting tool at the end of the cut, enables the thread to end abruptly, and leaves a neat finish. [Illustration: Fig. 1020.] On account of the broad cutting edge on a screw-cutting tool, the lathe is always run at a slower speed than it would be on the same diameter of work using an ordinary turning tool. After the tool is set to just clear the diameter of the work it is moved (for a right-hand thread) past the end of the work at the dead centre, and a cut is put on by operating the cross-feed screw. The feed nut is then engaged with the feed screw and the tool takes its cut as far along the work as the thread is to be, when the tool is rapidly withdrawn from the work and the lathe carriage traversed back again, ready to take another cut. If, however, the thread to be cut runs close up to a shoulder, head, or collar, the lathe may be run slower as the tool approaches that shoulder by operating the belt shipper and moving the overhead belt partly off the tight pulley and on to the loose one, or the lathe may be stopped when the tool is near the shoulder and the belt pulled by hand. An excellent method of finishing square threads after having cut them in the lathe to very nearly the finished dimensions is with an adjustable die in a suitable stock, such as in Figs. 1017 and 1018, in which S is a stock having handle H, and containing a die D, secured by a cap C, pivoted at P. To adjust the size of the die, two screws, _a_ and _b_, are used, _a_ passing through the top half of the die and threading into the half below the split, while _b_ threads into the lower half and abuts against the face of the split in the die, so that, by adjusting these two screws, the wear may be taken up and the size maintained standard. This device is used to take a very light finishing cut only, and is found to answer very well, because it obviates the necessity of fine measurement in finishing the thread. The die D is seated in a recess at the top and at the bottom so as to prevent it moving sideways and coming out. LATHE TOOL HOLDERS FOR OUTSIDE TOOLS.--When a lathe cutting tool is made from a rectangular bar of steel it requires to be forged to bring it to the required shape at the cutting end, and to avoid this labor, and at the same time attain some other advantages which will be referred to presently, various forms of tool holders are employed. These holders fasten in the tool post, or tool clamp, and carry short tools, which, from their shapes and the manner in which they are presented to the work, require no forging, and maintain their shapes while requiring a minimum of grinding. Fig. 1019 represents a side view of Woodbridge's tool holder at work in the lathe, and Fig. 1020 is a view of the same set at an angle to the tool rest. Fig. 1021 is an end view of the tool and holder removed from the lathe. The tool seat A is at an angle of about 4 degrees to the base of holder (a greater degree being shown in the cut for clearness of illustration), so that the side J of the tool will stand at an angle and have clearance without requiring such clearance to be produced by grinding. The seat B of the cap C upon the tool is curved, so that the cap will bind the middle of the tool and escape the edges, besides binding the tool fair upon its seat A. The top face is formed at the angle necessary for free and clean cutting, and the tools are, when the cutting edge is provided at one end only, hardened for half their length. The holder, and therefore the tool, may obviously be swung at any chosen angle of the work or to suit the requirements. [Illustration: Fig. 1021.] [Illustration: Fig. 1022.] [Illustration: Fig. 1023.] Fig. 1022 shows a right and left-hand diamond-point tool in position in the holder with the cap removed, the cutting edge being at G, the angle of the top face being from F to E. The tool, it will be observed from the dotted line, is supported close up to its cutting corner. [Illustration: Fig. 1024.] Fig. 1023 shows a right and left-hand side tool in position, the dotted line showing that it is supported as close to the cutting edge D as the nature of facing work will permit. When left-hand tools are used the holder is turned end for end, so as to support the tools in the same manner as for right-hand ones, and for this purpose it is that the holder is beveled off at each end. By grinding both ends of one tool, however, to the necessary shape and angle, one tool may be made to serve for both right and left, the tool holder being simply reversed end for end in the tool post. There are, however, furnished with each holder a right and left-hand diamond point and a right and left-hand side tool, each being hardened for half its full length. It is obvious, however, that there is no front rake to the tool, and that it therefore derives its keenness from the amount of side rake, which may be regulated to suit the conditions. When tool holders of this class are employed, the end face only of the tool requires grinding to resharpen the cutting edges; hence the area of metal requiring to be ground is much less than that on forged tools, and therefore the grinding occupies less time; and if the workman grinds the tools, he is enabled to run more lathes and not keep them idle so long while grinding the tool. Or if the tools are kept ground in stock (about 200 of the tools or cutters serving to run 24 lathes a week) the workman has but to slip in a new tool as the old one becomes dull, no adjustment for height being necessary as in the forged tool. When the tool requires to be set to an exact position, as in the case of screw cutting, it is desirable that the tool holder be so constructed that the tool may be removed therefrom and replaced without disturbing the position of the tool holder in the tool post or tool clamp; and means must therefore be provided for securing the tool to the holder independently of the tool post or clamp screw. Fig. 1024 represents a tool holder possessing these features: H is the holder provided with a clamp C, secured by a screw B, T representing the tool, which is in this case a chaser, having teeth down the full length of its front face; K is a key or feather fast in the holder H, and fitting into a groove provided in the side of the tool. The vertical angle of this feather obviously determines the angle of clearance at which the tool shall stand to the work. The Pratt and Whitney Company, who are the manufacturers of this holder, make this angle of clearance 15 degrees. The height of the tool in the holder is adjusted by the screw S, which has journal bearing in the holder, and threads to the end edge of the tool. Now it is obvious that the holder H, once being set to its proper position in the tool post, the tool T may be removed from and replaced in the exact same position, both in the holder and with reference to the work. In Fig. 1025, for example, is a top view of the holder with a single-pointed threading tool T in place. W represents a piece of work supposed to be in the lathe, and G a tool-setting gauge; and it is obvious that, if the holder is not moved, the tool T may be removed, ground up, and replaced with the assurance that it will stand in the exact same position as before, producing the exact same effect upon the work, providing that the height is maintained equal, and the tool is not altered in shape by the grinding. To maintain the height equal, all that is necessary is to have the upper face (H, Fig. 1024) of the holder horizontally level and in line with the line of centres of the lathe, and to set the top face of the tool level with that of the holder. In sharpening the tool the top face only is ground; hence the angles are not altered. Fig. 1026 represents the holder with a tool in position to true up a lathe centre, the angle of the tool holder to the line of centres being the same as in Fig. 1025; and Fig. 1027 represents various forms of tools for curves. All these serve to illustrate the advantages of such a tool holder. [Illustration: Fig. 1025.] If, for example, a piece of work requires the use of two or more such tools, and the holder is once set, the tools may be removed and interchanged with a certainty that each one put into place will stand at the exact angle and position required, not only with relation to the work, but also in relation to the other tools that have preceded it. Each hollow or round will not only be correct in its sweep, but will also stand correct in relation to the other sweeps and curves, no matter how often the tools may be changed. Inasmuch as the tool is ground at the top only for the purpose of resharpening, it maintains a correct shape until worn out. [Illustration: Fig. 1026.] The pin shown at _f_ in Fig. 1024 is fast in the holder, and fits loosely in clamp C to prevent it from swinging around on B when B is loosened. When the tool requires to preserve its exact shape it may also be made circular with the required form for the cutting edge formed round the perimeter. Thus Figs. 1028 and 1029, which are extracted from _The American Machinist_, represent tool holders with circular cutting tools. [Illustration: Fig. 1027.] The holder A fits the lathe tool post, carrying the cutting tool B, which is bolted to the holder and has at F a piece cut out to form the cutting edge. To facilitate the grinding, holes are drilled at intervals through B. A plan view of this tool and holder is shown at C, the shape of the cutting edge being shown at D. The cutting edge is shown in the side view to be level with the centre of the tool holder height, but it may be raised to the level of the top of the tool steel by raising the hole to receive the bolt that fastens the cutter, as is shown at E; or the cutter may be mounted on top of the holder as shown at H, having a stem passing down through the holder, and capable of being secured by the taper pin I. A plan view of this arrangement is shown at J. [Illustration: Fig. 1028.] [Illustration: Fig. 1029.] [Illustration: Fig. 1030.] [Illustration: Fig. 1031.] Another form of circular cutter is shown in Fig. 1030. It consists of a disk or cutter secured to a holder fitted to the tool post, the cutter edge being formed by a gap in the disk, as shown in the figure, which represents a cutter for a simple bead or round corner. The front end of the holder has a face A, whose height is level with the line of lathe centre when the holder is set level in the tool post. Hence the top face of the cutting edge may be known to be set level with the line of centres when it is fair with the face A of the holder. The bottom clearance is given by the circular shape of the cutter, while side clearance may be given by inclining the face B of the holder (against which the face of the cutter is bolted) to the necessary angle from a vertical line. The face C is ground up to resharpen the cutting edge, and may be reground until the circumference of the wheel is used up. Figs. 1031, 1032, 1033, and 1034 represent lathe tool holders by Messrs. Bental Brothers, of Fullbridge Works, Maldon, England. The holder consists of a bar A, having at the front end a hub H, containing a bush in two halves, through which the tool T passes; this tool consisting of a piece of [V]-shaped steel. A set screw on top of the hub clamps the two half-bushes together, and these, as their faces do not meet, grip the tool. [Illustration: Fig. 1032.] [Illustration: Fig. 1033.] [Illustration: Fig. 1034.] The advantage possessed by this form of holder is that the top face of the tool may be given any desired degree of side rake or angle required by the nature of the work by simply revolving the bushes in the hub of the holder. Thus, in Fig. 1034 the top face of the tool stands level, as would be required for brass work; in Fig. 1032 the tool is canted over, giving its top face angle a rake in the direction necessary when cutting wrought iron and feeding toward the dead centre; and in Fig. 1033 the tool is in position for carrying a cut on wrought iron, the feed being toward the live centre of the lathe. This capacity to govern the angle of the top face of the tool is a great advantage, and one not possessed by ordinary tool holders, especially since it does not sensibly alter the height of the tool point with relation to the work. Again, the [V]-shape of the tool steel causes the bushes to grip and support the tool sideways, and, by reducing the area of tool surface requiring to be ground, facilitates the tool grinding to that extent. Altogether, this is an exceedingly handy device. It is obvious, however, that it cannot be moved from side to side of the tool rest unless a right and left-hand tool holder be used; that is to say, there must be two holders having the hub on the opposite side of the body A. [Illustration: Fig. 1035.] [Illustration: Fig. 1036.] Figs. 1035, 1036, 1037, and 1038 represent tool holders in which the tools consist of short pieces of steel held end-wise and at a given angle, so that the amount of clearance is constant. The holders Figs. 1035 and 1036 are split, and the tool is secured by the screw shown. Fig. 1037 represents a tool holder in which the tool is held by a clamp, whose stem passes through the body of the holder so as to bring the fastening nut out at the end, where it is more convenient to get at than are the screw heads in Figs. 1035 and 1036. It is obvious, however, that such a holder is weak and unsuitable for any tools save those used for very light duty indeed, while all this class of holders is open to the objection that the side of the holder prevents the tool from passing up into a corner, hence the cut cannot be carried up to a shoulder on the work. This may, however, be accomplished by bending the end of the holder round; but in this case two holders, a right and a left, will be necessary. Fig. 1038 represents a form of tool holder of this kind in which the tool may be set for height by a set screw beneath it. [Illustration: Fig. 1037.] Fig. 1039 represents a tool holder and work-steadying device combined. The holder is held in the lathe tool rest in the usual manner, and affords slideway to a slide operated by the handle shown at the right-hand end. [Illustration: Fig. 1038.] The tool is carried at the other end of this slide, there being shown in the figure a cutting-off tool in position. At the end of the holder is a hub and three adjusting screws whose ends steady the work, and which are locked in their adjusted position by the chuck nuts shown. [Illustration: Fig. 1039.] THE POWER REQUIRED TO DRIVE CUTTING TOOLS.--From experiments made by Dr. Hartig, he concluded that by multiplying the weight of the metal cuttings removed per hour by certain decimal figures (or constants) the horse-power required to cut off that quantity of metal might be obtained. These decimal constants are as follows: Lbs. of metal cut off per hour, cast iron × .0314 = horse-power required to drive the lathe. " " " wrought iron × .0327 = " " " " steel × .4470 = " FOR PLANING TOOLS. Lbs. of steel cut off per hour × .1120 = horse-power required to drive planer. " wrought iron " × .0520 = " " " gun metal " × .0127 = " " CHAPTER XI.--DRILLING AND BORING IN THE LATHE. For drilling in the lathe, the twist drill is employed not only on account of its capacity to drill true, straight, and smooth holes, but also because its flutes afford free egress to the cuttings and obviate the necessity of frequently withdrawing the drill to clear the hole of the cuttings. In the smaller sizes of twist drill, the stem or shank is made parallel, as in Fig. 1040, while in the larger sizes it is made taper, as in Fig. 1041, for reasons which will appear hereafter. [Illustration: Fig. 1040.] The taper shanks of twist drills are given a standard degree of taper of 5/8 inch per foot of length, which is termed the Morse taper. A former standard, termed the American standard, is still used to a limited extent, its degree of taper being 9/16 inch per foot. [Illustration: Fig. 1041.] Parallel shanked twist drills are driven by chucks, while taper, shanked ones, are driven by sockets, such as in Fig. 1042, from C to D, fitting into the lathe centre hole, while the bore at the other end is the Morse standard taper, to receive the drills E E, which have a projection such as shown at A, which by fitting into a slot that meets the end of the taper holes in the socket, lock the drill and prevent its revolving in the socket, while affording a means of forcing the drill out by inserting a key K, as shown in the figure.[14] [14] See also Shanks and Sockets for Drills used in the Drilling Machine. [Illustration: Fig. 1042.] Each socket takes a certain number of different sized drills, the shanks of the smaller drills being in some cases longer than the drill body. Number 1 socket receives drills from 1/8 to 19/32 inch inclusive. " 2 " " 5/8 " 29/32 " " " 3 " " 15/16 " 1-1/4 " " " 4 " " 1-9/32 " 2 " " " 5 " " 2-1/32 " 2-1/2 " " These sockets are manufactured ready to receive the drills, but are left unturned at the shank end so that they may be fitted to the particular lathe or machine in which they are to be used, no standard size or degree of taper having as yet been adopted. A twist drill possesses three cutting edges marked A, B, C respectively in Fig. 1043, and of these C is the least effective, because it cannot be made as keen as is desirable for rapid and clean cutting, and therefore necessitates that the drill be given an unusually fine rate of feed as compared with other cutting tools. The _land_ of the drill--or, in other words, the circumference between the flutes--is backed off to give clearance, as is shown in Fig. 1044, a true circle being marked with a dotted line, and the drill being of full diameter from A to B only. The object of this clearance is to prevent the drill from seizing or grinding against the walls of the hole, as it would otherwise be apt to do when the outer corner wore off, as is likely to be the case. [Illustration: Fig. 1043.] [Illustration: Fig. 1044.] Twist drills having three and more flutes have been devised and made, but the increased cost and the weakness induced by the extra flutes have been found to more than counterbalance the gain due to an increase in the number of cutting edges, Further, the increase in the number of flutes renders the grinding of the drill a more delicate and complicated operation. The keenness and durability of the cutting edge of a twist drill are governed by the amount of clearance given by the grinding to the cutting edge, by the angle of one cutting edge to the other, and by the degree of twist of the flute. Beginning with the angle of the front face, we shall find that it varies at every point in the diameter of the drill, being greatest at the outer corner and least at the centre of the drill, whatever degree of spirality the groove or flute may possess. In Fig. 1045, for example, we may consider the angle at the corner C and at the point F in the length of the cutting edge. The angle or front rake of the corner C is obviously that of the outer edge of the spiral C D, while that of the point F is denoted by the line F _f_, more nearly parallel to the drill axis, and it is seen that the front rake increases in proportion as the corner C is approached, and diminishes as the drill centre or point is approached. [Illustration: Fig. 1045.] [Illustration: Fig. 1046.] [Illustration: Fig. 1047.] It follows, then, that if the angle of the bottom face of the drill be the same from the centre to the corner of the drill, and we consider the cutting edge simply as a wedge and independent of its angle presentation to the work, we find that it has a varying degree of acuteness at every point in its length. This may be seen from Fig. 1046, in which the end face is ground at a constant angle from end to end to the centre line of the drill, and it is seen that the angle A represents the wedge at point C and the angle B the wedge at the point F in the length of the cutting edge, and it follows that the wedge becomes less acute as the centre of the drill is approached from the point C. If, then, we give to the end face a degree of clearance best suited for the corner C, it will be an improper one for the cutting edge near the drill point; or if we adopt an angle suitable for the point, it will be an improper one for the corner C. This corner performs the most cutting duty, because its path of revolution is the longest, or rather of the greatest circumference, and it operates at the highest rate of cutting speed for the same reason, hence it naturally wears and gets dull the quickest. As this wear proceeds the circumferential surface near this corner grinds against the walls of the hole, causing the drill to heat and finally to cease cutting altogether. For these reasons it is desirable that the angle of the end face, or the angle of clearance, be made that most suitable to obtain endurance at this corner. It may be pointed out, however, that the angle of one cutting edge to the other, or, what is the same thing, its angle to the centre line of the drill, influences the keenness of this corner. In Fig. 1045, for example, each edge is at an angle of 60° to the drill axis, this being the angle given to drills by the manufacturers as most suitable for general use. In Fig. 1047, the angle is 45°, and it will be clearly seen that the corner C is much less acute; an angle of 45° is suitable for brass work or for any work in which the holes have been cored out and the drill is to be used to enlarge them. [Illustration: Fig. 1048.] Referring again to the angle of clearance of the end faces, it can be shown that in the usual manner of grinding twist drills the conditions compel the amount of clearance to be made suitable for the point of the drill, and therefore unsuitable for the corner C, giving to it too much clearance in order to obtain sufficient clearance for the remainder of the cutting edge. Suppose, for example, that we have in Fig. 1048 a spiral representing the path of corner C during one revolution, the rate of feed being shown magnified by the distance P, and the spiral will represent the inclination of that part of the bottom of the hole that is cut by corner C, and the angle of the end face of the drill to the drill axis will be angle R. The actual clearance will be represented by the angle between the end face S of the drill and the spiral beneath it, as denoted by T. But if we take the path of the point F, Fig. 1045, during the same revolution, which is represented by the spiral in Fig. 1049, we find that, in order to clear the end of the hole, it must have more angle to the centre line of the drill, as is clearly shown, in order to have the clearance necessary to enable the point F to cut, because of the increased spiral. It follows that, if the same degree of clearance is given throughout the full length of the cutting edge, it must be made suitable for the point of the drill, and will therefore be excessive for the corner C. This fault is inseparable from the method of grinding drills in ordinary drill-grinding machines, which is shown in Fig. 1050, the line A A representing the axis of the motion given to the drill in these machines. It is obvious that the line A A being parallel to the face of the emery-wheel, the angle of clearance is made equal throughout the whole length of the cutting edge. This is, perhaps, made more clear in Fig. 1051, in which we have supposed the drill to take a full revolution upon the axis A A, and as a result it would be ground to the cylinder represented by the dotted lines. We may, however, place the axis on which the drill is moved to grind it at an angle to the emery-wheel face, as at B, Fig. 1052, and by this means we shall obtain two important results: (1) The angle of B may be made such that the clearance will be the same to the actual surface it cuts at every point in the length of the cutting edge, making every point in that length equally keen and equally strong, the clearance being such as it is determined is the most desirable. (2) The clearance may be made to increase as the heels of each end face are approached from the cutting edge. This is an advantage, inasmuch as it affords freer access to the oil or other lubricating or cooling material. If we were to prolong the point of the drill sufficiently, and give it a complete revolution on the axis B, we should grind it to a cone, as shown by the dotted lines in Fig. 1052. [Illustration: Fig. 1049.] [Illustration: Fig. 1050.] [Illustration: Fig. 1051.] [Illustration: Fig. 1052.] [Illustration: Fig. 1053. Top View.] [Illustration: Fig. 1054. Sectional View.] In Fig. 1053 we have a top, and in Fig. 1054 a sectional, view of a conical recess cut by a drill, with a cylinder R lying in the same. P represents in both views the outer arc or circle which would be described by the outer corner, Fig. 1045, of the drill, and Q the path or arc described or moved through by the point at F, Fig. 1045, of the drill. At V and W are sectional views of the cylinder R, showing that the clearance is greater at V than at W. The cylinder obviously represents the end of a drill as usually ground. In Figs. 1055 and 1056 we have two views of a cone lying in a recess cut by a drill, the arcs and circles P and Q corresponding to those shown in Fig. 1055, and it is seen that in this case the amount of clearance between V and P and between W and Q are equal, V representing a cross-section of the cone at its largest end, and W a cross-section at the point where the cone meets the circle Q. It follows, therefore, that drills ground upon this principle may be given an equal degree of clearance throughout the full length of each cutting edge, or may have the clearance increase or diminished towards the point at will, according to the angle of the line B in Fig. 1052. In order that the greatest possible amount of duty may be obtained from a twist drill, it is essential that it be ground perfectly true, so that the point of the drill shall be central to the drill and in line with the axis on which it revolves. The cutting edges must be of exactly equal length and at an equal degree of angle from the drill axis. To obtain truth in these respects it is necessary to grind the drill in a grinding machine, as the eye will not form a sufficiently accurate guide if a maximum of duty is to be obtained. The cutting speeds and rates of feed recommended by the Morse Twist Drill and Machine Company are given in the following table. [Illustration: Fig. 1055. Top View.] [Illustration: Fig. 1056. Sectional View.] The following table shows the revolutions per minute for drills from 1/16 in. to 2 in. diameter, as usually applied:-- +----------+------+------+------++----------+------+------+------+ | Diameter |Speed |Speed |Speed || Diameter |Speed | Speed|Speed | |of Drills.| for | for | for ||of Drills.| for | for | for | | |Steel.|Iron. |Brass.|| |Steel.| Iron.|Brass.| +----------+------+------+------++----------+------+------+------+ | inch. | | | || inch. | | | | | 1/16 | 940 | 1280 | 1560 || 1-1/16 | 54 | 75 | 95 | | 1/8 | 460 | 660 | 785 || 1-1/8 | 52 | 70 | 90 | | 3/16 | 310 | 420 | 540 || 1-3/16 | 49 | 66 | 85 | | 1/4 | 230 | 320 | 400 || 1-1/4 | 46 | 62 | 80 | | 5/16 | 190 | 260 | 320 || 1-5/16 | 44 | 60 | 75 | | 3/8 | 150 | 220 | 260 || 1-3/8 | 42 | 58 | 72 | | 7/16 | 130 | 185 | 230 || 1-7/16 | 40 | 56 | 69 | | 1/2 | 115 | 160 | 200 || 1-1/2 | 39 | 54 | 66 | | 9/16 | 100 | 140 | 180 || 1-9/16 | 37 | 51 | 63 | | 5/8 | 95 | 130 | 160 || 1-5/8 | 36 | 49 | 60 | | 11/16 | 85 | 115 | 145 || 1-11/16 | 34 | 47 | 58 | | 3/4 | 75 | 105 | 130 || 1-3/4 | 33 | 45 | 56 | | 13/16 | 70 | 100 | 120 || 1-13/16 | 32 | 43 | 54 | | 7/8 | 65 | 90 | 115 || 1-7/8 | 31 | 41 | 52 | | 15/16 | 62 | 85 | 110 || 1-15/16 | 30 | 40 | 51 | | 1 | 58 | 80 | 100 || 2 | 29 | 39 | 49 | +----------+------+------+------++----------+------+------+------+ To drill one inch in soft cast iron will usually require: For 1/4 in. drill, 125 revolutions; for 1/2 in. drill, 120 revolutions; for 3/4 in. drill, 100 revolutions; for 1 in. drill, 95 revolutions. The rates of feed for twist drills are thus given by the same Company:-- Diameter of Revolutions per inch drill. depth of hole. 1/16 inch 125 1/4 " " 3/8 " 120 to 140 1/2 " " " 3/4 " 1 inch feed per minute 1 " " " " " 1-1/2 " " " " " Taking an inch drill as an example, we find from this table that the rate of feed is for iron 1/100th inch per drill revolution, and as the drill has two cutting edges it is obvious that the rate of feed for each edge is 1/200th inch per revolution. But it can be shown that this will only be the case when the drill is ground perfectly true; or, in other words, when the drill is so ground that each edge will take a separate cut, or so that one edge only will cut, and that in either case the rate of feed will be diminished one-half. In Fig. 1057, for example, is shown a twist drill in which one cutting edge (_e_) is ground longer than the other, and the effect this would produce is as follows. First, suppose the drill to be fed automatically, the rate of feed being 1/100th inch, and the whole of this feed would fall on cutting edge _e_, and, being double what it should be, would in the first place cause the corner _c_ to dull very rapidly, and in the second place be liable to cause the drill to break when _c_ became dull. [Illustration: Fig. 1057.] [Illustration: Fig. 1058.] In the second place the drill would make a hole of larger diameter than itself, because the point of the drill will naturally be forced by the feed to be the axis or centre of cutting edge revolution, which would therefore be on the line _b_ _b_. This would cause the diameter of hole drilled to be determined by the radius of the cutting edge _e_ rather than by the diameter of the drill. Again, the side of the drill in line with corner _c_ would bind against the side of the hole, tending to grind away the clearance at the corner _c_, which, it has been shown, it is of the utmost importance to keep sharp. But assuming 1/200th inch to be the proper feed for each cutting edge, and the most it can carry without involving excessive grinding, then the duty of the drill can only be one-half what it would be were both cutting edges in action. In Fig. 1058 is shown a twist drill in which one cutting edge is ground longer than the other, and the two cutting edges are not at the same angle to the axis _a_ _a_ of the drill. Here we find that the axis of drill rotation will be on the line _b_ from the point of the drill as before, but both cutting edges will perform some duty. Thus edge _e_ will drill a hole which the outer end of _f_ will enlarge as shown. Thus the diameter of hole drilled will be determined by the radius of corner _c_, from the axis of drill revolution, and will still be larger than the drill. A drill thus ground would drill a more true and round hole than one ground as in Fig. 1057, because as both cutting edges perform duty the drill would be steadied. [Illustration: Fig. 1059.] The rate of feed, however, would require to be governed by that length of cutting edge on _f_ that acts to enlarge the hole made by _e_, and therefore would be but one-half what would be practicable if the drill were ground true. Furthermore, the corner _c_ would rapidly dull because of its performing an undue amount of duty, or in other words, because it performs double duty, since it is not assisted by the other corner as it should be. In both these examples the drill if rigidly held would be sprung or bent to the amount denoted by the distance between the line _a_ _a_, representing the true axis of the drill, and line _b_ _b_, representing the line on which the drill point being ground and one-sided compels the drill to revolve; hence one side of the drill would continuously rub against the walls of the hole the drill produced, acting, as before observed, to grind away the clearance that was shown in figure and also to dull corner _c_. Fig. 1059 shows a case in which the point of the drill is central to the drill axis _d_ _d_, but the two cutting edges are not at the same angle. As a result all the duty falls on one cutting edge, and the hole drilled will still be larger in diameter than the drill is, because there is a tendency for the cutting edge _e_ to push or crowd the drill over to the opposite side of the hole. It will be obvious from these considerations that the more correctly the drill is ground, the longer it will last without regrinding, the greater its amount of feed may be to take an equal depth of cut, and the nearer the diameter of the hole drilled to that of the drill--the most correct results being obtained when the drill will closely fit into the hole it has drilled and will not fall through of its own gravity, a result it is somewhat difficult to attain. Professor John E. Sweet advocates grinding twist drills as in Fig. 1060 (which is from _The American Machinist_), the object being to have a keener cutting edge at the extreme point of the drill. In a paper on cutting tools read before the British Institution of Mechanical Engineers the following examples of the efficiency of the twist drill are given-- Referring to a 1/2 inch twist drill, it is said: "The time occupied from the starting of each hole in a hammered scrap-iron bar till the drill pierced through it varied from 1 minute 20 seconds to 1-1/2 minutes. The holes drilled were perfectly straight. The speed at which the drill was cutting was nearly 20 feet per minute in its periphery, and the feed was 100 revolutions per inch of depth drilled. The drill was lubricated with soap and water, and went clean through the 2-3/4 inches without being withdrawn, and after it had drilled each hole it felt quite cool to the hand, its temperature being about 75°. It is found that 120 to 130 such holes can be drilled before it is advisable to resharpen the twist drill. This ought to be done immediately the drill exhibits the slightest sign of distress. If carefully examined after this number of holes has been drilled, the prominent cutting parts of the lips which have removed the metal will be found very slightly blunted or rounded to the extent of about 1/100th inch, and on this length being carefully ground by the machine off the end of the twist drill, the lips are brought up to perfectly sharp cutting edges again. "The same sized holes, 1/2 inch diameter and 2-3/4 inches deep, have been drilled through the same hammered scrap-iron at the extraordinary speed of 2-3/4 inches deep in 1 minute and 5 seconds, the number of revolutions per inch being 75. An average number of 70 holes can be drilled in this case before the drill requires resharpening. The writer considers this test to be rather too severe, and prefers the former speed. "In London, upward of 3000 holes were drilled 5/8 inch diameter and 3/8 inch deep through steel bars by one drill without regrinding it. The cutting speed was in this instance too great for cutting steel, being from 18 to 20 feet per minute, and the result is extraordinary. Many thousands of holes were drilled 1/8 inch diameter, through cast iron 7/16ths inch deep with straight-shank twist drills gripped by an eccentric chuck in the end of the spindle of a quick-speed drilling machine. The time occupied for each hole was from 9 to 10 seconds only. Again, 1/4-inch holes have been drilled through wrought copper 1-3/8 inches thick at the speed of one hole in 10 seconds. With special twist drills, made for piercing hard Bessemer steel, rail holes, 13/16ths inch deep and 29/32nds inch diameter, have been drilled at the rate of one hole in 1 minute and 20 seconds in an ordinary drilling machine. Had the machine been stiffer and more powerful, better results could have been obtained. A similar twist drill, 29/32nds inch in diameter, drilled a hard steel rail 13/16ths inch deep in 1 minute, and another in 1 minute 10 seconds. Another drill, 5/8 inch diameter, drilled 3/4 inch deep in 38 seconds, the cutting speed being 22 feet per minute. This speed of cutting rather distressed the drill; a speed of 16 feet per minute would have been better. The steel rail was specially selected as being one of the hardest of the lot." [Illustration: Fig. 1060.] Drills ground by hand may be tested for angle by a protractor, as in Fig. 1061, and for equal length of cutting edge by resting them upon a flat surface, as B in Fig. 1062, and applying a scale as at S in the figure. In the case of very small drills, it is difficult to apply either the protractor or the scale, as well as to determine the amount of clearance on the end face. This latter, however, may be known from the appearance of the cutting edge at the point A in Fig. 1063, for if the line A is at a right angle to E, there is no clearance, and as clearance is given this line inclines as shown at B in the figure, the inclination increasing with increased clearance, as is shown at C. When this part of the edge inclines in the opposite direction, as at D in the figure, the curved edges _e_ _f_ stand the highest, and the drill cannot cut. The circumferential surface of a drill should never be ground, nor should the front face or straight side of the flute be ground unless under unusual conditions, such as when it is essential, as in drilling very thin sheet metal, to somewhat flatten the corner (C in Fig. 1062), in order to reduce its tendency to run forward, in which case care must be taken not to grind the front face sufficiently to reduce the full diameter. In Fig. 1064, for example, that part of the circumference lying between A and B being left of full circle, the faces of the flutes might be ground away as denoted by the dotted lines C D without affecting the drill diameter. [Illustration: Fig. 1061.] [Illustration: Fig. 1062.] [Illustration: Fig. 1063.] [Illustration: Fig. 1064.] [Illustration: Fig. 1065.] [Illustration: Fig. 1066.] Fig. 1065 represents the Farmer lathe drill, in which the flutes are straight and not spiral, by which means the tendency to run forward when emerging through the work is obviated. [Illustration: Fig. 1067.] When a twist drill is to be used for wood and is driven by a machine it is termed a bit, and is provided with a conical point to steady it, and two wings or spurs, as in Fig. 1066, which sever the fibres of the wood in advance of their meeting the main cutting edges and thus produce a smooth hole. The sharp conical point is used in place of the conical screw of the ordinary wood auger to avoid the necessity of revolving the drill or bit backwards to release the screw in cases in which the hole is not bored entirely through the work. [Illustration: Fig. 1068.] When the drill revolves and the work is to be held in the hands a rest or table whereon to rest the work and hold it fair is shown in Fig. 1067, the taper shank fitting in the dead centre hole and the tailstock spindle being fed up by hand to feed the drill to its cut. The face A A of the chuck is at a right angle to the shank, and a coned recess is provided at the centre, as denoted by the dotted lines, to permit the drill point to pass through the work without cutting the chuck. [Illustration: Fig. 1069.] For larger work a table, such as shown in Fig. 1068, is used, the cavity C permitting the drilling tool to pass through the work, there being a hole H provided for that purpose. The stem S fits in place of the dead centre. For cylindrical work the rest or chuck shown in Figs. 1069 and 1070 may be employed. It consists of a piece fitted to the tail spindle in place of the dead centre, its end being provided with [V]-grooves. These grooves are made true with the line of centres of the lathe, so that when the work is laid in them it will be held true. It is obvious that one groove would be sufficient, but two are more convenient--one for large work and one for small work--so that the side of the shaft to be drilled shall not pass within the fork, but will protrude, so that the progress of the work can be clearly seen. In Fig. 1070 an end view of this chuck is shown. It may be observed, however, that when starting the drill care must be taken to have it start true, or the drill may bend, and thus throw the work out of the true. For this reason the drills should be as short as possible when their diameters are small. For square work this class of work table or chuck may be formed so as to envelop the work and prevent its revolving, thus relieving the fingers of that duty, and it may be so formed as to carry the work back or off the drill when the latter is retired after the drilling is performed. [Illustration: Fig. 1070.] Another and quite convenient method of holding work to be drilled by a revolving drill in the lathe is shown in Fig. 1071. It consists of simply a bracket, _a_ _b_, fitted to the tool-box of the slide rest, carrying a spindle with one end screwed to receive any face plates or chucks that fit the lathe live spindle. The bracket is kept in position by two pins in the under side of it, fitting into holes in the bottom piece of tool-box. If it be required to drill a straight row of holes, the spindle is fixed by the set-screws in its bracket, and the work is bolted to the face plate at the proper level, and traversed across opposite the drill in the lathe mandrel, by the cross screw of the slide rest, while it is fed up to the drill by the upper screw or the rack and pinion. For circular rows of holes the centre line of the spindle is adjusted parallel with and at a proper distance from that of the mandrel. For holes in the edge of the work, the whole top of slide rest is turned round till the spindle is at right angles with the mandrel. [Illustration: Fig. 1071.] Work merely requiring to be held fast for drilling is bolted on one side of the face plate, and can then be adjusted exactly to the drill by the combined motions of the cross screw and the face plate on its centre. Small round work, while drilled in the end, can be held in a scroll chuck screwed on the spindle the same as a face plate. The convenience of this device consists in this, that the work turned on the chuck may be drilled without moving it from the chuck, which may be so set as to cause the drilled holes to be at any required angle to the work surface, which is quite difficult of accomplishment by other ordinary means. On account of the readiness with which a flat drill may be made to suit an odd size or employed to recess work with a flat or other required shape of recess, flat drills are not uncommonly used upon lathe work, and in this case they may be driven in the drill chucks already shown. A very convenient form of drill chuck for small drills is shown in Fig. 1072. It consists of a cylindrical chuck fitting from A to B into the coned hole in the live spindle so as to be driven thereby. At the protruding end C there is drilled a hole of the diameter of the wire forming the drill. At the end of this hole there is filed a slot D extending to the centre of the chuck. The end of the drill is filed half round and slightly taper, as shown in Fig. 1073 at D, so that the half-round end of the drill will pass into the slot of the chuck, therefore forming a driving piece which effectually prevents the drill from slipping, as is apt to occur with cylindrical stem or shank drills. If one size of wire be used for all drills, and the drill size be determined by the forging, the drill will run true, being held quite firmly, and may be very readily inserted in or removed from the chuck. [Illustration: Fig. 1072.] But the flat drill possesses several disadvantages: thus, referring to figure, it must be enough smaller at A than at B to permit the cuttings to find egress, and this taper causes the diameter of the drill to be reduced at each drill grinding. The end B may, it is true, be made parallel for a short distance, but in this case the cuttings will be apt to clog in the hole unless the drill be frequently removed from deep holes to clear the cuttings. For these reasons the fluted drill or the twist drill is preferable, especially as their diameters are maintained without forging. For deep holes, as, say, those having a depth equal to more than twice the diameter, the flat drill, if of small diameter, as, say, an inch or less, is unsuitable because of the frequency with which it must be removed from the hole to clear it of cuttings. [Illustration: Fig. 1073.] For fluted or twist drills the lathe may run quicker than for a flat drill, which is again an advantage. It sometimes becomes convenient in the exigencies which occur in the work of a general machine shop to hold a drill in a dog or clamp and feed it into the work with the lathe dead centre. In this case the drill should be held very firmly against the dead centre, or otherwise the drill may, when emerging through the back of the hole, feed itself forward, slipping off the dead centre, and causing the drill to catch and break, or moving the work in the chuck, to avoid which the drill should have a deep and well countersunk centre. [Illustration: Fig. 1074.] A very effective drill for holes that are above two inches in diameter and require enlarging is shown in Fig. 1074. It consists of a piece of flat steel A, with the pieces of wood B fastened on the flat faces, the wood serving to steady the drill and prevent it from running to one side in the work. This drill is sometimes used to finish holes to standard size, in which case the hole to be bored or drilled should be trued out a close fit to the drill for a distance equal to about the diameter of the drill, and the face at the entrance of the hole should be true up. This is necessary to enable the drill to start true, which is indispensable to the proper operation of the drill. This drill is made by being turned up in the lathe, and should have at the stock end a deep and somewhat large centre, so that when in use it may not be liable to slip off the dead centre of the lathe. The drill is held at the stock end by being placed in the lathe dead centre and is steadied, close to the entrance of the hole in the work, by means of a hook which at one end embraces the drill, as shown in Fig. 1075, in which A represents the hook and B the drill. [Illustration: Fig. 1075.] This drill will bore a parallel hole, but if the same be a long or a deep one it is apt to bore gradually out of true unless the bore of the hole is first trued from end to end with a boring tool before using the drill. It is often employed to enlarge a hole so as to admit a stout boring tool, and to remove the hard surface skin from which the boring tool is apt to spring away. [Illustration: Fig. 1076.] [Illustration: Fig. 1077.] HALF-ROUND BIT OR POD AUGER.--For drilling or enlarging holes of great depth (in which case it is difficult to drill straight holes with ordinary drills), the half-round bit--Figs. 1076 and 1077--is an excellent tool. Its diameter D is made that of the required hole, the cutting being done at the end only from A to B, from B to C being ground at a slight angle to permit the edge from A to B to enter the cut. When a half-round bit is to be used on iron or steel, and not upon brass, it may be made to cut more freely by giving the front face rake as at E F, Fig. 1078. [Illustration: Fig. 1078.] [Illustration: Fig. 1079.] To enable a bit of this kind to be adjusted to take up the wear, it may be formed as in Fig. 1079, in which a quarter of the circumference is cut away at _a_, and a cutter _c_ is bolted in position projecting into a recess at _b_ to secure the cutter in addition to the bolts. Pieces of paper may be inserted at _b_ to set out the cutter. An excellent form of boring bar and cutter is shown in Figs. 1080 and 1081. Fig. 1082 shows a side view of the cutter removed from the bar; Fig. 1081 an end, and Fig. 1080 a side view of the bar and cutter. The cutter is turned at A and B to fit the bore of the bar. The cutting edge C extends to the centre of the bar, while that at D does not quite reach the centre. These edges are in a line as shown in the end view. On account of the thickness of the cutter not equaling the diameter of the bore through the bar there is room for a stream of water to be forced through the bar, thus keeping it cool and forcing out the cuttings which pass through the passages G and H in the bar. The cutter drives lightly into the bar. By reason of one cutting edge not extending clear to the centre of the cutter there is formed a slight projection at the centre of the hole bored which serves as a guide to keep the cutter true, causing it to bore the hole very true. [Illustration: Fig. 1080.] For finishing the walls of holes more true, smooth, and straight, and of more uniform diameter than it is found possible to produce them with a drill, the reamer, or rymer, is employed. It consists of a hardened piece of steel having flutes, at the top of which are the cutting edges, the general form of solid reamer for lathe work being shown in Fig. 1083. The reamer is fed end-ways into the work at a cutting speed of about 15 to 18 feet per minute. [Illustration: Fig. 1081.] [Illustration: Fig. 1082.] The main considerations in determining the form of a reamer are as follows:-- 1. The number of its cutting edges. 2. The spacing of the teeth. 3. The angles of the faces forming the cutting edges. 4. Its maintenance to standard diameter. [Illustration: Fig. 1083.] As to the first, it is obvious that the greater the number of cutting edges the more lines of contact there are to steady it on the walls of the hole; but in any case there should be more than three teeth, for if three teeth are used, and one of them is either relieved of its cut or takes an excess of cut by reason of imperfections in the roundness of the hole, the other two are similarly affected and the hole is thus made out of round. An even number of teeth will not work so steadily as an odd one, for the following reasons. In Fig. 1084 is represented a reamer having 6 teeth and each of these teeth has a tooth opposite to it; hence, if the hole is out of round two teeth only will operate to enlarge its smallest diameter. In Fig. 1085 is a reamer having 7 teeth, and it will be seen that if any one tooth cuts there will be two teeth on the opposite side of the reamer that must also cut; hence, there are three lines of contact to steady the reamer instead of two only as in the case of the 6 teeth. An even number of teeth, however, may be made to operate more steadily by spacing the teeth irregularly, and thus causing three teeth to operate if the hole is out of round. Thus, in Fig. 1086 the teeth are spaced irregularly, and it will be seen that as no two teeth are exactly opposite, if a tooth on one side takes a cut there must be two on the opposite side that will also cut. The objection to irregular spacing is that the diameter of the reamer cannot be measured by calipers. Another method of obtaining steadiness, however, is to make the flutes and the cutting edges spiral instead of parallel to the axis, but in this case the spiral must be left-handed, as in Fig. 1087, or else the cutting edges acting on the principle of a screw thread will force the reamer forward, causing it to feed too rapidly to its cut. If, however, a reamer have considerable degree of taper, it may be given right-hand flutes, which will assist in feeding it. [Illustration: Fig. 1084.] [Illustration: Fig. 1085.] [Illustration: Fig. 1086.] [Illustration: Fig. 1087.] Referring to the second, the spacing of the teeth must be determined to a great extent by the size of the reamer, and the facility afforded by that size to grind the cutting edges to sharpen them. [Illustration: Fig. 1088.] The method employed to grind a reamer is shown in Fig. 1088, in which is shown a rapidly-revolving emery-wheel, above the reamer, and also a gauge against which the front face of each tooth is held while its top or circumferential face is being sharpened. The reamer is held true to its axis and is pushed end-ways beneath the revolving emery-wheel. In order that the wheel may leave the right-hand or cutting edge the highest (as it must be to enable it to cut), the axis of the emery-wheel must be on the left hand of that of the reamer, and the spacing of the teeth must be such that the periphery of the emery-wheel will escape tooth B, for otherwise it would grind away its cutting edge. It is obvious, however, that the less the diameter of the emery-wheel the closer the teeth may be spaced; but there is an objection to this, inasmuch as that the top of the tooth is naturally ground to the curvature of the wheel, as is shown in Fig. 1089, in which two different-sized emery-wheels are represented operating on the same diameter of reamer. The cutting edge of A has the most clearance, and is therefore the weakest and least durable; hence it is desirable to employ as large a wheel as the spacing of the teeth will allow, there being at least four teeth, and preferably six, on small reamers, and their number increasing with the diameter of the reamer. [Illustration: Fig. 1089.] It would appear that this defect might be remedied by placing the emery-wheel parallel to the teeth as in Fig. 1090; but if this were done, the wear of the emery-wheel would cause the formation of a shoulder at S in the figure, which would round off the cutting edge of the tooth. This, however, might be overcome by giving the emery-wheel enough end motion to cause it to cross and recross the width of the top facet; or the reamer R may be presented to the wheel W at an angle to the plane of wheel rotation, as in Fig. 1091, which would leave a straight instead of a curved facet, and, therefore, a stronger and more durable cutting edge. [Illustration: Fig. 1090.] [Illustration: Fig. 1091.] Another method of accomplishing the same object would be to mount the emery-wheel as in Fig. 1092, using its side face, which might be recessed on the side, leaving an annular ring of sufficient diameter to pass clear across the tooth, and thus prevent a shoulder from forming on the side face of the wheel. Yet another method is to use an emery-wheel bevelled on its edge, and mount it as in Fig. 1093, in which case it would be preferable to make the bevel face narrow enough that all parts would cross the facet of the tooth. [Illustration: Fig. 1092.] [Illustration: Fig. 1093.] Referring to the third, viz., the angles of the faces forming the cutting edges, it is found that the front faces, as A and B in Fig. 1094, should be a radial line, for if given rake as at C, the tooth will spring off the fulcrum at point E in the direction of D, and cause the reamer to cut a hole of larger diameter than itself, an action that is found to occur to some extent even where the front face is a radial line. As this spring augments with any increase of cut-pressure, it is obvious that if a number of holes are to be reamed to the same diameter it is essential that the reamer take the same depth of cut in each, so that the tooth spring may be equal in each case. This may be accomplished to a great extent by using two reamers, one for equalizing the diameters of the holes, and the other for the final finishing. The clearance at the top of the teeth is obviously governed by the position of the reamer with relation to the wheel, and the diameter of the wheel, being less in proportion as the reamer is placed farther beneath the wheel, and the wheel diameter is increased. In some forms of reamer the teeth are formed by circular flutes, such as at H in Fig. 1094, and but three flutes are used. This leaves the teeth so strong and broad at the base that the teeth are not so liable to spring; but, on the other hand, the clearance is much more difficult to produce and to grind in the resharpening. [Illustration: Fig. 1094.] [Illustration: Fig. 1095.] [Illustration: Fig. 1096.] As to the maintenance of the reamer to standard diameter, it is a matter of great importance, for the following reasons: The great advantage of the standard reamer is to enable holes to be made and pieces to be turned to fit in them without requiring any particular piece to be fitted to some particular hole, and in order to accomplish this it is necessary that all the holes and all the pieces be exactly alike in diameter. But the cutting edges of the reamer begin to wear--and the reamer diameter, therefore, to reduce--from the very first hole that it reams, and it is only a question of time when the holes will become too small for the turned pieces to enter or fit properly. In all pieces that are made a sliding or a working fit, as it is termed when one piece moves upon the other, there must be allowed a certain latitude of wear before the one piece must be renewed. One course is to make the reamer when new enough larger than the proper size to bore the holes as much larger as this limit of wear, and to restore it to size when it has worn down so that the holes fit too tightly to the pieces that fit them. But this plan has the great disadvantage that the pieces generally require to have other cutting operations performed on them after the reaming, and to hold them for these operations it is necessary to insert in them tightly-fitting plugs, or arbors, as they are termed. If, therefore, the holes are not of equal diameter the arbor must be fitted to the holes, whereas the arbor should be to standard diameter to save the necessity of fitting, which would be almost as costly as fitting each turned piece to its own hole. It follows, therefore, that the holes and arbors should both be made to a certain standard, and the only way to do this is to so construct the reamer that it may be readily adjusted to size by moving its teeth. It is obvious that a reamer must, to produce parallel holes, be held axially true with the holes, or else be given liberty to adjust itself true. Fig. 1095 shows a method of accomplishing this object. The reamer is made to have a slight freedom or play in the sleeve, being 1/32 inch smaller, and the hole for the pin is also made large so that the reamer may adjust itself for alignment. For short holes the shell reamer shown in Fig. 1096 may be employed. Its bore is coned so that it will have sufficient friction upon its driving arbor to prevent its coming off; when it is to be withdrawn from the work it is provided with two slots into which fit corresponding lugs on the driving arbor. Fig. 1097 shows the Morse Twist Drill and Machine Company's arbor. [Illustration: Fig. 1097.] [Illustration: Fig. 1098.] The rose reamer, or rose bit, has its cutting edges on the end only, as shown in Fig. 1098, the grooves being to supply lubricating material (as oil or water) only, and, as a result, will bore a more parallel hole than the ordinary reamer in cases in which the reamer has liberty to move sideways, from looseness in the mechanism driving it. Furthermore, when the work is composed of two parts, the outer one, through which the reamer must pass before it meets the inner one, guides the reamer without becoming enlarged by reason of the reamer having cutting edges, which is especially advantageous when the inner hole requires to be made true with the outer one, or in cases where a piece has two holes with a space between them, and one hole requires to be made true with the other, and both require to be made to the same diameter as the reamer. Fig. 1099 represents the Morse Twist Drill Company's shell rose reamer for short holes, corresponding in principle to the solid rose reamer, but fitting to an arbor for the same purposes as the shell reamer. Instead of having upon a reamer a flat tooth top to provide clearance, very accurate and smooth work may be produced by letting the back of the tooth, as A in Fig. 1100, proceed in a straight line to B, leaving the reamer, when soft, too large, so that after hardening it may be ground by an emery-wheel to size; and the clearance may be given by simply oilstoning the top of each tooth lengthwise, the oilstone marks barely effacing the emery marks at the cutting edge and removing slightly more as the back of the tooth is approached from the cutting edge. This produces cutting edges that are very easily fed to the cut, which must obviously, however, be a light one, as should always be the case for finishing, so that the wear of the teeth may be a minimum, and the reamer may therefore maintain its standard diameter as long as possible. [Illustration: Fig. 1099.] [Illustration: Fig. 1100.] When a solid reamer has worn below its required diameter, the same may be restored by upsetting the teeth with a set chisel, by driving it against the front face; and in determining the proper diameter for a reamer for work to be made to gauge under the interchangeable system the following considerations occur. Obviously the diameter of a reamer reduces as it wears; hence there must be determined a limit to which the reamer may wear before being restored to its original diameter. Suppose that this limit be determined as 1/1000 inch, then as the reamer wears less in diameter the bolts to fit the holes it reams must also be made less as the reamer wear proceeds, or otherwise they will not enter the reamed holes. But it is to be observed that while the reamer wears smaller, the standard gauges to which the pins or bolts are turned wear larger, and the wear is here again in a direction to prevent the work from fitting together. It is better then to make the reamer when new too large to the amount that has been determined upon as the limit of wear, so that when the work begins to go together too tight, the reamer requires resharpening and restoring. [Illustration: Fig. 1101.] A still better plan, however, is to use reamers adjustable for diameter, so that the wear may be taken up, and also the reamer sharpened, without being softened, which always deteriorates the quality of the steel. Reamers that are too small to be made adjustable for size by a combination of parts may be constructed as in Fig. 1101, in which the reamer is drilled and threaded, and countersunk at the end to receive a taper-headed screw S, which may be screwed in to expand the reamer, which contains three longitudinal splits to allow it to open. To cause S to become locked in its adjusted position a plug screw P is inserted for the end of S to abut against. It is obvious that in this form the reamer is expanded most at the end. Fig. 1102 represents a single-tooth adjustable reamer, in which the body A is ground to the standard diameter, and the wear of the cutter C is taken up by placing paper beneath the cutter. In this case the reamer cannot, by reason of the wear of the cutting edge, ream too small, because the body A forms a gauge of the smallest diameter to which the reamer will cut. The cutter may, however, be set up to the limit allowed for wear of cutting edge, which for work to fit should not be more than 1/5000 inch. [Illustration: Fig. 1102.] An adjustable reamer designed and used by the author for holes not less than 1-1/2 inches in diameter, is shown in Fig. 1103, in which A represents the body of the reamer containing dovetail grooves tapered in depth with the least depth at the entering end. The grooves receive cutters B, having gib heads. C is a ring or washer interposed between the gib heads of the cutter and the face or shoulder of A, the cutters being locked against that face by a nut and a washer E. By varying the thickness of C, the cutters are locked in a different position in the length of the grooves, whose taper depth therefore causes the cutters to vary in diameter. Suppose, for example, that with a given thickness of washer C, the cutters are adjusted in diameter so as to produce a hole a tight working fit to a plug turned to a 2-inch standard gauge: a slightly thinner washer may be used, setting the cutters so as to bore a hole an easy working fit to the plug; or a slightly thicker washer may be employed so as to produce a hole a driving fit to the same plug. Three or more washers may thus be used for every standard size, their thickness varying to suit the nature of the fit required. [Illustration: Fig. 1103.] It will be noted that it is mentioned that three _or more_ washers may be used, and this occurs because a diameter of fit that would be a driving fit for a hole of one length would be too tight for a driving fit of a much longer hole, the friction of course increasing with the length of hole, because of the increase of bearing area. For large sizes, a reamer of this description is an excellent tool, because if it be required to guide the reamer by means of a plain cylindrical shank, a washer, or sleeve, having a bore to fit the shank at the termination of the thread, may be used, but such a reamer is not suitable for small diameters, because of the reduction of shank necessary to provide for the nut and thread. Reamers for roughing out taper holes may be made with steps, as in Fig. 1104, which is taken from _The American Machinist_, there being a cutting edge where each step meets a flute. Such a reamer may be used to enlarge parallel holes, or to rough out taper ones, and the flutes (if not to be used for brass work) may be spiral, as in the figure. The end step being guided by the hole serves as a guide to the first cutting edge; the second step serves as a guide for the cutting edge that follows it, and so on. [Illustration: Fig. 1104.] [Illustration: Fig. 1105.] The steps are best turned a trifle larger, say 1/1000 inch larger, at the cutting end. Half-round taper reamers, such as shown in Fig. 1105, are used for finishing holes. The flat face is cut down, leaving rather more than a half circle; the clearance being filed or ground on the cutting side so as to enable the reamer to cut, and extending from the cutting edge to nearly half-way to the bottom of the reamer. For holes, however, that are large enough to admit a tool of sufficient strength, the single-pointed boring tool produces the most true work. Brass finishers use square taper reamers, which produce upon brass more true work than the half-round reamer. [Illustration: Fig. 1106.] [Illustration: Fig. 1107.] For reaming the bores of rifles, a square reamer, such as shown in Fig. 1106, is employed; the edges A B are the cutting ones, the edges C D being rounded off; E is a piece of wood, beneath which slips of paper are placed to restore the size as the wear proceeds. The entering end of the reamer is slightly tapered. On account of the extreme length of this reamer in proportion to its diameter, it is fed to its cut by being pulled instead of pushed as is usually the case, the pull placing the rod of the reamer under tension and thus stiffening it; the line of pull is of course true with the axis of the rifle bore. The reamer is revolved at high speed and freely supplied with oil. [Illustration: Fig. 1108.] By means of the slips of paper successive cuts and minute increases of diameter may be taken with the same reamer. Fig. 1107 represents a class of rose bit employed to reduce pins to a uniform diameter, and face off the shoulder under the head, or it may be used to cut a recess round a pin, or to cut a recess and leave a pin. For making a recess round a hole, or, in other words, for cutting a flat-bottom countersink, a facing countersink, Fig. 1108, may be used, its cutting edges being at A, B, C, &c. The clearance is given at the ends of the teeth only, being shown from B to D. The pin P steadies the tool, and is made a working fit to the hole in the work. Or if too small, a ferrule may be placed upon it, thus increasing the capacity of the tool. When a tool of this kind is to be used on iron, steel, or copper, and not upon brass, the front face of the teeth may be given rake by cutting the grooves at an angle, as in Fig. 1109. BORING TOOLS FOR LATHE WORK.--The principal object in forming a boring tool to be held in a slide rest is to have the body of the tool as large as can be conveniently got into the size of the hole to be bored; hence the cutting edge should not stand above the level of the top of the steel. By this means the tool will be as stiff as possible, and less liable to spring away from its cut, as boring tools are apt to do, especially when the cut or hole is a long one. It is so difficult a matter to bore a long hole parallel with a long boring tool that cutters of various forms are usually preferred, and these will be described hereafter. [Illustration: Fig. 1109.] [Illustration: Fig. 1110.] The boring tool is, upon cast iron and brass, exceedingly liable to chatter, but this may always be avoided by making the angles forming the cutting edge less acute: thus, in Fig. 1110 are three boring tools, A, B, C, operating in a piece of work D. Now the lateral pressure of a cut is exerted upon the tool at a right angle to the length of the cutting edge; hence (in addition to the vertical pressure) the lateral pressure of the tool A will be in the direction of the dotted line and arrow A, that on B in the direction of dotted line and arrow B, and that on C in the direction of dotted line and arrow C; hence the pressure of the cut would tend to force A towards the centre of the hole and off or away from its cut, B back from its cut, and C deeper into its cut. Now as the cut proceeds, the tool edge dulls, hence it would appear that a compromise between C and B would be the most desirable, as giving to the tool enough of the tendency to deepen its cut to compensate for the tendency to spring away from its cut, as the cutting edge dulls (which it does from the moment the cut begins). This is quite practicable in tools to be used on wrought iron, as shown in Fig. 1111, which represents the most desirable form. In this form the part of the cutting edge performing duty under a deep cut will be mainly in front of the tool, but in light cuts the cutting edge would be farther back, where it is more nearly parallel to the line of the work bore, and will hence cut smoother. [Illustration: Fig. 1111.] [Illustration: Fig. 1112.] Where a boring tool is intended for light cuts only on wrought iron it may have all, or nearly all, its rake at the top, as shown in Fig. 1112, from _a_ to B representing the cut, and C the tool. Under ordinary conditions that in the form of tool shown in Fig. 1113[15] is best for brass work, the face A being horizontal or slightly depressed towards the point. Boring tools require very little bottom rake, and the cutting points should be as rounded as they can be made without chattering. On wrought iron the top rake may be as much as is consistent with strength, and water should be freely applied to the cut. For cast iron the best form of tool is that shown in Fig. 1114, the edge A being parallel with the bore of the hole, and the feed being a coarse one, taking a very light cut when finishing. [15] From "The Complete Practical Machinist." [Illustration: Fig. 1113.] [Illustration: Fig. 1114.] In cases, however, where the tool point requires to cut up to a sharp corner, the form of tool shown in Fig. 1115 (which represents a top and end view) may be used. Its end face C is at an obtuse angle to the length of the tool, so that on passing up a bore and meeting a radial face the point only will meet that face. This angle, however, gives to the tool a keenness that will cause chattering on brass work unless the top face be bevelled to the tool body, as is A to B in the figure. [Illustration: Fig. 1115.] It frequently happens in boring cast iron that the skin or the surface of the metal is very hard, rapidly dulling the tool and forcing it away from its cut, unless the cut is deep enough to allow the point of the tool to cut beneath it, as shown in Fig. 1116, in which the hardness is supposed to extend from the bore to the dotted line. In this case a tool formed as at C is employed, the point cutting in advance of the rest of the tool, and entering the soft metal beneath the hard metal; the hard metal will then break away in lumps or pieces, without requiring to be absolutely cut into chips or turnings, because of being undercut, as shown at B. The cross slider or tool rest of a lathe should be adjusted to closely fit the cross slide of the lathe if true and parallel work is to be bored, because any lost motion that may exist in the slide is multiplied by the length the tool stands out from the tool post. Thus the centre of motion of the rest if it has play, as at B, Fig. 1117, and the direction of motion at the tool point, will be an arc of a circle of which B is the centre, the bend of the tool from the pressure of the cut will have its point of least motion or fulcrum at A; hence, both tend to cause the tool point to dip and spring unequally under the varying cut pressure that may arise from hard or soft places in the metal, and from inequalities in the cut depth. [Illustration: Fig. 1116.] The pressure of the cut increases as the tool point loses its sharpness, and this makes sufficient difference for the amount of tool spring in light boring tools or in long holes to cause the tool to bore a larger hole at the beginning than it does at the end of its feed traverse; or, in other words, to bore a taper hole, whose largest end is that at which the cut was started. If, therefore, the cut is traversed from the front to the back of the hole the latter will be of the smallest diameter at the back, and conversely if the cut proceeds from the back to the front of the hole the front will be of smallest diameter. The amount of the taper so caused (or in other words the error from parallelism) will obviously increase with the length of the hole. To obviate this taper, the slide of the rest should for the finishing cut be set up firmly, and the tool after being sharpened should take a finishing cut through the hole, and then let traverse back, which can be done providing that care be taken not to bore the hole too large. [Illustration: Fig. 1117.] A boring tool will take a smoother cut and chatter less if the final cut be from the back to the front of the hole, and for the following reasons: When the tool is fed in, the strain or pressure of the cut is in a direction to partly compress and partly bend the steel which is being pushed to its cut, but when it is fed in the opposite direction it is pulled to its cut and the strain is in a direction to stretch the steel, and this the tool is more capable of resisting, hence it does not so readily vibrate to cause chattering. In consequence, however, of the liability of a boring tool to spring away from its cut, it is far preferable to finish holes with standard cutters, reamers, or bits, in which case the boring tool may be employed to rough out and true up the hole, leaving a _fine_ cut for the finishing cutter or bit, so as to wear its cutting edge as little as possible. To further attain this latter object, the cutter or bit should be used at a slow cutting speed and with a coarse feed. [Illustration: Fig. 1118.] [Illustration: Fig. 1119.] If cutters or bits are not at hand, tool holders are desirable, and the forms of these depend upon the nature, or rather the diameter, of the hole to be bored. In all cases, however, the best results will be obtained when the diameter of the tool holder is as near that of the hole to be bored as will give it clearance. This occurs on account of the rigidity of the holder being greater than that of the tool. [Illustration: Fig. 1120.] [Illustration: Fig. 1121.] For large work tool holders are desirable, in that the tools, being short, are easier to forge, to handle, and to grind. For example, a tool holder of a cross section of two inches square may contain a tool whose cross section is 1 by 3/4 inch, in which case it is necessary to forge, grind, &c., the small tool only, whereas in the absence of the holder the tool would require to be of a cross section equal to that of the holder to obtain an equal degree of rigidity. A boring tool holder suitable for holes of from 2 to 4 or 5 inches is shown in Fig. 1118, in which A represents a round bar shaped at the end B to fit into the tool post of the slide rest, and having a groove across the diameter of the end C D to receive a short tool. The slot and tool may be either square or [V]-shaped, the tool being locked by a wedge. It is obvious that instead of shaping the end B as shown, the bar may be held (if the slide-rest head is provided with a clamp instead of a tool post) by two diametrically opposite flat faces. For holes of a greater diameter a holder such as shown in Fig. 1119 should be used, the body being a square bar, and the tool being held in the box A A by two set screws B. For holes of small diameter, as, say, less than 1-1/2 inches, a tool holder is especially desirable, because when a boring tool is forged out of a piece of tool steel, its length is determined, and in order to have tools suitable for various depths of hole a number of tools of varying lengths are requisite. Suppose, for example, that a piece of steel be forged into a boring tool suitable for a hole of an inch diameter, and 4 inches deep, then the steel must be forged round for a distance of at least 4 inches from the cutting end, and if such a tool were applied to a hole, say, two inches deep, the cutting edge would stand out from the tool post at least two inches more than is necessary, which would cause the employment of a tool weaker than necessary for the work. To enable the use of one tool for various depths of work, and yet hold it in each case as close to the tool post as the work depth admits, tool-clamping devices, such as in Fig. 1120 (which are extracted from _The American Machinist_), are employed. 1 and 2 are pieces of steel fitting in the tool post and clamping the tool, which for very small holes is made of octagon or round forged steel. The tool may be passed to any required distance through the clamp, so as to project only to the amount necessary for the particular depth of hole requiring to be bored. These clamping pieces 1 and 2 should bed upon the tool fairly along their full length; or, what is better, they may bed the firmest at their extremities, which will insure that the tool is gripped firmly as near to the cutting edge as possible. In place of a steel tool, a tool holder turned cylindrically true and parallel may be used to carry a short boring tool, as shown in Fig. 1121, in which A is the tool secured by the set-screw B into the holder C. The latter may be provided with a line running true longitudinally, and may have a fine groove similar to a thread, and having a pitch measuring some part of an inch, as 1/8, 1/4, 1/2 inch, &c., so that the distance the tool projects from the holder may be known without measuring the same. But when a tool and holder of this description are used, the tool cannot be employed unless the hole passes entirely through the work, which occurs because of the presence of the set-screw B. It is obvious that for a tool-holding bar such as this, a clamping device such as shown in Fig. 1120 is requisite, and that the position of the clamping device may be adjusted to suit the work by setting it more or less through the tool post. The manner in which the deflection of a boring tool will affect the bore of the work depends upon the height of the boring tool in the work. If the tool is above the horizontal centre of the work, as in Fig. 1122, the spring vertically will cause it to leave the cut, and bore the hole to a corresponding amount smaller; and since the tool gets duller as the wear proceeds, it will spring more at the latter end of each tool traverse, leaving the end of the hole last cut of smallest diameter. If, on the other hand, the tool be below the horizontal centre, as in Fig. 1123, the vertical spring will be in a direction to increase the amount of the cut, and thus offset the tapering effect of the increased tool spring due to the wear of the tool. Furthermore, the shaving will be easier bent if the tool be below than if above the horizontal centre, because the metal will be less supported by the metal behind it. It is always desirable therefore to have the cutting edge of a boring tool used on small work below rather than above the horizontal centre of the work. On large work, however, as say, having a bore of 6 inches and over, the curve of the bore in the length of the circumference affected by the cut or bending of the cut is so small, that the height of the tool is of less consequence. [Illustration: Fig. 1122.] To enable the use of a stout-bodied boring tool, while keeping its cutting edge below the centre, the top face of the tool may be depressed, as shown in Fig. 1123. [Illustration: Fig. 1123.] An excellent attachment for boring parallel holes is shown in Figs. 1124 and 1125, in which there is fixed to the cross slide A the bracket B, which is bored to receive a number of bushes C, whose bores are made to suit varying diameters of boring-bars or reamers D. The hub of the bracket is split on one side to enable it to be closed (by the bolt _e_) upon the bush C and grip it firmly, the bush also being split at _f_. The bracket B is provided with a taper pin G, which brings it in position upon the slide so that the bushes C are true with the line of lathe centres. It is also provided with the screws H, which lock it firmly to the cross slide and prevent any spring or movement from play or looseness. When the bracket is adjusted and the bar fastened up (by screw _e_), the lathe-carriage feeds the boring tool to the cut in the usual manner. Now suppose that, as shown in our illustrations, a pulley P requires to be bored, and the boring tool or reamer may be set to have its cutting end stand out just as far as the length of the hub requires, and no farther, so that the bar will be held and supported as close to the pulley hub as is possible from the nature of the job. There need not be a separate bush for every size of reamer, because the bodies of several size bars may fit to one size of bush, especially if the set of reamers for every size of bush be made with its smallest size equal to the bore of the bush; because in that case the whole of the set may be adjusted to bore any required depth of hole by sliding the reamer through the bush to the required distance. If there are a number of lathes in a shop, each lathe may have its own bracket B, all these brackets being bored to receive the same bushes, and therefore the same boring-bars or reamers. [Illustration: Fig. 1124.] [Illustration: Fig. 1125.] A bracket or stand of this kind may obviously be used to carry a bar, having a head such as is shown in Fig. 1126, each dovetail groove carrying a cutting tool, and for wrought iron or steel work these grooves may be at an angle to the bar axis, as in the figure, to give each cutter front rake, and increase its keenness. [Illustration: Fig. 1126.] BORING BARS FOR LATHE WORK.--Boring bars for lathe work are of two kinds, those in which the cutters are held in a fixed position in the length of the bar, and those in which the cutters are held in a head which traverses along the work. The former are the least desirable, because they require to be more than twice the length of the work, which must be on one side of the cutter at the commencement of the cut, and on the other at the termination of the same. But to traverse the head carrying the tools along the bar necessitates a feed screw either within the bar or outside of it. If within, the metal removed to give it place weakens the bar, while in small holes there is no room for it; hence solid bars with fixed cutting tools are used for small holes, and tools held in a traversing head for those sufficiently large to give room for a head without weakening the bar too much. A boring bar is best driven from both ends. [Illustration: Fig. 1127.] "The boring bar is one of the most important tools to be found in a machine shop, because the work it has to perform requires to be very accurately done; and since it is a somewhat expensive tool to make, and occupies a large amount of shop room, it is necessary to make one size of boring bar answer for as many sizes of hole as possible, which end can only be attained by making it thoroughly stiff and rigid. To this end a large amount of bearing and close fitting, using cast iron as the material, are necessary, because cast iron does not spring or deflect so easily as wrought iron; but the centres into which the lathe centres fit are, if of cast iron, very liable to cut and shift their position, thus throwing the bar out of true. It is, therefore, always preferable to bore and tap the ends of such bars, and to screw in a wrought-iron or steel plug, taking care to screw it in very tightly, so that it shall not at any time become loose. The centres should be well drilled and of a comparatively large size, so as to have surface enough to suffer little from wear, and to well sustain the weight of the bar. The end surface surrounding the centres should be turned off quite true to keep the latter from wearing away from the high side, as they would do were one side higher than the other."[16] [16] From "The Complete Practical Machinist." [Illustration: Fig. 1128.] The common form of the smaller sizes of boring bar is that shown in Fig. 1127. A A being the bar, D D the lathe centres, B the cutter passing through a slot or keyway in the bar, and C a key tapered (as is also the back edge of the cutter) to wedge or fasten the cutter to the bar. It is obvious that, if the cutter is turned up in the bar, and is of the exact size of the hole to be bored, it will require to stand true in the bar, and will therefore be able to cut on both ends, in which case the work may be fed up to it twice as fast as though only one edge were performing duty. To facilitate setting the cutter quite true, a flat and slightly taper surface should be filed on the bar at each end of the keyway, and the cutter should have a recess filed in it, as shown in Fig. 1128, the recess being shown at A, and the edges B B forming the diameter of the cutters. The backing off is shown at C, from which it will be observed that the cutting duty is performed by the edge C, and not along the edge B, further than is shown by the backing off. The recess must be made taper, and to fit closely to the flat places filed on the bar. Such a cutter, if required to be adjustable, must not be provided with the recess A, but must be left plain, so that it may be made to extend out on one side of the bar to cut any requisite size of bore; it is far preferable, however, to employ the recess and have a sufficient number of cutters to suit any size of hole, since, as already stated (there being in that case two cutting edges performing duty), the work may be fed up twice as fast as in the former case, in which only one cutting edge operates. Messrs. Wm. Sellers and Co. form the cutters for their celebrated car wheel boring bar machine as in Fig. 1129, the bottom or plain edge performing the cutting. By this means the recess to fit the bar is not reduced in depth from sharpening the tool. The tool is sharpened by grinding the ends of the lower face as shown by the unshaded parts, and the cutter is said to work better after the cutting part has begun to be oblique from grinding. [Illustration: Fig. 1129.] The cutter is hardened at the ends and left soft in the middle, so that the standard size of the cutter may be restored when necessary, by pening and stretching the soft metal in the middle. These cutters will bore from 50 to 250 car wheels, without appreciable reduction of size. The description of bar shown in Fig. 1127 may be provided with several slots or keyways in its length, to facilitate facing off the ends of work which requires it. Since the work is fed to the cutter, it is obvious that the bar must be at least twice the length of the work, because the work is all on one side of the cutter at the commencement, and all on the other side at the conclusion of the boring operation. The excessive length of bar, thus rendered necessary, is the principal objection to this form of boring bar, because of its liability to spring. There should always be a keyway, slot, or cutter way, near to the centre of the length of the bar, so as to enable it to bore a hole as long as possible in proportion to the length of the boring bar, and a keyway or cutter way at each end of the bar, for use in facing off the end faces of the work. If a boring bar is to be used only for work that does not require facing at the ends, the cutter, slot, or keyway should be placed in such position in the length of the bar as will best suit the work (keeping in mind the desirability of having the bar as short as possible), and the bar should be tapering from the middle towards each end, as shown in Fig. 1130. This will make the bar stronger in proportion to its weight, and better able to resist the pressure of the cut and the tendency to deflect. The parallel part at A is to receive the driving clamp, but sometimes a lug cast on at that end is used instead of a clamp. For bores too large to be bored by the bar alone, a tool-carrying head is provided, being sometimes fixed upon the bar by means of a locking key, and at others fed along the bar by a feed screw provided on the bar. [Illustration: Fig. 1130.] When the head is fixed on the bar the latter must be twice as long as the bore of the work, as the work is on one side of the head at the beginning, and on the other at the end of a cut; hence it follows that the sliding or feeding head is preferable, being the shortest, and therefore the most rigid, unless the bar slides through bearings at each end of the head. Fig. 1131 represents a bar with a fixed head in operation in a cylinder, and having three cutting tools, and it will be observed that if tool A meets a low spot and loses its cut, the pressure on tools B and C, both being on the opposite side of the head, would cause the bar to spring over towards A, producing a hole or bore out of round, and it follows that four tools are preferable. Fig. 1132 is a side view of a bar with four cutters, and Fig. 1133 an end view of the same shown within a cylinder, and it will be seen that should one of the cutters lose its cut, the two at right angles to it will steady the bar. [Illustration: Fig. 1131.] [Illustration: Fig. 1132.] When the cutters require to stand far out from the head, the bar will work more steadily if the cutters, instead of standing radially in the head, are placed as in Fig. 1134, so that they will be pulled rather than pushed to their cut. [Illustration: Fig. 1133.] [Illustration: Fig. 1134.] An excellent form of boring bar fixed head, employed by Messrs. Wm. Sellers and Co. on their horizontal cylinder boring machine, is shown in Fig. 1135. The boring head is split at A, so that by means of the bolt B it may be gripped firmly to the bar D, or readily loosened and slid along it. The head is provided with cutters C (of which there are four in the latest design of bar), fitting into the radial slots E. These cutters are secured to the head by the clamps and nuts at G. Fig. 1136 represents a boring bar, with a sliding head fed by a feed screw running along the bar, and having at its end a pinion that meshes upon a gear or pinion upon the dead centre of the lathe. [Illustration: Fig. 1135.] The tools employed for the roughing cuts of boring bars should, for wrought iron, cast iron, steel, or copper, have a little front rake, the cutting corner being at A in Fig. 1137. If the cutters are to be used for one diameter of bore only, they will work more steadily if but little or no clearance is given them on the end B, Fig. 1138, but it is obvious that if they are to be used on different diameters of bores they must have clearance on these ends. The same tool may be used both for roughing and finishing cuts. [Illustration: Fig. 1136.] The lip or top rake must, in case the bar should tremble during the finishing cut, be ground off, leaving the face level; and if, from the bar being too slight for its duty, it should still either chatter or jar, it will pay best to reduce the revolutions per minute of the bar, keeping the feed as coarse as possible, which will give the best results in a given time. In cases where, from the excessive length and smallness of the bar, it is difficult to prevent it from springing, the cutters must be made as in Fig. 1139, having no lip, and but a small amount of cutting surface; and the corner A should be bevelled off as shown. Under these conditions, the tool is the least likely to chatter or spring into the cut. The shape of the cutting corner of a cutter depends entirely upon the position of its clearance or rake. If the edge forming the diameter has no clearance upon it, the cutting being performed by the end edges, the cutter may be left with a square, slightly rounded, or bevelled corner; but if the cutter have clearance on its outside or diametrical edge, as shown on the cutters in Fig. 1137, the cutting corner should be bevelled or rounded off, otherwise it will jar in taking a roughing cut, and chatter in taking a moderate cut. The principle is that bevelling off the front edge of the cutter, as shown in Fig. 1139, tends greatly to counteract a disposition to either jarring or chattering, especially as applied to brass work. [Illustration: Fig. 1137.] The only other precaution which can be taken to prevent, in exceptional cases, the spring of a boring bar is to provide a bearing at each end of the work, as, for instance, by bolting to the end of the work four iron plates, the ends being hollowed to fit the bar, and being so adjusted as to barely touch it; so that, while the bar will not be sprung by the plates, yet, if it tends to spring out of true, it will be prevented from doing so by contact with the hollow ends of the plates, which latter should have a wide bearing, and be kept well lubricated. [Illustration: Fig. 1138.] It sometimes happens that, from play in the journals of the machine, or from other causes, a boring bar will jar or chatter at the commencement of a bore, and will gradually cease to do so as the cut proceeds and the cutter gets a broader bearing upon the work. Especially is this liable to occur in using cutters having no clearance on the diametrical edge; because, so soon as such a cutter has entered the bore for a short distance, the diametrical edge (fitting closely to the bore) acts as a guide to steady the cutter. If, however, the cutter has such clearance, the only perceptible reason is that the chattering ceases as soon as the cutting edge of the tool or cutter has lost its fibrous edges. The natural remedy for this would appear to be to apply the oil-stone; this, however, will either have no effect or make matters worse. It is, indeed, a far better plan to take the tool (after grinding) and rub the cutting edge into a piece of soft wood, and to apply oil to the tool during its first two or three cutting revolutions. The application of oil will often remedy a slight existing chattering of a boring bar, but it is an expedient to be avoided, if possible, since the diameter or bore cut with oil will vary from that cut dry, the latter being a trifle the larger. The considerations, therefore, which determine the shape of a cutter to be employed are as follows: Cutters for use on a certain and unvarying size of bore should have no clearance on the diametrical edges, the cutting being performed by the end edge only. Cutters intended to be adjusted to suit bores of varying diameter should have clearance on the end and on the diametrical edges. For use on brass work the cutting corner should be rounded off, and there should be no lip given to the cutting edge. For wrought iron the cutter should be lipped, and oil or soapy water should be supplied to it during the operation. A slight lip should be given to cutters for use on cast iron, unless, from slightness in the bar or other cause, there is a tendency to jarring, in which case no lip or front rake should be given. [Illustration: Fig. 1139.] "In boring work chucked and revolved in the lathe, such, for instance, as axle boxes for locomotives, the bar shown in Fig. 1140 is an excellent tool. A represents a cutter head, which slides along, at a close working fit, upon the bar D D, and is provided with the cutters B, B, B, which are fastened into slots provided in the head A by the keys shown. The bar D D has a thread cut upon part of its length, the remainder being plain, to fit the sliding head. One end is squared to receive a wrench, which resting against the bed of the lathe, prevents the bar from revolving upon the lathe centres F, F, by which the bar is held in the lathe. G, G, G are plain washers, provided to make up the distance between the thread and plain part of the bar in cases where the sliding head A requires considerable lateral movement, there being more or less washers employed according to the distance along which the sliding head is required to move. The edges of these washers are chamfered off to prevent them from burring easily. To feed the cutters, the nut H is screwed up with a wrench. "The cutter head A is provided in its bore with two feathers, which slide in grooves provided in the bar D D, thus preventing the head from revolving upon the bar. It is obvious that this bar will, in consequence of its rigidity, take out a much heavier cut than would be possible with any boring tool, and furthermore that, there being four cutters, they can be fed up four times as fast as would be possible with a single tool or cutter. Care must, however, be exercised to so set the cutters that they will all project true radially, so that the depth of cut taken by each will be equal, or practically so; otherwise the feeding cannot progress any faster than if one cutter only were employed."[17] [17] From Rose's "Complete Practical Machinist." [Illustration: Fig. 1140.] For use on bores of a standard size, the cutters may be made with a projecting feather, fitting into a groove provided in the head to receive it, as shown in Fig. 1141, which shows the boring bar and head, the nuts and washers being removed. A, A represent cutters, B the bar, C the sliding head, and D, D keys which fasten the cutters in the head. The cutters should be fitted to their places, and each marked to its place; so that, if the keyways should vary a little in their radius from their centre of the bar, they will nevertheless be true when in use, if always placed in the slot in which they were turned up when made. By fitting in several sets of cutters and turning them up to standard sizes, correctness in the size of bore may be at all times insured, and the feeding may be performed very fast indeed. For boring cannon the form of bar shown in Fig. 1142 is employed. The cannon is attached to the carriage or saddle of the lathe and fed to the boring bar. The working end only of the bar is shown in the figure, the shank stem or body of the bar being reduced in diameter to afford easy access to the cuttings. The cutters occupy the positions indicated by the letters A, A, A, being carefully adjusted as to distance from the axis of the bar by packing them at the back with very thin paper. As may be observed they are arranged in two sets of three each, of which the first set performs almost the whole of the work, the second being chiefly added as a safeguard against error in the size of the bore on account of wear of the cutting edges, which takes place to a small but an appreciable extent in the course of even a single boring. Following the cutters is a series of six guide-bars (B B B), arranged spirally, which are made exactly to fit the bore. Provided that the length of these is sufficient, and their fit perfect, it is evident that the cutters cannot advance except in a straight line. The spiral arrangement of the cutters is employed to steady the bar and to give it front rake. [Illustration: Fig. 1141.] [Illustration: Fig. 1142.] [Illustration: Fig. 1143.] [Illustration: Fig. 1144.] BORING TAPERS WITH A BORING BAR OR ATTACHMENT.--In cases where the degree of taper is very great a live centre may be bolted to a chuck plate, as in Fig. 1143, by which means any degree of taper may be bored. Instead of a star feed, a gear feed may be provided by fastening one gear, as A, on the dead centre, and another, as B, on the feed-screw. The cutting tool must stand on the side of the sliding-head--that is, farthest from the line of lathe centres. [Illustration: Fig. 1145.] [Illustration: Fig. 1146.] Small holes may readily be bored taper with a bar set over as in Fig. 1144, the work being carried by a chuck. The head H carries the cutting tool, having a feather which projects into the spline S to prevent the head from rotating on the bar. To prevent the bar from rotating, it is squared on the end F to receive a wrench. The head is fed by the nut N, which is screwed upon the bar. W, W, W, W are merely washers used to bring the nut N at the end of the thread when the head is near the mouth of the work, their number, therefore, depending upon the depth of the work. A bar of this kind is more rigid than a tool held in the tool post. Instead of setting the dead centre of the lathe over, the bar may be set over, as in Fig. 1145, in which the boring tool is carried in the sliding head at T, and is fed by a screw having a star feed on its end. At B is a block sliding in the end of the bar and capable of movement along the same, to adjust the degree of taper by means of the screw shown in the end view, Fig. 1146. N is a nut to secure B in its adjusted position. In this case the work must be bolted to the lathe carriage, and the tool feeds to the cut, and the largest end of the hole bored will be at the live spindle end of the lathe. But we may turn the bar around, as in Fig. 1147, driving the work in a chuck, and holding the dead centre end of the bar stationary, feeding the sliding head to the cut by the feed screw F. To increase the steadiness of the sliding head it may with advantage, be made long, as in Fig. 1148, in which S is a long sleeve fitting to the bar B at the head end H, and recessed as denoted by the dotted lines. The short cutting tool C may be fastened to H by a set-screw in the end of H, or by a wedge, as may be most desirable. The bar may obviously set over to bore tapers as in the cut, and the sliding head may be prevented from turning by a driver resting on the top of the tool rest, and pushed by a tool secured to the tool post, the self-acting carriage feed being put in operation. [Illustration: Fig. 1147.] [Illustration: Fig. 1148.] It is obvious that when a boring bar is set over to bore a taper, the lathe centres do not bed fair in the work centres, hence the latter are subject to excessive wear and liable to wear to one side more than to another, thus throwing the bar out of true and altering the taper it will bore. This, however, may be prevented by fitting to the bar at each end a ball-and-socket centre, such as shown in section in Fig. 1149. A spherical recess is cut in the bar, a spherical piece is fitted to this recess and secured therein by a cap as shown, the device having been designed by Mr. George B. Foote. [Illustration: Fig. 1149.] BORING DOUBLE TAPERS.--To prevent end play in journal bearings where it is essential to do so, the form of journal shown in Fig. 1150 is sometimes employed, hence the journal bearing requires to be bored to fit. [Illustration: Fig. 1150.] [Illustration: Fig. 1151.] Fig. 1151 represents a bearing box for such a journal, the brasses A, B having flanges fitting outside the box as shown. The ordinary method of doing such a job would be to chuck the box on the face plate of the lathe, setting it true by the circle (marked for the purpose of setting) upon the face of the brasses, and by placing a scribing point tool in the lathe tool post and revolving the box, making the circle run true to the point, which would set the box one way, and then setting the flanges of the box parallel with the face plate of the lathe to set the box true the other way; to then bore the box half way through from one side and then turn it round upon the face plate, reset it and bore the other half; thus the taper of the slide rest would not require altering. This plan, however, is a tedious and troublesome one, because, as the flanges protrude, parallel pieces have to be placed between them and the lathe face plate to keep them from touching; and as the face of the casting may not be parallel with the slide ways, and will not be unless it has been planed parallel, pieces of packing, of paper or tin, as the case may be, must be placed to true the ways with the face plate, and the setting becomes tedious and difficult. But the two tapers may be bored at one chucking, as shown in Fig. 1152, in which A represents the lathe chuck, and B is a sectional view of the bearing chucked thereon, C, C being the parallel pieces. Now it will be observed that the plane of the cone on the front end and on one side stands parallel with the plane of the cone on the back end at an exactly opposite diameter, as shown by the dotted lines D and E. If then the top slide of the lathe rest be set parallel with those lines, we may bore the front end by feeding the tool from the front of the bore to the middle as marked from F to G, and then, by turning the turning tool upside down, we may traverse or feed it along the line from H to J, and bore out the back half of the double cone without either shifting the set of the lathe rest or chucking the box after it is once set. [Illustration: Fig. 1152.] In considering the most desirable speed and feed for the cutting tools of lathes, it may be remarked that the speeds for boring tools are always less than those for tools used on external diameters, and that when the tool rotates and the work is stationary, the cutting speed is a minimum, rarely exceeding 18 feet per minute, while the feed, especially upon cast iron, is a maximum. The number of machines or lathes attended by one man may render it desirable to use a less cutting speed and feed then is attainable, so as to give the attendant time to attend to more than one, or a greater number of lathes. In the following remarks outside work and a man to one lathe is referred to. The most desirable cutting speeds for lathe tools varies with the rigidity with which the tool is held, the rigidity of the work, the purpose of the cut, as whether to remove metal or to produce finish and parallelism, the hardness of the metal and stoutness of the tool, the kind of metal to be cut, and the length the tool may be required to carry the cut without being reground. The more rigid the tool and the work the coarser the feed may be, and the more true and smooth the work requires to be the finer the feed. In a roughing cut the object is to remove the surplus metal as quickly as possible, and prepare the work for the finishing cut, hence there is no objection to removing the tool to regrind it, providing time is saved. Suppose, for example, that at a given speed and feed the tool will carry a cut 12 inches along the work in 20 minutes, and that the tool would then require regrinding, which would occupy four minutes, then the duty obtained will be 12 inches turned in 24 minutes; suppose, however, that by reducing the speed of rotation, say, one-half, the tool would carry a cut 24 inches before requiring to be reground, then the rate of tool traverse remaining the same per lathe revolution, it would take twice as long (in actual cutting time) to turn a foot in length of the work. If we take the comparison upon two feet of work length, we shall have for the fast speed 24 inches turned in 40 minutes of actual cutting time, and 10 minutes for twice grinding the tool, or 24 inches in 50 minutes; for the slow speed of rotation we shall have 24 inches turned in 80 minutes. In this case therefore, it would pay to run the lathe so fast that the tool would require to be ground after every foot of traverse. But in the case of the finishing cut, it is essential that the tool carry the cut its full length without regrinding, because of the difficulty of resetting the tool to cut to the exact diameter. It does not follow from this that finishing cuts in all cases require to be taken at a slower rate of cutting speed, because, as a rule, the opposite is the case, because of the lightness of the cut; but in cases where the work is long, the rate of cutting speed for the finishing cut should be sufficiently slow to enable the tool to take a cut the whole work length without grinding, if this can be done without an undue loss of time, which is a matter in which the workman must exercise his judgment, according to the circumstances. In tools designed for special purposes, and especially upon cast iron the work being rigid the tool may be carried so rigidly that very coarse feeds may be used to great advantage, because the time that the cutting edge is under cutting duty is diminished, and the cutting speed may be reduced and still obtain a maximum of duty; but the surfaces produced are not, strictly speaking, smooth ones, although they may be made to correct diameter measured at the tops of the tool marks, or as far as that goes at the bottom of the tool marks also, if it be practicable. In the following table of cutting feeds and speeds, it is assumed that the metals are of the ordinary degree of hardness, that the conditions are such that neither the tool nor the work is unduly subject to spring or deflection, and that the tool is required to carry a cut of at least 12 inches without being reground; but it may be observed that the 12 inches is considered continuous, because on account of the tool having time to cool, it would carry more than the equivalent in shorter cuts, thus if the work was 2 inches long and the tool had time to cool while one piece of work was taken out and another put in the lathe, it would probably turn up a dozen such pieces without suffering more in sharpness than it would in carrying a continuous cut of 12 inches long. The rates of feed here given are for work held between the lathe centres in the usual manner. CUTTING SPEEDS AND FEEDS. FOR WROUGHT IRON. +---------+--------+-----------+-------------+-----------+------------+ | Work |Roughing| Roughing |Feed as lathe| Finishing | Finishing | |diameter.| cuts. | cuts. | revolutions |cuts. Lathe| cuts. Lathe| | Inches. |Feet per| Lathe | per inch of |revolutions| revolutions| | | minute.|revolutions| tool travel.|per minute.| per inch | | | |per minute.| | |tool travel.| |---------+--------+-----------+-------------+-----------+------------| | 1/2 | 40 | 305 | 30 | 305 | 60 | | 1 | 35 | 133 | 30 | 133 | 60 | | 1-1/2 | 30 | 76 | 30 | 76 | 60 | | 2 | 28 | 53 | 25 | 53 | 60 | | 2-1/2 | 28 | 42 | 25 | 42 | 50 | | 3 | 28 | 35 | 25 | 35 | 50 | | 3-1/2 | 26 | 28 | 25 | 30 | 50 | | 4 | 26 | 24 | 20 | 26 | 50 | | 5 | 25 | 18 | 20 | 21 | 50 | | 6 | 25 | 15 | 20 | 16 | 50 | | CAST IRON. | | 1 | 45 | 163 | 30 | 163 | 40 | | 1-1/2 | 45 | 135 | 25 | 135 | 30 | | 2 | 40 | 76 | 25 | 76 | 25 | | 2-1/2 | 40 | 61 | 20 | 61 | 20 | | 3 | 35 | 44 | 20 | 50 | 16 | | 3-1/2 | 35 | 38 | 18 | 43 | 16 | | 4 | 35 | 33 | 18 | 38 | 16 | | 4-1/2 | 30 | 25 | 16 | 28 | 14 | | 5 | 30 | 22 | 16 | 26 | 14 | | 5-1/2 | 30 | 20 | 14 | 24 | 12 | | 6 | 30 | 19 | 14 | 22 | 12 | | BRASS. | | 1/2 | 120 | 910 | 25 | 910 | 40 | | 3/4 | 110 | 556 | 25 | 556 | 40 | | 1 | 100 | 382 | 25 | 382 | 40 | | 1-1/4 | 90 | 275 | 25 | 275 | 40 | | 1-1/2 | 80 | 203 | 25 | 203 | 40 | | 1-3/4 | 80 | 174 | 25 | 174 | 40 | | 2 | 75 | 143 | 25 | 143 | 40 | | 2-1/2 | 75 | 114 | 25 | 114 | 40 | | 3 | 70 | 89 | 25 | 89 | 40 | | 3-1/2 | 70 | 76 | 25 | 76 | 40 | | 4 | 70 | 66 | 25 | 66 | 40 | | 4-1/2 | 65 | 55 | 25 | 55 | 40 | | 5 | 65 | 50 | 25 | 50 | 40 | | 5-1/2 | 65 | 45 | 25 | 45 | 40 | | 6 | 65 | 41 | 25 | 41 | 40 | | TOOL STEEL. | | 3/8 | 24 | 245 | 60 | 245 | 60 | | 1/2 | 24 | 184 | 60 | 184 | 60 | | 5/8 | 24 | 147 | 50 | 147 | 60 | | 3/4 | 24 | 122 | 40 | 122 | 60 | | 7/8 | 20 | 87 | 30 | 87 | 60 | | 1 | 20 | 76 | 30 | 76 | 60 | | 1-1/4 | 20 | 61 | 25 | 61 | 50 | | 1-1/2 | 18 | 45 | 25 | 45 | 50 | | 2 | 18 | 34 | 25 | 34 | 50 | | 2-1/2 | 18 | 27 | 25 | 27 | 50 | | 3 | 18 | 22 | 25 | 22 | 40 | | 3-1/2 | 18 | 19 | 25 | 19 | 40 | | 4 | 18 | 17 | 25 | 17 | 40 | | 4-1/2 | 18 | 15 | 25 | 15 | 40 | +---------+--------+-----------+-------------+-----------+------------+ These cutting speeds and feeds are not given as the very highest that can be attained under average conditions, but those that can be readily obtained, and that are to be found used by skilful workmen. It will be observed that the speeds are higher as the work is smaller, which is practicable not only on account of the less amount of work surface in a given length as the diameter decreases, but also because with an equal depth of cut the tool endures less strain in small work, because there is less power required to bend the cutting, as has been already explained. When it is required to remove metal it is better to take it off at a single cut, even though this may render it necessary to reduce the cutting speed to enable the tool to stand an increase of feed better than excessive speed. Suppose, for example, that a pulley requires 1/4 inch taken off its face, whose circumference is 5 feet and width 8 inches. Now the tool will carry across a cut reducing the diameter 1/8 inch, at a cutting speed of 40 feet per minute, or 10 lathe revolutions per minute; but if the speed be reduced to about 35 feet per minute, the tool would be able to stand the full depth of cut required, that is, 1/8 inch deep, reducing the diameter of the pulley 1/4 inch. Now with the fast speed two cuts would be required, while with the slow one a single cut would serve; the difference is therefore two to one in favor of the deep cut, so far as depth of cut is concerned. The loss of time due to the reduced rotative speed of work would of course be in proportion to that reduction, or in the ratio of 35 to 50. It is apparent then that the tool should, for roughing cuts, be set to take off all the surplus metal at one cut, whenever the lathe has power enough to drive the cut, and that the cutting speed should be as fast as the depth of cut will allow. Concerning the rate of feed, it is advisable in all cases, both for roughing and finishing cuts, to let it be as coarse as the conditions will permit, the rates given in the table being in close approximation of those employed in the practice of expert lathe hands. It is to be observed, however, that under equal conditions, so far as the lathe and the work is concerned, it is not unusual to find as much difference as 30 per cent. in the rate of cutting speed or lathe rotation, and on small work 50 per cent. in the rate of tool traverse employed by different workmen, and here it is that the difference is between an indifferent and a very expert workman. An English authority (Mr. Wilson Hartnell), who made some observations (in different workshops and with different workmen) on this subject, stated that taking the square feet of work surface _tooled_ over in a given time, he had often found as much as from 100 to 200 per cent. difference, and that he had found the rate of _tooling_ small fly-wheels vary from 2 to 8 square feet per hour without any sufficient reason. The author has himself observed a difference of as much as 20 feet of work rotation per minute on work of 18 and less inches in diameter, and as much as 50 per cent. in the rate of tool traverse per lathe revolution. It is only by keeping the speed rotation at the greatest consistent with the depth of cut, and by exercising a fine discretion in regulating the rotations of feed and cutting speed, that a maximum of duty can under any given conditions be obtained. It has hitherto been assumed that the workman's attention is confined to running one lathe, but cases are found in practice where the lathes, having automatic feed and stop motions, one man can attend to several lathes, and in this case the feeds and speeds may be considerably reduced, so as to give the operator time to attend to a greater number of lathes. As an example, in the use of automatic lathes, several of which are run by one man, the following details of the practice in the Pratt and Whitney Company's tap and die department are given. [Illustration: Fig. 1153.] Lathe Number 1.--Lathe turning tool steel 3/8 inch in diameter and 1-1/4 long, reducing the diameter of the work 1/8 inch. Revolutions of work per minute 125. Feed one inch of tool travel to 200 lathe revolutions. Lathe Number 2.--Turning tool steel 2 inches long and 1/2 inch diameter, reducing diameter 1/8 inch. Revolutions of work 100 per minute. Feed 200 lathe revolutions per inch of tool travel. Lathe Number 3.--Turning tool steel 4 inches long and 7/8 inch in diameter, reducing the diameter 1/8 inch. Revolutions of work 40 per minute. Feed 200 lathe revolutions per inch of tool travel. Lathe Number 4.--Turning tool steel 6 to 8 inches long and 1-3/16 diameter, reducing work 1/8 inch in diameter. Revolutions of work 35 per minute. Feed 200 lathe revolutions per inch of tool travel. Lathe Number 5.--Turning tool steel 8 to 10 inches long, and 2 inches in diameter, reducing diameter 1/8 inch. Lathe revolutions 30 per minute. Feed 200 lathe revolutions per inch of tool travel. Lathe Number 6.--Turning tool steel 5 inches long and 3-1/2 inches diameter, reducing diameter 3/16. Lathe revolutions 19 per minute. Feed 200 lathe revolutions per inch of tool travel. The power required to drive the work under a given depth of cut varies greatly with the following elements:-- 1st. The diameter of the work, all other conditions being equal. 2nd. The degree of hardness of the metal, all other conditions being equal. 3rd. Upon the shape of the cutting tool; and-- 4th. Upon the quality of the steel composing the cutting tool, and the degree of its hardness. That the diameter of the work is an important element in small work may be shown as follows:-- [Illustration: Fig. 1154.] [Illustration: Fig. 1155.] In Fig. 1153 let W represent a piece of work having a cut taken off it, and the line of detachment of the metal from the body of the work will be represented by the part of the dotted line passing through the depth of the cut (denoted by C). Let Fig. 1154 represent a similar tool with the same depth of cut on a piece of work of larger diameter, and it will be observed that the dotted line of severance is much longer, involving the expenditure of more power. In boring these effects are magnified: thus in Fig. 1155 let W represent a washer to be bored with the tool T, and let the same depth of cut be taken by the tool, the diameter of the work being simply increased. It is manifest that the cutting would require to be bent considerably more in the case of the small diameter of work than in that of the large, and would thus require more power for an equal depth of cut. Again, from a reference to Figs. 950 and 952, it will be observed that the height of the tool will make a difference in the power required to drive a given depth of cut, the shaving being bent more when the tool is above the centre in the case of boring tools, and below the centre in the case of outside tools. But when the diameter of the work exceeds about 6 inches, it has little effect in the respects here enumerated. The following, however, are the general rules applicable when considering the power required for the cutting of metal with lathe or planer tools. The harder the metal, the more power required to cut off a given weight of metal. The deeper the cut the less power required to cut off a given weight of metal. The quicker the feed the less power required to cut off a given weight of metal. The smaller the diameter of outside work, and the larger the diameter of inside or bored work, the less power required. Copper requires less power than brass; yellow, and other brass containing zinc, less than brass containing a greater proportion of tin. Brass containing lead requires less power than that not containing it. Cast iron requires more power than brass, but less than wrought iron; steel requires more power than wrought iron. CHAPTER XII.--EXAMPLES IN LATHE WORK. TECHNICAL TERMS USED WITH REFERENCE TO LATHE WORK.--Work held between the lathe centres is said to run true, when a fixed point set to touch its perimeter will have an equal degree of contact all around the circumference, and at any part of the length of the same when the work is cylindrical and is rotated. When such a fixed point has contact at one part more than at another of the work circumference, it is said to run "out of true," "out of truth," or not to run true. Radial or side faces (as they are sometimes called) also run true when a fixed point has equal contact (at all parts of the revolution) with the work surface. Work that is held in chucks is said to be set true when it is adjusted in the intended position. To true up is to take off the work a cut of sufficient depth to cause a fixed point to touch the work surface equally at each point in the revolution. To clean work up is to take off it a cut sufficiently deep to cause it to run true, and at the same time removes the rough surface or scale from the metal. Roughing out work is taking off a cut which reduces it to nearly the finishing size, leaving sufficient metal to take a finishing cut, and reduce it to the proper size. _Facing_ a piece of work is taking a cut off its radial face. When a radial face or surface is convex, it is said to be _rounding_ or _round_, and when it is concave it is said to be _hollow_. When a radial face is at a right angle to a cylindrical parallel surface, it is said to be _square_; but in taper work, it is said to be _square_ when it is at a right angle to the axis of the taper. _Outside work_ includes all operations performed on a piece of work except those executed within the bores of holes or recesses, which is termed inside or internal work. _Jarring_ or _chattering_ is the term applied to a condition in which the tool does not cut the work smooth, but leaves a succession of elevations and depressions on it, these forming sometimes a regular pattern on the work. In this case the projections only will have contact with the measuring tools, or with the enveloped or enveloping work surface, when the two pieces are put together. Jarring or chattering more commonly occurs in the bores of holes or upon radial surfaces, than upon plain cylindrical surfaces, unless the latter be very long and slender. It occurs more also upon brass than upon iron work, and more upon cast than upon wrought iron or steel. It is caused mainly by vibrations of either the work or the tool. It is induced by weakness (or want of support) in the work, by weakness in the tool, or by its being improperly formed for the duty. Thus, if a tool have too broad a cutting surface it will jar; if it be held out far from the tool post it may jar; if it have too keen a top face for the conditions it will jar. Jarring may almost always be remedied on brass work by reducing the keenness of the top face, giving it if necessary negative rake, as shown in Fig. 964. On iron or steel work it may be avoided by using as stiff a cutting tool as possible, holding its cutting edge as close to the tool post as convenient, and reducing the length of cutting edge to a minimum. It may be prevented sometimes by simply placing the finger or a weight upon the tool, or by applying oil to the work, but if this be done it should be supplied continuously throughout the cut, as a tool will cut to a different depth when dry from what it will when lubricated. In using hand tools such as scrapers, too thin a tool may cause jarring, which may be obviated by keeping the tool rest as close to the work as possible, and placing a piece of leather between the work and the rest. EXAMPLES IN LATHE WORK.--The simplest class of lathe work is that cut from rods or short lengths of rod metal, which may be turned by being held in a small chuck, or between the lathe centres. Such work is usually of small diameter and short length, and is therefore difficult to get at if turned between the lathe centres, because the dog that drives it, the lathe face plate, and the dead centre are in the way; such work may be more conveniently driven by a small chuck. It is usually made of round wire or rod, cut into lengths to suit the conditions; thus if the lathe have a hollow spindle, the rod lengths may be so long as to pass entirely through the spindle, otherwise the lengths may be passed through the chuck, and as far as possible into the live spindle centre hole. In any event it is desirable to let the rod project so far out from the chuck as to enable its being finished and cut off, without removal from or moving it in the chuck, because such chucks are apt in course of time to wear, so that the jaws do not grip the work quite concentric to the line of centres; hence, if the work be moved in the chuck after having been turned, it is apt to run out of true. Sometimes, however, the existence of a collar on the work prevents it from being trued for fit at both ends without being cut off from the rod, in which case, if it requires correction after being cut off, it must be rechucked, and it may be necessary at this rechucking to grip it in several successive positions (partly rotating it in the chuck at each trial) before it will run true. Sometimes the length of work that may advantageously be driven by such a chuck is so great as to render the use of the dead centre to support one end necessary, in which case the rod should be removed from the chuck before each piece is turned, so as to centre drill the dead centre end. There is one special advantage in driving small work in a chuck of this kind, inasmuch as the work can be tried for fit without removing it from the lathe, while in some cases operations can be performed on it which would otherwise require its removal to the vice; suppose, for example, a thread of very small diameter and pitch requires to be cut on the work end, then a pair of dies or a screw plate may be placed on it, and the lathe pulled round by the belt; after the dies have commenced to start the thread, they may be released and allowed to rotate with the lathe, which will show if they are starting the thread true upon the work. In cases also where the end of the work requires fitting to a seat, or where it requires turning to a conical point, there is the advantage that the work can be tried to the seat, or turned to the point without taking from the lathe, or without any subsequent operations, whereas in the case of a conical point, the existence of a work centre would necessitate turning the cone some distance from the end, and cutting off the work centre. As the size of the work increases, the form of the chuck is varied to make it more powerful and strong to resist the strains, but when the size of the chuck becomes so large that it is as much in the way as the face place would be, it is better to turn the work between the lathe centres. For work to be turned between the lathe centres, it is essential that those centres run true, and be axially in line, and that both centres be turned to the same degree of angle or cone, which is usually for small lathes an angle of 60°, and for lathes of about 30 inches swing and over an angle of about 70°. Both centres should be of an equal angle, for the following reasons. It is obvious that the work centres wear to fit the dead centre, because of the friction between the two. Now in order to turn a piece of work from end to end, it is necessary to reverse it in the lathe, because at the first turning one end is covered by the carrier or driver driving it. At the first turning one work centre only will have worn to fit the lathe centre; hence when at the second, the other work centre wears to fit the dead centre and in the process of such wearing moves (as it always does to some degree) its location, the part first turned will no longer run true. To obviate this difficulty it is proper at the first turning to cut the work down to nearly the finished size, and then reverse it in the lathe and turn up the other end. At this second turning the work will have had both work centres worn to fit the dead centre, hence if it be of the same angle as the live centre, the work will properly bed to both centres, otherwise it will plainly not bed well to the live centre, and in consequence will be apt to run in some degree out of true at the live centre end. The lathe centres should, for parallel work, stand axially true one with the other, and this can only be the case when the live centre runs true. If the live centre does not run true the following difficulties are met with. [Illustration: Fig. 1156.] If one end only of the work requires to be turned and it can be completely finished without moving the work driver, the work will be true (assuming the live spindle to run true in its bearings and to fit the same). It will also run true if the work be taken from the lathe and replaced without moving the driver or carrier, providing that the driver be so placed as to receive the driving pressure at the same end as it did when the work was driven; and it is therefore desirable, on this account alone, to always so place the work in the lathe that the driver is driven by its tail end, and not from the screw or screw head. But if the work be turned end for end it will not run true, because the work centre at the unturned end of the work will not be true or central to the turned part of the work. It is obvious then that lathe centres should run true. But this will not be the case unless the holes into which they fit in the lathe are axially true one with the other and with the lathe spindles. If these holes are true, and the centres are turned true and properly cleaned before insertion, the centres may be put into their places without any adjustment of position. Otherwise, however, a centre punch mark is made on the radial or end face of the live spindle, and another is made on the live centre, so that both for turning up and for subsequent use the centre will run true when these centre punch marks are exactly opposite to each other. The best way to true lathe centres is with an emery-wheel. In some lathes there are special fixtures for emery grinding, while in others an attachment to go in the tool post is used. Fig. 1156 shows such an attachment. In the figure A is a frame to be fastened in the slide rest tool post at the stem A´. It affords journal bearing to the hand wheel B, to the shaft of which is attached the gear-wheel C, which drives a pinion D, on a shaft carrying the emery-wheel E, the operation being obviously to rotate wheel B, and drive the emery-wheel E, through the medium of the multiplying gear-wheels C, D. The emery-wheel is fed to its depth of cut on the lathe centre P, by the cross feed screw of the lathe, and is traversed by pulling or pushing the knob F, the construction of this part of the device being as follows: G and H are two bushes, a sliding fit in the arms of frame A, but having on top flat places I and J, against which touch the ends of the two set-screws _k_, _l_, to prevent them from rotating. The emery-wheel and gear pinion D are fast together, and a pin passes through and holds G and H together. Hence the knob F pushes or pulls, as the case may be, the bushes through the bearings G, H, in the frame A, the pinion and emery-wheel traversing with them. Hence pinion D is traversed to and fro by hand, and it is to admit of this traverse that it requires its great length. The stem A is at such an angle that, if it be placed true with the line of cross feed, the lathe centre will be ground to the proper angle. Fig. 1157 represents a centre grinding attachment by Trump Brothers, of Wilmington, Delaware. In this device the emery-wheel is driven by belt power as follows. A driving wheel A is bolted to the lathe face plate, and a stand carries at its top the over-head belt pulleys, and at its base the emery-wheel and spindle. This stand at C sets over the tool post, and is secured by a bar passing through C and through the tool post, whose set-screw therefore holds the stand in position. On the end of the emery-wheel spindle is a feed lever, by means of which the emery-wheel may be fed along the lathe centre. Cup piece B is for enabling wheel A to be readily set true on the lathe face plate, one end of B fitting the hub of A, while the other receives the dead centre which is screwed up so that B will hold A in place, while it is bolted to the lathe face plate, and at the same time will hold it true. In the absence of a centre grinding attachment, lathe centres may be turned true with a cutting tool, and finished with water applied to the tool so as to leave a bright and true surface. They should not, for the finest of work, be finished by filing, even though the file be a dead smooth one, because the file marks cause undue wear both to the lathe centres and the work centres. The dead centres should be hardened to a straw color, and the live centre to a blue; the former so as to have sufficient strength to resist the strain, and enough hardness to resist abrasion, and the latter to enable it to be trued up without softening it. [Illustration: Fig. 1157.] When, after turning them up, the centres are put into their places, the tailstock may be moved up the bed so that the dead centre projects but very little from the tailstock, and is yet close to the live centre, and the lathe should be run at its fastest speed to enable the eye to perceive if the live centre runs true, and whether the dead centre is in line with the live one, and the process repeated so that both centres may be tested. A more correct test, however, may be made with the centre indicator. [Illustration: Fig. 1158.] CENTRE INDICATORS.--On account of the difficulty of ascertaining when a centre runs quite true, or when a very small hole or fine cone as a centre punch mark runs true when chucked in a lathe, the centre indicator is used to make such tests, its object being to magnify any error, and locate its direction. Fig. 1158, from _The American Machinist_, represents a simple form of this tool, designed by Mr. G. B. Foote, for testing lathe centres. A is a piece of iron about 8 inches long to fit the lathe tool post, B is a leather disk secured to A by a plate C, and serving to act as a holding fulcrum to the indicator needle, which has freedom of movement on account of the elasticity of the leather washer, and on account of the hole shown to pass through A. It is obvious that if the countersunk end of the needle does not run true, the pointed end will magnify the error by as many times as the distance from the needle point to the leather washer is greater than that from the leather washer to the countersunk end of the needle. It is necessary to make several tests with the indicator, rotating the lathe centre a quarter turn in its socket for each test, so as to prove that the centre runs true in any position in the lathe spindle. If it does not run true the error should be corrected, or the centre and the lathe spindle end may be marked by a centre punch done to show in what position the centre must stand to run true. [Illustration: Fig. 1159.] The tension of the leather washer serves to keep the countersunk against the lathe centre without a very minute end adjustment. Or the same end may be attained by the means shown in Fig. 1159, which is a design communicated by Mr. C. E. Simonds to _The American Machinist_. The holder is cupped on one side to receive a ball as shown, and has a countersink on the other to permit a free vibration of the needle. The ball is fitted to slide easily upon the needle, and between the ball and a fixed collar is a spiral spring that keeps the ball in contact with its seat in the holder. [Illustration: Fig. 1160.] One end of the needle is pointed for very small holes or conical recesses, while the other is countersunk for pointed work, as lathe centres. The countersink of the needle may be made less acute than the lathe centre, so that the contact will be at the very point of the lathe centre, the needle not being centre-drilled. The end of the needle that is placed against the work should be as near to the ball or fulcrum as convenient, so as to multiply the errors of work truth as much as possible. In some forms of centre indicators the ball is pivoted, so that the needle only needs to be removed to reverse it end for end, or for adjusting its distance, it being made a close sliding fit through the ball. Thus, in Fig. 1160 the ball E is held in a bearing cut half in the holder A, and half in cap B, which is screwed to A by screws C D. Or the ball may be held in a universal joint, and thus work more frictionless. Thus, in Fig. 1161 it is held by the conical points of two screws diametrically opposite in a ring which is held by the conical points of two screws threading through an outer ring, these latter screws being at a right angle to those in the inner ring. The outer ring is held to the holder by the conical points of two screws, all the conical points seating in conical recesses. [Illustration: Fig. 1161.] It is obvious that the contact of the point of the needle and the work may be more delicately made when there is some elasticity provided, as is the case with the spiral spring in Fig. 1159. Indicators of this class may be used to test the truth of cylindrical work: thus, in Fig. 1162 is an application to a piece of work between the lathe centres, there being fitted to one end of the needle a fork _a_ that may be removed at pleasure. [Illustration: Fig. 1162.] One of the difficulties in turning up a lathe centre to run true arises from the difference in cutting speed at the point and at the full diameter of the cone, the speed necessary to produce true smooth work at the point being too fast for the full diameter. This may be remedied on centres for small work, as, say, three inches and less in diameter, by cutting away the back part of the cone, leaving but a short part to be turned up to true the centre. To permit the cutting off or squaring tool to pass close up to the centre, and thus prevent leaving a burr or projection on the work end, the centre may be thus relieved at the back and have a small parallel relief, as in Fig. 1164 at A, the coned point being left as large as possible, but still small enough to pass within the countersink. In centres for large and heavy work it is not unusual to provide some kind of an oil way to afford means of lubrication, and an excellent method of accomplishing this object is to drill a hole A, Fig. 1163, to the axis of the centre and let it pass thence to the point as denoted by the dotted line; there may also be a small groove at B in the figure to distribute the oil along the centre, but grooves of this kind make the returning of the centre more difficult and are apt to cause the work centres to enlarge more from wear, especially in turning tapers with the tailstock set over the lathe centre, these being out of line with the work centre. To enable a broad tool such as a chaser to meet work of smaller diameter than the lathe centre, the latter is cut away on one side as in Fig. 1164. It is obvious also that the flat place being turned uppermost, will facilitate the use of the file on work of smaller diameter than the lathe centre, and that placed in the position shown in the cut, it will permit a squaring tool to pass clear down to the centre and avoid leaving the projecting burr which is left when the tool cannot pass clear down the face to the edge of the countersink of the work centre. [Illustration: Fig. 1163.] [Illustration: Fig. 1164.] The method to be employed for centring work depends upon its diameter, and upon whether its ends are square or not. When the pieces are cut from a rod or bar in a cutting-off machine, the ends are square, and they may be utilized to set the work by in centring it. Thus, in Fig. 1165 is a top, and in Fig. 1166 is an end view of a simple device, or lathe attachment for centre drilling. S is a stand bolted to the lathe shears and carrying two pins P, which act as guides to the cup chuck or work guide G; between the heads of pins P and the hubs of G are spiral springs, forcing it forward, but permitting it to advance over the drill chuck; the work W is fed forward to the drill. At the dead centre end the work is supported by a female cone centre D in the tail spindle T. The work rests in mouths of G and D, and as the pieces are cut from the rod they are sufficiently straight, and being cut off in a cutting-off machine the ends are presumably square; hence the coned chucks will hold them sufficiently true with the ends, and the alignment of the centre drilled holes will not be impaired by any subsequent straightening processes; for it is to be observed, that if work is centre-drilled and straightened afterwards, the straightening throws the centre holes out of line one with the other, and the work will be more liable to gradually run out of true as its centres wear. [Illustration: Fig. 1165.] Thus, in Fig. 1167, let W represent a bent piece of work centre-drilled, and the axis of the holes will be in line as denoted by the dotted line, but after the piece is straightened the holes will lie in the planes denoted by the dotted line in Fig. 1168, and there will be a tendency for the work centres to move over towards the sides C D as the wear proceeds. [Illustration: Fig. 1166.] In Fig. 1169 is shown a centre-drilling machine, which consists of a live spindle carrying the centre-drilling tool, and capable of end motion for the drill feed. The work is held in a universal chuck, and if long is supported by a stay as shown in the figure. The axis of the work being in line with that of the chuck, the work requires no setting. [Illustration: Fig. 1167.] In this case the centre hole will be drilled true with that part of the work that is held in the chuck, and the alignment of the centre hole will depend upon the length of the rod being supported with its axis in line with the live spindle. If the work is not straightened after drilling, the results produced are sufficiently correct for the requirements; but it follows from what has been said, that work which requires to be straightened and tried for straightness in the lathe should be centred temporarily and not centre-drilled until after the straightening has been done. [Illustration: Fig. 1168.] In Fig. 1170 is shown a combined centre-drill and countersink not unfrequently used in centring machines. The objection to it is, that the cutting edges of the drill get dull quicker than those of the countersink, and in regrinding them the drill gets shorter. Of course the drill may be made longer than necessary so as to admit of successive grindings, but this entails drilling the centre holes deeper than necessary, until such time as the drill has worn to its proper length. To overcome this difficulty the countersink may be pierced to receive a drill as in Fig. 1171, the drill being secured by a set-screw S. [Illustration: Fig. 1169.] Among the devices for centring work by hand, or of pricking the centre preparatory for centre-drilling, are the following:-- [Illustration: Fig. 1170.] [Illustration: Fig. 1171.] In Fig. 1172 is a centre-marking square. A B C D represents the back and E the blade of the square. Suppose then that the dotted circle F represents the end of a piece of work, and we apply the square as shown in the cut and mark a line on the end of the work, and then moving the square a quarter turn around the work, draw another line, the point of contact of these two lines (as at G in the cut) will be the centre of the work, or if the work is of large diameter as denoted by the circle H H, by a similar process we obtain the centre E. In this case, however, the ends A B of the square back must be of equal lengths, so that the end faces at A B will form a right angle to the edge of the blade, and this enables the use of the square for ordinary purposes as well as for marking centres. [Illustration: Fig. 1172.] The point _a_ of the centre punch shown in Fig. 1173 is then placed at the intersection of the two lines thus marked, and a hammer blow produces the required indentation. The centre punch must be held upright or it will move laterally while entering the metal. The part _b_ of the centre punch is tapered so as to obstruct the vision as little as possible, while it is made hexagon or octagon at the upper end to afford a better grip. By increasing the diameter at C, the tool is stiffened and is much less liable to fly out of the fingers when the hammer blow does not fall quite fair. [Illustration: Fig. 1173.] In Fig. 1174 is shown a device for guiding the centre punch true with the axis of the work, so as to avoid the necessity of finding the same by lines for the centres. It consists of a guide piece B and a parallel cylindrical centre punch A, C representing a piece of work. B is pierced above with a parallel hole fitting and guiding the centre punch, and has a conical hole at the lower end to rest on the work, so that if the device be held upright and pressed down upon the end of the work, and the top of the centre punch is struck with the hammer, the indentation made will be central to the points of contact of the end of the work with the coned hole of B. If then the end of the work has no projecting burrs the centring will be centred true. [Illustration: Fig. 1174.] [Illustration: Fig. 1175.] In the absence of these devices, lines denoting the location for the conical recess or centre may be made, when either of the following methods may be pursued. [Illustration: Fig. 1176.] [Illustration: Fig. 1177.] [Illustration: Fig. 1178.] In Fig. 1175 is shown what is known as a pair of hermaphrodite calipers, which consists of two legs pivoted at the upper end; the bent leg is placed against the perimeter of the work, as shown, and held steadily, while with the point a line is marked on the work. This operation is performed from four equidistant (or thereabouts) points on the work, which will appear as shown in Fig. 1176, providing the radius to which the point was set be equal to the radius of the work. The point at which the lines meet is in this case the location for the centre. If, however, the radius to which the points are set is less than the radius of the work, the lines will appear as in Fig. 1177, in which case the location is in the centre of the inscribed square, as denoted by the dot; or if the radius be set too great the lines will appear as in Fig. 1178, and the location for the centre will again be as denoted by the dot. [Illustration: Fig. 1179.] Another and very old method of marking these lines is to place the work on a pair of parallel pieces and draw the lines across it, as shown in Fig. 1179, in which W represents the work, P, P the parallel pieces of equal thickness, S a stand (termed a scribing block) carrying a needle N, which is held by a thumb screw and bolt at B. The point of the needle is adjusted for the centre of the work, a line is drawn, the work is then rotated, another line drawn, and so on, until the four lines are drawn as in Fig. 1180, when the work may be turned end for end if light, or if heavy the scribing block may be moved to the other end of the work. [Illustration: Fig. 1180.] The centre locations are here made true with the part of the work that rests on the parallel pieces, and this is in some cases an essential element in the centring. Thus, in Fig. 1181, it is required to centre a piece true with the journals A B, and it is obvious that those journals may be rested on parallel pieces P, P, and the centres marked by the scribing block on the faces E, F in the manner before described. [Illustration: Fig. 1181.] If there is a spot in the length of a long piece of work where the metal is scant and out of round, so that it is necessary to centre the work true by that part, the surface gauge and parallel pieces may be used with advantage, but for ordinary centring it is a slow process. When a piece of work is not cylindrical, and it is doubtful if it will clean up, the centring requires care, for it must not always be assumed, that if two diametrically opposite points meet the turning tool at an equal depth of cut, the piece is centred so as to true up to the largest possible diameter. [Illustration: Fig. 1182.] This is pointed out in Fig. 1182, which is extracted from an article by Professor Sweet. "In a piece of the irregular form A, the points _a_ and _b_ might be even and still be no indication of the best location for the centre, and in the piece B it is evident that if _c_ and _d_ were even, nothing like the largest cylinder could be got from it. In the case of shape A, the two points _e_ and _f_ should be equidistant from the centre, and in the case of shape B, the three points _g_, _h_, _i_ should be equidistant from the centre." The depth of the centre drill holes should be such as to leave them in the work after it is cut off to its proper length, and will, therefore, be deeper as the amount to be cut off is greater. The diameter of the centre drill is larger as the size of the work increases, and may be stated as about 3/64 for work of about 1/2 inch, increasing up to 1/8 inch for work of about an inch, and up to three inches in diameter; for work of a foot or over the centre drill may be 3/16 inch in diameter. [Illustration: Fig. 1183.] The centre drilling and countersinking may, when the work is cut to length, be performed at one operation, but when it requires to be cut to length in the lathe, that should be done before the countersinking. A very simple chuck for centre drilling is shown in Fig. 1183, with a twist drill (which is an excellent tool for centre-drilling). If the work is held in the hand and fed to the drill by the lathe dead centre, the weight of the work will cause the hole to be out of straight with the work axis, unless the grip is occasionally relaxed, and the work made to rotate a half or a quarter turn as the drilling proceeds. After the work is centre-drilled and cut off to length, it must be finally countersunk, so as to provide ample bearing area for the lathe centres. [Illustration: Fig. 1184.] The countersinking should be true to the centre hole; and it is sometimes made to exactly fit the lathe centres, and in other cases it is made more acute than the lathe centre, so that the oil may pass up the countersink, while it is bedding itself to the lathe centres. If the countersinking is done before the end of the work is squared, it will not be true with the centre-drilled hole. In order that the countersinking may wear true with the centre-drilled hole, it may be made of a more obtuse angle (as, say, one degree) than the lathe centre, as in Fig. 1184, so that the hole may form a guide to cause the lathe centre to wear the countersinking true to the hole, and thus correct any error that may exist. [Illustration: Fig. 1185.] If the countersink is made more acute than the lathe centre, as shown in Fig. 1185, the wear of its mouth will act as a guide, causing the centre to be true with the countersinking; and when the bearing area extends to the centre-drilled hole, there will be introduced, if that hole does not run true, an element tending to cause the work to run out of true again, because the countersinking will have more bearing area on one side than on the other. It is to be observed, however, that if the difference between the countersink angle and that of the lathe centre be not more than about one degree, the work centre will bed itself fully to the lathe centre very rapidly, and usually before the first cut is carried over the work, unless the work centres have been made to have unduly large countersinks. [Illustration: Fig. 1186.] Fig. 1186 represents a half-round countersink, in which the cutting edge is produced by cutting away the coned point slightly below the dotted axial line. This secures two advantages: first, it gives the cutting edge clearance without requiring the grinding or filing such clearance; and, secondly, the cone being the same angle as the lathe centres, filing away more than half of it causes it to give the lathe centre at first a bearing at the small end of the countersink, as in Fig. 1184, and this secures the advantage mentioned with reference to that figure. It is obvious that such a reamer, however, does not produce strictly a cone countersink, as is shown in Fig. 1187, where the cutting away of the cone is carried to excess simply to explain the principle, and the cone becomes an hyperbolic curve. The small amount, however, that it is necessary to carry the face below the line of centres, practically serves to make the cone somewhat less acute, and is not therefore undesirable. [Illustration: Fig. 1187.] Another method of forming the half-round countersink is shown in Fig. 1188, in which the cone is of the same angle as the lathe centres; the back A is ground away to avoid its contact with the work and give clearance, while clearance to the cutting edge is obtained by filing or grinding a flat surface B at the necessary angle to the upper face of the cone. In this case it is assumed that the centre-drilling and countersinking are true one with the other. Yet another form of countersink is shown in Fig. 1189, consisting of a cone having three or four teeth. It may be provided with a tit, which will serve as a guide to keep the countersink true with the hole, and this tit may be made a trifle larger in diameter than the hole, and given teeth like a reamer, so as to ream the hole out while the countersinking is proceeding. [Illustration: Fig. 1188.] [Illustration: Fig. 1189.] Unless one side of a half-round reamer is filed away so as to give the cutting edge alone contact with the bore of the hole, an improper strain is produced both upon the work and the countersink. In Fig. 1190, for example, is shown, enlarged for clearness of illustration, a hole, and a half-round countersink in section, and it is evident that if the countersink is set central to the hole, it will have contact at A and at B, and A cannot enter the metal to cut without springing towards C. [Illustration: Fig. 1190.] [Illustration: Fig. 1191.] But when the lathe has made rather more than one-half a revolution, the forcible contact at B will be relieved, and either the work or the countersink will move back towards D. This may be remedied by setting the countersink to one side, as in Fig. 1191, or by cutting it away on one side, as in Fig. 1192, when the half-round reamer will, if the work be rigidly held while being countersunk, act as a cutting tool. But it is more troublesome to hold the work rigidly while countersinking it than it is to simply hold it in the hands, and for these reasons the square centre is an excellent tool to produce true countersinking. [Illustration: Fig. 1192.] [Illustration: Fig. 1193.] [Illustration: Fig. 1194.] Fig. 1193 represents a square centre, the conical end being provided with four flat sides, two of which appear at A B, or it may have three flat sides which will give it keener cutting edges, and will serve equally well to keep it true with the drilled hole. But it is questionable whether it is not an advantage not to have the cutting edges so keen as is given by the three flat faces, because the less keen the cutting edges are, the more true the countersinking will be with the hole, the extra pressure required to feed the square centre tending to cause it to remain true with the hole notwithstanding any unequal density of the metal on different sides of the hole. An objection to the square centre is that it involves more labor in the grinding to resharpen it, and is not so easy to grind true, but for fine work this is more than compensated for in the better quality of its work. [Illustration: Fig. 1195.] [Illustration: Fig. 1196.] This labor, however, may be lessened in two ways: first, the faces may be fluted, as in Fig. 1194, at A and at B, or its diameter may be turned down, as in Fig. 1195. In using the square centre it is placed in the position of the live centre and revolved at high speed, all the cutting edges operating simultaneously; the work is fed up by the dead centre and held in the hand. To prevent the weight of the work from causing the countersinking being out of true with the hole, the work should be occasionally allowed (by relaxing the grip upon it) to make part of a revolution, as explained with reference to centre-drilling without a work guide. Another and simple form of square centre for countersinking is shown in Fig. 1196. It consists of a piece of square steel set into a stock or holder. [Illustration: Fig. 1197.] Work that is to be hardened and whose centres are, therefore, liable to warp in the hardening, may be countersunk as in Fig. 1197, there being three indentations in the countersink as shown. This insures that there shall be three points of contact, and the work will run steadily and true. Furthermore, the indentations form passages for the oil, facilitating the lubrication and preventing wear both to the work and to the lathe centres. [Illustration: Fig. 1198.] These indentations are produced after the countersinking by the punch, shown in Fig. 1198. Except when tapers are turned by setting the lathe centres out of line with the lathe shears (as in setting the tailstock over), all the wear falls on the dead centre end of the work, as there is no motion of the work centre on the live centre, hence the work centres will not have worn to a full bearing until the work has been reversed end for end in the lathe. [Illustration: Fig. 1199.] [Illustration: Fig. 1200.] If it be attempted to countersink a piece of work whose end face is not square, the countersinking will not be true with the centre hole, and furthermore the causes producing this want of truth will continue to operate to throw the work out of true while it is being turned. Thus, in Fig. 1199, _a_ represents a piece of work and B the dead centre; if the side C is higher than side D of the work end, the increased bearing area at C will cause the most wear to occur at D, and the countersink in the work will move over towards D, and it follows that the face of a rough piece of work should be faced before being countersunk. Professor Sweet designed the centre-drilling device shown in Fig. 1200, which consists of a stock fitting the holes for the lathe centres, and carrying what may be called a turret head, in which are the centre drills, facing tools, and countersinks. The turret has 6 holes corresponding to the number of tools it carries, and each tool is held in position by a pin, upon a spring, which projects into the necessary hole, the construction being obvious. The facing tool is placed next to the drill and is followed by a countersink, in whatever direction the turret is rotated to bring the next tool into operation. The work should, on account of the power necessary for the facing, be driven in a chuck. [Illustration: Fig. 1201.] A similar tool, which may, however, be used for other work besides centring and countersinking, is shown in Fig. 1201. It consists of a stem fitting into the hole of the tail spindle, and carrying a base having a pin D, on which fits a cap having holes _b_, and set-screws C for fastening drills, countersinks, or cutting tools. The cap is pierced with six taper holes, and a pin projects through the base into these holes to lock the cap in position, this pin being operated by the spring lever shown. [Illustration: Fig. 1202.] Work that has already been turned, but has had its centres cut off, may be recentred as follows. One end may be held and driven by a chuck, while the other end is held in a steady rest such as was shown in Fig. 802, and the centre may then be formed in the free end by a half-round reamer, such as shown in Fig. 1190, placed in the position of the dead centre, or the square centre may be used in place of the dead centre, being so placed that one of its faces stands vertically, and therefore that two of its edges will operate to cut. The location for the work centre should be centre punched as accurately as possible, and the work is then placed in the lathe with a driver on it, as for turning it up; a crotch, such as shown in Fig. 1202, is then fastened in the lathe tool post, and fed up by the cross-feed screw until it causes the work to run true, and the square centre should then be fed slowly up and into the work, with a liberal supply of oil. If the work runs out of true, the crotch should be fed in again, but care must be taken not to feed it too far. So long as the square centre is altering the position of the centre in the work, it will be found that the feed-wheel of the tailstock will feed by jumps and starts; and after the feeding feels to proceed evenly, the crotch may be withdrawn and the work tried for being true. The crotch, as well as the square centre, should be oiled to prevent its damaging the work surface. It is obvious that in order to prevent the lathe dead centre point from seating at the point or bottom of the work centre, the square centre should be two or three degrees more acute in angle than the lathe dead centre. If the work is tried for truth while running on the square centre, the latter is apt to enlarge the work centre, while the work will not run steadily, hence it is better (and necessary where truth is a requisite) to try the work with the dead centre in place of the square one. In thus using a square centre to true work, great care should be taken not to cut the work centres too large, and this may be avoided by making the temporary centre-punch centres small, and feeding the crotch rapidly up to the work, until the latter runs true, while the square centre is fed up only sufficiently to just hold the work steady. [Illustration: Fig. 1203.] To test the truth of a piece of rough work, it may, if sufficiently light, be placed between the lathe centres with a light contact, and rotated by drawing the hand across it, a piece of chalk being held in the right hand sufficiently near to just touch the work, and if the chalk mark extends all round the work, the latter is as true as can be tested by so crude a test, and a more correct test may be made by a tool held in the tool rest. If the test made at various positions in the length of the work shows the work to be bent enough to require straightening, such straightening may be done by a straightening lever. In shops where large quantities of shafting are produced, there are special straightening tools or devices: thus, Figs. 1203 and 1204 represent two views of a straightening machine. The shaft to be straightened is rotated by the friction caused by its own weight as it lies between rollers, which saves the trouble of placing the shaft upon centres. Furthermore, the belt that is the prime mover of the gears driving these rollers is driven from the line shaft itself without the aid of any belt pulley. The tension of this driving belt is so adjusted that it will just drive the heaviest shaft the machine will straighten; but if the operator grasps the shaft in his hand, the driving mechanism will stop and the belt will slip, the shaft remaining stationary until the operator sets it in motion again with his hand, when the belt ceases to slip and the mechanism again acts to drive the shaft. Fig. 1203 represents the mechanism for driving the shaft S, to be straightened, which lies upon and between two rollers, R, R´. Upon the shafts of these rollers are the gear-wheels A and B, which are in gear with wheel C, the latter being driven by gear-wheel D. Motion to D is derived from a pair of gears, the pinion of which is driven by the belt from the line shaft. H is a head carrying all these gears (and the rollers) except D. There are two of these heads, one at each end of the machine, the two wheels D being connected by a rod running between the shears, but the motion is communicated at one end only of this rod, the shaft is driven between four rollers, of which two, R R´, are shown in the engraving. [Illustration: Fig. 1204.] [Illustration: Fig. 1205.] In Fig. 1204 the straightening device is shown. A frame consisting of two parts, F, F´, is gibbed to the edge of the shears at G and H. The upper part of this frame carries a square-threaded screw I, and is capable of sliding across the shears upon the part F´. It rests upon the shears through the medium of four small rollers (which are encased), two of which are at J, K, and two are similarly situated at the back of the frame F´. The motion of F across the machine is provided so that the upper part F may be pushed back out of the way, to permit the shaft being easily put on and taken off the friction rollers R R´. The motion along the shears is provided to enable the straightening device to be moved to the required spot along the shaft S´. The shaft S is laid on two pieces N, P, and a similar piece _r_ is placed above to receive the pressure of the screw I, which is operated by a hand lever to perform the straightening. The pieces N, P rest upon two square taper blocks V, which are provided with circular knobs at their outer ends to enable them to be held and pushed in or pulled out so as to cause N, P to meet the shaft before I is operated. This is necessary to accommodate the different diameters of shaft S. The operator simply marks the rotating shaft with chalk in the usual manner to show where it is out of true, and then straightens wherever it is found necessary. Fig. 1205 represents a similar device for straightening rods or shafts while they are in the lathe. A is a frame or box which is fitted to rest on the [V]s of the lathe shears, the straightening frame resting on the box. Instead, however, of simply adjusting the height of the pieces P to suit different diameters of the shaft, the whole frame is adjusted by means of the wedge W, which is inserted between the frame F and the upper surface of the box A. At H is a hole to admit the operator's hand to move A along the lathe shears. [Illustration: Fig. 1206.] A method of straightening wire or small rods that are too rigid to be straightened by hand, and on which it is inadvisable to use hammer blows, is shown in Fig. 1206. It consists of a head revolved in a suitable machine, and having a hole passing endways through it. In the middle is a slot and through the body pass the pins A, being so located that their perimeters just press the rod or wire when it is straight, and in line with the axis of the bore through the head, each successive pin A touching an opposite side of the wire or rod. It is obvious that these pins in revolving force out any crooks or bent places in the wire or rod, and that as the work may be pulled somewhat rapidly through the head or frame, the operation is a rapid one. When pieces of lathe work are to be made from rod or bar iron, they should be cut off to the proper length in a cutting-off machine, such as described in special forms of the lathe, and for the reasons set forth in describing that machine. An excellent tool, however, for cutting up rods of not more than 1/2 inch in diameter, is Elliott's cutting-off tool shown in Fig. 1207. It consists of a jaw carrying steadying pieces for the rod to be cut up, these pieces being adjusted to fit the rod by the screw and nut shown. On the same jaw is pivoted a tool-holder, carrying a cutting-off tool, which is fed to its cut by the upper handle being pressed towards the lower one. An adjustable stop or gauge is attached, by means of a small rod, to the swinging arm which carries the cutting tool, and can be removed when its use is not desirable. [Illustration: Fig. 1207.] The operation of this tool is as follows:--The rod to be cut up is held in the lathe chuck, projecting beyond any desired distance, and arranged to revolve at the same speed as for turning. The tool is placed upon the rod, and the movable jaw of the rest adjusted to a bearing. If several pieces are to be cut to a length, the gauge is adjusted, the tool moved along the rod till the gauge-stop comes in contact with the end, the handles pressed together, which moves the cutting tool up to the work in such a way that it will come exactly to the centre, thus cutting the piece entirely off, no adjustment of the tool ever being necessary to provide for its cutting to the centre, except keeping the cutting edge (which is not in this respect changed by grinding) at a distance specified in the directions from the part in which it is clamped. As the tool is moved up to cut, by the same operation the gauge is moved back out of contact with the end. When the pressure on the handles is removed, a spring returns the cutting tool to its original position, and also brings the gauge in position for determining the length of the next piece to be cut. The operation is repeated by simply moving the tool along the rod, the cutting up being done with great rapidity and accuracy. It will be noticed that all the appliances for cutting, gauging, &c., being a part of the tool itself, if the rod runs out of truth--in other words, wabbles--it will have no effect on the cutting, the rod to be cut forming the gauge for all the operations required; also that comparatively no time is lost in adjustment between the several pieces to be cut from a rod. The cutting tool is a piece of steel of the proper thickness, cleared on the sides by concave grinding. It is held in place by a clamp and two small screws, and requires grinding on the end only. When the work is centred, it should, for reasons already explained, have its end faces trued up. In doing this, however, it is desirable in some cases to cut off the work to its exact finished length. This possesses the advantage, that when the work is finished, the work centres will be left intact, and the work may be put into the lathe at any time, and it will run true to the original centres. But this is not always the best plan; suppose, for example, that there are a number of collars or flanges on the work, then it is better to leave a little extra length to the work when truing up the ends, so that if any of the collars are scant of metal, or if it be desirable to turn off more on one side of a collar than on another, as may be necessary to turn out a faulty place in the material, the end measurements on the work may be conformed to accommodate this requirement, and not confined to an exact measurement from the end of the work. Again, in the case of work having a taper part to be fitted, it is very difficult to obtain the exact proper fit and entrance of taper to an exact distance, hence it is best to leave the work a little too long, with its collars too thick, and to then fit the taper properly and adjust all other end measurements to suit the taper after it is fitted. Before any one part of a piece of work turned between the lathe centres is finished to diameter, all the parts to be turned should be roughed out, and for the following reasons, which apply with additional force to work chucked instead of being turned between the lathe centres. It is found, that all iron work changes its form if the surface metal be removed from it. Thus, though the lathe centres be true, and a piece of work be turned for half its length in the lathe, after it has been turned end for end in the lathe to turn the other half of its length, the part already turned will run out of true after the second half is turned up. This occurs from the tension and unequal internal strains which exist in the metal from its being forged or rolled at a constantly diminishing temperature, and from the fact that the surface of the metal receives the greatest amount of compression during the forging. In castings it is caused by the unequal and internal strains set up by the unequal cooling of the casting in the mould, because of one part being thicker than another. When the whole of the work surfaces have been cut down to nearly the finished size, this alteration will have taken place, and the finishing may be proceeded with, leaving the work as true as possible. In chucked work, or the most of it rather, it is impracticable (from being too troublesome) to rough out all over before finishing; hence at each chucking all the work to be done at that chucking is finished. The roughing cuts on a piece of work should always be taken with as coarse a feed as possible, because the object is to remove the mass of the metal to be cut away rather than to produce a finish, and this may be most quickly done by a deep cut and coarse feed. Theoretically also the finishing should be done with a coarse feed, since the coarser the feed, the less the length of time the cutting edge is in action. But the length of cutting edge in action, with a given tool and under a given depth of cut, increases as that edge is made longer to carry the coarse feed, and the long cutting edge produces a strain that tends to spring or bend the work, and that causes the tool to dip into seams or soft spots, or into spongy or other places, where the cutting strain is reduced, and also to spring away from hard spots or seams, where the cutting strain is increased. The most desirable rate of feed, therefore, is that which is as coarse as can be used without springing either the work or the tool, and this will depend upon the rigidity of the work of the lathe, and of the cutting tool. Short or slight work may be turned very true by a light cut fine feed and quick cutting speed, but the speed must obviously be slower in proportion as the length of the work increases, because the finishing cut should be taken without taking the tool out to resharpen it, since it is very difficult to set the tool to the exact proper depth a second time. Since the cutting edge will, at any given rate of cutting speed, retain its keenness better for a given surface of work in proportion as the time it is under duty is diminished, it follows, therefore, that the coarser the feed the better (so long as both the work and the tool are sufficiently rigid to withstand the rate of feed without springing). Under conditions of rigidity that are sufficiently favorable a tool, such as in Fig. 948, may be used on wrought or cast iron, at a feed of 1/2 or even 3/4 inch of traverse per lathe revolution, producing true and smooth work, providing that the tool be given a very slight degree of clearance, that its cutting edge is ground quite straight, that it is set parallel to the line of feed, or what is the same thing, to the work axis, and that the length of cutting edge is greater than the amount of tool traverse per lathe revolution, as is shown in the figure, the amount of tool traverse per lathe revolution obviously being from A to B. It may also be observed that the leading corner of the tool may with advantage be very slightly rounded as shown, so that there shall be no pointed corner to dull rapidly. In proportion as the work is light and the pressure of the cut may spring it, the feed must be lessened, so that on very slender work a feed of 100 lathe revolutions per inch of tool travel may be used. On cast-iron work the feeds may be coarser than for wrought-iron, the other conditions being equal, because cast iron cuts easier and therefore springs the work less for a given depth of cut. But since cast iron is apt to break out, exposing the pores of the metal, and thus leaving small holes plainly visible on the work surface, the finishing cut should be of very small depth, indeed a mere scrape; and if the surface is to be polished, a fine feed and a quick speed will leave a cleaner cut surface, and one that will require the least polishing operations to produce a clean and spotless surface. Brass work also is best finished with a fine feed and a quick speed. It is obvious that the top face of the tool should be given more rake for wrought iron than for cast iron or steel, and that in the case of the very fine feeds, the form of tool shown in figure is the best for finishing these metals. In turning a number of pieces requiring to be of the same diameter, it is to be borne in mind that a great part of the time is consumed in accurately setting the tool for the finishing cut, and that if one piece is finished at a time, this operation will require to be done separately for each piece. It is more expeditious, therefore, to rough all the pieces out, leaving enough metal for a fine finishing cut to be taken, and then finish these pieces without moving the tool; which may be done, after the tool is once set, by letting the tool stand still at the end of the first finishing cut, and taking the work out of the lathe. The carriage is then traversed back to the dead centre, and another piece of work is put in, and it is obvious that as the cross-feed screw is not operated after the tool is once set, the work will all be turned to the same diameter without any further measuring than that necessary for the first piece. If the tool is traversed back to the dead centre before the lathe is stopped or before the work is removed from the lathe, one of two results is liable to follow. If the lathe is left running, the tool will probably cut a spiral groove on the work, during its back traverse; or if the lathe be stopped, the tool point will mark a line along the work, and the contact of the tool point with the work will dull the cutting edge of the tool. The reason of this is as follows: When the slide rest and carriage are traversing in one direction, the resistance between the tool and the cut causes all the play in the carriage and rest, and all the spring or deflection of those parts, to be in an opposite direction. Now if the play and spring were precisely equal for both directions, the tool should cut to an equal diameter with the carriage traversed in either direction, but the carriage in feeding is fed by the feed nut or friction feed device, while when being traversed back the traversing handle is used; thus the power is applied to the carriage in the two cases at two different points, hence the spring of the parts, whether from lost motion, or play from wear, or from deflection, is variable. Again, even with the tool fed both to its cut and on the back traverse with the hand feed handle, the play is, from the altered direction of resistance of the cut, reversed in direction, and the depth of cut is therefore altered. Thus, in Fig. 1208, let S S represent the cross slide on the carriage and R R the cross slide of the tool rest shown in section, and suppose the tool to be traversing towards the live centre, then to whatever amount there may be play or spring between the slide and the slide way, the slide will from the pressure of the cut twist over, bearing against the slide way at A and B, and being clear of it at G and H. On reversing the direction of traverse of the rest, so as to feed the tool towards the dead centre, the exactly opposite condition will set in, that is, the pressure of the cut will force the slides in the opposite direction, or in other words, the contact will be as in Fig. 1209, at C, D, and the play at E, F. During the change of location of bearing between the slides and the way, there will have been a certain amount of tool motion altering the distance of the tool point from the line of centres, and therefore the diameter to which it will cut. The angle at which the body of the tool stands will influence the effect: thus, if when traversing towards the live centre the tool stands at an angle pointing towards the live centre, it would recede and cause the tool to clear the cut, if removed on the back traverse without being moved to or from the line of centres. Conversely, if the body of the tool was at an angle, so that it pointed towards the dead centre, and a cut was taken towards the live centre, and the tool was traversed back without being moved in or out, it would take another cut while being moved back. The conditions, however, are so uncertain, that it is always advisable to be on the safe side, and either wind the tool out from its cut before winding the rest and carriage back (thus destroying its set for diameter), or else to stop the lathe and remove the work before traversing the carriage back as already directed. If the latter plan is followed the trouble of setting the tool is avoided and much time is saved, while greater accuracy of work diameter is obtained. It is obvious that this plan may be adopted for roughing cuts in cases where two cuts only are to be taken, so as to leave finishing cuts of equal depths; or if three cuts are to be taken, it may advantageously be followed for the second and last cuts, the depth of the first cut being of less importance in this case. The following rules apply to all tools and metals: [Illustration: Fig. 1208.] [Illustration: Fig. 1209.] When the pressure between the tool and the work is sufficient, from the proportions of the work, to cause the work to spring or bend, the length of acting cutting edge on the tool should be reduced. As the diameter and rigidity of the work increases, the length of tool cutting edge may increase. The cutting edge of the tool should be kept as close as the work will conveniently admit to the slide rest tool post, 1/4 _inch even_ of this distance being _important_. The slide rest tool should always be resharpened to take the finishing cut, with which, for wrought iron or steel, soapy water with soda in it should be used, the soda serving to prevent the dripping water from rusting the parts of the lathe. Cast iron will cut with an exquisite polish if finished at a _very slow_ rate of cutting speed, and turned with a spring tool, such as was shown in Fig. 974, and water is used. But being a slow process it is not usual to finish it in this manner, though for round corners, curves, &c., this method is highly advantageous. For cast iron the tool should be as keen as the hardness of the metal of the work will permit. If an insufficiently keen tool, or too deep a cut, or too coarse a feed be taken, the metal will break out instead of cutting clean, and numerous fine holes will be perceived over the whole surface, impairing that dead flatness which is necessary to an even and fine polish. To remove these specks or holes in cylindrical work, the file may be used, but for radial faces hand-scrapers, such as shown in Fig. 1295, are used, the work rotating in either case at high speed. Such scrapers are oilstoned and held with the handle end above the horizontal level. The _rest_ should be so conformed to suit the shape of the work, that the scraper will be supported close to the work, which will prevent chattering, and a piece of leather should (as a further preventive of chattering) be placed beneath the scraper. A very good method of using a scraper is to adjust it to the work, and holding it still on the rest, traverse the slide rest to move the scraper to its cut. After the scraping, three methods of polishing radial faces are commonly employed; the first is to use emery paper only, and the second is by the use first of grain, emery, and oil, and the subsequent use of emery paper or cloth, and the third is by the use of emery wheels and crocus cloth. If the work is finished by emery paper only, and it requires much application of the same to efface the scraper marks, the evil will be induced that the emery cuts out the metal most where it is most porous, so that the finished surface is composed of minute hills and hollows, and the polish, though bright and free from marks, will not have that dead flat smooth appearance necessary to a really fine polish and finish; indeed, the finish is in this case to some extent sacrificed to obtain the polish. It is for this reason that stoning the work (as hereafter described) is resorted to, and that grain emery and lead is employed, which is done as follows:-- For a flat radial face, a flat piece of lead, say 3/8 inch thick, and of a size to suit the work, may be pivoted to the end of a piece of wood of convenient length and used with grain emery and oil, the work rotating quickly. To afford a fulcrum for the piece of wood, a lever or rest of some kind, as either a hand rest or a piece fastened in the tool post, is used. The rest should be placed a short distance from the work surface and the lever held partly vertical until the lead meets the work surface, when depressing the lever end will force the lead against the work. The lever end must be quickly moved laterally, so that the lead will approach and then recede from the work centre; this is necessary for two reasons. First, to prevent the emery from cutting rings in the work surface, and secondly, to prevent the formation of grooves behind any hollow spots or specks the work may contain. The reason of the formation of these grooves is that the emery lodges in them and works out from the contact of the lead, so that if on working out they move always in the same line they cut grooves. When a lathe is provided with belt motion to run both ways, it is an excellent plan to apply the lead with the lathe running forward and then with it running backward. When by this means the scraper marks are removed, the next object is to let the marks left by the lead be as fine and smooth as possible, for which purpose flour emery should be used; but towards the last no emery, but oil only, should be applied, the lead being kept in constant lateral motion, first quickly and then slowly, so that the marks on the work cross and recross it at different angles. For round or hollow corners the lead need not be pivoted to the stick, but should be spherical at the end, the marks being made to cross by partly rotating the lever first in one direction and then in the other. Sometimes the end of the lever is used without the addition of lead, but this does not produce so flat a surface, as it cuts out hollows in the pores of the metal. For polishing to be done entirely in the lathe, emery paper and crocus may follow the lead, being used dry and kept also in constant lateral motion. Each successive grade of emery paper must entirely remove all marks existing on the work at the time of its (the paper's) first application, and, furthermore, each successive grade should be continued until it is well worn, because of two pieces of emery paper of the same grade that most worn will cut the smoothest and polish the best. For the final polishing a piece of the finest emery paper should be prepared in the manner hereafter described for polishing plain cylindrical surfaces. The radial faces of wrought iron must be finished as smoothly and true as possible, because being harder than cast iron the emery acts less rapidly upon it. For radial faces on brass the surfaces should be finished as smooth as possible with the slide rest tool, which should be round nosed, with the round flattened somewhat where the tool cuts, and the tool should not, under any condition, have any rake on its top face, while the feed should be fine as, say, 32 revolutions per inch of tool travel. Under skillful manipulation scraping may then be dispensed with, although it may be used to a slight extent without impairing the truth. Very small radial surfaces of brass may best be finished by the scraper and polished with emery paper, while large ones may be finished with dry emery paper. Round corners on brass work should be finished with a spring tool, such as shown in Fig. 974, but having negative top rake; but if the corners are of small radius a well oilstoned hand-scraper is best. To enable the smooth and true turning of all radial faces of large diameter, the lathe head should, when it is possible, be steadied for end motion by placing a rod between the lathe centres, but if the radial face is solid at the centre so that such a rod cannot be put in, the end motion adjusting device of the lathe should be adjusted. The slides of the lathe should also be set up to have good firm contact, and the tool should be brought up to the work by putting the feed motion in gear and operating it by hand at the cone pulley, or gear-wheel on the feed spindle. If the lathe has no compound rest, the cut should be put on by this means, but otherwise the tool may be brought near the work by the feed motion and the cut put on by the compound rest, the object in both cases being to take up all lost motion and hold the rest firmly or steadily on the lathe shears, so that it shall not move back as the cut proceeds. Work of cast iron or brass and of small dimensions and irregular or curved outline should be finished with scraping tools, such as shown in Figs. 1303 and 1310, polished with emery cloth or paper. But whenever scrapers are made with curves to suit the form of the work, such tool curves should be so formed (for all metals) as not to cut along the whole length of cutting edge at once, unless the curve be of very small length as, say, 1/4 inch. This is necessary, because if the cutting edge operates on too great a length it will jar or chatter. For convex surfaces the curve on the scraper should be of greater radius than that of the work, while in the case of concave curves the tool should have a less radius. In both cases the tool will require a lateral movement to cause it to operate over the full width of work curve. If the work curves are sufficiently large, and the same is sufficiently rigid that a slide rest tool may be used, the length of cutting edge may be increased, so that under very favorable conditions of rigidity the tool edge may cut along its whole length without inducing either jarring or chattering, but the best results will always be obtained when with a broad cutting edge the tool is of the spring tool form shown in Fig. 974. Work of wrought iron or steel of small dimensions and of irregular form, must also be finished by hand tools, such as the graver shown in Figs. 1285 and 1286, and the finishing tool shown in Figs. 1289 and 1292, the shape of the tool varying to suit the shape of the work. Round corners or sweeps cannot on any kind of work be finished by a file, because the latter is apt to pin and cut scratches in the work. For the final tool finishing of lathe work of plain cylindrical outline, no tool equals the flat file if it be used under proper conditions, which are, that the work be turned true and smooth with slide rest tools, the marks left by these tools being exceedingly shallow and smooth. A dead smooth file that has been used enough to wear down the projecting teeth (which would cut scratches) should then be used, the work rotating at as fast a speed as the file teeth will stand without undue wear. The file strokes should be made under a light pressure, which will prevent the cuttings from clogging its teeth, and the cuttings should be cleaned from the file after every few strokes. Under these conditions work of moderate diameter may be turned to the greatest degree of smoothness and truth attainable with steel cutting tools, providing that the work makes several revolutions during each file stroke, and it therefore follows that the file strokes may be more rapid as the diameter of the work decreases, and should be more slow as that diameter increases. Allowing the greatest speed of the filed surface permissible, without too rapid destruction of the file teeth, to be 200 feet per minute, and the slowest speed of file stroke that will prevent the file teeth from being ground away or from becoming pinned (when used on wrought iron) to be one stroke in two seconds, the greatest diameter of work that can be finished by filing under the condition that the work must make more than one rotation per file stroke, is about 25 inches in diameter, running about 30 revolutions per minute. The same diameter and speed may be also taken for cast iron, but brass may be filed under increased speed, rendering it practicable to file it up to a diameter of about 36 inches under the above conditions of work rotation and file stroke speed. Supposing, however, that from hardness of the metal or from its increased diameter the work cannot make a rotation per file stroke unless that stroke be more slowly performed, then the cuttings gather in the teeth of the file, become locked and form projections, termed pins, above the file teeth, and these projections cut scratches in the work, and this it is that renders it impracticable to hold the file still while the work rotates. But suppose the file be applied to work of such a diameter that, with a stroke in two seconds and the work surface rotating at 200 feet per minute, each stroke acts on a fraction of the circumference only, then there can be no assurance that the filed surface will be cylindrical, because there is no means of applying the file equally over the whole surface. But it is to be noted, nevertheless, that the file acts with greater effect in proportion as the area filed is decreased, and that as the tool marks are filed out the area of surface operated upon is increased. Suppose, then, that starting from any point on the work circumference a file stroke be taken, and that it extends around one-third of the circumference, that the second file stroke extends around one-third also, but that there is an unfiled space of, say, two inches between the area of surface filed by these two strokes, and that at the third file stroke the file starts on the surface filed at the first stroke, passes over the two inches previously unfiled and terminates on the surface filed by the second stroke; then the conditions will be as follows:-- Part of the surface filed at the first stroke will have been filed twice, part of the surface filed at the second stroke will also have been filed twice, while the two inches will have been filed once only. But this latter part will have had much more taken off it during the third stroke than did the rest of the surface filed at that stroke, because it operated on the ridges or tool marks where, being unfiled, their area in contact with the file teeth was at a minimum. This condition will prevail until the tool marks are effaced, and tends to preserve the truth of the work up to that point, hence the necessity of leaving very fine tool marks becomes obvious. Apart from these considerations, however, there is the fact that filing work in the lathe is a very slow operation, and therefore inapplicable to large work; and furthermore, on large work the surface is not needed to be so smooth as in small work; for example, tool feed marks 1/1000 inch deep would upon work of 1/2 inch diameter leave a surface appearing very uneven, and the wearing away of those ridges or marks would destroy the fit of the piece; but in a piece, say, six feet in diameter, tool marks of that depth would not appear to much disadvantage, and their wearing away would have but little effect upon the fit of the piece. Finishing with the file, therefore, is usually applied to work of about 24 inches in diameter, and less, larger work being finished with the cutting tool or by emery grinding, where a greater degree of finish is required. Small work--as, say, of six inches, or less, in diameter--may be finished with the file so cylindrically true, that no error can be discovered by measurement with measuring tools of the calipering class, though the marks of contact if made apparent by gently forcing the work through a closely fitting ring-gauge may not appear to entirely cover the surface. To produce filed work thus true, all that is necessary is to set the cutting edge of the finishing tool at the horizontal centre of the work, properly adjust the live spindle of the lathe for fit to its bearings, adjust the slides of the slide rest so that there is no lost motion, and follow the rules already given with reference to the shape of the tool cutting edge, employing a cutting speed not so fast as to dull the tool before it has finished its cut, using a fine feed except in the case of cast iron, as already explained. The requirement that the tool shall not become dull before it has finished its cut, brings us to the fact that the length of work that can be thus accurately turned is limited, as the diameter of the work increases. Indeed, the length of the work in proportion to its diameter is a very important element. Thus, it would be very difficult indeed to turn up a spindle of an inch in diameter and, say, 14 feet long, and finish it cylindrically true, parallel, and smooth, because 1st. The slightness of the work would cause it to spring or deflect from the pressure or strain due to the cut. This may to some extent be remedied by steadying the work in a follower rest, but the bore of such follower itself wears as the cut proceeds, though the amount may be so small as to be almost inappreciable. 2nd. The work being better supported (by the lathe centres) at the two ends than in the middle of its length, the duty placed on the follower rest will increase as the middle of the work length is approached, hence the spring or deflection of the follower rest will be a disturbing element. 3rd. The tool gets duller as the cut proceeds, causing more strain from the cut, and, therefore, placing more strain on the follower rest; and, 4th. It would be necessary, on account of the length of the cut, to resharpen the tool before the cut was carried from end to end of the spindle, and it would be almost impracticable to set the reground tool to cut to the exact diameter. The second, third, and fourth of the above reasons operate together in causing increased work spring as the tool approaches the middle of the work length; thus the deflection of the follower rest, the increased weakness of the work, and the comparative dullness of the tool would all operate to cause the work to gradually increase in diameter as the cut proceeded towards the work centre (of length). Suppose, for example, a cut to have been carried from the dead centre, say, five feet along the work; at the end of this five feet the tool will be at its dullest, the shaft at its weakest, and supported the least from the dead centre and follower rest. Suppose, then, that the reground tool be placed in the rest again and set to just meet the turned surface without cutting it, then when it meets the cut to carry it farther along the work the cut will produce (on account of the tool being sharper) less strain on the work, which will therefore spring or deflect less. Precisely what effect this may have upon the diameter to which the tool will turn the work will depend upon various conditions: thus, if the top face of the tool be sufficiently keen to cause the strain due to bending the shaving cut or chip to pull the work forward, the tool would turn to a smaller diameter. If the depth of the cut be sufficient to cause the work to endeavor to lift, and the tool edge be above the centre of the work, it would be cut to smaller diameter. If the tool cutting edge were below the centre, or if its top face be at an angle tending to force the work away from the tool point, the diameter of the work would be increased. From these considerations it is obvious that the finishing cut should be started at the centre of the work length, and carried towards the lathe centres, because in this case the tool will be sharpest, and therefore will produce less tensional strain on the work at the point where the latter is the weakest, while the resisting strength of the work would increase as the cut proceeded, and the tool became dull from use. Furthermore, if it were necessary to regrind the tool, it would be reset nearer to the lathe centres, where the work would be more rigidly held; hence the tool could be more accurately set to the diameter of the finishing cut. By following this plan, however, it becomes necessary to have the shaft as near true and parallel as possible before taking the finishing cut, for the following reasons:-- Let the diameter of the spindle before the finishing cut be 1-1/32 inches, leaving 1/32 inch to be taken off at the finishing cut, then the ring in the follower rest must be at starting that cut 1-1/32 inch bore, and if the rest is to follow the cut the bush must be changed (so soon as it meets the finishing cut) to one of an inch bore. But if the spindle be turned as true and parallel as possible before the finishing cut the rest may lead the tool, in which case the bush need not be changed. There are differences of opinion as to the desirability of either changing the bush or letting the tool follow the rest, but there can be no dispute that (from the considerations already given) a spindle turned as true and parallel as may be with the tool started from the dead centre and carried forward can be improved by carrying yet another cut from the middle towards the dead centre. In any event, however, work liable to spring or too long to be finished at one cut without removing the tool to grind it, can be more accurately finished by grinding in a lathe, such as was shown in Figs. 676 or 679, than by steel-cutting tools, and for the following reasons:-- [Illustration: Fig. 1210.] If it be attempted with steel tools to take a very fine cut, as, say, one of sufficient depth to reduce a diameter, say 1/500 inch, the tool is apt to turn an uneven surface. There appears, indeed, to be a necessity to have the cut produce sufficient strain to bring the bearing surfaces of the rest into close contact and to place a slight strain on the tool, because under very light cuts, such as named above, the tool will generally momentarily leave the cut or take a reduced cut, and subsequently an increased one. It may be accepted that from these causes a finishing cut taken with a steel tool should not be less than that sufficient to reduce the diameter of the work 1/64 inch. Now an emery-wheel will take a cut whose fineness is simply limited by the wear of the wheel in the length of the cut. Some experiments made by Messrs. J. Morton Poole and Sons, of Wilmington, Delaware, upon this subject led to the conclusion that with corundum wheels of the best quality the cut could be made so fine that a 12-inch wheel used upon a piece of work (a calender roll) 16 inches in diameter and 6 feet long, would require about forty thousand traverses to reduce the diameter of the work an inch, leading to the conclusion that the wear of the wheel diameter was less than one eighty-thousandth part of an inch per traverse. Now the strain placed upon the work of an emery-wheel taking a cut of, say, 1/1000 inch, is infinitely less than that caused by a cutting tool taking a cut of 1/120 inch in diameter; hence the accuracy of grinding consists as much in the small amount of strain and, therefore, of deflection it places upon the work, as upon the endurance of the wheel itself. Since both in finishing and in polishing a piece of work the object is to obtain as true and smooth a surface as possible, the processes are to a certain extent similar, but there is this difference between the two: where polishing alone is to be done, the truth of the work or refined truth in its cylindrical form or parallelism may be made subservient to the convenience of polish. Thus, in the case of the stem of the connecting rod that has been turned and filed and finished as true as possible, the polishing processes may be continued with emery-cloth, &c., producing the finest of polish without impairing the quality of the work, whereas the degree of error in straightness or parallelism induced by the polishing may impair the degree of truth desirable for a piston rod. The degree of finish or polish for any piece of work is, therefore, governed to some extent by the nature of its use. Thus a piston rod may be finished and polished to the maximum degree consistent with maintaining its parallelism and truth, while a connecting rod stem may be polished to any required attainable degree. In finishing for truth, as in the case of journal bearings, the work, being turned as true and smooth as possible, may be filed with the finest of cut files, and polished with a fine grade of emery-cloth or paper; the amount of metal removed by filing and polishing being so small as not to impair to any practically important degree the truth of the work: a journal so finished will be as true as it is possible to make it without the use of a grinding lathe. Instead of using emery-paper, grain emery and oil may be used, but the work will not be so true, because in this case much more metal will be removed from the work in the finishing or polishing process. When it is required to polish and to keep the work as true and parallel as possible, these ends may be simultaneously obtained by means of clamps, such as shown in Fig. 1210, which represents a form of grinding and polishing clamp used by the Pratt and Whitney Company for grinding their standard cylindrical gauges. A cast-iron cylindrical body A is split partly through at B and entirely through at C, being closed by the screw D to take up the wear. The split B not only weakens the body A and enables its easy closure, but it affords ingress to the grinding material. It may be noted that cast iron is the best metal that can be used for this purpose, not only on account of the dead smooth surface it will take, but also because its porosity enables it to carry the oil better than a closer grained metal. For work of larger diameter, as, say, 2 or 3 inches, the form of lap shown in Fig. 1211 is used for external grinding, there being a hinge B C instead of a split, and handles are added to permit the holding and moving of the lap. The bore of this clamp is sometimes recessed and filled with lead. It is then reamed out to fit the work and used with emery and oil, the lathe running at about 300 feet per minute. [Illustration: Fig. 1211.] For grinding and polishing the bores of pieces, many different forms of expanding grinding mandrels have been devised, in most of which the mandrel has been given a slight degree of curvature in its length; or in other words, the diameter is slightly increased as the middle of the mandrel length is approached from either end. But with this curvature of outline, as small as it may be, it rather increases the difficulty of grinding a bore parallel instead of diminishing it. When expanding mandrels are caused to expand by a wedge acting upon split sections of the mandrel, they rarely expand evenly and do not maintain a true cylindrical form. Fig. 1212 represents a superior form of expanding mandrel for this purpose. The length A is taper and contains a flute C. The lead is cast on and turned upon the mandrel, the metal in the flute C driving the lead. The diameter of the lap is increased by driving the taper mandrel through it, and the lead is therefore maintained cylindrically true. While these appliances are supplied with the flour emery and oil, their action is to grind rather than to polish, but as they are used without the addition of emery, the action becomes more a polishing one. [Illustration: Fig. 1212.] Fig. 1213 represents at A A a wooden clamp for rough polishing with emery and oil. It consists of two arms hinged by leather at B and having circular recesses, as C, D, to receive the work. At J J is represented a similar grinding and polishing clamp for more accurate work. G and H are screws passing through the top arm and threaded into the lower, while E, F are threaded into the lower arm, and abut at their ends against the face of the upper arm. It is obvious that by means of these screws the clamp may be set to size, adjusted to give the required degree of pressure, and held firmly together. Lead bushes may be inserted in the bores as grinding laps. As this clamp is used by hand, it must be moved along the work at an exactly even speed of traverse, or else it will operate on the work for a longer period of time at some parts than at others; hence the greatest care is necessary in its use. The best method of polishing cylindrical work to be operated on entirely in the lathe, the primary object being the polish, is by means of emery paper, and as follows:-- In all polishing the lathe should run at a fast speed; hence special high speeded lathes, termed speed lathes, are provided for polishing purposes only. The emery paper or cloth should be of a fine grade, which is all that is necessary if the work has been properly filed, if cylindrical, and scraped if radial or of curved outline. In determining whether emery paper or cloth should be used, the following is pertinent:-- The same grade of emery cuts more freely on cloth than on paper, because the surface of the cloth is more uneven; hence the emery grains project in places, causing them to cut more freely until worn down. If, then, the surface is narrow, so that there is no opportunity to move the emery cloth endways on the work, emery paper should be used. It should be wrapped closely (with not more than one, or at least two folds) around a _smooth_ file, and not a coarse one, whose teeth would press the emery to the work at the points of its coarse teeth only. The file should be given short, rapid, light strokes. For work of curved outline emery cloth should be used, because it will bend without cracking, and the cloth should be moved quickly backwards and forwards across, and not round, the curve; and when the work is long enough to permit it, the emery paper or cloth should be moved rapidly backwards and forwards along the work so that its marks cross and recross at an obtuse angle. Now, suppose the grade of emery paper first used to be flour emery, and the final polish is to be of the highest order, then 0000 French emery paper will be required to finish, and it is to be observed that nothing will polish a metal so exquisitely as an impalpable powder of the metal itself: hence, while performing the earlier stages of polishing, it is well to prepare the final finishing piece, so as to give it a glaze of metal from the work surface. When, therefore, all the file marks are removed by the use of the flour emery cloth, the surface of the work should be slightly oiled and then wiped, so as not to appear oily and yet not quite dry, with a piece of rag or waste, then the piece of 0000 emery paper, or, what is equally as good, a piece of crocus cloth, to be used for the final finishing should be applied to the work, and the slightly oily surface will cause the cuttings to clog and fill the crocus cloth. The cloth should be frequently changed in position so as to bring all parts of its surface in contact with the work and wear down all projections on the cloth as well as filling it with fine cuttings from the work. Then a finer grade, as, say, No. 0 French emery paper, must be used, moving it rapidly endwise of the work, as before, and using it until all the marks left by the flour emery have been removed. One, or at most two drops of lard oil should then be put on the work, and spread over as far as it will extend with the palm of the hand, when the finishing crocus may again be applied and reversed as before in every direction; 00 emery paper may then be used until all the marks of the 0 are removed, and with the work left quite dry the crocus for final finishing may again be applied; 000 emery paper may then be used to efface all the marks left by the 00. This 000 emery paper should be used until it is very much worn, the final finish being laid with the glazed crocus. If this crocus has been properly prepared, its whole surface will be covered with a film of fine particles of metal, so that if the metal be brass the crocus surface will appear like gold leaf. If cast iron, the crocus surface will appear as though polished with plumbago or blacklead, while in any case the crocus surface will be polished and quite dry. The crocus should be pressed lightly to the work, so that its polishing marks will not be visible to the naked eye. If emery paper be applied to work finished to exact diameter it should be borne in mind that the process reduces to some extent the size of the work, and that the amount under proper conditions though small is yet of importance, where preciseness of diameter is a requisite. In the practice, however, of some of the best machine shops of the United States, the lathe alone is not relied upon to produce the best of polish. Thus, in the engine works of Charles H. Brown, of Fitchburg, Massachusetts, whose engines are unsurpassed for finish and polish, and which the majority of mechanics would suppose were finely silver plated, the following is the process adopted for polishing connecting rods. [Illustration: Fig. 1213.] The rod is carefully tool-finished with a fine feed. The tool marks are then erased with a fine smooth file, and these file marks by a dead-smooth file, the work rotating at a quick speed, little metal being left, so as to file as little as possible. Next comes _fine_ emery cloth to smooth down and remove the file marks. The lathe is then stopped and the rod stoned lengthwise with Hindostan stone and benzine, removing all streaks. The Scotch stone used with water follows, until the surface is without scratches or marks, as near perfect as possible. The next process is, for the finest work, the burnisher used by hand. But if not quite so exquisite a polish is required, the rod is finished by the use of three grades of emery cloth, the last being very fine. Sometimes, however, the streaks made by polishing with emery paper used before the application of the stones are too difficult to remove by them. In this case, for a very fine finish, the lathe is stopped and draw-filing with the finest of files is performed, removing all streaks; and the stones then follow the draw-filing. All stoning is done by hand with the work at rest, as is also all burnishing. After the burnisher comes fine imported crocus cloth, well worn, which makes the surface more even and dead than that left by the burnisher. The crocus is used with the lathe at its quickest speed, and is moved as slowly and as evenly as possible, the slower and more even the crocus movement along the rod, the more even the finish. If the rod has filleted corners, such corners are in all cases draw-filed before the stoning. The method of polishing a cylinder cover at the Brown Engine Works is as follows. [Illustration: Fig. 1214.] The finishing cut is taken with a feed of 32 lathe-revolutions per inch of tool traverse, and at as quick a cutting speed as the hardness of the iron will permit. This is necessary in order to have the tool-edge cut the metal without breaking it out as a coarse one would do. With the fine feed and quick speed the pores of the iron do not show; with a coarse feed the pores show very plainly and are exposed for quite a depth. After the lathe-tool comes a well oil-stoned hand-scraper, with a piece of leather between it and the tool rest to prevent the scraper from chattering. The scraper not only smooths the surface, but it cuts without opening the pores. It is used at a quick speed, as quick indeed as it will stand, which varies with the hardness of the metal, but is always greater than is possible with a slide-rest tool. After the scraper the cover is removed from the lathe, and all flat surfaces are filed as level as possible with a second-cut file, and then stoned with soft Hindostan stone, used with benzine or turpentine, so as to wash away the cuttings and prevent them from clogging the stone or forming scratches. In using all stones the direction of motion is frequently reversed so as to level the surface. Next comes stoning with Scotch stone (Water of Ayr), used with water; in this part of the operation great care must be taken, otherwise the cuttings will induce scratches. When the Scotch stone marks have removed all those left by the Hindostan stone, and left the surface as smooth as possible, the cover is again put in the lathe and the grain is laid and finished with very fine emery cloth and oil. The emery cloth is pressed lightly to the work and allowed to become well worn so as to obtain a fine lustre without leaving any streaks. [Illustration: Fig. 1215.] It will be noticed here that the use of the emery stick and oil is entirely dispensed with; but for a less fine polish it may be used, providing it be kept in quick motion radially on the work. The objection to its use is that if there be any speck on the work it is apt to cut a streak or groove following the spot like a comet's tail. TURNING TAPERS.--There are five methods of turning outside tapers; 1st, by setting over the tailstock of the lathe; 2nd, by the use of a former or taper turning attachment such as was shown in Fig. 508; 3rd, by the use of a compound slide rest; 4th, by means of a lathe in which the head and tailstock are upon a bed that can be set at an angle to the lathe shears on which the lathe carriage slides; and 5th, by causing the cross-feed screw to operate simultaneously with the feed traverse. Referring to the first method, it is objectionable, inasmuch as that the work axis is thrown at an angle to the axis of the lathe centres, which causes the work centres to wear rapidly, and this often induces them to move their positions and throw the work out of true. Furthermore, the tailstock has to be moved back in line with the live spindle axis for turning parallel again, and this is a troublesome matter, especially when the work is long. Fig. 1214 shows the manner in which the lathe centres and the work centres have contact, L being the live and B the dead centre; hence C C is the axis of the live spindle which is parallel to the lathe shear slides, which are represented by G; obviously A is the work axis. The wear is greatest at the dead centre end of the work, but there is some wear at the live centre end, because there is at that end also a certain amount of motion of the work centre upon the live centre. Thus, in Fig. 1215, let _c_ represent the live centre axis, _a_ the work axis, D the lathe face plate, and E F the plane of the driver or dog upon the work, and it is obvious that the tail of the driver will when at one part of the lathe revolution stand at E, while when diametrically opposite it will stand at F; hence, during each work revolution the driver moves, first towards and then away from the face plate D, and care must be taken in adjusting the position of the driver to see that it has liberty to move in this direction, for if obstructed in its motion it will spring or bend the work. [Illustration: Fig. 1216.] To determine how much the tailstock of a lathe must be set over to turn a given taper, the construction shown in Fig. 1216 may be employed. Draw the outline of the work and mark its axis D, draw line C parallel to one side of the taper end, and the distance A between this line and the work axis is the amount the tailstock requires to be set over. This construction is proved in Fig. 1217, in which the piece of work is shown set over, C representing the line of the lathe ways, with which the side F of the taper must be parallel. D is the line of the live spindle, and E that of the work, and the distance B will be found the same as distance A in Fig. 1216. It may be remarked, however, that in setting the tailstock over it is the point of the dead centre when set adjusted to the work length that must be measured, and not the tailblock itself. [Illustration: Fig. 1217.] Other methods of setting tailstocks for taper turning are as follows: If a new piece is to be made from an old one, or a duplicate of a piece of work is to be turned, the one already turned, or the old piece as the case may be, may be put in the lathe and we may put a tool in the tool post and set the tailstock over until the tool traversed along the work (the latter remaining stationary) will touch the taper surface from end to end. If, however, the taper is given as so much per foot, the distance to set the tailstock over can be readily calculated. Thus, suppose a piece of work has a taper part, having a taper of an inch per foot, the work being three feet long, then there would be three inches of taper in the whole length of the piece and the tailstock requires to be set over one-half of the three inches, or 1-1/2 inches. It will not matter how long the taper part of the work is, nor in what part of the work it is, the rule will be found correct so long as the tailstock is set over one-half the amount obtained by multiplying the full length of the work per foot by the amount of taper per foot. If we have no pattern we may turn at each end of the part that is to be taper a short parallel place, truing it up and leaving it larger to the same amount at each end than the finished size, and taking care that the parallel part at the small end will all turn out in the finishing. We then fasten a tool in the lathe tool post, place it so that it will clear the metal of the part requiring to be turned taper, and placing it at one extreme end of said part, we take a wedge, or a piece of metal sufficiently thick, and place it to just contact with the turned part of the work and the tool point (adjusting the tool with the cross-feed screw), we then wind the rest to the other end of the required taper part, and inserting same wedge or piece of iron, gauge the distance from the tool point to the work, it being obvious that when the tool point wound along is found to stand at an equal distance from each end of the turned part, the lathe is set to the requisite taper. [Illustration: Fig. 1218.] Figs. 1218 and 1219 illustrate this method of setting. A represents a piece of work requiring to be turned taper from B to C, and turned down to within 1/32 inch of the required size at E and F. If then we place the tool point H first at one end and then at the other, and insert the piece I and adjust the lathe so that the piece of metal I will just fit between the tool point and the work at each extreme end of the required taper part, the lathe will be set to the requisite taper as near as practicable without trying the work to the taper hole. The parallel part at the small end of the work should be turned as true as possible, or the marks may not be obliterated in finishing the work. Fig. 1220 (from _The American Machinist_) represents a gauge for setting the tailstock over for a taper. A groove is cut as at E and D, these diameters corresponding to the required taper; a holder A is then put in the tool point, and to this holder is pivoted the gauge B. The tailstock is set over until the point of B will just touch the bottom of the groove at each end of the work. [Illustration: Fig. 1219.] To try a taper into its place, we either make a chalked stripe along it from end to end, smoothing the chalked surface with the finger, or else apply red marking to it, and then while pressing it firmly into its place, revolve it backwards and forwards, holding it the while firmly to its seat in the hole; we move the longest outwardly projecting end up and down and sideways, carefully noting at which end of the taper there is the most movement. The amount of such movement will denote how far the taper is from fitting the hole, while the end having the least movement will require to have the most taken off it, because the fulcrum off which the movement takes place is the highest part, and hence requires the greatest amount of metal to be taken off. Having fitted a taper as nearly as possible with the lathe tool, that is to say, so nearly that we cannot find any movement or unequal movement at the ends of the taper (for there is sure to be movement if the tapers do not agree, or if the surfaces do not touch at more than one part of their lengths), we must finish it with a fine smooth file as follows: After marking the inside of the hole with a very light coat of red marking, taking care that there is no dirt or grit in it, we press the taper into the hole firmly, forcing it to its seat while revolving it backwards and forwards. By advancing it gradually on the forward stroke, the movement will be a reciprocating and yet a revolving one. The work must then be run in the lathe at a high speed, and a smooth file used to ease off the mark visible on the taper, applying the file the most to parts or marks having the darkest appearance, since the darker the marks the harder the bearing has been. Too much care in trying the taper to its hole cannot be taken, because it is apt to mark itself in the hole as though it were a correct fit when at the same time it is not; it is necessary therefore at each insertion to minutely examine the fit by the lateral and vertical movement of projecting part of the taper, as before directed. A taper or cone should be fitted to great exactitude before it is attempted to grind it, the latter process being merely intended to make the surfaces even. For wrought-iron, cast-iron, or steel work, oil and emery may be used as the grinding materials (for brass, burnt sand and water are the best). The oil and emery should be spread evenly with the finger over the surfaces of the hole and the taper; the latter should then be placed carefully in its place and pressed firmly to its seat while it is being revolved backwards and forwards, and slowly rotated forward by moving it farther during the forward than during the backward movement of the reciprocating motion. After about every dozen strokes the taper should be carefully removed from the hole and the emery again spread evenly over the surfaces with the finger, and at and during about every fourth one of the back strokes of the reciprocating movement the taper should be slightly lifted from its bed in the hole, being pressed lightly home again on the return stroke, which procedure acts to spread the grinding material and to make the grinding smooth and even. The emery used should be about number 60 to 70 for large work, about 80 to 100 for small, and flour emery for very fine work. Any attempt to grind work by revolving it steady in one direction will cause it to cut rings and destroy the surface. [Illustration: Fig. 1220.] Referring to the second method, all that is necessary in setting a former or taper attachment bar is to set it out of line with the lathe shears to half the amount of taper that is to be turned, the bar being measured along a length equal to that of the work. Turning tapers with a bar or taper-turning attachment possesses the advantage that the tailstock not being set over, the work centres are not thrown out of line with the live centres, and the latter are not subject to the wear explained with reference to Fig. 1214. Furthermore, the tailstock being kept set to turn parallel, the operator may readily change from turning taper to turning parallel, and may, therefore, rough out all parts before finishing any of them, and thus keep the work more true, whereas in turning tapers by setting the tailstock over we are confronted by the following considerations:-- If we turn up and finish the plain part first, the removing of the skin and the wear of the centres during the operation of turning the taper part will cause the work to run out of true, and hence it will not, when finished, be true; or if, on the other hand, we turn up the taper part first, the same effects will be experienced in afterwards turning the plain part. We may, it is true, first rough out the plain part, then rough out the taper part, and finish first the one and then the other; to do this, however, we shall require to set the lathe twice for the taper and once for the parallel part. It is found in practice that the work will be more true by turning the taper part the last, because the work will alter less upon the lathe centres when changed from parallel to taper turning than when changed from the latter to the former. In cases, however, in which the parts fitting the taper part require turning, it is better to finish the parallel part last, and to then turn up the work fastened upon the taper part while it is fast upon its place: thus, in the case of a piston rod and piston, were we to turn up the parallel part of the rod first and the taper last, and the centres altered during the last operation, when the piston head was placed upon the rod, and the latter was placed in the lathe, the plain part or stem would not run true, and we should require to true the centres to make the rod run true before turning up the piston head. If, however, we first rough out the plain part or stem of the rod, and then rough out and finish the taper part, we may then fasten the head to its place on the rod, and turn the two together; that is to say, rough out the piston head and finish its taper hole; then rough out the parallel part of the rod, but finish its taper end. The rod may then be put together and finished at one operation; thus the head will be true with the rod whether the taper is true with the parallel part of the rod or not. With a taper-turning attachment the rod may be finished separately, which is a great advantage. [Illustration: Fig. 1221.] If, however, one part of the length of a taper turning attachment is much more used than another, it is apt to wear more, which impairs the use of the bar for longer work, as it affects its straightness and causes the slide to be loose in the part most used, and on account of the wear of the sliding block it is proper to wind the tool out from its cut on the back traverse, or otherwise the tool may cut deeper on the back than on the forward traverse, and thus leave a mark on the work surface. [Illustration: Fig. 1222.] Referring to the third method, a compound slide rest provides an excellent method of turning tapers whose lengths are within the capacity of the upper slide of the compound rest, because that slide may be used to turn the taper, while the ordinary carriage feed may be used for the parallel parts of the work, and as the tailstock does not require to set over, the work centres are not subject to undue wear. If the seat for the upper slide of the rest is circular, and the taper is given in degrees of angle, a mark may be made on the seat, and the base of the upper slide may be marked in degrees of a circle, as shown in Fig. 1221, which will facilitate the setting; or the following construction, which is extracted from _Mechanics_, may be employed. Measure the diameter of the slide rest seat, and scribe on a flat surface a circle of corresponding diameter. Mark its centre, as A in Fig. 1222, and mark the line A B. From the centre A mark the point B, whose radius is that of the small end of the hole to be bored. Mark the length of the taper to be turned on the line A G and draw the line G D distant from A B equal to the diameter of the large end of the hole to be bored. Draw the line B D. Then the distance E F is the amount the rest must be swiveled to turn the required taper. It is obvious that the same method may also be used for setting the rest. [Illustration: Fig. 1223.--Top View.] Referring to the fourth method, by having an upper bed or base plate for the head and tailstock, so that the line of lathe centres may be set at the required angle to the [V]s or slides on which the carriage traverses, it affords an excellent means of turning tapers, since it avoids the disadvantages mentioned with regard to other systems, while at the same time it enables the turning of tapers of the full length of the carriage traverse, but it is obvious that the head and tailstock are less rigidly supported than when they are bolted direct to the lathe shears. [Illustration: Fig. 1224.--End View.] In turning tapers it is essential that the tool point be set to the exact height of the work axis, or, in other words, level with the line of centres. If this is not the case the taper will have a curved outline along its length. Furthermore, it may be shown that if a straight taper be turned and the tool be afterwards either raised or lowered, the amount of taper will be diminished as well as the length being turned to a curve. Figs. 1223 and 1224 demonstrate that the amount of taper will be changed by any alteration in the height of the tool. In Fig. 1223, A B represents the line of centres of the spindle of a lathe, or, in other words, the axis of the work W, when the lathe is set to turn parallel; A C represents the axis of the work or cone when the lathe tailstock is set over to turn the taper or cone; hence the length of the line C B represents the amount the tailstock is set over. Referring now to Fig. 1224, the cone is supposed to stand level, as it will do in the end view, because the lathe centres remain at an equal height from the lathe bed or [V]s, notwithstanding that the tailstock is set over. The tool therefore travels at the same height throughout its whole length of feed; hence, if it is set, as at T, level with the line of centres, its line of feed while travelling from end to end of the cone is shone by the line A B. The length of the line A B is equal to the length of the line B C Fig. 1223. Hence, the line A B, Fig. 1224, represents two things: first, the line of motion of the point of tool T as it feeds along the cone, and second its length represents the amount the work axis is out of parallel with the line of lathe centres. Now, suppose that the tool be lowered to the position shown at I; its line of motion as it feeds will be the line C D, which is equal in length to the line A B. It is obvious, therefore, that though the tool is set to the diameter of the small end, it will turn at the large end a diameter represented by the dotted circle H. The result is precisely the same if the taper is turned by a taper-turning attachment instead of setting the tailstock out of line. [Illustration: Side View. Fig. 1225. End View.] The demonstration is more readily understood when made with reference to such an attachment as the one just mentioned, because the line A B represents the line of tool feed along the work, and its length represents the amount the attachment causes the tool to recede from the work axis. Now as this amount depends upon the set-over of the attachment it will be governed by the degree of that set over, and is, therefore, with any given degree, the same whatever the length of the tool travel may be. All that is required, then, to find the result of placing the tool in any particular position, as at I in the end view, is to draw from the tool point a line parallel to A B and equal in length to it, as C D. The two ends of that line will represent in their distances from the work axis the radius the work will be turned to at each end with the tool in that position. Thus, at one end of the line C D is the circle K, representing the diameter the tool I would turn the cone at the small end, while at the other end the dotted circle H gives the diameter at the large end that the tool would turn to when at the end of its traverse. But if the tool be placed as at T, it will turn the same diameter K at the small end, and the diameter of the circle P at the large end. We have here taken account of the diameters at the ends only of the work, without reference to the result given at any intermediate point along the cone surface, but this we may now proceed to do, in order to prove that a curved instead of a straight taper is produced if the tool be placed either above or below the line of lathe centres. In Fig. 1225, D E F C represents the complete outline of a straight taper, whose diameter at the ends is represented in the end view by the outer and inner circles. Now, a line from A to B will represent the axis of the work, and also the line of tool point motion or traverse, if that point is set level with the axis. The line I K in the end view corresponds to the line A B in the side view, in so far that it represents the line of tool traverse when the tool point is set level with the line of centres. Now, suppose the tool point to be raised to stand level with the line G H, instead of at I K, and its line of feed traverse be along the line G H, whose length is equal to that of I K. If we divide the length of G H into six equal divisions, as marked from 1 to 6, and also divide the length of the work in the side view into six equal divisions (_a_ to _f_), we shall have the length of line G H in the first division in the end view (that is, the length from H to G), representing the same amount or length of tool traverse as from the end B of the cone to the line A in the side view. Now, suppose the tool point has arrived at 1; the diameter of work it will turn when in that position is evidently given by the arc or half-circle _h_, which meets the point 1 on G H. To mark that diameter on the side view, we first draw a horizontal line, as _h_ _p_, just touching the top of _h_; a perpendicular dropped from it cutting the line A B, gives the radius of work transferred from the end view to the side view. When the tool point has arrived at 2 on G H in the end view, its position will be shown in the side view at the line _b_, and the diameter of work it will turn is shown in the end view by the half-circle _k_. To transfer this diameter to the side view we draw the line _k_ _g_, and where it cuts the line _b_ in the side view is the radius of the work diameter when the tool has arrived at the point _b_ in the side view. Continuing this process, we mark half-circles, as _l_, _m_, _n_, _o_, and the lines _l_ _r_, _m_ _s_, _n_ _t_, _o_ _u_, by means of which we find in the side view the work radius when the tool has arrived at _c_, _d_, _e_, and _f_ respectively. All that remains to be done is to draw on the side view a line, as _u_ E, that shall pass through the points. This line will represent the outline of the work turned by the tool when its height is that denoted by G H. Now, the line _u_ E is shown to be a curve, hence it is proved that with the tool at the height G H a curved, and not a straight, taper will be turned. It may now be proved that if the tool point is placed level with the line of centres, a straight taper will be turned. Thus its line of traverse will be denoted by A B in the side view and the line I K in the end view; hence we may divide I K into six equal divisions, and A B into six equal divisions (as _a_, _b_, _c_, &c.). From the points of division I K, we may draw half-circles as before, and from these half-circles horizontal lines, and where the lines meet the lines of division in the side view will be points in the outline of the work, as before. Through these points we draw a line, as before, and this line C F, being straight, it is proven that with the tool point level with the work axis, it will turn a straight taper. [Illustration: Top View. Fig. 1226. End View.] It may now be shown that it is possible to turn a piece of work to a curve of equal curvature on each side of the middle of the work length. Suppose, for example, that the cutting tool stands on top of the work, as in the end view in Fig. 1226, and that while the tool is feeding along the work it also has a certain amount of motion in a direction at right angles to the work axis, so that its line of motion is denoted by the line B B in the top view. The outline of the work turned will be a curve, as is shown in Fig. 1227, in which the line of tool traverse is the line C D. Now the amount of tool motion that occurs during this traverse in a direction at right angles to the work axis is represented by the line F E, because the upper end is opposite to the upper end of C D, while the lower end is opposite the lower end of C D. We may then divide one-half of the length of F E into the divisions marked from 1 to 6. Now, as we have taken half the length of F E, we must also take half the length of the work and divide it into six equal divisions marked from _a_ to _f_. Now, suppose the tool point to stand in the line F S in the end view, its position in the top view will be at C. When it is at 1 on the end view it will have arrived at _p_ in the top view. The radius of work it will then turn is shown in the end view by the length of line running from 1 to the work centre. Take this length, and from _a_ in the work axis set it off on the line _a_ _h_, and make the length equal the height of 1 S. In like manner, when the tool point has arrived at 2, the radius it will cut the work is shown by the length of line _i_; hence from 2 on the work axis we may set off the length of 2 S, making 2 S and _b_ _i_ of equal length. Continuing this process, we make the length of _c_ _k_ equal that of 3 S, the length of _d_ _l_ equal 4 S, and so on. All that remains then is to draw a line, _o_ _g_, that shall meet the tops of these lines. This line will show the curve to which that half of the work length will be turned to. The other half of the work length will obviously be turned to the same curvature. [Illustration: Fig. 1227.] [Illustration: Fig. 1228.] It is obvious that the curvature of the work outline will be determined by the proportion existing between the length of the work and the amount of tool motion in a direction at right angles to the work axis, or, in other words, between the length of the work and that of the line F E. It is evident, also, that with a given amount of tool motion across the work, the curvature of outline turned will be less in proportion as the work length is greater. Now, suppose that the smaller and the larger diameter of the work, together with its length, are given, and it is required to find how much curvature the tool must have, we may find this and work out the curve it will cut by the construction shown in Fig. 1228, in which the circle K is the smallest and the circle P the largest diameter. The line _m_ C is drawn to just touch the perimeter of K, and this at once gives the amount of cross-motion for the tool. Hence, we may draw the line _m_ B and C B, and from their extremities draw the line B B representing the path of traverse of the tool point. We may then obtain the full curve on one side of the work by dividing one-half the length of _m_ C into six equal divisions and proceeding as before, except that we have here added the lines of division in the second half as from _f_ to _l_. It will be observed that the centre of the curve is at the point where the tool point crosses the axis of the work; hence, by giving to the tool more traverse on one side than on the other of the work axis, the location of the smallest point of work diameter may be made to fall on one side of the middle of the work length. In either turning or boring tapers that are to drive or force in or together, the amount to be allowed for the fit may be ascertained, so that the work may be made correct without driving each piece to its place to try its fit. Suppose, for example, that the pieces are turned, and the holes are to be reamed, then the first hole reamed may be made to correct diameter by fit and trial, and a collar may be put on the reamer to permit it to enter the holes so far and no farther. A taper gauge may then be made as in Fig. 1229, the line a representing the bore of the hole, and line B the diameter of the internal piece, the distance between the two being the amount found by trial to be necessary for the forcing or driving. The same gauge obviously serves for testing the taper of the holes reamed. CHUCKED OR FACE PLATE WORK.--This class of work requires the most skillful manipulation, because the order in which the work may most advantageously proceed and the method of chucking are often matters for mature consideration. [Illustration: Fig. 1229.] In a piece of work driven between the lathe centres, the truth of any one part may be perceived at any time while operating upon the others, but in chucked work, such is not always the case, and truth in the work is then only to be obtained by holding it truly. Again, the work is apt to be sprung or deflected by the pressure of the devices holding it, and furthermore the removal of the skin or surface will in light work sometimes throw it out of true as the work proceeds, the reason being already given, when referring to turning plain cylindrical work. TO TURN A GLAND.--There are three methods of turning a gland: first, the hole and the face on the outside of the flange may be turned first, the subsequent turning being done on a mandrel; second, the hole only may be bored at the first chucking, all the remaining work being done on a mandrel; and, third, the hole, hub, and one radial face may be turned at one chucking, and the remaining face turned at a separate chucking. If the first plan be adopted, any error in the truth of the mandrel will throw the hole out of true with the hub, which would be a serious defect, causing the gland to jamb against one side of the piston rod, and also of the gland bore. The same evil is liable to result from the second method; it is best, therefore, to chuck the gland by the hub in a universal chuck, and simply face the outer face of the flange, and also its edge. The gland may then be turned end for end, and the hole, the hub, the inside radial flange face, and the hub radial face, may then all be turned at one chucking; there is but one disadvantage in this method, which is that the gland must be unchucked to try its fit in the gland hole, but if standard gauges are used such trial will not be necessary, while if such is not the case and an error of measurement should occur, the gland may still be put on a mandrel and reduced if necessary. In either method of chucking, the fit of the hole to the rod it is intended for cannot be tested without removing the gland from the chuck. TO TURN A PLAIN CYLINDRICAL RING ALL OVER IN A UNIVERSAL CHUCK.--Three methods may be pursued in doing this simple job: first, the hole may be bored at one chucking, and the two radial faces and the circumference turned at a second chucking; second, the diameter may be turned, first on the hole and two radial faces turned at a second chucking; and third the hole and one radial face may be turned at one chucking, and the diameter and second radial face at a second chucking. The last method is best for the following reasons. The tool can pass clear over the surfaces at each chucking without danger of coming into contact with the chuck jaws, which would cause damage to both; second, at the last chucking, the chuck jaws being inside the ring, the latter may be tested for truth with a pointer fixed in the tool rest, and therefore set quite true. It is obvious that at neither chucking should the ring be set so far within the chuck jaws that there will be danger of the tool touching them when turning the radial face. In the case of a ring too thin to permit this, and of too large a bore to warrant making a mandrel for it, the ring may be held on the outside and bored, and both radial faces turned to within a short distance of the chuck jaws; at the second chucking, the chuck jaws being within the ring bore, the work may be set true with a pointer, as before, and finished. If, however, a number of such rings were to be turned, it would pay to turn up another and thicker ring, and use it as a mandrel after the bore and one radial face of the ring had been turned. TO TURN AN ECCENTRIC STRAP AND ECCENTRIC.--The eccentric strap should be turned first, because it can then be taken apart and its fit to the eccentric tried while the latter is in the lathe, which is not the case with the eccentric. The strap should first be held in a universal chuck bolted to the face plate, or held in dogs such as shown in Fig. 893 at C, and one face should be turned. It should then be turned round on the chuck to bore it, and face the other side. If the shape of the strap will admit it, it is best chucked by plates and bolts holding the face first turned to the face plate, because in this case there will be no pressure tending to spring the straps out of their natural shape; otherwise, however, it may be held in a universal or independent jaw chuck, or if too large for insertion in chucks of this kind (which are rarely made for large lathes) it may be held in dogs such as shown in Fig. 893 at C. [Illustration: Fig. 1230.] [Illustration: Fig. 1231.] If after an eccentric strap is bored, and the bolts that hold its two halves together have been slackened, its diameter at A and at C, Fig. 1230, be measured, it will be found that A is less than C. The cause of this is partly explained under the head of tension of castings; but it is necessary to add that the diameters at A and at C in the figure are equal while the strap is in the lathe, or until the bolts holding the two halves of the strap together are released, yet so soon as this is done the diameter at A will reduce, the bore becoming an oval.[18] [18] This occurs in all castings of similar form, as brasses, &c. Now, it is obvious that the eccentric must be turned to the diameter at C, or otherwise it will have lost motion in the strap. If, however, the eccentric be turned to the diameter of C, the strap cannot be tried on, as it will bind at the corners, as shown in Fig. 1231. To remedy this evil it is usual to put a piece of sheet tin or metal between the joint faces of the two halves of the eccentric straps before they are chucked to turn them, and to bore them too large to the amount of the thickness of sheet metal so employed. After the straps are bored these pieces of metal are removed, and the strap halves bolted together as in Fig. 1230, the diameter at C being that to which the eccentric must be turned. If the sheet metal so inserted were thick enough, the strap bore will measure the same at A as at C, Fig. 1230. If it were too thick the diameter at A will be greatest, while if too thin the diameter at A will be the least. There is no rule whereby the necessary thickness for a given size of strap may be known, and the workman is usually governed by his experience on castings of similar metal, or from the same moulding shop. He prefers, however, to be on the safe side by not putting in too great a thickness, because it is easier to scrape away the bore at the joint than it is to file away the joint faces. The following thicknesses for the respective diameters may be considered safe for castings that have not been reheated after casting. Diameter Thickness of metal to of place between the bore. strap valves. Inches. Inch. 6 1/64 12 1/32 18 3/64 24 1/8 In turning a new strap for an old eccentric, it will be necessary, when taking the diameter of the eccentric, to take a piece of tin of the same thickness as that placed between the eccentric lugs or jaws, and place it between the caliper leg and the eccentric, so that the diameter of the strap across C, Fig. 1230, may be made equal when the tin is removed to the diameter of the eccentric. In turning up the eccentric, the plain face should be faced first, setting it true, or nearly so, with the circumference of the eccentric, as will be the case if the circumference is held in a universal chuck, but if the hub is so long that this cannot be done because the chuck jaws cannot reach the circumference, the hub itself may be held in an independent jaw chuck. The face turned may then be turned round, so as to meet the face of the chuck against which it should bed fairly, so as to run true. At this chucking the hole bore, the hub, and the radial faces should be turned, all these surfaces being roughed out before any one surface is finished. The eccentric must then be again reversed, so that the face of the hub meets, the face plate being held by bolts as shown for a crank in figure, when the work being set to the lines marked (so as to give it the correct amount of throw) may be turned to fit the bore of the strap, the strap being taken apart so as to try it on, which this method of chucking will readily permit. Now, in an eccentric, the surfaces requiring to be most true one with the other are those of the bore and of the circumference where the strap fits, and since the latter was turned with the hub face to the chuck, and that hub face was turned at the same chucking as the hole was bored (and must, therefore, be true to the bore), the bore and circumference will be as true as it is practicable to get them, because upon the truth of the last chucking alone will the truth of the work depend. Small eccentrics may be held for all their chuckings in jaw chucks, but not so truly as if chucked on a face plate, because of the difficulty of keeping the radial faces of such jaws true, which occurs by reason of the causes explained with reference to Figs. 848 and 849. Eccentrics having so much throw upon them as to render it difficult to hold them for the last chucking by the method above given (by bolts through the bore), usually have openings through them on the throw side, and in this case parallel pieces may be placed behind the radial face (on the hub side of the eccentric), such parallel pieces being thick enough to keep the hub face clear of the chuck face, and bolts may be passed through the said opening to hold the eccentric. Another method would be as follows:-- The outside diameter of the eccentric may be gripped in a dog chuck, if the dogs of the chuck project out far enough to reach it (otherwise the dogs may grip the hub of the eccentric), while the hole is bored and the plain face of the eccentric turned. The eccentric must then be reversed in the lathe, and the hub and the radial face on that side must be turned. Then the plain face of the eccentric must be bolted to the face plate by plates placed across the spaces which are made to lighten the eccentric, and by a plate across the face of the hub. The eccentric, being set true to the lines, may then be turned on its outside diameter to fit the strap; to facilitate which fitting, thin parallel strips may be placed between the face plate and the plain face of the eccentric at this last chucking. It will be observed that, in either method of chucking, the outside diameter of the eccentric (that is to say, the part on which the strap fits) is turned with the face which was turned at the same chucking at which the hole was bored, clamped to the face plate. In cases where a number of eccentrics having the same size of bore and the same amount of throw are turned, there may be fitted to the face plate of the lathe a disk (such as shown in Fig. 888), of sufficient diameter to fit the hole of the eccentric, the said disk being fastened to the face plate at the required distance from the centre of the lathe to give the necessary amount of throw to the eccentric. The best method of fastening such a disk to the face plate is to provide it with a plain pin turned true with the disk, and let it fit a hole (bored in the face plate to receive it) sufficiently tightly to be just able to be taken in and out by the hand, the pin being provided with a screw at the end, so that it can be screwed tight by a nut to the face plate. The last chucking of the eccentric is then performed by placing the hole of the eccentric on the disk, which will insure the correctness of the throw without the aid of any lines on the eccentric which may be set as true as the diameter of the casting will permit, and then turned to fit the strap. TO TURN A CYLINDER COVER.--A cylinder cover affords an example of chucking in which the work done at one chucking requires to be very true with that done at a subsequent chucking, thus the gland hole which is on one side requires to be quite true with the diameter that fits into the cylinder bore, this diameter being on the opposite side. If the polished or gland side of the cover be turned first, the hole for the packing ring and that for the gland may be bored with the assurance that one will be true with the other, while the polished outside face may be turned at the same chucking. But when the cover is turned round in the lathe to turn the straight face, though the hole may be set true as far as can be ascertained in its short length, yet that length is too short to be an accurate guide, and the hole for the packing ring may appear true, while that for the gland, being longer, will have any error in the setting, multiplied by reason of its greater length. It is better, therefore, to turn the plain face first, gripping the cover by the gland flange so that the plain radial face, the step that fits the cylinder bore, and the outer edge of the cover flange may be turned at one chucking; then when the cover is turned round in the chuck, the flat face may be set true by resting against the radial surface of the chuck jaws, and the concentric truth may be set by the outer edge of the flange, which, being of the extreme diameter of the cover, will most readily show any want of truth in the setting. If in this case a universal chuck be used, and the work does not run quite true, it may be corrected by slacking the necessary dog or jaw on one side, and tightening up again from the screw of the necessary jaw on the other. This occurs because from the wear, &c., there is always some small amount of play or lost motion in the jaw screws, and in the mechanism operating them, and by the above means this is taken advantage of to true the work. If from any cause the work cannot be held for the first chucking by means of the gland hole flange, it must be held by the circumferential edge of the cover, letting the jaws envelop as small a distance over that edge as possible, the protruding part of it may then be turned up as close to the chuck jaws as possible, and this turned part may still be used to set the cover concentrically true at the second chucking. In a very small cover the gland hole may have a mandrel fitted to it and be turned therefrom on both radial faces, or on one face only, the other being turned at the chucking at which the holes were bored. In a cover too large to be held in a jaw chuck, the cover may be held in chucking dogs such as shown at C in Fig. 893, the edge protruding as much as possible from the dog screws, and being turned half way across at one chucking, and finished at the second chucking. To set the radial face at the second chucking, the surface gauge, applied as shown in Fig. 894, may be employed. If the bore of the packing ring or piston rod hole is large enough to permit it, that hole and the gland hole may be bored at the same chucking as that at which the plain face and step that fits in the cylinder bore is turned, thus ensuring truth in all the essential parts of the cover. But in this case these operations should be performed at the last of the two chuckings, so as to eliminate any error that might arise from the casting altering its shape by reason of the removal of the metal on the radial face of the gland hole side of the cover. TO TURN A PULLEY.--A pulley affords an excellent example of lathe work, because it may be operated upon by several different methods: thus, for boring it may be held, if small, in a dog chuck, with the jaws inside the rim; in a dog chuck with the jaws outside the rim; in a dog chuck by the hub itself (if the hub is long enough). A larger pulley may be chucked for boring by the rim held in a jaw chuck; by the rim held by bolts and plates, or by the rim held by dogs, such as shown in Fig. 893, or by the arms rested on pieces placed between them and the chuck, and then bolts and plates applied to those arms. The rim may be turned by placing the pulley on a mandrel and driving that mandrel by a dog or carrier; by placing it on a mandrel and driving it by a Clements driver such as shown in Fig. 753, and having two diametrically opposite driving pins, placed to bear against diametrically opposite arms; by holding the arms to the chuck as before described, and performing the boring and facing at one chucking; or by holding the rim on its inside by the chuck jaws, so as to turn and bore the pulley at one chucking, which can be done when the inside of the rim is parallel, or not sufficiently coned to cause it to slip off the jaws, or when the jaws will reach to the centre of the rim width. The advantages and disadvantages of these various methods are as follows:-- From the weakness of the pulley rim it is apt to distort when held with sufficient chuck-jaw pressure to enable the turning of the rim face and edge. But this would not affect the truth of the hole; hence the rim may be gripped in a chuck to bore the hole and face the hub. If so held it should be held true to the inside face of the rim, so that the bore will be true to the same, and then in turning the outside diameter it will be made as true as possible with the rim, which will preserve the balance of the pulley as much as possible. For these reasons the inside of the rim should be the part set to run true, whatever method of chucking be employed; hence, if the circumstances will permit of holding the hub to bore it, an independent jaw chuck should be employed (that is, of course, a chuck capable of independent jaw movement). If the pulley be chucked by the arms, it is well-nigh impossible to avoid springing those arms from the pressure of the bolts, &c., holding them, and as a result the pulley face, though turned true, will not be true of itself, nor true with the hole, when the arms are released from such pressure. If the pulley is of such a large size that its rim must be held by bolts and plates while the boring is progressing, such bolts, &c., must be placed on the outside of the rim, so as not to be in the way when setting the pulley true to the inside of the rim. A small pulley may be turned on a mandrel driven by a dog, which is the truest method of turning, because the rim is in this case strained by the pressure of the cut only. But a dog will not drive a cut at such a leverage as exists at the rim of a pulley above about 18 inches in diameter; furthermore, in a large wheel there would not be sufficient friction between a mandrel and the pulley bore to drive the roughing cut on the pulley face. It is necessary, therefore, to drive the pulley from the arms, while holding it on a mandrel, but if it be driven by one arm the whole strain due to driving will fall on that one arm, and on one side of the pulley only, and this will have a tendency to cause the rim at and near its junction with that arm to spring or deflect from its natural position, and, therefore, to be not quite true; all that can be done, therefore, is to drive by two arms with a Clements driver, so as to equalize the pressure on them. An excellent method of chucking a pulley, and one that with care avoids the disadvantages mentioned in the foregoing methods, is shown in Figs. 1232 and 1233. It consists of a clamping dog, Fig. 1234, that fastens to the lathe face plate, and secures the pulley by its arms, while supporting the rim and preventing it from chattering, if it is weak or slight. [Illustration: Fig. 1232.] This dog is bolted to the face plate by the two studs A and B. At C is a set screw for clamping the pulley arms against the screw D, and at F is a screw that steadies the pulley rim between the arms. [Illustration: Fig. 1233.] CUTTING SCREWS IN THE LATHE WITH SLIDE REST TOOLS.--In order to cut a thread in the lathe with a slide rest tool, it is necessary that the gear-wheels which transmit motion from the cone spindle to the feed screw shall be of the proportions necessary to give to the lathe carriage and slide rest sufficient lateral movement or traverse for lathe revolution to cut a thread of the desired pitch. [Illustration: Fig. 1234.] Suppose now that the feed screw makes a revolution in the same time that the cone spindle does, and it is evident that the thread cut by the slide rest tool will be of the same pitch as is the pitch of the lathe feed screw. If the feed screw gear-wheels of the lathe are what is called single geared (which means that no one stud in the change gearing carries more than one gear-wheel), it does not matter what are the sizes or how many teeth there are in the wheels used to convey or transmit motion from the cone spindle to the feed screw, for so long as the number of teeth on the cone spindle gear and that on the feed screw are equal, the feed screw will make one revolution in the same time as the cone spindle makes a revolution, and the cutting tool will travel a lateral distance equal to the pitch of the lead screw. [Illustration: Fig. 1235.] Suppose, for example, that Fig. 1235 represents the screw cutting gear or change wheels of a lathe, wheel D being the driver, I an intermediate wheel for transmitting motion from the driver D to the lead-screw wheel S. Suppose, also, that D has 32, I 80, and S 32 teeth, and we have a simple or single-geared lathe. In this case it may first be proved that we need not concern ourselves with the number of teeth in the intermediate I, because its number of teeth is of no consequence. For example, the 32 teeth in D will in a revolution move 32 of the teeth in I past the line of centres, and it is obvious that I will move the 32 teeth in S past the line of centres, causing it to make one revolution the same as D. If any other size of wheel be used for an intermediate, the effect will be precisely the same, the revolutions of D and of S remaining equal. Under these conditions the lathe would cut a thread whose pitch would be the same as that of the thread on the lead screw. [Illustration: Fig. 1236.] Now let us turn to Fig. 1236, representing an arrangement of gearing common in American practice, and we have within the lathe-head three gears, A, B, and C, which cannot be changed. Of these, B and C are simply intermediate wheels, the respective diameters of which have no effect upon the revolutions of the lead screw, except that they convey the motion to D. To demonstrate this, suppose the wheels to have the number of teeth marked respectively against them in the end view of the figure, C and D having each 20 teeth, and the one revolution of the live spindle wheel A will cause the lead-screw wheel to make one revolution, because A and S contain the same number of teeth. This may be made plain as follows: The 20 teeth in A will in one revolution cause B to make two revolutions, because B has but half as many teeth as A. The two revolutions of B will cause C to make but one revolution, because C has twice as many teeth as B has. Now, C and D are fast on the same shaft R; hence they revolve together, the one revolution of C simply being conveyed by the shaft R to D, and it is clear that the one revolution of A has been conveyed without change to D, and that, therefore, D may be considered to have simply taken the place of A, unaffected by the wheels B, C. Wheel I is again an intermediate, so that, whatever its diameter or number of teeth, one revolution of D will cause one revolution of S. Thus in this arrangement the lead screw will again revolve at the same speed as the live spindle, and the thread cut will be of the same pitch as the pitch of the lead screw. Practically, then, all the wheels between A and S, as thus arranged, act as simple intermediates, the same as though it were a single-geared lathe, which occurs because C and D have the same number of teeth, and we have, therefore, made no use of the shaft R to compound the gearing. [Illustration: Fig. 1237.] The term "compounded" as applied to the change gears of a lathe, means that there exists in it a shaft or some equivalent means by which the velocity of the wheels may be changed. Such a shaft is shown at R in Fig. 1236, and it affords a means of compounding by placing on its outer end, as at D, a wheel that has a different number of teeth to that in wheel C. In Fig. 1237 this change is made, wheel D having 40 teeth instead of the 20 it had before. As in the former case, however, it will make one revolution to one of C or one of A, but having 40 teeth it will move 40 of the teeth in I past the line of centres, and this will cause the lead screw wheel S to make two revolutions, because it has 20 teeth only. Thus, the compounding of C and D on shaft R has caused S to make two revolutions to one of A, or, what is the same thing, one revolution of A will in this case cause S to make two revolutions, and the thread cut would be twice as coarse as the lead-screw thread. In the case of a lathe geared as in either Fig. 1235 or 1236, all the wheels that we require to consider in calculating the change wheels are D and S. Now, the shaft R is called the "mandrel," the "stud," or the "spindle," all three terms being used, and the wheel D is the wheel on the stud, mandrel, or spindle, while in every case S is that on the lead screw, and the revolutions of this wheel D and those of the lead screw will be in the same proportion as exists between their numbers of teeth. In considering their revolutions it is to be borne in mind that when D has more teeth than S the speed of the lead screw is increased, and the lathe will cut a thread coarser than that of its lead screw, or when D has less teeth than S the speed of the lead screw is diminished, and the pitch of thread cut will be finer than that of the lead screw. [Illustration: Fig. 1238.] Another method of compounding is shown in Fig. 1238, the compounded pair C D being on a stud carried in the swing frame F. Now, suppose A has 32, C 64, D 32, and S 64 teeth, the revolution being in the same proportion as the numbers of teeth, C will make one-half a revolution to one revolution of A, and D, being fast to the same stud as C, will also make one-half revolution to one revolution of A. This one-half revolution of D will cause S to make one-quarter of a revolution; hence the thread cut will be four times as fine as the pitch of the thread on the lead screw, because while the lathe makes one turn the lead screw makes one-quarter of a turn. In this arrangement we are enabled to change wheel C as well as wheel D (which could not be done in the arrangement shown in Fig. 1236), and for this reason more changes can be made with the same number of wheels. When the wheel C makes either more or less revolutions than the driver A, it must be taken into account in calculating the change wheels. As arranged in Fig. 1236, it makes the same number as A, which is a very common, arrangement, but in Fig. 1238 it is shown to have twice as many teeth as A; hence it makes half as many revolutions. In the latter case we have two pairs of wheels, in each of which the driven wheel is twice the size of the driver; hence the revolutions are reduced four times. Suppose it is required to cut a thread of eight to an inch on a lathe such as shown in Fig. 1235, the lead screw pitch being four per inch, and for such simple trains of gearing we have a very simple rule, as follows:-- _Rule._--Put down the pitch of the lead screw as the numerator, and the pitch of thread you want to cut as the denominator of a vulgar fraction, and multiply both by the pitch of the lead screw, thus: Pitch of lead screw. {the number of teeth for the Pitch of lead screw 4 4 16 = {wheel on the spindle. - × - = -- Pitch to be cut 8 4 32 = {the number of teeth for the {wheel on the lead screw. There are three things to be noted in this rule; and the first is, that when the pitch of the lead screw and the pitch of thread you want to cut is put down as a fraction, the numerator at once represents the wheel to go on the stud, and the denominator represents the wheel to go on the lead screw, and no figuring would require to be done providing there were gear-wheels having as few teeth as there are threads per inch in the lead screw, and that there was a gear-wheel having as many teeth as the threads per inch required to be cut. For example, suppose the lathe in Fig. 1236 to have a lead screw of 20 per inch, and that the change wheels are required to cut a pitch 40, then we have 20/40, the 20 to go on at D in Fig. 1236 and the 40 to go on the lead screw. But since lead screws are not made of such fine pitch, but vary from two threads to about six per inch, we simply multiply the fraction by any number we choose that will give us numbers corresponding to the teeth in the change wheels. Suppose, for example, the pitch of lead screw is 2, and we wish to cut 6, then we have 2/6, and as the smallest change wheel has, say, 12 teeth we multiply the fraction by 6, thus: 2/6 × 6/6 = 12/36. If we have not a 12 and a 36 wheel, we may multiply the fraction by any other number, as, say, 8; thus: 2/6 × 8/8 = 16/48 giving us a 16 wheel for D, Fig. 1236, and a 48 wheel for the lead screw. The second notable feature in this rule is that it applies just the same whether the pitch to be cut is coarser or finer than the lead screw; thus: Suppose the pitch of the lead screw is 4, and we want to cut 2. We put these figures down as before 4/2, and proceed to multiply, say, by 8; thus: 4/2 × 8/8 = 32/16, giving a 32 and a 16 as the necessary wheels. The third feature is, that no matter whether the pitch to be cut is coarser or finer than the lead screw, the wheels go on the lathe just as they stand in the fraction; the top figure goes on top in the lathe, as, for example, on the driving stud, and the bottom figures of the fraction are for the teeth in the wheel that goes on the bottom of the lathe or on the lead screw. No rule can possibly be simpler than this. Suppose now that the pitch of the lead screw is 4 per inch and we want to cut 1-1/2 per inch. As the required pitch is expressed in half inches, we express the pitch of the lead in half inches, and employ the rule precisely as before. Thus, in four there are eight halves; hence, we put down 8 as the numerator, and in 1-1/2 there are three halves, so we put down 3 and get the fraction 8/3. This will multiply by any number, as, say, 6; thus: (8/3) × (6/6) = (48/18), giving us 48 teeth for the wheel D in Fig. 1236, and 18 for the lead screw wheel S. In a lathe geared as in Fig. 1235 the top wheel D could not be readily changed, and it would be more convenient to change the lead screw wheel S only. Suppose, then, that the lead screw pitch is 2 per inch, and we want to cut 8. Putting down the fraction as before, we have 2/8, and to get the wheel S for the lead screw we may multiply the number of teeth in D by 8 and divide it by 2; thus: 32 × 8 = 256, and 256 ÷ 2 = 128; hence all we have to do is to put on the lead screw a wheel having 128 teeth. But suppose the pitch to be cut is 4-1/4, the pitch of the lead screw being 2. Then we put both numbers into quarters, thus: In 2 there are 8 quarters, and in 4-1/4 there are 17 quarters; hence the fraction is 8/17. If now we multiply both terms of this 8/17 by 4 we get 32/68, and all we have to do is to put on the lead screw a wheel having 68 teeth. When we have to deal with a lathe compounded as in Fig. 1238, in which the combination can be altered in two places--that is, between A and C and between D and S--the wheel A remaining fixed, and the pitch of the lead screw is 2 per inch, and it is required to cut 8 per inch--this gives us the fraction 2/8, which is at once the proportion that must exist between the revolutions of the wheel A and the wheel S. But in this case the fraction gives us the number of revolutions that wheel S must make while the wheel A is making two revolutions, and it is more convenient to obtain the number that S requires to make while A is making one revolution, which we may do by simply dividing the pitch required to be cut by the pitch of the lead screw, as follows: Pitch of thread required, 8; pitch of lead screw, 2; 8 ÷ 2 = 4 = the revolutions S must make while A makes one. We have then to reduce the revolutions four times, which we may do by putting on at C a wheel with twice as many teeth in it as there are in A, and as A has 32, therefore C must have 64 teeth. When we come to the second pair of wheels, D and S, we may put any wheel we like in place of D, providing we put on S a wheel having twice as many. But suppose we require to cut a fractional pitch, as, say, 4-1/8 per inch, the pitch of lead screw being 2, all we have to do is to put the pitch of the lead screw into eighths, and also put the number of teeth in A into eighths; thus: In two there are 16 eighths, and in the pitch required there are 33 eighths; hence for the pitch of the lead screw we use the 16, and for the thread required we use the 33, and proceed as before; thus: Pitch of thread Pitch of lead required. screw. 33 ÷ 16 = 2-1/16 = the revolution which A must make while wheel B makes one revolution. The simplest method of doing this would be to put on at C a wheel having 2-1/16 times as many teeth as there are in A. Suppose then that A has 32 teeth, and one sixteenth of 32 = 2, because 32 ÷ 16 = 2. Then twice 32 is 64, and if we add the 2 to this we get 66; hence, if we give wheel C 66 teeth, we have reduced the motion the 2-1/16 times, and we may put on D and S wheels having an equal number of teeth. Or we may put on a wheel at C having the same number as A has, and then put on any two wheels at D and C, so long as that at S has 2-1/16 times as many teeth as that at D. Again, suppose that the pitch of a lead screw is 4 threads per inch, and that it be required to find what wheels to use to cut a thread of 11/16 inch pitch, that is to say, a thread that measures 11/16 inch from one thread to the other, and not a pitch of 11/16 threads per inch: First we must bring the pitch of the lead screw and the pitch to be cut to the same terms, and as the pitch to be cut is expressed in sixteenths we must bring the lead screw pitch to sixteenths also. Thus, in an inch of the length of the lead screw there are 16 sixteenths, and in this inch there are 4 threads; hence each thread is 4/16 pitch, because 16 ÷ 4 = 4. Our pitch of lead screw expressed in sixteenths is, therefore, 4, and as the pitch to be cut is 11/16 it is expressed in sixteenths by 11; hence we have the fraction 4/11, which is the proportion that must exist between the wheels, or in other words, while the lathe spindle (or what is the same thing, the work) makes 4 revolutions the lead screw must make 11. Suppose the lathe to be single geared, and not compounded, and we multiply this fraction and get-- 4 × 4 16 = wheel to go on lead screw. -- - = -- 11 × 4 44 = " " stud or mandrel. 4 × 5 20 = wheel to go on lead screw. Or, -- - = -- 11 × 5 55 = " " stud or mandrel. 4 × 6 24 = wheel to go on lead screw. Or, -- - = -- 11 × 6 66 = " " stud or mandrel. But suppose the lathe to be compounded as in Fig. 1235, and we may arrange the wheels in several ways, and in order to make the problem more practical, we may suppose the lathe to have wheels with the following numbers of teeth, 18, 24, 36, 36, 48, 60, 66, 72, 84, 90, 96, 102, 108, and 132. [Illustration: Fig. 1239.] Here we have two wheels having each 36 teeth; hence we may place one of them on the lathe spindle and one on the lead screw, as in Fig. 1239; and putting down the pitch of the lead screw, expressed in sixteenths as before, and beneath it the thread to cut also in sixteenths, we have: 4 × 6 24 = wheel to be driven by lathe spindle, -- - = -- 11 × 6 66 = " to drive lead screw wheel; the arrangement of the wheels being shown in Fig. 1239. We may prove the correctness of this arrangement as follows: The 36 teeth on the lathe spindle will in a revolution cause the 24 wheel to make 1-1/2 revolutions, because there are one and a half times as many teeth in the one wheel as there are in the other; thus: 36 ÷ 24 = 1-1/2. Now, while the 24 wheel makes 1-1/2, the 66 will also make 1-1/2, because they are both on the same sleeve and revolve together. In revolving 1-1/2 times the 66 will cause the 36 on the lead screw to make 2-3/4 turns, because 99 ÷ 36 = 2-3/4 (or expressed in decimals 2.75), and it thus appears that while the lathe spindle makes one turn, the lead screw will make 2-3/4 turns. Now, the proportion between 1 and 2-3/4 is the same as that existing between the pitch of the lead screw and the pitch of the thread we want to cut, both being expressed in sixteenths; thus: Pitch of lead screw in sixteenths 4 } }, and 11 ÷ 4 = 2-3/4; " to be cut in sixteenths 11 } that is to say, 11 is 2-3/4 times 4. Suppose it is required, however, to find what thread a set of gears already on the lathe will cut, and we have the following rule: _Rule._--Take either of the driven wheels and divide its number of teeth by the number of teeth in the wheel that drives it, then multiply by the number of teeth in the other driving wheel, and divide by the teeth in the last driven wheel. Then multiply by the pitch of the lead screw. [Illustration: Fig. 1240.] _Example._--In Fig. 1240 are a set of change wheels, the first pair of which has a driving wheel having 36 teeth, and a driven wheel having 18 teeth. The second pair has a driving wheel of 66 teeth, and a driven wheel of 48. Let us begin with the first pair and we have 36 ÷ 18 = 2, and this multiplied by 66 is 132. Then 132 ÷ 48 = 2.75, and 2.75 multiplied by 4 is 11, which is the pitch of thread that will be cut. Now, whether this 11 will be eleven threads per inch, or as in our previous examples a pitch of 11/16 inch from one thread to another or to the next one, depends upon what the pitch of the lead screw was measured in. [Illustration: Fig. 1241.] If it is a pitch of 4 threads per inch, the wheels will cut a thread of 11 per inch, while if it were a thread of 4/16 pitch, the thread cut will be 11/16 pitch. Let us now work out the same gears beginning from the lead screw pair, and we have as follows: Number of teeth in driver is 66, which divided by the number in the driven, 48, gives 1.375. This multiplied by the number of teeth in the driver of the other pair = 36 gives 49.5, which divided by the number of teeth in the driven wheel of the first pair gives 2.75, which multiplied by the pitch of the lead screw 4 gives 11 as before. Taking now the second example as in Fig. 1240, and beginning from the first pair of gears, we have, according to the rule, 36 ÷ 48 × 66 ÷ 18 × 4 = 11 = pitch the gears will cut; or proceeding from the second pair of gears, we have by the rule, 66 ÷ 18 × 36 ÷ 48 × 4 = 11 = the pitch the gears will cut. It is not often, however, that it is required to determine what threads the wheels already on a lathe will cut, the problem usually being to find the wheels to cut some required pitch. But it may be pointed out that when the problem is to find the result produced by a given set of wheels, it is simpler to begin the calculation from the wheel already on the lathe spindle, rather than beginning with that on the lead screw, because in that case we begin at the first wheel and calculate the successive ones in the same order in which we find them on the lathe, instead of having to take the last pair in their reverse order, as has been done in the examples, when we began at the wheel on the lead screw, which we have termed the second pair. The wheels necessary to cut a left-hand thread are obviously the same as those for a right-hand one having an equal pitch; all the alteration that is necessary is to employ an additional intermediate wheel, as at I in Fig. 1241, which will reverse the direction of motion of the lead screw. For a lathe such as shown in Fig. 1235, this intermediate wheel may be interposed between wheels D and I or between I and S. In Fig. 1236, it may be placed between D and I or between I and S, and in Fig. 1238 it may be placed between A and C or between D and S. [Illustration: Fig. 1242.] Here it may be well to add instructions as to how to arrange the change wheels to cut threads in terms of the French centimètre. Thus, an inch equals 254/100 of a centimètre, or, in other words, 1 inch bears the same proportion to a centimètre as 254 does to 100, and we may take the fraction 254/100 and reduce it by any number that will divide both terms of the fraction without leaving a remainder; thus, 254/100 ÷ 2 = 127/50. If, then, we take a pair of wheels having respectively 127 and 50 teeth, they will form a compound pair that if placed as in Fig. 1242 will enable the cutting of threads in terms of the centimètre instead of in terms of the inch. Thus, for example, to cut 6 threads to the centimètre, we use the same change wheels on the stud and on the lead screw that would be used to cut 6 threads to the inch, and so on throughout all other pitches. CUTTING DOUBLE OR OTHER MULTIPLE THREADS IN THE LATHE.--In cutting a double thread the change wheels are obviously arranged for the pitch of the thread, and one thread, as A in Fig. 251 is cut first, and the other, B, afterwards. In order to insure that B shall be exactly midway between A, the following method is pursued. Suppose the pitch of the lead screw is 4 threads per inch, and that we require to cut a double thread, whose actual pitch is 8 per inch, and apparent pitch 16 per inch, then the lead screw requires to make half a turn to one turn of the lathe spindle; or what is the same thing, the lathe spindle must make two turns to one of the lead screw, hence the gears will be two to one, and in a single-geared lathe we may put on a 36 and a 72, as in Fig. 1243, in which the intermediate wheels are omitted, as they do not affect the case. With these wheels we cut a thread of 8 per inch and then, leaving the lead screw nut still engaged with the lead screw and the tool still in position to cut the thread already formed, we make on the change wheels a mark as at S T, and after taking off the driving gear we make a mark at space _u_, which is 18 teeth distant from S, or half-way around the wheel. We then pull the lathe around half a turn and put the driving gear on again with the space _u_ engaged with the tooth T, and the lathe will cut the second thread exactly intermediate to the first one. If it were three threads that we require to cut, we should after the driving gear was taken off give the lathe one-third a revolution, and put it back again, engaging the twelfth space from S with tooth T, because one-third of 36 is 12. [Illustration: Fig. 1243.] It is obviously necessary, in cutting multiple threads in this way, to so select the change wheels that the driving gear contains a number of teeth that is divisible without leaving a remainder by the thread to be cut: thus, for a double thread the teeth must be divisible by two, hence a 24, 30, 34, 36, or any even number of teeth will do. For a triple thread the number of teeth in the driving gear must be divisible by 3, and so on. But suppose the driving gear is fast upon the lathe spindle and cannot be taken off, and we may then change the position of the lead screw gear to accomplish the same object as moving the lathe spindle. Thus for a double thread we would require to remove the driving gear as before, and then pull round the lead screw so that the eighteenth tooth from T would engage with space S, which is obviously the same thing as moving the driving gear round 18 teeth. In short work of small diameter the tool will retain its sharpness so long, that one tool will rough out and finish a number of pieces without requiring regrinding, and in this case the finishing cuts can be set by noting the position of the feed screw handle when the first piece is finished to size and the tool is touching the work, so that it may be brought to the same position in taking finishing cuts on the succeeding pieces; but the calipers should nevertheless be used, being applied to the threads as in Figs. 1244 and 1245, which is the best method when there is a standard to set the calipers by. [Illustration: Fig. 1244.] After a threading tool has carried its cut along the required length of the work, the carriage must be traversed back, so that the second cut may be started. In short work the overhead cross belt that runs the lathe backwards is sufficiently convenient and rapid for this purpose, but in long screws much time would be lost in waiting while the carriage runs back. In the Ames lathe there is a device that enables the carriage to be traversed back by hand, and the feed nut to be engaged without danger of cutting a double thread, or of the tool coursing to one side of the proper thread groove, which is a great convenience. The construction of this device is shown in Fig. 574. In lathes not having a device for this purpose, the workman makes a chalk mark on the tail of the work driver, and another on the top of the lead screw gear, and by always moving the carriage back to the same point on the lathe bed, and engaging the lead screw nut when these two chalk marks are at the top of their paths of revolution, the tool will fall into its correct position and there will be no danger of cutting a double thread. [Illustration: Fig. 1245.] In cutting [V] threads of very coarse pitch it will save time, if the thread is a round top and bottom one, to use a single-pointed slide rest tool, and cut up the thread to nearly the finished depth, leaving just sufficient metal for the chaser to finish the thread. In using the single-pointed tool _on_ the roughing cuts of very coarse pitches, it is an advantage to move the tool laterally a trifle, so that it will cut on one side or edge only. This prevents excessive tool spring, and avoids tool breakage. This lateral movement should be sufficient to let the follower side or edge of the tool just escape the side of the thread, and all the cut be taken by the leading side or edge of the tool. This is necessary because the tool will not cut so steadily on the follower as on the leading cutting edge, for the reason that the pressure of the cut assists to keep the feed screw nut against the sides of the feed screw thread, taking up the lost motion between them, whereas the pressure of a cut taken on the follower side of the thread tends to force the thread of the feed nut away from the sides of the feed screw thread and into the space between the nut thread afforded by the lost motion, and as a result the slide rest will move forward when the tool edges meet exceptionally hard places or spots in the metal of the work, while in any event the tool will not operate so steadily and smoothly. If the screw is a long one, the cutting should be done with a liberal supply of oil or water to keep it cool, otherwise the contraction of the metal in cooling will leave the thread finer than it was when cut. This is of special importance where accuracy of pitch is requisite. [Illustration: Fig. 1246.] In cutting a taper thread in a lathe, it is preferable that the taper be given by setting over the lathe tailstock, rather than by operating the cross slider from a taper-turning attachment, because the latter causes the thread to be cut of improper pitch. Thus, in Fig. 1246 is a piece of work between the lathe centres, and it will be readily seen that supposing the lathe to be geared to cut, say, 10 threads per inch, and the length A of the work to be 2 inches long, when the tool has traversed the distance A it will have cut 20 threads, and it will have passed along the whole length of the side B of the work and have cut 20 threads upon it, but since the length of line B is greater than that of A, the pitch of the thread cut will be coarser than that due to the change wheels. The amount of the error is shown by the arc C, which is struck from D as a centre; hence from C to E is the total amount of error of thread pitch. [Illustration: Fig. 1247.] But if the lathe tailstock sets over as in Fig. 1247, then the pitch of the thread will be cut correct, because the length of B will equal the length of tool traverse; hence at each work revolution the tool would advance one-twentieth of the length of the surface on which the thread is cut, which is correct for the conditions. [Illustration: _VOL. I._ =METHODS OF BALL TURNING.= _PLATE XIII._ Fig. 1248. Fig. 1249. Fig. 1250. Fig. 1251. Fig. 1252. Fig. 1253. Fig. 1254. Fig. 1255.] CHAPTER XIII.--EXAMPLES IN LATHE WORK. BALL TURNING.--One of the best methods of turning balls of the softer materials, such as wood, bone, or ivory, is shown in Figs. 1248 and 1249, in which are shown a blank piece of material and a tubular saw, each revolving in the direction denoted by the respective arrows. The saw is fed into the work and performs the job, cutting the ball completely off. In this case the saw requires to be revolved quicker than the work--indeed, as quickly as the nature of the material will permit, the revolving of the work serving to help the feed. Of course, the teeth of such a saw require very accurate sharpening if smooth work is to be produced, but the process is so quickly performed that it will pay to do whatever smoothing and polishing may be required at a separate operation. This method of ball cutting undoubtedly gave rise to the idea of using a single tooth, as in Fig. 1250. But when a single tooth is employed the work must revolve at the proper cutting speed, while the tooth simply advances to the feed. If the work was cut from a cylindrical blank the cutter would require to be advanced toward the work axis to put on a cut and then revolved to carry that cut over the work, when another cut may be put on, and so on until the work is completed. The diameter of ball that can be cut by one cutter is here obviously confined to that of the bore of the cutter, since it is the inside edge of the cutter that does the finishing. This naturally suggests the employment of a single-pointed and removable tool, such as in Fig. 1251, which can be set to turn the required diameter of ball, and readily resharpened. To preserve the tool for the finishing cut several of such tools and holders may be carried in a revolving head provided to the lathe or machine, as the case may be. In any event, however, a single-pointed tool will not give the smoothness and polish of the ball cutter shown in Fig. 1252, which produces a surface like a mirror. It consists of a hardened steel tube C, whose bore is ground cylindrically true after it has been hardened. The ball B is driven in a chuck composed of equal parts of tin and lead, and the cutter is forced to the ball by hand. The ball requires to revolve at a quick speed (say 100 feet per minute for composition brass), while the cutter is slowly revolved. A simple attachment for ball turning in an ordinary lathe is shown in Fig. 1253. It consists of a base A, carrying a plate B, which is pivoted in A; has worm-wheel teeth provided upon its circumference and a slideway at S, upon which slides a tool rest R, operated by the feed-screw handle H. The cut is put on by operating H, and the feed carried around by means of the screw at W. The base plate A may be made suitable to bolt on the tool rest, or clamped on in place of the tool, as the circumstances may permit; or in some cases it might be provided with a stem to fit in place of the dead centre. For boring the seats for balls or other curved internal surfaces the device shown in Fig. 1254 may be used. It consists of a stem or socket S, fitting to the dead spindle in place of the dead centre, and upon which is pivoted a wheel W, carrying a tool T. R is a rack-bar that may be held in the lathe tool post and fed in to revolve wheel W and feed the tool to its cut. At P is a pin to maintain the rack in gear with the wheel. Obviously, a set-screw may be placed to bear against the end of the tool to move it endwise and put on the cut. An equivalent device is shown in Fig. 1255, in which the tool is pivoted direct into the stem and moved by a bar B, held in the tool post. The cut is here put on by operating the tail spindle, a plan that may also be used in the device shown in Fig. 1254. The pins P upon the bar are for moving or feeding the tool to its cut. It is obvious that in all these cases the point of the tool must be out of true vertically with the axis of the work. [Illustration: Fig. 1256.] [Illustration: Fig. 1257.] In turning metal balls by hand it is best to cast them with a stem at each end, as in Fig. 1257. [Illustration: Fig. 1258.] [Illustration: Fig. 1259.] To rough them out to shape, a gauge or template, such as in Fig. 1256, is used, being about 1/32 inch thick, which envelops about one-sixth of the ball's circumference. After the ball is roughed out as near as may be to the gauge, the stems may be nicked in, as in Fig. 1257, and broken off, the remaining bits, A, B, being carefully filed down to the template. The balls are then finished by chucking them in a chuck such as shown in Fig. 1258,[19] and a narrow band, shown in black in the figure, is scraped, bringing the ball to the proper diameter. The ball is then reversed in the chuck, as in Fig. 1259, and scraped by hand until the turning marks cross those denoted by the black band. The ball is then reversed, so that the remaining part of the black band that is within the chuck in Fig. 1259 may be scraped down, and when by successive chuckings of this kind the lightest of scrape marks cross and recross each other when the ball is reversed, it may be finished by the ball cutter, applied as shown in Fig. 1252, and finally ground to its seat with the red-burnt sand from the foundry, which is better than flour emery or other coarser cutting grinding material. [19] From _The American Machinist_. [Illustration: Fig. 1260.] [Illustration: Fig. 1261.] CUTTING CAMS IN THE LATHE.--Fig. 1260 represents an end view of cam to be produced, having four depressions alike in form and depth, and arranged equidistant round the circumference, which is concentric to the central bore. The body of a cam is first turned up true, and one of the depressions is filed in it to the required form and curvature. On its end face there is then drilled the four holes, A, B, C, D, Fig. 1261, these being equidistant from the bore E. A similar piece is then turned up in the lathe, and in its end is fitted a pin of a diameter to fit the holes A, B, &c., it being an equal distance from bore E. These two pieces are then placed together, or rather side by side, on an arbor or mandrel, with the pin of the one fitting into one of the holes, as A. Two tool posts are then placed in position, one carrying a dull-pointed tool or tracer, and the other a cutting tool. The dull-pointed tracer is set to bear against the cam shown in Fig. 1262, while the cutting tool is set to take a cut off the blank cam piece. The cross feed screw of the lathe is disengaged, and a weight W, Fig. 1262, attached to the slider to pull the tracer into contact with the cam F. As a result, the slide rest is caused to advance to and recede from the line of lathe centres when the cam depression passes the tracer point, the weight W maintaining contact between the two. Successive cuts are taken until the tool cuts a depression of the required depth. To produce a second cam groove, the piece is moved on the mandrel so that the pin will fall into a second hole (as, say, B, Fig. 1261), when, by a repetition of the lathe operation, another groove is turned. The whole four grooves being produced by the same means, they must necessarily be alike in form, the depths being equal, provided a finishing cut were taken over each without moving the cutting tool. [Illustration: Fig. 1263.] It will be observed that this can be done in any lathe having a slide rest, and that the grooves cut in one piece will be an exact duplicate of that in the other, or guide groove, save such variation as may occur from the thickness of the tracer point, which may be allowed for in forming the guide or originating groove. From the wear, however, of the tracer point, and from having to move the cutting tool to take successive depths of cut, this method would be undesirable for continuous use, though it would serve excellently for producing a single cam. An arrangement for continuous use is shown in Fig. 1263, applied to a lathe having a feed spindle at its back, with a cam G upon it. This cam G may be supposed to have been produced by the method already described. A tracer point H, or a small roller, may be attached to the end of the slide-rest and held against G by the weight W, which may be within the lathe shears if they have no cross girts, as in the case of weighted lathes. The slide-rest may be arranged to have an end motion slightly exceeding the motion, caused by the cam, of the tracer H. Change gears may then be used to cause the cam G to make one rotation per lathe rotation, cutting four recesses in the work; or by varying the rotations of G per lathe rotation, the number of recesses cut by the tool T may be varied. Successive depths of cut may then be put on by operating the feed screw in the ordinary manner. In this arrangement the depth and form of groove cut upon the work will correspond to the form of groove upon the cam-roller G; or each groove upon G being of a different character, those cut on the work will correspond. The wear on the cross slide will, in this case, be considerable, however, in consequence of the continuous motion of the tool-carrying slider, and to prevent this another arrangement may be used, it being shown in Fig. 1264 as applied to a weighted and elevating slide rest. The elevating part of the slide rest is here pivoted to the lathe carriage at I, the weight W preventing play (from the wear) at I. A bracket J is shown fast to the elevating slide of the rest, carrying a roller meeting the actuating cam G. In this arrangement the cut may be put on by the feed screw traversing the slider in the usual manner, or the elevating screw K may be operated, causing the roller at the end of J to gradually descend as each cut is put on into more continuous contact with G as the latter rotates. The form of groove cut by the tool does not, in this case, correspond to the form on G, because the tool lifts and falls in the arc of a circle of which pivot I is the centre of motion, and its radius from I being less than the radius of G, its motion is less. But in addition to this the direction of its motion is not that of advancing and receding directly toward and away from the line of lathe centres, and the cam action is reduced by both these causes. [Illustration: Fig. 1264.] [Illustration: Fig. 1265.] The location of pivot I is of considerable importance, since the nearer it is to the line of centres the less the action of the cam G is reduced upon the work. As this is not at first sight apparent, a few words may be said in explanation of it. It is obvious that the farther the pivot I is from the tool point the greater will be the amount of motion of the tool point, but this motion is not in a direction to produce the greatest amount of effect upon the work, as is demonstrated in Fig. 1265; referring to which, suppose line A B C to represent a lever pivoted at B, and that end A be lifted so that the lever assumes the position denoted by the dotted lines D and E, then the end of C will have moved from circle F to circle G, as denoted by arc H; arm C of the lever being one-half the length of arm A B, and from circle F to circle G, measured along the line H, being one-half the distance between A and the end of the line D, the difference in the diameters of circles F and G will represent the effect of the cam motion on the tool under these conditions. Now, suppose A J is a lever pivoted at K, and that end A is raised to the dotted line D, then arm J, being one-half the length of A K, will move half as much as end A, and will assume the position denoted by dotted line L, and the difference in the diameter of circles F and M will represent the cam motion upon the tool motion under these conditions. From this it appears that the more nearly vertical beneath the tool point the pivoted point is, the greater the effect produced by a given amount of cam motion. On this account, as well as on account of the direction of motion, the shape of the actuating cam may be more nearly that of the form required to be produced in proportion as the pivoted centre falls directly beneath the tool point. But, on the other hand, the wear of the pivot, if directly beneath the tool point, would cause more unsteadiness to the tool; hence it is desirable that it be somewhere between points K and B, the location being so made that (B representing the pivoted point of the rest) the line B C forms an angle of 50° with the line B A. It is obvious that when the work is to be cam-grooved on a radial face the pivoted design is unsuitable, and either that in Fig. 1262 or 1263 is suitable. Similar cam motions may be given to the cross feed of a lathe: thus, the Lane and Bodley Company of Cincinnati, Ohio, employ the following method for turning the spherical surfaces of their swiveling bearings for line shafting. [Illustration: Fig. 1266.] [Illustration: Fig. 1267.] The half bearing B, Fig. 1266, is chucked upon a half-round mandrel, C being the spherical surface to be turned, a sectional view of C being shown in Fig. 1267. [Illustration: Fig. 1268.] In Fig. 1268 is a plan view of the chuck, work, and lathe rest; D is a former attachment bolted to the slider of the rest, and E a rod passing through the lathe block. The weight W, Fig. 1269, is suspended by a cord attached to the slide rest so as to keep the former D firmly against the end of E. As the slider is operated, the rest is caused by E to slide upon the lathe bed, and the cutting tool forms a spherical curve corresponding to the curve on the former D. The weight W of course lifts or falls according to the direction of motion of the slider. The cut is put on by operating handle G, thus causing E to advance. The weight W causes any play between the slider and the cross slide to be taken up in the same direction as the tool pressure would take it up, hence the cut taken is a very smooth one. The half-round mandrel being fixed to the lathe face plate will remain true, obviating the liability of the centre of the spherical surface being out of line with the axis of the bearing-bore. A method of producing cams without a lathe especially adopted for the purpose is shown in Figs. 1270 and 1272, which are extracted from _Mechanics_. The apparatus consists of a frame E, which fits on the cross ways of an ordinary lathe. The cross-feed screw is removed, so that E may slide backwards and forthwards freely. The frame E carries the worm-wheel A and the worm-gear B, which is operated by the crank F. The cam C to be cut is bolted on to the face of the worm-wheel, which faces the headstock of the lathe. The form for the cam, which may be made of sheet steel, or thicker material, according to the wear it is to have, is fastened to the face of the cam. [Illustration: Fig. 1269.] [Illustration: Fig. 1270.] [Illustration: Fig. 1271.] [Illustration: Fig. 1272.] A cutter, like a fluted reamer, such as is shown in Fig. 1271, is then put in the live centre of the lathe. Care must be taken that the shank is the same size as the fluted part, and that the flutes are not cut up farther than the thickness that the cam grooves are to be cut in the blank. Having attached a cord to the back of E, pass it over a pulley H, fastened on the rear of the lathe, and hang on a weight G. Fig. 1272 is an edge view of the device, looking from the back of the lathe. It shows the worm A, blank C, and former D all bolted together, while the cutter I is ready in its place on a line with the centre of the worm, and just at back of the former. The machine is operated by turning the crank F, which causes the worm A, also C and D, to revolve slowly, while the cutter I has a rather rapid rotation. The weight causes the cutter to be held firmly against the form F, and to follow its curves in and out. [Illustration: Fig. 1273.] [Illustration: Fig. 1274.] [Illustration: Fig. 1275.] KNURLING OR MILLING TOOLS.--In Fig. 1273 is shown the method of using the knurling tool in the slide rest of a lathe. It represents the tool at work producing the indentations which are employed to increase the hand grip of screw heads, or of cylindrical bodies, as shown in the figure by the crossed lines. Fig. 1274 is an end view of the tool, which consists of a holder to go in the slide rest tool post, and carrying two small hardened steel wheels, each of which is serrated all round its circumference, the serrations of one being in an opposite direction to those of the other. The method of using the tool is shown in Fig. 1275, where it is represented operating upon a cylindrical piece of work. If the knurling is to be carried along the work to a greater length than the thickness of the knurl wheels, the lathe slide rest is slowly traversed the same as for a cutting tool. As the knurling tool requires to be forced against the work with considerable pressure, there is induced a strain tending to force the tool directly away from the work, as denoted by the arrow in Fig. 1276, and this, in a weighted lathe, acts to raise the lathe carriage and weight. This is avoided by setting the tool at an angle, as in Fig. 1277, so that the direction of strain is below and not above the pivot on which the cross slide rests. This is accomplished by pivoting the piece carrying the wheels to the main body of the stem, as shown in Fig. 1277. For use by hand the knurling or milling tool is fitted to a holder and handle, as in Fig. 1278, and the hand tool rest is placed some little distance from the work so that the knurl can pass over it, and below the centre of the work. Knurls for screw heads are made convex, concave, or parallel, to fit the heads of the screws, and may be indented with various patterns. [Illustration: Fig. 1276.] [Illustration: Fig. 1277.] [Illustration: Fig. 1278.] WINDING SPIRAL SPRINGS IN THE LATHE.--Spiral springs whose coils are close, and which therefore act on distension only, may be wound by simply starting the first coil true, and keeping the wire as it winds on the mandrel close to that already wound thereon. [Illustration: Fig. 1279.] Spiral springs with open coils may be best wound as shown in Fig. 1279, in which is shown a mandrel held between the lathe centres and driven by a dog that also grips one end of the wire W, of which the spring is to be made. The wire is passed through two blocks B, which, by means of the set-screw in the lathe tool post, place a friction on it sufficient to place it under a slight tension which keeps it straight. The change gears of the lathe are arranged as they would be to cut a screw of a pitch equal to the thickness of the wire added to the space there is to be between the coils of the spring. The first turn of the lathe should wind a coil straight round the mandrel when the self-acting feed motion is put in operation and the winding proceeds, and when the spring is sufficiently long, the feed motion is disconnected, and the last coil is allowed to wind straight round the mandrel, thus giving each end of the spring a flat or level end. If the wire is of brass it will be necessary to close it upon the mandrel with blows from a lead mallet to prevent it from uncoiling on the mandrel when the end is released, which it will do to some extent in any event. [Illustration: Fig. 1280.] If it is of steel it may be necessary to heat the coil red-hot to prevent its uncoiling, and in the coiling it will, if of stout wire, require to be bent against the mandrel during winding with a piece of steel placed in the tool post, as in Fig. 1280, in which A represents the mandrel, B the spring wire, and D the lathe tool post. [Illustration: Fig. 1281.] [Illustration: Fig. 1282.] In the absence of a lathe with a self-acting feed motion, the mandrel may have a spiral groove in it and the piece of steel or other hard metal shown in figure must be used, the feed screw of the slide rest being removed so that the wire can feed itself along as the mandrel rotates. Near one end of the mandrel a small hole is drilled through, there being sufficient space between the hole and the end of the mandrel to admit of a loose washer being placed thereon; the bore of this washer requires to be rather larger in diameter than the outside diameter of the spring, when wound upon the mandrel, and also requires to be provided with a keyway and key. The washer D (Fig. 1281), is slipped over the mandrel, the end of the wire C is inserted in the hole B and the spring being wound, the washer is passed up to the end, and the key driven home as in Fig. 1282; when the wire is cut off and the mandrel may be taken from the lathe with the spring closely wound round it to be hammered if of brass, and heated if of steel. The hammering should be done over the whole circumference, not promiscuously, but beginning at one end and following along the wire with the blows delivered not more than 1/4 of an inch apart; for unless we do this we cannot maintain any definite relation between the size of the mandrel and the size of the spring. When a grooved mandrel is used, its diameter should be slightly less than the required diameter of spring, as when released the coils expand in diameter. [Illustration: Fig. 1283.] If it is not essential that the coils be exactly true, take a plain mandrel, such as shown in Fig. 1283, and a hook, such as shown at A, fasten the end of the wire either round the lathe dog, or in a hole in the mandrel as before, and wind one full coil of the spring upon the mandrel, then force this coil open until the hook end of A can be inserted between it and over the mandrel, the other end hanging down between the lathe shears, which will prevent it from rotating, starting the lathe while holding the unwound end of the wire against the hook with a slight pressure, and the winding will proceed as shown in the figure, the thickness of A regulating the width apart of the coils. It is obvious that if the coil is to be a right-handed one and is started at the carrier end, the lathe must revolve backwards. Spiral springs for railroad cars are wound while red-hot in special spring-winding lathes and with special appliances. TOOLS FOR HAND TURNING.--Many of the tools formerly used in hand turning have become entirely obsolete, because they were suitable for larger work than any to which hand turning is now applied; hence, reference to such tools will be omitted, and only such hand tools will be treated of as are applicable to foot lathes and wood turning, their purposes being those for which hand tools are now used. To the learner, practice with hand tools is especially advantageous, inasmuch as the strain due to the cut is felt by the operator; hence, the effects of alterations in the shape of the tools, its height or position with relation to the work, and also the resistance of the metal to severance, are more readily understood and appreciated than is the case where the tool is held in a slide rest or other mechanical device. If under certain conditions the hand tool does not operate to advantage, these conditions may be varied by a simple movement of the hands, altering the height of the tool to the work, the angle of the cutting edges to the work, or the rate of feed, as the case may be, and instantly perceiving the effects; whereas with tools held by mechanical means, such alterations would involve the expenditure of considerable time in loosening, packing, and fastening the tool, and adjusting it to position. Small work that is turned by hand may, under exceptionally expert manipulation, be made as interchangeable and more accurate in dimensions than it could be turned by tools operated in special machines. That is to say, it is possible to turn by hand a number of similar small pieces that will be when finished as true, more nearly corresponding in dimensions, and have a finer finish, than it is practicable to obtain with tools operated or guided by parts of a machine. This occurs because of the wear of the cutting tools, which upon small work may be compensated for in the hand manipulation in cases where it could not be in machine manipulation. But with ordinary skill, and under ordinary conditions, the liability to error in hand work induces greater variation in the work than is due to the wear of the tool cutting edges in special machine work; hence, the practical result is that work made by special machinery is more uniform and true to size and shape than that made by hand, while also the quantity turned out by special machines is very much greater. [Illustration: Fig. 1284.] The most desirable form of tool for taking a heavy hand cut is the heel tool shown in Fig. 1284, which, it may be remarked, is at present but little used on account of the greater expedition of tools held in slide rests. It consists of a steel bar, about 3/8 or 1/2 inch square, forged with a heel at F, so that it may firmly grip the hand rest, and having a cutting edge at E. This bar is about 8 inches long, and is held in a groove in a wooden stock by a strap passing over it, and having a stem which passes down through the handle D, in which is fixed a nut, so that by screwing up or unscrewing D the bar is gripped or released, as the case may be, in a groove in the stock. In use, the end H of the stock is held firmly against the operator's shoulder, the left hand grasps the stock and presses the tool firmly down upon the face of the hand rest, while with the right the handle D is moved laterally, causing the tool to move to its cut. The depth of the cut is put on and regulated by elevating the end H of the stock. The heel F is placed close enough to the work to keep E F nearly vertical, for if it inclines too much in any direction the tool gets beyond the operator's control. The position of the heel F is moved from time to time along the hand rest to carry the cut along. A cut of 1/8 inch deep, that is, reducing the work diameter 1/4 inch, may readily be taken with this tool, which, however, requires skilful handling to prevent it from digging into the work. The shorter the distance from the face E to the heel F the more easily the tool can be controlled; hence, as F serves simply as a sharp and gripping fulcrum it need not project much from the body of the steel; indeed, in many cases it is omitted altogether, the bottom of the steel bar being slightly hollowed out instead. No oil or water is required with the heel tool. The hand rest should be so adjusted for height that the cutting edge of the tool stands slightly above the horizontal level of the work, a rule which obtains with all hand tools used upon wrought iron and steel. [Illustration: Fig. 1285.] The graver is the most useful of all hand turning tools, since it is applicable to all metals, and for finishing as well as roughing out the work. It is formed by a square piece of steel whose end is ground at an angle, as shown in the top and the bottom view, Fig. 1285, A A being the cutting edges, C C the points, and D D the heels. It is held in a wooden handle, which should be long enough to grasp in both hands, so that the tool may be held firmly. For cutting off a maximum of metal in roughing out the work the graver is held as in Fig. 1286, the heel being pressed down firmly upon the tool rest. The cut is carried along the work by revolving the handle upon its axis, and from the right towards the left, at the same time that the handle is moved bodily from the left towards the right. By this combination of the two movements, if properly performed, the point of the graver will move in a line parallel to the centres of the lathe, because, while the twisting of the graver handle causes the graver point to move away from the centre of the diameter of the work, the moving of the handle bodily from left to right causes the point of the graver to approach the centre of that diameter; hence the one movement counteracts the other, producing a parallel movement, and at the same time enables the graver point to follow up the cut, using the heel as a pivotal fulcrum, and hence obviating the necessity of an inconveniently frequent moving of the heel of the tool along the rest. The most desirable range of these two movements will be very readily observed by the operator, because an excess in either of them destroys the efficacy of the heel of the graver as a fulcrum, and gives it less power to cut, and the operator has less control over the tool. [Illustration: Fig. 1286.] [Illustration: Fig. 1287.] [Illustration: Fig. 1288.] For finishing or smoothing the work the graver is held as in Fig. 1287, the edge being brought parallel to the work surface. For brass work the top faces of the graver should be slightly bevelled in the direction shown in Fig. 1288. The graver cuts most efficiently with the work revolving at a fast speed, or, say, at about 60 feet per minute, and for finishing wrought iron or steel requires an application of water. [Illustration: Fig. 1289.] To finish work that has been operated upon by a heel tool or by a graver, the finishing tool shown in Fig. 1289 may be employed. It is usually made about 5/8 or 3/4 inch wide, as the graver is employed for shorter work. It is ground so as not to let the extreme corners cut, and is used at a slow speed with water. The edge of this tool is sometimes oilstoned, causing it to cut with a clean polish. The tool is held level, brought up to the work, and a cut put on by elevating the handle end. To carry the cut forward, the tool is moved along the hand rest to nearly the amount of its width, and is brought to its cut by elevating the handle as before. When the work has been finished as near as may be with this tool, it may be finished by fine filing, the lathe running at its quickest speed; or the file may be used to show the high spots while using the finishing tool. [Illustration: Fig. 1290.] For facing the ends of work the tool shown in Fig. 1290, or that shown in Fig. 1291, may be used, either of them being made from an old three-cornered file. The cutting edge at A, Fig. 1290, should be slightly curved, as shown. The point of the tool is usually brought to cut at the smallest diameter of the work, with the handle end of the tool somewhat elevated. As the cut is carried outwards the handle end of the tool is depressed, and the point correspondingly elevated. It may be used dry or with water, but the latter is necessary for finishing purposes. [Illustration: Fig. 1291.] Another form of this tool is shown in Fig. 1291. It has two cutting edges A A, one of which rests on the hand rest while the other is cutting, the tool being shown in position for cutting a right-and a left-hand face, the face nearest to the work being shown in the lower view. This face should be placed against the radial face of the work, and the cut put on by turning the upper edge over towards the work while pressing the tool firmly to the lathe rest. [Illustration: Fig. 1292.] For cutting out a round corner the tool shown in Fig. 1292, employed either for roughing or smoothing purposes (water being used with it for the latter), the heel causes it to grip the hand rest firmly, and acts as a pivotal fulcrum from which the tool may be swept right and left round the curve, or a portion of it. This tool, as in the case of all tools used upon wrought iron or steel, should not cut all round its edge simultaneously, as in that case, unless indeed it is a very narrow tool, the force placed upon it by the cut will be too great to enable the operator to hold and control it; hence the cut should be carried first on one side and then on the other, and then at the point, or else the handle end should be moved laterally, so that the point sweeps round the work. It should be brought to its cut by placing its heel close to the work, and elevating the handle end until the cutting edge meets the work. The point or nose of the tool may obviously be made straight or square, as it is termed, to suit the work, the top rake being omitted for brass work. [Illustration: Fig. 1293.] In using this tool for cutting a groove it is better (if it be a deep groove, and imperative if it be a broad one, especially if the work be slight and apt to spring) to use a grooving tool narrower in width than the groove it is to cut, the process being shown in Fig. 1293, in which W represents a piece of work requiring the two grooves at A and B cut in it. For a narrow groove as A the tool is made about half as wide as the groove, and a cut is taken first on one side as at C, and then on the other as at D. For a wider groove three or more cuts may be made, as at E, F, G. In all cases the tool while sinking the groove is allowed to cut on the end face only; but when the groove is cut to depth, the side edges of the tool may be used to finish the sides of the groove, but the side and end edge must not cut simultaneously, or the tool will be liable to rip into the work. [Illustration: Fig. 1294.] HAND TOOLS FOR BRASS WORK.--In addition to the graver as a roughing-out tool for brass work, we have the tool shown in Fig. 1294, the cutting edge being at the rounded end A. It is held firmly to the rest, which is not placed close to the work (as in the case of other tools), so as to give the tool a wide range of movement, and hence permit of the cut being carried farther along without moving its position on the rest. It may be used upon either internal or external work. For finishing brass work, tools termed scrapers are employed. [Illustration: Fig. 1295.] Fig. 1295 represents a flat scraper, the two end edges A and the side edges along the bevel forming the cutting edges. [Illustration: Fig. 1296.] [Illustration: Fig. 1297.] [Illustration: Fig. 1298.] [Illustration: Fig. 1299.] In this tool the thickness of the end A is of importance, since if it be too thin it will jar or chatter. This is especially liable to occur when a broad scraper is used, having a great length of cutting edge in operation. This may be obviated to some extent by inclining the scraper as in Fig. 1296, which has the same effect as giving the top face negative rake, causing the tool to scrape rather than cut. The dividing line between the cutting and scraping action of a tool is found in the depth of the cut, and the presentation of the tool to the work, as well as in the shape of the tool. Suppose, for example, that we have in Fig. 1297, a piece of work W and a tool S, and the cut being light will be a scraping one. Now suppose that the relative positions of the size of the work and of the tool remain the same, but that the cut be deepened as in Fig. 1298, and the scraping action is converted into that class of severing known as shearing, or we may reduce the depth of cut as in Fig. 1299, and the action will become a cutting one. [Illustration: Fig. 1300.] But let the depth of cut be what it may, the tool will cut and not scrape whenever the angle of its front face is more than 90° to the line of tool motion if the tool moves, or of work motion if the work moves to the cut. In Fig. 1300, for example, the tool is in position to cut the angle of the front face, being 110° to the direction of tool motion. We may consider this question from another stand-point, however, inasmuch as that the tool action is a cutting one whenever the pressure of the cut is in a direction to force the tool deeper into the work, and a scraping one whenever this pressure tends to force the tool away from the work, assuming of course that the tool has no front rake, and that the cut is light or a "mere scrape," as workmen say. This is illustrated in Fig. 1301, the tool at A acting to cut, and at B to scrape, and the pressure of the cut upon A acting to force the tool into the work as denoted by the arrow D, while that upon B acts to force it in the direction of arrow C, or away from the work. In addition to these distinctions between a cutting and a scraping action we have another, inasmuch as that if a tool is pulled or dragged to its cut its action partakes of a scraping one, no matter at what angle its front face may stand with relation to the work. The end face of a flat scraper should be at a right angle to the body of the tool, so that both edges may be equally keen, for if otherwise, as in Fig. 1302, one edge as A will be keener than the other and will be liable to jar or chatter. [Illustration: Fig. 1301.] [Illustration: Fig. 1302.] The flat scraper can be applied to all surfaces having a straight outline, whether the work is parallel or taper, providing that there is no obstruction to prevent its application to the work. [Illustration: Fig. 1303.] [Illustration: Fig. 1304.] [Illustration: Fig. 1305.] [Illustration: Fig. 1306.] Thus, in Fig. 1303 we have a piece of work taper at _a_ and C, parallel at _e_, and with a collar at _d_, the scraper S being shown applied to each of these sections, and it is obvious that it cannot be applied to section _a_ because the collar _d_ is in the way. This is remedied by grinding the scraper as in Fig. 1304, enabling it to be applied to the work as in Fig. 1305. Another example of the use of a bevelled scraper is shown in Fig. 1306, the scraper S having its cutting edge parallel to the work and well clear of the arm H. [Illustration: Fig. 1307.] The round-nosed scraper is used for rounding out hollow corners, or may be made to conform to any required curve or shape. It is limited in capacity, however, by an element that affects all scraping tools, that if too great a length of cutting edge is brought into action at one time, chattering will ensue, and to prevent this the scraper is only made of the exact curvature of the work when it is very narrow, as at S in Fig. 1307. For broad curves it is made of more curvature, so as to limit the length of cutting edge, as is shown in the same figure at S´, and is swept round the work so as to carry the cut around the curve. There are, however, other means employed to prevent chattering, and as these affect the flat scraper as well as the round-nosed one, they may as well be explained with reference to the flat one. First, then, a thin scraper is liable to chatter, especially if used upon slight work. But the narrower the face on the end of the scraper, the easier it is to resharpen it on the oilstone, because there is less area to oilstone. A fair thickness is about 1/20 inch; but if the scraper was no thicker than this throughout its whole length, it would chatter violently, and it is for this reason that it is thinned at its cutting end only. Chattering is prevented in small and slight work by holding the scraper as in Fig. 1308, applying it to the top of the work; and to reduce the acting length of cutting edge, so as to still further avoid chattering, it is sometimes held at an angle as in the top view in Fig. 1309, S being the scraper and R the tool rest. When the scraper is applied to side faces, or in other cases in which a great length of cutting edge is brought into action, a piece of leather laid beneath the scraper deadens the vibration and avoids chattering. [Illustration: Fig. 1308.] [Illustration: Fig. 1309.] [Illustration: Fig. 1310.] It is obvious that the scraper may be given any required shape to meet the work, Fig. 1310 representing a scraper of this kind; but it must in this case be fed endways only to its cut, if the work is to be cut to fit the scraper. [Illustration: Fig. 1311.] [Illustration: Fig. 1312.] In Fig. 1311 is shown a half-round scraper, which is shown in Fig. 1312 in position to scrape out a bore or hole. This tool is made by grinding the flat face and the two edges of a worn-out half-round smooth file, and is used to ease out bores that fit too tightly. The cutting edges are carefully oilstoned, and the work revolved at a very quick feed. [Illustration: Fig. 1313.] [Illustration: Fig. 1314.] [Illustration: Fig. 1315.] When a number of small pieces of duplicate form are to be turned by hand, a great deal of measuring may be saved and the work very much expedited by means of the device shown in Fig. 1313. It consists of a tool stock or holder, the middle of which, denoted by A, is square, and contains three or four square slots, with a set-screw to each slot to hold different turning tools. Each end of the stock is turned parallel, as denoted by B, C. In Figs. 1313 and 1314, D, E, and F are the tools, and G, H, are the set-screws. Fig. 1315 represents top and side view of a plate, of which there must be two, one to fasten on the headstock and one on the tailstock of the lathe, as shown in Fig. 1316. In Fig. 1317 the manner of using the tool is shown, similar letters of reference denoting similar parts in all the figures. The plates P P are bolted by screws to the headblock H and the tailstock T of the lathe. The tool holder is placed so that the cylindrical ends B, C, rest on the ends of these plates, and in the angles P´ P´. The cutting tool D is sustained, as shown, upon the lathe rest R. In use the operator holds the stock A in his hands in the most convenient manner, using the tool E as a handle when there is a tool in the position of E. The cutting point of the tool is pressed up to the work W, and the feed is carried along by hand. It is obvious, however, that when the perimeters of A B meet the shoulders O O, Fig. 1315, of the plates P P, the tool cannot approach any nearer to the diametrical centre of the work; hence the diameter to which the tool will turn is determined by the distance of the shoulder O of the plate P from the centre of the lathe centres, as shown in Fig. 1316 by the line L. In carrying the cut along it is also obvious that the lateral travel of the stock or holder must end when the end of the square part A comes against the side face of either of the plates. In the engraving we have shown the tool D cutting a groove in the work W, while the shoulder of the holder is against the plate fastened to the lathe tailstock T; and so long as the operator, in each case, keeps the shoulder against that plate, the grooves upon each piece of work will be cut in the same position, for it will be observed that the position in the length of the work performed by each tool is determined by the distance of the cutting part of each tool from the end of the square part A of the tool holder. All that is necessary, then, is to adjust each tool so that it projects the proper distance to turn the requisite diameter and stands the required distance from the shoulders of the square to cut to the desired length, and when once set error cannot occur. [Illustration: Fig. 1316.] This plain description of the device, however, does not convey an adequate idea of its importance. Suppose, for example, that it is required to turn a number of duplicate pieces, each with a certain taper: all that is necessary is to adjust the plates P in their distances from the lathe centres. If the large end of the taper on the work is required to stand nearest the lathe headstock A, the plate P on the headstock must be moved until its shoulder O is farther from the lathe centre. If, however, the work requires to be made parallel, the plates P must be set the same distance for the axial line of the centres. If it be desired to have a parallel and a taper in proximity upon the same piece of work, the tool must have one of its cylindrical ends taper and use it upon the taper part of the work. [Illustration: Fig. 1317.] In Fig. 1317 the tool D is shown cutting a square groove. The tool at F serves to turn the parallel part X, and the tool E would cut the [V]-shaped groove I. All kinds of irregular work may be turned by varying the parallelism and form of the cylindrical ends B C; but in this event the shoulders O O, Fig. 1315, should be made [V]-shaped and hardened to prevent them from rapid wear. [Illustration: Fig. 1318.] [Illustration: Fig. 1319.] SCREW CUTTING WITH HAND TOOLS.--Screw threads are cut by hand in the lathe with chasers, of which there are two kinds, the outside and the inside chaser. In Fig. 1319 is shown an outside, or male, and in Fig. 1318 an inside, or female chaser. The width of a chaser should be sufficient to give at least four teeth, and for the finer thread pitches it is better to have six or eight teeth, the number increasing as the pitch is finer, and the length of the work will permit. The leading tooth should be a full one, or otherwise it will break off, and if in cutting up the chaser a half or less than a full tooth is formed it should be ground off. The tooth points should not be in a plane at a right angle to the chaser length, but slightly diagonal thereto, as in Fig. 1319, so that the front edge of the chaser will clear a bolt head or shoulder, and permit the leading tooth to pass clear up to the head without fear of the front edge of the steel meeting the shoulder. [Illustration: Fig. 1320.] [Illustration: Fig. 1321.] [Illustration: Fig. 1322.] The method of producing a chaser from a hob is shown in Fig. 1320, in which H is a hob, which is a piece of steel threaded and serrated, as shown, to give cutting edges to act, as the hob rotates, upon the chaser C. If the chaser is cut while held in a constant horizontal plane, its teeth will have the same curvature as the hob, or, in other words, they will fit its circumference. Suppose that the chaser, being cut up by the hob and then hardened, is applied to a piece of work of the same diameter as the hob and held in the same vertical plane, as in Fig. 1320, it is obvious that, there being no clearance, the teeth cannot cut. Or, suppose it be applied to a piece of work of smaller diameter, as in Fig. 1324, it cannot cut unless its position be lowered, as in Fig. 1322, or else it must be elevated, as in Fig. 1323. In either case the angle of the thread cut will be different from the angle of the sides of the chaser teeth, and the thread will be of improper depth. Thus, on referring to Fig. 1321, it will be seen that the chaser C has a tooth depth corresponding to that on the work W along the horizontal dotted line E only, because the true depth of thread on the work is its depth measured along a radial line, as line F or G, and the chaser teeth are, at the cutting edge, of a different angle. This becomes more apparent if we suppose the chaser thickness to be extended up to the dotted line H, and compare that part of its length that lies within the two circles I J, representing the top and bottom of the thread, with the length of radial line G, that lies within these circles. If, then, the chaser be lowered, to enable it to act, it will cut a thread whose sides will be of more acute angle than are the sides of the chaser teeth or of the hob from which it was cut. The same effect is caused by using a chaser upon a larger diameter of work than that of the hob from which the chaser was cut, because the increased curvature of the chaser teeth acts to give the teeth less contact with the work, as is shown in Fig. 1325, for the teeth cannot cut without either the lower corners A of the teeth being forced into the metal, or else the chaser being tilted to relieve them of contact. To obviate these difficulties and enable a chaser to be used upon various diameters of work, it is, while being cut up by the hob, moved continuously up and down, as denoted in Fig. 1326, by A and B, which represent two positions of the chaser. The amount of this movement is sufficient to make the chaser teeth more straight in their lengths, and to give them a certain amount of clearance, an example of the form of chaser thus produced being shown in Fig. 1327, applied to two different diameters of work, as denoted by the circle A and segment of a circle B, C representing the chaser. [Illustration: Fig. 1323.] [Illustration: Fig. 1324.] [Illustration: Fig. 1325.] [Illustration: Fig. 1326.] To obtain the most correct results with such a chaser, it must be applied to the work in such a way that it has as little clearance as will barely enable it to cut, because it follows from what has been said with reference to single-pointed threading tools that to whatever amount the chaser has clearance, a corresponding error of thread angle and depth is induced. In hand use, therefore, it does not matter at what height the chaser is applied so long as it is elevated sufficiently to barely enable it to cut. [Illustration: Fig. 1327.] [Illustration: Fig. 1328.] After the chaser is cut on the hob, its edges, as at C, and the corner, as at D, in Fig. 1328, should be rounded off, so that they may not catch in any burr which the heel of the hand tools may leave on the surface of the hand rest. [Illustration: Fig. 1329.] For roughing out the threads on wrought iron or steel the top face should be hollowed out, as shown in Fig. 1328, which will enable the chaser to cut very freely. For use on cast iron the top face should be straight, as shown in Fig. 1328 at A, while for use on soft metal, as brass, the top face must be ground off, as shown in Fig. 1329. [Illustration: Fig. 1330.] The Pratt and Whitney Co. cut up chasers by the following method: In place of a hob, a milling cutter is made, having concentric rings instead of a thread. The cutters are revolved on a milling machine in the ordinary manner. The chaser is fastened in a chuck fixed on the milling machine table, and stands at an angle of 15°. It is traversed beneath the milling cutter, and thus cut up with teeth whose lengths are at a right angle to the top and bottom faces of the chaser; hence the planes of the length of the teeth are not in the same plane as that of the grooves of the thread to be cut. Thus, let _a_, _b_, _c_, and _d_, Fig. 1330, represent the planes of the thread on the work, and _e_, _f_, _g_, _h_, will be the planes of the lengths of the chaser teeth. The chaser, however, is given 15° of bottom rake or clearance, and this causes the sides of the chaser teeth to clear the sides of the thread. [Illustration: Fig. 1331.] Now, suppose the top face A, Fig. 1331, of the chaser to be parallel with the face of the tool steel, and to lie truly horizontal and in the same plane as the centre of the work. This clearance will cause the thread cut by the chaser to be deeper than the natural depth of the chaser teeth. Thus, in Fig. 1331 is shown a chaser (with increased clearance to illustrate the point desired), the natural depth of whose thread is represented by the line F, but it is shown on the section of work that the thread cut by the tool will be of the depth of the line D, which is greater than the length or depth of F, as may be more clearly observed by making a line E, which, being parallel to A, is equal in length to D, but longer than F. Hence, the clearance causes the chaser under these conditions to cut a thread of the same pitch, but deeper than the grooves of the hub, and this would alter the angles of the thread. This, however, is taken into account in forming the angles of the thread upon the milling cutter, and, therefore, of the chaser, which are such that with the tool set level with the work centre, the thread cut will be of correct angle, notwithstanding the clearance given to the teeth. [Illustration: Fig. 1332.] In order to enable the cutting of an inside chaser from a hub, it requires to be bent as in Fig. 1332, in which H is the hub, R the lathe rest, and C the chaser. After the chaser is cut, it has to be straightened out, as shown in Fig. 1318, in which is represented a washer being threaded and shown in section; C is the chaser and R the lathe rest, while P is a pin sometimes let into the lathe rest to act as a fulcrum for the back of the chaser to force it to its cut, the handle end of the chaser being pressed inwards. [Illustration: Fig. 1333.] [Illustration: Fig. 1334.] When an inside chaser is cut from a hub (which is the usual method) or male thread, its teeth slant the same as does the male thread on the side of the hub on which it is cut, and in an opposite direction to that of the thread on the other side of the hub. Thus, in Fig. 1333, H is the hub, C the chaser, and R the lathe rest. The slope of the chaser-teeth is shown by the dotted line B. Now, the slant of the thread on the half circumference of the hub not shown or seen in the cut will be in an opposite direction, and in turning the chaser over from the position in which it is cut (Fig. 1333) to the position in which it is used (Fig. 1334), and applying it from a male to a female thread, we reverse the direction with relation to the work in which the chaser-teeth slant; or, in other words, whereas the teeth of the chaser should lie as shown in Fig. 1334 at A A, they actually lie as denoted in that figure by the dotted line B B. As a consequence, the chaser has to be tilted over enough to cause the sides of the chaser-teeth to clear the sides of the thread being cut, which, as they lie at opposite angles, is sufficient to cause the female thread cut by the chaser to be perceptibly shallower than the chaser-teeth, for reasons which have been explained with reference to Fig. 1321. It may be noted however, that an inside chaser cannot well be used with rake, hence the tilting in this case makes the thread shallower instead of deeper. To obviate these difficulties the hub for cutting a right-hand inside chaser should have a left-hand thread upon it, and _per contra_, an inside chaser for cutting a left-hand thread should be cut from a hub having a right-hand thread. The method of starting an outside thread upon wrought iron or steel to cut it up with a chaser is as follows:-- [Illustration: Fig. 1335.] The work is turned up to the required diameter, and the [V]-tool shown in Fig. 1335 is applied; the lathe is run at a quick speed, and the heel of the tool is pressed firmly to the face of the lathe rest, the handle of the tool must be revolved from right to left at the same time as it is moved laterally from the left to the right, the movement being similar to that already described for the graver, save that it must be performed more rapidly. It is in fact the relative quickness with which these combined movements are performed which will determine the pitch of the thread. The appearance of the work after striking the thread will be as shown in Fig. 1336, A being the work, and B a fine groove cut upon it by the [V]-tool. The reason for running the lathe at a comparatively fast speed is that the tool is then less likely to be checked in its movement by a seam or hard place in the metal of the bolt, and that, even if the metal is soft and uniform in its texture, it is easier to move the tool at a regular speed than it would be if the lathe ran comparatively slowly. [Illustration: Fig. 1336.] If the tool is moved irregularly or becomes checked in its forward movement, the thread will become waved or "drunken"--that is, it will not move forward at a uniform speed;[20] and if the thread is drunken when it is started, the chaser will not only fail to rectify it, but, if the drunken part occurs in a part of the iron either harder or softer than the rest of the metal, the thread will become more drunken as the chaser proceeds. It is preferable, therefore, if the thread is not started truly, to try again, and, if there is not sufficient metal to permit of the starting groove first struck being turned out, to make another farther along the bolt. It takes much time and patience to learn to strike the requisite pitch at the first trial; and it is therefore requisite for a beginner to leave the end of the work larger in diameter than the required finished size, as shown in Fig. 1336, so as to have sufficient metal to turn out the groove cut by the [V]-tool at the first trial cut, and try again. [20] See Fig. 253, Plate II., Vol. I. If the thread is to be cut on brass the [V]-tool must not have any top rake. Some turners start threads upon brass by placing the chaser itself against the end of the work and sweeping it rapidly from left to right (for a right-hand thread), thus obviating the use of the [V]-tool. In all cases the work should be rounded off at the end to prevent the chaser-teeth from catching. In applying the chaser to the groove cut by the [V]-tool the leading tooth should be held just clear of the work at first, and only be brought to touch the work after the rear teeth have found and are traversing in the groove. By this means the chaser will carry the thread forward more readily and true. The thread must be carried forward but a short distance at each passage of the chaser, gradually deepening the thread while carrying it forward. To start an inside thread the corner of the hole at its entrance should be rounded off and the back teeth of the chaser placed to touch the bore while the front teeth are clear. The lathe is to be run at a quick speed, and the chaser moved forward at as near the proper speed as can be judged. When the chaser is moved at the proper speed, the rear teeth will fall into the fine grooves cut by the advance ones, and start a thread, while otherwise promiscuous grooves only will be cut. It is an easy matter, however, to start a double thread with an inside chaser; hence, when the thread is started the lathe should be stopped and the thread examined. The chaser should be placed with its top face straight above the horizontal level of the work and held quite horizontal, and the handle end then elevated just sufficient to give the teeth clearance enough to enable them to cut; otherwise, with a chaser having top rake, the thread cut will be too deep, and its sides will be of improper angle one to the other. [Illustration: Fig. 1337.] Thus, in Fig. 1337, W represents a piece of work, R the lathe rest, and T the chaser. The depth of the thread cut in this case will be from the circle A to the circle B; whereas the depth of the chaser teeth, and therefore the proper depth for the thread, is from C to D. Thus tilting the handle end of the chaser too much has caused the chaser teeth to cut a thread too deep. If on brass work the chaser has its top face ground off as in figure, tilting the handle too much will cause the thread cut to be too shallow, and in both cases the error in thread depth induces a corresponding error in the angles of the sides of the thread one to the other and relative to the axial line of the bolt or work. If the chaser teeth are held at an angle to the work surface, the thread cut will be of finer pitch than the chaser, and the angles of the sides of the thread on the work will not be the same as those of the teeth. It is permissible, however, during the early cuts taken with a hand chaser to give the chaser a slight degree of such angle, because it diminishes the length of cutting edge, and causes the chaser to cut more freely, especially when the pitch of the thread is coarse and the chaser is becoming dull. In the case of a taper thread the same rule, that the thread may be roughed out with the chaser teeth at an angle to the surface lengthways of the work, but must be finished with the teeth parallel to the surface, holds good. [Illustration: Fig. 1338.] Thus, in Fig. 1338 is a taper plug fitting in a ring having a threaded taper bore, the threads matching, and having the thread sides in both cases at an equal angle to the surface, lengthways of the work, though the tops and bottoms of the thread are not parallel with the axial line of the work. WOOD TURNING TOOLS.--Wood turning in the ordinary lathe is generally performed by hand tools, and of these the principal is the gouge, which in skillful hands may be used to finish as well as to rough out the work (although there are other more useful finishing tools to be hereafter described). It is used mainly, however, to rough out the work and to round out corners and sweeps. The proper form for this tool is shown in Fig. 1339, the bevel on the end of the back or convex side being carried well round at the corners, so as to bring those corners up to a full sharp cutting edge on the convex or front side. The proper way to hold a gouge is shown in Fig. 1340, in which the cut taken by the tool is being carried from right to left, the face plate of the lathe being on the left side, so that by holding it in the manner shown the body and arms are as much as possible out of the way of the face plate, which is a great consideration in short work. But if the cut is to be carried from left to right, the relative position of the hands may be changed. When the work runs very much out of true, or has corners upon it, as in the case of square wood, the forefinger may be placed under the hand rest, and the thumb laid in the trough of the gouge, pressing the latter firmly against the lathe rest to prevent the tool edge from entering the work too far, or, in other words, to regulate the depth of the cut, and prevent its becoming so great as to force the tool from the hands or break it, as is sometimes the case under such circumstances. When the gouge is thus held, its point of rest upon the lathe rest may be used as a fulcrum, the tool handle being moved laterally to feed it to the cut, which is a very easy and safe plan for learners to adopt, until practice gives them confidence. The main point in the use of the gouge is the plane in which the trough shall lie. Suppose, for example, that in Fig. 1341 is shown a piece of work with three separate gouge cuts being taken along it, that on the right being carried in the direction of the arrow. Now the gouge merely acts as a wedge, and the whole of the pressure placed by the cut on the trough side or face of the gouge is tending to force the gouge in the direction of the arrow, and therefore forward into its cut, and this it does, ripping along the work and often throwing it out of the lathe. To avoid this the gouge is canted, so that when cutting from right to left it lies as shown at B, in which case the pressure of the cut tends rather to force the gouge back from the cut, rendering a slight pressure necessary to feed it forward. The gouge trough should lie nearly horizontal lengthwise, the cutting edge being slightly elevated. The gouge should never (for turning work) be ground in the trough (as the concave side is termed), and should always be oilstoned, the trough being stoned with a slip of stone lying flat along the trough, the back being rotated upon a piece of flat stone, and held with the ground surface flat on the surface of the stone, and so pressed to it as to give most pressure at and near the cutting edge. [Illustration: Fig. 1339.] [Illustration: Fig. 1340.] [Illustration: Fig. 1341.] [Illustration: Fig. 1342.] For finishing flat surfaces, the chisel shown in Fig. 1342 is employed. It should be short, as shown. It should be held to the work in a horizontal position, or it is apt to dig or rip into the work, especially when it is used upon soft wood. Some expert workmen hold it at an angle for finishing purposes, which makes it cut very freely and clean, but increases the liability to dig into the work; hence learners should hold it as shown. [Illustration: Fig. 1343.] [Illustration: Fig. 1344.] Another excellent finishing tool is the skew-chisel, Fig. 1343, so called because its cutting edge is at an angle, or askew with the body of the tool. This tool will cut very clean, leaving a polish on the work. It also has the advantage that the body of the tool may be kept out of the way of flanges or radial faces when turning cylindrical work, or may, by turning it on edge, be used to finish radial faces. It is shown in Fig. 1343 by itself, and in Fig. 1344 turning up a stem. It is held so that the middle of the edge does the cutting, and this tends to keep it from digging into the work. The bevels forming the cutting edge require to be very smoothly oilstoned. The whole secret of the skillful and successful use of this valuable tool lies in giving it the proper inclination to the work. It is shown in Fig. 1344, at E, in the proper position for taking a cut from right to left, and at F in position for taking a cut from left to right. The face of the tool lying on the work must be tilted over, for E as denoted by line A, and for F as denoted by the line B, the tilt being only sufficient to permit the edge to cut. If tilted too much it will dig into the work; if not tilted, the edge will not meet the work, and therefore cannot cut. For cutting down the ends of the work, or down a side face, it must be tilted very slightly, as denoted in figure by C D, the amount of the tilt regulating the depth of the cut, so that when the cutting edge of the tool has entered the wood to the requisite depth, the flat face of the tool will prevent the edge from entering any deeper. In cutting down a radial face the acute corner of the tool leads the cut, whereas in in plain cylindrical work the obtuse is better to lead. For cutting down the ends, for getting into small square corners, and especially for small work, the skew chisel is more handy than the ordinary chisel, and leaves less work for the sand-paper to do. Beginners will do well to practise upon black walnut, or any wood that is not too soft, roughly preparing it with an axe to something near a round shape. [Illustration: Fig. 1345.] For finishing hollow curves the tool shown in Fig. 1345 is employed, the cutting edge being at B; the degree of the curve determines the width of the tool, and, for internal work the tool is usually made long and without a handle. [Illustration: Fig. 1346.] [Illustration: Fig. 1347.] The tool shown in Fig. 1346 is employed in place of the gouge in cases where the broad cutting edge of the latter would cause tremulousness. It may be used upon internal or external work, being usually about two feet long. For boring purposes, the tools shown in Fig. 1347 are employed, the cutting edges being from the respective points along the edges C, D, respectively. But when the bore is too small to admit of the application of tools having their cutting edges on the side, the tool shown in Fig. 1347 at E is employed, which has its cutting edge on the end. [Illustration: _VOL. I._ =THE ROGERS-BOND UNIVERSAL COMPARATOR.= _PLATE XIV._ Fig. 1348. Fig. 1349.] CHAPTER XIV.--MEASURING MACHINES, TOOLS, AND DEVICES. Measurements are primarily derived in Great Britain and her colonies, and in the United States, from the English Imperial or standard yard. This yard is marked upon a bar of "Bailey's metal" (composed of 16 parts copper, 2-1/2 parts tin, and 1 part zinc), an inch square and 38 inches long. One inch from each end is drilled a hole about three-quarters through the whole depth of the bar, into which are fitted gold plugs, whose upper end faces are level with the axis of the bar. Across each plug is marked a fine line, and the distance between these lines was finally made the standard English yard by an Act of Parliament passed in 1855. A copy of this bar is in the possession of the United States Government at Washington, and all the standard measuring tools for feet, inches, &c., are derived from subdivisions of this bar. The standard of measurement in France and her colonies, Italy, Germany, Portugal, British India, Mexico, Roumania, Greece, Brazil, Peru, New Granada, Uruguay, Chili, Venezuela, and the Argentine Confederation, is the French mètre, which is also partially the standard in Austria, Bavaria, Wurtemberg, Baden, Hesse, Denmark, Turkey, and Switzerland. It consists of a platinum bar, called the "mètre des archives," whose end faces are parallel, and the length of this bar is the standard mètre. But as measuring from the ends of this bar would (from the wear) impair its accuracy, a second bar, composed of platinum and iridium, has been made from the "mètre des archives." This second bar has ruled upon it two lines whose distance apart corresponds to the length of the "mètre des archives," and from the distance between these lines the subdivisions of the mètre have been obtained. As all metals expand or contract under variations of temperature, it is obvious that these standards of length can only be accurate when at some given temperature: thus the English bar gives a standard yard when it is at a temperature of 62° Fahr., while the French standard bar is standard at a temperature of 32° Fahr., which corresponds to 0 in the centigrade thermometer. But if a bar is copied from a standard, and is found to be too short, it is obvious that if its amount of expansion under an increase of temperature be accurately known, it will be an accurate standard at some higher temperature, or in other words, at a temperature sufficiently higher to cause it to expand enough to compensate for its error, and no more. As all bars of metal deflect from their own weight, it is obvious that the bar must be supported at the same points at which it rested when the lines were marked, and it has been determined by Sir George Airy, that the best position for the points of support for any bar may be obtained as follows: Multiply the number of the points of support by itself (or, as it is commonly called, "square it"), and from the sum so obtained subtract 1. Then subtract the square root of the remainder, which gives a sum that divided into the length of the bar will represent the distance apart for the points of support. It will be obvious that the points of support must be at an equal distance from each end of the bar. Measurement may be compared in two ways, by sight and by the sense of feeling. Measurement by sight is made by comparing the coincidence of lines, and is called "line measurement." Measurement by feeling or touch is called "end measurement," because the measurement is taken at the ends. If, for example, we measure the diameter of a cylindrical bar, it is an end measurement, because the measurement is in a line at a right angle to the axis of the bar, and the points of touch on each side of the bar are the ends of the measurement, which is supposed to have no width. In measuring by sight we may, for rude measurements, trust to the unaided eye, as in using the common foot rule, but for such minute comparisons as are necessary in subdividing or transferring a standard, we may call in the aid of the microscope. The standard gauges, &c., in use in the United States have been obtained from Sir Joseph Whitworth, or duplicated from those made by him with the aid of measuring and comparing machines. It has been found, however, that different sets of these gauges did not measure alike, the variations being thus given by Mr. Stetson, superintendent of the Morse Twist Drill and Machine Co. At the time the Government established the use of the standard system of screw threads in the navy yards, ten sets of gauges were ordered from a manufacturer. His firm procured a duplicate set of these and took them to the navy yard in Boston and found that they were practically interchangeable. He also took them to the Brooklyn Yard Navy. The following tabular statement shows the difference between them:-- --------------------------------------------------------------- | |Morse Twist| |Navy Yard |Drill and | Morse Twist Drill and Size. |Male Gauge. |Machine Co.| Machine Co. | |Male Gauge.| Female Gauge. -------+------------+-----------+------------------------------ 1/4 | 0.25 | 0.25 | Interchanged 5/16 | .313 | .313 | " 3/8 | .375 | .3759 | 7/16 | .437 | .437 | Interchanged 1/2 | .505 | .505 | " 9/16 | .562 | .564 (-)| " 5/8 | Damaged | .626 | " 3/4 | .7505 | .751 | " 7/8 | .876 | .8758 | " 1 | 1.00075 | 1.00075 | " | | | { Navy Yard M. T. D. & M. Co. 1-1/8 | 1.125 (+)| 1.125 (-)| { --------- ----------------- | | | { (+) (-) 1-1/4 | 1.25 | 1.25 | Interchanged 1-3/8 | 1.375 | 1.375 | " 1-1/2 | 1.5 | 1.5 (-)| (-) 1-5/8 | 1.6245 | 1.624 | (-) 1-3/4 | 1.749 | 1.749 | Interchanged 1-7/8 | 1.8745 | 1.874 | (-) 2 | 1.999 | 1.999 | --------------------------------------------------------------- The sign (-) means that the piece is small, but not enough to measure. The sign (+) means that the piece is large, but not enough to measure. The advantages to be derived from having universally accepted standard subdivisions of the yard into inches and parts of an inch are as follows:-- When a number of pieces of work of the same shape and size are to be made to fit together, then, if their exact size is not known and there is no gauge or test piece to fit them to, each piece must be fitted by trial and correction to its place, with the probability that no two pieces will be of exactly the same size. As a result, each piece in a machine would have to be fitted to its place on that particular machine, hence each machine is made individually. Furthermore, if another lot of machines are afterwards to be made, the work involved in fitting the parts together in the first lot of machines affords no guide or aid in fitting up the second lot. But suppose the measurements of all the parts of the first lot are known to within the one ten-thousandth part of an inch, which is sufficiently accurate for practical purposes, then the parts may be made to measurement, each part being made in quantities and kept together throughout the whole process of manufacture, so that when all the parts are finished they may go to the assembling or erecting room, and one piece of each part may be taken indiscriminately from each lot, and put together to make a complete machine. By this means the manufacture of the machine may be greatly simplified and cheapened, and the fit of any part may be known from its size, while at the same time a new part may be made at any time without reference to the machine or the part to which it is to fit. Again, work made to standard size in one shop will fit to that made to standard size in another, providing the standard gauges agree. The Pratt and Whitney Company, of Hartford, Connecticut, in union with Professor Rogers, of Cambridge University, in Massachusetts, determined to inspect the Imperial British yard, to obtain a copy of it, and to make a machine that would subdivide this copy into feet and inches, as well as transfer the line measurements employed in the subdivisions into end measures for use in the workshops, the degree of accuracy being greater than is necessary in making the most refined mechanism, made under the interchangeable or standard gauge system. The machine made under these auspices is the Rogers-Bond Universal Comparator; Mr. Bond having been engaged in conjunction with Professor Rogers in its construction. The machine consists of two cylindrical guides, upon which are mounted two heads, carrying microscopes which may be reversed in the heads, so as to be used at the front of the machine for line measurements and on the back for end measurements. Fig. 1348 is a front, and Fig. 1349 a rear view of the machine, whose details of construction are more clearly shown in the enlarged views, Fig. 1350 and 1352. [Illustration: Fig. 1350.] [Illustration: Fig. 1351.] [Illustration: Fig. 1352.] Fig. 1350 is a top view, and Fig. 1352 a front view, the upper part of the machine being lifted up for clearness of illustration. X, X, are the cylindrical guides, upon which are the carriages I, K, for the microscopes. The construction of these carriages is more fully seen in Fig. 1351, which represents carriage K. It is provided with a hand-wheel R, operating a pinion in a rack (shown at T in the plan view figure of the machine) and affording means to traverse the carriage along the cylindrical guides. The microscope may be adjusted virtually by the screw M^{4}. The base upon which the microscope stands is adjustable upon a plate N, by means of the two slots and binding screws shown, and the plate N fits in a slideway running across the carriage. U is one of the stops used in making end measurements, the other being fixed upon the frame of the machine at V in the plan view, Fig. 1350. The micrometric arrangement for the microscope is shown more clearly in Fig. 1353. The screw B holds the box in position, the edge of the circular base on which it sits being graduated, so that the position of M may be easily read. In the frame M is a piece of glass having ruled upon it the crossed lines, or in place of this a frame may be used, having in it crossed spider web lines. These lines are so arranged as to be exactly in focus of the upper glass of the microscope, this adjustment being made by means of the screw S. The lines upon the bar are in the focus of the lower glass; hence, both sets of lines can be seen simultaneously, and by suitable adjustment of the microscope can be brought to coincide. [Illustration: Fig. 1353.] Beneath the cylindrical guides, and supported by the rack T that runs between and beneath them, are the levers P, in Fig. 1352, upon which weights may be placed to take up the flexure or sag of the cylindrical guides. In Fig. 1352, H, H, are heads that may be fixed to the cylindrical guides at any required point, and contain metallic stops, against which corresponding stops on the microscope carriages may abut, to limit and determine the amount to which these carriages may be moved along the cylindrical guides. The pressure of contact between the carriage and the fixed stops is found to be sufficiently uniform or constant if the carriage is brought up to the stops (by means of the hand-wheel R, Fig. 1351) several times, and a microscope reading taken for each time of contact. But this pressure of contact may be made uniform or constant for all readings by means of an electric current applied to the carriage through the metallic stops on heads H, H, and those on the carriage. We have now to describe the devices for supporting the work and adjusting it beneath the microscopes. [Illustration: Fig. 1354.] Referring, then, to Fig. 1352, E is a bed or frame that may be raised or lowered by means of the hand-wheel C, so as to bring the plate S (on which rests the bar whose line measure is to be compared) within range of the microscopes. The upper face of E is provided with raised [V] slideways, which are more clearly seen in the end view of this part of the machine shown in Fig. 1354. Upon these raised [V]s are the devices for adjusting the height of the eccentric rollers S^{3}, upon which the bars to be tested are laid, S^{2} representing one of these bars. To adjust the bars in focus under the microscope, these eccentric rollers are revolved by means of levers S^{4}. At S^{5} is a device for giving to the table a slight degree of longitudinal movement in the base plate that rests upon the raised [V]s; on the upper face of E and at S^{6} is a mechanism for adjusting the height of that end of the plate S. The base plate may be moved along the raised [V]s of E by the hand-wheel D. To test whether the cylindrical guides are deflected by their own weight or are level, a trough of mercury may be set upon the eccentric rollers S^{3}, Fig. 1352, and the fine particles of dust on its surface may be brought into focus in the microscope, whose carriage may then be traversed to various positions along the cylindrical guides, and if these dust particles remain in focus it is proof that the guides are level with the mercury surface. [Illustration: Fig. 1355.] The methods of using the machine are as follows: The standard bar has marked upon its upper face (which is made as true as possible and highly polished) a line B (Fig. 1355), which is called the horizontal line, and is necessary in order to set the bar parallel to the cylindrical guides of the machine. The lines A, A, are those defining the measurement as a yard, a foot, or whatever the case may be, and these are called the vertical lines or lines of measurement. Now, suppose we require to test a bar with the standard and the lines on its face are marked to correspond to those on the standard. The first operation will be to set the standard bar on the eccentric rollers S^{3} in Fig. 1352, and it and the microscopes are so adjusted that the spider web lines in the microscope exactly intersect the lines A and B on the standard, when the microscope carriage abuts against the heads H, Fig. 1352. The standard bar is then replaced by the bar to be tested, which is adjusted without altering the microscope adjustment or the heads H, and if the spider web lines in the microscope exactly coincide with and intersect the lines A and B, the copy corresponds to the standard. But if they do not coincide, then the amount of error may be found by the micrometer wheel G, Fig. 1353. [Illustration: Fig. 1356.] In this test the carriage is moved up against the stops H several times, and several readings or tests are made, so as to see that the force of the contact of the carriage against the stops H is uniform at each test, and if any variation is found, the average of a number of readings is taken. It is found, however, that with practice the carriage may be moved against the head H by means of the hand-wheel with such an equal degree of force that an error of not more than one fifty-thousandth of an inch is induced. It is found, however, that if too much time is occupied in this test, the heat of the operator's body will affect the temperature of the bars, and therefore expand them and vitiate the comparison. But in this connection it may be noted that if a bar is at a temperature of 40°, and is placed in an ice bath, it does not show any contraction in less than one minute, and that when it does so, the contraction is irregular, taking place in sudden movements or impulses. Professor Rogers' methods of testing end measures are as follows: To compare a line with an end measure, a standard bar is set upon the machine, its horizontal and vertical lines being adjusted true to the cylindrical guides by the means already described, and the microscope carriage is so adjusted that the spider web lines of the microscope coincide with the horizontal and vertical lines marked on the standard, while at the same time the stop (U, Fig. 1350) on the carriage K has contact with the fixed stop (V, Fig. 1350.) Carriage K is then moved along the cylindrical guides so as to admit the bar (whose end measure is to be compared with the lines on the standard) between the two stops, and if, with the bar touched by both stops U and V, the microscope spider lines intersect the vertical and horizontal line on the standard bar, then the end measure corresponds to the line measure; whereas, if such is not the case, the amount of error may be found by noting how much movement of the micrometer wheel of the microscope is required to cause the lines to intersect. It is obvious that in this test, if the cylindrical guides had a horizontal curvature, the test would not be perfect. THE HORIZONTAL CURVATURE.--The copy or bar to be tested may be set between the stops, and the standard bar may be placed on one side of it, as in Fig. 1356, and the test be made as already described. It is then set the same distance from the bar to be tested, but on the other side of it, as in figure, and again adjusted for position and tested, and if the readings on the standard bar are the same in both tests, it is proof that the measurements are correct. Suppose, for example, that the cylindrical guides were curved as in Fig. 1356, it is evident that the vertical lines would appear closer together on the standard bar when in the first position than when in the second position. In the Rogers machine the amount of error due to curvature in the cylindrical guides in this direction is found to be about 1/5000 part of an inch in 39 inches, corresponding to a radius of curvature of five miles. [Illustration: Fig. 1357.] [Illustration: Fig. 1358.] Another method of testing an end with a line measure is as follows: The bar to be measured is shaped as in Fig. 1357, the end measurement being taken at A, and the projection B at each end serving to preserve the end surfaces A from damage. The standard bar is then set upon the machine and its horizontal and vertical lines adjusted in position as before described. In connection with this adjustment, however, the bar to be tested is set as in Fig. 1358; C being a block of metal (having marked centrally upon it horizontal and vertical lines), placed between the bar and the fixed stop U, its vertical line being in line with the vertical line on the standard. This adjustment being made, the block C is removed and placed at the other end of the bar, as shown in Fig. 1359, when, if the end measure on the bar corresponds with the line measure on the standard, the vertical line at the other end of the standard will correspond with the vertical line on block C. [Illustration: Fig. 1359.] To prove that the vertical line is exactly equidistant from each end of the block C, all that is necessary is to place it between the bar and the fixed stop U, Fig. 1350, adjust the microscope to it and then turn it end for end, and if its vertical line is still in line with the spider web of the microscope it is proof that it is central on the block, while if it is not central the necessary correction may be made. It is obvious that it is no matter what the length of C may be so long as its vertical line is central in its length. In this process the coincidence of the vertical lines on the standard and on the piece C are employed to test the end measure on the bar with the line measure on the standard. [Illustration: Fig. 1360.--General View.] [Illustration: Fig. 1361.--Plan.] Figs. 1360 and 1361 represent the Whitworth Millionth Measuring Machine, in which the measurement is taken by the readings of an index wheel, and the contact is determined from the sense of touch and the force of gravity. It is obvious that in measuring very minute fractions of an inch one of the main difficulties that arise is that the pressure of contact between the measuring machine and the surfaces measured must be maintained constant in degree, because any difference in this pressure vitiates the accuracy of the measurement. This pressure should also be as small as is consistent with the assurance that contact actually exists, otherwise the parts will spring, and this would again impair the accuracy of the measurement. If the degree of contact is regulated by devices connected with the moving mechanism of the machine it is indirect, and may vary from causes acting upon that mechanism. But if it is regulated between the work and the moving piece that measures it, nothing remains but to devise some means of making its degree or amount constant for all measurements; so that if a duplicate requires to be compared with a standard, the latter may first be measured and the duplicate be afterwards measured for comparison. All that is essential is that the two be touched with an equal degree of contact, and the most ingenious and delicate method yet devised to accomplish this result is that in the Whitworth machine, whose construction is as follows:-- In a box frame A, is provided a slide-way for two square bars, B, C, which are operated by micrometer screws, one of which is shown at J (the cap over B being removed to expose B and J to view). The bars B, C, are made truly square, and each side a true plane. The groove or slide-way in which they traverse is made with its two sides true planes at a right angle to each other; so that the bars in approaching or receding from each other move with their axes in a straight line. At the two ends of the frame the micrometer screws are afforded journal bearings. The ends of the bars B, C, are true planes at a right angle to the axes of B, C. Bar B is operated as follows: Its operating screw J has a thread of 1/20 inch pitch; or in other words, there are twenty threads in an inch of its length. It is rotated by the hand-wheel F, whose rim-face is graduated by 250 equidistant lines of division. Moving F through a distance equal to that between, or from centre to centre of its lines of division, moves B through a distance equal to one five-thousandth part of an inch. The screw in head I for operating bar C also has a pitch of 1/20 inch (or twenty threads in an inch of its length), and is driven by a worm-wheel W, having 200 teeth. This worm-wheel W is driven by a worm or tangent-screw H, having upon its stem a graduated wheel G, having 250 equidistant lines marked upon the face of its rim. Suppose, then, that wheel G be moved through a distance equal to that between its lines of division, that is 1/250th of a rotation, then the worm H will move through 1/250th of a rotation, and the worm-wheel on the micrometer screw will be rotated 1/250th part of its pitch expressed in inches; because a full rotation of G would move the worm one rotation, and thus would move the worm-wheel on the screw one tooth only, whereas it has 200 teeth in its circumference; hence it is obvious that moving graduated wheel G, through a distance equal to one of its rim divisions will move the bar C the one-millionth of an inch; because: Pitch of Rotation of Rotation of thread worm-wheel graduated wheel 1/20 inch × 1/200 × 1/250 = 1/1000000 [Illustration: Fig. 1362.] Fixed pointers, as K, Fig. 1362, enable the amount of movement or rotation of the respective wheels F, G, to be read. A peculiarly valuable feature of this machine is the means by which it enables an equal pressure of contact to be had upon the standards, and the duplicates to be tested therewith. This feature is of great importance where fine and accurate measurements are to be taken. The means of accomplishing this end are as follows:-- In the figures, D is a piece in position to be measured, and between it and the bar C is a feeler consisting of a small flat strip of steel, E E, having parallel sides, which are true planes. When the pressure of contact upon this piece E E is such that if one end be supported independently the other will just be supported by friction, and yet may be easily moved between D and C by a touch of the finger, the adjustment is complete. At the sides of the frame A are two small brackets, shown at K, in the end view, Fig. 1362, E E being shown in full lines resting upon them, and in dotted lines with one end suspended. The contact-adjustment may thus be made with much greater delicacy and accuracy than in those machines in which the friction is applied to the graduated wheel-rim, because in the latter case, whatever friction there may be is multiplied by the difference in the amount of movement of the graduated rim and that of the bar touching the work. All that is necessary in the Whitworth machine is to let E E be easy of movement under a slight touch, though capable of suspending one end by friction, and to note the position of the lines of graduation on C with reference to its pointer. By reason of having two operative bars, B, C, that which can be most readily moved may be operated to admit the piece or to adjust the bars to suit the length of the work, while that having the finer adjustive motion, as C, may be used for the final measuring only, thus preserving it from use, and therefore from wear as much as possible; or coarser measurements may be made with one bar, and more minute ones with the other. So delicate and accurate are the measurements taken with this machine, that it is stated by C. P. B. Shelley, C.E., in his "Workshop Appliances," that if well protected from changes of temperature and from dust, a momentary contact of the finger-nail will suffice to produce a measurable expansion by reason of the heat imparted to the metal. In an iron bar 36 inches long, a space equal to half a division on the wheel G having been rendered distinctly measurable by it, this space indicating an amount of expansion in the 36-inch bar equals the one two-millionth part of an inch! The following figures, which are taken from _Mechanics_, represent a measuring machine made by the Betts Machine Company, of Wilmington, Delaware. [Illustration: Fig. 1363.] Fig. 1363 shows a vertical section through the length of the machine, which consists of a bed carrying a fixed and an adjustable head, the fixed head carrying the measuring screw and vernier while the adjustable one carries a screw for approximate adjustment in setting the points of the standard bars. These screws have a pitch of ten threads per inch, and the range of the measuring screw has a range of 4 inches, and the machine is furnished with firm standard steel bars (4-inch, 6-inch, 18-inch, and 24-inch). The measuring points of the screws are of hardened steel, secured axially in line with the screws, and of two forms, with spherical and flat points, one set of each being used at a time. The larger wheel C is indexed to 1000 divisions, each division representing the ten-thousandth of an inch at the points; the smaller wheel has 100 divisions, each representing the one-thousandth part of an inch at the points. Beside, and almost in contact with, the larger wheel is a movable or adjustable pointer E, upon which the error of the screw is indexed for each inch of its length; the screw error is of the utmost importance when positive results are desired. The screw is immersed in oil to maintain a uniform temperature throughout its length, and to avoid particles of dust accumulating on its surface. [Illustration: Fig. 1364.] As stated above, the readings are indexed to the ten-thousandth part of an inch, but variations to the hundred-thousandth part of an inch can be indicated. The machine will take in pieces to 24 inches in length, and to 4 inches in diameter. In measuring, the points are brought into easy contact and then expanded by turning the larger wheel, counting the revolutions or parts of revolutions to determine the distance between the points or the size of what is to be measured. The smaller machine is constructed so as to indicate by means of vernier attachment to the ten-thousandth part of an inch, and is of value in tool-rooms where standard and special tools are continually being prepared. By its use, gauges and other exact tools can be made, and at the same time keep gauges of all kinds to standard size by detecting wear or derangement. The machine consists of a frame with one fixed head; the other head is moved by a screw; on both heads are hardened steel points. As with the larger machine, the screw error is indicated in such a manner as to permit the operator to guard against reproducing its error in its work. These machines are used for making gauges, reamers, drills, mandrels, taps, and so on. The errors that may exist in the pitch of the measuring screw are taken into account as follows: The points of the measuring machine should be brought into light contact, the position of index-wheel, vernier, and the adjustable pointer which has the screw error indexed upon it should be as in Fig. 1364; that is, the zeros on index-wheel and vernier should be in exact line, the vernier covering half of the zero line on pointer. To measure 1/2 inch, for illustration, five complete revolutions of index-wheel should produce 1/2 inch, and would if we had a perfect screw, but the screw is not perfect, and we must add to the measurement already obtained one-half of the space, stamped upon corrective devise, 0-1. This space 0-1 represents the whole error in the screw from zero to 1 inch. The backlash of the screw should always be taken up. [Illustration: Fig. 1365.] [Illustration: Fig. 1366.] [Illustration: Fig. 1367.] [Illustration: Fig. 1368.] The details of this machine are as follows:-- In Fig. 1363 the points G are those between which the measuring is done, and the slide held by the nut K in position is adjusted by means of inch bars to the distance to be measured; H, the hand-wheel for moving one point, and F the wheel which moves the other. Fig. 1366 is a cross section of the movable head through the nut K and stud M, by which the movable head is adjusted, and Fig. 1365 is a cross section through the fixed head. The bars used in setting the machine are shown in Fig. 1367, and in Fig. 1368 the points of the measuring screws are shown on a large scale. The other figures show various details of the machine and their method of construction. The vernier, it will be observed, is a double one. This is shown in Fig. 1364, and is so arranged that the zero is made movable in order to correct the errors of the screw itself. These errors are carefully investigated and a record made of each. Thus, in Fig. 1363 the arm E is graduated so as to show the true zero for different parts of the screw; D can then be adjusted to a correct reading, and the divisions on the large wheel will then be correct to an exceedingly small fraction. This method of construction enables the machine to be used for indicating very minute variations of length. [Illustration: Fig. 1369.] In Fig. 1369 is shown a measuring machine designed by Professor John E. Sweet, late of Cornell University. The bed of the machine rests on three feet, so that the amount of support at each leg may remain the same, whether the surface upon which it rests be a true plane or otherwise. This bed carries a headstock and a tailstock similar to a lathe. The tailstock carries a stationary feeler, and the headstock a movable one, operated horizontally by a screw passing through a nut provided in the headstock, the axial lines of the two feelers being parallel and in the same plane. The diameters of the two feelers are equal at the ends, so that each feeler shall present the same amount of end area to the work. The nut for the screw operating the headstock feeler is of the same length as the screw itself, so that the wear of the screw shall be equalized as near as possible from end to end, and not be the most at and near the middle of its length, as occurs when the thread on the screw is longer than that in the nut. The pitch of the thread on the screw is 16 threads in an inch of length, hence one revolution of the screw advances the feeler 1/16 inch. The screw carries a wheel whose circumference is marked or graduated by 625 equidistant lines of division. If, therefore, this wheel be moved through a part of a rotation equal to one of these divisions, the feeler will move a distance equal to 1/625 of the 1/16th of an inch, which is the ten thousandth part of an inch, and as the bed of the machine is long enough to permit the feelers to be placed 12 inches apart, the machine will measure from zero to 12 inches by the ten-thousandth of an inch. To assist the eye in reading the lines of division, each tenth line is marked longer than the rest, and every hundredth, still longer. The pitch of the screw being 16 threads to an inch enables the feeler to be advanced or retired (according to the direction of the rotation of the wheel) a sixteenth inch by a simple rotation of the wheel, an eighth inch by two wheel rotations, a thirty-second inch by a quarter rotation, and so on; and this renders the use of that machine very simple for testing the accuracy of caliper gauges, that are graduated to 1/8, 1/16, 1/32, 1/64th inch, and so on, such a gauge being shown (in the cut) between the feelers. The bar or arm shown fixed to the headstock and passing over the circumference of the wheel at the top affords a fixed line or point wherefrom to note the motion of the wheel, or in other words, the number of graduations it moves through at each wheel movement. It is evident that in a machine of this kind it is essential that the work to be measured have contact with the feelers, but that it shall not be sufficient to cause a strain or force that will spring or deflect either the work itself (if it be slight) or the parts of the machine. It is also essential that at excessive measurements the feelers shall touch the work with the same amount of force. The manner of attaining this end in Professor Sweet's machine is as follows: Upon the same shaft as the wheel is an arm having contact at both ends with the edge of the wheel rim whose face is graduated. This arm is free to rotate upon the shaft carrying the graduated wheel, which it therefore drives by multiple friction on its edges at diametrically opposite points; by means of a nut the degree of this friction may be adjusted so as to be just sufficient to drive the wheel without slip when the wheel is moved slowly. So long, then, as the feelers have no contact with the piece to be measured, the arm will drive the graduated wheel, but when contact does take place the wheel will be arrested and the arm will slip. The greatest accuracy will therefore be obtained if the arm be moved at an equal speed for all measurements. [Illustration: Fig. 1370.] Fig. 1370 represents a Brown and Sharpe measuring machine for sheet metal. It consists of a stand A with a slotted upright having an adjusting screw C above, and a screw D, with a milled head and carrying a dial, passing through its lower part. One turn of the screw, whose threads are 1/10th inch apart, causes one rotation of the dial, the edge of which is divided into one hundred parts, enabling measurements to be made to thousandths of an inch. The sheet-metal to be gauged is inserted in the slot of the upright. The adjusting-screw is set so that when the points of the two screws meet, the zero of the dial shall be opposite an index or pointer which shows the number of divisions passed over, and is firmly secured by a set-screw. Next in importance to line and end measurements is the accurate division of the circle, to accomplish which the following means have been taken. What is known as "Troughton's" method (which was invented by Edward Troughton about 1809) is as follows: A disk or circle of 4 feet radius was accurately turned, both on its face and its inner and outer edges. A roller was next provided of such diameter that it revolved sixteen times on its own axis, while rolling once round the outer edge of the circle. This roller was pivoted in a framework which could be slid freely, yet tightly, along the circle, the roller meanwhile revolving by frictional contact on the outer edge. The roller was also, after having been properly adjusted as to size, divided as accurately as possible into sixteen equal parts by lines parallel to its axis. While the frame carrying the roller was moved once round along the circle, the points of contact of the roller divisions with the circle were accurately observed by two microscopes attached to the frames, one of which commanded the ring on the circle near its edge, which was to receive the divisions, and the other viewed the roller divisions. The exact points of contact thus ascertained were marked with faint dots, and the meridian circle thereby divided into 256 very nearly equal parts. The next part of the operation was to find out and tabulate the errors of these dots, which are called apparent errors, because the error of each dot was ascertained on the supposition that all its neighbors were correct. For this purpose two microscopes, which we shall call A and C, were taken with cross-wires and micrometer adjustments, consisting of a screw and head divided into 100 divisions, 50 of which read in the one and 50 in the opposite direction. These microscopes, A and B, were fixed so that their cross-wires respectively bisected the dots 0 and 128, which were supposed to be diametrically opposite. The circle was now turned half way round on its axis, so that dot 128 coincided with the wire of A, and should dot 0 be found to coincide with B, then the dots were sure to be 180° apart. If not, the cross-wire of B was moved till it coincided with the dot 0 and the number of divisions of micrometer head noted. Half this number gave clearly the error of dot 128 and was tabulated plus or minus according as the arcual distance between 0 and 128 was found to exceed or fall short of the removing part of the circumference. The microscope B was now shifted, A remaining opposite dot 0 as before, till its wire bisected dot 64, and by giving the circle one-quarter of a turn on its axis, the difference of the arcs between dots 0 and 64, and between 64 and 128 was obtained. The half of this distance gave the apparent error of dot 64, which was tabulated with its proper sign. With the microscope A still in the same position, the error of dot 192 was obtained, and in the same way, by shifting B to dot 32, the errors of dots 32, 96, 160 and 224 were successively ascertained. By proceeding in this way the apparent errors of all the 256 dots were tabulated. In order to make this method fully understood, we have prepared the accompanying diagrams, which clearly show the plan pursued. [Illustration: Fig. 1371.] Fig. 1371 illustrates the plan of dividing the large circle by means of the roller B. [Illustration: Fig. 1372.] Fig. 1372 shows the general adjustment of the microscope for the purpose of proving the correctness of the divisions. [Illustration: Fig. 1373.] Fig. 1373 shows the location of the microscope over the points 0 and 128. [Illustration: Fig. 1374.] Fig. 1374 shows the circle turned half-way round, the points 0 and 128 coinciding with the cross threads of the microscope. [Illustration: Fig. 1375.] Fig. 1375 shows a similar reading, in which the points do not coincide with the cross threads of the microscope. [Illustration: Fig. 1376.] Fig. 1376 shows the microscope adjusted for testing by turning the circle a quarter revolution. Fig. 1377 represents one of the later forms of Ramsden's dividing engine.[21] It consists first of a three-legged table, braced so as to be exceedingly stiff. Upon this is placed a horizontal wheel with deep webs, and a flat rim. The webs stiffen the wheel as much as possible, and one of these webs, which runs round the wheel about half-way between the centre and the circumference, rests upon a series of rollers which support it, and prevent, as far as possible, the arms from being deflected by their own weight. An outer circle, which receives the graduation, is laid upon the rim of the wheel and secured in place. The edge of this circle is made concave. A very fine screw, mounted in boxes and supported independently, is then brought against this hollow edge, and, being pressed against it, the screw, when revolved, of course cuts a series of teeth in the circumference, and this tooth-cutting, facilitated by having the screw threads made with teeth, was continued until perfect [V]-shaped teeth were cut all around the edge of the wheel. This Mr. Ramsden calls ratching the wheel. The number of teeth, the circumference of the wheel, and the pitch of the screw were all carefully adjusted, so that by using 2160 teeth, six revolutions of the screw would move the wheel the space of 1°. When this work was finished, and the adjustment had been made as perfect as possible, a screw without teeth--that is, one in which the thread was perfect--was put in the place of that which had cut the teeth from the wheel, and the machine was perfected. The wheel A B C in the drawings is made of bell metal, and turns in a socket under the stand, which prevents the wheel from sliding from the supporting or friction rolls Z, Z. The centre R, working against the spindle M, is made so as to fit instruments of various sizes. The large wheel has a radius of 45 inches, and has 10 arms. The ring B is 24 inches in diameter by 3 inches deep. The ring C is of very fine brass, fitting exactly on the circumference of the wheel, and fastened by screws, which, after being screwed home, were well riveted. Great care was taken in making the centre on which the wheel worked exceedingly true and perfect, and in making the socket for the wheel fit as exactly as possible. The revolving mechanism is all carried on the pillar P, resting on the socket C´. We may state here that the machine, as shown in the engravings, now in the possession of the Stevens Institute, is in some respects slightly improved on that shown in the original drawings published in "Rees' Cyclopædia" in 1819. After the wheel was put on its stand, and the pulleys in place, the instrument was ready for the turning mechanism. The upper part of this pillar P carries the framework in which the traversing screw revolves. [21] From _Mechanics_. In Fig. 1378 D is the head of this pillar, P the screw which turns the wheel. E^{1} E^{1} are the boxes, which are made conical so as to prevent any shake and to hold the screw firmly. Circles of brass, F and V, are placed on the arbor of the screw, and as their circumference is divided into 60 parts, each division consequently amounts to a motion of the wheel of 10 seconds, and 60 of them will equal 1 minute. Revolution is given to the screw by means of the treadle B´ and the cord Y, which runs over the guiding screw W, Fig. 1379, and is finally attached to the box U. A spring enclosed in the box U causes it to revolve, and winds up the slack of the cord whenever the treadle is relieved. In the original drawing the head of the pillar P was carried in a parallel slip in the piece surrounding its head. The construction as shown in Fig. 1379 is somewhat different. The result attained, however, is identical, and the spindles and attachments are held so as to have no lateral motion. The wheels V and X have stops upon them, so arranged that the screw may be turned definitely to a given point and stopped. These wheels are at the opposite ends of the screw W. A detail of one of them is shown at V in Fig. 1380, where X is the ratchet-wheel. This figure also illustrates the construction of the bearings for the screw arbor. We have not space to explain the method by which the perfection of the screw was obtained, nor to discuss the means by which was obtained the success of so eliminating the errors as to make the division of the instrument more perfect than anything which had been attempted previously. Success, however, was obtained, and by means of the first or tooth-cutting screw the teeth were brought to such a considerable uniformity that, together with the fact that the screw took hold of a number of teeth at one time, most of the errors which would have been expected from this method of operation were eliminated. The method of ruling lines upon the instrument was most ingenious. The frame L L, is connected to the head D, of the pillar P in front, by the clamps I and K, and to the centre M by the block R. A frame N N stiffens the back. The blocks O, O on the frame Q´ are secured to the frame L L, by set-screws C, C. [Illustration: Fig. 1377.] Fig. 1381 shows a side view of the frame Q´, which it is seen carries a [V]-shaped piece Q, which in turn carries another [V]-shaped piece S, Fig. 1378. The piece Q is supported on pointed screws _d_, _d_, and the piece S is supported on two similar screws _f_, _f_. The point of this piece S carries the cutting tool E, Fig. 1378. Of course S can move only in a radial line from the centre M towards the circumference. If the sextant, octant, or other instrument be fastened to the large wheel A, with its centre at M, and the large wheel be rotated by the screw, all lines drawn upon it by E will be radial, and the distances apart will be governed by the number of turns made by the screw. This improvement, we think, was originated by Mr. Ramsden, and was a very great advance over the old method of the straight-edge, and has been used in some of the Government comparators and dividing engines. The following is Mr. Ramsden's own description of the graduation of the machine, and of his method of operating it. It shows the extreme care which he took in correcting the mechanical errors in the construction:-- "From a very exact centre a circle was described on the ring C, about 4/10 inch within where the bottom of the teeth would come. This circle was divided with the greatest exactness I was capable of, first into five parts, and each of these into three. These parts were then bisected four times; that is to say, supposing the whole circumference of the wheel to contain 2160 teeth, this being divided into five parts, and these again divided into three parts, each third part would contain 144, and this space, bisected four times, would give 72, 36, 18, 9; therefore, each of the last divisions would contain 9 teeth. But, as I was apprehensive some error might arise from quinquesection and trisection, in order to examine the accuracy of the divisions, I described another circle on the ring C, Fig. 1378, 1/10 inch within the first, and divided it by continual bisection, as 2160, 1080, 540, 270, 135, 67-1/2, 33-3/4, and, as the fixed wire (to be described presently) crossed both the circles, I could examine their agreement at every 135 revolutions (after ratching could examine it at every 33-3/4); but not finding any sensible difference between the two sets of divisions, I, for ratching, made choice of the former, and, as the coincidence of the fixed wire with an intersection could be more exactly determined with a dot or division, I therefore made use of intersections on both sides, before described. "The arms of the frame L, Fig. 1381, were connected by a thin piece of brass, 3/4 inch broad, having a hole in the middle 4/10 inch in diameter; across this hole a silver wire was fixed, exactly in a line to the centre of the wheel; the coincidence of this wire with the intersections was examined by a lens of 1/10 inch focus, fixed in a tube which was attached to one of the arms L. Now (a handle or winch being fixed on the end of the screw) the division marked 10 on the circle F was set to its index, and, by means of a clamp and adjusting-screw for that purpose, the intersection marked I on the circle C´ was set exactly to coincide with the fixed wire. The screw was then carefully pressed against the circumference of the wheel by turning the finger-screw _h_; then, removing the clamp, I turned the screw by its handle nine revolutions, till the intersection marked 240 came nearly to the wire. Then, turning the finger-screw _h_, I released the screw from the wheel, and turned the wheel back till the intersection marked 2 exactly coincided with the wire, and by means of the clamp before mentioned, the division 10 on the circle being set to its index, the screw was pressed against the edges of the wheel by the finger-screw _h_, the clamps were removed, and the screw turned nine revolutions, till the intersection marked I nearly coincided with the fixed wire; the screw was released from the wheel by turning finger-screw _h_ as before, the wheel was turned back till intersection marked 3 coincided with the fixed wire; the division 10 in the circle being set to its index, the screw was pressed against the wheel as before, and the screw turned nine revolutions, till intersection 2 was nearly coincident with the fixed wire, and the screw released, and I proceeded in this manner till the teeth were marked round the whole circumference of the wheel. This was repeated three times round to make the impressions deeper. I then ratched the wheel round continuously in the same direction, without ever disengaging the screw, and, in ratching the wheel about 300 times round, the teeth were finished. [Illustration: Fig. 1378.] "Now, it is evident that if the circumference of the wheel was even one tooth, or ten minutes, greater than the screw would require, this error would, in the first instance, be reduced by 1/240 part of a revolution, or two seconds and a half, and these errors or inequalities of the teeth were equally distributed round the wheel at the distance of nine teeth from each other. Now, as the screw in ratching had continual hold of several teeth at the same time and thus constantly changing, the above-mentioned irregularities soon corrected themselves, and the teeth were reduced to a perfect equality. The piece of brass which carried the wire was now taken away, and the cutting-screw was also removed, and a plain one put in its place. At one end of the screw arbor, or mandrel was a small brass circle F, having its edge divided into 60 parts, numbered at every sixth division, as before mentioned. On the other end of the screw is a ratchet-wheel V (X, Fig. 1380) having 60 teeth, covered by the hollow circle (V, Fig. 1380), which carries two clicks that catch upon opposite sides of the ratchet-wheel. When the screw is to be moved forward, the cylinder W turns on a strong steel arbor E´´, which passes through the piece X´; this piece, for greater firmness, is attached to the screw-frame by the braces _w_. A spiral groove or thread is cut upon the outside of the cylinder W, which serves both for holding the string and also giving motion to the lever I on its centre, by means of a steel tooth _v_, that works between the threads of the spiral. To the lever is attached a strong steel pin _m_, on which a brass socket turns; this socket passes through a slit in the piece _u_, and may be tightened in any part of the slit by the finger-nut _y_. This piece serves to regulate the number of revolutions of the screw for each tread of the treadle B´." [Illustration: Fig. 1379.] [Illustration: Fig. 1380.] [Illustration: Fig. 1381.] [Illustration: Fig. 1382.] Figs. 1382, 1383, and 1384 represent a method adopted to divide a circle by the Pratt and Whitney Company. The principle of the device is to enable the wheel to be marked, to be moved through a part of a revolution equal to the length of a division, and to test the accuracy of the divisions by the coincidence of the line first marked with that marked last when the wheel has been moved as many times as it is to contain divisions. By this means any error in the division multiplies, so that the last division marked will exhibit it multiplied by as many times as there are divisions in the whole wheel. The accuracy of this method, so long as variations of temperature are avoided, both in the marking and the drilling of the wheel, appears to be beyond question. In the figures, W represents a segment of the wheel to be divided, and C what may be termed a dividing chuck. The wheel is mounted on an arbor in a gear-cutting machine. On the hub of the wheel (which has been turned up for the purpose) there is fitted, to a close working fit, a bore at the end of an arm, the other end of the arm being denoted by A in the figures. The dividing chuck is fitted to the slide S of the gear-cutting machine, and is of the following construction. Between two lugs, B and B´, it receives the end of arm A. These lugs are provided with set-screws, the distance between the ends of which regulate the amount of movement of the end of arm A. Upon A is the slide D, carrying the piece E, in which is the marking tool F, the latter being lifted by a spring G, and, therefore, having no contact with the wheel surface until the spring is depressed. H is an opening through the arm A to permit the marking tool F to meet the wheel face, as shown in Fig. 1384, which is an end view of the slide showing the arm A in section. The face of the wheel rests upon the chuck on each side of the arm at the points I, J, and may be clamped thereto by the clamps K. The arm may be clamped to the wheel by the clamp shown dotted in at L, the bolt passing up and through the screw handle M. N is simply a lever with which to move the arm A, or arm A and the wheel. Suppose all the parts to be in the position shown in the cuts, the clamps being all tightened up, the slide D may be moved forward towards K, while the spring is depressed, and F will mark a line upon the wheel. The handle M may then be released and arm A moved until it touches the set-screw in B´, when M may be tightened and another line marked. Clamps K are then tightened, and the wheel, with the arm A fast to it, moved back to the position shown in the cut, when the clamps may be tightened again and another line marked, the process being continued all round the wheel. To detect and enable the correction of any discoverable error in a division, there is provided the plate P, having upon it three lines of division (which have been marked simultaneously with three of the lines marked on the wheel). This plate is supported by an arm or bracket Q, on the rear edge of which are three notches R to hold a microscope, by means of which the lines on P may be compared with those on the wheel face, so that if any discrepancy should appear it may be determined which line is in error. The labor involved in the operation of marking a large wheel is very great. Suppose, for example, that a wheel has 200 lines of division, and that after going round the wheel as described it is found that the last division is 100th inch out; then in each division the error is the two-hundredth part of this 100th inch, and that is all the alteration that must be made in the distance between set-screws B and B´. [Illustration: Fig. 1383.] [Illustration: Fig. 1384.] Figs. 1385 and 1386 represent a method of originating an index wheel, adopted by R. Hoe and Co., of New York City. In this method the plan was adopted of fitting round a wheel 180 tapering blocks, which should form a complete and perfect circle. These blocks were to serve the same purpose as is ordinarily accomplished by holes perforated on the face of an index wheel. In their construction, means of correcting any errors that might be found, without the necessity of throwing away any portion of the work done, would also be provided. Further, this means would provide for taking up wear, should any occur in the course of time, and thus restore the original truth of the wheel. Fig. 1385 of the engravings shows the originating wheel mounted upon a machine or cutting engine. Upon the opposite end of the shaft is the worm-wheel in the process of cutting. After the master worm-wheel has been thus prepared by means of the originating wheel, it is used upon the front end of the shaft, in the position now occupied by the originating wheel, and operated by a worm in the usual manner. Subdivisions are made by change wheels. The construction of the originating wheel will be understood by the smaller engravings. Fig. 1386 is an enlarged section of a segment of the wheel, while Fig. 1387 is an edge view of this segment. Fig. 1388 is a view of one of the blocks employed in the construction of the wheel, drawn to full size. In the rim of the originating wheel there was turned a shoulder, C, Fig. 1387, 5 feet in diameter. Upon this shoulder there were clamped 180 blocks, of the character shown in Fig. 1386, as indicated by the section, Fig. 1387. These blocks were secured to the face of the wheel D by screws E, and were held down to the shoulder by the screw and clamp G F, shown in Fig. 1387. (They are omitted in Fig. 1385 for clearness of illustration.) In the preparation of these blocks each was fitted to a template T, in Fig. 1388, and was provided with a recess B, to save trouble in fitting and to insure each block seating firmly on the shoulder C. The shoulder, after successive trials, was finally reduced to such a diameter that the last block exactly filled the space left for it when it was fully seated on the shoulder C. The wheel thus prepared was mounted on a Whitworth cutting engine, as shown in Fig. 1385. The general process of using this wheel is as follows: The blocks forming the periphery of the originating wheel are used in place of the holes ordinarily seen in the index plates. One of them is removed to receive a tongue, shown in the centre of Fig. 1385, which, exactly filling the opening or notch thus made, holds the wheel firmly in place. After a tooth has been cut in the master worm-wheel, shown at the back of Fig. 1385, the block in the edge of the originating wheel corresponding to the next tooth to be cut is removed. The tongue is withdrawn from the first notch, the wheel is revolved, and the tongue is inserted in the second position. The block first removed is then replaced, and the cutting proceeds as before. This operation is repeated until all the teeth in the master wheel have been cut. The space being a taper, the tongue holds the originating wheel more firmly than is possible by means of cylindrical pins fitting into holes. The number of blocks in the originating wheel being 180, the teeth cut in the master wheel may be 180 or some exact divisor of this number. The advantages of this method of origination are quite evident. Since 180 blocks were made to fill the circle, the edges of each had 2° taper. This taper enabled the blocks to be fitted perfectly to the template, because any error in fit would be remedied by letting the block farther down into the template. Hence, it was possible to correct any error that was discovered without throwing the block away. Further, as the blocks themselves are removed to form a recess for locking the originating wheel in position while cutting the worm-wheel, the truth of the work is not subject to the errors that creep in when holes or notches require to be pierced in the originating wheel. Such errors arise from the heating due to the drilling or cutting, from the wear of the tools or from their guides, from soft or hard spots in the metal and other similar causes. To avoid any error from the heating due to the cut on the worm-wheel, in producing master wheels, Messrs. Hoe and Co. allowed the wheel to cool after each cut. The teeth were cut in the following order: The first three were cut at equidistant points in the circumference of the wheel. The next three also were at equidistant points, and midway between those first cut. This plan was continued until all the teeth were cut, thus making the expansion of the wheel from the heat as nearly equal as possible in all directions. There is one feature in this plan that is of value. It is that a certain number of blocks, for example six, may be taken out at two or three different parts of the originating wheel and interchanged, thus affording a means of testing that does not exist in any other method of dividing. The tools applied by the workmen to measure or to test work may be divided into classes. 1st. Those used to determine the actual size or dimension of the work, which may be properly termed measuring tools. 2nd. Those used as standards of a certain size, which may be termed gauges. 3rd. Those used to compare one dimension with another, as in the common calipers. 4th. Those used to transfer measurements or distances defined by lines. 5th. Those used to test the accuracy of plane or flat surfaces, or to test the alignment of one surface to another. Referring to the first, their distinctive feature is that they give the actual dimensions of the piece, whether it be of the required dimension or not. The second determine whether the piece tested is of correct size or not, but do not show what the amount of error is, if there be any. The third show whatever error there may be, but do not define its amount; and the same is true of the fifth and sixth. Fig. 1389 represents a micrometer caliper for taking minute end measurements. This instrument is capable of being set to a standard measurement or of giving the actual size of a piece, and is therefore strictly speaking a combined measuring tool and a gauge. The [U]-shaped body of the instrument is provided with a hub _a_, which is threaded to receive a screw C, the latter being in one piece with the stem D, which envelops for a certain distance the hub _a_. The thread of C has a pitch of 40 per inch; hence one revolution of D causes the screw to move endways 1/40 of an inch. The vertical lines of division shown on the hub _a_ are also 1/40 of an inch apart, hence the bevelled edge of the sleeve advances one of the divisions on _a_ at each rotation. This bevelled edge is divided into 25 equal divisions round its circumference, as denoted by the lines marked 5, 10, &c. If, then, D be rotated to an amount equal to one of its points of division, the screw will advance 1/25 of 1/40 of an inch. In the cut, for example, the line 5 on the sleeve coincides with the zero line which runs parallel to the axial line of the hub. Now suppose sleeve D to be rotated so that the next line of division on the bevelled edge of D comes opposite to the zero line, then 1/25 part of a revolution of D will have been made, and as a full revolution of D would advance the screw 1/40 of an inch, then 1/25 of a revolution will advance it 1/25 of 1/40 inch, which is 1/1000 inch. The zero line being divided by lines of equal division into 40ths of an inch, then, as shown in the cut, the instrument is set to measure 3/40ths and 5/25ths of a fortieth. It is to be observed that to obtain correct measurements the work must be held true with the face of the foot B, and the contact between the end of screw _c_ and the work must be just barely perceptible, otherwise the pressure of the screw will cause the [U]-piece to bend and vitiate the accuracy of the measurement. Furthermore, if the screw be rotated under pressure upon the work, its end will wear and in time impair the accuracy of the instrument. To take up any wear that may occur, the foot-piece B is screwed through the hub, holding it so that it may be screwed through the hub to the amount of the wear. To avoid wear as much as possible, the screws of instruments of this kind are sometimes hardened, and to correct the error of pitch induced in the hardening, each screw is carefully tested to find in what direction the pitch of the hardened thread has varied, and provision is made for the correction as follows:-- The zero line on the hub _a_ stands, if the thread is true to pitch, parallel to the axis of the screw C, but if the pitch of the thread has become coarser from hardening, this zero line is marked at an angle, as shown in Fig. 1390, in which A A represents the axial line of the screw and B the zero line. If the screw pitch becomes finer from hardening, the zero line is made at an angle in the opposite direction, as shown in Fig. 1391, the amount of the angle being that necessary to correct the error in the screw pitch. The philosophy of this is, that if the pitch has become coarser a less amount of movement of the screw is necessary, while if it has become finer an increased movement is necessary. It is obvious, also, that if the pitch of the thread should become coarser at one end and finer at the other the zero line may be curved to suit. [Illustration: Fig. 1392.] [Illustration: Fig. 1393.] [Illustration: _VOL. I._ =DIVIDING ENGINE AND MICROMETER.= _PLATE XV._ Fig. 1385. Fig. 1386. Fig. 1387. Fig. 1388. Fig. 1389. Fig. 1390. Fig. 1391.] Fig. 1392 represents a vernier caliper, in which the measurement is read by the coincidence of ruled lines upon the following principle. The vernier is a device for subdividing the readings of any equidistant lines of division. Its principle of action may be explained as follows: Suppose in Fig. 1393 A to be a rule or scale divided into inches and tenths of an inch, and B a vernier so divided that its ten equidistant divisions are equal to nine of the divisions on A; then the distance apart of the lines of division on A will be 1/10 inch; but, as the whole ten divisions on B measure less than an inch, by 1/10 inch, then each line of division is a tenth part of the lacking tenth less than 1/10 inch apart. Thus, were we to take a space equal to the 1/10 inch between 9 and 10 on A, and divide it into 10 equal parts (which would give ten parts each measuring 1/100th of an inch) and add one of said parts to each of the distances between the lines of division on B, then the whole of the lines on A would coincide with those on B. It becomes evident, then, that line 1 on B is 1/100 inch below line 1 on A, that line 2 on B is 2/100 inch below line 2 on A, line 3 on the vernier B is 3/100 inch below line 3 on the rule A, and so on, until we arrive at line 10 on the vernier, which is 10/100 or 1/10 inch below line 10 on A. Suppose, then, the rule or scale to rest vertically on a truly surfaced plate, and a piece of metal be placed beneath B, the thickness of the piece will be shown by which of the lines on B coincides with a line on A. For more minute divisions it is simply necessary to have more lines of division in a given length on A and B. Thus, if the rule be divided into inches and fiftieths, and the vernier is so divided that it has 20 equidistant lines of division to 19 lines on the rule, it will then lack one division, or 1/50 inch in 20/50 inch, each division on the vernier will then be the one-twentieth of a fiftieth too short, and as 1/20 of 1/50 is 1/1000, the instrument will read to one-thousandth of an inch. Let it now be noted that, instead of making the lines of division closer together to obtain minute measurements, the same end may be obtained by making the vernier longer. For example, suppose it be required to measure to 1/2000 part of an inch, then, if the rule or scale be graduated to inches and fiftieths, and the vernier be graduated to have 40 equidistant lines of division, and 39 of the lines on the scale, the reading will be to the 1/2000 part of an inch. But, in any event, the whole of the readings on the vernier may be read, or will be passed through, while it is traversing a division equal to one of the divisions on the scale or rule. In Fig. 1392 is shown a vernier caliper, in which the vernier is attached to and carried by a slide operating against the inside edge of the instrument. The bar is marked or graduated on one side by lines showing inches and fiftieths of an inch, with a vernier graduated to have 20 equidistant lines of division in 19 of the lines of division on the bar, and therefore measuring to the 1/1000th of an inch, while the other side is marked in millimètres with a vernier reading to 1/40th millimètre, there being also 20 lines of division on the vernier to 19 on the bar. The inside surfaces of the feet or jaws are relieved from the bar to about the middle of their lengths, so as to confine the measuring surfaces to dimensions sufficiently small to insure accurate measurement, while large enough to provide a bearing area not subject to rapid wear. If the jaw surface had contact from the point to the bar, it would be impossible to employ the instrument upon a rectangular having a burr, or slight projection, on the edge. Again, by confining the bearing area to as small limits as consistent with the requirements of durability a smaller area of the measured work is covered, and the undulations of the same may be more minutely followed. To maintain the surface of the movable jaw parallel with that of the bar-jaw, it is necessary that the edge of the slide carrying the vernier be maintained in proper contact with the edge of the instrument, which, while adjusting the vernier, should be accomplished as follows:-- The thumb-screw most distant from the vernier should be set up tight, so that that jaw is fixed in position. The other thumb-screw should be set so as to exert, on the small spring between its end and the edge of the bar, a pressure sufficient to bend that spring to almost its full limit, but not so as to let it grip the bar. The elasticity of the spring will then hold the edge of the vernier slide sufficiently firmly to the under edge of the bar to keep the jaw-surfaces parallel; to enable the correct adjustment of the vernier, and to permit the nut-wheel to move the slide without undue wear upon its thread, or undue wear between the edge of the slide and that of the bar, both of which evils will ensue if the thumb-screw nearest the vernier is screwed firmly home before the final measuring adjustment of the vernier is accomplished. When the measurement is completed the second thumb-screw must be set home and the reading examined again, for correctness, to ascertain if tightening the screw has altered it, as it would be apt to do if the thumb-screw was adjusted too loose. The jaws are tempered to resist wear, and are ground to a true plane surface, standing at a right angle to the body of the bar. The method of setting the instrument to a standard size is as follows:-- The zero line marked 0 on the vernier coincides with the line 0 on the bar when the jaws are close together; hence, when the 0 line on the vernier coincides with the inch line on the bar, the instrument is set to an inch between the jaws. When the line next to the 0 line on the vernier coincides with the line to the left of the inch line on the bar, the instrument is set to 1-1/1000 inches. If the vernier slide then be moved so that the second line on the vernier coincides with the second line, on the left of the inch on the bar, the instrument is set to 1-2/1000 inches, and so on, the measurement of inches and fiftieths of an inch being obtained by the coincidence of the zero line on the vernier with the necessary line on the bar, and the measurements of one-thousands being taken as described. But if it is required to measure, or find the diameter of an existing piece of work, the method of measuring is as follows:-- The thumb-screws must be so adjusted as to allow the slide to move easily or freely upon the work without there being any play or looseness between the slide and the bar. The slide should be moved up so as to very nearly touch the work when the latter is placed between the jaws. The thumb-screw farthest from the vernier should then be screwed home, and the other thumb-screw operated to further depress the spring without causing it to lock upon the bar. The nut-wheel is then operated so that the jaws, placed squarely across the work, shall just have perceptible contact with it. (If the jaws were set to grip the work tight they would spring from the pressure, and impair the accuracy of the measurements.) The thumb-screw over the vernier may then be screwed home, and the adjustment of the instrument to the work again tried. If a correction should be found necessary, it is better to ease the pressure of the thumb-screw over the vernier before making such correction, tightening it again afterwards. The reading of the measurement is taken as follows:-- If the 0 line on the vernier coincides with a line on the bar, the measurement will, of course, be shown by the distance of that line from the 0 line on the bar, the measurement being in fiftieths of inches, or inches and fiftieths (as the case may be), but if the 0 line on the vernier does not coincide with any line of division on the bar, then the measurement in inches and fiftieths will be from the next line (on the bar) to the right of the vernier, while the thousandths of an inch may be read by the line on the vernier which coincides with a line on the bar. Suppose, for example, that the zero line of the vernier stands somewhere between the 1 inch and the 1-1/50 inch line of division on the bar, then the measurement must be more than an inch, but less than 1-1/50 inches. If the tenth or middle line on the vernier is the one that coincides with a line on the bar, the reading is 1-10/1000 inches. If the line marked 5 on the vernier is the one that coincides with a line on the bar, the measurement is an inch and 5/1000, and so on. For measuring the diameters of bores or holes, the external edges of the jaws are employed; the width of the jaw at the ends being reduced in diameter to enable the jaw ends to enter a small hole. These edges are formed to a circle, having a radius smaller than the smallest diameter of hole they will enter when the jaws are closed, which insures that the point of contact shall be in the middle of the thickness of each jaw. In this case the outside diameter of the jaws must be deducted from the measurement taken by the vernier, or if it be required to set the instrument to a standard diameter, the zero line on the vernier must be set to a distance on the bar less than that of the measurement required to an amount equal to the diameter of the jaw edges when the jaws are closed. This diameter is, as far as possible, made to correspond to the lines of division on the bar. Thus in the instrument shown in Fig. 1392, these lines of division are 1/50 inch; hence the diameter across the closed bars should, to suit the reading (for internal measurements) on the bar, be measurable also in fiftieths of an inch; but the other side of the bar is divided into millimètres, hence to suit internal measurements (in millimètres or fractions thereof) the width of the jaws, when closed, should be measurable in millimètres; hence, it becomes apparent that the diameter of the jaws used for internal measurements can be made to suit the readings on one side only of the bar, unless the divisions on one side are divisible into those on the other side of the bar. When the diameter of the jaws is measurable in terms of the lines of division on the bar, the instrument may be set to a given diameter by placing the zero of the vernier as much towards the zero on the bar as the width of the jaws when closed. Thus, suppose that width (or diameter, as it may be termed) be 10/50 of an inch, and it be required to set the instrument for an inch interval or bore measurement, then the zero on the vernier must be placed to coincide with the line on the bar which denotes 40/50 of an inch, the lacking 10/50 inch being accounted for in the diameter or width of the two jaws. But when the width of the jaws when closed is not measurable in terms of the lines of division on the bar, the measurement shown by the vernier will, of course, be too small by the amount of the widths of the two jaws, and the measurement shown by the vernier must be reduced to the terms of measurement of the width of the jaws, or what is the same thing, the measurement of the diameter of the jaws must be reduced to the terms of measurement on the bar, in order to subtract one from the other, or add the two together, as the case may require. For example: Suppose the diameter of the jaws to measure, when they are close together, 250/1000 of an inch, and that the bar be divided into inches and fiftieths. Now set the zero of the vernier opposite to the line denoting 49/50 inch on the bar. What, then, is the measurement between the outside edges of the jaws? In this case we require to add the 250/1000 to the 49/50 in order to read the measurement in terms of fiftieths and thousandths of an inch, or we may read the measurement to one hundredths of an inch, thus: 49/50 equal 98/100, and 250/1000 equal 25/100, and 98/1000 added to 25/100 are 123/100, or an inch and 23/100. To read in 1/1000ths of an inch, we have that 49/50 of an inch are equal to 980/1000, because each 1/50 inch contains 20/1000 inch, and this added to 250/1000 makes 1230/1000, that is 1-230/1000 inches. The accuracy of the instrument may be maintained, notwithstanding any wear which may in the course of time take place on the inside faces of the jaws, by adjusting the zero line on the vernier to exactly coincide with the zero line on the bar, but the fineness of the lines renders this a difficult matter with the naked eye, hence it is desirable to read the instrument with the aid of a magnifying glass. If the outer edges of the jaws should wear, it is simply necessary to alter the allowance made for their widths. [Illustration: Fig. 1394.] Fig. 1394 represents standard plug and collar gauges. These tools are made to represent exact standard measurements, and obviously do no more than to disclose whether the piece measured is exactly to size or not. If the work is not to size they will not determine how much the error or difference is, hence they are gauges rather than measuring tools. It is obvious, however, that if the work is sufficiently near to size, the plug or male gauge may be forced in, or the collar or female gauge may be forced on, and in this case the tightness of the fit would indicate that the work was very near to standard size. But the use of such gauges in this way would rapidly wear them out, causing the plug gauge and also the collar to get smaller than its designated size, hence such gauges are intended to fit the work without friction, and at the same time without any play or looseness whatever. Probably the most accurate degree of fit would be indicated when the plug gauge would fit into the collar sufficiently to just hold its own weight when brought to rest while within the collar, and then slowly fall through if put in motion within the collar. It is obvious that both the plug and the collar cannot theoretically be of the same size or one would not pass within the other, but the difference that is sufficient to enable this to be done is so minute that it is practically too small to measure and of no importance. [Illustration: Fig. 1395.] When these gauges are used by the workmen, to fit the work to their wear is sufficient to render it necessary to have some other standard gauge to which they can be from time to time referred to test their accuracy, and for this purpose a standard such as in Fig. 1395 may be employed. It consists of a number of steel disks mounted on an arbor and carefully ground after hardening each to its standard size. But a set of plug and collar gauges provide within themselves to a certain extent the means of testing them. Thus we may take a collar or female gauge of a certain size and place therein two or three plug gauges whose added diameters equal that of the female or collar gauge. [Illustration: Fig. 1396.] In Fig. 1396, for example, the size of the female gauge A being 1-1/2 inches, that of the male B may be one inch, and that of C 1/2 an inch, and the two together should just fit the female. On the other hand, were we to use instead of B and C two males, 7/8 and 5/8 inches respectively, they should fit the female; or a 1/2 inch, a 5/8 inch and a 3/8 inch male gauge together should fit the female. By a series of tests of this description, the accuracy of the whole set may be tested; and by judicious combinations, a defect in the size of any gauge in the set may be detected. The wear of these gauges is the most at their ends, and the fit may be tested by placing the plug within the collar, as in Fig. 1397, and testing the same with the plug inserted various distances within the collar, exerting a slight pressure first in the direction of A and then of B, the amount of motion thus induced in the plug denoting the closeness of the fit. In trying the fit of the plug by passing it well into or through the collar, the axis of the plug should be held true with that of the collar, and the plug while being pressed forward should be slightly rotated, which will cause the plug to enter more true and therefore more easily. The plug should be kept in motion and not allowed to come to rest while in the collar, because in that case the globules of the oil with which the surfaces are lubricated maintain a circular form and induce rolling friction so long as the plug is kept in motion, but flatten out, leaving sliding friction, so soon as the plug is at rest, the result being that the plug will become too tight in the collar to permit of its being removed by hand. [Illustration: Fig. 1397.] The surfaces of both the plug and the collar should be very carefully cleaned and oiled before being tried together, it being found that a film of oil will be interposed between the surfaces, notwithstanding the utmost accuracy of fit of the two, and this film of oil prevents undue abrasion or wear of the surfaces. When great refinement of gauge diameter is necessary, it is obvious that all the gauges in a set should be adjusted to diameter while under an equal temperature, because a plug measuring an inch in diameter when at a temperature of, say, 60° will be of more than an inch diameter when under a temperature of, say, 90°. It follows also that to carry this refinement still farther, the work to be measured if of the same material as the standard gauge should be of the same temperature as the gauge, when it will fit the gauge if applied under varying temperatures; but if a piece of work composed, say, of copper, be made to true gauge diameter when both it and the gauge are at a temperature of, say, 60°, it will not be to gauge diameter, and will not fit the gauge, if both be raised to 90° of temperature, because copper expands more than steel. To carry the refinement to its extreme limit then, the gauge should be of the same metal as the work it is applied to whenever the two fitting parts of the work are of the same material. But suppose a steel pin is to be fitted as accurately as possible to a brass bush, how is it to be done to secure as accurate a fit as possible under varying temperatures? The two must be fitted at some equal temperature; if this be the lowest they will be subject to, the fit will vary by getting looser, if the highest, by getting tighter; in either case all the variation will be in one direction. If the medium temperature be selected, the fit will get tighter or looser as the temperature falls or rises. Now in workshop practice, where fit is the object sought and not a theoretical standard of size, the range of variation due to temperature and, generally, that due to a difference between the metals, is too minute to be of practical importance. To the latter, however, attention must, in the case of work of large diameter, be paid: thus, a brass piston a free fit at a temperature of 100° to a 12-inch cast-iron cylinder, will seize fast when both are at a temperature of, say, 250°. In such cases an allowance is made in conformity with the co-efficients of expansion. In the case of the gauges, all that is practicable for ordinary work-shop variation of temperature is to make them of one kind and quality of material--as hard as possible and of standard diameter, when at about the mean temperature at which they will be when in use. In this case the limit of error, so far as variation from temperature is concerned, will be simply that due to the varying co-efficients of expansion of the metals of which the work is composed. [Illustration: Fig. 1398.] To provide a standard of lineal measurement which shall not vary under changes of temperature it has been proposed to construct a gauge such as shown in Fig. 1398, in which A and B are bars of different metals whose lengths are in the inverse ratio of their co-efficients of expansion. It is evident that the difference of their lengths will be a constant quantity, and that if the two bars be fastened together at one end, the distance from the free end of B to the free end of A will not vary with ordinary differences in temperature. Plug and collar gauges may be used for taper as well as for parallel fits, the taper fit possessing the advantage that the bolt or pin may be let farther into its hole to take up the wear. In a report to the Master Mechanics Association upon the subject of the propriety of recommending a standard taper for bolts for locomotive work, Mr. Coleman Sellers says:-- "As the commission given to me calls for a decision as to the taper of bolts used in locomotive work, it presupposes that taper bolts are a necessity. In our own practice we divide bolts into several classes, and our rule is that in every case where a through bolt can be used it must be used. If we cannot use a through bolt we use a stud, and where a stud cannot be used we put in a tap bolt, and the reason why a tap bolt comes last is because it is part and parcel of the machine itself. There are also black bolts and body bound bolts, the former being put into holes 1/16 inch larger than the bolt. It is possible in fastening a machine or locomotive together to use black bolts and body bound bolts. With body bound bolts it is customary for machine builders to use a straight reamer to true the hole, then turn the bolt and fit it into its place. It is held by many locomotive builders that the use of straight bolts is objectionable, on the score that if they are driven in tight there is much difficulty in getting them out, and where they are got out two or three times they become loose, and there is no means of making them tighter. "There is no difficulty in making two bolts of commercially the same size. But there is a vast difference between absolute accuracy and commercial accuracy. Absolute accuracy is a thing that is not obtainable. What we have to strive for, then, is commercial accuracy. What system can we adopt that will enable workmen of limited capacity to do work that will be practically accurate? The taper bolt for certain purposes presents a very decided advantage. Bolts may be made practically of the same diameter, but holes cannot be made practically of the same diameter. Each one is only an approximation to correctness. We have here an ordinary fluted reamer (showing an excellent specimen of Betts Machine Company's make). That reamer is intended to produce a straight hole, but having once passed through a hole the reamer will be slightly worn. The next time you pass it through it is a little duller, and every time you pass it through the hole must become smaller. There have been many attempts made to produce a reamer that should be adjustable. That, thanks to the gentlemen who are making such tools a speciality, has added a very useful tool to the machine shop--a reamer where the cutters are put in tapered and can be set up and the reamer enlarged and made to suit the gauge. This will enable us to make and maintain a commercially uniform hole in our work. But the successful use of a reamer of this kind depends upon the drill that precedes this reamer being made as nearly right as possible, so that the reamer will have little work to do. The less you give a reamer to do the longer it will maintain its size. "The question of tapered bolts involves at once this difficulty: that we have to drill a straight hole, then the tapered reamer must take out all the metal that must be removed in order to convert a straight into a tapered hole. The straight hole is maintained in its size by taking out the least amount of metal. It follows that the tapered reamer would be nearest right which would also take out the least amount of metal. "Then you come to the question of the shape of the taper. When I was engaged building locomotives in Cincinnati, a great many years ago, we used bolts the taper of which was greater than I shall recommend to you. In regard to the compression that would take place in bolts, no piece of iron can go into another piece of iron without being smaller than the hole into which it is intended to go. If it is in any degree larger, it must compress the piece itself or stretch the material that is round it. So, if you adopt a tapered bolt, you cannot adopt a certain distance that it shall stand out before you begin to drive it, for there will be more material to compress in a large piece than in a small one. Metal is elastic. Within the elastic limit of the metal you may assume the compression to be a spring. In a large bolt you have a long spring, and in a short one you have a short spring. If you drive a half-inch bolt into a large piece of iron, it is the small bolt which you compress; therefore the larger the bolt the more pressure you can give to produce the same result. Hence, if you adopt the taper bolt, you will have to use your own discretion, unless you go into elaborate experiments to show how far the bolt head should be away from the metal when you begin to drive it. [Illustration: Fig. 1399.] "Certain builders of locomotives put their stub ends together with tapered bolts, but do not use tapered bolts in any other part of the structure. The Baldwin Works use tapered bolts wherever they are body bound bolts. They make a universal taper of 1/16 inch to the foot. An inch bolt 12 inches long would be 1-1/16 inches diameter under the head. They make all their bolts under 9 inches long 1/16 larger under the head than the name of the bolt implies. Thus a 3/4 inch bolt would be 13/16 inch under the head, provided it was 9 inches long or under. Anything over 9 inches long is made 1/8 inch larger under the head, and still made a taper of 1/16 inch to the foot. A locomotive builder informs me that a taper of 1/8 inch to the foot is sometimes called for, and the Pennsylvania road calls for 3/32 inch to the foot. But the majority of specifications call for 1/16 inch to the foot. The advantage of 1/16 inch taper lies in the fact that a bolt headed in the ordinary manner can be made to fill the requirements, provided it is made of iron. You may decide that bolts should be tapered, for the reason that when a tapered bolt is driven into its place it can be readily knocked loose, or if that bolt, when in its place, proves to be too loose, you have merely to drive it in a little farther: these are arguments in favor of tapered bolts, showing their advantage. It is easier to repair work that has tapered bolts than work that has straight bolts. If you adopt a tapered bolt, say, with a taper of 1/16 inch to the foot, you are going to effect the making of those bolts and the boring of those holes in a commercially accurate manner, so that they can be brought into the interchangeable system. To carry this out, you require some standard to start with, and the simplest system that one can conceive is this: Let us imagine that we have a steel plug and grind it perfectly true. We have the means of determining whether that is a taper of 1/16 inch, thanks to the gentlemen who are now making these admirable gauges. We have a lathe that can turn that taper. I think if you go into the manufacture of these bolts, you will be obliged to use a lathe which will always turn a uniform taper. Having made a female gauge, Fig. 1399, 8 inches long and 1-1/16 inches diameter with a taper of 1/16 inch to the foot, this is the standard of what? The area of the bolt, not of the hole it goes into. We now make a plug, Fig. 1399. Taking that tapered plug we should be able to drop it into the hole. Your taper reamer is made to fit this, but you require to know how deep the hole should be. Remember, I said this is the gauge that the bolts are made by. Now let us suppose that we have this as a standard, and to that standard these reamers are made. We decide by practice how much compression we can put upon the metal. For inch bolts, and, say, all above 1/2 inch, we might, say, allow the head to stand up 1/8 of an inch. Let us make another female gauge like Fig. 1399, but turned down 1/8 of an inch shorter. We then shall have the hole smaller than it was before. It is this degree smaller, .0065 of an inch; that is a decimal representing how much smaller that hole is when you have gone down 1/8 of an inch on a taper of 1/16 inch to the foot. [Illustration: Fig. 1400.] "Having got this tapered plug, you then must have the means of making the bolts commercially accurate in the shop. For that purpose you must have some cast-iron plugs. Those are reamed with a reamer that has no guard on it, but is pushed into it until the plug--this standard plug--is flush with the end of it. If you go in a little too far it is no matter. Having produced that gauge, we gauge first the one that is used on the lathe for the workman to work by, and he will fit his bolt in until the head will be pushed up against it. If you have a bolt to make from a straight piece of iron, I should advise its being done in two lathes. Here are those beautiful gauges of the Pratt and Whitney Company, which will answer the present purpose; one of these gauges measuring what the outside of the bolt will be, the other gauge 1/16 of an inch larger will mark the part under the head. Messrs. Baldwin have a very good system of gauges. All the cast-iron plugs which they use for this purpose are square. Holes are cut in the blocks the exact size of the bolts to be turned up, as shown in Fig. 1400. The object of this is that there shall be no mistake as to what the gauge is. These gauges can be readily maintained, because they have to go back into the room to the inspector. He puts this plug in. If it goes in and fits flush, it is all right. If the plug goes in too far, it is worn. He then turns a little off the end and adjusts it. "Now practically through machine shops we find that we have to use cast-iron gauges. We take, for instance, 2-inch shafting. Shafting can only be commercially accurate. Therefore we make cast-iron rings and if those rings will go on the shafting it is near enough accurate for merchantable purposes. But this ring will wear in a certain time. Therefore it must not be used more than a certain number of days or hours. Here you have a system that is simple in the extreme. You have all this in two gauges, one gauge being made as a mere check on that tapered plug which is the origin of all things, the origin being 1/8 or 7/16, or 1/4 of an inch shorter if the bolt is very large. There is where you have to use your own judgment. But having adopted something practical you then can use your reamer which is necessary to produce a hole of a given size. If this reamer wears, you then turn off this wrought-iron collar far enough back to let it go in that much farther. I know of no other way by which you can accomplish this result so well as by that in use at the Baldwin Locomotive Works. I think that the system originated with Mr. Baldwin himself. "I do not feel disposed to recommend to you any particular taper to be adopted, because it is not a question like that of screw-threads. In screw-threads we throw away the dies that are used upon bolts, which are perishable articles. The taper that has once been adopted in locomotive establishments is a perpetual thing. If the Pennsylvania railroad and all its branches have adopted 3/32, it is folly to ask them to change it to 1/16 of an inch, because their own connections are large enough to make them independent of almost any other corporation, and the need of absolute uniformity in their work would cause them to stick to that particular thing. Any of you having five, six, seven, or two or three hundred engines, must make up your minds what you will do. When we adopt a standard for screw-threads, a screw-thread is adopted which has a manifest advantage. A bolt that has one screw thread can be used on any machine. But once having adopted a taper on a road, it is very difficult to make a change; and whether it is wisdom for this Association to say that thus-and-so shall be the standard taper, is a question I am unable to answer. Therefore I am unwilling to present any taper to you, and only present the facts, but will say that 1/16 inch is enough. The less taper you have the less material you have to cut away. But to say that 1/16 inch is preferable to 1/32 inch is folly, because no human being could tell the difference. If a bolt has 5° taper on the side, it may set in place; if it has 7°, it may jump out. That is the angle of friction for iron or other metals. Five degrees would be an absurd angle for a taper bolt. Anything, then, that will hold; that is, if you drive the bolt it will set there. "This presentation may enable you to arrive at some conclusion. Nothing is more desirable than an interchangeable system. In making turning lathes we try to make all parts interchangeable, and we so fit the sliding spindle. Every sliding spindle in the dead head of the lathe has to be fitted into its own place. We know of no method of making all holes of exactly the same size that shall be commercially profitable. The only way we could surmount that difficulty was to put two conical sleeves in that should compress. We have so solved the problem. We now make spindles that are interchangeable, and we do not fit one part to the other. But that is not the case with bolts. You cannot put the compressing thimbles on them, therefore, you have to consider the question, How can you make holes near enough, and how can you turn the bolts near enough alike?" [Illustration: Fig. 1401.] Fig. 1401 represents, and the following table gives the taper adopted by the Baldwin Locomotive Works. Bolt threads, American standard, except stay bolts and boiler studs, [V]-threads, 12 per inch; valves, cocks and plugs, [V]-threads, 14 per inch, and 1/8 inch taper per 1 inch. Standard bolt taper 1/16 inch per foot. Length of bolts from head to end of thread equals A. Diameter of bolt under the head as follows:-- 3/64 inch larger at B for 9 inch and under 1/16 " " over 9 inch to 12 inch 3/32 " " " 12 " to 18 " 1/8 " " " 18 " to 24 " 5/32 " " " 24 " to 30 " 3/16 " " " 30 " to 36 " [Illustration: Fig. 1402.] It is obvious that a plug or collar gauge simply determines what is the largest dimension of the work, and that although it will demonstrate that a piece of work is not true or round yet it will not measure the amount of the error. The work may be oval or elliptical, or of any other form, and yet fit the gauge so far as the fit can be determined by the sense of feeling. Or suppose there is a flat place upon the work, then except in so far as the bearing marks made upon the work by moving it within the gauge may indicate, there is no means of knowing whether the work is true or not. Furthermore, in the case of lathe work held between the lathe centres it is necessary to remove the work from the lathe before the collar gauge can be applied, and to obviate these difficulties we have the caliper gauge shown in Fig. 1402. The caliper end is here shown to be for 3/4 inch, and the plug end for 13/16 inch. If the two ends were for the same diameter one gauge only would be used for measuring external and internal work of the same diameter, but in this case the male cannot be tested with the female gauge; whereas if the two ends are for different diameters the end of one gauge may be tested with that of another, and their correctness tested, but the workman will require two gauges to measure an external and internal piece of the same diameter. [Illustration: Fig. 1403.] For small lathe work of odd size as when it is required to turn work to fit holes reamed by a worn reamer that is below the standard size, a gauge such as in Fig. 1403, is sometimes used, the mouth A serving as a caliper and the hole B as a collar gauge for the same diameter of work. It is obvious that such a gauge may be applied to the work while it is running in the lathe, and that when the size at A wears too large the jaw may be closed to correct it; a plan that is also pursued to rectify the caliper gauge shown in Fig. 1402. [Illustration: Fig. 1404.] On large work, as, say, of six inches in diameter, a gauge, such as in Fig. 1404, is used, being short so that it may be light enough to be conveniently handled; or sometimes a piece such as in Fig. 1405 is used as a gauge, the ends being fitted to the curvature of the bore to be tested. Gauges of these two kinds, however, are generally used more in the sense of being templates rather than measuring tools, since they determine whether a bore is of the required size rather than determine what that size is. [Illustration: Fig. 1405.] [Illustration: Fig. 1406.] [Illustration: Fig. 1407.] For gauging work of very large diameter, as, say, several feet, to minute fractions of an inch, as is necessary, for example, for a shrinkage fit on a locomotive tire, the following method is employed. In Fig. 1406 let A represent a ring, say, 5 feet bore, and requiring its bore to be gauged to within, say, 1/100 inch. Then R represents a rod made, say, 1/2 inch shorter than the required diameter of bore, and W, Fig. 1407, represents a wedge whose upper surface C D is curved, its lower surface being a true plane. The thickness at the end C is made, say, 51/100 inch, while that at D is 48/100 inch; or in other words, there is 3/100 of an inch taper in the length of the wedge. Suppose then that the rod R is placed in the bore of A as in figure, and that the wedge just has contact with the work bore and with the end of the rod when it has entered as far as E in Fig. 1407, and that point E is one-third of the length of the wedge, then the bore of A will measure the length of the rod R plus 49/100 of an inch. But if the wedge passed in to line F, the latter being two-thirds the length of the wedge from D, then the bore would be 50/100 larger than the length of the rod R. It is obvious that with this method the work may be measured very minutely, and the amount of error, if there be any, may be measured. The rod must be applied to the work in the same position in which its measurement was made, otherwise its deflection may vitiate the measurement. Thus, if the rod measures 4 feet 11-1/2 inches when standing vertical, it must be applied to the work standing vertical; but if it was measured lying horizontal, it must be applied to the work lying horizontal, as there will be a difference in its length when measured in the two positions, which occurs on account of variations in its deflection from its own weight. [Illustration: Fig. 1408.] [Illustration: Fig. 1409.] For simply measuring a piece of work to fit it to another irrespective of its exact size as expressed in inches and parts of an inch the common calipers are used. Fig. 1408 represents a pair of spring calipers, the bow acting as a spring to keep the two legs apart, and the screw and nut being used to close them against the spring pressure. The slightness of the legs enables these calipers to be forced or to spring over the work, and thus indicate by the amount of pressure it requires to pass them over the work how much it is above size, and therefore how much it requires to be reduced. But, on the other hand, this slightness renders it somewhat difficult to measure with great correctness. A better form of outside calipers is shown in Fig. 1409, in which in addition to the stiffness of the pivoted joint a bow spring acts to close the caliper legs, which are operated, to open or close them, by operating the hand screw shown, the nuts in which the screw operates being pivoted to the caliper legs. The advantage of this form is that the calipers may be set very readily, while there is no danger of the set or adjustment of the calipers altering from any slight blow or jar received in laying them down upon the bench. [Illustration: Fig. 1410.] Fig. 1410 gives views of a common pair of outside calipers such as the workman usually makes for himself. When this form is made with a sufficiently large joint, and with the legs broad and stiff as in the figure, they will serve for very fine and accurate adjustments. [Illustration: Fig. 1411.] Fig. 1411 represents a pair of inside calipers for measuring the diameters of holes or bores. The points of these calipers should be at an angle as shown in the Fig. 1412, which will enable the points to enter a long distance in a small hole, as is denoted by the dotted lines in the figure. This will also enable the extreme points to reach the end of a recess, as in Fig. 1413, which the rounded end calipers, such as in this figure, will not do. [Illustration: Fig. 1412.] [Illustration: Fig. 1413.] [Illustration: Fig. 1414.] Fig. 1414 represents a pair of inside calipers with an adjustment screw having a right-hand screw at A and a left-hand one at B, threaded into two nuts pivoted into the arms, so that by operating the screw the legs are opened or closed, and are locked in position, so that they cannot move from an accidental blow. But as the threads are apt to wear loose, it is preferable to provide a set screw to one of the nuts so as to take up the wear and produce sufficient friction to prevent looseness of the legs. [Illustration: Fig. 1415.] [Illustration: Fig. 1416.] Calipers are sometimes made double, that is to say, the inside and the outside calipers are provided in the one tool, as in Fig. 1415, which represents a pair of combined inside and outside calipers having a set screw at C to secure the legs together after the adjustment is made. The object of this form is to have the measuring points equidistant from the centre of the pivot A in Fig. 1416, so that when the outside legs are set to the diameter of the work as at B, the inside ones will be set to measure a hole or bore of the same diameter as at C. This, however, is not a desirable form for several reasons, among which are the following:-- In the first place outside calipers are much more used than inside ones, hence the wear on the points are greatest. Again, the pivot is apt to wear, destroying the equality of length of the points from the centre of the pivot; and in the third place the shape of the points of calipers as usually made vitiates the correctness of the measurements. [Illustration: Fig. 1417.] Fig. 1417, for example, represents the ordinary form, the points being rounded; hence, when the legs are closed the point of contact between the inside and outside calipers will be at A, while when they are opened out to their fullest the points of contact will be at B. This may, however, be remedied to a great extent by bevelling off the ends from the outside as shown in Fig. 1416. [Illustration: Fig. 1418.] The end faces of outside calipers should be curved in their widths, as in Fig. 1418, so that contact shall occur at the middle, and it will then be known just where to apply the points of the inside calipers when testing them with the outside ones. Inside and outside calipers are capable of adjustment for very fine measurements; indeed, from some tests made by the Pratt and Whitney Company among their workmen it was found that the average good workman could take a measurement with them to within the twenty-five thousandth part of an inch. But the workman of the general machine shop who has no experience in measuring by thousandths has no idea of the accuracy with which he sets two calipers in his ordinary practice. The great difference that the one-thousandth of an inch makes in the fit of two pieces may be shown as in Fig. 1419, which represents a collar gauge of 5/8 inch in diameter, and a plug 1/1000 inch less in diameter, and it was found that with the plug inserted 1/8 inch in the collar it could be moved from A to B, a distance of about 5/16 inch, which an ordinary workman would at once recognise as a very loose fit. If the joints of outside calipers are well made the calipers may upon small work be closed upon the work as in Fig. 1420, and the adjustment may be made without requiring to tap or lightly knock the caliper legs against the work as is usually done to set them. But to test the adjustment very finely the work should be held up to the light, as in Fig. 1421, the lower leg of the calipers rested against the little finger so as to steady it and prevent it from moving while the top leg is moved over the work, and at the same time moving it sideways to find when it is held directly across the work. For testing the inside and outside calipers together they should for small diameters be held as in Fig. 1422, the middle finger serving to steady one inside and one outside leg, while one leg only of either calipers is grasped in the fingers. [Illustration: Fig. 1419.] [Illustration: Fig. 1420.] [Illustration: Fig. 1421.] [Illustration: Fig. 1422.] For larger dimensions, as six or eight inches, it is better, however, to hold the calipers as in Fig. 1423, the forefinger of the left hand serving to rest one leg of each pair on the contact being thus tested between the legs that are nearest to the operator. The adjustment of caliper legs should be such that contact between the caliper points and the work is scarcely, if at all, perceptible. If with the closest of observation contact is plainly perceptible, the outside calipers will be set smaller than the work, while in the case of inside calipers, they would be set larger; and for this reason it follows that if a bore is to be measured to have a plug fitted to it, the inside calipers should have barely perceptible contact with the work bore, and the outside calipers should have the same degree of contact, or, if anything, a very minute degree of increased contact. On the other hand, if a bore is to be fitted to a cylindrical rod the outside calipers should be set to have the slightest possible contact with the rod, and the inside ones set to have as nearly as possible the same degree of contact with the outside ones, or, if anything, slightly less contact. For if in any case the calipers have forcible contact with the work the caliper legs will spring open and will therefore be improperly set. Calipers should be set both to the gauge and to the work in the same relative position. Let it be required, for example, to set a pair of inside calipers to a bore, and a pair of outside calipers to the inside ones, and to then apply the latter to the work. If the legs of the inside calipers stand vertical to the bore for setting they should stand vertical while the outside calipers are set to them, and if the outside calipers are held horizontally while set to the inside ones they should be applied horizontally to the work, so as to eliminate any error due to the caliper legs deflecting from their own weight. [Illustration: Fig. 1423.] To adjust calipers so finely that a piece of work may be turned by caliper measurement to just fit a hole; a working or a driving fit without trying the pieces together, is a refinement of measurement requiring considerable experience and skill, because, as will be readily understood from the remarks made when referring to gauge measurements, there are certain minute allowances to be made in the set of the calipers to obtain the desired degree of fit. In using inside calipers upon flat surfaces it will be found that they can be adjusted finer by trusting to the ear than the eye. Suppose, for example, we are measuring between the jaws of a pillow-block. We hold one point of the calipers stationary, as before, and adjust the other point, so that, by moving it very rapidly, we can just detect a scraping sound, giving evidence of contact between the calipers and the work. If, then, we move the calipers slowly, we shall be unable, with the closest scrutiny, to detect any contact between the two. Calipers possess one great advantage over more rigid and solid gauges, in that the calipers may be forced over the work when the degree of force necessary to pass them on indicates how much the work is too large, and therefore how much it requires reducing. Thus, suppose a cylindrical piece of work requires to be turned to fit a hole, and the inside calipers are set to the bore of the latter, then the outside calipers may be set to the inside ones and applied to the work, and when the work is reduced to within, say, 1/100 inch the calipers will spring open if pressed firmly to the work, and disclose to the workman that the work is reduced to nearly the required size. So accustomed do workmen become in estimating from this pressure of contact how nearly the work is reduced to the required diameter, that they are enabled to estimate, by forcing the calipers over the work, the depth of the cut required to be taken off the work, with great exactitude, whereas with solid gauges, or even caliper gauges of solid proportions, this cannot be done, because they will not spring open. The amount to which a pair of calipers will spring open without altering their set depends upon the shape: thus, with a given joint they will do so to a greater extent in proportion as the legs are slight, whereas with a given strength of leg they will do so more as the diameter of the joint is large and the fit of the joint is a tight one. But if the joint is so weak as to move too easily, or the legs are so weak as to spring too easily, the calipers will be apt in one case to shift when applied to the work, and in the other to spring so easily that it will be difficult to tell by contact when the points just touch the work and yet are not sprung by the degree of contact. For these reasons the points of calipers should be made larger in diameter than they are usually made: thus, for a pair of calipers of the shape shown in Fig. 1410, the joint should be about 1-1/4 inches diameter to every 6 inches of length of leg. The joint should be sufficiently tight that the legs can just be moved when the two legs are taken in one hand and compressed under heavy hand pressure. [Illustration: Fig. 1424.] For measuring the distance of a slot or keyway from a surface, the form of calipers shown in Fig. 1424 is employed; the straight leg has its surface a true plane, and is held flat against the surface B of the slot or keyway, and the outside or curved leg is set to meet the distance of the work surface measuring the distance C. These are termed keyway calipers. There are in general machine work four kinds of fit, as follow: The working or sliding fit; the driving fit; the hydraulic press fit; and the shrinkage fit. In the first of these a proper fit is obtained when the surfaces are in full contact, and the enveloped piece will move without undue friction or lost motion when the surfaces are oiled. In the second, third, and fourth, the enveloped piece is made larger than the enveloping piece, so that when the two pieces are put together they will be firmly locked. It is obvious that in a working or sliding fit the enveloped piece must be smaller than that enveloping it, or one piece could not pass within the other. But the amount of difference, although too small to be of practical importance in pieces of an inch or two in diameter and but few inches in length, is appreciable in large work, as, say, of two or more feet in diameter. A journal, for example, of 1/10 inch diameter, running in a bearing having a bore of 1/1000 inch larger diameter, and being two diameters in length, would be instantly recognised as a bad fit; but a journal 6 inches in diameter and two diameters or 12 inches long would be a fair fit in a bearing having a bore of 6-1/1000 inches. In the one case the play would be equal to one one-hundredth of the shaft's diameter, while in the other case the play would equal but one six-thousandth part of the shaft's diameter. In small work the limit of wear is so small, and the length of the pieces so short, that the 1/1000 of an inch assumes an importance that does not exist in larger work. Thus, in watch work, an error of 1/1000 inch in diameter may render the piece useless; in sewing machine work it may be the limit to which the tools are allowed to wear; while in a steamship or locomotive engine it may be of no practical importance whatever. A journal 1/10 inch in diameter would require to run, under ordinary conditions, several years to become 1/1000 inch loose in its bearing. Some of this looseness, and probably nearly one half of it, will occur from wear of the bearing bore; hence, if a new shaft of the original standard diameter be supplied the looseness will be reduced by one-half. But a 6-inch journal and bearing would probably wear nearly 1/1000 inch loose in wearing down to a bearing which may take but a week or two, and for these reasons among others, standard gauges and measuring tools are less applicable to large than to small work. The great majority of fits made under the standard gauge system consist of cylindrical pieces fitting into holes or bores. Suppose then that we have a plug and a collar gauge each of an inch diameter, and a reamer to fit the collar gauge, and we commence to ream holes and to turn plugs to fit the collar gauge, then as our work proceeds we shall find that as the reamer wears, the holes it makes will get smaller, and that as the collar gauge wears, its bore gets larger, and it is obvious that the work will not go together. The wear of the gauge obviously proceeds slowly, but the wear of the reamer begins from the very first hole that it reams, although it may perform considerable duty before its wear sensibly affects the size of the hole. Theoretically, however, its size decreases from the moment it commences to perform cutting duty until it has worn out, and the point at which the wearing-out process may have proceeded to its greatest permissible limit is determined by its reduction of size rather than by the loss of its sharpness or cutting capacity. Obviously then either the reamer must be so made that its size may be constantly adjusted to take up the wear, as in the adjustable reamer, or else if solid reamers are used there must be a certain limit fixed upon as the utmost permissible amount of wear, and the reamer must be made above the standard size to an amount equal to the amount of this limit, so that when the reamer has worn down it will still bore a hole large enough to admit the plug gauge. To maintain the standard there should be in this case two sets of gauges, one representing the correct standard and the other the size to which the reamer is to be made when new or restored to its proper size. The limit allowed for reamer wear varies in practice from 1/1000 to 1/10000 of an inch, according to the requirements of the work. As regards the wear of the standard gauges used by the workmen they are obviously subject to appreciable wear, and must be returned at intervals to the tool room to be corrected from gauges used for no other purpose. To test if a hole is within the determined limit of size a limit gauge may be used. Suppose, for example, that the limit is 1/1000 of an inch, then a plug gauge may be made that is 1/1000 of an inch taper, and if the large end of this plug will enter the hole, the latter is too large, while if the small end will not enter, the hole is too small. When only a single set of plug and collar gauges are at hand the plug or the collar gauge may be kept to maintain the standard, the other being used to work to, both for inside and outside work. Suppose, for example, that a plug and collar gauge are used for a certain piece of work and that both are new, then the reamer may be made from either of them, because their sizes agree, but after they have become worn either one or the other must be accepted as the standard of size to make the reamer to. If it be the collar gauge, then the plug gauge is virtually discarded as a standard, except in that if the plug gauge be not used at all it may be kept as a standard of the size to which the collar gauge must be restored when it has worn sufficiently to render restoration to size necessary. If this system be adopted the size of the reamer will be constantly varying to suit the wear of the collar gauge, and the difficulty is encountered that the standard lathe arbors or mandrels will not fit the holes produced, and it follows that if standard mandrels are to be used the reamers must when worn be restored to a standard size irrespective of the wear of the gauges, and that the standard mandrels must be made to have as much taper in their lengths as the limit of wear that is allowed to the reamers. Suppose, for example, that it is determined to permit the reamer to wear the 1/2000 of an inch before restoring it to size, then in an inch mandrel the smallest end may be made an inch in diameter and the largest 1-1/2000 inch in diameter, so that however much the reamer may be worn within the limit allowed for wear the hole it produces will fit at some part in the length of the standard mandrel. But as the reamer wears smaller its size must be made as much above its designated standard size as the limit allowed for wear; hence, when new or when restored to size, the reamer would measure 1-1/2000 inches, and the hole it produced would fit the large end of the mandrel. But as the reamer wore, the hole would be reamed smaller and would not pass so far along the mandrel, until finally the limit of reamer wear being reached the work would fit the small end of the mandrel. The small end of the mandrel is thus the standard of its size, and the wear of the collar gauge is in the same direction as that of the reamer. Thus, so long as the collar gauge has not worn more than the 1/2000 of an inch it will, if placed upon the mandrel, fit it at some part of its length. Now suppose that the plug gauge be accepted as the standard to which the reamer is to be made, and that to allow for reamer wear the reamer is made, say, 1/2000 inch larger than the plug gauge, the work being made to the collar gauge. Then with a new reamer and new or unworn gauges the hole will be reamed above the standard size to the 1/2000 inch allowed for reamer wear. As the reamer wears, the hole it produces will become smaller, and as the collar gauge wears, the work turned to it will be larger, and the effect will be that, to whatever extent the collar gauge wears, it will reduce the permissible amount of reamer wear, so that when the collar gauge had worn the 1/2000 inch the work would not go together unless the reamer was entirely new or unworn. In a driving fit one piece is driven within the other by means of hammer blows, and it follows that one piece must be of larger diameter than the other, the amount of the difference depending largely upon the diameter and length of the work. It is obvious, however, that the difference may be so great that with sufficiently forcible blows the enveloping piece may be burst open. When a number of pieces are to be made a driving fit, the two pieces may be made to fit correctly by trial and correction, and from these pieces gauges may be made so that subsequent pieces may be made correct by these gauges, thus avoiding the necessity to try them together. In fitting the first two pieces by fit and trial, or rather by trial and correction, the workman is guided as to the correctness of the fit by the sound of the hammer blows, the rebound of the hammer, and the distance the piece moves at each blow. Thus the less the movement the more solid the blow sounds, and the greater the rebound of the hammer the tighter the fit, and from these elements the experienced workman is enabled to know how tightly the pieces may be driven together without danger of bursting the outer one. What the actual difference in diameter between two pieces may require to be to make a driving fit is governed, as already said, to a great extent by the dimensions of the pieces, and also by the nature of the material and the amount of area in contact. Suppose, for example, that the plug is 6 inches long, and the amount of pressure required to force it within the collar will increase with the distance to which it is enveloped by the collar. Or suppose one plug to be 3 inches and another to be 6 inches in circumference, and each to have entered its collar to the depth of an inch, while the two inside or enveloped pieces are larger than the outside pieces by the same amount, the outside pieces being of equal strength in proportion to their plugs, so that all other elements are equal, and then it is self-evident that the largest plug will require twice as much power as the small one will to force it in another inch into the collar, because the area of contact is twice as great. It is usual, therefore, under definite conditions to find by experiment what allowance to make to obtain a driving or a forcing fit. Thus, Mr. Coleman Sellers, at a meeting of the Car Builders Association, referring to the proper amount of difference to be allowed between the diameters of car axles and wheel bores in order to obtain a proper forcing or hydraulic fit, said, "Several years ago some experiments were made to determine the difference which should be made between the size of the hole and that of the axle. The conclusion reached was that if the axle of standard size was turned 0.007 inch larger than the wheel was bored it would require a pressure of about 30 tons to press the axle into the wheel." The wheel seat on the axle here referred to was 4-7/8 inches in diameter and 7 inches long. It is to be remarked, however, that the wheel bore being of cast iron and the axle of wrought iron the friction between the surfaces was not the same as it would be were the two composed of the same metal. This brings us to a consideration of what difference in the forcing fit there will be in the case of different metals, the allowance for forcing being the same and the work being of the same dimensions. Suppose, for example, that a wrought-iron plug of an inch in diameter is so fitted to a bore that when inserted therein to a distance of, say, 2 inches, it requires a pressure of 3 lbs. to cause it to enter farther, then how much pressure would it take if the bore was of cast iron, of yellow brass, or of steel, instead of wrought iron. This brings us to another consideration, inasmuch as the elasticity and the strength of the enveloping piece has great influence in determining how much to allow for a driving, forcing, or a shrinkage fit. Obviously the allowance can be more if the enveloping piece be of wrought iron, copper, or brass, than for cast iron or steel, because of the greater elasticity of the former. Leaving the elasticity out of the question, it would appear a natural assumption that the pieces, being of the same dimensions, the amount of force necessary to force one piece within the other would increase in proportion as the equivalents of friction of the different metals increased. This has an important bearing in practice, because the fit of pieces not made to standard gauge diameter is governed to a great extent by the pressure or power required to move the pieces. Thus, let a steel crosshead pin be required to be as tight a fit into the crosshead as is compatible with its extraction by hand, and its diameter in proportion to that of the bore into which it fits will not be the same if that bore be of wrought iron, as it would be were the bore of steel, because the coefficient of friction for cast steel on cast iron is not the same as that for steel on wrought iron. In other words, the lower the coefficient of friction on the two surfaces the less the power required to force one into the other, the gauge diameters being equal. In this connection it may be remarked that the amount of area in contact is of primary importance, because in ordinary practice the surfaces of work left as finished by the steel cutting tools are not sufficiently true and smooth to give a bearing over the full area of the surfaces. This occurs for the following reasons. First, work to be bored must be held (by bolts, plates, chuck-jaws, or similar appliances) with sufficient force to withstand the pressure of the cut taken by the cutting tool, and this pressure exerts more or less influence to spring or deflect the work from its normal shape, so that a hole bored true while clamped will not be so true when released from the pressure of the holding clamps. To obviate this as far as possible, expert workmen screw up the holding devices as tight as may be necessary for the heavy roughing cuts, and then slack them off before taking the finishing cuts. Secondly, under ordinary conditions of workshop practice, the steel cutting tools do not leave a surface that is a true plane in the direction of the length of the work, but leave a spiral projection of more or less prominence and of greater or less height, according to the width of that part of the cutting edge which lies parallel to the line of motion of the tool feed, taken in proportion to the rate of feed per revolution of the work. Let the distance, Fig. 1424A, A to B lie in the plane of motion of the tool feed, and measure, say, 1/4 inch, the tool moving, say, 5/16 inch along the cut per lathe revolution. Suppose the edge from B to D to lie at a minute angle to the line of tool traverse, and the depth of the cut to be such that the part from B to C performs a slight cutting or scraping duty, then the part from B to C will leave a slight ridge on the work plainly discernible to the naked eye in what are termed the tool marks. The obvious means of correcting this is to have the part A B of greater width than the tool will feed along the cut, during one revolution of the work (or the cutter, as the case may be); but there are practicable obstacles to this, especially when applied to wrought iron, steel, or brass, because the broader the cutting edge of a tool the more liable it is to spring, as well as to jar or chatter, leaving a surface showing minute depressions lying parallel to the line of tool feed. If the cutting tool be made parallel and cylindrical on its edges, and clearance be given on the front end of its diameter only, so as to cut along a certain distance only of its cylindrical edge, the rest being a close fit to the bore of the work, the part having no cutting edge, that is, the part without clearance, will be apt to cause friction by rubbing the bore of the work as the tool edge wears, and the friction will cause heat, which will increase as the cut proceeds, causing the hole to expand as the cut proceeds, and to be taper when cooled to an equal degree all over. This may be partly obviated by giving the tool a slow rate of cutting speed, and a quick rate of feed, which will greatly reduce the friction and consequently the heating of the tool and the work. On cast iron it is possible to have a much broader cutting edge to the tool, without inducing the chattering referred to, than is the case with wrought iron, steel, or brass, especially when the finishing cut is a very light one. If the finishing cut be too deep, the surface of the work, if of cast iron, will be pitted with numerous minute holes, which occur because the metal breaks out from the strain placed on it (and due to the cut) just before it meets the cutting edge of the tool. Especially is this the case if the tool be dull or be ground at an insufficiently acute angle. When the work shows the tool marks very plainly, or if of cast iron shows the pitting referred to (instead of having a smooth and somewhat glossy appearance), there will be less of its surface in contact with the surface to which it fits, and the fit will soon become destroyed, because the wearing surface or the gripping surface, as the case may be, will the sooner become impaired, causing looseness of the fit. In the one case the abrasion which should be distributed over the whole area of the fitting parts is at first confined to the projections having contact, which, therefore, soon wear away. In the other case the projecting area in contact compresses, causing looseness of the fit. Hydraulic press or forcing fits.--For securing pieces together by forcing one within the other by means of an hydraulic press, the plug piece is made a certain amount larger than the bore it is to enter, this amount being termed the allowance for forcing. What this allowance should be under any given conditions for a given metal, will depend upon the truth and smoothness of the surfaces, and on this account no universal rule obtains in general practice. From some experiments made by William Sellers & Co., it was determined that if a wheel seat (on an axle) measuring 4-7/8 inches in diameter and 7 inches long was turned 7/1000 of an inch larger than the wheel bore, it would require a pressure of about thirty tons to force the wheel home on the axle. At the Susquehanna shops of the Erie railroad the measurements are determined by judgment, the operatives using ordinary calipers. If an axle 3-1/2 diameter and 6 inches long requires less than 25 tons it is rejected, and if more than 35 tons it is corrected by reducing the axle. In order to insure a proper fit of pieces to be a driven or forced fit it is sometimes the practice to make them taper, and there is a difference of opinion among practical mechanics as to whether taper or parallel fits are the best. Upon this point it may be remarked that it is much easier to measure the parts when they are parallel than when they are taper, and it is easier to make them parallel than taper. On the elevated railroads in New York city, the wheel bores being 4-1/8 inches in diameter and 5 inches long, the measurements are taken by ordinary calipers, the workmen judging how much to allow, and the rule is to reject wheels requiring less than about 26 tons, or more than about 35 tons, to force them on. These wheels form excellent examples, because of the excessive duty to which they are subjected by reason of the frequency of their stoppage under the pressure of the vacuum brake. The practice with these wheels is to bore them parallel, finishing with a feed of 1/4 inch per lathe revolution, and to turn the axle seats taper just discernible by calipers. This may, at first sight, seem strange, but examination makes it reasonable and plain. Let a wheel having a parallel bore be forced upon a parallel axle, and then forced off again, and the bore of the wheel will be found taper to an appreciable amount, but increasing in proportion as the surface of the hole varied from a dead smoothness; in other words, varying with the depth of the tool marks in the bore and the smoothness of the cut. Let the length of the wheel bore be 7 inches long, and the amount allowed for forcing be .004 inch, and one end of the wheel bore will have been forced (by the time it is home on the axle) over the length of 7 inches of the axle-seat, whose diameter was .004 larger than the bore: a condensation, abrasion, or smoothing of the metal must have ensued. [Illustration: Fig. 1424A.] Now the other end of the same bore, when it takes its bearing on the shaft, is just iron, and iron without having suffered any condensation. If the tool marks be deep, those on one end will be smoothed down while those at the other remain practically intact. Clearly then, for a parallel hole, a shaft having as much taper as the wheel bore will get in being forced over the shaft best meets the requirements; or, for a parallel shaft or seat, and a taper hole (the taper being proportioned as before), the small end of the taper hole should be first entered on the shaft, and then when home both the axle and the wheel-bore will be parallel. It may be remarked that the wheel seat on the axle will also be affected, which is quite true, but the axle is usually of the hardest metal and has the smoothest surface, hence it suffers but little; not an amount of any practical importance. In an experiment upon this point made in the presence of the author by Mr. Howard Fry and the master mechanic of the Renovo shops of the Philadelphia and Erie railroad, an axle seat finished by a Whitney "doctor," and parallel in diameter, was forced into a wheel having a parallel bore, and removed immediately. On again measuring the axle, the wheel-seat was found to be 1/1000 taper in its length. The wheel-bore was found to be but slightly affected in its diameter, which is explained because it being very smooth, while the turning marks in the axle were plainly visible, the abrasion fell mainly upon the latter. When the enveloping piece or bore is not solid or continuous, but is open on one side, the degree of the fit may be judged from the amount that it opens under the pressure of the plug piece. [Illustration: Fig. 1425.] Thus the axle brasses of American locomotives are often made circular at the back, as shown in Fig. 1425, and are forced in endways by hydraulic pressure. The degree of tightness of the brass within the box may, of course, be determined by the amount of pressure it requires to force it in, but another method is to mark a centre punch dot as at J, and before the brass is put in mark from this dot as a centre an arc of a circle as L L. When the brass is home in the box a second arc K is marked, the distance between L and K showing how much the brass has sprung the box open widening at H. In an axle box whose bore is about 4 inches to 5 inches in diameter, and 6 inches long, 1/32 inch is the allowance usually made. Shrinkage fits are employed when a hole or bore requires to be very firmly and permanently fastened to a cylindrical piece as a shaft. The bore is turned of smaller diameter than its shaft, and the amount of difference is termed the allowance for shrinkage. The enveloping piece is heated so as to expand its bore; the shaft is then inserted and the cooling of the bore causes it to close or contract upon the shaft with an amount of force varying of course with the amount allowed for contraction. If this allowance is excessive, sufficient strain will be generated to burst the enveloping piece asunder, while if the allowance for shrinking is insufficient the enveloping piece may become loose. The amount of allowance for shrinkage varies with the diameter thickness, and kind of the material; but more may be allowed for wrought iron, brass, and copper, than for cast iron or steel. Again, the smoothness and truth of the surfaces is an important element, because the measurement of a bore will naturally be taken at the tops of the tool marks, and these will compress under the shrinkage strain, hence less allowance for contraction is required in proportion as the bore is smoother. In ordinary workshop practice, therefore, no special rule for the amount of allowance for shrinkage obtains, the amount for a desultory piece of work generally being left to the judgment of the workman, while in cases where such work is often performed on particular pieces, the amount of allowance is governed by experience, increasing it if the pieces are found in time to become loose, and decreasing it if it is found impossible to get the parts together without making the enveloping piece too hot, or if it is found to be liable to split from the strain. The strength of the enveloping piece is again an element to be considered in determining the amount to be allowed for shrinkage. It is obvious, for example, that a ring of 8 inches thick, and having a bore of, say, 6 inches diameter, would be less liable to crack from the strain due to an allowance of 1/50 inch for contraction, than would a ring of equal bore and one inch thick having the same allowance. The strength or resistance to compression of the piece enveloped in proportion to that enveloping it, is yet another consideration. The tires for railway wheels are usually contracted on, and Herr Krupp states the allowance for contraction to be for steel tires 1/100 inch for every foot of diameter; in American practice, however, a greater amount is often employed. Thus upon the Erie railroad a 5 foot tire is given 1/16 inch contraction. The allowance for wrought iron or brass should be slightly more than it is for steel or cast iron, on account of the greater elasticity of those metals. Examples of the practice at the Renovo shops of the Pennsylvania road are as follows: Class E, diameter of wheel centre, 44 inches; bore of steel tire, 43-15/16 inches. Class D, diameter of wheel, 50 inches; bore of tire, 49-9/16 inches. It is found that the shrinkage of the tire springs or distorts the wheel centre, hence the tires are always shrunk on before the crank-pin holes are bored. Much of the work formerly shrunk on is now forced on by an hydraulic press. But in many cases the work cannot be taken to an hydraulic press, and shrinkage becomes the best means. Thus, a new crank pin may be required to be shrunk in while the crank is on the engine shaft, the method of procedure being as follows: In heating the crank, it is necessary to heat it as equally as possible all round the bore, and not to heat it above a _very dark_ red. In heating it some dirt will necessarily get into the hole, and this is best cleaned out with a piece of emery paper, wrapped round a half-round file, carefully blowing out the hole after using the emery paper. Waste or rag, whether oiled or not, is not proper to clean the hole with, as the fibres may burn and lodge in the hole; indeed, nothing is so good as emery paper. It is desirable to heat the crank as little as will serve the purpose, and it is usual to heat it enough to allow the pin to push home by hand. It is better, however, to overheat the crank than to underheat it, providing that the heat in no case exceeds a barely perceptible red heat. If, however, the crank once grips the pin before it is home, in a few seconds the pin will be held so fast that no sledge hammer will move it. It is well, therefore, to have a man stationed on each side of the crank, each with a sledge hammer, and to push the crank pin in with a slam, giving the man in front orders to strike it as quickly as possible at a given signal; but if the pin does not move home so rapidly at each blow as to make it appear certain that it will go home, the man at the rear, who should have a ten-pound sledge, should be signalled to drive out the crank pin as quickly as he possibly can for every second is of consequence. All this should be done so quickly that the pin has not had time to get heated to say 100° at the part within the crank. So soon as the pin is home, a large piece of wetted cotton waste should be wrapped round its journal, and a stream of water kept running on it, to keep the crank pin cold. At the other end water should be poured on the pin end in a fine stream, but in neither case should the water run on the crank more than can be avoided. Of course, if the crank is off the shaft, the pin may be turned downward, and let project into water. The reasons for cooling the pin and not the crank are as follows: If the crank be of cast iron, sudden cooling it would be liable to cause it to split or crack. If the crank pin is allowed to cool of itself, the pin will get as hot as the crank itself, and in so doing will expand, placing a strain on the crank that will to some extent stretch it. Indeed, when the pin has become equally hot with the crank it is as tight a fit as it will ever be, because after that point both pieces will cool together, and shrink or contract together, and hence the fit will be a looser or less tight one to the amount that the pin expanded in heating up to an equal temperature with the crank. The correct process of shrinking is to keep the plug piece as cold as possible, while the outside is cooled as rapidly as can be without danger of cracking or splitting. The ends of crank pins are often riveted after being shrunk in, in which case it is best to recess the end, which makes the riveting easier, and causes the water poured upon its face to be thrown outward, thus keeping it from running down the crank face and causing the crank to crack or split. It sometimes becomes necessary and difficult to take out a piece that has been shrunk in, and in this event, as also in the case of a piece that has become locked before getting fully home in the shrinking process, there is no alternative but to reheat the enveloping piece while keeping the enveloped piece as cold as can be by an application of water. The whole aim in this case is to heat the enveloping piece as quickly as possible, so that there shall be but little time for its heat to be transmitted to the piece enveloped. To accomplish this end melted metal, as cast iron, is probably the most efficient agent; indeed it has been found to answer when all other means failed. [Illustration: Fig. 1426.] [Illustration: Fig. 1427.] The fine measurements necessary for shrinkage purposes render it necessary, where pieces of the same form and kind are shrunk on, to provide the workmen with standard gauges with which the work may be correctly gauged. These often consist of simple rods or pieces of iron wire of the required length. Figs. 1426 and 1427, however, represent an adjustable shrinkage gauge designed by H. S. Brown, of Hartford, Connecticut. Fig. 1427 is a sectional, and Fig. 1426 a plan side view of the gauge. A is a frame, containing at its lower end a fixed measuring piece B, and provided at its upper end with a threaded and taper split hub to receive externally the taper-threaded screw cap C, and threaded internally to receive a tube E, which is plugged at the bottom by the fixed plug F. The adjustable measuring leg G is threaded with the tube E, so as to be adjustable for various diameters of boxes, but it is locked when adjusted by the jamb-nut H. The operation is as follows: The cap-nut C and jamb-nut H are loosened and screwed back, allowing stem G and tube E to be adjusted to the exact size of the shaft for which a shrinkage fit is to be bored, as, say, in an engine crank. In setting the gauge to the diameter of the shaft, the cap end C and jamb-nut H are screwed home, so as to obtain a correct measurement while all parts are locked secure. The cap-nut C draws the split hub upon the tube E, and the jamb-nut H locks up G to E, so that the shaft measurement is taken with all lost motion, play and spring of the mechanism taken into account, so that they shall not vitiate the measurement. This being done, C is loosened so that E can be rotated, and raised up (by rotating) to admit the shrinkage gauge-piece J, whose thickness equals the amount to be allowed for the size of borer to be shrunk on the shaft. J being inserted, E is rotated back so as to bind J between the end of E and the foot piece B, when C is screwed down, clamping E again. Thus the measuring diameter of the gauge is increased to an amount due to the thickness of the gauge-piece J. At the right of Fig. 1426 an edge and side elevation of J is shown, the 12/1000 indicating its thickness, which is the amount allowed for shrinkage, and the 6-inch indicating that this gauge-piece is to be used for bores of 6 inches in diameter. The dotted circle K K L L represents a bore to which the gauge is shown applied. The system of shrinking employed at the Royal Gun Factory at Woolwich, England, is thus described by Colonel Maitland, superintendent of that factory:-- "The inside diameter of the outer tube, when cold, must be rather smaller than the outside diameter of the inner tube: this difference in the diameter is called the 'shrinkage.' While the outer coil is cooling and contracting it compresses the inner one: the amount by which the diameter of the inner coil is decreased is termed the 'compression.' Again, the outer coil itself is stretched on account of the resistance of the inner one, and its diameter is increased; this increase in the diameter of an outer coil is called 'extension.' The shrinkage is equal to compression plus the extension, and the amount must be regulated by the known extension and compression under certain stresses and given circumstances. The compression varies inversely as the density and rigidity of the interior mass; the first layer of coils will therefore undergo more compression than the secondhand the second more than the third, and so on. "Shrinking is employed not only as an easy and efficient mode of binding the successive coils of a built-up gun firmly together, but also for regulating as far as possible the tension of the several layers, so that each and all may contribute fairly to the strength of the gun. "The operation of shrinking is very simple; the outer coil is expanded by heat until it is sufficiently large to fit easily over the inner coil or tube (if a large mass, such as the jacket of a Fraser gun, by means of a wood fire, for which the tube itself forms a flue; if a small mass, such as a coil, in a reverberatory furnace at a low temperature, or by means of gas). It is then raised up by a travelling crane overhead and dropped over the part on to which it is to be shrunk, which is placed vertically in a pit ready to receive it. "The heat required in shrinking is not very great. Wrought iron, on being heated from 62° Fahr. (the ordinary temperature) to 212°, expands linearly about 1-1000th part of its length; that is to say, if a ring of iron 1000 inches in circumference were put into a vat of boiling water, it would increase to 1001 inches, and according to Dulong and Petit the coefficient of expansion, which is constant up to 212°, increases more and more from that point upward, so that if the iron ring were raised 150° higher still (_i.e._ to 362°) its circumference would be more than 1002 inches. No coil is ever shrunk on with so great a shrinkage as the 2-1000th part of its circumference or diameter, for it would be strained beyond its elastic limit. Allowing, therefore, a good working margin, it is only necessary to raise a coil to about 500° Fahr.,[22] though in point of fact coils are often raised to a higher degree of temperature than this in some parts, on account of the mode of heating employed. Were a coil plunged in molten lead or boiling oil (600° Fahr.) it would be uniformly and sufficiently expanded for all the practical purposes of shrinking, but as shrinkings do not take place in large numbers or at regular times, the improvised fire or ordinary furnace is the more economical mode, and answers the purpose very well. [22] The temperature may be judged by color; at 500° F. iron has a blackish appearance; at 575° it is blue; at 775° red in the dark; at 1,500° cherry red, and so on, getting lighter in color, until it becomes white, or fit for welding, at about 3,000°. "Heating a coil beyond the required amount is of no consequence, provided it is not raised to such a degree of temperature that scales would form; and in all cases the interior must be swept clean of ashes, &c., when it is withdrawn from the fire. With respect to the modes of cooling during the process of shrinking, care must be taken to prevent a long coil or tube cooling simultaneously at both ends, for this would cause the middle portion to be drawn out to an undue state of longitudinal tension. In some cases, therefore, water is projected on one side of a coil so as to cool it first. In the case of a long tube of different thickness, like the tube of a R. M. L. gun, water is not only used at the thick end, but a ring of gas or a heated iron cylinder is applied at the thin or muzzle end, and when the thick end cools the gas or cylinder is withdrawn from the muzzle, and the ring of water raised upward slowly to cool the remainder of the tube gradually. "As a rule, the water is supplied whenever there is a shoulder, so that that portion may be cooled first and a close joint secured there; and water is invariably allowed to circulate through the interior of the mass to prevent its expanding and obstructing or delaying the operation; for example, when a tube is to be shrunk on a steel barrel, the latter is placed upright on its breech end, and when the tube is dropped down on it, a continual flow of cold water is kept up in the barrel by means of a pipe and syphon at the muzzle. The same effect is produced by a water jet underneath, when it is necessary to place the steel tube muzzle downward for the reception of a breech coil. As to the absolute amount of shrinkage given when building up our guns, let us take the 12-1/2-inch muzzle-loading gun of 38 tons as an example. SHRINKAGES OF COILS OF 12.5 INCH R. M. L. GUNS. -------------+---------------------------+--------------------------- | Shrinkages. | +-------------+-------------+ | | In terms of | Coils. | In Inches. | diameter. | Remarks. +------+------+------+------+ | Rear.|Front.| Rear.|Front.| -------------+------+------+------+------+--------------------------- | | | D | D | Breech-piece| .022 | .026 | --- | --- | Shrunk on A tube. | | | 857 | 807 | | | | | | | | | D | D | B coil | .055 | .01 | --- | --- | " " | | | 561 | 190 | | | | | | | | | D | | B tube | .035 | nil. | --- | nil. | " " | | | 668 | | | | | | | | | | D | D | C coil | .03 | .06 | ---- | --- | Shrunk on to breech piece | | | 1134 | 729 | and rear end of 1 B coil." -------------+------+------+------+------+--------------------------- The objections to fitting work by contraction where accuracy is required in the work are, that if the enveloping piece is of cast iron its form is apt to change from being heated. Furthermore, if the enveloping piece, which is always the piece to be heated, is of unequal thickness all round the bore, the thin parts are apt to become heated the most, and to therefore give way to the strain induced by contraction when cooling, which, while not, perhaps, impairing the fit, may vitiate the alignment of parts attached to it. Thus, a crank pin may be thrown out of true by the alteration of form induced first by unequal heating of the metal round the crank eye, enveloping the shaft; and secondly, because of the weakest side of the eye giving way, to some extent, to the pressure of the contracting strain. To counteract this, the strongest part of the enveloping piece should be heated the most, or if the enveloping piece be of equal strength all round its bore, it should be heated equally all round. To effect this object heated liquids, as boiling water, or heated fluids, as melted lead, may advantageously be employed. In some practice, locomotive wheel tires are heated for shrinking in boiling water. The allowance for shrinkage is from .075 millimètre to every mètre in diameter, which is .02952 inch to every 39.37079 inches of diameter. The employment of hot water, however, necessitates that the tires be bored very smoothly and truly, and that the wheel rim be similarly true and smooth, otherwise the amount of expansion thus obtained will be insufficient to maintain a permanent fit under the duty to which a wheel tire is submitted. Shrinking is often employed to strengthen a weak place or part, or one that has cracked. The required size is, in this case, a cylindrical surface that is not a true cylinder, obtained by a rolling wheel rotated by friction over the surface to be enveloped by the band. Or if the surface is of a nature not to admit of this, a strip of lead or piece of lead wire may be lapped round it to get the necessary measurements. The bands for this purpose are usually of wrought iron, and require in the case of irregular surfaces to be driven on by hammer blows, so that the fit may be correct. As the band is forced on a heavy hammer is held against it, to prevent its moving back and off the work as the other parts are forced on. [Illustration: Fig. 1428.] Very slight bands may be forced on by levers: thus, wagon makers use a lever or jack, such as in Fig. 1428, for forcing the tires on their wheels. The wheel is laid horizontally on a table as shown, and the tire A forced out by the vertical lever, the arm B affording a fulcrum for the lever, and itself resting against the hub C of the wheel. The following extracts are from a paper read by Thomas Wrightson, before the Iron and Steel Institute of Great Britain. "The large amount of attention bestowed upon the chemical properties of metals, and the scientific methods adopted for their investigation, have led to the most brilliant results in the history of iron and steel industries. It must not, however, be overlooked that iron and steel have highly important properties other than those which can be examined by chemical methods. The cause for so little having been done in accurate observation of the physical properties of iron is twofold: 1. The molecular changes of the metals are so slow, when at ordinary temperatures and when under ordinary conditions of strain, that reliable observations, necessarily extending over long periods, are difficult to obtain: 2. When the temperatures are high--at which times the greatest and most rapid molecular changes are occurring--the difficulties of observation are multiplied to such an extent that the results have not the scientific accuracy which characterizes the knowledge we have of the chemical properties of metals. "The object of the present paper is to draw attention to some phenomena connected with the physical properties of iron and steel, and to record some experiments showing the behavior of these metals under certain conditions. "In experimenting the author has endeavored to adopt methods which would, as far as possible, eliminate the two great difficulties mentioned. "It is obvious that the possible conditions under which experiments may be made are so numerous that all which any one experimenter can do is to record faithfully and accurately his observations, carefully specifying the exact conditions of each observation, and this must eventually lead to a more complete knowledge of the physical properties of the metals. "The author's observations have been led in the following directions:-- "1. The changes in wrought and cast iron when subjected to repeated heatings and coolings. "2. The effect upon bars and rings when different parts are cooled at different rates. "3. These changes occurring in molten iron when passing from the solid to the liquid state, and _vice versâ_. PART I. "To illustrate the practical importance of knowing the effects of reiterated heating and cooling on iron plates, one of the most obvious examples is the action of heat upon the plates of boilers which are alternately heated and cooled, as in use or otherwise. When in use, the plates above the fire are subjected to the fierce flame of the furnace on one side, and on the other side to a temperature approximating to that of the steam and water in the boiler. Where the conducting surfaces of the metal are thickened at the riveted seams, a source of danger is frequently revealed in the appearance of what are known as 'seam-rips.' "The long egg-ended boilers, much used in the North of England, are very subject to this breaking away of the seams. From some tests made by the writer on iron cut from the plates of two different boilers which had ripped at the seams, and one of which seam-rips had led to an explosion resulting in the destruction of much property, though happily of no lives, it was found that the heat acting on the bottom of the boiler had, through time, so affected the iron at the seam as to make it brittle, apparently crystalline in fracture, and of small tensile strength. Farther from the seam the iron appeared in both cases less injuriously affected. But although the alternate heating and cooling of the plates over a long period had produced this change in the molecular condition of the iron, a method of restoration presents itself in the process of annealing. In subjecting the pieces cut from the seam-rips to a dull red heat, and then allowing them to cool slowly in sawdust, the writer found that the fibrous character of the iron appeared again, and renewed testing showed that the ductility and tensile strength were restored. "The same process of annealing is equally effectual in restoring the tenacity of iron in chains rendered brittle, and apparently crystalline, by long use, and is periodically applied where safety depends upon material in this form. Thus the heating and cooling of iron may be looked upon as the bane or the antidote according to the conditions under which the process is carried out. This affords an example of the importance of the physical effects produced by repeated changes of temperature. The change effected by one heating and cooling is so small that a cumulative method of experiment is the only one by which an observable result can be obtained, and this is the method adopted by the writer in the investigation now to be described. "It is well known that if a wrought-iron bar be heated to redness, a certain expansion takes place, which is most distinctly observed in the direction of its length. It is also known, although not generally so, that if a bar be thus heated and then suddenly cooled in water, a contraction in length takes place, the amount of this contraction exceeding that of the previous expansion, insomuch that the bar when cooled is permanently shorter than it originally was. If this process of heating and cooling be repeated, a further amount of contraction is found to follow for many successive operations. "Experiments Nos. 1 and 2 were made to verify this, and to show the increment of contraction after each operation. "EXPERIMENTS ON WROUGHT-IRON BARS 1-1/8 IN. SQUARE BY 30.05 IN. LONG, HEATED TO A DULL RED, THEN COOLED SUDDENLY IN WATER. ------------------+------------------------+------------------------ | EXPERIMENT NO. 1. | EXPERIMENT NO. 2. | Common Iron. | Best Iron. +------------+-----------+------------+----------- | |Percentage | |Percentage |Contraction.|on original|Contraction.|on original | | length. | | length. ------------------+------------+-----------+------------+----------- | Inches. | | Inches. | After 1st cooling | .04 | .13 | .04 | .13 " 2nd " | .10 | .33 | .10 | .33 " 3rd " | .16 | .53 | .14 | .46 " 4th " | .17 | .56 | .16 | .53 " 5th " | .23 | .76 | .20 | .66 " 6th " | .28 | .93 | .24 | .80 " 7th " | .31 | 1.03 | .27 | .89 " 8th " | .33 | 1.10 | .30 | 1.00 " 9th " | .40 | 1.33 | .33 | 1.10 " 10th " | .47 | 1.56 | .39 | 1.30 " 11th " | .52 | 1.73 | .42 | 1.40 " 12th " | .54 | 1.80 | .47 | 1.56 " 13th " | .58 | 1.93 | .51 | 1.70 " 14th " | .62 | 2.06 | .54 | 1.80 " 15th " | .68 | 2.26 | .56 | 1.86 ------------------+------------+-----------+------------+----------- "The Table of Experiment No. 5 shows that at the twenty-fifth cooling a contraction of 3.05 per cent. had taken place, or an average of .122 per cent. after each cooling. This is almost identically the same average result as shown in Experiment No. 1 with straight bars. "The above experiments only having reference to the permanent contraction of the iron in the direction of its length, the author made the following experiments to ascertain the effect in the other dimensions, and to see whether the specific gravity of the iron was affected in the reduction of dimensions. [Illustration: Fig. 1429.] "_Experiment No. 6._--Wrought-iron plate, .74 inch thick, planed on both surfaces and all edges to a form nearly rectangular, and of the dimensions given in Fig. 1429. "_Specific Gravity._--Two small samples were cut out of different parts of the same piece of plate from which the experimental piece was planed, and the specific gravity determined as follows:-- No. 1 piece 7.629 } No. 2 piece 7.651 } Mean, 7.64. "_Quality._--Subjecting a piece to tensile strain in the direction of the grain, it broke at 21.2 tons per square inch of section, the ductility being such that an elongation of 8.3 per cent. occurred before fracture, with a reduction of 9.6 per cent. of the area of fracture. This may be looked upon as representing a fairly good quality of iron. "A bar of wrought iron, 1-1/8 inches square and 30.00 inches long, was heated to redness, and then allowed to cool gradually in air. Measurements after each of five coolings showed no perceptible change of length. "_Experiment No. 4._--Wrought-iron bar, 1-1/8 inches square by 30 inches long, heated to a white heat and cooling gradually in air. ------------------+------------+----------------+---------------- |Contraction.| Percentage on | Remarks. | |original length.| ------------------+------------+----------------+---------------- | Inches. | | After 1st cooling | No change. | | ---- " 2nd " | " | | ---- " 3rd " | .02 | .07 | ---- " 4th " | .05 | .17 | ---- " 5th " | .05 | .17 | ---- ------------------+------------+----------------+---------------- "It may be remarked, that if the bars be heated to white heat a slight contraction does occur, as shown by Experiment No. 4, where a bar of the same dimensions as No. 3 contracted .17 per cent. after the fifth cooling. As, however, the further remarks on this subject have only reference to bars heated to redness and then cooled, the writer would summarize the results of Experiments Nos. 1, 2, and 3, by stating that wrought-iron bars heated to redness permanently contract in their length along the fibre when cooled in water of ordinary temperature; but when cooled in air, they remain unchanged in length. "To show that this is true as applied to circular hoops, Experiment No. 5 was made upon a wrought-iron bar of 1-1/8 inches square in section, welded into a circular hoop, 57.7 inches outside circumference. "_Experiment No. 5._--Wrought-iron hoop, 1-1/8 inches square by 57.7 inches outside circumference, heated to a dull red, then cooled suddenly in water. ------------------+------------+--------------+----------------------- | |Percentage of | |Contraction.| original | Remarks. | |circumference.| ------------------+------------+--------------+----------------------- | Inches. | | After 1st cooling | .06 | .10 | Red heat. " 2nd " | .06 | .10 | This was nearly white, " 3rd " | .16 | .28 | but before cooling " 4th " | .26 | .45 | red hot. " 5th " | .35 | .61 | " 6th " | .46 | .80 | " 7th " | .54 | .93 | " 8th " | .60 | 1.04 | " 9th " | .68 | 1.18 | " 10th " | .76 | 1.32 | " 11th " | .80 | 1.38 | " 12th " | .87 | 1.51 | " 13th " | .94 | 1.63 | " 14th " | 1.00 | 1.73 | " 15th " | 1.08 | 1.90 | " 20th " | 1.30 | 2.25 | On opposite edge 1.66; " 25th " | 1.76 | 3.05 | hoop splitting. ------------------+------------+--------------+----------------------- "This hoop was heated to redness and cooled in water twenty-five times, the circumference of the hoop being accurately measured after each cooling.[23] [23] The lengths of circumference were taken, in this and other hoops, after each cooling, by encircling the periphery with a very fine piece of "crinoline" steel, the ends of which were made just to meet round the original hoop. By again encircling the hoop with the same piece of steel the expansion was shown by a gap between the ends, and a contraction by an overlap, either of which was measured with great accuracy by means of a finely divided scale. "Two wrought-iron bars, 1-1/8 inches square and 30.05 inches long, were selected.[24] No. 1 was of common "Crown" quality; No. 2 of a superior quality known as "Tudhoe Crown." These bars were heated to redness in a furnace and then plunged into water of ordinary temperature, the length being accurately measured after each cooling. After fifteen heatings and coolings the permanent contraction on No. 1 bar was 2.26 per cent. of the original length, and that on No. 2 bar 1.86 per cent., or an average on the two bars of about .13 per cent. after each cooling, the increment of contraction being nearly equal after each successive operation. It is noticeable that after the first two coolings the better quality of iron did not contract quite so much as the common quality, and that in the latter the contraction was going on as vigorously at the fifteenth as at the first cooling. [24] In some of these experiments the original sizes of the iron were only measured with an ordinary foot-rule, in which case the dimensions are given in the ordinary fraction used in expressing the mercantile sizes of iron. When accurate measurement was taken decimals are invariably used both in this paper and the Tables of Experiment. "Similar bars of wrought iron, heated to redness and then allowed to cool in air at ordinary temperature, do not appear to suffer any permanent change in their length. "Experiment No. 3 was made to verify this. "_Experiment No. 3._--Wrought-iron bar, 1-1/8 inches square by 30 inches long heated to a dull red and cooled gradually in air. ------------------+------------+----------------+----------- |Contraction.| Percentage on | | |original length.| Remarks. ------------------+------------+----------------+----------- After 1st cooling | No change. | ---- | ---- " 2nd " | " | ---- | ---- " 3rd " | " | ---- | ---- " 4th " | " | ---- | ---- " 5th " | " | ---- | ---- ------------------+------------+----------------+----------- [Illustration: _Wrought iron rectangular plate. 14" thick × 11" 995 × 598 planed on both surface and edges. Heated to redness, and cooled in water 50 times. The dotted lines show original form, the black lines the form after the experiment._ (Two-ninths of full size.) Fig. 1430.] The plate was subjected to fifty heatings to redness and subsequent coolings in water of ordinary temperature. At every tenth cooling accurate measurements were taken of the contraction in superficial dimensions, and Fig. 1430 shows the final form after fifty coolings. The intermediate measurements at every tenth cooling showed a uniform and gradual decrease in the superficial dimensions, but the thicknesses were only measured after the fifty coolings had been completed. The thickness appears to have varied considerably; in some places, notably towards the centre and outside edges, being much reduced. Between the centre and outside edges the thickness appears to have increased, and in some few places the plate has been split open. The average dimensions in inches before and after the experiment were as follows (dimensions of cracks being allowed for):-- ----------------------+---------+----------+----------+----------- | | | | Cubic | Average | Average | Average | inches | length. | breadth. |thickness.|capacity. +---------+----------+----------+---------- | Inches. | Inches. | Inches. | Original | 11.995 | 5.98 | .74 | 53.08 After 50 coolings | 11.25 | 5.59 | .774 | 48.72 Per cent. variation { |Decrease |Decrease | Increase | Decrease from original { | of | of | of | of { |6.2 p. c.|6.52 p. c.| 4.6 p. c.| 8.2 p. c. ----------------------+---------+----------+----------+---------- "Three triangular pieces of iron were then cut out of the plate from positions indicated on the diagram; No. 1A from the part most reduced in thickness, No. 3A from the part most increased in thickness, and No. 2A from a part where the thickness was a mean between the thickest and thinnest part. The specific gravities were accurately determined as follows:-- No. 1A 7.552 thinnest part. No. 2A 7.574 average thickness. No. 3A 7.560 thickest part. "The average of these specific gravities is 7.562. "The average before experiment was 7.64. Hence the average loss in specific gravity has been 1.02 per cent. "The small triangular piece No. 1A, specific gravity 7.552 (already subjected to fifty heatings when forming part of the solid plate), was next heated and cooled fifty times more. The specific gravity at the end of the one hundred total coolings was 7.52, being .43 per cent. lower than after fifty heatings in plate, and 1.57 per cent. lower than 7.64, the original mean specific gravity of the plate. "The same piece, 1A, was then heated twenty-five times more, making 125 in all. On taking the specific gravity it was found to be 7.526, or practically the same as after 100 total heatings and coolings. "It thus appears that there is an undoubted decrease in specific gravity on repeated heating and cooling as described up to one hundred coolings, the specific gravity decreasing as much as 1.57 per cent.; that this percentage appears to be less when the pieces of iron operated upon are very small; that while there is a decrease of specific gravity there is also a decrease of total volume. [Illustration: Fig. 1431.] "From the above it was evident that the volume was affected by several causes:-- "1. By the permanent contraction of the outer skin, either the volume would be lessened, or relief by bulging out the sides must occur. "2. By the decrease of specific gravity an increase of volume must occur, which could also find relief in bulging. "3. A diminution of the whole mass must occur through scaling of the surface. "Having determined the change in specific gravity by Experiment 6, we only now want to determine the loss of volume due to surface scaling, and we can then infer the actual contraction of the outer skin. "_Experiment No. 7._--To ascertain the amount of scaling which took place in heating and cooling under same conditions as Experiment No. 6, a wrought-iron plate was cut from the same piece as No. 6, thickness .74 in., planed on both surfaces and all edges to a form nearly rectangular, and to the dimensions given in Fig. 1431. "The only difference (except the very small difference in the dimensions) between this and 1430, was that the principal grain of the iron was in 1431 in the direction of the arrow, whereas in the other it was lengthwise of the plate. "This piece was subjected to fifty heatings to redness and sudden coolings in water of ordinary temperature, as in the case of No. 6. The change in form was exactly the same in general character, but the contraction was not quite so great either in length or breadth; the increase in thickness, however, was proportionately greater, the volume (measured by displacement of water) after fifty heatings being 48.6 cubic inches, which is nearly the same as in No. 6 after the same number of heatings. The weight of the piece:-- Avoirdupois. lbs. oz. dr. Before heating 14 10 15 After fifty heatings 13 5 10 ------------ Difference 1 1 5 "This represents a loss of 9.07 per cent. of the original weight by scaling, and upon the whole original surface (sides and edges) represents a thickness of .0284 of an inch for the fifty immersions, or .00057 of an inch for the thickness of the film lost at each immersion over the whole surface. "Calculating the weight of No. 6 before and after experiment from the volumes and specific gravities, we find the following:-- Mean Weight of specific cubic inch Volume. gravity. water. Pounds. Weight before heating should be 53.08 × 7.64 × .036 = 14.599 " after " " 48.72 × 7.562 × .036 = 13.262 ------ Difference in weight 1.337 the ascertained difference in the case of No. 7 being 1.332, thus sufficiently accounting for the discrepancy between specific gravity and change of volume by the scaling. "By Experiment 7 it has been shown that the loss of thickness due to scaling after fifty immersions was .0284 inch over the whole surface (sides and edges.) Therefore, assuming this scaling as uniform over the surface, the girth, whether measured lengthwise or breadthwise, should be eight times .0284, or .23 inch less after immersion than before. Now the gross loss of girth is:-- --------------------------------------+-----------+------------ |Lengthwise.|Breadthwise. --------------------------------------+-----------+------------ | Inches. | Inches. In No. 6 | 1.38 | .86 In No. 7 | 1.2 | .52 +-----------+------------ Or for both experiments a mean of | 1.29 | .69 Deducting from them the loss of | | girth due to scaling | .23 | .23 +-----------+------------ Net contraction after fifty immersions| 1.06 | .46 Or in percentage of original girths, | | which were | 25.46 | 13.43 | per cent. | per cent. We have a percentage of | 4.16 | 3.42 Or for each immersion an average of | .083 | .07 --------------------------------------+-----------+------------ "Comparing these results with those of Experiments Nos. 1, 2, and 5, we find that the contraction of the skin of the plate is less for each immersion than that of a bar or hoop, in the proportion of .125 to .083. This is what might be expected, as the contraction of the plate is resisted by the volume of heated matter inside, which is eventually displaced by bulging, while the bar finds relief endwise without having to displace the interior. "We have now before us the following facts, substantiated by the experiments described:-- "1. That in heating to redness, and then cooling suddenly in water at ordinary temperatures, bars and plates of wrought iron, a reduction of specific gravity takes place, the amount being about 1 per cent. after fifty immersions, and 1.57 per cent. after one hundred immersions, further heatings and coolings not appearing to produce further change. "2. That a reduction of the surface takes place after each heating and cooling, this being due to two causes:-- "_a._ The scaling of the surface, which is shown to amount to a film over the (sides and edges) entire area of .00057 inch in thickness for each immersion, or 0.284 inch for fifty immersions (Experiment 7). "_b._ A persistent contraction, which takes place after each immersion. This varies according to the form of the iron, being in plates from .07 per cent. to 0.83 per cent. (Experiment 6), while in long bars it varies from .122 to .15 per cent. (Experiments 1, 2, and 5). This contraction continues vigorously up to fifty immersions, and probably much farther. "3. That in the case of plates a bulging takes place on the largest surfaces, increasing the thickness towards the centres, although the edges diminish in thickness. "4. That wrought-iron bars heated to redness, and allowed to cool slowly in air, do not show any change in dimensions (Experiment 3). "The reduction of specific gravity, and the bulging out of the sides, have been explained as follows by the learned Secretary of the Royal Society, Professor Stokes, who has taken considerable interest in these experiments, and who has kindly allowed the author to publish the explanation: "'When the heated iron is plunged into water, the skin tends everywhere to contract. It cannot, however, do so to any significant extent by a contraction which would leave it similar to itself, because that would imply a squeezing in of the interior metal, which is still expanded by heat, and is almost incompressible. The endeavor, then, of the skin to contract is best satisfied, consistently with the retention of volume of the interior, by a contraction of the skin in the two longish lateral directions, combined with a bulging out in the short direction. The still plastic state of the interior permits of this change. "'Conceive an india-rubber skin of the form of the plate in its first state, the skin being free from tension, and having its interior filled with water, treacle, or pitch. I make abstraction of gravity. It would retain its shape. But suppose, now, the india-rubber to be endowed with a tension the same everywhere similar to that of india-rubber that has been pulled out, what would take place? Why, the flat faces of considerable area, being comparatively weak to resist the interior pressure, would be bulged out, and the vessel would contract considerably in the long directions, increasing in thickness. This is just what takes place with the iron in the first instance. But when the cooling has made further progress, and the solidified skin has become comparatively thick and strong, the further cooling of the interior tends to make it contract. But this it cannot well do, being encased in a strong hide, and accordingly the interior tends to be left in a porous condition.' "The reduction by scaling does not require any explanation. The only fact which appears unaccounted for is this persistent contraction of the cooled iron skin, which does not appear to be explicable on any mechanical grounds; and we are, therefore, obliged to look upon it as the result of a change in the distance of the molecules of the iron, caused by the sudden change of temperature in the successive coolings. "Our next subject is the curious effect of cooling bars or rings by partial immersion in water. Bearing in mind the results at which we have arrived, viz., that wrought iron contracts when immersed in water after heating, and that when allowed to cool in air it remains of the same dimensions, let us ask what would be the behavior of a bar or circular hoop of iron cooled half in water and half in air, the surface of the water being parallel to the fibre and at right angles to the axis of the hoop? "Arguing from the results of Experiments 1, 2, and 5, it might be expected that the lower portion cooled in water would suffer permanent contraction; and, arguing from Experiment 3, that the upper or air-cooled edge would not alter. This apparently legitimate conclusion is completely disproved by experiments. This will be seen by a reference to Experiments 8, 9, and 10. [Illustration: Fig. 1432.--Experiments with a circular hoop of wrought iron. Appearance of the hoop at the beginning.] "In No. 8 a circular hoop of wrought iron was forged out of a 3-1/2-inch by 1/2-inch bar, the external diameter being about 18 inches, the breadth, 1/2 inch, being parallel to the axis of the hoop. This hoop, Fig. 1432, was heated to redness, then plunged into cold water half its depth, the upper half cooling in air. The changes in the external circumference of the hoop were accurately measured after each of twenty successive coolings, at the end of which the external circumference of the water-cooled edge had increased 1.24 inches, or 2.14 per cent. of its original length, and the air-cooled edge had contracted 7.9 inches, or 13.65 per cent. "_Experiment No. 8._--Wrought-iron hoop, 3-1/2 inches by 1/2 inch by about 18 inches in diameter, or exactly 57.85 inches in circumference at top, and 57.95 inches at bottom edge. -------------+--------------------+--------------------+-------------- | Top Edge. | Bottom Edge. | +--------+-----------+--------+-----------+ |Contrac-|Percentage | Expan- |Percentage | | tion. |of original| sion. |of original| | | circum- | | circum- | Remarks. | | ference. | | ference. | -------------+--------+-----------+--------+-----------+-------------- | Ins. | | Ins. | | After 1st dip| .50 | .86 | .08 | .14 | " 2nd " | .99 | 1.71 | .08 | .14 | " 3rd " | 1.47 | 2.54 | .26 | .45 | " 4th " | 1.92 | 3.32 | .30 | .52 | " 5th " | 2.30 | 3.97 | .34 | .59 | " 6th " | 2.60 | 4.49 | .40 | .70 |Slight crack | | | | |in expanded | | | | |edge. " 7th " | 2.94 | 5.25 | .44 | .76 | " 8th " | 3.40 | 5.98 | .50 | .86 | " 9th " | 3.70 | 6.39 | .56 | .96 | " 10th " | 4.40 | 7.60 | .62 | 1.07 | " 11th " | 4.42 | 7.64 | .66 | 1.14 | " 12th " | 4.85 | 8.40 | .70 | 1.22 | " 13th " | 5.24 | 9.02 | .78 | 1.34 | " 14th " | 5.74 | 9.92 | .80 | 1.39 | " 15th " | 6.00 | 10.37 | .86 | 1.49 | " 20th " | 7.90 | 13.65 | 1.24 | 2.14 |After de- | | | | |ducting for a | | | | |crack .06 inch | | | | |wide which | | | | |appeared at | | | | |sixth dip. -------------+--------+-----------+--------+-----------+-------------- "It will be observed that we have here two remarkable phenomena: 1. The reversal of the expansion and contraction as described. 2. The very large amount of contraction on the upper edge compared with what was exhibited in Experiment 5 of entire submersion. "The table showing Experiment 5 gives a contraction of 2.25 per cent. after the twentieth cooling, whereas the contraction on the air-cooled edge of Experiment 8 is 13.65 per cent., or six times the contraction of an entirely submerged hoop. [Illustration: Fig. 1433.--Condition of the hoop after the twentieth cooling.] "To ascertain whether these unexpected phenomena had any connection with the circular form of the hoop, Experiment 9 was made with a straight bar of iron 3-1/2 inches deep by 1/2 inch thick by 28.4 inches long. "_Experiment No. 9._--Wrought-iron bar, 3-1/2 inches by 1/2 inch by 28.4 inches long, heated to a dull red, then quenched half its depth in water. ------------------+--------------------+-------------------- | Bottom Edge. | Top Edge. +--------+-----------+--------+----------- | Expan- |Percentage |Contrac-|Percentage | sion. |on original| tion. |on original | | length. | | length. ------------------+--------+-----------+--------+----------- | Inches.| | Inches.| After 1st cooling | .05 | .18 | .26 | .91 " 2nd " | .10 | .35 | .43 | 1.51 " 3rd " | .10 | .35 | .54 | 1.90 " 4th " | .14 | .49 | .75 | 2.64 " 5th " | .20 | .70 | .92 | 3.24 " 6th " | .30 | 1.05 | 1.25 | 4.40 " 7th " | .34 | 1.20 | 1.50 | 5.28 " 8th " | .38 | 1.34 | 1.56 | 5.53 " 9th " | .39 | 1.37 | 1.66 | 5.84 " 10th " | .40 | 1.40 | 1.76 | 6.19 " 11th " | .41 | 1.43 | 1.84 | 6.48 " 12th " | .44 | 1.55 | 1.96 | 6.90 ------------------+--------+-----------+--------+----------- "This was cooled half in air and half in water, and the length of the two edges measured accurately after each of twelve coolings. At the end of this experiment the air-cooled edge had contracted 6.9 per cent., while the water-cooled edge had expanded 1.55 per cent. of the original length. The effect on the bar was to make it gradually curve, the water-cooled or extended edge becoming convex, the air-cooled or contracted edge concave. [Illustration: Fig. 1434.--Experiments with a wrought-iron bar. Appearance of the piece before heating.] "Experiment No. 10 was made in order to show the effect of reversing this cooling process. After five coolings, a bar of iron, 28 inches long, 3-1/2 inches deep, and 1/2 inch thick, was curved so that the versed sine of its air-cooled edge was 1-1/2 inches. The coolings were then reversed, what was the air-cooled edge being then immersed in water. After five more coolings the bar was restored to within 1/8 inch of being straight, and the eleventh cooling threw the concavity on the other side of the bar. [Illustration: Fig. 1435.--Appearance of the bar after the twelfth cooling.] "_Experiment No. 10._--Wrought-iron flat bar, 28 inches long by 3-1/2 inches by 1/2 inch, heated to dull red, then quenched half its depth in water, up to five heats, then the opposite edge dipped. -----------+-----------+------------+------------------ | | | Reversed Cooling. | | +------------------ |Versed sine| | Versed sine |of concave,| | of concave, | _i.e._ | | _i.e._ now |air-cooled | | water-cooled | edge. | | edge. -----------+-----------+------------+------------------ | Inches. | | Inches. 1st cooling| 5/16 | 6th cooling| 1-3/16 2nd " | 9/16 | 7th " | 7/8 3rd " | 13/16 | 8th " | 3/4 scant. 4th " | 1-3/8 | 9th " | 3/8 full. 5th " | 1-1/2 |10th " | 1/8 | |11th | Brought concavity | | | 1/8 in. on other | | | side. -----------+-----------+------------+------------------ [Illustration: Fig. 1436.--After the preceding experiment the same bar was reheated and reversed in the water, the eleventh cooling resulting in the above form, the bar bending in the opposite direction from that previously shown.] "When the author had proceeded thus far, these curious results were shown to several leading scientific men, who expressed interest in the subject, which encouraged the author to extend his experiments under varied conditions with a view of ascertaining the cause for these anomalous effects. These experiments (Nos. 11 to 17) are fully recorded, and the results shown on the diagrams; the actual rings are also on the table before you. "_Experiment No. 11._--Wrought-iron hoop, turned and bored, 37.1 inches, outside circumference, by 2.95 inches deep by .44 inch thick, the grain of the iron running the short way of the bar from which the hoop was made, heated to redness, then cooled half its depth in water (see Fig. 1437 at A for final form of hoop after ten heatings and coolings). -----------------+--------------------+-------------------- | Top Edge. | Bottom Edge. +--------+-----------+--------+----------- |Contrac-|Percentage | Expan- |Percentage | tion. |on original| sion. |on original | | length. | | length. -----------------+--------+-----------+--------+----------- | Inches.| | Inches.| After 1st cooling| .3 | .83 | .05 | .13 " 2nd " | .64 | 1.72 | .12 | .32 " 3rd " | 1.02 | 2.75 | .22 | .60 " 4th " | 1.38 | 3.72 | .30 | .80 " 5th " | 1.62 | 4.37 | .37 | 1.00 " 10th " | 3.14 | 8.46 | .76 | 2.05 -----------------+--------+-----------+--------+----------- "_Experiment No. 12._--Wrought-iron hoop, turned and bored, 6 inches diameter (18.85 inches circumference) outside, by 2 inches deep by .375 inch thick, heated to redness, then cooled, with lower edge barely touching the water (see Fig. 1437 at B for final form of hoop after twenty heatings and coolings). -----------------+--------------------+-------------------- | Top Edge. | Bottom Edge. +--------+-----------+--------+----------- |Contrac-|Percentage |Contrac-|Percentage | tion. |of original| tion. |of original |Outside | circum- |Outside | circum- |circum- | ference. |circum- | ference. |ference.| |ference.| -----------------+--------+-----------+--------+----------- | Inches.| | Inches.| After 5th cooling| .10 | .53 | .16 | .85 " 10th " | .22 | 1.17 | .34 | 1.80 " 15th " | .32 | 1.70 | .48 | 2.54 " 20th " | .48 | 2.54 | .62 | 3.30 -----------------+--------+-----------+--------+----------- "_Experiment No. 13._--Wrought-iron hoop, turned and bored, 6 inches diameter (18.85 inches circumference) outside by 2 inches deep by .375 inch thick, heated to redness, then cooled one-fourth its depth in water (see Fig. 1437 at C for final form of hoop after twenty heatings and coolings). -----------------+--------------------+-------------------------------- | Top Edge. | Bottom Edge. +--------+-----------+-------------------+----------- |Contrac-|Percentage | |Percentage | tion. |of original| |of original | | circum- | Extension. | circum- | | ference. | | ference. -----------------+--------+-----------+-------------------+----------- | Inches.| | Inches. | After 1st cooling| .06 | .32 | .02 | .10 " 5th " | .28 | 1.50 {|A hair's breadth | | | {|contraction. | " 10th " | .56 | 3.00 { |Returned to origi- | | | { |nal circumference. | " 15th " | .78 | 4.14 | .02 contraction. | .10 " 20th " | 1.12 | 6.00 | .02 contraction. | .10 -----------------+--------+-----------+-------------------+----------- "_Experiment No. 14._--Wrought-iron hoop, turned and bored. 6 inches diameter (18.85 inches circumference) outside by 2 inches deep by .375 inch thick, heated to redness, then cooled one-half its depth in water (see Fig. 1437 at D for final form of hoop after twenty heatings and coolings). -----------------+--------------------+-------------------- | Top Edge. | Bottom Edge. +--------+-----------+--------+----------- |Contrac-|Percentage | Expan- |Percentage | tion. |of original| sion. |of original |Outside | circum- |Outside | circum- |circum- | ference. |circum- | ference. |ference.| |ference.| -----------------+--------+-----------+--------+----------- | Inches.| | Inches.| After 5th cooling| .46 | 2.44 | .06 | .32 " 10th " | .96 | 5.00 | .09 | .48 " 15th " | 1.34 | 7.10 | .18 | .96 " 20th " | 1.80 | 9.10 | .26 | 1.38 -----------------+--------+-----------+--------+----------- "_Experiment No. 15._--Wrought-iron hoop turned and bored, 6 inches in diameter (18.85 inches circumference) outside by 2 inches deep by .375 inch thick, heated to redness, then cooled three-fourths its depth in water (see Fig. 1437 at E for final form of hoop after twenty heatings and coolings). -----------------+--------------------+------------------------------- | Top Edge. | Bottom Edge. +--------+-----------+-------------------+----------- |Contrac-|Percentage | |Percentage | tion. |of original| |of original | | circum- | Expansion. | circum- | | ference. | | ference. -----------------+--------+-----------+-------------------+----------- | Inches.| | Inches. | After 1st cooling| .05 | .26 | .015 | .08 " 5th " | .30 | 1.60 | .02 | .10 " 10th " | .56 | 3.00 {| A hair's breadth | | | {| contraction. | " 15th " | .74 | 3.92 { | .02 |} .10 | | { | contraction. |} " 20th " | 1.02 | 5.40 {| .03 | } .10 | | {| contraction. | } -----------------+--------+-----------+-------------------+----------- "_Experiment No. 16._--Cast-copper ring, turned and bored to same dimensions as Nos. 12, 13, 14, and 15, heated to redness, then cooled half its depth in water (see Fig. 1437 at F for final form of hoop after twenty heatings and coolings). -----------------+--------------------+-------------------- | Top Edge. | Bottom Edge. +--------+-----------+--------+----------- |Contrac-|Percentage | Expan- |Percentage | tion. |of original| sion. |of original | | circum- | | circum- | | ference. | | ference. -----------------+--------+-----------+--------+----------- | Inches.| | Inches.| After 1st cooling| .01 | .05 | .05 | .26 " 2nd " | .01 | .05 | .08 | .42 " 3rd " | .02 | .10 | .14 | .75 " 4th " | .02 | .10 | .17 | .90 " 5th " |} No change from | .22 | 1.17 " 10th " |} original size | .40 | 2.13 " 15th " |} from 5th to | .56 | 3.00 " 20th " |} 20th cooling. | .70 | 3.70 -----------------+--------------------+--------+----------- [Illustration: Fig. 1437.] "It will be unnecessary to occupy much time in analyzing the experiments, as any one who takes a practical interest in the subject will have full information in the diagrams and tables. Professor Stokes drew attention to the fact that, in 1863, similar phenomena had been noticed by Colonel Clark, of the Royal Engineers. His experiments, made at the Royal Arsenal, Woolwich, were published in the 'Proceedings of the Royal Society,' and Professor Stokes had himself attached an explanatory note, the outline of which was as follows:-- "Imagine a cylinder divided into two parts by a horizontal plane at the water-line, and in this state immersed after heating. The under part, being in contact with water, would rapidly cool and contract, while the upper part would cool but slowly. Consequently by the time the under part had pretty well cooled, the upper part would be left jutting out; but when both parts had cooled their diameters would again agree. Now in the actual experiments the independent motion of the two parts is impossible on account of the continuity of the metal; the under part tends to pull in the upper, and the upper to pull out the under. In this contest the cooler metal, being the stronger, prevails, and so the upper part gets pulled in a little above the water-line while still hot. But it has still to contract in cooling, and this it will do to the full extent due to its temperature, except in so far as it may be prevented by its connection with the rest. Hence, on the whole, the effect of this cause is to leave a permanent contraction a little above the water-line, and it is easy to see that the contraction must be so much nearer to the water-line as the thickness of the metal is less, the other dimensions of the hollow cylinder and the nature of the metal being given. When the hollow cylinder is very short, so as to be reduced to a mere hoop, the same cause operates, but there is not room for more than a general inclination of the surface, leaving the hoop bevelled. "The expansion of the bottom edge was not noticed in Colonel Clark's paper, perhaps owing to the much smaller hoops which he used in experimenting. Accepting Professor Stokes' explanation of the top contraction, it appears that expansion of the bottom may be accounted for by the reacting strain put on the cooled edge when forcing in the top edge, acting in such a way as to prevent the cooled edge coming quite to its natural contraction, and this, when sufficiently great, expresses itself in the form of a slight expansion. "_Experiment No. 14._--Forged steel hoop, turned and bored, 18.53 inches in circumference outside by 2.375 inches deep by .27 inch thick, heated to redness, then cooled one-half its depth in water (see Fig. 1437 at G for final form of hoop after three heatings and coolings). -----------------+--------------------+-------------------+------------- | Top Edge. | Bottom Edge. | +--------+-----------+-------+-----------+ |Contrac-|Percentage | Expan-|Percentage | | tion. |of original| sion. |of original| | | length. | | length. | -----------------+--------+-----------+-------+-----------+------------- | Inches.| |Inches.| | | | | | {|Cracked at | | | | {|water- After 1st cooling| .06 | .32 | -- | -- {|cooled | | | | {|edge one- | | | | {|third depth | | | | {|of ring. | | | | | " 2nd " | .12 | .64 | -- | -- | | | | | | | | | | {|After allow- | | | | {|ing for " 3rd " | .20 | 1.08 | .05 | .27 {|three small | | | | {|cracks in | | | | {|bottom edge." -----------------+--------+-----------+-------+-----------+------------- The shrinkage of iron and steel by cooling rapidly is sometimes taken advantage of by workmen to refit work, the principles involved in the process being as follows:-- Suppose in Fig. 1438 _a_ _a_ represents a piece of wrought-iron tube that has been heated to a bright red and immersed in cold water _c_ _c_ from the end B to D, _until that end is cold_. The part submerged and cold will be contracted to its normal diameter and have regained its normal strength, while the part above the water, remaining red-hot, will be expanded and weak. There will be, then, a narrow section of the tube, joining the heated and expanded part to the cooled and contracted part, and its form will be conical, as shown at D D. Now, suppose the tube to be slowly lowered in the water, the cold metal below will compress the heated metal immediately above the water-line, the cone section D being carried up into the metal before it has had time to cool; and the tube removed from the water when cold will be as shown in Fig. 1438, from _c_ to D, representing the part first immersed and cooled. To complete the operation the tube must be heated again from the end _c_ to a short distance past D, and then immersed from E nearly to D, and held still until the submerged part is cold, when the tube must be slowly lowered to compress the end _c_ D, making the tube parallel, but smaller in diameter and in bore, while leaving it of its original length, but thickening its wall. [Illustration: Fig. 1438.] [Illustration: Fig. 1439.] This process may, in many cases, be artificially assisted. Suppose, for example, a washer is too large in its bore; it should have its hole and part of its radial faces filled with fire-clay, as shown in Fig. 1439, in which A is the washer and B B the clay, _c_ _c_ being pieces of wire to hold the fire-clay and prevent its falling off. The washer should be heated to a clear red and plunged in the water D D, which will cool and shrink the exterior and exposed metal in advance of the interior, which will compress to accommodate the contraction of the outer metal, hence the hole will be reduced. This operation may be repeated until the hole be entirely closed. [Illustration: Fig. 1440.] [Illustration: Fig. 1441.] Another method of closing such a piece as an eye of large diameter compared to its section, is shown in Fig. 1440; first dipping the heated eye at A and holding it there till cold and then slowly lowering it into the water, which would close the diameter across C, and, after reheating, dipping at D till cold, and then slowly immersing, which would close the eye across E. To shrink a square ring, the whole ring would require to be heated and a side of the square dipped, as shown in Fig. 1441, until quite cold, and then immersed slowly for about an inch, the operation being performed with a separate heating for each side. Connecting rod straps, wheel-tires, and a large variety of work may be refitted by this process, but in each case the outside diameter will be reduced. CHAPTER XV.--MEASURING TOOLS. [Illustration: Fig. 1442.] [Illustration: Fig. 1443.] For what may be termed the length measurements of lathe work it is obvious that caliper gauges, such as shown in Fig. 1402, may be employed. Since, however, these length measurements rarely require to be so accurate as the diametrical measurements, the ordinary lineal rule is very commonly employed in work not done under the standard gauge system. It is obvious, however, that when a number of pieces are to be turned to corresponding lengths, a strip of sheet iron, or of iron rod made to the required length, may be employed; a piece of sheet iron filed to have the necessary steps being used where there are several steps in the work; but if the lineal measuring rule is used, and more than one measurement of length is to be taken, some one point, as one end of the work, should be taken wherefrom to measure all the other distances. Suppose, for example, that Fig. 1442 represents a crank pin requiring to have its end collar 1/4 inch thick, the part A 2 inches long, part B 3 inches long, collar C 1/2 inch thick, and the part D 7 inches long. If the length of each piece were taken separately and independently of the others, any errors of measurement would multiply; whereas, if some one point be taken as a point wherefrom to measure all the other distances, error is less liable to occur, while at the same time an error in one measurement would not affect the correctness of the others. In the case of the crank pin shown, the collar C would be the best point wherefrom to take all the other measurements. First, it would require to be made to its proper thickness, and the lengths of B, A, and the end collar should be measured from its nearest radial face. The length of D should then be measured from the same radial face, the thickness of the collar being added to the required length of D, or D may be measured from the nearest radial face of C, providing C be of its exact proper thickness. In measuring the length of the taper part D, a correct measurement will not be obtained by laying the rule along its surface, because that surface does not lie parallel to its axis, hence it is necessary to apply the measuring rule, as shown in Fig. 1443, in which S is a straight-edge held firmly against the radial face of the crank pin (the radial face being of course turned true), and R is the measuring rule placed true with the axial line of the crank pin. Whenever the diameters of the lengths to be measured vary, this mode of measuring must be employed. On small work, or on short distances requiring to be very exact, a gauge such as shown in Fig. 1444 at A may be employed, which will not only give more correct results, but because it is more convenient, as it can be conveniently held or tried to the work with one hand while the other hand is applied to the feed screw handle to withdraw the cutting tool at the proper moment, and to the feed nut to unlock it and stop the feed. [Illustration: Fig. 1444.] [Illustration: Fig. 1445.] On long work a wooden strip is the best, especially if the work has varying diameters and a number of pieces of work require to be made exactly alike. In Fig. 1445 S represents the wooden strip, and W the work. The strip is marked across by lines representing the distances apart the shoulders of the work require to be; thus the lines A, B, C, D, E, F, G, represent the distances apart of the radial faces _a_, _b_, _c_, _d_, _e_, _f_, _g_, on the work, and these lines will be in the same plane as the shoulders if the latter are turned to correct lengths. To compare the radial faces with the lines, a straight-edge must be held to each successive shoulder (as already described) that is of smaller diameter than the largest radial face on the work. If the wooden strip be made the full length of the work the dog or clamp driving the work will require to be removed every time the wooden gauge is applied, and since the work must be turned end for end in the lathe to be finished, it would be as well to let the length of the wood gauge terminate before reaching the work driver, as, say, midway between E and F. When a lineal distance is marked by lines, and this distance is to be transferred to another piece of work and marked thereon by lines, the operation may be performed, for short distances or radii, by the common compasses employed to mark circles, but for greater distances where compasses would be cumbersome, the trammels are employed. Fig. 1446 represents a pair of trammels made entirely of metal, and therefore suitable for machinists' use, in which the points require to be pressed to the work to mark the lines. A A represents a bar of square steel; or for very long trammels wood may be used. B represents a head fastened tightly to one end, and through B passes the leg or pointer C, which is thus adjustable as to its projecting distance, as C can be fastened in any position by the thumb-screw D. The head E is made to a good sliding fit upon the bottom and two side faces of A A; but at the top there is sufficient space to admit a spring, which passes through E. F is the leg screwed into E, which is locked in position by the thumb-screw G. The head E is thus adjustable along the whole length of the bar or rod A A. The object of the spring is as follows:--If the head E were made to fit the bar A A closely on all four sides, the burrs raised upon the top side of the rod A A by the end of the thumb-screw G would be likely to impede its easy motion. Then again, when the sliding head E has worn a trifle loose upon the bar A A, and is loosened for adjustment, it would be liable to hang on one side, and only to right itself when the screw G brought it to a proper bearing upon the under side of the bar A A, and thus tightening the head E would alter the adjustment of the point. The spring, however, always keeps the lower face of the square hole through E bearing evenly against the corresponding face of the bar, so that tightening the screw G does not affect the adjustment, and, furthermore, the end of the set-screw, bearing against the spring instead of against the top of the rod, prevents the latter from getting burred. [Illustration: Fig. 1446.] The flat place at I I is to prevent the burrs raised by the thumb-screw end from preventing the easy sliding of leg C through B. [Illustration: Fig. 1447.] In some cases a gib is employed, as shown at A in Fig. 1447, instead of a spring, the advantage being that it is less liable to come out of place when moving the head along the bar. The trammels should always be tried to the work in the same relative position as that in which they were set, otherwise the deflection of the bar may vitiate the correctness of the measurement; thus, if the rod or bar stood vertical when the points were adjusted for distance to set them to the required distance, it should also stand vertical upon the work when applied to transfer that distance, otherwise the deflection of the bar from its own weight will affect the correctness of the operation. Again, when applied to the work the latter should be suspended as nearly as convenient in the same position as the work will occupy when erected to its place. Thus, suppose the trammels be set to the crank pin centres of a locomotive, then the bar will stand horizontally. Now the side rod, or coupling rod, as it may be more properly termed, should be stood on edge and should rest on its ends, because its bearings wherever it will rest when on the engine are at the ends; thus the deflection of the trammel rod will be in the same direction when applied to the work as it was when applied to the engine, and the deflection of the coupling rod will be in the same direction when tried by the trammel as when on the engine. The importance of this may be understood when it is mentioned that if the coupling rod be a long one, resting it on its side and supporting it in the middle instead of at its ends will cause a difference of 1/50th inch in its length. [Illustration: Fig. 1448.] Another lineal measuring gauge employed in the machine shop is shown in Fig. 1448. It is employed to measure the distance between two faces, and therefore in place of inside calipers, in cases where from the extreme distance to be measured it would require the use of inside calipers too large to be conveniently handled. Its application is more general upon planing machine work than any other, although it is frequently used by the lathe hand or turner, and by the vice hand and erector. It consists of two legs A and B, held together by the screws C D, which screw into nuts. These nuts should have a shoulder fitting into the slots in both legs, so as to form a guide to the legs. The screws are set up so as to just bind both legs together but leaving them free enough to move under a slight friction. The gauge is then set to length by lightly striking the ends E, and when adjusted the screws C D are screwed firmly home. The ends E are rounded somewhat, as is shown, to prevent them from swelling or burring by reason of the blows given to adjust them. For striking circles we have the compasses or dividers, which are made in various forms. [Illustration: Fig. 1449.] Thus, Fig. 1449 represents a pair of spring dividers, the bow spring at the head acting to keep the points apart, and the screw and nut being employed to close and to adjust them. [Illustration: Fig. 1450.] Another form is shown in Fig. 1450, the legs being operated by a right and left-hand screw, which may be locked in position by the set-screw shown. For very small circles the fork scriber shown in Fig. 1451 is an excellent tool, since it may be used with great pressure so as to cut a deep line in the surface of the work. This tool is much used by boiler makers, but is a very useful one for the machinist for a variety of marking purposes, which will be described with reference to vice work. For larger work we have the compasses, a common form of which is shown in Fig. 1452, in which the leg A is slotted to receive the arc piece C, which has a threaded stem passing through E, and is provided with a nut at B; at D is a spring which holds the face of the nut B firmly against the leg E; at A is a thumb-screw for securing the leg to the arm C. The thumb-screw A being loosened, the compass legs may be rudely adjusted for distance apart, and A is then tightened. The adjustment is finally made by operating the nut B, which, on account of its fine thread, enables a very fine adjustment to be easily made. [Illustration: Fig. 1451.] [Illustration: Fig. 1452.] [Illustration: Fig. 1453.] It is often very convenient to be able to set one leg of a pair of dividers to be longer than the other, for which purpose a socket B, Fig. 1453, is provided, being pierced to receive a movable piece A, and split so that by means of a set-screw C the movable piece A may be gripped or released at pleasure. [Illustration: Fig. 1454.] For finding the centres of bodies or for testing the truth of a centre already marked, the compass calipers shown in Fig. 1454, are employed. It is composed of one leg similar to the leg of a pair of compasses, while the other is formed the same as the leg of an inside caliper. The uses of the compass calipers are manifold, the principal being illustrated as follows:-- [Illustration: Fig. 1455.] Let it be required to find the centre of a rectangular block, and they are applied as in Fig. 1455, the curved leg being rested against the edge and a mark being made with the compass leg. This being done from all four sides of the work gives the centre of the piece. [Illustration: Fig. 1456.] In the case of a hole its bore must be plugged and the compass calipers applied as in Fig. 1456. [Illustration: Fig. 1457.] For marking a line true with the axial line of a cylindrical body, we have the instrument W in Fig. 1457, which is shown applied to a shaft S. The two angles of the instrument are at a right angle one to another, so that when placed on a cylindrical body the contact will cause the edge of W to be parallel with the axis of the shaft. The edge is bevelled, as shown, so that the lines of division of inches and parts may come close to the work surface, and a scriber may be used to mark a line of the required length. A scriber is a piece of steel wire having a hardened sharp point wherewith to draw lines. On account of the instrument W finding its principal application in marking key seats upon shafts, it is termed the "key-seat rule." [Illustration: Fig. 1458.] For marking upon one surface a line parallel to another surface, the scribing block or surface gauge shown in Fig. 1458 is employed. It consists of a foot piece or stand D, carrying a stem. In the form shown this stem contains a slot running centrally up it. Through this slot passes a bolt whose diameter close to the head is larger than the width of the slot, so that it is necessary to file flat places on the side of the slot to permit the bolt to pass through it. On the stem of the bolt close to the head, and between the bolt head and the stem of the stand, passes the piece shown at F. This consists of a piece of brass having a full hole through which the bolt passes clear up to the bolt head. On the edge view there is shown a slot, and on each side of the slot a section of a hole to receive a needle. A view of the bolt is given at E, the flat place to fit the slot in the stem being shown in dotted lines, and the space between the flat place and the bolt head is where the piece of brass, shown in figure, passes. This piece of brass being placed on the bolt, and the bolt being passed through the slot in the stem, the needle is passed through the split in the brass, and the thumb-nut is screwed on so that tightening up the thumb-nut causes the needle to be gripped in the brass split in any position in the length of the stem slot in which the bolt may be placed. The advantage of this form over all others is that the needle may be made of a simple piece of wire, and therefore very readily. Again, the piece of brass carrying the needle may be rotated upon the pin any number of consecutive rotations backwards and forwards, and there is no danger of slacking the thumb-nut, because the needle is on the opposite side of the stem to what the thumb-nut is, and the flat place prevents the bolt from rotating. Furthermore, the needle can be rotated on the bolt for adjustment for height without becoming loosened, whereas when the thumb-nut is screwed up firmly the needle is held very fast indeed, and finally all adjustments are made with a single thumb-nut. The figure represents a view of this gauge from the bolt head and needle side of the stem, the thumb-nut being on the opposite side. This tool finds its field of application upon lathe work, planer work, and, indeed, for one purpose or another upon all machine tools, and in vice work and erecting, examples of its employment being given in connection with all these operations. [Illustration: Fig. 1459.] Fig. 1459 represents a scribing block for marking the curves to which to cut the ends of a cylindrical body that joins another, as in the case of a [T]-pipe. It is much used by pattern-makers. In the figure A is a stem on a stand E. A loose sleeve B slides on A carrying an arm C, holding a pencil at D. A piece of truly surfaced wood or iron W, has marked on it the line J. Two [V]s, G, G, receive the work P. Now, if the centres of G, G and of the stand E all coincide with the line J then E will stand central to P, and D may be moved by the hand round P, being allowed to lift and fall so as to conform to the cylindrical surface of P, and a line will be marked showing where to cut away the wood on that side, and all that remains to do is to turn the work over and mark a similar line diametrically opposite, the second line being dotted in at K. [Illustration: Fig. 1460.] The try square, Fig. 1460, is composed of a rectangular back F, holding a blade, the edges of the two being at a right angle one to the other and as straight as it is possible to make them. The form shown in the figure is an [L]-square. [Illustration: Fig. 1461.] Fig. 1461 represents the [T]-square, whose blade is some distance from the end of the back and is sometimes placed in the middle. When the square edges are at a true right angle the square is said to be true or square, the latter being a technical term meaning at practically a true right angle. The machinists' square is in fact a gauge whereby to test if one face stands at a right angle to another. It is applied by holding one edge firmly and fairly bedded against the work, while the other edge is brought to touch at some part against the face to be tested. If in applying a square it be pressed firmly into the corner of the work, any error in the latter is apt to escape observation, because the square will tilt and the error be divided between the two surfaces tested. To avoid this the back should be pressed firmly against one surface of the work and the square edge then brought down or up to just touch the work, which it will do at one end only if the work surface is out of square or not at a right angle to the face to which the square back is applied. [Illustration: Fig. 1462.] An application of the [T]-square is shown in Fig. 1462, in which W is a piece of work requiring to have the face A of the jaw C at a right angle to the face B C. Sometimes the [L]-square is employed in conjunction with a straight-edge in place of the [T]-square. This is usually done in cases where the faces against which the square rests are so far apart as to require a larger [T]-square than is at hand. It is obvious that if the face A of the work is the one to be tested, the edge B is the part pressed to the work; or per contra, if B C is the face to be tested, the edge of the blade is pressed to the work. [Illustration: Fig. 1463.] The plane of the edges of a square should, both on the blade and on the back, stand at a right angle to the side faces of the body or stock, and the side of the blade should be parallel to the sides of the back and not at an angle to either side, nor should it be curved or bent, because if under these conditions the plane of the square edge is not applied parallel with the surface of the work the square will not test the work properly. This is shown in Fig. 1463, in which W is a piece of work, and S a square having its blade bent or curved and applied slightly out of the vertical, so that presuming the plane of the blade edge to be a right angle to the stock or back of the square the plane of the blade edge will not be parallel with the plane of the work, hence it touches the work at the ends A B only, whereas if placed vertically the blade edge would coincide with the work surface all the way along. It is obvious then that by making the edge of the blade at a right angle, crossways as well as in its length, to the stock, the latter will serve as a guide to the eye in adjusting the surface of the blade edge parallel to that of the work by placing the stock at a right angle to the same. [Illustration: Fig. 1464.] There are three methods of testing the angle of a square blade to the square back. The first is shown in Fig. 1464, in which A is a surface plate having its edge a true plane. The square S is placed in the position shown by full lines pressed firmly to the edge of the surface plate and a fine line is drawn with a needle point on the face of the surface plate, using the edge of the square blade as denoted by the arrow C as a guide. The square is then turned over as denoted by the dotted lines and the edge is again brought up to the line and the parallelism of the edge with the line denotes the truth, for whatever amount the blade may be out of true will be doubled in the want of coincidence of the blade edge with the line. [Illustration: Fig. 1465.] A better plan is shown in Fig. 1465, in which A is the surface plate, B a cylindrical piece of iron turned true and parallel in the lathe and having its end face true and cupped as denoted by the dotted lines so as to insure that it shall stand steadily and true. The surface of A and the vertical outline of B forming a true right angle we have nothing to do but make the square S true to them when placed in the position shown. [Illustration: Fig. 1466.] [Illustration: Fig. 1467.] [Illustration: Fig. 1468.] If we have two squares that are trued and have their edges parallel, we may test them for being at a right angle by trying them together as in Figs. 1466 and 1467, in which A, B, are the two squares which, having their back edges pressed firmly together (when quite clean), must coincide along the blade edges; this being so we may place them on a truly surfaced plate as shown in Fig. 1468, in which S is one square and S´ the other, P being the surface plate. Any want of truth in the right angle will be shown doubled in amount by a want of coincidence of the blade edges. [Illustration: Fig. 1469.] For some purposes, as for marking out work on a surface plate, it is better that the square be formed of a single piece having the back and blade of equal thickness, as shown in Fig. 1469, which represents a side and edge view of an [L]- and [T]-square respectively. [Illustration: Fig. 1470.] For angles other than a right angle we have the bevel or bevel square (as it is sometimes called), shown in Fig. 1470, A representing the stock or back, and B the blade, the latter being provided with a slot so that it may be extended to any required distance (within its scope) on either side of the stock. C is the rivet, which is made sufficiently tight to permit of the movement by hand of the blade, and yet it must hold firmly enough to be used without moving in the stock. Instead of the rivet C, however, a thumb-screw and nut may be employed, in which case, after the blade is set to the required angle, it may be locked in the stock by the thumb-screw. Fig. 1471 represents a Brown and Sharpe bevel protractor, with a pivot and thumb-nut in the middle of the back with a half-circle struck from the centre of the pivot and marked to angular degrees. The pointer for denoting the degrees of angle has also a thumb-screw and nut so that the blade may, by loosening the pivot and pointer, be moved to project to the required distance on either side of the back. [Illustration: Fig. 1471.] [Illustration: Fig. 1472.] Swasey's improved protractor, however, is capable of direct and easy application to the work, forming a draughtsman's protractor, and at the same time a machinist's bevel or bevel square, while possessing the advantage that there is no protruding back or set-screw to prevent the close application of the blade to the work. This instrument is shown in Fig. 1472. The blade A is attached to the circular piece D, the latter being recessed into the square B B, and marked with the necessary degrees of angle, as shown, while the mark F upon the square B serves as an index point. The faces of A, B B, and D are all quite level, so that the edges will meet the lines upon the work and obviate any liability to error. The piece D is of the shape shown in section at G, which secures it in B B, the fit being sufficient to permit of its ready adjustment and retain it by friction in any required position. The dotted lines indicate the blade as it would appear when set to an angle, the point E being the centre of D, and hence that from which the blade A operates. [Illustration: Fig. 1473.] On account, however, of the numerous applications in machine work of the hexagon (as, for instance, on the sides of both heads and nuts), a special gauge for that angle is requisite, the usual form being shown in Fig. 1473. The edges A, B, form a hexagon gauge, and edges C, D, form a square, while the edge E serves as a straight-edge. All these tools should be made of cast steel, the blades being made of straight saw blade, so that they will not be apt to permanently set from an ordinary accidental blow; while, on the other hand, if it becomes, as it does at times, necessary to bend the blade over to the work, it will resume its straightness and not remain bent. For testing the straightness, in one direction only, of a surface the straight-edge is employed. It consists in the small sizes of a piece of steel whose edges are made straight and parallel one to the other. When used to test the straightness of a surface without reference to its alignment with another one, it is simply laid upon the work and sighted by the eye, or it may have its edge coated with red marking, and be moved upon the work so that its marking will be transferred to the high spots upon the work. The marking will look of the darkest colour in the places where the straight-edge bears the hardest. The most refined use of the straight-edge is that of testing the alignment of one surface to the other, and as this class of work often requires straight-edges of great length, as six or ten feet, which if made of metal would bend of its own weight, therefore they are made of wood. [Illustration: Fig. 1474.] Fig. 1474 represents an example of the use of straight-edge for alignment purposes. It represents a fork and connecting rod, and it is required to find if the side faces of the end B are in line with the fork jaws. A straight-edge is held firmly against the side faces of B in the two positions S and S´, and it is obvious that if they are in line the other end will be equidistant from the jaw faces, at the two measurements. [Illustration: Fig. 1475.] [Illustration: Fig. 1476.] [Illustration: Fig. 1477.] Figs. 1474, 1475, 1476, 1477, and 1478 represent the process of testing the alignment of a link with a straight-edge. First to test if the single eye E is in line with the double eye F at the other end, the straight-edge is pressed against the face of E, as in Fig. 1475, and the distance I is measured. The straight-edge is then applied on the other side of E, as in Fig. 1476, and the distance H is measured, and it is clear that if distances H and I are equal, then E is in line with the double eye. To test if the double eye F is in line with the single eye E, the straight-edge is pressed against the face of the double eye in the positions shown in Figs. 1477 and 1478, and when distances J and K measure equal the jaws of the double eye F are in line with those of the single eye E. [Illustration: Fig. 1478.] [Illustration: Fig. 1479.] [Illustration: Fig. 1480.] [Illustration: Fig. 1481.] [Illustration: Fig. 1482.] [Illustration: Fig. 1483.] It is obvious, however, that we have here tested the alignment in one direction only. But to test in the other direction we may use a pair of straight-edges termed winding strips, applying them as in Fig. 1479, to test the stem, and as in Fig. 1480 to test the eye E, and finally placing the winding strip C on the eye of F while strip D remains upon E, as in Fig. 1480. The two strips are sighted together by the eye, as is shown in Fig. 1481, in which S and S´´ are the strips laid upon a connecting rod, their upper edges being level with the eye, hence if they are not in line the eye will readily detect the error. Fig. 1482 represents an application to a fork ended connecting rod. Pattern-makers let into their winding strips pieces of light-coloured wood as at C, C, C, C, in Fig. 1483, so that the eye may be assisted in sighting them. It is obvious that in using winding strips they should be parallel one to the other; thus, for example, the ends A, B, in Fig. 1481, should be the same distance apart as ends C, D. If less than three straight-edges or parallel strips are to be trued they must be trued to a surface plate or its equivalent, but if a pair are to be made they should have the side faces made true, and be riveted together so that their edges may be trued together, and equal width may be more easily obtained. For this purpose copper rivets should be used, because they are more readily removable, as well as less likely to strain the work in the riveting. By riveting the straight-edges together the surface becomes broader and the file operates steadier, while the edges of the straight-edge are left more square. Furthermore parallelism is more easily obtained as one measurement at each end of the batch will test the parallelism instead of having to measure each one separately at each end. If three straight-edges are to be made they may be riveted together and filed as true as may be with the testing conveniences at hand, but they should be finally trued as described for the surface plate. In using straight-edges to set work, the latter is often heated to facilitate the setting, and in this case the straight-edge or parallel strips should be occasionally turned upside down upon the work, for if the heated work heats one side of the straightedge more than the other the increased expansion of the side most heated will bend the straight-edge or strips, and throw them out of true. In applying a straight-edge to test work it must never be pressed to the work surface, because in that case it will show contact with the work immediately beneath the parts where such pressure is applied. Suppose, for example, a true straight-edge be given a faint marking, and be applied to a true surface, the straight-edge itself being true; then if the hands are placed at each end of the straight-edge, and press it to the work while the straight-edge is given motion, it will leave the heaviest marks at and near the ends as though the work surface was slightly hollow in its length; while were the hand pressure applied to the middle of the length of the straight-edge the marks on the work would show the heaviest in the middle as though the work surface were rounding. This arises from the deflection due to the weakness of the straight-edge. For testing the truth of flat or plane surfaces the machinist employs the surface plate or planometer. The surface plate is a plate or casting having a true flat surface to be used as a test plate for other surfaces. It is usually made of cast iron, and sometimes of chilled cast iron or hardened cast steel, the surface in either of these two latter cases being ground true because their hardness precludes the possibility of cutting them with steel tools. A chilled or hardened surface plate cannot, however, be so truly surfaced as one that is finished with either the scraper or the file. The shape of the surface plate is an element of the first importance, because as even the strongest bars of metal deflect from their own weight, it is necessary to shape the plate with a view to make this deflection as small as possible in any given size and weight of plate. In connection, also, with the shape we must consider the effect of varying temperatures upon the metal, for if one part of the plate is thinner than another it will, under an increasing temperature, heat more rapidly, and the expansion due to the heating will cause that part to warp the plate out of its normal form, and hence out of true. The amount that a plate will deflect of its own weight can only be appreciated by those who have had experience in getting up true surfaces, but an idea may be had when it is stated that it can be shown that it is easily detected, in a piece of steel three inches square and a foot long. Now this deflection will vary in direction according to the points upon which the plate rests. For instance, take two plates, clean them properly, and rest one upon two pieces of wood, one piece under each end, and then place another plate upon the lower one and its face will show hollow, and, if the upper plate is moved backwards and forwards laterally it will be found to move from the ends as centres of motion. Then rest the lower plate upon a piece of wood placed under the middle of its length, and we shall find that (if the plates are reasonably true) the top one will move laterally with the middle of its length as a centre of motion. Now although this method of testing will prove deflection to exist, it will not show its amount, because the top plate deflects to a certain extent, conforming itself to the deflection of the lower one, and if the test is accurately made it will be found that the two plates will contact at whatever points the lower one is supported. If plates, tested in this manner, show each other to have contact all along however the lower one is supported, it is because they are so light that the upper one will readily bend to suit the deflection of the lower one, and true work is, with such a plate, out of the question. To obviate these difficulties the body of the plate is heavily ribbed, and these ribs are so arranged as to be of equal lengths, and are made equal in thickness to the plate, so that under variations of temperature the ribs will not expand or contract more quickly or slowly than the body of the plate, and the twisting that would accompany unequal expansion is avoided. [Illustration: Fig. 1484.] In Fig. 1484 is shown the form of surface plate designed by Sir Joseph Whitworth for plates to be rested upon their feet. The resting points of the plate are small projections shown at A, B, and C. The object of this arrangement of feet is to enable the plate to rest with as nearly as possible an equal degree of weight upon each foot, the three feet accommodating themselves to an uneven surface. It is obvious, however, that more of the weight will fall upon C than upon A or B, because C supports the whole weight at one end, while at the other end A and B divide the weight. [Illustration: Fig. 1485.] Fig. 1485 shows the form of plate designed by Professor Sweet. [Illustration: Fig. 1486.] In Fig. 1486 is shown a pair of angle surface plates resting upon a flat one. The angle plates may be used for a variety of purposes where it is necessary to true a surface standing at a true right angle to another. The best methods of making surface plates are as follows:-- The edges of the plates should be planed first, care being taken to make them square and flat. The surfaces should then be planed, the plates being secured to the planer _by the edges_, which will prevent as far as possible the pressure necessary to hold them against the planing tool cut from springing, warping, or bending the plates. Before the finishing cut is taken, the plates or screws holding the surface plate should be slackened back a little so as to hold them as lightly as may be, the finishing cut being a very light one, and under these circumstances the plates may be planed sufficiently true that one will lift the other from the partial vacuum between them. After the plates are planed, and before any hand work is done on them, they should be heated to a temperature of at least 200° Fahr., so that any local tension in the casting may be as far as possible removed. [Illustration: Fig. 1487.] Surface plates for long and narrow surfaces are themselves formed long and narrow, as shown in Fig. 1487, which represents the straight-edge surface plate made at Cornell University. [Illustration: Fig. 1488.] The Whitworth surfacing straight-edge, or long narrow surface plate, is ribbed as in Fig. 1488, so as to give it increased strength in proportion to its weight, and diminish its deflection from its own weight. The lugs D are simply feet to rest it on. Straight-edges are sometimes made of cast steel and trued on both edges. These will answer well enough for small work, but if made of a length to exceed about four feet their deflection from their own weight seriously affects their reliability. The author made an experiment upon this point with a very rigid surface plate six feet long, and three cast steel straight-edges 6 feet long, 4-1/2 inches wide, and 1/2 inch thick. Both edges of the straight-edges were trued to the surface plate until the light was excluded from between them, while the bearing surface appeared perfect; thin tissue paper was placed between the straight-edges and the plate, and on being pulled showed an equal degree of tension. The straight-edges were tried one with the other in the same way and interchanged without any apparent error, but on measuring them it was found that each was about 1/50 inch wider in the middle of its length than at the ends, the cause being the deflection. They were finished by filing them parallel to calipers, using the bearing marks produced by rubbing them together and also upon the plate; but, save by the caliper test, the improvement was not discernible. In rubbing them together no pressure was used, but they were caused to slide under their own weight only. A separate and distinct class of gauge is used in practice to copy the form of one piece and transfer it to another, so that the one may conform to or fit the other. To accomplish this end, what are termed male and female templates or gauges are employed. These are usually termed templates, but their application to the work is termed gauging it. [Illustration: Fig. 1489.] Suppose, for example, that a piece is to be fitted to the rounded corner of a piece F, Fig. 1489, and the maker takes a piece of sheet metal A, and cuts it out to the line B C D, leaving a female gauge E, which will fit to the work F. We then make a male gauge G, and apply this to the work, thus gauging the round corner. [Illustration: Fig. 1490.] Fig. 1490 represents small templates applied to a journal bearing, and it is seen that we may make the template as at T, gauging one corner only, or we may make it as at T´, thus gauging the length of the journal as well as the corners. [Illustration: Fig. 1491.] [Illustration: Fig. 1492.] Fig. 1491 represents a female gauge applied to the corner of a bearing or brass for the above journal, it being obvious that the male and female templates when put together will fit as in Fig. 1492. For measuring the diameters of metal wire and the thickness of rolled sheet metal, measuring instruments termed wire gauges and sheet metal measuring machines are employed. A simple wire gauge is usually formed of a piece of steel containing numerous notches, whose widths are equal to the intended thickness to be measured in each respective notch. These notches are marked with figures denoting the gauge-number which is represented by the notch. For wire, however, a gauge having holes instead of notches is sometimes employed, the wire being measured by insertion in the hole, an operation manifestly impracticable in the case of sheet metal. In Fig. 1493 is shown one of Brown and Sharpe's notch wire-gauges, the notches being arranged round the edge as shown: [Illustration: Fig. 1493.] The thickness of a given number of wire-gauge varies according to the system governing the numbering of the gauge, which also varies with the class of metal or wire for which the gauge has been adopted by manufacturers. Thus, in the following table are given the gauge-numbers and their respective sizes in decimal parts of an inch, as determined by Holtzapffel in 1843, and to which sizes the Birmingham wire-gauge is made. The following table gives the numbers and sizes of the Birmingham wire-gauge. BIRMINGHAM WIRE GAUGE. -----+------++------+------++------+------++------+------ Mark.| Size.|| Mark.| Size.|| Mark.| Size.|| Mark.| Size. -----+------++------+------++------+------++------+------ 36 | .004 || 26 | .018 || 16 | .065 || 6 | .203 35 | .005 || 25 | .020 || 15 | .072 || 5 | .220 34 | .007 || 24 | .022 || 14 | .083 || 4 | .238 33 | .008 || 23 | .025 || 13 | .095 || 3 | .259 32 | .009 || 22 | .028 || 12 | .109 || 2 | .284 31 | .010 || 21 | .032 || 11 | .120 || 1 | .300 30 | .012 || 20 | .035 || 10 | .134 || 0 | .340 29 | .013 || 19 | .042 || 9 | .148 || 00 | .380 28 | .014 || 18 | .049 || 8 | .165 || 000 | .425 27 | .016 || 17 | .058 || 7 | .180 || 0000 | .454 -----+------++------+------++------+------++------+------ In this gauge it will be observed that the progressive wire gauge numbers do not progress by a regular increment. This gauge is sometimes termed the Stubs wire-gauge, Mr. Stubs being a manufacturer of instruments whose notches are spaced according to the Birmingham wire-gauge. Since, however, Mr. Stubs has also a wire-gauge of his own, whose numbers and gauge-sizes do not correspond to those of the Birmingham gauge, the two Stubs gauges are sometimes confounded. The second Stubs gauge is employed for a special drawn steel wire, made by that gentleman to very accurate gauge measurement for purposes in which accuracy is of primary importance. From the wear of the drawing dies in which wire is drawn, it is impracticable, however, to attain absolute correctness of gauge measurement. The dies are made to correct gauge when new, and when they have become worn larger, to a certain extent, they are renewed. As a result the average wire is slightly larger than the designated gauge-number. To determine the amount of this error the Morse Twist-Drill and Machine Company measured the wire used by them during an extended period of time, the result being given in table No. 2, in which the first column gives the gauge-number, the second column gives the thickness of the gauge-number in decimal parts of an inch, and the third column the actual size of the wire in decimal parts of an inch as measured by the above Company. DIAMETER OF STUBS'S DRAWN STEEL WIRE IN FRACTIONAL PARTS OF AN INCH. -------+-------+--------++-------+-------+--------++-------+-------+-------- No. by |Stubs's|Measure-||No. by |Stubs's|Measure-||No. by |Stubs's|Measure- Stubs's|Dimen- |ment by ||Stubs's|Dimen- |ment by ||Stubs's|Dimen- |ment by wire- |sions. | Morse || wire- |sions. | Morse || wire- |sions. | Morse gauge. | | Twist- ||gauge. | | Twist- ||gauge. | | Twist- | | Drill || | | Drill || | | Drill | | and || | | and || | | and | |Machine || | |Machine || | |Machine | | Co. || | | Co. || | | Co. -------+-------+--------++-------+-------+--------++-------+-------+-------- 1 | .227 | .228 || 23 | .153 | .154 || 45 | .081 | .082 2 | .219 | .221 || 24 | .151 | .152 || 46 | .079 | .080 3 | .212 | .213 || 25 | .148 | .150 || 47 | .077 | .079 4 | .207 | .209 || 26 | .146 | .148 || 48 | .075 | .076 5 | .204 | .206 || 27 | .143 | .145 || 49 | .072 | .073 6 | .201 | .204 || 28 | .139 | .141 || 50 | .069 | .070 7 | .199 | .201 || 29 | .134 | .136 || 51 | .066 | .067 8 | .197 | .199 || 30 | .127 | .129 || 52 | .063 | .064 9 | .194 | .196 || 31 | .120 | .120 || 53 | .058 | .060 10 | .191 | .194 || 32 | .115 | .116 || 54 | .055 | .054 11 | .188 | .191 || 33 | .112 | .113 || 55 | .050 | .052 12 | .185 | .188 || 34 | .110 | .111 || 56 | .045 | .047 13 | .182 | .185 || 35 | .108 | .110 || 57 | .042 | .044 14 | .180 | .182 || 36 | .106 | .106 || 58 | .041 | .042 15 | .178 | .180 || 37 | .103 | .104 || 59 | .040 | .041 16 | .175 | .177 || 38 | .101 | .101 || 60 | .039 | .040 17 | .172 | .173 || 39 | .099 | .100 || 61 | .038 | .039 18 | .168 | .170 || 40 | .097 | .098 || 62 | .037 | .038 19 | .164 | .166 || 41 | .095 | .096 || 63 | .036 | .037 20 | .161 | .161 || 42 | .092 | .094 || 64 | .035 | .036 21 | .157 | .159 || 43 | .088 | .089 || 65 | .033 | .035 22 | .155 | .156 || 44 | .085 | .086 || | | -------+-------+--------++-------+-------+--------++-------+-------+-------- The following table represents the letter sizes of the same wire:-- LETTER SIZES OF WIRE. A. 0.234 | J. 0.277 | S. 0.348 B. 0.238 | K. 0.281 | T. 0.358 C. 0.242 | L. 0.290 | U. 0.368 D. 0.246 | M. 0.295 | V. 0.377 E. 0.250 | N. 0.302 | W. 0.386 F. 0.257 | O. 0.316 | X. 0.397 G. 0.261 | P. 0.323 | Y. 0.404 H. 0.266 | Q. 0.332 | Z. 0.413 I. 0.272 | R. 0.339 | By an Order in Council dated August 23rd, 1883, and which took effect on March 1st, 1884, the standard department of the British Board of Trade substituted for the old Birmingham wire-gauge the following:-- +-------------+--------------++---------------------------+ | Descriptive | Equivalents || Descriptive | Equivalents | | number | in parts || number | in parts | | B. W. G. | of an inch. || B. W. G. | of an inch. | +-------------+--------------++-------------+-------------+ | No. | Inch. || No. | Inch. | | 7/0 | 0.500 || 23 | 0.024 | | 6/0 | .464 || 24 | .022 | | 5/0 | .432 || 25 | .020 | | 4/0 | .400 || 26 | .018 | | 3/0 | .372 || 27 | .0164 | | 2/0 | .348 || 28 | .0148 | | 0 | .324 || 29 | .0136 | | 1 | .300 || 30 | .0124 | | 2 | .276 || 31 | .0116 | | 3 | .252 || 32 | .0108 | | 4 | .232 || 33 | .0100 | | 5 | .212 || 34 | .0092 | | 6 | .192 || 35 | .0084 | | 7 | .176 || 36 | .0076 | | 8 | .160 || 37 | .0068 | | 9 | .144 || 38 | .0060 | | 10 | .128 || 39 | .0052 | | 11 | .116 || 40 | .0048 | | 12 | .104 || 41 | .0044 | | 13 | .092 || 42 | .0040 | | 14 | .080 || 43 | .0036 | | 15 | .072 || 44 | .0032 | | 16 | .064 || 45 | .0028 | | 17 | .056 || 46 | .0024 | | 18 | .048 || 47 | .0020 | | 19 | .040 || 48 | .0016 | | 20 | .036 || 49 | .0012 | | 21 | .032 || 50 | .0010 | | 22 | .028 || | | +-------------+--------------++-------------+-------------+ [Illustration: Fig. 1494.] [Illustration: Fig. 1495.] The gauge known as the American Standard Wire-Gauge was designed by Messrs. Brown and Sharpe to correct the discrepancies of the old Birmingham wire-gauge by establishing a regular proportion of the thirty-nine successive steps between the 0000 and 36 gauge-number of that gauge. In the American Standard (which is also called the Brown and Sharpe gauge) the value of 0.46 or 46/100 has been taken as that for 0000 or the largest dimension of the gauge. Then by successive and uniform decrements, each number following being obtained from multiplying its predecessor by 0.890522 (which is the same thing as deducting 10.9478 per cent.), the final value for number 36 is reached at 0.005, which corresponds with number 35 of the Birmingham wire-gauge. The principle of the gauge is shown in Fig. 1495, which represents a gauge for jewelers, having an angular aperture with the gauge-numbers marked on the edge, the lines and numbers being equidistant. The advantage of this system is that the instrument is easy to produce, the difference between any two gauge-numbers being easily found by calculation; and the gauge is easy to originate, since the opening, being of the proper width at the open end, the sides terminating at the proper distance and being made straight, the intermediate gauge-sizes may be accurately marked by the necessary number of equidistant lines. Wire, to be measured by such a gauge, is simply inserted into and passed up the aperture until it meets the sides of the same, which gives the advantage that the size of the wire may be obtained, even though its diameter vary from a gauge-number. This could not be done with a gauge in which each gauge-number and size is given in a separate aperture or notch. A comparison between the Brown and Sharpe and the Birmingham wire-gauge is shown in Fig. 1494, in which a piece of wire is inserted, showing that No. 15 by the Birmingham gauge is No. 13 by the Brown and Sharpe gauge. The gauge-numbers and sizes of the same in decimal parts of an inch, of the American standard or Brown and Sharpe gauge, are given in the table following:-- ------+--------------------------++------+-------------------------- |American or New Standard. || | American or New Standard. +--------------------------++ +------------+------------- No. of|Size of each| Difference ||No. of|Size of each| Difference Wire- | number in | between ||Wire- | number in | between Gauge.| decimal | consecutive ||Gauge.| decimal | consecutive | parts of | numbers in || | parts of | numbers in | an inch. |decimal parts|| | an inch. |decimal parts | | of an inch. || | | of an inch. ------+------------+-------------++------+------------+------------- 0000 | .460 | ---- || 19 | .03589 | .00441 000 | .40964 | .05036 || 20 | .03196 | .00393 00 | .36480 | .04484 || 21 | .02846 | .00350 0 | .32495 | .03994 || 22 | .02535 | .00311 1 | .28930 | .03556 || 23 | .02257 | .00278 2 | .25763 | .03167 || 24 | .0201 | .00247 3 | .22942 | .02821 || 25 | .0179 | .00220 4 | .20431 | .02511 || 26 | .01594 | .00196 5 | .18194 | .02237 || 27 | .01419 | .00174 6 | .16202 | .01992 || 28 | .01264 | .00155 7 | .14428 | .01774 || 29 | .01126 | .00138 8 | .12849 | .01579 || 30 | .01002 | .00123 9 | .11443 | .01406 || 31 | .00893 | .00110 10 | .10189 | .01254 || 32 | .00795 | .00098 11 | .09074 | .01105 || 33 | .00708 | .00087 12 | .08081 | .00993 || 34 | .0063 | .00078 13 | .07196 | .00885 || 35 | .00561 | .00069 14 | .06408 | .00788 || 36 | .005 | .00061 15 | .05707 | .00702 || 37 | .00445 | .00055 16 | .05082 | .00625 || 38 | .00396 | .00049 17 | .04525 | .00556 || 39 | .00353 | .00043 18 | .0403 | .00495 || 40 | .00314 | .00039 ------+------------+-------------++------+------------+------------- This gauge is now the standard by which rolled sheet brass and seamless brass tubing is made in the United States. It is also sometimes used as a gauge for the copper wire used for electrical purposes, being termed the American Standard; but unless the words "American Standard" are employed, the above wire is supplied by the Birmingham wire-gauge numbers. The brass wire manufacturers have not yet adopted the Brown and Sharpe gauge; hence, for brass wire the Birmingham gauge is the standard. Gauges having simple notches are not suitable for measuring accurately the thickness of metal, because the edges of the sheets or plates frequently vary from the thickness of the body of the plate. This may occur from the wear of the rolls employed to roll out the sheet, or because the sheets have been sheared to cut them to the required width, or to remove cracks at the edges, which shearing is apt to form a burr or projection on one side of the edge, and a slight depression on the other. Again, a gauge formed by a notch requires to slide over the metal of the plate, and friction and a wear causing an enlargement of the notch ensues, which destroys the accuracy of the gauge. To avoid this source of error the form of gauge that was shown in Fig. 1370 may be used, it having the further advantage that it will measure thicknesses intermediate between the sizes of two contiguous notches, thus measuring the actual thickness of the sheet when it is not to any accurate sheet metal gauge thickness. It is to be observed that in the process of rolling, the sheet is reduced from a greater to a lesser thickness, hence the gauge will not pass upon the plate until the latter is reduced to its proper thickness. In applying the gauge, therefore, there is great inducement for the workman to force the gauge on to the sheet, in order to ascertain how nearly the sheet is to the required size, and this forcing process causes rapid wear to the gauge. It follows, therefore, that a gauge should in no case be forced on, but should be applied lightly and easily to the sheet to prevent wear. Here may be mentioned another advantage of the Brown and Sharpe gauge, in that its gauge-number measurements being uniform, it may be more readily known to what extent a given plate varies from its required gauge thickness. Suppose, for example, a sheet requiring to be of Number 1 Birmingham gauge is above the required thickness, but will pass easily through the 0 notch of the gauge, the excessive variation of those two gauge numbers (over the variations between other consecutive numbers of the gauge) leaves a wider margin in estimating how much the thickness is excessive than would be the case in using the Brown and Sharpe gauge. Indeed, if the edge of the plate be of uniform thickness with the body of the plate, the variation from the required thickness may be readily ascertained by a Brown and Sharpe gauge, by the distance the plate will pass up the aperture beyond the line denoting the 0 gauge number, or by the distance it stands from the 1 on the gauge when passed up the aperture until it meets both sides of the same. In addition to these standard gauges, some firms in the United States employ a standard of their own; the principal of these are given in comparison with others in the table following. DIMENSIONS OF SIZES, IN DECIMAL PARTS OF AN INCH. ------+---------+--------+----------+---------+---------+------------ Number| American|Birming-| Washburn | Trenton | G. W. |Old English, of | or Brown| ham, | & Moen |Iron Co.,|Prentiss,| from Brass Wire | & | or | Mfg. Co.,| Trenton,| Holyoke,| Manu- Gauge.| Sharpe. |Stubs's.|Worcester,| N. J. | Mass. | facturers' | | | Ms. | | | List. ------+---------+--------+----------+---------+---------+------------ 000000| ---- | ---- | .46 | ---- | ---- | ---- 00000| ---- | ---- | .43 | .45 | ---- | ---- 0000| .46 | .454 | .393 | .4 | ---- | ---- 000| .40964 | .425 | .362 | .36 | .3586 | ---- 00| .3648 | .38 | .331 | .33 | .3282 | ---- 0| .32495 | .34 | .307 | .305 | .2994 | ---- 1| .2893 | .3 | .283 | .285 | .2777 | ---- 2| .25763 | .284 | .263 | .265 | .2591 | ---- 3| .22942 | .259 | .244 | .245 | .2401 | ---- 4| .20431 | .238 | .225 | .225 | .223 | ---- 5| .18194 | .22 | .207 | .205 | .2047 | ---- 6| .16202 | .203 | .192 | .19 | .1885 | ---- 7| .14428 | .18 | .177 | .175 | .1758 | ---- 8| .12849 | .165 | .162 | .16 | .1605 | ---- 9| .11443 | .148 | .148 | .145 | .1471 | ---- 10| .10189 | .134 | .135 | .13 | .1351 | ---- 11| .090742 | .12 | .12 | .1175 | .1205 | ---- 12| .080808 | .109 | .105 | .105 | .1065 | ---- 13| .071961 | .095 | .092 | .0925 | .0928 | ---- 14| .064084 | .083 | .08 | .08 | .0816 | .083 15| .057068 | .072 | .072 | .07 | .0726 | .072 16| .05082 | .065 | .063 | .061 | .0627 | .065 17| .045257 | .058 | .054 | .0525 | .0546 | .058 18| .040303 | .049 | .047 | .045 | .0478 | .049 19| .03539 | .042 | .041 | .039 | .0411 | .04 20| .031961 | .035 | .035 | .034 | .0351 | .035 21| .028462 | .032 | .032 | .03 | .0321 | .0315 22| .025347 | .028 | .028 | .027 | .029 | .0295 23| .022571 | .025 | .025 | .024 | .0261 | .027 24| .0201 | .022 | .023 | .0215 | .0231 | .025 2S| .0179 | .02 | .02 | .019 | .0212 | .023 26| .01594 | .018 | .018 | .018 | .0194 | .0205 27| .014195 | .016 | .017 | .017 | .0182 | .01875 28| .012641 | .014 | .016 | .016 | .017 | .0165 29| .011257 | .013 | .015 | .015 | .0163 | .0155 30| .010025 | .012 | .014 | .014 | .0156 | .01375 31| .008928 | .01 | .0135 | .013 | .0146 | .01225 32| .00795 | .009 | .013 | .012 | .0136 | .01125 33| .00708 | .008 | .011 | .011 | .013 | .01025 34| .006304 | .007 | .01 | .01 | .0118 | .0095 35| .005614 | .005 | .0095 | .009 | .0109 | .009 36| .005 | .004 | .009 | .008 | .01 | .0075 37| .004453 | ---- | .0085 | .00725 | .0095 | .0065 38| .003965 | ---- | .008 | .0065 | .009 | .00575 ------+---------+--------+----------+---------+---------+------------ In the Whitworth wire-gauge, the mark or number on the gauge simply denotes the number of 1/1000ths of an inch the wire is in diameter; thus Number 1 on the gauge is 1/1000 inch, Number 2 is 2/1000ths inch in diameter, and so on. Below is given the Washburn and Moen Manufacturing Company's music wire-gauge. SIZES OF THE NUMBERS OF STEEL MUSIC WIRE-GAUGE. +--------+------------------++--------+------------------+ | No. of | Size of each No. || No. of | Size of each No. | | Gauge. | in decimal parts || Gauge. | in decimal parts | | | of an inch. || | of an inch. | +--------+------------------++--------+------------------+ | 12 | .0295 || 21 | .0461 | | 13 | .0311 || 22 | .0481 | | 14 | .0325 || 23 | .0506 | | 15 | .0343 || 24 | .0547 | | 16 | .0359 || 25 | .0585 | | 17 | .0378 || 26 | .0626 | | 18 | .0395 || 27 | .0663 | | 19 | .0414 || 28 | .0719 | | 20 | .043 || ---- | ---- | +--------+------------------++--------+------------------+ These sizes are those used by the Washburn and Moen Manufacturing Company, of Worcester, Mass., manufacturers of steel music wire. In the following table is the French Limoges wire-gauge. -------+-----------+-------++--------+-----------+------ Number | Diameter, | Inch. || Number | Diameter, | Inch. on | milli- | || on | milli- | gauge. | mètre. | || gauge. | mètre. | -------+-----------+-------++--------+-----------+------ 0 | .39 | .0154 || 13 | 1.91 | .0725 1 | .45 | .0177 || 14 | 2.02 | .0795 2 | .56 | .0221 || 15 | 2.14 | .0843 3 | .67 | .0264 || 16 | 2.25 | .0886 4 | .79 | .0311 || 17 | 2.84 | .112 5 | .90 | .0354 || 18 | 3.40 | .134 6 | 1.01 | .0398 || 19 | 3.95 | .156 7 | 1.12 | .0441 || 20 | 4.50 | .177 8 | 1.24 | .0488 || 21 | 5.10 | .201 9 | 1.35 | .0532 || 22 | 5.65 | .222 10 | 1.46 | .0575 || 23 | 6.20 | .244 11 | 1.68 | .0661 || 24 | 6.80 | .268 12 | 1.80 | .0706 || | | -------+-----------+-------++--------+-----------+------ The following table gives the Birmingham wire-gauge for rolled sheet silver and gold. +---------+------------++---------+------------+ | Gauge | Thickness. || Gauge | Thickness. | | number. | || number. | | +---------+------------++---------+------------+ | | Inch. || | Inch. | | 1 | .004 || 19 | .064 | | 2 | .005 || 20 | .067 | | 3 | .008 || 21 | .072 | | 4 | .010 || 22 | .074 | | 5 | .013 || 23 | .077 | | 6 | .013 || 24 | .082 | | 7 | .015 || 25 | .095 | | 8 | .016 || 26 | .103 | | 9 | .019 || 27 | .113 | | 10 | .024 || 28 | .120 | | 11 | .029 || 29 | .124 | | 12 | .034 || 30 | .126 | | 13 | .036 || 31 | .133 | | 14 | .041 || 32 | .143 | | 15 | .047 || 33 | .145 | | 16 | .051 || 34 | .148 | | 17 | .057 || 35 | .158 | | 18 | .061 || 36 | .167 | +---------+------------++---------+------------+ The following table gives the gauge thickness of Russia sheet iron,[25] the corresponding numbers by Birmingham wire gauge, and the thicknesses in decimal parts of an inch. [25] This iron comes in sheets 28 × 56 inches = 10.88 square feet of area. +----------+------------+-------------------+ | Russia | Birmingham | Thickness in | | gauge | wire-gauge | decimal | | number. | number. | parts of an inch. | +----------+------------+-------------------+ | 7 | 29 | .013 | | 8 | 28 | .014 | | 9 | 27 | .016 | | 10 | 26 | .018 | | 11 | 25 | .020 | | 12 | 24-1/2 | .021 | | 13 | 24 | .022 | | 14 | 23-1/4 | ---- | | 15 | 22-3/8 | ---- | | 16 | 21-1/2 | ---- | +----------+------------+-------------------+ The following table gives the gauge numbers to which galvanized iron is made.[26] [26] Galvanized iron is made to the Birmingham wire-gauge, the thickness includes the galvanizing, the sheets being rolled thinner to allow for it. +---------+------------++---------+------------+ | Gauge | Thickness. || Gauge | Thickness. | | number. | || number. | | +---------+------------++---------+------------+ | | Inch. || | Inch. | | 14 | .083 || 23 | .025 | | 16 | .065 || 24 | .022 | | 17 | .058 || 25 | .02 | | 18 | .049 || 26 | .018 | | 19 | .042 || 27 | .016 | | 20 | .035 || 28 | .014 | | 21 | .032 || 29 | .013 | | 22 | .028 || | | +---------+------------++---------+------------+ In the following table is given the American gauge sizes and their respective thicknesses for sheet zinc. --------------------------------++-------------------------------- Gauge and Thickness. || Gauge and Thickness. -------+-----------+------------++-------+-----------+------------ Number.|Approximate|Thickness in||Number.|Approximate|Thickness in |Birmingham |fractions of|| |Birmingham |fractions of |wire-gauge.| an inch. || |wire-gauge.| an inch. -------+-----------+------------++-------+-----------+------------ 1 | ---- | 0.0039 || 16 | ---- | 0.0447 5 | ---- | 0.0113 || 17 | ---- | 0.0521 6 | ---- | 0.0132 || 18 | ---- | 0.0596 7 | ---- | 0.0150 || 19 | ---- | 0.0670 8 | 28 | 0.0169 || 20 | ---- | 0.0744 9 | 27 | 0.0187 || 21 | ---- | 0.0818 10 | 26 | 0.0224 || 22 | ---- | 0.0892 11 | 25 | 0.0261 || 23 | ---- | 0.0966 12 | 24 | 0.0298 || 24 | ---- | 0.1040 13 | ---- | 0.0336 || 25 | ---- | 0.1114 14 | ---- | 0.0373 || 26 | ---- | 0.1189 15 | ---- | 0.0410 || | | -------+-----------+------------++-------+-----------+------------ The Belgian sheet zinc gauge is as follows: +---------+-------------++---------+-------------+ | Gauge | Thickness in|| Gauge | Thickness in| | number. |decimal parts|| number. |decimal parts| | | of an inch. || | of an inch. | +---------+-------------++---------+-------------+ | 1 | .004 || 14 | .037 | | 2 | .006 || 15 | .041 | | 3 | .008 || 16 | .045 | | 4 | .009 || 17 | .052 | | 5 | .011 || 18 | .059 | | 6 | .013 || 19 | .067 | | 7 | .015 || 20 | .074 | | 8 | .017 || 21 | .082 | | 9 | .019 || 22 | .089 | | 10 | .022 || 23 | .097 | | 11 | .026 || 24 | .104 | | 12 | .030 || 25 | .111 | | 13 | .034 || 26 | .120 | +---------+-------------++---------+-------------+ The gauge sizes of the bores of rifles are given in the following table,[27] in which the first column gives the proper gauge diameter of bore, and the second the actual diameter containing the errors found to exist from errors of workmanship. The standard diameters are supposed to be based upon the number of spherical bullets to the pound weight, if of the same diameter as the respective gauge sizes. [27] From _The English Mechanic_. No. of Diameter of Bore. Gauge. 4 varies from 1.052 to 1.000 6 " .919 " .900 8 " .835 " .820 10 " .775 " .760 12 " .729 " .750 14 " .693 " .680 16 " .662 " .650 20 " .615 " .610 24 " .579 " .577 28 " .550 " .548 The following table gives the result of some recent experiments made by Mr. David Kirkaldy, of London, to ascertain the tensile strength and resistance to torsion of wire made of various materials: +-----------------------+--------------------------+ | |Pulling stress per sq. in.| | Kind of wire tested. +-------------+------------+ | | Unannealed. | Annealed. | +-----------------------+-------------+------------+ | | Pounds. | Pounds. | |Copper | 63,122 | 37,002 | |Brass | 81,156 | 51,550 | |Charcoal iron | 65,834 | 46,160 | |Coke iron | 64,321 | 61,294 | |Steel | 120,976 | 74,637 | |Phosphor bronze, No. 1 | 159,515 | 58,853 | | " No. 2 | 151,119 | 64,569 | | " No. 3 | 139,141 | 54,111 | | " No. 4 | 120,900 | 53,381 | +-----------------------+-------------+------------+ +-----------------------+------------+----------------------+ | | Ultimate | No. of twists in | | Kind of wire tested. |extension in| 5 inches. | | | per cent. +-----------+----------+ | | Annealed. |Unannealed.| Annealed.| +-----------------------+------------+-----------+----------+ |Copper | 34.1 | 86.8 | 96 | |Brass | 36.5 | 14.7 | 57 | |Charcoal iron | 28 | 48 | 87 | |Coke iron | 17 | 26 | 44 | |Steel | 10.9 | [28] | 79 | |Phosphor bronze, No. 1 | 46.6 | 13.3 | 66 | | " No. 2 | 42.8 | 15.8 | 60 | | " No. 3 | 44.9 | 17.3 | 53 | | " No. 4 | 42.4 | 13 | 124 | +-----------------------+------------+-----------+----------+ [28] Of the eight pieces of steel tested, three stood from forty to forty-five twists, and five stood one and a half to four twists. The following, on some experiments upon the elasticity of wires, is from the report of a committee read before the British Association at Sheffield, England. "The most important of these experiments form a series that have been made on the elastic properties of very soft iron wire. The wire used was drawn for the purpose, and is extremely soft and very uniform. It is about No. 20 B.W.G., and its breaking weight, tested in the ordinary way, is about 45 lbs. This wire has been hung up in lengths of about 20 ft., and broken by weights applied, the breaking being performed more or less slowly. "In the first place some experiments have been tried as to the smallest weight which, applied very cautiously and with precautions against letting the weight run down with sensible velocity, will break the wire. These experiments have not yet been very satisfactorily carried out, but it is intended to complete them. "The other experiments have been carried out in the following way: It was found that a weight of 28 lbs. does not give permanent elongation to the wire taken as it was supplied by the wire drawer. Each length of the wire, therefore, as soon as it was hung up for experiment, was weighted with 28 lbs., and this weight was left hanging on the wire for 24 hours. Weights were then added till the wire broke, measurements as to elongation being taken at the same time. A large number of wires were broken with equal additions of weight, a pound at a time, at intervals of from three to five minutes--care being taken in all cases, however, not to add fresh weight if the wire could be seen to be running down under the effect of the weight last added. Some were broken with weights added at the rate of 1 lb. per day, some with 3/4 lb. per day, and some with 1/2 lb. per day. One experiment was commenced in which it was intended to break the wire at a very much slower rate than any of these. It was carried on for some months, but the wire unfortunately rusted, and broke at a place which was seen to be very much eaten away by rust, and with a very low breaking weight. A fresh wire has been suspended, and is now being tested. It has been painted with oil, and has now been under experiment for several months. "The following tables will show the general results of these experiments. It will be seen, in the first place, that the prolonged application of stress has a very remarkable effect in increasing the strength of soft iron wire. Comparing the breaking weights for the wire quickly broken with those for the same wire slowly broken, it will be seen that in the latter case the strength of the wire is from two to ten per cent. higher than in the former, and is on the average about five or six per cent. higher. The result as to elongation is even more remarkable, and was certainly more unexpected. It will be seen from the tables that, in the case of the wire quickly drawn out, the elongation is on the average more than three times as great as in the case of the wire drawn out slowly. There are two wires for which the breaking weights and elongations are given in the tables, both of them 'bright' wires, which showed this difference very remarkably. They broke without showing any special peculiarity as to breaking weight, and without known difference as to treatment, except in the time during which the application of the breaking weight was made. One of them broke with 44-1/4 lbs., the experiment lasting one hour and a half; the other with 47 lbs., the time occupied in applying the weight being 39 days. The former was drawn out by 28.5 per cent. on its original length, the latter by only 4.79 per cent. "It is found during the breaking of these wires that the wire becomes alternately more yielding and less yielding to stress applied. Thus from weights applied gradually between 28 lbs. and 31 lbs. or 32 lbs., there is very little yielding, and very little elongation of the wire. For equal additions of weight between 33 lbs. and about 37 lbs. the elongation is very great. After 37 lbs. have been put on, the wire seems to get stiff again, till a weight of about 40 lbs. has been applied. Then there is a rapid running down till 45 lbs. has been reached. The wire then becomes stiff again, and often remains so till it breaks. It is evident that this subject requires careful investigation." TABLES SHOWING THE BREAKING OF SOFT IRON WIRES AT DIFFERENT SPEEDS. I.--WIRE QUICKLY BROKEN. +------------------------+-----------+---------------+ | | Breaking | Per cent. of | | Rate of adding weight. | weight in | elongation on | | | pounds. | original | | | | length. | +------------------------+-----------+---------------+ | _Dark Wire._[29] | | | | 0-1/4 lb. per minute | 45 | 25.4 | | 1 " 5 minutes | 45-1/4 | 25.9 | | " 5 " | 45-1/4 | 24.9 | | " 4 " | 44-1/4 | 24.58 | | " 3 " | 44-1/4 | 24.88 | | " 3 " | 45-1/4 | 29.58 | | " 5 " | 44-1/4 | 27.78 | | _Bright Wire._[29] | | | | 1 lb. per 5 minutes | 44-1/4 | 28.5 | | " 5 " | 44-1/4 | 27.0 | | " 4 " | 44-1/4 | 27.1 | +------------------------+-----------+---------------+ [29] The wire used was all of the same quality and gauge, but the "dark" and "bright" wire had gone through slightly different processes for the purpose of annealing. II.--WIRE SLOWLY BROKEN. +--------------------+------------+--------------------+ | Weight added and | Breaking | Per cent. of | | number of | weight in | elongation on | | experiment. | pounds. | original length. | +--------------------+------------+--------------------+ | 1. 1 lb. per day | 48 | 7.58 | | 2. " " | 46 | 8.13 | | 3. " " | 47 | 7.05 | | 4. " " | 47 | 6.51 | | 5. " " | 47 | 8.62 | | 6. " " | 47 | 5.17 | | 7. " " | 46 | 5.50 | | 8. " " | 47 | 6.92 bright wire | | 1. 3/4 lb. per day | 49 | 8.50 | | 2. " " | 48-1/4 | 8.81 | | 3. " " | Broken by accident. | | 4. " " | 46 | 7.55 | | 5. " " | 46 | 6.41 | | 6. " " | 45-1/2 | 6.62 | | 1. 1/2 lb. per day | 48 | 8.26 | | 2. " " | 50 | 8.42 | | 3. " " | 49 | 7.18 | | 4. " " | 47 | 4.79} | | 5. " " | 46-1/2 | 6.00} bright wires | +--------------------+------------+--------------------+ The American Standard diameters of solid drawn or seamless brass and copper tube are as in the following table. +----------+-----------------+---------------+---------------+ | Outside |Thickness Stubs's| Weight per | Weight per | |diameter. | wire-gauge. | running foot. | running foot. | | | | Brass tubes. | Copper tubes. | +----------+-----------------+---------------+---------------+ | 5/8 | 18 | 3/8 | 3/8 | | 3/4 | 17 | 1/2 | 1/2 | | 13/16 | 17 | 9/16 | 9/16 | | 7/8 | 17 | 5/8 | 5/8 | | 15/16 | 16 | 11/16 | 11/16 | | 1 | 16 | 3/4 | 3/4 | | 1-1/8 | 16 | 7/8 | 7/8 | | 1-1/4 | 12 and 14 | 1-1/4 | 1-1/4 | | 1-3/8 | 12 " 14 | 1-3/8 | 1-3/8 | | 1-1/2 | 12 " 14 | 1-1/2 | 1-6/10 | | 1-5/8 | 12 " 14 | 1-5/8 | 1-7/10 | | 1-3/4 | 12 " 14 | 1-3/4 | 1-8/10 | | 1-13/16 | 12 " 14 | 1-13/16 | 1-9/10 | | 1-7/8 | 12 " 14 | 1-7/8 | 1-15/16 | | 1-15/16 | 12 " 14 | 2 | 2-1/10 | | 2 | 12 " 14 | 2-1/8 | 2-1/4 | | 2-1/8 | 12 " 14 | 2-1/4 | 2-3/8 | | 2-1/4 | 12 " 14 | 2-3/8 | 2-1/3 | | 2-3/8 | 12 " 14 | 2-1/2 | 2-2/3 | | 2-1/2 | 11 " 13 | 2-3/4 | 3 | | 2-5/8 | 11 " 13 | 3 | 3-1/8 | | 2-3/4 | 11 " 13 | 3-1/8 | 3-1/4 | | 2-7/8 | 11 " 13 | 3-1/4 | 3-3/8 | | 3 | 11 " 13 | 3-3/8 | 3-1/2 | | 3-1/8 | 11 " 13 | 3-1/2 | 3-3/4 | | 3-1/4 | 11 " 13 | 3-7/8 | 4-1/8 | | 3-3/8 | 11 " 13 | 4-1/8 | 4-1/4 | | 3-1/2 | 11 " 13 | 4-1/4 | 4-3/8 | | 4 | 11 " 13 | 5 | 5-1/4 | | 4-1/4 | 11 " 13 | 6 | 6-1/2 | | 5 | 10 " 12 | 7 | 8 | | 6 | 10 " 12 | 9 | 10 | +----------+-----------------+---------------+---------------+ CHAPTER XVI.--SHAPING AND PLANING MACHINES. The office of the shaping machine is to dress or cut to shape such surfaces as can be most conveniently cut by a tool moving across the work in a straight line. The positions occupied among machine tools at the present time by shaping and planing machines are not as important as was the case a few years ago, because of the advent of the milling machine, which requires less skill to operate, and produces superior work. All the cutting tools used upon shaping and planing machines have already been described with reference to outside tools for lathe work, and it may be remarked that a great deal of the chucking done on the shaping and planing machine corresponds to face plate chucking in the lathe. Both shaping machines and small planing machines, however, are provided with special chucks and work-holding appliances that are not used in lathe work, and these will be treated of presently. On large planing machines chucks are rarely used, on account of the work being too large to be held in a chuck. Shaping machines are also known as shapers and planing machines as planers. [Illustration: Fig. 1496.] The simplest form of shaping machine, or shaper as it is usually termed in the United States, is that in which a tool-carrying slide is reciprocated across the work, the latter moving at the end of each back stroke so that on the next stroke the tool may be fed to its cut on the work. Fig. 1496 represents a shaper of this kind constructed by Messrs. Hewes and Phillips, of Newark, New Jersey, in which P is a cone pulley receiving motion from a countershaft, and driving a pinion which revolves the gear-wheel Q, whose shaft has journal bearing in the frame of the machine. This shaft drives a bevel pinion gearing with a bevel-wheel in one piece with the eccentric spur-wheel S, which is upon a shaft having at its lower end the bevel-wheel B to operate the work-feeding mechanism. S drives an eccentric gear wheel R, fast upon the upper face of which is a projection E, in which is a [T]-shaped groove to receive and secure a wrist or crank pin which drives a connecting rod secured to the slide A by means of a bolt passing through A, and secured to the same by a nut D. When the gear-wheel R revolves, the connecting rod causes slide A to traverse to and fro endways in a guideway, provided on the top of the frame at X. On the end of this slide is a head carrying a cutting tool T, which, therefore, moves across the work, the latter being held in the vise V, which is fast upon a table W upon a carriage saddle or slider _p_, which is upon a horizontal slide that in turn fits to a slide vertical upon the front of the machine, and may be raised or lowered thereon by means of an elevating screw driven by a pair of mitre-wheels at F. The slider and table W (and therefore the vise and the work) are moved along the horizontal slide to feed the work to the tool cut as follows. A short horizontal shaft (driven by the bevel pinions at B), drives at its outer end a piece C, having a slot to receive a crank pin driving the feed rod N, which operates a pawl K engaging a ratchet wheel which is fast upon the horizontal screw that operates slider _p_. [Illustration: Fig. 1497.] The diameters of the eccentric gear-wheels E and S are equal; hence, C makes a revolution and the cross feed is actuated once for every cutting stroke. The swivel head H is bolted to the end of the slide or ram, as it is sometimes called, A, and is provided with a slide I upon which is a slider J, carrying an apron containing the tool post holding the cutting tool, the construction of this part of the mechanism being more fully shown in Fig. 1497. The eccentric gear-wheels R S are so geared that the motion of the slide A during the cutting stroke (which is in the direction of the arrow) is slower than the return stroke, which on account of being accelerated is termed a quick return. Various mechanisms for obtaining a quick return motion are employed, the object being to increase the number of cutting strokes in a given time, without accelerating the cutting speed of the tool, and some of these mechanisms will be given hereafter. [Illustration: Fig. 1498.] Referring again to the mechanism for carrying the cutting tool and actuating it to regulate the depth of cut in Fig. 1497, G is the end of the slide a to which the swivel head H is bolted by the bolts _a_ _b_. The heads of these bolts pass into [T]-shaped annular grooves in G, so that H may be set to have its slides at any required angle. I is a slider actuated on the slide by means of the vertical feed screw which has journal bearing in the top of H, and passes through a nut provided in I. To I is fastened the apron swivel J, being held by a central bolt not seen in the cut, and also by the bolt at _c_. In J is a slot, which when _c_ is loosened permits J to be swung at an angle. The apron K is pivoted by a taper pin L, which fits into both J and K. During the cutting stroke the apron K beds down upon J, but during the back stroke the tool may lift the apron K swinging upon the pivot L. This prevents the cutting edge of the tool from rubbing against the work during the return stroke. Thus in Fig. 1498 is a piece of work, and it is supposed that a cut is being carried down the vertical face or shoulder at A; by setting the apron swivel at an angle and lifting the tool during the return stroke, its end will move away from the face of the shoulder. The slider I obviously moves in a vertical line upon slides M. [Illustration: Fig. 1499.] To take up the wear of the sliding bar A, various forms of guideways and guides are employed, a common form being shown in Fig. 1499. There are two gibs, one on each side of the bar, and these gibs are set up by screws to adjust the fit. In some cases only one gib is used, and in that event the wear causes the slide to move to one side, but as the wear proceeds exceedingly slowly in consequence of the long bearing surface of the bar in its guides, this is of but little practical moment. On the other hand, when two gibs are used great care must be taken to so adjust the screws that the slide bar is maintained in a line at a right angle to the jaws of the work-holding vice, so that the tool will cut the vertical surfaces or side faces of the work at a right angle to the work surface that is gripped by the vice. To enable the length of stroke of slide A, Fig. 1496, to be varied to suit the length of the work, and thus not lose time by uselessly traversing that slide, E is provided with a [T]-slot as before stated, and the distance of the wrist pin (in this slot) from the centre of wheel E determines the amount of motion imparted to the connecting rod, and therefore to slide A. The wrist pin is set so as to give to A a rather longer stroke than the work requires, so that this tool may pass clear of the work on the forward stroke, and an inch or so past the work on the return stroke, the latter giving time to feed the tool down before it meets the work. The length of the stroke being set, the crank piece E (for its slot and wrist pin correspond to a crank) is, by pulling round the pulley P, brought to the end of a stroke, the connecting rod being in line with slide A. The nut D is then loosened and slide A may then be moved by hand in its slideway until the tool clears the work at the end corresponding to the connecting rod position when nut D is tightened and the stroke is set. [Illustration: Fig. 1500.] Now suppose it is required to shape or surface the faces _f_ and _f´_, the round curve S and the hollow curve C of the piece of work shown held in a vice chuck in Fig. 1500, and during the cutting stroke the slide _a_ will travel in the direction of _n_ in the figure, while during its return stroke it will traverse back in the direction of _i_. The sliding table W in Fig. 1496 would continuously but gradually be fed or moved (so much per tool traverse, and by the feeding mechanism described with reference to Fig. 1501) carrying with it the vice chuck, and therefore the work. When this feeding brought the surface of curve S, Fig. 1500, into contact with the tool, the feed screw handle in figure would be operated by hand so much per feed traverse, thus raising the slider, and therefore the tool, in the direction of _l_, and motion of the work to the right and the left of the tool (by means of the feed handle) would (if the amount of tool lift per tool stroke is properly proportioned to the amount of work feed to the right) cause the tool to cut the work to the required curvature. When the work had traversed until the tool had arrived at the top of curve S, the direction of motion of the feed-screw handle Z in Fig. 1496 must be reversed, the tool being fed down so much per tool traverse (in the direction of _m_) so as to cut out the curves from the top of S to the bottom of _c_, the face _f´_ being shaped by the automatic feed motion only. The feed obviously occurs once for each cutting stroke of the tool and for the vertical motion of the tool, or when the tool is operated by the hand feed-screw handle in Fig. 1496, the handle motion, and therefore the feed should occur at the end of the back stroke and before the tool again meets the work, so as to prevent the cutting edge of the tool from scraping against the work during its back traverse. In this connection it may be remarked that by setting the apron swivel over, as in Fig. 1498, the tool is relieved from rubbing on the back stroke for two reasons, the first having been already explained, and the second being that to whatever amount the tool may spring, bend, or deflect during the cutting stroke (from the pressure of the cut), it will dip into the work surface and cut deeper; hence on the back stroke it will naturally clear the surface, providing that the next cut is not put on until the tool has passed back and is clear of the work. [Illustration: Fig. 1501.] Referring now to the automatic feed of the sliding table W, in Fig. 1496, the principle of its construction may be explained with reference to Fig. 1501, which may be taken to represent a class of such feeding mechanisms. A is a wheel corresponding to the wheel marked M in Fig. 1496, or, it may be an independent wheel in gear with the feed wheel. On the same shaft as A is pivoted an arm B having a slot S at one end to receive a pin to which the feed rod E may connect. F is a disk rotated from the driving mechanism of the shaping machine, and having a [T]-shaped slot G G, in which is secured a pin to actuate the rod E. As F rotates E is vibrated to and fro and the catch C on one stroke falls into the notches or teeth in A and causes it to partly rotate, while on the return stroke of E it lifts over the teeth, leaving A stationary. The amount of motion of B, and therefore the quantity of the feed, may be regulated at either end of E; as, for example, the farther the pin from the centre of G the longer the stroke of E, or the nearer the pin in S is to the centre of B the longer the stroke, but usually this provision is made at one end only of E. To stop the feed motion from actuating, the catch C may be lifted to stand vertically, as shown in dotted lines in position 2, and to actuate the feed traverse in an opposite direction, C may be swung over so as to occupy the position marked 3, and to prevent it moving out of either position in which it may be set a small spring is usually employed. Now suppose that the tool-carrying slide A, Fig. 1496, is traversing forward and the tool will be moving across the work on the cutting stroke, as denoted by the arrow _k_ in Fig. 1502, the line of tool motion for that stroke being as denoted by the line _c_ _a_. At _a_ is the point where the tool will begin its return stroke, and if the work is moved by the feeding mechanism in the direction of arrow _e_, then the line of motion during the return stroke will be in the direction of the dotted line _a_ _b_, and as a result the tool will rub against the side of the cut. [Illustration: Fig. 1502.] It is to obviate the friction this would cause to the tool edge, and the dulling thereto that would ensue, that the pivot pin L for the apron is employed as shown in Fig. 1497, this pin permitting the apron to lift and causing the tool to bear against the cut with only such force as the weight of the apron and of the tool may cause. Now suppose that in Fig. 1503 we have a piece of work whose edge A A stands parallel to the line of forward tool motion, there being no feed either to the tool or the work, and if the tool be set to the corner _f_ its line of motion during a stroke will be represented by the line _f_ _g_. Suppose that on the next stroke the feed motion is put into action and that feeding takes place during the forward stroke, and the amount of the feed per stroke being the distance from _g_ to _h_, then the dotted line from _f_ to _h_ represents the line of cut. On the return stroke the line of tool motion will be from _h_ along the dotted line _h_ _k_, and the tool will rest against the cut as before. Suppose again that the feed is put on during the return stroke, and that _c_ _c´_ represents the line of tool motion during a cutting stroke, and the return stroke will then be along the line from _c´_ to _b_, from _c_ to _b_ representing the amount of feed per stroke; hence, it is made apparent that the tool will rub against the cut whether the feed is put on during the cutting or during the return stroke. Obviously then it would be preferable to feed the work between the period that occurs after the tool has left the work surface on the return stroke and before it meets it again on the next cutting stroke. It is to be observed, however, that by placing the pin actuating the rod E, Fig. 1501, on the other side of the centre of the slot G in F, the motion of E will be reversed with relation to the motion J of the slide; hence, with the work feeding in either direction, the feed may be made to occur during either the cutting or return stroke at will by locating the driving pin on the requisite side of the centre of G. [Illustration: Fig. 1503.] An arrangement by Professor Sweet, whereby the feed may be actuated during the cutting or return stroke (as may be determined in designing the machine), no matter in which direction the work table is being fed, is shown in Fig. 1504. Here there are two gears A and D, and the pawl or catch C may be moved on its pivoted end so as to engage either with A or D to feed in the required direction. [Illustration: Fig. 1504.] Suppose the slide to be on its return stroke in the direction of L, and F be rotated as denoted by the arrow, then the pawl C will be actuating wheel A as denoted by its arrow, but if C be moved over so as to engage D as denoted by the dotted outline, then with the slide moving in the same direction, C will pull D in the direction of arrow K´, and wheel A will be actuated in the opposite direction, thus reversing the direction of the feed while still causing it to actuate on the return stroke. Since the feed wheel A must be in a fixed position with relation to the work table feed screw, and since the height of this table varies to meet the work, it is obvious that as the work table is raised the distance between the centres of A and F in the figure is lessened, or conversely as that table is lowered the distance between those centres is increased; hence, where the work table has much capacity of adjustment for height, means must be provided to adjust the length of rod E to suit the conditions. This may be accomplished by so arranging the construction that the rod may pass through its connection with wheel F, in the figure, or to pass through its connection with B. Fig. 1505 represents a shaper that may be driven either by hand or by belt power. The cone pulley shaft has a pinion that drives the gear-wheel shown, and at the other end of this gear-wheel shaft is a slotted crank carrying a pin that drives a connecting rod that actuates the sliding bar, or ram, as it is sometimes termed. The fly-wheel also affords ready means of moving the ram to any required position when setting the tool or the work. Fig. 1506 represents a shaping machine by the Hewes and Phillips Iron Works, of Newark, N.J. The slide or ram is operated by the Whitworth quick return motion, whose construction will be shown hereafter. The vice sets upon a knee or angle plate fitting to vertical slideways on the cross slide, and may be raised or lowered thereon to suit the height of the work by means of the crank handle shown in front. The vice may be removed and replaced by the supplemental table shown at the foot of the machine. Both the vice and the supplemental table are capable of being swivelled when in position on the machine. The machine is provided with a device for planing circular work, such as sectors, cranks, &c., the cone mandrel shown at the foot of the machine bolting up in place of the angle plate. [Illustration: Fig. 1505.] [Illustration: Fig. 1506.] HOLDING WORK IN THE SHAPER OR PLANER VICE.--The simplest method of holding work in a shaper is by means of a shaper vice, which may be employed to hold almost any shape of work whose size is within the capacity of the chuck. Before describing, however, the various forms of shaper vices, it may be well to discuss points to be considered in its use. The bottom surface _a_ _a_, Fig. 1507, of a planer vice is parallel with the surfaces _d_, _d´_ and as surface _a_ is secured to the upper face of the slider table shown in figure, and this face is parallel to the line of motion of the slide A, and also parallel with the cross slide in that figure, it follows that the face _d_ is also parallel both with the line of motion of slide A and with the surface of the slider table. Parallel work to be held in the vice may therefore be set down upon the surface _d_ (between the jaws), which surface will then form a guide to set the work by. The work-gripping surfaces _b_ and _e_, Fig. 1507, of the jaws are at a right angle to surface _a_, and therefore also to _d_, therefore the upper surface of work that beds fair upon _d_, or beds fair against _b_, will be held parallel to the line of motion X of the tool and the line Z of the feed traverse. Similarly the upper surfaces A, B of the gripping jaws are parallel to _a_ _a_, hence they may be used to set the work true with the line of feed traverse. The sliding jaw, however, must be a sufficiently easy fit to the slideways that guide it to enable it to be moved by the screw that operates it, and as a result it has a tendency to lift upon its guideways so that its face _e_ will not stand parallel to _b_ or at a right angle to _d_. In Fig. 1508, for example, is a side view of a vice holding a piece of work W, the face _f_ of the work being at an angle. As a consequence there is a tendency to lift in the direction of C. If the jaw does lift or spring in this direction it will move the work, so that instead of its lower face bedding down upon face _d_, Fig. 1507, it will lie in the direction of H, Fig. 1508, while its face parallel to _f_, instead of bedding fair against the face of jaw J, will lie as denoted by the line _g_, and as a result the work will not be held fair with either of those faces and the value of faces _b_, _d_ and _e_ in Fig. 1507 is impaired. This lifting of the movable or sliding jaw is prevented in some forms of chuck, to be hereafter described, by bolts passing through which hold it down, but the tendency is nevertheless present, and it is necessary to recognise it in treating of chucking or holding work in such vices. [Illustration: Fig. 1507.] [Illustration: Fig. 1508.] The work gripping face _b_, Fig. 1507, of the fixed jaw, however, is not subject to spring, hence it and the surface _d_ are those by which the work may be set. The work, however, is held by the force of the screw operating the sliding jaw, hence the strain is in the direction of the arrow P in Fig. 1508, which forces it against the face of the fixed jaw. All the pressure that can be exerted to hold work down upon the surface _d_, Fig. 1507, is that due to the weight of the work added to whatever effort in that direction there may be induced by driving the work down by blows upon surface _d_ after the jaws are tightened upon the work. This, however, is not to be relied upon whenever there is any tendency for the work not to bed down fair. It follows, then, that surface _b_ of the work-gripping jaw is that to be most depended upon in setting the work, and that the surface that is to act as a guide at each chucking should be placed against this surface unless there are other considerations that require to be taken into account. [Illustration: Fig. 1509.] For example, suppose we have a thin piece of work, as in Fig. 1509, and the amount of surface bearing against the fixed jaw is so small in comparison to its width between the jaws that _e_ would form no practical guide in setting the work. If then the edges of such a piece of work were shaped first the face or faces may or may not be made at a right angle to them, or _square_ as it is termed. But if the faces were shaped first, then when the work was held by them to have the edges shaped there would be so broad an area of work surface bedding against the jaw surface, that the edges would naturally be shaped square with the faces. In cases, therefore, where the area of bedding surface of the work against the faces of the jaws is too small to form an accurate guide and the work is not thick enough to rest upon the surface _d_, Fig. 1507, it is set true to that surface by a parallel piece. If the work is wide or long enough to require it, two parallel pieces must be used, both being of the same thickness, so that they will keep the work true with the surface _d_. [Illustration: Fig. 1510.] Pieces such as P, Fig. 1510, are also used to set work not requiring to be parallel. Thus in figure are a number of keys placed side by side and set to have their edges shaped, and piece P is inserted not only to lift the narrow ends of the keys up, but also to maintain their lower edges fair one with the other, and thus insure that the keys shall all be made of equal width. They are also serviceable to interpose between the work and the vice jaws when the work has a projection that would receive damage from the jaw pressure. [Illustration: Fig. 1511.] Thus in Fig. 1511 the work W has such a projection and a parallel piece P is inserted to take the jaw pressure. By placing the broadest work surface _g_ against the fixed jaw the work will be held true whether the movable jaw springs or not, because there will be surface _g_ and surface H guiding it. [Illustration: Fig. 1512.] But if the work were reversed, as in Fig. 1512, with the broadest surface against K, then if K sprung in the direction of C, the work would not be shaped true. [Illustration: Fig. 1513.] When the work is very narrow, however, the use of a parallel piece to regulate its height is dispensed with, and the top surface B of the jaw, in Fig. 1513, is used to set the work by. A line is marked on the work surface to set it by and a surface gauge is set upon the face B, its needle point being set to the line in a manner similar to that already explained with reference to chucking work in the lathe. All work should be so set that the tool will traverse across the longest length of the work, as denoted by the tool in Fig. 1502, and the arrow marking its direction of traverse. The general principles governing the use of the shaper vice having been explained, we may now select some examples in its use. Fig. 1514 represents a simple rectangular piece, and in order to have the tool marks run lengthwise of each surface (which is, as already stated the most expeditious) they must be in the direction of the respective arrows. In a piece of such relative proportions there would be little choice as to the order in which the surfaces should be shaped, but whatever surface be operated on first, that at a right angle to it should be shaped second; thus, if _a_ be first, either _b_ or _d_ should be second, for the following reasons. [Illustration: Fig. 1514.] All the surfaces have sufficient area to enable them to serve as guides in setting the work, hence the object is to utilize them as much as possible for that purpose. Now, suppose that surface _a_ has been trued first, and if _c_ be the next one, then the bedding of surface _a_ upon the vice surface or the parallel pieces must be depended upon to set _a_ true while truing _c_. Now the surfaces _b_ and _d_ may both, or at least one of them, may be untrue enough to cause the work to tilt or cant over, so that _a_ will not bed fair, and _c_ will then not be made parallel to _a_. It will be preferable then to shape _a_ first and at the second chucking to set _a_ against the stationary jaw of the vice, so that it may be held true. [Illustration: Fig. 1515.] The sliding jaw will in this case be against face _c_, and if that face is out of true enough to cant the work so that _a_ will not bed fair, then a narrow parallel piece may be inserted between the sliding jaw and the work, which will cause _a_ to bed fair. The third face should be face _c_, in which case face _a_ will rest on one surface and face _b_ will be against the fixed jaw, and there will be two surfaces to guide the work true while _c_ is being trued. In this case also, however, it is better to use a parallel piece P, Fig. 1515, between the work and the sliding jaw, so as to insure that the work shall bed fair against the fixed jaw; and if necessary to bring up the top surface above the jaws, a second parallel piece P´ should be used. [Illustration: Fig. 1516.] Suppose now that we have a connecting rod key to shape, and it is to be considered whether the faces or the edges shall be shaped first. Now if the side faces are out of parallel it will take more filing to correct them than it will to correct the same degree of error in the edges; hence it is obviously desirable to proceed with a view to make all surfaces true, but more especially the side faces. As the set of the key while shaping these faces is most influenced by the manner in which the fixed jaw surface meets the work, and as an edge will be the surface to meet the fixed jaw faces when the side faces are shaped, it will be best to dress one edge first, setting the key or keys, as the case may be, as was shown in Fig. 1510, so as to cut them with the tool operating lengthways of the key; one edge being finished, then one face of each key must be shaped, the key being set for this purpose with the surfaced edge against the fixed jaw. As the width of the key is taper, either a chuck with a taper attachment that will permit the sliding jaw to conform itself to the taper of the key must be used (vices having this construction being specially made for taper work as will be shown hereafter), or else the key must be held as in Fig. 1516, in which K represents the key with its trued edge against the fixed jaw, at P is a piece put in to compensate for the taper of the key, and to cause the other edge to bed firmly and fairly against the fixed jaw. The first side face being trued, it should be placed against the fixed jaw while the other edge is shaped. For the remaining side face we shall then be able to set the key with a trued edge against the fixed jaw, and a true face resting upon a parallel piece, while the other edge will be true for the piece P, Fig. 1516, to press against, and all the elements will be in favor of setting the key so that the sides will be parallel one to the other, and the edges square with the faces. In putting in the piece P, Fig. 1516, the key should be gripped so lightly that it will about bear its own weight; piece P may then be pushed firmly in with the fingers, and the vice tightened up. [Illustration: Fig. 1517.] If there are two keys the edges and one face may be trued up as just described, and both keys K, Fig. 1517, chucked at once by inverting their tapers as shown in figure. But in this case unless the edges are quite true they may cause the keys not to bed fair on the underneath face, and the faces therefore to be out of parallel on either or both of the keys. If there are a number of keys to be cut to the same thickness it may be done as follows:-- [Illustration: Fig. 1518.] Plane or shape first one edge of all the keys; then plane up one face, chucking them with one planed edge against each vice jaw, and put little blocks (A, B, C, D, Fig. 1518) between the rough edges; then turn them over, chuck them the same way and plane the other face, resting them on parallel pieces; then plane the other edges last. In place of the small blocks A, B, C, D, a strip of lead, pasteboard, or wood, or for very thin work a piece of lead wire, may be used. [Illustration: Fig. 1519.] [Illustration: Fig. 1520.] Cylindrical work may be held in a vice chuck, providing that the top of the vice jaws is equal in height to the centre of the work, as in Fig. 1519, a parallel piece being used to set the work true. When, however, the work is to be shaped at one end only, it is preferable to hold it as in Fig. 1520, letting its end project out from the side of the chuck. In some vices the jaws are wider than the body of the chuck, so that cylindrical work may be held vertical, as in Fig. 1521, when the end is to be operated upon. Fig. 1522 represents a simple form of shaper or planer chuck, such chucks being used upon small planing machines as well as upon shaping machines. [Illustration: Fig. 1521.] [Illustration: Fig. 1522.] The base A is bolted to the work table, and is in one piece with the fixed jaw B. The movable jaw C is set up to meet the work by hand, and being free to move upon A may be used for either taper or parallel work. To fasten C upon the work, three screws threaded through F abut against the end of C; F being secured to the upper surface of A by a key or slip, which fits into a groove in F, and projects down into such of the grooves in the upper surface of A as may best suit the width of work to be held in the vice; C is held down by the bolts and nuts at G. The operation of securing work in such a chuck is as follows:--The screws both at F and at G being loosened, and jaw C moved up to meet the work and hold it against the fixed jaw B, then nuts G should be set up lightly so that the sliding jaw will be set up under a slight pressure, screws F may then be set up and finally nuts G tightened. [Illustration: Fig. 1523.] This is necessary for the following reasons:--The work must, in most cases, project above the level of the jaws so that the tool may travel clear across it; hence, the strain due to holding the work is above the level of the three screws, and the tendency, therefore, is to turn the jaw C upwards, and this tendency the screws G resist. A similar chuck mounted upon a circular base so that it may be swivelled without moving the base on the work table is shown in Fig. 1523. The capacity to swivel the upper part of the chuck without requiring the base of the chuck to be moved upon the table is a great convenience in many cases. [Illustration: Fig. 1524.] Fig. 1524 represents an English chuck in which the fixed jaw is composed of two parts, A which is solid with the base G, and D which is pivoted to A at F. The movable jaw also consists of two parts, B which carries the nut for the screw that operates B, and C which is pivoted to B at E. The two pivots E, F being above the surface of the gripping jaws C, D, causes them to force down upon the surface of G as the screw is tightened, the work, if thin, being rested, as in the case of the chuck shown in Fig. 1523, upon parallel pieces. [Illustration: Fig. 1525.] Fig. 1525 represents a chuck made by W. A. Harris, of Providence. The jaws in this case carry two pivoted wings A, B, between the ends of which the work C is held, and the pivots being above the level of the work the tendency is here again to force the work down into the chuck, the strain being in the direction denoted by the arrows. Here the work rests on four pins which are threaded in the collars H, so that by rotating the pins they will stand at different heights to suit different thicknesses of work, or they may be set to plane tapers by adjusting their height to suit the amount of taper required. The spiral springs simply support the pins, but as the jaws close the pins lower until the washer nuts H meet the surface of recess I. [Illustration: Fig. 1526.] [Illustration: Fig. 1527.] Figs. 1526 and 1527 represent Thomas's patent vice, which possesses some excellent conveniences and features. In Fig. 1526 it is shown without, and in Fig. 1527 with a swivel motion. The arrangement of the jaws upon the base in Fig. 1526 is similar to that of the chuck shown in Fig. 1522, but instead of there being a key to secure the piece F to the base, there is provided on each side of the base a row of ratchet teeth, and there is within F a circular piece G (in Fig. 1528) which is serrated to engage the ratchet teeth. This piece may be lifted clear of the ratchet teeth by means of the pin at H, and then the piece F may be moved freely by hand backwards or forwards upon the base and swung at any required angle, as in Fig. 1528, or set parallel as in Fig. 1527; F becoming locked, so far as its backward motion is concerned, so soon as H is released and G engages with the ratchet teeth on the base. But F may be pushed forward toward the fixed jaw without lifting H, hence the adjustment of the sliding jaw to the work may be made instantaneously without requiring any moving or setting of locking keys or other devices. [Illustration: Fig. 1528.] It is obvious that it is the capability of G to rotate in their sockets that enables F to be set at an angle and still have the teeth of G engage properly with those on the base plate. [Illustration: Fig. 1529.] [Illustration: Fig. 1530.] The mechanism for swivelling the upper part or body upon the base and for locking it in its adjusted position is shown in Figs. 1529 and 1530. The body D is provided with an annular ring fitting into the bore of the base, which is coned at Q. The half-circular disks R fit this cone and are held to the body of the chuck by four bolts N, which are adjusted to admit disks R to move without undue friction. K is a key having on it the nut V, which receives a screw whose squared end is shown at S. By operating S in one direction key K expands disks R, causing them to firmly grip the base at the bevel Q, hence the base and the body are locked together. By operating S to unscrew in the nut V, K is moved in the opposite direction and R, R release their grip at Q and the body D may be swung round in any position, carrying with it all the mechanism except base P. To enable the body to be readily moved a quarter revolution, or in other words, moved to a right angle, there is provided a taper pin, the base having holes so situated that the body will have been moved a quarter revolution when the pin having been removed from one hole in the base is seated firmly home in the other. Referring again to Fig. 1526, there are shown one pair of parallel pieces marked respectively A, having bevelled edges, and another pair marked respectively B. Both pairs are provided with a small rib fitting into a groove in the jaws of the chuck, as shown in the figure. [Illustration: Fig. 1531.] These ribs and grooves are so arranged that the upper pair (A, A) may be used in the place of the lower ones, and the uses of these pieces are as follows:-- Suppose a very thin piece of work is to be planed, and in order to plane it parallel, which is ordinarily a difficult matter, it must bed fair down upon the face of the vice, which it is caused to do when chucked as in Fig. 1531, in which the work is shown laid flat upon the face of the vice, and gripped at its edges by the pieces A, A. [Illustration: Fig. 1532.] These pieces, it may be noted, do not bed fair against the gripping faces of the jaws, but are a trifle open at the bottom as at _e_, _e_, hence when they are pressed against the work they cant over slightly and press the work down upon the chuck face causing it to bed fair. Furthermore, the work is supported beneath its whole surface, and has, therefore, less tendency to spring or bend from the holding pressure; and as a result of these two elements much thinner work can be planed true and parallel than is possible when the work is lifted up and supported upon separate parallel pieces, because in the latter case the work, being unsupported between the parallel pieces, has more liberty to bend from the pressure due to the tool cut, as well as from the holding pressure. [Illustration: Fig. 1533.] Fig. 1532 shows the chuck holding a bracket, having a projection or eye. The work rests on pieces B, B, and is gripped by pieces A, A. It will be observed that A, A being beveled enables the cut to be carried clear across the work. Fig. 1533 represents the chuck in use for holding a piece of shafting S to cut a keyway or spline in it. In this case a bevelled piece J is employed, its bevelled face holding the work down upon the chuck face. [Illustration: Fig. 1534.] Fig. 1534 represents a chuck termed shaper centres, because the work is held between centres as in the case of lathe work. The live spindle is carried in and is capable of motion in a sleeve, the latter having upon it a worm-wheel, operated by a worm, so that it can be moved through any given part of a circle, and has index holes upon its face to determine when the wheel has been moved to the required amount. For work that is too large to be operated upon in the class of shaping machine shown in Fig. 1506, and yet can be more conveniently shaped than planed, a class of machine is employed in which the tool-carrying slide is fed to the work, which is chucked to a fixed table or to two tables. [Illustration: Fig. 1535.] Fig. 1535 represents a machine of this class. The tool-carrying slide A, in this case, operates in guideways provided in B, the latter being fitted to a slideway running the full length of the top of the frame M. The base slider B is fed along the bed by means of a screw operating in a nut on the under side of B, this screw being operated once during each stroke of the tool-carrying slide A, by means of a pawl feeding arrangement at F, which corresponds to the feeding device shown in Fig. 1501. Two vertical frame pieces D, D are bolted against the front face of the machine, being adjustable along any part of the bed or frame length, because their holding bolts have heads capable of being moved (with the frame pieces D) along the two [T]-shaped grooves shown, their [T]-shape being visible at the end of the frame or bed. To frames D are bolted the work-holding tables E, E, the bolts securing them passing into vertical [T]-grooves in D, so that E may be adjusted at such height upon D as may be found necessary to bring the work within proper range of the cutting tool. The work tables E, E are raised or lowered upon D by means of a vertical screw, which is operated by the handle H, this part of the mechanism accomplishing the same end as the elevating mechanism shown in Fig. 1496. The swivel head J is here provided at its top with a segment of a worm-wheel which may be actuated to swivel that head by the worm G. The swivel head may thus be operated upon its pivot, causing the tool point to describe an arc of a circle of which the pivot is the centre. To steady the swivel head when thus actuated, there is behind the worm segment a [V]-slide that is an arc, whose centre is also the centre of the pivot. The tool-carrying slide A is operated as follows: The driving pulley P rotates a shaft lying horizontal at the back of the machine. Along this shaft there is cut a featherway or spline driving a pinion which operates a link mechanism such as described with reference to Fig. 1550. The means of adjusting the distance the head of A shall stand out from B, are similar to that described for Fig. 1496, a bolt passing through A, and in both cases attaching to a connecting rod or bar. At K is a cone mandrel such as has been described with reference to lathe work upon which is chucked a cross-head C. By means of suitable mechanism, this mandrel is rotated to feed the circular circumference of the cross-head jaws to the cut, the slider B remaining in a fixed position upon the bed M. To support the outer end of the cone mandrel a beam L is bolted to the two tables E, E. On L is a slideway for the piece P. At S is a lug upon E through which threads a screw R, which adjusts the height of the piece P, while Q is a bolt for securing P in its adjusted position. This cone mandrel and support is merely an attachment to be put on the machine as occasion may require. Fig. 1536 represents a shaping machine by the Pratt and Whitney Company. In this machine a single sliding head is used and the work remains stationary as in the case of the machine shown in Fig. 1535. The vice is here mounted on a slide which enables the work to be finely adjusted beneath the sliding bar independently of that bar, which is provided with a Whitworth quick-return motion. As the tool-carrying slide of a shaping machine leaves its guideways during each stroke, the tool is less rigidly guided as the length of slide stroke is increased, and on this account its use is limited to work that does not require a greater tool stroke than about 18 inches, and in small machines not to exceed 12 inches. The capacity of the machine, however, is obviously greatest when the length of the work is parallel to the line of motion of the feed traverse. Work whose dimension is within the limit of capacity of the shaper can, however, be more expeditiously shaped than planed because the speed of the cutting tool can be varied to suit the nature of the work, by reason of the machine having a cone pulley, whereas in a planing machine the cutting speed of the tool is the same for all sizes of work, and all kinds of metal. In shaping machines such as shown in Fig. 1537, or in similar machines in which the work table is capable of being traversed instead of the head, the efficiency of the work-holding table and of the chucking devices may be greatly increased by constructing the table so that it will swivel, as in Fig. 1538, which may be done by means of the employment of Thomas's swivelling device in Fig. 1530. By this means the ends of the work may be operated upon without removing it from the chuck. Or the work may be shaped taper at one part and parallel at another without unchucking it. Fig. 1539 shows a circular table swivelled by the same device, sitting upon a work table also swivelled. [Illustration: Fig. 1540.] Fig. 1540 represents a general view of a shaping machine having the motion corresponding in effect to a planing machine, the object being to give a uniform rate of speed to the tool throughout, both on its cutting and return stroke. The feed always takes place at the end of the return stroke, so as to preserve the edge of the tool, and the length of the stroke may be varied, without stopping the machine, by simply adjusting the tappets or dogs, the range of stroke being variable from 1/4 inch to 20 inches, while the return stroke is 40 per cent. quicker than the cutting one. There are two different rates of cutting speed, one for steel and the other for the softer metals. [Illustration: Fig. 1541.] The ram or bar is provided with a rack (Z, Fig. 1545) which engages with a pinion S, Fig. 1541, H being the driving shaft driven by the belt cones A and B. These two cones are driven by separate belts, but from the same counter-shaft, one being an open and the other a crossed belt. The open belt drives either the largest step of pulley B, giving a cutting speed suitable for steel, or the smaller step, giving a cutting speed for softer metals, as cast iron, &c. The crossed belt drives, in either case, the pulley A for the quick-return stroke, and this pulley revolve upon a sleeve or hub C, which revolves upon the shaft H. The sleeve or hub C is in one piece with a pulley C, whose diameter is such as to leave an annular opening between its face and the bore of the largest step of cone pulley B, and pulley A is fast to the hub or sleeve C. It will be seen that as the driving belts from the counter-shaft are one open and one crossed, therefore pulley A runs constantly in one direction, while pulley B runs constantly in the other, so that the direction of motion of the driving shaft H depends upon whether it is locked to pulley A or to pulley B. [Illustration: Fig. 1542.] [Illustration: _VOL. I._ =SHAPING MACHINES AND TABLE-SWIVELING DEVICES.= _PLATE XVI._ Fig. 1536. Fig. 1537. Fig. 1538. Fig. 1539.] In the annular space left between the face of pulley C and the cone B is a steel band G, Fig. 1542, forming within a fraction a complete circle, and lined inside and out with leather, and this band is brought, by alternately expanding and contracting it, into contact with either the bore of the largest cone step of B or with the outside face of pulley C. The ends of this band are pivoted upon two pins F, which are fast in two arms E and D, in Fig. 1542. Arm E is fastened to the driving shaft H, and its hub has two roller studs K, Fig. 1541, these being diametrically opposite on the said hub. The hub of arm D is a working fit upon the hub of E, and has two slots to admit the above rollers. Hub D is also provided with two studs and rollers placed midway between the studs K. These latter rollers project into the spiral slots K´ of the ring in Fig. 1543, this ring enveloping the hub of D and being enveloped by the sleeve M, which contains two spiral grooves diametrically opposite, and lying in an opposite direction to grooves K´, Fig. 1543. Sleeve M is prevented from revolving by rollers on the studs O, which are screwed into the bearing bush R, and carry rollers projecting into the slots in M. [Illustration: Fig. 1543.] It is evident that if the ring L, Fig. 1543, is moved endways with M, then the arms E, D, together with the band G, will be expanded or contracted according to the direction of motion of the ring, because the motion of M, by means of its spiral grooves, gives a certain amount of rotary motion to the ring L, and the spiral grooves in the ring give a certain amount of rotary motion to the arms D and E, Fig. 1542. When this rotary motion is in one direction the band is expanded; while when it is reversed it is contracted, and the direction of motion of shaft H is reversed. [Illustration: Fig. 1544.] [Illustration: Fig. 1545.] The outer sleeve M carries the rod T, Figs. 1544 and 1545, which is connected to the lever U, the upper arm of which is operated by the tappets or dogs X on the ram or sliding bar, and it is obvious that when U is vibrated sleeve M is operated in a corresponding direction, and the ring L also is moved endwise in a corresponding direction, actuating the band as before described, the direction of motion being governed, therefore, by the direction in which U is moved by the tappets or dogs. A certain degree of friction is opposed to the motion of lever U in order to keep it steady, the construction being shown in Fig. 1546, where it is seen that there is on each side of its nut a leather washer, giving a certain amount of elasticity to the pressure of the nut holding it in place on the shaft U. [Illustration: Fig. 1546.] The mechanism for actuating the feed at the end of the return stroke only, is shown in Fig. 1547. The shaft V (which is also seen in a dotted circle in Fig. 1545) carries a flange _c_, on each side of which is a leather disk, so that the pressure of the bolts which secure _b_ to the sleeve _a_ causes _c_ to revolve under friction, unless sleeve _a_, slotted bar _b_, and flange _c_ all revolve together, or, in other words, _c_ revolves under friction when it revolves within _a_ _b_. [Illustration: Fig. 1547.] [Illustration: Fig. 1548.] Fig. 1548 is an end view of Fig. 1547. [Illustration: Fig. 1549.] Fig. 1549 gives a cross-sectional view of the shaft sleeve, &c. The sleeve _a_ is provided with two pins _i_, _i_, and a pin _k_ is fast in the frame of the machine, and it is seen that _a_ and V may revolve together in either direction until such time as one of the pins _i_ meets the stationary pin _k_, whereupon the further revolving of _a_ will be arrested and V will revolve within _a_, and as flange _c_, Fig. 1547, revolves with V, it will do so under the friction of the leather washers. The pins _i_ and the pin _k_ are so located that _a_ can have motion only when the ram or sliding-bar is at the end of the return stroke, and the feed-rod _f_, being connected to _b_, is therefore actuated at the same time. Among the various mechanisms employed to give a quick return to the tool-carrying slide of shaping machines, those most frequently employed are a simple crank, a vibrating link, and the Whitworth quick-return motion, the latter being the most general one. The principle of action when a vibrating link is employed may be understood from Fig. 1550, in which P is a pinion driven by the cone pulley and imparting motion to D. At L is a link pivoted at C. At A is a link block or die capable of sliding in the slot or opening in the link and a working fit upon a pin which is fast in the wheel D. As D rotates the link block slides in the slot and the link is caused to travel as denoted by the dotted lines. R is a rod connecting the tool-carrying slide S to the upper end of link L, and therefore causing it to reciprocate with L. But S being guided by its slide in the guideway traverses in a straight line. [Illustration: Fig. 1550.] Since the rotation of P and D is uniform, the vibrations of the link L will vary in velocity, because while the link block is working in the lower half of the link slot it will be nearer to the centre of motion C of the link, and the upper end of C will move proportionately faster. The arrangement is such that during this time the tool-carrying slide is moved on its return stroke, the cutting stroke being made while the link block is traversing the upper half of the slot, or in other words, during the period in which the crank pin in A is above the horizontal centre of wheel D. Now suppose the arrangement of the parts is such that the front of the machine or the cutting tool end of the slide is at the end K of S, then S will be pushed to its cut by the rod R at an angle which will tend to lift S in the slideways. But suppose the direction of rotation of wheel D instead of being as denoted by the arrow at D be as denoted by the arrow at E, then S will be on its back stroke, the front of the machine being at J. In this case rod R will pull S to the cut, and S will, from the angularity of R, be pulled down upon the bed of the slideway guiding it, and will therefore be more rigidly held and less subject to spring, because the tendency to lift is resisted on one side by the adjustable gib only, and on the other by the projecting V, whereas the tendency to be pulled downwards is resisted by the strength of the frame of the machine. Furthermore, as the pressure on the cutting tool is below the level of the tool-carrying slide it tends to force that slide down upon the slideway, and it will therefore be more rigidly and steadily guided when the force moving the slide and the tool pressure both act in the same direction. To vary the length of stroke of S pin A is so attached to wheel D that it may be adjusted in its distance from the centre of D. [Illustration: Fig. 1551.] The Whitworth quick-return motion is represented in Fig. 1551. At P is the pinion receiving motion from the cone pulley or driving pulley of the machine and imparting motion to the gear-wheel G, whose bearing is denoted by the dotted circle B. Through B passes a shaft C, which is eccentric to B and carries at its end a piece A in which is a slot to receive the pin X, which drives rod R whose end Z is attached to the ram of the machine. At D is a pin fast in gear-wheel G and passing into a slot in A. Taking the position the parts occupy in the figures, and it is seen that the axis of B is the centre of motion of G and is the fulcrum from which the pin D is driven, the power being delivered at X. The path of motion of the driving pin D is denoted by the dotted circle H´, and it is apparent that as it moves from the position shown in the figure it recedes from the axis of C, and as the motion of G is uniform in velocity therefore D will move A faster while moving below the line M than it will while moving above it, thus giving a quick return, because the cutting stroke of the ram occurs while D is above the line M and the return stroke occurs while D is below M. In some constructions the pin X and pin D work in opposite ends of the piece A, as shown in Fig. 1552. This, however, is an undesirable construction because the shaft C becomes the fulcrum, and as the power and resistance are on opposite ends of the lever A, the wheel G is therefore forced against its bearing, and this induces unnecessary friction and wear. We may now consider the tool motion given by other kinds of slide operating mechanism. In Fig. 1553 is a diagram of the tool motion given when the slide is operated by a simple crank C, the thickened line R representing the rod actuating the slide and line on the line of motion of the cutting tool. The circle H denotes the path of revolution of the crank pin, and the black dots 1, 2, 3, 4, &c., equidistant positions of the crank pin. [Illustration: Fig. 1552.] Line _m_ represents the path of motion of the cutting tool. If a pair of compasses be set to the full length of the thick line R, that is from the centre of the crank pin to end B of line R, and these compasses be then applied to the centre of crank pin position 1, and to the line _m_, they will meet _m_ at a point denoted by line _a_, which will, therefore, represent the position of the tool point when the crank pin was in position 1. To find how far the tool point is moved while the crank pin moves from position 1 to position 2, we place the compass point on the centre of crank pin position 2 and mark line _b_. For crank position 3 we have by the same process line _c_, and so on, the twelve lines from _a_ to _l_ representing crank positions from 1 to 12. Now let it be noted that since the path of the crank pin is a circle, the tool point will on the backward stroke occupy the same position when the crank pin is at corresponding positions on the forward and backward strokes. For example, when the crank pin is in position 7 the tool point will be at point _g_ on the forward stroke, and when the crank pin is in position 17 the tool will be at point _g_ on the backward stroke, as will be found by trial with the compasses; and it follows that the lines _a_, _b_, _c_, &c., for the forward stroke will also serve for the backward one, which enables us to keep the engraving clear, by marking the first seven positions on one side of line _m_, and the remaining five on the other side of _m_, as has been done in the figure. [Illustration: Fig. 1553.] Obviously the distances apart of the lines _a_, _b_, _c_, _d_, &c., represent the amount of tool motion during equal periods of time, because the motion of the crank pin being uniform it will move from position 1 to position 2 in the same time as it moves from position 2 to position 3, and it follows that the cutting speed of the tool varies at every instant in its path across the work, and also that since the crank pin operates during a full one-half of its revolution to push the tool forward, and during a full one-half to pull it backward, therefore the speed of the two strokes are equal. [Illustration: Fig. 1554.] We may now plot out the motion of the link quick return that was shown in Fig. 1550, the dotted circle H´, in Fig. 1554, representing the path of the pin A, and the arc H representing the line of motion of the upper end of link L, and lines N, O, its centre line at the extreme ends of its vibrating motion. In Fig. 1554 the letters of reference refer to the same parts as those in Fig. 1550. We divide the circle H´ of pin motion into twenty-four equidistant parts marked by dots, and through these we draw lines radiating from centre C and cutting arc H, obtaining on the arc H the various positions for end Z of rod R, these positions being marked respectively 1, 2, 3, 4, &c., up to 24. With a pair of compasses set to the length of rod R from 1 on H, as a centre, we mark on the line of motion of the slide line _a_, which shows where the other end of the rod R will be (or, in other words, it shows the position of bolt B in Fig. 1550), when the centre of A, Fig. 1550, is in position 1, Fig. 1554. From 2 on arc H, we mark with the compasses line _b_ on line M, showing that while the pin moved from 1 to 2, the rod R would move slide S, Fig. 1550, from _a_ to _b_, in Fig. 1554. From 3 we mark _c_, and so on, all these marks being above the horizontal line M, representing the line of motion, and being for the forward stroke. For the backward stroke we draw the dotted line from position 17 up to arc H, and with the compasses at 17 mark a line beneath the line M of motion, pursuing the same course for all the other pin positions, as 18, 19, &c., until the pin arrives again at position 24, and the link at O, and has made a full revolution, and we shall have the motion of the forward stroke above and that of the backward one below the line of motion of the slide. On comparing this with the crank and with the Whitworth motion hereafter described, we find that the cutting speed is much more uniform than either of them, the irregularity of motion occurring mainly at the two ends of the stroke. In Fig. 1555 we have the motion of the Whitworth quick return described in Fig. 1551, H´ representing the path of motion of the driving-pin D about the centre of B, and H´ the path of motion of X about the centre C, these two centres corresponding to the centres of B and C respectively in Fig. 1551. Let the line M correspond to the line of motion M in Fig. 1551. Now, since pin D, Fig. 1551, drives, and since its speed of revolution is uniform, we divide its circle of motion H´ into twenty-four equal divisions, and by drawing lines radiating from centre B, and passing through the lines of division on H´, we get on circle H twenty-four positions for the pin X in Fig. 1551. Then setting the compasses to the length of the rod (R, Fig. 1551), we mark from position 1 on circle H as a centre, line _a_; from position 2 on H we mark line _b_, and so on for the whole twenty-four positions on circle H, obtaining from _a_ to _n_ for the forward, and from _n_ to _y_ for the motion during the backward stroke. Suppose, now, that the mechanism remaining precisely the same as before, the line M of motion be in a line with the centres C, B, instead of at a right angle to it, as it is in Fig. 1551, and the motion under this new condition will be as in Fig. 1556, the process for finding the amount of motion along M from the motion around H being precisely as before. [Illustration: Fig. 1555.] [Illustration: Fig. 1556.] The iron planing machine, or iron planer as it is termed in the United States, is employed to plane such surfaces as may be operated upon by traversing a work table back and forth in a straight line beneath the cutting tool. It consists essentially of a frame or bed A, Fig. 1557, provided on its upper surface with guideways, on which a work carrying table T may be moved by suitable mechanism back and forth in a straight line. This frame or bed carries two upright frames or stanchions B, which support a cross-bar or slide C, to which is fitted a head which carries the cutting tool. To enable the setting of the tool at such a height from the table as the height of the work may require, the cross slide C may be raised higher upon the uprights B by means of the bevel gears F, G, H, and T, the latter being on a shaft at the top of the machine, and operating the former, which are on vertical screws N, which pass down through nuts that are fast upon the cross slide C. To secure C at its adjusted height, the uprights are provided with [T]-shaped slots H H, and bolts pass through C, their heads being in the [T]-grooves, and their nuts exposed so that a wrench may be applied to them. The faces of the cross slide C are parallel one to the other, and stand at a right angle to the [V]-guideways on which the work table (or platen as it is sometimes termed) slides; hence the cross slide will, if the table is planed true or parallel with this cross slide, be parallel with the table at whatever height above the table it is set, providing that the elevating screws, when operated, lift each end of C equally. The construction of the head D corresponds to that of the head shown in Figs. 1497 and 1498 for a shaper, except that in this case the swivel head is secured to a saddle that slides along C, being provided with a nut operated by a feed screw J, which moves D along C. The mechanism for operating the work table or platen T is as follows:--P P´ are two loose pulleys and P´´ is a driving pulley fast on the same shaft. This shaft drives, within the casing at Q, a worm operating a worm-wheel, which actuates inside the frame A and beneath the work table a train of gears, the last of which gears with a rack, provided on the underneath side of the table. The revolutions of this last wheel obviously cause the work table to slide back and forth while resting on the [V]-guideways provided on top of the frame A, the direction of table motion being governed by the direction in which the wheel revolves. This direction is periodically reversed as follows:--The pulley P is driven by a crossed belt, while pulley P´ is driven by an open or uncrossed one, hence the direction of revolution of the driving pulley P´´ will be in one direction if the belt is moved from P to P´´, and in the other if the belt is moved from P´ to P´´. Mechanism is provided whereby first one and then the other of these belts is moved so as to pass over upon P´´ and drive it, the construction being as follows:-- To the edge of the work table there is fixed a stop R, which as the table traverses to the right meets and moves a lever arm S, which through the medium of a second lever operates the rod X, which operates a lever _u_, which has a slot through which one of the driving belts passes. The lever _u_ operates a second lever _w_ on the other side of the pulleys, and this lever also has a slot through which the other driving belt passes. When the stop R moves the lever arm S levers _u_ and _w_ therefore move their respective belts, one moving from the tight pulley P´´ to a loose one as P, and the other moving its belt from the loose pulley as P´ to the tight one P´´, and as the directions of belt motions are opposite the direction of revolution of P´´ is reversed by the change of belt operating it. There are two of the stops R, one on each side of the lever S, hence one of these stops moves the lever S from left to right and the other from right to left. Suppose, then, that the table is moving from right to left, which is its cutting stroke, and the driving belt will be on the pulley P´´ while the other belt will be on pulley P. Then as the stop R moves S and operates X the arm _u_ will move its belt from P´´ to P´, and arm _w_ will move its belt from P to P´´, reversing the direction of motion of P´´, and therefore causing the table T to move from left to right, which it will continue to do until the other stop corresponding to R meets S and moves it from right to left, when the belts will be shifted back again. The stroke of the table, therefore, is determined by the distance apart of the stops R, and these may be adjusted as follows:-- They are carried by bolts whose heads fit in a dovetail groove Z provided along the edge of the table, and by loosening a set screw may therefore be moved to any required location along the bed. To give the table a quick return so that less time may be occupied for the non-cutting stroke, all that is necessary is to make the countershaft pulley that operates during the back traverse of larger diameter than that which drives during the cutting traverse of the table. In order that one belt may have passed completely off the driving pulley P´´ before the other moves on it the lever motions of _u_ and _w_ are so arranged that when the belt is moving from P´´ to P lever _u_ moves in advance of lever _w_, while when the other belt is being moved from P´´ to P´ lever _w_ moves in advance of lever _u_. To enable the work table to remain at rest, one driving belt must be upon P and the other upon P´, which is the case when the lever arm S is in mid position, and to enable it to be moved to this position it is provided with a handle K forming part of lever S. To cause the tool to be fed to its cut before it meets the cut and thus prevent it from rubbing against the side of the cut, as was described with reference to Fig. 1503, the feed takes place when the table motion is reversed from the back or return stroke to the cutting or forward stroke by the following mechanism:-- [Illustration: Fig. 1557.] At _a_ is a rack that is operated simultaneously with S and by the same stop R. This rack operates a pinion _b_, which rotates the slotted piece _c_, in which is a block that operates the vertical rod _d_, which is attached to a segmental rack _e_, which in turn operates a pinion which may be placed either upon the cross-feed screw J, or upon the rod above it; the latter operates the vertical feed of the tool through mechanism within the head D and not therefore shown in the engraving. Thus the self-acting tool feed may take place vertically or across the work table at will by simply placing the pinion upon the cross-feed screw or upon the feed rod, as the case may be. [Illustration: Fig. 1558.] Fig. 1558 represents a planer by David W. Pond, of Worcester, Massachusetts, in which the rod _x_ is connected direct from S to a pivoted piece _y_ in which is a cam-shaped slot through which pass pins from the belt-moving arms _u_ and W. The shape of the slot in _y_ is such as to move the belt-moving arms one in advance of the other, as described with reference to Fig. 1566. The feed motions are here operated by a disk C, which is actuated one-half a revolution when the work table is reversed. This disk is provided on its face with a slide-way in which is a sliding block that may be moved to or from the centre of C by the screw shown, thus varying at will the amount of stroke imparted to the rod which moves the rack by means of which the feed is actuated through the medium of the gear-wheels at _f_. The handle _g_ is for operating the feed screw when the self-acting feed is thrown out of operation, which is done by means of a catch corresponding in its action to the catch shown in Fig. 1501. S and S´ are in one piece, S´ being to move the two driving belts on to the loose pulleys so as to stop the work table from traversing. The size of a planer is designated from the size of work it will plane, and this is determined by the greatest height the tool can be raised above the planer table, the width between the stanchions, and the length of table motion that can be utilized while the tool is cutting; which length is less than the full length of table stroke, because in the first place it is undesirable that the rack should pass so far over the driving wheel or pinion that any of the teeth disengage, and, furthermore, a certain amount of table motion is necessary to reverse after the work has passed the tool at the end of each stroke. Fig. 1559 represents a method employed in some English planing machines to drive the work table and to give it a quick return motion. In this design but one belt is used, being shifted from pulley A, which operates the table for the cutting stroke, to pulley J, which actuates the table for the return stroke. The middle pulley K is loose upon shaft B, as is also pulley J, which is in one piece with pinion J´. Motion from A is conveyed through shaft B and through gear C, D, E to F, and is reduced by reason of the difference in diameter between D and E and between F and G. Motion for the quick return passes from J direct to F without being reduced by gears D, E, hence the difference between the cutting speed and the speed of the return stroke is proportionate to the relative diameters or numbers of teeth in D and E, and as E contains 12 and D 20 teeth, it follows that the return is 8/12 quicker than the cutting stroke. In this design the belt is for each reversal of table motion moved across the loose pulley K from one driving pulley to the other, and therefore across two pulleys instead of across the width of one pulley only as in American machines. [Illustration: Fig. 1559.] [Illustration: Fig. 1560.] In American practice the rack R, Fig. 1559, is driven by a large gear instead of by a pinion, so that the strain on the last driving shaft S, in Fig. 1560, shall be less, and also the wheel less liable to vibration than a pinion would be, because in the one case, as in Fig. 1559, the power is transmitted through the shaft, while in the other, as in Fig. 1560, it is transmitted through the wheel from the pinion P to the rack R. [Illustration: Fig. 1561.] Fig. 1561 represents a planer, designed for use in situations where a solid foundation cannot be obtained, hence the bed is made of unusual depth to give sufficient strength and make it firm and solid on unstable foundations, such as the floors in the upper stories of buildings. In all other respects the machine answers to the general features of improved planing machines. [Illustration: Fig. 1562.] As the sizes of planing machines increase, they are given increased tool-carrying heads; thus, Fig. 1562 represents a class in which two sliding heads are used, so that two cutting tools may operate simultaneously. Each head, however, is capable of independent operation; hence, one tool may be actuated automatically along the cross slide to plane the surfaces of the work, while the other may be used to carry a cut down the sides of the work, or one tool may take the roughing and the other follow with the finishing cut, thus doubling the capacity of the machine. In other large planers the uprights are provided with separate heads as shown in the planer in Fig. 1563, in which each upright is provided with a head shown below the cross slide. Either or both these heads may be employed to operate upon the vertical side faces of work, while the upper surface of the work is being planed. The automatic feed motion for these side heads is obtained in the Sellers machine from a rod actuated from the disk or plate in figure, this rod passing through the bed and operating each feed by a pawl and feed wheel, the latter being clearly seen in the figure. To enable the amount of feed to be varied the feed rod is driven by a stud capable of adjustment in a slot in the disk. [Illustration: _VOL. I._ =EXAMPLES OF PLANING MACHINES.= _PLATE XVII._ Fig. 1561. Fig. 1563.] Fig. 1563 represents a planing machine designed by Francis Berry & Sons, of Lowerby Bridge, England. The bed of the machine is, it will be seen, [L]-shaped, the extension being to provide a slide to carry the right-hand standard, and permit of its adjustment at distances varying from the left-hand standard to suit the width of the work. This obviously increases the capacity of the machine, and is a desirable feature in the large planers used upon the large parts of marine engines. [Illustration: Fig. 1564.] ROTARY PLANING MACHINE.--Fig. 1564 is a rotary planing machine. The tools are here carried on a revolving disk or cutter head, whose spindle bearing is in an upper slide with 2 inches of motion to move the bearing endways, and thereby adjust the depth of cut by means of a screw. The carriage on which the spindle bearing is mounted is traversed back and forth (by a worm and worm-wheel at the back of the machine) along a horizontal slide, which, having a circular base, may be set either parallel to the fixed work table or at any required angle thereto. By traversing the cutter head instead of the work, less floor space is occupied, because the head requires to travel the length of the work only, whereas when the work moves to the cut it is all on one side of the cutter at the beginning of the cut, and all on the other at the end, hence the amount of floor space required is equal to twice the length of the work. The disk or cutter head is in one piece with the spindle, and carries twenty-four cutters arranged in a circle of 36 inches in diameter. These cutters are made from the square bar, and each cutting point should have the same form and position as referred to one face, side, or square of the bar, so that each cutter may take its proper share of the cutting duty; and it is obvious that all the cutting edges must project an equal distance from the face of the disk, in which case smooth work will be produced with a feed suitable for the whole twenty-four cutters, whereas if a tool cuts deeper than the others it will leave a groove at each passage across the work, unless the feed were sufficiently fine for that one tool, in which case the advantage of the number of tools is lost. The cutters may be ground while in their places in the head by a suitable emery-wheel attachment, or if ground separately they must be very carefully set by a gauge applied to the face of the disk. CHAPTER XVII.--PLANING MACHINERY. [Illustration: Fig. 1565.] Fig. 1565 represents a planer by William Sellers and Co., of Philadelphia, Pennsylvania. This planer is provided with an automatic feed to the sliding head, both horizontally and vertically, and with mechanism which lifts the apron, and therefore the cutting tool, during the backward stroke of the work table, and thus prevents the abrasion of the tool edge that occurs when the tool is allowed to drag during the return stroke. The machine is also provided with a quick return motion, and in the larger sizes with other conveniences to be described hereafter. The platen or table is driven by a worm set at such an angle to the table rack as to enable the teeth of the rack to stand at a right angle to the table length, and as a result the line of thrust between the worm and the rack is parallel to the [V]-guideways, which prevents wear between the [V]s of the table and of the bed. The driving pulleys are set at a right angle to the length of the machine, their planes of revolution being, therefore, parallel to the plane of revolution of the line or driving shaft overhead, and parallel with the lathes and other machines driven from the same line of shafting, thus taking up less floor space, while the passage ways between the different lines of machines is less obstructed. By setting the worm driving shaft at an angle the teeth of the worm rotate in a plane at a right angle to the length of the work-table rack, and as a result the teeth of the worm have contact across the full width of the rack teeth instead of in the middle only, as is the case when the axis of a worm is at a right angle to the axis of the wheel or rack that it drives. Furthermore, by inclining the worm shaft at an angle the teeth of the rack may be straight (and not curved to suit the curvature of the worm after the manner of worm-wheels), because the contact between the worm and rack teeth begins at one side of the rack and passes by a rolling motion to the other, after the manner and possessing the advantages of Hook's gearing as described in the remarks made with reference to gear-wheel teeth. By inclining the worm shaft, however, the side thrust incidental to Hook's gearing is avoided, the pressure of contact of tooth upon tooth being in the same direction and in line with the rack motion. As the contact between the worm teeth and the rack is uniform in amount and is also continuous, a very smooth and uniform motion is imparted to the work table, and the vibration usually accompanying the action of spur-gearing is avoided. The worm has four separate spirals or teeth, hence the table rack is moved four teeth at each worm revolution, and a quick belt motion is obtained by the employment of pulleys of large diameter. It is desirable that the belt motion of a planing machine be as quick as the conditions will permit, because the amount of power necessary to drive the machine can thus be obtained by a narrower belt, it being obvious that since the driving power of the belt is the product of its tension and velocity the greater the velocity the less the amount of tension may be to transmit a given amount of power. The mechanism for shifting the belt to reverse the direction of table motion is shown in Fig. 1566 removed from all the other mechanism. To the bracket or arm B are pivoted the arms or belt guides C and D and the piece G. In the position occupied by the parts in the figure the belt for the forward or cutting stroke would be upon the loose pulley P´, and that for the quick return stroke would be upon the loose pulley P, hence the machine table would remain at rest. But suppose the rod F be moved by hand in the direction of arrow _f_, then G would be moved upon its pivot X, and its lug _h_ would meet the jaw _i_ of C, moving C in the direction of arrow _a_, and therefore carrying the belt from loose pulley P´ on to the driving pulley P´´, which would start the machine work table, causing it to move in the direction of arrow W until such time as the stop A meets the lug R, operating lever E and moving rod F in the direction of arrow _d_. This would move G, causing its lug _h_ to meet the jaw _j_, which would move C from P´´ back to the position it occupies in the figure, and as the motion of G continued its shoulder at _g´_ would meet the shoulder or lug T of K (the latter being connected to D) and move arm D in the direction of _b_, and therefore carrying the crossed belt upon P, and causing the machine table to run backward, which it would do at a greater speed than during the cutting traverse, because of the overhead pulley on the countershaft being of greater diameter than that for the cutting stroke. It is obvious that since each belt passes from its loose pulley to the fast one, the width of the overhead or countershaft pulleys must be twice as wide as the belt, and also that to reverse the direction of pulley revolution one driving belt must be crossed; and as on the countershaft the smallest pulley is that for driving the cutting stroke, its belt is made the crossed one, so as to cause it to envelop as much of the pulley circumference as possible, and thereby increase its driving power. The arrangement of the countershaft pulleys and belts is shown in Fig. 1567, in which S is the countershaft and N, O the fast and loose pulleys for the belt from the line shaft pulley; Q´ is the pulley for operating the table on the cutting stroke (with the crossed belt), while Q is the pulley for operating the table on its return stroke. The difference in the speed of the table during the two strokes is obviously in the same proportions as the diameters of pulleys Q´ and Q. The feed rod, and feed screw, and rope for lifting the tool on the back stroke are operated as follows:-- Fig. 1568 is an end view of the mechanism viewed from the front of the machine, and Fig. 1569 is a side view of the same. The shaft of the driving pulleys (P P´ and P´´, Fig. 1567) drives a pinion operating the gear wheel W, upon the face of which is a serrated internal wheel answering to a ratchet wheel, and with which a pawl engages each time the direction of pulley revolution (or, which is the same thing, the direction of motion W) reverses, and causes the pawl and the shaft, to which the plate P, Fig. 1569, is fast, to make one-half a revolution, when the pawl disengages and all parts save the wheel W come to rest. From this plate P the feed motions are actuated, and the tool is lifted during the back traverse of the work table by the following mechanisms. [Illustration: Fig. 1566.] [Illustration: Fig. 1567.] [Illustration: Fig. 1568.] [Illustration: Fig. 1569.] [Illustration: Fig. 1570.] Referring to Fig. 1570, upon the plate P is pivoted a lever Q, carrying a universal joint at Z, and a nut pivoted at V, and it is obvious that at each half-revolution of P, the rod R is moved vertically. This rod connects to a universal joint J (shown in Fig. 1571) that is pivoted in a toothed segment (K, in the same figure) which engages with a pinion on the feed screw, this pinion being provided with a ratchet and feed pawl (of the usual construction) for reversing the direction of the feed or throwing it out of action. The amount of feed is regulated as follows:-- Referring to Figs. 1569 and 1570, the amount of vertical motion of rod R is obviously determined by the distance of the universal joint Z from the centre of the plate P, and this is set by operating the hand wheel T, which revolves the screw Y in the nut V. For lifting the tool during the return motion of the work and work table, there is provided in the plate P, Fig. 1570, a pin which actuates the rod B, which in turn actuates the grooved segment C. [Illustration: Fig. 1571.] From this segment a cord is stretched passing over the grooved pulley D, Fig. 1571, thence over pulley E, and after taking a turn around the pulley F, Fig. 1571, it passes to the other end of the cross slide, where it is secured. This pulley F is therefore revolved at each motion of the plate P, Figs. 1569 or 1570, or in other words each time the work table reverses its motion. In reference to Figs. 1571 and 1572, F, Fig. 1571, is fast upon a pin _g_, at whose other end is a pinion operating a gear-wheel _h_. Upon the face of this gear-wheel is secured a steel plate shown at _m_ in Fig. 1572, which is a vertical section of the sliding head. In a cam groove in _m_, projects a pin that is secured to the sleeve _n_, which envelops the vertical feed screw O. This sleeve _n_ has frictional contact at _p_ with the bar _q_, whose lower end receives the bell crank _r_, which on each return stroke is depressed, and thus moves the tool apron _s_, and with it the tool, which is therefore relieved from contact with the cut upon the work. The self-acting vertical feed is actuated as follows:-- Referring to Figs. 1571 and 1572 the gear segment K operates a pinion upon the squared end of the feed rod L, this pinion L having the usual pawl and ratchet for reversing the direction of rod revolution. The splined feed rod L actuates the bevel pinion M, which is in gear with bevel pinion N, the latter driving pinion P, which is threaded to receive the vertical feed screw O; hence when P is revolved it moves the feed screw O endways, and this moves the vertical slide R upon which is the apron box T and the apron _s_. To prevent the possibility of the friction of the threads causing the feed screw O to revolve with the pinion P, the journal _e_ of the feed screw O is made shorter than its bearing in R, so that the nut _f_ may be used to secure the feed screw O to the slide R. PLANER SLIDING HEADS.--In order that the best work may be produced, it is essential that the sliding head of a planer or planing machine be constructed as rigid as possible, and it follows that the slides and slideways should be of that form that will suffer the least from wear, resist the tool strain as directly as possible, and at the same time enable the taking up of any wear that may occur from the constant use of the parts. Between the tool point that receives the cutting strain and the cross bar or cross slide that resists it there are the pivoted joint of the apron, the sliding joint of the vertical feed, and the sliding joint of the saddle upon the cross slide, and it is difficult to maintain a sliding fit without some movements or spring to the parts, especially when, as in the case of a planer head, the pressure on the tool point is at considerable leverage to the sliding surfaces, thus augmenting the strain due to the cut. The wear on the cross slide is greater at and towards the middle than at the ends, but it is also greater at the end nearest to the operator than at the other end, because work that is narrower than the width of the planing machine table is usually chucked on the side nearest to the operator or near the middle of the table width, because it is easier to chuck it there and more convenient to set the tool and watch the cut, for the reason that the means for stopping and starting the machine, and for pulling the feed motions in and out of operation, are on that side. The form of cross bar usually employed in the United States is represented in Fig. 1573, and it is clear that the pressure of the cut is in the direction of the arrow _c_, and that the fulcrum off which the strain will act on the cross bar is at its lowest point _d_, tending to pull the top of the saddle or slider in the direction of arrow _e_, which is directly resisted by the vertical face of the gib, while the horizontal face _f_ of the gib directly resists the tendency of the saddle to fall vertically, and, therefore, the amount of looseness that may occur by reason of the wear cannot exceed the amount of metal lost by the wear, which may be taken up as far as possible by means of the screws _a_ and _b_, which thread through the saddle and abut against the gib. The gib is adjusted by these screws to fit to the least worn and therefore, the tightest part of the cross bar slideway, and the saddle is more loosely held at other parts of the cross bar in proportion as its slideway is worn. [Illustration: Fig. 1572.] In this construction the faces of the saddle are brought to bear over the whole area of the slideways surface of the cross bar, because the bevel at _g_ brings the two faces at _m_ into contact, and the set-screw _b_ brings the faces in together. Instead of the screws _a_ and _b_ having slotted heads for a screw driver, however, it is preferable to provide square-headed screws, having check nuts, as in Fig. 1574, so that after the adjustment is made the parts may be firmly locked by the check nuts, and there will be no danger of the adjustment altering. The wear between the slider and the raised slideways S is taken up by gibs and screws corresponding to those at _a_ and _c_ in the Fig. 1575, and concerning these gibs and screws J. Richards has pointed out that two methods may be employed in their construction, these two methods being illustrated in Figs. 1575 and 1576, which are taken from "Engineering." In Fig. 1575 the end _s_ of the adjustment screw _a_ is plain, and is let into the gib _c_ abutting against a flat seat, and as a result while the screw pressure forces the gib _c_ against the bevelled edge of the slideway it does not act to draw the surfaces together at _m_ _m_ as it should do. This may be remedied by making the point of the screw of such a cone that it will bed fair against gib _c_, without passing into a recess, the construction being as in Fig. 1576, in which case the screw point forces the gib flat against the bevelled face and there is no tendency for the gib to pass down into the corner _e_, Fig. 1575, while the pressure on the screw point acts to force the slide _a_ down upon the slideway, thus giving contact at _m_ _m_. The bearing area of such screw points is, however, so small that the pressure due to the tool cut is liable to cause the screw to indent the gib and thus destroy the adjustment, and on this account a wedge such as shown in Fig. 1577 is preferable, being operated endwise to take up the wear by means of a screw passing through a lug at the outer or exposed end of the wedge. The corners at _i_, Figs. 1575 and 1576, are sometimes planed out to the dotted lines, but this does not increase the bearing area between the gib _c_ and the slide, while it obviously weakens the slider and renders it more liable to spring under heavy tool cuts. Fig. 1578 represents a form of cross bar and gib found in many English and in some American planing machines. In this case the strain due to the cut is resisted directly by the vertical face of the top slide of the cross bar, the gib being a triangular piece set up by the screws at _a_, and the wear is diminished because of the increased wearing surface of the gib due to its lower face being diagonal. [Illustration: Fig. 1573.] [Illustration: Fig. 1574.] [Illustration: Fig. 1575.] [Illustration: Fig. 1576.] On the other hand, however, this diagonal surface does not directly resist the falling of the saddle from wear, and furthermore in taking up the wear the vertical face of the saddle is relieved from contact with the vertical face of the cross bar, because the screws _a_ when set up move the top of the saddle away from the cross bar, whereas in Fig. 1573, setting up screw _b_ brings the saddle back upon the vertical face of the cross bar slideway. [Illustration: Fig. 1577.] [Illustration: Fig. 1578.] [Illustration: Fig. 1579.] Fig. 1579 is a front view, and Fig. 1580 a sectional top view, of a sunk vertical slide, corresponding to that shown in Figs. 1573 and 1578, but in this case the gib has a tongue _t_, closely fitted into a recess or channel in the vertical slider S, and to allow room for adjustment, the channel is made somewhat deeper than the tongue requires when newly fitted. The adjustment is effected by means of two sets of screws, _a_ and _b_, of which the former, being tapped into the gib, serve to tighten, and the latter, being tapped into the slide, serve to loosen the gib. By thus acting in opposite directions the screws serve to check each other, holding the gib rigidly in place. To insure a close contact of the gib against the vertical surface of the slide, the screws _b_ are placed in a line slightly outside of the line of the screws _a_. Fig. 1581 represents a similar construction when the slideways on the swing frame project outwards, instead of being sunk within that frame. Fig. 1582 represents the construction of the Pratt & Whitney Company's planer head, in which the swivel head instead of pivoting upon a central pin and being locked in position by bolts, whose nuts project outside and on the front face of the swing frame, is constructed as follows:-- A circular dovetail recess in the saddle receives a corresponding dovetail projection on the swivel head or swing frame, and the two are secured together at that point by a set-screw A. In addition to this the upper edge B of the saddle is an arc of a circle of which the centre is the centre of the dovetail groove, and a clamp is employed to fasten the swivel head to the saddle, being held to that head by a bolt, and therefore swinging with it. Thus the swivel head is secured to its saddle at its upper edge, as well as at its centre, which affords a better support. The tool box is pivoted upon the vertical slider, and is secured in its adjusted position by the bolts _n_ in Fig. 1573, the object of swinging it being to enable the tool to be lifted on the back stroke and clear the cut, when cutting vertical faces, as was explained with reference to shaping machines. The tool apron is in American practice pivoted between two jaws, which prevent its motion sideways, and to prevent any play or lost motion that might arise from the wear of the taper pivoting pin _b_, in Fig. 1583, the apron beds upon a bevel as at _a_, so that in falling to its seat it will be pulled down, taking up any lost motion upon _b_. [Illustration: Fig. 1580.] [Illustration: Fig. 1581.] [Illustration: Fig. 1582.] [Illustration: Fig. 1583.] [Illustration: Fig. 1584.] [Illustration: Fig. 1585.] The bevel at _a_ would also prevent any side motion to the apron should wear occur between it and the jaws. In addition to this bevel, however, there may be employed two vertical bevels _c_ in the top view in Fig. 1584. In English practice, and especially upon large planing machines, the apron is sometimes made to embrace or fit the outsides of the tool box, as in Fig. 1585, the object being to spread the bearings as wide apart as possible, and thus diminish the effect of any lost motion or wear of the pivoting pin, and to enable the tool post or holder to be set to the extreme edge of the tool box as shown in the figure. It is desirable that the tool apron bed as firmly as possible back against its seat in the tool box, and this end is much more effectively secured when it is pivoted as far back as possible, as in Fig. 1585, because in that case nearly all the weight of the apron, as well as that of the tool and its clamp, acts to seat the apron, whereas when the pivot is more in front, as _m_, in Fig. 1573, it is the weight of the tool post and tool only that acts to keep the apron seated. In small planing machines it is a great advantage to provide an extra apron carrying two tool posts, as in Fig. 1586, so that in planing a number of pieces, that are to be of the same dimension, one tool may be used for roughing and one for finishing the work. The tools should be wider apart than the width of the work, so that the finishing tool will not come into operation until after the roughing tool has carried its cut across. When the roughing tool has become dulled it should, after being ground up, be set to the last roughing cut taken, so that it will leave the same amount of finishing cut as before. The advantage of this system is that the finishing tool will last to finish a great many pieces without being disturbed, and as a result the trouble of setting its cut for each piece is avoided; on which account all the pieces are sure to be cut to the same dimension without any further measuring than is necessary for the first piece, whereas if one tool only is used it rapidly dulls from the roughing cut, and will not cut sufficiently smooth for the finishing one, and must therefore be more frequently ground up to resharpen it, while it must be accurately set for each finishing cut. A double tool apron of this kind is especially serviceable upon such work as planing large nuts, for it will save half the time and give more accurate work. In some planing machines, and notably those made by Sir Joseph Whitworth, a swiveling tool holder is made so that at each end of the stroke the cutting tool makes half a revolution, and may therefore be used to cut during both strokes of the planer table. A device answering this purpose is shown in Fig. 1587. The tool-holding box is pivoted upon a pin A, and has attached to it a segment of a circular rack or worm-wheel, operated by a worm upon a shaft having at its upper end the pulley shown, so that by operating this pulley, part of a revolution at the end of each work-table stroke, one or the other of the two tools shown in the tool box, is brought into position to carry the cut along. Thus two tools are placed back to back, and it is obvious that when the tool box is moved to the right, the front tool is brought into position, while when it is moved to the left, the back or right-hand tool is brought into position to cut, the other tool being raised clear of the work. [Illustration: Fig. 1586.] [Illustration: Fig. 1587.] The objections to either revolving one tool or using two tools so as to cut on both strokes are twofold: first, the tools are difficult to set correctly; and, secondly, the device cannot be used upon vertical faces or those at an angle, or in other words, can only be used upon surfaces that are nearly parallel to the surface of the work table. [Illustration: Fig. 1588.] [Illustration: Fig. 1589.] Figs. 1588 and 1589 represent the sliding head of the large planer at the Washington Navy Yard, the sectional view, Fig. 1589, being taken on the line X X in Fig. 1588. C is the cross bar and S the saddle, F being the swing frame or fiddle, as some term it, and S´ the vertical slider; B is the tool box, and A the apron. The wear of the cross slider is taken up by the set screws _a_, and that of the vertical slide by the screws _b_. The graduations of the degrees of a circle for setting over the swing frame F, as is necessary when planing surfaces that are at an angle to the bed and to the cross slide, are marked on the face of the saddle, and the pointer (_f_, Fig. 1578) is fastened to the edge of the swing frame. When the swing frame is vertical the pointer is at 90° on the graduated arc, which accords with English practice generally. In American practice, however, it is customary to mark the graduations on the edge of the swing frame as in Fig. 1590, so that the pointer stands at the zero point _o_ when the swing frame is vertical, and the graduations are marked on the edge of the swing frame as shown, the zero line _o_ being marked on the edge of the saddle. In the English practice the swing frame is supposed to stand in its neutral or zero position when it is vertical, and all angles are assumed to be measured from this vertical zero line, so that if the index point be set to such figure upon the graduated arc as the angle of the work is to be to a vertical line, correct results will be obtained. Thus in Fig. 1591 (which is from _The American Machinist_) the pointer is set to 40° and the bevelled face is cut to an angle of 40° with the vertical face as marked. But if the head be graduated as in Fig. 1592, the face of the planer table being taken as the zero line _o_, then the swing frame would require to be set over to 30° out of its normal or neutral vertical position as is shown in figure, the bevelled face being at an angle of 50° from a vertical, and 40° from a horizontal line, hence the operator requires to consider whether the number of degrees of angle are marked on the drawing from a zero line that is vertical on one that is horizontal. [Illustration: Fig. 1590.] [Illustration: Fig. 1591.] [Illustration: Fig. 1592.] [Illustration: Fig. 1593.] [Illustration: Fig. 1594.] Referring again to Fig. 1588 the slots for the tool post extend fully across the apron, so that the tool posts may be set at any required point in the tool-box width, and the tool or tool holder may be set nearer to the edge of the tool box than is the case when fixed bolts, as in Fig. 1590, are used, because these bolts come in the way. This is mainly important when the tool is required to carry a deep vertical cut, in which case it is important to keep the tool point as close in to the holder as possible so that it may not bend and spring from the pressure of the cut. The tool or holder may be held still closer to the edge of the head, and therefore brought still closer to the work, when the apron embraces the outside of the tool box, as was shown in Fig. 1585, and referred to in connection therewith. [Illustration: Fig. 1595.] [Illustration: Fig. 1596.] A sectional side view and a top view of Fig. 1588 through the centre of the head is given in Figs. 1595 and 1596, exposing the mechanism for the self-acting feed traverse, and for the vertical feed. For the feed traverse the feed screw (_m_, Fig. 1588) passes through the feed nut N. For the vertical feed the feed rod (_n_, Fig. 1588) drives a pair of bevel-gears at P, which drives a second pair at Q, one of which is fast on a spindle which passes through the vertical feed screw, and is secured thereto by the set screw _e_. The object of this arrangement is that if the self-acting vertical feed should be in action and the tool or swing frame S´ should meet any undue obstruction, the set screw _e_ will slip and the feed would stop, thus preventing any breakage to the gears at P or Q. The feed screw is threaded into the top of S´. At E is the pin on which the tool box pivots to swing it at an angle. The mechanism for actuating the cross-feed screw and the feed rod is shown in the top view, Fig. 1597, and the side view, Fig. 1598, in which A is a rod operated vertically and actuated from the stop (corresponding to stop R in Fig. 1558) that actuates the belt shifting gear. Upon A is the sleeve B, which actuates rod C, which operates the frame D. This frame is pivoted upon a stud which is secured to the cross bar C, and is secured by the nut at E. Frame D carries pawls F and G, the former of which engages gear-wheel H, which drives the pinion _n_, Fig. 1598, that is fast on the feed rod, while the latter drives the gear K, which in turn drives pinion P, which is fast upon the feed screw in Fig. 1588. The feeds are put into or thrown out of action as follows:--On the same shaft or pin as the pawls G and F, is secured a tongue T, Fig. 1599, whose end is wedge shaped and has a correspondingly shaped seat in a plate V, whose cylindrical stem passes into a recess provided in D, and is surrounded by a spiral spring which acts to force V outwards from the recess. [Illustration: Fig. 1597.] [Illustration: Fig. 1598.] [Illustration: Fig. 1599.] In the position shown in the figure the end of T is seated in the groove in V, and the pressure of the spring acts to hold T still and keep the pawl G from engaging with the teeth of gear-wheel H. But suppose the handle W (which is fast on the pawl G) is pulled upwards, and T will move downwards, disengaging from the groove in V, and the upper end of pawl G will engage with the teeth of H, actuating in the direction of the arrow during the upward motion of rod A, and thus actuating pinion _n_ and putting the vertical feed in motion in one direction. When the rod A makes its downward stroke the pawl G will slip over the teeth of H, because there is nothing but the spiral spring to prevent the end of the pawl from slipping over these teeth. To place the vertical feed in action in the other direction, handle W is pressed downwards, causing the bottom end X of the pawl to engage with the teeth of H. PLANER BEDS AND TABLES.--The general forms of the beds of small planers are such as in Figs. 1557 and 1558, and those of the larger sizes such as shown in Fig. 1563. It is of the first importance that the [V]-guideways in these beds should be straight and true, and that the corresponding guides on the planer table should fit accurately to those in the bed; for which purpose it is necessary, if the greatest attainable accuracy is to be had, that the guideways in the bed first be made correct, and those on the table then fitted, using the bed to test them by. The angle of these guides and guideways ranges from about 60° in the smallest sizes to about 110° in the largest sizes of planers. Whatever the angle may be, however, it is essential that all the angles be exactly equal, in order that the fit of the table may not be destroyed by the wear. In addition to this, however, it is important that each side of the guides stand at an equal height, or otherwise the table will not fit, notwithstanding that all the angles may be equal. [Illustration: Fig. 1600.] Suppose, for example, that in Fig. 1600 all the sides are at an equal angle, but that side _e_ was planed down to the dotted line _e_, then all the weight of the table would fall on side _a_, and, moreover, the table would be liable to rock in the guideways, for whenever the combined weight of the table and the pressure of the cut was greatest on the right-hand of the middle _x_ of the table width and the feed was carried from right to left, then the table would move over, as shown exaggerated in Fig. 1601, because the weight would press guide _g_ down into its guideways, and guide _h_ would then rise up slightly and not fit on one side at all, while on the other side it would bear heaviest at point _p_. Great care is therefore necessary in planing and fitting these guides and ways, the processes for which are explained under the respective headings of "Examples in Planer Work," and "Erecting Planers." In some designs the bed and table are provided with but one [V]-guideway, the other side of the table being supported on a flat side, and in yet another form the table is supported on two flat guideways. Referring to the former the bearing surface of the [V] and of the flat guide must be so proportioned to that of the [V] that the wear will let the table down equally, or otherwise it would become out of parallel with the cross slide, and would plane the work of unequal thickness across its width. [Illustration: Fig. 1601.] [Illustration: Fig. 1602.] Referring to the second, which is illustrated in Fig. 1602, it possesses several disadvantages. [Illustration: Fig. 1603.] Thus, if there be four gibs as at A, B, and E, F, set up by their respective set-screws, the very means provided to take up the wear affords a means of setting the bed out of line, so that the slots in the table (and, therefore, the chucks fitting to these slots) will not be in the line of motion of the table, and the work depending upon these chucks will not be true. This may be avoided by taking up the wear on two edges only, as in Fig. 1603 at A, B, but in this case the bearing at E and F would eventually cease by reason of the wear. Suppose, for example, that the pressure of the tool cut tends to throw the table in the direction of arrow J, and the surfaces at A and F resist the thrust and both will wear. But when the strain on the table is in the direction of arrow K, the surfaces B, E, will both wear; hence while the width apart of the table slides becomes greater, the width apart of the bed slideways wears less, and the fit cannot be maintained on the inner edges of the guideways. It is furthermore to be noted that with flat guideways the table will move sideways very easily, since there is nothing but the friction of the slides to prevent it, but in the case of [V]-guides the table must lift before it can move sideways; hence, it lies very firmly in its seat, its weight resisting any side motion. [Illustration: Fig. 1604.] It is found in practice that the wear of the guides and guideways in planer tables and beds is greatest at the ends, and the reason of this is as follows:-- In Fig. 1604 is a top view of a planer table, the cutting tool being assumed to be at T, and as the driving gear is at G forcing the table in the direction of the arrow A, and the resistance is at T, the tendency is to throw the table around in the direction of arrows B and C. When the tool is on the other side of the middle of the table width as at F, the tendency is to throw the table in the opposite direction as denoted by the arrows D and E, which obviously causes the most wear to be at the ends of the slides. As the feed motions are placed on the right-hand side of the machines the operator stands on that side of the machine at X, and starts the cut from that side of the table; hence unless the work is placed in the middle of the table width, the wear will be most in the direction of arrows B and C. The methods of fitting the guideways and guides of planer beds and tables is given in the examples of erecting. [Illustration: Fig. 1605.] A very good method of testing them, however, is as follows:--Suppose that we have in Fig. 1605 a plate that has been planed on both edges G, H, and that in consequence of a want of truth in the planer guideways edge G is rounding and edge H hollow, the plate being supposed to lie upon the planer table in the position in which it was planed. [Illustration: Fig. 1606.] Now, suppose that it be turned over on the planer, as in Fig. 1606, the rounding edge, instead of standing on the right-hand side of the planer table, will stand on the left-hand side, so that if that edge were planed again in its new position it would be made hollow instead of rounding in its length. It is obvious, therefore, that if a planed edge shows true when turned over on the planer table, the [V]s of the planer are true, inasmuch as the table moves in a straight line in one direction, which is that affecting the truth of all surfaces of the work that are not parallel to the cross feed of the tool, or, what is the same thing, parallel to the surface of the planer table. PLANING MACHINE TABLES.--In order that the guides on the table of a planer may not unduly wear, it is essential that they be kept well lubricated, which is a difficult matter when the table takes short strokes and has work upon it that takes a long time to perform, in which case it is necessary to stop the planing operations and run the work back so as to expose the guideways in the bed, so that they may be cleaned and oiled. [Illustration: Fig. 1607.] It will often occur that the work will not pass beneath the cross slide, and in that case it should be raised out of the ways to enable proper oiling, because insufficient lubrication frequently causes the guides and guideways to tear one another, or cut as it is commonly termed. [Illustration: Fig. 1608.] The means commonly employed for oiling planer [V]s or guideways are as follows:--At the top of the guideways small grooves, _g_ _g_, Fig. 1609, are provided, and at the bottom a groove _x_. In the guides on the table there are provided pockets or slots in which are pivoted pendulums of the form shown in Fig. 1607 at A. Each pendulum passes down to the bottom of groove _x_ in which the oil lies, and is provided on each side with recesses _e_, which are also seen in the edge view on the right of the figure. The pendulums are provided with a long slot to enable them when the table motion reverses to swing over and drag in the opposite direction (as shown in Fig. 1607); as they drag on the bottom of groove _x_ of the bed they lift the oil it contains, which passes up the sides of the pendulum as denoted by the arrow, and into grooves provided on the surface of the table guide, as at _h_ in Fig. 1608, in which V´ is the table guide, V the guideway in the bed, _g_ oil grooves, (see sectional view, Fig. 1613), _x_ the oil groove at the bottom of the bed V, and _h_ _h_ the oil grooves which receive the oil the pendulum lifts. The oil grooves _h_ on the table guide run into the grooves _g_ in the [V]-guideway in the bed, hence grooves _g_ _g_ become filled with oil. But after the end of the table has passed and left the bed V exposed, the oil flows out of grooves _g_ down the sides of the guideway, and constant lubrication is thus afforded at all times when the stroke of the table is sufficient to enable the pendulums to force the oil sufficiently far along oil way _h_. When the table reverses the pendulum will swing over and lift the oil up into grooves or oil ways _h´_. [Illustration: Fig. 1609.] [Illustration: Fig. 1610.] Another and excellent method of oiling, also invented by Mr. Hugh Thomas, of New York, is shown in Figs. 1609 and 1610, in which P represents an oiling roll or wheel, [V]-shaped, to correspond to the shape of the [V]s. This roll is laced with cotton wick or braid, as shown by the dark zigzag lines, and is carried in a frame _f_, capable of sliding vertically in a box C, which is set in a pocket in the bed V, and contains oil. By means of a screw S, the roll P is set to touch the face of the table [V], and the friction between the roll and the [V], as the table traverses, rotates the roll, which carries up the oil and lubricates the table [V] over its whole surface. The dust, &c., that may get into the oil settles in the bottom of the box C, which can occasionally be cleaned out. In this case the oil is not only presented to the oil grooves (_h_, Fig. 1608), but spread out upon the [V]s; but it is nevertheless advisable to have the grooves _h_ so as to permit of an accumulation of oil that will aid in the distribution along the [V]s of the bed. This method of oiling has been adopted in some large and heavy planers built by R. Hoe & Co., and has been found to operate admirably, keeping the guides and guideways clean, bright, and well lubricated. Mr. Thomas has also patented a system of forced oil circulation for large planers. In this system a pump P, Fig. 1611, draws the oil from the cellars C (which are usually provided on the ends of planer beds) and delivers it through pipes passing up to the sides of the [V]s, thus affording a constant flow of oil. A reservoir at the foot of the pump enables the dirt, &c., in the oil to settle before it enters the pump, which can be operated from any desirable part of the planer mechanism. The pendulums are also used in connection with the forced circulation. As the work is fastened to the upper face of a planing machine table either directly or through the intervention of chucking devices, the table must be pierced with holes and grooves to receive bolts or other appliances by means of which the work or chuck, as the case may be, may be secured. For receiving the heads of bolts, [T]-shaped grooves running the full length of the table are provided, and in addition there are sometimes provided short [T]-grooves, to be shown presently. For receiving stops and other similar chucking devices, the tables are provided with either round or square holes. In Fig. 1612 is shown a section of a table provided with [T]-grooves and rows of round holes, _a_, _b_, _c_, _d_, _e_, which pass entirely through the table, and hence must not be placed so that they will let dirt fall through to the [V]-guides or the rack. Tables with this arrangement of holes and grooves are usually used upon small planers in the United States, and sometimes to large ones also. [Illustration: Fig. 1611.] [Illustration: Fig. 1612.] [Illustration: Fig. 1613.] It is obvious that the dirt, fine cuttings, &c., will pass through the holes and may find its way to the [V]-guideways. Especially will this be the case when water is used upon the tool to take smooth cuts upon wrought iron and steel. To obviate this the construction shown in Fig. 1613 is employed. Fig. 1613 represents a section of one guideway of a table and bed. On each side of the table [V] there is cut a groove leaving projecting ribs _b_, _c_, and whatever water, oil, or dirt may pass through the holes (Fig. 1612), will fall off these points _b_, _c_, Fig. 1613, and thus escape the guideways, while falling dust will be excluded by the wings _b_, _c_, from the [V]s. [Illustration: Fig. 1614.] The capacity of a planer table may be increased by fitting thereto two supplementary short tables, as shown in Fig. 1614, several applications of its use being given with reference to examples in planer work. These supplementary tables are secured to the main table by set-screws at A, and have been found of great value for a large variety of work, especially upon planing machines in which the table width is considerably less than the width between the uprights or stanchions. [Illustration: Fig. 1615.] Fig. 1615 represents the arrangement of square holes and [T]-grooves employed upon large planers. The square holes are cast in the table, and are slightly tapered to receive taper plugs or stops against which the work may abut, or which may be used to wedge against, as will be hereafter described, one of these stops being shown at S in the figure. [Illustration: Fig. 1616.] The [T]-shaped slots _f_, _g_, _h_, are to receive the heads of bolts as shown in Fig. 1616. The bolt head is rounded at corners _a_, _b_, and the square under the head has the corresponding diagonal corners as _c_ also rounded, so that the width of the head being slightly less than that of the slot it may be passed down in the slot and then given a quarter revolution in the direction of the arrow, causing the wings of the head to pass under the recess of the [T]-groove, as shown in Fig. 1617, which is a sectional end view of the groove with the bolt in place. The square corners at _e_ and at _f_ prevent the bolt from turning round more than the quarter revolution when screwing up the bolt nut, and when the nut is loosened a turn the bolt can be rotated a quarter revolution and lifted out of the groove. Now it is obvious that these slots serve the same purpose as the longitudinal [T]-grooves, since they receive the bolt heads, and it might therefore appear that they could be dispensed with, but it is a great convenience to be able to adjust the position of the bolt across the table width, which cannot be done if longitudinal grooves only are employed. Indeed, it might easily occur that the longitudinal grooves be covered by the work when the short transverse ones would serve to advantage, and in the wide range of work that large planers generally perform, it is desirable to give every means for disposing the bolts about the table to suit the size and shape of the work. [Illustration: Fig. 1617.] It is obvious that the form of bolt head shown in Fig. 1616 is equally applicable to the longitudinal grooves as to the cross slots, enabling the bolt to be inserted, notwithstanding that the work may cover the ends of the longitudinal slots. The round holes _a_, _b_, _c_, &c., in Fig. 1612, are preferable to the square ones, inasmuch as they weaken the table less and are equally effective. Being drilled and reamed parallel the plugs that fit them may be passed through them to any desirable distance, whereas the square plugs being taper must be set down home in their holes, necessitating the use of plugs of varying length, so that when in their places they may stand at varying heights from the table, and thus suit different heights of work. Whatever kind of holes are used it is obvious that they must be arranged in line both lengthways of the table and across it, so that they will not come in the way of the ribs R, which are placed beneath it to strengthen it. The longitudinal grooves are planed out to make them straight and true with the [V]-guides and guideways, so that chucking appliances fitting into the grooves may be known to be set true upon the table. [Illustration: Fig. 1618.] [Illustration: Fig. 1619.] In Fig. 1618, for example, is shown an angle piece A having a projection fitting into a longitudinal groove, the screws whose heads are visible passing through A into nuts that are in the widened part of the groove, so that operating the screws secures A to the table. The vertical face of A being planed true, a piece of work, as a shaft S, may be known to be set in line with the table when it is clamped against A by clamps as at P, or by other holding devices. Angle pieces such as A are made of varying lengths and heights to suit different forms and sizes of work. In some planing machine tables a [V]-groove is cut along the centre for the purpose of holding spindles to have featherways or splines cut in them, the method of chucking being shown in Fig. 1619. This, however, is not a good plan, as the bolts and plates are apt to bend the shaft out of straight, so that the groove cut in the work will not be straight when the spindle is removed from the clamp pressure. The proper method of chucking such work will, however, be given in connection with examples on planer work. For the round holes in planer tables several kinds of plugs or stops are employed, the simplest of them being a plain cylindrical plug or stop. [Illustration: Fig. 1620.] Fig. 1620 represents a stop provided with a screw B. The stem A fits into the round holes, and the screw is operated to press against the work. By placing the screw at an angle, as shown, its pressure tends to force the work down upon the planer table. [Illustration: Fig. 1621.] A similar stop, termed a bunter screw, S, Fig. 1621, may be used in the longitudinal slots, the shape of its hook enabling it to be readily inserted and removed from the slot. These screws may be applied direct to the work when the circumstances will permit, or a wedge W may be interposed between the screw and the work, as shown. [Illustration: Fig. 1622.] Fig. 1622 represents a form of planer chuck used on the smaller sizes of planers, and commonly called planer centres. A is the base or frame bolted to the planer table at the lugs L; at B is a fixed head carrying what may be termed the live centre D, and C is a head similar to the tailstock of a lathe carrying a dead centre; F is an index plate having worm-teeth on its edge and being operated by the worm G. At S is a spring carrying at its end the pin for the index holes. To bring this pin opposite to the requisite circle of holes, the bolt holding S to A is eased back and S moved as required. On the live centre D is a clamp for securing the work or mandrel holding dog. Head C is split as shown, and is held to the surface of A by the bolt H, which is tapped into the metal on one side of the split. It is obvious that polygons may be planed by placing the work between the centres and rotating it by means of G after each successive side of the polygon has been planed or shaped, the number of sides being determined by the amount of rotation of the index plate. [Illustration: Fig. 1623.] Fig. 1623 shows a useful chuck for holding cylindrical work, such as rolls. The base is split at E, so that by means of the bolt and nut D the [V]-block a may be gripped firmly; B and C are screws for adjusting the height of the [V]-block A. At F is the bolt for clamping the chuck to the planer table, and G is a cap to clamp the work W in the block A. It will be seen that this chuck can be set for taper as well as parallel work. [Illustration: Fig. 1624.] [Illustration: Fig. 1625.] Fig. 1624 represents a chucking device useful for supporting or packing up work, or for adjusting it in position ready to fasten it to the work table, it being obvious that its hollow seat at A enables it to set steadily upon the table, and that its screw affords a simple means of adjusting its height. It may also be used between the jaws of a connecting rod strap or other similar piece of work to support it, as in Fig. 1625, and prevent the jaws from springing together under the pressure of the tool cut. [Illustration: Fig. 1626.] Another and very useful device for this purpose is shown in Fig. 1626, consisting of a pair of inverted wedges, of which one is dovetailed into the other and having a screw to operate them endwise, the purpose being to hold the two jaws the proper distance apart and prevent their closure under pressure of the planer vice jaws. It is obvious that the device in Fig. 1625 is most useful for work that has not been faced between the jaws, because the device in Fig. 1626 would, upon rough work that is not true, be apt to spring the work true with the inside faces, which may not be true with the outside ones, and when the wedges were removed the jaws would spring back again, and the work performed while the inverted wedges were in place would no longer be true when they were removed. [Illustration: Fig. 1627.] Fig. 1627 represents a centre chuck to enable the cutting of spirals. The principle of the design is to rotate the work as it traverses, and this is accomplished as follows:-- Upon the bed of the machine alongside of the table is bolted the rack A A, into which gears the pinion B, which is fixed to the same shaft as the bevel-gear C, which meshes with the bevel-wheel D. Upon the same shaft as D is the face plate E, and in the spindle upon which D and E are fixed is a centre, so that the plate E answers to the face plate of a lathe. F is a bearing for the shaft carrying B and C, and G is a bearing carrying the spindle to which E and D are fixed. H is a standard carrying the screw and centre, shown at I, and hence answers to the tailstock of a lathe. K represents a frame or plate carrying the bearings F and G, and the standard H. L represents the table of the planing machine to which K is bolted. The reciprocating motion of the table L causes the pinion B to revolve upon the rack A A. The pinion B revolves C, which imparts its motion to D, and the work W being placed between the centres as shown, is revolved in unison with E, revolving in one direction when the table K is going one way, and in the other when the motion of the table is reversed; hence a tool in the tool post will cut a spiral groove in the work. To enable the device to cut grooves of different spirals or twist, all that is necessary is to provide different sizes of wheels to take the places of C and D, so that the revolutions of E, and hence of the work W, may be increased or diminished with relation to the revolutions of B; or, what is the same thing, to a given amount of table movement, or a stud may be put in so as to enable the employment of change gears. [Illustration: Fig. 1628.] Figs. 1628 and 1629 represent a universal planer chuck, designed and patented by John H. Greenwood, of Columbus, Ohio, for planing concave or convex surfaces, as well as ordinary plane ones, with the cross feed of the common planer. The base L of the chuck is bolted to the planer work table in the ordinary manner. The work-holding frame or vice is supported, for circular surfaces, by being pivoted to the base at O, O, and by the gibbed head D, which has journal bearing at E. The work is held between the stationary jaw _b_ or _b´_ (at option) and the movable jaw C which may face either _b_ or _b´_ (by turning C round). Suppose then, that while the chuck is passing the cutting tool, end I of the work-holding frame is raised, lifting that end of the work above the horizontal level (the work-holding frame swinging at the other end on the pivots O, O), then the tool will obviously cut a convex surface. Or if end I of the work-holding frame be lowered while the cut is proceeding, the tool will cut a concave surface. [Illustration: Fig. 1629.] Now end I is caused to rise or lower as follows:--The head D is adjusted by means of its gibs to be a sliding fit on the bar G in Fig. 1629, which bar is rigidly fixed at P to the planer bed; hence as the planer table and the chuck traverse, D slides along bar G. If this bar is fixed at an angle to the length of the planer head, D must travel at that same angle, causing end I of the work-holding frame to rise or lower (from O, O, as a centre of motion) as it traverses according to the direction of motion of the planer table. Suppose that in Fig. 1629, the planer table is moving on the back or non-cutting stroke, then head D will be moving towards the point of suspension P of the bar G, and will therefore gradually lower as it proceeds, thus lowering end I of the work-holding frame and causing the curved link to pass beneath the tool with a curved motion or suppose the table to be on its cutting traverse, then head D will be raised as the table moves and the cut proceeds, and the surface cut by the tool will be concave. Now, suppose that the bar G were fixed at an angle, with its end, that is towards the back end of the planer, inclined towards the table instead of away from it as in Fig. 1629, and then on the cutting traverse head D would cause end I (Fig. 1628) of the work-holding vice or frame to lower as the cut proceeded, and the tool would therefore plane a convex surface. Thus the direction of the angle in which G is fixed governs whether the surface planed shall be a concave or a convex one, and it is plain that the amount of concavity or convexity will be governed and determined by the amount of angle to which G is set to the planer table. When the chuck is not required to plane curved surfaces the bar G is altogether dispensed with, and the chuck becomes an ordinary one possessing extra facilities for planing taper work. Thus for taper work the work-holding frame may be set out of parallel with the base of the chuck to an amount answering to the required amount of taper, being raised or lowered (as may be most convenient) at one end by means of the gears M, of which there is one on each side meshing into the segmental rack shown, the work-holding frame being secured in its adjusted position by means of a set bolt. To set the work-holding frame parallel for parallel planing, a steady pin is employed, the frame being parallel to the base when that pin is home in its place. The construction of the chuck is solid, and the various adjustments may be quickly and readily made, giving to it a range of capacity and usefulness that are not possessed by the ordinary forms of planer chucks. PLANING MACHINE BEDS.--In long castings such as lathe or planer beds, the greatest care is required in setting the work upon the planer table, because the work will twist and bend of its own weight, and may have considerable deflection and twist upon it notwithstanding that it appears to bed fair upon the table. To avoid this it is necessary to know that the casting is supported with equal pressure at each point of support. In all such work the surface that is to rest upon the foundation or legs should be planed first. [Illustration: Fig. 1630.] Thus supposing the casting in Fig. 1630 to represent a lathe shears, the surfaces _f_ whereon the lathe legs are to be bolted should be planed first, the method of chucking being as follows:-- [Illustration: Fig. 1631.] The bed is balanced by two wedges A, in Fig. 1630, one being placed at each end of the bed, and the position of the wedges being adjusted so that it lies level. A line coincident with the face of the bed (as face _d_) is then drawn across the upper face of each wedge. Wedges (as B, C,) are then put in on each side of the bed until they each just meet the bed, and a line coincident with the bed surface is drawn across their upper surfaces. Wedge B is then driven in until it relieves A of the weight of the bed, and a second line is drawn across its upper face. It is then withdrawn to the first line, and the wedge on the opposite side of the bed is driven in until A is relieved of the weight, when a second line is drawn on this wedge's face. The wedges at the other end (as C) are then similarly driven in and withdrawn, being also marked with two lines, and then the four wedges (B, C, and the two corresponding ones on the opposite side of the bed) are withdrawn, having upon their surfaces two lines each (as A, B, in Fig. 1631). Midway between these two lines a third (as C) is drawn, and all four wedges are then driven in until line C is coincident with the bed surface, when it may be assumed that the bed is supported equally at all the four points. When the bed is turned over, surfaces _f_ may lie on the table surface without any packing whatever, as they will be true. Another excellent method is to balance the bed on three points, two at one end and one at the other, and to then pack it up equally at all four corners. To test if the surface of a piece of such work has been planed straight, the following plan may be pursued:-- [Illustration: Fig. 1632.] Suppose that surface E, Fig. 1632, is to be tested, it having been planed in the position it occupies in the figure, and the casting may be turned over so that face E stands vertical, as in Fig. 1632, and a tool may be put in the tool post of the planer, the bed being adjusted on the planer table so that the tool point will just touch the surface at each end of the bed. The planer table is then run so that the tool point may be tried with the middle of the bed length, when, if the face E is true, it will just meet the tool point at the middle of its length as well as at the ends. In the planing of the [V]-guides and guideways of a bed for a machine tool, such as, for example, a planer bed and table, the greatest of care is necessary, the process being as follows:-- Beginning with the bed it has been shown in Fig. 1601 that the sides of the guideways must all be of the same height as well as at the same angle, and an excellent method of testing this point is as follows:-- [Illustration: Fig. 1633.] In Fig. 1633 is shown at A a male gauge for testing the [V]-guideways in the bed, and at B a female gauge for testing those on the table. These two gauges are accurately made to the correct angle and width, and fitted together as true as they can be made, being corrected as long as any error can be found, either by testing one with the other or by the application of a surface plate to each separate face of the guides and guideways. The surfaces C and D of the respective gauges are made parallel with the [V]-surfaces, a point that is of importance, as will be seen hereafter. It is obvious that the female gauge B is turned upside down when tried upon the table. [Illustration: Fig. 1634.] Suppose it is required to test the sides _e_, _f_, of the bed guideways in Fig. 1634, and the gauge must be pulled over in the direction of the arrow so that it touches those two sides only; a spirit-level laid upon the top of the gauge will then show whether the two faces _e_, _f_, are of equal height. It is obvious that to test the other two faces the gauge must be pulled over in the opposite direction. This test must be applied while fitting the [V]s to the gauge. Suppose, for example, that when the gauge is applied and allowed to seat itself in the ways, the two outside angles _e_, _g_, are found to bear while the two inside ones do not touch the gauge at all, then by this test it can be found whether the correction should be made by taking a cut off _e_ or off _g_, for if the spirit-level stood level when the gauge was pulled in either direction, then both faces would require to be operated upon equally, but suppose that the gauge and spirit-level applied as shown proved end _e_ to be high, then it would be the one to be operated on, or if when the gauge was pulled over in the opposite direction end _g_ was shown (by the spirit-level) to be high, then it would be the one to be operated upon. By careful operation the table and bed may thus be made to fit more perfectly than is possible by any other method. To test the fit of the gauge to the [V]s it is a good plan to make a light chalk mark down each [V] and to then apply the gauge, letting it seat itself and moving it back and forth endways, when if it is a proper fit it will rub the chalk mark entirely out. It may be noted, however, that a light touch of red marking is probably better than chalk for this purpose. It is of importance that the [V]s be planed as smooth as possible, and to enable this a stiff tool holder holding a short tool, as in Fig. 1635 should be used, the holder being held close up to the tool box as shown. It will be obvious that when the head is set over to an angle it should be moved along the cross slide to plane the corresponding angle on the other side of the bed. Fig. 1636 represents a planer chuck by Mr. Hugh Thomas. The angle piece A is made to stand at an angle, as shown, for cylindrical work, such as shafts, so that the work will be held firmly down upon the table. The base plate B has ratchet teeth at each end C, into which mesh the pawls D, and has slotted holes for the bolts which hold it down to the table, so that it has a certain range of movement to or from the angle piece A, and may therefore be adjusted to suit the diameter or width of the work. The movable jaw E is set up by the set-screw F and is held down by the bolts shown. The pawls D are constructed as shown in Fig. 1637, the pin or stem S fitting the holes in the planer table and the tongue P being pivoted to the body R of the pawl. As the pawls can be moved into any of the holes in the table, the base plate B may be set at an angle, enabling the chuck to be used for taper as well as for parallel work, while the chuck has a wide range of capacity. In Fig. 1614 is shown a supplementary table for increasing the capacity of planer tables, and which has already been referred to, and Fig. 1638 represents an application of the table as a chucking device. A, A, &c., are frames whose upper surfaces are to be planed. An angle plate is bolted to the planer table and the supplementary table is bolted to the angle plate. The first frame is set against the vertical face of the supplementary table, and the remaining ones set as near as possible, B, B, &c., being small blocks placed between the frames which are bolted to the planer table as at C. [Illustration: Fig. 1635.] In many cases this method of chucking possesses great advantages. Thus in the figure there are six frames to be planed, and as they would be too long to be set down upon the planer table, only three or four could be done at a time, and a good deal of measuring and trying would be necessary in order to get the second lot like the first. This can all be avoided by chucking the whole six at once, as in figure. Another application of the same tables as useful chucking devices is shown in Fig. 1639, where two frames E, F, are shown bolted to the machine table and supported by the supplementary tables T, which are bolted to the main table and supported by angle-pieces _b_, _b_. Work that stands high up from the planer table may be very effectively steadied in this way, enabling heavier cuts and coarser feeds while producing smoother work. [Illustration: Fig. 1640.] As horizontal surfaces can be planed very much quicker than vertical ones, it frequently occurs that it will pay to take extra trouble in order to chuck the work so as to plane it horizontally, an excellent example being the planing of the faces of the two halves of a large pulley, the chucking of which is illustrated in Fig. 1640. Four pieces, as at A, are made to engage the rims of the two halves of the pulley and hold them true, one with the other. The two plates T´ and T´´ are set under the pulley halves to level the upper faces, and wooden clamps C, C, are bolted up to hold the pulleys together at the top, W representing wedges between the hubs. S represents supports to block up the pulley near its upper face, and at P are clamps to hold the two halves to the table. It is found that by this method of chucking more than half the time is saved, and the work is made truer than it is possible to get it by planing each half separately and laying them down on the table. Supplemental tables may also be made in two parts, the upper one being capable of swiveling as in Fig. 1641, the swiveling device corresponding to that shown for the Thomas shaper chuck in Fig. 1530. This enables the work to be operated upon on several different faces without being released from the chuck. Thus in figure the segment could be planed on one edge and the upper table swiveled to bring the other edge in true with the table, which would be a great advantage, especially if the face it is chucked by has not been trued. Figs. 1642 and 1643 show other applications of the same swiveling device. It is obvious that the chuck shown in Fig. 1636 can be mounted on a supplemental and swiveling table as shown in Fig. 1644, thus greatly facilitating the chucking of the work and facilitating the means of presenting different surfaces or parts of the work to the tool without requiring to unchuck it. The pawls, also, may in heavy work have two pins to enter the work-table holes and be connected by a strap as in Fig. 1645. In the exigencies of the general machine shop it sometimes happens that it is required to plane a piece that is too wide to pass between the uprights of the planing machine, in which case one standard or upright may be taken down and the cross slide bolted to the other, as in Fig. 1646, the blocks _a_, _a_, being necessary on account of the arched form of the back of the cross slide. In the example given the plates to be planed were nearly twice as wide as the planer table and were chucked as shown, the beam D resting on blocks E, F, and forming a pathway for the piece C, which was provided with rollers at each end so as to move easily upon D. The outer end of the plate was clamped between B and C, and the work was found to be easily and rapidly done. In this chucking, however, it is of importance that beam D be carefully levelled to stand parallel with the planer table face, while its height must be so adjusted that it does not act to cant or tilt the table sideways as that would cause one [V] of the planer ways to carry all or most of the weight, and be liable to cause it to cut and abrade the slide surfaces. [Illustration: _VOL. I._ =EXAMPLES IN PLANING WORK.= _PLATE XVIII._ Fig. 1636. Fig. 1637. Fig. 1638. Fig. 1639.] [Illustration: Fig. 1641.] [Illustration: Fig. 1642.] [Illustration: Fig. 1643.] [Illustration: Fig. 1644.] [Illustration: Fig. 1645.] [Illustration: Fig. 1646.] CUTTING TOOLS FOR SHAPING AND PLANING MACHINES.--All the cutting tools forged to finished shape from rectangular bar steel, and described in connection with lathe work, are used in the planer and in the shaper, and the principles governing the rake of the top face remain the same. But in the matter of the clearance there is the difference that in a planing tool it may be made constant, because the tool feeds to its cut after having left the work surface at the end of the back stroke, hence the clearance remains the same whatever the amount or rate of feed may be. [Illustration: Fig. 1647.] On this account it is desirable to use a gauge as a guide to grind the tool by, the application of such a gauge being shown in Fig. 1647. It consists of a disk turned to the requisite taper and laid upon a plate, whereon the tool also may be laid to test it. The tool should not be given more than 10° of clearance, unless in the case of broad flat-nosed tools for finishing, for which 5° are sufficient. [Illustration: Fig. 1648.] [Illustration: Fig. 1649.] The principle of pulling rather than pushing the tool to its cut, can, however, be more readily and advantageously carried out in planer than in lathe tools, because the spring of the tool and of the head carrying it only need be considered, the position of the tool with relation to the work being otherwise immaterial. As a consequence it is not unusual to forge the tools to the end of pulling, rather than of pushing the cutting edge. [Illustration: Fig. 1650.] In Figs. 1648 and 1649, for example, are two tools, W representing the work, and A the points off which the respective tools will spring in consequence of the pressure; hence the respective arrows denote the direction of the tool spring. As a result of this spring it is obvious the tool in Fig. 1648 will dip deeper into the work when the pressure of the cut increases, as it will from any increase of the depth of the cut in roughing out the work, or from any seams or hard places in the metal during the finishing cut. On the other hand, however, this deflection or spring will have the effect of releasing the cutting edge of the tool from contact with the work surface during the back stroke, thus rendering it unnecessary to lift the tool to prevent the abrasion, on its back stroke, from dulling its cutting edge. [Illustration: Fig. 1651.] [Illustration: Fig. 1652.] It will be noted that the radius from the point of support A is less for the tool in Fig. 1649 than for that in Fig. 1648, although both tools are at an equal height from the work, which enables that in Fig. 1649 to operate more firmly. In these two figures the extremes of the two systems are shown, but a compromise between the two is shown in Fig. 1650, the cutting edge coming even with the centre of the body of the steel, which makes the tool easier to forge and grind, and keeps the cutting edge in plainer view when at work, while avoiding the evils attending the shape shown in Fig. 1648. It is sometimes necessary, however, that a tool of the form in Fig. 1652 be used, as, for example, to shape out the surface of a slot, and when this is the case the tool should be shaped as in Fig. 1651, the bottom face having ample clearance (as, say, 15°) from the heel A to about the point B, and about 3° from B to the front end. The front face should have little or no clearance, because it causes the tool to dig into the work. A tool so shaped will clear itself well on the back stroke, whereas if but little clearance and front rake be given as in Fig. 1652, the tool will not only dig in, but its cutting edge will rub on the back or return stroke. [Illustration: Fig. 1653.] For broad feed finishing cuts the shape of tool shown in Fig. 1653 is employed, the cutting edge near the two corners being eased off very slightly with the oilstone. The amount of clearance should be very slight indeed, only just enough to enable the tool to cut as is shown in the figure, by the line A A. The amount of front rake may be varied to suit the nature and hardness of the metal, and the tool should be held as close in as possible to the tool clamp. Smoother work may be obtained in shaping and in planing machine tools when the tool is carried in a holder, such as in Fig. 1654, which is taken from _The American Machinist_ because in this case any spring or deflection either in the tool or in the shaper head acts to cause the tool to relieve itself of the cut instead of digging in, as would be the case were the tool put in front of the tool post as in Fig. 1654. In finishing large curves this is of great importance, because to obtain true and smooth curves it is necessary to shape the tool to cut upon the whole of the curve at once, and this gives so great a length of cutting edge, that the tool is sure to chatter if held in front of the tool post. [Illustration: Fig. 1654.] It is essential, therefore, to carry the tool at the back of the tool post as shown, and for curves that are arcs of circles tools such as in Fig. 1655 may be employed, or a circular disk will answer, possessing the advantage that its shape may be maintained by grinding its flat face to resharpen it. Cutters of the kind shown in Fig. 1655 may be made to possess several important advantages aside from their smooth action: thus they may be made after the principle explained with reference to the Brown & Sharpe rotary cutters for gear-teeth, in which case the front face only need be ground to resharpen them, and their shapes will remain unaltered, and they may be given different degrees of front rake by placing packing between one side and the holder, and any number of different shaped cutters may be fitted to the same stock. [Illustration: Fig. 1655.] TOOL HOLDERS FOR PLANING MACHINES.--The advantages of tool holders for planing machines are equally as great as those already described for lathes, but as applied to planing machines there is the additional advantage that the clearance necessary on the tool is less variable for planer work than for lathe work, because in lathe work the diameter of the work as well as the rate of tool feed affects the tool clearance, whereas in planer work the tool feed is put on before the tool begins its cutting action; hence the degree of clearance is neither affected by the size of the work nor by the rate of feed, and as a result the tools may be given a definite and constant amount of clearance. [Illustration: Fig. 1656.] Fig. 1656 represents a planer tool holder (by Messrs. Smith & Coventry), in which what is, in effect, a swivel tool post is attached to the end of the holder, thus enabling the tool to be used on either the right or left-hand of the holder at will. The shape of the tool steel is shown in section on the right-hand of the engraving, being narrow at the bottom, which enables the tool to be very firmly held and reduces the area to be ground in sharpening the tool. A side and end view of the holder is shown in Fig. 1657, in which it is seen that the tool may be given top rake or angle to render it suitable for wrought iron or steel or may be set level for brass work. [Illustration: Fig. 1657.] In Fig. 1658 the tool and holder are shown in position on the planer head, the front rake on the tool being that suitable for wrought iron. [Illustration: Fig. 1658.] It is to be noted, however, that the amount of front rake should, to obtain the best results, be less for steel than for wrought iron, and less for cast iron than for wrought, while for brass there should be none; hence the tool post should be made to accomplish these different degrees of rake in order to capacitate such holders for the four above-named metals. It is an advantage, however, that by inclining the tool to give the top rake, this rake may be kept constant by grinding the end only of the tool to sharpen it, and as the end may be ground to a gauge it is very easy to maintain a constant shape of tool. Furthermore as the tool is held by one binding screw only, it may be more readily adjusted in position for the work than is the case when the two apron clamp nuts require to be operated. [Illustration: Fig. 1659.] [Illustration: Fig. 1660.] Figs. 1659 to 1661, show this tool-holder applied to various kinds of work, thus in Fig. 1659 the tool is planing under the underneath side of a lathe bed flange, while in Fig. 1660 it is acting upon a [V]-slideway and escaping an overhanging arm, and in Fig. 1661 it is shown operating on a [V]-slideway and in a [T]-groove. [Illustration: Fig. 1661.] Fig. 1662 represents a tool holder by Messrs. Bental Brothers, the tool being held in a swivelled tool post, so that it may be used as a right or left-hand tool. In this case the front rake must be forged or ground on the tool, and there is the further objection common to many tool holders, that the tool if held close in to the tool post is partly hidden from view, thus increasing the difficulty of setting it to the depth of cut. [Illustration: Fig. 1662.] Another form of planer or shaper tool-holder is shown in Fig. 1663, in which a tool post is mounted on a tool bar, and may be used as a right or left-hand tool at will. [Illustration: Fig. 1663.] [Illustration: Fig. 1664.] Fig. 1664 represents a tool holder in which two tools may be held as shown, or a single tool right-hand or left-hand as may be required, or the tool may be held at the end of the holder as in Fig. 1665. The advantage of such a holder is well illustrated in the case of cutting out a [T]-shaped groove, because with such a holder a straight tool can be used for the first cuts, its position being shown in Fig. 1665, whereas in the absence of such a holder a tool bent as in Fig. 1666 would require to be used, this bend giving extra trouble in the forging, rendering the tool unfit for ordinary plain work, and being unable to carry so heavy a cut or to cut so smooth as the straight tool in Fig. 1665. In cutting out the widest part of such a groove the advantage of the holder is still greater, because by its use a tool with one bend, as in Fig. 1667, will serve, whereas without a holder the tool must have two bends, as shown in the figure, and would be able to carry a very light cut, while liable to dig into the work and break off. [Illustration: Fig. 1665.] [Illustration: Fig. 1666.] The tool itself should be so forged that one side is flush with the side of the tool steel as shown at A in Fig. 1668, for if there is a shoulder, as at C, it sometimes prevents the tool from entering the work as shown in the figure. [Illustration: Fig. 1667.] Other examples in the use of this tool holder are given in Figs. 1669 and 1670. [Illustration: Fig. 1668.] In Fig. 1669, we have the case of cutting out the [V]-slideways of a planer bed, and it is seen that the tool point may be held close to the holder, the side of the tool box still clearing the side of the [V]-slideway, whereas in the absence of the holder the tool would require to have a considerable bend in it, or else would have to stand out from the bottom of the tool apron to a distance equal to the length of one side of the slideway. [Illustration: Fig. 1669.] [Illustration: Fig. 1670.] In Fig. 1670 it is also seen that by the use of the holder the tool point may also be held as close as necessary to the holder, and still permit the side of the vertical slide S´ and the tool box B to clear the vertical face of the work. In all planer work it is an essential in the production of true and smooth surfaces that the tool be held as close in to the tool clamp or tool box as possible, and this forms one of the main advantages of tool holders. CHAPTER XVIII.--DRILLING MACHINES. POWER DRILLING MACHINES.--The drilling machine consists essentially of a rotating spindle to drive the drill, a work-holding table, and means of feeding the drill to its cut. The spindle speed and the force with which it is driven are varied to suit the work. The feeding is sometimes given to the spindle, and at others to the work table. In either case, however, the feeding mechanism should be capable of varying the rate of feed and of permitting a quick withdrawal of the drill. The spindle should be supported as near to its drill-holding end as possible. When the table feeds to the work the spindles may be held rigidly, because of their not requiring to pass so far out or down from the bearing supporting them; but when the spindle feeds, it must either pass through its bearings, or the bearing, or one of them, must either be capable of travel with the spindle or adjustable with relation to the machine framing. In using small drills in a machine it is of the first importance that the amount of pressure necessary to feed the drill be plainly perceptible at the hand lever or other device for feeding the drill or the work, as the case may be, as any undue pressure causes the drills to break. To attain sensitiveness in this respect the parts must be light and easy both to move and to operate. Fig. 1671 represents the American Tool Company's delicate drilling machine for holes of 1/4 inch and less in diameter. It consists of a head fixed upon a cylindrical column and affording journal bearing to the drill-driving spindle, which is driven by belt. The table on which the work is placed is carried by a knee that may be fixed at any required height upon the same round column. The knee and table may be swung out of the way, the column serving as a pivot. The table has journal bearing in the knee, and is fed upwards by the small lever shown. Fig. 1672 represents Elliott's drilling machine for drills from 1/32 inch to 3/4 inch in diameter. The work table may be revolved in the arm that carries it, and this arm may be swung round the column or post. It is operated upwards for the feed by the hand lever shown. The conical chuck shown lying on the work table fits into the hole that is central in the table, and is used to receive the end of cylindrical work and hold it true while the upper end is operated upon. The construction of the live spindle and its cone are shown in Fig. 1673. The drill chuck Q is attached to and driven by a one-inch steel spindle 19 inches long, which is accurately fitted through the sleeve bearings, within which it is free to move up and down, but is made to revolve with the cone by means of the connection O, one end of which slides upon the rods L. The drill is held up by means of the spiral spring M acting from the bottom of cone to the collar O. The weight of cone and spindle is carried upon a raw-hide washer, beneath which is the cupped brass P which retains the oil. The thrust of the feed lever G is also taken by a raw-hide washer R. The machine is provided with a hand and a foot feed by means of the compound lever W Z, Fig. 1674, actuating the feed rod J, which passes up within the column and connects to the lever K, the latter being suspended by a link H. Fig. 1675 represents Slate's sensitive drilling machine, in which the lower bearing for the live spindle is carried in a head H that fits to a slide on the vertical face of the frame, so that it may be adjusted for height from the work table W to suit the height of the work. L is a lever operating a pinion engaging a rack on the sleeve S to feed the spindle. The table W swings out of the way and a conically recessed cup chuck C is carried in a bracket fitting into a guideway in the vertical bed G. The cone of the cup chuck is central to or axially in line with the live spindle, hence cylindrical work may have its end rested in the cone of the cup chuck, and thus be held axially true with the live spindle. [Illustration: Fig. 1676.] Fig. 1676 represents a drilling machine in which the spindle has four changes of feed, and is fed by a lever handle operating a pinion that engages a rack placed at the back of a sleeve forming the lower journal bearing for the spindle. This lever is provided with a ratchet so that it may be maintained in a handy position for operating. The work table is raised or lowered by a pinion operating in a rack fast upon the face of the column, a pawl and ratchet wheel holding it in position when its height has been set. A lever is used to operate the pinion, being inserted in a hub fast upon the same spindle that carries the pinion and the ratchet wheel. Fig. 1677 represents a drilling machine by Prentice Brothers, of Worcester, Massachusetts. Motion for the cone pulley A is received by pulleys B and is conveyed by belt to cone pulley C, which is provided with back gear, as shown; the driving spindle D drives the bevel pinion E, which gears with the bevel-wheel F, which drives the drill spindle G by means of a feather fitting in a keyway or spline that runs along that spindle. Journal bearing is provided to the upper end of the spindle at H and to the lower end by bearings in the head J, which may be adjusted to stand at, and be secured upon any part of the length of the slideway K. By this arrangement the spindle is guided as near as possible to the end L to which the drill is fixed and upon which the strain of the drilling primarily falls. This tends to steady the spindle and prevent the undue wear that occurs when the drill spindle feeds below or through the lower bearing. [Illustration: _VOL. I._ =LIGHT DRILLING MACHINES.= _PLATE XIX._ Fig. 1671. Fig. 1672. Fig. 1673. Fig. 1674. Fig. 1675.] The feed motions are obtained as follows:-- On the drill spindle is a feed cone M which is connected by belt to cone N, which drives a pinion O, that engages a gear P upon the feed spindle Q, which has at its lower end a bevel pinion, which drives a bevel gear upon the worm shaft R. The worm shown on R drives the worm-wheel S, whose spindle has a pinion in gear with the rack T, which is on a sleeve U on the drill spindle G. It is obvious that when the rack T is operated by its pinion the sleeve U is moved endways, carrying the feed spindle with it and therefore feeding the drill to its cut, and that as the feed cone M has three steps there are three different rates of automatic feed. To throw the self-feed into or out of action the following construction is employed:-- The worm-wheel S has on its hub face teeth after the manner of a clutch, and when these teeth are disengaged from the clutch sleeve W the worm-wheel S rides or revolves idly upon its shaft or spindle, which therefore remains at rest. Now the clutch sleeve S has a feather fitting to its spindle or shaft, so that the two must, if motion takes place, revolve together, hence when W is pushed in so as to engage with S, then S drives W and the latter drives the spindle, whose pinion operates the rack T. A powerful hand feed to the drill spindle is provided as follows:-- [Illustration: Fig. 1677.] The worm shaft R is hollow, and through it passes a rod having at one end the hand nut V and at the other a friction disk fitting to the bevel gear shown at the right-hand end of the worm-shaft. This friction disk is fast upon the worm-shaft and serves to lock the bevel gear to the worm-shaft when the nut V is screwed up, or to release it from that shaft when V is unscrewed. Suppose, then, that V is unscrewed and shaft R will be unlocked from the bevel-wheel and may be operated by the hand wheel X, which is fast upon the worm-shaft, and therefore operates it and worm-wheel S, so that W being in gear with S the hand feed occurs when X is operated and V is released. But as the motion of S is, when operated by its worm, a very slow one, a second and quick hand feed or motion is given to the spindle G as follows, this being termed the quick return, as it is mainly useful in quickly removing the drill from a deep hole or bore. The spindle carrying S and W projects through on the other side of the head J and has at its end the lever Y, hence W being released from S, lever Y may be operated, thus operating the pinion that moves rack T, one revolution of Y giving one revolution to the pinion, both being on the same shaft or spindle. The work is carried and adjusted in position beneath the drill as follows:-- The base of the column or frame is turned cylindrically true at _a_, and to it is fitted a knee _b_ which carries a rack _c_. The knee _b_ affords journal bearing to a spindle which has a pinion gearing with the rack _c_, and at the end of this spindle is a ratchet-wheel _d_ operated by the lever shown. A catch may be engaged with or disengaged from ratchet _d_. When it is disengaged the lever may be operated, causing the pinion to operate on rack _c_ and the knee _b_ to raise or lower on _a_ according to the direction in which the lever is operated. As the knee _b_ carries the rack the knee may be swung entirely from beneath the drill spindle and the work be set upon the base plate _e_ if necessary, or it may be set upon the work table _f_ which has journal bearing in the knee _b_, so that it may be revolved to bring the work in position beneath the drill. [Illustration: Fig. 1678.] In the Sellers drilling machine, Fig. 1678, the drill spindle when in single gear is driven by belt direct, producing a uniform and smooth motion that is found of great advantage in drilling the smaller sizes of holes. The back gear is arranged to drive the spindle direct without the power requiring to be transmitted through a shaft, which induces vibration. The drill spindle is provided with variable rates of self-acting feed, but may also be moved rapidly by hand, and is counterbalanced. The work table is capable of revolving upon its axis, and the arm on which it is carried is pivoted in a slide upon a vertical slideway on the front of the main frame, so that the table and the arm may be swung out of the way for work that can be more advantageously rested on the base plate of the machine. A central hole is bored in the table, being true to the drill spindle when the arm is in its mid position, and clamps are provided to secure the circular table against rotation when it is set to place, and also to secure the swinging bracket to any required position. This form of table, like the compound table, has the advantage of permitting all parts of the table being brought in turn under the drill, but the motion is not in right lines. Holes are provided in the circular table to admit holding-down bolts. The rates of feed are proportioned to the kind of drilling to be done. When the back gear is not in use and small drills are to be driven, the range of feeds is through a finer series than when the back gear is being used, and large drills or boring bars are to be driven. Fig. 1679 represents a drilling machine of English design. The cone pulley A is provided with back gear B placed beneath it, the live spindle driving the drill spindle through the bevel gears C, one of which is fast upon a sleeve D through which the drill spindle E passes. The feed motions are obtained as follows:--I is the feed cone driving cone J, which drives a worm and worm-wheel at K. In one piece with the worm-wheel is a ratchet wheel L, and at M is a handle with a pawl that may be engaged with or disengaged from ratchet-wheel L. When it is engaged the handle, which is fast upon the vertical feed spindle N, is revolved by the worm-wheel and the automatic feed is put in operation; but when the pawl is disengaged the worm and worm-wheel revolve in the bearing while the spindle N remains at rest, unless it be operated by the handle M, which obviously revolves the spindle N more quickly than the worm and gives to a corresponding extent a quick motion to the drill spindle. Spindle N is provided with the gear-wheel O, which drives gear P, which is threaded upon the feed screw F and has journal bearing at Q. The sleeve D has journal bearing at G and at H. At R is a hand wheel upon a horizontal shaft at whose other end is a bevel gear engaging with a bevel gear on the vertical screw for the knee T which fits to the vertical slides V. The work table W is fitted to a horizontal slide upon the arm X, which is pivoted to the knee T at Y, the handle for operating the screw of the table being at Z. [Illustration: Fig. 1680.] RADIAL DRILLING MACHINE.--Fig. 1680 represents a radial drilling machine, the column of which envelops a sleeve round which it may be swung or revolved, the sleeve extending some distance up from the base plate. The arm fits to the column and may be raised or lowered to any desired height to suit the work, the construction being as follows:-- [Illustration: _VOL. I._ =HEAVY DRILLING MACHINE.= _PLATE XX._ Fig. 1679.] [Illustration: Fig. 1681.--Front View.] [Illustration: Fig. 1682.] [Illustration: Fig. 1683.--Side Elevation.] [Illustration: Fig. 1684.--Front Elevation.] Motion by belt is given to the spindle shown extending above the top of the column, and the pair of gears beneath it convey motion to the pair of bevels which drive the upper cone pulley which connects by belt to the lower one, which is provided with back gears to give the necessary changes of speed and power for the wide range of work the machine is intended for; the live spindle of the lower cone pulley extends past the collar and runs beneath the horizontal arm, giving motion to the drill spindle, which is carried in a sliding head. The spindle may be set at any required angle to the arm. The vertical screw on the right hand of the column passes through a nut in the column, so that by throwing the gearing at the upper end of the screw into action, the arm may be raised or lowered by power. The vertical rod appearing in the front of the column and having an arm at its top, is for putting this gearing in or out of action, the arm being raised or lowered according to the direction in which the rod is operated by the lever handle shown upon it, and in front of the column. The gearing at the top of the raising and lowering screw is constructed on the principle that was shown in Fig. 566, for reversing the direction of a lathe feed. The capacity to swing the drill spindle at an angle enables the drilling of long work such as the flanges of pipes, by setting the pipe at an angle and swinging the spindle so as to stand parallel to it, while the facility with which the arm may be moved to any required position makes it easier to move the arm to the work, so that the latter will require but one chucking or setting. Radial drilling machines are of various constructions. In some the drilling head is carried by an arm standing at a right angle to the main column or frame, and is capable of being moved to any required position upon the length of this arm. The arm itself is sometimes made capable of swinging upon its own axis, as shown in Fig. 1682. It is also capable of being adjusted at any height from the bed or base plate upon which the upright or main frame sits, or above the work table when one is used as in the figure. The advantage given by these facilities is that a heavy piece of work may be set upon the base plate or work table, and be drilled in various places without requiring to be moved. Figs. 1681 and 1682 represent a radial drilling machine, in which the radial arm is carried on a head, which fits a vertical slideway provided on the face of the upright column, and may be moved to any required height on this slideway by means of a rack and worm gear, the latter being shown in the front view. The seat of the arm on this head is cylindrical, the head being pivoted upon it in order that it may permit of its being rotated to hold the drill at an angle. The drill spindle is carried in a head sliding on the radial arm as already stated, and is driven as follows:-- Motion from the shop driving shaft is communicated by belt to the cone pulley shown at the base of the upright column. The spindle of this cone pulley drives a belt which passes up the column over an idle pulley on the sliding head that carries the radial arm; hence it passes along the front of the radial arm and partly round a pulley on the drill spindle, two idle pulleys holding it in contact with the drill spindle pulley. Hence it passes over a small pulley at the outer end of the radial arm, and returns along that arm through the sliding head, over an idle pulley to the pulley seen at the head of the vertical column, and from this pulley it passes to the pulley that is on the cone spindle shaft at the base of the column. The drill is provided with an automatic feed actuated by the worm shown on the drill spindle. In Figs. 1683, 1684, and 1685 is represented a combined drilling and boring machine. It is provided with an horizontal as well as with a vertical spindle, either of which may be used for boring as well as for drilling. In the case of the vertical spindle the boring bar may extend down and have journal bearing in a block, or bearing secured to the base plate I. Each spindle has eight changes of speed, four in single, and four in double gear, that is when the back gears at _a_ are in operation. Motion from the pulley K on the cone spindle is conveyed by belt B to pulley L, whose hub extends through the frame at R and affords journal bearing to that end of spindle S which has a feed motion at H. Motion is conveyed from the cone spindle to vertical spindle _m_ as follows:-- [Illustration: Fig. 1685.] Referring to Fig. 1685, bevel-wheel _f_ is on the end of the cone spindle and drives bevel-wheel _g_, which drives spindle _m_. This spindle is provided with an automatic as well as a hand-feed motion, the construction being as follows:-- Referring first to the automatic feed, the cone pulley E´, Fig. 1685, which is upon the main cone spindle of the machine, drives cone E, Fig. 1683, and the latter operates a worm W, Fig. 1684, engaging a worm-wheel W, which drives the bevel gear _a_, shown by dotted circles in Fig. 1685; _a_ drives the bevel gear _c_ upon the sleeve _o_, which has journal bearing (in the frame A of the machine) both at its upper end and immediately above C. The upper end of the sleeve _o_ is threaded to receive an inner sleeve _n_, within which is a spindle _v_, having journal bearing at each end of _n_ and being fast to _m_, so as to revolve with it. End motion to _n_ is prevented by a collar at its upper end _r_ and by three steel washers at _i_, the latter taking the thread when the drill spindle _m_ is in operation. The inner sleeve _n_ is prevented from revolving by means of a lug or projection which passes into a slot or groove running vertically in the bore of the outer casing A; hence when _o_ is revolved by _a_ it acts as a nut to _n_, causing the latter to move endways and feed the drill spindle _m_. To enable the engagement or disengagement of the automatic feed, there is at F, Fig. 1684, a friction disk, the female half of which is fast upon the spindle that drives bevel gear _a_ in Fig. 1685, while the male half is in one piece with the hand wheel Z, Fig. 1684, which has journal bearing upon the spindle of _a_. G is a hand nut for engaging or disengaging the friction disks. In addition to the ordinary work table T, the knee U carries on a projection X a work-holding vice V, which is a great convenience, especially for cylindrical work. The base of the machine is provided with a plate upon which work may be secured independent of the work table T, or the lower end of a boring bar may be steadied by a step bolted to the base plate. The construction of the machine, as will be seen, is very substantial throughout, since all the strains are central, the spindles are well supported, and there is a commendable absence of springs, pull-pins, and other light parts that are liable to get out of order from the wear and tear of the ordinary machine-shop tool. It may also be remarked that the combination of the two spindles is effected without impairing either the usefulness or handiness of the vertical spindle. [Illustration: Fig. 1686.] In Fig. 1686, which is taken from _Mechanics_, is illustrated a combined drilling and turning machine. In this machine the motion for both drilling and turning is received by belt on the cone pulley shown on the right, which is provided with back gear similar to that of a lathe. The live spindle thus driven has a face plate at the left-hand end, whereon work may be chucked to be operated upon by a tool in the compound slide rest shown on the cylindrical column. Motion to the drill spindle is conveyed by belt from a pulley on this same live spindle, hence the same cone pulley and back gear are utilized for either drilling or turning. The self-acting feed for the drill spindle is actuated by an eccentric on that spindle operating an arm, having a pawl engaging with the ratchet wheel on the lower end of the vertical feed spindle. Obviously when the pawl is thrown out of engagement with the ratchet wheel, the horizontal hand wheel may be used to feed the drill spindle by hand or to withdraw it, as the case may be. The work table for drilling operations has motion laterally in two directions (one at a right angle to the other) by means of being carried on slides, and is fitted to a vertical slide on the face of the column so that it may be raised and lowered to suit the height of the work by means of the worm and worm-wheel shown, the latter being on the same shaft as a pinion engaging with a vertical rack on the face of the upright frame or column. In Fig. 1687 is represented a horizontal drilling and boring machine. In this machine the work-holding table is provided with a hand feed, and the drilling or boring spindle with hand and self-acting feed, the latter being variable to suit different kinds of work. The table has a compound motion upon suitable slideways and rests upon a frame or knee that is elevated by two vertical screws that are operated by hand wheel. This knee fits to a vertical slideway on the main frame, so that its upper face, and therefore the face also of the work table, is maintained parallel with the drill spindle at whatever height it may be set from it. The arbor that carries the drill spindle is arranged with a face plate so that the machine can be used as a facing lathe. The feeds are arranged in two separate series, a fine and a coarse, and both of these series are applicable to any speed or any size of drill. The value of the coarse feed will be felt in all kinds of boring with bars and cutters, inasmuch as it is possible to rough out with a fine feed and finish with a light cut and a very coarse feed. For work that is too large to be conveniently lifted to the table of a machine the floor boring machine is employed. Fig. 1688 represents a machine of this class, which consists of two heads that may be moved about upon, and secured to, any part of its base or bed plate to which the work is secured. The boring bar it will be seen stands horizontal, and may be set at any height from the base plate between the limits of 14 inches and 6 feet 4 inches, the driving head being raised on its slideway on the face of its standard or column by automatic mechanism. The feed is automatic and variable in amount to suit the nature of the duty. The bar has eight speeds, four in single and four in double gear. In order to insure that the crank pins of locomotive driving wheels shall stand with their axes parallel to that of the wheel shaft, and that they shall also stand 90° apart when measured on the wheel circle, it is necessary that the holes for these pins be bored after the wheels are upon their shaft, it being found that if the crank pin holes are bored before the wheels are upon the shaft they are liable to be out of parallel and out of quarter. [Illustration: Fig. 1690.] To avoid these errors a quartering machine is employed, such as shown in Fig. 1689. This machine consists of two heads carrying stationary or dead centres to hold the wheel axle, as in a lathe. Each of these heads is provided with a boring bar having an automatic and adjustable feed, the axes of these bars being 90°, or one quarter of a circle, apart. As both crank pin holes are bored simultaneously and with the wheel rigidly fixed and held upon centres the work will obviously be true. This machine may also be used as an ordinary horizontal boring machine. [Illustration: Fig. 1691.] Multiple drilling machines are employed for two general purposes: first, those in which a number of holes may be advantageously drilled simultaneously; and second, where a number of operations require to be performed upon one and the same hole. When the object is to drill a number of holes spaced a certain distance apart in one piece of work, the spindles may be so constructed that their distances one from the other may be adjustable, so that they may be set to drill the holes equally or unequally spaced as may be required. In such machines it will be more convenient to feed the work to the drill, so as to have but one feed motion, instead of having a separate feed motion to each drill spindle. When, however, a number of separate operations are to be performed upon the same hole, it is preferable to rotate the table so that the work may be carried from one spindle to the other, the spindles feeding automatically and simultaneously. Fig. 1690 represents a three-spindle drilling machine. The main driving spindle is vertical and within the top of the column, having three pulleys to connect by belt to the vertical drill driving spindles, whose driving pulleys are of different diameters to vary the speed to suit different diameters of drilling tools. A foot feed is provided by means of the treadle, and a hand feed by means of the lever, the weight of the work table being balanced by means of the ball weight shown. The work table is adjustable for height in a main table, that is adjustable for height on the face of the column. Similar machines are made with four or more spindles. Fig. 1691 represents a four-spindle machine, in which each spindle has a separate and independent feed, which may be operated in unison or separately as may be required. [Illustration: _VOL. I._ =EXAMPLES IN BORING MACHINERY.= _PLATE XXI._ Fig. 1687. Fig. 1688. Fig. 1689.] The four spindles are driven by means of a gear-wheel engaging with a gear on the central or main driving spindle. The work-holding table rotates about the column of the machine, and is arranged with a stop motion that locks the table in position when the work-holding chucks are exactly in line with the drill spindles. Suppose, then, one spindle to drive a drill, the second driving an enlarging drill, a third driving a countersink, and a fourth a reamer. A piece of work may then be fastened beneath the first spindle and be drilled. The table may then be rotated one-fourth of a revolution, bringing it beneath the enlarging drill, while a second piece of work is placed beneath the first or piercing drill. The table may then be given another quarter rotation, bringing the piece of work first put in beneath the countersink, the second beneath the enlarging drill, while a third piece may be placed beneath the first or piercing drill. The table being again given one-quarter rotation the first piece will be brought beneath the reamer, the second beneath the countersink, the third beneath the enlarging drill, and a fourth may be placed beneath the piercing drill; all that will then be necessary is to remove the first piece when it arrives at the piercing drill and insert a new piece; the four spindles operating simultaneously, and the process continuing, the four operations proceed together. Thus the piece of work is finished without being released from the holding devices, which insures truth while requiring a minimum of attendance. The amount of feed being equal for all four spindles the depth to which each tool will operate is gauged by the distance it stands down from the feeding head, each spindle being capable of independent adjustment in this respect, so that the tool requiring to move the farthest through the work will meet it the first, and so on. [Illustration: Fig. 1692.] Figs. 1692 and 1693 represent a combined drilling and turning machine for boiler-maker's use. The machine consists of two uprights or drill standards which can be traversed along horizontal slides on beds which are fixed at right angles one to the other. The work to be drilled is carried on a turntable or work-holding table, the pivot and carrying frame of which can be traversed along a third set of guides lying between the other two and forming an angle of 45° with either of them. Thus, by adjusting the relative positions of the turntable and the drill standards (each of which carries two drills), either a large or a small boiler can be conveniently operated on. Worm-gear is provided for revolving the turntable, either to divide the pitch of the holes, or when the machine is used for turning the edges of flanged plates, or for boring the large holes for flue tubes. Longitudinal seams may be drilled by laying the boiler horizontally on chucks alongside one of the beds, and traversing the drill standard from hole to hole. Referring especially to Fig. 1693, A^{1} and A^{2} are the two wings of the bed plate, each being provided with [V]-slides to carry the uprights or standards B^{1}, B^{2}, on each of which is a drilling head C^{1}, C^{2}, these being each adjustable vertically on its respective standard by means of rack and pinion and hand wheels D^{1} and D^{2}. The heads are balanced so that the least possible exertion is sufficient to adjust them. The vertical standards B^{1} and B^{2} are provided at their bases with a gear wheel operated by means of pinions at G^{1}, G^{2}, so that they may be rotated upon the sliders E^{1} and E^{2}, by means of which they may be traversed along their respective bed slides. The drilling heads are composed of a slider on a vertical slide on the face of the vertical standard or upright, rotary motion and the feed being operated as follows: Power is applied to the machine through the cones K^{1} and K^{2}, working the horizontal and vertical shafts L^{1} and L^{2}, &c. On the vertical shafts are fitted coarse pitch worms sliding on feather keys, and carried with the heads C^{1} and C^{2}, &c. The worms gearing with the worm-wheels M^{1} and M^{2} are fitted on the sleeves of the steel spindles N^{1} and N^{2}. The spindles are fitted with self-acting motions O^{1} and O^{2}, which are easily thrown in and out of gear. The shell to be drilled is placed upon the circular table H, which is carried by suitable framework adjustable by means of screw on the [V]-slide I, placed at an angle of 45° with the horizontal bed plates. By this arrangement, when the table is moved along I it will approach to or recede from all the drills equally. J^{1} and J^{2} are girders forming additional bearings for the framework of the table. The bed plates and slides for the table are bolted and braced together, making the whole machine very firm and rigid. The machine is also used for turning the edge of the flanges which some makers prefer to have on the end plates of marine boilers. The plates are very readily fixed to the circular table H, and the edge of the flange trued up much quicker than by the ordinary means of chipping. When the machine is used for this purpose, the cross beam P, which is removable, is fastened to the two upright brackets R^{1} and R^{2}. The cross beam is cast with [V]-slides at one side for a little more than half its length from one end, and on the opposite side for the same length, but from the opposite end. The [V]-slides are each fitted with a tool box S^{1} and S^{2}, having a screw adjustment for setting the tool to the depth of cut, and adjustable on the [V]-slides of the cross beam to the diameter of the plate to be turned. This arrangement of the machine is also used for cutting out the furnace mouths in the boiler ends. The plate is fastened to the circular table, the centre of the hole to be cut out being placed over the centre of table; one or both of the tool boxes may be used. There is sufficient space between the upright brackets R^{1} and R^{2} to allow that section of a boiler end which contains the furnace mouths to revolve while the holes are being cut out; the plate belonging to the end of a boiler of the largest diameter that the machine will take in for drilling. The holes cut out will be from 2 ft. 3 in. diameter and upwards. Power for using the turntable is applied through the cone T. The bevel-wheels, worms, worm-wheels and pinions for driving the tables are of cast steel, which is necessary for the rough work of turning the flanges. [Illustration: Fig. 1693.] As to the practical results of using the machine, the drills are driven at a speed of 34 feet per minute at the cutting edges. A jet of soapsuds plays on each drill from an orifice 1/32 in. in diameter, and at a pressure of 60 lbs. per square inch. A joint composed of two 1-inch plates, and having holes 1-1/8 in. in diameter, can be drilled in about 2-1/2 minutes, and allowing about half a minute for adjusting the drill, each drill will do about 20 holes per hour. The machine is designed to stand any amount of work that the drills will bear. The time required for putting on the end of a boiler and turning the flange thereon (say, 14 ft. diameter), is about 2-1/2 hours; much, however, depends on the state of the flanges, as sometimes they are very rough, while at others very little is necessary to true them up. The time required for putting on the plate containing the furnace mouths and cutting out three holes 2 ft. 6 in. in diameter, the plate being 1-1/8 inches thick, is three hours. Of course, if several boilers of one size are being made at the same time, the holes in two or more of these plates can be cut out at once. The machine is of such design that it can be placed with one of the horizontal bed plates (say A^{1}) parallel and close up to a wall of the boiler shop; and when the turning apparatus is being used, the vertical arm B^{2} can be swivelled half way round on its square box E^{2}, and used for drilling and tapping the stay holes in marine boiler ends after they are put together; of course sufficient room must be left between bed plate A^{2} and the wall of boiler shop parallel with it, to allow for reception of the boiler to be operated upon. [Illustration: _VOL. I._ =BOILER-DRILLING MACHINERY.= _PLATE XXII._ Fig. 1694. Fig. 1695.] [Illustration: Fig. 1696.--CAR-WHEEL BORING MACHINE.] [Illustration: Fig. 1697.--PULLEY-BORING MACHINE.] [Illustration: Fig. 1698.--COMBINED DRILLING AND COTTER-DRILLING MACHINE.] In Figs. 1694 and 1695 is represented a machine which is constructed for the drilling of shells of steam boilers, to effect which the boiler is set upon a table, round which are placed four standards, each carrying a drilling head, so that four holes may be drilled simultaneously, and is provided with a dividing motion that enables the table to be revolved a certain distance, corresponding to and determining the pitch of the rivet holes. It is capable of drilling locker shells of any diameter between four and eight feet. The feed motion to each drill is driven from one source of power, but each drill is adjustable on its own account. The depth of feed is regulated by a patent detent lever which engages with the teeth of a ratchet wheel, till released therefrom by contact with the adjustable stop. The drill spindle is then instantly forced back by the spiral spring and the forward feed motion continues. It is the duty of the attendant to turn his dividing apparatus handle the required distance for the next hole, directly the drills are withdrawn, the amount of clearance between the drill point and the boiler shell being such as to give him proper time for this purpose, but no more. Self-acting water jets to the drills, and reflectors to enable the operator to see each drill, will be provided, but were not in action at the time views of the machine were made. With an ordinary boiler shell formed in three plates, the three drills work simultaneously, and the one movement of the dividing apparatus, of course, applies to all. If the object to be drilled be not divisible into multiples of three, any other divisions can be produced by the dividing gear, either one, two, or three drills being used, as the circumstances may permit. Two heads can be shifted round from the angle of 120°, at which they are shown, to positions diametrically opposite, as may be desired, and the third can be used or disused as wished. Vertical gauge rods are provided, duly marked out to the various pitches that may be needed for the vertical rows of holes, and the movement of the drill spindle saddles is so simple and steady that accurate adjustment can be made without the least difficulty. In the same way when the drill would, in its natural course, come in contact with one of the bolts by which the plates are held together, the attendant can run all the drills downwards a couple of inches or so, then turn the dividing apparatus two pitches instead of one, and on raising the three drills again he can continue the circular row as before. The entire control of the machine is governed by the attention of one man to two levers and the one dividing handle, which are all conveniently placed for the purpose. In Fig. 1696 is represented a machine for boring car wheels. The chuck is driven by a crown gear operated beneath by a pinion on the cone spindle. The feed motion for the boring bar is operated from the small cone shown on the cone spindle, there being three rates of automatic feed, which are communicated to the bar by a worm and worm-wheel operating a spindle carrying a pinion in gear with a rack on the back of a boring bar. The worm-wheel is provided with a friction disk operated by the small hand-wheel shown, to start and stop the automatic feed, the large hand-wheel operating the rack spindle direct, and therefore giving a rapid hand-feed or quick return motion for the boring bar. The boring bar is counterbalanced by a weight within the frame. On the side of the frame is a small crane for handing the car wheels. Fig. 1697 represents a special machine for boring pulleys, &c. The advantage possessed by this class of machine is fully set forth in the remarks upon Boring and Turning Mills, and with reference to Fig. 725. The tool bar is fed vertically to the rotating pulley, and has three changes of feed; viz. .0648, .0441, and .0279 of an inch per rotation of the work. Its weight is counterbalanced. The speed of rotation of the work table or chuck plate may, by means of the four steps on the cone pulley, be varied as follows:--63, 43, 19, or 10 revolutions per minute, which speeds are suitable for work bores ranging from 1 to 7-1/2 inches in diameter, the power exerted at the tool-point being for the latter diameter 1800 lbs. The tool bar feed is operated by the upper cone pulley, and the worm and worm-wheel shown, the small wheel giving the automatic feed by a suitable friction plate, and the large hand wheel operating the bar quickly to elevate it after it has carried its cut through. When the drill is given a traverse back and forth, it obviously cuts out a slot or keyway whose width is equal to the diameter of the drill, and whose length equals the amount of traverse given to the drill. Special forms of drill are used for this purpose, and their forms will be shown hereafter. The machines for using these drills are termed traverse or cotter drilling machines. In Fig. 1698 is represented a combined drilling and cotter drilling machine. This machine consists essentially of a drilling machine provided with automatic feed motions for cotter drilling; these motions consisting of a self-acting traverse to the sliding head carrying the drill spindle, and a vertical feed, which occurs at the end of each traverse, and during a short period of rest given to the sliding head carriage, or saddle as it is promiscuously termed. The slideway for this head stands vertical and extends across the top of the frame. The belt motion is conveyed up one end and then on the top of the slideway, driving the spindle direct by means of a pulley. The traverse of the head or saddle in cotter drilling is accomplished by means of a peculiar arrangement of screws and adjustable nuts, which can be instantly set to the required length of slot, and insures a uniform motion, back and forth, at each stroke, the length of the stroke being uniform, as is also the rate of its advance. The vertical position of the drill spindle is of great advantage in cotter drilling wrought iron or steel, as the slot in process of cutting can be kept full of oil. The feed motions for cotter drilling may be instantly thrown out of gear when not required, remaining at rest and leaving the machine a simple traverse drill with automatic feeds. CHAPTER XIX.--DRILLS AND CUTTERS FOR DRILLING MACHINES. DRILLING JIGS, GUIDES, OR FIXTURES.--When a large number of pieces are to be drilled alike, as in the case when work is done to special gauges, special chucking devices called jigs, or fixtures, are employed to guide the drill, and insure that the holes shall be pierced accurately in the required location, and test pieces or gauges are provided to test the work from time to time to insure that errors have not arisen by reason of the wear of these drill-guiding devices. [Illustration: Fig. 1699.] [Illustration: Fig. 1700.] Suppose, for example, that we have a link, such as in Fig. 1699, and that we require to have the holes throughout a large number of them of equal diameter at each end and the same distance apart, and if we could prevent the wear of the tools, and so continue to produce any number of links all exactly alike, we could provide a simple test gauge, such as shown in the figure, making it pass the proper distance apart, and of a diameter to fit the holes; but as we cannot prevent wear to the tools we must fix a limit to which such wear may be permitted to occur, and having reached that point they must be restored and corrected. We must at the same time possess means of testing in what direction the wear has induced error. Let it be assumed that the bore at A should be 1/2 inch and that at B 3/8 inch in diameter, that their distance from centre is to be, say, six inches, and that either bore may vary in diameter to the amount of 1/1000 inch, while the distance from centre to centre of the bores may also vary 1/1000 inch. Now let it be noted that if one piece be made 1/2000 inch too short, and another 1/2000 inch too long we have reached the extent of the limit, there being 1/1000 inch difference between them, although neither piece varies more than 1/2000 inch from the standard. Similarly in the bore diameters, if the bore, say at A, is 1/2000 inch too large in one piece and 1/2000 too small in another, there is a difference of 1/1000 between them, although each varies only the 1/2000 inch from the standard. In making test gauges for the holes, therefore, we must consider in what direction the tool will wear; thus, suppose that the finishing reamer for the holes is made when new to the standard diameter, and it can only wear smaller, hence a plug gauge of the standard diameter and 1/1000 inch smaller would serve thus, as so long as the smaller one will go in the limit of wear is not reached; when it will not go in sufficiently easily the reamer must be restored to fit the standard gauge. On the other hand, the reamer when new may be made 1/1000 inch above the standard size and restored when it has worn down to the standard size. In this case the bore diameter is still within the limit as long as the small gauge will enter; but when it fits too tight the reamer must be restored to the large plug gauge, the forms of these gauges being shown in Fig. 1700. [Illustration: Fig. 1701.] [Illustration: Fig. 1702.] In Figs. 1701 and 1702 we have a jig or fixture for holding the link during the drilling process. It consists of two parts, C and D, between which the link is held by the screws E and F. The two hubs, G and H, are provided with hardened steel bushes, I and J, which are pierced with holes to receive and guide the drilling tool or reamer, and it is evident that in time the bore of these bushes will wear, and if they wear on one side more than on another they may wear longer or shorter between the centres or axis; hence we require gauges such as shown in Fig. 1703, one being longer between centres and the other shorter, in each case to the amount of the prescribed limit. In this case, so long as the holes are kept within the prescribed limit of diameter, the distance apart of the two holes will be within the limit so long as neither of the limit gauges will enter; and when they will enter the bushes I J must be restored. It is to be remarked, however, that the variation in the diameter of the holes affects these standards, since if the holes are made sufficiently large either gauge would enter, although the axis of the holes and of the pins on the gauge might be the proper distance apart; hence the gauging for length depends to some degree upon the degree of accuracy in gauging for diameter. [Illustration: Fig. 1703.] Referring now to the construction of the jig, or fixture for drilling the link shown in Figs. 1701 and 1702: the base piece is provided with two short hubs, R and S, upon which the link is to sit, and it is obvious that these hubs must be faced off true with the bottom face of the base, while the link must also be faced so that it will be level, and not be bent or sprung when clamped by the screws E F. It is obvious that the hubs R and S may be omitted, and the link be flat on the base plate; but this would not be apt to hold the link so steadily, and greater care would be required to keep the surface clean. It is also obvious that in the form of jig shown there is a tendency of the screws E and F to bend the piece D; but in the case of small pieces, as, say, not exceeding 8 inches long, piece D may be made strong enough to resist the screw pressure without bending. If, however, the link were, say, 18 inches long, it would be preferable to have projections in place of the hubs R, S, and to let these projections extend some distance along each end of the link, using four holding screws, and clamping the piece D on the inside of the hubs H G. To facilitate the rapid insertion and removal of the link into and from the jig cap-piece, D is pivoted on screw F, while a slot V is cut at the other end, so that when the two screws E, F are loosened, the cap-piece D may be swung out of the way without entirely removing it. [Illustration: Fig. 1704.] [Illustration: Fig. 1705.] [Illustration: Fig. 1706.] [Illustration: Fig. 1707.] In Fig. 1704 we have a link in which a hole is to be bored at one end at a certain distance from a pin at the other, and the fixture, or jig for drilling, is shown in the sectional view, Fig. 1705, the side view, Fig. 1706, and the top view, Fig. 1707. It is obvious that the pin P and the face W of the link must be made true, and that a hardened steel bush may be placed in the hub to receive the pin P. The screw E binds one end of the cap D, and eye-bolts with thumb-nuts F bind the other, these bolts being pivoted at their lower ends, and passing through slots in D, so that as soon as nuts F are loosened, their bolts may be swung out clear of the cap, which may be swung on one side from the pin N as a pivot. [Illustration: Fig. 1708.] [Illustration: Fig. 1709.] In Fig. 1708 we have a piece containing three holes, which are to be drilled in a certain position with regard to each other, and with regard to the face A. This brings us to the consideration that in all cases the work must be chucked or held true by the faces to which it is necessary that the holes must be true, and as in this case it is the face A, the jig must be made to hold the piece true by A, the construction being as in Fig. 1709, which represents a top view, and a sectional side view. The upper plate D carries three hardened steel bushes, A, B, and C, to receive the drilling tools, and thus determine that the holes shall be drilled at their proper positions with relation to each other, and is provided with a face N, against which the face (A, Fig. 1708) may be secured by the screw H, and thus determine the positions of the holes with, regard to that face. At E, F, and G are eye-bolts for clamping the work between the cap and the base plate, which is made large so that it may lie steadily on the table of the drilling machine. When the nuts E, F, and G and the screw H are loosened the cap D may be lifted off and the work removed. If the holes are required to be made very exact in their positions with relation to one edge, as well as to the face A of the work, two screws K would be required, one binding the cap against the lug M of the base, and the other binding the edge of the work against the same lug. The usefulness of jigs, or fixtures, is mainly confined to small work in which a great many duplicate pieces are to be made, and their designing calls for a great deal of close study and ingenuity. They can obviously be applied to all kinds of small work, and as a general principle the holes and pins of the work are taken as the prime points from which the work is to be held. Drilling fixtures may, however, be applied with great advantage to work of considerable size in cases where a number of duplicate parts are to be made, an example of this kind being given in the fixtures for drilling the bolt holes, &c., in locomotive cylinders. [Illustration: Fig. 1710.] For drilling the cylinder covers and the tapping holes in the cylinder, the following device or fixture is employed: The flanges of the cylinder covers are turned all of one diameter, and a ring is made, the inside diameter of which is, say, an inch smaller than the bore of the cylinder; and its outside diameter is, say, an inch larger than the diameter of the cover. On the outside of the ring is a projecting flange which fits on the cover, as in Fig. 1710, _a_ being the cylinder cover, and _b_ _b_ a section of the ring, which is provided with holes, the positions in the ring of which correspond with the required positions of the holes in the cover and cylinder; the diameter of these holes (in the ring, or template, as it is termed) is at least one quarter inch larger than the clearing holes in the cylinder are required to be. Into the holes of the template are fitted two bushes, one having in its centre a hole of the size necessary for the tapping drill, the other a hole the size of the clearing drill; both these bushes are provided with a handle by which to lift them in and out of the template, as shown in Fig. 1711, and both are hardened to prevent the drill cutting them, or the borings of the drill from gradually wearing their holes larger. The operation is to place the cover on the cylinder and the template upon the cover, and to clamp them together, taking care that both cover and template are in their proper positions, the latter having a flat place or deep line across a segment of its circumference, which is placed in line with the part cut away on the inside of the cover to give free ingress to the steam, and the cover being placed in the cylinder so that the part so cut away will be opposite to the port in the cylinder, by which means the holes in the covers will all stand in the same relative position to any definite part of the cylinder, as, say, to the top or bottom, or to the steam port, which is sometimes of great importance (so as to enable the wrench to be applied to some particular nut, and prevent the latter from coming into contact with a projecting part of the frame or other obstacle): the positions of the cylinder, cover, template, and bush, when placed as described, being such as shown in Fig. 1712, _a_ _a_ being the cylinder, B the steam port, C the cylinder cover, D the template, and E the bush placed in position. The bush E having a hole in it of the size of the clearance hole, is the one first used, the drill (the clearance size) is passed through the bush, which guides it while it drills through the cover, and the point cuts a countersink in the cylinder face. The clearing holes are drilled all round the cover, and the bush, having the tapping size hole in it, is then brought into requisition, the tapping drill being placed in the drilling machine, and the tapping holes drilled in the cylinder flange, the bush serving as a guide to the drill, as shown in Fig. 1712, thus causing the holes in the cover and those in the cylinder to be quite true with each other. A similar template and bush is provided for drilling the holes in the steam chest face on the cylinder, and in the steam chest itself. While, however, the cylinder is in position to have the holes for the steam chest studs drilled, the cylinder ports may be cut as follows:-- [Illustration: Fig. 1711.] [Illustration: Fig. 1712.] [Illustration: Fig. 1713.] The holes in the steam chest face of the cylinder being drilled and tapped, a false face or plate is bolted thereon, which plate is provided with false ports or slots, about three-eighths of an inch wider and three-fourths of an inch longer than the finished width and length of the steam ports in the cylinder (which excess in width and length is to allow for the thickness of the die). Into these false ports or slots is fitted a die to slide (a good fit) from end to end of the slots. Through this die is a hole, the diameter of which is that of the required finished width of the steam ports of the cylinder; the whole appliance, when in position to commence the operation of cutting out the cylinder ports, being as illustrated in Fig. 1713, _a_ _a_ being the cylinder, B B the false plate, C the sliding die, and D D the slots or false ports into which the die C fits. Into the hole of the die C is fitted a reamer, with cutting edges on its end face and running about an inch up its sides, terminating in the plain round parallel body of the reamer, whose length is rather more than the depth of the die C. The operation is to place the reamer into the drilling machine, taking care that it runs true. Place the die in one end of the port, as shown in Fig. 1713, and then wind the reamer down through the die so that it will cut its way through the port of the cylinder at one end; the spindle driving the drill is then wound along. The reamer thus carries the die with it, the slot in the false face acting as a guide to the die. In the case of the exhaust port, only one side is cut out at a time. It is obvious that, in order to perform the above operation, the drilling machine must either have a sliding head or a sliding table, the sliding head being preferable. [Illustration: Fig. 1714.] The end of the slot at which the die must be placed when the reamer is wound down through the die and cylinder port, that is to say, the end of the port at which the operation of cutting it must be commenced, depends solely on which side of the port in the cylinder requires most metal to be cut off, since the reamer, or cutter, as it may be more properly termed, must cut underneath the heaviest cut, so that the heaviest cut will be forcing the reamer back, as shown in Fig. 1714, _a_ being a sectional view of the cutter, B the hole cast in the cylinder for the port, _c_ the side of the port having the most cut taken off, D the direction in which the cutter _a_ revolves, and the arrow E the direction in which the cutter _a_ is travelling up to its cut. If the side F of the port were the one requiring the most to be cut off, the cutter _a_ would require to commence at the end F, and to then travel in the direction of the arrow G. The reason for the necessity of observing these conditions, as to the depth of cut and direction of cutter travel, is that the pressure of the cut upon the reamer is in a direction to force the reamer forward and into its cut on one side, and backward and away from its cut on the other side, the side having the most cut exerting the most pressure. If, therefore, the cutter is fed in such a direction that this pressure is the one tending to force the cutter forward, the cutter will spring forward a trifle, the teeth of the cutter taking, in consequence, a deep cut, and, springing more as the cut deepens, terminate in a pressure which breaks the teeth out of the cutter. If, however, the side exerting the most pressure upon the reamer is always made the one forcing the cutter back, as shown in Fig. 1714, by reason of the direction in which the cutter is travelled to its cut, the reamer, in springing away from the undue pressure, will also spring away from its cut, and will not, therefore, rip in or break, as in the former case. [Illustration: Fig. 1715.] In cutting out the exhaust port, only one side, in consequence of its extreme width, may be cut at one operation; hence there are two of the slots D, Fig. 1713, provided in the false plate or template for the exhaust port. The cutter _a_ must, in this case, perform its cut so that the pressure of the cut is in a direction to force the cutter backwards from its cut. The time required to cut out the ports of an ordinary locomotive cylinder, by the above appliance, is thirty minutes, the operation making them as true, parallel, and square as can possibly be desired. DRILLS AND CUTTERS FOR DRILLING MACHINES.--In the drilling machine, as in the lathe, the twist drill is the best tool that can be used for all ordinary work, since it produces the best work with the least skill, and is the cheapest in the end. As, however, the twist drill has been fully discussed with reference to its use upon lathe work, it is unnecessary to refer to it again more than to say that it possesses even greater advantages when used in the drilling machine than it does when used in the lathe; because as the drill stands vertical the flat drill will not relieve itself of the cuttings, and in deep holes must be occasionally withdrawn from the hole in order to permit the cuttings to be extracted, an operation that often consumes more time than is required for the cutting duty. Furthermore, as flat drills rarely run true they place excessive wear upon the drilling machine spindle, causing it to wear loose in its bearings, which is a great detriment to the machine. Fig. 1715 represents a piece of work that can be readily drilled with a twist drill but not with a flat one, such work being very advantageous in cutting out keyways. All that is necessary is to drill the three holes B first, and if the drill runs true and the work is properly held and the drill fed slowly while run at a quick speed the operation may be readily performed. The speeds and feeds for twist drills are given in connection with the use of the drill in the lathe, but it may be remarked here that more duty may be obtained by hand than by automatically feeding a drill, because in hand feeding the resistance of the feed motion indicates the amount of pressure on the drill, and the feed may be increased when the conditions (such as soft metal) permits, and reduced for hard spots or places, thus preserving the drill. Furthermore, the dulling of the drill edges becomes more plainly perceptible under hand feeding. The commercial sizes of both taper and straight shank twist drills are as follows:-- --------+-------++-------+-------++-------+-------++--------+------- Dia- |Length.|| Dia- |Length.|| Dia- |Length.|| Dia- |Length. meter. | ||meter. | ||meter. | ||meter. | --------+-------++-------+-------++-------+-------++--------+------- 1/4 | 6-1/8 || 25/32| 9-7/8 ||1-5/16 |14-1/4 ||1-27/32 |16-3/8 9/32 | 6-1/4 || 13/16|10 ||1-11/32|14-3/8 ||1-7/8 |16-1/2 5/16 | 6-3/8 || 27/32|10-1/4 ||1-3/8 |14-1/2 ||1-29/32 |16-1/2 11/32 | 6-1/2 || 7/8 |10-1/2 ||1-13/32|14-5/8 ||1-15/32 |16-1/2 3/8 | 6-3/4 || 29/32|10-5/8 ||1-7/16 |14-3/4 ||1-31/32 |16-1/2 13/32 | 7 || 15/16|10-3/4 ||1-15/32|14-7/8 ||2 |16-1/2 7/16 | 7-1/4 || 31/32|10-7/8 ||1-1/2 |15 ||2-1/32 |16-1/2 15/32 | 7-1/2 ||1 |11 ||1-17/32|15-1/8 ||2-1/16 |17 1/2 | 7-3/4 ||1-1/32 |11-1/8 ||1-9/16 |15-1/4 ||2-1/8 |17 17/32 | 8 ||1-1/16 |11-1/4 ||1-19/32|15-3/8 ||2-3/16 |17 9/16 | 8-1/4 ||1-3/32 |11-1/2 ||1-5/8 |15-1/2 ||2-1/4 |17-1/2 19/32 | 8-1/2 ||1-1/8 |11-3/4 ||1-21/32|15-5/8 ||2-5/16 |17-1/2 5/8 | 8-3/4 ||1-5/32 |11-7/8 ||1-11/16|15-3/4 ||2-3/8 |18 21/32 | 9 ||1-3/16 |12 ||1-23/32|15-7/8 ||2-7/16 |18-1/2 11/16 | 9-1/4 ||1-7/32 |12-1/8 ||1-3/4 |16 ||2-1/2 |19 23/32 | 9-1/2 ||1-1/4 |12-1/2 ||1-25/32|16-1/8 || | 3/4 | 9-3/4 ||1-9/32 |14-1/8 ||1-13/16|16-1/4 || | --------+-------++-------+-------++-------+-------++--------+------- Twist drills are also made to the Stubs wire gauge as follows:-- +-----------------+---------++-----------------+--------+ |Numbers by gauge.| Length. ||Numbers by gauge.| Length.| +-----------------+---------++-----------------+--------+ | 1 to 5 | 4 || 31 to 35 | 2-5/8 | | 6 " 10 | 3-11/16 || 36 " 40 | 2-7/16 | | 11 " 15 | 3-1/2 || 41 " 45 | 2-1/4 | | 16 " 20 | 3-1/4 || 46 " 50 | 2-1/16 | | 21 " 25 | 3-1/16 || 51 " 60 | 1-3/4 | | 26 " 30 | 2-13/16 || 61 " 70 | 1-1/2 | +-----------------+---------++-----------------+--------+ [Illustration: Fig. 1716.] Fig. 1716 represents the flat drill, which has three cutting edges, A, B, and C. The only advantages possessed by the flat drill are that it will stand rougher usage than the twist drill, and may be fed faster, while it can be more easily made. Furthermore, when the work is unusually hard the flat drill can be conveniently shaped and tempered to suit the conditions. The drill is flattened out and tapered thinnest at the point C. The side edges that form the diameter of the drill are for rough work given clearance, but for finer work are made nearly cylindrical, as in the figure. The flattening serves two purposes: first, it reduces the point of the drill down to its proper thinness, enabling it to enter the metal of the work easily, and secondly, it enables the cuttings to pass upward and find egress at the top of the hole being drilled. The cutting edges are formed by grinding the end facets at an angle as shown, and this angle varies from 5° for drilling hard metal, such as steel, to 20° for soft metal, such as brass or copper. [Illustration: Fig. 1717.] The angle of one cutting edge to the other varies from 45° for steel to about 35° or 40° for soft metals. The object of these two variations of angles is that in hard metal the strain and abrasion is greatest and the cutting edge is stronger with the lesser degree of angle, while in drilling the softer metals the strain being less the cutting edge need not be so strong and the angles may be made more acute, which enables the drill to enter the metal more easily. The most imperfect cutting edge in a drill is that running diagonally across the point, as denoted by A in Fig. 1717, because it is less acute than the other cutting edges, but this becomes more acute and, therefore, more effective, as the angles of the facets forming it are increased as denoted by the dotted lines in the figure. It is obvious, however, that the more acute these angles the weaker the cutting edge, hence an angle of about 5° is that usually employed. It is an advantage to make the cutting edge at A, Fig. 1717, as short as possible, which may be done by keeping the drill point thin; but if too thin it will be apt either to break or to operate in jumps (especially upon brass), drilling a hole that is a polygon instead of a true circle. The cutting edges should not only stand at an equal degree of angle to the axial line of the drill, but should be of equal lengths, so that the point of the drill will be in line with the axial line of the drill. If the drill runs true the point will then be in the axial line of rotation, and the diameter of hole drilled will be equal to the diameter of the drill. If, however, one cutting edge is longer than the other the hole drilled will be larger than is due to the diameter of the drill. [Illustration: Fig. 1718.] Suppose, for example, the drill to be ground as in Fig. 1718, the cutting edge F being the longest and at the least angle, then the point G of the drill, when clear of the work, will naturally revolve in a circle around the axial line H of the drill's rotation. But when the drilling begins, the point of the drill meets the metal first and naturally endeavours to become the centre of rotation, drilling a straight conical recess, the work moving around with the point of the drill. If the work is prevented from moving, either the drill will spring or bend, the point of the drill remaining (at first) the centre of rotation at that end of the drill, or else the recess cut by the drill will be as in the figure, and the hole will be larger in diameter than the drill. [Illustration: Fig. 1719.] [Illustration: Fig. 1720.] If, however, the drill is ground as shown in Fig. 1719, the edge E being nearest to a right angle to the axial line H of the drill, the drilling will be performed as shown in the figure, the edge E cutting the cone L, the edge F serving simply to enlarge the hole drilled by E. Here, again, if the work is held so that it cannot move, the point of the drill will revolve in a circle, and in either case, so soon as the point of the drill emerges the diameter of the hole drilled will decrease, the finished hole being conical as shown in Fig. 1720 at A. It may be remarked that the eye of the workman is (for rough work, such as tapping or clearing holes) sufficient guide to enable the grinding of the drill true enough to partly avoid the conditions shown in these two figures (in which the errors are magnified for clearness of illustration), because when the want of truth is less in amount than the thickness of the drill point, the centre of motion of the drill point when the drill has entered the work to its full diameter becomes neither at the point of the drill nor in the centre of its diameter, but intermediate between the two. [Illustration: Fig. 1721.] [Illustration: Fig. 1722.] Thus, in Fig. 1721, A is the centre of the diameter of the drill, but the cutting edge C being shorter than D throws the point of the drill towards E, hence the extra pressure of D on the incline of the recess it cuts, over the like pressure exerted by C tends to throw the centre of rotation towards E, the natural endeavor of the drill point to press into the centre of the recess acting in the same direction. This is in part resisted by the strength of the drill, hence the centre of rotation is intermediate as at B in figure. The dotted circle is drawn from the axial line of the drill as a centre, while the full circle is drawn from B as a centre. The result of this would be that the point of the drill would perform more duty than is due to its thickness, and the recess cut would have a flat place at the bottom, as shown in Fig. 1722 at O. This, from the want of keenness of the cutting edge running diagonally across the drill point, would cause the drill to cut badly and require more power to drive and feed. [Illustration: Fig. 1723.] The edges at the flat end of the drill, as at A, A in Fig. 1723, should have a little clearance back from the cutting edge though they may be left the full circle as, at A, A, but in any event they should not have clearance sufficient to form them as at B, B, Fig. 1723, because in that case the side edges C, C would cut the sides of the hole. In large drills, especially, it is necessary that the edges have but little clearance, and that the form of the clearance be as shown in Fig. 1044, with reference to twist drills. When no edge clearance whatever is given the edges act to a certain extent as guides to the drill, but if the drill is not ground quite true this induces a great deal of friction between the edges of the drill and the side of the hole. In any case of improper grinding the power required to drive the drill will be increased, because of the improper friction induced between the sides of the drill and the walls of the hole. For use on steel, wrought iron, and cast iron the lip drill shown in Fig. 1724 is a very efficient tool. It is similar to the flat drill but has its cutting edge bent forward. It possesses the keenness of the twist drill and the strength of the flat drill, but as in the case of all drills whose diameters are restored by forging and hand grinding, it is suitable for the rougher classes of work only, and requires great care in order to have it run true and keep both cutting edges in action. It is sometimes attempted to give a greater cutting angle to a flat drill by grinding a recess in the front face, as at A in Fig. 1725, but this is a poor expedient. Fig. 1726 represents what is known as the tit drill. It is employed to flatten the bottoms of holes, and has a tit T which serves to steady it. The edges A, B of this drill may be turned true and left without clearance, which will also serve to steady the drill. The tit T should be tapered towards the point, as shown, which will enable it to feed more easily and cut more freely. The speed of the drill must be as slow again as for the ordinary flat drill, and not more than one-third as fast as the twist drill. To enable a drill to start a hole in the intended location the centre-punch recess in the centre of that location should be large enough in diameter at the top to admit the point of the drill, that is to say, the recess should not be less in diameter at the top than the thickness of the drill point. [Illustration: Fig. 1724.] [Illustration: Fig. 1725.] [Illustration: Fig. 1726.] [Illustration: Fig. 1727.] If the drill does not enter true the alteration is effected as shown in Fig. 1727, in which A represents the work, B a circle of the size of the hole to be drilled, and C the recess cut by the drill, while D is a recess cut with a round-nosed chisel, which recess will cause the drill to run over in that direction. [Illustration: Fig. 1728.] It is a good plan when the hole requires to be very correctly located to strike two circles, as shown in Fig. 1728, and to define them with centre-punch marks so that the cuttings and oil shall not erase them, as is apt to be the case with lines only. The outer circle is of the size of hole to be drilled, the inner one serves merely as a guide to true the drilling by. If the work is to be clamped to the work table an alteration in the location of the recess cut by the drill point may be made by moving the work. In this case the point of the drill may be fed up so as to enter into and press against the centre-punch mark made in the centre of the location of the hole to be drilled, which, if the drill runs true will set the work true enough to clamp it by. The alteration to the recess cut by the drill when first starting to bring the hole in its true position should be made as soon as a want of truth is discernible, because the shallower the recess the more easily the alteration may be made. Sometimes a small hole is drilled as true to location as may be, and tested, any error discovered being corrected by a file; a larger drill is then used and the location again tested, and so on; in this way great precision of location may be obtained. The more acute angle the cutting edges form one to the other, or in other words, the longer the cutting edges are in a drill of a given diameter, the more readily the drill will move over if one side of the recess be cut out as in Fig. 1727, and from some experiments made by Messrs. William Sellers and Co., it was determined that if the angle of one cutting edge to the other was more than 104° the drill would cease to move over. In drilling wrought iron or the commoner qualities of steel the drill should be liberally supplied with either water or oil, but soapy water is better than pure. This keeps the drill cool and keeps the cutting edge clean, whereas otherwise the cuttings under a coarse feed are apt to stick fast to the drill point if the speed of the drill is great. Furthermore, under excessive duty the drill is apt to become heated and softened. For cast steel oil is preferable, or if the steel be very hard it will cut best dry under a slow speed and heavy pressure. For brass and cast iron the drill should run dry, otherwise the cuttings clog and jam in the hole. When the drill squeaks either the cutting edge is dulled and the drill requires regrinding, or else the cuttings have jammed in the hole, and either defect should be remedied at once. As soon as the point of the drill emerges through the work the feed should be lessened, otherwise the drill is apt to force through the weakened metal and become locked, which will very often either break or twist the drill. This may be accomplished when there is any end play to the drilling machine spindle by operating the feed motion in a direction to relieve the feed as soon as the point of the drill has emerged through the bottom of the hole, thus permitting the weight of the spindle to feed the drill. In a drilling machine, however, in which the weight of the spindle is counterbalanced, the feed may be simply reduced while the drill is passing through the bottom of the hole. Drills for work of ordinary hardness are tempered to an orange purple, but if the metal to be cut is very hard a straw color is preferable, or the drill may be left as hard as it leaves the water; that is to say hardened, but not tempered. In these cases the speed of the drill must be reduced. To assist a drill in taking hold of hard metal it is an excellent plan to jag the surface of the metal with a chisel which will often start the drill to its cut when all other means have failed. It is obvious from previous remarks that the harder the drill the less the angle of the end facets. In cases of extreme hardness two drills may with advantage be used intermittently upon the same hole; one of these should have its cutting edges ground at a more acute angle one to the other than is the case with the other drill, thus the cutting edge will be lessened in length while the drill will retain the strength due to its diameter, so that a maximum of pressure may be placed upon it. When one drill has cut deep enough to bring its full length of cutting edge into action, it may be removed and the other drill employed, and so on. The drill (for hard steel) should be kept dry until it has begun to cut, when a very little oil may be employed, but for chilled cast iron it should be kept dry. Small work to be drilled while resting upon a horizontal table may generally be held by hand, and need not therefore be secured in a chuck or to the table, because the pressure of the drill forces the work surface to the table, creating sufficient friction to hold the work from rotating with the drill. For large holes, however, the work may be secured in chucks or by bolts and plates as described for lathe and planer work, or held in a vice. The following table for the sizes of tapping holes is that issued by the Morse Twist Drill and Machine Co. In reply to a communication upon the subject that company states. "If in our estimate the necessary diameter of a tap drill to give a full thread comes nearest to a 1/64 inch measurement, we give the size of the drill in 64ths of an inch. If nearest to a 32nd size of drill we give the drill size in 32nds of an inch." In the following table are given the sizes of tapping drills, to give full threads, the diameters being practically but not decimally correct:-- -------+-----------------+----------------------- Dia- | Number | Drill for meter | threads | [V]-thread. of tap.| to inch. | -------+-----------------+----------------------- 1/4 |16 18 20| 5/32 5/32 11/64 9/32 |16 18 20| 3/16 13/64 13/64 5/16 |16 18 --| 7/32 15/64 -- 11/32|16 18 --| 1/4 17/64 -- 3/8 |14 16 18| 1/4 9/32 9/32 13/32|14 16 18| 19/64 21/64 21/64 7/16 |14 16 --| 21/64 11/32 -- 15/32|14 16 --| 23/64 3/8 -- 1/2 |12 13 14| 3/8 25/64 25/64 17/32|12 13 14| 13/32 27/64 27/64 9/16 |12 14 --| 7/16 29/64 -- 19/32|12 14 --| 15/32 31/64 -- 5/8 |10 11 12| 15/32 1/2 1/2 21/32|10 11 12| 1/2 17/32 17/32 11/16|11 12 --| 9/16 9/16 -- 23/32|11 12 --| 19/32 19/32 -- 3/4 |10 11 12| 19/32 5/8 5/8 25/32|10 11 12| 5/8 21/32 21/32 13/16|10 -- --| 21/32 -- -- 27/32|10 -- --| 11/16 -- -- 7/8 | 9 10 --| 45/64 23/32 -- 29/32| 9 10 --| 47/64 3/4 -- 15/16| 9 -- --| 49/64 -- -- 21/32| 9 -- --| 51/64 -- -- 1 | 8 -- --| 13/16 -- -- 1-1/32 | 8 -- --| 53/64 -- -- 1-1/16 | 8 -- --| 55/64 -- -- 1-3/32 | 8 -- --| 57/64 -- -- 1-1/8 | 7 8 --| 29/32 15/16 -- 1-5/32 | 7 8 --| 15/16 31/32 -- 1-3/16 | 7 8 --| 31/32 1 -- 1-7/32 | 7 8 --|1 1-1/32 -- 1-1/4 | 7 -- --|1-1/32 -- -- 1-9/32 | 7 -- --|1-1/16 -- -- 1-5/16 | 7 -- --|1-3/32 -- -- 1-11/32| 7 -- --|1-1/8 -- -- 1-3/8 | 6 -- --|1-1/8 -- -- 1-13/32| 6 -- --|1-5/32 -- -- 1-7/16 | 6 -- --|1-5/32 -- -- 1-15/32| 6 -- --|1-3/16 -- -- 1-1/2 | 6 -- --|1-15/64 -- -- 1-17/32| 6 -- --|1-9/32 -- -- 1-9/16 | 6 -- --|1-9/32 -- -- 1-19/32| 6 -- --|1-5/16 -- -- 1-5/8 | 5 5-1/2 --|1-9/32 1-5/16 -- 1-21/32| 5 5-1/2 --|1-5/16 1-11/32 -- 1-11/16| 5 5-1/2 --|1-11/32 1-3/8 -- 1-23/32| 5 5-1/2 --|1-3/8 1-13/32 -- 1-3/4 | 5 -- --|1-13/32 -- -- 1-25/32| 5 -- --|1-7/16 -- -- 1-13/16| 5 -- --|1-15/32 -- -- 1-27/32| 5 -- --|1-1/2 -- -- 1-7/8 | 4-1/2 5 --|1-17/32 1-17/32 -- 1-29/32| 4-1/2 5 --|1-9/16 1-9/16 -- 1-15/16| 4-1/2 5 --|1-19/32 1-19/32 -- 1-31/32| 4-1/2 5 --|1-5/8 1-5/8 -- 2 | 4-1/2 -- --|1-21/32 -- -- -------+-----------------+----------------------- -------+---------------------+-------------------- Dia- | Drill for U.S.S. | Drill for meter | thread. | Whitworth of tap.| | thread. -------+---------------------+-------------------- 1/4 | -- -- 3/16| -- -- 3/16 9/32 | -- -- -- | -- -- -- 5/16 | -- 1/4 -- | -- 15/64 -- 11/32| -- -- -- | -- -- -- 3/8 | -- 9/32 -- | -- 9/32 -- 13/32| -- -- -- | -- -- -- 7/16 | 11/32 -- -- | 11/32 -- -- 15/32| -- -- -- | -- -- -- 1/2 | -- 13/32 -- | 3/8 -- -- 17/32| -- -- -- | -- -- -- 9/16 | 7/16 -- -- | -- -- -- 19/32| -- -- -- | -- -- -- 5/8 | -- 1/2 -- | -- 1/2 -- 21/32| -- -- -- | -- -- -- 11/16| -- -- -- | -- -- -- 23/32| -- -- -- | -- -- -- 3/4 | 5/8 -- -- | 5/8 -- -- 25/32| -- -- -- | -- -- -- 13/16| -- -- -- | -- -- -- 27/32| -- -- -- | -- -- -- 7/8 | 23/32 -- -- | 23/32 -- -- 29/32| -- -- -- | -- -- -- 15/16| -- -- -- | -- -- -- 21/32| -- -- -- | -- -- -- 1 | 27/32 -- -- | 27/32 -- -- 1-1/32 | -- -- -- | -- -- -- 1-1/16 | -- -- -- | -- -- -- 1-3/32 | -- -- -- | -- -- -- 1-1/8 | 15/16 -- -- | 15/16 -- -- 1-5/32 | -- -- -- | -- -- -- 1-3/16 | -- -- -- | -- -- -- 1-7/32 | -- -- -- | -- -- -- 1-1/4 |1-1/16 -- -- |1-1/16 -- -- 1-9/32 | -- -- -- | -- -- -- 1-5/16 | -- -- -- | -- -- -- 1-11/32| -- -- -- | -- -- -- 1-3/8 |1-5/32 -- -- |1-5/32 -- -- 1-13/32| -- -- -- | -- -- -- 1-7/16 | -- -- -- | -- -- -- 1-15/32| -- -- -- | -- -- -- 1-1/2 |1-9/32 -- -- |1-9/32 -- -- 1-17/32| -- -- -- | -- -- -- 1-9/16 | -- -- -- | -- -- -- 1-19/32| -- -- -- | -- -- -- 1-5/8 | -- 1-3/8 -- |1-23/64 -- -- 1-21/32| -- -- -- | -- -- -- 1-11/16| -- -- -- | -- -- -- 1-23/32| -- -- -- | -- -- -- 1-3/4 |1-1/2 -- -- |1-1/2 -- -- 1-25/32| -- -- -- | -- -- -- 1-13/16| -- -- -- | -- -- -- 1-27/32| -- -- -- | -- -- -- 1-7/8 | -- 1-5/8 -- |1-37/64 -- -- 1-29/32| -- -- -- | -- -- -- 1-15/16| -- -- -- | -- -- -- 1-31/32| -- -- -- | -- -- -- 2 |1-23/32 -- -- |1-45/64 -- -- -------+---------------------+-------------------- To drive all drills by placing them directly in the socket of the drilling machine spindle would necessitate that all the drills should have their shanks to fit the drilling machine socket. This would involve a great deal of extra labor in making the drills, because the socket in the machine spindle must be large enough to fit the size of shank that will be strong enough to drive the largest drill used in the machine, hence the small drills would require to be forged down from steel equal to the full diameter of the shank of the largest drill. To obviate this difficulty the sockets already described with reference to drilling in the lathe are used. The employment of these sockets preserves the truth of the bore of the drilling machine spindle by greatly diminishing the necessity to insert and remove the shank from the drill spindle, because each socket carrying several sizes of drills (as given with reference to lathe work) the sockets require less frequent changing. [Illustration: Fig. 1729.] Drill shanks are sometimes made parallel, with a flat place as at A in Fig. 1729, to receive the pressure of the set-screw by which it is driven. To enable the shank to run true it must be a close fit to the socket and should be about five diameters long. The objection to this form is that the pressure of the set-screw tends to force the drill out of true, as does also the wear of the socket bore. These objections will obviously be diminished in proportion as the drill shank is made a tight fit to the socket, and to effect this and still enable the drill to be easily inserted and removed from the socket, the drill shank may be first made a tight fit to the socket bore, and then eased away on the half circumference on the side of the flat place, leaving it to fit on the other half circumference which is shown below the dotted line B in the end view in the figure. The set-screw is also objectionable, since it requires the use of a wrench, and is in the way and liable to catch the operator's clothing. There is, however, one advantage in employing a set-screw for twist drills, inasmuch as that, on account of the front rake on a twist drill, there is a strong tendency for the drill, as soon as the point emerges through the work, to run forward into the work and by ripping in become locked. This is very apt to be the case if there is any end play in the driving spindle, because the pressure of the cut forces the spindle back from the cut; but so soon as the drill point emerges and the pressure is reduced, the weight of the spindle acting in concert with the front rake on the drill causes the spindle to drop, taking up the lost motion in the opposite direction. In addition to this the work will from the same cause lift and run up the drill, often causing an increase in the duty sufficient to break the drill. If the spindle has no lost motion and the work is bolted or fastened to the table or in a chuck, the drill if it has a taper shank only will sometimes run forward and slip loose in the driving socket. This, however, may be obviated by feeding the drill very slowly after its point emerges through the work. Yet another form in which the cylindrical shanks of drills have been driven is shown in Fig. 1730. The shank is provided with a longitudinal groove turning at a right angle; at its termination the socket is provided with a screw whose point projects and fits into the shank groove. The drill is inserted and turned to the right, the end of the screw driving the drill and preventing it from coming out or running forward. Flat drills are usually provided with a square taper shank such as shown in Fig. 1730, an average amount of taper being 1-1/4 inches per foot. There are several disadvantages in the use of a square shank. 1st. It is difficult to forge the drill true and straight with the shank. 2nd. It is difficult to make the square socket true with the axial line of the machine spindle, and concentric with the same from end to end. 3rd. It is difficult to fit the shank of the drill to the socket and have its square sides true with the axial line of the drill. 4th. It is an expensive form of shank to fit. It is a necessity, however, when the cutting duty is very heavy, as in the case of stocks carrying cutters for holes of large diameter. In order to properly fit a square shank to a socket it should be pressed into the socket by hand only, and pressed laterally in the direction of each side of the square. If there is no lateral movement the shank is a fit, and the spindle may be revolved to see if the drill runs true, as it should do if the body of the drill is true with the shank (and this must always be the case to obtain correct results). The drill must be tried for running true at each end of the cylindrical body of the drill, which, being true with the square shank, may be taken as the standard of truth in grinding the drill, so that supposing the hole in the driving spindle to be true and the drill shank to be properly fitted, the drill will run true whichever way inserted. If the body of the drill runs out of true it will cause a great deal of friction by rubbing and forcing the cuttings against the sides of holes, especially if the clearance be small or the hole a deep one. [Illustration: Fig. 1730.] In fitting the shank, the fitting or bearing marks will show most correctly when the shank is driven very lightly home, for if driven in too firmly the bearing marks will extend too far in consequence of the elasticity of the metal. If the hole in the spindle is not true with the axial line of the spindle, or if the sides of the hole are not a true square or are not equidistant from the axial line of the spindle, the drill must be fitted with one side of its square shank always placed to the same side of the square in the socket, and these two sides must therefore be marked so as to denote how to insert the drill without having to try it in the socket. Usually a centre-punch mark, as at E, Fig. 1731, is made on the drill and another on the collar as at _f_. To enable the extraction of the drill from the socket the latter is provided with a slot, shown in figure at C, the slot passing through the spindle and the end of the drill protruding into the slot, so that a key driven into the slot will force the drill from the socket. The key employed for this purpose should be of some soft metal, as brass or hard composition brass, so that the key shall not condense or press the metal of the keyway, and after the key is inserted it should be lightly tapped with a hammer, travelling in the direction of the line of the spindle and not driven through the keyway. The drill should not be given a blow or tap to loose it in the spindle, as this is sure in time to make its socket hole out of true. [Illustration: Fig. 1731.] [Illustration: Fig. 1732.] The thread shown on the end of the drill spindle in figure is to receive chucks for holding and driving drills. [Illustration: Fig. 1733.] The various forms of small drill chucks illustrated in connection with the subject of lathe chucks are equally suitable for driving drills in the drilling machine. Fig. 1732, however, represents an excellent three-jawed chuck for driving drills, the bite being very narrow and holding the drill with great firmness. Fig. 1733 represents a two-jawed drill chuck in which the screws operate a pair of dies for gripping parallel shank drills, the screws being operated independently. In other forms of similar chucks the bite is a [V] recess parallel to the chuck axis, the only difference between a drill chuck for a drilling machine and one for a lathe being that for the former the jaws do not require outside bites nor to be reversible. [Illustration: Fig. 1734.] Holes that are to be made parallel, straight, cylindrically true in the drilling machine, are finished by the reamer as already described with reference to lathe work, and it is found as in lathe work that in order that a reamer may finish holes to the same diameter, it is necessary that it take the same depth of finishing cut in each case, an end that is best obtained by the use of three reamers, the first taking out the irregularities of the drilled hole, and the second preparing it for the light finishing cut to be taken by the third. All the remarks made upon the reamer when considered with reference to lathe work apply equally to its use in the drilling machine. Another tool for taking a very light cut to smooth out a hole and cut it to exact size is the shell reamer shown in Fig. 1734, which fits on a taper mandrel through which passes a square key fitting into the square slot shown in the shell reamer. [Illustration: Fig. 1735.] Reamers may be driven by drill chucks, but when very true and parallel work is required, and the holes are made true before using the reamer, it is preferable to drive them by a socket that permits of their moving laterally. Especially is this the case with rose-bits. Fig. 1735, which is taken from _The American Machinist_, represents a socket of this kind, being pivoted at its driving or shank end, and supported at the other by two small spiral springs. The effect is that if the socket does not run quite true the reamer is permitted to adjust itself straight and true in the hole being reamed, instead of rubbing and binding against its walls, which would tend to enlarge its mouth and therefore impair its parallelism. Cotter drills, slotting drills, or keyway drills, three names designating the same tool, are employed to cut out keyways, mortises, or slots. Fig. 1736 represents a common form of cotter or keyway drill, the cutting edges being at A, A, and clearance being given by grinding the curve as denoted by the line C. In some cases a stock S and two detachable bits or cutters C, C, are used as in Fig. 1737, the bits being simple tools secured in slots in the stock by set-screws, and thus being adjustable for width so that they may be used to cut keyways of different widths. The feed of keyway drills should be light, and especial care must be taken where two spindles are used, to keep them in line, or otherwise the keyway will not come fair, as is shown in Fig. 1738, where the half drilled from side A and that drilled from side B are shown not to come fair at their point of junction C. This is more apt to occur when a deep keyway is drilled one half from each side. Hence in such a case great care must be exercised in setting the work true, because the labor in filing out such a keyway is both tedious and expensive. [Illustration: Fig. 1736.] [Illustration: Fig. 1737.] In producing holes of above or about two inches in diameter, cutters such as shown in Fig. 1739 may be employed. A is a stock carrying a cutter B secured in place by a key C. Holes are first drilled to receive the pin D, which serves as a guide to steady the stock. The amount of cutting duty is obviously confined to the production of the holes to receive the pin and the metal removed from the groove cut by the cutters, so that at completion of the cutter duty there comes from the work a ferrule or annular ring that has been cut out of the work. [Illustration: Fig. 1738.] For use on wrought iron or steel the front faces of the cutters may be given rake as denoted by the dotted line at E, and smooth and more rapid duty may be obtained if the cutter be set back, as in Fig. 1740, the cutting edge being about in a line with line A, in which case the front face may be hollowed out as at B, and take a good cut without the digging in and jumping that is apt to occur in large holes if the cutter is not thus set back. The larger the diameter of the work the greater the necessity of setting the cutting edge back, thus in Fig. 1741 the cutter is to be used to cut a large circle out of a plate P, as, say, a man-hole in a boiler sheet. The cutter C is carried in a bar B secured in the stock A by a screw, and unless the cutter is set well back it is liable to dip into the work and break. [Illustration: Fig. 1739.] [Illustration: Fig. 1740.] [Illustration: Fig. 1741.] It is obvious that the pin E in the figure must be long enough to pass into the hole in the plate before the cutter meets the plate surface and begins to cut, so that the pin shall act as a guide to steady the cutter, and also that in all cutters or cutter driving stocks the shank must be either of large diameter or else made square, in order to be able to drive the cut at the increased leverage over that in drilling. [Illustration: Fig. 1742.] In these forms of tube plate cutters it is necessary to drill a hole to receive the pin D. But this necessity may be removed by means of a cutter, such as shown in Fig. 1742, which is given simply as a representative of a class of such cutters. A is a cutter stock having the two cutters B B fitted in slots and bolted to it. C is a spiral spring inserted in a hole in A and pressing upon the pin D, which has a conical point. The work is provided with a deep centre-punch mark denoting the centre of the hole to be cut. The point of D projects slightly beyond the cutting edges of the cutters, and as it enters the centre-punch mark in the work it forms a guide point to steady the cutters as they rotate. As the cutters are fed to their cut, the pin D simply compresses the spiral spring C and passes further up the cutter stock. Thus the point of D serves instead of a hole and pin guide. [Illustration: Fig. 1743.] A simple form of adjustable cutter is shown in Figs. 1743 and 1744. It consists of a stock A A with the shank B, made tapering to fit the socket of a boring or drilling machine. Through the body of the stock is a keyway or slot, in which is placed the cutter C, provided in the centre of the upper edge with a notch or recess. Into this slot fits the end of the piece D, which is pivoted upon the pin E. The radial edge of D has female worm teeth upon it. F is a worm screw in gear with the radial edge of D. Upon the outer end of F is a square projection to receive a handle, and it is obvious that by revolving the screw F, the cutter C will be moved through the slot in the stock, and hence the size of the circle which the cutter will describe in a revolution of the stock A may be determined by operating the screw F. Thus the tool is adjustable for different sizes of work, while it is rigidly held to any size without any tendency whatever either to slip or alter its form. The pin G is not an absolutely necessary part of the tool, but it is a valuable addition, as it steadies the tool. This is necessary when the spindle of the machine in which it is used has play in the bearings, which is very often the case with boring and drilling machines. The use of G is to act as a guide fixed in the table upon which the work is held, to prevent the tool from springing away from the cut, and hence enabling it to do much smoother work. It is usual to make the width of the cutter C to suit some piece of work of which there is a large quantity to do, because when the cutter is in the centre of the stock both edges may perform cutting duty; in which case the tool can be fed to the cut twice as fast as when the cutter is used for an increased diameter, and one cutting edge only is operative. The tool may be put between the lathe centres and revolved, the work being fastened to the lathe saddle. In this way it is exceedingly useful in cutting out plain cores in half-core boxes. [Illustration: Fig. 1744.] In addition to its value as an adjustable boring tool this device may be used to cut out sweeps and curves, and is especially adapted to cutting those of double eyes. This operation is shown in Fig. 1744, in which D is the double eye, A is the tool stock, F is the adjusting screw, and C is the cutter. The circular ends of connecting rod strips and other similar work also fall within the province of this tool, and in the case of such work upon rods too long to be revolved this is an important item, as such work has now to be relegated to that slowest and most unhandy of all machine tools, the slotting machine. It is obvious that any of the ordinary forms of cutter may be used in this stock. [Illustration: Fig. 1745.] For enlarging a hole for a certain distance the counterbore is employed. Fig. 1745 represents a counterbore or pin drill, in which the pin is cut like a reamer, so as to ream the hole and insure that the pin shall fit accurately. The sides are left with but little clearance and with a dull edge, so that they will not cut, the cutting edges being at _e_, _c_ and the clearance on the end faces. [Illustration: Fig. 1746.] For counterboring small holes or for facing the metal around their ends, the form of counterbore shown in Fig. 1746 is employed. The pin must be an accurate fit to the hole, and to capacitate one tool for various sizes of holes the bit is made interchangeable. The stock has a flat place on it to receive the pressure of the screw that secures the counterbore, and the end of the stock is reduced in diameter, so that the counterbore comes against a shoulder and cannot push up the stock from the pressure of the feed; the end of the counterbore is bored to receive the tit pin, thus making it permissible to exchange the pin, and use various sizes in the same counterbore. [Illustration: Fig. 1747.] [Illustration: Fig. 1748.] Twist drills for use in wood work are given a conical point, as was shown with reference to lathe drills, and when the holes are to be countersunk, an attachment, such as shown in Fig. 1747, may be used. It is a split and threaded taper, so that by operating the nut in one direction it may be locked to the drill, while by operating it in the other it will be loosened, and may be adjusted to any required distance from the point of the drill, as shown in Fig. 1748. [Illustration: Fig. 1749.] For larger sizes of holes a stock and cutter, such as shown in Fig. 1749, may be employed, receiving a facing of counterboring cutter such as A, or a countersink bit such as B, and the bit may be made to suit various sizes of holes by making its diameter suitable for the smallest size of hole the tool is intended for, and putting ferrules to bring it up to size for larger diameters. The cutters are fastened into the stock by a small key or wedge, as shown. By having the cutter a separate piece from the stock, the cutting edges may be ground with greater facility, while one stock may serve for various sizes of cutters. The slot in the stock should be made to have an amount of taper equal to that given to the key, so that all the cutters may be made parallel in their widths or depths, and thus be more easily made, while at the same time the upper edge will serve as a guide to grind the cutting edges parallel to, and thus insure that they shall stand at a right angle to the axis of the stock, and that both will therefore take an equal share of the cutting duty. When cutters of this kind are used to enlarge holes of large diameter it is necessary that the pin be long enough to pass down into a bushing provided in the table of the machine, and thus steady the bar or stock at that end. For coning the mouths of holes the countersink is employed, being provided with a pin, as shown in Fig. 1750; and it is obvious that the pin may be provided with bushings or ferrules. The smaller sizes of countersinks are sometimes made as in Fig. 1751, the coned end being filed away slightly below the axis so as to give clearance to the cutting edge. [Illustration: Fig. 1750.] [Illustration: Fig. 1751.] [Illustration: Fig. 1752.] Fig. 1752 refers to a device for drilling square holes. The chuck for driving the drill is so constructed as to permit to the drill a certain amount of lateral motion, which is rendered necessary by the peculiar movement of the cutting edges of the drill which does not rotate on a fixed central point, but diverges laterally to a degree proportional to the size of the hole. For the chuck the upper part of the cavity of a metal cylinder is bored out so as to fit on the driving spindle. Below this bore a square recess is made, and below this latter and coming well within the diameter of the square recess, is a circular hole passing through the end of the chuck. The drill holder or socket is in a separate piece, the bottom portion of which is provided with a square or round recess for holding the drill shanks, and is held firmly in its socket by means of a set-screw. The upper part of the socket consists first of a screw (Fig. 1752) at S; secondly, of a squared shoulder B; thirdly, of a cylindrical shoulder D, and the circular part E, the drill shank being inserted at H. N is a nut holding the drill socket in the chuck. The socket being inserted in the chuck, the loose square collar C, which has an oblong rectangular slot in it, is put in, passing over the squared part of the socket. The nut N is then screwed up, bringing the face of E up to the face of the chuck, but not binding C, because C is thinner than the recess in which it lies. When this is done the socket will readily move in a horizontal plane to such a distance as the play between the two sides of the loose collar C and two of the sides of the recess will permit, while in the other direction it will move in a horizontal plane such distance as the play between the two sides of the square shoulder of the socket and the ends of the rectangular slot in the loose collar C will permit. The amount of this horizontal motion is varied to suit the size of the square hole to be drilled. Near to the lower end or cutting edges of the drill, there is fixed above the work a metal guide plate F having a square hole of the size requiring to be drilled. The drill is made three-sided, as shown, the dimensions of the three sides being such that the distance from the base to the apex of the triangle is the same as the length of the sides of the hole to be drilled. The drill may then be rotated through F as a guide, when it will drill a square hole. The method of operation is as follows: The three-sided drill being fixed in the self-adjusting chuck, the guide bar with the square guide hole therein rigidly fixed above the point in the work where it is required to drill, the drilling spindle carrying the chuck drill is made to revolve, and is screwed or pressed downwards, upon which the drill works downwards through the square guide hole, and drills holes similar in size and form to that in the guide. The triangular drill for drilling dead square holes may also be used without the self-adjusting drill chuck in any ordinary chuck, when the substance operated upon is not very heavy nor stationary; then, instead of the lateral movement of the drill, such lateral movement will be communicated by the drill to the substance operated upon. In making oblong dead square-cornered holes, either the substance to be operated upon must be allowed to move in one direction more than another, or the hole in the guide plate must be made to the shape required, and the drill chuck made to give the drill greater play in one direction. [Illustration: Fig. 1753.] The boring bars and cutters employed in drilling and boring machines are usually solid bars having fixed cutters, the bars feeding to the cut. [Illustration: Fig. 1754.] [Illustration: Fig. 1755.] [Illustration: Fig. 1756.] Figs. 1753, 1754, 1755, and 1756, however, represent a bar having a device for boring tapers in a drilling or boring machine. It consists of a sleeve A fixed to the bar S, and having a slideway at an angle to the bar axis. In this slideway is a slide carrying the cutting tool and having at its upper end a feed screw with a star feed. Fig. 1753 shows the device without, and Fig. 1754 with, the boring bar. A is a sleeve having ribs B to provide the slideway C for the slide D carrying the cutting-tool T. The feed screw F is furnished with the star G between two lugs H K. A stationary pin bolted upon the work catches one arm of the star at each revolution of the bar, and thus puts on the feed. To take up the wear of the tool-carrying slide, a gib M and set-screws P are provided, and to clamp the device to the boring-bar it is split at Q and furnished with screws R. The boring-bar S, furthermore, has a collar at the top and a nut N at the bottom. The tool, it will be observed, can be closely held and guided, the degree of taper of the hole bored being governed by the angle of the slideway C to the axis of the sleeve. CHAPTER XX.--HAND DRILLING AND BORING TOOLS AND DEVICES. HAND DRILLING AND BORING TOOLS.--The tools used for piercing holes in wood are generally termed boring tools, while those for metal are termed drilling tools when they cut the hole from the solid metal, and boring tools when they are used to enlarge an existing hole. Wood-boring tools must have their cutting edges so shaped that they sever the fibre of the wood before dislodging it, or otherwise the cutting edges wedge themselves in the fibre. This is accomplished, in cutting across the grain of the wood, in two ways: first, by severing the fibre around the walls of the hole and in a line parallel to the axial line of the boring tool, and removing it afterwards with a second cutting edge at a right angle to the axis of the boring tool; or else by employing a cutting edge that is curved in its length so as to begin to cut at the centre and operate on the walls of the hole, gradually enlarging it, as in the case of Good's auger bit (to be hereafter described), the action being to cut off successive layers from the end of the grain or fibre of the wood. Tools for very small holes or holes not above one-quarter inch in diameter usually operate on this second principle, as do also some of the larger tools, such as the nail bit or spoon bit and the German bit. [Illustration: Fig. 1757.] [Illustration: Fig. 1758.] The simplest form of wood-piercing tool is the awl or bradawl, shown in Figs. 1757 and 1758, its cutting end being tapered to a wedge shape whose width is sometimes made parallel with the stem and at others spread, as at C D in figure. It is obvious that when the end is spread the stem affords less assistance as a guide to pierce the hole straight. It is obvious that the action of an awl is that of wedging and tearing rather than of cutting, especially when it is operating endways of the grain. Thus in Fig. 1758 is shown an awl operating, on the right, across the grain, and, on the left, endwise of the same. In the former position it breaks the grain endwise, while in the latter it wedges it apart. Awls are used for holes up to about three-sixteenths of an inch in diameter. [Illustration: Fig. 1759.] Fig. 1759 represents the gimlet bit having a spiral flute at F and a spiral projection at S S, which, acting on the principle of a screw, pulls the bit forward and into its cut. These bits are used in sizes from 1/16 inch to 1/2 inch. The edge of the spiral flute or groove here does the cutting, producing a conical hole and cutting off successive layers of the fibre until the full diameter of hole is produced. The upper part of the fluted end is reduced in diameter so as to avoid its rubbing against the walls of the hole and producing friction, which would make the tool hard to drive. [Illustration: Fig. 1760.] [Illustration: Fig. 1761.] Figs. 1760 and 1761 represent the German bit, which is used for holes from 1/16 inch to 3/8 inch in diameter. This, as well as all other bits or augers, have a tapered square by which they are driven with a brace, the notch shown at N being to receive the spring catch of the brace that holds them in place. The cutting edges at A and B are produced by cutting away the metal behind them. [Illustration: Fig. 1762.] [Illustration: Fig. 1763.] Fig. 1762 represents the nail bit, which is used for boring across the grain of the wood. Its cutting edge severs the fibre around the walls of the hole, leaving a centre core uncut, which therefore remains in the hole unless the hole is pierced entirely through the material. If used to bore endways or parallel with the direction of the fibre or grain of the wood it wedges itself therein. The groove of the nail bit extends to the point, as shown by the dotted line in the figure. Nail bits are used in sizes from 1/16 to 3/8 inch. Fig. 1763 represents the spoon bit whose groove extends close to the point, as shown by the dotted line C. [Illustration: Fig. 1764.] Fig. 1764 represents the pod or nose bit, whose cutting edge extends half way across its end and therefore cuts off successive layers of the fibres, which peculiarly adapts it for boring endways of the grain, making a straight and smooth hole. It is made in sizes up to as large as four inches, and is largely used for the bores of wooden pipes and pumps, producing holes of great length, sometimes passing entirely through the length of the log. [Illustration: Fig. 1765.] Fig. 1765 represents the auger bit, which is provided with a conical screw S which pulls it forward into the wood. Its two wings W have cutting edges at D, D, which, being in advance of the cutting edges A, B, sever the fibre of the wood, which is afterwards cut off in layers whose thickness is equal to the pitch of the thread upon its cone S. The sides of the wings W obviously steady the auger in the hole, as do also the tops T of the twist. This tool is more suitable for boring across the grain than lengthways of it, because when boring lengthways the wings W obviously wedge themselves between the fibres of the wood. [Illustration: Fig. 1766.] This is obviated in Cook's auger bit, shown in Fig. 1766, in which the cutting edge is curved, so that whether used either across or with the grain the cutting edge produces a dished seat and cuts the fibre endways while removing the material in a spiral layer. The curve of the cutting edge is such that near the corners it lies more nearly parallel to the stem of the auger than at any other part, which tends to smooth the walls of the hole. This tool while very serviceable for cross grain is especially advantageous for the end grain of the wood. [Illustration: Fig. 1767.] [Illustration: Fig. 1768.] In the smaller sizes of auger bits the twist of the spiral is made coarser, as in Fig. 1767, which is necessary to provide sufficient strength to the tool. For the larger sizes the width of the top of the flute (T, Fig. 1765), or the land, as it is termed, is made narrow, as in Fig. 1768, for holes not requiring to be very exact in their straightness, while for holes requiring to be straight and smooth they are made wider, as at D, in Fig. 1769, and the wings A, B in the figure extend farther up the flutes so as to steady the tool in the walls of the hole and make them smoother. It is obvious that the conical screw requires to force or wedge itself into the wood, which in thin work is apt to split the wood, especially when it is provided with a double thread as it usually is (the top of one thread meeting the cutting edge A in Fig. 1765, while the top of the other thread meets cutting edge B). [Illustration: Fig. 1769.] [Illustration: Fig. 1770.] In boring end-grain wood, or in other words lengthways of the grain of the wood, the thread is very apt to strip or pull out of the wood and clog the screw of the auger; especially is this the case in hard woods. This may be to a great extent avoided by cutting a spiral flute or groove along the thread, as in Fig. 1770, which enables the screw to cut its way into the wood on first starting, acts to obviate the stripping and affords an easy means of cleaning. The groove also enables the screw to cut its way through knots and enables the auger to bore straight. In boring holes that are parallel with the grain or fibre of the wood, much more pressure is required to keep the auger up to its cut and to prevent the thread cut by the auger point from pulling or stripping out of the wood, in which case it clogs the thread of the auger point and is very difficult to clean it out, especially in the case of hard woods. [Illustration: Fig. 1771.] [Illustration: Fig. 1772.] Furthermore, after the thread has once stripped it is quite difficult to force the auger to start its cut again. To obviate these difficulties, the screw is fluted as shown. It is obvious also that this flute by imparting a certain amount of cutting action, and thereby lessening the wedging action of the screw, enables it to bore, without splitting it, thinner work than the ordinary auger. But it will split very thin work nevertheless; hence for such work as well as for holes in any kind of wood, when the hole does not require to be more than about twice as deep as that diameter, the centre bit shown in Figs. 1771 and 1772 is employed, being an excellent tool either for boring with the grain or across it. The centre B is triangular and therefore cuts its way into the work, and the spur or wing A extends lower than the cutting edge C, which on account of its angle cuts very keenly. [Illustration: Fig. 1773.] Fig. 1773 represents the twist drill which is used by the wood-worker for drilling iron, its end being squared to fit the carpenter's brace. [Illustration: Fig. 1774.] [Illustration: Fig. 1775.] Fig. 1774 represents an extension bit, being adjustable for diameter by reason of having its cutting edge upon a piece that can be moved endways in the holder or stem. This piece is ruled with lines on its face so that it may be set to the required size. Its upper edge is serrated with notches into which a dish screw or worm meshes, so that by revolving the worm the bit piece is moved farther out on the spur or wing side or end, it being obvious that the spur must meet the walls of the hole. A better form of extension bit for the end grain of wood is shown in Fig. 1775, the cutting edge being a curve to adapt it to severing the fibre in end-grained wood, as was explained with reference to Good's auger bit. [Illustration: Fig. 1776.] Fig. 1776 represents a drill for stone work, whose edge is made curved to steady it. This tool is caused to cut by hammer blows, being slightly revolved upon its axis after each blow, hence the curved shape of its cutting edge causes it to sink a dish-shaped recess in the work which holds that end steady. The end of the tool is spread because the corners are subject to rapid wear, especially when used upon hard stone, and the sides of the drill would bend or jam in the walls of the hole in the absence of the clearance caused by the spread. To prevent undue abrasion water is used. In soft stones the hammer blows must be delivered lightly or the cutting edge will produce corrugations in the seat or bottom of the hole, and falling into the same recesses when revolved after each blow the chipping action is impaired and finally ceases. To prevent this the cutting edge is sometimes curved in its length so that the indentations cross each other as the drill is revolved, which greatly increases the capacity of the drill, but is harder to forge and to grind. [Illustration: Fig. 1777.] The simplest hand-drilling device employed for metal is the fiddle bow drill shown in Fig. 1777. It consists of an elastic bow B, having a cord C, which passes around the reel R, at one end of which is the drill D, and at the other a stem having a conical or centre point fitting into a conical recess in a curved breast-plate. The operator presses against this plate to force the drill to cut, and by moving the bow back and forth the cord revolves the drill. [Illustration: Fig. 1778.] As the direction of drill revolution is reversed at each passage of the bow, its cutting edges must be formed so as to cut when revolved in either direction, the shape necessary to accomplish this being shown in the enlarged side and edge views at the foot of the engraving. It is obvious that a device of this kind is suitable for small holes only, as, say, those having a diameter of one-eighth inch or less. But for these sizes it is an excellent tool, since it is light and very sensitive to the drill pressure, and the operator can regulate the amount of pressure to suit the resistance offered to the drill, and therefore prevent the drill from breakage by reason of excessive feed. In place of the breast-plate the bow drill may be used with a frame, such as in Fig. 1778. the frame being gripped in a vice and having a pin or screw A. If a pin be used, its weight may give the feed, or it may be pressed down by the fingers, while if a screw is used it must be revolved occasionally to put on the feed. [Illustration: Fig. 1779.] Fig. 1779 represents a hand-drilling device in which the cord passes around a drum containing a coiled spring which winds up the cord, the latter passing around the drill spindle, so that pulling the cord revolves the spindle and the drill, the drum and spiral spring revolving the drill backwards. [Illustration: Fig. 1780.] Fig. 1780 represents a drilling device in which the drill is carried in a chuck on the end of the spindle which has right and left spiral grooves in it, and is provided with a barrel-shaped nut, which when operated up and down the spindle causes it to revolve back and forth. The nut or slide carries at one hand a right-hand, and at the other a left-hand nut fitting into the spindle grooves, and cut like a ratchet on their faces. Between these is a sleeve, also ratchet cut, but sufficiently short that when one nut engages, the other is released, with the result that the drill is revolved in one continuous direction instead of back and forth, and can therefore be shaped as an ordinary flat drill instead of as was shown in Fig. 1777. The drill is fed to its cut by hand pressure on the handle or knob at the top. [Illustration: Fig. 1781.] Fig. 1781 represents Backus' brace for driving bits, augers, &c., the construction of the chuck being shown in Fig. 1782. The two tongues are held at their inner ends by springs and are coned at their outer ends, there being a corresponding cone in the threaded sleeve, so that screwing up this sleeve firmly grips the tool shank and thus holds it true, independent of the squared end which fits into the inner tongue that drives it. In another form this brace is supplied with a ratchet between the chuck and the cranked handle, as shown in Fig. 1783, the construction of the ratchet being shown in Fig. 1784. The ring is provided on its inner edge with three notches, so that by pulling it back and setting it in the required notch the ratchet will operate the chuck in either direction or lock it for use as an ordinary brace. The ratchet enables the tool to be used in a corner in which there would be no room to turn the crank a full revolution. This end may, however, be better accomplished by means of the Backus' patent angular wrench shown in Fig. 1785, which consists of a frame carrying a ball-and-socket joint between it and the chuck, as shown. [Illustration: Fig. 1782.] [Illustration: Fig. 1783.] [Illustration: Fig. 1784.] [Illustration: Fig. 1785.] [Illustration: Fig. 1786.] [Illustration: Fig. 1787.] Figs. 1786 and 1787 represent the brace arranged to have a gear-wheel connected or disconnected at will, the object of this addition being to enable a quick speed to the chuck when the same is advantageous. [Illustration: Fig. 1788.] For drilling small holes in metal, the breast drill shown in Fig. 1788 is employed. It consists of a spindle having journal bearing in a breast-plate at the head, and in a frame carrying a bevel gear-wheel engaging with two gear-pinions that are fast upon the spindle, this frame and the bevel gear-wheel being steadied by the handle shown on the right. At the lower end of the spindle is a chuck for holding and driving the drill, which is obviously operated by revolving the handled crank which is fast upon the large bevel gear. The feed is put on by pressing the body against the breast-plate. It is obvious that but one bevel pinion would serve, but it is found that if one only is used the spindle is apt to wear so as to run out of true, and the bore of the gear-wheel rapidly enlarges from the strain falling on one side only. To avoid this the spindle is driven by two pinions, one on each side of the driving gear as in figure. Breast-drills do not possess enough driving power to capacitate them for drills of above about quarter inch in diameter, for which various forms of drill cranks are employed. [Illustration: Fig. 1789.] Fig. 1789 represents a drill crank which receives the drill at A, and is threaded at B to receive a feed screw C, which is pointed at D; at E is a loose tube or sleeve that prevents the crank from rubbing in the operator's hands when it is revolved. [Illustration: Fig. 1790.] To use such a drill crank a frame A, Fig. 1790, is employed, being held in a vice and having at T a table whereon the work W may be rested. The feed is put on by unscrewing the screw S in this figure against the upper jaws of A; holes of about half inch and less in diameter may be drilled with this device. [Illustration: Fig. 1791.] A very old but a very excellent device for hand drilling when no drilling machine is at hand is the drilling frame shown in Fig. 1791, which consists of two upright posts A, and two B, placed side by side with space enough between them to receive and guide the fulcrum lever and the lifting lever. The fulcrum lever is pivoted at C, and has an iron plate at E, and suspends a weight at its end which serves to put on the feed. The lifting lever is pivoted at D, and at F hooks on to the fulcrum lever. At its other end is a rope and eye G, and it is obvious that the effect of the weight upon the fulcrum lever is offset by any pressure applied to G, so that by applying the operator's foot at G the weight of drill feed may be regulated to suit the size of hole and strength of drill being used. The work is rested on a bench, and a drill crank or other device such as a ratchet brace may be used to drive the drill. This drill frame is capable of drilling holes up to about two inches in diameter, but it possesses the fault that the upper end of the brace or drilling device moves as the drill passes into the work in an arc H of a circle, of which the pin C is the centre. The posts A are provided with numerous holes for the pin C, so that the fulcrum lever may be raised or lowered at that end to suit the height of the work above the work bench. Another objection to this device is, it takes up a good deal of shop room. Ratchet braces are employed to drill holes that are of too large a bore to be drilled by tread drills, and that cannot be conveniently taken to a drilling machine. [Illustration: Fig. 1792.] In Fig. 1792 is represented a self-feeding ratchet brace. A is the body of the brace, having a taper square hole in its end to receive the square shank of the drill. L is a lever pivoted upon A, and having a pawl or catch B, which acts upon ratchet teeth provided upon A. When the lever L is moved backward the pawl B being pivoted rides over the ratchet teeth, but when L is pulled forward B engages the ratchet teeth and rotates A and therefore the drill. At F is a screw threaded into A, its pointed end abutting against some firm piece, so that unscrewing F forces the drill forward and into its cut. These features are essential to all forms of ratchet braces, but the peculiar feature of this brace consists in its exceedingly simple self-feeding devices, the feed screw F requiring in ordinary braces to be operated by hand when the drill requires to be fed. The construction and operation of the self-feeding device is as follows: The feed screw F is provided with a feather way or spline and with a feed collar C, operated by the pawl E. The feed-collar C has at D a groove, into which a flange on pawl E fits, and on its side face there is a groove receiving an annular ring on the face of lever L, these two keeping it in place. The pawl E is a double one, and may be tripped to operate C in opposite directions to feed or release the drill, as the case may be, or it may be placed in hind position to throw the feed off--all these operations being easily performed while the lever L is in motion. Collar C is in effect a double ratchet, since its circumference is provided with two sets of notches, one at _g_ and the other at _h_. Each set is equally spaced around the circumference, but one set or circle is coarser spaced than the other, while both are finer spaced than is the ratchet operated by pawl B. Suppose, now, that the lever L is at the end of a back stroke, and pawl E will fall into one of the notches on side _g_ of the feed-ratchet, and when lever L is moved on its forward stroke it will operate the feed ratchet and move it forward, A standing still until such time as pawl B meets a tooth of the ratchet on A. The feed screw F is provided with a left-hand thread, and the feed ratchet has a feather projecting into the spline in the feed screw; hence moving the feed ratchet at the beginning of the forward motion of L and before A is operated, puts a feed on, and the amount of this feed depends upon how much finer the notches into which pawl E falls are than those into which B falls. The feed takes place, be it noted, at the beginning of the lever stroke, and ceases so soon as pawl B operates A and the drill begins to cut. As shown in the figure, the feed collar is set for large drills (which will stand a coarser feed than small ones), because the notches are finer spaced at _g_ than at _h_. For small drills and finer feeds the collar is slipped off the screw and reversed so that side _h_ will fall under E, it being obvious that the finer the notches are spaced the more feed is put on per stroke. The spacings are made to suit very moderate feeds, both for large and small drills, because the operator can increase the feed at any stroke quite independently of the spacings on the feed ratchet. All he has to do is to give the lever handle a short stroke and more feed is put on; if still more feed is wanted, another short stroke may be made, and so on, the least possible amount of feed being put on when the longest strokes are made. In any event, however, there will be a certain amount of average feed per stroke if equal length of strokes is taken, the spacing being made to suit such ordinary variations of stroke as are met within every-day practice. When it is desired to stop feeding altogether, or to release the drill entirely from the cut, all that is necessary is to trip the feed-pawl E (without stopping the lever motion), and it will operate the feed screw in the opposite direction sufficiently to release the drill in a single backward stroke of the lever. The range of feed that is obtainable with a single feed ratchet is sufficient for all practical purposes, although it is obvious that if any special purpose should require it, a special feed ratchet may be made to suit either an unusually fine or coarse rate of feed. The feed screw is not provided with either a squared head or with the usual pin holes, because the feed ratchet is so readily operated that these, with their accompanying wrench or pin, are unnecessary. [Illustration: Fig. 1793.] [Illustration: Fig. 1794.] Figs. 1793 and 1794 represent a self-feeding ratchet brace for hand drilling in which the feed is obtained as follows: The inside or feed sleeve B, which screws upon the drill spindle, is fitted with a friction or outer sleeve A, in the head of which is secured a steel chisel-shaped pin C, the lower end of which is pointed and rests upon a hardened steel bearing D, fixed in the head of the inner sleeve B. This sleeve, with its bearing D, revolves upon the point of the pin C, and within the friction sleeve A. Having thus described its construction, we will now describe the operation of the self-feeding device. The head of the pin C being chisel-shaped, prevents the pin and the outer sleeve A from revolving. If the thumb or friction screw F is unscrewed, it will permit the inner sleeve B to rotate freely upon the bearing of pin C, and within the friction sleeve A. As the screw F is tightened, the friction upon the inner sleeve B is increased, causing it to remain stationary, and consequently causing the screw on the drill spindle to feed the drill until the friction on the drill becomes greater than the friction on the sleeve B. This then commences to rotate again within the outer sleeve A, and continues until the chip which the drill has commenced to cut is finished, when the same operation is repeated, thus giving a continuous feed, capable of being instantly adjusted to feed fast or slow as desired, by tightening or loosening the friction screw F, thereby causing a greater or less friction upon the inside or feed sleeve B. [Illustration: Fig. 1795.] To afford a fulcrum or point of resistance for the chisel-piece C, or the pointed centre used in the common forms of ratchet brace feed screws, various supporting arms, or stands are employed. Thus Fig. 1795[30] represents a boiler shell _a_, to which is attached an angle frame or knee _b_, carrying the angle piece _c_ (which may be adjusted for vertical height on _b_ by means of the bolt shown) affording a fulcrum for the feed sleeve _d_. This sleeve is sometimes made hexagonal on its outside to receive a wrench or to be held by the hand when feeding, or it may have holes near its centre end to receive a small pin or piece of wire; _e_ is a chain to pass around the boiler to secure _b_ to it, which is done by means of the device at _f_. [30] From _The American Machinist_. For many purposes a simple stand having an upright cylindrical bar carrying an arm that may be set at any height and set to its required position on the bar by a set-screw is sufficient, the base of the stand being secured to the work by a clamp or other convenient device. Fig. 1796 represents a flexible shaft for drilling holes inaccessible to a drilling machine, and in situations or under conditions under which a ratchet brace would otherwise require to be used. It consists of a shaft so constructed as to be capable of transmitting rotary motion though the shaft be bent to any curve or angle. A round belt driven from a line shaft rotates the grooved pulley, and the shaft transmits the rotary motion to bevel-wheels contained in a portable drilling frame, the fulcrum for the feed being afforded by a drilling post after the manner employed in ratchet drilling. The shaft is built up of several layers of wire (as shown in the view to the left), the number of layers depending upon the size and strength of shaft required, wound one upon the other helically. The layers are put on in groups of three to eight wires, parallel to each other, each successive layer containing groups of varying numbers of wires, thus giving a different pitch to the helices for each layer, the direction of each twist or helix being the reverse of the one upon which it is wound. When the shaft is laid up in this manner, the wires at each end for a short distance are brazed solidly together, and to these solidified ends the piercers are secured for the attachment of the pulley and tool which it is to drive. This construction, it will be readily seen, produces a shaft which will have considerable transverse elasticity, while it must necessarily offer great resistance to torsional strain, the reversed helices forming a kind of helical trussing, which effectually braces it against torsion. The case within which it turns is simply an elastic tube of leather or other suitable material, within which is wound a single helix of wire fitting its inside tightly, the inside diameter of the helix being a little greater than the outside diameter of the shaft, and wound in a contrary direction to the outer helices of the shaft. This forms a continuous bearing for the shaft; or at least serves as a bearing at the points of contact between the shaft and case which are brought about in the various bending of the whole when in use. [Illustration: Fig. 1796.] In order to give to the instrument all the transverse elasticity possible, that end of the shaft carrying the pulley is made with a feather so that it may slide endways in the pulley, while the latter is secured to the case, the case, however, not rotating with it. It will be readily seen that this is a necessary precaution, inasmuch as in the varying curves given to the instrument in use a difference will occur in the relative lengths of the shaft and tube. It might be supposed that the friction of the shaft within the tube would be so considerable as to militate against the success of the apparatus; but in practice, and under test for the determination of this, it has been found that the friction generated by running it when bent at a right angle does not exceed that when used in a straight line more than 15 per cent. of the latter. In the running of it in a bent position, not only will there be friction between the shaft and tube, but there must also be some little motion of the layers of wire one upon another in the shaft itself; and to provide against the wear and friction which would otherwise occur in this way, provision is made for not only oiling the bearings at the ends, but also for confining a small quantity of oil within the tube, by which all motion of the wires upon one another, or the shaft upon the interior of the tube, is made easy by its being well lubricated. In the figure the shaft is shown complete with a wood-boring auger in place at the shaft end. Shafts of similar but very light construction are employed by dentists for driving their dental drills and plugging tools, many of them having ingenious mechanical movements derived from the rotary motion of the shaft. [Illustration: Fig. 1797.] In Fig. 1797 is represented a drilling device in position for drilling a hole from the inside of a steam boiler. A represents a base piece made with a journal stud _b_. This base piece is provided with radial arms _a_, with threaded ends and nuts made with conical projecting ends, as shown at _a_^{2}. One of these pieces is used at each end of the machine when convenient, their use for centring and holding the frame being apparent. When not convenient to use two of them, one end of the frame is sustained as shown in the engraving, or in some other manner that may suggest itself. The casting B is made in two pieces, and is provided with a bearing for the pin _b_, and holds the ends of the rods C C. The actuating shaft G carries the bevel-wheel _g_, more clearly seen in the figure at side, which drives the drill spindle, whose ends are of different lengths, for convenience in reaching to different distances. The cross-head E may be slid along as required on the rods, and the revolving frame and drill turned around to different positions. [Illustration: Fig. 1798.] Fig. 1798 represents a small hand drilling machine to be fastened to a work bench. A suitable frame affords journal bearing to the upright spindle, upon which is a bevel-gear G, which is driven by a gear upon the same shaft as the wheel W. The spindle is threaded at S and is fed by the hand wheel F, which is threaded upon the screw S and has journal bearing in the cap C. Fig. 1799 represents a hand drilling machine for fixture against a post, the larger wheel serving as a fly-wheel and the smaller one being to feed with. SLOTTING MACHINE.--In the slotting machine the cutting tools are carried in a ram or slide that operates vertically, and the work table lies horizontal and beneath the ram. Fig. 1800 represents a slotting machine, and Fig. 1801 is a sectional view of the same machine. The cone spindle shaft has a pinion which drives a spur-wheel upon an horizontal shaft above. Upon the inside face of this spur gear is a cam groove for operating the feed motions, at the other end of the shaft is a Whitworth quick-return motion, such as has already been described with reference to shaping machines. The connecting rod from the quick-return motion attaches to the ram, which operates on a guide passing through a way provided at the upper end of the main frame, and bolting to the front face of the main body of the frame. The object of this arrangement is that by adjusting the height of this guide to suit the height of the work, the ram will be guided as close to the top of the work as the height of the latter will permit; whereas when the guide for the ram is fixed in position on the frame the ram passes as far through the guide when doing this as it does when doing thick work, and is therefore less closely guided than is necessary so far as the work is concerned. [Illustration: Fig. 1799.] [Illustration: Fig. 1800.] The ram, or slotting bar as it is sometimes termed, is counterbalanced by the weighted lever shown, so that the ram is always held up, and there is no jump when the tool post meets the work, because the tool motion is always taken up by the lever. [Illustration: Fig. 1801.] The work is held upon a circular table capable of being revolved upon its axis to feed the work to the cut. This table is carried upon a compound slide having two horizontal motions, one at a right angle to the other. The lower of these is operated by a rod running through the centre of the machine, as seen in the sectional view in Fig. 1801. The upper is operated through the larger of the two gear-wheels, seen at the side of the machine in the general view of the machine in Fig. 1800. The upper and smaller of these wheels operates a worm, which engages with worm-teeth cut on the periphery of the circular table to rotate the latter. Either or all of these feed motions may be put in simultaneous action, or all may be thrown out and the feeds operated by hand. As the tool is in many cases rigid on the ram or bar of a slotting machine, it is preferable that the feed should occur while the tool is at the top of its stroke and before it meets the work, so that it may not rub on the return stroke, and thus become rapidly dulled. Fig. 1802 represents a slotting machine in which the guideway for the slotting bar or ram is fixed in position, and the feed motions are entirely on the outside of the machine. In this case the worm-gear pinion is on the side of the machine not seen in the engraving. The cutting tools for slotting machines are carried in one of these ways: first, bolted direct to the slotting bar or ram, in which case they stand vertically; secondly, in a box that is bolted to the end of the ram and standing horizontally; and thirdly, held in a tool bar, in which case the tool may stand either horizontally or vertically. Fig. 1803 shows a tool B secured in a hole provided in a stout bar A by the set-screw C. The tool in this case being rigidly held the cutting edge is apt to rub against the work during the upward stroke and become rapidly dulled. To avoid this, various devices have been employed, but before describing them it will be well to point out that the shape of the tool has an important bearing upon this point. In Fig. 1804, for example, is a tool T bolted to the box B at the end of the slide S. W is a piece of work having the cut C taken off it. Now suppose that A is the centre of motion or fulcrum from which the spring of the tool takes place (and there is sure to be a little spring under a heavy cut), then the point of the tool will spring in the direction of the arrow E, and will cut deeper to the amount of its spring; but during the up stroke the tool being released from pressure will not spring, and therefore will partly or quite clear the cut according to the amount of the spring. This desirable action may be increased by giving the face of the tool which meets the cutting a slight degree of side rake, as shown in Fig. 1805, in which S is the slide, T the tool, B the box, and F the direction of the tool spring, which takes place in this case from the pressure of the cutting in its resistance to being bent out of the straight line. [Illustration: Fig. 1802.] [Illustration: Fig. 1803.] [Illustration: Fig. 1804.] In Fig. 1806 is a device for obviating to some extent this defect. A A is the tool box or bar containing a tool-holding piece pivoted at C, the tool being secured therein by the set-screw E B. A spiral spring sustains the weight of the pivoted piece and of the tool. During the down stroke the spiral spring holds the pivoted piece against the box or bar A, while during the up stroke the pivoted piece allows the tool to swing from the pivot C as denoted by the arrow D. In this case the friction on the tool edge is that due to overcoming the resistance of the spring only. [Illustration: Fig. 1805.] [Illustration: Fig. 1806.] [Illustration: Fig. 1807.] In round-nose tools that are slight, and which from having a maximum length of cutting edge are very subject to spring, additional strength may be given the tool by swelling it out at the back, as denoted by the dotted line B in Fig. 1807. [Illustration: Fig. 1808.] Excessively heavy cuts may be taken by the form of tool shown in Fig. 1808, in which A is the tool, B the tool box, and C the work, the depth of cut being from D to E, which may be made 2-1/3 inches if necessary. The face F of the tool is ground at an angle in the direction of I, so that the tool shall take its cut gradually, and that the whole length of the tool cutting edge shall not strike the cut at the same instant, which would cause a sudden strain liable to break either the tool or some part of the machine itself. So likewise the tool will leave its cut gradually and not with a jump. As shown in the cut, but a small part of the cutting edge would first meet the work, exerting for an instant of time only enough pressure and resistance to bring all the working parts of the machine up to a bearing, and as the tool descends (as denoted by the arrow G), the strain would increase until the whole length of tool cutting edge was in operation. For such heavy duty as this the tool is tempered down to a purple to give it strength. CHAPTER XXI.--THREAD CUTTING.--BROACHING PRESS. In Fig. 1809 is represented a front view of a patent die stock for threading pipe up to six inches in diameter. In the figure the three bits or chasers are shown locked in position by the face plate, which is shown removed in Fig. 1810. Fig. 1811 shows the machine with the face plate removed, the bit or chasers having pins in them which fit into the slots in the face plate, so that by rotating the plate the chasers may be set to size. [Illustration: Fig. 1809.] [Illustration: Fig. 1810.] [Illustration: Fig. 1811.] [Illustration: Fig. 1812.] The head carrying the chasers is revolved by means of the gear-wheel and pinion, and Fig. 1812 represents a ratchet lever for revolving the pinion, and is useful when the pipe is in the ground and the die stock is used to cut it off and thread it without lifting it from its position. [Illustration: Fig. 1813.] The method of gripping the pipe is shown in Fig. 1813, in which the machine is represented as arranged for operating by belt power, the pinion being operated by a worm and worm-gear. [Illustration: Fig. 1814.] Referring to the pipe-gripping vice it is seen in the figure that the back of the machine is provided with ways in which the gripping jaws slide. The lower jaw is adjusted for height to suit the size of pipe to be operated upon, and is firmly locked in its adjusted position. It is provided with an index pointer, and the face of the slideway is marked by lines to suit the different diameters of pipe, so that this jaw may at once be set to the proper height to bring the pipe central to the bits. The lower jaw being set, all that is necessary is, by means of the hand wheel, to operate the upper one to firmly grip the pipe. Fig. 1814 shows the front of the machine when arranged for belt power. The No. 1 die stock threads pipe from one to two inches in diameter, but has no cut-off. The large gear has cut teeth, and the pinion is of steel, working in gun-metal bearings. The gripping jaws are fitted with cast-steel faces, hardened. By a simple change the stock may be used to cut left-hand as well as right-hand threads, this change consisting in putting in left-hand bits and in replacing the right-hand screw ring with a left-hand one. After a piece of pipe has been threaded, all that is necessary is to turn the head in the opposite direction, and the bits retire from the pipe thread, so that the pipe may at once be withdrawn, which preserves the cutting edges of the bits as well as saves the time usually lost in winding the dies back. In threading machines the bolt (or pipe, as the case may be) may be revolved and the die held stationary, or the die may be revolved and the pipe held from revolving, the differences between the two systems being as follows, which is from _The American Machinist_:-- Fig. 1815 may be taken to represent a machine in which the pipe is held and the die revolved, and Fig. 1816 one in which the pipe is revolved and the dies are held in a head, which allows them to move laterally to suit the pipe that may not run true, while it prevents them from revolving. In the former figure the bolt or pipe is shown to be out of line with the die driving spindle, and the result will be that the thread will not be parallel with the axis of the pipe. Whereas in Fig. 1816 the thread will be true with the axis of the work, because the latter revolves, and as the die is permitted more lateral motion it can move to accommodate itself to the eccentric motion of the work, if the latter should not run true. If the end of a piece of pipe is not cut off square or at a right angle to the pipe axis, and the die has liberty to move, it will thread or take hold of one part, the longest one, of the pipe circumference first, and the die will cant over out of square with the pipe axis, and the thread cut will not be in line with the pipe axis. [Illustration: Fig. 1815.] [Illustration: Fig. 1816.] The two important points in operating threading machines is to keep the dies sharp and to well lubricate them with oil. When dies are run at a maximum speed and continuously at work they should be sharpened once or, if the duty is heavy, twice a day, a very little grinding sufficing. In nut tapping the oil lubrication is of the utmost importance, and is more difficult because the cuttings are apt to clog the tap flutes and prevent the oil from flowing into the cutting teeth. When the tap stands vertical and the nuts are put on at the upper end (the point of the tap being uppermost), the cuttings are apt to pass upwards and prevent perfect lubrication by the descending oil. When the taps stand horizontally, gravity does not assist the oil to pass into the nut, and it falls rapidly from the tap, hence it is preferable that the tap should stand vertical with its point downwards, and running in oil and water. In machines which cut the bolt threads with a solid die, it is obvious that after the thread is cut upon the bolt to the required distance, the direction of rotation of the bolt or die, as the case may be, requires to be reversed in order to remove the bolt from the die, and during this reversal of rotation the thread upon the bolt is apt to rub against and impair the cutting edges of the chasers or die teeth. To obviate this difficulty in power machines the dies are sometimes caused to open when the bolt is threaded to the required distance, which enables the instant removal of the finished work, and this saves time as well as preserving the cutting edges of the die or chaser teeth. In machines in which the bolt rotates, the machine must be stopped to take out each finished bolt and insert the blank one, which is unnecessary when the bolt is stationary, because so soon as the bolt is threaded to the required distance the dies may open automatically, the carriage holding the bolt at once withdrawn and a new one inserted. When the dies open automatically the further advantage is secured that the bolts will all be threaded to an equal distance or length without care on the part of the operator. [Illustration: Fig. 1817.] A hand machine for threading bolts from 1/4 inch to 3/4 inch in diameter is shown in Fig. 1817. It consists of a head carrying a live spindle revolved by hand, by the lever shown at the right-hand end of the machine, being secured to the live spindle by a set-screw, so that the handle may be used at a greater or less leverage to suit the size of the thread to be cut; on the front end of this spindle are the dies, consisting of four chasers held in a collet that is readily removable from the spindle, being held by a spring bolt which, when pressed downwards, frees the collet from the spindle. The work is held in a pair of vice jaws operated by the hand wheel shown, and this vice is moved endwise in its slideways on the bed by means of the vertical lever shown. The bolt being stationary, the small diameter of the die enables it to thread bent or crooked pieces, such as staples, &c. For bolts of larger diameter requiring more force than can be exerted by a hand lever, a geared hand bolt cutter is employed. [Illustration: Fig. 1818.] In Fig. 1818 is represented a hand bolt cutter. In this cutter the bolt is rotated, being held in a suitable chuck. The revolving spindle is hollow in order to receive rods of any length, and is operated by bevel-wheels as shown, so as to increase the driving power of the spindle by decreasing its speed of rotation. To provide for a greater speed of rotation than that due to the diameters of the bevel-pinion and wheel, the lever is made to slide through the pinion, effecting the same object and convenience as described for the machine shown in Fig. 1817. The threading dies are held in collets carried by a head or cylinder mounted horizontally on a carriage capable of being moved along the bed by means of a rack and pinion, the latter being operated by a handle passing through the side of the bed as shown. The cylinder also carries a collet adapted for recessed plates so as to receive square or hexagon nuts of different sizes for tapping purposes, the taps being held in the rotating chuck. The collets are capable of ready and separate extraction, and by removing the collet that is opposite to the one that is at work, the end of a bolt may pass if necessary entirely through the head or cylinder threading the work to any required length or distance. To insure that the die shall stand axially true with the revolving spindle, bolt holes are drilled in the lower part of the cylinder, and a pin passes through the carriage carrying the head, and projects into these holes, which are so situated that when the pin end projects into a hole and locks the head a collet is in line with the spindle. The dies consist of four chasers inserted in radial slots in collets held in place and bound together by a flat steel ring, which is let into the face of the collet and the external radial face of the chasers, and secured to the collet by screws. One chaser only is capable of radial motion for adjusting the diameter of thread the die will cut, and this chaser is adjusted and set by a screw in the periphery of the collet. The other two chasers being held rigidly in a fixed position in the ring act as back rests and cut to the diameter or size to which they are made, or according to the adjustment of the first chaser. The shanks of the collets are secured in the cylindrical head by means of either a bolt and key or by a set-screw. The chasers are sharpened by grinding the face on an ordinary grindstone or emery wheel. [Illustration: Fig. 1819.] The chasers are numbered to their places and are so constructed that if a single chaser of a set of three should require renewal, a chaser can be obtained from the manufacturers that will match with the remaining two of the set, the threads on the one falling exactly in line with those on the other two, whereas in other dies the renewal of one chaser involves the renewal of the whole number contained in the die. This is accomplished by so threading the dies that the thread starts from the same chaser (as No. 1) in each set. In Fig. 1819 is represented one of these machines, which is intended for threads from 3/8 to 1 inch in diameter. It is arranged to be driven by belt power, being provided with a pulley having three steps; on this pulley spindle is a pinion operating a gear-wheel on the die driving spindle, as shown. The oil and cuttings fall into a trough provided in the bed of the machine, but the oil drains through a strainer into the cylindrical receiver shown beneath the bed, whence it may be drawn off and used over again. [Illustration: Fig. 1820.] In Fig. 1820 is represented a bolt threading machine which is designed for bolts from 3/16 to 1 inch in diameter. The bolt to be threaded is gripped in the vice L, operated by hand by the hand wheel M, and is moved by hand up to the head D, by the hand wheel Q operating the pinion in the rack shown at the back of the machine. When the dies or chasers have cut or threaded the bolt to the required distance, the threading dies are opened automatically as follows:-- At H is a clutch ring for opening and closing the threading chasers, and at N is the lever operating the shoes in the groove of the clutch ring. This lever is upon a shaft running across the machine and having at its end the catch piece P; at Z is a catch for holding P upright against the pressure of a spring that is beneath the bed of the machine, and presses on an arm on the same shaft as the catch piece P. On the back jaw of the vice L is a bracket carrying a rod R, and the bolt or work is threaded until the end of rod R lifts catch Z, when the before-mentioned spring pulls lever N and clutch ring H forward, opening the dies and therefore stopping the threading operation. The length of thread cut upon the work is obviously determined by adjusting the distance rod R projects through V. The handle W is upon the same shaft as catch piece P and clutch lever N, and therefore affords means of opening the dies by hand. The operation of the machine obviously consists of gripping the work in vice L, moving it up to the head D by the hand wheel Q, setting the rod R to open the dies when the bolt is threaded to the required length, and moving the vice back to receive a subsequent piece of work. [Illustration: Fig. 1821.] [Illustration: Fig. 1822.] The construction of the head D and clutch and ring H is shown in Figs. 1821 and 1822. The body F is bolted by the flange I to a face plate in the live spindle or shaft of the machine, and through slots in this body pass the holders or cases C containing the chasers or dies. Upon F is the piece D provided with a slot to receive the die cases and a tongue to move them. This slot and tongue, which are shown at E´, are at an angle to the axis of F; hence if D be moved endways upon F the cases and dies are operated radially in or through the body F. To operate D laterally or endwise upon F the clutch ring H and the toggles G are provided, the latter being pivoted in the body F, and H being operated endwise upon F by the lever shown at N in the general view, Fig. 1820. The amount to which the dies will be closed is adjustable by means of the adjusting screws E, which are secured in their adjusted position by the set-screws R, Fig. 1821; it being obvious that when H meets the shoulder S of G and depresses that end of the toggle, head D is moved to the right and the dies are closed when the end of G meets E, and ceases to close when G has seated itself in F and can no longer move E. The backward motion of the clutch ring H, and therefore the amount to which the dies are opened, is regulated by the screw B and stop A in Fig. 1822, it being obvious that when B meets A the motion of H and D to the left upon F ceases and the dies are fully opened. The amount of their opening is therefore adjustable by means of screw B. J is simply a cap to hold the dies and cases in their places. [Illustration: Fig. 1823.] In the end view, Fig. 1823, E, E are the adjustment screws for the amount of die closure, and B, B those for the amount they will open to, T representing the screws for the cap J, which is removed for the insertion and extraction of the dies and die cases. [Illustration: Fig. 1824.] The construction of the dies P and cases C is shown in Fig. 1824. Two screws at N secure the dies in their cases and a screw M adjusts them endways so as to set them forward when recutting them. By inserting the dies in cases they may be made of simple pieces of rectangular steel, saving cost in their renewal when worn too short. [Illustration: Fig. 1825.] Fig. 1825 shows the machine arranged with back gear for bolts from 2 to 2-1/2 inches in diameter, the essential principles of construction being the same as in Fig. 1820. [Illustration: Fig. 1826.] In Fig. 1826 is represented a single and in Fig. 1827 a double "rapid" machine, constructed for sizes up to 5/8 inch in diameter, the double machine having a pump to supply oil to the dies. This pump is operated by an eccentric upon the end of the shaft of the cone pulley. The construction of the head of this machine is shown in Fig. 1827A. Z is the live or driving spindle, upon which is fast the head A. In A are pivoted at M the levers L which carry the dies D, which are secured in place in the levers by the set-screws B and adjusted to cut to the required diameter by the screws E. The levers L are closed upon the clutch C by means of the springs R and S, each of these springs acting upon two diametrically opposite levers, hence the action of the springs is to open the dies D. The clutch C has a cone at T and slides endways upon the live spindle Z. The clutch lever and shoes are upon a shaft running across the machine and actuated by a rod corresponding to the rod R in Fig. 1820. When the clutch and levers L are in the position shown in the figures the dies are closed for threading the bolt, and when this threading has proceeded to the required distance along the work, clutch C is moved by the aforesaid rod and lever in the direction of arrow W, and the springs R, S close the ends P of lever L down upon the body X of the clutch opening the dies and causing the threading to cease. [Illustration: Fig. 1827.] [Illustration: Fig. 1827A.] Fig. 1828 represents a "double" rapid machine for threading work up to four inches in diameter, and therefore having back gear so as to provide sufficient power. The gauge rod from the carriage here disengages a bell crank from the end of the long lever shown, and thus prevents the spring to operate the cross shaft and open the dies. In Fig. 1829 is represented a bolt threading machine or bolt cutter, which consists of a head carrying a live spindle upon which is a head carrying four bits or chasers that may be set to cut the work to the required diameter, and opened out after the work is threaded to the required length and the bolt withdrawn without losing the time that occurs when the dies require to run backward to release the work, and also preventing the abrasion and wear that occurs to the cutting edges of the die bits or chasers when revolved backward upon the work. This head is operated by the upright lever shown in the figure, this lever being connected to the clutch shown upon the live spindle. The details of construction of the clutch and of the head are shown in Figs. 1830, 1831, 1832, and 1833. The work to be threaded is gripped between jaws operated by the large hand wheel shown, while the vice moves the work up to or away from the head by means of the small hand wheel which operates pinions geared with racks on each side of the bed of the machine as clearly shown in the figure. Fig. 1830 is a longitudinal section of the head, and Fig. 1831 an end view of the same. P are the threading dies or chasers held in slots in the body _a_ by the annular ring face plate K. The ends of the dies are provided with [T]-shaped caps T fitting into corresponding grooves or slideways in the die ring B, and it is obvious that as the heads of their caps are at an angle therefore sliding the ring B along _a_ and to the right of the position it occupies in the figure will cause the dies P to close concentrically towards the centre or axis of the head _a_. At C is a ring capable of sliding upon _a_ and operated by the upright lever shown in the general view in Fig. 1829. The connection between the die ring B and the clutch ring C is shown in Figs. 1832 and 1833, the former being also a longitudinal sectional view of the head, but taken in a different plane from that in Fig. 1830. The barrel or body _a_ _a_ of the head is provided with two diametrically opposite curved rocking levers which are pivoted in recesses in _a_ _a_. The clutch ring C envelops body _a_ and passes between the curved ends of these rocking levers. The upper of the two rocker levers shown in the engraving connects with a lever E, which connects to a stud or plunger P, threaded to receive the adjusting screw I, which is threaded into the die ring B. Obviously when C is moved to the right along _a_ it operates the rocking lever and causes B to move to the right and to close the dies upon the work. The amount of die closure, and therefore the diameter to which the dies will thread the work, is adjustable by means of the adjusting screw I, which has a coarse thread in B and a finer one in P, hence screwing up I draws B to the left and farther over the plunger P, thus shortening the distance between the centre of the curved lever and limiting the motion of B to the right. On the other hand, unscrewing I moves B to the right, and it is obvious that in doing this the cap T in Fig. 1830 is forced down by the groove in B and the dies are moved endwise towards the axis _a_ _a_, or in other words, closed. It will be clear that a greater amount of power will be necessary to hold the dies to their cut than to release them from it, and on that account the lower curved rocking arm D connects through E to a solid plunger G, the screw H abutting against the end of G and not threading into it, because G is only operative in pushing B forward in conjunction with P, while P pulls B backward, the duty being light. It is obvious, however, that after the adjustment screw I is operated to set the dies to cut to the proper diameter, adjustment screw H must be operated to bring the ring B fair and true upon _a_ _a_ and prevent any lateral strain that might otherwise ensue. [Illustration: Fig. 1828.] [Illustration: Fig. 1829.] These two adjustments being made the clutch ring C is operated to the left to its full limit of motion to open the dies and to its full limit to the right to close them. It will be seen, by the lines that are marked to pass through the pivoting pins of the rocking lever D, that the joints marked 2 in Fig. 1832 are below these lines, and as a result the links E form in effect a toggle joint locking firmer in proportion as the strain upon them is greater. Fig. 1834 represents a bolt threading machine having two heads each of which is capable of threading bolts from 1/2 up to 1-1/2 inches in diameter. [Illustration: Fig. 1830.] [Illustration: Fig. 1831.] [Illustration: Fig. 1832.] [Illustration: Fig. 1833.] [Illustration: Fig. 1834.] The levers for operating the clutch rings are here placed horizontal, so that they may extend to the end of the machine and be convenient to operate, and a pump is employed to supply oil to the dies. The capacity of a double machine of this kind is about one ton of railroad track bolts per day of 10 hours' working time. In American practice it is usual to employ four cutting dies, bits, or chasers, in the heads of bolt threading machines, while in European practice it is common to employ but three. Considering this matter independently of the amount of clearance given to the teeth, we have as follows:-- If a die or internal reamer, the cutting points of which were all equidistant from a common centre, were placed over a piece of work, as a bar of iron shown in Fig. 1835, and set to take a certain cut, as shown by the circle outside the section, it is evident that if revolved, but left free to move laterally, or "wabble," the cutter would tend to adjust itself at all times in a manner to equalize the cutting duty--that is, if the die had two opposite cutting edges or points, and the piece operated upon were not of circular form, then, when one cutter reached the part that was not round, it would have either more or less cutting to do than before, and hence, the opposite cutter having the same amount, the tendency would be for the two cutting edges to travel over and equalize the cuts, and hence the pressure. With three cutting points, no two being opposite, the tendency would all the while be to equalize the cuts taken by all three; with four, spaced equally, the tendency would always be to equalize the cuts of those diametrically opposite; with five, the tendency would be to equalize the duty on each, and so on. Thus it will be noticed that there is a difference between the acting principle of a die having an even or an odd number of cutters, independent of the difference in the actual number of cutting edges, or points, as we are now considering them. [Illustration: Fig. 1835.] [Illustration: Fig. 1836.] To take an example, in Fig. 1835 is represented a die having four cutting points, placed upon a piece of iron of a round section, with the exception of a flat place, as shown. Now, in this position each one of the cutting points A, B, C, and D, is in contact with the true cylindrical part of the work only; hence, if the die were set to take the amount of cut shown, each point would enter the iron an equal distance, and the inner circle through the points would be the smallest diameter of the die. Upon revolving the die in the direction denoted by the arrow, an equal cut would continue to be taken off, and hence the circular form maintained, until cutter D had reached the edge _x_ of the flat, the opposite one B, being at _y_ (A at _r_ and C at _v_), proceeding as D moved from _x_ towards A, its cutting duty would continually become less and its pressure decrease, but as it is the cutting pressure of D that holds the opposite point B to its cut, as the pressure in D, after reaching _x_, continually becomes less, the die would gradually travel over so as to carry D toward the centre and cause it to take more cut, while B, on the opposite side, would travel out a corresponding distance and take less, thus keeping the duty equalized until the cutter D had reached H, the lowest part of the flat, when the die would have moved the greatest distance off the centre, assuming the position shown by dotted lines. Thus the cutting point at H has passed inside the true circle that all the cutters commenced to follow, while F has passed outside. Meanwhile, as H and F have shifted over, E and G have, of course, moved an equal amount and in the same direction, but the diameter of E and G being at right angles to that of H and F, the distances of E and G from the centre would be changed but an infinitesimal amount; hence, they would virtually continue to follow the true circle, notwithstanding the deviation of the other pair. As the die continues to revolve and H passes toward A, the lateral motion is reversed, the die tending to resume its original central position, which it does upon the completion of another quarter of a revolution, when the cutter that started at D has passed to H and finally to A. A cutting has now been removed from the entire circumference of the iron, leaving it of a form shown approximately in Fig. 1836, where A _z_, B _y_, C _v_, and D _x_, are the four true circular portions cut respectively by the points A, B, C, and D, before the flat place was reached. After the flat place was reached _x_ A is the depression cut by D, _y_ C the elevation formed by B, and _z_ B and _v_ D are the arcs, differing almost imperceptibly from the true circular ones cut by A and C. [Illustration: Fig. 1837.] [Illustration: Fig. 1838.] Fig. 1837 represents a die having three instead of four cutting points--that is, the point C of Fig. 1835 is left out, and the remaining ones A, B, and D, are equally spaced. This, placed upon a similar bar and taking an equal cut, would produce a truly circular form until D had reached _x_--with A and B at _z_ and _y_--after which the die would move laterally, tending to carry D toward the centre of the work and A and B away from it, so as to equalize the cuts on all three. Hence, when D had reached H and the three-cutter die attained the position shown by dotted lines in Fig. 1837, H would have made an indentation inside the true circle, while E and F have travelled away from it, thus forming protuberances. From H to A the lateral movement is reversed, and finally upon the completion of a third of a revolution, the die is again central and a cut has been carried completely around the bar, leaving it as shown in Fig. 1838. Comparing this with Fig. 1836, it will be seen that there are three truly cylindrical portions--viz., A _z_, B _y_, and D _x_ instead of four in Fig. 1836, but each one is longer; that there is a depressed place, _x_ A, of equal length to that in Fig. 1836, and two elevations, _z_ B and _y_ D, each of equal length to the one (_y_ C) in Fig. 1836. [Illustration: Fig. 1839.] [Illustration: Fig. 1840.] [Illustration: Fig. 1841.] Now, suppose the bar to have an equal flat place on its opposite side, becoming of a section shown in Fig. 1839, upon applying the dies and pursuing a similar course of reasoning, the die with four points would reduce the bar to the size and shape shown in Fig. 1840, or a true cylinder, while the triple-pointed cutter would produce the form shown in Fig. 1841, which is a sort of hexagon, coinciding with the true circle in six places--A, _z_, B, _y_, D, and _x_--while between A and _z_, and opposite, between _y_ and D, there is an elevation; also from _z_ to B and from D to _x_. A flattened portion, A _x_, with a similar one B _y_, opposite, completes the profile. Suppose, now, that a bar of the form shown in Fig. 1842, having two flat places not opposite, be taken, and the four-cutter and three-cutter dies are applied. The product of the four is shown in Fig. 1843, and that produced by the three-cutter die in Fig. 1844. The section cut with four coincides with the true circle at four points, A, B, C, D, and differs from it almost imperceptibly at _z_, _y_, _v_, and _x_. There are two elevations between A and B and between B and C; also two depressions between C and D and between D and A. The section from the three-cutter die is the perfect circular form between A _z_, B _y_, and D _x_, with a projection from _z_ to B and two depressions from _y_ to D and from _x_ to A. The four-die, applied to a section having three flats like Fig. 1845, would produce Fig. 1846, which does not absolutely coincide with the true circle at any point, although the difference is inconsiderable at A, _z_, _y_, C, _v_ and _x_; three equidistant sections A _z_, _y_ C, and _v_ _x_, are elevated and the three alternate ones depressed. [Illustration: Fig. 1842.] [Illustration: Fig. 1843.] [Illustration: Fig. 1844.] [Illustration: Fig. 1845.] [Illustration: Fig. 1846.] [Illustration: Fig. 1847.] The three-cutter die would in this case cut the perfectly circular form of Fig. 1847. Now, suppose both of the dies to have been made or set to some certain diameter--in fact, presume them to be made by taking a ring of steel having a round hole of the required diameter, say 1 inch, and removing the metal shown by the dotted lines, Fig. 1848, and leaving only the four cutting points in one case (and the three in the other). Then it is evident that our dies are both of the same diameter, and likewise both of the assumed diameter, or 1 inch; then it is fair to presume that the plugs or sections just cut by either one of the dies should enter a round hole of the same diameter as the dies; but it is obvious that only two, Figs. 1840 and 1847, will do so, all the rest being considerably too large, from their irregularity of form, notwithstanding the fact that the diameter of any of those cut by four cutters is never more than that of the die, while any one of the equal radii, taken at equal distances on any of the forms cut by the three-cutter die, will not exceed the radius of the die. Now, six of the pieces being too large when referred to the standard of a round hole of the size of the die, while two are of the correct size, it is obvious that if the four-die, for example, which cut Fig. 1846, were reduced enough to make Fig. 1843 just enter the standard, that, Fig. 1840, which is now just correct in size and form, would, when cut, be altogether too small. The same would be the case also with the three-cutter die. Now let us consider the two productions (Figs. 1840 and 1847) that answer the requirements, the two different sections (Figs. 1839 and 1845) from which they were cut, and also the other two pieces (Figs. 1841 and 1846) that were cut from the same bars at the same time. The general shape of Fig. 1839, is oval or four-sided, and while the four cutters operated upon it to produce perfectly circular work, the three cutters reproduced the general shape started with, only somewhat modified, as Fig. 1841 plainly shows. Upon the blank, Fig. 1845, the general shape of which is triangular, the very opposite is the case, for the three cutters now produce a perfect circle, while the four modify only the figure that they commenced to operate upon. [Illustration: Fig. 1848.] Considering that every irregular form may be approximated by a square, an equilateral triangle, or in general by either a parallelogram or a regular polygon, it will be found that from a flat, oval, or square piece of metal the four cutters will produce a true circle; from a triangular piece the three; from a heptagon neither will do so, while from a hexagon both the three and four cutters are calculated to do so. Following in the same manner, and increasing the sides, it will be found that the four cutters will produce a true circle from every parallelogram, whether all the sides are equal or not, while the three cutters will produce a true circle also from every regular polygon the number of sides of which is a multiple of three--that is, four cutters would operate correctly upon a figure having 4, 6, 8, 10, 12, &c., parallel sides, while the three would do so upon a figure having 3, 6, 9, 12, 15, &c., equal sides. Thus, for regular forms varying between these two series neither one would be adapted. Hence, if the general form of the work is represented by the first series, the four cutters are the best; if the general and average form of the material to be operated upon corresponds to the second series, then the three dies are the best adapted, so far as their two principles of action, mentioned at the outset, are concerned; hence, if it is considered that the material or bars of metal to be wrought vary from a circular form indifferently, then there is no choice between an even and an odd number merely on that account. Placing the same dies that cut these six irregular figures upon their respective productions would not serve to correct their form; as, for instance, if the die that cut Fig. 1846 were revolved around it--even if set up or reduced in diameter to take a cut--it would remove an equal amount all round and leave the same figure still. Similarly with, say, Fig. 1841, cut by the three; but if the three were run over Fig. 1846, cut by the four, it would tend to correct the errors, and likewise if the four were run over Fig. 1841, the tendency would be to modify the discrepancies left by the three that cut it. [Illustration: Fig. 1849.] As regards the number of cutting points, suppose that there were a certain number, as three, shown in Fig. 1849, all taking an equal cut; then, when the position indicated by the dotted lines was reached, where cutter H runs out, the entire duty would be only two-thirds as much as it was, and the die would shift laterally in the direction of the arrow enough to equalize this smaller amount of duty on all three, or make H, E, and D each cut two-thirds as much as at first. With four as shown in Fig. 1850 when H reached the depression where its cut would run out, the entire duty would be three-fourths of what it was at first, and the die would travel laterally in the direction of the arrow sufficiently to equalise the pressure upon H and F, and upon E and G. With five, as shown in Fig. 1851, in similar position the entire duty would be four-fifths as much; with six, five-sixths, and so on. Thus it can be seen that the variation between the least amount to be cut and the full amount is relatively less, the greater the number of cutting points that it is divided between, and hence the lateral movement would be less; therefore the general tendency of an increase in the number of cutting points would be to promote true work. [Illustration: Fig. 1850.] [Illustration: Fig. 1851.] Hence, from these considerations it appears that it is not material whether the number is odd or even merely on that account; so four would be preferable to three only on account of being one more, and, in turn, five would be better than four, and six better than five, and so on. It is found, however, that bar iron usually inclines to the elliptical form, and that an even number is, therefore, preferable. Thus far the cutting edges of the die have been assumed to be points equidistant about a circle--that is, it has been supposed to have absolute clearance, so that its movements would be regulated entirely by the depth of cut taken, in order to ascertain the inherent tendency to untruth caused by an odd or an even, a greater or a less, number of cutters. This tendency is, of course, modified in each case by the amount of clearance. [Illustration: Fig. 1852.] [Illustration: Fig. 1853.] [Illustration: Fig. 1854.] The position of the dies in the head and with relation to the work is, in bolt cutting machines, a matter of great importance, and in all cases the dies should be held in the same position when being hobbed (that is, having their teeth cut by the hob or master tap) as they will stand in when put to work, and the diameter of the hob must be governed by the position of the dies in the head. If they are placed as in Fig. 1852 the diameter of the hob must be 1/32 inch larger than the diameter of bolt the dies are intended to thread, so that the point or cutting edge may meet the work first and the heel may have clearance, it being borne in mind that the clearance is less at the tops than it is at the bottoms of the teeth, because of their difference in curvature. In this position the teeth are keen and yet retain their strength, acting somewhat as a chaser. If placed in the position shown in Fig. 1853 the hob or master tap must be 1/32 inch smaller than the diameter of bolt they are to thread, so as to give the teeth clearance. In this case the dies are somewhat harder to feed into their cut and do not cut quite so freely, but on the other hand they work more steadily as the bolt is better guided, while left-hand dies may be used in the same head. If placed as in Fig. 1854 they must be cut with a hob 1/32 inch larger in diameter than the bolt they are to thread, so that the teeth will have less curvature than the work, and will, therefore, have clearance. In this position the dies do not cut so freely as in Fig. 1852. The dies should be broad enough to contain at least as many teeth as there are in a length of bolt equal to its diameter, and should be thick enough to withstand the pressure of the cut without perceptible spring or deflection. [Illustration: Fig. 1855.] The cutting edges of dies may be brought in their best cutting position and the dies placed in radial slots in the head by forming the dies as in Fig. 1855. Face X is at an angle of 18° to the leading or front face of the die steel, and the heel is filed off at an angle of 45° and extends to the centre line of the die. This gives a strong and a keen die, and by using a hob 1/32 inch smaller than the diameter of bolt to be cut, the clearance is sufficiently maintained. [Illustration: Fig. 1856.] The heel of the die should not when the cutting edge is in front extend past the axis of the work, but should be cut off so as to terminate at the work axis as denoted by the dotted line G in Fig. 1856. [Illustration: Fig. 1857.] In hobbing the dies it is necessary that they be all of equal length so that the hob may cut an equal depth in each, and may, therefore, work steadily and hob them true. After the dies are hobbed their front ends should be reamed with a taper reamer as in Fig. 1857, chamfering off not more than three threads, and the chamfered teeth must then be filed, just bringing the front edges up to a cutting edge, but filing nothing off them, the reamed chamfer acting as a guide to file them by. This will cause each tooth to take its proper share of the cut, thus preserving the teeth and causing the dies to cut steadily. Back from the cutting edge towards the heels of the teeth the clearance may gradually increase so that the heel will not meet the work and cause friction. The chasers or dies are obviously changed for each diameter of bolt, and it follows that as the chasers all fit in the same slots in the head they must all be made of the same size of steel whatever diameter of bolt they are intended to cut, and this leads to the following considerations. Suppose the capacity of the machine is for bolts between 1/4 inch and 1-1/4 inches in diameter, and the size of the chaser or die will be 1-1/4 inches wide and 1/2 inch thick. The width of a die or chaser should never be less than the diameter of bolt it is to thread, so that it may contain as many threads as are contained in a length of bolt equal to the bolt diameter. Now the 1-1/4-inch chaser equals in width the diameter of bolt it is to cut, viz. 1-1/4 inches; but if the chaser for 1/4-inch bolts was threaded parallel and left its full width it would be five times as wide as the diameter of the bolt and the thread cut would be imperfect, because the chasers alter their pitches in the hardening process, as was explained with reference to taps, and it is found that the error induced in the hardening varies in amount and sometimes in direction: thus of the four chasers three may expand and become of coarser pitch, each varying in degree from the other two, and the other may remain true, or contract and become of finer pitch. [Illustration: Fig. 1858.] As a rule the dies expand, but do not so equally. The more teeth there are in the die the more the pitch error from the hardening; or in other words, there is obviously more error in an inch than there is in half an inch of length. Suppose then that we have a die for 20 threads per inch, and as the chaser is 1-1/4 inches wide, it will contain 25 teeth, and the amount of pitch error due to 1-1/4 inches of length; and this amount not being equal in all the chasers, the result is that the dies cut the sides of the thread away, leaving it sharp at the top but widened at the bottom, as shown in Fig. 1858, weakening it and impairing its durability while placing excessive duty on the dies and on the machine. [Illustration: Fig. 1859.] [Illustration: Fig. 1860.] [Illustration: Fig. 1861.] A common method of avoiding this is to cut away all the teeth save for a width of die equal to the diameter of the bolt, as shown in Fig. 1859. An equally effective and much simpler plan is to form the dies as in Fig. 1860, the diameter at the back B being slightly larger than that at the mouth A, so that the back teeth are relieved of cutting duty. This enables the dies to undergo more grindings and still retain sufficient teeth. For example, the chamfer at A may be ground farther towards B, and still leave in action sufficient teeth to equal in width of chaser the diameter of the bolt. To enable the threading of dies in this manner the hobs or master taps employed to thread them are formed as in Fig. 1861, the proportions of the master taps for the different sizes of bolts being as given in the following table:-- ------+-----------------------+---------------+----------------------------- Dia- | | | meter| | | of | | | Length bolt.| ---- | ---- |at A.|at B.|at C.|at D.|at E. ------+-----------------------+---------------+-----+-----+-----+-----+----- 1/4 |Dia. from G to H 15/64 |At J 7/32 | 1/2|1 |1 |1-1/2| 1/2 5/16| " " 19/64 | " 9/32 | 1/2|1 |1 |1-1/2| 1/2 3/8 | " " 23/64 | " 11/32 | 1/2|1 |1 |1-1/2| 1/2 7/16| " " 27/64 | " 13/32 | 1/2|1 |1 |1-1/2| 1/2 1/2 | " " 31/64 | " 15/32 | 1/2|1-1/2|1-1/2|1-1/2| 3/4 5/8 | " " 39/64 | " 19/32 | 1/2|1-1/2|1-1/2|1-1/2| 3/4 3/4 | " " 47/64 | " 23/32 | 1/2|1-1/2|2 |1-1/2| 3/4 7/8 | " " 55/64 | " 27/32 | 1/2|1-1/2|2 |1-1/2| 3/4 1 | Dia. at G 31/32 |At J 1/100 less| 1/2|4 |4 |1-1/2|1 1-1/8 | " 1-3/32 | ---- |1 |4 |4 |1-1/2|1 1-1/4 | " 1-7/32 | ---- |1 |4 |4 |1-1/2|1 1-3/8 | " 1-11/32| ---- |1 |4 |4 |1-1/2|1 1-1/2 | " 1-15/32| ---- |1 |4 |4 |1-1/2|1-1/4 1-5/8 | " 1-19/32| ---- |1 |5 |5 |2 |1-1/2 1-3/4 | " 1-23/32| ---- |1 |5 |5 |2 |1-1/2 1-7/8 | " 1-27/32| ---- |1 |6 |6 |2 |1-3/4 2 | " 1-31/32| ---- |1 |6 |6 |2 |1-3/4 ------+-----------------------+---------------+-----+-----+-----+-----+----- All over 2 in. same length as the 2 in. Shanks J turned to bottom of last thread. The cutting speeds for the dies and taps are as given in the following table, in which it will be seen that the speeds for bolt factories are greater than for machine shops. This occurs on account of the greater experience of the operators and the greater care taken in lubricating the dies and keeping them sharp:-- --------+-----------+-----------+--------+-----------+------------ Diameter|Revolutions|Revolutions|Diameter|Revolutions|Revolutions of bolt.|of dies for|of dies for|of bolt.|of dies for|of dies for | machine | bolt | | machine | bolt | shops. | factories.| | shops. | factories. --------+-----------+-----------+--------+-----------+------------ inch. | | | inch. | | 1/8 | 450 | 600 | 1-5/8 | 33 | 48 1/4 | 230 | 300 | 1-3/4 | 30 | 45 3/8 | 150 | 200 | 1-7/8 | 28 | 40 1/2 | 100 | 150 | 2 | 25 | 38 5/8 | 75 | 125 | 2-1/8 | 23 | 36 3/4 | 65 | 100 | 2-1/4 | 22 | 34 7/8 | 55 | 85 | 2-3/8 | 21 | 32 1 | 45 | 75 | 2-1/2 | 20 | 30 1-1/8 | 42 | 65 | 2-5/8 | 18 | 25 1-1/4 | 40 | 60 | 2-3/4 | 15 | 20 1-3/8 | 38 | 55 | 2-7/8 | 12 | 18 1-1/2 | 35 | 50 | 3 | 10 | 15 --------+-----------+-----------+--------+-----------+------------ Taps same speed as dies. [Illustration: _VOL. I._ =NUT-TAPPING MACHINERY.= _PLATE XXIII._ Fig. 1864. Fig. 1865. Fig. 1866. Fig. 1867.] [Illustration: Fig. 1862.] In Fig. 1862 is represented a nut threading or tapping machine. The vertical spindles have spring sockets in which the taps are held, so that they can be inserted or removed without stopping the machine. The nuts are fed down the slots of the inclined plates shown on the upper face of the circular base, and the spindles are raised and lowered by the pivoted levers shown. The nuts lie in a dish that contains water up to the level of the bottom of the nuts, the object being to prevent the taps from getting hot and therefore expanding in diameter. Upon the top of the water floats a body of oil about 1/2 inch deep, which lubricates the cutting edges of the tap. These machines are also made with six instead of four spindles, which in both machines run at different speeds to suit different sizes of nuts, and which are balanced by weights hanging inside the central hollow column or frame. [Illustration: Fig. 1863.] Fig. 1863 represents the socket for driving the tap, so devised that when the tap is strung for its intended length with nuts, the top nut releases the tap of itself, the construction being as follows: S is the socket that fits into the driving spindle of the machine; its bore, which fits the stem of the tap easily, receives two headless screws B, a pin P, which is a sliding fit, and the screw A. R is a ring or sleeve fitting easily to the socket, and is prevented from falling off by screw A. The tap is provided with an annular groove G. The flattened end of the tap passes up between and is driven by the ends of screws B, the weight of the collar ring or sleeve R forcing pin P into the groove G, thus holding the tap up. When the tap is full of nuts the top nut meets face V of ring R, lifting this ring upon the socket and relieving pin P of the weight of R, the weight of the tap and the nuts then causes the tap to be released. By this construction the tap can be inserted or removed while the machine is in motion. In Fig. 1864 is represented a rotary nut tapper, and in Fig. 1865, is also represented a sectional view of the same machine. The tap driving spindles are driven from a central vertical shaft S, driven by bevel-gear B. The horizontal driving shaft operates a worm C, to drive a worm-wheel in a vertical shaft, which drives a pinion _a_, driving a spur wheel W in the base of the spindle head, by which means this head is revolved so as to bring the successive spindles in front of the operator. A trough is provided at T to cool the tap with oil and water after it has passed through the nut. Fig. 1866 represents a nut tapping machine designed for light work, the spindles are raised after each nut is tapped by the foot levers and rods shown, the latter connecting to a shoe fitting into a groove in a collar directly beneath the driving pulleys of the spindles. Fig. 1867 represents a three-spindle nut tapping machine, in which the spindles are horizontal and the nuts are held in three separate heads or horizontal slideways and are traversed by the ball levers shown, and a self-acting pump supplies them with oil. The three spindles are driven by a cone pulley having four changes of speed to suit different diameters of taps. PIPE THREADING MACHINERY.--In Fig. 1868 is represented a machine for threading and cutting off pipe of large diameter. This machine consists of a driving head corresponding to the headstock of a lathe, but having a hollow spindle through which the pipe may pass. The pipe is driven by a three-jawed chuck, and the threading and cutting off tools are carried on a carriage which has a threading head for ordinary lengths of pipe, and one for short pieces such as nipples, the latter swinging out of the way when not in use. Between these two is a pair of steadying jaws for the pipe. A side view of the front of the carriage is shown in Fig. 1869, H H, &c., representing the threading dies used for nipples. It is movable along a slideway E and pivoted upon its slider. The dies are carried in a chuck G, and are opened or closed by the lever N; at L is the handle for the screw that operates the guide jaws A A. [Illustration: Fig. 1868.] [Illustration: Fig. 1869.] The threading head at H (right-hand end of Fig. 1868), is represented in Fig. 1870, being pivoted so that it also can be swung out of the way to permit of the removal of the pipe. The dies C are opened or closed by the hand wheel B, operating a worm meshing into a segment of a worm-wheel upon the body of the head, the amount of motion being regulated by the stop screw at F, which therefore regulates the size to which the dies can be closed, and therefore the diameter of thread the dies will cut. The construction of the cutting-off head is shown in Fig. 1871, T representing the cutting tool which is operated by the hand wheel K. The carriage is fed or traversed by means of two pinions operated by the six-handled wheel shown at W, Fig. 1868; these two pinions engaging racks beneath the carriage, and near the inside edges of the bed, one of them being seen at the extreme right-hand end of Fig. 1868. [Illustration: Fig. 1870.] [Illustration: Fig. 1871.] [Illustration: Fig. 1872.] In Fig. 1872 is represented a machine for threading or tapping the fittings for steam and gas pipe. The tap is carried in the end of the vertical spindle, and the work may be held in the vice upon the work table, or if too large the table may be swung out of the way. The general design of the machine corresponds somewhat to that of a drilling machine. BROACHING PRESS.--Broaching consists in forcing cutters through keyways or apertures, to dress their sides to shape. In Fig. 1873 is represented a broaching press. Its driving gear which is within the box frame is so constructed that it may be started and stopped instantly, notwithstanding its heavy fly wheel. Figs. 1874 to 1877 represent the method of cutting out a keyway by broaching. [Illustration: Fig. 1873.] [Illustration: Fig. 1874.] In Fig. 1874 A represents the end of a connecting rod having three holes, B, C, and D, pierced through it, their diameters nearly equalling the total finished width of keyway required. The punch D´ is first forced through, thus making the three holes into one. [Illustration: Fig. 1875.] [Illustration: Fig. 1876.] [Illustration: Fig. 1877.] The [V]-shape of the end of the cutting punch D´ tends to steady it while in operation, forces the cut outwards into the next hole, preventing them from jambing, and causes the strain upon the punch to begin and end gradually; thus it prevents violent action during the ingress and egress of the cutting punch. This roughing out process dispenses with the use of the hammer and chisel, and saves much time, since it is done at one stroke of the press. The next part of the process is the introduction of a series of broaches such as shown in Fig. 1875, the principles involved being as follow: It is obvious that from the large amount of cutting edge possessed by a single tooth extending all around such a broach, it would be impracticable to take much of a cut at once; hence a succession of broaches is used, some of them performing duty on the sides only, others at the ends only, but the last and final broach is usually made to take a very fine cut all over. All these broaches are made slightly taper; that is to say, the breadth of the lower tooth at A in Fig. 1875 is made less than that at B, the amount allowed varying according to the dimensions and depth of the keyway. The smallest of the set of broaches is entered first and forced through until its end stands level with the upper face of the work. Each broach is provided with a conical teat at one end and a corresponding conical recess at the other, so that when the second broach is placed on top of the first, the teat fitting into the recess below it, will hold the two broaches central one to the other. The head of each broach is made somewhat conical or tapered, and sets in a corresponding recess in the driving head in the machine, which, therefore, holds the broaches parallel one to the other. A succession of these broaches is used, each requiring one stroke of the press to force it within the keyway, and another to force it out. The following is an example of broaching, relating to which, the dotted lines shown on the broaches, Fig. 1876, indicate the depths and shapes of the teeth. The small end of each broach corresponds to the large end of the one that preceded it, which is necessary in order to permit it to enter easily. Of the ten broaches used the first two operate to straighten the side walls of the hole, No. 3 being the first to operate upon the circular corners, which are not cut to the rectangle until No. 8 has passed through. But as the duty in cutting out the corners diminishes, the walls and ends of the hole are operated upon to finish them to size; thus broach No. 3 leaves the hole 1-1/8 or 1.125 inches wide, and 2.7501 inches long, which No. 4 increases to 1.1354 inches wide and 2.7605 inches long. This increase of width and depth, or breadth, as it may more properly be termed, continues up to the last or tenth cutter, which is parallel and of the same dimensions as the large end of cutter No. 9. Fig. 1877 gives two views of the No. 10 broach. Broaches require a very free lubrication in order to prevent them from tearing the walls of the hole, and to enable them to cut easily and smoothly; hence it is found highly advantageous after the teeth are cut to cut out grooves or passages lengthways of the broach, and extending nearly to the bottom of the teeth, which eases the cut as well as affords the required lubrication; but it is obvious that the finishing cutter must not have such oil ways. MODERN MACHINE-SHOP PRACTICE [Illustration] ILLUSTRATED MODERN MACHINE-SHOP PRACTICE [Illustration: _Vol. II MODERN MACHINE-SHOP PRACTICE FRONTISPIECE_ COMPOUND MARINE ENGINE.] MODERN MACHINE-SHOP PRACTICE BY JOSHUA ROSE, M.E. ILLUSTRATED WITH MORE THAN 3000 ENGRAVINGS VOLUME II. NEW YORK CHARLES SCRIBNER'S SONS 1888 COPYRIGHT, 1887, 1888. BY CHARLES SCRIBNER'S SONS. Press of J. J. Little & Co. Astor Place, New York. CONTENTS. VOLUME II. PAGE CHAPTER XXII. =MILLING MACHINERY AND MILLING TOOLS.= =The Milling Machine=; Advantages possessed by 1 The hand milling machine 1 Power milling machine 2 Universal milling machines 2, 3 The Brown and Sharpe Universal Milling Machine, general view of 4 The construction of the bearings and of the head 5 Sectional view of head 6 The dividing mechanism 6 The index plate 7 Table of index holes for gear cutting 7 The automatic feed motion 8, 9 Special index plate for gear cutting 9 The Brainard Milling Machine 9 The various attachments of 10 The rotary vise 10 Universal head and back centre 10 Universal head for gear cutting 11 The head for cutting spirals 12 The cam cutting attachment 12 The Lipe Universal Milling Machine 12 Sectional view of the Lipe machine 13 The feed motions of the Lipe machine 13 The index head of the Lipe machine 14 The adjustable centre rest 14 The Universal Milling Machine for heavy work 15 Construction of the driving gear and feed motion 15 Pratt and Whitney's double spindle milling machine 16 =Milling Cutters or Mills= 16 to 24 Cutters with spiral teeth 17 Table of sizes of Brown and Sharpe standard cutters 17 Table of standard sizes of Brainard cutters 17 Face cutters 17 Twin cutters and right and left hand cutters 18 Advantages and disadvantages of face cutters 18 Angular cutters 19 Right and left angular cutters 19 The Brown and Sharpe patent cutters 19 Shank cutters 19 The direction of the feed for shank cutters 20 Applications of shank cutters 21 Sizes of shank cutters 21 Fly cutters 21 Different methods of making fly cutters, and the advantages and defects of each method 21 Circular cutters, and holders for fly cutters 22 Matched cutters; methods of matching cutters 23 Gang or composite cutters; cutters with inserted teeth 24 =Cutter Arbors= 25 =Milling= 25 to 30 Comparison of the advantages of end milling, face milling, and twin milling 25 The length of feed in face milling 26 Cutting grooves in cylindrical work 27 Angular cutters for groove cutting 27 The crowding of grooving cutters and how to avoid it 27 The direction of the feed in cutting spiral grooves 27 Setting angular grooving cutters 28 Cutting right and left hand grooves and determining the direction of the feed for the same 29 Fluting twist drills 29 Finding the angle of the cutter in cutting spiral grooves 29 Producing different shaped grooves with the same cutter 29, 30 Holding work on the milling machine; milling taper work 30 =Chucks for Milling Machines= 31 =Vertical Milling Machine= 31 =Profiling Machine= 31, 32 =Grinding Machine=, for milling cutters 32 to 37 Fixture for grinding parallel cutters 32 Errors in grinding milling cutters 32 Grinding thin cutters 33 Grinding taper cutters 33 Fixture for grinding taper work 33 Fixture for taper cutters and for face cutters 34 The position of the emery wheel and clearance on the cutter 35 Grinding the teeth of spiral cutters 36 Positions of emery wheels in cutter grinding as affecting the strength of the cutting edges 36, 37 CHAPTER XXIII. =EMERY WHEELS AND GRINDING MACHINERY.= =Grinding Operations=; Classification of 38 The qualifications of emery wheels 38 Cements used in the manufacture of emery wheels 38 Grades of coarseness and fineness of emery wheels 38 Grades of wheels and the work they are suitable for 39 Speeds of emery wheels 39 Balancing emery wheels 39 =Emery Grinding Machines= 40 The Sellers drill grinding machine 41 The construction of the drill holding chuck 41 Varying the drill position to suit the diameter of the drill, and thus maintain equal conditions for all diameters of drills 41 Errors of construction in ordinary drill grinding machines 41 The construction whereby the Sellers machine maintains an equal degree of clearance from end to end of the cutting edge upon all sizes of drills 41, 42, 43, 44 The Sellers attachment for thinning the points of large twist drills 44 The front rake of twist drills 44 Emery grinder for true surfaces 45 For engine guide bars 45 For car axle boxes 45 Emery grinder with traversing emery wheel 46 For rough work 46 For planing machine knives or cutters 46 Emery wheel swing frame for dressing large castings, &c. 46 Emery belt grinding machine 47 Presenting emery wheels to the work, or the work to the wheels 47 Annular emery wheels 48 Recessed emery wheel 48 The wear of emery wheels 48 =Polishing Wheels= 49 to 51 The construction of 49 Lapping the leather on 49 Method of keeping them true 50 Charging with emery 50 The speed of 50 Polishing materials for 50 Brush wheels for polishing 50 Speed of brush wheels 50 Polishing materials for brush wheels for brass work 50 Solid leather wheels 51 Rag polishing wheels 51 Polishing materials for rag wheels 51 Polishing device for engravers' steel plates 51 =Grindstones= and Tool Grinding 51 The various kinds of 51 Suitable for wood working tools 52 Suitable for saws or iron plates 52 The speeds of 52 The changes of pulley diameter necessary as the diameter of the stone decreases in order to maintain a nearly uniform circumferential speed of grindstone 52 Arrangement of, for saw plates 52 Hacking 53 Device for truing 53 Automatic traversing device for 53 Considerations that determine the position in which the work should be applied to 53 =Oil-stones=, the various kinds of 54 Truing oil-stones 54 Removing the feather edge left by 54 Oil-stoning edge tools 54 CHAPTER XXIV. =GEAR CUTTING MACHINES.= =Gear Cutters=--The Brainard Automatic 55 Plan view of the mechanism 55 Method of operating the cutter slide 55 The arrangement of the positive feed shipping motion 55 Arrangement and construction of the dividing mechanism 55 The Brainard half automatic gear cutting machine 56 Gear cutting engine with vertical cutter spindle 56 Gear planing machine 56 Piat's French gear cutting machine 56 to 61 CHAPTER XXV. =VISE WORK.= =Definition of Vise Work= 62 =The Vise= 62 The height of vise jaws 62 The wood-worker's vise 62 The Stephens vise 62 Swivelling vises 62 The Prentiss vise 62 Leg vise with parallel motion 63 Various forms of vise clamps 64 =Hammers= 64 The effects of the speed of a hammer blow 65 Experiments by Robert Sabine on the duration of a blow 65 Machinists' hand hammers 66 Shapes of hammer eyes 66 The proper method of putting handles in 67 Paning of pening hammers 68 The plate straightener's and saw maker's hammers 69 The principles involved in straightening plates 69 The dog-head hammer 69 The effects of hammer blows upon plates 69 Saw straightening and saw hammering 70, 71 Machinist's sledge hammer 71 The file cutter's hammers 71 Riveter's hammer 71 The cooper's hammer 71 The mallet 72 Pening or paning 72 Applications of pening to straighten work or refit it 72 Riveting crank pins 73 =Chisels= 73 Forms of bar steel for chisels 73 The widths and thicknesses of the cutting ends of 74 Angles of the cutting edges of 74 Shapes of the cutting edges of 74 Chisel holders 74 Cape or cross-cut 74 Round nosed 75 The cow-mouthed 75 Curved or oil groove 76 The diamond point chisel 76 Applications of machinists' chisels 76 The carpenter's chisel 77 The angle of presentation of chisels 77 =Plane Blades= 77 The form of, necessary to produce a given shape of moulding 77 Finding the shape of knives, plane blades, or cutters necessary to produce given shapes upon the work 78 to 83 Scale for marking out the necessary shapes of moulding knives 83 Instruments for 84 =Files= 85 Shapes of file teeth 85 The cut of files 85 Sizes and kinds of flat files 86 Groubet files 87 Rasps, the kinds and cut of 88 The names of files 88, 89 Round, half-round, and three-square files 90 Knife files, cross files, reaper files, tumbler files 91 The selection of files 91 Putting handles on files 92 Instruction on holding files 92 Slim files 92 The warping of files 93 Using bent files 93 Cross filing 93 Draw filing 94 Cleaning files 94 Filing out round corners 95 Using round files 95 Files for soft metals 95 Resharpening files 95 The Sand Blast process 96 =Red Marking= for vise work 96 =Hack Saw= 97 =Screw Drivers= and their proper shape 97 =Scrapers= for true surfaces 97 Angles for the facets of scrapers 97 Various forms of scrapers 97 =Reamers= 98 The spacing of reamer teeth 98 Odd and even numbers of reamer teeth 98 Adjustable reamers 98 Taper reamers 99 Reamers for framing 99 Half-round reamers 99 Square reamers 99 CHAPTER XXVI. =VISE WORK= (Continued). =Examples in Vise Work= 100 to 113 The use of chisels 100 File cutting 100 Cutting key seats 101 Sinking feathers in shafts 101 Methods of securing feathers 102 Filing up a double eye or knuckle joint 103 Filing pins 103 Blocks for filing pins 104 Hand vise 104 Filing bolt heads and nuts 104, 105 Making outside calipers 105, 106 Fitting keys 107 Cutting keyways by hand 108 Cutting out keyways by drifts 109 Forms of drifts 109 Methods of using drifts 109 Templates 110 Making male and female templates 110 to 112 CHAPTER XXVII. =VISE WORK= (Continued). =Examples in Vise Work= 113 to 127 The various form of connecting rods 113 Solid ended connecting rods 113 Clip ended connecting rod 114 Strap ended connecting rod 115 Double gibbed connecting rod 115 Locomotive connecting rod 115 Bolted connecting rod straps 115 Marine engine connecting rod 116 Tapered connecting rod ends and their advantages 117 Stepped connecting rod straps and their advantages 117 Fitting up connecting rods 117, 119 Welding up stub ends of connecting rods 118 Aligning welded connecting rods 118 Fitting on connecting rod straps 119 Filing out connecting rod keyways 119 Fitting the keys and gibs 119 Fitting connecting rod brasses to their straps 120, 122 The joint faces of connecting rod straps 121 Disadvantages of joints left open to take up the wear 121 Obviating this disadvantage 121 Marking the lengths of connecting rods 122 Fitting up a fork end connecting rod 122 Aligning fork end connecting rods 123 Repairing connecting rods 124 Setting connecting rod brasses together 125 Lining up connecting rod brasses 126 Adjusting the lengths of connecting rods 126 Setting up the keys of connecting rods 126 Shapes of the crowns of brasses 127 Fitting up a link motion 127 Templates for filing the link slot 127 =Case-hardening= 128 to 133 Sheehan's case-hardening process 128 Preparing work for 129 Setting work after 129 Fitting brasses to pillow blocks or axle-boxes 130 Bedding brasses 132 The proper shape for the patterns of brasses 132 =Originating a True Plane= 133 Finding which of three surfaces is the nearest to a true plane 133 Methods of testing the surfaces 134 A new process of originating surface plates 134 The deflection of surface plates 134 =The Friction of Plane Surfaces= 135 =Oiling True Surfaces= 135 CHAPTER XXVIII. =ERECTING.= =Spirit-level= 136 =Plumb-level= 136 =Joints= 136 to 141 Filing or making joints 137 Ground joints 137 Scraped joints 137 Cylinder covered joints 137 Making a scraped joint with the studs in their places 138 Joints for rough surfaces 138 Gauze wire joints 138 Water joints 138 Joints to withstand great heat 138 Rubber joints 139 Boiler fitting joints 139 Easily removable joints 140 Rust or caulked joints; caulking tools 141 Thimble joints 141 Expansion joint 141 =Pipes, Cocks and Plugs= 141 to 145 Pipe cutters 141 Pipe vises 141 Pipe tongs 143 Erecting pipe work 144 Refitting leaky cocks and plugs 144 Grinding cocks and-plugs 145 =Boxes and Brasses= 145 to 149 Fitting brasses to their journals 145 Various forms of bearings and brasses or boxes 147 Locomotive axle boxes 148 Lead lined brasses 148 Open brasses 149 =Lubrication= 149 to 154 Examples of oil cavities and oil grooves for brasses 150 Qualities of lubricants 151 Testing lubricants 151 Best method of using thin oils 152 The influence of the atmosphere on oils 153 Longevity of lubricants 153 Testing oils for salts and acids 153 Swiss watchmakers' oil tests 153 The blotting paper oil test 154 =Friction and Wear= 154 Morin's experiments on 154 Order of the value of metals to resist wear 154 White metal or babbitt metal lined boxes 155 Methods of babbitting boxes 156 The pressure on journals 156 =Cranks= 156 Placing at right angles 156, 157 =Engine Cylinders= 158 to 161 Fitting 158 Setting 159 Reboring cylinders in their places 160 Scraping out cylinder ends 161 CHAPTER XXIX. =ERECTING ENGINES AND MACHINERY.= =Engine Guide Bars= 162 Setting 162 The spring of 162 Testing 163 Setting by stretched lines 163 =Heating and Knocking of Engines= 164 The ordinary causes of 164, 166 =Aligning New Engines= 166 to 171 Classification of the errors in engine alignment 166 Testing the alignment of the crank 167 Showing separately the causes of beating and pounding 168 Methods of discovery and determining the errors of alignment 169 Errors of alignment in crank pins 170 Methods of discovering errors of crank pin alignment 170 Remedying errors of crank pin alignment 171, 172 =Slide Valves= 173 to 175 Finding the dead centre of the crank 173 Taking up the lost motion when setting the valve 174 Measuring the valve lead 174 Finding the dead centre with a spirit level 174 =Setting Eccentrics= on crank shafts 175 Setting double eccentrics by lines 175 =Erecting the Framework= of machinery 176, 177 =Repairing and Patching= broken frames 178 =Erecting an Iron Planer= 179 Foundations for an iron planer 180 Fitting up and erecting a lathe 181 =Testing Lathes= 181 Instruments for testing lathes 182 Testing lathe carriages 183 =Erecting Line Shafting= 184 to 186 CHAPTER XXX. =LINE SHAFTING.= =Line Shafting= 187 to 190 Sizes of 187 Cold rolled shafting 187 Distance between bearings of line shafting 187 Tests of hot rolled and cold rolled shafting 188 Collars for shafting 189 Diameters of line shafting 189 The strength of line shafting 190 Speeds for shafting 190 =Counter Shafts= 191 =Friction Clutches= 192 =Shafting Hangers= 193 Various forms of 193 Open-sided 193 Wall hangers 194 =Pillow Blocks= for shafting 194 =Couplings= 194 to 199 For line shafts 194 With split sleeves 195 Errors in 196 Self-adjusting 196 Plate 196 Clamp 197, 198 For light shafting 199 Universal 199 CHAPTER XXXI. =PULLEYS.= =Classification= 200, 201 Wood pulleys 200 Solid and split pulleys 200 Expansion pulleys 200 Self-oiling pulleys 200 Crowned pulleys 201 =Fastening= pulleys to their shafts 201 =Balancing= pulleys 202 =The Transmitting Power= of pulleys 204 Size of pulleys for countershafts 205 =Calculating the Speeds= of pulleys 206 CHAPTER XXXII. =LEATHER BELTING.= =Hides= 207, 208 The parts of a hide used for belting 207 The thickness and stretch of the parts of a hide 207 Experiments on the strength of the parts of a hide 208 =Single and double= belts 208 =Grain Side of Leather= 208 Weakness of the 208 Why the grain side should go next to a pulley 208 =Belts= 209 to 217 The length of 209 Belt clamp 210 The sag of belts 210 Belt connection at an angle 211 Guide pulleys for belts 211 The tension and creep of belts 212 Methods of joining the ends of belts 213 Forms of belt lacings 214 Covers for belt lacings 215 Lap joints for belts 215 Joining thin belts 215 Bevelled joints for belts 215 Pegged belts 215 Belt hooks and belt screws 216 Angular or V-belts 217 The line of motion of belts 217 Changing or shipping belts 217 Automatic belt replacer 218 Pull of a belt 218 The Sellers experiments on transmission of power 218 to 225 Belt 5-1/2" wide by 7/32" thick 219 Belt 2-1/4" wide by 5/16" thick 219 Rawhide belt 4" by 9/32" 220 Double oak tanned belt 4" by 5/16" 220, 221 Oak tanned belt 2" by 3/16" 222 Coefficient of friction and velocity of slip 222 Torsional moment 223 Increase of tensions 224 CHAPTER XXXIII. =FORGING.= =Testing Iron= by bending it 226 Testing machines 227, 228 =Tools for Blacksmiths= 228 to 232 Forges 228, 229 Chisels, &c. 230 Anvils 230 Swages 230, 231 Spring swages 231 Swage blocks 232 =Swaging= 232, 233 =Examples in Welding= 233, 235 Iron 233, 234 Steel to iron 234 Best method of 234, 237 =Examples in Forging= 238 to 252 Device for bolt forging 238 Forging turn buckles 239 Methods of bending iron 240 Device for bending iron 240, 241 Forging steel forks 241 Forging under the hammer 242, 243 Forging rope sockets 243, 244 Forging wrought iron wheels for locomotives 244, 245 Forging rudder frames 245, 246 Welding scrap iron for large shafts 247 Construction of furnace for heating scrap 247 Forging crank shafts 248, 249 Forging large crank shafts 249, 252 Forging machines 252 to 263 Foot-power hammer or Oliver 252, 253 Standish's foot-power hammer 252, 253 Power hammers and steam hammers 252, 253 Bradley's cushioned hammer 252, 253 Corr's power hammer 254, 255 Kingsley's trip hammer 255 The drop hammer 255, 256 Steam hammers 257, 258 Double frame steam hammer 258 Double frame steam drop hammer 258 Double frame steam drop hammer for locomotive and car axles and truck bars 259 The Edgemore Iron Works' hydraulic forging press 260 Dies for forging eye bars 260 Nail forging machine 260 Rolls for forming knife blades 261 Machine for forging threads on rods 261, 262 Finishing machine for horseshoes 262, 263 Circular saw for cutting hot iron 263 CHAPTER XXXIV. =WOOD WORKING.= =Pattern Making= 264, 267 Choice and preservation of wood for 264 =Bending Timber= 265, 266 The bending block 265, 266 Steaming wood for bending 266, 267 =Wood Working Tools= 267 to 274 Planes for pattern making 267 Compass planes 268 Stanley's iron frame block plane 269 Stanley's bull-nose rabbet plane 269 Bailey's patent adjustable planes 269 The combination plane 269, 270 The beading bit 270, 271 Tool for cutting material into parallel slips 271 The chisel and chisel handles 271 Firmer and paring chisels and gouges 272 Rip saws 272, 273 Cross cut saw 273 Common gauges for marking off work 274 Mortise gauge 274 Cutting gauge 274 =Wood Joints= 274, 275 Mortise joint 274 Tenon joint 274 Dovetail joint 275 Mitre joint 275 Half check joint 275 =Examples of Pattern Making= 275 to 285 Patterns for piston gland 275 Construction of piston gland pattern 276, 277 Rapping small cast gears 277 Casting pillow block 277 Pattern for pillow block 277 Pulley pattern 278, 279 Building up segments for patterns 278, 279 Getting out arms for pulleys 280 Making pipe patterns 280, 281 Globe valve pattern 281, 282 Angle valve pattern 283, 284 Branch pipes 284 to 286 CHAPTER XXXV. =WOOD WORKING MACHINERY.= =Classification= 287 =Circular Saws= 287 to 305 Gauges for circular saws 287 Table of diameters 287 Thickness 287 Size of mandrel hole 287 Shingle saw 287, 288 Concave saw 287, 288 Stretching of circular saws by heat 288 The tension of circular saws 288 Causes of alteration of tension and method of discovering the same 288 Truth of circular saws 288 Various effects of circular saws heating 288 Truing circular saws 288 Sharpening the teeth of circular saws 289, 290 The gumming, gulleting or chamfering machine 290 Inserted teeth of saws 290 Chisel teeth saws 290, 291 Inserting teeth in circular saws 290, 291 Swing frame saws 290, 292 Fence for swing frame saws 293 Examples of work done on swing frame machine 293 Swing machine with fixed table 294 Double saw machine 294, 295 Gauges for sawing machine 294 Method of employing the mitre gauge 294 Cropping and gauging gauge 296 Bevel or mitre sawing machines 296, 298 Roll feed circular saw machine 298, 300 Segmental circular saws 300 Fastening saw segments to their disks 301 Gang edging machines 301 Rack feed saw bench 301 Construction of the feed motion 301 to 304 Fibrous packing for circular saw 305 =Tubular Saw Machine= 305 =Cross Cutting or Gaining Machine= 305, 306 =Scroll Sawing Machine= 306 Construction of various scroll sawing machines 306, 307 =Band Sawing Machine= 308 to 312 Various kinds of teeth for band saws 308, 309 Pitch of teeth for band saws 309 The adjustment of the saws of band saw machines 309, 310 Filing the teeth of band saw machines 309 Re-sawing band saw machine 309, 310 To regulate the tension of band saws 310, 311 Construction of band saw guides 311 Various band saw machines 311, 312 =Reciprocating Cross Cutting Saw= 312 Construction of 312 =Horizontal Saw Frame Machine= 312 to 315 Construction of the saw driving mechanism 314 Construction of the feed motion 315 Construction of the saw 315 =Planing Machines= 315 to 341 Buzz planer 315 Construction of the work table 316 Construction of the cutter head 316 Skew knives 316 Roll feed wood planing machine 317 The construction of the feed rolls 317 Adjustment of the feed rolls 317 Construction of the pressure bars 317 Adjustment of the roll pressure 318 Adjustment of the work table 318 The roll driving mechanism 319 The cutter head 320 Three feed roll wood planing machine 322, 323 Pony planer 323 Construction of the feed mechanism 324 Balancing cutter heads and knives 324, 326 Farrar planing machine 326, 327 Planing and matching machine 328 Construction of the feed rolls 329 Construction of the upper cylinder 329 Construction of the lower cylinder 329 Construction of a matcher hanger 329 The timber planer 330, 331 Construction of parts of the timber planer 331 How the timber planer operates 331, 332 Panel planing and trying up machine 332, 334 Moulding machine 334 Double head panel raiser and double sticker 335, 336 Moulding cutters 336, 337 Cutter heads and circular cutters 337 The Shimer head 337 Head for producing match board grooves 337, 338 Jointing machine 338 Knives of jointing machine 338 Speed of cutter head or disc 338 Stroke jointers 338, 339 Machine for cutting mitre joints 339 Moulding or friezing machines 339 Important points of friezing machines 339 Construction of moulding and friezing machines 340, 341 Shape of cutters for moulding and friezing machine 341 Rotary cutters for all kinds of work, and for edge moulding and friezing machine 341 to 343 =Boring Machines= 342 Fences for 342 Augers or bits for 342 Boring machines for heavy work 343 =Mortising Machines= 344 Tools used in mortising machines 344 Motion of chisel bar and auger 344 Construction of bed 344 Adjustment of carriage 344 =Tenoning Machines= 344, 345 Construction of revolving heads 344, 345 Tenoning machine for heavy work 346 =Sand-papering Machines= 346, 349 Construction of sand-papering machines 347, 348 Movements of sand-papering machine 347 Cylinder sand-papering machines 348 Self-feeding sand-papering machine 348 Sizes of machines 348 Construction of feed rolls 348 Finishing and roughing cylinders 348 Brush attachment 348 Double wheel sanding machines 348, 349 CHAPTER XXXVI. =STEAM BOILERS.= =Strength of Boiler Shells= 350 =Strength of Boiler Plate= 351 Explanation of pressure in steam boilers 351 =Boiler Joints or Seams= 351 to 357 Forms of rivet joints 351 Single riveted lap joint 351 Double riveted lap joint 352 Single riveted butt joint with straps 352 Double riveted butt joint with straps zigzag riveted 352 Triple riveted lap joint zigzag riveted 352 Lap joint with covering plate 352 Double riveted lap joint chain riveted 353 Double riveted butt joints with double straps 353 Treble riveted butt joint with double straps 353, 354 Rules for spacing the rivets in boiler seams 353 Rule for finding diagonal pitch of riveted joints 353 High percentage joint 353 Rivets unevenly pitched 354 Rule for calculating the percentage strength of joint with unevenly pitched rivets 354 Strength of circumferential seams of stationary engine boilers 354, 355 Table of additions to be made to the factor of safety for various constructions of riveted joints 355 Table of diameter of rivets for single riveted lap joints 356 Rule for making rivet and plate area equal 336 Table of rivet diameter and pitch for single riveted lap joints 356 Rule for finding the pitch for double, diagonal riveted lap joints 356 Example in the use of rule for diagonal pitch of rivets 356 Rule for finding distance V where the diagonal pitch has been found 357 Comparing chain with zigzag riveted joints 357 =Interior of Boilers= 358 to 364 The internally fired flue boiler 358, 359 Boiler with Field tubes 350 Vertical water tube boiler 360 Construction of field tubes 360 Arrangement of field tubes 360 Vertical boilers with external uptakes 361 Horizontal return tubular boiler 361, 362 Construction of horizontal return tubular boiler 362, 363 Various arrangements of tubes in boilers 364 =Setting Boilers= 364, 366 Ground plan of brickwork 365 Setting full arch front boilers 365 Table of measurements for setting tubular stationary boilers with full arch front 366 Table of measurements for setting stationary boilers with half arch front 366 =The Evaporative Efficiencies of Boilers= 366 to 368 Table of the pressure, temperature and volume of steam 367 Calculating the evaporation of a boiler 368 =Care and Management of Boilers= 368 to 371 Examining safety valves 368 Water gauge glass 368 Gauge cocks 368 Lighting boiler fires 368 The thickness of the fire for boilers 368 Managing the fire 368 Shaking grate bars 369 The slice bar 369 The hoe 369 The poker 369 The clinker hook 369 The rake 369 The quantity of water in a boiler 369 Leaving the fire for the night 369 Leaving the safety valve for the night 369 Regulating the boiler feed 369 Dirty feed water 370 Defective feed pumps 370 Scale in boilers 370 Preventing the formation of scale 370 Feed water heaters 370 Low water in boilers 370 Priming or foaming 370 The known causes of priming 370 Wastefulness of priming 370 The detection of priming 370 To prevent or stop priming 370 Surface blow off cock or mechanical boiler cleaner 370 Blowing off a boiler 370 Blowing down a boiler 370 Washing out a boiler 371 Cleaning a boiler 371 Scaling a boiler 371 Examining a boiler 371 CHAPTER XXXVII. =STEAM ENGINES.= =Engine Cylinders= 372 to 374 The bores of 372 Sizes of 372 Wear of 372 Counterbore of 372 Clearance in 372 Lubrication of 373 The cocks of 373 Relief valves of 373 The steam ports of 373 Lagging 374 Jacketed cylinders 374 =Engine Pistons= 374 The speeds of 374 With releasing gears 374 With positive valve gears 374 The rings of 374 The follower 374 Testing the rings of 374 =Engine Piston Rods= 375 Methods of securing 375 Packing 375 Glands for 375 =Engine Cross Heads= 375 =Engine Guide Bars= 375 =Engine Connecting Rods= 375 Connecting rod keys 375 Angularity of 375 The lengths of 375 =Valves= 376 to 378 The D-valve 376 The point of cut off 376 Period of expansion of the steam 376 Point of release of the steam 376 Point of compression of the steam 376 Lead of 376 Point of admission of the steam 376 The lip 376 Exhaust lap 376 Steam lap 376 Tracing the action of 376 Double ported valves 377 The Allen valve 377 Webb's patent valve 377 Balanced valves 377 Circular valves 377 Piston valves 378 Separate cut off valves 378 Meyer's cut off valves 378 Gonzenback's cut off valve 378 =Eccentrics= 378 Shifting eccentrics 378 The action of 378 The angular advance of 378 =Designing Slide Valves= 380 =Valve Motions= 381 Diagram for designing 381 =Link Motion= 383 In full gear forward 383 In full gear backward 383 The action of 383 Setting the valves 383 =Governors= 384 Fly ball or throttling 384 Isochronal 384 Dancing 384 Speed of 384 Spring adjustment of 384 Sawyer's valve for 384 Speeder for 384 =Starting a Slide Valve Engine= 384 Crank position in 384 =Examination of an Engine= 385, 387 Adjusting connecting rod brasses 385 Adjusting main bearing 386 Taking a lead 386 Squaring a valve 386 Heating, to avoid 386 Setting a valve 386 Leaky throttle valves 386 Freezing an engine, prevention of 386, 387 =Pumps= 387, 388 Lift and force 387 Plunger 387 Rotary 387 Single-acting 387 Double-acting 387 Displacement of 387 Principles of action of 387, 388 Speed of 388 Capacity of 388 Air chamber of 388 Belt 388 CHAPTER XXXVIII. =THE LOCOMOTIVE.= =Modern Freight Locomotive= 389, 390 General construction 389 Course of steam from boiler to smoke stack 389 Boiler feed 389 Position of parts for starting 389 Steam supply to injectors 389 Oil supply to slide valve and cylinder 389 Control of safety valve 389 Pop valve 389 Automatic air brake 390 Draught of fire 390 Sand valves 390 =American Passenger Locomotive= 390 to 393 General construction 390 Steam reversing gear 390, 391 Link motion in full gear forward 391 In mid gear 392 In full gear backward 392 Reversing gear 392 Changing gear of link motion 393 Running forward 393 Running backward 393 =Special Operations= 394 Setting the slide valves 394 Getting the length of eccentric rods 394 Setting the lead 394 Backward eccentric 394 Marking sector notches 394 Setting Allen valves 395 =Special Parts= 395 to 400 The injector 395 to 397 Westinghouse automatic air brake 398 to 400 =Locomotive Running= 400 to 404 General discussion 400 Getting the engine ready 400 Laying the fire 400 Banking the fire 401 Starting up a banked fire 401 Examining the engine 401 Oiling the engine 401 Starting the engine 401 Saving fuel 402 Methods of firing 402 Examples of trips 402 =Accidents on the Road= 402 Knocking out cylinder heads 402 Heating of piston rods 403 Throwing off a wheel tire 403 Throwing off a driving wheel 403 Breaking a spring 403 Bursted tubes 403 Slipping eccentrics 403 Hot axle boxes 403 Breaking a lifting link 403 Breaking the saddle pin 403 Adjusting the wedges of the axle boxes 404 CHAPTER XXXIX. =THE MECHANICAL POWERS.= =Power= 405 =Lever= 405 The principles of 405 Wheels and pulleys considered as levers 405, 406 Power transmitted by gear wheels and pulleys combined 407 =Horse Power= 407 Calculating the horse power of an engine 407 Testing the horse power of an engine 408 =Safety Valve Calculations= 409 =Heat= 410 Latent heat 410 =Water= 410 =Steam= 410 Saturated 410 Superheated 410 Expansion of 411 Absolute pressure of 411 Weight of 411 Volume and pressure of 411 =Heat= 411 Conversion of heat into work 411 Joule's equivalent 411 Mechanical equivalent of heat 411 Mariotte's law 411 Radiation of heat 412 Conduction of heat 412 Convection of heat 412 CHAPTER XL. =THE INDICATOR.= =Computations from Indicator Diagrams= 413 =Indicators= 413 Description of 413 Thompson indicator 413 Tabor indicator 413 Diagrams 414 Admission of steam to indicator 414 Expansion line or curve 414 Exhaust line 414 Back pressure line 414 Atmospheric line 414 Theoretical diagram 414 Compression line or curve 415 Condensing engine diagram 415 Vacuum line of indicator diagram 415 (Barometer, construction of) 415 (Barometer, graduation of) 416 Indicator springs 416 Tables of springs for indicators 416 Attachment of indicators to an engine 416, 417 Pantagraph motions 417 Expansion curve, testing of 417, 418 Theoretical expansion curve 417, 418 Calculations from diagrams 418 to 421 Horse power 418, 419 Area 419 Rule for calculating horse power 419 Mean effective pressure 420 Steam used in engines 420 Water consumption 420, 421 Defective diagrams of engines 421 Excessive lead of engines 421 Theoretical compression curve of engines 422 CHAPTER XLI. =AUTOMATIC CUT-OFF ENGINES.= =Definition= 423 =Corliss Automatic Cut-off Engine= 423, 424 Valve gear of 424, 425 Governor of 425, 426 Admission of steam into 426 Lap of valve of 426, 427 =High Speed Automatic Engines= 427, 428 Speed of 427 Wheel governors for 427, 428 =Straight Line Automatic Engine= 428, 429 Important details of 429, 430 =Steam Fire Engine= 430, 431 Boilers of 430, 433 Pumps 431, 432 Heaters for 432, 433 CHAPTER XLII. =MARINE ENGINES.= =Various Kinds of Marine Engines= 434 to 451 High pressure engines 434 Compound condensing engines 434, 435 Triple expansion engines 436 Donkey engines 442 Trunk engines 446 Oscillating engines 446 Geared engine 446 Compound engine of the steamship _Poplar_ 447, 450, 451 =Arrangement of Marine Engine Pumps= 436 =Boilers of Marine Engines, Arrangement of= 436, 437 =Various Parts of Marine Engines, etc.= 438 to 449 Valve for intermediate cylinder of triple expansion engines 438 Link motions for triple expansion engines 438 Auxiliary or by-pass valve 438, 439 Oiling apparatus 439, 440 Surface condensers 440 Circulating pumps 440 The snifting valve 440 The blow-through valve 440 Air pumps 441 The air chamber 441 Feed escape or feed relief valve 441 Bilge injections for marine engines 441, 442 Surface condensing, advantages of 442 Valves of the surface condensing engine 442 Case hardening 442 Link motion for marine engines 443 The separate expansion valve 443 Friction of slide valves 443 Double beat valves 443 The siphon 443 Steam lubricators 444 Marine engine valves that are worked by hand 444 Vacuum gauge 444 Condenser, to find the total pressure in the 444 Paddle wheels 444, 445 Screw propeller 445 The thrust bearing 445 Marine engine, the principal parts of 445 Lagging marine engines 446 Propeller cylinders 446 Fuel required 446 Freezing of pipes 446 Failure of engine to start, causes of 446, 447 Defective vacuum, causes of 447 Heating, causes of 447 Construction of a triple expansion engine 447 to 449 CHAPTER XLIII. =MARINE BOILERS.= =Plates for Marine Boilers= 452 Iron 452 Steel 452 Strength of 452 =Boiler Stays= 452 Methods of securing 452 =Boiler Tubes= 452 Methods of securing 452 Causes of leaks 452 Repairing leaks 452 =The Up-take= 453 =The Receiver= 453 =The Fittings and their Uses= 453, 454 Valves 453, 454 Gauges 453, 454 Cocks 454 =Important Features and Facts= 454, 455 Boiler scale 454 The salinometer 454 Priming, the prevention of 454 Supplemental parts 454, 455 The superheater 454 The draught 455 Wasting of plates 455 Fuel, the quantity of 455 =To Relieve the Boiler in Case of Accident= 455 =Steel Marine Boiler= 456 =The "Martin" Boiler= 456 =Testing and Examining Boilers= 456 to 459 Hydraulic tests 456 Related to stays 456, 457 On new and old boilers 456, 457 Internal examinations 458 Preparation for 458 Safety valves 458 Bottom of the boiler 458 Bottom and sides of the furnace 458 Boxes and stays 458 Use of chipping hammer 458 Pit holes in the bottom of a furnace 458 Drilling through the plates 458 Flanges of furnaces 458 Deposits on the necks of stays 458 Man-hole door 458 Superheater 459 Proportions for grate surface 459 Outside examination 458 Cement beds for boilers 458 Proportions for circular tubular boilers 459 CHAPTER XLIV. =HARDENING AND TEMPERING.= =Purposes= 460 To resist wear 460 To increase elasticity 460 To provide a cutting edge 460 =Manufacturer's Temper= 460 =Blacksmith's Temper= 460 =Color Tempering= 460 =Practical Processes= 461 to 464 The muffle 461 Warping 461 Rapidity of reduction of temper 461 Brown and Sharpe's practice 461 Waltham Watch Co.'s practice 461 Pratt and Whitney Co.'s practice 461 Morse Twist Drill Co.'s practice 461 Outside hardening 462 Heating in fluxes 462 Monitor Sewing Machine Co.'s practice 462 Hardening saws 462 Drawing the temper 462 1. Lying in an open furnace 462 2. Stretched in a frame 462 3. Between dies 462 Stiffening saws 463 Tomlinson Carriage Spring Co.'s practice 463 Columbia Car Spring Co.'s practice 463 New Haven Clock Co.'s practice 464 APPENDIX. =Part I.--Test Questions for Engineers= 467 =Part II.--Dictionary of Workshop Terms= 473 FULL-PAGE PLATES. VOLUME II. _Facing_ _Frontispiece._ COMPOUND MARINE ENGINE. TITLE PAGE PLATE I. EXAMPLE OF MILLING MACHINE. 10 " II. EXAMPLES OF MILLING MACHINES. 12 " III. EXAMPLES OF MILLING MACHINES. 16 " IV. EMERY GRINDING MACHINERY. 45 " V. GRINDSTONE GRINDING. 54 " VI. FULL AUTOMATIC GEAR CUTTER. 55 " VII. GEAR CUTTING MACHINES. 56 " VIII. THE HAMMER AND ITS USES. 71 " IX. SCRAPERS AND SCRAPING. 97 " X. OIL-TESTING MACHINES. 153 " XI. TESTING PLANER BEDS AND TABLES. 180 " XII. EXAMPLES OF PULLEYS. 200 " XIII. THE ACTION OF SAW TEETH. 273 " XIV. EXAMPLE IN PATTERN WORK. 276 " XV. EXAMPLES IN STEAM HAMMER WORK. 232 " XVI. EXAMPLES IN HAND FORGING. 239 " XVII. FORGING UNDER THE HAMMER. 249 " XIX. DIMENSION SAWING MACHINE. 292 " XIX. RACK-FEED SAW BENCH. 302 " XX. PLANTATION SAW MILL. 305 " XXI. GAINING OR GROOVING MACHINE. 306 " XXII. BAND SAW WITH ADJUSTABLE FRAME. 311 " XXIII. BAND SAW MILL. 311 " XXIV. LOG CROSS-CUTTING MACHINE. 312 " XXV. HORIZONTAL SAW FRAME. 314 " XXVI. TRYING-UP MACHINE. 333 " XXVII. SANDING MACHINES. 348 " XXVIII. BOILER FOR STATIONARY ENGINES. 360 " XXIX. AMERICAN FREIGHT LOCOMOTIVE. 388 " XXX. AMERICAN PASSENGER LOCOMOTIVE. 390 " XXXI. LOCOMOTIVE LINK MOTION. 392 " XXXII. INJECTOR AS APPLIED TO A LOCOMOTIVE. 395 " XXXIII. LOCOMOTIVE AIR BRAKES. 396 " XXXIV. THE CORLISS VALVE GEAR. 425 " XXXV. STEAM FIRE ENGINE. 430 " XXXVI. COMPOUND MARINE ENGINE. 436 " XXXVII. TRIPLE EXPANSION MARINE ENGINE. 440 MODERN MACHINE SHOP PRACTICE. CHAPTER XXII.--MILLING MACHINERY AND MILLING TOOLS. THE MILLING MACHINE.--The advantages of the milling machine lie first in its capacity to produce work as true and uniform as the wear of cutting edges will permit (which is of especial value in work having other than one continuous plane surface); second, in the number of cutting edges its tools will utilize in one tool or cutter; and third, in its adaptability to a very wide range of work, and in the fact that when the work and the cutters are once set the operator may turn out the best quality of work without requiring to be a skilled machinist. The extended use of the milling machine, which is an especial feature of modern machine shop practice, is due, in a very large degree, to the solid emery wheel, which provides a simple method of sharpening the cutters without requiring them to be annealed and rehardened, it being found that annealing and rehardening reduces the cutting qualifications of the steel, and also impairs the truth of the cutting edges by reason of the warping or distortion that accompanies the hardening process. Rotary cutters are somewhat costly to make, but this is more than compensated for in the uniformity of their action, since in the case of the cutter the expense is merely that involved in forming the cutting edges with exactitude to shape; once shaped the cutter will produce a great quantity of work uniform in shape, whereas in the absence of such cutters each piece of work would require, to bring it to precise form, as much precision and skill as is required in shaping the cutter. If a piece of work is shaped in a planing machine, the different steps, curves, or members must be cut or acted upon by the tool separately, and the dimensions must be measured individually, giving increased liability to error of measurement, and requiring a fine adjustment of the cutting tool for each step or member. Furthermore, neither a planing machine or any other machine tool can have in simultaneous cutting operation so great a length of cutting edge as is possible with a rotary cutter. Again, in the planing machine each cut requires to be set individually, and cannot be so accurately gauged for its depth, whereas with a rotary cutter an error in this respect is impossible, because the diameters of the various steps on the cutter determine the depth of the respective cuts or steps in the work. In a milling machine the cut is carried continuously from its commencement to its end, whereas in a shaping or planing machine the tool does not usually cut during the back or return stroke. In either of these machines, therefore, the operator's skill is required as much in measuring the work, setting the tools feeds, &c., as in shaping the tools, whereas in the milling machine all the skill required lies in the chucking and adjustment of the work to the cutter, rather than in operating the machine, which may therefore be operated by comparatively unskilled labor. The multiplicity of cutting edges on a rotary cutter so increases its durability, and the intervals at which it must be sharpened are so prolonged, that, with the aid of the present improved cutter grinding machines, one tool maker can make and keep in order the cutters for many machines. The speed at which milling cutters are run varies very widely in the practice in different workshops. Thus upon cast iron, cutting speeds of 15 circumferential feet per minute will be employed upon the same class of work that in another shop would be done at a cutting speed of as high as fifty feet per minute. With the quick speeds, however, lighter feeds are employed. As the teeth of milling cutters are in cutting action throughout but a small portion of a revolution, they have ample time to cool, and may be freely supplied with oil, which enables them to be used at a higher rate of cutting speed than would otherwise be the case. Yet another element of importance in this connection is that when the cut is once started on a plain cutter, the cutting edges do not meet the surface skin of the metal, this skin always being hard and destructive to the cutting edges. [Illustration: Fig. 1878.] The simplest form in which the milling machine appears is termed the hand milling machine, and an example of this is shown in Fig. 1878. This machine consists of a head carrying a live spindle which drives the cutting tools, which latter are called cutters or mills. The front of the head is provided with a vertical slideway for the knee or bracket that carries an upper compound slide upon which the work-holding devices or chucks are held. The work is fed to the revolving cutter by the two levers shown, the end one of which is for the vertical and the other for the horizontal motion, which is in a direction at a right angle to the live spindle axis. In other forms of the hand milling machine the live spindle is capable of end motion by a lever. [Illustration: Fig. 1878_a_.] In Fig. 1878_a_ is shown Messrs. Brown and Sharpe's _plain_ milling machine, or in other words a milling machine having but one feed motion, and therefore suitable for such work only as may be performed by feeding the work in a straight line under the cutter, the line of feed motion being at a right angle to the axis of the cutter spindle. Machines of this class are capable of taking heavy cuts because the construction admits of great rigidity of the parts, there being but one slideway, and therefore but one place in the machine in which the rigidity is impaired by the necessity for a sliding surface. The construction of this machine is as follows: The head A which carries the cutter spindle is pivoted at C to a stiff and solid projection on the frame F, and means are provided to solidly clamp the two together. A bracket B supports the outer end of the head; at its upper end B is split so that by means of a bolt it may firmly clamp the cylindrical end of A, which carries the dead centre piece D. The two lower ends of B are bolted to the frame F. The work table T is gibbed to slideways in F, and is provided with suitable automatic feed and stop motion, and of course with a hand feed also. To adjust the height of the cutter, the lower ends of B are released from F and the head A is swung on its centre C. It is obvious that a machine of this class is suitable for cases where a large quantity of work of one kind is to be done and frequent changes of the adjustments are not required, and that for such work the solidity of the construction and the convenience of having all the handles employed in operating the machine accessible from one position are desirable elements obtained by a very simple construction. Fig. 1879 represents Pratt & Whitney's _power_ milling machine. The cone and live spindle are here carried in boxes carried in vertical slideways in the headstock, so as to be adjustable in height from the work table, and is provided with a footstock for supporting the outer end of the live spindle, which is necessary in all heavy milling. The carriage is adjustable along the bed, being operated by a screw whose operating hand wheel is shown at the left-hand end of the bed. The automatic feed is obtained as follows: The large gear on the right of the main driving cone operates a pinion driving a small four-step cone connected by belt to the cone below, which, through the medium of a pair of spur-gears, drives the feed rod, on which is seen a long worm engaging a worm-wheel which drives the feed screw. A suitable stop motion is provided. What is termed a universal milling machine is one possessing the capacity to cut spiral grooves on either taper or parallel work, and is capable of cutting the teeth of spur and bevel-gears or similar work other than that which can be held in an ordinary vice. These features may be given to a machine by devices forming virtually an integral part of the machine, or by providing the machine with separate devices which are attachable to the work table. In Fig. 1880 is represented a small size universal milling machine, in which A is the frame that affords journal bearing to the live spindle, in the coned mouth _a_ of which the mandrel carrying the rotary cutter is fitted, means being afforded for taking up the wear of the live spindle journal and bearings. B is the cone pulley for driving _a_. Upon the front face of A is a vertical slide upon which may be traversed the knee or table C, which by being raised, regulates the depth to which the cutters enter the work. To operate C the vertical screw _b_ is provided, it being operated (by bevel-gears) from a horizontal shaft whose handle end is shown at _c_. [Illustration: Fig. 1879.] [Illustration: Fig. 1880.] The nut for elevating screw _b_ is formed by a projecting lug from or on the main frame A. To enable C to be raised to a definite height so that the cutters shall enter successive pieces of work to an equal depth, a stop motion is provided in the rod _d_, which passes through a plain hole in the lug on A that forms a nut for _b_. Rod _d_ is threaded and is provided with a nut and chuck nut whose location on the length of the rod determines the height to which C can be raised, which ceases when the faces of the nuts meet the face of the projecting lug. The upper surface of C is provided with a slide on which is a slider D, which, by means of a feed screw whose handle end is shown at _e_, may be traversed in a line parallel to the axial line of the live spindle or arbor, as it is more often termed, this motion being employed to set the width of the work in the necessary position with relation to the rotary cutters. To D is attached E, which is pivoted at its centre so as to be capable of swinging horizontally, means being provided to fasten it to D in its adjusted position. This is necessary to enable the line of traverse of the work to be at other than a right angle to the axial line of the cutter spindle when such is desired, as in the case of cutting spirals; E serves as a guide to the carriage F, the latter being operated endwise by means of a screw whose handle is shown at _e´´_, the nut being attached to E, handle _e´´_ being to traverse E by hand. To feed F automatically gear-wheel _f_ is attached to the other end of the same screw, this automatic feed being actuated as follows:-- At the rear end of the live spindle is a three-stepped cone pulley attached by belt to cone pulley G, which connects by rod to and drives gear _f_. The construction of the rod is so designed as to transmit the rotary motion from G to F without requiring any adjustment of parts when C is raised or lowered or _f_ traversed back or forth, which is accomplished as follows:-- At _g_ _g_ are two universal joints attached respectively to G and F, and to two shafts which are telescoped one within the other. The inner rod is splined to receive a feather in the outer. The rotary motion is communicated from G to the universal joint, through that joint to the outer or enveloping shaft which drives the inner shaft, the latter driving a universal joint which drives _f_, the inner shaft passing freely within the outer or sliding out from it (while the rotary motion is continuing) to suit the varying distance from and position of _f_ with relation to G. This automatic feed motion may be adjusted to cease at any point in the traverse of E by a stop and lever provided for the purpose, so that if an attendant operates more than one machine, or if the feed require to be carried a definite distance, it will stop automatically when that point has been reached. The carriage F may carry various chucks or attachments to suit the nature of the work. As shown in the cut it carries a tailblock I and head J, both fitting into a way provided in F so that they will be in line one with the other at whatever part in the length of F they may be set or fixed. Both I and J carry centres between which the work may be held, as in the case of lathe work. Part _j_ is pivoted to J so that it may be set at an angle if required, thus setting the centre, which fits in the hole at _h_, above the level of that in I, as may be necessary in milling taper work, the raising of _j_ answering to the setting over of the tailstock of a lathe for taper turning. [Illustration: Fig. 1881.] To enable the accurate milling of a polygon, the spindle _h_ may be rotated through any given portion of a circle by means of the index wheel at _i_, it being obvious that if a piece of work be traversed beneath the cutter, and _h_ be rotated a certain portion of a circle after each traverse, the work will be cut to a polygon having a number of sides answering to the portion of a circle through which _h_ is rotated after each traverse. Means are also provided to rotate _h_ while F is traversing beneath the cutter; hence when these two feed motions act simultaneously the path of the work beneath the cutter is a spiral, and the action of the cutter in the work is therefore spiral; hence spiral grooves may be cut or spiral projections left on the work, as may be determined by the shape of the cutters. K is a chuck that may be connected to _h_ to drive the work, and H a work-holding vice, that may be used instead upon F in place of heads I J. The countershaft shown at the foot of the machine has two loose pulleys and a tight one between them, this being necessary because, in cutting spiral work, the work must rotate while on the back traverse as well as on the forward one, hence a crossed as well as an open belt is necessary. Fig. 1881 represents a large Brown & Sharp universal milling machine, in which the cone spindle is provided with back gear, and a supporting arm is also provided for the outer end of the cutter arbor. The feed motions for this machine correspond to those already described for the smaller one, Fig. 1880, the construction of the important parts being shown in the following figures. [Illustration: Fig. 1882.] [Illustration: Fig. 1883.] The construction of the bearings for the cutter driving spindle of the machine is as in Figs. 1882 and 1883. A is the spindle having a double cone to fit corresponding cones in the sleeve B, the fit of one to the other being adjusted by means of the nut C, which is threaded upon A. The mouth of A is coned to receive the arbors or mandrels for driving the mills or cutters. At the back bearing, Fig. 1883, the journal A´, and bore of the sleeve B´, is parallel, this sleeve being split at the top so that when it is (by means of nut D) drawn within the head E its coned exterior will cause it to close to a proper fit upon A´, by which means the wear of the parts may be taken up as they become perceptible. [Illustration: Fig. 1884.] [Illustration: Fig. 1885.] The head J, Fig. 1880, is used (in connection with the foot block I) to suspend or hold work by or between centres, its centre fitting into the spindle at _h_, which is capable of being revolved continuously (to enable the cutting of spirals), by means of change gears, and intermittently through a given part of a circle by means of the index wheel _i_. The block _j_ carrying the spindle is also capable of elevation for conical or taper work, two examples of such uses being shown in Figs. 1884 and 1885, in which C is the cutter and W the work. [Illustration: Fig. 1886.] [Illustration: Fig. 1887.] Fig. 1886 is a sectional view in a vertical plane through the centre of the head, and showing the construction of the spindle and the means of elevating the block _j_; _h_ is the spindle having journal bearing in _j_, and secured from end motion by the cone at _a_ and the nut _b_; its bore is coned at the front end to receive the arbor C carrying the centre D, upon which is the piece E for driving the work dog, which is secured within E by the set-screw _f_. Fast upon spindle _h_ is a worm-wheel F made in two halves, which are secured together by the screws _g_. At G is the worm-wheel (for driving F) fast upon the shaft H´. It is obvious that the block _j_ may be raised at its centre end upon H as a centre of motion, the worm F simply moving around upon G. At V is a bolt to lock _j_ to J, and thus secure it in its adjusted position. W W are lugs or blocks fitting into the slot in the work table, and serving to secure the head, being in line with the foot block (shown at 1 in Fig. 1880). A sleeve Z is used to cover the thread and protect it when a chuck is not used. [Illustration: Fig. 1888.] [Illustration: Fig. 1888_a_.] Fig. 1887 is an end view partly in section to show the construction of the worm shaft and the index plate. H is a sleeve upon which _j_ pivots, and H´ the worm shaft, which may be revolved by hand by the lever L, or automatically by means of the bevel-gear K, which connects with the train of change gears; these change gears being thrown out of operation when gear K (and therefore _h_) is not required to revolve automatically nor continuously. L is an arm for carrying the index pin _l_ for the index plate _i_. The pin _l_ is adjustable for radius from the centre of H (so as to come opposite to the necessary circle of holes on the plate _i_), the arm L being slotted to permit of this adjustment, and being secured in its adjusted position by the nut on the end of H´. Pin _l_ is pushed into the index holes by means of the spiral spring coiled around _l_ at _m_, which permits _l_ to be withdrawn from _i_ under an end pressure, but pushes it into _i_ when that pressure is released. To indicate the amount of rotation of _i_, without counting the number of holes, a sector N N´ is employed, it having two arms adjustable for their widths apart so as to embrace any given number of holes on the required circle. At R´ is a pin which is pulled forward and into holes provided in the plate _i_ to prevent its turning when using the lever L. N and N´ are held to the face of _i_ by the friction of the spring Q. A face view of index plate _i_ is shown in Fig. 1888, the lever L, Fig. 1887, being removed to expose N and N´. The surface of the plate is provided with rings of holes marked respectively 20, 19, 18, &c., the holes in each ring or circle being equidistantly spaced. The sector arms N and N´ may be opened apart or closed together so as to embrace any required number of holes in either of the circles. As shown in the cut they embrace one quarter of the circle of 20, there being five divisions between the holes S and _t_. The screw W secures them in their adjustment apart. Suppose that pin _l_ (Fig. 1887), is in S, and arm N´ is moved up against it, the arm N leaves _t_ open, and indicates that _t_ is the next hole for pin _l_, which is withdrawn from S, and lever L (Fig. 1887) is moved around until the pin will enter _t_, and the sector is then moved into the position shown in Fig. 1888A, indicating that hole _u_ is the next one for the pin. This obviates the necessity of counting the holes, and prevents liability to error in the counting. Three of these index plates are provided, each having different numbers of holes in the circles, and in the following tables are given those specially prepared for use in cutting the teeth of gear-wheels: ------+-------+------------++------+-------+------------ No. of| Index |No. of turns||No. of| Index |No. of turns teeth.|circle.| of index. ||teeth.|circle.| of index. ------+-------+------------++------+-------+------------ 2 | ANY | 20 || 35 | 49 | 1-7/49 3 | 39 | 13-13/39 || 36 | 27 | 1-3/27 4 | ANY | 10 || 37 | 37 | 1-3/37 5 | " | 8 || 38 | 19 | 1-1/19 6 | 39 | 6-26/39 || 39 | 39 | 1-1/39 7 | 49 | 5-35/49 || 40 | ANY | 1 8 | ANY | 5 || 41 | 41 | 40/41 9 | 27 | 4-12/27 || 42 | 21 | 20/21 10 | ANY | 4 || 43 | 43 | 40/43 11 | 33 | 3-21/33 || 44 | 33 | 30/33 12 | 39 | 3-13/39 || 45 | 27 | 24/27 13 | 39 | 3-3/39 || 46 | 23 | 20/23 14 | 49 | 2-42/49 || 47 | 47 | 04/47 15 | 39 | 2-26/39 || 48 | 18 | 15/18 16 | 20 | 2-10/20 || 49 | 49 | 20/49 17 | 17 | 2-6/17 || 50 | 20 | 16/20 18 | 27 | 2-6/27 || 52 | 39 | 30/39 19 | 19 | 2-2/19 || 54 | 27 | 20/27 20 | ANY | 2 || 55 | 33 | 24/33 21 | 21 | 1-19/21 || 56 | 49 | 35/49 22 | 33 | 1-27/37 || 58 | 29 | 20/29 23 | 23 | 1-17/23 || 60 | 39 | 26/39 24 | 39 | 1-26/39 || 62 | 31 | 20/31 25 | 20 | 1-12/20 || 64 | 16 | 10/16 26 | 39 | 1-21/39 || 65 | 39 | 24/39 27 | 27 | 1-13/27 || 66 | 33 | 20/33 28 | 49 | 1-21/49 || 68 | 17 | 10/17 29 | 29 | 1-11/29 || 70 | 49 | 28/49 30 | 39 | 1-13/39 || 72 | 27 | 15/27 31 | 31 | 1-9/31 || 74 | 37 | 20/37 32 | 20 | 1-5/20 || 75 | 15 | 8/15 33 | 33 | 1-7/33 || 76 | 19 | 10/19 34 | 17 | 1-3/17 || 78 | 39 | 20/39 ------+-------+------------++------+-------+------------ ------+-------+------------++------+-------+------------ No. of| Index |No. of turns||No. of| Index |No. of turns teeth.|circle.| of index. ||teeth.|circle.| of index. ------+-------+------------++------+-------+------------ 80 | 20 | 10/20 || 164 | 41 | 10/41 82 | 41 | 20/41 || 165 | 33 | 8/33 84 | 21 | 10/21 || 168 | 21 | 5/21 85 | 17 | 8/17 || 170 | 17 | 4/17 86 | 43 | 20/43 || 172 | 43 | 10/43 88 | 33 | 15/33 || 180 | 27 | 6/27 90 | 27 | 12/27 || 184 | 23 | 5/23 92 | 23 | 10/23 || 185 | 37 | 8/37 94 | 47 | 20/47 || 188 | 47 | 10/47 95 | 19 | 8/19 || 190 | 19 | 4/19 98 | 49 | 20/49 || 195 | 39 | 8/39 100 | 20 | 8/20 || 196 | 49 | 10/49 104 | 39 | 15/39 || 200 | 20 | 4/20 108 | 27 | 10/27 || 205 | 41 | 8/41 110 | 33 | 12/33 || 210 | 21 | 4/21 115 | 23 | 8/23 || 215 | 43 | 8/43 116 | 29 | 10/29 || 216 | 27 | 6/27 120 | 39 | 13/39 || 220 | 33 | 6/33 124 | 31 | 10/31 || 230 | 23 | 4/23 128 | 16 | 6/16 || 232 | 29 | 5/29 130 | 39 | 12/39 || 235 | 47 | 8/47 132 | 33 | 10/33 || 240 | 18 | 3/18 135 | 27 | 8/27 || 245 | 49 | 8/49 136 | 17 | 5/17 || 248 | 31 | 5/31 140 | 49 | 14/49 || 260 | 39 | 6/39 144 | 18 | 5/18 || 264 | 33 | 5/33 145 | 29 | 8/29 || 270 | 27 | 4/27 148 | 37 | 10/37 || 280 | 49 | 7/49 150 | 15 | 4/15 || 290 | 29 | 4/29 152 | 19 | 5/19 || 296 | 37 | 5/37 155 | 31 | 8/31 || 300 | 15 | 2/15 156 | 39 | 10/39 || 310 | 31 | 4/31 160 | 20 | 5/20 || 312 | 39 | 5/39 ------+-------+------------++------+-------+------------ [Illustration: Fig. 1889.] A plan view of one-half of the head is shown in Fig. 1889, the edge of J being graduated for a guide in elevating the head at an angle, at V is the bevel-gear for driving K, and at S is a pinion receiving motion from the change gears. The feed motions for the traversing table (F, Fig. 1880) is shown in Figs. 1889, 1890, and 1891, _g_ represents the universal joint rotating continuously the spindle _a_, which provides journal bearing to bevel pinion _b_ and the clutch _c_, these two being fixed together; _d_ is a clutch which rotates with _a_, but is capable of a certain amount of end motion on or along _a_ to enable it to engage or disengage with its mate _c_. When _d_ engages with _c_ the rotary motion of _a_ is transmitted through _d_, _c_, _b_, to _f_, which actuates the feed screw A, while when _d_ is disengaged from _c_, it rotates, leaving _c_ _b_ _f_ idle. _d_ is operated to engage with or disengage from _c_, its hub is enveloped by the fork _e_, which is attached to rod _h_, which is provided with a recess to receive one end of the bell crank _l_, the other end of which lies in a recess in the rod _m_, to the end of which is connected the lever handle _n_, which is pivoted at O; hence operating _n_ laterally as denoted by the arrows, throws _d_ in or out of gear with _c_, according to the direction of motion, direction _p_ being that to throw it out of, and _q_ to throw it into gear or engagement. At _r_ is a stop that can be fixed at any adjusted position or desired location along the bed upon which the feed table or carriage (F, Fig. 1880) slides, so that when that carriage is being self-actuated it will traverse until the inner end of _n_ meets the stop, whereupon the stop will move _n_ and thereby disengage _d_ from _c_, causing the automatic feed to cease. All that is necessary, therefore, is to set _r_ in such a position along the bed that it will operate _n_ when the milling cutter has operated to the required distance along or over the work; _s_ is the stud arm that carries wheel _t_ to engage with and drive the pinions shown in Fig. 1889, and _u_ is the stud for carrying the wheels for giving the required changes of rotation to K, Fig. 1889, the wheels on _u_ receiving motion from a gear placed at the seat V on the feed screw A. The stud arm _s_ being slotted, can be moved forward, transmitting motion from the change wheels on _u_ to wheel S, Fig. 1890, causing the automatic spiral feed to actuate; or by moving _s_ outwards, this feed is thrown out of action, and either the hand feed of handle W or the self-acting feed traverse may be employed. Thus the hand, and all the automatic feed motions are driven from the feed screw A, and each of the automatic feed motions may be started or stopped by operating the lever _n_, while the stop _r_ causes each of them to cease when the work has traversed to the required distance beneath the milling cutter. Fig. 1892 represents an attachment to this machine to facilitate cutting the teeth of gears, which it does because its index plate operates the work-holding mandrel direct, and may, therefore, be set quicker. The base bolts to the machine table and the index head and tailblock are traversed in the base by means of the four-levered handle shown. [Illustration: Fig. 1890.] Figs. from 1893 to 1899 represent a universal milling machine. This machine is so constructed that all the features essential to a universal milling machine are obtained by means of attachments (each complete in itself) which may be removed, leaving the work table clear, and, therefore, serviceable for large work, or work which may be more conveniently held without the use of attachments. The [T]-slots in the table are furnished to standard size, and are at right angles, so that the attachments will be held exactly parallel with, or at a right angle, as the case may be, to the live spindle of the machine; hence the machine will accomplish all the varied results required in the tool room or for machine work generally. Thus for the cutting of spirals, a fixture capable of originating any spiral right or left hand, from 2 inches to 6 feet pitch, is provided. Two bolts secure it to the machine table, and when the job is finished it is removed. Similarly for the cutting of cams, an attachment fastened to the work table by three bolts is used, which cuts either cylinder or face cams of considerable size, and as conveniently as a machine built solely for cam cutting. A gear-cutting device is also applied in the same manner, as well as plain or universal work-holding centres. The essential features of the machine are a standard A, Fig. 1894, with spreading base, carrying upon its top a driving cone B, which is fully back-geared like an engine lathe. The driving cone operates also the feed mechanism. Above the driving cone is an arch C, in which is inserted an arm D for supporting the outer end of the mill arbor when used for heavy work. Upon the face or front of the standard slides a knee E, which in its turn supports a carriage F, which traverses crosswise upon it and carries above it the work table, which is provided with an automatic feed at right angles with the movement of the carriage. These three movements, vertical, cross, and longitudinal, cover all that is usually required in a universal milling machine. [Illustration: Fig. 1891.] [Illustration: Fig. 1892.] Coming to details we start with the spindle or arbor, the front end of which runs in bearings of bronze. These are made in two parts, tapering upon the outside and straight upon the inside, a corresponding taper hole to receive the spindle bearings being bored in the solid iron of the standard. A check nut upon each end of the bushing or bearing abuts against the end faces of the standard bearing, and by drawing the bushing or bearing through the taper hole in the standard, produces the exact required closeness of fit between the spindle journal and its bearing bore, and thus compensates for the wear of either the spindle journal or its bearing or bushing bore, the front check nut also providing a dust cap. The back journal of the spindle runs in a bushing of considerable length. Upon the back end of the spindle is secured a train of feed gears G, the lower of which is upon a shaft that on its other end carries the first feed cone H. The corresponding feed cone I is fixed to the longer shaft J, carrying a worm (or tangent screw) K, which engages with the worm-gear L connected directly with the feed screw, for the longitudinal motion of the work table. This whole feed work is shown fully in outline in Fig. 1894. The arm M that supports the two lower feed gears pivots upon the outboard end of the back bushing, hence its centre coincides with that of the spindle. At its lower end a projection inwards forms a hub upon which a second lug or arm N is pivoted. The lower end of this arm is bored out to receive the threaded end of a lug O with the bearing of the second feed cone I. This threaded end carries a milled or hand nut P, so that to tighten or loosen the feed belt a turn of the nut is sufficient, the effect being to increase or diminish the distance between the feed cones H and I. The front end of the feed rod is supported in a drop box Q, and is splined to allow the worm K to travel upon it. It will be seen, therefore, that the feed mechanism is undisturbed either by the vertical movement of the knee, or the cross motion of the carriage, or the longitudinal feed of the table. The feed gears are covered with a shield R, a part of which is shown broken away. The knee with its appendages is actuated vertically by means of a crank connected with bevel gearing at S, which moves a perpendicular screw T under the centre of the knee. Rotating with this crank-shaft is a finger U held by friction. This finger is in close proximity to a dial V graduated to thousandths of an inch, and as one revolution of the finger indicates 1/8 of an inch of elevation to the knee E, the ordinary subdivisions of an inch are obtained either with or without an inner circle of graduations on the dial. A similar dial upon the cross feed motion (not shown in the engraving) is also put on, which likewise reads to thousandths of an inch. The feed of the work table is accomplished by means of a screw whose thread is in shape a half [V] and does not bear upon the bottom of the thread in the feed nut, which is in halves, with provision for closing up to compensate for wear, while check nuts on one end of the feed screw take up all end play. The automatic feed is self-stopping (so as to enable one attendant to operate several machines) by means of the following construction:-- In the general view, Fig. 1893, there is seen a stop that is secured in the required position in the [T]-groove shown at X in the outline view, Fig. 1894, and when this stop meets the bell crank Y it unlatches it from a lug which is on the drop box Q, Fig. 1893, hence this box falls and with it that end of the worm shaft J, throwing it out of gear with the worm-wheel L, and therefore stopping the feed. The attachments giving to this machine its universal qualifications are as follows:-- The rotary vice is shown on the work table in the general view, Fig. 1893; and requires but little description. Upon the underside of the base is a circular projection having beneath it a projection fitting into the [T]-slots in the work table. Two segmental slots in the base admit of a rotary movement of the vice within a range of 90°, and it is held to the table by two bolts. The crank or handle of the vice is made more convenient by means of two square holes that fit the end of the screw that actuates the movable jaw. Using the central hole allows the handle to clear the work table, but when the vice jaws need to be closed with considerable force the handle is shifted to the end or outer hole, thus doubling the leverage. [Illustration: _VOL. II._ =EXAMPLE OF MILLING MACHINE.= _PLATE I._ Fig. 1893. Fig. 1894.] THE UNIVERSAL HEAD AND BACK CENTRE.--This tool is used for making milling cutters either straight or angular, cutting small gears either spur or bevel, fluting taps or reamers, finishing nuts or bolt-heads, and a multitude of other jobs too numerous to particularise. The head consists, as seen in Fig. 1895, of a swinging block mounted centrally between the two upright sides or jaws of a base, and is clamped in any position by a set-screw on either side. The face of one side or jaw is laid out in degrees, and a finger or pointer on the block indicates its angle of elevation. On the front end of the spindle is secured a worm-wheel divided longitudinally, each half being used as a corrector (in the making) for the other half till all errors are eliminated. A dial is fixed upon the bushing through which passes the shaft that actuates the worm, and consequently revolves the worm-gear and the spindle. A pointer arm carrying a handle with a pointer and appendages is secured to the end of this shaft. Under it are the usual spaces for laying off or indicating the proper number of index holes for the required fraction of a circle the spindle is to be moved through. The spindle is hollow and has a screw on the outer end for taking a chuck or face plate. It has a taper hole for receiving the proper centre, which carries a lug for holding the dog used when the work to be finished is held between centres. Three index dials, which are made interchangeable, provide for most divisions except a few prime numbers to 360. [Illustration: Fig. 1895.] [Illustration: Fig. 1896.] To prevent or take up lost motion between the worm and the worm-gear the entire bracket carrying the worm and indexing mechanism is made adjustable as follows:-- Through the base of the bracket thread two sleeves whose ends abut against the top of the block, and therefore determine the engagement of the worm with the worm-wheel. Through these sleeves pass the bolts which thread into the block and lock the bracket in its adjusted position. A simple screw bolts the back end of the bracket. The degree of fit between the worm and the wheel may be very sensitively made by revolving the worm spindle by hand. The block carrying the back centre has some peculiar features, which enable it to be set in line with the axis of the work, whether the latter be parallel or taper, so as to suit the elevation or depression of the head, and enable the centre to fill the countersink of work held on centres, keeping it central and avoiding wear to one side. It consists of a block held between two uprights or jaws, and clamped thereto by two screw bolts. The block is slotted entirely through from side to side, the front slot being only wide enough to receive the bolt and making a changeable centre for the block to partially rotate upon. The rear slot is wider and is a segment of a circle. The screw bolts being slackened the back centre is raised, lowered, or tilted to any required position to bring the centre in line with the work axis, and is then clamped in place. One bolt holds this part of the machine to the work table. The centre is adjusted to place in the end of the work in the ordinary way, with a hand nut, &c. For gear cutting, the universal head is enlarged and somewhat modified in design, as is shown in Fig. 1896, the worm and worm-wheel being much larger in diameter and exceedingly accurate by the following method having been adopted to test them: Two cast-iron disks were placed side by side on an arbor or mandrel held between the centres, and lines of division were marked across the edges of both of them (the index plate, of course, being used for the division). The disks were then separated and one of them moved and the lines of division again compared with a microscope, and no sensible errors were apparent. The provisions for taking up the wear of the worm and its bearings, and of the worm and its wheel, are as follows: The worm-shaft runs in compensating bearings of phosphor bronze, and the bracket carrying the worm-shaft is adjustable towards the worm-wheel by the means already described for the ordinary universal head, and this head is said to be capable of making divisions as fine as one minute of an arc, or dividing the circle into 21,600 parts. The employment of a worm and a worm-wheel necessitates that the index pointer arm be given a certain number of revolutions, in order to move the spindle the requisite amount for all divisions except those equal in number to the number of teeth contained in the worm-wheel, and to avoid any mistake in counting the number of revolutions of this index pointer arm the following device is employed: On the worm shaft is a pin, and to the right of the index plate is a dial plate which is clearly shown in the engraving. The circumference of the latter is cut with ratchet teeth, and the length of the pin on the worm-shaft is such that at each revolution it moves one tooth of the dial plate. In front of the dial plate is a fixed pointer, and as the face of the ratchet wheel is graduated and marked 1, 2, 3, &c., it is obvious that the pointer shows how many revolutions the dial plate, and therefore the worm shaft, has made. After the requisite number has been made and the index pin has been set in the index wheel, the small lever, shown on the right of the dial plate, is moved and a spring brings the dial plate back so that its zero number comes back to the pointer ready to count the number of revolutions when the worm-shaft is revolved for the next division or movement of the worm and wheel. For this head there are three index plates drilled with 23 circles of holes, making, in combination with the worm and wheel, all divisions up to 90, all even divisions up to 180, with most of the other divisions between 90 and 180, or 135 divisions and multiples of these divisions up to 16,200. The index plates are interchangeable, and additional ones for other divisions may obviously be added. [Illustration: Fig. 1897.] The device for cutting spirals as arranged for hand feeding is shown in Fig. 1897, while in Fig. 1898 it is shown arranged for automatic feeding, and is shown in position on the machine. Referring to Fig. 1897 the hand wheel operates a worm engaging with a worm-wheel on the shaft of the largest gear shown in the engraving. From this gear motion is conveyed through intermediate wheels to the pinion on the same shaft as the first bevel-gear, which obviously drives the bevel-gear shown on the end of the head. The back face of this latter gear is provided with index holes, and the usual index arm and pin are provided. The change gears provided for this device are sufficient to cut twelve different pitches, ranging from one turn in 2 inches to one turn in 6 feet. Obviously right or left-hand spirals are produced according to the direction of revolution of the hand wheel. In the general view, Fig. 1898, the device is placed upon a box bolted to the work table, and obtains its automatic feed through the medium of the worm for the table feed. [Illustration: Fig. 1899.] The cam-cutting attachment, Fig. 1899, consists of a base bolted to the machine table and adjustable to any required position thereon. This base has a slide way in which a gibbed slide carrying a head is free to travel longitudinally. The pattern or former cam and the work are carried on the live spindle of the head, and the former cam is supported by circumferential contact with a roll carried on the vertical bracket shown on the right of the engraving. As shown, the device is arranged for cutting face cams, the cam-holding spindle being placed in line with the machine spindle. All that is necessary for cutting _cylinder_ cams is to set the device with its spindle at a right angle to the machine spindle and move the supporting bracket so that its roller will meet the perimeter of the former cam. In either case the slide carrying the head is pulled forward by weights suspended over the wheel shown on the end of the base, and the feed is put on by revolving the spindle by means of the worm and worm-wheel shown in the engraving, the ordinary crank handle of the machine fitting the worm shaft. A hand feed for cam cutters is preferable to the automatic feed, because in turning corners or curves the rate of the feed requires to be reduced in order to obtain smooth work. Fig. 1900 represents a universal milling machine. The live spindle head is fitted to a horizontal slide on the top of the main frame, and may therefore be moved on that slideway to adjust the cutters to the work, the motion being effected by a pinion operating a rack on the underside of the head, as shown in Fig. 1901, which is a sectional view of the machine. [Illustration: _VOL. II._ =EXAMPLES OF MILLING MACHINES.= _PLATE II._ Fig. 1898. Fig. 1900.] At the handle end of the pinion shaft there is provided a dial (which is seen in the general view of the machine) having an outer circle graduated to sixty-fourths of an inch, and an inner one graduated to fortieths of an inch. The driving shaft is at a right angle to the live spindle, and drives it by means of a hardened steel worm operating a bronze worm-wheel fast on the live spindle, and which runs in a trough of oil to provide ample lubrication. [Illustration: Fig. 1901.] The spindle is hollow and has tapered journals. The arm for supporting the outer end of the cutter arbor is cylindrical, and fits to a bore provided in the top of the frame of the head, which is split and has two binding screws. When these screws are loosened the arm may be readily adjusted for position, while when they are screwed up they lock the arm in its adjusted position. By this means the arm only projects out as far as the particular work in hand requires. The knee for carrying the work table and chucking devices terminates at its top in a circular box cast open on top. This box is covered with a circular cap, in the upper face of which are the slideways or guides for the work table. The cap is recessed into the box so as to be kept central, and is fastened therein by an expanding ring operated by a single stud which projects through the walls of the box. This ring has a [V]-shaped groove on its periphery, which in expanding closes over corresponding bevelled ledges on the inside of both the cap and the box. The edge of the cap is graduated for cutting spirals. By this arrangement the table can be set to move at any required angle with the live spindle and quickly clamped in position, while the ring being of larger diameter and bearing evenly around the entire circle, the cap is rigidly held. In this box, securely protected from the cuttings or dirt, is a large worm-gear secured to a short vertical shaft, on the upper end of which is a pinion projecting through the cap and engaging with a rack upon the underneath side or face of the work table. This shaft also carries a bevel-pinion which meshes with a pinion on the end of the short shaft seen projecting through the front of the box and provided with a hand crank, the hand lever shown behind this crank being for securing or releasing the cap to or from the box. The gearing is so arranged that one revolution of the hand crank traverses the work table a distance of 2 inches, thus providing for the rapid motion of the table to expedite putting in and taking out the work. The knee is operated vertically by a pair of bevel-gears, the shaft for operating which is shown on the left-hand side of the knee. On this shaft is a pointer for an indexed dial, which has two graduated circles, the outer of which is divided so that each division corresponds to a knee motion of 1/32 of an inch, while the inner one denotes a knee motion of 1/1000 inch. Automatic feed motion for the work table is provided as follows: The cone shaft projects through the live head and carries a leather-covered friction disk which drives a vertical shaft carried by a bracket hinged to the head. A small pulley splined on this shaft, and held at any point by a spring-pressed catch, bears against the leather-covered face of the disk, and it is obvious that the nearer to the centre of the disk the pulley is set the slower the latter will be revolved, and therefore the finer the feed will be, while the direction of revolution of the small pulley will be reversed if it be set on the upper half or above the centre of the disk, thus providing for reversing the direction of feed. By this arrangement both the rate and direction of the feed can be set without stopping the machine. This vertical feed shaft carries a splined worm driving a worm-gear splined on a horizontal shaft which is carried by the knee, which has a projecting arm or bracket for carrying the back end of the shaft, so that the latter rises or falls with the knee. A worm on this horizontal shaft engages a large worm-wheel within the box and fast upon the short upright shaft, whose pinion engages the table rack and thus completes the feed motion. It will be seen in the sectional view that the worm-wheel for the automatic feed is in one piece, with a smaller bevel-wheel engaging with a bevel-pinion for the hand feed. A clutch joint near the centre of the horizontal shaft affords the means for putting the automatic feed either into or out of action. The table can be fed its full length in either direction, and when placed so that one end will pass the main frame or column may be swung around parallel to the spindle, thus enabling the machine to be used as a boring mill for short holes, or by turning the table a half revolution work may be done on both sides of a piece at one chucking, thus insuring perfect parallelism. [Illustration: Fig. 1902.] [Illustration: Fig. 1903.] The construction of the index head of this machine is as follows: Fig. 1902 represents it on a plate with a back centre and a centre rest, and Fig. 1903 represents the head elevated. The head is a hollow box, the outline of which is about two-thirds of a circle. The opening, in front or chord side, is surrounded by a flange, and bored out as large as permissible. This forms the front bearing of the spindle and face plate, which is cast in one piece. A rear and smaller bearing is provided on the circular part of the case. The end of the spindle projects through the case, and is held from coming out by a recessed nut and washer. The spindle also carries an accurately-divided steel gear of sixty teeth. This gear is made as large as will go through the opening in front, or about 6 inches in diameter. Directly under this gear the box is pierced from the side. In this opening is inserted a long bush, through which a steel worm engages with the gear. An index plate secured to the outer end of the bush, and an adjustable arm and index pin attached to the projecting end of the worm, complete the dividing mechanism. Substantial but delicate adjustments are provided for eliminating lost motion. On the periphery of the case is turned a dovetail shoulder, which slides around in a corresponding groove in the quadrant-shaped base. The case is graduated on its edge, and may be clamped at any angle of elevation from 15 degrees below a horizontal line to a vertical position, being equally stable in all positions. The face plate is no farther from the bed in one position than another, and being seated to the case, and adapted to hold work directly on its face, forms a stiff and substantial device for cutting bevel-gears and other work requiring angular motion. The tail centre is also of a strong and substantial design. An adjustable centre rest of novel design also accompanies the outfit, and an extra bed or table, with straps for securing it to the table of the machine. With the centres arranged on this bed the line of centres may be set at any angle with the sliding table, A sufficient number of index plates are provided to divide all numbers up to 100 and all even numbers to 200. Fig. 1904 represents a machine in which the base column and the head are constructed upon the same design as that in Fig. 1900, but the circular top and cap are replaced with a larger and heavier knee of rectangular form, and the table is longer. A cross sectional view of the head is shown in Fig. 1905. The bearings for the live spindle are solid bushes slightly tapered, and are driven into the head from each end up to and against the flanges. The spindle is of tool steel 3-1/2 inches in diameter at the front bearing, tapering uniformly 3/4 inch per foot to the back end. This simple construction allows the spindle to be perfectly ground, and accurately fitted to the boxes by scraping. After this is done the spindle is withdrawn about the 1/100 part of an inch, and a flat babbitt metal washer fitted to exactly the space between the shoulder on the spindle and the front box. A check nut and sliding collar on the back end holds the spindle in place. A perfectly uniform space for oil is thus formed between the spindle and bearings. The worm-gear is forced tightly on the taper spindle with a nut, and keyed to prevent turning. The spindle has a hole 1-9/16 inches through its centre, tapering in front to receive the arbor to 1-7/8 inches. The taper is made 1/2 inch per foot, and for ordinary work is sufficient to prevent the arbor turning, but for driving gangs or large mills an arbor is used having a hexagon enlargement just outside the spindle. A cap to screw over the end of the spindle, having a hexagon opening in it to fit the arbor, completes a positive driver that has none of the objections to cutting a mortise or keyway in the spindle or otherwise disfiguring it. This cap protects the thread on the spindle, and may be readily removed for a face plate or large facing mills. [Illustration: Fig. 1904.] [Illustration: Fig. 1905.] The cone shaft and its bearings are made independent of the head. A long sleeve, which is provided with a large flange, projects through cored openings in the side of the head. The bosses around these openings are faced off square and parallel, and a large flat ring threaded on the end of the sleeve draws the flange against the opposite face. The large end of the sleeve is counterbored to receive the worm, and is cut away on the under side to allow the worm to drop into mesh with the gear. The worm is feathered on the shaft, the thrust of the worm being taken in one direction against the shoulder in the sleeve, and in the opposite direction (the machine can be driven either right or left-handed) against the end of a bush, which is screwed in the sleeve and forms one bearing for the cone shaft. Friction washers are placed to form the step, and all wear or lost motion can be removed by screwing in the bearing, which, when adjusted, is prevented from turning by a small set-screw. The cone-shaft bearings are babbitt lined, but the spindle bearings are made of cast iron, in which steel scrap has been melted. The worm-gear has 40 teeth, and the worm is triple threaded, thus making a back gear equivalent to 40-3, or 13-1/3 to 1. As the sleeve does not fit the openings in the head, the worm and gear may be readily adjusted to each other at all times, and held firmly and squarely in place by drawing the flange tight against the side of the head. Set-screws through the head prevent accidental displacement of the sleeve after being adjusted. [Illustration: Fig. 1906.] Fig. 1906 represents a double spindle milling machine. The second spindle is for driving the finishing cutters, so that as the two spindles are capable of independent adjustment, the work may be finished at one feed traverse, thus avoiding the necessity of removing the work or making special adjustments. Fig. 1907 represents a milling machine for globe valves and other similar work. Here there are two cutter-driving spindles, one on each end of the bed, and the work is held vertically. It is provided with an index wheel for milling squares, hexagons, or octagons, and the pen for the index wheel is operated by treadle. The work is fed across the bed, the chucking devices being carried on a slide rest. In the figure a globe valve is shown chucked between two plugs or arbors fitting its bore, but it is obvious that centres or other work-holding appliances may be used to suit the kind of work. Fig. 1908 represents an eighty-inch milling machine, the table of which has longitudinal motion; and provision for vertical and crosswise movements are made in the head which carries the driving mechanism. The machine table sets low on a bed supported by four box legs, and is actuated by a steel screw driven by a worm and worm-gear connected with a pair of spur-gears. The gearing is outside the bed, and therefore accessible, and is protected by a shield, as shown in cut. The arrangement for belting to feed works is also shown too plainly to need description. The head upon which the spindle carrier is mounted travels in ways upon the bed, and is adjusted crosswise on it by means of a screw connected with a hand wheel, partially shown at the left of engraving. For convenience and ease in fine adjustment this wheel, and also the wheel at top of machine, connected with the elevating screw, are worked by a hand lever, the wheels having sockets in their periphery for this purpose. The carrier, upon which is mounted the driving spindle, is gibbed to the head, and has a vertical range sufficient to allow work 18 inches high to pass under centres. From this carrier projects a large arm for outside centre support of mill spindle, intended for use on work where a back stand is not admissible. There is, however, as may be seen, a back stand or tailstock of a very solid character. The arm is readily removable, when desired, or the tailstock can be slid off its seat if required. In most cases, however, the arm need not be removed, the yoke on it being swung up out of the way, leaving the centre of mill arbor free to engage with that on the back stand. This combination provides for operating on a wide range of work. As shown in the engraving, the space between head and tailstock is about 24 inches, but if required the tailstock can be made to travel in line with the head, and its support be extended to any distance desired. The method of driving the spindle is simple and strong, and allows of free adjustment of the spindle without disarrangement of the driving and feed belts. The cone, which is made for 3-1/2 inch belt, is mounted in a stirrup which is pivoted to the bed, and the pinion which engages with the driving gear on the spindle is held at correct distance by a connecting yoke, and is driven by a feather. The machine has longitudinal feed only, but where it is desired an automatic feed motion can be applied to the elevating screw in the head, giving feed in a vertical direction. The table is arranged to be run back rapidly by power, by a device which is not seen in the engraving. As the table weighs one ton, the relief to the operator by this improvement is obvious. All the operations of the machine are intended to be conducted from the front side, without any change in the position of the operator. The feed can be thrown out by hand at any moment by means of a rod which connects with the latch shown in the front of the cut, and the power quick-return applied; or the table can be run back by hand, and the feed thrown in by a foot lever, which lifts the drop box shown in front of cut. Adjustable dogs automatically drop the feed motion at any point. The machine is massive in all its parts, and is intended for heavy milling of any description, but more particularly for shafting, railroad, or engineering shops, being specially adapted for key-seating long and heavy shafting, finishing guide bars, connecting rods, &c. Its weight is 7,500 pounds. The work table is 7 feet long by 20 inches wide; length of longitudinal feed, 84 inches; distance between uprights, 24 inches. The cast-steel spindle is 4 inches in diameter, and the mill arbor 2-1/2 inches diameter. Arm for outer centre support 5 inches diameter at its smallest part. [Illustration: Fig. 1909.] [Illustration: _VOL. II._ =EXAMPLES OF MILLING MACHINES.= _PLATE III._ Fig. 1907. Fig. 1908.] MILLING CUTTERS OR MILLS.--The simplest form of milling cutter is that shown in Fig. 1909, the teeth being equidistantly arranged upon the circumference only. Its size is usually designated by its length, which is termed the face. Thus a cutter having its teeth parallel to its axis and an inch long would be said to have 1 inch face. Cutters of more than about half an inch face usually, however, have their teeth cut spirally, as in Fig. 1910; the degree of spiral is one turn in a length of 3 feet for cutters between 2-1/4 and 4 inches in diameter. For cutters of less than 2-1/4 the degree in the spiral is increased; thus for an inch cutter, the degree is one turn in 15 inches, while for 6 inches one turn in about 60 inches is used. [Illustration: Fig. 1910.] In the following table is given the sizes of cutters as made by one company, the bores being 1 inch. +---------+-----------------------++---------+-----------------------+ | Width of| || Width of| | | face. | Diameter of cutter. || face. | Diameter of cutter. | +---------+-------+-------+-------++---------+-------+-------+-------+ | inch. | inch. | inch. | inch. || inch. | inch. | inch. | inch. | | 1/8 | 2-1/2 | 3 | 4 || 15/16 | 2-1/2 | 3 | 4 | | 3/16 | 2-1/2 | 3 | 4 || 1 | 2-1/2 | 3 | 4 | | 1/4 | 2-1/2 | 3 | 4 || 1-1/8 | 2-1/2 | 3 | 4 | | 5/16 | 2-1/2 | 3 | 4 || 1-1/4 | 2-1/2 | 3 | 4 | | 3/8 | 2-1/2 | 3 | 4 || 1-1/2 | 2-1/2 | 3 | 4 | | 7/16 | 2-1/2 | 3 | 4 || 1-3/4 | 2-1/2 | 3 | 4 | | 1/2 | 2-1/2 | 3 | 4 || 2 | 2-1/2 | 3 | 4 | | 9/16 | 2-1/2 | 3 | 4 || 2-1/4 | 2-1/2 | 3 | 4 | | 5/8 | 2-1/2 | 3 | 4 || 2-1/2 | 2-1/2 | 3 | 4 | | 11/16 | 2-1/2 | 3 | 4 || 3 | 2-1/2 | 3 | 4 | | 3/4 | 2-1/2 | 3 | 4 || 3-1/2 | 2-1/2 | 3 | 4 | | 13/16 | 2-1/2 | 3 | 4 || 4 | 2-1/2 | 3 | 4 | | 7/8 | 2-1/2 | 3 | 4 || | | | | +---------+-------+-------+-------++---------+-------+-------+-------+ The keyways are semicircular, the key being composed of a piece of No. 25 Stubbs steel wire. The following is a table of the sizes of milling cutters made by another company. +----------+------------+---------++----------+------------+---------+ | | | || | | | | Width of | Diameter | Size of || Width of | Diameter | Size of | | face. | of cutter. | hole. || face. | of cutter. | hole. | +----------+------------+---------++----------+------------+---------+ | inch. | inch. | inch. || inch. | inch. | inch. | | 1/8 | 2-1/4 | 1 || 3/4 | 2-7/8 | 1 | | 3/16 | 2-1/4 | 1 || 7/8 | 2-7/8 | 1 | | 1/4 | 2-1/2 | 1 || 1 | 2-1/2 | 1 | | 5/16 | 2-1/2 | 1 || 1-1/4 | 2-1/2 | 1 | | 3/8 | 2-5/8 | 1 || 1-1/2 | 2-1/2 | 1 | | 7/16 | 2-5/8 | 1 || 1-3/4 | 2-1/2 | 1 | | 1/2 | 2-3/4 | 1 || 2 | 2-1/2 | 1 | | 9/16 | 2-3/4 | 1 || 2-1/2 | 2-1/2 | 1 | | 5/8 | 2-3/4 | 1 || 3 | 2-1/2 | 1 | | 11/16 | 2-7/8 | 1 || | | | +----------+------------+---------++----------+------------+---------+ Cutters of 1 inch face and over have teeth of a spiral form. The object of providing spiral teeth is to maintain a uniformity of cutting duty at each instant of time. Suppose, for example, that the teeth are parallel to the cutter axis, when the cutter first meets the work the tooth will take its cut along its full length at the same instant, causing in wide cuts a jump to the work because of the spring of the various parts of the work-holding devices, and of the cutter driving spindle; furthermore as the cutter revolves the number of teeth in action upon the work varies. Thus in Fig. 1912 it is seen that one tooth only is in action, but when the cutter has revolved a little more there will be two teeth in action, as shown in Fig. 1913. This variation causes a corresponding variation of spring or give to the machine, producing a surface very slightly marked by undulations. But if the teeth are cut spiral the cut begins at one end of the tooth and proceeds gradually along it, thus avoiding violent shock, and after the cut is fairly started across the work the length of cutting edge in action is maintained uniform, producing smoother work, especially in the case of wide surfaces and deep cuts. [Illustration: Fig. 1911.] [Illustration: Fig. 1912.] [Illustration: Fig. 1913.] When the cutter is required to cut on the sides of the work as well as on its upper face it is termed a face cutter, and its side faces are provided with teeth, as shown in Fig. 1914; and when these cutters are arranged in pairs as in Fig. 1915, so as to cut in the side faces only of the work D, they are termed twin or straddle mills, both being of the same diameter. [Illustration: Fig. 1914.] In mills or cutters used in this way the cutting duty is excessive on the outer corners of the teeth, which, therefore, rapidly dull; hence it is usual to provide teeth on both sides of the cutter, as in Fig. 1916, so that after having been used in the position shown in the engraving until the teeth are dull the positions of cutters may be changed, bringing the unused cutting edges into use. [Illustration: Fig. 1915.] Twin or heading cutters are right and left hand, a right-hand one being that in which the teeth at the top of the wheel revolves towards the right, while a left-hand one revolves (at the top) towards the left. [Illustration: Fig. 1916.] [Illustration: Fig. 1917.] If the machine is belted so that it can be revolved in either direction, both sides of the cutter may be utilised by taking the cutters off the arbor, turning them around and then replacing them in their original positions on the same. Thus in Fig. 1917 we have at A a left-hand cutter that if reversed upon its arbor would be a right-hand one as at B, and it is obvious that the direction of revolution must be in each case as denoted by the arrows F G, which are in opposite directions. In this case the direction of work feed must be reversed, the work for A feeding in the direction of C, and that for B in the direction of D. It is to be observed, however, that the cutter could not be reversed if it was driven by an arbor that screwed upon the driving spindle of the milling machine. For if the machine has a right-hand thread then the cutter must revolve in the direction of G, and the work feed must be in that of C; whereas if the machine spindle drives its chucks, arbors, &c., by a left-hand thread, then the direction of cutter revolution must be as at F, and that of work feed as at D. But if the cutters are upon an arbor that is driven by a conical seat in the machine spindle, or by any other means enabling the arbor to revolve in either direction without becoming released from that spindle, then the cutter may be simply turned around and the feed direction reversed, as already explained. The reason for reversing the direction of feed when the direction of cutter revolution is reversed is as follows:-- [Illustration: Fig. 1918.] In Fig. 1918 A and B represent two pieces of work of which B is to be fed in the direction of arrow C, so that the pressure of the cut tends to force the work back from under the cutter, whereas in the case of the work A, feeding in the direction of D, the teeth act to pull the work beneath the cutter, which causes tooth breakage. Suppose, for example, that in Fig. 1919 P is a piece of work fastened to the table T, feeding in the direction of A, the cutter W revolving in the direction of arrow B, N representing the feed nut operated by the feed screw S. Now while the table is being pulled in the direction of A, the sides C of the feed screw thread will bear against the sides of the thread in the nut, and whatever amount of looseness there may be between the threads of the screw and nut will in this case be on the sides D of the threads. So soon, therefore, as the wheel meets the work P, it will suddenly pull the work forward to the amount of the play or looseness on the sides D of the threads, and this in addition to the feed given by the rotating screw S, would cause the wheel to lock upon the work surface. [Illustration: Fig. 1919.] In all milling operations, therefore, the work is fed against the cutter as at B, in Fig. 1918, unless, in the case of twin mills, it is fed (as at E and F in the same figure) in the middle of the cutters, in which case it is preferable to present it as at F, so that the pressure of the cut will tend to hold the work down to the table, and the table down upon its guideways. This position of the work presents some advantages for small work which will be explained hereafter. [Illustration: Fig. 1920.] Fig. 1920 represents angular cutters, the teeth being at an angle to the cutter axis. These cutters are made right and left as at A and B in Fig. 1921, the teeth of A being cut in the opposite direction to those at B, so as to be able to cut equal angles on the work when these angles lie in opposite directions, as C and D in the figure. Furthermore these cutters are sometimes screwed to their arbors, and can therefore be revolved in one direction only, which prevents their being turned around end for end, even though the machine be so belted as to be capable of revolving its spindle in either direction. [Illustration: Fig. 1921.] The angular cutters shown in Fig. 1921 have their teeth arranged for a Brainard milling machine, in which the live spindle has a right-hand thread for driving the chucks, arbors, &c.; hence the direction of cutter revolution, and the arrangement of the teeth are as in the figure. [Illustration: Fig. 1922.] [Illustration: Fig. 1923.] In Fig. 1922 are segments of two wheels, A and B (corresponding to A and B in Fig. 1921), but with their teeth arranged for a Brown and Sharpe milling machine, in which the machine spindle has a left-hand thread; hence the direction of cutter revolution is reversed, as denoted by the arrows in the two figures. [Illustration: Fig. 1924.] Fig. 1923 represents a round edge cutter; and it is obvious that the curvature or roundness of the cutting edges may be made to suit the nature of the work, whether the same be of regular or irregular form. In cutters of this description it would be a difficult matter to resharpen the teeth by grinding their backs, hence they are ground on the front faces; and to maintain the form or profile of the cutting edges, notwithstanding the grinding, we have a patent form of cutter, an example of which is shown in the gear tooth cutter in Fig. 1924. The backs of the teeth are of the same form throughout their entire length, so that grinding away the front face to sharpen the cutting edge does not alter the contour or shape of the cutting edge. This is of especial advantage in cutters for gear teeth, and those for irregular forms, Figs. 1925, 1926, and 1927 forming prominent examples. [Illustration: Fig. 1925.] End mills or shank cutters are formed as in Fig. 1928, the shank sometimes being made parallel with a flat place at A, to receive the set-screw pressure, and at others taper, the degree of taper being 1/2 inch per foot. The hole at the end facilitates both the cutting of the tooth in the making and also the grinding. Shank cutters may be used to cut their way into the work, with the teeth on the end face, and then carry it along, bringing the circumferential teeth into operation; or the end teeth may be used to carry the cut after the manner of a face cutter. [Illustration: Fig. 1926.] [Illustration: Fig. 1927.] Shank cutters are rarely made above an inch in diameter, and are largely used for cutting grooves or recesses, and sometimes to dress out slots or grooves that have been cast in the work, as in the case of the steam and exhaust ports of steam engine cylinders. In work of this kind the direction of the feed is of great importance and must be varied according to the depth of cut taken on the respective sides of the cutter. Suppose, for example, that the conditions are such as illustrated in Fig. 1929, the cut being deepest on the side A of the slot, and the cutter must be entered at the end of the slot and fed in the direction of D, so that the pressure of the cut may tend to push the cutter back, it being obvious that on the side B the cutter has a tendency to walk or move forward too rapidly to its cut, and if the cut was heaviest on that side it would do, this increasing the cut rapidly and causing tooth breakage. [Illustration: Fig. 1928.] [Illustration: Fig. 1929.] This tendency, however, is resisted by the pressure on the side A of the slot, which acts, as already stated, to push the cutter back. In starting the cutter therefore, it is necessary to do so at that end of the slot that will cause the deepest cut to act in the direction to retard the feed. Suppose, for example, that the heaviest or deepest cut, instead of being on the side A of the slot, as in Fig. 1929, was on the side B, and in that case it would be necessary to start the cut from the other end of the slot as in Fig. 1930, the arrow C denoting the direction of feed. [Illustration: Fig. 1930.] [Illustration: Fig. 1931.] Similarly when a groove has been roughed out from the solid, and it is determined to take a finishing cut, the direction of the feed for the latter is of importance. Suppose, for example, a [T]-groove is to be cut, and that a slot is first cut with a shank cutter as in Fig. 1931, leaving a light finishing cut of, say, 3/64 inch to finish the neck to the dotted lines A B, and entering to within 1/16 inch of the full depth as denoted by line C. The enlarged part of the groove may then be cut out, leaving about 3/64 inch at the top and bottom, D and E, the cutter having a plain shank (as in Fig. 1933), whose diameter should just clear the narrow part of the groove already roughed out. The work will then be ready for the finishing cutter, formed as in Fig. 1932, whose teeth (on both the shank and the enlarged end) should have a diameter of 3/32 less than that of the finished slot. In taking the finishing cut this cutter must be set first to cut the sides B E to finished size, the direction of the feed being such that the pressure of the cut acts to push the cutter back as already explained, and when the cut is finished on this side the finishing cut may be put on the side A D, without traversing the cutter back, or in other words the feed must be carried in the opposite direction, so that the cutter will run under the cut and be pushed back by it, so as to prevent it from running forward as explained with reference to figure. [Illustration: Fig. 1932.] For ordinary work not requiring great truth, however, the first cutter, Fig. 1931, may be made of the finished diameter, and be followed by a cutter such as in Fig. 1933, also of the finished diameter. [Illustration: Fig. 1933.[31]] [31] Figs. 1928, 1931, 1932, 1933, are from an article by John J. Grant, in _The American Machinist_. When a shank-cutter is required to enter solid metal endways, as in the case of cutting grooves around the circumferential surface of a cylinder, it is necessary to drill a hole to admit the cutter, leaving a light finishing cut for the diameter of the cutter, and sufficient in the depth to let the end face of the cutter remove or square up the cone seat left by the drill. Shank cutters may obviously be made taper, or to any other required angle or curvature, Figs. 1934 and 1935 being examples which can be used in situations where other cutters could not, as for example on the arms or spokes of wheels. [Illustration: Fig. 1934.[32]] [32] Figs. 1934, 1935, 1936, are from articles by John J. Grant, in _The American Machinist_. Fig. 1936, from _The American Machinist_, represents an example of the employment of shank cutters, the work being a handle for a lathe cross-feed screw, and it is obvious that the double cornering cutter may be used upon both edges, and the cut being carried around the hub by the parallel part of the cutter; the whole of the work on the handle including the boring, if the hole is cast in, may be done by the shank cutter, the handle end being finished and the boring done first, the hub being finished on an arbor. [Illustration: Fig. 1935.] Shank mills may obviously be made of various shapes; thus in Fig. 1937 is shown two applications of an end or shank mill, one for cutting a dovetailed groove and the other an angular one. In the case of the dovetail groove the cutter will work equally well, whether it be used on straight or spiral grooves; but this is not the case with angular grooves for reasons which are explained with reference to angular cutters and spiral groove cutting. [Illustration: Fig. 1936.] Shank cutters are provided with finer teeth than ordinary cutters, the following being the numbers of teeth commonly employed for the respective diameters:-- Diameter of cutter 1/8 or 3/16 inch, number of teeth 6 " " 1/4 " " " 7 " " 3/8 " " " 8 " " 1/2 " " " 8 " " 5/8 " " " 10 " " 3/4 " " " 10 " " 7/8 " " " 12 " " 1 " " " 14 The front faces of the teeth are radial as in other cutters, the angle of the back of the tooth being 40° for the smaller, 50° for the medium, and 60° for an inch cutter. [Illustration: Fig. 1937.] Fly cutters are single-toothed cutters, or rather tools, that are largely used by watchmakers for cutting their fine pitches of gear wheels. Fig. 1938 represents a fly cutter in place in its holder or arbor, its front face D being in line with the axis C of the arbor. [Illustration: Fig. 1938.] Let it be required to make a fly cutter for a very fine pitch of gear tooth, such as used for watches, and a template, shown greatly magnified at T in Fig. 1939, is made to fill a space and one half of each of the neighboring teeth. From this template a cutting tool is made, being carefully brought to shape with an oil-stone slip and a magnifying glass. This tool is used for the production of fly cutters, and may be employed by either of the following methods:-- [Illustration: Fig. 1939.] The piece of steel to form the cutter is fastened in an arbor back from the centre, as at D in Fig. 1940, and is then cut to shape by the tool before referred to. It is then set for use in the milling machine, or in such other machine as it may be used in, in the position shown in Fig. 1938, its front face D being in line with the axis C of the arbor. The change of position has the effect of giving the tool clearance, thus enabling it to cut while being of the same shape throughout its whole thickness; face D may be ground to resharpen the cutter without altering the shape it will produce. It is this capacity to preserve its shape that makes the fly cutter so useful as a milling machine tool, since it obviates the necessity of making the more expensive milling cutters, which, unless made on the principle of the Brown and Sharpe cutters, do not preserve their shapes. [Illustration: Fig. 1940.] It is to be observed, however, that a fly cutter made as above does not produce work to exactly correspond to the template it was made from, because moving it from the position it was made in (Fig. 1938) to the position it is used in (Fig. 1940) causes it to cut slightly shallower, but does not affect its width. [Illustration: Fig. 1941.] Another method of cutting up a fly cutter by the tool made to the template is shown in Fig. 1941. The blank cutter is placed at an angle to an arbor axis, and is cut to shape by the tool. For use it is placed in line with the arbor axis as in Fig. 1942, the change of position here again giving clearance as shown by the dotted arcs, the inside ones showing the arc the cutter revolved on when it was in the arbor in Fig. 1938. Here again, however, the change of position causes the fly cutter to produce a shape slightly different from the template to which the first tool was made, hence the best method is as follows:-- [Illustration: Fig. 1942.] The blank is let into an arbor of small diameter, as in Fig. 1943, its face D being in line with the arbor axis. It is then cut up with the tool made from the template. For use it is set in a larger arbor, as in Fig. 1944, the difference in its path of revolution giving it the necessary clearance. Thus, in the figure the inner dotted arcs show the path of revolution of the cutter when it was in the small arbor, and the outer arc of the path in the large arbor. The front face can be ground without altering the shapes; the cutter will produce this front face, being kept in line with the arbor axis by grinding the body of the steel as much as the front face is ground when it is resharpened. Curves or irregular shapes may be readily produced and preserved by fly cutters. [Illustration: Fig. 1943.] [Illustration: Fig. 1944.] It is obvious, however, that when the tool made to the original template is worn out, another must be made, and to avoid this trouble and preserve the original shape beyond possible error, we have recourse to the following additional method:-- [Illustration: Fig. 1945.] With the tool made from the template we may cut up a wheel, such as in Fig. 1945, and this wheel we may use as a turning tool to cut up fly cutters, the principle of the wheel cutter having been shown in connection with lathe tools. It may here be pointed out, however, that if a wheel or circular cutter, as it is termed, is to be used, we may make the template, and the master tool we make from it, for one side of a tooth only, and use the master tool to cut up one side only of the corner of the circular cutter, as shown in Fig. 1945. [Illustration: Fig. 1946.] [Illustration: Fig. 1947.] The method of using the circular cutter is illustrated in Fig. 1946, in which H is a holder, whose end face P is level with the axis of the cutter, which is held to the holder by a screw. The side face of the holder is out of the vertical so as to give the cutter side clearance. A second holder has its side face inclined in the opposite direction, thus enabling the one edge of the circular cutter to be used as a right or as a left-hand tool and insuring uniformity, because the same edge of the circular cutter is used in both cases, so that if used for say a tool for a gear tooth, both sides of the tool will be cut from the same side of the circular cutter. It is obvious that instead of having one continuous cutter, the necessary breadth of cutter face may be obtained by means of two or more cutters placed side by side. Thus to mill a piece of work two inches wide we may use two cutters of an inch face each (both of course being of equal diameter), or we may use one cutter, of 1-1/4 inch and another of 3/4 inch face. It is preferable, however, to use two cutters of an inch face each, and to set one beam left-hand and the other right-hand spiral teeth, because spiral teeth have considerable tendency to draw the machine spindle endways in its bearings, because the teeth correspond to a certain extent to a screw, and the work to a nut. A cutter with a left-hand spiral exerts end pressure tending to draw the driving spindle out from its bearings, while a right-hand one tends to push it within them; hence by making the two cutters of equal length and of the same degree of spiral, the effect of one cutter offsets that of the other. Furthermore, it is found that the tendency to chatter which increases with an increase in the width of the work, is diminished by using right and left spiral cutters side by side. [Illustration: Fig. 1948.] In order that the cutting edges of cutters placed side by side in this way may be practically continuous so as not to leave a line on the finished work, the teeth may be made to overlap in two ways as in Fig. 1948, both representing magnified portions of cutters. In the method shown on the left of the figure the usefulness of either cutter to be used singly is not impaired, all that is necessary to insure the overlapping being to cut the keyways in different positions with relation to the teeth; whereas on the left of the figure neither cutter would be efficient if used singly, except upon work as narrow as the narrowest part of the cutter. On the other hand, however, it affords excellent facilities for grinding, since the two cutters may be ground together, thus ensuring that they be of equal diameters except in so far as may be influenced by the wear of the emery wheel, which is, however, almost inappreciable even in cutters of considerable width of face. In the method shown on the left there is the further advantage that as the teeth are not in line the cutting action is more continuous and less intermittent, the arrangement having in a modified degree the same advantage as the spiral cutter. [Illustration: Fig. 1949.] In both methods some latitude is given to adjust the total width of face by placing paper washers between the cutters. If the plan on the right is employed the projections may occupy one-fourth of the circumference, there being two projections and two depressions on one end of the cutter. When cutters of different diameters and shapes are put together side by side on the same arbor the operation is termed gang milling. [Illustration: Fig. 1950.] Thus, in Fig. 1949 is shown a sectional view of a gang of three mills or cutters, A, B, and C, of which A and C are recessed to admit of the ends of B passing within them. The heavy black line representing a paper washer inserted to adjust the distance apart of A and C, it being obvious that this gives a means of letting them together after their side teeth at D and E have been ground. As shown in the figure, A has teeth on one only of its sides, while C has them on both sides as well as in its circumference, while all three are of different widths of face. This would capacitate A only for the inside cutter, as in the figure, while B would be serviceable only when there was a cutter on each side of it; or if used singly, only when its face overlapped the width of the work on each side. But C, being cut on each side, could be used singly for grooving or recessing, or for plain milling, or in the position of B or A in the figure; hence it is preferable in gang milling for general purposes to provide teeth on both sides as well as on the circumference of the mill or cutter. But if a gang of mills are to be made for some special purpose, and used for no other, the teeth may be provided on the sides or not, as the circumstances may require. [Illustration: Fig. 1951.] Suppose, for example, that steps, such as shown in Fig. 1950, were required to be cut in a piece of brass work, and that, the work requiring to be very true, a set of roughing and one of finishing cutters be used, then the latter may be put together as in Fig. 1951, there being eight separate cutters, and their ends being slightly recessed but without teeth. Such cutters would wear a long time and may be readily sharpened, and there being no side teeth, the widths of the cutters, individually and collectively, would not be altered by the grinding; hence no readjustment with washers would be necessary. The tooth corners must, however, be kept sharp, for in proportion as they get dull or blunt, the sides of the cutter wedge in the work, causing friction and extra power to drive them as well as producing inferior work. [Illustration: Fig. 1952.] Fig. 1952, which is from an article by John J. Grant, represents a gang of cutters arranged to mill out the jaws and the top faces of a head for a lathe; and it is obvious that a number of such heads may be set in line and all milled exactly alike. THE NUMBER OF TEETH IN MILLS OR CUTTERS.--The teeth of cutters must obviously be spaced wide enough apart to admit of the emery wheel grinding one tooth without touching the next one, and the front faces of the teeth are always made in the plane of a line radiating from the axis of the cutter. In cutters up to 3 inches in diameter, it is good practice to provide 8 teeth per inch of diameter, while in cutters above that diameter the spacing may be coarser, as follows:-- Diameter of cutter 6 inches, number of teeth in cutter 40 " " 7 " " " 45 " " 8 " " " 50 [Illustration: Fig. 1953.] MILLING CUTTERS WITH INSERTED TEETH.--When it is required to use milling cutters of a greater diameter than about 8 inches, it is preferable to insert the teeth in a disk or head, so as to avoid the expense of making solid cutters and the difficulty of hardening them, not merely because of the risk of breakage in hardening them, but also on account of the difficulty in obtaining the uniform degree of hardness or temper. The requirements for the heads for inserted teeth are, that the teeth shall be locked firmly in position without lost motion, and be easily set to gauge, ease of insertion and of removal being of secondary consideration, as such teeth should be ground in their places in the head, and are therefore rarely removed. The manner in which these requirements are attained in the Brainard heads are, as shown in Fig. 1953. A disk of wrought iron of suitable thickness and diameter is turned and squared, then a circle of index holes corresponding to the number of teeth required is drilled in its face; this circle of holes is used to insure the accurate spacing of the dovetail seats for the teeth, and to attain accuracy in grinding the teeth. All the teeth are a driving fit, and being milled are, of course, interchangeable. In order to obtain a larger number of teeth in a given size of head than could be got into the face, only one-half of the teeth are dovetailed into the periphery of the head and the other half into its face, but yet all the teeth are effective for face cutting, the construction being as follows:-- Between each pair of face teeth is a slit sleeve, which meets them and has a taper base, through which passes a taper bolt having a nut on the back face of the head. Tightening this nut expands the sleeve, thus locking the pair of teeth in their dovetail grooves. The circumferential teeth are each counter-based to receive a screw tapped in the head, and are firmly locked thereby. This affords a simple and reliable means of inserting and adjusting other teeth with the certainty that they will be true with those already in use. The large size of some of these heads makes it convenient and desirable to grind them in their places on the machine, and for this purpose a special grinder is made by the same company. This grinder sets upon the machine table and has a point or pin for the index holes or the cutter head; by this means the grinding may be made as accurate as in small milling cutters. The head shown in figure represents one that has been in use ten years, its cutters having been renewed but once; it is 28 inches in diameter, contains 84 teeth, and weighs 400 lbs. Arbors for milling cutters may be driven in two ways. In the first the shank is made taper to fit the taper bore of the live spindle. The standard taper is 1/2 inch per foot of length. The keyway is semicircular, as shown at G in Fig. 1954, the key consisting of a piece of No. 25 Stubbs steel wire, which being of uniform diameter enables a number of keys of different lengths to be easily obtained or made, and the nut is usually cylindrical, having two flat sides, A. Fig. 1955 (from _The American Machinist_) represents an arbor, having a cone at A, so that the cutter bore being coned to correspond, the cutter will run true, notwithstanding that it may not fit the stem B. It is obvious, however, that the nut and washer must be made quite true or the cutter will be thrown out of line with the arbor axis and therefore out of true, and also that such an arbor is not suitable for cutters of a less width of face than the length of the cone A. [Illustration: Fig. 1954.] [Illustration: Fig. 1955.] [Illustration: Fig. 1956.] Shank cutters that have parallel shanks as in Fig. 1928 should have their sockets eased away on the upper half of the bore as denoted by the dotted arc D in Fig. 1956, which will enable the cutter shanks to be made the full size of the socket bore proper, and thus run true while enabling their easy insertion and extraction from the socket. Or the same thing may be accomplished by leaving the socket bore a true circle fitting the cutter shanks in tight, and then easing away that half of the circumference that is above the centre line C in the figure. It is preferable, however, to ease away the bore of the socket, which entails less work than easing away the shanks of all the cutters that fit to the one socket. When the cutter is held in a socket of this kind it allows it to be set further in or out, to suit the convenience of the work in hand, which cannot be done when the cutter has a taper shank fitting into the coned bore of the machine spindles. [Illustration: Fig. 1957.] It is obvious that when the cutter requires to pass within the work, or cut its way, as in the case of milling out grooves, a nut cannot be used; hence, inch cutters are driven by a key as usual, but secured by a screw, as in Fig. 1957, which is from the pen of John J. Grant, in _The American Machinist_. [Illustration: Fig. 1958.] [Illustration: Fig. 1959.] In many cases it becomes a question whether it is better to do a piece of work with plain mills, with an end mill, or with face mills, a common hexagon nut forming an example. Thus, in Fig. 1958, we have a nut being operated upon by a plain mill; in Fig. 1959 by an end mill, and in Fig. 1960 by a pair of twin face mills. In the case of the plain mill, it is obvious that only one side of the nut is operated upon at a time, and as the whole of the pressure of the cut falls on one side of the work it acts to spring or bend the mandrel or arbor used to hold the nut, and this spring is sufficient, if several nuts are milled at once on the same arbor, to make the arbor bend and cause the nuts in the middle to be thicker than those at the ends of the arbor. In the case of hand-forged nuts in which there may be more metal to take off some nuts or some sides of nuts than off others, the extra spring due to an increased depth of cut will make a sensible difference to the size the work is milled to. In the case of the end mill the pressure of the cut falls in line with the arbor axis and downwards; hence the arbor spring is less and does not affect the depth of the cut. In the case of the face mills the pressure of the cut falls on both sides of the work, and the spring is mainly endways of the nut arbor; hence, it does not affect the depth of the cut nor the truth of the work. Furthermore, in both the end and the face mills, the work will be true notwithstanding that the cutter may not be quite true, because each point of the work surface is passed over by every tooth in the cutter, so that the work will be true whether the cutter runs true or not; whereas in the plain mill or cutter each tooth does its individual and independent proportion of finishing. This is shown in Figs. 1961 and 1962. In Fig. 1961 we have the plain mill, and it is obvious that the tooth does the finishing on the vertical line B, that being the lowest point in its revolution. After a tooth has passed that point the work in feeding moves forward a certain distance before the next tooth comes into action; hence to whatever amount a tooth is too high it leaves its mark on the work in the form of a depression, or _vice versâ_, a low tooth will leave a projection. [Illustration: Fig. 1960.] [Illustration: Fig. 1961.] [Illustration: Fig. 1962.] In Fig. 1962 we have a piece of work being operated on by a face mill, and it is obvious that while the teeth perform cutting duty throughout the distance A, yet after the work has fed past the line A it is met by the cutter teeth during the whole time that the work is feeding a distance equal to A on the other side; hence the prolonged action of the teeth insures truth in the work. On the other hand, however, it is clear that the work requires to feed this extra distance before it is finished. [Illustration: Fig. 1963.] Suppose, however, that the cutter being dead true the cutting action ceases on the centre line, and therefore exists through the distance A only, and if we take a plain cutter of the same diameter as in Fig. 1963 we see that its period of feed only extends through the length B, and it becomes apparent that to perform an equal amount of work the face cutter is longer under feed, and therefore does less work in a given time than the plain cutter, the difference equalling twice that between A and B in the two figures, because it occurs at the beginning and at the end of the cut. There is, however, another question to be considered, inasmuch as that the face cutter must necessarily be of larger diameter than the plain one, because the work must necessarily pass beneath the washer (C, Fig. 1915), that is between the two cutters; hence the cutter is more expensive to make. [Illustration: Fig. 1964.] We may in very short work overcome this objection by feeding the work, as at K in Fig. 1964, the face L to be milled requiring to feed the length of the teeth instead of the distance H in the figure. In the end mill the amount of feed also is greater for a given length of finished surface than it is in the plain cutter, as will be readily understood from what has already been said with reference to face mills. Face milling possesses the following points of advantage and disadvantage, in addition to those already enumerated: If the work is sprung by the pressure of the holding devices it is in a line with the plane of motion of the teeth, hence the truth of the work is not impaired. On the other hand, the teeth meet the scale or skin of the work at each cut, whereas in a cylindrical cutter this only occurs when the cutter first meets the work surface. The strain of the cut has more tendency to lift the work table than in the case of a cylindrical cutter. The work must be held by end pressure; hence the chuck or holding jaws must be narrower than the work, rendering necessary more work-holding devices. Since, however, both sides of the work are simultaneously operated on, there is no liability of error in parallelism from errors in the second chucking, as is the case with plain cutters. [Illustration: Fig. 1965.] [Illustration: Fig. 1966.] To cut [V]-shaped grooves in cylindrical work, when it is required that one face or side of the groove shall be a radial line from the centre of the work, two methods may be employed. First we may form the cutter, as in Fig. 1965, the side B of the cutter being straight and the point of the cutter being set over the centre of the work. The objection to this is that the finished groove will have a projection or burr on the radial side of the groove, as shown at D in the figure, entailing the extra labor of filing or grinding, to remove it; furthermore, that face will have fine scored marks upon it, as denoted by the arcs at C, these scores showing very plainly if the cutter has any high teeth upon it, and more especially in the case of cutting spirals, as will appear presently. The reason of this is that the side B of the cutter being straight or flat the whole of the teeth that are within the groove have contact with the side C of the groove, that is to say, all the teeth included in the angle E in the figure, because the teeth on the side A tend, from the pressure of the cut to force the cutter over towards the side C of the groove. The second method referred to, which is that commonly adopted for cutting the flutes of tapes, reamers, milling cutters, &c., is to form the cutter on the general principle illustrated in Fig. 1966, and set it to one side of the centre of the work so that one of its faces forms a radial line, as shown in the figure, the distance to which it is set to one side depending upon the angle of its cutting edge to the face of the cutter. [Illustration: Fig. 1967.] Fig. 1967 represents a common form of cutter of this class that is used for cutting spiral grooves on milling cutters up to 3 inches in diameter, which contain eight teeth per inch of diameter. The angle of the teeth on B is 12° to the side face A of the cutter, and the angle of the teeth at C is 40° to the face D. The effect produced by making face B at an angle instead of leaving it straight, or in other words, instead of cutting the teeth on the face A, may be shown as follows:-- [Illustration: Fig. 1968.] Suppose that in Fig. 1968 we have a sectional view taken through the middle of the thickness of a cutter for a rectangular groove, the circumferential surface being at a right angle to the side faces, and it is evident that the teeth, at every point in their length across the cutter, except at the extreme corner that meets the side faces as C, will have contact with the seat of the groove while passing through the angle F only (which is only one half of the angle E in Fig. 1965); or in other words, each tooth will have contact with the seat of the groove as soon as it passes the line G, which passes through the axis of the cutter; whereas, when the teeth are parallel with the side of the cutter, as was shown in Fig. 1965, the teeth continue to have contact with the side walls of the groove after passing the line G. By forming the cutter as in Fig. 1967, therefore, we confine the action to the angle F, Fig. 1968, the teeth having contact with the walls of the groove as soon as they pass the line G. [Illustration: Fig. 1969.] In cutting spiral grooves this is of increased importance, for the following reasons: In Fig. 1969 we have a cutter shown in section, and lying in a spiral groove. Now suppose a tooth to be in action at the bottom of the groove, and therefore on the line G G, and during the time that it moves from that line until it has moved above the level of the top of the groove, the work will have performed some part of a revolution in the direction of the arrow, and has therefore moved over towards that side of the cutter; hence, if that side of the cutter had teeth lying parallel, as shown at B in Fig. 1965, the walls of the groove would be scored as at C in that figure, whereas by placing the teeth at an angle to the side face, they recede from the walls after passing line G, and therefore produce smoother work. A cutter of this kind must, for cutting the teeth of cutters, be accurately set to the work, and the depth of cut must be accurate in order to cut the grooves so that one face shall stand on a radial line, and the top of the teeth shall not be cut to a feather edge. If the teeth were brought up to a sharp edge the width of the groove at the top would be obtained with sufficient accuracy by dividing the circumference of the work by the number of flutes or teeth the work is to contain, but it is usual to enter the cutter sufficiently deep into the work to bring the teeth tops up to not quite a sharp edge. The method of setting the cutter is to mark on the end of the work a central line R, Fig. 1970, and make the distance E in same figure equal to about one tenth the diameter of the work. [Illustration: Fig. 1970.] [Illustration: Fig. 1971.] Obviously the cutter is set on opposite sides of the work centre, according to which side of the groove is to have the radial face. Thus for example, in Fig. 1970, the cutter is set to the left of line R, the radial face of the groove being on the left, while in Fig. 1971 the cutter is set on the right of line R, because the radial face is on the right hand side of it, the work consisting (in these examples) in cutting up a right and a left-hand mill or cutter. The acting cutter J may in both cases be used to cut either a right or a left-hand flute, according to the direction in which the work W is revolved, as it is fed beneath the cutter J. [Illustration: Fig. 1972.] In Fig. 1972 we have an example of cutting straight grooves or teeth, with an angular cutter having one side straight, and it is seen that we may use the operating or producing cutter in two ways: first, so that the feed is horizontal, as at A, or vertical, as at B; the first produces a right-hand, and the second a left-hand cutter, as is clearly seen in the plan, or top view. The feeds must, however, be as denoted by the respective arrows being carried upwards for B, so that the cutter may run under the cut and avoid cutter breakage. [Illustration: Fig. 1973.] The number of grooves or flutes producible by an angular cutter depends upon the depth of the groove and the width of land or tooth between the grooves. Thus Fig. 1973 represents a cutter producing in one case four and in the other eight flutes with the same form of cutter, the left being for taps, and the right for reamers. For cutting the teeth of cutters or mills above 3 inches in diameter, the angles of the acting or producing cutter are changed from the 12° and 40° shown in Fig. 1967, to 12° as before on one side, and a greater number on the other; thus in the practice of one company it is changed to 12° and 48°, the 12° giving the radial face as before, and the 48° giving a stronger and less deep tooth, the deep tooth in the small cutters being necessary to facilitate the grinding of the teeth to sharpen them. In cutting angular grooves in which the angle is greater on one side than on the other of the groove, the direction of cutter revolution and the end of the work at which the groove is started; or in other words, the direction of the feed, is of importance, and it can be shown that the feed should preferably be so arranged that the side of the groove having the least angle to the side of the cutter should be the one to move away from the cutter after passing the lowest point of cutter revolution. [Illustration: Fig. 1974.] In Fig. 1974, for example, we have at R a cylinder with a right-hand groove in it, whose side C, representing the face of a tooth, is supposed to be a radial line from the cylinder axis, the side B representing the back of a cutter tooth, being at an angle of 40°. Now if the work revolves in the direction of arrow A, and the cut be started at end G (as it must to cut a right-hand groove with the work revolving as at A), then the side C of the groove will move over towards and upon the side of the cutter for the reasons explained with reference to Fig. 1969, and the teeth on this side being at the least angle to the side of the cutter, do not clear the cut so well, the teeth doing some cutting after passing their lowest point of revolution--or in other words, after passing the line G in Fig. 1968. The effect of this is to cause the cutter to drag, as it is termed, producing a less smooth surface on that side (C) of the groove or tooth. We may, however, for a right-hand groove revolve cylinder R, as denoted by arrow E, and start the cut at end D. The result of this is that the side C of the groove, as the roller revolves, moves away from the side of the cutter, whose teeth therefore do no cutting after passing their lowest point of revolution (G, Fig. 1968), and the dragging action is therefore avoided, and the cut smoother on this which is the most important side of the tooth, since it is the one possessing the cutting edge. When "dragging" takes place the burr that was shown in Fig. 1965 at D, is formed, and must, as stated with reference to that figure, be removed either by filing or grinding. Obviously if the direction of cutter revolution and of feed is arranged to cause side C to move away from the side of the cutter, then side B will move over towards the other side of the cutter; but on account of the cutter teeth on this side being at a greater angle to the side of the cutter, they clear better, as was explained with reference to Fig. 1968, and the dragging effect caused by the revolving of the work is therefore reduced. [Illustration: Fig. 1975.] We have now to examine the case of a left-hand groove, and in Fig. 1975 we have such a groove in a cylinder L. Let it be supposed that the direction of its revolution is as denoted by arrow F, and if the cutter is started at H (as it must be to cut a left-hand groove if the work revolves as at F), then the side C moves over towards the cutter, and the dragging or crowding action occurs on that side; whereas if the direction of revolution is as at K, and the cutter starts at N and feeds to H, then side B of the groove moves towards the cutter; hence face C of the groove is cut the smoothest. Obviously then the direction of cutter and work revolution and of feed, in cutting angular grooves in which one angle of the cutter is at a greater degree of angle than the other to the side of the cutter, should be so arranged that the work revolves towards that side of the cutter on which its teeth have the greater angle, whether the spiral be a right-hand or a left-hand one. In cutting grooves not truly circular the same principle should be observed. [Illustration: Fig. 1976.] In Fig. 1976, for example, it is better if the side B is the one that moves towards the cutter, the direction of revolution being as denoted by the arrow, whether the groove be a right-hand or left-hand (supposing, of course, that the cutter starts from end E of the work). Obviously, also, the greater the degree of spiral the more important this is, because the work revolves faster in proportion to the rate of feed, and therefore moves over towards the outer faster. In cutting spirals it is necessary first to put on such change gears as are required to revolve the work at the required speed for the given spiral, and to then set the work at such an angle that the cutter will be parallel to the groove it cuts, for if this latter is not the case the groove will not be of the same shape as the cutter that produces it. [Illustration: Fig. 1977.] In Fig. 1977 we have a spiral so set, the centre of the cutter and of the groove being in the line O O, and the work axis (which is also the line in which the work feeds beneath the cutter) being on the line C C. The degrees of angle between the centre of the cutter, or line O O, and the axis of the work, or line C C, are the number of degrees it is necessary to set the work over to bring the cutter and the groove parallel, this number being shown to be 20 in the example. [Illustration: Fig. 1978.] To find this angle for any given case we have two elements: first, the pitch of the spiral, or in other words, the length or distance in which it makes one complete turn or revolution; and second, the circumference of the work; for in a spiral of a given pitch the angle is greater in proportion as the diameter is increased as may be seen in Fig. 1978, in which the pitch of the spirals is that in Fig. 1977, while the angle is obviously different. To find the required angle for any given case we may adopt either of two plans, of which the first is to divide the circumference of the work in inches by the number of inches which the spiral takes to make one turn. This gives us the tangent of angle of the spiral. The second method of setting the work to cut a given spiral is to chuck the work and put on the necessary change gears. The cutter is then set to just touch the work and the machine is started, letting the work traverse beneath the cutter just as though the work was set at the required angle to the cutter: When the cutter has arrived at the end of the work it will have marked on it a line, as in Fig. 1979, this line representing the spiral it will cut with those change gears, and all that remains to do is to swing the work over so that this line is parallel with the face of the cutter, as shown in Fig. 1980. If the diameter of the cutter is small we may obviously secure greater accuracy by placing a straight-edge upon the side of the cutter so as to have a greater length to sight by the eye in bringing the line fair with the cutter. This being done it remains to merely set the cutter in its required position with reference to the work diameter. If an error be made in setting the angle of the work to the cutter the form of groove cut will not correspond to that of the cutter. This is shown in Fig. 1981, in which the cutter being at an angle to the groove the latter is wider than the cutter thickness, and it is obvious that by this means different shapes of grooves may be produced by the same cutter. In proportion, however, as the cutter is placed out of true the cutting duty falls on the cutting edges on one side only of the cutter, which is the leading side C in the figure, while the duty on the other side, B, is correspondingly diminished. [Illustration: Fig. 1979.] [Illustration: Fig. 1980.] [Illustration: Fig. 1981.] The simplest method of holding work to be operated upon in the milling machine is either between the centres or in the vice that is provided with the machine. The principles involved in holding work in the vise so as to keep it true and avoid springing it for milling machine work, are the same as those already described with reference to shaping machine vises. In milling tapers the work, if held in centres, should be so held that its axial line is in line with the axes of both centres, for the following reasons:-- [Illustration: Fig. 1982.] [Illustration: Fig. 1983.] [Illustration: Fig. 1984.] In Figs. 1982 and 1983 we have a piece of work in which the axes of the centres and of the work are not in line, and it is clear that the horn _d_ of the dog D will, in passing from the highest to the lowest point in its revolution, move nearer to the axis of the work. Suppose, then, that the driver E is moved a certain portion of a revolution with tail _d_ at its highest point, and is then moved through the same portion of a revolution with _d_ at its lowest point in its path of revolution, and being at a greater distance or leverage when at the top than when at the bottom it will revolve the work less. Or if the tail _d_ of the dog is taper in thickness, then in moving endways in the driver E (as it does when the work is revolved) it will revolve the work upon the centres. Suppose, then, that the piece of work in the figures required to be milled square in cross-section, and the sides would not be milled to a right angle one to another. This is avoided by the construction of the Brainard back centre, shown in Fig. 1984, in which T represents the surface of the work table and H the back centre. The block B is fitted within head H, and has two slots A A, through which the bolts S S pass, these bolts securing B in its adjusted position in H. The centre slide C operates in B; hence B, and therefore C, may be set in line with the work axis. [Illustration: Fig. 1985.] For heads in which the back centre cannot thus be set in line, the form of dog shown in Fig. 1985 (which is from _The American Machinist_) may be employed to accommodate the movement of the tail or horns through the driver. Its horn or tail B is made parallel so as to lie flat against the face of the slot in the driver. The other end of tail B is pivoted into a stud whose other end is cylindrical, and passes into a hub provided in one jaw of the dog, the set-screw A being loosened to permit this sliding motion. This locks the horn in the clamp and permits the dog to adjust itself to accommodate the motion endwise that occurs when it is revolved. The amount of this motion obviously depends upon the degree of taper, it being obvious (referring to Fig. 1982) that horn _d_ would pass through the chuck, as denoted by the dotted lines, when at the bottom of its path of revolution. [Illustration: Fig. 1986.] It is obvious that when the head or universal head of the machine is elevated so that it stands vertical, it may have a chuck screwed on and thus possess the capacity of the swiveled vise. It is preferable, however, to have a separate swiveled chuck, such as in Fig. 1986 (from _The American Machinist_), which will not stand so high up from the machine bed, and will therefore be more solid and suitable for heavy work. [Illustration: Fig. 1987.] Another very handy form of chuck for general work is the angle chuck shown in Fig. 1987, which is from an article by John J. Grant, in _The American Machinist_. The work-holding plate has [T]-grooves to chuck the work on and is pivoted at one end, while at the other is a segment and bolt to secure it in its adjusted angle. Two applications of the chuck are shown in the figure. [Illustration: Fig. 1988.] [Illustration: Fig. 1989.] Fig. 1988 represents a top, and Fig. 1989 an end view of a chuck to hold rectangular bars that are to be cut into pieces by a gang of mills. A, A, A, are grooves through the chuck jaws through which the cutters pass, severing the bar through the dotted lines. Each piece of the bar is held by a single screw on one side and by two screws on the other, which is necessary in order to obtain equal pressure on all the screws and prevent the pieces from moving when cut through, and by moving, gripping the cutters and causing them to break. In chucking the bar the two end screws D D must be the first to be set up to just meet the bar: next the screws B C on the other side must be set up, holding the bar firmly. The two screws between D D are then set up to just bind the bar, and then the middle four on the other side are screwed up firmly. By this method all the screws will hold firmly and the pieces cannot move. VERTICAL MILLING, DIE SINKING, OR ROUTING MACHINE.--Fig. 1990 represents Warner & Swazey's die sinking machine. The cutter driving spindle is here driven by belt direct, imparting a smooth motion. The knee is adjustable for height on the vertical slideway on the face of the column, which is provided with a stop adjustable to determine how high the knee and work-holding devices can be raised, and, therefore, the depth to which the cutter can enter the work, and a _former_ pin is placed 6 inches behind the cutter to act as a stop against which a pattern may be moved when work is to be copied from a _former_ or pattern piece. The work-holding device consists of a compound rest and a vise capable of being swiveled to any angle or of being revolved to feed the work to the cutter, hence the work may be moved in any required direction, in either a straight line, in a circle, or in any irregular manner to suit the shape of the work. PROFILING MACHINE.--The profiling machine is employed mainly to cut the edges of work, and to sink recesses or grooves in the upper surface of the same to correspond to a pattern. A provisional template of the form of the work is fastened on the bed of the machine, and from this is cut in the machine a thicker one termed the "former," which is then used to copy the work from. Fig. 1991 represents Pratt & Whitney's profiling machine. On the cross slide are two separate sliding heads, each of which carries a live spindle for the cutting tool, and beside it a spindle to receive a pin, which by being kept against the pattern or _former_ causes the work to be cut to the same shape as the former. The work is fastened to the table, which is operated upon the raised [V]s shown by the handle on the left, which operates a pinion geared to a rack on the underneath side of the table. The handle on the right operates the heads along the cross slide also by a rack and pinion motion. The gearing and racks in both cases are double, so that by two independent adjusting screws the wear of the teeth may be taken up and lost motion prevented. By means of these two handles the work may be moved about the cutter with a motion governed by the form or shape of the _former_, of which the work is thus made a perfect pattern both in size and shape. The tool used is a shank or end mill, such as was shown in Fig. 1928. In some profiling machines the spindle carrying the guide or former pin is stationary, in which case the provisional template is put beneath it and the _former_ is cut by the live spindle, and for use must be moved from the position in which it was cut and reset beneath the _former_ spindle. This machine, however, is provided with Parkhurst's improvement, in which the _former_ spindle is provided with a gear-wheel, by which it may be revolved from the live spindle, hence the provisional template may be set beneath the live spindle in which the guide pin is then placed. The cutter is then placed in the _former_ spindle, and the _former_ cut to shape from the provisional template while in the actual position it will occupy when used. [Illustration: Fig. 1990.] [Illustration: Fig. 1991.] [Illustration: Fig. 1992.] Fig. 1992 represents Brainard's machine for grinding milling cutters. It consists of a threaded column A to which is fitted the knee B, which as it fits the top of the threads on the column may be swung or revolved about the column without being altered in its height upon the same except by means of the threaded ring C. At D is a lever for clamping the knee B to the column after adjustment; W represents the emery wheel mounted on the end of the horizontal spindle having journal bearing at the top of the column. The face of the knee B has a slideway _d_ for the fixtures, &c., which hold the cutters to be ground, and at E is a lug pierced to receive an arbor whereon to place cutters to be ground, the lug being split and having a binding screw to lock the arbor firmly in place. F is a slide for receiving the grinding attachments, one of which is shown at K carrying a milling cutter in position to be ground on the face. Fig. 1993 shows the fixture employed to grind parallel cutters, S representing a stand upon slide F (which corresponds to slide F in the general view of the machine in Fig. 1992) in which is fixed the arbor H. The cutter C is slid by hand along arbor H and beneath the emery wheel, the method of guiding the cutter to the wheel being shown in Fig. 1994, which represents a front view of the machine. At E is the lug (shown also at E in the general view) which has a hole to receive a rod P, and is split through at S, so that operating binding screw L locks rod P in E. At R is a rod secured to the rod P, and G is a gauge capable of swivelling in the end of R and of being secured in its adjusted position. The end of this gauge is adjusted to touch the front face of the tooth to be ground on the cutter C, which must be held close against the end of the gauge in order to grind the cutting edge to a straight line parallel to its axis. A not uncommon error is to place the gauge G against the tooth in front of that which is being ground, as in Fig. 1995, the gauge being against tooth C while tooth B is the one being ground. In this case the truth of the grinding depends upon the accuracy of the tooth spacing. Suppose, for example, that teeth B and C are too widely spaced, tooth C being too far ahead, and this error of spacing would cause tooth B to be too near the centre of the emery wheel and its cutting edge to be ground too low. [Illustration: Fig. 1993.] [Illustration: Fig. 1994.] [Illustration: Fig. 1995.] The object of feeding the cutter by hand along the arbor H is twofold: first, the amount of cut must be very light and the feed very delicate, for if the grinding proceeds too fast the cutting edge will be what is termed burned, that is to say, enough heat will be generated to soften the extreme cutting edge, which may be discovered by holding the front face of the tooth to the light, when a fine blue tint will be found along the cutting edge, showing that it has been softened in the grinding, and this will cause it to dull very rapidly. [Illustration: Fig. 1996.] The second object is to insure parallelism in the cutter. Suppose, for example, that the cutter C was fast upon arbor H and was fed to the wheel by moving slide F, and if the arbor H stood at an angle, as in Fig. 1996, to the slide upon which F moved, the cutter would be ground taper, whereas if the cutter is fed along the arbor it will be ground parallel whether the arbor is true or not with the slideway of F, the only essential being that the arbor H be parallel and straight, which is much easier to test and to maintain than it is in the slideway (D, Fig. 1992). Here it may be noted that oil should not be applied either to arbor H or to the cutter bore or slideway D, as lubrication only increases the wear of the parts, causing the fine emery particles that inevitably fall upon them to cut more freely. As thin cutters would not have sufficient length of bore to steady them upon the arbor and insure parallelism, the cutter sleeve shown in Fig. 1997, which is from _The American Machinist_, is employed to hold them. It is provided with a collar, is threaded at T for the nut N to hold the cutter against collar C, and is bored to fit the cutter arbor H, which corresponds to H in Fig. 1993. This device also affords an excellent means of holding two or more thin cutters requiring to be ground of exactly equal diameters. It follows from what has been said that taper tools, such as taper reamers, must be held with their upper face parallel to the line of their motion in being fed to the wheel, as in Fig. 1998, in which line M represents this line of motion, line N the axis of the reamer, and line O the line on which the fixture that holds the reamer must move, O being parallel to M. Fig. 1999 represents Slate's fixture for this class of work. A is a stand that bolts upon the slideway _d_ in Fig. 1992. Upon A is fixed a rectangular bar B, upon which (a sliding fit) is the shoe C. Upon C fits the piece D, which is pivoted to shoe C by the pin at E. At the other end of D is a lug, against which abuts the end of screw G, which is threaded through the end of C, so that by operating the screw G, D may be set to any required angle upon C, and at F is a set-screw threaded through D and abutting against C, so as to lock D in its adjusted position. At P is a pointer for the graduations on C, which are marked to correspond with the graduations upon the taper turning attachment of a lathe. [Illustration: Fig. 1997.] [Illustration: Fig. 1998.] [Illustration: Fig. 1999.] The work is held between centres, the head H fitting to a slideway on the top of D, and being secured in its adjusted position by the screw I. The work should obviously be set so that its upper face lies horizontal, and is fed to the wheel by moving shoe C by hand along bar B, the long bearing keeping C steady, and the lightness of the moving parts making the feeding more sensitive than it would be were it required to move bar B. The tooth being ground is held by hand against the gauge G in Fig. 1994, as was described with reference to that figure, and the reamer, therefore, in the case of having spiral grooves, revolves upon its centre while being fed to the emery wheel. For tapers that are beyond the capacity of this device, and also for holding cutters to have their face teeth ground, the device shown in Fig. 2000 is employed. Upon the slide F is fixed knee K (the corresponding parts to which are seen in the general view, Fig. 1992), whose disk face at R is graduated as shown. Piece S is pivoted by a pin passing through the hub of K and having a nut T to secure it in its adjusted position. S is bored to receive the cutter arbor H, and is split through so that by means of the screw at V the arbor may be gripped and locked in S. The stud W for holding the gauge G passes into a bore in the bracket X, and is secured therein by the screw at Y, the lugs through which Y passes being split through into the bore for W. As shown in the figure, the arbor H is set for grinding the side teeth of the cutter, but it is obvious that S being pivoted to K may be swung out of the vertical and to any required angle, so as to bring the face of the tooth that is to be ground horizontally beneath the emery wheel, as shown in Fig. 2001, which represents an angular cutter in position. We have now to consider the adjustment of the cutter to the emery wheel, necessary in order that the cutting edges may be given the necessary clearance. First, then, suppose in Fig. 2002 that the line A A represents the line of centres of the emery-wheel spindle and the cutter arbor, and if the front face B of the tooth be set coincident with this line, as in the figure, then the top of the tooth partaking of the curvature of the wheel that grinds it would have its heel C the highest; hence the edge at B could not cut. If, however, the line A A in Fig. 2003, still representing the line of centres, we so set the gauge (G, Fig. 1994) that the heel C of the tooth comes up to line A A, then the curvature of the emery wheel would give clearance to the heel C, and therefore a cutting edge to face B of the tooth. [Illustration: Fig. 2000.] [Illustration: Fig. 2001.] [Illustration: Fig. 2002.] The amount of clearance that may be given in this way is limited by the spacing of the teeth and the diameter of the emery wheel, as is seen from Fig. 2004, it being obvious that when tooth A is being ground the emery wheel must clear the rear tooth B or it will grind its edge off, and it is obvious that the smaller the emery-wheel diameter the more the tooth to be ground may be set in advance of the line of centres of the wheel and spindle. It may be pointed out, however, that there are two methods of adjusting the cutter to the wheel. In Fig. 2005, for example, let A A represent the line of centres of the cutter and the wheel, and line B the plane of the front face of the tooth being ground; and in Fig. 2006 let line A represent a vertical line from the axis of the wheel, and B a vertical line passing through the axis of the cutter, the tooth edge C occupying the same position in both figures. Now suppose we employ cutting edge C as a centre and swing the cutter until its axis or centre moves along the arc D to the dot E, and it is evident that during this motion the heel of the tooth will have approached the axis of the emery wheel and that more clearance will therefore have been given to the cutting edge C. The actual curve of the top face, as C, Fig. 2007, of the tooth T will remain the same in either case, but its position with relation to the front face will be altered. As this curve is greater in proportion as the diameter of the emery wheel is diminished, and as the curvature weakens the cutting edge of the tooth, it is obviously desirable to employ a wheel of as large a diameter as possible. To eliminate this curvature it would appear that the position of the emery wheel might be reversed, as in Fig. 2008, but as the emery wheel would wear only where in contact with the tooth, it would gradually assume the shape in Fig. 2009, there being a shoulder at S that would destroy the cutting edge of the tooth. This may to a great extent be remedied by presenting the cutter diagonally to the wheel, as in Fig. 2010, employing a wheel so thin that the whole of its face will cross the tooth top during a revolution. Or if the side faces of the wheel be recessed, leaving only a narrow annular grinding ring at the circumference, the wheel might be mounted as in Fig. 2011, thus making the top of the tooth quite flat. It may be observed, however, that the usual plan is to revolve the wheel at a right angle to the work axis, as was shown in Fig. 1994. [Illustration: Fig. 2003.] [Illustration: Fig. 2004.] [Illustration: Fig. 2005.] [Illustration: Fig. 2006.] [Illustration: Fig. 2007.] [Illustration: Fig. 2008.] [Illustration: Fig. 2009.] [Illustration: Fig. 2010.] [Illustration: Fig. 2011.] In grinding cutters having their teeth a right-hand spiral, care must be taken that in grinding one tooth the emery wheel does not touch the cutting edge of the next tooth. Thus in Fig. 2013 it is seen that the corner C of the emery wheel is closer than corner D, and being at the back of the wheel and out of sight it is apt to touch at C unless a thin emery wheel be used. In a left-hand spiral, Fig. 2012, it is the corner D that is apt to touch the next tooth, the liability obviously being greatest in cutters of large diameter. The emery wheel should be of a grade of not less than 60 or more than 70. If it is too coarse it leaves a rough edge, which may, however, be smoothed with an oilstone slip. If the wheel is too fine it is apt to _burn_ the cutter, or in other words, to soften the cutting edge, which may be known by a fine blue burr that may be seen on the front face of the tooth, the metal along this line being softened. The diameter of the wheel may be larger for small cutters than for large ones, since the teeth of small cutters clear the wheel better. The larger the wheel the less the curvature on the top of the tooth. [Illustration: Fig. 2012.] [Illustration: Fig. 2013.] For general work a diameter of 2-1/2 inches will serve well, the thickness being about 5/16 inch or 3/8 inch. The speed of a wheel of this diameter varies in practice from 3,000 to 4,500 revolutions per minute, but either too fast or too slow a speed will cause the wheel to burn the cutter, and the same thing will occur if the cutter is fed too fast to the wheel, or if too deep a cut is taken. The finishing cut should obviously be very small in amount, especially in cutters of large diameter, for otherwise the wear in the diameter of the wheel will sensibly affect the teeth height, those last ground being the highest. CHAPTER XXIII.--EMERY WHEELS AND GRINDING MACHINERY. EMERY WHEELS AND GRINDING.--Emery grinding operations may be divided into four classes as follow:-- 1st. Tool or cutter grinding, in which the emery wheel is used to sharpen tools which, from their shape, were formerly softened and sharpened by the file, already largely treated in the preceding chapter. 2nd. Cylindrical grinding, in which both the work and the emery wheel are revolved, as has been explained with reference to grinding-lathes. 3rd. Flat surface grinding, in which the emery wheel takes the place of the ordinary steel cutting tool; and 4th. Surface grinding, in which the object is to remove metal or to smoothen surfaces. The distinctive feature of the various makes of solid emery wheels lies in the material used to cement the emery together, and much thought and experiment are now directed to the end of discovering some cementing substance which will completely meet all the requisite qualifications. Such a material must bind the emery together with sufficient strength to withstand the centrifugal force due to the high speeds at which these wheels must be run to work economically; and it must neither soften by heat nor become brittle by cold. It must not be so hard as to project above the surface of the wheel; or in other words, it should wear away about as fast as does the emery. It must be capable of being mixed uniformly throughout the emery, so that the wheel may be uniform in strength, texture, and density. It must be of a nature that will not spread over the surface of the emery, or combine with the cuttings and form a glaze on the wheel, which will prevent it from cutting. This glazing is, in fact, one of the most serious difficulties to be encountered in the use of emery wheels for grinding purposes, while it is a requisite for polishing uses, as will be explained farther on. Many of the experiments to prevent glazing have been in the direction of discovering a cement which would wear away under about the same amount of duty as is necessary to wear away the cutting angles of the grains of emery, thus allowing the emery to become detached from the wheel, rather than to remain upon it in a glazed condition. With the same grade of emery the wheel will cut more freely and glaze less in proportion as the cementing material leaves the wheel softer, but the softer the wheel the more rapidly it will wear away; indeed it is the dislodgement of the emery points as soon as they have become dulled that produces freedom from glazing. It may be remarked, however, that the nature of the material operated upon has a good deal to do with the glazing; thus wrought iron will glaze a wheel more quickly than hardened steel, and brass more quickly than wrought iron, while on the other hand soft cast iron has less tendency than either of them to glaze. Glazing occurs more readily in all cases upon fine than upon coarse wheels. Glazing is more apt to occur as the work is pressed more firmly to the wheel, and with broad and flat surfaces rather than with cylindrical ones. An excellent material for removing the glaze from an emery wheel is a piece of ordinary pumice stone. The principal cements used in the manufacture of emery wheels are as follows, each representing the cement for one make of wheel:-- 1. Hard rubber. 2. Chemical charcoal (leather cut down by acid and used to prevent shrinkage), and glue. 3. Oxychloride of zinc. 4. Shellac. 5. Linseed oil and litharge. 6. Silicate of soda and chloride of calcium. 7. Celluloid. 8. Oxychloride of magnesium. 9. Infusoria. 10. Ordinary glue. The vitrified emery wheel is made with a cement which contracts slightly while cooling, leaving small pores or cells through which water, introduced at the centre, is thrown (by centrifugal force) to the surface. This causes, when the wheel is rotating, a constant flow of water from the centre to the surface, carrying off the cuttings and the detached emery. In order that an emery wheel shall run true with its bore it must fit the driving spindle, and in order that it may do this closely the wheel bore is sometimes filled with lead, the latter being bored out to fit the spindle. If the bore of the emery wheel itself were made a tight fit to the spindle it would abrade the spindle in being put on, and the pressure of the fit if any would tend to split the wheel. A common method of securing emery wheels to their spindles is to fill the bore of the wheel with lead, and bore it out to fit the spindle of the emery grinding machine. The flanges between which the wheel is held are recessed so as to grip the wheel at and near their perimeters only. Between the flange and the wheel a thin disk of sheet-rubber is sometimes used to afford a good bedding for the flange. The forms of the perimeters of emery wheels are conformed to suit the form of the work to be ground, and it is found that from the great strength of the emery wheel it can be used to a degree of thinness that cannot be approached in any kind of grinding stone. For instance, vulcanite emery wheels 18 inches in diameter and having 3/16 inch thickness, or face as it is commonly termed, are not unfrequently used at a speed of some 5,000 feet of circumferential feet per minute, whereas it would be altogether impracticable to use a grindstone of such size and shape, because the side pressure would break it, no matter at what speed it were run. Indeed, in the superior strength of the emery wheels of the smaller sizes lies their main advantage, because they can be made to suit narrow curvatures, sweeps, recesses, &c., and run at any requisite speed under 5,000 feet per minute, and with considerable pressure upon either their circumferential or radial faces. GRADES OF COARSENESS OR FINENESS OF EMERY WHEELS.--Emery is found in the form of rock, and is crushed into the various grades of fineness. The crushing is done either between rollers or by means of stamps, the latter, however, leaves the corners of the grains the sharpest, and hence the best for cutting, though not for polishing purposes. The grades of emery are determined by passing the crushed rock through sieves or wire cloths having from eight to ninety wires to the inch; thus, emery that will pass through a sieve of sixty wires to the inch is called No. 60 grade. The finest grade obtained from the manufactory is that which floats in the atmosphere of the stamping room, and is deposited on the beams and shelves, from where it is occasionally collected. Washed emery is used by plate-glass workers, opticians, and others that require a greater degree of fineness than can be obtained by the sieve. The numbers representing the grades of emery run from 8 to 120, and the degree of smoothness of surface they leave may be compared to that left by files as follows: 8 and 10 represent the cut of a wood rasp 16 " 20 " " coarse rough file 24 " 30 " " ordinary rough file 36 " 40 " " bastard " 46 " 60 " " second cut " 70 " 80 " " smooth " 90 " 100 " " superfine " 120, F & FF " " dead smooth " The F and FF emery is flour emery which has been washed to purify it. The following are the kinds of wheel suitable for the respective purposes named:-- Kind of work. Kind of wheel. For rough grinding, such as on the edges of iron } or steel plates, for removing the protuberances on } Coarse grain and castings or on narrow surfaces where rough grinding } hard texture. is sufficient. } For narrow surfaces, such as moulding knives, lathe } Medium grain and tools, saw gumming, &c. } hard texture. For free cutting without gumming on broad surfaces } Medium grain and on iron, steel, or brass. } soft texture. For grinding fine tools, such as milling machine } cutters, or for work in which the duty is not great } Fine grain and while the wheel requires to keep its shape and keep } soft texture. true. } For smooth grinding on soft metals, as cast iron } Fine grain and and brass. } hard texture. [Illustration: Fig. 2014.] When the work is presented to the wheel unguided, the wheel wears out of true, because the work can follow the wheel, hence it becomes necessary to true the wheel occasionally. This can be done by a tool such as in Fig. 2014, which is applied by hand on the hand rest, and corresponds to the tool shown in Fig. 2061 for grindstones, or by the use of a diamond set in a tool to be held by hand or in a slide rest. The diamond produces the most true and smooth work, but the cut of the wheel is at first impaired by the action of the diamond, which is not the case with the tool in Fig. 2014. Corundum is a mineral similar to emery, and corundum wheels are made and used in the same manner as emery wheels. Their cutting qualifications are, however, superior to those of the emery wheel, both cutting more freely and being more durable with less liability to glaze. SPEEDS FOR EMERY WHEELS.--The speed at which an emery wheel may be run without danger of bursting varies according to the thickness or breadth of face of the wheel, as well as according to the quality of the cementing material and excellence of manufacture. Hence, although a majority of manufacturers recommend a speed of about 5,000 circumferential feet per minute, that speed may be largely exceeded in some cases, while it would be positively dangerous in others. It is, in fact, impracticable in the operations of the workshop to maintain a stated circumferential speed, because that would entail a constant increase of revolutions to compensate for the wear in the diameter of the wheel. Suppose, for example, that a wheel when new is a foot in diameter: a speed of about 1,600 revolutions per minute would equal about 5,000 circumferential feet; whereas, when worn down to 2 inches in diameter, the revolutions would require, to maintain the same circumferential speed, to be about 9,500 per minute, entailing so many changes of pulleys and counter-shafting as to be impracticable. In practice, therefore, a uniform circumferential speed does not exist, the usual plan adopted being to run the large-sized wheels, when new, at about the speed recommended by the manufacturer of the kind of wheel used, and to make such changes in the speed of the wheel during wear as can be accomplished by changing the belt upon a three-stepped cone pulley, and perhaps one, or at most two, changes of pulley upon the counter-shaft. It is sometimes practicable to use wheels of a certain diameter upon machines speeded to suit that diameter, and to transfer them to faster speeded machines as they diminish in diameter. Even by this plan, however, only an approximation to a uniform speed can in most cases be obtained, because as a rule certain machines are adapted to certain work, and the breadth of face and form of the edge of the emery wheel are very often made to suit that particular work. Furthermore, a new wheel is generally purchased of such a size, form, and grade of emery as are demanded by the work it is intended at first to perform. Neither is it, as a rule, practicable to transfer the work with the diametrically reduced wheel to the lighter and faster-speeded grinding machine. So that, while it is desirable to run all emery wheels as fast as their composition will with safety admit, yet there are practical objections to running small wheels at a rate of speed sufficient to make their circumferential velocities equal to those of large wheels. The speeds recommended for the various kinds of wheels now in use vary from about 2,700 to 5,600 circumferential feet per minute; but the speeds obtaining in workshops average between 2,000 and 4,000 feet for wheels 3 inches and less in diameter, and from about 3,000 to 5,600 feet for wheels above 12 inches in diameter. Wheels above 15 inches in diameter, and of ample breadth of face, are not unfrequently run at much greater velocities. On account of the high velocity at which emery wheels operate, it is necessary that they be very accurately balanced, otherwise the unequal centrifugal motion causes them to vibrate very rapidly, every vibration leaving its mark upon the work. The method of balancing adopted by one firm is as follows: The arbors are of cast iron, and are cast standing vertical so as to induce equal density in the metal, it having been found that if the arbors were cast horizontally the lower part of the metal would from the weight of the molten metal be more dense than that at the top of the casting. In casting the arbors upright, the difference in the density of metal simply causes one end of the arbor to be more dense than the other, and the difference being at a right angle to the plane of revolution has no tendency to cause vibration. The driving pulleys are cast horizontal to obtain equal density, and after being turned are carefully balanced. The driving pulleys are held to the arbors by being bored a driving fit, and are driven on so as to avoid the use of keys, which would throw the wheels out of balance. The centrepiece and flange to hold the wheel to the arbor are turned and balanced. The nut to hold the wheel is a round one, which is easier to balance than a hexagon nut. After the centrepiece is put on the arbor, the whole is tried for balance, and corrected if necessary. The pulley is then put on and the whole is again balanced, and so on, the arbor being balanced after each piece is added, so that while each piece is balanced of itself the whole is balanced after the addition of each separate piece. [Illustration: Fig. 2015.] [Illustration: Fig. 2016.] The emery or corundum wheel is then put on the arbor and tried for being in balance. The method of correcting the balance of the wheel is as follows: The arbor with the wheel on is placed in the lathe, the wheel turned true with a diamond tool (the wheel revolving at a comparatively slow speed). The arbor is then revolved at its proper speed (5,000 circumferential feet per minute), and a point applied to just meet the circumference will touch the wheel where it is heaviest, leaving a line as shown in Fig. 2015 at A. The centre of the arbor is then moved over towards this line as shown in Fig. 2016, in which W is the wheel, the location of the line A (marked as above) being as denoted by the arc A, and C represents the arbor whose centre is moved over towards the arc A. When therefore the arbor is again put in the lathe, it will run out of true by reason of the centre at one end having been altered. A cut is taken down that radial face of the wheel which faces the end of the arbor that has had its centre moved so that the wheel is turned thinner where the mark (A, Fig. 2016) is. The amount of cut to be taken off is a matter of judgment and trial, since it must be just sufficient to compensate for the greater density of the wheel on that side. This greater density, be it noted, occurs from the difficulty in mixing the corundum or other abrasive grains with the cementing material with entire uniformity throughout the mass. By this method of balancing, the wheel will remain in true balance notwithstanding its wear, because the balancing proceeds equally from the perimeter towards the centre of the wheel. [Illustration: Fig. 2017.] EMERY GRINDING MACHINES. (For grinding-lathes and roll grinding, see article on Lathes.)--Fig. 2017 represents Brown & Sharpe's grinding machine. The bed, the table, and the cross-feed motion of this machine closely resemble those of the planing machine, but its work is far more smoothly and accurately done than can be performed in a planing machine. The table traverses to and fro, accurately guided in ways, and the revolving emery wheel takes the place of the ordinary cutting tool, being carried in a sliding head upon a cross slide or cross bar. The drum for driving the emery wheel is at the back of the machine, as shown in the cut. [Illustration: Fig. 2018.] The vertical feed motion for adjusting the depth of cut of the emery wheel is capable of very minute adjustment, thus avoiding a difficulty commonly experienced in iron planing machines on account of the coarseness of feed-screw pitch, which coarseness is necessary to insure their durability. The means by which this capability of minute adjustment is effected is shown in Fig. 2018, in which D is the cross head of the machine and C the sliding head having the arm C´, which provides at B a pivot for the wheel-carrying arm A. F is a stud fast in C and carrying E, which forms the nut for the feed screw. Outside this nut is the spiral spring S, whose force steadies the upper end of A. Now suppose the feed wheel G be operated a full rotation, and the motion of that end of A will be that due to the pitch of the feed screw, but the motion at the centre H of the emery wheel will be the pitch of the screw divided by the difference between the length from the centre of H to the centre of the feed screw, and that from the centre of H to the centre of B. But even this diminished motion at H is still further reduced, so far as the depth of cut put on is concerned, because the motion of H is not directly vertical but an arc P, of which B is the centre. The standards carrying the cross slide are segments of a circle struck from the centre of the driving drum, which is necessary to enable the raising and lowering of the cross slide, and maintain a uniform tension on the belt driving the emery wheel without employing an idler wheel or belt tightener. [Illustration: Fig. 2019.] Fig. 2019 represents Wm. Sellers & Co.'s drill-grinding machine, in which the drill is held in a chuck operated by the hand wheel A. The jaws of the chuck grip the drill at the outer corners of the cutting edge as shown in Fig. 2020, and so as to grind the point of the drill central to those corners. In order to give to the cutting edges a suitable degree of clearance in their lengths, and to allow for the difference in thickness at their points between large and small drills, the following construction is employed. [Illustration: Fig. 2020.] Fig. 2020 represents the jaws J J holding on the left a small, and on the right a large drill. The line of motion of the right-hand jaw in opening and closing to grip the drill is along the line _r_, while that of the left-hand is along the line _p_ _p_, the centre upon which the chuck is revolved to grind the drill being denoted by the small circle at S. _x´_ represents the centre line of the large drill when held in the chuck, and it is seen that the action of the jaws in closing upon small drills is to lift the drill point closer to the centre S upon which the chuck revolves (the cutting edge being ground to be on the line _y´_ _y´_). The reason for this peculiar and simple but exceedingly ingenious construction is, as before remarked, to maintain the cutting edge in its proper relation to the thickness of the drill point (which thickness varies in different diameters of drills), and to maintain a proper degree of clearance at every point along the length of the cutting edge. In other drill grinding machines the drill when rotated to grind the clearance is moved on the axis A A in Fig. 2022 as a centre of motion, and as this line is parallel to the face of the emery wheel it follows that if the drill were given a full revolution its circumference would be ground to a cylinder as shown in Fig. 2021 by the dotted lines. In this machine the drill is rocked on the line B, Fig. 2023, as a centre of motion, this line corresponding to the axis of the shaft of lever F in Fig. 2019 upon which the chuck swings, and to the line B in Fig. 2024. As a result the surface is ground to the form of a cone as denoted by the dotted lines in Fig. 2024. The results of the two systems are shown in Figs. 2025 and 2026, which represent the conical holes made by a drill. [Illustration: Fig. 2021.] [Illustration: Fig. 2022.] [Illustration: Fig. 2023.] [Illustration: Fig. 2024.] In Fig. 2025 a cylinder R is shown lying in a conical recess, and end views of the cylinder are shown at V and W. Now suppose the line of contact of the roll or cylinder upon the recess represents the cutting edge of the drill, and that we consider the clearance at the outer end, and at that part that in revolving would describe the circle Q, and on referring to circle V and the outer circle of the recess, and also to circles W and Q, it is seen that there is more clearance for V than there is for W, and that the clearance of the latter would be still less if Q were of smaller diameter, and it follows that the clearance is less in proportion as the point of the drill is approached. In determining the amount of clearance, therefore, we are compelled to make it sufficient for the point of the drill, and this under this system of grinding is excessive for the outer diameter of the drill, causing it to dull quickly, it being borne in mind that as the outer corner of the cutting edge of a drill describes the largest circle of any point of the cutting edge it obviously performs the most cutting duty in removing metal, and furthermore revolves at the highest rate of cutting speed, both of which cause it to dull the most rapidly. In Fig. 2026 we have a cone R lying in the coned recess, an end view of the cone being shown at V and W, and if we again consider the line of contact of the cone on the recess to represent the cutting edge and the circumferential surface of the cone as the end surface of the drill, we observe in the end views V and W that the clearance is equal for the two positions, or by varying the degree of taper of the cone we may regulate the amount of clearance at will. It is found preferable, however, to give more clearance as the point of the drill is approached so as to increase the cutting capacity; hence, in this case, the outer corner of the drill has the least clearance, which greatly increases its endurance for the reasons already mentioned, and which were further pointed out in the remarks upon drilling in the lathe. There remains, however, an additional advantage in this method of grinding which may be pointed out, inasmuch as that the clearance produced by the method shown in Fig. 2019, while capable of being governed from end to end of the cutting edge, yet increases as the heel of the _land_ is approached, making the central cutting edge (C, Fig. 2028) more curved in its length so that it approaches the form of cutting edge of the fiddle drill and this enhances its cutting capability. [Illustration: Fig. 2025.] Referring again to the general view of the machine in Fig. 2019, the chuck is supported or carried by the shaft having the ball lever F, which is clearly seen in the rear view, Fig. 2027, and the rod carrying the sleeve B (which holds the centre for supporting the shank end of the drill) is secured to the back of the chuck, as seen in the same figure. When, therefore, lever F is moved over, the drill is moved through an arc of a circle of which the axis of the shaft of F is the centre, and this it is that gives clearance to the cutting edge of the drill. The drill being chucked, the emery wheel is brought up to it by means of the hand wheel E, which moves the frame C laterally, the grinding being done by the side face of the emery wheel. On the same shaft as E is a lever which may be used in connection with the stop or pin (against which it is shown lying) to enable an adjustment of the depth of cut taken by the wheel separately when grinding each lip, and yet to permit both cutting edges of the drill to be gauged to the same length. Suppose, for example, that the point of a drill has been broken so that it requires several cuts or traverses of the emery wheel to bring it up to a point again; then when this has been done on one cutting edge the lever may be set to the stop, so that when the grinding of the second cutting edge has proceeded until the lever meets the stop both edges will be known to be ground of the same length, and will, therefore, perform equal cutting duty when at work. The depth of cut being adjusted, the lever D is operated to pass the side face of the emery wheel back and forth along the cutting edge of the drill, this lever rocking the frame C on which the emery wheel is mounted back and forth in a line parallel to the cutting edge of the drill. Different angles of one cutting edge of the drill to the other are obtained by swivelling the frame carrying the shaft of lever F. The emery wheel is cased in except at a small opening where it operates upon the drill, and may, therefore, be liberally supplied with water without the latter splashing over. Water is continuously supplied to the emery wheel by an endless belt pump, which also delivers water on the end of the drill, enabling heavy grinding cuts to be taken without danger of softening the drill at the cutting edge, which is otherwise apt to occur. The following is the method of operating the machine: Open the jaws of the chuck by means of the hand wheel A, insert the drill from the back of the chuck towards the face of the stone, letting the end of the drill rest on the lower jaw, with the cutting edge just touching the end stop; close the jaws temporarily, while the back centre B is run up and clamped; then release the jaws, hold the drill back against the back centre B with the left hand, at the same time rotating hard against the two side stops on the jaws; then tightly closing the jaws, clamp the drill by means of the hand wheel A, using the right hand for this purpose. Throw ball-handle F part way back, and by means of hand wheel E feed up the stone until it just touches the drill. Bring ball-handle F forward and give additional feed; pass the stone over the face of the drill, back and forth, by lever D, moving ball-handle F back a little between each two cuts. This slices off the stock to be removed; then when entirely over the face of the lip being ground, hold lever D stationary, and rotate the drill against the stone by means of ball-handle F. By this means a heavy slicing cut can be taken and a final smooth finish obtained without any risk of drawing the temper of the drill. When one lip has been thus formed, slack up the jaws of the chuck, turn the drill half around, pressing its lips as before against the side stops on jaws, and at the same time be sure to hold the drill firmly back against the back centre B (pay no attention to the end stop, which is only used in locating the drill endways in the first setting), tighten chuck, and grind the second lip without any readjustment of the stone. The lips will then be of equal length. During all these manipulations the stop that is arranged in connection with hand wheel E can be slack, and may rest against the pin in the bed made to receive it. [Illustration: Fig. 2026.] Fig. 2027 represents a rear view of the machine, at which there is an attachment for thinning the point of the drill, which is advantageous for the following reasons. In Fig. 2028 we have a side and an end view of a twist drill, and it can be shown that the angular piece of cutting edge C that connects the two edges A and B cannot be given sufficient angle to make it efficient as a cutting edge without giving clearance and angle excessive to the edges A and B. In Fig. 2029 we may consider the angle of the cutting edge at the corner H and at the points F and G. First, then, it is obvious that the front face for the point H is represented by the line H _h_, that for F by line F _f_, and that for G by G _g_, and it appears that on account of the spiral of the flute the front face has less angle to the drill axis as the point of the drill is approached. [Illustration: Fig. 2027.] Considering the end of the drill, therefore, as a cutting wedge, and considering the cutting edge at the two points C and E, in Fig. 2030, the end face being at the same angle, we see that the point C has the angle A and point E the angle B; at the drill point there will be still less cutting angle, and it has, therefore, the least cutting capacity. To remedy this the attachment shown in the figure is employed, consisting of a frame or head carrying a thin emery wheel, and capable of adjustment to any angle to suit the degree of spiral of the drill flute. [Illustration: Fig. 2028.] By means of this emery wheel a groove is cut in the flute at the point of the drill, as shown in Fig. 2031, at A and B, thus reducing the length of C, and therefore increasing the cutting capacity and correspondingly facilitating the feed of the drill. It is found, indeed, that by this means the drill will perform 15 per cent. more duty. [Illustration: Fig. 2029.] [Illustration: Fig. 2030.] [Illustration: Fig. 2031.] It is obvious, however, that as the thickness of drills at the point increases in proportion to the diameter of the drill, this improvement is of greater advantage with large than with small drills. The reason for augmenting the thickness at the centre with the drill diameter is that the pressure of the cut acts to unwind the spiral of the drill, and if the drill were sufficiently weak at its axis this unwinding would occur, sensibly enlarging the diameter of hole drilled, more especially when the drill became partly dulled and the resistance of the cut increased. By means of the small grooves A and B, however, the point is thinned while the strength of the drill is left unimpaired. [Illustration: _VOL. II._ =EMERY GRINDING MACHINERY.= _PLATE IV._ Fig. 2032. Fig. 2033.] Fig. 2032 represents Brown & Sharpe's surfacing grinder, designed to produce true and smooth surfaces by grinding instead of by filing. In truing surfaces with a file a great part of the operator's time is occupied in testing the work for parallelism, and applying it to the surface plate to test its flatness or truth, whereas in a machine of this kind both the parallelism and the truth of the work are effected by the accurate guiding of the machine table in its guideways. Furthermore, a high order of skill is essential to the production of work by filing that shall equal for parallelism and truth work that is much more easily operated upon in the machine. The machine is provided with two feed motions, the first of which is in a line parallel with the axis of the emery wheel driving spindle, and is communicated (by means of the small hand wheel on the right) to the lower table, which moves in [V]-guides provided upon the base plate of the machine. Upon this lower, and what may be termed cross-feed table slides, in suitable guideways, the work-holding or upper table, which is operated (by the large hand wheel) to traverse the work back and forth beneath the grinding wheel. Both these feed motions are operated by hand, automatic feed motions being unnecessary for work of the size intended to be operated upon in this machine. The grinding wheel spindle is carried in a bearing carried in a vertical slide, and is fed to its depth of cut by means of the vertical feed screw and hand wheel shown. The spindle passes through the bearing and carries a pulley at the back of the machine, which pulley is driven by a belt passing over idler pulleys at the back of the machine, by means of which the tension of the driving belt may be regulated. Fig. 2033 represents The Tanite Co.'s machine for surface grinding such work as locomotive guide bars. The emery wheel N is mounted beneath a table T, whose upper surface is planed true, and which has two cylindrical stems C D fitting into the bored guides E. The stems are threaded at their lower ends to receive a screw, on the lower end of which is a bevel-gear F meshing into a similar gear G on the shaft actuated by the hand wheel W, hence by operating W the height of the table face may be adjusted to suit the diameter of the wheel. The surface to be ground is laid upon the face of the table, and the operator moves it by hand, slowly passing it over the emery wheel, which projects slightly through the opening shown through the centre of the table. The operator stands at the end of the machine so as to be within reach of the wheel, and the direction of rotation is towards him, so that the work requires to be pushed to the cut and is not liable to be pulled too quickly across the table by the emery wheel. [Illustration: Fig. 2034.] Fig. 2034 represents an emery grinding machine for grinding the bores of railroad car axle-boxes. The circumference of the emery wheel is dressed to the curvature of the box bore by a diamond tool A which swings on a centre in its frame, and can be adjusted to any arc. Once set, it can only turn the prescribed arc with accuracy. In order to avoid the necessity of the foreman having to set the tool, a gauge is also furnished. This consists of a spindle adjustable with a nut in such a way that its two points rest in the centres on which the diamond tool revolves. It is only necessary for a disk B turned accurately to the diameter of the bearing, to be prepared, and this the apprentice can place on the spindle, adjust the latter, and screw down the diamond tool until it touches the periphery of the disk. A nut is then fastened on the diamond tool, and the frame is lifted on the ways beneath the wheel, when the moving of the handle turns the face of the wheel to the exact circle desired. To adjust the brass in the chuck C, it is first set on the axle D. The chuck is then placed on frame E, in such a way that the [V]s fit. Handle F then moves a cam that clamps the brass between the jaws G, one set of which swings on a pivot at H. The brass is thus adjusted in such a manner that, despite the imperfections in moulding, it is ground accurately with the least removal of metal. The chuck C fits into planed guides on the table I, and is thus brought in exact line with the motion of the wheel. The crank J serves to move the table to and fro on the rods K, and the table also rises and falls on planed ways, being pressed up by springs. The hand wheel gives vertical adjustment to the whole bed by means of a chain beneath it. There is a pulley by which a suction fan, to remove dust, &c., may be driven. The machine is capable of fitting from 150 to 500 car brasses per day. [Illustration: Fig. 2035.] Fig. 2035 represents an emery planing machine. The emery wheel, which takes the place of the cutting tool of an ordinary shaping machine, is upon a spindle driven by the pulley A upon the spindle B, which is traversed endways by means of the connecting rod which is actuated by a crank E driven by the cone pulley C. The work-holding table G is traversed by the handle K or automatically through wheel H, which through suitable gearing drives the spindle I. The blower or fan is to draw off the cuttings and emery. It is obvious that any of the usual forms of work-holding devices may be employed. [Illustration: Fig. 2036.] Fig. 2036 represents an ordinary form of emery grinding machine for general purposes. A represents the frame affording journal bearing for the driving spindle driven by the cone pulley P, having the fast flanges _f_ and collars C, which are screwed up to hold the emery wheel by the nut N, the direction of spindle rotation being denoted by the arrows. The thread at the end K of the spindle must be a right-hand one, and that at the other end L must be a left-hand, so that the resistance against the nut shall in both cases be in a direction to screw the nuts up and cause them to bind or grip the wheels more firmly, and not unscrew and release the wheels. Upon the frame A are the lugs D to carry the hand rests R and S, which are adjustable, and are secured in their adjusted position by the handle nuts E. The rest S is of the same form and construction as a lathe hand rest, while that at R is angular, to support the tool while applying it to the side as well as to the circumference of the wheel. Fig. 2037 represents a machine for grinding the knives for wood-planing machines, and having a hand feed only. It consists of an emery wheel mounted upon a spindle and with a slide rest in front of it. Mounted on the slide rest is a frame for holding the knife, and a set-screw for adjusting the angle of the knife to the wheel. The slide rest is traversed by means of the hand wheel operating a pinion in the rack shown. Fig. 2038 represents a swing frame for carrying and driving an emery wheel to be used on the surfaces of castings, its construction permitting it to be moved about the casting to dress its surface. The overhead countershaft carries the grooved driving wheel A. At B is a vertical shaft pivoted at I by the forked bearing which swings upon the countershaft. The fork L at the lower end of shaft B carries a shaft on which is the fork C´, C having journal bearing on it, and the driving pulley J. Fork D has journal bearing on the same shaft as pulley J, and is fast upon the rod or arm E, which affords journal bearing to the emery wheel K on a shaft having handles H H. Motion to the emery wheel is conveyed through the belts F and G. To counterbalance the frame the weight W is employed, permitting the frame to be readily swung. The upper fork carrying B, being pivoted to the shaft of A, permits B to swing to any required position. The pivot at I permits B to rotate in a vertical plane; the pivot of C´ C at D affords vertical movement to E; the pivot at D allows E to rotate about its own axis, hence the wheel K can be moved about laterally, raised, lowered, or have its plane of revolution varied at will by simply swinging the handles H H to the required plane. The emery-wheel shaft is pivoted upon the fork carrying it, so that the emery wheel can be turned to stand in a horizontal plane if desired. [Illustration: Fig. 2037.] Fig. 2039 represents an emery belt machine, in which the belt runs vertically and its tension is adjusted by the idler pulley shown at the top of the frame. [Illustration: Fig. 2038.] It is obvious that if a piece of work, as A in Fig. 2040, be held steadily upon the rest R, its end will be ground to the curvature of the emery wheel W, and that if it be required to grind the surface flat the piece must be raised and lowered as denoted by the dotted lines, the amount of this motion being determined by the thickness of the piece. Furthermore, if the piece of work be of a less width than the thickness of the wheel, as in the top view in Fig. 2041, the work A will wear a groove on the wheel, and its side edges will therefore become rounded off unless it be given sufficient motion in the direction of D and E to cause it to traverse across the full width of the wheel face, and as this motion would require to be simultaneous with the vertical motion explained with reference to Fig. 2040, it is not practicable to grind true level surfaces upon the perimeter of the wheel. As the sides of the wheel are flat, however, it is self-suggestive to apply the work to the side faces. But in this case, also, that part of the wheel surface that performs grinding duty will gradually wear away, leaving a shoulder or projecting surface upon the wheel. Suppose, for example, that in Fig. 2042 the duty has been confined to that part of the wheel face from A to the perimeter and the wheel would wear as shown, the result being the same whether the width or distance from the shoulder A to the perimeter of the wheel represents the width of the work held steadily against the wheel or the traverse of a narrower piece of work. This difficulty may be overcome by recessing the wheel face, as in Fig. 2043, in which the wheel is shown in section. In some cases, as for grinding the knives for wood-working machines, hollow cylindrical wheels, such as in Fig. 2044. are used, the duty being performed on the end face B B of the wheel, and the work being traversed in the direction of the arrows. The wheel is here gripped between the flange F and the collar C, which fits accurately to the end of the driving spindle S, so as to be held true, and secured by screws passing through C and into F, or the end of S may be threaded to receive a nut to screw against C. The circumferential surface of a wheel may be employed to grind a flat surface, providing that the work be traversed to the wheel, as in the side view in Fig. 2045. In this case, however, the cut must be taken while the work P is travelling in the direction denoted by the arrow J, and no cutting must be done while the work is travelling back in the direction of K. After the work has traversed back in the direction of K, and is clear of the wheel, the cut is carried farther across the work by moving or feeding the work in the direction of the arrow in the front view, Fig. 2046. In this case the whole surface of the work passes beneath the wheel thickness, and the wheel face wears parallel to the wheel axis, producing a true plane (supposing the work to be moved in straight lines), save in so far as it may have been affected by the reduction of the diameter of the emery wheel from wear, which is not found sufficient to be of practical importance. If the whole surface of the work does not pass across or beneath the wheel thickness the wheel face may wear taper. Suppose, for example, that in Fig. 2047, P is a piece of work requiring to have produced in it a groove whose bottom is to be parallel to the lower surface F. Then the upper work surface being taper the thick side A would wear away the side B of the wheel, and the groove ground would not be parallel to F. [Illustration: Fig. 2039.] [Illustration: Fig. 2040.] [Illustration: Fig. 2041.] [Illustration: Fig. 2042.] [Illustration: Fig. 2043.] [Illustration: Fig. 2044.] Another method of grinding flat surfaces is to mount the emery wheel beneath a table T in Fig. 2048, letting the top of the wheel emerge through an opening in the table, and sliding the work upon the trued upper surface of the table. The surface of the table thus becomes a guide for the work. To obtain true work in this way, however, it is necessary that the cut taken by the emery wheel be a very light one, as will be perceived from the following considerations. [Illustration: Fig. 2045.] [Illustration: Fig. 2046.] [Illustration: Fig. 2047.] In Fig. 2049 T represents a table and B a guide bar thereon. The depth of cut taken will be equal to the height the emery wheel projects above the surface A of the table, hence when the bar has been moved nearly half-way across the table its surface will be as in Fig. 2050, the bar occupying the position shown in Fig. 2051. Now the part of the bar that has passed over the table will not rest upon it as is shown in Fig. 2051. When the bar has passed over the emery wheel more than half of the bar length, its end F, Fig. 2052, will fall to meet the half D of the table, and end E will lift from the half C of the table, causing the bar surface to be ground rounding in its length. If, however, the cut taken be a very light one the surface may be ground practically true, because the bar will bend of its own weight and lap down to fit the table at both ends. Furthermore it will be noted that in the case of a large surface in which the wheel might sensibly wear in diameter before it had operated over the whole of the work surface, the table may be lowered or the wheel may be raised (according to the construction of the machine), to offset the wear of the wheel, or rather to take it up as it were. [Illustration: Fig. 2048.] [Illustration: Fig. 2049.] [Illustration: Fig. 2050.] POLISHING WHEELS.--For polishing purposes as distinguished from that of grinding, various forms of polishing wheels are employed. For the rougher class of polishing, wooden wheels covered with leather coated with fine emery that is allowed to glaze are employed. For a finer degree of polish the wheels are covered with lead to which various polishing materials are occasionally applied, while for the finest polishing rag or buff wheels are the best. Wooden polishing wheels are built up of sections of soft wood fastened together by gluing, and with wooden pegs in place of nails or screws. [Illustration: Fig. 2051.] [Illustration: Fig. 2052.] [Illustration: Fig. 2053.] [Illustration: Fig. 2054.] [Illustration: Fig. 2055.] The joints of the sections or segments are broken--that is to say, suppose in Fig. 2053 that 1, 2, 3, &c., up to 6, represent the joints of the six sections of wood forming one layer of the wheel, the next six sections would have their joints come at the dotted lines A, B, C, &c., up to F. To prevent them from warping after being made into a wheel it is advisable to cut out the sections somewhere near the size in the rough and allow them to lie a day or two before planing them up and fitting them together; the object being to allow any warping that may take place to do so before the pieces are worked up into the wheel, because if the warping takes place afterwards it will be apt to throw the wheel out of true, whereas it is necessary that these wheels be very true, not only so that they may not prove destructive to their shaft bearings, but that they may run steady, and not shake or terrible, and because the work can be made much more true and smooth with a true than with an untrue wheel. Only one layer of segments should be put on in one day, and they should be put on as quickly as possible after the glue is applied, so that the latter shall not get cold. So soon as each segment is put into its place it should be clamped firmly to its seat and driven firmly up to the joint of the next one, and when the layer is completed it should be left clamped all night to dry. In the morning one clamp should be removed, and that section fastened by boring small holes and driving therein round and slightly tapered soft-wood pegs of about 1/4 inch diameter. The whole of the sections being pegged the next layer of segments may be added, and so on until the required width of wheel is attained. The whole wheel should then be kept two days before it is turned, and as little as possible should be taken off in the turning process. The circumferential surface should be turned slightly rounding across its width, and as smoothly as possible. It is practicable to proceed with the construction of the wheel without waiting between the various operations so long as here advised, but the wheel will in that case be more apt to get, in time, out of true. To cover the circumference of the wheel sole leather is used, its thickness being about 1/4 inch; it should be put on soft and not hardened by hammering at all, and with the flesh side to the wood. The joint of the leather should not be made straight but diagonal with the wheel face, the leather at the edge of the joint being chamfered off, as shown in Fig. 2054 at A, and the joint made diagonal, as shown in Fig. 2055 at A. If the leather were put on with a square butt joint there would likely be a crease in the joint, and the emery or other polishing material would then strike the work with a blow, as well as presenting a keener cutting edge, which would make marks in the work no matter what pains might be taken to prevent it. This, indeed, is found to occur to a slight extent upon very fine polishing, even when the joint of the leather is made as above; and the means taken to obviate it is to not put any polishing material on the immediate joint and to wipe off any that may get there, leaving 1/10 inch clear of polishing material. It is obvious that in fastening the wheel to its shaft it should be put on so that it will run in the direction of the arrow, providing the operator works with the wheel running from him, as is usually the case with large wheels, that is to say, wheels over 18 inches in diameter. In any event, however, the wheel should be put on so that the action of the work is to smooth the edge of the leather joint down upon the wheel, and not catch against the edge of the joint, which would tend to rough it up and tear it apart. The leather should be glued to the wheel, which may be slightly soaked first in hot water. The glue should be applied very hot, and the leather applied quickly and bound tightly to the wheel with a band. One end of the leather may be first glued to the wheel and fastened with a few tacks to hold it while it is stretched tightly round the wheel; the leather itself should be softened by an application of hot water, but not too much should be applied. After the leather is glued to the wheel it is fastened with soft wooden pegs, about 3/16 inch in diameter, driven through the leather into the wood and cut off slightly below the surface of the leather. [Illustration: Fig. 2056.] [Illustration: Fig. 2057.] Wheels of this kind are sometimes made as large as 5 or 6 feet in diameter, in which case the truth of the wheel may be preserved by letting in a wrought-iron ring, as shown in Fig. 2056, fastening the rings with wood screws. The wheels thus constructed are covered with emery of grades varying from No. 60 to 120, and flour emery. The coarser grades perform considerable cutting duty as well as polishing. The manner of putting the emery, and fastening it, upon the wheel is as follows:--The face of the wheel is well supplied with hot glue of the best quality, and some roll the wheel in the emery, in which case the emery does not adhere so well to the leather as it does when the operation is performed as follows:--Let the wheel either remain in its place upon the shaft, or else rest it upon a round mandrel, so that the wheel can revolve upon the same. Then apply the hot glue to about a foot of the circumference of the wheel, and cover it as quickly as possible with the emery. Then take a piece of board about 3/4 inch thick and 28 inches long, the width being somewhat greater than that of the polishing wheel, and placing the flat face of the board upon the circumferential surface of the wheel, work it by hand, and under as much pressure as possible, back and forth, so that each end will alternately approach the circumference of the wheel, as illustrated in Fig. 2057, the movement being indicated by the dotted lines. By adopting this method the whole pressure placed upon the board is brought to bear upon a small area of the emery and leather, and the two hold much more firmly together than would be the case if the circumference of the wheel were glued and then rolled in a trough of emery, because the time occupied in spreading the glue evenly and properly over the whole wheel surface would permit it to cool before receiving the emery, whereas it is essential that the glue be hot so that it may conform itself to the shape of the grains of emery and hold them firmly. The speed at which such wheels are used is about 7,000 feet per minute. The finest of emery applied upon such wheels is used for cast iron, wrought iron, and steel, to give to the work a good ordinary machine finish; but if a high polish or glaze is required, the wheels are coated with flour emery, and the wheel is made into a glaze-wheel by wearing the emery down until it gets glazed, applying occasionally a little grease to the surface of the wheel. Another kind of glaze-wheel is made by covering the wooden wheel with a band of lead instead of a band of leather, and then applying to the lead surface a mixture of rouge, crocus and wax, worn smooth by applying to it a piece of sheet steel or a piece of flint-stone before applying the work. Others add to this composition a little Vienna lime. For flat surfaces, or those requiring to have the corners or edges kept sharp, it is imperative that such wheels as above described--that is to say, those having an unyielding surface--be used; but where such a consideration does not exist, brush and rag wheels may be used. In Europe comparatively large flat surfaces requiring a high polish are finished upon wooden wheels made of soft wood and not emeried, the polishing material employed being Vienna lime. The lime for ordinary use is mixed with water, and is applied by an assistant on the opposite side of the wheel to the operator. For superfine surfaces the Vienna lime is mixed with alcohol, which increases its efficiency; and here it may be as well to note that Vienna lime rapidly deteriorates from exposure to the air, so that it should be kept as little exposed as possible. BRUSH-WHEELS.--These are polishing wheels of wood with a hair brush provided around the circumference. These wheels are excellent appliances, whether employed upon iron, steel, or brass. Their sizes run from 1-1/2 inch to about 8 inches in diameter, and the hair of the brush should not exceed from 1 to 1-1/4 inches in length. The speed at which they should be run is about 2,500 for the largest, and up to 4,500 revolutions per minute for the smaller sizes. In ordinary grinding and polishing practice in the United States, brush wheels are used with Vienna lime in all cases in which the lime is used by itself--that is to say, unmixed with wax, crocus, or rouge, or a mixture of the same. In watchmaking, however, and for other purposes in which the truth of the work is an important element, Vienna lime is applied to wooden or even metal, such as steel, polishing wheels, which are in this latter case always of small diameter. An excellent polishing composition is formed of water 1 gill, sperm oil 3 drops, and sufficient Vienna lime to well whiten the mixture. The brush may be let run dry during the final finishing. For polishing articles of intricate shape, brush wheels are superior to all others. If the articles to be polished are of iron, or steel, the first stage of the process is performed with a mixture of oil and emery, Vienna lime being used for final finishing only. The wheels to which Vienna lime is applied should not be used with any other polishing material, and should be kept covered when not in use, so as to keep them free from dust. For brass work, brush wheels are used with crocus, with rouge, or with a mixture of the two, with sufficient water, and sometimes with oil, to cause the material to hold to the brush and not fly off from the centrifugal force. For very fine brass polishing, the first stages are performed with powdered pumice-stone mixed with sufficient oil to hold it together. This material has considerable cutting qualifications. The next process is with rouge and crocus mixed, and for very fine finishing rotten-stone. Solid leather wheels are much used by brass-finishers. The wheels are made of walrus hide glued together in disks, so as to obtain the necessary thickness of wheel. The disks are clamped between pieces of board so soon as the glue is applied, so as to make a good joint, and also keep the wheel flat and prevent it from warping during the drying process. Such wheels may be run at a velocity of 8,000 feet per minute, and with any of the polishing materials already referred to. After the wheel is made and placed upon its spindle or mandrel it may be turned true with ordinary wood-turning tools--and it may here be remarked that rag wheels may be trued in the same way. The spongy nature of these wheels renders them very efficient for polishing purposes, for the following reasons: The polishing materials become imbedded in the leather and are retained, and become mixed and glazed with a fine film of the material being polished, which film possesses the very highest polishing qualifications. These walrus wheels may be used with pumice, crocus, rouge, or Vienna lime, according to the requirements of the case, or even with a mixture of flour emery and oil; and they possess the advantage of being less harsh than leather or lead-covered wheels, while they are more effectual than the latter, and will answer very well for flat surfaces. Rag polishing wheels are formed of disks of rags, either woollen or strong cotton, placed loosely side by side, and clamped together upon the mandrel at the centre only. Their sizes range usually from 4 to 8 inches in diameter, and they are run at a speed of about 7,000 feet per minute. They assume a disk form when in motion from the centrifugal force generated from the great speed of rotation. They are used for the fine polishing only, and not upon work requiring the surfaces to be kept very flat or the corners very sharp. For use upon steel or iron, they are supplied with a polishing material composed of Vienna lime 3 parts, crocus 3 parts, beeswax 3 parts, boiled up together, allowed to cool off, and then cut into cakes. These cakes are dipped in oil at the end, which is then applied to the rag wheel occasionally during the polishing process. For brass-work, an excellent polishing composition is composed of crocus 2 parts, wax 1 part, rouge 1/8 part, the wax being melted, and the ingredients thoroughly mixed. This mixture gives to the metal a rich color. It is dipped in oil and then applied to the rag wheel. It may be used to polish fine nickel-plating, for which purpose it is an excellent material. Nickel-plated articles having sharp corners should be polished with fine rouge mixed with clear water and a drop of oil, the mixture being applied to the rag wheel with the finger of the operator. Any of the compositions of rouge, crocus, and rotten-stone may be used for brass, copper, or nickel-plated work upon rag wheels, while for iron or steel work the same materials, separate or in combination, may be used, though they are greatly improved by the addition of Vienna lime. When, however, either of these materials is used singly, it should be applied to the rag wheels with a brush; and if it is used dry, it must be at a greatly reduced speed for the wheel, which is sometimes resorted to for very fine polishing. [Illustration: Fig. 2058.] Fig. 2058 represents a polishing device used to polish the surface of engravers' plates. It consists of a spindle D, carried in bearings B, and, having no collars, it is capable of end motion through those bearings. The spindle is pressed downward by a spring A, carrying at its end a piece C, which is capped to receive the end of the spindle D and the piece E which threads into the spindle, thus making a sort of universal joint. The spindle D is run by the pulley P, and carries a piece of stone S, the work W resting upon the plate or table T. The stone being set to one side of the centre of the spindle, each part of its surface describes a circle, the centre of which is outside of the stone, thus making the effectiveness of the centre of the stone greater by increase of motion. To raise the stone from the work the spindle is raised by means of the chord F, or the table T may have a simple lever motion. The work is moved about and around and beneath the revolving stone. Water, oil, benzine or alcohol is used to keep the stone clear and wash away the cuttings. The device saves a good deal of hand work in the preparatory stages of grinding, although it can be used only with soft stones. GRINDSTONES AND TOOL GRINDING.--The general characteristics of grindstones are as follow:-- For rapid grinding a coarse and an open grit is the most effective. The harder the grit the more durable the stone, but the liability of the stone to become coated or glazed with particles of the metal ground from the work is increased. With a given degree of coarseness a soft grit stone will grind a smoother surface than a hard grit one. The finer the grit the smoother the surface it will grind. In all stones, however, it is of prime importance that the texture be even throughout the stone, because the soft or open-grained part will wear more rapidly than the close or hard grained. All grindstones are softer when water-soaked than when dry, and will cut more freely, because the water washes away the particles of metal ground from the work, and prevents them from glazing the stone. It follows from this, however, that a stone should not be allowed to rest overnight with its lower part resting in water, as the wear of the stone will be unequal until such time as it has become equally saturated. Furthermore the balance of the stone is destroyed, and if run at a maximum speed, as in the case of stones used to grind up large edge tools, the unbalanced centrifugal force generated on the water-soaked side may cause the stone to burst. The following stones are suitable for the class of work named:-- FOR GRINDING MACHINISTS' TOOLS. ----------------+-------------+-----------------+---------------- Name of stone. |Kind of grit.|Texture of stone.|Color of stone. ----------------+-------------+-----------------+---------------- Nova Scotia. |All kinds, |All kinds, from |Blue or |from finest |hardest to |yellowish grey. |to coarsest. |softest. | | | | Bay Chaleur |Medium to |Soft and sharp. |Uniformly light (New Brunswick).|finest. | |blue. | | | Liverpool or |Medium to |Soft, with sharp |Reddish. Melling. |fine. |grit. | ----------------+-------------+-----------------+---------------- FOR WOOD-WORKING TOOLS. ----------------+-------------+-----------------+---------------- Name of stone. |Kind of grit.|Texture of stone.|Color of stone. ----------------+-------------+-----------------+---------------- Wickersly. |Medium to |Very soft. |Greyish yellow. |fine. | | | | | Liverpool or |Medium to |Soft, with sharp |Reddish. Melling. |fine. |grit. | | | | Bay Chaleur |Medium to |Soft and sharp. |Uniform light (New Brunswick).|finest. | |blue. | | | Huron, Michigan.|Fine. |Soft and sharp. |Uniform light | | |blue. ----------------+-------------+-----------------+---------------- FOR GRINDING BROAD SURFACES, AS SAWS OR IRON PLATES. ----------------+-------------+-----------------+---------------- Name of stone. |Kind of grit.|Texture of stone.| Color of stone. ----------------+-------------+-----------------+---------------- Newcastle. |Coarse to |The hard ones. |Yellow. |medium. | | | | | Independence. |Coarse. |Hard to medium. |Greyish white. | | | Massillon. |Coarse. |Hard to medium. |Yellowish white. ----------------+-------------+-----------------+---------------- The flanges for grindstones should be trued on both faces, and should pass easily over the grindstone shaft, and there should be between these collars and the stone an elastic disk, as of wood or felt, which will bed fully against the surface of the stone. It is preferable also if the under faces of these collars be recessed to within an inch of their perimeters so as to confine the grip to the outer edges of the faces. The process of grinding large surfaces is entirely distinct from that of small ones, because of the difficulty in the former of getting rid of the cuttings. As an illustration of this point it may be remarked that a stone that has become dulled and glazed from operating upon a broad area of surface, as say a large plate, may be both cleaned of the cuttings and sharpened by grinding upon it a roller of, say, 1 or 1-1/4 inches in diameter. This roller is laid across the "horn" or rut of the stone, and pressed firmly against it, the bar being allowed to slowly rotate. What is commonly termed grinding is the class of grinding that is followed as a trade, such as file grinding, saw grinding, plate grinding, edge tool and cutlery grinding. In all this class of grinding the speeds of the stones is very much greater than for machine-shop tool grinding. For all the above, save cutlery grinding, the stones when new are of a diameter from 5 to 8 feet, and of a width of from 8 to 15 inches. The stones used by cutlers are about 15 inches in diameter, and from 1/2 inch to 3 inches thick. The average speed of grindstones in workshops may be given as follows:-- Circumferential speed of stone. For grinding machinists' tools, about 900 feet per minute. " carpenters' " 600 " The speeds of stones for file grinding and other similar rapid grinding is thus given in the "Grinders' List." Diameter of stone. Revolutions ft. in. per minute. 8 0 135 7 6 144 7 0 151 6 6 166 6 0 180 5 6 196 5 0 216 4 6 240 4 0 270 3 6 308 3 0 360 These speeds are obviously obtained by reducing the diameter of the pulley on the grindstone shaft each time the stone has worn down 6 inches less in diameter, and give a uniform velocity of stone if the 8 feet stone be driven with a pulley 32 inches in diameter. Each shift (or change of pulley) giving a pulley 2 inches less in diameter. The following table (from the _Mechanical World_) is for the diameter of stones and the number of revolutions they should run per minute (not to be exceeded), with the diameter of change or shift pulleys required, varying each shift or change 2-1/2 inches, 2-1/4 inches, or 2 inches in diameter for each reduction of 6 inches in the diameter of the stone:-- +-------------+-------------+-----------------------------+ | | | Shift of pulleys in inches. | | Diameter of | Revolutions +---------+---------+---------+ | stone. | per minute. | 2-1/2 | 2-1/4 | 2 | +-------------+-------------+---------+---------+---------+ | ft. in. | | | | | | 8 0 | 135 | 40 | 36 | 32 | | 7 6 | 144 | 37-1/2 | 33-3/4 | 30 | | 7 0 | 154 | 35 | 31-1/2 | 28 | | 6 6 | 166 | 32-1/2 | 29-1/4 | 26 | | 6 0 | 180 | 30 | 27 | 24 | | 5 6 | 196 | 27-1/2 | 24-3/4 | 22 | | 5 0 | 216 | 25 | 22-1/2 | 20 | | 4 6 | 240 | 22-1/2 | 20-1/4 | 18 | | 4 0 | 270 | 20 | 18 | 16 | | 3 6 | 308 | 17-1/2 | 15-3/4 | 14 | | 3 0 | 360 | 15 | 13-1/2 | 12 | +-------------+-------------+---------+---------+---------+ | 1 | 2 | 3 | 4 | 5 | +-------------+-------------+---------+---------+---------+ "Columns 3, 4, and 5 are given to show that if you start an 8 feet stone with, say, a countershaft pulley driving a 40 inch pulley on the grindstone spindle, and the stone makes the right number (135) of revolutions per minute, the reduction in the diameter of the pulley on the grinding-stone spindle, when the stone has been reduced 6 inches in diameter, will require to be also reduced 2-1/2 inches in diameter, or to shift from 40 inches to 37-1/2 inches, and so on similarly for columns 4 and 5. Any other suitable dimensions of pulley may be used for the stone when 8 feet in diameter, but the number of inches in each shift named, in order to be correct, will have to be proportional to the number of revolutions the stone should run, as given in column 2 of the table." [Illustration: Fig. 2059.] [Illustration: Fig. 2060.] In all grinding operations it is necessary that the stone should run true. This is sometimes accomplished by so mounting the stones in their frames that their perimeters touch at the back of each stone, one stone running slightly faster than the other. Or sometimes the work is placed between the two stones, as in Fig. 2059, which represents a plan frequently used to grind circular saws; _c_ in the figure represents the grinding-stone and _a_ the saw. Long saws are mounted vertically as in Fig. 2060, _a_ representing a frame to which the upper end of the saw is attached and driven by a disk crank and connecting rod as shown, the two stones _c_ _e_ may, in this case, be of equal diameter. [Illustration: Fig. 2061.] Fig. 2061 represents a grindstone truing device (for tool-grinding stones) in which a series of serrated disks are employed in place on a threaded roll. The disks are fed to the stone by the hand wheel and screw, and are traversed back and forth across the stone face by means of the lever handle shown. The fast running grindstones used for heavy and coarse grinding are trued by a process known as hacking. The high spots of the stone are marked by holding a piece of coal to the stone while it revolves slowly, and a tool similar to an adze is used to cut or chop indentations in the stone. The highest spots will be most plainly marked by the coal, and the hacking is spaced closer together in these places, the hacking marks crossing each other and varying in depth to suit, obviously being deepest where the marks are blackest. The hacking also sharpens the stone. To prevent the stone from wearing uneven across its face the file grinder mounts the stone in a very ingenious manner, causing it to traverse automatically, back and forth, while rotating. [Illustration: Fig. 2062.] This device is shown in Fig. 2062, in which A represents the grindstone spindle having journal bearing at B B, but as there are no collars on the journals, A can move endwise through B B. Fast to A are the collars C and C´ (sometimes the face of the pulley hub is made to serve instead of C´); S is a sleeve fitting easily to A, and containing a return groove, as shown; D is a fixed arm carrying a pin which projects down into the groove of S, as shown; P is the pulley driving A, and W W are suspended weights. The operation is self-acting, as follows: The shaft revolving causes the sleeve to revolve by friction, and the pin causes the sleeve to move endwise; its end face abutting against the face of the collar on one side, or the face of the pulley on the other side, as the case may be, causing the shaft to travel in that lateral direction. When the pin has arrived at the end of the groove, the stone ceases lateral motion (there being left a little play between the faces of the sleeve and of the collar and pulley face for this special purpose), while the cam travels in the opposite lateral direction, getting fairly in motion until it strikes the face, when it slowly crowds the face over. In travelling to the right it crowds against the face of the collar C´, and in traveling to the left, as shown in the figure, against the face of the collar C. The swing thus given to the stone is a slow and very regular one, the motion exciting surprise from its simplicity and effectiveness, especially when it is considered that the friction of the rotation of a shaft about 2-1/2 inches diameter in a smooth hole about 6 inches long is all that is relied upon to swing a ponderous stone. The following are the considerations that determine in grinding tools or pieces held by the hands to the grindstone. Upon the edge of a tool that last receives the action of the stone there is formed what is termed a feather-edge, which consists of a fine web of metal that bends as the tool is ground, and does not become detached from the tool in the grinding. The amount or length of this feather-edge increases as the work is thinner, and is greater in soft than in hardened steel. It also increases as the tool or piece is pressed more firmly to the stone. To prevent its formation on such tools as plane blades or others having thin edges, the tool is held as at G in Fig. 2063, the top of the stone running towards the workman, and the tool is held lightly to the stone during the latter part of the grinding operation. With the tool held on the other side of the stone as at C, and pressed heavily to the stone, a feather-edge extending as long as from D to E may be formed if the tool has a moderate degree only of temper, as, say, tempered to a dark purple. The feather-edge breaks off when the tool is put to work, or when it is applied to an oil-stone, leaving a flat place instead of a sharp cutting edge. In well-hardened and massive tools, such as the majority of lathe tools, the amount of feather-edge is very small and of little moment, but in thin tapered edges, even in well-hardened tools, it is a matter of importance. After a tool is ground it is often necessary to remove the feather-edge without having recourse to an oil stone. This may be accomplished by pressing the edge into a piece of wood lengthways with the grain of the wood, and while holding the cutting edge parallel with the line of motion, draw it towards you and along the grain of the wood, which removes the feather-edge without breaking it off low down, as would be the case if the length of the cutting edge stood at a right angle to the line of motion. The positions in which to hold cutting tools while grinding them are as follows: The bottom faces of lathe tools and the end faces of tools such as scrapers should be ground with the tool laid upon the grindstone rest as in Fig. 2064, the stone running in the direction of the arrow. The best position for thin work as blades is at F providing the stone runs true, for otherwise the tool edge will be liable to catch in the stone. With an untrue stone the position shown in Fig. 2065 is the best, the blade being slowly reciprocated across the face of the stone. If the facet requires to be ground rounding and not flat the position at C, Fig. 2064, is the best, the work being moved to produce the roundness of surface. If the tool is to be ground hollow or somewhat to the curvature of the stone, as in Fig. 2066, the curve being from _b_ to _c_, the position at B is the best. At position D the tool cannot be held steadily; hence, that position is altogether unsuitable for tool grinding purposes. For grinding the top faces of lathe or planer tools or other similar shaped pieces that must be held with their length at a right angle (or thereabouts) to the plane of the rotation of the stone, the tool is held in the hands, and the hands are supported by the grindstone rest as in Fig. 2067, the fingers being so placed that should the tool catch in the stone it will slip from between the fingers and not carry them down with it upon the tool rest. Tools to be ground to a sharp point should be ground at the back of the stone, that is to say, with the top of the stone running away from the operator, and the point should be slowly moved across the width of the stone to prevent wearing grooves in its surface. To produce a finer edge than is possible with the grindstone, the oil-stone is brought into requisition, the shape of the oil-stone being varied to suit the shape of the tool. Three kinds of oilstone are in general use, Turkey stone, Arkansas stone, and Washita stone, the latter being softer and of inferior quality to the two former. The best quality of Arkansas stone is of a milky white color, of very fine and even grain, and very hard, being impervious to a file; but there are softer grades. An oil-stone should be of even grain throughout, so that it may wear even throughout, and produce a smooth and unscored edge. Arkansas stone is rarely obtainable in lengths above 6 inches, on account of the presence of fine seams of hard quartz, which wears less than the stone, and forms a projection that scores the cutting edge of the tool, and the same applies to the Turkey stones. For tools fully hardened and not tempered the hardest oilstones are best; but for tools that are tempered, as tools for woodwork, a softer grade of stone is preferable, since it will cut the most free. When an oil-stone has worn out of shape it may be dressed on a grindstone; but if a flat surface is required it is best to true it by a piece of coarse sand-paper laid upon a flat true surface. The action of an oil-stone is to smooth the surfaces; but while doing this the oil-stone itself forms what is termed a wire-edge, which resembles a feather-edge, except that it is smoother and more continuous. It is caused by the weak edge of the blade giving way under the pressure with which it is held to the stone. To reduce the wire-edge as much as possible the tool is pressed very lightly to the oil-stone during the latter part of the stoning, and is frequently turned over. If the motion of the tool upon the oil-stone is parallel with the line of cutting edge, the wire-edge will be greater than if the line of motion were at a right angle to it. Again, the strokes performed while the cutting edge is advancing upon the oil-stone produce less wire-edge than the return strokes, hence the finishing process consists of a few light strokes upon one and then upon the other facet repeated several times. Now let it be observed that, the wire-edge will never be turned toward the facet last oil-stoned, and cannot be obviated by the most delicate use of the stone; but after the stoning proper is finished, the operator will lay one facet quite level with the face of the stone, and then give to the blade, under a very light pressure, forward diagonal motion, and then perform the same operation with the other facet upon the stone, the last facet operated upon being usually the straight and not the bevelled one. To still further reduce the wire-edge for very fine work, the operator sometimes uses a piece of leather belt, either glued to a piece of wood, as upon the lid of the oil-stone box, or some attach it at each end to projecting pieces of wood, while yet others lap the tool upon the palm of the hand. In giving an edge to a razor, the process may be carried forward in the usual way by means of straps, the first strokes being long ones made under a slight pressure, the strokes getting shorter and the pressure lighter as the process proceeds, until at last the motion and contact are scarcely perceptible. [Illustration: Fig. 2068.] When, as in the case of plane blades and carpenters' chisels, the area of face is large, it is advantageous to grind the face somewhat concave, as in Fig. 2068, so that the heel and the point only of the tool has contact with the oil-stone, thus reducing the area to be stoned and steadying the tool, because, the area being small, the heel as well as the edge may be allowed to rest upon the oil-stone without unduly prolonging the stoning operation. [Illustration: _VOL. II._ =GRINDSTONE GRINDING.= _PLATE V._ Fig. 2063. Fig. 2064. Fig. 2065. Fig. 2066. Fig. 2067.] [Illustration: _VOL. II._ =FULL AUTOMATIC GEAR CUTTER.= _PLATE VI._ Fig. 2069. Fig. 2070.] CHAPTER XXIV.--GEAR-CUTTING MACHINES. [Illustration: Fig. 2071.] The Brainard automatic gear cutter, Figs. 2069, 2070, 2071 and 2072 is arranged to cut spur, bevel, and worm-wheels, and is of that class where the manipulations required in gear cutting are all performed by the machine itself, thus dispensing with the care of an attendant except to place the wheels in position and set the machine for the proper depth and length of cut. The manner in which these results are accomplished will be seen from the following description, reference being had to the engravings. The wheel to be cut (_a_, Fig. 2070) is held upon a mandrel _b_ fitted to the spindle _c_, which is mounted in firm bearings upon a column or standard _d_. To the face of the standard is gibbed a sliding knee _e_. Upon this knee is placed the cutter slide _f_, which is arranged to be inclined for bevel-gear cutting, and to be swung aside in cutting worm-wheels. Rotary cutters are carried on arbors fitted to the cutting spindle (_g_, Fig. 2071). Power for driving the cutter is applied to the pulley _h_, mounted upon the cutter spindle. The cutter slide _f_ is operated through the medium of a screw and bevel-gears from a shaft _h_^{1}, which is arranged to revolve alternately in opposite directions from a continuous motion of the driving cone pulley _t_, receiving, motion from the feed pulley _i_, through the means of a swinging arm, carrying a receiving pulley and cone as is shown in Fig. 2069. The method of obtaining these opposite motions of the shaft _h_^{1} will be seen in Fig. 2071. To the block _h_^{2} which supports the shaft _h_^{1} is secured a gear _h_^{3}, which engages with a pinion _h_^{4} mounted loosely on the cone pulley _i_^{1}. Side by side with this gear is placed a second gear _h_^{5} also engaging with the pinion _h_^{4} and having one tooth less than the gear _h_^{3}. This gear is mounted loosely on the shaft _h_^{1} and is sleeved through the block _h_^{2}, and to it is secured a ratchet clutch _j_. This arrangement produces a motion analogous to that of worm gearing; the revolution of the cone _i_^{1} carrying the pinion _h_^{4}, causes the gear _h_^{5} to be moved in the opposite direction to that of the cone _i_^{1}, and at a speed of one tooth for each revolution of the cone. The cone _i_^{1} carries on its outer end a second clutch _j_^{1}. The shaft _h_^{1} is made hollow, and two clutches are secured to a rod playing loosely on the hollow shaft, and arranged to be engaged alternately with the clutches _j_ and _j_^{1}. This engagement is effected by means of a bell crank _k_, operated by a shipper rod _k_^{1} on which adjustable dogs are placed, arranged to be operated by the cutter slide _f_. This arrangement of feed shipping motion is very positive in its action, and allows of a very quick return of the cutter slide. The parts are so proportioned that the slide returns thirty-three times as fast as the forward motion, and yet on the very fastest speeds there is no perceptible jar of the parts. The entire mechanism can be disconnected from the feed screw, when desired, by disengaging the clutch _j_^{3} on the feed screw. The means employed for spacing the wheel blank are shown in Figs. 2070 and 2072. At the rear end of the spindle _c_ is secured a worm-wheel _l_. This worm-wheel is made in two parts screwed firmly together. By this construction the wheel is made very accurately. The screw holes in the ring _l_^{1} are slightly elliptic. After the wheel has been hobbed out the position of the ring is changed and the wheel re-hobbed, and so on until the teeth will match perfectly in any position of the ring, when the ring is pinned and screwed on permanently. This wheel is driven by a worm _m_ in connection with change gearing _m_^{1}, _m_^{2}, in such a way that one turn of the shaft _m_^{3} serves for all divisions. To the shaft _m_^{3} is secured a graduated plate _o_, to which is secured a latch plate _o_^{1} by means of a [T]-slot and bolts. The latch plate _o_^{1} is secured in this manner in order that the plate _o_ may be turned any desired amount of "set over" in bevel-gear cutting, without disturbing the change gearing or latch. This dividing mechanism is driven by an independent belt from the countershaft to the pulley P, which is secured to a pinion P^{1}, running loose on a stud. The pinion P^{1} engages with a gear P^{2} mounted loosely on the shaft _m_^{3}. This gear is made to drive the latch plate _o_^{1} at the proper time by means of friction plates, which are set to the required tension by check nuts. The latch plate _o_^{1} is held by a spring latch _v_, which is secured to an arm _v_^{1} mounted loosely on a stud. The arm _v_^{1} is moved by a disk _v_^{2} carrying a secondary latch _v_^{3}. This secondary latch _v_^{3} has on one side a roll which engages with a fixed cam _v_^{4} which trips the latch _v_^{3} from its connection with the arm _v_^{1}, thus allowing the spring on the latch _v_ to return it to its seat in the latch plate _o_^{1}. The disk _v_^{2} is moved by a steel ribbon (S, Fig. 2070) which is connected to a pair of plates, _t_ _t_^{1}, held together by a [T]-slot and bolts, and mounted loosely upon the carriage which carries the cutter slide _f_. The object of the double plates is to take up the slack ribbon, in any required position of the carriage, on the knee _e_. To the inside plate _t_^{1} is connected a shipper rod _t_^{2}, which carries a dog and is operated by the return motion of the cutter slide _f_. A spiral spring coiled on the stud supporting the disk _v_^{2} returns the disk to its original position on the forward motion of the cutter slide _f_ and reseats the secondary latch _v_^{3} in its seat in the arm _v_^{1}. This arrangement of dividing mechanism requiring but one turn of the shaft _m_^{3} possesses some very decided advantages over the ordinary way of simple gearing and multiplied turns. The latch _v_ is tripped immediately after leaving its seat in the plate _o_^{1}, and is returned by its spring against the periphery of the plate, and is surely seated by means of a lip on the upper side of the plate. Should it, however, fail by reason of any accident no harm will be done as the gear will be correctly spaced whenever the latch is seated, only one or more spaces will have been missed. Another advantage is that the feed gear can be disconnected and the latch withdrawn, thus allowing the gear to be revolved for the purpose of examination without any necessity for remembering the exact number of turns. When the latch is again seated the gear will be always properly spaced. [Illustration: Fig. 2072.] Fig. 2073 represents the same machine made half automatic, or in other words the feed is automatic, but when the cut is through, the worm that actuates the feed is thrown out of gear by a catch which lets the box or bearing at the left hand of the worm shaft drop vertically, this catch being operated by a stop on the side of the cutter slide. The method of arranging the feed mechanism so that it shall remain undisturbed, and require no alteration or adjustment at whatever height the knee carrying the cutter slide may be, is substantially the same as that already described with reference to the universal milling machine in Fig. 1893, while the dividing mechanism and other general features are the same as in the full automatic, with the exception of the mechanism for operating the cutter during the return stroke, and operating the dividing mechanism, both of which operations are done by hand in the half-automatic machine. Fig. 2074 represents a Whitworth machine in which the cutter is carried in a vertical spindle carried in a sliding head. A is the driving pulley, B a pair of bevel-gears, and C a pinion driving the cutter spindle D, the cutter being at E. The cutter spindle has journal bearing at each end in arms upon the sliding head F, which is operated along the slideway of H by the gear-wheel G, receiving motion from the worm at C; at K is the index wheel, the wheel to be cut being carried on its shaft at M. The head N, carrying the index-wheel shaft, may be moved along the bed on which it slides by the handle P, which operates a screw within the bed, and engaging a nut on the under side of N. The worm for the worm-wheel K is carried beneath the wheel by a bracket from N, and being on a splined shaft moves with N. P is the handle for the divisions, the latter being obtained by means of change wheels at J, which connect with the worm shaft. By employing change gears the handle P makes a complete turn for any division, and is locked in a recess, which determines when an exact turn has been made. The range of a machine of this design is very great, because of the length of the bed on which the head N slides, which may be longer than would be practical if it stood upright. Fig. 2075 represents a gear planing machine, shown with a bevel-gear in place. The main spindle is horizontal upon a fixed head, and has its dividing mechanism at the back of the machine. A single pointed tool is used in a slide rest, operated (by crank motion) upon the horizontal slideway shown, which may be set at any required angle for bevel-wheels. The cut is carried from the point to the flank of the tooth, and is put on by a rod and ratchet motion, the rod striking against the stop seen beneath the cross slide for the slide rest, and on the side of the horizontal slideway. Figs. 2076, 2077, 2078, 2079, 2080, 2081, and 2082 represent different views of a gear-cutting machine, which consists of a bed plate A A, Figs. 2077, 2078, and 2079, having an extension at end A^{2}, to support the hollow cylindrical column A^{3}, which carries an overhead shaft _a_, at one end of which is a four-step cone A^{3}, for driving the cutter feed motions. At the other end are the tight and loose pulleys for driving this shaft, upon which is also a series of grooved pulleys _a_^{5}, arranged in the form of a cone. The object of this is to drive the cutter. At the base of the column A^{3} is a corresponding series of grooved pulleys, also arranged in the form of a cone _a_^{6}. A round belt is employed. The shaft on which _a_^{6} is placed extends through the column, and on its opposite end a grooved pulley is also placed. This serves to drive a belt which, passing over a series of idle pulleys, as will be seen by reference to Figs. 2076 and 2077, drives the rotary cutter. The wheel to be cut is carried as follows: Upon the bed-plate of the machine is placed a head B, Fig. 2078, corresponding to the headstock of a lathe, opposite which is a head B´, answering to the tailstock of a lathe. These two carry a mandrel D, to which is fastened a face-plate D´ against which the work is chucked. At the end of D´´ is fixed, in the usual manner, the worm-wheel for the dividing mechanism. The cutting arbor is held in a head that is carried in a cross slide C^{2}, Fig. 2077, this cross slide being a carriage that may be fed along the side extension of the bed, which is broken off in the plan view of the machine, Fig. 2078. The two slides thus provided in this machine form in effect a longitudinal and cross feed, answering to the feeds of a lathe carriage and tool rest. [Illustration: _VOL. II._ =GEAR-CUTTING MACHINES.= _PLATE VII._ Fig. 2074. Fig. 2075.] The cutter head M, Fig. 2077, is composed of two parts, C and M. Provision is made to swing the head in two directions, one of which is noted by the plain arrow and the other by the feathered arrow in the engravings. Between the two the cutter arbor, it will be perceived, may be set at an angle in whatever direction the nature of the work may require. Referring to Figs. 2076 and 2077, it will be seen that the cutter-driver mechanism operates as follows: The tight pulley _a_^{1}, driven in the direction noted by the arrow, turns the cone _a_^{6} which drives the pulley _b_. The belt from _b_ passes over grooved idlers, _b_^{1}, _b_^{2}, _b_^{3}, &c., to the grooved pulley _b_^{8}, which is fast on its shaft and drives a train of gearing that operates the cutter arbor, the train being best shown in Fig. 2077. The train of gearing thus driven is composed of gears _c_^{1}, _c_^{2} and _c_^{5}, the latter being on the cutter arbor. The object of this arrangement is to obtain a high belt velocity. It will be seen that all these gears have their teeth at an angle to their axes, a feature that has been introduced to obtain smoothness of action. To maintain equal tension of belt at whatever angle the cutter may be set, the idle pulley _b_^{2} acts as a belt tightener, being carried by the rods _t_ and _t_^{1}. [Illustration: Fig. 2073.] Referring now to the feed motions, the machine is provided with a quick return for the cutter, the mechanism of which is as follows: The cone pulley _a_^{4}, Fig. 2077, is mounted upon a driver shaft _d_, Fig. 2079. Upon this shaft are two loose bevelled pinions _d_^{2} _d_^{4}, between which, and splined to the shaft, is a clutch _f_. For the feed traverse the clutch _f_ is moved to engage with the pinion D^{4}, while for the quick return it engages with _d_^{2}. This device corresponds to the old-style quick-return motion used in some of the heavy English planing machines. The clutch _f_ is operated by a rod _l´_, and drives the bevelled pinions _d_^{2} _d_^{4} by friction. The hub of the clutch is coned to fit a coned recess in the hubs of the two pinions. A pair of gears, _d_^{6} _d_^{7}, transmit the motion of _d_^{5} to the shaft _d_^{1}, on the end of which is the pinion _e_^{1}, Motion is conveyed from this pinion to the feed-screw _e_, Fig. 2081, by the intermediate gears e^{2}, _e_^{3}, _e_^{4} and _e_^{5}, and also by the helical pinions _e_^{6} and _e_^{7}, the latter two being also shown in Fig. 2081. Referring to the dividing mechanism, E, Fig. 2077, is an index-wheel operated by a worm. E^{1} is an arm with a locking tongue. Motion from E is conveyed to the shaft _g_ through a swing-frame, shown in dotted lines in Fig. 2077, and a train of gears _g_^{2}, _g_^{3}, _g_^{4}, _g_^{5}, _g_^{6}. On shaft _g_, Fig. 2078, is a pair of angular-toothed beveled pinions, _h_^{1} _h_^{2}, and on shaft _h_, Fig. 2080, is a pinion _h_^{3}, driving a pinion _h_^{4}, which in turn drives pinions _i_ _i_^{1}. The latter drive the worm H´ which operates the wheel H. The two shafts carrying _i_ _i_^{1} are supported by a piece F, the arm of which appears in section. This is fixed on the large toothed wheel G, indicated by the dotted lines in the same figure. The piece F above referred to is not fully shown in the engraving, portions of it having been omitted in order to show the mechanism previously mentioned. The wheel H is mounted on shaft D´´, and is used to revolve the face plate D´, all as shown in Fig. 2078. The wheels _g_^{2} _g_^{3} are change wheels, whose relative diameters determine the number of turns the wheel E must make for a given pitch. The arm E^{1}, Fig. 2077, is provided with a spring to hold the index pin into the notch of the index wheel. From this description it is obvious that when the number of the teeth of the wheel to be cut is a multiple of that of the wheel H, the number of turns to be given to the tangent screw H´, Fig. 2080, is exactly determined by the ratio existing between these two numbers. On the other hand, where the number of teeth required is not a multiple of the teeth in the wheel H, the number of turns to be given to the screw will be equal to _n_ plus a fraction. In the first case, if all the intermediate gears between the dividing apparatus and the tangent screw are arranged to transmit to the former a number of definite turns, it will suffice to make the crank describe the number of turns indicated by the ratio the wheel E bears to the worm-wheel. In the second case, in order to give the tangent screw _n_ turns plus a fraction by giving the crank _n_ + turns, it is necessary to employ several wheels, for which the ratio must be calculated. If the division so obtained is not an exact divisor of the number of teeth of the wheel H, it is necessary that one of the wheels forming the combination shall have a number of teeth which is a multiple of the division mentioned. [Illustration: Fig. 2076.] Another consideration with reference to the number of turns to be given to the crank of the dividing apparatus is mentioned in the inventor's description of this machine. The smaller the number the greater will be the chance of error in the result; for example, if it be supposed that a division corresponding to one turn of the tangent screw is to be made, if only one turn of the crank is made, the play unavoidable where easy movement is secured will be repeated and multiplied in the same way that an error is produced after a certain number of divisions. If, on the contrary, the mechanism be arranged so that the number of turns of the crank is multiplied in obtaining one turn of the tangent screw, the error will be appreciably reduced. It is therefore recommended by the designer of this machine to arrange the train of gears so as to give a certain number of full turns to the crank in all cases. If, after having cut the teeth in the blank, it is desirable to go over them again, it is simply necessary to turn the screw _j_ which engages with the gear-wheel J^{1}. The next feature to be described is the adjustment of the cutter. In some cases it is necessary to incline the cutter in such a way that the axis of the shaft carrying it forms a certain angle with the vertical. This is the case in cutting angle teeth, as shown in Fig. 2076. In order to produce the necessary angle for such teeth, it is only necessary to turn the worm _k_ that engages with the worm-wheel _k_^{1}, Fig. 2077. This wheel is fast on to the piece M, and the latter, when set to the desired inclination, is kept in place by means of bolts O, Figs. 2077 and 2081. In some cases it is necessary to incline the cutter in such a way that the axis of the shaft that carries it does not cease to be in a vertical plane perpendicular to the shaft D, this being the case as illustrated in Fig. 2082. In order to obtain this obliquity the small shaft _m_ is turned, and the movement so obtained is transmitted by means of two small pinions _m_^{2} _m_^{3} to the shaft carrying at its extremity the screw _n´_. This screw gears with the segment _n´´_. The latter is fixed to a piece J, furnished with bearings for the reception of the shaft that drives the cutter spindle, which is adjusted endways by means of the nuts shown. [Illustration: Fig. 2077.] If it is desired to produce a wheel with angle teeth it is necessary, after having arranged the cutter as shown in Fig. 2076, and while the forward motion of the carriage takes place, that the wheel R shall turn with a slow, regular movement until the tooth operated upon is finished. After this the tool retraces its path at a somewhat higher speed. This automatic motion is obtained from a shaft (Fig. 2076), on which are placed the pinions _e_^{2} _e_^{3}. This shaft carries a third pinion _p_^{2}, which, by means of one or more pairs of wheels mounted two by two on a swinging frame _p_, as shown by _p_^{3} _p_^{4} _p_^{5}, turns the shaft _p´_ (Fig. 2080), which carries at one of its extremities the wheel _p_^{5} and at the other the screw _h_^{3}. This screw, by proper intermediates, operates the toothed wheel G, Fig. 2080, which in its rotation carries along the piece F, with all the parts supported by it. In this movement the pinion _h_^{3} does not turn, nor does the second pinion _h_^{4}, which slides on the former. The screw H´ slightly turns the large wheel H, which, as previously mentioned, is mounted on the shaft D, Fig. 2078. When the special tooth operated upon is finished the movement is reversed by operating the lever _l_. The table and the wheel R, Fig. 2077, then move in the opposite direction. When the original position is reached by the cutter, the reversing lever is thrown out of gear; the handle E´ is then used so as to effect the proper division, and the machine is again started. As has been shown, only a small portion of the circumference of the wheel G is subjected to wear. In this way it would be possible to limit the operation of cutting the teeth to a certain length of arc only. In that case, however, considerable wear would be produced; for this reason the constructor has preferred to provide the whole circumference with teeth, in order to change the working point from time to time, so as to distribute the wear. In order to permit this displacement it is necessary to disengage the worm K (Fig. 2076), which is accomplished by turning the hand wheel _v_, mounted on the shaft _v´_, Fig. 2078. This shaft carries at each extremity small pinions, _v_^{2}, _v_^{3}, gearing with other pinions fixed at the extremity of each of the supports of the shaft _p´_. [Illustration: Fig. 2078.] [Illustration: Fig. 2079.] [Illustration: Fig. 2080.] In order to make the operation of this machine better understood, we will conclude our description by some practical examples of the calculations required in making helical teeth. It will be observed that the two small movements necessary in cutting an angle tooth in a given inclination are obtained first by the screw _e_, Fig. 2077, feeding the cutter head, and second by the tangent screw K, Fig. 2076, that governs the rotary motion of the wheel G, and consequently of the shaft D, carrying the face plate and the blank to be cut. The second wheel H, mounted on this shaft, is driven by the endless screw H´, Fig. 2080, the supports of which are fixed on the wheel G. It will be observed at the same time that the speed of the screw _e_ acting upon the tool holder is the same as that of the shaft carrying the wheels _e_^{2} _e_^{3} and _p_^{2}, since the wheels _e_^{4} _e_^{5} _e_^{6} _e_^{7} have the same number of teeth. It is obvious, therefore, that that ratio of speed which will exist between the tangent screw K and the shaft of wheels _e_^{2} _e_^{3} and _p_^{2} will have to be the same as that between the driving screw _e_ of the cutter head and the tangent screw K. Consequently, the combinations of wheels that connect this tangent screw K to the shaft _e_^{2} _e_^{3} and _p_^{2} will produce the same effect as if they were connected directly with the feed screw _e_. This being established, the general formulæ determining the gearing to be employed in order to produce helical teeth inclined at a certain angle are obtained in the following manner: It should here be observed that the teeth produced will be what in the United States are called angle teeth, corresponding, however, so nearly to the helix as to be considered helical. Suppose that the number of teeth in the wheel G is 300, and that the pitch of the driving screw of the cutter head is 5 mm., using for convenience the French system of measurements. Let _x_/_y_ be the ratio of the four wheels that it is necessary to mount. Let M designate the degrees of inclination of the teeth. Let P equal the pitch of the desired helix, and D the diameter of the wheel to be operated upon. We then have cotan. M = P/(D × 3.14), from which we find P = cotan. M × D × 3.14, and in order to make the cutter head run over a distance corresponding to this pitch, the driving screw _e_ must make a number of turns equal to cotan. M × D × 3.141 -------------------- 5 But while the cutter head passes over a distance equal to the pitch, the wheel G makes one turn and the tangent screw 300 turns; consequently, the ratio to be established between the speed of the tangent screw and between that of the screw driving the carriage will be represented by _x_ 1500 --- = -------------------- _y_ cotan. M × D × 3.141 [Illustration: Fig. 2081.] [Illustration: Fig. 2082.] Thus, for a wheel with a diameter of 1.75 inches, the machine ought to have an inclination of 15° to the primitive circumference, and we would have, for the ratio to be established between the tangent screw and the driving screw, _x_ 1500 1500 --- = ------------------------- = -------- _y_ cotan. 15° × 1.75 × 3.141 20.51778 It should be remarked that, according as the angle should be either to right or to left, one or two intermediate pieces are placed on the swing-frame, the slide of which is nearly horizontal. The speed of the driving shaft, supported by the column mentioned in introductory remarks, is 120 revolutions; that of cutter equals from 20 to 30 revolutions; that of screw of cutter head, advance from 1 to 42 revolutions, return from 7 to 66 revolutions. CHAPTER XXV.--VICE WORK. Vice work may be said to include all those operations performed by the machinist that are not included in the work done by machine tools. In England vice work is divided into two distinct classes, viz., fitting and erecting. The fitter fits the work together after it has been operated upon by the lathe planer and other machine tools, and the erector receives the work from the fitter and erects it in place upon the engine or machine. Fitting requires more skill than turning, and erecting still more than fitting, but it is at the same time to be observed that the operations of the erector includes a great many of those of the fitter. In treating of the subjects of vice work and erecting, it appears to the author desirable to treat at the same time of some operations that are not usually included in those trades, because they are performed with tools similar to those used by the fitter, and may be treated equally as well in this way as in any other, while a knowledge of them cannot fail to be of great service to both the fitter and erector. Among the operations here referred to are some of the uses of the hammer; such, for example, as in straightening metal plates. The vice used by the machinist varies both in construction and size according to the class of work it is to hold. For ordinary work the vice may possess the conveniences of swiveling and a quick return motion, but when heavy chipping constitutes a large proportion of the work to be done the legged vice is preferable. The height of vice jaws from the floor is usually greater for very small work than for the ordinary work of the machine shop, because the work needs to be more clearly observed without compelling the operator to stoop to examine it. The gripping surfaces of vice jaws are usually made to meet a little the closest at the top, so as to grip the work close to the top and enable work cut off with a chisel to be cut clean and level with the jaws. [Illustration: Fig. 2083.] The jaws of the wood-worker's vice are made then as in Fig. 2083, and reach higher above the screw than the vices used for iron work, because the work is often of considerable depth, and being light will not lie still of its own weight, as is the case with iron. [Illustration: Fig. 2084.] An example of the ordinary vice of the machine shop is shown in Fig. 2084, which represents partly in section a patent swivel vice. A is the jaw in one piece with the body of the vice, and B is the movable jaw, being the one nearest to the operator. The movable jaw is allowed to slide freely through the fixed one (being pushed or pulled by hand), or is drawn upon and grips the work by operating the handle or lever H. The means of accomplishing this result are as follows: As shown in the cut, B is free to be moved in or out, but if H be pulled away from the vice, the shoulder C, meeting the shoulder _n_, will move the toggle G, and this, through the medium of G´, moves the tooth bar _t_, so as to engage with the teeth on the side of the movable jaw bar shown at T. As soon as the teeth _t_ meet the teeth T the two travel together, and the jaw B closes on and grips the work. But as the motion is small in amount, the jaw B should be placed so to nearly or quite touch the work before H is operated. To unloose the work, the handle H is operated in an opposite direction, and the hook M meets _m_ and pulls _t_ to the position shown. The spring S operates upon a hook at U, to engage the teeth _t_, with the rack T, as soon as the handle H is moved in the tightening direction. The vice grips with great force, because during the tightening the toggle, G is nearly straight, and its movement less than would be the case with a screw-vice having the ordinary pitch of thread and under an equal amount of handle movement. [Illustration: Fig. 2085.] In this vice the fixed jaw is made to fasten permanently to the work bench, but in others having a similar tightening mechanism the fixed jaw is so attached to the bench as to allow of being swivelled. The method of accomplishing this is shown in Fig. 2085, in which S is the foot of the vice bored conical to receive a cone on the casting R, which is fastened to the bench B. W is a washer and H the double arm nut. Loosening this nut permits of the vice being rotated upon R. When handle H is operated to release the movable jaw it can be moved rapidly to open and receive the work, and to close upon the work, when by a second handle movement the work can be gripped, the operation being much quicker than when the movable jaw is traversed by a screw and nut. In this vice the gripping surface of the jaws are always parallel one to the other, and attachments are employed to grip taper work as wedges. [Illustration: Fig. 2086.] [Illustration: Fig. 2087.] In Fig. 2086 is represented a patent adjustable jaw vice, which is also shown in Fig. 2087 with the adjustable jaw removed and upside down. From the construction it is apparent that the groove G, being an arc of a circle of which C is the centre, the jaw is, as it were, pivoted horizontally, and can swing so as to let the plane of the jaw surfaces conform to the plane of the work; hence a wedge can be gripped all along the length enveloped by the jaws, and not at one corner or end only. When the pin A is inserted the jaw stands fixed parallel to the sliding jaw. The pin A engages in a ratchet in the base below it to secure the back vice jaw in position when it is set to any required angle. A second convenience in this vice is that the whole vice can be swivelled upon the base that bolts to the bench, which is provided with a central hole and annular groove into which the base of the field jaw pivots; at B is a spring pin passing into holes in the bench plate, so that by lifting the pin B, the whole vice can be swung or rotated upon the base or bench plate, until the pin B falls into another hole in the base plate, which is provided with eight of these holes. The movable jaw is here operated by a screw and nut. [Illustration: Fig. 2088.] Fig. 2088 represents a form of leg vice for heavy work. In the ordinary forms of this class of vice the two gripping surfaces of the jaws, only stand parallel and vertical when at one position, because the movable leg is pivoted at P; but in that shown in the figure the movable jaw is supported by the arm A, passing through the fixed leg L, which carries a nut N. A screw S, having journal bearing in the movable leg, screws through the nut N, and is connected to the upper screw by the chain C, which passes around a chain wheel provided on each screw, so that the movable leg moves in an upright position and the jaw faces stand parallel, no matter what the width of the work. This is a very substantial method of obtaining a desirable and important object, and greatly enhances the gripping capability of the vice. Fig. 2089 represents a sectional view of another patent vice. A is the sliding and B the fixed jaw. P is the bed plate carrying the steel rack plate H. Attached to each side of the base of the handle is a disk. These disks are carried on the outer end of the movable jaw A, and are held in place by the friction straps T, adjusted by the screws S. On the radial face of the disk is the pin K, which, when the handle or lever is lifted or raised, depresses the end of lever J, which at its other end raises the clutch G, disengaging the same from the rack H, as shown in the engraving. The jaw A is thus free to be moved by hand, so as to have contact with the work. To tighten the vice the handle is depressed, whereon K releases J and the latter permits the toothed clutch G to engage with the teeth of H. At the same time the bar D, which is pivoted to the disks, is drawn outward. The end of the bar D, meeting the surface of the lug shown on A, acts (in conjunction with the toothed clutch H) as a toggle fulcrum from which the disks may force the movable jaw to grip the work. [Illustration: Fig. 2089.] This action may be more minutely described as follows: The end _d_ of D is pivoted upon the disks, as shown; hence when the handle is depressed the effort of the end _d_ is to move to the right, but D being fixed at the other end the pressure is exerted to force the movable jaw to the left, and therefore upon the work. The amount of jaw movement due to the depression of the handle is such that if that jaw is pushed near or close to the work the handle will stand about vertical downward when the vice firmly grips the work. For vices whose jaws cannot be swiveled horizontally to enable them to conform to taper work, attachments for the jaws are sometimes provided, these attachments having the necessary swiveling feature. So likewise for gripping pipes, and similar purposes, attachments are made having circular recesses to receive the pipes. [Illustration: Fig. 2090.] [Illustration: Fig. 2091.] To prevent the vice jaws from damaging the work surface, and also to hold some kinds of work more firmly, various forms of clamps, or coverings for the vice jaws are used. Thus Figs. 2090 and 2091 represent clamps for holding round or square pins. In the former the grooves pass entirely through the clamp jaws, so as to receive long pieces of wire, while in the latter the recesses are short, so as to form an abutment for the end of the pins, and act as a gauge in filing or cutting them off to length. [Illustration: Fig. 2092.] An excellent form of pin clamp is shown in Fig. 2092, the spring bow at the bottom acting to hold the jaws open and force the faces against the vice jaws when the latter are opened. The flanges at B B rest upon the tops of the vice jaws; hence it will be seen that the clamp is not liable to fall off when the vice is opened to receive the work, which is placed either in the hole at A or that at B, as may be most desirable. [Illustration: Fig. 2093.] Fig. 2093 shows such a clamp holding a screw, the clamp jaws being forced against the screw by the vice jaw pressure, when the vice jaws are opened the spring of the bow will cause the clamp jaws to open and release the screw. Clamps such as shown in Figs. 2090 and 2091, but without the pin holes, are also provided, being made one pair of copper and another of lead, the latter being preferable for highly finished work. As the filings are apt to imbed in the copper, and, furthermore, as the copper gradually hardens upon its surface, the copper clamps require to be annealed occasionally, which may be done by heating them to a low red heat and dipping them in water. Lead clamps will hold small work very firmly, and are absolutely essential for triangular or other finished work having sharp corners, and also for highly finished cylindrical work, which may be held in them sufficiently firmly to be clipped without suffering damage from the vice jaws. A piece of thick leather, such as sole leather, also forms a very good clamp for finished work, but to prevent its falling off the vice jaws it is necessary to cut it nearly through on the outside and at the bent corner. The hammer in some form or other is used in almost all kinds of mechanical manipulation, and in each of these applications it assumes a form varied to suit the nature of its duty, and of the material to be operated upon. In the machine shop it is used to drive, to stretch, and to straighten. The most skilful of these operations are those involving stretching operations, as saw and plate straightening, examples of which will be given. In using a hammer to drive, the weight and velocity of the hammer head are the main considerations. For example, the force of a blow delivered by a hammer weighing 1 lb., and travelling 40 feet in a second, will be equal to that weighing 2 lbs, and travelling 20 feet in a second; but the mechanical effects will be different. If received on the same area of impact the effects will sink deeper into the metal with the greater velocity, and they will extend to a less radius surrounding the area of impact. Thus in driving out a key that is fast in its seat, a quick blow is more effective than a slow one, both being assumed to have at the moment of impact an equal amount of mechanical force stored up in them. On the other hand, for riveting the reverse will be the case. In the stretching processes the hammer requires to fall with as dead a blow as possible. Thus the hammer handle is, for saw stretching, placed at such an angle to the length of the hammer that the latter stands about vertical when the blow is delivered. In straightening, the blow is varied to accommodate the nature of the work; thus a short crook or bend would be best straightened by a quick blow with a light hammer, and a long one by a slower blow with a heavier hammer, which would cause the effects of the blow to affect a greater radius around the part receiving the impact. As an example of the difference in mechanical effect between a number of blows aggregating a given amount of energy and a single blow having an equal amount of energy, suppose the case of a key requiring a given amount of power to start it from its seat, and every blow delivered upon it with insufficient force to loosen its hold simply tends to swell and rivet it more firmly in the keyway. Probably the most expert use of the hammer is required in the straightening of engravers' plates, as bank-note plates; and next to this comes the ornamental repoussé work of the manufacturing jeweller. The most expert hammer process of the machine shop is that of straightening rifle barrels and straightening saws and sheet metal plates. In straightening rifle barrels, the operator is guided as to the straightness as follows: A black line is drawn across a piece of glass elevated to the light, and the straightener looks through the bore at this line, which throws a dark line of shadow along the rifle bore. If this line appears straight while the barrel is rotated the bore is straight; but if the line waves the barrel requires straightening, the judgment of the operator being relied upon to determine the amount of the error, its location, and the force and nature of the blow necessary to rectify it. The following information on the duration of a blow is taken from _Engineering_, the results having been obtained from some experiments by Mr. Robert Sabine. These experiments, which were intended as preliminary to a more extended inquiry, were made with a view to find approximately how the duration of a blow varied with the weight of the hammer, its velocity of descent, and with the materials. An iron ball weighing 1/4 lb. was suspended by a fine wire from an insulated support upon the ceiling; so that when it hung vertically it just grazed the vertical face of an ordinary blacksmith's anvil placed upon its side on a table. By raising the ball and letting it swing against the face of the anvil a blow of varying force could be struck. On rebounding, the ball was arrested whilst the excursion of the galvanometer needle was observed. By measuring the angle through which the ball was separated, its vertical fall and final velocity could be easily deduced. In this way the greatest vertical height from which the iron ball was let fall on to the face of the iron anvil was 4 ft., the least about 1/80 inch. Six readings were taken for each height, and they were invariably found to agree amongst each other. The averages only are given in the following records: Vertical fall Duration of contact in inches. in seconds. 48 0.00008 36 0.00008 28 0.00008 17 0.00009 9-1/4 0.00010 4 0.00011 1 0.00013 0-1/4 0.00016 0-1/16 0.00018 0-1/32 0.00021 0-1/80 0.00030 From this it would appear that when the velocity of a blow is increased, the duration is decreased within a certain limit; but that it reaches a minimum. The velocity of impact in the first experiment was about sixty times as great as in the last one; but the duration of the blow appears to be reduced only to about one-fourth of the time. The blows given by two hammers of different weights were compared. No. 1 weighed 4 ozs., No. 2 weighed only 2-1/4 ozs. The durations of the blows were as follows: +----------------+---------------------------+ | | Duration of contact. | | Vertical fall. +-------------+-------------+ | | Ball No. 1. | Ball No. 2. | +----------------+-------------+-------------+ | inch. | seconds. | seconds. | | 1 | 0.000135 | 0.000098 | | 4 | 0.000096 | 0.000083 | +----------------+-------------+-------------+ It appears from this that a heavier hammer of the same material gives a longer duration of blow. In the course of these experiments it was observed that the ball after striking the anvil rebounded irregularly, sometimes to a greater, at others to a less height, and that some relation appeared to exist between the heights to which the ball rebounded and the excursions of the galvanometer needle due to the residue of the charge. In the next series, therefore, the rebounds of the iron ball from the iron anvil were measured and recorded, from which it appeared that when the rebound was greater the duration of contact was shorter, and _vice versâ_. +----------------+-------------------+-------------------+ | Vertical fall. | Vertical rebound. | Duration of blow. | +----------------+-------------------+-------------------+ | inch. | inch. | seconds. | | 6 | 2 | 0.000120 | | 6 | 2-1/2 | 0.000111 | | 6 | 3-1/4 | 0.000101 | | 6 | 3-1/2 | 0.000091 | | 14-1/2 | 3-1/4 | 0.000106 | | 14-1/2 | 4-1/2 | 0.000103 | | 14-1/2 | 5-1/4 | 0.000095 | | 14-1/2 | 6-1/2 | 0.000086 | | 25 | 7-3/4 | 0.000096 | | 25 | 8-1/4 | 0.000091 | | 25 | 9-1/2 | 0.000086 | | 25 | 12 | 0.000078 | +----------------+-------------------+-------------------+ The explanation of this is probably that when the energy of the blow is expended in bruising or permanently altering the form of the hammer or anvil by which the contact of the two is prolonged, it has less energy left to enable it to rebound, and _vice versâ_. Substituting a brass anvil and brass ball, it was found that the blow was duller, the rebound much less, and the duration contact nearly three times as great as when the iron ball and anvil were used. +----------------+-------------------+----------------------+ | Vertical fall. | Vertical rebound. | Duration of contact. | +----------------+-------------------+----------------------+ | inch. | inch. | seconds. | | 1-3/4 | 0-1/3 | 0.00036 | | 6 | 1 | 0.00033 | | 14-1/2 | 1-1/2 | 0.00026 | | 25 | 2 | 0.00027 | +----------------+-------------------+----------------------+ This series also shows the longer duration of the blow when its velocity is small. Using a brass anvil and iron ball the duration of the blow was greater than when both were of iron, but less than when both were of brass. +----------------+-------------------+----------------------+ | Vertical fall. | Vertical rebound. | Duration of contact. | +----------------+-------------------+----------------------+ | inch. | inch. | seconds. | | 1-3/4 | 0-1/8 | 0.00021 | | 6 | 0-1/2 | 0.00018 | | 14-1/2 | 1-1/3 | 0.00015 | | 25 | 2 | 0.00014 | +----------------+-------------------+----------------------+ Striking the brass anvil with a common hammer, the duration of the blow appeared shorter when struck sharply. Duration of contact. seconds. Moderate blow 0.00027 Harder blow 0.00019 Striking the blacksmith's anvil with a common carpenter's hammer, the duration appeared to be nearly constant. Duration of contact. seconds. Moderate blow 0.00011 Harder blow 0.00010 It was, of course, necessary to allow in each case the hammer to rebound freely, and not to prevent it doing so by continuing to exert any pressure at the instant of the blow. When this condition was observed, it was invariably found that the harder and sharper the blow the shorter was its duration. It was also noticed that whenever the anvil gave out a sharp ringing sound, the duration of the blow was much shorter than when the sound was dull. A very slight error would be introduced by reason of thermo-currents set up between the metals at the moment of the blow. By reversing the direction of charge of the accumulator, however, the effect from this cause was found to be quite inappreciable. [Illustration: Fig. 2094.] [Illustration: Fig. 2095.] [Illustration: Fig. 2096.] [Illustration: Fig. 2097.] [Illustration: Fig. 2098.] The machinists' hand hammer is usually made in one of the three forms shown in Figs. 2094, 2095 and 2096, and varies in weight from about 1-3/4 lbs. for heavy chipping to about 1/2 lb. for light work, the handle being about 15 inches long for the heavy, and about 10 or 12 for the light business. The round face is usually somewhat convex on its surface with its edge slightly rounded or beveled. The pane or pene A, Fig. 2097, is usually made in European practice to stand at a right angle to the axis of the handle as shown, while in the United States it is usually made to stand parallel with the handle as in Fig. 2096. The face end is sometimes given taper as in Figs. 2094 and 2095, and at others parallel as in Figs. 2097 and 2098, or nearly so. The pene is mostly used for riveting purposes, and it is obvious that with the pene at a right angle to the handle axis as in Fig. 2097, it will not matter whether the pene meets the work quite fair or not, especially as the pene is made slightly curved in its length, and it is easier to hold the hammer level sideways than it is to hold it so true lengthways that the pene, when forward, as in Fig. 2096, will meet the work fair. [Illustration: Fig. 2099.] [Illustration: Fig. 2100.] [Illustration: Fig. 2101.] The proper shape for the eye of a hammer is that shown in Figs. 2099 and 2100, a representing the top of the hammer. The two sides of the eye are rounded out from the centre towards each end, while the ends of the eye are made parallel. The form of the eye as viewed from the top A is as shown in Fig. 2102, while Fig. 2101 represents a view from the bottom B. The handle is fitted a driving fit and is driven in from side B, and is shaped as in Figs. 2103 and 2104 which are side and edge views. From C to D the handle fills the eye, but from D to E it fills the eye lengthways only of the oval. A saw-slot, to receive a wedge, is cut in the handle, as shown in Fig. 2104. The wedge is best made of soft wood, which will compress and conform itself to the shape of the slot. To drive the handle into the eye, preparatory to wedging it permanently, it should be placed in the eye held vertically, with the tool head hanging downward, and the upper end struck with a mallet or hammer, which is better than resting the tool head on a block. The wedge should be made longer than will fill the slot, so that its upper end may project well, and the protruding part, which may split or bulge in the driving, may be cut off after the wedge is driven home. [Illustration: Fig. 2102.] [Illustration: Fig. 2103.] The wedge should be driven first with a mallet and finally with a hammer. After every few blows on the wedge, the tool should be suspended by the handle and the end of the latter struck to keep the handle firmly home in the eye. This is necessary, because driving the wedge in is apt to drive the handle partly out of the eye. [Illustration: Fig. 2104.] [Illustration: Fig. 2105.] The width of the wedge should equal the full length of the oval at the top of the eye, so that one wedge will spread the handle out to completely fill the eye, as shown in Fig. 2105. Metal wedges are not so good as wooden ones, because they have less elasticity and do not so readily conform to the shape of the saw-slot, for which reasons they are more apt to get loose. The taper on the wedge should be regulated to suit the amount of taper in the eye, while the thickness of the wedge should be sufficiently in excess of the width of the saw-cut, added to the taper in the eye, that there will be no danger of the end of the wedge meeting the bottom of the saw-slot. [Illustration: Fig. 2106.] By this method, the tool handle is locked to the tool eye by being spread at each end of the same. If the top end of the tool eye were rounded out both ways of the oval, two wedges would be required to spread the handle end to fit the eye, one wedge standing at a right angle to the other. In this case, one wedge may be of wood and one of metal, the one standing across the width of the oval usually being the metal one. The thin edge of the metal wedge is by some twisted, as shown by Fig. 2106, which causes the wedge to become somewhat locked when driven in. In fitting the handle, care must be taken that its oval is made to stand true with the oval of the tool eye. Especially is this necessary in the case of a hammer. Suppose, for example, that in Fig. 2107 the length of the oval of the handle lies in the plane A B, while that of the eye lies in the plane C D, then the face of the hammer will meet the work on one side, and the hammer will wear on one side, as shown in figure at E. If, however, the eye is not true in the hammer, the handle must be fitted true to the body of the hammer; that is to say, to the line C D. The reason for this is that the hand naturally grasps the handle in such a manner that the length of the oval of the handle lies in the plane of the line of motion when striking a blow, and it is obvious that to strike a fair blow the length of the hammer should also stand in the plane of motion. [Illustration: Fig. 2107.] The handle should also stand at a right angle to the plane of the length of the hammer head, viewed from the side elevation, as shown in Fig. 2108, in which the dotted line is the plane of the hammer's length, while B represents a line at a right angle to A, and should, therefore, represent the axial line of the hammer handle. But suppose the handle stood as denoted by the dotted line C, then the face of the hammer would wear to one side, as shown in the figure at D. In the operation of straightening iron or steel plates by hammer blows, the process when correctly carried out is one of liberating the strains (whose existence throws the plate out of a true plane) by stretching those parts that are unduly contracted. Every hammer blow should, therefore, be directed towards this end, for one misdirected blow entails the delivery of many others to correct its evil influence; hence, if several of such misdirected blows are given, the plate will have upon it a great many more hammer marks, or "hammer sinks" or chops, as they are sometimes termed, than are necessary. As a result, not only will the painter (in fine work) be given extra trouble in stopping the hollows to make a smooth surface, but the following evil will result: Every blow struck by the hammer compresses and proportionately stiffens the small surface upon which it is delivered, and creates a local tension upon the surrounding metal. The misdirected blows then cause a tension acting in opposition to the effect of the properly delivered ones; and though the whole plate may be stiffened by the gross amount of blows, yet there will be created local tensions in various parts of the plate, rendering it very likely to spring or buckle out of truth again. If, for example, we take a plate of iron and hammer it indiscriminately all over its surface, we shall find it very difficult to straighten it afterwards, not only on account of the foregoing reasons, but for the additional and most important one that the effect of the straightening blows will be less, on account of the hammered surface of the plate offering increased resistance to the effects of each blow; and after the plate is straightened, there will exist in it conflicting strains, an equilibrium of which holds the plate straight, but the weakening of any of which will cause the preponderance of the others to throw the plate out of straight; for the effects of the blows cannot be permanent unless the whole body of the iron is acted upon to an equal extent by the hammer. Suppose, for example, that we take a flat plate, and deliver upon it a series of blows round about its centre. The effect will be to make it hollow on one side and rounding on the other, the effect of the blows being, not only to indent the plate in the spots where they fell, but to carry the whole body of the middle out of true; because, the area of the iron being increased by the stretching effect of the blows, the centre leaves the straight line to accommodate the increased area. Thus, if we mark off a circle of, say, a foot in diameter, in the middle of a plate, and hammer it so as to stretch it and increase its area 1/8 inch each way, the form of the plate must alter to suit this added area, and the form of a dish or curve is the only one it can assume. [Illustration: Fig. 2108.] The skilful workman, so soon as he has ascertained where the plate is out of true, sets to work to stretch it, so as to draw the crooked place straight, taking care that the shape and weight of the hammer and the weight of the blows delivered shall bear a proper relation to the thickness of the plate and the material of which it is composed. If it is of consequence that the finished work shall bear no marks of the hammering (as in the case of engravers' plates), an almost flat-faced hammer is employed; but for other work the shapes, as well as the weights, of the hammers vary. [Illustration: Fig. 2109.] [Illustration: Fig. 2110.] [Illustration: Fig. 2111.] Fig. 2109 represents what is called the long cross-face hammer, used in saw straightening for the first part of the process which is called the smithing. The face that is parallel to the handle is called the long one, and the other is the cross-face. These faces are at a right angle one to the other, so that without changing his position the operator may strike blows that will be lengthways in one direction, as at A, in Fig. 2110, and by turning the other face towards the work he may strike a second series standing as at B. Now, suppose we had a straight plate and delivered these two series of blows upon it, and it will bend to the shape shown in Fig. 2111, there being a straight wave at A, and another across the plate at B, but rounded in its length, so that the plate will be highest in the middle, or at C; if we turn the plate over and repeat the blows against the same places, it will become flat again. Both faces of this hammer are made alike, being rounded across the width and slightly rounded in the length, the amount of this rounding in either direction being important, because if the hammer leaves indentations, or what are technically called "chops," they will appear after the saw has been ground up, even though the marks themselves are ground out, because in the grinding the hard skin of the plate is removed, and it goes back to a certain, but minute, extent towards its original shape. This it will do more in the spaces between the hammer blows than it will where the blows actually fell, giving the surface a slightly waved appearance. [Illustration: Fig. 2112.] The amount of roundness across the face regulates the widths, and the amount of roundness in the face length regulates the length of the hammer marks under any given force of blow. As the thicker the plate the more forcible the blow, therefore the larger the dimensions of the hammer mark. The twist hammer, shown in Fig. 2112, is used for precisely the same purposes as the long cross-face, but on long and heavy saws or plates, and for the following reasons, namely: When the operator is engaged in straightening a short saw he can stand close to the spot he is hammering, and the arm using the hammer may be well bent at the elbow, which enables him to see the work plainly, and does not interfere with the use of the hammer, while the shape of the smithing hammer enables him to bend his elbow and still deliver the blows lengthways, in the required direction. But when a long and heavy plate is to be straightened, the end not on the anvil must be supported with the left hand, and it stands so far away from the anvil that he could not bend his elbow and still reach the anvil. With the twist hammer, however, he can reach his arm out straight forward to the anvil, to reach the work there, while still holding up the other end, which he could not do if his elbow were bent. By turning the twist hammer over he can vary the direction of the blow the same as with the long cross-face. [Illustration: Fig. 2113.] [Illustration: Fig. 2114.] It is obvious that by slightly bending the elbow and turning either of these hammers over the blows may be caused to be in any required direction, as shown in Fig. 2113. These two hammers are used for the straightening or smithing processes, and not to regulate the tension, because the effects of their blows do not extend equally around the part struck, but follow the form of the hammer marks, whose shapes are shown in Fig. 2114, at A and B, the radiating lines denoting the directions in which the effects extend; obviously the size of these marks depends upon the shape of the hammer face and the force of the blow. [Illustration: Fig. 2115.] [Illustration: Fig. 2116.] [Illustration: Fig. 2117.] An inspection of hammered saw plates, however, will show that the marks (which are scarcely visible, having a merely dulled surface), are usually about one-half wider than the thickness of the plate, and about four or five times as long as they are wide. Obviously, also, the direction of the effects of a blow follow the direction in which the hammer travels. If, for example, the long cross-face falls vertically its effects will extend equally all around the hammer mark, as at A in Fig. 2115, but if the hammer moved laterally to the left while falling its blows would have more effect on the left-hand side of the mark as at B, or if it moved away from the operator its effects would extend most in front as at C, the amount increasing with the force of the blow, and it may be remarked that quick blows are not used, because they would produce indentations or chops; hence, the force of the blow is regulated by the weight of the hammer rather than by the velocity it travels at. On account of the oval shape of the blow delivered by the long cross-face and by the twist hammers, the dog-head hammer, shown in Fig. 2116, is used to regulate the tension of the plate or saw, the effects of its blow when delivered vertically being circular, as at A, in Fig. 2117; obviously, however, if in falling it moved vertically in the direction of arrow C the effects would extend as at B. But while the dog-head is used entirely for regulating the tension, it may also be used for the same purposes as either the long cross-face or the twist hammer, because the smith operates to equalize the tension at the same time that he is taking down the lumps; hence he changes from one hammer to the other in an instant, and if after regulating the tension with the dog-head he should happen to require to do some smithing, before regulating the tension in another, he would go right on with the dog-head and do the intermediate smithing without changing to the smithing hammer. Or, in some cases, he may use the long cross-face to produce a similar effect to that of the dog-head, by letting the blows cross each other, thus distributing the hammer's effects more equally than if the blows all lay in one direction. In circular saws, which usually run at high velocity, there is generated a centrifugal force that is sufficient to actually stretch the saw and make it of larger diameter. As the outer edge of the saw runs at a greater velocity than the eye it stretches most, and therefore the equality of tension throughout the saw is destroyed, the outer surface becoming loose and causing the saw to wabble as it revolves, or to run to one side if one side of the timber happens to be harder than the other, as in the case of meeting the edge of a knot. The amount of looseness obviously depends upon the amount the saw expands from the centrifugal force, and this clearly depends upon the speed the saw is to run at; so the saw straightener requires to know at what speed the saw is to run, and, knowing this, he gives it more tension at the outside than at the eye; or, in other words, while the eye is the loosest, the tension gradually increases towards the circumference, the amount of increase being such that when the saw is running the centrifugal force, and consequent stretching of the saw, will equalize the tension and cause the saw to run steadily. If the eye of a circular saw is loose, or, in other words, if it is rim bound when running, it will dish, as in Fig. 2118, and the rounded side rubbing against the side of the saw slot or kerf, will cause the saw to become heated and the eye to expand more than the outer edges, thus increasing the dish. But if the saw strikes a knot on the hollow side it may throw the dish over to the other side of the saw in an instant. The remedy is to hammer the saw with the dog-head as shown in the figure, not touching the eye, and letting the blows fall closer together towards the circumference. [Illustration: Fig. 2118.] [Illustration: Fig. 2119.] [Illustration: Fig. 2120.] [Illustration: Fig. 2121.] [Illustration: Fig. 2122.] [Illustration: Fig. 2123.] [Illustration: Fig. 2124.] On the other hand, if the eye is tight and the circumference loose the saw will flop from side to side as it runs, and the remedy is to stretch it round about the eye, letting the blows fall wider apart as the outer edge of the saw is approached. The combinations of tight and loose places may be so numerous in circular saws that as the smith proceeds in testing with the straight-edge he marks them, drawing a circular mark, as at G, in Fig. 2119, to denote loose, and the zig-zag marks to indicate tight places. To cite some practical examples of the principles here laid down, suppose we have in Fig. 2120 a plate with a kink or bend in the edge, and as this would stiffen the plate there, it would be called a tight place. To take this out, the hammer marks would be delivered on one side, radiating from the top of the convexity, as on the left, and on the other as shown radiating from the other end of the concavity, as on the right, the smithing hammer being used. This would induce a tight place at A which would be removed by dog-head blows delivered on both sides of the plate. Suppose we had a plate with a loose place, as at G in Fig. 2121. We may take it out by long cross-face blows, as at A and B, delivered on both sides of the plate, or we might run the dog-head on both sides of the plate, both at A and at B, the effect being in either case to stretch out the metal on both sides of the loose place G, and pull it out. In doing this, however, we shall have caused tight places at E and F, which we remove with dog-head blows, as shown. If a plate had a simple bend in it, as in Fig. 2122, hammer blows would first be delivered on one side, as at A, and on the other side, as at B. A much more complicated case would be a loose place at G, in Fig. 2123, with tight places at H, J, K, and L, for which the hammer blows would be delivered as marked, and on both sides of the plate. Another complicated case is given in Fig. 2124, G G being two loose places, with tight places between them and on each side. In this case, the hammering with the long cross-face would induce tight places at D and E, requiring hammer blows as denoted by the marks. [Illustration: Fig. 2125.] [Illustration: _VOL. II._ =THE HAMMER AND ITS USES.= _PLATE VIII._ Fig. 2127. Fig. 2128. Fig. 2129. Fig. 2130. Fig. 2131. Fig. 2132. Fig. 2133. Fig. 2134.] The saw or plate straightener's anvil or block is about 12 by 18 inches on its face, which must be very smooth and is slightly convex, because it is necessary that the plate should be solid on the block, directly beneath the part of its surface which is being hammered, otherwise the effect of the blows will be entirely altered. If, for instance, A, in Fig. 2125, represents the straightening block, and B a plate resting thereon, then the blows struck upon the plate anywhere save over the very edges of the anvil will have but little effect, because of the spring and rebound of the plate; and the effect of the blow will be distributed over a large area of the metal, tending to spring it rather than give it a permanent set. If the blow is a quick one, it may indeed indent the plate without having any straightening effect. On the other hand, by stretching the skin on the upper side of the plate, it will actually, under a succession of blows, become more bent. In fact, to use a straightening block, so large in proportion to the size of the plate that the latter cannot be adjusted so that the part of the plate struck lies solid on the block, renders all the principles above explained almost valueless, and is a process of pounding, in a promiscuous way, productive of hammer marks, and altogether fatal to the production of true work. [Illustration: Fig. 2126.] To straighten the plate shown in Fig. 2125, we place it upon the anvil, as shown in Fig. 2126, striking blows as denoted at A, and placing but a very small portion of the plate over the anvil at first; and as it is straightened, we pass it gradually farther over the anvil, taking care that it is not, at any part of the process, placed so far over the anvil as to drum, which will always take place if the part of the plate struck does not bed, under the force of the blow, well upon the anvil. The methods employed to discover in what parts a plate requires stretching, in order to straighten it and to equalize its tension, are as follow: Suppose we have a plate, say 18 inches by 24, and having a thickness of 19 gauge, and we rest one end of it upon the block and support the other end in the left hand, as shown in Fig. 2127; then with the right hand we exert a sudden pressure in the middle of the plate; and quickly releasing this pressure, we watch where its bending movement takes place. If it occurs most at the outer edges, it proves that the plate is contracted in the middle; while, if the centre of the plate moves the most, it demonstrates that it is expanded in the middle. And the same rule applies to any part of the plate. This way of testing may be implicitly relied upon for all plates or sheets thin enough to be sprung by hand pressure. Another plan, applicable for either thick or thin plates, and used conjointly with the first named, is to stand the plate on edge with the light in front, as in Fig. 2128; we then cast one eye along the face of the plate upon which the light falls, and any unevenness will be made plainly visible by the shadows upon the surface of the plate. The eye should also be cast along the edges to note any twist or locate any kinks. We may take a thin piece of plate in the hands, and if it is loose in the middle and we lay a straight-edge upon its upper surface, and try to bend the middle of the plate downward with the fingers, it will go down under the finger pressure, the straight-edge showing a hollow place in the middle; and the same thing will occur if the straight-edge be tried with either side of the plate uppermost. But if the piece be tight in the middle and we test with the fingers and straight-edge in the same way, the middle instead of bending downwards, appears to rise up, the straight-edge showing it to be rounded. In the first case the middle moves because it is loose, and in the second the edges move because they are loose. Fig. 2129 represents a plate for a circular saw that is loose in the middle, and if we bend the middle down it will become concave on the top, as shown in the figure. But if it were tight in the middle and loose at the outer edge, it would become, under the same pressure, convex on the top, as in Fig. 2130, and here again the part that is loose moves the most. In thin saws, such as hand saws, the workman takes the saw in his hands, as in Fig. 2131, and bends it up and down so that by close observation he may see where it moves the most, and then discover the loose places, or he may watch for the tight places, since these are the places he must attack. [Illustration: Fig. 2135.] The sledge hammer used by the machinist is usually made in one of the two forms shown in Figs. 2132 and 2133, the latter being the most serviceable because it has two faces which may be used for driving purposes, which is the only use the machinist has for the sledge hammer. The coppersmith varies the shape of his hammer faces to suit the nature of the work, thus Fig. 2134 represents a coppersmith's hammer, its two faces being of different sizes and of different curvature, and both being used to form convex surfaces having different degrees of curvature, it being noted that the curvature of the hammer face is always less than that of the work. In other forms of coppersmith's hammers there are two penes and no face, one being at a right angle to the other, as in Fig. 2135, the penes being rounded as in the figure, or sometimes square. [Illustration: Fig. 2136.] Fig. 2136 represents a coppersmith's hammer with a square nosed pene, which is sometimes made to stand at a right angle to the handle as in the figure, and at others parallel to it. [Illustration: Fig. 2137.] Fig. 2137 represents the file cutter's hammer, whose handle is at the angle shown because the chisel is held at an angle, the point or cutting edge being nearest to the workman; hence if the handle were at a right angle to the hammer length his arm would require to be considerably elevated in order to let the hammer face fall fair on the chisel head, whereas by setting the handle at the angle shown the arm need not be elevated, and the blow may be given by a movement of the wrist. [Illustration: Fig. 2138.] [Illustration: Fig. 2139.] Figs. 2138 and 2139 represent hammers used by boiler-makers for riveting boiler seams. The faces are made small so that if the blows are properly directed the edge of the face will not meet the boiler plate and indent it. These hammers are made long and narrow so that the weight may lie in the same direction as the hammer travels in when delivering the blow, and thus cause the effects of the hammer blows to penetrate deeper than if the hammer was wider. In the cooper's hammer, shown in Fig. 2140, the face extends flush up to the head, thus enabling it to strike a hoop upon a barrel without danger of the extreme end or top of the hammer meeting the barrel, and preventing the hammer face from meeting the edge of the barrel hoop when driving it on the barrel. The face is square and its front edge therefore a straight line, which is necessary on account of the circular shape of the hoop of the barrel. [Illustration: Fig. 2140.] [Illustration: Fig. 2141.] The mallet is made in various forms to suit the nature of the work and the tools it is to be used upon. Thus the carpenter's mallet is a rectangular block, such as shown in Fig. 2141. It is composed of wood, because the carpenter's tools are held in wooden handles, and a metal hammer would split them in course of time. It is rectangular in shape so that it may be applied to tools held in a corner of the work, where a round mallet could not, if of sufficient diameter, give the necessary weight. For such carpenters' or wood-workers' tools as are for heavy duty, and the tools for which have ferrules at the head of their handles to prevent them from splitting, the mallet is made cylindrical or round, as it is termed, and has an iron band at each end to prevent the face from spreading or splitting. The stonemason's mallet is also of wood, and is disk-shaped, with the handle in the centre, the circumferential surface forming the face. The reason for this is that his tools are of steel and have no handles; hence if the blow continually fell on the same part or spot of the mallet face it would sink or indent holes in it, which is prevented by utilising the whole circumference of the mallet for the face. An excellent mallet for the machinist's use, for driving finished work without damaging it, is formed of raw hide secured in a metal eye that receives the handle. Or for the same purpose a lead hammer is used, being especially serviceable for setting work in machines. What is known as pening, or paning, consists of hammering the skin of metal to stretch it on the side that is hammered. It may be employed either to bend or to straighten. Suppose, for example, we have a piece of metal that is bent to a half circle, and if we take a light hammer and hammer it on the concave side and all over its surface the piece will straighten out to an amount depending on the amount of pening. Or if he hammers the convex side the piece will bend to a smaller circle. The principle involved is, that if one side of a piece is elongated and the other remains of its original length, the only shape it can assume to accommodate or permit the elongation is that of a curve of which the convex side is the longest. It follows, therefore, that the hammer blows must in pening be sufficiently light to condense or stretch the metal on one side only of the metal, and not forcible enough to effect it all through. In order to accomplish this stretching as rapidly as possible it is necessary to use a light hammer, with sufficient force to be expended in condensing the metal at its surface, and to so form the hammer that it shall expend its force upon the work with a dead blow, that is, with as little rebound as possible. These results are best accomplished with a ball pened hammer, such as shown in Fig. 2108 and weighing about 1/2 lb. The blows should fall dead; that is, the hammer should fall, to a great extent, by its own weight, the number rather than the force of the blows being depended upon; hence, the hammer marks will not be deep. This is of especial importance when pening has to be performed upon finished work, because, if the marks sink deeply, proportionately more grinding or filing is required to efface them; and for this reason the force of the blows should be as near equal as possible. Another and a more important reason, however, is that the effect of the pening does not penetrate deeply; and if much of the pened surface is removed, the effects of the pening will be also removed. The work should not be rested upon metal, but upon wood. [Illustration: Fig. 2142.] [Illustration: Fig. 2143.] The following are examples of pening. Fig. 2142 represents a shaft bent as shown, the arms being too wide at A, which may be corrected by pening at B. If the error was in the arms themselves and not in the stem, the side faces of the arms would require to be pened. Thus in Fig. 2143 the distance A is too short, and the pening must be at B C. [Illustration: Fig. 2144.] Fig. 2144 represents a strap requiring to be closed across A, the pening being at C or D. But as pening at D would bend the crown and unpair the bed of the brasses, it is preferable to pene at C. In either case the jaws will close as denoted by the dotted lines. Fig. 2145 represents another common form of connecting rod strap, and in this case the pening may be most quickly and effectively done at the crown as denoted by the dots; and as this would alter the inside curve, the brass or box fitting into it must be refitted. In case the pening should be overdone it is better to modify it by filing away some of the pened surface. Cast iron is more rapidly affected by pening than either wrought iron or steel. One of the most useful applications of pening is in the case of moulding patterns, which in time may become warped from the rapping of the pattern in the mould, and this warping may be corrected by judicious pening, or suppose that a number of plates, such as represented in Fig. 2146, having been cast, it is found that the ends of the tongues A B curl up when cooling in the mould, then the tongues may be pened as at C D, throwing them down to the requisite amount, and thus moulding the pattern to accommodate the curling in cooling. [Illustration: Fig. 2145.] [Illustration: Fig. 2146.] The riveting usually performed by the machinist is generally upon cold metal. The blows in this case should fall dead and the riveting be performed with a view to stretching the metal uniformly and evenly over the surface to be riveted. [Illustration: Fig. 2147.] [Illustration: Fig. 2148.] An excellent example of cold riveting is given in the crank pin P in Figs. 2147 and 2148. C is the crank (both being shown in section). The end of the pin should be recessed as shown at A, so that it may be the more readily riveted outward to fill the countersink shown in the crank at B, B. The crank-pin is rested upon a piece of copper D interposed between it and the iron block E to prevent damage to the finished face of the crank-pin. The riveting blows should be given with a ball-faced hammer, and delivered with a view to stretch the whole end face of the crank-pin evenly. Otherwise the riveted surface will be apt to split as shown. This usually occurs from not riveting the area at and near the circumference sufficiently, although it may occur from riveting that part of the area too much. The line of travel of the hammer should not be directly vertical, but somewhat lateral in a direction from the centre towards the circumference. If the countersink is a deep one, it is desirable to leave the crank-pin sufficiently too long, so that after the riveting has proceeded some time the surface of the metal which has become condensed and crystallized from the direct impact of the hammer blows, may be chipped away, leaving a surface that is swollen by the riveting without being so much condensed. This enables a much greater spreading of the metal without splitting it. If in this class of work the riveted piece (as the crank-pin) is not driven in very tight before riveting, the riveting blows will be apt to jar the pin back. Hence, it is necessary to occasionally drive the pin home. The riveting should proceed equally all over, as if one side be riveted in advance of the other it tends to throw the pin out of true. When, however, the riveting begins to bed the pin, four equidistant places may be riveted home in advance so as to bring the pin home and hold it firmly. [Illustration: Fig. 2149.] [Illustration: Fig. 2150.] [Illustration: Fig. 2151.] THE CHISEL.--The machinist's cold chisel is made from the two forms of steel shown in Figs. 2149, 2150, and 2151, and of these the former is preferable because it has two broad flats diametrally opposite and these form a guide to the eye in holding the chisel on the grindstone, and aid in grinding the facets that form the cutting edge true. Furthermore, as the cutting edge is in the same plane as these flats they serve as a guide to denote when the chisel edge lies parallel to the work surface, which is necessary to produce true and smooth chipping. The width of the chisel may be made greater, as in Figs. 2152 and 2153, for brass or cast-iron work than for wrought iron or steel for the following reasons. On account of the toughness and hardness of wrought iron and steel the full force of a 1-3/4 lb. hammer, having a handle 13 inches long, may be used on a chisel about 7/8 inch wide without danger of causing the metal to break out below the chipping line, but if such a chisel be used with full force blows upon cast iron or brass the metal is apt to break out in front of the chisel, the line of fracture often passing below the level it is intended to chip down to. Hence if a narrow chisel is used lighter blows must be delivered. But by using a broader chisel the force of the blow is distributed over a longer length of cutting edge, and full force blows may be used without danger of breaking out the metal. [Illustration: Fig. 2152.] [Illustration: Fig. 2153.] [Illustration: Fig. 2154.] [Illustration: Fig. 2155.] [Illustration: Fig. 2156.] [Illustration: Fig. 2157.] [Illustration: Fig. 2158.] The cutting end of the chisel should be kept thin, as in that case it cuts both easier and smoother. The total length of a chisel should not when new exceed 8 inches, for if made longer it is not suitable for heavy or smooth chipping, as it will bend and spring under heavy blows, and cannot be held steadily. The forged part should not exceed about 2-1/2 or 3 inches in length, as a long taper greatly conduces to springiness, whereas solidity is of great importance both to rapid and smooth work. The facets forming the cutting edge should be straight in their widths, as at B in Fig. 2154, and not rounded as at A, so that the face next to the work may form a guide in holding the chisel at the proper angle to maintain the depth of the cut. This angle depends upon the nature of the material to be cut; the facets forming an angle one to the other of about 65° for cast steel and about 50° for gun metal or brass. The more acute these angles the nearer the body of the chisel lies parallel with the work and the more effective the hammer blows. Thus in Fig. 2155 chisel C is the position of the chisel for wrought iron, and position D is for steel. The angles should always be made, therefore, as acute as the hardness of the material will permit. If they are too acute the cutting edge will be apt to bend in its length, while if not sufficiently acute they will not cut keen enough; hence the object is to make them as acute as possible without causing the cutting edge to bend in its length. For copper and other soft metals the angle may be about 30° or 35°, the chisel end being kept thin so that it may not become wedged between the work and the chipping, which will bend but little, and is, therefore, apt to grip the wedge end of the chisel. The cutting edge should be slightly rounded in its length, which will strengthen it and also enable a fine finishing clip to be taken off, as in Fig. 2156, the width of the chip not extending fully across the chisel width so that the corners are not under duty and are not, therefore, liable to break, or dig in and prevent smooth chipping. In some practice the edge is made straight in its length, as shown in Fig. 2149, which is permissible in heavy chipping when a cape chisel has been used, but in any event an edge rounded in its length is preferable. If the edge is hollow in its length, as shown in Fig. 2157, and magnified in Fig. 2158, the chip acts as a wedge to force the corners outwards as denoted by the arrows, causing them to break under a heavy cut, and, furthermore, a smooth cut cannot be taken when the corners of the chisel meet the work surface. If the facets are ground under on one side, those on the other, as in Fig. 2159, the edge will not be parallel with the flats of the chisel, so that in holding it the flats will not form a guide to determine when the edge lies parallel to the work surface as it should do. The edge should also be at a right angle to the length of chisel, as denoted by the lines, as in Fig. 2160, for if not at a right angle the chisel will be apt to move sideways after each blow, and cannot be held steadily. [Illustration: Fig. 2159.] [Illustration: Fig. 2160.] The chisel should be held as close to its head as possible, so that the hand will steady the head as much as possible, and should be pushed forward firmly and steadily to its cut, which will greatly facilitate rapid and smooth chipping, and for wrought iron and copper it is found better to occasionally moisten the chisel with oil or water, the former being preferable. [Illustration: Fig. 2161.] Messrs Tangye, of Birmingham, have introduced the employment of chisel holders, such as shown in Fig. 2161, the object being to fit to each holder a number of short pieces of steel for chisels so that a number can be ground or forged at one time; obviously chisels of different shapes require different forms of handle. [Illustration: Fig. 2162.] [Illustration: Fig. 2163.] [Illustration: Fig. 2164.] When a heavy cut is to be taken the cape (Fig. 2162) chisel is used, first to carry through grooves or channels, such as shown in Fig. 2176 at A, B, and C, the distance apart of these grooves being slightly less than the width of the flat chisel, whose cut is shown partly carried across at D in the figure. The width of a cape chisel should gradually decrease from A to B in Fig. 2163, so that its side will be free in the groove it cuts, and the chisel head will be free to be moved sideways, and the direction of the groove may be governed thereby. If the chisel end be made parallel, as at C in Fig. 2164, it will have no play in the groove and the head cannot be moved; hence if the groove is started out of line, as it is apt to be, it will continue so. [Illustration: Fig. 2165.] [Illustration: Fig. 2166.] [Illustration: Fig. 2167.] [Illustration: Fig. 2168.] The round-nosed chisel, Figs. 2165 and 2166, may be straight from H nearly to the point G, but should be bevelled at and near G, so that the chisel head may be raised or lowered to govern the depth of the cut. Its round nose should also be wider than the metal higher up, so that the chisel head may be moved sideways to govern the direction of the cut as in the cape chisel. The cow mouth chisel, Figs. 2167 and 2168, should be bevelled from G to the point to enable the governing of the depth of the cut, and should be of greater curvature than the corner it is to cut out, so that its corners cannot wedge in the work. [Illustration: Fig. 2169.] [Illustration: Fig. 2170.] The oil groove chisel, Figs. 2169 and 2170, should be wider at the cutting edge than at A for reasons already stated, and of less curvature than the bore of the brass or bearing it is to cut the oil groove in. [Illustration: Fig. 2171.] [Illustration: Fig. 2172.] [Illustration: Fig. 2173.] [Illustration: Fig. 2174.] [Illustration: Fig. 2175.] [Illustration: Fig. 2176.] The diamond point chisel, Figs. 2171 and 2172, may be made in two ways. First, as in Figs. 2173 and 2174, for shallow holes, and as in Figs. 2171 and 2172 for deep ones. In shallow holes the chisel can be leaned over, as in Fig. 2176 at _y_, whereas in deep ones it must be held straight so that the chisel body may not meet the other side of the hole, slot, or keyway. The form shown in Fig. 2172 is the strongest, because its point is brought into line with the body of the steel, as shown by the line Q. The side chisel, Fig. 2175, for cutting out the sides of keyways or slots, should be bevelled from W to the cutting edge for the reasons already given, and straight from W to V, the line V W projecting slightly above or beyond the body U. An application of the cow mouth chisel is shown at L, and one of the side chisel is shown at Z in Fig. 2176. All these chisels are tempered to a blue color. The chisel that is driven by hammer blows may be said to be to some extent a connecting link between the hammer and the cutting tool, the main difference being that the chisel moves to the work, while the work generally moves to the cutting tool. In many stone-dressing tools the chisel and hammer are combined, inasmuch as that the end of the hammer is chisel shaped; an example of this kind of tool being given in the pick that flour millers use to dress their grinding stones. On the other hand we may show the connection between the chisel and the cutting tool by the fact that the wood-worker uses the chisel by driving it with a mallet, and also by using it for a cutting tool for work driven in the lathe. Indeed, we may take one of these carpenter's chisels and fasten it to the revolving shaft of a wood-planing machine, and it becomes a planing knife; or we may put it into a carpenter's hand plane, and by pushing it to the work it becomes a plane blade. In each case it is simply a wedge whose end is made more or less acute so as to make it as sharp as possible, while still retaining strength enough to sever the material it is to operate upon. [Illustration: Fig. 2177.] In whatever form we may apply this wedge, there are certain well-defined mechanical principles that govern its use. Thus when we employ it as a hand tool its direction of motion, under hammer blows, is governed by the inclination of the face which meets the strongest side of the work, while it is the weakest side of the material that moves the most to admit the wedge and therefore becomes the chip, cutting, or shaving. In Fig. 2177, for example, we have the carpenter's chisel operating at A and B to cut out a recess or mortise, and it is seen that so long as the face of the chisel that is next to the work is placed level with the straight surface of the work the depth of cut will be equal; or in other words, the line of motion of the chisel is that of the chisel face that lies against the work. At C and D is a chisel with, in the one instance, the straight, and in the other the bevelled face toward the work surface. In both cases the cut would gradually deepen because the lower surface of the chisel is not parallel to the face of the work. If now we consider the extreme cutting edge of chisel or wedge-shaped tools it will readily occur that but for the metal behind this fine edge the shaving or cutting would come off in a straight ribbon, and that the bend or curl that the cutting assumes increases with the angle of the face of the wedge that meets the cutting, shaving, or chip. [Illustration: Fig. 2178.] I may, for example, take a piece of lead, and with a penknife held as at A, Fig. 2178, cut off a curl bent to a large curve, but if I hold the same knife as at B it will cause the shaving to curl up more. Now it has taken some power to effect this extra bending or curling, and it is therefore desirable to avoid it as far as possible. For the purpose of distinction we may call that face of the chisel which meets the shaving the top face, and that which lies next to the main body of the work the bottom face. Now at whatever angle either face of the chisel may be to the other, and in whatever way we present the chisel to the work, the strength of the cutting edge depends upon the angle of the bottom face to the line of motion of the chisel, and this is a principle that applies to all tools embodying the wedge principle, whether they are moved by a machine or by hand. [Illustration: Fig. 2179.] Thus, in Fig. 2179 we have placed the bottom face at an angle of 80° to the line of tool motion, which is denoted by the arrow, and we at once perceive its weakness. If the angle of the top face to the line of tool motion is determined upon, we may therefore obtain the strongest cutting edge in a hand-moved tool by causing the bottom angle to lie flat upon the work surface. [Illustration: Fig. 2180.] But in tools driven by power, and therefore accurately guided in their line of motion, it is preferable to let the bottom face clear the work surface, save at the extreme cutting edge. The front face of the wedge or tool is that which mainly determines its keenness, as may be seen from Fig. 2180, in which we have the wedge or tool differently placed with relation to the work, that in position A obviously being the keenest and less liable to break from the strain of the cutting process. [Illustration: Fig. 2181.] If we now turn our attention to that class of chisel or wedge-shaped tools in which the cutting edge is not a straight line, but may be stepped or curved--as, for example, the carpenter's plane blade--we shall find that so long as the blade stands at a right angle to the surface it is operating upon, as in Fig. 2183 at B, the shape of surface it cuts will exactly correspond to the shape of its cutting edge; but so soon as the tool is inclined to its line of motion its cutting edge will, if curved, produce a different degree of curvature on the work. [Illustration: Fig. 2182.] [Illustration: Fig. 2183.] Suppose, for instance, that we have in the figure a piece of moulding M and a plane blade B, and the length of the cutting edge is denoted by A, Fig. 2182; now suppose that the blade is inclined to its line of motion (as in the case of carpenters' planes) and stands at C, Fig. 2183: we then find that the cutting edge must extend to the length or depth D, and it is plain that the depth of the curve on the moulding is less than the depth of the cutting edge that produces it; the radius E being less than of D, so that if we place the cutter C upright on the moulding it will appear as shown in Fig. 2181. If, therefore, we are required to make a blade that will produce a given depth of moulding when moved in a straight line and presented at a given angle to the work, we must find out what shape the blade must be to produce the given shape of moulding, which we may do as follows: In Fig. 2184 let A be a section of the moulding, and if the blade or knife is to stand perpendicular, as shown at B, Fig. 2183, and if it is moved in a straight line in the direction of the length of the work, then its shape would necessarily be that shown at B, Fig. 2184, or merely the reverse of A. In the position mentioned it could be used only as a sweep applicable to some few uses, but not adapted to cutting. To become a cutting tool it must be inclined and stand at some angle of less than 90° to its line of motion. [Illustration: Fig. 2184.] [Illustration: Fig. 2185.] Thus in Fig. 2185 D B E represents the bottom of the moulding and line of motion of the cutter, and A B the cutter perpendicular to it, the highest point of the cutting edge, as _c_ of Fig. 2184, being at _c_, Fig. 2185. The height or thickness of the moulding cut would be the space between the lines E B D and _e_ _c_ _f_, but the cutter assuming the position B C at an angle of 30° from A B, the point _c_ is brought to _d_; consequently the highest line of the moulding would now be _g_ _d_ _h_, and its thickness less. This is further exhibited in Fig. 2186, where _a_ represents the original depth section of Fig. 2184 that would be formed by knife B of Fig. 2184 when standing perpendicular; and G shows the depth with the same knife when placed as B C, Fig. 2185, or at 30° inclination, and H shows the depth that would be cut with the same knife or cutter at 45°. It is now evident that every change in the inclination of the same cutter would effect a change in the shape of moulding which it cuts, and to produce a given style of moulding the shape of the cutter must be decided by its inclination, or the angle at which it is used. [Illustration: Fig. 2186.] [Illustration: Fig. 2187.] The method of projecting a given section of moulding in order to exhibit the form that the curve of the opening should assume on the face of the knife, is shown in Fig. 2187. Upon a horizontal line A B C D draw a section of the required style of moulding, as shown at A E B. To the right of this draw a line, as F C, to meet the base line A B C D, and as F C represents the cutter, it must stand at the same angle that the proposed cutter is to have--in this particular example 30° from the perpendicular. From the highest point of the section A E B draw a horizontal line E G, meeting F C in G. From points G and C draw lines, as C J and G H, of any convenient length, at right angles to F C. At any distance from G H draw K L parallel to G H, and upon K L trace the section of moulding A E B, as K M L. Draw lines from the extreme edges K and L of K M L, as K N, L J, perpendicular to K L, cutting G H and meeting C J at N and J. E G being parallel to A B C D, G will be the point on the cutter where the top E of the moulding will come on the highest point of the cutting edge, and C G will be the entire length of cutting edge or height of opening measured on the face of the cutter F C. C J being drawn from the lowest point C of the cutter and G H being drawn from G, the highest cutting point, both lines at right angles to G C, then their distance from each other, as P O, must obviously represent the extreme height of opening in the cutter in its new position or front view, and K L, representing the width of moulding transferred to N J by the parallel lines K N and L J, will show the width of opening in the cutter. Having now the height and width, it only remains to project an indefinite number of points and trace the curve through them. Divide A B into a number of parts, and to avoid confusion mark the points of division thus obtained upon A B--1, 2, 3, 4, &c. Divide K L in an exactly similar manner and into the same number of parts, and mark the divisions I., II., III., IV., &c. Erect perpendiculars from points 1, 2, 3, 4, &c., meeting the curve A E B, and from the points thus found on A E B draw horizontal lines to F C; from the termini of these horizontals on F C draw the remaining lines parallel to and between G H and C J. From the divisions _i._, _ii._, _iii._, _iv._, &c., on K L, let drop the perpendiculars, cutting the other series of lines at right angles. A point of the curve will then be at the intersection of the line from 1 on A B, with line I on K L; another at the intersection of the line originating at 2 with that from II, and so on, and the proper curve is found by tracing from N through the intersections to P, and from P to J. Then K N being one side of the cutter and L J the other, N P J is the curve that the opening or cutting edges must have to cut the profile A E B, with the cutter set at F C, or 30°. [Illustration: Fig. 2188.] The same method is shown in Fig. 2188, except that in this case, instead of dividing A B and K L, the divisions are made directly on the peripheries A 6 B and K VI. L by stepping round with the dividers. The cutter F C is shown in this case at an angle of 45°, in order that the change in form which the curve assumes with the cutter at different angles may be clearly seen by comparing the curve N P J of Fig. 2187 with the same in Fig. 2188. The two figures are similar in other respects, and as the lettering is the same on each, the description of Fig. 2187 will apply equally to Fig. 2188. [Illustration: Fig. 2189.] There remains one more case of cutters moving in right lines, and that is where, besides having an inclination backward, as at F C, Fig. 2187, making a vertical angle to the line of motion, they are placed at an angle across the guiding piece also, or "skewing," thus making an angle to the line of motion on a horizontal plane as well as on a vertical one. Thus, suppose an ordinary carpenter's plane to have the cutter or "iron" turned partly round and placed so that the cutting edge, instead of lying at a right angle across the body, crosses it at some other angle. Fig. 2189 represents an ordinary carpenter's plane with the blade so placed. Here the edge, or rather side, D B, of the blade inclines back at an angle, as A B D, which is 45° in this case, to the perpendicular line A B on the side of the plane. For convenience call A B D the vertical angle. The lower or cutting edge E B of the blade also crosses the bottom of the plane at an angle E B C--30° in this instance--to a line B C, crossing the bottom at right angles. Now, it is evident that this latter angle E B C will influence the form of the cutter, if, instead of being a flat plane, as represented for clearness in Fig. 2189, it had a cutting edge of curved outline for cutting mouldings or similar work. But in either case the angle that D B or one side of the blade makes to E B, or the cutting edge--that is, the angle D B E--must be found in order to cut off the blank for the cutter or knife at the right "slant." [Illustration: Fig. 2190.] The method given in Figs. 2187 and 2188 of determining the form of cutter to produce a moulding of given profile now undergoes a modification where there are two angles to be taken into consideration instead of one. As an example, suppose a cutter is required that is to be fixed in such a position in its carrier or block that the handle A B D, or "vertical angle," of Fig. 2189 is, say, 45°, and the angle E B C, or "horizontal angle," of Fig. 2189 shall be 30°. Required the angle at which the bottom of the blank for the cutter must be cut off; or the angle that the side D B and lower edge B E of Fig. 2189 would make to each other, measured on the face of the cutter, and required the outline of cutting edge to be traced on the face of cutter to cut the section of moulding A E B, Fig. 2190: draw a horizontal line, as A B C D, and erect a perpendicular, as C R. From C draw C F, making an angle to C R equal to the "vertical angle," or angle A B D, Fig. 2189, which is 45° in this case. Draw a profile of the required moulding, as A E B, with its back A B coincident to the horizontal line A B C D. Draw a horizontal line from the highest point of the profile, as E, to meet F C in G. Draw parallel lines C J and G H, from C and G respectively, of any convenient length and making right angles to F C. At right angles to G H and C J, and parallel to F C, draw K H J to represent one side or edge of the cutter, but the angle of the lower end or angle D B E of Fig. 2189 must now be determined; to do this, draw an indefinite horizontal line, A B C, Fig. 2191, and from any point, as B, drop a perpendicular B D; now, from B set off on A B C the distance C _b_ of Fig. 2190, obtaining point E, and from E extend a perpendicular above and below A B C, as F E H. From E on E F set off distance G _b_ of Fig. 2190, obtaining J on E F. From B draw a line, making the same angle to B D that the angle E B C is in Fig. 2189, or 30° in this case, and cutting E H in K. Set off distance E K from E on A C, obtaining L; draw L J. Now, on Fig. 2190, with centre at H, and radius L J of Fig. 2191, describe arc _w_ _x_, and from J as centre, on Fig. 2190, and B K of Fig. 2191 as radius, describe arc _y_ _z_. Through the intersection _v_ of arcs _y_ _z_ and _w_ _x_, J L M must be drawn, making the proper angle to the side J H K of the cutter; this angle is 69° in this case, as found by construction. From H draw H N parallel to J L, and from H draw H O at the same angle to H N that B K is to B D, Fig. 2191, or angle E B C, Fig. 2189. Place a duplicate of A E B, with its base coincident to H O and corner A at H, as H P R. From R draw R N at right angles to H R and cutting H N at N; through N draw S N L parallel to K H J. Then while K H J represents one edge of the cutter, S N L will be the other, and J L the cutting edge before the opening is cut out. Divide the curves E B and P R similarly, obtaining points 1, 2, 3, &c., and I., II., III., &c., respectively. From points 1, 2, 3, &c., lines are to be drawn parallel to E G, meeting G C, continued from G C parallel to G H, and meeting H J, and from H J parallel to H N, meeting N L. From points I., II., III., &c., lines are to be drawn perpendicular to H R, meeting H N and continued from H N, parallel to H J, to J L, thus intersecting the first series. Lines from points 1, 2, 3, &c., then determine the height of different points of the curve, and those from I., II., III., &c., their location laterally; hence, by tracing through the intersections of 1 with I., 2 with II., &c., the curve H T L is obtained. The two outside lines K H J and S N L may now represent the edges of a piece of steel of which the cutter is to be made, and H T L will be the contour of cutting edge that must be given it in order that when, fixed for use at the angles named, it will form the required moulding A E B. [Illustration: Fig. 2191.] [Illustration: Fig. 2192.] If the chisel, knife, or cutter revolves in a circle, instead of in a right or straight line, the problem is again different, and the shape of cutting edge necessary to produce a given shape of moulding is again altered. Let Fig. 2192, for example, represent the bar or head of a wood moulding machine, the bar or head revolving in the direction of the arrow, and the moulding being moved beneath it in a straight line endways as denoted by the arrow at N. In order that the nut that holds the cutter to the head may clear the top of the moulding the highest cutting point of the cutter must not come nearer to the corner of the head than 1/4 inch. This is shown in the end view of a 2-1/2 inch cutter head in Fig. 2193, the circle B representing the path of revolution of the nut. In larger heads the nut will clear better. Now we may consider that the cutter simply revolves about a circle whose diameter is the largest that can be described on the end of the square bar that drives it. If, for instance, we look at the end of the bar as it is presented in Fig. 2195, we see that the circle just fills the square, and that if we cut off all four corners, leaving the bar round, as denoted by the circle, the chisel will revolve in the same path as before. Now suppose we place beneath the revolving chisel a piece of square timber, and raise this timber while holding it horizontally, as would be done by raising the work table. It will cut the work to the shape shown in the two views in the figure, enabling us to observe the important point that the only part of the work that the chisel has cut to its finished shape is that which lies on the line A A. This line passes through the axis on which the bar and cutter revolve, and represents the line of motion of the work in feeding upward to the chisel. If now we were to move the work endways upon the table, we should simply cause the moulding to be finished to shape as it passes the line A; because all the cutting is done before and up to the time that the chisel edge reaches this line; or in other words, each part of the chisel edge begins to cut as soon as it meets the moulding, and ceases to cut as soon as it reaches this line. We may now draw this circle and put on it a chisel in two positions, one at the time its lowest cutting point is crossing the line A and the other at the time the highest point on its cutting edge is passing the line, these positions being marked 1 and 2 in Fig. 2196; the depth of moulding to be cut being shown at S. Now, since the chisel revolves on the centre of the circle, the path of motion on its highest cutting point C will be as shown by the circle B, and that of the lowest point or end E of its cutting edge will be that of the circle D, while the depth of moulding it will cut is the distance between C and E, measured along the line A A, this depth corresponding to depth shown at S. [Illustration: Fig. 2193.] [Illustration: Fig. 2194.] Clearly when the chisel has arrived at position 2, the moulding will be finished to shape, and it is therefore plain that it takes a length of cutter-edge from C to F to cut a moulding whose depth is S, or what is the same thing, C E. But to solve the question in this way, we require for every different depth of moulding to make such a sketch, and the square bar that drives the chisel is made in various sizes, each different size again altering the length or depth of chisel edge necessary for a given depth of moulding. [Illustration: Fig. 2195.] [Illustration: Fig. 2196.] But we may carry the solution forward to the greatest simplicity for each size of square bar, and for any depth of moulding that can be dressed on that size of bar, by the following means:--In Fig. 2197 we have the circle and the line A as before; the depth from C to E being the greatest depth of moulding to which the square bar is intended to drive the chisels; while point C is the nearest point to the square bar at which the top of the moulding must be placed. Line _a_ represents a chisel cutting at its highest point; line _b_ a chisel cutting the moulding to final shape at 1/4 inch below C, on the line A; line _c_ a chisel cutting the moulding to final shape at a distance of 1/2 inch below point C and measured on the line A; lines _d_, _e_, _f_, _g_, _h_, and _i_ represent similar chisel positions, the last meeting the point E, which is the lowest point at which the chisel will cut. Suppose, now, we set a pair of compasses one point at the centre A of the circle, and strike the arc _j_; this arc will represent the path of motion of that part of the chisel edge that would finish the moulding to shape at C; similarly arc _k_ represents the path of motion of that part of the chisel edge that cuts the moulding to final shape on the line A, and at a distance of 1/4 inch below C, and so on until we come to arc _r_, which represents the path of motion of the end of the chisel. All these arcs are carried to meet the first chisel position C _a_, and from these points of intersection with this line C _a_ we mark lines representing those on a common measuring rule. The first of these from C we mark 1/4, the next 1/2, the next 3/4, and so on to 2, these denoting the measurement or depth of chisel necessary to cut the corresponding depth of moulding. If, for example, we are asked to set a pair of compasses to the depth of cutting edge necessary to cut a moulding that is an inch deep, all we do is to set one leg of the compasses at C, and the other at line 1 on the line C _a_; or if the moulding is to be 2 inches deep, we set the compasses from C to 2 on line C _a_. We have here, in fact, constructed a graduated scale that is destined to be found among the tools of every workman who forms moulding cutters, and if we examine it we shall find that the line that is marked 1/4 inch from C is not 1/4 inch but about 5/16 inch; its distance from C being the depth of chisel edge necessary to cut a moulding that is 1/4 inch deep. [Illustration: Fig. 2197.] Again, the line marked 1 measures 1-3/16 inch from C, because it requires a chisel edge 1-3/16 deep to cut a moulding that is one inch deep. But if we measure from _c_ to the line marked 2 we find that it is 2-1/4 inches from C, and since it represents a chisel that will cut a moulding two inches deep, we observe that the deeper the moulding is the nearer the depth of cutting edge is to the depth of moulding it will produce. This occurs because the longer the chisel the more nearly it stands parallel to the line A, at the time when its point is crossing the line A. Thus, line _i_ is more nearly parallel to A than line _a_ is, and our scale has taken this into account, for it has no two lines equally spaced; thus, while that marked 1/4 is 5/16 inch distant from C, that marked 1/2 is less than 5/16 inch distant from that marked 1/4, and this continues so that the line marked 2 is but very little more than 1/4 inch from that marked 1-3/4. Having constructed such a scale we may rub out the circle, the arcs, the line A, and all the lines except the line from C to _a_ and its graduations, and we have a permanent scale for any kind of moulding that can be brought to us. If, for example, the moulding has the four steps or members _s_, _t_, _u_, _v_, in the figure, each 1/2 inch deep, then we get the depth of cutter edge for the first member _s_ on our scale, by measuring from _c_ to the line 1/2 on line C _a_. Now the next member _t_ extends from 1/2 to 1 on the moulding, and we get length of cutter edge necessary to produce it from 1/2 to 1 on the scale. Member _u_ on the moulding extends from 1 to 1-3/4; that is to say, its highest point is 1 inch and its lowest 1-3/4 inch from the top of the moulding, and we get the length for this member on a scale from the 1 to the 1-3/4; and so on for any number of members. After the depth of cutting edge for each member has thus been found, it remains to find the exact curve of cutting edge for each step, and, in doing this, the same scale may be used, saving much labor in this part also of the process, especially where a new piece of moulding must be inserted to repair part of an old piece that needs renewal in places only, as is often the case in railroad cars. In Fig. 2197A we have a scale or rule constructed upon the foregoing principles, but marked to sixteenths, and it may now be shown that the same scale may be used in finding the actual curve as well as the depth of cutter edge necessary to produce the moulding of any member of it. Let the lower curves _s_, _t_, for example, represent the moulding to be produced, and the upper outline represent the blank piece of steel of which the cutter is to be made, the edges C, D being placed in line one with the other. We may then draw across both the moulding and the steel, lines such as E E, F F, G G, H H, I I, J J, all these lines being parallel to the edges C, D. To get the total depth of cutter edge for the moulding we measure with a common measuring rule the total height of the moulding, and supposing it to measure an inch, we set a pair of compasses to an inch on our cutter scale, and with them mark from the base _m_ of the steel, the line P giving total depth of cutter edge. We next measure with a common rule the depth of member _s_ of the moulding, and as it measures 1/2 inch we set the compasses to the 1/2 on the cutter scale, and with these compasses mark from line _m_ line B, showing the depth of member _s_. In order to find the exact curve for each member, we have first to find a number of points in the curve and then mark in the curve by hand, and it is for the purpose of finding these points that the lines E E, F F, G G, H H, I I, J J, have been drawn. These lines, it may be remembered, need not be equally spaced, but they must be parallel, and as many of them may be used as convenient, because the greater their number the more correctly the curve can be drawn. [Illustration: Fig. 2197A.] [Illustration: Fig. 2198.] [Illustration: Fig. 2199.] The upper edge or base line, _m_ _m_, both of the steel and of the drawing, is that from which all measurements are to be taken in finding the points in the curve, which is done as follows: With an ordinary measuring rule we measure on the moulding and from line _m_ _m_ of the moulding as a base the length of the line F F below _m_ _m_, to the curve, which in this case measures say 5/16 inch; we then set a pair of compasses or compass calipers to the 5/16 on the cutter scale, and from base _m_ _m_ on the cutter steel, mark, on line F F, an arc, and where the arc cuts F F is one point in the curve. Similarly we measure on the moulding, or drawing of the moulding, the length of line G G from line _m_ _m_ to the moulding curve, and find that it measures, say 7/16 inch, hence we mark from base line _m_ _m_ of the steel, on line G G, arc V, distant 7/16 according to the cutter scale. Similar measurements are taken at each vertical line of the drawing which represents the moulding, and by means of the corresponding divisions of the cutter scale, arcs are marked on the vertical lines on the cutter steel, and where the arcs cut the vertical lines are points in the curve, and through these points the curve may be drawn by hand. We may make a cutter scale from an ordinary parallel rule, marking one end to correct inches and the other end for a cutter scale. Measurements from the moulding may then be made on one end of the rule; measurements for the cutter may be taken from the other end of the rule, and the rule may be used at the same time to draw the parallel lines E E, &c. Or, as each size of cutter head requires a different cutter scale, we may make a rule out of a piece of box or other close-grained wood, say 3/4 inch square, using one side for each size of cutter head. One end of each face of this rule may be marked in correct inches and parts of an inch (the divisions being thirty-seconds of an inch), and the other end may be marked as a cutter scale, the divisions being found as described with reference to Fig. 2197. An instrument, patented by R. Drummond, for finding the depth of cutting edge and also for finding the curves, is shown in Figs. 2198 and 2199. It consists essentially of a bar G bent at a right angle, thus making two arms. Upon one arm is a slide W (best seen in Fig. 2199) secured by a set-screw B, and having at A a pivot to carry a second bar H, which is slotted throughout its length to permit bar G to slide freely through it. Upon the other arm of G is a slide P secured by a set-screw C, and carrying a compass point E. The bar H carries an adjustable slide Z secured by a set-screw D and carrying the compass point F. [Illustration: Fig. 2200.] In using the instrument but three very simple operations are necessary. First, the two slides W and P are set to the numerals on the bar, which correspond to the size of the head on the moulding machine the cutter is to be used upon; thus in Fig. 2199 they are shown set to numeral 2, as they would be for a 2-inch cutter head. The instrument is next opened, its two bars occupying the position shown in Fig. 2199, and the two compass points are set to the height of the moulding or to any desired member of it, as the case may be. The bars are then opened out into the position shown in Fig. 2200, and the compass points at once give the depth of cutter edge necessary to produce the required depth of moulding. It will be noted that the pivot A represents the centre upon which the cutter revolves, and that while the face of the bar H corresponds to the line of moulding formation answering to line A A in Fig. 2196, the face of bar G corresponds to the face C F of the cutter in Fig. 2196; hence the instrument simply represents a skeleton head and cutter, having motions corresponding to those of an actual cutter head and cutter. [Illustration: Fig. 2201.] [Illustration: Fig. 2202.] THE FILE.--The file is a piece of hardened steel having teeth produced upon its surface by means of rows of chisel cuts which run more or less diagonally across its width at an angle that is varied to suit the nature of the material the file is to be used upon. The vertical inclination of the tooth depends upon the inclination of the face of the chisel with which it is cut, the two being equal, as is shown in Fig. 2201, which is an enlarged view of a chisel and some file teeth. In order that the tops of the teeth shall be sharp, and not rounded or curved, as in Fig. 2202, it is necessary that the edge of the chisel be kept sharp, an end that is greatly aided by the improved form of chisel shown in Fig. 2203. When a file possesses curved points, or caps, as they are technically termed, a few strokes upon a narrow surface will cause them to break off, reducing the depth of the teeth and causing the cuttings to clog in them. If, however, the file is used upon a broad surface these caps will remain, obviously impairing the cutting qualifications of the file, even when new, and as they soon get dulled the file loses its grip upon the work and becomes comparatively valueless. [Illustration: Fig. 2203.] Files were, until the past few years, cut entirely by hand--file cutting by machinery having previously been a wide field of mechanical experiment and failure. Among the most prominent causes of failure was that the teeth produced by the earlier machines were cut too regular, both as to their spacing and their height; hence the points of the rear teeth fell into the same channels as those in advance of them, thus giving the tooth points too little opportunity to grip the work. This also gives too broad a length of cutting edge and causes the file to vibrate on the forward or cutting stroke, an action that is technically known as chattering, and that obviously impairs its cutting capacity. The greatest amount of duty is obtained from a file when the rear tooth cuts off the projection left by the preceding one, because in that case the duty of the tooth is confined to cutting off a projection that is already weakened and partly separated from the main body by having the metal cut away around its base. Workmen always practically recognise this fact, and cause the file marks to cross each other after every few strokes. In the machine-cut files made by The Nicholson File Co., the teeth are arranged to attain this object by the following means:--1. The rows of teeth are spaced progressively wider apart from the point towards the middle of the file length by regular increments of spacing, and progressively narrower from the middle toward the heel. 2. This general law of the spacing is modified by introducing as the teeth are cut an element of controllable irregularity in the spacing, which irregularity is confined within certain limits, so that neither the increment nor decrement of spacing is entirely regular. 3. In arranging the teeth so that the successive rows shall not be exactly parallel one to the other, the angle of inclination being reversed as necessity requires. The irregularity of spacing, while sufficient to accomplish the intended object, is not enough to practically vary the cut of the file, or, in other words, it is insufficient to vary its degree of coarseness or fineness to any observable extent. But it enables the file to grip the work with as little pressure as possible, and enables the teeth to cut easily without producing deep file marks or furrows. Files and rasps have three distinguishing features: 1. Their length, which is always measured exclusively of their tangs. 2. Their cut, which relates not only to the character, but also to the relative degree of coarseness of the teeth. 3. Their kind or name, which has reference to the shape or style. In general, the length of files bears no fixed proportion to either their width or thickness, even though of the same kind. The tang is the spiked-shaped portion of the file prepared for the reception of a handle, and in size and shape should always be proportioned to the size of the file and to the work to be performed. The heel is that part of the file to which the tang is affixed. Of the cut of files we may say that it consists of three distinct forms; viz.: "single cut," "double cut" and "rasp," which have different degrees of coarseness, designated by terms as follows viz.:-- Single-cut. Double-cut. Rasp. Rough Coarse Coarse Coarse Bastard Bastard Bastard Second-cut Second-cut Second-cut Smooth Smooth Smooth Dead-smooth [Illustration: Fig. 2204.] The terms "rough," "coarse," "bastard," "second-cut," "smooth" and "dead-smooth," have reference only to the coarseness of the teeth, while the terms "single-cut," "double-cut" and "rasp" have special reference to the character of the teeth. The single-cut files (the coarser grades of which are sometimes called "floats") are those in which the teeth are unbroken, the blanks having had a single course of chisel-cuts across their surface, arranged parallel to each other, but with a horizontal obliquity to the central line, varying from 5° to 20° in different files, according to requirements. Its several gradations of coarseness are designated by the terms "rough," "coarse," "bastard," "second-cut" and "smooth." The rough and coarse are adapted to files used upon soft metals, as lead, pewter, &c., and, to some extent, upon wood. The bastard and second-cut are applied principally upon files used to sharpen the thin edges of saw teeth, which from their nature are very destructive to the delicate points of double-cut files. The smooth is seldom applied upon other than the round files and the backs of the half-rounds. Fig. 2204 represents the cut of single-cut rough files, their lengths ranging from 16 inches down to 4 inches. Fig. 2205 shows the cut of the coarse, bastard, and second-cut, whose lengths also range from 16 to 4 inches, and whose cut is also finer as the length decreases. The float is used to some extent upon bone, horn, and ivory, but principally by plumbers and workers in lead, pewter, and similar soft metals. It will be seen that the teeth are nearly straight across the file and are very open, both of these features being essential requirements for files to be used on the above-named metals. Double-cut files are those having two courses of chisel cuts crossing each other. The first course is called the over cut, and has a horizontal obliquity with the central line of the file, ranging from 35° to 55°. The second course, which crosses the first, and in most double cuts is finer, is called the up-cut, and has a horizontal obliquity varying from 5° to 15°. These two courses fill the surface of the file with teeth inclined toward its point, the points of which resemble somewhat, when magnified, those of the diamond-shaped cutting tools in general use. This form of cut is made in several gradations of coarseness, which are designated by the terms "coarse," "bastard," "second-cut," "smooth" and "dead-smooth." Fig. 2206 represents the cut of double-cut bastard files, from the 16 inch down to the 4 inch, and Fig. 2207 the cut of the coarse, second-cut, and smooth. For very fine finishing a still finer cut, called the dead-smooth, is made, being like the smooth, but considerably finer. It is a superior file for finishing work in the lathe, or for draw-filing machine work that is to be highly finished. The double-cut is applied to most of the files used by the machinist, and, in fact, to most of the larger number in general use. For unusually fine work, tool-makers and watch-makers use the Swiss or Groubet files--so called from their being made by M. Groubet, of Switzerland. These files are double-cut, and their degree of coarseness is denoted by number; thus, the coarsest is a bastard and the finest number 8. The prominent characteristics of these files are their exceedingly even curvature and straightness, and, in the finer grades, the unusual fineness of the cut, which feels soft and velvety to the touch. They are made in sizes ranging from 2 to 10 inches, and are always double-cut. [Illustration: Fig. 2205.] [Illustration: Fig. 2206.] [Illustration: Fig. 2207.] Rasps differ from the single or double-cut files in that the teeth are disconnected from each other, each tooth being made by a single-pointed tool, denominated by file-makers a punch, the essential requirement being that the teeth thus formed shall be so irregularly intermingled as to produce, when put in use, the smoothest possible work consistent with the number of teeth contained in the surface of the rasp. Rasps, like files, have different degrees of coarseness, designated as "coarse," "bastard," "second-cut" and "smooth." The character and general coarseness of these cuts, as found in the different sizes, are shown in Figs. 2208 and 2209. Generally speaking, the coarse teeth are applied to rasps used by horseshoers, the bastard to those used by carriage makers and wheelwrights, the second-cut to shoe-rasps, and the smooth to the rasps used by cabinet-makers. [Illustration: Fig. 2208.] [Illustration: Fig. 2209.] [Illustration: Fig. 2210.] [Illustration: Fig. 2211.] [Illustration: Fig. 2212.] Figs. 2210, 2211 and 2212 are respectively coarse, bastard, and finishing second-cut files, the first two being for brass. Fig. 2210 represents a file open in both its over and up-cut, which is not, therefore, expected to file fine, but fast, and is adapted for very rough work on the softer metals, as in filing off sprues from brass and bronze castings, filing the ends of rods, and work of a similar nature. It is also, to some extent, used upon wood. The essential difference between the bastard file shown in Fig. 2211 and that just described is the degree of fineness of the up-cut, which is nearly straight across the tool. This form of teeth, which may be applied to any of the finer cuts, and upon any of the shapes usually made double-cut, is especially adapted to finishing brass, bronze, copper and similar soft metals, and is not so well adapted to the rougher work upon these metals as the coarse brass file previously described. Fig. 2212 is a finishing file. The first or over-cut in this case is very fine, and, contrary to the general rule, has the least obliquity, while the up-cut has an unusual obliquity, and is the coarser of the two cuts. The advantages in this arrangement of the teeth are that the file will finish finer, and by freeing itself from the filings is less liable to clog or pin than files cut for general use. This form of cut is especially useful when a considerable quantity of finishing of a light nature is required upon steel or iron. It is not recommended for brass or the softer metals, nor should it be made of a coarser grade than the second-cut. The names of files are sometimes derived from the purpose for which they are to be used. Thus, we have saw files, slitting files, warding files, and cotter files. The term "warding" implies that the file is suitable for use on the wards of keys, while "cotter" implies that it is suitable for filing the slots for that class of key which the machinist terms a cotter. In other cases files are named from their sections, as in the case of "square," "round," "half-round," and "triangular," or "three-square" files, as they are often termed. The term "flat" may be considered strictly as meaning any file of rectangular section whose width exceeds the thickness. Hence, "mill files," "hand files," and "pillar files" all come under the head of flat files, although each has its own distinguishing features. The general form of the flat file is shown in Fig. 2213, while the cross-sections of various quadrangular files are shown in Figs. from 2214 to 2218. From these views it will be seen that the thicknesses gradually increase from the mill to the square file. Mill files are slightly tapered from the middle to the point both in their width and thickness. They are single-cut, and are usually either bastard or second-cut, although they are sometimes double-cut. Mill files of both cuts are principally used for sharpening mill saws, mowing-machine knives and ploughs, and in some machine shops for rough lathe work, and, to some extent, in finishing composition brasswork. Mill sections are occasionally made blunt--that is to say, their sectional shape is alike from end to end--in which case they are mostly double-cut, and seldom less than 8 inches in length. They are suitable for filing out keyways, mortises, &c., and for these purposes should have at least one safe edge. A safe edge is one having no teeth upon it, which allows the file to be used in a corner without cutting more than one of the work surfaces. When the corner requires to be very sharp it is preferable to take a file that has teeth upon its edge and grind the teeth off, so as to bring the corner of the file up sharp, which it will not be from the cutting, because the teeth do not come fully up to a sharp corner. [Illustration: Fig. 2213.] [Illustration: Fig. 2214.] [Illustration: Fig. 2215.] [Illustration: Fig. 2216.] [Illustration: Fig. 2217.] Hand-files are tapered in thickness from their middle towards both the point and the tang, and are, therefore, well curved or bellied on each side. This fits them for the most accurate of work, on which account they are generally preferred by expert workmen. They are nearly parallel in width and have one safe edge and one edge cut single, while the face is cut double. Hand-files are also made equaling, the term equaling meaning that, although apparently blunt or of even thickness throughout the length, yet, in fact, there is a slight curvature, due to the file being thickest in the middle of its length. An equaling hand-file is especially suitable for such purposes as filing out long keyways, in which a great part of the file length is in action, and it can, therefore, be easily pushed in a straight line. The flat file, Fig. 2213, when 10 inches and under in length, is made taper on both its sides and edges, from the middle to the front of the file, and when longer than 10 inches they should be made full taper--that is to say, the taper should extend from the middle toward the heel, as well as toward the point. Flat files are usually double-cut, the coarse-cut being used upon leather, wood, and the soft metals. The flat bastard is that most commonly used, the flat second-cut, smooth, and dead-smooth being used by machinists for finishing purposes, the latter preceding the polishing processes. Pillar files are tapered in thickness from the middle to each end; the width is nearly parallel, and one of the edges is left safe. They are double-cut, and, although not in general use, are especially adapted to narrow work, such as in making rifles, locks, &c. The square file ranges from 3 to 16 inches in length, and is made for general purposes with considerable taper. It is usually double-cut, the bastard being the principal cut, the second-cut and smooth being mainly used by the machinist. Square blunt files range from 10 to 20 inches in length, of the same sectional sizes as the square taper, and are cut double, usually bastard. For machinists' use, however, they are used in the second-cut also, and are provided with sometimes one and sometimes two safe sides. Square equalling files are in every respect like the square blunt, except in the care taken to prepare a slight curve or belly in the length of the file, which greatly enhances their value in filing out the edges of keyways, splines, or mortises. The fault of the square blunt, when used for fine, or true work, is that the heel, having no belly, is apt to come into too prominent action. [Illustration: Fig. 2218.] Warding files, Fig. 2218, are made parallel in thickness, but are considerably tapered on their edges. They range in size from 3 to 8 inches in length, progressing by half-inches in the sizes below 6 inches. They are cut double, and usually on both edges, and are mainly used by locksmiths and jewellers, and to but a limited extent by machinists. Some of the warding files are provided with teeth upon their edges only, which are made quite rounding, the cut usually being second-cut, single. [Illustration: Fig. 2219.] [Illustration: Fig. 2220.] [Illustration: Fig. 2221.] Files deriving their sections from the circle are shown from Figs. 2219 to 2222. "Round files" are circular in section, as shown in Fig. 2219, their lengths ranging from 2 to 16 inches, and are usually of considerable taper. The small bastards are mostly single-cut and the larger sizes double-cut. The second-cuts and smooths are rarely double-cut, except in some of the very large sizes. In imitation of double-cut, however, they are sometimes made with the first, or overcut, very open, called "hopped," which adds, however, but very little to the cutting capacity of the file. The very small sizes--as, say, those of one-quarter inch and less in diameter--are often called "rat-tailed" files. For some classes of work--as for instance, the circular edges of deep keyways--round, blunt files are used, their sizes running up to 18 and 20 inches, their principal cut being bastard and double. The gulleting file is a round, blunt saw file, and, like most other files for this purpose, is single-cut (except for a small space at the point, which is left uncut). Its principal use is for extending the gullet of what are known as gullet-tooth and briar-toothed saws. Half-round files are of the cross-section shown in Fig. 2220, and although their name implies a semicircle, yet, as generally made, their curvature does not exceed the third part of a circle. They are made taper; the bastard is usually double cut on both its sides; the second-cut and smooth is double-cut on their flat sides, and single-cut on the curve side, except occasionally in the larger sizes, when it is double-cut or hopped. Half-round files for wood usually range in size from 10 to 14 inches, and are of the same shape and taper as the regular half-rounds. They are cut coarse and double, and are used by wood-workers generally. Half-round rasps are also like the regular half-round in shape, the sizes usually called for being 10, 12, and 14-inch. They are used principally by wheelwrights and carriage builders, but are to some extent used by plumbers and marble workers. [Illustration: Fig. 2222.] Cabinet files are of the section shown in Fig. 2222, being both wider and thinner than the half-rounds, the sectional curvature being somewhat less than the fifth part of a circle. They are made taper from near the middle to the point, while both the files and the rasps are made from 6 to 14 inches in length; 8, 10, and 12 inches are the sizes in most common use. As usually known, the cabinet file is a bastard double-cut. The cabinet rasp is punched smooth, and both the cabinet rasp and file are rarely made of any other degree of coarseness. They are used by cabinet, saddle-tree, pattern, and shoe-last makers, and also by gunstockers and wood-workers generally. [Illustration: Fig. 2223.] Three-square files are made with equilateral triangular sections, as in Fig. 2223. They are tapered to a small point with considerable curve, and are double-cut. The larger sizes--say, from 10 to 14 inches--are usually bastard, and are used to a considerable extent in rolling mills. The smaller sizes are not unfrequently smooth or dead-smooth, and are used in machine shops quite generally for filing interval angles more acute than the rectangle, clearing out square corners, sharpening cutters, &c. Three-square blued files of sizes from 3 to 6 inches are sometimes made. They are mostly second-cut, or smooth and double-cut, and are principally used in machine shops for filing up cutters for working metals. [Illustration: Fig. 2224.] [Illustration: Fig. 2225.] Cant files, whose cross-sections are shown in Fig. 2224, are usually made blunt and double-cut, mostly bastard, on all three sides. These sizes are usually 6, 8, and 10 inches. Lightning files are of the cross-section shown in Fig. 2225, the term lightning being known principally by those using the saws of this name, and to some extent by those using other cross-cut, [M]-shaped saw teeth. The obtuse angle of this file is five-canted, while the regular cant is hexagon or six-canted, and it is found to be too obtuse for the purposes required of the saw file. They are made blunt, and range in length from 4 to 12 inches, and are cut (except for a short space near the point) single on their three sides. [Illustration: Fig. 2226.] [Illustration: Fig. 2227.] [Illustration: Fig. 2228.] Knife files are of the section shown in Fig. 2226, and rarely exceed 10 inches in length, the principal sizes being 4, 5, and 6-inch. They are tapered, resembling somewhat the blade of a knife, and are cut double. The very acute angle of the sides of this file makes it especially useful in filing the inner angles of the rear and main springs of a rifle lock and work of similar shape. These files are also made blunt. Cross files (sometimes called double half-round or crossing files) are of the section shown in Fig. 2227. They are mostly made to order, either blunt or tapered, and usually double-cut. "Feather-edge" files (Fig. 2227) are but little used by the mechanics of this day. They were formerly used in filing feather springs (as the rear spring of a gun lock is sometimes called), and also the niches in currycombs, which led them to be called by some currycomb files. The few files of this kind which are now made are usually blunt and double-cut. Half-round "shoe rasps" as generally made are of the cross-section shown in Fig. 2228, their sizes ranging from 6 to 12 inches, while 8, 9, and 10 inch are the most common. They are made parallel in width, but with their sides slightly tapered from the middle; the ends are rounded and cut single; the edges are safe or uncut, or if cut are usually made half-file and half-rasp reversed (1/4 rasp and 3/4 file, while sometimes made, are the exception). The file quarters are bastard double-cut, and the rasp quarters second-cut. This form of shoe rasp is the one in general use at this time, having almost entirely superseded the flat and swaged rasps formerly in use. [Illustration: Fig. 2229.] Reaper files (B, Fig. 2229), so called from their use in sharpening the knives of reaping and mowing machines, are of the cross-section shown. They range in length from 7 to 10 inches, are slightly tapered, and are cut single and on their sides only. Tumbler files, whose cross-section is shown at A, Fig. 2229, were formerly much used to file the tumblers of gun locks, but are now rarely called for. They are taper and cut double. It will be seen, however, that unless for some special purpose, the pitsaw round or half-round file will be found to answer the same purpose as the tumbler file. It is obvious that in the use of files the coarser cuts are for use when it is required to remove a maximum quantity of material, and the finer to produce a more smooth and true surface, and also that the form of file selected is that which will best conform to the shape of the work, or can be best admitted upon or into the work. In selecting the length of the file, the size of the work and the delicacy of the same are the determining considerations; thus, a 14-inch file would be a clumsy tool upon a small piece of work, as, say, one having an area of 1/2 inch square. In selecting the shape of the file there are, however, other considerations than the shape of the work. Among these considerations may be enumerated that, in proportion as the number of teeth on any given file, performing cutting duty simultaneously, is increased, the less metal will be taken off, because the pressure on each tooth is reduced, and the file does not bite or take hold of the work so well; hence it cuts smoother. To fit the handles to small files, as 6-inch or less, it is simply necessary to bore suitable-sized holes in the handles, and force in the tang of the file. In doing this care should be taken to bore the hole axially true with the handle, so that the latter may stand true with the file, which greatly assists the production of true and rapid filing. For larger files the handle should have a small hole bored up it as before, the file tang should be made red hot (a piece of wet rag or cotton waste being wrapped around the heel of the file, so that it shall not get hot and be softened), and forced into the handle by hand, the file and handle being rotated during the operation, and sighted to insure that the handle is kept true with the centre line of the file. So soon as the tang of the file has entered three-quarters or thereabouts of its length it should be removed and gradually cooled by dipping in water. [Illustration: Fig. 2230.] [Illustration: Fig. 2231.] When the surface of the work is so large that the file handle would meet the work before the point had reached fully across it, the raised handle shown in Fig. 2230 is employed. The square end of the handle has a dovetail groove into which the tang of the file is fitted. In the figure the file is shown applied to a connecting rod end, and in such broad surfaces it is especially necessary to vary the line of motion of the file after every few strokes, so as to cause the file marks to cross and recross, as shown in Fig. 2231. The height at which work should be held to file it to the best advantage depends entirely upon its size, the amount of metal to be filed off, and the precision to which the filing requires to be executed. Under ordinary conditions the work should stand about level with the operator's elbow when he stands in position to file the work. This is desirable so that the joint of the arm from the elbow to the wrist may be in the same plane as the line of motion of the file, which will give the workman the least fatigue. But when the work surface is very broad it should be lower down, so that the operator may reach over all parts of its surface. On the other hand, on very small round work, or work so small as to require but one hand to hold the file, the work may be so high as to require the operator to stoop but very little, in which case the fatigue will be less, while the work will be more in sight, and can be better scrutinized. [Illustration: Fig. 2232.] When the file is pushed endways it is termed cross-filing, and the teeth cut on the forward or pushing stroke only, and in this case the file should be held as in Fig. 2232, the end of the file handle abutting against the palm of the right hand. But when the file is held in one hand only, the forefinger may be placed uppermost, and either on the file handle or on the file itself, as may be found most convenient. In cross-filing the file should be relieved of cutting duty on the return or back stroke, but should not be removed from the work surface. For heavy cross-filing on iron or brass, a 15-inch file is sufficiently large for any of the ordinary duty required by the machinist, and will require all the pressure one man can put on it to enable it to cut freely, and move at a suitable speed. The workman should for heavy cross-filing stand well off or away from the work so as to require to bend the body well forward. His feet should in this case be spread apart so that when the pressure of the hands is placed upon the file it will relieve the forward foot of a great part of the weight of the workman's body, which will be thrown upon the file. The rear foot operates during the forward stroke as a fulcrum, wherefrom to push the file. At each forward stroke the workman's body should move somewhat in unison with the file; his arms being less extended than would otherwise be the case, and the file being under more pressure and better control. During the backward stroke the forward foot should again take the workman's weight, while he recovers the upright position. For less heavy filing and for smooth filing, the workman should stand more nearly upright and nearer to the work. The heavier the pressure (either in cross-filing or draw-filing), the coarser the file cuts, and the more liable it is to pin and scratch. In the case, however, of slim files, the pressure is apt to bend the file, causing it to cut at the edges or ends only of the work, as shown at A, in Fig. 2233. This may be avoided by holding the file as in the figure, the pressure of the fingers in the direction of the arrows causing the file to bend, and produce more straight work. From the nature of the processes employed to cut the teeth of files, they are unequal in height, and as the file in addition to this varies in its straightness or warps in the process of hardening, it becomes necessary in many cases to choose for certain work files whose shape is best suited for it. Suppose, however, that files were produced whose teeth or tops or points were equal in height from end to end of the file, and it would be necessary for the workman to move the file in a true straight line in order to file a straight surface. This the most expert filers cannot accomplish. It is for this reason that hand files are made as in Fig. 2234, being thickest in the middle M, and of a curved taper both towards the point P and the heel H, so that when applied to the work the file will bear on the work at A, Fig. 2235, and be clear of it at B and C, which allows the file motion to deviate from a straight line without cutting away the work too much at B and C. The file curvature also enables any part of the file length to be brought into contact with the work or with any required part of the surface of the same, so as to locate or limit its action to any desired part. If a bellied file (as this shape of file is sometimes termed) be moved in a straight line it will file flat so long as it is moved to have contact clear across the work, but if the file is concave in its length it can only cut at that part which is in contact with the edge of the work, and the latter must be filed convex. [Illustration: Fig. 2233.] It becomes obvious then that for flat work a bellied file must be used, and that the belly should preferably be of even sweep from end to end. But files, whatever their shape, and however evenly formed when soft, warp (as already remarked) in the hardening process, sometimes having crooks or bends in them, such as at E and D, in Fig. 2236. In such a file the teeth at E would perform no duty unless upon work narrower than the length of the concavity at E, while on the other side D, the extra convexity would give the file great value for work, in which particular spots only required to be filed, because the teeth at D could be brought to bear on the required spot without fear of cutting elsewhere. [Illustration: Fig. 2234.] If, however, we have a taper flat file, such as in Fig. 2234, the thickness being equal from H to M, and a curved taper from M to P only, then it would be impossible to file flat unless only that part from M to P be used, because the heel H would meet the work at the same time as M, and it could not be known where the file would cut, more than that the most prominent teeth would cut the most. [Illustration: Fig. 2235.] [Illustration: Fig. 2236.] [Illustration: Fig. 2237.] An excellent method of testing the truth of a file, and of finding its high spots is to chalk a piece of board, press the file firmly to it and take several strokes and the chalk will be transferred to the highest parts of the file, showing very distinctly every hill and hollow in the teeth, even on the finest of Groubet files, and it will be found from this test that but very few of the best-made files are true, and that very great care is necessary in selecting a file for flat and true work. [Illustration: Fig. 2238.] The curvature or belly on a file not only enables but few teeth to be brought into action at any one turn, and thus cause it to cut more freely; but it also enables all parts of the file length to be used and worn equally. Thus in Fig. 2238 are shown two positions of a file, one cutting at A and the other at B, these different locations being due to different levels of the file which may be given by elevating or depressing it at the handle end. [Illustration: Fig. 2239.] If a file is hollow in one side of its width, and rounding on the other, as in Fig. 2239, the hollow side is unfit for any but the roughest of work, since it will not file any kind of work true; but the rounded side is very effective for flat surfaces, since the number of teeth in action is more limited and their grip is therefore greater, while by canting the file any part of its width may be brought into action. The rounded side is especially advantageous for draw-filing (a process to be hereafter explained). In all cross-filing, whether performed to clean up a surface, remove a maximum of metal, or prepare the work for draw-filing, or for reducing the work to shape, the file should be given a slight lateral as well as a forward motion, and it will be found that this lateral motion is more effective if made from right to left, leaving the file marks in the direction of marks B, in Fig. 2240, because the workman has more control over the file (especially if a large one) than when the lateral motion is from left to right; but this latter motion must be given occasionally to prevent the file from cutting deep scratches, and to keep the file surface true. [Illustration: Fig. 2240.] [Illustration: Fig. 2241.] A new file should be used at first on broad surfaces so that the teeth may not grip or bite the work so firmly that the strain will cause their fine sharp edges to break off, which is apt to occur unless their edges are slightly worn off. As a file becomes worn it may be used on narrower work, because the narrower the surface the more readily the file will bite. When a file is much worn, or when it is desired to remove a quantity of metal as quickly as possible, the file may be used at different angles upon the work, as shown in Fig. 2241, which by reducing the number of teeth in action facilitates the cutting, but if this be done with a new file it will break off the points of the teeth. Cast iron, brass, and copper require a sharper file than do either steel or wrought iron, hence for the first named metals (especially brass and copper) new files are used, and these should not be used upon wrought iron or steel until worn out for the above metals. In the case of unusually hard cast iron or tempered steel a second-cut file will cut more freely than a coarser grade. Work to be draw-filed should first be cross-filed with smooth or at the coarsest with second-cut files, so as to remove the scratches of the bastard or rough file before the draw-filing, which should not be done with a rough or bastard file. Draw-filing consists in moving the file in a line at a right angle to its length, the file being grasped at each end independently of its handle, which may be removed from the file if it be in the way, as in the case of files used on broad surfaces. Draw-filing is employed for two purposes: first and most important, to fit work more accurately than can be done by cross-filing, and secondly to finish surfaces more smoothly, and lay the grain of the finish lengthwise of the work. The greater accuracy of draw-filing occurs because the high parts of the file can be selected and the file so balanced that this high part covers the place on the work requiring to be filed, while the strokes may be made to suit the length of the spot to be filed. In draw-filing the file can be moved more steadily than in cross-filing, and will, therefore, rock so much less that even the novice can with care produce very true work. [Illustration: Fig. 2242.] Suppose, for example, that a piece of work requires filing in the middle of its length and half way along its width and half along its length, and a well bellied file may be balanced upon C, Fig. 2242, and grasped at its two ends A and B, and used with strokes of a sufficient length to file half the work length as required. In draw-filing the file should be pressed to the cut on the pushing stroke only, and not on the return or pulling stroke. Draw-filing produces with a given cut of file a smoother surface than cross-filing, but it will not remove so much metal in a given time. In draw-filing short strokes will produce better work than long ones, because with the latter the file cuttings are apt to become locked in the teeth of the file, and cut scratches in the work. This is called _pinning_, and the pins cutting deeper than the file teeth produce the scratches. To avoid this pinning the file surface may be well chalked, which will at the same time cause the file to cut smoother although not quite so freely. It is necessary, however, to clean the file after every ten or twelve draw-filing strokes so as to remove the filings. This removes the chalk also, hence it requires occasional renewal. For this purpose lumps of chalk are employed, but great care is necessary in its selection, because it sometimes contains small pieces of flint or other stones, and these score and greatly damage the file teeth. To dislodge the chalk and filings the file surface may be rubbed two or three strokes with the hand, and the file lightly tapped on the vice back. But it will also be found necessary to occasionally clean the file with a file-brush or file-card. The file-card is brushed across the width of the file so that the wire may reach the bottoms of the rows of teeth and clean them out. [Illustration: Fig. 2243.] If the pins have lodged too firmly in the teeth to be removed, the scorer shown in Fig. 2243 is employed. This scorer is a piece of copper or brass wire flattened out thin at the end E, which end is pressed firmly to the file teeth and pushed across the width of the file. By this means the thin edge becomes serrated, and the points of the teeth forming the serrations pass down the bottoms of the rows of file teeth and force out the pins. Here it may be remarked that pinning takes place in cross-filing as well as in draw-filing, and is at all times destructive to either good or quick work. Oil is sometimes used to prevent pinning and produce a dead finish, which will hide scratches, but it is much more dirty than chalk and no more effective. Neither of these substances, however, is employed upon cast iron, brass, copper, or other than the fibrous metals. In removing the cross-file marks it will be found that the file will cut more freely if it be slightly canted so that it cuts most at and near the edge, as shown in Fig. 2244, the edge A B meeting the work, the file stroke having progressed from C as shown. This is especially advantageous if the metal be somewhat hard or have a hard skin upon it, or in case of a hard spot, because it will enable the file to bite when, if pressed flat upon the work, it would slip over it. [Illustration: Fig. 2244.] When draw-filing is resorted to, to obtain a very fine surface, to be finished with emery paper and crocus cloth, it is best to reverse the direction of the file strokes so as to cause the file marks to cross and recross as shown in Fig. 2244, where the marks C cross those previously made, which will not only produce smoother work, but it will partly prevent the file from pinning. It will also be found that the draw-filing will be smoother and pinning less liable to occur when the file strokes cross the fibres or grain of the metal than when they are parallel to that grain; hence when the finishing marks are to be left in a line with the grain and a very smooth surface is required, the draw-filing marks should, just before the final finishing, be across the grain, the final finishing being with the grain simply to reverse the direction of the marks. Half-round files should be well curved in their lengths on the half-round side, so that when applied to the work any part of the file's length may be brought to bear upon the required spot on the work, as was explained for the flat file, and shown in Fig. 2238. If the flat side is straight or hollow in its length it is of little consequence, because it can be used upon convex or upon narrow surfaces. The sweep or curve of the file should in its cross-section always be less than the curve of the work it is to operate upon, and the teeth should be brought up sharp on the edges, and over the whole area of the half-round side, which is in inferior files not always the case, because the rows of chisel cuts are too far apart in the width of the file; hence, there is along the length of the file between the rows of full teeth, rows that are not brought fully up, which impair the cutting qualifications of the file. [Illustration: Fig. 2245.] [Illustration: Fig. 2246.] [Illustration: Fig. 2247.] In using a half-round file to cross file it should at each stroke be swept first from right to left, and after a few strokes from left to right, so that the file marks appear first as in Fig. 2245, running somewhat diagonal from right to left, and then, when the side sweep of the file is reversed in direction, the file marks will cross after the manner shown exaggerated in Fig. 2247. Unless this is done, the curve will be apt to have a wave in it as in Fig. 2246, or in large curves there may be several waves, and the same thing may occur if the direction of side sweep is not reversed sufficiently often. The file should also be partly swept around the curve, so that if at the beginning of a stroke it meets the work at the upper position in Fig. 2247, then at the end of the stroke it should be as at the lower one, which will also prevent the formation of waves. The larger the curve the less the amount of this sweep can be, the operator giving as much as convenient for the size of curve being filed. In draw-filing the file should be slightly rotated, so that if at the beginning of a stroke it stands as at A, Fig. 2247, at the end of that stroke it should stand as at position B, and it should at the same time be given sufficient end motion, so as to cause the file marks to cross as shown. A round file should always be a little smaller at its greatest diameter than the hole in the work. Before inserting it in the hole it should be rotated in the fingers, and the eye cast along it, to select the part having the most belly, which may then be brought to bear on the required spot in the work, without filing any other place, and without filing away the edges at the ends of the hole. For very accurate work it is sometimes desirable to grind on a round file, a flat place forming a safe edge. So likewise a safe edge flat file requires grinding on its safe edge, because in cutting the teeth a burr is thrown over on the safe edge, rendering it capable of scoring the work when filing close up to a shoulder. The work should be held as near down to the surface of the jaws of the vice as will allow the required amount of metal to be filed off without danger of the file teeth coming into contact with those jaws, and should be placed so that the filing operation when finished shall be as near as possible parallel with the top of the vice jaws. These jaws then serve somewhat as a guide to the filing operation, showing where the metal requires filing away. For cutting steel that contains hard spots or places, a second-cut file is more effective than a rough or bastard file. Rough files are more suitable for soft metals, the bastard cut being usually employed upon wrought iron, cast iron, and steel by the machinist. But in any case the edge of the file is employed to remove small spots that are excessively hard. The file should be clean and dry to cut hard places or spots, and used with short strokes under a heavy pressure, with a slow movement. When a file has been used until its cutting edges have become too dull for use, it may be to some extent resharpened by immersion in acid solutions; but the degree of resharpening thus obtained has not proved sufficient to bring this process into general or ordinary application; hence, the files are either considered useless, or the teeth are ground off and new ones formed by recutting them. A recut file is of course thinned by the process, but if properly done is nearly, if not quite, as serviceable as a new one, providing that in grinding out the old teeth the file be ground properly true to curve; but, unfortunately, this is rarely found to be the case. An excellent method of resharpening files, and also of increasing the bite of new files (which is an especial advantage for brass work), is by the means of the sand blast. The process consists of injecting fine sand against the backs of the teeth by means of a steam jet, and is applicable to all files, from the rasp to the finest of Groubet files. The action of the sand is to cut away the backs of the file teeth, thus forming a straight bevel on the teeth back, and giving a new cutting edge, and the process occupies from three to five minutes. [Illustration: Fig. 2248.] Fig. 2248 represents a machine constructed for this purpose. Steam is conveyed by the piping to the nozzles A, A, which connect by rubber hose H, H to sand pipe K, so that the steam jets passing through A, A carry with them the mixture of quartz, sand, and water in the sand box. By means of the overhead guide frame at D, E the file clamp C is caused to travel when moved by hand in a straight line between the nozzles A, A in the steam box, from which the expended sand and water flow down back to the sand box. Thus both sides of the file are sharpened simultaneously, and from the fixed angles of the nozzles and true horizontal motion of the file the angles of all the teeth are equal and uniform. To distribute the sharpening effects of the sand equally across the width of the file, the carriage has lateral or side motion, as well as endwise, and on the apparatus represented adjustable rollers regulate this side movement. Having the two motions, any part of the file can be presented to the blast. The following is from _Engineering_:--"A comparative trial of the cutting power of the sharpened files was lately made with the following results: A piece of soft wrought iron was filed clean and weighed; 1200 strokes were made by a skilled workman with one side of a new 10-inch bastard file, the iron was again weighed, and the loss noted. The other side of this file was then subjected to the sand blast for five seconds, and 1200 strokes were made with this sand-blasted side on the same piece of iron, great care being taken to give strokes of equal length and pressure in both cases. The iron was then weighed, and the loss found to be double as much as in the first case. "These operations were repeated many times, counting the strokes and weighing the metal each time, and the quantity cut was found to gradually become less for both sides as these became worn. When the weight of metal cut away by 1200 strokes of the sand-blasted side was found to be no greater than had been cut by the first 1200 strokes of the ordinary side when quite new, a second sand blasting was applied to it for 10 seconds, and in the next 1200 strokes its rate of cutting rose to nearly its first figure. When the cut made by the ordinary side of the file fell to about four-tenths of its cut when new, it was considered by the workman as worn out, and a new file of the same size and maker was used to continue the comparison with the one sand-blasted side; 83 sets of 1200 strokes each and 13 sand-blastings were made on the same side of this file, and in that time it cut as much metal as six ordinary sides. In 99,600 strokes it cut away 14 ozs. avoirdupois of wrought iron, and 16.4 ozs. of steel. "With an equal number of strokes its average rate of cutting was, on wrought iron, 50 per cent. greater than the average of the ordinary sides, and on steel 20 per cent. greater. As the teeth became more worn, the time of the application of the sand blast was lengthened up to one minute. After the thirteenth re-sharpening its rate of cutting was nine-tenths that of the ordinary side when quite new. "When the teeth become so much worn that the sand blast ceases to sharpen them effectively, the file can be recut in the usual way, and each set of teeth can be made to do six times as much work as an ordinary file, and to do it with less time and labor, because it is done with edges constantly kept sharp. The time required to sharpen a worn-out 14-inch bastard file is about four minutes, or proportionately less if sharpened before being entirely worn out. Smooth files require much less time. About 4 horse power of 60 lb. steam used during four minutes, and one pint per minute of sand (passed through a No. 120 sieve), and the time of a boy are the elements of cost of the operation." RED MARKING OR MARKING.--This is a paint used by machinists to try the fit of one piece to another, or to try the work by a test piece or surface plate. It should be composed of dry Venetian red, mixed with lubricating oil of any kind. Instead of Venetian red, red lead is sometimes used for marking, but it is too heavy and separates from the oil, and furthermore will not spread either evenly or sufficiently thin, and is therefore much inferior to Venetian red. It is applied to the surface of the test piece or piece of work, and the latter is brought to bear on the surface to be tested, so that it leaves paint marks disclosing where the surfaces had contact, and therefore what parts of the surface require removing in order to make the surfaces have the desired degree of contact. When either the test piece or the work can be put in motion while testing, one piece is rubbed upon the other or passed along the same in order that the bearing marks may receive the marking more readily and show the bearing spots more plainly, the operation coming under the head of fitting. When neither piece can be given motion, one is made to mark the other by being struck with a mallet or hammer, or to avoid damage to the work from the hammer blows, a piece of wood or copper is interposed. This operation is termed "bedding." [Illustration: _VOL. II._ =SCRAPERS AND SCRAPING.= _PLATE IX._ Fig. 2252. Fig. 2253. Fig. 2254. Fig. 2255. Fig. 2256. Fig. 2257. Fig. 2258. Fig. 2259. Fig. 2260.] The thickness of the coating of marking varies with the kind of work, the finer fit the work requires to be, the thinner the coat of marking. Thus in chipping a thick coat is applied, for rough filing a thinner, for smooth filing a still thinner coat, and so on, until for the finest of work the coat is so thin as to be barely perceptible to the naked eye. When either the work or the testing piece can be given motion and the surfaces rubbed together, a thinner coat of marking may be used. Marking is usually applied with a piece of rag doubled over and over, and bound round with a piece of twine so as to form a kind of paint-brush. This will give the surface a lighter and more evenly spread coat than would be possible with a brush of any kind. For very fine work red marking may be spread the lightest and the most even with the palm of the hand, which will readily detect any grit, dirt, or other foreign substance which the marking may contain from being left exposed. [Illustration: Fig. 2249.] [Illustration: Fig. 2250.] THE HACK-SAW.--The hack-saw is employed by the machinist for severing purposes, and also for sawing slots in the heads of screws. The blade should be tightly strained in the frame, which will prevent saw breakage. The ordinary method of doing this is to provide the end of the saw frame with a sliding stud threaded at its end to receive a thumb nut. The studs at each end of the blade should be squared where they pass through the frame, as at A, B in Fig. 2249, so that the blade shall not be permitted to twist. An improved form is shown in Fig. 2250, in which the end E has a saw slot to receive the blade F. At the handle end of the blade it is held by a stud sliding through the frame, being squared at B; at C is a nut let into and screwed in the handle, and into or through the nut is threaded the end of the stud, so that by rotating the handle the blade is strained. The curve in the back at A gives a little elasticity to it, and therefore a better strain to the blade. A hack-saw should always be used with oil, which preserves the cutting edge of the teeth. In sharpening a hack-saw it is best to rest the smooth edge of the blade on a piece of hard wood or a piece of lead, and spread the tops of the teeth by light hammer blows, which serves a two-fold purpose, first it thickens them and enables them to cut a groove wide enough to let the blade pass freely through, and secondly it enables the teeth to be filed up to a sharp cutting edge with less filing. [Illustration: Fig. 2251.] The screw-driver to be used in saw slots should have its end shaped as at A in Fig. 2251, which will tend to prevent it from slipping out of the saw slot, as it will be apt to do if wedge-shaped as at B, because in that case the action of the torsional pressure or twist is to lift the screw-driver out of the slot. SCRAPERS AND SCRAPING.--The process of scraping is used by the machinist to true work, and to increase the bearing area of surfaces, while the brass finisher employs it to prepare surfaces for polishing, applying it mainly to hollow corners and sweeps. For scraping work to fit it together the flat scraper is used, ordinary forms being shown in Figs. 2252 and 2256. That shown in Fig. 2252 may be made of a flat smooth file, of about an inch wide, and 3/16-inch thick, which is large enough for any kind of work. Two opposite faces, one of which is shown at A, are ground beveled so as to leave the end face B about 1/16-inch thick. This end face is then ground square as denoted by the dotted lines, producing two cutting edges of equal angles, and therefore equally keen. If it were attempted to grind face B at an angle as denoted by the dotted lines G, in Fig. 2253, the lower edge H would cut too keenly, causing the scraper to chatter and cut roughly, while the upper one I would not cut sufficiently easily. For very smooth work the scraper may be formed as in Fig. 2256, the front face E being ground slightly out of square as shown, and the bottom face F being given considerable angle to the body of the scraper. For very rapid cutting, however, the front face E may be at an angle of less than 90° to the top of the scraper. The only objection to this form is that the eye lends no assistance in bringing the edge fair with the work surface. The scraper should not exceed about 6 inches in length, exclusive of the handle, for if longer it will not cut well or smoothly, and its end face should be slightly rounded as in Fig. 2254. Its facets should be ground square or straight and carefully oil-stoned after the grinding, the oil-stoning process being repeated for two or three resharpenings, after which it must be reground upon the grindstone. The scraper should be grasped very firmly in the hands, and held as in Fig. 2255. It requires to be pressed hard to the work during the cutting and lightly during the backward stroke. The strokes should not exceed for the roughing courses, say, half an inch in length, the first course leaving the work as represented in Fig. 2257. The second course should be at a right angle to the first, leaving the work as in Fig. 2258, and after these two courses the work should be tested by surface plate, or with the part to which it is to fit, as the case may be. Previous to the testing, however, the work must be carefully wiped clean with old rag, as new rag or waste is apt to leave ravelings behind. The surface plate should be given a light coat of red marking, and then moved backward, forward, and sideways over the work, or, if the work is small, it may be taken from the vice and rubbed upon the surface plate, and the high spots upon the work will be shown very plainly by the marks left by the plate. The harder the plate bears upon the work the darker the marks will appear, so that the darkest parts should be scraped the heaviest. After applying the plate, the scraper may again be applied, the marks being at an angle to the previous operation, the testing and marking by the plate and scraping process being continued until the job is complete, appearing as shown in Fig. 2259. It will be noted that the scraper marks are much smaller and finer at and during the last few scrapings; and it may be here remarked that the scrapings are very light during the last few finishing processes. The strokes of the scraper being made of a length about equal to the acting width of its edge cuts, makes the scraper mark approximately square, on which account it is sometimes termed "block" scraping. It gives an excellent finish, while not sacrificing the truth of the work to obtain the finish. The scraper will not remove a quantity of metal so quickly as a file, and on this account it is always preferable to surface the work with a file before using the scraper, even though the work be well and smoothly planed. Not until the file has almost entirely removed the planer marks, and the surface plate shows the surface to be level and true, should the scraper be brought into requisition, the first courses being applied vigorously to break down the surface. It would appear that scraping might be more quickly done by taking long scraper strokes promiscuously over the work, but in this case the bearing marks are not well defined and do not show plainly, which leads to confusion and causes indecision as to where the most or heaviest scraping requires to be done, whereas in the block scraping the marks are clearly defined and the high patches or spots on the work show very plainly, and the workman is able to proceed intelligently and with precision. Fig. 2260 represents a three-cornered or "three-square" scraper, which is used principally upon hollow or very small flat surfaces. The half-round scraper is employed upon holes, bores, or large concave surfaces, such as brasses. Both these tools are for vice work, used in the same manner as described for flat scrapers, while all scrapers cut smoother when the edge is kept wetted with water, as is essential when used upon wrought iron, copper, and steel. HAND REAMERS OR RYMERS.--The hand reamer is employed for two purposes, first, to make holes of standard diameter and smooth their walls, and second, to bring holes in line one with the other. [Illustration: Fig. 2261.] Fig. 2261 represents an ordinary solid hand reamer for parallel holes. The teeth are ground so that their tops form a true circle, this grinding being done after the reamer has been hardened and tempered, because in these processes the reamer is apt to get both out of round and out of straight. [Illustration: Fig. 2262.] In some practice the reamers are formed as shown in Fig. 2262, and are made in sets of three for each size; the first is slightly taper from end to end, the second is slightly tapered at the entering end for a length about or nearly equal to the diameter, and the third is parallel and rounded on the end like the second, and in many cases only three teeth are employed. [Illustration: Fig. 2263.] [Illustration: Fig. 2264.] Fig. 2263 represents a reamer in which the distance between the cutting edges A B, Fig. 2264, is greater than between B C, and so on, the spacing decreasing from tooth A to tooth _a_. The spacing of _a_, _b_, &c. to _f_ on the other side is also irregular, so that if the reamer be given half a revolution no two teeth will have arrived at similar positions except A and _a_, the former arriving at the position occupied by the latter. Now suppose that a hole to be reamed has a hollow or spongy seam along it, and if the reamer be regularly spaced, there will at this point occur a lateral movement of the reamer that will impair the roundness of the hole, and this lateral movement the irregular spacing tends to prevent. If a solid reamer is made to standard gauge diameter when new, and the bolts or pins turned to standard diameter, then by reason of the wear of the reamer the work will become gradually a tighter fit and finally will not go together, hence the reamer must be restored to standard diameter, which may be done by upsetting the teeth with a set chisel. Furthermore the workman's measuring gauges are themselves subject to wear, those for measuring the pins wearing larger and those for the holes wearing smaller, and this again is in a direction to prevent the work from fitting together. It is preferable, therefore, to employ adjustable reamers. Thus Fig. 2265 represents an adjustable reamer in which the teeth fit tightly into dovetail grooves, that are deeper at the entering than at the shank end of the reamer, so that by forcing the teeth up the grooves towards the shank the diameter is increased. Both castings and forgings are found to alter somewhat in shape in proportion as their surfaces are removed by the machine tools, so that the shape of the work undergoes continuous alteration. Suppose, for example, that a piece of metal two inches square and four inches long, has a hole cast in it of an inch in diameter, and when finished it is to be 1-3/4 inches square, 3-3/4 inches long, and have a hole 1-1/8 diameter. Let it be chucked in a lathe or shaping machine and have its surfaces cut down to the required dimensions. Removing the metal to true the first surface will reduce the strain on that side of the casting and alter the shape of the whole body, but this alteration of form will not occur to its full extent until the piece is removed from the pressure of the chuck jaws, or other clamping device holding it in the machine, because this pressure holds it; as a result the surface will not be so true after leaving the machine as it was before. On surfacing the second side of the piece, the internal strain is still further reduced, and a second alteration of form ensues, and so on at the surfacing of every side of the piece. Now let the piece be chucked true to have the hole bored out, and the removal of the metal in the hole will again reduce the internal strain and the form of the body will again alter. Suppose, however, that the piece after having its surfaces thus removed, and its hole bored as true as may be, were again trued over each surface, and in its bore there will still be at each surfacing and at the boring an alteration of form, although it may be to a very minute degree, and from these causes the use of the reamer for work requiring to be very true becomes indispensable. [Illustration: Fig. 2265.] [Illustration: Fig. 2266.] Fig. 2266 represents a taper hand reamer with straight flutes. It is preferable, however, to give the flutes a left-hand spiral, as was explained with reference to reamers for lathe work. [Illustration: Fig. 2267.] The frames of large machines are frequently composed of parts that are bolted together after having the holes for shafts, &c. bored, and to insure the alignment of these holes after the frames are put together a hand reaming bar, such as in Fig. 2267, is employed, A and B being two shell reamers fastened to the bar by a pin. [Illustration: Fig. 2268.] Reamers are sometimes employed to enlarge holes or bring them fair one with another, without reference to their being precise to a designated diameter; thus Fig. 2268 represents a half-round reamer of the form used by boiler makers to bring rivet holes fair, and sometimes by machinists to ream the holes for taper securing pins. The flat face is cut down to below the centre line, so that the back requires no clearance ground upon it. [Illustration: Fig. 2269.] The square reamer shown in Fig. 2269 is used for rough work generally, although with careful grinding and use it will produce excellent results upon work of small diameter. Brass finishers generally prefer a square reamer to all others for reaming the bores of brass cocks, &c., and some of them prefer that one edge only be sharpened to cut, the other three being oilstoned off so as not to cut, but simply serve as guides. The square reamer is very easily sharpened whether by grinding or oil-stoning; the flat sides are operated on, taking care to keep them straight and the thickness even on the two diameters, so that, the sides being straight and the reamer square, it will cut taper holes whose sides will be straight. If the reamer is not ground square, two only of the edges will be liable to have contact with the work bore, causing the reamer to wabble, and rendering it liable to break. [Illustration: Fig. 2270.] Another and very good form of reamer for the rapid removal of metal is shown in Fig. 2270, having three teeth and a good deal of clearance, which enables it to work steadily and cut freely. CHAPTER XXVI.--VICE WORK--(_Continued_). In most of the operations of the machine-shop, the work of the chisel is followed by that of the file; hence, as an example in the use of the chisel independent of that of the file, the cutting of the teeth upon files may be given as follows:-- [Illustration: Fig. 2271.] [Illustration: Fig. 2272.] [Illustration: Fig. 2273.] [Illustration: Fig. 2274.] The largest and smallest chisels commonly used in cutting files are represented in two views and half size in Figs. 2271 and 2272. The first is a chisel for large rough files; the length is about 3 inches, the width 2-1/2 inches, and the angle of the edge about 50°; the edge is perfectly straight, but the one bevel is a little more inclined than the other; this chisel requires a hammer of about 7 or 8 pounds weight. Fig. 2272 is the chisel used for small superfine files; its length is 2 inches, the width 1/2 inch; it is very thin, and sharpened at about the angle of 35°; it is used with a hammer weighing only 1 or 2 ounces; as it will be seen, the weight of the blow mainly determines the distance between the teeth. Other chisels are made of intermediate proportions, but the width of the edge always exceeds that of the file to be cut. The first cut is made at the point of the file; the chisel is held in the left hand, at a horizontal angle of about 55° with the central line of the file, as at _a_ _a_, 2273, and with a vertical inclination of about 12° to 4° from the perpendicular, as represented in Fig. 2274, supposing the tang of the file to be on the left-hand side. The following are nearly the usual angles for the vertical inclination of the chisels, namely: For rough rasps, 15° beyond the perpendicular; rough files, 12°; bastard files, 10°; second-cut files 5°, and dead-smooth-cut files 4°. The blow of the hammer upon the chisel causes the latter to indent and slightly to drive forward the steel, thereby throwing up a trifling ridge or burr; the chisel is immediately replaced on the blank, and slid from the operator until it encounters the ridge previously thrown up, which arrests the chisel or prevents it from slipping farther back, and thereby determines the succeeding position of the chisel. The chisel having been placed in its second position, is again struck with the hammer, which is made to give the blows as nearly as possible of uniform strength, and the process is repeated with considerable rapidity and regularity, 60 to 80 cuts being made in one minute, until the entire length of the file has been cut with inclined parallel and equidistant ridges, which are collectively denominated the "first course." So far as this one face is concerned, the file, if intended to be single-cut, would be then ready for hardening, and when greatly enlarged its section would be somewhat as in Fig. 2274. The teeth of some single-cut files are much less inclined than 58°; those of floats are in general square across the instrument. Most files, however, are double-cut, and for these the surface of the file is now smoothed by passing a smooth file once or twice along the face of the teeth, to remove only so much of the roughness as would obstruct the chisel from sliding along the face in receiving its successive positions, and the file is again greased. The second course of teeth is now cut, the chisel being inclined vertically as before, or at about 12°, but horizontally about 5° to 10° from the rectangle, as at _b_ _b_, Fig. 2273. The blows are now given a little less strongly, so as barely to penetrate to the bottom of the first cuts, and consequently the second course of cuts is somewhat finer than the first. The two series of courses fill the surface of the file with teeth which are inclined toward the point of the file. If the file is flat and to be cut on two faces, it is now turned over; but to protect the teeth from the hard face of the anvil a thin plate of pewter is interposed. Triangular and other files require blocks of lead having grooves of the appropriate sections to support the blanks, so that the surface to be cut may be placed horizontally. Taper files require the teeth to be somewhat finer toward the point, to avoid the risk of the blank being weakened or broken in the act of its being cut, which might occur if as much force were used in cutting the teeth at the point of the file as in those at its central and stronger part. Eight courses of cuts are required to complete a double-cut rectangular file that is cut on all faces, but eight, ten, or even more courses are required in cutting only the one rounded face of a half-round file. There are various objections to employing chisels with concave edges, and therefore, in cutting round and half-round files, the ordinary straight chisel is used and applied as a tangent to the curve. It will be found that in a smooth, half-round file 1 inch in width, about twenty courses are required for the convex side, and two courses alone serve for the flat side. In some of the double-cut, gullet-tooth saw-files, as many as twenty-three courses are sometimes used for the convex face, and but two for the flat. The same difficulty occurs in a round file, and the surfaces of curvilinear files do not therefore present, under ordinary circumstances, the same uniformity as those of flat files. [Illustration: Fig. 2275.] The teeth of rasps are cut with a punch, which is represented in two views, Fig. 2275. The punch for a fine cabinet rasp is about 3-1/2 inches long and 5/8 inch square at its widest part. Viewed in front, the two sides of the point meet at an angle of about 60°; viewed edgewise, or on profile, the edge forms an angle of about 50°, the one face being only a little inclined to the body of the tool. In cutting rasps, the punch is sloped rather more from the operator than the chisel in cutting files, but the distance between the teeth of the rasp cannot be determined, as in the file, by placing the punch in contact with the burr of the tooth previously made. By dint of habit the workman moves--or, technically, hops--the punch the required distance; to facilitate this movement, he places a piece of woollen cloth under his left hand, which prevents his hand from coming immediately in contact with and adhering to the anvil. As an example in the use of the chisel for chipping purposes, let it be required to fasten a feather on a shaft. There are four methods of inserting feathers: First, a shaft may have a parallel recess sunk into it and a parallel feather may be driven in; second, the feather may be made slightly taper and driven in; third, the feather may be dovetailed on the sides and ends both, or on the ends only, and as one or the other of these is the proper method, and the process is the same for both, one only need be described. [Illustration: Fig. 2276.] [Illustration: Fig. 2277.] [Illustration: Fig. 2278.] In Fig. 2276 let S represent a shaft and F a feather, required by the drawing to be permanently fixed therein. The drawing will not, in ordinary shop practice, give any instructions as to how the feather is to be fastened; hence the mechanic usually exercises his own judgment about the matter, or is governed by the practice of the shop. If left to his own judgment he may determine to so fix it that it may be locked on all four sides, as in Fig. 2277, or he may simply set it in as in the similar views shown in Fig. 2278. The method shown in Fig. 2277 is the most secure and best job; but, on the other hand, it is the most difficult and costly. The difficulty consists in filing the parallel part above the surface of the shaft to a line that shall be quite even with the surface of the shaft. This difficulty may be overcome by leaving the sides parallel, and making the length A equal to the length of the acting part of the key, and the bottom B as much longer as may be required to get the required amount of dovetail on the feather ends. [Illustration: Fig. 2279.] [Illustration: Fig. 2280.] [Illustration: Fig. 2281.] [Illustration: Fig. 2282.] The first thing to do is to mark off the keyway by scribing lines on the surface of the shaft, indicating the location for the feather seat; and for this purpose nothing is better than the key seat rule shown in Fig. 2279, in which W is the key seat rule, and S the shaft. After the lines are drawn they should be defined by centre-punch dots, as in Fig. 2280, and then the metal should be cut out on the sides first, using a cape chisel, and cutting close to the side lines, as in Fig. 2281, in which A is a cape chisel cut taken along one side, D a second cape chisel cut, being carried along the other side, C the cape chisel, C´ the cut taken by the chisel, and B a piece of metal to be cut out after the cape chisel has done its work. Suppose, now, the mass of the metal is removed, then the dovetailing is performed as follows: Next the _setting_ or _upsetting_ is proceeded with as shown in Fig. 2282, which is a side sectional view. S is a set chisel driven by hammer blows against the walls of the feather seat (as against the end _e_), causing it to bulge up, as shown at _f_. This setting will enlarge the feather seat or recess, so that the wide part of the dovetail on the feather will just pass in (the dotted lines shown in Fig. 2281 having, of course, been marked to the size of the feather, where it will, when fixed, meet the surface of the shaft). The feather is then placed in its seat and bedded properly by red marking applied to its bottom surface to show the high spots on the seat of the recess, and when properly bedded it is fastened, as in Fig. 2283, in which S is a set chisel, which, by being struck with hammer blows, closes the bulged metal back again on the dovetail of the feather, and firmly locks it in the shaft. And all that remains is to file the shaft surface around the feather level with the surrounding surface, there being usually a little surplus metal from the upsetting. [Illustration: Fig. 2283.] [Illustration: Fig. 2284.] [Illustration: Fig. 2285.] [Illustration: Fig. 2286.] [Illustration: Fig. 2287.] As an example of chipping and filing let it be required to chip and file to shape and to fit a knuckle joint (or a double and single eye, as it may more properly be termed), such as in Fig. 2284. The eye being marked out by lines, the first operation will be to remove the surplus metal around the edges by chipping, which should be done (with the pin in place, so that it may support the eye) before the joint faces are filed at all, and should be carried in a direction around the eye, as shown in Fig. 2285, in which _v_ is the vice jaw, E a lead clamp, C the cut, and D the chisel. By chipping in this direction two ends are served: first, the force of the chipping blows is less likely to bend the eye if it is a light one, and, secondly, the chipping will not break out the metal at the edge of the eye, which it would be apt to do if the chipping was carried across. This is shown in Fig. 2286, where a chisel cut is supposed to have been carried across from A to B and a piece has broken out at B. If the width of the eye is too broad for one chisel cut, a cape chisel should be run around it, as in Fig. 2287, A D showing the cutting, the flat chisel cuts B, C being taken separately afterwards. In order to illustrate the filing clearly, it will be necessary to show more metal to be filed off than would be the case in practice, unless the eye were very small, in which case it would not pay to chip. [Illustration: Fig. 2288.] Put the eyes together with the pin in and let the two lowest places on the edges coincide. Then file a flat place clear across them, as shown in Fig. 2288 at F, making it parallel to the pin, and, say, down to within 1/100 of the finished depth. To test the parallelism of the flat place, take out the pin and apply to the flat place a square, rested against the radial face of the double eye, or measure its distance from the hole of the eye on each side of the double eye, that is at each end of the hole. [Illustration: Fig. 2289.] When it is true and down to the required size, put the eyes together and let their relative positions be such that the flat places do not coincide, and that on the double eye will serve as a guide to carry the filing around the single eye, while that on the single eye will serve as a guide to carry the filing around the double eye, as will be seen on reference to Fig. 2289, in which the flat places A, B on the double eye serve as a guide to file C down to, while the flat place on the single eye at D is a guide to file the metal at E, F down to, and it is obvious that by moving the eyes to different positions the eye may on that side be filed true and to circle. When the filing has thus been carried around as far as the movement of the eyes permits on that side, turn the single eye over in the double eye, and they will appear as shown in the end view, Fig. 2290, A being the filed side of the single and E D that of the double eye; hence the metal at C, B must be filed down level with A, and that at F down level with E, D. [Illustration: Fig. 2290.] We have assumed that the edges only required finishing irrespective of the joint faces; but let it be assumed that the whole of the eye has been dressed up by machine tools, and that it requires fitting and finishing by the file both on its joint faces and on its edges. If the eye has been bored and faced in the lathe the faces will be about true with the hole, but if it has had its faces trued in a machine, as a planer or slotter, and the hole bored subsequently in a slotting machine, the hole may not be true to the faces. This may occur from want of truth in the chucking devices, from these devices having been held to a table or carriage moving on slides, and having lost motion or play, in which case from the leverage of the pressure of the boring tool-reamer or bit, this table may have lifted to the extent of such play, in which case the hole will not be at a right angle to the face or faces. [Illustration: Fig. 2291.] First, then, these faces must be tested for truth and smoothed by filing. The best testing device is a pin and washer, the pin neatly fitting the hole in the eye and the washer neatly fitting the pin. The radial face of the pin head and of the washer should then be given a light coat of marking, and be inserted in the eye, as shown in Fig. 2291, in which _a_ is the pin head and B the washer. If each be then rotated under pressure against the eye, they will mark the high spots, which may be filed and draw-filed until an even contact all around is shown. The single eye should be similarly faced and fitted, a somewhat tight fit, into the double eye. In a job of this kind, where accuracy of fit is essential, it is usual to bore the hole about 1/100 inch smaller than its finished diameter, and after fitting the two eyes, to ream out the eyes while bolted together. For the reaming the two eyes should be clamped together. The single eye is left somewhat too tight a fit to the double eye to permit of the finishing being done after the holes are reamed, because the reaming may slightly alter the axial line of the hole. The two bolts holding the clamping plates should be brought just home on the plates, and then tightened up gradually and alternately, so that the eyes may be gripped fair, and not liable to move during the reaming. The bores of the eyes should be set as true as possible one with the other before the plates are tightened upon the eyes, for if it is attempted to set the eyes true by hammer blows afterwards, the pressure of the plates would cause the arm or hub of the double eye which received the hammer blow to move more than the other, or, in other words, to spring out of its normal position, and the eye will be distorted. But when released from the pressure of the clamping plate the double eye will resume its normal shape, and the holes will not be axially true in the two eyes. After the holes are reamed the temporary pin and washer used for the facing will be too loose, and the proper pin should be used for all future operations. The eyes should be put together with a light coat of marking on both faces of the single eye, and, with the pin in place, one eye should be moved back and forth, when they may be taken apart again and filed on the high spots. When by repetition of this process they fit properly the outside edges may be filed up, as already described. It is obvious, however, that the pin and washer shown in the figure may be hardened and used to file the edges up before the reaming, in which case, their diameters being equal, and equal to that of the required finished diameter of the eye, it is easy to file the eye edges true and to size; but even in this case the eyes should be finished by reversing and moving as before described. There is, however, the objection to filing the edges--first, that the joint will show plainer, because in filing the side faces to fit the single into the double eye, that part of each face near the edge is apt to be filed away slightly too much, causing the joint to show; but if the circumferential edges of the eye be filed last, the part so filed away is removed and the joint may be made almost invisible. The best plan of all is to first fit the eyes, then ream them out and then provide a hardened pin and washer to fit the reamed hole, then file down the circumferential edges nearly level with the pin and washer and finish by reversing and moving the eyes as before described. In the absence of any pin and washer, such as shown in Fig. 2291, the inside faces of the jaws of the double eye must be filed parallel to the outside radial faces of the single eye, the outside surfaces being trued when the hole is bored. If none of the surfaces have been trued with the hole, the outer ones should first be trued, using a [T]-square (if there is no pin) to test the truth of the face with the hole, and the inside jaw faces must be trued with the outside, measuring each jaw with outside calipers, and the width between the jaws with inside calipers. [Illustration: Fig. 2292.] Let us now suppose that it were attempted to first fit the single to the double eye a tight fit, then to ream the hole and then to make the joint an easy working fit. In this case the finished hole in one eye may become out of true with that in the other, that is, it may not be parallel with that in the other, and for the following reasons:--The holes of the two eyes will rarely come quite true with each other, even though the radial faces of the eyes be turned in the lathe or faced in a machine when the holes are bored, and it is the duty of the reamer to true as well as smooth them in whatever direction they may be out of true or face one with the other until they are put together. Now, if they be put together a tight fit, the outside jaws are sprung open to some extent. Again, they may be sprung slightly atwist, and if the hole be reamed true and this twist taken out afterwards the hole will come atwist or out of fair in proportion as the jaws lose their twist from being fitted. Again, reaming the hole slightly alters its axial line, and the radial faces, if at a right angle to the hole before reaming, will not be so after reaming, and it is not practicable to discover in just what direction and to what degree reaming the hole will alter its axial direction; hence, the single eye must be fitted as near as may be before the holes are reamed, and finished afterwards as described. Let it be required to reduce by filing, the diameter of a round pin or to file it to fit a taper hole, and the diameter of the pin being small it may be held by one end in the vice jaws or by means of the clamps, shown in Fig. 2091 or those in Fig. 2092. But the filing can be more truly and easily finished as in Fig. 2292, in which there is shown fastened in the vice a filing block having [V]-grooves (of varying width to suit varying diameters of work), in which the pin to be filed may be rested. The pin is held by the hand vice shown, and is rotated towards the operator during the forward file stroke (one hand holding the hand vice and the other the file), and in the opposite direction during the back stroke. After every few file strokes the hand vice is partly rotated in the hand so that the whole of the pin surface may be subjected to the file. The hand vice enables the pin to be forced into its hole and rotated, to show by the contact or bearing marks where it requires filing to adjust the fit. [Illustration: Fig. 2293.] Fig. 2293 represents an excellent form of hand vice for holding pins, &c., the jaws being pivoted to a cross piece and opened by a cone, the handle threading to the stem of the cross piece, and being hollow so that the work may pass through it. The work is thus very firmly gripped and not liable to move in the jaws as it is when the hand vice is fastened upon the work by a thumb nut. Very thin pieces of metal cannot be well held in the vice jaws, and as an example of this kind of work holding, let it be required to file up a caliper leg, which being curved cannot well be held in any of the vice fixtures heretofore shown. [Illustration: Fig. 2294.] In Fig. 2294 there is a block of wood having an extension at A that may be gripped in the vice jaws. Upon the surface of the block the caliper leg is held by brads or nails driven around its edge, as shown, or it is obvious screws may be used. [Illustration: Fig. 2295.] An excellent example of filing is to file up a hexagon nut or a bolt head. This is apparently a simple piece of work, but it is in fact a job that requires a good deal of care and precision to properly accomplish. The requirements are that the nut shall measure alike across the flats, that each flat shall be parallel to the axial line of the bolt, and at a proper and equal angle to both of its neighbors, and that the nut shall be of equal thickness all round. The method of accomplishing this result is as follows: Let Fig. 2295 represent a bolt head, after it has been turned in the lathe. It will be observed that the end face of the bolt head is rounded. Now a bolt head of this form gives a very neat appearance, but it presents difficulties in the filing up, as we shall see presently. [Illustration: Fig. 2296.] [Illustration: Fig. 2297.] [Illustration: Fig. 2298.] [Illustration: Fig. 2299.] Suppose that one flat (which we will call flat A) of a nut, is nearest to the bore, then to make the nut of equal thickness all around, the other flats must be so filed down as to approach the bore as nearly as A does, and it is assumed that there is metal enough to permit this. The flat A will then be the first one to be filed up, taking off just sufficient to make it true when tested by the nut gauge, applied as in Fig. 2296, in which N is the nut, and G the gauge. The flat must also be filed true when tested by the gauge, as in Figs. 2297 and 2298, the gauge G being tried rested on A and applied to B, and then rested on A and applied to C. A should be filed so that, if possible, it will be at the proper angle to both B and C, but if, from errors in the angles of B and C, this is impossible, the error should be divided between the two, as shown, for example, in Figs. 2299 and 2300, where the gauge is shown in the two positions necessary to test each respective flat, B and C; the amount of error being equal at H and I. The next flat to file will be E, Fig. 2299. Now, in a small nut, the chamfer of the nut edge will be sufficient guide to the eye in filing E to an equal thickness (that is, equal for distance from the bore to A). In order that the finished nut shall be so true that the nut gauge shall show that the flats or angles are true one with the other all around the nut, it is necessary that the flat E shall stand parallel to A; hence it should be made so by measurement with calipers, irrespective of its angle to either D or F. After E is filed it will serve as a base from which D and F may be filed to angle, while A will serve as a base from which the flats D and C may be filed to angle; but, while testing the angle with the gauge, C and D should be tried for parallelism, and F and B for parallelism, while the diameters across these flats should be equal on all sides. [Illustration: Fig. 2300.] If it were attempted to go all around the nut, filing to the gauge, as, for example, filing C, Fig. 2300, from A, F from C, E from F, D from E, and B from D, all the error in the angle of the gauge, or errors of workmanship, will (supposing the latter to be always in the same direction) be multiplied upon, or rather added to B when tested with A, and these two will not be of correct angle. Again, any error made upon one flat will be copied upon the one filed to gauge angle from it; whereas, filing E parallel to A insures the correctness of these two, and testing the parallelism of the others, as B, F, serves to discover and correct any error of angle that may exist. It is obvious that in filing each flat the gauge must be applied as in Fig. 2296, as well as in Fig. 2298. In filing the opposite flats to diameter to fit the wrench or gauge, if one be used, it is best to leave them a tight fit until all are nearly finished, so that any error that may be discovered may be corrected while finishing them. [Illustration: Fig. 2301.] [Illustration: Fig. 2302.] In small nuts, if two are to be filed, a better plan may be followed. The two nuts may be put upon a short piece of screw, as shown in Fig. 2301, and screwed firmly together. In doing this, however, it may be found that the nuts will not tighten against each other, with the flats fair one with the other. This, however, may be accomplished by winding around the piece of screw, and between the nuts, a piece of waste, twine, or rag, and then screwing them together until they bind sufficiently and the sides come fair; the nuts may then be put in the vice, the jaws of the latter meeting the end A of the screw and the face B of the nut in the figure. Select the thinnest flat on either of the two nuts, and file it and the one coincident to it, but on the other nut, at the same time taking care that both are filed equidistant from the screw. To test this, apply the gauge as shown in Fig. 2296. File these faces down a little above size, and then loose the nuts and put in an addition of waste or twine, so that the same faces shall not coincide, and the two filed faces will serve as guides, down to which their new contiguous faces may be filed, the hexagon gauge being applied as before. By adding waste or twine, this process may be repeated, the original, or first-filed faces serving as guides down to which to file all the others, which will insure equal thickness of all the flats. After roughing out all the flats in this manner, reverse the nuts on the screw, so that the two chamfered faces come together, as in Fig. 2302, and any want of truth in the parallelism of the flats one with the other, or with the axial line of the screw, will become at once apparent, and will be corrected in the finishing, providing that an equal amount be filed off the respective sides that are in the same plane as are A and B in the figure. Of course nuts filed in this way require the application of the calipers and gauges, the same as described for a single nut; but uniformity will be assured and the filing truer, because the filing in small nuts, as an inch or less, will be more true on account of there being a larger area for the file to rest and steady upon. It is obvious that a plain cylindrical piece, instead of a piece of screw, may be used, in which case the waste or twine will be unnecessary; but in this case the plug, or cylindrical piece, should be shorter than the length of the two nuts, and should not be so tight a fit to the bores as to damage the threads. In small nuts it will not pay to chip off the surplus metal, because they cannot be held sufficiently firmly in the vice without suffering damage from the vice-jaws, or even from copper clamps, while lead ones are too soft to hold them. [Illustration: Fig. 2303.] The finishing marks, if any, should be in a line with the bore of the nut, which gives the neatest appearance. The process is the same for a bolt head, such as shown in Fig. 2295, as for a single nut, with the exception that the gauge must be applied as in Fig. 2303, when testing the truth of the flats with the axial line of the bolt, this being necessary because of the roundness of the end face A, in Fig. 2303. The distances D and C will be equal when the flat is true in that direction. A pair of outside calipers form an excellent example in vice work. The material should be good cast steel of an even thickness, and therefore (unless for very large ones) saw blade will answer the purpose. It should be well softened by being made to a low red heat and buried in fine cinder ashes or lime, and allowed to cool there; the proper width of this piece of steel being sufficiently greater than the size of the caliper washer, to allow room for a chisel cut and leave a little to file off in truing up the joint. The length should be somewhat more than that required to make the legs, because a piece will be required to be cut off the narrow end to give substance enough for the points. The size of the washer should be drawn at each end of the steel, the centre of the washer should be centrepunch-marked, and a line should then be drawn to set off the two legs. The steel is then severed along this line, thus getting out the two rough legs. When shears are not at hand, or when it is not designed to use them for this purpose, three methods of dividing may be pursued: First, we may drill small holes along the line, and cut between the holes with a chisel. The objection to this is that the blade is sometimes very hard to drill. Secondly, we may make centrepunch marks along the line, and then cut along the line with a chisel; and thirdly, we may drill a few holes at each end, and cut the middle with the centrepunch and chisel. The entire drilling is the safest, and the centrepunching the most hazardous, but it can be accomplished if the centrepunching is done lightly and gone over several times, with the chisel applied between the centrepunch marks, which will be much the quickest plan of the three. The hole is next drilled for the rivet, care being taken to make it about 1/32 inch smaller than the proper size, because the drill will not make a sufficiently true and parallel hole, and the latter must be reamed or trued out; and again because the legs have to go into the fire to be bent, and hence the holes may become damaged. There is another consideration, however, in determining the size to drill this hole, which is that the two legs require to be riveted together to bend them, and it is as well to drill the hole to suit the piece of metal intended to be used for this temporary rivet, which should be of brass or copper, so as to drive out easily after the bending is done. During the bending process the points should be thickened, care being taken not to twist them in the process. If the vice hand does the bending, the following instructions are pertinent: Heat the steel slowly and turn it over and over in the fire so that the points may not get burned before the wider parts are sufficiently heated. Let the fire be a clean one, that is, with no gaseous or blazing coal about it, or the coal will stick to the sides of the calipers, and they will get cool while being cleaned of adhering coal after being taken from the fire. Begin the bending from the thick end, carrying it forward by degrees. Strike light but rapidly succeeding blows, placing the steel upon the round point of the anvil. The bending completed, and the points being thickened, the edges of the legs are trimmed upon an emery wheel or with a file, using the latter lengthwise of the edges if a new one, or crosswise if an old one. A full 1/32 inch may be left to trim off after the calipers are put together. The temporary rivet may next be driven out, first, however, gripping the legs firmly and near to the rivet end with a hand vice, putting a piece of sheet brass between each jaw of the hand vice and the steel; otherwise the teeth of the latter will mark the steel, entailing a great deal of extra labor to file the marks out. The rivet hole is then reamed out to the required size, the two legs being held together by the hand vice to render the reaming more steady and true by making the hole longer when the two are together. The next operation is to turn the rivet and washers. It is a very common practice to turn two separate washers and a rivet. On account, however, of the small amount of bearing in the washer holes, such washers are apt to rivet up out of fair one with the other, making an unsightly joint and causing them to be out of round when the edges of the joint are filed up. A better plan is to turn a pin and washer, taking care to make the diameters of the two exactly equal and the flat faces of each quite level. The pin should be turned about 1/64 inch taper, the small end being made a neat fit to the holes in the caliper legs, and should be made of cast steel properly annealed. When finished, the head of the pin should be gripped by a pair of lead clamps in the vice, the end being left protruding so that the legs can be put upon it and revolved back and forth with a good supply of oil and under hard pressure, so that the pin will be forced a good and rather tight fit into the holes. This process will also smooth out the holes and condense the metal around both the holes and the pin. It is well to leave the pin to fit about one half as tight as the finished joint requires to be. The washer should be countersunk about three-quarters of the way through the hole, the latter being left a close working fit to the pin. The legs should be rough filed, second-cut filed, and smooth filed before being draw-filed, care being used to keep the files clean, so as to avoid scratches. During this filing, however, the pin should be tried in the hole to see if the head comes fair down upon the face; thus the pin forms a guide and test in facing up the joint of the leg, and this is one of its advantages over the two-washer plan. After carefully draw-filing and polishing the sides of the legs the fitting of the joint is finished as follows: Place the two legs upon the pin in their proper position, and then put the washer into its place. Then behind the washer place another temporary one that will protrude beyond the end of the pin; then grip the whole tightly between a pair of lead clamps or pieces of thick leather in the vice; this will bring all parts of the joint home. Take hold of one leg in each hand and move them backward and forward as far as the vice will let them go, repeating the operation about a dozen times or more. This will mark the high spots upon the legs, which may then be taken apart again and have the bright parts removed by a scraper. It is also well to place the flat face of the washer upon a smooth file and rub it backward and forward under finger pressure, which will tend to correct any defect in its flatness. When the faces of the joint bear all over, it may be put together with oil and placed in the vice as before. Work it well back and forth, take it apart again and cut off the rivet to the required length, taking care very slightly to recess the end to assist the riveting. The whole joint should then be wiped quite clean, freely oiled, and put together ready to rivet. The head of the pin should be rested upon a block of lead, so that it will not get damaged. The riveting should be done with a small light ball-pened hammer, the blows being delivered very lightly and evenly all round the edge. As the riveting continues it is necessary to move the legs occasionally to see how the tightening proceeds, and when the legs are sufficiently tight, one of them may be gripped between pieces of leather in the vice, while the other is well worked and lubricated with oil. Then the riveted end should be filed off to very nearly its proper height and shape, and the joint well worked back and forth and round and round in the hand until it gets quite warm, when it may be cooled in water and tried for tightness. If too tight, it may be either worked until easy, or the riveted end of the pin may be tapped with a hammer to loosen it slightly. The riveting being completed, and the end filed smooth, the rounded part of the washer and the pin head should be draw-filed with a very fine file moved in varying directions, and then the polishing may be done with emery paper. FITTING KEYS.--Keys that have been planed or milled will still require fitting with the file to insure that they bed properly. If the key to be fitted is taper and intended to fit top and bottom, the sides should first be filed true to a surface plate, and fitted into the keyway in the shaft, so that it can be slid up and down a good working fit. While fitting it, however, it is well to try it once or twice in the keyway in the wheel, as well as in the shaft, so as to see by the marks whether the keyways in the shaft and wheel require any fitting at all, either to make them quite square with the outside face, supposing it to be turned off, or to give them a good even bearing surface. The key being fitted sideways we must give the two keyseats a coating of red marking just sufficient to show that the surface is of a red tint, and then put the wheel in its place on the shaft. Then we bevel off the edges of the key at each end, leaving a chamfer of 1/16 inch, and after facing off the top of the key with a bastard file, we place it in the keyway and tap it very lightly to a gentle bearing. After driving the key lightly home and taking it out again, we may file it on the top and bed it on the bottom, according to the indication of the marking, and re-insert it, tapping it up until it is home, top and bottom, without being a driven fit at all; on taking it out we file it according to the marks again, and if we continue this process until the key is a good fit, it will not spring the wheel the least out of true, no matter how tight, reasonably, it is finally driven. The key must never be driven in or out dry, for it will, in that case, inevitably cut during the first part of the operation; the marking put on the keyway is sufficient lubrication, but after two or three insertions the key also should be itself given a light coat, which will serve as lubrication, as well as denote the fit. The bearing or contact marks upon a key driven home very lightly may show at one end or on one side only, while if the key was driven farther in those marks may show all over, making the key appear to fit much better than it actually does. This occurs from the elasticity and compression of the metal of the keyway and key, the metal giving most where the contact is hardest; from this it is apparent that a wheel truly bored and a good fit may be set out of true by the key. In Fig. 2304, for example, is a wheel hub W, assumed to be a good fit to the shaft S, while the key K fits at the end A only. If the key be driven tightly home, the wheel will spring over, so that instead of the plane of its diameter standing at a right angle to the axial line of the shaft as at D in Fig. 2305, it will stand at an angle as at E, throwing the wheel out of true in that direction. This would occur not only on account of the elasticity and compression of the metal of the keyway, but also because the surface of the bore of the wheel and of the shaft is not, even under the best of turning, smooth enough to come into close contact all over, but are covered with slight projections or protuberances, which may occur in spirals because of the turning tool marks, or in localities because of differences in the texture of the metal. In driving the key home these protuberances give way, and they do so most where the contact pressure is greatest, which would be at G in Fig. 2305, causing the wheel to cant over. If the wheel is not a good fit to the shaft it will not in this case touch the shaft at C, Fig. 2305. [Illustration: Fig. 2304.] [Illustration: Fig. 2305.] [Illustration: Fig. 2306.] Now suppose the key to bear at _a_ and _b_, Fig. 2306, only, then the wheel would be thrown out of true in a direction at a right angle to the length of the key as denoted by the line E, which should stand as at D. A properly bedded key binds the opposite half of the circumference of the wheel bore to the corresponding half circumference of the shaft; but if the key binds at one end only, as in Fig. 2304, the contact will be at the end H only; hence the surfaces will soon compress, on account of all the strain of the key falling on a small area, and the key will get loose. It is obvious then that if a wheel has not been bored to run true the error may be to some extent corrected in fitting the key, but in this case the key must be driven well home, and the wheel rim tried for running true during the fitting process, the key being so bedded as to true the wheel as far as the elasticity and compression will permit; but a key thus bedded will not hold so firmly. The distance a key of a certain length, breadth, and thickness, and of a given taper, will drive after being pushed home by hand or lightly tapped in with a hand hammer depends upon how closely it fits to its seat, and upon the elasticity of the metal, as well as upon the force with which it is driven. The workman usually, while fitting the key, drives it well home occasionally, to see how much of its length to allow for the final driving, and while doing so, if the key is a small one, a hand set chisel or a piece of copper should be interposed between the key head and the hammer (a blacksmith's set chisel is used for large keys) to prevent the hammer from damaging the key. In fitting keys to old keyways the key is made too long, and cut off after being driven home. A long key is apt to bend in the driving, hence it is not unusual to support it by holding a second hammer beneath and against it to support it while being driven. In driving a key out, especially if it is fast home, a quick heavy blow is best, as it is less likely to burr, swell, or bulge the end of the key. But after the key has started lighter blows will answer. To make a key for an old sunk keyway, it is as well to fit a piece of wood thereto as a guide in forging and fitting the key. If a _fast_ running grindstone or emery wheel is at hand, many will forge the key a trifle large and then grind it as near as possible, and finish by filing. This, however, does not produce good work; it is better to plane the key all over, leaving a little in size for fitting. In preparing the piece of wood referred to, it should not in the fitting be driven or even forced in and out to try the fit, for the wood will compress and the marks mislead as to the actual fit. The proper way is to chalk the piece of wood and push it up the keyway just tightly home, then withdraw and fit it again. In cases where the key is forged to very nearly the finished size, and is finished by the file, as sometimes occurs when away from the shop, it is best to forge the key with a gib head, as in Fig. 462, to assist in extracting it, especially when it is difficult to drive the key out from the back end, or when the keyway does not pass entirely through. The key should be finished with a smooth file and with the file marks lengthways; it is, in fact, better to use a small smooth file and draw-file it, taking care to ease the high spots the most; and before driving it home both it and the keyway should be oiled. If a keyway is to be cut by hand through a bore, as in a pulley or gear-wheel bore, its width should be marked with a [T]-square. If its width does not exceed 1/2 inch a cape chisel a little less (say 1/32 inch less) than the finished width of keyway should be used, which will leave a little metal for the sides to be filed true. If the keyway be an inch wide it is better to take a cape chisel about 1/4 inch wide and cut a groove along each side of the keyway (keeping close to the marked line), and then cut out the middle with a flat chisel. The sides and bottom of the keyway should be surfaced true with the file. If a keyway is to be cut in a shaft the cape chisel should be used in the same manner as above. But in both cases it is best, when filing, to occasionally ease out the corners with the edge of a half-round file, for reasons which will be explained presently. In chipping a keyway in a bore the cut must not be carried entirely through from one side, or the metal at the end of the cut will break out, and even in wrought iron this is apt to occur, so that it is necessary to cut the keyway from each end, or, at least, nick it in at one and cut it from the other end. In long key ways it is handiest to cut them half-way from each side, using, in the absence of anything better, a piece of planed wood and red marking or chalk to try the keyway with. [Illustration: Fig. 2307.] In cutting out through keyways by hand the location of the keyway is marked off by lines on both sides of the stub end of the rod, and then the mass of the metal is removed by drilling through as many holes as can be got in the size of keyway required, as shown in Fig. 2307, in which W is the work, B C D E the location of the keyway, and 1, 2, 3, 4 are the holes, taking care to have the drill rather smaller than the width of requisite keyway. The holes are drilled half-way through from each side, which is done to keep the keyway true; for if the drills were to run a little to one side, as they are apt to do from a variety of causes, a great deal of work would be required to correct the error. If the keyway is of sufficient dimensions to admit of the use of a chisel, the pieces left between the drilled holes are chipped out, and for this purpose a side chisel is found very useful, not only to nick the sides of the pieces left by the drilling, but also to take the finishing chipping cuts on the sides of the keyway. To cut out the square corners of the keyway, the diamond-point chisel shown in Fig. 2171 is employed. [Illustration: Fig. 2308.] If, however, the keyway is a very deep one, requiring long and slight chisels, the chipping process may be greatly reduced, or in fact entirely dispensed with, by plugging up the holes first drilled in the stub end by driving pieces of round iron tightly into them, and then drilling new holes, having their centres midway between the pieces so driven in, as at A in Fig. 2308. After the latter drilling, the remaining pieces of plugs are driven out, leaving the centre of the keyway cut clear through and the sides with a series of flutes in them, as shown at B, Fig. 2308 (in which 1 2 are the plugs and A is a centre for the new hole at that end), which should be filed away with a file as thick or strong as the clear space will allow. These plugs must be of the same metal as that in which the keyway is cut, otherwise the drill will be apt to run to one side. To insure truth in the surfaces, a surface plate to test with is an absolute necessity, while to test the parallelism, a small sheet iron gauge is used, which gauge may afterwards be employed as a guide whereby to plane the thickness of the gib and key. In cases where a slotting machine is at hand, it is sometimes the practice to cut out one end of the keyway to a sufficient length to admit a slotting tool, and then to slot out the remainder. This plan is often resorted to in getting out keyways of unusually large dimensions. A much more usual method, however, is to employ slotting or keyway drills. It is obvious that the ends of the keyways cut by drills are half round; hence, if square corners are required, they must be cut out square with the chisel shown in Fig. 2176, and afterwards filed out true. As a general rule, keyways cut with these drills require filing on the sides to get proper smoothness and bearing for the keys; and here it may be remarked that, in filing the corners of the keyway, a safe-edge file must be used, so that the two faces forming the corner will not be operated upon simultaneously, because that would require that the file be used in a straight line laterally as well as horizontally, and this is impracticable even in the hands of the most skilful. Even the square file should have a safe edge upon it, and such an edge is usually produced by grinding the teeth off one face of the file. In selecting the face to have the teeth ground off, choose a face that is hollow in its length, or, if none of the faces is hollow, then select a face that is at a right angle to a good face of the file. It will be noted that with one safe edge only the square file will require turning over in order to operate upon both corners and maintain in each case a safe edge of the file against the flat sides of the keyway. For this reason many workmen select the two best parallel faces of the file and grind off the two other faces, giving to the file two safe edges, one opposite to the other. In this case either of the cutting faces of the file may be used upon the whole end face of the keyway operating close up to the corner, or if the file is much narrower than the keyway it may be used with a side sweep that will prevent the file from pinning, and produce much truer filing. It is useless to attempt to cut out a square corner with a square file unless one edge of the latter is ground safe, because the teeth of the file itself do not form a square corner, and it is therefore only by grinding the teeth off one side that the points of the file teeth can be brought full up to a sharp angle. Here, however, it may be noted that even if the filing is performed with the best of safe-edge files, and as carefully as possible, it will still be necessary to square out the fine corners with the edge of a fine smooth half-round file. If the edges of the keyways are rounding, as they are sometimes made where strength is required in the strap, it is better to take a file nearly or about 1/8 inch larger in diameter than the width of the keyway, and grind two safe edges on it, otherwise the round file is very apt to go astray and cut the sides as well as the edge of the keyway. An equaling file is much better for keyways than one actually parallel. [Illustration: Fig. 2309.] Another way employed to finish small keyways is by the aid of the tools shown in Figs. 2309 and 2310, which are termed drifts, because they are driven through with a hand hammer. That shown in Fig. 2309 is intended for holes having but little depth and not requiring to be very true, such, for instance, as those cut in the ends of keyways or bolts to receive cotters; the thickness at A A is made greater than at B C to give the cutting edge clearance. The form shown in Fig. 2309 is for use by hand, the teeth being cut diagonally instead of across, as at A A, to preserve the strength. This end may also be attained by making the serrations round at the bottom, as shown in the figure. [Illustration: Fig. 2310.] The slant of the teeth on one side of the drift should cross the slant of the teeth on the diametrally opposite side, because if the teeth on opposite sides were parallel one to the other the drift would have a tendency to move over to one side, and crowd there during the process of drifting. In using these drifts the keyway should first be filed out to very nearly the finished size, leaving very little duty for the drift to perform, although the drift may be driven a short distance into the keyway occasionally during the filing, so as to show where filing is requisite. The work must lie flat and level upon a metal block, lead being preferable, and oil freely supplied to the drift. "If the hole is a deep one, and the cuttings clog in the teeth, or if the cut becomes too great (which may be detected by the drift making but little progress, or by the blows sounding solid) the drift must be driven out again, the cuttings removed, and the surplus metal, if any, removed by filing. The drift must again be freely oiled, and driven in as before, and the operation continued until the drift is driven through the keyway. After the drift has passed once through it should be reversed (or, if a square one, turned a quarter revolution) and again driven through, so that each side of the drift will have cut on each side of the hole, which is done to correct any variation in the size of the drift" ("Complete Practical Machinist"). The great desideratum in using these drifts is to drive them true, and to strike fair blows, otherwise they will break. While the drift is first used, it should be examined for straightness at almost every blow; and if it requires drawing to one side, it should be done by altering the direction in which the hammer travels, and not by tilting the hammer face. [Illustration: Fig. 2311.] In Fig. 2311, suppose A to be a piece of wood and B and C drifts which have entered the keyways out of plumb, as shown by the dotted lines D and E. If, to right the drift C, it was struck by the hammer F in the position shown, and travelling in the direction denoted by G, the drift C would be almost sure to break; but if the drift B was struck by the hammer H, as shown, and travelling in the direction denoted by I, it would draw the drift B upright without breaking; or, in other words, the hammer face should always strike the head of the drift level and true with it, the drawing of the drift, if any is required, being done by the direction in which the hammer travels. When it is desired to cut a very smooth hole, two or more drifts should be used, each successive one being a trifle larger in diameter than its predecessor. Drifts slight in cross-section or slight in proportion to their lengths would be tempered evenly all over to a blue, while those of stout proportions would be tempered to a deep brown, bordering upon a bright purple. For cutting out long narrow keyways, that are too narrow to admit of a machine cutting tool, and for very true holes, not to be cut out in quantities all of the same dimensions, it has no equal. [Illustration: Fig. 2312.] Hand drifts are sometimes used to cut keyways in small bores, as in small hubs, the method being shown in Fig. 2312, in which A represents a pulley with a keyway to be cut in the hub _b_; _c_ is a plug, and _d_ slips of iron placed between _c_ and the drift _e_ to press the latter to its cut. It is obvious that in this case the keyway in the pulley will be cut parallel, and the taper must be provided for in the key seat in the shaft. Keyways cut in this way are more true than those filed out. It is also obvious that the sides of the keyway, as well as its depth, may be finished by a drift, and this is very desirable (on account of insuring parallelism) when the key is to act as a feather that is to have contact on the sides and not bind top and bottom. The most improved form and method of using this class of tool, however, is as follows:--If a keyway is to be cut out of solid metal, holes are drilled as closely together as the length of the keyway will admit, their diameter nearly equaling the required width of keyway, after these holes are drilled through the metal remaining between them. TEMPLATES.--Templates for vice work are used for two purposes: first to serve as guides in filing work to shape and size, and secondly to test the finished work. When used as guides to file the work they are mainly used to work of irregular, curved, or angular form, to which the square and other ordinary vice tools cannot be applied. Fig. 2313 represents a template for filing out a square hole. The edges A, B are at a right angle to each other, the wire simply serving as a handle. There are two methods of applying this template; the first is to file out two opposite surfaces of the hole to the required diameter, making them true and parallel one to the other, and to then employ the template while filing out the remaining two sides; the other is to file out one side and apply the template from that as a base for the other sides. The first is preferable because the liability to error is a minimum. When work is to be from a template, the latter obviously becomes the original standard, and in many cases the best method of forming it so as to insure correctness and enable its proper application to the work is a matter of great consideration. The shape of the template must, of course, be marked by lines which should be as fine and as deep as possible. But it does not matter how closely the template may be filed to these lines, it will still have some error, and this can in many cases be discovered and corrected during its application to the work. In the following examples there are principles which will be found of general application:-- [Illustration: Fig. 2313.] [Illustration: Fig. 2314.] [Illustration: Fig. 2315.] [Illustration: Fig. 2316.] [Illustration: Fig. 2317.] Let it be required to make or test a piece of work such as in Fig. 2314, the teeth to be equally spaced, of the same angle, and of equal height. A template must be made of one of the two forms shown in Fig. 2315. To begin with, take a piece of sheet metal equal in width to at least two teeth, and, assuming that the template is to have two teeth, file its sides P Q, in Fig. 2316, parallel, and make the width equal to twice the pitch of the teeth. We next divide its width into four equal parts by lines, and mark the height, as shown in Fig. 2316. If we desire to make the template such as at A, we cut out the shaded portion; or for the template at B, the shaded portion. It will be observed, however, that in template A there are two corners C and D to be filed out, while at B there is but one E, the latter being the easier to make, since the corners are the most difficult to file and keep true. The best method of producing such a corner is to grind the teeth off the convex side and at the edge of a half-round file, producing a sharper corner than the teeth possess, while giving at the same time a safe edge on the rounded side that will not cut one angle while the other is being filed. But when we come to apply these templates to the work, we shall find that A is the better of the two, because we can apply the square S, Fig. 2317, to the outside of the template, and also to the edge F of the work, which cannot be done to the edges G of the work and H of the template, because the template edge overhangs. We can, however, apply a square S´ to the other edge of B, but this is not so convenient unless the tops of the teeth are level. [Illustration: Fig. 2318.] [Illustration: Fig. 2319.] Assuming, therefore, that the template A is the one to be made, we proceed to test its accuracy, bearing in mind that for this purpose the same method is to be employed whatever shape the template may be. Consequently, we make from the male template A, Fig. 2318, a female template K, beginning at one end of K and filing it to fit A until the edges of A and K are in line when tested by a straight-edge S. We then move the template A one tooth to the right, and file another tooth in K, and proceed in this way until a number of teeth have been made, applying a square as at S, Fig. 2319, to see that the template A is kept upright upon K. When K has been thus provided with several teeth that would fit A in any position in which the latter may be placed, we must turn template A around upon K to test the equality of the angles. Thus, suppose at the first filing the edges _a_, _b_, _c_, _d_, upon A accurately fit the template K, and the straight-edge shows the edges fair; then if we simply turn the template A around, its angles, which were before on the right, will now be on the left, as is shown at the right of Fig. 2318. Thus in one position _a_ fits to _e_, in the other it fits to _h_, or _b_ fits to _f_, and when turned around it fits to _g_, and so on. Supposing that when thus turned around the angles do not coincide, then half the error will be in the teeth of A and one-half in those of K, and the best plan will be to correct them on A to the necessary amount as near as judgment will dictate, and then to apply K as before, continuing this process until A will fit anywhere in K, and may be turned around without showing any error. But at each correction the straight-edge must be applied, and finally should be tried to prove if the teeth tops are level. We thus have two interchangeable templates, of which A may be used on the work and K kept to correct A when the latter becomes worn. It may be as well to add, however, that in first applying A to K it is best to press the straight-edge S against the edge of K, and hold it there, and then to place A against S, and slide it down into K. [Illustration: Fig. 2320.] [Illustration: Fig. 2321.] Fig. 2320 represents an example in which, the form being a curve, it would be best to have the template touch more than two teeth, as shown in the cut. By letting the side A, Fig. 2321, of the template T terminate at the centre line of the two curves, and the end B terminate at the top of a curve, turning the template around would cause end A to envelop side C of the middle curve, thus increasing the scope of the template. Suppose, however, that the base curve D required to be true with the teeth, then a second template T´ must be used, its ends at E and F measuring an equal length or height, so that when they are placed even with the ends of the work, the distances G H being equal, the corrugations will be true to the curve D D. Now let it be supposed that, instead of making a template to test a piece of work such as in Fig. 2321, it is required to make a template for use in making another piece of work that is to fit to piece W, then template T in Fig. 2321 will not answer, because it is a female template, whereas a male one is required, so that the edge of the template may coincide with that of the work. But we may convert T, Fig. 2321, into a male template by simply cutting off the edge A as far as the line J, and causing its right-hand edge to coincide with the edge of the work so that the latter, after being fitted to the template, may be turned upside down and fit upon the piece of work. [Illustration: Fig. 2322.] [Illustration: Fig. 2323.] [Illustration: Fig. 2324.] In Fig. 2323 is an example in which the forms of both sides of a piece require to be exactly alike, and the easiest method of accomplishing this is as follows:--The face A should first be made true, and face B made parallel to A. A centre line C may then be drawn, and from it the lines E, E may be marked. The lines D are then drawn parallel to A A, lines E being made square to D and to A. The sides E may be calipered to width and parallelism, and all that will then remain is to file the angles F, F and the ends G, G to their required lengths. For F, F all that is necessary is a template formed as in Fig. 2324. The object of dressing the ends G, G last is that if they were finished before, their faces E would have to be made at exactly correct distances from them, which would render the job considerably more difficult. [Illustration: Fig. 2325.] [Illustration: Fig. 2326.] Fig. 2325 represents a sketch for a piece of work whose two sides are to be shaped exactly alike, requiring a template of the form of the work, as shown. From this a second template, Fig. 2326, is made, and to this latter the work may be filed. To make the template in Fig. 2325, which represents the work, the edge _x_ _x_ must be made straight, and the edge D parallel to it at the proper height. A centre line S is then marked, and the edges at E may be filed equidistant from S and square to D; hence they will be parallel to each other. The side sections F should then be filed equidistant from S and parallel to each other. They should be the proper width apart and square to D, being tested in each of these respects. The line joining E and F should be left full, as denoted by the dotted line at A on the right. The edges at C, C should then be filed, calipering them from the edge _x_ _x_. Edges G, G are obviously equidistant from S and parallel to S, or, what is the same thing, at a right angle to _x_ _x_, from which they may therefore be tested with a square, and, finally, the edges B are made parallel to _x_ _x_, and the ends H made square to _x_ and equidistant from S. We have now to file the angular groove at A, and to get this true after marking its depth from the lines at A, we file it first to the lines as near as may be by the eye and very nearly to the full depth. We then make a small supplemental male template T, Fig. 2327, equal in width to the distance E F, or, in other words, to the width of the step at A, and having its edges quite parallel. Its end is then filed to fit the groove at A, when its edge meets and coincides with edge E, as in Fig. 2327, T representing the supplemental template. It is clear that when the [V]-groove A is so filed that T will fit it with either of its edges against E, the angles of the groove will be alike, and we may then make a male gauge, as in Fig. 2326, that may be used to mark or line out the work and to use as a template to file it to, its edge H being kept parallel to face D, Fig. 2325, of the work. [Illustration: Fig. 2327.] CHAPTER XXVII.--VICE WORK--(_Continued_). [Illustration: Fig. 2328.] [Illustration: Fig. 2329.] There are two principal kinds of connecting rods, first those in which the brasses fit in spaces provided in the solid rod, and which are known as solid-ended connecting rods, and second those in which the brasses fit in a strap secured by bolts or keys to the end of the rod. In Fig. 2328 is shown the simplest form of solid-end connecting rod. It consists of a rod enlarged at its end to receive a brass held up to the journal by a set-screw as shown, one-half the bore being provided in the rod and one-half in the brass. The objection to this kind of rod is that as the bore wears the rod gets shorter and no means is provided to restore its length, and that during the pulling stroke of the rod the whole of the strain is concentrated on the end area of the set-screw, and this causes it to imbed in the brass, giving play to the brass unless frequent adjustment is made. It is, therefore, difficult to readily maintain a very accurate adjustment of fit with a simple set-screw of this kind. This may be to some extent remedied by the construction shown in Fig. 2329 in which the half brass A threads upon the stem of the rod, so that when it wears shorter to the amount of half the pitch of the thread upon the rod end, the brass may be unscrewed half a turn, and the original length will be restored. The cap is held on by two screws, which may have slotted heads as shown, or screws with check-nuts to prevent the screws from slackening back, as all screws are apt to do that receive alternating strains in reverse directions. [Illustration: Fig. 2330.] [Illustration: Fig. 2331.] [Illustration: Fig. 2332.] [Illustration: Fig. 2333.] Yet another simple form of solid-end connecting rod is shown in Fig. 2330, there being two brasses with a key on one side and a set-screw on the other. In this case, as soon as either brass is moved by the key it can fit the rod at the top and at the bottom only; hence there is but little to hold the brasses sideways in the rod, and furthermore the brasses are damaged from the key and the set-screw acting directly upon them, as will be explained with reference to strap-ended rods. In Fig. 2333 is shown a very substantial form of solid-ended rod, a sectional view being shown in Fig. 2331. The bottom or back brass A has a flange, as shown in Figs. 2331 and 2332 at A, which secures it to the rod end at the back. The top or key brass B has the keyway partly sunk in it, and the key binds against one side as well as on the bottom of the keyway, and this draws that brass close down to the face of the rod, as shown in Fig. 2331. In this as in all other connecting rods in which one edge of the key beds against the back of the brass, the taper for the key should be cut in the rod so that the edge which meets the brass will stand square across the opening for the brass; in this way the back of the brass will also stand square across, which is easier to mark off and cut, plane, and fit. If the taper for the key is cut on the brass, marking the latter and fitting it become more difficult, as it must be put in and out of its place to fit and bed the taper for the key edge, whereas, in the other case, it can be squared with a square while planing and fitting. As the bore of connecting-rod brasses wears, and the lost motion incident thereto is taken up (by driving in the key) the location of the brasses in the rod end is altered, making the rod longer or shorter according to the location of the key. But when this wear has been sufficient to let the key pass through the rod, slips of iron termed liners are inserted between the backs or bedding faces of the brasses and the end of the rod or crown of the strap, as the case may be. In putting in these liners the location of the brasses in the rod end may be adjusted so as to bring the brass back to its original position and restore the rod to its proper length, and in doing so the back brass, as distinguished from the key brass, is the one to be lined first. [Illustration: Fig. 2333.] [Illustration: Fig. 2334.] In the rod ends shown in Figs. 2333 and 2334 the joint faces (that is the faces where the brasses meet) must be filed away to take up the wear, hence the rods get shorter. In Fig. 2333 the liner may be placed behind either brass, A or B, or behind both, the thickness of that behind A adjusting the length of the rod (which is always measured from centre to centre of the respective brass bores), while the thickness of that placed behind B would simply act to prevent the key from passing so far through the keyway. To prevent as far as possible the wear from altering the length of the rod, the key at one end of the rod is placed outside the crank pin or at the outer end of the rod, as in Fig. 2333, while at the other end it is placed between the brasses and the stem of the rod, as in Fig. 2334. In this latter case the thickness of liner placed behind the key brass B (as the brass against which the key bears, or the brass next to the key, is always termed) would adjust the length of the rod, while the thickness of liner placed behind the back brass (as the other brass is termed) would be the one to adjust the distance the key would pass through the keyway. [Illustration: Fig. 2335.] In this form of rod end, as in many other solid-ended rods, the flange or collar of the crank pin, if solid with the pin, requires to pass through the opening in the rod end which receives the brasses. This may be accomplished by making that opening large or wide enough to pass over the crank-pin collar (which will increase the width of the brasses, and hence that of the rod end); or else the crank-pin collar may have two flat places filed on it, as in the end view shown in Fig. 2335. The objection to this plan is that the rod can only be taken on and off in one position of the engine; that is, when the two flat places A and B, Fig. 2335, stand parallel with the length of the rod. [Illustration: Fig. 2336.] [Illustration: Fig. 2337.] [Illustration: Fig. 2338.] [Illustration: Fig. 2339.] [Illustration: Fig. 2340.] [Illustration: Fig. 2341.] [Illustration: Fig. 2342.] It will be noticed in Fig. 2331 that the brass B does not fill the space in the rod. This is because that brass has to pass in over crank-pin collar and push up into the journal after it is in the rod. To make this space as small as possible, and to enable giving the crank pin as large a collar as possible, the key brass is sometimes beveled off, as shown in Fig. 2336 at A B. Another form of this rod end is shown in Fig. 2336, in which there are two keys to the brasses, the object being to adjust the keys to maintain the rod of its proper length. In order to facilitate making this adjustment, there should always be upon the face of the rod end centrepunch marks, as shown in Fig. 2338 at F and G, or else two deep marks, as shown at C D in Fig. 2337. Then, in lining up the brasses to set the key back, the rod may be restored to its original length by putting behind the back brass a piece of metal of such thickness as will bring the centre of the bore of the back brass B even with the centrepunch or other marks. This being the case, it does not matter about the exact thickness of the piece of metal put behind the other brass, since a variation in that will only act to let the key come more or less through the rod end without affecting the length of the rod. In Fig. 2337 is shown a form of rod end sometimes used. The end being open, the brasses pass through it. In this case the whole strain of the pull of the rod falls upon the edge of the gib at top and bottom of the strap, causing the gib to wear out very fast; furthermore, the back brass condenses the metal at the back of the brass opening, acting to pene it and throw the points of the rod end open, which it always does, the jaws of the gib imbedding in the jaws of the rod. This opening of the rod jaws makes the brasses loose in their places; hence this is a weak and undesirable form of rod end, though very convenient to take on and off. In Figs. 2338, 2339, 2340, and 2341 is shown a form of solid-ended rod of more modern construction. In this case a wedge A is used instead of a key, being adjusted by screws passing through the rod at the top and bottom, it being obvious that the set-screws may have check-nuts added. B is the back brass, and C the key brass. In this case the flange of the brass goes next to the crank pin, and a plate D is provided to serve as a flange on the front face of the brass. In Fig. 2338 this plate is removed to show the wedge A; but it is shown in the plan view, 2339, and the end view, 2340, and by itself in Fig. 2341. A groove is cut on each side of the two brasses and the plate spans the brasses, passing up the groove being held in position by a screw at E. The opening for the brass (in the rod end) is here shown wide enough for the rod end to pass over the collar of the crank pin, but in many cases, with this as well as with other forms of solid-ended rods, the crank pin may be made plain--that is, without a flange--and have a washer secured by a screw, so that by removing the washer the rod may be put on with the brasses already in place, and made no thicker (at the joint face) than is necessary for strength. In Fig. 2342 is shown what may be termed a clip-end connecting rod, the screw closing the rod end (to take up the wear) against the spring of the metal. It is obvious that in this case the hole may receive a brass bush split as is the rod end and secured from turning by a pin. Fig. 2343 presents another form of solid-end rod, which admits of the use of a brass having a flange on both sides of the strap, and will take on and off by removing the cap B. If the crank-pin collar is solid, the brasses must be placed on the crank pin, and the rod, with the wedge in place, lifted or lowered to the brasses; but if the crank pin has a washer and bolt, the rod may be put together and slipped on its place. A compromise between the solid and the strap-rod end is shown in Fig. 2344, which represents a design used upon the fast engines of the Pennsylvania Railway. The piece A takes out to enable putting on the rod or taking it off, A being secured in position by the bolt and nuts shown. This forms a solid and durable rod that is much less costly to make than strap-ended rods. [Illustration: Fig. 2343.] [Illustration: Fig. 2344.] [Illustration: Fig. 2345.] [Illustration: Fig. 2346.] [Illustration: Fig. 2347.] [Illustration: Fig. 2348.] The simplest form of strap-ended connecting rod is that shown in Fig. 2345; S is the strap, secured to the rod end by the key D and gib C. A is the top, and B the bottom, or crown brass, and E the set-screw for securing the key in its place. [When the rod ends are forged in separate pieces, to be afterwards welded to the stem of the rod after the strap brasses are fitted up (which is done for convenience in handling them while fitting them up), they are termed stub ends.] This form of rod affords great facility for connection with the journals as the strap is easily removed. As the strap, however, is only secured to the rod by the gib and key, and as these have a small amount of area on the sides, it is not unusual to employ two gibs and one key, as in Fig. 2346, which holds the strap more securely, and more effectually prevents its movement sideways upon the rod end. In rods in which gibs and keys alone are used to hold the strap to the rod, the strap moves along the rod as the key passes farther through the strap, and the fit of the strap to the rod must be easy enough to permit of this motion; hence it cannot be locked to the rod. This, however, may be done by the employment of a bolt as well as a gib and key, as is shown in Fig. 2347. The edge of the gib here abuts against the back of the top brass, or key brass, as it is sometimes termed, which is objectionable, inasmuch as that it is apt to indent the brass, as shown in Fig. 2348 at B. This causes the bore to close at A, and causes the journal to heat, while it makes the brass fit loosely between the jaws of the strap, because it stretches the metal at the back of the brass, which has the same effect as pening it with the hammer. In Fig. 2349 is shown an end of a connecting rod, such as is employed on American locomotives, the use of a gib being dispensed with, and the strap being held by two bolts. To prevent the edge of the key from imbedding in the brass, a piece of hardened steel is sometimes placed between the key and the brass, as shown in the figure. In some designs this method is reversed, the gib being prolonged in a screw-thread, as shown in Fig. 2350, and the key head is carried over as shown. Two wing nuts are provided for adjusting the key, which enables its adjustment without the employment of a wrench or hammer. To prevent the end of the set-screw from raising a burr on the key, which would prevent its easy motion through the keyway, a shallow groove is sometimes cut along the key, as in Fig. 2351 at A, the end of the set-screw binding on the bottom of that groove. In other forms of rod a gib and key are used as well as two bolts. This not only holds the strap very firmly, but it prevents to a certain extent the pening of the back of the brass, explained with reference to Fig. 2348. It is obvious that in the absence of a gib the key moving under friction against the brass stretches the metal more than a gib that presses against the brass, but has no motion endways. [Illustration: Fig. 2350.] [Illustration: Fig. 2351.] [Illustration: Fig. 2352.] In Fig. 2352 the strap is held by bolts having nuts at each end, instead of a solid head at one end and nuts at the other. The single nuts at the top serve to draw the bolts out when the rod is to be taken apart, thus saving the use of the hammer for that purpose. [Illustration: Fig. 2353.] In Fig. 2353 is shown a form of rod in which the strap is held by two dies A B, and a bolt which passes through the strap, the dies, and the rod end. [Illustration: Fig. 2354.] In Fig. 2354 is a form of rod end in which the strap ends are keyed against abutments on the rod by means of the key A. The abutments and strap ends being bevelled, keying up the strap with A closes it down upon the rod. [Illustration: Fig. 2355.] In Fig. 2355 is a form of rod end largely used upon marine engine work; A is the end of the rod, B, B the brasses, and D, D bolts passing through the brasses. Here we have no means of correcting the alteration of length due to the wear, unless a line is marked on the rod end, as at C, and the distance that line should stand from the centre of the brass bore is marked beside it, as is denoted by the figure in the cut, indicating that the line should stand 9 inches from the cuts of the brass bore. In general practice the inside jaw faces of connecting rod straps and the faces of the rod are made parallel, which serves very well when the duty and wear is not great; but when the wear and tear is great, as in locomotive work, it is much better to make them taper; indeed, they are in any event better taper, because in that case the brasses can be made a tighter fit. The reason for making them parallel is because they can be more readily planed so than taper; but a parallel strap is more difficult to fit, and cannot be made so good a fit as a taper one, even when new, while it is very much more difficult and expensive to repair. [Illustration: Fig. 2356.] When the faces of the stub end (or, more properly speaking, of the block) are parallel one to the other, and the inside faces of the strap are also parallel, the strap must be made a very easy fit to the block, in order to be an equal fit from end to end; for if the strap fits as tightly as it should to be a good job, it will, when put on the rod, spring open, fitting across A, Fig. 2356, only; this because the strap springs open from contact at A. The fit, then, can only be such as will not have force enough to spring the strap open, and this is very small indeed even in a very strong strap. It is within the mark to state that in a strap measuring 4 inches between jaws, at A in Fig. 2356, it can be forced by hand on the rod sufficiently tight to spring them open 1/16th of an inch at B, B. When the brasses are fitted into the strap a second difficulty arises, inasmuch as they must be made a very easy fit, or else they will spring the strap open so that it will neither fit at A nor at B, whereas it is desirable that the bottom brass drive home, and the top brass, or one nearest the rod, just push home by hand. When the rod requires repairing a more serious difficulty arises. Suppose, for example, that the strap requires refitting to the rod, then it must evidently be closed between the jaws, especially if the rod end requires filing up, as it usually does. Now the jaws being parallel cannot be closed without being taken to the blacksmith shop and closed across the crown, as at A in Fig. 2357; for if the jaws are closed (as they might be) by pening the corners B, C the jaws would close as denoted by the dotted lines. The brasses will have to be made larger than the diameter at D, in order to fill the space at A, and will be an easier fit as they pass from D to A, whereas the opposite should be the case. The strap must therefore be closed across A in the blacksmith's fire; this will scale the crown end and render it necessary to file down the whole of the surface on each of the side faces of the strap and rod in order to make them parallel, as they must be to have the flanges of the brasses fit when home in the strap. [Illustration: Fig. 2357.] The blacksmithing will in most cases render it necessary to file out the keyways, and this again entails the making of a new gib and key. All this extra work may be avoided by making the block and strap a little taper. But before proving this it may be noted that when the rod is made parallel the strap may be made to fit tightly by making the jaws taper, as shown by dotted lines in Fig. 2357; so that when the strap is on the rod, and the jaws spring open by reason of the close fit, the fitting surfaces will be parallel. Such a construction would be faulty however, for the brasses would fit too tight when entering the strap, and get easier as they passed to their places, whereas, as already stated, the exact opposite should be the case. [Illustration: Fig. 2358.] Let us now observe the advantages of a strap, whose inside faces are made as in Fig. 2358; smaller at A than at B, and also at C than at D, while the thickness from A to B is greater than that from C to D, while the widths C D are less than the corresponding width of the rod. First, as to fitting the strap to the rod. It may be made so tight to the rod that it will only just pass on when pushed by the hand. Second, this will render possible a tighter fit than would be possible with a parallel strap and rod. Third, the width B A being taper, the brasses may be easier made a good fit, because there will be some metal to fit on after they enter at B. Fourth, the brasses may be made a tighter fit, the bottom brass being tight enough to spring the strap a trifle, easing but not destroying its fit on the rod. Fifth, the top brass may be made a handsliding fit to the strap without springing the strap open, which being already under a tension because of the spring due to the bottom brass, will be more rigid and permit of a tighter degree of top brass fit, without springing open and away from the rod. Sixth, this will leave the bottom brass a tight driving fit, and the top a hand sliding fit, which is desirable, because the top brass has to be taken out to get the rod off while the bottom brass remains in its place. [Illustration: Fig. 2359.] Seventh, what is of more consequence than all, the strap can be more easily and cheaply refitted to repair it. Thus, in Fig. 2359, suppose the strap to have been closed by pening at D; then whether the end D will be narrowed will depend on the amount the strap was closed, and the amount of taper it had before closing. Let us take, however, the most unfavorable conditions, and suppose that the amount of taper was so small, and the amount of closing by pening so great, that the jaws were made taper and smallest at D. Then the amount to be filed off to bring the width of jaw correct, and a fit to the strap, will be less than if the strap jaws were formed as in Fig. 2357, as will be seen by comparing Fig. 2357 with Fig. 2359, the amount to be filed away being that between the dotted and the full lines in both figures; the amount of closure being the same in the two figures. But there is another great advantage, inasmuch as in pening, the strap may be pened and tried on the rod, the strap being pened and tried alternately until the required fit is obtained, which is not practicable with upsetting in the blacksmith's shop. Again, the keyways in the strap will not be set out of true with those in the rod, as they are apt to be when upsetting is resorted to, nor will the strap be scaled; hence the side faces will require but little filing. Furthermore the step may be located so as to come against the rod end when the wear has let the key down, and this will prevent the strap from passing too far upon the rod, and, therefore, tend to prevent the rod length from being improperly altered from errors in the thickness of the liners placed behind the brasses to take up the wear. FITTING UP CONNECTING RODS.--The method of fitting up a connecting rod depends entirely upon its size. Very small rods to be made in numbers are usually got out by means of special devices which leave the fitter but little to do; indeed, sometimes the machine work is so accurately and finely fitted and finished as to finish the rod without the aid of the vice hand, save to put it into its place upon the engine or machine. As, however, the dimensions of the rod increase, this method of manipulation is in practice departed from, and the filing, fitting, and adjusting operations increase. In any event, however, the principles to be observed in the manipulation are the same, because the points to be observed in the fitting by hand work must be accomplished by the machine if the rods are to be finished by machine work. Let Fig. 2360 represent a connecting rod; A representing the centre line in the side, and F the centre line in the edge view, and it is obvious that the axial lines, B and C, of the brass bores must stand at a right angle to line F, and be parallel to each other, because the journals on which they fit will do so. Furthermore, the faces of the brasses, as E, must stand their proper distance from the centre line F, this distance being at each end respectively half the whole width D, and the faces E must be in the same plane whatever their widths may be. The centre lines A and F are imaginary lines not worked to (except it be in marking or lining the rod out for the planing operations); but the method employed to fit up the rod must be such as will make all parts true to those lines if they were tested by them. The process of fitting up a connecting rod may be tersely stated as follows: 1st, the rod is planed; 2nd, the straps are planed; 3rd, the straps are fitted to the rods; 4th, the straps are drilled and bolted to the rod; 5th, the keyways are cut, and the keys and gibs fitted; 6th, the side faces of the rod ends are again planed with the straps on; 7th, the brasses are fitted and the rods marked off for length and the brasses bored; and, 8th, the file finishing and polishing done. [Illustration: Fig. 2360.] [Illustration: Fig. 2361.] [Illustration: Fig. 2362.] [Illustration: Fig. 2363.] [Illustration: Fig. 2364.] In the case of very large rods the two ends are made and fitted up as separate pieces, and are afterwards welded to the body or stem of the rod, and the setting of the ends true one to the other after the welding affords such an excellent insight into the alignment of rods that it may be well to describe it. First, then, the rod being laid on its side, two straight-edges, or rather winding strips, S and S´, Fig. 2361, are placed on the side faces, and the rod will be set in this direction when their ends A, B, C, D, appear parallel when sighted by the eye. If the winding strips are adjusted to stand straight across the rod, and, therefore, parallel one to the other, any twist or wind in the two rod faces will be very plainly discernible by the sighting process. The rod is then stood on edge, as in Fig. 2362, to test the alignment of the side faces. A straight-edge S is pressed firmly against one of the faces, as H in the figure, with the other end elevated as shown. The elevated end is then lowered, the motion serving to keep the end fairly bedded against face H. The distance, I J, Fig. 2363, is then measured. The straight-edge is then used in the same manner on the other side of the rod as at S in the figure, and the distance K L is measured, the setting in this direction being correct when distances I J and J K are equal. The straight-edge is then applied to the edge faces of end H of the rod, as in Fig. 2364, at M and at N, the distances O, P, are made equal. During these operations a straight-edge is applied along the body of the rod to see where to set it to effect any required adjustment, and if that body is straight the adjustment is made near the end at which the straight-edge is pressed to the rod. The setting of the small end I is effected in the same manner, but the straight-edge will in this case fall over the face at the larger end, as is shown in Fig. 2365; hence, instead of measuring, lines as G and T are marked coincident with the edge of the straight-edge and the distances T U, I G, are made equal. Winding strips are applied to the edge faces as well as to the side faces, and as making one adjustment or alignment may alter another, the whole process must be repeated until the whole of the tests prove the setting to be true. [Illustration: Fig. 2365.] [Illustration: Fig. 2366.] [Illustration: Fig. 2367.] [Illustration: Fig. 2368.] Now suppose the rod to have been forged solid and all these faces to have been made true in the planing, and the first operation is to fit the straps to the rod ends. The strap should be put in place on the rod and moved laterally, when the centre of its motion where it moves the least will be the place where it binds and therefore requires filing. If its side faces come atwist with the side faces of the rod end, as shown in section in Fig. 2366, either the faces of the rod end or the inside faces of the jaw are out of square as denoted by the dotted lines. In any event the face E, Fig. 2367, of the rod end should be surfaced true and made at a right angle to the side face, and if to be made parallel to M, also at a right angle to K, a square and a surface plate are used to test them. If the diameter J is to be smaller than that at H, then the angle of both face E, and its opposite, should be equal with reference to K. These faces should be finished by draw-filing, with the file marks lengthwise of the rod. To fit the strap, proceed as follows: To find where it requires filing, place it on the rod (having previously put red marking on the rod end), and move it endwise and sideways, observing where the least motion takes place when the strap is moved sideways by pressing its crown end, for this point of least motion is always where it fits the tightest. To test the jaw faces for being square apply a straight-edge S, and a square P, Fig. 2368, pressing S against the strap, and P firmly against S. [Illustration: Fig. 2369.] When the strap shows to bed well on the rod and its motion is an ambling one (and not a pivoted one), it fits properly, and if both rod and strap have been filed square, their side faces will come fair or even. The keyways being drilled, may then if necessary be filed out, for which purpose it is necessary to bolt the strap to the rod, a process that requires very skilful treatment, because if the tightening of the bolts moves the strap on the rod, or if the strap be moved on the rod after the clamp is tightened, the keyways will not come fair when the clamp is taken off. In Fig. 2369 the strap is shown held to the rod by plates C and bolts B, the rod being shown in position ready to file out the keyway. It is better, however, to let the side face of the rod stand vertical as the strap will stand steadier that way. The strap should be set fair with the outside faces, which will bring the keyway fair if it is properly located. The bolt nuts should be tightened gradually, first one a little and then another, going over all four once or twice before they are fully tightened, and if the strap is not fair when they are all tight, all must be loosened before the strap is adjusted, or the clamp pressure will cause the strap jaws to spring out of true, and the keyways will not come fair when the clamp is removed. Should the keyways not come fair when the strap sets fair on the rod the strap may be set to accommodate the keyways, and thus save filing, but this must be done before clamping it to the rod end. Care must, however, be taken to see if cutting the strap out to suit the keyway may not leave too little metal on one side of the keyway when the strap is subsequently planed. The sides of the keyway should be filed true to a surface plate, using a well-bellied file and as stout a one as possible, so that it may not bend under the pressure, and file away the edges of the keyway. The keyway should be made parallel to the side face of the strap, so that it may be fair with the centre line F in Fig. 2360. It should be made of equal width throughout, a piece of iron being used as a gauge in place of the key, and this same piece of sheet iron will serve as a gauge to plane the keys to thickness. The corners of the keyway, if to be made square, should be filed out with the corner of a smooth half-round file, because the corners even of safe-edge files do not come up sharp enough. For filing out the end faces of rectangular keyways, a square file with both edges safe must be used, the safe edges being on opposite sides of the file. For roughing out, a taper square, but for finishing, a parallel, or equalizing file is preferable. The next operation is to fit the keys and gibs. The key should first be fitted and should be filed true to a surface plate, for in no other way can a really good reliable gib be obtained, no matter how well the keys may have been planed or milled. It should be filed a tight fit to the keyway so that it may be used (with a light coat of red marking) to show tight places in the keyway, driving the key in for that purpose from first one and then the other end of the keyway. If, however, it is driven too forcibly, it may seize or cut, and it will be difficult to get it out, besides damaging both it and the keyway. When the keys are reduced so that they will drive lightly into the keyway, they should be tried in the rod and in the strap separately, moving the key laterally or edgeways, so that it may mark any high places in the keyway of either of them. The finished key and gib should be left tight enough, that they will hold themselves in any position in the keyway of the strap or of the rod when standing vertical. [Illustration: Fig. 2370.] The head of the gib should be chamfered as in Fig. 2370, so that it may be driven in and out to fit without raising burrs which would prevent it from passing into the keyway, and the key should be similarly chamfered and rounded in its width. [Illustration: Fig. 2371.] The width of the key and gib should be such as to just fill the key ways, leaving no draw when the key is down in the keyway so that its head is level with the head of the gib, as in Fig. 2371, A equaling the keyway width; and their edges should bed fairly one against the other, and against the edges of the keyway. The strap must then be keyed upon the rod, and the side faces of the rod and strap planed to thickness, placing a bolt and nut in the rod end in place of the brasses, so that the key may lock the strap and bind it in position. The rod end should be planed to thickness for the brasses and of equal thickness on each side of the keyway. The brasses should be planed after the rod end is planed to thickness. The width for the brasses should be measured while the strap is on the rod end, because the width between the jaws of the strap is greater when the strap is in place on the rod end than when it is off, because in order to make the strap jaws a tight fit to the rod end it is made narrower between the jaws than the width of the rod end, so that the jaws spring open when the strap is pushed on the rod end. The sizes for the brasses to be planed to will then be the width of the strap across its edge face, and the width of the strap between the jaws _when it is on the rod_; and for these sizes a wire gauge should be made; or an adjustable gauge may of course be set. The method to be pursued in planing the brasses is an important consideration. It is most convenient to plane both the brasses together, by which means much time is saved. To obtain this end the brasses are sometimes cast together, as in Fig. 2372, and after planing and before boring are cut in two at the narrow section A. In this case the brasses are cast sufficiently wide from crown to crown as denoted by B to allow for the length cut away in separating them. In other practice the joint faces of the brasses are faced first and then soldered together for the planing; but very large brasses are planed separately. In either case the joint face of the brass should be made at a right angle to the faces of the brass that fit the strap. [Illustration: Fig. 2372.] The brasses should be fitted separately to the strap, and hence should, if joined, be separated, being cut in two in a shaper, if of the form shown in Fig. 2372, and split by driving a keen chisel between the corners of the joint faces, if the latter have been soldered. The back or crown brass, and not the key brass, should be fitted first. The corners of the ways, in the brass, for the strap should be eased just clear with the edge of a smooth half-round file, because otherwise they will rub down the sharp edges of the strap, and make the strap jaws appear to be a bad fit when on the rod. The brass should be driven in and out of the strap to fit, using a block of wood to strike on, otherwise the skin of the bore may become pened, and when the brasses are bored they will close in at the sides and become loose in the strap. [Illustration: Fig. 2373.] As a guide when fitting the bottom brass in the strap, place the strap on the rod as in Fig. 2373, and take the measure of the strap at A A, the strap overlapping the rod to admit the calipers or gauge. Each time the brass is driven in the strap to try the fit, the calipers so set should be tried in the strap (the brass being in the strap), as in the figure, and when the calipers very nearly touch the strap jaws, the strap with the back brass still in should be tried on the rod end, or in the case of a very heavy strap the caliper measurement minutely taken may be relied on to show that the brass does not spring the strap jaws too wide open. It is better, however, to leave the brasses a little too tight in the strap as they close slightly in the boring, becoming easier in the strap. [Illustration: Fig. 2374.] [Illustration: Fig. 2375.] After the brass has been tried in the strap, and before it is filed again, it should be tried with a square, using a straight-edge also if the square back is too short to cross both faces of the brass. The method of testing is shown in Fig. 2374, in which B represents the brass, S the square, and T the straight-edge. The inside face of the flange should also be tried as in Fig. 2375, in which P represents the surface plate, S the square, and B the brass. This will insure that the brass face joint is square as it should be, and is further necessary because the bearing marks on the brass are not to be altogether relied upon. [Illustration: Fig. 2376.] In Fig. 2376, for example, the brass is shown in section in the strap, and the side A of the brass has a bearing against the jaw B of the strap, and hence would show marks of contact. The succeeding blows in driving the brass, however, may cause the brass to have contact on the side C with the jaw D; hence the bearing marks would show the brass to fit well when such was not the case. This may be detected by striking the brass on its joint face, and then measuring from E and from F to the end of the strap, and then striking the joint face at F and again measuring both distances, when any canting of the brass will readily be detected. It is better, however, to also apply the square, as shown in Figs. 2374 and 2375, because by this means the joint faces E F being parallel to the crown face G of the brass, the brass will be fitted so that when G meets the crown face H of the strap, the two will be parallel to each other and require but little filing to fit or bed together. The crown of the brass should be bedded very finely to the strap, or it will spring the strap jaws away from the rod when the key is driven home. Suppose, for example, that the crown of the brass did not bed well at A in Fig. 2377, then keying up the strap would spring its jaws away from the rod end, as shown at B C, the least error in the bedding having this effect notwithstanding the fit of the gib jaws. [Illustration: Fig. 2377.] The second brass must be made to just fit the strap when the back brass is in its place, and is small enough when the calipers, set as shown in Fig. 2373, and tried as shown in Fig. 2376, just fit the strap. This will insure that both brasses fit the strap when it is in its place on the rod. When both pairs of brasses have been fitted to their straps, the latter should (if held by bolts) be bolted to their places on the rod, and the centre of the respective spaces for the brasses will be the location for the marks G, G, Fig. 2360. A pair of trammels should, however, be set to the proper length of the rod and these marks tested. If the strap is held by gibs and keys, as in the small end in Fig. 2360, the strap should be put on its place with the gibs in, and drawn up the rod by slowly forcing the key in until the mark G at that end stands in its proper distance from G at the other end, at which time the key should come through its proper distance. The thickness of the brasses must be measured from these marks G, G to the crowns of the straps and the ends of the rod respectively. If the rod is of its proper length and the straps are in their proper positions, these marks will come in the centre of the space for the brasses. If, however, there is any error, as there is apt sometimes to be in very large rods, the course to be pursued depends upon the kind of rod end. If both straps are bolted to the rod end, the error may be divided equally at each end. If one end has a key and gib or gibs, but no bolt, as at the small end in Fig. 2360, the key brass may be made of such thickness as to butt against the end of the rod and meet the mark G. [Illustration: Fig. 2378.] For the large end, the thickness of the key brass, or, in other words, the distance D in Fig. 2378, must be taken after the face of the crown brass has been squared up, as described with reference to Figs. 2374 and 2375, the connecting rod strap being placed in such position that the key will be up in its proper place. When the joint faces of brasses do not meet, but are left open to take up the wear, it is a difficult matter to properly adjust the brass bore to the journal. If the flanges of the brasses do not quite fit the length of the journal, as is very commonly the case, it is customary to tighten the key until the rod end can just be moved by hand so as to force the brass flanges against first one and then the other end of the journal. This is an approximate adjustment; and if the journal heats at all, the key is slacked back a trifle; whereas if it pounds, the key is set up a little. As a matter of fact, then, nothing is actually known of the precise fit of the brass to the journal; and while looseness may be detected by the pounding, the brass may be tight enough to cause undue wear without very sensibly heating the journal, especially if the latter is freely lubricated. If, however, the brasses fit the length of the journal, and do not butt, it is usual to drive the key in till the brasses bind the journal, and to then slack the key back to the necessary amount. What that amount should be cannot be stated, because it varies with the taper of the key and the force with which it is driven home. As a result, then, the operation is left to the judgment, or, in other words, to guess-work, of men, many of whom are not well experienced in the operation; while under any circumstances the actual fit is not positively known. A plan not infrequently adopted is to insert a piece of lead wire of small diameter between the brasses, the key is first driven tightly home, and then slacked back until the lead wire is just freed. It is estimated that the adjustment will then be correct; there is no actual certainty of the fit, however, even in this case. Another objection is that the oil is apt to flow out of the opening, and the brass having communication with the oil cup is better lubricated than the other brass. In cases where the brasses are difficult to get out of the strap, because of the location or of the size and weight of the parts, a piece of sheet brass is sometimes placed between the joint faces, and this piece is filed thinner to let the brasses together, the necessary thickness for the piece being ascertained by the lead wire process described. If the strap is held to the rod end by a gib and key only, and the joint faces are left open, there is nothing to lock the strap to the rod end save the jaws of the gib, whereas when the brasses butt, the key binds the brasses to the end face of the rod and the strap to the brasses, which if there is any wear sideways (as in locomotives), prevents the keys from wearing the sides of the key ways and the brass flanges from wearing the straps. A method of overcoming this defect is shown in Fig. 2379, where the joint faces are left open, and four set-screws S, S, two on each side of the rod, pass through the flange of one brass and abut against the face of the other, serving to adjust the fit of the brasses to the journal, and lock them in their adjusted position, locking at the same time the brasses to the strap and the strap to the rod end. When the rods are finished so far as the fitting of its various parts are concerned, the brasses should be marked so that the bore, when bored out, will leave an equal thickness of metal between the brass and the strap on each side of the bore, while the rod will be of proper length. To accomplish this, mark on the outside face of the top brass two lines level with the faces which fit against the inside jaws of the strap, as shown in Fig. 2380, A, B being the lines referred to. We then key up the brasses in their places in the rod and fasten a centre piece in the brasses at each end of the rod. Upon these centre pieces we first mark a line parallel with and central between the lines A, B, and then a line across the joint of the brasses if the joint faces meet, and in the centre of the space between them if they do not meet. [Illustration: Fig. 2379.] [Illustration: Fig. 2380.] Before applying the trammels to test the rod length, the latter should be stood or placed in the position in which it works when on the engine; for all rods deflect by their weight, the amount of such deflection depending upon the position in which the rod is suspended. The trammels also deflect, it is true, but their deflection is allowed for in setting them, whereas the deflection of the rod will not be accounted for unless it is trammelled when standing or lying in the position in which it works. FITTING UP SOLID-ENDED CONNECTING RODS.--In fitting up solid-ended rods the side faces require to be filed up first and the jaws to receive the brasses next, taking care to file them out either square with the faces, or if slightly taper, as they should be, then each inside face should be an equal degree of taper to the side faces. This is necessary so that if the brasses are bored true to their own faces, the bore of the brasses at one end of the rod shall stand parallel to the bore of those at the other end. The fitting of the keys and brasses is performed as described for strap-ended rods. The reason that the jaws or box that receives the brasses is but a trifle taper is that in that case they are easier made a good fit, as they can be tried in their places while being fitted and before being reduced to the finished size, and furthermore because they can be put in and taken out easier. FITTING UP A FORK-END CONNECTING ROD.--A fork-end connecting rod affords as good an example of vice work as can be found, because any faulty workmanship, either in the individual truth of the parts, or their relative truth one part to another, will make itself very plainly apparent. [Illustration: Fig. 2381.] [Illustration: Fig. 2382.] Fig. 2381 represents a side and plan view of an ordinary form of fork-end rod, and the requirements are that the centre line A of the brass bores at the fork end shall be parallel with the centre line B of the bore at the butt end; that the side faces of all the brasses shall be parallel one to the other; that the side faces at the fork end shall be equidistant, or at the required distance, from the side faces at the butt end as denoted by C, D; that the bores of the brasses shall be at the proper distance apart to make the length of the rod come right; that the brasses at the fork end shall be the right distance apart, and that they shall stand parallel to each other, as well as to the bore at the butt end, as denoted by the line E in Fig. 2382. If the rod were of a size that it could be conveniently handled and planed, if forged solid, the fitting up would be much simplified, because the setting of the rod for the machine operation would, to a great extent, insure truth in the relative alignment of the parts. Thus all the side faces of the rod ends could be planed at one chucking, in which case they would necessarily be parallel, and their proper relative distances apart, if the rod was properly marked out by lines and planed to the lines. The jaws or ways to receive the brasses would be slotted out together, and necessarily true, if the rod was chucked true on the machine table. But even in this case the rod has to be marked out by lines denoting where the metal is to be cut off to, and the principles involved in the lining are just the same as those involved in the fitting up. [Illustration: Fig. 2383.] [Illustration: Fig. 2384.] If the rod be large, the ends may be, and usually are, forged and fitted up separately, and subsequently welded to the body of the rod, which has been forged separately. In this case, the alignment of the parts is a part of the process in welding the rod, and setting it after welding. All the principles involved in making the rod ends separate, and afterwards welding them, or in marking out a small and complete forged rod, are, however, involved in the process of refitting an old rod in the jaws, and putting in new brasses; hence a description of that process will cover the whole ground. The first thing to do is to file up the side faces, as F, G, Fig. 2381, and, in doing this, all that is necessary is to file F up true, when tested by a straight-edge applied as in Fig. 2383, in which R is the fork and S a straight-edge, whose edge should measure the same distance at H as it does at I from the side face F, while the face C measures the same distance from face A of the other fork end, or from the imaginary centre line X, Fig. 2381. Then turning the rod on its side, a straight-edge should be placed across the face F, and one across the face G, as in Fig. 2384, at S and S´; and the edges of the two straight-edges should stand parallel, when sighted in such a position that the edges are very nearly in line with the eye, as shown in the figure. The inside faces of the fork jaws may be filed to measurement from the outside ones. [Illustration: Fig. 2385.] [Illustration: Fig. 2386.] [Illustration: Fig. 2387.] The ways for the brasses should be filed square with the outside faces, as shown in Fig. 2385, in which S is a [T]-square; but if one jaw is wider than the other, as sometimes occurs, it will not matter, providing that, with the square applied, resting against the side and the face of the ways on the narrow jaw, the ways of the other jaw are equidistant from the square blade, as would be the case; for example, if the width of the ways of the jaw J extended to the dotted lines at K, L, because the line P would still form the centre line of both jaws, standing at a right angle to the side faces of the fork end, and parallel to the bore of the brasses at the butt end. Before filing up the side faces at the butt end, the strap should be fitted on and keyed up, so that its side faces may be filed up with those on the rod. To test the truth of the side faces at the butt end, a straight-edge should be applied, as at S and S´´, Fig. 2386, being pressed firmly to the side faces at the butt B, the fork faces being measured from the edge of the straight-edge at that end, and also with straight-edges, as in Fig. 2384. The brasses, after being fitted into the ways of the jaws, should have their joint faces squared, as in Fig. 2387, the top of each jaw being shown broken away, so as to fully expose the brasses. S is a square held firmly against the side face of a jaw, the brasses having their joint faces true with the square blade, and true also when tested with a square, applied as in Fig. 2388, in which B is the brass and S the square. The brasses at the other end should be filed true to the side faces of the strap in a similar manner, and, the fitting being completed, it simply remains to mark off the brasses for boring. The joint faces of the brasses should form the centre of their respective bores; hence, all that is necessary, is to insure that the brasses be of equal thickness, top and bottom, and this may be accomplished as follows: Mark across each face a line even with the ways of the brass, as shown in Fig. 2389, at A, C, and carry these lines around the side face, as shown in the figure at B, D. Place the brasses in the strap, put in a piece of wood whereon the compasses may be rested, as shown in Fig. 2390, which represents one jaw, and mark on this piece of wood a line even with the joint faces of the brasses, and on this line a centre-punch dot equidistant between the lines B, D. From this dot, as a centre, strike the circle shown, and define it by centre-punch dots, and if the lathe-hand chucks the brasses true to the ways that fit the rod jaws, and to the dotted circle, the bores will stand true in every respect. [Illustration: Fig. 2388.] [Illustration: Fig. 2389.] [Illustration: Fig. 2390.] REPAIRING CONNECTING RODS.--In repairing connecting rods the following is the work usually required to be done, and in the order named: Refitting straps, refitting gibs, and perhaps new gibs and keys, filing up the side faces of rod ends and straps, lining up brasses to make them fit the strap, lining up the rod to length and fitting the brasses together so as to fit their journals. [Illustration: Fig. 2391.] If the strap is taper and can be closed by pening, the outside of the back should be pened; but if the strap requires closing in the blacksmith's shop, then it should be tested by winding strips as shown in Fig. 2391, to insure that the faces are true, and thus save filing at the key ways and on the side faces to make them come fair with the rod ends. The rod ends should then be filed up and the straps fitted on. [Illustration: Fig. 2392.] [Illustration: Fig. 2393.] [Illustration: Fig. 2394.] Next comes putting in the new key and gib, or refitting the old gib. If the jaw of the gib has cut into the strap, as it will do in some cases (especially in marine and locomotive rods), this may be repaired as follows: Cut out the recess shown in Fig. 2392 at A, making it dovetail-shaped as shown, and with a set chisel set up its sides as shown in Fig. 2393, which is a sectional side elevation through the line of B. Cut out a piece of wrought iron and bevel its edges as shown in Fig. 2394, filing it to fit into the recess cut at A, Fig. 2392, and letting the bevelled edge be uppermost. Then take a set chisel and close down again upon the bevelled edge of the piece the metal that was set up, as shown in Fig. 2393, and the piece will be riveted, and it and the gib jaw may be refitted to touch the piece thus let in. [Illustration: Fig. 2395.] The jaws of the gib are sometimes made slightly taper at A, Fig. 2395. To refit the brasses to the jaws of the strap, the flanges which do not as a rule wear much are usually tinned with a soldering iron, and given a lining of babbitt metal. This must be done all around the flanges (of both pairs of brasses) that come on the same side of the rod, so as to keep the faces of the brasses leading fair. [Illustration: Fig. 2396.] The fit between the jaws is restored by riveting pieces of sheet brass to that side of the brasses that has worn the most (usually the top which carries the weight of the rod). Fig. 2396 shows this operation carried out, A being the pieces of sheet brass which are sometimes soldered as well as held by rivets. These rivets are screwed into the brass, being composed of softened brass wire riveted after being screwed in. If these pieces, which are called liners, are placed on the top of the brasses at one end, they should also be placed at the top of the brasses at the other end of the rod. They should not be less than about the 1/24 inch thick, the body of the brass being cut off to admit them if necessary. In filing the joint faces of the brasses to let them together so as to take up the lost motion due to the wear of the brass bore and of the crank pin, the following considerations are met. [Illustration: Fig. 2397.] If the brass faces are to come "brass and brass," that is, butt together, when their bore is of the diameter of the journal, file those faces away until the bore appears just perceptibly too large for the journal, when measured with calipers, as in Fig. 2397, the bore measuring parallel all the way through. But, in doing this, it is necessary to be careful to file each brass so that it shall embrace one-half the journal diameter, which will be the case when the two brasses measure correctly as above, and alike, when tested, as in Fig. 2398, in which P is a planed surface, C a pair of inside calipers, and B a brass resting on P. When filing the joint faces, test them with a square as in Fig. 2399, in which _s_ is a square and B a brass, and also in Fig. 2400, in which _s_ is a square and B the brass shown in section, thus making the faces quite square. [Illustration: Fig. 2398.] [Illustration: Fig. 2399.] [Illustration: Fig. 2400.] The necessity of having their faces quite square when the brasses come brass and brass may be shown as follows:-- [Illustration: Fig. 2401.] Suppose the joint to be at an angle as at A, A, Fig. 2401, instead of square across, as denoted by the dotted lines B, B, then the respective brasses will be forced by the key-pressure in the direction of the respective arrows, and there will be a tendency to twist the brasses in the strap. Or suppose the joint faces to be out of square as at C, C, instead of square as at D, then there will be a tendency to twist the respective brasses in the direction of E, F, and therefore to cause these to move in the direction of G, H, and as a result the brasses will spring the strap away from the rod, as shown at I, J. [Illustration: Fig. 2402.] To line up the brasses for length we proceed as follows: One of the liners adjusts the length of the rod and the other simply serves to set the key back to its proper height, so that it shall not pass too far through the keyway, as the wear of the brasses lets it down. Which of the liners will be the one by which to alter or adjust the length of the rod depends upon the design of the rod itself; but, in the case of all solid-ended rods, or those in which the position of the strap is fixed by means of bolts, it is the liner behind the end brass, as D, in Fig. 2402, as stated in the opening of this discussion, and it is the first one, therefore, to be fitted. The space at E is where the second liner requires to be placed, its thickness being that necessary to lift up the key from its bottom or lowest position, as shown in the cut, to the highest position. [Illustration: Fig. 2403.] In strap-ended rods in which the strap is not bolted to the rod, but moves farther upon the rod as the key passes farther through the keyway, it is the brass next to the rod end, as B, in Fig. 2403, by which to adjust the length of the rod, and its liner L is, therefore, the one to be fitted first; the space E is, in this case, the one to be fitted with a liner of sufficient thickness to lift the key up. It will now be noted that the thickness of L in both figures requires to be exact, so that the rod may be of correct length, which is necessary, so that there may be the same amount of clearance or space between the piston head and the cylinder cover when the piston is at the respective ends of the stroke. But the liners to fill the respective spaces E need not necessarily be of the exact thickness (although it is better that they should be), because if too thin the only effect will be that the key will pass farther through the keyway than otherwise. In considering in any form of rod which is the liner to be put in first to bring the rod to length, we have the general rule that the brass that moves in the strap or rod end when the key is moved farther through the keyway is the one to be lined last. The method of obtaining the proper thickness of the liners L, Figs. 2402 and 2403, are as follows: If the rods have been correctly made at first, the centre of the brass bores will be midway in the spaces for the brasses (denoted by F in the two figures). If the oil-holes in the strap or rod end (as the case may be) have been drilled in the centre of this space F as they should be, then the line _g_ will represent the centre of F and the centre of the oil-holes, and all that will be necessary will be to place behind D and B respectively a liner of sufficient thickness to bring the joint face of these brasses (D and B) even with the line _g_. To ascertain the thickness of liner necessary for this purpose, suppose the case of a rod end of the design shown in Fig. 2402, then, with the strap off the rod, drive the brass D down until its crown face beds fairly against the strap C, and with a scriber mark on the inside face of the jaw of the strap a line coincident with the joint face of the brass, then set the brass up the strap until its joint face comes fair with the centre of the oil-hole or the central line _g_, and then mark a second line so that on taking the brass out of the strap there will appear two lines, and the distance between these two lines is the necessary thickness of liner. In the case of the form of rod end shown in Fig. 2403, the process would be as follows: Let the strap have placed in it the brass B only, place it upon the rod, and set it so that it binds the gib and key, when the key is lifted up to its required position, then, with the brass B bedding fairly against the rod end, mark on the strap a line coincident with the joint face of the brass as before. Then move the brass in the strap until its face comes fair with the centre of the oil-hole or line _g_, and mark another line, and the thickness between these lines is the thickness of liner required at L. [Illustration: Fig. 2404.] [Illustration: Fig. 2405.] [Illustration: Fig. 2406.] If the brass is to be lined sufficiently to merely bring the key up without respect to the length of the rod we may drive the key home as in Fig. 2404, and mark on it a line coincident with the edge A of the strap. We then lift the key up to its proper height and mark a second line, so that when removed from the keyway the key will have on it the two lines shown in Fig. 2405, A being the first and B the second line; and the difference between the width of the key at A and its width at B will be the thickness of the liner necessary to be placed behind the brass nearest to the key. To ascertain the precise amount of this difference (because a very small error as to this amount causes a great deal of extra labor), we set a pair of outside calipers to the width at A; and then passing the caliper points down to B, we keep one of the points even with the line B, and insert a wedge until it just fills the space between the other point and the side of the key, as shown in Fig. 2406, C being the wedge, which should be chalked along its surface so that, when inserted until it touches against the caliper point, the latter will leave a mark on the wedge, denoting exactly how far the wedge entered, and hence the exact required thickness of liner. [Illustration: Fig. 2407.] [Illustration: Fig. 2408.] It has thus far been supposed that the joint faces of the brasses are made to come brass and brass, that is to say, butt close together from the key pressure, when the brass bores properly fit the journal. Suppose, however, that the joint of the brass is left open as in Fig. 2407, and in that case a strip of metal F, whose diameter equals that of the journal, may be inserted between the brasses as shown, and at its centre should be provided a small centre-punch mark, denoting the centre of the bore. A piece of this kind should be inserted in the brasses at each end of the rod and placed in the middle of the length of the bore, the centre-punch marks being to apply the trammels to. Or if the rod was made of correct length when new, and the bore of the brasses, therefore, requires to stand central in space F, Fig. 2403, then the pieces F, Fig. 2407, may be dispensed with by marking a line B, Fig. 2408, central to space F, Fig. 2403. Then put the strap on the rod (with the brasses, gib, and key in place), and pull the strap back to hold the key up to its proper height. [Illustration: Fig. 2409.] The two brasses should then be placed as far apart as possible in the strap, each bedding fairly against its back or crown. Then, using the joint face of the back brass as a straight-edge or guide, a line should be marked on the side face of the strap, this line representing the position of that face when the brass is bedded fairly home, and being shown in Fig. 2408 at A. This brass should then be moved forward until the bore of the pair of brasses at D, Fig. 2408, measures equal to the diameter of the journal (of the crank pin or of the cross-head pin as the case may be) and a second line B, also coincident with the joint face of the brass, should be marked upon the strap, and the strap will then have marked on it the two lines shown in Fig. 2409, in which it is shown removed from the rod; the distance apart of these two lines will be the thickness of the two liners combined, hence half this thickness will be the thickness necessary for each liner. Suppose, however, that it is not known whether the rod has been correctly made, and therefore it be unknown whether, in order to have the rod of the correct length, the brass bore should stand in the centre of the space or not. This is often the case in repairs, and sometimes on new rods, in which slight inaccuracies of workmanship are apt to occur. In this case it is best to mark a line, as G, in Fig. 2410, representing at each end of the rod the centre of the space F in that figure. Then set a pair of trammels to the correct length of the rod, and with one point of the trammel resting on the point at the intersection of line C with line D (the latter being the line G transferred to the centre of the bore) at the small end of the rod, we mark a line at the other end. If the lines D are too far apart, making the rod too long, the trammels will mark a line R, and the distance between lines R and D at the large end will be the amount the rod is too long, while half this distance will be the thickness of liner to go behind each bottom brass if the error of length is to be equally divided between the two ends of the rod, in which case a line T, midway between D and R, must be marked, the trammel then being rested on T, and the line S marked. These two lines, S and T, are then the centre lines for the bores of the brasses. [Illustration: Fig. 2410.] If it is determined that one pair of brasses shall be central in its space F, all the error being thrown on the other pair, this may be done by lining one pair up so that its bore is true to line D, and putting behind the back brass at the other end a liner whose thickness is equal to the distance between D and R at the large end of the rod. It is obvious that the measurement for rod length must be taken on the line C. Having thus determined what thickness of liner is necessary to bring the rod to its proper length, it remains to find the thickness of liner necessary for the other half brass, to bring the key up to its proper position, the process for which has already been explained. After, however, the various liner thicknesses have been found, and the sheet metal selected to cut them from, it is well to try if the thickness is correct by cutting off a small piece of the metal, putting it in place behind the brass, and then, after keying up the brasses, the rod length may be trammelled. As the liners placed behind connecting-rod brasses require to be very finely bedded, the facility with which their forms permit them to be fitted is an important consideration. [Illustration: Fig. 2411.] In Fig. 2411 is shown the forms commonly given, the requisite form of liner being shown beneath each. Form 1 will bed very firmly to its seat, but it will be observed that its liner is a difficult one to make, the bottom section A being thicker than the sides or wings B. This is a troublesome form of liner to fit as well as to make. If it be made of wrought iron, the wings B must be either forged or filed to their reduced thickness. In the form at 2 in the figure we have the same defect, while in addition the liner will not adjust itself so readily in position to its bed. This latter is an easier form to make in the moulding pattern, and easier to mould, and somewhat easier to fit, but it is not so firm as the first. To cause this form of brass to bed easily to its proper position it is sometimes given a lug on the bottom, as at 3 in the figure, the lug extending part of the width across only, because if it extended fully across, the liner would require to be in two pieces, causing trouble both in fitting them and in getting them into their places. When the lug extends partly across, the liner must have a slot to pass over and admit the lug, and this causes trouble in bending the liner to the required curve. In the form shown at 4 in the figure all these difficulties are avoided, while, if the lower corners are made square instead of rounding, a simple piece of sheet metal will serve as a liner requiring but little fitting and bedding if it be of the proper thickness. [Illustration: Fig. 2412.] To fit up a link motion, assuming the machine work to be done, the first thing to do is to face up the side faces of the links, making them parallel, and true to a surface plate. The slot is then filed out square to the side faces, its curve being filed to a template T, Fig. 2412, which is provided with a piece of wire for a handle. It is supplied with red marking, and is rubbed upon the slot to mark the high spots. The same template may be used to prepare the link block or die; but as soon as the block can be moved in the slot with slight hammer blows (using a mallet or a block of wood) it should be used instead of the template, the bearing marks serving to correct and finish the block as well as the slot. In filing up the block care should be taken to make it of even thickness on each side of its hole and with its sides parallel to the hole, the latter being of great importance. When the block is a sufficiently easy fit in the slot to permit it, a round stick of wood may be put through it and used to move it up and down the link slot for the marking process. The next operation is to fit the eccentric rod eyes to the link, and to then ream out the holes in both the link and the eyes while they are put together. The block may then be placed in the link, and the rocker pin passed through the block and into the rocker arm, so that the working fit of these parts when put together may be tested and adjusted if necessary. The link hanger may then be fitted to the saddle pin, when the whole will be ready for the file finishing and polishing, after which it may be case-hardened. CASE-HARDENING.--Case-hardening consists in the conversion of the surface of wrought iron into steel, or in converting the grade of a low steel into a sufficiently high grade to render it capable of hardening. The depth to which this conversion occurs depends upon the material used to produce it, and the length of time the process is continued, varying from 1/64 inch under the prussiate of potash process to 1/16 or 1/8 inch in the case of long-continued box case-hardening. Work that is thoroughly case-hardened has a dull white, frosted-looking surface. If the surface of the work is mottled, or has patches of fancy water-mark colors, it may be hard, but it is not so to the highest attainable degree. To thoroughly test this, take a new dead-smooth file and apply its corner edge under heavy pressure to the work on an edge where the fancy colours are, and then on an edge where the surface is white, and the latter will be found to be the hardest as well as hardened the deepest. The simplest method of case-hardening is by the prussiate of potash process, for which it is essential that the prussiate of potash be finely powdered, and contain no small lumps. The piece being heated may then, if small, be dipped in the prussiate of potash, or if large have the same spread upon it. In either case, however, the work must be hot enough to cause the potash to fuse and run over the work surface, and this action may be assisted by using a piece of iron wire, spoon-shaped at the end, wherewith to apply potash to the work and rub it upon the work surface. After the potash has thoroughly fused and run over the entire surface of the work it will usually have become somewhat cooled, and will require reheating before quenching in the water. If this reheating be done in the blacksmith's fire, it is not well to put the blast on; it is better to let the blast on gently while applying the potash to the work, so as to have a live clear fire to put the work in, and reheat it with the blast turned off. While the work is in the fire it should be constantly rotated, not only to heat it evenly, but to let the adhering potash run over the entire surface, and as soon as the required heat is attained the work should be removed from the fire quickly and quenched in water. It may be added, however, that if after the potash has been applied and fused more potash be added, so that it will adhere to the work and not fuse until the work is put into the fire a second time, then, after the work is quenched and taken from the water, there will be found on it a thick white and closely adhering fur of melted potash, and the work will be a dead white, with no fancy colors on it, and as hard as it is possible to make it. The prussiate of potash process is, of course, from its expensiveness, both in material and labor, too costly for work to be done in quantities, and box-hardening is therefore resorted to. In box case-hardening the work is case-hardened all over. It consists in packing the work in an iron box containing the hardening material, and subjecting the whole to a cherry-red heat for some hours. A very common process is to fill a sheet-iron box with the work closely packed about with bone-dust, the pieces of the work having at least a thickness of 3/8ths of an inch of bone-dust around them. The seams of the box are well luted with clay to prevent the gases from the consumed bone-dust from escaping, and to exclude air. Various ingredients are used to effect case-hardening. One process is as follows: 20 lbs. of scrap leather and 15 lbs. of hoofs (cut into pieces of about an inch square), 4 lbs. of salt, and one gallon of urine are prepared, and a wrought iron box with a lid capable of being fastened on is obtained. The fastenings must be capable of ready unfastening when hot. A layer of leather and pieces of hoofs about 1-1/2 inches thick is first laid in the box, then a layer of salt, and then a layer of work. Leather and hoof are then packed closely around the work and above it for a thickness of about an inch, and a second layer of work added, and so on, the last layer being of leather, &c., completely filling the box; the urine is then added, and the box well sealed with clay. The box is placed in a furnace and kept at a red heat for about fourteen hours, and is then taken to a deep tank, and the work quickly immersed, so as not to be exposed to the air after the box is opened. If the pieces are of solid proportions, so as not to be liable to bend or warp in the cooling, the contents of the box are simply dumped into the tank, the water being allowed to flow freely in the tank to keep up a circulation and cool the work quickly; some work, however, requires careful dipping to prevent it from warping. Thus a link or a double-eye would be dipped endwise, a plate edgewise; but all pieces should be immersed as quickly as possible after the box is opened. Sheehan's patent process for box case-hardening, which is considered a very good one, is thus described by the inventor: DIRECTIONS TO MAKE AND USE SHEEHAN'S PATENT PROCESS FOR STEELIFYING IRON. No. 1 is common salt. No. 2 is sal soda. No. 3 is charcoal pulverized. No. 4 is black oxide of manganese. No. 5 is common black rosin. No. 6 is raw limestone (not burned). Take of No. 1, 45 lbs., and of No. 2, 12 lbs. Pulverize finely and dissolve in as much water as will dissolve it and no more--say 14 gallons of water in a tight barrel; and let it be well dissolved before using it. Then take three bushels of No. 3, hardwood charcoal broken small and sifted through a No. 4 sieve. Put the charcoal in a wooden or iron box of suitable size made water-tight. Next take of No. 4, 5 lbs., and of No. 5, 5 lbs., the rosin pulverized very fine. Mix thoroughly No. 4 and No. 5 with the charcoal in your box. Then take of the liquid made by dissolving No. 1 and No. 2 in a barrel as stated, and thoroughly wet the charcoal with the whole of said liquid, and mix well. The charcoal compound is now ready for use. A suitable box of wrought or cast iron (wrought iron is preferable) should next be provided, large enough for the work intended to be steelified. Now take No. 6, raw limestone broken small (about the size of peas), and put a layer of the broken limestone, about 1-1/2 inches thick, in the bottom of the box. A plate of sheet iron, one-tenth of an inch in thickness, is perforated with 1/4-inch holes one inch apart. Let this plate drop loose on the limestone inside the box. Place a layer of the charcoal compound, two inches thick, on the top of said perforated plate. Then put a layer of the work intended to be steelified on the layer of charcoal compound, and alternate layers of iron and of the compound until the box is full, taking care to finish with a thick layer of compound on the top of the box. Care should also be taken not to let the work in the box come in contact with the sides or ends of the box. Place a suitable cover on the box and lute it with fire-clay or yellow mud. The cover should have a quarter-inch hole in it to permit the steam to escape while heating. The box should now be put in an open fire or furnace (furnace preferred), and subjected to a strong heat for five to ten hours, according to the size of the box, and the bulk of iron to be steelified. Remove the pieces from the box one by one and clean with a broom, taking care not to waste the residue, after which, chill in a sufficient body of clear, cold water, and there will be a uniform coat of actual steel on the entire surface of the work to the depth of 1/16 or 1/8 of an inch, according to the time it is left in the fire. The longer it is left in the fire the deeper will be the coat of steel. Then remove the residue that remains in the box, and cool with the liquid of No. 1 and No. 2, made for the purpose with 20 gallons of water, instead of 14 gallons, as first used with the charcoal compound. The residue must be cooled off while it is hot, on a piece of sheet iron or an iron box made for the purpose. Turn the residue into the supply box, and it will be ready for use again. The more it is used, the better and stronger it will be for future work. There is nothing to be renewed for each batch of work but the limestone, and that, after each job, will be good burned lime. A process used at the Elevated R.R. shops in New York city is as follows: The materials used are: leather, 1 part; bone dust, 5 parts; salt, 1 part. Heat for 48 hours to a red heat in a box sealed with fire clay, and quench in a solution of 3 pounds of potash to 30 gallons of water. The wrought iron thus treated is impervious to a new smooth file at a depth of 1/16 of an inch. The potash water is said to prevent both warping and the formation of blister marks on the work. The durability of work case-hardened is greatly enhanced, but it is an expensive process; not so much by reason of the cost of it, but because it involves resetting and a refitting of the parts. The resetting is necessary because the work warps under or during the process. This warping can be prevented to some extent by placing the heaviest pieces in the bottom of the box, and so packing the same that the weight of the top pieces shall not tend to bend those beneath them when the hardening material has burned away, and so placing the upper pieces that they shall not be bent by their own weight. Thus both in packing and locating the work in the box the utmost care is necessary. SETTING WORK AFTER HARDENING IT.--Work that has been hardened or case-hardened usually swells during the hardening process, and therefore requires refitting afterwards. This swelling usually occurs in all directions, thus holes and bores become of smaller dimensions, while the outside dimensions also increase, bolts become of larger diameter and sometimes increase in length. In very exceptional cases, however, the dimensions of a piece of work will not alter. This renders it usually necessary to refit the work after it has been hardened, thus holes which are ground out by laps or bolts may be ground to diameter in a grinding lathe. In some practice, however, the work to be hardened is made a somewhat too easy fit, the holes tapped out and the bolts ground in by direct application of the bolts to their holes in connection with flour emery and oil. This latter plan is also adopted for forms not easily ground out in a machine, as, for example, a die in a link of a link motion. [Illustration: Fig. 2413.] [Illustration: Fig. 2414.] To prevent surfaces or forms of this class from altering their shape or dimensions during the hardening process, slips of iron are sometimes fitted to them before they are placed in the hardening box. Thus Fig. 2414 represents a double eye, and Fig. 2413 a link having thin pieces fitted in as shown at A in both figures. The heating for the hardening process is also apt to impair the alignment of the work, causing it to require resetting by the aid of parallel strips and straight-edges. [Illustration: Fig. 2415.] The faces of the link having been set, the width of the link slot must be set, for it may open or close in places. If it opens it may be closed by the jaws of a powerful vice, while if it closes it may be opened by a pair of inverted keys, inserted as shown in Fig. 2415, and driven in by the hammer. At each trial, however, a mark should be made on the driven key, so that it may be known how far to drive it at the next trial. [Illustration: Fig. 2416.] [Illustration: Fig. 2417.] Fig. 2416 represents a link that is supposed to have been case-hardened, and to therefore require resetting. The stem from A to B should first be straightened to a straight-edge on both its side and edge faces. It should then be tested for winding with the winding strips, C, D, placed as in Fig. 2416, and then as in Fig. 2417. [Illustration: Fig. 2418.] [Illustration: Fig. 2419.] To test the alignment of end E, press a straight-edge S fair against its side face, as in Fig. 2418, and measure the distance H. Then place the straight-edge on the other side face of E and measure the distance I, Fig. 2419, and these distances both measuring alike, E will be true providing that the jaws at end F have not altered from their proper width apart. To test the alignment of the jaws at end F, press a straightedge against the outside face of the hub and measure the distance J, Fig. 2420, then apply it on the other side and measure distance K, Fig. 2421, and when distances J and K are equal and the width L between the jaws is correct, end F is in line in one direction. To test it in the other direction, apply a pair of parallel strips, placing one on end E as in Fig. 2417, and the other across the face of the hub of end F to see if there is any twist. [Illustration: Fig. 2420.] [Illustration: Fig. 2421.] Suppose, however, that distances J K are unequal, then if distance L is too narrow (when tested by the piece that fits between the jaws) then the jaw at F that gives the widest distance at E is the one that requires correction, or if distance L is too wide, the jaw that shows the least distance at end E is the one requiring correction. The link should be warmed to about 300°, or nearly _black_ hot, and pieces of sheet copper placed between the work and the anvil, and between the blacksmith's tools and the work, so that the latter may not be bruised by the blows delivered to effect the straightening. After the process has been performed at each end individually the testing should be repeated, because setting the end F may have impaired the setting of end E, in the alignment to F. It is obvious that the same setting or aligning process would be required in the case of a large link, where the ends were forged separately and welded to the body after the machine work and fitting had been done to them. [Illustration: Fig. 2422.] [Illustration: Fig. 2423.] [Illustration: Fig. 2424.] [Illustration: Fig. 2425.] [Illustration: Fig. 2426.] FITTING BRASSES TO BOXES OR TO PILLAR BLOCKS.--In the operation of fitting brasses to their boxes or to pillar blocks there are two things to be especially guarded against: First, having the brass let down one-sided, as shown in Fig. 2422; and next, aslant, as shown in Fig. 2423. The first depends on taking the proper amount off the two side faces, and the second in cutting the inside of the flanges fair. To cut the side faces fair, grip the brass in the vice, as shown in Fig. 2424 (the brass being shown in section), in which a is A block of wood. Take the measure of the box, down where the brass will come when home, and, if there be any taper to the box, set the inside calipers to the top of the location for the brass, and after the brass is in the vice place a square under one side-face, as at B in Fig. 2426, and see how much there is to come off. This saves the use of outside calipers, and is better because, not only is the trouble of setting the latter avoided, but the inside calipers can be tried to the box and the work in an instant, and a correction can at once be made if the calipers have got shifted. The cape chisel, or cross-cut, as it is sometimes termed, should first be used, taking a cut close to the flange, and making it half as deep as the calipers (applied as shown in Fig. 2426) show there is metal to come off. Then a similar cut should be taken close to the other flange, especial care being taken to take both cuts equally deep, and leaving as much to come off the other side face of the brass; otherwise, the brass will come atwist. Then take a straight-edge, and, placing its edge fair with the two chisel-grooves, while holding it firmly against the joint face of the brass, mark a line running from one chisel groove to the other; this line serving as a guide for the depth of all the other cape-chisel grooves. Now cut off the intermediate spaces with the flat chisel, using a straight-edge as a guide. If the box is taper, chip the side face to a corresponding taper, using a bevel-square, or estimating the amount by the eye if it is not too much. Now file the chipped surface flat and true, and then turn the brass upside down, gripping it with the wood as before, and dress the other side face (applying the inside calipers as in Fig. 2426), and bring that face down to within about 1/64 inch of the size to which the calipers are set. If the block of wood is made a little shorter than the length of the brass, the calipers can be applied without moving the brass from or in the vice. The method of applying the square to these side faces is shown in Fig. 2425, in which A is the brass in section, B a straight-edge, and C a square. [Illustration: Fig. 2427.] [Illustration: Fig. 2428.] [Illustration: Fig. 2429.] [Illustration: Fig. 2430.] We now turn our attention to the flanges, and apply a square to the crown of the box, bringing the edge of the blade fair with the edge of the box, as shown in Fig. 2428, A representing the box in section, and B the square. Supposing the crown of the box to stand square, as shown in the engraving, and as it should do, we set the brass upon a truly-surfaced iron plate and square up the joint face, as shown in Fig. 2427, in which A is the surfaced iron, B the brass, and C the square. Since, however, the joint face of the brass may not be parallel with the crown face, we may place the square so that its blade edge comes fair with the crown face--that is, as shown at D in Fig. 2427--and set the brass crown (by means of inserting a wooden wedge under its face) truly perpendicular or parallel with the square blade edge. Now try the square with the side face of the brass, setting the latter true with the square blade, as in Fig. 2430; A being the iron plate and B the square; and, supposing the box to be true, as it usually is, we may set a scribing-block, as shown in Fig. 2427, and mark off how much is to come off the flanges by scribing a line around the flange, sufficiently depressing the scriber-point to allow an equal amount to come off each of the flanges. Sometimes, however, the inside faces of the box are not true with the outside face. To test this, we place a straight-edge across the outside face, place a square on it, and apply it to the inside face of the box, as in Fig. 2429, which is a plan view of the box, A being the straight-edge and B the square. If the square thus applied shows a want of truth in the box, we may set the brass over when adjusting it (as in Fig. 2427) to a corresponding amount, and thus mark off the flanges to suit the box. [Illustration: Fig. 2431.] To hold the brass while operating on the flanges, we resort to the device shown in Fig. 2431, in which A is a bolt, B the brass, C a piece of hard wood, and P a clamp fastened down by a nut D. To sustain the plate P, so that it shall not fall down on the piece of wood every time the brass is taken out to try it in the box, we may insert the spiral spring S, shown in the separate view of the bolt, nut, and plate. One such holding device will do for different sizes of brasses, by either gripping the bolt lower down in the vice jaws or putting washers between the nut and the plate. This will hold the brass very firmly, and at the same time leave the whole of the flange easily got at. When the flanges are dressed, we may try the brass in the box, putting red-lead marking on the box to mark where the brass binds. While letting the brass down, however, we must be careful to let it down fair, to avoid the state of things shown in Figs. 2422 and 2423. A ready method of doing this is (supposing the box to be true, as it should be, and making the necessary allowance if it is not), to set a pair of inside calipers to the joint face of the brass and the top of the box, as shown in Fig. 2432, trying the calipers (in the two positions there shown) on both sides of the box. This should be done every time the brass is tried in the box, until such time as the brass begins to bed against the bottom of the box. [Illustration: Fig. 2432.] We now come to the bedding of the brass to its seat in the box. This requires skillful treatment; for one mistake will involve a great deal of extra work to rectify it. In fitting the brass to the box care must be taken to leave it a rather tighter fit to the box than it requires to be when finished, that is after the bore has been made, because in the boring operation the sides of the brass are apt to close and loosen the fit of the brass to the box. [Illustration: Fig. 2433.] When the side faces and flanges are so far fitted as to render probable the brass driving home at the next trial, the bed of the box should be given a coat of red-lead marking, and small pellets of stiff red lead or putty should be stuck on the bottom of the box, two at each end of each bevel, and two at each end of the bottom, with one in the middle of the bottom and each bevel, as shown at A, B, C, D, E, F, in Fig. 2433, by the black spots. Then when the brass comes home, it will flatten these pellets, and their thickness (when the brass is taken out) will show how much the bevels are out, and how much to take off the brass to make it bed. These pellets _must_ be restored to their original shape every time the brass is tried; otherwise, they may mislead. To insure their sticking to the box, and not coming out with the brass, the bottom of the box must have red-lead marking kept upon it. The chipping should continue until the pellets flatten out equally on the two bevels, but are left a little thicker on the bottom. If this is not done, the bottom will bed first, causing a great deal of extra filing, because filing the side bevels will let the bottom down too far. In driving the brass in and out of the box while fitting it, a piece of wood must be used to strike on, otherwise the brass will stretch during the fitting and come loose in the box during the boring.[33] [33] See remarks on Pening, p. 162. [Illustration: Fig. 2434.] [Illustration: Fig. 2435.] The patterns from which the castings for brasses are moulded should not be made of the same angle or sweep on the bedding part or bottom as the bottom of the box, pedestal, or pillar block, because the brass casting, in cooling in the mould, contracts across the bore; thus if in Figs. 2434 and 2435 the full lines denote the shape of the pattern the dotted lines denote the shape the casting will be. [Illustration: Fig. 2436.] [Illustration: Fig. 2437.] The result of this is that when the brass is let down in the box it will bed on the crown and not at the sides. Thus in Fig. 2436, A is a pedestal, and B a brass which beds at C, but not at D or E. In Fig. 2437 is shown an example of a brass, with a circular bottom, which would bed at the crown C, but not at the sides D E, until the metal was cut down to the dotted circle F. The amount to which this contraction in the mould occurs varies with the size of the brass, the difference in the thickness at the crown and at the face joint, the composition of the metal of which the casting is made, and the temperature of the metal when poured into the mould. It should always be allowed for, however, for the following reasons. Referring again to Fig. 2436, it will be noted that it requires a heavy cut off C to bring E, D to a bearing, while it is apparent that if the brass met the box at E, D before it did at C, but little filing at E, D would let the brass down a long way. It saves work, therefore, to so make the pattern as to insure that the brass casting shall have bedding contact at D and E before it does at C. As an example of the allowance to be made for this purpose, it may be stated that in brasses of 6 inches bore and 9 inches long, the hexagon of the brass pattern at D, E, Fig. 2436, would require about 1/16 inch put on them to compensate for the contraction, supposing that the hexagon on the brass pattern were made at first to fit the hexagon of the pedestal or axle box. To originate a true flat surface we proceed as follows: In the absence of a standard plate to go by, we must have three plates, and one of them must be accepted as a provisional or temporary standard. This we will call No. 1, and we fit Nos. 2 and 3 to it and then try them together, and if they also fit it is proof that No. 1 was true, and that all three are therefore true. It will very rarely happen, however, that this is the case; but Nos. 2 and 3 merely serve to show how much No. 1 was out of true. Suppose, for example, that No. 1 is concave in its length, and we fit No. 2 to it, as in Fig. 2438, and then fit No. 3 to it as in Fig. 2439, and when we come to put Nos. 2 and 3 together, as in Fig. 2440, we find that they are out of true to twice the amount that No. 1 is, and that all the work that has been done to them to fit them to No. 1 has been thrown away, and possibly to make them worse instead of better. It becomes important therefore to select the most true plate for No. 1, and this we may do as follows:-- [Illustration: Fig. 2438.] [Illustration: Fig. 2439.] [Illustration: Fig. 2440.] [Illustration: Fig. 2441.] [Illustration: Fig. 2442.] If we have a straight-edge that is known to be true, we may lay it on the face of a plate and move it laterally from each end alternately, and if it swings from the centre the plate face is rounding, while if it shuffles across moving first at one end and then at the other the face is hollow; but if it glides as it were across, the surface is nearer true. The straight-edge must not be pressed to the plate, but merely touched laterally to make it move laterally, for if we take a true straight-edge and press it vertically to a true surface while moving it, it will show the marks of contact the most plainly immediately beneath the parts where it is pressed. Selecting by this means the two plates that appear to be the most true we proceed to test them further as follows: We give to one of them which we will call No. 1 a light coat of red marking, and placing it upon the other or No. 2, we move it about in all directions and then take the two apart to examine the bearing marks. Suppose then that No. 1 shows the bearing marks to be at the shaded places, A and B, in Fig. 2441, while the bearing marks on No. 2 are as at the shaded parts A and B in Fig. 2442, the two ends A having been placed together; then we know that B is a high spot on No. 1, and A a high spot on No. 1 for the following reasons. The marks at A, No. 2, have been made by the marking at A on No. 1, and will extend across No. 2, a distance depending upon how much No. 1 has moved across No. 2, for if corner A of No. 1 had only moved half-way across No. 2, it could only have marked half-way across it. Similarly spot B on No. 1 has marked spot B in No. 2, because it has been moved all the way across, it being evident that the marking on B, No. 1, can only mark plate 2 as far across its width as it is moved across it. From this it follows that the higher or more prominent a spot is the less will be the area of the bearing mark at that spot. [Illustration: Fig. 2443.] [Illustration: Fig. 2444.] Now suppose that the two plates were curved to an equal degree as in Fig. 2443, and the bearing marks would extend all over both surfaces; but we may discover this error by turning one plate at a right angle, as in Fig. 2444, in which case the bearing marks would show along the edges of No. 1 and along the middle of No. 2, and we may correct each with the file until both plates mark all across and from end to end when tried together lengthways as in Fig. 2443, and one across the other as in Fig. 2444. But the plates may be curved to a different degree, as in Fig. 2445, and it then becomes necessary to know which to file the most in correcting them and fitting them together, which we may discover as follows:-- [Illustration: Fig. 2445.] [Illustration: Fig. 2446.] [Illustration: Fig. 2447.] We give one plate a light coat of red marking and rub it upon the other both sideways and lengthways. Suppose that on being separated and examined the bearing marks, shown as at A A and B B, Fig. 2446, on one plate, and at C C and D D, Fig. 2447, on the other, and as those at A A and B B are the narrowest, or in other words extend the least distance across the plate, it is proof that this plate is more concave than the other plate is convex, and therefore needs the most correction. This is plain because whatever part of a plate touches another, will, if the two are merely pressed together, only leave a bearing mark equal in area to itself, while this area will obviously be increased in proportion as one plate is moved about upon the other. [Illustration: Fig. 2448.] When the object is to merely produce a flat surface, independent of the thickness or parallelism of the plate, it is not always necessary to file or scrape the whole of the area showing bearing marks. Suppose, for example, that the marks appear as in Fig. 2448, and as the bearing marks at A A show that edge of the plate to be straight already, all that is necessary is to ease the surface at B in order to let that side of the plate come up. When we have fitted two of the three plates together we must accept one of them as a true one and (calling it No. 1) fit Nos. 3 and also 2 to it, and then try Nos. 2 and 3 together. If these require correcting the amount of correction must be made equal on each, and when this is done we must accept one of these two (say No. 3) as the standard, fit No. 1 to it, so that Nos. 1 and 2 both having been fitted to No. 3 may be tried together and both corrected equally; nor will the surfaces of any of them be true until all three will interchange in this manner and show a perfect contact. It is to be noted, however, that in this process we have not altogether eliminated the error due to the deflection of each plate. Suppose, for example, a plate to be resting on its feet and its middle will sag or deflect to some extent (very minute though it may be in a small plate), and when we place another plate upon it the latter will also sag or deflect if its points of contact are far apart, and in any event the truing is performed by the bearing-marks, which the operator knows show the darkest and the brightest where the contact is greatest; hence by the time the contact marks show equally strong all over, the top plate will have been fitted to suit the deflection of the lower one. Since, however, the nearer the points of contact (between the plates) are together the less the degree of deflection, it is better in trying them to place the test plate on the top of the one being operated on. If the plates are long ones it will not answer to have more than three points of rest for the lower plate, unless the foundation on which the plate rests is made so true that each resting point of the plate will bear with equal pressure on the foundation plate or stone. To eliminate as far as possible the deflection, the three plates may be got up by the process described, and then finished by trying them when resting on their edges (the trued surfaces standing vertical), interchanging the three plates as before. In this case the surface will be true when standing vertical as finished, but there will still be some untruth from deflection when the plates are rested on their feet, though it will be less in amount than if the plates were finished on their feet as first described. In finishing surface plates with a hand scraper, we have a surface that bears in fine spots only, these spots being the tops only of the scraper marks. Now the depth of the scraper marks are unequal, because immediately after the scraper is sharpened it cuts the easiest and the deepest, the scraper cutting less deep as its edge dulls. The operator regulates this to some extent by applying a greater pressure to the scraper as it gets dull, but from differences in the texture of the metal and from other causes it is impracticable to make the scraper cut equally deep at each stroke, as a result the tops of the scraper marks, which are the points of contact of the plates, wear away quickest, and the plate soon loses, to some extent, its truth. Again, work that is so small as to cover part of the plate surface only, wears the part of the plate to which it is applied, and although the careful workman usually applies small work at and near the outside edges of the plate only, still these are all elements tending to produce increased local wear and to throw the plate out of true. To obviate this difficulty the surface should be got up to bear all over, thus greatly increasing its bearing area and proportionately decreasing its wear. To produce such a surface the following plan was adopted by the author in 1876. The filing process was continued with fine Groubet files, and testing the plates, rubbing them together sufficiently to mark them without the use of oil. Very short file strokes must be employed, and great care taken to apply the file to the exact necessary spots and places. Then instead of using the scraper, No. 0 French emery paper was used, wrapped over the end of a flat file. The plates being interchanged and trued with No. 0, No. 00 was used, and the testing and interchanging repeated. These grades of emery paper were then wrapped or folded over the curved end of a piece of wood, the plates interchanged and rubbed together as before, and the emery paper used as described for the scraper. Subsequently Nos. 000 and 0000 French emery paper were similarly applied until the plates were finished. Much assistance to this method may be rendered by taking a piece of Water of Ayr stone, and truing its surfaces by rubbing them on the plates after the fine filing and before the emery papering. Then while applying the finer grades of emery paper the stone may be rubbed (with oil or water) in various directions over the surface. This has the effect of wearing off the very fine protuberances due to the emery paper cutting the metal most around its pores, and furthermore it causes the marks made in testing to show more plainly. In skillful hands this process very far surpasses, both in the superiority of its results and in rapidity of execution, the scraping process, leaving a brilliant polished surface, so smooth that it feels as soft as satin, and the contact becomes so complete that no bearing marks can be distinguished. In this process great care must be taken in cleaning the surfaces before applying them together, as the finest particle of dust will cut scratches, which though imperceptible on scraped surfaces, appear very coarse and deep on these smooth ones. The amount of metal taken off by the finer grades of emery paper is so small as to be scarcely appreciable, save that it slightly discolors the emery paper. The finest test for plates finished in this way is to rest the lower one quite level, clean it with alcohol, wipe it clean with old linen rag and finally with the palm of the hand, which if quite dry is more effective than anything else. The eye should carefully sight the plate surface with the light reflecting on that surface, when particles too fine to be felt may be observed and wiped off with the hand. In dry weather it is a difficult matter to clean the plates perfectly, as while one is being cleaned the fine particles of matter floating in the air rest upon the other; but in rainy weather the cleaning is much easier. The plates being cleaned one must be lowered vertically on the other where it will float, there being a film of air between the two which it is almost impossible to exclude by pressure even though the plates be moved while pressed together. If under these conditions the surfaces are not true and the top plate be set in motion in various directions, by a light finger touch it will swing round, the parts of the surface most in contact being the centre of motion. Suppose then the top plate to swing from one end it should be turned end for end on the bottom plate, and if the location of the centre of motion is still at the same end of the top plate, that plate is high there, while if the centre of motion in both cases is at the same end of the bottom plate it is the one that contains the error. If the top plate swings upon its own centre of motion it must be moved farther off the bottom one, first on one side and then on the other, to discover if it or the bottom plate is in error; while if the top plate swings first from one end and then from the other, one or both of the plates are hollow and the top one must again be moved farther off the lower one, and the test by motion continued. The error discoverable in this way is very much finer than can be discovered by the marks of contact, since a plate showing quite even contact when quite dry and clean, and tested as lightly and carefully as may be will show error by this motion test. The error being so small in amount that it may be corrected by rubbing the plate with rag and oil, applied under hand pressure to the plate. To cause the plates to bind together so that rubbing one on the other will leave contact marks, the top plate must be placed about an inch over the corner of the bottom one, pressed closely to it and forced laterally over it. A pair of plates of the Whitworth pattern (such as shown in Fig. 2449) placed by the author in the Centennial Exhibition, required, when put together dry as above, 341-1/2 lbs to _slide_ the top one over the other, which was due to the friction caused between the surfaces by the atmospheric pressure acting on the back surface of the plate, the latter having a superficial area of 12 by 8 inches. Here it may be added that a plate of the same dimensions, and having its surface finished simply by filing with a dead smooth file, which plate was made for exhibition at a lecture on hand work, delivered before the Spring Garden Institute of Philadelphia, required a force of 22 lbs. to slide on the one on which it rested. [Illustration: Fig. 2449.] If two plates finished by the above method be placed together by sliding one upon the other it will be found that with the hands applied as in Fig. 2449, they can be separated or pulled apart with less force than it requires to slide one upon the other, because the plates bend and unlap, as would be the case if two sheets of paper were wetted and placed together and then taken apart by pulling two edges in opposite directions. But if the power to pull the plates apart be applied at the middle of the plate it will require a much greater force to separate them, although how much is problematical, no experiments having been made upon the subject. Furthermore the friction between two such plates will be greater if the surfaces be lubricated than if quite dry. Thus, with the surfaces cleaned by alcohol, the top plate will move comparatively easily, but if the surfaces be slightly oiled and then wiped apparently quite clean with old dry rags, the friction will be a maximum. If then a piece of rag, say of an area of an inch, have one drop of oil upon it and be then applied to the surfaces of two plates after they have been cleaned with alcohol, the friction will still be about 3 lbs. per inch of area of one plate. With the surfaces well lubricated it will still require more power to slide one plate upon the other than would be the case were both plates quite dry. The reason of this is that when quite dry it is impracticable to exclude the air from between the surfaces, whereas with the lubrication the air is more perfectly excluded and the atmospheric pressure forces the plates together. CHAPTER XXVIII.--ERECTING. ERECTING.--The term erecting is applied in large work to the operations involved in fitting the parts to their places on the engine or machine, as well as to placing them upon their foundations and putting them together ready to run. In vice work or fitting, the various parts are put together ready to be erected, each part being complete in itself, but not adjusted with relation to the others. Thus, while a link motion may be complete in itself, the length of its eccentric rods will usually require correcting when placed upon the engine. Furthermore the position of the eccentric is to be adjusted. The boiler fittings may be complete in themselves, but will still require to be fitted or erected upon or to their places. Erecting requires the greatest of skill, care, and judgment, in order that the work may be put together properly aligned and any defects of construction corrected in the finished machine. In erecting a machine, as in building a house--or, indeed, as in everything that man constructs--the work must be begun at the foundation. In a machine in which the working parts are carried and contained upon framework, such framework becomes the foundation so far as the erector is concerned. In a stationary steam engine the cylinder and bed plate form the erector's foundation while the engine is in the shop, the mason's foundation being an after consideration. In a locomotive the boiler is the foundation to which all the other parts are either directly or indirectly affixed. The erector uses all the measuring tools used by the fitter or vice hand, and in addition many others, as stretched lines, the spirit-level and plumb-level. Either of these tools forms the readiest means of testing whether surfaces that are widely removed and in different positions about a machine are parallel one to the other, it being evident that all surfaces standing vertical will be parallel, or all those standing horizontal will also be parallel, one to the other. Spirit-levels are often made of wood, which is very objectionable for the erector's use, because the lower or testing surface is apt to catch and hold particles of metal, and furthermore it is very susceptible to abrasion, and wears rapidly. It is preferable, therefore, that it be of iron or steel. The test of a spirit-level is its sensitiveness, and it is found in a properly constructed one that the bubble will move to a perceptible extent if a piece of gold leaf be inserted under one end. In a spirit-level which came into the hands of the author of this work he found the warmth of the finger when placed on its top sufficient to cause the bubble to move nearly the full length of its tube, the body of the level being a block of iron 1-1/4 inches square and 9 inches long. The movement of the bulb was caused by the heat of the finger expanding the top of the spirit-level and causing it to bend. To test the truth of a spirit-level, it should be placed upon a true surface, as a surface plate, and if the bubble comes to rest at the same spot in the length of the spirit tube when the level is tried turned end for end, the level is true. The test should be made several times. [Illustration: Fig. 2450.] The plumb-rule, though less used by machinists than formerly, is better for machinists' use than the ordinary wooden-bodied spirit-level, since it is more delicate if properly constructed. It should be formed as in Fig. 2450, the sides A A and B B being straight and parallel one to the other; C and D are two plugs of soft yellow brass let in so as to keep the line _l_ _l_ clear of the face of the level, so that there shall be no friction between them. At N are notches to secure the line, which should be as fine and as closely spun as possible. [Illustration: Fig. 2451.] The plumb-level, Fig. 2451, is also preferable to the ordinary spirit-level; its edges A, B must be straight and at a right angle one to the other, C and D representing brass plugs as before. The edge A of the rule or of the level should be laid upon a surface plate, and a fine line drawn on the face of these plugs with a scribing block, the coincidence of the line _l_ with these marked lines testing the truth of the work. FITTING OR MAKING JOINTS.--The best form of joint to withstand pressure is the ground joint, and next to this, but more expensive, is the scraped joint. The difference between the two is as follows:-- For a ground joint the fitting with files or scrapers is only carried far enough to bring the fit sufficiently near that it may be finished by grinding the surfaces by rotating one upon the other with oil and emery interposed between them. To grind a joint it is obvious that all the bolts or studs must be removed. In a scraped joint the scraping is carried to such a point of correctness that the fit will be tight without grinding. Joints in new work are easily ground, because the bolts or studs being new have not become rusted in their places and may therefore be readily removed; furthermore the joint may be ground before the studs are inserted. But in the case of old joints the studs may have become so rusted to their places as to render them liable to break off in the effort to extract them, and in such case it is better in most cases to make a scraped joint, which may be done with the studs left standing in their places. To make a ground joint, as say a cylinder cover joint, proceed as follows:-- Put a thin coat of red marking upon the joint face of the cover, and after it is coated lightly and smoothly all over, the hand should be passed over the whole surface marked, because any grit left on the surface will cut the faces of the joint when they are rubbed together to fit them, and there is no wiping material that will so effectually clean dust from the surface as the hand will; and furthermore, the sense of touch will instantly detect any grit present. The cover may now be put into its place on the cylinder and rotated back and forth a turn or so to insure that it is properly seated; then we may strike it a light blow in different places with a piece of wood or the end of the handle of the chipping hammer; and if the cover does not fit pretty closely to its seat, a sharp metallic sound will be distinctly heard when the blow is struck over the parts of the face that are much out of true. Hence, by striking the blows all around the flange, we can easily find not only the high and low spots, but can determine, after a little practice, by the degree of the sound, how much the faces are out of true. We next rub the cover back and forth on its seat, so that the marking on the cover will mark the high spots on the cylinder face. If, however, we make the forward reciprocating movement of the cover a longer one than the backward, we shall give to it a gradually rotary as well as a reciprocating movement, and this will tell us if the face of the cover is true or not, for if the marking is removed from the face of the cover in two diametrically opposite places only, it shows that the cover itself is not true; and if the cylinder face also marks on two diametrically opposite places only, it is proof that both the faces are a good deal out of true: but there is no knowing which one is the most out, and so we must file off each an equal amount. If either face marks in more than two places it is evidence that it is pretty nearly true, and it follows that that face does not need much filing. Here it becomes necessary to state why the movement of the cover must, when being tried to its place, be back and forth, as well as rotated by the movement already explained. If we revolve a radial surface of metal upon a similar surface they are extremely liable to cut or abrade each other, and the presence of the least grit will inevitably cause them to cut; and if cutting once begins, the metal gathers upon the cutting part, increasing its size so that the groove cut will get deeper until a complete revolution has been made, and this rule applies to all revolving surfaces, but more particularly to radial or conical ones. By making the movement a partly reciprocating one we destroy this tendency, and either imbed the grit into the iron or else work it out. To proceed, however. If during our testing the blows induced a secondary and metallic sound as above described, we take a rough file and ease the high spots on both the cover and the cylinder face, filing a good deal off the face that shows diametrically opposite bearing spots only, and but very little off the face that shows three or more bearing spots. In this latter case, indeed, it is better to use a second-cut than a rough file. We next wipe both faces quite clean, apply the marking to the cover as before, and try it to its seat again; rubbing it in the same manner to its seat and testing it for the metallic sound as in the first case. So soon as this sound ceases we may take a second-cut file and fit the faces until they bear in at least four different places, when a smooth file should be used and the fitting and trying continued, until a very light coat of the red marking will show both the cover and the cylinder face to mark in spots not more than an inch apart; and we may then take a flat scraper, ease away the high spots, pressing the scraper firmly to its work and making it cut fine scrapings, using the scraper in strokes of about 1/2 inch for a large face and 1/4 inch for a small one. When the two faces show about an even contact all over, the grinding may be performed as follows:-- The two faces must be wiped quite clean, and then with an oil-can we can run a line of oil around both the cylinder and cover faces, and then with the fingers sprinkle on them some dry grain emery, of a grade of about 50 for a cylinder whose diameter is, say, 14 inches or over, and of a grade of about 60 to 65 for smaller diameters; if, however, only coarser grades of emery are at hand it may be ground finer by abrasion on an iron block, using a hammer face to grind it with. The emery and oil being applied, we place the cover in its place upon the cylinder, and give to it the reciprocative rotatory movement already described, continuing the movement until the cover moves so smoothly and noiselessly that it is evident that the emery has done its duty. We then take the cover off and examine the faces. If there are prominently bright spots upon either face, denoting that the emery has not operated upon them, it will pay to take the scraper again and ease away the dullest and most frosted-looking spots, which denote that they have suffered most during the grinding operation. The difference between the spots that have been the most and those the least affected by the grinding will be very plainly visible if the faces are wiped clean. We must continue the grinding operation with this grade of emery until the marks show the grinding to have been performed pretty evenly all over the faces, and we then apply a coating of oil and emery, as in the previous operations, the latter being in this case of a grade of about 70, moving the cover as before until it revolves so smoothly and noiselessly as to indicate that the emery is no longer doing any duty. Having continued this process, applying fresh emery and oil until the face appears true, we may perform the finishing and testing process, which is of the utmost importance, since it will detect the faintest possible defect in the job. Wiping the faces quite clean, we put the cover in place upon the cylinder again, and move it as before back and forth, and yet slowly advancing; but it must be borne in mind that if the cover makes the least jarring noise during the operation we must at once remove it and wipe it clean again, or the faces will abrade and become destroyed. There is no danger of this, however, if the cover be at once removed when the jarring sound is heard. If it be not heard, we continue the operation until the cover has made four or five revolutions, and then remove it, and we shall find that the emery and oil, which had impregnated the surfaces, have worked out. We again wipe the faces clean and put them together and rub one upon the other as before, bearing in mind that if the faces cling much one to the other, we must wipe them clean again. Usually the finishing process requires performing about three times, and then the faces will have become as bright and clear as a mirror, magnifying the slightest defect in the joint. Joints made in this way will stand any pressure without leaking (unless the pressure be so great as to spring the metal of the cover). It is well, however, when making the joint, to put a little oil or pure tallow on it, and it is from this that it is called in England a grease joint, while in the United States it is termed the ground joint. It is common, however, in England to finish the whole joint by scraping; but this is a much more tedious job, and not so good a one, after all. Here it becomes necessary to remark, that in order to be able to handle the cover readily, it is best to bolt to it a wooden lever overhanging both sides of the cover, and to serve as a handle in moving it. And during the grinding we may place a weight on the cover, which will greatly expedite the process. It would appear that this is a long job, but such is not the case; indeed, a 16-inch cylinder face and cover 1/32 inch out of true one with the other can be got up in half an hour. It is to be observed, however, that the cylinder cover that contains the stuffing box for the piston rod often carries one end of the guide bars, and in any event carries the gland whose bore requires to stand in line with the cylinder bore. It must be remembered that if more is filed off the top than off the bottom of the face, or _vice versâ_, the gland bore may be thrown out of parallel with the cylinder bore, and the guide bar seatings will be thrown out of parallel in the same direction. To facilitate the making of ground and scraped joints it is preferable that the surface of the joint, both on the cylinder and the cover, project from the rest of the flange, from the bolt holes to the bore in the one case, and from the bolt holes to the body in the cover in the other, so that the bearing surface of the joint shall extend from the inside edge of the bolt holes to the cylinder bore only. This provides ample surface to make a joint, while reducing the surface to be operated upon. TO MAKE A SCRAPED JOINT.--Let us now suppose that the studs are in their places, and it is decided, for fear of breaking them in taking them out, to make a scraped joint, and the process is as follows:-- The testing and marking of the high spots or places must be made by giving to one of the surfaces a light coat of red marking and then bolting up the cover moderately tight, screwing up the nuts at first until they just grip the work all around, and not letting one part of the cover face bear at any time with greater pressure against the cylinder face than there is on the diametrically opposite side of the cover, for the side under most pressure will receive the marking most readily. Especially is this the case when the two faces first meet, because even a low part of the face will show most contact under such circumstances, and then easing such marks away will make the cover a worse fit than it was before. When the cover is bolted home, the marking on the cylinder face may be made to transfer itself on to the high spots of the cylinder cover face more plainly if a piece of wood be placed on the cover and struck lightly with a hammer, moving the wood around and between the studs. If the wood be struck heavily it will cause an almost endless and assuredly a faulty job, because the force of the blow will spring that part of the cover to its seat on the cylinder face, whether it fits in that particular spot to its seat or not, and hence the filing or scraping may be done in places where it is not required, because the marking misleads. If the bolt holes are very close together, as in English practice, lightly striking the cover will prove an assistance; but where they are several inches apart, as in American practice, it is better to omit it, for the bedding marks will show plainly and properly if the marking be evenly distributed by the hand over the cylinder face, and the cover is bolted at each trial tightly to its seat, providing of course that the red marking is free from grit. In a job of this kind it is difficult to know, when a leak occurs, whether the defect is in the cylinder face or the cover, and it is very desirable to perform the operation with a view to correct the defect rather than bed one face to the incorrectness of the other. If then the stud holes are equidistant apart and concentric (so as to permit it), the cover may be tried on in one or two positions, and, if the bearing marks occur on the cover at each trial in the same places it is the cover that is out; or if this occurs on the cylinder face, it is that face which is out. Since the studs are in their places the cylinder face may be best operated on by a scraper, while for the first part of the operation on the cylinder cover a file may be used. The corner at the junction of the cylindrical part of the cover (where it fits into the cylinder bore) should be scraped well clear, or it will be apt to bind on the edge of the cylinder bore and prevent the cover from screwing fairly home to the cylinder face. The joint should be made to bed well inside of the bolt holes, and coated with oil or grease when finally put together. JOINTS FOR ROUGH OR UNTRUE SURFACES.--The most permanent form of joint for a rough or untrue surface is, for steam pressure, a gauze, and for water pressure, a pasteboard, or a duck or canvas joint. A gauze joint is composed of copper wire gauze, having square meshes of about 1/32 inch square; this gauze is cut out to fit over the joint surfaces, a single, double, or treble thickness being used according to the unevenness of the surfaces. A coating of red-lead putty is first spread over the joint with a piece of smooth surfaced metal; the wire gauze is then put on, and over it another coating of red lead; the cover is then put on, and the nuts screwed lightly home so as to bring the cover to bear against the red lead. Then any nut may be given a quarter or a half-turn, and the diametrically opposite one also given a half-turn, this process being continued until all the nuts have been screwed home a half-turn, when the process may be continued until the nuts are screwed firmly home. This is necessary, because if the nuts on one side are screwed home in advance of those on the other, the red lead on that side may be squeezed out too much and the joint will leak. In joints of this class the surfaces being rough it is not unusual to cut out the gauze wire as follows: Lay the sheet of gauze over the joint and cut it to the size by lightly hammering it over the sharp edges of the joint, which will cause the sharp edges to cut the copper wire. To cut out the holes place the ball piece of a hand hammer on the wire and over a hole and strike the hammer face several light blows, and the corners of the hole will cut the wire through. The gauze joint will answer equally well for hot water as for steam joints, provided that it be given time to dry and become hard. If the joint can have a week in which to dry the red-lead putty may have about one-sixth of its bulk of white lead mixed with it, being made to a consistency of soft dough so that it will spread easily; and the amount being sufficient to fairly cover the gauze and no more, the soundness of the joint may be known by the lead squeezing out all around the joint edge as the bolts are screwed home. If the joint is to be used in a day or so after being made, the white lead should be omitted. In either case the lead should be mixed stiffly at first; the best lead should be used and it should be well hammered on an iron block, after which it may be thinned with boiled oil, or with a little varnish, which will cause it to harden more quickly. For water joints requiring to stand high pressure, and to be used as soon as made, a paper, pasteboard, or a duck or canvas joint are best. The joint is made by using, in place of the gauze wire, one or two thicknesses of the pasteboard, duck, or canvas, cut out to the size of the flange, and with the necessary holes to receive the standing bolts and leave the bore of the pipe clear. If the flange of the joint is of copper, brass, or wrought iron, or, if of cast iron, is of sufficient strength to permit it, one disk may be made the full size of the flange, and a second may be made to have an external diameter sufficiently large to fit snugly inside of the bolt holes, which will form sufficient thicknesses if the flange is a fair fit to its seat; if it is not, however, three, or even four, thicknesses may be used, in which case at least one of them should fit inside the diameter of the flange across the bolt holes, as described. The disks being prepared, we spread on the first one a thin coating of red-lead putty, and then lay another canvas disk on, again adding the putty until the whole is completed. We then spread a thin layer of the putty around the hole of the seat and that of the flange, place the disk in position and screw the joint up, tightening down the nuts until they bring the flange to an equal seating all around and not sooner on one side than on another, for in that case the red-lead putty will be squeezed unevenly, and too much on the side screwed up to excess. The nuts should be screwed up very tight; the joint wiped, the protruding canvas cut off, and the joint is complete. For very rude and rough joints, whether used under pressure or not, we may make, for either water or steam, a joint as follows: Taking four or five strands of hemp, we saturate them with a coating of white lead ground in oil, applying just sufficient to make the fibres of the hemp cling well together. We then plait the strands and coat the whole rope thus formed with red-lead putty, and place the strand around the hole of the joint, taking care that the ends lap evenly, so that the joint shall be of even thickness. It is better, however, to bend a piece of lead or iron wire to suit the size and shape of the hole in the joint, and then wind the hemp and red lead around the wire. And in cases where the flanges of the joint are sufficiently strong to have no danger of their breaking from the pressure due to screwing up the nuts, the piece of lead wire, if given a neat butt joint or neatly lapped, may be employed without any red-lead putty or hemp; this does not, however, make a good permanent joint. In cases where a joint requires to be made thick to accommodate the length of the pipe, pasteboard may be used in the place of canvas, giving to it a thinly-spread coating of red-lead putty on each side, and, if possible, leaving the pasteboard a trifle too thick and springing open the flanges of the joint to get the pasteboard into position without scraping off the red-lead putty. Where it is required that a joint stand great heat or fire, asbestos board, about 1/16 inch thick, makes a good and permanent joint. It is coated with red lead mixed thinly with boiled oil, containing as much as it will soak up, leaving a thin layer of the lead upon the surface of the asbestos. The holes for the bolts to pass through in the duck, canvas, pasteboard, or asbestos joint should be cut large enough to well clear the bolts. For cold water, where it is not subject to great variations of temperature, common sheet lead makes a very good joint; but under excessive changes of temperature the expansion of the pipes will soon cause the sheet lead to squeeze out and the joint to leak. Joints are frequently made with copper wire rings, made of a diameter to pass around the hole of the joint and lie within the diameter of the bolt holes, and brazed together at the ends; but if the joint be rectangular instead of circular the wire must either lie in a recess, or else a shoulder must be left for the wire to abut against, which will prevent its blowing or becoming forced out by the pressure. In some practice softened sheet copper about 1/32 inch thick is used to make joints on surfaces that have been planed. Joints of this kind are used for locomotive steam chests. Rubber joints are used to make steam, water, and air-tight joints, and are usually made from what is known as combination rubber--that is, sheet rubber having a linen or other web running through it; with one such web it is called single, and with two webs two-ply, and so on. There is in many cases, however, an objection to this form of joint, in that it compresses; and hence in the case of the steam chest, for example, it affects the distance of the slide-spindle hole in the chest from the seat, and throws it somewhat out of line with the eccentric. In long eccentric rods the variation is of course minute; but still it exists, and must exist, since it is impossible to tell exactly how much the rubber will compress in making the joint. Furthermore, if it is required to break such a joint, the rubber will very often cling so tenaciously to the seat in one place and to the chest in the other, that it will tear asunder in breaking the joint. To obviate this as much as possible, however, we may chalk the rubber on one face and slightly oil it on the other, so that the oil will aid the rubber in clinging to one face, while the chalk will assist it in separating from the other face of the joint. Rubber joints slowly compress after being under pressure a day or so, and also if subjected to heat; hence they should have their bolts screwed up after becoming heated, or after having stood some time. It is advisable also that the rubber be as thin as the truth of the surfaces will admit. If it is necessary to use more than one thickness of rubber, the thickness may be made up of rings, whose diameter will just pass within the bolt holes. The holes in a rubber gasket should be made larger than the bolt holes, so that there shall be no danger of the bolt, when being inserted, catching the gasket. If the flanges should not come fair, and it is determined not to set them fair, the rubber should be as thick as the widest part of the opening between them, and shaved off to suit the thin side of the joint, and in this case the bolts must be tightened very uniformly and gradually around the joint to secure a tight one. If there is room to shave the gasket to the amount of taper, and use in addition a ring around the bolt holes, it will make a safer job. When the gasket requires to be split to pass it around or over a rod, it should be cut through to the canvas on one side, and a short distance off cut through to the canvas on the other side; the rubber may then be stripped carefully back from the canvas and the latter cut through and passed over the rod, when the rubber may be put back and sewed to the canvas again. Sheet rubber with a gauze wire insertion instead of canvas makes an excellent joint. [Illustration: Fig. 2452.] In Fig. 2452 is shown a method of making a steam-tight joint largely employed in England, upon the steam chest joint where the cylinders of crank shaft (inside cylinder) engines are bolted together. A is the flange of one cylinder, which is bolted to the other by the bolt B. C is a strip of copper let into a dovetail groove cut one half in one cylinder, and the other half in the other. After the bolts B are all firmly screwed home, hammer blows are delivered upon the top of the copper strip as denoted by the arrow E, expanding the copper so that it completely and closely fills the dovetail groove, and makes a steam-tight groove. In riveting the copper it is necessary to hammer it evenly all along lightly, and only sufficiently to make it closely fill the groove, otherwise it will spring the joint open, and cause it to leak, notwithstanding the bolts B, which will give under the extreme strain. Temporary joints are sometimes made by bending a piece of lead wire into a ring or frame, of such a size as to well clear the inside of the bolt holes. The ends are neatly joined, and the lead wire compressing and accommodating itself to the inequalities of the surfaces forms a joint. [Illustration: Fig. 2453.] [Illustration: Fig. 2454.] JOINTS FOR BOILER FITTINGS.--Let it be assumed that the casting shown in Figs. 2453 and 2454 requires to be fitted to a boiler, both being new. In this case, the holes for the studs or bolts should first be drilled in the flange of the casting, which will reduce its weight and render it easier to handle. The casting should then be held against the boiler in its proper position and location; and, with a fork scriber whose width of points is equal to the widest space between the face of the casting flange and the boiler, pass the fork scriber around the fitting or casting with one point against the boiler shell and the other pressed against the edge of the casting, the result being to mark around the flange of the latter a line exactly following the surface or contour of the boiler, and at a distance from the boiler the nearest that will suffice to properly bed the casting to the boiler surface, or, in other words, the line that will exactly mark the amount of metal requiring to be cut off the flange face to make it bed all over; and that face may, therefore, be cut down to the line. In chipping and filing it, however, the straight-edge may be used to advantage as follows:-- [Illustration: Fig. 2455.] Suppose the casting flange to be gripped in the vice facing the operator, as in Fig. 2455, and that L L represents the scribed line: then the cape chisel cuts may be carried clear across the flange, coming exactly down to the line on each side of the flange, while a straight-edge S may be used as shown to show when the cut is carried across level. Then, when the intermediate spaces are cut out with the flat chisel the surface will be of correct shape, and the surface may be rough filed. The casting should be cut clear down to the lines, and if the job has been properly set, marked and faced, no further trying will be necessary previous to marking the bolt or stud holes in the boiler. It is well, however, if the operator is inexperienced in this kind of work, to again set the casting in its proper position to correct the fit. But, with proper care, all the holes in the boiler may be marked without any second fitting of the flange, since the operation properly performed is bound to give correct results. In doing a job of this kind it must be borne in mind that it is very easy to consume more time in trying and altering the job than is required under proper conditions to do the entire job; hence, in setting the casting, preparatory to marking it with the fork scriber, nothing is near enough that does not carry with it a conviction of perfect reliability; and if any doubt exists it is better to go through the process again. If the casting flange varies much in shape from its seat, and rocks or is unsteady, wooden wedges may be placed beneath it, or a few pellets of stiffly mixed red lead may be placed on the boiler where there is most room between it and the casting, the boiler surface being coated or painted with red marking, so that the pellets shall adhere to it and not to the flange face. If the casting is too heavy to be steadied by hand, one hole may be drilled in the boiler and a temporary bolt inserted to hold the casting while setting it in position, and marking with the fork scriber. When the flange is approaching a fit, it must be placed in position on the boiler and the stud holes marked on the boiler with an ordinary scriber, its point being pressed against the boiler while it is pressed against the side of the hole in the casting flange and traversed around it, so as to scribe on the boiler surface circles corresponding to the holes in the flange. From the centres of these circles others of the proper size of the tapping holes may be struck and the tapping holes may then be drilled, and the studs put in. The remainder of the fitting operation consists in applying red marking on the boiler surface, bolting the casting to its place and filing the high spots. The marking is made to show plainly upon the flange by light hammer blows with a piece of wood interposed between the hammer and the flange face to prevent piercing the latter. These blows, however, should be lightly delivered, or they will cause the marking to be deceptive. [Illustration: Fig. 2456.] The fit of the flange to the boiler, however, should vary according to the kind of bolt used to hold the fitting to the boiler. If stud bolts are used they are supposed to screw into the boiler steam-tight, hence the flange may be fitted so that it has the closest contact with an annular ring extending from the outside of the bolt holes to the central hole of the flange, as shown in Fig. 2456, in which the area within the dotted circle C encloses the area to be most closely bedded. This is a highly important consideration in flange joints of every description, for, if a joint is made there, that is all that is necessary, and the fit outside of the bolt holes--that is to say from the bolt holes to the perimeter of the flange--has nothing to do with making the joint, unless the studs or bolts leak, and in that case the leak will find egress beneath the nut, unless grummets are used. A grummet is a washer made of twisted hemp, cotton, or other material, and coated with red-lead putty, and is placed beneath the heads of bolts, or under washers placed beneath nuts to stop leaks. It is not necessary to ease the flange from the bolt holes outward much, but to merely make the flange, or fitting, bed clearly and distinctly the most around the main hole, and outwards to the inside of the bolt holes; for, if there was given too much clearance, the flange would bend from the pressure of the nuts, and would in consequence spring if made of brass, or perhaps break if made of cast iron. To make the joint, gauze wire, pasteboard, or asbestos board may be used, or if the joint is to have ample time to set, a red-lead joint without the gauze may be used; but in this case it is an advantage to cut up into pieces about 3/8 inch long, and thoroughly shred some hemp, and well mix it in the lead, well beating the same with a hammer. To preserve red-lead putty from becoming hard and dry, as it will do if exposed to the air, it should be kept covered with water. In some cases joints of flanges to boilers are made by riveting the flanges to the boiler and caulking or closing the edge of the flanges to the boiler shell; but this possesses the disadvantage that the rivets must be cut off to remove the fitting from the boiler when necessary, and access to the interior of the boiler is necessary in order to attach the fitting again by rivets. [Illustration: Fig. 2457.] Fig. 2457 (which is taken from _The American Machinist_), represents a joint for boiler fittings, designed to facilitate the breaking and re-making of the joint. C represents, say, a boiler plate, B a piece having a ball joint seat in C ground steam tight, and A a flange, say, for a feed pipe; the studs D thread permanently into C, and the joint is bolted up by the stud nuts E. It is obvious that the ball joint between B and C permits the flange A to set at an angle if necessary. RUST JOINTS.--These are joints made by means of filling the space between the flanges, or annular spaces, as the case may be, with cast-iron turnings, and compacting them with a caulking tool. Any interstices through which steam or water, &c., might leak become filled by the subsequent rusting of the iron cuttings, the rust occupying considerably more space than the iron from which it was formed. [Illustration: Fig. 2458.] Rust joints are employed upon very uneven surfaces, and for pipes for mains to go under ground. In former times this class of joints was much used in engine and boiler work, but of late years it has been to a great extent abandoned. In Fig. 2458 is shown the method of construction for a rust joint for what are known as spigot and socket joints for pipe work. S is the spigot and P the socket. R R is a metal ring, bound over with either dry hemp fibre or tarred twine or rope. The remainder of the space between the pipes at A A being filled with a cement composed of Sifted cast-iron borings 100 lbs. Sal-ammoniac 1/2 lb. Sulphur 1/2 lb. but when required to set quickly, 1 lb. sal-ammoniac may be used. These ingredients are thoroughly mixed with water immediately before being used, and just covered with water when used intermittently. The cement is put into the space A A, in quantities sufficient to fill up about 3/4 inch in length of the annular space A A, and then caulked by being driven in with the tool shown in Fig. 2459. Cement is then again put in and the caulking repeated, the process being continued until the whole space is filled. [Illustration: Fig. 2459.] In some cases (as in gas mains) the space A A is filled with melted lead, and when cold caulked with the tool described. [Illustration: Fig. 2460.] In Fig. 2460 is shown the method of making a rust flange joint; A A being a ring covered with hemp twisted around it, the cast-iron cement being caulked in as before. The wire rings should be firmly gripped by the bolts to prevent them from moving from the caulking blows, which should be at first delivered lightly. [Illustration: Fig. 2461.] In some cases pipes are joined with rust joints, as in Fig. 2461 in which A A is a sleeve, there being two rings of wire and hemp inserted as shown. When flanged joints are made with a scraper, or ground joint, or with rubber, duck, or other similar material to make the joint, the length of the pipe, from face to face of the joint, must be made accurate. [Illustration: Fig. 2462.] Fig. 2462 is a face, and Fig. 2463 (which are from _Mechanics_), a sectional edge view of an expansion joint, being that used by the New York Steam Supply Company for the steam pipes laid under the streets to convey steam to buildings. The object is to provide a joint which shall permit and accommodate the expansion and contraction of the pipe under varying temperatures. P P are corrugated copper disks secured to the faces of the pipe ends by flanges, as shown, and gripped at their edges by the flanges of the cast-iron casing, and it is obvious that the ends of the pipe may move longitudinally carrying the corrugated disks with it. The cavity A is filled with steam, and to support the disks P against the pressure segmental blocks B of cast iron are placed behind them, the number of these blocks being as indicated by the dotted radial lines in the figure. It may be added that this joint has been found to answer its purpose to great perfection. [Illustration: Fig. 2463.] Pipe cutters, for cutting steam or gas pipe by hand, are usually provided with either a rotary wheel which severs by rolling an indentation, or else are provided with cutting tools. The rolling wheel has the advantage that it makes no cuttings, cuts very readily and is not apt to break; on the other hand it is apt to raise around the severed end of the pipe a slight ridge, which with a worn cutter may be sufficiently great as to require to be filed off before the threading dies will grip the pipe. Cutting tools are apt to break and require frequent grinding; hence, as a rule, the rolling wheel cutter is generally preferred. [Illustration: Fig. 2464.] Fig. 2464 represents a cutter of this kind, the piece A carrying the cutter B, which is operated in the stock C by means of the threaded handle H. [Illustration: Fig. 2465.] Fig. 2465 represents a pipe cutter in which are a pair of anti-friction rollers and a severing tool bevelled on one edge only so as to leave the end of the pipe face cut square, and the piece cut off bevelled on its face; or by turning the cutter round the reverse will be the case, the piece cut off being flat on its end. The action of this cutter is, as in the case of the wheel cutter, simply that of a wedge, hence no cuttings are formed. [Illustration: Fig. 2466.] Fig. 2466 represents a pipe cutter in which a cutting tool is employed, being fed to its cut by the handle which is threaded similar to the handle shown in Fig. 2464. The end jaw is operated to suit different diameters of pipe by means of the milled nut shown, which receives a threaded stem on the adjustable jaw. [Illustration: Fig. 2467.] PIPE VICE.--The ordinary bench vice is sometimes provided with an attachment to enable it to grip pipe at three points, and, therefore, hold it sufficiently firmly without squeezing it oval, but it is preferable to use a proper pipe vice, such as shown in Fig. 2467, which consists of a base frame bolted to the work bench and receiving a serrated die to grip the pipe. The upper die is carried to a frame pivoted on both sides to the base, and is operated to grip or release the pipes by means of the handled screw shown. [Illustration: Fig. 2468.] To change the dies one pivot is removed and the upper frame swung open, as in Fig. 2468. [Illustration: Fig. 2469.] The proper shape for pipe tongs depends upon the number of sizes of pipe the tongs are intended for, but in all cases the point at which the gripping point should be is about as shown in Fig. 2469. This enables the edge at A to enter the work and grip it. If this point of contact were nearer to C it would be apt to slip upon the pipe, whereas, were it farther towards B, it would present a less acute angle to the pipe, which would be apt to jam in the tongs. It is obvious that, if the tongs be moved in the direction of H, the whole power applied to F acts to cause the edge at A to grip the pipe, and that the length from A to G has an important bearing on the grip of A to the pipe; because the nearer A is to G not only the greater the leverage of the leg F, but also the less A, with a given amount of movement of F on its pivot, endeavors to enter the pipe; hence the movement of A in a direction to grip the pipe is less in proportion to the movement of F, and has a corresponding increase of force. It follows then that the nearer the grip of A is to C, the less, and the nearer the grip to B the greater, its grip upon the pipe. But, by making the length of A such as to grip the pipe in about the position shown in the cut, there is latitude enough in the location at which it will grip the pipe to permit of the tongs being used upon pipe of a somewhat greater or less external diameter, increasing the availability of the tongs. Furthermore, if A gripped the pipe at or too near to B, it would be apt to indent it. The crown of the jaw D may be made to fit to the pipe or to be clear of it; for thin pipe, as solid drawn brass pipe, it should fit so that the pressure will not indent the pipe, but for strong iron pipe it is better to let it clear, which will not only afford a firmer grip, but will also better fit the tongs to take in different diameters of pipe. In some cases, as in adjustable pipe tongs, the jaw surface D is, for this purpose, considerably [V]-shaped, as will be seen presently. It is obvious that as A grips the pipe automatically, the tongs may be moved through any portion of a rotation that the location may render most desirable. Pipe tongs are designated for size by the diameter of the pipe they are intended for; thus, a pair of inch tongs are suitable for pipe an inch in diameter of bore, the handles or legs of the tongs coming so close together that both can be readily grasped in one hand applied at their extreme ends. If, however, the tongs be applied to pipe of a larger diameter the legs will be wider apart, and one hand will be required to be applied to each leg to force them together. A complete set of pipe tongs, therefore, includes as many pairs as there are diameters of pipe, unless adjustable tongs be used. [Illustration: Fig. 2470.] [Illustration: Fig. 2471.] [Illustration: Fig. 2472.] Adjustable tongs are made of various forms; thus a simple plan is shown in Fig. 2470. The gripping surface of the jaw is shaped as at V, so as to admit varying diameters of pipe, the smaller diameters passing farther up the V, the distance of the end A of jaw, or leg F, being regulated to grip the pipe in the proper place by operating the screw S, which is tapped into the jaw F and pivoted in B, the slot C enabling F to move along B. The capacity of tongs of this design is about three diameters of pipe, as 1, 1-1/4, and 1-1/2 inches. There are various other forms of adjustable pipe tongs, but most of them possess the disadvantage that the adjustable jaw hangs loosely, involving some extra trouble in placing them upon the pipe, because one hand must be employed to guide the loose jaw and adjust its position on the pipe. Fig. 2471 represents tongs of this class, the gripping size being varied by moving the jaw A upon B at the various notches. The end of B is serrated to afford a firmer grip upon the pipe. Fig. 2472 represents another adjustable pipe tongs, which is made in two parts, a straight lever A and hooked lever B, the former passing through a slot in the latter. The back of the straight lever is notched and a serrated fulcrum piece C is pivoted in the slotted lever by a pin upon which the lever B receives its support when the tongs are in operation. The fulcrum piece is provided with a spring which retains the serrated edge in proper position to engage the notches in the lever A. By means of the thumb piece D, the piece C can be moved in either direction to increase or diminish the gripping size of the tongs. When the tongs are open the lever A can be moved within the slot and adjusted so that the tongs will fit the pipe. The fulcrum piece C, being pivoted, allows the full length of its serrated edge to come into contact with the corresponding portion of the lever A, so that the parts always have a firm bearing and are subjected to an equal wear. A common form of pipe tongs of this class is shown in Fig. 2473, B being pivoted to A by a pin, and changing to various holes in A to suit different diameters of pipe. ERECTING PIPE WORK.--In erecting pipe work care must be taken to have it align as true as possible, as well as to have the joints tight enough to stand the required pressure without leakage. If the elbows, tees, or other fittings are not threaded true, a pipe whose thread is not true with its axis may be selected or cut purposely to suit the error in the fitting, so as not to leave an unsightly finish to the job. [Illustration: Fig. 2471.] [Illustration: Fig. 2474.] Suppose, for example, that in Fig. 2474, _e_ is a pipe erected parallel to the wall, but that the holes in its elbows are tapped at an acute instead of at a right angle, then by cutting the thread on the end of pipe _d_ untrue with its axis, its far end will rotate out of true as denoted by the shaded and by the plain lines, and all that will be necessary is to screw up the pipe sufficiently firm to make the joint, but to leave it in the position shown in the plain lines. If the pipe tightens sufficiently before it has reached that position it may generally be eased by rotating it back and forth in the elbow with the pipe tongs. If this does not suffice, the pipe must of course be threaded sufficiently further along. To cut a pipe out of true to suit an untrue elbow, a very good plan is to cut the end of the pipe at an angle to its axis, which will cause the dies to cant over when starting the thread, but little practice being required to educate the judgment as to how much to do this to suit any given degree of error. In erecting pipe it is best to begin at one end and screw each successive piece firmly home to its place before attaching another, so that the lengths of the pieces may be accurate and not vitiated by screwing them up and causing them to enter farther into the fittings. If it is probable that the piping may have to be taken down after erection, it should be put up at first screwed together rather tighter than will be necessary, as the thread fits become eased by being moved one within the other. This is especially the case with brass fittings, upon which it is best in cutting the lengths of pipe to have it of full length, as the threads will conform to each other sufficiently to cause the pipe to enter a thread or so farther if the pipe be rotated back and forth a few times in the fitting. The fit should in all cases be made by tightness of thread fit, and not by the union or elbow face jambing against the end of the thread or the pipe, as joints in which this is the case will usually leak if used under pressure. The thread of both the pipe and the fitting should be smeared with a thick lead paint. If the pipe is to be used as soon as erected, plain red lead and boiled oil should be used for the paint; but if it may stand a few days it is better to mix white and red lead in about equal quantities, as this, if given time to dry, makes a tighter job. The quantity of this paint should not be more than will thinly cover the threads, otherwise it will squeeze out when the pipes are screwed home, and falling from the end of the pipe within the fitting be apt to be carried by the steam or water to the valves, and getting between them and their seats cause them to leak. The iron cuttings should be carefully cleaned both from the pipe and the fitting for the same reason. In cases where the piping may require to be used under heavy pressure as soon as erected, it is a good plan to use dry red lead in varnish, thoroughly hammering it to mix it well, and thinning it after it has been so hammered. In case of emergency a loose pipe may be somewhat improved by wrapping around its thread a piece of lamp wick saturated with this varnish lead, beginning at the end of the pipe and wrapping the thread from end to end. It is preferable that the stem of the valve stand nearly horizontal, so that any water of condensation may pass freely away with the steam and not collect and lie in the pipe as it does when vertical. If it be quite horizontal the water of condensation will drip through the stuffing box; hence it is better that it stand 10 or 12 degrees from the horizontal. It is better in all cases to purchase nipples than to make them by hand, because when made in a machine the threads are more true to the axis than those made by hand; especially is this the case in short nipples in which there is not sufficient length to use the guide socket when engaged in threading the nipple with the hand dies. It is a very good plan in making such short nipples to cut them off the end of a length of pipe that has been threaded by machine, and to screw on the threaded end a coupling. Into this coupling a piece of pipe may be threaded to afford a hold in the vice. If then the nipple is long enough, a guide to suit the size of the nipple may be used in the threading dies, or a guide socket to fit the diameter of the coupling may be used. A globe valve should be so placed on the pipe that the pressure will, when the valve is closed, fall on the bottom face of the valve, so that the steam may be shut off while the valve stem is being packed. Cotton lamp wick plaited to fit the packing space, and well oiled, is as good as anything to pack the stem with. In taking old pipe down a refractory joint may be sometimes loosened by striking it with a hammer while it is under full pipe tongs pressure; or these means failing, the elbow or tee may be heated, which should be done as quickly as possible, so that the fitting may be hotter than the pipe. A very good method of doing this, where it is desired to save the fitting, is to pour red-hot lead over the fitting. If it is not important to save the fitting, it may be split by a flat chisel, or by cutting a groove along it with a narrow cape chisel; or if the pipe is free the elbow may be rested on an anvil and hammered around its circumference, which will either free it or break it, if of cast iron. When pipes are to be taken down and re-erected elsewhere they should all be marked to their fittings and places before being taken down, as this will preserve their lengths as near as possible for re-erection. Black japan is an excellent marking for this purpose because it dries quickly. RE-FITTING THE LEAKY PLUGS AND BARRELS OF COCKS.--When a cock leaks, be it large or small, it should be refitted as follows, which will take less time than it would to ream or bore out the cock or to turn the plug, unless the latter be very much worn indeed, while in either case the plug will last much longer if refitted, as hereinafter directed, because less metal will be taken off it in the re-fitting. After removing the plug from the cock, remove the scale or dirt which will sometimes be found on the larger end, and lightly draw-file, with a smooth file, the plug all over from end to end. If there is a shoulder worn by the cock at the large end of the plug, file the shoulder off even and level. Then carefully clean out the inside of the cock, and apply a very light coat of red marking to the plug, and putting it into the cock press it firmly to its seat, moving it back and forth part of a revolution; then, while it is firmly home to its seat, take hold of the handle end of the plug, and pressing it back and forth at a right angle to its length note if the front or back end moves in the cock; if it moves at the front or large end, it shows that the plug is binding at the small end, while if it moves at the back or small end, it demonstrates that it binds at the front or large end. In either case the amount of movement is a guide as to the quantity of metal to be taken off the plug at the requisite end to make it fit the cock along the whole length of its taper bore. If the plug shows a good deal of movement when tested as above, it will be economical to take it to a lathe, and, being careful to set the taper as required, take a light cut over it. Supposing, however, there is no lathe at hand, or that it is required to do the job by hand, which is, in a majority of cases, the best method, the end of the cock bearing against the plug must be smooth-filed, first moving the file round the circumference, and then draw-filing; taking care to take most off at that end of the plug, and less and less as the other end of the plug is approached. The plug should then be tried in the cock again, according to the instructions already given, and the filing and testing process continued until the plug fits perfectly in the cock. In trying the plug to the cock, it will not do to revolve the plug continuously in one direction, for that would cut rings in both the cock and the plug, and spoil the job; the proper plan is to move the plug back and forth at the same time that it is being slowly revolved. As soon as the plug fits the cock from end to end, we may test the cock to see if it is oval or out of round. The manner of testing the cock is as follows:-- First give it a very light coat of red marking, just sufficient, in fact, to well dull the surface, and then insert the plug, press it firmly home, and revolve it as above directed, then remove the plug, and where the plug has been bearing against the surface of the cock the latter will appear bright. If, then, the bore of the cock appears to be much oval, which will be the case if the amount of surface appearing bright is small, and on opposite sides of the diameter of the bore, those bright spots may be removed with a half-round scraper. Having eased off the high spots as much as deemed sufficient, the cock should be carefully cleaned out (for if any metal scrapings remain they will cut grooves in the plug), and the red marking re-applied, after which the plug may be again applied. If the plug has required much scraping, it will pay to take a half-round smooth file that is well rounding lengthwise of its half-round side, so that it will only bear upon the particular teeth required to cut, and selecting the highest spot on the file, by looking down its length, apply that spot to the part of the bore of the cock that has been scraped, draw-filing it sufficient to nearly efface the scraper marks. The process of scraping and draw-filing should be continued until the cock shows that it bears about evenly all over its bore, when both the plug and the cock will be ready for grinding. Here, however, it may be as well to remark that in the case of large cocks we may save a little time and insure a good fit by pursuing the following course, and for the given reasons. If a barrel bears all around its water-way only for a distance equal to about 1/16th of the circumference of the bore, and the plug is true, the cock will be tight, the objection being that it has an insufficiency of wearing surface. It will, however, in such case wear better as the wearing proceeds. Plug and barrel being fitted as directed, we may take a smooth file and ease away very lightly all parts of the barrel save and except to within, say, 3/8 inch around the water or steam-way. The amount taken off must be very small indeed, just sufficient, in fact to ease it from bearing hard against the plug, and the result will be that the grinding will bed the barrel all over to the plug, and insure that the metal around the water or steam-way on the barrel shall be a good fit, and hence that the cock be tight. The best material to use for the grinding apparatus is the red burnt sand from the core of a brass casting, which should be sifted through fine gauze and riddled on the work from a box made of, say, a piece of 1-1/2 pipe 4 inches long, closed at one end and having fine gauze instead of a lid. A very good material, however, is Bath brick rubbed to a powder on a piece of clean board. Neither emery nor ground glass is a good material, because they cut too freely and coarsely, which is unnecessary if the plug has been well fitted. Both the barrel and the plug should be wiped clean and free from filings, &c., before the sand is applied; the inside of the barrel should be wetted in and the plug dipped in water, the sand being sifted a light coat evenly over the barrel and the plug. The plug must then be inserted in the barrel without being revolved at all till it is home to its seat, when it should be pressed firmly home, and operated back and forth while being slowly revolved. It should also be occasionally taken a little way out from the barrel and immediately pressed back to its seat and revolved as before, which will spread the sand evenly over the surfaces and prevent it from cutting rings in either the barrel or the plug. This process of grinding may be repeated, with fresh applications of sand, several times, when the sand may be washed clean from the barrel and the plug, both of them wiped comparatively dry and clean, and the plug be re-inserted in the barrel, and revolved, as before, a few revolutions; then take it out, wipe it dry, re-insert and revolve it again, after which an examination of the barrel and plug will disclose how closely they fit together, the parts that bind the hardest being of the deepest colour. If, after the test made subsequent to the first grinding operation, the plug does not show to be a good even fit, it will pay to ease away the high parts with a smooth file, and repeat afterwards the grinding and testing operation. To finish the grinding, we proceed as follows: Give the plug a light coat of sand and water, press it firmly to its seat and move it back and forth while revolving it, lift it out a little to its seat at about every fourth movement, and when the sand has ground down and worked out, remove the plug, and smear over it evenly with the fingers, the ground sand that has accumulated on the ends of the plug and barrel, then replace it in the barrel and revolve as before until the plug moves smoothly in the barrel, bearing in mind that if at any time the plug, while being revolved in the barrel, makes a jarring or grating sound, it is cutting or abrading from being too dry. Finally, wipe both the barrel and the plug clean and dry, and revolve as before until the surfaces assume a rich brown, smooth and glossy, showing very plainly the exact nature of the fit. Then apply a little tallow, and the job is complete and perfect. In place of the tallow a soft paste of good beeswax and castor oil is an excellent application, the two being heated in order to thoroughly mix them. The grinding material must be frequently changed to produce smooth work, because if the grinding cuttings accumulate in it, they will scratch and score the work. Indeed, it is a good plan when convenient, to hold the cock and plug under water while grinding them, and to occasionally lift the plug out, so as to wash out the cuttings. The surface of a well-ground plug will be in all cases polished, and not have that frosted appearance which exists so long as active grinding is proceeding, and all that is necessary to produce this polish is to well work the plug in its barrel while keeping it quite clean. [Illustration: Fig. 2475.] FITTING BRASSES TO THEIR JOURNALS.--Brass bores always require fitting to their journals after having been bored, because the finished hole is not a true circle, but too narrow across the joint face, as at F in Fig. 2475, in which the full lines represent the form of the brass before, and the dotted line its form after being bored and released from the pressure of the devices or chuck that held it while it was being bored. This almost always occurs to a greater or less degree, and it arises from local strains induced from the unequal cooling of the casting in the mould, which strains are released as the metal is removed (in the process of boring) from the surface of the bore. It would appear, however, that if the finishing cut taken by the boring cutter be a very fine one it should leave the hole true and round, but the pressure which is placed upon the bearing to hold it against the force of the cut prevents the bearing from assuming its natural form until released from that pressure. If a bearing be bored to very nearly its finished size and first released altogether from the pressure of the holding chuck, or other device, and then re-chucked, it is probable that the finished bore would be practically quite round and true, but such re-chucking is not the usual practice. Suppose, however, that the bearing shown in Fig. 2475, be properly fitted to a journal, still improper conditions arise from wear, because the area of the surface D becomes from the weight and from vibration condensed, and finally it stretches, causing the bore at F to close upon the journal and bind it with undue friction. [Illustration: Fig. 2476.] If the shape of the bedding part of the brass, or bearing, be such as shown in Fig. 2476, the surfaces A B and C will condense and stretch, closing the diameter of the bore at E and making the sides G G fit loosely in their places. It is to be observed that a similar condensation of the metal occurs to some extent around the bore of the bearing; but this surface is being continuously worn away by the journal, and it is, therefore, at all times less stretched and condensed than that on the bedding surface. [Illustration: Fig. 2477.] There is, therefore, a constant action causing the brass to bind unduly hard at and near its joint face E, Fig. 2476, and thus to cause heating and undue abrasion and wear. To prevent this it is necessary to ease away that part of the brass bore, as is shown in Fig. 2477 from J to K, clear of the journal. But in the case of bearings receiving thrust, as in engine main bearings, the line of pressure is in a horizontal direction; and hence the most effective bore area to resist that pressure has been removed. Furthermore, the bearing area of the brass bore has been reduced, thus increasing the pressure per square inch on the remaining area. [Illustration: Fig. 2478.] The methods employed to avoid this evil are as follows:--In the form shown in Fig. 2478 the joint faces are at an angle instead of being horizontal and parallel to the line of the thrust, or the joint faces may be made to stand at a right angle to the line of journal thrust, so that the crown of the brass will receive the thrust. But the brasses will still close across the joint faces (as already described) as the wear proceeds, and the areas from J to K in Fig. 2477, must still be eased away, requiring frequent attention and giving a reduced bearing area. Furthermore, in proportion as the line of the joint faces of the brasses is at an angle to the line of thrust, the strain on the top or cap brass will fall on the bolts, so that if those joint faces be at a right angle to the line of thrust, the whole strain of that thrust will fall on the bolts that hold the cap and cap brass. [Illustration: Fig. 2479.] Another plan is to make the bearing in parts, as in Fig. 2479, in which the top and bottom parts of the bearing extend to the joint face on one side, but admit a chock or gib, A in the figure, which may be adjusted by a set-screw as shown. By this means the bearing area may extend all around the bore. In some cases two of such chocks and set-screws, one on each side of the journal, are employed. [Illustration: Fig. 2480.] In place of the set-screws, whose ends, from receiving the pressure of the thrust, are apt to imbed themselves into the chock and to thus loosen the adjustment, wedges lifted by bolts passing up through the cap, as shown in Fig. 2480, are employed, being preferable to the screws. In the Porter Allen engine the wedges pass clear through the bearing, as in Fig. 2481, so that they may be pushed up after the manner of a key and their pressure against the side chocks judged independently of the nuts at the top. In some designs the top and bottom parts of the bearing are free to move in the line of the thrust, and the side chocks or blocks alone are relied on to resist the thrust. When the brasses are in two halves, they may be fitted so as to have a known degree of bearing pressure upon the journal, and the fit may thus be accurately adjusted, in which case they will wear a long time before requiring re-adjustment. On the other hand when the side chocks are used the wear in the line of the thrust may be taken up as it proceeds. In one case the attending engineer cannot alter the fit of the bearing nor the alignment of the shaft, while in the other he can do both. Thus the facilities that enable him to make these adjustments properly also enable him to make them improperly. But this would be of no consequence, providing it could be determined whether the adjustment were improving the conditions without first making it. With an engine at rest it is easy to determine, by means of the connecting rod, whether the chock adjustment is correct, so far as the adjustment of the shaft is concerned, but it is not easy so to determine the pressure of the chock on the journal; nor when each chock has two adjusting screws is it easy to determine when they both bear alike. [Illustration: Fig. 2481.] When the bearing is in four pieces, and three of them have two screws each, it is still more difficult to operate all so as to have the bearing equal on the journal. The fit to the journal can only be determined by the results: if too easy, the bearing pounds; if too tight, the bearing heats and wears. But undue wear may take place without heating, and this is one of the greatest objections to this method of adjustment. [Illustration: Fig. 2482.] A design of bearing used in American locomotive practice is shown in Fig. 2482. Here the joint faces C, B of the brass is bevelled, fitting into a corresponding bevel in the box, which prevents the brass from closing across the joint face; hence, the bearing on the journal may extend all around the brass bore from the oil cavity A to the edges B C. The brass is, in this case, forced to its place in the axle box under hydraulic pressure, and this pressure springs the box open at H, making it wider; but when the box is put to work the brass compresses somewhat, and its surfaces conform more closely to the bedding surface of the box than when first put in, and this causes the box to close slightly at H. To prevent this closure from carrying the brass with it and close it across the joint face (as in the case of the brass shown in Fig. 2476) the following plan is adopted. The brasses, after having been turned in the lathe, are filed along the entire surface (on each side) for a distance of about 1-1/2 or 2 inches, so as to clear the bore of the box near the bevels B, C. When the box is put into the hydraulic press, to have the brass forced in, a centre-punch mark J is made, and part of a circle L L is struck; when the brass is home in the box the arc of circle K is made, the distance between K and L showing how much the box has been sprung open by the brass; the amount allowed is about 1/32 of an inch. If, as the brass is pressed in, it is found that this will be exceeded, it is taken out and eased. When the engine is running and the boxes spring to some extent they do not carry the brass with them, because the sides being eased away gives liberty to the box to come and go slightly; the bevels also tend to keep the brass bore open. Here, then, the brasses may be fitted to align the axle perfectly, and it is not permitted to the engineer to alter that alignment, while at the same time the fit of the brass to the journal being made correct, the engineer cannot alter it. Under these conditions the whole area of the brass is effective in holding the journal, which increases the durability of the brass by keeping the pressure per square inch on the brass bore at a minimum. If side chocks are used, however, it is better to set them up by wedges than by screw bolts, because from the tightness of the fit of such screws in the tapped holes, it is difficult to determine, with precision, with what degree of pressure the chocks are forced against the journal. Furthermore, the screws may not fit with an equal degree of tightness; hence, when screwed up with an equal degree of pressure, one end of the same chock may be set tighter to the journal than the other end, and any undue pressure of fit at either end tends to throw the shaft out of line as well as inducing undue wear. But when wedges are used to set up the side chocks the nuts operating those wedges may be an easy fit without fear of their becoming loosened (as set-screws in the line of thrust are apt to do). On the fast engines of the Pennsylvania Railroad solid bronze boxes, without brasses, are used, and when the boxes require truing from having cut or from having worn oval they close them under a steam hammer, closing the bore across and enabling it to be trued out in the lathe without taking much metal out of the crown of the bore. The wedges and adjusting shoes are thickened when this becomes necessary by reason of the box closure or width. If a brass bore does not bed fully and equally over the entire intended bearing area the part not fitting will at first perform no duty as bearing area, and the whole strain will be thrown upon a less area than is intended by the construction, causing undue abrasion until the brass bore has what is termed worn down to a bearing. The amount of this wearing down to a bearing may be so small as to be scarcely perceptible to ordinary observation, but if the oil that has passed through the journal be smeared upon stiff white paper, as writing paper, it will be found to contain the particles of abraded metal, which will be plainly distinguishable. Under these conditions the journal will have a dull, though perhaps a smooth appearance, and will not have that mirror-like surface which is characteristic of a properly fitted and smooth working bearing, while under a magnifying glass the journal will show a series of fine rings or wearing marks. It is necessary, therefore, that each brass be properly fitted to its journal so that it shall bed fairly and evenly over all the area of its bore that is intended to bear upon the journal. The most expeditious method of fitting a new bearing box or brass to its journal is to first file the bore until it fits the journal when simply placed thereon by hand, and without going to the trouble to put the brass or the journal in position in the frame which holds them. So soon, however, as the crown of the brass beds to the journal along its whole length, the brass should be placed in its box, or in the frame, and the journal adjusted in its place and rotated so as to leave its bearing marks upon the brass bore, to assist which it may have a faint coat of red marking on its surface. The fitting should be continued both with file and scraper until the whole area of the part intended to bed fits well and is smooth and polished. To produce this result the finishing should be done with a very smooth half-round file, draw-filing so as to leave the marks in a line with the circumference of the bore, and finally with a half round scraper, which will remove the file marks. The degree of contact should be such that, when the bearing is bolted up, brass and brass, as it is termed (which means that the joint faces of the brasses are held firmly together), the journal will rotate as freely as when the top brass is removed, while the contact marks on the top brass have been removed by scraping. By this means the fit will be just sufficient to permit the lubricating oil to pass between the journal and the bearing, and the journal will work freely and easily without any play, knock, or pound. If, when the top brass or bearing is bolted home and the shaft is rotated by hand, that brass on removal shows contact marks on its bore, although it may rotate comparatively easily it will be so tight a fit that the oil cannot pass, and as a result the wear, instead of producing a glossy surface, will produce a dull one, and undue abrasion will ensue even though no rings appear. When brasses are held in rods that connect two journals together the fitting of the brass bore must be conducted with a view to have the brasses fit their journals all over the intended bearing area of their bores, which can only be accomplished by trying the brass bores to their journals while in the rod, in the manner to be hereafter described with reference to connecting rods and to lining engines. When a journal is worn in rings, or so rough as to cause destructive abrasion and undue friction, it may be refitted as follows:--First, with a smooth file draw-file the journal in the direction of its length, taking off all the projecting rings. Then sweep a very smooth file that is somewhat worn (which will cut smoother than a sharp file) around the circumference of the journal so that the file marks will be in the plane of revolution. Then wrap a piece of fine and somewhat worn emery paper around the journal, and wrap around it (say twice around) a piece of coarse string, leaving the two ends about two feet long. Take one end of the string in each hand and pull first one end and then the other, causing the emery paper to revolve around the journal and smooth it. To refit the bearings, first with a smooth half-round file remove the rings or rough surface, and then fit the surface with the file, so that when in its place the journal is rotated the contact marks show a proper bearing. Then draw-file the bore with a smooth half-round file and finish with a half-round scraper, easing away the high spots until the bore shows proper contact and is smooth. A piece of fine emery paper may then be wrapped around a half-round file and the surface smoothed with the emery paper moved across the bore and not in the direction of the circumference of the same. The emery paper should be well worn for the finishing and of a fine grade number, so as to leave a bright polish and not dull marks. In some practice the bores of brasses are left rough-filed, the file marks being lengthways of the bearing of bore. If the journal requires smoothing it is draw-filed lengthways of the journal. The philosophy of this is, that the file marks will hold the oil and afford unusually free lubrication while the bearing and journal are wearing down to a bearing. But where the framework holding the bearings and journals are rigid, these bearings and journals may, with care, be fitted to a polished and equal bearing, leaving a smoother surface than that produced by wearing down to a bearing. But if, as in the case of a locomotive, the framework is subject to torsion, rough surfaces left to adjust themselves are possibly better than those accurately fitted, because the whole framework holding the bearings changes its form when the full load is upon it and after put to work, and the fitting done when there was no load upon the parts is no longer quite correct. The lubrication of the bearing, however, should be very free, and the effort appears at present to be to afford more ample oil ways than hitherto even at some sacrifice of bearing area. LEAD-LINED JOURNAL BEARINGS.--If a journal is worn in grooves or undulations it becomes impracticable to properly fit the brass to it without reducing its diameter to remove the rings, and to obviate the cutting and heating which necessarily follow, as well as to obviate the necessity of fitting the brasses at all, Mr. D. A. Hopkins introduced lead-lined bearings; the lead lining being merely auxiliary to the bearing proper, which is made preferably of hard bronze, and to which the thin layer or facing of lead is firmly attached by a soldering process, so that the two metals are virtually one piece. Into this lead facing the journal, under the pressure of the car, moulds or imbeds itself from the start, and afterwards gradually wears its way through it into the hard metal. The perfect fit thus secured under all conditions of the journal, aided with proper lubrication, not only prevents heating, but secures the full wear of the brasses, and makes them at all times perfect counterparts of the journal surfaces. [Illustration: Fig. 2483.] Fig. 2483 shows at the top an unfitted bearing without the lead lining, resting upon a worn and badly-cut journal, the only points of contact being near the ends. For obvious reasons such a journal is sure to run hot. The engraving below shows the application of the lead lining to the same journal, the dark shading between the journal and bearing representing the lead which has been pressed into the worn and hollow surface of the journal, forming a complete bearing and distributing the weight equally upon its surface. [Illustration: Fig. 2484.] Fig. 2484 represents an end view of an unfitted journal and the same lead lined. The lead compresses until the brass meets the journal and thus permits between the two contact over the area that does fit or touch; while the lead fills the remaining area of the brass bore, giving it a bearing on the journal, thus relieving the touching points from receiving the whole weight of the load, and preventing the cutting or abrasion that would otherwise occur. As, however, the wear takes place the lead compresses, permitting the journal and brass to come into bearing over its full area, being obviously effective providing the bearing be kept free from grit, which would imbed in the bearing and cause it to unduly wear the journal. If a brass is too tight a fit upon its journal, heating and abrasion, or "cutting" as it is termed, ensues. But if a brass or box does not fit close to its journal, lost motion and sometimes knocking or pounding ensues. When the joint faces of brasses abut, or come brass and brass as it is termed, they should be a proper fit to the journal when they are keyed, or otherwise set up close together; hence there is no danger of either having a pound in the brass, or of heating and cutting. The objection to this plan is that the brasses must be removed from their boxes and the joint faces filed away to let the brasses together, to take up the wear; hence, in positions in which it is difficult to get the brasses out, the joints should be left open, while in all cases where they can be readily removed they should be made brass and brass. It is to be observed that brasses that come brass and brass require less adjusting and last longer than those left open, because the latter often suffer from the abrasion due to an improper adjustment. In brasses that are left open, it is not an uncommon practice to adjust the fit as follows: Between the brass joint faces at each of the four corners a piece of lead wire is inserted; the brasses are keyed as close home as can be upon the journals, which compresses the lead wire; the top brass is then released until the piece of lead wire can be moved freely between the brass joints. [Illustration: Fig. 2485.] [Illustration: Fig. 2486.] A compromise between the brass and brass and the open joint is sometimes effected by the insertion of slips, as shown in Fig. 2485 at A, B. These slips may be taken out by simply removing the top brass, while their reduction of thickness lets the brasses together to take up the wear. The thickness for these strips may be readily obtained by means of the pieces of lead wire used as already described. In the case of large brasses which come brass and brass, much of the filing on the joint faces to let them together may be saved by reducing their thickness and area by cutting away part of the metal, as at A A in Fig. 2486. [Illustration: Fig. 2487.] To enable the removal of bearings for renewal, or to refit them without taking the shaft out, various forms of construction are employed, of which Fig. 2487, which shows a main bearing, is an example. Thus, when the cap is removed the side chocks, or gibs as they are sometimes called, can be lifted out by eye-bolts screwed into the holes at _c_; the weight of the shaft can then be sustained while the bottom piece D is removed. A great deal of trouble in fitting journals and bearings may be avoided if the best conditions are observed in their manufacture. If, for example, the conditions of casting are uniform, and the diameter of the bearing bore and journal bores are constant, that is to say, when a great number of pieces are to be bored, the amount the bearings will close across the joint being definitely determined, the conditions of boring may be made such as to allow for the closure, and the fitting in this respect may be facilitated; but this applies to small bores only, as, say, three inches and less in diameter, because in larger diameters there will be sufficient variation in the amounts of contraction across the joint face to render it necessary to fit to some extent at least the bores to their journals. In some cases slips of paper are placed between the joint faces of the bearings, or if the joint faces do not meet, slips of brass may be placed between them; or again the conditions of chucking or holding the bearings to bore them may be such as to hold them a certain amount farther apart than they will require to be when on the journal. The bore is then made sufficiently larger than the diameter of the journal that it will be as nearly as possible round after being removed from the boring machine, and will bed down fairly upon the journal without being fitted with a file, which saves considerable labor. But unless the bearings are so held as to be to some extent self-adjusting for alignment, there is liability of the axis of the bore not being quite true with the axis of the journal, the amount being so small as to escape detection save by trial for fit with the shaft, and the bearings in their respective positions. It is a difficult matter, in the absence of special holding devices, to chuck a bearing, especially if a long one, so true in a boring machine or lathe as to insure that its bore shall stand in absolutely correct alignment with the journal when placed in its position in the framing where it is to operate, and it is for this reason that many bearings are bored while in their frames. In some cases, however, this difficulty is overcome by so constructing the bores and the pieces holding them that the boxes may swivel and adjust themselves, as in the case of the bearings of line shafting. Examples of the oil cavities for bearings are given as follows:-- For journals of small diameter oil cups screwing into the bearing cups, with feed-regulating devices, are generally used, and the same are used in the case of two half-brasses. But if the journals are of large diameter, as, say, 5 inches or more, oil receptacles are often cast in the caps. In the absence of side chocks in the bearing all the oiling usually proceeds from the top, save perhaps that an oil groove may be provided in the crown of the bottom brass. Fig. 2488 represents a bearing lubricated from the top and bottom; thus in the cap is an oil cup or cavity from which passes nearly down to the bearing a brass tube containing cotton wick, which slowly feeds the oil to the bearing. Fig. 2489 represents this tube and wick removed from the bearing. This plan of feeding is largely used on marine engines and on locomotives. When used upon stationary bearings the cotton wick need not fill the tube, but if used on reciprocating parts it should fill so that the oil may not spill over and pass too freely down the tube. In either case, however, it is desirable to twist in the cotton a piece of fine copper wire, and bend the ends over the top of the tube to keep the wick in place in the tube. [Illustration: Fig. 2488.] The bottom of the bearing, Fig. 2488, is provided with an oil cavity and a similar tube and wick. Usually, however, the oil is fed in at the top only, except in the case of locomotives, because in them all the weight falls on the top brass; hence, the bottom may be utilised as an oil receptacle. In English locomotive practice this receptacle as a rule merely catches the oil that has passed through the bearing box, but sometimes a roller is inserted and forced against the journal by springs so as to rotate, by friction, with the rotating journal. [Illustration: Fig. 2489.] The bottom of the roller runs in oil so that the roller feeds the journal with oil, but ceases to feed when the journal ceases to rotate, an advantage not possessed by self-feeding oil cups, or by the cotton wick syphons shown in Fig. 2489. The oil ways or oil grooves are usually provided in small journal brasses as follows:-- [Illustration: Fig. 2490.] [Illustration: Fig. 2491.] [Illustration: Fig. 2492.] It is obvious that if the joint faces of the brasses are left open and oil be supplied to one brass only, a great part of the oil supplied will pass out between the joint faces before reaching the other brass, and one brass will therefore be better lubricated than the other, unless each brass be lubricated independently. Even in this event, however, a great part of the lubricating material will be lost from finding rapid egress through the opening of the brasses. This may be to some extent prevented in brasses whose joint faces lie horizontally by chamfering the edges of the bore so as to form a trough extending nearly to the ends of the brass, as shown in Fig. 2492. Now it is obvious that the oil hole must always be above the journal or bearing bore; hence when the joint faces stand horizontal, the oil hole should come through the crown of the brass, and oil grooves are necessary to convey and distribute the oil along the bore. A single groove, as in Fig. 2490, is sufficient for light duty, but for heavy duty a double groove, such as shown in Fig. 2491, is necessary. [Illustration: Fig. 2493.] When, however, the joint faces stand vertically and come brass and brass, the oil hole may be filed half in the joint face of each brass, and the edges chamfered off as in Figs. 2492 and 2493, A B representing the chamfers and C the oil hole, the two brasses put together appearing as shown in section in Fig. 2493. This plan has the advantage that the oil is confined within the journal, except in so far as it may in time work through the ends of the journal bore, while there are two oil grooves provided without reducing the bearing or bedding area of the brass. When the oil grooves run diagonally, as in Fig. 2491, there is the advantage that the length is greater, and lying nearer to the plane of rotation the oil flows along the grooves easier, being assisted by its frictional contact with the journal, but on the other hand the bearing area of the brass on the journal is so much the more reduced. Oil holes that are not provided with oil cups should be provided with small wooden plugs, which will serve to keep the dirt and dust out; they should be made of as small diameter as the quantity and nature of the lubricant to pass through them will admit of, and should be left plain at the top and not countersunk, because the countersinking simply forms a dish that will collect dust, &c., which the oil applied will carry down into the bearing. In some cases there is provided an oil dish around the oil hole, and this dish is filled with tallow that will not melt under the normal temperature at which the brass is supposed to operate. But if from defective oil lubrication or other cause the bearing begins to heat, the tallow will melt, and flowing through the oil hole afford the needed lubrication. It is to be observed that the lubrication of a bearing in which the pressure is moved alternately from one half of the bearing to the other is far easier to attain, and more perfect, than in one in which the direction of the journal pressure is constant, because in the latter case the journal pressure acts to squeeze out and exclude the oil continuously, whereas when the pressure is relieved alternately on each brass, the oil has an opportunity to pass back between the relieved surfaces. Again the lubrication is more perfect when the direction of the journal motion is periodically reversed, as the passage of the oil through the bearing is retarded by the motion, and yet again the abrasion is reduced because, as stated when referring to rotating radial surfaces, the particles of metal abraded add themselves together and form cutting pieces when the motion is continuous in one direction, whereas in a reversing motion the particles are kept separated and flow out more freely with the oil that passes through the journal. If a shaft having a continuous direction of rotation be given end play so that while rotating it may move endwise, the particles abraded are again kept separated, and the conditions of lubrication are such as to give a minimum of wear, because the formation of fine rings or serration is avoided, the end motion serving to cause the wear to smooth the surfaces. [Illustration: Fig. 2494.] When a shaft has a collar, that is subject to end pressure, the oil way may be carried up the face of the collar as in Fig. 2494 at B. So also where very free lubrication is required, an oil groove may also be cut in the journal itself, as at C in the figure. This plan is adopted by some American engineers upon the crank pins of steam engines, the grooves being cut on diametrally opposite sides of the pin in a line with the throw of the crank. Referring now to the oil itself, it is generally conceded that a pure sperm or lard oil is equal to any that can be used for general journal lubrication, but the ordinary purchaser has no means of knowing if the oil is pure. The requirements of an oil for lubricating purposes are given in the following paper on testing the value of lubricants, which was read by Mr. W. H. Bailey before the Manchester (England) Institution of Employers, Foremen and Draughtsmen:-- "A fact in connection with oil and lubrication is probably about as difficult a thing to describe as anything which agitates the minds of engineers and mechanical men. We appear to have very little published information on the subject, except that which describes the labors of Morin, of France, about forty years ago, and that which has been given to us by Professor Rankine more recently in this country. Those investigators who preceded Morin do not appear to have published information of very much value, or which can be used with profit for the discussion of lubricants, for their researches have been more concerning the proportions of bearings, and the value of different materials of construction, rather than the value of different lubricants. "At the present moment so little is known generally concerning the performance of different oils, that the public are much at the mercy of the vendors of these oils, who can make almost any assertion they like without fear of contradiction. "The valuable discoveries of our distinguished townsman, Dr. Joule, have enabled us to look upon the cost of friction and the cash value of heat as mere questions of arithmetic. Dr. Joule's investigations have been put into such forcible and elegant English by Professor Tyndall, and other students of the science of force, as to cause us to understand that when friction is produced heat is lost, and that all energy thus wasted passes away in this heat, which may be measured and valued with nearly as much facility as any article of commerce. We may gather from this knowledge, when we apply it to workshop economy, that if a pedestal or bearing becomes so hot through friction as to cause 1 lb. of water to be raised only one degree Fahrenheit in temperature in one minute, that heat has been lost equal to that which would be created by a weight of _one pound falling through a space of 772 feet_. We are told that if we apply this conversely, that heat has been lost which would lift 1 lb. weight 772 feet; and if we apply these illustrations still further, and imagine forty-two pedestals or bearings losing heat by friction in a similar manner, we may inform ourselves that we are losing nearly 1 horse-power, because they represent 32,424 foot-pounds of force; and if we know from our books what our coal costs, it will take very little trouble to give us the exact cash value of this friction and destructive action. "What is friction? It may be described as the effect produced by two bodies sliding one upon the other, which have upon their opposing surfaces minute asperities, which interlock with each other. The sliding movement which forcibly removes these minute irregularities creates what we call friction. Friction is reduced when these asperities are small, and lubrication is resorted to to prevent that loss of power caused by motion under these conditions. The chief lubricants used are oil and tallow, which have a less coefficient of friction than the parts in contact. It may be well now to state that the term 'coefficient of friction' is an expression which indicates the proportion which resistance to sliding bears to the force which presses the surfaces together. There is little friction when this amounts to only one-twentieth, it is moderate when it is one-tenth, and it is very high when it is a quarter or twenty-five per cent. of the force which presses the surfaces, together, as I before said. "QUALITIES OF LUBRICANTS.--Good lubricants should have the following qualities: (1) Sufficient body to keep the surfaces free from contact under maximum pressure. (2) The greatest possible fluidity consistent with the foregoing condition. (3) The lowest possible coefficient of friction. (4) The greatest capacity for storing and carrying away heat. (5) A high temperature of decomposition. (6) Power to resist oxidation; or in other words, the influence of the atmosphere upon them. (7) Freedom from corrosive action on the metals upon which they are used. It will thus be seen that many conditions have to be carefully taken into consideration; and further, it may be stated that an oil which may be good for heavy bearings may not be desirable for use on light spindles, and for delicate machinery like clocks and watches, where very little power is required to be transmitted beyond that of overcoming their own inertia; and also that oil which is good for small machinery running at quick speeds is very often useless for heavy pressures and large shafting. For very heavy bearings tallow and other solid lubricants are used, such as mixtures of sulphur and tallow, asbestos, soapstone with asbestos, graphite, caustic soda, beeswax, and other similar mixtures, which find favor among locomotive engineers and those in charge of heavy machinery. The pressure that can be borne by a good lubricant for a useful length of time depends upon the nature of the bearings as well as upon the lubricant itself. The velocity of the rubbing action also must be taken into consideration. The maximum of pressure that solid lubricants will bear without destruction is unknown. For steel surfaces, lubricated with best sperm oil moving slowly, 1,200 lbs. pressure per square inch of bearing surface has been found permissible. Under the pivots of swinging bridges several thousand pounds per square inch have been found to work, and for iron journals 800 lbs. per square inch should not be exceeded. "Lubricants in the market vary much in cost as well as in quality, and very often it is found that the varying prices bear little or no relation to the value of the article purchased. Probably the best test of value is one with which I was familiar some years ago. It consisted of a small engine very much overworked, which stopped and refused to move or go at the proper speed if the shafting had not been lubricated with good oil. "TESTING BY DESTRUCTION.--The instrument here illustrated, in Figs. from 2495 to 2501, to which I call attention, consists of a bed-plate, having upon it a piece of shafting upon which friction is created by means of two brass steps, the speed at which it is driven being about 300 revolutions per minute. The friction is brought to bear by levers and weights somewhat after the manner of a friction brake as shown in Figs. 2495 and 2500. In the top step is a thermometer for indicating any increase of temperature caused by the friction. A small index indicates the number of revolutions that the shaft makes for any given temperature which the friction causes the thermometer to indicate. The machines used for testing oil have the friction shaft where the oil is destroyed three inches in diameter. Those for tallow are of larger dimensions. It will be seen that on ascertaining the number of revolutions which may be obtained without generating heat, or with the lowest possible increase of heat, that the value of the oil can be obtained. That oil which allows the greatest heat to accumulate with the fewest revolutions must be a bad lubricant. This tabular method of keeping an account of experiments has been found useful. The machine is stopped when the thermometer indicates 200 degrees, as it is considered that an oil has not much lubricating power left if it permits that heat. ------------+--------+--------------+--------------+------------------ Name of oil.| Price. |Revolutions to| Temperature |No. of revolutions | |200 degrees F.|of atmosphere.| to each degree. ------------+--------+--------------+--------------+------------------ | | | | ------------+--------+--------------+--------------+------------------ "When testing with this machine a definite quantity of oil should be placed on the friction roller, the top step being removed for that purpose; the quantity should be about five drops. A glass tube or small tin measure should be used, as drops vary in size according to the temperature of the oil, and also differ with the specific gravity. The inventor of this machine is Mr. Heinrich Stapfer. I believe he may be considered the inventor of the first instrument for testing oils by destroying them by friction under the actual conditions in which oils are used as lubricants. In using this machine I found that, although it was supposed to test lubricants in the way in which they are used in manufactories, a slight difference existed, which prevented accurate results. [Illustration: Fig. 2495.] [Illustration: Fig. 2496.] [Illustration: Fig. 2497.] "BEHAVIOR OF THIN OILS.--The first machines were made with the brass steps lipped or recessed, to prevent the oil running away, (see Fig. 2496), which, when thus tested, gave results very much different to those which are accepted by those who are familiar with the use of lubricants. For instance, some thin mineral oils were found to be quite as valuable as, and in some cases superior to, sperm; and this was caused by the lips on the sides, which prevented the oil from running off the bearing when an increased fluidity was caused by friction, and by any slight elevation of temperature. This is a very important quality in lubricating oils, probably next to the capacity to resist oxidation, the most important to be criticised by those who wish to value a lubricant. Although this experiment points out to us that it may be advisable to make the journals of heavy bearings similar to these, if we wish to obtain the best results from cheap thin oils, yet, as oil should be criticised and prepared to be used on bearings with parallel necks, such as are used in works, it was considered proper to alter the tester to that shape to make the conditions similar. This illustration (see Fig. 2497) permits the oil when tested to run away from the bearing if its increased fluidity gives it a tendency to do so. It is this severe test which has enabled sperm oil to rise superior to all rivals, because it has these two apparently opposite attributes--body or thickness, which keep it on its bearing, combined with sufficient fluidity for lubricating purposes. Permit me further to illustrate what I mean in another manner. Suppose we take an oil, good as a lubricant in all other respects, and place it on a bearing, and that 40 per cent. works quickly away because of its extra fluidity when subjected to an increase of frictional temperature, and then compare it with another oil under similar conditions which only wastes, say, 5 per cent. This latter will be 35 per cent. superior as an oil having body, and even if slightly inferior as a lubricant, it may be the most valuable, because strong in this one great quality of remaining at its duty when placed in position. Still another illustration will inform us that in the one case we obtain, say, 60 gallons of lubricating material out of every 100 purchased, and in the other we obtain 95 gallons. [Illustration: Fig. 2498.] "THE BEST METHODS OF USING THIN OILS.--This will show us that oils which are deficient in body, but which are good in other respects, may be used with good results if doled out in small quantities, as required, by automatic oil-cups like the Lieuvain needle lubricator, Fig. 2498, or any other means. Journals which cannot be fed by means of automatic oil-cups in positions difficult of access should be fed with oil which has a good body. If time permitted, much might be said of the proper shape for bearings of machinery--a subject which would lead to valuable results if discussed by the members of this Society, many of whom must have great experience of those designs which have produced the best results, as well as of those mixtures of metals which are the most durable for light high speed and heavy slow shafting. If any member will take up this subject, or if several members will read short notes, giving their actual experience of different sorts of footsteps, pedestals, and spindles, as well as of the use of different sorts of oil-cups and lubricators, it will be highly advantageous knowledge, which must be of great value to all who use machinery. [Illustration: _VOL. II._ =OIL-TESTING MACHINE.= _PLATE X._ Fig. 2501. Fig. 2502.] "FLUIDITY OF OILS.--Continuing my remarks on the thinness or fluidity of oils, I wish to call attention to an ingenious arrangement for testing the fluidity when subject to a slight increase of temperature, and also for detecting any tendency which they may have for combining with the oxygen of the atmosphere; this latter quality being advantageous in oils which are used to mix with paint, but which is a great evil when used for lubricating purposes. A piece of plate-glass placed at an angle is made warm to 200° Fahr. A drop of oil when placed on the upper end of this glass will flow down a few inches and thus indicate its fluidity when subjected to increase of temperature. Fig. 2499 shows a ready method I have designed for testing oil in this way. It consists of a tin box in which is fixed the glass, through which can be seen a thermometer. A graduated scale at the side of the box enables the track of the oil to be measured. The box has a door at the back which enables a copper vessel full of boiling water to be introduced; the box is lined with felt to prevent rapid radiation, and when the door is closed it will be seen that several experiments may be conducted before the apparatus becomes too cool for use. I think this a cleaner way than using a lamp for the purpose. The copper may also be used by itself for indicating the behavior of oil on copper when slightly warm in making it discolored or otherwise. As I have before stated, there are many oils which are good lubricants, but which become too thin when exposed to slight heat, and I do not hesitate to reiterate the statement, as I wish to have some influence on the future designs of bearing in this district. A correspondent writing to _Engineer_ from Queensland says that for six months in the year oil runs off the machinery like water and seems to have no lubricating power; he says that the thermometer registers in the summer 140° in the sun, and 110° in the shade. Great difficulty seems to have been experienced by him in keeping oil on the bearings; his experiments on locomotives show that it costs for lubricating a locomotive there about a halfpenny to three farthings a mile, according to the mixture used. [Illustration: Fig. 2499.] "INFLUENCE OF THE ATMOSPHERE ON OILS.--There are some oils which are excellent lubricants for the first few hours of use, but which have a low capacity for resisting the influence of the oxygen of the atmosphere upon them. The warm glass test may be used for indicating this weakness. If after the test for fluidity the oil be permitted to remain on the glass any exhibition of a resinous or varnish quality may be observed. Another test for this resinous or gummy quality is one which has been suggested to me by Mr. F. R. Wheeldon, of Bilston. He has made many experiments. He found that by permitting oil to remain on a Stapfer friction tester after one test which had been recorded, he tested again on the following day, without adding any fresh oil. This is a severe test, as the thermometer was made to indicate 200° Fahr. each time. [Illustration: Fig. 2500.] "LONGEVITY OF LUBRICANTS.--Supposing an oil to possess all the qualities which we think a good lubricant should have--that it has fluidity in season, and that it does not combine with the atmosphere and become varnish, that it does not become like water in summer and like mutton suet in winter, and is in most respects satisfactory. We then want to know its powers of endurance, its capacity to resist wear and tear--in other words, its longevity. A good test for longevity or durability of oil when subject to either heavy or light frictional pressure is one suggested by Mr. W. H. Hatcher, a very careful investigator, and chief of the Laboratory of Price's Patent Candle Company, who are extensive oil manufacturers. It consists in taking away the bottom step of the Stapfer tester and placing a small dish containing oil underneath the friction roller (as in Fig. 2500). This oil is carefully weighed before and after several hours' frictional wear and tear. The drawing (Fig. 2501) shows the application of this mode, which I have designed, for testing solid lubricants, such as lard and sulphur and other railway and steamship mixtures. It will be seen that the material is kept to its duty by the weighted lever, and its progress of diminution can be tested in its place by the scale-beam arrangement. When it is used with the pressure on the top step it is advisable to drive it at about 2,000 revolutions per minute; otherwise much time will be occupied in destroying a weighable quantity of oil. The large Stapfer tester (Fig. 2502) was designed a few months ago for this purpose for the Government railways of New South Wales, and it is also used by the Manchester, Sheffield, and Lincolnshire, the Lancashire and Yorkshire, and other railways. I have not been able to get any results of these tests in time for our subject on this occasion, but hope to do so at some future time. The frictional roller is 6 inches in diameter, the pressure amounts to 1 cwt. on each step. As it takes a considerable time to wear away half a pound of solid lubricant, it may be advisable to measure by minutes instead of using the speed index. The speed should be at least 1,500 revolutions per minute. The Stapfer tester should be used in a room of equal temperature, and should not be subject to draughts of cold air, as it will be obvious these will interfere with the indications of the thermometer. A recent alteration in the Stapfer tester permits the quantity of oil used for testing to be measured with greater accuracy than before. A small oil-hole is made in the top step (see Fig. 2502 at _a_ and at _c_) in which is placed a glass tube. This only holds a few drops, and can be filled by simply dropping the oil in, holding the finger at the bottom to prevent it running away, and then place it in the hole. If a small needle lubricator be weighed and then filled with oil of a definite weight, and placed in this hole (see Fig. 2502 at _b_), oil may be tested for longevity and for its anti-frictional properties for a longer period than with the small tube. If oil be placed in this at the same time that oil is placed in the lubricators in the works and the oil tester be driven from the same shafting, permitting it to stop and start when the engine stops and starts, the effect of a week's work upon the weight of the oil may be seen; notice should be taken of the difference of the temperature between the thermometer on the instrument and the temperature of the atmosphere of the workshop. "TESTING FOR SALTS AND ACIDS, ETC.--It will be obvious that however good as a lubricant an oil is, and however valuable its properties may be when examined, if it possesses any corrosive quality which will be injurious to the metals upon which it is placed, it will soon become detrimental to the machinery, and may also cease to be valuable as a lubricant. Mr. William Thomson, analytical chemist, of Manchester, read a paper on this subject at the British Association at Glasgow, and he stated the results of elaborate experiments conducted by him to discover the influence of various oils of commerce upon bright strips of copper. He permitted the copper strips to remain entirely covered by oil. He also conducted similar tests with half of the strip below the surface of the oil, and the other half exposed to the atmosphere, in order to see what influence the oil had, when the surface line touching the metal would, of course, be acted on by the atmosphere. After noticing the effect upon the brightness or dulness of the copper, he carefully tested the oils in order to detect the quantity of metal which had been dissolved. Mr. Thomson found the following oils dissolved the largest proportions of copper, leaving the surfaces of the copper slips bright--rape, linseed, sperm, raw cod-liver, Newfoundland cod, and common seal oils; and that the following dissolved much smaller proportions of copper, also leaving the slips bright--seal, whale, cod, shark, and East Indian fish oils; and that mineral oils seem to have no dissolving power on the copper, the only effect being a slight discoloration on the copper slip of a greyish color. "SWISS WATCHMAKERS' TEST FOR FLUIDITY AND CAPACITY TO RESIST COLD.--It seems, according to the _Watchmaker and Jeweller_ (a monthly trade journal), that the plan I have described, and what may be called the warm glass test, seems to be looked upon with favor for testing oil in Switzerland. The degree of heat used for testing the fluidity of oil is 200° Fahr., and if this causes the oil to become a varnish two or three days after the test the oil is considered unfit for use. Another test is one to which I have not alluded, and that is, capacity to resist low temperatures. Oils are tried for their capability to withstand low temperature in the following manner: Fifteen parts of Glauber salts are put into a small glass vessel, a small bottle of oil to be tested is immersed into this; this done, a mixture of five parts of muriatic acid and five parts of cold water is placed over the salt. By means of a thermometer the temperature is indicated, and when it shows a very low temperature, the behavior of the oil, subject to this freezing mixture, may be observed and noted. Mr. Thomson, however, considers that this mixture is not so good or so cheap as ice alone, or a mixture of ice and common salt. "BLOTTING-PAPER TEST.--It seems it is considered that the blotting-paper test for fluidity is more reliable, according to the writer of the article, than the inclined plane experiment. In order to use this test we must saturate the strip of blotting-paper with oil, and watch whether the drops fall off in pearls or have an inclination to spread out. The latter is a certain sign, the writer says, of a viscid oil. Although this may be considered viscid oil, and may not be valuable for watches, it may, however, be a good oil for heavier machinery." The amount of friction between a journal and its bearing varies with the kind of metal of which the journal and bearing are composed; on the area of surface in contact in proportion to the load or pressure sustained by the bearing surfaces; on the nature or degree of the lubrication afforded; on the diameter of the journal in proportion to its length; on the manner in which the journal fits or beds to its bearing, and on the kind of motion, as whether the same be continuous, intermittent, rotatory, or reciprocating. Referring to the friction as influenced by the nature of the metals in contact: the friction varies with the hardness of the metal; thus, with hard cast iron, there will, under equal conditions, be less friction than with soft cast iron. The friction is greater when the surfaces in contact are both of the same metal than when they are of different metals. Mr. Rankine summarizes General Morin's experiments on the friction of various bodies not lubricated as follows:-- GENERAL MORIN'S EXPERIMENTS ON FRICTION. --------------------------------------+----------------+------------ | Angle of |Friction in Surfaces. | repose. |terms of the | | weight. --------------------------------------+----------------+------------ | degrees. | Wood on wood, dry |14 to 26-1/2|.25 to .5 " " soaped |11-1/2 " 2 |.2 " .04 Metals on oak, dry |26-1/2 " 31 |.5 " .6 " " wet |13-1/2 " 14-1/2|.24 " .26 " " soapy |11-1/2 |.2 " elm, dry |11-1/2 " 14 |.2 " .25 Hemp on oak, dry |28 |.53 " " wet |18-1/2 |.33 Leather on oak |15 " 19-1/2|.27 " .38 " metals, dry |29-1/2 |.56 " " wet |20 |.36 " " greasy |13 |.23 " " oily | 8-1/2 |.15 Metals on metals, dry | 8-1/2 " 11-1/2|.15 " .2 " " wet |16-1/2 |.3 Smooth metal surfaces occasionally | 4 " 4-1/2|.07 " .08 greased | | " " " continuously | 3 |.05 greased | | " " " best results | 1-3/4 " 2 |.03 " .036 Bronze on lignum-vitæ, constantly wet | 3(?) |.05(?) --------------------------------------+----------------+------------ "The 'angle of repose' given in the first column is the angle which a flat surface will make with the horizon when a weight placed upon it just ceases to move by gravity. The column of 'friction in terms of the weight' means the proportion of the weight which must be employed to draw the body by a string in order to overcome its friction, and the proportionate weight is sometimes called the _coefficient of friction_."[34] [34] From Bourne's "Handbook of the Steam Engine." In the following table are given some of the results obtained from Morin's experiments with unguents interposed. ------------------------------+-----------------+--------------------- Nature of surfaces in contact.| Coefficient of | | friction during | Kind of | motion. | unguent. ------------------------------+-----------------+--------------------- Brass upon brass | .058 | Olive oil. Cast iron upon brass | .078 | " " " " cast iron | .314 | Water. Steel upon cast iron | .079 | Olive oil. " " brass | .056 | Tallow or olive oil. Wrought iron upon brass | .103 | Tallow. " " " cast iron | .066 | Olive oil. " " " wrought iron| .136 | " ------------------------------+-----------------+--------------------- Morin's experiments demonstrated that friction is always proportional to the pressure and independent of the area pressed in contact, providing that the pressure is not so great as to cause the surfaces to abrade in the manner or to the degree commonly known as cutting, which occurs when the area of bearing surface in proportion to the pressure is so small as to press out the lubricating material. Now, between the degree of abrasion that is sufficient to cause a bearing to heat and the minimum, possibly lies a wide range that is very difficult of classification, and that influences the friction of the bearing and journal. Under any given dimensions of journal area and any given pressure of the same to its bearing, the abrasion, and, therefore, the friction, will be less in proportion as the fit of the journal to its bearing extends over its whole area and with an equal pressure of contact. Under these conditions, and with a bearing area ample for the given pressure, the surfaces of a journal and bearing have a smooth, glossy appearance, with a surface as glossy as plate-glass. This degree of perfection, however, is only occasionally reached in practice, because of imperfections in the fitting and lubrication. Now, between this condition of glossy smoothness and the degree of abrasion known to practical men as _cutting_ lies, as already stated, a wide range of degrees of abrasion, and each of these has its own coefficient of friction. This may be readily proved by freely lubricating the bearings of a number of journals working under the usual conditions of practice and smearing the oil just as it passes through the bearings upon a sheet of white note paper, when it will be found to contain fine particles of metal, the number and size of particles in a given quantity of the oil decreasing as the surfaces of the bearings are glossy, and increasing as those surfaces appear dull. The order of value to resist wear is generally considered in practice to be as follows:-- 1st in value, hardened steel running on hardened steel. 2nd (and by some considered equal to the first when the pressure per square inch of area is light), cast iron either upon cast iron, hardened wrought iron, or hardened steel. 3rd, under light duty cast iron upon wrought iron or steel not hardened. 4th, wrought iron upon hard composition or brass. 5th, wrought iron upon some anti-friction metal, as Babbitt metal. Cast iron appears to be an exception to the general rule, that the harder the metal the greater the resistance to wear, because cast iron is softer in its texture and easier to cut with steel tools than steel or wrought iron, but in some situations it is far more durable than hardened steel; thus when surrounded by steam it will wear better than will any other metal. Thus, for instance, experience has demonstrated that piston-rings of cast iron will wear smoother, better, and equally as long as those of steel, and longer than those of either wrought iron or brass, whether the cylinder in which it works be composed of brass, steel, wrought iron, or cast iron--the latter being the more noteworthy, since two surfaces of the same metal do not, as a rule, wear or work well together. So also slide-valves of brass are not found to wear so long or so smoothly as those of cast iron, let the metal of which the seating is composed be whatever it may; while, on the other hand, a cast-iron slide-valve will wear longer of itself, and cause less wear to its seat, if the latter is of cast iron, than if of steel, wrought iron, or brass. The duty in each of these cases is light; the pressure on the cast iron, in the first instance cited, probably never exceeding a pressure of ten pounds per inch, while in the latter case two hundred pounds per square inch of area is probably the extreme limit under which slide-valves work; and what the result under much heavier pressures would be is entirely problematical. Cast iron in bearings or boxes is found to work exceedingly smoothly and well under light duty, provided the lubrication is perfect and the surfaces can be kept practically free from grit and dust. The reason of this is that cast iron forms a hard surface skin when rubbed under a light pressure, and so long as the pressure is not sufficient to abrade this hard skin, it will wear bright and very smooth, becoming so hard that a sharp file or a scraper made as hard as fire and water will make it will scarcely cut the skin referred to. Thus in making cast-iron and wrought-iron surface plates or planometers, we may rub two such plates of cast iron together under moderate pressure for an indefinite length of time, and the tops of the scraper marks will become bright and smooth, but will not wear off; while if we rub one of cast iron and one of wrought iron, or two of wrought iron, well together, the wrought-iron surfaces will abrade so that the protruding scraper marks will entirely disappear, while the slight amount of lubrication placed between such surfaces to prevent them from cutting will become, in consequence of the presence of the wrought iron, thick and of a dark blue color, and will cling to the surfaces, so that after a time it becomes difficult to move the one surface upon the other. If, however, the surfaces are pressed together sufficiently to abrade the hard skin from the cast iron, a rapid cutting immediately takes place, which is very difficult to remove. To obtain the best results from cast-iron bearings the bedding of the journal to the bearing must be full and perfect, and the surfaces bright and smooth, in which case it will wear better than hardened steel, unless it be very heavily loaded. Again, a cast-iron surface will hold the lubricating oil better than either steel, wrought iron, or brass of any kind. Indeed, if a cast-iron surface be made very true and smooth so that it is polished and no marks are visible upon its surface, it will take _much patient_ rubbing and cleaning with a _dry clean rag_ to remove the oil entirely, whereas other metals will clean comparatively easy. In testing this matter upon surface plates the author has found that the only safe method, and by far the quickest, of removing the oil from cast iron is an application of alcohol or spirits of turpentine, because the oil will enter and to some extent soak into the pores of cast iron and gradually work out again as it is continuously wiped, so that if apparently quite clean (after having been oiled and wiped) a short period of rest will cause oil to again be present to some extent upon the surface. As a general rule motion in a continuous direction causes more wear under equal conditions than does a reciprocating one, because when a revolving surface commences to abrade, the particles of metal being cut are forced into and add themselves, in a great measure, to the particles performing the cutting, increasing its size and the strain of contact of the surfaces, causing them to cut deeper and deeper until at least an entire revolution has been made, when the severed particles of metal release themselves, and are for the most part forced into the grooves made by the cutting. In reciprocating surfaces, when any part commences to cut, the edge of the protruding cutting part is abraded by the return stroke; which fact is clearly demonstrated in either fitting or grinding in the plugs of cocks, in which operation it is found absolutely necessary to revolve the plugs back and forth, to prevent the cutting which inevitably and invariably takes place if the plug is revolved in a continuous direction. Furthermore, when a surface revolves in a continuous direction, any grit that may lodge in a speck, hollow spot, or soft place in the metal, will cut a groove and not easily work its way out, as is demonstrated in polishing work in a lathe; for be the polishing material as fine as it may, it will not polish so smoothly unless kept in rapid motion back and forth. Grain emery used upon a side face, such as the radial face of a cylinder cover, will lodge in any small hollow spots in the metal and cut grooves, unless the polishing stick be moved rapidly back and forth between the centre and the outer diameter. If a revolving surface abrades so much as to seize and come to a standstill, it will be found very difficult to force it forward, while it will be comparatively easy to move it backward, which will not only release the particles of metal already severed from the main body, and permit them to lodge in the grooves due to the cutting, but will also dislodge the projecting particles which are performing the cutting, so that a few reciprocating movements and ample lubrication will, in most cases, stop the cutting and wash out the particles already cut from the surfaces of the metal. In determining the metals to be used for a journal and bearing it is preferable to use the softer metal, or that which will wear the most, in the position in which it can be the most easily and cheaply replaced, which is usually in the bearing rather than in the journal; and since two metals of a different kind run better together than two of the same kind, the bearing is usually of a different kind of metal from that composing the journal. It may be stated, however, that under _light duty_ cast iron will wear upon cast iron better than wrought iron or brass upon cast iron (for reasons which have already been stated), especially if the bearing area be broad and the lubrication ample and perfect. To facilitate the removal of the bearings, brasses or boxes are provided, but in the case of small journals, as, say, of about 3 inches and less in diameter, the duty being light, the lubrication ample and equally distributed, and the journals an easy working fit when new, it is found that solid cast-iron boxes will last for a great length of time without sensible wear. In some cases cast-iron boxes are cast with a receptacle for some soft metal, such as the various compound metals known under the general name of Babbitt metal. Babbitt metal is composed of tin, antimony, and copper, mixed in varying proportions. A good mixture for general use where the duty is light is composed of 50 parts tin, 5 parts antimony, and 1 part copper. A harder composition, sometimes termed white metal, is composed of tin 96 parts, copper 4 parts, and antimony 8 parts. This mixture is especially suitable for journal boxes or bearings. It is mixed as follows: Twelve parts of copper are first melted, and then 36 parts of tin are added; 24 parts of antimony are put in, and then 36 parts of tin, the temperature being lowered as soon as the copper is melted in order not to oxidize the tin and antimony; the surface of the bath being protected from contact with the air. The alloy thus made is subsequently remelted in the proportion of 50 parts of alloy to 100 tin. For brass bearings or boxes a mixture of 64 parts copper, 8 parts tin, and 1 part zinc is found to answer well; but for bearings not requiring so hard a metal, the quantity of zinc is increased, and that of the tin diminished. [Illustration: Fig. 2503.] Bearings or boxes that are to be babbitted are usually cast as in Fig. 2503, there being a rib at A, B, and C, forming a cavity at D, into which the melted metal is poured. The ribs (in new boxes) are sometimes bored out, or for rougher work may be chipped and filed out to fit the shaft, and hold it in line; and to prevent the ribs A, B, &c., from bearing and cutting the shaft, a piece of pasteboard is laid on ribs A and B, thus confining the journal bearing to the babbitt. The best method is to pour the bearing and then rivet the babbitt well into the cavity D, which is made wider at the bottom, to prevent the babbitt from coming loose, and then bore out the bearing in the usual manner. The principal advantage of a babbitted bearing is the ease with which it can be renewed, and the fact that the metal will soon bed itself to the journal. This is of great advantage in the case of solid bearings in the framing of fast-running machines, and in situations where it would be awkward or difficult to take brasses or bushes out to fit them, or align them to the shaft, which in many cases would also require to be taken out to remove the brasses. On the other hand, any particles of grit that may find ingress to babbitted boxes are apt to become bedded into the babbitt metal and cut or grind away the journal. Since the babbitt metal in a bearing is apt to close across the bore when cooling after being poured, a mandrel of slightly larger diameter than the diameter of the journal should be used in place of the working journal to run the bearing on. Some effect the same purpose by wrapping writing paper around the journal; but it is wrong to use the journal, for the following reasons: To get a good, sound, well-fitting babbitt metal box, the metal should be poured as cool as possible, for if made red hot it contracts so much in cooling that it does not fit well in the box or frame of the machine. On the other hand unless the metal be well hot it is apt to cool and set too soon and be unsound. To remedy this the journal, or whatever represents it, must be heated. The heating is very apt to bend it. It is obvious then that instead of the journal a temporary bar of iron of slightly larger diameter than the working journal should be used, heating it to a good black hot heat, so that the babbitt metal may be poured less hot than would otherwise be permissible, and the contraction of the babbitt in the box reduced to a minimum. A little powdered resin sprinkled in the box will help the babbitt to flow easily and make a sound casting. The temporary spindle, or journal, should also be oiled, and as soon as the metal has well set, the temporary journal should be revolved to free it. Babbitt bearings cast in two halves should be fitted to the journal as already described for brasses, which will well repay the cost and trouble. To prevent the metal from running out of the bearing, its ends are closed by means of either clay or putty closely packed against the bearing ends and the shaft, and in pouring in the melted metal it is best to pour it on the top of the shaft, and let it run down its sides into the cavity of the bearing. This heats the shaft equally, and prevents it bending from unequal expansion, as it would do if it met the heated metal on its lower half only, it being obvious that if the shaft bends the bore of the bearing will not be cast in line; hence, the shaft will bear at the end only, and will require to wear the babbitt down to a bearing. Babbitting is sometimes employed to refit parts that have worn loose, or to bush the bores of work. Suppose, for example, that in a case of emergency a pulley of a certain diameter is required, and that the only one at hand has too large a bore, then we may take a mandrel or arbor of the diameter of the shaft the pulley is required for, and drive on it two thin washers and turn them to fit the bore of the pulley, and cut a recess in each to enable the metal to be poured through. We may then put the arbor and washers in the pulley (the washers serving to hold the arbor true), and fill in the bore with babbitt metal, leaving the pulley set-screw in place and set to just touch the arbor, so as to cast the thread in the babbitt bushing, and thus save drilling and tapping. PROPORTIONS OF JOURNALS.--It follows from what has been already said that under a given amount of duty the friction will be less and the durability greater in proportion as the bearing area of a journal is increased. But it is an important consideration whether such area shall be obtained in the diameter or in the length of the journal, or, in other words, what shall be the proportions between the diameter and length of a journal. It is found in practice that a journal wears better in proportion as its length exceeds its diameter, providing that the stress is not sufficient to cause sensible flexure, because in that case the pressure is reduced at that part of the journal where the most flexure occurs, and increased where the journal is most rigid. As a result, the abrasion increasing with the pressure becomes locally excessive, the glossy smoothness is lost and increased friction ensues. If, however, the length of a journal is limited by the exigencies of its location or the design of the machine, the diameter of journal must be increased if necessary in order to obtain sufficient bearing area to withstand the stress without causing undue abrasion. Referring to the bearing area in proportion to the load, Prof. R. H. Thurston writes, in an article in the _Railroad Gazette_ of January 18th, 1878, as follows:-- "A pressure of 800 pounds to the square inch can rarely be attained on wrought iron at even low speeds, while 1,200 pounds is not infrequently adopted on the steel crank-pins of steamboat engines. I have known of several thousand pounds pressure per inch being reached on the slow-working and rarely moved pivots of swing bridges. In my own practice, I never, if I can avoid it, use higher pressures than 600 and 1,000 on iron and on steel, and, for general practice, make the pressure less as the speed is greater." W. Sellers and Co. state that under a pressure of 50 lbs. per square inch, and with oil well distributed over the surface of the box, the metal of the journal will not touch that of the bearing box bore. In practice bearings are made with a length varying from that equal to the diameter of the journal to about four times that diameter, and but few cases occur in which these limits are exceeded in either direction. It is to be observed, however, that diminishing the length is apt to increase the abrasion unless the duty is very light indeed, while increasing it increases the durability while not affecting the friction, unless the shaft bends. There are special cases in which within certain limits the proportions of journals are nearly uniform in practice; thus the length of engine crank-pin bearings rarely exceeds once and a half times the diameter, while the main shaft bearings are often similarly limited in width from the exigencies of designing the engine so that the eccentric shall come in line with the slide-valve spindle. In the case of crank-pins the pin cannot be held sufficiently rigidly to prevent spring or flexure; hence it is desirable to limit its length so that its pressure shall be as short a leverage as possible to the crank. The solid bearings in the framing of machines usually admit of room enough to make their lengths three or four times the diameter. Again, in the case of line shafting, boxes having a length equal to three or four times the diameter may be employed, providing that the alignment be made correct, or that the boxes are self-adjusting. But in all cases the longer the bearings the greater the necessity for correct alignment, so that the axis of the bearing bore may be in line with the axis of the shaft, the error manifestly increasing with the length of the bearing. PLACING TWO CRANKS ON A SHAFT SO THAT THEIR CENTRE LINES SHALL STAND AT A RIGHT ANGLE.--It is obvious that the keyways in both the crank and the shaft must be cut accurately in their proper positions, because it is a tedious operation to file out the sides of the keyways when the cranks are placed upon the shaft. To mark the keyways in the absence of any tools or appliances specially designed for the purpose we proceed as follows: Placing the shaft upon a marking-off table, we plug up the centres upon which the shaft has been turned by driving a piece of lead in them, leaving the surface level with those of the shaft; and then from the perimeter of the shaft we carefully mark, upon the lead plugs, the centres of the shaft. From this centre we describe a circle whose diameter will be equal to the required widths of the keyway, and then taking a square we place its stock upon the face of the marking-table, and bringing the edge of the blade even with the edge of the circle, we mark a perpendicular line upwards from the circle to the perimeter of the shaft, and then draw a similar line on the other side of the circle, as shown in Fig. 2504, in which A represents the shaft and B the circle, C the perpendicular line struck on one side of the circle, and D the square placed upon the marking-table E, in position to mark the line on the other side of the circle, F and G being wedges to keep the shaft A from moving its position upon the table. We next mark with a scribing-block or surface gauge the depth of the keyway as denoted by the line H, and the marking at that end of the shaft is completed. Passing to the other end of the shaft we find the centre of the shaft, and describe around it a circle equal in diameter to the required width of keyway, and from the edges of the circle to the perimeter of the shaft draw two lines with a scribing-block, as shown in Fig. 2505, A representing the shaft, B the circle, C D the breadth of the keyway, E the marking-off table, F and G the wedges, and H the depth of the keyway, which must, in this case, be marked with a square resting on the table. [Illustration: Fig. 2504.] [Illustration: Fig. 2505.] If, however, the shaft is too heavy or large to be placed on a marking-off table, we may proceed as follows: Strike as before the circle B, Fig. 2504, equal in diameter to the required width of keyway, and adjust a straight-edge held firmly against the end face of the shaft, so that its upper edge is coincident with the perimeter of this circle, while the straight is horizontally level-tested by a spirit-level. Draw a line along the shaft face, using the straight-edge as a guide. This will give us the line C in Fig. 2505. By a similar process the line D, Fig. 2505, may be drawn. At the other end of the shaft similar lines, but standing vertical, may be marked, which will give the positions of the keyways. [Illustration: Fig. 2506.] We have now marked off on the end faces of the shaft a keyway at each end, one standing at a right angle to the other; but it must be borne in mind that we have paid no attention as to which crank shall lead; that is to say, suppose in Fig. 2506 A and B represent cranks placed upon the shaft C, and running in the direction indicated by arrow D, it is evident that the crank B leads in the direction in which the engine is to run, and hence the keyway E stands in advance of the keyway F; and therefore, as shown in the figure, the right-hand crank leads. To have made the left-hand crank lead, when the engine runs in the direction of the arrow D, we should, supposing the keyway F to be already cut, have to cut the keyway E on the directly opposite side of the shaft; or, what is the same thing, supposing the keyway E to be already cut, the keyway F would require to be cut on the diametrally opposite side of the shaft. It is obvious that if the engine ran in the direction of the arrow G, the left-hand crank would lead, supposing in each case the cylinders to stand at H. Here it may be necessary to explain the manner of determining which is the right-hand and which the left-hand crank. Suppose then that the figure represents a locomotive crank, the cylinders being at H, then as the engineer stands in the cab, facing his engine, A will be the left-hand and B the right-hand crank. It is usual in locomotives to make the left-hand crank lead when the engine is running forward, the practical difference being, that if the workman were by mistake to make the right-hand crank lead, the engine would run forward when the reversing lever was placed to run backward, and _vice versâ_. It makes no difference whether the shaft can be turned end for end or not: if the right or left crank is required to lead when the crank is required to revolve in a given direction the keyways in the shaft must be marked off in the relative positions on the shaft necessary to obtain that result. The keyways may be carried along the circumference of the shaft by a square applied to its end face, or if that face is not flat by the ordinary keyway marking tool. [Illustration: Fig. 2507.] To mark off the keyways in the cranks, we place a centre-piece in the bore of the crank, as shown in Fig. 2507, in which A represents a crank having a centre-piece of sheet iron B placed in the bore. On the face of this centre-piece we mark the centre of the hole into which it fits, and from that centre we describe the circle C, which must be of exactly same diameter as the crank-pin if it is in its place, or otherwise of the crank-pin hole. We then draw the lines D and E, using as a guide a straight-edge placed one end upon the crank-pin journal, or even with the edge of the crank-pin hole, as the case may be, and the other end (of the same edge of the straight-edge) exactly even with the circumference of the circle C. From D and E we find the centre of the circle F, which must be central between D and E, and whose diameter must be exactly equal to the required width of keyway; and we then mark the circle G, describing it from the centre of the hole, and therefore of the circle C. By drawing the lines H and I, which must be even with the circumference of the circles F and G, using a straight-edge as a guide, we shall obtain the correct position for the keyway K, and the whole of the keyways may be cut, care being taken to cut them quite true with the lines, and of an exact equal width. To put the cranks on the shaft, first provide a temporary key, a close fit on the sides, but clear top and bottom, so that it will bind just easily on the sides of the keyways in both the shaft and the crank. The shaft must be placed and wedged with its keyway downwards, so that in putting the crank on, the pin end may hang downwards, which will render it more easy both to put on, handle, and adjust. As soon as the shaft has entered the crank, say a quarter of an inch, we must insert the temporary key (which may have its end edges well tapered off to assist the operation of entering it) sufficiently far into the keyway of the shaft that it will not fall out, and we may then proceed to put the crank on the shaft to the necessary distance, keeping the temporary key sufficiently far in the keyway to enable it to act as a guide--that is to say, up to at least half the length of the keyway. [Illustration: Fig. 2508.] [Illustration: Fig. 2509.] To put on the second crank, we first place the shaft so that the crank already on stands exactly horizontal, setting it by placing a spirit-level, as shown in Fig. 2508, in which A represents either the crank-pin journal or the crank-pin hole in the crank, and B a circle struck on the end face of the shaft and from its centre, the diameter of the circle B being exactly the same as that of A. If then we so adjust the position of the crank that a spirit-level applied to the exact circumferences of the circles A and B stands level, the crank will stand level, and we have only to put the second crank on with its centre-line standing perpendicular, and the two cranks will be at a right angle one to the other. We now proceed to put on the second crank, pursuing the same method employed in putting on the first one, save that the temporary key need not be inserted so far into the keyway, because, if the keyways have been cut the least out of true, it will make a great difference at the crank-pin, because of the increased distance of the latter from the centre of the crank-shaft. As soon as the second crank is placed to its position on the shaft we must ascertain if it stands vertical, which we may do by applying the spirit-level as shown in Fig. 2509, bringing its edges exactly fair with the edges of the circles A and B, and moving the crank until the bubble of the level stands true, and taking out the temporary key if it is necessary to adjust the crank at all. If, however, the crank is to be forced on by hydraulic pressure, this latter adjustment should be made when the crank is just sufficiently far on the crank shaft to enable it to bind enough to well support its own weight, to facilitate which the end of the shaft is sometimes slightly tapered for a very short distance--a practice which is sometimes rendered unnecessary by reason of there being attachments fitted to the hydraulic presses which of themselves adjust the position of the cranks, and insure their being at a right angle one to the other. After the cranks are on their places the keys may be fitted, care being taken that, if the crank last put on had to be moved to adjust it, the sides of the keyways be filed even, otherwise driving the key will tend to move the crank. FITTING ENGINE CYLINDERS.[35]--When engine cylinders are made in quantities, as in locomotive building shops, a great deal of the fitting work is saved by the machine work; but when a single cylinder or a pair of cylinders only are to be fitted up it will not pay to make jigs and appliances; hence, they are usually fitted up entirely by hand. The first thing to do is to mark off all the holes requiring to be drilled, and have the drilling done. [35] From the "Complete Practical Machinist." In marking the holes in the cylinder covers it is to be noted whether that part of the cylinder cover which fits into the cylinder has a portion cut away to give room for the steam to enter (as is usually the case), and if so, first mark a line across the inside flange of the cover, parallel to the part cut away, and then scribe each end of the line across the edge of the flange. Then mark a similar line across the cylinder end, parallel to the steam port where it enters the cylinder, and scribe each end of this line across the cylinder flange, so that, when the cylinder cover is placed into the cylinder and the lines on the flanges of the cylinder and the cover are placed parallel to each other, the piece cut away on the cover will stand exactly opposite to the steam port, as it is intended to do. The cover may then be clamped to the cylinder, and holes of the requisite size for the tap (the tapping holes, as they are commonly called) may be drilled through the cover and the requisite depth into the cylinder at the same time. [Illustration: Fig. 2510.] The cylinder covers must, after being drilled, as above, be taken from the cylinder, and the clearing drill put through the holes already drilled so that they will admit the bolts or studs, the clearing holes being made 1/16 inch larger than the diameter of the bolts or studs. The steam chest may be either clamped to the cylinder, and tapping holes drilled through it and the cylinder (the same as done in the case of the covers), or it may have its clearing holes drilled in it while so clamped, care being taken to let the point of the drill enter deep enough to pass completely through the steam chest, and into the cylinder deep enough to cut or drill a countersink nearly or quite equal to the diameter of the drill. If, however, the steam chest is already drilled, it may be set upon the cylinder, and the holes marked on the cylinder face by a scriber or by the end of a piece of wood or of a bolt, which end may be made either conical or flat for the purpose, marking being placed upon it; so that, by putting it through the hole of the chest, permitting it to rest upon the cylinder face (which may be chalked so as to show the marks plainly), and then revolving it with the hand, it will mark the cylinder face. This plan is generally resorted to when the holes in the chest are too deep to permit of being scribed. To true the back face, round a hole against which face the bolt head or the face of the nut may bed, in cases where such facing cannot be done by a pin countersink or a cutter used in a machine, the tool shown in Fig. 2510 may be employed, _a_ being a pin provided with a slot at one end to admit the cutter B, which is held fast by the key C, and is also provided with a square end _f_, by which it may be turned or revolved by means of a wrench, and with a thread to receive the nut E, _d_ being a washer; so that, by screwing up the nut E, the cutting-edges of the cutter are forced against the cylinder _g_, and will, when revolved, cut the face, against which they are forced, true with the hole in the cylinder through which the pin _a_ is passed. After the drilling the cylinder should be placed on end and all the holes that can be got at should be tapped. Then the cover joint, supposing it to be a ground joint, should be made according to the directions given for making ground joints, when the cylinder may be turned upside down and the other cover fitted. Then the holes for the cylinder cocks and for the steam and exhaust pipe should be tapped, and the faces for these pipe joints fitted as required. The steam-chest holes should then be tapped and the ports marked out and chipped and filed to the lines, such lines being marked as described in the remarks on lining out work. The face for the steam-chest seat and the steam-chest cover may then be prepared by filing, scraping, or grinding, as may be required, and simultaneously the valve seat and valve face may be fitted. If the cylinders are to be bolted together as in a locomotive, the holes for holding them together should be drilled about 1/64 inch smaller than the bolts, so that they may be reamed out together after the cylinder bores are aligned. One cylinder face should be marked and drilled first, and the two cylinder bores being set to align true the other cylinder should be marked from the other, or if there is a saddle between the two cylinders both cylinders may be marked and drilled, and also the holes on one side of the saddle. Temporary bolts may then be put through the holes that are drilled in the cylinder and saddle and clamps used to hold the undrilled cylinder to the saddle, when the cylinder bores may be set true one to the other, and the holes on the remaining side of the saddle marked through those already drilled in the cylinder. These latter holes being drilled, temporary bolts of smaller diameter than the holes (so as to give room to move the cylinders to align their bores) may be used to bolt the cylinders together while their bores are accurately aligned, which alignment may be effected as follows:-- [Illustration: Fig. 2511.] The bores should be set as near true as possible, tested by a spirit-level rested on the bore and placed as near true as can be judged with the length of the bore, and a plumb rule may be applied to the end faces where the cover joint comes. Then a straight-edge should be applied, as in Fig. 2511, in which S is the straight-edge, and C and D the two cylinder ends. The method of testing is shown in Fig. 2511, where the straight-edge S is shown in three positions, marked respectively 1, 2, and 3 at one end, and F, G, and H at the other. [Illustration: Fig. 2512.] [Illustration: Fig. 2513.] The first test should be made by simply placing the straight-edge across the two cylinder faces, as at G 3; and when the cylinders are set apparently true and the spirit-level applied to the respective bores shows them true, greater accuracy may be secured by placing the straight-edge in position 1 H, being pressed firmly to its cylinder face with end 1 above the other cylinder face. Then, while end H is held firmly to its cylinder, let end 1 lower until it passes entirely over the face of cylinder C, whose face it should just touch; if on meeting C the straight-edge strikes it or does not meet it, further adjustment of the cylinder positions is necessary. Next place the straight-edge in position 2, pressing end F firmly against cylinder D, and passing the other end entirely over the end of cylinder C, which it should just touch, and no more. It will then be necessary to repeat this process, pressing the straight-edge against cylinder C and testing the other end with cylinder D, and the cylinders thus set will be (if the end faces are true, as they should be, and usually are) more truly aligned than is possible by the use of the spirit-level. This method also brings the end faces of the cylinders in the same plane, so that each piston head will travel central in the length of the cylinder bore, approaching the cylinder covers equally, and therefore keeps the clearance equal. Incidentally, also, this secures accuracy in the cross-head traverse on the guide bars (supposing these bars to be bolted to the cylinder cover). The holes for bolting the cylinders together may then be reamed and the bolts driven in and screwed up. To guide the tap when tapping the cylinder cover and steam-chest holes the guide stand S, shown in Fig. 2512, should be employed. It is bolted to the cylinder face by the bolt B, which passes through a slot in the stand. The tap T is inserted through the two arms of the stand and its end inserted in the hole to be tapped when bolt B is tightened up. The stem of the tap should be of slightly larger diameter than the tap thread, so as to fit in the holes of the guide or stand. When, however, one end of the guide bars is carried on the cylinder cover, it is necessary when setting that cover to be marked for the drilling, to so set it that the seats for the guide bar ends shall be horizontally level when the cylinder is on the engine; and when setting the bores of the cylinder in line to mark the holes for bolting the cylinders together or to the saddle, this point should also be looked to, as if these seats are not in line the faces of the guide bars will not be in line, and will not, therefore, bed fair to the cross-head guide unless the error is in some way corrected. It is desirable that these seatings be quite true and in line one with the other on both cylinders, so that if liners require to be made, or if the ends of the bars require to be filed to let the bars together at any time, the surfaces may be filed true to the face of the bar, and thus be set true and to fit the cross-head guides without requiring to put the bars on and off to fit them true by trial. [Illustration: Fig. 2514.] [Illustration: Fig. 2515.] REBORING CYLINDERS IN THEIR PLACES ON THE ENGINE.--When a cylinder bore becomes so worn out of cylindrical truth, or becomes grooved or cut, as it is termed, as to require to be rebored, it may be done with the class of boring bar shown in Fig. 2513. It consists of a bar having journal bearing in castings which bolt on to the two ends of the cylinder in place of the cylinder covers. On the bar is fitted a sliding head carrying the cutting tool and fed by a screw passing within the bar. To operate the bar and simultaneously the feed screw, the hand-wheel and worm-wheel is employed, giving rotary motion to the worm-wheel which is fast upon the bar. Fast also upon the bar is the inside one of the two small gears shown, which operates the inner of the two small gears shown above it. The outer of the upper gears engages with the outer of the lower ones, the latter being fast upon the feed screw. In the inner pair the lower is of largest diameter, but in the outer pair the upper is the largest, and as a result the outer of the lower rotates the fastest, and hence rotates the feed screw, causing the tool to feed to its cut. The proportions of these wheels are, first or inside pair, lower wheel 36, upper 37; outside pair, upper 37, lower 36, so that the feed per bar rotation is in amount that produced by moving the outer lower gear a part of a rotation equal to twice the pitch of the teeth, the cutting tool motion depending upon the pitch of the feed screw. To enable the rapid traverse of the head from end to end of the bar, the upper pair of gears are mounted on an eccentric stud, so that by operating the small handle shown they may be disengaged from the lower feed gears and the feed screw operated direct by means of the handle shown. [Illustration: Fig. 2516.] [Illustration: Fig. 2517.] In setting such a bar to a cylinder bore it is to be remembered that two methods may be employed. First, the bar may be set to accommodate the cylinder bore, truing it out with as light a cut as possible. In this case the bore of the cylinder may be made out of line with the guide bars and with the centre of the length of the crank-pin journal. In the second the bar may be set with a view to bore it out in line with the guide bars and crank pin, and then taking as much cut as will be necessary to true the bore. The latter plan is the preferable of the two, unless the repairs are so extensive as to require the guide bars to be redressed and the main bearing renewed, in which case those parts requiring to be re-aligned, the cylinder may be rebored with a view to take out as little metal as possible, and the other parts set to suit the new bore. To set the bar true to the guide bars and crank pin, and thus retain the axis of the new bore true with that of the original bore, the bar should be set true with the recessed counterbore at each end of the cylinder, which being unworn remains true. If, however, only one cylinder cover can be conveniently taken off, the piece of wood will require to fit in the counterbore at the open end, and in the cylinder bore at the closed end of the cylinder; hence we make it large enough for the counterbore, and after having removed the ridge at that end we cut the length of the wood down to fit the cylinder bore, whereas if we made our rest to fit the bore at first we should require to use wedges to make it fit the counterbore. In some cases holes might be bored near the ends of the rest or fulcrum to serve the same purpose as the notches. The method of using the scraper, Fig. 2516, is shown in Fig. 2514, which latter represents an engine cylinder. At B is shown the wooden rest or fulcrum; and at C the lever scraper operating on the ridge at the closed end of the cylinder. The lever C is worked on the pulling stroke only, and is so held that the edge presents a keen scraping tool which will cut very freely. The fulcrum B should be adjusted as closely as convenient to the work, so as to obtain good leverage for the scraper. It should be moved in its position, so that during the roughing out only the lower notches in the fulcrum are used. A plan was lately resorted to on the White Star Line of steamships for re-boring a cylinder. The cylinder heads and piston follower were taken off; a groove was cut from the outer end of the cylinder along the bore as far and as deep as the counterboring was required to be done. The counterboring was then accomplished in the manner shown in Fig. 2515. The junk ring was provided with a small tool holder, such as is used upon boring bars. The tool was fastened in the holder while its cutting edge was in the groove referred to, cut as deep and as far up the cylinder as the counterboring was to be. To the junk ring was fastened, by two long bolts, a wooden lever extending above and across the cylinder. Two men walked around pushing the lever, and when the tool at each revolution arrived at the groove, a fresh cut was taken by moving the engine so as to raise the piston the necessary amount. It is obvious that the piston head may be steadied and held true in the bore of the cylinder by means of a few wooden wedges. Thus we see that in this operation the junk ring was made to serve as a boring bar head, the men furnishing the necessary rotative motion, the feed motion to the tool being obtained by advancing the piston toward the end of the cylinder where the work was being done. The ridges which in time form at the two ends of a cylinder bore are usually removed by the hand-boring bar shown in Fig. 2513, but they may, in cylinders of from 12 to 24 or 30 inches in diameter, be readily cut out by hand as follows:-- Take a bar of steel 9/16 inch square and 3 feet 6 inches long; forge it at one end to the shape shown in Fig. 2516, in which from A to B is the forged end. This end must then be heated along its entire length to a cherry red, and dipped vertically into cold water to harden it; after which it must be ground from A to B on all four faces square across, and as nearly of an even curve as can be ascertained by the eye. Next take a piece of hard wood--oak, for instance--about an inch thick and 3 inches wide; cut it to such a length that when placed upright its ends will wedge tightly into the counterbore of the cylinder. Into the edges of this piece of wood saw out a series of notches, making its finished appearance to be such as shown in Fig. 2517. The object of fitting its length tightly into the counterbore of the cylinder is as follows: If both cylinder covers are off or can be conveniently taken off, the ridge can be operated upon at each end of the cylinder; hence our piece of wood, which is merely an improvised rest to act as a fulcrum for the bar scraper shown at the top of the figure, would require to fit into the counterbore. CHAPTER XXIX.--ERECTING ENGINES AND MACHINERY. In engines having suspended guide bars, it is not uncommon to set those bars by the working parts of the engine, instead of by lines. This is an advantage when the parts of the engines are not taken down, and, if care is taken, will make a true and smooth working job; but otherwise, it is likely to introduce errors in the lining of the engine, which throw it out of proper line, and cause a great deal of friction. The proper method of setting the bars depends upon the condition of the engine as to wear. Suppose, for example, that a new piston head has been put in, then, if the gland is new also, or is a good fit to both the piston rod and the bar of the stuffing box, the bars may be set as follows:-- [Illustration: Fig. 2518.] Place the piston at the back end of the cylinder, and put the cross head and guide blocks in proper place on the rod. Put up the bottom guide bars so that they just touch the cross-head guides. Now, in adjusting these bottom bars there are two essential points: first, that the plane of their upper surfaces shall stand parallel with the axial line of the main shaft, and secondly, to place the upper surface parallel with the axial line of the cylinder (it being of course assumed that the cylinder and crank shaft are in proper line). The first of these essential points will be attained when a spirit-level, placed truly along the bore of the cylinder, shows the bubble to stand in the same position in the tube, as it does when placed upon and along the bar. The second will be attained when a spirit-level, placed across the bars, as in Fig. 2518, at A, shows the bubble to stand the same as it does when the level is placed on a parallel part of the shaft, as in the figure at B. When the bars are thus temporarily set, the liners, or pieces of iron, may be fitted to the proper thickness, so that the gland will pass in and out of the stuffing box easily by hand, no matter in what position the piston may be in the cylinder. To get the thickness of these liners, take wedges made of iron, wood, or lead, and insert the thin end between the faces of the bars and those of the supports, forcing the wedges in sufficiently to leave a mark upon them. By chalking the faces of the wedges they will exhibit the marks more plainly. The wedges should be inserted at each end and on both sides of the bar, for one bar at a time, the liners being got out a trifle too thick so as to allow some for fitting. If the liners require to be very thin and are difficult to hold in the vice without springing, take a piece of soft wood faced true, and grip it in the vice, and fasten the liner on it by means of brads driven in around the edge of the liner. When the four liners are ready place them in position between the bars and their seatings. Bolt the bars firmly in position, wipe them clean and test them lengthwise with the spirit-level to ascertain if they are parallel with the cylinder bore, and place the level across the bars at each end to test parallelism with the engine shaft, as in Fig. 2518, and, having noted where further adjustment is necessary, put marking upon the bars and move the cross head back and forth to ascertain how much the respective liners require reducing. If the gland is a fit upon the piston rod and in the stuffing box, moving the gland in and out of the stuffing box will be an admirable test of the guide-bar adjustment. [Illustration: Fig. 2519.] The straight-edge should also be applied to test if the surfaces of the bars lead true one to the other; thus, in Fig. 2519, A and B are the bars and E the straight-edge, which by being pressed firmly to the surface of A discloses that the surface of A is not in line with B, because if it were so the straight-edge would meet the face of B as in Fig. 2519, where the straight-edge F pressed to the surface of C leads true to the surface of the bar D. All four of the bars require testing in this manner. If the seatings for the bars or the liners are not made flat and of equal thickness, or if from any other cause the bars do not bed properly upon the liners, then bolting up the bars will spring them as shown in Fig. 2520, in which, at A, is shown a bar sprung in the bolting up, because the liners fit at the ends B C only; while at E is shown a bar sprung or bent because the liners fit at the ends D D only. In either case the cross head would be forced to travel in a curve, bending the piston rod, and inducing much friction. The way to test the bars in this respect is, after the above operations, and before loosening the bolts, place a long straight-edge lengthwise along each bar and move it laterally at one end. If it swings from the centre the bar is rounding, while if it shuffles across first at one end and then at the other the bar is hollow in its length and we must find at which end of the bar this spring exists. To do this, slightly slacken the bolt or bolts at one end and again apply the straight-edge, if the spring is removed the error lies in the bedding of the liner at that end. If not removed, retighten the bolts at that end and slacken those or that at the other end, and again apply the straight-edge, and thus may it be determined how much of the spring is due to each of the liners, and this must be remembered and allowed for in filing the liner to its final adjustment. Before putting the liners in a second time it is better to give them a light coat of marking to show where they bear. At each trial of the bars the spirit-level and straight-edge should be applied and the cross head should be moved back and forth to show by the bearing marks how the cross-head guides fit to the bars. These marks are a great deal finer test than any spirit-level adjustment, hence the last part of the fitting should be performed with strict reference to the bearing marks upon both the bars and the cross-head guides as well as upon the liner, the cross-head flanges being adjusted and fitted at the same time as the face fitting. [Illustration: Fig. 2520.] To set the top bars place the cross head in the middle of its stroke, and place them upon the cross-head guides. Then, with the wedges applied as before, ascertain the required thickness of the respective liners one at a time, leaving them, as previously, a trifle too thick, and testing them while fitting by marking placed upon their faces. The top bars may be entirely adjusted from the contact marks left by the cross-head guides when moved along the bars, thus dispensing with the use of the straight-edge and spirit-level. As the bolts supporting the bottom bars often require to be loosened to get the top bars off, pieces of wood may be placed beneath the bottom bars to retain them in position when the bolts are loosened. These pieces must be removed during the testing, for if left so as to wedge the bars they may spring them, and thus mislead in the adjustment. After the top bars are adjusted the whole bearing surfaces should be oiled, and the cross head pulled back and forth by hand without the use of a lever, providing the size of the piston does not exceed about eighteen inches diameter. The bars when set true should be clamped to their seatings and the holes reamed out to receive the proper bolts, and, finally, mark each bolt, bar, and liner to its place. When the bars, tested with the straight-edge and spirit-level as described, show true, if the gland will pass freely in and out of the stuffing box with the cross head at any part of its stroke, the guide bars are set. In this operation let it be noted that the close fit of the piston to the cylinder bore and of the gland to the stuffing box is alone depended upon as a guide whereby to so set the guide bars that the axial line of the piston rod and its plane of motion shall be in line with the centre of the crank shaft. [Illustration: Fig. 2521.] Suppose, however, that the piston head is a new one, and the gland is worn a loose fit to the stuffing box, then setting the bar to the gland would produce the result shown in Fig. 2521, in which the dotted line A A is a line or cord stretched axially true with the cylinder bore, and coincident with the centre of the pillow block at B. The gland being a loose fit permits the piston rod to fall below its proper level, and the surface of the bars, if set by the gland only, without using the spirit-level, would be set true to the full line C C, and therefore out of true line. If the bars are set by spirit-level true to the length of the cylinder bore, the gland becomes useless as a guide to set the bars by. It is a not uncommon practice, when the gland has play, to insert in the stuffing-box bore, at the bottom, a piece of tin or sheet brass, equal in thickness to one-half the amount to which the gland is too small, or to insert a similar piece beneath the piston head if it is too small. As a rule, however, there will be at least as much play between the piston rod and the gland bore as between the gland and the stuffing-box bore; hence, if there is any play, it is better to discard the use of the gland altogether. The proper method of setting guide bars by a stretched line is as follows:-- [Illustration: Fig. 2522.] The cord or line is set true to the cylinder bore, and coincident with the centre of the pillow block, as at A A in Fig. 2521, and the two bottom bars are put up in line horizontally with the axial line of the crank shaft, and at a distance below the stretched line equal to one-half the height of the guides for the cross head, as in Fig. 2522, in which A represents the stretched line, B, B the bottom bars, C C a straight-edge, and D a piece of wire whose length from point to point is equal to one-half the height or thickness of the guide blocks. The width apart of the bars is set to suit the width apart of the flanges of the guide blocks on the cross head, by means of a square. The square is applied in the following manner: On a straight-edge mark two lines A and D, Fig. 2523, a distance apart equal to the distance between the flange edges of the cross-head guides. Midway between A and D mark the line C; place the straight-edge across the bars as shown, and when the edge of a square, placed on the straight-edge, coincides with C and the stretched line, and the marks A and D coincide with the edges of the bars, the latter are set true, and will come right for distance apart, and distance from the centre line, supposing the flange edges of the cross-head guides to be equidistant from the centre of the length of the cross-head journal. If, however, such is not the case, the width from A to C and from C to D must be made to suit, C representing the centre of the length of the cross head journal, D the flange on one guide and A the flange on the other guide. Here it may also be remarked that, if the thicknesses of the cross-head guides vary, or if they are not central to the axial line of the cross-head journal, the bars must be set for distance from A in Fig. 2523, to suit the error, because in that figure the straight-edge is supposed to stand parallel to the axial line of the shaft, as it is also in Fig. 2522, the aim in both cases being to so set the bars that the cross-head journal shall stand parallel with the crank shaft. [Illustration: Fig. 2523.] It is the liability of variation in the thickness of the guide blocks, and of their not being central to the cross-head journal, that constitutes the disadvantage of setting the bars by lines, it being obvious that the bars must be either set to suit any errors in the guides, or those errors must be eliminated before setting the bars. The top bars must be set parallel to the bottom ones, at a distance from the bottom ones equal to the thickness of the guide blocks, and parallel to one another. It is preferable to set the top ones with the cross head and guides in place, observing all the precautions as to springing them given in the case of the bottom bars. [Illustration: Fig. 2524.] The bars thus set will be in line with the crank axle, but unless the piston accurately fits the cylinder bore, they will not long remain in line with the line of motion of the piston rod. For example, Fig. 2524 shows a piston head too small for the cylinder bore, the guides fitting the bars properly, and the gland and stuffing box fitting the piston rod; the piston will be suspended in the cylinder, its overhanging weight being supported by the guides B, the gland, and packing ring. This would cause friction and rapid wear of the gland bore and guide surfaces in a direction parallel to the line C, which would gradually let the piston fall to the bottom of the cylinder bore, touching at the end of D first. In some engines provision is made to adjust the piston to take up its wear, which is, it will be seen, a great advantage. THE HEATING AND POUNDING, OR KNOCKING, OF ENGINES.--The heating of any part of an engine occurs from one of two causes, viz., either the fit of the parts is too close, inducing undue friction, or the parts are not in line. When the former is the cause the remedy is to ease the fit. If the parts are not in line, the heating may also be remedied by loosening the fit of the parts; but this will often induce a pound or knock, hence the true remedy is to properly align the parts. The location of a pound may be discovered by placing a piece of metal wire between the teeth, and resting the other end of the wire upon each end of the cylinder, guide bars, and bearings of the main shaft, repeating the operation in each place, and the sense of feeling will distinctly indicate the location of the knock, by imparting a more severe shock to the teeth when the vicinity of the knock is approached. The most prominent location of the causes of a pound are, first, in the crank pin, from causes to be hereafter explained, and from its wearing oval at the cross-head journal; and second, at the ends of the cylinders, or the ends of the guide bars, because of a ridge forming there as the wear proceeds. A crank pin cannot wear oval if the brasses are kept adjusted to fit it, because in that case the brass bore must wear it round; but if there is any play it wears oval, because the pressure of contact between the journal and the brass bores is least when the pin is at and near the points of dead centre, and the most when it is at and near half stroke. The cross-head pin wears oval because the pressure between the pin and its bearing is in a line with the connecting rod, and there is but little wear on the pin in a direction at right angles to the rod. Ridges form at the ends of the cylinder bore and at the ends of the guides for the following reasons:-- Referring to the cylinder, the location of the piston stroke in the cylinder bore alters as the connecting-rod keys pass through the rod, because that alters the length of the connecting rod, and therefore the path of the cross-head guides on the guide bars, and also that of the piston in the cylinder. As the piston rod is shortened there is less wear at the extreme end of the cylinder bore farthest from the crank, and the same remark applies to the guide bars. If the piston head travels past the end of the cylinder bore and into the counterbore at each end, a distance equal to the amount of taper on the connecting-rod keys, or equal to the amount the connecting-rod length will alter while those keys are passed through the rod (to take up the journal and brass wear), the piston head will (if the rod is kept to its original length within that amount) always travel to the end of the cylinder bore, and no ridge should form on account of the length of the rod altering; but even then a slight ridge may form because the wear is naturally less at the ends. Thus in the middle of the cylinder length the whole thickness of the piston head, piston rings, and of the follower passes over the bore, while at the ends only the flange of the piston head at one end and the follower at the other passes over the metal of the bore; hence the friction and wear are less. The ordinary cause of pounding and heating is a want of truth in the alignment of the crank pin, or in that of the cylinder, main shaft, or guide bars. [Illustration: Fig. 2525.] The method to be employed to line an engine, or to discover if it is out of line, depends upon the design of the engine and its condition; thus an engine having a Corliss frame has the slides to receive the cross head made at a true right angle to the end face which meets the cylinder end; equidistant from the centre of the gland hole or axis of the piston rod, and the end of the frame fitting either the bore of the piston or the turned flange of the cylinder cover; hence the guide bars must be true if the frame is got up true, the fit of the frame end to the cylinder end insuring truth in the guide or cross-head slides, providing that the centre line of the frame, during the turning and planing operations, leads from the centre of the cylinder end of the frame to the centre of the crank-shaft brass; or, in other words, the planing and boring of the frame must be true with a line running from the centre of the cylinder end of frame to the centre of location for the crank shaft. This will not only cause the outside of the frame casting to stand at its proper level when the cylinder bore stands horizontally level; but it will insure that the crank-shaft bearing brasses both be of equal and of a proper thickness through the crown. The engine being properly lined at first will not be liable to get out of line, excepting so far as affected by the wear of the crank-shaft bearing, which will cause the crank shaft to drop, as shown in Fig. 2525, where A A represents the true centre line of the cylinder and guide bars, which, when the crank is in the position shown in the cut, should be coincident with the centre line of the connecting rod and the crank, but the crank brass having worn below the centre line of the connecting rod and crank, the crank will get out of line as denoted by the line B B. [Illustration: Fig. 2526.] As a result, a portion of the piston movement and pressure which should be exerted on the crank after leaving the dead centre, will be exerted on it before it reaches the dead centre, thus causing a back pressure, involving a loss of power. Furthermore, the relative position of the eccentric to the valve gear will be altered, impairing the proper set of the valves; hence it follows that the wear of the crank bearing in this direction should be taken up (by raising the lower brass) before it becomes excessive. To find how much the bottom brass requires raising, or whether it requires raising or not, find the centre of the crank shaft, and from this centre strike the circle B, in Fig. 2526, whose diameter must equal that of the crank pin A, and place the edge of a spirit-level coincident with the perimeters of the crank pin and circle, as shown in the cut. When the bubble of the spirit-level stands in the same position as it does when the level is placed upon the bore of the cylinder or along the piston rod, the crank will be in line with the cylinder bore. As a rule, the cylinder bore of a horizontal engine stands horizontally true, and the crank centre line should also stand so when the crank is on its dead centre, but if such is not the case the crank centre line must nevertheless stand true with the axial line of the cylinder, when the crank is on the dead centre. [Illustration: Fig. 2527.] If, instead of having a Corliss frame and fixed guide bars, the engine has a flat bed and adjustable guide bars, as shown in Fig. 2527, the operation is as follows:-- In setting up a new engine it is obvious that if the flanges of the cylinder are planed parallel with its bore and at the proper distance from its axial line, and the pillow block is made of the proper height, a line stretched axially true with the cylinder bore will pass through the centre of bore of pillow-block brasses, or be equal in height from the engine bed; but the length of the cylinder being only about one-fifth of the distance from the cylinder to the centre of pillow block, any error in the planing of the cylinder flange true to the cylinder bore becomes magnified five times at the pillow block; hence it is necessary to stretch a line through the cylinder bore and set the cylinder so that the line, being axially true with its bore, will pass the pillow block at the centre of the bore of its brasses. This is sometimes done by inserting thin pieces of sheet tin, metal, or even paper beneath the cylinder flanges and the bed, and in the requisite positions. The method of stretching the line is shown in Fig. 2527. F is a device for holding the line at that end. It consists of a frame in the form of a cross, with adjusting screws at the end of each arm, and a small hole at its centre to receive the line. The other end of the line A must be secured, under as much tension as the line will safely bear, to a piece of wood clamped to the engine frame at R. The adjustment of the line is made by measuring its distance from the walls of the bore of the cylinder at one end and of the bore of the gland hole at the other end, using a pair of inside calipers or a wire gauge. The latter should be bent in its length to admit of adjusting the same by straightening to increase, or still further bending to diminish, its length to suit the requirements. The wire, when applied, should only just meet or touch the line and not bear the least hard, or it will spring the line, causing an error of adjustment that will be serious when multiplied by the length of the line to the pillow block as compared with the length of the cylinder bore. If the pillow block is planed on its bottom face and has its brasses fitted, the latter may be marked off for boring from the line A, Fig. 2527, when stretched to set the cylinder, thus avoiding a second adjustment of the line A A. Suppose now that it is required to line the brasses in the pillow blocks true to be bored (the pillow blocks being bolted in position). The distance of the face P, of the brass from the stretched line A, in Fig. 2527, must equal the distance from the centre of the length of the crank-pin journal, to the face of the large crank hub, and this distance may be shown by a line marked on the edge of the brass flange. Place a straight-edge C, Fig. 2527, having a line D parallel with its edge E, so that this line will be in the centre of the width of the pillow-block jaws, and at a right angle to the line A. The line D will then represent the axial line of the crank shaft, and may be used as the centre from which to mark the lines on the brasses used to set them by for boring. To test if A and D are at a right angle, or to set D to A, a large square should be used. If the side face P P of the pillow block stands parallel to A, as it should do when it is true, it will serve to chuck the pillow block by, thus boring the brasses in their places in the pillow block, with the centre line of the bore at a right angle to P. If otherwise, two flat places should be filed on the brasses, as shown in Fig. 2528, in which C is the straight-edge, and A the stretched line as before, H and I representing the flat places whose distance from A, as shown at J J, may be made to represent the thickness of the crank from its large hub face to the centre of length of crank-pin journal; hence the depth of the flat places will show how much to take off the face of the brass to leave it of the proper thickness. [Illustration: Fig. 2528.] A straight-edge placed across these flat places, or true to the lines H I, must stand at a right angle to the line D, so that by setting the brasses by the flat places they will be bored to stand at a right angle to A. To set the brasses the other way a circle is struck from D, as a centre, upon the faces of the brasses as in the end view, Fig. 2528, in which the straight-edge C is shown wedged in the bore of the brasses, which is the most convenient way when it can be done. The line D is carried down on the end face of the straight-edge, and the latter is used as a support for the compass points while striking the circle M, which is defined more clearly by indenting it with fine centre-punch marks. The height of the centre for bore of brasses may be carried from the centre line of the cylinder A A to the end of the straight-edge C, by placing another straight-edge across the engine bed and measuring from the end of C to A. Suppose now that the brasses are bored, and the position of the pillow block is to be set, and the process is the same, the line D being marked true from the bore of the brasses, and the pillow blocks adjusted until D is at a right angle to line A A. Though in a new engine every part may be made as true as possible in the details of manufacture, yet when the parts come to be put together errors of alignment will generally be found to exist. These errors may be too minute for discovery in the separate piece, and yet form important defects in the finished engine. In rough practice these defects are left to remove themselves by abrasion and wear, the process being to allow the parts to be somewhat loose (wherever possible) in their adjustment, and adjust them closer as the abrasion proceeds. This is termed letting the parts _wear down to a bearing_. But the very process of wearing _down to a bearing_ attests that the parts have not been properly fitted to a bearing, whereas to attain the best possible results the parts should be fitted to a bearing, because in wearing down to a bearing, undue abrasion, and to some extent or in some degree, roughness of the wearing surfaces, must ensue, because the strain intended to be distributed over the whole _intended_ bearing area is limited to the _actual_ bearing area. It is necessary, therefore, that, in putting an engine together, each part be properly fitted to its place, and that it be subsequently adjusted in its fit and position with relation to the other parts to which it is connected. The fitting of the single piece is a test of its individual or disconnected truth; the subsequent or second adjustment is a test of its truth with relation to the others. Thus a pair of brasses may fit a journal perfectly, but that is no assurance that the brasses are so bored as to bring the rod holding them in proper line to enable connection at the other end without springing or bending the rod. Furthermore, it often happens that the frame work of an engine does not form a base for the whole of the parts, thus in a large stationary engine, the end of the main shaft or crank shaft farthest from the crank (generally called the _outboard_ bearing) is generally supported by a bearing having an independent foundation, and as this foundation does not exist until the engine comes to be permanently fixed for operation, its alignment must be performed when setting the engine. In an old engine this foundation may settle, or the wear itself may throw the engine out of line, so that the lining of an engine becomes periodically a necessity. As a general rule a want of alignment induced by wear or incurred from repairs to the parts principally affects the main shaft, the cross head remaining more nearly true; and, with the exception of the crank pin, the same holds good with reference to a new engine. Now while an error of alignment may exist in any direction, it is true, nevertheless, that an error in any direction will be discoverable if the parts be tested at four equidistant parts of the stroke or revolution, as, for instance, on the two dead centres of the crank and at the highest and lowest points of the path of rotation of the crank pin; hence attention may be confined to those four points. Suppose then an engine already put together requires to be tested for being in line, and we have to test-- 1st. The alignment of the main or crank shaft vertically. 2nd. The alignment of the main shaft horizontally. 3rd. The axial truth of the crank pin with the main or crank shaft. 4th. The adjustment of the crank shaft for vertical height, with relation to the cross-head journal. Referring to this last, it may be necessary to remark that the axial line of the main shaft may be parallel when viewed either vertically or horizontally with the cross-head journal, and yet if a line be passed through the centre of the cylinder bore, and prolonged past the crank centre, the latter may fall above or below that line, but it will generally be below, because from the weight of the crank shaft its bottom bearings wear the most; and, further, to whatever extent those bearings wear after being in proper line, the crank shaft will fall too low. We may now subdivide the errors of alignment of a crank shaft thus:-- 1st. Its axial line, when viewed vertically, may form an acute angle to the axial line of the cross-head journal. 2nd. It may form an obtuse angle with the cross-head journal when so viewed. 3rd. It may, when viewed from the crank-pin end of the engine on about a horizontal position, be too high or too low at the crank-pin end only. 4th. It may be too high or too low at the outboard end only. 5th. It may be too high or too low at both ends, although parallel to the cross-head journals. It will be found on consideration that with the exception of the last-named case, the connecting rod forms the best test whereby to discover an error in any of these directions, because it magnifies the error and makes it more plainly discernible. It will further be found upon careful observation, that although a combination of these errors may exist, the connecting rod will serve to discover each error separately, as well as the collective error, because, although in some respects two distinct errors may have the same general result, yet the result will be different if taken in detail, and it follows, therefore, that the testing must be taken or made in detail first. [Illustration: Fig. 2529.] To test the parallelism of the axial line of the crank shaft with that of the cross-head journal, when viewed vertically: In Fig. 2529, let A A represent a line true axially with the bore of the cylinder, and B B a line at a right angle to A A, and passing through the centre of the pillow block or bearing spaces. If the engine were in line, B B would be coincident with the axial line of the crank. Suppose, however, that line B C represents the actual centre line of the crank, not then being at right angles to A, the end E of the connecting rod, if connected to the crank pin as shown, and made a good working fit so that there is no play of the pin in the brasses, will not come fair laterally with the bearing in the cross head. The amount of the error is the amount it is out of true in the length of the crank-pin journal, multiplied by the product of the length of the connecting rod (from centre to centre of the bores of the brasses) divided by the length of the crank-pin journal. It is apparent, however, that if the crank shaft be set to have its axial line at B B instead of at B C, the error at E D will be corrected, and thus we may employ the connecting rod to set the crank shaft in line. It is, however, not sufficient to try the crank on one dead centre only (as will be seen presently), hence we place it on the other, and move the cross head to the other end of its stroke, and again try the end E of the connecting rod with the cross-head journal, and if it falls to one side, and _on the same side as before, but to a less amount_, it demonstrates that the axial line of the crank forms with the line A A an acute angle. If, however, instead of falling too much laterally towards the side F of the cross head, it fell too much towards D, but more so when tried with the crank on the dead centre nearest to the cylinder than when tried with the crank on the other dead centre, then it is proof that the axial line of the crank shaft forms with A A an obtuse angle. [Illustration: Fig. 2530.] The reason that the error will be more plainly shown with the crank on one dead centre than when on the other is shown in Fig. 2530, in which A A is a line coincident with the axial line of the cylinder bore, and B B the axial line of the crank shaft, from C to D is the plane of revolution of the crank pin, while G represents the crank centre. The points at C and F denote points central to the length and diameter of the crank-pin journal. Now, the centre line of the connecting rod for one dead centre is represented by E D, and for the other by F C, and it will be seen that the point at E is farther from A than is the point at F. It will be observed that the point D falls _outside_, while the point C falls _inside_ of A A, and yet the centre line of the connecting rod stands, in both cases, at the same angle to the centre line A A of the engine, and in both cases throwing the end of the connecting rod, represented by the points at E F, _outside_ the line A A. If the connecting rod does not, when connected to the engine, as in Fig. 2529, fall true into the cross-head bearing, the error is the same _in amount_ and comes on the outside of the cross-head journal with the crank placed on each respective dead centre, it is proof that either the flange of the crank-shaft brass (which is between the crank face and the frame) is too thick, or the inside flange of the connecting-rod on the crank pin is too thick, or else the crank is too thick, measured from the crank-pin journal to its inside hub face, the error being in the new crank or new brass, if one has been put in. [Illustration: Fig. 2531.] It may here be remarked that if the bore of the crank-pin brasses of the connecting rod is not at right angles to the centre line of the rod itself, the end E, Fig. 2529, might fall either inside or outside, laterally, of the cross-head bearing, but in this case the error will show more at one end of the stroke than at the other, for reasons which are explained with reference to Fig. 2530; hence it follows that the connecting-rod brasses should be properly fitted to their journals, and made to lead true before using the rod to line the engine by. In some cases it is more convenient to connect the rod at the cross-head end, and try the other end with the crank-pin journal, as shown in Fig. 2531. In this case, however, the connecting rod will (whenever the axial line of the crank shaft is out of square, forming an acute angle with the centre line A A, as in Figs. 2529 and 2530), fall laterally inside the crank-pin journal when on one dead centre, as in Fig. 2531, and outside when on the other dead centre, as in Fig. 2532, the respective amounts of error being in this case equal for the two positions. The reason for this is that the plane of revolution of the crank pin falls outside of the centre line in one case, and inside for the other, as shown in Fig. 2530 at D C. [Illustration: Fig. 2532.] [Illustration: Fig. 2533.] [Illustration: Fig. 2534.] [Illustration: Fig. 2535.] If the axis of the crank axle formed an obtuse angle to the engine centre line A A in Fig. 2529, the connecting-rod end tried with the crank pin, as shown in Fig. 2531, would fall outside of the crank-pin journal when the latter was on the dead centre nearest to the cylinder, as shown in Fig. 2534, and inside of the crank-pin journal when on the other dead centre, as in Fig. 2535. Now, suppose either of the errors to exist, and the alignment be neglected, then if the brasses at each end be keyed up to fit their respective journals, then the body of the rod must be bent into a bow shape, and the strain of forcing or springing it into this shape will fall upon the journals, which will heat and pound in consequence. It is now to be explained how to test if the axial line of the crank shaft is at a right angle to that of the cross-head journal, when viewed from the crank-shaft end and horizontally. From a want of parallelism in this direction, heating of the crank pin and cross-head journals is _sure_, and a pound or thump is, to some extent, liable to occur, and the cause, if the error is slight, is difficult to discover, save by using the connecting rod to test it with. When a thump occurs at the end of the stroke (when the crank is on a dead centre), it may arise from a ridge at the cylinder, or at the guide-bar end, or from the connecting-rod brasses being insufficiently keyed up; but when it occurs while the crank is at half stroke these causes are eliminated, and the cause must be looked for in either a crank pin not parallel to the crank shaft, or, as in the case now under consideration, because of one or the other of the crank-shaft journals being too low. Assuming the crank pin and crank shaft to be axially true, one with the other, we may proceed to show separately the cause of the heating and that of the pounding, if the crank journal is too low at either end. [Illustration: Fig. 2536.] In Fig. 2536, let A represent the cross-head journal, and B B a line parallel to it. Let B C represent the axial line of the crank shaft (being out of parallel because the crank end is too high or the other end too low). Let F F represent the centre line of the crank pin when at the top, and G G when at the bottom of its path of rotation, and it will be observed that the vertical distance between the crank pin and the axial line of the cross-head journal is less on one side than on the other; thus in the figure distance D is less than E. We have in this case measured these distances on a plane at a right angle to the cross-head journal, but it will make no difference if we measure them on a plane with the path of rotation of the crank pin, as will be seen in Fig. 2537, in which the distance from the centre of the crank pin at two opposite points in its path is represented by dots shown at E F, and from E to H measures less than from F to H, H representing the centre of the cross-head journal. [Illustration: Fig. 2537.] In Fig. 2537, let A represent the axial line of the cross-head journal, B a vertical line at a right angle to A; C representing the crank shaft extended by a dotted line, so as to enable comparison with A; D the crank, E and F the centre of the crank-pin journal, and G G a line at a right angle to cross-head journal A. Now G, being at a right angle to A, represents what should be the plane of rotation of the crank pin, whereas C, being out of parallel with A, causes the path of rotation to be in the path from E to F, or as D compared to B; supposing then that the bores of the connecting-rod brasses to be axially parallel one to the other, and keyed up properly, and when at E one bore of those brasses will stand parallel to E while the other is parallel to A, or when at the bottom of the crank rotation, one bore will be parallel to F and the other parallel to A. Thus the rod will be twisted, and the strain due to this twist will cause the bearings to heat. That this twisting is continuous throughout the whole revolution may be seen by the want of parallelism of the dotted line (representing the crank pin when on the dead centre) with A (representing the cross-head journal). It is now to be observed that if the plane of the crank rotation were at a right angle to the axis of the cross head, as it should be, the path of the centre of the crank-pin journal would be in the plane of G G, whereas it falls outside as at E, and inside as at F, while at H it is coincident; hence it appears that starting from a dead centre H, the rod bends, passing at that end outward to E (when the crank has made a quarter revolution), where it attains its maximum bend, thence diminishing until finally ceasing, when the crank reaches the other dead centre. As soon, however, as it passes the last dead centre a bend in the opposite direction takes place, attaining its maximum at F, and ceasing at H. This bending also causes undue friction and the consequent heating of the journals; furthermore, if there be any _end_ play between the brasses and the journals, there will be a pound, as the brasses jump from one end of the journal to the other at different parts of the stroke. It is obvious that if the crank end of the crank shaft was too high instead of too low, as in our example, then the effects would be the same, but E would fall on the inside instead of the outside of G, while F would fall outside instead of inside. [Illustration: Fig. 2538.] [Illustration: Fig. 2539.] [Illustration: Fig. 2540.] To discover if the crank shaft is out of parallel in the direction here referred to, connect the connecting rod to the cross-head journal, setting the brasses up to a close working fit. At the other end of the connecting rod put the strap keys and brasses in their places, but not on the crank-pin journal. Place the crank in its highest position, and lower the end of the rod down to the crank-pin journal, as shown in Fig. 2538, and if the crank shaft is parallel (in the respect here referred to) to the cross-head journal, the brass flanges will just meet the faces of the crank-pin journal, as shown in Fig. 2539. If, however, the crank end of the crank shaft is too low, as in our example, the flanges of the brasses will fall to one side of the crank-pin journal, and that side will be toward B, Fig. 2540, when the crank pin is at the top, and toward C, Fig. 2541, when it is at the bottom of its path of rotation. The effects will be precisely the same, and in the same direction with relation to the various parts of the crank's revolution, if the crank-pin end of the shaft was of correct height; but the other end was too high, hence, in correcting the error, it is desirable to place the engine on the dead centre, so as to determine which end of the shaft to operate on--that is to say, whether to raise the crank-pin end or lower the other end. But suppose the error to be that the crank-pin end of the shaft was too high instead of too low, then, the testing being continued as before, the effects will be of the same general character, but altered with relation to the specific parts of the revolution. Thus, when the crank is at the bottom, the rod would fall towards A, Fig. 2542, and when at the top, it would fall in the opposite direction--that is, towards D, Fig. 2542. [Illustration: Fig. 2541.] [Illustration: Fig. 2542.] We now come to one of the most common errors in the alignment of the parts of an engine, and to the one that it is the most difficult to locate or discover, namely, a want of parallelism between the axial line of the crank pin and that of the crank shaft. This generally arises from improper methods in the chucking of the crank to bore it, or from errors induced in fastening the crank to its shaft. The results are precisely alike in both cases, supposing, of course, the errors to exist in the same direction in the two cases. The error in chucking usually consists in planing one surface of the crank, and bolting the planed surface against the chuck to bore both crank holes. In this case the crank holes will be out of true to twice the amount the lathe face plate may be out of true, and to whatever amount the crank may alter its form from having its surface metal removed. To avoid these errors the large bore and its hub face should be turned at one chucking, and this hub face should be bolted to the face plate for the second chucking, the small end swinging free, except in so far as the ends of the plates may touch against it to steady it. [Illustration: Fig. 2543.] The error in putting the crank on may occur from the key springing the crank out of true, and if the crank is shrunk on from too great an allowance for shrinkage or improper heating for the shrinkage or contraction, as it is sometimes termed. Referring to the error in keying, it is more liable to occur when the crank bore and its seat upon the shaft are made taper, than when made parallel, because it is a difficult matter to insure accuracy in the fit of the taper, and the key pressure will spring the crank over on the side at which it is the easiest fit. In Fig. 2543 let A represent the end of the crank shaft; B the key, and C the crank shown partly in section: suppose the crank bore (whether made taper or parallel) has a slightly easier fit on the side D than on the side E, and the pressure of the key (supposing it to fit properly top and bottom) would spring the crank over in the direction shown in the figure, the axial line of the crank pin standing at the angle denoted by the line F, instead of parallel to the axial line of the shaft. Suppose the crank to be put on by hydraulic pressure, and the key to fit on the sides and not on the top and bottom, then its fit to its seat on the shaft would depend on the truth and smoothness of its bore and seat on the shaft, the amount allowed for the forcing fit and the amount of the error. If the latter amount was so small that the crank would fit at both ends, but simply fit tighter at E E than at D, the crank would remain true, but might possibly get loose in time. This would be especially liable to occur if the tool marks on the bore and seat were so deep that the contact was mainly at the tops of those marks or ridges which would be apt to compress. But if the surfaces were cylindrically true and smooth, and the amount allowed for forcing was sufficient as stated to give the bore and seat contact at D, with a key fitting sideways, the crank would probably remain tight and true. Were the bore and its seat parallel the crank would remain true, no matter whether the key fitted on the sides or at the top and bottom, providing the key fitting top and bottom were bedded fairly from end to end. When the surfaces are not smooth, but contain tool marks or ridges, an unequal pressure of the key at one end, as compared to the other, sets the crank over, as shown in the figure, because the key pressure compresses the ridges and lets the crank move over. [Illustration: Fig. 2544.] Supposing the strain of the key, or keys, to be depended upon to hold the crank, they must fit top and bottom, and their accurate fit becomes of the first importance; because not only is it necessary that they fit equally at each end, but they must also fit equally across the width of the key at each end. For example, in Fig. 2544 is a key binding most at the opposite corners, as denoted by the dotted surfaces A B, and the result will be that the key pressure would tend to twist the crank in the direction of D E, having C as a centre of motion, providing that the error was equal at A and B; but in proportion as the error was greatest and the fit tightest at A, or at B, would the centre of motion be moved nearer to either point. Supposing now that the crank is to be shrunk, or contracted on, then the points of consideration are (supposing the crank to fit properly to its seat, whether the same be either parallel or taper) that the hub of the crank opposite to the throw is the weakest and is likely to give most in the process of contraction, so that if one part (as F) of the crank be made hotter than another (as G) it will give way more, and this will twist the crank. This is specially liable to occur if an excessive amount of difference in the bore and seat diameters has been allowed for contraction. [Illustration: Fig. 2545.] It may not happen that a crank pin is out of truth in a direction in which the error will show plainest when the crank is on its dead centres, or at half-stroke; but if a crank pin, tested in those four positions, fails to show any error when tested by the connecting rod, it will be true enough for all practical purposes, and true enough to avoid heating and pounding, both of which evils accompany an untrue crank pin. Suppose, now, that a crank pin stands out of true in the direction shown in Fig. 2545, in which A A represents the axial line of the cylinder bore prolonged, and B B the axial line of the crank shaft (the two being parallel or in proper line). Let E E represent the centre line of the connecting rod when the crank is on one dead centre, the axial line of the crank pin being at C C. Then the brasses being keyed up to fit the crank pin, the centre or axial line of the connecting rod would stand as denoted by E E. But the brasses at the other end of the rod being keyed up to fit the cross-head journal, and their lines being at a right angle to the line A A, we have that the rod is at that end endeavored to be held parallel to A A; hence, keying up the connecting-rod brasses on the crank pin would tend to bind the rod, one end standing parallel to A A, and the other parallel to E E. This would place great strain on the outer radial face of the cross-head journal, as well as on the cylindrical body of the journal. When, however, the crank pin arrives at the opposite dead centre, as denoted by the dotted lines in Fig. 2545 (G G representing its axial line, and F F the centre line of the connecting rod at a right angle to G G), the want of truth in the pin throws the cross-head end of the connecting rod against the inside face of the cross-head journal. Hence, twice in each revolution is the connecting rod bent, and twice does it jam from side to side of the cross-head journal. It may now be pointed out that if we take either dead centre singly, and connecting the rod at the crank-pin end, try it at the cross-head end, and it will be a difficult matter to determine whether any want of truth at the latter end is caused by the crank pin being out of axial truth, or whether it is the crank shaft itself that is out of line. But there is this difference between the two cases. When the error is due to want of alignment in the crank shaft, the connecting rod will show the error _on the same side_ of the cross head, no matter on which dead centre the crank pin stands; but when it is due to the crank pin, the rod will fall inside the cross head on one dead centre, and outside when tried on the other dead centre, as is shown by the respective lines E and F, in Fig. 2545; E being at a right angle to C, and F at a right angle to G. [Illustration: Fig. 2546.] Again, it has been shown that when the shaft was out of line, a point on the crank-pin journal passed outside of the cylinder centre line at one dead centre and inside at the other; but when the pin is axially out of parallel, the path of a point on its journal will remain in the true plane, as is shown in Fig. 2546, the point being taken at the intersection of E and C C. A A represents the path of rotation of the same, which is parallel to the true face B of the crank. From the angle of the axial line of the pin being in opposite directions, when on opposite dead centres to the axial line of the crank shaft, the bore of the brasses cannot wear to suit the error, which, therefore, only diminishes by the wear of the crank pin. Suppose the error to be 1/64 inch in a crank-pin journal 3 inches long, and that the connecting rod is 6 feet long, the error at the cross-head end of the rod will amount to 3/8 inch. [Illustration: Fig. 2547.] In Fig. 2546 the error is shown to exist in an opposite direction, throwing the rod to the other side of the cross-head journal. But, in this case, the crank, when on the dead centre nearest to the engine cylinder, throws the connecting-rod end against the inside face of the cross-head journal, as denoted by the line E, which is on the opposite side of A A to what it is in Fig. 2545. Again, when on the other dead centre, the line F F, in Fig. 2546, falls _outside_, while F F, in Fig. 2545, falls _inside_ of A A, and it is by this difference that we are enabled to know in which direction the crank pin is out of true. To find the amount to which it is out of true in the length of its journal, place the crank on one dead centre, and with the connecting-rod brasses keyed up firmly home on the crank pin, and the other end of the connecting rod entirely disconnected from the cross head, mark on the latter a line coincident with the side face of the rod end, as at D, Fig. 2547. Then, with the crank pin placed on the other dead centre, mark another line on the cross head, coincident with the other side face of the rod, at C, Fig. 2547. Now, suppose that the line D shows the rod to fall 3/8 too much on that side, and line C shows it to fall (when on the other dead centre) 3/8 too much on the other side of the journal, and that the length of the rod is 6 feet, while that of the crank-pin journal is 3 inches, then the latter, divided into the former, gives 24, and this sum divided into the 3/8, the rod end falling out of true at C and D, Fig. 2547, gives us 1/64-inch as the amount the crank pin stands out of true in its length; hence, to correct the error, we may file on the crank pin a flat place at each end, as shown in Fig. 2548 by the lines C D, and then file on the top and the bottom of the crank pin a flat place B, 1/128-inch deep, and of equal depth all along the journal; by then filing the crank pin round and bringing the flat places just up to a circle, we shall have reduced the diameter of the crank pin by 1/64 inch, and have made it axially true with the cross-head journal. It is important, however, to bear in mind that, in this case, the crank pin is supposed to be out of true in the direction shown in Fig. 2545, and to stand axially true with the cross-head journal, when the crank is placed at half stroke, top and bottom, the crank shaft being in proper line. [Illustration: Fig. 2548.] If the axial line of the cross-head journal stands truly horizontal, the flat places on the crank pin may be filed horizontally level, with the crank placed on the corresponding and respective dead centres. But as the length of the cross-head journal is so short, it is difficult to gauge, if it does stand axially exactly horizontal, hence it is better to try the rod, or follow the above directions; especially as the cross-head journal and crank shaft may be in line without being axially horizontal. Suppose now that the axial line of the crank pin stands true with that of the cross-head journal when the crank is on either dead centre, but out of true when at the top and bottom half stroke. The connecting rod, connected as before, and tried with the cross head, will fall first to one and then to the other side of the cross-head journal, and the direction in which the crank is out of true may be known from the position of the crank pin when the error shows itself. [Illustration: Fig. 2549.] [Illustration: Fig. 2550.] If the error exists to an extent that is practically measurable, a pound in the journals, as well as their heating, is the inevitable result. In Fig. 2549, for example, the rod end is shown in section, and it will be noted that the error being in the direction there shown, and the crank pin in the respective positions there shown, the brass bore only contacts with the journal at each end, and that the diameter of the bore of the brasses is greater than the diameter of the crank pin journal to _twice_ the amount the crank pin is out of line. Now let us place the crank at the top of its revolution, as in Fig. 2550, and as its axial line then stands parallel to that of the cross-head journal, the brass bore is too large to fit the crank pin journal and there is lost motion. From the time the crank pin passes the dead centre this lost motion increases in amount until it becomes sufficiently great to slam the rod over against the side of the cross-head journal, while at the same instant the crank pin pounds in the connecting-rod brasses. At what precise part of each quarter crank revolution this action will occur, depends upon the amount the crank pin is out of line; but the more it is out the nearer to the dead centre it will be, and, conversely, the nearer true it is the nearer the crank will approach its highest and lowest positions before the pound takes place. If it is attempted to key up the brasses so as to spring the rod and let them close along the journal, the brasses will heat in proportion to the amount of error; hence when the crank pin pounds with the brass properly adjusted, and heats while keyed up enough to stop the pound, the crank pin is out of true. To test the alignment of an engine with stretched lines take out the piston and rod, and take off the connecting rod, then fasten a piece of iron at the open end of the cylinder so that it will hold a stretched line true with the axis of the cylinder bore. Provide at the crank end of the engine bed a fixed piece of wood to hold the other end of the line, and then with a piece of wire as a gauge set this line (tightly stretched) true with the cylinder bore. Then place the crank pin at the top of its path of rotation and drop a plumb line from the centre of its journal length, and this line should, if the crank shaft is horizontally level, just meet the stretched line. If it does not do so place a spirit level on a parallel part of the crank shaft, and if the shaft is not level it should be made so, and so adjusted that the line from the centre of the length of the crank pin journal just meets the stretched line from the cylinder bore. To test if the axial line of the crank shaft is at a right angle to the cylinder bore axis move the crank pin nearly to its dead centre, and measure the distance from the middle of its length to the stretched line. Then move the crank pin over to nearly the opposite dead centre, and (by means of the plumb line) measure the distance of the plumb line from the stretched line. To be correct the plumb line from the crank pin will during this movement just touch the stretched line. To test if the stretched line is fair with the centre of the crank shaft place a square on the end of that shaft and even with its centre, and the blade should then just meet the stretched line. The edges of the guide bars may also be tested with the stretched line, and the top and bottom of the guide-bar flanges may be tested to prove if the bars are of the correct height. To further test the bars place a spirit-level across them and lengthwise on them. If the piston rod and connecting rod are in place the alignment may be tested as follows; Let the piston rod be as far out of the cylinder as possible, and stretch a line to one side of it, just far enough off to clear the guide bars, &c. Set this line as follows: Let it be in line with the rod as sighted by the eye when standing some few feet away from it but horizontally level with the centre of the rod, set it parallel to the rod with a rule or its equivalent. Then the centre of the crank-pin journal should measure from the stretched line, the distance of the line from the piston rod added to half the diameter of that rod. This test, however, is not very accurate on account of the difficulty in setting the line, and because the piston rod may not have worn equally on each side. SETTING SLIDE-VALVES--An engine slide-valve may be so set as to accomplish either one of three objects. First, to give equal lead for each stroke; second, to cause the live steam to be cut off and expansion to begin at an equal point in each stroke; and third, for the exhaust to begin at an equal point in each stroke. If we, set the eccentric so that the exhaust will begin at corresponding points for the two strokes, the valve lead will not be equal, and the exhaust opening will be greater when the piston is at one end of the cylinder than it will be when the piston is at the other end. If the eccentric be set to cut off the steam at corresponding points for the two strokes, then the lead, the admission, and the exhaust of the steam at one port will differ (with relation to the piston movement) from that at the other. It is generally preferred to set the eccentric so as to give equal lead for the two ports when the piston is at the respective ends of its stroke, which gives an equal amount of exhaust opening when the piston is at the respective ends of its stroke. The only operations properly belonging to the setting of a slide-valve are those of finding the true dead centres of the crank pin, and setting the eccentric to give the valve the desired amount of lead. It is generally found, however, that the length of the eccentric rod requires a little correction, and as this must be done before the eccentric can be set, the setting operations should be conducted with a view to making the correction as early as possible. In many of the instructions given by various writers it is directed to first square the valve, which is to attach the parts and move the engine crank, or fly-wheel, through one revolution, to ascertain if the valve moves an equal distance on each side of the centre of the cylinder ports, correcting the length of the eccentric rod until this is the case. This is an error, because on account of the angle of the eccentric rod the valve does not, when set to have equal lead at each end of the stroke, move an equal distance on each side of the cylinder ports, but travels farther over the port nearest than it does over that farthest from the crank. When the travel of the valve is equal to twice the width of the steam port, added to twice the amount of steam lap, the valve does not fully open the farthest port from the crank. When the valve-travel is more than this amount both ports may open fully, but the error due to the unequal valve-travel from the angularity of the eccentric rod is increased. That the amount of error induced by squaring the valve is appreciable, may be seen from the fact that with 1-1/4 inch steam ports, 3/4 inch steam lap, and 4-1/2 inches of valve-travel, it amounts to about 1/8 inch with an eccentric rod 4 feet long. As the eccentric rod has (if a solid one, as in the case of a locomotive) to be operated upon by the blacksmith to alter its length, and requires some accurate setting for alignment after having its length corrected, it is obviously preferable to obtain its exact length at once. This may be done with less work than by the squaring process, which is entirely superfluous. [Illustration: Fig. 2551.] Assuming, then, that all the parts are properly connected and oiled, the valve is set as follows: Upon the face or edge of the fly-wheel an arc, true with the centre of the wheel, should be drawn, as at A B, in Fig. 2551, marking it on opposite sides of its diameter and opposite to the crank pin P. The engine should then be moved in the opposite direction to that in which it is to run, until the guide block I is very near its full travel. A straight-edge must then be placed to bear against, or be coincident with, the end face of block I, and held firmly while a line is drawn across the edge of the guide bars, as shown at C. There should then be fastened to the floor (which must be firm, and not give under the engineer's weight), a piece of iron W, having a deep centre-punch mark, or its equivalent. A steel tram-rod T, pointed at each end, is then set in the centre-punch mark at W, and with the upper end D a line made across the wheel edge or face. The fly-wheel must then be moved so that the crank passes the dead centre, the guide block moves back and away from the line C, and then approaches it again. When the end of the guide block is again coincident with the line C, the tram should be set as before and a second line, F, marked on the fly-wheel rim, and from these two lines, D and F, the crank may be placed upon its true dead centre as follows:-- [Illustration: Fig. 2552.] In Fig. 2552 a section of the fly-wheel rim is shown (enlarged for clearness of illustration); from the lines D, F the centre E is found, and marked with a centre punch dot to define it. It will be obvious, then, that if the fly-wheel be moved until this line and dot come fair with the upper edge of the tram T, the guide block will be at the exact end of its travel, and the crank, therefore, on its dead centre. By a similar operation performed with the guide block at the other end of the guide bars, and with lines on the other side of the wheel rim (as shown at B, J, K), the other centre L may be found. In obtaining these centres, however, a question arises as to the direction in which the wheel should be moved for bringing the guide block up to the lines at C, and for marking the lines D F and J K, or for bringing E or L true with the tram point. If the fly-wheel be moved in the opposite direction to that in which the engine is to run, the cross-head journal and crank pin will bear against the boxes of their brasses in the direction in which they will have contact when the engine is running. Suppose, for example, that the top of the fly-wheel when the engine is in motion moves from the cylinder, then the cross-head and crank-pin journals, driven by the piston, will bear against the half-brass nearest to the cylinder, which, _when the force-producing motion is applied to the fly-wheel instead of to the piston_ will be the case when the fly-wheel is moved in the opposite direction. By moving the fly-wheel in an opposite direction to that in which the engine is to run, the lost motion in the journals and bearings is therefore taken up in the proper direction so far as the connecting-rod brasses are concerned, and any lost motion between them and their journals will not impair the set of the valve, as would be the case were the fly-wheel moved in the direction in which it is to run. But by moving the fly-wheel backwards the play in the eccentric and in all the joints between it and the valve spindle is up in the wrong direction, because the power to move the rods is being applied in the opposite direction to that in which it will be applied when the engine is running, and, therefore, the play motion of the jointed or working parts will cause a lost motion impairing the set of the valve. Now there are generally more working parts between the eccentric and the valve than between the crank pin and the piston, and hence more liability for lost motion to exist, and it follows that in such case it is better to move the engine in the direction in which it is to run. It may be remarked, however, that the play may be taken up in the proper direction in both cases, and the engine be brought upon its dead centre, by moving it in the opposite direction to that in which it is to run, and that in setting the eccentrics they be moved on the shaft in the direction in which the engine is to run, as forward for the forward eccentric, and backward for the backward one (assuming the engine to have a link motion, and, therefore, two eccentrics). It is obvious that any other resting place may be used instead of the floor for the tram; thus in a locomotive the wheel guard may be used, the tram T being used to mark lines on the upper part of the wheel rim, instead of opposite the crank. To set the valve, place the fly-wheel on its dead centre, moving the fly-wheel as directed until one of the points (E or L, say E) comes fair with the point of the tram; then move the eccentric on the shaft until the steam port is open to the required amount of lead, and fasten the eccentric to the main shaft. Next move the fly-wheel around until on the opposite dead centre, and if the lead is the same in amount for both ports the valve is set. Suppose, however, that in this last case the lead is too great; then it shows that the eccentric rod is too long, and it must be shortened to an amount equal to half the difference in the lead. Or suppose that the lead when the wheel was tried on the last dead centre L, was less than for the other port; then the eccentric rod must be lengthened to half the amount of the difference. Assuming that the rod was too long by 1/32 of an inch, then it may very often be shortened by simply heating about six inches of its length to a low red heat, and quenching it in water. If the rod has a foot which bolts on a corresponding foot on the eccentric, then to lengthen it a liner of the requisite thickness may be placed between the two feet. [Illustration: Fig. 2553.] Suppose there is an equal amount of lead at each end but the amount is not sufficient or is too great: then the eccentric must be moved on the shaft until the proper amount of lead appears at the port. The lead must then be again tried at the other dead centre. In moving the eccentric, however, it must, under all conditions, be moved in the direction in which it will rotate, for reasons already given. The best method of measuring the lead where the lines on a rule cannot be seen is with a lead wedge P, as shown in Fig. 2553; this, if slightly forced in, will mark itself, showing how far it entered. [Illustration: Fig. 2554.] In some practice the position of the valve is transferred to the valve stem outside of the stuffing box or gland, as shown in Fig. 2554, sectional view. The valve stem being disconnected from the rod or arm that drives it, the valve is moved by hand to have the proper lead, as at A; a centre-punch mark is then made outside the stuffing box and a tram B rested thereon; with the other end of the tram a mark C is made on the valve stem. A similar mark is made on the stem when the crank is on the other dead centre, and the tram and marks, applied as shown, are employed instead of measuring the lead at the ports themselves. This involves extra work, but gives no more correct results. It involves marking lines on the valve stem, which is objectionable. If several trials have to be made there is a confusion of lines on the valve stem, and the wrong one is apt to be taken. On the other hand it affords a facility for setting the valve without having the steam chest open, which may in some cases be desirable. If this plan be adopted the lines on the valve rod should not be defined by centre-punch marks, for they will cut the packing in the stuffing box. When the eccentrics are secured to the shaft by a set-screw only, and not by a feather, it is an excellent plan, after they are finally set, to mark their positions on the shaft, so that if they should move they may be set to these marks without moving the engine around. For this purpose take a chisel with the cutting end ground to the form of a fiddle drill, one cutting edge being at a right angle to the other. The chisel must be held so that while one edge rests upon the axle, the other edge will bear against the radial face of the eccentric. A sharp blow with a hammer upon the chisel head will make a clean indented cut upon the axle and the eccentric, the two cuts exactly meeting in a point where the eccentric bore meets the axle circumference, so that when they coincide the eccentric is in its proper position. If the eccentrics of a locomotive should slip when the engine is upon the road, and there are no marks whereby to readjust them, it may be done approximately as follows:--Put the reverse lever in the end notch of the forward gear, then place the crank as nearly on a dead centre as the eye will direct, and open both the cylinder cocks, then disconnect the slide-valve spindle from the rocker arm, and move the valve spindle until the opening of the port corresponding to the dead centre on which the crank stands will be shown by steam blowing through the cylinder cock, the throttle valve being opened a trifle. The position of the valve being thus determined, the eccentric must be moved upon the shaft until the valve spindle will connect with the rocker arm without being moved at all. The throttle valve should be very slightly opened, otherwise so much steam will be admitted into the cylinder that it will pass through any leak in the piston and blow through both cylinder cocks before there is time to ascertain which cock first gives exit to the steam. Instead of finding when the crank pin is on the dead centre by means of the process shown in Fig. 2551, it may be found as in Fig. 2555, which is for a vertical engine. On the face of the crank and from the centre of the crank shaft as a centre, draw a circle B equal in diameter to the diameter of the crank pin. Then take a spirit-level C and apply it to the cylinder bore and note where its bubble stands. Then apply the spirit-level to the perimeter of the crank pin A and circle B, and move the crank until the spirit-level bubble stands in the same position as it occupies when applied to the cylinder bore. If the cylinder bore stands truly vertical the bubble will in both cases stand in the middle of the spirit tube; but in any event, the bubble must stand in the same position when applied to the crank as when applied to the cylinder bore, in which case the crank will be on its dead centre whether the cylinder bore be horizontal, vertical, or at an angle, the dotted line E passing through the centre of the crank and the axis of the cylinder bore. [Illustration: Fig. 2555.] When an engine has two eccentrics, so as to enable the engine to run in either direction, as in the case of a locomotive, it is necessary to consider which eccentric is to be set for the forward, and which for the backward motion. In American locomotive practice it is usual to let the eccentric nearest to the wheel, and, therefore, the most difficult to get at, be for the backward motion, which is the least used, and therefore the least liable to get loose upon the axle. The eccentric that connects to the top of the link is usually that for the forward motion, and hence that which connects with the eccentric farthest from the wheel. In testing the lengths of the eccentric rods, work may be saved after the engine is first placed on its dead centre by putting the reverse-lever in the forward notch of the link, and adjusting the forward eccentric until the valve has the proper lead. Then set the reverse-lever in the back notch and move the backing eccentric (in both cases moving them in the direction in which they will run), until the proper amount of lead appears. The engine may then be placed on the other dead centre, and the lead both for forward and backward gear measured, so that if there are any errors both the rods may be corrected for length; but for the final trial the crank pin must be set on its dead centre for each direction of motion separately, so as to take up any lost motion in the connecting-rod brasses. [Illustration: Fig. 2556.] In the case of large marine engines it is not practicable to move or rotate the engines to set the valves, and the eccentrics are therefore adjusted to their positions on the crank shaft by lines before the crank shaft is put into its place or bearings. First, the throw of the crank is set to stand horizontally true by the following method: From the centre of the crank shaft strike a circle of the diameter of the crank pin, as shown in Fig. 2556, at A, and draw upon the face of the crank a line that shall just meet the two circles as denoted by the line B, using a straight-edge, one end of which rests upon the crank pin, while the other end is coincident with the perimeter of the circle A. [Illustration: Fig. 2557.] By means of the wedges shown at C D adjust the crank until the line B stands horizontally level, tested by a spirit-level. A straight-edge having straight and parallel edges is set horizontally level, beneath the eccentric, so that its edges will stand parallel with the throw line of the crank. On this straight-edge, and parallel to the edges, is marked the line A A, Fig. 2557. The first process is to mark on A A the centre of the crank shaft K, which is done as follows: Over K is placed the fine line B B, suspending the weights or plumb bobs at B B; coincident with this line and across A A, are marked two lines C D; midway between C D is marked E, which therefore stands directly beneath the shaft centre. From E the line F is drawn distant from E to the amount of lap added to the lead the valve is to have. From F as a centre two lines are drawn across A, their distance apart equalling the full diameter of the eccentric; the plumb line is then placed over the eccentric, and the latter is rotated on the shaft until the plumb lines come exactly fair with the lines G H. [Illustration: Fig. 2558.] It is obvious that instead of using plumb lines a square may be employed to mark the lines C D, and to set the eccentric to the lines G H, the square being applied as at S and S´, in Fig. 2558. [Illustration: Fig. 2559.] In this example it has been assumed that the direction of crank rotation was to be as denoted by the arrow; but, suppose the crank rotation required to be in the opposite direction, then the marks on the straight-edge would require to be located precisely the same, but the position of the eccentric throw-line would require to be as in Fig. 2559, the perimeter of the eccentric being set to the lines G H as before. The eccentric rod being supposed to connect direct to the valve spindle, without the intervention of a rock shaft, for if there is no rock shaft the eccentric leads in the direction of rotation, while if the engine has a rock shaft the eccentric follows the crank-pin in the direction of rotation, and F must be marked on the crank-pin side of E, as in Fig. 2560. [Illustration: Fig. 2560.] [Illustration: Fig. 2561.] If two eccentrics are used, as in a link motion, the lines for setting one eccentric are equally applicable to both; the lap and lead line F being located on the crank-pin side of E when there is a rock shaft, as is supposed to be the case in Fig. 2561; and on the other side of E when there is no rock shaft; and in this case the eccentric that is to operate the valve to make the engine run forward must have its throw-line following the crank pin, as at J, in Fig. 2561; the eccentric K operating the valve for running backward. Conversely, in the absence of a rock shaft, the throw-line of the forward eccentric leads, while that of the backward eccentric follows the crank pin. When the line of connection of the eccentric rod is not parallel to the axial line of the cylinder bore, the crank must be placed horizontally level (or if it be a vertical engine, on the dead centre), but instead of the straight-edge being placed parallel to the throw-line of the crank, it must be placed at a right angle to the line of connection of the eccentric rod. [Illustration: Fig. 2562.] Thus in Fig. 2562 the engine is supposed to be a vertical one, and the crank is, therefore, placed on its dead centre, its throw-line being vertical instead of horizontal as in our previous examples (which were supposed to be for a horizontal engine). It is also supposed to have a rock shaft A; hence the straight-edge is set at a right angle to the line of connection of the eccentric rod which is denoted by B. It is obvious that to set the crank throw-line vertical the circle B in Fig. 2509 may be used, the spirit-level being resorted to to discover when the crank stands vertical. [Illustration: Fig. 2563.] An example in the erection or setting of framed work is shown in Fig. 2563, which represents a side elevation of a frame put together in four parts, two side and two end frames. A and B are journal bearings requiring to stand parallel and true one to the other, B being capable for adjustment in distance from A by means of the adjusting screws G, H. The bearings C, D, E, F, are to be parallel one to the other and to A, B. Their proper relative distances apart, and the axes of all the shafts, are to stand at a right angle to the side frames. [Illustration: Fig. 2564.] Fig. 2564 represents an end view of the frame, the ends T being bolted to the side frames S and S´ at I, J, K, and L. Now it is obvious that the ways for the bearings A, B, C, &c., may be trued out, ready to have the brasses fitted before the framework is put together, and that from their positions they would have to be planed out at separate chuckings; supposing, of course, the frame to be too large to be within the capacity of the machine table. It would be difficult to cut all the surfaces of the bearing ways to stand in the same plane, unless there were some true plane to which all might be made common for parallelism. Furthermore, unless the surfaces where T is fastened to S and S´ are properly bedded to fit each other, bolting them up would spring and bend the frames out of their normal planes. To meet these requirements, there are given to the side frames a slightly projecting surface where the feet of T meet them, and furthermore, the feet of T themselves project beyond the sides of T as shown. These projecting pieces may therefore be planed to a common plane without planing the sides of the respective frames; and this plane should be as nearly as can be parallel with the body of each frame surface. The surfaces of the bearing ways may then be planed parallel to those of the projections, and the jaw surfaces true to the side surfaces, and all the bearing ways will stand true if the frames be properly set--when put together with the bolts. But unless the bedding surfaces at I, J, K, L, be made to bed and fit properly, the whole truth of the bearing ways and their distances apart across the framework may be altered. Thus, supposing the feet of T at I and J to meet S as denoted by the dotted lines O R, and whether the fault lie with the feet of T or with the projections on S the result will be that the pressure of the bolts holding I J to S will bend S so that its plane will be a curve as denoted by the dotted line P P, and the distances apart of the journal ways B B and D D respectively will be wrong, being too wide on account of the bend outward of S. But the feet may touch on the opposite corners, the surfaces of S´ or of T being out of true or out of full contact, as denoted by the dotted lines V W on K, L; in this case the frame S´ would be bent to the curve Q Q, and the journal ways would be too close together. On the other hand, the want of fit between these surfaces may be in the direction of the length of the frame instead of the direction of its height, as has been supposed; or it may be in one direction on one foot and in another direction on another foot. But in whatever direction it does exist, it will inevitably bend and twist the frame. It must not be taken for granted, that because these surfaces have been planed or milled, that therefore they are true; because frames of this class cannot, if large, be held without springing them to some extent from the pressure of the bolts or other devices necessary to hold them to be cut. It is not uncommon to plane the surfaces as true as may be, and put the frames together, bolting them up tight, and then applying the straight-edge trammel and rule to test the truth, correcting any error that may be found by inserting pieces of paper, sheet tin or material of requisite thickness on one side of the surfaces, so as to offset the error in their fit and bring the framing true; but this is not the proper way, because it reduces the area of contact, and furthermore renders a new testing and adjustment necessary whenever the frames are taken apart. It is better therefore to apply a straight-edge to the surfaces and true them to it, testing them vertically as by placing the straight-edge across K L, and longitudinally across S´, at K and the corresponding projection at the other end of the frame, filing them until they appear true. The holes through the frame may be drilled before filing these surfaces, so as to reduce the area to be filed. Since the end frames T do not in this example carry any journals or mechanism, the position of T is not so particular as it otherwise would be; hence, the holes in its feet may be marked off and drilled independently of the frame, the holes being drilled a little too small to allow for reaming with the holes in the frame. The framing will then be ready to put together (all machine work upon them being supposed to be done). The feet of all such frames should be planed true, so that the frame, when put together, may stand true and steady when placed upon a level floor or foundation, and in this case the distance and parallelism of the feet surfaces will be true with the ways or bearings, affording much assistance in holding the frame while putting it together. The height of the holes may be measured and marked from the feet surface, thus insuring truth as far as height is concerned. Lines may be drawn or marked on each side frame, at the proper distance from and parallel with the jaws of the ways A, B, thus completing on the side frames the marking of the location of the centres of the holes for bolting the end frames on. If the frames were of a size to be sufficiently easily handled, the end frames might be put in their places, and the whole framework set true, so as to mark the holes in the end frames from those already drilled in the side frame. But if the use of a crane were necessary to lift them, it would be better to mark the holes on the end frames, and drill them before putting the framework together at all, leaving sufficient to ream out of the holes to bring them fair, notwithstanding any slight error in drilling them. In this case, a line denoted by the dotted line X in Fig. 2564, should be drawn across the frame, and the holes at I and J be made equidistant on each side of it, as well as the proper distance apart. X must be at a right angle to the trued foot surfaces at I J, so as to cause the side frames to stand vertical while their feet are horizontal. Supposing now the holes to be drilled and the frames are to be bolted together, the whole frame may be held temporarily together by bolts passing through the side frames at each end, or a bolt may be passed through the holes F to steady it. Indeed, if these holes F have been accurately bored, a neatly fitting mandrel passed through them should hold the side frames true. The end frames T having been set to stand at a right angle to the side frames, and with their holes at I J, &c., as near fair as may be with the holes in the side frames, two feet, as I J, may have their holes reamed fair with the holes in the side frames, and tightly fitting bolts be driven in and screwed firmly home. Before reaming the other holes (as K L) of each end frame, the jaws to receive the bearing boxes should be tested for alignment one with the other. Truth, in this respect, being of the utmost consequence for the following reasons: Suppose the bearing ways on one side frame to stand higher than those on the other, then, the shafts will not stand level in the frame unless (except in the case of the brasses or boxes in B) the lower brasses are made of unequal thickness through the crown, to an amount equal to that of the error. In the case of the brasses in A, C, D, E, the joint faces of all the brasses of one side frame would require to be made thinner beneath the journal than above it on the high frame, and thicker beneath than above on the low frame, This would entail much extra work in planing, marking, and boring the bearing boxes or brasses, and be an inferior job when done. Again, the bores of all the brasses would not be parallel to the crown or bedding faces, and this error would entail the following extra work: 1. Ascertaining the amount of the error, and allowing for it in marking the brasses; 2. The setting of the ways of the brasses out of true with the ways when clinking them for boring; and, finally, extra fitting or filing the brass bores when fitted with the shafts in place. This extra fitting would be necessary for the following reasons: When the surfaces of work are to be parallel, they can be measured with calipers. Surfaces to be at a right angle can be tested with a square; those to be in line can be tried with a straight-edge, and in each case the truth or alignment of the surfaces is tested by contact of the testing tool. But in the cases where surfaces at an angle are tested or measured the tools must be set to a line or lines, and the work must be measured or cut to lines, thus: Suppose it were found that the bedding surface of the brass B was a certain amount out of alignment with the corresponding bedding surface on the other side frame, and, by measurement, this amount determined to be 1/64 inch, then there is a liability to error in measuring this 1/64. The brasses must be marked (for boring the same 1/64 out of square, inducing another liability of error in marking that amount); this marking being done by lines, there is a liability to error in setting the work to the lines. From these liabilities to error, it is generally found that work not true in alignment requires, when it comes to be put together, to have each piece fitted to its place and corrected for alignment. But, suppose the ways are made true and in proper alignment, then the brass bores are simply made of equal thickness at the crown, and on the sides at a right angle to the inside faces of the ways; and truth, in these respects, may be measured by actual contact, with the square or calipers, eliminating the chance of error. In repairing the machine, or putting in new bearings or brasses; the measurement and transferring of the error in the ways to the brasses has all to be gone through with again, and the parts fitted for alignment; whereas, if the ways are true, the brasses can be made true, and to go together, with but little, if any, adjustment when tried in their places. [Illustration: Fig. 2565.] The most accurate method of testing the adjustment of the ways is as follows: Fig. 2565 represents a plan view of the frame; N represents a straight-edge applied to the surfaces of the jaws _a_ _b_. The method of applying this straight-edge is to place one end across a jaw, as _a_, while the other end is elevated above _b_; then, while pressing the end firmly against _a_, lower the other end to the face of _b_; if its edge at that end falls fair with _b_, so as just to touch it, the process may be reversed--one end being pressed to _b_, and the other lowered upon _a_. By this means, it will not only be discovered whether the jaws _a_ and _b_ stand square across the frame, but also whether the frame on either side is sprung. A square _c_ may also be rested against N, and its blade _d_ tested with the side face of the way, as shown. The same process of testing should be applied to the other jaw faces _e_, _f_. Suppose, however, that the width between the jaws _a_, _f_ was less than that between _e_, _b_, then the straight-edge, when pressed to _a_, would show a space between its edge and _b_; and also a space between its edge and _e_, when its other end was pressed to _f_; and, when these spaces were equal in amount, the frames would be set true in one direction. To test the truth in the other direction, the straight-edge should be applied after the same manner to the bottom surfaces _g_, _h_. It will not answer to rest the straight-edge against the two surfaces and observe their coincidence with its edge, because any error cannot be sufficiently, readily, or accurately tested by this means. Nor will it answer to test by the bearing marks of a straight-edge applied with marking, unless the coat of marking be very fine and the straight-edge be moved without any vertical pressure on it; because, under such pressure, the straight-edge will bend. The ways for all the bearings should be tested in this manner; so that, if from any error in the machine work, some of them will not come fair, the frames may be set to align those that it is of most importance to align truly; or if there is no choice in this respect, then those carrying the largest bearing should be set true; because, if it be decided to correct the error on the other bearing or bearings, there will be less area to file or operate upon. The setting being complete the holes may be reamed and the remaining bolts put in, the testing being repeated after the frame is finally bolted together. If this final test shows that bolting the frame up has altered the alignment by springing the frame, the bolts in one foot, as say I, Fig. 2564, may be slackened and the test repeated; and, if the frame is then found true, it is the bolting at I that causes the spring, on account of the bedding surfaces not fitting properly. If I is not found to be at fault, it may be bolted up again and J tested by loosening its bolts, and so on, until the location of the error is detected. Furthermore, when the frame is bolted up, the width of the bearings, as from _a_ to _b_, should be tested; for in a job of this kind, it will pay to have the framework so true to the drawing that, if the other parts, as the shafts, bearing parts, &c., be also made to the drawings, the parts will go together, thus avoiding the necessity of varying all the other parts from the drawing to accommodate errors in the framework. [Illustration: Fig. 2566.] Among the jobs that the erector is often called upon to perform is that of patching or repairing pieces that have cracked or broken. Fig. 2566 represents a case of this kind, the fracture being at D. The principle to be observed in work of this kind is to cause the bolts to force the fractured pieces together, so that the irregularity or crookedness of the crack, as at D in the figure, may serve to lock the pieces together. [Illustration: Fig. 2567.] Suppose, for example, we were to put on a patch P, Fig. 2567, and there would be but little to prevent the crack from opening under severe strain, and the patch would stretch, permitting the crack to open and finally causing the bolts to break or sheer off. A preferable plan, therefore, is to put two patches on the sides in the following manner:-- The holes should be drilled through the beam and the plates held against the beam so that their holes may be marked by a scriber passed through the holes in the beam. The holes in the plates should be drilled closer together than those in the beam, so that when driven in they will serve as keys to close the two sides of the crack together, as shown in Fig. 2568, where it is seen that one side of the bolt bears against the holes in the patch and the other against the holes in the beam. To facilitate getting the bolts in place the plates may be heated so as to expand them. In cases in which it would not be permissible to drill so many holes through the beam on account of weakening it, we may use patch bolts with countersunk heads, as in Fig. 2569. Two only of the bolts pass entirely through, and it is best to let them be taper, as at A in the figure, the head not meeting the patch. The hole in the beam, after being reamed taper, should be filed out on the side B, and that in the patch plates on the other side, as at C and D, so that the bolts will serve as keys. After these two bolts are in place and their nuts firmly screwed home, the holes for the patch bolts may be drilled through the plates and into the beam. When the countersunk head bolts are fitted they should be turned down behind the head, so as to leave a part weaker than the bolt, and then screwed in until the required end breaks off. The taper bolts should be of steel, but those with countersunk heads may be of iron. [Illustration: Fig. 2568.] [Illustration: Fig. 2569.] ERECTING AN IRON PLANER.--If an iron planer be properly fitted and erected, the table will be quite solid in the [V]-ways in the bed, and will not rock or move even though a heavy vertical cut be taken at the extreme sides of the table, but any error of truth of alignment or fit either in the bed-ways or the table [V]'s will cause the table to lie improperly in the [V]'s and to be apt to rock as it traverses. The author has had planed upon a planer thirty years old, at the Freeland Tool Works, in New York City, a cast-iron surface 12 × 20 inches, the metal weighing about 60 lbs., and the surfaces were so truly planed that one would lift the other by reason of a partial vacuum between the two. These planed surfaces were exhibited by the author at the American Institute Exhibition in 1877, and were awarded a medal of superiority. The manner in which this planer was fitted and erected, and the principles involved in such fitting and erecting, are as follows: While it is essential that the foot or resting surface of a planer bed (whether it stands on legs or rests direct upon its foundation) be as true as it is practicable to plane it, still it is more essential that the [V]'s or ways be true, and as the casting will be apt to alter its form from having the surface metal removed, it is best to plane the side on which the ways are the last. When the bed is placed upon the machine to have its resting surface planed, the casting being uneven, it will be necessary to place packing pieces of suitable thickness beneath the places where the clamping plates hold it, so that the pressure of those plates may not spring or bend the casting. These packing pieces require to fill up solidly (without lifting the bed) the hollow places, and it is a good plan to place among them a piece of strong writing paper for reasons which will appear presently. In planing the bed all the surfaces should be roughed out before any are finished. Before any finishing cuts are taken all the clamping bolts should be loosened and the pieces of paper tried by pulling them, so that if the casting has altered its form it will be made apparent by some one of the pieces of paper becoming loose. In this case the packing must be readjusted, clamping both as lightly as will hold the work, and all as equally as possible, when the finishing cuts may be taken. [Illustration: Fig. 2570.] The best form of template to plane the ways to is that shown in Fig. 2570, in which B is a side and A an end view. A corresponding female template being shown at D to be used in planing the table [V]'s. The length C of the [V] of the template must not be longer than from 4 to 6 inches, or it will be liable to spring or twist from its own weight. This template is not intended to be used in any sense as a straight-edge to test the truth of the length of the ways, but rather as one to test their width apart, and the correctness of the angles. The top surface A B should be quite true with the [V]'s, being equidistant from them, so that by testing that surface with a spirit-level it may be known whether the ways are level either crosswise or lengthwise. The [V]'s of the template require to have red marking on them so as to mark the ways when the template is moved, and show that the ways accurately fit to the template, which is highly important. In planing the table or platen it is essential to bear in mind that the area to be planed on the [V] side is always small in comparison with that to be planed on the other or work-holding side of the table, and as the planing of this latter surface is sure to cause the casting to alter its form, it is necessary to plane it first, so that the alteration of form may occur before and not after the [V]'s have been planed. In chucking the table to plane its work-holding surface, the packing pieces must be used as described for the bed, and the bolts placed as there described. Both bed and table being planed they require to be fitted together (no matter how expertly the planing has been done) if a really first-class job is to be made of them. In doing this it is essential that the bed be supported at the same points as it will be when the machine is put to work, for in large or long casting the deflection or bending from its own weight is sufficient to have an important practical effect. The same fact will also apply to the table and even to the cross slide, even though the latter be heavily ribbed and but, say, 5 feet long. If, therefore, the bed is to be supported by legs, its guideways or [V]'s should be fitted after the legs are attached. The bed must be carefully levelled so that the ways may stand horizontally true, which may be tested by placing the template A B in Fig. 2570 in place and applying a spirit-level first across and then lengthwise of the upper surface of the template. If the bed rests upon a foundation at several points in its length it should be rested at those points while being fitted and carefully levelled as before, the template and spirit-level being tried at every two or three feet of the bed length. To test the width of the [V]'s and their widths apart in the fitting, the template A B, Fig. 2570, must be used in connection with red marking, but to true the lengths of the ways a surface plate about 4 feet long and slightly wider than the width of one side of the ways must be used, and if the template and the surface plate show the ways true they will be of the correct width, of correct angle and true planes. But this does not insure that the two ways are in line one with the other, and for this purpose separate test blocks are necessary, because the template is too narrow in width to give a good test, and cannot be made wider, because in that case its own weight would cause it to spring or deflect to suit any error in the work. [Illustration: Fig. 2571.] These test blocks are simply two pieces of metal, such as shown in Fig. 2571. The lengths of these blocks should be about 8 inches, and the best way to obtain them true and exactly alike is to make one block and then cut it into two. They possess an advantage not possessed by a template that spans both ways, inasmuch as they may be turned end for end in each way and thus test the accuracy of the angles of each way. Again, both may be placed in one way, and by various applications in connection with straight-edge, surface plate, and level they will test the truth of the ways, both individually and one with the other in a better manner than by any other method. Fig. 2572 represents the various positions of the [V] blocks for the testing, A, B, C, D, E, F, G, H, representing the blocks; straight-edges may be placed as at I, at J, and at K, and if the ways are true the straight-edge, lightly coated with marking, should have contact clear across the upper surface of both [V]-blocks, and a spirit-level placed on the straight-edge (in each position of the same) should show them to be level. The surface P, on which uprights or standards on that side of the plane, rest, being planed with the [V]-ways will be true with them, and the uprights may be erected thereon, their base surfaces being fitted to P until the standards stand truly vertical and parallel in their widths apart. In testing these uprights they should be bolted home as firmly as they will be when finally erected, as they will be liable to alter their set if bolted up more firmly than when tested. These front surfaces should be at a right angle to the length of the bed [V]-ways, and this may be tested by placing a straight-edge across their surfaces and testing it with a square rested against the edge of the planer table. The method of erecting planers at the Pratt and Whitney Company's shops is as follows:-- To test the [V]'s, a plate P, Fig. 2573, is applied as shown, its lugs _a_, _a_^{1} fitting to corresponding sides of the two [V]s; as B, B. In Fig. 2573 the test is made by inserting thin pieces of tissue paper between _a_, _a_^{1} and the [V]-sides, the friction with which the paper is held showing the nature of the fit. Thus, if the paper will move easily at one end and is tight at the other end of either of the lugs _a_, _a_^{1} the fit is shown to be defective. When the fit on these sides is corrected, the plate P is turned around, as in Fig. 2574, and from a similar tissue-paper test, the other sides are corrected. Thus the outside angles of the two [V]s are fitted to the same angle; inside angles are also fitted to the same angle. But it will be observed that it does not follow that the inside angles of the [V]s are of the same degree of angle as are the outside halves or angles, unless the two lugs _a_, _a_^{1} of the plate P have equal angles. It is on this account that the test is made by tissue paper, rather than by the bearing marks produced by rubbing P along the [V]s, since that might in time wear the angles _a_, _a_^{1} out of true. The same plate P may be used to true the male [V]s on the work-holding table of the machine, as is shown in Figs. 2575 and 2576, where the table is seen upside down, as is necessary in order to apply the plate. Here, again, the outside angles or halves of the [V]s are fitted from the same [V] (_a_^{1}) of the plate, so that the fit of the table will be true to the bed, even though the angle on one side of the [V]-ways were not precisely correct, and there is less liability to error than would be the case were a male and female plate used instead of a single plate. The alignment next in importance is that of the uprights, standards, or side frames of a planing machine, and to enable the correct erection of these, the device A, Fig. 2577, is employed. It consists of a solid plate fitting into the [V]-ways of the planer-bed and having two steps, B and C, which receive the side frames to be erected. The width D is the width apart of the side frames, and the side surfaces of the steps (as G) are vertical to the centre line of the [V]-ways of the bed, so that the side frames may be rested against G on one side, and the corresponding surface on the other step. The surfaces E, F are at a right angle to the [V]-ways of the bed, so that when the side frames are against E, F they will be set square across the machine. The top face of the plate A is planed parallel to the [V]s of the plate, so that in addition to resting each side frame against the surfaces (as F G) a square may be rested on plate A and applied to their trued surfaces, and thus may these side frames be set true and square, both one with the other, and with the ways in the bed, without the use of stretched lines and straight-edges, which secures greater accuracy and saves considerable labor. [Illustration: Fig. 2578.] All the smaller parts of the machine may then be erected true to the bed or the side frames, as may be required, and if it be a small planer, in which the bed rests upon feet, all that will be necessary in setting the machine in position to work is to set the surface of the work-table level. But in the case of a large heavy planer a solid foundation must be built for the bed, because it will spring, bend, and deflect from its own weight, and thus the side frames, as well as the bed, may be thrown out of true and alignment. Fig. 2578 is a side and plan view of the foundations for a planer, showing the bed-plate in position upon the same. [Illustration: _VOL. II._ =TESTING PLANER BEDS AND TABLES.= _PLATE XI._ Fig. 2572. Fig. 2573. Fig. 2574. Fig. 2575. Fig. 2576. Fig. 2577.] The stone blocks forming the base of the foundation require themselves to rest upon a solid base, and not upon a soil or gravel that is liable to sink beneath them. The brickwork above them is best laid in cement, which should be properly set before the planer bed is placed in position. Near the centre of the bed, and directly beneath the cross-slide, is shown a screw jack, to take up any sag of the bed, and cause the [V]s to have a good bearing directly beneath the cutting tool, which is essential to prevent the table from springing from the pressure of the tool cut. FITTING UP AND ERECTING A LATHE.--The first operation will be to true the bed or shears. If the lathe has raised [V]s on the bed it will be sufficient to true them only, without truing the flat surfaces. The bed should during the fitting be supported at the same points as it will be when in use. [Illustration: Fig. 2579.] The method of aligning the lathe heads at the Pratt and Whitney Company's workshops is as follows: Fig. 2579 is a side and an end view of a part of a lathe shears A, with the tailstock B thereon. To the bore of the tailstock there is closely fitted an arbor C, accurately turned in the lathe, and having at the end D and at E two short sections of enlarged diameter. A plate F is fitted to the inside [V]s of the shears (upon which [V]s the tailstock sits). This plate carries a stand G, and a second gauge or stand G. Stand G fits at its foot into a [V] provided in F, as shown, the object of which is to so hold G to F that its (G's) face will stand parallel to arbor C. The stand is so adjusted that a piece I may be placed between C and G and just have contact with both, and it is obvious that if this is found to be the case with the tailstock and the stand placed at any position along the bed, the arbor C, and, therefore, the bore of the tailstock, must be true, sideways, to the inside [V]s of the lathe shears. The testing, however, is made at the enlarged sections D and E, G of course being firmly bolted to F. To test the height of the arbor C from the [V]s, and the parallelism in that direction, stand H is provided. It carries a pointer or feeler K, whose end is adjusted to just touch the enlarged sections D and E of C, it being obvious that when the degree of contact is equal at these two sections, with the tailstock and the plate F moved to various positions along the bed, the adjustment or alignment in that direction is also correct. The adjustment and corrections may then be made with the headstock of the lathe in place of the tailstock, the arbor fitting into the bored boxes of the lathe and extending from it, and having two sections of the same diameter, as sections E in the figure. Now, suppose that in the test thus made the bar C proves to stand true in some locations, but not in others, upon the bed; then it is proof that it is the [V]s that require correction, while the tailstock is in error in all cases in which the error is constant, with the tailblock moved in various positions along the shears. In some practice the heads are bored after being fitted to the ways, and in this case the boring bar may be supported by standards fitting to the lathe bed, running in bearings, and not on centres. There should be three of these bearings, one at one end of the head, and as close to it as convenient, another at the other end, as close as will permit the insertion of the cutters, and the third as far from the second as will permit the insertion on the bar and between them of a pulley to drive the bar, which must be splined to receive a feather in the pulley, so that the bar may be fed through its bearings and through the pulley to the cut. After the live head has been bored the tailstock or back-head may be bored from the other end of the bar, so that the standards will not require to be moved on the bed until the boring is completed. The bar may be fed by hand, or an automatic feed motion may be affixed to one of the standards. The heads being secured to the bed while being bored, there is no liability of error in their alignment, because, even if the holding bolts spring the heads in clamping them to the bed, the holes will be true when the heads are firmly home upon the bed, as they will be when in use, whereas under this condition such will not be the case if the holes for the spindles are bored before the seats are planed and fitted. The feed screw must be placed quite parallel to the [V]s or guides of the bed, or otherwise the pitches of threads cut in the lathe will be finer than they should be, and the screw will bind in the feed nut, causing undue wear to both. The method employed to test the truth of lathe shears and heads in the David W. Pond Works, at Worcester, Massachusetts, is as follows:-- [Illustration: Fig. 2580.] The planing, both of the lathe shears and of the heads, being done as accurately as possible, the heads are provided with a mandrel or arbor, to the end of which is secured the device shown in Fig. 2580, in which A is a hollow cylindrical piece having a threaded and split end, so that by means of a nut the bore may be closed to tightly fit the arbor referred to; B, B are two arms, a sliding fit in A, to enable their adjustment for the width of lathe [V]s, and having a flat place on one side, as at C C, to receive the pressure of a locking device D, by means of which B, B may be fastened in their adjusted positions; E, E are cylindrical arms, a sliding fit in B, B, also having flat sides, and capable of being secured in their adjusted positions by means of locking devices F, F. [Illustration: Fig. 2581.] [Illustration: Fig. 2582.] Fig. 2581 is an end view of the device in position on a lathe tail stock, and Fig. 2582 is an enlarged view (being half full size) of the devices at the lower end of arms or rods E, E. At the lower ends of E, E are provided two pieces G, G, which are capable of adjustment to fit the [V]s H, H of the lathe, as follows:-- The middle pins I are fast in the arms J, but are pivoted in G, the end pins, as K, are pivoted in G, are flat where they pass through J, and threaded to receive the nuts, L, of which there are four, two to each piece G. By operating these nuts, G may be adjusted to bed fair on the angles on the lathe [V]s H. At M are two fixed pins which afford a fulcrum, at N and O respectively, to four index needle arms. Two of these index arms only are seen in the cut, marked respectively P and Q, which are pivoted at N. Two similar pointer or needle arms are on the other side of M, being behind P and Q, these two being pivoted respectively at O. At the lower end of P is a point resting in the centre of the nut, and similarly the end of Q rests in the centre of the nut on that side. Similarly the two needles not seen have pointed ends resting in the centre of the nuts marked respectively L. Between G and J are two springs placed back to back, which act to hold G away from J. But it will be seen that if either end of G be forced towards J, as by passing over a projection on the [V] H, then the pin K, will push nut L, and this will raise the end of the pointer or needle to a corresponding degree, and the pointer being pivoted (as at N), its upper end will move and denote on the graduated index R that there is an error in the lathe [V], the amount of the error being shown multiplied on account of the leverage of the needle arms from the pivots. The pieces G being adjusted to bed fairly on the lathe [V]s, the heads of the lathe are moved along the lathe shears, and if the [V]s are true to angle the upper ends of the needles will remain stationary, a projecting part of a [V] will, however, cause the needle point to move toward E, while a depression on a [V] would cause the springs K to move G in, keeping it in contact with the [V], while the needle point would move away from E. To maintain the needle arms in contact with the nut heads L, springs S are employed. Variations in the widths apart of the [V]s on either side of the shears would obviously be shown in the same manner, the defect being located by the needle movement. The corrections are made from the contact marks of the heads, caused by moving the heads along the [V]s and by careful scraping. Notwithstanding that every care and attention may be taken to make a lathe true in the process of manufacture, yet when the whole of the parts are assembled it is found essential to test the truth of the finished lathe, because, by the multiplication of minute errors the alignment of the lathe, as a whole, may be found to need correction. A special inspector is therefore employed to test finished machines before they leave the works, and in Fig. 2583 is represented the device employed for testing the alignment of the line of centres of lathes. Upon the face of the face plate and near its perimeter there are turned up two steps, as denoted by B and C. The tail-spindle is provided with a stud S, which fits in the place of the dead centre, and carries what may be termed a double socket, one-half of which (as F) envelops the stud S, while the other half (A) envelops and carries a rod R. These two halves are in reality split sleeves, with set screws to close them and adjust the fit. By means of the screws E, the sleeve F may be made a tight working fit upon S, while, by means of screws G, sleeve A may be made to firmly grip the rod R, which may thus be securely held while still capable of being swung upon stud S. Upon the outer end of the rod R is another sleeve I, which is also split and secured to the rod R by means of screws corresponding to those shown at G. It also carries a pin, upon which a disk K is pivoted, and a lug through which the adjusting screw V is threaded. Upon K is a lug which has on one side of it the end of a spring T, and it is obvious that by operating V the disk K will be rotated upon its central pin. K carries two lugs, L and M, the latter being threaded and split. These two lugs receive a sleeve N, threaded into M, and a close plain fit in L. The small end of this sleeve is split and is threaded slightly taper, and is provided with the nut P. Through this sleeve passes a needle Q Q, one end of which is bent as shown, and it is obvious that by screwing nut P upon N the sleeve will be closed and will tightly grip the needle Q Q. Now, suppose that the head of N is operated, and it will move endwise through L and M, carrying with it the needle Q Q, which will remain firmly clasped in the sleeve; or suppose that screw V is operated, and K will revolve, carrying with it the needle Q Q, which will still remain firmly gripped, and it follows that there is thus obtained a simple means of adjusting the needle without releasing it. [Illustration: Fig. 2583.] The application of the instrument is as follows: To test if the head and tailstocks are of equal height from the bed, the instrument is set and adjusted exactly as shown in the engraving, the needle being adjusted to just touch the diameter of the step at B. The rod R is then swung around so that the needle comes opposite to the same step B at the bottom of the face plate, and if the needle just touches there also the adjustment for tailstock height is correct. Similarly for testing if the tailstock is set true sideways the needle may be tried in the same manner and upon the same step, but upon the two opposite sides of the face plate, instead of at the top and bottom. It now remains to test if the tailstock is in line in a horizontal direction with the live spindle, and this is done by reversing the needle end for end in the sleeve N, and setting it to just touch the face C of the turned step on the face plate, and if it just touches at the top and bottom as well as at the two sides the tail-spindle is obviously in line. It may be observed, however, that if an error in any one direction is found, it is necessary to go through the whole series of tests in order to precisely locate the error. Suppose, for example, that the needle, being adjusted as in the engraving to just touch the step at B, does not touch it when tried at the bottom of the plate, then the error may be caused in three ways--thus, in the first place, the whole tailstock may be lower than the headstock; in the second place, the front end of the tailstock may be too low; or, in the third place, the back end of the tailstock may be too high. If the first was the cause, the test with the needle point tried with face C would show correct. If the second or third was the cause of the error, the needle point when tried to face C would touch when applied at the top, but would not touch when tried at the bottom of the face plate. Another case may be cited. For example, suppose the needle applied as shown touched at the bottom but not at the top of the step B, then the test with the needle reversed would show whether the whole tailstock was too high, or whether the front end only was too high, or the back end too low. There is one excellent feature in this device to which attention may be called, which is that the tests are made on as large a diameter of face plate as possible, which shows the errors magnified as much as possible. The same device is used to test if the cross slide of the carriage or saddle is at a right angle to the lathe shears, the method of its application being as shown in Fig. 2584. The split sleeve A receives in this case a rod R, which is laid in the slideway S of the carriage or saddle, and a long rod H carries the needle-holding devices. The rod R is held fair against the slideway, and the face of the sleeve A is held against the edge of the carriage or saddle. The needle Q is then adjusted to just touch the edge D of the lathe bed. When this adjustment is made the rod H is swung over to the right and the coincidence of the needle point again tried with the edge of the lathe bed, the cross slideway being at a right angle when the needle point touches the edge D of the lathe bed when tried on the left hand, and also on the right hand, of the carriage. The stiffening rod U is brought under tension by a nut operated against a lug on X. To counterbalance the overhanging weight of the rod H and its attachments, a rod carrying a weight W is employed. It is obvious that the truth of the operation depends wholly upon the straightness and parallelism of the enlarged sections P of the rod R, upon keeping the end face of A in contact with the carriage at Z, and upon the correct adjustment of the needle to the edge of the lathe bed. [Illustration: Fig. 2584.] SETTING LINE SHAFTING IN LINE.--The following method of adjusting line shafting or setting it in line, as it is termed, is that generally adopted in the best practice. [Illustration: Fig. 2585.] [Illustration: Fig. 2586.] [Illustration: Fig. 2587.] First prepare a number of rude wooden frames, such as shown in Fig. 2585. They are called targets, and are pieces of wood nailed together, with the outer edge face A planed true, and having a line marked parallel with the planed edge and about three-quarters of an inch inside of it. Upon this frame we hang a line suspending a weight and forming a plumb-line, and it follows that when the target is so held that the plumb-line falls exactly over and even all the way down with the scribed line, the planed face A, Fig. 2586, will stand vertical. To facilitate this adjustment, we cut a small [V] notch at the top of the scribed line, the bottom of the [V] falling exactly even with the scribed line, so that it will guide the top of the plumb-line even with the scribed line at the top; hence the eye need only be directed to causing the two lines to coincide at the bottom. To insure accuracy, the planed edge A should not be less than a foot in length. Then tightly stretch a strong closely-twisted and fine line of cord beside the line of shafting, as shown in Fig. 2587, placing it say six inches below and four inches on one side of the line of shafting, and equidistant at each end from the axial line of the same, adjusting it at the same time as nearly horizontally level as the eye will direct when standing on the floor at some little distance off and sighting it with the line shaft. In stretching and adjusting this line, however, we have the following considerations:--It must clear the largest pulley hub on the line of shafting, those pulleys having set-screws being moved to allow it to pass. If the whole line of shafting is parallel in diameter, we set the line equidistant from the shafting at each end. If one end of the shafting is of larger diameter, we set the line farther from the surface of the shafting, at the small end, to an amount equal to one-half of the difference in the two diameters; and since the line is sufficiently far from the shafting to clear the largest hub thereon, it makes, so far as stretching the line is concerned, no difference of what diameter the middle sections of shafting may be. The line should, however, be set true as indicated by a spirit-level. We may now proceed to erect the targets as follows: The planed edge A in Fig. 2585 is brought true with the stretched line, and is adjusted so that the plumb-line B in Fig. 2586 will stand true with the line or mark B. When so adjusted, the target is nailed to the post carrying the shafting hanger. In performing this nailing, two nails may be slightly inserted so as to sustain the target, and the adjustment being made by tapping the target with the hammer, the nails may be driven home, the operator taking care that driving the nails does not alter the adjustment. [Illustration: Fig. 2588.] In Fig. 2588 A A represents the line of shafting, B, B two of the hanger posts, and C, C two of the adjusted targets. [Illustration: Fig. 2589.] We have now in the planed edges A of the targets a rigid substitute for the stretched line, forming a guide for the horizontal adjustment, and to provide a guide for the vertical adjustment we take a wooden straight-edge long enough to reach from one post to another. Then beginning at one end of the shafting, we place the flat side of the straight-edge against the planed edge of two targets at a distance of about 15 inches below the top of the shafting; and after levelling the straight-edge with a spirit-level, we mark (even with the edge of the straight-edge) a line on the planed edge of each target, and we then move the straight-edge to the next pair of targets, and place the edge even with the mark already made on the second target. We then level the straightedge with a spirit-level, and mark a line on the third target, continuing the process until we have marked a straight and horizontally level line across all the targets, the operation being shown in Fig. 2589, in which A represents the line of shafting, B the hangers, and C the targets. D represents the line on the first target, and E the line on second. F is the straightedge, levelled ready to form a guide whereby the line D may be carried forward, as at E, level and straight, to the third target, and so on across all the targets. [Illustration: Fig. 2590.] [Illustration: Fig. 2591.] The line thus marked is the standard whereby the shafting is to be adjusted vertically; and for the purpose of this adjustment, we must take a piece of wood, or a square, such as is shown in Fig. 2590, the edges A and B being true and at a right angle to each other. The line D, in Fig. 2589, marked across the targets being 15 inches below the centre line of the shaft at the end from which it was started, we mark upon our piece of wood the line C in Fig. 2590, 15 inches from the edge A (as denoted by the dotted line); and it is evident that we have only to adjust our shaft for vertical height so that, the gauge being applied at each target in the manner shown in Fig. 2591, the shaft will be set exactly true, when the mark C on the piece of wood comes exactly fair with the lines D marked on the targets. [Illustration: Fig. 2592.] For horizontal adjustment, all we have to do is to place a straight-edge along the planed face of the target, and adjust the shaft equidistant from the straight-edge, as shown in Fig. 2592, in which A is the shaft, B the target, C the straight-edge referred to, and D a gauge or distance piece. If, then, we apply the straight-edge and wood gauge to every target, and to the adjustment, the whole line of shafting will be complete. There are several points, however, during the latter part of the process at which consideration is required. Thus, after the horizontal line, marked on the targets by the straight-edge and used for the vertical adjustment, has been struck on all the targets, the distance from the centre of the shafting to that line should be measured at each end of the shafting, and if it is found to be equal, we may proceed with the adjustment; but if, on the other hand, it is not found to be equal, we must determine whether it will be well to lift one end of the shaft and lower the other, or make the whole adjustment at one end by lifting or lowering it, as the case may be. In coming to this determination we must bear in mind what effect it will have on the various belts, in making them too long or too short; and when a decision is reached, we must mark the line C, in Fig. 2590, on the gauge accordingly, and not at the distance represented in our example by the 15 inches. The method of adjustment thus pursued possesses the advantage that it shows how much the whole line of shafting is out of true before any adjustment is made, and that without entailing any great trouble in ascertaining it; so that, in making the adjustment, the operator acts intelligently and does not commence at one end utterly ignorant of where the adjustment is going to lead him to when he arrives at the other. Then, again, it is a very correct method, nor does it make any difference if the shafting has sections of different diameters or not, for in that case we have but to measure the diameter of the shafting, and mark the adjusting line, represented in our example by C, in Fig. 2590, accordingly, and when the adjustment is complete, the centre line of the whole length of the line of shafting will be true and level. This is not necessarily the case, if the diameter of the shafting varies and a spirit-level is used directly upon the shafting itself. In further explanation, however, it may be well to illustrate the method of applying the gauge shown in Fig. 2590, and the straight-edge C and gauge D shown in Fig. 2592, in cases where there are in the same line sections of shaftings of different diameters. Suppose, then, that the line of shafting in our example has a mid-section of 2-1/4 inches diameter, and is 2 inches at one, and 2-1/2 inches in diameter at the other end: all we have to do is to mark on the gauge, shown in Fig. 2590, two extra lines, denoted in figure by D and F. If the line C was at the proper distance from a for the section of 2-1/4 inches in diameter, then the line D will be at the proper distance for the section of 2 inches, and E at the proper distance for the section of 2-1/2 inches in diameter; the distance between C and D, and also between C and F, being 1/8 inch, in other words, half the amount of the difference in diameters. In like manner for the horizontal adjustment, the gauge piece shown at D in Fig. 2592 would require when measuring the 2-1/4 inch section to be 1/8 inch shorter than for the 2 inch section, while for the 2-1/2 inch section would require to be 1/8 inch shorter than that used for the 2-1/4 inch section, the difference again being one-half the amount of the variation in the respective diameters. Thus the whole process is simple, easy of accomplishment, and very accurate. If the line of shafting is suspended from the joists of a ceiling instead of from uprights, the method of procedure is the same, the forms of the targets being varied to suit the conditions. The process only requires that the faced edges of the targets shall all stand plumb and true with the stretched line. It will be noted that it is of no consequence how long the stretched line is, since its sag does not in any manner disturb the correct adjustment, but in cases where it is a very long one it may be necessary to place pins that will prevent it from swaying by reason of air currents or from jarring. The same system may be employed for setting the shafting hangers, the bores of the boxes being used instead of the shafting itself. CHAPTER XXX.--LINE SHAFTING. LINE SHAFTING.--A line of shafting is one continuous run or length composed of lengths joined together by couplings. The main line of shafting is that which receives the power from the engine or other motor, and distributes it to other lines of shafting, or to the various machines to be driven. In some practice each line of shafting is driven by a separate engine or motor, so that it may be stopped without stopping the others. This same object may be obtained by providing a clutch for each line. It is obvious that in each line of shafting the length nearest to the driving motor transmits the whole of the power transmitted by the line, and that the diameter of the shafting may, therefore, be reduced as it proceeds from the engine in a proportion depending upon the degree to which the power it is required to transmit is reduced. It is desirable, therefore, so far as the shafting is concerned, to place the machines requiring the most power to drive as near as possible to that end of the shafting that receives power from the motor. Line shafting is supported in bearings provided in what are termed hangers, which are brackets to be bolted to either suitable framing, to walls, posts, or to the ceiling or floor of the building. The short lengths of shafting that are provided to effect changes of speed, and to enable the machine to be stopped or started at pleasure, are termed countershafts. When there is interposed a countershaft between the motor and the main line of shafting, it is sometimes termed a jack shaft. Shafting is usually made cylindrically true either by special rolling processes as in what is known as "cold-rolled," or "hot-rolled" shafting, or else it is turned up in the lathe. In either case it is termed bright shafting. What is known as black shafting is simply bars of iron rolled by the ordinary process and made cylindrically true only where it receives its couplings, and for its journal bearings, &c. The diameter of black shafting varies by a quarter of an inch, and is usually above its designated diameter by about 1/32 inch. The main body of the shafting not being turned cylindrically true and parallel, the positions of the pulleys cannot be altered upon the shafts, nor can pulleys be added to the shaft as occasion may require without the sections being taken down and seatings turned for the required pulleys to be added. Furthermore black shafting does not run true, and is in this respect also objectionable. Nevertheless, black shafting is used for some special cases where extra pulleys are not likely to be required and the shafting is exposed to the weather, as in the case of yards for the manufacture of building bricks. The diameters of bright or turned shafting (which is the ordinary form in which shafting is made, unless otherwise specified) vary by 1/4 inch up to about 3-1/2 inches in diameter; but the actual diameter is 1/16 inch less than the denominated commercial diameter, which is designated from the diameter of the round bar iron from which the shafting is turned; thus a length of what is known as 2-inch shafting will have an actual diameter of 1-15/16 inches, being parallel, or as nearly parallel as it is practicable to turn it in the ordinary lathe. Cold-rolled shafting has its actual diameter agreeing with its designated or commercial diameter, and is parallel throughout its length. In England the diameters of shafting vary by eighths of inches for diameters of an inch and less, and by quarters of an inch for diameters above an inch, the commercial and the actual diameters being alike. The strains to which a line of shafting is subject are as follows: The torsional strain due to rotating the line of shafting, independent of the power transmitted; the torsional strain due to the amount of the power transmitted; and the transverse strain due to the unequal belt pressures and distances from the bearings of the driving or transmitting pulleys. The first and the last are, however, so intimately connected in practice that they may be considered as one: hence we have, 1st, the torsional strain due to driving the whole load, and, 2nd, the transverse strain due to the belt pressures being exerted more on one side than on another of the shaft, and to the belt pulleys being at unequal distances from the hanger bearings. The first may be reduced to a minimum by so proportioning the strength of the line of shafting that it shall be capable of transmitting the required amount of power at the various sections of its length without suffering distortion of straightness beyond certain limits, and shall be at the same time as light as is consistent with this duty and a certain factor of safety. Referring for a moment to the above limitation, the weight of the shaft itself will cause it to deflect between the hanger bearings, and the amount of this deflection will depend upon the distance apart of the points of support, or, in other words, of the distance apart of the hanger bearings. The second may be reduced to a minimum by so regulating the distance apart of the hanger bearings that the deflection of the shaft from the belt pressures shall not be sufficient to produce sensible irregularities in the axis of rotation of the shaft; by so connecting the bearings to the hangers that they shall be rigidly held, and yet capable as far as possible of automatically adjusting their bores to be true with the shaft axis, notwithstanding its deflection from any cause; by placing the pulleys transmitting the most power as near to the hanger bearings as practicable; by so disposing the driving belts as to deliver the power as near as possible equally on all sides of the shaft; and by having the shafting and the pulleys balanced so as to run true, so that the strains on the pulleys shall be equal at each point in the shaft rotation. From this it appears that the distance apart of the shafting hangers may vary according to the amount of power transmitted by a shaft of a given diameter. The following table (given by Francis) gives the greatest admissible distances between the bearings of continuous shafts subject to no transverse strain except from their own weight, as would be the case were the power given off from the shaft equally on all sides, and at an equal distance from the hanger bearing. +----------------+------------------------------------+ | Diameter of | Distance between bearings, in feet.| |shaft in inches.+--------------------+---------------+ | |Wrought-iron shafts.| Steel shafts. | +----------------+--------------------+---------------+ | 2 | 15.46 | 15.89 | | 3 | 17.70 | 18.19 | | 4 | 19.48 | 20.02 | | 5 | 20.99 | 21.57 | | 6 | 22.30 | 22.92 | | 7 | 23.48 | 24.13 | | 8 | 24.55 | 25.23 | | 9 | 25.53 | 26.24 | +----------------+--------------------+---------------+ These conditions, however, do not usually obtain in the transmission of power by belts and pulleys, and the varying circumstances of each case render it impracticable to give any rule which would be of value for universal application. For example, the theoretical requirements would demand that the bearings be nearer together on those sections of shafting where most power is delivered from the shaft, while considerations as to the location and desired contiguity of the driven machines may render it impracticable to separate the driving pulleys by the intervention of a hanger at the theoretically required location. The nearer together the bearings the less the deflection either from the shaft's weight or from the belt stress, and since the friction of the shaft in its bearings is theoretically independent of the journal-bearing area, the closer the bearings the more perfect the theoretical conditions; but since it is impracticable to maintain the true alignment of the shaft, and as the friction due to an error in alignment would increase with the nearer proximity of the bearings, they are usually placed from about 7 to 12 feet apart, according to the facilities afforded in the location in which they are to be erected. It is to be observed, however, that the nearer together the bearings are the less the diameter, and, therefore, the lighter the shafting may be to transmit a given amount of power, and hence the less the amount of power consumed in rotating the shafting in its bearings. COLD-ROLLED SHAFTING--This is shafting made cylindrically round and parallel by means of cold rolling, which leaves a smooth and bright surface. The effects of cold rolling upon the metal have been determined by Major Wm. Wade, U.S.A., Sir William Fairbairn, C.E., and Professor Thurston, of the Stevens Institute, as follows:-- The experiments were made upon samples of cold-rolled shafting submitted by Messrs. Jones and Laughlins, of Pittsburgh, Pennsylvania. SUMMARY OF THE RESULTS OBTAINED BY MAJOR WADE FROM NUMEROUS EXPERIMENTS WITH ORDINARY HOT-ROLLED BAR IRON, COMPARED WITH THE RESULTS OBTAINED FROM THE SAME KINDS OF IRON ROLLED AND POLISHED WHILE COLD BY LAUTH'S PATENT PROCESS. ------------------------------------------+-------------+---------+--------- | Iron rolled | Ratio of|Average | while | increase|rate per +------+------+ by cold |cent. of | Hot. | Cold.| rolling.|increase. ------------------------------------------+------+------+---------+--------- TRANSVERSE.--Bars supported at both | | | | ends; load applied in the middle; distance| | | | between the supports, 30 inches. Weight | | | | which gives a permanent set of one-tenth | | | | of an inch, viz. | | | | } 1-1/2 inch square bars | 3,100|10,700| 3.451 |} } Round bars, 2 inch diameter| 5,200|11,100| 2.134 |} 162-1/2 } Round bars, 2-1/4 " " | 6,800|15,600| 2.294 |} | | | | TORSION.--Weight which gives a permanent| | | | set of one degree, applied at 25 inches | | | | from centre of bars. Round bars, 1-3/4 | | | | inch diameter, and 9 inches between the | | | | clamps | 750| 1,725| 2.300 | 130 | | | | COMPRESSION.--Weight which gives a | | | | depression, and a permanent set of | | | | one-hundredth of an inch to columns 1-1/2 | | | | inches long and 5/8 inch diameter |13,000|34,000| 2.615 | 161-1/2 Weight which bends and gives a permanent | | | | set to columns 8 inches long and 3/4 inch | | | | diameter, viz. | | | | } Puddled iron |21,000|31,000| 1.476 |} } Charcoal bloom iron |20,500|37,000| 1.804 |} 64 | | | | TENSION.--Weight per square inch, which | | | | caused rods 3/4 inch diameter to stretch | | | | and take a permanent set, viz. | | | | } Puddled iron |37,250|68,427| 1.837 |} } Charcoal bloom iron |42,439|87,396| 2.059 |} 95 Weight per square inch, at which the same | | | | rods broke, viz. | | | | } Puddled iron |55,760|83,156| 1.491 |} } Charcoal bloom iron |50,927|99,293| 1.950 |} 72 | | | | HARDNESS.--Weight required to produce | | | | equal indentations | 5,000| 7,500| 1.500 | 50 ------------------------------------------+------+------+---------+--------- NOTE.--Indentations made by equal weights, in the centre, and near the edges of the fresh cut ends of the bars, were equal; showing that the iron was as hard in the centre of the bars as elsewhere. GENERAL SUMMARY OF THE RESULTS OBTAINED BY SIR WILLIAM FAIRBAIRN'S EXPERIMENTS. --+-------------------+-----------+-------------------+------------ | | Breaking | | Strength, | Condition of bar. | weight of |Breaking weight per| the un- | |bar in lbs.| square inch. |touched bar | | | |being unity. --+-------------------+-----------+-------------------+------------ | | | In lbs. In tons. | 1| Untouched (black) | 50,346 | 58.628 26.173 | 1.000 3| Rolled cold | 69,295 | 88.230 39.388 | 1.505 4| Turned | 47,710 | 60.746 27.119 | 1.036 --+-------------------+-----------+-------------------+------------ NOTE.--In the above summary it will be observed that the effect of consolidation by the process of cold rolling is to increase the tensile powers of resistance from 26.17 tons per square inch, to 39.38 tons, being in the ratio of 1:1.5, one-half increase of strength gained by the new process of cold rolling. Extract from the general conclusions arrived at by Professor R. Thurston from experiments. "The process of cold rolling produces a very marked change in the physical properties of the iron thus treated. "It increases the tenacity from 25 to 40 per cent., and the resistance to transverse stress from 50 to 80 per cent. "It elevates the elastic limit under torsional as well as tensile and transverse stresses, from 80 to 125 per cent.... "It gives the iron a smooth bright surface, absolutely free from the scale of black oxide unavoidably left when hot rolled. "It is made exactly to gauge diameter, and for many purposes requires no further preparation. "The cold-rolled metal resists stresses much more uniformly than does the untreated metal. Irregularities of resistance exhibited by the latter do not appear in the former; this is more particularly true for transverse stress. "This treatment of iron produces a very important improvement in uniformity of structure, the cold-rolled iron excelling common iron in density from surface to centre, as well as in its uniformity of strength from outside to the middle of the bar. "This great increase of strength, stiffness, elasticity, and resilience is obtained at the expense of some ductility, which diminishes as the tenacity increases. The modulus of ultimate resilience of the cold-rolled iron is, however, above 50 per cent. of that of the untreated iron. "Cold-rolled iron thus greatly excels common iron in all cases where the metal is to sustain maximum loads without permanent set or distortion." From this it appears that cold-rolled iron is peculiarly adapted for line shafting. Suppose, for example, a given quantity of power to transmit, and that a length of cold-rolled and a length of hot-rolled iron be connected together to form the line. Then the diameters of the two being such as to have equal torsional strength, we have-- 1st. That the weight of the cold rolled will be the least, and it will, therefore, produce less friction in the hanger bearings. 2nd. That the cold rolled will be harder, and will therefore suffer less from abrasion of the journals. 3rd. That being of smaller diameter the journals are more easily and perfectly lubricated. The resistance to transverse stress (say) 50 per cent.; but the elastic limit under transverse stress is increased from 80 to 125 per cent., accepting the lesser amount we have in the case of the two shafts. 4th. That the resistance to permanent set or bend will be 30 per cent. more in the cold rolled. 5th. The accuracy to gauge diameter enables the employment of a coupling having a continuous sleeve, and gives an equal bearing along the entire coupling bore. 6th. The reduction of shaft diameter enables the employment of a smaller and lighter coupling; and 7th. The hubs of the pulleys may be made smaller and lighter, are easier to bore, and may be bored to gauge diameter with the assurance that they will fit the shaft. The friction between the journals of a line shafting and its bearings depends so intimately upon the distance apart of the bearings, upon the alignment of the same, upon the accurate bedding of the shaft journals to the bearings, and upon the amount of transverse strain; and this latter is so influenced by the amount of power that may be delivered from one side of the shaft more than from another, that the application of rules for determining the said friction under conditions of perfect alignment rigidity would be practically useless. The conditions found in actual practice are so widely divergent and so rarely alike, or even nearly alike, that the consideration of this part of the subject would, in the opinion of the author, be of no practical value. The reader, however, is referred to the remarks made with reference to the friction of journals. To prevent end motion to a line of shafting it is necessary that there be fixed at some part of the line two shoulders, or collars, on relatively different sides of a bearing, or of the bearings, these collars meeting the side faces of the bearing. If shoulders are produced by reducing the diameter of the journal bearing of the shaft, the strength of the shafting is reduced to that at the reduced bearing, because the strength of the whole can be no greater than its strength at the weakest part. If collars are placed one on each end of the line of shafting, the difficulty is met that the collars will permit end motion to the shaft whenever the temperature of the shaft is greater than that which obtained at the time at which the collars were adjusted, which occurs on account of the increased expansion of the shaft. On the other hand the collars will bind against the side faces of the bearing boxes whenever the shaft is at a lower temperature than it was at the time of setting the shaft, because of the contraction of the shaft's length, and this would cause undue friction, abrasion, and wear. It is preferable, therefore, to place such collars one on each side of one bearing, so that the difference in contraction and expansion from varying temperatures shall be confined to the difference in expansion between the metal of which the bearing and shaft respectively are composed in the length of the bearing only, instead of being extended to the difference in expansion between the shaft throughout its whole length and that of the framework to which the hangers, or bearings, are bolted. [Illustration: Fig. 2593.] The collars may be shrunk on to the shaft so as to avoid the necessity of set-screws, or if set-screws are used they should be as short as is practicable so as to avoid the liability to catch against the lacings, &c., of belts, which, on slipping off the pulley may come into contact with the set-screw head. The Lane and Bodley Co., of Cincinnati, employ a collar (for loose pulleys, &c.) in which the radius of the collar for a width equal to the diameter of the set-screw head, is equal to that of the set-screw head thus projecting from the centre of the collar circumference, a slot in the ring affording access to the set-screw head, as shown in Fig. 2593. By this means the head of the set-screw is protected from contact with a belt, in case the latter should be off the pulley and resting upon the shaft. As a rule it is preferable that the collars, to prevent end motion to the shaft, be placed at the bearing nearest to the engine or motor; and this is especially desirable where bevel-wheels are employed to drive the shaft, because in that case the pitch lines of the wheels are kept to coincide as nearly as practicable, and the teeth are prevented from getting too far into or out of gear. DIAMETERS OF LINE SHAFTING.--The necessary diameters of the various length of the shafts composing a line of shafting, should be proportioned to the quantity of power delivered by each respective length, and in this connection the position of the various pulleys upon the length and the amount of power given off by the pulley is an important consideration. Suppose, for example, that a piece of shafting delivers a certain amount of power, then it is obvious that the shaft will deflect or bend less if the pulley transmitting that power be placed close to a hanger or bearing than if it be placed midway between the two hangers or bearings. The strength of a shaft to resist torsion is the cube of its diameter in inches, multiplied by the strength of the material of which the shaft is composed, per square inch of cross-sectional area, giving the strength in statical foot-pounds. The application of this rule is to find the necessary strength of the shaft to convey power irrespective of the distance from its centre at which it delivers such power. But since the point at which the power to produce torsion is applied is at the rim of the pulley, the amount of torsion produced upon a shaft by a given stress must be obtained by multiplying the given amount of stress by the radius of the pulley in inches and parts of an inch. Example: the static stress upon a pulley, 24 inches diameter, is 100 lbs., what static torsion does it exert upon the shaft? Here, stress 100 × 12 (radius of the pulley) = 1200 = static torsional stress. In the following rules for finding the necessary diameters and strengths of shafts, the margin of extra diameter for strength necessary for safety is included, so that the given sizes are working diameters. To find the necessary diameter of shaft from a given torsional stress.--Rule, divide the torsional stress expressed in statical foot lbs., by 57.2 for steel, by 27.7 for wrought iron, or by 18.5 for cast iron, and the cube root of the quotient is the required working diameter of shaft expressed in inches. To find the maximum amount of horse-power capable, within good working limits, of being transmitted by a _shaft_ of a given diameter.--Rule, multiply the cube of the diameter of the shaft, in inches, by its revolutions per minute and divide by 92 for steel, by 190 for wrought-iron, or by 285 for cast-iron shafts, and the quotient is the amount of horse-power. Since, in this rule, the horse-power is a given quantity, the diameter of the pulley is of no consequence, since with a given stress it must have been taken into account in obtaining the horse-power. To find the revolutions per minute a shaft will require to make to transmit a given amount of horse-power.--Rule, multiply the given amount of horse-power by 92 for steel, by 190 for wrought-iron, or by 285 for cast-iron shafts, and divide the product by the cube of the diameter of the shaft expressed in inches, and the quotient is the required revolutions per minute for the shaft. The rule adopted by William Sellers and Co. to determine the size of shafts to transmit a given horse-power is:--Rule, divide the cube root of the horse-power by the revolutions per minute and multiply the quotient by 125, the product is the diameter of shaft required. This gives a shaft strong enough to resist flexure, if the bearings are not too far apart. The distance apart that the bearings should be placed is an important consideration. Modern millwrights differ slightly in opinion in this respect: some construct their mills with beams 9 feet 6 inches apart, and put one hanger under each of the beams; others say 8 feet apart gives a better result. We are clearly of opinion that with 8 feet distance, and shafting lighter in proportion, the best result is obtained. The following table (from "Machine Tools," by Wm. Sellers and Co.) gives the strength of round wrought iron as given by Clark:-- TABLE SHOWING STRENGTH OF ROUND WROUGHT-IRON SHAFTING. +--------+---------------------------------------------------------+ | | TORSIONAL ACTION. | | +----------+------------+-----------+----------+----------+ | Dia- | Ultimate | Working | Work for | Horse | Speed in | | meter | resist- | stress. | one turn | Power at | turns | | of | ance. | | per | the rate | per | | shaft. | | | minute. | of one | minute | | | | | | turn per | for | | | | | | minute. | one- | | | | | | | horse | | | | | | | power. | +--------+----------+------------+-----------+----------+----------+ | =1= | =2= | =3= | =4= | =5= | =6= | +--------+----------+------------+-----------+----------+----------+ | Inches.| Stat'l. | Stat'l ft. | Ft. lbs. | H. P. | Turns. | | |ft. tons. | lbs. | | | | | 1 | .42 | 27.7 | 174 | .00526 | 190 | | 1-1/4 | .82 | 54.1 | 340 | .01028 | 97.3 | | 1-1/2 | 1.42 | 93.5 | 587 | .01779 | 56.2 | | 1-5/8 | 1.80 | 118.9 | 746 | .02259 | 44.3 | | 1-3/4 | 2.25 | 148.4 | 932 | .02820 | 35.4 | | 1-7/8 | 2.77 | 182.6 | 1,147 | .03469 | 28.8 | | 2 | 3.36 | 221.6 | 1,391 | .04211 | 23.7 | | 2-1/8 | 4.00 | 265.8 | 1,669 | .05062 | 19.8 | | 2-1/4 | 4.80 | 315.5 | 1,981 | .05995 | 16.7 | | 2-3/8 | 5.62 | 371.1 | 2,330 | .07051 | 14.2 | | 2-1/2 | 6.56 | 432.8 | 2,718 | .08224 | 12.2 | | 2-3/4 | 8.73 | 576.1 | 3,618 | .1094 | 9.14 | | 3 | 11.3 | 747.9 | 4,697 | .1421 | 7.04 | | 3-1/4 | 14.4 | 951.0 | 5,972 | .1807 | 5.54 | | 3-1/2 | 18.0 | 1,188 | 7,458 | .2257 | 4.43 | | 3-3/4 | 22.1 | 1,461 | 9,173 | .2775 | 3.60 | | 4 | 26.9 | 1,773 | 11,136 | .3368 | 2.97 | | 4-1/4 | 32.2 | 2,127 | 13,345 | .4040 | 2.48 | | 4-1/2 | 38.2 | 2,524 | 15,851 | .4796 | 2.09 | | 4-3/4 | 45.0 | 2,969 | 18,635 | .5642 | 1.77 | | 5 | 52.5 | 3,463 | 21,750 | .6579 | 1.52 | | 5-1/4 | 60.7 | 4,008 | 25,177 | .7616 | 1.31 | | 5-1/2 | 69.8 | 4,609 | 28,936 | .8758 | 1.14 | | 5-3/4 | 79.8 | 5,266 | 33,077 | 1.000 | 1.00 | | 6 | 90.6 | 5,983 | 37,584 | 1.137 | .880 | | 6-1/2 | 117 | 7,606 | 47,780 | 1.445 | .692 | | 7 | 144 | 9,501 | 59,682 | 1.805 | .554 | | 7-1/2 | 177 | 11,680 | 73,254 | 2.220 | .450 | | 8 | 215 | 14,180 | 89,088 | 2.694 | .371 | | 8-1/2 | 258 | 17,010 | 106,836 | 3.232 | .309 | | 9 | 306 | 20,190 | 126,846 | 3.837 | .261 | | 9-1/2 | 360 | 23,750 | 149,118 | 4.512 | .222 | | 10 | 420 | 27,700 | 174,000 | 5.260 | .190 | | 11 | 559 | 36,870 | 231,594 | 7.005 | .143 | | 12 | 725 | 47,860 | 300,672 | 9.095 | .110 | | 13 | 922 | 60,860 | 382,278 | 11.83 | .0865 | | 14 | 1,152 | 76,010 | 477,456 | 14.44 | .0693 | | 15 | 1,417 | 93,490 | 587,250 | 17.76 | .0563 | | 16 | 1,720 | 113,500 | 712,704 | 21.56 | .0464 | | 17 | 2,062 | 136,100 | 854,862 | 25.86 | .0387 | | 18 | 2,447 | 161,500 | 1,014,768 | 30.69 | .0326 | | 19 | 2,880 | 190,000 | 1,193,466 | 36.10 | .0277 | | 20 | 3,360 | 221,600 | 1,392,000 | 42.11 | .0237 | | | | NOTE.--To find the corresponding values for shafts of cast iron | | or steel, multiply the tabular values by the following | | multipliers: | | | | Cast | | | | | | | iron | 2/5 | 2/3 | 2/3 | 2/3 | 1.5 | | Steel | 1.2 | 2.06 | 2.06 | 2.06 | .48 | +--------+----------+------------+-----------+----------+----------+ +--------+---------------------------+ | | TRANSVERSE ACTION. | | +-----------------+---------+ | | Under | Under | | | the gross | the net | | | distributed |weight of| | Dia- | weight. | shaft. | | meter |-----------------+---------+ | of |Distance| Gross |Distance | | shaft. |of bear-| weight |of bear- | | |ings for| for |ings for | | | the | the | the | | |limiting| span. |limiting | | |deflec- | |deflec- | | | tion. | | tion. | +--------+--------+--------+---------+ | =1= | =7= | =8= | =9= | +--------+--------+--------+---------+ | Inches.| Feet. | Lbs. | Feet. | | | | | | | 1 | 6.6 | 30 | 7.9 | | 1-1/4 | 7.7 | 55 | 9.2 | | 1-1/2 | 8.6 | 89 | 10.3 | | 1-5/8 | 9.2 | 112 | 11.0 | | 1-3/4 | 9.6 | 134 | 11.5 | | 1-7/8 | 10.1 | 163 | 12.1 | | 2 | 10.5 | 193 | 12.7 | | 2-1/8 | 11.0 | 227 | 13.2 | | 2-1/4 | 11.4 | 264 | 13.7 | | 2-3/8 | 11.8 | 305 | 14.2 | | 2-1/2 | 12.5 | 359 | 15.0 | | 2-3/4 | 13.0 | 450 | 15.6 | | 3 | 13.7 | 566 | 16.5 | | 3-1/4 | 14.5 | 701 | 17.4 | | 3-1/2 | 15.2 | 854 | 18.3 | | 3-3/4 | 16.0 | 1,029 | 19.2 | | 4 | 16.7 | 1,225 | 20.1 | | 4-1/4 | 17.4 | 1,439 | 20.9 | | 4-1/2 | 18.1 | 1,679 | 21.7 | | 4-3/4 | 18.8 | 1,943 | 22.6 | | 5 | 19.4 | 2,220 | 23.3 | | 5-1/4 | 20.0 | 2,525 | 24.0 | | 5-1/2 | 20.6 | 2,854 | 24.7 | | 5-3/4 | 21.2 | 3,210 | 25.4 | | 6 | 21.6 | 3,600 | 26.2 | | 6-1/2 | 22.9 | 4,421 | 27.5 | | 7 | 24.2 | 5,426 | 29.0 | | 7-1/2 | 25.3 | 6,518 | 30.4 | | 8 | 26.5 | 7,774 | 31.8 | | 8-1/2 | 27.6 | 9,133 | 33.1 | | 9 | 28.7 | 10,650 | 34.4 | | 9-1/2 | 29.8 | 12,320 | 35.7 | | 10 | 30.8 | 14,100 | 36.9 | | 11 | 32.8 | 18,180 | 39.4 | | 12 | 34.7 | 22,880 | 41.7 | | 13 | 36.6 | 28,330 | 44.0 | | 14 | 38.5 | 34,560 | 46.2 | | 15 | 40.3 | 41,530 | 48.4 | | 16 | 42.1 | 49,330 | 50.5 | | 17 | 43.3 | 57,970 | 52.6 | | 18 | 45.5 | 67,490 | 54.6 | | 19 | 47.2 | 78,040 | 56.6 | | 20 | 48.8 | 80,660 | 58.5 | | | | NOTE.--To find the corresponding | | values for shafts of cast iron or | | steel, multiply the tabular values | | by the following multipliers: | | | | Cast | | | | | iron | .86 | .81 | .86 | | Steel | 1.05 | 1.07 | 1.05 | +--------+--------+--------+---------+ "It is advantageous that the diameter of line shaft be kept as small as is possible with due regard to the duty, so as to avoid extra weight in the shafting hangers, pulley hubs and couplings, whose weights necessarily increase with the diameter of the shafting. "SPEEDS FOR SHAFTING.--The speed at which shafting should run is determined within certain limits by the kind of machinery it is employed to drive. Shafting to drive wood-working machines may, for example, be made to rotate much faster than that employed to run metal-cutting machines, because the motions in the wood-working machines themselves are faster than those in metal-cutting machines. In a general sense, the rotation of shafting is greater in proportion as the movements of the machines driven require to run faster. "This occurs because in proportion as the driving pulleys of the machines require to rotate faster than the line shaft, the diameters of the pulleys on the line shaft must be larger than the diameters of those on the machines; hence a great variation in speed would demand a corresponding increase of diameter of pulley on the line shaft, and the extra weight of this pulley would be so much added to the weight causing friction, as well as so much added to the cost. If small pulleys were used and countershafts employed to multiply the speed the cost would be increased, extra room would be taken up; indeed, this is so obvious as to require no discussion, further than to remark that the faster the shafting rotates the smaller may be its diameter to transmit a given horse-power. From deflection and weakness to resist transverse strains and other obvious causes it is not found in practice desirable to employ line shafts of less than about 1-1/4 inches in diameter, and the diameters of shafting employed are usually arrived at from a calculated speed of about 120 revolutions per minute for metal-cutting machines such as used in machine shops, 250 revolutions per minute for wood-working machines, and from 300 to 400 revolutions per minute for cotton and woollen mills, and the countershafts for the machines usually have pulleys of the requisite diameters to convert this speed of rotation into that required to run each respective machine. Tubular or hollow shafting has been made to run at 600 revolutions per minute, but this kind of shafting has been of very limited application because of its expensiveness. "It is obvious that since the speed of a line shaft is used as a multiplier in the calculation of the horse-powers of shafts, a given diameter of shaft will transmit more power in proportion as its speed is increased. Thus a shaft capable of transmitting 20 horse-power when making 120 revolutions per minute will transmit 40 horse-power if making 240 revolutions per minute. "There are now running in some factories lines of shafting 1,000 feet long each. The power is generally applied to the shaft in the centre of the mill and the line extended each way from this. The head shaft being, say, 5 inches in diameter, the shafts extending each way are made smaller in proportion to the rate of distribution, so that from 5 inches they often taper down to 1-3/4. "When very long lines of shafting are constructed of small or comparatively small diameter, such lines are liable to some irregularities in speed, owing to the torsion or twisting of the shaft as power is taken from it in more or less irregular manner. Shafts driving looms may at one time be under the strain of driving all the looms belted from them, but as some looms are stopped the strain on the shaft becomes relaxed, and the torsional strain drives some part of the line ahead, and again retards it when the looms are started up. This irregularity is in some cases a matter of serious consideration, as in the instance of driving weaving machinery. The looms are provided with delicate stop motion, whereby the breaking of a thread knocks off the belt shifter and stops the loom. An irregular driving motion is apt to cause the looms to knock off, as it is called, and hence the stopping of one or more may cause others near to them to stop also. This may in a measure be arrested by providing fly-wheels at intervals on the line shaft, so heavy in their rim as to act as a constant retardant and storer of power, which power is given back upon any reaction on the shaft, and thus the strain is equalized. We mention this, as at the present time it is occupying the thoughts of prominent millwrights, and the relative advantage and disadvantage of light and heavy fly-wheels are being discussed, and is influencing the proportions of shafting in mill construction.[36]" [36] From "Machine Tools," by William Sellers and Co. Countershafts are separate sections of shafting (usually a short section) employed to increase or diminish belt speed, to alter the direction of belt motion, to carry a loose as well as a fast pulley (so that by moving the belt on to the loose pulley it may cease to communicate motion to the machine driven), and for all these purposes combined. [Illustration: Fig. 2594.] [Illustration: Fig. 2595.] An excellent form of countershaft hanger is shown in Fig. 2594, the guide for the slide being adjustable along the arm, and fixed in its adjusted position by means of the set-screws. The bearing is self-adjusting horizontally for alignment. The countershaft is shown in Fig. 2595, _a_ _b_ being the bearings, _c_ the cone pulley, _d_ the fast and _e_ the loose pulley, which is placed next to the bearing, so that it may be oiled without having to reach past the belt and fast pulley. By reducing the journal for the loose pulley no collar is needed, the shaft shoulder and the face of the bearing serving instead. [Illustration: Fig. 2596.] When the direction of rotation of the cone pulley on the countershaft requires to be occasionally reversed, there are two belts, an open one and a crossed one, from the line shaft to the countershaft, and there are three pulleys on the countershaft, their arrangement being as shown in Fig. 2596. L L´ are two loose pulleys, one receiving the open and the other the crossed belt, both these pulleys being a little more than twice the width of the belt; F is a fast pulley. By operating the belt skipper or shifter in the requisite direction either the open or the crossed belt is brought upon the fast pulley, the other belt merely moving across the width of its loose pulley, which must be twice that of the fast one. In the position of the belt shifter shown in the cut, both belts would be upon the loose pulleys L L´, hence the countershaft would remain at rest. If the direction of rotation of one pulley is required to be quicker than the other, two fast pulleys, each slightly more than twice the width of the belt, may be placed upon the line shaft, one of them being of enlarged diameter, to give the requisite increased velocity. [Illustration: Fig. 2597.] In Fig. 2597 Pratt's patent friction clutch is shown applied to a countershaft requiring to rotate in both directions, but quicker in one direction than in the other; hence, one of the pulleys is of smaller diameter than the other. The pulleys are free to rotate upon the countershaft unless engaged by the clutch, which is constructed as follows:-- The inside surface of the pulley rim is bored and the end surface of the shoes is turned to correspond. The shoes are in the form of a bell crank, upon the exposed end of which is provided a small lug, clearly shown in the cut. To prevent end motion of the pulley a collar is placed on one side of it and secured to the countershaft, while, on the other, the sleeve to which the shoes are pivoted is also secured to the countershaft; upon the shaft between the two pulleys there is a sleeve, having at each end a conical hub. When this sleeve is moved to the right, its right-hand coned hub passes between the lugs on the exposed ends of the shoes, forcing these lugs apart and causing the shoes to grip the bore of the large pulley, which thereupon rotates the shaft through the medium of the sleeve upon which the shoes are pivoted. Similarly, if the engaging (and disengaging) sleeve be moved to the left it will pass between the lugs of the shoes on the left-hand pulley, which will, therefore, be caused to drive the shaft. In the position shown in the cut the engaging sleeve is clear of the ends of all the shoes, hence the pulleys would be caused to rotate (by their belts), but the shafts, &c., would remain stationary. In yet another form the inner face of the pulley rim is coned, and in place of shoes a disk, whose circumference is coned to fit the pulley rim, is fast upon the shaft. The shaft is provided with a fixed collar, and from this collar, as a fulcrum, the pulley and disk are (by means of short levers attached to a sleeve upon the countershaft) brought into contact, the thrust on the other side of the pulley being sustained by a conical surface on the sleeve, fitting to a similar cone on the hub of the pulley. Thus the pulley is gripped between two coned surfaces, one on each side, and is released by moving the sleeve laterally so as to relieve the grip, which it does noiselessly. By this means motion to the shaft is communicated from the pulley without the sudden shock incidental to the impact of two fixed pieces, because the grip of the cones is gradual, and a certain amount of slip may occur until such time as the grip of the surfaces is sufficient to drive by friction. [Illustration: Fig. 2598.] Fig. 2598[37] represents a cone friction clutch pulley. The outer half is a working fit upon the shaft, but is secured against end motion by the collar D. The sliding half is coned and covered with leather as shown at C C, the outer half being coned to correspond. The sliding half is driven by a feather fast in its bore, and sliding in a feather-way or spline in the shaft. [37] From _The American Machinist_. The driving power of the device is obtained by means of the friction of the coned surfaces. The less the angle _x_ of the cones the more power transmitted with a given pressure of the internal to the external cone. On the other hand, however, this angle may be so little that the external cone will not release the internal one when the end pressure on the latter is removed. The object is, therefore, to so proportion the angle _x_ of the cones that their friction will be a maximum, while the internal cone may be moved endwise and unlocked from the external without undue effort or strain at the moving clutch bar E. If the angle be 30 degrees, the clutch will release itself when the lateral pressure is removed. If the angle be 25 degrees the internal cone will require a slight lateral pressure to release it. If the angle be 20 degrees, the internal cone cannot be released by end pressure applied by hand. The transmitting capacity of the clutch depends upon the pressure applied to maintain the cones in contact, and therefore upon the leverage of the clutch bar, whose fork end is shown in section at E. It is desirable that the end pressure be as small as possible, because of the friction between E and the hub of the sliding half of the pulley. The hangers which carry the bearing boxes supporting shafting may be divided into four principal classes:--Those in which the bearing boxes are permitted to swivel, and to a certain extent to adjust themselves, to the axial line of the shafting, and having means to adjust the vertical height of the bolts. Those in which the bearings are incapable of such adjustments. Those in which the bearing boxes are supported on each side; and those in which the bearing is supported on one side only, so that the shafting may be taken down without disturbing the couplings. The first named are desirable in that they eliminate to a certain extent the strains due to the extra journal bearing friction which occurs when the shafting is sprung out of its true alignment, and obviate to a great extent the labor involved in fitting the bore of the bearing boxes to the journals of the shafting, so as to hold the same with its axis in a straight line, while they permit of vertical movement to attain vertical alignment. [Illustration: Fig. 2599.] Fig. 2599 represents Wm. Sellers & Co.'s ball-and-socket hanger which has come into extensive use throughout the United States: _a_ represents the frame of the hanger threaded to receive the cylindrical threaded plungers _d_ _e_, which therefore by rotation advance or recede respectively from the centre of the bearing boxes _b_ _c_. The ends of these plungers are concave, and the top and bottom halves of the bearing boxes are provided with a spheroidal section fitting into the concaves of the plungers, so that when the plungers are adjusted to fit (a working fit) against the boxes, the latter are held in a ball-and-socket or universal joint, which permits motion in any direction, the centre of such motion being central to the spherical concaves on the ends of plungers _e_ _d_. To adjust the vertical height of the bearings or boxes, it is simply necessary to rotate the plungers _d_ _e_, in the threaded holes in the frame. F is simply a dish to catch the lubricating oil after it has passed through the bearing. It is obvious that if a shaft be aligned axially true, and held in a box of this design, the centre of a length of shaft on either side of the box may be sprung or deflected out of alignment, and that the box will adjust itself so that its bore will be parallel with the axis of the shaft thus deflected, hence the friction between the shaft journal and the bearing box will be at all times a minimum. This feature of self-adjustment permits of the employment of longer bearings, which reduces the wear, as well as the friction, and by providing sufficient bearing and wearing area, enables the bearings to be composed of cast iron, which is the cheapest as well as the very best material of which a bearing can be made, provided that its area of bore is sufficiently large in proportion to the duty, or load, to have a pressure of not more than about 60 lbs. per square inch of area. Again, if the alignment of the shaft should require readjustment from the warping or sinking of beams, as is a very common occurrence where hangers are fixed to the joists of ceilings, the adjustment is readily and easily effected by means of the plungers, nor need the boxes be fitted to the shaft more than to see that when free from the hangers they bed firmly down until the crowns of their bore have contact with the shaft. The hangers themselves require no refinement of alignment, because that may be secured by means of the plungers, and the boxes require no fitting to the shafts after the hangers are erected. In hangers in which the self-adjusting ball-and-socket feature is omitted, the bottom hangers must not only be accurately aligned, but the boxes must, to avoid friction and undue wear, all be fitted to the shaft, and the latter must, during such fitting, be tried in the boxes; the operation, if properly performed, costing far more in labor than is equivalent to the difference in the first cost of the ball-and-socket adjustable hangers and those solid or not self-adjustable, especially if the boxes be long ones, as about, or not less than, three times the diameter of the shaft, as they should be. [Illustration: Fig. 2600.] An external side elevation of this hanger is shown in Fig. 2600, it being obvious that the hanger is designed for bolting to timbers, or framing overhead. [Illustration: Fig. 2601.] Fig. 2601 represents a hanger of this class. In this the lower part carrying the bottom bearing is held to the upper by two bolts, as shown, the object being to enable the same to be placed in position on a line of shafting without disturbing the pulleys or the couplings. The lower section with the bottom bearing is removed and again put on after the hanger is set over the shaft. [Illustration: Fig. 2602.] Fig. 2602 represents an open-sided ball-and-socket hanger in which the plungers can be retired, the bearings removed, and the hanger erected on an existing line of shafting without removing the pulleys or couplings, or disturbing the line of shafting. [Illustration: Fig. 2603.] When the face of the framing to which the hangers are to be bolted stands vertical, the hangers are formed as in Fig. 2603, in which the ball-and-socket or swivelling feature is maintained as before. Fig. 2604 represents a wall hanger, which is open in front similar to the hanger shown in Fig. 2602, and for the same purpose. [Illustration: Fig. 2604.] The section of shafting receiving power from the engine or prime mover is usually supported in bearings or pillow blocks. Pillow blocks are also used for vertical shafts, and in cases where the foundation or framing is not liable to lose correct horizontal adjustment. [Illustration: Fig. 2605.] Fig. 2605 represents a pillow block, in which the ball-and-socket principle shown in Fig. 2602 is embodied. The bearings have each a ball section fitting into spherical recesses or cups provided in the body of the block, and in the cap, so that the bearings are capable of swivelling as already described with reference to the hanger Fig. 2599. [Illustration: Fig. 2606.] [Illustration: Fig. 2607.] A sectional view of a pillow block having this adjustable feature is shown in Fig. 2606. To provide increased seating bearing, and also means of side adjustment to pillow blocks, they are sometimes bolted to base plates as in Fig. 2607, room being left in the bolt holes to permit of their being moved and adjusted upon the plate. The adjustment may be made by means of wedges, as at A, B in Fig. 2607. These base plates are usually employed when the pillow block is to be held against a wall. [Illustration: Fig. 2608.] An inverted pillow block of similar construction, but designed for the head line (as the length receiving power from the engine or motor is termed) of the shafting, is shown in Fig. 2608, but an improved form of the same has plungers so as to effect a vertical adjustment of the bearings. [Illustration: Fig. 2609.] When a pillow block requires to be enveloped by a wall it is provided with a wall box as shown in Fig. 2609, and within this box is set the pillow block as shown, space being sometimes left to adjust the pillow block laterally within the box by means of a wedge as shown. In cases where the shafting requires to stand off from a wall to allow room for the pulleys, brackets or knees, such as shown in Fig. 2610, are employed. COUPLINGS FOR LINE OR DRIVING SHAFTS.--The couplings for connecting the ends of line shafts should accomplish the following objects:-- 1. To hold the two shaft ends axially true one with the other. 2. To have an equal grip along the entire length of shaft enveloped by the coupling. 3. To have a fastening or locking device of such a nature that it will not be liable to work loose from the torsional strains due to the flexure of the shaft, which is caused by the belts springing or straining the axial line of shafting out of the straight line. [Illustration: Fig. 2610.] 4. To be capable of easy application and removal, so as to permit the erection or disconnection of the lengths of shafting with as little disarrangement of the hangers and bearings as possible, and to be light, run true, and be balanced. To these requirements, however, may be added that, since it is well-nigh impracticable to obtain lengths of lathe-turned shafting of exactly equal diameter, couplings for such shafting require to fill the following further requirements: 5. The piece or pieces gripping the shaft ends must be capable of concentric and parallel closure along the entire area, enveloping the end of each shaft, and must do this at each end independently of the other, and the piece or pieces exerting the closing or compressing pressure must grip the closing piece or pieces, enveloping the shafting over the entire area. [Illustration: Fig. 2611.] [Illustration: Fig. 2612.] [Illustration: Fig. 2613.] If, for example, a sleeve be split at four equidistant parts of its circumference, and from each end nearly to the middle of its length, as in Fig. 2611, any pressure that may be applied to its circumference to cause it to grip the shaft it envelops will cause it to grip the shaft with greater force at one part than at another, according to the diameter of the shaft and the location of the external pressure. Thus, if the pressure be applied equally along the length A B, the weaker end B will close most readily, while at A the support afforded by the unsplit section offers a resistance to closure at the ends A of the split, hence the shaft, even though a working fit to the sleeve bore, will be gripped with least force at the end A. If the shaft were simply a close fit, as, say, just movable by hand on the sleeve bore, the form of the coupling bore would, when compressed upon the shaft, be as shown in Fig. 2612, the bend on the necks _a_, _b_, _c_, _d_, being magnified for clearness of illustration. If the compressing piece covered the compressed sleeve for a lesser distance, the grip would be more uniform, because there would be a greater length of the sleeve to afford the curves _a_, _b_, _c_, _d_, as shown in Fig. 2613. The grip may be more equalised by boring the sleeve of slightly smaller diameter than the shaft. [Illustration: Fig. 2614.] Fig. 2614 represents a sleeve carrying out this principle. It is composed of two halves, as shown, bored slightly smaller than the shaft diameter, and is to be compressed on the shaft, which, acting as a wedge, would spring open the sides of the bore until the crown of the bore bedded against the shaft. This, in the case of parallel shaft ends of equal diameter, would hold them with great force axially true, and with equal force and bearing, thus meeting all the requirements. If, however, the end of one shaft were of larger diameter than the end of the other (as has hitherto been supposed to be the case), the end accomplished by boring the sleeve of smaller diameter than the shaft is, that the end of the sleeve is afforded the extra elasticity due to the transverse spring of the sleeve, which permits the edges of each half of the sleeve to bear along a greater length of the shaft end than would otherwise be the case; but the bearing is in this case mainly at and near the edges of the split. It will be perceived, then, that under this principle of construction, when applied to shaft ends of varying diameters, the metal is left to spring and conform itself to the shape of the parts to be connected, and that there is nothing outside of the condition of relative diameter of shaft to sleeve bore to determine what the direction of the spring or closure of sleeve shall be; but, on the other hand, the principle possesses excellence in that the sleeve being cylindrical and its closure taking place equally at similar points of contact the shafts will be held axially true, one with the other; or in other words, the movements of the metal while sleeve closure is progressing are equally radial to the axis of the sleeve, and there is no element tending to throw the shaft axis out of line one with the other. If a sleeve have a single split, the manner in which it will grip a shaft smaller than the sleeve's bore depends upon the manner in which the compression is effected. In Fig. 2615, for example, is a ring supposed to be compressed by a pressure applied at A and at B, causing the ring to assume the form shown by the dotted lines. The centre of the ring bore would therefore be moved from C to D. Now, suppose that the end of one section of shafting were to fit the sleeve bore, then compressing the sleeve upon it would not practically move the centre of the bore; but if the shaft at the other end of the sleeve were smaller than the sleeve bore, the compression of the sleeve to grip the shaft would move the centre of the bore, and, therefore, of the shaft towards D, hence the axial lines of the shafts would not be held true one with the other. To accomplish this latter object, the compression must be equal all round the sleeve, or it may be applied at the points E and F, Fig. 2616, although it is better to have the compression area embrace all the circumferential area possible of the sleeve, and to have the movement that effects the compression simultaneous and equal at all points on the circumference of the ring or sleeve, because if these movements are independent, more movement or compression may be given at one point than at another, and this alters the centre of the bore; thus, if more pressure were exerted at E than at F, in figure, the centre of the bore would be thrown towards F, or _vice versâ_. If the pressure be concentric, the single split ring or sleeve grips the shaft all round its circumference; hence it is only necessary in this case to maintain the circumference of the sleeve in line to insure that the shaft ends be held axially true one with the other; and if the pressure on the ring be applied equally from end to end its closure will also be parallel and equal, and the shaft will be held with equal force along that part of its length enveloped by the coupling. It is obvious, however, that the piece or sleeve gripping the end of one shaft must be independent of that gripping the other, so as to avoid the evils shown in Fig. 2612, while at the same time the casing or guide enveloping the two independent rings or sleeves must guide and hold them axially true, one with the other. [Illustration: Fig. 2615.] [Illustration: Fig. 2616.] [Illustration: Fig. 2617.] In Fig. 2617 is shown an excellent form of _plate coupling_, in which most of the requirements are obtained. A and B are the ends of the two lengths of shafting to be connected, C and D are the two halves of the coupling driven or forced on the ends of the shafting, and further secured by keys. The end of one half fits into a recess provided on the other half, so as to act as a guide to keep the shafts axially true one with the other, and also to keep the two halves true one with the other, while drilling the holes to receive the bolts E which bolt the coupling together. The objections to this form are, that it is costly to make, inasmuch as truth cannot be assured unless each half coupling is fitted and keyed to the shaft, and turned on the radial or joint faces afterwards. Furthermore, if the coupling were taken off in order to get a solid pulley on the shaft, the coupling is apt to be out of true when put together again, and, therefore, to spring the shaft out of true. Also, that the bearing, support, or hanger must be open-sided to admit the shaft, and that each coupling, being fitted and turned to its place, would be apt to run out of true if removed and applied to another shaft, whether the same be of equal diameter or not; but if each half coupling be provided with a feather instead of the usual key, the coupling may be readily removed and will remain true when put on again. [Illustration: Fig. 2618.] Fig. 2618 represents a plate coupling, in which one end of the shaft passes into the bore of the half coupling on the other length of shaft, which serves to keep the shafts in line one with the other. [Illustration: Fig. 2619.] Fig. 2619 represents a single cone coupling composed of an external sleeve having a conical bore and a split internal sleeve bored to receive the shaft, and turned on its outer diameter to the same cone as the bore of the outer or encasing sleeve. The bolts pass through the inner sleeve, the bolt head meeting the radial face of the inner sleeve while the nut meets the radial face of the outer sleeve, so that screwing up the nut forces the inner sleeve into the outer and closes the bore of the former upon the shaft. This coupling is open to the objection that it cannot grip the ends of the shafts equally unless both shafts be of exactly equal diameter, and the bearing on the smaller shaft will be mainly at the outer end only, as explained in Fig. 2611. As a result, the transverse strains on the shaft will cause the couplings to come loose in time. [Illustration: Fig. 2620.] Fig. 2620 represents a coupling composed of a cylindrical sleeve split longitudinally on one side, as at _d_; the bolts _c_ pass through the split. Diametrally opposite is another split passing partly through as at _b_. A key is employed at right angles to the two splits as shown. Here, again, the pressure on a shaft that is smaller than the other, of the two shafts coupled, will be mainly at one end, but separation of the shaft ends is provided against by means of two cylindrical pins on the ends of the key fitting into corresponding holes drilled in the shaft, as shown in the side elevation in the figure. [Illustration: Fig. 2621.] [Illustration: Fig. 2622.] In Fig. 2621 is shown a coupling whose parts are shown in Fig. 2622. It consists of a cylindrical ring turned true on the outside and bored conical from each end to the middle of its length, as shown. The split cones are bored to receive the shaft and contain a keyway to receive a spline provided in the shaft ends, and are turned on the external diameter to fit the conical borings in the sleeve. Three square bolts pass through the split cones, which, being square, are prevented from rotating while their nuts are being screwed up. To put the coupling together one split cone is passed over the end of one shaft and the other over that of the other. The sleeve is then put between the ends of the shaft, the position of the shaft adjusted for length and the split cones pushed up into the sleeve; the bolts are then passed through and screwed up. The forcing of the split cones into the conical borings of the sleeve causes the former (from being split) to close upon the shaft ends and grip them equally tight, notwithstanding any slight difference in the diameters of the shaft, there being left between the ends of the split cones sufficient space to allow them to pass through the conical borings sufficiently to close upon the respective ends of the shafts; the pressure being parallel and equal on each shaft end, because when the cone has gripped the largest shaft the whole movement due to screwing up the nuts is transferred to the cone enveloping the smaller shaft, and by reason of the cones fitting, the closure of the holes in the cones is parallel, giving an even grip along the shaft end and an equal amount of grip to each shaft end. To remove the coupling the bolts are removed, and the sleeve being moved endways the cones open from their spring and relieve the grip upon the shaft. It is evident that in their passage through the sleeve casing the cones will move with their axial lines true with the axial line of the casing; and it is equally evident that the taper on the cone accurately fitting the taper in the sleeve bore, the closure of the cone bores must be equal; while at the same time the pressure on the two cones upon the respective shaft ends must be equal, because it is the friction of the cone bores upon the shaft ends which equally resists the motion of both, while the pressure applied to the respective cones is derived from the same bolts, and hence is equal and simultaneous in its action. To loosen this coupling for removal the bolts must be stacked back and a few blows on the exterior of the outer shell with a billet of wood may loosen the coupling; but if not, a wedge or a cold chisel may be driven in the splits of the cones to loosen them, but such wedge or chisel should not have contact with the sides of the split, either near the bore or near the perimeter, for fear of raising a burr. [Illustration: Fig. 2623.] [Illustration: Fig. 2624.] In Fig. 2623 is shown a patent internal clamp coupling. It is formed of a cylindrical piece containing a pair of separate clamps, and between these clamps and the outer casing are four screws, two to each clamp; these screws are tapered so as to close the clamp when screwed up and release it when screwed outwards. The holes to receive the shaft ends are bored somewhat smaller than the shafts they are to fit, and the clamps opened to permit the easy insertion of the shaft ends by means of wedges A driven in the split B of each clamp, as shown in Fig. 2624. The lower edge of the wedges should be slightly above the bore of the clamp to prevent the formation of a burr or projection of metal when the wedge is driven in. When placed upon the shaft ends and in proper position the wedges are removed and the clamp bore will have contact at and near the edges of the longitudinal split and on the opposite sides of the bore where the keyway is shown, but the pressure of the tape screws will spring the clamps on the side of the longitudinal splits, and increase the bearing area at those points. The main features of this device are that though the bore be made a driving fit to the shaft, it can, by the employment of the wedges, be put on the shaft with the same ease as if it were an easy fit, while the clamps being separated by a transverse groove may open and close upon the shaft independently of each other, so as to conform separately to any variation in the diameters of the two shaft ends it couples. But it may be noted that since the circumference of each shaft end has a bearing along the line of the coupling bore diametrally opposite to the longitudinal splits, the shafts will not be held quite axially true one with the other unless there be as much difference in the diameters of the separate clamp bores as there is in the diameters of the shaft ends; because to hold two shafts of different diameters axially true one with the other the longitudinal planes of the two circumferences must not at any part of the circumferences form a straight line, as would be the case at that part of the coupling bore at and near the keyway. It is to be noted, however, that this coupling is formed of one solid piece, and that the strain on the tightening bolts or screws is one of compression only, which tends to hold them firmly and prevent their coming loose. If the workmanship of a plate coupling, such as in Fig. 2617, be accurately and well done, and the proportions of the same are of correct design, so that the strain placed on the same in keying and coupling it up does not distort it, the coupling and the shaft will run true, because the strain due to the key pressure will not be (if properly driven) sufficient to throw the coupling out of true. But the degree of accuracy in workmanship necessary to attain this end is greater than can be given to the work and compete in the market with work less accurately made, because the difference in the quality of the workmanship will not be discernible save to the most expert and experienced mechanic, and not to him even unless the pieces be taken apart for examination. If the bore of the coupling be true and smooth and of proper fit to the shaft the key pressure, if the key fits on its top and bottom, will not, as stated, be sufficient to throw the coupling out of true. It is true, however, that such pressure is exerted on one half the bore _of the coupling_ only, being the half bore opposite to the key. On the other diametral side of the coupling the strain due to the key is exerted on the top face of the key. If, therefore, the key seats in the shaft and in the couplings are in line or parallel, and both therefore in the same plane, the strain due to the key may throw the coupling out of true to the amount that the key pressure may relieve the bore of the coupling (on the half circumference of the shaft of which the key is the centre) from contact or pressure with the shaft. As a result, the coupling may run to that extent out of true, but the shaft would run true nevertheless so long as the nature of the surfaces on the shaft and on the coupling bore was such that the key pressure caused no more compression or closer contact in the case of one half coupling than in the case of the other. It is obvious that a plate coupling will require at least as much force to remove it from the shaft as it took to put it on, and sometimes, from rusting of the keys, &c., it requires more. If it be removed by blows it becomes damaged, and damage is likely to be also caused to the shaft, while the surfaces having to slide in contact under the pressure of the fit the surfaces abrade and compress, and the fit becomes impaired. But in couplings such as shown in Fig. 2621, the gripping pieces are relieved of pressure on the shaft by the removal of the bolts, and the removal of the coupling becomes comparatively easy. The interchangeability of plate couplings is further destroyed by the fact already stated, that turned shafting is not, as a rule, of accurate gauge diameter, and the least variation in the pressure or fit of the coupling to its shaft is apt to cause a want of truth when the key bears on its top and bottom. The fit of the coupling to its shaft may be, it is true, relied on to do the main part of the driving duty, and the key fitting on the sides only may be a secondary consideration, but in proportion as the fit is relied on to drive, that fit must be tighter, and the difficulty of application and removal is increased. Another and important disadvantage of the plate coupling in any form is that it necessitates the use of hangers open on one side to admit the shaft, because the couplings must be fitted upon the shaft before the same is erected and should not be removed after being fitted, as would be necessary to slide the end of the shaft through the bearing. When plate couplings are constructed as in Fig. 2617, the removal of a section involves either the driving back of one-half of the coupling so that the other half will clear it, or else the moving endwise of the whole line to effect the same object. With a plate coupling the half coupling on one end of the shaft must be removed when it is required to put an additional pulley on the shaft, unless, indeed, a split pulley be used, whereas with a clamp coupling, such as shown in Fig. 2621, the half coupling at each end may be slacked and moved back, one end of the shaft released, a solid pulley placed on the shaft and the coupling replaced, when it will run as true as before, and the pulley may be adjusted to its required position on the length of shafting. It is to be remarked, however, that a well-made plate coupling, such as in Fig. 2618, makes a good and reliable permanent job that will not come loose under any ordinary or proper conditions. [Illustration: Fig. 2625.] [Illustration: Fig. 2626.] In Fig. 2625 is shown a patent self-adjusting compression clamp, which is peculiarly adapted to connect shafting that is of proper gauge diameter. It consists of a sleeve A made in two halves, each embracing nearly one-half of the shaft circumference and being bored parallel and slightly smaller than the diameter of the shaft ends. Over this sleeve passes at each end a ring D E, bored conical and fitting a similar cone on the external diameter of the sleeve. On each end of the sleeve is the nut F G, which by forcing the cone ring up the taper of the sleeve causes the two halves of the latter to close upon and grip the shaft. For shafts less than two inches in diameter there are provided in the sleeve two pins to enter holes in the shaft ends in place of keys, but for sizes above that keys are employed. All parts of this coupling being cylindrical it is balanced. The separate parts of this coupling are shown in Fig. 2626. [Illustration: Fig. 2627.] [Illustration: Fig. 2628.] [Illustration: Fig. 2629.] [Illustration: Fig. 2630.] In Figs. 2627 to 2630 are shown a side elevation and sectional view of another form of shaft coupling. A is the sleeve, B B nuts on the ends of the sleeve, and C C cones fitting taper holes in the sleeve. These cones are split, as shown in Fig. 2629, to permit them to close upon the shaft ends. The shaft ends themselves are matched with a half dovetail, as in Fig. 2630, which dispenses with the employment of a key. In coupling shafts of different diameters it is usual to reduce the diameter of the end of the larger to that of the smaller shaft, and to employ a size of coupling suitable for the smaller shaft; but in this case it is necessary that the coupling be placed on the same side of the hanger or bearing as the smaller shaft, otherwise it is obvious that the strength of the larger would, between its bearings, be reduced to that of the smaller shaft. The couplings for line shafting are usually placed as near to the bearings or hangers as will leave room for the removal of the couplings by sliding them along the shaft. The couplings on the length of shaft receiving power from the motor are placed outside the bearings, hence on the succeeding lengths there will be one coupling between each pair of bearings, the couplings being in each case as close to each bearing as will allow the coupling to be moved towards the bearing sufficiently to permit the length to be removed without disconnecting the adjacent length from its bearings. [Illustration: Fig. 2631.] Fig. 2631 represents a very superior form of coupling for line shafts. The ends of the line shaft are reduced to half diameters as shown, and lapped with a horizontal joint at an angle to the axis of the shaft as denoted by the dotted line, which prevents end motion; the ends of the shaft and their abutting surfaces are dovetailed, as shown A and B, and, therefore, perform driving duty. A sleeve envelops the whole joint and is secured by a key. This coupling accomplishes all that can be desired, but requires very accurate workmanship, and on this account is expensive to make. [Illustration: Fig. 2632.] Fig. 2632 represents a form of coupling suitable for light shafting. It consists of two halves A A, of cast iron, which are drawn together by the bolt C; the centre of the coupling is recessed to enable the coupling to take a better hold on the shaft, which is prevented turning by the pins D D. This coupling has no projections to catch clothes or belts, and is quickly applied or removed. [Illustration: Fig. 2633.] Fig. 2633[38] represents a form of coupling for heavy duty, the transmitting capacity only being limited by the strength of the projections A. If the shafts are not axially in line, this form of coupling accommodates the error, since the projections A may slide in their recesses, while if the axial lines of the shafts should vary from flexure of the bearings or foundations, as in steamships, clearance between the ends of A and the bottom of the recesses may be allowed, as shown at B. [38] From Rankine's "Machinery and Millwork." [Illustration: Fig. 2634.] In Fig. 2634 is shown a coupling (commonly known as the universal joint coupling) which will transmit motion either in a straight line, or at any angle up to 45°. It is formed of two double eyes, such as A, connected to a yoke or crosspiece B as shown at C. It is mainly used for connecting shafts or arms carrying tools of some kind, such as rubbers for polishing stone, tools for boring, or other similar purposes in which the tool requires to be rotated at varying angles with the driving shaft. CHAPTER XXXI.--PULLEYS. Pulleys for the transmission of power by belt may be divided into two principal classes, the solid and the split pulley. The former is either cast in one entire piece, or the hub and arms are in one casting, and the rim a wrought-iron band riveted on. The latter is cast in two halves so that they may be the more readily placed upon or removed from the shaft. On account of the shrinkage strains in large pulley castings rendering them liable to break, it is usual to cast pulleys of more than about 6 feet in halves or parts which are bolted together to form the full pulley. On account of these same shrinkage strains it was formerly considered necessary to cast even small pulleys with curved arms, so that the strains might be accommodated or expended in bending or straightening the curves of the respective arms. It is found, however, that by properly proportioning the amount of metal in the hub, arms, and rim of the pulley, straight arm pulleys may be cast to be as strong as those with curved arms, and being lighter they are preferable, as causing less friction on the shafting journals, and, therefore, being easier to drive. It is obvious that a pulley for a double belt requires to be stronger than is necessary for a single one, but the difference is not sufficiently great to give any practical advantage by making separate pulleys for single and double belts; hence all pulleys are made strong enough for double belts. Pulleys are weaker in proportion to their duty as the speed at which they rotate is increased, because the centrifugal force generated by the rotation acts in a direction to burst the pulley asunder, so that if the speed of rotation be continuously increased a point will ultimately be reached at which the centrifugal force generated will be sufficient to cause the wheel to burst asunder. But the speed at which pulleys are usually run is so far within the limits of the pulley's strength, that the element of centrifugal force is of no practical importance except in the case of very large pulleys, and even then may be disregarded provided that the pulleys be made in a sufficient number of pieces to avoid undue shrinkage strains in the castings, but if solid pulleys are rotated at high velocities the internal strains due to unequal cooling in the mould has been known to cause the wheels to fly asunder when under high speeds. Fig. 2635 represents a solid pulley, the tapered arms meeting the rim in a slightly rounded corner or fillet, and the rim being thickened at and towards its centre. When the width of rim is excessive in proportion to one set of arms a double set is employed as in Fig. 2636. In some forms of pulley the arms and hub are cast in one piece and the rim is formed of a band of wrought iron riveted to the arms. By this means shrinkage strains are eliminated and a strong and light pulley is obtained. Fig. 2637 represents a split pulley in which the two halves are bolted together after being placed on the shaft. Variable motion may be transmitted by means of an oval driving pulley, as in Fig. 2638, it being obvious that the belt velocity will vary according to the position of the major axis of the oval. Arrangements of this kind, however, are rarely met with in practice. In Fig. 2639 is shown an expanding pulley largely employed on the drying cylinders of paper machinery, and in other similar situations where frequent small changes of revolution speed is required. Each arm of the wheel carries a segment of the rim, and is moved radially to increase or diminish the rim diameter by sliding in slots provided in the hub of the wheel, a radial screw operated by bevel gears receiving motion from the hand wheel and gear-wheels shown in the engraving. It is obvious that in this case the driving belt must be made long enough to embrace the pulley when expanded to its maximum diameter, the slack of the belt due to reduction of diameter being taken up by a belt tightener. [Illustration: Fig. 2640.] [Illustration: Fig. 2641.] [Illustration: Fig. 2642.] In Fig. 2640 is shown a wooden pulley having a continuous web or disk instead of arms. It is built up of segments, the web being secured to the shaft as follows. In Figs. 2641 and 2642 A, B are clamping plates, and C a split sleeve fitting easily to the shaft and passing through A, B, while receiving the nut E on the other side. The web of the pulley fits on the shoulder J, and the flange B fits on the shoulder K, so as to keep these parts true or concentric to A. The bore of A is taper to fit the taper of C; hence the nut E in drawing C through A, causes C to close upon and grip the shaft, while the flanges A, B grip the pulley and hold it to C. In Figs. 2643 and 2644 are represented the Otis self-oiling loose pulley, designed to automatically oil itself upon its starting or stopping. [Illustration: _VOL. II._ =EXAMPLES OF PULLEYS.= _PLATE XII._ Fig. 2635. Fig. 2636. Fig. 2637. Fig. 2638. Fig. 2639.] [Illustration: Fig. 2643.] [Illustration: Fig. 2644.] The hub D is cored out in such manner as to form within it an annular chamber or cavity B B, entirely surrounding the bore, and serving as a reservoir to contain oil or other lubricating liquid. This chamber or reservoir has no direct communication with the bore of the hub, but a communication is formed between it and the bore through one or more chambers C C, which are termed supply chambers, and which are partitioned off within the bore from the reservoir B, by coring the hub in a suitable manner. These supply chambers have openings N N in their sides or ends communicating with the reservoir B, and also openings C C communicating with the bore of the pulley. These supply chambers are filled with wick or other fibrous or capillary material, which is also inserted into the openings N N, to draw the oil from the reservoir by capillary attraction and supply it in moderate quantities between the bore of the pulley and the shaft on which it runs. Three or more openings are provided in the outer shell of the hub for the introduction of oil into the reservoir B, which openings are closed by thumb-screws, plugs, or other stoppers E E. There being three of these openings, one will always be at or near the top when the pulley is at rest, and through this the oil may be introduced without difficulty. It is not intended that the reservoir should at any time contain more than one-third its capacity of oil, so that whenever the pulley is at rest the surface of the oil will be below the lowest point of the bore, thus preventing any waste of oil at such times. When the pulley is in motion, the centrifugal force imparted to the oil in the reservoir throws it outwardly, causing it to be distributed in an even layer against the inner surface of the shell which encloses and forms the reservoir, thus preventing any possible waste when the pulley is in motion. But when the pulley is either stopped or started, the oil is caused to change its position, and in so doing is brought into contact with the wicks protruding from the small openings N N, by which it is conveyed into the supply chamber, and thence to the shaft. By thus taking advantage of what is a necessity in all business establishments in which machinery is employed--to wit, the stopping and starting of the machinery at regular intervals--to insure the supplying, at such times, of a small quantity of oil to the bearings of the loose pulleys, the makers claim that a perfect and reliable means is obtained for guarding against any needless waste of the lubricant. [Illustration: Fig. 2645.] A crowning or crowned pulley is of largest diameter in the middle of its width or face, the object being to cause the belt to run on the middle of the pulley width. It would appear that this crowning would give to the belt a greater degree of tension at its centre than at its edges, but it is shown by experiment that if a piece of belt be clamped square across its width at each end and stretched, the centre as section _b_, in Fig. 2645, will stretch the most, and that if the piece be divided along its centre lengthwise, and both halves again stretched, they will again do so the most in the middle of their widths. From this it appears that the crowning serves to produce a tension equal across the pulley width, because it will stretch the belt the most in the middle of its width, where it has the greatest capacity to stretch. The amount of crowning employed in practice varies from about 3/16 to 3/8 inch per foot of width of pulley face, the minimum being employed where the belt requires to be moved or slipped laterally from one pulley to another of equal diameter, as from a fast to a loose pulley and _vice versâ_. To relieve the belt of strain when on a loose pulley the loose pulley is sometimes made of smallest diameter, and has a coned step up which the belt moves when pressed against it. During this passage of the belt, however, one edge is stretched more than the other, while in passing from the large to the smaller pulley the same edge is under tension, while the other is released from tension; hence, with the belt passing either to or from the large pulley there is a tendency to unduly stretch one of its edges. On the other hand, however, in cases where the belt requires to run for long periods on the loose pulley relieving it from tension is a great advantage. In fixing pulleys so that they shall run true upon their shafts several difficulties are met with. First, it is difficult to turn the shafts quite parallel and to exact standard gauge diameter. Second, the bore of the pulley must be made a sufficiently easy fit to enable their being moved by hand along the shaft to the required location. As a result the set-screw pressure throws the pulley out of true, unless the mandrel on which the pulley is turned in the lathe be the same diameter as the pulley shaft, and the pulley be held upon the mandrel by the set-screw pressure, and not by driving the mandrel into the pulley bore. In this case two set-screws must be used one on each end of the pulley hub, so as to steady the pulley on the mandrel. A pulley thus trued will still run out of true when on its shaft unless the shaft be of the same diameter as the mandrel. One means of obviating this difficulty is to reduce the diameter of the shaft between the pulley seats sufficiently to allow the pulley to pass easily, and to make the pulley bores a driving fit to their seats. This, however, is only practicable in cases where the locations of the pulleys are permanently fixed, and no occasion arises for the addition of new pulleys. [Illustration: Fig. 2646.] To obviate this difficulty what is termed an internal clamp pulley has been constructed. This pulley is shown in Fig. 2646. The bore is made sufficiently smaller than the shaft diameter to be a forcing fit. A slot in the form of an arc of a circle is formed in the hub as shown, and a split runs from this arc into the bore. As a result a wedge driven between the walls of the split will spring open the bore and permit its easy passage along the shaft to its required location, when the removal of the wedge will permit the bore to close upon the shaft. To secure the pulley to the shaft four set-screws are employed, two of them being shown in the cut, and the other two being similarly located on the other side of the pulley. By this means there will be less difference between the diameters of the pulley bore and of the shaft should the latter be slightly less than its standard diameter, and as a result the pulley will run more true. Split pulleys are bored a tight fit to the shaft when the two halves are bolted firmly together. They may, however, be made to grip the shaft in two ways; first, if bored when bolted together the edges of the bore will meet the shaft and clip it so firmly as to require each half bore to spring open to permit it to pass on the shaft, but by inserting between the two halves of the hub two thicknesses of writing paper, and boring out the hole the thicknesses of the paper too large (which may be done by placing two pieces of the same paper beneath the calipers or gauge) the bore will be slightly oval when the paper is removed, and will grip the shaft at the crown of each half bore, but the grip thus obtained will not be so firm. Pulleys of small diameter, as three feet or less in diameter, are usually held to their shafts by set-screws, the consideration of their shapes and position having been already treated of when referring to the applications of keys and set-screws. Pulleys of large diameters, and those which act as fly-wheels as well as pulleys, are usually held by keys. BALANCING PULLEYS.--A pulley (more especially those running at high speed) should be balanced or in balance when rotating at the greatest speed at which it is intended to run. This is necessary, because if the centrifugal force generated by the pulley's rotation be greater on one side than on another of the pulley, it will cause the pulley shaft to vibrate and shake whenever the amount of unbalanced centrifugal force becomes, on account of the speed of rotation, sufficient to bend the shaft or deflect the framing holding the shaft. The balancing of a pulley will not be correct unless the centrifugal force is equal at all points on the perimeter in the same plane, as will appear presently. In practice two methods of testing the balance of a pulley are employed: first, the standing; and second, the running balance. A standing balance does not in any sense balance a pulley, but merely corrects the want of balance to a limited degree. A running balance correctly balances a pulley when running up to the speed at which the balance was made, but does not balance for greater speeds. [Illustration: Fig. 2647.] [Illustration: Fig. 2648.] A standing balance is effected when the shaft being supported horizontally and with as little friction as possible, the pulley will remain at rest in any position in which it can be placed. Thus, in Fig. 2647 let C C represent the two centres of a lathe adjusted in their distance apart so as to sustain the shaft S with just sufficient force to prevent end movement or play of the shaft, and if the pulley P remains motionless when arrested at any point of rotation it is in standing balance. A common method of balancing is to set the pulley in slow rotation several times in succession, and if the same part of the pulley's circumference comes to rest in each case at the bottom as at B then it is heaviest and its weight must be reduced, or weight must be added on the diametrically opposite side of the pulley. Another method is to rest the shaft horizontally on a pair of metallic strips as B B in Fig. 2648, the strips resting on a flat horizontal surface D, the testing being applied as before. Sometimes, however, cylindrical pieces are used in place of the strips or pieces B B. [Illustration: Fig. 2649.] A pulley that is in balance thus tested, may not, however, be in balance when rotated, or, as already stated, a standing balance may not be a running balance, for the following reasons: In Fig. 2649 is a pulley that if turned true inside and out would be of correct standing balance, because the weight is equal on each side of the shaft; thus the point A, though farther from the axis than B, would be counterbalanced by C, while B would be counterbalanced by D, but as soon as the pulley was put in rotation there would be more centrifugal force generated at A than at B, and more at C than at D, because, though the weights would be equal, the velocities of A and C would be greatest. Now, suppose that instead of a continuous wide pulley several pulleys were used, being out of true so as to be practically equal in shape to Fig. 2649, and it is apparent that the fact of pulley A B being out of balance is not removed by pulley C D being out in an opposite direction, and that each pulley will tend to bend the shaft in the direction of its excessive centrifugal force. [Illustration: Fig. 2650.] The effect of this inequality of centrifugal force will depend, in each case, upon the strength of the shaft in comparison with the amount of unbalanced centrifugal force. Suppose, for example, that the centrifugal force at a point A in Fig. 2650 were 10 lbs. greater than at B at a given velocity, and that the strength of the shaft be such that it will bend 1/32 inch under a weight of 10 lbs., then the effort of the point A will be to swing in a circle 1/16 inch larger than that due to its diameter. Suppose, then, the stand be so firmly fixed at C as to be motionless in a vertical direction under this effort, then the point A will swing in an oval, as denoted by the dotted lines, the shaft vibrating as denoted by the arrows. [Illustration: Fig. 2651.] Thus vibrations of the shaft, bearing, &c., occur whenever the excess of centrifugal motion on one side of a pulley is sufficient to spring the shaft, bearings, standard or foundation, as the case may be, and will occur most in the direction in which those parts will most easily succumb. From this it is evident that a pulley practically in balance, so far as being free from vibration at a certain speed, may be considerably out of balance at an increased speed. Thus, suppose a pulley P, in Fig. 2651, has a rim of equal thickness, but the distance of A from the axis of rotation is 6 inches, while the distance of B is 8 inches; then the centrifugal force at B will, at any speed of rotation, be one-quarter more than that at A, because the distance is one-quarter greater. Suppose, then, that its shaft, bearings, and foundation be capable of resisting 100 lbs. without sensible flexure, but that sensible flexure of those parts will occur under any pressure over 100 lbs. The centrifugal force of 1 lb. at A and at B, respectively, may be calculated by the following rule:-- _Rule._--Multiply the square of the number of revolutions per minute by the diameter of the circle of rotation in feet, and divide the product by 5,870. The quotient is the centrifugal force in terms of the weight of the body. In the case of A the pulley making, say, 200 revolutions per minute, we have by the rule: 200^{2} × 1 ----------- = 6.81 = the centrifugal force. 5,870 Likewise, centrifugal force at B = (200^{2} × 1.25)/5,870 = 8.51 = the centrifugal force, 1 and 1.25 being diameters of circle of rotation of A and B in feet. Now, suppose the revolutions to be 2,000 per minute, we have in the case of A 2,000 × 2,000 × 1 (= 4,000,000) ÷ 5,870 = 681 lbs. centrifugal force. Add one-quarter more, or 170 lbs., to obtain the centrifugal force at B = 851 lbs.; the unbalanced centrifugal force = 170 lbs.; and this being 70 lbs. more than the shaft, bearings, &c., are capable of resisting without flexure, a corresponding vibration will occur, whereas at 200 revolutions the unbalanced centrifugal force was: Centrifugal force at B = 8.51 lbs. less that at A = 6.81 = 1.70 lbs. unbalanced centrifugal force, and it becomes apparent that while at 200 revolutions the pulley would rotate without sensible vibration, at 2,000 revolutions (in the same time), sensible vibration would occur; hence, the sensible vibration of a pulley is in the proportion as the unbalanced centrifugal motion is to the resistance of the shaft, bearings, &c., to flexure, and further, as the unbalanced centrifugal motion increases with the velocity, so also does the sensible vibration increase with the velocity. But there are two ways of increasing the velocity of a pulley: 1st, by increasing the revolutions of a given pulley; 2nd, by employing a pulley of a larger diameter, but making the same number of revolutions. In our example we increased the speed tenfold (from 200 revolutions to 2,000) but the centrifugal force was increased one hundredfold, according with the law that the centrifugal force increases with the square of the revolutions, and 10 × 10 = 100. But if the velocity had been increased by augmenting the diameter of the pulley, the centrifugal force would have increased in the same ratio as the pulley diameter was increased; hence it appears that under equal velocities larger pulleys generate less centrifugal force per unit of unbalanced weight than do smaller ones. [Illustration: Fig. 2652.] A device for testing the balance of pulleys is shown in Fig. 2652; it consists of a frame carrying a vertical spindle, which may be rotated by suitable bevel-wheels, and the hand wheel shown. In this case it would be preferable to balance the pulley at the greatest speed at which it would be convenient to run it by hand with the wheel shown, because a pulley balanced at any given speed will be balanced at any lesser speed, although not at a greater one. But the pulley should not be driven by the arms, because the pressure against the same will affect the balance. It would be better therefore to let the spindle of the machine be small enough in diameter to fit the smallest bore of pulley to be balanced, to employ sleeves fitting the spindle and the bores of all larger bored pulleys, and to obtain the most correct results the pulley should be fastened to the sleeve by its set-screws, or keys of the pulley, as the case might be, so that whatever error there might be induced by tightening the same will be accounted for in the balancing. It is obvious also that the pulley bore should fit the sleeve with the same degree of tightness as it will fit the shaft to which it is to be fixed. The heaviest side of the pulley will rotate through a circle of larger diameter, and may be marked by a point, as a tool point moved up to it by a slide rest, or roughly by a piece of chalk steadily moved up to it by hand until it just touches the high side of the pulley. [Illustration: Fig. 2653.] The methods of correcting the balance are as follows: The heavy side of the pulley having been found, a weight is attached to the diametrically opposite side of the pulley; a convenient form of light weight for this purpose is shown in Fig. 2653; it consists of what may be termed a spring clamp, since it holds to the edge of the pulley rim, on which it is forced by hand, by reason of the spring of the jaws. There are numerous clamps of this form, each having a definite weight, as 2 ozs., 3 ozs., 4 ozs., &c.; but for weights above about 1-1/2 lb. a clamp with a set-screw is employed. For a running balance a set-screw is indispensable. It is obvious that pulleys will be more easily and correctly balanced when the inner side of their rim is turned up, as far as the arms will permit, in the lathe; but on account of the expense this is not usually done, except in the case of large pulleys. In the best practice, however, the pulley is set in the lathe, so that the inside of the rim runs as true as possible. Remarks on this subject are given under the head of chucking pulleys. When the balance is to be effected by adding weight to the pulley mushroom-shaped pieces of metal are made for the purpose, their weights varying by ounces; the stems are driven through holes drilled through the rim to receive them, and riveted on the face side. The stems are of wrought iron, while the heads may be of cast iron, but are better of lead, because in that case they may be set with a hammer to fit the inner surface of the pulley rim. In some practice, protuberances, or a web in the middle of the pulley, are cast on the pulley, and the balance is effected by cutting this away to reduce the weight on the heavy side. When pulleys are to revolve at very high speeds, as in the case of those for emery-wheel spindles, the shafts themselves require to be balanced, especially if of cast iron, because that part of the shaft uppermost in the mould will be of less density and weight than that at the bottom of the mould. The pulley should be balanced separately, and the whole again balanced after being put together, because the weight of the key or set-screw will be sufficient to destroy the balance under a sufficiently high speed of rotation. The edges of pulley rims should be trued up in the lathe when the rim is turned so that the pulleys to receive a belt may be set in line by pressing a straight-edge, or setting a line to have contact with (as near as possible) diametrically opposite points of the edge of one pulley, and setting the other to have its corresponding edge in line. Pulleys should run true so that the strain or tension of the belt shall be equal at all parts of the revolution, and the transmitting power shall be equal. The smoother and more polished the surface of the pulley the greater its driving power. The transmitting power of a pulley may be increased by covering the pulley face with leather or rubber bands, but the thickness of these should be equal both across the width and all around the circumference so as to run true. The amount of increase of driving power due to this covering is variously stated, but may be taken at about 20 to 30 per cent. A cement for fastening such pulley coverings may be made as follows: Take one ounce of caoutchouc (pure or native rubber) and cut it into thin slices, place it in a tinned sheet-iron vessel with six or seven ounces of sulphide of carbon; the vessel is then to be placed in a water tank previously heated to about 86° Fahr. To prevent the solution from becoming thick and unmanageable, mix with a solution consisting of spirits of turpentine, in which half an ounce of caoutchouc in shreds has been dissolved over a slow fire, and then a quarter of an ounce of powdered resin; from an ounce and a half to two ounces of turpentine being afterwards stirred in, to be added in small quantities. This cement must be kept in a large-mouthed bottle well corked, and in using clean the parts to be united thoroughly with benzine; apply two coats of cement, allowing each to dry before applying the next; when applying the last coat allow the cement to dry so as to become very sticky, then press the surfaces firmly together and allow to thoroughly dry. This is waterproof. A pulley that imparts motion to the belt enveloping or partly enveloping it is termed a driving pulley or driver. A driven pulley is one that receives motion from, or is driven by, the belt; hence in every pair of pulleys connected by belt, one is termed the driver and the other the driven. The revolutions of two pulleys connected by belt will vary in the same proportion as their diameters, although their rim velocity will be equal. Suppose, for example, that a pulley of 7 in. diameter drives one of 14 in. diameter, then if there is no slip on either pulley both pulleys will run at the same velocity as the belt, and this velocity must be equal to the velocity of the driver, because the belt is moved by the driver. Now, suppose the driver which is of 7 in. diameter makes one revolution in a minute, and as it is only one-half the diameter of the driven wheel, its circumference will also be half that of the driven, so that it must make two revolutions to carry around length of belt enough to pass once around the driven pulley. The revolutions of the two are, therefore, in the same proportions as are their diameters, which in this case is two to one. As the driven pulley is the largest diameter, it will make one revolution in the same time that the driver makes two. But suppose the driving pulley was 14 and the driven was 7 inches in diameter, then the proportion would still be two to one, and the driven would make two revolutions to every revolution of the driver. [Illustration: Fig. 2654.] If we are given the number of revolutions a driving pulley makes and the diameter or circumference of both pulleys, and require to find the number of revolutions the driven pulley will make to one or to any given number of the driver, we may consider as follows: Suppose the circumference of the driver to be 24 inches and that of the driven to be 18 inches, then in Fig. 2654 let circle A represent the driver, and circle B the driven pulley. If we divide the circumference of A into four equal divisions, as at 1, 2, 3, and 4, each of these divisions will equal 6 inches, because the whole circumference being 24 inches, one quarter of it will be 6. If we divide the circumference of B into six-inch divisions there will be but three of them as marked, because one-third of 18 (its circumference) is 6. Now three of the divisions at A will move A a full revolution, and the remaining division on A will move B through another one-third of a revolution, hence, each revolution of A equals 1-1/3 revolutions on B. The proportions of the circumference are, therefore, as 1-1/3 to 1, or as 133 is to 100, taking A as the driver, and, therefore, as the basis of the proportion. But suppose we take B as the basis of the proportion, and one revolution of B will cause A to make three quarters of a revolution, or during 100 revolutions of B, A will make 75. But nevertheless during the period that A is making 100 revolutions B will have made one-third more, or 133-1/3, because B makes 1-1/3 revolutions to cause A to make one revolution. From this it will be seen that the proportion is as the greater is to the lesser, and not as the lesser is to the greater, or, in other words, it is in this case as 24 is to 18, which is one and one-third times, for one-third of 18 is 6, and 18 + 6 = 24. Suppose, now, we take the four divisions on A and the three on B to consider their proportions, and we may say 4 is 1-1/3 times 3, or we may with equal propriety say 3 is 3/4 of 4, hence 4 is not in the same proportion to 3 that 3 is to 4. Let it now be supposed that a driven pulley B is 18 inches in diameter, and requires to be driven one quarter faster than the driver, what then must be the diameter of that driver? As the revolutions require to be increased one-fourth the pulley diameter must be increased one-fourth. Thus one quarter of 18 = 4-1/2, and this added to 18 is 22-1/2, which is therefore the diameter of the driving pulley, as may be proved as follows: Suppose the circumferences instead of the pulley diameters to be 22-1/2 and 18 respectively, and that the largest pulley makes 100 revolutions, then it will pass 2,250 (22-1/2 × 100 = 2,250) inches of belt over its circumference, and every 18 inches of this belt will cause the small pulley to make one revolution; hence we divide 2,250 by 18, which gives us 125 as the revolutions made by the small pulley, while the large one makes 100. Thus it appears that we obtain the same result whether we take the circumferences or the diameters of the pulleys, because it is their relative proportions or relative revolutions that we are considering, and their actual diameters do not affect their proportions one to the other. Thus, if a 10-inch pulley drives a 30-inch one, the proportions being three to one, the revolutions will be three to one, and the driven being three times the largest, will make one revolution to every three of the driver. If the driver was 3 inches in diameter and the driven 9, the revolutions would be precisely the same as before, but with equal revolutions the velocities would be different, because in each revolution of the driver it will move a length of belt equal to its circumference; hence, the greater the circumference the greater length of belt it will move per revolution. To take the velocity into account, we must take into consideration the number of revolutions made in a given time by the driver. Suppose, for example, that the driver being 3 inches in diameter makes one revolution in a minute, then it will move in that minute a length of belt equal to its circumference, so that the circumference of the driver, multiplied by the number of its revolutions per minute, gives its velocity per minute. Thus, if a pulley has a circumference of 50 inches, and makes 120 revolutions per minute, then its velocity will be 6,000 inches per minute, because 50 × 120 = 6,000. The velocity of the belt, and therefore that of the driven wheel, will also be 6,000 inches per minute, as has already been shown. From this train of reasoning the following rules will be obvious:-- To find the diameter of the driving pulley when the diameter of the driven pulley and the revolutions per minute of each are given: _Rule._--Multiply the diameter of the driven by the number of its revolutions, and divide the product by the number of revolutions of the driver, and the quotient will be the diameter of the driver. The diameter and revolutions of the driver in a given time being known, to find the diameter of a driven wheel that shall make a given number of revolutions in the same time: _Rule._--Multiply the diameter of the driver by its number of revolutions, and divide the product by the number of revolutions of the driven. The quotient will be the diameter of the driven. To find the number of revolutions of a driven pulley in a given time, its diameter and the diameter and revolutions of the driver being given: _Rule._--Multiply the diameter of the driver by the number of its revolutions in the given time, and divide by the diameter of the driven, and the quotient will be the number of revolutions of the driven in the given time. Suppose, however, that the speed of the shaft only is given, and we require to find the diameter of both pulleys, as, for example, suppose a shaft makes 150 revolutions per minute, and we require to drive the pulley on a machine 600 revolutions per minute. Here we have two considerations: first, the relative diameters of the two pulleys, and secondly, the diameter of pulley and width of belt necessary to transmit the amount of power necessary to drive the machine at the speed required. Leaving the second to be discussed hereafter in connection with the driving power of belts, we may proceed to determine the first as follows: The pulley on the machine must be as much smaller than that on the main shaft, as the speed of the pulley on the machine requires to run faster than does the main shaft, hence we divide the 600 by 150 and get four, which is the number of times smaller than the driver that the driven pulley must be. Suppose then the driver is made a 24-inch pulley, then the driven must be a 6-inch one, because 24 ÷ 4 = 6; or we may make the driver 36, and the driven 9, because 36 ÷ 4 = 9; or the driver being 48 inches in diameter, the driven must be 12, because 48 ÷ 4 = 12. To reverse the case, suppose the shaft to make 200 revolutions per minute, and the machine pulley to make 50, then since 200 ÷ 50 = 4, the driven (or machine pulley) must have a diameter four times that of the driver, and any two pulleys of which one is four times the diameter of the other may be used, as say: Pulley on line shaft 10 inches in diameter, pulley on machine 40 inches in diameter; or, pulley on line shaft 20 inches in diameter, pulley on machine 80 inches in diameter. Now, in nearly all cases that are met with in practice, it would be inconvenient to have so large a pulley as 80 inches in diameter to drive a machine, and again in most cases a driving pulley of 10 inches in diameter would be too small. So likewise in cases where the machine pulley requires to run faster than the line shaft, a single pair of pulleys will be found to give, where great changes of revolution are required, too great a disproportion in the diameter of the pulleys; thus in the case of a shaft making 150, and the machine requiring to make 600, we may use the following pairs of pulleys:-- On Main Shaft. On Machine Shaft. First 32 inch diameter 8 inch diameter. Second 40 " " 10 " " Third 48 " " 12 " " Fourth 60 " " 15 " " But the machine may require so much power to drive it, that with the width of belt it is desired to employ, a pulley larger than either of these is necessary, as, say, one 20 inches in diameter. Now, with a 20-inch driven pulley, the driver would require to be 80 inches in diameter, because 20 × 4 = 80. But there may not be room between the shaft and the ceiling for a pulley of so large a diameter, or such a large pulley may be too heavy to place on the shaft, or it may be too costly, and to avoid these evils, countershafts are used. By the employment of a countershaft we simply obtain--with two pairs of pulleys and by means of small pulleys--that which could be obtained in a single pair, providing the great difference in their diameters (necessary to obtain great changes of rotation), were not objectionable; all that is necessary, therefore, is to accomplish part of the required change of rotation in one pair, and the remainder in the other. In doing this, however, while the velocity of each driver and driven will be equal (as was explained with reference to a single pair), notwithstanding the difference in their diameters, yet the velocity of one pair will necessarily differ from that of the other, so that the pulley on the machine will vary in its velocity as well as in its rotation from that of the first driver. The first driver is that on the main or driving shaft, and the pulley it drives is the first driven. The second driver is the second pulley on the countershaft, and the second driven is the one it drives or that on the machine. Suppose, then, a driving shaft makes 100 revolutions per minute, and the machine requires to make 600, then the speed of rotation requires to be increased six times. Now we may effect this change of six times in several ways; thus: Suppose we increase the rotations three times in the first pair, then the second pulley will make 300 rotations, or three times those of the main shaft, and all we have to do is to make the second driven one-half the diameter of the second driver, and its rotations will be double those of the second driver, which will give the required speed of 600 revolutions. Suppose, however, we change the speed four times in the first pair, and the 100 of the shaft becomes 400 on the countershaft, and to increase this to 600 on the second driven, all that is required is to make its diameter one-half less than that of the second driver, because 600 is one-half more than 400. From this it will be perceived that the number of changes or amount of increase or decrease of speed being given, the proportion of diameters for both pairs of pulleys will be represented by any two numbers which, multiplied together, will give a sum equal to the number of increased revolutions required. Having found the proportions for each pair, it remains to determine their actual diameters, and they will be found to vary under different conditions. Suppose, for example, we have the following conditions: Main shaft runs 100; machine must run 600. The pulley on the line shaft is 36 inches in diameter; required, the diameters for the other three pulleys. To make three changes in the first pair, the first driven must be 1/3 the diameter of the first driver, which is 12 inches. Now the second pair we may make any diameters that are two to one; and since the second driver is to be the smallest, we may select as small a pulley as will answer for the machine, and make its driver twice its diameter. But suppose it is the diameter of the pulley on the machine that is fixed, and the diameter of the other three require to be found. Let the diameter of the second driven be 12; then its driver on the countershaft must be 24. The other two must have diameters 3 to 1 as before, any suitable wheels being selected. Yet another condition may occur. Thus, suppose the countershaft is on hand, and that it has on it two pulleys, as a 12 and a 24-inch; then a 36 on the inner shaft will be three times as large as the 12, and a 12-inch on the machine will be twice as small; or, what is the same, one half as large as the 24. When the principle is clearly understood the calculations can be performed mentally with ease so far as the required diameters to attain the necessary speed is concerned, but there are other considerations that claim attention. Thus, for example, to multiply the rotations 6 times we may proportion the first pair as follows: Driver 48, driven 16; second pair, driver 30, driven 15 inches in diameter. Or we may proportion them as follows: First pair: driver 36, driven 12; second pair: driver 28, driven 14 inches in diameter. In the second arrangement of diameters the drivers are each 2 inches, and the driven each 1 inch less in diameter than in the first; hence their cost would be diminished, as would also be the wear of the journals, on account of the reduced weight of the pulleys; hence, if the driving capacity of each pulley is equal to the requirements the second arrangement would be preferable. In considering this part of the subject, first let it be shown that although the horse-power transmitted by the two belts is equal whatever be the proportions of the pulleys (provided, of course, that the belts do not slip), yet the strain or wear and tear of the belts varies, and the requirements for one belt are therefore different from those for the other. [Illustration: Fig. 2655.] In Fig. 2655 let A represent a 36-inch pulley on the driving shaft, B a 12-inch, and C a 24-inch pulley on a countershaft, and D a 12-inch pulley on a machine shaft. Let the main shaft make 100 revolutions per minute, and the machine requires a force to move it equal to 50 pounds applied to the perimeter of D. Now the rotations of D will, with these pulleys, be six to one of the main shaft or A, which gives D 600 revolutions per minute, thus: 100 × 6 = 600. The circumference of D is about 37.69 inches, which, multiplied by 600 (the number of its revolutions), gives 22,614 inches, or 1,884.5 feet as its speed per minute. This multiplied by the 50 pounds it takes to move the machine at the perimeter of D, gives 94,225 as the foot pounds per minute required to drive the machine 600 revolutions per minute, and this, therefore, is the amount of power transmitted by each belt. On the second belt this is shown to be composed of 50 pounds moving 1,884-1/2 feet per minute, hence we may now find how it is composed on the first belt, as follows:-- The diameter of the first driver is 36 inches, and its circumference 113.09 inches, or 9.42 feet; this, multiplied by its revolutions per minute, will give its speed, thus: 9.42 × 100 = 942 feet per minute. To obtain the necessary amount of pull for this first belt, we must divide this speed into the number of foot pounds it takes to drive the machine, thus: 94,225 ÷ 942 = 100.02. The duties of the two belts are therefore as follows:-- First belt, weight of pull 100.02 " speed per minute 942 feet. Second belt, weight of pull 50.00 " speed per minute 1884.5 feet. The duty in foot pounds being equal, as may be shown by multiplying the feet per minute by the force or weight of the pull, leaving out the fractions, thus:-- 942 × 100 = 94,200. 1884 × 50 = 94,200. The difference in the requirements is, then, that the first belt must have as much more weight or force of pull than the second as its speed is less than that of the second. It is obvious that in determining the proportions of the pulleys this difference in the requirements should be considered, and the manner in which this should be done depends entirely upon the conditions. Thus, in the case we have considered, the speed was increased, but the object of the countershaft may be to decrease the speed, and in that case the conditions would be reversed, inasmuch as though the foot pounds transmitted by both belts would still be equal, yet the speed would be greatest and the strain or pull the most on the second belt instead of on the first. It is obvious, then, that the proportions of the pulleys being determined the actual diameters must be large enough to transmit the required amount of power without unduly straining the belt. CHAPTER XXXII.--Leather Belting. The names of the various parts of a hide of leather as known to commerce are as follows:-- [Illustration: Fig. 2656.] In Fig. 2656 the oblong portion between the two belly parts marked G G is known as the "butt," and when split down the ridge, as shown by the dotted line down the centre, the two pieces are known as "bends;" the two pieces marked Y are "belly offal;" D is known as "cheeks and faces." The butt within the dotted line may extend in length from A to B, or from A to C; if cut off between B and C that portion is called the "range" or the whole from B to X may be cut in one piece and termed a "shoulder." Sometimes the range is cut off and the rest would be called a shoulder with "cheeks and faces" on; or, again, the range and shoulder may be in one nearly square piece. The manner of cutting this part depends upon the spread and size of the hide. [Illustration: Fig. 2657.] The part of the hide that is used to manufacture the best belting is shown in Fig. 2657, on which the characteristics of the various parts are marked. The piece enclosed by the dotted lines is that employed in the manufacture of the commonest belting, while that enclosed by the full lines B, C, D is that used for the best belting. The former includes the shoulder, which is more soft and spongy, while it contains numerous creases, as shown. These creases are plainly discernible in the belt when made up, and may be looked for near the belt points. [Illustration: Fig. 2658.] The centre of the length of the hide will stretch the least, and the outer edges on each side of the length of the hide the most. Hence it follows that the only strip of leather in the whole hide that will have an equal amount of stretch on each edge is that cut parallel to line A, and having that line as a centre of its width. All the remaining strips will have more stretch on one edge than on the other, and it follows that, to obtain the best results the leather should be stretched after it is cut into strips, and not as a whole in the hide, or in that part of it employed for the belt strips. It is found, indeed, that, even though stretched in strips, the leather is apt in time to curve. Thus a belt that is straight when rolled in the coil will, on being unrolled, be found to be curved. It is to be observed, also, that each time the width of the strips is reduced, this curving will subsequently take place; thus, if a belt 8 inches wide and quite straight, be cut into two belts of 4 inches wide, the latter will curve after a short time. The reason of this is almost obvious, because it is plain that the edge that was nearest the centre line of the hide offers the greatest resistance to stretching; hence, when the strip is stretched straight, and an equilibrium of tension is induced, reducing the width destroys to some extent this equilibrium, and the leather resumes, to some extent, its natural conformation. This, however, is not found to be of great practical importance, so long as the outer curve of one piece is on the same side as the outer curve of its neighbor, as shown on the left view in Fig. 2658, in which case the belt will run straight, notwithstanding its curve; but if the curves are reversed, as on the right in Fig. 2658, the belt will run crooked, wabbling from side to side on the pulley. To avoid this, small belts may be made continuous by cutting them from the hide, as shown in Fig. 2659; but in this case it is better that the belt be cut from the centre strip of the hide. [Illustration: Fig. 2659.] If the leather is stretched in strips after being cut from the hide, the amount of the stretch is about 6 inches in a length of 4-1/2 feet of a belt, say, 4 inches wide, but the stretch will be greater in proportion as the width of the strip is reduced. But if stretched as a whole, the amount of stretch will be about 1 inch per foot of length, the shoulder end stretching one-third more. If the leather has been properly stretched in strips the length of the belt may be cut to the length of an ordinary tape line drawn tightly over the pulleys, which allows the same stretch for the belt as there is on the tape line, added to the degree of tension due to cutting the belt too short to an amount equalling its thickness (as would be the case if the belt is cut of the same length as the tape line); or if the belt is a double one, the belt thus cut to length would be too short to an amount equal to twice the thickness of the strips of leather of which it is composed. When the amount to which the leather has been stretched is an unknown quantity (as is commonly the case), the workman cuts the belt too short, to an amount dictated solely by judgment, following no fixed rule. If, as in the case of narrow belts, the stretching be done by hand, the belt is placed around the pulleys, stretched by hand, and cut too short to an amount dictated by judgment, but which may be stated as about 2-1/2 per cent. of its length. But the stretch of a belt after it is put to work proceeds very much more rapidly if it has been stretched in the piece and not in the strip, hence it gets slack in the course of a few hours, or of a day or more, according to how much it has been stretched; whereas one properly stretched in the strip will last for weeks, and sometimes for months, without getting too slack. [Illustration: Fig. 2660. +----------------+----------------+-----------------+----------------+ |2,000 1/4 3. |2,050 3/16 3.1|2,150 3/16 3.2 |2,175 1/4 3.3 | +----------------+----------------+-----------------+----------------+ |1,400 9/32 2.12|2,000 1/8 3. |2,625 3/16 3.4 |2,325 7/32 3.4 | +----------------+----------------+-----------------+----------------+ |2,000 1/4 2.11|2,075 3/16 3.1|2,375 7/32 3.4 |2,175 7/32 3.5 | +----------------+----------------+-----------------+----------------+ |2,075 1/4 2.12|2,700 7/32 3.3|2,600 7/32 3.4 |2,275 5/32 3.7 | +----------------+----------------+-----------------+----------------+ |2,450 1/4 2.13|3,025 9/32 3.7|2,575 11/32 3.8 |2,225 7/32 3.10| +----------------+----------------+-----------------+----------------+ |2,475 1/4 3. |2,975 5/16 3.6|3,200 9/32 3.10|2,175 3/8 3.10| +----------------+----------------+-----------------+----------------+ |2,575 11/32 3.2 |2,875 9/32 3.7|3,475 11/32 3.13|1,850 11/32 3.11| +----------------+----------------+-----------------+----------------+ |2,675 11/32 3.2 |3,075 11/32 3.8|3,450 9/32 4. |1,950 1/4 3.11| +----------------+----------------+-----------------+----------------+ |2,650 3/8 3.2 |2,900 9/32 3.6|3,150 3/16 3.15|2,225 1/4 3.10| +----------------+----------------+-----------------+----------------+ |2,800 1/4 3.1 |3,050 5/16 3.6|2,850 1/4 3.13|2,275 3/16 3.7 | +----------------+----------------+-----------------+----------------+ |2,700 1/4 3. |3,150 7/32 3.5|3,000 3/16 3.10|2,600 1/4 3.5 | +----------------+----------------+-----------------+----------------+ |2,650 1/4 2.13|3,000 7/32 3.4|3,400 1/8 3.6 |2,550 1/4 3.4 | +----------------+----------------+-----------------+----------------+] The results of some experiments made by Messrs. J. B. Hoyt & Co. on the strength of the various parts of a hide are given in Fig. 2660. One side of the part of the hide used for leather belting was divided off into 48 equal divisions, each piece being 11-3/4 inches long, and two inches wide, the results of each test being marked on the respective pieces. The first column is the strain under which the piece broke; the second column is the amount in parts of an inch that the piece stretched previous to breaking; and the third column is the weight of the piece in ounces and drachms. From the table it appears that the centre of the hide which has the most equal stretch has the least textile strength, while in general that which has the most stretch has the greatest textile strength, but at the same time the variations are in many cases abrupt. A single belt is one composed of a single thickness of leather put together, to form the necessary length, in pieces, riveted and cemented together at the joint, or sewed or pegged as hereafter described. A double belt is similarly constructed, but is composed of two thicknesses of leather cemented and riveted, pegged, or sewed together throughout its whole length, as hereafter described. The object of a double belt is to increase the strength without increasing the width of the belt. Belts are usually made in long lengths coiled up for ease of transportation, the length of belt required being cut from the coil. To find the length in a given coil that is closely rolled--Rule: the sum of the diameter of the roll and the eye in inches, multiplied by the number of turns made by the belt, and this product multiplied by the decimal .1309, will equal length of the belt in feet. [Illustration: Fig. 2661.] The grain or smooth side of the leather is the weakest, as may be readily found by chamfering it to a thin edge, when it will tear like paper, and a great deal more easily than will the flesh side under similar treatment. Again, it will crack much more readily: thus, take a piece of leather and double it close with the grain side outward, and it will crack, as shown in Fig. 2661 at C, whereas if doubled, however closely, on the flesh side no cracks will appear. If the edge of a clean-cut piece of leather be examined, there will be found extending from the grain side inward a layer of lighter color than the remainder of the belt; and this whole layer is less fibrous and much weaker than the body of the belt, the strongest part of which is on the flesh side. If the grain side is shaved off thin and stretched slightly with the fingers it will exhibit a perfect network of small holes showing where the hair had root. Here, then, we have weakness and excessive liability to crack on the grain side of the leather, and it is obvious that if this side is the outside of the belt, as in Fig. 2662, at A, the tendency is to stretch and crack it, especially in the case of small pulleys, whereas if the grain side were next to the pulley the tendency would be to compress it, and therefore, rather to prevent either cracking or tearing. Furthermore, very little of the belt's strength is lost by wearing away its weakest side. [Illustration: Fig. 2662.] Another and important consideration is, that the grain side will lie closest and have most contact over a given area with the pulley surface. In making double belts of extra good quality, it is not uncommon to cut away or shave off the grain side of both belts, and place those surfaces together in making up the belts. If the grain side of a belt is the outside when on the pulleys, and a crack should consequently start, the destruction of the belt proceeds rapidly, because the line of crack is the weakest part of the belt, and the belt has less elasticity as a continuous body, and more at the line of crack. Cracking may, to some extent, be provided against by oiling the belt, and for this purpose nothing is better than castor oil. In the manufacture of belts, extra pliability is induced by an application of fish oil and tallow, applied when the belt (after having been wetted), is in a certain stage of progress toward drying. The oil and tallow are supposed to enter the pores of the leather and supply the place of the evaporated water. LENGTH OF BELTS.--Since the stretch of a belt is variable in different belts of the same length, no rule can be given for the amount to which a belt should be cut shorter than the measured length around the pulleys, and it follows, therefore, that the length of a belt cannot be obtained precisely by calculation. In practice the necessary length for a belt to pass around pulleys already in their places upon the shaft is usually obtained by passing a tape line or cord around the pulleys, the stretch of the tape line being allowed as that necessary for the belt. Then when the belt is placed around the pulleys it is shortened if it should appear to require more tension. If, however, the belt length for pulleys not in position is required, it may be obtained as follows, the error being so slight as to be within the margin of difference of stretch in different belts, and therefore of no practical moment:-- [Illustration: Fig. 2663.] For open belts let the distance between the shaft centres, as _a_ _b_ in Fig. 2663, be the base of a right angle triangle, and the difference between the semi-diameters, as _b_ _c_, the perpendicular. Square the base and the perpendicular, and the square root of the sum of the two will give the hypothenuse, and this multiplied by 2 and added to one-half the circumference of each pulley is the required length for the belt. This will give a belt too long to the amount to be cut out of the belt to give it the necessary tension when on the pulleys. _Example._--Let the distance between centres in Fig. 2663 be 48 inches; diameter of large pulley 24 inches; diameter of small pulley 4 inches-- Here distance between centres 48 " " " 48 --- 384 192 ---- 2304 Square of perpendicular 100 ---- 2404 Square root of 2404 = 49.03 Multiply by 2 2 ----- 98.06 Half circumference of large pulley 37.699 ------- 135.759 Half circumference of small pulley 6.283 ------- Length of belt 142.042 A simpler rule which gives results sufficiently accurate for practical purposes is as follows:-- _Rule._--Add the diameter of the two pulleys together, divide the result by 2, and multiply the quotient by 3-1/4, then add this product to twice the distance between the centres of the shafts, and you have the length required. When the length of a crossed belt is required, and the pulleys are not erected upon the shafts, it is, on account of the abstruseness of a calculation for the purpose, preferred in workshop practice to mark off by lines the pulleys set at their proper distance apart (either full size or to scale), and measure the length of the side of the belt, supposing the belt to envelop one-half the circumference only of each pulley, and to add to this one-half the circumference of each pulley; or if there is a great difference between the relative diameters of the pulleys and the distance apart of the shafts is unusually small, the lengths of the straight sides of the belt are measured and the arcs of contact around the pulleys are stepped around by compasses, the set of the compasses being not more than about one-tenth the circumference of the pulleys. This gives a more near result than that obtained by calculation, because although it will give a belt shorter than by calculation, yet the belt will be too long on account of the stretch necessary to the tension required for ordinary conditions. [Illustration: Fig. 2664.] In narrow belts, as, say, three inches and less in width, the belt may be cut to the length of a tape line passed over the pulleys, and when placed over the pulleys it may be strained under a hand pull and cut as much shorter as the tension under hand pressure indicates as being necessary. But if the belt is a wide one a stretching clamp, such as shown in Fig. 2664, is employed, the screws being right hand at one end and left hand at the other, so that operating them draws the clamps, and therefore the ends of the belt, together. The stretch of a belt not stretched in the piece proceeds slowly when the belt is at work, hence if laced at first to a proper degree of tension it will get slacker in a few hours or in a day or so, and must be tightened, or taken up as it is termed, by cutting a piece out. For this purpose a butt joint possesses the advantage that the piece to be taken out may be less, and still leave the end clear for new holes to be punched, than is the case with a lap joint, which occurs because the butt joint occupies a shorter length of the belt than is the case with a lap joint. [Illustration: Fig. 2665.] [Illustration: Fig. 2666.] When a belt is under tension upon two pulleys and at rest, the friction or grip of the belt upon the respective pulleys (supposing them to be of the same diameter and therefore to have the same arc and area of contact) will depend upon the relative positions of the pulleys; thus suppose one pulley to be above the other as in Fig. 2665, the upper pulley P will have the grip due to the tension of the belt added to that due to the weight of the belt, whereas if placed horizontally, as in Fig. 2666, the weight of the belt will fall equally on the two pulleys, and for this reason vertical belts of a given width require to have a greater tension to transmit the same amount of power as the same belt would if placed horizontally. But as soon as motion was transmitted, by the belt, from one pulley to the other, the belt on one side of the pulley would be under greater tension then that on the other. [Illustration: Fig. 2667.] Suppose, for example, a belt to transmit motion and power from pulley A in Fig. 2667, to pulley B, then the side C of the belt is that which drives or pulls B, and it is therefore called the driving side of the belt, the resistance to rotation offered by B causing the driving side of the belt to be the most strained; and hence the straightest, whereas the side D will be free of the tension due to the resistance of B. [Illustration: Fig. 2668.] But if the direction of motion be reversed as in Fig. 2668, A still being the driving pulley, the side D will be the one most tightly strained, and therefore, the driving side of the belt; or, in other words, the driving side of a belt is always that side which approaches the driving pulley, and the slack side is always that which recedes from the driving pulley. In horizontal belts, however, the driving side of the belt is not a straight line, because of the belt sagging from its own weight no matter how tightly it may be strained, but the shorter the belt the less the sag. [Illustration: Fig. 2669.] It is always, therefore, desirable, so far as the driving power of the belt is concerned, to have the lower half (of belts running horizontally) the driving side, because in that case the sag of the belt causes it to envelop a greater arc of the pulley, which increases its driving power. If the circumstances will not permit this and the sag of the belt operates to practically incapacitate the belt for its duty, what is termed an idle wheel or idler may be employed as shown in Fig. 2669 at E, serving to prevent the sag and to cause the belt on the driving side to envelop a greater portion of the pulley's circumference, and hence increase its friction on the pulley and therefore its driving power. In the example the two pulleys A and B are of equal diameters; hence the idle wheel is placed midway between them, but when such is not the case the idle wheel should be located according to the circumstances and the following considerations. The idle wheel requires a certain amount of power to drive it, and this amount will be greater as the idle wheel is nearer to the smallest wheel of the pair connected; but on the other hand, the closer the idle wheel to the small pulley (all other factors being equal) the greater the arc of small pulley surface enveloped by the belt, and hence the greater the belt's driving power. When therefore a maximum increase of driving power is required, the idler must be placed near to the smallest pulley, the desired effect being paid for in the increased amount of motive power required to rotate the driving pulley. But under equal conditions the larger the diameter of the idle wheel the less the power required to drive it, because the less its friction on its journal bearing. A belt tightener should whenever practicable be placed on the slack side of the belt. Belt tighteners are sometimes used to give intermittent motion, as in the case of trip hammers; the belt being vertical is made long enough to run loose, until the tightening pulley closes the belt upon the pulley, taking up its slack and increasing the arc of contact. [Illustration: Fig. 2670.] When the direction of rotation of the driven pulley requires to be reversed from that of the driving pulley, the belt is crossed as in Fig. 2670. A crossed belt has a greater transmitting power than one uncrossed (or, as it is termed, than an "open belt") because it envelops a greater arc of both pulleys' circumference. This is often of great advantage where the two pulleys are of widely varying diameter, especially if the small pulley requires to transmit much power, and be of very small diameter. But a crossed belt is open to the objection that the surfaces of the belt rub against each other at the point of crossing, which tends to rapidly wear out the laced joint of the belt. By crossing a vertical belt the lower pulley receives part of the weight of the belt. When a belt connects two pulleys whose respective planes of revolution are at an angle one to the other, it is necessary that the centre line of the length of the belt shall approach the pulley in the plane of the pulley's revolution, which is sufficient irrespective of the line of motion of the belt when receding from the pulley. This is shown in Fig. 2671, which represents what is known as a quarter twist; A, B are two pulleys having their planes of revolution at a right angle, the belt travelling as denoted by the arrows, then the centre line C of the belt being in the plane of rotation of A on the side on which it advances to A, the belt will continue to run upon the same section of A. If the pulley positions be reversed, as in Fig. 2672, the same rule applies, and the side D in the figure being that which advances upon B must travel to B in the plane of B´s rotation, otherwise the belt would run off the pulley; hence it is obvious that the belt motion must occur in the one direction only. [Illustration: Fig. 2671.] [Illustration: Fig. 2672.] [Illustration: Fig. 2673.] Shafts at any angle one to another may have motion communicated from one to the other by a similar belt connection, providing that a line at a right angle to the axis of one shaft forms also a right angle with the axis of the other. Thus in Fig. 2673 the axis of shaft A may be set at any required angle to the plane of rotation of pulley B, provided that the axial line of A be made to lie at a right angle to the imaginary line _l_, which is at a right angle to the axis of the shaft of B, and that the side of the driving pulley which delivers the belt (as C, Fig. 2671) is in line with the centre line of the driven pulley, as denoted by the dotted line C. [Illustration: Fig. 2674.] But when this provision cannot be carried out, pulleys to guide the direction of motion of the belt must be employed; thus in Fig. 2674 are an elevation and plan[39] of an arrangement of these guide or mule pulleys; A B is the intersection of the middle planes E E and F F of the pulleys P and P´ to be connected by belt. Select any two points, A and B, on this line and draw tangents A C, B D to the principal pulleys. Then C A C and D B D are suitable directions for the belt. The guide pulleys must be placed with their middle planes coinciding with the planes C A C, D B D, and the belt will then run in either direction. [39] From Unwin's "Elements of Machine Design." [Illustration: Fig. 2675.] In Fig. 2675 is an arrangement of guide pulleys by which two pulleys not in the same plane are connected, while the arc of contact of the smaller pulley C is increased by the idlers or guide pulleys A B, while either C or D may be driven running in either direction. [Illustration: Fig. 2676.] In Fig. 2676 is shown Cresson's adjustable mule pulley stand, which is a device for carrying guide pulleys, and admitting of their adjustment in any direction. Thus the vertical post being cylindrical, the brackets can be swung around upon it and fastened in the required position by the set-screws shown. The brackets carrying the pulleys are also capable of being swung in a plane at a right angle to the axis of the guide pulleys, and between these two movements any desired pulley angle may be obtained. It is obvious that by moving the brackets along the cylindrical post their distance apart may be regulated. When a belt is stretched upon two pulleys and remains at rest there will be an equal tension on all parts of the belt (that is to say, independent of its weight, which would cause increased tension as the points of support on the pulleys are approached from the centre of the belt between the two pulley shafts); but so soon as motion begins and power is transmitted this equality ceases, for the following reasons:-- [Illustration: Fig. 2677.] In the accompanying illustration, Fig. 2677, A is the driving and B the driven pulley, rotating as denoted by the arrows; hence C is the driving and D the slack side of the belt. Now let us examine how this slackness is induced. It is obvious that pulley A rotates pulley B through the medium of the side C only of the belt, and from the resistance offered by the load on B, the belt stretches on the side C. The elongation of the belt due to this stretch, pulley A takes up and transfers to side D, relieving it of tension and inducing its slackness. The belt therefore meets pulley B at the point of first contact, E, slack and unstretched, and leaves it at F, under the maximum of tension due to driving B. While, therefore, a point in the belt is travelling from E to F, it passes from a state of minimum to one of maximum tension. This tension proceeds by a regular increment, whose amount at any given point upon B is governed by the distance of that point from E. The increase of tension is, of course, accompanied by a corresponding degree of belt stretch, and therefore of belt length; and as a result, the velocity of that part of the belt on pulley B is greater than the velocity of any part on the slack side of the belt; hence the velocity of the pulley is also greater than that of the slack side of the belt. In the case of pulley A the belt meets it at G under a maximum of tension, and therefore of stretch, but leaves it at H under a minimum of tension and stretch, so that while passing from G to H the belt contracts, creeping or slipping back on the pulley, and therefore effecting a reduction of belt velocity below that of the pulley. To summarize, then, the velocity of the part of the belt enveloping A is less than that of A to the amount of the creep; hence the velocity of the slack side of the belt is that of A minus the belt creep on A. The velocity of the part of the belt on B is equal to that of the slack side of the belt plus the stretch of the belt while passing over B; and it follows that if the belt or slip creep on one pulley is equal in amount to the belt stretch on the other, the velocities of the two pulleys will be equal. [Illustration: Fig. 2678.] Now (supposing the elasticity of the belt to remain constant, so that no permanent stretch takes place) it is obvious that the belt-shortening which accompanies its release from tension can only equal the amount of elongation which occurs from the tension; hence, no matter what the size of the pulleys, the creep is always equal in amount to the stretch, and the velocity ratio of the driven pulley will (after the increase of belt length due to the stretch is once transferred to the slack side of the belt) always be equal to that of the driving pulley, no matter what the relative diameters of the pulleys may be. In Fig. 2678, for example, are two pulleys, A and B, the circumference of A being 10 inches, while that of B is 20; and suppose that the stretch of the belt is an inch in a revolution of A (A being the driving pulley). Suppose the revolutions of a to be one per minute, then the velocity of the belt where it envelops A and B, and on the sides C and D, will be as respectively marked. Thus the creep being an inch per revolution of A, the belt velocity on the side C will be nine inches per minute, and its stretch on B being an inch, the velocity of B will be ten inches per minute, which is equal to the velocity of the driving pulley. It is to be observed, however, that since A receives its motion independently of the belt, its motion is independent of the creep, which affects the belt velocity only: but in the case of B, which receives its motion from the belt, it remains to be seen if stretch is uniform in amount from the moment it meets this pulley until it leaves it, for unless this be the case, the belt will be moving faster than the pulley at some part of the arc of contact. [Illustration: Fig. 2679.] Thus suppose P, Fig. 2679, represents a driven pulley, whose load is 1,000 pounds, and that from A to B, from B to C, from C to D, and from D to E, represent equal arcs of contact between belt and pulley, then arc A B will have on it the amount of stretch due to a pull of 250 pounds at B, diminishing to nothing at A. Arc C B will have on it the amount of stretch due to a pull of 500 pounds at C and 250 at B; arc D C will have on it the amount of stretch due to a load of 750 at D, and 500 at C; and arc D E will have the tension due to a load of 1,000 pounds at E, and 750 pounds at D. Suppose, then, that the amount of belt stretch is greater between B and C than it is between D and E, then the belt will travel faster between B C than between D E to an amount equal to the difference in stretch, and will at B C slip over the pulley to that amount; or if the friction of the belt at B C is sufficient to move the pulley in accordance with the stretch, then the belt must move the pulley at a greater velocity than the belt motion from D to E. But since the friction of the belt is greatest at D E, it will hold the pulley with the greatest force, and hence the velocity of the belt and pulley will be uniform, or at least the most uniform, at D E. Here arises another consideration, in that the stretch of the leather is not uniform, and the section of belt at C B may stretch more or less under its load than section C D does under its load, in which event the velocities of the respective belt sections cannot be uniform, and to whatever amount belt slip ensues the velocity of the driven wheel will be less than that of the driver. Attention has thus far been directed to the relative velocities of the pulleys while under continuous motion. But let us now examine the relative velocities when the two pulleys are first put in motion. Suppose, then, the belt and pulley to be at rest with an equal degree of tension (independently of the weight of the belt, as before) on both sides of the belt. On motion being imparted to the driving pulley, the amount of belt elongation due to the stress of the load on the driving pulley has first to be taken up and transferred to the slack side of the belt, and during such transfer a creep is taking place on the arc of belt contact on the driving pulley. [Illustration: Fig. 2680.] Furthermore, let it be noted that while under continuous motion the belt first receives full stress at point F, Fig. 2677; at starting it first receives it at point E, and there will be a period of time during which the belt stretch will proceed from E towards F, the pulley remaining motionless. The length of duration of this period will, in a belt of a given width, and having a given arc of contact on the driven pulley, depend on the amount of the load. Thus, referring to Fig. 2680, if the amount of the load is such that the arc of contact between the top and the point B is sufficient to drive the pulley, the pulley will receive motion when the belt stretch has proceeded from A to B; but if the load on the pulley be increased the belt stretch will require to proceed farther towards C. At the top the stretch will proceed simultaneously with that of the driving side of the belt, between the points F G, Fig. 2677; but from the friction between the belt and pulley, the stretch of the part enveloping the pulley will be subsequent and progressive from F towards E, Fig. 2677. It follows, then, that the velocity of the driven wheel will be less than that of the driver at first starting than when in continuous motion. As the length of the belt is increased, the gross amount of stretch, under any given condition, increases, and hence the longer the belt, the greater the variation of velocity at first starting between the driven pulley and the driver. From what has been said, it follows that when a mathematically equal velocity ratio is essential, belts cannot be employed, but the elasticity that disturbs the velocity ratio possesses the quality of acting as a cushion, modifying on one pulley any shocks, sudden strains, or jars existing on the other, while the longer the belt and less strained within the limit of elasticity, the greater this power of modification; furthermore in case of a sudden or violent increase of load, the belt will slide on the pulley, and in most cases slip off it, thus preventing the breakage of parts of the driving gear or of the machine driven that would otherwise probably ensue. Furthermore, belt connections are lighter and cheaper than gear-wheel or other rigid and positive connections, and hence the wide application of leather belts for the transmission of power, notwithstanding the slight variations of pulley velocity ratio due to the unequal elasticity of the various parts of the leather composing the belt. [Illustration: Fig. 2681.] The ends of belts are joined by two principal methods, the butt and the lap joint. In butt joints the holes are pierced near the ends of the belts, and the ends of the belt are brought together by means of a leather lace threaded through these holes. If the duty is light a single row of holes is all that is necessary. An example of this kind is shown in Fig. 2681, in which there are five holes on one side, and four on the other of the joint, the extra hole coming in the middle of its end of the belt. The lace is drawn half-way through this extra hole, and laced each way to the side and back again to the middle, the ends being tied on the outside of the belt, which does not come in contact with the pulley surface. By this means the lacing is double through all the holes, and if the knot should slip the slackness will begin at the middle of the belt and extend gradually towards the edges; whereas, if the lacing terminated at one side, and the knot or fastening should slip, all the tension would be thrown on one edge of the belt, unduly stretching it, and rendering it liable to tear. By this method of lacing the lace is not crossed on either side of the belt, which is desirable, because it is found in practice that a crossed lace does not operate so well as an uncrossed one. [Illustration: Fig. 2682.] If the power to be transmitted is so much as to render it desirable to have the strength of the laced joint more nearly approach that of the solid belt than is obtainable with a single row of holes, a double row is provided, as shown in Fig. 2682. For belts of about 3 inches wide and over, these holes are made as follows: A, B, and C, D, E, about an inch apart and 5/8 inch from the line of joint; F, G, H, and I, J, being about 1/2 inch behind A, B, and C, D, E, respectively. For thinner belts the holes may be closer together, and to the edges of the belt the exact distances permissible being closer together as the duty is lighter; but however narrow the width of the belt, it should contain at least two holes on each side of the joint. The sizes of these holes are an important element, since the larger the hole the more the belt is weakened. The following are the sizes of holes employed in the best practice:-- Width of Belt. Size of Punched Hole. Up to 4 inches 1/4 inch. From 4 to 8 inches 5/16 " From 8 inches upwards 3/8 " [Illustration: Fig. 2683.] The holes are usually made round, but from the pliability of the lace, which enables it to adapt itself to the form of the hole to a remarkable degree, it is not unusual to preserve the strength of a belt by making an oblong hole, as in Fig. 2683 at A, or a mere slit, as at B, which, from removing less material from the belt, leaves it to that extent stronger. [Illustration: Fig. 2684.] [Illustration: Fig. 2685.] The ends of the belt should be cut quite square, and at a right angle to the edges, so that when the two ends are drawn together by the lace the edges of the belt will remain straight, and not curved, as they would do if either end of the belt were not cut at a right angle. Suppose, for example, that the ends of a belt were cut aslant, as in Fig. 2684, when laced up the edge of the belt would come as in Fig. 2685. [Illustration: Fig. 2686.] The holes must be punched exactly opposite to each other, or lacing the belt will bring the edges out of fair, as shown in Fig. 2686, the tension of the lace drawing the holes opposite to each other, irrespective of where the edges of the belt will come. If some of the holes are opposite and others are not, the latter will throw the edges of the belt out of line to some extent, especially if the lace is first entered in the holes that are not opposite, because, in that case, drawing the lace tight at once throws the belt edges out, and the subsequent lacing has but a limited effect in correcting the error, unless, indeed, the majority of the holes are opposite, and but one or two are out of line. The lace should be drawn sufficiently tight to bring the ends of the belt firmly together, and should be laced with an even tension throughout, and for a belt doing heavy duty should have its ends tied in a knot at the back, and in the middle of the belt. The width of the lace is usually about as follows:-- Width of Belt. Width of Lace. 24 inches and over 1/2 inch 6 to 24 inches 3/8 " 2 to 4 inches 5/16 " 2 inches and less 1/4 " Since belts are tightened by cutting a piece off one end (preferably the end which shows the holes most stretched), it is obvious that a butt-joint possesses an advantage, because as less of the belt length is occupied by the holes they may be cut quite out and new ones punched, whereas, in some cases, the length of the belt occupied by the holes in a lap-joint is more than the length of belt required to be cut out to tighten it. [Illustration: Fig. 2687.] [Illustration: Fig. 2688.] [Illustration: Fig. 2689.] There are many different methods of lacing a belt, but those here described are generally preferred. Thus referring to Fig. 2687 the lace is first passed through holes G and D, the ends being of equal length from the belt and emerging on the side that is to be the outside of the belt, thence each end of the lace is laced towards the edge of the belt, the dotted lines in the cut showing the path of the lace. It is then laced back to the middle of the belt, the second inside lacing exactly overlaying the first, the laces never crossing; the outside appearing as in Fig. 2688. The ends are in some cases tied in a knot on the outside, and in others fastened as shown in Fig. 2689, in which case the ends are merely held by friction, which will serve very well unless for a belt that is tightly strained. By this method of lacing all the crossing of the lace is on the outside of the belt, which is an advantage, because from the creep of the belt the lace undergoes considerable friction, which is apt to rapidly wear out the lace, especially if it be crossed on the side of the bed that meets the pulley surface. [Illustration: Fig. 2690.] Fig. 2690 shows a method of lacing in which the crossing of the lace is entirely avoided, the knot being on the outside at _a_ _a_. The path of the lace on one side of the belt is shown in full lines, and on the other side in dotted lines. The objections to lacing are that the lace lifts the belt from the pulley surface, which throws all the wear on the lace, causing it eventually to break, and which also reduces the area of belt (at the joint) in contact with the pulley surface and reduces the driving power of the belt at the time the joint is passing over the pulley. In fact, in running belts this reduction of transmitting capacity is not great, because of the rapidity with which the joint passes over the pulley, but in slow moving belts slip is very apt to occur when the lace meets the pulley, especially if the power transmitted is great in proportion to the width of the belt. [Illustration: Fig. 2691.] [Illustration: Fig. 2692.] There are considerable movement and friction between the lace and the belt, more especially when the latter passes over a pulley of small diameter, and this with the friction due to whatever amount of slip the belt may experience, wears away the lace so that in time it breaks. Sometimes a cover is employed as shown in Fig. 2691 at A, to protect the lace, the cover being riveted or cemented to the belt on the side that is to meet the pulley surface. A similar means is also sometimes employed to make a butt joint. Thus in Fig. 2692 A is the cover riveted or cemented to the two ends B C, of the belt so as to dispense with lacing. [Illustration: Fig. 2693.] Fig. 2693 represents an excellent method of joining very thin belts, the operation being as follows:-- Place the two ends of the belt together with the edges fair one with the other, and with an awl make a row of holes at _a_, through both ends; then take about half a yard of strong twine (in some cases a lace or gut is better) and draw half the length through the first hole, then pass each end of the twine through the second hole, one end to the right and the other to the left, and draw both tight at the same time, and so on until the last hole is reached, when one end only of the twine is passed through; the two ends of the twine are then knotted tight together and the excess cut off. The middle sketch shows the joint when the belt is stretched. The lower sketch shows it passing over a small pulley, where it will be seen that in the act of bending over the curve there is no friction between the lace and the belt, and this is the reason of its superiority over other methods, where there is always more or less friction between the lace and the belt when bending over a curve. Another advantage is, that in this system the lace does not come into contact with the pulley, so that whatever friction or slipping may take place between the belt and the pulley, the lacing is perfectly unaffected by it. [Illustration: Fig. 2694.] A lap joint is one in which the two ends of the belt overlap, as in Fig. 2694. The overlap is cut down to a plain bevel so as to reduce the joint to nearly or quite the same thickness as the main body of the belt. The lap joint is employed to join together the strips of leather forming the belt, and to fasten the ends of the finished belt together. In making the belt the overlap is cemented and riveted, while in joining the ends it may be cemented, or riveted, or laced. The advantage of rivets lies simply in that they are easily applied. Their disadvantages are that they grip but a small area of the belt, namely, that portion beneath the rivet head and washer surface; hence, when rivets are used the joint should always be cemented also. A more important defect is, however, that the heat generated by the compression of the rivet while riveting it is sufficiently great to _burn the leather_ beneath the rivet-head. The reason that the leather under the head and not under the washer or burr at the riveted end of the rivet burns is, that although the heat due to riveting is most at the burr end of the rivet, its passage from the rivet to the washer is less rapid than it is through the body of the rivet, because in the one case it has to be transferred from one body to another (from the rivet to the burr), while in the other its passage is uninterrupted and continuous. [Illustration: Fig. 2695.] Rivets for lap joints are usually placed about, as in Fig. 2695, the rows A and C being about 1/2 inch from the edges B and D respectively, and the row F about 3/8 inch from the edge F of the lap, while the rivets are about 5/8 inch apart in the rows. For comparatively narrow belts as, say, four inches wide, a single row G would be placed in the middle, additional middle rows should for wider belts be about 1-1/4 inches apart. The rivet holes should be a close fit to the rivets, the latter being left just long enough to hold the washer or burr and sink with it, in the riveting, to the level surface of the belt. The heads of the rivets should be on the side of the belt that is to run next to the pulley. The strongest method of forming a belt is by means of small taper wooden pegs, such as are used in boot and shoe manufacture, the joint being cemented, and the pegs inserted. In this case the belt is merely pierced with an awl, hence none of the leather is removed. [Illustration: Fig. 2696.] The arrangement of wooden pegs should be as in Fig. 2696, the rows A and B being respectively about 5/8 inch from the edges C D, the row E being about 1/4 inch from the edge of the joint, and H about 3/4 inch from that edge. The pegs are placed about 1/2 inch apart in the rows. A cemented and pegged joint is the strongest made, and it preserves a more equal tension throughout the belt than any other, while the belt is strong, since the hole for the pegs may be pierced with an awl, which does not remove any leather from the belt, as is the case with punched holes. The length of the lap in some of the best practice is as follows: When the strips of leather are cut from the hide in such lengths that the part termed the shoulder of the hide is utilised, a uniform lap of 8 inches is employed for all widths of belt. When the strips do not contain the shoulder of the hide, the following are the respective lengths of lap:-- Width of single belt. Length of lap. 1 to 4-1/2 inches 4-1/4 inches. 5 inches 5 " 6 to 8 inches 6 " 9 inches 6-1/2 " 10 to 14 inches 7 " 15 to 24 " 8 " All double belts are given a 6 inch lap. [Illustration: Fig. 2697.] Another and excellent method of joining a belt, or of fastening two thicknesses together to form a double belt, is to sew it together with lace leather, as shown in Fig. 2697. The lace is in this case about 1/4 inch wide, the holes being pierced so as to have the lace diagonal, as shown in the cut. Sometimes four rivets are added at the joint as shown in the cut. [Illustration: Fig. 2698.] Other methods of fastening the ends of leather belts are by means of metal hooks of various forms. Fig. 2698 represents a fastening of this kind, the appearance of both sides of the joint being shown in the figure. In this case considerable leather is removed from the belt, but this is to some extent compensated for, because the hook holds each end of the belt in two places; that is to say, in the crook of the hook as well as at the end. This, however, while it has the effect of increasing the grip of the hook on the belt, still leaves the belt as a whole weaker, by reason of the removal of leather to form the holes. [Illustration: Fig. 2699.] [Illustration: Fig. 2700.] In Figs. 2699 and 2700 is shown a belt screw, intended to take the place of rivets, and thus avoid the burning of the leather which accompanies the use of rivets. It consists of two screws, one having a right and the other a left-hand thread. The former is of bronze, and has a coarse exterior thread cut conically, while it is hollow with a fine thread tapped inside. The latter is of steel, and has a conical shoulder underneath. The heads of both screws are slightly rounded and formed with circular grooves on the under side, to give them a firm grip on the leather. The conical screw is first run into the leather, and the steel screw is then introduced. The belt is run with the head of the latter on the inner side. If the body of a narrow belt is riveted it contains two rows only of rivets; but as the width of the belt increases, other rows are introduced, all the rows running the entire length of the belt. In some cases two separate single belts running one over or outside the other are employed in place of an ordinary double belt, and the arrangement works well. Two single belts applied in this manner are especially preferable to a double belt when used upon a small pulley, because they will bend to the curvature of the pulley more readily, being more pliable; whereas a double belt will from its resistance to bending not envelop as much of the circumference of the belt as is due to the relative sizes of the pulleys, and the distance apart of their axes. Round leather belts are made in two forms, the solid and the twisted. The first consists of a simple leather cord, hence its diameter cannot exceed the thickness of the leather. The second consists of a strip of leather twisted into cylindrical form, the grain side of the leather being outside. The ends of round belts are usually joined by means of cylindrical hooks and eyes, which are threaded so as to screw on to the end of the belt, but for twisted round belts it is better to place in the centre of the belt a small core of soft wood. The ends of the belt should be slightly tapered, and the hook and eye screwed firmly home. Sometimes from the smallness of the pulleys the inflexibility of the hook and eye becomes objectionable, and a simple hook is employed on solid round belting. The length of twisted round belting may be altered by twisting or untwisting it, which renders it unnecessary to cut the belt for a small amount of shortening. Round belts should bear upon the sides, and not on the bottom of the pulley-groove, which increases their transmitting power. Thus, if the groove is a semicircle of the same radius as is the belt when new, the stretch of the belt as it wears decreasing its diameter, it will then touch only on the bottom of the groove. Furthermore, when the belt bears on the sides only of the groove it becomes wedged to a certain extent in the sides of the pulley groove. [Illustration: Fig. 2701.] [Illustration: Fig. 2702.] [V]-belting is formed of strips of leather welted together, as shown in Figs. 2701 and 2702, the latter showing the joint or splice of the belt. The pulleys are [V]-grooved as shown. The tension of the belt causes it to grip the sides of the groove on the wedge principle, and the belt is flat at the apex of the [V] so that it shall not bottom in the groove, which would impair its wedging action. This class of belt is largely employed for connecting shafts at an angle, especially in cases where the distance between the shafts is small, in which case it will last much longer than a flat belt. From the construction, the rivets joining the pieces forming the belt do not come into contact with the surfaces of the pulley, and from the tension of the belt causing it to wedge into the sides of the pulley groove, the driving power is greater than that simply due to the area of contact and the tension of the belt. [Illustration: Fig. 2703.] A belt will run to the largest diameter of a pulley, thus in Fig. 2703, the belt would, unless guided, gradually creep up to the side A of pulley P, and following this action would move to side C of pulley D. [Illustration: Fig. 2704.] If the pulleys are parallel, but the axis of their shafts are not in line, then the belt will run towards that side on which the axes are closest; thus in Fig. 2704 the belt would run towards the side P of the large pulley, because the belt B will meet the pulley surface at _a_, and if a point on the belt at _b_ travelled coincident with the point on the pulley with which it took contact, its plane of rotation, while on the pulley, would be as denoted by the dotted line _b_. But to follow this plane of rotation, the belt would require to bend edgeways, as denoted by the dotted line _b_, which it does to some extent, carrying the belt with it. CHANGING OR SLIPPING BELTS ON PULLEYS.--To change a belt on a stepped cone, proceed as follows:-- Suppose the belt to be on the small step of the driving cone, and to require to run on the largest step. Throw the belt on the smallest step of the lower cone and place the palm of the hand on the inside face of the belt on the side on which it approaches that cone. Draw the belt tight enough (with the palm of the right hand) to take up the slack and cause the lower cone to rotate. When it is in full motion place the palm of the left hand against the inside face of the other side of the belt (while still keeping the pressure of the right hand against the slack side of the belt). Release suddenly the pressure of the right hand and immediately with a quick and forcible lateral motion of the left hand force the belt towards the larger step of the upper cone, which will cause it to mount the next step, when the operation may be repeated for each succeeding step. If the steps of the cone are too steep, or the belt is too long for this method, a wooden rod may be used, its end being applied to the side of the belt that runs on the upper cone and close to the cone. Then lift the belt with the rod, while the lower end of the rod is inclined away from the step the belt is to mount, when the belt will mount the step of the rotating cone. In the case of broad heavy belts it is best to stop the running pulley and place the belt on it, then lift the belt edge on the stationary pulley at the point where the belt will first meet it when in motion, forcing the belt on by hand as far as possible. Take a strong cord, as, say 3/8 inch diameter, and double it, pass the loop between the pulley arms around the belt and over the pulley face. Pass the two free ends of the cord through the loop (formed by doubling the cord) and pull the free ends as tight as possible by hand. While standing on the side of the pulley opposite to that of the belt, communicate slow motion to the driving pulley and release the ends of the cords as soon as the belt is on. The belt, in travelling from the pulley, will then undo the cord of itself. A belt may be taken off a pulley, either by pressing it in the required direction and as close to the pulley as possible, or by holding the two sides of the belt together, which should be done as far from the running pulley as possible, or as far from the pulley the belt is required to come off as possible. [Illustration: Fig. 2705.] In Fig. 2705 is shown a device for automatically replacing a belt that has slipped off a pulley. A is the pulley and B the device, which has a curved projection which is of the full width of the device at one end, where it comes even with the perimeter of A, and tapers laterally towards the outside edge of the device. As a result the belt will easily pass on the broad end and cause the device to rotate, the belt running up the curved projection and therefore lifting clear of the pulley A, but on account of the taper of the projection the belt finally has contact with the projection on one edge only, and therefore tips over to the other side, and as a result falls on A, because it is under tension and naturally adjusts itself to be in line with the pulley at the other end of the belt. It would appear that the belt, if running, would move on the pulley, driving it, and this would be the case if sufficient time were allowed for it to do so, but the action of the device is too quick, and furthermore, when the belt is off one pulley and therefore loose its motion is apt to become greatly reduced, which retards its moving laterally on the pulley driving it. It is obvious that the device must be applied to that side of the pulley on which the belt is found to run off, but it may be noted that belts are not apt to run off the loose pulley, but off the driving one, and only at times when from excessive resistance or duty the velocity of the pulley is reduced below that of the belt, or the velocity of the belt is less than that of the pulley driving it; hence the device must be applied on the outside of the fast or tight pulley. The driving power of a belt is determined principally by the amount of its pull upon the pulley, and the speed at which it travels. The amount of pull is determined by its tension, or in other words, the degree with which it grips the pulley and the closeness with which it lies to the pulley surface. The amount of tension a single belt is capable of withstanding with a due regard to its durability has been fixed by various experimenters at 66-2/3 lbs. per inch of its width. The pull of the belt under this degree of tension will vary as follows:-- It will be more with the grain or smooth side than it will with the flesh or fibrous side of the belt in contact with the pulley face, some authorities stating the amount of difference to be about 20 per cent. It will be more with a smooth and polished surface on the pulley than with one less smooth and polished. At high speeds it will be diminished by the interposition of air between the belt and pulley surface, and from the centrifugal force generated by the passage of the belt around the pulley. It will be more when the pulley is covered with leather rubber or other cushioning substance than when the pulley is bare, even though it be highly polished, some authorities stating this difference to be about 20 per cent. It will be increased in proportion as the belt envelops a greater proportion of the pulley circumference, the part of the pulley enveloped by the belt when the pulley is at rest (or what is the same thing, at any point of time when it is in motion) being termed the arc of contact. It is obvious that the arc of contact taken to calculate the belt power must be the least that exists on either the driving or the driven pulley, because when the belt slips it ceases to transmit the full amount of the power it receives, the remainder being expended in the friction caused by the belt slipping over the pulley. The speed at which a belt may run is limited only by reason of the centrifugal force generated during its passage around the pulley, this force tending to diminish its pressure upon the pulley. The maximum of speed at which it is considered advisable to run a belt is about 6,000 feet per minute; but the amount of centrifugal force generated at this speed depends upon the diameter of the pulley, because the centrifugal force increases in direct proportion as the number of revolutions is increased, or in other words it increases in the same proportion as the velocity; but in a given circle it increases as the square of the velocity. Suppose, then, that it be required to double the velocity of a belt, and that the same pulley be used running at twice the velocity, this will increase fourfold the centrifugal force generated; but if the diameter of the pulley be doubled the centrifugal force generated will be simply doubled; hence it appears that the larger the pulley the less the centrifugal force of the belt in proportion to its velocity. This will be apparent when it is considered that the larger the pulley the nearer will the curve of its circumference approach to a straight line. The following experiments on the transmission of power by belting were made Messrs. Wm. Sellers & Co. [40]These experiments were undertaken with a view to determine, under actual working conditions, the internal resistances to be overcome, the percentage of slip, and the coefficient of friction on belt surface. They were conducted, during the spring of 1885, under the direction of Mr. J. Sellers Bancroft. [40] From a paper read before the American Society of Mechanical Engineers by Wilfred Lewis. These experiments seemed to show that the principal resistance to straight belts was journal friction, except at very high speeds, when the resistance of the air began to be felt. The resistance from stiffness of belt was not apparent, and no marked difference could be detected in the power required to run a wide double belt or a narrow light one for the same tension at moderate speeds. With crossed and quarter-twist belts the friction of the belt upon itself or upon the pulley in leaving it was frequently an item of more importance, as was shown by special experiments for that purpose. In connection with the experiments upon internal resistances, some interesting points were noted. Changes in tension were made while the belt was running, commencing with a very slack belt and increasing by definite amounts to the working strength. As this point was approached, it was found necessary, to maintain a constant tension, that the tightening bolt should be constantly operated on account of stretch in the belt. Then, again, as the tension was reduced from this limit, it was found that at lower tensions the belt would begin to shrink and tighten for a fixed position of the sliding frame. This stretching and tightening would continue for a long time, the tightening being, of course, limited, but the stretching indefinite and unlimited. The first series of experiments was made upon paper-coated pulleys 20" diameter, which carried an old 5-1/2" open belt 3/16" to 1/4" thick and 34 ft. long, weighing 16 lbs. The arc of contact on the pulleys has been calculated approximately from the tension on slack side, and for this purpose the width and length of the belt were taken. The percentage of slip must be considered as equally divided between the two pulleys, and from observations made it is easy to calculate the velocity of sliding when the speed is given. Some of the most important results obtained with this belt are given in Table I. in which the experiments have been selected to avoid unnecessary repetition. In all cases the coefficient of friction is shown to increase with the percentage of slip. The adhesion on the paper-covered pulleys appears to be greater than on the cast-iron surfaces, but this difference may possibly have been due to some change in the condition of the belt surfaces. After a fresh application of the belt dressing known as "Beltilene," the results obtained are even higher on cast iron than on paper surfaces, but after a time it was found that the adhesive property of this substance became sensibly less and less. Flakes of a tarry nature rolled up from the belt surface and deposited, themselves on the pulleys, or scaled off. So much was found to depend upon the condition of the belt surface and the nature of the dressing used, that the necessity was felt for experiments upon some standard condition which could be easily realized and maintained. For this purpose a belt was taken from a planing machine when it had become perfectly dried by friction. The results of experiments upon this belt are given in Table II. When dry, as used on the planer, the coefficients for any given percentage of slip were much smaller than those given in Table I. This was naturally to be expected, and the experiments were continued to note the effect of a belt dressing in common use, known as "Sankey's Life of Leather," which was applied to the belt while running. At first, the adhesion was very much diminished, but it gradually increased as the lubricant became absorbed by the leather, and in a short time the coefficient of friction had reached the unprecedented figures of 1.44 and 1.37. TABLE I. STRAIGHT OPEN BELT 5-1/2" WIDE BY 7/32" THICK AND 34 FT. LONG, WEIGHING 16 LBS., IN GOOD PLIABLE CONDITION, WITH HAIR SIDE ON PULLEYS 20 IN. DIAM. RUNNING AT 160 R. P. M., OR ABOUT 800 FT. PER MINUTE. Legend column headings: [A] = No. of Experi'nt. [B] = Sum of Tensions. _T_ + _t_ Initial. [C] = Sum of Tensions. _T_ + _t_ Working. [D] = Sum of Tensions. _T_ + _t_ Final. [E] = _T_ - _t_ Working.[41] [F] = _T_[41] [G] = _t_[41] [H] = _T_/_t_[41] [I] = Percentage of Slip. [J] = Velocity of Slip in ft. per min. [K] = Arc of contact. [L] = Coefficient of Friction. [M] = Remarks. ---+---+---+---+---+-----+-----+-----+----+----+----+----+--- [A]|[B]|[C]|[D]|[E]| [F] | [G] | [H] | [I]| [J]| [K]|[L] |[M] ---+---+---+---+---+-----+-----+-----+----+----+----+----+--- 17|200|210| |100|155 | 55 | 2.82| .4| 1.6|177°|.336|[A] 19| |220| |140|180 | 40 | 4.50| .6| 2.4|176 |.490| 21| |246| |180|213 | 33 | 6.45| 1.2| 4.8|175 |.610| 22| |260| |200|230 | 30 | 7.67| 2.6|10.4|174 |.671| 23| |270|180|220|245 | 25 | 9.80| 7.9|31.6|173 |.756| ---+---+---+---+---+-----+-----+-----+----+----+----+----+ 24|300|316| |200|258 | 58 | 4.45| .7| 2.8|177 |.483| 27| |344| |260|302 | 42 | 7.20| 1.0| 4 |176 |.643| 28| |350| |280|315 | 35 | 9 | 1.8| 7.2|175 |.719| 29| |364| |300|332 | 32 |10.4 | 2.8|11.2|175 |.784| 30| |380|260|320|350 | 30 |11.7 | 5.5|22 |175 |.805| ---+---+---+---+---+-----+-----+-----+----+----+----+----+ 31|400|422| |200|211 |111 | 1.90| .5| 2 |179 |.205| 33| |440| |280|360 | 80 | 4.50| .8| 3.2|178 |.484| 35| |470| |360|415 | 55 | 7.54| 1.1| 4.4|177 |.654| 36| |506| |400|453 | 53 | 8.54| 2.1| 8.4|177 |.694| 37| |520|380|420|470 | 50 | 9.40| 5 |20 |177 |.725| ---+---+---+---+---+-----+-----+-----+----+----+----+----+--- 60|200|205| | 80|147.5| 67.5| 2.18| .5| 2 |178 |.251|[B] 61| |210| |100|155 | 55 | 2.82| .9| 3.6|177 |.336| 62| |215| |120|167.5| 47.5| 3.52| 1.7| 6.8|177 |.407| 63| |220| |140|180 | 40 | 4.50| 3 |12 |176 |.490| 65| |246|180|180|213 | 33 | 6.45|12 |48 |175 |.610| ---+---+---+---+---+-----+-----+-----+----+----+----+----+ 66|300|300| |120|210 | 90 | 2.33| .5| 2 |179 |.270| 68| |310| |160|235 | 75 | 3.13| .8| 3.2|179 |.365| 69| |315| |180|247.5| 67.5| 3.67| 1 | 4 |178 |.418| 70| |320| |200|260 | 60 | 4.33| 1.7| 6.8|178 |.472| 71| |325| |220|272.5| 52.5| 5.19| 2.6|10.4|177 |.545| 72| |340| |240|290 | 50 | 5.80| 3.8|15.2|177 |.569| 73| |350| |260|305 | 45 | 6.77| 5.5|22 |176 |.623| 74| |360| |280|320 | 40 | 8 | 8.6|34.4|176 |.677| 75| |375| |300|337.5| 37.5| 9 |15.2|60.8|175 |.719| ---+---+---+---+---+-----+-----+-----+----+----+----+----+--- 76|400|420| |200|310 |110 | 2.82| .6| 2.4|179 |.336|[C] 78| |460| |280|370 | 90 | 4.11| 1 | 4 |179 |.452| 81| |480| |340|410 | 70 | 5.86| 1.5| 6 |178 |.569| 84| |510| |400|455 | 55 | 8.27| 2.2| 8.8|177 |.684| 86| |535| |440|487.5| 47.5|10.2 | 4.5|18 |177 |.760| 88| |560|385|480|520 | 40 |13 | 8.4|33.6|176 |.834| ---+---+---+---+---+-----+-----+-----+----+----+----+----+ 89|300|320| |120|220 |100 | 2.20| .4| 1.6|179 |.252| 93| |350| |200|275 | 75 | 3.67| .8| 3.2|178 |.418| 97| |390| |280|335 | 55 | 6 | 1.6| 6.4|177 |.580| 101| |440| |360|400 | 40 |10 | 3.1|12.4|176 |.750| 104| |470|310|420|445 | 25 |17.8 | 8.6|34.4|173 |.953| ---+---+---+---+---+-----+-----+-----+----+----+----+----+--- Legend Remarks: [A] = Paper-covered pulleys. [B] = Cast-iron surfaces. [C] = Belt dressed with "Beltilene." [41] _T_ represents the tension on the tight part, and _t_ on the sag part of the belt. An interesting feature of these and subsequent experiments is the progressive increase in the sum of the belt tensions during an increase in load. This is contrary to the generally accepted theory that the sum of the tensions is constant, but it may be accounted for to a large extent by the horizontal position of the belt, which permitted the tension on the slack side to be kept up by the sag. That this is only a partial explanation of the phenomenon, and that the sum of the tensions actually increases as their difference increases for even a vertical position of the belt, will be shown by a special set of experiments. If a belt be suspended vertically, and stretched by uniformly increasing weights, it will also be found that the extension is not uniform, but diminishes as the load is increased, or, as already stated, the stress increases faster than the extension. A little reflection will show that when this is the case the tensions must necessarily increase with the load transmitted. TABLE II. DOUBLE BELT 2-1/4" WIDE BY 5/16" THICK, AND 32 FT. LONG, WEIGHING 9-1/2 LBS., ON 20" CAST-IRON PULLEYS. THIS BELT HAD BEEN USED ON A PLANING MACHINE, WAS QUITE PLIABLE, DRY, AND CLEAN. 160 R. P. M. Legend column headings: [A] = No. of Experi'nt. [B] = Sum of Tensions. _T_ + _t_ Initial. [C] = Sum of Tensions. _T_ + _t_ Working. [D] = Sum of Tensions. _T_ + _t_ Final. [E] = _T_ - _t_ Working. [F] = _T_ [G] = _t_ [H] = _T_/_t_ [I] = Percentage of Slip. [J] = Velocity of Slip in ft. per min. [K] = Arc of contact. [L] = Coefficient of Friction. [M] = Remarks. ---+---+---+---+---+-----+-----+-----+----+----+----+-----+--- [A]|[B]|[C]|[D]|[E]| [F] | [G] | [H] | [I]| [J]| [K]| [L] |[M] ---+---+---+---+---+-----+-----+-----+----+----+----+-----+--- 105|100|104| | 40| 72 | 32 | 2.25| .3| 1.2|177°| .263| 106| |110| | 60| 85 | 25 | 3.40| .8| 3.2|177 | .395| 107| |122| | 80| 101 | 21 | 4.81| 1.7| 6.8|176 | .511| 108| |138| |100| 119 | 19 | 6.26| 4.3|17.2|175 | .600| ---+---+---+---+---+-----+-----+-----+----+----+----+-----+--- 109|200|208| | 80| 144 | 64 | 2.25| .4| 1.6|179 | .260| 110| |212| |100| 156 | 56 | 2.81| .7| 2.8|179 | .331| 111| |216| |120| 168 | 48 | 3.50| 1 | 4 |179 | .401| 112| |220| |140| 180 | 40 | 4.50| 1.8| 7.2|178 | .484| 113| |230| |160| 195 | 35 | 5.57| 4.4|17.6|178 | .553| ---+---+---+---+---+-----+-----+-----+----+----+----+-----+--- 114|300|308| |120| 214 | 94 | 2.28| .4| 1.6|180 | .262| 116| |316| |160| 238 | 78 | 3.05| .8| 3.2|180 | .355| 118| |322| |200| 261 | 61 | 4.28| 1.6| 6.4|179 | .465| 119| |330|285|220| 275 | 55 | 5 | 2.6|10.4|179 | .516| ---+---+---+---+---+-----+-----+-----+----+----+----+-----+--- 121|400|404| |160| 282 |122 | 2.31| .7| 2.8|180 | .267| 124| |410| |220| 315 | 95 | 3.37| 1.5| 6 |180 | .387| 125| |412| |240| 326 | 86 | 3.79| 2.3| 9.2|180 | .424| 126| |414| |260| 338 | 78 | 4.33| 3.7|14.8|179 | .469| 127| |416|370|280| 348 | 68 | 5.12|10.1|40.4|179 | .523|[A] ---+---+---+---+---+-----+-----+-----+----+----+----+-----+ 128|500|516| |200|358 |158 | 2.27| .5| 2 |180 | .261| 131| |520| |260|390 |130 | 3 | 1.1| 4.4|180 | .350| 133| |525| |300|412.5|112.5| 3.67| 1.8| 7.2|180 | .414| 134| |525| |320|422.5|102.5| 4.11| 2.7|10.8|180 | .450| 135| |525|460|340|432.5| 92.5| 4.67| 5.1|20.4|180 | .490| ---+---+---+---+---+-----+-----+-----+----+----+----+-----+--- 136|100|105| | 40| 72.5| 32.5| 2.02| .2| .8|177 | .228|[B] 137| |110| | 60| 85 | 25 | 3.40| .4| 1.6|177 | .396| 138| |125| | 80|102.5| 22.5| 4.56| .6| 2.4|176 | .494| 140| |150| |120|135 | 15 | 9 | 1.8| 7.2|174 | .723| 141| |164| |140|152 | 12 |12.7 | 2.8|10.8|172 | .779| 142| |180| |160|170 | 10 |17 | 5 |20 |170 | .954| 144| |215| |200|207.5| 7.5|27.7 | 7.3|29.2|166 |1.15 | 146| |250| |240|245 | 5 |49 |10.6|42.4|158 |1.41 | 147| |270| 90|260|265 | 5 |53 |17.7|70.8|158 |1.44 | ---+---+---+---+---+-----+-----+-----+----+----+----+-----+--- 149|100|105| | 40| 72.5| 32.5| 2.02| .2| .8|177 | .228|[C] 150| |110| | 60| 85 | 25 | 3.40| .3| 1.2|177 | .396| 151| |120| | 80|100 | 20 | 5 | .4| 1.6|176 | .524| 153| |150| |120|135 | 15 | 9 | .7| 2.8|174 | .723| 155| |182| |160|171 | 11 |15.5 | 1.2| 4.8|172 | .913| 156| |202| |180|191 | 11 |17.3 | 3 |12 |172 | .950| 157| |216| |200|208 | 8 |26 | 5.8|23.2|167 |1.12 | 158| |232| |220|226 | 6 |37.3 | 7 |28 |161 |1.29 | 159| |252| |240|246 | 6 |41 | 9.8|39.2|161 |1.32 | 161| |292| |280|286 | 6 |47.7 |13.7|54.8|161 |1.37 | ---+---+---+---+---+-----+-----+-----+----+----+----+-----+--- Legend Remarks: [A] = Belt almost slipped off. [B] = Here the belt was coated with "Sankey's Life of Leather," and run until in good working condition before noting experiments. [C] = Three days later without any additional dressing. A piece of belting 1 sq. in. in section and 92 ins. long was found by experiment to elongate 1/4 in. when the load was increased from 100 to 150 lbs., and only 1/8 in. when the load was increased from 450 to 500 lbs. The total elongation from 50 to 500 lbs. was 1-11/16", but this would vary with the time of suspension, and the measurements here given were taken as soon as possible after applying the loads. In a running belt the load is applied and removed alternately for short intervals of time, depending upon the length and speed of the belt, and the time for stretching would seldom be as great as that consumed in making the experiments just mentioned. The differences between the initial and final tensions unloaded, as given in the tables, show the effect of extension or contraction during the course of the experiments made at a fixed position of the pulleys. The percentage of elongation which a belt undergoes in passing from its loose to its tight side, is the measure of the slip which must necessarily take place in the transmission of power. This is a direct loss, and within the assumed working strength of 500 lbs. per sq. in. for cemented belts without lacings, experiment indicates that it should not exceed 1-1/2 or 2 per cent. When, therefore, an experiment shows less than 2 per cent. of slip, the amount may be considered as allowable and proper, and the belt may be relied upon to work continuously at the figures given. Table III. gives the results of experiments upon a soft and pliable rawhide belt made by the Springfield Glue and Emery Co. This belt had been used by the Midvale Steel Co. for a period of seven months, at its full capacity, and was sent in its usual working condition to be tested. It had been cleaned and dressed with castor oil at intervals of three months, and was received three weeks after the last dressing. Commencing with the light initial tension of 50 lbs. on a side, it was found impossible with the power at command to reach a limit to the pulling power of the belt, and in order to do so the experiment was made of supporting the slack side of the belt upon a board to prevent sagging. TABLE III. RAWHIDE BELT 4" WIDE BY 9/32" THICK AND 31 FT. LONG, WEIGHING 15 LBS. 160 R. P. M. ON 20" CAST-IRON PULLEYS. Legend column headings: [A] = No. of Experi'nt. [B] = Sum of Tensions. _T_ + _t_ Initial. [C] = Sum of Tensions. _T_ + _t_ Working. [D] = Sum of Tensions. _T_ + _t_ Final. [E] = _T_ - _t_ Working. [F] = _T_ [G] = _t_ [H] = _T_/_t_ [I] = Percentage of Slip. [J] = Velocity of Slip in ft. per min. [K] = Arc of contact. [L] = Coefficient of Friction. [M] = Duration of run at time of experiment. [N] = Remarks. ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- [A]|[B]|[C]|[D]|[E]| [F] | [G] | [H] | [I]| [J] | [K]| [L] | [M] |[N] ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 171|100|118| | 40| 79 | 39 | 2.03| .2| .8 |177°| .229| | 173| |140| | 80|110 | 30 | 3.67| .4| 1.6 |176 | .423| | 175| |168| |120|144 | 24 | 6 | .6| 2.4 |174 | .590| | 177| |202| |160|181 | 21 | 8.62| .8| 3.2 |172 | .661| | 179| |232| |200|216 | 16 | 13.5 | 1 | 4 |170 | .897| | 181| |268| |240|254 | 14 | 18.1 | 1.2| 4.8 |167 | .993| | 183| |302| |280|291 | 11 | 26.5 | 1.4| 5.6 |163 | 1.15 | | 184| |318|110|300|309 | 9 | 34.3 | 1.6| 6.4 |160 | 1.27 | | ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 185|100|150|115|140|145 | 5 | 29 | 1.6| 6.4 |180 | 1.02 | |[A] ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+ 186|200|258| |240|249 | 9 | 27.4 | 1.2| 4.8 |180 | 1.05 | | 188| |290| |280|285 | 5 | 57 | 2.2| 8.8 |180 | 1.29 | | ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 189|300|412| |400|406 | 6 | 67.7 | 1.7| 6.8 |180 | 1.34 | | 190| |428| |420|424 | 4 |106 | 1.8| 7.2 |180 | 1.48 | | 191| |446|275|440|443 | 3 |148 | 3.3|13.2 |180 | 1.59 | | ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+ 192|400|570|360|560|565 | 5 |113 | 2 | 8 |180 | 1.47 | | ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 329|100|110| | 40| 75 | 35 | 2.14| .3| .6 |177 | .246| |[B] 330| |135| | 80|107.5| 27.5| 3.90| .6| 1.2 |175 | .446| | 331| |198| |160|179 | 19 | 9.42| 1 | 2 |171 | .751| | 332| |275| |240|257.5| 17.5| 14.7 | 1.5| 3 |169 | .911| | 334| |345| |320|232.5| 12.5| 18.6 | 2 | 4 |165 | 1.01 | | 336| |420|110|400|410 | 10 | 41 | 3.2| 6.4 |162 | 1.31 | | ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 339|200|230| |160|195 | 35 | 5.86| .8| 1.6 |176 | .576| | 340| |360| |320|340 | 20 | 17 | 1.6| 3.2 |171 | .949| | 341| |435| |400|417.5| 17.5| 23.8 | 2 | 4 |169 | 1.07 | | 342| |505| |480|492.5| 12.5| 39.4 | 2.7| 5.4 |165 | 1.28 | | 343| |590|200|560|575 | 15 | 38.3 | 5 |10 |168 | 1.24 | | ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 344|300|400| |320|360 | 40 | 9 | 1.4| 2.8 |175 | .719| | 345| |450| |400|425 | 25 | 17 | 1.7| 3.4 |173 | .938| | 346| |520| |480|500 | 20 | 25 | 2.1| 4.2 |171 | 1.08 | | 347| |600| |560|570 | 10 | 57 | 3 | 6 |162 | 1.43 | 1 min.| 348| |600|280|560|570 | 10 | 57 | 3.4| 6.8 |162 | 1.43 | 5 min.| ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 350|400|500| |400|450 | 50 | 9 | 1.6| 3.2 |176 | .715| | 352| |605| |560|577.5| 17.5| 21.3 | 2.3| 4.6 |169 | 1.04 | | 353| |680| |640|660 | 20 | 33 | 3.2| 6.4 |171 | 1.17 | 1 min.| 354| |680| |640|660 | 20 | 33 | 3.7| 7.4 |171 | 1.17 | 5 min.| 355| |680| |640|660 | 20 | 33 | 4.1| 8.2 |171 | 1.17 |10 min.| 356| |680| |640|660 | 20 | 33 | 6.1|12.2 |171 | 1.17 |15 min.|[C] 357| |600| |560|580 | 20 | 29 |10 |20 |171 | 1.13 |20 min.|[D] 358| |600| |560|580 | 20 | 29 |17.2|34.4 |171 | 1.13 |25 min.| 359| |530| |480|505 | 25 | 20.2 | 5.2|10.4 |173 | .955|30 min.| 360| |530|350|480|505 | 25 | 20.2 | 2.8| 5.6 |173 | .955|35 min.| ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 361|500|570| |400|485 | 85 | 5.71| 1.3| 2.6 |178 | .561| | 364| |700| |640|670 | 30 | 22.3 | 2.3| 4.6 |174 | 1.02 | | 365| |755| |720|637.5| 17.5| 36.4 | 3.2| 6.4 |169 | 1.22 | | 366| |820| |800|810 | 10 | 81 | 6.6|13.2 |162 | 1.55 +-------+[E] 367| |750| |720|735 | 15 | 49 | 5.1|10.2 |168 | 1.32 | 1 min.| 368| |750| |720|735 | 15 | 49 |11 |22 |168 | 1.32 | 5 min.| 369| |690| |640|665 | 25 | 26.6 |12 |24 |173 | 1.09 +-------+[F] 370| |610| |560|585 | 25 | 23.4 |14.4|28.8 |173 | 1.05 | 1 min.| 371| |610| |560|585 | 25 | 23.4 |20 |40 |173 | 1.05 | 4 min.| 372| |550| |480|515 | 35 | 14.7 | 7.4| 14.8|175 | .880| 1 min.| 373| |550|410|480|515 | 35 | 14.7 | 2.3| 4.6|175 | .880| 5 min.| ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 374|600|680| |480|580 |100 | 5.8 | 1.5| 3 |178 | .566| | 376| |755| |640|697.5| 57.5| 12.1 | 2.1| 4.2 |177 | .807| | 378| |850| |800|825 | 25 | 33 | 2.8| 5.6 |173 | 1.16 | 1 min.| 379| |850| |800|825 | 25 | 33 | 3.5| 7 |173 | 1.16 | 5 min.|[G] 380| |780| |720|750 | 30 | 25 | 8.8|17.6 |174 | 1.06 | 1 min.| 381| |680| |560|620 | 60 | 10.3 |11.2|22.4 |177 | .755| 5 min.| 382| |680| |560|620 | 60 | 10.3 | 2 | 4 |177 | .755+-------+[H] 383| |730| |640|685 | 45 | 15.2 | 2.5| 5 |176 | .886| 1 min.| 384| |730| |640|685 | 45 | 15.2 | 2.4| 4.8 |176 | .886| 5 min.| 385| |780| |720|750 | 30 | 25 | 4.6| 9.2 |174 | 1.06 | 1 min.| 388| |780|550|720|750 | 30 | 25 | 8.8|17.6 |174 | 1.06 | 5 min.| 389| |780| |720|750 | 30 | 25 | 4 | 8 |174 | 1.06 | 1 min.|[I] 390| |780| |720|750 | 30 | 25 | 6.4|12.8 |174 | 1.06 | 5 min.|[E] 391| |730| |640|685 | 45 | 15.2 | 3.7| 7.4 |176 | .886| 1 min.| 392| |730|550|640|685 | 45 | 15.2 | 3.9| 7.8 |176 | .886| 5 min.| ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 396|600|680| |400|540 |140 | 3.86| 2 | .45|170 | .432| |[J] 397| |820| |720|770 | 50 | 15.4 |17.2| 3.87|176 | .890| | 398| |750| |640|695 | 55 | 12.6 |15 | 3.37|177 | .874| | 399| |700| |560|630 | 70 | 9 | 9.4| 2.17|177 | .711| | 400| |670| |480|575 | 95 | 6.05| 4.5| 1.12|178 | .579| | 401| |630|550|400|515 |115 | 4.48| 3.5| .75|178 | .483| | 402| |830| |720|775 | 55 | 14.1 |26 | 5.85|177 | .856| | 403| |630| |320|475 |155 | 3.06| 1.5| .30|179 | .358| | 404| |610| | 60|335 |275 | 1.22| .7| .16|180 | .063| | ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- 408|600|610| |120|365 |245 | 1.49| .2| .09|180 | .127| |[K] 413| |660| |400|530 |130 | 4.08| 1 | .45|179 | .450| | 415| |710| |560|635 | 75 | 8.46| 1.9| .86|177 | .691| | 416| |750| |640|695 | 55 | 12.6 | 3.2| 1.44|177 | .820| | 417| |800| |720|760 | 40 | 19 | 3.8| 1.71|175 | .964| | 418| |340| |200|274 | 70 | 3.91| .6| .27|177 | .441| | 419|300|380| |280|330 | 50 | 6.6 | 1.2| .54|176 | .614| | 421| |450| |400|425 | 25 | 17 | 3.2| 1.44|173 | .938| | 423| |515| |480|497.5| 17.5| 28.4 | 4 | 1.8 |169 | 1.13 | | 425| |580| |560|570 | 10 | 57 | 5 | 2.25|162 | 1.43 | | 427| |695| |680|687.5| 7.5| 91.7 | 7 | 3.15|155 | 1.67 | | ---+---+---+---+---+-----+-----+------+----+-----+----+------+-------+--- Legend Remarks: [A] = Slack side of belt running on a board to prevent sagging. [B] = 10" cast-iron pulleys. [C] = Belt slipped off 4 m. later. [D] = Continuing. [E] = Belt slipped off 2 m. later. [F] = Belt slipped off 3 m. later. [G] = Belt slipped off 5 m. later. [H] = After running 5 minutes at _T_ - _t_ = 560. [I] = Belt scraped. [J] = 18 r. p. m. 10" cast-iron pulleys. [K] = 20" cast-iron pulleys. 18 r. p. m. These experiments, however, are subject to an error arising from the friction of the belt upon the board, the amount of which was not determined. All of the experiments, in fact, are subject to slight errors which were extremely difficult to eliminate or properly allow for, but an effort has been made throughout to obtain results which should approximate as closely as possible to the truth. The sum of the tensions, as determined by measuring scales, was subject only to errors in observation. This part of the apparatus was carefully tested by a horizontal pull of known amount and made to register correctly. The difference of the tensions _T_ - _t_, as computed from the reading of the scales, was measured by the force of an equivalent moment at 20" radius. This moment, divided by the radius of the pulley was taken to be the difference _T_ - _t_. In this calculation, it will be noticed that two slight corrections have been omitted which are opposite in effect and about equal in degree. One is the friction of the brake shaft in its bearings, which of course was not recorded on the scales, and the other is the thickness of the belt which naturally increases the effective radius of the pulley. Both of these errors are somewhat indefinite, but the correctness of the results obtained was tested in a number of cases by the sag of the belt, and the tension _t_, as calculated from the sag, was found to agree closely with the tension calculated by the adopted method. As the limiting capacity of the belt was reached, the difficulty of obtaining simultaneous and accurate observations was increased by the vibrations of the scale beams. This was apparently due to irregularity in the slip, and it was only by the use of heavily loaded beams and a dash-pot that readings could then be taken at all. The dash-pot consisted of a large flat plate suspended freely in a bucket of water by a fine wire from the scale beam. This provision, however, was applied only to the scales on which the vibrations were more pronounced. TABLE IV. DOUBLE OAK-TANNED LEATHER BELT 4" WIDE BY 5/16" THICK AND 30 FT. LONG, WEIGHING 17 LBS., ON 10" CAST-IRON PULLEYS. 160 R. P. M. Legend column headings: [A] = No. of Experi'nt. [B] = Sum of Tensions. _T_ + _t_ Initial. [C] = Sum of Tensions. _T_ + _t_ Working. [D] = Sum of Tensions. _T_ + _t_ Final. [E] = _T_ - _t_ Working. [F] = _T_ [G] = _t_ [H] = _T_/_t_ [I] = Percentage of Slip. [J] = Velocity of Slip in ft. per min. [K] = Arc of contact. [L] = Coefficient of Friction. [M] = Duration of run at time of experiment. [N] = Remarks. ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- [A]|[B]|[C]|[D]|[E]| [F] | [G] | [H] | [I]| [J] | [K]| [L] | [M] |[N] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 209|120|120| | 48| 84 | 36 | 2.33| .4| .8 |176°| .275| | 210| |140| | 80|110 | 30 | 3.67| .6| 1.2 |175 | .426| | 211| |168| |120|144 | 24 | 6 | .9| 1.8 |174 | .590| | 212| |198| |160|179 | 19 | 9.42| 1.6| 3.2 |170 | .756| | 213| |235| |200|217.5| 17.5|12.4 | 2.3| 4.6 |174 | .829| | 214| |270| |240|255 | 15 |17 | 3.2| 6.4 |168 | .966| | 215| |310| |280|295 | 15 |19.7 | 5.1|10.2 |168 |1.02 | |[A] 216| |345|122|320|332.5| 12.5|25.8 | 9.4|18.8 |164 |1.13 | |[B] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 217|200|200| | 48|124 | 76 | 1.63| .4| .8 |179 | .156| | 219| |240| |160|200 | 40 | 5 | 1 | 2 |176 | .524| | 220| |360| |320|340 | 20 |17 | 2.7| 5.4 |170 | .954| | 221| |430| |400|415 | 5 |27.7 |15 |30 |167 |1.13 | | ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 222|300|318| |160|239 | 79 | 3.03| .8| 1.6 |179 | .354| | 223| |350| |240|295 | 55 | 5.36| 1.2| 2.4 |177 | .543| | 224| |400| |320|360 | 40 | 9 | 2 | 4 |175 | .719| | 225| |470| |440|455 | 15 |30.3 | 8 | 1.6 |167 |1.17 | |[C] 226| |450| |400|425 | 25 |17 | 4 | 8 |172 | .943| 1 m.| 227| |450| |400|425 | 25 |17 | 8 |16 |172 | .943| 5 m.| 228| |450| |400|425 | 25 |17 |17.3|34.6 |172 | .943| 10 m.|[D] 229| |418| |360|389 | 29 |13.4 | 3 | 6 |173 | .859| 15 m.|[E] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 230|400|405| |160|282.5|122.5| 2.30| .8| 1.6 |179 | .267| | 232| |455| |320|387.5| 67.5| 5.74| 1.4| 2.8 |177 | .566| | 233| |495| |400|447.5| 47.5| 9.42| 1.9| 3.8 |176 | .730| 1 m.| 234| |495|370|400|447.5| 47.5| 9.42| 2.1| 4.2 |176 | .730| 5 m.| 235| |560| |480|520 | 40 |13 | 2.7| 5.4 |175 | .859|Start.| 236| |560| |480|520 | 40 |13 | 4.5| 9 |175 | .859| 5 m.| 237| |560| |480|520 | 40 |13 | 7.5|15 |175 | .859| 10 m.| 238| |550|380|480|465 | 85 | 5.47|20 |40 |178 | .547| 15 m.| ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 239|400|560| |480|520 | 40 |13 | 3.4| 6.8 |175 | .859| 1 m.|[F] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 240|500|610| |480|545 | 65 | 8.38| 2.1| 4.2 |177 | .688| 1 m.| 241| |610| |480|545 | 65 | 8.38| 2.5| 5 |177 | .688| 5 m.| 242| |660| |560|610 | 50 |12.2 | 3.2| 6.4 |176 | .814| 1 m.| 243| |655| |560|607.5| 47.5|12.8 | 8.4|16.8 |176 | .830| 5 m.|[G] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 244|600|700| |560|630 | 70 | 9 | 1.9| 3.8 |177 | .711| 1 m.| 245| |700| |560|630 | 70 | 9 | 2.1| 4.2 |177 | .711| 5 m.| 246| |690|550|560|625 | 65 | 9.69| 2.3| 4.6 |177 | .735| 10 m.| ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 247|600|750| |600|675 | 75 | 9 | 2.2| 4.4 |177 | .771| 1 m.| 248| |740|585|600|670 | 70 | 9.57| 2.4| 4.8 |177 | .731| 5 m.| ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 249|600|770| |640|705 | 65 |10.8 | 2.5| 5 |177 | .770| 1 m.| 250| |765| |640|702.5| 62.5|11.2 | 3.5| 7 |177 | .782| 5 m.| 251| |770|600|640|685 | 85 | 8.06| 4.2| 8.4 |178 | .672| 10 m.| ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 252|600|790| |680|735 | 55 |13.4 | 4.3| 8.6 |176 | .845| 1 m.| 253| |790| |680|735 | 55 |13.4 | 6.3|12.6 |176 | .845| 5 m.|[H] ---+---+---+---+---+-----+-----+-----+-----+-----+----+-----+------+--- 254|100|100| | 44| 72 | 28 | 2.57| .6| 1.2 |176 | .307| |[I] 256| |160| |120|140 | 20 | 7 | 2.1| 4.2 |172 | .648| | 257| |200| |160|180 | 20 | 9 | 4 | 8 |171 | .736| | 258| |230| |200|215 | 15 |14.3 | 6.6|13.2 |168 | .907| 1 m.| 259| |230|100|200|215 | 15 |14.3 | 7.2|14.4 |168 | .907| 5 m.| ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 261|100|100| | 44| 72 | 28 | 2.57| .6| 1.2 |176 | .307| |[J] 263| |160| |120|140 | 20 | 7 | 2.8| 5.6 |172 | .648| | 264| |200| |160|180 | 20 | 9 | 5.1|10.2 |171 | .736| | 265| |230| |200|215 | 15 |14.3 | 7.3|14.6 |168 | .907| 1 m.| 266| |230| |200|215 | 15 |14.3 | 7.9|15.8 |168 | .907| 5 m.| 267| |270| |240|255 | 15 |17 |10.7|21.4 |168 | .966| 1 m.|[K] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 268|300|350| |240|295 | 55 | 5.36| 1.4| 2.8 |177 | .544| | 269| |400| |320|360 | 40 | 9 | 3 | 6 |175 | .719| | 270| |450| |400|425 | 25 | 17 | 6.8|13.6 |172 | .943| 1 m.|[K] 271| |418| |360|389 | 29 |13.4 | 8.8|17.6 |173 | .859| 1 m.| 272| |418| |360|389 | 29 |13.4 |15.6|31.2 |173 | .859| 5 m.|[G] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 273|600|700| |560|630 | 70 | 9 | 6.3|12.6 |177 | .711| | 274| |650| |480|565 | 85 | 6.65| 3.1| 6.2 |178 | .610| 1 m.| 275| |650| |480|565 | 85 | 6.65| 3.9| 7.8 |178 | .610| 5 m.| 276| |650| |480|565 | 85 | 6.65| 4.4| 8.8 |178 | .610| 10 m.| ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 277|600|652| |400|526 |126 | 4.17| 1.4| 2.8 |178 | .460| |[L] 279| |715| |560|637.5| 77.5| 8.23| 2.4| 4.8 |177 | .682| | 280| |705| |560|632.5| 72.5| 8.72| 2.8| 5.6 |177 | .701| | 281| |700|560|560|630 | 70 | 9 | 3 | 6 |177 | .711| | ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 282|560|750| |640|695 | 55 |12.6 | 4.1| 8.2 |176 | .824| 1 m.| 283| |735|535|640|682.5| 47.5|14.3 |22 |44 |176 | .866| 5 m.|[M] 284| |770| |640|705 | 65 |10.7 | 5.4|10.8 |177 | .767| 1 m.|[N] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 285|300|350| |240|295 | 55 | 5.36| 1.2| 2.4 |177 | .543| |[O] 286| |400| |320|360 | 40 | 9 | 1.8| 3.6 |175 | .719| | 287| |430| |360|395 | 35 |11.3 | 2.7| 5.4 |174 | .798| | 289| |465| |400|432.5| 32.5|13.3 | 5.3|10.6 |174 | .852| | 290| |455| |400|427.5| 27.5|15.5 | 7.3|14.6 |173 | .907| | 291| |460| |400|430 | 30 |14.3 |11.6|23.2 |173 | .881| | ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 292|100|100| | 44| 72 | 28 | 2.57| .5| 1 |176 | .307| | 293| |125| | 80|102.5| 22.5| 4.55| .8| 1.6 |173 | .502| | 294| |165| |120|142.5| 22.5| 6.33| 1.2| 2.4 |173 | .611| | 295| |200| |160|180 | 20 | 9 | 2.1| 4.2 |171 | .736| | 296| |230| |200|215 | 15 |14.3 | 3.4| 6.8 |168 | .907| | 297| |230| |200|215 | 15 |14.3 | 3.9| 7.8 |168 | .907| | ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 298|100|270| |240|225 | 15 |17 | 5.7|11.4 |168 | .966| 1 m.| 299| |270| |240|255 | 15 |17 | 7.6|15.2 |168 | .966| 5 m.| 300| |270| |240|255 | 15 |17 | 9.3|18.6 |168 | .966| 10 m.|[P] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 303|100|110| | 40| 75 | 35 | 2.14| .1| .4 |177 | .246| |[Q] 304| |132| | 80|106 | 26 | 4.08| .4| 1.6 |174 | .463| | 305| |160| |120|140 | 20 | 7 | 1 | 4 |172 | .648| | 306| |195| |160|177.5| 17.5|10.1 | 1.9| 7.6 |169 | .814| | 307| |230| |200|215 | 15 |14.3 | 3 |12 |168 | .907| 1 m.| 308| |230| 90|200|215 | 15 |14.3 | 3.5|14 |168 | .907| 5 m.| 309| |270| |240|255 | 15 |17 | 4.5|18 |168 | .966| 1 m.| 310| |270| |240|255 | 15 |17 | 5.8|23.2 |168 | .966| 5 m.| 311| |270| |240|255 | 15 |17 | 6.2|24.8 |168 | .966| 10 m.| 312| |270| |240|255 | 15 |17 | 6.2|24.8 |168 | .966| 15 m.|[R] 313| |270| |240|255 | 15 |17 | 2 | 8 |168 | .966| 1 m.| 314| |270| |240|255 | 15 |17 | 2.1| 8.4 |168 | .966| 5 m.|[S] 315| |305| |280|292.5| 12.5|23.4 | 3.4|13.6 |165 |1.09 | 1 m.| 316| |305|100|280|292.5| 12.5|23.4 | 3.5|14 |165 |1.09 | 5 m.| ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 317|100|335| |320|327.5| 7.5|43.7 | 5.2|20.8 |152 |1.42 | 1 m.| 318| |335| |320|327.5| 7.5|43.7 | 6.5|26 |152 |1.42 | 5 m.| ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 319|300|380| |320|350 | 30 |11.7 | 1.3| 5.2 |173 | .814| 1 m.| 320| |380| |320|350 | 30 |11.7 | 1.4| 5.6 |173 | .814| 5 m.| 321| |440| |400|420 | 20 |21 | 2.1| 8.4 |170 |1.03 | 1 m.| 322| |440|260|400|420 | 20 |21 | 2.4| 9.6 |170 |1.03 | 5 m.| ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- 323|300|480| |440|460 | 20 |23 | 2.8|11.2 |170 |1.06 | 1 m.|[T] 324| |480|285|440|460 | 20 |23 | 3 |12 |170 |1.06 | 5 m.| 325| |510| |480|495 | 15 |33 | 3.2|12.8 |167 |1.20 | 1 m.| 326| |510| |480|495 | 15 |33 | 5 |20 |167 |1.20 | 5 m.|[U] ---+---+---+---+---+-----+-----+-----+----+-----+----+-----+------+--- Legend Remarks: [A] = Sag 10" at middle of belt. [B] = Finally slipped off. [C] = Belt finally slipped off. [D] = Belt slip'd off. [E] = Continuing. [F] = After running 5 m. without load. [G] = Belt slipped off 2 m. later. [H] = Belt sl. off 2 m. lat. Pul. warm. [I] = Belt scraped. [J] = Belt dres'd with preparation recommend'd by maker. [K] = Belt slipped off 3 m. later. [L] = One day later. [M] = Belt slipp'd off. [N] = After 3 min. intermission. [O] = Temp. 52°. [P] = Belt slipped off 4 m. later. [Q] = 20 in. pulleys. [R] = Temp. 56°. [S] = Temp. 42°. [T] = Temp. 46°. [U] = Belt sl. off 5 m. lat. Pul. warm. A peculiar and important feature of Tables III. and IV. is the effect of time upon the percentage of slip. In previous experiments the percentage of slip was measured at once after the load was applied, but it was accidentally discovered that repeated measurements seldom agreed, and investigation showed that these discrepancies were principally due to the duration of the experiment. The continual slipping of the belt was found to cause a deposit of a thick black substance upon the surface of the pulley, which, acting as a lubricant, continued to increase the slip still further. Upon removing the load on brake-wheel, this deposit would be again absorbed by the belt, and the original adhesion would be restored. The temperature was also found to affect the slipping, and, in general, the colder the weather the slower would this deposit take place. Experiments 353 to 360 inclusive were made to determine the limit at which the belt would run continuously without increasing its percentage of slip. After the pulleys had become well coated and the slip had reached a high per cent., the load on the brake-wheel was gradually removed until a marked improvement was reached, as shown by experiments 359 and 360. The highest allowable coefficient of friction for this belt is therefore estimated to be somewhere between 1.13 and .995, or we may safely say 1. The highest coefficient obtained was 1.67, but, of course, this was temporary. The diameter of the pulley also appears to affect the coefficient of friction to some extent. This is especially to be noticed at the very slow speed of 18 revolutions per minute on 10 in. and 20 in. pulleys, where the adhesion on the 20 in. pulleys is decidedly greater; but, on the other hand, at 160 revolutions per minute the adhesion on the 10 in. pulleys is often as good, and sometimes better, than appears for the 20 in. at the same velocity of sliding. It might be possible to determine the effect of pulley diameter upon adhesion for a perfectly dry belt, where the condition of its surface remains uniform, but for belts as ordinarily used it would be very difficult, on account of the ever-changing condition of surface produced by slip and temperature. It is generally admitted that the larger the diameter the greater the adhesion for any given tension, but no definite relation has ever been established, nor, indeed, does it seem possible to do so except by the most elaborate and extensive experiments. It should be observed, however, that such a variation, if true, implies a corresponding variation in the coefficients of friction for different intensities of pressure upon the same pulleys, and that, consequently, our experiments should show higher coefficients under the lighter loads for the same velocity of sliding. Referring to Table II., where the condition of the belt is dry and uniform for a large range of tensions, we find that this inference is generally sustained, although there are some few exceptions. Experiment 106 may be compared with 116, and 112 with 133, also 108, 113, and 135, all showing great reductions in the coefficients of friction for increments in tension. The exceptions are all to be found under the smallest velocities of sliding, and appear only in the third decimal place, so that the weight of their record against the probability of such a law is light. By a similar inference it should also follow that a wide belt would drive a little more at a given tension than a narrow one, on account of the reduction in pressure per square inch against the pulley. The mean intensity of pressure of a belt against its pulley may be considered as proportional to the sum of the tensions divided by the product of pulley diameter and width of belt, and an analysis of the experiments referred to will show the relation there existing between intensity of pressure and coefficient of friction. If we let [Iota] = intensity of pressure, and [phi] = coefficient of friction, we shall find that [phi] is approximately proportional to [Iota]^{-.15}, or, in other words that doubling the width of belt or diameter of pulley would apparently increase the coefficient of friction about 10 per cent. of its original value. This relation is not proved, of course, and it is given only as a suggestion toward the solution of the question. If the coefficient of friction does vary with the intensity of pressure, the problem of determining the driving power of a belt on strictly mathematical principles will indeed be complicated. The coefficient of friction in the tables has been calculated by a well-known formula, developed upon the assumption of a uniform coefficient around the arc of contact, but this could no longer be considered as correct if the coefficient is known to vary with the pressure. Referring from Table II. to Table III., we shall find at once the proof and contradiction of the inferences drawn from Table II., and we are left as much in the dark as ever respecting the value of pressure intensity. Practical millwrights all know, or think they know, that an increase of pulley diameter increases the drive, and it is a matter of common observation that when large and small pulleys are connected by a crossed belt, the smaller pulley will invariably slip first. On one side a great deal of testimony can be adduced to show that pressure intensity should be an important factor in the theory of belt transmission, and, on the other hand, we have strong evidence to the contrary. I may refer, in this connection, to the experiments of Mr. Holman in _Journal of Franklin Institute_ for September, 1885, in which there is no indication that the coefficient of friction varies at all with the pressure. The coefficients obtained by Mr. Holman follow the variations in slip like our own, and it gives us pleasure to observe that our general results and conclusions are so strongly corroborative of each other. There is at the same time a great difference in the methods pursued in arriving at the same results. In his experiments, the velocity of sliding was the fixed condition upon which the coefficient of friction was determined, while, in ours, the conditions were those of actual practice in which the percentage of slip was measured. Our least amount of slip, with a dry belt running at the extremely slow speed of 90 feet per minute, was 1.08 inches, and ten times this would be perfectly proper and allowable. A great many of Mr. Holman's experiments are taken at rates below 1" per minute, and the coefficients obtained are very much below the average practice, as himself seems to believe. The velocity of sliding which may be assumed in selecting a proper coefficient is directly proportional to the belt speed, and may safely be estimated at .01 of that speed. For a pair of pulleys we should have .01 on each pulley, and therefore .02 for slip. Few belts run slower than 200 or 300 ft. per minute, and consequently a slip of less than 2 or 3 ft. per minute need seldom be considered. Another point of difference which may possibly affect the coefficients obtained, is that, in Mr. Holman's case the same portion of belt surface was subject to continuous friction, while in ours, the friction was spread over the belt at successive portions as in actual work. This we consider a new and important feature of our experiments. As a matter of practical importance, care was taken to observe, as nearly as possible, the maximum slip which might safely take place before a belt would be thrown from its pulley. A number of observations taken throughout the experiments led to the final conclusion that 20 per cent. of slip was as much as could safely be admitted. This information has been found of value in cases where work is done intermittently by a fly-wheel and the belt has to restore the speed of the wheel. It cannot be said in regard to a maximum value of [phi] that any was determined or even indicated, although it is certain that the increase at high rates of slip becomes less rapid. We have now seen that the driving power of a leather belt depends upon such a variety of conditions, that it would be manifestly impracticable if not impossible to correlate them all, and it is thought better to admit the difficulties at once than to involve the subject in a labyrinth of formulæ which life is too short to solve. The relative value of pulley diameters may vary with different belts, and all that can be expected or desired is some general expression covering roughly the greatest number of cases. Our apparatus did not admit of extensive variations in this respect, and our attention was given principally to the question of slip. The coefficients given in Table III. are remarkably high, and show a great superiority for the rawhide over tanned leather in point of adhesion. The belt in question was very soft and pliable, but a little twisted from use on a cone pulley where it had rubbed against one side. It is not desirable, on account of its soft and adhesive nature, to use this kind of belt where frequent shifting is required, and when used on cone pulleys it is liable to climb and stretch against the side of the cone; but for a plain straight connection, there seems to be little room for improvement. Table IV. contains the results of similar experiments upon an oak-tanned leather belt made by Chas. A. Shieren & Co. Here the coefficients are much smaller than those given in Table III., and there is quite a marked difference between the coefficients for 10 in. and 20 in. pulleys. As before noticed, the outside temperature has its effect, and it is probable that much lower results would have been obtained had the experiments been made in the heat of midsummer. The high coefficients obtained, together with the rapid increase of tension, show that the pulling power of a long horizontal belt must, in many cases, be limited by its strength rather than by its adhesion. Table V. gives the results of experiments upon a light planer belt at very slow and very high speeds. As would naturally be expected, much higher coefficients were found at the high speed on account of the greater velocity of sliding. TABLE V. OAK-TANNED LEATHER BELT 2" WIDE BY 3-16" THICK AND 30' 4" LONG, WEIGHING 4 LBS., ON 20" CAST-IRON PULLEYS. DRY AND SMOOTH, TAKEN FROM SERVICE ON PLANER. Legend column headings: [A] = No. of Experi'nt. [B] = Sum of Tensions. _T_ + _t_ Initial. [C] = Sum of Tensions. _T_ + _t_ Working. [D] = Sum of Tensions. _T_ + _t_ Final. [E] = _T_ - _t_ Working. [F] = _T_ [G] = _t_ [H] = _T_/_t_ [I] = Percentage of Slip. [J] = Velocity of Slip in ft. per min. [K] = Arc of contact. [L] = Coefficient of Friction. [M] = Duration of run at time of experiment. [N] = Remarks. ---+---+---+---+---+-----+----+----+----+------+----+----+------+--- [A]|[B]|[C]|[D]|[E]| [F] | [G]|[H] | [I]| [J] | [K]| [L]| [M] |[N] ---+---+---+---+---+-----+----+----+----+------+----+----+------+--- 429|100|110| | 40| 75 |35 |2.14| 1.2| .54|179°|.243| |18 430| |115| | 60| 87.5|27.5|3.18| 6.1| 2.75|178 |.372| |r. 431| |118| | 70| 94 |24 |3.92|16.5| 7.42|178 |.440| |p. 432| |105| | 20| 62.5|42.5|1.47| .3| .14|179 |.123| |m. 433| |112| | 50| 81 |31 |2.61| 3.5| 1.57|178 |.309| | ---+---+---+---+---+-----+----+----+----+------+----+----+------+--- 435|200|204| | 40|132 |82 |1.61| .2| .09|180 |.152| | 436| |206| | 60|133 |73 |1.82| .7| .32|180 |.191| | 437| |208| | 80|144 |64 |2.25| 1.8| .81|179 |.260| | 438| |210| |100|155 |55 |2.82| 3.7| 1.66|179 |.332| | 439| |212| |120|166 |40 |3.61| 7.7| 3.47|179 |.411| | 440| |215| |140|177.5|37.5|4.73|18.4| 8.28|179 |.497| | ---+---+---+---+---+-----+----+----+----+------+----+----+------+--- 442|100|110| | 60| 85 |25 |3.40| .3| 7.12|178 |.394| |950 443| |120| | 80|100 |20 |5 | .7| 16.62|178 |.518| |r. 445| |125| | 90|107.5|17.5|6.14| 3 | 71.25|177 |.587|Start.|p. 446| |125| | 90|107.5|17.5|6.14|25 |593.7 |177 |.587|min. |m. ---+---+---+---+---+-----+----+----+----+------+----+----+------+--- 448|200|200| | 80|140 |60 |2.33| .4| 9.5 |179 |.271| | 449| |200| |100|150 |50 |3 | .5| 11.87|179 |.352| | 450| |195|175|120|157.5|37.5|4.20| .8| 19 |179 |.459| | ---+---+---+---+---+-----+----+----+----+------+----+----+------+--- 451|150|175| |120|147.5|27.5|5.36| .9| 21.38|178 |.540| | ---+---+---+---+---+-----+----+----+----+------+----+----+------+--- 452|135|160| |120|140 |20 |7 |20 |475 |178 |.626| | ---+---+---+---+---+-----+----+----+----+------+----+----+------+--- It may here be mentioned that the sum of the tensions was the horizontal pressure of the belt against the pulleys, and that no allowance was necessary for the effect of the centrifugal force. At the speed here used, the tension indicated in the belt at rest was about 50 lbs. greater than when in motion. TABLE VI. SHOWING THE AVERAGE COEFFICIENT OF FRICTION AND VELOCITY OF SLIP FOR A NUMBER OF EXPERIMENTS IN WHICH THE SLIP APPROXIMATED 2 PER CENT. -------------------------------------+--------------+----------------- No. exper'ts in av'ge. | | |Percentage of Slip. | | | |Veloc. of Sl. in ft. per m. | | | | |Coefficient of Fric- | | | | |tion. | | | | | | Belt. | Pulleys. | Remarks. --+----+-----+-----+-----------------+--------------+----------------- 3|1.4 | 5.6 | .661|5-1/2" old belt. |20" diam. |Belt in nor. | | | |Table I |pap. cov'd |w'k'g con. --+----+-----+-----+-----------------+--------------+ 2|1.7 | 6.8 | .44 |5-1/2" old belt. |20" di. | " " | | | |Table I |cast-iron sur.| --+----+-----+-----+-----------------+--------------+----------------- 2|1.55| 6.2 | .575|5-1/2" old belt. |20" di. |Belt dressed | | | |Table I |cast-iron sur.|with "Beltiline." --+----+-----+-----+-----------------+--------------+----------------- 5|1.7 | 6.8 | .452|2-1/4" dbl. belt.|20" di. |B't dry as us. | | | |Table II |cast-iron sur.|on plan'r. --+----+-----+-----+-----------------+--------------+----------------- 2|1.5 | 6 | .818|2-1/4" dbl. belt.|20" di. |Belt dressed | | | |Table II |cast-iron sur.|with "Sankey's | | | | | |Life of Leather." --+----+-----+-----+-----------------+--------------+----------------- 2|1.7 | 6.8 |1.38 |4" r´hide b. |20" di. |Belt in nor. | | | |Table III |cast-iron sur.|w'k'g con. --+----+-----+-----+-----------------+--------------+ 11|1.8 | 3.6 | .861|4" r´hide b. |10" diameter. | " " | | | |Table III | | --+----+-----+-----+-----------------+--------------+ 1|2 | .45| .432|4" r´hide b. |10" diameter. | " " | | | |Table III | | --+----+-----+-----+-----------------+--------------+ 1|1.9 | .86| .691|4" r´hide b. |20" diameter. | " " | | | |Table III | | --+----+-----+-----+-----------------+--------------+ 7|1.94| 3.88| .617|4" o.tan'd b. |10" diameter. | " " | | | |Table IV | | --+----+-----+-----+-----------------+--------------+ 4|1.85| 7.40| .906|4" o.tan'd b. |20" diameter. | " " | | | |Table IV | | --+----+-----+-----+-----------------+--------------+----------------- 2|1.5 | .67| .251|2" o.tan'd b. |20" diameter. |B't dry as us. on | | | |Table V | |plan'r. --+----+-----+-----+-----------------+--------------+ 2| .8 |38 | .529|2" o.tan'd b. |20" diameter. | " " | | | |Table V | | --+----+-----+-----+-----------------+--------------+----------------- The conclusion to be drawn from this series of experiments is the great importance of high speed in the economy of belt transmission. The friction of belts on pulleys is evidently dependent on the velocity of sliding, and, as a general rule, the greater the velocity the greater the friction. There are but few apparent exceptions to this rule, and investigation of them has led to the inference that in all such cases, the condition of the belt or pulley surface had undergone a change either by heating or by deposit from the belt on the pulley. The percentage of slip is the measure of the power lost in transmission by the belt itself, and the higher the speed the less this becomes. There is a limit, however, to the power which may be transmitted as the speed is increased, and this limit is caused by the reduction in pressure against the pulley arising from the action of centrifugal force. This point has been clearly demonstrated in a paper read before this Society by Mr. A. F. Nagle on the "Horse Power of Leather belts,"[43] and the formula there developed is written thus: _HP_ = _CVtw_(_S_ - .012_V_^{2}) ÷ 550, (1.) in which _C_ is a constant to be determined from the arc of contact and coefficient of friction as expressed in the equation: _C_ = 1 - 10^{-.00758_f[alpha]_}, (2.) _V_ = velocity of belt in feet per second. _t_ = thickness of the belt in inches. _w_ = width " " _S_ = working strength of leather in lbs. per square inch. _f_ = coefficient of friction. _[alpha]_ = arc of contact in degrees. [43] Transactions A. S. M. E., Vol. II., page 91. See also Mr. Nagle's Tables I., II., and III., in Appendix VI. to this paper for values of _C_ and _H.P._ The velocity at which the maximum amount of power can be transmitted by any given belt is independent of its arc of contact and coefficient of friction, and depends only upon the working strength of the material and its specific gravity. From equation (1.) we obtain for the maximum power of leather belts the condition: _____ _V_ = \/28_S_, (3.) and for any other material whose specific gravity is _y_, we find ____ /_S_ _V_ = \ / --- \/ _y_ The coefficient of friction .40, adopted by Mr. Nagle, appears from these experiments to be on the safe side for all working requirements, except in cases where dry belts are run at slow speeds. If we assume 2 per cent. as the greatest allowable slip, and select within this limit the coefficient corresponding to the nearest approximations to it, we can form some idea of the coefficients which can be relied upon at different speeds. Table VI. gives the average results obtained for this maximum allowance of slip, and shows an extreme variation in the coefficient of friction from .251 for a dry oak-tanned belt at the slow speed of 90 feet per minute to 1.38 for a rawhide belt at the moderate speed of 800 feet per minute. For continuous working, it is probable that the coefficient 1.38 is too high, but still it is certain that a coefficient of 1.00 can be steadily maintained for an indefinite length of time, and we may say that in actual practice the coefficient of friction may vary from .25 to 1.00 under good working conditions. This extreme variation in the coefficient of friction does not give rise, as might at first be supposed, to such a great difference in the transmission of power. It will be seen by reference to formula (1.) that the power transmitted for any given working strength and speed is limited only by the value of _C_, which depends upon the arc of contact and the coefficient of friction. For the usual arc of contact, 180°, the power transmitted when _f_ = .25 is about 24 per cent. less than when _f_ = .40, and when _f_ = 1.00, the power transmitted is about 33 per cent. more, from which it appears that in extreme cases the power transmitted may be 1/4 less or 1/3 more than will be found from the use of Mr. Nagle's coefficient of .40. TABLE VII. SHOWING THE TORSIONAL MOMENT IN LBS. REQUIRED TO OVERCOME JOURNAL FRICTION AND OTHER INTERNAL RESISTANCES, FOR BELTS AT VARIOUS SPEEDS AND TENSIONS ON DIFFERENT ARRANGEMENTS OF PULLEYS. ------+-----+-------+-----+-----+-----+------+-------------+-------------- No. of|Ten- |Moment |Dia- |Revo-|Width|Thick-| | exper-|sion.|in inch|meter|lut's| of | ness | Manner of | im'nt.|_T_ +| lbs. | of |per |Belt.| of | Driving. | Remarks. | _t_ | |pul- |min. | |Belt. | | | | |leys.| | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 1 | 100| 20 | 20" | 160 | 6" |7/32" |Straight open| 3 | 300| 25 | | | | |belt. | 5 | 500| 30 | | | | | | 7 | 700| 35 | | | | | | 10 | 1000| 45 | | | | | | 45 | 100| 15 | | | | | | 47 | 300| 22.5 | | | | | | 49 | 500| 27.5 | | | | | | 51 | 700| 35 | | | | | | 54 | 1000| 50 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 163 | 100| 17.5 | 20" | 160 | 4" |9/32" |Straight open| 165 | 300| 25 | | | | |belt. | 167 | 500| 30 | | | | | | 169 | 700| 35 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 194 | 100| 17.5 | 10" | 160 | 4" |5/16" |Straight open| 196 | 300| 27.5 | | | | |belt. | 198 | 500| 40 | | | | | | 200 | 700| 55 | | | | | | 202 | 900| 70 | | | | | | 203 | 1000| 80 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 327 | 100| 20 | 10" | 18 | 4" |5/16" |Straight open| 328 | 1000| 80 | | | | |belt. | 393 | 100| 20 | | | | | | 394 | 1000| 100 | | | | | | 395 | 600| 60 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 405 | 100| 20 | 20" | 18 | 4" |9/32" |Straight open| 406 | 1000| 160 | | | | |belt. | 407 | 600| 100 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 428 | 100| 20 | 20" | 18 | 2" |9/32" |Straight open| 434 | 200| 25 | | | | |belt. | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 441 | 100| 25 | 20" | 950 | 2" |3/16" |Straight open| 447 | 200| 30 | | | | |belt. | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 453 | 100| 25 | 20" | 160 | 6" |7/32" |Crossed belt.|14' 6" between 454 | 500| 60 | | | | | |pulleys. 455 | 1000| 110 | | | | | |14' 6" bet. | | | | | | | |pul'ys. ------+-----+-------+-----+-----+-----+------+-------------+-------------- 459 | 100| 15 | 20" | 160 | 6" |7/32" |Straight open|14' 6" between 460 | 500| 25 | | | | |belt. |pulleys. 461 | 1000| 65 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 462 | 100| 25 | 20" | 160 | 6" |7/32" |Straight open|With 8" 463 | 500| 60 | | | | |belt. |tightener. 464 | 1000| 110 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 465 | 100| 45 | 20" | 160 | 6" |7/32" |Crossed belt.|8 feet between 466 | 500| 105 | | | | | |pulleys. 467 | 1000| 180 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 470 | 100| 25 | 20" | 160 | 6" |7/32" |Quarter turn | 471 | 500| 80 | | | | |belt on 16" | 472 | 750| 145 | | | | |diameter mule| 473 | 1000| 250 | | | | |pulleys. | 474 | 750| 170 | | | | | | 475 | 500| 110 | | | | | | 476 | 1000| 220 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 477 | 1000| 140 | 20" | 160 | 6" |7/32" |Quarter turn |Freshly oiled. 478 | 750| 100 | | | | |belt on 16" | 479 | 500| 70 | | | | |diameter mule| 480 | 100| 20 | | | | |pulleys. | 481 | 50| 60 | 20" | 160 | 6" |7/32" |Quarter turn |Belt rub. 482 | 25| 120 | | | | |on 16" mule |against low. | | | | | | |pulleys. |guide m. pul. ------+-----+-------+-----+-----+-----+------+-------------+-------------- 483 | 100| 20 | 20" | 160 | 6" |7/32" |Quarter turn |Well oiled, 484 | 500| 50 | | | | |on 16" mule |after a run of 485 | 750| 70 | | | | |pulleys. |2 hrs. at _T_ 486 | 1000| 105 | | | | | |+ _t_ = 100. ------+-----+-------+-----+-----+-----+------+-------------+-------------- 495 | 250| 30 | 20" | 160 | 6" |7/32" |Half turn | 496 | 500| 50 | | | | |belt on 16" | 497 | 750| 90 | | | | |mule pulleys.| 498 | 1000| 170 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 503 | 1000| 260 | 20" | 160 | 6" |7/32" |Quarter |10 feet 504 | 750| 190 | | | | |twist. |between 505 | 500| 130 | | | | | |pulleys. 506 | 250| 80 | | | | | | 507 | 100| 30 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 513 | 100| 50 | 20" | 160 | 6" |7/32" |Quarter |7' 6" between 514 | 250| 105 | | | | |twist. |pulleys. 515 | 500| 200 | | | | | | 516 | 750| 290 | | | | | | 517 | 1000| 380 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 523 | 100| 25 | 20" | 160 | 4" | 1/4" |Quarter |10 feet 524 | 250| 50 | | | | |twist. |between 525 | 500| 95 | | | | | |pulleys. 526 | 750| 145 | | | | | | 527 | 1000| 210 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 528 | 100| 65 | 20" | 160 | 4" | 1/4" |Quarter |6 feet between 529 | 250| 135 | | | | |twist. |pulleys. 530 | 500| 245 | | | | | | 531 | 750| 380 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 533 | 100| 25 | 20" | 160 | 6" |7/32" |Quarter |16' 6" between 534 | 250| 40 | | | | |twist. |pulleys. 535 | 500| 75 | | | | | | 536 | 750| 105 | | | | | | 537 | 1000| 165 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 539 | 1000| 130 | 20" | 160 | 6" |7/32" |Quarter twist|7' 6" between 540 | 750| 110 | | | | |with 16" |pulleys. 541 | 500| 90 | | | | |diameter | 542 | 250| 60 | | | | |carrying | 543 | 100| 40 | | | | |pulley. | 544 | 100| 30 | | | | | | 545 | 250| 55 | | | | | | 546 | 500| 90 | | | | | | 547 | 750| 120 | | | | | | 548 | 1000| 170 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- 569 | 100| 25 | 20" | 160 | 6" |7/32" |Straight open| 571 | 500| 55 | | | | |belt. | 572 | 750| 70 | | | | | | 573 | 1000| 90 | | | | | | ------+-----+-------+-----+-----+-----+------+-------------+-------------- The percentage of slip is the most important factor affecting the efficiency of belt transmission, but in addition to this we have journal friction, the resistance of the air, and with crossed belts the friction of the belt upon itself. These have been termed internal resistances, and their values for some of the most common arrangements of pulleys are given in Table VII. From this table it appears that the moment required to run a straight belt varies from 15 to 25 inch lbs. at 100 lbs. tension for all speeds. At 160 revolutions per minute and 1,000 lbs. tension, the required moment varied from 45 to 90 inch lbs., and at 18 revolutions per minute and at the same tension it varied from 80 to 150 inch lbs. From the average of these quantities we find the moment of resistance to be expressed by the following formulæ for straight open belts between 2" journals: At 160 r. p. m.: _M_ = .053_S_ + 14.7, (5.) At 18 r. p. m.: _M_ = .11_S_ + 9, (6.) in which _M_ = moment of resistance in inch lbs. _S_ = sum of tensions. When a crossed belt does not rub upon itself, the resistance is the same as for an open belt. The resistance offered by the introduction of carrying pulleys and tighteners is appreciable, and depends upon the pressure brought to bear against their journals. If the belt rubs against the flanges of the carrying pulleys, the resistance is very much increased, and this is often liable to occur in horizontal belts from a change of load. The friction on journals of carrying pulleys may be estimated by the formulæ already given if we substitute for _S_ the pressure against their journals. In the experiments which were made upon internal resistances, the greatest resistance was offered by a quarter-twist belt 6 feet between journals on 20-inch pulleys. The equation for this belt may be written: _M_ = .35_S_ + 58, (7.) but the introduction of a carrying pulley reduced the resistance to no more than what might be expected from the same number of journals with a straight belt. With quarter-twist belts the resistance lies chiefly in slip, which occurs as the belt leaves the pulleys, and this naturally depends upon the distance between journals in terms of the diameters of the pulleys. The effect of time upon the tension of the belt used in Table VIII. is plainly shown by experiments 588 to 613 inclusive, between which the pulleys remained at a fixed distance apart, and the belt slowly stretched from a tension of 380 to 280 lbs. To estimate the efficiency of belt transmission for an average case, we may assume 40 in. lbs. as the moment of internal resistance for a belt whose tension is 500 lbs. and 40 in. lbs. statical moment = about 20 ft. lbs. per revolution. If the belt is transmitting 400 lbs. with two per cent. of slip on 20 in. pulleys, then .02 × 400 × 5 = 40 ft lbs. are lost per revolution in slip, making a total loss of 60 ft. lbs. per revolution. TABLE VIII. SHOWING THE INCREASE IN THE SUM OF THE TENSIONS ON A VERTICAL BELT 4" WIDE BY 1/4" THICK, AND 24 FT. LONG, ON 20" CAST-IRON PULLEYS, AT 120 R. P. M. ------+---------+-----------+-----+-----+--------+---------+---------- No. of| Scales | Tension | | | Incre- |Percen'e | exper-+----+----+-----+-----+ | | m´nt |of Incre-| Date. im'nt.| A. | B. |_T_ +|_T_ -| _T_ | _t_ |of _T_ +| ment. | |[44]|[44]| _t_ | _t_ | | | _t_ | | ------+----+----+-----+-----+-----+-----+--------+---------+---------- 578 | 93 | 101| 194 | 16 |105 | 89 | 0 | |5-15-1885. 579 | 70 | 142| 212 | 144 |178 | 34 | 18 | | 580 | 67 | 170| 237 | 206 |221.5| 15.5| 43 | | 581 | 66 | 180| 246 | 228 |237 | 9 | 52 | | 582 | 66 | 188| 254 | 244 |249 | 5 | 60 | .323 | 583 | 91 | 101| 192 | 20 |106 | 86 | -2 | | ------+----+----+-----+-----+-----+-----+--------+---------+---------- 584 |202 | 210| 412 | 16 |214 |214 | 0 | |5-15-1885. 585 |167 | 250| 417 | 166 |292.5|292.5| 5 | | 586 |145 | 300| 445 | 310 |376.5|376.5| 33 | .171 | 587 |185 | 195| 380 | 20 |200 |200 | -32 | | ------+----+----+-----+-----+-----+-----+--------+---------+---------- 588 |190 | 199| 380 | 0 |190 |190 | 0 | |5-18-1885. 589 |133 | 250| 393 | 214 |303.5| 89.5| 13 | .033 | ------+----+----+-----+-----+-----+-----+--------+---------+---------- 590 |177 | 177| 354 | 0 |177 |177 | 0 | |5-19-1885. 591 |156 | 203| 359 | 94 |226.5|132.5| 5 | | 592 |138 | 235| 373 | 194 |283.5| 89.5| 19 | | 593 |135 | 250| 385 | 230 |307.5| 77.5| 31 | | 594 |128 | 275| 403 | 294 |348.5| 34.5| 49 | | 595 |125 | 300| 425 | 350 |387.5| 37.5| 71 | | 596 |123 | 325| 448 | 404 |426 | 22 | 94 | .333 | 597 |168 | 168| 336 | 0 |168 |168 | -18 | | ------+----+----+-----+-----+-----+-----+--------+---------+---------- 598 |143 | 143| 286 | 0 |143 |143 | 0 | |5-25-1885. 599 |140 | 148| 288 | 16 |152 |136 | 2 | | 600 |130 | 160| 290 | 60 |175 |115 | 4 | | 601 |122 | 170| 292 | 196 |194 | 98 | 6 | | 602 |116 | 180| 296 | 28 |212 | 84 | 10 | | 603 |112 | 190| 302 | 156 |229 | 73 | 16 | | 604 |108 | 200| 308 | 184 |246 | 62 | 22 | | 605 |105 | 210| 315 | 210 |262.5| 52.5| 29 | | 606 |102 | 220| 322 | 236 |279 | 43 | 36 | | 607 |100 | 230| 330 | 260 |295 | 35 | 44 | | 608 | 99 | 240| 339 | 282 |310.5| 28.5| 53 | | 609 | 98 | 250| 348 | 304 |326 | 22 | 62 | | 610 | 98 | 260| 358 | 316 |337 | 21 | 72 | | 611 | 99 | 270| 369 | 342 |355.5| 13.5| 83 | | 612 |100 | 280| 380 | 360 |370 | 10 | 94 | .357 | 613 |140 | 140| 280 | 0 |140 |140 | -6 | | ------+----+----+-----+-----+-----+-----+--------+---------+---------- [44] Scales A recorded the reduction of the load on the testing device for _vertical_ belts by the tension of the loose part of the belt (_t_). Scales B, by that of the tight side of the belt (_T_). The total power expended per revolution is about 2,000 ft. lbs., therefore .03 is lost. Under light loads, the internal resistance, which is nearly constant in amount, may be a large percentage of the power transmitted, while under heavy loads the percentage of slip may become the principal loss. It would be difficult to work out, or even to use, a general expression for the efficiency of belt transmission, but, from the foregoing, it would seem safe to assume that 97 per cent. can be obtained under good working conditions. When a belt is too tight, there is a constant waste in journal friction, and when too loose, there may be a much greater loss in efficiency from slip. The allowance recommended of 2 per cent. for slip is rather more than experiment would indicate for any possible crawl or creep due to the elasticity of the belt, but in connection with this, there is probably always more or less actual slip, and we are inclined to think that in most cases this allowance may be divided into equal parts representing creep and slip proper. Under good working conditions, a belt is probably stretched about 1 per cent. on the tight side, which naturally gives 1 per cent. of creep, and to this we have added another per cent. for actual slip in fixing the limit proposed. The indications and conclusions to be drawn from these experiments are: 1. That the coefficient of friction may vary under practical working conditions from 25 per cent. to 100 per cent. 2. That its value depends upon the nature and condition of the leather, the velocity of sliding, temperature, and pressure. 3. That an excessive amount of slip has a tendency to become greater and greater, until the belt finally leaves the pulley. 4. That a belt will seldom remain upon a pulley when the slip exceeds 20 per cent. 5. That excessive slipping dries out the leather and leads toward the condition of minimum adhesion. 6. That rawhide has much greater adhesion than tanned leather, giving a coefficient of 100 per cent. at the moderate slip of 5 ft. per minute. 7. That a velocity of sliding equal to .01 of the belt speed is not excessive. 8. That the coefficients in general use are rather below the average results obtained. 9. That when suddenly forced to slip, the coefficient of friction becomes momentarily very high, but that it gradually decreases as the slip continues. 10. That the sum of the tensions is not constant, but increases with the load to the maximum extent of about 33 per cent. with vertical belts. 11. That, with horizontal belts, the sum of the tensions may increase indefinitely as far as the breaking strength of the belt. 12. That the economy of belt transmission depends principally upon journal friction and slip. 13. That it is important on this account to make the belt speed as high as possible within the limits of 5,000 or 6,000 ft. per minute. 14. That quarter-twist belts should be avoided. 15. That it is preferable in all cases, from considerations of economy in wear on belt and power consumed, to use an intermediate guide pulley, so placed that the belt may be run in either direction. 16. That the introduction of guide and carrying pulleys adds to the internal resistances an amount proportional to the friction of their journals. 17. That there is still need of more light on the subject. CHAPTER XXXIII.--FORGING. FORGING.--The operation of forging consists in beating or compressing metal into shape, and may be divided into five classes, viz., hand-forging, drop-forging, machine-forging, forging under trip or steam hammers, and hydraulic forging. In purely hand forging much work is shaped entirely by hand tools, but in large shops much work is roughed out under trip or steam hammers, and finished by hand, while some work is finished under these hammers. In drop forging the work is pressed into shape by dead blows, which compress it into shape in dies or moulds. In machine forging the work is either formed by successive quick blows rather than by a few heavy ones, or in some machines it is compressed by rolling. In hydraulic forging the metal is treated as a plastic material, and is forced into shape by means of great and continuous pressure. In all forging the nature or quality of the iron is of primary importance; hence the following (which is taken from _The English Mechanic_), upon testing iron, may not be out of place. "The English Admiralty and Lloyds' surveyor's tests for iron and steel are as follows:-- "Two strips are to be taken from each thickness of plate used for the internal parts of a boiler. One-half of these strips are to be bent cold over a bar, the diameter of which is equal to twice the thickness of the plate. The other half of the strips are to be heated to a cherry-red and cooled in water, and, when cold, bent over a bar with a diameter equal to three times the thickness of the plate--the angle to which they bend without fracture to be noted by the surveyor. Lloyds' Circular on steel tests states that strips cut from the plate or beam are to be heated to a low cherry-red, and cooled in water at 82° Fahr. The pieces thus treated must stand bending double to a curve equal to not more than three times the thickness of the plate tested. This is severe treatment, and a plate containing a high enough percentage of carbon to cause any tempering is very unlikely to successfully stand the ordeal. Lloyds' test is a copy of the Admiralty test, and in the Admiralty Circular it is stated that the strips are to be one and a half inches wide, cut in a planing machine with the sharp edges taken off. One and a half inches will generally be found a convenient width for the samples, and the length may be from six to ten inches, according to the thickness of the plate. If possible, the strips, and indeed all specimens for any kind of experimenting, should be planed from the plates, instead of being sheared or punched off. When, however, it is necessary to shear or punch, the piece should be cut large and dressed down to the desired size, so as to remove the injured edges. Strips with rounded edges will bend further without breaking than similar strips with sharp edges, the round edges preventing the appearance of the small initial cracks which generally exhibit themselves when bars with sharp edges are bent cold through any considerable angle. In a homogeneous material like steel these initial cracks are apt to extend and cause sudden fracture, hence the advantage of slightly rounding the corners of bending specimens. [Illustration: Fig. 2824.] "In heating the sample for tempering it is better to use a plate or bar furnace than a smith's fire, and care should be taken to prevent unequal heating or burning. Any number of pieces may be placed together in a suitable furnace, and when at a proper heat plunged into a vessel containing water at the required temperature. When quite cold the specimens may be bent at the steam-hammer, or otherwise, and the results noted. The operation of bending may be performed in many different ways; perhaps the best plan, in the absence of any special apparatus for the purpose, is to employ the ordinary smithy steam-hammer. About half the length of the specimen is placed upon the anvil and the hammer-head pressed firmly down upon it, as in Fig. 2824. The exposed half may then be bent down by repeated blows from a fore-hammer, and if this is done with an ordinary amount of care it is quite possible to avoid producing a sharp corner. [Illustration: Fig. 2825.] "An improvement upon this is to place a cress on the anvil, as shown at Fig. 2825. The sample is laid upon the cress, and a round bar of a diameter to produce the required curve is pressed down upon it by the hammer-head. [Illustration: Fig. 2826.] "The further bending of the pieces thus treated is accomplished by placing them endwise upon the anvil-block, as shown in Fig. 2826. If the hammer is heavy enough to do it, the samples should be closed down by simple pressure, without any striking. [Illustration: Fig. 2827.] "Fig. 2827 is a sketch of a simple contrivance, by means of which a common punching machine may be converted temporarily into an efficient test-bending apparatus. The punch and bolster are removed, and the stepped cast-iron block A fixed in place of the bolster. When a sample is placed endwise upon one of the lower steps of the block A the descending stroke of the machine will bend the specimen sufficiently to allow of its being advanced to the next higher step, while the machine is at the top of its stroke. The next descent will effect still further bending, and so on till the desired curvature is attained. It would seem an easy matter, and well worth attention, to design some form of machine specially for making bending experiments; but with the exception of a small hydraulic machine, the use of which has, I believe, been abandoned on account of its slowness, nothing of the kind has come under the writer's notice. "The shape of a sample after it has been bent to pass Lloyds' or the Admiralty test is that of a simple bend, the sides being brought parallel. While being bent the external surface becomes greatly elongated, especially at and about the point of the convex side, where the extension is as much even as fifty per cent. This extreme elongation corresponds to the breaking elongation of a tensile sample, and can only take place with a very ductile material. While the stretching is going on at the external surface, the interior surface of the bend is being compressed, and the two strains extend into pieces till they meet in a neutral line, which will be nearer to the concave than to the convex curve with a soft specimen. When a sample breaks, the difference between the portions of the fracture which have been subject to tensile and compressive strains can easily be seen. [Illustration: Fig. 2828.] "Fig. 2828 shows a piece of plate folded close together; and this can generally be done with mild steel plates, when the thickness does not exceed half an inch. "Common iron plates will not, of course, stand anything like the foregoing treatment. Lloyds' test for iron mast-plates 1/2 inch thick, requires the plates to bend cold through an angle of 30° with the grain, and 8° across the grain; the plates to be bent over a slab, the corner of which should be rounded with a radius of 1/2 inch. [Illustration: Fig. 2829.] "When the sample of metal to be tested is of considerable thickness, as in the case of bars, it is often turned down in a lathe to the shape shown in Fig. 2829, so as to reduce its strength within the capacity of the machine. The part to be tested has usually a length between the shoulders of 8, 10, or 12 inches, and must be made exactly parallel with a cross-sectional area apportioned to the power of the machine and the strength of the material to be tested. When it is desired to investigate the elastic properties of materials, it is desirable to have the specimens of as great a length as the testing apparatus will accommodate. [Illustration: Fig. 2830.] [Illustration: Fig. 2831.] "Many of the early experiments on the tensile strength of wrought iron were made with very short specimens, such as in Fig. 2830, which is a sketch of that used formerly in the royal arsenal at Woolwich. This had no parallel length for extension at all, its smallest diameter occurring at one only point. Mr. Kirkaldy, to whom is due in a great measure the honour of having raised 'testing' to an exact science, discovered that this form of specimen gave incorrect results. He found that experiments with such specimens, more especially when the metals were ductile, gave higher breaking strains than were obtained with specimens of equal cross-sectional area having the smallest diameter parallel for some inches of length. This was due to the form of the specimen resisting to some extent the 'flow' or alteration of shape which occurs in soft ductile materials previous to fracture. He accordingly commenced to use a specimen of the form shown in Fig. 2831, with a parallel portion for extension of several inches in length, and specimens like that in Fig. 2830 became a thing of the past. "The specimens shown in the figures admit of being secured in the testing machine in many different ways. But whatever description of holder be employed, two absolute requirements must be kept in view. The holders must be stronger than the sample, and they must transmit the stress in a direction parallel to the axis of the sample without any bending or twisting tendency. [Illustration: Fig. 2832.] "Fig. 2832 gives two views of a very effective method of holding round specimens, used by Mr. Kirkaldy in his earlier experiments carried out for Messrs. Napier & Sons, of Glasgow. The enlarged ends of the samples are clasped in split sockets provided with eye-holes for attaching them to the shackles of the testing machine, the halves of the sockets being held together during the experiment by small bolts passing through the projecting lugs. [Illustration: Fig. 2833.] "Fig. 2833 explains the plan adopted for testing the strength of bolts and nuts in the same series of experiments. [Illustration: Fig. 2834.] "A good holder for lathe-turned samples is shown in Fig. 2834. Close fitting socket-pieces _b_ _b_ embrace each end of the specimen, and also the turned collar at the extremity of the shackle _a_. The halves of the socket are held together by a collar _c_, the interior of which and exterior of the socket rings are turned to an equal taper, so that the socket-pieces are held quite firmly when the collar _c_ is simply slipped over them by hand. When the experiment is over, a few taps with the hammer will remove the collar _c_. [Illustration: Fig. 2835.] "Samples of plates for tensile testing are usually shaped like Fig. 2835. The parallel portion B is generally 8, 10, or 12 inches long, as in the case of the turned specimens. Two minor points in the preparation of specimens may be here alluded to. In the first place the holes _a_ _a_ must be made large enough to obviate any danger of the pins which are placed in these holes to secure the specimen being sheared in two before the specimen breaks. In the second place, enough material must be left around these pin or bolt holes to prevent the probability of the metal tearing away between the hole and the edge of the plate. The pin holes must be placed exactly in a line with the axis of the specimen, and the part B must be quite parallel in width, so that the strength (and the elongation during the testing) may be, as nearly as possible, equal throughout the length of B. The shoulders, as _c_, should be easy curves, so that sharp corners may be avoided. When a number of such specimens are required at the same time, the strips of plate may be clamped together and planed or slotted to the desired width as one piece, but the tool marks should be afterwards removed by careful draw-filing. "When the plates are thin, small side pieces are riveted on the sides of the ends to be clamped, as shown in Fig. 2836. These stiffen those ends and afford a larger bearing for the securing pins. The connection with the shackles is made by means of steel pins passing through the end holes, and when specimens like 2835 are properly prepared, the direction of the stress on them must be in a line with their axis. Fig. 2837 shows another form of plate specimen in which the holes are dispensed with, the ends being held in the machine by friction clips, as shown. These specimens are more easily prepared, and from the absence of holes may be made of a very narrow strip of plate. [Illustration: Fig. 2836.] [Illustration: Fig. 2837.] "In Fig. 2837 the jaws or forked arms of the shackle are closed to form a rectangular ring, as shown in section in the figure. Two of the interior faces are tapered inwards to the same angle as the back of the wedges or clips _a a´_, which are perfectly smooth and free to slide upon the inclined or tapered surfaces of the shackles. The faces of the wedges, however, which come in contact with and grip the specimen to be tested, as _b_, are fluted or grooved, so that the friction of the edges against the specimen is much greater than against the inside surfaces of the shackles. The result of the arrangement is, that when the shackles are pulled, the wedges _a a´_ are tightened against the specimen with a degree of force proportionate to the load on the specimen, which is prevented from slipping through the clips by the 'bite' of their fluted faces. The grooves on the faces of the clips need not be deep--a depth of a little more than 1/16, with about the same distance apart, answering well for ordinary loads. With deep grooves and a wider pitch apart, the danger of the specimen breaking in the clips is increased. The inclination of the backs of the wedges _a a´_ to the faces may be at an angle of 5 or 6 degrees. When the taper is too small, the removal of the halves of the specimen after breaking is sometimes difficult, while on the other hand, when too great, the specimen is apt to slip between the wedges while being tested. The wedges exert a very considerable outward pressure, and the jaws of the shackles must be made strong enough to resist any strain likely, under extreme conditions, to fall on them, otherwise they will speedily become unfit for use. In securing a specimen care must be taken that its axis is in the direct line of strain, and the opposite clips should be driven in equally so that the stress may act fairly upon it. Parallel planed strips of metal, without any enlargement at the ends, may be tested in these friction clips, though, of course, there is a chance of the specimen breaking within them. Turned specimens may also be held by such clips; as also may rough, unturned round and square bars, an advantage when it is desired to immediately ascertain approximately the strength of metal samples." Open fires for hand forging purposes are mainly of two classes, those having a side and those with a bottom or vertical blast. [Illustration: Fig. 2838.] Fig. 2838 represents a side draft forge. F is the fireplace, usually from 3 to 5 feet long, T is the tuyère through which the blast enters the fire, B being the blast pipe. To prevent T from being burned away it is hollow as at S, and two pipes P and P´ connect to the water-tank W, thus maintaining a circulation of water through S; V is simply a valve or damper to shut off the supply of air from the tuyère; D is the opening to the chimney C. The side blast, though not so much used as in former years, is still preferred by many skilful mechanics, on the ground that it will give a cleaner fire with less trouble. The method of accomplishing this is to dig out a hole in the fire bed and fill it in with coked coal, which will form a drain through which the slag or clinker may sink, instead of remaining in the active fire and obstructing the blast. In cases where the fire requires to be built farther out from the chimney wall than the location of the tuyère permits, it may be built out as follows:-- [Illustration: Fig. 2839.] [Illustration: Fig. 2840.] A bar B, Fig. 2839, is placed in the tuyère hole and supported at the other end at P. The coal is well wetted and packed around and above the bar, which is then pulled out endwise, leaving a blast hole through the coal, as is shown in the end view Fig. 2840. [Illustration: Fig. 2841.] Fig. 2841 represents a patent tuyère of vertical or bottom draft, in which the blast passes through pipe A and circulates around B, finding egress at C into the fire. C is hollow and receives water from the tank F by the pipe D. The steam generated in the nozzle C is conveyed to the tanks by the pipe E. Figs. 2842 and 2843 represent a blacksmith's forge, for work up to and about 4 inches in diameter. It consists of a wind-box A, supported on brickwork which forms an ash-pit G beneath it. To this box is bolted the wind-pipe B, and at its bottom is the slide E. In an orifice at the top of A is a triangular and oval breaker D, connected to a rod operated by the handle C. This rod is protected from the filling which is placed between the brickwork and the shell F of the forge by being encased in an iron pipe I. The blast passes up around the triangular oval piece D. The operation is as follows: when D is rotated, it breaks up the fire and the dirt falls down into the wind-box, cleaning the fire while the heat is on. At any time after a heat the slide E may be pulled out, letting the slag and dirt fall into the ash-pit beneath. It is a great advantage to be able to clean the fire while a heat is on without disturbing the heat. [Illustration: Fig. 2842.] [Illustration: Fig. 2843.] Blacksmiths' anvils are either of wrought iron steel faced, or of cast iron steel faced, the faces being hardened. It is sometimes fastened to the block by spikes driven in around the edges. A better plan, however, is to make the block the same size as the anvil, and secure the latter by two bands of iron and straps, as shown in Fig. 2844, because in this way the block will not come in the way of arms or projecting pieces that hang below the anvil. The square hole is for receiving the stems of swages, fullers, &c., and for placing work over to punch holes through it, and the round is used for punching small holes. The proper shape for blacksmiths' tongs depends upon whether they are to be used upon work of a uniform size and shape, or upon general work. In the first case, the tongs may be formed to exactly suit the special work. In the second case, they must be formed to suit as wide a range of work as convenient. Suppose, for example, the tongs are for use on a special size and shape of metal only; then they should be formed so that the jaws will grip the work evenly all along, and therefore be straight along the gripping surface. It will be readily perceived, however, that if such tongs were put upon a piece of work of greater thickness, they would grip it at the inner end only, and it would be impossible to hold the work steady. The end of the work would act as a pivot, and the part on the anvil would move about. It is better, therefore, for general work to curve the jaws, putting the work sufficiently within the jaws to meet them at the back of the jaw, when the end will also grip the work. By putting the work more or less within the tongs, according to its thickness, contact at the end of the work and at the point of the tongs may be secured in one pair of tongs over a wider range of thickness of work than would otherwise be the case. This applies to tongs for round or other work equally as well as to flat or square work. To maintain the jaw pressure of the tongs upon the work, a ring is employed, the tong ends being curved to prevent the ring from slipping off. After a piece of work has left the fire it should, if there are scales adhering upon it, have them cleaned off before being forged, for which purpose the hammer head or an old file is used, otherwise the forging will not be smooth, and the scale will be hammered into the surface. This will render the forging very hard to operate upon by steel cutting tools, and cause them to dull rapidly. For the same reason it is proper to heat a finished forging to a low red heat and pass a file over its surface, which will leave the forging soft as well as free from scale. A forging should not be finally finished by being swaged or forged after it has become black hot, because it produces a surface tension that throws the work out of true as the metal is cut away in finishing it. Work to be drawn out is treated according to the amount of elongation and reduction of diameter required. Thus, suppose a piece of square work to require to be drawn out, then it is hammered on its respective sides, being turned upon the anvil so that each successive side shall receive the hammer blows. It is essential, however, that the piece be forged square, or in other words, that during the forging the sides be kept at a right angle one to the other, or else the work will hammer hollow, as it is termed; that is to say, the iron will split at the centre of the bar, which occurs from its being forged diamond-shaped instead of square. If a piece required to be forged diamond-shaped, it must be forged square until reduced to such dimensions as will leave sufficient to draw out while altering its form from the square to the diamond-shape. In very small work, which is more apt to hammer hollow than large work, the end of the piece is left of enlarged size, as shown in the figure, the strength of the enlarged end serving to prevent the hammering hollow, which usually begins at the end of the piece; the end is in this case forged last. In the case of round work the same rule holds good, inasmuch as that a round bar may be forged smaller to some extent, either by hammer blows or by swaging, but if the forging by hammer blows be excessive, hammering hollow is liable to ensue. The blacksmith's set of chisels consists of a hot chisel for cutting off hot iron, a cold chisel for cutting cold metal, a hardy, which sets in the square hole in the anvil, [C]-chisels, which are curved somewhat like the carpenter's gouge, and a cornering or [V]-chisel, in which the cutting edges are at a right angle one to the other. [Illustration: Fig. 2844.] The hot chisel has its edge well curved in its length, and is kept cool by lifting it from the work after each hammer blow, and by occasionally dipping it in water. Lifting it also prevents it from wedging in the work. The cold chisel is tempered to a blue, and answers virtually to the machinist's chisel. The hardy is used for small work, which is laid upon it and struck with the hammer. The [C]-chisel is used, not only in curved corners, but also to cut off deep cuts, answering, like the cape or cross-cut chisel of the machinist, to relieve the corners of the hot chisel. The cornering chisel is used for square corners, situated so that the hot chisel cannot be used. The blacksmith's punch is made well taper, so that it shall not wedge in the hole it produces. For large holes a small punch is first used, and the hole enlarged in diameter by driving in punches of larger diameter. If this swells the work at the sides, it is forged down while the punch is in the hole. The first blow given to the punch is a light one, so as to leave an indentation that will mark the location, and enable its easy correction if necessary. The blows delivered after the correct location is indented are quick and heavy; but a piece of soft coal is inserted and the punch placed on top of it, the gases formed by the combustion of the coal serving to prevent the punch from binding in the hole. Between the blows the blacksmith lifts the punch and moves the handle part of a lateral rotation, which prevents it from becoming fast in the hole. The punch should not be suffered to get red hot, but must be removed and cooled, a fresh piece of green soft coal being inserted in the hole just previous to the punch. If the punch is allowed to become as heated as the work, the end will "upset" or swell and become firmly locked. Should the punch lock in the hole a few blows will usually loosen it, but in extreme cases it is sometimes necessary to employ another punch from the opposite side of the work. Unless in very thin work, the hole is punched half way from each side, because by that means a short stout punch may be used. It is obvious that when the hole requires to be bell-mouthed or of any other form, the punch must be made to correspond. The tools employed by the blacksmith, other than tongs, hammers, chisels, and punches, are composed mainly of "fullers" and "swages" of various kinds. The fuller is essentially a spreading tool, while the swage may be termed essentially a shaping one. [Illustration: Fig. 2845.] In Fig. 2845, for example, let A represent an end view of an anvil, B the bottom, and C the top fuller, and the effects of blows upon C will be mainly to stretch the piece in the direction of its length without swelling it out sideways. [Illustration: Fig. 2846.] [Illustration: Fig. 2847.] [Illustration: Fig. 2848.] [Illustration: Fig. 2849.] If the work requires to be swelled sideways we turn the fuller the other way around, as in Fig. 2846, in which it is supposed that one side of the work is to be kept flat, hence no bottom fuller is employed. The action of a fuller may be increased in the required direction by leaning in the direction in which we desire to drive the iron; thus, suppose we require to spread the end of a rectangular bar from the full lines to the dotted ones in Fig. 2847 and the first fuller across the piece as at A, Fig. 2848, and then spread out the end by fullering, as in Fig. 2849, inclining the fuller in the direction in which we desire to forge the iron. [Illustration: Fig. 2850.] It is the roundness of the face of the fuller that serves to control the direction in which it will drive the iron, since the curve acts somewhat on the principle of a wedge. Suppose, for example, that the faces were flat, as in Fig. 2850, and the iron would spread in both directions, the same as though the hammer were used direct, and if the work were intended to be kept parallel it would frequently require to be turned on edge to forge down the bulge that would form on the edge. [Illustration: Fig. 2851.] Fullers are, however, also used as finishing tools for curves or corners, an example being given in Fig. 2851, which represents a fuller applied to finish the round corner of a collar. [Illustration: Fig. 2852.] [Illustration: Fig. 2853.] [Illustration: Fig. 2854.] For finishing plane surfaces the flatter shown in Fig. 2852 is employed, W representing the work. For inside surfaces the flatter requires to be offset, as in Fig. 2853, in which L represents a link whose face A may be flattened by the flatter F. There is a tendency in this case for the flatter to tip or cant; and to avoid this and regulate the flatter upon the work, a side foot is sometimes added, as at A in Fig. 2854. Swages are shaped according to the kind of work they are to be used for. [Illustration: Fig. 2855.] [Illustration: Fig. 2856.] Fig. 2855, for example, represents a top and bottom swage for rounding up iron. For general work the recesses or seats of such swages would be made considerably oval, as in Fig. 2856, the work being revolved slightly after each blow. This capacitates one swage for different sizes of iron. When, however, a swage is to be used for one particular size only, its cavity may be made more nearly a true half circle and may envelop one half the diameter of the work, so that when the top and bottom swages meet, the work will be known to be of the required diameter without measuring it. If the seat were made a true half circle it would lock upon the work, preventing the smith from revolving it and making it difficult to remove the swage. [Illustration: Fig. 2857.] If the conditions are such that a swage must be used to perform forging rather than finishing, its seat should be [V]-shaped and not curved. Suppose, for example, that a piece of iron, say, 6 inches in diameter, required a short section to be forged down to a diameter of 3 inches, then the swages should be formed as in Fig. 2857, because otherwise the effects of the blow will act to a certain extent to force the iron out sideways, for reasons which will be explained presently. [Illustration: Fig. 2858.] [Illustration: Fig. 2859.] [Illustration: Fig. 2860.] In some cases, for small work, the upper swage is guided by the lower one: thus, in Fig. 2858 is a swage for a cross piece, and the outside of its base is squared and fits easily within the upper part of the lower one shown in Fig. 2859. For very small work, on which the hand hammer is sufficiently heavy to perform the swaging, a spring swage may be use: thus, in Fig. 2860 is a swage for pieces of 3/8, 5/16, and 1/4 inch in diameter, and having a square stem fitting into the square hole in the anvil. Fig. 2861 represents a spring swage for a pin having a collar, and it may be observed that the recess to form the collar must be tapered narrowest at the bottom, so that the top swage will readily release itself by the force of the spring, and so that the work may easily be revolved in the lower one. A similar tool is shown in Fig. 2862, designed for punching sheet metal cold, the die D being changeable for different sizes of punches P. [Illustration: Fig. 2861.] [Illustration: Fig. 2862.] [Illustration: Fig. 2863.] For large hand-made forgings the swage block, such as in Fig. 2863, is employed, S representing a stand for the block, whose dimensions are larger than the block, so that the latter may be rested on its face in the stand when the holes are to be used. [Illustration: Fig. 2864.] Fig. 2864 represents a swage block mounted on bearers, so that it may be revolved to bring the necessary cavity uppermost. [Illustration: Fig. 2865.] [Illustration: Fig. 2866.] [Illustration: Fig. 2867.] Swages for trip hammers or for small steam hammers are for work not exceeding about 4 inches in diameter, made as in Fig. 2865, the weight of the top swage being sufficient to keep the two closed as in the figure; for larger sizes the bottom swage fits to the anvil, and the top one is provided with a handle, as in Fig. 2866, B representing the anvil block, S´ the bottom, and S the top swage, having a handle H. The flange of the bottom swage is placed as in Fig. 2867, so as to prevent the swage from moving off the anvil block when the work is pushed through it endways. Obviously such swages are employed when the part to be swaged is less in length than the width of the hammer or of the anvil face. If the hammer and anvil face is rounded as in Fig. 2868, or if dies thus shaped are placed in them, their action will be the same as that of the fuller, drawing the work out lengthways, with a minimum of effect in spreading it out sideways. Detached fullers, such as shown in Figs. 2869 and 2870, are, however, used when the section to be acted upon is less in length than the hammer face. In the case of trip hammers, steam hammers, &c., blocks fitted to the hammer and anvil block may take the place of detached swages and fullers. Thus, in Fig. 2871 is represented the hammer and anvil block for flat work, the corners being made rounded, because if left sharp they would leave marks on the work. The blocks or dies A and B are dovetailed into their places, and secured by keys K; hence they may be removed, and dies of other shapes substituted. When the work is parallel it may be forged to its finished dimensions by forming in the lower die recesses whose depth equals the required dimensions. Thus, in Fig. 2872 the recess A in the lower die equals in depth the depth A of the work, while the depth of the recess B in the die equals the thickness of the bar; hence by passing the work successively from A to B, and turning it over a quarter turn, it will be made to finished size, when the faces C D of the dies meet. For this class of work the recesses must obviously be made in the lower die, because it would be difficult to hold the work upon the lower die in the proper position to meet a recess cut in the upper one: and, furthermore, the recesses in the die should be wider than the work, to avoid the necessity of holding the work exactly straight in the recess, and keeping it against the shoulder or vertical face of the recess. If, however, the work is to be made taper, we may obviously make the recess taper, so as to produce smooth work, the die recess being made to be of the correct depth for the smallest end of the work. [Illustration: _VOL. II._ =EXAMPLES IN STEAM HAMMER WORK.= _PLATE XV._ Fig. 2868. Fig. 2869. Fig. 2870. Fig. 2871. Fig. 2872. Fig. 2873. Fig. 2874. Fig. 2875. Fig. 2876. Fig. 2877. Fig. 2878.] When the shape of the work is such that it cannot be moved upon the die during the forging, the operation is termed stamping, or if the hammer or upper die falls of its own weight it is termed drop forging, and in this case the finishing dies are made the exact shape of the work, care being taken to let the work be enveloped as much as possible by the bottom die, so that the top one shall not lift it out on its up stroke. In forging large pieces from square to round we have several important considerations. In order to keep the middle of the work sound, it must be drawn square to as near as possible the required diameter before the finishing is begun. During this drawing-down process the blows are heavy and the tendency of the work is to spread out at the sides, as in Fig. 2873. When the work is ready to be rounded up it is first drawn to an octagon, as shown in Fig. 2874, so as to bring it nearer the work, nearer to cylindrical form. The corners are then again hammered down, giving the work sixteen sides, the work during this part of the process being moved endways, as each corner is hammered down. The blows are during this part of the forging lighter, but still the tendency is to spread the work out sideways. The final finishing to cylindrical form is done with light blows, the work being revolved upon the anvil without being moved endways, so that a length equal to the width of the anvil is finished before the work is moved endways to finish a further part of the length. The tendency to spread sideways is here unchecked, because the iron is squeezed top and bottom only. We may check it to some extent, however, by employing a bottom swage block, as in Fig. 2875, in which case the contact of the swage and the work will extend further around the work circumference than would be the case with a flat anvil. If we were to use a top and a bottom swage, as in Fig. 2876, the circumferential surface receiving the force of the blow will be still further increased, but there will still be a tendency to spread at the sides, as at A B, in Fig. 2876. A better plan, therefore, is to use a [V]-block with the hammer, as in Fig. 2877, in which case the effects of the blow are felt at A, B, and C, and the points A B of resistance being brought higher up on the work, its tendency to spread is obviously diminished. By using a top and bottom [V]-block, as shown in Fig. 2878, the effect will be to drive the metal towards the centre, and, therefore, to keep it sound at the centre, it being found that if the metal is swaged much without means being taken to prevent spreading, it "hammers hollow," as it is termed, or in other words, splits at its centre. [Illustration: Fig. 2879.] The points A B of resistance to the blow at C are higher and the tendency to spread sideways is better resisted. For cutting off under the steam hammer, the hack shown in Fig. 2879 is used, being simply a wedge with an iron handle. WELDING.--In the welding operations of the blacksmith there are points demanding special attention: first, to raise the temperature of the metal to a proper heat; second, to let the temperature be as nearly equal as practicable all through the mass; third, to have the surfaces to be welded as clean and free from oxidation as possible; fourth, have the parts to be welded of sufficient diameter or dimensions to permit of the welded joint being well forged. The following remarks on the theory of welding are from a paper read by Alexander L. Holley before the American Institute of Mining Engineers:-- "The generally received theory of welding is that it is merely pressing the molecules of metal into contact, or rather into such proximity as they have in the other parts of the bar. Up to this point there can hardly be any difference of opinion, but here uncertainty begins. What impairs or prevents welding? Is it merely the interposition of foreign substances between the molecules of iron, or of iron and any other substance which will enter into molecular relations or vibrations with iron? Is it merely the mechanical preventing of contact between molecules, by the interposition of substances? This theory is based on such facts as the following: "1. Not only iron but steel has been so perfectly united that the seam could not be discovered, and that the strength was as great as it was at any point, by accurately planing and thoroughly smoothing and cleaning the surfaces, binding the two pieces together, subjecting them to a welding heat, and pressing them together by a very few hammer blows. But when a thin film of oxide of iron was placed between similar smooth surfaces, a weld could not be effected. "2. Heterogeneous steel scrap, having a much larger variation in composition than these irons have, when placed in a box composed of wrought-iron side and end pieces laid together, is (on a commercial scale) heated to the high temperature which the wrought-iron will stand, and then rolled into bars which are more homogeneous than ordinary wrought iron. The wrought-iron box so settles together as the heat increases that it nearly excludes the oxidizing atmosphere of the furnace, and no film of oxide of iron is interposed between the surfaces. At the same time the enclosed and more fusible steel is partially melted, so that the impurities are partly forced out and partly diffused throughout the mass by the rolling. "The other theory is that the molecular motions of the iron are changed by the presence of certain impurities, such as copper and carbon, in such a manner that welding cannot occur, or is greatly impaired. In favor of this theory it may be claimed that, say, 2 per cent. of copper will almost prevent a weld, while, if the interposition theory were true, this copper could only weaken the weld 2 per cent., as it could only cover 2 per cent. of the surfaces of the molecules to be united. It is also stated that 1 per cent. of carbon greatly impairs welding power, while the mere interposition of carbon should only reduce it 1 per cent. On the other hand, it may be claimed that in the perfect welding due to the fusion of cast iron, the interposition of 10 or even 20 per cent. of impurities, such as carbon, silicon, and copper, does not affect the strength of the mass as much as 1 or 2 per cent. of carbon or copper affects the strength of a weld made at a plastic instead of a fluid heat. It is also true that high tool steel, containing 1-1/2 per cent. of carbon is much stronger throughout its mass, all of which has been welded by fusion, than it would be if it had less carbon. Hence copper and carbon cannot impair the welding power of iron in any greater degree than by their interposition, provided the welding has the benefit of that perfect mobility which is due to the fusion. The similar effect of partial fusion of steel in a wrought-iron box has already been mentioned. The inference is, that imperfect welding is not the result of a change in molecular motions due to impurities, but of imperfect mobility of the mass--of not giving the molecules a chance to get together. "Should it be suggested that the temperature of fusion, as compared with that of plasticity, may so change chemical affinities as to account for the different degrees of welding power, it may be answered that the temperature of fusion in one kind of iron is lower than that of plasticity in another, and that as the welding and melting points of iron are largely due to the carbon they contain, such an impurity as copper, for instance, ought, on this theory, to impair welding in some cases and not to affect it in others. "The obvious conclusions are: 1st. That any wrought iron, of whatever ordinary composition, may be welded to itself in an oxidizing atmosphere at a certain temperature, which may differ very largely from that one which is vaguely known as 'a welding heat.' 2nd. That in a non-oxidizing atmosphere heterogeneous irons, however impure, may be soundly welded at indefinitely high temperatures. "The next inference would be that by increasing temperature we chiefly improve the quality of welding. If temperature is increased to fusion, welding is practically perfect; if to plasticity and mobility of surfaces, welding should be nearly perfect. Then how does it sometimes occur that the more irons are heated the worse they weld? "1. Not by reason of mere temperature, for a heat almost to dissociation will fuse wrought iron into a homogeneous mass. "2. Probably by reason of oxidation, which, in a smith's fire especially, necessarily increases as the temperature increases. Even in a gas furnace a very hot flame is usually an oxidizing flame. The oxide of iron forms a dividing film between the surfaces to be joined, while the slight interposition of the same oxide, when diffused throughout the mass by fusion or partial fusion, hardly affects welding. It is true that the contained slag, or the artificial flux, becomes more fluid as the temperature rises, and thus tends to wash away the oxide from the surfaces; but inasmuch as any iron with any welding flux can be oxidized till it scintillates, the value of a high heat in liquefying the slag is more than balanced by its damage in burning the iron. "But it still remains to be explained why some irons weld at a higher temperature than others; notably, white irons high in carbon, or in some other impurities, can only be welded soundly by ordinary processes at low heats. It can only be said that these impurities, as far as we are aware, increase the fusibility of iron, and that in an oxidizing flame oxidation becomes more excessive as the point of fusion approaches. Welding demands a certain condition of plasticity of surface; if this condition is not reached, welding fails for want of contact due to mobility; if it is exceeded, welding fails for want of contact due to excessive oxidation. The temperature of this certain condition of plasticity varies with all the different compositions of irons. Hence, while it may be true that heterogeneous irons, which have different welding points, cannot be soundly welded to one another in an oxidizing flame, it is not yet proved, nor is it probable, that homogeneous irons cannot be welded together, whatever their composition, even in an oxidizing flame. A collateral proof of this is, that one smith can weld irons and steels which another smith cannot weld at all, by means of a skilful selection of fluxes and a nice variation of temperatures. "To recapitulate. It is certain that perfect welds are made by means of perfect contact due to fusion, and that nearly perfect welds are made by means of such contact as may be got by partial fusion in a non-oxidizing atmosphere or by the mechanical fitting of surfaces, whatever the composition of the iron may be within all known limits. While high temperature is thus the first cause of that mobility which promotes welding, it is also the cause, in an oxidizing atmosphere, of that 'burning' which injures both the weld and the iron. Hence, welding in an oxidizing atmosphere must be done at a heat which gives a compromise between imperfect contact due to want of mobility on the one hand, and imperfect contact due to oxidation on the other hand. This heat varies with each different composition of irons. It varies because these compositions change the fusing points of irons, and hence their points of excessive oxidation. Hence, while ingredients such as carbon, phosphorus, copper, &c., positively do not prevent welding under fusion, or in a non-oxidizing atmosphere, it is probable that they impair it in an oxidizing atmosphere, not directly, but only by changing the susceptibility of the iron to oxidation." In welding steel to iron both are heated to as high a temperature as possible without burning, and a welding compound or flux of some kind is used. In welding steel to steel the greatest care is necessary to obtain as great a heat as possible without burning, and to keep the surfaces clean. An excellent welding compound is composed as follows: Copperas 2 ozs., salt 4 ozs., white sand 4 lbs., the whole to be mixed and thrown upon the heat, as is done when using white sand as described for welding iron. An equally good compound is made up of equal quantities of borax and pulverized glass, well wetted with alcohol, and heated to a red heat in a crucible. Pulverize when cool, and apply as in the case of sand only. A welding compound for cast steel given by Mr. Rust in the _Revue Industrielle_ is made up as follows: 61 parts of borax, 20 parts of sal-ammoniac, 16-3/4 parts of ferrocyanide, and 5 parts of colophonium. He states that with the acid of this compound cast steel may be welded at a yellow red heat, or at a temperature between the yellow, red, and white heats. The borax and sal-ammoniac are powdered, mixed, and slowly heated until they melt. The heating is continued until the strong odor of ammonia ceases almost entirely, a small quantity of water being added to make up for that lost by evaporation. The powdered ferrocyanide is then added, together with the colophonium, and the heating is continued until a slight smell of cyanogen is noticed. The mixture is allowed to cool by spreading it out in a thin layer. [Illustration: Fig. 2880.] [Illustration: Fig. 2881.] The lap weld is formed as follows: Suppose it is required to weld together the ends of two cylindrical pieces, and the first operation is to pump or upset the ends to enlarge them, as shown in Fig. 2880, so as to allow some metal to be hammered down in making the weld without reducing the bar below its proper diameter. The next operation is to scarf the ends forming them, as shown in Fig. 2881, and in doing this it is necessary to make the scarf face somewhat rounding, so that when put together as in the figure contact will occur at the middle, and the weld will begin there and proceed as the joint comes together under the blows towards the outside edges. This squeezes out scale or dirt, and excludes the air, it being obvious that if the scarf touched at the edges first, air would be enclosed that would have to find its escape before the interior surfaces could come together. It is obvious, that if the two pieces require to weld up to an exact length and be left parallel in diameter when finished an allowance for waste of iron must be made; and a good method of welding under these conditions is as follows:-- [Illustration: Fig. 2882.] [Illustration: Fig. 2883.] Let the length of the two pieces be longer than the finished length to an amount equal to the diameter. Then cut out a piece as at A, in Fig. 2882, the step measuring half the diameter of the bar as shown. The shoulder A is then thrown back with the hammer, and the piece denoted by the dotted line B is cut off, leaving the shaft as shown in Fig. 2883. The faces of the scarf should be somewhat rounding, so that when the weld is put together contact will take place in the centre of the lapping areas. Then, as the surfaces come together, the air and any foreign substances will be forced out, whereas, were the surfaces hollow the air and any cinder or other foreign substances would be closed in the weld, impairing its soundness. The lap of the two pieces, when scarfed in this manner, is shown in Fig. 2884. [Illustration: Fig. 2884.] To take the welding heat the fire should be cleaned out and clear coked coal, and not gaseous coal, used. The main points in a welding heat are, to heat the iron equally all through, to obtain the proper degree of heat, and to keep the scarfed surfaces as free from oxidation, and at the same time as clean, as possible. To accomplish these ends the iron must not be heated too quickly after it is at a good red heat, and the fire must be so made that the blast cannot meet it at any point until it has passed through the bed of the fire. When the iron is getting near the welding heat it may be sprinkled with white sand, which will melt over it and form a flux that will prevent oxidation and cool the exterior, giving time to the interior to become equally heated. The sand should be thrown on the work while in the fire, as removing the work from the fire causes it to oxidize or scale rapidly. The work should be turned over and over in the fire, the scarf face being kept uppermost until the very last part of the heating, when the blast must be put on full, the bed of the fire kept full and clear so that there shall be sufficient bed to prevent the blast from meeting the heat until it has passed through the glowing coals. When the heat is taken from the fire it should meet the anvil with a blow, the scarfed face being downwards, to jar off any dirt, cinder, &c., and the scarf should be cleaned by a stroke or two of a wire brush. But as every instant the iron is in the air it is both cooling and oxidizing, these operations must be performed as quickly as possible. The two scarfs being laid together as shown in Fig. 2884, the first blows must be delivered lightly, so as not to cause the upper piece to move, and as quickly as possible, the force of the blows being increased regularly and gradually until the weld is sufficiently firm to hold well together, when it may be turned on edge and the edges of the scarf hammered to close and weld the seam. If this turning is done too soon, however, it may cause the two halves to separate. When the weld is firmly and completely made the enlarged diameter due to the scarfing may be forged down, working the iron as thoroughly as possible. [Illustration: Fig. 2885.] [Illustration: Fig. 2886.] To form the scarf of a ring or collar, one end is bevelled, as at B in Fig. 2885 and after the piece is bent to a circle it is cut off and bevelled as at A. When a slight band is to be welded, and it is difficult to steady the ends to bring them together, a clamp may be used to hold them as in Fig. 2886. [Illustration: Fig. 2887.] Fig. 2887 represents a tongue weld, and it is obvious that to insure soundness the wedge piece should fit in the bottom of the split, which may be well closed upon it by the hammer blows. [Illustration: Fig. 2888.] Fig. 2888 represents an example of a [V]-weld applied to welding up a band that is to be square when finished, and as the lengths of the sides must be equal when finished, the side on which the weld is made should be made shorter, so that in stretching under the welding blows it will be brought to its proper length. The [V] form of weld is employed because it stretches less in welding than the lap weld. The [V]-piece to be welded in should bear at the bottom of the [V], and the weld made by fullering. [Illustration: Fig. 2889.] [Illustration: Fig. 2890.] Welds of this kind are obviously most suitable for cases in which the weld is required to influence the shape of the piece as little as possible. The figures above, which are taken from _Mechanics_, illustrate as an example the repairing of a broken strap for the beam of a river steamboat. The crack is at A, Fig. 2889, and is held together by a clamp as shown; a [V]-recess is cut out as in Fig. 2890, and this recess is fullered larger, as in Fig. 2891. A [V]-block is then welded in. The strap is then turned over a second [V]-groove, cut out and fullered out, and a second [V]-piece welded in. By thus welding one side at a time the welding is taken in detail as it were, and the blows can be less heavy than if a larger weld were made at one heat, as would be the case if but one [V] block were used. A similar form of weld may be employed to form a square corner, as is shown in Fig. 2892, which is taken from "The Blacksmith and Wheelwright." In this example the inside corner is shown to have a fillet, which greatly increases the difficulty of the job. The weld is made by first fullering the [V]-piece on the sides and on the rounded corner and then laying the piece on the anvil to forge down, the fullering leaving the finished job as in Fig. 2893. [Illustration: Fig. 2891.] [Illustration: Fig. 2892.] [Illustration: Fig. 2893.] [Illustration: Fig. 2894.] [Illustration: Fig. 2895.] When one piece has to be driven on to the other, the weld is called a pump-weld, for which the ends should be rounded as in Fig. 2894, so that they will meet at their centres, and will, when struck endways to make the weld, come to the shape shown in Fig. 2895. [Illustration: Fig. 2896.] It is obvious that in this case the interior of the iron comes together and is welded, and that dirt, &c., is effectually excluded; hence if the iron is properly heated the weld may be as sound as a lap weld, and is preferred by many as the sounder weld of the two. When a stem requires to be welded to a large flat surface, the pump weld is the only one possible, being formed as in Fig. 2896, in which the stem is supposed to be welded to a frame. The plate is cupped as shown, and the metal being driven up on the sides as much as possible, the stem overlaps well at C B, so that it may be fullered there. The stem should first meet its seat at A, so that dirt, &c., may squeeze out as the welding proceeds. [Illustration: Fig. 2897.] [Illustration: Fig. 2898.] Figs. 2897 and 2898 represent an example of welding a collar on round iron. The bar is upset so as to enlarge it at A, where the collar is to be. The collar is left open at the joint, and while it is cold it is placed on the red-hot bar and swaged until the ends are closed. The welding of the whole may then be done at one heat, swaging the outside of the collar first. Unless the bar is upset there would be a crack in the neck B of the collar on both sides. WELDING ANGLE IRON.--Let it be required to form a piece of straight angle iron to a right angle. [Illustration: Fig. 2899.] The first operation is to cut out the frog, leaving the piece as shown in Fig. 2899; the width at the mouth A of the frog being 3/4 inch to every inch of breadth measured inside the flange as at B. The edges of the frog are then scarfed and the piece bent to an acute angle; but in this operation it is necessary to keep the scarfs quite clean and not to bend them into position to weld until they are ready for the welding heat; otherwise scale will form where the scarfs overlap and the weld will not be sound. The heat should be confined as closely as possible to the parts to be welded; otherwise the iron will scale and become reduced below its proper thickness. The iron is then bent to the shape shown in Fig. 2900; and the angle to which it is bent is an important consideration. The object is to leave the overlapping scarf thicker than the rest of the metal, and then the stretching which accompanies the welding will bring the two arms or wings to a right angle. [Illustration: Fig. 2900.] It is obvious, then, that the thickness of the metal at the weld determines the angle to which the arms must be bent before welding. The thicker the iron the more acute the angle. If the angle be made too acute for the thickness of the iron at the weld there is no alternative but to swage the flange down and thin it enough to bring the arms to a right angle. Hence it is advisable to leave the scarf too thick rather than too thin, because while it is easy to cut away the extra metal, if necessary, it is not so easy to weld a piece in to give more metal. In very thin angle irons, in which the wastage in the heating is greater in proportion to the whole body of metal, the width of the frog at A in Fig. 2901 may be less, as, say, 9/16 inch for every inch of angle-iron width measured as at B in the figure. For angles other than a right angle the process is the same, allowance being made in the scarf-joint and bend before welding for the stretching that will accompany the welding operation. The welding blows should be light and quick, while during the scarfing the scale should be cleaned off as soon as the heat leaves the fire, so that it will not drive into the metal and prevent proper welding. The outside corner should not receive any blows at its apex; and as it will stretch on the outside and compress on the inside, the forging to bring the corner up square should be done after the welding. [Illustration: Fig. 2901.] The welding is done on the corner of an angle block, as in Fig. 2901, in which A is the angle iron and B the angle block. [Illustration: Fig. 2902.] To bend an angle iron into a circle, with the flange at the extreme diameter, the block and pins shown in Fig. 2902 are employed. The block is provided with the numerous holes shown for the reception of the pins. The pins marked 1 and 2 are first inserted and the iron bent by placing it between them and placed under strain in the necessary direction. Pins 3 and 4 are then added and the iron again bent, and so on; but when the holes do not fall in the right position, the length of the pin-heads vary in length to suit various curves. To straighten the iron it is flattened on the surface A and swaged on the edge of the flange B, the bending and straightening being performed alternately. [Illustration: Fig. 2903.] When the flange of the angle iron is to be inside the circle, as in Fig. 2903, a special iron made thicker on the flange A is employed. The bending is accomplished, partly by the pins as before, and partly by forging thinner, and thus stretching the flange A while reducing it to its proper thickness. TO FORGE A BOLT BY HAND.--The blanks for bolts must be cut off sufficiently long to admit of one end being upset to form the head, the amount of this allowance, obviously, being determined by the size of the head. [Illustration: Fig. 2904.] [Illustration: Fig. 2905.] Fig. 2904 is a side view, partly in section, and Fig. 2905 a top view of an anvil block for upsetting the ends of blanks to form the heads of bolts. The stem fits into the square hole of the anvil. The tongue is pivoted as shown in the top view to two lugs provided on the block; upon the tongue rests a steel pin whose length determines the height to which the blank will project above the top of the block, and, therefore, the amount or length of blank that will be upset to form the head, this amount being three times the diameter of the bolt for _black heads_. [Illustration: Fig. 2906.] [Illustration: Fig. 2907.] The hole for the blank is made about 1/64 inch larger in diameter than the designated size of the bolt, to permit of the easy extraction of the blank after it is upset, this extraction being accomplished by striking the end of the tongue with the hammer. If the block is made of cast iron the upper end of the hole will become worn after forging five hundred or six hundred bolts, leaving the bolts with a rounded neck, as at C C in Fig. 2906; a steel block, however, will forge several thousand bolts without becoming enlarged. An excellent plan is to provide the block with removable dies, such as at _d_ _d_ in Fig. 2907, which are easily renewed, a number of such dies having different diameters of bore fitted to the same block. When the bolt end is sufficiently reset or enlarged to form the head it is laid in a bottom swage, containing three of the six sides of the hexagon, and a hammer blow on the uppermost part of the end forges a flat side. After each blow the work is revolved one-sixth of a revolution, and as the angles of the swage are true they obviously true the angles of the bolt head. After the head has been roughed down it is necessary to flatten it again under the head and on the end, for which purpose it may be placed in the heading block shown in Fig. 2904, after which the sides of the head may be finished and the cupping tool for chamfering the head applied. The bolt may require passing from the heading tool to the swage several times, as forging it in one direction spreads it in another. [Illustration: Fig. 2908.] In shops where bolt-making is of frequent occurrence a special bolt-making device is usually employed. It consists of an oliver or foot hammer, having two hammers and an anvil; in the square hole at one end of the anvil fits a hardy or bottom chisel, such as shown in Fig. 2908, for cutting up the bar or rod iron into bolt blanks; A is the anvil, H the hardy, and G a gauge to determine the length cut off the rod R to form a blank. An upsetting or heading device corresponding to that in Fig. 2907 is provided, and at the other end of the anvil is the swage for forming the bolt head. The object of having two hammers is that one may be used for the upsetting of the blank and the other for the swage. The swaging hammer is provided with a hole and set-screw to receive top swages, and bolt hammers are adjustable for height so that they may be set so that their faces will meet the work fair. [Illustration: Fig. 2909.] [Illustration: Fig. 2910.] [Illustration: Fig. 2911.] Figs. 2909 to 2911 represent front, side, and top views of Pratt & Whitney's portable bolt-forging device. It is provided with an elevating screw that permits the employment of a single bolster-pin for all lengths of bolt for a given diameter, instead of requiring a separate pin for each different length of bolt. In the figures, A is a frame carried upon wheels, and to which is pivoted at C C the jaw D. The bolt-gripping dies are shown at E F. A treadle G is pivoted at H, and acts upon the lower end of D, causing the die F to grip or release the bolts, as may be required. The bolster-pin rests upon the end of the screw I, which enters at its foot a split nut J, which is caused to grip and lock the screw by operating the nut of the bolt K that passes through the split of the nut. L is a spring that lifts the treadle when it is relieved of the pressure of the operator's foot. At M is a leather washer to protect the nut J from the scale that falls from the forging. The operation is as follows:-- The nut K is released and the screw I operated to suit the length of bolt required. Then J is caused to clamp the screw by operating the nut K. The blank for the bolt is placed in the dies resting on the bolster-pin, which in turn rests upon the end of the screw I. The treadle G is depressed, and the bolt blank clamped between E and F. The helper then with the sledge upsets the blank end to form the bolt head, and the blacksmith forges it to shape in the former bar B, which is provided with impressions for the form of head required, these impressions being of varying sizes, as shown. The device is so strongly proportioned as to be very solid, and is found to be a most useful addition to the blacksmith's shop. [Illustration: _VOL. II._ =EXAMPLES IN HAND FORGING.= _PLATE XVI._ Fig. 2917. Fig. 2918. Fig. 2919. Fig. 2920. Fig. 2921. Fig. 2922. Fig. 2923. Fig. 2924. Fig. 2925. Fig. 2926.] [Illustration: Fig. 2912.] [Illustration: Fig. 2913.] [Illustration: Fig. 2914.] [Illustration: Fig. 2915.] [Illustration: Fig. 2916.] To forge a turn buckle, such as in Fig. 2912, we bend two rings, such as in Fig. 2913, and weld into the open ends a piece as shown in Fig. 2914, on the opposite side a recess A, Fig. 2915, is cut out to receive a second piece, which being welded in the work appears as in Fig. 2916, and the end may be drawn taper. Two such pieces welded together obviously complete the job. Fig. 2917 represents a yoke for the slide valve of a steam engine or a locomotive, which may be forged by either of the following methods: Fig. 2918 represents a stem A welded into the bar B, which may be bent to the required rectangle and welded at the ends. A second method is to jump the stem D and split it open as in the side view in Fig. 2919. The bar E is forged with a projecting piece to go in the split of D, and after the weld is made, bar E is drawn to size as shown, leaving the two projections _x_ where the corners are to come, which is necessary in order to have sufficient stock to bring the corners up square. The ends of E are split open as in the end view at F, and a piece G is then welded to F. In a third method the end of the stem is rounded for the weld, as shown in Fig. 2920. The ends of the bar J are then split open and piece K welded on. It is to be observed with reference to the two last methods that in hammering to forge the weld the frame is closed, so that after welding the swaging to finish may be carried on until the frame is brought to square, and any superfluous metal may be cut away; whereas if the kind of weld is such as to stretch the sides, it may happen that to get a sound weld will stretch the side welded too long and throw the frame out of shape. Suppose, for example, that a scarf weld were made on the side of the yoke opposite to the stem, and if, in welding, the scarf is hammered too much, it would draw it out too much and throw the whole frame out of shape, as in Fig. 2921, so that the welded side would require to be jumped to bring it back to the proper length again. A fourth method is to take a piece of iron and punch a hole in it, and then split it open up to the hole, as in Fig. 2922, and by opening out the split form the stem and part of the frame out of the solid, forging the remainder of the frame by the plan described for either the second or third methods. A fifth method is to make the weld of the stem as in Fig. 2923, then forge out the bar B, leaving projections _x_ _x_ to bring the corners _y_ _y_ up square, and after bending to shape and squaring up to weld in a piece C. A sixth method is to form the band first as in Fig. 2924, form the stem as in Fig. 2925, and weld as in Fig. 2926. [Illustration: Fig. 2927.] [Illustration: Fig. 2928.] [Illustration: Fig. 2929.] Figs. 2927, 2928, and 2929 represent a method of forging a fifth wheel for a vehicle. A rectangular piece of Norway iron is fullered to form the recess at C in Fig. 2927. Holes are then punched at _h_ and splits are made to the dotted lines shown in the figure. The ends are then opened out, forming a piece such as in Fig. 2928. The letter A represents the same face of the work in all the figures, being the edge in Fig. 2927, and the top face after the ends are opened out. The four arms may then be dressed to shape, the two lower ones being drawn out and threaded before being finally closed to shape. A piece may then be welded on one end, as at B, to complete the circle. [Illustration: Fig. 2930.] [Illustration: Fig. 2931.] [Illustration: Fig. 2932.] To forge a double eye, such as in Fig. 2930, we may take a piece of sufficient size and fuller at _a_ _a_, Fig. 2931; a hole is then punched at _b_, and it is then split through to the dotted line in Fig. 2931, and opened out as in Fig. 2932, and then forged to shape. [Illustration: Fig. 2933.] BENDING.--Fig. 2933 represents a tool for bending pieces of small diameter to a short curve, either when cold or heated. In bending hot iron it is advantageous to confine the heat as closely as possible to the part to be bent, as a more true bend may then be obtained. [Illustration: Fig. 2934.] [Illustration: Fig. 2935.] [Illustration: Fig. 2936.] As an example in bending, let it be required to bend a straight shaft into a crank shaft, and the following method (from "The Blacksmith and Wheelwright") is pursued. The shaft is first bent as in Fig. 2934. The piece is next bent as in Fig. 2935, and finally as in Fig. 2936, the corners A A and B B corresponding in all the figures. [Illustration: Fig. 2937.] BLACKSMITH'S BENDING BLOCKS.--In cases where a great number of pieces of the same size and shape are required to be bent during the forging process, a great deal of time may be saved and greater accuracy secured in the work by the employment of bending devices. Thus, in Fig. 2937 is shown at A a clip requiring to be bent to the shape at B. A pair of tongs is provided with a hole at C to receive the stem of the clip, and the jaw D is made of the necessary width to close the ends of the forging upon. It is obvious that the hole C being in the middle of the width of the tong jaw, the wings will be equidistant from the pin. Figs. from 2938 to 2943 represent bending devices. [Illustration: Fig. 2938.] [Illustration: Fig. 2939.] [Illustration: Fig. 2940.] [Illustration: Fig. 2941.] Figs. 2938, 2939, and 2940, represent a "former" for a stake pocket for freight cars. A is a cast-iron plate having a projection B, around which the stake pocket C is bent. D is fast upon A, and affords a pivoted joint for the bending levers E F. The work is placed in the former as shown in Fig. 2939, and levers E F are swung around to the position shown in Fig. 2938. To enable the work to be put in and taken out rapidly and yet keep it firmly against the end of B, a hand-piece G is used as in Fig. 2940, its form being more clearly shown in the enlarged Fig. 2941. Sufficient room is allowed between B and D to admit the work, and the end of the piece G, which is pressed in the direction denoted by the arrow in Fig. 2940, forcing the work against B. A number of the pieces are piled on the fire so as to heat them sufficiently fast to keep the former at work, and the bottom piece is the one taken out. The corners of the work are by this process brought up square and the faces are kept out of wind. The surface A forms a level bed. These advantages will be readily appreciated by all smiths who have had comparatively thin work to bend to a right angle in the ordinary way. [Illustration: Fig. 2942.] [Illustration: Fig. 2943.] Figs. 2942 and 2943 represent a similar former for the step irons of freight cars. In Fig. 2942 the piece is thrown in place ready to be bent, its ends being fair with the lines J K on the bending levers E F. In Fig. 2943 the levers are shown closed and the work C therefore bent to shape. The bed plates A are mounted on a suitable frame to raise them to a convenient height for the blacksmith. FORGING A STABLE-FORK.--In the manufactories where stable and hay forks are made, the whole process of forging is done under the trip hammer, and is conducted as follows:-- [Illustration: Fig. 2944.] [Illustration: Fig. 2945.] [Illustration: Fig. 2946.] [Illustration: Fig. 2947.] [Illustration: Fig. 2948.] To forge a four-tined fork, such as in Fig. 2944, a blank piece of steel is employed, its dimensions being 5-3/4 inches long, 7-3/4 inches wide, and 1/2 inch thick. The first operation is to swage down one end, as at A in Fig. 2945. A split is then cut down as at B in Fig. 2946. The split is then opened out as in Fig. 2947, and is fullered and drawn out at C. Two more splits are then made at D D, and the ends are bent open as in Fig. 2948, when the four tines E E and F F are drawn out and shaped out. The stem, A, Fig. 2945, is then finished for the handle. [Illustration: Fig. 2949.] The following example of forging under the hammer is derived from _The Engineer_, of London, England. Fig. 2950 shows the piece to be forged. A block of iron, Fig. 2951, is drawn out as in the figure, the dimensions of A and B being considerably above the finished ones. A forked tool T, Fig. 2952, may be used to nick the two grooves shown in Fig. 2953, which marks the locations for the hub and forms a starting guide for the two fullering tools shown in Fig. 2954, one of which is held by the blacksmith and the other by the helper. After this fullering the forging will appear as in Fig. 2955. The ends E, F may then be drawn out, having the shape as in Fig. 2956. To shape the curve between the side of the hub and the body of the stem, grooves are formed as in Figs. 2957 and 2958, Y and B being top and bottom half-round fullers, and these two grooves are subsequently made into one by means of larger half-round fullers, as in Fig. 2959. The object of making two small fullered grooves and then making them into one is to prevent the fullering from spreading the body of the stem by lessening the strain due to using a large fuller at once. The piece now appears as in Fig. 2960. [Illustration: Fig. 2950.] [Illustration: Fig. 2951.] [Illustration: Fig. 2952.] [Illustration: Fig. 2953.] [Illustration: Fig. 2954.] [Illustration: Fig. 2955.] [Illustration: Fig. 2956.] [Illustration: Fig. 2957.] [Illustration: Fig. 2958.] [Illustration: Fig. 2959.] [Illustration: Fig. 2960.] The next operation is to cut or punch away the metal between the ends of the hub and the body of the piece, which is accomplished as follows: [Illustration: Fig. 2961.] A top and bottom die and block are made to contain the work, as in Fig. 2961, A and B being the work ends. Through these dies are two holes for two punches which are driven through together as marked; the dies are held fair, one with the other, by four holes in the lower and four pins in the upper one, a section and top view of the dies being shown in Fig. 2962. The piece is at this stage roughed out to shape all over, and may be finished between the pair of finishing dies shown in Fig. 2963, which also represents a plan and sectional view, _a_, _b_, _c_, _d_ being the holes to receive guide pins in the upper die. An excellent example of forgings in Siemens Martin steel is given in the following figures, being the rope sockets for the Brooklyn Bridge. [Illustration: Fig. 2962.] [Illustration: Fig. 2963.] [Illustration: Fig. 2964.] [Illustration: Fig. 2965.] Fig. 2964 represents two views of the forgings, and it will be readily perceived that they are very difficult to make on account of the taper hole, which is shown in dotted lines. The first operation was to take a bar of steel 6-1/2 inches square and punch a hole, as at A Fig. 2965. [Illustration: Fig. 2966.] [Illustration: Fig. 2967.] [Illustration: Fig. 2968.] Next the piece was fullered at B, C by the fuller A, Fig. 2966, and cut partly off as at D. The fullering at B was then extended by a spreading fuller, shaped as at B, and the end E was drawn out. Then the piece was cut off at D. Next the spreading fuller was applied to C, and the forging appeared as in Fig. 2967. The end F was then drawn out, and the appearance was as in Fig. 2968. [Illustration: Fig. 2969.] The next operation was to enlarge the hole A, Fig. 2965, by drawing taper mandrels through it, the mandrels being about 7 in. long, having 1/2-in. tapes on them, and being successively larger. With the last of these mandrels in the hole the hub was drawn out to length and diameter, leaving the forging roughly shaped, but having the form shown in Fig. 2969. [Illustration: Fig. 2970.] To finish the hole the forging was then placed in a block such as shown at G, in Fig. 2970, a finishing punch being shown at H in the figure. [Illustration: Fig. 2971.] The next operation was to let the steam hammer down upon the face of the punch and bring up the wings E F parallel, but not more than parallel, as then the mandrel could not be got out; the forging then appearing as in Fig. 2971. The next process was to put in a bar mandrel such as shown in Fig. 2972 at I, the pieces J, K fitting on their sides to the mandrel and being curved outside to the circular and taper shape of the hole. The wings E F may then be closed on the mandrel to their proper width and the whole hub end being trimmed by hand, all the previous work having been done under the steam hammer. The hub being finished the key M may be taken out and the washer L taken off, when I can be pulled out, leaving J K to be taken out separately. A pair of tongs are then put through the finished hub end, while the wings are punched and trimmed under the steam hammer, and subsequently finished by hand. [Illustration: Fig. 2972.] [Illustration: Fig. 2973.] [Illustration: Fig. 2974.] The forging of wrought-iron wheels for locomotives is an excellent example. The spokes are first forged in two pieces, as 1 and 2 in Fig. 2973, and then welded to form the complete spoke. Piece 1 is first forged in dies under the steam hammer to the form shown in Fig. 2974, the dimensions being correct when the faces of the dies meet. The stud C D is then drawn out to the required length and dimensions. [Illustration: Fig. 2975.] [Illustration: Fig. 2976.] [Illustration: Fig. 2977.] [Illustration: Fig. 2978.] The upper half of the spoke is first blocked out under dies to the shape shown in Fig. 2975, and the block B spread so as to form a section of the wheel rim, as shown in Fig. 2976, in which D is a die, L a movable piece wedged up by the wedges W W, and removable to enable the extraction of the forging, and F is an end view of the fuller, the use of which is necessary to cause the metal to spread sufficiently in the direction of the dotted lines. The corners of the rim are then cut off, as shown in Fig. 2973, and the rim is bent in a block having its top face of the necessary curve, as in Fig. 2977, A being the block, and B a piece movable, to allow the extraction of the work, and fastened in place by the key or keys C. The two pieces are then welded together, their lengths, &c., being gauged by a sheet-iron template, formed as in Fig. 2978. The welding is usually performed with sledge-hammers, but as soon as the pieces will hold well together, the drawing down is done under a steam hammer. [Illustration: Fig. 2979.] The spokes thus forged are then put together, as in Fig. 2979, B representing a wrought-iron band, encircling the rim of the wheel and closed upon the same by the bolt and nut at N. [Illustration: Fig. 2980.] Two washers are then forged, to be placed and welded in as at W W, in Fig. 2980. The welding together of the spokes and of the washers to the spokes proceeds simultaneously. The washers are heated to come to a welding heat at the same time as the wheel hub is at a welding heat, and the two are welded together under a steam hammer. During the heating of the wheel hub, however, the band B, Fig. 2979, is tightened up with the screw to bring the spokes into closer contact when heated to the welding point. [Illustration: Fig. 2981.] [Illustration: Fig. 2982.] The seams between the spokes at the circumference of the hub are welded with bars as shown in Fig. 2981, in which R R are two bars of iron which are operated by hand as rams. The wedge shape of the washers on their inside faces performs important duty in spreading the metal as well as simply compressing it, giving a much more sound weld than a flat washer or plain dish would. The rim of the wheel is welded up as follows: In Fig. 2982 are shown four spokes of the rim as they appear after the hub is welded. Into the [V] spaces, as _a_, _b_, _c_, _d_; wedges of metal, of the form shown at E, are welded, after which the surplus metal of E is cut away, and the rim is solid as at F. In this process, however, it is necessary to weld all the pieces on one side of the wheel, as at _a_ _b_, &c., except one, which must be left unwelded until all the pieces save one on the other side are welded, and the wheel must be allowed to become quite cool before these last two pieces are welded. Otherwise the strain induced by the contraction of the wheel rim while cooling will often cause the rim to break with a report as loud as that of a rifle. In those cases in which this breakage does not occur the wheel will be very apt to break at some part of the rim, when subjected to heavy shocks or jars. The Figs. 2983 to 2999 (which are taken from _Mechanics_), illustrate the method employed to forge the rudder frame of the steamship _Pilgrim_. [Illustration: Fig. 2983.] A side elevation of the rudder frame is shown in Fig. 2983. The forging is made in eight separate pieces, which are so united as to make three pieces. These three pieces are finally joined by five welds. The whole length being 29 feet 11-3/4 inches, and the weight 6,500 pounds. [Illustration: Fig. 2984.] [Illustration: Fig. 2985.] [Illustration: Fig. 2986.] [Illustration: Fig. 2987.] [Illustration: Fig. 2988.] [Illustration: Fig. 2989.] The work is commenced by piling and welding on the porter-bar at the point in the shaft marked A. The stubs B and C having been previously prepared, the pile on the porter-bar is heated and welded up and drawn, shown in Fig. 2984, and scarfed as shown in Fig. 2985; the piece, shown in Fig. 2986, is then laid in the scarf and welded; then the part from B to A is finished to size, the finished forging of the post being shown in Fig. 2984. The surplus stock to the right of B, Fig. 2984, is worked down into the post E, and the distance from B to F is thus made correct without loss of stock or time. The curve at D, Fig. 2983, was worked down somewhere near, and then another pile and weld carries the job to G. Here the same operations as at first are repeated, and the arm C is welded in. There is left a good lump of stock in front of C, and by another pile and weld enough is added to make the job to I, as shown in Fig. 2987. Holes are then punched at J and L, and the piece of stock M cut entirely out. A cut is made to L with a hack opening out the piece N from the shaft. A taper punch, with a 3-inch point and a 4-inch head, is then driven at L; to throw the piece N out into the position shown at N^{1}, Fig. 2983; N^{1} is then finished, and the post from L to J brought to forging size; then, by the ordinary process of piling, welding and drawing, the shaft is finished from I to O. Next the porter-bar is cut off, so as to leave stock enough to make the lower part of the shaft, as shown in Fig. 2988. A hole was punched at Q, and the stubs drawn out, as shown in Fig. 2989, which gives the post complete. [Illustration: Fig. 2990.] The pieces S and T, and the tiller V, having been forged, as shown in Fig. 2991, the upper member of the frame is started on the porter-bar at W, Fig. 2983, and filed, welded and drawn to make the job as far as X^{1}. Wooden templates, such as in Fig. 2992, are provided for the pieces of the frame, the first extending from W to X^{1} and X, and the second including the part from X^{1} to X^{2} and X^{3}. After W, X^{1} has been drawn out with lumps left where the tiller and the arm S are to be joined, the scarf is made for the tiller and that is welded in, and the job finished to piece S. The scarf for S is then made, and S welded in. This makes the upper member of the frame. The lower member is made in the same way, starting at X^{3}. These two members are shown complete in Fig. 2993. The post, Fig. 2989, was sent to the machine shop, and was turned, planed, bored, and slotted, as shown in Fig. 2990. The frame was now ready to be pieced up, by welds at W, X, X^{1}, X^{2}, and X^{3}, Fig. 2983. [Illustration: Fig. 2991.] [Illustration: Fig. 2992.] [Illustration: Fig. 2993.] [Illustration: Fig. 2994.] [Illustration: Fig. 2995.] [Illustration: Fig. 2996.] [Illustration: Fig. 2997.] [Illustration: Fig. 2998.] [Illustration: Fig. 2999.] The several sections are now ready to be welded together for the complete frame, these welds being made as follows: The ends are upset as in Fig. 2994 to receive on each side a [V]-piece such as in Fig. 2995, which is heated on a porter-bar, and is of a more acute wedge than the ends to be welded, so that when laid in as in Fig. 2996 it will touch at the bottom first, and thus allow the air and whatever dirt there may be on the surfaces to squeeze out as the welding proceeds. The method of heating the frame for these welds is as follows: The [V]-block (which has the grain of the iron running in the same direction as that of the frame) being heated in the blacksmith's forge, the frame is clamped together and counterbalanced by means of weights, so that it may be laid over a fire pot, constructed as in Fig. 2997. This fire pot is lined with brick, and has its blast supplied through a piece of flexible tube. The anvil is of cast iron, shaped as in Fig. 2998, and placed on the other side of the frame and opposite to the fire pot or portable forge, as shown in Fig. 2997, so that the frame, when the heat is ready, may be turned over upon the blocks on which it rests, and the part to be welded will come upon the anvil. After one side is welded the anvil and the portable forge change places, and the second side of the weld is made. In the following figures (which are taken from _Mechanics_) is illustrated the method employed to build up the shaft shown in Fig. 3001, which was for the steamer _Pilgrim_. Forgings of such large dimensions are built up of pieces or slabs, called blooms, which are themselves forged from scrap iron, which is piled as in Fig. 3000. For the forging in question this scrap iron consisted of old horseshoes, boiler-plate clippings, boiler rivets and old bolts, and the first step in the manufacture is to form this scrap into piles ready for the furnace. [Illustration: Fig. 3000.] [Illustration: Fig. 3001.] [Illustration: Fig. 3002.] [Illustration: Fig. 3003.] These piles are made upon pieces of pine board 1/2 inch thick by 16 inches long by 10 inches wide. On these the scrap is piled about 14 inches high, each pile weighing about 270 pounds. After piling, the scrap goes into the furnace and is raised to a welding heat, the board retaining its form as a glowing coal almost to the last. The pile of scrap is heated so nearly to melting as to stick together enough so that it can be picked up in a long pair of tongs with peculiarly-shaped jaws, and, as these tongs are suspended by a chain from an overhead traveller running on an iron track, the bloom is easily transferred to the anvil of the steam hammer, where, after one or two blows, a small porter-bar with a crank end, such as shown in Fig. 3003, is welded on, and the pile is rapidly drawn out into a square bar. When completed the porter-bar is cut off, and the bar is laid aside to cool. The pile of scrap has now become a "bloom," such as shown in Fig. 3002, and has been reduced in weight from 270 lbs. to 240 lbs. The bloom is about 30 inches by 5 inches by 5 inches in dimensions, and has rounded, ragged ends, and a surface full of lines marking welding of the individual pieces, and at the ends looking as though the scrap had united by melting rather than by any welding process. [Illustration: Fig. 3004.] These blooms are then taken to the large steam hammer and furnace by which the shaft is to be built up. The porter-bar, although merely a tool whereby to handle the mass, forms practically a base wherefrom to build up the shaft. The construction of the furnace is shown in Fig. 3004, the heat, after passing the work being used for the steam boiler that supplies steam to the steam hammer. The porter-bar is held by a crane, the chain being placed in such position in the length of the porter-bar as to balance it. On the end of the porter-bar is a clamp, having arms by which the bar may be turned in the furnace and when under the hammer. Fig. 3005 represents the bar in position in the furnace, the aperture through which it was admitted having been closed up by bricks luted with clay, one brick only being left loose, so that it may be removed to examine the heat of the bar. The end of the bar is flattened somewhat, and a slab is laid upon it as in Fig. 3006, the appearance after the first weld being shown in Fig. 3007. It is then turned upside down, and blooms are piled upon it as in Fig. 3008. After these are welded the end is shaped up round and to size. The extreme end is again flattened, or "broken down," as it is termed, and first a slab, and after reheating, blooms are added, as already explained; when these are welded and forged enough to consolidate the mass the mass is rounded up again, thus increasing the length of finished shaft. The end is again broken down and a slab added, and so on, the shaft thus being forged continuously from one end, and being composed of alternating slabs and blooms. To forge this shaft 118,000 lbs. of blooms, 185 tons of coal, and 360 days of labor were required, the time occupied being 34 working days. The slabs are simply forged pieces of larger dimensions than the blooms, and more thoroughly worked, the difference between slabs and blooms being that there is more waste with the blooms than with slabs, because the blooms heat quicker than the forged part of the crank. Between both the slabs and the blooms there are placed rectangular pieces to hold them apart, and let the furnace heat pass between them, the arrangement of these pieces being shown in Figs. 3009 and 3010. Figs. 3011 to 3024 (which are taken from _Mechanics_), represent the method employed to forge the crank shaft of the United States steamship Alert. [Illustration: Fig. 3005.] [Illustration: Fig. 3006.] [Illustration: Fig. 3007.] [Illustration: Fig. 3008.] [Illustration: Fig. 3009.] [Illustration: Fig. 3010.] [Illustration: Fig. 3025.] [Illustration: Fig. 3026.] [Illustration: Fig. 3027.] [Illustration: _VOL. II._ =FORGING UNDER THE HAMMER.= _PLATE XVII._ Fig. 3011. Fig. 3012. Fig. 3013. Fig. 3014. Fig. 3015. Fig. 3016. Fig. 3017. Fig. 3018. Fig. 3019. Fig. 3020. Fig. 3021. Fig. 3022. Fig. 3023. Fig. 3024.] Fig. 3011 represents the crank shaft, and Fig. 3012 an end sectional view, showing how the throws were built up. The first operation was to forge the saddles shown in Fig. 3013, these being the pieces that are shown between the cap and the wrist. These saddles were made in halves, each half appearing as in Fig. 3014. From a pile and weld of blooms on the porter-bar, enough to make the two halves, one half was cut off. The other half was then drawn down on the porter-bar, and the first half was then piled on the latter, as shown in Fig. 3015. The square cross bar goes clear across and projects about an inch at each side. The back pieces were short bits. The square cross bar makes the saddle less liable to split in welding it on to the square shaft. Two "caps" were also made before the forging of the shaft itself began. These are shown in Fig. 3016, and their position in the finished work is shown in Fig. 3012. The shaft itself was piled, welded, and drawn on the porter-bar in the usual manner, until the location of a crank was reached. Then a part of the work some distance from the new end was squared, as shown in Fig. 3017, and on this square the saddle was piled to heat and weld, as shown in Fig. 3018. As will be seen, the saddle rested upon the outer lines of the angle. The first blow was struck square on the top of the saddle, and after three or four blows the job presented the appearance shown in Fig. 3019. The piece was now turned so as to lie as shown in Fig. 3020, and worked with blows on the sides to the shape shown in Fig. 3021. This opened the top of the juncture of the saddle and squared the shaft down to the point where the weld was good. The piece was then turned back to the position shown in Fig. 3019, and worked with blows which again closed the angle on top, and made the weld good all through. The piece was then returned to the furnace, and at the next heat the saddle was squared up and finished, and the cap was piled on top of the saddle, as shown in Fig. 3022. The cap was welded on at the next heat, and two cheeks, like that shown in Fig. 3023, were laid upon one flat of the crank and pinned with 1-5/8-inch round pins. One of these pins is shown in the figure. Bits of iron were put under these cheek pieces in the usual manner. As the cheeks were very much smaller in section than the crank body, it was necessary to turn them over away from the fire, or else the cheeks would be burned before the crank body was hot enough to weld. To prevent the cheeks from falling off in the furnace the pins were put in as described before heating. After two cheek pieces had been welded on one side, two more were added on the opposite side, and then the crank was finished, as shown in Fig. 3024. As will be seen by inspection of Fig. 3012, the weld between the cap and the saddle comes about the middle of the wrist, and the cheek pieces support the cap sideways. By means of the piles and welds described, the grain of the iron was so disposed as to offer the most resistance to working strains. This method was devised by Mr. Farrell Dorrity, of the Morgan Iron Works. FORGING LARGE CRANK SHAFTS.[45]--The following paper describes the method of forging marine crank shafts adopted at the Lancefield Forge, Glasgow. It will be better understood if a short account is first given of the ordinary methods in use for the same purpose. [45] From a paper read at the Glasgow meeting of the Institution of Mechanical Engineers, by W. L. E. MacLean. "_First Method._--The most common method is technically termed by the forgeman, 'finishing the piece before him.' He begins with a staff or stave, as shown in Fig. 3025, suspended by a chain from the crane, and made round for the convenience of manipulating under the steam hammer; this stave is used over and over again for many forgings, as it is merely the "porter" to carry the piece and enable it to be worked. The forging is begun by two or three slabs being placed on the stave as at S S S, and then inserted in the furnace. These slabs are flat blocks made up of pieces of scrap iron, which have been piled and heated, and then welded together. After being brought to a welding heat in the furnace, the slabs are withdrawn, placed under the steam hammer, and beaten down solid. The piece is then turned upside down, and two or three similar slabs placed on the opposite side, as shown at S S. When sufficient iron has been thus added to form the collar of the shaft (assuming it is to have a collar), it is rounded under the hammer, as at C, Fig. 3026, and the body of the shaft next to the collar is roughly formed, as at D. More slabs, S S S, are added to bring out the body, and afterwards the crank itself is proceeded with, on the same plan. The piece will begin to assume the appearance of A, Fig. 3026. Then more slabs are welded on the top, as at S S S, till the depth of the crank is obtained, after which the forgeman proceeds to finish the collar and body of the shaft, as shown. The collar on being finished is cut all round, as shown at C D, Fig. 3027, so that it may be more easily detached from the stave when the shaft is completed, leaving only sufficient connection to carry it till then. The forgeman then cuts the gable of the crank as at E G, and rounds up the body and neck as at B N, Fig. 3027. "This, it will be observed, is a speedy process, and would invariably be adopted if it were not attended with a very serious drawback; it is very hazardous to the solidity of the forging. For it will be easily understood that not above a third of the crank itself can be thus formed, because the iron at the neck N would not carry a greater mass; if the whole mass of the crank, or even the half of it, was formed before the body and neck of the shaft were finished, a proper heat could not be taken on the body and neck for finishing, without the neck giving way or rupturing. Indeed, as it is, the undue proportion often causes the shaft to be strained at this part, where most strength should be, so that it is rendered weak, and a flaw is developed which by-and-by causes it to be removed from the steamer as dangerous and useless, if indeed it does not break outright; so that the forgeman, if he adopts this method, must be very careful to proportion the amount of iron he has massed in the furnace to the size of the body he is finishing, otherwise the weakening above mentioned will take place. All marine engineers will easily recognise this defect, which frequently occurs, but the cause of which is probably not well understood. Such a flaw will present a similar appearance to that shown at F, Fig. 3033, taken from an actual example. [Illustration: Fig. 3028.] [Illustration: Fig. 3029.] "This difficulty of proportioning the part of the crank first forged to the size of the neck, will be still better understood by the appearance of it in the furnace, as shown in Fig. 3028. Having reached this stage, with one end of the shaft completed, as also that portion of the crank itself which of necessity was completed before the collar was cut, in order that the neck might be finished, no more iron can be added on the top edge, as it is up to the full depth already; it must therefore be added on the flat, as in Fig. 3029, where the piece is shown on its flat side in the furnace, the finished portion being outside the furnace door. A number of slabs S S S are then placed side by side to bring out the width of the crank further; these being welded down, the piece is turned upside down, and the process repeated on the other side. Afterwards other slabs are similarly placed on both sides, as shown in Fig. 3030, of which one is the flat, and the other is the edge view of the crank at this stage; and this is continued until sufficient iron has been massed to allow of the other gable of the crank being cut down, as at A, Fig. 3031, and sufficient also to allow of the other part of the body B being rounded and prepared for further piecing out. [Illustration: Fig. 3030.] [Illustration: Fig. 3031.] [Illustration: Fig. 3032.] "Now it will be observed that the first gable finished has the slabs all welded on the edge of the crank, and the hammering has all been on the edge; hence the subsequent hammering on the flat has a tendency to open up the weldings, if they have not been thoroughly made. A section taken at A B, Figs. 3028 and 3029, will show as in Fig. 3032, on the left, the weldings being across the web of the crank; the circle indicates the section which the crank pin would present if cut through there. But when the slabs are placed on the flat afterwards, some of the joinings of the ends of the slabs, or "scarf ends," are certain to fall within the crank pin, as seen in Figs. 3028 and 3029; therefore the section through C D, Fig. 3030, will show somewhat like Fig. 3032 on the right, and the crank pin necessarily includes some of these flaws. The flaw thus produced, called 'a scarf end in the pin,' is readily recognizable by all marine engineers; at F, Fig. 3033, is a sketch from an actual occurrence. "When the second gable is cut, and the other end is rounded, there is only the other collar to be put on (if a double-collared shaft), and the forging is completed. [Illustration: Fig. 3033.] This method is so speedy, compared with any other, that it is often resorted to even at the risk of making a bad forging; and too many broken shafts testify to the fact. Besides, it may be observed that in making a double crank shaft, while the one crank may be made in this way, the other must; for, the first crank, A, Fig. 3033, being completed, and the body, B, between the two cranks, also completed, the second crank, C, must of necessity be pieced off this body, even at the risk of the neck N being strained. This may account for the many instances in which one of the cranks of a double crank shaft gives way, rendering the shaft useless; and also for the plan, now almost universal, of making the two cranks separately and coupling them together; a further object being, no doubt, to have the means of replacing a defective half, if need be, without losing the whole shaft. "At Lancefield, when a double crank shaft is to be made, the after crank, A, is first made by the method afterwards described, so as to insure that this crank, through which, as being next the propeller, all the power of the engine passes, is perfectly sound; and in piecing the other crank off the body, it is worked with slabs on the flat instead of on the edge, as afterwards described. "The writer's own opinion is that the crank is the most important part of the shaft, and, therefore, at all costs, should be made first. Others, no doubt, may take the same view, and, to avoid the risks just mentioned, may adopt the process described in the second method. [Illustration: Fig. 3034.] [Illustration: Fig. 3035.] "_Second Method._--This method builds the middle first, and is called "turning the shaft end for end." The shaft is begun from a stave, by the addition of slabs, as shown in Figs. 3034 and 3035; Fig. 3034 shows it with iron added in slabs, till a butt is formed, as at B, to form the nucleus of the crank; slabs S S S are then piled on it to bring the crank up to the height. [Illustration: Fig. 3036.] "These are beaten down and welded, and more are added, as at S S S, Fig. 3035, till the full height of the crank is reached. Should the web (or edgeway of the crank) be thick, two slabs are frequently used to make up the breadth, placed edge to edge, as shown in Fig. 3035 on the right hand of the figure; the widths of these slabs are limited by that at which the shinglers can conveniently work and turn them under the steam hammer. The crank, however, is completed without any "side slabs," for the beating down of the slabs on the edge will broaden out the mass, and give sufficient material to forge out the crank to the proper height by hammering on the flat. The crank is afterwards cut at the off gable at G, Fig. 3036, the body B pieced out and rounded, the collar welded on, and then a small stave S is drawn upon the end, to enable the forgeman to handle the piece when he "turns it end for end" to complete the other end of the shaft. [Illustration: Fig. 3037.] "This method, though better than the last, is also objectionable; for though there is not equal risk of 'scarf ends' in the pin, yet the weldings are all on the edge, as in the lower view, in Fig. 3036, where the section of the crank pin is shown by the dotted circle; and the cheeks of the crank, O O, are thus liable to give way if a heavy strain comes on the crank when at work. The defects arising from this cause are shown in Fig. 3037, and will be readily recognised by all engineers. "_Third Method._--Considerations such as these have led to the adoption of the third or Lancefield method. [Illustration: Figs. 3038 and 3039.] "Fig. 3038 shows the piece begun from the stave in the usual way, with the slabs all welded, however, on the flat, till a basis is formed for the building up of the crank. A portion A is roughly rounded to form the one end of the shaft, and the butt of the crank will present the appearance of a slightly elongated square, as shown at B, Fig. 3039. The workman then "scarfs" or hollows it down at one edge all along the side, as indicated in the end view by the dotted line from C to D; it will then present the appearance shown by the end view, Fig. 3040, being somewhat bulged outward at the points E and F. Three long thin slabs, Fig. 3042, shaped for the purpose, are then placed on the hollowed part, the piece lying flat in the furnace. These slabs are tapered a little the broad way, not on the length, and little pieces of iron are interposed between them, to keep the surfaces apart, and allow the flame free access between them. The object of making them thin is that they may be all equally heated, which is not so readily achieved when the slabs are thick; and the object of the tapering is to allow the slag to flow out freely when the uppermost slab is struck by the steam hammer. The surfaces thus get solidly welded. [Illustration: Figs. 3040 and 3041.] [Illustration: Fig. 3042.] "Fig. 3041 represents the slabs thus placed in elevation, and the figure on the right, in section. The slabs are forged long enough to go right across the whole width of the crank, excepting about 6 inches; this margin is necessary to allow of the lengthening out of the slabs to the whole width under the process of forging. After these slabs are perfectly welded, the piece is turned upside down, and the process is repeated on the other side, as shown in Fig. 3042. When welded down the mass has increased in depth as well. Another scarfing takes place on the first side, and then another on the second side, as shown in the figure, and so on, till the full size is obtained; and it will be seen, as in the right-hand view in Fig. 3042, that by this process of "scarfing" equally from, both sides, the iron from the very middle of the body of the shaft is drawn up quite to the crank pin. The location of the pin is indicated by A A, and it will be seen that by no possibility can there be a "scarf end" in the crank pin, as the slabs in all cases go right across the crank, and also that the cheeks of the cranks have no edge weldings crossing them, as in the previous cases; for the tail of a slab may be at R, Fig. 3042, while the other end may be at S. The fibre is also developed by the continuous drawing up of the iron consequent upon the repeated flat scarfings across the whole width of the crank. When the crank has been thus massed sufficiently large, it is cut at the gable, with sufficient material left to piece out the other body of the shaft. This is now done, the coupling welded on, and a small stave drawn on the end to enable the forgeman to manipulate it, when it is turned end for end, to complete the other end. "These proceedings occupy longer time than either of the other two methods, and consequently costs a little more; but the advantage is well worth all the difference, as greater confidence can be entertained that the forging is every way satisfactory. In brief, by making the crank first, is avoided the liability to weakness at the neck, characteristic of the forgeman's making the shaft before him, as in the first method; by the repeated 'side scarfing' is avoided the liability to fracture across the cheeks, consequent upon the edge weldings of both first and second methods; while by having the slabs the whole length of the width of the crank, any 'scarf end' in the length way of the crank pin is impossible (such as may occur in the first method); and the welding of the mass of the crank being wholly on the flat must tend to form a more solid forging than if hammered otherwise. Thus, if the forging is well heated and properly hammered, the system promises to insure that no weak part will be found in the shaft after it is finished and put to work. The writer believes, from the success which has already followed in every case the adoption of this method, that it will eventually be found that almost more depends on the mode in which a crank shaft forging is constructed than on the material of which it is made. "This leads him to some observations regarding the material for such shafts. It is of course well known that in the early days of engineering, before the time when steam navigation had received a great impetus by the invention of the screw propeller, the connecting rods, cranks, shafts, &c., of land engines were all formed of cast iron; except, indeed, where the connecting rods were made of wood, strapped with plates of wrought iron, as frequently was the case with pumping, winding and blowing engines. In fact, all the parts that could be made of cast iron were so made, and the piston rods, bolts, keys, straps, and other smaller parts were alone made of malleable iron, the smaller pieces being made from rolled bars direct, as at present, and the larger made of similar bars, but placed side by side and bound together or 'fagoted,' as they were called, from their resemblance to a bundle of fagots. These bars, thus fagoted, were either brought to a welding heat in a smith's hearth and welded under the sledge-hammers of the men called 'strikers,' or hammermen; or else heated in a furnace, and welded under the tilt hammer worked by a steam engine. By-and-by it was found necessary to adopt the stronger material, wrought iron, for parts hitherto confined to cast iron, because the latter was found too deficient in cohesion to stand the strains due to the power of high-pressure steam, which was now almost universally superseding the use of low-pressure steam in the condensing engine. The system of fagoting, however, was still carried out, even far into the history of marine engineering; but when the rapid increase in the dimensions of engines, both stationary and marine, called forth the steam hammer, and so rendered the forging of heavy masses comparatively easy, the system of fagoting fell into disuse, for the following reason: In making up a fagot, say, of 18 inches or 20 inches square, it was found, that in the furnace the outside bars would reach a welding heat much sooner than those in the middle; consequently on welding this fagot under the steam hammer, though the blow might reach to the centre, yet the interior would not be welded, while the surface was; hence the shaft or other forging would not be welded throughout, and it was no uncommon thing for a shaft to break and expose the internal bars quite loose and separate from each other. "When it was seen that malleable was so much superior to cast iron, and that the system of fagoting was so imperfect, the adoption of 'scrap iron,' which was then composed principally of parings of boiler plates, pieces of cuttings from smiths' shops, old bolts, horseshoes, angle iron, &c., became general. These being piled together in suitable pieces, and in a pile of suitable size, for the convenience of working, were brought to a welding heat, and beaten out into a slab, or oblong-shaped piece, ready for the forgeman; who would build two or three together, adding more when required, and so bring out his piece to a sufficient size to enable him to shape his forging out of it. Then it was that engineers, seeing what an increase of strength they obtained by these means, invariably specified on their drawings (as many of them still do), 'These forgings are to be made of carefully selected scrap iron, free from flaws and defects.' "To meet the requirements of their customers, therefore, forge-masters had now nothing to do but to select and use the best available scrap iron; but the universal adoption of iron hulls in place of wooden ones, conjoined with the rapid and unprecedented increase in steam navigation, soon introduced a class of scrap iron which did not possess the qualifications of good scrap, and also called for a very much greater supply of forgings than could be obtained in superior scrap iron. The consequence was that shafts of scrap iron, when turned and finished, became liable to exhibit streaks and seams, not due alone to imperfect welding in the forging, but likewise to the laminations and imperfections of the original scrap iron, which the process of piling and shingling into the slab was not sufficient to obliterate. So constantly does this yet occur that it causes a strong temptation to make such forgings of new iron puddled direct from the pig and then shingled into slabs or blooms, under the idea that these streaks and seams will thus be avoided, and that the iron will be improved almost to the condition of scrap iron, while being forged under the steam hammer. This, however, is found not to be the case. The forging is certainly free from the streaks of the scrap iron, but this is obtained at the expense of strength; for the material is too raw; it wants cohesion, and has not had the proper kind or amount of working to bring it to the condition of superior wrought iron. This method is still further tempting, inasmuch as it is far cheaper than the other; the material costs less than scrap iron, and, as it welds at a lower temperature, a forging can be much more quickly and easily made. Still, for whatever class of machinery it may be fitted, it should certainly be renewed in every case for a crank shaft or propeller shaft. "From these considerations it has been the custom at Lancefield, in the preparation of the iron for crank shafts, to improve upon the ordinary condition of the scrap iron in the following manner: The pile is made up of carefully cleaned and selected scrap; it is brought to a welding heat, and then hammered under the steam hammer. But instead of being beaten into a flat slab for the forgeman, it is beaten into a square billet, which is afterwards rolled in the rolling-mill into a flat bar, as if for 'best best' merchant iron. By this additional heating, hammering and rolling, all the different qualities of the scrap iron composing the pile are merged into one homogeneous material, having the fibre given to it that was lost in the separated portions of the scrap iron; and this, when cut up into proper lengths, and again piled and shingled into the slab, results in a material possessing somewhat the closeness and density of steel, while retaining all the toughness and tenacity of superior malleable iron. The improved method of constructing the forging, previously detailed, is worthy the use of this superior material; and both having been adopted at Lancefield with results which have commended themselves so unmistakably to many engineers, that they now not only specify the material, but stipulate for the mode of manufacture, it is thought the system has only to be more widely known in order to be universally adopted. It is certain to give greater confidence in the endurance of such important parts of the machinery, although this confidence may have to be obtained by a small increase in the cost, due to the extra workmanship both on the material and on the forging. "When we take into consideration the vastly accelerated speed of the marine engine in late years, and the many disastrous effects which follow the breaking of a shaft at sea--also that the tendency of the age is still towards much higher pressures, and further lengthening of stroke it is not surprising that improvement in such an important part as the crank shaft should be eagerly sought after; but it has hitherto been sought in the direction of the material alone. Cast steel has been advocated, and brought to some extent into use; but its expense renders such shafts costly out of all proportion to the other parts of the engine; while, in the event of their heating when at work (a very frequent casualty), and having the water-hose directed upon the crank pin or journals, it cannot be expected that the material will behave any better, or even so well, as tough wrought iron. What is termed puddled steel is liable to the same objection, and probably, from its mode of manufacture, in a still greater degree. The so-called mild steel is no doubt proving itself a superior material, and yielding good results when rolled into ship or boiler plates. But thus prepared it is more costly than 'rolled scrap bar;' and if not rolled, but cast into an ingot, then it possesses some of the crystalline characteristics of steel, with all the disadvantages attending its manipulation into a forging. "For extra large crank shafts, the fear of unsoundness, arising from the ordinary mode of forging, has led some engineers to consider the propriety of building the shafts and cranks in separate pieces. This, with engineers generally, has not hitherto been looked upon with favor; as the fewer the pieces the more rigid the shaft. Moreover, the increased weight necessitated by this separate building is viewed as a disadvantage, even although it were not attended with greater cost, as undoubtedly it is. "The material and mode of manufacture advocated in this paper may tend to dissipate some of these apprehensions. They will not obviate defective construction in the engines themselves, or faulty proportion of their parts, or neglectful supervision of their working, but they will reduce to a minimum the risk of breakage in such untoward circumstances. If any objection be taken on the score of extra size, the enterprise which a quarter of a century ago engaged in the making of the unusually large shafts necessary for the 'Great Eastern' may still be trusted to meet the advancing requirements of the present day." Fig. 3043 represents a foot-power hammer or Oliver. The hammer is upon a shaft in bearings, and is held in the position shown by an open coiled spring. On the shaft is a chain pulley, the other end of the chain being connected through a leather strap to the treadle. Means are provided to adjust the height to which the hammer will lift to bring the hammer face fair with the work and to give the required degree of tension to the spring. Fig. 3044 represents a Standish's foot-power hammer, in which the hammer and the anvil are provided with dovetail seats for receiving dies, swages, &c. The force of the blow is regulated by the height to which the hammer is raised, which may be adjusted by the nuts beneath the spiral springs. The handle on the hammer is for pulling the hammer down by hand when adjusting the lower die fair with the upper one. What are known as power hammers are those driven by belt and pulley; while those known as trip hammers have their helve lifted through the medium of revolving lugs or cams. Steam hammers are those in which the hammer is lifted by a piston in a steam cylinder; while in hydraulic hammers, the hammer is moved by water pressure. Fig. 3045 represents a Justice's power hammer, in which the hammer is guided in a slideway and is operated by leather straps attached to the ends of a spring, at the crown of which is attached a connecting rod driven by a crank disk. The stroke is altered by means of placing the crank pin in the required position in the slot in the crank disk. By means of gibs the hammer may be set to match the dies. The pulley is provided with a friction clutch operated by the treadle, shown. Fig. 3046 represents a Bradley's Cushioned Hammer, in which motion is obtained by a belt passing over a pulley on a crank shaft, whose connecting rod R is capable of adjustment for length, so as to govern the distance to which the hammer shall fall, which obviously varies with different sizes of work. The hammer is lifted through the medium of a rubber cushion A, seated in a casting to one end of which is connected the rod R, while the other end is pivoted. The lever to which the hammer is affixed is raised against the compression of the rubber cushion B, and at the top of its stroke also meets the rubber cushion C; hence these two cushions accelerate its motion after the crank has passed its highest point of revolution. The cushion D prevents the rebound of the hammer after the blow is struck; hence as a result of these cushions, heavy or light blows may be struck with great rapidity and regularity. The weight W is on a lever that actuates a break upon the wheel shown at the side, so as to enable the stopping of the hammer quickly. The machine is put in motion by pressing the foot upon the treadle T, which operates a belt tightener, the belt running loose when the treadle is released. [Illustration: Fig. 3043.] [Illustration: Fig. 3044.] [Illustration: Fig. 3045.] [Illustration: Fig. 3046.] The hammer lever or helve is adjustable for height by means of the screw G and hand-wheel H, which raise or lower the bearings in which the helve journals are carried. This is necessary, because as the helve moves in the arc of a circle the faces of the upper and lower die, or of the hammer and the anvil, as the case may be, can only come fair at one particular point in the path of the hammer; hence in proportion as the blow terminates (by meeting the work surface) farther from the anvil face, the pivot or journal of the helve must be raised, so that the journal will be horizontally level (or as nearly so as possible) with the hammer face at the moment the blow is delivered. By giving motion to the helve through the medium of cushions, a direct mechanical connection, and the destructive concussion that would accompany the same, is avoided; hence a high speed may be obtained without the frequent breakage that would otherwise ensue. [Illustration: Fig. 3047.] Fig. 3047 represents Corr's power hammer, the construction being as follows: The semi-elliptic springs, shown on top and bottom of the beam, serve to balance the stroke, so that the hammer may run from 350 to 450 strokes per minute, with safety to the machinery. The hammer is adapted to almost any form or kind of forging. Large dies may be inserted for various kinds of forming and welding, such as making plough-shares and other articles, which require that the operation be commenced with a light tap, and increased to a heavy blow at the will of the operator. The whole structure is mounted on a substantial iron bed V, 18 inches deep, 22 inches wide and 5-1/2 feet long. Attached to this bed V are two circular arms L; between them is pivoted near their top, at K, an oscillating frame H, having a longitudinal opening, in which is attached two semi-elliptic springs G G, and two plates I, with trunnions projecting laterally through the oscillating frame at K; the hammer beam F is inserted between the springs G G, and the trunnion plates I, which are bolted firmly to beam F at I; the ends of the trunnions and outsides of the oscillating frame H rest evenly against the inside of the circular arms L; at K a shaft is passed through the trunnions and beam F, and made rigid in them with its ends resting in boxing at K. Caps are provided to cover the ends of the boxing and shaft with set-screws projecting against the ends of the shaft, which secures it against end play. By these mechanical arrangements the beam F and oscillator H are securely attached independently, vibrating on one common centre, allowing no side play of the hammer E, admitting F to the free action of the springs G G; in the lower end of the oscillating frame at N is a lateral opening 10 inches vertically by 6 inches longitudinally and 4 inches laterally, with flanges projecting longitudinally one inch into this opening from both sides. This makes the opening two inches smaller on the outside than the internal cavity; the rear and front internal walls are provided with steel plates, 4 by 10 inches, 1/4 thick, resting against the inner ends of four set-screws, not shown, provided to adjust these plates to or from the sliding box at N, to compensate for wear and prevent lost motion. These plates and flanges form slides and guides between which a loose box and eccentric is provided with shaft projecting laterally through boxing at N, which project upwards from an adjustable frame immediately under the oscillator H; this permanently locates the eccentric and shaft in the lateral opening in the oscillator H, at N. The adjustable frame mentioned rests on suitable bearings on the inside of the circular arms L, and is fastened down by four bolts passing through suitable slots in the adjustable frame, entering the bearings on the arms L. This frame is adjusted back or forth by set-screws S S; this adjustment is for the purpose of giving a greater or less distance between the anvil and hammer at D, as may be desired for large or small work, long or short dies, &c. The anvil B, weighing about 500 lbs., sits down in the bed at R and rests on circular bearings (between R and B), which radiate to the centre of the top of the anvil at D, and is held rigidly in any position longitudinally desired by set-screws Q Q, with their inner ends resting on shoulders on the sides of the anvil B, which projects down about ten inches; between this lower projection and the internal wall of the bed is sufficient space to admit of any adjustment desired. This lateral adjustment is accomplished by set-screws R, passing through the sides of the bed V, with their inner ends resting against the anvil which holds it rigid at any lateral adjustment. By this arrangement the anvil is accommodated to all and any class of work or shape of dies. The anvil is constructed in two parts. Four inches of the top C may be taken off, leaving a suitable place to insert large dies for various purposes, such as dies for welding plough-shares and dies for forging journals on large shafts. A counter-shaft, provided with suitable pulleys, is attached on the rear end of the bed; this shaft is kept constantly in speed and power by the vertical belt in the direction indicated by the arrow; the other end of the shaft is provided with a flanged pulley, corresponding to a flanged pulley M, on the eccentric shaft; around these pulleys is placed a loose belt, as shown; in contact with this is a press pulley T, adjustably attached by two arms to the projecting end of the treadle P at O. If the foot be placed on the treadle at U and it be pressed down, the break on the opposite side breaks contact with the balance wheel (not shown); the press pulley will at the same time tighten the loose belt on the flanged pulleys. This gives motion to the pulley M, in the direction indicated by the arrow. Its motion is increased by a heavier pressure until it attains the same speed as the other flanged pulley; this would be the full speed, which may be diminished to any speed desired by lessening the pressure on the loose belt. By this means motion and power is given to the eccentric, which carries back and forth the lower end of the oscillating frame H; this gives vertical motion to the springs G G, and this imparts corresponding motion to the beam F. These springs accomplish a threefold object: 1st. They carry the hammer E up and down. 2nd. They cushion the hammer at the returning points and give off that power which was stored in them while cushioning. 3rd. By the power exerted in the machinery they follow up and impart still greater force to the blow. It is found by this arrangement of eccentric loose box and oscillator that when the machinery is moved in the direction indicated by the arrow, that the downward stroke is one-sixth quicker than the up stroke; this is a natural result, for the down stroke is performed while the eccentric is revolving above the centre of its shaft and nearest the fulcrum of the operator H. With the present arrangement the downward stroke is performed with 5/12 of the revolution and the up stroke is performed with 7/12; the difference is 2/12, which equals one-sixth. The up stroke is performed while the eccentric is revolving below the centre of its shaft and in that part farthest from the fulcrum of the oscillator H, so if the machinery were reversed the quick stroke would be up and the slow stroke would be down. [Illustration: Fig. 3048.] In Fig. 3048 is shown a Kingsley's trip hammer. The main bed or foundation plate A carries the bed plate or frame B, at one end of which are the pillar blocks C, which afford journal bearing to the casting carrying the hammer shaft E, being fastened thereto by the clamp D. These journals are the centre of motion of the hammer helve E. At the other end of the bed plate B, are the pillar blocks F, affording journal bearing to the cam and fly-wheel shaft, _a´´_ is the tripping cam, which is provided with two toes or cam arms, which meet the tripping piece _b´´_, and this gives the hammer two strokes in a revolution of the fly-wheel shaft or cam shaft G. The stroke of the hammer may be altered by means of the set-screws _c´´_, which move the pillar blocks F, so that the cam toes _a´´_ have contact with the tripping piece _b´´_ through more or less of the revolution of _a´´_; the pillar blocks F being retained in their adjusted position by means of the set-screws shown below them in the bed piece B. By the following means provision is made whereby the face of the hammer may be set out of parallel with that of the anvil block or lower die _d´_. [Illustration: Fig. 3049.] Fig. 3049 is a sectional view through the pillar blocks C, and casting and clamp D. The pillar blocks C C are carried in a semicircular frame _a´_, hence by unscrewing the bolts _b´_ and screwing up the pillar block on the other side, the journals are thrown out of parallel, and the plane of motion of the hammershaft is altered so that the face of the upper die does not meet that of the anvil die fair to an amount which may be varied at will by operating the screws _b´_. The object of this is to enable the forging taper (as in sword blades) with common dies, and thus to save the making of special dies for each degree of taper required. Similar provision is made in the anvil block which is easier to set, providing the degree of taper is within the limit of its range, of movement, otherwise the hammer also may be set. Fig. 3050 represents a drop hammer, and Fig. 3051 is a sectional view of the lifting mechanism. This machine consists of a base or anvil, a hammer which moves up and down between two uprights, and a lifting device, which is secured to the top of the uprights. A board secured to the hammer passes up between two friction rolls, which revolve in opposite directions. When the two rolls are moved towards each other, the friction on the board causes the hammer to rise; and when again separated the hammer will fall. The _back_ roll is keyed to a shaft, on each end of which is a driving-pulley; and thus by the use of two pulleys on the same shaft, equal wear comes on the bearings in which it revolves. The _front_ roll turns freely on its shaft, and is driven by the back roll being geared to it. To secure to the gears both strength and durability, they are made with wide faces, are geared at both ends, and the teeth are of peculiar shape. The bearings to the shaft, on which the front roll revolves freely, are eccentric to the roll, and a partial revolution of the shaft moves the _front_ towards the _back_ roll, pinching the board. To an arm which is secured to the front shaft is fastened the upright rod, the _upward_ movement of which _opens_ the rolls, and whose downward movement closes the same; the weight of the rod being sufficient to cause the hammer to rise. This arrangement, simple and yet substantial, dispenses with the two eccentric-armed bushings, and the spreading of the upright rod at the top to reach both bushings, which caused so much trouble in the old way. In place of the dog which is usually used to hold up the hammer, (which is limited in adjustment to holes located at fixed distances in one of the uprights, necessitating not only the removal of the dog to another hole, and connecting and disconnecting the same to the treadle, but also the most accurate adjustment of the collar on the upright rod to the dog holding the hammer), we use a pair of clamps, located on the lifter, under the rolls. These clamps, holding the hammer centrally, prevent the side blow against the upright, the inevitable result of the contact of hammer and dog, when the former is only held on one side, as it must be, by the use of the dog. The opening of the clamps by the foot-treadle allows the hammer to fall; and the clamps are so made that the hammer will ascend freely, whether the foot is on the treadle or not, and if the foot is off the treadle, will hold up the hammer at any point where it may be arrested in its upward movement. It will be readily seen that the only adjustment required is that of the collar on the upright rod, to any height of blow desired. [Illustration: Fig. 3050.] This machine has two treadles, one connected to the clamps, and the other to a lever which operates the upright rod. [Illustration: Fig. 3051.] To obtain repeated blows with one motion of the foot, place the foot upon the treadle connected to the clamps. If variable blows are wanted, place the foot upon the _other_ treadle, and the hammer will follow the motion of the foot. This extra treadle is a late improvement, and is not shown in the cut. The operation required to obtain automatically any number of blows of the same height is described as follows:-- [Illustration: Fig. 3052.] Pressure upon the treadle opens the clamps and allows the hammer to fall; just before the dies come together, the trip at the bottom which holds up the upright rod is released, and allows the rod to drop; this closes the rolls, causing the hammer to ascend. The hammer continues to rise until it strikes the collar on the upright rod, and, lifting the rod, opens the rolls, removing the pressure upon the board, and allows the trip at the bottom to go under to hold the rod up, and the hammer remains suspended, provided the foot is off the treadle. So long as pressure is kept on the treadle, the blows of the hammer will be continuous; but upon removal of the pressure, the hammer will assume its original position. [Illustration: Fig. 3053.] [Illustration: Fig. 3054.] [Illustration: Fig. 3055.] To procure variable blows, the operation is as follows:-- Pressure upon the treadle connected to the lever which operates the upright rod communicates itself to the treadle that opens the clamps, and the hammer falls; a locking device (not shown in cut) keeps this treadle down, and on completion of the variable blows wanted, removal of the foot from the treadle disconnects the locking device, and the hammer goes up to its original position, and is there held by the clamps. When the work is such that the operator requires an assistant, variable blows may be obtained by the use of the hand lever by this assistant. A gentle pressure upon the treadle will allow the hammer to go down slowly, but it will stop and remain suspended at any point as soon as the pressure is removed. The hammer can also be arrested at any point on its way up, by bringing into action the hand lever, so that the next blow can be given from a state of rest at a less height than the collar is set for. The clamps in holding up the hammer keep the board from touching either roll, and prevent the same from being worn uneven when not in use. The back roll is made adjustable to different thicknesses of lifting board, as are also the clamps. [Illustration: Fig. 3056.] Figures from 3052 to 3056 represent a steam hammer. The head A is set at an angle in the frame. The anvil or die C is oblong, as is also the anvil die D. The object of this arrangement is to enable the workman, after drawing out his work across the short way of the die, to turn it and finish it lengthwise without being inconvenienced by the frame. By this means skew and [T]-shaped dies can be dispensed with, and the full service of the ram utilised. The latter is moved between the guides E E, and held in place by the steel plate F, bolted through the frame B. The valve G is a plain cylinder of cast iron, enlarged at each end to work in the cylindrical seats H H, in which the ports I I are placed. Steam is admitted through the valve J, and circulates round the valve G, between the seats. The exhaust chamber K is below the cylinder, which therefore drains condensed steam into it at each stroke through the lower steam port. The exhaust above the piston passes down through the interior of the valve, as shown by the arrow on the drawing. The valve stem L is connected with the valves in the exhaust chamber. No stuffing box is therefore required, there being only atmospheric pressure on each side of it. This combination enables the valve to be so perfectly balanced that it will drop by its own weight while under steam. [Illustration: Fig. 3057.] [Illustration: Fig. 3058.] The automatic motion is obtained by an inclined plane M upon the ram A, which actuates the rocker N, the outer arm of which is connected by a link to the valve stem, and thus gives motion to the valve. The valve is caused to rise in the up-stroke by means of the rocker N and its connections, through the inclined plane. The steam is thus admitted to the top, which drives down the piston, while the valve and its connections follow by gravity, thus reducing considerably the friction and wear upon the valves. In very quick work the fall of the valves may be accelerated by the aid of a spring; or it may be retarded in heavy work by friction springs, so as to obtain a heavier blow by a fuller admission of steam. For general work, however, the arrangement shown is perfectly effective, and as the rocker N is hung upon the adjustment lever P, any required variation can be obtained by the movement of the lever. Single blows can be struck with any degree of force, or a rapid succession of constant or variable strokes may be given. The anvil O rests upon a separate foundation, in order to reduce the effect of concussion upon the frame. The drawing illustrates the arrangement. The bed is long, extending beyond the hammer on each side so as to give plenty of area, and the ends are left open for convenient access in case the anvil should settle and require re-adjustment. Other forms of hammers having the same general principles of construction are as follows:-- Fig. 3057 represents a double frame hammer, the weight of the hammer being supplemented by steam pressure. The spiral springs shown beneath the cylinder are to prevent the hammer from striking the cylinder and causing breakage from careless handling by the operator. The valve gear is arranged for operation either automatically or by hand. Fig. 3058 represents a double frame steam drop hammer for stamping work out in formers or dies. The frames are bolted to the anvil base and the ram for the top die is guided by vertical slides on the inner face of the frame. Shoes are provided, whereby the wear of the ram and of the slides may be taken up, and the upper die kept properly matched with the lower one. [Illustration: Fig. 3059.] [Illustration: Fig. 3060.] [Illustration: Fig. 3061.] [Illustration: Fig. 3062.] [Illustration: Fig. 3063.] Fig. 3059 represents a double frame steam drop hammer for locomotive and car axles and truck bars. The frame is spread at the base to admit wide work, and the upper surface of the base is provided with rollers supported by springs, these rollers supporting the work. The same may be operated automatically or by hand. The hydraulic forging press at the Edgemore Iron Works of Wilmington, Delaware, consists of a piston operating in a cylinder, and having at its lower end a head guided by four cylindrical columns that secure the base plate, or anvil, as it may be termed, to the cylinder. To the above-mentioned head is secured the upper die, the lower one being secured to the base plate. Fig. 3060 represents a female die, and Fig. 3061 plan of another female die, and Fig. 3062 plan of male die used in connection with the press to forge the eye bars for the Brooklyn Bridge, five pieces each an inch thick being welded to the bar and pressed into shape at one operation. [Illustration: Fig. 3064.] [Illustration: Fig. 3065.] [Illustration: Fig. 3066.] Figures from 3063 to 3066 represent a locomotive driving wheel ready to have its hub welded by hydraulic pressure. The spokes having been forged are held together by a band or hoop, as shown. The thickness of the hub or boss is made up by the rings or washers shown in the sectional view. The dies under which the welding is done are shown in Figs. 3064 and 3066. [Illustration: Fig. 3067.] Thin forgings are often made by compression between two rollers, the form of the surface of the rollers, or projections or depressions upon the same, pressing the forging to shape. Thus, in Fig. 3068 are shown a pair of rolls A B, P representing a piece of work, and C D two cam pieces fast upon the roll surfaces; S is a fixed stop. Suppose the work to be pushed through the rolls and to rest against the stop S, then when the cams C D meet it they will pull it through and reduce its thickness by compression towards the workman. The rollers are obviously rotated by gear wheels; but they are sometimes provided with a certain amount of give or elasticity at their bearings, so that the reduction of work diameter may be obtained by several passages of the work through the rolls. [Illustration: Fig. 3068.] [Illustration: Fig. 3069.] The shape of the cams, as C D, determines that of the work; thus in Fig. 3069 is shown a pair of rolls for forming knife blades, each cam having sunk in it a die equal in depth to half the thickness of the knife. If the work is very short in comparison with the circumference of the rolls, two, three, or more cams may be arranged around the circumference, making an equal number of forgings or impressions, as the case may be, at each revolution of the rolls. In Fig. 3067 is shown a nail-forging machine for producing, from strip iron, nails similar to hand-made, at rates varying from two to three hundred per minute, and lengths of from six to one inch, two nails being completed at each revolution of the driving shaft of the machine. The framing consists chiefly of a main casting, to which are fixed an upper frame, carriages for the driving shaft, and other details. The principal moving part is a heavy steel slide, deriving its motion from a crank pin with adjustable throw; this slide carries two shears, two gripping dies, and sundry indispensable appendages, to some of which it imparts motions for guiding the nails between the stages of cutting off and finishing. The successive operations by which each nail is perfected are as follows:-- A piece of iron about six inches long, and of a width and thickness respectively of the finished nail, is inserted at a red heat to the feeder of the machine; a narrow strip is immediately cut off the lower side of the heated iron, and by the motion of the steel slide is carried to and pressed against a fixed die; while in this position another die rises at right angles and presses the partially formed nail against another fixed die. Thus the headless nail is firmly held on its four sides, and while in this position a lever, moved by a cam, and carrying a suitable tool, advances and forms the head, thus completing the nail. The return motion of the steel slide releases the nail, leaving it free to fall, but as its weight is not sufficient to insure this happening, a "knocker off" is provided, which at the right moment forcibly ejects the nail by way of a guiding shoot into a receptacle placed outside the machine. It is to be noted that the tools for shearing and gripping, and which have to be changed with each different size of nail, are made of a special mixture of cast iron. They are thus easy of preparation and renewal, while at the same time answering their intended purpose as well as or better than the finest cast steel, at less than half the cost. The whole of the machine is carried upon an open-top cast-iron water tank, serving as a receptacle for the tongs and tools heated in withdrawing the iron from the furnace. [Illustration: Fig. 3070.] Figs. 3070 and 3071 represent a machine for forging threads on rods and screws. As forgings, the threads are beautifully clean, and for the general work of coach screws much stronger than the cut threads. A perspective view of the machine is given in Fig. 3070, and a vertical of it shown in Fig. 3071. In the former figure, _a_ _b_ are the screw dies. The rod or bolt to be threaded is placed upon the lower die _b_, and fed forward while screwing it. The upper die is mounted on a slide _c_, which is actuated in the downward direction by an eccentric _e_ on the main shaft and the toggle-bar _d_, the upward motion being obtained by an internal spiral spring _f_. The lower die _b_ is carried in a slide _g_, and is adjusted at the proper distance from the upper die by means of wedge _h_, and the inclined plate _i_, beneath the slide _g_. The wedge _h_ is operated by a pedal _l_, and secured in its highest position by a bolt _j_, received in a mortice made in the plate _i_, the bolt being operated by a pedal _m_. In order to release the wedge and return it to its lowest position, the bolt is raised by pressing down the pedal _m_, whereby the wedge is free to be returned by the counterweights _k_, in connection with pedal _l_; slide _g_, carrying the lower die, then descends by its own gravity, and so separates the two dies sufficiently to allow of the removal of the screw-bolt or rod therefrom. To compensate for the wear of the dies, and admit of their adjustment, another wedge _o_, with screw adjustment, is disposed below the inclined plate _i_. Fig. 3072 represents a lag screw forged by the machine. [Illustration: Fig. 3071.] [Illustration: Fig. 3072.] [Illustration: Fig. 3073.] Fig. 3073 represents a finishing machine for horseshoes. The bars of iron are rolled with the creases (for the nail heads of the finished shoe) in them. The blanks for the shoes are then cut to length and bent, and the nail holes punched. The shoes then pass to a machine, Fig. 3073, which consists of a frame A B, carrying the roll C, above the table D, and a second roll, not shown in the cut, but being directly beneath C, there being between these two rolls sufficient space to let the dies (which press the shoes into shape) pass. These dies rest upon the table D, and are carried around upon it in a direction from left to right of the chain H, to the links of which the dies are attached. This chain is operated by the vertical shaft J, having a pulley for belt power at K. As each die approaches the rollers, a shoe (cut to length, creased, and punched as already described) is placed on it, and on reaching the rolls the shoe is pressed into form on the die by the rolls, the bottom roll serving as a rolling bed so as to reduce the friction that would be due to a sliding motion on the bottom of the die. The top roll C, which presses the shoe into the die is driven by power. [Illustration: Fig. 3074.] [Illustration: Fig. 3075.] A plan view of the machine is shown in Fig. 3074, and a view showing the shape of the dies is given in Fig. 3075. [Illustration: Fig. 3076.] The surface _h_ forms the frog. To give the required concavity to the toe and sides of the shoe, the surface _i_ is made convex, and tapered or inclined towards _h_. The tread _e_ is deepest at the heel on both sides, and highest at the toe. It is obvious that by suitably shaping the surfaces _h_, _i_, and _e_, any required form may be given to the shoe. Fig. 3076 represents a shoe creased, punched, and bent ready to be passed to the machine. [Illustration: Fig. 3077.] Fig. 3077 represents a circular saw for cutting off hot iron; A is the frame of the machine, the arm B pivoted at C carrying the saw D; F is a spring bolted to the frame and serving to hold the saw in the position shown. The work E is gripped by the lever L, which is pushed over by hand. The lever L is adjusted to suit different sizes of work by the screw G, which raises or lowers the piece H, to which L is pivoted. The saw is brought into contact with the work, and fed to it by applying the foot to the lever or arm B at I, the screw J being made to contact with the foot of the machine by the time the saw has passed through the work, thus preventing the saw from moving too far forward after passing through the work. CHAPTER XXXIV.--WOOD-WORKING. PATTERN-MAKING.--Of the different kinds of wood serviceable to the pattern-maker, pine is, for many reasons, usually employed. It should be of the best quality, straight-grained, and free from knots; it is then easy to work in any direction, possessing at the same time sufficient strength for all but the most delicate kinds of work, and having besides the quality of cheapness to recommend it. Care taken in its selection at the lumber-yard will be amply repaid in the workshop. When it is straight-grained, the marks left by the saw will show an even roughness throughout the whole length of the plank; and the rougher the appearance, the softer the plank. That which is sawn comparatively smooth will be found hard and troublesome to work. If the plank has an uneven appearance--that is to say, if it is rough in some parts and smooth in others--the grain is crooked. Such timber is known to the trade as cat-faced. In planing it the grain tears up, and a nice smooth surface cannot be obtained. Before purchasing timber, it is well to note what convenience the yard possesses for storing. Lumber on the pile, though it be out in all weathers, does not deteriorate, but becomes seasoned; nevertheless its value is much increased if it has an extemporised roof to protect it from the sun and rain. But as it is not convenient to visit the pile for every customer, quantities are usually taken down to await sale, and for such a shelter must be provided, otherwise it will be impossible to insure that the lumber is dry, sound, and fit for pattern-making. It is obvious that the foregoing remarks on the storage of lumber apply to all woods. The superiority of pine for pattern-making is not, however, maintained when we come to fine delicate patterns or patterns requiring great durability. When patterns for fine work, from which a great many castings are to be made, are required, a fine pattern wherefrom to cast an iron pattern is improvised, because, if pine were employed, it would not only become rapidly worn out, but would soon warp and become useless. It is true that a pine pattern will straighten more easily than one made of a hard wood; but its sphere of usefulness in fine patterns is, for the above reasons, somewhat limited. Iron patterns are very desirable on account of their durability, and because they leave the sand easily and cleanly, and because they not only do not warp but are also less liable than wooden ones to give way to the sand, while the latter is being rammed around them by the moulder, a defect that is often experienced with light patterns, especially if they are made of pine. Iron patterns, however, are expensive things to make, and therefore it is that mahogany is extensively employed for fine or durable pattern work. Other woods are sometimes employed, because they stand the rough usage of the moulding shop better and retain the sharp corners, which, if pine be used, in time become rounded impairing the appearance of the casting. Mahogany is not liable to warp, nor subject to decay; and it is exceedingly durable, and is for these reasons the most desirable of all woods employed in pattern-making, providing that first cost is not a primary consideration. There are various kinds of this beautiful wood: that known as South American mahogany is chiefly used for patterns. Next to mahogany we may rank cherry, which is a very durable wood, but more liable to twist or warp than mahogany, and it is a little more harsh to the tool edge. If, however, it is stored in the workshop for a length of time before being used, reliable patterns may be made from it. In addition to these woods, walnut, beech, and teak are sometimes employed in pattern-making. The one property in all timber to be specially guarded against is its tendency to warp, bend, expand, and contract, according to the amount of humidity in the atmosphere. Under ordinary conditions, we shall be right in supposing a moisture to be constantly given off from all the exposed surfaces of timber; therefore planks stored in the shop should be placed in a rack so contrived that they do not touch one another, so that the air may circulate between the planks, and dry all surfaces as nearly alike as possible. If a plank newly planed be lying on the bench on its flat side, the moisture will be given off freely from the upper surface, but will, on the under surface, be confined between the bench and the plank: the result being that a plank, planed straight, and left lying as described, will be found, even in an hour, to be curved, from the contraction of the upper surface due to its extra exposure; therefore it is obvious that lumber newly planed should be stored on end or placed on edge. Lumber expands and contracts with considerable force across the grain; hence if a piece, even of a dry plank, be rigidly held and confined at the edges, it will shrink and break in two, often with a loud report. There is no appreciable alteration lengthwise in timber from the above causes; and if two pieces be glued together so that the grain of one crosses that of the other, they can never safely be relied upon to hold. Hence they had better be screwed so that there will be a little liberty for the operation or play of the above forces, while the screws retain their hold. The shrinkage, expansion, and warping of timber may perhaps be better understood by the following considerations: The pores of wood run lengthwise, or with its grain, and hence the moisture contained in these passes off more readily endwise or from any surface on which the pores terminate. THE SHRINKAGE OF TIMBER.--The direction in which timber shrinks in seasoning or drying is shown in the following figures, which are extracted from a lecture delivered by Dr. Anderson before the Society of Arts in London, England. The shrinkage of timber lengthwise of the grain is very slight, its shrinkage in a direction across or at a right angle to the length of the grain being much greater and depending upon the part of the log from which it is cut. [Illustration: Fig. 2706.] The shrinkage is greater on the outside than near the heart of the tree; thus if a log be cut into four quarters it will shrink as in Fig. 2706, from the full block outside to the inside or white outline; or if we cut out a square as in figure, one corner extending to the heart, it will shrink to the form shown in the figure. If we sever the log by the four parallel saw cuts it will shrink as shown by the black outline, the shrinkage of the middle piece being more clearly shown in Fig. 2707. [Illustration: Fig. 2707.] [Illustration: Fig. 2708.] It is evident, therefore, that to obtain a uniform degree of shrinkage throughout the length of a piece of timber, it should be sawn as near as possible parallel with the grain of the log. Thus in Figs. 2708 and 2709 we have a side and an end view of a log, the saw cuts at A being from logs that have been squared, the upper slab B being waste material, and the planks being parallel to the squared sides of the log. [Illustration: Fig. 2709.] The lines from A to C on the lower half of Fig. 2709 represent planks that are what is termed flitched, the saw cuts following the taper of the tree, and it is plain that the shrinkage would be more uniform; thus the outside plank is near the bark from end to end, while at the top of the figure the outside plank is near the outside at the small end only of the log, and would therefore shrink most at the right hand end. Furthermore as the planks at A cross the grain of the log at its large end, they are therefore weaker and more liable to split at that end. BENDING TIMBER.--By bending a piece of timber to bring it as near as possible the required shape the strength of the work is increased, because the grain of the wood runs parallel with the shape of the work, and, furthermore, the cutting tools act on this account to better advantage. In bending a piece of timber it is obvious that either the convex side must stretch, or the concave one compress, or if no extraneous pressure is brought to bear upon the piece, both of these actions may occur, and as the side of the piece that was nearest to the heart of the tree is the hardest and strongest, it will stretch less if made the convex side, or compress less if made the concave side of the timber, but the bent piece will maintain its shape better if the heart is the convex or outside of the curve. The modern method of bending wood is to fasten on the outside, or convex side of the piece, a strap that will prevent it from stretching. And it is found that wood thus bent is stronger, stiffer, and heavier than before it was bent, because the fibres become interwoven, and it is found that the wood is harder to split than before. [Illustration: Fig. 2710.] [Illustration: Fig. 2711.] [Illustration: Fig. 2712.] Suppose we require to bend a piece to a half circle, and after it has been boiled, steamed, or heated with a dry heat it is placed in an iron strap, such as shown in Fig. 2710, having an eye at each end in which a hook may be inserted to hold the piece in shape (after it is bent) until it is dry again. The piece with this strap on its outside or uppermost surface is laid on the _former_ or forming piece shown in Fig. 2711, which has a projection at A, fitting into the recess A of the bending block in Fig. 2712. On the outside of the piece is then placed the strap, shown in Fig. 2713, its blocks of wood fitting to the ends of the piece to be bent. The winch of the bending block is provided with a rope, whose ends have two hooks which are engaged in the eyes of the straps, shown in Fig. 2714, and by operating the winch the piece is bent to shape, as shown in Fig. 2714. While in this position a hook is placed through the eyes of the band that is around the bent piece of work, so that when removed from the forming block or stand it appears as in Fig. 2715. [Illustration: Fig. 2713.] [Illustration: Fig. 2714.] [Illustration: Fig. 2715.] [Illustration: Fig. 2716.] [Illustration: Fig. 2717.] [Illustration: Fig. 2718.] When, however, the piece requires to be bent to more than one sweep or bend, the process requires to be changed somewhat. Thus, suppose the middle is to be bent circular and the two ends left straight, and the strap on the piece to be bent is provided with a piece, such as in Fig. 2716, the ends B engaging in eyes in the strap, and the screw A abutting against the end of the piece to bind the strap firmly upon the ends, as in Fig. 2717, in which the piece is shown within the strap. After it has been bent to the former it is held there by straps and wedges, as shown in Fig. 2718. [Illustration: Fig. 2719.] The next operation is to lock the curve, as shown in Fig. 2719, between an inside and outside former by means of straps A A and wedges C, when the ends D of the piece may be bent up to the dotted lines and locked to the ends of the top former by straps and wedges. The length of time a piece should be boiled or steamed for the bending process depends upon the size of the piece and the kind of wood, hard wood requiring longer boiling or steaming. A piece of ash, say 2 by 4 inches in cross section, would require about six hours' steaming with a low pressure of moist or wet steam, but it would not suffer damage if it were steamed for a day. Pieces not over half an inch thick may be bent after steaming them about half an hour. If the wood is steamed too much it loses its elasticity and will pucker on the inside surface of the bend when in the former or bending block. The period during which the piece should be held to its bent shape before being released varies from twelve hours for thin pieces to twenty-four hours for thick ones, and it is found that pieces which have been bent in a strap so as to prevent the outside from stretching, will, in drying, increase their bend or curvature, while those not confined at their ends straighten out. [Illustration: Fig. 2720.] [Illustration: Fig. 2721.] [Illustration: Fig. 2722.] The cracks that are found in timber are termed _shakes_; thus in Fig. 2720 the black lines represent what are called heart shakes, while those in Fig. 2721, being wider, are termed star shakes. When the shakes are circular, as in Fig. 2722, they are called cup shakes. Many of the tools used by the pattern-maker have been described in connection with hand turning, hand boring tools, lathe tools, &c., and therefore need no further reference. PLANES.--For roughing out the work the jack plane is employed, varying in size from 14 inches long with a cutter knife or blade 2 inches wide, to 27 long with a blade 2-1/4 inches wide, and as its purpose is to make a flat surface, it is preferable that it be as long as the work will conveniently permit. The jack plane is followed by the fore plane, the truing, or trying plane, which varies in size from about 18 inches long with a blade 2-1/8 inches wide, to 20 inches long with a cutter or blade 2-3/8 inches wide. When the fore plane is made longer, as for planing long joints, it is termed a jointer plane, the length being as much as 30 inches and the blade 2-5/8 inches wide. The smoothing plane varies from about 5 inches long with a blade 1-1/2 inches wide, to 10 inches long with a blade 2-3/8 inches wide. Smoothing planes are, as the name implies, used to simply smoothen the work surface after it has been trued. The angle of the plane blade to the sole of the plane is for ordinarily soft wood 45°, but 50° or 55° may be used for very hard woods. [Illustration: Fig. 2723.] [Illustration: Fig. 2724.] To break the shaving the blade is attached to what is termed a cover, which is shown in Fig. 2723, B representing the blade and A the cover. The cover is curved to insure that it shall bed against the blade at its very end, and, therefore, as near to the cutting edge as a maximum distance 1/16 inch for rough and 1/32 inch for finishing cuts. The blade of a jack plane is most efficient when it is ground well away towards the corners, as at A B in Fig. 2724, thus producing an edge curved in its length. When the blade is in position in the stock for cutting off the maximum of stuff, its blade should project nearly 1/16 through the sole of the stock, while the corners A B are about level with the face of the stock. The bevelled face should stand at about an angle of 25° to the flat face. In grinding it care should be taken to grind it as level as possible, rounding off the corners as shown above. The grindstone should be kept true and liberally supplied with water; the straight face should not be ground away, nor indeed touched upon the stone, except to remove the burr which will sometimes turn over. The pressure with which the blade is held against the grindstone should be slight at and toward the finishing part of the grinding process, so as not to leave a long ragged burr on the end of the blade, as is sure to be the case if much pressure is applied, and it will occur to a slight extent even with the greatest of care. The blade should not be held still upon the grindstone, no matter how true, flat, or smooth the latter may be; but it should be moved back and forth across the width of the stone, which will not only grind the blade bevel even and level, but will also tend to keep the grindstone in good order. In oilstoning a plane blade, the straight face should be held quite level with the face of the oilstone, so that the cutting edge may not be bevelled off. Not much application to the oilstone is necessary to the straight face, because that face is not ground upon the grindstone, and it only requires to have the wire edge or burr removed, leaving an oilstone polish all along the cutting edge. The oilstoning should be performed alternately on the flat and bevelled faces, the blade being pressed very lightly on the oilstone toward the last part of the operation, so as to leave as fine a wire edge as possible. The wire is the edge or burr which bends or turns over at the extreme edge of the tool, in consequence of that extreme edge giving way to the pressure of the abrading tool, be it a grindstone or an oilstone. This wire edge is reduced to a minimum by the oilstone, and is then so fine that it is practically of but little account; to remove it, however, the plane blade or iron may be buffed backwards and forwards on the palm of the hand. The blade being sharpened, we may screw the cover on, adjusting it so that its edge stands a shade below the corners of the iron, and then screwing it tight; the blade or iron and the cover must now be placed in the mouth of the plane stock, and adjusted in the following manner:-- The plane iron should be passed through the mouth of the stock until as much in depth of it is seen to protrude from the bottom face of the stock as is equal to the thickness of shaving it is intended to cut: to estimate which, place the back end of the plane upon the bench, holding the stock in the left hand with the thumb in the plane mouth, so as to retain the iron and wedge in position, the wedge being turned towards the workman. A glance down the face of the stock will be sufficient to inform the operator how much or how little the cutting edge of the iron protrudes from the face of the plane stock, and hence how thick his shaving will be. When the distance is adjusted as nearly as possible, the wedge may then be tightened by a few light hammer blows. If, after tightening the wedge, the blade is found to protrude too much, a light blow on the fore end on the top face of the plane will cause it to retire; while a similar blow upon the back end will cause it to advance. In either case the wedge should be tightened by a light blow after it is finally adjusted. In using a jack plane we commence each stroke by exerting a pressure mostly on the fore part of the plane, commencing at the end and towards the edge of the board, and taking off a shaving as long as the arms can conveniently reach. If the board is longer than can be reached without moving, we pass across the board, planing it all across at one standing; then we step sufficiently forward, and carry the planing forward, repeating this until the jack planing is completed. To try the level of the board, the edge or corner of the plane may be employed; and if the plane is moved back and forth on the corner or edge, it will indent and so point out the high places. The fore plane (or truing plane, as it is sometimes called) is made large, so as to cover more surface, and therefore to cut more truly. It is ground and set in the same manner as the jack plane, with the exception that the corners of the iron or blade, for about one-eighth inch only, should be ground to a very little below the level of the rest of the cutting edge, the latter being made perfectly straight (or as near so as practically attainable) and square with the edge of the iron. If the end edge of the cover is made square with the side edge, and the iron is ground with the cover on, the latter will form a guide whereby to grind the iron edge true and square; but in such case the cover should be set back so that there will be no danger of the grindstone touching it. The oilstoning should be performed in the manner described for the jack plane, bearing in mind that the object to be aimed at is to be able to take as broad and fine a shaving as possible without the corners of the plane iron digging into the work. The plane iron should be so set that its cutting edge can only just be seen projecting evenly through the stock. In using the fore or truing plane, it is usual, on the back stroke, to twist the body of the plane so that it will slide along the board on its edge, there being no contact between the cutting edge of the plane iron and the face of the board, which is done to preserve the cutting edge of the plane iron from abrasion by the wood: as it is obvious that such abrasion would be much more destructive to the edge than the cutting duty performed during the front stroke would be, because the strain during the latter tends mainly to compress the metal, but, during the former, the whole action tends to abrade the cutting edge. The face of the fore plane must be kept perfectly flat on the underside, which should be square with the sides of the plane. If the under side be hollow, the plane iron edge will have to protrude farther through the plane face to compensate for the hollowness of the latter; and in that case it will be impossible to take fine shavings off thin stuff, because the blade or iron will protrude too much, and as a consequence there will be an unnecessary amount of labor incurred in setting and resetting the plane iron. The reason that the under surface should be square, that is to say, at a right angle to the sides of the body of the plane, is because the plane is sometimes used on its side on a shooting board. When the under surface of the plane is worn out of true, let the iron be wedged in the plane mouth, but let the cutting edge of the iron be well below the surface of the plane stock. Then, with another fore plane, freshly sharpened and set very fine, true up the surface, and be sure the surface does not wind, which may be ascertained by the application of a pair of winding strips, the manner of applying which will be explained hereafter. If the mouth of a fore plane wears too wide, as it is apt in time to do, short little shavings, tightly curled up, will fall half in and half out of the mouth, and prevent the iron from cutting, and will cause it to leave scores in the work, entailing a great loss of time in removing them at every few strokes. The smoothing plane is used for smoothing rather than truing work, and is made shorter than the truing plane so as to be handier in using. It is sometimes impracticable to make a surface as smooth as desirable with a truing plane, because of the direction of the grain of the wood. [Illustration: Fig. 2725.] Fig. 2725 represents an ordinary compass plane, which is a necessary and very useful tool for planing the surfaces of hollow sweeps. This tool is sometimes made adjustable by means of a piece dovetailed in the front end of the plane, which, by being lowered, alters the sweep and finally converts it from a convex to a concave. [Illustration: Fig. 2726.] In Fig. 2726 is shown a much superior form of circular or compass plane. Its sole consists of a flexible steel blade, whose ends are attached to levers that are connected together by toothed segments. By means of the large hand-screw the levers are operated, causing the sole to bend to the required curvature, and by reason of the toothed segments the levers move equally, and therefore give the sole a uniform curve throughout its length. [Illustration: Fig. 2727.] [Illustration: Fig. 2728.] Planes are also made with the sole and the cutting edge of the blade made to conform to the shape of the work. Thus Fig. 2727 represents a rabbeting plane, and Fig. 2728 a side rabbet plane. The latter is, however, very seldom used, but is especially useful in planing hard wood cogs fitted to iron wheels, or the teeth of wheel patterns or other similar work. For ordinary use, it is sufficient to have two, a 3/4 and a 1-1/4 inch, and two or three having a flat sole for flat bottom grooves. What is known as a core box plane has its sole at an angle of 90°, or a right angle; the principle of its action is that in a semicircle the angle is that of 90°. [Illustration: Fig. 2729.] [Illustration: Fig. 2730.] In Fig. 2729, for example, it is seen that if a right angle be laid in a semicircle so that its sides meet the corners of the same when revolved, its corner will describe a true circle; hence at each plane stroke the plane may be slightly revolved, to put on the cut, which must be very light, as the core box plane is only suitable for finishing purposes. For planing across the end grain of wood, what are termed block planes are used, the angle of the blade to the sole being from 65 to 85 degrees, as shown in Fig. 2730, which represents the Stanley iron frame block plane. In block planes the bevel that is ground to sharpen the blade is placed in front and therefore meets the shaving instead of the flat face as in other planes. [Illustration: Fig. 2731.] [Illustration: Fig. 2732.] Fig. 2731 represents the Stanley bull-nose rabbet plane for getting close into corners, and Fig. 2732, a block plane, in which the blade may be set in the usual position or at one end of the stock as denoted by the dotted lines. [Illustration: Fig. 2733.] [Illustration: Fig. 2734.] For fine work planes having an iron body are much preferable to the wooden ones, and in the improved form of planes there is provided a screw mechanism, whereby the blade may be set much more accurately and easily than by hammer blows, such as are necessary with ordinary wedge-fastened blades. Thus Fig. 2733 represents Bailey's patent adjustable planes, the handles only being of wood. The blade is secured by a simple lever movement, and is set by means of the thumb screw shown beneath and behind the blade. The metal stock possesses several advantages, such as that the sole keeps true, the mouth does not wear too large, as is the case with wooden planes. Planes are also made having a wooden body and an iron top, the latter containing the mechanism for locking the blade and setting it quickly. Fig. 2734 represents one of these planes. [Illustration: Fig. 2735.] Figs. 2735 to 2744 represent a combination plane. Fig. 2735 is a side, and Fig. 2736 a top view of the tool as a whole. Pieces A and B form the body of the plane, between which the bits or all the tools are carried except the slitting knife, which is carried by A alone. In the figures T is a beading tool shown in position, having a bearing or seat in both A and B so as to support it on both sides, and being locked in position by the thumb-screw C. At G is a depth gauge which is moved over into the hole at D, when that position is most suitable for the kind of work in hand. Piece B is made adjustable in its distance from A so as to accommodate different widths of bits by sliding it on the arms M, securing it in its adjusted position by the set-screws S. Similarly the fence F slides on arms M, and is secured in its adjusted position by the set-screws H, thus enabling it to regulate the distance from the edge of the board at which the bits shall operate, and also guiding the bits true to the edge of the board or work. F is provided with an upper pair Q, and a lower pair R of holes (as seen in Fig. 2737) so that it may be set on the arms M at two different heights as may best suit the nature of the work. In Fig. 2736 it is shown with arms M passing through the lower pair of holes. The points of the set-screws H meet the bores of both pairs of holes and therefore lock F to the arms, whether the upper or lower holes are upon the arms. For rabbeting and fillister work the upper holes Q are used, while using ploughs the lower ones are brought into requisition. [Illustration: Fig. 2736.] [Illustration: Fig. 2737.] [Illustration: Fig. 2738.] [Illustration: Fig. 2739.] [Illustration: Fig. 2740.] At W, Fig. 2735, is a spur for cutting the end grain of the wood in advance of the bit, as is necessary in dado and other across grain work, the construction of the spur is seen more clearly in Fig. 2738. The pieces A and B are provided with a recess having four arms or branches, while the spur itself has but three, so that the spur may be set as in Fig. 2735 and be out of action, or its screw being loosened it may be given a half-turn, so that one of its arms will come below B as at X in Fig. 2738. The cutting edges of the spur come exactly flush with the outside faces of A and B, and the bits are so held in their seats that their edges also come flush with these outside faces, which therefore act as guide to the bit; thus Fig. 2739, shows a beading bit in position, and Fig. 2740 a section of work finished, A and B being in section. Fig. 2741 shows a plough in position on the work, A and B being shown in section. It is seen that their inner edges being bevelled, will in using a beading tool, act as a gauge regulating the thickness of shaving taken at each plane stroke, which will equal the depth to which the bit edge projects beyond the bevels of A and B. Similarly in grooving or ploughing the amount to which the bits project below the lowest edges of A and B regulates the thickness of the shaving, and as A and B follow the bit into the work, the blade being once set requires no further attention, the depth gauge regulating the total depth of tool action. [Illustration: Fig. 2741.] [Illustration: Fig. 2742.] [Illustration: Fig. 2743.] [Illustration: Fig. 2744.] This principle of the side pieces entering the work with the bits and being adjustable to suit various widths of bits, gives to the tool a wide range of capacity. Fig. 2742 represents the tool arranged for slitting thin stuff into parallel slips, the piece B being removed. The depth gauge is not shown in figure, because it would hide the slitting knife from view, but it is obvious that it would rest on the surface of the work and thus steady the plane. Fig. 2743 is an example of a number of operations performed by this one tool. For tonguing, the bit shown in Fig. 2744 is employed, the depth gauge _g_ being adjustable in the groove by means of the slot shown. CHISELS.--The principal kinds of chisels are the paring chisel which is used entirely by hand, and the firmer chisel which is used with the mallet. The difference between the two lies in the shapes of their handles, and that the paring chisel is longest. A paring chisel worn to half its original length will serve for a firmer chisel, because when so worn it is long enough for the duty. A chisel should not, however, be used alternately as a paring and a firmer chisel, because the paring chisel requires to be kept in much better condition than the firmer chisel does. Mortice chisels are made thicker than either the paring or the firmer because of their being longer and requiring rougher usage. It is necessary to have several sizes of chisels, varying in width from an eighth of an inch to one and a half inches. [Illustration: Fig. 2745.] [Illustration: Fig. 2745_a_.] [Illustration: Fig. 2746.] Fig. 2745 represents the form of handle for a paring chisel, its total length being 6 inches, and from A to B being 1-1/2 inches. The diameter at C is 1-1/2 inches, the hollow below D of 3/8 of an inch radius, the diameter at D 1 inch, and the length from B to E 1-1/2 inches. This form affords a firm grip to the hand, the end E being applied to the operator's shoulder. The shape of handle for a firmer chisel is shown in Fig. 2746. Chisels require great care both in grinding and oilstoning them, being held very lightly upon the grindstone when finishing the grinding so as to avoid as far as possible the formation of a long feather edge. The flat face of the chisel should never be ground, as that would make it rounding in its length, hence there would be nothing to guide it in cutting straight and the value of the tool would be almost destroyed. In oilstoning the chisel, great care is necessary in order to avoid forming a second facet at a different angle to that at which it was ground, because such a facet is too narrow to form any guide whereby to move the chisel in a straight line, and the consequence is that the edge is oilstoned rounding and cannot do good service. The whole length of the ground facet or bevel should rest on the oilstone, but the pressure should be directed mainly to the cutting end so that at that edge the oilstone will entirely remove the grinding marks, which will, however, remain at the back. If there is at hand a grindstone of sufficiently small diameter, the chisel may be made hollow on the bevel, as shown in Fig. 2745_a_, so that when laid on the oilstone the bevel will touch at the back and at the end only, and this will enable the chisel to be pressed evenly down on the stone, thus producing a very even and flat edge, while leaving but a small area to be oilstoned. The motion of the hands should not for the oilstoning be simply back and forth, parallel with the oilstone length, but partly diagonal, which will assist in keeping the chisel level. The back of the chisel should be laid flat upon the oilstone and moved diagonally, under a light pressure, which will remove the wire edge, which may be further removed by lapping the chisel on the operator's hand. [Illustration: Fig. 2747.] Chisels for turning work in the lathe are best if made short, and to enable the cutting edge to get up into a corner, the chisel is sometimes given two cutting edges, as at A, in Fig. 2747, the edges forming an angle, one to the other, of less than 90°. For finishing curves in the lathe the chisel shown at B in the figure is employed, or for deeper work, as in the bores of holes, handles are dispensed with, chisels being formed as at C and D in the figure. Gouges, like chisels, are made "firmer and paring," the distinction being precisely the same as in the case of chisels. When the bevel is on the outside or convex side of the gouge it is termed an outside, while when the bevel is on the inside or concave side it is termed an inside gouge. [Illustration: Fig. 2748.] Fig. 2748 represents an outside firmer gouge. The inside gouge may be ground a little keener than the chisel, and requires great care in grinding, because it must be held on the corner of the grindstone, which is rarely of the desired curve. In oilstoning the concave side of a gouge an oilstone slip is employed, the gouge being held in the left hand and the slip in the right, the latter being supplied with clean oil. The convex side of an outside gouge should be made level on the face of the oilstone, and while the gouge is moved to and fro its handle must be revolved so as to bring all parts of the curve in contact with the oilstone. The small amount of surface on the gouge in contact with the grindstone makes it very liable to have a long feather edge, hence it must be very lightly pressed to the stone, and the same remark applies to the oilstoning in order to reduce the wire edge. [Illustration: Fig. 2749.] Fig. 2749 represents a gouge for lathe work, its handle being made long enough to be held in both hands and used as described with reference to turning with hand tools. Another tool, very useful to the pattern-maker, is the skew chisel, which is also described in connection with hand turning. SAWS.--There are two principal kinds of saws, the rip saw for cutting lengthwise of the grain of the wood, and the cross-cut saw for cutting across the grain. In shaping these saws the end to be obtained is to enable them to sever the fibre of the wood in advance of the effort to remove it from the main body. [Illustration: Fig. 2750.] [Illustration: _VOL. II._ =THE ACTION OF SAW TEETH.= _PLATE XIII._ Fig. 2751. Fig. 2752. Fig. 2753. Fig. 2754. Fig. 2755. Fig. 2756.] In Fig. 2750, for example, the grain of the wood runs lengthwise and the throat, or front face of each tooth, is hooking or hooked, so that the cutting edge will cut through the fibres at their ends before it is attempted to remove them from the main body of the wood. Suppose, for example, that the saw shown in Fig. 2750 was put into a piece of timber and a tooth pressed hard enough on the wood to leave a mark, and this mark would appear as in Fig. 2751 at E, extending across a width equal to the full width of the saw tooth. It would do this because the front face or throat B and the back face A are both at a right angle to the saw length as is denoted by the dotted lines. As the grain is supposed in Fig. 2751 to run lengthways of the timber, clearly the fibre between the indentation E and the saw slot is severed and would be removed as the tooth passed farther down through the wood, the action of first severing the fibre at its end and then removing it being carried on by each tooth. In Fig. 2752 is shown a cross-cut saw in action upon a piece of wood in which the grain or fibre runs across the timber, and in this case the teeth require to be shaped to cut on each side of the saw instead of directly in front of it, because in that way only can the ends of the wood fibre be severed before it is dislodged from its place. To enable the cross-cut saw to accomplish this, one tooth cuts on one side of the saw slot and the next tooth on the other, as at A and B in Fig. 2751, from which it will be seen that as the grain runs lengthways of the timber, the fibres between the lines A and B will be severed at their ends by the extreme edges of the teeth before the thicker part of the tooth reaches them to remove them. The necessity for this action may be plainly perceived if we apply the rip saw for cross-cutting and the cross-cut saw for ripping. Suppose, for example, we place the saw shown in Fig. 2750 to cut across the grain of the piece of timber, and as its tooth met the wood it would indent it as at G, Fig. 2751, and as this is in line with the grain, the tooth would wedge in the piece and the piece cut could not be dislodged without first tearing the fibres apart at each end. Or suppose we take the cross-cut saw and apply it for ripping (as cutting lengthways of the grain is called) and if we indented the surface with a single tooth it would leave a mark as at F, Fig. 2751, which is lengthways of the fibre, so that the tooth would here again wedge between the fibres and not cut them. The next tooth would make a mark parallel to F, but on the other side of the saw slot or kerf as it is called, still leaving the fibre unsevered at its ends where it should be severed first. In order that the saw may not rub against the sides of the slot or kerf, and thus be hard to move or drive, it is necessary that the kerf be wider than the thickness of the saw blade, and to accomplish this the teeth are bent sideways, each alternate tooth being bent in an opposite direction, as shown in the front view of the teeth in Fig. 2753. This bending is called the set of the saw, and should be sufficient to make the kerf about two-thirds wider than the thickness of the saw blade. While preserving the feature of severing the fibre before attempting to dislodge it from its place, we may at the same time give the teeth of rip saws more or less sharpness by fleaming their faces. In Fig. 2754, for example, the throat face is filed square across or at a right angle to the length of the saw, but the back face A is at an angle, making the points of the teeth sharper, and therefore enabling them to cut more freely. The result of this fleam would be that the tooth, instead of cutting equal and level all the way across as in Fig. 2751 at E, would cut at the corner first and only across its full width as it entered deeper into the wood; we have, in fact, placed the leading part of the cutting edge more at the extreme point and less in front of the tooth. In Fig. 2755 the throat or front face of the saw is given fleam, as shown by the line B, which is not at a right angle to the saw length, and as a result the cutting edge is carried still more advanced at the point and more towards the side of the tooth and we have, therefore, to a certain extent, qualified it as a cross-cut saw. We might give the face B so much angle as to carry the leading part of the cutting edge to the side of the saw, thus giving it the characteristics of a cross cut. In Fig. 2756, both the throat face B and the back face A are given fleam, making the points extremely sharp, and showing the leading part of the cutting edge towards the side, the corner leading still more. [Illustration: Fig. 2757.] In Fig. 2757 we have two saws R and S, the latter having fleam on the front and the former on the back face of the tooth, the amount or degree of fleam being equal. [Illustration: Fig. 2758.] In Fig. 2758 we have indentations of their teeth. The teeth of S would leave a mark as at E F, and R would leave a mark as at G H. The side cut F being more than the side cut G, and the front cut E being at a less angle to F than the front cut H to G, it follows that the saw S would be the best, provided the grain of the wood ran diagonally as shown, not only because it has more side and less front cut, but also because its cutting edge is keener on the side, as is seen on comparing the lines P and A in Fig. 2757. [Illustration: Fig. 2759.] If we give fleam to both faces we alter the indentation, as denoted in Fig. 2759, in which E F represents the line of tooth cut when one face has fleam, and G H the line of tooth cut when both faces are fleamed, the shape of the actual saw cut being shown at J. Obviously the fleam makes the points weak, but this in coarse saws may be partially remedied by shaping the teeth as in Fig. 2760. Fleam on the front face or throat of the tooth has the effect of preserving its set, the pressure of the cut being as shown by the arrows in Fig. 2753. It is evident that the finer the point of the tooth the sooner it will become dulled, and that the harder the timber the more quickly the tooth will become dull. So soon as this occurs the teeth refuse to cut freely, and the extra pressure on them acts to spring them upward and to take off the set. It is obvious that for soft wood the teeth may be given fleam on both faces, and that the front face should have some fleam, even for the hardest of wood, whether the back face has fleam or not. Also, that in proportion as the grain of the wood runs more across the saw kerf than in line with it the teeth should be filed to cut on the side, and the hook of the front face may be lessened, while _vice-versâ_, in proportion as the grain of the wood runs parallel with the kerf, the tooth may have hook and fleam on the back face with a slight fleam on the front one. [Illustration: Fig. 2760.] [Illustration: Fig. 2761.] GAUGES.--Of gauges for marking on the work lines parallel to its edges there are several kinds, a common form being represented in Fig. 2761, in which the block that slides against the edge of the work is secured by a set-screw. A better method, however, is to use a key set at a right angle to the stem, so that the head may be tightened or loosened by striking it, as if it were a hammer, against anything that may happen to lie on the bench, hence the gauge may be set and adjusted with one hand while the other is holding the work, as is often necessary when marking small work. The marking point should be a piece of steel wire fitted tightly in the stem, the protruding part being ground or tiled to a wedge, with the two facets slightly rounding, and whose broad faces stand at a right angle to the stem of the gauge, the point or edge only projecting sufficiently to produce a line clear enough to work by; otherwise it will not be suitable for accurate work. [Illustration: Fig. 2762.] The mortice gauge, Fig. 2762, is similar to the above as regards the stem and sliding piece, but it is provided with two marking points, their distance apart being adjustable. The head screw works in brass nuts. [Illustration: Fig. 2763.] For lines that are to be marked more than about ten inches from the edge of the work a broader base is necessary to the head or block, which may be shaped as shown in Fig. 2763. [Illustration: Fig. 2764.] The lines drawn upon pattern work require to be very fine, and for this purpose the cutting scriber, Fig. 2764, is employed. The end A is bevelled off on both sides like a skew chisel. The end B is ground to a fine point and both ends are oilstoned. The point end is for drawing lines with the grain, and the knife end for lines across the grain of the wood. The wooden handle is to afford a firm grip. [Illustration: Fig. 2765.] In Fig. 2765 we have the cutting gauge, in which a steel cutter takes the place of the marking point, being wedged in position. It is employed to cut thin strips of wood, that is to say, of thicknesses up to about a quarter of an inch. The cutter point should be tempered to a dark straw color. The principal forms of joints employed by the pattern-maker are as follows:-- [Illustration: Fig. 2766.] Fig. 2766 represents the mortice and tenon, the thickness of the tenon being one-third that at C, which leaves a thickness at E and D equal to that of the tenon. When the mortice is away from the end of the work the breadth B of the tenon is made less than the breadth F of the work so as to leave stuff at A to strengthen the mortised piece. To make this joint the two pieces, having been planed or otherwise made to size as required, are marked for the position and length of the mortice in one case, and for the length of the tenon in the other; both pieces are now gauged with a mortice gauge, both being marked alike; and then from the face side we mark a tenon or mortice of the dimensions required. [Illustration: Fig. 2767.] If the stuff is broad two or more tenons and mortices may be given, as shown in Fig. 2767. [Illustration: Fig. 2768.] To lock the tenon in the mortice two methods may be employed. In the first and preferable one the mortice is tapered, as in Fig. 2768, and the two wedges are inserted and driven home. In the second the tenon is provided with saw cuts to receive the wedges. [Illustration: Fig. 2769.] A very superior method of jointing is the dovetail, shown in Fig. 2769, which is serviceable for connecting the ends and sides of a box, or any article in that form. The strength of the corner formed in this way is only limited by that of the material itself; therefore it should be preferred when available in making standard patterns, or for work too thin to admit nails or screws; the corner formed by this joint is not limited to 90° or a square, so called, but may form any angle. Nor is it imperative that the sides or ends of the box or other article be parallel. They may incline towards one another like a pyramid; a mill hopper is a familiar example of this. If it be required to dovetail a box together, get out four pieces for the sides and ends, to be of the full length and width respectively of the box outside. They are to be planed all over, not omitting the ends. The gauge, that is already set to the thickness of the stuff, must now be run along the ends, marking a line on both sides of each piece. Then mark and cut out the pins as on the piece A; the dovetail openings in B are traced from the pins in A. The pieces having been tried and found to go together are finally brought into contact and held in their places with glue. [Illustration: Fig. 2770.] Fig. 2770 is a mitre joint, the only one serviceable to mouldings, pipes, and other curved pieces. It is not a strong form of joint, and is only used where the preceding kinds are inapplicable. It is made with glue, the pieces having been previously sized; and as an additional precaution, if the work will admit, nails, brads, or screws are inserted at right angles to one another. [Illustration: Fig. 2771.] Fig. 2771 represents the half check joint, and it is obvious that the thickness at A must equal that at H, and be half that at B, which will give each half equal strength. A gland for an engine piston rod forms a simple example of the different ways in which a pattern may be formed. Fig. 2772 represents the drawing for the gland.[46] [46] From the "Pattern Maker's Assistant." "Let us suppose the pattern-maker to be uninformed of the purpose the casting is to serve, or how it is to be treated: in such a case he is guided partly by his knowledge of the use of such patterns, and a consideration of being on the safe side. The form shown in Fig. 2773 would suggest itself as being a very ready method of making the pattern; by coring out the hole, it can be made parallel, which the drawing seems to require. The advantage of leaving the hole parallel is that less metal will require to be left for boring in case it should be necessary; because, if the hole is made taper, the largest end of the bore will require to have the proper amount of allowance to leave metal sufficient to allow the hole to be bored out true, and the smaller end would, therefore, have more than the necessary amount; while just the least taper given to the exterior would enable the moulder to withdraw the pattern from the mould. Made in this way, it would be moulded as shown in Fig. 2774, with the flange uppermost, because almost the whole of the pattern would be imbedded in the lower part of the flask, the top core print being all that would be contained in the cope; and even this may be omitted if the hole requires to be bored, since the lower core print will hold the core sufficiently secure in small work, unless the core is required to be very true. The parting of the mould (at C D, Fig. 2774) being level with the top face of the flange, much taper should be given to the top print (as shown in Fig. 2773), so that the cope may be lifted off easily. Were this, however, the only reason, we might make the top print like the bottom one, providing we left it on loose, or made it part from the pattern and adjust to its place on the pattern by a taper pin; but another advantage is gained by well tapering the top print, in that it necessitates the tapering of the core print at that end; so that, when the two parts of the mould are being put together, that is to say, when the cope is being put in place, if the core has not been placed quite upright, its tapered end may still arrive and adjust itself in the conical impression, and thus correct any slight error of position of the core. The size of the core print should be, at the part next the pattern, the size of the core required; for if the extremities are made of the size of the core, and the taper or draft is in excess, there will be left a useless space around the core print, as shown at A B in Fig. 2774, into which space the metal will flow, producing on the casting, around the hole and projecting from the end face, a useless web, which is called a fin, which will of course require to be dressed off the casting. [Illustration: Fig. 2772.] "We will now suppose that our piece, when cast, is to be turned under the flange and along the outside of the hub or body, and that the hole also is to be bored. In this case the pattern made as above would still be good, but could be much more easily made and moulded if it has to leave its own core, its shape being as shown in Fig. 2775; because the trouble of making a core is obviated, and the core is sure to be in the centre of the casting, which it seldom is when a core is used. We must, however, allow more taper or draft to a hole in a pattern than is necessary on the outside; about one-sixteenth inch on the diameter for every inch of height on work of moderate size is sufficient. The allowance for boring should be one-sixteenth inch at the large end of the hole, provided the diameter of the hole is not more than five or six inches, slightly exceeding this amount as the diameter increases; whereas, if the pattern had been made with core prints, an allowance of one-eighth inch for small, and three-sixteenths inch for larger work would be required. These are the advantages due to making the pattern leave its own core. We have still to bear in mind, however, that, if the casting require a parallel hole, a core must be used; and furthermore, if the hole is a long one, we have the following considerations: The separate dry sand core is stronger, and therefore better adapted to cases where the length of the hole greatly exceeds the diameter. Then again, if the hole require to be bored parallel, it can be more readily done if the hole is cast parallel, because there will be less metal to cut out. The casting also will be lighter, entailing less cost, provided it has to be paid for by the pound, as is usually the case. The moulder is given more work by making the core; but the saving in metal, and in turning, more than compensates for this, provided the length of the hole is greater than the diameter of the bore. "Let it now be required that the casting is to be finished all over. It would, in that case, be preferred that if the casting should contain any blow or air holes, they should not be on the outside face of the flange, and this will necessitate that the piece be moulded the reverse way to that shown in Fig. 2773: that is to say, it must be moulded as shown in Fig. 2776, with the flange downwards; for it may be here noted that the soundest part of a casting is always that at the bottom of the mould; and furthermore, the metal there is more dense, heavier, and stronger than it is at the top, for the reason that the air or gas, which does not escape from the mould, leaves holes in the top of the casting or as near to the top as they can, by reason of the shape of the casting, rise. The bottom metal also has the weight of the metal above it, compressing it, and making an appreciable difference in its density. It must, therefore, be remembered that faces requiring to be particularly sound should be cast downwards, or at least as near the bottom of the mould as they conveniently can. Following this principle, our gland will require to be moulded as shown in Fig. 2777, P P representing the line of the parting of the mould; so that, when the cope is lifted off, the loose hub A will rise with it, leaving the flange imbedded in the lower half of the mould. It is evident that in this case the pattern must be made, as shown in Fig. 2776, the body and core prints being in one piece and the flange in another, fitting easily on to a parallel part on one end, and adjoining the core print, as shown at A. For glands of moderate size, this method is usually adopted, and it answers very well for short pieces; but in cases where the length of the body approaches, say, three diameters, the horizontal position is the best, and the pattern should be made as shown in Figs. 2778, 2779, or 2780. Even in short pieces, when the internal diameter approaches that of the external, this plan is the best, because it is difficult for the moulder to tell when his core is accurately set in position. [Illustration: Fig. 2780.] "For a pattern to be moulded horizontally, Fig. 2780 shows the best style in which it can be made. Its diameters are turned parallel; the required draft is given by making the rim of the flange a little thinner than at the hub, and by making the end faces of the hub and the core prints slightly rounding. If the hub is very small, as, say, a half-inch or less, and the flange does not much exceed it, the pattern may be made solid, as shown in Fig. 2778; but if the hub be small and the flange large, it should be made as shown in Fig. 2776. [Illustration: _VOL. II._ =EXAMPLE IN PATTERN WORK.= _PLATE XIV._ Fig. 2773. Fig. 2774. Fig. 2775. Fig. 2776. Fig. 2777. Fig. 2778. Fig. 2779.] "To construct the pattern shown in Fig. 2773, we proceed as follows: From a piece of plank we saw off a piece of wood a little larger and thicker than the required flange, and turn it up between the lathe centres, using a pattern makers' contraction rule, which has its measurements larger than the actual standard ones in the proportion of one-eighth inch per foot: so that a foot on the contraction rule is 12-1/8 standard inches, and an inch is 1-1/96 standard inches. The reason for this is, that when the metal is poured into the mould, it is expanded by heat; and as it cools it contracts, and a casting is, therefore, when cold, always smaller than the size of the mould in which it was made. Brass castings are generally said to be smaller than the patterns in the proportion of one-eighth inch per foot, and cast-iron castings one-tenth inch per foot; and so, to avoid frequent calculations and possible errors, the contraction rule has the necessary allowance in every division of the foot and of the inch. It is not, however, to be supposed that the possession of such a rule renders it possible for the pattern-maker to discard all further considerations upon the contraction of the casting; because there are others continually stepping in. Such, for example, is the fact that the contraction will not be equal all over, but will be the greatest in those parts where the casting contains the greatest body of metal. "In the smaller sizes of patterns, such as those of 6 inches and less in diameter, there is another and a more important matter requiring attention, which is, that after a moulder has imbedded the pattern in the sand, and has rammed the sand closely around it, it is held firmly by the sand and must be loosened before it can be extracted from the mould. To loosen it, the moulder drives into the exposed surface of the pattern a pointed piece of steel wire, which he then strikes on all sides, causing the pattern to compress the sand away from the sides of the pattern in all directions; and as a result, the mould is larger than the pattern. In many kinds of work, this fact may be and is disregarded, but where accuracy is concerned, it is of great importance, especially in the matter of our example (brasses for journals), for they can be chipped and filed to fit their places much more rapidly than they can be planed, and it is necessary to have the castings as nearly of the correct conformation as possible. In cases where it is necessary to have the castings of the correct size without any work done to them, the shake of the pattern in the sand is of the utmost importance. If it is required to cast a piece of iron 3 inches long and 1 inch square, supposing the pattern were made to correct measure by the contraction rule, the moulder, by rapping the pattern (as the loosening it in the mould is termed) would, by increasing the size of the mould above that of the pattern, cause the casting to be larger than the pattern; that is to say, it would be longer and broader, and therefore, in those two directions, considerably above the proper size, since even the pattern was too large to the amount allowed for contraction. The depth, however, would be of correct size, because the loosening process or rapping does not drive the pattern any deeper in the mould. It follows that, to obtain a casting of as nearly the correct size as possible, the pattern must be made less in width and in length than the proper size, to the amount of the rapping; and to insure that the moulder shall always put the pattern in the sand with the same side uppermost, the word "top" should be painted on the face intended to lie uppermost in the mould. The amount to be allowed for the rapping depends upon the size of the pattern, and somewhat upon the moulder, since some moulders rap the patterns more than others; hence, where a great number of castings of accurate size are required, it is best to have two or three castings made, and alter the pattern as the average casting indicates. For castings of about 1 inch in size, the patterns may be made 1/32 inch too narrow and the same amount too short; but for sizes above 6 inches, allowance for rapping may be disregarded. "In patterns for small cast gears, the rapping is of the utmost consequence. Suppose, for instance, we have six rollers of 2 inches diameter requiring to be connected together by pinions, and to have contact one with the other all along the rollers; if we disregard the allowance for rapping, the pinions will be too thick, and we shall require to file them down, entailing a great deal of labor and time, besides the rapid destruction of files. [Illustration: Fig. 2781.] [Illustration: Fig. 2782.] "Let it be required to cast a pillow block to contain a babbitt-metal bearing. In this case there requires to be a cavity to receive and hold the babbitt metal. This is provided by casting ridges of metal around the edges of the bearing, as shown in Fig. 2781, at D E and on each side at F, the pieces D E may be made solid with the pattern, but those for the sides must be removable, having dovetails as at _c_ _c_ to hold them in position while being moulded, or in place of the dovetails, wires as at F F may be employed, in either case the pattern would be extracted from the mould, leaving the side strips to be removed afterwards. If, instead of a pillow block, a bracket or frame, such as in Fig. 2782, were required, it must be moulded in the direction of the arrow, and in that event it would be desirable to core out the journal bearing. This would be accomplished by providing a core print to block up the whole opening B. A suitable core box for the bearing would be as in Fig. 2783. The core print must project below the casting so as to form in the mould a core print for the core, and it is obvious that the core itself must be made of increased depth to the amount allowed for core print; hence the end piece B, Fig. 2783, is increased in thickness to the amount allowed for core print." [Illustration: Fig. 2783.] Patterns for cylindrical bodies, especially those that are hollow and thin, are constructed in pieces by a process termed "building up." The pieces are usually segments of circles, and the manner of marking them is as follows:-- [Illustration: Fig. 2784.] [Illustration: Fig. 2785.] [Illustration: Fig. 2786.] [Illustration: Fig. 2787.] Let it be required to make a pattern for a flanged pulley, such as shown in section in Fig. 2784. It would be constructed in two halves composed of a number of courses as from 1 to 8, and each course would be composed of segments of the form shown in Fig. 2785. The length of the arc of these segments must be such that it will require a certain number of these to complete the circle of that part of the cylinder which the segment is to form; and the manner of accomplishing this is shown in Fig. 2786, in which the circle C is of the diameter of the outside, while circle D is that of the outside of the pulley proper, circle E is of the diameter of the inside of the pulley rim. These circles are divided into as many equal divisions as there are to be segments in the circumference; hence the number of divisions determines the length of arc of the segments. Thus A would be a segment for the body of the pulley, and F a segment for the rim. A template is then made of each one of these segments, as at A and F. This template must be made slightly larger in every direction than the respective divisions, to allow for the stuff that will be turned off in truing the pattern in the lathe and in jointing the segments to one another during the building. The templates are employed to mark out on the board which should first be planed to the required thickness. This will be a trifle thicker than the course so as to allow for truing the surface of each finished course in the lathe. The courses are best built up on the chuck of the lathe on which they are to be turned, and a saving in time will be effected if there are two chucks, so that a course on one half of the pattern may be built up while the glue of another course on the other half is drying. On the lathe chuck, and directly beneath, where the joints of the segments will come, pieces of paper as at _a_, _c_, _e_, _g_, Fig. 2787, and if the segments are long ones, intermediate pieces of paper, as _b_, _d_, _f_, _h_, will be necessary. The radial edges of the segments are trimmed on what is termed a shooting board, which is a device such as shown in Fig. 2788, in which A is a piece of board on which is fastened the piece B. S is a piece projecting above B, and is provided to rest the segment S´ against, the flat surface of the latter lying on the board B. It is thus held in a fixed position, ready to have its edges E planed, the whole being laid upon the bench against the bench stop G. If, however, it is more convenient to rest the shooting board across the bench, a piece C may be fastened beneath A, so as to come against the edge of the bench as in Fig. 2789, in which T is the bench. The plane is laid with its side on A as in Fig. 2790, so that the surface of A acts as a guide, keeping the edge of the plane vertical, and thus planing the edges of the segment square. The plane is operated by hand in the usual manner (save that it lies on its side), taking its cut most off the outside or inside of the edge of the segment S´, according as the position of the latter is varied. In some of the shooting boards manufactured by tool makers, the height of B from A is adjustable, so that all parts of the plane blade edge may be used, which saves grinding, since only that part of the edge that is used dulls. Also there is provided means whereby the required lateral position of the segment may be adjusted; such a device is shown at P, Fig. 2788, which is a plate having a slot through it, through which passes the thumb screw V, which screws into S. Hence the plate may be adjusted so that when one end of the segment rests against the end of S, and the other against the end of P, its edge E will be in the proper position to be planed to correct angle by the plane, whose line of action is in this case rendered positive by means of a slide on the plane, acting in a groove in the base A. [Illustration: Fig. 2788.] [Illustration: Fig. 2789.] [Illustration: Fig. 2790.] The first segment is glued to the pieces of paper on the chuck, as shown in Fig. 2787, S´ representing the segment. A second segment is then added, being set fair to the pencil circle O, and jointed and glued both to the chuck and to the ends of the first segments. Successive segments are added until the whole circle or course is completed, and when dry the radial face of this course is turned in the lathe so as to be true, flat, and of the required thickness, and the diameter is trued. The second course may then be added, but the joints at the ends of the segments should not come over those of the first course, but in the middle as shown by the dotted line. The ends of the segments should be made to bed properly against each other, and glue should be applied to the joint between the two courses and at the ends. By adding the successive courses the whole may be built up on the chuck ready to receive the arms. As each segment is added it should be clamped or weighted to press it firmly to its seat and press out the excess of glue. If the pattern consists of two, or say three, courses, the glue will be sufficient to hold it to the chuck while turning, but if there are more courses a screw should be inserted through the chuck and into each segment of the first course. The cylinder must then be turned inside and out ready to receive the spokes. These are made of pieces equal in length to the internal diameter of the rim, or a trifle longer, so that the ends may be let into the rim. A line is then marked along the edge of the rim, dividing its thickness into two divisions, and in the centre of the length a recess should be cut out from the face to the line, the width of the recess equalling the width of the arm, so that one arm will let into the other, forming a cross, of which the flat surfaces lie in the same plane. This cross is let into the rim of the wheel and fixed temporarily with brads. The lathe may then be started and the centre of the arms (and therefore that of the cylinder or pulley) be found by a pencil point moved until it marks a point and not a circle when the lathe revolves. The arms may then be marked to shape and a recess turned at their centre to receive the hub. The arms being marked to their respective places and their outside faces being marked with a pencil so that they may be replaced in the same position in the wheel, they may be removed and shaped to the required dimensions and form, and then replaced and glued to the rim. If the wheel is to have six arms they may be constructed as follows:-- Instead of taking two pieces of the diameter of the rim, as in the case of four arms, three pieces are necessary, and in this case the thickness of the edge of each piece is divided by two marked lines which will divide the thickness of the edge into three equal divisions, as shown by the dotted lines 1 and 2 in Fig. 2791, which will divide the thickness of the edge into three equal divisions of thickness. From the centre of the lengths of each of the three pieces we mark on the flat face a circle whose diameter will equal the width on the flat face of the pieces themselves. With an angle square having its adjustable blade set to an angle of 60°, and set so that the back is fair with the edge of the piece, and one edge coincident with the perimeter of the circle, lines tangent to the circle and crossing each other are drawn on the pieces A C. On the piece B four of such tangent lines (two on each side) must be drawn. The piece A is recessed between one pair of tangent lines to the depth of the second lines on its edge, or, in other words, to a depth of two-thirds its thickness, and between the other pair to a depth of one-third, as shown, the two-thirds at D, the one-third at E. The piece D must be recessed between its tangents on each side to a depth of one-third its thickness, as denoted at F F, while on C the whole space between the tangent lines must be recessed to a depth equal to two-thirds its thickness, as shown at G. The pieces may then be put together so that the two diametrically opposite arms will be in one piece. If an odd number of arms is employed this form of construction cannot be followed; hence each spoke will be a separate piece, extending from the rim to the centre and jointed at the latter, as in Fig. 2792, which is for five arms. For this construction draw a circle _c_, Fig. 2792, and divide it into as many equal points of division as there are to be arms in the wheel. From these points of division draw lines to the centre, and these lines will show the required bevel at the end of each spoke, as shown in the figure. The ends should be verified for bevel by striking from the common centre a second circle, as D; and measuring if the arms are equidistant, measured at the circle and from the edge of the arm to that of the next, finished along the full length. When fitted, corrected, glued and dry, the spokes may be let into the wheel and a recess turned into the centre to receive the hub. The rim and all parts that can be got at may then be turned in the lathe, the pattern then being reversed in the lathe to turn the inside of the rim, or the other side of the spokes, when the job will be complete. When, however, the rim is to be a very thin one, it may be necessary to fasten the segments together at the ends by other means as well as glue, hence a saw-cut may be made in each end, and a tongue inserted. [Illustration: Fig. 2791.] [Illustration: Fig. 2792.] It is obvious that each half of the pattern is constructed by similar segments, the line of parting being through the centre of the arms, as at A B, in Fig. 2791. To keep the two halves coincident when in the mould, pins are inserted in the rim and arms of one half, fitting closely into holes provided in the other half. To construct a pattern for a pipe, the pattern would be made in two halves, and constructed of what are termed staves, that is, pieces of wood running lengthways of the pipe. The number of these staves is optional, save that it must be even, so that each half pattern will contain an equal number. [Illustration: Fig. 2793.] Let it be required to make a pattern for a pipe 18 inches in diameter, and to be 1 inch thick. Draw the line A B, Fig. 2793, and from a point on it, as C, draw a semicircle A B, equal in diameter to the diameter of the outside of the pipe. Also the circle D E F, equal to the diameter of the inside of the pipe, and these will represent an end view of the pipe. Divide these semicircles into as many equal divisions as it is decided to have staves in the half pattern--as 1, 2, 3, 4, 5, 6; and from one of these divisions make a template as denoted by the oblique lines at 2, leaving it slightly larger than the division, to allow stuff to work on in fitting the staves, &c. [Illustration: Fig. 2794.] Now, when the staves are cut out it is necessary to have some kind of a frame or support to hold them while jointing them; hence, draw also from the points of division, as D, E, F, the lines _a_, _b_, _c_, _d_, _e_, _f_, and these will form the sides of a half-disk polygon, whose diameter is from D to F. A sufficient number of these polygonal half-disks are cut out to stand about two feet apart along the whole length of the pipe, as in Fig. 2794, and on these, temporarily fastened to the board B, the staves are jointed and fastened together by glue while each stave is held to its place on each half-disk by a screw. The top stave may be put on first, as it will act as a stay to the half-disks. If the pipe is so long that it is composed of more than two pieces, the end pieces should be put on first, and the intervening space filled up last, which enables the ends to abut firmly. The second half may be added to the first one, putting a piece of paper between the edges of the two to prevent their sticking together. If the pipe has a bend, it is built up separately, instead of being formed of staves, the process being as follows:-- [Illustration: Fig. 2795.] [Illustration: Fig. 2796.] In Fig. 2795 let B represent the centre of the bend curve, the line C representing one end, G the other end, H the inner and J the outer arc of the bend. Let it be determined to build up the bend in five pieces, as shown at 1, 2, 3, 4, 5, which represents an end view of the half pattern. Templates are then made for each of the pieces 1, 2, &c., being formed as denoted by the oblique lines, whose dimensions slightly exceed the half circle E of the pattern, to allow wood for dressing up. To find the curve for these pieces, set the compasses to a radius from B to the outer corner of piece 1, and draw the arc K. Set the compasses to the radius from B to the inner corner of piece 1, and draw the arc L, and the space between these two arcs, which space is marked 1 T, is a template for the curve of piece 1. By a similar process applied to pieces 2, 3, 4 and 5 similar templates for their respective curves are obtained; and selecting timber of a proper thickness, we mark out the respective curves from these templates, which may be of thin board or of stiff paper. In putting these pieces together the lower ones are set to lines forming a plan of the bend, being set a little outside the lines to allow wood for truing the pieces to shape after they are put together. The lower pieces are temporarily fixed to the board on which the plan is marked, and the upper ones fastened to the lower by glue, the joint surfaces of each line being planed true previous to being glued. It is a great assistance, however, to cut out two half circles, representing the ends of the pipe, and to place them on the board to build upon. When a bend of this kind occurs in a covering for a pipe that is exposed to view, it is necessary, for the sake of appearance, to have the pieces composing the bend to correspond with those on the straight part of the pipe, as shown in Fig. 2796. The part A would be got out in staves, as described for the pattern of a pipe. The bend B would be also got out as described for that figure for a bend, save that the number of staves for the bend would equal the number on the pipe. But in this case each stave should be fitted to its fellow by pins, or its edge fitting into dowels on the edge of its fellow; thus one edge of a stave would have the dowels and the other the pins; the whole, when finished, being bound together by metal bands, as shown in the figure. [Illustration: Fig. 2797.] The patterns for a globe valve, such as shown in section in Fig. 2797, would be made as follows (which is taken from "The Pattern Makers' Assistant"):-- [Illustration: Fig. 2798.] [Illustration: Fig. 2799.] "The flanges vary in shape; but as a rule small valves are provided with hexagons and large ones with round flanges suitable for bolting to similar flanges to make joints. For small valves, say up to 2 inches, the pattern is usually made with the hexagons cut out of the solid, but for sizes above that, they should be made in separate pieces, as shown in Fig. 2798, and screwed to the pattern, so that in case of necessity they may be removed, and flanges substituted in their stead. In Fig. 2799, we have a perspective view of the finished pattern; and Fig. 2800 represents the pattern as prepared, ready to receive a flange or hexagon as may be required. A globe valve pattern should be made in halves, as shown in Fig. 2801, the parting line of the two halves being denoted by A B. To make this pattern, we first prepare two pieces of wood so large that, when pegged together, the ball or body of the pattern can be turned out of them, and long enough not only to reach from P to P, in Fig. 2799, but also to allow an excess by means of which the two pieces may be glued or otherwise fixed together. These two pieces we plane to an equal thickness, and then peg them to retain them in a fixed position, taking care, however, that the pegs do not occur where the screws to hold the flanges will require to be. We also place two pegs within a short distance of what will be the ends of the pattern when the excess in length referred to is turned off. We next prepare, in the same way, two more pieces, to form the two halves of the branch, shown at B, in Fig. 2801, for which, however, one peg only will be necessary. These pieces must be somewhat wider than the size of the required hexagon across the corners, that is, supposing the hexagon is to be solid with the branch; otherwise we must make them a little wider than the diameter of the hub of the flange, or of the round part of the hexagonal pieces. Their lengths must be such as to afford a good portion to be let into the ball or body of the pattern (as shown by the dotted lines in Fig. 2800), which is necessary to give sufficient strength. The two pieces must be firmly fixed together, and then turned in the lathe. [Illustration: Fig. 2800.] [Illustration: Fig. 2801.] [Illustration: Fig. 2802.] "During the early stages of the turning, or, in other words, during the roughing out, we must occasionally stop the lathe and examine the flat places on the body; for unless these places disappear evenly, the work is not true, and one half will be thicker than the other, so that the joint of the pattern will not be in the middle. It was to insure this that the pieces were directed to be planed of equal thickness, since, if such is the case, and the flat sides disappear equally and simultaneously during the turning, the joint or parting of the pattern is sure to be central. If the lathe centres are not exactly true in the joint of the two pieces, they may be made so by tapping the work on the side having the narrowest flat place, the process being continued and the work being trued with the turning tool at each trial until the flat places become equal. By this means, we insure, without much trouble, two exact halves in the pattern, which is very important in a globe valve pattern on account of the branch and other parts, not to mention the moulding. Having turned the body of the pattern to the requisite outline, and made, while in the lathe, a fine line around the centre of the ball where the centre of the branch is to come, as shown in Fig. 2800 by the line A, we make a prick point (with a scriber) at each crossing of the line A and the joint or parting of the pattern. We then mount the body upon a lathe chuck, in the manner shown in Fig. 2802. A point centre should be placed in the lathe and should come exactly even with the line A. In Fig. 2802, V V are two [V]-blocks made to receive the core prints. These [V]s are screwed to the lathe chuck, and the pattern is held to them by two thin straps of iron, placed over the core prints and fastened to the [V]s by screws. If the chuck and centre point run true, the [V]-blocks are of equal height, and the core prints are equal in diameter, the prick point opposite to the one placed to the centre point will run quite true; and we may face off the ball or body to the required diameter of branch, and bore the recess to receive the same. We make the holes in the flanges of the same size as the core prints; but we should not check in the print, because, if a flange with a different length of hub were substituted, it would be a disadvantage. To obtain the half flanges, we take a chuck and face it off true in the lathe; then, with a fine scriber point, we mark the centre while the chuck is revolving. We then stop the lathe, and, placing a straight-edge to intersect the chuck centre, we draw a straight line across the chuck face. We then take two pieces suitable for the half flanges, and plane up one flat side and one edge of each piece. If the flanges are not large ones, they may be planed all at once in a long strip. We place the pieces in pairs, and mark on each pair a circle a little larger than the required finished size of flange. We then fix each pair to the chuck, with the planed faces against the chuck, and the planed edges placed in contact, their joint coming exactly even with the straight line marked on the chuck face, and we may then turn them as though they were made in one piece and to the requisite size. [Illustration: Fig. 2803.] "In Fig. 2803 we have a representation of one half of a suitable core box, the other half being exactly the same, with the exception that the position of the internal partition is reversed. To get out this core box, we plane up two pieces of exactly the same size and length as the pattern, and of such width and thickness as will give sufficient strength around the sphere, allowing space for the third opening. After pegging these two pieces together, we gauge, on the joint face of each, lines representing the centres of the openings and the centre of the sphere. We then chuck them (separately) in the lathe, and turn out the half sphere. We next place the two halves together, and chuck the block so formed in the three positions necessary to bore out the openings; or if preferred, we may pare them out. The partition (A, in Fig. 2803) follows the roundness of the centre hole, and is on that account more difficult to extract from the core than if it were straight and vertical. When, however, the partitions are of this curved form, the pieces of which they are formed are composed of metal, brass being generally preferred. Patterns have in this case to be made wherefrom to cast these pieces, and they may be made as follows: First, two half pieces are turned; each is then cut away so as to leave the shape as shown at A in the same figure, and is then fitted into the spherical recess in the core box, letting each down until both are nearly but not quite level. The two wing pieces are then fastened on, and this pattern is complete. When the pieces are cast, they must be filed to fit the core box, and finished off level with its joint face, a small hole being drilled in the centre, and a pin being driven through the piece and into the box to steady the corners. We then saw the pieces in halves with a very fine saw. [Illustration: Fig. 2804.] "If the partition, instead of following the roundness of the valve seat, is made straight, the construction of the core box is much more simple. In this case, a zigzag mortice is made clear through each half of the box, its size and shape being that of the required partition. Fig. 2804 represents a half-core box of this kind. A piece of wood A is fixed, as shown, to the partition, to enable the core maker to draw it out before removing the core from the box. The mortice for the partition should be turned out before the half-spherical recess, the mortice being temporarily plugged with wood to render easy the operation of turning. [Illustration: Fig. 2805.] "In very large valves (say 10 or 12 inches) a half-core box is generally made to serve by fitting the two half partitions, shown at A, in Fig. 2803, to a half-core box, and keeping them in position by means of pegs, a half-core being made first with one and then one with the other in the core box. It is often necessary to form a raised seat in the body of an angle valve, such as shown in Fig. 2805, which represents a section of such a body. It is shown with flanged openings, though in small valves hexagons to receive a wrench would be substituted. [Illustration: Fig. 2806.] [Illustration: Fig. 2807.] "Fig. 2806 is a plan of half the core box necessary for forming the raised seat. From this construction, it will be seen that the large core, though solid with the branch core, is not solid with that forming the hole in the seat and the part below it; therefore the core prints on the body pattern must be left extra long to give sufficient support in the mould for the overhanging cores. The loose round plug P, is made of the size of the outside of the seat and fitted to the box. The part outside the box is a roughly shaped handle to draw it out by. The diminished part D is a print, and into the impression left by it is inserted the core made in box shown in Fig. 2807. The print D is of the same diameter as the hole in the seat; and the print on the pattern is of the size of the increased diameter below the seat. Large angle valves are made with half a core box by making a branch opening in the box right and left, a semicircular plug being provided. Two half-cores are made with the plug, first in one and then in the other branch opening. The plug P should be in this case only half round." [Illustration: Fig. 2808.] For finding the lengths of the sides of regular polygons, scales, such as shown in Figs. 2808 and 2809, may be used, the construction being as follows:-- [Illustration: Fig. 2809.] Draw a horizontal line O P, Fig. 2809, and at a right angle to it the line O B. Divide these two into inches and eighths of an inch, and draw lines meeting the corresponding divisions on O P, O B. From the point O draw the following lines: A line at 55-1/2 degrees from line O P, which is to serve for polygons having 9 sides; a line at 52-1/2 degrees to serve for polygons having 8 sides; a line at 49 degrees for polygons having 7 sides; a line at 45 degrees for 6 sides; a line at 40 degrees for polygons having 5 sides. It may be added, however, that additional lines may be drawn at the requisite angle for any other number of sides. The application of the scale is as follows:-- The point O represents the centre of the polygon; hence from O to the requisite line of division on O B represents the radius of the work. From the line O B to the diagonal line (measured along the necessary horizontal line of division) is shown the length of a side of the polygon. From the point O, measured along the line having the requisite degrees of angle, to the horizontal line denoting the radius of the work, gives the diameter across corners of the polygon. The diameter across the flats of a square being given, its diameter across corners will be represented by the length of a line drawn from the necessary line of division on O B to the corresponding line of division on O P. A cylindrical body is to have six sides, its diameter being 2 inches, what will be the length of each side? Now, the radius of the 2-inch circle of the body is 1 inch; hence, find the figure 1 on line O B and measure along the corresponding horizontal line the distance from the 1 to the line of 45 degrees, as denoted by the thickened line. A body has six sides, each side measuring an inch in length, what is its diameter across corners? Find a horizontal line that measures an inch from its intersection of the line O B to the line of 45 degrees, and along this latter to the point O is one-half the diameter across corners. _Example 3._--It is desired to find the diameter across corners of a square whose side is to measure 3 inches. Measure the distance from the 3 on line O P to the 3 on line O B, which will give the required diameter across corners. This scale lacks, however, one element, in that the diameter across the flats of a regular polygon being given, it will not give the diameter across the corners. This, however, we may obtain by a somewhat similar construction. Thus, in Fig. 2808, draw the line O B, and divide it into inches and parts of an inch. From these points of division draw horizontal lines; from the point O draw the following lines and at the following angles from the horizontal line O P:-- A line at 75° for polygons having 12 sides. " 72° " 10 " " 67-1/2° " 8 " " 60° " 6 " From the point O to the numerals denoting the radius of the polygon is the radius across the flats, while from point O to the horizontal line drawn from those numerals is the radius across corners of the polygon. A hexagon measures 2 inches across the flats, what is its diameter measured across the corners? Now, from point O to the horizontal line marked 1 inch, measured along the line of 60 degrees, is 1-5/32 inches; hence the hexagon measures twice that, or 2-5/16 inches across corners. The proof of the construction is shown in the figure, the hexagon and other polygons being marked for clearness of illustration. [Illustration: Fig. 2810.] [Illustration: Fig. 2811.] Let it be required to make a pattern for a section of pipe such as shown in section and in plan in Fig. 2810, which is from "The Pattern Maker's Assistant." This pattern would be made to mould, as shown in the section, lying horizontally, and must therefore be made in two halves, the line of joint for the two halves being along A B in Fig. 2811. "The body A and the branch B would be made separate from the flanges, and would be reduced in diameter at the ends to receive them. To form A, take two pieces of timber, say three inches longer than the length of A, including the core prints, and measuring a little more than half the diameter of the pipe one way, and a little larger than the full diameter of the pipe the other way, and glue them together at the ends for a distance of 1-1/2 inches, which will serve to hold them while turning them in the lathe. "The pieces may then be turned in the lathe to the required diameter. During this turning, however, it is essential to insure that the joint of the two pieces be exactly in the centre, otherwise one half of the pattern will be (when the halves are separated) thicker than the other. "The ends are then turned down to receive the flanges, the reduced diameter being necessary so as to leave a shoulder for the flanges to abut against to keep them true, or at a right angle to the axial line of the body. The branch is turned up in the same way, and the flanges are then turned and put on. "The end of the branch may be cut to fit the circumference of the body as follows:-- "Set a bevel square to an angle of 45°. Take the halves of the branch apart, and rest the stock or back of the bevel against the end face, and let the blade lie on the joint face, and mark two lines A B in Fig. 2812, which lines must just meet in the centre of the branch at the end. Cut away the angular pieces C and D down to the lines A B. This performed on each half will leave them when given a quarter turn as shown in Fig. 2812, and the curve shown by the junction of the horizontal with the vertical shading lines is the curve for the end; hence the surface covered with the horizontal lines requires to be cut away. [Illustration: Fig. 2812.] "When this is done on both halves the branch will fit to the body, as shown in Fig. 2813, in which A is the body and B C the two half branches. For a temporary pattern the branch may be fastened to the body with a few screws; but for a permanent pattern it should be glued also, which is done as follows:-- [Illustration: Fig. 2813.] [Illustration: Fig. 2814.] [Illustration: Fig. 2815.] "Lay one half of the body A, Fig. 2813, on a board, with the flange overhanging to be out of the way, and clamp it there; lay the branch also on the board, and draw it firmly up to the body by clamps, while also clamping it flat down to the board, as shown in Fig. 2814. This will insure that the joint faces are true with one another, that is, lie in the same plane. Paper should, however, be placed between the joint faces and the board to prevent them from becoming glued to the board, and the edges, therefore, from breaking away. The second half can be put together as the first one, paper being put between the two to prevent them from being glued together; and to further strengthen the joint, let into each half a piece of hard wood P, Fig. 2815, and put in the screw shown at A. "Suppose now that the diameter of the branch had been smaller than that of the body of the pattern, then the length of curve necessary on the branch end to let it abut fairly against the cylindrical pattern body may be found as follows:-- [Illustration: Fig. 2816.] [Illustration: Fig. 2817.] [Illustration: Fig. 2818.] "Draw on a piece of board the line A B, Fig. 2816, and from any point C mark a semicircle equal in radius to that of the radius of the body of the pattern, draw the line E parallel to A B, and distant from it to an amount equal to the radius of the branch, then from the junction of E with the semicircle as at D, mark the line F at a right angle to A B. Let it now be noted that the semicircle A G represents half the pattern body, and E D F B the branch; hence from F to G is the length of the branch end that will require to be curved to fit the circumference of the body, while it is also the length to be added to the distance the branch requires to stand out from the body. To draw the curve on the end D F G of the branch the gauge or marking instrument, shown in Fig. 2817, is employed. The branch P is placed in [V]-blocks (Fig. 2818), resting upon a plane surface. The gauge consists of a stand E carrying a vertical bar A; upon A is the closely fitting cross-tube carrying the arm C, which in turn carries the marking pointer D, which is set distant from the centre of the bar A to the amount of the radius of the piece of work or the cylinder is to fit against. [Illustration: Fig. 2819.] "If the branch required to stand at an angle to the body, as in Fig. 2819, the marking may be performed by the same gauge and in the same manner, but the axial line of the branch must be set, when marking one side, at an acute angle to the axial line of A, and at an obtuse angle to A when turned over to mark the other side, which may be done in each case by raising one of the [V]-blocks until the branch lies in either case at the same angle to A as it will require to stand to the body on which it is to fit. "When the body is much larger in diameter than the branch, a hole may be bored in the former to receive the end of the latter, by giving to the branch end a stem, as in Fig. 2820, and then cutting in the body a recess for the branch end and its additional stem. This recess may be cut out in the lathe, chucking the body as in Fig. 2821. [Illustration: Fig. 2820.] [Illustration: Fig. 2821.] "Should it occur that one end of the [T] is of larger diameter than the other, one chucking [V] must be deeper than the other, and we may find their respective depths by the following process:-- [Illustration: Fig. 2822.] "Draw line A B, Fig. 2822, which line represents the chuck face. Let point C represent the centre of the lathe. Mark line C E and set a pair of compasses to the radius of the body of the pattern at the centre of the branch location. Then take a radius from C and about 1/16 inch up from line A B, and with this radius we mark on the line C E the point E. From this centre we mark the two arcs having radii corresponding to the unequal diameters of the pattern at the location where the chucking [V]'s are to be placed. We then draw tangent lines to each of these arcs, and thus obtain the correct depth of [V] necessary to hold the axial line of the pattern parallel to the lathe chuck. [Illustration: Fig. 2823.] "The core box would, unless the pattern were a small one, be built up in courses, as shown in Fig. 2823. The box would be drawn in plan, and end and side views drawn as shown, so as to draw in the half circle representing the bore of the half-core box and mark off the courses as from 1 to 6. These courses need not be of equal or of any particular thickness, but may suit that of any suitable timber at hand. Courses 1 and 2 should extend over the whole outline of the box, while the pieces 3 and 4 are made in width to suit the curvature of the core as shown, and to extend the full length of the box. The pieces 7, 8, 9, and 10 are of the length of the branch, and are made in width to suit the curvature of the branch core. If the branch core were a short one it could be cut out of the solid; but in any event, the grain of the wood should be as shown, and the holding pieces at G and H should be employed." CHAPTER XXXV.--WOOD WORKING MACHINERY. The machines employed in wood working may be divided into 7 classes as follows: 1. Those driving circular saws. 2. Those driving ribbon or band saws. 3. Those driving boring or piercing tools. 4. Those employing knives having straight edges for surfacing purposes and cutting the work to thickness. 5. Those employing knives or cutters for producing irregular surfaces upon the edges of the work. 6. Those employed to produce irregular surfaces on the broad surface of work. 7. Those employed to finish surfaces after they have been acted upon by the ordinary steel cutting tools. CIRCULAR SAWS. [Illustration: Fig. 3078.] The thicknesses of circular saws is designated in terms of the Birmingham wire gauge, whose numbers and thicknesses are shown in Fig. 3078, where a Birmingham wire gauge is shown lying upon two circular saws, which show the various shapes of teeth employed upon saws used for different purposes. The teeth numbered 1 are for large saws, as 36 inches in diameter, to be used on hard wood. Numbers 2 and 5 are for soft wood and a quick feed. Numbers 3 and 4 are for slabbing or converting round logs into square timber. Number 6 is for quick feeds in large log sawing. Numbers 7, 8, 9 and 10 are for bench saws, or, in other words, saws fed by hand or self-feeding saws. Number 8 is known as the "London Tooth," because of being used in London, England, on hard and expensive woods. Number 9 is the regular rip-saw tooth for soft woods. Number 10 is the Scotch gullet tooth. Number 11 is for either cross-cutting or rip sawing by circular saws used on soft woods. Number 12, is for large cross-cut saws; the flat place at the bottom of the tooth prevents the teeth from being unnecessarily deep and weak. Number 13 is for cross-cutting purposes generally. Number 14 is for rip sawing on saws of small diameter. It is also used for tortoise-shell, having in that case a bevel or fleam on the front face, and no set to the teeth. The following table gives the ordinary diameters and thicknesses of circular saws and the diameters of the mandrel hole: ---------+------------+------------------- Diameter.| Thickness. | Size Mandrel Hole. ---------+------------+------------------- 4 inch.| 19 gauge. | 3/4 5 " | 19 " | 3/4 6 " | 18 " | 3/4 7 " | 18 " | 3/4 8 " | 18 " | 7/8 9 " | 17 " | 7/8 10 " | 16 " | 1 12 " | 15 " | 1 14 " | 14 " | 1-1/8 16 " | 14 " | 1-1/8 18 " | 13 " | 1-1/4 20 " | 13 " | 1-5/16 22 " | 12 " | 1-5/16 24 " | 11 " | 1-3/8 26 " | 11 " | 1-3/8 28 " | 10 " | 1-1/2 30 " | 10 " | 1-1/2 32 " | 10 " | 1-5/8 34 " | 9 " | 1-5/8 36 " | 9 " | 1-5/8 38 " | 8 " | 1-5/8 40 " | 8 " | 2 42 " | 8 " | 2 44 " | 7 " | 2 46 " | 7 " | 2 48 " | 7 " | 2 50 " | 7 " | 2 52 " | 6 " | 2 54 " | 6 " | 2 56 " | 6 " | 2 58 " | 6 " | 2 60 " | 5 " | 2 62 " | 5 " | 2 64 " | 5 " | 2 66 " | 5 " | 2 68 " | 5 " | 2 70 " | 4 " | 2 72 " | 4 " | 2 ---------+------------+------------------- Circular saws are sometimes hollow ground or ground thinner at the eye than at the rim, to make them clear in the saw kerf or slot with as little set as possible, and therefore produce smooth work while diminishing the liability of the saw to become heated, which would impair its tension. They are also made thicker for a certain portion of the diameter and then bevelled off to the rim. This is permissible when the work is thin enough to be easily opened from the log by means of a spreader or piece that opens out the sawn piece and prevents it binding against the saw. The shingle saw, shown in Fig. 3079, is an example of this kind, the saw bolting to a disc or flange by means of countersink screws. The concave saw shown in Fig. 3080, is employed for barrel heads. The three pieces for a barrel head are clamped together and fed in a circular path, so that the saw cuts out the head at the same time that it bevels the edge. The advantage of the circular saw lies mainly in the rapidity of its action, whether used for ripping or cross-cutting purposes. In order, however, that it may perform a maximum of duty, it is necessary that the teeth be of the proper shape for the work, that they have the proper amount of set, that they be kept sharp, and that the tension of the saw is uniform throughout when running at its working speed. [Illustration: Fig. 3079.] [Illustration: Fig. 3080.] The centrifugal force created by the great speed of a circular saw is found to be sufficient to cause it to stretch and expand in diameter. This causes the saw to run unsteadily unless it is hammered in such a way as to have it rim bound when at rest, leaving the stretching caused by the centrifugal force to expand the saw and make its tension equal throughout. The saw obviously stretches least at the eye, and the most at its circumference, because the velocity of the circumference is the greatest, and the amount of stretch from the centrifugal force is therefore the greatest. It is obvious that the amount of centrifugal force created will depend upon the speed of the saw, and it therefore follows that the hammering must be regulated to suit the speed at which the saw is to run when doing cutting duty, and in this the saw hammerer is guided solely by experience. A circular saw may have its tension altered and impaired from several causes as follows: 1. From the saw becoming heated, which may occur from the arbor running hot in its bearings, or from the work not being fed in proper line with the saw. 2. From the reduction in diameter of the saw by frequent resharpening of the saw, this reduction diminishing the amount of centrifugal force generated by the saw, and therefore acting to cause the saw to become loose at the eye. 3. From the saw teeth being allowed to get too dull before being sharpened, which may cause the saw teeth to heat, and thus destroy the tension. 4. From stiffening the plate at the throats of the teeth when gumming the saw, an effect that is aggravated by using a dull punch. 5. From the saw teeth having insufficient set, and thus causing the saw to heat. The methods of discovering the errors of tension in a saw, and the process of hammering to correct them, have already been explained with reference to the use of the hammer on pages from 68 to 70 of volume 2 of this work. Before hanging a saw on a mandrel, it is necessary to know that the mandrel itself runs true in its bearings or boxes. In a new machine this may be assumed to be the case, but it is better to know that it is so, because if the mandrel does not run true several very improper conditions are set up. First, the saw will run out of true circumferentially, and therefore out of balance, and the high side of the saw will be called upon to do more cutting duty than the low side. Second, the centrifugal force will be greatest on the high side, and the saw will be stiffer, thus setting up an unequal degree of tension. Third, the saw will run out of true sideways, cutting a wider kerf than it should, thus wasting timber while requiring more power to drive. The collar on the saw arbor should be slightly hollow, so that the saw will be gripped around the outer edge of the collar, and the arbor or mandrel should be level so that the saw will stand plumb. The boxes or bearings of the arbor should be an easy working fit to the journals, and there should be little, or what is better, no end play of the arbor in its bearings. If a saw arbor becomes heated enough to impair the tension of the saw, it has been hot enough to impair its own truth, and should be examined and trued if necessary. The most important point in this respect is that the face of the collar against which the saw is clamped should run true, bearing in mind that if it is one hundredth of an inch out of true in a diameter of, say 3 inches, it becomes twenty hundredths or one-fifth of an inch at the circumference of a saw that is 60 inches in diameter. In cases of necessity, a saw that wabbles from the collar face of the mandrel running out of true, may be set true by means of the insertion of pieces of paper placed between the saw and the face of the collar. The first thing to do in testing the saw is to take up the end motion of the saw arbor, or if this cannot be done, then a pointed piece of iron or wood should be pressed on the end of the mandrel so as to keep it from moving endways while the saw is being tested. The saw should be revolved slowly, and a piece of chalk held in the cleft of a piece of wood should be slowly advanced until it meets some part of the face of the saw just below the bottom of the saw teeth. As soon as the chalk has touched and the saw has made one or two revolutions the chalk should be moved a trifle farther on from the teeth, and another mark made, and then moved on again, and so on, care being taken to notice how much space there is between the high and low sides of the saw. It will be found, however, that the shorter the chalk marks are the more the saw is out of true. A more correct method is to chalk the face of the saw and use a pointed piece of iron wire of about one-quarter inch in diameter, but in any case the saw should only be touched lightly. The pieces of paper should be portions of rings or segments, and should extend an equal distance below the circumference of the collar, because the same thickness of paper will alter the saw more in proportion, as it is inserted farther in toward the eye of the saw. If it should happen that two thicknesses of paper are necessary to true the saw, one should be made about half the length of the other, and the long one may extend farther in toward the eye of the saw. Thus one ring of paper may be an inch deep and the other one-half inch deep. If but one piece of thin paper is needed, it may be simply a straight piece inserted half way down the collar and trimmed off level with the collar. In placing the paper, the middle of its length should be on that side of the saw that is diametrically opposite to the marks left by the chalk on the face of the saw. When the saw is trued and is started it will be loose on the outside, but as its speed increases it should stiffen up so as to run true and steadily when running at its working speed. If the saw is to be tried by actual work, it must be borne in mind that the tension of the saw must be right for its speed when in actual use, and not when running idle. If the machine has belt power enough to maintain the same speed whether the saw is cutting at its usual rate of feed, or whether it is running idle, the tension will not be altered by putting on the feed, but if the saw has been hammered to run at the full speed of the machine when not cutting and the feed is heavy enough to slacken the speed, then the tension of the saw will not be correct for its working speed. [Illustration: Fig. 3081.] The eyes of small saws are either made to fit the mandrel an easy sliding fit, or else the mandrel is provided with cones to accommodate various sizes of holes, an ordinary construction being shown in Fig. 3081, in which A is the saw arbor, fast on which is the collar B, S representing a section of the saw, W a washer or loose collar, and N the nut for tightening up W. The cone _c_ is screwed upon A and passed through the saw until it just fills the hole, and thus holds the saw true. In putting on the saw, it should be passed up to the collar, and _c_ screwed home until it binds in the saw eye with enough force to bring the threads of _c_ fairly in contact with those on the mandrel A, but if screwed home too tightly it may spring the saw, especially if the saw is a very thin one. As _c_ must be removed from the arbor or mandrel every time the saw is changed, the wear on its thread is great, and in time it becomes loose, which impairs its accuracy. [Illustration: Fig. 3082.] This objection is overcome in the construction shown in Fig. 3082, which is that employed by the S. A. Woods Machine Company. It is seen in the figure that the cone _c_ fits externally in a recess in the collar B, and at the coned end also upon the plain part _e_ of the arbor. The cone is hollow and receives a spiral spring _s_, S. When the saw is put on it first meets _c_, and as nut N is screwed up, the saw S and cone are forced along arbor _e_ until the saw meets the face of B, and the clamping takes place. The strength of the spring _s_ is sufficient to hold the saw true, and as the motion of cone _c_ is in this case but a very little, therefore its wear is but little, which makes this a durable and handy device, while the saw cannot be sprung from over-pressure of the cone. Circular saws of large diameter, as from 40 inches upwards, are made a fair sliding fit upon their arbors or mandrels, and are provided with two diametrically opposite pins that are fast in the arbor collar. The pins should be on diametrically opposite sides of the arbor, and an easy sliding fit to the holes in the saw, but they should not bind tight. Both pins should bear against the holes in the saw, and if both the pins and the holes in the saw are properly located, the saw will pass up to the collar with either side against the arbor collar, or in other words, the saw may be turned around upon the arbor. If the pins, or either of them, bind in the holes of the saw, and the latter is forced on the arbor, it will spring the saw out of true, and when this is the case care should be taken in making the correction to discover whether it is the pins or the holes in the saw that are wrongly located. If it is the pins, the error will show the same whichever side of the saw is placed next to the arbor collar, while if the error is in the holes, the error will show differently when the saw is reversed on the arbor. When a saw becomes worn, and its teeth require sharpening, the first thing to do is to _joint_ it, that is to say, bring down all its teeth to the same height, which may be done by holding an emery block or file against it while the saw is running, care being taken to hold the block or file firmly, and to continue the process until the tops of the teeth run true. The next operation is to gum and sharpen the teeth. Gumming a saw is cutting out the throats, or gullets between the teeth, so as to maintain the height of the tooth, and it follows that on saws that have sharp gullets (or in other words, saws in which the back of one tooth and the face of the next tooth join in a sharp corner), the sharpening process with the file may be made to also perform the gumming. In the case of teeth of coarse pitch, however, this would entail too much labor in filing, and furthermore, as the height of the teeth increases with the pitch or distance apart of the teeth of circular saws, and as the higher the tooth the weaker it is, therefore coarse pitched teeth are given round gullets so as to strengthen them as much as possible. The gumming of a saw should always be performed before the sharpening, and the sharpening before the setting. When the sharpening is to be done with the file, the cutting strokes of the file should be in the same direction as the teeth lean for the set, as this leaves a sharper cutting edge, and it follows that the proper plan is to file every other tooth first, going all around the saw, and to then turn the saw around in the vise, and file the remaining teeth. The height of the teeth and the diameter of the saw will be best maintained by filing the front face of the tooth to bring it up to an edge, but in filing the front face the spacing of the teeth should be kept as even as possible. If the front face has been filed until a tooth is as widely spaced as those already filed, and the edge is not brought up sharp, then the edge may be brought up by filing the back of the tooth. [Illustration: Fig. 3083.] A saw gumming, gulleting or chambering machine to be operated by hand, and constructed by Henry Disston & Sons, is illustrated in Fig. 3083. It consists of a frame spanning the saw, and having screws B B, B B, to adjust to the saw thickness; 4 and 5 are two saw teeth, and 6 the cutter, K is a wheel for the feed screw G, and C and D gauges for regulating position and depth of the gulleting. The cutter 6 is driven or revolved by means of the handles H H, but an important point in the construction is, that a pawl and ratchet wheel is used to drive the cutter, so that if the handles H H were revolved in the wrong direction, the cutter would not be revolved. This saves the cutter teeth from breakage. The machine is operated as follows: Run the cutter back by means of screw G as far as necessary, then place the machine on the saw, with the cutter close up in the chamber of the tooth to be gummed. If the teeth are regular and the same distance apart, start the cutter in any chamber; but if they are irregular, make them even by commencing in the smallest space. After gumming the saw a few times the teeth must become regular. F is a set-screw to regulate the depth of gullet. Fasten the machine to the saw by means of the screws B B, and proceed to gum the first tooth, one of the points of the star being struck at each revolution by a projection on the handle, steadily feeding the cutter until arrested by set-screw F. Remove the machine to the next tooth towards you, after having run the cutter back, and proceed as before until the whole of the teeth are gummed. The cutter is so arranged as to slide on its axis, and when one portion becomes dull, remove a washer from back to front, and thus present a new sharp cutting surface; and so continue changing the washers until the whole face of the cutter becomes dull. Set is given to saw teeth in two ways: first, by what is called _spring set_, which is applied to thin saws and to cross-cut saws; and second, _swage set_, which is given to thick saws and to inserted teeth. Spring set consists of bending the teeth sideways so as to cause the saw to cut a passageway or _kerf_, as it is termed, wide enough to permit the saw to pass through the timber without rubbing on its sides. Swage set consists of upsetting the point of the tooth with a swage, thus spreading it out equally on both sides of the body of the saw plate, as shown at A, Fig. 3084. The set of the teeth, whether given by swaging or upsetting, or by spring set, should be equal throughout the saw, so that each tooth may have its proper share, and no more, of duty to perform. If spring set is employed, it should not extend down more than half the depth of the teeth, and this point is one of considerable importance for the following reasons. The harder the saw is left in the tempering the easier the teeth will break, but the longer they will keep sharp. Now a tooth that is hard enough to break if it is attempted to carry the set down to the root or bottom, will set safely if the set is given to it for one-half its depth only. If a saw is to be sharpened by filing, it should be made as hard as it can be to file properly, even at the expense of rapidly wearing out the file, because the difference in the amount of work the saw will do without getting dull enough to require resharpening is far more than enough to pay the extra cost of files. Circular saws with inserted teeth are made of thicker plate than solid saws of corresponding diameters, which is necessary in order that they may securely hold the teeth. The principal difference in the various forms of inserted teeth lies in the method of locking or securing the teeth in the saw. Figs. 3084 and 3085 represent the chisel tooth saws of R. Hoe and Company. The No. 2 tooth is that used on gang edging machines and for bench work. No. 3 tooth is that used in miscellaneous sawing, for hard woods and for frozen lumber. No. 4 is the shape used in the soft and pitchy woods of southern and tropical countries. The method of inserting the teeth is shown in Fig. 3084 on the left, the pin wrench being shown in position to move the socket whose projection at C carries the tooth D home to its seat and locks it there. The sockets for the numbers 3 and 4 tooth are, it is seen, provided with a split, which gives to them a certain amount of elasticity that prevents the sockets from getting loose. Swing-frame saws are made in various forms, generally for cross-cutting purposes or cutting pieces to length. [Illustration: Fig. 3084.] [Illustration: Fig. 3085.] [Illustration: Fig. 3086.] Fig. 3086 represents a swing-frame saw that is mounted over a work bench, and can therefore be used without necessitating carrying the work from the bench. It consists essentially of a frame pivoted at the upper end to the pulley shaft and carrying below a circular saw driven by belt over pulleys on the upper shaft and the saw arbor. In this machine the iron hubs carrying the frame have sockets fitting over the outer diameter of the hanger hubs, so that the frame hangs upon those hubs and not upon the pulley shaft. The advantage of this plan is that the frame joint is relieved of the wear which would ensue were it hung upon the revolving spindle, while at the same time the movement of the joint is so small as to induce a minimum of abrasion. To counterbalance the frame while it is placed out of the perpendicular, there is provided a compensating weight as shown in the engraving. [Illustration: Fig. 3087.] Fig. 3087 represents an example of that class of cutting-off saw bench in which the length of the work is determined by the width apart of the saws. This machine is constructed by Trevor and Company, and is designed for cutting barrel staves to exact and uniform lengths. [Illustration: Fig. 3088.] The stave is laid upon the bars of the upright swing-frame (which is pivoted at its lower end), and the latter is vibrated by hand, which may obviously be done both easily and quickly on account of the lightness of the swing-frame and its vertical position. A dimension sawing machine, by G. Richards and Company, is shown in Fig. 3088. This machine is designed for general fine work, such as pattern making, and its general features are as follows: It carries two saws (a cross-cut and a rip-saw), mounted on a frame that can be quickly revolved by a worm and worm wheel to bring either saw into position as may be required. There is a fixed table and adjustable fence on one side of the saw, and a movable table and fence on the other. The saws are ground thin at the centre, as shown in Fig. 3089, so that but little or no set need be given to the saw teeth; hence the cutting edges of the teeth are more substantial and true, and as a result the work is cut very smoothly, and if the machine is kept in thoroughly good order, the sandpaper may follow the saw. In Fig. 3088, A is a substantial box frame, to which is bolted the fixed table T. T´ is the movable table which runs on rollers, and is guided by the [/\] slideway at _e_. This table the workman pushes to and fro by hand, the work being adjusted upon the table or to the fence, as the case may be. At W is the wheel for swinging the frame to bring the required saw into position. [Illustration: _VOL. II._ =DIMENSION SAWING MACHINE.= _PLATE XVIII._ Fig. 3089.] In Fig. 3089 the worm gear for swinging the saws into position is shown, and also a sectional view of one saw arbor and of the movable table. A is the main frame, and _f_ the disc frame carrying the two saw arbors. The disc _d_ is turned to fit a seating formed in the base, while the other end of the disc frame fits through a substantial bearing B; W´ is the worm wheel, and W´´ the worm for swinging the disc frame. The worm teeth fit closely to the worm wheel teeth, and backlash or play is prevented by means of the spring bearing shown at D, the spiral springs forcing the worm teeth into the worm wheel teeth. Thus _a_ is the bearing for the worm carried in the box _c_, upon which is the spiral spring whose tension is regulated by the screw _g_. The end of the worm is therefore held in a swivel joint that causes it to operate very easily. [Illustration: Fig. 3090.] Fence F, Fig. 3088 is for slitting, and is made to swing back for bevel cutting, while F´ is for cross cutting, and is adjustable for angle cutting. Fence F is fitted to a plate P, Fig. 3090, which rests on the table top, and also rests on the long slide _g_. This slide fits in a beveled way _h_, and contains a [_|_] groove. A tongue likewise beveled fits in the top of this groove, the tongue being permanently fast to the fence plate. The [_|_] bolt passes through the tongue and fence plate, having at its upper end a milled or knurled thumb wheel R, which when tightened up fastens the fence plate and the slide together. Upon slacking the thumb wheel R, the fence plate and [_|_] bolt may be readily shifted, setting the fence as near to gauge as possible by hand, and the thumb wheel is then tightened, and the slide (which carries the fence bodily with it) is adjusted by means of the hand wheel H and its screw which threads into a lug from the table. The fence F is pivoted to plate P at _p_, and the angling link which holds it in position is secured by a hand nut M. The front journal of the saw arbor has a double cone, and by means of the nuts _n n´_, Fig. 3089, can be regulated for fit independently of the back bearing and journal, the latter being also coned and capable of independent adjustment by means of the adjustment nuts _m m´_. The countershaft for driving the saw arbors is below the machine, so that the saw that is not in use remains stationary. [Illustration: Fig. 3091.] Examples of the work done on this machine are shown in Fig. 3091, the various sections shown being produced by the vertical movement of the saw through the table and the cross movement of the fence. For example, for cutting out a core box, such as shown at 6, small grooves are cut through to remove the bulk of the wood, and the saw marks at the bottom of each saw cut serve as gauge lines for the workman in finishing the circular bore with the gouge, etc. An example in which the table is fixed to the frame and the saw is adjusted for height above the table is shown in Fig. 3092. The saw arbor is here carried in a frame that is pivoted at one end to the main frame, while at the other end is a handle through which passes a locking screw for securing that end of the saw arbor frame to the arc slot shown on the main frame. [Illustration: Fig. 3092.] In a more expensive form of this machine an adjusting screw is used for regulating the height of the saw, and an iron table is employed instead of a wooden one. [Illustration: Fig. 3093.] A double saw machine constructed by P. Pryibil is shown in Fig. 3093. In this machine each saw is carried in separate frames, that are pivoted at one end to the main frame and secured at the other to segments, so that either saw may be elevated to the required distance above the work table. One saw is for ripping and the other for cross cutting, and the arbor of the latter is provided with an adjusting screw operated by the hand wheel shown on the right hand of the machine. As the saws are on independent arbors, they can be speeded differently to suit different saw diameters, which is an advantage because, as machines of this class are for the lighter classes of work, the ripping saw will rarely be required for work of more than about 3 or 4 inches thick, and a rip saw of large diameter is not therefore necessary. The cross cut saw however requires to be of larger diameter, as its work includes cross cutting up to 8 or 10 inches diameter, and the saw being larger does not require so high a speed of revolution. Both saws are provided with ripping gauges and with right and left hand mitre fences, adapted to the application of either short or long work, and provided with length gauges. [Illustration: Fig. 3094.] Fig. 3094 illustrates the various gauges in place upon the table of a machine. The table is provided with a slideway, or slot, on each side of the saw, and parallel with it, and also with a slideway at one side of the table. In the figure, the mitre gauge, or gauge for sawing at an angle, is shown in two positions. The gauge A A A is for cutting work to length, and for cropping the ends at the same time, an extension frame being used, as shown for unusually long work. [Illustration: Fig. 3095.] [Illustration: Fig. 3096.] Fig. 3095 illustrates the method of employment of the mitre gauge. The pointer is set to the degree of angle the work is to be cut to, and is fastened to its adjusted position by the set screw H. The stop is set to the required length, and the work is held by hand against the face of the gauge, and at the same time endways against the stop, and the gauge is then moved along the slot, feeding the work to the saw. When the work is sawn and is to be withdrawn, care must be taken to keep the work fair, both against the gauge and against the stop. [Illustration: Fig. 3097.] Figs. 3096 and 3097 show the application of the gauges for cropping off the ends of work and cutting it to exact length. There are two stops, S and T, each of which is secured in position by a set screw, and has a tongue that may be thrown over, as occasion may require--thus, suppose it is desired to merely crop off the end of the work--and both stops may be set for the work to rest against as in Fig. 3096, and the end of the work may be cut off or cropped to square it or remove a defective part. Stop S may then be thrown over as in Fig. 3097, and the squared or cropped end of the work rested against stop T, to gauge the length to which the work will be cut. This is a simple and convenient method of cropping and gauging. [Illustration: Fig. 3098.] Fig. 3098 represents a circular saw machine, constructed by the Egan Company, in which the table is carried on a vertical slide, and may be raised or lowered by means of the hand-wheel, bevel gears, and screw shown, and may be set at any required angle to the saw for cutting bevels. The saw arbor or mandrel is carried by the main frame, and is therefore rigidly held. The fences can be used on either side of the saw, which is very convenient when the table sets out of the level. BEVEL SAWING MACHINE OR COMBINATION MITRE SAWING MACHINE. In this machine, which is shown in Figs. 3099, 3100, and 3101, the construction permits of the saw being set so as to revolve at other than a right angle to the work table, which is rigidly secured to the frame of the machine. This machine is constructed by J. S. Graham & Company, and its action may be understood from the following: Fig. 3099 is a general view, while Figs. 3100 and 3101, are sectional views of the machine. The table is firmly bolted to the frame, and is fitted with the necessary groove slides and fences for rip sawing and cross cutting. It is also provided with a removable piece, which allows the use of wabbling saws, dado heads, etc. [Illustration: Fig. 3099.] [Illustration: Fig. 3100.] The sides of this machine A, A, Fig. 3099, are cast with an extension for countershaft. Referring now to Figs. 3100 and 3101, the upright piece I, I, with arms B B, and G, G, is bolted to the frame as shown. The arbor frame M, M, is gibbed to T, T, by the circular piece U, and is moved to any angle by the hand wheel Z, which operates the worm W, which in turn moves the arbor frame M, M. This arrangement does not require any locking device to hold the saw in position. As the centre upon which the arbor swings is in the intersection of the planes of the saw and table top, the opening in the table needs not be larger than for the ordinary saw. When cutting a mitre the saw takes the position J, Fig. 3101. When cutting at a right angle the saw takes the position J´ and the arbor takes the position P´ N´. [Illustration: Fig. 3101.] The saw arbor can be raised and lowered by the use of the hand wheel which operates the screw _b_ (Fig. 3100.) There is an accurate index located in front of the machine in sight of the operator, marked from 0 to 45°. The iron table is of one piece 4 feet by 3 feet and fitted with the necessary groove slides for ripping and cross cutting gauges. It is also provided with removable piece E, Fig. 3101, allowing the use of dado head, etc. The table is provided with a bevel slitting gauge S´, and cross cut or mitering gauge X´, Fig. 3099, which in connection with the angular adjustment of the saw enables the operator to get every conceivable plain or double mitre ever required. The pulleys A´, B´, are made wide to allow the belt to travel as the saw is inclined. The pulley B´ takes up the slack of the belt. The countershaft and tightener are a part of the machine and can be run wherever a belt can be brought to them. ROLL FEED CIRCULAR SAWS. Figs. from 3102 to 3105 represent a roll feed circular saw, by J. Richards. Fig. 3102 is a side elevation, Fig. 3103 a plan, and Fig. 3104 a cross-sectional view through the rolls. In Fig. 3102, P is the saw-driving pulley, T a stand for carrying the saw guides _a_, _b_, _c_, _d_, which are adjustable for height by means of the arm whose set screw is shown at U; at W is the spreader for opening out the board after it has been cut by the saw, and thus prevent its binding against the saw and heating it. The construction of the feed motion is shown in Figs. 3103, 3104, and 3105. On the saw arbor is the feed cone C, Fig. 3103 having four steps so as to give four rates of feed. This cone connects by belt to feed cone D, whose shaft drives feed pulley E, which drives F by belt connection. F drives two worms shown by dotted lines at H and I, and these drive the worm wheels which drive the feed rolls, one of these worm wheels being shown at K, in the side view, Fig. 3102. The feed roll L (Fig. 3103) is supplemented by a fence or gauge face P, which guides the work closer up to the saw than would be possible with a roll, and a supplemental roll is provided at M, thus affording a guiding surface for the work from M to the end of P. The stand for guide roll L fits in a slideway, and is adjustable along it by means of the screw S. Similarly the stand for roll N is fed along its slideway by screw R. There are three separate sets of saw guides, all of which are shown in the plan view Fig. 3103, and of these the top ones, _a_, _b_, _c_, _d_, _e_, _f_, _g_, and _h_ are adjustable by nuts. The front ones, _l_, _m_, _n_, _o_, _p_, _q_, and the back ones, _i_, _j_, _k_, and _r_, _s_, _t_, are adjustable by means of the wedges _w_. At Z is a wedge for adjusting the spreader W so as to keep it close to the saw whatever the diameter of the latter may be. [Illustration: Fig. 3102.] [Illustration: Fig. 3103.] Fig. 3105 is an end view of the machine showing the feed worms H and I, and the belt tightener V, which is carried on the arm _u_ on whose shaft is the weight _y_, attached to which is the handle X. [Illustration: Fig. 3104.] [Illustration: Fig. 3105.] SEGMENTAL CIRCULAR SAWS. [Illustration: Fig. 3106.] A segmental circular saw is one in which the saw is composed of segments secured by screws to a disc, the construction being such as shown in Fig. 3106, in which A is the saw arbor, D the disc, and E, F, G, H, I, J, etc., the segments. The segments are made of varying thicknesses at the cutting edge, and are tapered for a distance for from 6 to 8 inches inwards from the teeth points. Thus in the figure there is shown at P an edge view of a segment, from _a_ to _b_ being parallel, and from _b_ to _c_ being ground off taper. The segments are held to the disc by the two sets of screws, R, S, and are further secured at their edges by pieces of copper, as shown at W. Between the edges of the segments there is left a space or opening of about 1/16 inch, which is necessary to insure that the segments shall not bind together edgeways, as that might prevent their seating fairly against the face of the disc D. The seats for these pieces of copper are shaped as shown in the face views at W, and in the edge views at W´, the mouth of the slot being widened on each side, so that riveting up the pieces of copper will prevent the segments from moving sideways. In fitting in these pieces of copper, it is essential to take care that they do not completely fill the slots, but leave a small opening at each end of the slot, as at _f_ and _g_ in the figure, and in order to do this the copper must be left about 1/8 inch narrower than the width of the slot. If the copper is, in riveting up, brought to bear against the end of the slot, it will twist the segments out of line one with the other, causing the saw to drag, cut roughly and produce bad work. [Illustration: Fig. 3107.] [Illustration: Fig. 3108.] Figs. 3107 and 3108 represent portions of segmental saws for cutting veneering. In some of these saws the screw holes are so arranged that the segments can be moved out to maintain the diameter of the saw as it wears. GANG EDGING MACHINES. For dressing the edges of planks parallel and to width what are called gang edgers or gang edging machines are employed. A gang edger consists of an arbor driving two or more circular saws, through which the boards to be edged are fed. Means are provided whereby the distance apart of the saws may be rapidly adjusted while the saws are in motion, so that if a board will not true up to a given width, the saws may be set to cut it to a less one without delay. [Illustration: Fig. 3109.] Fig. 3109 represents a self-feeding gang edger, constructed by J. A. Fay & Company, and in which the left-hand saw may be fixed at any required position on the left-hand half of the saw arbor, while the two right-hand ones may be adjusted independently along the arbor, while the machine is running. At the back of the saw is a feed roll, and above it a pressure roll, whose pressure may be regulated by means of the weight and bar shown at the back of the machine. The object of placing the feed and pressure rolls at the back of the saws, is, that if a board is found to be too narrow for the adjustment of the saws, it may be withdrawn without stopping or reversing the machine, and the saws may be drawn together sufficiently to suit the case. Fig. 3110 is a plan and Fig. 3111 an edge view of the work table, and show the means of adjusting the saws. A is the saw arbor, and 1, 2, 3, the circular saws. Saw 1 is carried by the sleeve B, which is secured in its adjusted position by the set screw C. The mechanism for traversing saws 2 and 3 corresponds in design, and may be described as follows: The arbor A has a spline S to drive the sleeves D, D´, which hold the saws and are carried by arms E, E´, which operate in slideways and have racks F, F´, into which gear pinions whose shafts G, G´, are operated by the hand wheels H, J. It is obvious that by means of the hand wheels H, J, saws 2 and 3 may be regulated both in their distances apart or in their distances from saw 1, while the machine is in full motion, the bushes or sleeves D and D´ being carried by and revolving in the slide pieces or sliding bearings E and E´ respectively. Now suppose that E´ be moved to the left by hand wheel J, until it abuts against the end of D, at the slide end, and a further movement of D´ will also move D, causing it to operate its pinion and revolve the hand wheel H, hence D and D´ may be simultaneously moved without disturbing their distances apart by operating hand wheel J. On the yoke above the saws is a coarse-figured register plate to enable the setting of the saws to accurate widths apart. RACK FEED SAW BENCH. This machine is employed for the purpose of reducing balks or logs into planks of any thickness required. The machine is fixed on the floor of the saw mill, all the gearing being underneath the floor, so that the table may be set level with the floor, which is a great convenience when heavy logs are to be operated upon. The machine consists of a substantial bed plate or frame A, Fig. 3112, carrying the saw and the feed works. The carriage runs on rollers, some of which are fixed to the frame A, and others to the framing timbers B, which are long enough to support the carriage throughout its full length, when the carriage is at either end of its traverse. [Illustration: Fig. 3110.] [Illustration: Fig. 3111.] The driving pulley for the saw arbor is shown at C, Fig. 3112, in dotted lines and in Fig. 3113 in full lines. Upon the saw arbor is a cone pulley D, Fig. 3113, for operating the carriage to the feed, the construction being as follows: Referring to Figs. 3112 and 3113, cone pulley D connects by a crossed belt to cone pulley E, on whose shaft is a pulley _e_ which drives the pulley F, on whose shaft is the pinion _f_, which drives the gear G. On the same shaft as G is a pinion _g_, which drives the gear wheel H, which engages the rack J, on the carriage, and feeds the carriage to the cut. The diameters of pulleys E, F, and of _f_, G, and _g_, are proportioned so as to reduce the speed of the cone pulley D, down to that desirable for the carriage feed. But, as there are four steps on the cones D, E, therefore there are four rates of cutting feed or forward carriage traverse, which varies from 15 to 30 feet per minute. The speed of the saw varies in practice, some running it as slow as 9,000 feet per minute at the periphery of the saw, and others running it as high as 16,000 feet per minute. The latter speed however, is usually obtained when the saws are packed with fibrous packing, which will be explained presently. The quick return motion for the carriage is obtained as follows: Referring to Figs. 3113, and 3114, K is a fast and K´ a loose pulley on the shaft _k_, and receiving motion by belt from a countershaft. [Illustration: _VOL. II._ =RACK-FEED SAW BENCH.= _PLATE XIX._ Fig. 3112.] The speed of the fast pulley K is such as to give a return motion to the carriage of about 50 or 60 feet per minute, being about twice as fast as the carriage feed motion. We have now to explain the methods of putting the respective carriage feed motions into and out of operation, and insuring that both shall not be in gear at the same time. [Illustration: Fig. 3113.] Referring therefore to Figs. 3113 and 3114, suppose the carriage to have completed a feed or cutting traverse, and the operator pushes with his knee the lever or handle _h_, Fig. 3114, which revolves shaft _m_, on which is an arm that moves the belt-shifting rod _n_, thus moving the belt from fast pulley F to loose pulley F´, thus throwing the feed gear out of engagement and causing the carriage to stop. He then presses down the foot lever L, Fig. 3113, which operates the belt-shifting rod _p_, Fig. 3114, and moves the belt from loose pulley K´, to fast pulley K, which having a crossed belt, operates the pulley F in the reverse direction and traverses the carriage backwards, or on the return motion. Upon releasing the foot from the lever L, the weight W operates the foot lever L, and the belt is re-shifted from fast pulley K to loose pulley K´, and the carriage stops. The carriage is formed of iron plates with an open space of about 1/2 inch between them, as shown in Fig. 3114, this space forming a race to permit the carriage to travel past the saw. The only connection between the two sections or parts of the table, is a wide plate at the rear end which secures them together, and causes the lighter portion of the table, which is merely driven by the friction of the rollers C, to always travel with the lower or under portion, which is driven by the rack J. In larger machines for the heaviest work, both sections are driven by a rack motion. The guide motion for the carriage is constructed as follows: _a_, _a_, are brackets placed at intervals along the whole frame work. These brackets support rollers _c_, which have flanges on them to prevent any side motion of the carriage, the construction being most clearly seen in Fig. 3113; _b_ being a bearing for the shaft _v_ of the rollers. Each section of the carriage, it will be seen, has two ribs or ways which rest on the rollers, which are arranged four on each shaft _v_ (_i.e._ two for each section of the carriage). The fence or gauge against which the face of the work runs is very simply arranged as is shown in Figs. 3113, and 3114, being secured to the shaft _q_, by a long bolt _t_, threaded into the top of the fence, and at its lower end abutting against a shoe fitting partly around the top of the shaft _q_. It is squared at the top to receive a wrench or handle _u_, and it is obvious that unscrewing the handle releases the fence from shaft _q_, so that the fence may be moved rapidly by hand across the table to approximate the adjustment of the fence from the saw. The fence having been thus approximately adjusted, and locked to the shaft by means of the handle _u_, the final adjustment is made by means of the hexagon nut _w_, on the bed of the shaft nut _x_, serving as a lock nut, to hold _q_ in its adjusted position. FIBROUS PACKING.--The fibrous packing before referred to is composed of hemp, plaited in a four strand plait and inserted in an open-top trough, along the sides of the saw for a distance about two inches less than the radius of the smallest saw the machine uses. [Illustration: Fig. 3114.] This packing steadies and stiffens the saw, and also affords a means of adjusting its tension, while the saw is running. Suppose for example, that the saw is rim bound,[47] and the fibrous packing may be rammed tightly to the saw, as near to the saw rim as possible, and less tight as centre of the saw is approached. [47] For the principles involved in hammering saws to equalize the tension see page 69 (Vol. II.) _et seq._ This warms the saw, but makes it warmer at the circumference than at the centre, expanding the circumference, and by equalizing the tension, enables the saw to run straight. [Illustration: Fig. 3115.] When the packing is to be adjusted, the carriage is run out of the way, and the packing operation is performed by hand, with a caulking tool. The packing and its box, as applied to a rack saw bench is shown in Fig. 3115, by the dark rectangles. By thus packing the saw to guide it and keep it straight, thinner saws may be used, saws 52 inches in diameter, and having a thickness of but 7 or 8 gauge being commonly employed, and in some cases of 9 gauge. Saws that are thus packed, produce much smoother work. The packing, it may be observed, is kept well lubricated with oil, and the following is the method of adjusting it. [Illustration: _VOL. II._ =PLANTATION SAW MILL.= _PLATE XX._ Fig. 3117.] The side of the saw on which the operator stands is the last to be packed, the packing on the other side being inserted so as bed fairly but lightly against the saw, so as not to spring it, which may be tried with a straight-edge. The packing on the other side is then inserted to also bed fairly against the saw, without springing it, and the saw is run until it gets as warm as it may, from the friction of the packing. If, then, the saw flops from side to side, the outside (circumference) is _loose_, and the packing is rammed together on both sides of the saw and near the saw arbor or mandrel, care being taken that in ramming the packing the saw is not unduly pressed on either side. Expert sawyers generally change the packing when the saw is changed, and thus keep for each saw its own packing. The slot or pocket in which the packing lies is about 1-1/4 inches deep, and 1/2 inch wide. [Illustration: Fig. 3116.] In ordinary circular saw benches or machines the packing comes about up to the level of the table, as shown in Fig. 3116, in which A is a hand hole for putting in and lifting out the plate B, so as to put in or remove the wooden pieces C, D, upon which the packing rests. Fig. 3117 represents a saw mill constructed by the Lane & Bodley Company. In this machine two circular saws are employed, the upper one being of small diameter and revolving in the same direction as the log feed. A is the driving pulley for the main saw arbor _a_, and B the driving pulley for the upper saw arbor _b_. The carriage feed is obtained by belt from cone pulley C to cone pulley D, on whose shaft is a friction pulley _e_, which, for the feed motion, is moved by lever E into driving contact with pulley F, whose shaft drives the pinion G, which gears with the rack of the carriage. The three steps on the cones C, D, give three rates of feed, and a quick return motion is given to the carriage by engaging the friction pulley with a wheel not shown in the engraving. The log to be sawn rests upon the slideway S S´, and is secured thereon by the dogs J, J, which are capable of sliding up or down upon the heads H, H´. When the handles K are raised the slides carrying dogs J are free to be moved up and down H, H´, whereas when handles K are depressed the dogs J are locked and hold the log. The operation is to raise the dog slides to the top of H, H´, set the log up to the faces of H, H´, and then by raising handles K, let the dog slides fall, their weight forcing the dogs into the log, and the depression of K locks the dog slides upon H, H´, respectively. The log feed is obtained from the lever L, which operates the ratchet wheel T, which drives bevel gears V and W, which operate the screws that slide the heads H, and H´, along the slideways S and S´. Three rates of log feed are obtained by regulating the amount of motion that can be given to the lever L, the construction being as follows: In the lever L is a slot in which a stop _r_ can be secured at different heights, and the piece M has four notches. The limit to which L can be moved to the left is until it comes against the stop _x_, but the limit to which it can be moved to the right is governed by the height of the stop _r_ in the slot in L. If stop _r_ is set at its highest position in the slot, L can be moved to the right until the stop _r_ meets the right hand step on the circumference of M, and a maximum of log feed is given. TUBULAR SAW MACHINE. [Illustration: Fig. 3118.] Fig. 3118 represents a tubular saw machine. The saw runs in fixed bearings, the work feeding on the table B, running on ways on A. The work is here obviously sawn to a curve corresponding to that of the circumference of the saw. CROSS CUTTING OR GAINING MACHINE. In Figs. 3119 and 3120 is represented a machine constructed for either cross cutting or gaining, the gaining head shown on the machine being replaced by a cross-cut saw when cutting off is to be done. [Illustration: Fig. 3119.] It consists of a vertical column or standard, upon the face of which a slideway A for the arm B, on which is a slideway C, along which the head for carrying the saw arbor traverses. When the saw is to be used, the carriage or work table must be locked in position and adjusted so that the saw will come fair in the groove, provided in the table, but it is not necessary to dog or fasten the work to the table, because the saw itself draws the work over fair against the fence. When the machine is used for gaining, the work must be dogged fast to the table, so that the work and table may be moved accurately together and the widths apart of the gains kept accurate. Joshua Oldham's combination saw for grooving or gaining is shown in Fig. 3121. It consists of two outside saws, such as shown at the top of the figure, and having spur teeth between the ordinary cutting teeth. The tops of the spur or cross-cutting teeth are a little higher than the other teeth, so that they sever the fiber before the ordinary teeth attempt to remove it, and thus produce very smooth work. The inside pieces, shown at the bottom of the figure, go between the two outside saws, if necessary, to make up the required width of gain. They are made 1/8 inch thick, with an odd one 1/16 inch thick, and will thus make gains advancing in widths by sixteenths of an inch. SCROLL SAWING MACHINES. The scroll sawing machine derives its name from the fact that it is particularly fitted for sawing scroll or curved work by reason of the saw (which is a ribbon of steel with the teeth cut on one edge) being very narrow. The principal points in a scroll sawing machine are to have the saw held under as nearly equal tension as possible throughout the whole of the stroke; to render the machine readily adjustable for different lengths or sizes of saws, to provide it with means of taking up lost motion, and to avoid vibration when the machine is at work. A scroll sawing machine constructed by the Egan Company is shown in Fig. 3122, a sectional view of the saw straining mechanism being shown in Fig. 3123. A, A, is a casting having slides for the head B, which is adjustable upon A to suit different lengths of saws, and is secured in its adjusted position by the bolt C and nut D. To the ends of the springs S, a strip or band of leather is secured, the other end passing around the small step F of a roller R, and being secured thereto. The roller R is so supported that it may rise and fall with the strokes of the saw. A second leather band G is secured at T, passes over the large step of R, and at its lower end hooks to the saw, which is strained by the springs S. This reduces the motion of the springs, and thus serves to equalize their pressure throughout the saw stroke. The lower end of the saw is gripped in a slide or cross-head that is driven by the connecting rod and crank motion shown in the general view Fig. 3122. The lever shown at the foot of the machine moves the belt to the fast or loose pulley to start or stop the machine, and operates a brake to stop the machine quickly. [Illustration: _VOL. II._ =GAINING OR GROOVING MACHINE.= _PLATE XXI._ Fig. 3120. Fig. 3121.] Fig. 3124 represents a scroll saw constructed by H. L. Beach. This machine is provided with a tilting table, which can be set at any angle up to 39 degrees, either to the right or left, the exact angle being indicated by a graduated arc. [Illustration: Fig. 3122.] [Illustration: Fig. 3123.] [Illustration: Fig. 3124.] The straining device, including the springs, air pump, guide-ways, cross-head and steel bearing, are all attached to the vertical tubular shaft, which is secured to the heavy cast back support by the box E and eccentric lever F. By raising the lever F, the shaft, being balanced, is free to move up or down to suit any length of saw. At the same time, the steel bearing L forms a support for the back and sides of the saw, and can be raised or lowered to suit any thickness of work. The under guide-ways are so constructed that their expansion by tightening does not tighten the cross-head. Instead of the ordinary tight and loose pulleys, the crank shaft carries a friction pulley and combination brake by which the saw is stopped or started instantly, by a single motion of the foot. This leaves the hands entirely free, and saves considerable time in stopping and starting. The lower end of the saw is held by a steel clamp; when the saw breaks it can be used again by filing a notch. Both ends of the saw are arranged to take up lost motion and wear. Any desired strain from 10 to 75 pounds can be given to the saw, and the strain is equal at all points of the stroke. BAND SAWING MACHINES. [Illustration: Fig. 3125.] The simplest form of band sawing machine is that in which the work is fed to the saw by hand, a machine of this class, constructed by J. A. Fay & Co., being shown in Fig. 3125. It consists of a standard or frame A, carrying the saw-driving wheel B, and the upper wheel C, the saw being strained upon these two wheels. The lower wheel runs in fixed bearings, while the bearing of the upper wheel is carried in a slide provided in the frame, being operated in the slide by a screw, whose hand wheel is shown at E, so that it may be suited for different lengths of saws. The bearing of the upper wheel is so arranged that the tension placed on the saw may be governed by a weighted lever F, which enables the upper bearing to lower slightly, so that if a chip should fall between the saw and the lower wheel, it may not overstrain, and therefore break the saw. At J, is a bar carrying a guide G, which sustains the saw against the pressure of the cut, a similar guide being placed below the table T, at G´. This latter guide is fixed in position, whereas the upper one, G, is adjustable for height from the work table, so that it may be set close to the top of the work, let the height of the latter be what it may. G´´ is a guide and shield for the saw at the back of the machine, and H is a shield to prevent accident to the workman, in case the saw should break. Band saws are ribbons of steel, brazed together at their ends and having their teeth provided on one edge. The widths of band saws vary from 1/16 inch to 8 inches, and their thicknesses from gauge 18 to 22 gauge, according to width. The advantage of the band saw lies in that it may be run at high velocity, may be made thin, and its cutting action is continuous. As a band saw is weak, it is desirable to have the teeth as short as possible and leave enough room for the sawdust, so that it shall not pack in the teeth. [Illustration: Fig. 3126.] In a circular saw, the centrifugal force acts to throw the sawdust out, while in a frame saw, the backward motion of the saw acts to clear the teeth of the dust, whereas in a band saw the dust is apt to pack in the teeth while they are passing through the work. The remedy is to space the teeth widely, thus giving room for the dust without having a deep tooth, an ordinary form of tooth being shown in Fig. 3126. [Illustration: Fig. 3127.] A stronger form of tooth is shown in Fig. 3127, the tooth gullets being well rounded out, and the teeth shallow at the back, while having ample room in front for the dust. In determining the shapes of the teeth of band saws, we have the following considerations: [Illustration: Fig. 3128.] One of the principal objects is to have the back edge of the saw bear as little as possible upon the saw guide, and as the feed tends to force that edge against the guide, we must so shape the teeth as to relieve the back guide as much as the circumstances will permit. This may be done by giving to the front faces of the teeth as much rake as the nature of the work will permit. Thus, in Fig. 3128, it will be seen that from the front rake, or _hook_ of the teeth, as it is commonly called, there is a tendency for the cut to pull the saw forward, this tendency being caused by the pressure, on the teeth in the direction of the arrows, and obviously acting to prevent the saw from being forced against the back guide. For sawing soft woods, such as pine, the teeth may be given a maximum of front rake or hook, whereas for hard woods, the front faces must be made to stand at very nearly a right angle to the length of the blade, and the feed must therefore be lighter, in order to relieve the back edge of the saw from excessive contact with the back guide, which would not only rapidly wear the guide, but acts to crystallize the edge of the saw and cause it to break. [Illustration: Fig. 3129.] The set of the teeth of band saws is given in two ways, _i. e._ by spring set, which consists of bending each alternate tooth sideways, as in Fig. 3129, or by swage set (upsetting or spreading the points of all the teeth), a plan that may be followed with advantage for all saws thicker than about 20 gauge. Spring set is given either by bending, or by hammer blows, and swage set either by blows or by compression. In spring set, each tooth cuts on one side, and there is consequently a pressure tending to bend the tooth sideways, and break it at the root, whereas in spread set, the tooth cuts on both sides equally. As the front faces of band saw teeth are filed straight across, as in Fig. 3129, and are not given any fleam for any kind of woodwork, the set, whether spring or a spread, should be equal in amount for every tooth, and the pitch and depth of the teeth should be exactly alike, so that no one tooth will take more than its proper share of the cut. The bend or set of the tooth in spring set saws, should not extend more than half way down the depth of the tooth, which will make the set more uniform and save tooth breakage, it being borne in mind, that a tooth hard enough to break if the set extends down to the root, will set easily if it extends half way down only, and that a saw may be soft enough to file, and of a proper temper, and yet break if the spring set is attempted to be carried too far down the tooth. [Illustration: Fig. 3130.] If as in the case of fine pitched teeth, the teeth are filed with a triangular or _three_ square file but little front rake or hook can be given, without pitching the teeth widely. This is shown in Fig. 3130, in which S, is the section of a saw, and F, a section of a three square file. The front faces have no rake, and the file is shown as acting on both faces. [Illustration: Fig. 3131.] In Fig. 3131, we have the same pitch of teeth, but as the file is canted over, so as to give front rake or hook to the tooth, the tooth depth is reduced, and there is insufficient room for the sawdust. In order, therefore, to give to the teeth front rake, and maintain their depth while keeping the pitch fine, some other than a three square file must be used. The principal defect of the band saw is its liability to break, especially in band saws of much width, as say 3 inches and over. A saw that is 6 inches wide will ordinarily break by the time it has worn down to a width of 4 inches. Now for heavy sawing it is necessary that wide saws be used, in order to get sufficient driving power without over-straining the saw. [Illustration: Fig. 3132.] The causes of this saw breakage are as follows: In order that the saw may be regulated to run on the required part of the upper wheel, and lead true to the lower wheel, it is necessary that the upper wheel be canted out of the vertical, and band sawing machines are provided with means by which this may be done. If the upper wheel were set level, as in Fig. 3132, the saw itself would be held out of level, and the toothed edge would be more tightly strained than the back edge. Furthermore the middle of the saw cannot bed itself perfectly to the wheel. Furthermore, the velocity of the toothed edge would be greater than that of the back edge because of its running in a circle of larger diameter when passing over the wheels. [Illustration: Fig. 3133.] This is to some extent remedied by setting the wheel out of the vertical, as in Fig. 3133, in which case the two edges will be more equally strained, and have a more equal velocity while passing over the wheels. [Illustration: Fig. 3134.] There will still however, be an unequal strain or tension across the saw width, and it is found that unless the saw is made what is known as loose,[48] it is liable to break, and will not produce good work. It is to be observed however, that the above may be to a great extent, and possibly altogether, overcome by means of having the rim face of the wheel, or of both wheels, curved or crowned in their widths, so that the saw will be in contact with the face of the wheel, nearly equally across the full saw width. This would also cause the saw to run in the middle of the wheel width, and thus enable the alignment of the saw to be made without requiring the upper wheel to be set out of level. [48] See page 69, Vol. II., for what is technically known as looseness in a saw. RE-SAWING BAND SAW MACHINE. A re-sawing machine is one used to cut lumber (that has already been sawn) into thinner boards. Fig. 3134 represents a band saw machine, constructed by P. Pryibil, having a self-acting feed motion, consisting of four feed rolls, all of which are driven, and two small idle rolls, which are so arranged as to guide the last end of the stuff or work after it has left the driven rolls. Four rates of feed are provided, and the upper wheel can be set at the required angle from a perpendicular while the machine is in motion. The upper guide wheel, and the mechanism by which it is carried, is counterbalanced by a weight that hangs within the column or main frame, and is therefore out of sight. [Illustration: Fig. 3135.] The construction of the parts by means of which the upper wheel is adjusted in height to regulate the tension of the saw, and which also cants the wheel out of the vertical, is shown in Fig. 3135, which represents a portion of the main frame or column, on which is a slideway B, for the slide C, which carries the bearing for the upper wheel. The method of moving the slide C for moving the upper wheel to adjust the saw tension is as follows: By means of the handle H and the worm and worm wheel at W, the shaft S is revolved. The upper end of S is threaded into the nut N, which is capable of end motion in its bearing at _e_, and which abuts against the lever L, the latter abutting against the end of the screw M, and acting at its other end on the rubber cushion P. Now suppose that S be revolved in the direction denoted by the arrow, and the effect will be to raise the nut N. This effect will be transferred through the screw M to the slide C, which will rise up on B, carrying with it the upper wheel bearing and wheel. When the upper wheel receives the strain of the saw, then the continued revolution of shaft S will cause the nut N to lift endways in its bearing _e_, the screw M acting as a fulcrum to cause the lever L to compress the rubber cushion P. The amount of tension on the saw is tested by springing it sideways with the hands. Now suppose the saw to be properly strained, and that a piece or chip of wood accidentally gets between the saw and the lower wheel, and the result will be that the slide C will (from the extra strain caused by the chip) move down on its slideway B, which it is capable of doing, because the long arm of the lever L can move down, compressing P, and this will prevent the saw from breaking. To cant the wheel for leading the saw true to the lower wheel, the following means are provided: The upper wheel bearing rests on the fulcrum at _a_, and is guided sideways by the screws _c_ and _d_. At _f_ is a stud threaded into the bottom half of the upper wheel bearing, the wheels _g_ and _h_ threading upon _f_. The weight of the upper saw wheel endeavors to lift the end J of the wheel bearing, and wheel _h_ determines how much it shall do so, while wheel _g_ acts as a check nut to lock the adjustment. [Illustration: _VOL. II._ =BAND SAW WITH ADJUSTABLE FRAME.= _PLATE XXII._ Fig. 3139.] [Illustration: _VOL. II._ =BAND SAW MILL.= _PLATE XXIII._ Fig. 3140. Fig. 3141. Fig. 3142.] The feed rolls are carried in slides which are operated in slideways by means of screws, and the two back rolls, or those nearest to the column are maintained vertical. The two front ones, however, are provided with means by which they may adjust themselves to bear along the full depth of the work, notwithstanding that it may be taper. The construction by means of which this is accomplished is shown in Figs. 3136 and 3137, in which A is front and B a back feed roll. The bearings of feed roll A abut against rubber cushions C, C, whose amount of compression is regulated by the set screws D, D. [Illustration: Fig. 3136.] [Illustration: Fig. 3137.] [Illustration: Fig. 3138.] The construction of the saw guides is shown in Fig. 3138, which is a plan view partly in section. S S are hardened steel plates set up to the saw by means of studs whose nuts are shown at N N. W is a friction wheel which supports the saw against the thrust caused by the work feeding to the saw. The adjustment of the wheel W to the saw is obtained by means of the wheel H. The hand wheel H operates the screw _r_ _r_, that adjusts the wheel W to the saw, the wheel J serving to lock the screw in its adjusted position. Fig. 3139 represents Worssam's band saw machine, in which the standard may be set at any required angle for cutting bevels. When the work is heavy and not easily handled it is preferable to set the standard and saw at the required angle, rather than to set the table at an angle and have the saw remain vertical. In Worssam's machine this is accomplished as follows: A is the main frame carrying the work table T, and having circular guideways B, B´, which carry the standard C having guide C´ for working in the circular guideways B, B´. The saw-driving wheel D, is carried in bearings provided in C, and, therefore moves when the standard C is moved. At the upper end of C, is the slide E, which carries the bearing for the upper wheel F, this slide being adjusted to regulate the saw tension by the hand wheel O, whose screw threads into a nut in the slide E. H carries the front guide G, for the saw, the back guide G´ being carried by a bracket bolted to C. The back guide is fixed in position, but the front one is adjustable to suit the height of the work by raising or lowering it. The means for setting the saw at the required angle to the work table are as follows: At the back of the standard C is a rack J, whose pitch line is an arc of a circle of which the axis of the guideway C´ is the centre. Into the rack J fits the worm wheel K, at the bottom of the shaft of which is a pair of bevel gear wheels L, which are operated by the hand wheel M. A band saw machine constructed by Messrs. London, Berry & Orton, is shown by Figs. 3140, 3141 and 3142, in plate XXIII. The saw-driving wheel D, has wrought iron arms turned true and screwed into the wheel hub. The wooden segments have their grain lengthways of the rim, and between them are placed pieces of soft wood with the grain across the rim. This acts to keep the joints tight, notwithstanding the expansion and contraction of the wood. The upper wheel is adjusted for straining the saw, and for leading the saw true, by the following construction. It is carried in a U-shaped frame F, which is pivoted at _y_ to a slide that is gibbed to the main frame, and by operating the screw shown at X, the frame F is set to the required level. To regulate the tension of the saw, the hand wheel K is operated, which drives the pair of bevel gears J and I, the latter of which operates the threaded shaft H, whose upper end G connects with the slide which carries F. Within G is a spring to act as a cushion to the slide, and thus prevent saw breakage should a chip pass between the saw and its driving wheel. The saw guide frame is secured to the main frame at _m´_, _m´_. Upon the face of _m_, is a slideway for the saw guide arm _n_, which may thus be adjusted as closely to the upper face of the work as possible. The weight of arm _n_ is counterbalanced by a rope passing over the pulley V, and supporting the counterbalance weight _w_. The feed motion is constructed as follows: On the same shaft as the main fast and loose pulleys A, B, is the feed pulley L, which by belt connection drives pulley M, which is on the shaft W, upon which is a friction disc N, by means of which the rate of feed is regulated. The feed disc N drives the wheel O; the degree of contact between these two (N and O) is regulated by means of the weight T, on the lever U. On the same shaft as the friction wheel O, is a pinion driving the gear X, which is on the same shaft as the pinion Y, which drives the two gears Y´ and Y´´. Referring now to Fig. 3142, gear Y´ drives the pair of bevel gears Z and Z´, for the feed roll _e_, and the pair of bevel gears shown at Z´´, the feed roll _f_. The gear Y´´ drives similar gearing for the feed rolls _e´_ and _f´_, seen in the plan Fig. 3140. Referring now to the plan Fig. 3140, and the side elevation, Fig. 3142, the feed roll _f_ is carried in a frame _g_, which is fitted on the slideway _d_, _d_, and receives a screw _i_, upon which is a hand wheel _h_; at the back of this wheel is the lever _j_, which is weighted as shown, so that the force with which feed roll _f_ grips the work is determined by the weighted lever _j_, and may be varied to suit the nature of the work by moving the weight along _j_. The construction of the gear for feed roll _f´_ is similar, as may be seen in the plan Fig. 3140, _f´_ being in a slide _g´_, which has a screw _i´_, and hand wheel _h´_, a weighted lever corresponding to _j_ acting against wheel _h´_. In proportion as _f_ and _f´_ are opened out to admit thick stuff or work, the hand wheels _h_ and _h´_, respectively are used to screw the screws _i_ and _i´_ into their respective slides _g_ and _g´_, and thus maintain the weighted levers in their requisite horizontal positions. The feed rolls _e_ and _e´_ are carried in slides _c_ and _c´_, and are adjusted to suit the thickness of the stuff or work by a hand gearing, which consists of the hand wheel _a_, seen in the plan and in the front elevation, Fig. 3141, which drives the pinions _b_ and _b´_, which operate screws for the slides _c_ and _c´_, the latter being a left hand screw. The front rolls _e_ and _e´_ are therefore held in a fixed position, whereas the back ones _f_ and _f´_ may open out under the pressure of the weighted levers _j_, and thus accommodate any variation in the thickness of the work. The rate of feed is varied to suit the nature of the work by the following construction: The friction wheel O and the hand wheel R are connected by a yoke _q_, Fig. 3142, at the ends of which are the joints P, Q, seen in the plan, Fig. 3140. Hand wheel R is threaded to receive the screw S, and it follows that by revolving R, the friction wheel O may be moved towards the centre of the friction disc N, which would reduce the velocity with which N would drive O, and therefore reduce the rate of feed. If the friction wheel O be moved from the position it occupies in the plan Fig. 3140, to any point on the other side of the centre of the friction disc N, the direction of feed motion would be reversed. A band saw machine for the conversion of logs into timber, and constructed by Messrs. London, Berry & Orton, is shown in Fig. 3143. The logs are fixed to the carriage by dogs and the carriage traverses the log to the feed. RECIPROCATING CROSS CUTTING SAW FOR LOGS.--The machine shown in Figs. 3144 and 3145 is designed for the purpose of cutting heavy and long logs into convenient lengths preparatory to cutting the logs up in other machines, and it is usually therefore placed at the entrance to the mill, where it is of immediate service as the lumber comes into the building. The machine here shown is intended for logs up to 36 inches in diameter, is simple in construction, requires very little foundation, is easy to handle, and occupies but very little room. The saw is here fed mechanically to its cut, whereas in some machines it is fed by its own weight, and therefore requires great care to be taken, when the saw is finishing its cut, in order to prevent it from falling after it has passed through the log. Fig. 3145 is a side elevation and Fig. 3144 a plan of the machine, in which A is the frame of the machine on which are the bearings for the shaft B carrying the fast pulley C, loose pulley D and fly-wheel E at one end, and at the other, a crank disc F, whose pin is shown at G. This drives the saw K through the medium of the connecting rod H. The saw is fast at the butt end to along slide J, J, which works in a long guide formed on the face of the swinging frame L, which pivots at one end on the shaft B and at the other is carried by a slide P, on the vertical slideway M, and is fed down the same to give the saw its cut by the screw whose hand wheel is shown at N. V is a second guide for the saw, and being connected to the slide feeds down with the saw until it meets the log. A counterweight W balances the weight of the slides and saw, so that there being a pit beneath the balance weight the saw and its guides may be raised so that the saw stands out of the way when not in use. Y is a dog for holding the log, which is also blocked by the wedges Z Z´. [Illustration: Fig. 3146.] The construction of the main bearing is shown in Fig. 3146, in which it is seen that the hub or boss of the loose pulley is much longer than that of the fast one, thus providing a large amount of bearing surface, which is advantageous because the belt will remain longer at the loose pulley than it will on the tight one. The sleeves or bushes in which the shaft runs afford a simple means of renewal to restore the fit when the shaft has worn loose in its bearings. It is obvious that as the guide frame L is pivoted to the shaft B, it carries the end of the saw (as it is fed down) in an arc of a circle of which the axis of B is the centre, whereas the slideway M is straight, and slide P therefore moves in a straight line instead of in the required arc. Provision however is made to accommodate these two motions as follows: [Illustration: Fig. 3147.] [Illustration: Fig. 3148.] Fig. 3147 is a sectional view of the slides on the slideway M and Fig. 3148 a plan of the same. The hand wheel N corresponds to N in Fig. 3145. Upon the vertical slideway (in Fig. 3145) of the standard fits the slide P, which has a horizontal slideway for the slide R, which is free to slide automatically, having no screw or other device to restrain it, save the guide frame L, and therefore as this frame is lowered to feed the saw the slide R moves automatically to accommodate the arc of a circle in which the guide moves on account of being pivoted at B. HORIZONTAL SAW FRAME.--This machine is designed for the more expensive woods, such as mahogany, and is finding much favor because it will cut at a very high speed, the saw travelling about 150 feet per minute. [Illustration: _VOL. II._ =LOG CROSS-CUTTING MACHINE.= _PLATE XXIV._ Fig. 3144. Fig. 3145.] [Illustration: Fig. 3143.] The roughest shaped trunk may be easily fixed on the travelling table, and a thin saw may be used as it may be very tightly strained. This machine is used either for breaking down timber, or for converting it from the log to any desired thickness, the thickness of the boards being very readily and easily varied. The machine consists essentially of a framework carrying either one or two very thin and tightly strained saws operating horizontally and cutting on both strokes, so that the feed is continuous, the construction being as follows: [Illustration: Fig. 3150.] Referring to Figs. 3149 and 3150, A is a base plate or bed carrying two uprights or standards B, B, having guideways C, C, for the cross-head D, which has slideways E, E´, for carrying the frame F, F, which carries the saw G, which is guided on each side of the work by the guides H, H´. The frame F, F is connected to the slides J, J´, and has the rod K, to which the connecting rod pin L is attached, and the rod M, which acts as a stretcher. A connecting rod P, connects the pin L to the crank pin Q, on the crank Q´, which is driven by belt from the pulley T, a fly-wheel being provided at S. It is obvious that as the crank revolves the saw reciprocates, its line of motion being determined by the guideways E, E´. The construction of the saw is shown in Fig. 3151, and it is seen that for half its length, the teeth are formed to cut when the saw moves in one direction, while for the other half the teeth slope in the opposite direction, and are therefore arranged to cut when the saw is on the opposite or return stroke, and the construction whereby the saw is enabled to cut on both strokes is obtained as follows: [Illustration: _VOL. II._ =HORIZONTAL SAW FRAME.= _PLATE XXV._ Fig. 3149.] Referring to Fig. 3149, the two slides E, E´, on which the saw-carrying frame F F slides, are not in line or parallel one with the other, but each slide is at an angle of about 85 degrees to the line of feed, so that as frame F is reciprocated at each stroke, one end of the saw advances towards the cut, and the other recedes from it, thus causing the saw to cut first on one half and then on the other of its length, one half cutting on the forward, and the other on the return stroke. [Illustration: Fig. 3151.] The studs or saw-buckles for attaching the saw to the frame are shown in Fig. 3151, in place on the ends of the saw, the part I, that fits in the frame F, Fig. 3149, being squared so that the saw cannot be twisted in tightening up the nuts of the saw-buckle. The belt works for driving the saw are arranged as follows: at T are the fast and loose pulleys for driving pulley R, the belt passing from T over two pulleys (shown dotted in, Fig. 3149), U, U´, whence it stretches to the crank driving pulley R, whose bearing is provided on the cross-head, so that the two move together when the cross-head is altered in height from the work-table or carriage, to accommodate different thicknesses or diameters of logs. It is obvious that in proportion as the cross-head is set nearer to the carriage, the belt from T to U, U´ would become slack; provision is made however, to prevent this as follows: Pulley U, is carried on a frame or swing lever X, to which is attached by rope V the weight W, which therefore regulates the tension of the belt. The cross-head D may be raised or lowered by belt power or by hand, as occasion may require, the usual course being to move it to nearly the required position by belt power, and then complete the adjustment by hand, a graduated scale being provided as shown, whereby the rack can be set to cut the required thickness of plank without measuring the timber. The belt motion for raising or lowering the cross-head is obtained by the pulleys at Y, the wheel for the hand adjustment being shown at Y´. In either case the bevel gear wheels Z, Z´ operate, respectively, a vertical screw engaging a nut on the cross-head. The log feed is obtained by a motion separate from the return motion, there being three rates of feed and a quick return motion, the construction being as follows: Referring to Figs. 3149 and 3150, a is a belt pulley fast on the crank shaft, and driving pulley _b_, which is also shown dotted in. Pulley _b_ drives the vertical shaft _c_, on which is the cone pulley _d_, having three steps, and which drives (by means of belt _d´_) cone pulley _e_, on which is a worm _f_, driving the worm wheel _g_, which runs idle on its shaft unless engaged therewith by means of the clutch _h_. The shaft of worm wheel _g_ is omitted in Fig. 3149, so as to leave the belt-shifting mechanism for pulleys _q_, _q´_ exposed to view. On this shaft however is a pinion driving the gear wheel _k_, on whose shaft is a pinion _l_, driving the gear _m_, which engages the rack _n_, on the under side of the carriage. The clutch _h_ is engaged by the lever _i_, to the upper arm of which is attached the rod _j_, _j_, from the lever _p_, hence operating _p_ (which is done by hand), back and forth, throws clutch _h_ into and out of gear with the worm wheel _g_, and puts the carriage feed on or throws it out, according to the direction in which _p_ is moved. The upper end of shaft _c_ is carried in a bearing on the cross-head, and is provided with a featherway or spline, so that as the cross-head is raised or lowered the upper end of _c_ passes through its upper bearing, and the pulley _b_ travels with the cross-head. The three rates of carriage feed are obviously obtained by means of the three steps on the cone pulleys _d_ and _e_. We have now to explain the construction of the mechanism for traversing the table back, and giving it a quick return motion, or in other words a quicker motion on the back than on the feed traverse, and this is arranged as follows: _q_, is a fast and _q´_, _q´´_, are loose pulleys, one driven by an open belt _r_, Fig. 3150, and the other by a crossed belt _r´_, from a countershaft. The belt-shifting forks are operated by lever _s_, whose upper end engages with the rod _t_, which is operated by the lever _u_. The loose pulleys _q´_ and _q´´_ are twice as wide as the fast pulley _q_. Now suppose that lever _u_ is moved to the right, and the belt would be moved from the loose pulley _q´´_ to the fast pulley _q_, while the other belt would merely be moved or shifted from one to the other side of loose pulley _q´_. Similarly if lever _u_, be moved to the left, the belt on the loose pulley _q´_ will be moved on to the fast pulley _q_, and the belt on pulley _q´´_ would simply be moved across the face of the pulley, and as the countershaft pulleys for the two pulleys are of different diameters, therefore two rates of motion are obtained. The shaft _v_, on which pulley _q_ is fast, drives the pinion _l_, which drives _m_, the latter gearing with the rack beneath the carriage. The carriage is guided by the wheels _z_, which are secured to it, and run on the iron guideways _z´_, the flanges of the wheels preventing side play, and causing the carriage traverse to be in a straight line. WOOD-PLANING MACHINES. [Illustration: Fig. 3152.] The simplest form of planing machine for wood work, is the hand planer or buzz planer, as it is termed, an example of this class of machine being shown in Fig. 3152, which has been designed and constructed by George Richards, for the use of pattern-makers. It consists of a frame carrying a revolving shaft, which is by some called the _cutter head_, and by others the cutter bar, and to which the cutters or knives are attached. The work is rested upon the work table, or else pressed against a guide or _fence_, and fed by hand over the revolving knives, whose cutting edges protrude above the surface of the table, to the amount of the depth of cut it is intended to take. [Illustration: Fig. 3153.] In this example, however, the table is made in two sections, the front one of which is below the cutter edges to an amount equal to the depth of the cut, and the back one level with the cutter edge, when the latter is at its highest point in its path of revolution, the construction being shown in Fig. 3153, in which J, J, represents the top part of the main frame of the machine, C the cutter head, B the front or feed table, A the back or delivery table, and W a piece of work being fed in the direction of the arrow. Upon the upper surface of the frame J, J, and on the feed side of the cutter head is the carriage G, to which are pivoted two links L, L, which support the feed table B. At D is a hand wheel whose screw has journal bearing in a lug from the table, while the screw threads into a nut provided in the carriage. Obviously then by operating the hand wheel D, carriage G is moved along the top of the frame J, and the height of table B is adjusted. Thus if the carriage G is traversed to the left, the link L would fall more nearly to a horizontal position, and table B would lower. Or if G were moved to the right, links L would stand more nearly vertical, and table B would be raised, it being understood that table B is not permitted to move endways. Similarly by means of hand wheel C, carriage H may be moved to adjust the height of table A. By this construction, the work can bed fairly on the delivery side, as well as on the feeding side of the cutter head, which is not the case when a single table is used. It is obvious that the work must be fed in opposition to the pressure of the cut, which endeavors to push the work back from the cutter, and this limits the size of work that the machine can operate upon. [Illustration: Fig. 3154.] The work can be fed easier however, with a cutter skewed or set out of line with the axis of the cutter head. Thus in Fig. 3154, is the common form of cutter head, carrying two knives placed diametrally opposite, so that the weight of one counterbalances that of the other, and the head will therefore run steadily and smoothly. The knives K, K´ are here set parallel with the axis of the cutter head, hence the whole length of the cutting edge meets the work at the same instant, and a certain amount of time must pass after one cutting edge has left the work before the other cutter edge meets it. [Illustration: Fig. 3155.] This is remedied by the construction of cutter head shown in Fig. 3155, in which three cutters are used, and each cutter is set askew, or out of parallel with the axis of cutter head, so that the knife begins to cut at one end, and the cutting action gradually extends to the other, hence the cutting action is more continuous and uniform, and better work is produced, while less power is required to drive and feed the machine. [Illustration: Fig. 3156.] Fig. 3156 shows a cutter head with two skew cutters. The cutter head is provided with a cover or guard, which is arranged as follows: In the table is cut a groove or slideway, in which a slide fits, and to this is attached a thin sheet-iron guard. To the slide is attached a weight, which draws the guard back to the fence after the work has passed over the cutter head. By this means the guard covers all the knife edge that protrudes beyond the work, no matter what the width or thickness of the work may be; the guard can however be fixed in position when a number of pieces of the same size are to be planed. The fence provides a guide surface for the work, and its face may be set at any required angle to the surface of the work table. Suppose, for example, that the sides or edges of a piece of work require to be at an angle of 100 degrees to the top and bottom surfaces, then the top surface may be planed first, and the fence being set at an angle of too degrees to the table surface, the top of the work may be pressed to the surface of the fence while fed across the cutter, and as a result, the side or edge will be planed at 100 degrees to the top. ROLL FEED WOOD PLANING MACHINE. [Illustration: Fig. 3157.] Fig. 3157 represents a roll feed wood planing machine, designed and constructed by George Richards & Co., of Broadheath, near Manchester, England, the construction being more fully shown in the detailed figures following. The machine consists essentially of a framework, carrying a cutter head with two knives, and having a pair of feed rolls, in front and a pair behind it. The front pair feed the timber to the cutter head and the back pair deliver it from the cutter head. [Illustration: Figs. 3158, 3159.] Each pair of rolls is geared together, so that both the top and bottom rolls act to give a positive feed. Immediately in front of the cutter head and between it and the feed rolls (_i. e._ the front pair of rolls), is a pressure bar extending across the full width of the machine, and having at its lower extremity a steel spring which presses the work down to the table, and thus causes it to be planed of an equal thickness throughout its length. Immediately behind the cutter head and between it and the delivery rolls (_i. e._ the back pair of rolls), is a pressure bar that also extends across the machine and prevents the timber from rising up from the table after it has passed the cutters, all timber being found to have a tendency to rise after having been acted upon by the cutters. The arrangement of the feed rolls, delivery rolls and pressure bars is shown in Fig. 3158, in which T, T, T, represents three sections of the work table and W, W, a piece of work passing through the machine in the direction of the arrow. Feed roller F is fluted to increase its grip upon the work and insure a positive feed. The lower feed roller F´, and the lower delivery roller D´, are fixed in position, their upper surface projecting above the work table to about 1/100 inch. This is necessary to take the thrust of the upper rolls (F, D) and prevent them from forcing the work down upon the surface of the table with an undue amount of pressure, which would induce friction and consume an unnecessary amount of power in driving the rolls. The method of adjusting the lower rolls will be explained presently. Between the cutter head C and the feed roll F is the pressure bar P, and behind the cutter head is the pressure bar B, both these bars being more clearly seen in Fig. 3159, in which the work W is shown entering the machine, and the lower rolls and work table are removed. Pressure bar P has at its lower end a steel spring J, Fig. 3159, and is supported at each end by circular links Y, projecting into grooves provided in the main frame of the machine, as shown in Figs. 3160 and 3161, in which C is the cutter spindle, Y the circular link at the end of pressure bar P, and _y_ the circular link at the end of pressure bar B, the two fitting into the one stepped groove. [Illustration: Fig. 3160.] [Illustration: Fig. 3161.] This groove is concentric with the cutter spindle C, so that the pressure bars keep at a positive or equal distance from the edges of the cutter, no matter what the thickness of the work or the depth of the cut may be. [Illustration: Fig. 3162.] In Fig. 3162, the work is shown passing beneath the two upper rollers, and the spring J (which extends the whole length of the pressure bar), is depressed from the weight of the bar. By this construction, the work is pressed to the table at a point as close as possible to the cutters. The pressure bar P cannot drop beyond a certain point, because of its tail piece _y´_, Fig. 3160, which rests on the top of the frame at _y´´_ when the bar P has fallen to its required limit. The feed pressure bar P is bolted to its circular links, as shown in Fig. 3162, in which Y is a part of the circular link which is bolted to the pressure bar P. The delivery pressure bar B (Fig. 3160) is riveted to and forms part of its links _y_. It acts through the medium of spiral springs _s_, which are carried in cases or boxes _s´_, which overhang the end of the bar B. A set screw _s´´_ regulates the pressure of the spring, and a screw _a_ (Fig. 3162) regulates the height of the pressure bar. The adjustments of the feed and delivery rollers are made as follows: The feed pressure is obtained through the medium of weights, shown at W, W´, in Fig. 3163, upon the bars A, A´, whose ends are pivoted to the lower ends of links _m_, _n_, the upper ends of which are pivoted to the side frame of the machine. Bar A engages or rests at _e_, on a lug or projection on the link I, which fits in a recess provided in the side of the frame. This link I, extends up and has a bearing to receive the feed roller (F, Fig. 3160), whose driving gear is shown at O. It is obvious therefore, that the amount of pressure on the feed roller F may be varied by moving the weight W along the bar A. Similarly for the delivery pressure roller, the weight W´ is adjustable along the bar A´, which is pivoted to link _n_, and rests upon I at _e´_. The link I´ is guided in ways in the side frame of the machine, and at its upper end carries the delivery roller D, whose driving gear is shown at O´ (Fig. 3163). It is obvious that there are bars A, A´, and links I, I´, on both sides of the machine, so as to adjust the feed rollers at both ends. The work table and the two lower rollers are adjusted for different thicknesses of work as follows: Between the two main side frames M and M´, Fig. 3164, are two frames having corresponding inclines or slideways, of which the upper carries the work table and the lower rolls. [Illustration: Fig. 3163.] The lower incline sits on ways K, K, Fig. 3164, cast on the side frame, and is capable of being moved endwise by means of the hand wheel R, Figs. 3163 and 3164, which operates a screw threaded into the lower incline. When the lower incline is moved endways, the upper one, which carries the work table, is moved vertically, and as the lower feed rolls are carried by the upper incline, and the upper rolls are guided to move vertically only, the lower rolls maintain their position beneath the upper ones, or in other words, the table and lower rolls move together in a vertical direction only, when the lower incline is operated. The lower rollers run in bearings formed in the links Q, Q, Fig. 3160, which are pivoted at their other ends to the upper incline. On the sides of the incline are lugs through which pass adjustment screws _z_, which by operating beneath the outer ends of the links Q, Q, adjust the heights, bearings of the lower rollers so that the uppermost point on the circumference stands about 1/100 inch above the level of the work table surface. The upper surface of the lower incline is shown by the dotted line _f_, _f_, _f_, in Fig. 3163. We may now consider the means employed to drive the rolls, first remarking that the upper rolls F and D, are given a motion slightly quicker than the lower ones, so as to cause them to clean themselves (from particles of wood that might otherwise cling to them), by a sort of rubbing action which is due to their velocity being greater than the lower rolls and the work. This rubbing action is due to the fact that the work has the slower motion of the lower rollers, resisting the quicker motion of the upper ones, and as a result there is a certain amount of slip between the upper rollers and the work. Another and important feature, is that the upper delivery roller (D, Fig. 3260), is placed from 1/4 to 1/2 inch nearer to the cutter head than the bottom delivery roll, which assists in keeping the work down upon the table. The mechanism for driving the feed rolls is shown in Figs. 3163, 3164 and 3165, in which L, L are the pulleys which receive motion from a countershaft, and drive the cutter head, being fast upon its shaft, as is also the pulley S, which connects by belt and drives pulley T, on whose shaft is the stepped pulley U, which connects by a crossed belt to pulley V, which drives the feed gear through the medium of the pinion _a_. The two steps on pulleys U and V, obviously give two rates of feed. The pinions O and O´, both receive motion from the gear wheel E, this part of the gearing consisting of gears _a_, _b_, _c_, _d_ and E, and as both pinions receive motion from the same gear, their revolutions are equal. The lower feed roll is driven by the pinion _p_, which gears with and is driven by wheel _d_, whose face is broad enough to meet _p_, which sits nearer to the frame than pinion O does, so that the teeth of _p_ may escape those of O. Now the velocities of all the wheels O, O´, E, _d_ and _p_, will be equal at the pitch circles, because they constitute a simple train of gearing. Thus if _d_ moves through a part of a revolution equal to the pitch E, then O and O´ will move through the same distance, because the wheels are in continuous gear. Now as _d_ drives _p_, therefore the velocity of _p_ must at the pitch circle be the same as _d_, let the numbers of teeth in the respective wheels be what it may, and it follows that the velocities of O, E, _d_ and _p_ are at the pitch circles equal. But by making the diameter of the upper roll greater than the pitch circle of its gear O, and the diameter of the lower roll correspondingly less than the diameter of the pitch circle of its pinion _p_, the velocity of the circumference of the upper roll will be greater than that of the lower roll, and the rubbing action before referred to with reference to the upper roll will thus be induced. [Illustration: Fig. 3164.] Referring now to the lower delivery roll, its pinion _x_ receives motion through gear _w_, which is also driven by gear E, which has a broad face so as to gear with _x_, which is behind and below gear O´. In this case the circumstances are the same, as will be seen from the following. An inch of motion of the pitch circle of E will produce an inch of motion at the pitch circles of O´ and of _w_ and _x_, hence the velocities of the pitch circles will be equal, and if the diameters of the upper and lower rolls are equal, or the same as the pitch circles, the velocities of the circumferences of the respective rolls will be equal, but by making the diameter of the upper delivery roll greater than that of the pitch circle of its pinion, and that of the lower roll less, a rubbing action is induced between the roll and the work, and this rubbing action will keep the roll clear of any dust, etc., that might otherwise cling to it. The cutter head is formed triangular, as in Fig. 3166, carrying three knives. The knives are set at an angle to the axis of the cutter bar or cutter head. When the knives are at an angle, they take their cut gradually, and the cutting action is more continuous, which diminishes the vibration of the machine, and causes the finished surface to be smoother. Furthermore, the knives take a shearing cut, and therefore cut more easily and freely. In some practice the knives are made spiral, but spiral knives are difficult to bed properly to the cutter head, and also difficult to grind. The cutter head is made of a solid mild centre steel forging, and runs in phosphor bronze journals, in which it has about 1/8 inch end play, which tends to distribute the oil along the bearing. It is driven by a pulley at each end, the pulleys seating on a cone. The amount of skew is about 3/4 inch for a cutter head carrying a knife 30 inches long, and about 3/8 inch for a cutter head whose knives are 10 or 12 inches long. [Illustration: Fig. 3165.] [Illustration: Fig. 3166.] [Illustration: Fig. 3167.] Figs. 3167 and 3168 represent a machine in which there are three feed rolls and one delivery roll, all being driven. First there is the pair of feed rolls the bottom roll of which is set sufficiently above the surface of the table to relieve the work of friction upon the table. The work next meets an upper feed roll that acts to force the work down to the table surface (there being in this case no lower feed roll). After passing the knives, the work is carried out by a delivery roll that also acts to keep the work down to the table face. All three upper rolls are provided with rubber springs in the casings H, H´. P, P, are the pulleys for the cutter head and B, those for the feed works, which have two speeds. The feed is thrown in and out by the lever _d_, which moves the pinion D endways and engages or disengages it from its gear wheel. [Illustration: Fig. 3168.] [Illustration: Fig. 3169.] Figs. 3169, 3170, 3171 and 3172 represent a pony planer, by P. Pryibil. [Illustration: Fig. 3170.] Referring to the sectional view Fig. 3170, the work table slides in vertical slideways S, in the side frames, the elevating screw being operated by the bevel gears at G, which receive motion from the hand wheel M in Figs. 3170 and 3171. There are four upper rolls, marked 1, 2, 3 and 4 respectively, and of these the first two are fluted in the usual way. There are two lower rolls, marked respectively 5 and 6. The fluted feed rolls 1 and 2 are weighted, the weight lever acting on the rod R, which at its upper end connects to the cap Y, which covers the bearings of feed rolls 1 and 2. By this construction the two rolls are acted upon by the same weights and levers, the rolls being of course weighted at each end, or in other words on both sides of the machine. The delivery rolls 3 and 4 receive their pressure by the construction shown in Fig. 3172, the bearings of the rolls being held down by rubber cushions receiving pressure from the cap E, screwed down by the bolt and nut. The rolls 5 and 6 are idle rolls, and are set to just relieve the work from undue pressure on the work table. By this construction of feed mechanism the following ends are attained. First, sufficient feed power for heavy cuts is obtained without driving the lower rolls. Second the work is held to the table on both sides of the cutter head, hence there will not be left on the end of the work the step that is left when but two upper and two lower rolls are used, and which occurs because the work falls after leaving the feed rolls, whereas, in this machine the work is held to the table by rolls 2 and 3. The cutter head H, Fig. 3170, has in front of it the pressure bar P, whose lever is shown at L and the weight at W. On the delivery side of the cutter head is a pressure bar _r_, which is acted upon by a spiral spring in the box C. In the engraving to the right of Fig. 3170 the knife K is shown in action on a piece of work, and it is seen that the end of the pressure bar P coming close to the edge of the knife prevents the pressure of the cut from splitting or splintering off the end of the work at _a_, and therefore acts as what is termed a _chip break_. Furthermore, the sides of the cutter head between the knives being hollowed out gives the shavings _s_ room to curl in and prevent the work from splintering at the end when the cut is terminating. BALANCING CUTTER HEADS AND KNIVES.--Planer knives must be balanced as accurately as possible, in order that they may run steadily and smoothly, and therefore produce smooth work. The first requisite for proper balancing is that the cutter head itself be properly balanced, and in order that this may be the case the faces forming the knife seats must be equidistant from the axis of the cutter head, and the journals must run true, being best tested on dead centres. The holes for the cutter bolts should all be drilled to the same depth, and tapped equally deep. The faces or seats for the knives should be parallel one to the other, and this may be tested by a pair of straight edges, one pressed to each face and the width between them measured at each end, or if a long surface plate is at hand, one face of the head may be rested on the surface plate, and the straight edge ruled on the other face, and its distance measured from the surface plate at each end, with a pair of inside callipers delicately adjusted. A straight edge rested lengthways along the knife seat of the head and projecting over the journal will show whether each knife seat is equidistant from the journal as it should be, the measurement being taken with a pair of inside callipers adjusted to just sensibly touch the journal and the straight edge. This measurement should be taken at each end of the head. In all tests made with straight edges, the straight edge should be turned end for end and each measurement repeated, because, if the straight edge is true, turning it end for end will make no difference to the measurement, while if the straight edge is not true the measurement will vary when the straight edge is reversed. If the cutter head is square, the straight edge tests may be applied to all four of its faces, and they may then be tested with a square, and if the head shows no error under these tests, and the bolt holes or slots are of equal diameter and depths, the head will be correct as far as it can be tested without running it. [Illustration: Fig. 3171.] [Illustration: Fig. 3172.] A cutter head may be roughly tested by placing it between the lathe centres, both centres being oiled and delicately adjusted so as to just prevent end motion of the head without perceptible friction when the head is revolved by hand. The first thing to test is whether the journals run true, which may be tested by a pointer fastened in the slide seat, and moved up to just touch the journal. The pointer should be soft, and not a cutting tool, unless indeed it be set so high in the slide rest that it cannot cut. If the journals do not run true, the next thing to test is whether the body of the head runs true to the centres, which may be done by first setting a pointer to just touch the extreme corners of the head at each end and in the middle of its length, and if there is an error in the same direction as the test at the journal shows, then the centres of the head are out of true, and must be corrected before a test of this kind can be proceeded with. But the body of the head may show true at the corners while the journals do not run true, and if this is the case we may further test the body of the head as follows: With the lathe slide rest at one end of the head we may set a pointer so that it will just pass on the flat of the cutter seat and make a mark when the slide rest is traversed along the lathe bed. We then move the slide rest so as to bring the pointer to the journal end of the head; give the head a half a revolution on the centres and try the pointer on the flat of the cutter seat, and if it makes a mark of equal strength, then two faces of the head are equidistant from the axis of the head. The next thing to do is to make the same test at the other end of the head, and in order to do this without moving the pointer, and therefore without altering its adjustment, we must move the slide rest so as to bring the pointer opposite to the lathe centre, and out of the way of the body of the head, and take the cutter head out of the lathe and turn it end for end, and then repeat the test with the pointer, which will show whether both ends of those two flats are alike. This test we repeat on the other two faces of the head, and if they show true, then the head is true, except the journal, which must be made true with the head. This testing will clearly show any want of truth in either the head or the journals, and in what direction correction needs to be made. Now suppose the above tests do not disclose any error, either in the journals or in the head, and we may continue the tests by revolving the head by hand between the dead centres, and apply the pointer to the journals while the head is revolved as quickly as possible; as, however, the head cannot be revolved very fast in this way, we may adjust the lathe centres as before described, and revolve the head as rapidly as possible by hand, and letting it come to rest mark which side is at the bottom, and if on several tests the same side comes to the bottom of the plane of revolution at each test, that side is the heaviest and must be corrected. If it is found to be a flat side or cutter seat that comes to rest at the bottom, the correction can be made by deepening the bolt holes on that side, measuring to see which bolt hole is the shallowest, and making all as nearly as possible equally deep. If the head has T slots instead of bolt holes, the slots may be cut or filed out to effect the balance, care being taken to make the slot equal in distance from the edges of the cutter seat face. The next essential in order to have a properly balanced cutter head is that the bolts and nuts all weigh alike, and that the bolts be of the same length. The bolts should be turned to an equal diameter of equal length and threaded for an equal distance along the body of the bolt, and the nuts should be of equal depth and all fit accurately to the same wrench, and the weight of the bolts and nuts when put together may then be equalized by reducing the heads of the heavy ones. We now come to the balancing of the knives, which must be made of equal thickness and width throughout, with the slots for the bolts of equal widths and depths. The knives require to be as accurately balanced as it is possible to make them, for otherwise they will cause the head to jar and vibrate violently, thus producing rough work. The knives weighed individually may be of the same weight, and yet the head may run out of balance by reason of one end of a knife being heavier than the other end. [Illustration: Fig. 3173.] Fig. 3173 represents a machine constructed by J. A. Graham & Co., for balancing planer knives, moulding knives, cap screws, and knives in rotary cutter heads of all kinds. Let it be supposed that the knives are the same specific weight, but that there is an excess of weight at one end; when revolving on the head, a violent jarring or throwing will be caused by reason of the excess. The knives could be reduced to the same specific weight by the aid of common grocers' scales, but the ends could not be made the same proportional weight as on such balance. In the cut S S is the base of the scale; L, M the standards for the support of the scale beams B B and K K. _d_, _d´_ are two pivots of the scale beams. D is the loop on which the pivot _d_ works. E is a joint in the loop. D´, E´, and F show the loop and connection. _c_ is the sliding table which has the stop _c´_, and is adjustable for different lengths of knives. _a_ _a_ is a knife in position for balancing endwise. G is a slotted piece, and is held to the scale beam by the screw _v_. The slot in G is shown at G´, and limits the travel of the scale beams. H is an angular piece fastened to the lower scale beam, and receives the screw J. I is a small weight used for fine adjustment. O, O are weights which slide along the scale beam K K, and are held in place by the thumb screws P, P. N shows side view of weight, which is so constructed as to allow it to be easily removed. In using the machine the lightest cutter or knife of the set is first found and its two ends balanced, by turning it end for end on the scales, and reducing the weight of the heavier end. The other knife or knives are then balanced without disturbing the adjustment of the machine as made for the first knife. ENDLESS BED OR "FARRAR" WOOD SURFACING MACHINE. This class of machine has a bed composed of slats which are connected together and driven by a chain. Fig. 3174 represents an endless bed double surfacer constructed by the Egan Company. The upper cylinder may be raised or lowered to suit the thickness of the work. The front feed roll is in two sections, enabling two boards of unequal thickness to be planed simultaneously to an equal thickness. These rolls are held to the work by a leaf spring, as shown in the cut, the tension on the spring being adjusted by the screw at D, _d_ serving as a check-nut. A longitudinal section through the centre of the machine is shown in Fig. 3175. The spring S bears at each end on a block T, which carries the bearings for the feed roll. Feed roll M is held down by the screws E, E, acting on a rubber cushion or spring, and is provided with a scraper to clean it from dirt, etc. The travelling bed is composed of slats S connected together by the chain shown, and resting upon slides A, A, supported by the girts B, B. The chain is operated by the spur or sprocket wheel W, and is therefore pulled and not pushed, which tends to keep it under tension, and therefore rigid upon the top side. The ends of the slide A, A are depressed so that the slats shall not tilt up at one corner above the level of the slide when in the positions denoted by S´. The lower cutter head is carried in a sliding head or frame J, adjusted for height by the gears at H, which operate screw _h_, while the bed above it is adjusted by the gears at F. It is obvious that the bottom surface of this bed is set at the same height as the lowest point in the path of revolution of the cutting edges of the knives of the front cutter head or cylinder. The upper delivery roll N is provided with a scraper. PLANING AND MATCHING MACHINE. Planing and matching machines that are made narrow to suit the planing and matching of boards for flooring are sometimes called _flooring_ machines, the distinctive feature of a flooring machine being that it is (unless in the case of a double machine) made narrow (because flooring boards are narrow), and this makes the machine very stiff and capable therefore of a high rate of feed and speed. [Illustration: Fig. 3174.] [Illustration: Fig. 3175.] [Illustration: Fig. 3176.] [Illustration: Fig. 3177.] Fig. 3176 is a general view, and 3177 a longitudinal section through a standard planing and matching machine of recent design, constructed by Messrs. J. S. Graham & Company. The plank passes through two pairs of rollers before meeting the front cutter head. The side heads then come into operation cutting (in the case of flooring) the tongue on one side of the plank and the groove on the other, the under side of the plank being dressed last. The machine is built in three widths viz., 8", 14" and 26", each planing to 6" thick and matching as wide as it planes. In place of matching heads, heads for beading, rabbeting, or fancy siding may then be used. The board R (Fig. 3177) is fed in over the grate _m´_ until it reaches the rolls E and F´, which are held in place by the boxes fitted to the roll stand _n´_, and brought to bear on the lumber by means of the screw _a´_, equalizing bar _m_ and nuts _p_, _p_, together with the lever Y Y and the weight _x_. [Illustration: Fig. 3178.] After the lumber leaves the second pair of rolls, it runs over the bed plate W (Fig. 3178) and under the shoe L, the duty of which is to hold the board firmly against the bed plate, and also to break the chips on a heavy cut. After leaving the shoe it is operated on by the upper cutter head H, then it passes beneath the pressure bar _g_, which holds the lumber firmly while it is acted on by the matcher _c_. [Illustration: Fig. 3179.] It then passes beneath the cleaner E´´ (Fig. 3177) and under the delivering roll, which is held down by the weight U in connection with the lever V and screw _a´_, the top which is shown at C (Fig. 3179). The board then passes underneath the pressure bar Q (Figs. 3177, 3180) and over the under cutter S, from which it passes finished. The pressure bar Q is moved up and down by turning the shaft _a´´_, the motion of which is given to the screw _h´_ by means of a pair of bevel gears. _k´_ is also a scraper that cleans the board before it passes under the pressure bar Q. The under cutter is adjusted for depth of cut by turning hand wheel A´, which moves the screw U´. The rolls are raised and lowered by turning the shaft at P (Fig. 3176). In feeding two boards through the machine, one thicker than the other, that end of the roll that passes over the thick board can raise up without taking the pressure off the thin one at the other end of the roll. This raising mechanism is shown in Fig. 3179. The bevel gear C works over a ball joint Q´. The shoulder B´ on the screw _a´_ works on the under side of the ball Q´. The shaft _a_ passes through the tubular shell B to the opposite end of the roll. The cross tie J is bolted to the roll box K´´. C, Fig. 3178, shows matcher hanger in position. It is gibbed to the bed plate Z by the gib _f_, which is so constructed as to be free from dirt. The sliding gib _f_ is adjustable for wear. One matcher hanger is moved by the screw _e_, the other by _e´_. The left hand matcher hanger is moved by the shaft _l´_ (Fig. 3177), which passes along the side of the machine until it reaches the shaft _e_, where its motion is imparted to the screw by means of a pair of spiral gears. An index at the rear of the machine enables the operator to set the matcher heads to any desired width. The right hand matcher hanger, together with the guide, can be moved across the machine by turning the screw _e´_ at the side of the machine (Fig. 3176). The upright D which carries the pulley which drives the top cutter head, or cylinder as it is sometimes termed, is set at an angle so that the cylinder belt will always be of the same tension. The top cylinder is raised by the shaft _d_ (Fig. 3176) and screw _b_. It is held in place by the nut M (Fig. 3177). The bar I ties the cylinder boxes together. K is held down by the weight I, and yields with the pressure bar L. The spindle of the matcher _c´_ (Fig. 3177) is driven by a belt which comes from the pulley _h_ and passes over the guide pulley _k_, and then to the pulley _b´_. The lower end of the matcher is held in place by being gibbed to the cross tie _p´_, Fig. 3177, which is adjusted and kept in position by the screw _o´_. S´ sustains the matcher spindle by means of an adjustable step. Y´, Fig. 3176, is the feed shaft which drives the gearing that operates the rolls. The pulley that drives the feed shaft is shown at L´ (Fig. 3176). The belt passes over this pulley and under and over the tightener pulleys _w´_, _w´_, then to the pulley U´ which is on the feed shaft Y´. [Illustration: Fig. 3180.] The apron M´ in front of the under cutter S (Fig. 3180) is easily dropped to M´´ by loosening the nut R´ and releasing the bolt T´ so as to allow the apron M´ to drop. This enables the operator to have free access to the under cutter for sharpening knives, etc. _z´_ is the bed plate over which the lumber passes before it reaches the under cutter. [Illustration: Fig. 3181.] [Illustration: Fig. 3182.] A planing and matching machine designed and constructed by Messrs. London, Berry and Orton is represented in Fig. 3181. In this machine the upper surface of the board is surfaced first, and the matching second, the under surface being operated upon the last. The method of suspending the upper feed rolls of this machine is shown in Fig. 3182, in which A is an upper and B a lower feed roll. The upper roll A is suspended by the link C, which is supported by the link D, and also by link E, these three links forming a parallel motion which guides A in a vertical line. At F (which is fast to E) is a bearing for the screw G, and the pair of bevel gears _g_ that drives it. This screw threads into the nut H on the rod I, which receives the pressure of the bar J and weight K. The lower feed rolls being larger in diameter gives them increased grip on the work, and gives it a better base, and also makes it enter and leave the rolls easier. Each matcher bracket is fitted with a screw by which it can be moved at will across the machine, and by turning one other screw with the same wrench that moves the others, both brackets are firmly set to the slide and all screws held firmly. There are three changes of feed. The top cutter head is provided with improved pressure bars, which are set to or from the head by means of a double eccentric, which, while they can be set at any desired distance from the knives, limits their movement when moved towards them, rendering it impossible to get them into the cutters. TIMBER PLANER. The term timber planer implies that plain knives only are used in the machine, which is therefore intended for producing plane surfaces. It also implies that the machine is designed for heavy or large work, such as is found in ship yards, bridge construction or car works, etc., etc. In such work the cuts taken by the machine are sometimes very heavy, and as a result the feed works of the machine require to be very powerful and positive. Fig. 3183 represents a timber planer designed and constructed by J. S. Graham & Co., to plane all four sides of the timber at one passage through the machine. The timber passes through three pairs of feed rolls before reaching the first cutter head, which planes the bottom surface. It then passes to the side heads, which dress both sides simultaneously, and then passes beneath the cutter head that finishes the upper surface, and is finally delivered from the machine by a pair of delivery rolls. The work is passed over roller B, the fence or gauge being shown at B´. 1 and 2 are the first pair of feed rollers, _a_ and _b_ being merely adjustable intermediate wheels, which by means of the pieces _c´_, _b´_, may be set so as to connect rollers 1 and 2 together, whatever their distance apart may be, or in other words whatever the thickness of the work may be. [Illustration: Fig. 3183.] From 1 and 2 the work passes to the second pair of feed rolls 3 and 4, _c_ and _d_ being the intermediates. Similarly 5, 6, 7 and 8 are feed rolls, and _e_, _f_, _g_, _h_ intermediates. The first head is shown at K´, the side heads at H, and the last head at I´, the latter being carried on a sliding head J, which is secured in its adjusted position by nuts I. On the side of the frame D on which J slides is a graduated index to denote the adjustment of the head I´. [Illustration: Fig. 3184.] The construction of the parts in immediate connection with the front cutter head is shown in Fig. 3184. N is the frame corresponding to N in Fig. 3183, the rolls 5 and 6 also corresponding in the two figures. Upon N is a slide S having an arm G, carrying the roll G´, which holds the timber down to the cut of the cutter head K´. The pressure of roll G´ to the work is given through the medium of the rod _a´_, which receives the pressure of the equalizing bar _x_, Fig. 3183. The bottom surface of the timber passes over the bed plate U, Fig. 3185, which raises and lowers with the lower feed rolls, being connected by the screw _i_, Fig. 3184, to the bearing box of feed roll 6. All the lower feed rolls are operated simultaneously by means of the rod _l_, having for each lower feed roll a worm, driving a worm wheel _l´_ on a screw threaded into a hub _m_ in each feed roll bearing; the crank for operating _l_ is seen at P, Fig. 3183. [Illustration: Fig. 3185.] The passage of the timber through the machine is continued in Fig. 3185, in which it is seen that after the lower surface of the timber has been planed it passes from the cutter head K´ to a bed plate V and is thus supported by a flat and true surface while the side cutter heads plane the two sides, one of these side heads being shown at H. The side heads are carried in hangers, one of which is shown at _p´_. It is gibbed to the under cutter frame U´ by the sliding gib _x_, the left hand head H being moved across the frame by the screw _f´_. The hanger is held at the bottom by the gib _t_ and the cross tie _t´_. _p_ is the pulley for the side head H, the end wear of whose shaft is taken up by the adjusting screw _s´_, _r´_ being a leather washer, and _r_ the end of the shaft. [Illustration: Fig. 3186.] The top box H´ moves across the machine in the slideway _b´´_, Figs. 3186, _a´´_ being a part of the box H´. Upon leaving the side heads the timber will have been planed on three sides and the side surfaces dressed to a right angle with the bottom surface. It is then guided to the upper cylinder as follows: The friction rolls K, K are to relieve the bed A´´ from the pressure due to the feed roll Z´ and the roll J´, which holds the timber after it has left the cutter I´, and thus prevents it from vibrating. After leaving the pressure roll J´, the timber passes under the scraper _d´_, Fig. 3183, and thence to the delivery roll 7, which is held down by the weight L, in connection with the lever L´. By means of this construction all the cutter heads act upon the timber within the short distance of 22-1/2 inches, while the side heads act within 8-1/2 inches of the under cutter. This is desirable, being conducive to the production of true work, which it is more difficult to produce in proportion as the cutter heads are wider apart. This machine will joint as narrow as 2 inches, and plane as thin as 3/4 inch. The upper cylinder I´, Fig. 3183, is adjusted for height or thickness of cut by means of the screw _f_, and is locked in its adjusted position on D by the nut I. The feed is started or stopped by operating the hand wheel _o´_. The upper rolls are raised or lowered simultaneously by power, by means of the shaft _s_, and the bevel gears _r_, which operate the screw _a´_. The upper cylinder is driven by belt from the pulley Q, the under cylinder from Q´ (both these cylinders being driven from both ends). P´ is the driving pulley for the feed belt, which passes to N´, which, through K´´ and Y´, drives Y, which drives the feed rolls. The machine will feed from 25 to 60 feet per minute. PANEL PLANING AND TRYING-UP MACHINE. This class of machine is employed for the production of true surfaces, and is now used upon much of the work that was formerly assigned to the Daniels class of planing machine. In this machine, as in the case of the Daniels planing machine, the work is secured to the table, which travels to carry the work to the feed. Fig. 3187 represents a machine by J. Richards, in which a cutter head with skew cutters is employed, and a pressure roll is placed in front and at the back of the cutter head, the construction being as follows: Upon the main frame are the slideways _t_, _t´_, upon which the cross-head or cutter head frame Z is carried, the elevating screw S raising or lowering the frame Z, to suit the thickness of the work. The cutter head C, whose driving pulleys are shown at P, P, is carried in frame Z, which also carries the pressure roll in front of the cutter (the bearing for this roll being shown at R), and a similar roll behind the cutter. To the frame Z are pivoted the pressure bars B, B´, weighted with weights W. These bars rest on the cross-heads Y, whose pins _p_ act on the bearing boxes of the pressure rolls. The cutter head frame may be raised or lowered, for varying thicknesses of work, either by hand or by power. The hand movement is obtained from the hand wheel W, Fig. 3188, which operates bevel gears _b´´_ and _b´_, the latter being threaded to receive the elevating screw. [Illustration: _VOL. II._ =TRYING-UP MACHINE.= _PLATE XXVI._ Fig. 3187.] The power or belt motion for raising or lowering the cutter head frame is obtained from rope wheel _w´_, which receives motion from the guide pulleys shown in Fig. 3187. The wheel _w´_ drives its shaft by the friction cone of its bore, which is forced against the corresponding cone on the shaft by the hand nut L. The handle _v_, Fig. 3187, is for operating the upper guide pulley _q_, which acts as a belt-tightening pulley as well as a guide pulley, and the hand wheel _t_ holds _v_ in its adjusted position. When _v_ is pushed downwards the rope (E) is loosened upon the pulleys, and both rope and pulleys remain idle. [Illustration: Fig. 3188.] The pulley that drives rope E is shown in Fig. 3189 at R. The feed motions for the work table are shown in Fig. 3189, and the construction is such that for ordinary work the table has a quick return motion, while for heavy work the feed and return motions of the table are speeded alike. The driving pulley B, Fig. 3189, for operating the feed mechanism, receives motion by belt connection from the countershaft, and drives the shaft on which are the bevel gears _b_ and _d_, and from these gears the feed motion and quick return are derived, while from gear _e_ and pulley R the cutter head may be raised and lowered by belt power as occasion may require. Beginning with the feed motion, the gear _d_ drives gears _e_ and _f_, which are a working fit on the shaft S. Between these two gears is the clutch _r_, _r_, which is operated by the handle shown in the perspective view, Fig. 3187, at _v_. To operate the feed, clutch _r_ is operated to engage gear _e_ with the shaft S, upon which is the friction wheel _m_, which engages with the internal surface of the wheel or drum _g_, which drives the rope wheel A, which drives the rope for the work table traverse--wheel A and the rope being seen in the perspective view, Fig. 3187. The shaft N has bearing in a piece that is virtually a sleeve eccentric, because its bore is eccentric to its circumference; to this sleeve is attached a lug _h´_ to which the handle _h_, Fig. 3187, is bolted. Now suppose that handle _h_ is depressed, and then G will partly revolve wheel _g_ and cause it to engage with the friction wheel _m_, which will drive _g_, and therefore A. Diametrally opposite to _m_ is a friction wheel _n_, which is driven by the bevel gear _c_, and which is brought into or out of action with _g_ by the eccentric action of sleeve G, it being obvious that when the sleeve G moves _g_ in the direction of _n_, _m_ is engaged and _n_ disengaged from contact with _g_. Raising the handle _h_ therefore places _n_ in gear with _g_, which revolves it in the direction necessary to draw the work table on the back or return stroke. The return motion of the table is more rapid than the feed motion because gear _c_ is of smaller diameter than _b_, and _n_ is larger than _c_ and than _m_. In the case of heavy work, however, the return motion may be made to have the same speed as the feed motion by simply moving the clutch _r_ so as to engage wheel _f_ with the shaft S. The rope groove in the pulley A is waved as denoted by the dotted lines, and this prevents the rope from slipping, notwithstanding that the rope envelops but half the circumference of A. The wire rope from A operates a drum, in which are waved grooves for the table traversing rope which winds around this drum, and attaches to pins (K, Fig. 3187) carried in brackets at the ends of the table, and one of which is shown in Fig. 3187, at _z_. The slack of the rope is readily taken up (as occasion may require) as follows: [Illustration: Fig. 3189.] The pin _k_, to which the rope is fastened, has at one end a squared head to receive a wrench to revolve the pin and wind up the rope, set screw _l_ locking the pin after the rope tension is adjusted. We have now to explain the method of holding the work, which is as follows: The side frames forming the bed are bolted to the main frame and form the ways on which the work table travels. The table frame J, Fig. 3187, is provided with rollers, which rest on the upper surface of the bed and reduce the friction. The table is made in convenient sections bolted to the table frame J, and at their points of junction the work-holding dogs are placed, the construction being shown in Fig. 3190, in which T´ is the end of one, and T´´ the end of another section of the table. Referring now to Figs. 3187 and 3190, upon the edge of the table are the abutment pieces _a´_, _a´´_, against which the work is pulled by the dog, which is operated by the screw, which is squared at its outer end to receive the handle M, Fig. 3187. The rate of work feed is 30 feet per minute and the quick return motion is 60 feet per minute. MOULDING MACHINES. In moulding machines for light work the feed rolls and cutter head overhang the frame, such machines being designated as outside moulding machines. Fig. 3191 represents a machine of this class constructed by J. A. Fay & Company. The table T slides on vertical ways on the main frame, being adjusted for height by the hand wheel W. The work while fed over table T is pressed against the vertical face A by the four springs shown, whose pins swing to suit the width of the work. [Illustration: Fig. 3190.] [Illustration: Fig. 3191.] The two feed rolls are made up in sections or discs and the pressure bar is pivoted and has the weight shown to adjust its pressure to suit the work, and is combined with the bonnet whose shape throws the shavings outwards from the side of the machine. The particular machine here shown is constructed substantially enough to permit of its being used for light planing or work not exceeding 6 inches in width, a head with planing knives being shown in place on the machine. In a machine of this kind it is essential that the cutter head spindle and its bearings be rigid, and with ample journal bearings and free lubrication to prevent wear, and for these reasons the arbor is of steel running in self-oiling bearings of large diameter. The arbor frame is capable of lateral movement to enable an accurate adjustment of the cutters to the work. The term _sticker_, as applied to a machine of this class, means that it is suitable for light work such as window sash and door stiles, blind slats, etc., etc. Fig. 3192 represents a machine termed by its manufactures (the Egan Company) a "double head panel raiser and double sticker combined." The term panel raiser means that the edges of the work may be dressed down so as to leave a raised panel. To fit the machine for such work the bed or table T is made wide. The upper feed rolls are in sections, and the lower one extends nearly across the bed. The upper feed rolls are held down by a spring, whose tension may be regulated by a hand wheel with an adjustment at the back end to give a lead to both rolls. By this is meant that the plane of revolution of the feed rolls inclines toward the cutter head so that as the rolls feed they exert a pressure on the work, holding it securely against the face A. A long spring extends from the front of the feed rolls past the back or bottom cutter head, passing as shown beneath the pressure bar, and is adjustable for height from the bed or table face T by having its ends pass through two studs in which they may be secured by set screws. This serves to keep the work down to the surface of T. The cutter heads for panelling have three cutters set askew or at an angle to their plane of revolution so as to give a more continuous and a shearing cut, which is conducive to smooth work. The bed above the lower cylinder is adjustable for height by means of the screw at H. MOULDING CUTTERS. [Illustration: Fig. 3192.] In the ordinary or common form of moulding cutter, the front face is flat and the lower end is bevelled off and filed to shape so as to give the required shape and keenness to the cutting edges, Fig. 3193 giving examples of such cutters. [Illustration: Fig. 3193.] Cutters of this class must be sharpened by filing the bevelled edge, which requires considerable skill in order to preserve the exact shape of the moulding. SOLID MILLED CUTTERS. [Illustration: Fig. 3194.] [Illustration: Fig. 3195.] In the solid milled cutter the bevelled surface at the cutting end of the cutter is a plane, and a curved, stepped or other shape is given to the cutting edge by cutting or milling suitably shaped recesses on the front face of the cutter as shown in Figs. 3194 and 3195, the former being a tongue cutter for cutting a groove, and the latter a grooved cutter for cutting a tongue. [Illustration: Fig. 3196.] [Illustration: Fig. 3197.] Other examples for such cutters are given as follows: Fig. 3196 represents a cove cutter and Fig. 3197 an ogee. Fig. 3198, a double beading, and Fig. 3199 a bevel cutter, and it is obvious that by a suitable arrangement and shape of groove cutting edges of any of the ordinary forms may be produced. [Illustration: Fig. 3198.] [Illustration: Fig. 3199.] The advantages of such cutters are that the plain bevelled face or facet of the cutter may be ground (to sharpen the cutter) on an ordinary emery wheel or grindstone, and the shape of the cutting edge will remain unaltered, providing that the cutter is always held to the grinding wheel or stone at the same angle, so that the length of the bevel remains the same. A common practice is when making the cutter to so regulate the depth of the grooves or recesses in its face that the cutting edge will be of the required shape when the length of the bevelled facet is equal to three times the thickness of the cutter. The method of finding the shape of cutter necessary to produce a given shape of moulding has been fully explained on pages 80 to 85, Vol. II. [Illustration: Fig. 3200.] [Illustration: Fig. 3201.] Various forms of side heads are shown in the figures from 3200, to 3207. Fig. 3200 is a two-sided plain head, or in other words two diametrally opposite sides of the head are provided with bolt holes, for cutter fastening bolts. Fig. 3201 represents a four-sided slotted head, each side having T grooves, so that the cutter may be adjusted endways on the head. This enables the use of four narrow cutters, thus taking the cut in detail as it were. [Illustration: Fig. 3202.] [Illustration: Fig. 3203.] The two-sided head shown in Fig. 3202 is provided with a set screw, by means of which a delicate adjustment of the height of the cutter may be made. Fig. 3203 represents a three-sided slotted head, or in other words T-shaped grooves, and not bolt holes are used. CUTTER HEADS WITH CIRCULAR CUTTERS. [Illustration: Fig. 3204.] This form of cutter head was invented by S. J. Shimer, and are generally known as Shimer cutter heads. The principle of construction is shown in Fig. 3204, which is for an ogee door pattern. The cutters are circular in form and are seated at an angle to the flange to which they are bolted, this angle giving side clearance to the cutting edges. [Illustration: Fig. 3205.] [Illustration: Fig. 3206.] The full amount of cut is taken in successive stages or increments; thus in the figure, the two upper cutters would produce one half the moulding, and the two lower ones the lower half. As the cutters are sharpened by grinding the front face, therefore they will maintain correct shape until they are worn out. Fig. 3205 represents a Shimer head for producing the tongue, and Fig. 3206 a similar head for producing the groove of matched boards. [Illustration: Fig. 3207.] Fig. 3207 shows the action of the groove head, the cutter or bit D being shown in full lines and the second cutter being shown in dotted lines. Cutter D, it will be seen, operates on one half of the groove, and cutter C on the other half, each cutter having side clearance, because of being seated on a seat whose plane is not at a right angle to the axis of revolution of the head. By thus taking the cut in detail, the head works steadily, while the side clearance makes the cutters cut clean and clear. JOINTING MACHINE. "Jointing" a piece of wood or timber, means producing a surface, so that the joint between two pieces that are to come together or be glued shall be close. In order to produce surfaces that shall be true enough for this purpose, it is necessary that the work be held in such a way that it is not sprung or deflected by the holding devices or feeding apparatus. [Illustration: Fig. 3208.] Fig. 3208, for example, represents a jointing machine, in which the work abuts against an inclined plate P at one end, while the other end is clamped down to the table, which is traversed past the revolving head H, to which are secured two gouge-shaped cutting tools, one of which is seen at T. By using tools of this class, the amount of cutting edge in action is small, and will not therefore spring the work, and if the cutter spindle is adjusted to have no end motion, the work will be true, notwithstanding any slight vibration of the head, because its plane of revolution coincides with the plane of the surface being surfaced or jointed. [Illustration: Fig. 3209.] In some jointing machines, knives are set on the face of a revolving disc, an example of this class of machine being shown in Fig. 3209, which is for facing the spokes of wheels and for finishing the mitre joint on them. Three cutters are used, each being set at an angle to a radial line, so that the inner edge of the knife will meet the work first. This gives the knives a shearing cut, and prevents the whole of the cutting edge from striking the work at once. The spokes are placed against a stop on the table, and brought into contact with the cutters by the foot treadle. The table has beneath it a spiral spring at each end, which returns the table as soon as the foot pressure is released from the treadle. The cutter head or disc is 10 inches in diameter, and should make 2,000 revolutions per minute. Stroke jointers are machines (such as shown in Fig. 3210) in which a long plane _e_ of the ordinary hand plane type is worked along a slide by a connecting rod C, operated by a crank motion. A machine of this class will do very accurate work, but is obviously suitable for thin work only. A machine constructed by J. J. Spilker, for cutting mitre joints by hand, is shown in Fig. 3211. The frame A carries a slideway for the slide to which the mitre cutting knife K is secured. The handle G operates a pinion gearing into a rack, which gives vertical motion to the slide and knife. At _c_ is a fence or gauge against which the work is rested, and which is capable of a horizontal motion, so as to bring the work more or less under the knife. For heavy work, the fence _c_ is set back, so that the first cut of the knife will leave the moulding, as shown at H, partly severed, and a second cut is necessary to sever it; for very fine work, a fine shaving may be taken off by a cut taken on the end of each piece separately, after the piece is severed. At D is a graduated scale or rule for cutting the work to exact dimensions, and as its lines are ruled parallel to the right hand edge of the knife K, the inside measurements of a mitre joint may be taken at the outer edge, and outside measurements at the inner end of each line, a set stop at E serving to gauge the pieces for length. [Illustration: Fig. 3210.] [Illustration: Fig. 3211.] MOULDING OR FRIEZING MACHINES. These are machines that cut mouldings on the edges of the work. The term friezing is applied by some, when the machine has but one cutter spindle, while by others these machines, whether having one or two spindles, are termed edge moulding machines. Still another term applied to this class of machine is that of variety moulders or variety moulding machines. In machines of this class, it is of primary importance that lost motion or play in the bearings be avoided, because the cutter end of the spindle overhangs its bearings, and any side play of the spindle in its bearings is multiplied at the cutting edges of the cutters. Perfect lubrication of the spindle bearings, and ample bearing surface on the journals and bearings, are therefore of the first importance. The work is rested on the upper surface of the table, and is fed to the cutters by hand. [Illustration: Fig. 3212.] [Illustration: Fig. 3213.] [Illustration: Fig. 3214.] [Illustration: Fig. 3215.] [Illustration: Fig. 3216.] Figs. 3212 to 3215 represent a machine by J. S. Graham. The frame B, B, Fig. 3213, of this machine is cast in one piece cored out, and the base is wide, so as to give necessary solidity. The hollow column is fitted with a door W, and shelves V, V, forming a very complete case for the reception of tools, cutters, etc. The spindle boxes and slides C are one casting. They are planed on centres and held in the frame B´, Fig. 3215, by large gibs L, and sliding surfaces shown in C´, Fig. 3214. They are adjustable vertically by hand wheels K, in front of frame in connection with nut O, as shown in Fig. 3214, and require no lock to hold them at the proper height. The cap O´ (Fig. 3213) has an oil chamber J and wick which feeds the oil to the upper bearing. The lower box is fitted with a patent self-oiling and adjustable step shown at _a_, _b_, _c_. The cap _a_, upon which the spindle D rests, has a small opening in the centre. The circular block _b_, under it, also has a hole in the centre. The bolt _d_ has two holes in it, one horizontal and the other vertical. The chamber surrounding this step and cup is filled with oil. The motion of the spindle D on the cap _a_ causes the oil to flow from the chamber through the openings to the spindle. Thus the oil is kept in constant circulation. The end of this spindle D is by this arrangement kept always lubricated. The spindles D are of 1-7/8 hammered tool steel accurately turned and fitted in the boxes, which are of extra length, and lined with the best genuine Babbitt metal. They are 30" from centre to centre, and have independent screw tops, as shown at S, enabling the operator to use various sizes for large or small work, or clear the table of either spindle for special work. H is the threaded part of the screw top, G is the nut, and F the fill-up collars. The iron table A, A is 5 feet by 4 feet, planed and fitted with concentric rings E, E around the spindle, to suit the various sizes of heads and cutters. A heavy wooden table, made of narrow glued-up strips of hard wood, can be used if preferred. This machine has been run up to 6,000 revolutions per minute, without perceptible jar, and cutter heads as large as 8" diameter may be used on it for heavy work. Fig. 3216 represents an edge moulding machine by J. H. Blaisdell. In this machine the table is raised or lowered by the hand wheel upon the central column. The construction of the spindle and its bearings is shown in the sectional view, which also shows the square threaded screw by means of which the table is raised. The spindle has a coned hole for receiving the cutter sockets, which are therefore readily removable. [Illustration: Fig. 3217.] Figs. 3217 to 3220 represent examples of the shapes of cutters for use on edge moulding or friezing machines. Fig. 3217 represents a cutter for bevelling the edge of the work, the cutting edges being at A, B, or at C, D, according to the direction in which the cutter is revolved. [Illustration: Fig. 3218.] Fig. 3218 represents an ogee cutter, in position on the cutter spindle. As these cutters are made solid and accurately turned in the lathe, they are balanced so long as the cutting edges are kept diametrally opposite. The front faces only being ground to sharpen the cutting edges, the cutter always produces work of the same shape. [Illustration: Fig. 3219.] [Illustration: Fig. 3220.] Fig. 3219 represents a cutter (in a chuck) for cutting a dove-tailed groove, and Fig. 3220 one for rounding an edge, it being obvious that a wide range of shapes may be given to such cutters, and that, as they may be sharpened on an emery wheel, they may be left comparatively hard, thus enhancing their durability. To regulate the depth to which a cutter such as shown in Fig. 3220 will cut, a collar or washer is placed beneath it to act as a guide to the edge of the work. [Illustration: Fig. 3221.] Fig. 3221 represents a machine in which rotary cutters are used to produce all kinds of panel work, as well as edge moulding or friezing. In this case the cutter is above the table, the latter being adjustable for height to suit the thickness of the work. Examples of some of the work are shown at the foot of the machine. WOOD BORING MACHINES. The rapidity with which holes may be bored in wood enables the feed to be most expeditiously performed by hand or by foot motion. A foot motion leaves both the workman's hands free to adjust and change the work, and is therefore suitable for light work or work having holes of a moderate depth. The work tables of wood boring machines are provided with suitable fences for adjusting the work in position, and in some cases with stops to adjust the depth of hole. Any of the augers or bits that are used in boring by hand may be used in a boring machine, but it is obvious that, as the bit or auger is forced to its feed by hand or foot, and as its revolution is very rapid, the screw point, which is intended as an aid in feeding when the bit is used by hand, is not necessary. On this account most augers for use in machines are provided with triangular points instead of screw points. [Illustration: Fig. 3222.] In Fig. 3222 is shown a wood boring machine by J. A. Fay & Co. The table is gibbed to a vertical slide on the face of the column, and is adjustable for height by the hand wheel A, which, through the medium of its shaft and a pair of bevel gears, operates the elevating screw B. The spindle C feeds through its bearings, the supporting rod D being pivoted at its lower end to permit C to feed in a straight line vertically. The feeding is done by the treadle F, which operates the rod E. The table may be set at an angle of 30 degrees from the horizontal position. The weight W counterbalances the treadle and brings it to its highest position when the workman's foot pressure is removed. The holes may all be gauged to an equal depth (when they are not to pass through the work) by so adjusting the height of the table that the hole is of the required depth when the treadle is depressed to its lowest point, or limit. [Illustration: Fig. 3223.] Fig. 3223 represents a horizontal boring machine such as used in furniture and piano factories. The spindle feeds through the driving cone, being operated by the treadle shown. The work table is adjustable for height by the hand wheel and elevating screw. The usual fences, stops, and clamping devices may be applied to the table, which is on compound slides to facilitate the adjustment of the work. Fig. 3223_a_ shows a double spindle horizontal boring machine, in which the table and work are fed up to the boring tools by hand. The spindles are adjustable in their widths apart, and may also be set at an angle. The work table is adjustable for height, and the spindle carrying head is adjustable across the machine. [Illustration: Fig. 3223_a_.] [Illustration: Fig. 3224.] Fig. 3224 represents a machine by J. A. Fay & Co., for heavy work, rollers taking the place of the work table. The drill spindles are fed by hand from the stirrup handles shown, which are weighted to raise up the spindles as soon as they are released. MORTISING MACHINES. The mortising machine for wood work consists essentially of an ordinary auger, which bores the holes, and a chisel for cutting the corners so as to produce the square or rectangular mortise that is usually employed in wood work. The chisel is reciprocated and its driving spindle is provided with means whereby the chisel may be reversed so as to cut on either the sides or the ends of the mortise. The chisel is fed gradually to its cut. [Illustration: Fig. 3225.] Fig. 3225 represents a mortising machine for the hubs of wheels. The auger spindle is here fed vertically by a hand lever, the depth bored being regulated by a rod against which the hand lever comes when the hole is bored to the required depth. Fig. 3226 represents a mortising machine in which the mortising tool consists of a hollow square chisel containing an auger, and having at its sides openings through which the cuttings escape. The chisel is rectangular in cross section, but its cutting edges are highest at the corners, as may be clearly seen in the figure. The work is firmly clamped to the work table and simultaneously to the fence, the upper hand wheel being operated to bring the work-holding clamp down to the work, and the lower one to clamp it so as to press it to both the table and the fence at the same time. The chisel bar is mounted horizontally in a slide way on a substantial bed that is mounted on a vertical slideway, which enables the chisel bar to be set for height from the work table. It has a horizontal traverse motion or feed, the amount of this motion being governed by the horizontal rod with its nuts and check nuts as shown. The auger runs continuously, and works slightly in advance of the cutting edge of the chisel, which is passive except when making the mortise. The chisel bar and auger have a slow, reciprocating motion, and will complete a hole the size of the chisel used. An inch chisel will cut an inch-square hole, consequently a mortise 1" × 4" would only require four strokes forward to complete it. It has a capacity to work mortises from 3/4" to 3" square, and 5" in depth, and any length desired. The boring spindle is driven by an idler pulley, direct from the countershaft. The bed upon which the timber is placed to be mortised is gibbed to a sliding frame, which allows it to be set to any position, with the chisel straight or at an angle. It is adjustable to and from the chisel bar, to suit the size of material, the under side of which always remains at one height. Adjustments are provided for moving the carriage forward, for regulating the depth of the mortise, the position of the chisel from the face of the material, and the adjustment of the chisel bar, controlling the mortises to be made in the timber. Two treadles are used upon the side of the machine; the pressure upon one carrying the chisel bar attachment forward, completing the mortise, while the other will instantly force it back when it is desired to withdraw it from the wood, without allowing it to cut its full depth. Provision is made by stops for regulating the length of the stroke as well as the depth of the mortise. TENONING MACHINES. In tenoning machines, the lengths of the pieces usually operated upon render it necessary that the work should lie horizontally upon the table, while the shortness of the tenon makes an automatic feed unnecessary. The revolving heads carrying the cutters in tenoning machines are so constructed that the cutting edges of the cutters are askew to the sides of the heads, but so set as to produce work parallel to the axis of the cutter shaft. This causes the cutting action to begin at one end of the cutter edge, and pass along it to the other, which enables a steady hand feed, and reduces the amount of power required to feed the work. Fig. 3227 represents a cutter head for a tenoning machine, _a_, _a_ and _b_, _b_ being the cutters and _c_, _c_, _d_, _d_ spurs which stand a little farther out than the cutter edges, so as to sever the fibre of the wood in advance of the cutter edges coming into action, and thus preserve a sharp shoulder to the tenon, and prevent the splitting out at the shoulder that would otherwise occur. To bring the outer edge of the shoulder in very close contact with the mortised timber, the cutters are for some work followed by what is termed a cope head, which is a head carrying two cutters bent forward as in Fig. 3228, to make them cut very keenly, as is necessary in cutting the end grain of wood. The cope head undercuts the shoulder, as shown at _a_, _a_, in Fig. 3229, which is a sectional view of a mortise and tenon. [Illustration: Fig. 3226.] [Illustration: Fig. 3227.] [Illustration: Fig. 3228.] [Illustration: Fig. 3229.] [Illustration: Fig. 3230.] Fig. 3230 represents a tenoning machine for heavy work, constructed by J. A. Fay & Co., adjusted for cutting a double tenon, the upper and lower heads revolving in a vertical plane, and the middle head in a horizontal plane. A is a vertical slideway for the heads C, D, carrying the shafts for the cutter heads _a_, _b_. At B is the hand wheel for adjusting D, and at E that for adjusting C. The pulley _d_ is for driving the cope heads, one of whose cutters is seen at _c_. The work carriage H is provided with rollers which run on the slide on K, and is supported by the arm I, which rises and falls to suit the cross motion of H. The fence G, for the work, is adjustable by means of the thumb nuts. [Illustration: Fig. 3231.] SAND-PAPERING MACHINES. Sand-papering machines are of comparatively recent introduction in wood working establishments, but are found very efficient in finishing surfaces that were formerly finished by hand labor. Fig. 3231 represents a sand-papering machine, by P. Pryibil, in which a spindle has three stepped cones on one end, and a parallel roller or cylinder at the other. The steps on the spindle are covered with a rubber sleeve, and the sand paper is cut to a template, and the edges brought together and joined by gluing a strip of tough paper under them. When this has become dry the paper is slightly dampened everywhere except at the joint, and is then slipped on the taper drums. In drying it shrinks and becomes tight and smooth upon the rubber covering with which the drums are provided. These are of different sizes to fit different curves in the work. Flat work is done upon the table, which is hinged and provided with an adjusting screw to regulate its height, and it can be raised to give access to the drum. When sand paper is applied in this way, every grain is brought into contact with the work, whereas at first only the larger grains cut when it is used on the faces of revolving discs, as in some machines of this class. Furthermore, when used on drums it is offered ample opportunity to clear itself of dust; it therefore does not become clogged, and, as a consequence, it lasts longer and does more and better work than when used on discs. [Illustration: Fig. 3232.] Fig. 3232 represents a similar machine, but having a spindle vertical also, so that one face of the work can be laid on the table, which acts as a guide to keep the work square, the table surface being at a right angle to the vertical spindle. The vertical cylinder or drum is split on one side, and provided with internal cones, so, that by screwing down the nut shown the drum can be expanded to tightly grip the sand paper, which is glued and put on as already described. Besides these rotary motions, these drums receive a slow vertical motion, the amount of which is variable at the operator's pleasure. This provides for using the full face of the drum on narrow work, while it prevents the formation of ridges or grooves in the work. For sand-papering true flat surfaces the flat table is provided, there being beneath it a parallel revolving drum, whose perimeter just protrudes through the upper surface of the table. The surface of the table thus serves as a guide to steady the work while the sand-papering is proceeding. By using sand paper in this manner, every grain of the sand is brought into contact with the work; furthermore, a small area of sand paper is brought into contact with the work, and the wood fibre can fly off and not lodge in the sand paper; while at the same time the angles of the grains of sand or glass are presented more acutely to the work, and therefore cut more freely and easily. Hence the sand paper lasts much longer, because a given pressure is less liable to detach the sand from the paper. The machine is constructed entirely of iron, and the drum is intended to revolve at about 800 revolutions per minute. [Illustration: Fig. 3233.] Fig. 3233 represents a sand-papering machine in which a long parallel cylinder is employed, the work resting on the surface of the table and being fed by hand. In using a machine of this class the work should be distributed as evenly as possible along all parts of cylinder, or one end of the cylinder may become worn out while the other is yet sharp; this would incapacitate the machine for wide work unless a new covering of sand paper were applied. Fig. 3234 represents a sand-papering machine constructed by J. A. Fay & Co., for finishing doors and similar work. The frame constitutes a universal joint enabling the sand paper disc to be moved anywhere about the door by hand. An exhaust fan on the top of the main column removes the dust from the work surface. The head carrying the disc is moved vertically in a slideway to suit different thicknesses of work. Fig. 3235 represents a self-feeding sand-papering machine constructed by J. A. Fay & Co. It is made in three sizes, to work material either 24", 30", or 36" wide by 4" thick and under; it has a powerful and continuous feed, and gives to the lumber a perfect surface by once passing it through the machine. The feeding mechanism consists of six rollers, in three pairs, driven by a strong train of gearing. The upper feeding rollers, with the pressure rollers over the drum are lifted together in a perfect plane by the movement of four raising screws, operated by a chain and hand wheel. The lower feeding rollers always remain in perfect line with the drums. It is supplied with two polishing cylinders, placed in the body of the machine, on which the upper frame rests, both having a vibratory lateral motion for removing lines made by irregularities in the sand paper. The finishing cylinder is placed so that the discharging rollers carry the lumber from it, thus running through and finishing one board, if desired, without another following, and these rollers are arranged for a vertical adjustment to suit the dressed reduction on the material to be worked. The roughing cylinder carries a coarse grade of sand paper, and the finishing one a finer grade. They may be driven in opposite or in the same direction, as may be necessary. The lower frame is hinged at each end to the upper frame, so that by removing a pin, either cylinder can be reached by raising the frame with the screw and worm gear, operated by a hand wheel at the end of the machine. A brush attachment (not shown in the cut) is now placed at the end of the machine just beyond the finishing cylinder, which is a most complete device for brushing the material clean after it leaves the sand-papering cylinders. Fig. 3236 represents a double wheel sanding machine by J. A. Fay & Co. This machine is intended for accurately finishing the tread of the wheel ready for the tire, and is one of the most useful and labor-saving machines that can be placed in a wheel shop. The frame is built entirely of iron, and has a heavy steel arbor running in long bearings, with tight and loose pulleys in the centre. On each end of the arbor is a large sand paper disc for polishing the tread of the rim. The wheel to be finished is laid on a rotating carrying frame, having two upright drivers. These are attached to a jointed swinging frame, with flexible connections, adjustable to suit wheels of varying diameters. The first section of the jointed frame is driven by a shaft and bevel gears, and swings upon it. The second one has the wheel-carrying frame, and swings upon the extreme end of the first one, and is driven from it by a chain connection. [Illustration: _VOL. II._ SANDING MACHINES. _Plate XXVII._ Fig. 3235. Fig. 3236.] A roller wheel is secured at the bottom of the leg, affording a floor support; also a chain to regulate the proper distance of the wheel from the discs. A wrought iron supporting frame is attached upon each side of the sand paper discs, adjustable for different sizes. [Illustration: Fig. 3234.] The wheel when placed in the machine is carried by the gearing against the sand paper discs, which finishes the tread in the most accurate and perfect manner. Machines are made both single and double. The latter are the most desirable, as the operator has only to place a wheel in position on one side, when it feeds and takes care of itself. By the time this is done, the wheel on the opposite side will be finished and ready to be removed, when a fresh one is put in, and the operation continued, the only care required being to put in and remove them. Its capacity is 150 set of wheels per day, and it will do the work better than can be done by hand. CHAPTER XXXVI.--BOILERS FOR STATIONARY STEAM ENGINES. The boiler for a steam engine requires the most careful usage and inspection, in the first case because a good boiler may be destroyed very rapidly by careless usage, and in the second case because the durability of a boiler depends to a great extent upon matters that are beyond ordinary control, and that in many cases do not make themselves known except in their results, which can only be discovered by careful and intelligent inspection. All that the working engineer is called upon to do is, to use the boiler properly, keep it clean, and examine it at such intervals as the nature of the conditions under which it is used may render necessary. The periods at which a boiler should be cleaned and inspected depend upon the quality of the water, whether the feed water is purified or not, and to a certain extent upon the design of the boiler; hence these periods are variable under different circumstances. The horse power of a boiler is estimated in various ways, and there is no uniform practice in this respect. Some makers estimate a boiler to have a horse power for every fifteen square feet of heating surface it possesses, while others allow but 12 square feet. The heating surface of a boiler of any kind is the surface that is exposed to the action of the fire on one side, and has water on the other; hence the surface of the steam space is not reckoned as heating surface, even though it may be exposed to the action of the heat. The effectiveness of the heating surface of a boiler obviously, however, depends upon the efficiency of the fire, and this depends upon the amount of draught, hence the estimation of horse power from the amount of its heating surface, while affording to a certain extent a standard of measurement or comparison while the boiler is not in use, has no definite value when the boiler is erected and at work. Thus whatever amount of steam a boiler may produce under a poor or moderate draught, it will obviously produce more under an increased draught; hence the efficiency of the same boiler depends to a certain extent upon the draught, or in other words upon the quantity of fuel that can be consumed upon its fire bars. The amount of water required in steam boilers varies from 16 lbs. to 40 lbs., per horse power per hour, and it has been proposed to compute the horse power of boilers from the water evaporation, taking as a standard 30 lbs. of feed water at a temperature of 70 degrees, evaporated into steam at a temperature of 212 degrees, at which temperature the steam is assumed to equal the pressure of the atmosphere. [49]"The strength of the shell of a cylindrical boiler to resist a pressure within it, is inversely proportional to its diameter and directly, to the thickness of the plate of which it is formed. [49] From "_Steam Boilers_." "For instance, take three cylindrical boilers each made of 1/2 inch plate, the first one 2 feet 6 inches in diameter; the second twice that, or 5 feet in diameter; and the third twice that again, or 10 feet in diameter; and if the 2 foot 6 inch boiler is fit for a safe working pressure of 180 lbs. per square inch, then the 5 foot boiler will be fit for exactly one-half that amount, or 90 lbs. per square inch; and the ten foot boiler will be fit for half the working pressure of the five foot boiler, hence we have: -----------------+------------+-------------------------- Diameter of | Thickness |Relative working pressure. boiler shell. | of plate. | -----------------+------------+-------------------------- 2 feet 6 inches.| 1/2 inch. | 180 lbs. per square inch. 5 " | " " | 90 " " " " 10 " | " " | 45 " " " " -----------------+------------+-------------------------- "The reverse applies to the thickness of the plate. For instance, if we take two cylindrical boiler shells, each 5 feet in diameter, the first one made of plate 1/2 inch thick, and the second twice that, or 1 inch thick, and if the first is equal to a safe working pressure of 90 lbs. per square inch, then the second is equal to a safe working pressure of twice as much, or 180 lbs. per square inch, providing, of course, that the riveted seams are of equal strength in each case, and that both boilers are allowed the same margin for safety; hence we have: ----------------+------------+-------------------------- Diameter of | Thickness | Safe working pressure. boiler. | of shell. | ----------------+------------+-------------------------- 5 feet. | 1/2 inch. | 90 lbs. per square inch. 5 " | 1 " | 180 " " " " ----------------+------------+-------------------------- [Illustration: Fig. 3237.] [Illustration: Fig. 3238.] "These principles (namely, that the strength of a boiler is, all other things or elements being equal, inversely proportional to its diameter, and directly proportional to its thickness) afford us a groundwork upon which we may lay down rules for determining by calculation the strength of the solid part[50] of any boiler shell, and the bases of these calculations are as follows: [50] In the case of the riveted joints or seams other considerations come in, as will be shown hereafter. "If the shell plate of a cylindrical boiler is 1/2 inch thick, there is one inch section of metal to be broken before the boiler can be divided into two pieces, that is to say there is 1/2 inch on each side of the shell, as shown in Fig. 3237, and the two together will make 1 inch. If we take a ring an inch broad, as, say, at A in Fig. 3238, we shall obviously have a section of 1 square inch of metal to break before the ring can be broken into two pieces. "The next consideration is, what is the average strength of a plate of boiler iron? Now suppose we have a strip of boiler iron 2 inches wide and 1/2 inch thick, or, what is the same thing, a bar of boiler iron 1 inch square, and that we lay it horizontally and pull its ends apart until it breaks, how many lbs. will it bear before breaking? Now for our present purpose we may assume this to be 47,040 lbs., and if this number of lbs. be divided by the diameter of the boiler in inches, it will give the bursting pressure in lbs. for any square inch in the ring, or any other square inch in the cylindrical shell of the boiler. "The reason for dividing by the diameter of the boiler is as follows: [Illustration: Fig. 3239.] "Of course the steam pressure presses equally on all parts of the interior surface of the shell, and may be taken as radiating from the centre of the boiler, as in Fig. 3239, which represents an end view of a strip an inch wide, of one half of a boiler. Now leaving the riveted seam out of the question, and supposing the shell to be truly cylindrical, and the metal to be of equal quality throughout, it will take just as much pressure to burst the shell apart in one direction as it will in another, hence we may suppose that the boiler is to be burst in the direction of arrow _a_, and it is the section of metal at _b_ _b_ that is resisting rupture in that direction. "Now suppose we divide the surface against which the steam presses into six divisions, by lines radiating from the centre C, and to find the amount of area acting on each division to burst the shell in the direction of arrow _a_, we drop perpendicular lines, as line _e_, from the lines of division to the line _b_ _b_, and the length of the line divided off (by the perpendicular) on the diameter represents the effectiveness of the area of that division to burst the boiler in the direction of arrow _a_; thus for that part of the boiler surface situate in the first division, or from _b_ to line _e_, the area acting to burst the boiler in the direction of _a_ is represented by the length of the line _k_, while the general direction of the pressure on this part of the shell is represented by arrow _m_. "Similarly, for that part of the shell situate between vertical line _e_ and vertical line _f_, the general direction of the steam pressure is denoted by the arrow _l_, while the proportion of this part that is acting to sever the boiler in the direction of _a_ is represented by the distance _n_, or from the line _e_ to line _f_ measured on the line _b_ _b_. [Illustration: Fig. 3240.] "By carrying out this process we shall perceive that, although the pressure acts upon the whole circumference, yet its effectiveness in bursting the boiler in any one direction is equal to the boiler diameter. Thus in Fig. 3240, the pressure acting in the direction of the arrows _a_ (and to burst the boiler apart at _b_ _b_) is represented by the diametral line _b_ _b_, while the pressure actually exerted upon the whole boiler shell is represented by the circumference of the boiler. "To proceed, then, it will now be clear that the ultimate strength of the boiler material, multiplied by twice the thickness of the boiler shell plate in inches or decimal parts of an inch, and this sum divided by the internal diameter of the boiler, in inches, gives the pressure (in lbs. per square inch) at which the boiler shell will burst." We have here only considered the strength of the solid plate of the shell, and may now consider the strength of the riveted joints, because, as the boiler cannot be any stronger as a whole than its weakest part is, and as the riveted joints are the weakest parts of a cylindrical boiler,[51] therefore the strength of the riveted joint determines the strength of the boiler. [51] It may be here noted that the riveted joint of a flat plate is stronger than the flat surface of the plate, because at the joint the plate is doubled, or one plate overlaps the other. [52]"The strains to which a riveted joint is subjected are as follows: That acting to shear the rivet across its diameter is called the _shearing_ strain. But the same strain acts to tear the plate apart; hence, when spoken of with reference to the action on the plate, it is called the _tearing_ strain. [52] From "_Steam Boilers_." "The same strain also acts to crush and rupture the plate between the rivet hole and the edge of the plate, and in this connection it is called the _crushing_ strain. [Illustration: Fig. 3241.] "Thus, Fig. 3241 represents a single riveted lap joint, in which the joint at rivets A, B, and C is intact, the metal outside of D has crushed, the rivets E, F have sheared, and the plate has torn at H, leaving a piece J on the rivets K L. "It is obvious that, since it is the same strain that has caused these different kinds of rupture, the joint has, at each location, simply given way where it was the weakest. [Illustration: Fig. 3242.] "If a riveted joint was to give way by tearing only, the indication would be that the proportion of strength was greatest in the rivets, which might occur from the plate being of inferior metal to the rivets, or from the rivets being too closely spaced. If the rivets were to shear and the plate remain intact, it would indicate insufficient strength in the rivets, which might occur from faulty material in the rivets, from smallness of rivet diameter, or from the rivets being too widely spaced. "The object then, in designing a riveted joint is to have its resistance to tearing and shearing proportionately equal, whatever form of joint be employed." The English Board of Trade recommends that the rivet section should always be in excess of the plate section, whereas, in ordinary American practice, for stationary engine boilers, the plate and rivet percentages are made equal. The forms of riveted joints employed in boiler work are as follows: [Illustration: Fig. 3243.] [Illustration: Fig. 3244.] Fig. 3242 represents a single riveted lap joint. Fig. 3243 represents a double riveted lap joint, chain riveted; and Fig. 3244, a double riveted lap joint, with the rivets arranged zigzag. [Illustration: Fig. 3245.] [Illustration: Fig. 3246.] Fig. 3245 represents a single and Fig. 3246 a double riveted butt joint, so called because the ends of the boiler plate abut together. The plates on each side of joint are called butt straps. The advantages of the butt joint are, first, that the boiler shell is kept more truly cylindrical, and the joint is not liable to bend as it does in the lap joints, in the attempt of the boiler (when under pressure) to assume the form of a true circle, and second that the rivets are placed in double shear. That is to say, if in a lap joint the rivet was to shear between the plates, the joint would come apart, whereas, in a butt joint, the rivet must shear on each side of the plate, and therefore in two places. [Illustration: Fig. 3247.] Fig. 3247 represents a form of joint much used in locomotive practice in the United States. It is a lap joint, with a covering plate on the inside of the joint; rivets E and F are in single and rivets D in double shear. [53]"When we have to deal with comparatively thin boiler plates, there is no difficulty in obtaining a sufficiently high percentage of strength in the joints, by using the ordinary double riveted joint, but when we have to deal with thick plates, as in the case of large marine boilers, as 1 inch or upwards, a more costly form of joint must be employed, in order to obtain the required percentage of strength at the joint; hence the ordinary double riveted joint is replaced by various other forms as follows: [53] From "_Steam Boilers_." [Illustration: Fig. 3248.] "First, a triple zigzag riveted lap joint, such as shown in Fig. 3248, or a chain riveted joint as in Fig. 3249, in both of which the third row of rivets enables the rivet pitch to be increased, thus increasing the plate percentage, while the third row of rivets also increases the rivet percentage. "Second, by employing butt joints with butt straps, either double or treble riveted. [Illustration: Fig. 3249.] [Illustration: Fig. 3250.] [Illustration: Fig. 3251.] [Illustration: Fig. 3252.] "A double riveted butt joint with double straps is shown in Fig. 3250, and a treble with double straps in Figs. 3251 and 3252. "Third. By various arrangements of the rivets in conjunction with butt joints and double straps, with which it is not necessary, at this point, to deal. "One of the great advantages obtained by the use of the double strap is that of bringing the rivet into double shear (or in other words, the rivet must shear on each side of the plate, or in two places, instead of between the plates only, before the joint can give way by shearing), and thus obtaining an increased calculated strength of 1-3/4 times the ordinary or single shear, the rule being to find the rivet strength in the ordinary way (as before explained), and then multiply the result by 1.75. "The Board of Trade rules for spacing the rivets of these joints are as follows: "Dimension E is the distance from the edge of the plate to the centre of the rivet hole. Dimension V is the distance between the rows of rivets, dimension _p_ is the pitch of the rivets, which is always measured from centre to centre of the rivets, and dimension _pd_ is the diagonal pitch of the rivets. "The rule for finding dimension E, whether the plates and rivets are either of steel or iron, is as follows: "Multiply the diameter of the rivet by 3 and divide by 2, the formula being as follows: 3 × _d_ ------- = E. 2 "To find the distance V between the rows of rivets in chain riveted joints. This distance must not be less than twice the rivet diameter, and a more desirable rule is four times the rivet diameter plus 1 divided by 2, thus: 4_d_ + 1 -------- = V. 2 "To find the distance between the rows of zigzag riveted joints: _____________________________ \/(11_p_ + 4_d_) × (_p_ + 4_d_) ------------------------------- = V, 10 that is, multiply 11 times the pitch plus 4 times the rivet diameter, by the pitch plus 4 times the rivet diameter, then extract the square root and divide by 10. "To find diagonal pitch _pd_, multiply the pitch _p_ by 6, then add 4 and divide by 10, thus: 6_p_ + 4 -------- = _pd_." 10 [Illustration: Fig. 3253.] Fig. 3253 represents a form of high percentage joint, used upon marine boilers of 10 to 14 feet diameter, and carrying from 100 to 190 lbs. pressure of steam. The rivets are what are termed unevenly pitched, or, that is to say, on each side of the joint, there are three rows of rivets, of which the inner and outer rows are wider pitched than the middle row. [54]"The advantage gained by this spacing is that the shear of the outer row of rivets is added to the plate section at the narrow pitch, that is to say, if the plate section broke through the line of rivet holes at the narrow pitch, it has yet to shear the outer row of rivets before the plate can separate." [54] From "_Steam Boilers_." [Illustration: Fig. 3254.] Fig. 3254 represents a second example of joint with rivets unevenly pitched, this form finding much favor in recent practice. The four inner rows of rivets are spaced at narrow pitch and the two outer rows are wide pitched. [55]"The strength percentage of this joint is calculated from three points of view, as follows: [55] From "_Steam Boilers_." "First. The plate section at the wide pitched rivets. "Second. The rivet section in one pitch. "Third. The plate section at the narrow pitch plus half the double shear of the outer or wide pitched rivet." The steam pressures generally employed in the boilers of stationary engines range from about 60 to 100 lbs. per square inch, and as a result of these comparatively low pressures less perfect forms of construction are employed than would be permissible if higher pressures were used. The strength of the shell plate of boilers of small diameter is always largely in excess of the requirements, and as a result the strength of the joints may bear a very low percentage to that of the solid plate, and yet give a sufficient factor of safety for the working pressure. Take, for example, a boiler shell of 36 inches internal diameter with a shell plate 1/4 inch thick, and allowing the strength of the material to be 48,000 lbs. per inch of section, and with a factor of safety of 4, the working pressure will be 166 lbs. per square inch, thus: Strength Plate thickness of the material. × 2. 48000 × (.25 × 2) --------------------------------- = 666-2/3 lbs. = bursting pressure. 36 Diameter of boiler. By dividing this 666 by the factor of safety 4 we get 166-2/3 lbs. as the working pressure of the shell plate independent of the riveted joint. Usually, however, such a boiler would not be used for a pressure above about 60 lbs. per inch, and this leaves a wide margin for the reduction of strength caused by the riveted joints. Suppose, for example, that a single riveted lap joint is used, and the strength of this joint is but 50 per cent. of that of the solid plate, and we have as follows: Strength of % strength Twice material. of riveted the plate joint. thickness. 48000 × .50 × (.25 × 2) ---------------------------------- = 83-1/3 lbs. = W.P. 36 × 4 Internal diam. Factor of of boiler. safety. Here then we find that the working pressure of the solid plate is double that of the riveted joint, and that the working pressure of the boiler is 83 lbs. per square inch, notwithstanding that the strength of the riveted joints is but 50 per cent. of that of the solid plate. Such a boiler would not, however, be used for a pressure of over 60 lbs. per square inch. If the above-named boiler was double riveted so as to bring the percentage of joint strength up to say 70 per cent, of that of the solid plate, its working pressure would be 116 lbs. per square inch, thus: Strength of % strength Twice material of riveted the plate joint. thickness. 48000 × .70 × (.25 × 2) ---------------------------------- = 116-2/3 lbs. = W.P. 36 × 4 Internal diam. Factor of of boiler. safety. But in practice such a boiler would not be used for pressures above about 75 lbs. per square inch, hence the shell plate thickness is still largely in excess of the requirements, and it may be remarked that plates less than 1/4 inch thick are not used on account of the difficulty of caulking them and keeping them steam tight. On account therefore of the excessive strength of the shell plates in boilers of small diameter, butt straps are rarely used in stationary boilers, while punching the rivet holes and other inferior modes of construction are employed. We may now consider the circumferential seams of the boilers for stationary engines, such boilers sometimes being of great length in proportion to the diameter. In proportion as the length of a boiler (in proportion to its diameter) is increased, the construction of the circumferential or transverse seams, as they are sometimes called, becomes of more importance. The strength of the circumferential seams is so much greater than that of the longitudinal seams that it is often taken for granted that they are sufficiently strong if made with a lap joint and single riveted, but that such is not always the case will be shown presently. [Illustration: Fig. 3255.] In Fig. 3255 is represented a boiler composed of three strakes (_i. e._, three rings or sections), and it is clear that as the thickness of the shell is doubled at the circumferential seams where the ends of the middle strake pass within the end strakes, therefore the strength of the lapped joint of the shell to resist rupture in a transverse direction, as denoted by the arrows A, B, is actually increased by reason of the lap of the riveted joint. But suppose this boiler to be supported at the ends only, and the weight of the shell and of the water within it will be in a direction to cause the middle of the boiler to sag down, and therefore places a shearing strain on the rivets of the circumferential seams. Moreover, the temperature of the outside of the boiler cannot be made or maintained uniform, because the fire passing beneath the bottom of the boiler first will keep it hotter, causing it to expand more, and this expansion acts to shear the rivets of the circumferential seams. In proportion as the heat of the fire varies in intensity, the amount of the expansion will vary, and the consequence is that the circumferential seams may get leaky or the joint may work, especially in boilers that are long in proportion to their diameters. It is clear, therefore, that for the very best construction at least a double riveted circumferential joint should be employed. Leaving these considerations out of the question, however, we may find the amount of stress on the circumferential seams by multiplying the area of the end of the boiler by the working pressure, and dividing by the cross-sectional area of all the rivets in one circumferential seam. Suppose, for example, that the diameter of the boiler is 36 inches, the working pressure 60 lbs. per square inch, and that there are in each circumferential seam 50 rivets, each 3/4 inch in diameter, and we proceed as follows: The area of a circle 36 inches in diameter = 1017.87 square inches. The area of a rivet 3/4 inches in diameter = .4417 square inch. Then Area of Working boiler end. pressure. 1017.87 × 60 ------------------ = 2765 lbs. per cross-sectional square inch of rivet. 50 × .4417 Number Area of of rivets. each rivet. By multiplying the area of the boiler end by the working pressure, we get the total steam pressure acting to shear the rivets, and by multiplying the number of rivets by the area of one rivet, we get the total area resisting the steam pressure, and then by dividing the one quantity into the other, we get the shearing stress per square inch of rivet section. In the case of longitudinal seams, we have as follows, the pitch being say 2-1/8 and the rivets 3/4. Diameter Steam Pitch. of boiler pressure. in inches. 36 × 60 × 2.125 ------------------------------ = 5196 lbs. per square inch of rivet 2 × .4417 area. Rivets in Area of one pitch. rivet. It is seen, therefore, that the stress placed by the steam pressure on the transverse seam is about one-half of that it places on the longitudinal seam. But, as before remarked, the transverse seam is subject to racking strains, from which the longitudinal seams are exempt; thus, for example, the expansion of the boiler diameter, whether uniform or not, does not strain the longitudinal seam, whereas it may severely strain the transverse seam. The English Board of Trade rules, in assigning values to the various constructions and qualities of workmanship, assign a certain value, in the form of an addition to the factor of safety, which takes into account the difference in the stress upon the transverse and longitudinal seams, the quantities in each case having been determined both from experiment and from experience. A comparison of the different values may be made as follows: The rules take a boiler shell made of the best material, with all the rivet holes drilled after the strakes are rolled into shape and put together, with all the seams (both longitudinal and transverse) fitted with double butt straps each at least five-eighths of the thickness of the shell plates they cover, and with all the seams at least double riveted, with rivets having an allowance of not more than 75 per cent. over the single shear, and provided that the boilers have been open to the inspection of their surveyors during the whole period of construction, and say that such a boiler shell shall be allowed a factor of safety (divisor of seam strength) of 5. But for every departure from this, which they deem the best mode of construction, a penalty in the shape of an addition to the factor of safety is made. These additions to the factors of safety with reference to the longitudinal as compared to the transverse seams, are given in the following table: -------------------------------------+----------------+--------------- |Addition to the |Addition to the |factor 5 if the |factor 5 if the Nature of the deviation in the |deviation is in |deviation is in construction or workmanship. |the longitudinal|the transverse | seam. | seam. -------------------------------------+----------------+--------------- The holes not fair and good | .75 | .2 Holes drilled out of place after | | bending | .15 | .1 Holes drilled before bending | .3 | .15 Holes punched after bending | .3 | .15 Holes punched before bending | .5 | .2 Joints lapped and double riveted | | instead of having double butt straps | .2 | .1 Joints double riveted but have single| | butt straps | .3 | .1 Joints single riveted and have a | | single butt strap | 1.0 | .2 Joints lapped and single riveted | 1.0 | .2 -------------------------------------+----------------+--------------- [Illustration: Fig. 3256.] An addition of .25 is also made to the factor of safety, when the strakes are not entirely under or over. In Fig. 3256 for example, strake _b_ is within or under strake _a_ at one end and strake _c_ at the other end, hence _b_ is entirely under; strake _c_ is over _b_ and _d_, and therefore entirely over; while strake _d_ is under _c_, and over _e_, and therefore not entirely under nor entirely over. When the rivet holes are punched they do not match properly, and unless the holes are punched somewhat smaller than the required size and reamed out afterwards, some rivets receive more stress than others, and may consequently shear in detail. It is customary, however, to punch the holes for ordinary stationary boilers, and it is with seams having punched holes therefore that we have at present to deal. In the United States the rivet diameter and plate percentages are, in the boilers of stationary engines, usually made equal, and the reasons advanced both for and against this are as follows: First, in favor of a greater plate percentage than rivet section, it is advanced that the plate gets thinner by wear, whereas the rivet does not, hence the wear reduces the plate section; that the plate is weakened by the punching process, and requires a greater percentage to make up its strength as compared to the rivet; that the rivets are usually of better material than the plates. In favor of a greater rivet section than plate section, it is advanced that the shearing strength of iron is but about four-fifths of the tensile strength, and that with equal plate and rivet sections the rivet is therefore the weakest; that with punched holes the rivets may be sheared in detail, and that the rivets may be sheared gradually by the working of the joint from varying expansion and contraction. From these premises the assumption is drawn that the weakening of the plate from being punched and from corrosion about offsets the excess of the tensile over the shearing strength, and that it is best therefore to employ such a pitch that the area of the rivet and of the metal left between the rivet holes shall be equal. In order to do this the diameter of the rivet must be determined, and the following are the proportions given by the various authorities named: TABLE OF THE DIAMETERS OF RIVETS FOR VARIOUS THICKNESSES OF PLATES WITH SINGLE RIVETED LAP JOINT. ---------+------------------------------------------------------- | DIAMETER OF RIVETS. +-------+---------+----------+----------+-------+------- Thickness|Lloyds'|Liverpool| English |Fairbairn.| Unwin.|Wilson. of Plate.|Rules. | Rules. |Dockyards.| | | ---------+-------+---------+----------+----------+-------+------- in. | in. | in. | in. | in. | in. | in. 5/16 | 5/8 | 5/8 | 1/2 | 5/8 | 11/16 | 5/8 3/8 | 5/8 | 5/8 | 5/8 | 3/4 | 3/4 | 11/16 7/16 | 5/8 | 3/4 | 3/4 | 21/32 | 13/16 | 3/4 1/2 | 3/4 | 13/16 | 3/4 | 3/4 | 7/8 | 3/4 ---------+-------+---------+----------+----------+-------+------- 9/16 | 3/4 | 13/16 | 7/8 | 27/32 | 7/8 | 7/8 5/8 | 3/4 | 7/8 | 7/8 | 15/16 | 15/16 | 7/8 11/16 | 7/8 | 7/8 | 7/8 | 1-1/32 |1 | 7/8 3/4 | 7/8 | 15/16 | 1 | 1-1/8 |1-1/16 | 1 ---------+-------+---------+----------+----------+-------+------- 13/16 | 7/8 | 1 | 1 | 1-7/32 |1-3/32 | 1 7/8 |1 | 1-1/8 | 1-1/8 | ... |1-1/8 | 1 15/16 |1 | 1-3/16 | 1-1/8 | ... |1-3/16 | 1-1/8 1 |1 | 1-1/4 | 1-1/8 | ... |1-1/4 | 1-1/8 ---------+-------+---------+----------+----------+-------+------- From the above it is seen that with thin plates the diameter of rivet employed is about twice the thickness of the plate, whereas as the thickness of plate increases the proportion of rivet diameter decreases, and the reasons for this are, first, that with rivets twice the thickness of thick plates and pitched so as to equalize the rivet and plate sections the pitch would be too great to permit of the seams being caulked steam tight. The diameter of the rivet having been determined, the rivet area and area of plate left between the rivet holes may be made equal by determining the pitch by the following rule: _Rule._--To the area of the rivet divided by the plate thickness add the diameter of the rivet, and the sum so obtained is the pitch. The correctness of this rule may be shown as follows: Suppose the rivet diameter to be 7/8 inch = decimal equivalent .875, and its area will be .6013 square inch. Suppose the thickness of the plate to be 9/16 = decimal equivalent .5625, then by the rule: Rivet area. Plate thickness = .5625 ) .6013 ( 1.0689 5625 ---- 38800 33750 ----- 50500 45000 ----- 55000 50625 To this 1.0689 we are to add the rivet diameter, thus: 1.0689 .8750 = rivet diameter. ------ 1.9439 = pitch of the rivets. We have thus found the required pitch to be 1.9439 inches, and as the joint is single riveted there are two half rivets or one whole one to one pitch, and if we subtract the diameter of the rivet from the pitch we shall get the width of the metal or plate left between the rivets, thus: 1.9439 = pitch of rivets. .8750 = diameter of rivet. ------ 1.0689 = distance in inches between the rivets. If now we multiply this distance between the rivets by the thickness of the plate, we shall get the area of the plate that is left between the rivet holes, thus: 1.0689 = width of plate between rivets. .5625 = thickness of plate. ------ 53445 21378 64134 53445 --------- Area of plate = .60125625 between rivets Here then we find the area of plate left between the rivet holes to be 6.01 square inches, and as the area of the rivet is 6.01 square inches, the two are shown to be equal. We may now place the various rivet diameters and the pitches that will make the rivet area and plate area in a single riveted joint equal in a table as follows: TABLE OF RIVET DIAMETERS AND PITCHES FOR SINGLE RIVETED LAP JOINTS. -------------------+------------------+-------- Thickness of Plate.|Diameter of Rivet.| Pitch. -------------------+------------------+-------- 1/4 | 1/2 | 1-1/4 5/16 | 5/8 | 1-5/8 3/8 | 11/16 | 1-11/16 7/16 | 3/4 | 1-3/4 1/2 | 3/4 | 1-5/8 9/16 | 7/8 | 2 5/8 | 7/8 | 1-7/8 11/16 | 7/8 | 1-3/4 3/4 | 1 | .. 13/16 | 1 | 2 7/8 | 1 | 1-1/8 15/16 | 1-1/8 | 2-1/8 1 | 1-1/8 | 2-1/8 1-1/16 | 1-1/8 | 2-1/8 1-1/8 | 1-3/16 | 2-1/4 1-1/4 | 1-3/16 | 2-1/8 -------------------+------------------+-------- The rivets in double riveted lap joints, and in butt strap joints having a single cover, are spaced alike, because in both cases there are two rivets in one pitch, and the rivets are in single shear. As there are two rivets in one pitch (instead of only one as in a single riveted joint), therefore the percentage of rivet section is doubled, and the plate section must therefore be doubled if the plate and rivet sections are to be made equal, and the rule for finding the required pitch is as follows: _Rule._--To the amount of rivet area in one pitch, divided by the thickness of the plate, add the diameter of the rivet. _Example._--Let the plate thickness be as in the last example 9/16, decimal equivalent = .5625, and the rivet diameter be 7/8 inch = decimal equivalent .875, the area of one rivet being .6013 square inch, and the pitch is calculated as follows: .6013 = area of one rivet. 2 = the rivets in one pitch. ------ Plate thickness = .5625 ) 1.2026 ( 2.1377 1.1250 ------ 7760 2.137 5625 .875 = rivet diameter. ---- ----- 21350 3.012 = pitch. 16875 ----- 43750 39375 ----- 43750 39375 ----- 4375 We find, therefore, that the pitch is 3.012, or 3 inches (which is near enough for practical purposes), and we may now make it clear that this is correct. [Illustration: Fig. 3257.] In Fig. 3257 the joint is shown drawn one-half full size, and the length a of plate left between the rivet holes measures (as nearly as it is necessary to measure it) 2-5/32 inches, or 2.156, and if we multiply this by the thickness of the plate = .5625 inch, we get 1.2 square inches as the area of the plate left between the rivet holes. Now there are two rivets in a pitch (as one-half of B, one-half of C, and the whole of F), and as the area of each rivet is .6, therefore the area of the two will be 1.2, and the plate section and rivet section are shown to be equal. The area at _a_ is obviously the same as that at A, because the pitches of both rows of rivets are equal, this being an ordinary zigzag riveted joint. We may now consider the diagonal pitch of the rivets, using the rule below. The pitch × 6, + 4 times the rivet diameter ------------------------------------------- = the diagonal divided by 10 pitch _p__{D}. In this example the pitch has been found to be 3 inches, hence we have .875 = diameter of rivet. 4 = constant. ----- 3.500 3 = pitch of the rivets. 6 = constant. -- 18 3.5 = rivet diameter multiplied by 4. ---- 10 ) 21.5 (2.15 = the diagonal pitch. 20 -- 15 10 -- 50 The diagonal pitch, that is, the distance _p__{D}, Fig. 3257, is therefore found to be 2.15, or 2-1/8 inch full. The amount of metal left between the rivets, measured on the diagonal pitch, is twice the dimension H multiplied by the thickness of the plate, and as this (with the diagonal pitch determined as above) always exceeds the pitch A or _a_, therefore if the plate fails, it will be along the line _a_, and not through the diagonal pitch. We may now consider the total amount that the plates overlap in a double riveted lap joint zigzag riveted, this amount being twice the distance E, added to the distance V between the rows of rivets. The distance E, Fig. 3257, is usually made one and a half times the diameter of the rivet, this being found to give sufficient strength to prevent the edge of the plate from tearing out and to prevent the rivet from shearing the plate out to the edge, rupture not being found to occur in either of these directions. The rule for finding the distance V, when the diagonal pitch has been determined by the rules already explained, is as follows: _Rule._--To the pitch multiplied by 11, add 4 times the rivet diameter, then multiply by the pitch, plus 4 times the rivet diameter. Then extract the square root and divide by 10. Placed in formula, the rule appears as follows, _d_ representing the rivet diameter, and _p_ the pitch. __________________________ \/(11_p_ + 4_d_)(_p_ + 4_d_) ---------------------------- = distance V between the rows of rivets. 10 As this rule involves the extraction of the square root of the sum of quantities above the line, and as in determining the diagonal pitch, we have already determined the distance V, it is unnecessary to our purpose to carry out this latter calculation, as it is easier to find the diagonal pitch, and then, after drawing the joint, the distance between the rows of rivets can be measured if it is required, as it might be in finding the length of plate required to roll into a strake for a boiler of a given diameter and having a double riveted lap joint. We may now consider chain riveted joints in comparison with zigzag riveted joints, which is especially necessary, because it has been assumed by some that the second row of rivets in a chain riveted joint added nothing to the strength of the joint. [Illustration: Fig. 3258.] Fig. 3258 represents a chain riveted joint, having the same thickness of plate, rivet diameter and pitch as the zigzag riveted joint in Fig. 3257, and it will be seen that the plate sections at a and at _a_ are the same in the two figures, and as there are four half rivets, which are equal to two rivets, in one pitch, therefore the strength of the two joints is equal. Each joint can be as efficiently caulked as the other, as the rivet spacing is the same and the edge of the plate is the same distance from the rivets in both cases. The pitch of the rivets is obtained by the same rule as for zigzag riveted joints, and all we have now to consider is the distance apart of the two rows of rivets or distance V in the Fig. 3258, and for this there are two rules, the first being that it shall not be less than twice the diameter of the rivet, which would leave a dimension at H in the figure equal to the diameter of the rivet. The second rule is that a better proportion than the above is to multiply the diameter of the rivet by 3. This makes the dimension at H equal to twice the rivet diameter. When the joints have double buttstraps, the rivets may be spaced as wide as the necessity for tight caulking will admit, because, on account of the rivets being in double shear, the rivet percentage exceeds the plate percentage. [Illustration: Fig. 3259.] The allowance for the rivets being in double shear is 75 per cent., or in other words, a rivet in double shear is allowed 1.75 times the area of the same size rivet in single shear. STATIONARY ENGINE BOILERS. The simplest form of horizontal boiler is the plain cylinder boiler, an example of which is given in Fig. 3259, and which is largely used in iron works and coal mines. Boilers of this class are easily cleaned, because the whole interior can be readily got at to clean. As the bottom of this boiler gets thinned from wear, the boiler is turned upside down, thus prolonging its life. [Illustration: Fig. 3260.] Fig. 3260 represents an internally fired flue boiler, known as the Cornish or Lancashire boiler. The furnace is at one end of the flues, the fire passing through them to the chimney. There is here obviously more heating surface than in the plain cylinder boiler, but somewhat less facility for cleaning. The Galloway boiler is of this class, but has vertical water tubes placed at intervals in the flues. These water tubes are wider at the top than at the bottom. They serve to break up the body of heat that passes through the flues, and increase the heating surface while extracting more of the heat and promoting the circulation of the water in the boiler. A water tube is one in which the water is inside and the fire outside, as distinguished from a fire tube, in which the fire passes through the tube and the water is outside. A water tube is stronger than a fire tube, because the former is subject to bursting pressure and the latter to collapsing pressure. Vertical boilers are internally fired, and in the ordinary forms have no return tubes or flues, examples of those used for small stationary engines being given as follows. [Illustration: Fig. 3261.] Fig. 3261 represents an ordinary form with vertical tubes. The upper ends of the tubes here pass through the steam space--a condition that under the moderate pressures and firing that this class of boiler is subjected to is of less importance than it is in boilers having higher chimneys and therefore a more rapid draught, and using higher pressures of steam. Furthermore, the small diameters and lengths or heights in which these boilers are made give them ample strength with shells and tubes of less thickness, while the condition of tube ends with steam on one side and fire on the other is permissible without the injurious effects that ensue under rapid combustion and high pressures. [Illustration: Fig. 3262.] The crown sheet of the fire boxes or furnaces of this class of boiler is very effective heating surface, first, because of the great depth (and therefore weight) of water resting upon it insuring constant contact between the water and the plate, while there is no danger of the crown sheet burning from shortness of water. A similar boiler, but with the upper ends of the tubes below the water level, is shown in Fig. 3262. From the small diameters of these boilers, the flat surfaces are not stayed except to the extent that the holding power of the tubes serves that end. [Illustration: Fig. 3263.] [Illustration: Fig. 3264.] A return flue vertical boiler is shown in Figs. 3263 and 3264. The whole of the surfaces having contact with the fire also have contact with the water, and the height of the crown sheet removes it from the intense heat of the fire. It is stayed to the top of the boiler. The fire box or combustion chamber being taper increases the effectiveness of its sides as heating surface, since the heat in its vertical passage impinges against it. The products of combustion pass from the top of the combustion chamber through short horizontal flues, which enter an annular space surrounding the lower section of the boiler, and from this space vertical flues pass to a corresponding space at the bottom of the boiler. The passage of the steam generated at the sides of the combustion chamber is facilitated by the taper of the chamber, which gives increased room for the steam as it gathers in ascending. Vertical boilers for high pressures, as from 60 to 120 lbs. per inch, are represented in the figures from 3265 to 3269. In boilers of this class, a majority contain water tubes, which, when properly arranged, promote rapid evaporation and circulation. A boiler with _Field_ tubes is shown in Fig. 3265. It consists of an outer shell and a cylindrical fire box, from the crown sheet of which a number of Field tubes are suspended in the fire box or combustion chamber. Fig. 3266 is a sectional view of a Field tube, the construction being as follows: The outer tube, which is expanded into the tube plate, is enclosed at its lower end, and has at its upper end in the water space of the boiler a perforated mouth piece, from which is suspended an inner tube that extends nearly to the bottom of the outer tube. As the outer tube is bathed in the fire, steam is generated very rapidly, and a thorough and rapid circulation is kept up, the water passing down the inner and up the outer tubes, as denoted by the arrows. The outer tube is spread out at the upper end to a slight cone, so that it cannot be forced out of the tube sheet by the pressure, and as it hangs free, there is no liability for it to loosen or get leaky from expansion and contraction. From the great amount of heating surface obtained with these tubes, the fire box may be kept at a minimum diameter for the duty, while still leaving a wide space for the water leg, which facilitates the circulation. [Illustration: Fig. 3265.] [Illustration: Fig. 3266.] The damper, which is suspended in the uptake, spreads the fire sideways. [Illustration: Fig. 3267.] Fig. 3267 represents the arrangement of Field tubes in a boiler. A boiler of this form may for a given capacity be made lighter and smaller than in any other of the ordinary forms, while the rapid circulation acts to keep the tubes clean. The inner tubes may be thin, because they are under pressure both inside and out, while the outer tubes may be thin, because they are under a bursting strain, whereas a fire tube is under collapsing pressure. [Illustration: Fig. 3268.] A design of high rate boilers, in which the uptake does not come into contact with the water, and water tubes are employed, is shown in Fig. 3268. In the fire box is an inclined tube which promotes the circulation, and is very effective heating surface, and in the combustion chamber are a number of vertical water tubes. Two manholes give access for cleaning purposes. The efficiency of the heating surface in this class of boiler is increased from the fact that, as the heat does not pass direct through the boiler, it impinges against the surface. In Fig. 3269, for example, the exit from the spherical fire box is on one side of the boiler, and the uptake on the other, the heat passing from the fire box into a combustion chamber, and thence through the horizontal fire tubes to the uptake. The crown sheet is here stayed by gusset stays, but if made spherical, as in Fig. 3270, the stays may be omitted. [Illustration: _VOL. II._ =BOILER FOR STATIONARY ENGINES.= _PLATE XXVIII._ Fig. 3271.] Figs. 3271, 3272, and 3273 illustrate a 60-inch horizontal return tubular boiler constructed by the Hartford Steam Boiler Inspection and Insurance Company. This class of boiler has found much favor in the United States. It is an externally fired, return tube boiler, the fire passing beneath the boiler and returning through the tubes to the front end of the boiler, whence it passes through the drum to the chimney. [Illustration: Fig. 3269.] [Illustration: Fig. 3270.] [Illustration: Fig. 3272.] The boiler is supported on the brackets B, B´, the front one, B, resting on an iron plate imbedded in the brickwork, and the back ones on rollers which rest on the plates P´ imbedded in the brickwork. This allows the boiler to expand and contract endways under variations of temperature without racking the brickwork. [Illustration: Fig. 3273.] A, A, etc., are for holding the brickwork together. The blow-off pipe C is for emptying or blowing down the boiler. The feed-pipe F enters the front end of the boiler, passes along it, and then crosses over. A pipe H from the steam space of the boiler supplies steam to the steam gauge G, and to the upper end of the gauge glass, which is on the casting K. The lower end of the gauge glass receives water from a pipe which passes into the water space of the boiler; at J are the three gauge cocks for testing the height of the water in the boiler. The manhole affords ingress into the boiler for inspecting and for scaling or cleaning it, the nozzles being for a safety valve. At E is a hand-hole for washing out and cleaning the boiler. P is a damper in the fire door for admitting air above the fire bars, and R is a damper for regulating the draught. In the brick walls that support the boiler there are air spaces to prevent the conduction of the heat through and prevent cracking of the brickwork. The tubes are arranged in vertical and horizontal rows and are equally spaced throughout. Fig. 3274 represents the front end, and Fig. 3275 a longitudinal sectional view of the front end of a boiler of this class. In this case, however, the pipes for the water gauge pass direct into the boiler. In some practice the tubes are arranged as in Fig. 3276, being wider pitched or spaced in the middle of the boiler to increase the circulation of the water in the boiler. Another arrangement is shown in Fig. 3277, the tubes being _staggered_ or arranged zigzag. This permits of the employment of a greater number of tubes, but does not afford such free circulation of the water. Fig. 3278 represents an arrangement where the tubes are in rows both vertically and horizontally. Fig. 3279 represents a boiler by the Erie Iron Works, the details of the setting being as follows: [Illustration: Fig. 3274.] [Illustration: Fig. 3275.] [Illustration: Fig. 3276.] [Illustration: Fig. 3277.] [Illustration: Fig. 3278.] [Illustration: Fig. 3279.] [Illustration: Fig. 3280.] [Illustration: Fig. 3281.] Fig. 3280 is an end view of the setting with the brickwork in section. Fig. 3281 side view of the boiler and setting. [Illustration: Fig. 3282.] [Illustration: Fig. 3283.] Fig. 3282 a front end view of the boiler, and Fig. 3283 a ground plan of the brickwork. When the front plate of the boiler setting extends above the middle of the boiler, as in Fig. 3279, it is said to have a "full arch front." Whereas when this plate or casting extends to the middle only of the boiler, it is said to have a half arch front. [Illustration: Figs. 3284, 3285, 3286, 3287.] Figs. 3284, 3285, 3286, and 3287 show the setting for a half arch front boiler, the dimensions of the settings of both these boilers being given in the following tables: MEASUREMENTS FOR SETTING TUBULAR STATIONARY BOILERS WITH FULL ARCH FRONTS. REFERENCE LETTERS ON DIAGRAMS. ------+---+----+----+----+----+----+------+----+----+----+----+---- No. | A | B | C | D | E | F | G | H | I | J | K | L ------+---+----+----+----+----+----+------+----+----+----+----+---- |Ft.|Ins.|Ins.|Ins.|Ins.|Ins.| Ins. |Ins.|Ins.|Ins.|Ins.|Ins. 1 | 7| 32 | 12 | 20 | 16 | 45 |44 | 7 | 32 | 64 | 85 | 26 2 | 7| 34 | 12 | 20 | 16 | 48 |47 | 8 | 34 | 66 | 90 | 26 3 | 8| 36 | 12 | 20 | 16 | 48 |47 | 8 | 36 | 68 | 92 | 26 3-1/2| 10| 36 | 12 | 20 | 16 | 48 |47 | 8 | 36 | 68 | 92 | 26 4 | 8| 42 | 14 | 20 | 16 | 48 |47 | 8 | 42 | 74 | 98 | 27 5 | 10| 42 | 14 | 20 | 16 | 48 |47 | 8 | 42 | 74 | 98 | 27 6 | 10| 44 | 14 | 24 | 16 | 48 |47 | 10 | 44 | 76 |100 | 27 7 | 12| 44 | 14 | 24 | 16 | 48 |46-1/2| 10 | 44 | 76 |100 | 27 7-1/2| 14| 44 | 14 | 24 | 16 | 47 |45-1/2| 10 | 44 | 76 | 99 | 26 8 | 12| 48 | 16 | 24 | 16 | 47 |45-1/2| 10 | 48 | 88 |103 | 26 9 | 14| 48 | 16 | 24 | 16 | 47 |45-1/2| 10 | 48 | 88 |103 | 26 10 | 12| 54 | 16 | 24 | 20 | 50 |48-1/2| 10 | 54 | 94 |112 | 26 10-1/2| 15| 54 | 16 | 24 | 20 | 50 |48-1/2| 10 | 54 | 94 |112 | 26 11 | 12| 60 | 18 | 24 | 20 | 50 |48-1/2| 12 | 60 |108 |118 | 26 12 | 14| 60 | 18 | 24 | 20 | 50 |48-1/2| 12 | 60 |108 |118 | 26 13 | 16| 60 | 18 | 26 | 20 | 50 |48 | 12 | 60 |108 |118 | 26 14 | 15| 66 | 18 | 28 | 20 | 50 |48-1/2| 12 | 66 |114 |124 | 26 15 | 16| 66 | 18 | 28 | 20 | 50 |48 | 12 | 66 |114 |124 | 26 16 | 16| 72 | 20 | 30 | 20 | 50 |48 | 12 | 72 |120 |130 | 26 ------+---+----+----+----+----+----+------+----+----+----+----+---- ------+----+-------+----+----+----+----+----+----+----+------+------ | | | | | | | | | | | NO. | | | | | | | | | | |COMMON | | | | | | | | | | |BRICK | | | | | | | | | |NO. OF|ABOVE No. | M | N | O | P | Q | R | S | T | U | FIRE |FLOOR | | | | | | | | | |BRICK.|LEVEL. ------+----+-------+----+----+----+----+----+----+----+------+------ |Ins.|Ft.Ins.|Ins.|Ins.|Ins.|Ins.|Ins.|Ins.|Ins.| | 1 | 19 | 11-6 | 20 | 40 | 12 | 16 | 36 | 34 | 4 | 600 | 6800 2 | 22 | 11-6 | 20 | 40 | 12 | 16 | 36 | 34 | 4 | 600 | 7500 3 | 22 | 12-6 | 24 | 40 | 12 | 16 | 36 | 34 | 4 | 650 | 7700 3-1/2| 22 | 14-6 | 28 | 46 | 12 | 16 | 42 | 42 | 4 | 720 | 8500 4 | 21 | 12-8 | 24 | 40 | 12 | 16 | 36 | 34 | 4 | 730 | 8500 5 | 21 | 14-8 | 28 | 46 | 12 | 16 | 42 | 42 | 4 | 770 | 9600 6 | 21 | 15-0 | 28 | 46 | 12 | 16 | 42 | 42 | 4 | 880 | 10500 7 | 21 | 17-0 | 32 | 52 | 12 | 16 | 48 | 49 | 4 | 940 | 10800 7-1/2| 21 | 19-0 | 36 | 58 | 12 | 16 | 54 | 84 | 4 | 1120 | 11500 8 | 21 | 17-2 | 32 | 52 | 12 | 20 | 48 | 49 | 4 | 1120 | 13600 9 | 21 | 19-2 | 36 | 58 | 12 | 20 | 54 | 84 | 4 | 1140 | 15700 10 | 24 | 17-6 | 32 | 52 | 12 | 20 | 48 | 49 | 4 | 1160 | 16200 10-1/2| 24 | 20-8 | 36 | 56 | 16 | 20 | 54 | 90 | 4 | 1270 | 17500 11 | 24 | 17-10 | 32 | 50 | 16 | 24 | 48 | 49 | 4 | 1400 | 20500 12 | 24 | 19-10 | 36 | 56 | 16 | 24 | 54 | 84 | 4 | 1500 | 23000 13 | 24 | 22-0 | 40 | 56 | 16 | 24 | 54 | 96 | 4 | 1540 | 25300 14 | 24 | 21-2 | 36 | 56 | 16 | 24 | 54 | 90 | 4 | 1590 | 26000 15 | 24 | 22-2 | 40 | 56 | 16 | 24 | 54 | 96 | 4 | 1620 | 27000 16 | 24 | 22-6 | 40 | 56 | 16 | 24 | 54 | 96 | 4 | 1750 | 30000 ------+----+-------+----+----+----+----+----+----+----+------+------ NOTE.--In setting "Standard" boilers, the side walls should be so built that the longitudinal seams of the shell will be protected from the fire. MEASUREMENTS FOR SETTING TUBULAR STATIONARY BOILERS WITH HALF ARCH FRONTS. REFERENCE LETTERS ON DIAGRAMS. ------+---+----+----+----+----+------+------+----+----+----+------- No. | A | B | C | D | E | F | G | H | I | J | K ------+---+----+----+----+----+------+------+----+----+----+------- |Ft.|Ins.|Ins.|Ins.|Ins.|Ins. | Ins. |Ins.|Ins.|Ins.| Ins. 1 | 7 | 32 | 14 | 20 | 16 |46 |45 | 7 | 32 | 64 | 73 2 | 7 | 34 | 14 | 20 | 16 |46 |45 | 8 | 34 | 66 | 75 3 | 8 | 36 | 14 | 20 | 16 |46 |45 | 8 | 36 | 68 | 77 3-1/2|10 | 36 | 14 | 20 | 16 |46 |45 | 8 | 36 | 68 | 77 4 | 8 | 42 | 18 | 20 | 16 |46 |45 | 8 | 42 | 74 | 83 5 |10 | 42 | 18 | 20 | 16 |46 |45 | 8 | 42 | 74 | 83 6 |10 | 44 | 18 | 24 | 16 |46 |45 | 10 | 44 | 76 | 85 7 |12 | 44 | 18 | 24 | 16 |46 |44-1/2| 10 | 44 | 76 | 85 7-1/2|14 | 44 | 18 | 24 | 16 |46 |44-1/2| 10 | 44 | 76 | 85 8 |12 | 48 | 19 | 24 | 16 |50 |48-1/2| 10 | 48 | 88 | 93 9 |14 | 48 | 19 | 24 | 16 |50 |48-1/2| 10 | 48 | 88 | 93 10 |12 | 54 | 19 | 24 | 20 |50 |48-1/2| 10 | 54 | 94 | 99 10-1/2|15 | 54 | 19 | 24 | 20 |50 |48-1/2| 10 | 54 | 94 | 99 11 |12 | 60 | 21 | 24 | 20 |46-3/4|45-1/2| 12 | 60 |108 |101-3/4 12 |14 | 60 | 21 | 24 | 20 |46-3/4|45 | 12 | 60 |108 |101-3/4 13 |16 | 60 | 21 | 26 | 20 |46-3/4|45 | 12 | 60 |108 |101-3/4 14 |15 | 66 | 24 | 28 | 20 |47 |45-1/2| 12 | 66 |114 |108 15 |16 | 66 | 24 | 28 | 20 |47 |45-1/2| 12 | 66 |114 |108 16 |16 | 72 | 24 | 30 | 20 |48 |46-1/2| 12 | 72 |120 |115 ------+---+----+----+----+----+------+------+----+----+----+------- ------+------+------+--------+----+------+----+----+----+----+---- No. | L | M | N | O | P | Q | R | S | T | U ------+------+------+--------+----+------+----+----+----+----+---- | Ins. | Ins. |Ft. Ins.|Ins.| Ins. |Ins.|Ins.|Ins.|Ins.|Ins. 1 |26 |20 | 10-3 | 20 |33 | 12 | 16 | 36 | 34 | 4 2 |26 |20 | 10-3 | 20 |33 | 12 | 16 | 36 | 34 | 4 3 |26 |20 | 11-3 | 24 |33 | 12 | 16 | 36 | 34 | 4 3-1/2|26 |20 | 13-3 | 28 |39 | 12 | 16 | 42 | 42 | 4 4 |27 |19 | 11-3 | 24 |32-1/2| 12 | 16 | 36 | 34 | 4 5 |27 |19 | 13-3 | 28 |38-1/2| 12 | 16 | 42 | 42 | 4 6 |27 |19 | 13-7 | 28 |38-1/2| 12 | 16 | 42 | 42 | 4 7 |27 |19 | 15-7 | 32 |44-1/2| 12 | 16 | 48 | 49 | 4 7-1/2|27 |19 | 17-7 | 36 |50-1/2| 12 | 16 | 54 | 84 | 4 8 |26 |24 | 15-7 | 32 |48 | 12 | 20 | 48 | 49 | 4 9 |26 |24 | 17-7 | 36 |54 | 12 | 20 | 54 | 84 | 4 10 |26 |24 | 15-11 | 32 |48-1/2| 12 | 20 | 48 | 49 | 4 10-1/2|26 |24 | 19-1 | 36 |52-1/2| 16 | 20 | 54 | 90 | 4 11 |26 |20-3/4| 16-1 | 32 |47 | 16 | 24 | 48 | 49 | 4 12 |26 |20-3/4| 18-1 | 36 |53 | 16 | 24 | 54 | 84 | 4 13 |26 |20-3/4| 20-3 | 40 |53 | 16 | 24 | 54 | 96 | 4 14 |26 |21 | 19-5 | 36 |52-1/2| 16 | 24 | 54 | 90 | 4 15 |26 |21 | 20-5 | 40 |52-1/2| 16 | 24 | 54 | 96 | 4 16 |28-1/4|19-3/4| 20-7 | 40 |52-1/2| 16 | 24 | 54 | 96 | 4 ------+------+------+--------+----+------+----+----+----+----+---- ------+------+------+----+----+----+------+------ | | | | | | | NO. | | | | | | |COMMON | | | | | | |BRICK | | | | | |NO. OF|ABOVE No. | V | W | X | Y | Z | FIRE |FLOOR | | | | | |BRICK.|LEVEL. ------+------+------+----+----+----+------+------ | Ins. | Ins. |Ins.|Ins.|Ins.| | 1 |36 | 9 | 24 | 12 | 7 | 600 | 6150 2 |36 | 9 | 28 | 12 | 7 | 600 | 6200 3 |36 | 9 | 28 | 12 | 15 | 650 | 6700 3-1/2|36 | 9 | 28 | 12 | 25 | 720 | 7050 4 |32-3/4|12-1/4| 32 | 16 | 11 | 730 | 7700 5 |32-3/4|12-1/4| 32 | 16 | 25 | 770 | 8700 6 |32-3/4|12-1/4| 36 | 16 | 25 | 880 | 8800 7 |32-1/4|12-1/4| 36 | 20 | 35 | 940 | 9300 7-1/2|32-1/4|12-1/4| 36 | 24 | 45 | 1120 | 9500 8 |36-1/4|12-1/4| 36 | 20 | 35 | 1120 | 11100 9 |36-1/4|12-1/4| 36 | 24 | 45 | 1140 | 12900 10 |34 |14-1/2| 42 | 20 | 35 | 1160 | 13200 10-1/2|34 |14-1/2| 42 | 24 | 57 | 1270 | 14200 11 |31 |14-1/2| 48 | 20 | 37 | 1400 | 16700 12 |30-1/2|14-1/2| 48 | 24 | 45 | 1500 | 19200 13 |30-1/2|14-1/2| 48 | 24 | 65 | 1540 | 21500 14 |31 |14-1/2| 54 | 24 | 57 | 1590 | 22100 15 |31 |14-1/2| 54 | 24 | 65 | 1620 | 23100 16 |27-1/2|19 | 54 | 24 | 65 | 1750 | 26000 ------+------+------+----+----+----+------+------ NOTE.--In setting "Standard" boilers, the side walls should be so built that the longitudinal seams of the shell will be protected from the fire. THE EVAPORATIVE EFFICIENCIES OF BOILERS. [56]"Many tests have been undertaken to ascertain the evaporative power of different classes of boilers in actual work; but few of these are of any value, owing to the unreliable means usually employed to measure the quantity of water evaporated. The easiest method, and consequently the one most frequently adopted, is to measure the quantity by the difference of its height in the water-gauge glass at the beginning and end of the trial, and also at intermediate stages. This method is very rude and uncertain, since there can be little doubt that in many boilers at work the surface of the water is not level, but is usually higher over the furnace, or where the greatest ebullition occurs. The difference in height at any moment will greatly depend upon the intensity of the ebullition, which is ever varying during the intervals between firing. With mechanical firing the difference of height is probably reduced to a minimum. [56] From "_A Treatise on Steam Boilers_," by Robert Wilson. "The meters employed for measuring the water are sometimes not trustworthy. The only sure method of ascertaining the quantity of water evaporated is by actual measurement with a cistern or vessel whose cubic contents are accurately known. The quantity of water in the boiler before and after the trial should be measured at the same temperature, which should not exceed 212° to insure accuracy. But even when the amount of water introduced and the quantity passed off from the boiler are accurately ascertained, there yet remains a doubt as to how much has been actually evaporated, and how much may have passed off in priming, unless the trial has been conducted with the boiler open to the atmosphere, which appears to be the only condition under which accuracy can be insured, unless a suitable apparatus can be provided for accurately measuring the weight and temperature of all the steam and water given off, when the boiler is working above atmospheric pressure. "There are very few boilers that do not prime more or less, and the quantity of water passed off in this manner is sometimes very considerable, and has led to the impossible results of 16 and 17 lbs. of water evaporated per lb. of ordinary coal in locomotive and water-tube boilers being seriously recorded. Externally fired boilers, that have given the moderate result of 5 lbs. of water per lb. of coal at atmospheric pressure, have shown the unexpected result of 10 and 12 lbs. of water evaporated at 40 lbs. pressure. In fact, unless the amount of water passed over with the steam by priming or foaming, when working under pressure, can be accurately ascertained, the evaporative results are not to be relied upon, however careful in other respects the trial may have been conducted. It is customary to give the quantity of water evaporated from and at a temperature of 212°, or the boiling point at atmospheric pressure, to which the results of evaporation are reduced." The quantity corresponding to any temperature of feed water and working pressure can readily be found with the aid of the annexed table, taken from _The Encyclopædia Britannica_, wherein are presented the relations of the properties of steam, as now accepted by the best authorities. TABLE GIVING THE PRESSURE, TEMPERATURE, AND VOLUME OF STEAM. -----------+-----------+-----------+----------+---------+------------- Total pres-| | | | |Relative vol- sure per |Gauge pres-| Sensible |Total heat|Weight of| ume of steam square inch| sure or |temperature|in degrees|one cubic|compared with measured | pressure | in |from zero |foot of | the water from a | above | Fahrenheit| of | steam. |from which it vacuum. |atmosphere.| degrees. | Fahren- | lbs. | was lbs. | lbs. | | heit. | | evaporated. -----------+-----------+-----------+----------+---------+------------- 1 | --- | 102.1 | 1144.5 | .0030 | 20582 2 | --- | 126.3 | 1151.7 | .0058 | 10721 3 | --- | 141.6 | 1156.6 | .0085 | 7322 4 | --- | 153.1 | 1160.1 | .0112 | 5583 5 | --- | 162.3 | 1162.9 | .0138 | 4527 6 | --- | 170.2 | 1165.3 | .0163 | 3813 7 | --- | 176.9 | 1167.3 | .0189 | 3298 8 | --- | 182.9 | 1169.2 | .0214 | 2909 9 | --- | 188.3 | 1170.8 | .0239 | 2604 10 | --- | 193.3 | 1172.3 | .0264 | 2358 11 | --- | 197.8 | 1173.7 | .0289 | 2157 12 | --- | 202.0 | 1175.0 | .0314 | 1986 13 | --- | 205.9 | 1176.2 | .0338 | 1842 14 | --- | 209.6 | 1177.3 | .0362 | 1720 14.7 | 0 | 212.0 | 1178.1 | .0380 | 1642 15 | .3 | 213.1 | 1178.4 | .0387 | 1610 16 | 1.3 | 216.3 | 1179.4 | .0411 | 1515 17 | 2.3 | 219.6 | 1180.3 | .0435 | 1431 18 | 3.3 | 222.4 | 1181.2 | .0459 | 1357 19 | 4.3 | 225.3 | 1182.1 | .0483 | 1290 20 | 5.3 | 228.0 | 1182.9 | .0507 | 1229 21 | 6.3 | 230.6 | 1183.7 | .0531 | 1174 22 | 7.3 | 233.1 | 1184.5 | .0555 | 1123 23 | 8.3 | 235.3 | 1185.2 | .0580 | 1075 24 | 9.3 | 237.8 | 1185.9 | .0601 | 1036 25 | 10.3 | 240.1 | 1186.6 | .0625 | 996 26 | 11.3 | 242.3 | 1187.3 | .0650 | 958 27 | 12.3 | 244.4 | 1187.8 | .0673 | 926 28 | 13.3 | 246.4 | 1188.4 | .0696 | 895 29 | 14.3 | 248.4 | 1189.1 | .0719 | 866 30 | 15.3 | 250.4 | 1189.8 | .0743 | 838 31 | 16.3 | 252.2 | 1190.4 | .0766 | 813 32 | 17.3 | 254.1 | 1190.9 | .0779 | 789 33 | 18.3 | 255.9 | 1191.5 | .0812 | 767 34 | 19.3 | 257.6 | 1192.0 | .0835 | 746 35 | 20.3 | 259.3 | 1192.5 | .0858 | 726 36 | 21.3 | 260.9 | 1193.0 | .0881 | 707 37 | 22.3 | 262.6 | 1193.5 | .0905 | 688 38 | 23.3 | 264.2 | 1194.0 | .0929 | 671 39 | 24.3 | 265.8 | 1194.5 | .0952 | 655 40 | 25.3 | 267.3 | 1194.9 | .0974 | 640 41 | 26.3 | 268.7 | 1195.4 | .0996 | 625 42 | 27.3 | 270.2 | 1195.8 | .1020 | 611 43 | 28.3 | 271.6 | 1196.2 | .1042 | 598 44 | 29.3 | 273.0 | 1196.6 | .1065 | 595 45 | 30.3 | 274.4 | 1197.1 | .1089 | 572 46 | 31.3 | 275.8 | 1197.5 | .1111 | 561 47 | 32.3 | 277.1 | 1197.9 | .1133 | 550 48 | 33.3 | 278.4 | 1198.3 | .1156 | 539 49 | 34.3 | 279.7 | 1198.7 | .1179 | 529 50 | 35.3 | 281.0 | 1199.1 | .1202 | 518 51 | 36.3 | 282.3 | 1199.5 | .1224 | 509 52 | 37.3 | 283.5 | 1199.9 | .1246 | 500 53 | 38.3 | 284.7 | 1200.3 | .1269 | 491 54 | 39.3 | 285.9 | 1200.6 | .1291 | 482 55 | 40.3 | 287.1 | 1201.0 | .1314 | 474 56 | 41.3 | 288.2 | 1201.3 | .1336 | 466 57 | 42.3 | 289.3 | 1201.7 | .1364 | 458 58 | 43.3 | 290.4 | 1202.0 | .1380 | 451 59 | 44.3 | 291.6 | 1202.4 | .1403 | 444 60 | 45.3 | 292.7 | 1202.7 | .1425 | 437 61 | 46.3 | 293.8 | 1203.1 | .1447 | 403 62 | 47.3 | 294.8 | 1203.4 | .1469 | 424 63 | 48.3 | 295.9 | 1203.7 | .1493 | 417 64 | 49.3 | 296.9 | 1204.0 | .1516 | 411 65 | 50.3 | 298.0 | 1204.3 | .1538 | 405 66 | 51.3 | 299.0 | 1204.6 | .1560 | 399 67 | 52.3 | 300.0 | 1204.9 | .1583 | 393 68 | 53.3 | 300.9 | 1205.2 | .1605 | 388 69 | 54.3 | 301.9 | 1205.5 | .1627 | 383 70 | 55.3 | 302.9 | 1205.8 | .1648 | 378 71 | 56.3 | 303.9 | 1206.1 | .1670 | 373 72 | 57.3 | 304.8 | 1206.3 | .1692 | 368 73 | 58.3 | 305.7 | 1206.6 | .1714 | 363 74 | 59.3 | 306.6 | 1206.9 | .1736 | 359 75 | 60.3 | 307.5 | 1207.2 | .1759 | 353 76 | 61.3 | 308.4 | 1207.4 | .1782 | 349 77 | 62.3 | 309.3 | 1207.7 | .1804 | 345 78 | 63.3 | 310.2 | 1208.0 | .1826 | 341 79 | 64.3 | 311.1 | 1208.3 | .1848 | 337 80 | 65.3 | 312.0 | 1208.5 | .1869 | 333 81 | 66.3 | 312.8 | 1208.8 | .1891 | 329 82 | 67.3 | 313.6 | 1209.1 | .1913 | 325 83 | 68.3 | 314.5 | 1209.4 | .1935 | 321 84 | 69.3 | 315.3 | 1209.6 | .1957 | 318 85 | 70.3 | 316.1 | 1209.9 | .1980 | 314 86 | 71.3 | 316.9 | 1210.1 | .2002 | 311 87 | 72.3 | 317.8 | 1210.4 | .2024 | 308 88 | 73.3 | 318.6 | 1210.6 | .2044 | 305 89 | 74.3 | 319.4 | 1210.9 | .2067 | 301 90 | 75.3 | 320.2 | 1211.1 | .2089 | 298 91 | 76.3 | 321.0 | 1211.3 | .2111 | 295 92 | 77.3 | 321.7 | 1211.5 | .2133 | 292 93 | 78.3 | 322.5 | 1211.8 | .2155 | 289 94 | 79.3 | 323.3 | 1212.0 | .2176 | 286 95 | 80.3 | 324.1 | 1212.3 | .2198 | 283 96 | 81.3 | 324.8 | 1212.5 | .2219 | 281 97 | 82.3 | 325.6 | 1212.8 | .2241 | 278 98 | 83.3 | 326.3 | 1213.0 | .2263 | 275 99 | 84.3 | 327.1 | 1213.2 | .2285 | 272 100 | 85.3 | 327.9 | 1213.4 | .2307 | 270 101 | 86.3 | 328.5 | 1213.6 | .2329 | 267 102 | 87.3 | 329.1 | 1213.8 | .2351 | 265 103 | 88.3 | 329.9 | 1214.0 | .2373 | 262 104 | 89.3 | 330.6 | 1214.2 | .2393 | 260 105 | 90.3 | 331.3 | 1214.4 | .2414 | 257 106 | 91.3 | 331.9 | 1214.6 | .2435 | 255 107 | 92.3 | 332.6 | 1214.8 | .2456 | 253 108 | 93.3 | 333.3 | 1215.0 | .2477 | 251 109 | 94.3 | 334.0 | 1215.3 | .2499 | 249 110 | 95.3 | 334.6 | 1215.5 | .2521 | 247 111 | 96.3 | 335.3 | 1215.7 | .2543 | 245 112 | 97.3 | 336.0 | 1215.9 | .2564 | 243 113 | 98.3 | 336.7 | 1216.1 | .2586 | 241 114 | 99.3 | 337.4 | 1216.3 | .2607 | 239 115 | 100.3 | 338.0 | 1216.5 | .2628 | 237 116 | 101.3 | 338.6 | 1216.7 | .2649 | 235 117 | 102.3 | 339.3 | 1216.9 | .2674 | 233 118 | 103.3 | 339.9 | 1217.1 | .2696 | 231 119 | 104.3 | 340.5 | 1217.3 | .2738 | 229 120 | 105.3 | 341.1 | 1217.4 | .2759 | 227 121 | 106.3 | 341.8 | 1217.6 | .2780 | 225 122 | 107.3 | 342.4 | 1217.8 | .2801 | 224 123 | 108.3 | 343.0 | 1218.0 | .2822 | 222 124 | 109.3 | 343.6 | 1218.2 | .2845 | 221 125 | 110.3 | 344.2 | 1218.4 | .2867 | 219 126 | 111.3 | 344.8 | 1218.6 | .2889 | 217 127 | 112.3 | 345.4 | 1218.8 | .2911 | 215 128 | 113.3 | 346.0 | 1218.9 | .2933 | 214 129 | 114.3 | 346.6 | 1219.1 | .2955 | 212 130 | 115.3 | 347.2 | 1219.3 | .2977 | 211 131 | 116.3 | 347.8 | 1219.5 | .2999 | 209 132 | 117.3 | 348.3 | 1219.6 | .3020 | 208 133 | 118.3 | 348.9 | 1219.8 | .3040 | 206 134 | 119.3 | 349.5 | 1220.0 | .3060 | 205 135 | 120.3 | 350.1 | 1220.2 | .3080 | 203 136 | 121.3 | 350.6 | 1220.3 | .3101 | 202 137 | 122.3 | 351.2 | 1220.5 | .3121 | 200 138 | 123.3 | 351.8 | 1220.7 | .3142 | 199 139 | 124.3 | 352.4 | 1220.9 | .3162 | 198 140 | 125.3 | 352.9 | 1221.0 | .3184 | 197 141 | 126.3 | 353.5 | 1221.2 | .3206 | 195 142 | 127.3 | 354.0 | 1221.4 | .3228 | 194 143 | 128.3 | 354.5 | 1221.6 | .3250 | 193 144 | 129.3 | 355.0 | 1221.7 | .3273 | 192 145 | 130.3 | 355.6 | 1221.9 | .3294 | 190 146 | 131.3 | 356.1 | 1222.0 | .3315 | 189 147 | 132.3 | 356.7 | 1222.2 | .3336 | 188 148 | 133.3 | 357.2 | 1222.3 | .3357 | 187 149 | 134.3 | 357.8 | 1222.5 | .3377 | 186 150 | 135.3 | 358.3 | 1222.7 | .3397 | 184 155 | 140.3 | 361.0 | 1223.5 | .3500 | 179 160 | 145.3 | 363.4 | 1224.2 | .3607 | 174 165 | 150.3 | 366.0 | 1224.9 | .3714 | 169 170 | 155.3 | 368.2 | 1225.7 | .3821 | 164 175 | 160.3 | 370.8 | 1226.4 | .3928 | 159 180 | 165.3 | 372.9 | 1227.1 | .4035 | 155 185 | 170.3 | 375.3 | 1227.8 | .4142 | 151 190 | 175.3 | 377.5 | 1228.5 | .4250 | 148 195 | 180.3 | 379.7 | 1229.2 | .4357 | 144 200 | 185.3 | 381.7 | 1229.8 | .4464 | 141 210 | 195.3 | 386.0 | 1231.1 | .4668 | 135 220 | 205.3 | 389.9 | 1232.3 | .4872 | 129 230 | 215.3 | 393.8 | 1233.5 | .5072 | 123 240 | 225.3 | 397.5 | 1234.6 | .5270 | 119 250 | 235.3 | 401.1 | 1235.7 | .5471 | 114 260 | 245.3 | 404.5 | 1236.8 | .5670 | 110 270 | 255.3 | 407.9 | 1237.8 | .5871 | 106 280 | 265.3 | 411.2 | 1238.8 | .6070 | 102 290 | 275.3 | 414.4 | 1239.8 | .6268 | 99 300 | 285.3 | 417.5 | 1240.7 | .6469 | 96 -----------+-----------+-----------+----------+---------+------------- Here we see that at 212° the total quantity of heat in the steam is 1178.1°, which gives a difference of 966.1°. This heat, usually termed latent, is absorbed in performing the work of expanding the particles of water from the liquid to the gaseous state. Now, suppose the water is evaporated at 60 lbs. pressure, the steam will have a temperature of 307°, and a total heat of 1207°. If the feed has been introduced at 60°, it is evident that 1147° of heat have been imparted. As the amount evaporated is inversely proportional to the quantity of heat required, we have 1147 ÷ 966 = 1.2. Multiplying by this factor, the quantity evaporated at 60 lbs. pressure from 60°, we obtain the amount that would be evaporated at 212° by the same quantity of fuel. By the same table can be ascertained the comparatively small increase of heat required to evaporate water at higher pressures. Suppose we take water evaporated at 45 lbs. pressure from a feed temperature of 60°, then each lb. of water will require 1202.7-60 = 1142.7 for its conversion into steam. If we take the pressure at 100 lbs., we shall have 1216.9-60 = 1156.9° as the quantity required. The difference between these two total quantities is only 14.2°, and is so small as to be scarcely worth considering. Leaving out of account the loss due to the slight reduction of the conducting power of the material, the increased amount of heat required for the higher pressure will be only 1/36 of the total heat required at 60 lbs. With an evaporation of 7 lbs. of water from 1 lb. of coal, it will be obtained by using 1/563 more fuel, or about 1 lb. in about 556 lbs., a quantity not appreciable to the ordinary modes of weighing coal. The economy is then manifest of using steam of high pressures when at the same time advantage is taken of the facilities it offers for working the steam more expansively to the engine cylinders. The saving that may be effected by heating the feed water may be shown as follows: If we take the normal temperature of the feed water at 60°, the temperature of the heated water at 212°, and the boiler pressure at 20 lbs., the total heat imparted to the steam in one case is 1192.5° - 60° = 1132.5° and in the other case 1192.5° - 212° = 980.5° 152° the difference being 152°, or a saving of ------- 1132.5° which is 13.4 per cent. If the pressure be taken at 120 lbs., instead of 20 lbs., the saving will be 13.1 per cent, showing a slight diminution in the economy effected by heating the feed water when a high boiler pressure is employed. THE CARE AND MANAGEMENT OF STATIONARY ENGINE BOILERS. The first thing to do in taking charge of a stationary engine boiler is to know from personal inspection that the safety fittings and the boiler-feeding apparatus are in good order. The safety valve is the first thing to inspect, as it is liable to stick in its seat, especially in cases in which it is set at a greater pressure than is got up in the boiler, because in that case it is not lifted from the seat and in time sticks fast there. In such cases it is proper to lift the valve at least once a day while steam is on. For this purpose a cord may be attached to the lever, passing over a pulley directly above the lever, and thence to some convenient place near the boiler, but where it is not liable to get caught and pulled accidentally. Before lighting the fire, see that there is sufficient water in the boiler. If there is a gauge glass on the boiler, it should show three-quarters full, or three-quarters of a glass, as it is called. The gauge glass may show a false water level, and to be sure that such is not the case, open the top gauge cock and the cock at the bottom of the gauge glass, letting the water run through the gauge glass. Open and close the cock below the gauge glass two or three times to see that the water comes to the same level each time. If the steam pressure has been allowed to fall in the boiler without any of the cocks being opened, there will be a partial vacuum in the boiler, and air must be let in before the true water level will be shown either by the gauge glass or by the gauge cocks. Opening the upper gauge cock will let in the air, and it should not be closed again until enough steam has been got up in the boiler to expel the air again, or in other words, until steam begins to issue from it. The grate bars and ash pit should be cleaned of clinker, ashes, etc., and it should be seen that the tubes are clear of ashes, etc., before the fire is laid; if the grate is a shaking one, the lever should be applied to see that the grate will shake properly. TO LIGHT THE FIRE--In the case of anthracite or hard coal, as it is sometimes termed, first cover the bars with a thin layer of coal and then put in pieces of lighted greasy waste (if it is at hand) distributed about the furnace, taking especial care to light the fire at the fire-door end and in the corners, because the fire will spread from the front end towards the back easier than it will from the back end towards the front. The fire should light from the bottom and not from the top, hence the thinnest pieces of the wood should be put in first. If there is any soft coal at hand, a small quantity of it will accelerate lighting the fire, as it burns easier and quicker than hard coal. Before putting on the coal the wood should be well lighted, the bottom portion of it having ceased flaming. This causes the lighted wood to spread over the bars and the fire to light evenly. Charge the coal lightly, first covering the places that have burned up the most. FIRING.--The fire door should be kept open as little as possible, as it admits cold air that is detrimental to the combustion, as well as to the draught, hence firing should be done quickly. A good fireman will maintain as even a temperature as possible in the fire box by charging the coal lightly and quickly. Some firemen will, after the fire is at its proper depth all over the grates, charge the fire in the front end, that is, at the fire-door end, and push it back as it burns up, to keep up the thickness of the fire at the back. The thickness of the fire depends upon the size and kind of coal. With small coal a fire from 4 to 6 inches deep will answer, while, if the lumps are five or six inches in diameter, a fire from a foot to 15 inches deep may be maintained, as is done in some locomotives. The object is to have the fire thick enough to prevent it from burning through in spots or letting cold draughts of air pass through it. The sides of the furnace require particular attention, not only because cold air is more likely to get through there, but also in boilers having fire boxes the cool sides of the box keep the temperature of the fuel down, hence a thicker fire is necessary around the sides than in the middle of the furnace or fire box. Three things are to be considered in cleaning a fire--first, that the boiler pressure will fall during, and for a short time after, the cleaning; second, that the depth of fire will be diminished by the cleaning; and third, that the temperature of the fire will fall during the cleaning. SHAKING GRATE BARS. When a furnace has shaking grate bars, the cleaning of the fire is greatly facilitated, and with bars that shake singly (and good coal) the fire is often not disturbed during the day, except to shake the bars occasionally, passing the poker through it and using the hoe to keep it evenly spread. If the grate shakes in sections, more cleaning will be required to break up the clinker, while, if the bars do not shake, the cleaning assumes greater importance. Before cleaning, therefore, see that there is sufficient water in the boiler, that it need not be fed while cleaning, nor just after cleaning the fire. Prepare for cleaning by having a thick fire on the grate, so that after cleaning it will burn up quickly, and let the cleaning be done as quickly as possible. [Illustration: Fig. 3288.] The tools used for cleaning the fire are the slice bar, Fig. 3288, which is pushed along the top of the fire bars to loosen up the fire, and let the ashes fall through the bars. [Illustration: Fig. 3289.] [Illustration: Fig. 3290.] The hoe, Fig. 3289, which is used to push the fire to the back of the furnace and to pull it forward. The poker, Fig. 3290, which dislodges any clinker that may be between the bars, and lets the ashes fall through. [Illustration: Fig. 3291.] [Illustration: Fig. 3292.] The clinker hook or devil's claw, Fig. 3291, which is used to haul clinker out of the fire, and the rake, Fig. 3292, which is used to spread the fire evenly over the bars after it is cleaned. In cleaning a fire, first use the slice bar to loosen up the fire and let the ashes fall through, and also dislodge clinkers from the surface of the bars. Then push the fire to the back of the furnace. Next use the poker to clean out clinker from between the exposed part of the bars. Then with the hoe pull a part of the fire forward and pull out the clinker that may be in this part, doing so with the hoe as far as possible, as that will save time, but if it should be necessary, use the clinker hook. Then pull forward a second portion of the fire, and spread it on the bars, removing the clinker as before. When all the fire has thus been cleaned, use the rake to spread it evenly over the bars, and put on a light charge of coal, covering the brightest parts of the fire first, and taking care that no part of the fire bars is left uncovered. The cleaning should be done quickly. DRAUGHT.--The draught should be decreased while the fire is being cleaned, but the damper should never be entirely closed, as this might cause an explosion in the fire box and tubes. During a temporary interruption, as in the case of the engine stopping, partly close all the dampers, as it is wasteful to make steam and blow it off through the safety valve. COMBUSTION.--A blue flame is evidence of incomplete combustion, but there may be a blue flame and imperfect combustion at the back end of the furnace, and a white flame and perfect combustion at the other end. This is likely to occur with heavy firing near the fire door, and a thin fire at the tube sheet end of the fire box. In this case the unconsumed gases produced near the fire door (as evidenced by the blue flame) are consumed in passing over the bright fire at the tube plate end of the furnace. AT NIGHT.--Always leave plenty of water in the boiler when leaving it for the night, not only to allow for any leak, but also because it gives a fair start in the morning and more time to remedy any defect in the feed pump if it arise. By plenty of water, very nearly a full gauge is meant, or if there is no gauge glass to the boiler, let the water stand above the second or middle cock. The usual method of leaving the fire for the night is to bank it. There is an element of danger, however, in banking a fire, unless it is done to suit the circumstances, because steam may generate very rapidly, and perhaps more rapidly than the safety valve can carry it off. A safe method is to clean the fire, leaving the clinker and ashes covering the front half of the grate and the fire piled up on the back half. The damper and ash pit door should be closed tight, the fire door open, and the fire well covered with fresh coal, choosing small rather than large coal. If this method is found not to keep up the fire sufficiently, the same plan may be employed, except that the ashes and clinker may be removed, and if this still leaves too cold a boiler, and too poor a fire in the morning, the fire may be left spread over the grate, but heavily covered with fresh coal, the draught being stopped as much as possible by closing the dampers and opening the furnace door. To further insure safety, the weight on the safety valve lever should be pushed towards the valve, so as to cause the safety valve to blow off at a less pressure than during the day. IN THE MORNING.--In starting up a banked fire in the morning, first close the fire door and open the damper, so as to give the fire all the draught possible, and let it burn up a little; then, if it has been piled up at the back of the furnace, clean out the ashes by passing the T bar beneath the fire, and spread it over the grate, letting it burn up a little before making up a fire. BOILER-FEED.--The fireman should endeavor, if possible, to so regulate the boiler feed that it is kept going as nearly continuously as possible while maintaining a uniform quantity of water in the boiler, and this, with uniform firing, will give the greatest economy. When pumps are used to feed with, the amount of the lift of the valves can be regulated by a screw, so as to vary the amount of water the pump will deliver, and in this case it is comparatively easy to set them so that the pump may be kept going without putting too much water in the boiler. When injectors are used, however, the feed will be intermittent, and a uniform quantity of water in the boiler is best obtained by feeding at short intervals, stopping the feed when the fire door is opened much, as when cleaning the fire. If the feed water is dirty, the gauge glass should be kept clean by first shutting off the upper cock and opening the lower one, so as to let the water blow through the lower cock, and then shutting off the lower cock from the boiler, and opening the upper one, which will let the steam blow all the water out of the glass. This should be done two or three times a day, so as to keep the holes in the boiler and those in the cocks from closing up with fur or scale. If the water falls in the glass, or if the gauge cocks show the water to be falling, notwithstanding that the feed pump has been started, it is evident that the pump is not working. This may occur from a stuck valve, a leak in the suction pipe, from the feed water being too hot, or from the pump failing to start in action from leaky or choked valves. A stuck valve may generally be relieved by striking a few blows on the outside of the pump with a hammer and a block of wood, or if this does not answer, with the hammer only. Check valves are the ones most likely to stick. If a pump fails to work by reason of the feed water being too hot, the remedy is to open the pet cock to let the steam out of the pump, but if this does not succeed, cold water may be poured on the outside of the pump, which will start it, after which, in most cases, the pump will keep going and the pet cock may be closed. If the suction pipe has a joint, a leak there will impair the action of the pump, and, if the leak is great enough, will stop it; the remedy is to make the joint tight. Plunger pumps sometimes fail to act because the plunger has worn so small in diameter that there is sufficient air between the plunger and the pump barrel to expand and compress without lifting the valve; the remedy is obviously a new plunger of as large diameter as the pump gland will admit of, boring the gland out to admit the new plunger. All the impurities in the water are left in the boiler when the water has evaporated, and it is obvious these impurities must be blown off or they will form scale on the internal surface of the boiler and the external surface of the tubes or flues. This scale obstructs the passage of the heat from the iron to the water, and if let get thick enough will cause the iron to rapidly burn out. To prevent the formation of scale, two principal methods are employed, one being to purify the feed water, and the other to occasionally blow the impurities out of the boiler. Feed-water heaters generally serve also as purifiers, and their effectiveness is increased in proportion as the water can pass quietly through them, and has a large area on which the impurities can settle. Horizontal heaters have the advantage that they have a large settling area, and a less distance for the impurities to fall through. The water-gauge glass and the lower gauge cock are usually set so as to have a margin of about three inches of water above the tubes or crown sheet of the fire box, hence if it is known that the water is but just below the bottom of the gauge glass or gauge cock, there is no positive danger, although it is improper to let it get so low. If the water is out of sight, and it is not known exactly how low it is, then it is dangerously low, and every minute is of vital importance. Should the water get dangerously low in the boiler, the most dangerous thing to do is to lift the safety valve or pump in cold water, especially if it is not known how much water there is in the boiler. As quickly as possible cover the fire with ashes, coal, earth, sand, or anything that is at hand that will smother the fire, then close the draught to the fire, leaving the fire door and the chimney damper open. Leave all the steam outlets just as they are, and also the feed. PRIMING.--Priming, which is also called "foaming," is that the steam carries up water into the steam space. This may arise from several causes, but it is well known that what will stop priming in some cases will cause it in others. The known causes of priming are--first, too little room for the steam in the boiler, and it follows that a high water level may cause priming; second, it may be caused by a difference of temperature between the water and the steam in the boiler. Suppose, for example, that the pressure of the steam and water in the boiler is 160 lbs. by gauge, and its sensible temperature will be 370 degrees. Suppose then that enough steam is permitted to escape from the boiler to reduce the steam pressure to 140 lbs., and its temperature will be reduced to 361 degrees. But the water will remain at 270 degrees, and the result will be that it will pass into steam so rapidly that it will carry up the water and hold it in suspension among the steam. The water will pass with the steam into the engine cylinder, and the boiler will be said to "prime," "foam," or "work water." The same thing may happen if the water is heated very rapidly. Priming is wasteful because it rapidly empties the boiler of its water, and dangerous because it may cause the piston to knock out the cylinder head or cover. When the safety valve blows off, priming may be induced, especially if the engine is at work, because in this case the boiler is being forced, or, in other words, is making steam more rapidly than it is designed to do, and the passage of so large a body of steam through the water is apt to lift it. Muddy water will sometimes cause foaming or priming, as will also insufficient circulation of the water in the boiler or sometimes the presence of grease or oil. Priming may be detected from the discharge of water with the steam when the gauge cock is opened, the steam looking white and fluttering as it escapes, and also by violent motion of the water in the gauge glass, or by a thump or pound at the ends of the piston stroke. To stop priming, the steam from the boiler should be decreased by slackening the speed of the engine, or if necessary, by stopping it. The true water level can then be seen, and if there is too much water in the boiler some of it may be blown off, while if the quantity of water in the boiler will permit it, the feed may be put on. If the boiler has a surface blow-off cock, or a mechanical boiler cleaner, it is best to blow off from that, as it carries off the scum at the same time as relieving the boiler. To prevent priming, a steady and uniform rate of boiler feed, the use of pure water, a clean boiler, and steady firing are the best means, turning on the steam slowly so as not to violently disturb the water in the boiler. The engine as well as the boiler requires attention when the boiler primes. Thus the cylinder cocks should be opened to let out the water from the cylinder and prevent breakage of the cylinder cover. SCALE IN BOILERS.--The steam leaves behind it all the impurities that the water contained, and these impurities deposit in form of mud and scale, which must be got rid of because it causes a loss of fuel, and if allowed to get thick enough will cause the boiler to burn. The use of boiler compounds or scale preventatives may be resorted to with advantage, providing they are of a nature to suit the water, but mechanical cleaning must also be resorted to at periods determined by the nature of water. Boilers are cleaned in two ways--first, by blowing off the impurities before they have formed into scale; and second, by removing at certain intervals whatever scale has formed. Blowing down may be done in two ways--first, from the surface of the water by means of mechanical cleaners; and second, by blowing out from the bottom of the boiler. The first draws off the impurities as they are thrown to the surface, the second draws them off after they have become more condensed and sink to the bottom. How often a boiler should be blown down depends upon the kind of water fed to the boiler; where purifiers are used, less blowing down is obviously needed. It is best to blow off from the bottom of the boiler when no steam is being used, as during dinner time, letting the water blow down about a quarter of the glass, or from the upper to the middle gauge cock. As no steam is being used, the feed can then be put on to restore the quantity of water without reducing the temperature of the boiler so much. The feed should be gradual and the fire regulated to keep the steam pressure even. How often a boiler should be washed out and cleaned depends upon the quality of the water it uses, and varies from about once a week to once a month, according to whether bad and unpurified water or purified water is used. The first thing to do is to draw the fire, leaving the chimney damper open and closing all the other dampers so that as little cold air as possible can get into the boiler, while the heat can pass away up the chimney. Let the steam and water all remain in the boiler until there is a gauge pressure of about 5 lbs. in the boiler. Then open the blow-off cock and let out the water. If the water is blown off under a high pressure, then after the waste is all out the iron is hot enough to dry up the scale, making it hard and very difficult to remove. After all the water is blown off, take out all the mud plugs and the man-hole and hand-hole covers, and wash out the boiler under as much water pressure as can be had, directing the hose so to reach all parts of the boiler and tubes, and continuing the washing until the water leaves the boiler clean. Then with a wooden hoe on a piece of gas-pipe of small diameter for a handle, and small enough to pass through the hand-hole, draw all the loose scale to the hand-hole and remove it, letting the water run slowly, so as to carry the small pieces of scale towards the hand-hole as fast as the hoe disturbs it. Then get inside the boiler, and a few blows with a light ball-pened hammer will loosen the scale, and a steel scraper will remove more, which must be washed down and drawn out with a hoe. After the cleaning and scaling are complete, the engineer, with lamp in hand, should carefully examine the interior of the boiler and of the fire box, paying especial attention to the stays to see that they are not broken. The hammer test should also be applied. It consists of sounding the boiler by light blows given by a light ball-pened hand hammer, the sound indicating defective places. CHAPTER XXXVII.--THE STEAM ENGINE. The high pressure steam engine, in whatever form it exists, consists of a frame or bed plate carrying two distinct mechanisms, first, the driving or power-transmitting mechanism, and second, the valve gear or valve motion, and to these are added such other mechanisms as the nature of the duty the engine is to perform may require. The most prominent of these additional mechanisms is a governor for regulating the speed at which the engine is to run; nearly all steam engines require a governor in some form or other, while for electric lighting and some other purposes it constitutes the main feature in the design of the engine. In a locomotive the air brake and the sand box are elements not found in other engines. In a jet condensing engine, the condenser and injection water, or condensing water mechanism, is a part of the engine. In a surface condensing engine, the air pumps and circulating pumps are a part of the engine. In marine engines there are mechanisms for turning the engine around when no steam is up; for moving the reversing gear quickly, and for varying the point of cut off, and therefore the amount of expansion, and various other and minor mechanisms. [Illustration: Fig. 3293.] Referring now to the simplest form of high pressure stationary steam engine, such as represented in Figs. 3293, 3294, and 3295, its valve gear or valve motion consists of the eccentric and its strap, the eccentric rod, the valve rod guide A, the valve rod or valve spindle, and the valve _v_, these parts controlling the admission of steam to one side of the piston, and the exhaust from the other. The piston, piston rod, cross head, connecting rod, crank, crank shaft, main shaft or driving shaft, and the fly wheel constitute the driving or power-transmitting mechanism. The steam side of the piston is that against which the steam is pressing, as side S in Fig. 3295. The exhaust side, E, of the piston is that on which the steam is passing out or exhausting. The governor for a common D valve engine regulates the engine speed by varying the opening in the bore of the pipe through which the steam passes from the boiler to the steam chest, leaving a wider opening in proportion as the engine runs slower, and reducing the opening when the engine runs faster. Assuming the engine to be running at its slowest, or its load to be so great that a full supply of steam is required in order to keep the engine up to its proper speed, and the governor will be open at its widest, so that all the further action the governor can have is to reduce the steam pipe opening, and thus cause the pressure in the steam chest to be less than that in the steam pipe. This action is called wire-drawing the steam, and the governor is called a throttling governor. An engine bed or bed plate is a frame that is seated or bedded to its foundation along its whole length. An engine frame is seated to its foundations at two or more places, but not continuously throughout its length. THE CYLINDER. Cylinders are secured to the engine frames in three principal ways, as follows: by bolting them down to the bed plate; by bolting them to one end of the bed plate, so that they may expand and contract without springing the bed plate; and in vertical engines, by bolting them to the top of the frames. The bores of cylinders require to be parallel, so that the piston rings may fit to the bore without requiring to expand and contract in diameter at different parts of the stroke. Cylinders are designated for size by the diameter of the cylinder bore and the length of the stroke; thus, a 10 × 12 cylinder has a piston of ten inches diameter and 12 inches stroke. The wear of a cylinder bore is (if the engine is kept in proper line and the piston rings, or packing rings as they are sometimes termed, fit to the bore with an equal pressure throughout the stroke) greatest near the middle of the length and least at the ends of the stroke. But when the piston rings are set out by the steam pressure, and the point of cut off occurs early in the stroke, the wear may be greatest at the ends of the cylinder bore, because of the pressure of the steam diminishing during the expansion. The counterbore of a cylinder is a short length at each end of the cylinder, that is made of larger diameter than the rest of the bore, so that the piston head may travel completely over the working bore, and thus prevent the formation of a shoulder at each end of the cylinder. Such a shoulder forms when there is a part of the bore over which the piston does not pass. The length of the counterbore should exceed the amount of the taper on the connecting rod key, so that as the connecting rod length alters from the wear, the piston shall not strike the cylinder head. The clearance of a cylinder is the amount of space that exists between the face of the piston when it is at the end of its stroke and that of the valve when it covers the port, the piston being at the end of the stroke, and as this space exists at each end of the cylinder, the total clearance for a revolution is twice the above amount. The clearance at the crank end of the cylinder is reduced by the piston rod passing through it. The amount of clearance may be measured by the following method, which has been given by Professor John E. Sweet: [Illustration: Fig. 3294.] [Illustration: Fig. 3295.] See that the piston and valves are made tight, and the valves disconnected; arrange to fill the clearance spaces with water through the indicator holes, or holes drilled for the purpose. Turn the engine on the dead centre; make marks on the cross-head and guide that correspond; weigh a pail of water, and from it fill all the clearance space. Weigh the remaining water, so as to determine how much is used. Then weigh out exactly the same amount of water, turn the engine off the centre, pour in the second charge of water, and turn back until the water comes to the same point that it did in the first case. Make another mark on the cross-head, and the distance between these marks is exactly what you really wish to know; that is, it is just what piston travel equals the clearance. This gives the proportion that the clearance space bears to the space in the cylinder occupied by the steam at the end of the piston stroke. Thus, if it takes one pound of water to fill this space, and to admit the one pound of water the piston must be moved one inch, then the clearance bears the same relation to the capacity of the engine as one inch bears to the stroke of the piston. Thus, under these circumstances, in an engine of ten-inch stroke, it would be said the engine had ten per cent. clearance. When a cylinder is to be rebored, the boring bar should be set true or central to the circumference of the counterbore, so that the bore of the cylinder may be brought to its original position with reference to the bore of the stuffing box. Cylinders require lubricating, both to avoid friction and wear of the cylinder bore, as well as of the valve and valve seat. The amount of lubrication required depends upon the degree of tightness of the piston rings, upon the speed of the piston, upon the amount of pressure of the valve to its seat, and upon the method of operating the side valve. Cylinders with releasing valve gears require freely lubricating, because the closure of the valve depends upon the dash pot, and undue friction retards the closing motion. The less the movement of the valve at the moment of its release, the easier it is to move it, because the friction is less, and less lubrication is required. Cylinders are lubricated by automatic oilers placed on the steam pipe of the engine, the oil being distributed over the surfaces by the steam. Cylinder oilers sometimes have a pump to force the oil in, and in others the steam in the oiler condenses, and the water thus formed floats the oil over the top of a tube, or up to an orifice through which the oil gradually feeds as the condensation proceeds. In other oil feeders, the feed is regulated by increasing or diminishing the opening through which the steam passes from the cup to the steam pipe. Sight oil feeders are those in which there is a glass tube or body, in which the passage of the oil can be seen as it drops. Cylinder cocks are employed at each end of the cylinder to let out the water that condenses from the steam when admitted to a cold or partly cooled cylinder. The two cocks are usually connected together by a rod, so that both may operate together. Cylinder relief valves are valves at each end of the cylinder to relieve the cylinder from the charges of water that sometimes enter from the boiler with the live steam. Steam ports give a quicker admission in proportion as their length is increased, and this reduces the amount of valve travel, and are sometimes given a length equal to the diameter of the cylinder bore. The bottoms of the steam ports are sometimes so placed as to be below the level of the cylinder bore, so as to drain off the water of condensation of the steam. Rule to find the required area of steam port. Multiply the area in square inches of the piston, by the number opposite to the given piston speed in the following table: Speed of piston in Number by which to feet per minute. multiply the piston area. 100 0.02 200 0.04 300 0.06 400 0.07 500 0.09 600 0.1 700 0.12 800 0.14 900 0.15 1,000 0.17 The cylinder exhaust port must be open when the valve is at the end of its travel, to an amount equal to the width of the steam port, but what this width will be in any given case depends upon the width of the bridges, the amount of the steam lap and the travel of the valve, as will be explained with reference to the slide valve. Jacketed cylinders are those in which there is a space around the cylinder that is filled with live steam. The object of jacketing is to prevent the loss of heat from the steam within the cylinder by radiation. The steam in the jacket should be received direct from the boiler, and should not be drawn from the jacket into the steam chest because the jacket reduces its temperature and condenses it. The water of condensation of a steam jacket should not be allowed to accumulate in any part of the jacket, but should drain off and pass back to the boiler. To render the jacket as effective as possible, it should extend from end to end of the cylinder, the exhaust steam pipe leading directly away, so as to have as little communication with both the cylinder and the jacket as possible. The jacket should have open communication with the boiler at all times, so as to have the pressure in the jacket at the same pressure as that in the steam chest, while the cylinder being kept hot, it will be unnecessary to blow steam through in order to warm the cylinder when starting the engine. The steam should enter the jacket at the highest point, so as to prevent the accumulation of air in the jacket. Or, if the steam is admitted at some other point, it should be so arranged as to permit its thorough circulation in the jacket. When a jacket is used, the metal of the cylinder body should be as thin as possible, because the transmission of heat through the metal is, both in time and quantity, inversely as the distance or thickness passed through. The steam in the jacket should be as dry as possible, so that all wet steam admitted during the live steam period may be evaporated by the heat received from the steam in the jacket. The outside of the jacket should be thoroughly protected from cooling by being lagged or clothed with felt or some other material that is a non-conductor of heat. From experiments made by Mr. Charles A. Smith, of St. Louis, it was found that the amount of variation of temperature that occurred during the stroke in a locomotive cylinder was inversely proportional to the speed of engine revolution, which shows the advantages of jacketing cylinders and of lagging them, as well as the advantage of a high rotative speed. A lagged cylinder is one clothed, which is sometimes done with wood or metal strips, leaving an air space around the cylinder, while in others this space is filled with felt or some non-conducting material. Experiments made by Charles E. Emery gave the following general results: The thickness of the pipes and of the non-conducting materials was kept constant. Hair felt was the best non-conducting material of all those tested, and the value of a thickness of two inches of hair felt was taken as unity and the maximum. The value of two inches of mineral wool as a non-conductor was 0.832 of hair felt; two inches of mineral wool and tar was 0.715. Two inches of sawdust, 0.68; two inches of a cheaper grade of mineral wool, 0.676; charcoal, 0.632; two inches of pine wood, across the grain, 0.553; two inches of loam, 0.55. This was from the Jersey flats, and almost all vegetable fibre not yet become compact. Slaked lime from the gas works, expressed decimally, with hair felt as unity, 0.48; coal ashes, 0.345; coke, only 0.277, the same as used for fuel; two inches of air space, only 0.136, which dashes a great many people's hopes, and is as interesting as any part of the data; two inches of asbestos, 0.363; two inches of Western coke, about the same as the other coke; two inches of gas house charcoal, 0.47. These are very interesting, particularly so this matter of an air space. It has been supposed that an air space around a pipe is as good as anything we can have. The fact is, convection or circulation takes place; the air is cooled on one side of the space, descends, and rises on the other, and it is necessary to break up the air space, and that undoubtedly accounts for the efficiency of these different materials. It is the air probably that is the non-conductor; but it should be kept quiescent instead of being allowed to circulate. The air space itself is of very little value until the circulation is prevented. THE PISTON. In calculating the power of an engine it is the piston speed that is taken into account, and not the length of the stroke, the latter being used merely in order to obtain the piston speed. Long strokes are usually employed upon engines running at moderate piston speeds, as from 300 to 500 feet per minute, and short strokes for piston speeds from 400 to 800 feet per minute. The Porter Allen engine has been run noiselessly at 1,100 feet per minute. In determining the stroke of an engine the nature of the valve-operating mechanism is taken into account. In releasing mechanisms, or those in which connection between the eccentric rod and valve spindle is broken in order to permit the valve to close quickly, too high a speed of revolution may cause the tripping mechanism to fail to act, hence a high piston speed is obtained by means of employing a comparatively long stroke. In positive valve gears, or those in which the valve is controlled throughout the whole of its movement by the eccentric, the valve mechanism may operate quicker without danger of missing, hence the piston speed may be greater. When the stroke equals the diameter of the cylinder bore, the cylinder presents the least amount of exposed surface in proportion to its cubical contents. To obtain the same amount of expansion in a short as in a long stroke engine, the steam must be expanded through an equal proportion of the stroke; thus, if the steam is cut off at half stroke in both cases, the amount of this expansion will be equal. Pistons are made an easy fit to the cylinder bore, a steam-tight fit between the two being obtained by means of the piston rings. Solid pistons are provided with snap piston rings. A snap piston ring is one that is larger in diameter than the cylinder bore, and is closed in to get it into the cylinder, while it depends on its own spring outwards for its fit to the cylinder bore, having no supplementary rings or springs to force it out. Piston rings that are expanded by supplementary springs should be tapering in thickness, the thickest part being opposite to the split, and the thinnest at the split. This causes the ring to conform itself to the cylinder bore, and makes it sit more evenly around its whole circumference. These rings are made larger in diameter than the cylinder bore, in proportion of about 1/8 inch per foot of diameter, the split being closed when the ring is sprung into place in the cylinder. But if made of brass, the split must be left open enough to allow for the expansion, or otherwise the ring expanding more than the cylinder will seize and cut single. The split of a piston ring should be placed on the bottom of the piston (in a horizontal engine), so that the piston head, in resting on the cylinder bore, will cover up the opening of the ring. When two or more rings are employed, the splits may be placed on the lower half of the cylinder, so as to cover up their splits as much as possible. The follower of a piston is a plate or cover that is employed to hold the piston rings in place, and the piston rings should be so fitted that the follower should be bolted firmly up, or otherwise the bolts may come loose and work out, and getting between the piston and the cylinder cover, may cause the piston to knock the cylinder cover out. Piston followers are necessary when the rings are set out by springs or other parts adjustable within the piston head. Snap piston rings, however, permit the use of a solid piston, dispensing with the need for a follower. The effectiveness of a piston ring may be tested, when the construction of the engine will permit it, by disconnecting the valve for the head end, setting it so that it covers the port, and then taking off the cylinder cover at the head end and admitting steam through the crank end steam port, when any leak in the piston rings will be seen by the escape of the steam. THE PISTON ROD. Piston rods should be of slightly diminishing diameter at the ends, so that the wear shall not leave a shoulder at each end of the rod. In determining the diameter of the piston rod, allowance is made for turning it occasionally in the lathe to restore its parallelism, the wear reducing its diameter more in the middle than at the ends. The diameter of a piston rod is found in practice to range between one-sixth and one-tenth the diameter of the cylinder bore. Steel piston rods wear better than those of wrought iron, being free from scaly seams which are apt to cut the packing and cause the rod to wear in grooves. The best method of securing a piston rod to a piston head and to the cross head is by a taper seat and a key, so that no nut is needed, and the cylinder cover need not have a recess to receive the nut when the piston is at the end of the stroke, and the amount of clearance is correspondingly reduced. Piston head key ways are sometimes given so little clearance that the key completely fills the keyway when driven fully home. This prevents the edges of the keys from bulging into the clearance space in the keyway, which action is apt to cause the key to loosen in time. The key should have a safety pin at its small end. When piston rods are threaded into the cross head, or into the piston, the threads are made an easy fit, and taper seats or split hubs secured by clamping screws are relied upon to keep the rod true to the cross head or piston, it being found that the screw alone cannot be relied upon for this purpose. PISTON ROD PACKING. Piston rod packing, of fibrous or similar material, should be cut in rings that will not quite fully envelop the piston rod, and the first ring should be placed with its split upwards. After two or three rings have been inserted, each having its split at a different part of the bore, so as to "break joints," the gland should be screwed up enough so as to carry the packing home to the back of the stuffing box. This process should be continued until the stuffing box is filled for about two-thirds of its depth, when the gland may be screwed home. The gland should be screwed up quite evenly, so that the packing in the stuffing box shall be compressed equally all around the rod, and will not cause the gland to bind on the rod or in the stuffing box bore. The wrench should be applied first to one nut, giving it a turn or two, and then to the other, and after the gland is firmly home the nuts should be eased back about two turns. When a gland requires packing, it is proper to take out all the old packing that has become hard and set. A leak in piston rod packing may sometimes be remedied by taking out three or four rings of the packing and reversing it. If the packing is tightened up while the engine is running, it should be done very gently and evenly, as a very little screwing up may stop the leak, while excessive screwing produces undue friction. Piston rods are in some of the most advanced practice packed with metallic packing, or packing composed of soft metal. In some forms of metallic packing the construction is such that the gland and packing do not attempt to restrain the line of motion of the piston rod, this duty being left to the guide blocks and guide bars, where it properly belongs. THE CROSS HEAD. In engines having Corliss frames, the cross head is provided with shoes and adjusting screws, to take up the wear. When guide bars are shaped thus __|¯¯ the cross head is provided with gibs (usually of brass composition) to take up the wear. In either case care must be taken to make the adjustment correct, and thus keep the piston rod in line. The shoes or gibs should not bear hard upon the guides, but be an easy sliding fit without lost motion. Cross head pins should be kept eased away on the two parts of their circumference which are within the connecting rod brasses or boxes and near the joint faces of the same. This is necessary because the wear is greatest on the crowns of the boxes, and the pins are apt to wear oval. In some engines, the surface of the pin is cut away, but if it is not, and the pin can be revolved in the cross head, it is a good plan to give it half a turn occasionally, which will keep it round. THE GUIDE BARS. The guide bars of an engine require to be set exactly in line with the axis of the cylinder bore, so that they may guide the piston to travel in a straight line. They should be an easy sliding fit to the cross-head guide. The top bar is more difficult to lubricate than the bottom one, especially when it receives the most pressure, as is the case when the top of the fly-wheel runs towards the cylinder. Cast iron guide bars wear better than either brass, iron, or steel ones, so long as they are properly lubricated. The face of each guide bar should be cut away, so that the ends of the cross head guides will travel past it. This will prevent a shoulder forming at the ends of the bar as the face wears away. Such shoulders are apt to cause a knock as the connecting rods are lined up, because in the lining the connecting rod is restored to its original length, and the path of the cross-head guides along the bars may be altered. THE CONNECTING ROD. There are two principal kinds of connecting rods, the "strap ended" and the "solid ended." The solid ended wear the best, but are more difficult to get on and off the engine. Connecting rod straps are secured to the stub ends (as the ends of the rod are called), either by bolts or by one or two gibs, and the brasses are set up by a taper key or wedge. The taper for connecting rod keys is about an inch per foot. The angularity of a connecting rod is a term that applies to its path of motion, which is (during all parts of the stroke except on the dead centre) at an angle to the line of engine centres. The effect of this angularity is to cause the piston motion to be accelerated at one part of the stroke and retarded at another, thus causing the point of cut-off to occur at different points of the two strokes. The direction of the variation is to cause the point of cut-off to occur later on the stroke when the piston is moving from the head end of the cylinder towards the crank. The amount of variation caused in the two points of cut off by the connecting rod depends upon the proportion that exists between the length of the crank and that of the connecting rod, and is less in proportion as the length of the connecting rod is greater than that of the crank. An ordinary length of connecting rod is six times the length of the crank, or _six cranks_, as it is commonly termed. Fig. 3296 represents a cylinder, piston and rod, cross head, connecting rod, and crank. The piston _b_ is shown in the middle of the cylinder, the cross head at E, and the crank pin at B, instead of being at G´, as it would but for the connecting rod, or if the connecting rod was infinitely long. Now take a pair of compasses and set it from _b_ to E, and then try it from _a_ to D, and from _c_ to F, and it will be seen that the three cross head positions D, E, and F correspond correctly to the three piston positions _a_, _b_, _c_. Then take a pair of compasses and set them to the length of the connecting rod (from E to B) and try them from D to A, from B to E, and from C to F, and it will be seen that crank pin positions A, B, and C correspond to cross head positions D, E and F, and therefore that the crank is not at half stroke when the piston is in the middle of the cylinder. Take these same compasses, and resting one point at (G´) mark the arc H, and that is where the cross head would be when the crank was at (G´). Now then we see that the connecting rod causes the piston to move slower while running from _a_ to _b_ than it does while running from _b_ to _c_. [Illustration: Fig. 3296.] THE D SLIDE VALVE. The various events which are governed by the D slide valve of a steam engine are as follows: The live steam period is that during which the steam is admitted from the steam chest into the cylinder and the steam admitted during this period is termed _live_ steam. The point of cut off is that at which the valve closes the steam port, and the admission of steam into the cylinder is stopped, hence the point of cut off is at the end of the live steam period. The period of expansion is that during which the steam is allowed to expand in the cylinder, and therefore begins at the point of cut off, and ends at the point of release. The point of release is that at which the valve opens the port and permits the steam to escape. The point of compression is that at which the exhaust port is closed, which occurs before the piston has reached the end of its stroke; the steam that has not passed out of the cylinder is therefore compressed, the compression continuing until the valve opens for the lead. The lead of the valve is the amount the port is open to the live steam when the crank is on the dead centre. The point of admission is that at which the port opens for the live steam to enter, and it follows that the lead and compression both act as a cushion, arresting the motion of the piston when it reaches the end of the stroke. Cushioning begins, however, at the time the exhaust port is closed enough to arrest the escape of the steam, while compression begins when the valve has closed the exhaust port. [Illustration: Fig. 3297.] The construction of a common slide valve is shown in Fig. 3297, in which the valve is shown in its mid-position. P P are the cylinder steam ports (as the openings through which the steam passes from the steam chest to the cylinder are termed), and at X is the cylinder exhaust port, through which the steam escapes from the cylinder. Z is the valve exhaust port or exhaust cavity. The lip of a valve is the width of its flange face, or the distance L, which is measured from the steam edge A to the exhaust cavity Z. At the other end of the valve, H is the lip extending from the steam edge B to the exhaust cavity. Steam lap is the distance the steam ends (or the steam edges as they are called) A, B overlap the steam ports, this distance being shown on the ends of the valve at _a_ C. If the valve had no steam lap, its steam edges would just cover the ports, as denoted by the dimension W. Exhaust lap is the amount the exhaust cavity Z overlaps the bridges _q q´_, as at _p_, _r_. Unequal steam lap is given to cause the point of cut off to occur at equal points in the piston stroke; thus in the figure there is more steam lap at the head end than at the crank end of the valve. But unequal lap could also be given in order to greatly vary the points of cut off for the two piston strokes, if such was desired. Unequal exhaust lap may be given to equalize the point of release, or to equalize the points of compression. The head end of the valve (or of the cylinder) is that which is furthest from the crank shaft, the other end, or that nearest to the crank shaft, being termed the crank end. THE ACTION OF A COMMON SLIDE VALVE. The action of a common slide valve may be traced as follows: [Illustration: Fig. 3298. Port _a_, open to the amount of the lead.] [Illustration: Fig. 3299. Port _a_, full open for the admission.] [Illustration: Fig. 3300. Port _a_, closed off for cut.] [Illustration: Fig. 3301. Valve opening port _a_, for the exhaust.] [Illustration: Fig. 3302. Port _a_, full open for the exhaust.] Suppose the port _a_ to be at the head end of the cylinder and open to the amount of the lead with the crank on the corresponding dead centre, and if the valve travel be made equal to twice the lap and the lead, the various positions of the valve will be as marked in Figs. from 3298 to 3302; the event corresponding to each valve position being stated in the figures. DOUBLE PORTED VALVES. The term _port_ applies strictly to the area of opening of the steam passage where it emerges upon the valve seat. The term _steam passage_ includes the full length of the opening from the cylinder bore to the face upon which the valve is seated. A double ported steam port is one in which there are _two_ openings or steam ports, leading into _one steam passage_. A double ported valve is one in which there are two ports _at each end_ of the valve. These two ports in some cases admit steam to a single cylinder port, and in others to two steam ports, terminating in one steam passage. A griddle valve is one that has two or more ports at each end upon a seat that has two or more ports for each steam passage. Double ported valves are employed in some cases to increase the admission of live steam to the cylinder, and in others to increase the exhaust openings also. The effectiveness of a double ported valve is mainly valuable at the beginning of the stroke, and is especially valuable in cases when the travel of the valve is diminished to hasten the point of cut off, because in such cases the outer edges of the valve do not open the steam port to its full width, and a single port is apt to wire draw the steam. By the employment of more than one port, or several ports, a sufficient admission may be obtained with less valve travel. [Illustration: Fig. 3303.] The Allen double ported valve is one in which the second port increases the port opening for the admission only, as shown in Fig. 3303, in which the valve is moving in the direction of the arrow; the port K will receive steam through the opening at _g_, and from a port passing through the valve, the steam entering it as shown by the arrow. The second port forms part of the lap of the valve, and enables the travel to be short enough to be cut off at early points in the stroke, without employing so much steam lap as to widely distort the points of cut off, this latter being a defect of the D valve. Webb's patent slide valve is circular, and is so arranged as to be free to revolve in the hoop of the valve rod, the effect being that the valve moves around, or to and fro in the hoop, without any special mechanism to produce such movement, and the result is, that the valve and port facings wear smooth and even without any tendency to become grooved. BALANCED VALVES. A balanced valve is one in which means are employed to relieve the back of the valve of the steam pressure, and thus prevent its being forced to its seat with unnecessary pressure. In some of the most successful balanced valves this is accomplished by providing a cover plate, which may be set up to exclude the steam from the back of the valve which works (a sliding fit) between the valve face and the face of the cover plate. Such a method of balancing is sufficiently effective for all practical purposes, if the following conditions are observed: The valve rod must be accurately guided so as to avoid side strains; the valve must fit accurately to its seat and to the cover plate, and the adjustment so made that the valve slides freely at first, being steam tight, and yet allowing room for lubrication to enter. When the travel of a valve, balanced by a cover plate, is varied to alter the point of cut off, the construction must be such that the ends of the valve at the shortest stroke pass over the ends of the seat and cover plate faces, or otherwise the middle of the seat and cover plate faces will wear hollow. The Buckeye, Porter-Allen, and Straight-Line Engines are examples of practically balanced valves. The first of these has a balancing device that follows up the wear; the second has an adjustment whereby the cover plate may be set up to take up the wear; and in the third the wear is reduced to a minimum, by accurately fitting and guiding the parts. [Illustration: Fig. 3304.] The construction of the valve in the Straight-Line Engine is shown in Fig. 3304, in which B represents the cylinder bore; the valve _v_ rests on a parallel strip _n_, and on its top rests the parallel strip _m_, the pressure relieving plate P is set up firmly against the pieces _m_ _n_, whose thicknesses are such as to leave the valve a working fit between the faces of R R and of P. [Illustration: Fig. 3304 _a_.] Instead of the valve sliding on a flat face, it may work upon a shaft or spindle as a centre, its face moving in an arc of a circle, and its action will be the same as a flat valve having the same proportions. Fig. 3304_a_ represents a valve V of this construction, whose shaft is at S, A being an arm fast on S, and driven by the eccentric rod R. To find the necessary amount of travel for such a valve, we draw lines, as _f_, _g_, from the inner edges of the steam ports, through the centre of the shaft S, and also draw an arc through the centre of the eye of arm A, and where lines _f_ _g_ cut the arc, as at _d_ and _e_, are the extremes of motion of A. PISTON VALVES. [Illustration: Fig. 3305.] A piston valve acts the same as a flat or plain (D) valve, having the same amount of lap lead and travel. In Fig. 3305 we have a cylinder with a flat valve on one side and a piston valve on the other, the head end ports being about to take steam, and it is seen that the eccentrics occupy the same positions for the two valves. The steam ports are, for the piston valve, annular grooves provided in the bore in which the valve fits. The piston valve is balanced because it receives its steam pressure on the ends, but it will not follow up its wear as the flat valve does, hence it is liable to leak. SEPARATE CUT OFF VALVES. [Illustration: Fig. 3306.] Meyer's cut off valve is constructed as shown in Fig. 3306, M being the main valve, and _v_ _v_ the two cut off valves, whose sole duty is to cut off the steam at an earlier point than the main valve would do. If the engine is to have a fixed point of cut off, or, in other words, if the cut off is always to occur at some one particular point in the stroke, the valves may be set to do so, and equalize the points of cut off. Variable points of cut off with the Meyer's valve may be obtained by shifting the position of the eccentric that operates the cut off valve, but it is usually done by means of moving the valve by a right and left hand screw, such as shown in Fig. 3306. The cut off eccentric is set ahead of the main eccentric, so that the cut off valve will close the ports before the main valve would do so; thus, in the figure the cut off valve is shown to have effected the cut off for port _a_ by the time the main valve has fully opened port _a_, and is reversing its motion. If the engine requires to reverse its motion, the cut off eccentric is set exactly opposite to the crank, but otherwise, it may be set 8 or 10 degrees either ahead of or behind the crank, but if set too little ahead of the crank, the port may reopen after the cut off has been effected. [Illustration: Fig. 3307.] Gonzenback's cut off valve is constructed as in Fig. 3307, the steam chest having two compartments. A, A are the cylinder steam ports, C the main valve, and E the cut off valve, whose ports (as G) are made wider than the ports F. Reducing the travel delays the point of cut off in the Gonzenback valve, whereas in the common slide valve it gives an earlier cut off. THE ECCENTRIC. When a single eccentric is used, it is simply termed _the_ eccentric. If a cut off valve (or two cut off valves) are used upon the engine, then the eccentric that works the main valve is called the main eccentric, while that which works the cut off valve or valves is called the cut off eccentric. The main valve is that which works on the cylinder face; the cut off valve is that which effects the cut off. A shifting eccentric is one that is _moved across_ the shaft so as to alter its amount of throw, and, therefore, the amount of valve travel, the effect being to vary the point of cut off. In engines where a constant amount of lead is given, or in other words, when the eccentric position is intended to be fixed, the eccentric should be secured to the crank shaft by a feather or key sunk into the crank shaft so as to prevent the eccentric from moving, while enabling it to be taken off and replaced without requiring any operations to adjust its position with relation to the crank. The feather should fit tight on the sides, as well as on the top and bottom, and may have a slight taper on the sides, which will make it easier to fit the featherway or keyway to the feather, and easier to put the eccentric on or take it off. By this means the eccentric cannot shift, and may be replaced after being taken off without having to set the whole valve motion over again. When the amount of valve lead or of compression is varied to suit the speed at which the engine is to run, or to aid the counterbalancing of the engine, a feather cannot be used because it will not permit the eccentric to be moved to effect the adjustment. Set screws possess disadvantages, inasmuch as that the point of the set screw may leave an indentation, which, if the eccentric is moved a trifle, may cause the set screw point to fall back into the old indentation, thus rendering it difficult to make a small adjustment of eccentric position. [Illustration: Fig. 3308.] An eccentric is the exact equivalent of a crank having the same amount of throw, as may be seen from Fig. 3308, in which the outer dotted circle represents the path of the crank and the inner one the path of the centre of the eccentric. A small crank is marked in, having the same throw as the eccentric has, and the motion given by this small crank is precisely the same as that given by the eccentric whose outer circumference is denoted by the full circle. Considering the motion of both the crank and the eccentric, therefore, we may treat them precisely the same as two levers, placed a certain distance apart, revolving upon the same centre (the centre of the crank shaft), and represented by their throw-lines. [Illustration: Fig. 3309.] In Fig. 3309, let the full circle E E represent an eccentric upon a shaft whose centre is at C, and let the centre of the eccentric be at _e_. The path of revolution of the eccentric centre will be that of the dotted circle whose diameter is B, D. As the eccentric is in mid-position (_e_ being equidistant from B and D), the valve will be in mid-position as denoted by the full lines at the bottom of the figure. Now suppose the eccentric to be revolved on the centre C, until its centre moves from _e_ to V, its circumference being denoted by the dotted circle A A, and if we draw from V a vertical line cutting the line B, D at _f_, then from C to _f_ will be the distance the eccentric would move the valve, which would then be in the position denoted by the dotted lines at the bottom of the figure. It becomes clear then that if we suppose the eccentric to have moved from mid-position to any other position, we may find how much it will have moved the valve by first drawing a circle representing the path of the centre of the eccentric, next drawing a line (as B D) through its centre, and then drawing a vertical line as (C _e_) through its mid-position and also a vertical line from the eccentric centre in its new position, the distance between these two vertical lines (as distance C _f_ in the figure) being the amount the eccentric will have moved the valve. It may have been noticed that the diameter of the eccentric does not affect the case, the distance B D, or the diameter of the circle described by the centre of the eccentric, being that which determines the amount of valve motion in all cases. This being the case, we may use the circle representing the path of the eccentric centre for tracing out the valve movement without drawing the full eccentric, and the diameter of that circle will of course equal the full travel of the valve. [Illustration: Fig. 3310.] The position of an eccentric upon a shaft is often given in degrees of angle, which is very convenient in some cases. If a valve has no lap or lead, the eccentric will stand at a right angle or angle of 90 degrees when the crank is on the dead centre. The division of a circle into degrees may be explained as follows: Suppose we take a circle of any diameter whatever and divide its circumference into 360 equal divisions, then each of these divisions will be one degree. The number 360 has been taken as the standard, and this being the case, there are 360 degrees in a circle, in a quarter of a circle there will therefore be 90 degrees, because 90 is one quarter of 360. By means of dividing a circle in degrees therefore we have a means of measuring or defining any required portion of it. In Fig. 3310 the degrees of a circle are applied for defining the relative positions of a crank and an eccentric. As the zero position of the crank is on a dead centre, it is so placed in the figure, while as the zero position of the eccentric (which is for a valve having no steam lap) is at 90 degrees from the crank, therefore the dotted circle representing the path of the eccentric centre has its O or zero point at 90 degrees from the crank. Now suppose the eccentric centre stood at _v_ and the eccentric throw line at _c_ _v_, and it will stand at 30 degrees from O, hence the angular advance of the eccentric is in this case 30 degrees, or in other words, it is 30 degrees in advance of its zero position, or the position it would occupy when the crank is on the dead centre and the valve has no lap and no lead. If we measure the distance apart of the crank and the eccentric in degrees, we find it is 120 degrees, hence place the crank where we may, we can find the corresponding eccentric position because it is 120 degrees ahead of the crank. The sign for degrees is a small ° placed at the right hand of the figures and slightly above them; thus, thirty degrees would be written 30°. FINDING THE WORKING RESULTS GIVEN BY A D SLIDE VALVE. Although not strictly within the line of duty of an engineer or engine driver, he is nevertheless sometimes called upon to find out how a valve of given proportions will dispose of the steam, or what proportions to give to a valve to accomplish certain results. This is easy enough when either the travel of the valve or the amount of the lap and the width of the port are given, but if the width of the port alone is given, and all the other elements are to be found, it becomes a more difficult problem. An engineer, however, is rarely called upon to solve the question from this stand-point, which properly belongs to the draughtsman or engine designer. If the amount of valve travel is given, however, all the other elements may readily be found by the following construction: [Illustration: Fig. 3311.] Suppose that in Fig. 3311 a D valve is to be designed to cut off the steam when the piston has travelled from position B´ to R´, or at three-quarters of its stroke. Then to find the position the crank pin will be in when the cut off occurs, we draw a circle, B D, representing the path of the crank on the same scale that the length of the piston stroke is represented. The straight line from B to D will, therefore, represent the piston stroke without drawing the piston or cylinder at all (this being done in the figure to make the explanation clear). When the crank is on its dead centre, B, the piston, will be at B´, and the valve in the position shown (supposing it to have no lead). As soon as the crank and valves begin to move, the steam will enter steam port _a_, and to find where the crank will be when the piston is at three-quarters stroke, and is, therefore, in position R´, we mark a point at R three-quarters of the distance from B to D. Then, taking no account of the length of the connecting rod, we draw a vertical line Y from R to the circle, and this line gives at H the position the crank will be in when the piston is at R. We have so far, therefore, that while the piston travels from B´ to R´, the crank will travel from B to H. Now, it will be found that if we set a pair of compasses from B to F, which is half-way from B to H, and then rest the compasses at D, and mark an arc V, then a line from V to the centre of the crank will give us the proper position of the eccentric. As the centre of the crank pin and also the centre of the eccentric both travel in a circle, we may, therefore, take a circle having a diameter equal to twice the throw of the eccentric, (or, what is the same thing, equal to the full travel of the valve), and let it represent the paths of both the eccentric centre and the crank pin centre, the latter being drawn to a scale that is found by dividing the length of the piston stroke by the travel of the valve; thus, if the travel is 3 inches and the stroke 30 inches, the diameter of a 3 inch circle will represent the valve travel full size, and the piston stroke one-tenth full size, because 30 ÷ 3 = 10. It has been shown on page 376 that the length of the connecting rod affects the motion of the piston by distorting it, and it is necessary to take this into account in constructing the actual diagram, which may be done as follows: The valve travel and point of cut off being given, to find the required amount of lap, there being no lead, draw a circle equal in diameter to the travel of the valve, and draw the line of centres B D, Fig. 3312; mark on the line of centres a point R, representing the position the piston is to be in at the time the cut off is to take place. Set a pair of compasses to represent the length of the connecting rod on the same scale as the circle B D represents the path of the crank; thus, if the connecting rod is three times the length of the stroke, the compasses would be set to three times the diameter of the circle B D. [Illustration: Fig. 3312.] A straight line from B to D and passing through the centre C of the crank will represent the line of centres of the engine, which must be prolonged to the right sufficiently to rest the compasses on it and draw the arc Y, which will give at H the position of the crank when the piston is at R, and the cut off is to occur. We have thus found that the amount of circular path the crank will move through from the dead centre to the point of cut off is from B to H, and as the eccentric is fast upon the same shaft, it will, in the same time, of course, move through the same part of a circle. One half of its motion will be to open and one half to close the port, so that we may by means of the arcs at F get the point F, which is midway between B and H, and with the compasses set from B to F, mark from D the two arcs V and V´ whose distance apart will obviously be the same as from B to H. Then from V to V´ draw the line P, and from this line to the centre C of the crank shaft is the amount of steam lap necessary for the valve, while from this line (P) to D is the width of the steam port. The proof of the diagram is as follows: When the crank is on the dead centre, the centre of the eccentric is at V, its throw line being represented by the line from V to C, and the valve is about to open the port as shown in the figure. While the eccentric is moving from V to D, the valve will move in the direction of the arrow and will fully open the port, while the crank pin will move from B to F. Then, while the crank moves from F to H, the eccentric will have moved the valve to the position it occupies in the figure, having closed the port and effected the cut off. We have here found the amount of lap and the position of the eccentric necessary for a given point of cut off when the latter is given in terms of the piston stroke. If, however, the point of cut off had been given in terms of the crank pin position, we might find the required amount of lap at once, by simply drawing a line from the centre B, the point to H where the crank pin is to be when the cut off occurs. From this line we could then draw the dotted circle G, and just meeting the line P, which would give the eccentric position. To find the piston position, the arc Y would require to be drawn by the same means as before. [Illustration: Fig. 3313.] [Illustration: Fig. 3314.] If the valve is to have lead, the diagram may be constructed as in Fig. 3313, in which the circle has a diameter equal to the travel of the valve and the cut off is to occur when the piston is at R and the crank at H. When the valve is at the end of its travel and has fully opened the port, the eccentric will be at D, hence from D we mark an arc G distant from D to an amount equal to the width of the steam port, drop the vertical _m_ from G, and at its lower end V´ is the position of the eccentric centre at the point of cut off. Then draw a line P, distant from _m_ equal to the lead, which will give at V the position of the eccentric when the crank is on the dead centre, and the valve is open to the amount of the lead. The lap is obviously the distance from the centre C of the crank shaft to the arc G. We have here found all the points necessary except the point at which the valve will open the port for the lead, and this we may find by setting a pair of compasses to the radius B H (or to radius V V´, as both these radii are equal), and from V as a centre, mark at A an arc, which will give the crank pin position at the time the port first opens for the lead, or in other words it will give the position. The proof of the construction is, that if we set the compasses to the distance between the crank pin position on the dead centre and the point of cut off (or from B to H), we may apply the compasses to the points V, V´, which represent the eccentric position when the port is opened to the amount of the lead, and when the cut off occurs. If the point of cut off only is to be found, we mark from C, Fig. 3314, an arc G representing the amount of valve lap and arc S representing the lead. A vertical P gives the eccentric position V when the crank is on the dead centre at B, and a vertical _m_ from G gives at V´ the eccentric position at the point of cut off. Then with the compasses set to the points V V´, we may mark from B an arc, locating at H the position of the crank at the point of cut off, and from this with compasses set to represent the length of the connecting rod on the same scale as the circle represents the path of the crank, we may, from a point on the line of centres, mark an arc Y giving at R the piston position at the point of cut off. When, therefore, the lap is given, we mark it from the center C of the crank shaft, and find the other elements from it, whereas, when the lap is to be found, we mark the width of the port from the end D of the valve travel, and find the other elements from that. A proof of all the constructions is given in Fig. 3314, in which the letters of reference correspond to those in the previous figures, and the positions of the parts are marked in degrees of angle. To find the piston position at the point of cut off, measured in inches, of the piston stroke it must be borne in mind that as the circle B D represents the full travel of the valve, the diagram gives all the positions of the eccentric and valve full size, but that as it represents the crank path on a reduced scale, therefore we must multiply the measurement on the diagram by that scale. Suppose, for example, that the piston stroke is 10 inches, and the valve travel 2-1/2 inches, and the circle being 2-1/2 inches in diameter, is, when considered with relation to the eccentric motion, full size, but when considered with relation to the piston or crank motion, it is only 1/4 the size, hence to find the piston position at the time of cut off, we must multiply the distance from B to R by 4. [Illustration: Fig. 3315.] LINK MOTION FOR STATIONARY ENGINES. The ordinary mechanism employed to enable a stationary engine to be reversed or run in either direction is the Stephenson link motion. Other forms of link motion have been devised, but the Stephenson form has become almost universal. [Illustration: Fig. 3316.] Fig. 3315 represents this link motion or reversing gear with the parts in position for the full gear of the forward motion, and Fig. 3316 represents it in full gear for the backward motion. The meaning of the term full gear is that the parts are in the position in which the steam follows the piston throughout the longest or greatest part of the stroke. When in full gear the link motion operates the valve almost precisely the same as if the eccentric rod was attached direct to the valve spindle and no link motion was used. Besides enabling the engine to run in both directions, however, the link motion provides a means of reducing the amount of valve travel and thus causes the live steam to be cut off earlier in the piston stroke, thus using the steam more expansively. This is done by moving the reversing lever more upright, the earliest point of cut off being obtained when it is upright and the latch is in the notch marked O on the sector in Fig. 3315. If with the engine standing still we move the link motion from full gear forward to full gear backward and watch the valve, we shall find that the valve lead increases as the reversing lever approaches the upright position, or mid gear as it is termed, and that after passing that point it gradually diminishes again, the valve being so set that the lead is the same for full gear forward as it is for full gear backward. The reversing lever is used to move the link into the required position and to hold it there (the end of the latch fitting into the notches in the sector being the detaining or locking device); as the link is suspended by its saddle pin S and the link hanger, therefore its motion is to swing or partly rotate on the pin S, and at the same time ending in the arc of a circle whose centre of motion is in the pin at the upper end of the link hanger which is pivoted to the lower arm of the lifting shaft (which is sometimes termed the tumbling shaft). It will clearly be seen that with the position the parts occupy in Fig. 3315, and the crank motion being in the direction of the arrow, the forward eccentric will move the top of the link to the right and therefore the valve will move to the right, while the backward eccentric will move the bottom end of the link to the left. In full gear, however, the bottom eccentric rod has but a very slight effect indeed on the motion of the valve because both the link hanger and the link block will permit the link to swing on centre of the link block pin as a pivot. If now we turn to Fig. 3316 for the full gear backward, we shall see that these conditions are reversed and the backward eccentric becomes the effective one, being in line with the valve spindle. By shifting the link from one gear to the other, therefore, we have merely changed the direction in which the link will move the valve, and, therefore, the direction in which the engine would run. In Fig. 3315 for the full gear the parts are shown in position, with the piston at the crank end of the cylinder, and the crank pin on the dead centre, and the eccentrics must be set as shown in the cut, the eccentric rods being open and not crossed. When, however, the crank is on the other dead centre and the piston at the head end of the cylinder, the rods will cross each other, and it is necessary to remember that the rods should be open when the piston is at the crank end of the cylinder. If, however, the running gear contains a rock shaft, or rocker (as is the case in American locomotives), then these conditions are reversed, and the eccentric rods will cross when the piston is at the crank end of the cylinder. In setting the slide valve of an engine having a link motion, there are two distinct operations. First, to put the crank on the respective dead centres, which will be fully described on page 394 and need not be repeated; and second, to set the eccentrics in their proper positions on the shaft, and correct, if necessary, the lengths of the eccentric rods. The crank being on the dead centre, with the piston at crank end of the cylinder, the eccentric should be moved around on the shaft by hand until there is the desired amount of lead at the crank end port, and temporarily fastened there, a set screw usually being provided (in the eccentric) for this purpose. The lead is best measured with a wedge, W, Fig. 3315. The crank is then put on its other dead centre, and the lead for the head end port is measured. If the lead is to be made equal for the two ports (as is usually the case in horizontal engines) and it is found to come so, the valve setting for the forward gear is complete. If the lead is not equal, the forward eccentric rod or else the valve spindle must be altered so as to make the lead equal. In some engines adjusting screws are provided for the purpose of regulating the length of either the eccentric rod or else of the slide spindle; it does not matter which is altered. The link motion is then put in full gear for the backward motion, and, with the crank on the dead centre (it does not matter which dead centre), the eccentric is moved by hand upon the crank shaft until there is the required amount of valve lead. The eccentric is then fastened on the shaft and the crank put on the other dead centre, and the lead tried for the other port, and made equal by lengthening or shortening the backward eccentric rod. It is to be noted that altering the length of the eccentric rod or of the valve spindle makes it necessary to reset the eccentric, as it affects the amount of lead at both ports; hence, if any alteration of rod length is made, the whole process here described must be repeated after each alteration of rod length. FLY BALL OR THROTTLING GOVERNORS. An isochronal governor is one in which the two opposing forces are equal throughout the whole range of governor action, or, in other words, equal, let the vertical height of the plane in which the balls revolve or swing be what it may. A dancing governor is one that acts spasmodically. Such an action may occur from undue friction in the parts of the governor or of its throttle valve. The friction offers a greater resistance to starting the parts in motion than it does to keep them in motion after being started; hence, the parts are apt to remain at rest too long, and to move too far after being put in motion. Rule to find the number of revolutions a governor should make. Divide the constant number 375.36 by twice the square root of the height of the cone in inches. The quotient is the proper number of revolutions per minute. _Example._--A governor with arms 30-1/2 inches long, measuring from the centre of suspension to the centre of the ball, revolves, in the mean position of the arms, at an angle of about thirty degrees with a vertical spindle forming a cone of about 26-1/2 inches high. At what number of revolutions per minute should this governor be driven? Here the height of the cone being 26.5 inches, the square root of which is 5.14 and twice the square root 10.28, we divide 375.36 by 10.28, which give us 36.5 as the proper number of revolutions per minute at which the governor should be driven. The construction of the Pickering governor is as follows: [Illustration: Figs. 3317, 3318.] In Fig. 3317 it is shown in its simplest form, and in Fig. 3318 with the driving pulley and speeder (or engine speed regulating device) attached. This speeder consists of a spiral spring whose tension may be adjusted to more or less resist the rise of the governor balls, and thus enable the engine to run at a greater speed for a given amount of rise of the governor balls, hence by increasing the tension the engine speed is increased. THE SPRING ADJUSTMENT. The adjustment of the spring tension is made by a worm actuating a worm wheel on a rod passing through the spring, and to which one end of the spring is attached, the other acting on an arm that projects into a slot in the governor spindle. It is obvious that the speeder can be adjusted while the engine is running. [Illustration: Fig. 3319.] In Fig. 3319 the governor is shown with the speeder and Sawyer's valve, the latter enabling the governor valve to be opened or closed without affecting the rise and fall of the governor balls, which is done by operating the arm shown on the right, whose ends are provided with loops, so that a cord may be attached, enabling the engineer to operate the governor from a distance. The safety stop or stop motion is shown on the right, Fig. 3320. It acts to close the governor valve and stop the engine in case the belt that drives the governor should get off the pulley or break. This stop motion consists of a pulley suspended by a rod, and riding on the belt which supports its weight. Should the governor belt break, this pulley falls and severs the connection between the valve and the governor, closing the valve, and holding it closed. Fig. 3321 shows the governor in section to expose the construction of the valve. The valve V is what is termed a poppet or poppet valve, which is balanced, because the steam entering at I, and taking the course denoted by the arrows, acts equally on both ends of the valve and does not press it in either direction, while as the steam surrounds the valve it is not pressed sideways. At B is a gland or stuffing box to keep the spindle or rod steam-tight. At A is the slot for receiving the arm from the speeder and from the stop motion. P is obviously the driving pulley, imparting motion to the bevel wheels G, which drive the outer spindle S, the inner spindle _s´_ being connected to A. The balls are upon ribbon springs D, which are secured at their lower ends to a link fast to the spindle S. The centrifugal force generated by the balls causes them to move outwards, their upper ends pulling down the cap to which they are secured, and this cap operates the valve. Governors of this class are sometimes termed _fly-ball_ governors. STARTING A PLAIN SLIDE-VALVE ENGINE. The method to be pursued before starting a plain slide-valve engine depends upon what the engineer knows about the condition of the engine. If he knows the engine is in proper running order, all that is necessary is to first attend to the oil cups and start them feeding. Then, if it is necessary, move the crank into the required position to start it easily; open the waste water cocks to relieve the cylinder of the water that will be condensed from the steam when it enters a cool cylinder, and turn on the steam; giving the throttle valve enough opening to start the engine slowly. The best position for the crank pin to be in to enable its starting easily is midway between the horizontal and vertical position (or, in other words, at an angle of 45° to the line of centres) and inclining toward the cylinder, so that when the engine moves the piston will travel toward the crank shaft. There are two reasons why this is the best position for starting. The first applies to all engines because there is a greater piston area for the steam to act on when the piston is moving toward the crank than there is when it is moving away from it. This occurs because the piston rod excludes the steam from a part of the face of the piston. The second applies to all plain slide-valve engines whose slide valves have equal laps and both steam ports of equal widths, because the live steam follows further on the stroke when the piston is moving toward the crank than it does when it is moving away from it, and it follows that more piston power is developed, and the engine is less likely to stop when passing the dead centre. [Illustration: Fig. 3320.] [Illustration: Fig. 3321.] When first taking charge of an engine, it is proper, before starting it, to ascertain that it is in fair working order. A complete examination of an engine should include a test of the fit of the piston to the cylinder bore, of the cross head to the guide bars, of the connecting rod brasses to the crank pin and cross head journals, and of the crank shaft to its bearings. It would also include a testing of the alignment of the crank shaft and of the guide bars, as well as the set of the valves and the adjustment of the governor. The least examination permissible with a due regard to safety would be to move the engine throughout at least one full revolution by hand, and to see that the connecting rod brasses and the main bearings do not fit too tight to their respective journals, and to then start the engine slowly by giving it only enough steam to move it, keeping the hand on the throttle valve so as to be able to shut off steam instantly should it become necessary. A thorough examination should be made in the following order: First, slightly loosen the nuts on the crank shaft bearings and also the connecting rod keys. Then move the fly wheel around until the crank points straight to the cylinder, which will bring the piston up to the outer end of the cylinder bore. Take off the cylinder cover and also the follower from the piston head, and see that the piston rings are set out to fit the cylinder bore but not to bind it tight. Then bolt the follower up firmly in place again. Take off the connecting rod and move the piston until it touches the cylinder cover at the other or crank end of the cylinder, and then draw a line across the side face of the cross head guide and on the guide itself. Put on the cylinder cover and push the piston back until it abuts against it, and then make another line on the cross head guide and the guide bar, and these two lines will show the extreme positions to which the piston can be moved when the connecting rod is disconnected. Next put on the connecting rod, carefully adjust the keys or wedges, so that the bores of the brasses fit easily to the crank pin and cross head pin, seeing that the oil holes are clear, and that oil will feed properly to the journals. In making this adjustment it is a good plan, if there is any end play of the brasses on the crank pin, to set up the key or wedge until the rod can just be moved by hand on the pin, by first pulling the rod to one end of the pin, and then pushing it to the other. In putting on the rod, it will be necessary to move the piston a trifle towards the crank. In making the adjustment of the crank pin fit to the rod brasses, it is a good plan to drive the key home until the brasses are known to bind the crank pin, and then mark a line across the side face of the key and fair with the top face of the connecting rod strap, to then slacken back the key enough to ease back the brasses to a proper fit, and then mark another line on the key. The first line will form a guide as to how much to slacken back the brasses to adjust the fit, and the second one will form a guide as to how much the key is moved when making a second adjustment, if one should be found necessary after the engine has been running. Similarly in adjusting the main bearing boxes to the crank shaft, either the nuts, or what are called leads, may be taken to adjust the fit. Leads are necessary when the joint faces of the brasses do not meet, but are left open so that the wear can be taken up while the engine is running. It is better, however, to let the brasses abut together, so that it may be known that the fit is correct when the nut is screwed firmly home. The method of taking a lead is as follows: The top brass is loosened, and between the joint faces of the brasses or boxes on each side of the shaft a piece of lead wire is inserted. For a shaft of, say, four inches in diameter, the lead wire will be about 7/16 inch in diameter, or for a 10 inch shaft the wire should be 1/8 inch in diameter, and should be as long as the brass. The nuts are then screwed firmly home, and the wire will be squeezed between the brasses and thus flattened on two opposite sides, the thickness showing how far the joint faces of the brasses are apart when the bore grips the journal. A liner, fit strip, distance piece, or shim (all these names meaning the same thing) is a strip of metal placed between the joint faces of the brasses to hold them the proper distance apart to make a working fit of the journal and brasses, when the latter are firmly bolted up. The fit of the top brass therefore depends upon the fit strip being of the proper thickness from end to end. Now the lead wire is the gauge for the thickness of the fit strip, the latter being made a trifle thicker than the flattened sides of the lead. If the lead is thicker one end than the other, or if one lead is thicker than the other, the fit strips must be made so, and the leads must be marked so that it may be known which way they were placed between the brasses so that the proper fit strip may be on the proper side of the brass, and the proper end towards the crank. Another method that is adopted in the case of large brasses is to screw down the nuts until the brasses bind the journal, and then make a mark on the nut and on the bolt thread. The nut is then slackened back as much as the judgment dictates, and a note made of how much this is, the marks forming a guide. As the wear takes place, and the nuts screw farther down, a new mark is made on the nut, so that it may always be known how much to screw up or unscrew the nut, to make a light adjustment. To avoid heating, it is a good plan to press some tallow into the bottom or in one corner of the oil cup, and then pour in the oil used for ordinary lubrication. So long as the bearing remains cool, the oil will feed and the tallow remain. If the bearing heats, the tallow will melt, and, having a heavier body, will give a more suitable lubrication. To find if the connecting rod is of the right length to give, as it should do, an equal amount of clearance (or space between the piston and the cylinder cover) at each end of the stroke, move the fly wheel a trifle in either direction, and then move it back until the crank is on the dead centre, and draw a line across the cross head guide and guide bar, and the distance between this line and that drawn when the connecting rod was disconnected, shows the amount of clearance at that end of the cylinder. Then move the crank pin over to its other dead centre, and mark a line across the cross head guide and the guide bar, and the distance between this line and that drawn before the connecting rod was put on will show the clearance at this end of the cylinder. If the clearance is not equal for the two ends, it should be made so by putting liners behind the connecting rod brasses so as to lengthen or shorten the connecting rod (according as the case may require), and equalize the clearance, while at the same time bringing the connecting rod keys up to their proper heights. To test the set of the valve, the steam-chest cover must be taken off, the crank placed alternately on each dead centre, and the lead measured for each port. An unequal or an equal degree of valve lead may be given by suitably altering the length of the eccentric rod, but when the lead is equal for the two ports, its amount must be regulated by moving the position of the eccentric upon the crank shaft. SQUARING A VALVE.--A method not uncommonly pursued in setting a valve is to what is called _square it_ before trying it. This squaring process consists in so adjusting the length of the eccentric rod that the valve travels an equal distance over or past the steam edge of each steam port; but since the valve does not, when set to give equal lead, travel equally past each port, therefore the work done in squaring a valve is all thrown away, and may result in altering the eccentric rod from its proper length to an improper one, necessitating that it be altered back again in order to set the lead right. The proper method is to adjust both the length of the rod and the position of the eccentric, by testing the lead at once, lengthening the eccentric rod to increase the lead at the crank end, or vice versa. Each alteration of eccentric position may render necessary an alteration of rod length, or vice versa, each alteration of rod length may render it necessary to alter the eccentric position, hence the lead should be tried at both ends of the cylinder after each alteration of either rod length or eccentric position. In vertical engines the weight of the crank shaft causes it to wear the bottom brass or part of the bearing box the most, thus lowering its position, while the eccentric straps and pins wear most in the same direction; hence the wear increases the lead at the head end of the cylinder when the latter is above the crank, and at the crank end when the crank is above the cylinder. When the cylinder is above the crank, the weight of the piston, cross head and connecting rod is counterbalanced at the end of the downward piston stroke by giving the crank end port more lead; but when the cylinder is below the crank, it is the head end port that must be given increased lead to prevent a pound or knock, or to allow for the wear downwards of the parts. After an engine is started, the pet cocks should (if they are not automatic) be closed as soon as dry steam issues, and if this cannot be seen, it may be assumed to occur after the engine has made about 20 revolutions. The parts that will then require particular attention are the crank pin, main bearings, cross head guides and the pump, if there is one. The former must be kept properly lubricated, so that they may not get hot and the cylinder lubricator (which is usually placed on the steam pipe) must be set to self feed properly. If the crank shaft bearings should begin to heat, loosen the cap bolts and lubricate more freely, or, if it is at hand, some melted tallow may be applied with the oil, as a heavier lubricant may stop the heating. The crank pin requires the most attention and is the most difficult to keep cool and to examine, because of its circular path rendering it difficult to feel it. This may be done, however, in two ways, first by standing at the end of the engine bed and gradually extending the hand, until the end of the rod meets it as it passes, and, second, by placing the hand on the connecting rod as near to the end of the guide bar as possible where its motion is diminished and moving the hand towards the crank pin, by which means the end of the crank pin may be approached gradually. If the end of the rod is hot, the engine speed should be reduced or the engine should be stopped so that the connecting rod key or wedge may be eased back and the oil feed made more copious. Then, after the engine has been stopped for the night, the brasses should be taken out and any rough surface, either on the brasses or on the pin, smoothed down with a file. Hot crank pins may occur from several causes, but by far the most common ones are from improper oiling, or from the engine being out of line. A heavier oil will often stop, or at least modify, the heating, but its cause should always be discovered and remedied. Engines that are used out of doors or are exposed to temperatures below the freezing point must be left so that steam leaks may not condense in any of the parts or pipes and burst them. Leaky throttle valves may, for example, cause water to accumulate in the steam chest and freeze, perhaps bursting the steam-chest cover. To prevent this let the engine stand with the crank just past the dead centre, so that the steam port will be open, and open the waste water cocks on the cylinder, and also on the steam chest if there is any. If the cylinder is jacketed all the drain cocks for the jacket should also be opened. A leaky check valve may cause the steam to condense in the pump and freeze it up solid or burst it or the pipes. To avoid this, open the pump pet cock. Open all the drain cocks on the heater and water pipes. If the water is left in the boiler all night it is liable to freeze. To prevent this leave a well banked fire. In extreme weather remember that on exposed engines the oil, if of such quality as sperm or lard oil, may freeze and prevent feeding until the bearings get hot and melt the oil. To prevent this use a lighter oil, as, for example, a mineral oil. Or, in case of freezing, melt the oil in the cups with a piece of wire made red hot while getting up steam in the morning. A good plan to prevent oil from freezing and yet have a good quality of oil is to mix two parts of lard oil with one part of kerosene. Portable engines should stand as nearly level as possible, so that the water will stand level above the tubes and crown sheet of the fire box. When feed water is drawn from a natural supply, as from a stream, the strainer at the end of the suction pipe should be clear of the bottom of the stream, where it is liable to be choked. When the exhaust steam is used to feed the boiler, do not open the valve that lets the exhaust steam into the feed-water tank until a little while after the engine has started, because the oil fed to the cylinder will otherwise pass into the feed tank and may cause priming. In engines having plunger pumps for feeding the boiler it is essential to keep the plunger properly packed, as a leak there impairs or stops the pump from acting. A gauge glass may be cleaned when the engine is cold by shutting off the cocks leading from the boiler and filling the glass with benzine, allowing it to stand two hours; the benzine must be let out at the bottom of the glass tube, and not allowed to enter the boiler. In starting a new engine be careful to let the bearings be slightly loose. At first give only enough steam to just keep the engine going, and keep the hand on the throttle valve ready to shut off steam instantly if occasion should require. PUMPS. Pumps are divided into the following classes: Lift pumps, in which the water flows freely away from the pump, which performs lifting duty only. Force pumps, which deliver the water under pressure. Plunger pumps, in which a "plunger," or "ram," as it is sometimes termed, is used. Piston pumps have a piston instead of a plunger. A double acting pump is one in which water enters into and is delivered from the pump at each stroke of its piston or plunger, or, in other words, one in which, while water is being drawn in at one end of the pump, it is also being forced out at the other. A single acting pump is one in which the water enters the pump barrel during one piston or plunger stroke, and is expelled from the pump during the next stroke, hence the action of the suction and of the delivery is intermittent, although the pump is in continuous action. For very heavy pressures plunger pumps are generally used, the plunger being termed a _ram_. The advantage of the plunger or ram is that it gives a positive displacement, whereas in a piston pump a leaky piston permits the water from the suction side to pass through the leak in the piston, to the delivery side. Piston pumps possess the advantage that there is less difference between the contents of the pump and the displacement than is the case in plunger pumps. The displacement of a piston pump is found by multiplying the area of the pump bore by the length of the piston stroke. The displacement of a plunger pump is less than the above, by reason of there being a certain amount of clearance or space between the circumference of the plunger and that of the cylinder bore. It is desirable to keep the clearance space in all pumps as small as the conditions will allow, especially if the pump is liable to lose its water. Losing the water means the falling of the suction water back into the source of supply, which may occur when the engine has to stop temporarily, and there is a leak in the suction valves. [Illustration: Fig. 3322.] Rotary pumps are those in which the piston revolves, an example of the most successful form of rotary pump being shown in Fig. 3322, which is that used by the Silsby fire engine. The advantage possessed by a rotary pump is that it keeps the water passing through the suction in a continuous and uniform stream, as it has no valves. It may therefore be run at a high velocity or attached direct to the engine shaft. If a rotary pump leaks, the efficiency is not impaired so much as in a piston or plunger pump, all that is necessary being to run the pump at a high speed. [Illustration: Fig. 3323.] The principles of action of a pump may be understood from Fig. 3323, which represents a single acting plunger pump shown in section, and with the suction pipe in a tank of water, the pump being empty. The surface of the water in the tank has the pressure of the atmosphere resting upon it, and as the pump is filled with air, the surface of the water within the pipe is also under atmospheric pressure. Now suppose the plunger to move to the right, and as no more air can get into the pump, that already within it will expand, and will therefore become lighter, hence there will be less pressure on the surface of the water within the suction pipe than there is on the outside of it, and as a result the water will rise up the pipe, not because the plunger draws it, but because the air outside the pipe presses it up within the pipe. [Illustration: Fig. 3324.] The water inside the pipe will rise above that outside in proportion to the amount to which it is relieved of the pressure of the air, so that if the first outward stroke of the plunger reduces the pressure within the pump from 15 lbs. to 14 lbs. per square inch (15 lbs. per square inch being assumed to be its normal pressure), the water will be forced up the suction pipe to a distance of about 2-1/4 feet, because a column of water an inch square and 2-1/4 feet high is equal to 1 lb. in weight. In Fig. 3324 the pump plunger is shown to have moved enough to have permitted the water to rise above the suction valve, and it will continue to rise and enter the pump barrel as long as the plunger moves to the right. When the plunger stops, the suction valve will fall back to its seat and enclose the water in the pump; but as soon as the plunger moves back to the left hand and enters the barrel pump further, the delivery valve will rise, and the plunger will expel from the pump a body of air or water equal in volume to the cubical contents of the plunger, or rather of that part of it that is within the barrel, and displaces water. If the plunger was at the end of its first stroke to the right and the pump half filled with air, then this air will be expelled from the pump before any water is; whereas if the pump was filled with water, the latter only will be delivered. Now suppose the first plunger stroke reduces the air pressure from 15 to 14 lbs., and that the second drawing stroke of the plunger reduces the air pressure in the pipe to 13 pounds per inch, the water will rise up it another 2-1/4 feet, and so on until such time as the rise of a column of water within the pipe is sufficient to be equal in weight to the pressure of the air upon the surface of the water without; hence it is only necessary to determine the height of a column of water that will weigh 15 lbs. per square inch of area at the base of the column to ascertain how far a suction pump will cause water to rise, and this is found by calculation or measurement to be a column nearly 34 feet high. It is clear then, that however high the pump may be above the level of the water, the water cannot rise more than 34 feet up the suction pipe, even though all the air be excluded from it and a perfect vacuum formed, because the propelling force, that is, the atmospheric pressure, can only raise a column of water equal in weight to itself, and it is found in practice to be an unusually good pump that will lift water thirty feet. [Illustration: Fig. 3325.] Fig. 3325 shows the plunger making a delivery stroke, the suction valve being closed, and the delivery valve open where it will remain until the plunger stops. To regulate the quantity of water the pump will deliver in cases where it is necessary to restrict its capacity, as in the case of maintaining a constant boiler feed without pumping too much water in the boiler, the height to which the suction valves can lift must be restricted, so as to limit the amount of water that can enter the pump at each drawing stroke. The delivery valve should lift no more than necessary to give a free discharge without causing the valve to seat with a blow; but if the pump has a positive motion, the delivery valve must open wide enough to let the water out, or pressure enough may be got up in the pump to break it. A check valve is merely a second delivery valve placed close to the boiler and serving to enable the pump to be taken apart if occasion should arise, without letting the water out of the boiler. The lift and fall of both valves act to impair the capacity of the pump. Thus, while the suction valve is falling to its seat, the water already in the pump passes back into the suction pipe, and similarly, while the delivery valve is closing, the delivery water passes back. A foot valve is virtually a second suction valve placed at the bottom or foot of the suction pipe. The capacity of a pump is from 70 to 85 per cent. of the displacement of the plunger or piston, and varies with the speed at which the plunger or piston runs. If a pump runs too fast, the water has not sufficient time to follow the piston or plunger, especially if the suction pipe has bends in it, as these bends increase the friction of the water against the bore of the pipe. The speed of the piston or plunger should not exceed such as will require the water to pass through the suction pipe at a speed not greater than 500 feet per minute, and better results will be obtained at 350 feet per minute. An air chamber placed above the suction pipe of any pump causes a better supply of water to the pump by holding a body of water close to it, and by making the supply of water up the suction pipe more uniform and continuous. Air chambers should be made as long in the neck as convenient, so that the water in passing through the pump barrel to the delivery pipe could not be forced up into the chamber, as, if such be the case, the air in the chamber is soon absorbed by the water. Belt pumps are more economical than independent steam pumps, because the power they utilize is more nearly the equivalent of the power it takes to drive them, whereas in steam pumps there is a certain amount of steam, and therefore of power, expended in tripping the valves and in filling the clearance spaces in the cylinder. Furthermore, the main engine uses the steam expansively, whereas the steam pump does not. [Illustration: _VOL. II._ =AMERICAN FREIGHT LOCOMOTIVE.= _PLATE XXIX._ Fig. 3326.] CHAPTER XXXVIII.--THE LOCOMOTIVE. In Fig. 3326 is shown a modern freight locomotive, the construction being as follows: For generating the steam we have the boiler, which at the front end is firmly bolted to the engine cylinders, which are in turn bolted to the frames, while at the back end the boiler is suspended by the links B (one at each end of the fire box on each side of the engine). The starting bar is shown in position to start the engine, and it is seen that the rod _a_ and bell crank _b_ are in such a position as to open the valve T, and thus admit steam from the dome to the pipe _e_, whence it passes through pipes _f_, _g_ and _r_ into the steam chest _i_, the slide valve V distributing the steam to the cylinder. The exhaust occurs through the exhaust port _d_, whence it passes up the exhaust pipe and out at the smoke stack. The boiler is fed with water as follows: The _feed pipe from the tender_ supplies water to the injector, which is forced by the injector through the _feed pipe to boiler_ and into the latter. In the figure the parts are shown in position for the engine to go ahead, hence the reversing gear is in the extreme forward notch of the sector, and the valve gear is in full gear for the forward motion. The lever _m_ is for opening and closing the cylinder cocks, which are necessary to let the water of condensation out of the cylinder when the engine is first started and the cold cylinder condenses the steam. To supply steam to the injectors (of which there are two, one on each side of the engine) and to the steam cylinder of the pump, there is a steam pipe leading from the dome to the steam drum, the pipe K supplying steam to the injector, and pipe J supplying steam to the steam cylinder of the air pump. The pipe for supplying oil to the slide valve and cylinder is furnished with a sight feed oil cup, the oil being carried by steam from the steam drum. This pipe passes beneath the lagging until it reaches the smoke box, which is done to keep it warm and prevent the oil from freezing, while the steam pressure enables the oil to feed against the steam pressure in the steam chest. The slide valve is balanced by means of strips let into its back, and bearing against a plate fixed to the steam chest cover. The frame on the side of the engine shown in the engraving is shown broken away from the yoke A to the fire box, so as to expose the link motion to full view, the shaded portion of the frame being that on the other side of the engine. The yoke or brace A carries one end of the guide bars. The safety valve S may be raised to see that it is in working order, or to regulate the steam pressure, by the lever O, which has a ratchet tongue engaging with the notches at _l_. [Illustration: Fig. 3326_a_.] [Illustration: Fig. 3326_b_.] In addition to the safety valve with spring balance, however, a pop safety valve is employed on the part of the dome that is shown broken away, the construction of this pop valve being shown in the outside view, Fig. 3326_a_, and a sectional view, Fig. 3326_b_, the casing being removed from the latter. In the valve seat B is a recess _a_, and upon the circumference of the valve is a threaded ring C´. When the valve lifts, the steam is somewhat confined in the annular recess of the valve, and the extra valve area thus receiving pressure causes the valve to lift promptly and the steam to escape freely. The degree of this action is governed as follows: The sleeve C´ is threaded upon the upper part of the valve, so that by screwing it up or down upon the valve the amount of opening between the annular recess _a_ _a_, and the lower edge of the sleeve C´ C´, is increased or diminished at will; the less this opening, the more promptly the valve will rise after lifting from its seat. To secure the sleeve or ring in its adjusted position, the ends of the screws L, L seat in notches cut in the upper edge of the sleeve. In many engines pop valves alone are used, and in some cases levers are provided by means of which the pop valve can be raised from its seat to test if it is in working order. Referring again to Fig. 3326, H is the handle for operating the injector, and _w_ a rod for opening the injector overflow. We now come to the automatic air brake; steam for the steam cylinder of which, is received from the steam drum through the pipe J, passing through the pump governor, or regulator G. The exhaust pipe for the steam cylinder of the air pump passes into the smoke box. The air cylinder receives its supply of air through the small holes at _k_, _k_, and delivers it through the pipe C into the air reservoir or tank, from which it passes through the tank pipe up to the threeway cock or engineer's brake valve, whose handle is shown at M. The brakes are kept free from the wheels and out of action so long as there is air pressure in the air reservoir and in the train pipe, hence the normal position of the handle M is such as to let the air pass from the air reservoir up the pipe _x_ and into the train pipe. When the brakes are to be applied, handle M is moved so that there is an open connection made between the train pipe and the _pipe to open_ air, which releases the air pressure and then puts on the brakes not only on each car, but also on the engine, because the engine brake cylinders receive their air pressure from the pipe shown leading to the train pipe. From the tank pipe _x_ a pipe _h_ leads to the top of the pump governor G, whose action is to shut off the steam from the steam cylinder of the air pump whenever the pressure in the air reservoir or tank exceeds 70 lbs. per square inch. A small pipe leads up from pipe _h_ to the air pressure gauge. For regulating the draught of the fire there is a damper door at each end of the ash pan, and to increase the draught, a pipe leads from the steam drum into the smoke box, where it passes up alongside of the exhaust pipe, its end being shown at Z. This is called the _blower_, and its pipe is on the other side of the engine. The plate shown at P, P in the smoke box checks the draught in the upper tubes, and therefore distributes it more through the lower ones. [Illustration: Fig. 3327.] There are two sand valves, both of which are operated by one rod, the construction being shown in Fig. 3327, which is a plan showing the bottom of the sand box broken away to expose the gear for moving the valves. The two valves _v_, _v_ for the sand pipes are on raised seats _e_, _e_, and are fast on the same shafts as the segments _s_, _s_, but the valves are obviously above, while the segments are beneath the bottom of the sand box. The gear wheel W is pivoted to the under side of the bottom of the sand box, and the arm L is fixed to the wheel. At _t_ are pieces of wire, which, being fast in the spindle, revolve with it and stir up the sand when the valves are moved. As shown in the figure, the two sand pipes _a_, _a_ are open, but suppose the rod is moved endways and L will revolve W, which will move _s_, _s_ and the valves _v_, _v_, causing the latter to move over and cover the pipes _a_, _a_, and shut off the sand from the pipes. Fig. 3328 represents an American passenger locomotive with a steam reversing gear, or in other words, a reversing gear that is operated by steam. The link motion is substantially the same as that shown in Fig. 3326 for a freight locomotive, the eccentric rods in this case being straight, as there is no wheel axle in the way. The injector for feeding the boiler is the same as that shown on the freight locomotive. The ash pan is provided with two dampers, one at each end, and the front one is operated by the bell crank _a_ _c_. The sand boxes are here fastened to the frame, both sand valves being operated by the lever _m_, which at its lower end connects to a rod, _u_, which at its back end connects to an arm, _p_, on a shaft that extends across the fire box and connects to a rod corresponding to rod _u_, but situated on the other side of the engine and connecting with the other sand valve. The steam pump for the automatic air brake is on the other side of the engine, and the air reservoirs, of which there are two, are horizontal and situated beneath the front end of the boiler. The air pipe to the triple valve here connects to the front pipe of the three beneath the triple valve, the middle pipe being that which is open to the atmosphere, which is the usual construction. The engine brake receives its air from a pipe on the other side of the engine which feeds the pipes G, V, for the brake cylinder shown in the figure. When the engine is running backwards, the train brakes are operated through the medium of the "pipe to air brake and to front end of engine" which is shown broken off. The construction of the steam reversing gear is shown in Fig. 3328_a_. A is a steam cylinder and B a cylinder filled with oil or other liquid. Each of these cylinders has a piston, the two being connected together by their piston-rods C C´. These rods are also connected to a lever D E F, which works on a fulcrum E. The lower end of the lever is connected to the reverse rod F G, the front end of which is attached to the vertical arm of the lifting or reverse shaft. It will readily be seen that if the piston in B is free to move and steam is then admitted to either end of the steam cylinder A, the two pistons will be moved in a corresponding direction, and with them the lever D E F, and the other parts of the reversing gear. A valve, H, is provided, by which communication is opened between the cylinder A and the steam inlet pipe. Another valve, I, is placed between H and the cylinder A, by which the steam may be admitted either into the front or back end of the cylinder. It will be apparent, though, that if the piston in A is thus moved, and the reverse gear placed in any required position, some provision must be made to hold it there securely. This is accomplished by the oil cylinder and piston B. To it a valve, J, is provided, by which communication between the front and back ends of the cylinder may be opened or closed. It is evident that if the piston B is in any given position, and both ends of the cylinder are filled with liquid, the former will be held securely in that position if the liquid in one end cannot flow into the other. If, however, communication is opened between the two ends, then, if a pressure is exerted on the piston B, it will cause the liquid to flow from one end of the cylinder to the other, and thus permit B to move in whichever direction the pressure is exerted. [Illustration: _VOL. II._ =AMERICAN PASSENGER LOCOMOTIVE.= _PLATE XXX._ Fig. 3328.] [Illustration: Fig. 3328_a_.] R is the reverse lever, made in the form of a bell crank, the short end of which works in a slot _c_, in the upper end of a shaft or spindle _d_. This shaft is inclosed by a tubular shaft S, to which the fulcrum of R is fastened. The tubular shaft has an arm _b_. The reverse lever has two movements, the one to raise the end up, and the other to turn on the axis of the tubular shaft. The arm _b_ on the latter is connected by a rod, _f_, with the valves J and H. The lower end of the shaft _d_ is connected with a bell crank, _f´_, which, in turn, is connected by a rod, _k_ _l_, with the valve I. Therefore, by turning the lever R so as to partly revolve the shaft S, the valves J and H may be opened or closed, and by moving the lever R up or down, the valve I is moved to admit steam to the front or back end of A. To reverse the engine, therefore, the lever R is turned so as to open the valves J and H. This opens communication between the opposite ends of B, and H admits steam to I. Now, by reversing the end of the reverse lever R, the valve I is moved so as to admit steam to either end of A, the pressure in which will move the reverse gear to the desired position. When this is done, the valves J and H are closed. This prevents the fluid in B from flowing from one end of the cylinder to the other, and thus securely locks the piston B in the position it may happen to be in, and at the same time the valve H shuts off steam from the cylinder A. The bar K is graduated, as shown in the plan of R, K, to indicate to the locomotive runner the position of the reversing gear. This apparatus enables the reversing gear to be handled with the utmost facility, and with almost no exertion on the part of the engineer. The engine can be reversed almost instantly, and it can be graduated with the most minute precision. THE LINK MOTION AND REVERSING GEAR. The link motion of an American locomotive is shown in Figs. 3329 and 3330. In Fig. 3329 it is shown in full gear for the forward gear, or in other words, so as to place the engine in full power for going ahead. The meaning of the term full power is that, with the link motion in full gear, the steam follows the piston throughout very nearly the full stroke. [Illustration: Fig. 3331.] [Illustration: Fig. 3332.] In Fig. 3331 the link motion is shown in mid gear, in which position the engine is at its least power, the cut off occurring at its earliest point, and in Fig. 3332 it is shown in full gear for the backward motion. [Illustration: _VOL. II._ =LOCOMOTIVE LINK MOTION.= _PLATE XXXI._ Fig. 3329. Fig. 3330.] Referring to Fig. 3329 for the full gear forward, the reversing gear proper consists of the reversing lever, the segment, the reach rod, the tumbling shaft, and its counterbalance rod and spring; while the link motion proper consists of the eccentrics and their rods, the link, the link block or die, the suspension link S, the rock shaft and the rod P P. These, however, are terms applied for shop purposes, so as to distribute the work in sections to different men, it being obvious that a _complete_ link motion includes the reversing gear, the eccentrics, the link and its block, the rock shaft, the rod P P, and the valve and its spindle or stem. This mechanism, as a whole, may also be called, and is sometimes called, the valve gear, because it is the mechanism or gear that operates the slide valve. The link motion may be moved from full gear forward to full gear backward or to any intermediate position, whether the engine is running or at rest, but is, when the engine is running, harder to move from full gear forward toward back gear, and easier to move from full gear backward toward mid and forward gears, which occurs because of the friction of the eccentrics in the straps, and it follows that this will be the case to a greater extent in proportion as the revolutions of the eccentrics are increased. If in a properly constructed link motion we move the link from full gear forward to mid gear when the engine is standing still, and watch the valve, we shall find that the lead or opening at _f_ gradually increases; and if we then move it from mid gear to full gear backward, the lead will gradually decrease and finally become the same as it was in full gear forward. The construction of the parts is as follows: Referring to Fig. 3329 (full gear forward), the segment is fixed in position and the reversing lever is pivoted at its lower end. _r_ _r_ is a bell crank, which is pivoted to the reversing lever and to which the latch rod is pivoted at its upper end. The spring acts on the end of _r_ _r_, and thus forces the tongue of the latch into the notches on the sector as soon as the tongue comes fair with the notch and _r_ _r_ is released from the hand pressure. As the reversing lever is moved over from full gear forward, the reach rod moves the tumbling shaft, whose lower arm _i_ (through the medium of the suspension link S) lifts the link and brings the centre of the saddle pin nearer to the centre of the pin in the link block, which reduces the amount of motion given to the lower arm (B, Fig. 3331) of the rock shaft, and therefore reduces the amount of valve travel, thus causing the point of cut-off to occur earlier in the piston stroke. The weight of the eccentric rods, the link, suspension link S, and the tumbling shaft arm _i_, is counterbalanced by the counterbalance spring in the box _s_ _s_, whose rod attaches to the lug _g_ on the tumbling shaft. To regulate the proper amount of counterbalancing, the nuts at _m_ are provided, these nuts regulating the amount of tension on the spring _s_ _s_. The forward eccentric E is that which operates the valve when the link motion is in full gear forward, as in Fig. 3329, and the backward eccentric is that which moves the valve when the link motion is in back gear, as in Fig. 3332. This occurs because it is the eccentric rod that is in line or nearest in line with the link block that has the most effect in moving the valve. When the link is in full gear, the motion of the valve is almost the same as though there was no link motion and the eccentric rod was attached direct to the rod P P, the difference being so slight as to have no practical importance. This will be seen by supposing that we were to loosen the backward eccentric F upon the shaft and revolve it around the shaft by hand, in which case it would swing the lower end of the link backward and forward with the centre of the link block as a pivot or centre of motion, the forward eccentric rod rising and falling a trifle only, and therefore moving the rock shaft to a very slight amount. Let it now be noted that the suspension link not only sustains the weight of the link and eccentric rods, but also compels the centre of the saddle pin to swing (as the link is moved by the eccentrics) in an arc of a circle of which the centre is the upper end of the suspension link. Suppose, therefore, that the backward eccentric rod was to break, or was taken off and the engine could still run forward, but no motion would be given to the valve, if the link was placed in mid gear, because in that case the forward eccentric rod would simply swing the link on the centre of the link block as a pivot. Now, suppose the forward eccentric rod was to break or be taken off, and the engine may be made to go ahead by setting the backward eccentric fair with the forward eccentric and connecting its rod to the upper end of the link. Similarly, if the engine was running with the smoke stack toward the train and the link motion in backward gear, and the backward eccentric rod was to break, we may take it off, shift the forward eccentric so that it comes fair or stands in line with the backward eccentric and connect its rod to the lower end of the eccentric and with the link motion in backward gear, the engine would still haul the train. If the reach rod was to break, the tumbling shaft could be held in position by loosening the cap bolts of the tumbling shaft journal and putting between the cap and the tumbling shaft journal a piece of metal, which, on bolting up the cap screws again, would firmly grip the shaft and prevent it from moving. [Illustration: Fig. 3333.] SETTING THE SLIDE VALVES OF A LOCOMOTIVE.--The principles of designing, and the action of D valves, such as are used upon locomotives, have been so thoroughly explained with reference to stationary engines, that there is no need to repeat them in connection with the locomotive, and we may proceed to explain how to set the valves of a locomotive. In doing this, there are two distinct operations, one of which is to place the crank alternately exactly on its respective dead centres, and the other is to set the position of the eccentrics, and get the eccentric rod of the proper length. These two operations comprise all that require to be done to set the valves, under ordinary and workmanlike conditions; hence we may proceed at once to explain the operation. The first thing to be done is to put the crank pin on a dead centre, and it does not matter which one. In Fig. 3333 it is supposed that the piston is to be at the head end of the cylinder when the crank is on its corresponding dead centre. The first thing to do is to put the reversing gear in full gear forward, so as to set the forward eccentric, and see if its rod is of proper length. The next thing to do is to move the wheel so that the crank pin is nearly on the dead centre, and then take a tram (such as shown in the figure), pointed at each end, and mark on the splash plate, or any other convenient place, a centre punch dot in which the point _b_ of the tram can rest. Next, from the centre of the axle as a centre, mark arcs or portions of circles _a_, _a_. This being done, point _b_ of the tram is rested in the centre punch dot before referred to, and with the other end a line _c_ is marked, a straight edge is then rested against the ends _e_ _e_ of the cross head, and a line _d_ is marked on the guide bar, this line being exactly even or fair with the end _e_ _e_ of the cross head. We then move the wheel in the direction of the arrow, and as soon as we begin to do so, the cross head will move to the left and away from the line _d_ on the guide bar. But as soon as the crank pin has passed its dead centre, the cross head will begin to move to the right, and as soon as the end _e_ _e_ comes again exactly in line with the line _d_ marked on the guide bar, we must stop moving the wheel, and again resting the point _b_ of the tram in the centre punch mark before mentioned, we move its other end so as to mark a second line, which will be the line or arc _f_. The next thing to do is to mark a fine centre punch dot, where _c_ and _f_ cross the arc or line _a_, and then find the point _g_ midway between _f_ and _c_, and mark a fine centre punch mark there. This being done, we must move the wheel back into the position it occupies in the figure, and then slowly move it in the direction of the arrow, until with the end _b_ of the tram resting in the centre punch dot, the other end of the tram will fall dead into the centre punch dot at _g_, at which time the crank pin will be exactly on the dead centre. During this part of the process we have nothing to do with anything except getting the crank pin on the dead centre, but there is one point that requires further explanation, as follows: In this operation we have first put the crank on one side of the dead centre and then put it to the same amount on the other side of the dead centre, both being improper positions; but by finding the mean or mid position between the two, we have found the proper position. In doing so, however, we have moved the wheel, the wheel has moved the connecting rod, and the connecting rod has moved the piston. But in the actual running of the engine, this order of things will be reversed; for the steam will move the piston, the piston will move the connecting rod, and the connecting rod will move the crank and therefore the wheel. The difference between the two operations is this: Suppose there is lost motion or play between the connecting rod brasses and the crank pin, or between the connecting rod brasses and the cross head pin, and then if we move the wheel in the direction denoted by the arrow, we take up this lost motion, so that if the tram was fair with the centre punch at _g_ and steam was admitted to the piston, then there would be no lost motion to take up, and as soon as the piston moved the crank pin would move. But if we moved the wheel in the opposite direction to that denoted by the arrow, then we are placing any lost motion there may be in the opposite direction, and if steam were turned on, the piston and connecting rod might move before the crank and wheel moved. In which direction the wheel should be moved while placing the crank on the dead centre depends upon the condition of the engine, as will be explained presently, the assumption being at present that the engine is in thorough good order, in which case the wheel should (while placing the crank on the dead centre) be moved in the direction of the arrow in the figure. The object is under all conditions to bring the working surfaces to bear (while setting the valve) in the same way as they will bear when the engine is actually at work. Having placed the crank on the dead centre, and thus completed the first operation in valve setting, we may turn our attention to the second, viz., correcting the lengths of the eccentric rods and setting the valve lead. Almost all writers who have dealt with this part of the subject have fallen into a very serious error, inasmuch as they began the operation by what they call _squaring_ the valve. This means so adjusting the length of the eccentric rod that the valve will travel an equal distance each way from its mid position, so that if the engine wheel is revolved and the extreme positions of the valve marked by a line, these lines will measure equally from the edges of the steam ports, or, what is the same thing, from the centre of the cylinder exhaust port. This procedure is entirely erroneous, because, on account of the angularity[57] of the eccentric rod, the valve cannot, if equal lead is to be given to the valve, travel equally beyond the two steam ports, and if the eccentric rods are so adjusted for length as to _square the valve_, they are made wrong. [57] See page 376, Vol. II., for the meaning of angularity. The valve lead, and the lead only, it is that determines the length of the eccentric rods. Suppose that, as is generally the case, the lead is to be equal, or, in other words, that there is to be as much valve lead when the piston is at one end of the cylinder as there is when it is at the other, and if we make the eccentric rods of such a length that the valve travels equally on each side of the steam port, there will be less lead at the head end port than there is at the crank end port. The proper method, therefore, is (as soon as the crank is on the dead centre and the link in full gear, as in Fig. 3334) to set the eccentric so as to give the desired amount of lead, and then give the wheel a half revolution, the lower end of the tram falling into the centre punch dot at _s_, when the crank pin will be on its other dead centre and ready for the lead to be measured again. If the lead is equal at each end, one eccentric rod is of the right length, and all we have to do is to set the eccentric so that the right amount of lead is given. We now turn our attention to the backward eccentric and its rod, putting the reversing lever in full gear for the backward motion, and putting the crank on the respective dead centres, and testing the lead for both ports as before, and when the required amount of valve lead is given the valve setting is complete. In some practice the wheel is blocked up on the pedestal guides while setting the valves, but a more correct method is to let the engine rest on the rails and push it back and forth with a crowbar to revolve the wheels when putting the crank pin on the dead centre. The best thing to measure the lead with is a wooden or leaden wedge having but a slight degree of taper, as say 3/16 or 1/4 inch in a length of four inches. We have in this example of valve setting supposed the parts to be of the proper dimensions, as they would be in a new engine or in an engine that had been running and merely had a new valve or a new eccentric put in. But suppose the notches were not cut in the sector, and we have then to mark them off while setting the valves. All the difference that this makes to the operation is that we must clamp the reversing lever to the sector while setting the valve, taking care to so clamp it that there is the same space between the top end of the link block and the end of the link slot in the full forward gear as there is between the bottom end of the link block and the end of the link slot when the engine is in full backward gear. In this connection it is, however, to be remarked that when the link is in full gear, either forward or backward, and the crank is on the dead centre, the link block is not at the end of its motion toward the end of the link slot; hence it is a good plan to move the wheels around and to so regulate the length of the reach rod and the position of the reversing lever on the sector, that when the link block is at the highest point in the link slot for the forward gear and at the lowest point in the link slot for the backward gear, it comes an equal distance from the end of the link slot. [Illustration: _VOL. II._ =INJECTOR AS APPLIED TO A LOCOMOTIVE.= _PLATE XXXII._ Fig. 3337. Fig. 3338.] [Illustration: Fig. 3334.] The setting for an Allen valve is the same as that for an ordinary one, but in determining the amount of the lead it is to be borne in mind that it is virtually twice as much as it measures at the port because there are two openings for the steam. This will be seen from Fig. 3335, in which the valve is open to the amount of the lead at _f_. But the steam also enters at _e_, and passes through the port in the valve and into steam port _a_. We have now to call attention to the fact, that the eccentric rods, when properly connected, are, in an American locomotive, crossed when the piston is at the crank end of the cylinder. In Fig. 3334, the piston is at the head end of the cylinder, and the rods are open. In Fig. 3336, however, the crank pin is supposed to be at B, and the eccentric rods are crossed, F being the forward and E the backward eccentric. THE INJECTOR. The injector shown in the general view of a freight locomotive, Fig. 3326, is that constructed by William Sellers & Co., and there are two, one on each side of the engine. The details of its construction are as follows: Fig. 3337 is a side elevation, Fig. 3338 a section on a vertical plane, Fig. 3339 a section on a horizontal plane, Fig. 3340 an end view of the injector at the right-hand side of the engine, and Fig. 3341 a plan of the injector on the left-hand side of the engine. This injector is self-contained, or in other words, it has both steam and check valves, so that it can be connected directly without other fittings, although, of course, it is generally desirable to place another stop valve in the steam pipe, and a check valve in the delivery pipe, so that the injector can be taken to pieces or disconnected at any time. Another important feature of this injector is, that it is operated by a single handle, and that the waste valve is only open at the instant of starting. Referring to Fig. 3338, A is the receiving tube, which can be closed to the admission of steam by the valve X. A hollow spindle passing through the receiving tube into the combining tube is secured to the rod B, and the valve X is fitted to this spindle in such a way that the latter can be moved a slight distance (until the stop shown in the figure engages with valve X) without raising the valve X from its seat. A second valve W, secured to the rod B, has its seat in the upper side of the valve X, so that it can be opened (thus admitting the steam to the centre of the spindle) without raising the valve X from its seat, if the rod B is not drawn out any farther, after the stop on the hollow spindle comes in contact with the valve X. D is the delivery tube, O an overflow opening into space C, V the check valve in delivery pipe, and Z the waste valve. The upper end of the combining tube has a piston N N attached to it, capable of moving freely in a cylindrical portion of the shell M, M, and the lower end of the combining tube slides in a cylindrical guide formed in the upper end of the delivery tube. The rod B is connected to a cross head which is fitted over the guide rod J, and a lever H is secured to the cross head. A rod W, attached to a lever on the top end of the screw waste valve, passes through an eye that is secured to the lever H; and stops T, Q control the motion of this rod, so that the waste valve is closed when the lever H has its extreme outward throw, and is opened when the lever is thrown in so as to close the steam valve X, while the lever can be moved between the positions of the stops T, Q without affecting the waste valve. A latch F is thrown into action with teeth cut in the upper side of the guide rod J, when the lever H is drawn out to its full extent and then moved back; and this click is raised out of action as soon as it has been moved in far enough to pass the last tooth on the rod J. An air vessel is arranged in the body of the instrument, as shown in the figure, for the purpose of securing a continuous jet when the injector and its connection are exposed to shocks, especially such as occur in the use of the instrument on locomotives. [Illustration: Fig. 3335.] [Illustration: Fig. 3336.] The manipulation required to start the injector is exceedingly simple--much more so in practice, indeed, than it can be rendered in description. Moving the lever H until contact takes place between valve X and stop on hollow spindle, which can be felt by the hand upon the lever, steam is admitted to the centre of the spindle, and, expanding as it passes into the delivery tube D and waste orifice P, lifts the water through the supply pipe into the combining tube around the hollow spindle, acting after the manner of an ejector or steam siphon. As soon as solid water issues through the waste orifice P, the handle H may be drawn out to its full extent, opening the steam valve X and closing the waste valve, when the action of the injector will be continuous as long as steam and water are supplied to it. To regulate the amount of water delivered, it is necessary only to move in the lever H until the click engages any of the teeth on the rod J, thus diminishing the steam supply, as the water supply is self-regulating. If too much water is delivered, some of it will escape through O into C, and, pressing on the piston N N, will move the combining tube away from the delivery tube, thus throttling the water supply; and, if sufficient water is not admitted, a partial vacuum will be formed in C, and the unbalanced pressure on the upper side of the piston N N will move the combining tube toward the delivery tube, thus enlarging the orifice for the admission of water. From this it is evident that the injector, once started, will continue to work without any further adjustment, delivering all its water to the boiler, the waste valve being kept shut. By placing the hand on the starting lever, it is easy to tell whether or not the injector is working; and, if desired, the waste valve can be opened momentarily by pushing the rod W, a knob on the end being provided for the purpose. [Illustration: Fig. 3339.] [Illustration: Fig. 3340.] [Illustration: Fig. 3341.] THE WESTINGHOUSE AUTOMATIC AIR BRAKE. Figs. 3342, 3343 and 3344 represent the Westinghouse automatic air brake applied to an engine and tender, and in the following figures details of the construction of various parts are shown. [Illustration: Fig. 3345.] The pump governor, which is shown at G in Fig. 3326, of a modern freight locomotive, is shown in section in Fig. 3345. The pump governor is employed for the purpose of cutting off the supply of steam to the pump when the air pressure in the train pipe exceeds a certain limit, say 70 lbs. per square inch. Its operation is as follows: When valve 10 is (by means of hand wheel 8) screwed home to its seat the steam is entirely shut off from the steam cylinder, but by operating wheel 8 to unscrew spindle 9, valve 10 is permitted to open and let the steam pass through A and B to the steam cylinder which operates, forcing air into the reservoir and thence into the train pipe. A pipe from the train pipe connects to the upper end of the pump governor, hence air from the train pipe passes around the stem 14 to the upper side of the thin diaphragm 18, which is held in its position by the spring 12 with a force sufficient to enable it to resist, without moving, a pressure of 70 lbs. per square inch. But when the pressure exceeds 70 lbs. per square inch it forces the diaphragm down, pushing down valve 13 and allowing the steam in A to pass up through valve 13 and out of the exhaust pipe 6. The steam pressure in A being thus reduced, that in B acts on the under side of the valve, causing it to rise and seat itself and thus cut off the supply of steam to the pump. [Illustration: _VOL. II._ =LOCOMOTIVE AIR BRAKES.= _PLATE XXXIII._ Fig. 3342. Fig. 3343. Fig. 3344.] When the pressure in the train pipe is diminished by the brakes being applied, the diaphragm is restored to the position it occupies in the figure by the action of the spring 16. Then valve 13 is seated by the spring 12, and the steam pressure accumulates on the upper end of valve 10, forcing it down and letting the steam from A into B and thence into the steam cylinder, starting it into action, which continues until the pressure in the train pipe exceeds 70 lbs. per square inch. The use of this governor not only prevents the carrying of an excessive air pressure in the train pipe, which may result in entirely preventing the wheels from revolving and causing a flat place to wear on the wheel tire, but it also causes the accumulation of a surplus of air pressure in the main reservoir, while the brakes are applied, which insures the release of the brakes without delay. It also obviates the unnecessary working of the pump when the desired air pressure has been obtained. [Illustration: Fig. 3346.] A sectional view of the steam and air cylinders is shown in Fig. 3346, the construction being as follows: Steam is distributed to the steam cylinder by means of a piston valve, composed of three pistons, marked 16, 14, and 20 respectively, the steam entering between pistons 16 and 14, and, in the positions in which the parts occupy in the figure, steam can pass through the bushing 18 and beneath the steam piston 7, propelling it upwards until the bottom of the hole in its piston rod strikes the end of rod 12, and raises it and valve 13. The chamber 23, in which valve 13 works, receives steam through a suitable port from the steam space between valves 14 and 16; and the steam from chamber 23, it is that (in the positions the parts occupy in the figure), acting on the area of the large valve piston 20, holds the valve down against the pressure on the bottom face of piston 14 of the valve. As soon, however, as the piston rod 7 strikes and raises rod 12 and valve 13, the steam is exhausted from the top of piston 20 of the valve, and the steam beneath piston 14 of the valve raises the valve, opening the lower port in the sleeve 18 for the exhaust, and piston 14 admits steam to the upper side of the steam piston 7. The construction of the air cylinder differs somewhat from that shown in the freight locomotive, Fig. 3326, this air pump corresponding with that shown on the engine and tender, Fig. 3342. A detail list of the parts may be given as follows: No. 2. Steam cylinder head (with reversing cylinder, piston, and valve bushes). 3. Steam cylinder (with main valve and bushes). 4. Centre piece. 5. Air cylinder (with lower discharge valve). 6. Air cylinder head. 7. Steam piston and rod. 8. Air piston. 9. Piston rings. 10. Steam piston plate. 11. Steam piston bolt. 12. Reversing rod. 13. Reversing valve. 14. Piston valve. 15. Piston valve rings. 16. Piston valve rings. 17. Upper valve bushing. 18. Lower valve bushing. 19. Reversing piston casing. 20. Reversing piston. 21. Piston rings. 22. Reversing cylinder cap. 23. Reversing valve bush. 24. Reversing valve cap. 25. Piston rod nut. 26. Piston packing gland. 27. Piston packing nuts. 28. Packing glands. 29. Right Chamber cap. 30. Left chamber cap. 31. Air valve bushing. 32. Air valve. 33. Air valve. 34. Air valve. 35. Delivery union. 36. Exhaust steam outlet. 40. Steam cylinder gasket. 42. Top air-pump gasket. 43. Bottom air-pump gasket. 44. Waste water pipe. 46. Exhaust union stud. 49. Air exhaust union stud. A side view of the driving wheel brakes is shown in Fig. 3347 and an end view in Fig. 3348. The brakes are, it is seen, suspended by links so that their weight tends to keep them from the wheels. The brake piston rod carries at its end two links which attach to the arms attached to the brakes. The ends of these arms being curved roll together, the arrangement forming in effect a rolling toggle joint. The construction of the piston of the driving wheel brake is shown in Fig. 3349. The piston is made air tight by leather packing indicated by 11, held out by a spring 12. The piston rod packing, 7, is leather held in place by the cap 6 and the spring 8. The air for operating the brake enters below the piston. [Illustration: Fig. 3347.] [Illustration: Fig. 3348.] LOCOMOTIVE RUNNING. The engineer's duty in running a locomotive is more arduous and requires more watchfulness than any other engine running, because of the peculiarities attending it. In the first place, the jolts and jars to which the engine is subject are liable to cause nuts, pins, etc., to come loose, and some of the parts to become disconnected and cause a breakdown of the engine. This renders necessary a careful examination of the engine, which should be made both before and after each trip. In the second place, we have that the amount of load the engine has to pull varies with every varying grade in the railroad track, and the variation is so great that on some descending grades the engine may require no steam whatever, while on ascending grades the utmost power attainable from the engine may be required. In firing, feeding the pumps, oiling the parts, and determining the depth of water in the boiler, the grade and the length of each grade has an important bearing, and so has the weather, since it is clear that between the heat of summer and the blizzards of winter there is a wide range of the conditions under which the engine runs. In former times, from the less perfect construction of locomotives, the engineer's duties were greatly enhanced from breakdowns, which are comparatively rare with modern locomotives, and there is promise that from improved construction and safeguards they will become less frequent in the future. It is as important for the locomotive engineer to be familiar with the track as it is to be with the engine, and there is no field of engine driving or running in which more scope is permitted to the engineer to exercise judgment and skill in his management, so as to effect economy in fuel consumption. The quality and size of the coal is another element that requires attention and observation on the part of the engineer, in order that his train may keep its time and the fuel consumption be kept down. GETTING THE ENGINE READY. The first thing to be done in getting ready for a trip is to see that there is sufficient water in the boiler, so that if there is not, there is time to supply the deficiency. If the boiler is cold it may be that the condensation of the steam in cooling may have left a partial vacuum in the boiler, and it will be necessary in that case to open the top gauge cock and let in air so that the water will come to its proper level in the gauge glass. Similarly, in filling the boiler, it may be necessary to open a gauge cock to let the air out. The lower cock of the gauge glass should be opened to let the steam blow through if there is pressure on the boiler, or to let a little water out if there is not. The safety valve should next be examined and moved to see that it works properly and does not stick to its seat. Before laying the fire the fire bars and ash pan should be cleared of ashes and clinkers, and the grate bars tried with the shaking levers to see that the grates will shake properly. It should be seen that the tubes, etc., are clear of ashes. In laying a new fire an ample supply of lighting material should be used, disposing it so that the fire will light evenly and not in spots, and a good layer of wood should be evenly distributed over the bars, the thinnest pieces being at the bottom as they will light easiest, and it is necessary to light the fire at the bottom, so that the heat from the wood that is first lighted shall pass through that to be lighted. The wood should be kept burning without coal until the lower stratum has ceased to blaze and covers the bars, while there is an even layer of blazing wood above it. [Illustration: Fig. 3349.] The quantity of coal to be fed at a time, and the depth of fire to be kept, depends upon the size of the coal, because the larger the coal the less it obstructs the draught, and the thicker the layer required in order to prevent currents of air from passing through without entering into combination with the gases from the coal. If the coal is mixed, containing large lumps, they should be broken. The first layer of coal should be enough to cover the fire to a depth of about two inches, which will permit of a good draught. This will get well alight while the wood is still serviceable, and a second layer may be applied of another two inches. The third feeding should be given with a view to have a greater depth of fire at the sides than at the middle of the fire box, because the cool sides of the box prevent perfect combustion, and currents of cold air are more apt to find their way through the sides than in the middle of the fire box. Banking a fire consists of piling it up at the back half of the fire box and covering it up with green coal, so that it may keep alight and keep the boiler hot without increasing the steam pressure. The air passing through the uncovered half of the fire bars prevents rapid combustion and a dead fire is maintained. In starting up a banked fire, the first thing to do is to clean it of ashes, clinker, etc., shaking up the bars to see that they will work properly. The fire is then spread evenly over the bars, and wood fed to enliven the fire and promote the draught. The blower or blast pipe is then set going, and coal gradually fed a little at a time, evenly distributed, covering those parts the most where the fire burns through the most brightly. A steady fire is better than one that is forced, because the combustion is more perfect and less clinker is formed, hence less cleaning will be necessary, and the fire door will not be kept open so long to let in cold air. This is important because a steady temperature in the fire box promotes its durability, as well as giving a uniform boiler pressure. The strains placed upon a fire box by a fierce fire suddenly cooled by a heavy charge of coal or of cold air from an open fire door are highly destructive. Furthermore, the greatest economy of fuel is attained by keeping the boiler pressure up, and using the steam expansively by hooking up the links to shorten the point of cut-off. A safety valve steadily blowing off steam, whether the engine is running or not, is a sign of bad firing and wastefulness. It is the fireman's duty to attend to the fire, but nevertheless a careful engineer will be as much interested in proper firing as in his own duties, and as the engineer has more experience than the fireman, he is warranted in exercising an ordinary supervision on the firing, which will be welcome to an earnest or ambitious fireman. The engineer should examine, with a wrench in hand, the bolts and nuts about the trucks and axle boxes, as these are apt to become loose and come off on the road. A proper construction would remedy this defect almost entirely, and by a proper construction is meant the more frequent employment of split pins, cotters, and other similar safety appliances now omitted for the sake of economy of manufacture. Nothing in the future of the locomotive is more certain than improvement in this respect, and nothing is more urgently needed, as any engineer will become satisfied if he will gather up along a mile of ordinary railroad the nuts and washers that lay along the track. The eccentric straps and the pins in the link motion require an examination, which may be done while oiling the parts of the engine. The oiling requires careful attention; first the cups themselves sometimes become loose, an argument in favor of having, wherever possible, the cups solid on the parts, as done in European practice. Oil holes are apt to get choked by gumming, which is that the oil in time forms into a brown gummy substance that fills the oil hole. Perfect lubrication does not imply wasteful lubrication by any means, but a wasteful use of oil is probably less expensive than insufficient lubrication. A thorough engineer will use no more oil than is necessary; he will leave nothing to conjecture or chance, but know from personal inspection that his engine is in complete working order, and to this end the lubrication of the working parts is a vital element. After having oiled the eccentric straps, the link motion and the reversing gear beneath the engine, the reversing lever and the parts above the frame must be oiled, and the reversing lever moved back and forth several times, from end to end of the sector or quadrant, so as to distribute the oil throughout the joints and working surfaces. The axle boxes require careful attention in oiling. In English practice, tallow is packed in the corners of the cavities of the top of the box, so that if the box should begin to heat the tallow will melt, and afford extra lubrication with a heavier lubricant than usual, which will often stop the heating. The connecting and coupling rods then require attention, the cups being filled and the lubrication adjusted. When steam is up the gauge glass should be blown through again, and it will be found that the water stands higher in the glass than it did before the boiler was under pressure. The packing of the piston and of the pump glands, if the engine has pumps, should be known to be properly set up, bearing in mind that a leaky pump gland lets air into the pump and impairs its action. The sand box should contain dry sand, as wet sand will not feed properly. If steam is raising too rapidly, close the lower damper to reduce the consumption of fuel and save blowing off steam through the safety valve, which should always be avoided as much as possible. Before starting the engine, open the cylinder cocks and keep them open until the sound discloses that dry steam, and not steam and water, is issuing. Open the throttle enough to start the engine easily and not with a jump, and be prepared to shut off steam instantly if a blow in any part of the engine should indicate an obstruction to its working. In starting a train, the reversing lever is put in the end forward notch and the cylinder cocks opened. Then the throttle is opened a little at first, so as to avoid starting with a violent shock that might break the couplings. If in starting (or in ascending gradients) the wheels are forced to slip, the sand lever should be operated, a slight sprinkling of sand serving better than a heavy one. If the sand is damp, it will fall in lumps and not distribute evenly as it should do, while at the same time a great deal more sand will be found necessary. When the train is fairly under way, the aim should be to maintain full boiler pressure, so as to keep up the required speed with the links hooked up to work the steam as expansively as possible, bearing in mind that the higher up the links are hooked the more expansively the steam is used, and that therefore less steam is used to do the work and the boiler pressure can be kept up easier. To understand this clearly, let it be supposed that the steam pressure in the boiler is 90 lbs. per square inch, and that the piston area is 400 inches, and the total pressure impelling the piston will be 36,000 lbs.; if this follows the piston for 22 inches, the power becomes 792,000 inch lbs. per stroke. Now suppose the pressure is 150 lbs. per square inch, and this multiplied by the piston area (400) gives 60,000 lbs. impelling the piston, and this would require to follow the piston but 13.2 inches in order to give 792,000 inch lbs. In the one case we have 22 inches, and in the other 13.2 inches of the cylinder to fill with steam. Of course it will take more fuel under the heat of firing to keep the pressure up to the 150 lbs.; but on the other hand, when the steam is cut off in the cylinder there will be 160 lbs. per square inch in it, and all the work that this does in expanding is gained during the rest of the stroke, so that the required amount of power would be obtained by cutting off earlier than at 13 inches. The water should, under ordinary conditions, be kept at an uniform level in the boiler. Steam can of course be made quicker with a small than with a large quantity of water, but the smaller the quantity of water the more the steam pressure is liable to fluctuate, and the closer the firing must be attended to. Furthermore, the more water there is in the boiler, the greater the safety, because the longer the boiler can go without feeding, and, if the pumps or injectors, as the case may be, should act imperfectly, there is more time to get them working properly. In testing the water level, the gauge glass alone is not to be entirely depended upon, hence the gauge cocks should be opened. The water should not be allowed to go below the middle gauge cock. It is obvious that when the water is below a certain gauge cock, the gauge glass only can give any information as to how far it is below it, hence it must be used for this purpose. When using it, it should be blown through by opening its lower cock, and if there is any doubt about its showing the proper water level it should be blown through two or three times, watching the level of the water in the glass at each trial. A constant boiler feeding is the best, as it is more conducive to a uniform boiler pressure and temperature. The fire should be fed in small charges, the fire door being kept open as little as possible, because a high temperature in the firebox is necessary to perfect combustion. If heavy charges of coal are given at once, then for some time the fire box will be cooled, and then, as the fire burns through, a fierce heat will be generated. This alternate heating and cooling is very destructive to the fire box and the tubes, as it causes an expansion and contraction that rack the joints and seams. There are several ways of firing, each having its advocate. Upon the following points, however, there is no dispute. First, a slow combustion is the most perfect, because it produces less clinker, which saves fuel and also saves a large amount of fire cleaning and therefore of admission of cold air to the fire box. A high temperature is necessary to combustion, and the temperature of the fuel is most difficult to keep up at the sides of the fire box. By light and frequent firing the bright fire will never be covered up, hence the temperature will be maintained. This favors an even distribution over a large surface of the fire of each shovelful of coal. But if at any point the draught is lifting the fire, and small bright pieces of fire are lifting up, it is an evidence that the fire is thinnest there or else that the bars are cleanest there. In either case, an extra amount of coal is required at that spot. Some engineers will charge one side of the fire box lightly and then the other, this being done so as to keep up the temperature in the fire box. Others will fire first the front and then the back of the box, which answers the same purpose, but in no case should the charge be heavy. A fireman may become so accustomed to the road and his engine, that under some conditions he may fire when he reaches certain points on the road, regulating it like clockwork. On a trip from Philadelphia to Reading, on an engine having a Wooten fire box (whose special feature is a large fire box, which enables slow combustion), the firing was conducted as follows: The fire was was not fed or touched until just before reaching Bridgeport, 18 miles from Philadelphia, when a thin layer of coal Was spread evenly on the fire. Eleven miles were then made without opening the fire door, the next firing taking place just before reaching Phoenixville. Ten miles were run before the next firing, which occurred just before arriving at Pottstown. The next firing occurred at Bordenboro', three miles from Pottstown. The remaining 8 miles were made without firing. The steam pressure did not vary more than 10 lbs. per square inch during the trip. On a trip from New York to Philadelphia by the lightning express train the firing was conducted as follows: The coal was anthracite and in lumps from 5 to 7 inches in diameter; at one end it reached up to the level of the fire door, while at the tube plate end of the fire box it was about 6 inches deep. The grate bars were constructed to shake in three sections, and shaking the bars to clear out the fire caused it to feed forward of itself, and the combustion of the coal caused it to break up into lumps about 2 inches in diameter at the tube plate, where the fire was much brighter than at the fire door end. The steam pressure varied about 10 lbs. during the trip. We now come to the best times to fire, to feed, and to oil the valves, and this depends on the level of the road. On a level road these matters could be attended to with regularity, but as the engine has most work to do in ascending inclines, it is necessary to prepare for such emergencies: First, by having a good fire prepared, so that the fire door may be kept closed as much as possible while the engine is ascending; second, by having plenty of water in the boiler, so as to keep steam, without feeding any more than possible when the engine is calling for more steam, by reason of the reversing lever being put over towards full gear. The speed is kept well up before reaching the incline, and the reversing lever moved forward a notch or two at a time to maintain the speed, while at the same time moving the sand lever to feed the sand as soon as the engine speed shows signs of reducing. ACCIDENTS ON THE ROAD. The accidents to which the locomotive is most liable when running upon the road, and the course to be pursued by the engineer to enable him to take the engine to the depot or complete the trip, are as follows: KNOCKING OUT THE FRONT CYLINDER HEAD OR COVER.--This arises from various causes, such as a breakage of a connecting rod strap, or of a piston rod or cross head. It is the practice of some locomotive builders to cut in the cylinder cover flange a small groove close to the part that fits the cylinder bore, so that the cover shall break out in the form of a disc, leaving the cover, flange, bolts, and nuts intact, and diminishing the liability to break the cylinder itself as well as the cover. The provisional remedy for this accident is to take off the connecting rod (on the side of the broken cover) and also the valve motion, either at the rock shaft arm or by taking down the eccentric rod straps. Then place the valve in the centre of its travel so that it shall cover and enclose both the cylinder steam ports and leave the exhaust port open. Then block the cross head firmly on the forward centre, and go ahead with the other cylinder. HEATING OF PISTON RODS.--This the engineer can often discover by sight, or by smelling it from the cab. The remedy is to stop the engine and slack back the gland until the steam from the engine cylinder leaks freely through the packing. Then apply a little extra lubrication or water while _running slowly_. BREAKING OF A PISTON ROD.--If the piston rod breaks, but does not knock out the cylinder head or cover, pursue the same course as directed for breaking the cylinder cover, taking the additional precaution to block the piston, which may be done by fitting pieces of wood between the guide bars, making the pieces long enough to fit between the cross head and guide yoke. The cylinder or waste water cocks on the side of the accident must also be opened, to prevent any leakage of steam past the slide valve from getting into the cylinder and driving the piston against the cylinder cover, and breaking the cylinder cover or even the cylinder itself. If the piston rod breaks from the cross head, it is safest to remove it from the cylinder, though this is unnecessary, if it be securely blocked against the cylinder head so that it cannot move, though steam may leak in on either side of it. BREAKING A CRANK PIN.--This is a somewhat frequent accident, but seldom takes place on both sides of the engine at once. The remedy is to take off all the parallel or coupling rods, and if it is the crank pin on the driving wheels which breaks, take off the connecting rod also, and securely block the cross head, disconnecting the valve motion as before directed, and opening the cylinder waste water cocks. In the case of this accident occurring, it is absolutely essential to take off the parallel rods on both sides of the engine, or otherwise the crank pins on the other side are apt to break. THROWING OFF A WHEEL TIRE.--In this case the best plan is to block the tireless wheel entirely clear of the track, which may be done by putting a block of wood into the oil cellar of the driving box, and then tow the engine to the repair shop; for if the engine is run to the shop, and the wheel touches the rail, it will impair its diameter for the proper size of tire. THROWING OFF A DRIVING WHEEL.--This is not a common accident, but nevertheless it sometimes occurs; they break usually just outside of the driving axle box. In this case take out the driving box and fit in its place a block of wood affording journal bearing for the axle. Let this block rest on the pedestal cap, holding the axle up in the centre of the pedestal. Then secure the piston and disconnect the valve gearing and open the cylinder cocks as before, and the engine can be run _slowly_ to the repair shop without danger of further accident, or, if convenient, it can be towed by another engine. BREAKING A SPRING OR SPRING HANGER.--Lift the engine with the jacks until the driving wheel axle box is about in the centre of the pedestal, and put any convenient piece of iron across the top of the driving axle box and between it and the engine frame, thus taking the weight of the engine on the frame instead of on the spring. Place also a block of iron between the end of the equalizing bar and the top of the engine frame, so as to prevent the movement of the equalizing bar, and to allow the spring at the other end of the equalizing bar to operate without moving the said bar. Every engineer should carry in his tool box pieces of metal suitable for this purpose, because this is a frequent accident. It does not, however, materially affect the working of the engine, and should not delay a train more than a few minutes. BURSTED FLUES AND TUBES.--These are usually plugged by tapering a piece of pine wood and driving it into the bursted tube by means of an iron bar. Taper iron plugs are often carried, and then driven into the end of the tube after the wooden one has been driven in. To enable this job to be done, it is necessary to thickly cover the fire with green coal, which operates to cool the tubes and prevent the loss of the water in the boiler. Sometimes careful engineers prepare for use pine plugs turned slightly taper, and a little slack, for the inside of the tube. In case of leak, this plug is inserted in the flue, and driven along it until it covers the fracture, the expansion due to its saturation causing it to become locked in the tube. SLIPPING OF ECCENTRICS.--Place the reverse lever in the forward notch of the sector. Place the crank on its forward dead centre, as near as can be judged by the eye, and loosen the set screw of the forward eccentric, that is to say, the eccentric which connects to the upper end of the link. Move that eccentric round upon the axle until the slide valve leaves the steam port at the front end of the cylinder open to the amount of required valve lead. In moving the eccentric round upon the shaft, move it in the direction in which it will rotate when the engine is running forward, so as to allow for and take up any lost motion there may be in the eccentric straps, in the eccentric rod eyes and bolts, and in the other working parts of the valve gear; for if the eccentric was moved backward, all such lost motion would operate to vitiate the set of the valve. The eccentric being placed as directed fastens its set screw securely. If the backward eccentric is the loose one, throw the reverse lever to the backward notch of the sector, lifting the link up so that the eccentric connected to the lower end of the link may be approximately adjusted by moving it around upon the axle in the direction in which it will rotate when the engine is running backward, until the back cylinder port is open to the amount of the valve lead. Another very ready plan of temporarily adjusting the eccentrics is as follows: Place the reverse lever in the end notch forward, and place the engine crank or driving crank pin as near on a dead centre as the eye will direct, and open both the cylinder waste water cocks. Then disconnect the slide valve spindle from the rocker arm, and move the slide valve spindle until the opening of the cylinder steam port corresponding to the end of the cylinder at which the piston stands will be shown by steam blowing through the waste water cock at that end of the cylinder; the throttle valve being opened but a trifle, to allow a small steam supply to enter the steam chest and cylinder, for if much steam is admitted, it may pass through a leak in the piston and blow through both the waste water cylinder cocks. The position of the valve being thus determined, the eccentric must be moved upon the driving axle until the valve spindle will connect with the rocker arm without being moved, or moving the valve at all. HOT AXLE BOXES.--If not convenient to reduce the speed of the engine, or if that and free lubrication do not cool the box, a plentiful supply of cold water should be administered, it being well to have at hand a small hose pipe, by means of which water from the tender tank can be used. If the brasses have Babbitt metal in them and it should melt, it is better, if possible, to cool the axle box while the engine is moving, which will injure the journal less than if the journal is stopped to cool the box, because in the latter case the brass or box is apt to become soldered to the journal of the axle, and when the engine is again started, the cutting or abrasion will recommence with extreme violence. BREAKING A LIFTING LINK OR THE SADDLE PIN THAT CONNECTS THE SLOT LINK TO THE REVERSE SHAFT.--Cut a piece of wood and tie it into the slot of the link, over the link block or die, making it of a length to keep the link in the position for hauling the train. Then fasten another piece of wood in the link slot beneath the sliding block or die, thus securing that die in the proper position for the engine to go ahead. In this case, the engineer must be careful in stopping, as he cannot reverse the engine on the crippled side. Secondary accidents are almost sure to occur if a disconnected piston is not securely blocked in the cylinder, or from blocking the piston aright and attempting to let the slide valve run, or from attempting to run with the parallel rods on one side only disconnected. There are numerous accidents, which only common sense and a familiarity with the locomotive can provide a temporary remedy for, but those here enumerated are by far the most common. ADJUSTING THE PARTS OF A LOCOMOTIVE. When the wedges of the axle boxes are to be adjusted for fit to the pedestal shoes, the engine should be moved until the coupling rods on one side of the engine are in line with the piston rod, because in this position the rod will, to a certain extent, act as a guide in keeping the axles parallel to each other, and at a right angle to the line of engine centres. Bear in mind that the distance from the centre to centre of axle boxes must be the same as the distance from centre to centre of the crank pins, and that when the coupling or side rods are in line with the piston rod, they act to resist the axle boxes from being set up too close together. [Illustration: Fig. 3350.] The importance of a proper adjustment of the axle boxes, coupling boxes, and connecting rods cannot be overestimated, and it is necessary therefore to explain it thoroughly. In Fig. 3350, then, _s_, _s_ represent two wheel axles, whose boxes are between their wedges. At S, S´ are the screws for setting up the shoes or wedges W and W´ respectively. The axles are shown on the line of centres C, C of the engine, the piston being at the head end of the cylinder, and the crank pins on the line of centres as denoted by the small black circles. The wedges W and W´ are shorter than the leg of the pedestal, so that they may be set up by the set screws S and S´, and take up the wear. In some engines the wedges V and V´ are also shorter for the same purpose. Now it is clear that setting up the screws S and S´ will move the axles _s_, _s´_ to the left, and this will alter the clearance between the piston when it is at the end of the stroke and the cylinder cover. It is clear that the distance between the centres of the two axles must be the same as the distance between the centres of the two crank pins, or else the frame will be subjected to a great strain, tending to break the crank pins and the side rods. In order to keep the clearance equal and to know when it is equal, it is necessary, at some time when the cylinder cover at the head end is off, to disconnect the connecting rod and push the piston clear up against the left hand cylinder cover, and from the cross head as a guide, make on the side of the guide a line L´. Then put on the cylinder cover at the head end and push the piston up against it and mark a line L. Then when the connecting rod is put on again, the wheels may be moved around if the engine is jacked up, or, if not, the engine may be moved along the rails with a pinch bar, and the clearance will be equal when the cross head (at the ends of the stroke) comes within an equal distance of the respective lines L´, L when the crank is on the dead centres, and it is well to adjust the wedges W W´ so that the cross head does travel within an equal distance, and mark on the guide bar two more lines, one at each end of the bar. These lines are a permanent guide in setting up the shoes or wedges, and lining up the connecting rods, and coupling or side rods, because it is clear that from the method employed in marking them the distance between the end of the cross head, when at the end of its stroke, and the line L, and that between the face of the piston and the cylinder cover, will be equal. A proper adjustment, therefore, should be made as follows: The piston should be at the end of its stroke, the crank pins being on the line of centres. Screw S should be operated to set up the wedge W, taking up the wear of the sides of the box, and bringing the edge of the cross head the proper distance from the line L. The connecting rod brasses should then be set up to fit the pins, and the screw S´ operated to set up wedge W´ to have easy contact with the side of its axle box. If, however, there has been so much wear on the axle boxes that they are still too loose between the wedges, both wedges may be set up to take up this wear, since it is more important to have the axle boxes a proper fit between the wedges than it is to maintain an exactly equal amount of clearance at each end of the cylinder. The engine will then be in proper tram on this side, or, in other words, the distance from the centre to centre of the crank pins will be the same as that from centre to centre of the axles. On the other side of the engine the process is the same, the engine being moved until the crank pins are on the line of centres C C and the wedges set up according to the lines. CHAPTER XXXIX.--THE MECHANICAL POWERS. LEVERS, PULLEYS, GEAR WHEELS, ETC. Power is distinguishable from force or pressure in that the term power means force or pressure in motion, and since this motion cannot occur without the expenditure of the force or pressure, power may, with propriety, be termed the expenditure of force or pressure. If we suppose a piston to stand in a vertical cylinder sustaining a weight upon its surface and compressing the air within the cylinder, so long as there is no motion no work is done, as the term "work" is understood in a mechanical sense, and the weight merely produces a pressure. If, however, the weight be removed, the compressed air will force the piston upward, performing a certain quantity of work which may best be measured by the amount of power exercised or expended. The mechanical value of a given amount of power cannot be either increased, diminished or destroyed by means of any mechanical device or appliance whatsoever through which it may be transmitted. It may be concentrated, as it were, by decreasing the amount of its motion. It may be distended, as it were, by increasing the distance through which it moves, or it may be expended in giving or producing motion, but in either case the amount of duty or work done is the exact equivalent of the amount of power applied. A gain or increase in speed is not, therefore, a loss of power, but merely a variation in the mode of using or utilizing such power. For instance, 1 lb. moving through a distance of 12 inches in a given time represents an amount of power which may be employed either as 1 lb. moving a foot, 2 lbs. moving six inches, or 1/2 lb. moving through 24 inches, in the same space of time, the amount of the power or duty remaining the same in each case, the method of utilization merely having differed. It is an inexorable law of nature that power is concentrated in proportion as the amount of its motion is diminished, or distended in precise proportion as such motion is increased. [Illustration: Fig. 3351.] Suppose, for example, that in Fig. 3351 L is a lever having its fulcrum at F, which is 4 inches from end A, and 8 inches from end B, and (leaving the weight of the lever out of the question) if we place an 8 lb. weight on a it will just balance 4 lbs. at B. If the lever is moved, the amount of motion will be twice as much at end B as it is at end A. If we apply the power at A, the lever has become a means of converting 8 lbs. moving a certain distance into 4 lbs. moving twice that distance, and nothing has been either gained or lost. If we apply the power at B, the lever has merely been used as a means of converting 4 lbs. moving a certain distance into 8 lbs. moving one half that distance, and nothing has been gained or lost. Suppose that end A was moved an inch, and the power at that end will be 8 inch pounds or 8 lbs. moving an inch, whereas at the end B the power is 4 lbs. moving 2 inches; we have, therefore, reduced the weight in the same proportion that we have increased the distance moved through. Suppose now that the lever is moved to the position denoted by the dotted line M M, and the leverages will be altered; that at end A becoming that denoted by the distance from F to the vertical C, and that for end B being denoted by the distance from F to the vertical D. This occurs because we are dealing with gravity, which always acts in a vertical line. [Illustration: Fig. 3352.] A crow bar is an excellent example of the application of the lever. In Fig. 3352, for example, we have a 1 lb. weight on the long end of the lever, and as we are dealing with a weight, the effective length of the long end of the lever is from the fulcrum _f_ to _w_, which is divided into 10 equal divisions. The short end of the lever is from _f_ to _p_, which is equal to one division, hence the 1 lb. is balanced by the 10 lbs. [Illustration: Fig. 3353.] A simple method of distending power is by means of pulleys or gear wheels. Suppose, for example, that in Fig. 3353, we have a weight of 12 lbs. suspended from a shaft or drum, whose radius _a_ is 10 inches, and that on the same shaft there is a pulley, whose radius _b_ is 20 inches, and the two weights will balance each other. In this case the falling of either weight would not effect the leverage, because the distance of both weights would remain the same from the centre of the shaft. The leverage of the 12 lbs. is denoted by the line _a_, and that of the 6 lbs. by _b_. So far as the transmission of power is concerned, therefore, pulleys are in effect revolving levers, which may be employed to concentrate or to distend power, but do not vary its amount. [Illustration: Fig. 3354.] Suppose we have two shafts, on the first of which are two pulleys, B and C, Fig. 3354, while upon the second there are two pulleys D and E. A belt H, connecting C to D. Let the pulleys have the following dimensions: If we take the first pair of wheels B and C, we have that the velocity will vary in the same ratio or degree as their diameters vary, notwithstanding that their revolutions are equal. Radius. Diameter. Circumference. B = 5-1/8 inches. 10-1/4 inches. 32.2 inches. C = 10-1/4 " 20-1/2 " 64.4 " D = 7-5/8 " 15-1/4 " 47.9 " E = 15-1/4 " 30-1/2 " 95.8 " The velocity is the space moved through in a unit of time, and as it is the circumference of the pulley that is considered, the velocity of the circumference is that taken; thus, if we make a mark on the circumferences of the two pulleys, B and C, Fig. 3354, the velocity of that on C will be twice that upon B, or in the same proportion as the diameters. Let there be suspended from the circumference of B 10 lbs. weight, and let us see the degree to which this power will be distended by this arrangement of pulleys, supposing the weight to rotate B, and making no allowance for the friction of the shaft. Suppose the weight to have fallen 32.2 inches, and we have 10 lbs. moving through 32.2 inches, this power it will have transmitted to pulley B. To find what this becomes at the perimeter of C, we must reduce the number of lbs. in the same proportion that the perimeter of C moves faster than does that of B; hence we divide the circumference of one into the other, and with the sum so obtained divide the amount of the weight; thus, 64.4 (circumference of C) ÷ 32.2 (circumference of B), = 2; and 10 lbs. ÷ 2 = 5 lbs., which, as the circumference of C is twice that of B, will move twice as fast as the 10 lbs. at B, hence for C we have 5 lbs. moving through 64.4 inches. Now C communicates this to D by means of the belt H, hence we have at D the same 5 lbs. moving through 64.4 inches. Now E moves twice as fast as D, because its circumference is twice as great, and both are fast upon the same shaft, hence the 5 lbs. at D becomes 2-1/2 lbs. at E, but moves through a distance equal to twice 64.4, which is 128.8 inches. To recapitulate, then, we have as follows: The weight gives 10 lbs. moving through 32.2 inches. Pulley B " 10 " " " 32.2 " " C " 5 " " " 64.4 " " D " 5 " " " 64.4 " " E " 2-1/2 " " " 128.8 " That the amount of power is equal in each case, may be shown as follows: For C, 5 lbs. moving through 64.4 inches is an equal amount of power to 10 lbs. moving through 32.2 inches, because if we suppose the first pair of pulleys to be revolving levers, whose fulcrum is the centre of the shaft, it will be plain that one end of the lever being twice as long as the other, its motion will be twice as great, and the 5 at 10-1/4 inches just balances 10, at 5-1/8 inches from the fulcrum, as in the common lever. In the case of D we have the same figures both for weight and motion as we have at C, because D simply receives the weight or force and the motion of C. In the case of E, we have the motion of the weight multiplied four times; for the distance E moves is 128.8 inches, which, divided by 4, gives 32.2 inches, which is the amount of motion of the weight, hence the 10 lbs. of the weight is decreased four times, thus 10 lbs. ÷ 4 = 2-1/2 lbs., hence the 2-1/2 lbs. moving through 128.8 inches is the same amount of power as 10 lbs. moving 32.2 inches, and we may concentrate or convert the one into the other, by dividing 128.8 by 4, and multiplying the 2-1/2 lbs. by 4, giving 10 lbs. moving 32.2 inches. If, therefore, we make no allowance for friction, nothing has been lost and nothing gained. Thus far, we have taken no account of the time in which the work was done, more than as one wheel is caused to move by the other, and all of them by the motion of the weight, they must all have begun and also have to move at the same time. Suppose, then, that the time occupied by the weight in falling the 32.2 inches was one minute, and the amount of power obtained may be found by multiplying the lbs. of the weight by the distance it moved through in the minute, thus 10 lbs. moving 32.2 inches in a minute gives 32.2 inch lbs. per minute, being the amount of power developed by the 10 lb. weight in falling the 32.2 inches. We may now convert the power at each pulley perimeter or circumference into inch pounds by multiplying the respective lbs. by the distance moved through in inches, as per the following table: Distance moved. Lbs. Inches. Inch lbs. of power. Weight at B 10 × 32.2 = 322 " " C 5 × 64.4 = 322 " " D 5 × 64.4 = 322 " " E 2-1/2 × 128.8 = 322 If we require to find the power in foot lbs. per minute, we divide by 12 (because there are 12 inches in a foot), thus 322 inch lbs. ÷ 12 = 26.83 foot lbs. per minute. Now suppose that B was moved by a belt, with a pull of 10 lbs. at its perimeter, and made 100 revolutions in a minute instead of one, then the pull at the perimeters of C, D, and E would remain the same, but the motion would be 100 times as great, and the work done would therefore be increased one hundred fold. It will be apparent, then, that the time is as important an element as the weight. The velocity and power of gear wheels are calculated at the pitch circle. Now suppose the gear A in Fig. 3355 has 30, gear B 60, gear C 10 and gear E 80 teeth, and that 5 lbs. be applied at the pitch circle of A; to find what this 5 lbs. would become at the pitch circle of E, we multiply it by the number of teeth in B and divide it by the number of teeth in C, thus: Lbs. At pitch of circle A 5 Number of teeth in B 60 --- Number of teeth in C 10 ) 300 --- 30 -- Answer, 30 lbs. at the pitch circle of E. Now suppose that on the shaft of A there is a pulley 20 inches in diameter, and that on this pulley there is a belt exerting a pull of 5 lbs., while on the shaft of E there is a pulley 16 inches in diameter, and to find how much this latter pulley would pull its belt, we proceed as follows: 2 ) 20 = Diameter of pulley on A. -- 10 = Radius of pulley on A. 5 = Pull on pulley A. -- Number of teeth in A = 30 ) 50 = Pull at centre of shaft ----- of A. 1.666 60 = Number of teeth on B. ------ Number of teeth on C = 10 ) 99.960 = Pull at axis of shaft ------ of B. 9.996 80 = Number of teeth on E. ------- Radius of pulley on shaft of E 8 ) 799.680 Pull at axis of shaft E. ------- 99.96 Pull at perimeter of last pulley. We have in this case treated each pulley as a lever whose length equalled the radius of the pulley, while in the case of the wheel we have multiplied by the number of teeth when the power was transmitted from the circumference to the shaft, and divided by the number of teeth (the number of teeth representing the circumference) when the power was transmitted from the shaft to the teeth. We thus find that power is composed of three things, first, the amount of impelling force; second, the distance that force moves through; and third, the time it takes to move that distance. If we take a number of pulleys, say four, and arrange them one after another so that they drive by the friction of their circumferences, then the amount of power transmitted by each will be equal and the velocities will be equal, whereas, if we arrange them as in Fig. 3354, the power will be equal for each, but the velocities or space moved through in a given time will vary. What is known as the unit of power is the foot lb., being the amount of power exerted in raising or lifting one lb. one foot, and from what has already been said, it will be perceived that this is the same amount of power as 12 lbs. moving a distance of one inch. Watt determined that the power of a horse was equal to that necessary to raise 33,000 lbs. one foot high in a minute, and this is accepted, in English speaking countries, as being a horse power. An engine or machine has as much horse power as it has capacity to lift 33,000 lbs. a foot high in a minute. CALCULATING THE HORSE POWER OF AN ENGINE. The horse-power of an engine may be calculated as follows: _Rule._--Multiply the area of the piston by the average steam pressure upon the piston throughout the stroke, and by the length of the stroke in inches, which gives the number of inch pounds received by the piston from the steam during one stroke. As there are two piston strokes to one revolution of the engine, we multiply by two, and thus get the number of inch pounds received by the piston in one revolution. By multiplying this by the number of revolutions the engine makes in a minute, we get the number of inch pounds of power received by the piston in a minute. By dividing this by 12, we get the number of foot pounds the piston receives per minute, and dividing this by 33,000 lbs. we get the horse-power of the engine. It has already been stated that Watt determined that a horse was capable of exerting a power equal to the raising of 33,000 lbs. one foot high in a minute, hence, having foot pounds of the engine per minute, dividing them by 33,000 gives the horse power. This gives the amount of power received by the piston, but it is evident that the engine cannot exert so much power, because part of it is expended in overcoming the friction of the moving parts of the engine. The amount of the piston power expended in overcoming the friction depends upon the fit of the parts, upon the lubrication and the amount of the load. Thus, the friction of the cross head guides, of the cross head pin, of the crank pin and of the crank shaft bearings will increase with the amount of resistance offered to the piston motion. The average pressure on the piston is a difficult thing to find, however, for several reasons. First, because the pressure in the cylinder may, during the live steam period, vary from that in the steam chest because of the ports being too small or from the passages being choked from a defective casting. Second, because the steam is wire drawn during the time that the slide valve is closing the port to effect the cut off. Third, because the live steam in the port and passage at the time the cut off occurs gives out some power during the period of expansion. Fourth, because there is some condensation of the steam in the cylinder after the point of cut off, and there is no means of finding by calculation how much loss there may be from this cause. During the live steam period there is also loss from condensation in the cylinder, but this is made up for by steam from the steam chest. Fifth, the loss from condensation after the cut off has occurred will vary with the speed of the engine, and is greater in proportion as the piston speed is less, because there is more time for the condensation to occur in. Sixth, there is some pressure on the piston between the time that the exhaust begins and the piston ends its stroke. Seventh, because the compression absorbs some of the piston power. Assuming the average pressure on the piston to be known, however, we may calculate the horse power as follows: _Example._--What is the horse power of an engine whose piston is 20 inches in diameter, and stroke 30, the revolutions per minute being 120, and the average pressure on the piston 60 lbs. per square inch? Diameter of piston 20 Diameter of piston 20 --- Diameter of piston squared 400 --- .7854 400 ------------ Area of piston = 314.1600 ([<--] these two ciphers neglected.) 60 average steam pressure. -------- lbs. pressure on piston 18849.60 ([<--] this cipher neglected.) 30 length of stroke in inches. -------- 565488.0 inch lbs. per stroke. 2 two piston strokes per revolution. ------- 12 ) 1130976 inch lbs. per revolution. ------- 94248 foot lbs. per revolution. 120 revolutions per minute. ------- 1884960 94248 -------- 11309760 foot lbs. per minute. 33000 ) 11309760 ( 342.72 = horse power of engine. 99000 140976 132000 ------ 89760 66000 ----- 237600 231000 ------ 66000 66000 ----- In working out the calculation, the ciphers that are decimals and are on the right hand are neglected or taken no account of, because they represent no value and may therefore be discarded. [Illustration: Fig. 3355.] Thus the area of the piston is 314.1600 inches, the two right hand ciphers having no value. Again the lbs. pressure on the piston is 18849.60 lbs., and the right hand cipher, having no value, is discarded. The inch lbs. per stroke is 565488.0, and the decimal cipher, representing nothing, is discarded when multiplying by the 2. We have in this case taken no account of the fact that the piston rod prevents the steam from acting against a part of the piston area during one stroke; hence for correct results we must subtract from the area of the piston one half the area of the piston rod. The horse power thus obtained is that which the engine receives from the steam, and is more than the engine is capable of exerting to drive machinery, because a part of this power is consumed in overcoming the friction of the working parts of the engine. TESTING THE HORSE POWER OF AN ENGINE. [Illustration: Fig. 3356.] The useful horse power of a stationary engine may be readily and accurately obtained by means of a pair of scales, and a brake, as shown in Fig. 3356, which is constructed and used as follows: On the crank shaft of the engine is a pulley enveloped by a friction brake, which consists of an iron band, to which wooden blocks are fastened. The ends of the iron band do not meet, but are secured together by a bolt as shown. By screwing up the bolt the wood blocks are brought to press against the circumference of the wheel. This forms a friction brake that would revolve with the wheel, were it not for two arms that are secured to the brake, and rest at the other end upon a block placed upon a pair of scales. The principle of action of this device is that the amount of friction between the brake and the wheel is weighed upon the scales, and this amount, multiplied by the velocity of the wheel at its circumference and divided by 33,000, is the horse-power of the engine. It is necessary, in arranging this brake, to have its end rest upon the scale at the same height from the floor as the centre of the crank shaft, so that the line marked 5' 3" (5 feet 3 inches), which represents the length of the lever, shall stand parallel with the surface of the platform of the scale. To test the horse-power, we proceed as follows: Suppose the pressure of the end of the lever on the scale is found by the weight on the scale beam to be 540 lbs., the diameter on which the brake blocks act being 3 feet, the length of the leverage being 5 feet 3 inches, as marked, and the engine making 150 revolutions per minute, and the calculation is as follows: 540 lbs. on scale. 5.25 leverage in feet. ----- 2700 1080 2700 ------ radius of pulley in feet 1.5 ) 2835.00 ( 1890 lbs. at pulley perimeter. 15 --- 133 120 --- 135 135 ---- ...0 ==== Then 3.1416 3 diameter of pulley in feet. ------ 9.4248 circumference of pulley in feet. 150 revolutions per minute. ------- 4712400 94248 --------- 1413.7200 velocity of pulley perimeter. 1890 pounds at pulley perimeter. --------- 12723480 1130976 141372 ---------- 2671930.80 foot lbs. per minute. ========== Then 33000 ) 2671930.80 ( 80.9 264000 ------ 319308 297000 ------ 223080 ====== Answer, 80-9/10 horse power. In this calculation we have nothing to do with the size of the cylinder or the steam pressure, because the scale beam tells us how many lbs. the brake exerts on the scale, and we treat the brake and brake pulley as levers. Thus by multiplying the lbs. on the scale by the leverage of the brake arm we get the number of lbs. exerted at the centre of the crank shaft, and by dividing this by the radius of the brake pulley we get the number of lbs. on the circumference, or, what is the same thing, the perimeter of the brake pulley. By multiplying the circumference of the pulley in feet by the revolutions per minute, we get the speed at which the pounds travel, and by multiplying this speed by the number of lbs. we get the foot lbs. per minute, which, divided by 33,000, gives us the effective horse power of the engine. This effective horse power is correct, because in loading the engine by the brake the crank pin, the cross head guides, etc., are all placed under the same friction as they would be if it was a circular saw, or some other piece of machinery or machine that the engine was driving. SAFETY VALVE CALCULATIONS. Among the most frequent questions asked in an engineer's examination are those relating to the safety valves of boilers. These questions may be easily answered from a study of the following: The safety valve is a device for relieving the boiler of steam after it has reached a certain pressure. This it accomplishes by letting the steam escape after it has reached the required pressure. At what pressure the safety valve will blow off depends upon the position of the weight on the safety valve lever. The calculations referring to this part of the subject are, finding how much weight will be required to be placed at a given point on the lever, in order, with a given sized valve, to blow off at a given pressure. Finding the position on the lever of a given amount of weight, in order to blow off at a certain pressure. Finding, with a given sized valve and a given weight, how to mark off the lever and where the notches must be cut for given pressures. In each of these calculations there are three elements: first, the area of the valve and the steam pressure, which constitute the effect of acting to lift the valve; second, the amount of the weight and its position upon the lever, which acts to keep the valve closed; and third, the weight of the lever and of the valve, which act to keep the valve closed. [Illustration: Fig. 3357.] In Fig. 3357 we have a drawing of a safety valve shown in section, and if there was no weight upon the lever, the pressure of steam the valve would hold in the boiler would be that due to the weight of the valve and of the lever upon the valve. To find out how much this would be, we would have to put the valve itself and the pin _a_ on a pair of scales and weigh them. Then put a piece of string through the hole at _a_ in the lever, and see how much it weighed when suspended from that point. Suppose the valve and pin to weigh 2 lbs. and the lever (suspended by the string) 10, and the total will be 12 lbs. Next we find the area of the valve, and suppose this to be 8 square inches; then we may find how much pressure the valve would keep in the boiler, by dividing the area of the valve into the weight holding the valve down, thus: Lbs. Weight of valve and pin, 2 " " lever, 10 -- Area of valve, 8 ) 12 --- Pressure the valve would hold, 1.5 lbs. The area of the valve is that part of its face receiving the steam pressure when the valve is seated, so that if the smallest part of the valve diameter is equal to the diameter of the seat bore, the diameter from which the valve area is to be calculated will be that denoted by D in the figure, and cannot in any case be less than this. But if the smallest end of the valve cone is of larger diameter than the smallest end of the seat cone (which should not, but might be the case), then it is the smallest diameter of valve cone that must be taken in calculating the area, because that is the area the steam will press against. Now suppose we rest a 20 lb. weight on the top of the valve that is on the point denoted by I, and there will be 32 lbs. holding the valve down, thus, weight of valve 2 lbs., of lever 10, and weight added, 20 lbs., and to find how much pressure this would hold in the boiler, we divide it by the valve area, thus: Weight on valve. Valve area = 8 ) 32 -- 4 = pressure valve will hold. But suppose we put the weight on the lever, in the position shown in the figure, which is six times as far from the fulcrum F of the lever as the valve is, and its effect on the valve will be six times as great as it would if placed directly upon the valve, so that leaving the weight of the valve and of the lever out of the question (as is commonly done in engineers' examinations), we may find out what pressure the valve will hold, as follows: _Rule._--Divide the length of the lever by the distance from the centre of the valve to the centre of the fulcrum. Multiply by the amount of the weight in lbs., and divide by the area of the valve. _Example._--The area of the valve is 8 inches, the distance from the centre of the fulcrum to the centre of the valve is 4 inches, and the distance from the fulcrum to the point of suspension of the weight 24 inches, the weight is 40 lbs., what pressure will the valve hold? Length of lever. From fulcrum to valve, 4 ) 24 -- 6 40 amount of weight. --- Area of valve, 8 ) 240 --- 30 Lbs. per square inch the valve will hold = 30. The philosophy of this is clear enough when we consider that as the weight is six times as far from the fulcrum as the valve is, and each 1 lb. of weight will press with a force of 6 lbs. on the valve, hence the 40 lbs. will press 240 lbs. on the valve, and as the valve has 8 square inches, the 240 becomes 30 lbs. for each inch of area. _Example._--The area of a safety valve is 8 inches, the distance from the fulcrum to the valve is 4 inches, and the weight is 40 lbs., how far must the weight be from the fulcrum to hold in the boiler a pressure of 30 lbs. per square inch? In lbs. From fulcrum to valve, 4 ) 40 amount of weight. -- 10 Area of valve, 8 square inches. Pressure required, 30 --- 10 ) 240 --- 24 Answer = 24 inches from the fulcrum. _Example._--The diameter of a safety valve is 4 inches, the distance from the centre of the fulcrum to the valve is 3 inches, a 50 lb. weight is 30 inches from the fulcrum, what pressure will the valve hold? 3 diameter of valve. 3 -- 9 .7854 ----- 36 45 72 63 ------ 7.0686 = area of valve. ====== 3 ) 30 -- 10 50 = weight 10 = leverage of weight. ------- Area of valve, 7.068 ) 500.000 ( 70.7 = lbs. pressure per sq. in. 49476 ------- 52400 49476 ----- 2924 HEAT. The heat unit, or the unit whereby heat is measured, is the quantity of heat that is necessary to raise 1 lb. of water from its freezing temperature (which is 32° Fahrenheit) 1°, and this unit is sometimes termed a _thermal unit_. The reason that some specific temperature, as 32° Fahrenheit, is taken, is because the quantity of heat required to heat a given quantity of water 1° increases with the temperature of the water; thus, it takes more heat to raise 1 lb. of water from 240° to 245° than it does to raise it from 235 to 240, although the temperature has been raised 5° in each case. The whole quantity of heat in water or steam is not, however, sensible to the thermometer, or, in other words, is not shown by that instrument. The heat not so shown or indicated is termed _latent_ heat. Water obtains latent heat while passing from a solid to a liquid state, as from ice into water, and while passing from a liquid to a gaseous state, as while passing from water into steam, and the existence of latent heat in steam may be shown as follows: If we take a body of water at a temperature above freezing, and insert therein a thermometer, the decrease in the temperature as the water becomes frozen will be shown by the thermometer. If, then, its temperature being say at zero, heat be continuously imparted to the ice, the thermometer will mark the rise in temperature until the ice begins to melt, when it will remain stationary at 32° so long as any ice remains unmelted, and it is obvious that all the heat that entered the water from the time the ice began to melt until it was all melted became latent, and neither sensible to the sense of feeling nor to the thermometer. Similarly, if the water, after the ice is all melted, be heated in the open air, the thermometer will mark the rise of temperature until the water boils, after which it will show no further rise of temperature, although the water still receives heat. The heat that enters the water from boiling until it is evaporated away is the latent heat of steam. The latent heat of water is 143° Fahrenheit, and that of steam when exposed to the pressure of the atmosphere, or under an atmospheric pressure of 15 lbs. (nearly), is 960°, which may be shown as follows: If a given quantity of water, as say 1 lb., has imparted to it a continuously uniform degree of heat sufficient to cause it to boil in one hour, then it will take about 5-1/3 more hours to evaporate it all away, hence we find the latent heat by taking the difference in the amount of heat received by the water, and that shown by the thermometer thus: Degrees. Temperature by thermometer at boiling point 212 Less the temperature of the water at first 32 --- Heat that entered the water in the first hour 180 Hours that the water was subsequently heated 5-1/3 ------- 900 One-third of 180 = 60 --- Heat that entered the water during the 5-1/3 hours 960 degrees. This, however, is not quite correct, as it would take slightly more than 5-1/3 hours to boil the water away, and the heat that entered the water after it commenced to boil would be about 966 degrees. If the steam that arose from the water while it was boiling were preserved without increasing the pressure under which it boiled, and without losing any of its heat, it will have a temperature the same as that of the water from which it was boiled, which is a temperature of 212°, so that neither the steam nor the water account, by the thermometer, for the 966° of heat that entered the water after it boiled, hence the 966° became latent, constituting the latent heat of the steam when boiled from and at a temperature of 212°. The total heat of steam is the sensible heat, or that shown by the thermometer, added to the latent heat; hence the heat necessary to evaporate water into steam at a temperature of 212° (which corresponds to a pressure of 14.7 lbs. per square inch) is 212° + 966°, which is 1178°, and these, therefore, are the number of degrees that must be imparted by the coal to the water, in order to form steam at a temperature of 212°. WATER. Water is at its greatest density when at a temperature of 39.1° Fahrenheit, that is to say, it occupies its least space and weighs the most per given quantity (as per cubic inch) when at that temperature. At a lower temperature water expands, its freezing point being 32° Fahrenheit, below which it forms ice. The weight of a cubic foot of water when at its maximum density (39.1) is 62.382 lbs. Water also expands as its temperature is increased above 39.1°; thus, while it is heated from 39.1 to 212°, its volume increases from 1 to 1.04332. The expansion for each degree of heat added to its temperature increases from 0 at 40° Fahrenheit to .0043 at 212°. The rate of expansion of water at a temperature above 212° is unknown. STEAM. At every temperature above freezing point water passes from the liquid into a gaseous state, the gas being termed steam. While water is below its boiling point its evaporation occurs at its surface only; but when its mass is heated to boiling point, and additional heat is imparted to it, evaporation occurs from the water lying against the surface from which it receives the heat, and an ebullition is caused by the vaporized water passing through the mass, the ebullition being what is known as boiling. The temperature at which water boils depends upon the pressure acting upon its surface, the boiling point being at a lower temperature in proportion as the pressure is reduced; thus water at the top of a mountain, where the pressure of the atmosphere is less than at the sea level, would boil at a lower temperature than 212°, which is the boiling point when the atmospheric pressure is 14.7 lbs., which it is assumed to be at the sea level. Conversely, the boiling point is raised in proportion as the pressure upon its surface is raised, whether that pressure consists of air or of steam. As, however, the pressure is increased, the boiling point is at a higher temperature. So long as the steam is in contact with the water both are at the same temperature, as denoted by the thermometer (although they do not contain the same quantity of heat, as will be show presently), and the steam is termed _saturated_ steam. The pressure of saturated steam cannot be either increased or diminished without either increasing or diminishing its temperature, hence there is a definite relation of pressure to temperature, which enables the pressure to be known from the temperature, or conversely, the temperature to be known from the pressure. But if the steam be separated from the water and heated, it may be what is termed _superheated_, which is that it may be surcharged with heat or contain more heat than saturated steam at the same pressure. Such additional heat, however, is latent. The pressure of steam is the lbs. of force it exerts upon a given area, as upon a square inch. In non-condensing engines the effective pressure of the steam is its pressure above that of the atmosphere, because the exhaust side of the piston being exposed to the atmosphere receives the atmospheric pressure, which must be overcome by a corresponding pressure of steam on the steam side of the piston, and this pressure is not, therefore, available for producing work or power in the engine. In condensing engines, however, the exhaust side of the piston is (as nearly as practicable), relieved of the atmospheric pressure, and assuming a perfect vacuum to be formed, the whole of the steam pressure is exerted to propel the piston, in which case the steam pressure is termed the _absolute_ pressure. In considering the weight or density or the expansion of steam, its _absolute_ and not its effective pressure must obviously be taken. What is termed dry steam is _saturated_ steam that does not contain what may be termed entrained water, which is water held in suspension in the steam, which may be caused by the surface of the water through which the steam is allowed to rise being too small in proportion to the volume of steam formed, in which case the rapid passage of the steam through the water causes it to carry up water with it and hold it in suspension, this action being termed _foaming_ or _priming_. Suppose, for example, that a boiler be filled with water up to the bottom of the steam dome, then all the steam formed would require to find exit from the water within the area of the dome, and the violence of the ebullition would cause foaming. Obviously, then, to obtain dry steam there must be provided a sufficient area of water surface for the steam to pass through. But water so entrained is evaporated into steam, if the steam is wire drawn, that is, allowed to expand and reduce in pressure. THE EXPANSION OF STEAM. A cubic inch of water, when evaporated into steam at a pressure of 14.7 lbs. per square inch, occupies as steam a space or volume of 1644 cubic inches, and its weight will be equal to that of the water from which it was evaporated. If additional heat be imparted (after its evaporation into steam), such additional heat becomes latent and does not cause an increase of sensible temperature or of pressure. The weight of a given volume of steam, therefore, bears a definite and constant relation to the pressure and sensible temperature of the steam, so that the pressure or the sensible temperature being known, the weight of a given volume, as say a cubic foot, may be known therefrom. Or the weight of a cubic foot of steam being known, its sensible temperature and pressure may be known therefrom. This would not be the case if steam expanded by heat. Suppose, for example, we have a cubic foot of steam at any absolute pressure, as say 15 pounds per square inch, a cubic foot weighing .0387 of a lb., and its sensible temperature will be 213°. Now it is evident that the weight will remain the same whatever the amount of heat that may be imparted to the steam. Now if the steam were maintained within the cubic foot of space, and was capable of expansion by the absorption of additional heat, its pressure would increase and its weight remaining the same, there would be no definite relation between the weight and the temperature and pressure. But if the cubic foot of steam were allowed to expand so as to occupy more space, then additional heat is necessary to prevent its condensation. The relation between the temperature, pressure, and weight of steam is not quite proportional to the volume, because steam is not a perfect gas, and does not, therefore, strictly follow Mariotte's law. A perfect gas is one that during expansion or compression follows the law laid down by Boyle and Mariotte, this law being that, if maintained at a constant temperature, the volume is inversely proportional to the pressure. For example, the quantity of gas that, if confined in a cubic inch of space, would give a pressure of 80 lbs. per square inch, would give a pressure twice as great (or 160 lbs. per inch of area), if confined in one-half the space, that is, if compressed into one-half of a cubic inch. Conversely, if the cubic inch was allowed to expand until its pressure was 40 lbs., it would occupy 2 cubic inches of space, assuming, of course, that the temperature remains the same. Since, however, if a gas be compressed, its temperature is increased by reason of the friction of the particles moving one upon the other, the law of Mariotte may be better explained as follows: Suppose we have three vessels, A, B, and C, filled with a fluid which is a perfect gas, the temperatures being equal. Let the pressure be: A 40, B 80, and C 160 lbs. per square inch, then 2 cubic inches of the fluid in B will weigh the same as 4 cubic inches in A, because that in B is at twice the pressure of that in A, and the 2 cubic inches in B will weigh the same as 1 cubic inch in C, because its pressure is one-half that of C, or, what is the same thing, whatever number of cubic inches of the fluid in C it takes to weigh a pound, it will take twice as many in B, and four times as many in A to weigh one pound. But steam is not a perfect gas, as is evidenced by the fact that its volume does not increase in a ratio inverse to its pressure. For example, if a cubic inch of water be evaporated into steam at a pressure of 14.7 lbs. per square inch, its volume will be 1644 cubic inches, and its temperature 212° Fahrenheit. But if the cubic inch of water be evaporated into steam at twice the pressure, which is 29.4 lbs per square inch, its volume will be 838 inches. The volume then is not inversely as the pressure, although the actual quantity and weight remain the same, as is proven by the fact that if the steam at either pressure were condensed it would pass back into the cubic inch of water from which it was generated. This may be accounted for in the difference in the boiling point of the water in the two pressures, or in other words, by the difference in the temperatures; thus the boiling point of the water at a pressure of 14.7 lbs. is 212°, while that for the pressure of 29.4 is increased about 38.4 degrees, and the steam is at the higher pressure expanded by these 38.4 degrees of heat, which adds to its pressure, although not affecting its actual quantity or weight. The amount of this expansion may be estimated as follows: Taking the 1644 cubic inches, and supposing the steam to be a perfect gas, we divide it by 2 to obtain half the volume, 1644 ÷ 2 = 822. If then we subtract this 822, which is the volume of the steam if it acted as a perfect gas from the 838 it actually occupies, we get 16 (838-822 = 16), which is the number of cubic inches of expansion due to the increase in the boiling temperature. THE CONVERSION OF HEAT INTO WORK. When steam performs work a certain portion of the heat it contains is converted into work, the steam simply being a medium of conveying the heat into the cylinder in which the motion of the piston converts this proportion of heat into work. It has been proven that a given quantity of heat will pass into a given quantity of work, and conversely that a given quantity of work is convertible into a given quantity of heat, and it has also been proven that so much heat is convertible into so much work, independent of the temperature of the heat during its conversion into work, power, or energy, all three of these words being used to imply pressure, force, or weight in motion. The accepted measurement of the conversion of heat into work is known as _Joule's equivalent_; _Joule_ having determined that the amount of power exerted in raising 772 lbs. one foot is the equivalent of the amount of heat that is required to raise the temperature of 1 lb. of water when at or near its freezing point (that is, at a temperature of 32°) one degree. This is called the _mechanical equivalent of heat_, being merely the quantity of heat necessary to do a certain amount of work, but having no relation to the time in which that work was done. The conversion of heat into work and of work into heat may be demonstrated as follows: Suppose a cylinder to be so situated that heat can neither be transferred to it or from it, and that saturated steam be admitted under the piston so as to fill one-half of the cylinder at a pressure of 50 lbs. Suppose then that we raise the piston from an independent application of power, the steam simply expanding to fill the space given by the piston, but not exerting its force to move the piston. Now suppose the experiment is repeated, permitting the force of the steam to lift the piston, and the temperature of the steam will be less in the second than it was in the first, proving that in the second experiment a certain portion of the heat in the steam was converted into the work of raising the piston. If we desire to reconvert the work into heat, we may force the piston back again to its original position, and its temperature will be restored to what it was before we allowed it to raise the piston. It is here, of course, assumed that there is no friction in moving the piston in the cylinder. The apparent or external work performed by steam in expanding and moving a piston against a given resistance is measurable by multiplying the amount of the resistance against which the piston moved by the distance it moved through, thus: Suppose a piston weighs 100 lbs. and had resting upon it a weight of 50 lbs., and that it be raised by the expansive action of steam a distance of a foot, then, since the total resistance it moved against would be (supposing it to move frictionless in the cylinder) 150 lbs., and since the amount of motion was 1 foot, the external or apparent amount of work performed by the steam will be 150 foot lbs., or 150 lbs. moved 1 foot. But in expanding, the steam has performed a certain amount of what is called _internal_ work, that is to say, its particles or atoms have done work in expanding, and this work has been done at the expense of some of the heat in the steam, so that the loss of heat due to the motion of the piston is the amount of heat converted into work in moving the piston against the piston resistance, added to that converted into the internal work due to the expansion of the steam. It is because of this internal work that the steam in expanding does not strictly follow Mariotte's law. The mechanical theory of heat is, that the atoms of which bodies are composed are at absolute rest when at a temperature of 461.2° below the zero of Fahrenheit, which is supposed to be absolute cold, and at any degree of temperature above this the atoms are in motion; the extent and force of their motion determines what we know as the temperature of the body. Atoms are capable of transmitting their motion to adjoining atoms of the same or of other bodies, losing, of course, the amount of motion they transmit, and it is in this way that heat is conveyed from one to another part of the same body, or from one body to another, this being known as the heat of _conduction_. But heat may be conveyed by means of what is known as _radiation_, and also by _convection_. Thus, the air surrounding a heated body becomes heated, and by reason of its expansion it then becomes lighter and rises, a fresh supply of cooler air taking its place, becoming in turn heated, and again giving place to cooler air; the heat thus conveyed away by the fluid or air is conveyed by what is termed _convection_. Heat also passes from a body in straight lines or rays, which do not heat the air through which they pass to their own temperature, but do impart that temperature to a solid body, as iron or water; the heat that passes from a body in this manner is termed radiant heat, or the heat of _radiation_. In the cylinder of a steam engine, therefore, the heat contained in the steam is disposed of as follows: A certain portion of it is converted into work through the medium of the piston. Another portion is conveyed away by the walls of the cylinder, this portion including the heat of convection and that of radiation. Yet another portion is converted into internal work. Referring to the latter, suppose that steam is permitted to expand and its atoms will be in motion, which motion has been derived at the expense of or from the conversion of a certain quantity of heat. The amount of the heat so converted obviously depends upon the amount of the motion. Suppose, for example, that steam is generated in a closed vessel as in a steam boiler, and that a certain pressure having been attained, the steam is permitted to pass off as fast as it is formed from the boiler, then the amount of atomic motion will remain constant, because the pressure remains constant; but suppose instead of the steam passing off, it be confined within the boiler, then the pressure will increase and there will be a greater resistance to the motion of the atoms, hence their motion will be less, and less of their heat will therefore be converted into atomic motion, and, as a consequence, more of it will exist in the form of sensible heat; hence while the pressure of steam continues to increase, its heat is increased, not only by reason of the heat it receives from the furnace, but also by reason of that abandoned by the steam, because it is prevented by the pressure, from expending it in atomic motion. CHAPTER XL.--THE INDICATOR. The indicator is an instrument which marks or draws a figure, or diagram as it is called, which shows the pressure there is in the cylinder at every point in the piston stroke, while it also shows the resistance offered by the same body of steam to the piston on its return stroke. From the form of this figure or diagram, the engineer is enabled to discover whether those parts of the engine whose operation regulates the admission of the steam to and its exhaust from the cylinder are correctly adjusted. From the diagram the engineer may find the average or mean effective pressure of steam on the piston throughout the stroke, for use in calculating the power of the engine. He may also locate the point of cut off, of release, the amount of back pressure, the degree of perfection of the vacuum in a condensing engine, and the amount of compression. From the area of the diagram the engineer may also estimate the quantity of steam that is used, and supposing it to be dry steam, he may calculate the amount of water used to make the steam, and assuming one pound of coal to evaporate so much water, he may calculate the amount of coal used to produce the steam. The indicators commonly used upon steam cylinders contain two principal mechanical movements; first, a drum revolving the piece of paper upon which the diagram is to be marked, and second, a piston and parallel motion for moving the pencil to mark the diagram upon the revolving paper. The drum is given a motion that, to insure a correct diagram, is exactly timed with the piston motion. The pencil is given a vertical movement; this movement must bear a constant and uniform relation to the pressure of the steam in the engine cylinder. [Illustration: Fig. 3358.] An indicator may be attached to each end of the cylinder or in the middle, with a pipe passing to each end of the cylinder, as in Fig. 3358, but an indicator of the usual construction and such as here referred to, can take a diagram, or _card_ as it is sometimes called, from but one end of the cylinder at a time. The stop valves A and B are used, so that the communication between the indicator and one end of the cylinder may be shut off while a diagram is being taken from the other end, while both ends may be shut off when the indicator is not being used. In the figure a piece of paper (or card, as it is commonly called) is shown in place upon the drum with a diagram upon it. [Illustration: Fig. 3359.] [Illustration: Fig. 3360.] The Thompson Indicator is shown in Fig. 3359, and in section in Fig. 3360. The Tabor Indicator is shown in Fig. 3361, and in section in Fig. 3362. Both are made with the piston and parallel motion as light as possible, in order to enable the taking of diagrams at as high a speed of engine revolution as possible. Each consists of a cylinder and piston, the bottom surface of the latter being in communication with the bore of the engine cylinder, so as to receive whatever steam pressure there may be in the cylinder. This indicator piston receives, on its upper surface, the pressure of a spiral spring, which acts to resist the steam pressure. The indicator piston rod actuates an arm or line on the end of which is a pencil, which, by means of a parallel motion, is caused to move in a straight line. The paper or _card_ being in place upon the drum, and steam let into the indicator, the pencil lever is moved until the pencil touches the paper as lightly as possible, and as a result of the combined movements of the pencil and drum, the diagram is marked, its form being illustrated in Fig. 3363, which represents a diagram placed above a cylinder, and the engine piston in three positions; first at the beginning of the stroke; second, at the point of cut off (which is supposed to be at one-third of the stroke); and third, at the point of release where the valve first opens the port for the exhaust. For convenience, the diagram is shown as long as the cylinder, but the actual diagram usually measures about 2-1/2 inches high and 4-1/4 inches long. [Illustration: Fig. 3361.] [Illustration: Fig. 3362.] [Illustration: Fig. 3363.] Supposing the cylinder to be filled with air, and the engine piston in position 1, and the indicator piston would be at the corner A of the diagram; but if steam were admitted, the pencil would rise vertically, marking the line from A to B, which is therefore called the _admission line_, or by some, the _induction line_. If on reaching B the pressure was enough to move the engine piston, that piston and the indicator drum would move simultaneously, and as long as live steam was admitted the line from B to C would be drawn, hence this is called the _steam line_, its length denoting the live steam period. The cut off occurs when the engine piston is in position 2, and the indicator pencil at C. From this point the pencil will fall, in proportion as the steam pressure falls from expansion until the exhaust begins, the piston then being in position 3, and the pencil at D. The line from C to D is therefore called the _expansion line_ or _expansion curve_, and the point D the _point of release_ or _point of exhaust_. We have now to explain that in reality the whole of the remainder of the line of the diagram is, in reality, the exhaust line, yet there is a difference between the part of the line from point D to the end E of the diagram, and that part from E to A, inasmuch as that during the period of exhaust from D to E, the pressure is helping to propel the piston, while after E is reached, whatever steam pressure there may remain in the cylinder acts to retard the piston. The line from D to E is therefore the exhaust line, and that from E to A is the _back pressure line_ or _counter pressure line_. In this example it has been supposed that while the piston was moving from position 3 to the end of its stroke, and the pencil from D to E, the indicator piston would have a steam pressure on it equal to atmospheric pressure, hence the line from E to A, in this case, represents the atmospheric line, and also the back pressure line. The atmospheric line is a line drawn when there is no steam admitted to the indicator, and represents a pressure above a perfect vacuum equal to the pressure of the atmosphere. Its use is to show the amount of back pressure, and in a condensing engine to show the degree of vacuum obtained. It also forms a line wherefrom the line of perfect vacuum, or that of full boiler pressure, may be marked. The steam pressure at any point in the stroke is denoted by the height of the diagram above the atmospheric line, but the steam pressure thus taken is obviously above atmospheric, and is thus the same as the pressure of a steam gauge, which is also above the atmospheric pressure, and therefore represents the pressure that produces useful effect in a non-condensing engine. This is what may be called a theoretical diagram, because, first, it supposes the steam not to be admitted to the cylinder until the piston was at the end of its stroke, and to attain its full pressure in the cylinder before the piston lead begins to move, whereas, in order to attain a full steam pressure at the beginning of the stroke, the valve must have lead. Second, it supposes the cut off to be effected simultaneously, whereas the valve must have time to move and close the port, and during this time the steam pressure will fall, and the curve C of the diagram will therefore be rounded more or less according to the rapidity with which the valve closed. Third, it supposes the steam to have exhausted down to atmospheric pressure by the time the piston had reached the end of the stroke, whereas the piston will have moved some part of the back or return stroke before the steam will have had time to exhaust down to atmospheric pressure; and, Fourth, it supposes the steam to remain at atmospheric pressure until the piston arrives at the end of its return stroke, whereas the valve will begin to close the port and cause the steam remaining in the cylinder to compress before the piston has completed its return stroke. In practice the diagram will, under favorable conditions, accord nearer to the shape shown in the lower part of Fig. 3363, in which the closure of the port for the cut off is shown by the curve at F. At the point denoted by _g_ the valve began to close, and at the point denoted by _h_ the cut off was completely effected, and the expansion curve began. The curve beginning at D is caused by the gradual opening of the exhaust port. The height of the line of back pressure above the atmospheric line shows the amount of back pressure. At the point _m_, where the back pressure line rises into a curve, the valve had closed, shutting in the cylinder a portion of the exhaust steam, which is afterwards compressed by the piston. This curve is therefore called the _compression line_ or _compression curve_. The point at which it begins cannot be clearly seen when the exhaust port is closed slowly. The compression curve ends at _p_, where it merges into the admission line, but the exact point where the compression ends and the admission begins cannot always be located, this being the case when the port is opened slowly or the compression extends through a large portion of the stroke. The admission line is, however, in most cases nearly vertical when the valve has lead, because the valve opens the port quickly while the engine piston is moving at its slowest. A diagram as drawn by the indicator does not account for all the steam that is used in the cylinder, however, as will be seen from Fig. 3363, because, as the paper drum of the indicator receives its motion from the engine cross head, its length represents the length of the piston stroke, whereas, there is a part of the cylinder bore between the piston (when it is at the end of the stroke) and the cylinder cover that is filled with steam as is also the steam passage. This steam performs no useful work during the live steam period, but obviously expands during the expansion period, and therefore affects the expansion curve, and must be taken account of in calculating the consumption of steam, of water, or of coal from the diagram, or in marking in the true expansion curve. In calculating the horse power, however, it may be neglected, as it does not enter into that subject. But in any calculation involving the amount of steam used, the clearance must be marked in by a line at a right angle to the admission line and distant from the nearest point of the admission line to an amount that bears the same proportion to the whole length of the diagram as the clearance does to the whole contents of the cylinder. The clearance line is shown at L, L´, in Fig. 3363, its distance from the admission line representing the amount of clearance which includes the contents of the steam port and passage, as well as that of the cylinder bore that is between the cylinder cover and the piston, when the latter is at the end of the stroke. A method of measuring the amount of clearance has already been given with reference to stationary steam engines. [Illustration: Fig. 3364.] A diagram for a condensing engine is shown in Fig. 3364, which corresponds to Fig. 3363, except that the line of perfect vacuum or no pressure is marked in. It represents a perfect vacuum, and must be marked on all diagrams from which the consumption of steam is to be calculated, because the quantity of steam used obviously includes that which is used in counter balancing the pressure of the atmosphere. Learners often get confused on this point, hence it may be more fully explained as follows: Suppose the engine piston to be blocked, in the middle of the cylinder, and has on one side of it a pressure of 20 lbs. of steam by steam gauge, and on the other the pressure of the atmosphere, and we might pump out the steam, thus leaving the cylinder empty on that side of the piston. The atmosphere would then exert a pressure of about 14-1/2 lbs. per square inch on one side of the piston, and if we slowly admitted steam again, it would have to get up a pressure of 14-1/2 lbs. per square inch before the atmospheric pressure would be counterbalanced and the piston be in equilibrium. But the steam gauge would at this time stand at zero, and not show that there was any steam in the cylinder, because the zero of the steam gauge is atmospheric pressure. When, therefore, the steam gauge showed a pressure of 20 lbs. of steam in the cylinder, there would actually be a pressure of 34-1/2 lbs. of steam per square inch. The clearance line and the vacuum line must both, therefore, be marked on the diagram when the quantity of steam used is to be computed from the diagram, and also when the proper or theoretical expansion curve is to be marked on the diagram. This is clear, because in finding the expansion curve for a given volume of steam the whole of its volume must be taken into account, and this whole volume is represented by the area inclosed within the clearance line, the steam line, the expansion curve, the exhaust line, and the line of perfect vacuum, or line of no pressure. The atmospheric line should be drawn after the diagram has been taken, and while the indicator is hot, as the expansion of the indicator affects the position of this line. It is drawn with the steam shut entirely off from the indicator, whose piston therefore has atmospheric pressure on both sides of it. Whether the engine is condensing or non-condensing, the same amount of steam (all other things being equal) is used, the only difference being that in a condensing engine a greater portion of the steam is available for driving the piston. If the condenser produced a perfect vacuum, the whole of the steam would be utilized in propelling the piston. The "line of no pressure," or of perfect vacuum, is marked as far below the atmospheric line as will represent the pressure of the atmosphere, which is, at the sea level, about 14.7 lbs. per square inch when the barometer stands at 29.99 inches. THE BAROMETER. A barometer is an instrument for denoting the pressure or weight of the atmosphere, which it does by means of a column of mercury inclosed in a tube, in which there is a vacuum, which may be produced as follows: A tube having a parallel bore and closed at one end is filled with mercury and while the finger is placed over the open end of the tube, it is turned upside down and inverted in a cup of mercury that is open to receive the pressure of the atmosphere. The finger is then removed from the end of the tube and the mercury will fall, leaving a vacuum at its upper end. The pressure of the atmosphere on the surface of the mercury in the cup forces the mercury up the tube, because the surface of the mercury in the tube has no atmospheric pressure on it, the action being the same as that already described with reference to the principles of action of a pump. The weight of the atmosphere is equal to the weight of that part of the column of mercury that is above the surface of the mercury in the cup, hence lines may be drawn at different heights representing the weight of the atmosphere, or of any other gas, when the column of mercury stands at the heights denoted by the respective lines. But as mercury expands by heat, a definite degree of temperature must be taken in marking a column, to represent the weight, this temperature being 32° Fahrenheit. Similarly, as the weight of the atmosphere varies, according to the height at which it is taken from the surface of the earth, a definite height must be taken. The sea level is that usually taken, the mean or average atmosphere (at that level) being 14.7 lbs. per square inch. For higher altitudes, the mean atmospheric pressure in lbs. per square inch may be found by multiplying the altitude or height above sea level by .00053, and subtracting the product from 14.7. Each pound on the square inch is represented by a height of 2.036 inches of mercury, hence the height of a column of mercury at a temperature of 32° that will balance the mean weight of the atmosphere is 29.92 inches, and to avoid fractions, it is usual (for purposes not requiring to be very exact) to say that the atmospheric pressure at sea level is represented by 30 inches of mercury. The atmospheric pressure is also, to avoid using fractions, taken roughly at 15 lbs. per square inch at sea level. Each 2 inches of mercury will, under these conditions, represent 1 lb. of pressure. Vacuum gauges are based upon the same principles and subject to the same variations as to altitude as mercury gauges or the barometer. To find the absolute pressure, or pressure above zero, or a perfect vacuum, we may add the pressure of the boiler steam gauge to that shown by the mercury gauge or barometer. In Fig. 3364 the line of no pressure is marked at 15 lbs. per square inch below the atmospheric line of the diagram, the atmospheric pressure being for convenience taken as 15 lbs. above a perfect vacuum. The line of no pressure serves as a guide in showing the effectiveness of the condenser, as well as for computing the volume of steam used, but is not necessary in computing the horse power of a non-condensing engine, because the gauge pressure has its zero marked to correspond with the atmospheric pressure. In computing the consumption of steam or water from the diagram, therefore, both the clearance line and the line of no pressure must be marked on the diagram, and lines of the diagram extended so as to include them, thus accounting for all the steam that leaves the steam chest from the piston stroke. Indicator springs are varied in strength to suit the pressure of steam they are to be used for. The scale of the spring is the number of lbs. pressure per square inch represented by a vertical motion of the pencil; thus, a 40 lb. spring is one in which a pressure of steam of 40 lbs. per square inch would cause the piston to rise an inch above the atmospheric line of the diagram. The strength or tension of the spring is so adjusted as to cause the diagram to be about 2-1/2 inches high, let the steam pressure be what it may. The following are the scales of springs of the Thompson and Tabor indicator. THOMPSON INDICATOR. Scale of Used for pressure above atmosphere spring. if not more than 15 lbs. 21 lbs. per square inch. 20 " 38 " " " " 30 " 94 " " " " 40 " 90 " " " " 60 " 143 " " " " TABOR INDICATOR. 10 lbs. 14 " " " " 12 " 20 " " " " 16 " 30 " " " " 20 " 40 " " " " 24 " 48 " " " " 30 " 60 " " " " 32 " 64 " " " " 40 " 80 " " " " 48 " 96 " " " " 50 " 100 " " " " 60 " 120 " " " " 64 " 128 " " " " 80 " 160 " " " " A spring that is strong enough for a given pressure may be used for any less pressure. The height of the diagram will, however, be less, and accuracy is best secured by having the diagram up to the limit of about 2-1/2 inches, using a spring that is light enough to secure this result. Diagrams of high speed engines, however, will have their lines more regular in proportion as a stronger spring is used. This occurs because the spring, being under more tension, is less liable to vibration. An indicator requires careful cleaning and oiling with the best of oil, as the slightest undue friction seriously impairs the working of the instrument. Instructions upon the care of the instrument, and how to take it apart, etc., are usually given by the makers of the indicator. There are various methods of giving to the paper drum of the indicator a motion coincident with that of the engine piston, but few of them give correct results. Reducing levers, such as shown in Fig. 3365, are constructed as follows: [Illustration: Fig. 3365.] Fig. 3365 represents a reducing lever with the indicators attached. A C is a strip of pine board three or four inches wide and about one and one-half times as long as the stroke of the engine. It is hung by a screw or small bolt to a wooden frame attached overhead. A link C one-third as long as the stroke is attached at one end to the lever, and at the other end to a stud screwed into the cross head, or to an iron clamped to the cross head by one of the nuts that adjust the gibs, or to any part of the cross head that may be conveniently used. The lever should stand in a vertical position when the piston is at the middle of the stroke. The connecting link C, when at that point, should be as far below a horizontal position as it is above it at either end of the stroke. The cords which drive the paper drums may be attached to a screw inserted in the lever near the point of suspension; but a better plan is to provide a segment, A, B, the centre of which coincides with the point of suspension, and allow the cord to pass around the circular edge. The distance from edge to centre should bear the same proportion to the length of the reducing lever as the desired length of diagram bears to the length of the stroke. On an engine having a stroke of 48 inches, the lever should be 72 inches, and the link C 16 inches in length, in which case, to obtain a diagram 4 inches long, the radius of the segment would be 6 inches. It is immaterial what the actual length of the diagram is, except as it suits the operator's fancy, but 4 inches is a length that is usually satisfactory. It may be reduced to advantage to 3 inches at very high speeds. The cords should leave the segment in a line parallel with the axis of the engine cylinder. The pulleys over which they pass should incline from a vertical plane and point to the indicators wherever they may be located. If the indicators and the reducing lever can be placed so as to be in line with each other, the pulleys may be dispensed with and the cords carried directly from the segment to the instruments, a longer arc being provided for this purpose. The arm which holds the carrier pulleys on each indicator should be adjusted so as to point in the direction in which the cord is received. In all arrangements of this kind the reduced motion is not mathematically exact, because the leverage is not constant at all points of the stroke. Pantagraph motions have been devised for overcoming these defects. Two forms have been successfully used, which, if well made, well cared for, and properly handled, reproduce the motion on the reduced scale with perfect accuracy. They are shown in working position in Figs. 3366 and 3367. [Illustration: Fig. 3366.] Fig. 3366 represents the manner of attaching the pantagraph motion, or _lazy tongs_, as it is sometimes called, when the indicators are applied to the side of the cylinder. It works in a horizontal plane, the pivot end being supported by a post B erected in front of the guides, and the working end receiving motion from an iron attached to the cross head. By adjusting the post to the proper height and at a proper distance in front of the cross head, the cords may be carried from the cord pin C to the indicators, without the intervention of carrier pulleys. [Illustration: Fig. 3367.] If the indicators are attached to the side of the cylinder, the simplest form of pantagraph shown in Fig. 3367 may be used. The working end A receives motion from the cross head, and the front piece B is attached to the floor. The cord pin D is fixed in line between the pivot and the working end, and the pulleys E, attached to the block C, guide the cords to the indicators. The indicator rigging that gives the best results at high speeds is a plain reducing lever like that first described, provided at the lower end with a slot that receives a stud, screwed into the cross head. The length of the lever should be one and one-half times the engine stroke, as given on the preceding page. Whatever plan is followed, it is desirable to avoid the use of long stretches of cord. If the motion must be carried a long distance, strips of wood may often be arranged in their place and operated with direct connections. Braided linen cord, a little in excess of one-sixteenth of an inch in diameter, is a suitable material for indicator work. To take a diagram, a blank card is stretched smoothly upon the paper drum, the ends being held by the spring clips. The driving cord is attached and so adjusted that the motion of the drum is central. For convenience two diagrams, one from each end of the cylinder, may be made on the same card, as shown in Fig. 3368. [Illustration: Fig. 3368.] TESTING THE EXPANSION CURVE. The usual manner of testing the expansion curve of a diagram is to compare it with a curve representing Mariotte's law for the expansion of a perfect gas. A theoretic expansion curve that will accord with Mariotte's law may be constructed on the diagram by the following method: The diagram, as drawn by the indicator, will have the atmospheric line upon it, and from this as a basis we may mark in the line of no pressure or line of perfect vacuum. To do this we draw, beneath the atmospheric line, a line as far beneath it as will represent the atmospheric line, on the same scale as the spring used, in the indicator, to draw the diagram. Suppose, for example, that a 30 lb. spring was used, and assuming the atmospheric pressure to be 15 lbs. per inch, then the line of no pressure would be drawn half an inch below the atmospheric line, because 15 lbs. pull on the spring would cause it to distend half an inch. The clearance line must then be drawn in, according to directions that have already been given. The next thing to do is to divide the length of the diagram into any convenient number of equal parts, by vertical lines parallel to, and beginning at, the clearance line, as shown in Fig. 3369. These lines are numbered as shown, ten of them being used because that is a convenient number, but any other number would do. We next decide at which part of the diagram its expansion curve and the test curve shall touch, and in this example we have chosen that it shall be at line 10. We have now to find what pressure the length of line 10 represents on the scale of the indicator spring, which in this case we will suppose to be 25 lbs., the line measuring 25/30 of an inch, and a 30 lb. spring having been used to draw the diagram. Next multiply the pressure (25 lbs.) by the number of the line (10), and divide the product (250) by the number of each of the other lines in succession, and the quotient will be the pressures to be represented by the lines. For example, for line 9 we have that 250 divided by 9 gives 27.7, hence line 9 must be long or high enough to represent a pressure of 27.7 lbs. above a perfect vacuum, or in this case 27.7/30 of an inch. For line 8 we have that 250 divided by 8 gives 31.25 lbs., hence line 8 must be high enough to represent a pressure of 31.25 lbs. above a perfect vacuum. The atmospheric line is, in this case, of no other service than to form a guide wherefrom to mark in the line of no pressure, or of perfect vacuum. [Illustration: Fig. 3369.] Now take the case of line 5, and 250 divided by 5 gives 50, hence the height of line 5 must represent a pressure above vacuum of 50 lbs. Having carried this out for all the lines from line 10 to line 1, we draw in the true expansion curve, which will touch the tops of all the lines. [Illustration: Fig. 3370.] Another method of drawing this curve is shown in Fig. 3370. Having drawn the clearance line B C, and vacuum line D C, as before and chosen where the curves shall touch (as at _a_), then draw from _a_ a perpendicular _a_ A. Draw line A B, parallel to the vacuum line, and at any convenient height above or near the top of the diagram. From A draw A C, and from _a_ draw _a_ _b_ parallel to D C, then from its intersection with A C, erect the perpendicular _b_ _c_, locating on A B, the theoretical point (_c_) of cut-off. From a number of points on A B (which may be located without regard to equally spacing them), such as E, F, G and H, draw lines to C, and also drop perpendicular lines, as E _e_, F _f_, G _g_, H _h_. From the intersection of E C with _b_ _c_, draw a horizontal line to _e_. From the intersection of F C with _b_ _c_, draw a horizontal line, and so on; and where these horizontals cut the verticals (as at _e_, _f_, _g_, _h_) are points in the curve, which begins at _c_, and passes through _e_, _f_, _g_, _h_, to _a_. But this curve does not correctly represent the expansion of steam. It would do so if the steam remained or was maintained at a uniform temperature; hence it is called the isothermal curve, or curve of same temperature. But in fact steam and all other elastic fluids fall in temperature during their expansion, and rise during compression, and this change of temperature slightly affects the pressure. A curve in which the combined effects of volume and resulting temperatures is represented is called the _adiabatic_ curve, or curve of no transmission; since, if no heat is transmitted to or from the fluid during change of volume, its sensible temperature will change according to a fixed ratio, which will be the same for the same fluid in all cases. A sufficiently close approximation to the adiabatic curve to enable the non-professional engineer to form an idea of the difference between the two may be produced by the following process: Taking a similar diagram to that used for the foregoing illustrations, as in Fig. 3371. Fix on a point A near the terminal, where the total pressure is 25 pounds. As before, this point is chosen in order that the two curves may coincide there. Any other point might have been chosen for the point of coincidence; but a point in that vicinity is generally chosen, so that the result will show the amount of power that should be obtained from the existing terminal. This point is 3.3 inches from the clearance line, and the volume of 25 pounds 996, that is, steam of that pressure has 996 times the bulk of water. Now if we divide the distance of A from the clearance line by 996, and multiply the quotient by each of the volumes of the other pressures indicated by similar lines, the products will be the respective lengths of the lines measured from the clearance line; the desired curve passing through their other ends. Thus, the quotient of the first or 25 lb. pressure line divided by 996 is .003313; this, multiplied by 726, the volume of 35 lbs. pressure, gives 2.4, the length of the 35 lb. pressure line; and so on for all the rest. The application of either of the above curves will show that some diagrams are much more accurate than others, even though taken from engines of the same design and quality of workmanship. As a general rule, those from large engines will be more correct than from small ones, and those from high more correct than from low speeds, and in either case efficiently covering the steam pipes and jacketing the cylinder, to prevent condensation, will improve the diagram. The character of the imperfection in the expansion curve, shown by the application of a test curve, is generally too high a terminal pressure for the point of cut off, the first part of the curve being generally the most correct, and nearly all the inaccuracy appearing in the last half. The usual explanation of this is, that the steam admitted during the live steam period condenses because of having to heat the cylinder, and that this water of condensation re-evaporates during the latter part of the stroke when this water of condensation is at a higher temperature than the expanded steam, and thus increases the pressure. A leaky admission valve may generally, however, be looked for (or else wet steam), if the expansion curve rises much during its lower half. TO CALCULATE THE HORSE POWER FROM A DIAGRAM. In calculating the horse power of an engine, the only assistance given by the indicator is, that it provides a means of obtaining the average pressure of the steam throughout the piston stroke. There are two methods of doing this, one by means of a planimeter or averaging instrument, and the other by means of lines called _ordinates_. The ordinates or lines are drawn at a right angle to the atmospheric line, as shown in Fig. 3372, and each line is taken to represent the average height or length of one-half of the space between itself and the next lines. [Illustration: Fig. 3371.] Suppose, for example, that we require to get the area of that part of the diagram that lies between the dotted lines in the figure, and it is clear that the average height of this part of the diagram is represented by the height of the full line between them. Any number of ordinates may be used, and the greater their number the greater the accuracy obtained. It is, however, usual to draw 10. [Illustration: Fig. 3372.] The end ordinates A and D, in the figure, should be only half the distance from the ends of the diagram that they are from the next ordinate, as will be seen when it is considered that the ordinate is in the middle of the space it represents. The ordinates being drawn their lengths, are added together, and the sum so obtained is divided by the number of ordinates, which gives the average height of the ordinates. Suppose, then, that the average height of the ordinate is two inches, and that the scale of the spring of the indicator that took the diagram was 30 lbs., then the average pressure, shown by the diagram, will be 60 lbs. per square inch. Or in other words, each inch in the height of the ordinate represents 30 lbs. pressure per square inch. The mean effective pressure having been found, the indicated horse power (or I. H. P. as it is given in brief) is found by multiplying together the area of the piston (minus half the area of the piston rod when great accuracy is required) and the travel of the piston in feet per minute, and dividing the product by 33,000, an example having been already explained. It is to be observed, however, that when great accuracy is required a diagram should be taken from each end of the cylinder, as the mean effective pressure at one end of the cylinder may vary considerably from that at the other. This will be the case when a single valve is used with equal lap, because, in this case, the point of cut off will vary on one stroke as compared with the other, which occurs by reason of the angularity of the connecting rod. When cut off valves or two admission valves are used, it may occur from improper adjustment of the valves. It occurs in all engines, because on one side of the piston the piston rod excludes the steam from the piston face, unless, indeed, the piston rod passes through both covers, in which case the rod area must be subtracted from the piston area. If the expansion curve in a diagram from a non-condensing engine should pass below the atmospheric line, then the mean effective pressure of that part of the card that is below the atmospheric line must be subtracted from the mean effective pressure of that part that is above the atmospheric line, because the part below represents back pressure or pressure resisting the piston motion. The planimeter affords a much quicker and more accurate method of obtaining the average steam pressure from a diagram. [Illustration: Fig. 3373.] Coffin's averaging instrument or planimeter is shown in Fig. 3373. The diagram is traced by the point O, and the register wheel gives the area of the diagram. A quick method of approximating the mean effective pressure (or M. E. P. as it is called) of a diagram is to draw a line _a_ _b_, in Fig. 3374, touching the expansion curve at _a_, and so inclined that the space _e_ is, as near as the eye can judge, equal to the space _d_. Then the line _f_ drawn in the middle of the diagram, and measured on the scale of the spring that was used to take the diagram, represents the mean effective pressure, or M. E. P. of the diagram. CALCULATING THE AMOUNT OF STEAM OR WATER USED. The amount of water evaporated in the boiler is not accounted for by an indicator diagram or card, and the full reasons for this are not known. It is obvious, however, that the loss, from the steam being unduly wet or containing water held in suspension, is not shown by the diagram, and this amount of loss will vary with the conditions. Thus the loss from this cause will be less in proportion as the point of cut off occurs earlier in the stroke, because, as the water is at the same temperature as the steam, it will, as the temperature of the steam reduces from the expansion, evaporate more during the expansion period, doing so to a greater extent in proportion as the cut off is early, on account of there being a wider variation between the temperature of the steam at the point of cut off and at the end of the stroke. On the other hand, however, in proportion as the cut off is earlier, the proportionate loss from condensation during the live steam period is greater, because a greater length of the cylinder bore is cooled during the expansion period, and it has more time to cool in. Whatever steam is saved by the compression, from the exhaust, must be credited to the engine in calculating the water consumption from the indicator card or diagram, since it fills, or partly fills, the clearance space. In engines which vary the point of cut off, by varying the travel of the induction or admission valve, the amount of compression is variable with the point of cut off, and increases in proportion as the live steam period diminishes; hence to find the actual water or steam consumption per horse power per hour, diagrams would require to be taken continuously from both ends of the cylinder during the hour; assuming, however, that the point of cut off remains the same, that the amount of compression is constant, that the steam is saturated, and neither wet nor superheated, steam and the water consumption may be computed from the diagram as follows: WATER CONSUMPTION CALCULATIONS.--An engine driven by water instead of steam, at a pressure of 1 lb. per square inch, would require 859.375 lbs. per horse power per hour; the water being of such temperature and density that 1 cubic foot would weigh 62-1/2 lbs. If the mean pressure were more than 1 lb., the consumption would be proportionately less; and, if steam were used, the consumption would be as much less as the volume of steam used was greater than an equal weight of water. Hence, if we divide the number 859.375 by the mean effective pressure and by the volume of the terminal pressure, the result will be the theoretical rate of water consumption in pounds per I. H. P. per hour. [Illustration: Fig. 3374.] For the terminal pressure we may take the pressure at any convenient point in the expansion curve near the terminal, as at A, Fig. 3375, in which case the result found must be diminished in the proportion that the portion of stroke remaining to be made, A _a_, bears to the whole length of the stroke _a_ _b_; and it may also be diminished by the proportion of stroke remaining to be made after the pressure at A has been reached in the compression curve at B. In other words, A B is the portion of the stroke A B, during which steam at the pressure at A is being consumed. Hence the result obtained by the above rule is multiplied by A B, and the product divided by _a_ _b_. To illustrate, suppose the mean effective pressure of the diagram to be 37.6 lbs., and the pressure at A, 25 lbs., of which the volume is 996. Then 859.375/(37.6 × 996) = 22.94 pounds water per I. H. P. per hour, the rate that would be due to using an entire cylinder full of steam at 25 pounds pressure every stroke. But as the period of consumption is represented by B A (_b_ _a_ being the stroke), the following correction is required: (22.94 × 3.03)/3.45" = 20.15; 3.03 inches being the portion B A, and 3.45 inches being the whole length _b_, _a_. This correction allows for the effects of clearance as well as compression, since, if more clearance had existed, the pressure at A would not have been reached till later in the stroke, and the consumption line B A would have been longer. [Illustration: Fig. 3375.] But such a rate can never be realized in practice. Under the best attainable conditions, such as about the load indicated on the diagram, or more on a large engine with steam tight valves and piston, and well protected cylinder and pipes, the unindicated loss will seldom be less than 10 per cent., and it will be increased by departure from any of the above conditions to almost any extent. It will increase at an accelerating ratio as the load is diminished, so that such calculations applied to light load diagrams would be deceptive and misleading; in fact, they have but little practical value, except when made for comparison with tests of actual consumption for the purpose of determining the amount of loss under certain given conditions. DEFECTIVE DIAGRAMS. In seeking the causes that may produce a defective diagram, the following points should be remembered: The indicator must be kept in perfect order, thoroughly clean and well lubricated, so that its parts will move freely. It should always be cleaned throughout after using. The motion of the indicator drum should be an exact copy, on a reduced scale, of that of the piston at every point in the stroke. The steam pipes from the cylinder to the indicator, if any are used, must be large enough to give a free and full pressure of steam, and care must be taken that the water of condensation does not obstruct them or enter the indicator. The cord should be as strong as possible, or if long, fine wire should be substituted. The pencil should be held to the card with just sufficient force to make a fine line with a sharp pencil. The diagram should be as long as the atmospheric line, any difference in this respect showing unequal tension of the cord, probably from unequal pressure of the pencil to the paper or card. A fall in the steam line could arise from too small a steam pipe, and this could be tested by a diagram taken from the steam chest. It could also occur from too small a steam port or an obstructed steam passage as well as from a leaky piston. An expansion curve that is higher than it should be may arise from a leaky valve, letting in steam after the cut off had occurred, or if at the later point of expansion curve, it may be caused by the steam being wet or containing water, which evaporates as the temperature falls from the expansion. An expansion curve that is lower than it should be may be caused by a leaky piston, by a valve that leaks on the exhaust side but not on the steam side, or if the exhaust valve is separate from the steam valve, it may leak while the steam valve is tight. It may also be caused by the cylinder being unduly cooled, as from water accumulating in a steam jacket. There are many defects in the adjustment of the valve gear, or of improper proportion in the parts, that may be clearly shown by a diagram, while there are defects which might exist and that would not be shown on the diagram. It is possible, for example, that a steam valve and the engine piston may both leak to the same amount, and as a result the expansion curve may appear correct and not show the leak. Insufficient valve lead would be shown by the piston moving a certain portion of its stroke before the steam line attained its greatest height in Fig. 3376, in which from A upwards, the admission line, instead of rising vertically, is at an angle to the right, showing that the piston had moved a certain portion of its stroke before full pressure of steam was admitted. That too small a steam port or steam pipe did not cause this defect may be known from the following reasoning: The port opened when the pencil was at A, which shows that the valve had lead. At this time the piston was near the dead centre and moving slower than it was when the pressure reached its highest point on the diagram, and since the steam line is fairly parallel with the atmospheric line, it shows that the port was large enough to maintain the pressure when the piston was travelling fast, and therefore ample when the piston was moving slow. The remedy in this case is to set the eccentric back. With less compression the point A would be lower. Excessive lead is shown in Fig. 3377 by the loop at A, where the compression curve extends up to the steam line, and the lead carries the admission line above it, because of the piston moving against the incoming steam. To mark in the theoretical compression curve, the vacuum line and the clearance line must be drawn in as in the figure, and ordinates must be drawn. According to the diagram, in Fig. 3377, the compression is clearly defined to have begun at C, and at that time the space filled by steam is represented by the distance from C to the clearance line. The pressure above vacuum (or total pressure) of the steam in the cylinder when the compression began is represented by the length or height of the dotted line 1. Now suppose the piston to have moved from the point C, where compression began, to line 2 (which is midway between line 1 and the clearance line), and as the compressed steam occupies one-half the space it did when the piston was at C, therefore the steam pressure will be doubled, and line 2 may be drawn making it twice as high as line 1. [Illustration: Fig. 3376.] [Illustration: Fig. 3377.] Line 2 is now the starting point for getting the next ordinate, and line 3, must be marked midway between line 2 and the clearance line, and twice as high as line 2, because at line 3 the steam will occupy half the space it did at line 2. Line 4 is obviously midway between line 3 and the clearance line. Through the tops of these lines we may draw the theoretical compression curve, which is shown dotted in. To find the amount of steam actually saved by the compression, we have to consider the compression curve only, beginning at the point of the diagram where it is considered that the compression actually began, and ending where the compression line joins the admission line, and the horizontal distance between these two points represents the length of the cylinder bore filled by the compression. To find the average amount to which the steam is compressed, we must draw within this length of the diagram, and within the boundaries of the compression curve, and the line of no pressure ordinates corresponds to those given for finding the average shown pressure of a diagram, as explained with reference to that subject, taking care to have the end ordinates spaced half as wide as the intermediate ones, as explained with reference to Fig. 3372. CHAPTER XLI.--AUTOMATIC CUT OFF ENGINES. An automatic cut off engine is one in which the valve gear is so acted upon by the governor as to keep the speed of the engine uniform under variations of the load the engine drives, and notwithstanding variations in the boiler pressure. This it accomplishes by varying the point in the piston stroke at which the live steam is cut off. This is economical because it enables the engine to use the steam more expansively than is possible with engines having throttling governors, which govern the engine speed by wire drawing the steam. There are two principal forms of automatic cut off engines, first, those in which the steam valve spindle or rod is released from the parts that move it to open for admission, while dash pots, weights, or springs close the valve to effect the cut off; and second, those in which the travel of the valve is varied so as to alter the point of cut off. The first usually employ fly ball governors which actuate cams or stops to trip the valves for the steam cylinders. The second usually employ wheel governors or speed regulators, as they are sometimes termed. The distinctive features in the action of the first, of which the Corliss engine is the most important, is that as two admission and two exhaust valves are used, therefore the amount of the valve lead, the point of exhaust and amount of the compression remain the same at whatever point in the piston stroke the cut off may occur; whereas in the second, the lead increases, the cut off occurs earlier, and the compression increases in proportion as the cut off occurs earlier in the piston stroke. In this class of engine the steam valve travels as quickly when opening the steam port for a short and early period of cut off as it does for a late one, hence the amount of steam port opening is as full, with reference to the piston motion, for an early as it is for a late point of cut off. In other words, there is the same amount of steam port opening for the first, second, third, and fourth inch of piston motion, let the point of cut off occur at whatever point in the piston motion it may. In engines which vary the point of cut off by reducing the travel of the slide valve, this is accomplished by using double ported valves or griddle valves. [Illustration: Fig. 3378.] Fig. 3378 represents the arrangement of the valves in a Corliss engine, V and V^{1} being the steam valves and V^{2} and V^{3} the exhaust valves. These valves, it will be seen, extend crossways of the cylinder and are circular. In the figure the valves are shown in the position they would occupy when the piston was at the crank end of the cylinder, as in the figure. The principles of a Corliss valve gear will be understood from the following, which is derived from a book by the author of this work, and entitled _Modern Steam Engines_. In 3379 and 3380 the valve gear (which is the distinctive feature of the engine) is represented with the parts in the position they occupy when the cut off occurs at half stroke, the piston having moved from the head end of the cylinder. In Figs. 3381 and 3382 the parts are shown in position with the crank on the dead centre and the piston at the crank end of the cylinder, valve _v_ having opened its port to the amount of the lead. Referring to Fig. 3379, motion from the eccentric is imparted by the rod M to the wrist plate Y, to which are connected the rods C, C´, for operating the admission valves, whose shafts are seen at S, S´, and the rods F, F´, for operating the exhaust valves, whose shafts are seen at T, T´. The mechanism for the steam or admission valves may be divided into three elements: first, that for operating the valve to open the port for admission; second, that for closing the valve to effect the cut off; and third, that which determines the point in the stroke at which the cut off shall occur. The first consists of the rod M, wrist plate Y, and the rods C and C´, which operate the bell cranks _r_ _r_, _r´_ _r´_ which are fast on the valve shafts S, S´. Upon the ends of bell cranks _r_ _r_, _r´_ _r´_, are pivoted latch links _u_, _u´_, which have in them a recess for the latch blocks, of which one is seen at _e_ (the rod R´ and its connection with the valve stem being shown broken away to expose _e_ to view). During the admission the latch block abuts against the end _y_ of the recess _w_ and is tripped therefrom by the cam _n´_. The ends of arms _g_ of the latch links abut against the hub of the arms _d_, _d´_ upon which are cams _n_, _n´_, and at _a_, _a´_ are springs for keeping the ends _g_ of latch links _u_, _u´_ against the hubs and cams of _d_, _d´_. Referring now to the valve mechanism at the head end only, suppose the piston to be at the head end of the cylinder, and latch block _e_ will be seated in the recess provided in _a_ to receive it, and as the bell crank moves, the latch block will be raised by the latch link, which is carried by a crank arm corresponding to that seen at _x_ at the crank end of the cylinder, and as this crank arm is fast upon the valve spindle, the lifting of _e_ will open the valve for admission. As soon, however, as the end _g_ of the latch link meets the cam _n´_, the latch link will be moved so that the end _y_ of its recess will leave contact with the latch block _e_ and the dash pot will cause rod R´ to descend instantaneously and close the valve, thus effecting the cut off. The period of admission, therefore, is determined by the amount of motion the latch link _u´_ is permitted to have before its end _g_ meets the cam _n´_, which trips the latch link, and therefore frees _e_ from the latch link recess. [Illustration: Fig. 3379.] The point at which the cut off will occur, therefore, is determined by the position of the cam _n´_, because if _n´_ is out of the way, the end _g_ of the latch link will not meet it, the latch link will not disengage from the latch block _e_, and the cut off would be effected by the lap of the valve, and independently of the dash pot. As in Fig. 3379 the parts are shown in the positions they occupy at the instant the cut off is to occur, therefore the cam _n´_ has just tripped the latch link, and the end of _e_ has just left contact with the end _y_ of the recess _w_ in the latch link _u´_. The point in the stroke at which the tripping of _u´_ from _e_ will occur and effect the cut off is determined by the governor, because _d´_ is connected to the governor through the rod G´. In proportion as the governor balls rise, _d´_ is moved from left to right, and the end of cam _n´_ meets _g_ earlier, or, vice versa, in proportion as the governor balls fall, the arm _d´_ is moved to the left, _g_ will meet the end of cam _n´_ later, and the point of cut off will be prolonged. [Illustration: _VOL. II._ =THE CORLISS VALVE GEAR.= _PLATE XXXIV._ Fig. 3381.] We now come to the means employed to close the valve quickly and without shock when the latch block is released from the latch link. Referring then to the crank end of the cylinder, the latch block for that valve is carried upon arm _x_, to which is attached the rod R from the dash pot piston (the arm corresponding to _x_, but at the head end being shown removed to expose the latch block to view). We may now turn again to the head end of the cylinder, rod R´ corresponding to rod R at the other end, and it is seen that R´ connects to a dash pot piston _p´_ having a stepped diameter, the lower half fitting into bore H´, and the upper half fitting into a bore H. The piston _p´_ fits the bore H´ and fills it when the rod R´ is at the bottom of the stroke, hence as _p´_ is raised there is a vacuum in H that acts to cause _p´_, and therefore R´ and _x_, to fall quickly and close the valve the instant the latch block is released from the latch link. To prevent the descent of rod R´ and piston _p´_ from ending in a blow, a cushion of air is given in H by the following construction: [Illustration: Fig. 3380.] At S and S´ are valves, threaded to screw and unscrew, the ends forming a valve for a seat entering H. As the rod R´ and its piston _p´_ descend, the air in H finds exit through a hole at _h_ until that hole is closed by the piston _p´_ covering it, after which the remaining air in H can only find exit through the opening left by the end of the valve S´, and this amount of opening is so regulated by the adjustment of S´ that a certain amount of air cushion is given, which prevents _p´_ from coming to rest with a blow. The head of valve S´ is milled or knurled, and a spring _t´_ fits, at its end, into the milled indentation, thus holding it in its adjusted position. The under surface of the upper part of _p´_ is covered by a leather disc, while the part that fits in H´ is kept air-tight by a leather-cupped packing. The connection of the cam arms _d_ and _d´_ with the governor is shown in Figs. 3381 and 3382, in which the parts are shown in the position they would occupy when the crank is on the dead centre and the piston at the crank end of the cylinder. The rod G´ connects the cam arm _d´_ with the upper end of lever A, which is connected to the governor and vibrates on its centre as the governor acts upon it. [Illustration: Fig. 3382.] Now suppose the speed to begin to diminish, and the governor balls to fall, and the direction in which A will move will be for its lower end to move to the right, thus moving _d_ to the right and carrying its cam away from the end of the latch link, which will therefore continue to open the port for a longer period of admission. Or, referring to Fig. 3381, it is plain that, if the governor balls were to lower from a reduced governor speed, G´ would move to the left and cam _n´_ would be moved away from contact with the end _g_ of the catch link, which, not being tripped, the admission would continue. On the other hand, suppose the governor balls to rise from an increase of governor speed, and _d´_ (Fig. 3379) would be moved to the right, and the cam _n´_ meeting _g_ earlier, correspondingly hastening the cut off. The governor is driven by a belt from a pulley on the crank shaft to the pulley W, Fig. 3381, whose shaft conveys motion to the governor spindle through the medium of a pair of bevel pinions in which _v_ represents (referring again to Fig. 3378) the steam or admission valve for the crank end port, and _v_^{1} that for the head end port, while _v_^{2} is the exhaust valve for the crank end, and _v_^{2} that for the head end of the cylinder. All four valves are shown in the positions they would occupy when the crank was on the dead centre and the piston at the crank end of the cylinder, hence the valve positions shown correspond to the positions the parts of the valve motion occupy in Fig. 3381. The faces of the valves are obviously arcs of circles of which the axes of the shafts _s_, _s´_ are the respective centres. Valve _v_ has opened its port to the amount of the lead, which in this class of engine varies usually from 1/32 to about 1/16 inch. As separate exhaust valves are employed, the point of release, and (as the same valve edge that effects the release also effects the compression) therefore that of the compression, may be regulated at will by adjusting the lengths of the rods F, F´, Fig. 3379, which have at one end a right and at the other a left hand screw, so that by turning back the check nuts and then revolving the rods their lengths will be altered. Similarly the amount of admission lead may be adjusted by an adjustment of the lengths of rods C, C´, which also have right and left hand screws. Referring now to the admission valve _v_, it is seen that its operating rod C is at a right angle to bell crank _r_, _r_, hence the amount of valve motion will not be diminished to any appreciable extent by reason of the wrist plate end of rod C moving in an arc of a circle, and the point of attachment of rod C to the wrist plate is such that, during the admission, the valve practically gives as quick an opening as though rod C continued at a right angle to _r_. But, if we turn to valve _v´_, which has closed its port and covers it to the amount of the lap, we find that bell crank _r´_ and its operating rod C´ are in such positions with relation to the wrist plate, that the motion of the latter will have but little effect in moving the bell crank _r´_. This is an especial feature of the Corliss valve motion and is of importance for the following reasons: The lap of the valve (which corresponds to the lap of a plain D slide valve) is usually, in this class of engine, such as to cut off the steam at about 7/8 stroke, but the adjustment of the cam position is usually so made that, from the action of the governor, the latest point of cut off will occur when the piston has made 5/8 of its stroke, the range of cut off being from this to an admission equal to the amount of the lead. As the eccentric is fixed upon the shaft, the speed at which the valve opens the port for the admission is the same for all corresponding piston positions. Thus suppose the piston has moved an inch from the end of the stroke, and the valve speed will be the same, whether the cut off in that stroke is to occur at quarter stroke or half stroke, and as the valve continues to open the port until it is tripped, therefore, at the moment it is tripped, the direction of valve motion must be suddenly reversed. As the duty of its reversal falls upon the dash pot, it is desirable to make this duty as light as possible, which is accomplished by the wrist motion, which acts to reduce the valve motion after the port is opened a certain amount for the admission. We have, therefore, that during the earlier part of the admission, the port opening is quick because of the eccentric throw being a maximum, while during the later part of the port opening, this rapid motion is offset or modified by the wrist motion, thus lessening the duty of the dash pot and enabling it to promptly close the valve. The range of governor action, so far as the governor itself is concerned, is obviously a constant amount, because a certain amount of rise and fall of the governor balls will move the cams a given amount. But the range of cut off may be varied as follows: At Z, Z´, are adjustment nuts, by means of which the lengths of rods G, G´ may be varied. Lengthening rod G obviously moves arm _d_ and its cam _n_ further from the end of the latch link _u_, and therefore prolongs the admission period. Shortening the rod G´ causes cam _n´_ to move around and away from the leg _g_ of the latch link, and prolongs the admission. The adjustment of the lengths of G and G´ may therefore be employed for two purposes; first, to prolong the point of cut off, and maintain the speed when the engine is overloaded, or to hasten the point of cut off for a given engine speed, and thus adjust the engine for a lighter load. HIGH SPEED AUTOMATIC CUT OFF ENGINES. What are termed high speed engines are those whose pistons run at a velocity of more than about 600 feet per minute, some making as high as 800 or 900 feet in regular work. High speed engines are usually provided with an automatic cut off, and a majority of them vary the point of cut off, by means of shifting the eccentric across the shaft, so as to reduce the eccentric throw, and therefore the valve travel. This causes the valve to cut off the steam earlier. The eccentric, instead of being fixed upon the crank shaft, has an elongated bore, and is hung on an arm that is pivoted at its other end after the manner of a pendulum. This arm is called the eccentric hanger. A wheel governor is usually employed to shift the eccentric across the shaft. In some cases, however, two valves are employed, one effecting the admission, the release, and the compression, and the other the cut off. When two valves are employed, the lead, the point of cut off, the point of release, and the point of compression may be maintained equal for all points of cut off; whereas, when a single valve is employed, the lead, the point of release, and the compression will vary with the point of cut off, or, in other words, will be different for every different point of cut off. The general principles upon which a wheel governor is constructed is, that two weights or weighted levers in moving outwards from the engine shaft, from the action of centrifugal force, move or rather shift the eccentric across the shaft, reducing its throw, and therefore by reducing the travel of the valve hasten the point of cut off and reduce the power of the engine. In the governor of the Buckeye engine, the centrifugal force may be varied by increasing or diminishing the distance of the weights from the pivots of the arms on which they swing. [Illustration: Fig. 3382_a_.] This is shown in Fig. 3382_a_, in which it is seen that the weights A are adjustable along the arms _a_, _a_. The points of attachment _d_, _d_ of the springs to the weight arms are also adjustable. When reversing is done, by shifting the eccentric across the shaft, the lead cannot be kept equal, but will, if the eccentric is swung from a pivot that is on the line of centres, when the crank is on a dead centre, be greater at the head end than at the crank end of the cylinder. The discrepancy may, however, be equalized by swinging the eccentric from a pivot that is not on the line of centres at a time the crank is on a dead centre. But this equalization will only exist at some one point in the eccentric position, or in other words, if the eccentric is shifted across the crank shaft, simply to reverse the engine, and not to vary the point of cut-off, it will naturally be moved, in reversing the engine across the shaft, to a given and constant amount, and in this case, the pivot on which its hanger is hung may be so located with reference to the line of centres and the crank (the latter being on a dead centre when the point of suspension of the eccentric hanger is found) that the lead is equal for both the backward and forward gears. But if the eccentric is shifted across the shaft to vary the point of cut off as well as to reverse the direction of engine revolution, the lead cannot be kept equal. It is better, in this case, to so locate the point of eccentric hanger suspension as to let the lead be the most at the head end cylinder port, because the piston travels fastest at that end of the cylinder, and therefore requires more lead, in order to cushion the piston. [Illustration: Fig. 3383.] A construction for shifting the eccentric across the shaft is shown in Fig. 3383, in which D, D is a disc, having at _b_ a pivot for the eccentric hanger. The amount the throw line of the eccentric must be shifted to reverse from full gear forwards to full gear backwards is from the line _b_ _x_ to line _b_ _x´_, and the shifting is done by two racks F and J, having teeth at an angle of 45° to their lengths. F is fast to the eccentric, and J is carried in a sleeve that slides along the shaft, and sliding it moves the eccentric across the shaft by reason of the teeth of one rack being at a right angle to those of the other. It is obvious that the eccentric may be moved around the shaft in place of across it, the distance its throw line requires to be moved being the same in either case. To shift an eccentric so as to reverse the direction of engine revolution, all that is necessary is to place the crank on either dead centre and measure the amount of valve lead. Then loosen the eccentric from the crank shaft, and while the crank is stationary, move it around upon the shaft until it has opened the port full, and nearly closed it again, leaving it open to the same amount as it was before the eccentric was moved, or in other words, open to the amount of the lead. [Illustration: Fig. 3384.] Fig. 3384 represents a side elevation of a high speed wheel governor engine, designed and constructed by the Straight Line Engine Company of Syracuse, New York, the construction of the governor being shown in Fig. 3385, in which R is the eccentric rod, the eccentric being carried in a lever strap pivoted at A, and connected at B to two links C and D, the former of which connects to the spring E, and the latter to the weighted lever F. The centrifugal force generated by the weighted end of F endeavors to move the eccentric inwards, and thus reduce its throw, which reduces the valve travel and hastens the point of cut off. On the other hand, the tension of the spring E acts to move the eccentric in the opposite direction, and maintain the full throw of the eccentric and maximum point of cut off. These two forces are so calculated in the design and proportion of the parts that under a maximum load the engine will run at its proper speed, while, if the load decreases, the action of F will hasten the point of cut off enough to allow for the decreased engine load, and thus keep the engine still going at the same speed. [Illustration: Fig. 3385.] Other novel and interesting details in the construction of this engine are as follows: The two arms forming the frame are cast with and run in straight lines from the cylinder to the two main bearings, and rest upon these self-adjusting points of support. There are two fly wheels, both between the main bearings, and one of which carries the governor so that the centre of the valve is brought in line with the centre of the eccentric. [Illustration: Fig. 3386.] In order to simplify the explanation, the mechanism has been separated into three separate sections. Figs. 3386 and 3387 show such of the details of the parts between the cylinder and crank as are peculiar to this engine. The cross head is of the slipper guide style, and the illustration, Fig. 3386, shows the simple method adopted for adjusting the guide to the proper height to maintain the alignment. Another feature peculiar to the straight line not mentioned above, that of making the cross head pin fast in the connecting rod, is used in this engine also, but in a somewhat different form. As will be seen by Fig. 3387, the pin is made much larger, and this allows of its being made of "steel casting" and cast hollow with cross bars at each end for centring. These pins are held in the rod by a binding screw which catches in a groove that is milled around one-fourth of its circumference. After the pin is placed in the rod and the binding bolt is inserted, the pin is prevented from working out endwise, and the binding bolt prevents it from turning; but when the binding bolt is slackened, the pin can be rotated one-fourth of a revolution. The scheme is as follows: After running the engine for a while, the engineer is instructed to slack the binding bolt, give the pin a quarter turn and bind it fast. By repeating this, the pin can be kept more nearly round, probably, than by any other plan. By referring again to Fig. 3386, it will be seen that the plan for taking up the wear in the cross head pin bearings is simply that of setting up the common half box, and the endurance of the arrangement, with the hardened and ground steel pin running in babbitt lined boxes of double the ordinary size and length, must be satisfactory. [Illustration: Fig. 3387.] The drop oil cups for lubricating the cross head pin are located so as to have the drop "picked" off just as the cross head completes its stroke at the cylinder end, and while it is travelling at its slowest speed. The oil, as it leaves the wearing surfaces of the pin, is conveyed to the lower slide. [Illustration: Fig. 3388.] [Illustration: Fig. 3389.] Figs. 3388 and 3389 show the parts that connect the eccentric with the valve. The method of connecting the rod to the eccentric strap is convenient. The lower joint in the eccentric strap is set up tight, metal to metal, and the upper joint left open 1/8 of an inch. STEAM FIRE ENGINE. In a steam fire engine the prime requisites are rapidity of getting up steam and efficiency with lightness, economy of fuel being a secondary consideration. Fig. 3390 is a general view of a steam fire engine constructed by the Clapp & Jones Manufacturing Company. Fig. 3390_a_ is a longitudinal section through the boiler and one steam cylinder and pump. The construction of the boiler is shown in Figs. 3390_a_ and 3391, the former being a vertical section of the engine and boiler bearing the steam pipe and exhaust pipe shown in place, and one of the draught tubes shown in section, and the latter a vertical central section. The outside shell is represented at _a´´_, _a´´_. This shell extends the whole length of the boiler. The fire box sheet _b´´_, _b_ is less in length, extending only to the lower tube sheet. The lower tube sheet C´´ is perforated by all the tubes; the heavy lines showing the coil tubes in fire box, the others are smoke tubes. The upper tube sheet _d_ has holes only for the smoke tubes. The smoke or draught tubes are shown at _e´´_, _e´´_, _e´´_; these also answer the important purposes of drying and superheating the steam. F´´, F´´, F´´ are the sectional coil tubes, the main feature of this boiler. They are in the form of a spiral coil, the spiral bend being enough to leave room for five others of the same size between, so that there are six of these coils in each circular row. The number of rows is determined by the size of the boiler and the amount of steam required. Each coil is connected with the lower tube sheet by screw joints, all right hand, that require no fibrous or elastic packing, an angle elbow being used to get the short bend at the end. The tubes then make about one turn around the fire box, and are joined to the side sheet of the same, with the same union used at its upper end, which makes a joint that never gets loose from any kind of work it may be subjected to. These unions or couplings are made of different kinds of metal, and put together so that no two pieces of iron come in contact to corrode and stick together; and should it, from any cause whatever, become necessary to take these coils out, it can be done, and the same tubes replaced without destroying any part of them, or damaging any piece so that it could not be used again. G´´, G´´ is the ornamental dome or covering for the upper end; _g´´_, _g´´_ is the smoke bonnet and pipes for concentrating the hot escaping products of combustion for the purpose of making a draught of air through the fuel. H´´ are grate bars, and I´´ fire door. J´´, J´´ is the water line. The height has been determined by experiment, yet should be varied a little to get the best drying effect of the coal. A coal that makes a flame would call for a higher range of the water line, while coal that produces heat without the flame would call for a lower range; this the engineer will soon find. The working of the boiler is as follows: The fire being started in the fire box, as soon as the water in the coils begins to heat circulation commences from natural causes (nor is it at any time necessary to use a hand pump or any other artificial means for keeping it up), the heated water passing up in the steam drum, and the colder water from the leg and drum taking its place, as is shown by the arrows in the leg, till the whole is heated to the steam making temperature. At this point steam pressure begins to show, which goes up very fast, as the water is all so near the steam temperature. Of course, it is better to carry the water at about the height shown, as a uniform pressure of steam is easier maintained, which is always desirable; yet the limit of safety is not reached till the water is nearly all out, or so long as it is not below the connection of the coils in the leg; and even at this point the only danger is in the damage to the coils from the heat when there is no water to protect them. [Illustration: _VOL. II._ =STEAM FIRE ENGINE.= _PLATE XXXV._ Fig. 3390_a_.] [Illustration: Fig. 3390.] [Illustration: Fig. 3391.] In Fig. 3391_a_, one engine and pump is shown in side elevation, and the other in section, the cranks being at a right angle, one to the other. A yoke from the piston rod spans the crank, so that the steam and pump pistons are in line and directly connected. From the lower end of this yoke, a rod connects to the crank shaft upon which are the two fly wheels and the eccentrics for the steam valves. It will be seen in the longitudinal section, Fig. 3390_a_, that the steam valve face is a segment of a circle and therefore answers, so far as the distribution of the steam is concerned, to a simple D slide valve, which exhausts through the pipes _m_, _p_. The steam pipe _n_ enters the bottom of the steam chest at _n´_. The two main pumps _a_ are made in one piece, entirely of composition; one of them is shown in section. The piston is a solid piece of brass, as well as the cylinder in which it works, but are made of different composition, one hard, the other soft, to prevent cutting. The valves are of India rubber; the discharge valve is a ring, one for each end of the pump, as shown at _b_, Fig. 3391_a_. One is shown open, while the other is closed. They are held in place by grooved rings of brass; these rings fit in grooves in the rubber, which, when they are put in the pump, and their set screws are in, with their points in the grooves in the brass rings spoken of above, the discharge valves are complete for work. The suction valves are shown at K on Fig. 3391_a_, and will be easily understood. They are of a design for this special use and place, which is around the pump cylinder in a circular chamber. The water ways covered by these valves are long and narrow, one valve covering two of these openings, they being held in place by two studs that go through the centre part of the valve, a wire going through these studs, and close to the back of the valve which keeps it up to the seat, the only spring to either of these valves being the elasticity of the rubber. The opening and connection D, D is the inlet to the pump, and where the suction hose goes on, there being a pipe or chamber with branches for the two air chambers, and at each end is a discharge gate and a connection for the leading hose. The part _d_ is the feed pump for the boiler supply, _e_ is the air chamber on the pipe that leads to the boiler to ease off the shocks caused by the plunger striking the water, when the pump does not fill. It is drawn broken off to show the upper part of the pump barrel and stuffing box. The pipe _f_ is the feed water pipe from the pump to boiler, shown from different points in Figs. 3390_a_ and 3391_a_. _g_ is what we call the suction pipe to the feed pump. It connects to the main pump in the discharge part of it. A piece of hose pipe connects to the boiler at a point just above the water line, so that hot water or steam (according to the height of the water in the boiler) may be applied to any part that may have become frozen. [Illustration: Fig. 3391_a_.] Heaters are almost universally used in connection with steam fire engines to keep the water hot, and in many cases to keep a few pounds pressure to shorten the time of going to work should the fire be close at hand. This boiler has an advantage for this kind of heating; the circulation is so perfect and free that all the water in it is heated alike; so when the fire is lighted the steam starts immediately up, instead of having to wait till some cold water has been heated that had not been reached by the very limited circulation in them, there being some parts that the circulation produced by the heater does not reach, leaving, of course, this water cold. The arrows K´´ (Fig. 3391), show the direction of the circulation when working with fire in the fire box; those marked L´´ show the direction of it when on the heater which is directly opposite. The outside pipe connected at about the water line is the outlet from the heater, and the inlet to the boiler, which carries the heated water over the crown sheet, where, as it gets cooler, it enters the coils, descends into the leg, and from there to the pipe near the bottom of the boiler; this pipe leads to the heater, so that the water is kept moving just in proportion to the heat given it; any kind of a heater can be used with the same result. CHAPTER XLII.--MARINE ENGINES. Marine engines are made in the following forms: 1. With a single or with two cylinders receiving live steam from the boilers, and exhausting into the atmosphere. These are termed high pressure engines, let the steam pressure be what it may. They are also, and more properly, termed non-condensing engines. [Illustration: Fig. 3392.] In the small sizes, such as are used for launch engines, it is simply a non-condensing engine, with a link motion for varying the point of cut off as well as for reversing purposes. Fig. 3392 represents an engine of this class constructed by Chas. P. Willard & Co. The cylinder is what is called "inverted," meaning that it is above the crank shaft. The slide spindle or valve rod passes through a guide and connects direct to the link block or die, as it is sometimes called. The thrust block is provided in the bearing of the crank shaft, and consists, as seen in the sectional view, of a series of collars on the crank shaft bearing. 2. The addition to each high pressure cylinder of a low pressure cylinder constitutes a compound engine, and if the engine has also a condenser, it is a compound condensing engine, an example being shown in Fig. 3392_a_, which represents an engine in which the link motions are employed to vary the points of cut off of both cylinders, as well as to reverse the engine. The engine being small, the power required to move the links is small enough to permit of their operation by hand, by means of the hand lever L, which is secured to its adjusted position on the sector T by the small lever nut shown on the side of the lever. The lever L operates a shaft D which shifts both link motions. The air and circulating pumps are at the back of the condenser, being operated from the beams B, B, each beam connecting to rods J which connect to rod _c_, which drives the air and circulating pumps. The steam from the high pressure cylinder exhausts into a receiver or chamber between the two cylinders, and from which the low pressure cylinder receives its steam. [Illustration: Fig. 3392_a_.] [Illustration: Fig. 3395.] [Illustration: Fig. 3396.] The exhaust from the low pressure cylinder passes into the condenser, where it is condensed, leaving a partial vacuum on the exhaust side of the low pressure piston. Figs. 3393 and 3394 show the arrangement of the pumps on a pair of compound engines for a dredger. The steam from the low pressure cylinder passes into the body of the condenser with which the air pump is in communication, as shown in the end elevation. At _a_ is the foot valve of the condenser. The piston of the air pump has a similar valve, and at _e_ is the delivery valve. The circulating pump is shown in the back elevation (Fig. 3394), being a piston pump which forces the water through the tubes of the condenser. There are two principal methods of compounding, in one of which the two cylinders are placed one above the other, with their axes in line, and both pistons connecting to the same crank, while in the other the cylinders are side by side, and each connects to its own crank, the two cranks usually being at a right angle. When one cylinder is placed above the other, as in Fig. 3395, R being the high pressure and S the low pressure piston, no receiver is employed, the steam passing direct from the high pressure cylinder through the pipe P to the low pressure steam chest _c_. The high pressure steam valve V and the low pressure valve V are on the same stem, a cut off valve V´ being provided for the high pressure cylinder. 3. Triple expansion engines have three cylinders, a high pressure, an intermediate, and a low pressure cylinder. In a triple expansion engine the intermediate cylinder receives the steam that is exhausted from the high pressure cylinder, and expands it further. The low pressure cylinder receives its steam from the exhaust of the intermediate cylinder, and exhausts into the condenser. [Illustration: Fig. 3397.] [Illustration: Fig. 3398.] In the illustrations from Fig. 3396 to Fig. 3406 are represented the triple expansion engines of the steamship _Matabele_, constructed by Messrs. Hall, Russell & Company, of Aberdeen, Scotland. Fig. 3396 is a cross sectional view of the vessel showing the engine and its connections, and Fig. 3397 a similar view, showing the boilers. Fig. 3398 is a back elevation of the engine, showing the boilers also, and Fig. 3399 a plan of the same. Fig. 3400 is a sectional view, and Fig. 3401 an end view of the boilers. Fig. 3402 is a plan, Fig. 3403 an end elevation, and Fig. 3404 a front elevation, partly in section, of the engines. H P is the high pressure cylinder, I C the intermediate cylinder, and L P the low pressure cylinder. The high pressure cylinder has a piston valve, the steam chest being shown at A. The intermediate cylinder is provided with a double ported flat valve as shown at B, and the low pressure cylinder is provided with a similar valve whose weight is counterbalanced by the small piston at E; at F are the relief valves for relieving the cylinders of water. [Illustration: _VOL. II._ =COMPOUND MARINE ENGINE.= _PLATE XXXVI._ Fig. 3393. Fig. 3394.] [Illustration: Fig. 3399.] [Illustration: Fig. 3400.] [Illustration: Fig. 3401.] [Illustration: Fig. 3402.] Each steam valve is provided with a link motion that may be used for varying the point of cut off (and therefore the expansion) as well as for reversing purposes. The link motions are all shifted from one shaft, which may be operated by hand or by steam, the construction being as follows: For shifting by hand, the wheel W is operated, its shaft having a worm driving the worm wheel G, Fig. 3403, which operates rod H, and through the lever J and rod K shifts the link L, one pair of eccentric rods being shown at N and P. The shaft of the wheel W is, however, a crank shaft, and at M is a small engine, which may be connected or disconnected at will to shaft W. The lever J operates a shaft R in Fig. 3404, which connects (by a rod corresponding to rod K in Fig. 3403) to each link motion; hence all the links reverse together, and the ratio expansion of one cylinder to the other cannot be varied, or in other words, the point of cut off will be alike for each cylinder, let the link motion be shifted to whatever position it may. The beam S, Fig. 3403, for working the air, circulating and feed pumps, is driven from the cross head of the intermediate cylinder. The boilers are of the Scotch pattern that is usually employed for high pressures, as 160 or more lbs. per square inch, and have Fox corrugated furnaces and stay tubes. Each cylinder requires a starting valve (which is sometimes called an auxiliary valve or a bye pass valve), which is used to warm the cylinder before starting the engine, and also (when there is no vacuum in the condenser) to admit high pressure steam when the high pressure piston is on the dead centre, in which case, there being no vacuum and no admission of steam to the low pressure cylinder, the engine would not have sufficient power to start. [Illustration: Fig. 3403.] In some cases the high pressure cylinder has no starting valve, the reversing gear being used to admit steam to one end or the other of the high pressure piston, and the starting valve being used to admit enough live steam to the low pressure cylinder to compensate for the absence of the vacuum. When the vacuum in the low pressure cylinder is maintained while the engine is standing still, its starting valve obviously need not be used, except for warming purposes, before starting the engine; as soon, however, as the engine has started, the starting valve must be closed. Each cylinder is provided with a relief valve, both at the top and at the bottom, to relieve the cylinder from a heavy charge of water, such as may occur if the boiler primes heavily. Each cylinder is also provided with drain cocks, to permit of the escape of the ordinary water of condensation in the cylinders when the engine is started, and also for use if the boiler primes. The low pressure relief valve also prevents the accumulation of too great a pressure in the low pressure cylinder, which, from its large diameter, is not strong enough to withstand high pressure. The oiling apparatus for the cylinders is arranged as follows: In some cases pumps, and in others automatic or self-feeding devices are used. Oil is fed to the steam pipe of the high pressure cylinder, and this lubricates both the valves and the cylinders, but in many cases it is also fed to the steam chest, so as to afford more perfect lubrication to the valve. For the low pressure cylinder the oil is fed into the receiver, and usually at a point near the slide valves. Large marine cylinders are usually constructed with a separate lining, which may be replaced when worn or otherwise required. A surface condenser consists of a cast iron shell or chamber forming the back of the engine frame. At each end of this chamber is a short partition, so that the condenser is divided lengthways into what may be called three compartments, of which the middle one is the longest and contains a number of thin brass tubes about 5/8 or 3/4 inch in diameter, the ends of these tubes being held in the plates or tube sheets forming the partitions. The object of providing tubes of small diameter is to obtain a large area of cooling surface. The exhaust steam from the engine generally passes into the shell or body of the condenser, filling the middle partition and surrounding the tubes. The condensing or circulating water passes through the tubes, and by keeping them cool condenses the steam and forms a vacuum or partial vacuum in the condenser, which, having open communication with the low pressure cylinder, therefore gives a corresponding degree of vacuum on the exhaust side of the low pressure piston. In some designs, however, the steam passes through the tubes and the circulating water fills the middle compartment of the condenser. As, however, there is no pressure to counterbalance the weight of the water, it is preferable to have the water inside the tubes, so that they are subjected to a bursting pressure, in which case they may, for a given strength, be made thinner, because the strength of the tube to resist bursting is greater than its strength to resist collapsing, hence the circulating water usually passes through the tubes. The chamber at the ends of the condenser permits the water to distribute through all the tubes. In some cases the chamber at one end is divided horizontally into two compartments, so that the water is compelled to pass through one half and return through the other half of the tubes. The water of condensation falls to the bottom of the condenser, from which it is removed by the air pump, which delivers it to the hot well. The hot well is situated on the side of, and extends above, the pump, whose upper end it covers, thus water sealing the top of the air pump and preventing air from passing into it through a leaky valve or bucket. The top of the hot well is provided with a _vapor pipe_, which permits the air and gases to pass overboard. This pipe emerges through the side of the ship above the water line, and as there is no valve between the hot well and the sea, no pressure can possibly accumulate in the hot well. The boiler feed is taken from the hot well either by the feed pump or by injectors, as the case may be. In case the boiler feed should stop working, however, the hot well is provided with a pipe of large diameter, and called the overboard discharge pipe, so that the water of condensation may not accumulate a pressure in the hot well if the boiler feed ceases. This overboard discharge pipe is provided with a weighted valve (placed at the side of the ship), which is constructed after the manner of a safety valve, relieving the hot well of pressure if the water accumulates, and preventing the sea water from entering the hot well. To prevent loss of fresh water, the exhaust steam from the various engines and pumps (if any) about the ship passes to the condenser and is pumped into the hot well. In some cases, however, a separate and independent condenser is used for the smaller engines about the ship. An independent condenser is one whose air pump and circulating pump are not worked from the main engine, and can therefore be operated when the main engine is standing still. If the main condenser is independent, it may be started so as to form a vacuum before the main engine is started, and thus obviate the use of the starting valve on the low pressure cylinder except to warm the cylinder before starting. Feed water for the boilers when the engine is standing is obtained by a pipe from the bottom of the condenser, so that the water of condensation of steam blown through the engine cylinders, and from the exhausts from the smaller engines about the ship, may be pumped or forced direct from the bottom of the condenser to the boiler. This feed from the bottom of the condenser is necessary when the air pump is not working, and the water of condensation is not pumped into the hot well. If the water thus obtained is not enough to keep the boilers supplied, an auxiliary or salt water feed admits extra water from the circulating water to the inside of the condenser to supply the deficiency. This secondary suction pipe is provided with a valve because it must be shut off before the engine is started. All the drain pipes from the cylinder pass into the condenser so as to save the fresh water. The air pump is usually worked by a beam, receiving motion from the cross head of the low pressure cylinder. The circulating pump is usually worked by the same beam as the air pump, or receives its motion from some other part of the main engine. In some cases, however, an independent circulating pump is employed. It receives its water from a pipe leading to the sea, which is provided with an injection cock or Kingston valve, placed close to the side of the ship and well below the sea level. This valve is used to shut off the circulating water and prevent its flooding the ship in case of accident to the condenser or circulating pump. The circulating water, after passing through the condenser, discharges overboard through the circulator discharge pipe. This pipe is also provided with a valve placed close to the ship's side, at or above the water level, so that the opening at the ship's side may be closed, and sea water prevented from entering the ship in case of breakage to the condenser, etc. To enable a surface condenser to be used as a jet condenser in case of accident to the circulating pump, a pipe leads from the injection cock of the circulating supply pump into the bottom of the exhaust pipe or column, where it enters the condenser. This pipe is supplied with a spray or rose nozzle, which divides up the injection water and causes it to condense the steam as it enters the condenser. An additional pipe is sometimes added to the suction side of the circulating pump, for use in pumping out the bilge by means of the circulating pump in case of emergency, and also for pumping out ballast tanks when the vessel is provided with such tanks. An air valve is sometimes fitted to a reciprocating double acting circulating pump. It admits air to the water during the up stroke of the pump, and closes on the down stroke. The air thus admitted acts as a cushion to soften the shock of the water. A snifting (or snifter valve, as it is sometimes called) is a valve fitted to the condenser and that opens upwards to permit of the discharge of the air and gases before the engine is started. It also serves to prevent any water from leaky condenser tubes from filling the condenser and flooding the engine cylinders. It is so loaded with dead weight that it opens automatically when the water in the condenser has reached a certain height and must be placed as low down on the condenser as possible, so as to receive the weight of the full height of the water in the condenser. Condenser tubes are made water tight in the tube plates of the condenser by wooden or sometimes paper ferrules, which fit the tube and drive into the tube plate. In other cases, however, the tube ends project through the plates, and a rubber washer is placed on the end of each tube. A covering plate is then bolted over the whole of the tube ends, the holes in the covering plate being parallel for a short distance, and then reduced in diameter so as to form a shoulder. The rubber rings compress and make a joint, and the shoulders prevent the condenser tubes from working out endways from expansion and contraction. The tubes are usually about 3/64 inch thick. [Illustration: _VOL. II._ =TRIPLE EXPANSION MARINE ENGINE.= _PLATE XXXVII._ Fig. 3404.] A blow through valve is a valve attached to the casing or steam chest, and connecting by a pipe to condenser to blow out the air and gases that may have collected there when the engine is standing still, and that also connects to the exhaust port of the high pressure cylinder, so as to supply live steam to the low pressure cylinder in case the high pressure cylinder should get disabled. A bucket air pump is one in which there is a valve or valves in the pump piston, hence the pump is single acting, drawing on the lower side of the piston and delivering on the upper, hence the capacity of the pump per engine revolution is equal to the diameter of the bucket multiplied by the length of its stroke. The suction or foot valve is at the foot of the pump, and the delivery valve at the head. A piston air pump is double acting, since it draws on each side alternately of the piston, one side delivering while the other is drawing, hence two suction and two delivery valves are required. A plunger air pump is one in which a plunger is used in place of a piston, the delivery being due to the displacement of the plunger. An air pump trunk is a hollow brass cylinder attached to or in one piece with the piston or bucket of the air pump. The rod which drives the piston passes through the trunk, and connects to a single eye at the bottom of the trunk. A trunk air pump is necessary when the pump rod is driven direct from the crank shaft, and therefore has sufficient lateral motion to push the pump piston sideways, which would cause friction and excessive wear to the gland that keeps the trunk tight. The delivery capacity of the pump is obviously diminished to an amount equal to the displacement of that part of the plunger that passes through the gland and within the pump bore, whereas in a piston pump the delivery capacity is only diminished to an amount corresponding to the displacement of the pump piston rod. A bucket pump may in some cases be worked without either a foot or a head valve, since the bucket valve will answer for both in cases when the delivery water cannot pass back into the pump on the down stroke of the bucket. It will, however, be more efficient with the addition of either of them, and most efficient with both. A bucket pump with a foot valve and no discharge valve would, however, suffer more from a leaky gland than if it had a discharge valve and no foot valve, because the air would, on the ascent of the bucket and the closing of the bucket valve, pass to the suction side of the bucket and impair the vacuum. Let the delivery valves be where they may, the foot valve will always have some water above it, and the pump bucket will dip into this water, and on lifting produce a vacuum that will cause the pump to fill with water. Notwithstanding that the gland may leak air on the other side of the bucket, this air will in a single acting pump be expelled with the water, but in a double acting pump it will impair the vacuum, and therefore the suction, on the gland side of the piston. Bucket air pumps are provided with a valve or pet cock on the top or delivery side of the bucket and above the bucket, when the latter is at the highest point of its stroke. This valve opens on the descent of the bucket, admitting air to act as a cushion between the surface of the water and the delivery valve, when the water is about to meet the latter. It obviously reduces the effectiveness of the pump, and in a double acting pump is inadmissible, because of its impairing the vacuum and the suction. This valve also enables the engineer to know whether the air pump is working properly. A pet cock is also supplied to the feed pumps for this same purpose. A bilge injection is one in which the injection water is taken from the bilge, which may be done when the ship makes more water than the bilge pumps can get rid of. The fittings necessary for a bilge injection are a cock or globe valve placed on the side of the condenser, and at or near the foot of the exhaust pipe, with a spray or rose inside that pipe. From the cock a pipe, usually lead, leads to the bilge, having at its end a strainer or strum, and care must be taken that this strum does not get choked and let the condenser get hot from the exhaust steam not being condensed. The water in the hot well of a surface condenser is usually kept at a temperature of about 100° Fahrenheit. A higher temperature than 100° Fahrenheit injures the rubber valves of the air pump, while lower temperatures cool the engine cylinders too much and cause waste from cylinder condensation. Moreover, it is obvious that, since the boiler feed is taken from the hot well, it is desirable to keep it as hot as the valves and as the desired degree of vacuum will permit. An air vessel or air chamber is a vessel fitted to the delivery and sometimes also to the suction side of a pump. Its office is to maintain a steady flow of water through the pipes. Thus, in the case of the delivery air chamber, when the pump piston is travelling at a speed above its average for the stroke, the water accumulates in the air chamber, and the air is more compressed, while, when the pump is on the dead centre, or at the end of its stroke and the delivery valve closes, the air compressed in the air chamber continues the delivery or discharge, thus maintaining a more uniform flow. Pumps sometimes have an air or vacuum chamber on the suction side, from which the air is exhausted when the pump starts, leaving a vacuum which causes a steady flow of water up the suction pipe. Both these chambers are more effective as the speed of the pump increases. The chamber on the delivery side is apt to lose its air, which is gradually absorbed by the water, which should be let out when the pump is standing still. Feed escape valves or feed relief valves are fitted to the feed pumps, so that in case all the feed water cannot pass into the boiler it may pass back to the hot well. The construction of a feed escape valve is as follows: It is an ordinary mitre valve held to its seat by the compression of a spiral spring, whose pressure upon the valve may be regulated by an adjusting screw, whose end abuts upon a stem provided for the purpose. In proportion as the valve is relieved of the pressure of this spring, a greater proportion of the water delivered by the feed pump will pass back into the hot well, hence the amount of boiler feed may be regulated by the feed escape valve, which also acts as a safety valve, preventing undue pressure in the feed pipe. When no feed escape valve is employed, the delivery water from the feed pump must pass unobstructed to the boiler, or the feed pipes may burst from over pressure, and it follows that the feed check valve on the side of the boiler must not be restrained in its amount of lift, hence it must not have a lift adjusting screw. The amount of the boiler feed must, in this case, be regulated from the suction side of the pump, the suction pipe being fitted with a cock or valve whose amount of opening may be adjusted so as to regulate the amount of water drawn per pump stroke from the hot well. If the feed valve on the suction side, or the escape valve on the delivery side of the pump, as the case may be, is adjusted to permit of a proper amount of boiler feed, and yet the feed is insufficient or ceases altogether, it may occur from the following causes: 1st. From the suction valve sticking or being choked, or from the delivery valve being choked and not seating itself, thus either letting the suction water pass back into the hot well, or the delivery water pass back into the pump. 2d. Through leaks in the joints of the pump or of the suction pipe. 3d. From the water in the hot well being too hot. 4th. Through the spring of the escape valve having become disarranged. 5th. If two or more boilers are connected, and one has less pressure in it than the other, it may take most of the feed water, or the water of the other may empty itself into it. Bilge Injection. The injection water for a common or jet condenser may be obtained in one of two ways: first, direct from the sea, which is that for ordinary use; and secondly from the bilge, which is resorted to to assist the bilge pump in cases of emergency. The necessary fittings for a bilge injection are, a pipe leading from the condenser to the bilge, with a cock at the condenser end and a strainer at the bilge end. This pipe should be fitted with a check valve, which opens by lifting upwards so that no water can pass down it into the bilge, or otherwise, if the main and bilge injections should happen to be left open together, the water from the main injection might pass down into the bilge. This check valve should be so constructed that its amount of lift can be regulated and as much of the bilge water used for injection as the circumstances may require. In the case of surface condensers, the bilge water is drawn off by the circulating pump and used to supplement the main circulating water. The pipe from the bilge in this case leads to the suction side of the circulating pump, and requires a strainer at the bilge end, a cock at the circulating pump, and a check valve. A ship's side air pump discharge valve is an ordinary dead weight mitre valve that opens to let the water pass out into the sea, but seats itself and closes if the water attempts to pass inwards. It differs from a common stop valve in being weighted, and therefore self-acting. It requires to be lifted before starting the engine, as such valves are liable to stick in their seats. The course of the main injection water of a jet condenser is as follows: From the rose plate or strainer, through the injection valve and pipe to the condenser, where it mingles with the exhaust steam and from which it is pumped with the products of condensation into the hot well. From the hot well it passes mainly overboard through the Kingston valve, but that part of it used for the boiler feed passes through the suction pipe and valve into the pump, and thence through the delivery valve, pipe and check valve into the boiler. The course of the main circulating water of a surface condenser is through the Kingston valve (on the ship's side or bottom), and the circulator inlet pipe, either direct to the condenser, from which it is _drawn_ by the circulating pump, or else it passes through it, and is _forced_ through the condenser. It circulates through the condenser twice or thrice according to the construction, and is forced overboard by the action of the circulating pump, passing through a valve on the ship's side or bottom. The advantages of surface condensation are, first, that the feed water is obtained at a higher temperature than if injection water was fed to the boiler. Second, the feed water is purer, and therefore less water requires to be blown out of the boiler in order to keep it clean. Third, the boiler does not scale so much, hence its heating surface is maintained more efficient; and fourth, the boiler suffers less from expansion and expansion strains when hot feed water is used. Surface condensers foul from the grease with which the cylinders are lubricated and from the salt in the injection water. The condenser is cleaned by the admission of soda with the exhaust steam and by washing out. A condensing engine has the following cocks and valves on the skin of the ship in the engine room: The main Kingston valve for the injection, or circulating water, the main delivery valve from the condenser, the bilge delivery valves, and the water service cocks for keeping the main bearings of the engine cool with streams of cold water. A donkey engine is a small engine used to feed the boiler, and has the following connections: A steam pipe from the boiler to drive the donkey engine; and exhaust pipe into the condenser; a suction pipe from the hot well or from the sea, as the case may be; and a delivery pipe to the boiler; a suction pipe from the bilge, so that the donkey pump can assist in pumping the bilge out; a suction pipe to the condenser, to circulate the water when the main engines are stopped, and thus maintain the vacuum; and a suction pipe from the water ballast tanks, to pump them out when necessary. The pipes that lead from, or go to, the sea are: Boiler blow off pipe, sea injection or circulator pipe, condenser discharge pipe, and, in some cases, donkey feed suction pipe. The parts of an engine that are generally made of wrought iron are those in which strength with a minimum of weight and size is desired; for example, the piston rod, cross head, connecting rod, crank shaft, crank, eccentric rods, link motion, valve spindle pump rods, and all studs, bolts, and nuts. The parts generally made of cast iron are those where strength and rigidity are required, and which are difficult to forge, while weight or size is of lesser importance, such as the bed plate, cylinders, pistons, condensers, and pumps. The parts sometimes made of steel are those subject to great wear, and for which strength with a minimum of size is necessary, as piston springs, piston rods, connecting rods, cranks, crank pins, and valve rods. The parts generally made of brass are those subject to abrasion or corrosion, as the connecting rod brasses, the bearings for the crank shaft, the pump plungers or pistons, and their rods, linings for the pump barrels or bores, the bores of the glands, the condenser tubes, and all cocks and valves. White metal or babbitt metal is sometimes used in place of, or in connection with, brasses, serving as an anti-abrasion surface. It is easily renewed, as it is cast into its place, but will melt and run out at a temperature of about 600° Fahrenheit. Muntz metal is used where iron or steel would suffer greatly from corrosion when in contact with salt water. It can be forged. The difference in the composition of cast iron and steel has never been determined; the difference lies in the percentage of carbon they contain and the structure of the metal. Cast iron will not weld. Cast iron is brittle, of granular structure, and always breaks short, having a very low elastic limit. Wrought iron is tough and fibrous, will weld but will not harden, and is stronger than cast iron. Steel is stronger than wrought iron, and will weld and harden and temper. The breaking strain of wrought iron varies from about 42,000 to 60,000 lbs. per square inch of section. Steel is tempered by first being heated red hot and suddenly cooled (usually by plunging it into cold water), which hardens it. The surface is then brightened, and on being reheated the tempering colors appear, beginning at a pale yellow, and deepening into red, brown, purple, and blue, the latter gradually fading away as the metal is re-heated to a red heat. The higher the temperature to which the hardened steel is reheated the softer or lower it is tempered. These colors merely indicate the temperature to which the piece is reheated, since they will appear on steel not hardened and upon iron. Case hardening is a process that converts the surface of wrought iron into steel, which is accomplished by placing them in a box filled with bone dust, animal charcoal, or leather hoofs, etc. The box is sealed with clay, heated red hot for about 12 hours, and the pieces are quenched in water. The parts usually case hardened are the link motion, and other light working parts that are of wrought iron. The forgeable metals used in engine work are wrought iron, steel, copper, and Muntz metal. The brittle or short metals are cast iron and brass. Welding is the joining of two pieces solidly together. Wrought iron, steel, and Muntz metal can be welded. All the metals used in the construction of marine engines expand by heat, and this is allowed for in adjusting the lengths of the eccentric rods, or of the valve spindles when setting the valve lead. In the case of two marine boilers being connected together, the steam pipe is fitted with an expansion joint, one pipe end having an enlarged bore to receive the other. The joint is made by packing, which is squeezed up by a gland, whose bore fits on the outside of the pipe which moves through the gland bore, from the expansion and contraction. The piston of a marine engine steam cylinder is a disc of cast iron, into which the piston rod is secured. Its body is cored out to lighten it. Around its circumference is a recess to receive the packing ring or rings, each of which is split across so that it may be expanded (to fit the bore of the cylinder) by means of the packing or of the springs. The split is closed in the centre by a tongue piece let into the ring, and fastened to one end of the ring. To hold the piston rings or ring in place, a junk ring is employed, being an annular ring bolted to the piston. The piston rings are set out to fit the cylinder bore by suitable springs. The round plugs seen on the piston face merely fill the holes used to support the core in the mould and to extract it from the finished casting. Cylinder drain cocks sometimes have a check valve upon them, so that while the water may pass out of the cylinder the air cannot pass in and destroy or impair the vacuum. Cylinder escape or relief valves are provided at the top and at the bottom of the cylinders, and consist of a spring loaded valve with an adjusting screw to regulate the pressure at which they shall act. They are most needed when the boiler primes heavily, and the water might knock out the cylinder heads or covers. They should be enclosed in a case with a pipe to lead the water away, thus preventing it from flying out and scalding the engineer. A link motion is a valve gear by which the engine may be reversed (caused to run in either direction), or which may be used to vary the point of cut off. The advantage of the link motion is its simplicity and durability. A link motion for a marine engine is usually of the Stephenson type, and consists of two eccentrics or eccentric sheaves fixed upon the crank shaft, and so set as to give more lead at the bottom than the top ports, because the wear of the journals, brasses, and pins gradually increases the lead at the upper, and correspondingly diminishes that at the lower port. In addition to this, however, more lead is required at the bottom port, to counterbalance the weight of the piston at the end of its descending stroke. The eccentric hoops or straps drive the rods which connect to the ends of the link. The link may be a curved, solid, or a slotted bar, and in either case has fitted to it a block or die which connects to the valve spindle. The link is pivoted at its centre to a swinging arm or suspension link,[58] and by this arm may be moved endways to bring the required end of the link beneath the valve rod or spindle. From the positions in which the eccentrics are set, one end of the link operates the valve to go ahead, while the other end operates it to go astern; hence all that is necessary (so far as the link motion is concerned) to reverse the engine is to move the link endwise to the requisite amount, which, for full gear, is so that the block is at or near the end of the link. [58] See page 383 for the construction of a link motion. In proportion as the link block is (by moving the link endways) brought nearer to the middle of the link, the valve travel is reduced and the point of cut off is hastened, thus increasing the expansion. When the link block is in the middle of the link, the latter is in mid gear, and the valve only opens the ports to the amount of the lead, and the link action is the same, whether the engine moves backwards or forwards. The motion of the link is as follows: The two ends are vibrated by the eccentrics from the central pin of the link hanger (or suspension link) as a centre of motion, while at the same time this end of the link hanger swings in an arc of which its other end is the centre of motion. In small engines the link is sometimes used for varying the expansion as well as for reversing the direction of engine revolution. In large engines it is used for reversing only, a separate expansion valve being used for varying the point of cut off. In small engines the link is moved endwise for forward or backward gear by a simple arrangement of hand levers. In large engines these levers are supplemented by a worm and worm gear, and in still larger engines a steam reversing gear is used for shifting the links from forward to backward gear, or vice versa. When there is no link motion, a Joy valve gear, a Marshall valve gear, or a loose eccentric may be used. A loose eccentric is one that can be moved around the shaft to reverse the engine. It may be moved around the shaft by mechanical means, or the eccentric rods may be disconnected, and the valve worked by hand, to cause the engine to run in the required direction, until a pin fast in the shaft meets a lug on the eccentric and drives it, there being two such lugs or shoulders spaced the requisite distance apart on the eccentric. This plan is obviously only suitable for small engines. A separate expansion valve is a valve employed to effect the cut off and vary the expansion. It does not affect either the admission or exhaust of the steam to the cylinder. It is used because by its means an early point of cut off and high rate of expansion may be obtained with a fixed point of exhaust, a fixed amount of compression, and a fixed amount of lead, whereas with the link motion alone the exhaust occurs earlier in the stroke, and the compression and the lead increase as the link is moved from full gear towards mid gear. The expansion valve should, when the engine is to be started, be set for the latest point of cut off. The eccentric for the expansion valve is set opposite to the crank, in order that its action may be the same, whether the engine runs backward or forward. The small cylinders on top of the steam chests are for the purpose of guiding the upper ends of the valve spindles, and are fitted with pistons having steam beneath, the space above being in communication with the condenser. The steam pressure on the piston supports the weight of the valves and valve gear. The friction of a slide valve may be relieved or reduced by excluding the steam from its back, which is done by various means, such as by a ring cast on its back and working steam tight against a plate held independently of the valve. The interior of the ring should be open to the exhaust. The friction of a slide valve is caused by the steam pressing it to its seat, the amount of this pressure varying with the fit of the valve to its seat, and its position over the ports, or, in other words, upon how much of the valve area has steam pressing on one side only. The travel of the eccentric rod is the distance it moves measured on a straight line. It is equal to twice the throw of the eccentric. The throw of an eccentric is the distance between the axis of its bore and the centre or axis from which its circumference was turned in the lathe. Double beat valves are composed of two discs or mitre valves, one above the other on the same stem, so that as the steam presses on the opposite faces of the two discs the valve is balanced. The objection to their use as safety valves is, that they are balanced and would not lift unless the area of the upper disc was made larger than that of the lower one, in which the objection would remain that the two discs do not expand equally, hence they are apt to leak. They are sometimes used instead of slide valves, but are objectionable because a separate admission and exhaust valve is required at each end of the cylinder, and because at quick speeds of revolution they fall to their seats with a shock or blow which wears out both the valve and the seat. When a high piston speed is obtained by great length of piston stroke, and not by high rotative speed, their use is less objectionable. Expansion joints are joints which permit the parts they connect to expand and contract without straining them. They are necessary on the steam pipe connecting one boiler to another, and on the main steam pipe from the boilers to the engine. The working surfaces require to be of brass, so that they will not corrode. They require the collar on the internal pipe of the joint (on which the gland fits) to be permanently fixed by soldering or brazing, and check nuts on the studs, so that the internal pipe shall not be blown out from the steam pressure. This pipe is also sometimes fitted with chains or stops, in case the studs should break, or the nuts or collar strip. An oil cup is either a cavity cast in the piece or a cup shaped vessel or hollow cylinder screwed in. It contains a pipe extending up about three-fourths of its height, and through this pipe the oil is fed to the surface required to be lubricated. A hinged lid or, in some cases, a screwed cap covers the oil cup to exclude dust, etc. The syphon or worsted consists of a number of threads of worsted or lamp wick of equal lengths; a piece of lead or copper wire is laid across the middle of the worsted, the copper wire is doubled and twisted and is then pushed down the tube, carrying the doubled end of the worsted with it. The upper ends of the wire are bent over the end of the tube so as to hold the worsted, whose lower end should pass down below the level of the bottom of the oil cup. The oil feeds (on the syphon principle) through the medium of the wick or worsted, which should not fit the tube tight but quite easily, its upper ends hanging over the top of the tube to the bottom of the cup. The worsted may be cleaned with scalding water, or by water thrown upon it from the boiler. Tallow cups for high pressure cylinders must have two cocks, so that after the cup is filled the top cock may be closed and the bottom one then opened. The top cock prevents the tallow or oil from being blown out of the cock by the steam. For the low pressure cylinder a cup with a single cock will answer, as the cock may be opened when the vacuum is at that end of the cylinder, and the air will force the oil or tallow in. A steam lubricator or impermeator is an automatic oil feeding device placed on the steam pipe of the high pressure cylinder. Steam lubricators are made in various forms, some having a positive feed by a pumping arrangement, while in others the oil floats upon water in the body of the lubricator to which steam is admitted; the condensation of the steam increases the quantity of water and causes the floating oil to overflow and feed through a pipe leading into the steam pipe or steam chest, as the case may be. Cooling the impermeator causes more rapid condensation, and increases the amount of oil fed to the steam. Cylinder escape or relief valves do not let all the water out of the cylinder because of the clearance,[59] hence the amount of water left in will equal the amount of clearance. [59] See page 372, on clearance. The small cylinders on top of the steam chest are for the purpose of guiding the upper ends of the valve spindles, and are fitted with pistons having steam beneath, the upper end being in communication with the condenser. The effort of the piston to rise supports the weight of the valves and valve gear. The valves of a marine engine that are worked by hand are, the stop valves for letting on steam from the boiler, the safety valve, which is lifted to see that it is in proper working order, the Kingston valve for letting in the circulating water, the blow through or starting valve for warming the cylinders and starting the engines. The valve for adjusting the rate of boiler feed has its lift adjusting screw operated by hand. The slide valve may also be operated by hand before the engine is started, or it may be operated by a steam reversing gear. The expansion valves are also set by hand to regulate the point of cut off or amount of expansion. The valves that are operated automatically, or from the motion of the parts, are the slide and expansion valves, the suction and delivery and check valves of all pumps, the air pump bucket valves, the snifting valves, and the ship's side overboard discharge valves. When the engine is stopped and the steam shut off, close the dampers to check the draught and open the drain cocks on the high pressure cylinders. If the engine is soon to start and the pressure in the boiler is at the blowing off point, start the boiler feed, if the height of the water in the boiler will permit it, and this is a good time to clean the fires. If the engine is to stop for any length of time, shut off the impermeator and the injection supply. A vacuum gauge is an instrument for measuring the total or absolute pressure, or pressure above a perfect vacuum, and it is used to indicate the degree of vacuum that exists in the condenser, which, when the various joints about the cylinder and condenser are tight, averages about 27 inches of mercury when the temperature in the hot well is about 100° Fahrenheit. In round numbers a column of mercury 32 inches high equals the weight of the atmosphere,[60] hence taking the weight of the atmosphere at sea level to be 15 lbs. per square inch, then each two inches of mercury represents an atmospheric pressure of 2 lbs. Suppose then that a bent U shaped tube, each leg of which is 30 inches high, is half filled with mercury, and that one end is in communication with the condenser, and the other end is open to the atmosphere, and if there was a perfect vacuum in the condenser, the pressure of the atmosphere in the open leg would force all the mercury into the leg that communicated with the condenser, hence there would be a column of 30 inches of mercury in one leg, and air in the other. [60] See "Barometer," Chapter XL. If there was in the condenser a pressure of 1-1/2 pounds per square inch above a perfect vacuum, the mercury would stand 27 inches high in one leg, and 3 inches in the other, and so on, hence from the height of the column of mercury above its natural level the degree of vacuum in the condenser may be known. But the pressure of the atmosphere varies with its temperature, and the weight of mercury also varies with its temperature. To find the total pressure in the condenser, therefore, we subtract height of the column of mercury given by the condenser from the height of the column in the barometer, and divide the remainder by 2. _Examples._--The barometer stands at 29.5 and the vacuum gauge at 26, what is the absolute pressure in the condenser? Here, 29.5 - 26 = 3.5 ÷ 2 = 1.75 Answer, 1-75/100 lbs. per square inch. A dial vacuum gauge of the Bourdon construction is similar to the Bourdon steam gauge, that is used upon the boiler, except that the inside of the elliptical tube is in communication with the condenser and the atmospheric pressure bends the tube into a curve of smaller radius (instead of to a larger one, as in the case of the steam gauge). Obviously, therefore, the zero of the dial vacuum gauge is atmospheric pressure. Suppose the dial vacuum gauge shows 10 lbs., the steam gauge 120 lbs., and the barometer 15 lbs., and we may find the total pressure or pressure above vacuum of the steam in the boiler is as follows: One-half Pressure by steam gauge = 60 lbs. A perfect vacuum = 15 lbs. -- Total pressure supposing condenser had a perfect vacuum = 75 lbs. To make the correction necessary because there is not a perfect vacuum in the condenser, we then proceed as follows: Barometer 30 inches of mercury = 15 lbs. per sq. in. Dial vacuum gauge = 10 " " " " -- Actual pressure in condenser = 5 " " " " Then Total pressure supposing condenser had a perfect vacuum = 75 Actual pressure in condenser = 5 -- Actual pressure of the steam = 70 Racing means a sudden acceleration of the engine speed, and occurs when the propeller is not fully immersed in the sea, as by reason of the pitching of the ship. Racing augments the strain on the working gear of the pumps, and is likely to lead to accident. It is obviated by the use of a governor or by partly shutting off the steam by hand. A marine governor is a device for controlling the engine speed, by reducing the supply of steam to the engine cylinder whenever the engine begins to race. The governor is driven by band or rope on the crank shaft. Governors are made in various forms; thus, in one the shaft has a fly wheel and a friction clutch, one half of which is fast on the governor shaft, while between it and the other is a spiral spring which connects the two halves. If the speed accelerates, the sliding half of the clutch is moved along the governor shaft, and by means of links it closes the throttle valve of the main steam pipe, thus wire drawing the steam, reducing its pressure and thereby controlling the engine speed. A common paddle wheel has a cast iron centre into which the wrought iron arms are set and secured by wrought iron bolts and nuts. The bolts have hook heads to grip the back of the arm, and receive a nut and plate to secure the paddles. Paddle wheels are sometimes provided with cast iron floats to act as counterweights to some unbalanced part of the engine. They are mostly required on side lever engines having a single crank; they are placed nearly opposite to the crank, but not quite, so that they may prevent it from stopping on the centre, and be difficult to start again. Paddle wheels for engines having a single crank sometimes have their floats of varying breadths, so as to keep the speed of revolution as uniform as possible. This is accomplished by making some of the floats wider than the others. The broadest floats are in action when the crank is at its points of greatest power, and the narrowest at the time the engine is on a dead centre, hence there are four general graduations of breadth in the circumference of the wheel. A radial paddle wheel is one in which the floats are fixed to the paddle arms, and their ends are in a line radiating from the centre of the paddle shaft. A feathering paddle float is pivoted at the centre of its ends, and so arranged that by a mechanical movement it will remain vertical when in the water, notwithstanding the circular path it revolves in. The object of feathering is to cause the thrust of the float to be as nearly as possible in a horizontal line, and therefore more nearly parallel to the line of the ship's motion, and thus utilize more of the paddle power to drive the ship. The eccentric for feathering the floats is fixed to the ship's side, and sometimes carries a plummer block or pillow block for the paddle shaft bearing. The centre of the eccentric sheave or wheel is placed ahead of and level with the paddle shaft axis. The working surfaces of a feathering wheel are of brass, and the bushes of the paddle arms of lignum vitæ. The surfaces are lubricated by the water, but sometimes oil lubrication is provided for the eccentric sheave. A disconnecting paddle engine is one in which the paddles may be driven separately or together. This is effected at the inner port bearing by a clutch wheel, which slides endways on the shaft and is driven by feathers seated in the shaft. This clutch wheel is operated by a lever so as to engage or disengage with the crank pin, which is fast in the outer crank. Disconnecting paddle engines are always fitted with loose eccentrics, such engines being used for steam tugs and ferry boats, where quickness of turning and of reversing is of great importance. The thread of a screw propeller is its length measured along the outer edge of the blade. The angle of the thread is its angle to the axial line of the propeller shaft. The length of the thread is the length of the outer or circumferential edge of the blade. The area is the surface of one side of the blade. The diameter is the distance apart of the two points on the edges that are diametrically opposite and furthest apart. The pitch of a propeller is its degree of spirality, and is represented by the distance it would move forward if the water was a solid. It is measured by drawing a line representing the axis of the propeller shaft, and at a right angle to it a line representing in its length the circumference of the circle described by the tips of the blades; from the point of intersection of these two right angle lines a diagonal line is drawn representing the angle the blade at its outer edge stands at the propeller shaft axis. The greatest distance between the diagonal line and the line representing the propeller circumference is the pitch of the propeller. A left handed propeller has a left hand thread or spiral, and revolves from left to right to move the ship ahead. A right hand propeller has its blades inclined in the opposite direction, and of course revolves in the opposite direction to a left hand one. The slip of a propeller is the difference between the distance the ship is moved by the propeller and the distance it would move if the water was solid. Slip is usually expressed in the percentage that the distance the ship actually travels bears to the distance she would have travelled if there had been no slip. From 10 to 20 per cent. is lost in slip. A screw of increasing pitch is one in which the angle of the face of the propeller blade to the axis of the shaft increases as the thread recedes from the shaft, or from the centre to the circumference of the blade, or in both directions. In a uniform pitch the angle of the blade to the propeller axis is the same at all distances from the axis. An example of a screw of uniform pitch would be a piece of angle iron wound around a parallel shaft. If wound on a tape shaft, the largest diameter being nearest to the ship's stern, it would have an increasing pitch. If wound around a parabola, the pitch would vary at every point in its diameter and thread. A thrust bearing is a journal bearing provided with a number of corrugations or collars fitting with corresponding corrugations or recesses in the thrust block, the area thus provided serving to resist the end thrust placed by the propeller upon the shaft. It must be freely lubricated by ways leading to each collar or corrugation, and so situated that it is accessible for examination. It is sometimes at the end of the first length of shaft aft of the engine. A stern tube is a sleeve enveloping the aft end of the propeller shaft to protect it from the sea water, which would corrode it. At the aft end of the stern tube is a gland and stuffing box. At the inner end, which extends to the aft bulkhead, it has a flange which is bolted to the bulkhead. The bearing area of the shaft and stern tube are lined with brass (about half an inch thick) to prevent their oxidation from the action of the sea water. A lignum vitæ bearing is a wooden bearing generally fitted to the outer end of the stern tube in propeller engines, or to the outer ends of the paddle shaft of paddle engines. It consists of strips of lignum vitæ dovetailed into the bearing or bush, and running lengthways of it. These strips are prevented from working out by a check plate at each end of the bearing. Screw propellers may be fastened to their shafts in several ways, as by a key or feather sunk in the shaft, and projecting into a keyway in the propeller bore, and a nut on the end of the shaft with a safety pin outside the nut, or by a key passing through the boss of the propeller, and a safety pin or plate upon the key. The principal pipes of a marine engine and boiler, and the parts they connect, are, the main steam pipe, connecting the stop valve on the superheater to the steam chest of the engine cylinders; the waste steam pipe from the safety valve to the open air; the blow-off pipe, connecting the blow-off cocks on the bottom of the boiler with the blow-off Kingston cock on the ship's side; cylinder jacket pipe from the stop cock on the boiler to the steam jacket. The circulating suction pipe, connecting the main Kingston valve with the bottom of the circulating pump; the circulating delivery pipe, connecting the discharge compartment of the condenser with the main delivery valve on the ship's skin; the air pump suction, connecting the body of the condenser with the suction side or bottom of the air pump; the main exhaust pipe, connecting the exhaust passage of the low pressure cylinder with the condenser; the feed water suction pipe, connecting the donkey feed pipe with the hot well; the feed water delivery pipe, connecting the donkey feed pump with the check valve on the boiler; the bilge suction pipe, connecting a strum box in the bilge with the bilge pump; a suction pipe from the strum in the bilge to the donkey pump; the bilge pump delivery pipe, connecting the bilge pumps with bilge delivery valves on the ship's side. A mud box is a rectangular box usually placed in the engine room, and serving to clear the bilge water from foreign substances, as small pieces of wood, coal, etc.; the construction is as follows: It is on the suction side of the bilge pumps, and is provided with a hinged lid that affords access to clean it out, and that must obviously close air tight, or the bilge pumps will not draw. The box is divided into two compartments by a loose division plate that stands vertical, and is perforated so as to act as a strainer. The steam from the boiler passes through the superheater, main stop cock or valve, main steam pipe, separator, regulating and throttle valve, steam chest, steam port, steam passage into cylinder, returns through steam passage and port, exhaust cavity of valve into either the condenser or the low pressure cylinder, as the case may be, finally exhausting into condenser, whence the water of condensation is pumped by the air pump into the hot well. In the case of a jet condenser part only of the condensed steam goes back to the boiler, the rest going into the sea through the injection discharge pipe. A steam jacket[61] is an outer casing to a steam cylinder, the space between it and the cylinder being filled with steam direct from the boiler, with the object of preventing condensation of the steam in the engine cylinder. [61] See page 374 on steam jackets. A drain cock is supplied to the bottom of the jacket to pass off condensed water. Steam jackets should be lagged or felted to prevent condensation. The parts of an engine that require to be felted or lagged are the cylinders and the steam pipes; the boilers also should be felted or otherwise covered to prevent loss of heat by radiation, and the uptake protected by means of thin plates, kept, by means of distance pieces and bolts, at a distance of two or three inches from the plates of the uptake. Various non conducting substances are employed to prevent radiation, as, for example, felt, mineral wool, asbestos, and various kinds of cement. The pieces of the engine through which the steam pressure is received and transmitted are as follows: The piston, piston rod, cross head, cross head gudgeon, connecting rod, crank pin, crank shaft and couplings to the propeller shaft. Trunk engines are generally used in war vessels where it is required to have the engines below the water line. The trunk passes through the cylinder and the piston is upon the trunk, the connecting rod passes down into the trunk and connects direct to the piston. A stuffing box and gland in each cylinder cover keeps the trunk steam tight. The trunk forms a guide to the piston in place of the ordinary cross head and guides, and thus saves the room required by those parts. The cylinders for a right handed propeller should be on the starboard side of the vessel, so that the pressure on the piston, when the engine is going ahead, shall be in a direction to lift the trunk in the cylinder, and thus act to relieve the gland and cylinder bore of the weight of the trunk and piston. An oscillating engine is one in which the cylinder is mounted on bearings called trunnions, so that the cylinder can swing and keep its bore and the piston pointing to the crank at all parts of the engine revolution. This enables the connecting rod and slide bars to be dispensed with. The trunnions are hollow, one containing the steam and the other the exhaust passage. Oscillating engines are used for paddle steamers, because their construction permits of a good length of piston stroke, while still keeping the engine low down in the vessel. The valve motion for an oscillating engine consists of an ordinary eccentric gear or motion, with the addition of various mechanical arrangements to accommodate the valve gear to the vibrating motion of the valve chest. The stuffing box of an oscillating engine is made deeper than usual because the gland bore has more strain on it, and extra wearing surface is therefore required to prevent its wearing oval. Geared engines are those with gear wheels to increase the revolutions of the shaft above those of the engine, and thus obtain a high propeller speed without a high piston speed. The pressure that propels a vessel is taken by the thrust block in a screw propeller engine. The pressure that drives a paddle steamer is applied to the hull at the shaft bearings and their holding beams, and to the bed plates. The amount of fuel required per horse power per hour, by modern compound engines, is from about 1-1/2 to 3 lbs., and by common condensing engines from 3 to 5 lbs. per horse power per hour. The unit or measure of a horse power is the amount of power required to lift 33,000 lbs. one foot high in a minute.[62] [62] See page 407, Vol. II. Nominal horse power is a term used to represent the commercial rating or power of an engine, and is usually based upon the area of the piston. It gives no measure of the engine power, however, because it does not take the piston speed into account.[63] [63] See page 374, Vol. II. In a surface condensing engine the duty of the air pump is to merely pump the condensed steam and vapor from the condenser to the hot well, whereas in a jet condensing engine it has to also take the condensing water from the condenser, hence an air pump for a surface condenser may be made smaller than that for a jet condenser. As the air pump works against the pressure of the atmosphere, therefore the smaller it is the less of the engine power is absorbed in working it. The injection cocks are regulated for opening by rods having handles attached. If the injection cocks are not open wide enough, the condenser will get hot and impair the vacuum, while if opened too wide, the water in the hot well will be cold and the boiler feed will be cold. These cocks should be so regulated as to keep the temperature in the hot well at about 100° Fahrenheit. The parts of a marine engine that are exposed to danger in a cold climate are all pipes through which cold water circulates, and are liable to freeze. The precautions necessary to prevent freezing in cold climates are to cover all pipes liable to freeze, to keep the water circulating through them, or to let it out of them if necessary, as in the case of the engine standing. A marine engine may fail to start, or may be prevented from starting by the following causes: 1st. The H. P. slide valve may be off, or away from its seat, thus admitting the steam to both sides of the piston at the same time. 2d. The engineer may have forgotten to disengage the hand turning gear from the crank shaft. 3d. The propeller may be fouled with a piece of timber, or by a chain or rope (these causes sometimes occurring when the ship is in port), or there may be something wrong with the outer bearing of the propeller shaft. 4th. In the case of a propeller fitted with a banjo frame (for the purpose of raising the propeller) the propeller may be locked. 5th. An obstruction, as a block of wood, in the crank pit may prevent the crank from turning. 6th. The slide valve nut may have slackened back, thus loosening the slide valve. 7th. The slide valve spindle may have broken. 8th. When an engine has no auxiliary or starting, but an _impulse_ valve that merely lets a puff of steam into the receiver, this impulse valve may leak, and if the escape or relief valve on the receiver is too much loaded, it may gag the H. P. piston by giving it high pressure steam on both sides, and this may throw the valve off its seat. Similarly, if the engine has an auxiliary or starting valve, and it leaks, high pressure steam may be admitted to both sides of the L. P. piston, thus gagging it and causing its slide valve to throw back and away from its seat. 9th. The cylinders may be choked with water, and the drain cocks choked up. 10th. The crank shaft bearings may be screwed up too tightly. 11th. The air or the circulating pump may be choked with water, either the air pump overflow valve or the circulating discharge valve being secured down.[64] [64] The air pump overflow valve should never be permanently fastened down. More engines have been broken down from this than from almost any other neglectful cause, because, from great leaks in the condenser tubes and engines standing for a length of time, a larger quantity of water may require to be got rid of during the first few strokes of the pump than can pass through the small air or vapor pipe, which is usually fitted from the hot well either into the bilge or else overboard. Unless the valve in this overflow pipe is heavy enough of itself (which is very rarely the case), it should be loaded by a spring or weight, so that when the puff of the air pump causes it to lift, and the vessel is rolling, sea water may not pass into the hot well. To avoid this, some engineers erroneously fasten this valve down. An experienced engineer states that in his experience five engines have been broken down from this cause alone. 12th. From the engines being allowed to stand a long time in one position, and the glands being too tightly packed. An engine should be turned a little daily when not in use. 13th. From the piston rings being set out too tight to the cylinder bore. 14th. From the throttle or stop valve being shut, as from its spindle being broken. 15th. From the eccentric sheave, or wheel, having shifted on the shaft, some eccentrics having a key that is not sunk in the sheave, which is done so that the eccentric may shift rather than break if it should seize in its strap. 16th. From the H. P. piston leaking badly, or its ring being broken, which will permit the cylinder to fill with steam and the slide valve to unseat. 17th. If the engine has been overhauled, the forward eccentric may have been connected to the wrong end of the link, thus giving an improper motion to the slide valve. 18th. The expansion may be set to cut off too early in the stroke. 19th. From the air pump rod, or from the circulating pump rod being broken, or from the valves being broken. 20th. From the cylinder casing or the receiver being cracked so as to admit steam to both sides of the piston at the same time. A defective vacuum, or loss of vacuum, may occur from the following causes: 1st. From the glands of the low pressure cylinder leaking. 2d. From the pet cock of the air pump being left open. 3d. From the joints of the connections about the condenser leaking.[65] [65] To discover a leak about a condenser, pass an exposed light, as a candle, about the joints, etc., and where there is a leak the flame will be drawn in towards the condenser. 4th. From the condenser being cracked, and therefore leaky. 5th. From the injection cock or valve being closed. 6th. From the condenser tubes being foul for lack of being cleaned. From the L. P. cylinder escape valves or cylinder cocks being leaky, and therefore letting in air. 7th. From the slide valve and piston of the L. P. cylinder leaking. 8th. From the air pump valve being leaky or broken. From the circulating pump being defective, as from having leaky valves. 9th. From the Kingston injection valve not being properly opened, or from its outside orifice being choked. 10th. The bilge injection may be so connected with the air pump or condenser as to impair the vacuum when its valve is accidentally stuck and its stop cock is left open.[66] [66] It is obvious that a defective vacuum may or may not prevent an engine from starting, according to the degree of defectiveness. The principal causes of heating are: 1st. The bearing caps being screwed down too tight. 2d. The bearings being left uncovered, thus allowing the brick dust used for cleaning the machinery, the dirt from coaling the ship, or the sand used for cleaning the decks, to get into the bearing. 3d. The oil grooves in the brasses being worn out or too shallow, or the brasses not being cleared at the sides. 4th. Improper fitting of the distance pieces or fit strips between the brasses. 5th. Bad oil or too light an oil. 6th. If the brasses are too slack and thump or pound, the back of the brass may be stretched by pening, causing the sides of the brass to close in upon and bind the crank journal or crank pin, and this will cause heating. For other information concerning the engine see as follows: Page. Angularity of connecting rod 375 The slide valve 376 Double ported and griddle valves 377 Balanced valves 377 Piston valves 378 Separate cut off valves 378 Reversing gears 383 Finding the working results of a slide valve 376 Condensing engines 442, 444 Calculations on the mechanical powers 405 The unit of power 407 Calculating horse power 407 Calculations of safety valves 409 Heat, water, and steam 410 The expansion of steam 411 The conversion of heat into work 411 The indicator 413 Indicator diagrams 414, 421 The barometer 415 Calculating the horse power from indicator diagrams 419 Finding the steam of water consumption from an indicator 421 Figs. 3405 and 3406 represent a triple expansion marine engine, the construction being as follows: The high pressure cylinder has a piston valve and the intermediate and low pressure cylinders flat valves. Each cylinder has a link motion, and all three link motions are shifted from the same shaft, which is moved by a steam reversing gear. At _a_, Fig. 3405, are the eccentrics for the link B, for the high pressure cylinder; _b´_, _b´_ are those for link B´, for the intermediate cylinder; and _c´_ _c´_ are those for the link C´, for the low pressure cylinder. From each link are rods E, Fig. 3406, connected to arms on the shaft F _f_, to an arm on which is connected the rod G, from the worm wheel H, whose actuating worm I is on a crank shaft operated by the small steam cylinder J. The slide spindles D work in guides, and their cross heads C span the edges of the links, gibs being provided to take up the wear. The gear for turning the engine when there is no steam in the main boilers is constructed as follows: On the shaft of the wheel _m_, Fig. 3405, is a worm _n_ operating a worm wheel _p_, on whose shaft is a worm which operates the large worm wheel shown on the main crank shaft. Figs. 3407 and 3408 represent the compound engines of the steamship _Poplar_, concerning which _The Engineer_ (from which the engravings are taken) says: "Both the cylinders of these engines are fitted with piston valves, placed at the back of the cylinders and worked by the single eccentric valve gear, which has been so largely adopted and so successfully carried out by this firm in triple expansion as well as compound engines. It will be noticed that whilst this valve gear permits of the cylinders being close together, it allows of the crank shaft being made in two similar pieces, and affords exceptionally long main and crank pin bearings, of the former of which there are only three, instead of the usual four. In the case of the _Poplar_ the cylinders are 29 in. and 55 in. in diameter and 33 in. stroke, and the crank pins are 11 in. long, whilst the centre main bearing, which does duty for both the engines, is 23-3/4 in. in length, each of the outer bearings being 18 in. in length, the diameter of the crank shaft being 9-1/2 in. Another very interesting feature about these compact little engines is the design of the front framework. Instead of the ordinary upright columns in front of each engine there is an arrangement which gives exceptional stiffness to the whole structure whilst affording the fullest possible accessibility to the main working parts, and which has the appearance of an arch, from the shoulders of which there are branches worked up to receive the feet of the cylinders, thus accommodating the close centres and providing for the support of the reversing wheel without in the least obstructing the gear below. The condenser is divided horizontally through the centre on a plan strongly advocated by the builders, the whole of the base of the engines being cast in one piece and made level on the under side, so as to enable it to receive support from, and be bolted to, the engine seating immediately beneath the crank shaft, as well as round the margin." [Illustration: Fig. 3405.] [Illustration: Fig. 3406.] [Illustration: Fig. 3407.] [Illustration: Fig. 3408.] CHAPTER XLIII.--MARINE BOILERS. Boilers for marine engines are, in England, made of special qualities of plate, the best being termed Yorkshire, and a nearly equal grade, Staffordshire. The plates for the shell, the furnace bottoms and the gusset stays are made of Staffordshire, while the tube plates, furnace tops, and such parts as require to be flanged and are subject to more intense heat, are made of Yorkshire plate, which has more ductility. In the United States the grades of iron used for boilers are C H No. 1 S, or charcoal hammered No. 1 shell iron, for the shell, and C H No. 1 F, or charcoal No. 1 flange iron, which is used for the furnaces and such parts as require flanging. In both countries steel is also used for boilers, except for the tubes, for which it is not entirely reliable if very high pressures are to be used. Both the iron and steel plates are tested for tensile strength and ductility. The breaking strain is that which is sufficient to cause rupture, while the _proof strain_ is that which the metal is required to withstand with safety. The safe working strain, or working pressure, W P, is the strain under which it is considered safe to work the boiler. The strength of a boiler of a given diameter and thickness of plate varies according to the construction of the riveted seams or joints. Boiler stays or braces are rods, ribs, or plates for supporting the weaker parts of the boiler. Thus the tube plates may be stayed by rods passing through both plates and screwed into them, or nuts and washers may be used on the stays one on each side of each tube plate. Gusset stays are iron plates which are riveted to [T] irons or in some cases to [L] irons, which are riveted on the surfaces to be stayed. Stay tubes are thick tubes (usually about 3/16 inch thick), which screw into the tube sheets and are riveted over at the ends. A superior construction, however, is to provide nuts and washers to the ends of the stay tubes, one on each side of each tube plate. Boiler stays are usually made of such diameters that when new they will sustain a tensile strain of not more than 5,000 lbs. per square inch of cross section, this being the rule of the Board of Trade. Stays are sometimes screwed into the tube plates and then riveted over at the outside ends. A better method, however, is to let the ends of the stays receive a nut on each side of each tube plate. Boiler tubes are secured in their tube plates by being _expanded_ in. This may be done by driving in a taper steel mandrel, and then clinching them over, or by using a tube expander. There are two principal kinds of tube expanders, in one of which small rolls travel around the bore of the tube and expand it, while in the other a number of segments, held together by a spring, are forced outwards by a mandrel driven in by hammer blows. Too much expanding is apt to weaken the tube close to the inside face of the tube sheet. Boiler tubes leak first at the end which receives the greatest heat from the fire, the leakage being caused by the expansion and contraction of the tube, which is obviously hotter than the water which causes the tube to expand more than the boiler shell. The remedy is to re-mandrel or expand the tube. The scale that forms on the face of the tube sheet keeps the water away from contact with the plate, which with an undue thickness of scale will crack between the tube holes. A tube that is split or that cannot be made steam tight by being re-mandrelled or expanded is plugged up at each end by means of either wooden or iron plugs. The best plan, however, is to use iron discs having a stepped diameter, so that one end will fit the bore of the tube, and the other will form a shoulder that will cover the end of the tube. [Illustration: Fig. 3409.] Each disc has a hole through its centre, so that a wrought iron rod or bolt may be passed through the hole and receive a nut at each end. Beneath the flange of each disc, a grummet of spun yarn and white lead is placed, so as to make a steam tight joint when the nuts are screwed home. This stays the tube plates as well as stopping the leaky tube. If wooden plugs are used, they are made a driving fit in the tube bore, and driven through until they have passed the split, and a second wooden plug is driven tightly from the same end of the tube. The up take of a marine boiler is the casing or passage way through which the heat and gases pass after leaving the boiler. A dry up take is one which is outside of the boiler, as in Fig. 3409, which represents an outside view of a boiler such as shown in Figs. 3410 and 3411. A wet up take is one which passes through the boiler, and therefore has fire on one side and steam on the other. It is therefore under a collapsing pressure. The furnace of a marine boiler extends from the fire door to the combustion chamber (_i. e._, the box in which the heat of the furnace passes before returning through the tubes). The superheater of a marine boiler is a cylindrical vessel receiving the steam from the boiler, and delivering it to the main steam pipe, whence the steam is delivered to the engines, etc. When it has no connection with the up take, it may, however, be more properly termed a steam driver, since it serves to separate the steam from entrained water, and does not superheat the steam. In some cases, however, the superheater takes the form of a spherical ended cylinder standing in the up take. The receiver of a marine boiler is a drum or cylinder that receives the steam from the boiler and from which the steam passes through the steam pipe to the engine. The receiver is by some called the _steam chest_ of the boiler. The fittings essential for a marine boiler are: The safety valves; the test cocks (or gauge cocks, as they are sometimes termed); the water gauge glass; the stop valves; the check valve for the boiler feed pipe, and the valves for letting on steam to the main engine and such other engine or engines as may take steam from the main boiler; the scum cocks; the blow off cocks; and a small cock to enable the drawing of water from the boiler to test its degree of saltness. There are two kinds of safety valves, the dead weight and the spring loaded. A dead weight safety valve is one in which the valve is held to its seat by dead weight, the objection to which is, that when the vessel rolls the effect of the weight or weights upon the valve is diminished; hence under heavy rolling the steam may blow off at a less pressure than the valve is set for. A lock up safety valve is a dead weight safety valve, the top of whose spindle is provided with a cast iron cap or bonnet with two handles on. This cap is keyed to the spindle, and the keyway is so disposed that no extra weight can be added to the valve, while at the same time the valve can be lifted from its seat and turned around. A spring loaded safety valve is one in which the valve is held down by the pressure of a spiral spring, and this pressure will obviously not vary, no matter how much the ship rolls. In proportion as the valve lifts and the spring compresses, its resistance increases, and this tends to impair the accuracy of the valve. This, however, is offset from the fact that when the valve rises from its seat it presents a greater area for the steam to act against. The area of safety valve required by the English Board of Trade is about 1/2 square inch of valve area per square foot of fire grate area.[67] [67] See page 409, Vol. II., for safety valve calculations. There are three test cocks, which are sometimes placed in a diagonal row on the front of the boiler, and sometimes on the fitting for the gauge glass. The top test cock shows highest level to which the water should rise in the boiler, and the lowest one the lowest level, the middle cock indicating the average. There is usually a vertical distance of about 4 inches between the test cocks, which gives a permissible range of 8 inches in the level of the water in the boiler. Test cocks are prevented from choking with scale by passing a wire through the cock and clear into the boiler, a plug being provided, which, when removed by unscrewing, permits the insertion of the wire. This cleaning must obviously be performed when there is no steam on the boiler. A gauge glass is a glass tube whose bore is open to the boiler. It is fitted at each end to a brass socket that is screwed into the boiler, each socket having a cock that permits communication between the gauge glass and the boiler to be shut off in case the glass should break. The bottom socket is also fitted with a cock, which, on being opened, permits the water and steam to blow through the gauge glass and clean it of scum or dirt. The gauge glass must be plainly in sight, and placed at such a height that when the desired quantity of water is in the boiler it will half fill the gauge glass. Glass water gauges, instead of attaching to the boiler, are sometimes fitted to a fitting that connects to the top and bottom of the boiler, with the object of attaining, for the gauge glass, water free from the scum and impurities which collect at and near the surface of the water in the boiler. This fitting should have cocks in each pipe leading to the boiler, so that in case the gauge glass breaks, steam can be shut off from the boiler. In some cases the test cocks are also attached to this fitting, and in this case the construction should be such that shutting off communication between the gauge glass and the boiler will not at the same time shut off communication between the test cocks and the boiler. When the boiler is priming or steaming very fast, the gauge glass may show a false water level, hence reading should be compared with that of the test cocks. If the water gets too low, the first parts of the boiler to be injured will be the top of the flame box, or the combustion chamber, and the top row of tubes, because they are the first surfaces that the water will fall below and leave exposed to the heat without having water on the other side.[68] [68] See page 370, Vol. II., on low water in boilers. The pressure in the boiler is shown by a steam gauge, pressure gauge, or dial gauge as it is promiscuously called. A Bourdon dial gauge or pressure gauge consists of a dial casing, containing a hollow thin brass hoop, oval in cross section, which receives steam from the boiler. This hoop is fixed at one end, while the other end is closed and free to move. The free end is connected by a small link to a toothed sector, which gears or engages with a small pinion fast upon the spindle of the pointer or needle. When the steam is admitted into the hoop, it straightens out or expands in diameter to an amount that is proportionate to the amount of the pressure within the hoop, and thus causes the needle or index pointer to revolve, and denote from the markings or readings of a dial plate the amount of pressure within the hoop. If the pressure within the hoop is released, it will move to its normal or zero position. In the course of time, however, the hoop is apt to get a slight permanent set and not indicate correctly. It may, however, be approximately tested for accuracy by testing its readings with that of the safety valve. The working parts of the gauge, and its casings also, are made of brass, so that they shall not corrode, and to prevent the heat of the steam from permeating the gauge and impairing the action from expanding the parts, a small quantity of water interposes between the gauge and the steam, the construction being as follows: Outside the gauge casing the steam pipe is bent into a loop forming an inverted syphon which is to contain the water. At the lowest point in the bend of the syphon a small cock is inserted, which lets the water out of the leg of the syphon nearest to the boiler, because water in that leg would, from its weight, cause the gauge to show a pressure higher than that in the boiler. The pressure shown by a steam gauge is that above atmosphere,[69] and not that above vacuum. [69] See page 367, Vol. II., for remarks on total pressure and pressure by gauge. The stop valve of a marine boiler is a valve that is opened to let the steam into the main steam pipe. A blow off cock is a cock employed to blow off, or let all, or a part of, the water out of a boiler. There are generally two, one on the bottom of the boiler, and the other at the ship's side, so that if the pipe was to break or get damaged, the cock at the vessel's side can be closed to keep the sea water out, while that on the boiler may be closed to keep the water and steam in the boiler. These two ends cannot obviously be obtained if one blow off cock only was used. Blow off cocks are opened and closed by a spanner or key that is removable from the cock, and to prevent the possibility of taking off the spanner or key, before the blow off cock is closed, a spanner guard is employed. A spanner guard is a cap having a lug or tongue, which projects into the hole in the spanner guard, through which the spanner or key must pass before it can fit on the head of the blow off cock, and the key or spanner has a corresponding recess, so that the spanner or key can only be put on or taken off when the cock is closed. Blowing off a boiler is emptying it entirely, as for examining the whole interior of the boiler. Blowing down a boiler is letting out a portion of the water, so as to carry off the loose scale, mud, or sludge that may accumulate on the bottom of the boiler. The mud or sludge would form into scale if allowed to remain. A scum cock is a cock employed to blow off a portion of the surface water in a boiler, and thus remove the scum, salt, and impurities which float or are thrown up to the surface. Two scum cocks are employed, one on the side of the boiler, and one on the side of the ship. These two cocks are connected by a pipe. That on the boiler is placed a little below the working level, which is supposed to be (and is kept as nearly as possible) about 9 inches above the top row of tubes. Sluice valves are doors sliding, water tight, in ways at the entrance to the bulkheads on both sides of the ship. They should be worked from above, in order that they may be shut when the depth of water in the bulk heads might prevent them from being worked from below. These valves should be operated occasionally to ensure that they slide easily and are in working order. Scale in marine boilers using salt water is composed of sulphate of lime. It is most objectionable on the furnace tops, on the sides and tops of the combustion chamber, on the tubes and on the tube plates. It may be prevented to some extent from forming by a rapid circulation of the water in the boiler, by blowing down the boiler through the scum cocks, by the suspension in the boiler of zinc plates in contact with iron ones, by impregnating the water with chemical antidotes, which maintain the impurities in the form of mud or sludge, and by purifying the feed water. If surface condensers are used, scaling is obviously diminished by feeding as little salt water as possible, which may be done by not getting up a steam pressure high enough to cause the safety valve to blow off, and by preserving the water from the exhausts of the donkey or other engines about the ship. A thin coating of scale, as say 1/32 inch thick, may serve as a protection against the chemical action of water that would act to corrode the surfaces, as in the case of harbors receiving the waste waters from chemical works or other impure waters. A thick coating of scale causes the plates to burn on the side receiving the furnace heat, and causes blisters to rise, while at the same time it decreases the value of the heating surface. Scale on the tubes causes them to expand more, and therefore leak in the tube sheets. This extra expansion sometimes breaks away the scale at the neck of the tube in the tube sheet and gives access to the water there, and the chemical action of water will in some cases cause the tube to be eaten through close to the tube plate. Scale is removed mechanically by chisels, scrapers and chipping hammers, which are applied to all the surfaces that can be got at from the inside of the boiler (the man hole affording access to the boiler). After the scale has thus as far as possible been removed, it is washed out of the boiler. The efficiency with which scale may be removed from the tube sheets and tubes depends, to a great extent, upon the facilities the arrangement of the rows of tubes affords in giving access to the scaling chisels. The salinometer. Salt water is heavier than fresh water, hence the amount of saltiness of water may be known from its density or weight. A salinometer is an instrument that determines from the density of the water the amount of salt contained in the water. It consists of a graduated stem at whose extremity is a weighted bulb which partially sinks the tube in the water; the depth to which the bulb sinks shows the density of the water. The reading of a salinometer is taken at the water level, and is read on the tube, which is graduated as follows: The mark furthest from the bulb or highest up the stem is marked O, and if the zero line is level with the surface of the valve in which the salinometer floats, it indicates fresh water. If salt be added to the fresh water, the salinometer will rise in the water, and when the water contains 1 lb. of salt to 32 lbs. of water (which is the average degree of saltiness of sea water), the line marked 1/32 on the salinometer tube will be level with the surface of the water. If the saltiness of the water be increased, the salinometer will rise in the water until, at 2 lbs. of salt to 32 lbs. of water, a line (on the tube) marked 2/32 will be level with the surface of the water. The space between the 1/32 and 2/32 is divided into halves and quarters. As the density of the water varies with its temperature, therefore the readings on the salinometer must agree with some specific temperature, which is usually 200° Fahrenheit, and the reading of the salinometer is correct only when the water is at that temperature. If, however, the water varies a few degrees from the standard of temperature for which the salinometer is marked, a correction of the reading may be made by adding 1/8 of 1/32 for each 10 degrees, that the water is hotter, or subtracting the same for each 10 degrees that it is cooler than the temperature at which the salinometer is correct. The density or specific gravity of ordinary sea water is 1.027 (that of distilled water being unity or 1), and it contains about 4 oz. of salt per imperial gallon. Tallow is sometimes forced into a boiler fed with salt water to stop priming, by means of a syringe that is screwed into a tallow cock provided upon the boiler below the water level. If the boiler is fed with fresh water, tallow is apt to cause priming. Angle irons are used in boiler construction to be riveted to plates that require supporting or strengthening, or for gusset stays to be riveted to. Flanged plates are used in the construction of the furnaces, flame, boxes or combustion chambers, boiler ends and tube plates or tube sheets. Division plates are fitted in some boilers to prevent the water from passing from one side of the boiler to the other when the vessel rolls heavily. This prevents some of the tubes from being left uncovered by water, and thereby getting injured from undue heat. These division plates are neither steam nor water tight, and stand fore and aft of the ship. Similar division plates are sometimes used, however, to prevent the tops of the combustion boxes from getting overheated from the motion of the ship leaving them uncovered with water, their location being subserved to this end and varying with the position of the boiler. The superheater of a marine boiler is provided with a safety valve, and sometimes with a pressure gauge to enable the comparing of the steam pressure with that in the boiler, and should also be provided with a gauge glass, to show when heavy priming is going on. The main stop valve is upon the superheater, as is also the blast pipe. Priming is a lifting, into the steam space of the boiler, of a part of the water, and may arise from heavy firing, from the safety valve blowing off, from too little steam space, and from other causes. Priming[70] often occurs when the boiler feed is changed from salt water to fresh water, or from fresh to salt water. [70] See page 370 Vol. II., on priming. A separator or interceptor is a device fitted to either the superheater or to the steam receiver, for separating entrained water from the steam. It consists of a rectangular box or chamber with a partition plate extending from the top half down into the box. The entering steam strikes the face of the partition plate against which the water collects, and from which it drops to the bottom of the box, while the steam passes under the partition and out at the other side to the engine. The draught of a boiler is caused by the heat expanding the air and lightening it, thus causing it to ascend. It can be checked by stopping the exit of heated air up the funnel by means of a damper, by checking the flow of cold air into the furnace, by closing the dampers, by opening the furnace doors and letting cold air in the furnaces above the fires.[71] [71] See page 368, Vol. II. A blast pipe is a small pipe leading from the superheater to the funnel, and provided with a stop cock. It is used for letting a jet of steam up the funnel to promote the draught. Flame seen at the top of the funnel is caused by the combustion of gases that would have been consumed in the furnace had there been sufficient air or sufficient room for complete combustion. It may be caused in a variety of ways, as insufficient openings between the fire bars, too narrow a space between the bridge wall and the boiler, or too deep a fire upon the bars. It is detrimental, because it obviously wastes fuel. Dampers are used to regulate the draught in the furnace; they are fitted to the ash-pits or to the funnel, and should be fitted to both, because closing a damper in the funnel sets up a certain amount of pressure in the furnace by holding the heat, whereas dampers at the ash pit doors and none in the funnel lets the heat out and prevents cold air from getting in to promote combustion. When there are no dampers the furnace doors are open instead, to check the draught; this is, however, highly injurious to the boilers. The most rapid wasting of the plates of a marine boiler occurs alongside the fire bars, on the furnace tops, at the back of the flame box or combustion chamber, and in those plates generally that receive the most intense heat, and especially when they are heavily coated with scale and are not covered with water. The scale that forms on the face of the tube sheet keeps the water away from contact with the plate, which, with an undue thickness of scale, will crack between the tube holes. A tube that is split or that cannot be made steam tight by being re-mandrelled or expanded is plugged up at each end by means of either wooden or iron plugs. The best plan, however, is to use iron discs having a stepped diameter, so that one end will fit the bore of the tube, and the other will form a shoulder that will cover the end of the tube. Each disc has a hole through its centre, so that a wrought iron rod or bolt may be passed through the hole and receive a nut at each end. Beneath the flange of each disc, a grummet of spun yarn and white lead is placed, so as to make a steam tight joint when the nuts are screwed home. This stays the tube plates as well as stopping the leaky tube. If wooden plugs are used, they are made a driving fit in the tube bore, and driven through until they have passed the split, and a second wooden plug is driven tightly from the same end of the tube. Black smoke is an evidence of incomplete or imperfect combustion, and may be, to a great extent, prevented by careful firing, as by feeding gradually and evenly, by the admission of the proper quantity of air, or by a jet of steam admitted above the dead plates. The furnace bars are ordinarily of cast iron about 1-1/4 inches thick at the top, tapered towards the bottom, and with an air space of from 1/2 to 3/4 inch between them. They require less air space for Welsh than for Newcastle coal, as the latter is the flaming or gaseous coal, and burns the fastest. The quantity of coal burned in marine boiler furnaces is about 15 lbs. per square foot of fire grate area per hour; hence the quantity burnt per day with common average engines with 4 furnaces, 3 feet wide and 5 feet long, may be found by multiplying the area of the 4 furnaces (60 feet) by the number of lbs. (15) burned per foot of grate per hour, which will give the total lbs. weight burned per hour, which, divided by 112 lbs., will give the hundredweight burned per hour, and this, multiplied by the number of hours reckoned as constituting a day, gives the fuel consumption per day, based upon 15 lbs. coal per square foot of fire grate area. The number of tons of steam coal burnt per day to drive an ordinary steamer of 40 feet beam 10 knots an hour by steam alone (or without sail), will depend upon the kind of engine used. Experience teaches us that with average vessels, the beam squared equals the consumption of coal for 40 days, in the case of an ordinary jet condenser engine; 50 days with a surface condensing engine; and 60 days with a compound engine; hence, in the present example, assuming the engine to be jet condensing, we may calculate the fuel consumption per day, for a vessel 40 feet beam giving 10 knots an hour, as follows: The beam squared gives 1600 (40 × 40 = 1600), which divided by 40 (40 days) gives 40 tons per day. For surface condensing the 1600 would be divided by 50, giving 32 tons per day; and for a compound engine the 1600 would be divided by 60, giving 26 tons 13-1/3 cwt. per day. It is obvious, however, that calculations of this kind, in which the ratio of expansion is not stated, are the merest approximations. The number of tons of steam coal that will be burnt per day with a pair of average surface condensing engines having cylinders 50 inches in diameter will be, under average conditions, 16 tons per day, the calculations being based upon the common assumption that the diameter of one cylinder squared and divided by 100 gives the consumption of fuel in tons per day for condensing engines not compounded; thus, 40 × 40 = 1600 ÷ 100 = 16 tons of coal burned per day. Here again, the ratio of expansion not being specified, the calculation has no real practical value. If at sea and short of coal, bear in mind that the consumption of fuel per mile run is greater for fast than for slow speeds; hence the following points should be attended to: Reduce the speed of the ship to say half the usual. Regulate the fire so as to keep up full boiler pressure without blowing off. This will allow the expansion or cut off valve to be set to cut off early in the stroke, and thus save steam. If, under these conditions, the steam should sometimes blow off at the safety valve, cover up part of the fire grate area. Use a thin, rather than a thick, fire, but be careful that it is not so thin as to let currents of cold air pass through. TO RELIEVE THE BOILER IN CASE OF EMERGENCY.--Suppose an engine breaks down at a time when the fires are heavy and going full, that the steam gauge shows blowing off pressure, but that the safety valve is stuck, or from some cause or other is prevented from blowing off, and cannot be eased or lifted, and the following is the course to be pursued: 1st. Close the ash pit dampers and open the smoke box door and fire door. If there are no ash pit doors, close the damper in the up take and open the fire and smoke box doors. 2d. Start the donkey engine to feed cold water into the boilers. 3d. Start the steam winches, and any other small engines that take steam from the main boilers. 4th. Slacken the escape valves, and open the drain cocks of the cylinders and receivers, and steam will blow through the H.P. cylinder escape valve and drain cock at once. The H. P. slide valve may then be worked by hand, back and forth, to let steam pass into the receiver and blow through its escape valves and drain cock. 5th. Open the scum or brine cocks and keep them open, also open all gauge or test cocks, etc., about the boiler.[72] [72] It is not safe to draw the fire at a time when the pressure is at a dangerous point, especially if heavy, as disturbing it may temporarily increase the combustion and the danger of explosion. [Illustration: Fig. 3410.] Figs. 3410 and 3411 represent an example of a steel marine boiler, designed for a working pressure of 160 lbs. per square inch, with a margin of safety of 5. The dimensions are as follows: Diameter of shell 12 feet 6 inches. Shell plate 1-1/8 " thick. Front and back upper plates 31/32 " " Back rivet plates 7/8 " " Back lower plates 7/8 " " Front tube plate 15/16 " " Front lower plate 13/16 " " Furnaces 17/32 " " Inner tube plate 3/4 " " Combustion chamber back 17/32 " " Combustion chamber sides 17/32 " " Outer sides of wing combustion chambers 9/16 " " And bottom of centre one to be 9/16 " " Shell of receiver 7/16 " " Beds of receiver 5/8 " " Receiver connecting pipe 3/4 " " The riveted joints have all holes drilled. The longitudinal seams are made with butt joints treble riveted, and with double butt straps. The circumferential seams are lapped and treble riveted. Fig. 3412 represents the "Martin" boiler for marine engines. In the return flue there are a number of vertical water tubes which are very effective in promoting circulation as well as in generating steam. These boilers are used largely in the United States navy for moderate pressures. The following upon the testing and examining of a boiler of this class is from _Modern Steam Boilers_: "Every new boiler should, when complete, be tested by water pressure to double the amount of the intended working pressure; for while the wisdom of applying as high a pressure as three times the working pressure, which is sometimes done, may be questionable, experience has shown that a test by hydraulic pressure will reveal defects that would otherwise be apt to pass unnoticed. "For instance, when the top plate of a combustion box is stayed against the pressure by girder stays that are not stayed to the boiler shell, the girder stay merely acts to stiffen the top plate, and as a result the whole pressure on the area of the top plate falls on the walls of the combustion box. The back tube plate therefore springs down and transfers part of this pressure to the furnace, causing it to become elliptical, as may generally be found by the application of rod gauges fitted to it before testing and tried while the pressure is on. [Illustration: Fig. 3411.] [Illustration: Fig. 3412.] "This flattening under test naturally drew attention to the defectiveness of girder stays. Another instance may be given with reference to gusset stays, which, if fitted so as to support too large an area of back plate, in proportion to the area of combustion box it supports, may cause the combustion box to distort from its natural shape, pulling the tube sheet back and flattening the furnace. The amount of distortion may be only 1/16 inch in some cases, but that is sufficient to show the existence of unequal strains which require attention in boiler designing. "This brings us to the important fact that in almost every instance where the furnaces of marine boilers collapse, they come down at the sides, notwithstanding that when collapse occurs from overheating, the crown of the furnace must have been left bare of water first, and should therefore come down first, flattening the furnace at the top. This points to the conclusion, that the top of the furnace received some extraneous support. "When a furnace collapses from corrosion, it naturally gives way at the most corroded part. An hydraulic test to twice the working pressures is recommended for new boilers only, unless it be small vertical cylindrical and steam launch boilers, which may always be subjected to the same test as new main boilers. "In the case of old main boilers, however, and particularly rectangular ones, an hydraulic test of less than twice the working pressure may be employed, the amount being governed by the circumstances of the case. If, for instance, a boiler has undergone a thorough repair and received new furnaces, then every part of the boiler should have received proportionate consideration and an hydraulic test depending upon the judgment of the responsible engineer, but not less than one and one-half times the working pressure should be made, while one of one and three-quarter times could scarcely be objected to. This, however, is a subject upon which there is some controversy, especially in the case of old boilers having a good foundation of strength, but patched or local weak spots, such as combustion chamber backs and sides, these patches having been, perhaps, made with a view to a more extensive repair in the near future. "In such a case as this an hydraulic test sufficient to prove the tightness of the seams and joints may, perhaps, be all that is absolutely essential. "After a boiler has been tested by hydraulic pressure it should be examined internally, as it sometimes occurs that a stay may break under the test (especially if gusset stays are employed), and the extra strain thrown on the adjacent parts may cause them to fail, and thus cause the destruction of the boiler when under strain. "When an examination is to be made inside and outside of a boiler, the boiler must be properly prepared for the same, which may be done as follows: "The tubes should be swept; the furnace cleaned out; the fire bars should be taken out; the bridges in the furnace should be taken down; the up take smoke box and combustion box should be cleaned out and swept; every man hole and hand hole or peep hole door should be removed; the bottom of the boiler should be cleaned out and dried (in damp weather a little heat may be necessary for this purpose); all impediments, if any, should be removed in order to allow the bottom outside to be inspected; at the time of inspection a few mats, good lights, a hand hammer and small chipping hammer should be at hand. In the case of a boiler having any plates weakened by corrosion, a 5/8 inch tapping drill with a drilling brace should also be provided to test the thickness of such plates if considered necessary. "The safety valves should invariably be taken out for examination, and it is a commendable feature sometimes followed to take out the feed valves, stop valves, blow off and brine cocks; at the same time, all the deposits that would prevent a thorough examination of the boiler should be removed. In some cases, however, there may not be time for the scaling before it is necessary for the repairs to be gone on with, and, in that case, a good examination may with care be made by an experienced man. "To proceed, then, with the examination, the boiler should be entered through the man hole door beneath the furnaces, examining the boiler bottom and the bottom and sides of the furnaces all the way along, and on arriving at the end of the boiler the water space and stays at the backs of the combustion boxes can be examined as well as the midship combustion box stays and plates. In an old and corroded boiler it may be found necessary to use a chipping hammer very freely about the furnaces, particularly below the lap of the furnace. "The most corroded part of a furnace will generally be found about on a line with the fire bars, but the furnaces may have suffered from some other cause than the corrosion due to ordinary wear, as, for example, from chemical or galvanic action, and in that case they may be found comparatively good at the sides but with the extreme bottoms in a _dangerously_ corroded state, perhaps in the form of pit holes extending half through the plate and _hidden by a coating of red scale, which requires to be chipped away before the pit holes are brought to light_. "Corrosion by galvanic action may have produced honey combing or a general attack over the surfaces, which have a dark or _dark and sparkling appearance_, the latter more particularly when corrosive action has been very active. "Of these various classes of corrosion that which is the most deceiving is that which attacks the plates over the largest surface of the plate, leaving at the same time an apparently smooth exterior surface, for in this case the extent of the waste cannot be so clearly detected by the eye, and the only reliable way of testing the thickness is by drilling a hole through the plate. "The flanges of the furnaces should always be examined in the bends, for flaws, for such defects, although not very common, do at times unexpectedly make their appearance, and might, if not detected, be the means of breaking the boiler down at sea. This part of the inspection being made, any drilling that is to be done to ascertain the thickness of suspected plates may be proceeded with before the rest of the inspection is made. "It may, however, be well to remark that a very common defect is the wasting away of the combustion box plates around the necks of the stays or the internal surface of the plates, and it is a usual thing for deposits to accumulate around these necks, hence, unless these deposits have been removed (particularly in the case of boilers about three years old), the true condition of the boiler may not be known. "The plate around the man hole door should next be examined, a great defect from waste at the surface that makes the water tight joint. Next comes the man hole door itself, which should have the rubber or other material used to make the joint cleaned off, for cases have occurred where the surface beneath was found apparently sound, whereas the application of a chisel showed that the iron was so corroded that but little iron was left in the flange, causing great surprise that the whole door had not blown out. This defect may generally be looked for in old boilers, and serves to emphasize the necessity for strong wrought iron doors. "The outside surfaces of the end plate in the vicinity of the furnace fronts are a great source of trouble in some boilers, particularly where plane furnaces are fitted and flush rivets used for connecting them to the end shell plates. "The insides of the furnaces and combustion boxes next require attention. The most common defects here are lamination of the furnace plate (if of iron), slight collapsing of furnaces, wasting of the furnace plates (particularly when anthracite coal has been used), and wasting when the fire bar bearers or bridges have rested against the plate. "In the combustion box the buckling of flat plates may have occurred; plates may have wasted from leaks, distortion of the crown sheet from shortness of water may have occurred, or tubes may leak, and whenever, after sounding with the hammer, doubt exists as to the strength of the plate, a hole should be drilled through to test the thickness. "The wing sides of the furnace may next be examined (through the usual peep holes or by having a boiler mounting taken off for the purpose), and the shell plating on the sides of the boiler, paying special attention to the plates where the feed water enters. "We may next examine the outside of the bottom of the boiler, which should never be totally inaccessible to the eye, and should always be capable of being reached by a long-handled paint brush, for if kept well painted, the bottom of the boiler is, so far as the exterior is concerned, as durable as the other parts of the shell. "If, however, the bottom is not kept painted and gets damp, and more particularly from bilge water, it will corrode rapidly, and the boiler must be lifted for examination. Under these circumstances a new boiler _must_ at five years, at the very most, be lifted for examination, and if found comparatively good it should not be taken as an indication of the probable condition of any other boiler working under similar conditions, for the only means of avoiding a great risk in this matter is to rigidly inspect. "In the case of flat bottomed boilers in small vessels a good result has obtained by placing them on a bed of cement, which if properly done excludes the bilge water from approaching the plate; but even this precaution would scarcely be sufficient to justify an engineer in neglecting to lift the boiler at reasonable periods for examination of the bottom. "The internal examination of the boiler is continued from the top by examining the stays in the steam space, the tube and tube plates, getting down between the nests of tubes and reaching the crowns of the furnaces. The surface of the shell plates should also be examined, more particularly if the boiler contains plates subject to heat on the outside and steam on the other (as in the case of wet up take boilers), for under these conditions a steel plate may become as weak and unreliable as a piece of cast iron. "If the boiler is fitted with the superheater, the examination of the latter is of the utmost importance, as rapid destruction is here a common occurrence. In the case of a circular marine boiler of any size, nothing need be taken for granted, even though an hydraulic test be made up to twice the working pressure, because there is room for a thorough internal inspection which may disclose defects that would not be shown from the hydraulic test. The proper proportions of fire grate surface, heating surface, steam space, etc., in a marine boiler differ with the type of boiler and engine, and the steam pressure and degree of expansion employed. "Upon the question of steam space, for example, it is asserted by many that marine boilers are not so liable to prime under the higher pressures, and as a result of this asserted fact the steam receiver is in some cases being dispensed with. "It may be observed, however, that priming to any extent is so costly and detrimental that much consideration needs to be exercised before dispensing with the provisions ordinarily made to prevent it. "For circular tubular boilers, having a working pressure of from 60 to 80 lbs. per square inch and to be used for compound engines, the following proportions represent current practice. "1st. One square foot of fire grate area to every indicated horse power of the engine. "2d. 28 square feet of heating surface[73] to 1 square foot of fire grate area. [73] The heating surface here referred to includes the total interior surface of the tubes, the sides, backs, crowns and tube plates of the combustion boxes, and that part of the furnace that is above the level of the fire bars, but does not include the front tube plate (_i. e._, the tube plate in the smoke box). "3d. 6-1/2 to 8 cubic feet of steam space to each square foot of fire grate area. "4th. 8 to 10 square feet of tube surface to the total heating surface in single ended boilers. "5th. 8-1/2 to 10 is about the ratio of tube surface to the total heating surface in double ended boilers. "6th. The diameters of boiler tubes should be about one-half inch for each foot of length of tube. If less, the tube is liable to choke. About 14 cubic feet of steam (of from 60 to 80 lbs. pressure) should be made for each square foot of fire grate area. "Each square foot of fire grate will burn from 13 to 18 lbs. of steam coal per hour. About 1-1/2 cubic feet of live steam (of the above pressure) is required for each indicated horse power." CHAPTER XLIV.--HARDENING AND TEMPERING. Hardening and tempering processes are performed upon steel for three purposes: 1st. To enable it to resist abrasion and wear. 2nd. To increase its elasticity. 3rd. To enable it to cut hard substances and increase the durability of the cutting edge. Of these, the first is the simplest, because the precise degree of hardness imparted is not of vital importance. The second is more difficult, because the quality of the steel employed for such purposes is variable, and hence the tempering process must be varied to suit the steel. The third is of the greatest importance, because the articles to be tempered are the most expensive to make, the duty obtained is of the greatest consequence to manufacturing pursuits, and the fine grade of steel employed renders it more liable to crack in the hardening process. In those mechanical parts of machines which are hardened to resist abrasion and wear, the quality or grade of the steel is very often selected with a view to obtain strength in the parts and ease of mechanical manipulation in cutting them to the required shape, rather than to the capacity of the steel to harden. Hence, tougher and more fibrous grades of soft steel termed "Machine" steel, are employed, meaning that the steel is especially suitable for the working parts of machines. This class of steel is of a lower grade than that known as "tool" steel. It is softer, works, both on the anvil and in the lathe, more easily, and will bear heating to a higher temperature without deteriorating. It approaches more nearly to wrought iron, and is sometimes made of so low a grade as to be scarcely distinguishable therefrom. The kinds of steel used where elasticity is desired are known as spring steel, blister steel, and shear or double-shear steel, although, for small springs, steel of the tool-steel class is often employed. The word _temper_, as used by the manufacturer of steel, means the percentage of carbon it contains, the following being the most useful tempers of cast steel. _Razor Temper_ (1-1/2 per cent. carbon).--This steel is so easily burnt by being overheated that it can only be placed in the hands of a very skilful workman. When properly treated it will do twice the work of ordinary tool steel for turning chilled rolls, &c. _Saw-file Temper_ (1-3/8 per cent. carbon).--This steel requires careful treatment, and although it will stand more fire than the preceding temper should not be heated above a cherry red. _Tool Temper_ (1-1/4 per cent. carbon).--The most useful temper for turning tools, drills, and planing-machine tools in the hands of ordinary workmen. It is possible to weld cast steel of this temper, but not without care and skill. _Spindle Temper_ (1-1/8 per cent. carbon).--A very useful temper for mill picks, circular cutters, very large turning tools, taps, screwing dies, &c. This temper requires considerable care in welding. _Chisel Temper_ (1 per cent. carbon).--An extremely useful temper, combining, as it does, great toughness in the unhardened state, with the capacity of hardening at a low heat. It may also be welded without much difficulty. It is, consequently, well adapted for tools, where the unhardened part is required to stand the blow of a hammer without snipping, and where a hard cutting edge is required, such as cold chisels, hot salts, &c. _Set Temper_ (7/8 per cent. carbon).--This temper is adapted for tools where the chief punishment is on the unhardened part, such as cold sets, which have to stand the blows of a very heavy hammer. _Die Temper_ (3/4 per cent. carbon).--The most suitable temper for tools where the surface only is required to be hard, and where the capacity to withstand great pressure is of importance, such as stamping or pressing dies, boiler cups, &c. Both the last two tempers may be easily welded by a mechanic accustomed to weld cast steel. The preference of an expert temperer for a particular brand of steel is, by no means, to be taken as proof of the superiority of that steel for the specific purpose. It may be that, under his conditions of manipulation, it is the best, but it may also be that, under a slight variation of treatment, other brands would be equal or even superior. It may be accepted as a rule that the reputation of a steel for a particular purpose is a sufficient guarantee of its adaptability to that purpose, and all that is necessary to a practical man is to be guided by the reputation of the brand of steel, and only change when he finds defects in the results, or ascertains that others are using a different steel with superior results. Where large quantities of steel are used the steel manufacturers in many cases request customers to state for what particular purposes the steel is required, their experience teaching them what special grade of their make of steel is most suitable. To harden steel it is heated to what is termed a "cherry red" and then dipped into water and held there until its temperature is reduced to that of the water. _Tempering_ steel as the blacksmith practises it consists in modifying, lowering, or tempering the degree of hardness obtained by hardening. The hardening of steel makes it brittle and weak in proportion as it is hardened, but this brittleness and weakness are removed and the steel recovers the strength and toughness due to its soft state in proportion as it is lowered or tempered. When therefore a tool requires more strength than it possesses when hardened, it is strengthened by tempering it. Tempering proceeds in precise proportion as the temperature of the hardened steel is raised. When the steel is heated to redness the effects of the hardening are entirely removed, and the steel, if allowed to cool slowly, is softened or annealed. To distinguish maximum hardness from any lesser degree the terms to give the steel "all the water," or to harden it "right out" are employed, both signifying that the steel was heated to at least a clear red, was cooled off in the water before being removed from the same, and was not subsequently tempered or modified in its hardness. If a piece of steel has its surface bright and is slowly heated, that surface will assume various colors, beginning with a pale straw color (which begins when the steel is heated to about 430°) and proceeds as in the following table:-- Fahr. Very pale yellow 430° Straw yellow 460 Brown yellow 500 Light purple 530 Dark purple 550 Clear blue 570 Pale blue 610 Blue tinged with green 630 It happens that between the degree of hardness of hardened steel and the temper due to reheating it up to about 600° Fahr. lie all the degrees of hardness which experience has taught us are necessary for all steel-cutting tools. Hence we may use the appearance of colors as equivalent to a thermometer, and this is called color-tempering. The presence of these colors or of any one of the tints of color, however, is no guarantee that the steel has been tempered or possesses any degree of hardness above the normal condition, because they appear upon steel that is soft or has not been hardened. To obtain exact results by color tempering, therefore, the steel must first be thoroughly hardened, and this is known in practice by the whiteness of the hardened surface. Any number of pieces hardened so as to have a white surface may be tempered to an equal degree of color, or heated to an equal thermometrical temperature, with the assurance that they will possess a degree of hardness sufficiently uniform for all practical purposes; but if their hardened surfaces have dark patches, tempering to an equal tint of color is no guide as to their degree of temper. Successful tempering, therefore, must be preceded by proper hardening. The muffle should therefore bear such a proportion in size that when heated to a blood red, and taken from the fire, its temperature will be reduced to nearly that of the steel when it has acquired its proper degree of temper. The shape of the bore of the muffle should always conform to that of the article tempered; for round work, a round muffle; for square work, a square one; and so on. The muffle should be shorter than the work, so that the tempering of either end of the work may be retarded, if it is proceeding too fast, by allowing that end to protrude through the muffle. Color tempering, it will be observed, gives us no guide or idea of any of the degrees of temper which occur while the hardened steel is being heated up to about 430° Fahr.; and thus it leaves us in the dark as to all the ranges of hardness existing in steel thoroughly hardened and tempered to any degree less than that due to about 430° degrees of reheating. How wide this range may be can be appreciated when it is remembered that in the color test there are only 200° of heat between the hardness known as straw color, which is hard enough for almost all cutting purposes, and blue, tinged with green, which is almost normal softness. It is for this reason (among others) that where very exact results are to be obtained and a large number of pieces are to be tempered, fluxes, heated to the required temperature, are very often employed. Color tempering is conducted in different ways. In a muffle, in heated sand, with hot pieces of flat iron, and in boxes heated to the requisite temperature in an oven, the temperature being indicated by a pyrometer or heat-gauge. The articles to be tempered remain in the oven a length of time determined by experiment or experience, these being influenced by the size and substance, or thickness, of the pieces. A muffle is a tube or cylinder receiving its heat from the outside and open at the end or ends to receive the steel. Where tempering is carried on continuously the muffle is kept in the fire, although it is claimed by many that better results are obtained by removing it from the fire when heated. It is obvious that if the muffle is heated evenly the steel will temper most evenly by being held in the centre of the muffle, or the piece may be revolved and moved endways in the muffle in order that the steel may heat evenly. The tempering should always proceed slowly, otherwise the heat may not have time to penetrate the steel to the centre, the outside tempering more quickly, thus the tool will be weak because of the undue hardness of the interior metal. Furthermore, protruding edges, or slight sections of the steel, may reduce to the required temper before the main body of the steel, which induces either serious weakness of the insufficiently tempered part, or softness in the thin sections, providing that the steel is kept long enough in the muffle to temper the main body to the proper degree. In heating steel to harden it, especial care is necessary, particularly when the tool is one finished to size, if its form is slight or irregular, or if it is a very long one, because unless the conditions both of heating and cooling be such that the temperature is raised and lowered uniformly throughout the mass, a change of form known as _warping_ will ensue. If one part gets hotter than another it expands more, and the form of the steel undergoes the change necessary to accommodate this local expansion, and this alteration of shape becomes permanent. In work finished and fitted this is of very great consideration, and, in the case of tools, it often assumes sufficient importance to entirely destroy their value. If, then, an article has a thin side, it requires to be so manipulated in the fire that such side shall not become heated in advance of the rest of the body of the metal, or it will become locally distorted or warped, because, though there may exist but little difference in the temperature of the various parts, the more solid parts are too strong to give way to permit the expansion: hence the latter is accommodated at the expense of the form of the weakest part of the article. Pieces, such as long taps, are very apt to warp both in the fire and in the water. In heating, they should rest upon an even bed of coked coal, and be revolved almost continuously while moved endways in the fire; or when the length is excessive, they may be rested in a heated tube, so that they may not bend of their own weight. So, likewise, spirals may be heated upon cylindrical pieces of iron or tubes to prevent their own weight from bending or disarranging the coils. Experiments have demonstrated that the greater part of the hardness of steel depends upon the quickness with which its temperature is reduced from about 500° to a few degrees below 500°, and metal heated to 500° must be surrounded by a temperature which renders the existence of water under atmospheric pressure impossible; hence, so long as this temperature exists the steel cannot be in contact with the water, or, in other words, the heat from the steel vaporizes the immediately surrounding water. The vapour thus formed penetrates the surrounding water and is condensed, and from this action there is surrounding the steel a film of vapour separating the water from the steel, which continues so long as the heat from the steel is sufficiently great to maintain the film against the pressure of the water and the power of the water which rushes toward the steel to fill the spaces left vacant by the condensation of the vapour as it meets a cooler temperature and condenses. The thickness of the vapour film depends mainly upon the temperature of the steel; but here another consideration claims attention. As the heated steel enters the water the underneath side is constantly meeting water at its normal temperature, while the upper side is surrounded by water that the steel has passed by, and, to a certain extent, raised the temperature of. Hence, the vapour on the underneath side is the thinnest, because it is attacked with colder water and with greater force, because of the motion of the steel in dipping. For these reasons it is desirable, especially with thick pieces of steel, to inject the water in a full stream upon the article, as is done in the Brown & Sharpe hardening tanks. In cases where a great many pieces are to be hardened and tempered to an even degree, the steel is heated for the hardening in a flue with the advantage that contact between the heated steel and the impurities (as sulphur or silicon) of ordinary fuels is avoided, and also that all the pieces may be heated, and therefore hardened, to a uniform degree. The capacity of this system is great, because a number of pieces can be heated without fear of any of them becoming overheated if not attended to immediately. Thus the Waltham Watch Co. heat their mainsprings for the hardening in a flux composed of melted salt and cyanide of potash, the latter serving to clean the surface of the steel; but as the latter wastes it requires to be added occasionally. The Watch Company, however, find this mixture will not do for the hair springs, as it alters (to a very small degree, however) the nature of the steel; hence these springs are heated for hardening in melted glass. The Pratt and Whitney Co. heat their taps, &c., for hardening in a composition of equal quantities of salt and cyanide of potash, adding the latter as it wastes, and temper them by the cold test. The Morse Twist Drill Co. use a similar compound for heating to harden, and the following apparatus for dipping. In a large tank having a free water circulation, stand two pots of a capacity of about five gallons each, one of these contains cyanide of potash and salt, and another sperm oil. The heated work is dipped for an instant into the pot containing the potash and salt, which clean the surface of the steel, and then cooled in the main water tank; but if the work is, from its shape, liable to crack, it is at the final cooling dipped in the pot of sperm oil instead of in the water. Before heating the steel it is dipped in soft soap to prevent oxidation, and on dipping it into the potash and salt pot it causes a cracking sound, the operator knowing from the sound if the mixture is proper, and how long to hold the steel therein. This company first fill the heating pot with salt, and then add cyanide of potash until a trial of the tool gives quite satisfactory results, adding cyanide of potash as the work proceeds to make up for the evaporation and keep the mixture of the compound correct. In many cases it is considered an advantage to harden the outside of an article, keeping the inside as soft as possible so as to increase the strength. In such case the article may be heated in red-hot lead, the surface of which may be covered with charcoal. Under these conditions the outside of the article, especially if thick, will get red hot in advance of the inside. Articles having thick and thin sections may be heated in fluxes to great advantage, the thick side being immersed first, and the article being lowered very slowly into the pot of lead. If the shape of the article is such as to render it liable to crack in the water because of containing holes or sharp corners in weak parts, these holes and sharp corners may be filled with fire-clay, the dipping water may be heated to about 50°, and salt (1 lb. per gallon of water) added to it. The Monitor Sewing Machine Company harden and temper their spiral springs at one operation, by heating them to a blood-red heat and quenching them in a mixture of milk and water, which will give an excellent result, providing that the springs are heated to precise uniformity and the mixture of milk and water is correct. For a process of this kind (which is very expeditious, because the hardening and tempering is performed at one operation), the steel should be heated to a very uniform temperature, and a mixture of, say, two-thirds milk and one-third water tried at first, more milk being added to lower the temper, or more water to increase it if necessary. Saws are hardened in compositions of animal oil, such as whale-oil, with which resin, pitch, and tallow are sometimes mixed. Resin hardens but somewhat crystallises the metal, but it is used because, on common saws, the scale will not strike properly without it. Tallow gives body to the liquid and causes it to extract the heat quickly from the steel (and the hardening is solely due to the rapid extraction of the heat). In addition to this, the saws hardened in oil and tallow show a very fine grain if fractured, and are tough. The effect of pitch is much the same as that of resin. In place of tallow, bees-wax is sometimes used, giving an excellent result. A very little spirits of turpentine mixed with the oil every time it is used (that is, for every batch) is an excellent ingredient to cause the scale to strike, but being very inflammable, it is somewhat dangerous. If none of these ingredients are used, and the scale does not strike, it acts as a fine separating lining, preventing the contact between the metal and the liquid, and hence retarding the cooling, and therefore the hardening. Let us suppose some thin saws of the finest grade of steel are to be tempered. The liquid would be about half a barrel of tallow to a barrel of whale-oil (which will harden as hard as glass). After the temperature of the saw is reduced to that of the bath, it is removed, the adhering oil is removed, and the surface dried by an application of sawdust, and the tempering process may be proceeded with. There are three methods of drawing the temper. One is with the saw lying in the open furnace; a second, an English plan, is with the saw stretched in a frame, so as to prevent its warping, and in fact, to cause the tempering to aid in straightening the saw; and the third is to temper between flat dies. In the first, the temper is determined by the appearance of the saw in the furnace. The saw absorbs some of the liquid in which it was quenched to harden it; and as it is reheated to temper it, this oil passes off as a cloud, or rather as a breath passes off the surface of a window-pane. This action takes place first on the lower surface of the saw, nearest to the furnace bottom, the oil exuding in a mist-like form. The length of time the saw must remain in the furnace after the cloud has passed off is determined by the thickness of the saw and the heat of the furnace, the operator being guided entirely by experience; but when the saw is taken from the furnace, it will have a very dark-red glimmer, and must be laid flat and allowed to cool off in the air, for if again dipped it would be too hard. When cool, the saw thus tempered will be of a sky-blue color, and will spring from point to butt without bend or break. This process requires skilful management and good judgment, but will give most excellent results. The main objection to it is, that it is expensive, since it gives no aid to the straightening processes. The straightening frame, or English tempering system, is as follows: The plates of steel are made of a size that will cut into four saws. The furnace front is provided with a tramway extending to the floor of the furnace, and on this runs the stretcher-frame. The plates are stretched in the frame, which is run into the furnace so that the plate is heated under a tension, which operates to straighten them. As the temper lowers, the screws of the stretcher are turned, increasing the tension; when the tempering is done, the screws are made to stretch the plates very tight just previous to taking it from the fire, and the plates are allowed partly to cool off while kept in the frame. In this process the indications of the temper are determined as in the first process. In the third process, the saws are placed between a stationary and a movable die provided in the body of the furnace, the movable one descending and pressing the saw to the other die; thus the tempering is accompanied by a flattening process (the dies being operated by pressure). The degree of temper is regulated by the temperature to which the saws are heated, which is ascertained by a pyrometer. The furnace is kept at a constant temperature, and the length of time the saw remains between the dies is varied to suit the thickness of the saw. The gain due to this system is, that less straightening is required and a determinate temperature is secured. Some makers claim that in this system the vapour of oil that exudes from the saw has no means of escape, and that a chemical effect injurious to the steel ensues; and furthermore that the temperature of the dies will be greatest at or near their circumference, and hence the teeth and back and the ends of the saw will be softer than the middle of the width and length of the saw, and that if two saws, one above the other, be placed on the dies at once, the contacting surfaces of the saws will be the hardest, and those surfaces will be black by reason of the oil burning into the steel, instead of exuding, as in the open furnace process. The floor of the tempering furnace should be flat and even; for if any part of the saw-plate lies suspended, it will sag when heated, greatly increasing the amount of straightening required. The furnace must be so constructed as to heat evenly all over, otherwise the temper of the saw will not be even. The air must be carefully excluded to prevent the steel from decarbonizing, which being thin, it is very apt to do. Thin saws warp proportionally as they are heated more, and if they are allowed to remain longer in the furnace and not heated too quickly, existing buckles or bends will partly straighten themselves in the furnace. Care must be taken to keep the tongs clear of the teeth, and in taking the saws from the furnace the length of the saw must stand at a right angle to the operator (two pairs of tongs being used), so that the saw's own weight shall not cause it to bend. The saw must be transferred from the furnace to the bath very quickly, to prevent, as much as possible, its cooling in the air; for such cooling would take place unequally, causing the saw to warp, as well as impairing the temper. It should be dipped with the length horizontal, the teeth downward and the side faces vertical, and plunged quickly into the bath. On being dipped in the hardening liquid, they warp again, but the dipping may be manipulated to partly regulate the warping. From the moment the cold air strikes the plate a warping process sets in, hence quickness in transferring from the furnace to the bath is a great point. When the saw is hot enough to temper, the scale will begin to rise upon its surface, and if the furnace is unequally heated, the scale will arise first at the hottest part, instantly notifying the operator of the defect. From the appearance of the surface of the saw after it comes from the hardening bath, the operator can see if it is properly hardened. If so, the scale will be what is termed "struck," that is, it has come off, leaving the surface from a grey to a white color; while if the scale remains in dark patches, the saw is too soft in those parts. After the saws are tempered they are allowed to cool in the open air, and then require to be straightened by the hammer, and in this process the tempering has been interfered with, inasmuch as that the elasticity due to the tempering has been counterbalanced to some extent by the local condensation of the metal induced by the immediate effects of the hammer blows. The condensation of the metal has impaired the natural grain or fibre of the metal, and stiffens it so that if the saw be bent these stiffened hammer marks will cause it to remain set instead of springing back straight, as it should do. To remove this defect the saws are what is termed _stiffened_, that is, they are heated until the surface assumes a yellow color, when they are removed and allowed to cool. This causes the metal condensed by the hammer to assume its natural structural condition, and permits the tempering to spring the saw back straight, even though it be bent until the two ends touch, and the bend carried half way along the blade by carrying one end forward along the blade surface. The yellow color is subsequently removed by an application of a solution of muriatic acid. The method employed by the Tomlinson Carriage Spring Company for carriage springs is as follows:-- The spring plates are heated to bend them to the _former_, which is a plate serving as a gauge whereby to bend the plate to its proper curve, which operation is performed quickly enough to leave the steel sufficiently hot for the hardening; hence the plates after bending are dipped edgeways and level into a tank of linseed oil which sets in a tank of circulating water, the latter serving to keep the oil at about a temperature of 70° when in constant use. About 3 inches from the bottom of the oil tank is a screw to prevent the plates from falling to the bottom among the refuse. To draw the temper the hardened springs are placed in the furnace, which has the air-blast turned off, and when the scale begins to rise, showing that the adhering oil is about to take fire, they are turned end for end in the furnace so as to heat them equally all over. When the oil blazes and is freely blazed off, the springs are removed and allowed to cool in the open air, but if the heat of a plate, when dipped in the oil to harden is rather low, it is cooled, after blazing, in water. The cooling after blazing thus being employed to equalize any slight difference in the heat of the spring when hardened. The furnace is about 10 inches wide and about 4 inches longer than the longest spring. The grate bars are arranged _across_ the furnace with a distance of 3/8 inch between them. The coal used is egg anthracite. It is first placed at the back of the furnace, and raked forward as it becomes ignited and burns clearly. For shorter springs the coal is kept banked at the back of the furnace, so that the full length of the furnace is not operative, which, of course, saves fuel. By feeding the fire at the back end of the furnace, the gases formed before the coal burns clearly pass up the chimney without passing over the plates, which heat over a clear fire. For commoner brands of steel, what is termed a water-chill temper is given. This process is not as good as oil-tempering, but serves excellently for the quality of steel on which it is employed. The process is as follows: The springs are heated and bent to shape on the _former_ plate as before said; while at a clear red heat, and still held firmly to the _former_ plate, water is poured from a dipper passed along the plate. The dipper is filled four or five times, according to the heat of the plate, which is cooled down to a low or very deep red. The cooling process on a plate 1-1/2 × 1/4 inches occupies about 6 seconds on an average, but longer if the steel was not at a clear red, and less if of a brighter red, when the cooling began. Some brands of steel of the _Swede steel_ class will not temper by the water-chill process while yet other brands will not harden in oil, in which case water is used to dip the plates in for hardening, the tempering being blazing in oil as described. In all cases, however, steel that will not harden in oil will not temper by the water-chill process. The Columbia Car Spring Company temper their springs as follows:--Using "Gregory crucible steel," heating is performed in a furnace consuming gas coke, but the furnace has a number of return enclosed flues, and between these flues (one over the other), are ovens, the heat passing through the brick-work forming the flues into the ovens. To facilitate renewing the ovens (which of course also renews the flues), the floor of each oven (which forms the ceiling of the oven below), is built on iron supports, protected by the brick-work and suitable fire clay, the bricks all being made to pattern, thus involving very little labor in building. The furnace doors are at the ends, and are kept closed as much as possible. In this way the steel has no contact with the products of combustion of the fuel, and the air is excluded as far as practicable (two valuable features). The furnaces are long and narrow, and not being connected with the flue there is but little disposition for the cold air to rush in when the furnace doors are opened. The hardening and tempering of springs whose coils are of thick cross-section is performed at one operation as follows: The springs are heated in the furnace or oven described, and are first immersed for a certain period in a tank containing fish oil (obtained from the fish "_Moss Bunker_," and termed "_straights_"), and are then removed and cooled in a tank of water. The period of immersion in the oil is governed solely by the operator's judgment, depending upon the thickness of the cross-section of the spring coil, or, in other words, the diameter of the round steel of which the spring is made. The table below gives examples of the hardening and tempering in this way of springs of the following dimensions:-- Number of coils in spring 5-3/4 Length of the spring 6 inches. Outside diameter of coils 4-3/4 Diameter of steel 1 +-----------+-----------+-----------+ | | Time of | Number of | | Examples. | Immersion | Swings in | | | in Oil. | Oil. | +-----------+-----------+-----------+ | | Seconds. | | |First | 28 | 35 | |Second | 36 | 46 | |Third | 27 | 36 | |Fourth | 38 | 40 | +-----------+-----------+-----------+ As will be seen, the spring in the first example was immersed in the oil and slowly swung back and forth for 28 seconds, having been given 35 swings during that time. Upon removal from the oil the spring took fire, was redipped for one second, and then put in the cold water tank to cool off. The following are examples in hardening and tempering springs of the following dimensions:-- Number of coils in the springs 6 Length of the springs 9 inches. Inside diameter of coils 3-1/4 Size of steel 1 × 1-1/2 square. +-----------+-----------+-----------+ | | Time of | Number of | | Examples. | Immersion | Swings in | | | in Oil. | Oil. | +-----------+-----------+-----------+ | | Seconds. | | |First | 9 | 12 | |Second | 8 | 12 | |Third | 8 | 12 | |Fourth | 9 | 12 | |Fifth | 9 | 12 | |Sixth | 9 | 12 | +-----------+-----------+-----------+ To keep the tempering oil cool and at an even temperature, the tank of fish oil was in a second or outer tank containing water, a circulation of the latter being maintained by a pump. The swinging of the coils causes a circulation of the oil, while at the same time it hastens the cooling of the spring. The water tank was kept cool by a constant stream and overflow. If a spring, upon being taken from the oil, took fire, it was again immersed as in the first example. Resin and pitch are sometimes added to the oil to increase its hardening capacity, if necessary. The test to which these springs were subjected was to compress them until the coils touched each other, measuring the height of the spring after each test, and continuing the operation until at two consecutive tests the spring came back to its height before the two respective compressions. The amount of set under these conditions is found to vary from 3/8 inch, in comparatively weak, to 7/8 inch for large stiff ones. The New Haven Clock Company heat their springs in a furnace burning wood, the springs being _kept in the flames only_, and quenched in a composition of the following proportions:--"To a barrel of oil 10 quarts of resin and 12 quarts of tallow are added." If the springs "fly," that is, break, more tallow is added, but if the fracture indicates brittleness or granulation of the steel, rather than excessive hardness, a ball of yellow beeswax, of about 6 inches in diameter, is added to the above. These springs are tempered, singly, to a reddish purple by being placed on a frame having horizontally radiating arms like a "star," which is attached at the end of a vertical rod. The spring is laid on the "star" and lowered into a pot of melted lead, being held there a length of time dictated by the judgment of the operator. The star-shaped frame is termed a sinker, and if upon being lifted from the lead the colour of the spring is too high, a second immersion is given. APPENDICES APPENDIX--PART I. TEST QUESTIONS FOR ENGINEERS. An efficient engineer must certainly be able to determine any practical question that may arise in the management, not only of his engine and boiler, but also in that of such shafting, pulleys, gear wheels, etc., as may constitute the driving gear connected with the engine. A very moderate examination of an engineer (whether to test his suitability for employment or for promotion) should therefore include questions tending to determine his capability to give such directions as may be necessary when the engine or shafting breaks down, or when alterations are to be made and he is consulted with reference to them. The following questions have been framed with a view to include such information as a first-class engineer, and even an assistant or night engineer, may be expected to possess, and a large proportion of these questions have been taken from actual engineers' examinations in various parts of the country. In many cases engineers of manufactories are required to make, as far as possible, their own repairs and sometimes indeed also the repairs to the machinery the engine drives, but to give questions covering this ground would be to refer the reader to nearly every page in the two volumes, which is manifestly impracticable. =Matching gear wheels.=--Suppose you were running a hoisting engine whose pinion had 15 teeth, driving a wheel with 150 teeth in it; if the pinion had teeth with radial flanks, what orders would you send to get another wheel that would work with the pair?--For answer, see Volume I., page 15. =Radial flanks.=--If a pinion has radial flanks what information does that give to the engineer if at any time he requires to order another wheel to work with it? I. 15. =Teeth of gear wheels.=--What is the difference between an epicycloidal tooth and an involute tooth of a gear wheel? I. 8, 13. =Ordering bevel gears.=--Two lines of shafting are to be connected by a pair of bevel gears and one is to run twice as fast as the other; how would you find the bevel of the wheels so as to be able to tell the maker what was wanted, and what dimensions would you give, leaving the pitch and the shape of the teeth out of the question? I. 22. =Ordering taps.=--Suppose you were ordering a set of taps for use in the engine room, what precautions would you be obliged to take as to the shape of the thread in order to get proper taps? I. 85. =Fitting a nut.=--Will a nut having a United States standard thread fit a bolt having a common V thread, both threads having the same pitch and diameter, and how could you tell one bolt from the other? I. 85. =Curing a pounding cam.=--Suppose some part of the machinery driven by an engine had a cam motion with a small roller which hammered and pounded on the cam, how would you cure the defect? I. 83. =Ordering a new spur wheel.=--Suppose a spur wheel broke and you wanted to give the diameter for a new one, where would you measure the diameter of the old one? I. 1. =Comparing screw threads.=--What is the difference between the common V thread and the United States standard thread? I. 85. =Using two set screws.=--When two set screws are placed in a hub how should they be located? I. 127. =Best lathe tool.=--What is the most useful turning tool for a hand lathe, such as is sometimes provided for an engineer to make repairs with? I. 331. =Fitting a crank pin.=--How would you proceed to put in by a contraction fit a crank pin, the crank being on the engine? I. 366. =Increasing strength of teeth.=--Suppose you had to order a new pair of wheels to replace a pair whose teeth frequently broke, what alterations in the dimensions of the wheels would you make so as to get stronger teeth in wheels of the same diameter? I. 65. =Wear of a cam roller.=--If an engine had a valve motion worked by a parallel roller in a parallel cam groove, would the roller wear out quick, and why? I. 84. =Altering the speed of a shaft.=--Do a pair of mitre wheels alter the speeds of the shaft they drive or not? I. 1. =Driving out a key.=--In driving out a key is a quick or a slow hammer blow the most effective? II. 65. =Riveting a crank pin.=--For riveting a crank pin what shape should the pene or pane of the hammer be? II. 73. =Face of a cold chisel.=--What is the proper shape for the face of a cold chisel? II. 73. =Key bearing.=--What is the effect upon a wheel if its key bears upon opposite corners? II. 107. =Fitting a key.=--Should a key be driven lightly or not when fitting it, and why? II. 106. =Angle Of wrench jaws.=--What angle should the jaws of a wrench be to its body in order to enable it to turn a nut in a corner with greatest advantage? I. 123. =Chucking a crank.=--How should a crank be chucked in order to prevent the crank pin from being out of true, and the engine from beating and pounding? I. 247. =Chucking a cross-head.=--How should a cross-head be chucked so as to have its piston rod and wrist pin at a true right angle? I. 252. =Length of drill edges.=--Why should both edges of a drill be exactly equal in length and of equal angle? I. 277. =Boring bar edges.=--Should a boring bar for an engine cylinder have one, two, three or four cutters? I. 289. =Spiral spring.=--Give a method of making a spiral spring. I. 329. =Expansion fit.=--What is meant by an expansion or a contraction fit, say for an engine crank pin? I. 366. =Fitting brasses.=--Suppose the joint faces of a pair of brasses are not square with the sides of the box or strap in which the brasses fit, what will the effect be when the brasses are locked tight together by the key? II. 125. =Wear of brasses.=--When an engineer is taking up the wear of connecting rod brasses, what must he do to keep the rod of the proper length? II. 124-127. =Case hardening.=--Describe the simplest method of case hardening. II. 128. =Fitting pillar block brasses.=--State the proper order of procedure in fitting in a new pair of main bearing or pillar block brasses for an engine. II. 130. =Driving brasses.=--What will be the effect of driving a brass in and out with a hammer and without a block of wood to strike on? II. 72 and 132. =Originating a true plane.=--How is a true plane or flat surface originated? II. 133. =Cover joint.=--What is the best form of joint for an engine cylinder cover? II. 137. =Grinding a cover.=--How must a cylinder cover be moved when grinding it? II. 137. =Appearance Of a joint.=--What is the appearance of a finished ground joint? II. 137. =Grade of emery.=--About what grade of emery would you use to make a ground joint? II. 137. =Best heat joint.=--What is the best kind of joint to withstand great heat or flame? II. 138. =Best water joint.=--What are the best kinds of joints for withstanding water pressure? II. 138. =Fitting a flange.=--In fitting a flange to a boiler what part of the flange face should bed most? II. 140. =Rust joint.=--How are rust joints made? II. 140. =Leaky plug.=--How would you test the fit of a leaky plug in a cock? II. 144. =Well-ground plug.=--What is the appearance of a well-ground plug? II. 145. =Quick brass fitting.=--Describe the quickest method of fitting a new brass or bearing box to its journal. II. 147. =Babbitt bearing.=--What is the principal advantage of a Babbitted bearing? II. 156. =Adjusting guide bars.=--What two essential points are there in adjusting the bottom guide bars of an engine? II. 162. =Setting guide bars.=--Describe roughly the method employed to set guide bars by means of a stretched line or cord? II. 163. =Pounding journals.=--What are the two principal causes of the beating or pounding of the journals of an engine? II. 164. =Locating a pound.=--How may the location of a pound be discovered? II. 164. =Cause of pounding.=--What is the ordinary cause of beating and pounding in an engine? II. 164. =Wearing down.=--What is the defect induced by letting the parts of an engine wear down to a bearing? II. 166. =Testing alignment.=--What are the tests that should be made to find out what part of an engine is out of line? II. 166. =Best test for alignment.=--What part of an engine can be used to form the best test of alignment to cure pounding? II. 167. =Connecting rod alignment.=--State in a general way the method of using the connecting rod to place the engine in line, and thus prevent beating and pounding. II. 167 to 172. =Difficult alignment.=--What error in the alignment of the parts of an engine is the most difficult to discover? II. 170. =Alignment of crank pin.=--What is the general cause of a crank pin being out of line with the crank shaft? II. 170. =Pound at quarter stroke.=--When a pound occurs in an engine at the time the crank pin is at quarter stroke, or thereabouts, where would you look for the cause? II. 170 to 172. =Setting a slide valve.=--What are the three objects, either of which a slide valve may be so set as to accomplish? II. 173. =Essentials of slide valve setting.=--What are the two operations essential to the setting of a slide valve? II. 173. =Squaring a valve.=--Why is the common process of squaring the valve an improper proceeding? II. 173, 394. =Crank pin on dead centre.=--How would you proceed to put an engine crank pin exactly on the dead centre for setting the valve? II. 173, 394. =Direction of movement.=--What are the considerations that determine in which direction the engine should be moved when setting the valve? II. 173, 174, 394. =Setting eccentrics.=--What tools are used to set eccentrics upon shafts before the shafts are upon the engine? II. 175. =Patching a break.=--In patching a broken beam or frame, how may the bolts be made to serve to act as keys closing the crack? II. 178. =Erecting shafting.=--Give a general or rough description of the method of adjusting or aligning or erecting shafting. II. 184 to 186. =Kinds of shafting.=--What is the difference between bright and black shafting? II. 187. =Fitting a pulley.=--If you had a pulley whose bore was 1-15/16 inches, what diameter of bright shafting would you order for it? II. 187. =Locating collars.=--What is the best location for the collars that prevent end motion on a line shaft? II. 189. =Ball and socket hangers.=--What are the advantages of hangers having a ball and socket adjustment? II. 192. =Shaft couplings.=--What four objects should the couplings for line shafts accomplish? II. 194. =Universal joint.=--What object does a universal joint accomplish? II. 199. =Crowning a pulley.=--What is the object of crowning a pulley? II. 201. =Pulley balance.=--Why should a pulley be balanced? What is a running and what a standing balance for a pulley? At what speed should a running balance be made? II. 202. =Size of pulleys.=--If a shaft makes 150 revolutions per minute, and it is required to drive a pulley on a machine at 600 revolutions, what proportions must the diameter of the two pulleys have, and what determines the diameters of the pulleys? II. 205, 206. =Testing belts.=--What appearance in leather belting indicates that it was cut from the spongy shoulder? II. 208. =Stronger side of belts.=--Which is the stronger side of leather, the smooth or grain side or the rough or flesh side? II. 208. =Placing a belt tightener.=--Should a belt tightener be placed on the tight or slack side of a belt? II. 210. =Crossed vs. open belt.=--Which will transmit more power, an open or a crossed belt, and why? II. 210. =Crossed belt.=--What are the objections to a crossed belt? II. 210. =Shortening a round belt.=--Can a round twisted belt be shortened without removing either the hook or the eye and how? II. 216. =Wide belt.=--How would you get a very wide belt on a pulley? II. 217. =Mending an eccentric rod.=--Suppose an eccentric rod broke, and you were required to weld it again, what shape could you make the scarf for the weld? II. 234. =Butt weld.=--What is a butt or pump weld? II. 236. =Scarf weld.=--Describe roughly the means you would employ to make a scarf weld. II. 235. =Tongue weld.=--What are the shapes of the two pieces that come together in a tongue weld? II. 235. =Strain on boiler joint.=--How would you calculate the amount of stress there is upon the riveted joint of a boiler? II. 350. =Shearing strain.=--What is meant by the terms, shearing, tearing and crushing strains of a steam boiler? II. 351. =Lapped and butt joints.=--How does a lapped joint differ from a butt joint or seam in a boiler? II. 352. =Chain and zigzag riveting.=--How does a chain riveted joint differ from a zigzag riveted joint? II. 352. =Butt joint.=--What are the advantages of the butt joint? II. 352-353. =Margin for holes.=--How would you find the proper distance the rivet holes should be from the edge of the plate in a boiler seam? II. 353. =Spacing rows Of rivets.=--How would you find the distance apart for the rows of rivet holes in a double riveted joint? II. 353. =High percentage joint.=--What is meant by a "high percentage" riveted joint? II. 353. =Single and double shear.=--What is meant by a rivet being in single shear or double shear? II. 353. =Allowance for shear.=--How much additional allowance is made in the shearing strength of a rivet in double shear over that of the same rivet if in single shear? II. 358. =Taking charge of a boiler.=--What is the first thing you would do in taking charge of a boiler? II. 368, 400. =First inspection.=--What part of the boiler would you inspect first? II. 368. Safety valve defect.--To what defect is a safety valve most liable? II. 368, 400. =Water supply.=--How much water should there be in the boiler when the fire is lit? II. 368. =Reliability of gauge glass.=--Is a gauge glass always reliable for showing the height of the water in the boiler? II. 368, 402. =Testing gauge glass.=--What would you do to find out if the gauge glass was showing the correct water level? II. 368. =Condensation in boiler.=--What is likely to happen if the steam condenses in the boiler without any of the cocks being open? II. 368, 400. =Cleaning a boiler.=--What parts of the boiler would you clean before lighting the fire? II. 368. =Laying a fire.=--How would you lay the fire? II. 368. =Quick combustion.=--Does bituminous (soft) or anthracite (hard) coal light more easily? II. 368. =First coal.=--How soon would you put coal on after the fire is lit? How deep would you make the first layer of coal? II. 368, 401. =Amount of coal.=--How much coal would you put on the fire at a time? II. 368, 401. =Even heat.=--How can an even temperature be kept up in the fire box? Why is it necessary to keep an even temperature in the fire box? II. 368, 370. =Shaking grate.=--What is the advantage possessed by shaking grate bars? II. 369. =Before cleaning a fire.=--What preparations would you make before cleaning the fire? II. 369. =Fire tools and their uses.=--What tools are used in cleaning a fire? And what is the use of each? II. 369. =Draught while firing.=--How should the draught be regulated while the fire is being cleaned? II. 369. =Temporary interruption.=--What should be done to prevent blowing off through the safety valve when the engine is stopped and no steam is being taken from the boiler? II. 369. =Blue flame.=--What does blue flame in the fire box indicate? II. 369. =Water supply at night.=--How much water would you have in a boiler when leaving it for all night? II. 369. =Fire at night.=--How would you leave the fire for the night? II. 369. =Banking.=--What is banking a fire? Give a safe method of banking a fire. II. 369, 401. =Dampers at night.=--How should the dampers be left when the fire is banked? II. 369. =Safety valve at night.=--How would you set the safety valve for a banked fire? II. 369. =Opening a banked fire.=--What is the first thing to do in starting up a banked fire? II. 369, 401. =Regulating boiler feed.=--How would you regulate the boiler feed? II. 369. =Regulating a pump.=--How can a pump be regulated so as to be kept pumping without surcharging the boiler? II. 369. =Even boiler injection.=--Can a continuous feed be maintained if injectors are used? II. 370. =Stuck valve.=--How may a stuck valve or a check valve be released? II. 370. =Hot feed water.=--What would you do if the feed water got so hot that the pump worked imperfectly or not at all? II. 370. =Scale.=--What causes scale to form in the boiler and what effect does scale have on the boiler? II. 370. =Preventing scale.=--What are the principal methods employed to prevent the formation of scale in the boiler? II. 370. =Horizontal heater.=--What advantage does a horizontal heater possess? II. 370. =Dirty gauge glass.=--What should be done to the gauge glass if the feed water is dirty? How many times a day should the gauge be blown out? II. 370. =Priming.=--What is the priming or foaming of the water in a boiler? What are the known causes of priming? Why is priming wasteful? Can blowing off at the safety valve cause priming? What are other causes of priming? How can priming be detected? What would you do to stop priming? What would you do to prevent priming? What parts of the engine would you attend to if the boiler primes? II. 370. =Low water.=--What would you do if the water got dangerously low in the boiler? In such a case how would you regulate the dampers? What do you consider dangerously low? What is blowing down a boiler? II. 370. =Cleaning a boiler.=--How often would you clean a boiler? II. 371. =Water falling.=--What would you suppose was going wrong if the pump was kept going and the water still fell in the boiler? II. 370. =Empty pump.=--What causes a pump to fail? II. 370. =Blowing down.=--How much would you blow down a boiler? How low should the pressure get before the water is let out? What would be the result if the boiler was blown off under a high pressure? What would you do after the water is all out of the boiler? II. 371. =Special examination.=--What parts would you pay special attention to in examining the boiler after cleaning it? II. 371. =Hammer test.=--What does the "hammer test" consist of? II. 371. =Washing and scaling.=--What determines the periods at which a boiler should be washed out and scaled? II. 371. =Regulating dampers.=--How would you regulate the dampers when letting the fire out? II. 371. =Naming the parts.=--Name all the parts of a simple or plain D slide-valve engine, beginning with the cylinder. II. 372. =Dividing the parts.=--Into what three divisions may the parts of a plain slide-valve engine be divided? II. 372. =Defining clearance.=--What is the meaning of the word "clearance" as applied to an engine cylinder? II. 372. =Finding equal clearance.=--How would you proceed to find if the clearance in the cylinder was equal at each end? II. 372, 404. =Parts of valve motion.=--What parts constitute the valve motion or valve gear? II. 372. =The driving parts.=--What parts constitute the driving or power-transmitting mechanism? II. 372. =Lubricating attachments.=--Name the attachments used upon an engine cylinder to lubricate the piston and valves. II. 373. =Pet cock.=--What is the difference between a cylinder pet cock and a cylinder relief valve? II. 373. =Relief valves.=--What are cylinder relief valves used for? II. 373. =Quick steam admission.=--Which gives the quickest steam admission, a long and narrow or a wide and short steam port, both having the same area? II. 373. =Placing the piston-ring split.=--At what part of the cylinder bore should the split of a piston ring be placed? II. 374. =Fitting a piston ring.=--How tight should a piston ring fit to the cylinder bore? II. 374. =Testing steam tightness.=--How would you test the steam tightness of a piston? II. 374. =Jacketed.=--What is a jacketed cylinder? II. 374. =Valve gear.=--What is a releasing valve gear? What is a positive valve gear? II. 374. =Packing a stuffing box.=--About how full of packing would you fill a stuffing box for a piston gland? II. 375. =Connecting rods.=--What are the two principal kinds of connecting rods? What is meant by the angularity of a connecting rod? II. 375. =Oiling guide bars.=--Which guide-bar is the most difficult to oil, the top or the bottom one? II. 375. =Effect of angularity.=--What effect does the angularity of the connecting rod have on the piston motion? Is this effect increased or diminished by shortening the connecting rod? II. 375. =Crank at full power.=--When the crank is at its point of full power, is the piston in the middle of the cylinder? Is it nearer to the crank-end or the head-end of the cylinder? II. 375. =Piston motion irregular.=--What causes the piston to have irregular motion? II. 375. =Live steam period.=--What constitutes the live steam period of a position? II. 376. =Cut-off.=--What is the point of cut-off? II. 375.--What is a separate cut-off valve, and what event does it control in the supply of the steam to the cylinder? How is the point of cut-off varied when a cut-off valve is used? II. 378. =Working expansively.=--What causes the steam to be worked expansively in an engine cylinder? II. 402. =Follower.=--What is a piston follower? II. 374. =Valve lead.=--What is the lead of valve? II. 376. =Valve lap.=--What is the lap of a valve? II. 376. =Admission.=--What is the point of admission? II. 376. =Cushioning.=--At what point in the valve travel does cushioning begin? II. 376. =Release and compression.=--What are the points of release and of compression? II. 376. =Double-ported valve.=--What is a double-ported valve? II. 377. =Valves.=--What is a griddle valve? What is a balanced valve? II. 377.--What is a piston valve? II. 378. =Slide and piston valves.=--Is there any difference between the action of a plain slide valve and a piston valve if both have the same amount of lap, lead, and travel? II. 378. =Cut-off diagram.=--Make a diagram to give the dimensions of a slide valve, to cut off at 3/4 stroke, the valve travel being 4 inches. II. 380. =Reversing an engine.=--What is the ordinary means provided for reversing an engine? II. 383. =Full gear.=--What is the meaning of the term full gear, with regard to a link motion? II. 383. =Third use Of link motion.=--What does a link motion accomplish besides enabling the engine to run in either direction? II. 383. =Slide valve for link motion.=--What are the two operations to be performed in setting the slide valve of an engine having a link motion? Describe these two operations. II. 383. =Governors.=--What is a throttling governor? What is an isochronal governor? What is a dancing governor? II. 384. =Forward.=--What is full gear forward? II. 383. =Backward.=--What is full gear backward? II. 383. =Starting.=--How would you proceed to start a plain slide valve? II. 384, 400. =Crank position.=--What is the best position for the crank to be in to start the engine, and why is it the best position? II. 384. =Taking charge.=--What is the first thing you would do in taking charge of an engine? II. 385. =Length of connecting rod.=--How would you find out if the connecting rod was the right length to give an equal amount of clearance at each end of the cylinder? II. 385, 404. =Order of examination.=--In what order should a thorough examination of the engine be made? II. 385. =Least examination.=--What would constitute the least permissible examination of an engine, with a due regard to safety? II. 385. =Thorough examination.=--What would constitute a complete examination of a plain slide-valve engine? In what order should such an examination be made? II. 385. =Quick examination.=--What examination should an engineer make of a plain slide-valve engine, if called upon to start it as quickly as possible without knowing its condition? II. 385. =Taking a lead.=--How would you take a lead for adjusting the fit of a bearing to its journal? II. 386. =Set of slide valve.=--How would you test whether the slide valve was set properly? II. 386. =Squaring a valve.=--Is it proper to square a plain slide valve? II. 386. =Lead affected by wear.=--How does the wear of the parts affect the lead in vertical engines? II. 386. =Heating of crank-shaft.=--What would you do if the crank-shaft bearings began to heat? II. 386. =Hot crank-pins.=--What are the principal causes of hot crank-pins? II. 386. =Heating.=--What part of the engine is the most likely to get hot from the friction of the fit? II. 386. =Use of lead.=--What is a lead used for in adjusting the fit of a brass to its journal? II. 386. =Fit of top brass.=--When a liner is used between the two brasses, what does the fit of the top brass depend upon? II. 386. =Oiling.=--In oiling the engine, what precaution would you take to prevent the journals from heating? II. 401. =Cold weather.=--What is liable to happen to an engine that is used out of doors in cold weather? II. 386. =Leaky throttle valve.=--What damage might a leaky throttle valve do, and how would you prevent it? II. 386. =Leaky check valve.=--What damage may a leaky check valve do, and how would you prevent it? II. 387. =Freezing in the pump.=--How would you prevent the water from freezing in the pump? II. 387. =Freezing oil.=--How would you prevent the oil from freezing? II. 387. =Thawing oil.=--How would you thaw frozen oil? II. 387. =Setting a portable engine.=--How should a portable engine stand when it is at work, and why should it stand so? II. 387. =Natural supply of water.=--What precaution would you take when feed water is drawn from a stream, or other natural source of supply? II. 387. =Pumps.=--Into what classes may pumps be divided? What is a force pump? What is a piston pump? What is a single-acting pump? What is a double-acting pump? II. 387. ="Suction."=--What causes the flow of water up the suction pipe of a pump? How high can a pump lift water, or cause it to lift or rise? II. 388. =Regulating a pump.=--How can the quantity of water a pump will deliver be regulated? II. 388. =Pump valves.=--What is the check valve of a pump? What is the foot valve of a pump? II. 388. =Speed of pumping.=--What is the highest speed at which a pump should run? What is the consequence if a pump runs too fast? II. 388. =Locating the air chamber.=--When should the air chamber be placed on a pump, and what is its use? II. 388. =Belt pump.=--What is the advantage possessed by a belt pump? II. 388. =Starting bar.=--What is a starting bar, and what is it used for? II. 389. =Link sketch.=--Make a rough sketch of a locomotive link motion. II. 392. =Link gear and eccentric.=--Does a link motion when in full gear operate the valve much different to what a simple eccentric motion would do? II. 393. =Exchanging eccentric rods.=--If the forward eccentric rod was to break, could the backward eccentric be utilized to run the engine forward? If so, how? II. 393. =Broken reach rod.=--How would you hold the tumbling shaft if the reach rod broke? II. 393. =Eccentric and crank motions.=--Does the acting eccentric lead or follow the crank when the link is in full gear? II. 393. =Setting a slide valve.=--In what position would you place the link motion when the slide valve is to be set? II. 394. =Length of eccentric rod.=--What determines the length of the eccentric rods when setting the slide valve? II. 394. =Setting an Allen valve.=--What difference is there between setting a common slide valve and another (an Allen) valve? II. 395. =Injector.=--What is an injector? II. 395. =Before firing.=--What should be done before laying the fire? II. 400. =Kindling the fire.=--How long should the wood burn before putting on coal? II. 400. =Oiling.=--What points require examination when oiling the engine? II. 401. =After oiling.=--What points would you move after having oiled the engine? II. 401. =Using tallow.=--Where would you place tallow in oiling the engine, and for what purpose would you use it? II. 401. =Fire too hot.=--What would you do if steam was rising too rapidly? II. 401. =Link position.=--Where should the link be when starting the engine? II. 402. =Even steam pressure.=--Why should the steam pressure be kept up, and what difference does it make in the consumption of the fuel? II. 402. =Quick steaming.=--Can steam be made quickest with a large or with a small quantity of water in the boiler? II. 402. =Best boiler feed.=--Which is better, a constant or an intermittent boiler feed? II. 402. =Best firing.=--Which is better, heavy firing at long intervals or light and frequent firing, and why? II. 402. =Broken cylinder cover.=--What would you do if the cylinder cover got knocked out while on the road? II. 402. =Hot piston rod.=--What would you do if the piston rod got hot? II. 403. =Broken piston rod.=--What if the piston rod broke? II. 403. =Broken crank-pin.=--What if the crank-pin broke? II. 403. =Tire off.=--What if a wheel tire came off? II. 403. =Driving wheel off.=--What if a driving wheel came off? II. 403. =Broken lifting link.=--What if a lifting link or saddle-pin broke? II. 403. =Slipping eccentric.=--What if an eccentric slipped? II. 403. =Hot axle-box.=--What if an axle-box got hot? II. 403. =Broken spring hanger.=--What if a spring or spring hanger broke? II. 403. =Bursted tube.=--What if a tube bursted? II. 403. =Fitting axle-box wedges.=--In what position should the engine be placed when the axle-box wedges are to be adjusted for fit to the pedestals? II. 404. =Changing clearance.=--What is it that, as the engine wears, tends to alter the amount of clearance? II. 404. =Crank-pin centres.=--How would you get the distance from centre to centre of the crank-pins when adjusting the axle-boxes and the side rods, parallel rods, or coupling rods, as they are promiscuously termed? II. 404. =Adjusting Shoes.=--In what position would you place the crank when adjusting the shoes or wedges of the axle-boxes? Why is this adjustment important? II. 404. =Force, pressure, and power.=--What is the difference between force or pressure and power? II. 405. =Increase of power.=--Can we increase a given amount of power by means of mechanical appliances? II. 405, 406. =Speed vs. power.=--Is a gain in speed a loss in power? II. 405. =Lever.=--Explain the principle of the lever. II. 405. =Elements of power.=--What are the three elements composing power? II. 407. =Horse-power.=--What is a horse-power as applied to steam-engine calculations? How would you calculate the horse-power of a steam engine? II. 407.--Give a method of testing the effective horse-power of an engine. II. 408. =Safety-valve problem.=--A safety valve is three inches in diameter; the lever is twenty-eight inches long from the point of suspension of the weight to the pivoted end of the lever; the valve pin is four inches from the pivot; the weight is twenty pounds. What is the greatest pressure of steam the valve will hold, leaving the weight of the valve and of the lever out of the question? II. 409. =Thermal unit.=--What is the heat unit or thermal unit? II. 410. =Latent heat.=--Is all the heat in steam or water shown by a thermometer? What is the latent heat of water? What is the latent heat of steam? II. 410. =Sensible heat.=--What is the sensible heat of steam? II. 410. =Total heat.=--What is the total heat of steam? II. 410. =Heaviest water.=--At what temperature is water at its greatest density? What is the weight of a cubic foot of water when at its maximum density? II. 410. =Heat of boiling water.=--What determines the temperature at which water will boil? II. 410. =Heat of steam.=--Can steam be made hotter than the water while they are in contact? What is superheated steam? II. 410. =Absolute pressure.=--What is meant by the absolute pressure of steam? II. 411, 416. =Dry steam.=--What is meant by dry steam? II. 411. =Weight of steam.=--Is there any difference between the weight of water and that of the steam it will evaporate into? II. 411. =A perfect gas.=--What is Marriotte's law, or Boyle's law? Is steam a perfect gas? II. 411. =Joule's equivalent.=--What is meant by the conversion of heat into work? What is Joule's equivalent? What is the mechanical equivalent of heat? II. 411. =Indicator.=--What is a steam-engine indicator? II. 413.--How are indicators attached to an engine? II. 416. =Indicator diagram.=--What are the names of the lines of a diagram? Why is a theoretical diagram not correct? II. 414.--What difference is there between the lines of a diagram of a condensing and those of a non-condensing engine? II. 415.--How is the expansion curve of a diagram tested? II. 417. =Barometer.=--What is a barometer, and for what purpose is it used in connection with engine diagrams? II. 415. =Horse-power by diagram.=--How do you calculate the horse-power of a steam engine from an indicator diagram? II. 418. =Diagram vs. diagram.=--What difference is there between the diagram taken from one end and that taken from the other? II. 419. =Consumption of steam by diagram.=--How would you calculate the consumption of steam or water of an engine from an indicator diagram? II. 420. =Steam line.=--What would a fall in the steam line of a diagram indicate? II. 421. =Expansion curve.=--If the expansion curve is above the true expansion curve, what defect in the engine does that indicate? If the expansion curve falls too low, what does it indicate? II. 421. =Valve lead by diagram.=--How would insufficient valve lead be shown on a diagram? II. 421. =Excessive lead.=--How is excessive lead shown on a diagram? II. 421. =Automatic cut-off.=--What is an automatic cut-off engine? What are the principal forms of automatic cut-off engines? II. 423. =Releasing valve governor.=--What kinds of governors do engines with releasing valves have? II. 423. =Corliss engine valves.=--How many valves does a Corliss engine have? Explain the action of a Corliss valve gear. II. 423. =Crab claw.=--What duty does the latch-link or crab-claw of a Corliss valve gear perform? II. 423. =Valve trip.=--What means are employed in a Corliss engine to trip the admission valve? II. 423, 424. =Point of cut-off.=--What determines the point of cut-off in a Corliss engine, and how does it do so? II. 424. =Valve closing.=--What closes the valve in a Corliss engine? II. 424. =Dash-pot.=--What is a dash-pot? What enables the dash-pot of a Corliss engine to work noiselessly? II. 424.--How is the amount of air cushion in the Corliss dash-pot regulated? II. 425. =Shape of Corliss valve.=--What shape is a Corliss valve, and how far would its lap, as ordinarily constructed, carry the live steam period, leaving the cut-off mechanism out of the question? II. 426. =High-speed engines.=--What is meant by the term high-speed engines? II. 427. =Adjusting for load.=--What adjustments would you make if the engine had been running a very light load, and required to be adjusted for a heavy load? II. 427. =High-speed governor.=--What class of governor is generally used upon high-speed engines? II. 427. =Varying the cut-off.=--What is the usual method of varying the point of cut-off on high-speed engines? II. 427. =Wheel governor.=--State, in a general way, what a wheel governor consists of. II. 427. =Even valve lead.=--Can the valve lead be kept equal when the point of cut-off is varied by shifting the eccentric across the shaft or crank-axle? II. 427. =Marine engine.=--What forms of engine are used for marine purposes? II. 434. =Inverted cylinder.=--What is an inverted cylinder engine? II. 434. =Receiver.=--What is a receiver? II. 434, 453. =Triple expansion.=--What is a triple-expansion engine? II. 436. =Condensing engine.=--What is a condensing engine? II. 434. =Compound engine.=--What is a compound engine? II. 434. =Arranging compound cylinders.=--What are the two methods of arranging compound cylinders? II. 436. =Condenser.=--What is a surface condenser? II. 440. =Hot well.=--What is a hot well? II. 440. =Steam condensation.=--Describe the means by which the steam is condensed after it is exhausted from the cylinder in a surface condensing engine, and state what becomes of the water of condensation and the injection, circulating, or condensing water. II. 440. =Condenser tubes.=--How are condenser tubes made tight? II. 440. =Blow-through valve.=--What is a blow-through valve? II. 440. =Air pumps.=--What is a bucket air pump, and is it single or double acting? What is a piston air pump? What is a plunger air pump? What is a trunk air pump? When is a trunk air pump necessary? II. 441. =Air-pump valves.=--Are a foot valve and a head valve always necessary to an air pump? II. 441. =Pet cock.=--Why are bucket pumps provided with a valve or pet cock? II. 441. =Bilge injection.=--What is a bilge injection? What fittings are necessary for a bilge injection? II. 441. =Hot-well temperature.=--At what temperature is the water in the hot well usually kept? II. 441. =Use of air chamber.=--What is an air vessel or air chamber used on a pump for? II. 441. =Feed escape.=--What is a feed relief, or feed escape valve? II. 441. =Checked boiler feed.=--What causes may act to stop the boiler feed? II. 441. =Admitting the exhaust.=--When the exhaust steam is condensed for boiler-feeding purposes, how soon after the engine has started would you let the exhaust into the feed tank? II. 441. =Ship's side discharge.=--What is a ship's side air pump discharge valve? II. 442. =Course of water.=--What is the course of the main injection water of a jet condenser? What is the course of the main circulating water of a surface condenser? II. 442. =Surface condensing.=--What are the advantages of surface condensing? How are surface condensers cleaned out? II. 442. =Engine-room cocks and valves.=--What cocks and valves are there in the engine room of a condensing engine? II. 442. =Donkey engine.=--What is a donkey engine? What pipes connect to a donkey engine, and what are their uses? II. 442. =Pipes to the sea.=--What are the pipes that lead from or go to the sea? II. 442. =Parts classified.=--What parts of a marine engine are generally made of wrought iron, of cast iron, of brass, and what of steel? II. 442. =Use of Babbitt.=--What is Babbitt metal or white metal used for? II. 442. =Use of Muntz.=--What is Muntz metal used for? II. 442. =Breaking strain.=--About what is the breaking strain of wrought iron per square inch of section? II. 442. =Tempering.=--How is steel tempered? II. 442, 460-463. =Case-hardening.=--What is case-hardening? What parts of an engine are usually case-hardened? II. 442. =Forging.=--What are the forgeable metals used in engine construction? II. 442. =Welding.=--What is welding? II. 442. =Metal expansion.=--What metals used in engine construction expand by heat, and what allowances are made in the construction on this account? II. 442. =Composition of iron and steel.=--What is the difference in the composition of cast iron and steel? II. 442. =Marine piston.=--Describe a marine engine piston. II. 442. =Drain cocks.=--What are cylinder drain cocks? II. 442. =Link motion.=--What is a link motion? What is a link motion used for? II. 443. =Expansion valve.=--What is a separate expansion valve? II. 443. =Top cylinders.=--What are the small cylinders on top of the steam chests used for? II. 443. =The throw.=--What is the throw of an eccentric? II. 443. =Double beat.=--What is a double-beat valve? II. 443. =Expansion joint.=--What is an expansion joint? II. 141, 443. =Oil cup.=--What is an oil cup? II. 443. =Siphon.=--What is a siphon or worsted? II. 443. =Impermeator.=--What is a steam lubricator or impermeator? II. 444. =Hand-worked valves.=--What are the valves of a marine engine that are worked by hand? II. 444. =Vacuum gauge.=--What is a vacuum gauge? What is a mercury vacuum gauge? II. 444. =Total condenser pressure.=--How would you find the total pressure in a condenser? II. 444. =Racing.=--What is meant by the racing of an engine? II. 444. =Uniform paddle-wheel revolution.=--How may the speed of revolution of single crank paddle-wheels be made uniform? II. 444. =Paddle-wheel construction.=--What is the construction of a common paddle wheel? What is a radial paddle wheel? What is a feathering paddle wheel? II. 445. =Disconnecting engine.=--What is a disconnecting paddle engine? II. 445. =Propeller thread.=--Where is the thread of a screw propeller measured? II. 445. =Propeller pitch.=--What is the pitch of a propeller? II. 445. =L. H. propeller.=--What is a left-hand propeller? II. 445. =Thrust bearing.=--What is a thrust bearing? II. 445. =Propeller fastening.=--How are screw propellers fastened to their shafts? II. 445. =Marine engine pipes.=--What are the principal pipes of a marine engine and boiler? II. 445. =Mud box.=--What is a mud box? II. 445. =Course of steam.=--Describe the course of the steam from the boiler to the hot well. II. 445. =Exposure to cold.=--What parts of an engine are exposed to danger in a cold climate? II. 446. =Preventing freezing.=--What precautions are necessary to prevent the engine from freezing in cold climates? II. 446. =Failure to start.=--Name all the reasons that may cause a marine engine to fail to start when it is expected to do so. II. 446. =Pressure pieces.=--Name all the pieces of an engine through which the steam pressure is received and transmitted. II. 446. =Horse-power.=--What is the unit or measure of horse-power? What is the meaning of nominal horse-power? II. 446. =Lost vacuum.=--Name all the causes from which the vacuum may become defective or lost. II. 447. =Hot journals.=--What are the principal causes of the heating of engine journals? II. 447. =Stays.=--What is a boiler stay? What is a gusset stay? What is a tube stay or a stay tube? II. 452. =Stress per square inch.=--How much stress is usually allowed per sectional square inch of boiler stay? II. 452. =Breaking of tubes.=--What is the commonest cause of boiler tubes breaking? II. 452. =Split tube.=--How is a split tube stopped up? II. 452. =Uptake.=--What is the uptake of a marine boiler? What is a wet uptake? II. 453. =Superheater.=--What is the superheater of a marine boiler? II. 453. =Fittings.=--What fittings are essential to a marine boiler? II. 453. =Safety valves.=--What is a dead-weight safety valve? What is a spring-loaded safety valve? What is a lock-up safety valve? II. 453. =Test cocks.=--What do the three boiler test cocks show? How are boiler test cocks cleaned? II. 453. =Steam gauges.=--What is a gauge glass or water-gauge glass? What is a Bourdon dial gauge? What pressure is shown by a boiler steam gauge? II. 453. =Scum cocks.=--How many scum cocks are used in a marine boiler? II. 454. =Sluice valves.=--What are sluice valves in steamships? II. 454. =Removing scale.=--How is scale removed in boilers? II. 454. =Salinometer.=--What is a salinometer? II. 455. =Salt in sea water.=--About how much salt does sea water contain? II. 454. =Division plates.=--What are division plates in boilers? II. 455. =Intercepter.=--What is the separator or intercepter of a marine boiler? II. 455. =Boiler draft.=--What causes the draft in a boiler? II. 455. =Rapid wasting.=--Where does the most rapid wasting occur in marine boilers? II. 455. =Coal consumption.=--About how much coal is consumed per square foot of grate in marine boilers? II. 455. =Short of coal at sea.=--If at sea and short of coal, what course would you pursue in order to save coal and get into port? II. 455. =Boiler relief in extreme danger.=--How would you relieve a marine boiler in case of the safety valve being locked down from some accidental cause, the engine also being disabled? II. 455. =Pressure test.=--At what pressure should a new boiler be tested? II. 456. =Boiler examination.=--State what you would consider a proper examination, inside and out, of a marine boiler that had been in sufficient service to require examining. II. 458. APPENDIX--PART II. DICTIONARY OF WORKSHOP TERMS. A =Addendum.= That part of a gear wheel tooth that extends beyond or outwards from the pitch line. =Addendum-circle.= The circle representing the full or greatest circumference of a gear wheel. =Adjustable reamer.= A reamer whose teeth may be adjusted to the required diameter. =Angle-iron.= A shape of wrought iron or steel having two flanges at a right angle; thus, [L] =Angle-plate.= A plate having surfaces at a right angle, one to bolt to the machine work-table, the work being bolted to the other. =Angle-tooth.= A gear wheel tooth that runs across the face of the wheel in a line that envelops part of the wheel circumference. =Angular cutters.= Cutters, whose teeth are on a circumferential surface, that is, at an angle to the cutter axis, such angle not being that of 90° to either the side face nor to the axis of the cutter. =Angular-velocity.= Velocity measured in degrees of angle. =Annular.= In the form of a ring. =Apron.= 1. The piece that carries the tool port or clamp on an iron planing machine. 2. The front plate of a lathe carriage. =Arbor.= 1. A mandrel used to drive work upon. 2. A spindle or shaft of a machine. =Arc.= A portion of a circle. =Archimedean drill= (är-k[)i]-m-[e.]-d[=e]'an) A drilling device in which a nut moved endwise on a stock or handle causes the drill to revolve back and forth. =Arc of approach.= That part in the revolution of a pair of gear wheels in which the teeth in contact approach the line of centres of the two wheels. =Arc of recess.= That part in the revolution of a pair of gear wheels in which the teeth in contact recede from the line of centres of the two wheels. =Arc-pitch.= The pitch of gear wheel teeth when measured around the pitch circle. =Attachment.= A work-holding device that may be attached to a machine. =Auger.= A wood-boring tool having two spiral plates and a pointed screw to feed it, the cutting edge being at the end of the tool. =Axle-box.= The bearing in which an axle revolves. B =Back-gear.= The toothed wheels on the spindle of a lathe and at the back of the lathe-head, by means of which the speed of the lathe is reduced. =Back-geared lathe.= A lathe having a back gear to reduce its motion. =Back-knife gauge-lathe.= A lathe in which the work is finished and cut to size and shape by a knife at the back of the lathe. =Balanced pulley.= A pulley whose weight is so equally distributed that it will run steadily and smoothly at the speed for which it is balanced. =Balanced valve.= A valve so constructed as to move with equal force in either direction. =Ball and socket joint.= A universal joint consisting of a ball on the end of a shaft and in a casing that envelops it and yet permits it to be moved in its casing. =Ball-cutter.= A tool for finishing metal balls. =Ball-pene.= A spherical pene of a hammer. =Band-saw.= A continuous ribbon of steel having saw teeth on one of its edges. =Band-saw machine.= A machine for operating a band-saw. =Bastard file.= A file whose teeth are one degree or grade coarser than a _second_ cut file and one degree finer than a _coarse_ cut file. =Belt.= A leather band employed to drive pulleys, for transmitting motion. =Belt-clamp.= A clamp for pulling the ends of a belt together, to lace it, while the belt is upon the pulleys. =Belt-hook.= A hook employed to fasten the ends of belts together. =Belt-pulley.= A wheel that drives or is driven by a belt. =Belt-shipper.= A device for moving a belt from one pulley to another. =Belt-tightener.= A pulley employed to cause a belt to tighten upon another pulley to enable it to transmit motion periodically instead of continuously. =Bevel-sawing machine.= A wood-working machine in which the saw or the work table may be set to cut a surface at other than a right angle to the face of the work that rests against the work table or the fence as the case may be. =Bevel-square.= A square whose blade may be set to any required angle to the stock that holds it. =Bevel-wheel=, _or_ =bevel-gear.= A gear wheel with its teeth at an angle to its shaft. =Bit.= 1. A boring tool. 2. A tool that is carried in a holder. =Blank.= A piece of material roughly formed and ready to be formed into some definite shape. =Blast-pipe.= 1. The pipe conveying the blast or air to a fire furnace or cupola. 2. A small pipe through which steam escapes up a locomotive chimney to increase the draught of the fires. =Blob.= An extremely loose place in a plate or saw blade. =Block-plane.= A short plane. =Boiler-shell.= The outer casing of a steam-boiler. =Bolt.= 1. A holding device having a head at one end and at the other a threaded stem to receive a nut. 2. A short piece of a round log. =Bolt-cutter.= A machine for cutting screw threads upon bolts or similar work. =Boring-bar.= A bar that carries boring tools. =Boring-machine.= A machine for boring holes in metal or wood. =Boring-mill.= A form of lathe used mainly for boring. =Boring-tool.= A tool for cutting out and enlarging a bore or hole. =Boss.= An enveloping piece on an axle or shaft and having upon it an arm, arms, or spokes. =Bottoming-tap.= A tap having a full thread up to its very end so that it will cut a full thread to the bottom of a hole. =Box-chuck.= A rectangular two-jawed chuck used by brass finishers. =Box-tool.= A tool used in screw machines and turret heads, and which guides the work while it is being operated upon. A box tool in many cases carries more than one cutting tool. =Box-wrench.= A wrench which fits over the head of the bolt and passes endways upon it. =Brace.= 1. A rod, bar, or beam that braces or supports. 2. A device for revolving cutting tools. =Bracket.= A projecting frame that is bolted to its supporting pieces or frame. =Brad-awl.= An awl for piercing small holes in wood and having a wedge-shaped end. =Branch-pipe.= A pipe leading out of another. =Brass-and-brass.= A term used to denote that the two brasses or boxes of a bearing are locked together by the key, cap, or set-screw. =Brasses.= Pieces fitted into a frame and intended to afford a bearing for a journal. =Break-lathe= _or_ =gap-lathe.= A lathe having a break or gap in the bed and beneath the face plate to let chucked work of large diameter pass. =Broach.= A toothed tool for cutting the walls of a hole. =Broaching-press.= A machine that forces a broach to its cut. =Bunter-dog.= A work-gripping device for a planing machine, and consisting of a piece having a hook end to engage in the T-slot of the table, and a set-screw to bind the work. =Butt-joint.= A riveted joint in which the ends of the plate abut fair, one against the other. =Butt-strap.= A strip or band of iron employed to hold the joint together in a butt-joint. =Butt-weld.= A weld in which the end of one piece merely abuts against the other when the two pieces are put together to weld. =Buzz-planer.= A wood-planing machine in which the work is fed by hand. C =Calender-roll.= A roll for calendering paper. =Caliper-gauge.= A gauge in the form of a solid caliper. =Calipers.= A hinged tool for measuring work. =Cam.= A revolving disc whose actuating surface is not a true circle. =Cam-motor.= A cam together with the rod it actuates. =Cap.= The plate or upper part of a bearing that holds the top half of the box or brasses in place. =Cape-chisel.= A narrow machinist's chisel. =Caps.= The backward curves on the points of file teeth. =Cap-screw.= A screw with a collar and a square head. =Carrier.= A device for driving lathe work. =Case hardening.= A process of hardening the surface of wrought iron, the hardening usually extending about 1/32 inch in depth. =Cat-head.= A sleeve fastened by set-screws to slender lathe work and running in a bearing so as to steady the work. =Caulking-tool.= A tool used for caulking riveted joints and in making rust-joints. =Centre-bit.= A bit having a triangular conical point with its cutting edge on one-half of the end and a spur on the other half. =Centre-punch.= A tool having a coned point for marking the centres to work. =Chamfer.= A facet that removes the corner of a right angle. =Change-gears= _or_ =change-wheels.= The gear wheels employed to change the revolutions of a lead screw or feed motion. =Chaser.= A toothed tool for cutting threads by hand in a lathe. =Check.= A crack. =Check nut.= A second nut screwed against the first to check it from slackening back. =Chip-break.= A piece that rests upon the work of a wood-working machine and prevents the cutter from splitting out the wood as the cut leaves the surface. =Chipping-hammer.= A machinist's hand hammer. =Chips.= 1. The cutting from a metal cutting machine tool. 2. The thick cuttings from a wedge-shaped wood-working tool, as from an axe or adz. =Chisel.= A wedge-shaped tool. =Chisel-tooth saw.= A saw having inserted teeth with a maximum of front rake. =Chop= _or_ =hammer-sink.= A mark left on a plate by a sawmaker's or plate straightener's hammer. =Chord-pitch.= The pitch of gear wheel teeth measured in a straight line. =Chuck.= A work-holding or tool-holding device. =Chucked.= Held in a chuck. =Chucking-lathe.= A lathe having a large face plate for chucking purposes, and usually a short bed. =Chuck-plate.= A large face plate on which work may be chucked. =Circular saw.= A saw having its teeth arranged around its circumference. =Clamp.= A device for fastening or holding work together or to some other part. =Clearance.= 1. The amount to which one piece clears or escapes another. 2. On a lathe tool, clearance is the amount to which the back face of the tool escapes the metal it is cutting. =Clements driver.= A device for driving work in a lathe, and that places an equal strain on each end of the lathe dog or carrier. =Clutch.= A device for engaging or disengaging so as to cause the motion of one piece to be communicated to another, or to stop such communication. =Cock.= A device for opening or closing the bore of a pipe. =Cog.= A wooden tooth for a gear wheel. =Collapsing-taps.= A tap that is so formed that its teeth close inwards when the thread is cut so that the tap can be withdrawn without winding it backwards. =Collar.= 1. A disc-shaped enlargement on a cylindrical piece. 2. A hollow cylindrical piece containing a set screw, to prevent a shaft from end motion. =Collet.= A casing for holding tools or drawers in position. =Combination-chuck.= A chuck in which the jaws may be moved simultaneously or independently. =Comparator.= A machine for comparing measurements, for testing them and originating sub-divisions. =Compass-calipers.= A pair of calipers having one bent leg and one leg with compass joint. =Compasses.= A tool answering the same purpose as dividers, but with longer legs and a set screw to secure the position of the legs. =Compass-plane.= A plane whose sole or bottom is curved in its length. =Compound gears.= A train of gear wheels in which there are two wheels fixed on the same shaft but of different diameters so as to vary the velocity. =Compound slide-rest.= A slide-rest having two slides, one above the other. =Cone-bearing.= A bearing (for a journal) that contains a coned sleeve that may be moved endways to take up wear. =Cone-mandrel.= A mandrel that holds hollow work by means of two cones. =Cone-plate.= A device for steadying work in the lathe by supporting one end in a coned mouth. =Cone-pulley.= A pulley having steps of different diameters. =Cone-shaft.= The shaft for a cone-pulley. =Cook's auger.= An auger rounded at the end for cutting end-grain wood. =Cope-cutter.= A cutter for under-cutting the shoulder of a tenon on wood-work. =Cope-head.= A head for a cope-cutter in a tenoning machine. =Core.= A body of sand that produces a hole or cavity in a casting. =Core-box.= The box in which a core is made. =Cored.= Containing a hole or recess. =Cotter= _or_ =cottar.= A term applied to small keys that are very broad in proportion to their thickness. =Cotter-drill.= A drill used in cutting out keyways in a machine. =Cotter-file.= A file thin in proportion to its length, for filing out keyways or slots. =Counterbore.= 1. A parallel recess at the mouth of a hole. 2. A tool for producing such a recess. =Countershaft.= A shaft with pulleys upon it, employed to permit a machine to be started and stopped without stopping and starting the line shaft, also, to afford means for varying the speed of a machine. =Countersink.= A tool for cutting a coned mouth to a hole. =Countersunk.= Having a coned mouth. =Coupling.= A piece used to connect two pieces together. =Covering-plate.= A plate used to cover the seams of a boiler. =Cow-mouth chisel.= A machinist's chisel shaped at the cutting end like a carpenter's gouge. =Crank.= An arm that is fast to a shaft and is used as a lever wherewith to revolve the shaft. =Crank-shaft.= A shaft having a crank. =Cross-cut.= A narrow machinist's chisel. =Cross-cut saw.= A saw whose teeth are shaped to cut across the fibre or grain of wood. =Cross-face.= A plate straightener's or saw maker's hammer, having one face at a right angle to the other. =Cross-feed.= That feed of a lathe which runs across the bed. =Cross-filing.= That class of filing in which the file is pushed in the line of its length. =Cross-head.= That part of an engine that connects the piston rod to the connecting rod. =Cross-slide.= A slide that stands across a work-table. =Crowning.= Highest in the middle when tested by a straight edge. =Crown-wheel.= A gear wheel having its teeth upon its side face. =Cup-chuck.= A chuck having a coned or cupped mouth. =Cup-shape.= A crack of circular form in a piece of timber or a log. =Cutter.= A tool that is held or carried in a stock bar or mandrel. =Cutter-bar.= The bar or shaft that carries the cutting knives in a wood-planing machine. =Cutter-grinder.= A machine for grinding cutters. =Cutter-head.= 1. A head that carries cutters. 2. The head that carries the cutters in a wood-moulding machine. =Cutting-off lathe.= A lathe used for cutting up rods into required lengths, and having a hollow spindle through which the rod passes. =Cutting-off saw.= A sawing machine designed for cropping the ends of work and cutting it to length. =Cutting-off tool.= A tool for cutting up rods or bars, and used in the common lathe and in the cutting-off lathe. =Cycloid= (si'kloid). A curve generated by a pencil fixed in the perimeter of a circle that is rolled upon another circle. =Cylinder.= 1. That part of a steam-engine in which the steam is utilized to drive the piston. 2. The shaft that carries the knives in a wood-planing machine. =Cylinder-head=, _or_ =cylinder-cover.= A piece that encloses or seals the end of a cylinder. D =Dead centre.= The stationary centre of a lathe. =Dead-smooth file=, _or_ =superfine file.= The finest or smoothest cut of file. =Delivery-rolls.= Rolls that remove the work from a machine or from its cutters or knives. =Describing-circle.= The circle or cylinder containing the pencil for rolling a curve. =Diametral pitch.= A system of designating the pitches of gear wheels. =Diamond-point.= A machinist's chisel, square in cross-section, having a diamond-shaped face at the end, and two cutting edges, one at a right angle to the other. =Die.= 1. A tool for cutting threads upon external surfaces, such as bolts. 2. A chumpy sliding piece. =Differential screw.= A screw having a coarse and a fine thread, the difference between the two pitches enabling a more powerful strain to be endured by the thread. =Dimension planer.= A wood-planing machine, for planing accurately to size. =Disk= _or_ =disc.= A cylinder whose length is very short in proportion to its diameter. =Dividers.= A tool having two legs with sharp points at their ends for measuring distances or drawing circles. =Dog.= A work holding device. =Dog-chuck.= A chuck containing independent dogs or jaws. =Dog-head.= A hammer used in plate or saw straightening. =Double-eye= _or_ =knuckle-joint.= A joint in which one piece is forked at its end, to receive the other, and a pin passes through both. =Double-thread.= A screw thread, having two spirals in the same bolt or body. =Dovetail.= A groove that is wider at the bottom than at the top, or a projection thicker at the top than at the bottom. =Draw-filing.= That class of filing in which the line of file motion is in the direction of the width of the file. =Drawn-down.= Decreased in diameter, width or thickness, by forging or swaging. =Drawn-out.= Increased in length, by forging or swaging. =Drift.= A tool that cuts the walls of a hole while it is driven through by hammer blows. =Drift-pin.= A taper pin that is used by boiler makers to drive through holes that do not come fair, or match properly. =Drill.= A tool to pierce holes. =Drill-chuck.= A chuck used to hold drills. =Drilling-machine.= A machine for drilling holes in metal. =Driver.= 1. A device for driving work in the lathe and sometimes called a dog or carrier. 2. A gear wheel which drives another. =Drop-hammer.= A forging or stamping hammer which is lifted by power and let fall of its own weight. =Drunken thread.= A screw thread that is not a true spiral, but is waved in its course. =Duplex slide-rest.= A feed motion in which there are two slide-rests in one slide-way. =Dutchman.= A piece let in to restore a worn part, or to hide a defect. E =Edge-moulding machine.= A machine for dressing the edges of wood-work to shape, and usually for forming a moulding thereon. =Emery grinder=, _or_ =emery-grinding machine.= A machine in which emery wheels are used to grind the work. =Emery wheel.= A wheel composed of emery cemented together under pressure. =Endless screw.= A short length of screw formed to drive the teeth of a worm wheel. =End-mill.= A milling-machine cutter, having teeth on its end face. =Engine-lathe.= A lathe having a feed motor for the cutting tool. =Epicycloid= ([)e]p-i-s[=i]'-kloid). A cycloidal curve in which the rolling circle is rolled outside the fixed or base circle. =Equalizing-file.= A file that is slightly thicker in the middle than it is at either end. =Expanding-chuck.= A chuck that is capable of expanding to accommodate a slight variation of work-diameter and usually holding the work from its bore. =Expanding-mandrel.= A mandrel whose diameter may be varied, usually by means of moving jaws or pieces. =Expansion-joint.= A joint capable of permitting the parts it connects to expand and contract under variations of temperature. =Extension-bit.= A bit in which a cutter can be set so as to bore different sizes of holes. =Extension-lathe.= A lathe whose bed is in two longitudinal divisions so that the upper one may be moved endways and thus form a gap to let chucked work of large diameter pass. F =Face.= 1. The broadest surface of a piece, or that having the largest area. 2. The circumferential surface of a wheel or pulley. 3. A surface on a gear-wheel tooth. =Face-cam.= A cam in which the actuating surface is on its side or sides. =Face-cutter.= A milling cutter having its teeth upon its circumferential surface. =Face-plate.= A plate or table having a plain or flat surface for holding work. =Facing-cutter.= A cutter for levelling a face or surface. =Farrar planer.= A wood-planing machine in which a travelling bed is used to feed the work to the cutter head. =Feather.= A key that is fast in one piece of the work, and an easy fit to the other, so that the latter may be moved along the feather. =Feed-motor.= That part of a machine that feeds either the work or the tool, so as to put on the cut. =Feed-rolls.= Rolls that move the work to machines or to cutting tools. =Feed-screw.= A screw that is used to feed the cutting tool in a machine. =Fence.= A plate in a wood-working machine, against which the work is set or moved to hold it in proper position for the cutting operations. =Fiddle-drill.= A drill that is revolved back and forth by a device similar to a fiddle-bow. =Fifth wheel.= The circular slideway that enables the front axle of a vehicle to turn horizontally. =File.= A hand tool for cutting metal, wood, ivory, bone and all other hard substances except stone. =File-card.= A wire-brush for cleaning files. =Fillet.= A curved piece for filling in a corner. =Fillister-head.= A screw-head that is cylindrical and contains a screw slot. =Firmer-chisel.= A stout carpenter's chisel that is used for cutting out mortises and similar heavy work. =Fit-strip.= A projection usually about an inch wide that is intended to be fitted to bed the piece properly and save bedding the whole surface of the piece. =Fixture.= A device for holding work in an exact position, true with some one face, hole, or pin, as the case may be. =Flat-chisel.= A wedge-shaped machinist's chisel. =Flat-drill.= A drill whose body is rectangular in cross-section. =Flatter.= A swage for flat surfaces. =Fleam.= Acuteness given to saw teeth by filing their front faces at an acute angle to the plane of the saw blade. =Flexible shaft.= A shaft composed of wire, similar to a wire rope, for transmitting rotary motion, notwithstanding that the shaft may be an arc of a circle. =Flooring-machine.= A machine for planing and matching at the same time, and generally used for floor boards. =Flute.= A groove. =Fly-cutter.= A cutting tool fastened in an arbor or spindle, and used for producing irregular shapes. =Follower.= A gear wheel that receives motion from another gear wheel. =Follower-rest.= A rest that steadies work on the lathe and travels with the slide rest. =Foot-block.= A work-holding device containing a dead centre, used upon a milling machine. =Foot-lathe.= A lathe operated by foot-power. =Fore-plane= _or_ =jack-plane.= A roughing out plane. =Forging.= A piece or part that has been forged into shape. =Fork-centre.= A centre used to drive woodwork in the lathe. =Fork-scriber.= A double pointed tool used by boiler-makers to mark small circles. =Former.= 1. A piece that acts as a guide to control the movement of a cutting tool. 2. A template or block on which a piece is bent or shaped. =Fox-lathe.= A brass finisher's lathe, having a turret head and spiral thread-cutting devices that obviate the use of a lead screw or change gears. =Friction-clutch.= A clutch that operates by frictional contact. =Friction-gearing.= Wheels that transmit motion by the frictional contact of their circumferences. =Friction-rollers.= Rollers employed to reduce the friction of the parts. =Friction-wheel.= A wheel that drives by the frictional contact of its surface. =Friezing-machine= _or_ =edge-moulding-machine.= A machine for cutting mouldings on the edge of wood work. =Front-tool.= A tool having its cutting edge in front, and used for plain surfacing work. =Fuller.= A blacksmith's tool for spreading the metal in any particular direction. G =Gang-drill.= A drilling machine on which a number of drills may be used simultaneously. =Gang-edger= _or_ =gang-edging machine.= A machine in which a gang of saws are employed to trim the edges of boards or cut them to width. =Gang-mills.= Milling machine cutters that are placed in gangs and side by side on the same arbor. =Gap-lathe= _or_ =break-lathe.= A lathe having a gap in its bed to enable the chucking of work that would not otherwise pass over the bed. =Gauge.= 1. A standard of measurement. 2. A standard of shape. =Gear.= A term applied to a piece of mechanism that accomplishes a single object: thus a valve-gear operates a valve; a steering-gear steers the vessel. =Geared.= Placed in gear or connected together. =Gear-wheel.= A wheel provided with teeth to engage with similar teeth upon another wheel. =Generating-circle.= The circle that is supposed to move in the construction of cycloidal curves. =Gib.= 1. A piece that may be set up to take up the wear. 2. A piece for holding a strap, and forming an abutting piece for a key. =Gimlet.= A wood-boring hand tool, having a threaded conical end to pull it to its cut. =Gimlet-bit.= A fluted gimlet having no thread at its end, but a spiral flute so shaped as to pull the bit forward to its cut. =Gland.= A piece enveloping a stem and used to make a tight working joint. =Globe-valve.= A valve, having a spherical body, used in pipe-work. =Goose-neck.= A frame affording a fulcrum for a ratchet brace. =Gouge.= A wood-cutting hand tool that is curved in its cross-section. =Gravis.= A hand tool, rectangular in cross-section and having cutting edges at its end that are formed by grinding the end face at an acute angle to the body of the tool. =Groove-cam.= A cam in which the actuating surface is in the form of a groove. =Ground joint.= A joint that is finished by grinding the parts together, usually with oil and emery. =Guide-bar= _or_ =slide-bar.= A bar that forms a guide for the crosshead of an engine or other moving piece. =Gum.= 1. The bottom of the space between saw teeth. 2. A rubber-like substance formed of oil that has dried. H =Hack.= A tool used for cutting iron in two under a steam hammer. =Hack-saw.= A saw held in a frame and used by hand for cutting metal. =Half-check joint.= A joint in which a piece is let into the other, so that the surfaces come level. =Half-round file.= A file that is half round in cross-section. =Hand-file.= A superior class of file that is parallel in width and thickest in the middle of its length. =Hand-hammer.= A hammer that can be used in one hand. =Hand-lathe.= A lathe with which hand cutting tools are used. =Hand-nut.= A nut that may be screwed up by hand without the aid of a wrench. =Hand-planer.= A wood-planing machine in which the work is fed by hand. =Hand-rest.= The rest on which hand-turning tools are supported in a lathe. =Hand-tap.= A tap that is used by hand. =Hand-vise.= A small vise for use in the hand. =Hanger.= A frame that is bolted to another frame or part, and carries another piece, usually a shaft of some kind. =Hardened.= Hardened steel is that which has been made hard by heating to a cherry red and suddenly cooling it, usually by quenching it in water. =Hardy.= A blacksmith's chisel that fits into the anvil. =Heading-block.= A block used in upsetting the heads of bolts or pins. =Heart-shake.= A split radiating from the centre of a log. =Heating-surface.= That part of the surface of a steam-boiler that receives heat on one side and has water on the other. =Heel-tool.= A hand turning tool having a projecting heel to cross the tool rest, and usually held in a wooden stock or handle. =Herring-bone tooth.= A form of gear wheel tooth in which the tooth, instead of passing direct across the wheel face, curves partly around the circumference and then back again, so that the two ends of the tooth only are opposite to each other. =Hindley's-screw.= A short length of screw used to drive a worm wheel, and sometimes termed an endless screw. =Hob= _or_ =hub.= A tool for cutting the threads on screw cutting tools, such as chaser dies. =Hour-glass screw.= A worm or tangent screw which is formed to envelop part of the arc of circumference of a worm wheel, and therefore assumes in outline the form of a sand hour-glass. =Hunting-tooth.= An extra tooth put into a pair of gear wheels that would otherwise contain the same number of teeth, the object being to prevent the same teeth from always falling together. =Hypocycloid= (h[=i]-po-s[=i]'kloid). A cycloidal curve in which the rolling circle is rolled within the fixed or base circle. I =Idle pulley= _or_ =guide pulley.= A pulley employed to guide a belt. =Independent chuck.= A chuck in which each jaw is operated separately. =Index-plate.= A plate having holes or notches accurately dividing a circle into equal divisions. =Inserted-tooth cutter.= A cutter in which the teeth are inserted in a disc or head. =Inside calipers.= Calipers used to measure inside dimensions, as boxes, recesses, etc. =Intermediates.= The wheels that are between the front driver and last follower of a train of gear wheels. =Involute.= A curve generated by the path of a given point in a straight line, as the line is rolled upon a circle. (Vol. I. p. 31.) J =Jack-plane.= A plane employed to rough out the work. =Jig.= A device for holding work and guiding the operating tool. =Jointing-machine.= A machine for truing the surfaces of wood-work that are to form a joint. =Journal.= That part of a shaft that runs in a bearing which guides or limits the motion of the shaft. =Jump= _or_ =upset.= To enlarge at the end by a forging process. K =Kerf.= The passageway or slot cut by a saw. =Key.= A rectangular wedge for locking two pieces together. =Knife.= The cutting tool used on a wood-planing or wood-splitting machine. =Knurling-tool= _or_ =milling-tool.= A tool used to press indentations into the edges or upon the surface of metal, in order to increase the hand grip of it. L =Land.= That part of a tap or a reamer that lies between its plates and carries the cutting edges or teeth. =Lantern.= A primitive form of gear in which rungs are used instead of teeth. =Lap.= A grinding device consisting of a lead or other soft metal surface, on which emery and oil is used. =Lap-joint.= A joint in which one piece overlaps the other. =Lap-weld.= A weld in which both pieces are beveled at the ends and one end overlaps the other where the two are put together to weld. =Lathe.= A machine that revolves work to be operated by cutting tools. =Lathe-bed.= The frame that carries the head and tail stock of a lathe, and that rests upon a solid foundation. =Lathe-carriage.= The sliding piece that carries the tool rest of a lathe. =Lathe-centre.= The piece or part of a lathe that enters the coned recess of lathe work that is held between centres. =Lathe-saddle.= The sliding piece that carries the tool rest of a lathe. =Lathe-shears.= The frame of a lathe that carries the head and tail stocks, and that rests on legs. =Lead-screw.= A screw for a lathe that is used for screw cutting only. =Left-hand thread.= A screw thread in which the nut must be revolved in a direction opposite to that in which the hands of a watch move, in order that the nut may screw upon the bolt. =Leg-vise.= A machinist's or blacksmith's vise having legs. =Line of centres.= A line, real or imaginary, passing from one centre to another. =Line out.= To mark on work lines denoting the depth of surface that is to be cut away. =Liner.= A piece of iron put behind or upon a piece to take up its wear. Line-shaft. A shaft employed to transmit motion from an engine or motor to distant points. =Link.= A piece having holes or pins at its end to connect two other pieces together. =Live centre.= The centre of the live spindle of a lathe. =Live spindle.= The revolving spindle of a lathe. =Loose.= A term used to denote a part of a plate or saw that is not under tension. =Lost motion.= Motion that is not transmitted on account of the looseness of the parts. =Lug.= A small projection. M =Machine-bolt.= A bolt and nut of the sizes kept in stock by machinery dealers, the bolt usually being black or unturned. =Machine-screw.= A small screw made to the Birmingham wire gauge. =Machine-tap.= A long taper tap used in threading nuts in a machine. =Machine-tool.= A machine that performs work by means of cutting tools. =Mandrel.= 1. A cylindrical piece which is driven into hollow work and holds it while it is turned in the lathe. 2. A piece or bar on which work is driven or forced. 3. A shaft running in bearings. =Mangle-wheel.= A gear wheel whose teeth are so arranged that the wheel is reciprocated back and forth on its centre, and does not make a full revolution. =Marking-gauge.= A tool used by wood-workers to draw a line upon work. =Master-tap.= A standard tap used for producing thread-cutting tools, or kept as a standard of size. =Matched.= A board that has a tongue on one edge and a groove on the other so that the edges of the boards will match or be fitted together. =Matching-machine= _or_ =matcher.= A wood-working machine which cuts a groove on one edge and a tongue on the other edge of a board or piece of work. =Measuring-machine.= A machine for determining the measurement of a piece. =Micrometer.= (m[=i]-kr[)o]m'e-ter). A tool for measuring to minute fractions of an inch. =Mill-file.= A single cut file used for filing sheet steel, saw teeth, etc. =Milling-cutter= _or_ =mill.= The cutter or cutting tool used in a milling-machine. =Milling-machine.= A machine in which revolving cutters are used to dress the surfaces of metal and cut them to size and shape. =Mitre-cutting machine.= A machine for cutting mitre joints. =Mitre-joint.= A joint at an angle of 45 degrees to the plane of the pieces it joins. =Mitre-wheel.= A bevel gear having its teeth at an angle of 45 degrees to its shaft. =Mortise.= A recess slot usually square or rectangular, and employed to receive a tenon from another piece. =Moulding-cutters.= The cutters employed to produce mouldings on wood. =Multiple-drilling machine.= A drilling-machine in which more than one drilling-tool may be used, and separate and successive operations may be performed upon the work, carrying it from one drill-spindle to another. =Mute-pulley.= A belt-guiding pulley that can be adjusted to various positions upon its stand. N =Nail-bit.= A boring tool for wood, used for cutting across the grain of wood. =Nut.= A threaded piece for receiving a screw. O =Odontograph= ([=o]-d[)o]n'-to-gr[)a]f). An instrument employed in making or drawing gear-wheel teeth. =Oliver.= A foot-power hammer used by blacksmiths, mainly for forging bolts or studs. =Outside-calipers.= Calipers used to measure external surfaces. P =Panelling-machine.= A machine for cutting mouldings upon panels. =Parallel-file.= A file whose thickness is equal from end to end. =Parallel-vise.= A vise in which the gripping face of the movable jaw is maintained parallel to that of the fixed jaw. =Paring-chisel.= A wood-worker's chisel that is pushed to its cut by hand pressure. =Pattern-lathe.= A lathe designed for the use of pattern-makers. =Pawl.= A tongue that engages with a ratchet. =Pene= (p[=e]n) _or_ =pane.= The lightest end of a hammer. =Pening= (p[=e]n'ing). The hammering of the surface of metal in order to stretch it and alter the shape of the piece. =Pillow-block=, =pillar-block= _or_ =plumber-block.= A piece that affords a bearing for a shaft and is bolted to a pillar or frame. =Pin-block.= A wooden block used to steady small pins when filed in the vise. =Pinion.= The smallest wheel in a pair of wheels or in a train of gearing. =Pin-wrench.= A wrench having a pin to enter holes in the nut. =Pipe-cutter.= A hand tool for cutting pipe into lengths. =Pipe-die.= A tool for cutting threads on pipes. =Pipe-tongs.= A hand tool for gripping pipes. =Piston.= 1. That part of a steam-engine that moves under steam pressure. 2. A disc that fits a bore and slides therein. =Pitch.= The distance apart of two pieces. =Pitch-circle.= A circle drawn through these parts in a gear wheel where the face of the tooth meets the flank, this circle representing the diameter of the wheel for calculations involving its velocity. =Pitch-line.= A part of a pitch circle. =Pitman.= A name sometimes given to a connecting rod. =Planer-shaper.= A metal-cutting machine in which the ram or slide carrying the tool is moved after the manner of a planing machine. =Planimeter= (pla-n[)i]m'-e-ter). An instrument for finding the area of irregularly shaped plane surfaces. =Planing-machine.= 1. For iron. A machine having a travelling work-table sliding in guideways, the tool being carried in a slideway that spans the table, two or more slide-rests are used in the larger-sized machines. 2. Wood-planing machine. A machine in which the work is fed to a revolving shaft or head carrying long planing knives. =Platen.= 1. A work-holding table. 2. The plane surfaced plate which presses on the type in printing. =Play.= Looseness of fit. =Plug.= The interior piece of a cock. =Plug-and-collar gauge.= A pair of gauges for the same size, the plug being sometimes termed the male and the collar the female gauge. =Plug-tap.= A tap that follows the taper taps and has but two or three of its teeth eased off at the end. =Plumb-level.= A levelling tool depending for its accuracy on a weighted line and an edge that is straight. =Plumb-rule.= A straight edge containing a plumb-bob. =Pod-bit= _or_ =nose-bit.= A wood-boring tool, having a cutting lip at its end. =Point.= The surface or the extremity of a gear-wheel tooth. =Polishing-lathe.= A lathe that is used for polishing and therefore requires no tool-carrying devices. =Poppet-head.= The main head of a lathe. =Porter-bar.= A bar for handling heavy forgings, which is welded to the forging and afterwards cut off. =Pressure-bar.= A bar or piece that presses the work to the table in a wood-planing machine. =Protractor.= A tool having a blade which may be set to the degrees of a circle which are marked upon the back or stock of the protractor. =Pulley.= A wheel that receives or drives a band, belt or rope. =Pulley= _or_ =belt-pulley.= A wheel that drives or is driven by a belt. Q =Quadrant.= 1. A piece forming one-fourth of a circle. 2. A piece forming the segment of a circle. =Quick return.= A motion by means of which a head ram or work-table is moved faster during its return traverse than during its cutting traverse. R =Rabbet.= A step at the end of a piece of wood. =Rabbeting-plane.= A plane for rabbeting. =Rack.= A straight body, having on it, (1) teeth corresponding to the teeth in the wheel that drives it or that it drives; (2) notches to engage a pawl or ratchet. =Rack-feed.= A feed motor in which the work-table has a rack driven by a gear-wheel. =Rake.= The inclination of the front face of a cutting tool to the body of the steel of which it is made. =Ratchet.= A pawl or tongue one end of which engages in notches in a rack or wheel. =Ratchet-brace.= A hand-drilling device, in which a lever carries a pawl that engages with a ratchet-wheel, which drives the drill. =Rat-tail file.= A taper round file of small diameter or less than one-fourth of an inch. =Reamer=, =rymer=, _or_ =rimer.= A tool for smoothing and enlarging bores or holes. =Recut-file.= A file whose original teeth have been ground off and new teeth have been cut. =Red-marking.= A mixture of Venetian red and common oil, used to put on a piece of work when trying its fit, and serving to denote the fit. =Return-cam.= A secondary cam used to move a piece back, after the main cam has moved it forward. =Reverse-keys.= An arrangement of keys or wedges, that releases two pieces that have been keyed together. =Rib.= A projecting strip usually employed to strengthen a piece, as the arm of a wheel. =Right-hand thread.= A screw thread in which, with the end of the bolt towards you, the top of the nut must revolve from left to right like the hands of a watch in order to cause it to screw upon the bolt. =Rip-saw.= A saw whose teeth are shaped to cut lengthways of the grain of the wood. =Rod-feed.= A feed motion that is operated by a rod. =Roll-feed.= A feed motion in which the work is fed to the cutting tool by revolving rolls. =Rope-socket.= A socket in which the ends of a wire rope are secured. =Rose-bit.= A reamer that cuts at the end only. =Rotary planer.= An iron planing machine in which a number of cutters are set in a revolving face plate that is fed to the cut by a head on a slide. =Round-nosed chisel.= A machinist's chisel whose cutting edge is shaped so as to cut a groove circular in cross-section. =Round-nosed tool.= A tool whose cutting edge is circular in its course or length. =Routing-machine.= A machine using a revolving cutter to cut away some parts of a surface and leave the rest in relief. =Rust-joint.= A joint that is made by being filled with cast-iron cuttings mixed with sal-ammoniac and sulphur to cause the cuttings to rust and form a solid body. S =Safe-edge file.= A file having no teeth upon one of its edges. =Sanding= _or_ =sand-papering machine.= A machine in which sand-paper-covered rollers or wheels are used for finishing wood-work. =Saw-arbor.= The arbor or mandrel on which a circular saw is driven. =Saw-bench.= A circular saw machine. =Saw-gummer.= A machine for deepening the spaces between saw teeth. =Saw-packing.= Plaited hemp that is packed on both sides of a circular saw to warm it and equalize its tension when it is running. =Scale.= 1. A rule or measuring device having lines of division upon it. 2. Proportion of size. =Scarf.= The bevel of a piece of metal that is to be lap welded. =Scraper.= A hand tool that scrapes rather than cuts the metal. =Screw-cutting lathe.= A lathe that has a screw feed with change gears to enable it to cut threads or screws upon the work. =Screw-cutting lathe with independent feed.= A lathe that has a lead screw for cutting threads and a separate feed motion for ordinary tool traverse. =Screwing-machine.= A machine used to cut screw threads. =Screw-machine.= A form of lathe in which the spindle is hollow and a revolving head or turret is employed to carry the cutting tools. =Screw-plate.= A tool for cutting external threads on small work. =Screw-thread.= The thread upon a screw or other piece of work. =Screw-tool.= Another name for a chaser. =Scribing-block= _or_ =surface-gauge.= A tool that carries a needle or scriber for marking on work lines denoting its finished size or the amount of metal that is to be cut off, and that is also used for setting work. =Second-cut file.= A file whose teeth are coarser than a _smooth_ file and finer than a bastard file. =Sector.= A device used in connection with an index plate to denote the holes to be used in any particular division of a circle. =Segment.= A piece having the shape of a segment of a circle, used for building up a hollow cylinder. =Segmental saw.= A saw that is composed of parts secured to a frame or disc. =Self-acting lathe.= A lathe having an automatic feed motion for the cutting tool. =Set.= 1. The bend to one side of the body of the blade of the teeth of saws. 2. Adjustment or alignment. 3. Binding two pieces together. =Set-screw.= A screw that binds or secures two pieces together by being screwed through one piece and against the other. =Shafting-rest.= A slide rest carrying several cutting tools and usually employed for turning shafting in the lathe. =Shake.= A crack in timber. =Shank-mill.= A milling machine cutter that is provided with a shank or stem. =Shaper-centres.= A chuck in which the work is held between centres. =Shaper= _or_ =shaping-machine.= 1. A machine for cutting such surfaces on iron work as can be cut by a tool travelling in a straight line. 2. A woodworking machine in which cutting tools are revolved on an upright spindle projecting above a work table. =Shavings.= The cuttings from a paring tool. =Shell.= 1. The body of a steam-boiler. 2. An outer casing. =Shell-reamer.= A short reamer that is driven by fitting to a coned mandrel. =Shimer-heads.= A form of cutter head for woodworking machines, in which circular cutters are used. =Shingle saw.= A saw thick in the body and beveled off for about two or three inches of its outer diameter. =Shooting-board.= A device upon which pieces are held when required to have their ends dressed to exact shape or angle. =Shrinkage-fit= _or_ =contraction-fit.= A means of securing two pieces together by leaving the hole of one too small to receive the other, and then expanding the piece containing the hole so that it will go on and bind fast as it cools and contracts. =Side-chisel.= A machinist's chisel shaped to cut on the sides of slots or keyways, and having its cutting edge on one side of the end facet. =Side-tool.= A tool used to cut the ends of lathe work that is held between the lathe centres. =Single-geared lathe.= A lathe in which there is no back gear. =Single-riveted joint.= A joint having but one row of rivets in a lap joint and one row of rivets on each side of the plate joint in a butt joint. =Single-thread.= A screw thread having a single spiral. =Skew-bevel.= A bevel gear wheel in which the teeth sides do not form lines radiating from the wheel centre, but point to one side of it. =Skew-chisel.= A carpenter's chisel in which the cutting edge is not at a right angle to the body of the tool. =Skew-cutter.= A cutter in which the cutting edge does not stand parallel to the axis of the shaft that drives it. =Slab.= 1. A rough square piece of iron forged from scrap. 2. The first piece cut from the side of a log of wood. =Sleeve.= An enveloping piece that is usually cylindrical and too long to be termed a ring. =Slide-valve.= The valve that governs the admission of steam into and its exhaust out of a cylinder. =Slot.= A rectangular passage or hole passing entirely through the material. =Slotting-machine.= A machine having a vertical bar or ram that carries the cutting tool on its lower end and has a vertical reciprocating motion. =Smooth-file.= The finest cut of file that is made for ordinary use. =Smoothing-plane.= A carpenter's short plane for producing a smooth surface. =Socket.= A piece that is hollow and receives another. =Socket-wrench.= A wrench that envelops the whole of the head of a bolt. =Solid milled cutters.= Cutters for woodwork, in which an irregular shaped cutting edge is obtained by recesses cut in the flat face of the cutter. =Space= _or_ =spaces.= The opening between the teeth of gear wheels. =Spanner.= A form of wrench. =Spindle.= A shaft that is used to transmit purely rotary motion, and that is usually of small diameter in proportion to its length. =Spiral cutter.= A milling cutter having its teeth cut spirally and not parallel to the axis of its bore. =Spiral head.= A device for holding work and revolving it in a milling machine. =Spirit-level.= An instrument in which an air-space or bubble is utilized to disclose whether the surface upon which the spirit level is laid is horizontal. =Spline.= A long feather-way. =Split-pin.= A pin that is split so that its end can be opened out to prevent its coming out of place. =Spoke.= The arm that connects the hub of a wheel to its rim or felloe. =Spoon-bit.= A wood-boring tool that is shaped somewhat like a gouge. =Spring.= 1. A piece of elastic metal. 2. The movement or deflection of a piece of metal on a tool, by its own weight or from the strain placed on it. =Spring-tool.= A tool so formed as to have a slight give or spring to it. =Spur.= A sharp cutting edge placed on some kind of wood-cutting tools to sever the fibre before the cutting edge removes the wood cuttings. =Spur-wheel.= A gear-wheel having its teeth upon its circumferential surface. =Square-centre.= A lathe centre having four cutting edges at its coned end. =Square thread.= A screw-thread that is rectangular in cross-section. =Stanchion= (st[)a]n'shun). A vertical frame. =Standard.= An upright piece. =Standing-bolt.= A bolt that screws into the work, and does not therefore require a nut. =Stave.= 1. A piece that forms part of a hollow wooden casing. 2. A pin on a gear-wheel that has pins instead of teeth. =Steady-rest= _or_ =back-rest.= A device for steadying work in the lathe. =Steam-boiler.= A boiler used to generate steam and hold it at a pressure above that of the atmosphere. =Steam-hammer.= A forging machine in which the hammer is raised or lifted by steam, and is sometimes also forced downwards by steam. =Steam-space.= That part of the boiler that is above the level of the water. =Sticker.= A machine that operates on wood of small cross-sectional area in proportion to its length, such as picture frame moulding. =Stock.= Material. =Stocks-and-dies.= Tools for cutting external threads by hand. =Stop.= 1. A piece that arrests the motion of another piece. 2. A part of a gauge, against which the work abuts. =Stop-motion.= A device for preventing the overwinding of clocks and watches. =Straddle-mills.= Milling-machine cutters that are used in pairs and straddle the work, both cutters being of the same diameter. =Straight edge.= A piece or strip having one or both edges made straight to use as a guide in testing work. =Stub end.= The end of a connecting rod. =Stud.= 1. A bolt that screws into the work at one end and receives a nut at the other. 2. A piece that screws into the work at one end. =Stuffing-box.= The box in which a gland fits. =Surface-plate.= A plate having a true flat surface to test the flatness of work by. =Swage.= A blacksmith's tool for smoothing and shaping surfaces. =Swing-frame.= A frame having a movable stud for carrying the change gears of a lathe. =Swing-saw.= A saw that is suspended in a swinging frame. =Swivel-vise.= A vise that may be swiveled or revolved upon its base plate. T =[T]= or =tee=. A pipe fitting having two bores at a right angle, one to the other. =Tailstock= _or_ =tailblock.= That part of a lathe that carries the dead centre. =Tangent-wheel.= A wheel whose teeth are formed to work with a screw or worm. =Tap.= 1. A tool for cutting threads in holes or bores. 2. A device for shutting off or turning on the flow of water through a pipe. =Taper-tap.= A tap that has part of the thread turned off in order that it may enter the hole easily and start to cut the thread. It is sometimes termed the first tap. =Tapped.= 1. Threaded internally. 2. Having a connection that branches from the main pipe or flow. =Target.= A frame used in setting shafting in line. =Temper.= 1. The degree of hardness that has been imparted to steel by heating and suddenly cooling it. 2. A term employed by steel makers with reference to the percentage of carbon contained in steel. =Tempering.= Tempering consists in reheating hardened steel and thus modifying or reducing its degree of hardness. =Template= _or_ =Templet.= A piece of metal made to shape, to serve as a pattern for one or more of the work surfaces. =Thread-gauge.= A threaded cylinder or bore that serves as a standard of reference for the shape and diameter of a screw thread. =Threading-tool.= A tool for cutting screws in the lathe. =Throw-line.= The travel of a piece, moved by an eccentric. =Thumb-nut.= A nut so shaped that it may be screwed up or unscrewed by hand. =Tight.= A term used to denote those parts of a plate or saw that are under undue tension, and prevent the other parts of the plate from lying flat. =Timber-planer.= A wood-planing machine for thick work, usually having side heads as well as cutter bars. =Tire.= The iron band surrounding a wheel rim. =Tit-drill.= A drill having a point or teat, and employed to cut flat-bottomed holes. =Tool-post.= The device employed in a slide-rest to grip the cutting tool. =Train.= An arrangement of gear wheels in which there are more than two gear wheels employed. =Trammels= _or_ =tram.= A device for measuring distances too great to be measured by ordinary compasses. =Trip-hammer.= A forging machine in which the helve or hammer holding beam is tripped by a revolving cam. =Trundle.= A gear-wheel having rungs in place of teeth. =Trying-up.= A term usually employed to indicate that the work is accurately done or fitted. =Try-square.= A tool having a rectangular back, and a blade whose edges are a right angle to the edges of the back. =[T] Slot.= A slot or groove, shaped to receive a bolt head and prevent it from turning when the nut is screwed up. =Turnbuckle.= A socket that receives and holds the ends of two rods and permits either to be revolved independently of the other or the socket to be revolved without revolving either rod. =Turret-lathe.= A lathe in which a revolving head or turret carries the cutting tools. =Tuyère= (tw[=e]'ar). The nozzle through which air is forced into a blacksmith's fire, a furnace or a cupola. =Twin-mills.= Milling cutters that are used in pairs, and have teeth on their side faces as well as upon the circumference. =Twist-drill.= A drill having a spiral flute along it. =Twist-hammer.= A sawmaker's hammer having its two faces parallel, so that by turning it over in the hand its marks will be in opposite directions. =Two-jawed chuck.= A chuck having two jaws. U =Universal chuck.= A chuck in which the jaws move simultaneously. =Universal joint.= A joint or connection that permits a piece to be moved about in any required direction. =Universal milling-machine.= A milling-machine that is capable of cutting spirals, and is provided with an index head. =Upright.= A vertical post or frame. =U. S. standard thread.= A V-shaped thread having a flat place at the top and bottom. V =Vernier= (vër'ni-er). A measuring device in which two sets of lines of division are employed, one set being narrower spaced than the other, but so spaced that in a certain number of divisions the two end lines of each piece measure exactly alike: this provides a means of making a minute measurement. =Vise.= A work-holding device in which one jaw is movable and the other stationary. =Vise-clamp.= A piece of metal placed on the vise jaw and passing between it and the work to prevent the jaw teeth from indenting the work. =[V]-thread.= A V-shaped thread, sharp at the top and bottom. W =Warding file.= A thin file suitable for filing out the wards of the keys of door locks, etc. =Washer.= A perforated disc of metal, usually forming a seating for some other piece as a rest or a pin. =Wheel lathe.= A lathe for turning wheels. =Whitworth's quick-return motion.= A mechanism employed to move a cutting tool faster on its return than on its cutting stroke. =Whitworth's thread.= A screw thread designed by Sir Joseph Whitworth, and having a rounded top and bottom. =Winding strips.= A pair of straight edges, used to detect any wind or twist in surfaces that ought to be parallel. =Wing-nut.= A nut having wings so that it may be screwed up with the fingers. =Wire-gauge.= A gauge having notches in it that are standards of size for wire, for the thickness of sheet metal, for screws, etc., etc. =Worm-wheel.= A wheel whose teeth are formed to work with a worm or screw. =Wrench.= A tool for turning nuts, etc. Y =Yoke.= A piece that embraces two other pieces to hold them together, or adjust their distance apart. INDEX TO THE TWO VOLUMES. A Absolute steam pressure, ii, 411. Accidents to locomotives, ii, 402. Accurate standards, i, 341. Admission of steam to indicator, ii, 414. point of, ii, 376. Adjustable centre rest, ii, 14. chucks for true work, i, 235. cutters, i, 448. with half-round bit, i, 281. die stock, i, 448. drivers for bolt-heads, i, 224. end measurement gauges, i, 377. or jamb dies, i, 98. planes, ii, 269. reamers, i, 189, 284, ii, 99. shell reamers, i, 284. tap wrenches, i, 110. taps, i, 104. wrenches, various forms of, i, 125. Adjusting connecting rod brasses, ii, 385. length of connecting rods, ii, 126. main bearings, ii, 386. parts of a locomotive, ii, 404. Adjustment of band saws, ii, 309. by differential screw, i, 119. Advantages of face cutters, i, 108. of involute gear teeth, i, 34. Air brake for locomotives, ii, 398. Air chambers, ii, 388, 441. Air pumps, ii, 441. Aligning connecting rods, ii, 119, 124. Alignment in crank pins, errors, ii, 169. of cranks, testing the, ii, 167. of lathe tail stocks, i, 145. Allen valve, ii, 377. Allowance, for contraction fits, i, 366. for hydraulic fits, i, 365. Alteration of shape of threads from the wear of tools, i, 89. Angle irons, welding of, ii, 236. of clearance in lathe tools, i, 257. plate chucking, examples of, i, 251. plates for planer tables, i, 418. valve patterns, ii, 283, 284. Angles for the facets of scrapers, ii, 97. of cutting edges of chisels, ii, 74. of thread cutting tools, i, 91. Angular advance of eccentrics, ii, 380. cutters, ii, 19. cutters for groove cutting, ii, 27. of helical teeth, i, 69. teeth, and thrust of, i, 69. herring-bone, i, 69. velocity of gear-wheels, i, 6. Angularity of connecting rods, ii, 375. Annular emery wheels, ii, 47. wheels, i, 1. compared with spur, i, 32. Anvils, ii, 230. Apparatus for oiling, ii, 439, 440. Appliances for bending timber, ii, 265. for tapping standard work, i, 111. Aprons, lathe, feed motion for, i, 168. Apron tools for planers, i, 411. Arbors, adjustable, i, 227. cutter, ii, 25. emery wheel, construction of, i, 198. expanding, i, 227. for eccentric work, i, 229. shell reamers, i, 283. threaded work, i, 228. lathe, i, 227. Arc of approach of gear-wheels, i, 13, 16. of contact of gear-wheels, i, 17, 25. of recess of gear-wheels, i, 13, 16, 20. Area of the indicator diagram, ii, 419. Arms for pulleys, ii, 279. pivoted, for tooth templates, i, 44. Atmosphere, influence of, on oils, ii, 153. Auger bit, i, 453. Augers for end-grain wood, i, 454. Augers for wood boring, ii, 342. Automatic air brake, ii, 398. cut-off engines, ii, 423. engine, high speed, ii, 427. engine, straight line, ii, 428. wheel governors, ii, 427. feed motions, i, 408; ii, 8. gear cutter, ii, 54. nut tapping machine socket, ii, 475. grindstone traversing device, ii, 53. Auxiliary valve, ii, 438, 439. Ax handle lathes, i, 210. Axle boxes, hot, ii, 403. locomotive, ii, 148. brasses, testing, i, 366. Axles, crank, lathes for turning, i, 152. forging, ii, 259. B Babbitting boxes, methods of, ii, 155. Babbitt metal-lined boxes, ii, 155. Back-gear of lathe, i, 135, 145. throwing in and out, i, 165. treble, i, 143. Back-knife gauge lathe, i, 211. Back rest, i, 233. Balanced valves, ii, 377. Balancing cutter heads, ii, 324, 326. emery wheels, ii, 39. pulleys, ii, 202. Ball turning, i, 325. Banking fires, ii, 401. Band saw machines, ii, 308, 311, 312. Band saw guides, ii, 311. teeth, ii, 308-310. pitch of, ii, 309. tension, ii, 310, 311. Bar cutters, boring, i, 289. the shapes of, i, 291. Bar iron, straightening, i, 305. Barometer, graduation of, ii, 416. construction of, ii, 415. Bars, boring, i, 289. boring, with fixed heads, i, 290. Bar steel, forms of, for chisels, ii, 73. Beading bits, ii, 270, 271. Bearings, adjusting, ii, 386. for lead screw, i, 139. of engine lathes, i, 134. of line shafting, ii, 166. surfaces of keys, i, 126. thrust of, ii, 445. various forms of, ii, 147. wear of, i, 158. Beating and pounding, causes of, ii, 168. Bedding brasses in their boxes, ii, 132. Beds, planer, flat guideways for, i, 414. planer, oiling devices for, i, 415. Belt stretching clamps, ii, 210. lacings, covers for, ii, 215. forms of, ii, 214. Belt pumps, ii, 388. shifting mechanism, i, 406, 407. Belts, bevelled joints for, ii, 215. changing or shipping, ii, 217. driving power of, ii, 208-225. friction, coefficient of, ii, 222. grain side, weak, ii, 208. to pulley, ii, 209. guide pulleys for, ii, 211. lap joints for, ii, 215. length of, ii, 209. line of motion of, ii, 217. parts of hide used for, ii, 207. pegged, ii, 215. single and double, ii, 208. stretch of, parts of hide, ii, 208. the creep of, ii, 222. length of, ii, 209. sag of, ii, 210. tension of, ii, 211, 224. torsional moment, ii, 223. [V] or angular, ii, 217. Bench lathes, i, 130. Bending appliances, ii, 226, 265. block for wood, ii, 265, 266. iron, ii, 226, 240. timber, ii, 265, 266. wood, modern methods, ii, 265. Bent files, use of, ii, 93. Bevel gear teeth, originating, i, 22. pinion, drawings for, i, 59. protractors, i, 380. squares, i, 380. wheel, body pattern, i, 59. Bevel wheels, i, 1, 21, 61. formation of the teeth of, i, 22. testing the angle of, i, 60. Bilge injection marine engines, ii, 441. Billiard cues, steady rest for, i, 233. Birmingham wire gauge for gold and silver, i, 387. Bit, half round, i, 281. Bits for wood working, ii, 342. Blacksmith's anvils, ii, 230. drilling levers, i, 456. fire, side blast for, ii, 228. forges, ii, 228, 229. swages, ii, 230, 231. temper, ii, 460. tools, ii, 229, 230. work, swaging, ii, 232. Blade, form of, necessary to produce a given shape of moulding, ii, 77. Block planes, ii, 269. Blocks for filing pins, ii, 104. pillow for shafting, ii, 194. or pillar, patterns for, ii, 277. swage, ii, 232. Blotting paper, oil test, ii, 154. Blowing down boilers, ii, 370. Blows upon plates, effects of, ii, 69. Blow through valve, ii, 440. Boiler fitting joints, ii, 140. Boilermakers, drilling machine, i, 435. drilling machine, feed motion, i, 436. Boilermakers' turning machine, i, 435. Boiler, blowing down, ii, 370. cleaning, ii, 370. evaporative efficiency of, ii, 366. examining, ii, 458. factors of safety of, ii, 355. feed water, ii, 370. feeding, instruction upon, ii, 370. fire cleaning, ii, 369. cleaning tools, ii, 369. for stationary engine, ii, 350. gauge cocks, ii, 368. grate bars, ii, 369. bars, shaking, ii, 369. horizontal, return tubes, ii, 361. lighting the fire under, ii, 368. internally fired, ii, 358. plate, the strength of, ii, 351. settings, ii, 364-366. seams, diameter of rivets, ii, 356. treble riveted, ii, 353. shells, drilling machines for, i, 436. the strains on, ii, 351. the strength of, ii, 350. strains on, ii, 355. the care and management of, ii, 368. tubes, for fire engines, ii, 431. vertical, ii, 359. external uptakes, ii, 361. water gauge glass of, ii, 368. with Field tubes, ii, 359. Boilers, low water in, ii, 370. of marine engines, ii, 436, 437. of steam fire engines, ii, 431. priming in, ii, 370. Bolt-cutting machine, head of, i, 466. dies, i, 473. rapid, i, 467. the construction of dies for, i, 473. with automatic stop motion, i, 466. back gear, i, 467. Bolt-forging, ii, 238. Bolt-threading machinery, i, 468. capacity of, i, 471. construction of, i, 468-472. Bolted connecting-rod straps, ii, 116. Bolt-heads, adjustable drivers for, i, 224. bedding, i, 117. filing, ii, 105. Bolt-holes, classification of, i, 112. Bolts and nuts, table for, i, 114. Bolts, classification of, i, 112. countersunk, i, 112. devices for forging, ii, 238. for foundations, forms of, i, 113. planer tables, forms of, i, 417. quick removal, i, 116. forms of drivers for, i, 224. hook, i, 113. not passing through the work, i, 117. rapid construction of, i, 468. removing corroded, i, 122. self-locking, i, 117. Bore gauge, i, 387. Boring and turning mill or lathe, i, 211. bar, centres for, i, 293. cutters, i, 289. cutters, shapes of, i, 291. bars, i, 289. for taper work, forms of, i, 292. three or four cutters for, i, 290. with fixed heads, i, 290. with sliding heads, i, 290. double-coned work, i, 293. end grain wood, augers for, i, 453. head with nut feed, i, 291. heads, i, 288. lathe for engine cylinders, i, 219. with double heads, i, 220. with traversing spindle, i, 218. mill, i, 211. purposes, chucking lathe for, i, 152. tool holders, i, 287. tools for brass, lathe, and small work, i, 285-287. octagon, holders for, i, 175. the spring of, i, 286. Boring-machine, i, 431. for car wheels, i, 438. wood, ii, 342. horizontal, i, 433. pulley, i, 438. the feed motion of, i, 432. Box wrenches, i, 124. body chucks, i, 237. tools for screw machines, i, 208. Brace drill, i, 455. with multiplying gear, i, 456. ratchet motion, i, 456. Brad awl, i, 452. Brake for lathe pulley, i, 149. for pattern lathe, i, 149. lathe, i, 151. Branch pipe core boxes, ii, 286. Brasses, fitting to their journals, ii, 145. Brasses, for connecting rods, adjusting, ii, 120-127, 130-132. lead lined, ii, 148. oil cavities for, ii, 150. open, ii, 149. various forms of, ii, 127, 147. Brass work, boring tools for, i, 286. front tools for, i, 264. hand tool for roughing out, i, 332. side tools for, i, 264. special lathes for, i, 217. Breast drill with double gear, i, 456. Broaches, construction of, i, 479. Broaching press, i, 478. Broken frames, repairing, ii, 178. Brush wheels, for polishing, ii, 50. speed of, ii, 50. Built-up gearwheels, i, 61. Burnishing lathe work, i, 311. Butt joints, boiler, ii, 352. Butt welds, ii, 236. Buzz planer, ii, 315. By-pass valve, ii, 438. C Calculating the horse power of engines, ii, 407, 419. revolutions of, and power transmitted by, gear wheels, i, 5. speeds of pulleys, ii, 204. strength of gear teeth, i, 65. strength of riveted seams, ii, 354. horse power by indicator diagrams, ii, 418, 419. Calculations, safety-valve, ii, 409. Calendar roll lathe, i, 195, 215. Caliper, the micrometer, i, 354. Calipers, compass, i, 378. holding and using, i, 361, 362. inside, i, 360. spring, i, 360. with locking devices, i, 360. Cam chuck for irregular work, i, 328. motion for an engine slide-valve without steam lap, i, 83. motions, applications of, i, 327. for engines, i, 83. return or backing, i, 82. Cams, finding the pitch line of, i, 80. finding the working face of, i, 80. originating in the lathe, i, 326. return, finding the shapes of, i, 82. Capacity of pumps, ii, 388. of thread cutting machine, i, 471. Cape chisels or cross-cut chisels, ii, 74. Car axle lathe, i, 147. the feed motions of, i, 148. Carpenter's chisel, ii, 77. Carriages, lathe, testing, ii, 182. for lathes, i, 137, 145. Carriers, lathe, i, 222. Car wheels, boring machine for, i, 438. Case-hardening, ii, 128, 442. finished work, ii, 129. preparing work for, ii, 129. Casting pillow blocks, ii, 277. Cast gear, contact of the teeth of, i, 67. iron, internal strains, i, 306. teeth, contact of, i, 67. scale for curves of, i, 51. side clearance, i, 53. Cat head, i, 233. steady rest, i, 233. Caulking tools, ii, 141. Cement chuck, i, 242. Cements used in the manufacture of emery wheels, ii, 38. Centre bit, i, 454. dead, methods of removing, i, 159. drill and countersink, i, 300. chuck, i, 302. drilling lathe attachment, i, 300. chucks for, i, 303. machine, i, 300. live, removing, i, 159. of rough work, i, 301. planer, i, 408. punch, i, 300. guide, i, 301. Centres for boring bars, i, 293. for hollow work, i, 226. lathe, i, 296. shaping machines, i, 397. taper work, i, 226. live, tapers for, i, 159. Centring devices for crank axles, i, 230. square, i, 300. work with the scribing block, i, 301. Chain riveted joints, ii, 352. Chambering or gumming, ii, 290. Change gears, arrangement of, i, 319. gears, compounded, i, 321. table for finding, for screw cutting, i, 180. hanging, i, 158. wheels, pitches of teeth, i, 182, 321. Changing or slipping belts, ii, 217. Chasers, errors in applying, i, 336. forms of, i, 268. holders, i, 268. improved form of, i, 90. outside and inside, i, 335. setting, i, 268. Check valves, ii, 388. Chisels, angle of presentation, ii, 77. angles of cutting edges, ii, 74. blacksmith's, ii, 230. cape or cross-cut, ii, 74. carpenter's, ii, 77. cow-mouthed, ii, 75. curved or oil groove, ii, 76. cutting ends of, ii, 74. diamond point, ii, 76. dimensions of, ii, 74. for wood, ii, 271. handles for, ii, 271. holders, ii, 74. machinist's application of, ii, 76. round-nosed, ii, 76. shapes of cutting edges, ii, 74. the use of, ii, 76. Chucking device for pulleys, i, 318. devices for planer tables, i, 408. errors in, i, 250. lathe for boring purposes, i, 152. machine beds, on a planer, i, 421. on angle plates, i, 251. reamers, for true work, i, 283. the halves of large pulleys on a planer, i, 422. Chucks and chucking, i, 234. Chucks, box body, i, 237. cement, i, 242. combination, i, 237. cone, i, 232. contracting, for lathes, i, 188. drill, i, 446. drill-holding, construction of, ii, 41. expanding, i, 188. for centre-drilling and countersinking, i, 303. large planing machines, i, 422. milling machines, ii, 31. screw machine, i, 205. straightening wire, i, 305. true work, adjustable, i, 235. wood-working lathes, i, 242. independent, i, 238. planer, for curved work, i, 420. planer, for grooved work, i, 419. reversible jawed, i, 237. special forms of, i, 234-241. swivelling, i, 395. tailstock for drilled work, i, 279. the wear of, i, 240. three and four-jawed, i, 237. two-jawed, i, 236. universal, i, 238. various forms of, i, 394. vise, for vise work, i, 396. vise, holding taper work in, i, 394. vise, rapid motion, i, 396. Circle, dividing the, i, 348. rolling, for change gears, i, 16. Circular cutters, i, 272; ii, 22. cutters, tool holders for, i, 272. cutting tools, i, 267. plane, ii, 268. saw gauges, ii, 287. inserting teeth, ii, 290, 291. machine, roll feed, ii, 298, 300. mandrel hole, size of, ii, 287. segmental, ii, 300. stretching by heat, ii, 288. tension, ii, 288. Circular slide valves, ii, 377. Circulating pumps, ii, 440. Circumferential seam strength, ii, 356. grindstone speed, ii, 52. Clamp couplings, ii, 197. Clamping work on face plates, i, 245. Clamps, belt, ii, 210. chucking, i, 245. for steady rests, i, 233. polishing for lathe-work, i, 311. steady rest, i, 233. vise, various forms of, ii, 64. Classification of bolts, i, 112. of bolt heads, i, 112. of lathes, i, 129. of measuring tools, i, 354. Cleaning boilers, ii, 370. files, ii, 94. Clearance in cast gear teeth, i, 53. of front tools, i, 254. of planer tools, i, 424. of taps, i, 102. of tools for square threads, i, 269. of twist drills, i, 274, 275. on cutter, ii, 35. Clements driver, i, 223. Clinker hook, ii, 369. Clip-ended connecting-rod, ii, 115. Clock wheels, i, 21. Clutches, friction, ii, 192. Cocks and plugs, grinding, ii, 144. leaky, ii, 145. Cogged gear-wheels, i, 63. Cogs, durability of, i, 66. strength of, i, 66. thickness of, i, 66. methods of fastening, i, 63. Cold-rolled shafting, ii, 187. Collapsing tap, screw machine, i, 107. taps, tapping machine, i, 107. Collar gauges and standard plug, i, 356. for threads, i, 91. testing, i, 356. Collars for shafting, ii, 189. Color tempering, ii, 460. Combination chucks, i, 237. Combination planes, ii, 269, 270. Combined centre-drill and countersink, i, 300. cutting off tools and holders, i, 273. drilling machine and lathe, i, 433. Compass planes, ii, 268, 269. Compasses, i, 377. Compound engines, ii, 434, 435. slide rest, i, 140. tool holders for, i, 174. Compounded gears, i, 320. Compounds for welding, ii, 234. Compression curve of engines, ii, 422. Compression curve, ii, 415. line, ii, 415. the point of, ii, 376. Concave saw, ii, 287, 288. Condenser, total pressure in, ii, 444. Condensing engine diagram, ii, 415. Cone chuck, i, 232. Connecting-rods, adjusting the length of, ii, 126. angularity of, ii, 375. brasses, adjusting, ii, 385. joint faces of, ii, 122. lining up, ii, 126. double gibbed, ii, 116. ends, tapered, ii, 117. fitting up, ii, 118. keys, ii, 375. keyways, filing out, ii, 120. locomotive, ii, 115. length of, ii, 123. marine engine, ii, 116. marking length of, ii, 123. repairing, ii, 125. setting up keys of, ii, 126. solid-ended, ii, 114. strap-ended, ii, 115. straps, ii, 120. bolted, ii, 116. stepped, ii, 117. trammelling the length of, ii, 122. various forms of, ii, 117. welding up stub ends of, ii, 119. Construction of gland patterns, ii, 276. of groove cams, i, 84. of lathe carriages, i, 137. of emery wheel arbors, i, 198. of tailstock of engine lathe, i, 135. of reciprocating cross-cut saw, ii, 312. of scroll sawing machines, ii, 306, 307. of the barometer, ii, 415. Contact of cast teeth, i, 67. Contracting chucks for lathes, i, 188. Contraction or shrinking fits, i, 366. Convection, ii, 412. Conversion of heat into work, ii, 411. Cope cutters, ii, 344. Core boxes for branch pipes, ii, 286. Core box plane, i, 269. Cored work, drivers for, i, 225. Corliss engine, ii, 423, 424. valve, lap of, ii, 426, 427. valve gear, ii, 424, 425. Correcting the errors of thread pitch caused by hardening, i, 109. Corroded bolts, removing, i, 122. nuts, removing, i, 122. Cotter or keyway drilling machine, i, 438. drills, i, 446. Counterbore and drill, i, 449. Countershafts, ii, 191. Countersink cutters, i, 449. Countersink, for hardened work, i, 303. for lathe work, i, 302. with adjustable drill, i, 300. Countersinking, chucks for, i, 303. Countersinks, i, 285. Countersunk bolt heads, i, 112. Coupling for light shafting, ii, 198. plate, ii, 196. universal, ii, 199. Couplings, clamp, ii, 197. for line shafting, ii, 194. for split sleeves, ii, 195. self-adjusting, ii, 196. Covers for belt lacings, ii, 215. Cow mouthed chisel, ii, 75. Crank, application of slide-rest, i, 152. axles, centring devices, i, 230. axles, lathe for turning, i, 152. drill, i, 457. lathe for turning, i, 154. motion for shaping machines, i, 401. simple, i, 13. placing at right angles, ii, 156. Crank-pin aligning, errors, ii, 158, 170. remedying errors of, ii, 171. riveting, ii, 73. Crank-pins, hot, ii, 386. Crank position, engine starting, ii, 384. Crank-shaft, forging, ii, 248, 249. setting eccentrics on, ii, 174. Cranks, placing at right angles, ii, 156. special lathe chuck for, i, 248. testing the alignment of, ii, 167. Creep of belts, ii, 211. Cropping gauge, ii, 296. Cross-bar, construction of, i, 409. Cross-cut, or cape chisels, ii, 74. saws, ii, 272, 273, 312. Cross-cutting or gaining machine, ii, 305. Cross-feed motion, construction of, i, 138. Cross-files, ii, 91. Crossfiling, ii, 92, 93. Cross-head chucking, i, 251, 253. Cross-heads of steam engines, ii, 375. Crowding of cutters, to avoid, ii, 27. Crowned pulleys, ii, 200. Crowns of brasses, shapes of, ii, 127. Crown wheels, i, 1. Curve of expansion of indicator diagrams, ii, 414. of gear wheel teeth, variation of, i, 12. Curved or oil groove chisel, ii, 76. work, planer chuck for, i, 410. work, turning, i, 314, 315. Curves, compression, ii, 415. marking, by hand, i, 45. of gear teeth for bevel gear, i, 22. templates for, i, 384. Cushioned hammers, ii, 252, 253. Cut, and kinds of rasps, ii, 87. of files, ii, 86. gear-wheel teeth, strength of, i, 65. Cut-off engines, ii, 423. the point of, ii, 376. valves, ii, 378. Cutter, adjustable, i, 448. adjustable on half-round bit, i, 281. angle for worm wheels, i, 43. angle of, for spiral grooves, ii, 29. arbors, ii, 25. boring-bar, the shapes of, i, 291. clearance of, ii, 35. grinding taper, thin edge, ii, 33. heads, ii, 337. heads for planing machines, ii, 320. revolving, for gear teeth, i, 37. Cutters, angular, ii, 18. angular, grooving, setting of, ii, 28. circular, ii, 22. countersink, i, 449. crowding, to avoid, ii, 27. face, ii, 17. fly, ii, 21. for drilling machines, i, 442. edge moulding, ii, 341. friezing machines, ii, 340. moulding machines, ii, 340. mouldings, ii, 336, 337. standard shapes, i, 111. gang or composite, ii, 23. holders for fly, ii, 22. matched, ii, 73. milling, ii, 16. milling, errors in grinding, ii, 32. parallel, fixture for grinding, ii, 32. right and left-hand, ii, 18. rotary, for all kinds of work, ii, 341. shank, ii, 19. sizes of, ii, 17. slide of gear-cutter, operating, ii, 55. spiral, grinding teeth of, ii, 36. tube-plate, i, 448. twin, ii, 18. with inserted teeth, ii, 24. with spiral teeth, ii, 17. Cutting cams in the lathe, i, 326. coarse pitch square threads, i, 269. double threads, i, 322. edge of chisels, angles of, ii, 74. of chisels, shapes of, ii, 74. on drills, clearance, ii, 43, 44. edges for dies, number of, i, 471. for taps, number of, i, 105. ends of chisels, ii, 74. feeds for wrought iron, i, 294. files, ii, 101. gauge, ii, 274. grooves in cylindrical work, ii, 27. helical teeth in the lathe, i, 69. iron when hot, ii, 263. keyways by hand, ii, 108. left-hand threads, i, 322. out keyways by drifts, ii, 109. steam ports, jigs for, i, 441. right and left-hand grooves, ii, 29. right or left-hand thread, single, double, or treble, with same dies, i, 99. screws by the metric system, i, 322. screw thread by hand, i, 62. speeds, examples of, i, 295. for threading dies, i, 474. for wrought iron, i, 294. taper threads, i, 338. threads, multiple, i, 322. on taper work, i, 324. tools, circular, i, 267. producing gauges for, i, 92. power required to drive, i, 273. the utmost duty of, i, 258. wheels, angle of cutter for, i, 43. wood slips, ii, 271. worm-wheel teeth in the lathe, i, 42. Cutting-off machine, i, 193. tool for screw machines, i, 208. tools, i, 262, 273. Cycloidal curves for gear teeth, i, 8. Cylinder boring lathe with facing slide rests, i, 219. cover joints, ii, 137. cover, turning a, i, 318. ends, scraping out, ii, 161. Cylinder heads, knocking out, ii, 402. Cylinders, bores of, ii, 372. clearance in, ii, 372. counterbore of, ii, 372. for steam engines, ii, 372. jacketed, ii, 374. lagging, ii, 374. lubricating, ii, 373. reboring in place, ii, 160. relief valves for, ii, 373. steam, ports of, ii, 373. waste water cocks of, ii, 373. wear of, ii, 372. Cylindrical work, cutting grooves, ii, 27. D Dancing governors, ii, 384. Dead-centre, finding the, ii, 174. methods of removing, i, 159. of the crank, finding the, ii, 172. Deflection of surface plates, ii, 135. Depth of gear wheel teeth, i, 42. Designing slide valves, ii, 380. Detachable slide rest, i, 143. Determining the pitches of the teeth for change wheels, i, 182. Diagram, theoretical, ii, 414. the uses of, ii, 413. Diagrams for condensing engine, ii, 415. indicator, ii, 414. defective, ii, 421. Diameter at the roots of threads, i, 269. of circle for generating curves of gear teeth, i, 10. of the pitch circle of wheels, i, 1. Diameters of line shafting, ii, 189. Diametral clearance of twist drills, i, 274. Diamond point chisel, ii, 76. Diamond pointed tool for lathe work, i, 254. Dictionary of work-shop terms, ii, 473. Die stock for pipe-threading by hand, i, 463. by power, i, 463. Dies, adjustable, i, 98. for finishing square threads, i, 269. for forging eye-bars, ii, 260. for gas and steam pipes, i, 101. or chasers in the heads of bolt-cutting machines, i, 463. the wear of, i, 89. with four cutting edges, i, 100. Differential threads for locking, i, 119. Displacement of pumps, ii, 387. Distance between bearings of line-shafting, ii, 186. Dividers, i, 377. Dividing device for circle, i, 352. engine, i, 349. mechanism for gear cutting, ii, 57. Division of the circle, i, 348. Dog-head hammer, ii, 69. Dogs, lathe, various kinds of, i, 222. movable for face-plate work, i, 250. Donkey engines, ii, 442. Double beat valves, ii, 443. eye, filing up a, ii, 103. forging of, ii, 240. eyes, fitting pins in, i, 121. gibbed connecting rod, ii, 115. head panel raiser and sticker, ii, 335. heads for planing machines, i, 404. ported side valves, ii, 377. rapid bolt threading machine, i, 467. riveted lap joint, ii, 352. saw machine, ii, 294, 295. spindle milling machine, ii, 16. threads, cutting, i, 322. tool holder for slide rest, i, 169. wheel sanding machines, ii, 348. Double-coned work, boring, i, 293. Dovetail joint, ii, 275. Draught of keys, i, 127. Draw filing, ii, 93. Drawing the temper, ii, 462. Drawings for bevel pinion, i, 59. for gear wheels, i, 59. Drifts, forms of, ii, 109. methods of using, ii, 160. Drill, and counter-bore, i, 449. brace, i, 445. universal joint for, i, 456. with multiplying gear, i, 456. with ratchet motion, i, 456. chucks, i, 446; ii, 41. cranks, i, 457. for stone, i, 454. for wood work, i, 449. grinding, varied for diameter, ii, 41. conditions for all diameters, ii, 41. holders, flat, for lathe work, i, 281. holders, twist, i, 274. machine, grinding, ii, 41. position, for all drills, ii, 41. shanks, i, 445. shank, improved form of, i, 446. sockets, i, 445. with cord, i, 455. with spring motion, i, 455. Drilled work, tailstock chucks for, i, 279. Drilling and boring machine, i, 431. feed motion of, i, 432. device for lock work, i, 459. engine cylinders, jigs for, i, 440, 441. hard metal, i, 445. Drilling holes true to location with flat drills, i, 442. levers for blacksmith, i, 457. square holes, device for, i, 450. taper holes, i, 451. and turning machine for boiler makers, i, 435. machine, and lathe combined, i, 433. cotter or keyway, i, 438. feed motion of, i, 432. feed motions of, i, 436. for boiler shells, i, 436. four-spindle, i, 434. hand, i, 459. lever feed, i, 428. power, i, 428. three-spindle, i, 434. with automatic motions, i, 428. with quick return, i, 428. machines, counterbores for, i, 449. cutters for, i, 447. drills for, i, 442. fixtures for, i, 439. flat drills for, i, 442. jigs for, i, 439. radial, i, 430, 431. stocks for, i, 447. Drills and cutters, i, 442, 447. cotter or keyway, i, 446. flat, errors in grinding, i, 443. flat, for drilling machines, i, 442. flat, for lathe work, i, 280. for wood work, i, 279. square-shanked, i, 446. disadvantages of, i, 446. stock, with spiral grooves, i, 445. twist, diametral clearance of, i, 274. fluting, ii, 29. front rake of, i, 275; ii, 44. grinding by hand, i, 279. large, grinding, ii, 41. speeds and feeds for, i, 277. Driver, and face plate, i, 223. Drivers, equalizing, i, 223. for bolt heads, i, 224. coned work, i, 225. lathe mandrels or arbors, i, 227. steady rest work, i, 22. threaded work, i, 225. wood, i, 225. lathe, i, 222. the elements, i, 223. Driving cones, steps of, i, 159-164. drills, flexible shaft for, i, 458. gear of universal milling machine, ii, 15. gear table, i, 404. Drop hammers, ii, 255, 256. Duration of a hammer blow, experiments on, ii, 65, 66. Duplex slide-rests, i, 143. E Eccentrics, fixed and shifting, ii, 378. slipping, ii, 403. turning in the lathe, i, 317. Eccentric work, lathe mandrels for, i, 229. Edge tools, oilstoning, ii, 54. Effects of hammer blows, ii, 69. of speed of a hammer blow, ii, 65. Elevating slide rests, i, 168. Elliptical gears, tooth curves of, i, 73. gear wheels, i, 70. gears, the pitch lines of, i, 70. taps, in cross section, i, 109. Emery belt grinding machine, ii, 47. grinder for car axle boxes, ii, 45. for engine guide bars, ii, 45. machine knives, ii, 46. rough work, ii, 46. true surfaces, ii, 45. with revolving emery wheel, ii, 40. machines, grinding, ii, 40. charging, polishing wheels, ii, 50. paper, use on lathe work, i, 308. wheel arbors, i, 198. arbors, positions of, ii, 35. swing frame for dressing large castings, ii, 46. wheels, annular, ii, 48. balancing, ii, 39. cements used in the manufacture of, ii, 38. clearance of, ii, 39. coarseness and fineness of, ii, 38. positions of, i, 282; ii, 36, 37. presenting to work, ii, 47. qualifications of, ii, 38. recessed, ii, 47. speeds of, ii, 39. wear of, ii, 48. End, face and twin milling, ii, 25. grain wood boring, i, 453. measurements of lathe work, i, 376. milling, advantages of, ii, 25. thrust of angular teeth, i, 69. Endless screw thread, cutting, i, 62. Engine, alignment, errors in, ii, 166. calculating the power of, ii, 407. connecting rods, ii, 375. crank turning, i, 247. crossheads, ii, 375. crosshead turning, i, 252. cylinder covers, turning, i, 318. cylinders, bores of, ii, 372. boring lathe for, i, 219. clearance in, ii, 372-404. counterbore of, ii, 372. fitting, ii, 158. jacketed, ii, 374. lagging, ii, 374. lubricating, ii, 373. relief valves for, ii, 373. steam ports, ii, 373. waste water cocks of, ii, 373. wear of, ii, 372. eccentrics, ii, 378. turning a cover, i, 318. gear cutting, ii, 56. glands, turning, i, 316. guide bars, ii, 375. setting, ii, 162. spring of, ii, 162. testing, ii, 163. lathe, i, 129, 147. construction of carriage, i, 137. of the back gear, i, 135. of the bearings, i, 134. of the head stock, i, 134. general construction of, i, 133. lead screw and change wheels of, i, 139. shears of, i, 134. link motion, designing, ii, 389. plain slide valve, starting, ii, 384. valves, ii, 376-378. balanced, ii, 377. circular, ii, 377. cut-off, ii, 378. double ported, ii, 377. exhaust lap of, ii, 376. lead of, ii, 376. point of admission, ii, 376. slide and piston, ii, 378. slide, designing, ii, 380. testing horse power of, ii, 408. the Allen, ii, 377. the D, ii, 376. tracing the action of, ii, 376. Webb's, ii, 377. Engines, compound, ii, 434, 435. donkey, ii, 442. heating and knocking of, ii, 164. subject to freezing, ii, 386. Engineers, test questions for, ii, 467. Engraver's plates, polishing, ii, 51. Epicycloidal gear teeth, curves, i, 8. teeth, the strength of, i, 64. filleting the roots of, i, 53. Equalizing drivers for lathe work, i, 223. Erecting, ii, 137. a lathe, ii, 181. an iron planer, ii, 179. pipe-work, ii, 143. the framework of machinery, ii, 176. Errors in alignment, determining, ii, 158-167. in chucking, i, 250. crank pin alignment, ii, 169. cutting threads on taper work, i, 324. cutting up inside chasers, i, 337. drill-grinding machines, ii, 41. grinding flat drills, i, 443. grinding milling cutters, ii, 32. jigs, limits of, i, 439. shafting couplings, ii, 196. Evaporative efficiency of boilers, ii, 366. Examining a boiler, ii, 368. a locomotive, ii, 401. Excessive lead of engines, ii, 421. Exhaust lap, ii, 376. Expanding bit, i, 454. chucks for lathes, i, 188. for ring work, i, 241. for large work, i, 228. laps, i, 311. mandrels, i, 227. taps, i, 107. Expansion, ii, 376. curve of indicator, ii, 417, 418. testing of indicator, ii, 417, 418. joint, ii, 141. line of diagrams, ii, 414, 415. of steam, ii, 411. pulleys, ii, 200. valves, separate, ii, 443. Experiments on duration of a blow, ii, 65, 66. on the strength of the parts of a hide, ii, 208. Extension lathe, i, 151. Eye-bar dyes, ii, 260. Eyes, hammer, shapes of, ii, 66. F Face and taper cutters, fixture, ii, 34. cutters, ii, 17. advantages of, ii, 18. disadvantages of, ii, 18. fixtures for, ii, 34. milling, advantages of, ii, 26. length of feed, ii, 26. plate, clamping work on, i, 245. clamps, i, 245. errors in, and their effects, i, 243. for wood-work, i, 247. work, examples of, i, 249. work, movable dogs for, i, 250. Facets of scrapers, angles for, ii, 97. Facing and countersink cutters, i, 449. cutters, i, 449. rests, boring lathe with, i, 220. tool with reamer-pin, i, 449. Facing tools or knife tools, i, 262. Factors of safety, boiler seams, ii, 355. Fastening cogs, i, 63. pulleys to their shafts, ii, 201. Feather-edge, removing, ii, 54. Feathers and their applications, i, 127. methods of securing, ii, 102. sinking into shafts, ii, 101. Feed, direction, for shank cutters, ii, 20. for spiral grooves, ii, 27. escape valve, ii, 441. gear, i, 197. for screw machine, i, 205. in cutting spiral grooves, ii, 28. length, in face milling, ii, 26. motions, automatic, i, 408. construction of, i, 390. examples of, i, 170. for boiler-maker's drilling and turning machine, i, 436. for boring machine, i, 432. boring mills, i, 215. cam turning, i, 326. car-axle lathe, i, 148. carriage or saddle, i, 137. chucking lathe, i, 150. drilling machine, i, 432. grinding lathe, i, 200. lathe aprons, i, 168. milling machine, ii, 13. planer heads, i, 413. reversing traverse, i, 168. special lathe, i, 146. weighted slide rest, i, 168. wood-working, i, 209. friction wheels for, i, 78. nut, position of, i, 177. ratchet, i, 173. regulators for screw cutting, i, 171. spindle bearings, i, 139. spindle for lathe, i, 139. spindle, giving motion to, i, 135. water, heating, ii, 370. Feeds, cutting, for wrought iron, i, 294. for roughing cuts, i, 306. for twist drills, i, 277. Feed-water, ii, 370. from natural supply, ii, 387. Fiddle drill with feeding device, i, 455. Field tube for boilers, ii, 359. Fifth wheel, forging of, ii, 239. File cutters' hammers, ii, 71. cutting, ii, 101. teeth, shapes of, ii, 85. Files, ii, 85. bent, using, ii, 93. cleaning of, ii, 94. cross, ii, 91. cut of, ii, 86. flat sizes and kinds, ii, 86, 87. for soft metals, ii, 95. Groubet, ii, 87. half-round, ii, 90. instruction on holding, ii, 92. knife, ii, 91. names of, ii, 88. putting handles on, ii, 92. reaper, ii, 91. resharpening, ii, 95. round, ii, 90. selection of, ii, 91. thin, ii, 93. three square, ii, 90. tumbler, ii, 91. warping, ii, 93. Filing bolt heads, ii, 105. cross, ii, 93. draw, ii, 93. fixture for lathes, i, 189. lathe work, i, 308. nuts, ii, 105. out connecting rod keyways, ii, 120. out round corners, ii, 95. pins, ii, 105. pins, blocks for, ii, 104. the link slot, template for, ii, 127. the teeth of band saws, ii, 309. Filleting the roots of gear teeth, i, 53. Finishing cast iron with water, i, 307. cast iron work, specks in, i, 307. cuts, rates of feeds for, i, 307. horseshoes, machines for, ii, 262. internal work, laps for, i, 311. lathe work, scrapers for, i, 307. Fire cleaning, ii, 369. cleaning tools, ii, 369. engine boiler tubes, ii, 431. engine heaters, ii, 432, 433. engines, steering gear for, i, 75. Firing boilers, ii, 368. methods of, ii, 402. Firmer chisels, ii, 272. Fits, shrinkage or contraction, i, 366. Fitting brasses to connecting rod straps, ii, 121. brasses to journals, ii, 146. engine cylinders, ii, 158. keys, ii, 107. keys, examples of, ii, 107. straps, ii, 120. taper pins, i, 122. taper work, i, 313. the keys and gibs, ii, 120. up connecting rods, ii, 118. a double eye, ii, 103. a fork end connecting rod, ii, 123. a lathe, ii, 181. a link motion, ii, 127. Fixed pins, i, 122. Fixture for grinding cutters, ii, 32, 33. for grinding taper work, ii, 33. Fixtures for drilling machines, ii, 439. Flank contact of gear teeth, i, 28. Flat drill holders, i, 281. drills, drilling with, i, 444. errors in grinding, i, 443, 444. for lathe work, i, 280. files, sizes and kinds, ii, 86, 87. guideways for planer beds, i, 414. side lathe shears, i, 183. Flexible shaft for driving drills, i, 458. Flue boiler, ii, 358. Flutes, shapes of taps, i, 105. the number of, i, 107. Fluting twist drills, ii, 29. Fluxes, heating in, ii, 462. Fly ball governors, ii, 384. cutters, ii, 21. holders for, ii, 22. making, ii, 21. methods of originating, ii, 21. Follower rests, i, 234. Foot lathe, i, 130. Foot-power hammers, ii, 252, 253. Foot valves, ii, 388. Forges for blacksmiths, ii, 228, 229. side blast for, ii, 228. Forging bolts, ii, 238. crank shafts, ii, 248, 249. hydraulic, ii, 260. machine thread, ii, 261. nails by machinery, ii, 261. of bolts, ii, 238. press, ii, 260. rope sockets, ii, 243, 244. rudder frames, ii, 245, 246. steel forks, ii, 241. threads on rods, ii, 261, 262. turn buckles, ii, 239, 240. under the hammer, ii, 242, 243. under a steam hammer, ii, 241. wheels, ii, 244, 245. Fork end connecting rod, fitting, ii, 123. aligning, ii, 124. Fork forging, ii, 241. Former of Corliss bevel gear-wheel engine, i, 45. Form of lead screw threads, i, 177. worm to give a period of rest, i, 74. Forms of lathe shears, i, 183. of outside calipers, i, 360. pin wrenches, i, 126. riveted joint, ii, 352. taps, i, 102. templates for gear teeth, i, 44. wrenches, i, 125. Foundations for an iron planer, ii, 179. Four-jawed chucks, i, 237. Four-spindle drilling machine, i, 434. Fractional pitch change gears, i, 34. Frames for rudders, forging, ii, 245, 246. of machinery, erecting, ii, 176. Freezing, preventing an engine from, ii, 386. French gear-cutting machine, ii, 56-61. Friction clutches, ii, 192. experiments on, ii, 154. of jamb dies, i, 98. plane surfaces, ii, 135. slide valves, ii, 443. taper taps, i, 103. tap threads, i, 108. wheels, i, 77. for feed motion, i, 78. materials for, i, 77. paper, i, 78. to reduce journal strain, i, 79. Friezing machines, cutters for, ii, 340. or moulding machines, ii, 334, 339. Front rake of twist drills, ii, 44. tools for brass work, i, 264. rake and clearance of, i, 254. Fullers, blacksmith's, ii, 230. Furnaces for scrap iron, ii, 247. G Galvanized iron, gauge for, i, 387. Gang edging machines, ii, 301. Gang or composite cutters, ii, 23. Gap, or break lathe, i, 151. Gas pipe, dies for, i, 101. Gauge cocks for boiler, ii, 368. Gauges, i, 356-359. adjustable, i, 377. cropping, use of, ii, 296. cutting, ii, 274. for American sheet zinc, i, 387. circular saws, ii, 287. cutting tools, i, 92. galvanized iron, i, 387. lathe work, i, 359. marking wood, ii, 274. music wire, i, 386. planer tools, i, 423. planing V-guideways, i, 421. Russian sheet iron, i, 387. setting over taper work, i, 313. shrinkage fits, i, 367. threading tools, i, 266. woodworking machine, ii, 295. forms of laps for, i, 310. hexagon, i, 381. instrument, standard, i, 96. mitre, use of, ii, 294. mortise, ii, 274. notch wire, i, 384. plug and collar, comparing, i, 356. screw thread, producing, i, 92. standard for taper work, i, 316. standard, comparing, i, 356. surface, i, 378. vacuum, i, 444. wire, i, 387. Gauging the pitch of threads, after hardening, i, 108. Gear cutter, automatic, ii, 55. cutting engine, vertical spindle, ii, 56. machine, half-automatic, ii, 56. machine, French, ii, 56-61. table of index holes for, i, 417. racks, i, 77. Gear-teeth, i, 73. arc of approaching contact, i, 16. of receding contact, i, 16. pitch of, i, 2. calculating strength of, i, 65. chord pitch of, i, 2. curve of, for bevel gear, i, 22. curves, templates for rolling, i, 43. cutting by hand, i, 62. cutting templates for, i, 35. elliptical, i, 70. depth or height of, i, 1. errors produced by wear, i, 18. faces of, i, 1. factors of safety for, i, 64. flank contact of, i, 18. depth or height, i, 1. flanks of, i, 1. forms of template for, i, 44. generating involute curves, i, 31. helical, i, 69. line of centres of, i, 2. pitch line of, i, 2. point of, i, 2. requirements of curves, i, 7. revolving cutters for, i, 37. rolling and sliding motion of, i, 16. curves for, i, 43. strength of, i, 65. table of cutters for, i, 41. variation of curve, i, 12. of shape, i, 16. Gear-wheels, i, 1. angular velocity of, i, 6. bevel, i, 21. drawing for built-up, i, 61. pinion, drawings for, i, 59. calculating revolutions of, i, 5. chord pitch, i, 3. cogged, i, 63. cogs, i, 67. durability of, i, 66. diameters of pitch circles of, i, 4. drawings for, i, 59. driver and follower, i, 3. for rapid increase of motion, i, 75. reciprocating motion, i, 77. reversing motion, i, 75. steering steam fire engines, i, 75. variable motion, i, 74. generating curves for, i, 11. hunting tooth in, i, 7. interchangeable gearing, i, 16. internal, compared with spur, i, 25. or annular, i, 23 to 27. making cogs for, i, 63. mortised, i, 63. motion at a right angle, i, 69. patterns, i, 54-61. power of, ii, 406. transmitted by, i, 5. skew bevel, i, 61. spacing teeth on, i, 58. stop motion of, i, 7. strength of, i, 66. table of pitches, i, 3. table giving strength of, i, 67. thickness of, i, 66. tracing path of contact, i, 13. value of cutters, table, i, 41. various applications of, i, 74. velocity of, uniform, i, 16. with dovetail teeth, i, 60. involute teeth, i, 31-34. stepped teeth, i, 69. Gear-worm or endless screw, i, 62. Gears, for screw cutting, i, 320. Generating the involute curve, i, 31. German bit, i, 452. Gibbed elevating slide-rest, i, 169. Gimlet bit, i, 452. Gland patterns, ii, 275. Globe valve patterns, ii, 281, 282. Gonzenback's cut-off valve, ii, 378. Gouge for wood, ii, 272. use of, i, 338. Governors, dancing, ii, 384. fly ball or throttling, ii, 384. for automatic engines, ii, 427, 428. for stationary engines, ii, 425, 426. isochronal, ii, 384. Sawyer's valve for, ii, 384. speed of, ii, 384. speeders for, ii, 384. spring, adjustment of, ii, 386. Grate bars, cleaning, ii, 368. Grades of emery wheels, ii, 38. Graduations of planer heads, i, 412. Grain side of leather, weakness of, ii, 208. Graver, i, 330. Grinder, emery, for axle boxes, ii, 45. for engine guide bars, ii, 45. Grinder for planing machine cutters, ii, 46. for rough work, ii, 46. for true surfaces, ii, 45. Grinding clamps for lathe work, i, 311. cocks and plugs, ii, 145. operations, ii, 38. taper cutters, ii, 33. taper work, i, 313. teeth of reamers, i, 282. teeth of spiral cutters, ii, 36. thin cutters, ii, 33. twist drills by hand, i, 279. universal, i, 195. with elevating rest, i, 194. with traversing wheel, ii, 46. Grinding-lathes, i, 193. for calendar rolls, i, 199. construction of tailstock, i, 200. special chuck for, i, 196. Grinding-machine, drill, ii, 41. emery belt, ii, 47. for milling cutters, ii, 32. errors in construction, ii, 41. Grindstones and tool grinding, ii, 51. application of work to, ii, 53. for saws or iron plates, ii, 52. wood-working tools, ii, 52. hacking, ii, 53. speeds of, ii, 52. traversing device for, ii, 53. truing device for, ii, 53. various kinds of, ii, 51, 52. Gripping devices, ii, 227. Groove cams, i, 84. proper construction of, i, 84. wear of, i, 84. with double roller, i, 84. Groove cutting, angular cutters, ii, 27. Grooved friction wheels, wear of, i, 79. Grooves, producing different shapes with same cutter, ii, 29, 30. right and left-hand, ii, 29. Groubet files, ii, 87. Ground joint, ii, 137. Guide-bars, ii, 375. setting by stretched lines, ii, 163. Guide pulleys for belts, ii, 211. Guide for centre punches, i, 301. Guide-ways, flat, i, 414. planing, i, 422. Guides for band saws, ii, 311. Gumming or gulleting, ii, 290. H Hacking grindstones, ii, 53. Hack saw, ii, 97. Half-round bit for true work, i, 281. for wrought iron or steel, i, 281. or pod auger, i, 281. reamers, ii, 99. with adjustable cutter, i, 281. Hammer, ii, 64. blow, effects of, ii, 65, 69. coopers', ii, 71, 72. cushioned, ii, 252. dog-head, ii, 69. drop, ii, 255. eyes, shapes of, ii, 66. foot power, ii, 252. forging, methods, ii, 242. file cutters', ii, 71. handles, putting in, ii, 67. machinists' hand, ii, 66. paning or pening, ii, 68. plate and saw makers', ii, 68. power, ii, 252. riveters', ii, 71. sledge, machinists', ii, 71. steam, ii, 256-259. trip, ii, 254. Hand bolt threading machine, i, 97. device to straighten lathe work, i, 305. drilling machine, i, 459. finishing tool, i, 331. hammers, machinists', ii, 66. lathe, i, 130. watch manufacturers', i, 191. milling machine, ii, 1. planer, i, 391. reamers, ii, 98. shaping machine, i, 392. side tools, i, 331. tools for brass-work, i, 332. round nosed, for iron, i, 331. screw cutting, i, 96. threading machine, head, i, 465. turning, i, 330. vise, ii, 104. work, swages for, ii, 230. Handles for chisels, ii, 271. of files, putting on, ii, 92. of hammers, putting in, ii, 67. Hangers, shafting, forms of, ii, 192. wall, ii, 194. Hardening, case, ii, 128, 442. outside, ii, 462. saws, ii, 462. to resist wear, ii, 460. increase elasticity, ii, 460. provide a cutting edge, ii, 460. Hard metal, drilling, i, 444. Head boring, i, 288. with nut feed, i, 291. Heads, construction of, i, 408. double for planing machines, i, 404. Heads for match board grooves, ii, 337, 338. for tenoning machines, ii, 345. of the rapid machines, i, 468. planer, feed motions for, i, 414. safety devices for, i, 413. V-guideways for, i, 414. Headstock lathe, construction, i, 153. of engine lathes, i, 134. grinding lathes, i, 200. special lathe, i, 144. Heat, ii, 410. conversion of, into work, ii, 411. latent, ii, 410. radiation of, ii, 412. Heaters for fire engines, ii, 432, 433. Heating and knocking, ii, 164. feed-water, ii, 370. showing the causes of, ii, 168. Heavy oil for hot bearings, ii, 386. Heel tool, i, 330. Height of lathe tools, ii, 260. of vise jaws, i, 62. Helical teeth, cutting in the lathe, i, 69. Herring-bone gear-teeth, i, 69. Hexagon gauge, i, 381. Hide, parts of, used for belting, ii, 208. High pressure steam engine, ii, 372. High speed automatic engines, ii, 427. Hobbing dies, methods of, i, 473. Hob for threading dies, i, 474. Hobs and their uses, i, 335. for cutting up dies, i, 99. threading dies, i, 474. Hoe, ii, 369. Holders, for chasers, i, 268. for fly cutters, ii, 22. octagon boring tools, i, 175. Holding chisels, ii, 74. Hollow work, centres for, i, 226. Hook bolts, i, 113. Hooks, belt, ii, 216. Horizontal boring machine, i, 433. Horse-power, from diagram, ii, 418. of an engine, calculating, ii, 407, 419. testing, ii, 408. Horseshoes, finishing, machine for, ii, 262, 263. Horizontal tubular boiler, ii, 361-366. saw frame, ii, 312. Hydraulic fits, allowance for, i, 365. parallel holes and taper plugs for, i, 365. forging, ii, 260. press, ii, 260. pressure, i, 366. Hypocycloidal curves, i, 8. I Inclination of skew bevel teeth, i, 61. Index plate of milling machine, ii, 7. Index wheel, originating, i, 342, 353. Indicator, ii, 413. attachment of, to engine, ii, 416. diagram, area of the, ii, 419. diagrams, ii, 414. defective, ii, 421. expansion curve, ii, 417, 418. springs, ii, 416. vacuum line, ii, 415. Injector, feed, ii, 370. for locomotives, ii, 395. Inside calipers, i, 360. chasers, i, 335. errors in cutting up, i, 337. Interchangeable gearing, i, 16. Intermediate gears, i, 3. wheels, i, 319. rolling circle, i, 24. Internal gear wheels, i, 23-27. strains in cast iron work, i, 306. threading tools, i, 264. wheels, i, 23. Involute curves for gear teeth, i, 8. teeth, advantages of, i, 34. Iron and steel welding, ii, 234. bending, ii, 240. devices, ii, 240. galvanized, gauge for, i, 387. planer, erecting an, ii, 179. foundation for, ii, 180. plates, grindstones for, ii, 52. testing, ii, 226. Irregular forms, lathes for, i, 210. motion, cams for, i, 80. work, turning, i, 326. Isochronal governors, ii, 384. J Jacketed cylinders, ii, 374. Jam dies, i, 98. nuts, i, 119. Jeweller's rests for lathes, i, 189. Jigs, designing, i, 440. errors in, limit of, i, 439. for cutting out steam ports, i, 441. drilling engine cylinders, i, 440. drilling machines, i, 439. simple work, i, 440. Jointing machines, ii, 338. Joints, boiler fitting, ii, 140. butt, boiler, ii, 352. cylinder cover, ii, 137. dovetail, ii, 275. easily removable, ii, 141. expansion, ii, 140. for boiler work, ii, 352. rough surfaces, ii, 138. gauze, ii, 138. ground, ii, 137. half check, ii, 275. lap, boiler, ii, 352. mitre, ii, 275. mortise, ii, 274. open, for wear, ii, 121. riveted, proportioning, ii, 355, 356. rubber, ii, 139. rust or caulked, ii, 141. scraped, ii, 137. tenon, ii, 274. thimble, ii, 141. to withstand great heat, ii, 138. water, ii, 138. Joule's equivalent, ii, 411. K Key seats, cutting, ii, 101. Keys and gibs, fitting, ii, 120. bearing surfaces of, i, 126. draught of, i, 127. forms of, i, 126. for parallel rods, i, 128. seating rule, i, 378; ii, 101. with set-screws, i, 127. Keyway calipers, i, 363. Keyways, cutting by hand, ii, 101, 108. cutting out by drifts, ii, 109. Knife blade rolls, ii, 261. files, ii, 91. Knives for balanced heads, ii, 324-326. for jointing machines, ii, 338. moulding machines, ii, 336-340. moulding, scale for shapes of, ii, 83. Knurling tool, improved forms of, i, 328. L Lap joint, boiler, ii, 352. of Corliss engine valve, ii, 426. Latent heat, ii, 410. Lathe, advantages of, i, 129. apron, i, 138. feed motion for, i, 168. back gear, i, 144. bench, i, 130. boring devices for, i, 288. tools, shapes of, i, 285. break, i, 151. capacity, i, 130. carriage, i, 145. feed motion for, i, 37. testing, ii, 182. carriers, i, 222. centre drilling attachment, i, 300. centres, i, 290. removing, i, 159. shapes of, i, 299. testing, i, 298. change wheels for, i, 139. chucks for, i, 188. chucking for boring purposes, i, 152. clamps, i, 223. classification of, i, 129. cutting fractional threads on, i, 181. helical teeth in the, i, 69. screws in the, i, 319. cutting-off machine, i, 193. cylinder boring, i, 219. dogs, various kinds of simple, i, 222. drivers, i, 222. English chucking, i, 149, 150. erecting a, ii, 180. extension, i, 151. face-plates, i, 243. chucking, i, 246. clamps for, i, 245. errors in, i, 143. for wood work, i, 247. feed-motions, i, 144. feed-screw, i, 175. feed, spindle for, i, 139. filing, fixtures for, i, 189. fit of the live spindle of a, i, 157. fitting up, ii, 180. foot, i, 130. for axe handles, i, 210. engine cylinders, i, 219. irregular forms, i, 210. taper turning, i, 142. turning crank shafts, i, 152, 154. turning wheel hubs, i, 221. gap, i, 151. grinding, i, 193. universal, i, 195. with elevating rest, i, 194. hand, i, 130. headstock, construction of, i, 153. importance and advantages of, i, 129. jewellers', rest for, i, 189. locking spindles of, i, 186. lead-screw, i, 175. bearings for, i, 139. nuts for, i, 140. supporting long, i, 176. mandrels, drivers for, i, 227. expanding, i, 227. for eccentric work, i, 229. nuts, i, 229. threaded work, i, 228. tubular work, i, 227. forms of, i, 229. with expanding cones, i, 278. with expanding pieces, i, 228. motions for turning cams, i, 326. open spindle, tailstocks for, i, 189. pattern makers', i, 148. pulley, i, 150. screws, errors of pitch, i, 79. screw slotting, i, 192. self-acting, English, i, 148. shears, the legs of, i, 184. various forms of, i, 183. methods of ribbing, i, 184. or beds, i, 182. with flat slides, i, 183. [V] and flat slides, i, 183. [V] slides, i, 183. sizes of, i, 130. slide-rest for, i, 131, 145. lost motion of, i, 133. special chucks for, i, 190. swing frames, i, 158. tailblock, i, 185. setting over, for tapers, i, 136. various methods of testing, i, 187. wear of the spindles of, i, 185. with rapid spindle motion, i, 185. releasing devices, i, 185. testing, i, 186. instruments for, ii, 182. tool-holders for outside work, i, 270. with clamp, i, 271. tools, angle of clearance of, i, 257. height of, i, 260. shapes of, i, 254. watchmakers', i, 188. with compound slide-rest, i, 140-143. elevating rest, i, 194. flat chucking surface, i, 143. rapid spindle motion, i, 185. sliding heads, i, 290. variable speed, i, 192. wooden bed, i, 149. work, boring tools for, i, 285. burnishing, i, 311. chisels for, i, 339. countersinks for, i, 302. end measurements of, i, 376. filing, i, 308. flat drills for, i, 280. holders for, i, 281. forms of countersink for, i, 302. gauge for, i, 359. grinding clamps for, i, 311. holding straps for, i, 244. mandrels or arbors for, i, 227. method of polishing, i, 308. polishing clamps for, i, 311. side tools for, i, 261. technical terms used in, i, 296. use of emery paper on, i, 308. Lead-lined brasses, ii, 149, 386. Lead of a valve, adjusting the, ii, 386. Lead of slide valves, ii, 376. Lead-screw, bearings for, i, 139. conveying motion to the, i, 147. nuts, i, 180. for lathes, i, 175. forms of threads of, i, 177. long supporting, i, 176. swing frame for, i, 139. with three threads per inch, i, 177. five threads per inch, i, 178. Leather, grain side, weak, ii, 208. Left-hand threads, cutting, i, 322. Leg vise with parallel motion, ii, 63. Lever feed drilling machine, i, 428. drilling, for blacksmiths, i, 457. principles of, ii, 405. Lift and force pumps, ii, 387. Line of contact of skew bevel gear wheels, i, 61. Line shafts, couplings for, ii, 194. Line shafting, diameters of, ii, 189. ordinary, ii, 186. setting in line, ii, 184, 185. sizes of, ii, 186. the strength of, ii, 189. Lined boxes, babbitt metal, ii, 155. Lining connecting rod brasses, ii, 126. Link-motion, gear, ii, 383. fitting up, ii, 127. for expansion engines, ii, 438. for marine engines, ii, 443. quick return shaper, i, 399. setting the valves for, ii, 383. the action of, ii, 383. Link slot, templates for filing, ii, 127. Lip drill, i, 443. Live centres, tapers for, i, 159. spindle, end adjustment of, i, 158. wear of bearings, i, 158. with coned journals, i, 157. Locking, differential threads for, i, 119. Lock work, drilling device for, i, 459. Locomotive ash pan, ii, 390. automatic air brake, ii, 390, 398. axle boxes, ii, 147. blower, ii, 390. boiler and frames, ii, 389. connecting-rod, ii, 116. freight engine, ii, 389-404. injector, ii, 395. link motion, ii, 391-393. passenger engine, ii, 390. reversing gear, ii, 391. sand valves, ii, 390. safety and pop valves, ii, 389. Locomotive wheel forging, ii, 244. yoke and guide bars, ii, 389. Longevity of lubricants, ii, 153. Lost motion in valve setting, ii, 174. Low water in boilers, ii, 370. Lubricants, longevity of, ii, 153. qualities of, ii, 152. testing, ii, 152. Lubricators, steam, ii, 444. M Machine centre drilling, i, 300. cross cutting or gaining, ii, 305, 306. for cutting mitre joint, ii, 338. finishing horseshoes, ii, 262. forging threads, ii, 261, 262. gang edging, ii, 301. gumming or gulleting, ii, 290. horizontal saw frame, ii, 313. moulding, ii, 334. scroll sawing, ii, 306. Machinery for wood working, ii, 287. Machinists' chisels, applications, ii, 76. hand hammers, ii, 66. sledge hammer, ii, 71. Main bearings, adjusting, ii, 386. Mallet, ii, 72. Mandrels, expanding, i, 227. for threaded work, i, 228. lathe, i, 227. expanding, i, 228. for eccentric work, i, 229. for nuts, forms of, i, 229. with expanding cones, i, 228. with expanding pieces, i, 228. or arbors for lathe work, i, 227. Mangle gearing, various forms of, i, 76. Manufacturers' temper, ii, 460. Marine-engine boilers, ii, 436, 437. connecting-rod, ii, 116. link motion, ii, 443. pumps, ii, 436. valves, ii, 444. Marine engines, pipes of, ii, 445. various, ii, 434. Marriotte's law, ii, 411. Matched cutters, ii, 23. Matching and planing machines, ii, 326. Mean effective steam pressure, ii, 420. Measurements, the standards of, in various countries, i, 341. Measuring by sight, and feeling, i, 341. machine for sheet metal, i, 348. special, i, 342-346. tools, classification of, i, 354. valve lead, ii, 173. Mechanical equivalent of heat, ii, 411. powers, ii, 405. Metal, soft, files for, ii, 95. Metric pitch screws, i, 322. Meyer's cut-off valve, ii, 378. Micrometer caliper, i, 354. gauge for thread angles, i, 91. Mill boring, i, 211. turning, i, 211. Milling-cutters, grinding, ii, 32. or mills, ii, 16. with inserted teeth, ii, 24. Milling-machine, ii, 1-16. advantages of, ii, 1. chucks for, ii, 31. cam cutting attachment, ii, 12. cutters, ii, 17-31. double-spindle, ii, 16. fixtures for, ii, 10. hand, i, 410. head for spiral cutting, ii, 12. holding work on, ii, 30. power, ii, 2. rotary vise for, ii, 10. universal, ii, 2, 4, 12, 15. head and back centre, ii, 10. head for gear cutting, ii, 11. vertical, ii, 31. Milling or knurling tools, i, 328. Milling taper work, ii, 30. Mitre gauge, use of, ii, 295. joint, ii, 275. machine, ii, 338. wheels, i, 1. Monkey wrench, i, 125. Mortise gauge, ii, 274. Mortised gear-wheels, i, 63. Mortising machines, ii, 344. Moulding knives, scale for marking out the necessary shapes of, ii, 83. Moulding-machines, ii, 334, 339. cutters for, ii, 336, 337, 341. Muffle, ii, 461. Mule pulleys for belts, ii, 211. Music wire, gauge for, i, 386. N Nail bit, i, 452. Nail forging machines, ii, 261. Non-condensing engine, ii, 372. Nose bit, i, 453. Notch wire gauges, i, 384. Number of cutters used for a train of wheels, i, 41. of cutters on boring bars, i, 290. of cutting edges on taps, i, 105. of cutting edges on reamers, i, 282. Nut-tapping-machine, i, 475. automatic socket for, i, 475. rotary, i, 475. three-spindle, i, 475. Nuts, filing, ii, 105. jam, i, 119. lock, i, 119. lost motion in, i, 120. removing corroded, i, 122. securing by cotters, i, 121. by notched plates, i, 121. by taper pins, i, 121. devices, i, 120. steam tight, the forms of, i, 118. taking up the wear of, i, 120. O Odontograph, using, i, 47, 49. Oil and lubrication, ii, 151. cavities for brasses, ii, 150. groove or curved chisel, ii, 76. for brasses, ii, 150. heavy, for hot bearings, ii, 386. stones, truing, ii, 54. various kinds of, ii, 54. test, Swiss, ii, 153. Oiling apparatus, ii, 439, 440. devices for planer beds, i, 416. true surfaces, ii, 135. Oils, testing for acids, ii, 153. testing for salts, ii, 153. Oilstoning edge tools, ii, 54. Olivers, ii, 252, 253. Open brasses, ii, 149. sided shafting hangers, ii, 193. spindle lathes, tailstocks for, i, 187. Originating angles for screw threads, i, 92. cams, i, 326. fly cutters, ii, 21. gear teeth, i, chaps. I, II, III. index wheels, i, 345. surface plates, ii, 135. templates for screw threads, i, 92. Outside and inside chasers, i, 335. calipers, making, ii, 105. the various forms of, i, 360. threads, starting, i, 338. P Paddle wheels, ii, 444, 445. Panel planing, ii, 332, 333. Paning or pening, ii, 72. hammers, ii, 68. Pantagraph engine for dressing the cutters for gear teeth, i, 38. motions, ii, 417. Paper friction wheel, i, 78. Parallel cutters, grinding, ii, 32. holes and taper plugs for hydraulic fits, i, 365. rods, keys for, i, 128. Paring chisels, ii, 271. Patching broken frames, ii, 178. Path of gear tooth contact, i, 13, 16. Pattern lathe, brake for, i, 149. slide-rest for, i, 149. with wooden bed, i, 149. Pattern-makers' lathe, i, 148. pipe gauge, i, 379. Pattern-making, woods for, ii, 264. Patterns, building up, ii, 278. brasses, proper shape for, ii, 132. choice of wood for, ii, 264, 265. for angle pipe, ii, 284, 285. glands, ii, 275. globe valves, ii, 281, 282. pillow blocks, ii, 277. pipes, ii, 280, 281. pulleys, ii, 278, 279. spacing gear-wheel teeth on, i, 58. Pattern-wheel scale, i, 51. Pening or paning, ii, 72. Piat's gear cutting machine, ii, 56-61. Pillow-block casting, ii, 277. fitting brasses to, ii, 131. for shafting, ii, 194. patterns, ii, 277. Pinion bevel, drawings for, i, 59. with dovetail teeth, i, 60. Pins, securing, for adjustment, i, 121. filing, ii, 103. fitting in double eyes, i, 121. fixed, i, 122. taper, i, 128. working, i, 122. wrench, i, 126. Pipe cutters, ii, 142. gauge, pattern-makers', i, 379. patterns, ii, 280, 281. threads, taper for, i, 95. tongs, ii, 143. vises, ii, 142. work, erecting, ii, 144. Pipe-threading by hand, i, 463. by power, i, 463. machine, i, 475-477. machines, construction of, i, 463. Piston valves, ii, 378. Pitch, alteration in hardening, i, 108. circle, the diameter of, i, 1. correcting the errors of, i, 109. gauging the, after hardening, i, 108. line of cams, i, 80. lines of elliptical gear-teeth, i, 70. number of teeth, and pitch diameter, i, 68. of screw threads, i, 85. Pitch of teeth for band saws, ii, 305. Pivoted arms for tooth templates, i, 44. Plane blades, ii, 77. blades, finding shapes of, for mouldings, ii, 78-83. Planer beds, flat guideways for, i, 414. beds, oiling devices for, i, 416. centres, i, 408. chuck, for curved work, i, 420. chucking halves of pulleys on, i, 423. chucks, i, 419. for spiral grooved work, i, 419. for timber, ii, 330, 331. head slides, wear of, i, 410. or iron planing machine, i, 402. shapers, reversing, i, 398, 399. swivel heads for, i, 411. swivelling tool holder, i, 411. tool, aprons for, i, 411. heads, feed motions for, i, 414. graduations of, i, 390. safety devices for, i, 413. [V]-guideways for, i, 414. tables, angle plates for, i, 418. chucking devices for, i, 422. chucking machine beds on, i, 421. forms of bolts for, i, 417. supplementary tables for, i, 417. tool-holder, applications of, i, 425. with tool post, i, 425. examples of application of, i, 426. simple form of, i, 426. tools for coarse finishing feeds, i, 423. for slotted work, i, 424. clearance of, i, 424. shapes of, i, 423. gauge for, i, 423. Planes, ii, 267-270. circular, ii, 268. combination, ii, 269. compass, ii, 268. core-box, ii, 269. for pattern making, ii, 268, 269. fore, ii, 268. grinding of, ii, 267. jack, ii, 267. oilstoning of, ii, 267. rabbeting, ii, 268. Plane surfaces, friction of, ii, 135. Planet motion, i, 75. Planimeter, ii, 420. Planing and matching machine, ii, 326. curved work, i, 420. guideways, i, 421. Planing-machine, i, 406-426. gear, ii, 56. large, chucks for, i, 423. motions of, i, 402, 403. tables, i, 414. tables, slots and holes in, i, 415. with double heads, i, 404. wood, ii, 326. Plate couplings, ii, 196. straightener's hammers, ii, 68. Plates, angle, for planer tables, i, 418. iron, grindstones for, ii, 52. saw, grindstones for, ii, 52. straightening, ii, 69. Plug and collar gauges, i, 357. Plug gauges for threads, i, 91. Plumb level, ii, 136. rule, ii, 136. Plunger pumps, ii, 370, 387. Point of compression, ii, 376. cut off, ii, 376. release, ii, 376. Poker, ii, 369. Polishing clamps, i, 311. device for engraver's plates, ii, 51. materials, for brush wheels, ii, 50. for polishing wheels, ii, 50. for rag wheels, ii, 51. wheels, ii, 49-51. construction of, ii, 49. emery charging, ii, 50. for brass work, ii, 50. lapping leather on, ii, 49. large, keeping true, ii, 50. materials for, ii, 50. rag, ii, 51. speed of, ii, 50. Polygons, measuring sides, ii, 283. Pony planer, ii, 323. Position of emery wheel, ii, 35-37. of dies in bolt cutting, i, 473. of taper pins for locking, i, 128. Positive feed, gear cutter, ii, 55. Pounding, the causes of, ii, 168. Power drilling machine, i, 428. hammer, ii, 252. lathes, i, 130. milling machine, i, 470. of an engine, testing, ii, 408. threading machine, i, 465. Powers, mechanical, ii, 405. Preserving wood, ii, 264. Press for forging, ii, 260. Pressure and volume of steam, ii, 411. Priming, its causes and prevention, ii, 370. Profiling machine, ii, 31, 32. Protractors, bevel, i, 380. Propeller, screw, ii, 445. Pulley arms, ii, 280. Pulley balancing, device for, ii, 203. boring machine, i, 438. considered as a lever, ii, 405. diameter, change for grindstone speed, ii, 52. crowned, ii, 201. expansion, ii, 200. lathe, i, 150. patterns for, ii, 278. self-oiling, ii, 200. solid and split, ii, 200. calculating speeds of, ii, 204. transmitting power of, ii, 204. turning, i, 318. turning, special lathe for, i, 211. wood, ii, 200. Pump air chambers, ii, 388. capacity of, ii, 388. displacement, ii, 387. plunger, ii, 387. principles of action of, ii, 387. Pumps belt, ii, 388. for circulating, ii, 440. double acting, ii, 387. lift and force, ii, 387. for marine engines, ii, 436. regulating, ii, 388. rotary, ii, 387. single acting, ii, 387. Q Quartering machine, i, 434. Questions for Engineers, ii, 467. Quick removal, bolts for, i, 116. Quick-return motion, Whitworth's, i, 401. shapers, link motion for, i, 399. R Rabbet planes, ii, 269. Rack and pinion wheel, i, 1. Rack feed saw bench, ii, 301. Radial drilling machines, i, 430, 431. Radiation of heat, ii, 412. Rag polishing wheels, ii, 51. wheel, polishing materials for, ii, 51. Raised [V]-guideways, lathes with, i, 182. Rake, ii, 369. Ramsden's dividing engine, i, 349. Rasps, kinds and cut of, ii, 87. Ratchet brace, i, 457. feeds, i, 173. Rates of feed for finishing cuts, i, 307. Reamers, adjustable, ii, 99. chucking, i, 280. chucking for true work, i, 283. for framing, ii, 99. grinding the teeth of, i, 282. half-round, ii, 99. hand, ii, 98. number of teeth for, i, 282. rose-bit or rose, i, 283. shell, i, 283. shell rose, i, 284. spacing the teeth of, i, 282. spiral teeth for, i, 282. square, ii, 99. taper, ii, 99. Reamer-pin, with facing tool, i, 449. Reamer-teeth, odd or even, i, 282. spacing of, i, 282. Reaper-files, ii, 91. Reboring cylinders in place, ii, 160. Recentring turned work, i, 304. Recessed emery wheels, ii, 47. Reciprocating motion, gear for, i, 77. Red marking for vise work, ii, 96. Reducing knife, i, 209. Reduction of temper, ii, 461. Refitting leaky cocks and plugs, ii, 144. Regulating pumps, ii, 388. Release, the point of, ii, 376. Releasing devices, tailblock with, i, 185. Relief feed valve, ii, 441. Removing corroded bolts, i, 122. corroded nuts, i, 122. feather-edge, ii, 54. Repairing broken frames, ii, 178. connecting rods, ii, 124. Resharpening files, ii, 95. Rests, follower, i, 234. Return cams, designing, i, 82. motions compared, i, 401. Reversible jawed chucks, i, 237. Revolving cutters for gear teeth, i, 37. Ribbing lathe shears, i, 184. Right and left angular cutters, ii, 18. and left hand cutters, ii, 18. Ring work, expanding chucks for, i, 241. Rings, welding, ii, 235. Rip saws, ii, 272, 273. Rivet diameters, ii, 356. Riveter's hammer, ii, 71. Riveting crank pins, ii, 73. Riveted-joints, forms of, ii, 352. proportioning, ii, 354-356. strength of, ii, 354. unevenly spaced rivets, ii, 353. Rivets, diagonal pitch of, ii, 353. spacing of, ii, 353. Rod-feed for screw machines, i, 206. Roll-feed circular saw, ii, 298-300. wood planing machine, ii, 317. Rolling motion of gear teeth, i, 16, 27. Rolling-circles, by using two, the pinion may contain but one tooth less than the wheel, i, 26. circles for internal gearing, i, 25. curves for gear teeth, i, 43. Roll-turning lathe, i, 215. lathe, tools for, i, 216. calender, method of driving, i, 200. Rolls for knife blades, ii, 261. Rope socket, forging, ii, 243. Rose-bit or rose reamers, i, 283. Rotary nut tapping machine, i, 475. planing machine, i, 395. pumps, ii, 387. Roughing cuts, feeds for, i, 306. Rough surfaces, joints for, ii, 138. Round corners, filing out, ii, 95. files, using of, ii, 95. half-round, three-square files, ii, 90. Round-nosed chisels, ii, 75. tools, i, 258. Rudder frame, forging, ii, 245. Rule for finding horse-power, ii, 418. for locating pitch line of worm, i, 29. for finding the chord pitch, diametral pitch, and arc pitch, i, 3. for proportioning the steps of the driving cone, i, 159, 161. Russian sheet iron, gauge for, i, 387. Rust or caulked joints, ii, 140. S Safety devices for planer heads, i, 413. Safety-valve, the inspection of, ii, 368. calculations for, ii, 409. Sag of belts, ii, 210. Salts and acids, testing oils for, ii, 153. Sand blast process, ii, 96. Sand-papering machines, ii, 347-349. Saturated steam, ii, 410. Saw bench, rack feed, ii, 301. frame, horizontal, ii, 312. hack, ii, 97. hammering, ii, 70, 71. machine, tubular, ii, 305. machines, re-sawing band, ii, 310. maker's hammer, ii, 68. plates, grindstones for, ii, 52. straightening, ii, 70, 71. teeth, shapes of, ii, 273, 287. Sawing hot iron, ii, 263. Saws, chisel teeth for, ii, 290. concave, ii, 287, 288. cross-cut, ii, 272, 273. for swing frame, ii, 292. grindstones for, ii, 52. hardening, ii, 462. heating of circular, ii, 288. insertion of teeth in, ii, 290. rip, ii, 272, 273. sharpening the teeth of, ii, 290. shingle, ii, 287, 288. stiffening, ii, 463. tension of, ii, 288. truth of circular, ii, 288. Sawyer's valve for governors, ii, 384. Scale for moulding knives, ii, 83. of tooth proportions, i, 54. Scraped joint making, ii, 137. Scrapers, angles for facets of, ii, 97. applications of, i, 332. for finishing, i, 307. for true surfaces, ii, 97. various forms of, ii, 97. Scraping out cylinder heads, ii, 160. Scrap iron, furnaces, ii, 247. welding, ii, 247. Screw-cutting, driver for, i, 223. face plate for, i, 223. feed regulators for, i, 171. hand tools, i, 96. pitches, metric system, i, 322. reversing tool traverse in, i, 168. with hand tools, i, 334. Screw-driver, and shape, ii, 97. Screw-machine, box tools for, i, 208. chuck for, i, 205. cross-slide for, i, 205. feed gear for, i, 205. cutting off tool for, i, 208. examples of use of, i, 203. for heavy work, i, 201. light work, i, 203, 204. or screw making lathe, i, 200. stop motion for, i, 206. threading tool for, i, 208. tool holders and tools for, i, 202. turret of, i, 205. with special wire feed, i, 206. Screw-propeller, ii, 445. Screw-slotting lathe, i, 192. Screw-thread angles, gauge for, i, 91. cutting tools, the wear of, i, 89. standard forms of, i, 85, 86. Screw-threads, alteration of shape, i, 89. pitch of, i, 85. requirements of, i, 86. self-locking, i, 85. tools for cutting, i, 87. variation of pitch, i, 87. Screws, i, 115. belt, ii, 216. set, i, 127. variation of pitch, i, 87. Scroll chucks, i, 238. chuck threads, wear of, i, 238. sawing machine, ii, 306. Seams for boilers, forms of, ii, 352. Securing feathers, methods of, i, 120. devices, nut, i, 120. pins for exact adjustments, i, 121. Segmental circular saws, ii, 300. Segments, for patterns, ii, 278, 279. saw, fastening to discs, ii, 301. Self-acting lathe, English form of, i, 148. locking bolts, i, 117. nuts, i, 85. screw threads, i, 85. Self-adjusting couplings, ii, 198. Self-oiling pulleys, ii, 201. Set-screws, i, 115. application to hubs, i, 127. Setting angular grooving cutters, ii, 28. brasses to pillow-blocks or axle-boxes, ii, 131. double eccentric by lines, ii, 175. connecting-rod brasses, ii, 125. eccentrics on crank shafts, ii, 174. engine cylinders, ii, 159. engine guide bars, ii, 162. guide-bars by stretched line, ii, 163. line shafting in line, ii, 184, 185. locomotive slide valves, ii, 394. numbers and tabular values for odontograph, i, 50. over tailstock to turn tapers, i, 312. slide valves, ii, 173. threading tools, i, 266. up or aligning new engines, ii, 165. up axle box wedges, ii, 404. up keys of connecting rods, ii, 127. work after case hardening, ii, 129. Settings for boilers, ii, 364. Shaft, flexible, for driving drills, i, 459. forging, ii, 249-252. Shafting, collars for, ii, 189. couplings, errors in, ii, 196. pillow blocks for, ii, 194. speeds for, ii, 190. tests of, ii, 188. turning, three-tool slide-rest, i, 143. hangers, open-sided, ii, 193. various forms of, ii, 192. Shafts, sinking feathers in, ii, 101. welding to exact lengths, ii, 234. Shaking grate bars, ii, 369. Shank cutters, ii, 19. cutters, applications of, ii, 20. feed for, ii, 20. sizes of, ii, 21. drill, improved form of, i, 446. Shanks, drill, i, 445. Shapes of boring bar cutters, i, 291. of centres for large work, i, 299. crowns of brasses, ii, 127. cutting edges of chisels, ii, 74. file teeth, ii, 85. hammer eyes, ii, 66. lathe boring tools, i, 285. lathe tools, i, 254. planer tools, i, 423. Shaping-machine, centres for, i, 397. crank motions for, i, 401. general description of, i, 389. or planer shaper, with tappet motion for reversing, i, 399. quick return link motion, i, 399. with traveling head, i, 397. Shears, lathe, i, 182. Sheet iron, gauge for, i, 387. metal, measuring, machine for, i, 348. zinc, gauge for, i, 387. Shell reamers, i, 283. reamers, arbor for, i, 283. rose reamers, i, 284. Shimer heads, ii, 337. Shingle saw, ii, 287, 288. Shrinkage fits, i, 366. gauge for, i, 367. of iron, i, 368, 374. system at the royal gun factory at Woolwich, i, 367. Shrinking work, to refit it, i, 374. Side rake in lathe tools, i, 256. tools for lathe work, i, 261. Siphon, ii, 443. Size of mandrel holes for saws, ii, 287. Sizes of lathes, i, 130. Skew bevel gear-wheels, i, 61. cutters, ii, 316. knives, ii, 316. Sledge hammer, machinist's, ii, 71. Slice bar, ii, 369. Slide, construction of, i, 390. Slide-rest, American form of, i, 132. application of, to a crank, i, 155. compound tool-holder for, i, 174. detachable, i, 143. double tool-holder for, i, 169. English form of, i, 132. for lathe crank turning, i, 154. lathes, i, 131. pattern lathe, i, 149. special lathe, i, 145. spherical-work, i, 133. gibbed, elevating, i, 169. various forms of, i, 132. Slides of planers, construction of, i, 410. of planer heads, wear of, i, 410. Sliding motion of gear teeth, i, 16, 27. motion of worm-wheel teeth, i, 28. Slide-valve, exhaust lap of, ii, 376. lead adjusting, ii, 386. setting a, ii, 386, 394. squaring, ii, 386. the Allen, ii, 377. the D, ii, 376. Webb's, ii, 377. Slide-valves, balanced, ii, 377. circular, ii, 377. designing, ii, 380. double ported, ii, 377. Slide-valves, steam lap of, ii, 376. the lead of, ii, 376. Slots and holes in planing-machine tables, i, 417. Slotted work, tools for, i, 424. Slotting-machine, i, 459. sectional view of, i, 460. tool-holders, i, 460, 461. tools, i, 461. Snifting valve, ii, 440. Socket forging, ii, 243, 244. wrench, i, 125. Sockets, drill, i, 445. Solid and split pulleys, ii, 200. ended connecting rods, ii, 114. leather wheels, ii, 51. tap wrenches, i, 110. Spacing gear-wheel teeth, i, 57, 58. reamer teeth, i, 282, ii, 98. rivets in boiler seams, ii, 353. Special chucks for watchmakers' lathes, i, 190. index plate for gear cutting, ii, 7. forms of chucks, i, 241. lathe for pulley turning, i, 211. for wood working, i, 208. for brass work, i, 216. Specks in cast-iron work, i, 307. Speeders for governors, ii, 384. Speed of a hammer blow, effects of, ii, 65. of automatic engines, ii, 427. brush-wheels, ii, 50. cutter heads or discs, ii, 338. emery-wheels, ii, 39. governors, ii, 384. grindstones, ii, 52. pulleys, calculating, ii, 204. polishing wheels, ii, 50. shafting, ii, 190. Speeds and feeds for twist drills, i, 277. for cutting wrought iron, i, 294. Spherical work, slide-rest for, i, 133. Spindles live, with coned journals, i, 157. various methods of locking, i, 186. Spiral cutters, grinding teeth of, ii, 36. feed in cutting, ii, 27. grooves, drill stock with, i, 445. planer chucks for, i, 419. springs, winding in the lathe, i, 329. teeth for reamers, i, 282. Spirit levels, ii, 136. Spoon bit, i, 452. Spring adjustment of governors, ii, 384. calipers, i, 360. of engine guide-bars, ii, 162. swages for blacksmiths, ii, 231. tools, i, 263. Springs for indicators, ii, 416. Spur-wheel, annular, i, 23. compared with annular, i, 32. construction of pattern for, i, 54. Square work, steady rest for, i, 233. centre, advantage of, i, 303. various forms of, i, 303. centring, i, 300. holes, device for drilling, i, 450. reamers, ii, 99. bevel, i, 380. shanked drills, i, 446. the T, i, 379. the try, i, 379. Squaring a valve, ii, 386. Square-threads, clearance of tools, i, 269. cutting, i, 269. dies for finishing, i, 270. worms to work with, i, 29. Stable fork, forging of, ii, 241. Standard-cutters, ii, 17. Standard bar for the United States standard of measurement, i, 341. gauges, diameter of work limits the application of, i, 363. for taper work, i, 316. for wire, etc., i, 384. plug and collar gauges, i, 91. screw threads, i, 91. sizes of washers, i, 123. taps, i, 104. variations in, i, 341. Starting a slide valve engine, ii, 384. a locomotive, ii, 400. Stationary engine boilers, ii, 350-371. Steady-rest, cat-head, i, 233. clamps, i, 233. for square and taper work, i, 232. improved form of, i, 233. or back rest, i, 231. work, drivers for, i, 225. Steam, ii, 410. admitted to indicator, ii, 414. amount of, used in engines, ii, 420. engine high pressure, ii, 372. expansion of, ii, 411. fire engine, ii, 430, 431. hammer forging, examples in, ii, 241. hammers, ii, 252-259. laps of slide valves, ii, 376. lubricators, ii, 444. pipe thread, tapping machine, i, 477. pipes, dies for, i, 101. ports, jigs for cutting out, i, 431. pressure absolute, ii, 411. reversing gear, locomotive, ii, 390. saturated, ii, 410. superheated, ii, 410. tight nuts, i, 118. volume and pressure of, ii, 411. weight of, ii, 411. Steaming, wood for bending, ii, 266, 267. Steel and iron welding, ii, 233, 234. plates, engraver's, polishing, ii, 51. Steering gear for fire engines, i, 75. Stepped connecting-rod straps, ii, 117. reamers for taper work, i, 285. Stiffening saws, ii, 463. Stock, adjustable, i, 448. Stocks and dies, i, 97, 101. for drilling machines, i, 449. forms of, i, 101. Stone drill, i, 454. Stop motion for gear-wheels, i, 7. for screw machines, i, 206. Straight-edge and applications, i, 381. Straightening saws, ii, 70, 71. lathe work, device for, i, 305. machine for bar iron, i, 304. plates, ii, 69. wire, check for, i, 305. work by pening, ii, 72. Straight-line-engine, automatic, ii, 428. important details of, ii, 429, 430. Strains on boiler shells, ii, 351. Strap ended connecting rod, ii, 116. Straps, connecting rod, ii, 115. connecting rod, fitting, ii, 120. Strength of boiler plate, ii, 350. boiler shells, ii, 350. gear-wheel cogs, i, 66. gear-wheel teeth, i, 64. line shafting, ii, 190. wire, experiments on the, i, 387. Stroke jointers, ii, 338, 339. Studs, i, 115. Sun-and-planet motion, i, 75. Superheated steam, ii, 410. Supplementary planer tables, i, 417. Surface condensers, ii, 440, 442. condensing engine valves, ii, 442. Surface gauge, i, 378. Surface plates, originating, i, 383; ii, 132. Surfaces, rough, joints for, ii, 138. true, scrapers for, ii, 97. Swage blocks, ii, 232. Swages, spring, ii, 232. for blacksmiths, ii, 230, 231. Swaging, blacksmiths' work, ii, 232, 233. Swing-frame, i, 158. attaching, i, 166. for lead screw, i, 139. saws, ii, 290, 291. Swing machine with fixed table, ii, 294. Swing machine bevel or mitre, ii, 296. Swiveled tool-holding devices, i, 411. Swiveling vise chucks, i, 395. vises, ii, 63. Swivel-heads, construction of, i, 389. for planers, i, 411. Swiveling tool-rest, i, 174. T Table of arc and diametral pitches, i, 3. change wheels, screw cutting, i, 180. circular saw diameters, ii, 287. feeds for twist-drills, i, 277. index holes for gear cutting, ii, 7. natural sines, i, 3. of wrought iron tubes, i, 95. pitch-diameter, pitch, and number of teeth in gear-wheels, i, 68. pressure, temperature and volume of steam, ii, 367. screw threads, i, 95, 96, 107. sizes of, bolts and nuts, i, 114. milling-machine cutters, ii, 17. tapping drills, i, 445. twist drills and shanks, i, 442. speeds for twist drills, i, 277. spring for indicators, ii, 416. standard for the V-thread, i, 95. Tabular values and setting numbers for odontograph, i, 51. Tail-block lathe, i, 185. Tailstock, adjustments of, i, 245. chucks, i, 135, 145. construction of, i, 209. for drilled work, i, 279. engine lathe, i, 135. open spindle lathes, i, 189. securing and releasing, i, 136. Tangent screw, i, 1. Tap-wrenches, adjustable, i, 110. Taper bolts, standards, i, 359. cutters, fixtures for, ii, 34. for pipe threads, i, 95. grinding, ii, 33. holes, device for drilling, i, 451. milling, ii, 30. pins, fitting, i, 128. position for locking, i, 128. plugs for hydraulic fits, i, 365. reamers, ii, 99. taps for blacksmiths, i, 106. threads, cutting, i, 338. turning attachments, i, 143. lathe, i, 142. Tapered connecting-rod ends, ii, 117. Taper-work, centres for, i, 226. chucking, i, 394. fitting, i, 313. fixture for grinding, ii, 33. gauge for setting over, i, 313. grinding, i, 313. plug and collar gauges for, i, 357. standard gauges for, i, 316. Taper-work, steady rest for, i, 233. stepped reamers for, i, 285. turning, i, 312, 313. wear of lathe centres in, i, 312. Tapers for live centres, i, 159. Tapping, i, 111. drills, table of sizes of, i, 445. machine for steam pipe thread, i, 477. Taps, clearance on, i, 102. collapsing, machine, i, 107. for lead, i, 109. for very straight holes, i, 109. form of, i, 103, 104. improved forms of, i, 103. number of cutting edges, i, 106, 471. taper, for blacksmiths, i, 106. taper, the friction of, i, 102. wear of, i, 89. Technical terms in lathe work, i, 296. Tees, patterns for, ii, 284. Teeth, angular, end thrust of, i, 69. angular or herring bone, i, 69. band saw, ii, 308, 309. cast, the contact of, i, 67. curves of elliptical, i, 73. file, shapes of, ii, 85. gear-wheel, factors of safety, i, 64. for variable motion, i, 74. requirements of curves, i, 7. helical, i, 69. reamer, number of, i, 282. spacing of, ii, 98. saw, ii, 273, 287. Temper, blacksmiths', ii, 460. drawing, the, ii, 462. manufacturers', ii, 460. reduction of, ii, 461. Tempering, ii, 460-464. color, ii, 460. heating in fluxes, ii, 462. methods of, special, ii, 461-464. outside, ii, 462. using a muffle, ii, 461. warping in, ii, 461. Template, ii, 110-112. of Corliss bevel-gear-engine, i, 45. for curves, i, 384. marking division lines on the face of a gear wheel, i, 59. filing a link slot, ii, 129. gear-teeth, i, 43, 44. involute curves, i, 32. planing teeth to shape, i, 54. rolling gear-tooth curves, i, 43. gauges for end measurements, i, 376. Tenoning machines, ii, 344. Tenon joints, ii, 274. Tension of band saws, ii, 310, 311. belts, ii, 211. circular saws, ii, 288. Testing angle of bevel wheels while in the lathe, i, 60. boilers, strength of, ii, 456. engine alignment, ii, 166-172. engine guide-bars, ii, 163. indicator expansion curves, ii, 417. iron, ii, 226-228. lathe carriages, ii, 182. lathe tailblock, i, 187. lathes, i, 180, 181. lubricants, ii, 152. machines for iron, ii, 227, 228. oils, ii, 153, 154. shafting, ii, 188. squares, various methods of, i, 379. the power of an engine, ii, 408. various methods of, i, 187. Theoretical compression curve, ii, 421. diagram, ii, 415. expansion curve, ii, 417, 418. Thimble joints, ii, 141. Thinning twist-drill points, ii, 44. Thread angles, gauge for, i, 91. cutting, i, 111. avoiding friction in, i, 474. dies, i, 97. taps, i, 102. tools, angles of, i, 91. wear of, i, 88. pitch varied by hardening, i, 87. screw, forms of, i, 85. Threaded work, drivers for, i, 225. Threading dies, cutting speeds for, i, 474. dies, hob for, i, 474. machine, hand bolt, i, 464. hand, revolving head, i, 465. pipe, i, 463, 475-477. power, i, 466. tools, circular, i, 264, 267. for gauges, i, 266. screw machine, i, 203. holders, i, 267. internal, i, 264. setting, i, 266. the level of, i, 265. Threads, diameter at the roots of, i, 269. left-hand cutting, i, 322. square, clearance of tools for, i, 269. Three and four-jawed chucks, i, 237. Three-spindle drilling machine, i, 434. nut tapping machine, i, 475. Three-tool slide-rest for shafting, i, 143. Three or four boring bar cutters, i, 290. Throttle valves leaky, ii, 386. Throttling governors, ii, 384. Thrust bearings, ii, 445. Thrust on wheel shafts, i, 16. Timber, bending, ii, 265, 266. Timber, shakes or cracks in, ii, 264. shrinkage of, ii, 264. steaming to bend it, ii, 266. Timber-planer, ii, 330, 331. Tit drill, i, 443. Tongs, blacksmith's, ii, 229. Tool aprons for planers, i, 411. edge, oilstoning, ii, 54. front for lathe work, i, 254. facing with reamer pin, i, 449. grinding and grindstones, ii, 51. holders, boring, i, 287. combined, i, 273. for compound slide-rests, i, 174. circular cutters, i, 272. octagon boring tools, i, 175. screw machine, i, 202. lathe for outside work, i, 270. planer, i, 426. slotting machine, i, 460, 461. swiveled, i, 273. threading, i, 267. holding devices, i, 173. swiveled for planers, i, 411. rest, swiveling, i, 174. taps, improved, i, 103. Tools, caulking, ii, 141. bolt heading, ii, 237. box for screw machine, i, 208. circular cutting, i, 267. cutting-off or grooving, i, 262. cutting, the utmost duty of, i, 258. diamond-pointed, i, 254. facing or knife, i, 262. for blacksmiths, ii, 229, 230. cutting rods in pieces, i, 305. screw threads, i, 87. wood slips, ii, 271. a worm in a lathe, i, 62. mortising machines, ii, 344. roll turning, i, 215. screw machine, i, 202. standard shapes, i, 111. testing lathe centres, i, 298. planer, clearance of, i, 424. for coarse finishing feeds, i, 423. slotted work, i, 424. gauge for, i, 423. shapes of, i, 423. round-nosed, i, 258. spring, i, 263. square-nosed, i, 260. thread-cutting, i, 97. threading for screw machine, i, 264. wood working, grindstones for, ii, 52. with side rake, i, 256. Tooth form, variation of, i, 15. proportions, scale of, i, 54. templates, pivoted arms for, i, 44. Trammeling connecting rods, ii, 122. Trams or trammels, i, 377. Traversing grindstones, automatic, ii, 53. spindle lathe, i, 218. Triple riveted joints, ii, 353. Triple-expansion-engine, ii, 436. link motions of, ii, 438. valves of, ii, 438, 439. Trip-hammers, ii, 254. swages for, ii, 231. Trying-up machines, ii, 332. Try-squares, i, 379. True surfaces, scrapers for, ii, 97. surfaces, oiling, ii, 135. plane, originating, ii, 132. Truing grindstones, ii, 53. lathe centres, devices for, i, 297. oilstones, ii, 54. Trundle-wheels, i, 1. T-squares, i, 379. Tube plate cutters, i, 448. Tubular saw machine, ii, 305. Tubular work, lathe mandrels for, i, 227. Tubes, boiler, arrangement of, ii, 364. bursted, ii, 403. Tumbler-files, ii, 91. Turn-buckle, forging, ii, 239. Turned work, recentring, i, 304. Turning a cylinder cover, i, 318. calendar rolls, i, 215. crank axles, lathe for, i, 152. crank, lathe for, i, 154. irregular shapes, i, 210. machine, feed motions of, i, 436. for boiler makers, i, 435. mill, i, 211. outside threads, i, 338. pulleys, i, 318. shafting, three tool slide rest, i, 143. tapers, i, 136, 312. Turret for screw machine, i, 205. Twin cutters, ii, 18. milling, advantages, ii, 25. Twist-drills, i, 274. clearance of, i, 274; ii, 41-44. effect of improper grinding, i, 276. fluting, ii, 29. feeds and speeds for, i, 277. front rake of, i, 275; ii, 44. grinding, i, 276. large, thinning the points of, ii, 44. table of sizes of, i, 442. Two-jawed chucks, i, 236. U United States standard for gas pipe, i, 93. for finished bolts and nuts, i, 113. rough bolts and nuts, i, 114. United States standard for screw thread, i, 86. Universal chucks, i, 238. coupling, ii, 199. grinding lathes, i, 195. joint for drill brace, i, 456. milling-machines, ii, 2-15. for heavy work, ii, 15. V Vacuum gauge, ii, 444. line of indicator diagram, ii, 415. Valve, cut off, ii, 378. expansion, ii, 443. for marine engines, ii, 444. for triple expansion engines, ii, 439. gear, principles of the Corliss, ii, 424. globe, pattern for, ii, 281. Kingston, ii, 440. lead adjusting, ii, 386. measuring, ii, 173. motion, designing, ii, 381. of surface condensing engines, ii, 442. snifting, ii, 440. squaring a, ii, 386. throttle freezing, ii, 386, 387. Velocity, uniform for gear wheels, i, 16. Vertical boilers, ii, 359, 361. milling machine, ii, 31. water tube boiler, ii, 360. V-guideways for planer heads, i, 414. Vise, ii, 62, 63. chucks for vise work, i, 396. construction of, i, 393. chucking work in, i, 393. holding taper work in, i, 394. rapid motion, i, 396. swiveling, i, 395. various forms of, i, 394. clamps, various forms of, ii, 64. hand, ii, 104. jaws, heights of, ii, 62. leg, with parallel motion, ii, 63. wood workers', ii, 62. work, classification of, ii, 62. examples in, ii, 102-135. red marking for, ii, 96. Vises, swiveling, ii, 63. Volume and pressure of steam, ii, 411. V-slide lathe shears, i, 182. V-thread standard, i, 93. V-tool for starting threads, i, 337. W Wall hangers, ii, 193. Warping, ii, 461. Warping of files, ii, 93. Washers, i, 123. standard sizes of, i, 123. Watchmakers' lathes, i, 188. Watch manufacturers' hand lathe, i, 191. lathe, details of, i, 190. Water, ii, 410. evaporation, calculation of, ii, 420. gauge glass, ii, 368. joints, ii, 139. tube boiler, vertical, ii, 360. Wear of dies, i, 89. of back bearings, i, 158. emery wheels, ii, 48. groove cams, i, 84. nuts, i, 120. planer head slides, i, 410. scroll chuck threads, i, 238. spindles of lathe tailblock, i, 185. taps, i, 89. worm and worm-wheel, i, 28. upon grooved friction wheels, i, 79. Weight of steam, ii, 411. Weighted elevated slide rest, i, 168. slide-rest, feed motion for, i, 168. Weld, butt, ii, 234. lap, ii, 234. split, ii, 235. Welded connecting rods, aligning, ii, 118. Welding iron and steel, ii, 233, 234. scrap iron, ii, 247. stub ends of connecting rods, ii, 118. theory of, ii, 233. Wheel, emery, position of, ii, 35. forging of fifth, ii, 239. hubs, lathe for turning, i, 221. lathe, i, 151. rack and pinion, i, 1. rim, spacing the teeth on, i, 56, 58. shafts thrust on, i, 16. tire, throwing off, ii, 403. worm, i, 1. Wheels, bevel line of faces, i, 22. brush, for polishing, ii, 50. speed of, ii, 50. clock, i, 21. considered as levers, ii, 405. emery, annular, ii, 47. balancing, ii, 39. grades of, ii, 39. presenting, to work, ii, 47. qualifications of, ii, 38. recessed, ii, 47. swing frame, large work, ii, 46. speeds of, ii, 39. wear of, ii, 48. work suitable for, ii, 39. friction, i, 77. material for, i, 77. for transmitting motion, i, 21. gear drawings for, i, 59. intermediate, i, 319. locomotive, forging, ii, 244. number of cutters for a train of, i, 39. paddle, ii, 444. polishing, construction of, ii, 49. charging with emery, ii, 50. for brass work, ii, 50. large, method of truing, ii, 50. polishing materials for, ii, 50. rag, ii, 51. speed of, ii, 50. solid leather, ii, 51. trundle, i, 1. White-metal lined boxes, ii, 155. Width and thickness of chisels, ii, 74. Winding spiral springs, i, 329. strips and their use, i, 382. Wire-feed for screw machines, i, 206. gauge, i, 387. Wire, strength of, experiments on, i, 387. Wood bending block, ii, 265, 266. boring machines, ii, 343. for patterns, ii, 264. gouges, ii, 272. moulding machines, knives of, ii, 84. planing machine, ii, 317-341. pulleys, ii, 200. steaming, ii, 266. turning, hand tools for, i, 338. work, chisels for, ii, 271. counterbore for, i, 449. drill for, i, 449. drivers for, i, 225. forms of joints for, ii, 275. lathe, face plates for, i, 247. on swing frame machine, ii, 292. twist drills for, i, 279. worker's vise, ii, 62. Wood-working, circular-saw gauges for, ii, 295. lathes, chucks for, i, 242. machinery, ii, 287-349. special lathe for, i, 208. tools, grindstones for, ii, 52. Woods for patterns, ii, 264. Work, cored, drivers for, i, 225. face plate, examples of, i, 249. holding straps, i, 244. hollow centres for, i, 226. shrinking, to refit, i, 374. Worm and worm-wheel, i, 28. gears, i, 62. wheel, application of, i, 30. cutting teeth of, i, 42. enveloping teeth, i, 28. number of teeth in, i, 29. teeth, sliding motion of, i, 28. Worm to work with a square thread, i, 29. Wrench, adjustable, i, 125. for carriage bolts, i, 125. jaws, angle for, i, 123. monkey, i, 125. pin, i, 126. sockets, i, 125. various forms of, i, 125. Wrought iron, cutting speeds for, i, 294. Y Yoke and guide-bars, ii, 389. Z Zigzag riveted seams, ii, 352. Zinc gauge, the American sheet, i, 387. gauge, the Belgian sheet, i, 387. THE END. +------------------------------------------------------------------+ | TRANSCRIBER'S NOTES | | Text: | | * Minor obvious typographical errors (including punctuation) have| | been corrected silently. | | * Footnotes have been moved to directly under the paragraph or | | table they belong to. | | * Mid-dots (·, inconsistently used as decimal points) have been | | replaced with periods (.). | | * Calculations and rounding of results have not been changed, | | except when they contained obvious errors (see below). | | * Inconsistent spelling has not been changed, except as mentioned| | below (see "Changes made"). Inconsistencies that occur in the | | original work include variants such as vice/vise, colour/color,| | gray/grey, ...er/...re (center/centre, fiber/fibre, etc.) adze/| | adz, axe/ax, draft/draught, cotter/cottar, ...ise/...ize | | (crystallise/crystallize, equalize/equalise, etc.), mould/mold,| | intercepter/interceptor, mandrel/mandril, planimeter/ | | planometer, l/ll inconsistencies (jeweller/jeweler, travelling/| | traveling, etc.), Beltiline/Beltilene, Stubb/Stub, and Swasey/ | | Swayzey. The plural of [V] is sometimes written [V]s, sometimes| | [V]'s. | | * Inconsistent hyphenation has not been changed either, except as| | listed below under "Changes made". Many compound words are | | variously spelled hyphenated, spaced or as a single word. | | * Volume I, Page 61: let the Fig. 166 ...: part of sentence | | appears to be missing. | | * Volume I, Page 369: heading PART I. There does not appear to | | be a PART II (or further). | | * Volume I, Page 370, Fig. 1430: 995 and 598 should probably be | | .995 and .598. | | | | Illustrations: | | * Illustrations and plates are given in the order in which they | | are found in the original work. In some cases, the plates | | contain illustrations that are out of their numerical order. | | * In Volume II the numbering of illustrations is as expected up | | to Fig. 2705, after which follow Figs. 2824 through 3077, | | followed by Figs. 2706-2823, after which the numbering | | continues as expected. This has been maintained in this e-text.| | * Similarly in Volume II, plates are numbered I-XII, followed by | | Plates XV-XVII, then XIII-XIV, followed by Plate XVIII et seq. | | This has not been changed either. | | | | Tables: | | * Many tables have been split or otherwise re-arranged. In | | several tables the headings have been changed to legends [A], | | [B], etc.; these are explained directly above the table. In | | other tables, remarks have been changed to [A], [B], etc.; | | these are explained directly underneath the tables. | | | | Changes made to the text: | | | | Volume I: | | Page number Original work Changed to | | ----------- -------------------------- ------------------------- | | page xi Machine 309 Machine 300 | | page 7 under wear undue wear | | page 30 Hindleys' Hindley's | | page 37 Fig. 106 Fig. 109 | | page 40: (for 97 bears... (for 96 bears... | | page 47, table in fig. 135: row 16 teeth, 2nd last value: | | 191 119 | | page 49: 1/2 = 500 1/2 = .500 | | page 67: After very few blows After every few blows | | page 84: maintained a close fit maintained in a close fit | | page 87: second reference to Fig. Fig. 259 (description | | 258 clearly refers to 259) | | page 95: apt to have a waver apt to have a wave | | page 95: closing " added (after 'a single operation.') | | page 96: Whitworth table, Hydraulic Piping, 1" ID, row 2: | | 1-3/8 1-5/8 | | page 107, table: | | 5-12/16 5-13/16 | | page 127: .937/1000 937/1000 | | page 136: in figure : in Fig. 498: | | page 162, column 1, row ending in 0.00: | | unclear .0594 | | column 1: column 2 moved to between columns 1 and 3 | | column 33, row ending in 0.72: | | 1.22 0 1.2200 | | column 31, row ending in 0.96: | | .8 94 .8994 | | page 186: gibbs gibs | | page 234: out if true out of true | | page 274, table, first row: | | 1/6 1/8 | | page 307: Fig. 1029 Fig. 1209 | | page 312: smoothes smooths | | page 321: 66 ÷ 36 = 2-3/4 99 ÷ 36 = 2-3/4 | | page 322: as at J in Fig. 1241 as at I in Fig. 1241 | | page 335: Fig. 1334 Fig. 1324 | | page 344: Fig. 1532 Fig. 1352 | | page 356: Lloyd's Lloyds' (as elsewhere) | | page 366: if it is found possible if it is found impossible | | page 367: will expend will expand | | page 370, Fig. 1430: | | smart quotes " (inches) | | x × | | page 373, third table: | | 0.2 .02 (twice) | | page 388: reamless seamless | | page 388, table, row 2" column 3: | | 1/5 1/8 | | page 406: Fig. 1669 Fig. 1569 | | page 442 first table, row 11/16, column 2: | | 8-1/4 9-1/4 | | | | Volume II: | | page x: Mariotte's law Marriotte's law (as in | | text) | | page 7, table, row 25 teeth, column 3: | | 12/0 12/20 | | page 7/8, table: rearranged to become continuous, repeat headings| | removed | | page 17: a length of 3 inches a length of 3 feet | | page 88: Figs. 2211, 2212 and 2213 Figs. 2210, 2211 and 2212 | | page 132, footnote [33]: | | p. 162 p. 68 | | page 151: Figs. 2405 and 2500 Figs. 2495 and 2500 | | page 154, first table, row Smooth metal surfaces, occasionally | | greased, second column: | | 4 to 1-1/2 4 to 4-1/2 (as in Bourne's| | book (Rose's source) at | | archive.org) | | page 208, table in illustration, row 7, column 5: | | 9.32 9/32 | | all fractions transcribed as x/y for consistency | | within table | | page 224, second formula: | | 11. .11 | | page 311: Ortow Orton (as elsewhere) | | page 319: Fig. 3260 Fig. 3160 | | page 348: 4' 4" (thickness) | | page 354, first formula: | | by 2 2 | | page 354: formula resulting in 116-2/3 lbs.: | | + × | | page 356: found the required pitch found the required pitch | to to be | | page 367, table row Total pressure 33, column 3: | | 225.2 252.2 | | table row Total pressure 44, column 6: | | 595 585 | | table row Total pressure 61, column 6: | | 403 430 | | page 401: colters cotters | | page 407, first calculation: | | line added under 5 (third row) | | page 471: Marriott's Marriotte's | | page 476: Tuyere Tuyère (as in text) | | Verneer Vernier (as in text) | | page 479: featheredge feather-edge (as in text) | | page 480: Gimblet Gimlet (as in text) | | doghead dog-head (as in text) | | Guideways Guide-ways (as in text) | | page 481: Marriott's Mariotte's | | rabbetting rabetting (as in text) | | Piaté Piat's as in Table of | | Contents (word does not | | occur in text) | | page 482: featheredge feather-edge (as in text) | +------------------------------------------------------------------+